Abstract: A circuit interrupter includes an interchangeable trip unit removably disposed in the circuit interrupter housing and connected between a current transformer and a trip mechanism. The trip unit contains electronic circuitry for activating the trip mechanism to open the contacts upon detection of overload current therethrough and includes rejection means provided to ensure that only a trip unit having circuitry compatible with the electrical characteristics of the circuit interrupter can be inserted into the housing. The rejection means comprise a plurality of pins mounted within the housing and extending into the recess to be occupied by the trip unit. The pins are arranged in a pattern unique to all circuit interrupters having identical electrical characteristics. A pattern of holes is provided in the enclosure of the trip unit, the hole pattern being unique to trip units having identical electrical characteristics.

Abstract: A circuit interrupter includes an adjustable trip unit for tripping the circuit breaker to the open circuit position upon overload current conditions. The trip unit includes a shorting plug adjuster comprising a pair of connecting pins electrically connected together and insertable into cooperating sockets in the trip unit housing. One of the pins is common to all adjustment positions and is of greater length, having a retaining clip at the end thereof to permit the adjuster to be partially withdrawn, pivoted about the common pin, and inserted into the desired position. The adjuster comprises a flange which covers the trip unit panel socket in all positions, thereby providing protecting against dust and other contamination. The adjuster is cheaper and more reliable than the prior art, providing increased protection against shock, vibration, and contact bounce.

Abstract: A circuit interrupter is provided with a trip unit removably inserted into the housing of circuit interrupter through the cover thereof. The trip unit is secured to the housing by spring clips mounted therein cooperating with recesses in the enclosure of the trip unit to permit insertion of the trip unit with the cover installed but preventing removal of the trip unit without prior removal of the circuit interrupter cover.

Abstract: A circuit interrupter characterized by a manually operated fast acting switch and an overload relay for tripping of switch in response to current overload. The switch comprises means for moving electric contacts between open and closed and tripped positions which means includes a releasable arm which is movable between latched and unlatched positions. The switch also comprises a pair of pushbuttons for manually opening and closing the switch which pushbuttons are effective to move a lever which in turn actuates an overcenter toggle mechanism for opening and closing the switch.

Abstract: A circuit breaker responsive to abnormal currents in conductors of an electrical distribution system characterized by separable contacts and trip means therefor, which means comprises a stationary magnetic structure for each conductor including a magnetic coil and core assembly and armature therefor, a lever associated with each stationary magnetic structure removing a trip bar to an unlatched position, the lever comprising the armature and being movable in response to abnormal currents in at least one of the conductors, and tension means for varying tension on the lever and including a manually operable cam, cam follower, and tension spring operatively connected between the cam follower and the lever for adjusting the force required to attract the armature to said assembly.

Abstract: A multi-pole circuit breaker with adjustable thermal trip unit characterized by a circuit breaker mechanism having a plurality of pole units, means releasable when released from a latched position to effect simultaneous opening of the circuit breaker contacts, a multi-pole trip device including trip means for each of said pole units, each of said trip means being constructed to operate upon the occurrence of certain current conditions to effect release of said releasable means, and each pole unit comprising a bimetal element responsive to current flow to effect heating thereof.