Molded case circuit breaker with a movable electrical contact positioned by a spring loaded ball

摘要

A molded case circuit breaker includes a movable upper electrical contact member having an end portion with an arcuate cam surface formed thereon for engaging an exposed spherical surface of a spring-loaded ball that is disposed in a pocket provided in a rotatable cross-bar of the operating mechanism of the circuit breaker. A compression spring is also disposed in the pocket between the cross-bar and the ball to supply sufficient biasing force to the end portion of the movable upper electrical contact member to enable the upper electrical contact member 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 rotates and the arcuate cam surface thereof moves against the exposed surface of the then stationary spring-loaded ball. The arcuate cam surface of the end portion is configured to provide a 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 exposed surface of the spring-loaded ball to retain the movable upper electrical contact member in a BLOWN-OPEN position, thereby minimizing the possibility of contact restrike.