GB238358A - Electromagnetic interrupters for the intermittent illumination of electric lamps - Google Patents

Abstract

238,358. British Thomson-Houston Co., Ltd., (General Electric Co.). July 26, 1924. Electromagnetic interrupters.- A continuous slowacting interrupter for flashing lamps on buoys, the operation of which is unaffected by wave-motion, comprises a rocking armature 20, the ends of which are attracted by the poles of a U-shaped electromagnet, carried on a central pivot 19 so as to be mechanically balanced on a non-magnetic lever 17 itself carried on a fixed pivot 16 and mechanically balanced by the weight 31 and the screw adjustment 32. The armature is normally drawn away from the poles by a spring 22, so that the lever 17 rests against an adjustable stop 25, and a contact blade 27 bears against the contact 26. To provide for a slow time-period of interruption the magnetic circuit of the electromagnet is made of low permeability and a thick conducting sleeve or thick closed coil is arranged round each core. This gives a long time constant to the electromagnet, and further to slow down the rate of interruption one of the poles has secured to it a channel-shaped pole-piece 35 constituting a double pole. The stop 25 is adjusted so that the end of the armature lies midway between the poles of the double pole-piece, and, with this adjustment, the armature is not attracted at that end until the maximum flux has been built up in the electromagnet. The circuit arrangements are shown in Fig. 4, the lamp 41 and the electromagnet being supplied separately from the battery 39 each through the make-and-break contact 27.