Lock

A lock for a wing movable between respective open and closed positions relative to a frame comprising a casing, a bolt operable to extend from or to retract into said casing, an operating member arranged to be operable at one side of the wing, in use, to effect retraction of the bolt, first lock means arranged, in use, for operation at the other side of the wing, and blocking means operable from said one side of the wing, in use, to prevent operation of the operating member to retract the bolt, the arrangement being such that, in use, in a locked, closed position of the wing said bolt is extended and said blocking means, if operated, prevents retraction of the bolt by said operating member, operation of said first lock means both de-actuating said blocking means, if operated, and retracting the bolt wherein the blocking means can be actuated from said one side only of the wing to prevent operation of the operating member to retract the bolt, wherein the blocking means is operable to prevent operation of the operating member to retract the bolt by second lock means at said one side of the wing, wherein said second lock means is operable at said one side of the wing to de-actuate the blocking means, wherein the blocking means is an angularly moveable cam, wherein the cam is on a second member arranged for limited angular movement by operation of said operable second lock means at said one side of the wing, wherein said second member has first and second ends, and wherein an angularly movable plug of said second lock means has a part received in a recess at the first end of said second member with lost motion between said plug and said second member.

A lock for a wing movable between respective open and closed positions relative to a frame comprising a casing, a bolt operable to extend from or to retract into said casing, an operating member arranged to be operable at one side of the wing, in use, to effect retraction of the bolt, first lock means arranged, in use, for operation at the other side of the wing, and blocking means operable, in use, to prevent operation of the operating member to retract the bolt, the arrangement being such that, in use, in a locked, closed position of the wing said bolt is extended and said blocking means, if operated, prevents retraction of the bolt by said operating member, operation of said lock means de-actuating said blocking means, if operated,

• wherein the blocking means are operable from said one side only of the wing to prevent operation of the operating member to retract the bolt,
• wherein the blocking means are operable to prevent operation of the operating member to retract the bolt by second lock means at said one side of the wing,
• wherein said second lock means are operable at said one side of the wing to de-actuate the blocking means,
• wherein the blocking means is an angularly movable cam,
• wherein the cam is on a member arranged for limited angular movement by operation of said second lock means at said one side of the wing,
• wherein an angularly movable plug of said second lock means has a part received in a recess at one end of said member with lost motion between said plug and said member,
• wherein the key of said second lock means can be inserted into or withdrawn from said plug only when said plug is in a first position, angular movement of said plug in one direction from said first position to a second position operating said cam to block said operation of said operating member, with said plug then being angularly movable to said first position to take up said lost motion, and thereafter angular movement of said plug in the opposite direction from said first position to a third position de-activating said cam to remove said blocking, with the plug then being angularly movable to said first position to take up said lost motion.