| 摘要 |
<p>A combination lock includes an over-center mechanism for moving the fence of the lock between two alternative positions with a snap action, the over-center mechanism comprising a lever arm secured to the fence and turning about a pivot on the bolt assembly and a stressed spring connected at one end to the lever arm and at the other end to a member capable of movement between two positions in relation to the bolt assembly. In one of the two positions the line of action of the spring passes to one side of the pivot of the lever arm and in the other position it passes to the other side of the pivot, so that when the member moves from one position to the other the lever arm is biased to move the fence from one alternative position to the other. The member is controlled by rotation of the dial of the lock in such a way that the fence remains in the first of its two positions for the majority of a revolution of the dial, being moved to the second position, in which it is capable of responding to the gates in the combination wheels, only for the remaining small fraction of a revolution. In a lock in which the dial is mounted on a shaft offset from that carrying the combination wheels, the member capable of movement between two positions is controlled by the shaft carrying the dial, preferably by means of a flat on the shaft.</p> |
