Title of Invention

AN INJECTION DEVICE

Abstract An injection device for use with a syringe (30) having a bore (32) extending from an end surface (34), a needle (36) communicating with the bore through the end surface and a dispensing piston (38) movable in said bore towards said end surface so as to expel the content of the syringe through the needle, the injection device including a housing (60) having an opening (64) at one end through which the needle may extend, a resilient member for biassing the syringe and needle inwardly of the housing, a drive element (66) movable towards said one end so as to move the needle of the syringe out of the opening against the bias of the resilient member and to move the dispensing piston of the syringe towards the end surface, a delatch mechanism (72) operable to release the syringe such that the needle moves inwardly of the housing, a drive coupling (40) for extending from said drive element to the dispensing piston of the syringe so as to transfer movement of said drive element to the dispensing piston, wherein the drive coupling gradually reduces in length such that, after the drive element has moved the dispensing piston to the end surface, the drive element continues to move to said predetermined piston to the end surface, the drive element continuous to move to said predetermined position at which said delatch mechanism releases the syringe.
Full Text

The present invention relates to an htf ecticn device, in particular an injection device which, having dispensed the contents of a syringe, automatically retracts the needle of the 5 syringe.
Devices exist which are spring loaded to extend automatically the needle of a syringe from the device, dispense the contents of the syringe and then automatically retract the needle, WO 95/35126 describes such a device.
As illustrated in Figure 1 of the accompanying drawings, the device includes a 10 housing 2 inwbich a syringe 4 is contained. The housing 2 includes an opening 6 through • which the nsedle 8 of the syringe 4 may extend A retraction spring 10 "biases the syringe 4 away from the opening 6. The device also includes a drive element 12 which is biassed by a spring 14 to drive a coupling 16 to move the dispensing piston J8 of the syringe 4. In use, a release mechanism 20 releases the drive element 12 such that the syringe 4 is first 15 moved forwards and the .needle 8 projects through the opening 6, Subsequently, the dispensing piston 18 is moved so as to expel the contents of the syringe 4. The device is designed to include a dclatch mechanism, in particular, at the point at which the dispensing piston 18 reaches the end of the bore in fee syringe 4, arms 22 at the end of the coupling 16 are deflected by a collar 24 within the housing 2 so as to disengage from the drive 20 element 12, The arms 22 and coupling 16 may then move within a central passage of the drive element 12, ■ A$ a result, by virtue of Hie bias of spring 10, the coupling 16 moves inside the drive element 12, the syringe 4 is driven away from the opening 6 and the needle 8 is retracted within the opening 5.
Other similar delatch or retract arrangements have also been proposed, For 25 instance, EP-A-0 516 473 discloses one embodiment in which, at'the point at which the disp&sifig piston reaches the end of die bore in the syringe, a portion of the coupling instantaneously collapses in length as the retraction spring retracts the needle of the spring.
M practice, all of these proposals suffer a problem that, due to a stack up of tolerances of the various manufactured components of the assembled device (the 30 dimensions of all manufacture components vary around a mean)* it cannot be assured thai

the delaich mechanism *wiU enable retraction of the syringe and needle at precisely the moment "at which the dispensing'piston reaches the end of the bore, M practice, either the mechanism delatches beiore me dispensing piston reaches, the fend of the bore, such that the syringe is not emptied, or the piston reaches the end of the bore before the mechanism has moved sufficiently fax to delated
Although this problem has been recognised before, for instance in US 6,159,151, the proposed solution has been to provide a usefr actuated retraction mechanism rather than an automatic cue. This is considered to be undesirable.
It is an obiect of the present invention to provide an Injection device which is relatively simple and of low cost (so as to be useful as a single juse device) and which overcomes or at least reduces the problems identified above.
According to the present invention there is provided an, injection device including:
a housing for containing a syrmge haying a bore extending from an end surface, a needle communicating with the bore through the end'surface and a dispensing piston movable in said bore towards said end sirrfacc so as to expel the contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend;
a resilient member for biassmg the syringe and needle inwardly of the housing;
a drive element movable towards said one end so as to move the needle of the
■i
syringe out of the opening, preferably against, the bias of the rejnlient member, and to move the dispensing piston of the syringe towards the end surface;
a mechanism, such as a delatch or retract mechanism, operable to release the syringe such that ifce needle moves inwardly of the bousing;
a drive coupling for extending from said drive element ito the dispensing piston of the syringe so as to transfer movement of said drive element to the dispensing piston; wherein.
die drive coupling is compressible in length, preferably whilst overcoming the bias of the resilientmcmber, such that,- aftar the drive element has moved the dispensing piston

to tfcie sad surface, the drive coupling gradually reduces in lsagth wkiisr the dispensing piston is maintained at the and surface y^til said mechanism releases the syringe,
According to the present invention there is also provided a drive? coupling far use La m injection deyice, the drive coupling having:
a. length for extending from the drive element to the dispensing piston of the syringe so as to transfer movement of the driva element to the dispensing piston; wherein
the drive coupling is compressible in length, preferably whilst overcoming the bias of the resilient member, such that, after the drive etement has moved the dispensing piston to the end surface, the drive coupling gradually reduce* in. length whilst the dispensing* piston is maintained at the end surface until the mechanism releases the syringe.
Thus, since the drive coupling is able to gradually reduce in length whilst maintaining the needle in its extended position, it is possible to design the injection device to operate the mechanism at some point after the dispensing piston has reached the end surface, and fully expelled the contoats of the syringe. Since the mechanism is now triggered'at some uncritical point of time after the contents of the syringe have been expelled, tolerances of the various components are no longer a problem. Preferably, the drive coupling is capable of reducing in length whilst providing a resistive force to overcome the resilient member.
It will be appreciated that the length of the drive coupling here is the effective length, ie the length measured from the drive element to the dispensing piston, such that, according to the present invention, the length gradually decreases and the drive dement moves relatively towards the dispensingpiston. To produce this reduction in langth, it is sufficient to provide components which are relatively movable in any way which allows the drive element to move towards the dispensing piston. Indeed, the drive coupling can be provided by a component which is movable in any way relative to the drive element which allows drive to and relative movemeht to the dispensing piston.
Preferably, the mechanism is operable when the drive element reaches a. predetermined position in said housing and the drive coupling gradually reduces in length such that, after the dispensing pistpn reaches the end surface, the drive element continues to move in saidhousing to said predetermined position.

The drive element may continue to move over a period of time as the drive coupling continues to reduce in length such that, even though the dispensing piston has' reached the-end of its travel and abuts the end suifece, the drive element can assuredly.. move to the necessary position to trigger the return mechanism. It is merely sufficient to ■ ensure that the drive element does not reach the position for triggeimg the mechanism before the dispensing piston reaches the end surface, of the syringe.
It will be appreciated that, contraiy to previous mechanisms, in particular the collapsing structures of EP-A-0 516 473, the drive coupling of the present invention does not collapse instantaneously but reduces in length gradually. Indeed, the length of the drive coupling continues to reduce in length gradually even after the dispensing piston abuts the end. surface. Furthermore, whilst collapsing, the drive coupling still transfers sufficient force to rnaiVuvn'ri the needle in its extended position and, preferably, overcome the bias of the retraction sprang
In contrast, at some point up to and including that at which the dispensing piston abuts the end surface, previous collapsing couplings collapse instantaneously under the influence of the retraction spring and do not resist its bias. In particular, once the collapsing coupling of EP-A-0 516 473 starts to reduce in length, it offers virtually no resistance to the retract spring and, hence, is almost instantaneously collapsed.
' Furthermore, in previous arrangements, once the dispensing piston abuts the end surface, the drive element and drive, coupling can move no further and, hence, collapsing of the drive coupling cannot be initialed, However, with the present invention, even after the dispensbg piston abuts the end surface, the drive element can continue to move -whilst the -dispensing piston is maintained at the end surface.
The present invention could be considered as a damped collapse of the drive coupling such that the force and motion of the drive element maintain the syringe and needls ha position, even after the dispensingpiston abuts the end surface, until the drive element reaches the predetermined position.
Depending on the exact nature of the arrangement, the drive coupling may only start to collapse when the dispensing piston reaches the end surface or it may start to collapse at some predetermined point just before the piston reaches the end surface.

Before it starts to collapse* it is preferably rigid. A reloadable latch may be provided to prevent any collapse of the drive coupling until the drive element and dispensing piston reach respective predetermined positions.
Provided that there is sufficient length and thai the drive element causes the dispensing piston to expel the contents of the syringe sufficiently quickly, it is possible for the drive coupling to reduce in length gradually throughout the entire operation and file entire movement of die drive element However, since the controlled collapsing of the drive coupling is only required in the region of the dispensing piston reaching the end surface, it is preferable that the drive coupling remains of constant length before then. Thus, preferably, the drive coupling does not reduce in length until the dispensing piston has reached'* position at least proximate the end surface.
The drive coupling may include a chamber defined between first and second relatively movable walls, the first wall being movable by said drive element and said second wall being operable to move the dispensing piston, and a bleed orifice for bleeding flowable material, preferably from the chamber-In this way, drive from the drive element and the Sist wall is transmitted through flowable material in the chamber^ the second wall and the dispensing piston. Bv means of the bleed orifice, material may gradually bleed from thechamber such that, in a preferred embodiment, the first and second walls move gradually towards one another and the length of the drive coupling is reduced.
Thc flowable material merely has to provide the property of resisting flow through a restriction and need not be a true fluid but could be a Binghan* plastic for example, hi a preferred embodiment, the material is preferably a fluid such as a liquid or gas.
A bleed orifice could be included in the first wall so as to enable fluid to bleed from the fluid chamber when the drive element moves the first wall and compresses the drive coupling and fluid chamber.
The dimensions of any bleed orifice are chosen such that pressure of the fluad in the fluid chamber is maintained sufficient to force the dispensing piston to the end surface of the syringe.

Preferably, the drive coupling includes a main body fo£ mounting on the syringe so as to have a position fixed relative to fee bore and the needle, the main body having a bounding or peripheral wall defining an elongate passage within which the first and second walls are both moyable, the fluid chamber being defined by the peripheral wall and the first and second walls.
in this way, as the drive element moves towards the first end, both the first and second walls are moved within the elongate passage, the fluid chamber being defined by the space between them.
■ A bleed orifice may be formed, at a predetermined longitudmalpositio" airfn a &e peripheral wall such that it is only exposed to the fluid chamber once the second wall passes the predetermined longitudinal position.
in this way, until the second wall reaches the predetermined longixuamai position, the fluid chamber remains of constant volume and the effective length of the drive coupling does not reduce. However, once the second wall reaches the predetennined longitudinal position, Said bleeds through the bleed orifice so that the length between the first ?r>^ second walls and the effective length of the drive coop ling gradually reduces so as to ensure that the drive element triggers the delatch and retract mechanism.
It should be appreciated that the present invention can be applied to injection devices which house conventional syringes or which house other mass produced cartridges' of a standard design. However, it is also possible to form the drive coupling jp, the syringe itself.
The first and second walls may be movable in the bore of the syringe such thai the fluid chamber is defined by the bore and the first and seconu waus. , In this way, the number of component parts may be reduced. The second wall may form an integral pari of the dispensing piston or may drive th As described above, a bleed orifice could be. formed in the first wall so as to enable fluid to bleed from the fluid chamber. However, preferably, the bleed orifice is formed at a predetermined longitudinal position along the bore and is only opened to the fluid chamber .once the second waU passes the predetermined longitudinal position.

