GB2431961A

GB2431961A - Tubular latch incorporating secondary spring means

Info

Publication number: GB2431961A
Application number: GB0522270A
Authority: GB
Inventors: Mark Naylor
Original assignee: Architectural Products & Compo
Current assignee: Architectural Products & Compo
Priority date: 2005-11-01
Filing date: 2005-11-01
Publication date: 2007-05-09
Also published as: GB0522270D0

Abstract

A latch bolt (18,19) is slidably mounted in a casing (10,12) with its bolt head (19) urged outwardly under the action of a first spring (22). It is retractable, against the action of the first spring (22), by a mechanism which includes a rotatable follower (24) having an aperture (25) to accommodate a door furniture spindle (not shown). A secondary spring (40) acts between the follower (24) on the one hand and the casing or a member fixed within the casing on the other hand to return the follower (24) to its initial position upon return of the latch bolt (18, 19) to its non-retracted position. However, a further secondary spring (42) is provided within the casing (10, 12) also acting between the follower (24) on the one hand and the casing or a member fixed within the casing on the other hand. In circumstances where the latch is mounted in an inverted condition in a door which opens at the opposite side, this further secondary spring (42) acts, in place of the first mentioned secondary spring (40), to return the follower (24) to its initial position upon return of the latch bolt to its non-retracted position . The further secondary spring (42) may also serve to limit movement of the follower (24) as it returns to its initial position under the action of the first secondary spring (40).

Description

TUBULAR LATCH INCORPORATING SECONDARY SPRING MEANS

This invention relates to a tubular latch incorporating secondary spring means.

Tubular latches are known which include a first spring, generally a coil spring, arranged to act on the latch bolt to urge it to a retracted position, and a second spring which acts upon a follower within the latch mechanism. A spindle of a door handle or knob is mounted to the follower and the purpose of the torsion spring is to provide the necessary additional force to return said spindle to its initial position once the latch bolt has been released from retraction without the need for providing springs within the handle or knob itself. Examples of such latch arrangements, in which the second spring is in the form of a torsion spring, are disclosed in GB2409878A, JP04189987A, US5,813,708 and US2,614,876.

Tubular latches of this general type may be required to be mounted in doors which open inwardly at a right hand side or at a left hand side. In these two different situations the orientation of the head of the latch bolt has to be reversed so that a substantially flat face lies in the direction of opening of the door while a sloping face lies in the direction of closing the door towards its frame.

An object of the present invention is to provide a tubular latch which can be mounted in right or left opening doors simply by being inverted (turned upside down) and which will then operate satisfactorily without any requirement for modification by the person fitting the latch.

According to the present invention a latch comprising a casing, a latch bolt slidably mounted in the casing, a first spring disposed within the casing so as to act on the latch bolt to urge the latch bolt out of the casing and a retraction mechanism, also within the casing which serves to retract the latch bolt against the action of the spring, said mechanism ncluding a follower having an aperture to accommodate a door furniture spindle and a secondary spring which acts between the follower and a member which is non-rotatable with respect to the follower to return the follower to its initial position upon return of the latch bolt to its non-retracted position, is characterised in that a further secondary spring is provided within the casing also acting between the follower and a member which is non-rotatable with respect to the follower, said further secondary spring acting in place of the first mentioned secondary spring to return the follower to its initial position upon return of the latch bolt to its non-retractable position in circumstances where the latch is mounted in a door which opens at the opposite side.

In known latches where a single secondary torsion spring is provided the initial position of the follower is determined by a projection (or cam) on the follower abutting a fixed member in the casing. This fixed member is typically a post extending across the casing between aligned bores in matching halves of the casing, said bores and said post being provided specifically for this purpose. However, in preferred embodiments of the latch of the present invention the additional secondary spring can be located and mounted in such a way that it serves to limit movement of the follower as it returns to its initial position.

Additionally or alternatively the initial position of the follower may be defined between the respective secondary springs.

The need for a special post acting as an abutment is therefore obviated.

In the present invention, the first secondary spring is advantageously in the form of a folded leaf spring, more specifically a spring which is folded almost in the manner of hair pin spring. This provides a compact form of spring for location in the lock housing, and also a type of spring which is not prone to failure after prolonged usage. The additional secondary spring is advantageously also in the form of a folded leaf spring. Indeed, in preferred embodiments the two secondary springs may be identical in form and they may be mounted substantially symmetrically within the casing.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-section through a preferred practical embodiment of the latch of the present invention taken along the line I-! in figures 2 and 3; Figure 2 is a plan view of the latch shown in figure 1; Figure 3 is a rear end view of the latch shown in figure 1; Figure 4 is a fragmentary enlarged scale view of the rear portion of the interior of the casing of the latch shown in figure 1; and Figure 5 is a perspective view of the same rear portion as shown in figure 4.

Referring to the drawings, a preferred embodiment of the latch of the invention comprises a tubular casing consisting of two casing halves 10, 12, which are adapted to mate together. An inner forend 14 having a central recessed area 15 is mounted on the mating casing halves 10, 12 at one end of the casing. The inner forend 14 is held in place at the end of the casing by suitable projections or other means. The casing halves 10, 12 are each provided, adjacent their other ends, with aligned bores in which a pair of posts 16 and 17 are located.

Slidably mounted in the casing is a latch bolt lath 18, which consists of a U-shaped strip having a web and respective arms. A bolt head 19 is mounted on the end of the lath by means of a pin 20.

A spacer plate 21 is fixedly mounted between the two casing halves 10, 12 and a coil spring 22 is mounted between this plate 21 and the end of the lath 18 so as to urge the lath 18 towards the forend 14. The bolt head 19 is accordingly urged to a position projecting out of the casing.

