GB2196376A - Change-key locks - Google Patents

Abstract

A lock has a swinging bolt 4 deadlocked by a stump 8 on a slide 6 blocked by a lever pack 10. The levers 10 are all identical, differing in their required lifts being obtained by differing their positions of engagement on a pin 11, each lever having a three-celled hole 18 by which it can be borne on the pin 11 at three different heights. To change the coding of the lock the existing correct key is used to set the levers and draw the stump 8 into the gates 13. The pivot pin 11 is then unscrewed from the lock to leave the levers floating on the stump 8. The new key to pass is then inserted and turned to scramble the levers following which the pivot pin 11 is replaced, the latter now engaging in different ones of the cells of the lever holes 18 appropriate to the lifts set by the new key. <IMAGE>

Description

SPECIFICATION Locks The present invention relates to locks and in one aspect seeks to provide a change-key lock-that is to say a key-operated lock having provision for reprograming of the key-recognition mechanism to pass differently coded keys, without replacement of the key-recognition elements-of simple and low-cost construction such as to be amenable to embodiment as, for example, a domestic window lock.

In one aspect the invention resides in a lock comprising a casing; a bolt borne for extension from and retraction into said casing; means within the casing for deadlocking the bolt in its extended condition and for enabling retraction of the bolt under the control of a key-recognition mechanism; the key-recognition mechanism comprising a plurality of levers borne upon removable pivot means having a defined axis within said casing; each said lever having a gate into which an abutment of the deadlocking means can be received to enable retraction of the bolt when the levers are set by engagement with a correct key and each said lever having a plurality of bearing formations at different locations on the lever any selected one of which can serve to mount the respective lever upon said pivot means; all constructed and arranged so that the key-recognition mechanism can be reprogramed to pass a new key by the steps of: setting the levers by engagement with an existing correct key; placing said abutment into the gates of the levers; withdrawing said pivot means from the levers and removing the existing key; engaging the levers with the new key so that the levers are pivoted on said abutment to adopt new relative positions; and replacing said pivot means so as to engage with the said bearing formation of each lever which corresponds to said defined axis of the pivot means while the levers are in said new relative positions.

A preferred embodiment of a lock in accordance with the invention will now be more particularly described, by way of example, with reference to the accompanying drawings in which: Figure 1 is an underneath plan view of the lock with its base plate removed; Figure 2 is a iongitudinal section through the lock; and Figure 3 is a transverse section through the lock.

The lock illustrated in the drawings is intended particularly for securing hinged windows and comprises a cast casing part 1 closed by a base plate 2 and having screw holes 3 by which to fix the lock to the surface of a window leaf. A flat bolt 4 is borne to be swung into and out of the casing by manipulation of an external thumb turn 5. Associated with the bolt 4 is a slide 6 which is borne in the casing and biased by a spring 7 towards a position (leftwards in the sense of Figures 1 and 2) in which a stump 8 upstanding from the slide can engage in a cut-out 9 in the bolt 4 to deadlock the latter in its extended position.

Withdrawal of the stump 8 to permit retraction of the bolt 4 is under the control of a key-recognition mechanism comprising a pack of, say, five levers 10 borne on a pin 11 in the casing and each biased to a rest position by a respective spring 12. Each lever has a gate 13 in its nose which, when a correct key is inserted through the keyhole 14 and turned to engage the lever bellies 15, becomes aligned with the stump 8 to permit retraction of the slide by continued turning of the key in engagement with a drive surface 16 on the slide. With the slide held retracted by the key and the stump 8 in the gates 13, the bolt can be swung in to its unlocking position by manipulation of the turn 5, whereafter the slide is held in its rightward (as viewed) position, by the stump 8 engaging the arcuate surface 17 of the bolt, when the key is removed.The bolt can be swung out again when required without use of the key, the stump 8 riding on the surface 17 and then snapping into the cutout 9 under the bias of the spring 7 when the bolt is fully thrown.

All of the levers 10 in this lock are of identical form, including the relative position of the gate 13 to the belly 15 in each one, differing of the lifts required to set each gate 13 to the stump 8 being achieved by differing the locations at which the levers engage the pivot pin 11. More particularly, each lever has a triple aperture formation 18 in its tail, as shown in Figure 1, any one cell of which can be used for mounting the respective lever to the pin 11. With three possible mounting positions for each one of five levers, therefore, locks as illustrated in the drawings can be produced with more than 200 practical differs. Moreover, this lock construction makes it possible to reprogramme the levers to pass a different key, by the process now to be described.

