Abstract: A so-called blow-off type current limiting circuit breaker is constructed with a contact pressure spring that also holds the contact arm in open contact position when the contacts are blown open by electrodynamic forces. A multi-section cam means transmits contact opening and closing forces produced by a spring powered overcenter toggle type operating mechanism to the movable contact arm. A follower on the latter is biased into engagement with the cam means by the contact pressure spring. The cam means is so constructed that during contact blow-off the movable contact arm requires relatively little motion to move overcenter in the opening direction. One section of the cam means is constructed so that when the contact arm moves overcenter in the opening direction during contact blowoff, speed of the contact arm is controlled to an extent that contact rebound does not become a problem.

Abstract: An electromagnetic contactor having a removable cover in front of its contact area is provided with a molded plastic interlock member biased by a torsion spring toward a blocking position in the path of the movable contact carrier. In this position of the interlock member the latter prevents closing of the contactor. However, when the cover is secured in its closed position, engaged complementary inclined cam formations on the cover and interlock member hold the latter in a position remote from the movable contact carrier thereby permitting the contactor to be closed.

Abstract: An electric switch mounted within an enclosure having a hinged cover is manually operated from outside the enclosure by a handle mechanism secured to the enclosure. The cover is provided with a single aperture near the edge thereof remote from the cover hinges, with this aperture providing clearance for the operating handle and housing of the mechanism when the cover is closed and also providing clearance for a catch which holds the cover closed. A defeatable cover interlock prevents opening of the cover when the switch is closed, and a defeatable switch interlock prevents closing of the switch when the cover is open. The cover interlock includes a catch and means biasing the catch to cover holding position. When the cover is open, holding means operate and maintain the catch in cover releasing position to permit slamming of the cover without damaging the catch. Rotatable tool operated means on the handle mechanism also locks the cover closed.