MOLDED CASE CIRCUIT BREAKER WITH AN IMPROVED INTERNAL VENTING SYSTEM

The invention relates to a molded-case circuit breaker with an improved internal arc gas expansion and venting system. … Next to the arcing region at one end of the arc chute (54) where electrical arcs are initiated upon contact separation, there is provided a gas expansion chamber (408) which is open toward the arc chute. A stationary contact structure (426, 428, 430-436) is disposed in the expansion chamber and has a configuration enabling arc gas to expand directly into the expansion chamber, and causing air forced from the expansion chamber by the expanding arc gas to be directed into the arc chute. At its opposite end, the arc chute communicates with vent means (420) in a wall portion of the circuit breaker housing through an additional gas expansion chamber (406).