Importance

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Abstract

A combination lock includes various features that make the lock manipulation-resistant. The lock has a rocker arm with a curved underside section that contacts a roller on a cam that rotates when the lock dial is rotated. The smooth curve and an angled contact portion on the rocker arm causes the force applied to the rocker arm by the roller to be gradual rather than abrupt, ensuring that the contact point between the rocker arm and the roller is unpredictable. The lock may also include various spring-biased relocking devices that are biased away from the travel path of the bolt when the back cover is attached to the housing. The biasing force in the relocking device causes the device to move into the travel path of the bolt when the back cover is displaced or removed, preventing the bolt from moving to an unlocked position. The lock may also include a toothed washer having a trapezoidal tooth and a corresponding trapezoidal notch in a tube in the lock housing to eliminate transfer of rotation from one wheel to another. The trapezoidal shapes eliminate air gaps between the tooth and the notch, tightening the dial span of the lock.

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First Claim