M this way, as* described above, the fluid chamber remains of constant volume until the second wall reaches the predetermined longitudinal position such that the effective length of the drive coupling starts to reduce only in the region where lie dispensing piston reaches the end surface.
The bleed orifice may be circular. Alternatively, it may have a cross-section which is elongate and/or there maybe an array of bleed orifices extending towards the end surface such that as a second wall moves towards die end surface, fluid bleeds fester from the fluid chamber.
The orificesmay be arranged in this way .such that, once the dispensing piston
V
reaches the end surface, the second wall exposes a sufficient area of the bleed orifice(s) to allow fluid to bleed from the fhiid chamber at a rate appropriate to allow the resilient member to retract the syringe and needic.
Indeed, according to the present invention, there may be provided an injection device including:
a housing containing a syringe with a syringe body having a bore extending ftom an end surface, a needle communicating with the bore through the end surface and a dispensing piston movable in said bore towards said end surface so as to expel the : contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend;
a resilient member for biasing the syringe and needle inwardly of the housing;
a drive element movable towards said one end so as to move the needle of the syringe out of the opening, preferably against the bias of the resilient member, and to move the dispensing piston oFthe syringe towards the end surface; wherein
the syringe further includes:
a secondary piston movable in said bore, the dispensing piston and the secondary ' piston defining a fluid filled chamber* therebetween; and
a bleed orifice commumcatiog with said bore; wherein
the bleed orifice is positioned at a distance from the end surface and Die dispensing piston is of such a length that the dispensing piston exposes the bleed orifice to the fluid

filled chamber as the dispensing -piston reaches the end surface and loss of fluid from the fluid chamber allows retraction of the needle by virtue of the b&s of the rerJieut membex. Since the point of retraction is only dependent on the position of the bleed orifice and the length of the dispensing piston, the number of tolerances affecting the point of retraction are reduced such that the syringe can be assuredly retracted al the point at which the contents is fully dispensed
Alternatively, the drive coupling may include a drive Motional surtacs engaging a driven factional surface, the drive fiictionai surface being movable by the drive element and the driven fractional; surface.being operable to move the dispensing piston such that, when the dispensing piston reaches the ead surface, the &st fiictionai surface slips relative to the second Motional surface.
Thus, in this case, the drive coupling only f educes hx length, once the dispensing piston reaches the end surface. The drive element continues to apply a force to &e drive coupling by virtue of the fiictionai resistance such that the frictkmal surfaces slip, the drive coupling reduces in length and the drive element reaches the required position to trigger the return mechanism.
The drive fiictionai surface maybe rotatable about aa axis generally pezpeadipulasf' to the jsurface apd be moved by the drive element at a position cjffset from the suds.
Similarly, the driven fiictionai surface may be rotatable kbout an axis generally parallel to the surface and may be operable to move the dispensing piston from a position ofiset from the axis,
in other words, drive to or from the rotational fractional jswface may be by mc^s of a crank mechanism 3uch that, when the surfaces slip and rotate,, the connection points to the drive element and the dispensing piston move closer together.
The drive coupling may include a rack and a pbion geai therein one of the rack andthapinion gear is movable by the drive element'and the othjar of the rack and the pinion is operable to move the dispensing piston.
In this way, as the drive element exerts a compression force on the drive coupling, the rack will tend to rotate the pirdon gear.

The pinion gear may include a friction brake to pioventj rotation and allow the cinve. element to move the dispensing piston. When the dispensing piston reaches the end surface, the friction brake slips and the teagth of tbe drive coupling is reduced.
Alternatively, the pinion gear can drive a fly wheel suclji that when the dispensing piston reaches the ead surface, the pinion gear is turned against the inertia! resistance of the fly wheeL Thus, once again, the length of the drive coupling is reduced.
As explained above, previous injection devices drive the dispensing piston to first move the syringe as a whole and position the needle outside of iheinjection device housing. This woiks well for fine needles where the back pressure on the fluid for injection is relatively high and the force required to insert the needle is relatively low. However, where there is more difficulty in inserting the needle, there is a possibility that seme fluid will be dispensed from the needle before it is correctly inserted below the skin.
Hence, preferably,, the injection' device further includes an engagement for transferring drive directly from the drive coupling to the syringe body such that movement of the drive element towards said one end causes no relative movement of the dispensing piston in the syringe wherein the engagement is releasable once;the needle of the syringe extends out of the opening such that movement of the drive element towards said "one end causes relative movement of the dispeonsing piston in the syringe body. ■
Thus, iterthennore, according to jhe present invention, thtere is provided an injection device including:
a housing for containing a syringe having a bore extending in a syringe body from an end surface, a needle communicating with the bore through the end surface and a dispensing piston movablein said bore towards said end surface so as to expel the contents of the syringe through the needle, the housing having ah opening at one end through which the needle may extend;
a drive element movable towards said one end so as to move the needle of the syringe out of the opetaing and to move the dispensing piston of the syringe towards the end surface;
a drive coupling for extending, from said drive element to the dispensing piston of the syringe so as to transfer movement of said drive element to the dispensing piston; and

an*engagemant for traasfcrring drive directly from title drive coupling "to the syringe body such that movement of the drive element towards said one end causes no relative
movement of the dispensing piston in the syringe; wherein
the engagement is releasable once the needle of the syringe extends out of the
opening such that movement of the drive element towards said one end causes relative
movement of the dispensing piston in the syringe body
This ensures that the drive element correctly positions rfce syringe with the needle
protruding ftojm the housing before the dispesasing piston is moved to dispense the contents
of the syringe.
-. Preferably, the injection device includes a resilient member for biassing the syringe
and needle inwardly of the housing- The drive element may move the needle of the syringe
out of the opening against the bias of the resilient member.
Preferably, the housing includes a release portion which interacts with fee
engagement to release drive to the syringe-la this way, engagement may be,released by virtue "of the relative position of the
syringe in the housing.
Preferably, the release portion is located in the housing at a predetermined position;
and the engagement includes a trigger which is operated by the release portion to release
drive to the syringe upon reaching the predetermined position-In. tins way, the needle is assuredly extended by ihe right amount Preferably, the engagement includes a resilient latch and the release portion
includes at least a recess ixx a wall of the housing allowing deflection of the resilient latch to
release the drive to the syringe.
, Hence, the watf of the housing may maintain the resilient latch in a. position of
engagement until it reaches a recess or even an opening in the wall.
preferably, the at least a recess engages the resilient latch'so as to prevent further
relative movement of the syringe body in the housing.
Thus, when the resilient latch moves into -the recess or opening it may then engage
with the recess or opening -so as to .fix the relative position between the syringe and the
housing.

As described above,, the drive coupling may include a fluid chamber defined between first and second relatively movable walls, the first wall being part of a piston and the resilient latch operating on the piston.
By engaging with either the dispensing piston or a secondary piston (forming with the dispensing piston a fluid chamber), the relative position between the dispensing piston and the syringe body can be fixed, such that any drive applied to the drive coupling or dispensing piston will result in movement of the syringe raiher than the dispensing piston relative to the syringe.
The drive, coupling may include a rigid element extending from the drive element, the engagement may include at least one protrusion on a surface of the rigid element and a latch fixed relative to the syringe body engaging the protrusion and the release portion may include a stop on the housing for mgaging the latch wherein the rigid element moves the latch-with the protrusion until the latch abuts the stop, whereupon the Latch releases from the protrusion.
The latch may be deflected resiliency past the protrusion, However, alternatively, . the-latch maybe hinged as a cantilever at a point between an end engaging protrusion and an opposite end wherein the stop deflects the opposite end so as to release engagement with the protrusion*
The latch may be hinged at the point at which it is attached to the syringe or alternatively to a part of the drive coupling mounted to the syringe with a fixed relative position to the needle.
The engagement may releasably connect the &ive coupling to the syringe. Alternatively, the engagement may releasably connect a part of the drive coupling movable with the drive element to a part of the drive coupling to be mounted to the syringe in a feed relative position to the needle,
The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which:
Figure 1 illustrates aknown construction for an injection device;
Figure 2 illustrates, a drive ooupling according to the present invention;

Figure. 3 illustrates the drive coupling of Figure 2 iacarpjorated into an iaj ecticn device axmflgr to that illustrated in Figure 1;
• Figure 4 illustrates schematically an injection device in Which, the drive coupling is incorporated into the syringe cartridge itself;
Figure 5 illustrates an embodiment providing direct drive to the syringe; Figure 6 illustrates an alternative embodiment providing direct drive to the syringe. Figure 7 illustrates schematically a friction plate embodiment; ' Figure ,8 illustrates schematically a rack and pinion embodiment; Figure 9 illustrates schematically a rack and pinion construction using a flywheel; and
Figures 10 to 15 illustrate an alternative embo Figures 16 to 21 illustrate schematically another embodiment of a drive coupling of the present invention.
As will be apparent from the above, the present invention concerns injection devices and is based on driving the dispensing piston of a. syringe with a drive coupling which can gradually reduce in length so as to ensure that the dispensing piston is moved fully along the length of the syringe and that the needle is held in its exteaded position by an appropriate force until that time.
Figure 2 illustrates an embodiment of a suitable drive coupling. The drive coupling is for use with a syringe 30, such as ja standard syringe or cartridge, which includes a bore, 32 extending from, an end surface 34 within that bore and' a needle 36 which communicates with the bore 32 through the end surface 34. A dispensing piston 38 is movable along the bore 32 towards the end surface 34. In particular, by moving the dispensing piston along the length of !the syringe until it abuts tfte end surfkee 34, the totire contents of the syringe may be expelled through the syringe needle 36.'
As illustrated, the drive coupling 40 includes a main body 42 which mares with the end of the syringe 30.

The mam body 42 includes an elongate through passage along which a first piston 44 and a second piston 46 may move. The first piston 44 ,defiaes a first wall 48 facing a second wall 50 defined by the second piston 46,
The first wall 48 and second wall 50, together with the elongate passage 43, defim. a chamber. 52 filled with fluid a material which is substantially incompressible, mobile under pressure and capable of extrusion. Materials such as powders, greases and soft-solids may be used However, in a preferred embodiment, a fluid is used such that chamber 52 will be described as a fluid chamber. Ihis fluid as preferably liquid and suhstarHflWv incompressible,.
.The first piston 44- and, hence, the first wall 48 may be driven by the drive element of an injection device. This is illustrated more clearly in Figure 3.
As the first piston 44 is moved along the elongate passage 43, since the fluid in the fluid chamber 52 is substantially incompressible, the second wall 50 and, hsace, the second piston 46, is also moved along the elongate passage.
For convenience of design, a spacing element 54 transfers drive from the second piston 46 to the-dispensing piston 38 of the syringe 30,
Thus, the drive coupling 40 transfers movement to the dispensing piston 38. At a predetermined position along the length of the passageway 43, a bleed orifice' 56 is provided. Once the second wall 50 passes the bleed orifice 56, fluid is able to bleed from the flxdd chamber 52 to outside the main body 42. As tins fluid bleeds away, the volume of the fluid chamber 52 will be reduced and the distance between the fir« wall 48 and the second wall 50 wiS also be reduced.
The predetermined position of the blesd orifice 56 is chosen such thai, with the main body 42 mated to the syringe 30 and having a fixed relative position, the second wall 50 will pass die bleed orifice 56 just before the dispensing piston 38 reaches the end surface 34.
It will be appreciated that, theoretically, the second wall 50 could open the bleed orifice 56 just as the dispensing piston 38 reaches-the end surface 34, However, the present invention is based on a recognition that tolerances, particularly the compound effect of tolerances of different components, mean that such design cannot be guaranteed.

