Pick-resistant axial split-pin tumbler-type lock mechanism

Abstract

An axial split-pin tumbler-type lock mechanism includes a rotatable operating part and a stationary part, which adjoin at an interfacial plane. Tumblers each including a driver element and a follower element are mounted in bores in the parts. The bores meet in alignment at the interfacial plane, and the tumblers are movable back and forth in the aligned bores. When the joints between the tumbler elements coincide with the interfacial plane upon insertion of a key, the operating part may be rotated by means of the key, to accomplish a desired function. The lock mechanism is provided with structure making is resistant to picking, including adjacent pairs of aligned bores in longitudinal communication with each other to permit sidewise engagement of an element of a tumbler in one pair with an element of a tumbler in the remaining pair, and mechanical interlock means on a side surface of an element of a tumbler disposed in each of the adjacent pairs of aligned bores, the interlock means on respective elements being adapted for engagement with each other to interengage the elements, whereby when one of the latter tumbler elements bridges the interfacial plane, application of picking torque to the operating part tends to move the elements laterally relative to each other to cause such interengagement thereof and thereby constrain the elements to move together as a unit in the axial direction.