GB759205A - Improvements in electric circuit breakers - Google Patents

Abstract

759.205. Electromagnetic switches. MAGNETIC DEVICES, Ltd. (Guardian Electric Manufacturing Corporation). March 30, 1954, No. 9278/54. Class 38(5) A sealed casing of an electromagnetic heavy direct current breaker comprises a metal can 20 with a flanged cover 24 soldered thereto at 24b, the cover 24 having two diagonally disposed apertures 26 for the threaded stems of the contacts 34 and two smaller apertures 28 on the other diagonal for the threaded stems of the terminals 36 for the solenoid 60. The inner ends 34a, 36a of the members 34, 36 are hexagonal and received in similarshaped recesses in an inner insulating plate 30. the ends 34a having a convex contact surface engaged by a bridging bar 54 when the solenoid is energized (Fig. 8, not shown), to move a plunger 58 against a spring 62. The threaded stems of the members 34, 36 extend through holes 30b. 30a in the plate 30 and through larger holes 32a, 32b in an outer insulating plate 32, the holes 32a, 32b containing a bowed spring washer 42 or 48, a flat washer 44 or 33, and a rubber washer 46 or 52. Thus by tightening circular nuts 38, 40 on the threaded stems the members 34, 36 are sealed in the casing cover. To extinguish the arc on circuit breaking, a permanent magnet washer, Fig. 9, formed in two parts 64, 66, is clamped beneath the contact heads 34a, the washers having depending ears 64c. 66c and being magnetized such one pair of mating ears 64c, 66c is a +ve pole and the other pair a -ve pole. To cool the arc a copper washer 68, Fig. 10, is clamped beneath the heads 34a, the washer having a baffle portion 68c on which the arm impinges. The casing may be evacuated and filled with nitrogen.