Therefore, the second wall 50 exposes the bleed orifice 56 when the dispensing piston 38 is at a position proximate the end surface 34 so as to ensure that the bleed orifice 56 is open by the time the dispensing piston 38 abuts the end surface 34.
It will be appreciated that, even with the bleed orifice 56 open, some driving force will still be transmitted to the second piston 46 such that the dispensing piston 3 8 will be driven the final small distance to the end surface 34 to dispmse the remaining contents of the syringe 30.
With the dispensing piston 38 abutting the end surface 34, the second piston 46 and second wall 50 will move no further. However, as fluid bteeds ftom the fluid chamber 52, the. first wall 48 and first piston 44 will continue to move towards the end surface 34 until a return delatch mechanism is operated to retract the syringe 30 and needle 36 back into the housing of the injection device.
The particular nature of the return delatch mechanism is not essential to the present invention and aay suitable mechanism may be employed. Similarly, the drive dement may
be operated in any known manner, for instance using springs, gas pressure, manual
*
operation, etc. Nevertheless, Figure 3 illustrates an injection device similar to that of Figure 1 incorporating a drive coupling like that of Figure 2
The syringe 30 is contained within the housing 60 of the injection device. The housing 60 hasa first end 62 in which an opening 64 is formed
In use, a drive element 66 is released using a button 68 and a drive spring moves 'the drive element.66 towards the end 62.
As with the device of Figure 1, a latch 72 in the form of resihcntly deflectable aims, is provided between the drive coupling 40 and the drive element 66. By means of the latch arrangement 72 and the drive coupling 40, the syringe 30 is driven towards the end 62 against the bias of the return spring 74 so that the needle 36 extends out of the device,
^.particular, a rubber seal 3i is provided over the needle 36- so as to maintain sterility. The rubber seal 37 abuts the sucround of opening 64, the needle pierces the rubber seal 37 and then the rubber seal concertinas as the syringe moves forward. It-will be appreciated that the rubber seal provides some resistance to movement of the syriage . and that the coupling 40 needs to overcome the resistance.

As explained above, the drive coupling 40 Ufa* enables the dispensing piston 3$ to be moved all tie way to the end surface 34 so as to expel the entire "contents of the syringe 30. By means of the drive coupling, in this embodiment using the fluid chamber 52 and bleed orifice 56, the drive coupling reduces in length under the force of .the drive element 66 and drive spring 70 until the collar 76 deflects the arms of the latch mechanism 72 allowing the drive coupling to move within the drive element 66 and the return spring 74 tc retxact the syringe 30 and needle 36.
Thus, tfie drive coupling acts as a controlled collapsing element which remains rigi It will be appreciated that fluid escaping from the bleed orifice will have to be captured. Although not illustrated, this may be achieved by any suitable means, for instance wicking it on to a suitable absorbent material (held within the device) or trapping it between seals in the device.
Although the preferred embodiment as described above allows the drive ccupliLD to reduce in length only when the dispensing piston approaches Hie end surface of the syringe, where the drive coupling reduces in length at a rate which is relatively slow wiih-respect to movement of the dispensing piston 38, it is possible for the drive coupling to gradually reduce in length throughout the entire dispensing operation. As a modification of

the embodiment described above, one or- more bleed orifices along Hie leagth of the passageway 43 may achieve this or, alternatively, bleed orifices through one or both of the first piston 44 and second piston 46, Indeed, any other suitable fluid damped collapsing arrangement could be used.
The description given above principally concerns tne use ux «. un** coupling with standard unmodified known syringes or cartridges. However, by providing syringes or cartridges intended specifically for this use, a drive coupling according to the present invention may-be implemented as part of the syringe, itself This is illustrated schematically in Figure 4(a).
■Rather than provide a separate body and passageway for the fluid chamber, as illustrated, a fluid chamber 80 is provided within the bore 82 of the syringe 84 itself. The fluid chamber 80 is formed between a first wall S6 and a second wall 88*. However, although the first wall 86 is formed on a first piston 90, the second wall 88 is formed on the dispensing piston 92, Of course, it would also be possible to provide a second piston in the bore 82 for driving die dispensing piston 92.
3B ainaiiner'ficjuivaleait to that described for the embodiment of Figure 3, a bleed hole 94 is provided through the wall of the syringe 84. Thus, in die same way, the bleed orifice 94 is positioned such that it connects with the fluid chamber 80 jllst before ine dispensing piston 92 contacts the end surface 96 of li* syringe 84. After the dispensing piston 92 contacts the end surface 96 bleeding of fluid from the fluid chamber 80 will allow the first piston 90 to continue moving along the syringt until art appropriate retract mechanism is operated
For the illustrated embodiment, it will be appreciated that the moment at which the bleed orifice 94 opens to the fluid chamber 80. is dependent only on tolerances of the dispensing piston 92 and the position of the bleed orifice 94, Following on from this, it h possible-to make farther use of the bleed orifice 94-'
la particular, by providing a bleed orifice 94 which is elongate k the direction of travel of the dispensing piston 92 or by providing an array of orifices extending in that direction, it means that, as the dispensing piston 92 jnoves towards the end surface 96, the crass-sectional area available fox bleeding increases. Hence, increased bleeding can be

obtained as the dispensing piston 92 reaches the end surface 96, Tins may enhance or decrease the time needed to actuate the retraction mechanism* | Indeed, "by providing a large bleed cross-sectional area at exactly the position where the dispensing piston 92 reaches the end surface 96, it is possible to empty fluid from tbje fluid chamber 80 at a sufficient rate to allow the return spring 98 to retract the syringe 84 and needle 100. Hence, the fluid chamber 80 and bleed orifice 94 effectively forms the return mechanism with the return spring 98.
Figure,4(b) illustrates a possible triangular cross-section for the bleed orifice 94, Figure 5(a) illustrates schematically a similar device having a latch mechanism.-
i
illustrated more clearly in Figure 5(b), the outer wall of the syrijnge 84 includes latches 102
which are deflected'inwardly by the inner surface 104 of the housing 106 of the injection
device. As a result, the first piston SO, far instance by means of a flange 108 engages the
inwardly deflected latch 102, Thus, when the fixst piston. 90 is moved to operate the
syringe 84, it is not able to move relative to the syringe 84 by sliding within the bore 82.
i Instead, it pushes upon the latghes 102 and directly moves the sjyringe 84 so as to move
the needle 100 .through the opeuing 110 in the injection device.:
Openings 112. are provided in the housing 106 al radial positions corresponding b the positions of the latches 102, Thus, when the first piston 90 icaoves the syringe 84 forward to the point where the latches 102 reach'fee openings 112, the latches 102 move outwardly into the openings 112, thereby releasing the first piston 90. In this Embodiment, the latches 102 also prevent further forward movement of the springe 84 itself. Subsequent movement of the first piston 90 will cause compression of the Quid in the fluid chamber 80 and movement of the dispensing piston 92 in the manner described above.
. By virtue of the sloped profile of the latches 102, when the syringe 84 is retracted, the latches are once again deflected inwardly of the housing 106 out of the openings 112, thereby flowing movement of the syringe 84.
Figure 6 illustrates an embodiment similar to that of Figitre 4(a) but incorporating an alternative to the latch of Figure 5(b).

As illustrated two or more latch levers 200 extend fbrwardly from a rear portion of
i drive coupling 202. They engage with the drive coupling by means of a detent
mangement; As illustrated, the drive coupling includes one or more protrusions 204.
la use, when the drive element 206 starts to travel along the device, the detent
arrangement, for instance the protrusions 204, engage the ends of the levers 200. The
Levers k torn push on the housing 210. of the syringe, for example by the ends of the levers
200 abutting the end of the syringe body. Hence, the syringe is assuredly pushed forward
until the needle 212 extends from the opening 214.
When the opposite ends of the levers 200 reach abutments 214 in the housing,
former movement of the drive element 206 overcomes the detent such that the piston is.
theindriven.
This may be achieved by forming the ends of ttos levers 200 as a single resilient ring
which merely deflects around the protrusions 204. However, as illustrated, the levers 200
are actually pro vided with hinges 218; such that the inwardly sloping walls, of the housing
cause the levers to disengage from the protrusions 204. The hinges may attach the levers
200 to the syringe body and indeed the levers, hinges and syringe body may be formed
integrally as a single unit
• It will be appreciated that other detent or latch arrangements arc also possible, for
instance with the ends of the levers 200 engaging in recesses in the drive coupling 202.
It is also possible to make use of a resilient o-ring to provide, aa inward bias to the
levers 200.
This general construction ensures that the syringe is fully extended from the
injection device before any fluid is expelled from the syringe. It will be appreciated that
equivakntmechariszns may be used in conjunction with the other embodiments, fox
instance providing latches in the main body of the drive coupling- Indeed, this construction
• > — fc
couldalso be used in other arrangements without the'arrangement of the drive coupling
which reduces in length,
The present invention need not be implemented only with a collapsible fluid
chamber. Any other suitable collapsible arrangement may also be U3ed.

Figure 7 illustrates schematically an alternative arrangement A dnve plate 300 is rotatable about an axis 302 and includes a fiictional surface mating with the friciionaj surface of a driven plate 304, As illustrated, the driven plate 304 is to be connected to a dispensing piston of a syringe, whereas the drive plate 3 00 is moved by a drive element of an injection device.
As illustrated, the drive clement connects to the drive plate 300 at a position offset from the rotational axis 302 so as to form a crank arrangement.
In use, the drive element applies a tangential force to the drive plate 300. hut because of the fractional resistance, between the Motional surfaces of the drive plate 3 00 and the driven plate 304, the drive plate 300 does not rotate about its axis 302, Instead, the entire arrangement is moved in the direction of the force so that the driven plate 304 moves the dispensing piston of the syringe. Once the dispensing piston reaches the end of its travel and the driven plate 304 can move no further, the fiictional resistance between the plate 304 is overcome and the drive plate 300 starts to rotate about its axis 302. Because of the offset connection to the drive plate 300, this allows the drive element of the ejection device to move further and the retraction mechanism to be operated. The fiictional resistance between the two plates will maintain the force on the dispensing piston of the syringe.
Figure 8 illustrates schematically an embodiment in which the drive coupling includes one component having a rack gear 40(5 and another component xotatably supporting a pinion gear 402, The pinion gear is provided with some means to resist rotation, for instance by means affection contact
When the drive coupling is used to move the dispensing piston of a syringe, the pinion gear 402 will resist rotation and, hence, the drive coupling will maintain its length. However, once the dispensing piston reaches the end of its travel in the syringe;, the drive coupHng^will come under a compressive load and the pinion geax 402 will be rotated by the rack gear 400. In this way, the length of the drive coupling will gradually be reduced whilst the frictional resistance of the pinion gear 402 will maintain the force on the dispensing piston of the syringe. Hence, the drive element will continue to move until to appropriate retract mechanism is operated. * ■

