Patent ID: 7181941
Filing Date: 2007-02-27
Classification: E05B,Y10T

Abstract:
1. A lock system comprising: a key comprising a bow portion and a blade which longitudinally extends from said bow portion to a tip, said blade having a pair of spaced parallel top and bottom edges which are interconnected by opposed side faces, said blade being provided with surface irregularities which define the key bitting, and a rigid camming projection transversely extending from one edge; a shell having a longitudinal axis, said shell including a first cylindrical portion having a first diameter, at least a first row of primary pin tumbler receiving chambers being located in said first portion, said shell having a second cylindrical portion which is also coaxial with said first portion, said second portion having a second diameter which is greater than said first diameter, an auxiliary pin tumbler receiving chamber being provided in said second portion; a plug rotatably mounted in said shell, said plug having a face and further having a longitudinally extending keyway formed therein, said keyway having a first portion in registration with said shell first portion and a second portion in registration with said shell second portion, said keyway second portion opening through said face and extending into registration with said shell second portion, said plug also having first and second cylindrical portions of different diameter which are generally complementary to and received in said shell first and second portions, said plug defining at least a first row of primary pin tumbler receiving chambers in said first portion thereof, said first row of primary pin tumbler receiving chambers being alignable with said shell primary pin tumbler receiving chambers, said plug defining an auxiliary pin tumbler receiving chamber in said second portion thereof, said auxiliary pin tumbler receiving chamber being alignable with said shell auxiliary pin tumbler receiving chamber, first and second shear lines respectively being defined between said shell and said plug first and second portions; and pin tumblers reciprocally mounted in said receiving chambers, said pin tumblers each including at least a bottom pin and a driver pin, said pin tumblers including biasing means for urging a pin of each of said pin tumblers to a position of bridging a shear line when a key is not present in said keyway, insertion of a properly bitted key into the keyway displacing said pin tumbler against associated biasing means whereby the interface between the bottom and driver pins is located on a shear line, the underside of the auxiliary bottom pin defining a cavity, the displacement of the pin tumbler positioned in said auxiliary pin tumbler receiving chamber being caused by contact with the camming projection of the inserting key such that the auxiliary bottom tumbler rises along the projection and the proper shear line between the auxiliary bottom pin and the auxiliary driver pin is established when the projection enters and remains in the cavity to form a detent; whereby rotation of said plug relative to said shell is permitted by said pin tumbler displacement, but withdrawal of said key subsequent to said relative rotation is prevented by the detent formed between the cavity of the auxiliary bottom pin and the projection.