Patent GB-570847-A (GB)
Title: Improvements in latches and combined locks and latches
IPC: E05B55/00
Filed: 1943-06-02
Abstract: 570,847. Door latches and locks. BRYAN, S. P. June 2, 1943, No. 8803. [Class 44] A latch casing is in two parts, one comprising an end plate a<1> fitting the width of the door edge and integral with or secured to side plates a having central depressions a2 the other part being an inner casing C which houses the mechanism and is secured between the depressions a<2> by a screw a4. The casing is applied to the door by sliding into a notch provided in the door edge, the notch being of a size to receive the depressions a<2> and casing C, whilst the marginal portions of plates a overlie the faces of the door and are apertured to receive securing screws. Securing screws may also be applied through apertures in plate a<1>. The latch is operated by lever handles B housed wholly or partly in the depressions, the free ends b of the handles being turned into the depressions, to avoid catching on clothing, &c. With the above arrangement it is desirable to provide for adequate throw of the bolt with limited angular movement of the handle. Fig. 3 shows a suitable mechanism in which the horns el of the follower bear against inclined levers F at points intermediate their ends, the forward ends of the levers being pivoted in the casing and the free rear ends making rubbing contact with inclined ribs d3 provided on a plate portion of the bolt d, which also has a rearwardly extending tail rod d<2> surrounded by a compression spring d4 bearing at its rear end against a fixed block cl through which the tail rod is slidably guided. The bolt d may be locked in shot position by a slidable lock-bolt G locked by ordinary tumblers g and gated at gl for operation by a key inserted through the keyholes a<3>, c<2>. Movement of bolt G brings a projection g<2> thereon into or out of position behind the end of the tail rod. A modification is described in which the sliding bolt G is replaced by a pivoted spring-biased member which can be oscillated to bring a projection thereon into or out of position behind the end of the tail rod by means of a spindle the outer end of which carries a thumb-piece and the inner end a radial projection resembling a key bit which co-operates with a gate in the member. Figs. 6, 8 show respectively a slam-bolt mechanism and striking plate for use therewith. The unchamfered bolt k is withdrawn by a lever N pivoted at its forward end and bearing, towards its free end, against an inclined surface k5 on a bolt projection k<2>. The horn m of a follower M bears against the lever at a position nearer the pivot than surface k<5>. When the bolt is retracted it is held withdrawn by a detent P which is tripped by contact of an auxiliary bolt having a rounded projecting head Q, with the striking plate R, Fig. 8. allowing the bolt k to shoot into aperture r. The striking plate has a groove r<1> extending for enough to allow bolt head Q to project and release the detent, when the door is being opened, so that the detent may engage and hold the bolt k before it leaves the striking plate. The follower is held stationary in normal position as the bolt k shoots by a projection m<1> on the follower engaged in a recess in the lever N.