Abstract: A contact arrangement for a circuit breaker utilizes magnetic attraction between parallel conductors in the movable contacts to open the contacts during a short circuit, high current condition. An elongated, pivotable, main contact arm includes a movable main contact at a first end that engages a fixed main contact in a closed circuit position. An elongated, arcing contact arm, pivotable in the same plane as the main contact arm, includes a movable arcing contact at a first end that engages a fixed main contact in a closed circuit position. The contact arms are spring biased in the closed circuit position such that a gap is defined between the arms. An attractive electromagnetic force tends to keep the first end of the arcing contact arm in contact with the fixed arcing contact until after the main contact arm has lifted. A hinge assembly for the main contact arm and the arcing contact arm assists in opening the contacts during the high current condition.

Abstract: A molded case circuit breaker having current limiting capabilities optimized for relatively smaller frame sizes. More specifically, one aspect of the invention relates to a two-piece carrier assembly for carrying the main and arcing contact arms which allows the main and arcing contacts to be blown open during short circuit conditions. The two-piece carrier assembly includes an inner carrier and an outer carrier pivotally connected together. The contact arms are carried by the inner carrier. When sufficient magnetic repulsion forces are exerted on the contacts due to a short circuit condition, the inner carrier pivots relative to the outer carrier to allow the contact arms to blow open. In order to control the amount of force required for blow open, a compression spring loaded cam assembly is provided.

Abstract: A molded case circuit breaker having current limiting capabilities is dimensionally optimized for relatively smaller frame size circuit breakers. The handle yoke is supported with rollers thereby allowing the crossbar to be disposed in the space normally utilized for the handle yoke pivot axis. A clinch joint arcer assembly with a plurality of arcing contact arms, each pivotally connected by a clinch joint to a pivotally mounted main contact arm permits additional main contact arms to be provided in the same space normally occupied by the arcing contact arms alone. Additionally, arcing contact spring housings protect the arcing contact springs from deterioration due to corrosive ionizing gases generated during interruption. A positive off link assembly prevents the operating handle from being placed on an OFF position when the main contacts are welded together and transfers the force applied to the operating handle to the upper link to allow the weld to be broken.

Abstract: A molded case circuit breaker is provided. Key blocks with a key shaped projection along one side are received in key shaped grooves in the sidewalls of the base. The kay shaped projections and the key shaped grooves may be formed as a dovetail connection. These key blocks provide support for the sidewalls from forces resulting from relatively high overcurrent conditions, such as a short circuit condition. In addition to supporting the sidewalls, the key blocks also form a barrier between the main contacts and other components in the circuit breaker to reduce the amount of arc products allowed to interact with the other components in the circuit breaker. The key block also form a stop surface for capturing the arc chutes to prevent movement of the arc chutes along the longitudinal axis of the circuit breaker. Lastly, the key blocks also hold the insulation barrier on the line conductor in place, thus obviating the need to use adhesives.

Abstract: A multiphase circuit breaker has a magnetic trip assembly which includes an adjusting bar slidable longitudinally to simultaneously adjust the bias applied by individual torsion springs to the rotatable armature of the magnetic trip assembly for each pole over a range of trip currents from a high setting to a low setting. Adjusting screws carried by the adjusting bar provide for adjustment of the gap between the armature and stationary magnetic structure independently at the high and low settings separately for each pole. An additional set of adjusting screws can be inserted in the adjusting bar to provide a single adjustment of the gap over the full range of spring bias settings.

Abstract: A draw out interlock comprises an elongated interlock member which is coupled to the manual trip mechanism of a circuit breaker. The interlock member is springed bias to an extended position where it projects through the back wall of the circuit, but is retained in a retracted position by the surface against which the circuit breaker is mounted. As the circuit breaker is removed from the mounting surface, the interlock member extends actuating the manual trip mechanism and interrupting current before the circuit breaker becomes disconnected from the protected conductor to prevent arcing at the disconnects.

Abstract: A molded case circuit breaker is provided with side plates having twist tabs extending downwardly from a bottom edge for fastening the side plates to the circuit breaker base. Spin plates with slots are carried by the base for receiving the twist tabs. The twist tabs are formed with a shank portion, a tapered portion and a head portion. The tapered portion defines a sloped surface which contacts the slot in the spin plate. When the twist tab is twisted, the shank is shortened drawing a wider portion of the sloped surface into the engagement with the slot to secure the side plate to the base.

Abstract: Electrical switches and circuit breakers in which the contacts and operating mechanism are enclosed within an insulating housing by an insulating cover and which have an elongated operating handle extending through an elongated slot in the cover have an enlarged terminal portion of the operating handle which is wider than the slot to prevent removal of the cover except in positions of the handle at which the electrical contacts are open and the slot is wider than the terminal portion of the handle. Preferably, this is only the OFF position of the switch or breaker, however, in circuit breakers with a notch at the trip position to expose indicia indicating the breaker operating condition, a transverse pin through the operating handle permitting removal of the cover only with the operating handle in the trip position, provides an economical backfit.

Abstract: A trip bar interlock for a circuit breaker characterized by an electrically insulating housing having an apertured bottom wall. A rotatable trip bar is in the housing for releasably holding the circuit breaker in an untripped condition. An actuator is provided for releasing the trip bar when the circuit breaker is dismounted from a mounting surface. The trip bar and the actuator have engaging surfaces and the actuator has an end portion extending through the aperture. The actuator is biased toward the mounting wall.

