Molded case circuit breaker with resettable combined undervoltage and manual trip mechanism

Claim 1

An electrical circuit breaker comprising: a first electrical contact; a second electrical contact; operating means for moving said first and second electrical contacts into engagement and out of engagement; undervoltage trip means for actuating said operating means to perform a trip operation to disengage said first and second contacts upon the occurrence of an undervoltage condition; and a case for housing said first and second contacts and said operating means and said undervoltage trip means; said trip means maintaining said operating means in a tripped condition until said trip means is reset and comprising; a solenoid having an electrical coil; a pair of first and second separable ferromagnetic plungers serially disposed within said coil; a compression spring disposed between said first and second plungers for separating said plungers, the compressive force of said compression spring being less than the electromagnetic force provided by said coil when energized by a voltage greater than a predetermined value; and reset means engageable externally of said circuit breaker for resetting said trip means, set reset means comprising a reset button in engagement with said first plunger and adapted to extend exteriorly of said case through an aperture formed therethrough.