Apparatus for electrically isolating circuit breaker rotor components

Abstract
An electrically isolating iso bearing for a circuit breaker is provided that comprises an inner surface, an outer surface, and a body extending therebetween, said inner surface comprising a pair of bosses and a pair of openings, said outer surface comprising at least one boss, said body comprising a pair of rotor protective flaps.
Description




BACKGROUND OF INVENTION




This invention relates generally to circuit breakers, and more particularly to circuit breakers for use with rotary contact assemblies.




Circuit breakers are used to interrupt a flow of current when current exceeds a specified value. Such a condition is sometimes referred to as a short circuit condition or an overcurrent value. In a short circuit condition, the circuit breaker robustly separates a pair of contacts that, under normal operating conditions, conduct the current. Separating the contacts electrically isolates the circuit wiring and associated circuit components from potentially damaging currents. At least some known circuit breakers are thermally or magnetically actuated.




In at least some circuit breakers, when the contacts are separated, an electrical arc may be undesirably generated between the contacts. In addition, within at least some circuit breakers, during a short circuit interruption, a dielectric breakdown may occur between the components. Continued operation of the circuit breaker with components that have dielectrically deteriorated, may be detrimental to the performance of the circuit breaker, may contribute to a poor transfer of the arc within an arc chamber, and over time, may limit the ability of the circuit breaker to isolate the components in a robust and timely manner.




To facilitate extending a useful life of the circuit breaker, at least some known circuit breakers use rotary contact assemblies, including iso bearings. The iso bearings facilitate shielding mounting springs on the face of the rotor and facilitate a smooth rotation of the rotor during circuit breaker mechanism operations. However, because of a relative position of the iso bearings with respect to the circuit breaker, the iso bearings do not facilitate protecting conductive rotor parts positioned along a perimeter of the rotor.




SUMMARY OF INVENTION




In one aspect an iso bearing for a circuit breaker is provided that comprises an inner surface, an outer surface, and a body extending therebetween, the inner surface comprising a pair of bosses and a pair of openings, the outer surface comprising at least one boss, and the body comprising a pair of rotor protective flaps.




In one aspect a rotary contact assembly is provided that comprises a rotor assembly comprising a plurality of pins, a linkage assembly, and a pair of rotor halves, each rotor half comprising an inner and an outer surface and a perimeter, the outer surface comprising a plurality of bosses. A contact arm configured to be mechanically and electrically coupled to the rotor assembly inner surface by the plurality of pins and the linkage assembly. A plurality of iso bearings mechanically coupled to the rotor assembly outer surface by the plurality of rotor bosses, the iso bearing comprising a pair of rotor protective flaps partially circumscribing rotary contact assembly perimeter to facilitate shielding the plurality of pins and the link assembly.




In one aspect a circuit breaker is provided that comprises a pair of electrically insulative cassette half pieces comprising a cavity therein, a plurality of electrically conductive straps positioned within the half piece, and a rotary contact assembly positioned in the cavity. The rotor contact assembly is positioned in the cavity and comprises a plurality of pins, a linkage assembly, and a pair of rotor halves, each rotor half comprises an inner and an outer surface and a perimeter, the outer surface comprising a plurality of bosses. A contact arm is configured to be mechanically and electrically coupled to the rotor assembly inner surface by the plurality of pins and the linkage assembly. A plurality of iso bearings mechanically coupled to the rotor contact assembly outer surface by the plurality of rotor bosses, each iso bearing comprises a pair of rotor protective flaps partially circumscribing the rotary contact assembly perimeter to facilitate shielding the plurality of pins and the link assembly. An operating mechanism is configured to separate the conductive straps and the contact arm, and a plurality of arc chambers are coupled to the half pieces.











BRIEF DESCRIPTION OF DRAWINGS





FIG. 1

is perspective view of an electrically isolating iso bearing.





FIG. 2

is perspective view of a rotary contact assembly used with the iso bearing shown in FIG.


1


.





FIG. 3

is a perspective view of a circuit breaker used with the iso bearing shown in FIG.


1


.











DETAILED DESCRIPTION





FIG. 1

is perspective view of an electrically isolating iso bearing


10


that may be coupled to an electrical circuit (not shown in FIG.


1


). Iso bearing


10


has a diameter


12


and a perimeter


14


that are variably selected based on the circuit requiring protection and an associated circuit breaker. In one embodiment, iso bearing diameter


12


is approximately thirty-three mm. In one embodiment, iso bearing


10


is fabricated from a nonconductive material. In another embodiment, iso bearing


10


is molded from Zytel® 103HSL nylon which is commercially available from DuPont, Wilmington, Del. In an alternative embodiment, iso bearing


10


is molded from polycarbonate or polyester.




