Patent GB-758877-A (GB)
Title: Locks
IPC: E05B21/00
Filed: 1954-05-19
Abstract: 758,877. Locks. PARKES & SONS, Ltd., J., FRYER, E. C., and BUTTER, F. J. April 26, 1955 [May 19, 1954], No. 14636/54. Class 44. Relates to locks of the kind in which a key acts to lift security levers or sliders to release a bolt or bolt-actuating member, before the key can directly move the latter to either of its extreme positions. According to the invention, the lock is provided with oppositely disposed sets of levers or sliders operable respectively by bits of different form of a two-bitted key and having overlapped portions of reduced thickness which carry slots for engagement by a toe or projection on a bell-crank lever, the arrangement being such that when the two sets of levers or sliders have been lifted correctly in opposite directions by the respective bits of the key, slots in the overlapping portions of all the levers or sliders of the two sets coincide to admit the toe or projection of the bell-crank lever when the latter is actuated bv an abutment or abutments on the bolt or bolt-actuating member or a part which moves therewith. As shown, in which a bolt 10 is slidably engaged with stumps 15, 16 in a lock case 17, two sets of sliders A and Bare guided respectively by the stump 16 and an additional stump 21, and by the stump 15 and an additional stump 22, the sliders of one set being spring-loaded towards the sliders of the other set. The sliders of both sets are provided with extensions 25 and 26 respectively, the extension of each slider being half the thickness of the slider body and the extensions being interdigitated so that the total thickness of the eight slider extensions is equivalent to that of four sliders. The extensions are engaged by a toe 27 of a spring-loaded lever 28 pivoted on the stump 21, the lever 28 being engaged by a pin 30 on a member 31 rigid with the bolt 10, the arrangement being such that when slots 35, 36 in the lever extensions are aligned by the bits of a two-bitted lock key, the pin 30 moves the toe 27 into engagement with the slots as the bolt is thrown by rotation of the key, until the pin 30 engages a surface 34 of the lever 28 to permit the toe 27 of the latter to disengage from the extension slots and the sliders to return to the positions shown. Master keying may be provided by providing additional slots in the overlapping portions of certain or all of the sliders. The set of sliders A associated with the bolt 10 for operating by the same key bit are arranged to require a larger key bit than that required to operate the set of sliders B. A forked rocker member prevents insertion of the key wrong way round by masking the appropriate end of the key slot. Alternatively the bolt lath may be provided with two slot-masking extensions. In another arrangement, Figs. 3 and 4 (not shown), the mechanism is displaced by 90 degrees, to bring the key hole to a vertical position, the bolt being actuated by a member which slides vertically and imparts sliding movement to the bolt by means of a bell-crank lever pivoted in the lock case. The invention is applicable to a lock having pivoted levers and the toe 27 of the lever 28 may be replaced by a member carried by the lever and guided for rectilinear movement. Specification 661,501 is referred to.