GB2480089A

GB2480089A - Lever tumbler lock with blocking means to prevent pivotal movement of its levers

Info

Publication number: GB2480089A
Application number: GB1007552A
Authority: GB
Inventors: Christopher E Belcher
Original assignee: UAP Ltd
Current assignee: UAP Ltd
Priority date: 2010-05-06
Filing date: 2010-05-06
Publication date: 2011-11-09
Also published as: GB201007552D0

Abstract

A lever tumbler lock comprises a plurality of spring—loaded levers 15 that each define a gate 17 and are each pivotally mounted such that the gates 17 are normally held out of alignment with one another- by said spring loading. A bolt 7 is provided that is movable by a key 5 inserted in the lock. A fence 9 is provided for travel through the gates 17 of the levers 15 when the gates 17 have been aligned against the bias of said spring-loading by means of the key 5. A blocking means 18 is also provided to prevent pivotal movement of the levers 15 against the bias of the spring loading when the bolt 7 is in a latched position and thereby retain the gates 17 in an unaligned condition. This frustrates attempts to pick the lock as the levers 15 cannot be moved to align their gates 17 to allow passage of the fence 9 without the use of the key 5. The blocking means 18 may be spring-loaded.

Description

IMPROVEMENTS TO LEVER TUMBLER LOCKS

The present invention relates to lever tumbler locks and, in particular, to improving their resistance to interference by unauthorized persons.

In a conventional lever tumbler lock, a set of "lever" tumblers are used to prevent a locking bolt from moving in the lock. Each lever has a cutout, called a gate, through which part of the locking bolt, called a fence or stump, must travel. The gates of the levers are normally out of alignment and to open or close the lock a bitted key has to be used. The key raises the levers to different eves so that their gates align and simukaneousy moves the fence through the aligned gates, thereby throwing the bolt. Usually, the levers are pivotally mounted on part of the lock case and the fence forms part of the bolt so that it moves when the bolt is thrown. However, in a travelling-lever lock construction, the levers are pivotally mounted on the bolt and the fence is fixed to the lock case. Such a construction is substantially less common than the conventional arrangement. However, in both cases picking these locks involves applying torque to the bolt and raising the gates to the correct height so that they are aligned. It is usually possible to raise and pick the levers one at time.

It is an object of the present invention to provide a lever tumbler lock that resists picking in a simple, inexpensive yet effective manner.

According to the present invention there is provided a lever tumbler lock comprising a plurality of spring-loaded levers each defining a gate and each pivotally mounted such that their gates are normally held out of alignment with one another by said spring loading; a bok movable by a key inserted in the lock in order to latch or unlatch the lock; a fence adapted to move relative to the levers through the gates when the gates have been aligned by pivotal movement of the levers against the bias of said spring-loading by means of said key; and a blocking means adapted to prevent pivotal movement of the levers against the bias of said spring-loading when the bolt is in a latched position and thereby retain the gates in an unaligned condition.

It will be appreciated that prevention of the pivotal movement of the levers when the lock has been latched frustrates attempts to pick the lock as the levers cannot be moved to align their gates by the insertion of a lock pick into the ock in p'ace of the key.

Preferably, the blocking means is spring-loaded into contact with side edges of the levers.

Preferably also, the blocking means is mounted on the bolt or on an element connected to the bolt.

Preferably also, the bolt is activated by a cam that is rotatable about anaxisbythekey.

Advantageously, the cam is adapted to ease the bolt and thereby the blocking means from the levers as it is initially rotated during retraction of the bolt from its latched position, this easement freeing the levers from the clamping action of the blocking means.

Preferably also, the blocking means comprises a blocking lever that is pivotally mounted on the bolt or on an element connected to the bolt.

Further preferred but non-essential features of the present invention are further described in the dependent claims appended hereto.

An embodiment of the present invention will now be described with reference to the accompanying drawings, in which:-Fig. 1 is exploded perspective view of an embodiment of lever tumbler lock in accordance with the present invention; Fig. 2 is a view to an enlarged scale of part of Fig. 1 showing a bolt and a blocking means; Figs. 3 to 7 are side elevations showing the interior of the lock shown in Fig. 1 when assembled but with a cover omitted and form a sequence showing the relative positions of the parts of the lock as the bolt is moved from a retracted, unlatched position, as shown in Fig. 3, to an extended, latched position, as shown in Fig. 7, by a key shown inserted into the lock; and Figs. 8a and 8b are side and end elevations respectively of a curtain with an edge forming a cam forming part of the lock shown in Fig. 1 but to the scale of Fig. 2.

