US Patent 7533550 Rapid-change lock

A changeable lock assembly suitable for re-keying a lock without disassembly of the lock. The assembly includes a housing having a bore therein, and a plug rotatably mounted in the bore. The plug includes a longitudinal axis and a keyway. The keyway is adapted to receive at least a first user key and a second user key. The lock further includes a change member movable within the lock between a first position to a second position. The change member can move solely in response to operation of the second key. Thus, when the change member is in the first position, the first key operates the lock, and when the change member is in the second position, the first key does not operate the lock. The lock assembly can also employ a change tool that, when inserted into a change slot, can move a change ball from the second position back to the first position.