Locks – Operating mechanism – Key
Patent
1980-03-24
1981-06-30
Wolfe, Robert L.
Locks
Operating mechanism
Key
70375, E05B 3508, E05B 904
Patent
active
042755778
ABSTRACT:
A lock arrangement is provided which may be actuated by two different keys. A master key may be used to lock and unlock the device. A subordinate key may be used to lock the device only. The lock is of the pin-tumbler type in which the lock's rotatable core plug includes a shallow, longitudinal step groove cut into the top of the core plug. The subordinate key is identical to the master key except that one or more of the subordinate key's bittings is cut deeper than the corresponding groove or grooves on the master key, the additional depth corresponding to the depth of the step. When the master key is inserted in the keyway in the core plug, the pin tumblers are raised in the normal fashion so that the tops of the pins are even with the shear line between the core plug and the cylinder. The core plug may then be rotated in either direction. When the subordinate key is inserted in the core plug keyway, one or more of the tumbler pins is raised so that the top of the pins is located at a point below the shear line, but at or slightly above the level of the bottom of the step groove. In this manner the core plug may only be turned in one direction so as to be able to lock, but not unlock, the device.
REFERENCES:
patent: 1598523 (1922-08-01), Heyer
patent: 1650564 (1927-11-01), Wolff
patent: 1685022 (1928-09-01), Clearer
patent: 1788834 (1931-01-01), Hurd
patent: 2009640 (1935-07-01), Stone
patent: 3771340 (1973-11-01), Krakstrom
patent: 3875773 (1975-04-01), Thimot
patent: 3973421 (1976-08-01), Patriquin
patent: 4075879 (1978-02-01), Christopher
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