Improved circuit breaker trip mechanism

A miniature circuit breaker which is wholly contained within a screw-type envelope for a type S fuse. The breaker trip mechanism is of the type which has a resetting plunger, and a current sensing device which moves relative to the plunger. In order to limit the travel of the current sensing device under trip conditions, stop shoulders are formed on the body of the plunger. The current sensing device takes the form of a bimetallic member formed with a leading latch edge and a trailing edge. In order to prevent the trailing edge from engaging a cooperating latch member during resetting of the circuit breaker, a tang projects from the trailing edge across the cooperating latch member. The circuit breaker housing is of one-piece construction, and has an open end through which the trip mechanism is inserted. The trip mechanism incorporates a plunger-biasing coil spring at the bottom of the trip mechanism. In order to retain the compression spring in assembly with the plunger while the trip mechanism is dropped into the open end of the breaker housing, the spring is frictionally received within a recess formed at the bottom of the plunger. The current sensing device includes a pair of bimetallic pincers embracing the plunger, and one of these pincers is formed with a through cut in order to divert all of the current to the opposed pincer, at least under trip conditions. One of the external electrodes of the breaker is formed of inexpensive round wire stock.