GB711391A - Improvements in or relating to thermally operated electric overload circuit breakers - Google Patents

Abstract

711,391. Automatic circuit-breakers. BELLING, & LEE, Ltd. Sept. 5, 1952 [Jan. 17, 1952], No. 1411/52. Class 38(5) A miniature circuit breaker for mounting in radio and television receivers comprises a movable contact 26 normally retained against the tension of an integral helical spring 27 by the jaws 18 of a clip 12 formed by bending a bimetallic strip back upon itself at 13, an eyelet 16 securing the clip to a base 10. The clip 12 is surrounded by insulation 21 and a heater coil 22, one end 23 of the coil being secured to the eyelet 16 and the other end 24 to a terminal tag 25, the other tag 28 being connected to the spring 27. Hence the circuit is normally completed between tags 25, 28 through the coil 22, clip 12 and contact 26. On overload the jaws 18 separate to release the contact 26 and open the circuit, a coloured sleeve 30 on the contact indicating its position. In another construction, not shown, the circuit breaker is mounted in a cartridge similar to a cartridge fuse, and comprises a pair of bimetallic strips welded together at one end to form a clip as in the previous example. The welded end of the strips is insulatingly secured to one end cap of the cartridge and is surrounded by a heater coil connected at one end to the strips and at the other end to the end cap. A helical tension spring is secured to the other end cap, the free end of the spring having a transverse contact portion which is normally retained by the clip against the spring tension. On overload the clip releases the contact and the spring retracts. The end of the transverse contact portion is bent back through the centre of the spring and extends through a hole in the end cap to which the spring is secured, the projecting spring end carrying a coloured indicator, depression of which resets the breaker.