Title of Invention

AN AUTOINJECTROR

Abstract The present invention provides a reusable spring driven autoinjector. The drive mechanism of the autoinjector of the present invention includes one or more drive springs formed of a shape memory alloy. Therefore, by alternating the shape memory alloy forming the one or more drive springs between austenite phase before an injection and a martensite phase after injection, the reusable autoinjector of the present invention is capable of providing an injection force that is higher than the compressive force required to cock the drive mechanism in preparation for a subsequent injection operation.
Full Text REUSABLE, SPRING DRIVEN AUTOINJECTOR
BACKGROUND
[0001] Field of the Invention: The present invention relates to reusable automatic
injection devices. In particular, the present invention relates to automatic injection
devices including a spring-loaded drive mechanism that incorporates one or more drive
springs formed of a shape memory alloy.
[0002] State of the Art: Automatic injectors (hereinafter referred to as
"autoinjectors") incorporating needled injection mechanisms are well known and are
thought to exhibit several advantages relative to simple hypodermic syringes. For
instance, because autoinjectors may be designed to automatically and reliably deliver a
desired dose of medicament, they facilitate quick, convenient, and accurate delivery of
medicaments. In particular, autoinjectors are well suited for use by subjects who must
self-administer therapeutic substances or by healthcare workers who must inject
multiple subjects over a relatively short period of time. Moreover, autoinjectors
incorporating a needled injection mechanism may be designed so that the needle is
hidden from view before, during, and even after an injection operation, thereby
reducing or eliminating any anxiety associated with the act of penetrating a visible
needle into the subject's tissue. Though their precise specifications vary widely,
needled autoinjectors generally include a body or housing, a needled syringe or similar
device, and one or more drive mechanisms for inserting a needle into the tissue of the
subject and delivering a desired dose of liquid medicament through the inserted needle.
[0003] The drive mechanisms included in state of the art needled autoinjectors
generally include a source of energy capable of powering the drive mechanism. This
energy source may be, for example, mechanical (i.e., spring-loaded), pneumatic,
electromechanical, or chemical, as described in U.S. Patents 6,149,626, 6,099,504,
5,957,897, 5,695,472, 5,665,071, 5,567160, 5,527,287, 5,354,286, 5,300,030,
5,102,393,5,092,843,4,894,054,4,678,461, and 3,797,489, the contents of each such
patent being incorporated herein by reference. International Publications numbered
WO 01/17593, WO 98/00188, WO 95/29720, WO 95/31235, and WO 94/13342 also
describe various injectors including different drive mechanisms. Nevertheless, needled
autoinjectors more often incorporate drive mechanisms that utilize a coil spring as an
energy source. Such spring-loaded drive mechanisms are desirable because they are
thought to facilitate the creation of reliable autoinjectors that are relatively simple in
design and inexpensive to manufacture.
[0004] In light of the growing desire to deliver increasingly viscous medicaments
via a needled injection device, however, known spring-loaded drive mechanisms
exhibit significant disadvantages. Specifically, the spring-loaded drive mechanisms
included in state of the art needled autoinjectors are typically designed to generate
forces sufficient for the injection of low viscosity medicaments, such as insulin and
epinephrine, which generally exhibit viscosities near that of water (i.e., about 1
centipoise at 20° C). Consequently, the spring-loaded drive mechanisms included in
known autoinjectors are designed to exert only small injection forces (e.g., ranging
from about 1 lb. to about 5 lbs.), which are not suitable for the delivery of emerging,
injectable medicaments, such as bioerodible depot formulations, having viscosities
much higher than that of water. As can be predicted using the Hagen-Poiseuille Law (F
= 8QµL(R.2/r4)), wherein "F" represents the injection force required, "Q" represents the
flow rate of the material injected, "u" represents the viscosity of the material injected,
"L" represents the length of the needle used, "R" represents the internal diameter of the
reservoir containing the material to be injected, and "r" represents the internal diameter
of the needle used, the injection forces required to deliver a dose of medicament
through a needle of desirable gauge will easily exceed those typically provided by state
of the art spring-loaded autoinjectors if the viscosity of the medicament to be delivered
increases significantly beyond 1 centipoise.
[0005] A possible solution to the need for a spring-loaded drive mechanism capable
of generating injection forces suitable for delivering higher viscosity medicaments
would be to simply provide a drive mechanism including a heavier conventional spring
capable of exerting a higher injection force. Yet, such an approach is not without
difficulties. In particular, where the injector is designed as a multiple use device, the
spring-loaded drive mechanism must be cocked such that the drive spring is held in a
compressed position before each use, and in order to cock a conventional spring-loaded
drive mechanism, a force that is equal to or greater than the maximum force exerted by
the drive spring must be applied to the drive mechanism. It can be appreciated, men,
that as the viscosity of the medicament to be delivered increases, not only does the
injection force required to deliver the medicament increase, but the force required to
cock the drive mechanism also increases. Where the material to be injected exhibits
viscosities that approach those of proposed depot materials, the force required to cock a
spring driven mechanism designed for delivery of the medicament could exceed that
