GB848574A - Improvements in and relating to electric circuit breakers - Google Patents

Abstract

848,574. Automatic circuit - breakers. MECHANICAL PRODUCTS Inc. Aug. 21, 1957 [Sept. 5, 1956], No. 26366/57. Class 38 (5). A circuit-breaker has a contact-carrying member 39 pivoted at 41 on a plunger 17 and normally latched in the closed position by a bimetallic element 51 against the opening bias of a spring 47, the plunger being retained against the bias of a spring 23 in the " on " position by a latch 69, Fig. 1. In the event of an overload condition the bimetallic element 51 disengages from a shoulder 59 on the member 39 which pivots under the action of the spring 47 to open the contacts 15, 43. A rivet 65 on the member 39 then causes the latch 69 to turn about its pivot 71 and disengage from a shoulder 75 on the plunger 17 so that the plunger is forced down by the spring 23 to its " off " position, Fig. 3. Resetting is effected by pushing in the plunger whereon a cam 33 on the plunger initially moves the latch 69 away to permit movement of the plunger to the position in which the latch 69 is relatched with the shoulder 75 by the force of a spring 77. The inward movement of the plunger re-engages the shoulder 59 with the bimetallic element and then moves the member 39 to reclose the contacts. The plunger 17 is in two parts 19, 21 which are interconnected by a rivet and slot connection 37, 31 which provides lost motion between the two parts of the plunger. This enables the circuit-breaker to be opened manually by pulling the plunger outwardly so that the cam 33 which is on the part 21 moves the latch 69 to release the part 19 which is provided with the shoulder 75. The plunger is then moved outwardly by the spring 23 to open the contacts 15, 43.