Figure 9 illustrates a development of the embodiment of Figure 8 in which the Srictional resistance to the praion gear 402 is replaced by the injsrtial resistance of a fly wheel 404 or the like.
It should be appreciated that the fictional sad iuertial asraigeaxients of Figures 7 to 9 could also be replaced with viscous dampers.
Figures 10 to 15 illustrate schematically componects of a further embodiment of . the present invention. For simplicity of understanding the functioning of the device, the Figures illustrate only those components of importance to the difference between this embodiment and those described above. For instance, the housing, retraction spring arid release mechanism are not illustrated*
The drive coupling in this embodiment comprises three; components, namely a connection member 500a, a pinion gear 500b and a rack 500c. The drive element can be considered to be the cad portion 502 of the rack 500c. A drive ispring 504 is connected to the end portion or drive element 502 so as to bias the drive element 502? drive coupling 500a, b and c and the syringe 4 towards one'end of the housing as described previously above.
The pinion 500b is rotatably mounted on the end of the member 500a. Teeth,of the pinion 500a engage with the teeth of the rack 500c. Within the housing, means are provided to prevent the pinion 500b fixna rotating. Thus, ra the illustrated embodiment, a pair of longitudinally extending rails 506a and 506b extend either side of an axially extending protrusion 508 on the pinion 500b. Of course, it will be appreciated that only one such rail could be used or indeed, it could be replaced with! a channel section.
hi use, the drive spring 504 acts to move the rack 500c k a direction to eject the needle 8 of the syringe 4. The teeth of the rack 500c act on theipinion 50Ob. However, since the pinion 500b is restrained fiom rotating, the shaft 500a is moved longitudinally so as to- mtfve the syringe 4 and extender eject the needle 8. This lis illustrated in Figure 11.
The mcacs for preventing rotation of the pinion 500b, in the illustrated embodiment, the rails 506a and 506b only extend for a predetermined length,, in particulax: the components are airangetf such that just before the dispensing piston 18 reaches the end surface of the syringe 4 the axial protrusion 508 moves beyond the end of

thcrails 506a and 506b as illustrated in Figure 12. At this point, further movement of the rack 500c will rotate the pinion gear 500b rather than move the pmember 500a. According to this embodiment of the present invention, some fonn of resistance, preferably in the'fona of damping is introduced to.rotation of the pinion 500b with resjpect to the member 500a. In this way, the member 500a will continue to move the dispensing piston 18 towards the end surface of the syringe 4 whilst the rack 500c continues to mbve. This is illustrated in Figure 13, The drive coupling 500a, b, c thus gradually reduce^ in length whilst the dispensing pisjon 18 is maintained at the end surface of the syringe 4.
A retract mechanism could be provided which is dependent on the position of tht rack 5Q0c; if the components are arranged such that the retract mechanism is only triggered once the rack 500c has reached a position in which it is ensured the dispensing piston 18 has'reached the end surface of the syringe 4, then retraction of the syringe 4 will only occur after the entire contents of the syringe has been expelled. *
According to the illustrated embodiment, however, the rack 500c and pinion 500b themselves provide the retract mechanism. In particular, as illustrated in Figure 14, the rack 500c continues to move, until its last tootfi disengages with the pinion 500b. At .this point, the pinion 500b, member 500a and syringe 4 are released such that a retract spring can retract the syringe 4 and needle 8 inwardly of the device.
hi the illustrated embodiment; the components, in particular the pinion 500b, are arranged such that, during travel of the rack 500c, the pinion 500b is turned through 180 degrees. In this way, the axial protrusion 503 may once again pass through the rails 506a and 506b, However, as illustrated in Figure 15, since the dispensing piston 18 has moved within the syringe 4, it may not be necessary for die pinion 5 00b to move back that far in order to retract the needle 8.
Figare 16 to 21 illustrate yet another embodiment of the present invention. \ h this embodimeol, as with others described above, a drive spring 600 acts on a drive element 602 so as to move a drive coupling. The drive coaling in this embodiment includes a non rotatable component 604a engaging by means of a thread with a rotatable component 604b. Ih the illustrated embodiment, the rotatable component 6C4b is generally hollow in cross section and includes a female thread for receiving a male thread

of a threaded portion 606 on the end of the non rotatable component 604a. A bearing 608 is provided between the cad of the rotatable portion 604b end the dispensing piston 18 of the syringe 4. In this way, the rotatable portion 604b is able to rotate relative to the non rotatable portion 604a such that, by means of the male and female threads, tie con " rotatable portion 604a and the rotatable portion 604b move longitadinaliy relative to one . another.
Along a predetermined extent of the housing of the. injection device, means are provided to prevent the rotatable portion 604b from rotating. As illustrated, the rotatable portion 604b includes at least one laterally extending arm SI0 which engages with a longitudinally extending rib 612' having a pie&texmined length.
In use, when the, drive spring 600 expands, the drive element 602 and drive costing 604a, 604b move longitudinally so as to project the needle 8 of the syringe 4 out of the housing. This is illustrated in Figure 17.
By virtue of engagement of the aims 610 with the ribs 612, the rotatable portion 604b is not able to rotate relative to the non rotatable portion 604a such that the drive coupling 604a, 604b imJnta-infi a constant length.
Further expansion of the drive spring 600 causes the drive coupling 604a, 604b to > move the dispensing piston 18 within the boxe of the syringe 4 so as to ekpel the contents of the syringe 4 through the needle 8. However, as illustrated in Figure 18, the extent of the rib 612 is such that the lateral aim 610 moves to a position beyond the end of the rib ■ 612 just before the dispensing piston 18 reaches the end surface of the needle 4, At this time, the rotatable portion 604b is able to rotate relative to the non rotatable portion 604a, Hence, as illustrated in Figure 19, the threaded portion 606 moves inwardly of the rotatable portion 604a. By providing some resistance to movement, preferably in the- fonn of damping, the rotatable portion 604a ia.stLIl moved Ibngitudinally so as to move the dispenskig piston 18 to the end lace of the syringe 4. Hence, the drive coupling 604a, 604b gradually reduces in length whilst the dispensing piston 18 is maintained at the end surface.

In a preferred embodiment, the ami 610 is intended to spin against the resistance of air. It may take the form of a simple flap or a maybe part of a turbine or propeller cross section. JJX the illustrated embodiment,-at least apair of flaps are provided.
The release mechanism may be dependent on the position of the drive element 602 and/or non rotatable component 604a. la particular, the.syringe 4 and needle 8. may-be retracted when the drive element 602 and non rotatable portion 604a reach a predetermined position in which it is certain that the dispensing piston 18 will have reached the end surfacp of the needle 4.
fa the illustrated embodiment, the drive coupling 604a, 604b itself ferms part of the retract mechanism.
As illustrated, the rotatable portion 604b-defines an internal hollow space 614 which" is not threaded and.which is larger that the outer cross section of the threaded
portion 606.
■ As illustrated in Figure 20, the overall length of the drive coupling 604b will reduce in length pnKfl the pon rotatable components 604a has moved to a position in which its male thread disconnects fern the female thread of the rotatable portion 604b. At this time, the rotatable portion.604b and the syringe 4 will be released such that the. syringe 4 and needle; ■8 can be retracted aa illustrated in Figure 21. It is merely necessary for-the internal hollow section 614 to be of sufficient length to allow foil retraction of the needle 3.


The present invention relates to an htf ecticn device, in particular an injection device which, having dispensed the contents of a syringe, automatically retracts the needle of the 5 syringe.
Devices exist which are spring loaded to extend automatically the needle of a syringe from the device, dispense the contents of the syringe and then automatically retract the needle, WO 95/35126 describes such a device.
As illustrated in Figure 1 of the accompanying drawings, the device includes a 10 housing 2 inwbich a syringe 4 is contained. The housing 2 includes an opening 6 through • which the nsedle 8 of the syringe 4 may extend A retraction spring 10 "biases the syringe 4 away from the opening 6. The device also includes a drive element 12 which is biassed by a spring 14 to drive a coupling 16 to move the dispensing piston J8 of the syringe 4. In use, a release mechanism 20 releases the drive element 12 such that the syringe 4 is first 15 moved forwards and the .needle 8 projects through the opening 6, Subsequently, the dispensing piston 18 is moved so as to expel the contents of the syringe 4. The device is designed to include a dclatch mechanism, in particular, at the point at which the dispensing piston 18 reaches the end of the bore in fee syringe 4, arms 22 at the end of the coupling 16 are deflected by a collar 24 within the housing 2 so as to disengage from the drive 20 element 12, The arms 22 and coupling 16 may then move within a central passage of the drive element 12, ■ A$ a result, by virtue of Hie bias of spring 10, the coupling 16 moves inside the drive element 12, the syringe 4 is driven away from the opening 6 and the needle 8 is retracted within the opening 5.
Other similar delatch or retract arrangements have also been proposed, For 25 instance, EP-A-0 516 473 discloses one embodiment in which, at'the point at which the disp&sifig piston reaches the end of die bore in the syringe, a portion of the coupling instantaneously collapses in length as the retraction spring retracts the needle of the spring.
M practice, all of these proposals suffer a problem that, due to a stack up of tolerances of the various manufactured components of the assembled device (the 30 dimensions of all manufacture components vary around a mean)* it cannot be assured thai

the delaich mechanism *wiU enable retraction of the syringe and needle at precisely the moment "at which the dispensing'piston reaches the end of the bore, M practice, either the mechanism delatches beiore me dispensing piston reaches, the fend of the bore, such that the syringe is not emptied, or the piston reaches the end of the bore before the mechanism has moved sufficiently fax to delated
Although this problem has been recognised before, for instance in US 6,159,151, the proposed solution has been to provide a usefr actuated retraction mechanism rather than an automatic cue. This is considered to be undesirable.
It is an obiect of the present invention to provide an Injection device which is relatively simple and of low cost (so as to be useful as a single juse device) and which overcomes or at least reduces the problems identified above.
According to the present invention there is provided an, injection device including:
a housing for containing a syrmge haying a bore extending from an end surface, a needle communicating with the bore through the end'surface and a dispensing piston movable in said bore towards said end sirrfacc so as to expel the contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend;
a resilient member for biassmg the syringe and needle inwardly of the housing;
a drive element movable towards said one end so as to move the needle of the
■i
syringe out of the opening, preferably against, the bias of the rejnlient member, and to move the dispensing piston of the syringe towards the end surface;
a mechanism, such as a delatch or retract mechanism, operable to release the syringe such that ifce needle moves inwardly of the bousing;
a drive coupling for extending from said drive element ito the dispensing piston of the syringe so as to transfer movement of said drive element to the dispensing piston; wherein.
die drive coupling is compressible in length, preferably whilst overcoming the bias of the resilientmcmber, such that,- aftar the drive element has moved the dispensing piston

to tfcie sad surface, the drive coupling gradually reduces in lsagth wkiisr the dispensing piston is maintained at the and surface y^til said mechanism releases the syringe,
According to the present invention there is also provided a drive? coupling far use La m injection deyice, the drive coupling having:
a. length for extending from the drive element to the dispensing piston of the syringe so as to transfer movement of the driva element to the dispensing piston; wherein
the drive coupling is compressible in length, preferably whilst overcoming the bias of the resilient member, such that, after the drive etement has moved the dispensing piston to the end surface, the drive coupling gradually reduce* in. length whilst the dispensing* piston is maintained at the end surface until the mechanism releases the syringe.
Thus, since the drive coupling is able to gradually reduce in length whilst maintaining the needle in its extended position, it is possible to design the injection device to operate the mechanism at some point after the dispensing piston has reached the end surface, and fully expelled the contoats of the syringe. Since the mechanism is now triggered'at some uncritical point of time after the contents of the syringe have been expelled, tolerances of the various components are no longer a problem. Preferably, the drive coupling is capable of reducing in length whilst providing a resistive force to overcome the resilient member.
It will be appreciated that the length of the drive coupling here is the effective length, ie the length measured from the drive element to the dispensing piston, such that, according to the present invention, the length gradually decreases and the drive dement moves relatively towards the dispensingpiston. To produce this reduction in langth, it is sufficient to provide components which are relatively movable in any way which allows the drive element to move towards the dispensing piston. Indeed, the drive coupling can be provided by a component which is movable in any way relative to the drive element which allows drive to and relative movemeht to the dispensing piston.
Preferably, the mechanism is operable when the drive element reaches a. predetermined position in said housing and the drive coupling gradually reduces in length such that, after the dispensing pistpn reaches the end surface, the drive element continues to move in saidhousing to said predetermined position.

