A rekeyable lock cylinder with a cylinder body, an inner sleeve, and a plug assembly is provided. The plug assembly includes a plurality of key followers and a corresponding plurality of first racks and second racks disposed in carriers. The first racks correspond to operation of a user key and the second racks correspond to operation of a master key. As such, the lock cylinder is usable in a user/master key system. Disengaging either of the first or second racks from the key followers allows rekeying of the lock cylinder for the user key or the master key.

A lock core device based on matching the cross-sectional shape of a multiple key and a corresponding lock key, the lock contains a keyway, and the outer contour of the keyway is configured as a first section contour and a second section contour after superimposition, and its' a union outer contour. By adapting to existing keys with various cross-sectional profiles, the lock cylinder does not need to be manufactured separately according to the cross-sectional profile of the key, thus effectively reducing its manufacturing and inventory costs; A method for configuring a lock ball slot so that, in response to the deviation of the position of the teeth of the keys with different cross-sectional profiles, the teeth of the keys with different cross-sectional profiles can correspond to the lock ball slot for unlocking, thus ensuring stability and effectiveness during unlocking.

A lockset includes a lock cylinder, a lock casing, a first lock member, a second lock member and an anti-theft member. The lock cylinder includes a key hole and a first lock slot. The lock casing includes a second lock slot. The first lock member is accommodated in the first lock slot. The second lock member is accommodated in the second lock slot. The anti-theft member is sandwiched in between the first lock member and the second lock member. When two ends of the anti-theft member are respectively located in the first lock slot and the second lock slot, the lock cylinder and the lock casing are locked. When a contact surface between the anti-theft member and the first lock member or the second lock member is aligned with a rotation interface between the lock cylinder and the lock casing, the lock cylinder and the lock casing are unlocked.

A rekeyable lock cylinder with a cylinder body, an inner sleeve, and a plug assembly is provided. The plug assembly includes a plurality of key followers and a corresponding plurality of first racks and second racks disposed in carriers. The first racks correspond to operation of a user key and the second racks correspond to operation of a master key. As such, the lock cylinder is usable in a user/master key system. Disengaging either of the first or second racks from the key followers allows rekeying of the lock cylinder for the user key or the master key.

A door lock has a body (1) equipped with an internal chamber (2), an external chamber (3) and an interspace containing a mobile unit (4) having an internal cam (40) suitable for receiving and retaining a inner key end, and an external cam (41) adapted to receive and retain an outer key end. A plurality of springs (13) are positioned in the inner chamber (2) in passages parallel to the direction of insertion of the keys; pins (15) of a plurality of pins (15), loaded by respective springs (13) of said plurality of springs (13), are slidable in respective passages extending into the inner chamber (2), in the interspace and in the outer chamber (3) along a direction parallel to the key insertion direction. The external key can be modified to open locks of this type.