Abstract: A circuit breaker contact arm (56) contains a straight elongate through-slot (112) that runs generally lengthwise of the contact arm and is closed at both lengthwise ends. Adjacent each slot, a respective side wall (106, 108) of a cross bar (58) contains a bent slot (114) having a knee (116). A respective cylindrical blow-open pin (118) passes through all three of these slots. A small helical coiled spring (120) occupies the contact arm through-slot and is compressed between the blow-open pin and the end of the contact arm slot that is proximate a cross bar/contact arm hinge pin (110). The spring is laterally confined by the adjacent side walls of the cross bar so as to remain in the contact arm slot about which the contact arm swings. The spring acts between the blow-open pin and the contact arm to bias the blow-open pin in a direction away from the cross bar/contact arm hinge axis.

Abstract: A circuit breaker mechanism has a contact arm (56) forming a portion of an interruptable load current path through the circuit breaker and mounted with respect to a pivot (110) for swinging motion to break the current path. A spring-loaded, over-center operating mechanism includes a toggle mechanism having an upper toggle (74) and a lower toggle (122) coupled by a spring pin (128) to form a toggle joint about which the toggles can relatively pivot. The spring pin has a circular groove (128b) at which it operatively connects to the toggle joint, and a circular surface (128a) adjacent the groove is disposed in the path of travel of the contact arm as the contact arm swings to break the current path.