Patent GB-757470-A (GB)
Title: Improvements relating to automobile door latches
IPC: E05B65/32
Filed: 1954-10-21
Abstract: 757,470. Latch fastenings. GENERAL MOTORS CORPORATION. Oct. 21, 1954 [Nov. 16, 1953], No. 30365/54. Class 44. An automobile door latch comprises a pivoted detent 25, adapted by engagement with ratchet teeth 24a to block pivotal unlatching movement of a pivoted latch bolt 18 (Fig. 3), a latch operating member 43 for withdrawing the detent 25 to permit unlatching movement of the bolt 18, and a twoarmed lever 31 having its fulcrum 32 spaced from the detent pivot 26 and acting to transmit the motion from the latch operating member 43 to the detent 25 with a mechanical advantage. The mechanism is carried by a frame having a plate portion 15 parallel with the jamb edge of the door, and a portion 16 which is parallel with the inner door panel. The bolt 18 is in the form of a gear carried by a shaft 20 on which is rigidly mounted a cam 24 carrying the teeth 24a with which the detent 25 engages as shown in Fig. 2. The latch bolt 18 co-operates with teeth on a keeper member (Fig. 5, not shown) which also carries a spring- pressed nylon shoe. The two-armed lever 31 has one arm 33 in engagement with the detent 25 and a second arm 35 which is adapted to be engaged by one limb 52 of a bifurcated lever 50 pivotally connected at 49 to the member 43. The member 43 comprises a lever which is pivotally mounted on the plate 15 at 44, its other end carrying the pivot 49. The angular movement of the member 43 is limited by stops formed by the outer end of the lever and cutaway parts of the frame 15. A spring 27 acts between the end 43a of the member 43 and an extension 29 of the detent 25. An outside unlatching push button 38 (Fig. 3) acts via a pushrod 41 on a flange 42 of the member 43. A remote unlatching turn handle (not shown) on the inside of the car acts via a link 59 on one arm 60 of a bell-crank 61, the other arm 62 of which is pivotally connected to a third arm 36 of the lever 31. A locking plate 71 is pivotally mounted at 72 on the frame portion 16. A bifurcated portion 73, 74 extending at right angles to, and carried by, the plate 71, straddles the second limb 51 of the link 50. The locking plate 71 is positioned in either an unlocking position (shown), or a locking position (Fig. 7), by an over-centre spring 77. The plate 71 is operated by a bell-crank 86 connected by a link 85 to a push-button (not shown) mounted in the lower portion of the window frame of the vehicle. The cylinder 69 of a tumbler lock (Fig. 3) carries a member 84 which engages the end 83 of a lever 81 pivoted at 82 to the frame 15. The other end of the lever 81 is connected by a link 80 to the locking plate 71. In operation, when the parts are shown in the unlocked position of Fig. 2, the door may be unlatched by pressing the push button 38. This acts via the member 43 to displace the link 50. The limb 52 engages the arm 35 of the lever 31, the arm 33 of which operates on the detent 25 to release it from engagement with the cam 24. The resilient door-sealing weather strip (not shown) will then force the door open slightly. The latch bolt 18 may also be released by operation of the remote lever connected to the link 59. This causes rotation of the lever 31 as before. When the plate 71 is turned to the locking position either by the lever 86 or by operation of the key-operated lock 69, the member 51 of the link 50 is deflected, so that when the link 50 is deflected by the member 43, the arm 35 of the lever 31 enters the space between the members 52 and 53, instead of being engaged by the limb 52. In the embodiment shown in Fig. 7, this automatic return of the plate 71 to the unlocked position may be avoided by the appropriate setting of a link 107. One end of the link 107 carries a pin which is engageable with either limb 104 or 105 of a V-shaped slot in the plate 71. The other end of the link 77 carries a pin which engages an L-shaped slot 101 formed in a lever arm 100 which is pivotally mounted on the pivot 63 of the arm 60. The pin on this end of the link 77 extends through to a slot 102 which is formed in the arm 60. The link 59 is now connected to the lever 100 instead of to the arm 60. An over-centre spring 108 urges the link 77 to either of its respective positions in the slots 104, 105. When it is in the slot 104, the pin at the other end of the link 77 engages the vertical (horizontal as viewed in Figs. 7 and 8) limb 101b of the L-shaped slot 101. Thus when the remote handle is operated to deflect the lever 100, the movement of the latter will be transmitted via a pin on the link 77 and slot 102 to the arm 60 resulting in unlatching movement of the lever 31. When however the upper end of the link 107 engages the slot 105 of the plate 71, the lower end of the link 107 engages the slot 101a. This end of the link 107 then idles in the slot 101a when the remote lever is operated, and the movement is not passed on to the arm 60. In this embodiment, the link 85 operates directly on to the plate 71, instead of through the intermediate bell-crank 86. In both embodiments, the shape of the nose 30 of the detent 25, and the shape of each of the faces of the cam 24 is of arcuate shape, the centre of which is located at a point a little displaced from the axis of the pivot 26 of the detent 25. The direction and amount of this displacement is such that the detent 25 tends easily to disengage from the cam 24.