Combination lock

Abstract

 A combination lock of the kind having an assembly (W) of gated tumbler wheels rotated by a lock dial shaft (114), and a fence lever (116) biased by a spring (120) towards an operative position in which, when the tumbler wheels are in a predetermined alignment, a nose (116') of the force lever (116) engages a slot (118') in a drive disc (118) to enable the bolt (124) to be withdrawn. A wire spring (140) is connected to the fence lever (116) and to a cam plate (130) slidable between a non-displaced position (Fig. 3) and a displaced position (Fig. 4). In the non-displaced position, the wire spring (140) exerts a force on the fence lever (116) which overcomes the force of its spring (120), and so holds the nose (116') of the fence lever (116) out of engagement with the drive disc (118). In the displaced position of the cam plate (130), the tension on the wire spring (140) is relieved, so that its force no longer overcomes that of the spring (120), which moves the fence lever (116) to its operative position. The cam plate (130) is held in the non-displaced position by a cam disc (126) associated with the drive disc (118), except for a brief period once during each revolution of the disc, when a cut-away segment (126') of the cam disc (126) engages a straight side (132") of an opening (132) in the cam disc. The nose (116') of the fence lever (116) therefore engages the drive disc (118) only momentarily once in each revolution of the disc, so preventing tampering of the lock by detecting engagements of the nose of the fence lever with the slot in the drive disc.

Description

[0001] This invention relates to combination locks.

[0002] More particularly, the invention relates to tumbler scrambling manipulation combination locks, of the kind including a housing with a lock dial shaft rotatably mounted therein, a lock bolt movable in the housing, a fence lever coupled to the lock bolt, a spring means constantly urging the fence lever into an operative lock bolt displacing position thereof, an assembly of gated tumbler wheels rotatable by the lock dial shaft, and a slotted disc mounted on the tumbler wheel assembly, the fence lever being adapted to close against the said gated tumbler wheels when in alignment therewith and thereby enter its operative position to enable the displacement of the lock bolt by the fence lever.

[0003] It has been recognised long ago that combination locks of this kind are liable to be tampered with by skilled manipulators, see for example Australian Patent No. 159,448 and United States Patent Nos. 3,991,596, 4,722,207 and 4,756,176.

[0004] The conceptually common solution proposed for rendering such locks "manipulation proof" was based on the idea of avoiding the sequential contact of the fence lever with the rotatable tumbler wheels, one at a time during dialling, which was thus indicative of the correct combination, namely allowing the snapping of the lever into engagement with all of the tumbler wheels upon completion of the combination.

[0005] Various arrangements and mechanisms have thus been proposed, however of rather complicated design.

[0006] It is an object of the invention to provide a more simple and straightforward solution to the above described problem.

[0007] It is a further object of the invention to provide means adapted to be easily installed in most types of commercially available ordinary combination locks thereby rendering same manipulation protected.

[0008] In accordance with this invention, there is provided a displaceable spring cam plate coupled to a cam disc associated with the slotted disc so that on every revolution of the cam disc the cam plate becomes displaced a short distance, a second spring means coupled between the fence lever and the cam plate, effective, in the non-displaced position of the plate, to restrain the pivoted movement of the fence lever under the biasing of the first spring means, and, in the displaced position of the plate, to allow movement of the fence lever into the operative position thereof.

[0009] The invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a plan view of a conventional, non-manipulation proof combination lock (with its cover removed);

Fig. 2 shows a schematic, three-dimensional, exploded view of the main components of a lock in accordance with the invention;

Fig. 3 is a plan view of a lock incorporating the components of Fig. 2 in a non-operative position; and

Fig. 4 shows the lock of Fig. 3 in the operative position thereof.

[0010] Referring to Fig. 1 there is shown a conventional combination lock mechanism generally denoted 10 disposed within a housing 12. As is well known, the mechanism 10 comprises a plurality of tumbler wheels, generally denoted W (the upper, exposed tumbler wheel is designated W1), axially mounted and coupled to a lock shaft 14. Every tumbler wheel is provided with a recess or gate G (for example the tumbler wheel W1 comprises a gate G1). Upon completion of the dialling of the pre-set combination by lock shaft 14, the gates G of all wheels become aligned, so that fence arm feeler pin 16'' (shown only from above) can enter into the space formed by the gates G and, thereby, nose 16' of the pivoted, spring-biased fence lever 16 enters cam slot 18' of driver disc 18. A spring 20 is coupled to the fence lever 16 for normally urging the fence lever 16 into its active, gates penetrating position. The driver disc 18 is keyed to the lock shaft 14 by key 22. Turning the lock shaft 14 from the outside of the door by the dial knob (not shown) causes the withdrawal of lock bolt 24 to open the door. All these features of construction and operation are well-known and need not be further described in the present context.

[0011] Turning now to Fig. 2, there is shown the plurality of tumbler wheels W of a combination lock, each provided with its respective gates G. A driver disc 118 provided according to the present invention is of a little smaller diameter than the disc 18 of the conventional lock mechanism of Fig. 1. Furthermore, the disc 118 is formed with an upwards protruding, concentric cam disc 126 (which may conveniently be integrally made with the driver disc 118). The cam disc 126 is circular except for a segment 126' which is removed or cut away as shown. The location of the segment 126' relative to the fence lever nose engaging recess 118' is preset according to a functional consideration explained below.

[0012] The fence lever 116 having the conventional fence feeler pin 116'' further comprises a tiny bore 128 for a purpose to be described further below.

[0013] Further provided is a cam spring plate generally denoted 130. The cam spring plate comprises a generally U-shaped opening 132, configured at one side with a radius 132' somewhat larger than that of the cam disc 126, and at its other side with a linear surface 132''. The cam spring plate 130 further comprises at its other end U-shaped cut-off 134 configured to slidingly receive between its legs 134a and 134b the head portion of the conventional bolt 136.

