Patent GB-818460-A (GB)
Title: A new or improved door latch
IPC: E05B65/32
Filed: 1954-12-07
Abstract: 818,460. Door locks. HUMBER Ltd., and PRIESTMAN, F. D. Dec. 7, 1955 [Dec. 7, 1954], No. 35427/54. Class 44 In a door latch for use where the door exerts an opening force, the latch comprises a striker 5, secured or to be secured to a fixed door frame member, and having an abutment surface facing against the direction of opening of the door, a catch supported or to be supported, on the door by means which permit movement of a catch abutment surface 10 on the catch in a direction transverse to the opening force into and out of latching engagement with the striker abutment surface, the support means and the engagement between the abutment surfaces of the striker and catch being such that the opening force produces a disengaging force tending to move the catch abutment surface 10 in the disengaging direction, stop means 18, 21 positively resisting the disengaging force and manually operable means 19 or 119 for rendering the stop means ineffective and for moving the catch out of latching engagement with the striker. In a first construction, Fig. 1, the abutment surface of the striker is on a tooth 6 and a second tooth 7 having a similar surface is also provided. The catch consists of two parts 9 and 15 the surface 10 being on the part 9 and forming an arc about a pivot 11 between the two parts. The catch part 9 is urged downwardly by a spring 12 acting between the two parts and the movement is limited by a stud 13 on the part 9 engaging a slot 14 in the part 15. Thus when the door is shut the engagement of the part 9 with the striker causes the part 9 to lift against the action of the spring 12 and to engage the striker without operating any other part of the latch mechanism. The stop means comprise a pin 21 which engages a slot 18. The catch part 15 is pivoted at 16 to a base 17 and has the slot 18 at its upper end. The pin 21 is carried by the means 19 which is in the form of a lever 19 pivotally mounted on the base plate 17. A part 22 of the slot 18 is tangential to a circle centred on the pivot 20 of the lever 19 and when the pin 21 is in this portion of the slot it locks the catch part 15 against movement. Since an unlocking force caused by compression of a door seal or buffer normally exists between the tooth 6 and the surface 10 which is approximately balanced by the frictional force between the tooth 6 and surface 10 little force other than that required to overcome a spring 23 is necessary to rotate the lever 19 to raise the catch and to release the striker. The lever 19 is rotated either by a push button 24 on the outside of the door which operates the lever 19 through a contactor 25 or by a handle on the inside of the door which rotates the lever 19 through a bell-crank lever 29. To prevent release of the catch by the push button a locking lever 38 is pivoted to the base plate 17. The lever 38 is rotated from the outside of the door by means of a key lock of the cylinder type in the outside door handle which is connected by a slotted link (not shown) to an extension 32 of lever 38 and movement of the lever 38 moves a surface 30 on the lever into the path of movement of the contactor 25 and prevents movement of the contactor. The lever 38 can also be moved to its locking position from the inside of the door by means of a rod (not shown) which acts through a lever 34 engaging a projection 35 on the lever 38. The lever 38 is held in its locking or unlocking positions by a toggle spring 31. If the lever 38 is in its locking position when the door is closed it is moved to its unlocking position by a projection 36 on the catch part 9 which engages a part 37 of the lever 38. The projection 36 also acts on the locking lever when it is moved by the inside handle. The door is vertically located by engagement of the striker with a dovetail on the door, the top surfaces of the teeth 6 and 7 of the striker bearing against the upper surface of the dovetail and the lower surface of the striker bearing against a sliding wedge 8. In a modification, Fig. 3, the striker 5 and two part catch 9, 15 are similar to those of the first construction and a manually operated lever 119 has a similar pin 21 and slot 18 connection with the part 15 of the catch. The outside push button 24 however engages a contactor 125 which is pivoted at 144 to the manually operated lever 119. The lever 119 has a projection 128 which is engageable by a bell-crank lever 129 operated from an internal door handle and it is loaded by a spring 123 to the latching position. The contactor 125 is mounted on a slide 149 by means of a pin 145 which engages a slot 146 in the contactor. When the slide 149 is in its uppermost position as shown, the pin and slot connection of the contactor and the slide allows the slide to move in a straight line to operate the lever 119, but when the slide, which has a pin and slot connection with the body of the latch, moves downwardly it controls the movements of the contactor so that the push button 24 becomes aligned with a slot in the contactor and hence is ineffective to release the latch. The slide 149 is moved from the outside of the door by a key lock in an external handle carrying a cam 147, Fig. 6, which engages in the slot 148 in the contactor 125 and thus when the key lock is rotated the contactor and slide are moved downwardly to their locking positions. The contactor and slide can also be moved to the locking position from the inside of the door by means of a lever 155 which is pivoted on the pin 145 of the slide and which has a slot 156 embracing the pivot pin 144 which serves as a fulcrum for the lever. The lever is rocked from the inside of the door through a lever 134 which is controlled by a rod (not shown). The slide and contactor are moved to their unlocking position when the catch is released from the inside of the door or when the door is closed from the outside by a surface 158 on the catch part 9 which engages the lower end 159 of the slide. The Specification also states that the catch part 9 can be guided on the part 15 for sliding movement transversely to the opening and closing direction of the door. It also states that the catch can have one part only which is movable transversely of the opening and closing direction of the door against a return spring.