GB787667A - Improvements relating to electro-magnetic switches - Google Patents

Abstract

787,667. Electromagnetic switches. STONE & CO. (DEPTFORD), Ltd., J. April 6, 1956 [April 13, 1955], No. 10653/55. Class 38 (5). A switch intended for use as a cutin switch in a train-lighting installation &c. for automatically connecting a generator to a battery and/or a load at a predetermined generator voltage, comprises shunt and series windings 2, 3 mounted on a yoke 1 and controlling a clapper armature 6 carried on a structure 7 pivoted by a cross leaf spring hinge 9. Arms 10 on the structure 7 operate, respectively, a normally open main contact 11 and a normally closed main contact 12, the contacts being pivoted at 13 and biased by springs 14. An arcing contact 15 carried by the structure 7 and connected in shunt with the contact 11 closes before and opens after the latter contact. A spring 19 connected at one end to a temperature-compensating bimetal 23 and at the other end to an adjustable screw device 24 mounted on an arm 17 of the structure 7, restores the armature. The winding 3 is in series with the contact 11 and the load, the winding 2 being initially energized through contacts 26, 35 of an auxiliary switch which short-circuit an adjustable economy resistance 25. The circuit is given in Fig. 5, not shown. The auxiliary switch comprises a blade 27 connected at its lower end to a pivot pin 33 carried in a mounting 34, the blade being held in a bowed condition by a pair of coil springs 30 connected between eyes 31 in the upper end of the blade and ends of the pin. The contact 26 on the blade is operated with a snapaction between a pair of fixed contacts 35, 36 by a bifurcated finger 28 embracing the blade with lost-motion and fixed to the structure 7. The arrangement produces a large operating differential relative to the position of the armature 6 so that when the coils 2, 3 are energized the blade 27 is not snapped to disengage contact 35 and engage contact 36 until the armature has nearly completed its movement, whereas when the armature releases, the blade 27 is not returned until the armature has nearly engaged its back stop 20.