which could be reasonably applied by a user, even if the injector is provided with a
cocking mechanism that provides some mechanical advantage that reduces the force
that must be directly applied by the user to cock the drive mechanism.
[0006] It would be an improvement in the art, therefore, to provide a multiple use,
spring-loaded autoinjector that includes a drive mechanism that can be cocked by a
force that is lower than the injection force provided by the drive mechanism. Such an
autoinjector could be designed to provide an injection force that is higher than the
injection forces typically exerted by state of the art spring-loaded autoinjectors, while
still allowing the user to cock the drive mechanism for reuse through the application of
a force that is practically applicable.
SUMMARY OF THE INVENTION
[0007] The present invention provides a reusable, spring-driven autoinjector. The
autoinjector of the present invention includes a body, a spring-loaded drive mechanism,
a trigger mechanism, and a replaceable syringe cartridge. The body of the autoinjector
of die present invention includes proximal and distal portions, with the proximal
portion housing the drive mechanism and the distal portion housing the syringe
cartridge. The drive mechanism includes one or more drive springs in association with
a drive member, and the drive member is configured such that, upon compression of the
one or more drive springs, the drive mechanism interacts with the trigger mechanism to
place the drive mechanism in a cocked position within the proximal portion of the body
of the autoinjector. The syringe cartridge provided in the autoinjector of the present
invention includes a reservoir for containing the medicament to be delivered and a
needle suitable for delivery of the medicament from the reservoir of the syringe
cartridge and into the tissue of a subject. To prepare the autoinjector of the present
invention for injection of a desired dose of medicament, the drive mechanism is placed
in a cocked position and a syringe cartridge containing the medicament to be delivered
is loaded into the proximal portion of the autoinjector body.
[0008] Once the drive mechanism is cocked and a syringe cartridge containing the
desired medicament is loaded into the autoinjector of the present invention, the
medicament contained in the syringe cartridge is injected into the subject by positioning
the autoinjector at a desired injection site and actuating the trigger mechanism. Upon
actuation of the trigger mechanism, the drive member is released from the cocked
position, allowing the one or more springs included in the drive mechanism to expand
from their compressed state. As the one or more drive springs expand from their
compressed position, the drive member acts against the syringe cartridge in such a way
that the needle of the syringe cartridge is inserted into the tissue of the subject and the
medicament contained in the syringe cartridge is delivered through the needle at the
injection site. After the medicament contained in the syringe cartridge has been
delivered, the empty syringe cartridge may be removed from the distal portion of the
body of the autoinjector and the drive mechanism can be re-cocked in preparation for
another injection.
[0009] Advantageously, the one or more drive springs included in the drive
mechanism of the autoinjector of the present invention are designed such that the drive
mechanism can exert an injection force that is higher than the compressive force
required to cock the drive mechanism. In order to achieve this capability, the one or
more drive springs included in the autoinjector of the present invention are fabricated
using a shape memory alloy (SMA). As used herein, the terms "shape memory alloy"
and "SMA" include all alloys that exhibit two temperature dependent crystal structures
or phases, with the lower temperature crystal phase being a "martensite" phase and the
higher temperature crystal phase being an "austenite" phase. A drive spring made of an
SMA is relatively stiff and capable of exerting a larger spring force when in an
austenitic phase, but the same drive spring made of the same SMA becomes
increasingly compliant and may be compressed through application of a relatively small
force as the spring transitions into a martensite phase. Therefore, with the one or more
drive springs in a martensite phase, the drive mechanism of the injector of the present
invention can be cocked by the application of a relatively small compressive force,
while transitioning the one or more drive springs into an austenite phase after the drive
mechanism has been cocked allows the drive mechanism to exert a relatively large
injection force upon triggering the injector. Through the use of one or more SMA drive
springs, the injector of the present invention provides a reusable, spring-loaded
autoinjector suitable for delivering medicaments requiring injection forces higher than
those typically provided by state of the art autoinjectors, while simultaneously
providing a device that can be cocked for re-use by the application of a compressive
force that is practically applicable by a user.
[0010] The present invention also includes a method of injecting a medicament into
a desired subject. The method of the present invention includes providing an
autoinjector including a spring-loaded drive mechanism, using a first force to cock the
spring-loaded drive mechanism, releasing the spring-loaded drive mechanism from the
cocked position, and generating an injection force that is greater than the first force
required to cock the spring-loaded drive mechanism and is sufficient to inject a desired
dose of a medicament. The method of the present invention is easily varied, and
specific embodiments of the method of the present invention may be tailored to suit
virtually any desired operational context calling for the injection of a dose of
medicament.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 provides a cross-sectional representation of an injection device
according to the present invention.
