Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Automatic circuit-interrupting devices
Reexamination Certificate
2000-01-25
2001-04-10
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Automatic circuit-interrupting devices
C361S042000
Reexamination Certificate
active
06215378
ABSTRACT:
RELATED APPLICATION
Commonly owned, concurrently filed application entitled “Circuit Breaker with Common Test Button for Separate Testing of Ground Fault and Arc Fault Function” and bearing Ser. No. 09/496,566.
FIELD OF THE INVENTION
This invention relates to circuit breakers provided with two test circuits, such as a ground fault test circuit and an arc fault test circuit, and a single, dual function test button for selectively activating switches in the test circuits which are remote from the common test button.
BACKGROUND INFORMATION
Circuit breakers provide overcurrent and short circuit protection for electric power systems. In the small circuit breakers, commonly referred to as miniature circuit breakers, used for residential and light commercial applications, such protection is typically provided by a thermal-magnetic trip device. Such a device includes a bimetal which is heated and bends in response to a persistent overcurrent condition thereby unlatching a spring powered operating mechanism which opens the separable contacts of the circuit breaker to interrupt current flow in the protected power system. An armature attracted by the sizable magnetic forces generated by a short circuit also unlatches, or trips, the operating mechanism.
In many applications, the miniature circuit breaker also provides ground fault protection. An electronic circuit detects leakage of current to ground and generates a ground fault trip signal. This signal energizes a shunt trip solenoid which unlatches the operating mechanism, typically through actuation of the thermal-magnetic trip device.
Recently, there has been considerable interest in also providing protection against arcing faults. Arcing faults are intermittent high impedance faults which can be caused for instance by worn insulation, loose connections, broken conductors, and the like. Because of their intermittent and high impedance nature, arcing faults do not generate currents of sufficient instantaneous magnitude or sufficient average current to rigger the thermal-magnetic trip device. Consequently, separate electrical circuits have been developed for responding to arcing faults.
Ground fault protection circuits and arc fault protection circuits typically include test circuits for affirming their continued operability. Currently, separate test switches, each with its own test button, are provided for performing the ground fault and arc fault tests. However, the molded cases of the miniature circuit breakers have been standardized for interchangeable use in load centers. There is limited space available in the standardized miniature circuit breakers for all of the additional circuitry required for ground fault and arc fault protection, let alone the test circuits.
U.S. patent application Ser. No. 09/069,355 filed on Apr. 29, 1998 discloses a miniature circuit breaker with a common rocker button which is rotated in one direction to actuate the ground fault test circuit, and the opposite direction to actuate the arc fault test circuit. The ground fault and arc fault test circuits are mounted on a common printed circuit board (PCB) and each has a spring contact arm projecting from the printed circuit board and which is deflected into contact with a common flexible contact extending between them by a separate finger on the common rocker button to actuate the associated test circuit. This arrangement works fine for circuit breakers where the circuit board is in close proximity to the common rocker button so that the spring contact arms can be directly engaged by the rocker button.
Unfortunately, on other miniature circuit breakers, the printed circuit board on which the test circuit is implemented is spaced from the test button so that the above-described direct engagement between a common rocker button and test switches is not possible.
There is a need, therefore, for improved miniature circuit breakers having both ground fault and arc fault test circuits.
More particularly, there is a need for such circuit breakers with a common test button which can separately actuate the ground fault and arc fault test circuits even though and the associated actuating switches are not in close proximity to the common test button.
SUMMARY OF THE INVENTION
These needs and others are satisfied by the invention which is directed to a circuit breaker which includes a molded housing containing electronic trip means having a first test circuit with a first test switch including a first test contact, and a second test circuit with a second test switch including a second test contact spaced from the first test contact. A common test contact associated with both the first and second test contacts is positioned between them. The circuit breaker also has a dual test switch actuating assembly which includes a common test button mounted in the molded housing remotely from the test switches. This common test button is coupled to a common actuating member which is moved by the common test button, preferably generally rectilinearly, between a first test position and a second test position. In the first test position, either the first test contact or the common test contact is deflected by the common actuating member into engagement with the other to actuate the first test switch in the first test circuit. In the second test position, either the second test contact or the common test contact is deflected by the common actuating member into engagement with the other to actuate the second test switch and thereby activate the second test circuit. The circuit breaker further includes bias means biasing the actuating member and also the common test button to a neutral position between the first and second test positions.
Preferably, the common test button is pivotally mounted for rotation in a first direction to move the actuating member against the bias means to the first test position and for rotation in a second direction opposite the first direction to move the actuating member against the bias means to the second test position.
In a preferred embodiment of the invention, the bias means comprises a cantilevered spring member engaging the actuating member and extending laterally relative to the generally rectilinear movement of the actuating member. Most preferably, the actuating member is a molded member and the cantilevered spring member is integrally molded with the actuating member. In the exemplary embodiment of the invention, the integrally molded cantilever member terminates in a tip which seats in recess in the molded housing. The tip rotates in this recess as the actuating member moves generally rectilinearly.
Preferably, the electronic circuits include a printed circuit (PCB). The first and second switch contacts are mounted on the printed circuit board and the common spring contact comprises an electrically conducting leaf spring secured at a first end to the PCB and deflectable at a second end in the first direction of the generally rectilinear movement of the actuator to engage the first switch contact. This common electrically conductive leaf spring is deflectable in the second direction of the generally rectilinear movement of the actuator to engage the second switch contact. Preferably, the first switch contact and the second switch contact arc electrically conductive leaf springs mounted on the PCB and deflectable with the common test contact.
Finally, the common test leaf spring is an elongated U-shaped flat member with two ends adjacent to one another. This shape allows for required deflection without overstressing while minimizing the amount of space occupied on PCB.
REFERENCES:
patent: 4686600 (1987-08-01), Morris et al.
patent: 4823225 (1989-04-01), Foster et al.
patent: 4851951 (1989-07-01), Foster, Jr.
patent: 5260676 (1993-11-01), Patel et al.
patent: 5293522 (1994-03-01), Fello et al.
patent: 5459630 (1995-10-01), MacKenzie et al.
patent: 5546266 (1996-08-01), Mackenzie et al.
patent: 5552755 (1996-09-01), Fello et al.
Erb Michael Joseph
Gibson Jeffrey Scott
Lockhart Jeffrey Wayne
Donovan Lincoln
Eaton Corporation
Moran Martin J.
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