Patent GB-797582-A (GB)
Title: Locking latches
IPC: E05B55/00
Filed: 1955-10-01
Abstract: 797,582. Latches. PARKES & SONS. Ltd.. J., and BUTTER. F. J. Oct. 1. 1956 [Oct. 1, 1955], No. 27983/55. Class 44. Relates to locking latches of the type wherein a dog which is normally retained in an inoperative position is allowed, by a spring loaded slide associated with the bolt. to take up a bolt obstructing or locking-out position, when the slide is prevented, say by encountering the face of a striking plate, from being shot out with the bolt and in which means having a connection with bolt, is operable, by the initial part of the withdrawal movement of a knob-actuated follower, retractor or other bolt-withdrawal device, to release the dog and so free the bolt for withdrawal by the continued operation of the device. According to the invention, in which the dog is loaded towards its bolt-obstructing position by either the spring which shoots the bolt or that which loads the associated slide, or by both of these springs, the dog is in the form of a cranked lever having a forwardly-directed arm with which the slide and releasing means co-operate, and a downwardly extending arm upon which the or each spring bears to press it back towards or against the rear end of the latch casing. As shown, applied to a tubular mortice latch comprising a casing 10 having an integral rear wall 11 and a disc 15 fitted therein provided with wings 16 for engaging the casing of an operating unit fitted in a hole through the door, a latch bolt head 19 and a slide 20 are slidably mounted on guide pins 17, 18 respectively projecting inwardly from the disc 15. A tail 23 of the bolt head 19 projects through the disc 15 and end wall 11 and terminates in a foot 24 for engagement with a bolt retractor (not shown). The slide 20 is provided with a face 25 which abuts the rear face of the bolt head to permit the slide to be retracted by the bolt. A dog 26 which is normally supported in an inoperative position by the slide 20 is maintained in that position during retraction of the bolt head, by the upper edge of the bolt tail 23. If however the slide 20 is prevented from moving outwardly with the bolt head by, for example, its engagement with the face of a striking plate, the slide 20 allows the dog 26 to assume the position shown in Fig. 4 in which it blocks the bolt head 19. The dog 26 is released from its blocking position by a releaser 27 associated with the bolt tail 23. The releaser comprises a cam surface or ramp 28, a stem portion extending through the disc 15 and end wall 11 and a foot 29, there being a lost-motion connection 23<SP>x</SP>-30. with the bolt tail. The arrangement is such that upon withdrawal of the bolt head and releaser, when the door is closed the ramp 28, returns the dog 26 to its normal inoperative position to free the bolt head. When the door is opened the bolt and releaser are released by the bolt spring 21 and the slide 20 is released by its spring 22 and supports the dog 26. The dog 26 is formed as a cracked-lever, a downwardly directed arm of which straddles the bolttail 23 and the releaser 27 and is loaded by the springs 21, 22. The pins 17, 18 pass through clearance holes in the limbs of the arm which are formed with "pips" 32 on which the dog 26 pivots. Alternatively the arm may be formed with a projecting rib to serve as a pivot for the dog. The dog 26 may be operated by one only of the spring 21, 22. The end wall 11 is provided with a slot 33, Fig. 7, of width corresponding to the combined thickness of the bolt tail stem 23, and releaser stem 27. A. T-shaped slot 34 is formed in the disc 15. the centre limb of the slot being disposed horizontally and of width dimension corresponding to that of the stems, and the cross-section of the slot being long enough to pass singly, the feet 24, 29 to admit the stems to the horizontal portion of the slot. the cross-portion of which becomes blanked-off by the rear end wall 11 when the disc is assembled into the casing 10. Theseparate holes for the wings and stems in the wall 11 may be replaced by an I-shaped slot. The T-shaped slot in the disc 15 may be replaced by a horizontally disposed slot running into an edge of the disc. Specification 797.583 is referred to.