[0014] An opening 138 which is preferably but not necessarily elongated, is provided in the cam spring plate 130 at a portion 139 thereof, which extends in the direction of the respective housing wall (see Fig. 4), and comprises a linear surface 139'.

[0015] Finally, there is provided according to the present invention a profiled wire spring 140 comprising four portion 140a, 140b, 140c and 140d which are bent away relative to each other as shown. In the assembled state, the portion 140a is inserted from above into the opening 128 of the fence lever 116 and the portion 140d, in turn, is inserted from below into the opening 138 of the cam spring plate 130.

[0016] The operation of the improved lock 110 will now be described, with reference to Figs. 3 and 4.

[0017] In the assembled state of the lock the tension of the wire spring 140 is such that in one position of the plate 130 relative to the fence lever 116 (as explained below), the spring 140 overcomes the force of the spring 120, and in another position of the plate the spring 120 overcomes the attraction of the spring 140.

[0018] In the assembled state of the lock 110, the cam spring plate 130 is seated over both the driver disc 118 and the fence lever 116. The cam disc 126 freely fits into the opening 132, and the bolt 136 into the cut-out 134. The spring 140 is installed as described above so that in the depicted, inoperative position of the lock, the spring is in tension, biasing the portion 140b to more in the clockwise direction (as seen in Figure 3), so that the lever 116 is constantly pushed away from the tumbler wheels engaging position, i.e. neutralizing the force of the spring 120. Therefore, for as long as the plate 130 is stationary, no contact will be made between the lever 116 and the driving disc 118. During rotation of the driver disc 118 (and of the cam disc 126) by the dial shaft 114 in the conventional manner, the cam plate 130 remains in fact stationery, except for when the cut-away segment 126' becomes operative - see Fig. 4 - namely once on every full rotation. At such point, the displacement of the plate 130 by a small distance (to the right) under the influence of the spring 140 relieves some of the tension of the spring, so that it no longer overcomes the force of the spring 120. The spring 120 therefore moves the lever 116 towards its operative position allowing momentary contact of the fence feeler pin 116'' against the rim of the tumbler W or of the nose 116' into the engaging recess 118', if the proper combination dialling has been completed.

[0019] Now, as is known, the manipulation tampering method is based on the fact that, in the known lock, the nose 16' of the fence lever 16 (Fig. 1) becomes released from the outer contour of the driver disc 18, to somewhat enter into and then withdraw from the slot 18' in a cyclic fashion, and that the skilled manipulator is able to detect these two occurrences ("contact points").

[0020] With the arrangement of the present invention, the nose 116' is held out of contact with the driver disc 118' except for the momentary contact area during each revolution of the disc. It is thus clear that due to the operation of the spring cam plate 130, such tempering method is completely obviated.

[0021] Once the complete alignment of the gates G is achieved according to the normal dialling procedure, the dial shaft must be rotated in a reverse direction (from the "0" position). The nose portion 116' will become engaged by the cam slot 118', as shown in Figure 4, and the lock bolt 124 may thus be displaced into its unlocked, withdrawn position , Fig. 4.

[0022] The application of the present invention is extremely simple and low-cost. It involves the addition of only two additional components (cam spring plate 130 and spring 140) and minor alteration of the driver disc 18; the general design of the convention lock is not upset whatsoever, which renders the incorporation of the extra parts in most existing models of non-manipulation-proof combination locks fairly convenient.

[0023] Those skilled in the art will readily appreciate that various changes and modifications may be applied to the heretofore described embodiment of the invention.

Claims

1. A combination lock including a housing (112) with a lock dial shaft (114) rotatably mounted therein, a lock bolt (124) movable in the housing (112), a fence lever (116) coupled to the lock bolt (124), a spring means (120) constantly urging the fence lever (116) into an operative, lock bolt displacing position thereof, an assembly (W) of gated tumbler wheels (W1) rotatable by the lock dial shaft (114), and a slotted disc (118') mounted on the tumbler wheel assembly (W), the fence lever (116) being adapted to close against the said gated tumbler wheels (W) when in alignment therewith and thereby enter its operative position to enable the displacement of the lock bolt (124) by the fence lever (116), characterised in that there are provided a displaceable spring cam plate (130) coupled to a cam disc (126) associated with the slotted disc (118') so that on every revolution of the cam disc (126) the cam plate (130) becomes displaced a short distance, a second spring means (140) coupled between the fence lever (116) and the cam plate (130), effective, in the non-displaced position of the plate (130), to restrain the pivoted movement of the said fence lever (116) under the biasing of the first spring means (120), and in the displaced position of the plate, to allow the said pivoted movement of the fence lever (120) into the operative position thereof.

2. The combination lock as claimed in Claim 1 wherein the said second spring means (140) is a wire spring.

3. The combination lock as claimed in Claim 2, in which the wire spring (140) has a first portion (140b) connected at one end (140a) to the fence lever (116) and a second portion (140c) connected at one end to the cam plate (130), the two portions (140b, 140c) being arranged at an angle to one another so that the spring (140) is in tension when the cam plate (130) is in the non-displaced position with the first portion (140b) biased to exert a force on the fence lever (116) which overcomes the force exerted by the first spring means 9120), the tension of the spring (140) being at least partially relieved when the cam plate (130) is in the displaced position so that the force exerted by the first spring means (120) overcomes the force exerted on the fence lever (116) by the wire spring (140).

4. The combination lock as claimed in Claim 2 or Claim 3 wherein the spring cam plate (130) is coupled to the cam disc (126) by an opening (132) of generally closed U-shape, the cam disc (126) being circular with a removed segment portion (126') engageable with the closed side (132'') of the opening (132).

Drawing