Patent GB-210834-A (GB)
Title: Improvements in and relating to locks for doors and the like
IPC: E05B63/20
Filed: 1922-11-02
Abstract: 210,834. Johnston, G. W. P. Nov. 2, 1922. Latches, sliding. - In a fastening for doors, more particularly on railway, motor &c. coaches, in which a catch which holds the latch in an intermediate position is released when the door is slammed so as to allow the latch to be fully shot by its spring, the catch is controlled by a spring which acts to complete the movement of said catch in either direction and to hold it either engaged or disengaged. The spring-pressed latch a, Fig. 1, is held in an intermediate position when the door is open by a pivoted catch l having a projection p with a knife-edge q which is acted on by the V-shaped part of a spring r. When the latch a is pressed in, on the door being slammed, the incline 1 on the latch forces the catch l out of the notch o in the latch, the knifeedge q being forced past the apex of the V of the spring which then holds the catch l disengaged so as to allow the latch to be fully shot by its spring f. In this arrangement, the latch a is withdrawn by an arm g on a spring-pressed slide h co-operating with a projection e on the latch the slide h being operated either by a handle j or by a follower w acting on the arm g. The follower w may be extended to form an operating handle, or a second pivoted lever acting on the slide and extending beyond the upper edge of the lock may be provided. An incline t on the slide h acts on a lateral projection on the catch l as the slide is drawn inwards to press the catch l past the apex of the V of the spring r towards the notch o. On the latch a being completely withdrawn, however, the incline 1 on the latch forces the catch l upwards again, the catch being finally forced downwards past the apex of the V of the spring, which then urges it into the notch o, to hold the latch in its intermediate position, by a second incline u on the slide h as the slide and latch are moved outwards again by their springs. In the modification, Fig. 5, the latch a is held in its intermediate position by the pivoted catch l engaging a projection ox on the latch, the catch l being provided with projections p<x>, v<x> between which is situated a spring r<x> carried by a plate h<x> journaled on one of the trunnions x<1> of the follower w with which it has a' pin-and-slot connection so that the follower imparts motion to the plate h<x> just before it reaches its extreme positions. When the latch a is pressed in on the door being slammed, the catch l is swung clear of the projection ox by the spring r<x> acting on the projection v<x>, the latch then being fully shot by a. pivoted arm 4 acting on the projection e and connected by a spring 6 with the follower w. The latch a is withdrawn by the follower w acting on the projection e<1>, and just before the follower w reaches its inner. most position it moves the plate h<x> so as to cause the spring r<x> to press on the projection px so as to swing the catch l back into the path of the projection ox on the latch so as to engage said projection and hold the latch in its intermediate position, when the latter is moved outwards again by the arm 4 and spring 6.