Abstract: A key with a blade portion which is bitted for actuating the tumbler pins of a cylinder lock has improved cross-sectional strength despite deep cut bittings which extend well into the thickness of the blade. The key is generally flat with upper and lower surfaces and opposite short side edges. The bittings are cut across at least one of the surfaces so as to extend arcuately through the thickness of the blade and one of the side edges. The volume of key blank material which is adjacent the deep cut bittings after the key is cut is substantially more than conventional keys and provides the key blade with increased strength to prevent breakage. The bittings are cut into the key blade by a rotary cutter wheel which is dimensioned to form an arcuate bitting surface rather than a flat surface.

Abstract: A hierarchical lock and key system includes a plurality of locks and keys wherein each key is provided with at least one unique bitting surface that engages a complementarily shaped tumbler pin tip to cause the tumbler pin to rotate and be positioned at a predetermined location. In one system, one key is provided with bittings to rotate the tumbler pins in a lock that is able to determine the rotational position of the tumbler pins. The one key may also operate a lock which does not determine the rotational position of the tumbler pins by positioning a tumbler pin at its proper elevation in the cylinder. Another key which has at least one different bitting from the one key will operate the latter lock (in which the tumblers do not have to be rotated). However, the other key will not operate the former lock because the bitting does not properly rotate the tumbler pin to its unlocking location.

Abstract: A hierarchical lock and key system includes a plurality of locks and keys wherein each key is provided with at least one unique bitting surface that engages a complementarily shaped tumbler pin tip to cause the tumbler pin to rotate and be positioned at a predetermined location. In one system, one key is provided with bittings to rotate the tumbler pins in a lock that is able to determine the rotational position of the tumbler pins. The one key may also operate a lock which does not determine the rotational position of the tumbler pins by positioning a tumbler pin at its proper elevation in the cylinder. Another key which has at least one different bitting from the one key will operate the latter lock (in which the tumblers do not have to be rotated). However, the other key will not operate the former lock because the bitting does not, properly rotate the tumbler pin to its unlocking location.

Abstract: A tumbler pin tip and key surface are configured so that when engaged, the tumbler pin tip fully and precisely seats in the key bitting, and thus is rotationally positioned at a predetermined location. The contacting surfaces are generally sloped from one edge of the tumbler (and key surface) to the other in tapered form and the sloping surface may be flat, concave, convex or a combination as disclosed.

Abstract: A cylinder lock is capable of providing a changeable keyway by means of elongated warding members which are insertable into a keyway access slot which has a cross-sectional configuration larger than for a desired key. There may be one or more warding members which are insertable into the plug and extend the length of the keyway access lot to define the cross-sectional area of a desired key.

Abstract: A dropbolt lock having a pair of dropbolts movable between knuckles is assembled on a formed steel assembly plate which is attached to a base plate, the assembly plate providing the spaced knuckles. A cam operator operates the dropbolts between true dead lock positions. On the inside of the lock, a cylinder lock or a thumb turn may be assembled by a single screw. The cover is provided with attachment screws which are concealed by the locking bolt when in locked position.