A retraction mechanism which serves to retract the latch bolt lath 18 against the action of the spring 22 includes a follower 24 and intermediate elements which link the follower 24 to the lath 18. The follower 24 is mounted in conventional manner rearwardly of the plate 21 between aligned circular apertures in the casing halves 10, 12. The follower has a square section bore 25 for receiving the spindle of a door handle and assembly (not shown). The follower 24 also has three projections/cams 26, 27, 28. The casing halves 10, 12 have aligned recess regions which provide openings 30, 32 in upper and lower feces of the casing, as shown in figure 2. Two of the follower cams 26, 27 are symmetrically arranged and project into these openings 30,32.

An intermediate frame element 34 in the form of a further generally U-shaped strip having respective kinked legs is arranged between the spacer plate 21 and the follower 24. The legs of this frame element are provided with outwardly directed tabs 36 adjacent their respective free ends, which tabs 36 project outwardly of the openings 30, 32 and behind which the cams 26, 27 engage, as shown in figure 1.

A lever arm 38 is pivotally mounted within the casing and projects through openings in the intermediate frame element 34 to engage behind a lip 13 formed at the rear end of the lath 18. Therefore, as the follower 24 is rotated, as in use, one or other of the cams 26, 27 serves to pull back the intermediate frame element 34, which in turn pivots the lever arm 38, and this pulls back the lath 18 against the action of the coil spring 22.

At the inner end of the casing, a first folded leaf spring 40, which is bent almost in a manner of a hairpin spring, is mounted on the post 16, and a second folded leaf spring 42 of identical shape is mounted symmetrically on the post 17. The legs of the first leaf spring 40 act between an upper wall of the casing and the cam 28 of the follower 24, while the legs of the second leaf spring 42 act correspondingly between a lower wall of the casing and the cam 28. However, additional stop members 44, 46 are mounted onto one half 10 of the casing to limit the opening of the legs of the springs 40, 42 in the direction of the cam 28.

The two casing halves 10, 12 are also provided with two aligned apertures 45, 47.

In use, the casing of the latch will be located in a bore in a door. The latch needs to be mounted in the door with its bolt head 19 in a correct orientation, depending on whether the door opens at its right or left hand edge, with a sloping face of the bolt head 19 directed towards the door frame in the direction of closing of the door.

The apertures 45, 47 enable the passage of bolts whereby bolt through furniture, such as handles or knobs, can be fitted to the door. A square section spindle, on the end of which said handles or knobs are mounted, is located in the square section bore 25 in the follower 24. The forend 14 is secured to the door by locating an outer forend faceplate 39 over said inner forend 14 and then applying fixing screws through aligned apertures in both to engage in the material of the door.

When one of the handles or knobs is turned, the square spindle will cause the follower 24 to rotate against the action of whichever leaf spring 40, 42 lies below the follower cam 28 in the lower region of the casing. Whichever follower cam 26, 27 is projecting through the opening in the upper surface of the casing will serve to retract the latch bolt lath 18 by way of the retraction mechanism, as already described above, against the action of the coil spring 22. As soon as force on the handle or knob is released, the coil spring 22 once again pushes the bolt head 19 out of the casing and at the same time whichever leaf spring 40, 42 has been compressed in the lower region of the casing urges the follower 24 and the handle/knob back to their initial positions. In this respect, the movement of the follower cam 28 is limited and damped by the presence of the oppositely mounted further leaf spring 40 or 42, respectively.

The foregoing is illustrative and not limitative of the scope of the invention. Many variations in detail may be made in other embodiments. In particular, the exact form of the retraction mechanism within the casing may differ from that described above. Also, the secondary springs need not be leaf springs, and can differ from each other in other embodiments.

Claims

CLAIMS

1. A latch comprising a casing, a latch bolt slidably mounted in the casing, a first spring disposed within the casing so as to act on the latch bolt to urge the latch bolt out of the casing and a retraction mechanism, also within the casing which serves to retract the latch bolt against the action of the first spring, said mechanism including a follower having an aperture to accommodate a door furniture spindle and a secondary spring which acts between the follower and a member which is non-rotatable with respect to the follower to return the follower to its initial position upon return of the latch bolt to its non-retracted position, characterised in that a further secondary spring is provided within the casing also acting between the follower and a member which is non-rotatable with respect to the follower, said further secondary spring acting in place of the first mentioned secondary spring to return the follower to its initial position upon return of the latch bolt to its non-retractable position in circumstances where the latch is mounted in a door which opens at the opposite side.

2. A latch according to claim 1 wherein the further secondary spring serves to limit movement of the follower as it returns to its initial position.

3. A latch according to claim 1 wherein the initial position of the follower is defined between the respective secondary springs.

4. A latch according to claim 1, 2 or 3 wherein the respective secondary springs are mounted within the casing in such a disposition as to allow at least one bolt for door furniture to extend therebetween and through the casing.

5. A latch according to any preceding claim wherein the first secondary spring is a folded leaf spring.

6. A latch according to any preceding claim wherein the further secondary spring is a folded leaf spring.

7. A latch according to any preceding claim wherein the respective secondary springs are mounted substantially symmetrically within the casing.

That is the 8. A latch according to any preceding claim wherein the respective secondary springs are mounted separately in an upper region and a lower region, respectively, of the casing.

9. A latch according to any preceding claim wherein the follower comprises respective cams one of which serves to retract the latch bolt against the action of the first mentioned spring when the foflower is rotated in one direction and the other of which serves to retract the latch bolt when the follower is rotated in the other direction, when its mounting position is inverted.

10. A latch substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.