The drive element may continue to move over a period of time as the drive coupling continues to reduce in length such that, even though the dispensing piston has' reached the-end of its travel and abuts the end suifece, the drive element can assuredly.. move to the necessary position to trigger the return mechanism. It is merely sufficient to ■ ensure that the drive element does not reach the position for triggeimg the mechanism before the dispensing piston reaches the end surface, of the syringe.
It will be appreciated that, contraiy to previous mechanisms, in particular the collapsing structures of EP-A-0 516 473, the drive coupling of the present invention does not collapse instantaneously but reduces in length gradually. Indeed, the length of the drive coupling continues to reduce in length gradually even after the dispensing piston abuts the end. surface. Furthermore, whilst collapsing, the drive coupling still transfers sufficient force to rnaiVuvn'ri the needle in its extended position and, preferably, overcome the bias of the retraction sprang
In contrast, at some point up to and including that at which the dispensing piston abuts the end surface, previous collapsing couplings collapse instantaneously under the influence of the retraction spring and do not resist its bias. In particular, once the collapsing coupling of EP-A-0 516 473 starts to reduce in length, it offers virtually no resistance to the retract spring and, hence, is almost instantaneously collapsed.
' Furthermore, in previous arrangements, once the dispensing piston abuts the end surface, the drive element and drive, coupling can move no further and, hence, collapsing of the drive coupling cannot be initialed, However, with the present invention, even after the dispensbg piston abuts the end surface, the drive element can continue to move -whilst the -dispensing piston is maintained at the end surface.
The present invention could be considered as a damped collapse of the drive coupling such that the force and motion of the drive element maintain the syringe and needls ha position, even after the dispensingpiston abuts the end surface, until the drive element reaches the predetermined position.
Depending on the exact nature of the arrangement, the drive coupling may only start to collapse when the dispensing piston reaches the end surface or it may start to collapse at some predetermined point just before the piston reaches the end surface.

Before it starts to collapse* it is preferably rigid. A reloadable latch may be provided to prevent any collapse of the drive coupling until the drive element and dispensing piston reach respective predetermined positions.
Provided that there is sufficient length and thai the drive element causes the dispensing piston to expel the contents of the syringe sufficiently quickly, it is possible for the drive coupling to reduce in length gradually throughout the entire operation and file entire movement of die drive element However, since the controlled collapsing of the drive coupling is only required in the region of the dispensing piston reaching the end surface, it is preferable that the drive coupling remains of constant length before then. Thus, preferably, the drive coupling does not reduce in length until the dispensing piston has reached'* position at least proximate the end surface.
The drive coupling may include a chamber defined between first and second relatively movable walls, the first wall being movable by said drive element and said second wall being operable to move the dispensing piston, and a bleed orifice for bleeding flowable material, preferably from the chamber-In this way, drive from the drive element and the Sist wall is transmitted through flowable material in the chamber^ the second wall and the dispensing piston. Bv means of the bleed orifice, material may gradually bleed from thechamber such that, in a preferred embodiment, the first and second walls move gradually towards one another and the length of the drive coupling is reduced.
Thc flowable material merely has to provide the property of resisting flow through a restriction and need not be a true fluid but could be a Binghan* plastic for example, hi a preferred embodiment, the material is preferably a fluid such as a liquid or gas.
A bleed orifice could be included in the first wall so as to enable fluid to bleed from the fluid chamber when the drive element moves the first wall and compresses the drive coupling and fluid chamber.
The dimensions of any bleed orifice are chosen such that pressure of the fluad in the fluid chamber is maintained sufficient to force the dispensing piston to the end surface of the syringe.

Preferably, the drive coupling includes a main body fo£ mounting on the syringe so as to have a position fixed relative to fee bore and the needle, the main body having a bounding or peripheral wall defining an elongate passage within which the first and second walls are both moyable, the fluid chamber being defined by the peripheral wall and the first and second walls.
in this way, as the drive element moves towards the first end, both the first and second walls are moved within the elongate passage, the fluid chamber being defined by the space between them.
■ A bleed orifice may be formed, at a predetermined longitudmalpositio" airfn a &e peripheral wall such that it is only exposed to the fluid chamber once the second wall passes the predetermined longitudinal position.
in this way, until the second wall reaches the predetermined longixuamai position, the fluid chamber remains of constant volume and the effective length of the drive coupling does not reduce. However, once the second wall reaches the predetennined longitudinal position, Said bleeds through the bleed orifice so that the length between the first ?r>^ second walls and the effective length of the drive coop ling gradually reduces so as to ensure that the drive element triggers the delatch and retract mechanism.
It should be appreciated that the present invention can be applied to injection devices which house conventional syringes or which house other mass produced cartridges' of a standard design. However, it is also possible to form the drive coupling jp, the syringe itself.
The first and second walls may be movable in the bore of the syringe such thai the fluid chamber is defined by the bore and the first and seconu waus. , In this way, the number of component parts may be reduced. The second wall may form an integral pari of the dispensing piston or may drive th As described above, a bleed orifice could be. formed in the first wall so as to enable fluid to bleed from the fluid chamber. However, preferably, the bleed orifice is formed at a predetermined longitudinal position along the bore and is only opened to the fluid chamber .once the second waU passes the predetermined longitudinal position.

M this way, as* described above, the fluid chamber remains of constant volume until the second wall reaches the predetermined longitudinal position such that the effective length of the drive coupling starts to reduce only in the region where lie dispensing piston reaches the end surface.
The bleed orifice may be circular. Alternatively, it may have a cross-section which is elongate and/or there maybe an array of bleed orifices extending towards the end surface such that as a second wall moves towards die end surface, fluid bleeds fester from the fluid chamber.
The orificesmay be arranged in this way .such that, once the dispensing piston
V
reaches the end surface, the second wall exposes a sufficient area of the bleed orifice(s) to allow fluid to bleed from the fhiid chamber at a rate appropriate to allow the resilient member to retract the syringe and needic.
Indeed, according to the present invention, there may be provided an injection device including:
a housing containing a syringe with a syringe body having a bore extending ftom an end surface, a needle communicating with the bore through the end surface and a dispensing piston movable in said bore towards said end surface so as to expel the : contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend;
a resilient member for biasing the syringe and needle inwardly of the housing;
a drive element movable towards said one end so as to move the needle of the syringe out of the opening, preferably against the bias of the resilient member, and to move the dispensing piston oFthe syringe towards the end surface; wherein
the syringe further includes:
a secondary piston movable in said bore, the dispensing piston and the secondary ' piston defining a fluid filled chamber* therebetween; and
a bleed orifice commumcatiog with said bore; wherein
the bleed orifice is positioned at a distance from the end surface and Die dispensing piston is of such a length that the dispensing piston exposes the bleed orifice to the fluid

filled chamber as the dispensing -piston reaches the end surface and loss of fluid from the fluid chamber allows retraction of the needle by virtue of the b&s of the rerJieut membex. Since the point of retraction is only dependent on the position of the bleed orifice and the length of the dispensing piston, the number of tolerances affecting the point of retraction are reduced such that the syringe can be assuredly retracted al the point at which the contents is fully dispensed
Alternatively, the drive coupling may include a drive Motional surtacs engaging a driven factional surface, the drive fiictionai surface being movable by the drive element and the driven fractional; surface.being operable to move the dispensing piston such that, when the dispensing piston reaches the ead surface, the &st fiictionai surface slips relative to the second Motional surface.
Thus, in this case, the drive coupling only f educes hx length, once the dispensing piston reaches the end surface. The drive element continues to apply a force to &e drive coupling by virtue of the fiictionai resistance such that the frictkmal surfaces slip, the drive coupling reduces in length and the drive element reaches the required position to trigger the return mechanism.
The drive fiictionai surface maybe rotatable about aa axis generally pezpeadipulasf' to the jsurface apd be moved by the drive element at a position cjffset from the suds.
Similarly, the driven fiictionai surface may be rotatable kbout an axis generally parallel to the surface and may be operable to move the dispensing piston from a position ofiset from the axis,
in other words, drive to or from the rotational fractional jswface may be by mc^s of a crank mechanism 3uch that, when the surfaces slip and rotate,, the connection points to the drive element and the dispensing piston move closer together.
The drive coupling may include a rack and a pbion geai therein one of the rack andthapinion gear is movable by the drive element'and the othjar of the rack and the pinion is operable to move the dispensing piston.
In this way, as the drive element exerts a compression force on the drive coupling, the rack will tend to rotate the pirdon gear.

The pinion gear may include a friction brake to pioventj rotation and allow the cinve. element to move the dispensing piston. When the dispensing piston reaches the end surface, the friction brake slips and the teagth of tbe drive coupling is reduced.
Alternatively, the pinion gear can drive a fly wheel suclji that when the dispensing piston reaches the ead surface, the pinion gear is turned against the inertia! resistance of the fly wheeL Thus, once again, the length of the drive coupling is reduced.
As explained above, previous injection devices drive the dispensing piston to first move the syringe as a whole and position the needle outside of iheinjection device housing. This woiks well for fine needles where the back pressure on the fluid for injection is relatively high and the force required to insert the needle is relatively low. However, where there is more difficulty in inserting the needle, there is a possibility that seme fluid will be dispensed from the needle before it is correctly inserted below the skin.
Hence, preferably,, the injection' device further includes an engagement for transferring drive directly from the drive coupling to the syringe body such that movement of the drive element towards said one end causes no relative movement of the dispensing piston in the syringe wherein the engagement is releasable once;the needle of the syringe extends out of the opening such that movement of the drive element towards said "one end causes relative movement of the dispeonsing piston in the syringe body. ■
Thus, iterthennore, according to jhe present invention, thtere is provided an injection device including:
a housing for containing a syringe having a bore extending in a syringe body from an end surface, a needle communicating with the bore through the end surface and a dispensing piston movablein said bore towards said end surface so as to expel the contents of the syringe through the needle, the housing having ah opening at one end through which the needle may extend;
a drive element movable towards said one end so as to move the needle of the syringe out of the opetaing and to move the dispensing piston of the syringe towards the end surface;
a drive coupling for extending, from said drive element to the dispensing piston of the syringe so as to transfer movement of said drive element to the dispensing piston; and

an*engagemant for traasfcrring drive directly from title drive coupling "to the syringe body such that movement of the drive element towards said one end causes no relative
movement of the dispensing piston in the syringe; wherein
the engagement is releasable once the needle of the syringe extends out of the
opening such that movement of the drive element towards said one end causes relative
movement of the dispensing piston in the syringe body
This ensures that the drive element correctly positions rfce syringe with the needle
protruding ftojm the housing before the dispesasing piston is moved to dispense the contents
of the syringe.
-. Preferably, the injection device includes a resilient member for biassing the syringe
and needle inwardly of the housing- The drive element may move the needle of the syringe
out of the opening against the bias of the resilient member.
Preferably, the housing includes a release portion which interacts with fee
engagement to release drive to the syringe-la this way, engagement may be,released by virtue "of the relative position of the
syringe in the housing.
Preferably, the release portion is located in the housing at a predetermined position;
and the engagement includes a trigger which is operated by the release portion to release
drive to the syringe upon reaching the predetermined position-In. tins way, the needle is assuredly extended by ihe right amount Preferably, the engagement includes a resilient latch and the release portion
includes at least a recess ixx a wall of the housing allowing deflection of the resilient latch to
release the drive to the syringe.
, Hence, the watf of the housing may maintain the resilient latch in a. position of
engagement until it reaches a recess or even an opening in the wall.
preferably, the at least a recess engages the resilient latch'so as to prevent further
relative movement of the syringe body in the housing.
Thus, when the resilient latch moves into -the recess or opening it may then engage
with the recess or opening -so as to .fix the relative position between the syringe and the
housing.

