GB2028910A - Key-operable Locks - Google Patents

Abstract

A cylinder lock has apertured disc- tumblers (9) that are abutted by the key (12) to one side or the other within their apertures (19) in dependence upon the way up with which the key (12) is inserted, so that the cut of key-step required to withdraw the tumblers (9) into the barrel (1) for release of the lock depends on the way up of key- insertion. For some tumblers the cut required differs from one side to the other of the aperture (19), whereas the others it is the same. "Dummy" tumblers are spring biased to be normally withdrawn and to be displaced upon key-entry so that the tumbler projects from the barrel to preclude release of the lock, unless the abutting key-step is of the correct cut to result in an overall zero displacement. Noses of rectangular cross-section project into the key- passageway and key slot (22) to assist guidance of the key (12) during its insertion. <IMAGE>

Description

SPECIFICATION Key-Operable Locks This invention relates to key-operable locks.

The invention is concerned particularly with key-operable locks of the kind in which a barrel is restrained from movement by tumblers that project from the barrel until a key with the correct stepped-profile is inserted to withdraw the tumblers by abutment with them individually, and in which the barrel is freed for movement whichever way up the key is inserted.

Key-operable locks of this kind (referred to hereinafter as "the specified kind") are wellknown, especially in the context of motor vehicles where they find application as door locks and ignition and steering-column locks. The ability to use the key either way up is regarded as especially desirable in this context, but the provision of this facility, which is commonly referred to as "double entry", normally results in a reduction in security. In particular, at least some of the tumblers of the lock are normally accommodated in the barrel in pairs, with the two tumblers of each pair projecting in opposite directions from one another, so that the doubleentry facility can only be provided if the same height or cut of key-step is utilized for their withdrawal.This then reduces the number of differs that can be provided, and although the number could be increased by addition of further pairs of tumblers to the barrel, there are in general ;quite strict limits on the length of barrel (and therefore the number of tumblers) that can be used. Accordingly there is normally the problem that it is necessary to make sacrifices in security when the double-entry facility is incorporated.

It is an object of the present invention to provide a key-operable lock of the specified kind that can be utilized to reduce the above problem.

According to the present invention there is provided a key-operable lock of the specified kind wherein each tumbler is abutted by the key to one side or the other in dependence upon which way up the key is inserted, there being for at least some of the tumblers difference between the two sides so that key-steps of different cut are required for tumbler-withdrawal in the two waysup of key insertion.

Thus with the key-operable lock according to the present invention it is not necessary to provide the same cut of key-step from one tumbler to the next, since each tumbler may be withdrawn by either of two key-step cuts according to the way-up with which the key is inserted.

The tumblers may be disc tumblers each having an aperture therethrough, the key abutting each disc to one side or the other within the aperture in dependence upon which way up the key is inserted. Furthermore in the case of at least one tumbler, there may be no difference between the two sides that are abutted by the key, so that key-steps of the same cut are required for withdrawal of that tumbler in the two ways-up of key insertion.

The tumblers may include at least one 'dummy' tumbler which in the absence of the key remains withdrawn, but which upon insertion of the key is displaced to project from the barrel and obstruct movement of the barrel unless that tumbler is abutted by a key-step of predetermined cut. The key may abut the 'dummy' tumbler to one side or the other in dependence upon which way up the key is inserted, and in these circumstances there may be difference between the two sides abutted so that the said predetermined cut of key-step required to maintain the 'dummy' tumbler withdrawn when the key is inserted, is dependent upon the way-up of key insertion.

Noses of substantially rectangular section may project into the key-passageway to assist guidance of the key during its insertion.

A key-operable lock in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1 and 2 are a sectional side-elevation and an end-elevation, respectively, of the lock; Figure 3 is a sectional side-elevation corresponding to Figure 1 showing the key inserted in the lock; Figure 4 is a sectional end-elevation of the lock with the key inserted, the section being taken on line IV--IV of Figure 3; Figure 5 is a sectional end-elevation of a barrel of the lock with the key inserted, the section being taken on the line V-V of Figure 3; Figure 6 is a part sectional end-elevation of the lock with the key inserted, the section being taken, on the line VI--VI of Figure 3;; Figure 7 is a perspective view illustrating further, engagement of the key within the lock on the line VI--VI of Figure 3; Figure 8 is a sectional end-elevation of the barrel of the lock with the key inserted, the section being taken on the line VIll-VIll of Figure 3; Figures 9 to 11 are views corresponding to those of Figures 6 to 8 respectively when the key is inserted into the lock the other way up: Figure 12 is a sectional end-elevation corresponding to that of Figure 4 when the key is inserted into the lock the other way up; and Figures 1 3 to 1 6 illustrate various forms of tumbler applicable to the lock.

