Patent GB-606340-A (GB)
Title: Latch devices
IPC: E05B65/28
Filed: 1945-01-10
Abstract: 606,340. Latches. ENDTER, W. A. Jan. 10, 1945, No. 840. Convention date, Feb. 28, 1944. [Class 44] Latch mechanism for doors &c. comprises a keeper carried by one part (e.g. the door post), a bolt carried by the other part (e.g. the door) and bodily movable relatively thereto to a position of latched engagement with the keeper, and holding means operating to maintain a constant thrust of the bolt against the keeper in the latched position and at the same time to exert against the closure member (i.e. the door) a constant thrust tending to swing it towards the stationary part (i.e. the door post) and with relation to the keeper and the bolt. The mechanism comprises a case 10, Figs. 1 and 2, having flange portions 11, 12 carrying respectively the bolt and cam assembly, Fig. 2, and the operating mechanism for retracting the bolt, Fig. 1. The bolt 19 is of the swinging type engaging a keeper comprising a base 16 and a pair of spaced projections 17, 18. The bolt 19 is pivoted in a pivoted yoke 20, and a cam device 21, which may comprise one or more individual cams, is also pivoted in yoke 20 and exerts a thrust on the latter, by action against a fixed part of the casing, which tends to force the bolt against the keeper in the latched position. The bolt 19, Figs. 3, 4 and 9, has one arm formed with an outer flange 27 concentric with its pivot, and an arm 30 with a projecting pin 31 which is engaged by a slide to retract the bolt. The cam 21 is a quadrantshaped plate with a flanged edge 34 formed to a curve of increasing radius clockwise as viewed in Fig. 3. The yoke 20 is pivotally mounted on a fixed shaft 48, secured to a bracket 44 and an inner plate 47 fixed to the flange 11 of the casing. A pin 50 secured in the arms of the yoke carries bolt 19 and cam 21. The case flange 11 carries a roller 52 engaging and guiding the inner face of the flange of cam 21,. and the curved surface of the cam engages the inner face of section 12, so that rotation of the cam produces angular movement of yoke 20 on shaft 48. As shown in Figs. 6 and 7, counterclockwise rotation of the cam tends to thrust the bolt more tightly against keeper 17 on the door post, so forcing the door against the usual cushions on the jamb. The bolt is biassed by a spring 55, Fig. 4, located around the pin 50, to latching position, and cam 21 is biassed against releasing rotation by a second spring 58. The bolt 19 and cam 21 are retracted from the projected position of Fig. 3 by means of a slide 63, Fig. 3, guided on a pin 65 on the casing, and having an opening 68 in which engages pin 31 on arm 30 of the bolt, forming a lostmotion connection. The slide 63 is operated by a lever 73, Fig. 1, pivoted at 74, and having an arm 75 engaging under a projection 66 on the slide. A link 76 to an inside handle has a pin-and-slot lost-motion connection with the upper part of the lever 73. The outside handle rotates a spindle socket 78 which has an integral arm 80 pivoted to a link 82 which has lost-motion connection with lever 73, so that downward movement of arm 80 rotates lever 73 to lift slide 63. The latter is normally retained in its lower or bolt releasing position by a spring-urged arm 85. A locking element 91 can be turned on the pivot 92, by means of either a push-rod 96 or a key lock 97, so that its end 93 prevents movement of lever 73. The lever 91 is held yieldingly in either position by a spring. Movement of bolt 19 against keeper 17 as the door swings to latched position causes slide 63 to move upwardly, and to move the cam in the releasing direction. If the latch mechanism should happen to be locked with the door open, the locking element 91, Fig. 1, is engaged by a cam surface 106 on arm 85 as the latter is moved by the upward motion of slide 63, and swung to release position. With the door open, the bolt normally projects from the upper part of casing 44. As the door is shut, the curved surface 108 of the bolt abuts against the end of keeper 17, Fig. 6, and the bolt is forced down, after which it snaps into a safety catch recess 111. On further movement of the door, the bolt is forced downwardly again, during which movement pin 31 raises link 63 sufficiently to engage lug 36 on cam 21 to prevent downward swinging of the cam under the influence of spring 58.. Latching rotation of the bolt into the position of Fig. 6 is thus unopposed by the cam thrust. After the bolt assumes the position of Fig. 6, slide 63 is automatically shifted downwardly and away from cam lug 36 by thrust of arm 85, freeing the cam to effect take-up under the action of its spring, which tends to rotate it to the position of Fig. 7 and so swing yoke 20 to press the bolt against the keeper. In opening, slide 63, raised by operation of either the outside or the inside handle, first engages cam lug 36 to retract the cam, and then engages pin 31 to swing the bolthead downwardly. In a modification, the curved surface of cam 21 which bears on case section 12 to produce the thrust is replaced by a surface having a number of successive straight sections, resulting in a more positive dogging action. Alternatively, a dogging cam with such straight sections may be mounted beside a cam of the form first described.