As described above,, the drive coupling may include a fluid chamber defined between first and second relatively movable walls, the first wall being part of a piston and the resilient latch operating on the piston.
By engaging with either the dispensing piston or a secondary piston (forming with the dispensing piston a fluid chamber), the relative position between the dispensing piston and the syringe body can be fixed, such that any drive applied to the drive coupling or dispensing piston will result in movement of the syringe raiher than the dispensing piston relative to the syringe.
The drive, coupling may include a rigid element extending from the drive element, the engagement may include at least one protrusion on a surface of the rigid element and a latch fixed relative to the syringe body engaging the protrusion and the release portion may include a stop on the housing for mgaging the latch wherein the rigid element moves the latch-with the protrusion until the latch abuts the stop, whereupon the Latch releases from the protrusion.
The latch may be deflected resiliency past the protrusion, However, alternatively, . the-latch maybe hinged as a cantilever at a point between an end engaging protrusion and an opposite end wherein the stop deflects the opposite end so as to release engagement with the protrusion*
The latch may be hinged at the point at which it is attached to the syringe or alternatively to a part of the drive coupling mounted to the syringe with a fixed relative position to the needle.
The engagement may releasably connect the &ive coupling to the syringe. Alternatively, the engagement may releasably connect a part of the drive coupling movable with the drive element to a part of the drive coupling to be mounted to the syringe in a feed relative position to the needle,
The invention will be more clearly understood from the following description, given by way of example only, with reference to the accompanying drawings, in which:
Figure 1 illustrates aknown construction for an injection device;
Figure 2 illustrates, a drive ooupling according to the present invention;

Figure. 3 illustrates the drive coupling of Figure 2 iacarpjorated into an iaj ecticn device axmflgr to that illustrated in Figure 1;
• Figure 4 illustrates schematically an injection device in Which, the drive coupling is incorporated into the syringe cartridge itself;
Figure 5 illustrates an embodiment providing direct drive to the syringe; Figure 6 illustrates an alternative embodiment providing direct drive to the syringe. Figure 7 illustrates schematically a friction plate embodiment; ' Figure ,8 illustrates schematically a rack and pinion embodiment; Figure 9 illustrates schematically a rack and pinion construction using a flywheel; and
Figures 10 to 15 illustrate an alternative embo Figures 16 to 21 illustrate schematically another embodiment of a drive coupling of the present invention.
As will be apparent from the above, the present invention concerns injection devices and is based on driving the dispensing piston of a. syringe with a drive coupling which can gradually reduce in length so as to ensure that the dispensing piston is moved fully along the length of the syringe and that the needle is held in its exteaded position by an appropriate force until that time.
Figure 2 illustrates an embodiment of a suitable drive coupling. The drive coupling is for use with a syringe 30, such as ja standard syringe or cartridge, which includes a bore, 32 extending from, an end surface 34 within that bore and' a needle 36 which communicates with the bore 32 through the end surface 34. A dispensing piston 38 is movable along the bore 32 towards the end surface 34. In particular, by moving the dispensing piston along the length of !the syringe until it abuts tfte end surfkee 34, the totire contents of the syringe may be expelled through the syringe needle 36.'
As illustrated, the drive coupling 40 includes a main body 42 which mares with the end of the syringe 30.

The mam body 42 includes an elongate through passage along which a first piston 44 and a second piston 46 may move. The first piston 44 ,defiaes a first wall 48 facing a second wall 50 defined by the second piston 46,
The first wall 48 and second wall 50, together with the elongate passage 43, defim. a chamber. 52 filled with fluid a material which is substantially incompressible, mobile under pressure and capable of extrusion. Materials such as powders, greases and soft-solids may be used However, in a preferred embodiment, a fluid is used such that chamber 52 will be described as a fluid chamber. Ihis fluid as preferably liquid and suhstarHflWv incompressible,.
.The first piston 44- and, hence, the first wall 48 may be driven by the drive element of an injection device. This is illustrated more clearly in Figure 3.
As the first piston 44 is moved along the elongate passage 43, since the fluid in the fluid chamber 52 is substantially incompressible, the second wall 50 and, hsace, the second piston 46, is also moved along the elongate passage.
For convenience of design, a spacing element 54 transfers drive from the second piston 46 to the-dispensing piston 38 of the syringe 30,
Thus, the drive coupling 40 transfers movement to the dispensing piston 38. At a predetermined position along the length of the passageway 43, a bleed orifice' 56 is provided. Once the second wall 50 passes the bleed orifice 56, fluid is able to bleed from the flxdd chamber 52 to outside the main body 42. As tins fluid bleeds away, the volume of the fluid chamber 52 will be reduced and the distance between the fir« wall 48 and the second wall 50 wiS also be reduced.
The predetermined position of the blesd orifice 56 is chosen such thai, with the main body 42 mated to the syringe 30 and having a fixed relative position, the second wall 50 will pass die bleed orifice 56 just before the dispensing piston 38 reaches the end surface 34.
It will be appreciated that, theoretically, the second wall 50 could open the bleed orifice 56 just as the dispensing piston 38 reaches-the end surface 34, However, the present invention is based on a recognition that tolerances, particularly the compound effect of tolerances of different components, mean that such design cannot be guaranteed.

Therefore, the second wall 50 exposes the bleed orifice 56 when the dispensing piston 38 is at a position proximate the end surface 34 so as to ensure that the bleed orifice 56 is open by the time the dispensing piston 38 abuts the end surface 34.
It will be appreciated that, even with the bleed orifice 56 open, some driving force will still be transmitted to the second piston 46 such that the dispensing piston 3 8 will be driven the final small distance to the end surface 34 to dispmse the remaining contents of the syringe 30.
With the dispensing piston 38 abutting the end surface 34, the second piston 46 and second wall 50 will move no further. However, as fluid bteeds ftom the fluid chamber 52, the. first wall 48 and first piston 44 will continue to move towards the end surface 34 until a return delatch mechanism is operated to retract the syringe 30 and needle 36 back into the housing of the injection device.
The particular nature of the return delatch mechanism is not essential to the present invention and aay suitable mechanism may be employed. Similarly, the drive dement may
be operated in any known manner, for instance using springs, gas pressure, manual
*
operation, etc. Nevertheless, Figure 3 illustrates an injection device similar to that of Figure 1 incorporating a drive coupling like that of Figure 2
The syringe 30 is contained within the housing 60 of the injection device. The housing 60 hasa first end 62 in which an opening 64 is formed
In use, a drive element 66 is released using a button 68 and a drive spring moves 'the drive element.66 towards the end 62.
As with the device of Figure 1, a latch 72 in the form of resihcntly deflectable aims, is provided between the drive coupling 40 and the drive element 66. By means of the latch arrangement 72 and the drive coupling 40, the syringe 30 is driven towards the end 62 against the bias of the return spring 74 so that the needle 36 extends out of the device,
^.particular, a rubber seal 3i is provided over the needle 36- so as to maintain sterility. The rubber seal 37 abuts the sucround of opening 64, the needle pierces the rubber seal 37 and then the rubber seal concertinas as the syringe moves forward. It-will be appreciated that the rubber seal provides some resistance to movement of the syriage . and that the coupling 40 needs to overcome the resistance.

As explained above, the drive coupling 40 Ufa* enables the dispensing piston 3$ to be moved all tie way to the end surface 34 so as to expel the entire "contents of the syringe 30. By means of the drive coupling, in this embodiment using the fluid chamber 52 and bleed orifice 56, the drive coupling reduces in length under the force of .the drive element 66 and drive spring 70 until the collar 76 deflects the arms of the latch mechanism 72 allowing the drive coupling to move within the drive element 66 and the return spring 74 tc retxact the syringe 30 and needle 36.
Thus, tfie drive coupling acts as a controlled collapsing element which remains rigi It will be appreciated that fluid escaping from the bleed orifice will have to be captured. Although not illustrated, this may be achieved by any suitable means, for instance wicking it on to a suitable absorbent material (held within the device) or trapping it between seals in the device.
Although the preferred embodiment as described above allows the drive ccupliLD to reduce in length only when the dispensing piston approaches Hie end surface of the syringe, where the drive coupling reduces in length at a rate which is relatively slow wiih-respect to movement of the dispensing piston 38, it is possible for the drive coupling to gradually reduce in length throughout the entire dispensing operation. As a modification of

the embodiment described above, one or- more bleed orifices along Hie leagth of the passageway 43 may achieve this or, alternatively, bleed orifices through one or both of the first piston 44 and second piston 46, Indeed, any other suitable fluid damped collapsing arrangement could be used.
The description given above principally concerns tne use ux «. un** coupling with standard unmodified known syringes or cartridges. However, by providing syringes or cartridges intended specifically for this use, a drive coupling according to the present invention may-be implemented as part of the syringe, itself This is illustrated schematically in Figure 4(a).
■Rather than provide a separate body and passageway for the fluid chamber, as illustrated, a fluid chamber 80 is provided within the bore 82 of the syringe 84 itself. The fluid chamber 80 is formed between a first wall S6 and a second wall 88*. However, although the first wall 86 is formed on a first piston 90, the second wall 88 is formed on the dispensing piston 92, Of course, it would also be possible to provide a second piston in the bore 82 for driving die dispensing piston 92.
3B ainaiiner'ficjuivaleait to that described for the embodiment of Figure 3, a bleed hole 94 is provided through the wall of the syringe 84. Thus, in die same way, the bleed orifice 94 is positioned such that it connects with the fluid chamber 80 jllst before ine dispensing piston 92 contacts the end surface 96 of li* syringe 84. After the dispensing piston 92 contacts the end surface 96 bleeding of fluid from the fluid chamber 80 will allow the first piston 90 to continue moving along the syringt until art appropriate retract mechanism is operated
For the illustrated embodiment, it will be appreciated that the moment at which the bleed orifice 94 opens to the fluid chamber 80. is dependent only on tolerances of the dispensing piston 92 and the position of the bleed orifice 94, Following on from this, it h possible-to make farther use of the bleed orifice 94-'
la particular, by providing a bleed orifice 94 which is elongate k the direction of travel of the dispensing piston 92 or by providing an array of orifices extending in that direction, it means that, as the dispensing piston 92 jnoves towards the end surface 96, the crass-sectional area available fox bleeding increases. Hence, increased bleeding can be

obtained as the dispensing piston 92 reaches the end surface 96, Tins may enhance or decrease the time needed to actuate the retraction mechanism* | Indeed, "by providing a large bleed cross-sectional area at exactly the position where the dispensing piston 92 reaches the end surface 96, it is possible to empty fluid from tbje fluid chamber 80 at a sufficient rate to allow the return spring 98 to retract the syringe 84 and needle 100. Hence, the fluid chamber 80 and bleed orifice 94 effectively forms the return mechanism with the return spring 98.
Figure,4(b) illustrates a possible triangular cross-section for the bleed orifice 94, Figure 5(a) illustrates schematically a similar device having a latch mechanism.-
i
illustrated more clearly in Figure 5(b), the outer wall of the syrijnge 84 includes latches 102
which are deflected'inwardly by the inner surface 104 of the housing 106 of the injection
device. As a result, the first piston SO, far instance by means of a flange 108 engages the
inwardly deflected latch 102, Thus, when the fixst piston. 90 is moved to operate the
syringe 84, it is not able to move relative to the syringe 84 by sliding within the bore 82.
i Instead, it pushes upon the latghes 102 and directly moves the sjyringe 84 so as to move
the needle 100 .through the opeuing 110 in the injection device.:
Openings 112. are provided in the housing 106 al radial positions corresponding b the positions of the latches 102, Thus, when the first piston 90 icaoves the syringe 84 forward to the point where the latches 102 reach'fee openings 112, the latches 102 move outwardly into the openings 112, thereby releasing the first piston 90. In this Embodiment, the latches 102 also prevent further forward movement of the springe 84 itself. Subsequent movement of the first piston 90 will cause compression of the Quid in the fluid chamber 80 and movement of the dispensing piston 92 in the manner described above.
. By virtue of the sloped profile of the latches 102, when the syringe 84 is retracted, the latches are once again deflected inwardly of the housing 106 out of the openings 112, thereby flowing movement of the syringe 84.
Figure 6 illustrates an embodiment similar to that of Figitre 4(a) but incorporating an alternative to the latch of Figure 5(b).

