GB571997A - Improvements in or relating to electric circuit breakers provided with overload release devices - Google Patents

Abstract

571,997. Automatic circuit-breakers. BEST, N. M. Jan. 25, 1944, No. 1378. [Class 38 (v)] A loose-handle circuit-breaker, adapted to be manually operated to close and open the circuit, comprises a contact-arm 36 pivoted in slots 38 by means of a pin 37 normally retained by a latch. Rotation of hand-lever 35 about pivot 27 causes the arm 36 to be moved to, and held in, the "on" position against a phosphor-bronze spring 40 forming part of the circuit. The retaining latch 46 can be moved about its pivot 47 against spring-action 48 either by an electromagnet 45 of short-circuit rating attracting its core 50 linked to the latch at 49, or the core 50 can be moved by a series bimetal strip 52 on prolonged light overloads. When released, the pin 37 is driven down its slots 38 by spring 40 using the cam-part of the lever 35 as a fulcrum, but after a certain movement, arm 36 moves the lever 35 to the " off" position and the arm is relatched ready for reclosure. In Fig. 2 (Prov.), the spring-controlled latch-lever 18 is pivoted at 20 and loosely carries armature 16. The bimetal 15 acts as a latch for a lever 30, which is pivoted at 31 and acted upon by a resetting-spring 33 and a compression spring 28 taking the place of that 40 of Fig. 1 (Comp.). When in closed position, spring 28 applies the force to lever 30 to deflect latch 18 and open the breaker, but when in open position, spring 33 is strong enough to overcome 28 and restore the lever 30 to a position to be reengaged by the strip 15. The side-cheeks 25 of the magnet are extended about the contacts 11, 13 to form a magnetic blow-out.