Electricity: magnetically operated switches – magnets – and electr – Electromagnetically actuated switches – Tripping means
Reexamination Certificate
2000-02-15
2001-05-01
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Electromagnetically actuated switches
Tripping means
C335S167000, C200S400000
Reexamination Certificate
active
06225883
ABSTRACT:
Related Application: Commonly owned, concurrently filed application entitled “Circuit Breaker with Instantaneous Trip Provided by Main Conductor Routed Through Magnetic Circuit of Electronic Trip Motor” and identified by application Ser. No. 09/506,871.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to circuit breakers in which the toggle mechanism that opens and closes the breaker contacts and the latch which trips the toggle mechanism to automatically open the contacts operate in substantially perpendicular planes. Such an arrangement is particularly advantageous for subminiature circuit breakers, but can also be applied to larger breakers.
2. Background Information
One use of subminiature circuit breakers is in aircraft electrical systems where they not only provide overcurrent protection but also serve as switches for turning equipment on and off. As such, they are subjected to heavy use and therefore must be capable of performing reliably over many operating cycles. They also must be small to accommodate the high density layout of circuit breaker panels which make circuit breakers for numerous circuits accessible to a user. Subminiature circuit breakers can be used in an environment where they are subject to vibration. The circuit breaker must trip consistently within tolerance yet not be tripped out by vibration or shock loading.
Typically, subminiature circuit breakers have only provided protection against persistent overcurrents implemented by a latch triggered by a bimetal responsive to I
2
R heating resulting from the overcurrent. Some aircraft systems have also provided ground fault protection, but through the use of additional devices, namely current transformers which in some cases are remotely located from the protective relay. There is a growing interest in providing additional protection, and most importantly arc fault protection. Currently available subminiature circuit breakers do not respond to arc faults which are typically high impedance faults and can be intermittent. Nevertheless, such arc faults can result in a fire. Finally, there is an interest in providing an instantaneous trip in response to very high overcurrents such as would be drawn by a short circuit.
While larger circuit breakers, even the “miniature” circuit breakers used in residential applications provide multiple protection functions, the currently available subminiature circuit breakers do not have such combined features. Again, the challenge is to provide alternative protection in a very small package which will operate reliably with heavy use over a prolonged period. A device which meets all the above criteria and can be automatically assembled is desirable.
SUMMARY OF THE INVENTION
The present invention is directed to a circuit breaker with a structure which can be miniaturized yet provide multiple protection functions and operate reliably in an environment which can include vibration. The circuit breaker includes a toggle mechanism for opening and closing separable contacts which operates in one plane and a latch member which operates in a plane perpendicular to the operating plane of the toggle mechanism to unlatch the toggle mechanism and thereby automatically open the separable contacts. The latch is operated by an overcurrent assembly which provides response to I
2
R heating, very high overcurrents such as caused by short circuits, and other conditions such as an arc fault.
In particular, the circuit breaker includes a housing in which the separable contacts of a separable contact assembly are mounted. The toggle mechanism includes first and second pivotally connected toggle links moveable in a first plane and coupled to the contact assembly for opening and closing the separable contacts. A handle coupled to the toggle mechanism is used to manually open and close the separable contacts. The circuit breaker further includes a latch assembly latching the toggle mechanism in a latched condition in which it can be manually operated by a handle assembly between a toggle open and a toggle closed position to open and close the separable contacts. This latch member is moveable in a second plane perpendicular to the first plane to latch the toggle mechanism in the latched condition and to unlatch the toggle mechanism and trip the separable contacts open. An overcurrent assembly responsive to selected current conditions moves the latch member in the second plane to unlatch the toggle mechanism and thereby trip the separable contacts open.
The latch assembly also includes a latch lever pivotally mounted to move in the first plane. The latch member has a latch surface engaging the latch lever to latch the toggle mechanism in the latched condition. The separable contact assembly includes a fixed contact and a moveable contact carried by a pivotally mounted contact arm. The first end of the first toggle link is pivotally connected to the contact arm. The first end of the second toggle link is pivotally connected to the latch lever and a knee pin pivotally connects the second ends of the two toggle links. The handle assembly is connected to this knee pin for manually operating the toggle mechanism.
The overcurrent assembly includes a trip motor which pivots the latch member in the second plane out of the latch position to release the latch lever when the solenoid is energized. The trip motor is energized by a trip circuit which can respond for instance to arc faults. The latch member is magnetically permeable and forms an armature for the trip motor.
The overcurrent assembly also includes a helical bimetal which provides I
2
R heating protection. The free end of this helical bimetal is coupled in series with a cantilevered ambient temperature compensating bimetal which is secured to and pivots the latch member.
The housing comprises first and second molded insulative sections which join along a mating plane which is substantially parallel to the first plane in which the toggle links pivot. The separable contact assembly, the toggle mechanism, the latch member and the bimetals are all dropped into the first housing section. The trip motor is then inserted into the metal frame supporting these elements along with a trip circuit and is enclosed by the second section of the housing.
REFERENCES:
patent: 3758887 (1973-09-01), Ellsworth et al.
patent: 3792403 (1974-02-01), Bullock
patent: 3984736 (1976-10-01), Rai
patent: 4812799 (1989-03-01), Cobb, III et al.
patent: 5224006 (1993-06-01), MacKenzie et al.
patent: 5757602 (1998-05-01), Meili et al.
Hall Thomas Michael
Hetzmanseder Engelbert
McCormick James
Moldovan Peter Klaus
Rollmann Paul Jason
Donovan Lincoln
Eaton Corporation
Nguyen Tuyen
Union Marvin L.
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