Abstract: A multipole circuit breaker having a single contact operating mechanism for all poles and a fault current sensing means for automatic tripping of the breaker is provided with alarm switch means to indicate when opening of the circuit breaker has been caused by a fault condition. The operating mechanism includes a metal frame to which a latchable cradle is pivotally mounted. The frame includes parallel guide slots through which a formed pin actuator extends to be moved by the cradle as it operates between its latched and released (tripped) positions. A spring connected between the mechanism frame and the pin actuator biases the latter toward the cradle. An insulating extension element is adjustably mounted on the actuator to transmit motion of the latter to operate a switch in an alarm circuit, in accordance with cradle position.

Abstract: In a circuit breaker, the movable contact carrying contact arm is pivotally connected to the contact carrier which pivots on the circuit breaker frame; the contact arm is stamped copper; the contact arm carrier pivot connection includes a pin passing through the walls of the carrier and with respect to which the contact arm pivots; also, improved means for establishing pressure of movable contacts.