Key-exchangeable lock

A key-exchangeable lock including a lock housing, and within said lock housing a running plate provided with a fence, a locking bar longitudinally movable with said running plate and a plurality of tumblers adapted to cooperate with said fence so as to allow, in a predetermined unlocking position, the running plate to be retracted, wherein said tumblers are moved to said unlocking position and said running plate is retracted to its unlock position by rotation of a prescribed key;

• and wherein said prescribed key is exchangeable with another prescribed key by displacing the rotational axes of said tumblers, characterized in that
• said tumblers and running plate are formed with openings;
• a conversion shaft rotatably supported in the lock housing extends through said openings formed in said tumblers and running plate;
• said conversion shaft is provided with an eccentric portion adapted to be pressed against an end surface of said opening formed in said tumblers to fix the rotational axes of said tumblers when said conversion shaft occupies a predetermined fixed position but to release said rotational axes of the tumblers when said conversion shaft occupies a predetermined conversion position, a stop piece adapted to cooperate with said opening of the running plate so as alternatively to block and to allow rotation of said conversion shaft and a locking piece adapted to cooperate with another locking piece provided on a key guiding member rotatably supporting said prescribed key so as alternatively to block and to allow rotation of the conversion shaft;
• said stop piece engages one edge of the opening formed in said running plate to hold said conversion shaft at its fixed position when the running plate occupies its lock position and said stop piece is disengaged from said opening in the running plate to allow rotation of the conversion shaft;
• when the running plate occupies its unlocking position;
• and
• when the running plate occupies its unlocking position while the prescribed key occupies its locking position, said locking piece is engaged with said another locking piece of said key guiding member to hold the conversion shaft at its conversion position and said stop piece is engaged with one edge of the opening formed in the running plate to block advancement of said running plate.

A key interchangeable lock mechanism comprising a slide plate longitudinally movable between advanced and retracted positions, a lock bar longitudinally movable with said slide plate, a fence carried by and movable with said slide plate, a plurality of transversely spaced rockable tumblers having, each tumbler at its outer end a gate movable into and out of longitudinal registry with said fence and at its inner end a plurality of vertically spaced pivot points, a fixed fulcrum member releasably engaged with a selected pivot point of each of said tumblers and a key guide member for supporting a key for rotation into engagement with said tumblers to rock said tumblers about said fulcrum member, said lock being characterized by:

• conversion means movable between retracted and advanced positions for longitudinally shifting said tumblers between advanced positions with a pivot point of each of said tumblers engaging said fixed fulcrum member and retracted positions with said pivot points being longitudinally disengaged from said fixed fulcrum member;
• means for disabling said conversion means from longitudinally retracting said tumblers from rocking engagement with said fulcrum member when said slide plate is in advance of its fully retracted position;
• said tumblers in their retracted positions being rockable about said fence to vertically move said disengaged pivot points to positions responsive to the shape of a key engaging and rotatable with said key guide, and upon said tumblers being longitudinally advanced by said conversion means said key determined tumbler pivot points engaged said fulcrum member.