GB222179A - Improvements in electro-magnetic control devices for electric switches and other apparatus - Google Patents

Abstract

222,179. English Electric Co., Ltd., and Zweigbergk, T. June 20, 1923. Electromagnetic switches producing a controlling effect while the current in a circuit exceeds a predetermined limit comprise two current carrying coils, one fixed and the other movable, linked with the magnetic circuit, there being provided a moving part whose motion does not affect the reluctance of the magnetic circuit and a coil associated with the' moving part and connected in parallel with the fixed coil so that the coils may carry the controlled current or a current proportional thereto. The fixed coil 1 is mounted on a core 2 secured by a nut in a bell-shaped iron casing 4 so as to leave an annular aperture 6 within which is the moving coil 7 connected to terminals 8, 9 of the coil 1 and carried by a non- magnetic member 10. The latter is pivoted about a centre 40 on adjusting and centring screws 13, 14, and holds an insulating part 15 on which is rotatably mounted a disc 16 co-operating with contacts 17, 18 of a control switch. The member 10 is controlled by a spring 20, of which one end is hooked on to a threaded spindle 21 adjustably carrying a member 22 which rests in grooves in arms 23 on the member 10, while the other end is hooked on to a pointer 24 moving over a dial 26 and adjustable by means of a segment 27 and tightening screws 28. The terminals 8, 9 and dial 26 are carried on an insulating piece 30 which covers an opening along one side of the casing 4 only partially, so that air may cool the coil 1.The member 10 carries an insulating piece 32 through each of two holes in which a set of terminal wires of the coil 7 are brought out, each set being sweated into the bend of a copper strip 35, riveted to the piece 32 and forked to receive copper laminations 36 of which the other end is connected between copper strips 37 leading to terminals 8, 9. An initial adjustment of the spring 20 may be made by means of the screwed spindle 21 with the pointer 24 in its mid-position, and an incision 39 made in the spindle 21 to mark this setting, the dial 26 being subsequently calibrated. When the current in the coil 1 reaches a predetermined value, the coil 7 is drawn inwards, and with it the disc 16, so that the contacts 17, 18 are no longer bridged and the control action becomes effective. When the current falls, the spring 20 restores the member 10 and the control action becomes ineffective. The magnetic circuit could be laminated, and the member 10 could be gravity-controlled and given a time-lag; also the control switch may be arranged to make a circuit: to make the control action effective.