[0012] FIG. 2 provides a cross-sectional representation of a second injection device
according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0013] A schematic representation of one embodiment of the inj ector 10 according
to the present invention is provided in FIG. 1. As can be seen by reference to FIG. 1,
the injector of the present invention includes a housing 20, a drive mechanism 30, a
syringe cartridge 40, and a trigger mechanism 50. As can be appreciated in FIG. 1, the
housing 20 of the injector 10 is divided into a proximal portion 22 and a distal portion
24. The proximal portion 22 serves to house the drive mechanism 30, which includes
an SMA drive spring 32 and a drive member 34, while the distal portion 24 of the
housing 20 houses a syringe cartridge 40 including a reservoir 42 suitable for
containing a medicament 44, a piston 46 for expelling the medicament 44 from the
reservoir 42, and a needle 48 through which the medicament 44 can be injected into a
subject. This distal portion 24 of the housing 20 is configured such that the syringe
cartridge 40 can be loaded into the distal portion 24 of the housing 20 in preparation for
an injection and then removed after an injection has been completed. The trigger
mechanism 50 of the injector 10 interacts with the drive member 34 of the drive
mechanism 30 such that the drive member 34 is released from its cocked position upon
actuation of the trigger mechanism 50.
[0014] As it is illustrated in FIG. 1, the drive mechanism 30 of the injector 10 is in
its cocked position, with the drive member 34 maintained in a retracted position and the
SMA drive spring 32 in a compressed state. Once the drive mechanism 30 is in its
cocked position, the SMA drive spring 32 is transitioned into an austenitic state. With
the drive mechanism 30 in a cocked position, the SMA drive spring 32 in an austenitic
state, and a loaded syringe cartridge positioned in the distal portion 24 of the housing
20, an injection is initiated simply through actuation of the trigger mechanism 50.
Actuation of the trigger mechanism 50 releases the drive member 34 from its cocked
position, and upon release of the drive member 34, the SMA drive spring expands,
motivating the drive member 34 axially with a desired injection force. In the
embodiment illustrated in FIG. 1, as the drive member 34 is motivated by the SMA
drive spring 32, the drive member 34 acts against the piston 46 of the syringe cartridge
40, causing the syringe cartridge 40 to move axially through the distal portion 24 of the
housing 20 until me syringe cartridge 40 reaches a stop 26. Axial movement of the
syringe cartridge 40 to the stop 26 causes the needle 48 associated with the syringe
cartridge 40 to extend out from the distal portion 24 of the housing 20 and into a
subject. The SMA drive spring 32 continues to expand even after the syringe cartridge
40 reaches the stop 26, which causes the drive member 34 to exert a continued injection
force against the piston 46 of the syringe cartridge 34 and results in the expulsion of the
medicament 44 from the reservoir 42 through the needle 48.
[0015] After the drive mechanism 30 of the injector 10 has been actuated and the
medicament 44 contained in the syringe cartridge 40 has been expelled, the syringe
cartridge 40 can be removed from the distal portion 24 of the housing 20 and the drive
mechanism 30 can be re-cocked in preparation for a subsequent injection. In the
embodiment shown in FIG. 1, the distal portion 24 of the housing 20 must be separated
from the proximal portion 22 in order to either remove the syringe cartridge 40 or re-
cock the drive mechanism 30. Before re-cocking the drive mechanism 30, the SMA
drive spring 32 is transitioned back into a martensite phase. After the SMA drive
spring 32 has been transitioned into a martensite phase, the drive mechanism 30 is
manually re-cocked by simply applying a compressive force against the drive member
34 sufficient to compress the SMA drive spring 32 and force the drive member 34 back
within the proximal portion 22 of the housing 20 such mat drive member 34 is again
retained in a cocked position by the trigger mechanism 50. Because the SMA drive
spring 32 is transitioned to a martensite phase before the drive mechanism is re-cocked,
the force required to compress the SMA drive spring 32 and re-cock the drive
mechanism 30 is significantly reduced relative to the injection force exerted by the
same SMA drive spring 32 in an austenitic state. After re-cocking the drive mechanism
30, the injector 10 is again made ready for an injection by loading an unused syringe
cartridge 40 having a charge of medicament 44 into the distal portion 24 of the housing
20, reattaching the proximal portion 22 and distal portion 24 of the housing 20, and
transitioning the SMA drive spring 32 into an austenitic state.
[0016] Though FIG. 1 provides a schematic representation of one embodiment of
the injector of the present invention, the injector of the present invention is not limited
to the representation provided in FIG. 1. Moreover, FIG. 1 provides only a general
representation of each of the various components of the inj ector of the present invention
for the purposes of illustration. Therefore, in each embodiment of the injector of the
present invention, the components of the injector may vary, as desired, from the
representation provided in FIG. 1, and each component of the injector may be embodied
by any structure or mechanism suitable for providing a reusable injector including a
drive mechanism that incorporates an SMA drive spring.
[0017] Though not represented in FIG. 1, the drive mechanism included in the
injector of the present invention may also include more than one SMA drive spring.
Providing the drive mechanism of the injector of the present invention with two or
more SMA drive springs may be done in order to achieve an injection force that could
not be practically achieved by a single spring. Where two or more SMA drive springs
are used, the springs may be provided in a nested configuration, that is, with one or