To reprogramme the levers, the existing correct key is first used to set the levers to the stump 8 and to withdraw the latter into the gates 13, in which position the mechanism is held by turning the bolt 4 to its retracted position. The key is then removed and the pivot pin 11 is also withdrawn from the levers. In the latter respect it will be seen from Figure 2 that the pin 11 is formed with a threaded end 1 1A which can be screwed into and out of the base plate 2, and a slot 11B at its other end for engagement by an ordinary screwdriver.Access to the slotted head of the pin can be gained through an aperture 19 in the casing 1 and an aperture 20 in the slide 6 which aligns with it when the slide is withdrawn to the unlocking position, (but which misaligns to leave the pin masked by the slide 6 when in the locking position shown in Figure 2, to prevent tampering with the pin). Unscrewing the pin and withdrawing it through the apertures 19 and 20 leaves the levers 10 floating on the stump 8 under their spring biases 12.

The new key which it is desired to pass is now inserted and turned to lift the levers on the stump 8. The pin 11 is then replaced, to engage whichever of the cells in formation 18 of each lever is now closest to the position of the pivot pin axis. With the pivot locations of each lever set on the pin, the new key can be removed and the bolt re-locked, the lever pivot locations now having been matched to the steps of the new key so that its subsequent operation on the levers will set their gates 13 to the stump 8.

An advantage of the change-key facility of this lock is that an end-user can from time to time change the coding of the levers to pass different keys and reduce the risk of compromise through a lost or stolen key for example. A number of similar locks, perhaps acquired at different times, can also readily be coded all to pass the same key if desired. A practical advantage, in the context of marketing this device e.g. as a domestic window lock, is that a retailer can offer, say, 100 or 200 differs simply by stocking the requisite number of different keys with which any one or more locks of this pattern can be coded, without having to stock a corresponding number of differently-coded locks.In this respect it is envisaged that the locks will be stocked each with the same factory-set coding and accompanied by the same corresponding key, and at the point of sale a key from the stock of differs will be selected and the factory-set coding will then be changed to pass the selected key. The cost of producing and stocking locks with all the available number of differs can therefore significantly be reduced in comparison with a pattern of lock which has a fixed-code key-recognition mechanism and no change-key facility.

Although not illustrated, to facilitate onehanded operation of the lock a detent spring may be included within the casing to hold the key under resilient bias when turned to retract the slide 6, so that the key need not be held in this position by hand while the thumbturn 5 is turned to withdraw the bolt 4.

Although described above in terms of its embodiment as a window lock, for which thelow-cost change-key facility is particularly useful, it will be appreciated that the invention can equally be applied to locks for doors, or other purposes. The bolt mechanism which the above-described reprogrammable levers control is also open to considerable variation.

For example a lock modified from that illustrated could be produced in which the swinging bolt and thumb turn are omitted and the slide 6 itself carries a bolt head.

Claims (10)

1. A lock comprising a casing; a bolt borne for extension from and retraction into said casing; means within the casing for deadlocking the bolt in its extended condition and for enabling retraction of the bolt under the control of a key-recognition mechanism; the keyrecognition mechanism comprising a plurality of levers borne upon removable pivot means having a defined axis within said casing; each said lever having a gate into which an abutment of the dead-locking means can be received to enable retraction of the bolt when the levers are set by engagement with a correct key and each said lever having a plurality of bearing formations at different locations on the lever any selected one of which can serve to mount the respective lever upon said pivot means; all constructed and arranged so that the key-recognition mechanism can be reprogrammed to pass a new key by the steps of: setting the levers by engagement with an existing correct key; placing said abutment into the gates of the levers; withdrawing said pivot means from the levers and removing the existing key; engaging the levers with the new key so that the levers are pivoted on said abutment to adopt new relative positions; and replacing said pivot means so as to engage with the said bearing formation of each lever which corresponds to said defined axis of the pivot means while the levers are in said new relative positions.

2. A lock according to claim 1 wherein said pivot means comprises a pin having screw threads at one end for engagement with the casing and a tool-engageable formation at the other end for turning the pin, whereby the pin is removable from and replaceable in the casing.

3. A lock according to claim 2 wherein access to said tool-engageable formation of the pin is blocked by a movable member within the casing when the bolt is in its extended position and is unblocked by said member only when the latter is moved by movement of a correct key to set the levers.

4. A lock according to claim 2 or claim 3 wherein said bearing formations each comprise an aperture with a plurality of cells within any selected one of which said pin can be received.

5. A lock according to any preceding claim wherein each said lever is of identical form.

6. A lock according to any preceding claim wherein said abutment is carried by a slide which is movable by a correct key out of a deadlocked position when the levers are set by the key to receive the abutment in their gates.

7. A lock according to claim 6 wherein the bolt is a rotary member separate from said slide and with which the slide engages to deadlock the same in its extended position.

8. A lock according to claim 6 wherein said slide carries a bolt head.

9. A lock according to any one of claims 6 to 8 when appended to claim 3 wherein said movable member is said slide.

10. A lock substantially as hereinbefore described with reference to the accompanying drawings.