MOLDED CASE CIRCUIT BREAKER WITH A MOVABLE ELECTRICAL CONTACT POSITIONED BY A CAMMING LEAF SPRING

摘要

A molded case circuit breaker includes a movable upper electrical contact carried by a contact member having an end portion with an arcuate cam surface formed thereon for engaging an outwardly projecting cam surface of a leaf spring. The leaf spring is secured to and disposed around an enlarged portion of a rotatable cross-bar of the operating mechanism of the circuit breaker. The leaf spring has an outwardly protruding cam surface and is mechanically configured to provide sufficient biasing force to the end portion of the movable upper electrical contact member to enable the upper electrical contact member and upper contact to move in unison with the cross-bar during normal operation of the breaker. Upon the occurrence of a high level short circuit or fault current of sufficient magnitude, the upper electrical contact member and upper contact rotate and the arcuate cam surface thereof is moved against the then stationary cam surface of the leaf spring. The arcuate cam surface of the leaf spring and the arcuate cam surface of the end portion of the contact member are configured to provide decreased biasing force as the upper electrical contact member rotates to its BLOWN-OPEN position. A detent or groove is formed along the arcuate cam surface of the end portion of the contact member for receiving the outwardly projecting cam surface of the leaf spring to retain the movable upper electrical contact and contact member in a BLOWN-OPEN position, thereby minimizing the possibility of contact restrike.