The embodiment of tumbler cylinder lock shown in the drawings comprises a case 1 with an end plate 2 and a cover plate 3. The case 1 and the cover plate 3 define keyholes 4 for a key 5 for use with the lock. The end plate 2 defines an aperture 6 through which a bolt 7 can be extended and retracted by operation of the key 5 in the lock. The bolt 7 comprises a lath 8 with a fence 9 and a curved shoulder 10 against which an edge of a cam 11 bears. The cam 11 is formed by a closed edge of a lock curtain 12 and has a barrel 13 into which the end of a shaft of the key 5 locates when the key 5 is inserted into the lock through either of the keyholes 4. The cam 11 can be rotated by the key 5 against the bias of a spring-loading formed by a leaf spring ia mounted within the case 1 to one side of the cam 11 over a tag 14b formed by a projection in the case 1. The leaf spring ia is flexed over the tag 14b by some surfaces of the cam 11 so that the spring ia biases the cam when it is in certain positions. As described below, the spring ia acts to retain the cam ii and thereby the curtain 12 and barrel 13 in position when the lock is in a latched or unlatched state.

A plurality of spring-loaded levers 15 are pivotally mounted on a pivot i6 attached to the case. Six levers 15 are shown in Fig. 1 and typically lever tumbler locks comprise four, five or six levers 15. The levers 15 are urged by their spring-loading into contact along their lower edges with the barrel 13 of the cam 11 on one side of the curtain 12. Each of the levers 15 defines a gate 17 through which the fence 9 projects. When the levers 15 are all in contact with the barrel 13 their gates 17 are out of alignment. When the key 5 is inserted in the lock its shaft engages the barrel 13 and when it is turned the lever steps on the pin of the key 5 are adapted to contact the lower edges of all the levers i and to raise them against the bias of their spring-loading.

When the correct key 5 for the lock is being used, the bitting pattern of the lever steps is such that the levers 15 are raised so that their gates 17 align. At the same time, the key turns the cam 11 which throws the bolt 7 into or out of a latched position. Only if the gates 17 align can the fence 9 pass along the gates 17 permitting the bolt 7 to move.

In order to frustrate attempts to pick the lock, a blocking means i8 is provided that acts to prevent pivotal movement of the levers i when the bolt is in a latched position. In the illustrated embodiment the blocking means 18 comprises a spring-loaded blocking lever that is pivotally mounted on the lath 8 of the bolt 7 and that is spring-loaded into contact with upper side edges 19 of the levers 15.

The blocking lever 18 is pivotally mounted via a bar 20 at one end of a cover 21 defined by the lath 8 that projects over the upper side edges 19 of the levers 15. The cover 21 is domed or otherwise shaped, as shown in the drawings, so as not to impede pivotal movement of the levers 15 during travel of the bolt 7. In an alternative arrangement the blocking lever 18 could be mounted on a separate element attached to the bolt 7. The spring-loading for the blocking lever 18 comprises a torsion spring 22. In this embodiment, a first leg 23 of the spring 22 is inserted in a cavity 24 defined by the blocking lever 18 and a second leg 24 of the spring 22 is inserted in a cavity 25 defined by the cover 21. The spring 22 urges the lever 18 into contact with the edges 19 of the levers 15 so that as the bolt 7 is thrown into or out of a latched position, the blocking lever 18 rides along the edges 19 of the levers 15. The edges 19 of the levers 15 each define a projecting portion 26 against which the blocking lever 18 bears acts when the bolt 7 has been fully extended and is in the latched position. Preferably, the projecting portions 26 define a substantially flat shoulder at the ends of the levers 15 furthest from the pivot i6. These, together with the blocking lever 18 and the cam 11, are arranged such that in the latched position the spring 22 urges the blocking lever 18 into a plane that is tangential to the barrel 13 thereby clamping the levers 15 between the blocking lever 18 and the barrel 13. As is explained in more detail below, when the bolt 7 is retracted by turning the correct key in the lock, the cam 11 is adapted to ease the bolt 7 and blocking lever i8 from the levers 15 as it is initially rotated. This easement frees the levers 15 by enabling the blocking lever 18 to move and to ride back over the side edges 19 of the levers 15 as the bolt 7 retracts into the case 1.

