GB871931A - Improvements in and relating to multi-pole electric circuit breakers - Google Patents

Abstract

871,931. Automatic circuit-breakers. FEDERAL PACIFIC ELECTRIC CO. June 30, 1958 [July 3, 1957 (2)], No. 20922/58. Class 38 (5). A multi-pole circuit-breaker has a currentresponsive latch and a contact arm for each pole, the arms being coupled to a common handle by toggle connections arranged so that the displacement of the toggle of one pole, when that pole is tripped on overload allows collapse of the toggles of the other poles to initiate their opening movement before the contacts of the overloaded pole separate. Each pole has a contact arm 50 pivoted on a spring 52 and carrying a bimetal latch 62 and magnet core 76, all generally similar to the unit described in Specification 778,952. The end of the latch 62 engages a bimetallic compensating member 60 on an arm 56 insulatingly pivoted at 54 on the contact arm. The handle 30a is an extension of a moulded member 30 which is coupled by a metal shaft 34 to two further moulded members 28, 32 which are journalled in the composite casing. The members 28, 30, 32 form a composite operating member which has two extensions 28a, 32a enclosing members 36 having projecting pivots 36a which engage in slots 40 in the ends of a common trip-bar 38. This bar has apertures for three wire members 42a, 42b, 42c which are pivoted at 58 to the arms 56 of each pole, and normally engage stops 38a of the bar 38. Fig. 2 shows one pole in the open position with the pivot 36a at the top of the slot 40 owing to a spring-biased plunger 78 on the bar 38 engaging the member 30. During movement to the closed position, Fig. 1, the toggle formed by the members 36, 38 passes over-centre and the knee pivot 36a passes to the lower end of the slot 40. When the latch 62 disengages the member 60 the spring 52, which is stressed in the closed position, causes the arm 56 to move about the contacts to the Fig. 3 position before the spring 72 opens the contacts. This movement causes anticlockwise rotation of the bar 38 and collapse of the retaining toggles of the other two poles and all their contacts open substantially simultaneously even if the handle 30a is held in the " on " position. The handle is automatically restored to the "off" position to reset the toggles but it may be held in an intermediate position by friction so as to require hand resetting. The apertures in the bar 38 for the ends of the members 42a, 42b, 42c are formed by aligned ends of openings moulded in opposite faces of the bar (Figs. 9 to 12, not shown). Specifications 737,604 and 739,620 also are referred to.