Iso bearing


10


includes a body


20


having an inner surface


16


, and an oppositely-disposed outer surface


18


. Body


20


is circumscribed by perimeter


14


. In the exemplary embodiment, body


20


is substantially circular. Inner surface


16


and outer surface


18


are substantially planar. Inner surface


16


includes a pair of diametrically disposed bosses


22


that are each sized to receive a rotor pin (not shown in

FIG. 1

) therein. More specifically, bosses


22


extend outwardly from inner surface


16


. Bosses


22


are substantially circular and are adjacent perimeter


14


. Inner surface


16


also includes a pair of diametrically disposed semi-circular openings


24


that are each sized to receive a rotor boss (not shown in

FIG. 1

) therethrough. More specifically, each opening


24


has a diameter


26


and extends between outer surface


18


and inner surface


16


. Openings


24


are defined by a portion of perimeter


14


.




A pair of alignment channels


28


extend substantially diametrically across inner surface


16


. More specifically, channels


28


are both positioned between each set of bosses


22


and openings


24


, and are configured to couple iso bearing


10


to a rotor halve (not shown in FIG.


1


). In the exemplary embodiment, channels


28


are substantially parallel and are spaced a distance


30


apart. An inner surface cavity


31


of a bearing boss (not shown in

FIG. 1

) is positioned between each channel


28


and concentrically with respect to rotor contact assembly center axis (not shown in FIG.


1


).




Iso bearing body


20


has a thickness


32


measured between inner surface


16


and bearing outer surface


18


. A pair of diametrically opposed rotor protective flaps


40


extend substantially perpendicularly outwardly from inner surface


16


along bearing perimeter


14


. Specifically, each rotor protective flap


40


is adjacent each boss


22


and opening


24


. Each rotor protective flap


40


has a length


42


, a thickness


44


, and a height


46


. Length


42


is measured between a first end


48


that is adjacent opening


24


and a second end


50


that is circumferentially spaced from end


48


. Width


44


is measured between a first sidewall


52


and a second sidewall


54


. Flaps


40


are positioned such that first sidewall


52


is substantially aligned with respect to body perimeter


14


. Flap height


46


is measured between inner surface


16


and an outer surface


18


, and is substantially greater than body thickness


32


. Flap


40


dimensions


42


,


44


, and


46


are variably selected based on the size of a rotary contact assembly (not shown in FIG.


1


). Rotor protective flap length


42


and height


46


facilitate flaps


40


shielding the rotor components (not shown in

FIG. 1

) from electrical engagement with circuit breaker components (not shown in FIG.


1


).





FIG. 2

is perspective view of a rotary contact assembly


70


including iso bearing


10


. Bearing outer surface


18


includes a bearing boss


74


that extends from outer surface


18


a distance


76


. Bearing boss


74


has a diameter


78


and is positioned concentrically with respect to a center axis


80


of rotary contact assembly


70


. Boss diameter


78


is smaller than bearing diameter


12


(shown in FIG.


1


), such that bearing boss


74


facilitates aligning rotary contact assembly


70


with a cassette half piece (not shown in FIG.


2


).




Rotary contact assembly


70


includes a rotor


82


that is substantially circular and includes a first half


84


and a second half


86


connected together by a plurality of pins


88


and a linkage assembly


90


that extends therebetween. In one embodiment, rotor


82


has a diameter


92


and a perimeter


94


that are substantially equal to iso bearing diameter


12


and perimeter


14


, respectively. Rotor halves


84


and


86


, each have an inner surface


96


and an outer surface


98


. Each rotor half


84


and


86


, include a pair of rotor bosses


100


having a diameter


102


sized to couple with bearing openings


24


. A plurality of openings


104


are disposed within rotor bosses


86


. Boss openings


104


have a diameter


106


sized to receive a fastener (not shown) for attaching rotor


82


to cassette half piece (not shown in FIG.


2


). Boss opening diameter


106


is smaller than rotor boss diameter


102


.




Rotor pins


88


and linkage assembly


90


are mechanically coupled with iso bearing


10


, rotor


82


and a rotary contact arm


120


. Contact arm


120


extends between the rotor halves inner surfaces


96


and


98


and has a length


122


that is substantially longer than rotor diameter


92


. In one embodiment, contact arm


120


is a one-piece assembly. Contact arm


120


includes a first moveable contact


124


and a second moveable contact


126


attached to each end oppositely.