more smaller springs sized and wound to fit within the inner diameter of one or more
larger springs. If two or more nested drive springs are provided in the drive mechanism
of the injector of the present invention, the drive mechanism may be designed such that
each drive spring is partitioned from the other drive spring(s) or is contained within its
own sleeve or seat. However, two or more nested SMA drive springs may also be
provided within the drive mechanism without partitioning. Where two or more SMA
drive springs are nested without being partitioned one from another, each spring is
preferably counter wound such that interference between the coils of the nested springs
is prevented or minimized as the nested springs are repetitively compressed and
released. Instead of two or more nested springs, the drive mechanism of the injector of
the present invention may also include two or more SMA drive springs positioned in
spaced apart relation to one another. For example, the drive member of the drive
mechanism may be provided with two or more seats, with each seat positioned in a
spaced apart relation to each of the other seats and each seat corresponding to one of the
two or more SMA drive springs included in the drive mechanism. Regardless of
whether the springs are nested or located in a spaced apart relationship one from
another, however, where the drive mechanism of the injector of the present invention
includes two or more SMA drive springs, the drive mechanism is configured such that
the force generated by each of the SMA drive springs upon triggering the injector is
exerted against the drive member included in the drive mechanism.
[0018] Instead of utilizing a simple coil spring (as is illustrated in FIG. 1), the drive
mechanism of the injector of the present invention may also utilize a coiled wave spring
formed of an SMA. Coiled wave springs are commercially available from, for
example, Smalley® Steel Ring Company of Lake Zurich, Illinois, U.S.A. As the name
suggests, the material forming a coiled wave spring is not only coiled but waved, and
due to such a structure, coiled wave springs can reduce the spring height necessary to
achieve a desired spring force at a given spring rate over a given stroke by as much as
50%. Therefore, the use of an SMA coiled wave spring as the drive spring in the drive
mechanism of the injector of the present invention may facilitate the fabrication of an
injector that is relatively shorter in length when compared to an injector powered by a
simple SMA coil spring designed to provide a comparable spring force at a given rate
over a given stroke.
[0019] The one or more SMA drive springs included in the drive mechanism of the
injector of the present invention are not only variable in number and configuration, but
the formulation of the SMA used to fabricate the one or more drive springs can also be
varied to achieve desired performance characteristics. Though any SMA suitable for
use in an injector may be used to fabricate the one or more drive springs incorporated in
the drive mechanism of the injector of the present invention, SMA alloys that are
presently preferred include NiTi, CuZnAl, NiTiCu, and CuAlNi alloys.
Advantageously, SMA compositions, such as the preferred alloys noted herein, are
easily varied to create drive springs exhibiting force and rate characteristics that provide
a desired range of spring forces over a stroke that ensures both insertion of the needle
associated with the syringe cartridge and delivery of a desired dose of medicament.
[0020] The alloy compositions used to fabricate the one or more SMA drive springs
included in the injector of the present invention may also be varied to control the
temperatures at which the springs enter their martensite or austenite phases. Generally,
upon heating and cooling, SMA compositions do not undergo a complete phase
transformation at a single, specific temperature. Instead, the transformation from one
crystal phase to another begins at one temperature (i.e., the martensite start (Ms)
temperature or the austenite start (As) temperature) and is completed at a second
temperature (i.e., the martensite finish (Mf) temperature or the austenite finish (Af)
temperature), with the difference between the temperature at which the SMA is about
50% transformed in the austenite phase (Ap) and the temperature at which the SMA is
about 50% transformed in the martensite phase (Mp) defining the hysteresis width of
the SMA. By altering the relative percentages of the metals included in an SMA or by
including additional metals, such as, for example, iron or chromium, in an SMA
composition, the drive springs included in the drive mechanism of the injector of the
present invention can be formulated to exhibit a desired hysteresis width with
martensite and austenite transition points within one or two degrees of a pre-defined set
of Ms,Mf, As, and Af temperatures. Beyond adjustments to the alloy composition, the
martensite and austenite transition temperatures or hysteresis width for a given SMA
can also be adjusted through known annealing processes.
[0021 ] The variability of SMA compositions allows the injector of the present
invention to be tailored for use in virtually any desired range of operational
temperatures. As it is used herein the phrases "range of operational temperatures" and
"operational temperature range" indicate the temperature range required to achieve the
desired austenite and martensite phase transitions in the one or more SMA drive springs
included in the drive mechanism. Though the operational temperature range of the
injector of the present invention will typically extend above or below the anticipated
ambient temperature range of the environment of use in order to achieve desired
martensite and austenite transitions, the anticipated ambient temperature range for the
anticipated environment of use will fall within the operational temperature range of the
injector. In one embodiment, the SMA used to create the one or more drive springs
included in the drive mechanism of the injector of the present invention is formulated
