GB527971A - Improvements in and relating to door latches - Google Patents

Abstract

527,971. Latches. TAYLOR, J. W. March 18, 1939, No. 8731. [Class 44] Relates to latch mechanism of the kind in which the bolt is held in partly retracted position when the door is open, and is released by inward movement of the bolt on engaging the striking plate when the door is being closed, the bolt being then fully shot by its spring and deadlocked. The bolt 1, which may be cast, has an aperture la to receive a compression spring, not shown, and also has a bifurcated tail providing arms 2, 3, each having a terminal projection 11 and lateral cam surface 15. The symmetrical arrangement allows the bolt to be reversed for right or left-hand use, only the uppermost projection 11 and lowermost cam 15 being operative as described below. The follower which is biassed anticlockwise by spring 16 bearing against an arcuate projection 17 is rotatable clockwise by inside handle 8 or outside cylinder lock, not shown, and has an arm 9 co-operating with projection 11 on bolt arm 2 to retract the bolt, and an eccentric cam surface 7 terminating in a shoulder 14. Fig. 3 shows the bolt deadlocked by a lever 4, pivoted at 5, biassed to raised position by spring 6 and ending in a hook projection 13 engaging behind the end of arm 3. The projection is extended laterally so that cam 7 overlies the extension. In clockwise rotation of the follower, cam 7 depresses lever 4 and arm 9 then retracts the bolt so that bolt arm 3 rides over hook 13, when the bolt has been partly withdrawn, shoulder 14, which now projects below bolt arm 3, snaps past hook 13, by which its movement is prevented, so that the bolt, although capable of further retraction to release it from the keeper, cannot return to fully shot position, when the handle &c. is released. When the door is subsequently closed, the bolt is moved inwards by the striking plate, the lower cam 15 depressing lever 4 to disengage hook 13 from shoulder 14. Spring 16 then returns the follower to the position shown, and the bolt is shot by its spring and deadlocked by hook 13. Alternative dispositions of lever 4 are described. A thimble 25, rotatable by the outside cylinder lock, may retract the bolt by direct engagement with projection 17, but as shown, it rotates a second concentrically mounted member 26 with a projection 27 engaging projection 17. Rotation of member 26 in reverse direction brings its projection 27 into engagement with the opposite side of projection 17 and blocks the inside handle. Additional manually operated dead-locking means such as is described in Specification 524,590 may be provided.