As illustrated two or more latch levers 200 extend fbrwardly from a rear portion of
i drive coupling 202. They engage with the drive coupling by means of a detent
mangement; As illustrated, the drive coupling includes one or more protrusions 204.
la use, when the drive element 206 starts to travel along the device, the detent
arrangement, for instance the protrusions 204, engage the ends of the levers 200. The
Levers k torn push on the housing 210. of the syringe, for example by the ends of the levers
200 abutting the end of the syringe body. Hence, the syringe is assuredly pushed forward
until the needle 212 extends from the opening 214.
When the opposite ends of the levers 200 reach abutments 214 in the housing,
former movement of the drive element 206 overcomes the detent such that the piston is.
theindriven.
This may be achieved by forming the ends of ttos levers 200 as a single resilient ring
which merely deflects around the protrusions 204. However, as illustrated, the levers 200
are actually pro vided with hinges 218; such that the inwardly sloping walls, of the housing
cause the levers to disengage from the protrusions 204. The hinges may attach the levers
200 to the syringe body and indeed the levers, hinges and syringe body may be formed
integrally as a single unit
• It will be appreciated that other detent or latch arrangements arc also possible, for
instance with the ends of the levers 200 engaging in recesses in the drive coupling 202.
It is also possible to make use of a resilient o-ring to provide, aa inward bias to the
levers 200.
This general construction ensures that the syringe is fully extended from the
injection device before any fluid is expelled from the syringe. It will be appreciated that
equivakntmechariszns may be used in conjunction with the other embodiments, fox
instance providing latches in the main body of the drive coupling- Indeed, this construction
• > — fc
couldalso be used in other arrangements without the'arrangement of the drive coupling
which reduces in length,
The present invention need not be implemented only with a collapsible fluid
chamber. Any other suitable collapsible arrangement may also be U3ed.

Figure 7 illustrates schematically an alternative arrangement A dnve plate 300 is rotatable about an axis 302 and includes a fiictional surface mating with the friciionaj surface of a driven plate 304, As illustrated, the driven plate 304 is to be connected to a dispensing piston of a syringe, whereas the drive plate 3 00 is moved by a drive element of an injection device.
As illustrated, the drive clement connects to the drive plate 300 at a position offset from the rotational axis 302 so as to form a crank arrangement.
In use, the drive element applies a tangential force to the drive plate 300. hut because of the fractional resistance, between the Motional surfaces of the drive plate 3 00 and the driven plate 304, the drive plate 300 does not rotate about its axis 302, Instead, the entire arrangement is moved in the direction of the force so that the driven plate 304 moves the dispensing piston of the syringe. Once the dispensing piston reaches the end of its travel and the driven plate 304 can move no further, the fiictional resistance between the plate 304 is overcome and the drive plate 300 starts to rotate about its axis 302. Because of the offset connection to the drive plate 300, this allows the drive element of the ejection device to move further and the retraction mechanism to be operated. The fiictional resistance between the two plates will maintain the force on the dispensing piston of the syringe.
Figure 8 illustrates schematically an embodiment in which the drive coupling includes one component having a rack gear 40(5 and another component xotatably supporting a pinion gear 402, The pinion gear is provided with some means to resist rotation, for instance by means affection contact
When the drive coupling is used to move the dispensing piston of a syringe, the pinion gear 402 will resist rotation and, hence, the drive coupling will maintain its length. However, once the dispensing piston reaches the end of its travel in the syringe;, the drive coupHng^will come under a compressive load and the pinion geax 402 will be rotated by the rack gear 400. In this way, the length of the drive coupling will gradually be reduced whilst the frictional resistance of the pinion gear 402 will maintain the force on the dispensing piston of the syringe. Hence, the drive element will continue to move until to appropriate retract mechanism is operated. * ■

Figure 9 illustrates a development of the embodiment of Figure 8 in which the Srictional resistance to the praion gear 402 is replaced by the injsrtial resistance of a fly wheel 404 or the like.
It should be appreciated that the fictional sad iuertial asraigeaxients of Figures 7 to 9 could also be replaced with viscous dampers.
Figures 10 to 15 illustrate schematically componects of a further embodiment of . the present invention. For simplicity of understanding the functioning of the device, the Figures illustrate only those components of importance to the difference between this embodiment and those described above. For instance, the housing, retraction spring arid release mechanism are not illustrated*
The drive coupling in this embodiment comprises three; components, namely a connection member 500a, a pinion gear 500b and a rack 500c. The drive element can be considered to be the cad portion 502 of the rack 500c. A drive ispring 504 is connected to the end portion or drive element 502 so as to bias the drive element 502? drive coupling 500a, b and c and the syringe 4 towards one'end of the housing as described previously above.
The pinion 500b is rotatably mounted on the end of the member 500a. Teeth,of the pinion 500a engage with the teeth of the rack 500c. Within the housing, means are provided to prevent the pinion 500b fixna rotating. Thus, ra the illustrated embodiment, a pair of longitudinally extending rails 506a and 506b extend either side of an axially extending protrusion 508 on the pinion 500b. Of course, it will be appreciated that only one such rail could be used or indeed, it could be replaced with! a channel section.
hi use, the drive spring 504 acts to move the rack 500c k a direction to eject the needle 8 of the syringe 4. The teeth of the rack 500c act on theipinion 50Ob. However, since the pinion 500b is restrained fiom rotating, the shaft 500a is moved longitudinally so as to- mtfve the syringe 4 and extender eject the needle 8. This lis illustrated in Figure 11.
The mcacs for preventing rotation of the pinion 500b, in the illustrated embodiment, the rails 506a and 506b only extend for a predetermined length,, in particulax: the components are airangetf such that just before the dispensing piston 18 reaches the end surface of the syringe 4 the axial protrusion 508 moves beyond the end of

thcrails 506a and 506b as illustrated in Figure 12. At this point, further movement of the rack 500c will rotate the pinion gear 500b rather than move the pmember 500a. According to this embodiment of the present invention, some fonn of resistance, preferably in the'fona of damping is introduced to.rotation of the pinion 500b with resjpect to the member 500a. In this way, the member 500a will continue to move the dispensing piston 18 towards the end surface of the syringe 4 whilst the rack 500c continues to mbve. This is illustrated in Figure 13, The drive coupling 500a, b, c thus gradually reduce^ in length whilst the dispensing pisjon 18 is maintained at the end surface of the syringe 4.
A retract mechanism could be provided which is dependent on the position of tht rack 5Q0c; if the components are arranged such that the retract mechanism is only triggered once the rack 500c has reached a position in which it is ensured the dispensing piston 18 has'reached the end surface of the syringe 4, then retraction of the syringe 4 will only occur after the entire contents of the syringe has been expelled. *
According to the illustrated embodiment, however, the rack 500c and pinion 500b themselves provide the retract mechanism. In particular, as illustrated in Figure 14, the rack 500c continues to move, until its last tootfi disengages with the pinion 500b. At .this point, the pinion 500b, member 500a and syringe 4 are released such that a retract spring can retract the syringe 4 and needle 8 inwardly of the device.
hi the illustrated embodiment; the components, in particular the pinion 500b, are arranged such that, during travel of the rack 500c, the pinion 500b is turned through 180 degrees. In this way, the axial protrusion 503 may once again pass through the rails 506a and 506b, However, as illustrated in Figure 15, since the dispensing piston 18 has moved within the syringe 4, it may not be necessary for die pinion 5 00b to move back that far in order to retract the needle 8.
Figare 16 to 21 illustrate yet another embodiment of the present invention. \ h this embodimeol, as with others described above, a drive spring 600 acts on a drive element 602 so as to move a drive coupling. The drive coaling in this embodiment includes a non rotatable component 604a engaging by means of a thread with a rotatable component 604b. Ih the illustrated embodiment, the rotatable component 6C4b is generally hollow in cross section and includes a female thread for receiving a male thread

of a threaded portion 606 on the end of the non rotatable component 604a. A bearing 608 is provided between the cad of the rotatable portion 604b end the dispensing piston 18 of the syringe 4. In this way, the rotatable portion 604b is able to rotate relative to the non rotatable portion 604a such that, by means of the male and female threads, tie con " rotatable portion 604a and the rotatable portion 604b move longitadinaliy relative to one . another.
Along a predetermined extent of the housing of the. injection device, means are provided to prevent the rotatable portion 604b from rotating. As illustrated, the rotatable portion 604b includes at least one laterally extending arm SI0 which engages with a longitudinally extending rib 612' having a pie&texmined length.
In use, when the, drive spring 600 expands, the drive element 602 and drive costing 604a, 604b move longitudinally so as to project the needle 8 of the syringe 4 out of the housing. This is illustrated in Figure 17.
By virtue of engagement of the aims 610 with the ribs 612, the rotatable portion 604b is not able to rotate relative to the non rotatable portion 604a such that the drive coupling 604a, 604b imJnta-infi a constant length.
Further expansion of the drive spring 600 causes the drive coupling 604a, 604b to > move the dispensing piston 18 within the boxe of the syringe 4 so as to ekpel the contents of the syringe 4 through the needle 8. However, as illustrated in Figure 18, the extent of the rib 612 is such that the lateral aim 610 moves to a position beyond the end of the rib ■ 612 just before the dispensing piston 18 reaches the end surface of the needle 4, At this time, the rotatable portion 604b is able to rotate relative to the non rotatable portion 604a, Hence, as illustrated in Figure 19, the threaded portion 606 moves inwardly of the rotatable portion 604a. By providing some resistance to movement, preferably in the- fonn of damping, the rotatable portion 604a ia.stLIl moved Ibngitudinally so as to move the dispenskig piston 18 to the end lace of the syringe 4. Hence, the drive coupling 604a, 604b gradually reduces in length whilst the dispensing piston 18 is maintained at the end surface.

In a preferred embodiment, the ami 610 is intended to spin against the resistance of air. It may take the form of a simple flap or a maybe part of a turbine or propeller cross section. JJX the illustrated embodiment,-at least apair of flaps are provided.
The release mechanism may be dependent on the position of the drive element 602 and/or non rotatable component 604a. la particular, the.syringe 4 and needle 8. may-be retracted when the drive element 602 and non rotatable portion 604a reach a predetermined position in which it is certain that the dispensing piston 18 will have reached the end surfacp of the needle 4.
fa the illustrated embodiment, the drive coupling 604a, 604b itself ferms part of the retract mechanism.
As illustrated, the rotatable portion 604b-defines an internal hollow space 614 which" is not threaded and.which is larger that the outer cross section of the threaded
portion 606.
■ As illustrated in Figure 20, the overall length of the drive coupling 604b will reduce in length pnKfl the pon rotatable components 604a has moved to a position in which its male thread disconnects fern the female thread of the rotatable portion 604b. At this time, the rotatable portion.604b and the syringe 4 will be released such that the. syringe 4 and needle; ■8 can be retracted aa illustrated in Figure 21. It is merely necessary for-the internal hollow section 614 to be of sufficient length to allow foil retraction of the needle 3.



