Abstract: An electronically driven trip actuator for multipole industrial rated molded case circuit breakers is installed within a common housing with the circuit breaker operating mechanism. The trip actuator consists of a mechanical actuator cooperatively connected with a magnetic latch. The magentic latch arrangement holds the trip actuator against an actuating spring bias. Upon receiving an appropriate signal response, the magnetic latch releases, allowing the mechanical actuator to move into contact with the circuit breaker latch under the influence of the actuator spring. The arrangement of the mechanical actuator and actuator spring provides a low latching force to the magnetic latch, while providing a large trip force to the circuit breaker latch.

Abstract: An electric circuit breaker having fast short circuit response along with reduced arc energy is provided by means of a current limiting contact arm arrangement. The contact arm is arranged to pivot independently of the circuit breaker operating mechanism under the influence of magnetic repulsion forces. A contact spring configuration controls the rate at which the contacts separate, thereby limiting the energy of the arc created upon contact separation.

Abstract: High speed trip facility is provided within a molded case circuit breaker used within industrial applications. The movable contact arm is pivotally arranged to open independently of the trip unit-driven operating mechanism. A "latch kicker" arrangement interfaces between the mechanism trip bar and the circuit breaker intermediate latch whereby rotation of the trip bar causes the latch kicker to immediately displace the intermediate latch from the circuit breaker cradle thereby allowing the interrupter mechanism to untoggle the mechanism and open the breaker contacts.

Abstract: An interlock arrangement is provided between adjoining circuit breaker compartments by the addition of a contact arm operated interlock to circuit breakers which contain trip arm operated interlocks. The contact arm interlock comprises a paddle mounted on the rear surface of each of the adjoining breakers for sensing the condition of the contacts in one breaker and for interreacting with the trip arm interlock mechanism to trip the breaker when an attempt is made to close the first breaker contacts while the adjoining breaker contacts are closed. A stop lever mounted in the first breaker compartment interconnects with a similar lever mounted in the compartment of the adjoining breaker to prevent the first breaker contacts from being closed while the adjoining breaker contacts are closed. The compartment interlock arrangement finds utility when one of the interconnected circuit breakers connects with a utility power source and the other circuit breaker connects with an auxiliary generator.

Abstract: A switchgear unit contains interlocked circuit breaker and fuse compartments. The interlock prevents the fuses from being withdrawn from their power stabs until the circuit breaker is withdrawn from its power stabs first. A mechanical linkage arrangement causes an interference between the racking tool and the fuse compartment racking shaft until the breaker is withdrawn from the breaker compartment power stabs.

Abstract: A thermal magnetic circuit interrupter with instantaneous short circuit current response utilizes a hook-shaped contact arm pivotally mounted on the operating mechanism at the end of the contact arm most distant from the contact. A saddle-type torsion spring proximate the pivot end of the contact arm provides adequate contact pressure while allowing the contact to immediately respond to magnetic forces generated under short circuit conditions. The immediate separation of the contacts reduces the current let-through the operating mechanisms while the tripping mechanism operates to trip the breaker.

Abstract: A movable contact arm for circuit breakers allows the contact opening characteristics to be determined over an entire range of breaker ratings. The contact arm is provided with a camming surface with the contact closure spring arranged as a cam follower. Under short circuit conditions, the contact repulsion force is sufficient to overcome the bias provided by the contact closure spring and to drive the cam follower along the camming surface so that the resulting spring torque rapidly changes from a high initial torque on the contact arm to zero torque in a very short period of time. The contact arm is linked with the contact operating mechanism to open upon current overload in response to the trip mechanism.

Abstract: A secondary disconnect plug is arranged on the sidewall of a circuit breaker compartment for mating with a complimentary receptacle attached to the sidewall of a track-mounted circuit breaker for allowing auxiliary electrical functions to be maintained when the circuit breaker is partially withdrawn from the compartment to a test position. The disconnect plug is floatingly attached to the compartment sidewall and contains a centering and aligning mechanism to provide a wide range of tolerance when the circuit breaker is moved in and out of the compartment.

Abstract: A shield mechanism for isolating line and load stabs within a 2500-4000 ampere circuit breaker compartment is disclosed having a primary operating arm for operating a lower moveable shield and an upper moveable shield interconnected by a reversing bell crank link. Interconnection between the bell crank link and an intermediate lever is made by means of a lower expansion link. The corresponding downward motion fo the lower expansion link, when the circuit breaker is inserted in the compartment, forces the upper moveable shield to pivot into an open clockwise direction by connection between the upper moveable shield, the bell crank link and an upper expansion link against the force exerted by a return spring. Direct connection between the lower moveable shield and the intermediate lever forces the lower moveable shield into an open counterclockwise direction.

Abstract: A shield unit for interchangeable fit within circuit breaker compartments of various manufacture contains a split linkage arrangement of two pivotally connected arms, a return spring and a connecting spring to operate a shield linkage mechanism. The shield assembly comprises two moveable shields brought into a closed configuration when a circuit breaker is removed from the breaker compartment and into an open configuration when the circuit breaker is inserted within the breaker compartment. The interposition of the moveable shields between the power stabs within the breaker compartment and the breaker plugs prevents inadvertent contact by an operator when the circuit breaker unit is disconnected from the stabs. A balanced arrangement of shield linkage mechanisms on both sides of the shield unit prevents manual operation by an operator in any attempt to bypass the shield unit.

