GB2067645A

GB2067645A - Plate tumbler lock

Info

Publication number: GB2067645A
Application number: GB7930681A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-09-04
Filing date: 1979-09-04
Publication date: 1981-07-30
Also published as: GB2067645B

Abstract

The tumblers of a plate-tumbler lock are so shaped as to preclude picking of the device. An end of a tumbler is shaped to provide a rebate (17) at one corner and a hook formation (18) at the other corner. The hook formation (18) is capable of interlocking engagement with a side wall of a pocket (15) in which the tumbler is received. <IMAGE>

Description

SPECIFICATION Locking devices This invention relates to locking devices, particularly locking devices for use in motor vehicles, for example, locking devices for controlling opening of a vehicle door or a steering column lock.

The invention is concerned with that kind of locking device which includes a cylinder rotatable within an outer housing, the cylinder containing a plurality of spring-loaded plate-like tumblers arranged to cooperate with an inserted key such that, when a correct key is inserted into a key slot in the cylinder, the tumblers are moved into positions in which they do not project from the cylinder which can thus be rotated within the outer housing, whereas the tumblers normally project from the cylinder for engagement in pockets formed in all the inner surface of the housing so as to prevent rotation of the cylinder within the housing.

Locking devices of the above kind are extremely widely used. However, they are susceptible to picking so that the degree of security which they afford is low. It is accordingly an object of the invention to provide a locking device which has anti-pick characteristics.

According to the invention, at least one of the tumblers of the locking device is rebated at one of the corners of its forward end, i.e. the end thereof which is caused to project from the cylinder under its ;pring-loading in the absence of an inserted key, and an adjacent tumbler is shaped at the corresponding corner to provide a hook formation, the corresponding side wall of the pocket in the housing being shaped to interlock with said hook formation such that, when the hook formation is in interlocking engagement with the side wall, retraction of said adjacent tumbler against the action of its spring loading is prevented.

In a preferred arrangement, each tumbler is provided with a rebate at one corner of its forward edge and with a hook formation at the other corner of its forward edge so that interlocking engagement is provided for either direction of rotation of the cylinder. However, if the locking device is such that rotation thereof out of its locked position-can only be effected in one direction, alternate rebates hook formations will be provided only along one row of corners of the tumblers.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a sectional view of a locking device showing the first of a series of eight tumblers, Figure 2 is another sectional view of the device showing the second of a-series of eight tumblers.

Figure 3 is a view corresponding to Figure 1 showing the cylinder of the device turned through an angle X and with the first tumbler in a partially retracted position, Figure 4 is a view corresponding to Figure 2 showing the position occupied by the second tumbler when the cylinder is turned through the angle X, and Figure 5 is a part-sectional plan view of the device.

The device shown in the drawings includes a cylinder 10 rotatable within an outer housing 11, the cylinder 10 being enlarged at its outer end to provide a head portion 12 and being provided at its inner end with attachment means (not shown) whereby the cylinder 10 can be coupled to a mechanism, such as a steering column locking mechanism, to be operated by the device. The cylinder 10 has a key slot to enabie a key (not shown) to be inserted to effect retraction of a series of eight tumblers A, B, C, D, E, F, G and H contained within slots in the cylinder. The tumblers are acted upon by springs 1 3 such that four of the tumblers A, B, E and F are urged upwardly as viewed in Figure 5 whereas the other four tumblers are urged downwardly as viewed in that figure.The springs 1 3 are arranged alternately at opposite sides of the tumblers as can be seen from Figure 5 and a comparison of Figures 1 and 2 so that the provision of the pockets in which the springs 13 are located does not reduce the strength of the die-casting forming the cylinder 10.

Each tumbler A, B, C, D, E, F and G has a side limb 14 which is acted upon by the associated spring 13 so that the forward end of the tumbler is urged into a pocket 1 5 formed in the inner surface of the housing 11. The tumblers A and B thus normally occupy the positions shown in Figures 1 and 2. If, however, the tumblers are retracted to their fullest extent, the rearward end of each tumbler A, B will project into the opposite pocket 1 6. In view of the arrangement shown, the forward ends of tumblers A, B, E and F project normally into pocket 1 5 and the forward ends of tumblers C, D, G and H project normally into pocket 16. Each of the pockets 1 5, 1 6 has inclined side walls such that the base of the pocket has a greater circumferential extent than the mouth of the pocket.

At the forward end of tumbler A, a rebate 17 is provided at one corner and a hook formation 18 is provided at the other corner, the hook formation 1 8 being of such configuration that when the cylinder 10 is turned through an angle X in the clockwise direction, the hook formation 1 8 makes an interlocking engagement with the adjacent pocket side wall and the tumbler A cannot then be retracted against the action of its spring 13.

The forward end of tumbler B is of similar form, except that the relative positions of the rebate 1 7 and hook formation 1 8 are reversed. Thus, when the cylinder 10 is turned through an angle X in the anti-clockwise direction, the hook formation of tumbler B makes an interlocking engagement with the adjacent pocket side wall and tumbler B cannot then be retracted against the action of its spring 13.

Similar configurations are provided at the forward ends of tumblers E and F, which engage in pocket 1 5, and at the forward ends of tumblers C, D, G and H, which engage in pocket 16.

The tumbler configuration described above is such that, if an attempt is made to pick the lock by means of a jiggling device and a torque is applied to the cylinder 1 0 whilst first fully retracting tumbler A and then moving the tumbler A forward, tumbler A will be moved into position shown in Figure 3 in which the edge of pocket 1 5 has entered the rebate 1 7, the cylinder 10 has turned through an angle X and the hook formation 18 of tumbler B has engaged with the adjacent pocket side wall so as to become interlocked therewith. In this interlocked condition, tumbler B cannot be retracted and, in order to promote jiggling thereof, it will be necessary to return the cylinder towards its original angular position whereupon tumbler A will no longer be displaced.

This same situation will apply with successive pairs of tumblers as an attempt is made to pick the lock and picking will thus be rendered extremely difficult.

Claims

1. A locking device of the kind which includes a cylinder rotatable within an outer housing, the cylinder containing a plurality of spring-loaded plate-like tumblers arranged to cooperate with an inserted key such that, when a correct key is inserted into a key slot in the cylinder, the tumblers are moved into positions in which they do not project from the cylinder which can thus be rotated within the outer housing, whereas the tumblers normally project from the cylinder for engagement in pockets formed in the inner surface of the housing so as to prevent rotation of the cylinder within the housing, characterised in that at least one of the tumblers is rebated at one of the corners of its forward end, i.e. the end thereof which is caused to project from the cylinder under its spring-loading in the absence of an inserted key, and an adjacent tumbler is shaped at the corresponding corner of its forward end to provide a hook formation, the corresponding side wall of the pocket in the housing being shaped to interlock with said hook formation such that, when the hook formation is in interlocking engagement with the side wall, retraction of said tumbler against the action of its spring-loading is prevented.

2. A locking device according to claim 1, wherein each tumbler is provided with a rebate at one corner of its forward edge and with a hook formation at the other corner of its forward edge.

3. A locking device according to claim 1, which is such that the rotation of the cylinder out of its locked position can only be effected in one direction, wherein alternate rebates and hook formations are provided along one row of corners of the forward end of the tumblers.

4. A locking device having anti-pick characteristics, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.