Utility lock and key

Abstract

Utility type locks have a lock body including a head and a shank, a plunger axially slidably received in the lock body, and locking balls forced outwardly from the shank or retracted within the shank depending upon the position of the plunger. A coil spring biases the plunger away from the head of the lock, and is dimensioned such that it must be fully compressed for the plunger to permit the balls to retract. The plunger face defines a shallow annular groove surrounding a center post which resists picking tools. A preload bushing surrounds the plunger with a deformable lip engaging a shoulder of the plunger. The preload bushing holds the utility lock open with the balls retracted, and application of force to the plunger deforms the lip to release the plunger. A key for the lock comprises a finger member terminating in a plurality of individual fingers surrounding a spreader member having an enlarged end, and means for incrementally moving the spreader member to spread the fingers and thereafter moving the spreader member and fingers together. The spreader defines a central opening for matingly receiving the center post of the plunger face. In additional generations of the lock and key therefor, the center post and spreader member opening are both longer, wherein the keys for later generation locks open earlier generation locks and the keys for earlier generation locks will not open later generation locks. Permutations of the locks and keys are provided by altering the mating shapes of the center post and spreader member opening.