Title of Invention

A TUBULAR LATCH

Abstract

A tubular latch comprises a casing consisting of two casing halves (1,2), a latch bolt lath in the form of a U-shaped strip (8,9,10) slidably mounted in the casing and an inner forend (3) having a central recessed area (4) secured to one end of the casing. A first spring (15) is arranged to act on the web (8) of the latch bolt lath to urge the latch bolt through an aperture in the inner forend and a follower (19) is arranged to act on one of the arms (9) of the latch bolt to retract the latch bolt lath against the action of the spring (15). The latch bolt is provided with a bolt head (11) which projects from the inner forend (3). A second spring in the form of a torsion spring (21) is coiled round the follower (19), one end (22) of the spring engaging in a slot in the follower and the other end (23) of the torsion spring engaging a side wall of the casing half (1). The follower has a central core containing an aperture for the reception of a spindle and a driving plate (26) with a shoulder (27) which is engageable with an upstand (17) projecting from the arm (9) of the latch bolt lath. The follower (19) can be turned by means of a handle or knob on a spindle extending through the central aperture in the follower and this turning movement of the follower entrains the latch bolt lath by virtue of the engagement of the upstand (17) by the shoulder (27) to retract the bolt head (11). An aperture (28) and a cut-out region (29) in the walls of the casing halves permit the use of bolt-through furniture.

