Patent ID: 7406847

Claim:
A cylinder lock comprising; a housing secured to a base body, a cylinder incorporated in the housing, a rotor having a tumbler capable of protruding and retracting to and from the cylinder and rotating in the cylinder when the tumbler is retracted from the cylinder by insertion of an authorized key, a connection member movable in the axial direction together with the cylinder and detachably fitted to the rotor, an unlocking member engaged to the connection member such that it can rotate integrally with the connection member and connected by way of a transmission member to a locking device, cam means disposed between the housing and the cylinder for moving the cylinder to the unlocking member and releasing the connection between the connection member and the rotor, and a spring for resiliently energizing the connection member in the direction fitting to the rotor, wherein an engaging portion that engages the rotor in the rotational direction only when the cylinder moves toward the unlocking member is provided to the cylinder, whereby the engaging portion provided to the cylinder and a rotor engaging protrusion formed to the rotor are engaged when an unauthorized key is withdrawn out at a position of a key insertion/withdrawn position.