Patent GB-617775-A (GB)
Title: Door latches
IPC: E05C3/36
Filed: 1944-09-05
Abstract: 617,775. Latches. ENDTER, W. A. Sept. 5, 1944. No. 16945. Convention date, Nov. 27, 1943. [Class 44] Latch mechanism comprises a keeper on one part (e.g. the door post) a rotatable keeper engaging bolt on the other part (e.g. the door) and movable relatively to the keeper while in engagement therewith, and releasable holding means operable independently of the bolt during its movement .in latching direction and while engaged with the keeper to lock the parts against' movement apart at different relative positions. In the form shown in Figs 1 and 2. a rotating bolt 14 is mounted in the catch casing in the door and is engaged by a stationary keeper 11, on the door post. The keeper is received in the closed position of the door between the bolt 14 and a boss 20 which carries the releasable holding means comprising a catch 52 which is arranged to enter notches 60, 61, 62 in the keeper. The rotating bolt 14 is actuated by cam mechanism 22, which may comprise one or more cams. 23, 24, acting on the inner part of the latch, optionally with a stepped locking plate 28 similar to that described in Specification 617,774. The release mechanism for retracting the cams and step plate may comprise a vertically sliding plate 33, actuated by a follower on a handle shaft 43 or by a link 46 and an arm 48, which disengages the cams from the inner parts of the bolt. The releasable holding means comprises a pivoted and spring biased catch having an arm 53 formed with one end projecting through the lower wall of the boss 20 'and adapted to engage in the notches 60-62 in the keeper, and an arm 54 which is engaged by the plate 33 to release the catch. The catch is mounted on the pin 25 carrying cams 23, 24 so'that its arm 54 lies against cam 24, and the top shoulder of the arm is engageable by the arm 38 of the retracting plate 33. The arm 53, at the outer end of the catch, is formed with a dog 57, one face 58 of which has a centre of curvature at the axis of the pin 25. In the action as the door is closed, the bolt head 14 Fig. 4, first engages the keeper, and after a range of initial rotation of the bolt, the safety catch dog 57 snaps into notch 60 on the keeper. As the bolt is further advanced towards the latched position, the advance is resisted by engagement of the inner parts of the bolt, the cams 23, 24 until the latter become displaced upwardly to the tripping position in which they slide past one bolt head into engagement with the next, as shown in Fig. 5. At this point or substantially so, the dog 57 snaps into notch 61 on the keeper. At or slightly before the fully latched position of Fig 1, dog 57 snaps into notch 62. In a modified form shown in Figs. 12 and. 13, the bolt and cam assembly in the casing 68 is received between two keepers 74, 75 with which engage the safety catch 87 and the bolt 70 respectively. The bolt actuating means comprises a pair of vertically sliding wedges or cams 80, 81, urged into wedging engagement with the bolt by springs 85. The safety catch comprises an arm 87, with a dog 92 engaging in notches in the keeper 74. A retracting plate 97 is 'pivoted on the bolt shaft 71 and has a lug 98 engageable with the lower ends of the cams, and a shoulder 99 engageable with the lower end 100 of the safety catch arm. The plate 97 also, carries an arm 105 projecting through flange 66 to be engaged by a lug 108 on a member 106 which is rotated to release the latch by means of a link 115 or of a follower 112 actuated by the inside and outside handles respectively. The action is similar to that of the first described form.