Abstract: A pushbutton resettable circuit breaker is shown having features to prevent manual opening by simply pulling outwardly on the pushbutton. In one embodiment, the pushbutton (16) is formed with slots (16b) which are configured to provide a reaction surface essentially inaccessible without a special purpose contact opening tool (30). The tool is provided with portions that are insertable into the slots and into engagement with the reaction surfaces for pulling the pushbutton out and manually opening the contacts. In a second embodiment, a small aperture 16k is formed through the rating tab and top and wall of the button and in alignment with a movable plunger (28). A special purpose contact opening tool (32, 34) can be inserted through the aperture to apply a force to the plunger and mechanically trip the circuit breaker.

Abstract: A miniature aircraft type circuit breaker (10') has a threaded mounting bushing (18) in which a push button (20) is slidably received. Push button (20) is coupled to a movable contact arm (24) to move a movable electrical contact (26) into and out of engagement with a stationary electrical contact (28). A flexible fluid splash barrier sleeve (32) is telescopically received on a reduced diameter portion (34) of push button (20) above a white indicator portion (30) of the push button and has a lower distal end portion (36) which engages an annular top surface (38) of the bushing when push button (20) is depressed to bring the electrical contacts into engagement. Adhesive material may be used to affix the barrier sleeve to the reduced diameter portion (34) which optionally can have a roughened surface to enhance adhesion.

Abstract: A circuit breaker has a thermally responsive bimetallic member of substantial resistance properties disposed in the breaker circuit so that it self-heats and moves to trip a mechanism to open the breaker circuit after a selected period of time when a selected overload current occurs in the circuit. Conductors are joined by a thermally separable bond and are disposed in the breaker circuit in selected heat transfer relation to the high resistance bimetallic member to be thermally separated after a selected delay period by heat transferred to the bond from the bimetallic means, thereby to open the circuit in the event that movement of the thermally responsive member is ineffective to open the circuit. Spring means preferably bias the conductors to separate to assure circuit opening when thermal separation of the noted bond occurs. Preferably one of the conductors has a part of reduced cross-section adapted to rupture and open the circuit under alternate circuit conditions.

Abstract: In order to eliminate contact bounce and electrodynamic repulsive forces upon closure in a standard high rating circuit breaker device when a fault exists, an armature is disposed on the movable contact assembly and an iron core pole is disposed adjacent the stationary contacts, the normal current path providing a partial turn about the core. As current passes through the contact assembly the resulting magnetic field attracts the armature and hence the movable contact assembly toward the stationary contacts.