Full Text

2 This invention relates to tubular latches. A common form of existing tubular latch employs a single spring which is arranged to act on the latch bolt. With such an arrangement, it is not possible to use unsprung door handles or knobs because the spring does not have sufficient force to return the handles or knobs to their usual position. If a heavier spring is used to provide a suitable return force, the force on the latch bolt is then too high. One solution to this problem has been to employ a first spring to act on~the latch bolt and a second spring to act on the follower. This arrangement allows for a relatively light spring to act on the latch bolt while a heavier spring can be used on the follower to permit the use of unsprung handles or knobs. A major disadvantage of this arrangement is that coil springs have been utilised and this precludes the use of bolt-through furniture. JP 4189987 teaches a hub spring consisting of a torsional coil spring in which the right side spring edge part is engaged with the rear wall surface of a case body and a left side spring edge part is engaged with the engaging projection of the first surface plate part on the cover side of a hub, said torsional coil spring being installed on the hub as a turning operation member assembled below the right edge part of a latch bolt. The engagement position of the spring edge part is adapted to be changed from the outside by a screwdriver through a rectangular hole. The spring force may thereby be varied by varying the initial torsional deformation quantity of the torsional coil spring. However, the spring force adaptability of the torsional spring is difficult to be regulated in a controlled manner by the aforesaid method. The present invention seeks to overcome the problems of the prior arrangements by providing a tubular latch which will accept bolt-through furniture and which can support unsprung door handles. According to the invention, there is provided a tubular latch comprising a casing, a latch bolt slidably mounted in the casing, an inner forend secured to one end of 3 the casing, a First spring arranged to act on the latch bolt to urge the latch bolt out of the casing through an aperture in the inner forend and a follower arranged to act on the latch bolt to retract the latch bolt against the action of the spring, wherein the follower is provided with a second spring in the form of a torsion spring whereby the latch can be operated by unsprung handles, wherein the latch bolt has a latch bolt lath in form of a U-shaped strip, the bolt head being mounted on the web of the U-shaped strip, and wherein one of the arms of the U-shaped strip is provided with a projection which is located in an elongated aperture in the casing, the engagement of the projection against one end of the aperture serving to retain the latch bolt lath in the casing. According to a preferred embodiment of the invention, the follower comprises a centre core having an aperture to accommodate a door furniture spindle; a driving plate located around the aperture in the centre core and engageable with the latch bolt lath and a projecting portion engageable with a fixed point in the casing. Preferably, the second spring takes the form of a torsion spring having one end engaged with the follower, an intermediate region coiled round the follower and the other end engaging a member which is non-rotatable with respect to the follower. The said one end of the second spring may be engaged in a hole or slot in the follower or it may be arranged to engage with a projection on the follower. The other end of the second spring is desirably arranged to engage with a side wall of the casing. The latch bolt is desirably provided with a bolt head which is rotatably mounted on the latch bolt lath whereby the bolt head can be turned through 180° to produce either a left-handed or a right-handed latch. Preferably, the inner forend comprises a plate having a recess in which the bolt head is located. 'Die invention will now be described in detail, by way of example, with reference to the drawings, in which: - 4 Fig. 1 is a front view of one embodiment of a latch according to the invention; Fig, 2 is a section taken on the line II-I1 in Fig. 1 in the direction of the arrows; and Fig. 3 is apian view of the latch shown in Figs. 1 and 2. Referring to the drawings, the latch according to the invention comprises a tubular casing consisting of two casing halves 1 and 2 which are adapted to mate together. An inner forend 3 having a central recessed area 4 is mounted on the mating casing halves 1,2 at one end of the casing, the forend being held in place by projecting ears 5 formed at the ends of the casing halves 1,2. The casing halves are each provided, adjacent their other ends, with aligned bores in which a pair of posts 6 and 7 are located. Slidably mounted in the casing is a latch bolt lath in the form of a U-shaped strip consisting of a web 8 and arms 9 and 10. A bolt head 11 is mounted on the web 8 of the latch bolt lath by means of a pin 12 so as to be rotatable with respect to the web. In the normal position of the latch bolt lath, the bolt head 11 is located in the recessed area 4 of the forend 3 and is slightly spaced therefrom so that it can be rotated with respect to the forend 3. A spacer plate 13 is engaged in slots in the two casing halves, the spacer plate having a central raised area 14 for locating one end of a coil spring 15. The other end of the coil spring 15 is located on the rear of the pin 12. The coil spring thus serves to urge the latch bolt lath in a direction towards the forend 3 and out of the casing. One arm 9 of the latch bolt lath is longer than the other arm and is provided with a recessed region 16 which terminates in a projecting upstand 17. The upstand 17 is arranged to be located in a slot formed by recessed regions 18 in the side walls of 5 the casing halves 1 and 2. Location of the upstand 17 in the slot thereby serves to limit the extent of movement of the latch bolt lath in the casing. Each casing half is further provided with a circular aperture and the ends of a follower 19 are located in the apertures. The follower has a square sectioned bore 20 for receiving the spindle of a door handle assembly (not shown). A torsion spring 21 is mounted on a cylindrical central region of the follower 19, one end 22 of the torsion spring being engaged in a slot in the follower and the other end 23 of the torsion spring being arranged to engage with a side wall of the casing half 1 in the region of the recessed region 16 in the arm 9 of the latch bolt lath. The follower 19 has a first radially outwardly extending cam member 24 having a shoulder 25 which is normally held against the post 6 by the action of the torsion spring 21. The follower 19 also has a second radially outwardly extending cam member 26 having a shoulder 27 which engages the upstand 17 on the latch bolt lath. The upstand is held against the shoulder 27 by the force of the coil spring 15. The two casing halves 1 and 2 are also provided with aligned apertures 28 and cut-out regions 29 at the ends remote from the forend 3. In use, the casing of the latch according to the invention will be located in a bore in a door or the like. The apertures 28 and cut-out regions 29 in the casing enable the passage of bolts whereby bolt-through furniture such as handles or knobs can be fitted to the door or the like. A square-sectioned spindle on the ends of which