Patent GB-791080-A (GB)
Title: Improvements in and relating to latches for doors
IPC: E05B65/34
Filed: 1954-11-26
Abstract: 791,080. Door latches. THORNE, H. Nov. 16, 1955 [Nov. 26, 1954], No. 34279/54. Class 44 In a door latch of the type wherein the outer handle is fixed and the bolt 31 is operated by a push button incorporated in said handle, operation of the bolt from inside being effected by an inner lever handle 38, "child-safety" deadlocking means are provided adapted to be brought into operation by a movement of the inner handle to a position beyond the normal deadlocking position, release of the "childsafety" deadlocking means being under the control of the outer push-button mechanism. In the construction shown in Fig. 1, movement of the bolt 31, which is of the rotary type is normally prevented by a pawl on a plate 30 which is pivotally mounted on a pin 34 and held into contact with the bolt by a coiled spring. Also mounted on the pin 34 is a second plate 32 which is loaded by a spring 35 and which is connected to the plate .30 by a pin 33 engaging an aperture in the plate 30. Movement of the plate 32 is limited by a stop pin 37 engaging a projection 36. When an inner lever handle 38, Fig. 2 is actuated the plate 32 is rotated to release the bolt by a bellcrank which is connected to the handle 38 by a link 141. Movement of the handle 38 anti-clockwise as shown in Fig. 2 causes an arm 40 of the bellcrank to move downwardly and it bears on an arm 39 of the plate 32 to rotate it, the rotation of the plate causing a movement of the plate 30 through the pin 33 and hence the bolt is released. The bolt is released by the outside push button through a pin 43. The pin 43 engages a flange 42 on a pivotally mounted plate 41, a pin 44 on which engages a projection 45 on the pawl plate 30 so that when the push button is depressed the pawl is moved away from the bolt. Movement of the handle 38 clockwise to its deadlocking position causes an inclined surface 46 on a finger 47 which is mounted on the link 141 to rotate a spring biased detent 49, which is pivotally mounted beneath the pawl plate 30. The detent rotates to a position in which it engages the flange 42 on the plate 41 so that the push button cannot release the bolt. The detent is returned to its normal position by its spring so that the push button can release the bolt, when the handle 38 is returned to its normal position, since it is no longer held rotated by the finger 47. The handle 38 is held in its normal and deadlocking positions by a spring loaded pin engaging depressions on a cam secured to the handle. The pin also serves to return the handle to said positions from the releasing and deadlocking positions by engaging surfaces in the cam. The link 141 also carries a pivotally mounted catch 50 which is spring biased to a position in which a tooth 51 can engage a surface 52 on the latch casing. When the handle 38 is moved clockwise to the childsafety position the tooth 51 of the catch 50 becomes engaged with the surface 52 so that the handle 38 is held in this position, the catch being guided to this position by a plate 53. When the handle 38 is in this position the engagement of the catch 50 with the surface 52 prevents its release from inside the door and it can only be released by depression of the outside push button. This depression of the push button is possible since the additional movement of the finger 47 rotates the detent 49 beyond the position in which it prevents movement of the push button and hence when the push button is depressed it rotates the plate 41 which in turn rotates the pawl plate 30. The pin 33 on the pawl plate 30 causes a rotation of the plate 32 and downward movement of an arm on this plate on to the tooth 51 releases it from the surface 52. The handle 38 can then be returned manually either to its locking or its normal position. The detent 49 is returned by its biasing spring. In a further construction Fig. 8 movement of a rotary bolt can be prevented by a pivotally mounted pawl 56 which engages a multitoothed rotary cam 55 connected to the bolt. The pawl 56 is moved to a releasing position from an inside handle by means of a bell-crank which is connected to the handle by a link 61, Fig. 10. When the link 61 is moved to the right as shown in Fig. 10 an arm 59 of the bellcrank is raised and it raises an arm 58 of the pawl to release the pawl from the rotary cam 55. The pawl can also be removed from the cam by an outside push button. When the push button is depressed it engages a part 65 of a plate 64 which is pivotally mounted on the same pin as the pawl 56 and rotates the plate 64. The plate 64 in turn rotates the pawl in a releasing direction since it is engaged by a bent-up projection 62 on the pawl 56. The pawl 56 and plate 64 are returned to their normal positions when the push button is released by a spring 67. Pivotally mounted below the plate 64 is a detent 68 which has an arm 69 and a bent-over projection 70. The projection 70 lies in the path of the arm 59 of the bellcrank connected to the inner handle and when the inner handle is moved in the reverse direction to the deadlocking position so that the link 61 moves to the left as shown, the arm 59 of the bellcrank engages the projection 70 and pivots the detent 68 to bring its arm 69 in the path of the part 65 of the plate 64 so that movement of the outer push button is prevented. If the inner handle is moved in the reverse direction to the child safety position the arm 59 is moved further downwardly and a shoulder on a pivoted spring loaded locking plate 71 engages it and prevents its return so that the inner handle cannot be moved back to its normal position. The inner handle can however be released by depression of the outer push button since the further movement of the arm 59 pivots the detent 68 beyond its normal locking position so that the push button can be depressed. When the push button is so depressed an arm 74 which is connected to the part 65 of the plate 64 engages the locking plate 71 and releases it from the arm 59 of the bellcrank. The inner handle can then be moved manually to its normal position. In a modification of this construction the locking plate is automatically released if a car in which the latch is fitted hits an object or is run into by a following vehicle. In this modification, Fig. 16, a locking plate 71a is provided with a weight 81 which increases its inertia and it is mounted so that in addition to a movement which engages a pin 83 with the arm 84 of a bellcrank connected to the inner handle it can move sideways in either direction. The arm 84 of the bellcrank is provided with recesses 85, 86 so that when sideways movement occurs the pin 83 moves over one or other of the recesses so that the arm 84 is released and hence the inner handle. A spring 82 tends to keep the plate 71a in a central position and also serves to bias the plate into its arm engaging position. The pin 83 is bevelled so that the arm 84 can move over it easily when the inner handle is moved to the position in which it is locked by the pin. The Provisional Specification describes a construction in which the inner handle can be locked by a pivoted spring loaded catch on the latch casing which can engage a notch in the link which connects the handle with the latch. The catch is released by a flange connected to the outside push button.