GB684984A - Improvements in door latch mechanisms - Google Patents

Abstract

684,984. Latches. GILL, W. A., and WHISTLECROFT, A. W. Oct. 11, 1951 [July 13, 1950], No. 17546/50. Class 44 A door latch comprises a body 1, Figs. 1 and 2, having parallel bores 3, 4, a spring shot latch bolt 6 slidable in the bore 4, an auxiliary bolt 5 slidable in the bore 3 adapted to control the position of a locking member 17 and a ball 11 movable in a bore 10 interconnecting the bores 3, 4 adapted to engage selectively in grooves 6b, 17a in the latch bolt and locking member respectively, the latch bolt has a roller 12 pivoted in a slot in the nose and its movement is limited by a stop 9 engaged in a slot 6a. A spring 18 bears between the bolt 5 and the locking member 17 and a second spring 16 bears between the locking member and a large steel ball 15 which is engaged in a U-shaped cam notch in a rod 8 slidable in a cross-bore 7 in the body 1 and having a handle for moving it. The striking plate 20, Fig. 4, has an opening 13 to receive the roller ended bolt 6 and a chamfered edge portion 21 to delay the inward movement of the bolt 5 when the door is shut. Fig. 1 shows the door-open position of the parts. When the door closes the bolt 6 is driven in by the engagement of its roller by the edge of the striking plate, the ball 11 being displaced into the groove 17a to hold the locking member 17. The auxiliary bolt 5 is then pressed in by the striking plate, the spring 18 being compressed. When the bolt 6 registers with its opening 13 it moves out again, releasing the locking member which is then displaced by the spring 18 to a position where it abuts the ball 15 and in which the ball 11 is blocked in locking position in the groove 6b by a solid part of the locking member 17 (see Fig. 2) To release the bolt 6 the rod 8 is displaced to move the ball 15 and the locking member 17 outwards to the position where the groove 17a registers with the bore 10 and receives the ball 11. Further pull on the handle causes the roller 12 to roll out of the opening 13 and retract the bolt 6. The Provisional Specification describes a method of operating the lock electrically, the movement of the sliding rod 8 being controlled by the armature of a solenoid. In another arrangement the striking plate is fitted with a movable portion controlled by a solenoid adapted to be displaced to release the auxiliary bolt. In this form the rod 8 and ball 15 are omitted, the spring 16 bearing on a blank end of the bore 3.