such that the one or more drive springs are in a desired austenite phase within the
anticipated ambient temperature range but require cooling in order to achieve a desired
martensite phase. In an alternative embodiment, the SMA used to create the one or
more drive springs is formulated such that the one or more drive springs are in a desired
martensite phase within the anticipated ambient temperature range, but require heating
in order to achieve a desired austenite phase. In yet a further embodiment, the SMA
used to create the one or more drive springs is formulated such that heating above the
anticipated ambient temperature range is required to achieve a desired austenite phase
and cooling below the anticipated ambient temperature range is required to achieve a
desired martensite phase.
[0022] Health care facility and home environments are exemplary environments of
use for the injector of the present invention. In such environments, the operational
temperature ranges of injectors according to the present invention will preferably fall
between temperatures typical for refrigerated storage (about 4° C) and temperatures
approximating human body temperature (about 37° C). Of course, where desired, the
operational temperature range for an injector designed for use in a health care facility or
home environment may extend above or below such a temperature range. The ambient
temperature range in a health care facility or home environment may be taken generally
as room temperature (between about 20° C and about 25° C). Therefore, where the
injector of the present invention is designed for use in a health care facility or home, the
injector preferably incorporates one or more SMA drive springs that achieve a desired
martensite phase at or above about 4° C, while achieving a desired austenite phase at or
below about 37oC. More preferably, to ease the use of an injector according to the
present invention designed for health care facility or home use, the SMA used to create
the one or more drive springs of the injector preferably provides an operational
temperature range that either extends below or above an ambient temperature between
about 20° C and about 25° C but does not extend both above and below such an
ambient temperature range. For example, in a presently preferred embodiment, the
injector includes one or more SMA drive springs that transition to a desired austenite
phase between about 20° C and about 25° C, while transitioning to a desired martensite
phase at or above about 4° C. In another presently preferred embodiment, the injector
of the present invention includes one or more SMA drive springs that transition to a
desired austenite phase at about 37° C, while transitioning to a desired martensite phase
between about 20° C and about 25° C. Of course, the injector of the present invention
is not limited to injectors designed for health care facility or home use, and the one or
more drive springs included in the drive mechanism of the injector of the present
invention may be fabricated of an SMA formulated to perform in an operational
temperature range that is suitable for virtually any desired environment of use.
[0023] Where the temperature required to achieve a desired austenitic phase is
higher than the anticipated ambient temperature of the environment of use {e.g., room
temperature), the injector of the present invention may be provided a heating
mechanism. Such a mechanism may be internal to or external to the housing of the
injector. Where the heating mechanism is internal to the housing of the injector, the
internal heating mechanism may be embodied by any suitable radiant heat or electrical
energy source. For example, an internal heating mechanism may incorporate a heating
mechanism that utilizes one or more batteries to transfer electrical energy to the one or
more SMA drive springs, which, in turn, increases the temperature of the one or more
SMA drive springs and allows a desired austenite phase to be achieved. Where the
heating mechanism is external from the housing of the injector, any known external
heating technology may be used to warm the one or more drive springs to a desired
austenite phase.
[0024] Though shape memory alloys may be formulated to provide a superelastic
mode of operation, wherein the transformation between the martensite and austenite
states occurs through the application of a stress or other force load, the SMA used to
fabricate the one or more drive springs included in the drive mechanism of the injector
of the present invention is preferably formulated and processed to provide a shape
memory mode of behavior within the anticipated operational temperature range. In
order to achieve an SMA drive spring that operates in a shape memory mode, the SMA
composition used to create the one or more SMA drive springs included in the injector
preferably exhibits Af and Mf temperatures within the anticipated operational
temperature range of the injector. Such a composition advantageously ensures that the
one or more SMA drive springs included in the injector of the present invention are
fully martensitic in the lower end of the injector's operational temperature range and
fully austenitic at the upper end of the injector's operational temperature range.
[0025] However, achieving a shape memory mode of behavior does not necessitate
that the one or more drive springs transition to either a fully austenite phase or a fully
martensite phase within the anticipated operational temperature range. The SMA
composition used to form the one or more drive springs need only exhibit enough shape
memory behavior to provide a crystal phase transition within the operational
temperature range that is sufficient to reduce the force required to compress the one or
more SMA drive springs as they cool from the upper end of the operational temperature
range to the lower end of the operational temperature range. Regardless of whether the
SMA composition is fully martensitic or fully austenitic within injector's operational
temperature range, the SMA composition used to form the one or more drive springs of
