Locks – Operating mechanism – Key
Reexamination Certificate
1999-03-03
2001-07-24
Gall, Lloyd A. (Department: 3627)
Locks
Operating mechanism
Key
C029S426400, C029S434000, C070S360000, C070S375000, C070S383000, C070S422000, C225S002000, C225S093000
Reexamination Certificate
active
06263713
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to cylinder locks having key operable tumblers. Cylinder locks have been widely used to secure doors and padlocks and in other applications. In certain applications, it is desirable that a single key fits a plurality of locks. For example in automotive applications, users may desire to have a single key that opens the doors, glove compartment and trunk that also operates the ignition. If one of the locks requires replacement at a later time, the replacement lock may require a new key for operation if the replacement lock is unable to be fitted to the original key.
U.S. Pat. No. 1,979,939 discloses a device and method for shearing projections of tumbler ends to fit a lock to a particular key. Spring loaded, wafer-like tumblers, having a length greater than the diameter of the plug of a lock, are inserted into the plug with the tumbler ends projecting axially beyond the plug. When a key is inserted in the keyway of the lock, the notches and cams on the blade of the key displace the tumblers and springs, projecting certain portions of the tumbler beyond the ends of the plug. A tool having two complementary cutters is used to shear the projected ends off the tumblers. When the key is removed and the plug is inserted in the shell, the springs are allowed to expand, forcing the tumblers to protrude into slots in the shell of the lock and preventing the rotation of the plug within the shell. As all of the tumblers are sheared together, a significant shearing force is required.
U.S. Pat. Nos. 5,697,239 and 5,735,153 disclose a method and apparatus for the manufacture of a pin tumbler cylinder lock with shearable assembly pins. The pins have a plurality of selectively weakened locations for an initial configuration of the lock corresponding to the shape of a notched key. The pins are biased radially into the plug of the lock by springs located in the lock shell. The pins can be sheared by the manufacturer or a locksmith, with the sheared portions of the pins functioning as the driver and the tumbler pins.
The disclosed methods and apparatus require the use of cutting tools or a significant shear force to fit the lock to a particular key. There is a need for a method of manufacture of a lock that provides greater case in keying or rekeying locks without comprising the security of the lock.
SUMMARY OF THE INVENTION
The present invention is related to a lock having a shell, a plug mounted in the shell and a plurality of tumblers that extend into the shell. The tumblers have a plurality of grooves notched on both ends such that when a key is inserted in the lock, the key lifts the tumblers according to the notches on the key, aligning the grooves on the tumblers. The shell and plug are forced axially toward each other shearing the tumblers along the aligned grooves to fit the lock to the key. The present invention is further directed to a shell and plug configuration that reduces the total shearing force required for shearing the tumblers and to a method of manufacturing a lock having shearable tumblers for a preselected key.
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Calfee Halter & Griswold LLP
Gall Lloyd A.
Master Lock Company
LandOfFree
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