GB574658A - Improvements in or relating to electric overload circuit breakers - Google Patents

Abstract

574,658. Automatic circuit-breahers. SHEPHERD, G. R. (Westinghouse Electric International Co.). Feb. 1, 1944, No. 1838. [Class 38 (v)] An electromagnetically and thermally-released circuit-breaker, adapted also to be manually opened and closed, comprises an insulating casing 7 having a removable side-plate 23, Fig. 5, in recesses in which the parts are pivoted or housed. The movable contact 15 is mounted on a lever 31 fulcrummed in the apex 53 of a V-lever 33 pivoted at 43 and normally retained by a latch 57. The operating lever 35 is fulcrummed in a bearing surface 45 in the casing 7 and connected to the contact lever 31 by a dead-centre spring 37 which is anchored to the lever 35 by a pin 51 carrying a roller (not shown) rolling on a surface of side-plate 23. When the latch 57 releases the lever 33 on overload, the spring 37 carries the lever 33 round until the apex 53 is above the spring- axis, whereupon the contact-arm 31 opens and the lever 35 moves down to an intermediate indicating position determined by a resetting projection 55 thereon engaging the lever 33. To reclose, the lever 35 is moved to its lowest position so that projection 55 moves the lever 33 to its latched position, the lever 35 being then restored to the position shown to re-engage contacts 13, 15. An arc-chute 29 with U-shaped magnetic plates 27 is provided. The latch 57, Fig. 5, has pivots 63 and cut-away parts to form a segmental latch-surface 60, Fig. 1, and to receive a lever arm 65 secured to it at 67. One arm of lever 65 has secured to it (or is formed as) a plate-like armature 75 having an integral or attached rib 79 projecting into the gap of a U-shaped magnet 77 energized by a series bimetal strip 61. The latter is adjustable by screw 89 and engages the remote end of arm 65 through a pivoted multiplying cam 83, the final movement of the arm 65 being in this case assisted by the magnet 77. The arm 65 has an ear engaged by one end of a control spring 69 coiled about a stud 71, the spring-force being adjustable by moving its other end into any one of a series of holes 73 in the casing 7. A pigtail 81 connects the bimetal strip with the lever 33.