| 摘要 |
<p>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a nose (116') of the force lever (116) engages a slot (118') in a drive disc (118) to enable the bolt (124) to be withdrawn.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. <IMAGE></p> |
