GB569971A - Improvements in or relating to automatic electric circuit breakers - Google Patents

Abstract

569,971. Automatic circuit-breakers. SHEPHERD, G. R. (Westinghouse Electric International Co.). Dec. 31, 1943, No. 21936. [Class 38 (v)] A circuit-breaker preferably of the " deadfront " type, has a trip mechanism comprising an electromagnetic and a thermal trip means independently operable to actuate an axially-rotatable trip bar to cause opening of the breaker with predetermined circuit-conditions, and means for controlling the operation of the trip mechanism independently of the circuit-conditions. The base 1 has knife contacts 10, 11 for removably engaging clips 12, 13 on a panel 14, the contact 10 being recessed to engage a pin 22 on the clip 12 to ensure separation at 11, 13 first. Movable contact 5 co-operates with contact 3 in a magnetic-plate arc-chute and is carried by an arm 4 pivoted at 23 and movable, together with the arms 4 of other poles, manually on and off, by means of a spring-toggle arrangement, provided a cradle 33, pivoted at 34, is retained by a latch 80, Fig 4. A unitary trip structure comprises a base 46 accommodating a bimetal and an electromagnetic, trip for each pole. The latch 80 is slot pivoted to a pin 73, and biased clockwise, Fig. 5, by a spring 79 to oppose the thrust of cradle 33. The tail 76 is held by a part 77 of a common trip bar 66 which is biased by spring 68 clockwise about its pivot in brackets 87, Fig. 4, and movable against this bias by a series bimetal strip 49 or trip magnet. The trip coil comprises a copper strip 64 and highresistance strip 65, which serves also as heater for the bimetal, encircling the centre limb of the E-shaped coil 57 riveted at 62 to the base 46. The armature 58 is urged about pivot 59 by a compression spring 61 so as to bear on a setting- member 84 pivoted on screw 85, Fig. 5. To ensure tripping of the breaker when being removed from panel 14, the trip bar 66 is engagable by the widened part of a push rod 87 which projects through a hole in the base and is urged to bear normally on the panel surface by a spring 88, resetting of the trip mechanism being impossible while the breaker is detached. In a modification, Fig. 2 (not shown), the back of the panel supports a remote control electromagnet, the armature of which operates a trip rod similar to rod 87 of Fig. 1 and prevents resetting so long as it is engaged. In a further form, Fig. 3 (not shown), the trip bar 66 is locked by depression of a push-button as, for example, in starting a motor. In further forms, Figs. 6, 7 (not shown), the electromagnet trip armature of each or all the poles can be locked against operation by a separate or common push-button, the thermal release being free to operate the trip bar in both cases. In all these forms, the push-button may be latched in the operative position to prevent resetting.