Patent GB-1108996-A (GB)
Title: Improvements relating to magnetic latches
IPC: E05C19/16
Filed: 1965-07-26
Abstract: 1,108,996. Magnetic fastenings. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 26 July, 1965 [29 July, 1964], No. 31750/65. Heading E2A. A magnetic latch e.g. for a door, comprises a casing 1 having a bolt guide 5 pivotally mounted therein, a bolt 4 co-operating magnetically with a keeper 28, the bolt being arranged to slide in the bolt guide and also to tilt relative to the keeper about a fulcrum parallel to the pivotal axis of the bolt guide so that the bolt can be separated from the keeper, an operating shaft 24 of the kind which is operated by pushing or pulling, and a bolt blocking mechanism 14 which operates to prevent the bolt from being tilted and is coupled to the operating shaft so that before the bolt can be released the operating shaft must be moved axially to disengage the bolt blocking mechanism so that the bolt can be tilted away from the keeper. In the construction shown the magnetic bolt 4 consists of a sandwich composed of two soft iron pole plates 7 and 8 between which is located a flat ceramic permanent magnet 6. The bolt guide 5 is made of bronze so that the bolt can slide easily through it and the bolt normally projects through a rectangular aperture 3 in a brass cover plate 2 of the casing 1. The bolt guide has a recess 9 in one side and a stop member 11 attached to the bolt limits the projection of the bolt by abutting against an adjusting screw (not shown) carried by the bolt guide 5. The bolt guide 5 is pivoted in the casing 1 by means of pins mounted in lugs 12 and 13 and in the normal latching position it abuts against the side of the casing which is located opposite to the lugs. The blocking mechanism comprises a nylon pawl 14 which is journalled near one end on a shaft 15 and which is biased by a spring 19 surrounding the shaft to a position in which it prevents pivotal movement of the bolt guide. A coupling arm 16 is conneated to the shaft 15 and the spring 19 operates between the arm and the pawl to hold the pawl in blocking position. This position relative to the arm 16 is determined by studs 22 on the pawl which engage the arm under the bias of the spring 19. The operating shaft 24 extends through the casing and also through a slot 23 formed in the coupling arm. The shaft is provided with two abutment sleeves 25a, 25b which can bear against the coupling arm and at each end it has a knob 27 so that pulling on one knob or pushing on the other pivots the arm 16 and through the engagement of the arm with the studs 22 pivots the pawl out of blocking engagement with the bolt guide. If the pull or push on the appropriate knob is continued the bolt is then caused to pivot relative to the keeper which reduces the force of attraction of the bolt for the keeper and the bolt then slides over a ramp 29 of the keeper to release the door so that it can be opened. Once the door is opened and the knob is released a spring 26 restores the operating shaft to its original position and the guide 5 returns to its initial positon as a resullt of attraction between the bolt and an iron section 31 of the wall of the casing. The pawl can move relative to the arm 16 to allow this because of its lost motion connection with the arm 16. A modification is described in which the bolt guide has a rear wall made of soft iron so that when a door to which the latch is fitted is open the bolt is pulled into the casing by its attraction for the said wall.