GB2331785A

GB2331785A - Locks with geared bolts

Info

Publication number: GB2331785A
Application number: GB9725223A
Authority: GB
Inventors: Daren John Jackson
Original assignee: Reynolds
Current assignee: Reynolds
Priority date: 1997-11-28
Filing date: 1997-11-28
Publication date: 1999-06-02
Also published as: GB9725223D0

Abstract

A lock has a casing 10 with a bolt 16 that can be extended from the casing and retracted into the casing by rotation of a key. This rotation of the key also rotates a boss 20 which includes the segment 23 of a toothed gear that engages with the bolt. In this way, the throw of the bolt is increased on rotation of the key.

Description

2331785 1 LOCKS The invention relates to locks.

A typical lock comprises a casing, a bolt and a rotatable key As the key rotates, a f ace of the key engages a rotatable member which in turn engages a face of the bolt either to extend the bolt from the casing or to retract the bolt into the casing.

It will be appreciated that the distance by which the key can move the bolt is limited by the radius between the axis about which the key rotates and the face of the rotatable member that contacts the bolt. The throw can be increased by increasing this radius but there is plainly a limit on the size of the rotatable member. Indeed it is often preferred to have the smallest size possible rather than the largest.

According to the invention, there is provided a lock comprising a casing, a bolt and a member rotatable on rotation of the key, said member being in toothed engagement with the bolt to convert said rotation of the member into movement of the bolt to extend or retract the bolt into or from the casing.

1 2 By using a gearing between the member and the bolt, the distance the key throws the bolt could be increased.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:-

Figure 1 is side elevation of a lock showing a bolt of the lock in an extended position relative to a casing of the lock, and Figure 2 is a detailed view of a part of Figure 1 showing the engagement between a member of the lock and the bolt.

Referring first to Figure 1, the lock comprises a casing indicated generally at 10 with a generally rectangular back plate 11 having two longer side edges 12a,12b and two shorter side edges 13a,13b. A side wall 14 extends in a plane normal to the back plate 11 along the two shorter side edges 13a,13b and along one of the longer side edges 12a. The other side edge 12b of the back plate 11 carries a face plate 15 lying in a plane normal to the back plate 11 and extending beyond both ends of the associated side edge 12b.

3 The casing 10 is closed by a front plate (not shown) of similar shape to the back plate and engaging the side wall 14. A screw (not shown) connects the cover plate to the back plate 11.

The bolt 16 is formed with a cooperating toothed rack 24 extending in a direction parallel to the direction of movement of the bolt 16 between the extended and retracted positions.

The casing 10 mounts a bolt 16 which, in Figure 1, is shown in an extended position relative to the casing 10. The bolt 16 is mounted for rectilinear movement within the casing between the extended position shown in Figure 1 and a retracted position (not shown) in which the bolt 16 is accommodated within the casing 10. The face plate 15 has an aperture 17 through which the bolt 16 extends and retracts. The bolt 16 may be guided in this movement by a pin 18 engaging in a slot 19 provided in the back plate 11.

The casing 10 also contains a boss 20 formed with a key-shaped aperture 21. The boss 20 is mounted in the casing 10 for rotation about an axis 22 concentric with the axis of the circular cross-section portion of the aperture 21. As best 4 seen in Figure 2, the boss 20 has a toothed portion 23 in the shape of a segment of a toothed gear having an axis coaxial with the axis of rotation 22 of the boss 20.

The casing 10 also includes a number of conventional tumblers 25 which prevent extension and retraction of the bolt 16 unless lifted by a correct key.

The casing 10 will also contain a mechanism operatable by a handle to extend and retract a latch (not shown) on rotation of the handle. This is not described in any detail because it does not form part of the invention.

is In use, the casing 10 is inserted in the edge of a door, for example, with the face plate 15 flush against an edge surface of the door. The associated frame (not shown) is provided with a keeper for receiving the bolt 16 and aligned with the aperture 17 in the face plate 15.

When the correct key is inserted into the casing 10, it passes through a boss 20 and engages the boss 20. It the key is then rotated, it lifts the tumblers 25 to free the bolt 16 for movement and then the toothed portion 23 engages the bolt rack 24 to move the bolt 16 to the extended position shown in Figure 1.

is Since the engagement between the boss 20 and the bolt 16 is a rack and pinion arrangement, the rotation of the key can throw the bolt 16 from the casing 10 a greater distance than would be the case in the absence of the rack and pinion arrangement. The bolt 16 can thus engage in the keeper in the frame to a greater depth than would otherwise be the case and this gives added security.

Unlocking the bolt 16 is achieved by reverse rotation of the key. The commencement of this reverse rotation is the position shown in Figure 1 where the boss 20 is rotating in an anti-clockwise direction (as seen in Figure 1) and the toothed part 23 is just about to engage the rack 24. As it does so, continued rotation of the boss draws the bolt 16 back into the casing 10 with the key simultaneously lifting the tumblers so that the tumblers no longer prevent such movement.

In the embodiment illustrated with reference to the drawings, the toothed part 23 has three teeth and the rack 24 has three 6 corresponding indentations. It will be appreciated that there may be more or less than three teeth as required.

7

Claims

CLAIMS is A lock comprising a casing, a bolt and a member rotatable on

rotation of a key, said member being in toothed engagement with the bolt to convert said rotation of the member into movement of the bolt to extend or retract the bolt from or into the casing.
2. A lock according to claim 1 wherein the member receives the key and rotates about an axis co-axial with the rotational axis of the key when the key is received in the member.
3. A lock according to claim 2 wherein the member includes a segment of a toothed gear, the bolt including a rack meshing with said toothed segment as the key is rotated.
4. A lock according to any one of claims 2 to 3 wherein the member comprises a boss mounted on the casing for rotation.
5. A lock according to any one of claims 1 to 4 and including a plurality of tumblers, the key engaging the tumblers on rotation to free the bolt for movement before the 8 member engages the bolt to move the bolt.
6. A lock substantially as hereinbefore described with reference to the accompanying drawings.