GB1220383A - Lock mechanism - Google Patents

Abstract

1,220,383. Locks. GENERAL ALARM CORP. 11 March, 1968 [15 March, 1967], No. 11821/68. Heading E2A. Lock mechanism comprises cylinder means, a plurality of key slotted locking plugs supported for separate and independent rotation therein and arranged so that access to a second plug is obtainable only via the key slot of a first plug, each of the plugs being lockable against rotation and being unlockable for simultaneous rotation by placement of a proper key within their respective slots, and bolt-actuating means operable only by simultaneous rotation of all the plugs. In the arrangement according to Figs. 1, 2, a lock mechanism comprises plugs 12, 14, 15 each having a key slot 30 and rotatably mounted in a cylinder closed by an end plate 24 and an escutcheon 21. A hardened steel spacer 20 is located between the plug 12 and the escutcheon 21. Each of the plugs is provided with bores 22 for pin tumblers which co-operate with spring loaded tumblers in the cylinder. A bolt operating member 27 is attached to the plug 15, the arrangement being such that all plugs must be operated simultaneously by a single key to free the bolt. In another arrangement, Figs. 3, 5 and 6, comprising two plugs 44, 54 rotatable in cylinders 41, 51 arranged in tandem, a switch 75 for actuating an alarm, is located between adjacent ends of the cylinders and is operated to a closed condition by a cam 61 attached to the plug 44 whenever that plug is moved in either direction from the position in which a follower 76 on the switch is prevented from engagement with a recess 66 on the cam 61 and with a recess 71 of a second cam 69. A pin and slot connection 82, 84 between adjacent end faces of the plugs prevents operation of plug 54 unless plug 44 is also operated. A coaxial sleeve 80 and recess 81 prevents ingress of any fluid which might be used to interfere with the cam or switch operation. In a further arrangement, Figs. 8 and 11 the switch includes a spring- loaded contact 106 in a bore lined with an insulating sleeve 109. The contact 106 cooperated with a contact 112 mounted in an insulated segment 115 of a disc positioned in a slot 113 in the lock cylinder. The segment includes an extension 116 and engages at its lower end, a ball 119. The arrangement is such that relative movement of the lock plugs 92, 94 moves the segment 115 so as to separate the contacts 106, 112 to activate an alarm, the plugs being provided with depressions 125, 126 and 124 respectively beneath the ball 119. Mating depressions 129 at the abutting ends of the plugs constitutes a depression into which the ball drops if the plugs are rotated through 180 degrees by unauthorised means prior to retraction of the bolt. In another arrangement Figs. 15 16 (not shown), the adjacent faces of the plugs are recessed for a ball (144) loaded by a spring plunger which prevents relative rotation of the plugs of the lock. (For Figures see next page)