Abstract: An actuator (144) for initiating a trip of a circuit breaker. Load current passes through a conductor (66) that is electrically coupled to a contact arm (56) by a braid (62). A thermally responsive bi-metal (64) has a first end portion which is disposed against a portion of the conductor (66) and through which at least a portion of load current carried by the contact arm, the braid, and the conductor passes. The bi-metal further has a second end portion that is disposed in spaced relation to the conductor and is cantilever-mounted on the portion of the conductor via the bi-metal's first end portion. The bi-metal is nominally flat and straight, but increasingly warps as thermal energy in the bi-metal increases. Upon attaining a certain degree of warping, the bi-metal initiates a trip of the circuit breaker by causing the contact arm to swing from a circuit-making to a circuit-breaking condition.

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.

Abstract: A current limiting circuit breaker including novel clutch arrangements between the contact arms of the circuit breaker and the crossbar. The clutch arrangements include cam surfaces formed on the crossbar from plastic and a cam follower attached to each contact arm. A cam surface is located on each side of each contact arm and each surface may be formed integrally with an insulating barrier. To reduce wear on the cam surfaces, each cam follower includes a roller which contacts the respective cam surface. The cam surfaces are configured to permit the contact arms to blow open under unacceptable fault conditions even though the crossbar remains stationary.

Abstract: A current limiting circuit breaker including a novel spring arrangement between the contact arms of the circuit breaker and the crossbar. The spring arrangement includes a single spring which holds the cam follower attached to each associated contact arm in contact with cam surfaces of the crossbar. The longitudinal axis of the spring is located within a plane passing through the longitudinal axis of the contact arm, wherein the plane is also perpendicular to the rotational axis of the contact arm. The cam surfaces and spring are configured to permit the contact arm to blow open under unacceptable fault conditions even though the crossbar remains stationary.

Abstract: A multi-phase circuit breaker including novel crossbar for opening and closing the circuit breaker contact arms. The crossbar is a one-piece plastic component molded to include an operating arm, insulating barriers for separating the contact arms of each phase, and the cam surfaces which interact with the cam followers of the contact arms. The operating arm is linked to the operating mechanism of the circuit breaker so that operation of the mechanism will pivot the crossbar which pivots the contact arms between their open and closed positions.

Abstract: A circuit breaker has a pair of poles, either of which can experience a ground fault. A sensing device senses an imbalance of current between the phases and neutral, and a trip device responsive to the sensing device simultaneously trips both of the poles when an imbalance of current (ground fault) is sensed in either of the poles. The trip device includes a trip lever engageable with each of the poles and a single solenoid for controlling operation of the trip lever.

Abstract: A housing is provided for a circuit breaker. The circuit breaker has contacts capable of being in an open state or a closed state, of movement between the open and closed states, and of generating a hot gas in consequence of that movement. An electronics module is provided for controlling movement of the contacts from the closed state to the open state. The housing has a first portion housing the contacts and a second portion housing the electronics module. The second portion is formed of a material subject to damage by the hot gas, and the first portion is constructed to protect the second portion from damage by the hot gas. The first portion is ideally formed of a thermosetting material resistant to damage by the hot gas and the second portion is ideally formed of a thermoplastic material, which reduces the cost of manufacturing the housing. A quick-mounting construction for assembling the second portion with the first portion further reduces the cost of assembly.

Abstract: A pivoting lower contact arm arrangement and a circuit breaker including the arrangement. The pivoting lower contact arm arrangement includes a pivoting lower contact arm and a biasing arrangement. The biasing arrangement maintains the contact arm in an operating position with a first force, and biases the arm from a blown-open position toward the operating position with a second force. The first force is greater than the second force to provide increased separating speed when the pivoting lower contact arm blows apart from a pivoting upper contact arm of the circuit breaker and moves from its operating position. The biasing arrangement also variously provides magnetic shielding and coupling between the pivoting lower contact arm and other current carrying components of the circuit breaker. The magnetic shielding enhances the blow-apart forces between the pivoting upper contact arm and the pivoting lower contact arm.

Abstract: A pivoting lower contact arm arrangement and a circuit breaker including the arrangement. The pivoting lower contact arm arrangement includes a pivoting lower contact arm and a biasing arrangement. The biasing arrangement maintains the contact arm in an operating position with a first force and biases the arm from a blown-open position toward the operating position with a second force. The first force is greater than the second force to provide increased separating speed when the pivoting lower contact arm blows apart from a pivoting upper contact arm of the circuit breaker and moves from its operating position. The biasing arrangement also variously provides magnetic shielding and coupling between the pivoting lower contact arm and other current carrying components of the circuit breaker. The magnetic shielding enhances the blow-apart forces between the pivoting upper contact arm and the pivoting lower contact arm.