Patent GB-597949-A (GB)
Title: Improvements in or relating to door latches and locks
IPC: E05B55/00
Filed: 1945-04-16
Abstract: 597,949. Latches and locks. BACKHOUSE, H. T. April 16, 1945, No. 9472. [Class 44] A door latch mechanism of the kind having two independently operable handles, each of which may be operated in one direction to retract the bolt and operated in the reverse direction to block the bolt in shot position, is housed in a cylindrical casing adapted to be accommodated in a cylindrical bore in the edge of the door. Figs. 1, 2 show a cylindrical casing 12 with end flange 13 to receive fixing screws, a hollow cylindrical slide 11 guided in the casing carrying a bevelled bolt head 10 of square crosssection projecting through a corresponding aperture in a face plate 15. The bolt is shot by a spring 16 in compression between the inner end of slide 11 and a fixed abutment ledge 17. Retraction may be effected by either of two independent handle spindles 18, 19 each of which has a pinion 20, 21 engaging lateral teeth on an associated rack bar 24, 25. Each bar has two projections 32, 33 and a forward end extending into the bore of slide 11 and provided with hooked extremity 27 engaging an inturned flange 26 of the slide. Operation of either handle in closewise direction, Fig. 1 moves the corresponding rack to the right, the other handle and rack remaining idle. The hook 27 of the operated rack retracts the bolt. To effect locking by reverse movement of a handle a pivoted pawl is employed as claimed in Specification 597,984. The pawl comprises two identical portions (only one seen in Fig. 1) spaced apart and situated at opposite sides of the racks so that one co-operates with each rack, the two portions being integrally or otherwise connected at the forward end so that the two portions rock as one about a common pivot 31. Each portion presents a forwardly directed arm 28 normally held in register with the aperture in flange 26 by a spring 14 so as not to impede rearward movement of the slide, an upwardly directed arm to co-operate with the corresponding projection 33, and a rearwardly extending arm 30 with notched extremity adapted when raised to engage the corresponding projection 32. Anticlockwise movement of either handle moves the corresponding rack to the left (the other handle and rack remaining idle) so that its projection 33 engages the corresponding arm 29 and rocks the pawl so that arms 28 lie behind the flanged inner end of the slide to prevent inward movement of the bolt. At the same time the arm 30 of the other pawl portion is raised so that its end engages the projection 32 of the other rack so that its movement to the left is prevented. The other handle is thereby locked against reverse movement, whilst its movement in unlocking direction is prevented through its hook 27 engagement with the blocked bolt. Each handle is held in its normal and locking positions respectively by flats 45, 46 on the pinion boss engaged by a plate spring 47. In a modification, Fig. 4, the cylindrical slide 53 guided in the cylindrical casing 55 has a central bore 59 housing the spring 61 surrounding a bar 60 supported at its rear end by a fixed division plate, a pair of recesses 68 receiving the forward portions of bars 66 the front ends of which have inturned hooks 70 engaging a cross-pin 71 carried by the slide, and a recess 80 to receive arms of the locking pawl during normal retraction of the bolt. Retraction is effected by arms 64 on the independent handle spindles 63. Clockwise rotation of either handle retracts the bolt by engagement of the operated arm with a projection on the tail of corresponding bar 66. Anticlockwise rotation of either handle causes the end of arm 64 to pass over the curved rear face of the two-armed locking pawl pivoted at 73 and thereby rock the pawl clockwise, lifting its horizontal arm 74 out of register with recess 80, to form a locking abutment for the bolt slide 53. The operated handle is held in blocking position by a pin 64a on its arm engaging a recessed spring 92. Clockwise movement of the other handle is prevented by the blocking of the bolt, and its anticlockwise movement is prevented by arm 75 of the corresponding pawl which now lies in the anticlockwise path of the arm 64 operated by that handle. Key looking may be effected by providing a key lock 90, Fig. 9, below the tubular casing of the latch bolt and with a sliding bolt 91 projecting through a slot in the casing into engagement with the looking pawl so that the pawl is rocked to locking position when bolt 91 is shot, this process simultaneously blocking the latch bolt and locking both handles against movement in either direction from normal position. The bolt head may be reversible for left-hand. or right-hand use. In Fig. 1 the aspect of the bolt-head is maintained by a fixed cross-pin 40 extending through slots 41 in the bolt slide 11. Face-plate 15, though shown, is not necessary, and may be omitted. On removal of plate 15 if present, both handles are simultaneously turned anti-clockwise, thus allowing spring 16 to move slide 11. far enough to the left to clear slots 41 from pin 40. The bolt 10 may then be turned through 180 degrees and the handles then returned to normal position so that pin 40 again enters slots 41, In Fig. 4 the bolt head 50 is of square crosssection fitting a square hole in face-plate 58, and is rotatably mounted on slide 53 by crosspins 54, 54a carried by head 10 and engaging an annular recess in slide 53, so that reversal can be effected after removal of plate 58.