GB612110A - Improvements in or relating to non-free-tripping overload circuit breakers - Google Patents

Abstract

612,110. Automatic circuit-breakers; tumbler switches; thermal switches. IGRANIC ELECTRIC CO., Ltd. May 10, 1945, No. 11720. Convention date, May 10, 1944. [Class 38 (v)] In a non-trip-free circuit-breaker provided with a bimetal overload release, the bimetallic element is protected against burning out should the circuitbreaker be held closed, by an auxiliary switch which closes its contacts to short out the bimetallic element and its associated heating coil. A lever 16 actuates a contact arm 46 which rocks on a forked conductive pivot 44 and completes a circuit between terminals 100 comprising a strip 107, 105, 42, 44, the arm 46, contacts 47, 37, strips 36, 35 and 80, 79, a bimetal strip 65, a conical heater coil 102 and a strip 96, 97. The lever 16 is initially biassed to the " off " position, shown dotted in the Figure, by the enlarged end 31 of a slidable insulating plunger 30, urged by a spring 33. As it slides in a recess 29 the plunger 30 causes a lug 58 on a metal plate 54 to traverse a slot 61 in an insulating plate 60, which is interposed between upper and lower moulded insulating members 11, 12. A lug 63 welded to the bimetal strip 65 normally latches the lug 58 when the lever 16 is moved to the " on " position, retaining it there when the operating force is removed until an overload current heats the strip 65 and deflects it downwards. As the lugs 63, 58 unlatch, the plunger 30 moves the lever 16 to the " off " position. If the lever 16 is held " on " during a sustained overload, an arm 82, rigidly joined to the strip 65 at 81, continues to move downwards until contacts 90, 91 close, short-circuiting and thus protecting the strip 65 and the coil 102. The ends of the strip 65 are pressed upwards by springs 86, 75 against a free pin 83 and the enlarged end 71 of a threaded member 73. An internally-threaded rivet 93 with a rectangular head 94 secures the strip 96 to the member 12 and carries a stud 92 on which the contact 91 is mounted. The sensitivity of the overload protection is varied by a factory adjustment of the members 73, 92 and the spaces 77, 99 sealed. The lever 16 is pivoted at 17 between a metal plate 10 and the member 11, the parts 10, 11, 12 being held together by four long rivets. The circuit-breaker is mountable as a unit behind a panel by screws entering two resilient locking nuts 115. An insulating cup 123 is a push fit over the strips 35, 80 or is stuck on to the member 12. The contacts 37, 47, 90, 91 may be of silver. The Specification as open to inspection under Sect. 91 describes and illustrates a circuitbreaker having no auxiliary switch to protect the bimetallic element which is without a heating coil, and also refers to U.S.A. Specification 2,342,945. This subject-matter does not appear in the Specification as accepted.