the injector of the present invention preferably provides a drive spring that exhibits at
least a 20% reduction in the force required to compress the drive spring as the drive
spring transitions from an austenite phase at the upper end of the operational
temperature range to a martensite phase at the lower end of its operational temperature
range. More preferably, the SMA material used to form the one or more drive springs
provides a drive spring exhibiting at least a 30% reduction in the force required to
compress the drive spring as the drive spring is transitioned from an austenite phase to a
martensite phase at the upper and lower ends of its operational temperature range,
respectively. Even more preferably, the SMA material used to form the one or more
drive springs provides a drive spring exhibiting at least a 40% reduction in the force
required to compress the drive spring as the drive spring is transitioned from an
austenite phase to a martensite phase at the upper and lower ends of its operational
temperature range, respectively. Most preferably, the SMA material used to form the
one or more drive springs provides a drive spring exhibiting at least a 50% reduction in
the force required to compress the drive spring as the drive spring is transitioned from
an austenite phase to a martensite phase at the upper and lower ends of its operational
temperature range, respectively.
[0026] However, the composition, structure, and number of the one or more SMA
drive springs included in the injector of the present invention are not the only
components of the injector that may be varied to achieve an injector exhibiting desired
performance characteristics. The representation provided in FIG. 1 is meant only to
facilitate an understanding of the injector of the present invention and does not limit the
specific configuration of any of the components of the injector 10 of the present
invention. For example, as shown in FIG. 2, a schematic representation of a second
embodiment of the injector 10 of the present invention, the distal portion 24 of the
housing 20 may include a bias spring 60 positioned to bias the syringe cartridge 40 in a
retracted position within the distal portion 24 of the housing and to dampen the
injection force sensed by the user or the subject. As can be seen in FIG. 2, where a bias
spring 60 is included in the distal portion 24 of the housing 20, it is preferably
positioned to act against the reservoir 42 of the syringe cartridge 40, not directly against
the drive mechanism 30. Such a configuration allows the dampening of the spring force
sensed by the user or subject, without actually reducing the injection force that is
exerted by the drive mechanism 30 against the medicament 44 to be delivered.
[0027] Each of the components included in the injector of the present invention
may be configured as desired to achieve an injector providing one or more targeted
performance characteristics. Various structures for two-part injector housings,
triggering mechanisms, and syringe cartridges are known in the art and may be used as
desired in fabricating an injector according to the present invention. Patent publications
teaching such structures include, for example, U.S. Patents 6,149,626, 5,957,897,
5,695,472, 5,665,071, 5,354,286, 5,300,030, 5,102,393, 5,092,843,4,678,461, and
3,797,489, the contents of each of which are incorporated herein by this reference.
However, the injector of the present invention is not limited to the housings, triggering
mechanisms, and syringe cartridges taught in these patents. The injector of the present
invention may include any structure or mechanism for providing a housing, triggering
mechanism, or syringe cartridge that is suitable for use in a reusable injector including a
drive mechanism that incorporates one or more SMA drive springs. Moreover, the
injector of the present invention may include features not encompassed by the
schematic illustrations provided in FIG. 1 and FIG. 2. For example, the injector of the
present invention may incorporate one or more needle safe mechanisms, such as a drive
mechanism that provides automatic retraction of the needle within the distal portion of
the housing upon completion of an injection or a spring-loaded sleeve positioned on the
distal portion of the housing, the spring-loaded sleeve designed to automatically extend
over a needle extending from the distal portion of the housing upon removal of the
injector from the injection site.
[0028] Though the injector of the present invention may be embodied by injectors
of varying specifications, each embodiment of the injector according to the present
invention includes one or more SMA drive springs that provide a drive mechanism that
exerts an injection force that is greater than the compressive force required to cock the
drive mechanism. The injector of the present invention therefore facilitates the creation
of relatively simple autoinjection mechanisms capable of exerting injection forces
higher than the injection forces typically achieved by state of the art spring-loaded
autoinjectors, while providing a drive mechanism that can be practically cocked by the
user. However, as described herein, the one or more SMA drive springs included in the
injector of the present invention may be fabricated to exert a wide range of injection
forces. Thus, the injector of the present invention is not limited to an injector exerting
an injection force that is greater than the injection forces typically exerted by state of
the art injectors. If desired, the injector of the present invention may in fact be
configured to exert an injection force that is equal to or even below the injection forces
typically exerted by state of the art spring driven autoinjectors. Such an injector would
still achieve the benefit of exerting an injection force that is higher than the force
required to cock the drive mechanism and thereby serve to increase the ease with which
a user can use and re-use the injector.
[0029] The present invention also includes a method of injecting a medicament into
