Lock mechanism

Claim 1

A lock mechanism comprising (a) a housing (3) having a bore therein, (b) a sleeve (2) located within said bore, (c) means (9) for indexing said sleeve within said bore at a selected angular disposition in relation to said sleeve, (d) a rotor (1) which is rotatably mounted and axially slidable within said sleeve, said rotor having a longitudinally extending key slot, (e) pistons slidable within bores in said sleeve and rotor between a first position where said sleeve and rotor are coupled together for simultaneous rotation and a second position on insertion of an appropriate key in said slot where said sleeve and rotor are uncoupled, and (f) an operating element (18) for effecting movement of mechanism to be controlled, said rotor (1) being movable axially from a first position where it is disengaged from said operating element and a second position where it drivably engages said operating element, (g) a piston element axially movable between a first rest position and second position within said casing engaging an end face of the rotor opposite to the key entry slot, and (h) resilient return means for urging said piston element against said end face of the rotor, said piston element and said casing comprising cooperating means for angular coupling of the piston element and casing and said piston element and said operating element comprising cooperating means for angular coupling of the piston element and the operating element when said piston element is in its rest position, said cooperating means for coupling the piston element with the operating element being disengaged when said piston element is moved to its second position on entry of said appropriate key.