Referring to Figures 1 to 8, the lock includes a diecast barrel 1 of generally cylindrical form that is housed coaxially within a cylindrical outercasing 2. The barrel 1 fits closely within the casing 2 to be capable of easy sliding within the casing 2, along, and also about, their common longitudinal axis 3. Two springs 4 (Figure 4), which are retained in diametrically-opposed longitudinal slots 5 in the casing 2 by inserts 6 of plastics, act on the head 7 of the barrel 1 to urge it forwardly of the casing 2 so as to project slightly from the front-end of the lock (as illustrated by Figure 1).

The casing 2 is slotted longitudinally to provide two diametrically-opposed slots 8 into which eight of ten disc-tumblers 9 carried by the barrel 1 normally project to restrain rotation of the barrel 1. The barrel 1 has five transverse slots 10 (Figures 4, 6 and 8) in which the ten tumblers 9 are located in pairs 9A and 9B, 9C and 9D, 9E and 9F, 9G and 9H, and 9J and 9K. Each tumbler 9 is biased by a respective spring 11, and of the ten tumblers 9 all except the tumblers 9A and 9G are so biased as to project outwardly from within the barrel 1 with the five tumblers 9B, 9D, 9F, 9H and 9K projecting in one direction into one of the slots 8 and the tumblers 9C, 9E, and 9J in the opposite direction into the other, diametrically-opposed slot 8. The biasing of the tumblers 9A and 9G on the other hand is such that neither of these projects into either slot 8.Rotation of the barrel 1 within the casing 2 is accordingly obstructed by projection into the two slots 8 of eight of the ten tumblers 9.

Withdrawal of the eight projecting tumblers 9 from the slots 8 to enable rotation of the barrel 1 within the casing 2 can only be achieved by insertion of an appropriate key 1 2 into the barrel 1 as illustrated in Figures 3 to 8. In this respect the lock has a longitudinally-extending key passageway which is defined in the head 7 of the barrel 1 by a slot 13. The head 7 is provided with a steel cap 14 that is dished and siotted appropriately to receive the tip 1 5 of the key 12.

When the key 12 is pushed through the slot 13 into the barrel 1 the tip 1 5 engages in succession with the five pairs of tumblers 9 to displace them, where appropriate, transversely against the actions of their respective springs 11. As the key 12 is pushed fully home the tip 1 5 strikes an obstructing cast-tumbler 1 6 at the back, closed end 17 of the barrel 1. Pressure on the key 12 against the obstructing tumbler 1 6 urges the barrel 1 backwardly against the action of the springs 4 until the tumbler 1 6 is squeezed outwardly beyond the back end 1 8 of the casing 2 as illustrated in Figures 3 and 5.Such outward movement of the tumbler 1 6 enables the key 12 to be fully inserted so as to bring the tip 1 5 into abutment with the closed end 1 7 of the barrel 1.

It also serves to block return movement of the barrel 1 under the action of the springs 4, for as long as the key 12 remains fully inserted in the lock.

Provided the key 12 is the corrent key for the lock, its full insertion frees the barrel 1 for rotation within the casing 2. More particulariy, each tumbler 9 has an aperture 19 therethrough which is entered by the key 12 during its insertion into the barrel 1, abutment of the relevant step of the key 12 within the aperture 1 9 serving to displace the tumbler 9 against its spring 11.