Abstract: A molded case circuit breaker includes a clear viewing window through its top cover to enable the position of its internally disposed separable electrical contacts to be externally visually discerned. A manually engagable handle extending through an opening formed in the top cover of the molded case of the circuit breaker has an electrically insulating strip or barrier secured thereto and movable therewith for covering the clear viewing window when the separable contacts are in their CLOSED position to prevent smoke and other arc products resulting from circuit breaker interruptions from obstructing the clear viewing window. The viewing window may be inserted in the top cover during the molding process or may be subsequently disposed in the top cover in the form of an insert fixedly secured thereto.

Abstract: A circuit breaker characterized by a ratchet mechanism for manual or electrical charging system and comprising a pair of separable contacts coupled with a rechargeable spring to close the contacts. The spring is indirectly connected to a drive shaft on which a ratchet wheel is fixedly mounted for rotation of the shaft in one direction. A drive wheel is rotatably mounted on the shaft for rotating the ratchet wheel and a brake wheel is mounted on the shaft for preventing rotation of the shaft in the other direction. Rotating means are provided for rotating the drive shaft.

Abstract: A circuit breaker with hinged arcing contact characterized by an insulating housing enclosing a circuit breaker mechanism, an electromagnetic trip device therefor, separable contact means including stationary contacts and movable main and arcing contacts and the arcing contacts being pivotally mounted on the main contacts whereby the arcing contacts are forced against the stationary contacts as the main contacts open.

Abstract: A circuit breaker with a magnetic circuit for delaying the trip function and characterized by a dual variable magnetic circuit air gap which allows a time delay at low level overcurrents, such that motor starting transient currents do not prematurely trip the circuit breaker.

Abstract: A circuit breaker characterized by a movable contact on a contact-carrying arm movable between open and closed positions of a stationary contact mounted on one leg of a U-shaped conductor with another leg secured to the circuit breaker housing, a U-shaped brace between the legs and having a first support supporting and insulated from the other leg and having second supports on opposite sides of the one leg for retaining it against opposing repulsion magnetic forces due to current overloads.

Abstract: A circuit breaker with a shock-absorbing mechanism characterized by a movable contact arm operable between open and closed positions of separable contacts, a stop member for stopping movement of the contact arm which member is integral with a housing for the circuit breaker, and a shock-absorbing plate on the member for spreading the energy released when the contact arm collides with the stop member.

Abstract: A molded case circuit breaker includes a new and improved calibration adjusting means for a bimetal in a trip mechanism. The trip mechanism also includes a bimetal having a portion movable in response to predetermined overload conditions, an intermediate control lever for adjusting the spatial disposition of the movable portion of the bimetal with respect to a trip bar of the trip mechanism and a rotatable adjustment means for adjusting the spatial disposition of the intermediate control lever in the circuit breaker. By rotating the adjustment means, the distance between the movable portion of the bimetal and the trip bar can be precisely adjusted via the intermediate control lever. The intermediate control lever is coupled to a relatively stationary portion of the bimetal thereby enabling such adjustment without applying undue stress to the movable portion of the bimetal.

Abstract: An arc chute assembly for a circuit breaker or similar device comprising a series of metallic arc chute plates that are locked in stacked spaced-apart relationship between a pair of insulative side panels by elongated key members of non-conductive material that are wedged between the flat surfaces of the side panels and notched portions of pairs of T-shaped tabs which extend from each side edge of the respective plates. The tabs interlockingly engage a series of laterally-extending slot openings in the side panels in such a manner that the key members are in press-fitted engagement with only one of the tabs in each pair of tabs.

Abstract: A terminal assembly for connecting a line cable to the bus conductor of a circuit interrupter or similar device by means of a locking screw that extends through the top wall of a metal lug component and clamps the inserted ends of the cable and bus conductor in overlapping relationship with each other and positive electrical contact with the bottom wall of the lug component. The bus conductor is held in slip-fitted interlocked position at the bottom of the lug component opening by the coaction of a pair of undercut grooves in the side walls of the lug component that accommodate the side edges of the bus conductor and cooperates with a coupling screw which extends through the bottom wall of the lug component and engages an unthreaded hole in the inserted end of the bus conductor.

Abstract: A plug-in type electric circuit breaker utilizing a detachably fastened stab assembly for interconnecting the circuit breaker to current carrying members such as bus bars. The stab assembly incorporates a plurality of opposed, independently movable spring-biased contact fingers having limited axial and arcuate motion allowing for good electrical and mechanical interconnection between misaligned circuit breakers and bus bars and reduction in the amount of force required for installation while preventing the engagement of the circuit breaker with oversized or undersized conductors.

Abstract: A molded case circuit breaker includes an adjustable stationary lower electrical contact having a one-piece formed conductive contact and a separately formed spacer bracket. One longitudinal end of the formed contact forms an external electrical terminal of the circuit breaker. The formed contact also includes a base portion and a stationary contact arm that has a contact for physically and electrically contacting a movable upper electrical contact of the circuit breaker fixedly secured at its other longitudinal end. The spacer bracket includes a base portion spaced above the base portion of the formed contact by a plurality of deflectable legs. The spacer bracket also includes a contact support portion fixedly secured to the underside of the stationary contact arm. A threaded aperture is formed through the base portion of the spacer bracket for the receipt of a mounting screw.