Importance

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Abstract

A manipulation resistant combination lock includes a housing, a drive cam attached a drive shaft, a moveable bolt, a fence attached to a fence lever, and tumbler wheels. A fence lever is pivotally attached to the bolt, and has a nose portion engageable with a drive cam gate in the drive cam which is keyed to the drive shaft and includes two spaced multi-surface contact rollers of magnetically attractable material on opposite sides of the drive cam gate. Each contact roller has a plurality of non-identical surfaces which is uniquely radially positioned and oriented relative to the axis of rotation of each contact roller. A permanent magnet is mounted in the nose portion of the fence lever thereon to assert an attraction force which rotates the contact roller as the contact roller approaches the nose portion of the fence lever due to rotation of the drive cam. The nose portion physically contacts the contact roller and causes it to rotate to a new position of rotation in which a different surface of the roller is positioned to contact the nose during subsequent rotation of the cam, so as to defeat successful manipulation of the lock.

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First Claim