GB112983A - Improvements in and relating to Electromagnetic Switches. - Google Patents

Abstract

112,983. British Thomson - Houston Co., (General Electric Co.). Feb. 1, 1917. Electro-magnetic switches. - An electro-magnetic lock-out switch for starting electric motors has a shunt coil 10 energizing the upturned polepiece 14 and a series holding-out coil 32 energizing the pole-piece 31. The pole-piece 14 acts upon two separate armatures; one, the armature 24, depending from the contact-carrying magnetic member 23 pivoted at 17, and the other, the armature 33, directly pivoted at 17. The pivot 17 carries also a frame 27 provided with an holding-out armature 30 co-operating with the holding-out magnet 31. The frame 27 is provided with an offset cross-bar 28 between which and the armature 33 a compression spring 34 is located. The parts assume the positions shown by gravity and, when the coil 10 is energized, it serves to retain the switch in the ' off ' position by the attracton between the pole-pieces 14 and the armature 24 notwithstanding the counter-attraction between the member 23 and the core 11. The attraction between the pole-piece 14 and the armature 33 compresses the spring 34 which tends tomove the frame against the action of the holding-cut magnet. When the series current in the coil 32 diminishes sufficiently, the frame is released and, under the action of the spring 34, the offset portion 28 strikes the armature 24 and knocks i away from the influence of the polepiece 14 whereupen increased attraction between the member 23 and the core 11 causes the magnetic closure of the switch. A copper band 15 retards the rise of the flux in the pole-pieces 14 and softens the blow of the armature 33 on the pole-piece. A non-magnetic adjusting screw 25 serves as an abutment for the end of the armature 24 and determines the size of the gap between the armature and the pole-piece 14 and, consequently, the current-setting of the switch.