GB744186A - Improvements in or relating to electro-magnetic switches - Google Patents

Abstract

744,186. Electromagnetic switches. PARVEX. June 17, 1953 [July 28, 1952], No. 16700/53. Class 38(5) A switch intended for starting a single phase motor has its operating winding 3 connected in series with the main motor winding whereby the heavy current flow upon switching on of the motor causes downward movement of a plunger core 4 against the action of a spring 10 to close the motor starting winding through contacts 7, 8. The contacts 7, 8, Figs. 2, 4, are carried by a conducting strip 9 secured, cross-wise, to a blade spring 6 stressed between the resilient arms of a strap 5 attached to the plunger 4. When the core is attracted, the strip 9 engages abutments 16, 17 of the insulated switch casing 1 and forces the blade 6 overcentre so that it is upwardiy bowed and the contacts 7, 8, bridge fixed contacts 12, 13. When the current decreases after the motor has started, the spring 10 moves the strap 5 upwards and the spring 6 is reversed to its initial position due to the reaction between the contacts 7, 8, 12, 13, which then separate. A screw 11 permits adjustment of the operating-current value. The abutments 16, 17 may comprise auxiliary contact studs. In a modification. Fig. 8, a pair of blades 22, 23 act between the strap 5 and a contact-carrying cross-piece 24 of inverted channel section. The coil 3 may be enclosed in a magnetic sheath, and a dashpot may be provided to give a timedelay.