handles or knobs are mounted is located in the square-sectioned bore 20 in the follower 19. The bolt head 11 can be rotated as required for either a left-hand or right-hand opening door or the like. The forend 3 is secured to the door or the like by locating an outer forend faceplate 31 over the inner forend 3 and then fixing screws which pass through apertures 32 in the outer forend or faceplate and aligned apertures in the inner forend and engage in the material of the door or the like. 6 Jf one of the handles or knobs is turned, the square spindle will cause the follower 19 to rotate, against the action of the torsion spring 21, and the shoulder 27 will force the upstand 17, against the action of the coil spring 15, to move the latch bolt lath into the casing whereby the latch boit head 11 will also be moved into the casing so that the door or the like is unlatched and can be opened. When the handle is released, the force of the torsion spring 21 will move the follower back to the position in which the shoulder 25 bears against the post 6 and the shoulder 27 is returned to a position in which the coil spring 15 can force the bolt head 11 out of the casing such movement being restrained only by the engagement of the upstand 17 on the shoulder 27. The coil spring 15 can be considerably weaker than the torsion spring 21 because it merely has to impart a small spring-loaded action to the latch bolt lath. A force of between 6 and 12 NT's is envisaged. The more powerful torsion spring allows the use of unsprung door handles because these are returned to the normal position by the force of the torsion spring 21. The invention is not restricted to the above-described embodiment but variations and modifications may be made. For example, instead of being located in a slot in the follower 19, the said one end of the torsion spring 21 could be mounted in a bore in the follower or could be arranged to engage a projection on the follower. In the claims appended hereto, any reference signs placed between the parentheses shall not be construed as limiting the claims 7 I CLAIM: 1. A tubular latch comprising a casing (1,2), a latch bolt slidably mounted in the casing, an inner forend (3) secured to one end of the casing, a spring (15) arranged to act on the latch bolt to urge the latch bolt out of the casing through an aperture in the inner forend (3) and a follower (19) arranged to act on the latch bolt to retract the latch bolt against the action of the spring (15), wherein the follower (19) is provided with a second spring (21) in the form of a torsion spring whereby the latch can be operated by unsprung handles, wherein the latch bolt has a latch bolt lath in the form of a U-shaped strip (8,9,10) a bolt head (11) being mounted on the web (8) of the U-shaped strip, and wherein one of the arms (9) of the U-shaped strip is provided with a projection (17) which is located in an elongated aperture in the casing, the engagement of the projection against one end of the aperture serving to retain the latch bolt lath in the casing. 2. A tubular latch according to claim 1, wherein the follower (19) comprises a central core having an aperture (20) to accommodate a door furniture spindle, a driving plate located around the aperture in the central core and engageable with the latch bolt lath and a projecting portion (24) engageable with a fixed point in the casing. 3. A tubular latch according to claim 2, wherein the said fixed point comprises a post (6) projecting from a wall of the casing. 4. A tubular latch according to any one of the preceding claims, wherein the second spring (21) takes the form of a torsion spring having one end (22) engaged with the follower (19), an intermediate region coiled round the follower and the other end (23) engaging a member which is non-rotatable with respect to the follower. 5. A tubular latch according to claim 4, wherein the said one end (22) of the second spring (21) is engaged in a hole or slot in the follower (19). 8 6. A tubular latch according to- claim 4, wherein the said one end (22) of the second spring is engaged with a projection on the follower (19). 7. A tubular latch according to any one of claims 4 to 6, wherein the other end (23) of the second spring (21) is arranged to engage twith a side, wall of the casing (1). 8. A tubular latch according to any one of the preceding claims, wherein the casing is provided with at least one through aperture to permit the passage of a spindle for handles or knobs, said spindle being adapted to be located in an aperture in the follower (19). 9. A tubular latch according to claim 8, wherein the casing is provided with at least one cut-out region (29) and/or further aperture (28) to permit the passage of bolts of bolt-through furniture. 10. A tubular latch according to any one of the preceding claims, wherein the latch bolt has a bolt head (11) which projects from the inner forend (3) and wherein the bolt head is rotatably mounted on the latch bolt lath whereby the bolt head can be turned through 180° to produce either a left-handed or a right-handed latch 11. A tubular latch according to claim 10, wherein the inner forend (3) comprises a plate having a recess (4) in which the bolt head (11) is located. 12. A tubular latch substantially as described herein with reference to the drawings. A tubular latch comprises a casing consisting of two casing halves (1,2), a latch bolt lath in the form of a U-shaped strip (8,9,10) slidably mounted in the casing and an inner forend (3) having a central recessed area (4) secured to one end of the casing. A first spring (15) is arranged to act on the web (8) of the latch bolt lath to urge the latch bolt through an aperture in the inner forend and a follower (19) is arranged to act on one of the arms (9) of the latch bolt to retract the latch bolt lath against the action of the spring (15). The latch bolt is provided with a bolt head (11) which projects from the inner forend (3). A second spring in the form of a torsion spring (21) is coiled round the follower (19), one end (22) of the spring engaging in a slot in the follower and the other end (23) of the torsion spring engaging a side wall of the casing half (1). The follower has a central core containing an aperture for the reception of a spindle and a driving plate (26) with a shoulder (27) which is engageable with an upstand (17) projecting from the arm (9) of the latch bolt lath. The follower (19) can be turned by means of a handle or knob on a spindle extending through the central aperture in the follower and this turning movement of the follower entrains the latch bolt lath by virtue of the engagement of the upstand (17) by the shoulder (27) to retract the bolt head (11). An aperture (28) and a cut-out region (29) in the walls of the casing halves permit the use of bolt-through furniture.

Documents:

000773-kol-2004 abstract.pdf

000773-kol-2004 claims.pdf

000773-kol-2004 correspondence.pdf

000773-kol-2004 description(complete).pdf

000773-kol-2004 drawings.pdf

000773-kol-2004 form-1.pdf

000773-kol-2004 form-18.pdf

000773-kol-2004 form-2.pdf

000773-kol-2004 form-3.pdf

000773-kol-2004 form-5.pdf

000773-kol-2004 letters patent.pdf

000773-kol-2004 p.a.pdf

000773-kol-2004 priority document.pdf

773-kol-2004-granted-abstract.pdf

773-kol-2004-granted-claims.pdf

773-kol-2004-granted-description (complete).pdf

773-kol-2004-granted-form 2.pdf

773-kol-2004-granted-specification.pdf

773-kol-2004-priority document.pdf