GB573165A - Improvements in or relating to door locks - Google Patents

Abstract

573,165. Door latches. WIRZ, A. Aug. 17, 1943, No. 13346. [A Specification was laid open to inspection under Sect. 91 of the Acts, Feb. 14, 1944.] [Class 44] In a door latch of the kind in which the main bolt is held by a detent in the retracted position, the detent being tripped on closing the door to allow the bolt to shoot, and an auxiliary bolt is provided to retain the door closed until the main bolt has been retracted far enough to ensure the engagement of the retaining indent, the auxiliary bolt being thereafter retracted, the main and auxiliary bolts are connected by a link or lever arranged so that when the door has been opened and the handle released, the follower in its return movement to normal position acts on the link to complete retraction of the auxiliary bolt. As shown, the main bolt 7 is shot by spring 8 and an auxiliary bolt 9 is slidably housed in the main bolt and shot relatively thereto by a spring 10. The main bolt carries a pivoted lever the upper end 15a of which engages a recess in the auxiliary bolt. The follower 3 and handles 5 carried by the spindle 2 are biased to normal position by a spring 4. The follower arm has a projection 6 engaging a lateral projection on the main bolt, which is withdrawn by depression of handle 5, and a projection 14 adapted to engage the lower end 15 of the lever. When the handle is depressed, both bolts are at first retracted without alteration of their relative position shown until bolt 9 clears the keeper and the door can be opened. At this stage the main bolt has been sufficiently retracted to allow a detent to engage so as to retain the bolt retracted. The detent shown comprises a horizontal lever 12 biased by a torsion spring 11 (anticlockwise Fig. 5) at its pivot so that a depending projection 13 snaps in front of a shoulder on the bolt and a terminal projection 18 projects through the back plate of the casing 1 so as to contact with and be pressed in by the fixed door pane when the door is closed, thus tripping the detent to allow the bolts to shoot. In the dooropening position referred to above, the lever has reached a fixed stop 17. If at this stage the handle be released, the main bolt is arrested by the detent, and the anticlockwise movement of the follower arm causes projection 14 to rock the lever clockwise, thus retracting bolt 9 within bolt 7. If, on the other hand, handle 5 be further depressed before release, stop 17 at first rocks the lever clockwise to retract bolt 9, but when the handle is released, the follower action described above occurs to ensure final retraction of bolt 9 within bolt 7. Stop 17, by engaging a shoulder behind projection 6, limits the extent to which the bolts can be shot.