Hierarchical cylinder lock and key system

In a hierarchical system of locks and keys including at least a first lock and a second lock which are different from each other, and at least a first key and a second key which are different from each other, the first key operating less than the total number of locks and the second key operating more locks than the first key, the locks being cylinder-type locks having tumbler pins which, when operated with the proper keys, are positioned to permit operation of the cylinder, with improvements in the system comprising:

• said first and second locks each having at least one tumbler pin with an offset tip surface shaped to slope from adjacent one side surface of the tumbler pin to adjacent an opposite side surface of the tumbler pin to provide a single slanting contact surface for cooperating with a complementarily bitted surface formed on the first and second keys;
• the first and second keys each having at least one bitting surface shaped substantially complementarily to the shaped-tip of the tumbler pin of said first and second locks, such that the bitting surface of each key cooperates with the single slanting contact surface of the tumbler pin of each lock to cause the tumbler pin to rotate about its axis and be positioned to a proper unlocking elevation relative a shear line of the first and second locks;
• the first lock being operable by either the first key or the second key with the bitting surface of the key rotating the tumbler pin with a single slanting contact surface to the proper unlocking position at which the tumbler pin is elevated to clear a shear line of the first lock such that the cylinder thereof may be operated;
• the second lock being operable by one of the first and second keys but not both keys, the second lock having means for determining whether at least one additional tumbler pin therein is properly positioned rotationally so as to permit the second lock to be operated, wherein the bitting surface of the key which operates the second lock rotates said at least one additional tumbler pin therein to a proper unlocking position at which said at least one additional tumbler pin is elevated to clear a shear line of the second lock and is positioned rotationally so as to permit operation of the cylinder of the second lock, and the key which does not operate the second lock does not rotate said at least one additional tumbler pin therein to the proper rotational position.