L An injection device including:
a housing for conlaining a syringe having a bore extending from an end surface, a needle communicating with the bore through, the end surface and a dispensing piston movable in said bote towards said end surface so as to expel the contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend;
a resilient member for biassing the syringe and needle inwardly of the housing**
a drive element movable towards said one end so as to move the needle of the syringe out of the opening and to move the dispensing piston of the syringe towards the end surface;
a mechanism operable to release the syringe such .that the needle moves inwardly of the housing;
a drive coupling for extending from said drive element to the dispensing piston of the syringe so as to transfer movement of said drive element to the dispensing piston; wherein
the drive coupling is compressible in length such that, after the drive element has moved the dispensing piston to the end surface, the drive coupling gradually reduces in length whilst the dispensing piston is maintained at the end surface until said mechanism releases the syringe.
2. An injection device according to claim I wherein the mechanism is
operable when the drive element reaches a predetermined position in said housing and the
r
drive coupling gradually reduces in length such that, after the dispensing piston reaches the end surface, the drive element continues to move m said housing to said predetermined position,
3. An injection device according to claim 1 or 2 wherein the drive coupling
includes:

a chamber defined between first and second relatively movable walla, the first wail being movable by said drive dement and said second wall being operable to move the dispensing piston; and .
a bleed orifice for bleeding flowable material fim the chamber.
4. An iyection device according to claim 3 wherein the drive coupling
includes:
a main body &r mounting on the syringe relative to the bore and the needle, the
main body haying a bounding wall defining an elongate passage within which the first and
second walls are both movable, the chamber bdng defined by the ' . . v
bounding wall and the first and second walls.
5. An injection device according to claim 4 wherein the bleed orifice, is formed at a predetermined longitudinal position along the bounding wail and is only exposed to the chamber once the second wall passes the predetermined longitudinal position.
6. An injection device according to claim 3 including a syringe contained in the housing, the syringe having a bore extending from an end surface, a needle communicating with the bore through the end surface and a dispensing piston movable in said bore towards said and surface so, as to expel the contents of the syringe through the • needle wherein:
the drive coupling is formed in. the syringe.
7. An injection device according to claim 6 wherein the first and second wall* are movable in said bore and the chamber is defined by the bore and the first,and second walls.
8. An injection device according to claim 7 wherein the bleed orifice is formed at a.predetenniaed longitudinal position along the bore and is only opened to the chamber once the second wedl passes the predetermined longitudinal position.
9. An injection device according to claim 5 or 8 wherein the bleed orifice has a cross-section which is elongate such that, as the second wall moves towards the end suzfiace, flowabie material bleeds faster from the chamber.

10. An injection device according to claim 5, 8 or 9 further including an array of bleed orifices extending towards said end surface such that, as the second wall moves towards the end surface, fiowable 'material bleeds faster from the chamber.
■ 1L An injection device according to claim 1 or 2 wterem the drive coupHng includes;
a drive fractional surface engaging a driven frictional surface, the drive fnctional surface being movable by said drive element and said driven factional surface being operable to move the dispensing piston such .that when the dispensing piston reaches the end surface the drive fiictional surface slips relative to the driven fiictional surface.
12.,. An injection device according to claim 11 wherein the drive frictiona! surface is rotatable about an axis gsaearally pexpeodicular to the surface and is moved by said drive element at a position offset from the axis.
13. An injection device according to claim 11 or 12 whereiuthe driven Motional surface is rotatable about an axis generally perpendicular to the surface and is operable to move the dispensing piston from a position ofiset from the axis.
14* An injection device according to claim 1 or 2 wharein the drive coupling includes:
a rack; and
a pinion gear, wherdn
one of the rack and the pinion gear is movable by said drive element and the other :>f the rack and the pinion gear is operable to move the dispensing piston.
15.' An injection device according to claim 14 vmerein. the pinion gear includes i friction-brake such thai, when the dispensing piston reaches the end surface, the friction ?rake 3lips>
16. An injection device according to claim 14 wherein the pinion gear raves a
ly wheelsuch thai, when thfi dispensing piston reaches the end surface, the pinion gear is
umed against the inertial resistance of the fly wheel
17. ' An injection device according to any preceding claim wherein the drive
-oupbng does not reduce in length- until the dispensing piston has reached a position at least
iroximate the end surface.

18. An injection device according to any one of claims 3 to 10 wherein, the main body is fabricated out of plastic, for instance by injection moulding, and tie bleed orifice is formed by drilling, for instance mechanically, fluid or laser, or in the injection ■ moulding process itself.
19. An injection device according to any one of claims 3 to 10 fiirther including an absorbent wicking material to retain material which has escaped frpm the bleed orifice.
20. A drive coupling for use in an irrj action device according to any preceding claim, the drive coupling having:
4 length for extending from the drive element to the dispensing; pigton of.the "syringe so as to transfer movement of the drive element to the dispensing piston; wherein
the drive coupling is compressible in length whilst overcoming the bias of the resilient member such that,, after the drive clement has moved the dispensing piston to the end surface, the drive coaling gradually reduces in length whilst the dispensing piston is maintained at the end surface until the mechanism releases the syringe.
21. An injection device according to any one of claims 1 to 19 further
including:
an engagement for transferring drive directly from the drive coupling to the synn° body such that movement, of the drive element towards said one end causes no relative . movement of the dispensing piston in the syringe; wherein
the engagement is releasable once the needle of the syringe extends out of the
>
opening such that movement of the drive element towards said one end causes relative movement of the dispensing piston in the syringe body.
22. An injection device including:
r
a housing for containing a syringe having a bore extending in a syringe body from an end surface, a needle communicating with the bore through the end surface and a dispensing piston moyablfc in said boie towards said end surface-so as to expel the contents of the syringe through the needle, the housing having an opening at one end through which the needle may extend;
a resilient member for biassing the syringe and needle inwardly of the housing;

a drive element movable towards said one end so as to move the needle of the syringe out of the opening and to move the dispensing pistou of the syringe towards the cad surface;
a drive coupling for extending from said drive element to the dispensing piston of the syringe, so as to transfer movement of said drive element to the dispensing piston- and
afci engagement for transferring drive directly from the drive coupling to the syringe body such that movement of the drive element towards said one end causes no relative movement of the dispensing piston in the syringe; wherein
the engagement is releasable once the needle of the syringe extends out of the opening such that movement of the drive element towards said one end causes relative movement of the dispensing piston in the-syringe body.
23. An injection device according to. claim 21 or 22 wherein the housing includes a release portion which interacts with the engagement to release drive to the syringe-
24. An injection device according to claim 23 wherein the release portion is located in the housing at a predetermined position and the engagement includes a trigger which is operated hy the release portion to release drive to the syringe upon reaching the , predetermined position.
25. An injection device according to claim 23 or 24 wherein me engagemeni includes a resilient latch and the resilient portion includes at least a recess in a wall of the. housing allowing deflection of the resilient latch to release the drive to the syringe.
26. An inj ection device according to claim 25 wherein the at least a recess engages the resilient latch so as to prevent further relative movement of the syringe body in the housing.
27. An injection device according to claim 25 or 26 wherein the drive coupling includes a fluid chamber defined between first and second relatively movable walls, the first wall being part of a piston and the resilient latch operating on the piston.
28. An injection device according to claim 23 or 24 wherein;
.the drive coupling includes a rigid element extending from the drive element;

the engagement includes at least one protrusion on a surface of the rigid element and a latch, fixed relative to Hie syringe body engaging the protrusion; and the release portion includes a stop on the housing for engaging the latch; wherein
the rigid element moves the latch with the protrusion until thelateh abuts the atop, whereupon the latch releases from the protrusion.
29. An injection device according to claim 28 wherein the latch is deflected
rosiliently past the protrusion. '
30- An injection device according to claim 28 wherein the latch is yiino*A »* * ■ cantilever at a point between an end engaging the protrusion and an opposite end and wherein the stop deflects the opposite end so as to release engagement with the protrusion*
31." An iqection device according to any one of claims 21 to 30 wherein the engagement reieasably connects the drive coupling to the syringe.
32. An-injection device according to any one of claims 21 to 30. wherein the
engagement releaaably connects a part of the drive coupling movable with the drive
*
element to a part of the drive coupling for mounting to the syringe in a fixed relative position to the needle.
33. An injection device according to claim 1 wherein the drive coupling
includes a longitudinally extending member, a pinion gear rotatably mounted on said
member and a longitudinally extending rack gear for engagement with the pinion.
,34. An injection device according to claim 33 wherein features are provided to resist rotation of the pinion relative to said member,
35. An injection device according to claim 34 wherein said features comprise a damper,
36. An injection device according to claim 33, 34 or 35 wherein a guide structure is provided to engage with a portion of the pinion to prevent rotation cf the pinion until the pinion has travelled past a predetermined longitudinal position in the device where upon the pinion starts to rotate and the drive coupling reduces in length
37. An injection device according to claim 33,34,35 or 26 wherein the rack has a predetermined length such that after a predetermined rotation of the pinion, the pinion

travels beyond the end of the rack and said member and the syringe are released to move inwardly of the housing.
33. An injectioa device according to claim 1 therein the drive coupling comprises first and second relatively rotauble members.
39. An injection device according to claim 38 wherein features are provided to resist relative rotation of the.firstand second members.
40. An injection device according to claim 39 wherein said features comprise a . daznpex
41. An injection device according to claim 39 or 40 wherein said features comprise aUeast one component for spinning against air resistance.
42," An injection device according to any one of claims 38 to 41 wherein a guide structure is provided to engage ■with at least one of the first and second members so as to -prevent relative rotation until the drive coupling has travelled past a predetermined longitudinal position in the device whereupon relative rotation starts and the drive coupling reduces in length,
43.- An injection device according to any one of claims 38 to 42 wherein the first and second members are joined by means of corresponding threads such that relative rotation causes th$ drive coupling to reduce in length.
44- An injection device according to claim 33 wherein the corresponding threads have a predetermined extent such that, after a predetermined amount of relative rotation, the corresponding threads and the first and second members disengage and the syringe is released to move inwardly of the housing.

45. An injection device substantially as herein described with reference to the accompanying drawings.



Documents:

2469-CHENP-2004 AMENDED CLAIMS 08-09-2010.pdf

2469-CHENP-2004 AMENDED PAGES OF SPECIFICATION 08-09-2010.pdf

2469-CHENP-2004 EXAMINATION REPORT REPLY RECIEVED 08-09-2010.pdf

2469-chenp-2004 form-1 08-09-2010.pdf

2469-CHENP-2004 FORM-13 02-07-2008.pdf

2469-chenp-2004 form-3 08-09-2010.pdf

2469-chenp-2004 form-5 08-09-2010.pdf

2469-chenp-2004 form-6 05-07-2007.pdf

2469-CHENP-2004 FORM-6 07-05-2009.pdf

2469-CHENP-2004 OTHER PATENT DOCUMENT 08-09-2010.pdf

2469-CHENP-2004 POWER OF ATTORNEY 08-09-2010.pdf

2469-chenp-2004-claims.pdf

2469-chenp-2004-correspondnece-others.pdf

2469-chenp-2004-correspondnece-po.pdf

2469-chenp-2004-description(complete).pdf

2469-chenp-2004-drawings.pdf

2469-chenp-2004-form 1.pdf

2469-chenp-2004-form 3.pdf

2469-chenp-2004-form 5.pdf

2469-chenp-2004-pct.pdf


Patent Number 244277
Indian Patent Application Number 2469/CHENP/2004
PG Journal Number 49/2010
Publication Date 03-Dec-2010
Grant Date 26-Nov-2010
Date of Filing 01-Nov-2004
Name of Patentee CILAG GmbH INTERNATIONAL
Applicant Address Landis & Gyr-Strasse 1, CH-6300 Zug, Switzerland
Inventors:
# Inventor's Name Inventor's Address
1 MARTIN, Jeffrey 30 Vale Drive, Barnet, Herts EN5 2ED, United Kingdom
2 HUGHES, Martin, Lawrence 11 Ridgeway, Woburn Sands, Bucks MK17 8UT
PCT International Classification Number A61M 5/20
PCT International Application Number PCT/GB2003/001946
PCT International Filing date 2003-05-02
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 0210123.6 2002-05-02 U.K.
2 0229384.3 2002-12-17 U.K.