Abstract: A molded case circuit breaker having current limiting capabilities is dimensionally optimized for relatively smaller frame size circuit breakers. The handle yoke is supported with rollers thereby allowing the crossbar to be disposed in the space normally utilized for the handle yoke pivot axis. A clinch joint arcer assembly with a plurality of arcing contact arms, each pivotally connected by a clinch joint to a pivotally mounted main contact arm permits additional main contact arms to be provided in the same space normally occupied by the arcing contact arms alone. Additionally, arcing contact spring housings protect the arcing contact springs from deterioration due to corrosive ionizing gases generated during interruption. A positive off link assembly prevents the operating handle from being placed on an OFF position when the main contacts are welded together and transfers the force applied to the operating handle to the upper link to allow the weld to be broken.

Abstract: A molded-case circuit breaker having an undervoltage release device housed therein is provided with a flexible molded double ended lever for resetting the undervoltage release device and a torsion spring braced upon the two arms of the lever so as to minimize the effects of stress and creep on the molded members when manually actuating repeatedly to reset the undervoltage release device against the biasing spring of the device.

Abstract: Apparatus for adjusting the calibration of a thermal trip unit which is to be used in conjunction with an electrical circuit breaker. A rotatable knob is provided which adjusts the trip unit to between one hundred percent of the rating of the circuit breaker and some value which is less than one hundred percent. An adjustable stop screw is provided to engage the rotatable knob when the knob is rotated to adjust the calibration of the trip unit to the desired value which is less than one hundred percent of the rating of the breaker. The adjustable stop screw thereby limits travel of the adjustable knob between only one hundred percent of the rating of the circuit breaker and the desired value which is less than one hundred percent.

Abstract: A molded case circuit breaker is provided with side plates having twist tabs extending downwardly from a bottom edge for fastening the side plates to the circuit breaker base. Spin plates with slots are carried by the base for receiving the twist tabs. The twist tabs are formed with a shank portion, a tapered portion and a head portion. The tapered portion defines a sloped surface which contacts the slot in the spin plate. When the twist tab is twisted, the shank is shortened drawing a wider portion of the sloped surface into the engagement with the slot to secure the side plate to the base.

Abstract: A trip bar interlock for a circuit breaker characterized by an electrically insulating housing having an apertured bottom wall. A rotatable trip bar is in the housing for releasably holding the circuit breaker in an untripped condition. An actuator is provided for releasing the trip bar when the circuit breaker is dismounted from a mounting surface. The trip bar and the actuator have engaging surfaces and the actuator has an end portion extending through the aperture. The actuator is biased toward the mounting wall.