The shape of the cam ii will now be described in more detail with reference to Figs. 8a and 8b. As described above, the cam 11 is formed by the edge of the lock curtain 12 and the levers 15 are spring-loaded against its barrel 13. It can be seen in Fig. 8b that the cam ii has two straight surfaces 27 and 28, which are parallel to one another and arranged on opposite sides of the camli. These surfaces 27 and 28 are adjoined by opposing surfaces 29 and 30. The surface 29 is curved and has a notch 31 at one side adjacent one end of the surface 27 whereas the surface 30 is substantially straight but has an off-centre curving bulge 32 where it adjoins the surface 28. As shown in Figs. 3 to 7, the leaf spring ia bears against the surfaces 29 and 30, and in particular the notch 31 and the bulge 32, of the cam 11 as it is turned within the lock by the key 5.

The operation of the lock will now be described with particular reference to Figs. 3 to 7 and the significance of the surfaces of the cam 11 in relation thereto will be explained.

Fig. 3 shows the lock in an unlatched state with the bolt 7 retracted into the case 1. In this position, the cam 11 sits with the surface 29 in contact with the internal bottom face of the case 1 and with the leaf spring ia flexed over the tag 14b by the notch 31 of the cam ii. The cam 11 is thereby retained in this position by the leaf spring ia and in turn retains the bolt 7 in the retracted state. In this position, the levers 15 are biased into contact with the barre' 13 and their gates 17 are not aligned. The key 5 is shown inserted into the lock but has not been turned.

Fig. 4 shows the lock when the key 5 has been turned, in an anti-clockwise, locking direction as shown in Fig. 4, through approximately 135°.

The key 5 has moved the cam 11 so that it is no longer retained by the leaf spring ida, the notch 31 now being located on the opposite side of the barrel 13 from the spring ida. The surface 30 of the cam 11 is now parallel to the leaf spring ida, having partially moved the bolt 7 via the bulge 32 so that it extends a short way out of the aperture 6. The blocking lever 18 has also moved an equivalent distance along the edges 19 of the levers 15 but their gates 17 still remain unaligned as the key has yet to act on them.

Fig. 5 shows the lock when the key has been turned through 180°.

During rotation of the key between 135° and i8o° the lever steps of the key have engaged the levers 15 and raised them against the bias of their spring-loading. In Fig. the levers 15 are shown raised to their highest extent so that their gates 17 have now aligned. In addition, the curved surface 29 of the cam ii has acted on the bolt 7 and extended it further through the aperture 6 and moved the fence 9 half-way along the aligned gates 17. The blocking lever 18 has also been moved further along the edges 19 of the levers 14.

During turning of the key 4, the bulge 32 on the cam 11 passes and bears on the leaf spring ia so that the key 5 has to be turned against the bias of the spring ida.

In Fig. 6 the lock is shown when the key 5 has been turned through a further 450* At this point, the key 5 is just about to disengage from the levers and the fence 9 has travelled almost all the way along the aligned gates 17 so that the bolt 7 has been extended further out through the aperture 6. The cam ii has been turned by the key 5 so that the bulge 32 has cleared the leaf spring ida. The blocking lever i8 has now been moved up over the top of the projecting portions 26 of the levers 15. As the levers 15 are still in a raised condition, the blocking lever i8 is pivoted upwards, against the bias of the torsion spring 22 sO that it lies almost flat against the projecting portion 26 of the highest lever 15.

Fig. 7 shows the lock when it is in a latched condition with the bolt fully extended and the key 5 has now been turned through 3600 and can be removed from the lock. In this position, the cam 11 now again sits with the surface 29 in contact with the internal bottom face of the case 1 and is retained in position by the leaf spring ida, which is flexed over the tag 14b by the notch 31 of the cam 11. The bulge 32 of the cam 11 is opposite the notch 31 and is in contact with the shoulder 10 of the lath 8. This raises the lath 8 very slightly. The levers 15 have also returned to the position shown in Fig. 3 and the gates 17 have fallen out of alignment. The fence 9 is thereby trapped by the levers 15 at the end of the gates 17 furthest from the pivot i6 so that the bolt 7 cannot be pushed back into the case 1 against the bias of the leaf spring ida. As the levers 15 fell back to their lowest position into contact with the barrel 13 of the cam 11 under the bias of their own spring-loading, the blocking lever i8 was biased by the spring 22 into the position shown in Fig. 7 50 that its edge bears against the flat shoulders defined by the projecting portions 26 of the levers 15. In this position, the blocking lever lies in a plane substantially tangential to the barrel 13 thereby clamping the levers 15 between the blocking lever 18 and the barrel 13. It will be appreciated that in this position, it is not possible to raise any of the levers 15 by means of a pick tool inserted into the lock in place of the key 5. The lock is, therefore, now protected against picking.

