Abstract: A trip mechanism (140), including two trip actuators, namely a bi-metal trip actuator (144) and a magnetic trip actuator (142), that act on a plunger (160). A plunger guide (162) guides motion of the plunger along a straight line path of travel. Each trip actuator is capable of moving the plunger independently of the other trip actuator to cause the circuit breaker to trip in response to detection of either a thermal fault or a magnetic fault.

Abstract: An actuator (144) for initiating a trip of a circuit breaker. Load current passes through a conductor (66) that is electrically coupled to a contact arm (56) by a braid (62). A thermally responsive bi-metal (64) has a first end portion which is disposed against a portion of the conductor (66) and through which at least a portion of load current carried by the contact arm, the braid, and the conductor passes. The bi-metal further has a second end portion that is disposed in spaced relation to the conductor and is cantilever-mounted on the portion of the conductor via the bi-metal's first end portion. The bi-metal is nominally flat and straight, but increasingly warps as thermal energy in the bi-metal increases. Upon attaining a certain degree of warping, the bi-metal initiates a trip of the circuit breaker by causing the contact arm to swing from a circuit-making to a circuit-breaking condition.

Abstract: A stationary contact assembly is provided for a circuit breaker which has a base, a line terminal and an arc chute. The stationary contact arm is J-shaped and formed from a single piece of conductive material which has a contact affixed to the short leg of the J and is connected to the line terminal. The short leg of the J has a length sufficient for creating electromagnetic blow open forces in response to current flow of a preselected magnitude. An arc runner is positioned between the legs of the J for drawing out an arc into the arc chute and intensifying the electromagnetic repulsion forces.

Abstract: A movable contact arm assembly is provided for a circuit breaker. The contact assembly includes a carrier which has first and second guide plates with aligned roller guides and bracket supports and a roller which has a middle portion extending between the guide plates and the end portions and engaging the roller guides. A bracket extends between the guide plates and engages the bracket supports. A spring is positioned between the bracket and roller which urges the roller along the roller guide. The contact arm has first and second cam surfaces and is positioned between the guide plates and pivotally connected thereto. The roller rides in the guide on the first and second cam surfaces and the roller moves from the first cam surface to the second cam surface as the contact arm moves from a closed position to an open position in response to preselected electromagnetic repulsion forces.

Abstract: A current-limiting electrical apparatus is provided including a housing with first and second electrical terminals contained therein. A pair of electrical contacts is disposed within the housing and electrically connected in series with the first and second terminals. A biasing means applies a biasing force to the pair of electrical contacts to bias them to a closed position. The pair of electrical contacts is configured to cause the contacts to electromagnetically repel each other and to overcome the biasing force and open when the current flowing through the contacts exceeds a predetermined value. A mechanism is provided responsive to the current flowing through the pair of electrical contacts for decreasing the biasing force as the current flowing in the electrical contacts approaches the predetermined value, to thereby decrease the predetermined value causing the electrical contacts to immediately open.

Abstract: An improved anti-rebound mechanism for circuit breakers having a blow-off, current-limiting feature is provided. The improvement consists of a ferromagnetic latch which is activated by any massive current surge through the circuit breaker sufficient to cause blow-off current interruption. The latch is caused to be magnetically attracted to, and engage with, a notch on a movable arm of a circuit breaker to maintain the arm in an open position until the circuit breaker is manually reset in a closed position.

Abstract: A blocking attachment to limit movement of a circuit breaker operating handle consists of a single member constructed of material having the resilient properties of sheet steel. Outwardly extending tabs at opposite ends of the attachment are inwardly movable for mounting and dismounting the attachment with respect to a circuit breaker housing. An inverter L-shaped section of the attachment defines a freeway wherein the circuit breaker handle is movable from On to Trip positions and is readily viewable to determine when automatic tripping has taken place. Handle movement is limited to the freeway so that the circuit breaker may not be opened manually while the blocking attachment is operatively mounted to the circuit breaker.

Abstract: A molded elongated arcuate shield is snap-fitted to a circuit breaker operating handle to achieve a lost motion connection thereto. The operating handle projects through an elongated wall opening in the circuit breaker housing and is movable longitudinally thereof. The shield is disposed between an arcuate interior surface of housing and an arcuate surface of an apron formed integrally with the handle. While the apron above is too short to close the wall opening for all positions of the handle, the apron in cooperation with the shield fully closes the wall opening for all positions of the handle. Latch tabs formed integrally with the shield engage a blocking formation internally of the housing to hold the shield stationary while the handle moves from its On to Trip position. In the former position ON indicia carried by the apron is viewable through an aperture in the shield through which the handle extends, and when the handle is in its Trip position the latched shield blocks the ON indicia from view.

Abstract: A compact molded case circuit breaker having a high interrupting capacity is provided with an arc chute constructed of stacked metal plates notched to form a passage for the movable contact as it moves between open and closed circuit position. The stationary contact is at one end of the arc chute and the arc plate at the other end of the arc chute is provided with a tab that extends outside of the arc chute. In its fully open position, the movable contact is positioned so that at least half of it is outside the arc chute, adjacent the free end of the tab on the last contact plate, and slightly spaced therefrom. The movable contact, in the terminal portion of its movement toward full open circuit position, moves generally parallel to the tab of the last arc plate. This construction assures that all of the arc plates will become active almost instantaneously at the time the movable contact reaches the tab.

Abstract: A multi-pole circuit breaker is provided with a molded insulating housing defining an internal chamber wherein the mechanical trip free contact operating mechanism is disposed, an external recess wherein an auxiliary switch unit is removably mounted, and an external cavity wherein a shunt trip assembly is removably mounted. The switch unit includes one switch operable by the mechanism as it opens and closes the circuit breaker contacts and a second switch operated by the latchable cradle of the mechanism to indicate automatic tripping. The shunt trip assembly includes an electromagnet having an operating member which engages the cradle latch to release the latter.

Abstract: A single pole molded case circuit breaker having a spring powered trip free contact operating mechanism including an extendable toggle connected at one end to a releasable cradle and connected at the other end to a movable contact, a latch for holding the cradle in reset position, and an automatic trip means for operating the latch to release the cradle upon the occurrence of predetermined overload conditions, is provided with anti-rebound means which prevents the movable contact from moving toward closed circuit position except under the influence of the operating mechanism. The anti-rebound means includes engaging formations of the cradle and toggle which cooperate to block the toggle from being extended unless the cradle is in its reset position. As the cradle moves to trip position it engages the toggle to kick the contact arm toward open position.

Abstract: A unitized combination motor starter is provided with a single insulated housing wherein a plurality of pole units are disposed in side-by-side relationship. The pole units are electrically connected in series with an electromagnetic contactor disposed within the insulated housing and located at one end of the pole units. A spring powered contact operating mechanism for the pole units is disposed on one side of the pole units. An overload sensing electromagnet coil, provided for each of the pole units, is positioned for removal and replacement after opening the front cover of the insulated housing.