GB769778A - Polarized electro magnetic relays - Google Patents

Abstract

769,778. Electromagnetic relays. WESTINGHOUSE AIR BRAKE CO. May 27, 1955 [June 10, 1954], No. 15369/55. Class 38(5) A relay in which the armature is gravity biased to the released position, is held by a polarizing magnet in that position, and is picked-up by energization of the operating winding by a current of a certain polarity, comprises an armature 26 pivoted along its rear edge at 25 to operate between a pair of upper pole pieces 6, 7 and lower pole pieces 20, 21 and control front and back contacts (not shown). The pole pieces 6, 20 and 7, 21 are connected by permanent magnets 22, 23 magnetized across their width and these magnets hold the armature in its released position against the pole pieces 20, 21, the flux path being completed by cores 2, 3, connected to the pole pieces 6, 7, and by a backstrap 19 connecting the upper ends of the cores. The cores 2, 3 each form part of a pair of closed magnetic loops including'upper and lower extensions 10b, 10a and 11b, 11a, together with permanent magnets 16, 17, the magnet 17 producing a loop flux which passes downwards in the core 3 and the magnet 16 a flux which passes upwards in the core 2. Operating windings 12, 13 on the cores are connected in series and when these are energized to produce a flux in the cores in the same direction as that produced by the magnets 16, 17 the armature 26 is raised towards the pole pieces 6, 7, the operating flux path being completed by the backstrap 19. Energization of the coils 12, 13 by a current of reverse polarity is ineffective to raise the armature, due to the magnets 16, 17. Iron shunts 14, 15 serve as keepers for the magnets 16, 17.