When the key 12 is pushed fully home the displacement experienced by the tumbler 9 will be of such an extent and sense as to locate that tumbler 9 wholly within the compass of the barrel 1. The net displacements experienced by the two tumblers 9A and 9G are accordingly zero, but for all the other eight tumblers 9 are the appropriate extent and sense to withdraw, and thereby disengage, them from the slots 8. Accordingly when, as illustrated in particular in Figure 3, the bitting profile of the fully-inserted key 12 appropriately matches the apertures 1 9 of all the tumblers 9, the barrel 1 is free to be turned in the casing 2 using the key 12. This latter general requirement for releasing the lock, is fundamental to all locks of the disc-tumbler kind, but there are important distinctions over known forms of lock of this kind embodied in the present lock.Firstly the key 12, which is asymmetrical in its stepped profile or bitting, can be used to release the lock whichever way up it is inserted. This "doubleentry" feature can in general be achieved using known forms of lock only if the two tumblers of each pair are arranged to be withdrawn by the same height or cut of key-step, so that the key is then necessarily symmetrical in its bitting, that is to say has the same profile of steps on both edges. With the lock of the present invention on the other hand, the double-entry feature is achievable using different cuts of key step for withdrawal of the two tumblers of each pair, so that a key asymmetrical profile is involved.This ability to use different cuts of key-step as between the two tumblers of each pair, has the distinct advantage of increasing significantly the number of different combinations or differs that may be utilized within any one particular specification of double-entry lock. In the present case utilizing five pairs of tumblers 9, the number of differs can be increased by a factor of 243.

Reception of the asymmetrical key 12 either way up, for lock operation, is achieved in the present example by virtue of the fact that the relevant step of the key 12 abuts with each tumbler 9 to one side or the other of the respective aperture 19 depending on which way up the key 12 is inserted. To this end, the bitting 20 of the key 12 on both edges is, as shown especially in Figures 4, 6 and 7, confined to the one side of the key 12 (in conventional doubleentry keys the steps on the two edges are on opposite sides of the key from one another). In these circumstances the configuration of the aperture 1 9 to one side can be appropriate to insertion and operation of the key 1 2 one way up, and the configuration of the same aperture 1 9 to the other side can be appropriate to insertion and operation of the key the other way up. Figures 6 and 7 illustrate accommodation of the key 12 within the aperture 1 9 of the tumbler 9J, and Figure 8 within the aperture 1 9 of the tumbler 9F, when the key 12 is with the orientation shown in Figure 3. On the other hand, Figures 9 and 10 illustrate accommodation of the key 12 within the aperture 19 of the tumbler 9J, and Figure 11 within the tumbler 9F, when the key 12 is inserted with the opposite, alternative orientation.

Abutment in the one case is confined to one side of each aperture 19, and in the other case to the other side.

The same circumstances apply to abutment of the key 12 with the non-projecting or 'dummy' tumblers 9A and 9G. For example, the key 12 is accommodated within the aperture 1 9 of the tumbler 9A as illustrated in Figure 4, when inserted with the orientation shown in Figure 3, but is accommodated as illustrated in Figure 12, to abut the opposite side of the aperture 1 9 when the key 1 2 is inserted the other way up.

With the lock illustrated, three key-step increments each of 0.8 mm and designated as (1), (2) and (3) respectively, are utilized for the key profile. Thus there are nine different configurations of tumbler-aperture 1 9 that may be used; three configurations, namely (1,2), (2,3) and (1,3) illustrated in Figure 13, and the three 'reverse' configurations, namely (3,1), (3,2) and (2,1) illustrated in Figure 14, involve different step-heights or cuts on opposite edges of the key, whereas three, namely (1,1), (2,2) and (3,3) illustrated in Figure 1 5, involve steps of the same cut on the opposite edges.

The security of the lock against picking is increased by the use of tumblers that do not normally project from the barrel 1, that is to say, of tumblers such as the tumblers 9A and 9G. The three forms of 'dummy' tumbler that may be introduced (either way up) into the form of lock illustrated, are shown in Figure 1 6. In any attempt to pick a lock of this nature, using solely conventional tumblers, there is uncertainty as to the extent to which each tumbler has to be displaced in order to free the lock barrel for rotation. However with the introduction of 'dummy' tumblers such as shown in Figure 16 there is with each tumbler the added uncertainty as to whether it requires to be displaced at all.

Such added uncertainty contributes to the security that can be achieved.

