GB565451A - Improvements in or relating to electric overload responsive circuit interrupters - Google Patents

Abstract

565,451. Automatic circuit-breakers. SHEPHERD, G. R. (Westinghouse Electric International Co.). Dec. 31, 1943, No. 21934. [Class 38 (v)] In order to render the ambient-temperature compensation of a thermally-released circuitbreaker constant in effect, the compensating means is connected to the thermal control element without any possibility of lost motion between them. The invention is shown as applied to the construction in which the movable contact is manually operable in both directions with a snap action. The contact arm 25 is fastened to a carrier 31 which is pivoted at 35 to the base and at 71 to a toggle 47, 49, the upper pivot 73 of which engages the crutch of a cradle 45 pivoted at 63 and normally held latched at 91. The toggle knee is connected by D.C. springs to a handle-lever 43 pivoted at 55 and having a member 61 for resetting the cradle 45 after tripping.- Latch 91 is a screw which is factory-adjusted and sealed in the current-carrying bimetal strip 79 which is secured to a 'bracket 81 pivoted at 85 to a further bracket 83 and biassed clockwise by a spring 119: Bracket 81 also carries an insulating thrust member 111 which is urged by spring 119 against an adjustable screw 109 in the compensating bimetal strip 103, the point of engagement being on the line connecting pivot 85 with the nearest fixed part of strip 103. The latter flexes downwards on temperature-, increases, and spring 119 causes bracket 81 to rotate clockwise, so compensating for the anticlockwise flexure of 79. The hole 121 accommodating members 109, 111 is not large enough to allow heat within the casing to affect the strip 103, even when the breaker is oil-immersed. In Fig. 3, the strip 129, instead of acting as a latch, trips by a positive clockwise movement and accordingly the strip 103 moves upwards, the bias spring 165 tends to rotate bracket 81 anti-clockwise, and a piano steel wire connection - 157 is held in tension between an adjustable screw 155 and a washer 161 insulatingly carried on bracket 81 by the bushing 159 and nut 163. Strip 129, or each strip of a multi-phase switch, rotates a common trip shaft 123 clockwise, whereby a slot 139 in a bracket 137 slips round .a projection 131 on shaft 123, under the action of a spring 145 strained by the projection 131 and biassing the bracket 137 anti-clockwise about its pivot 141. The cradle-latch 151 thus moves clear of a slot 149, the lower end of which is engaged by the descent of the cradle to reset the latch prior to the handle-lever being moved back to the closed position.