GB556438A - Improvements in electric switches having automatic tripping means - Google Patents

Abstract

556,438. Electricallyreleased switches. ARROW ELECTRIC SWITCHES, Ltd. April 2, 1942, No. 4394. Convention date, April 12, 1941. [Class 38 (v)] A thermally-released circuit-breaker which can be operated manually on and off by a snap-action spring, comprises a pair of movable spring-contacts 44, 46 arranged one behind the other and in separate compartments of an insulating base 10. The hand-lever 12 is pivoted by means of pin 16 guided in slots 18 in the walls of recesses 10s and has a hooked end anchoring one end of a dead-centre spring 20, the other end of. which is fixed to the yoke of a U-shaped member 22. The free ends of member 22 are bifurcated at 22a to engage holes on either side of a part 26b on an adjustment plate 26. A lever 30 pivoted at 28 to member 22 is formed with a detent surface 32 engageable with a bimetal member 34, and with a part 38 adapted to engage a guided insulating plate 40. To close the contacts, by moving from the Fig. 1 to the Fig. 2 position, the lever 30 first moves with member 22 until its surface 32 engages the bimetal 34 and then rotates clockwise using 32 as a fulcrum-point, to raise plate 40. When 34 deflects on overload, the springiness of the contacts causes them to open and return lever 30 to the Fig. 1 position. An adjustment which avoids stressing the bimetal, is provided by means of a screwed rod 80 which moves plate 26, and hence the mechanism itsself, bodily up or down so as to vary its position with respect to the strip. The latter and contact 44 are secured by means of a hollow rivet 50 and a terminal screw 51 therein is connected to one end of a heater coil 60 in a heat-casing 62. The other end of coil 60 is connected to a circuit terminal so as to carry the load in one of the poles.. A terminal 54 and one similar to 50 for contact 44 constitute terminals for the other pole.