The key 12 may be (as illustrated in Figure 3) of the same nominal width along substantially its entire length so as to improve guidance into the lock. The depth of key insertion (which is the same whichever way up it is inserted) is in these circumstances limited, as illustrated in Figure 3, simply by abutment of the flat tip 1 5 of the key 12 on the closed end 1 7 within the key-passageway of the barrel 1. Two noses 21 (see Figure 2 especially) of generally rectangular section (rather than the more usual triangular section) project into the key-passageway to assist guidance of the key 12 during insertion, the noses 21 engaging in longitudinal grooves 22 (Figures 3, 7 and 10) of the same clean, rectangular section, in the two side faces of the key 12. Guidance is furthermore assisted by bridge portions 23 (Figures 1 and 3).

It is readily possible to accommodate different key profiles within the system so as thereby to enable the range to be extended.

The two key-guidance grooves 22 of the key 12 are located off-centre, one above and the other below, the key centre-line (the noses 21 are correspondingly located out of register with one another). It has been found however that there is advantage in iocating both guidance grooves on the key centre-line or as close to it as possible (and correspondingly relocating the noses), in that this reduces considerably the extent to which the chamfered faces down to the flat tip 1 5 at the nose of the key, are broken into. Smoothness of these faces improves key entry.

The lock described above may be utilized with advantage in the context of a steering-column lock of a motor vehicle. In this respect a lug 24 on the barrel 1 may be coupled to a cam or other mechanism that responds to rotation of the barrel 1 by the key 12 (following the backward movement upon its insertion), to withdraw a bolt from locking engagement with the steeringcolumn. The mechanism in these circumstances should, for safety, not allow the bolt to re-engage until such time as the key has been returned to its initial insertion position and withdrawn. The action of the tumbler 1 6 of the lock described above may be readily utilized to achieve this function in conjunction with the cam or other mechanism, since once the key 12 has been inserted the barrel 1 remains displaced backwardly until the whole of the key 12 has been withdrawn from the barrel 1. The barrel 1 can move forwardly under the action of the springs 4 to the position shown in Figure 1, only when the tumbler 1 6 disengages from the back end 18 of the casing 2, and this can occur only when the key 1 2 is withdrawn a substantial, controlled distance to break abutment of the tumbler 1 6 upon the key 12. Furthermore the key 1 2 cannot be withdrawn before the barrel 1 has been rotated back to the original insertion position, since until then the tumblers 9 abut the inside surface of the casing to trap it within the lock. Thus the forward movement of the barrel 1 can be utilized in the cam or other mechanism as the appropriate criterion for release and reengagement of the locking bolt with the steeringcolumn.

Claims (7)

Claims

1. A key-operable lock in which a barrel is restrained from movement by tumblers that project from the barrel until a key with the correct stepped-profile is inserted to withdraw the tumblers by abutment with them individually, and in which the barrel is freed for movement whichever way up the key is inserted, wherein each tumbler is abutted by the key to one side or the other in dependence upon which way up the key is inserted, there being for at least some of the tumblers difference between the two sides so that key-steps of different cut are required for tumbler-withdrawal in the two ways-up of key insertion.

2. A key-operable lock according to Claim 1, wherein each tumbler is a disc having an aperture therethrough, the key abutting the disc to one side or the other within the aperture in dependence upon which way up the key is inserted.

3. A key-operable lock according to Claim 1 or Claim 2, wherein the tumblers include at least one for which the two sides abutted by the key are the same, so that key-steps of the same cut are required for withdrawal of that tumbler in the two ways-up of key insertion.

4. A key-operable lock according to any one of the preceding claims, including at least one 'dummy' tumbler which remains withdrawn in the absence of the key and which upon insertion of the key is displaced to project from the barrel and obstruct movement of the barrel uniess that tumbler is abutted by a key-step of predetermined cut.

5. A key-operable lock according to Claim 4, wherein the key abuts the 'dummy' tumbler to one side or the other in dependence upon which way up the key is inserted, and there is difference between the two sides abutted so that the said predetermined cut of key-step required to maintain the 'dummy' tumbler withdrawn when the key is inserted, is dependent upon the way-up of key insertion.

6. A key-operable lock according to any one of the preceding claims, wherein noses of substantially rectangular section project into the key-passageway to assist guidance of the key during its insertion.

7. A key-operable lock substantially as herebefore described with reference to the accompanying drawings.