The present invention generally relates to tumbler scrambling combination locks. More specifically, the present invention relates to manipulation proof combination locks.
It has long been recognized that combination locks, based on the operation of an articulated, spring biased fence lever, are liable to be tampered with by skilled manipulators. Examples of such combination locks are shown in U.S. Pat. Nos. 3,991,596; 4,722,207; 4,756,176; and others.
A number of solutions have been proposed to alleviate this problem. One common solution to render the locks "manipulation proof" is based on the idea of avoiding the sequential contact of the fence lever with the rotatable tumbler wheels, one at a time during dialing. Allowing the snapping of the lever into engagement with all of the tumbler wheels upon completion of the combination was indicative of the correct combination.
Various arrangements and mechanisms have thus been proposed to solve this problem. The proposed arrangements and mechanisms are, however, rather complicated in design. A need, therefore, exists for an improved tumbler scrambling combination lock which is manipulation proof.