Patent GB-488936-A (GB)
Title: Improvements in and relating to door locks
IPC: E05B65/28
Filed: 1937-01-15
Abstract: 488,936. Automatic catches. McKENZIE, S. B. Jan. 15, 1937, No. 1304, [Class 44] A latch comprises a movable wedge-shaped block coacting with a fixed wedge-shaped block or sliding on an inclined surface, and adapted to enter a wedge-shaped pocket forming the keeper, the blocks being so formed that movement of the movable block towards the large end of the pocket increases the wedging action. The flange 2 of the body 1 of a rim latch, Figs. 1, 2 and 3, is adapted to fit on the edge of a door and carries a fixed wedgeshaped block 3 on which slides a second wedgeshaped block 7, preferably by means of a dovetail connection. The keeper comprises a wedgeshaped pocket 24 vertically slidable in a casing 22 adapted to be fixed to the door frame. On encountering the narrow mouth of the keeper, the block 7 is forced down the block 3 until it can enter the keeper when it is returned to an upper position, to engage the block 26 of the keeper, by a spring 20 acting on a pin 10 projecting from the block 7 through a slot 9 in the flange 2. Any force tending to withdraw the latch from the keeper results in a tightening of the wedging action, as does any vibration of the door. Turning the handle 18 in either direction causes the block 7 to be retracted by means of the cam 17 and bell-crank levers 16, 15 and 14, 11. The angle between the upper surface of the block 7 and the lower surface of the block 3 is less than that between the upper and lower surfaces of the block 3, suitable values being 16‹ for the former and 19‹ for the latter. In a modification, Fig. 7, applied to an automobile door, the keeper is adjustably secured to the door post by screws passing through slotted holes 41, 42, and the blocks 37, 38, are given a small degree of angular freedom by being mounted on the base-plate 36 by pin-and-slot connections 39, 40, the curved outer surfaces of the blocks bearing on curved flanges on the base-plate. The latch casing mounted on the door is correspondingly shaped to embrace the flanges of the base-plate when the door is closed. The keeper may be mounted in rubber or in any other resilient manner instead of or in addition to being mounted for vertical movement, as in the first embodiment, or for pivotal movement, as in the second embodiment. The Provisional Specification describes a modification applied to an automobile door in which two wedge-shaped blocks slide on opposite edges of a tapered block pivoted to a plate fixed to the door edge. The fixed block may be pivoted when only one sliding block is used. The pocket of the keeper may be parallel or tapered, and the wedge-shaped blocks may have a dovetail engagement with the surfaces of the pocket. The wedge-shaped blocks and the pocket may also be tapered in the direction of the plane of the door. The Provisional Specification also discloses an automobile latch comprising a cylindrical boss carried by or formed integrally with an attachment plate secured to the edge of the door. A portion of the boss is removed by two cuts, one on a radial line and the other on a line perpendicular to the radial line and intersecting it at a point mid-way between the centre and circumference of the boss. In the pocket so formed is disposed a roller, or other jamming member such as a wedge or cam, which is urged towards the periphery of the boss by resilient means such as a spring. The plate has an aperture, coinciding with the pocket, through which an operating finger actuated by the door handle projects in front of the roller to retract it. A hollow cylindrical cover having external teeth is mounted on the boss and is prevented from rotating in one direction by the jamming action of the roller, but can rotate freely in the opposite direction to engage a rack mounted on the door post. To prevent jamming of the teeth during the closing movement of the door, one or more teeth of the rack or of the cylindrical cover may be pivotally, slidably or otherwise loosely mounted. Conveniently, one or more teeth of the rack may be pivoted so as to be capable of moving in the direction of closure of the door but not in the opposite direction. To restrain the door against vertical displacement, an inclined surface may be provided to engage the cylindrical cover on the side opposite the rack.