Patent GB-850831-A (GB)
Title: Latches for doors
IPC: E05B63/20
Filed: 1957-11-11
Abstract: 850,831. Latch fastenings. LEGGE & CO. Ltd., J., and LEGGE, J. E. Nov. 7, 1958 [Nov. 11, 1957], No. 35011/57. Class 44. In a latch for doors of the kind wherein when the door is closed an auxiliary spring loaded bolt or slide 13 which normally shoots out with the main bolt 12 is pushed back and is retained in a retracted position by the striking plate or staple to allow a dogging lever 17 to take up automatically an operative position to prevent the main bolt being forced back by the insertion of an instrument between the fore end of the latch and the striking plate or staple, and in which the main bolt is adapted to be retracted by a followeroperated runner 14 with which it has a lost motion connection and which is adapted as the lost motion is taken up to move the dogging lever out of its locking-out position and so free the main bolt for retraction by continued follower operation of the runner, the dogging lever is pivoted about a vertical axis for swinging movement across the latch case 10 and is laterally spring-loaded towards its operative locking-out position in which its free end enters and engages a cut-out or recess 26 in the lath 18 of the main bolt and in that the dogging lever is normally held in its inoperative position clear of the cut-out or recess by a lateral cam or ramp 29 on the tail of the auxiliary bolt or slide whilst an oppositely directed lateral cam or ramp 25 on the followeroperated runner is adapted to disengage the dogging lever from the cut-out or recess as the lost motion between the main bolt and the runner is taken up during the initial part of the follower operation of the latter to retract the main bolt. The cut-out or recess 26 is in a longitudinal edge of the lath 18 and the runner has a laterally projecting longitudinal flange 24 flanking the said edge of the lath and terminating in the cam or ramp 25. The cam or ramp 25 crosses the lath edge at a position normally just forwardly of the cut-out or recess 26 and as the runner is moved to take up the lost motion between itself and the main bolt the cam or ramp engages the end of the dogging lever and moves it out of the cut-out or recess so that continued movement of the runner can retract the main bolt. The extent of the lost motion between the runner and the main bolt is determined by a stump 20 on the runner which engages a slot 19 in the lath 18. The runner is loaded by a spring 21 and rides in guides 22 of the latch case 10 the auxiliary bolt or slide 13 is loaded by a spring 27 and is guided by a fixed stump 28 in the case 10. When the door is open the dogging lever is held away from the cut-out or recess 26 by the cam or ramp 29 on the tail of the auxiliary bolt but as the door is closed the main bolt is first pushed back by engagement with the striking plate or staple so that the cut-out or recess travels rearwardly beyond the end of the dogging lever before the bolt or slide 13 starts to move; when the main bolt is shot out by its spring into its latching position the cut-out or recesses 26 is brought into register with the end of the dogging lever and since the bolt or slide 13 is held retracted by engagement with the striking plate or staple the end of the dogging lever enters the recess or cut-out 26 to lock out the main bolt. Both a knob operated follower 15 and a cylinder lock operated follower 16 are provided for retracting the runner 14. The main bolt 12 is symmetrical with respect to its longitudinal centre line so that it can be reversed in position for doors which open inwardly or outwardly and the lower edge of the lath 18 is formed with an alternative cut-out or recess 26x and an alternative slot 19x is provided corresponding to the slot 19. The auxiliary bolt or slide 13 has a chamfer on both sides so that it can function whether the door opens inwardly or outwardly.