| 摘要 |
The present invention comprises an improvement in a lock of the type having a cylinder with an associated internal cavity, a key operated lock plug rotatably mounted in the cylinder cavity and a coupling mounted for rotation relative to the lock cylinder for association with a lock member that is movable upon rotation of the coupling between locked and open states. Shoulders are provided on the plug and coupling and upon effecting relative rotation between the coupling and plug through a change key the shoulders can be selectively brought into interfering, facing relationship to prohibit withdrawal of the plug or misaligned to allow removal of the plug. An access key, that is longer than the change key, in a fully seated position in the plug keyway, extends into the coupling opening and is thereby keyed to the coupling so that turning of the control key directly operates the coupling.
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