Cylinder lock

Abstract

A cylinder lock for use in motor vehicles and elsewhere has a case for a rotatable and axially movable sleeve-like guide which receives a rotatable cylinder having a keyhole and being locked to the guide by tumblers when the key is withdrawn. A detent is installed between the case and the guide to normally prevent rotation of the guide except when the guide is acted upon by a large force which causes it to deactivate the detent as a result of certain axial movement of the guide and cylinder in the case. A clutch between the cylinder and a motion transmitting element for a bolt of the lock is engaged as long as the detent is operative but is disengaged not later than when the detent permits the guide to turn in the case. If the cylinder is rotated by an implement other than a fitting key, and the implement applies the large force, the detent is deactivated as a result of axial movement of the guide and cylinder relative to the case whereby the clutch is disengaged and the cylinder cannot turn the motion transmitting element and the locking bolt. The detent has one or more projections in an end face of the guide one or more complementary sockets in an end face of the case, and a spring which biases the end face of the guide toward the end face of the case.