a desired subject. In general, the method of the present invention includes providing an
autoinjector including a spring-loaded drive mechanism, using a first force to cock the
spring-loaded drive mechanism, releasing the spring-loaded drive mechanism from the
cocked position, and generating an injection force that is greater than the first force
required to cock the spring-loaded drive mechanism and is sufficient to inject a desired
dose of a medicament. In a specific embodiment, the method of the present invention
further includes providing an autoinjector including a spring-loaded drive mechanism
incorporating one or more drive springs formed of an SMA, placing the one or more
drive springs in a martensite phase before cocking the drive mechanism, and placing the
one or more drive springs in an austenitic phase after the drive mechanism is cocked
but before the spring-loaded drive mechanism is released from the cocked position. Of
course, the method of the present invention is as variable as the injector of the present
invention and, as is easily appreciated, the method of the present invention may be
tailored to suit various delivery contexts just as the various components of the injector
of the present invention may be varied to achieve targeted performance characteristics.
CLAIMS
We claim:
1. An injection device comprising:
a housing;
a reservoir for containing a medicament;
a needle for delivering the medicament; and
a drive mechanism capable of exerting a force sufficient to expel the medicament from
the
reservoir through the needle, the drive mechanism comprising one or more drive
springs formed of a shape memory alloy.
2. The injection device of claim 1, wherein the one or more drive springs are
formulated to provide a shape memory mode of behavior within an operational
temperature range of the injection device.
3. The injection device of claim 1, wherein the one or more drive springs are
fabricated of a shape memory alloy that is in an austenite phase within an ambient
temperature range of an environment of use of the injection device.
4. The injection device of claim 3, wherein the ambient temperature range of the
environment of use is about 20° C to about 25° C.
5. The injection device of claim 4, wherein the one or more shape memory alloy
drive springs are fabricated using a shape memory alloy that is in a martensite phase at
a temperature that is at or above about 4° C.
6. The injection device of claim 1, wherein the one or more drive springs are
fabricated of a shape memory alloy that is in a martensite phase within an ambient
temperature range of an environment of use of the injection device.
7. The injection device of claim 6, wherein the ambient temperature range of the
environment of use is about 20° C to about 25° C.
8. The injector of claim 7, wherein the one or more shape memory alloy drive
springs are fabricated using a shape memory alloy that is in a austenite phase at or
above about 37° C.
9. The injection device of claim 1, wherein the shape memory alloy forming the
one or more drive springs is formulated to achieve a full austenite phase and a full
martensite phase within an operational temperature range of the autoinjector.
10. The injection device of claim 9, wherein the operational temperature range of
the autoinjector is from about 4° C to about 37° C.
11. An autoinjector comprising
a housing;
a reservoir for containing a medicament;
a needle for delivering the medicament; and
a drive mechanism comprising a shape memory alloy drive spring, the shape
memory alloy being formulated to provide a drive spring that exerts a first force
when the drive spring in a martensite phase and a second force, which is larger
than the first force, when the drive spring is in an austenite phase.
12. The autoinjector of claim 11, wherein the first force is at least 20% less than the
second force.
13. The autoinjector of claim 11, wherein the first force is at least 30% less than the
second force.
14. The autoinjector of claim 11, wherein the first force is at least 40% less than the
second force.
15. The autoinjector of claim 11, wherein the first force is at least 50% less than the
second force.
16. The autoinjector of claim 11, wherein the shape memory alloy drive spring is
formulated to provide a shape memory mode of behavior within an operational
temperature range of the injection device.
17. The autoinjector of claim 11, wherein the shape memory alloy drive spring is
fabricated of a shape memory alloy that is in an austenite phase within an ambient
temperature range of an environment of use of the injection device.
18. The autoinjector of claim 17, wherein the ambient temperature range of the
environment of use is about 20° C to about 25° C.
19. The autoinjector of claim 18, wherein the shape memory alloy drive spring is
fabricated using a shape memory alloy that is in a martensite phase at a temperature that
is at or above about 4° C.
20. The autoinjector of claim 11, wherein the shape memory alloy drive spring is
fabricated of a shape memory alloy that is in a martensite phase within an ambient
temperature range of an environment of use of the injection device.
21. The autoinjector of claim 20, wherein the ambient temperature range of the
environment of use is about 20° C to about 25° C.
22. The autoinjector of claim 21, wherein the shape memory alloy drive spring is
fabricated using a shape memory alloy that is in a austenite phase at or above about 37°
C.
23. The autoinjector of claim 11, wherein the shape memory alloy drive spring is
formed of a shape memory alloy formulated to achieve a full austenite phase and a full
martensite phase within an operational temperature range of the autoinjector.
24. The autoinjector of claim 23, wherein the operational temperature range of the
autoinjector is from about 4° C to about 37° C.
25. The injection device of claim 1, wherein the one or more drive springs are
coiled wave springs.
26. The injection device of claim 11, wherein the shape memory alloy drive spring
is a coiled wave spring.