Abstract: A shield assembly for isolating line and load stabs within a circuit breaker compartment when the circuit breaker is removed from the compartment. The assembly consists of a pair of separately hinged shields interconnected by a link which terminates in a moveable pin. The pin is captured in a first slot within the assembly actuator arm and in a second slot within a supportive side frame. Movement of the actuator arm in a first direction causes the connecting link pin to move within the first slot to open the shields. Return of the actuator arm in an opposite direction causes the connecting link pin to travel within the second slot in an opposite direction to close the shields. The shield assembly contains actuating mechanisms at both sides of the breaker compartment in order to defeat any attempt by an operator to open the shields with the breaker withdrawn from the compartment.

Abstract: A slideably mounted insulating shield is positioned over the terminals of a secondary disconnect attached to the side wall of a circuit breaker compartment. Inserting the circuit breaker into the compartment brings the secondary disconnect terminals on the breaker into engagement with the secondary disconnect terminals in the compartment by displacing the insulating shield. Removal of the breaker from the compartment forces the insulating shield to return to position over the compartment secondary disconnect terminals thereby isolating the disconnect terminals from inadvertent contact with an operator.

Abstract: A compact and economic shield mechanism is used within circuit breaker compartments where a minimum separation distance exists between the end of the circuit breaker and the end of the compartment when the circuit breaker is first inserted within the compartment. The combination of an actuating lever and an extension spring converts the motion of the circuit breaker into a linear force sufficient to rapidly open the line and load shields within the minimum distance travelled by the breaker. The compartment line and load shields return to their closed position under a restoring force provided by the combination of a linear spring and a torsion spring when the breaker is withdrawn from the compartment.

Abstract: A pivotally mounted primary latch lever carries a latch pin for latchingly engaging a cradle to sustain it in a reset position against the bias of the breaker mechanism operating springs. An intermediate latch lever, pivotally mounted to the primary latch lever, is formed with a pair of latch shoulders for respective latching engagement with a pair of latch pins associated with a pivotally mounted secondary latch lever. The geometry of the latch assembly parts and their various latching engagements are such that an exceptionally light trip initiating force on the secondary latch lever is effective in releasing the cradle from its reset position.

Abstract: A reset lever is actuated in response to circuit breaker movable contacts swinging from their closed position to their tripped open position to exert a resilient force effective in reseating the plunger of a flux shifting-type trip solenoid. The reset lever also actuates a trip lever into tripping engagement with a circuit breaker trip latch assembly in the event the movable contacts are blown open by a high level fault current.

Abstract: In an industrial circuit breaker having a spring-powered movable contact operating mechanism and a spring-powered charging mechanism, each having the facility of storing a charge rendering the circuit breaker capable of being closed, condition indicator apparatus includes a first indicator for indicating whether the breaker movable contacts are open or closed and a second indicator for indicating whether or not a charge is stored in either the operating mechanism or the charging mechanism.

Abstract: In a circuit breaker equipped with a hook releasably holding movable contacts in a hooked open position, the plunger of an undervoltage release solenoid is releasably latched in its seated position to inhibit premature tripping of the breaker latch and thus enable the operating mechanism to be charged. Articulation of the hook leading to release of the contacts from their hooked open position precipitates unlatching of the plunger and discharge of the operating mechanism to preclude breaker closure into an undervoltage condition. Resetting of the plunger is effected under the control of the operating mechanism by a separate spring-power reset arm.

Abstract: A circuit breaker trip latch assembly includes a primary latch having a latching member releasably latching a cradle in its reset position against the bias of charged operating mechanism springs. The primary latch and either one of the first and second secondary latches commonly engage a latch pin carried by the free end of a pivotally mounted, elongated intermediate latch. The geometry of this common engagement is such as to greatly reduce the force of the charged mechanism springs ultimately absorbed by the first secondary latch as the cradle is relatched and the second, trip initiating, secondary latch while the breaker is closed.

Abstract: Compound hook apparatus for intercepting and holding circuit breaker contacts in a hooked open position against the closing force of charged operating mechanism springs includes a primary hook releasably latching an intermediate hook in a hooking position to fixedly dispose a pin in intercepting relation with a hook cam carried by a breaker movable contact assembly. The primary hook is articulated to unlatch the intermediate hook, freeing the latter to thereby release the movable contacts from their hooked open position.

Abstract: A normally open close switch and a normally open arming switch are connected in series with a closing solenoid operatively coupled with hook apparatus for releaseably holding breaker movable contacts in a hooked open position against the closing force of a charged breaker operating mechanism. An arm actuates the arming switch in response to the movable contacts assuming their hooked open position, such that subsequent actuation of the close switch effects closing solenoid activation of the hook apparatus to release the movable contacts from their hooked open position. A holding solenoid, wired in shunt with the arming switch, prevents the arm from reactuating the arming switch in the event of sustained actuation of the close switch.