Multiple function plate tumbler-type cylinder lock mechanism

Abstract

A plate tumbler-type cylinder lock mechanism includes a plurality of longitudinal internal splines therearound adapted for receiving tumbler ends, means providing at least three internal circumferentially extending tumbler movement paths on the barrel and extending between one spline and another spline which is different for each path, a key plug assembly rotatable in the barrel and including a key plug and a plurality of spring-pressed plate tumblers mounted in the plug, the tumblers being mounted for reciprocal transverse movement upon insertion and withdrawal of a bitted key with opposite tumbler ends projecting alternately from opposite sides of the plug, certain tumblers being adapted to be projected outwardly with their ends in respective registering movement paths when a key is inserted, whereby such ends may travel in the movement paths when the plug is rotated, and means adjacent to at least one end of each movement path adapted for engagement with the tumbler end traveling in the path to prevent travel thereof beyond such end, whereby a plurality of different keys may be employed for rotating the plug assembly with each key rotating the assembly to a different limited extent, such keys each engaging a different one of the tumblers having an end registering with a movement path, to cause such end to project into the movement path and thereby limit rotation of the plug assembly.