The present invention provides a reusable spring driven autoinjector. The drive
mechanism of the autoinjector of the present invention includes one or more drive
springs formed of a shape memory alloy. Therefore, by alternating the shape memory
alloy forming the one or more drive springs between austenite phase before an injection
and a martensite phase after injection, the reusable autoinjector of the present invention
is capable of providing an injection force that is higher than the compressive force
required to cock the drive mechanism in preparation for a subsequent injection
operation.

Documents:

252-kolnp-2004-abstract-1.1.pdf

252-kolnp-2004-abstract.pdf

252-kolnp-2004-assignment.pdf

252-KOLNP-2004-CLAIMS-1.1.pdf

252-kolnp-2004-claims.pdf

252-KOLNP-2004-CORRESPONDENCE-1.1.pdf

252-kolnp-2004-correspondence.pdf

252-KOLNP-2004-DESCRIPTION (COMPLETE)-1.1.pdf

252-kolnp-2004-description (complete).pdf

252-kolnp-2004-drawings-1.1.pdf

252-kolnp-2004-drawings.pdf

252-KOLNP-2004-FORM 1-1.1.pdf

252-kolnp-2004-form 1.pdf

252-kolnp-2004-form 18.pdf

252-KOLNP-2004-FORM 2-1.1.pdf

252-kolnp-2004-form 2.pdf

252-KOLNP-2004-FORM 3-1.1.pdf

252-kolnp-2004-form 3.pdf

252-kolnp-2004-form 5.pdf

252-KOLNP-2004-FORM-27.pdf

252-kolnp-2004-intenational publication.pdf

252-kolnp-2004-international search report.pdf

252-KOLNP-2004-OTHERS.pdf

252-KOLNP-2004-PA.pdf

252-kolnp-2004-pct request form.pdf

252-KOLNP-2004-PETITION UNDER RULE 137.pdf

252-KOLNP-2004-REPLY TO EXAMINATION REPORT.pdf

252-kolnp-2004-specification.pdf


Patent Number 249517
Indian Patent Application Number 252/KOLNP/2004
PG Journal Number 43/2011
Publication Date 28-Oct-2011
Grant Date 24-Oct-2011
Date of Filing 23-Feb-2004
Name of Patentee ALZA CORPORATION
Applicant Address JOHNSON & JOHNSON ONE JOHNSON & JOHNSON PLAZA, WH3221, NEW BRUNSWICK, NJ
Inventors:
# Inventor's Name Inventor's Address
1 GILBERT, SCOTT 1275 AVY AVENUE, MENLO PARK, CA 94025
2 DELA SERNA, PEDRO 375 PATTON AVENUE, SAN JOSE, CA 95128
PCT International Classification Number A61M 5/20
PCT International Application Number PCT/US2003/019988
PCT International Filing date 2003-06-24
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 60/391,322 2002-06-24 U.S.A.