To unlatch the lock, the key 5 is inserted into the lock and turned in the opposite direction, clockwise with respect to Figs. 3 to 7, which thereby turns the cam 11 in the opposite direction too so that the sequence of events described above are reversed. It will be appreciated that in the latched condition as shown in Fig. 7, the bulge 32 is in contact with the lath 8 of the bolt 7. However, when the cam 11 is turned to the position shown in Fig. 6, the bulge 32 has moved away from the bolt 7 thereby easing the bolt 7 and thereby the Mocking ever 18 from the evers 15. This easement frees the levers 15 by enabling the blocking lever 18 to ride back over the side edges 19 of the levers 15 as the bolt is retracted 7 into its unlatched position.

It will be appreciated that only one embodiment of the invention has been described above and that other arrangements within the scope of the invention are possible. In particular, in other embodiments, the blocking means i8 may comprise a spring-loaded plunger instead of a spring-loaded lever. In other embodiments, the blocking means may comprise a fixed projection. Such an arrangement would be suitable for use in an embodiment with a travelling-lever construction. In this case the levers would be pivotally mounted on the bolt and the fence and blocking means fixed to the lock case. Movement of the levers against a fixed blocking means secured to or integral with the case when the lock is latched would prevent lifting of the levers to enable the lock to resist picking.

Claims

CLAIMS1. A lever tumbler lock comprising a plurality of spring-loaded levers each defining a gate and each pivotally mounted such that their gates are normally held out of alignment with one another by said spring loading; a bolt movable by a key inserted in the lock in order to latch or unlatch the lock; a fence adapted to move relative to the levers through the gates when the gates have been aligned by pivotal movement of the levers against the bias of said spring4oading by means of said key; and a blocking means adapted to prevent pivotal movement of the levers against the bias of said spring-loading when the bolt is in a latched position and thereby retain the gates in an unaligned condition.
2. A lock as claimed in Claim 1, wherein the blocking means is spring-loaded into contact with side edges of the levers.
3. A lock as claimed in Claim 2, wherein the side edge of each of the levers defines a shoulder against which the blocking means bears when the lock is latched.
4. A lock as claimed in Claim 3, wherein the levers are mounted on a pivot and said shoulders are located at ends of the levers furthest from the pivot.
5. A lock as claimed in any of Claims 1 to 4, wherein the blocking means is mounted on the bolt or on an element connected to the bolt.
6. A lock as claimed in any of Claims 1 to 5, wherein the bolt is activated by a cam that is rotatable about an axis by the key.

-10 -
7. A lock as claimed in Claim 6, wherein the bolt comprises a lath with a fence and a curved shoulder against which the cam bears.
8. A lock as claimed in Claim 6 or Claim 7, wherein the cam is defined by a closed edge of a lock curtain.
9. A lock as claimed in any of Claims 6 to 8, wherein the cam comprises a barrel; the levers are urged by their spring-loading into contact with the barrel; and the blocking means acts by clamping the levers between itself and the barrel.
10. A lock as claimed in Claim 9 when dependent on Claim 5, wherein the cam is adapted to ease the bolt and thereby the blocking means from the levers as it is initially rotated during retraction of the bolt from its latched position, this easement freeing the levers from the clamping action of the blocking means.
ii. A lock as claimed in any of Claims 1 to 10, wherein the blocking means comprises a blocking lever that is pivotally mounted on the bolt or on an element connected to the bolt.
12. A lock as claimed in Claim ii when dependent on Claim 2, wherein the blocking lever is pivotally mounted to a portion of a lath of the bolt that forms a cover over said side edges of the levers.
13. A lock as claimed in Claim 12, wherein the cover is shaped so as not to impede pivotal movement of the levers during latching or unlatching of the bolt.
14. A lock as claimed in Claim 12 or Claim 13 when dependent on Claim 9, wherein the blocking lever rides along side edges of the levers during alignment of the gates and is urged by its spring-loading into a -11 -plane tangential to the barrel to clamp the levers between itself and the barrel.
15. A lock as claimed in Claim 2 or in any of Claims 3 to 14 when dependent on Claim 2, wherein the spring-loading for the blocking means comprises a torsion spring, a first leg of which is inserted in a cavity defined by the blocking means and a second leg of which is inserted in a cavity defined by the bolt or an element connected to the bolt.
i6. A lever tumbler lock substantially as described herein with reference to the accompanying drawings.