Iso bearing


10


is positioned on rotor


82


such that rotor protective flap


40


arcuately extends perpendicularly towards rotor


82


and covers pins


88


and linkage assembly


90


. Flaps


40


facilitate preventing electrical arcing between conductive straps (not shown in

FIG. 2

) and pins


88


and linkage assembly


90


of rotor


82


.





FIG. 3

is a perspective view of a circuit breaker


200


including iso bearing


10


and rotary contact assembly


70


. More specifically, rotary contact assembly


70


is coupled within an electrically isolative cassette half piece


202


, and iso bearing


10


is coupled to rotary contact assembly


70


. Half piece


202


is attached to a similar cassette half piece (not shown) to form a cassette (not shown). An opposing line-side contact strap


204


and a load-side contact strap


206


are adapted for communication with an associated electrical distribution system (not shown) and a protected electrical circuit (not shown), respectively. Line-side


204


and load-side


206


straps each include a first fixed contact


208


and a second fixed contact


210


, respectively. Rotary contact assembly


70


is positioned intermediate line-side contact strap


204


and load-side contact


206


and associated arc chambers


222


and


224


, respectively.




Moveable contacts


124


and


126


are coupled to opposite ends of rotary contact arm


120


for making moveable connection with fixed contacts


208


and


210


to permit electrical current flow from line-side contact strap


204


to load-side contact strip


206


. Rotor


82


is coupled with the circuit breaker operating mechanism (not shown) by means of rotor pins


88


and rotor linkage assembly


90


. Contact arm


120


moves simultaneously with rotor


82


which, in turn, moves moveable contacts


124


and


126


between a CLOSED position (not shown) and a OPEN position as depicted. During a short circuit or an overcurrent condition, perspective contact pairs


124


and


210


, and


126


and


208


are separated. When perspective contact pairs


124


and


210


, and


126


and


208


are separated, electrical arcing occurs between perspective contact pairs


124


and


210


, and


124


and


208


. These arcs are cooled and quenched within arc chambers


222


and


224


and not permitted to occur between the contact pairs


124


,


210


and


126


,


208


and rotor pins


88


and linkage assembly


90


due to the iso bearing rotor protective flaps


40


, thus facilitating the prevention of damage to rotary contact assembly


70


and circuit breaker


200


.




Iso bearing rotor protective flap


40


facilitates protecting conductive rotor parts along rotor perimeter


92


. This helps facilitate the useful life and robust operation of circuit breaker


200


.




While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.



Claims
  • 1. A circuit breaker comprising:a pair of electrically insulative cassette half pieces comprising a cavity therein; a plurality of electrically conductive straps positioned within each said half piece; a rotor contact assembly positioned in said cavity, said assembly comprising a plurality of pins, a linkage assembly, and a pair of rotor halves, each said rotor half comprising an inner and an outer surface and a perimeter, said outer surface comprising a plurality of bosses; a contact arm configured to be mechanically and electrically coupled to said rotor assembly inner surface by said plurality of pins and said linkage assembly; a plurality of iso bearings mechanically coupled to said rotor contact assembly outer surface by the plurality of rotor bosses, each said iso bearing comprising an inner surface, an outer surface, and a body extending therebetween, said inner surface comprising a pair of bosses and a pair of openings, said outer surface comprising at least one boss, said body comprising a pair of rotor protective flaps; an operating mechanism configured to separate said conductive straps and a contact arm; and a plurality of arc chambers coupled to each said half pieces.
  • 2. A circuit breaker in accordance with claim 1 wherein said pair of rotor protective flaps are diametrically opposed, said flaps extend substantially perpendicularly from said rotary contact assembly perimeter.
  • 3. A circuit breaker in accordance with claim 1 wherein said rotor includes a first half and a second half, said contact arm positioned between said first and second rotor halves.
  • 4. A circuit breaker in accordance with claim 1 wherein said rotor further includes a plurality bosses positioned on each of said first and second halves such that said iso bearings mechanically couple to said rotor.
  • 5. A circuit breaker in accordance with claim 1 wherein each of said iso bearing is fabricated from a nonconductive material.
  • 6. A circuit breaker in accordance with claim 1 wherein said pair of rotor protective flaps are diametrically opposed, said flaps extend substantially perpendicularly from said rotary contact assembly perimeter.
  • 7. A circuit breaker in accordance with claim 1 wherein said iso bearings and said contact arm are configured to rotate about the same axis of rotation.
US Referenced Citations (6)
Number Name Date Kind
4649247 Preuss et al. Mar 1987 A
5313180 Vial et al. May 1994 A
5351024 Juds et al. Sep 1994 A
6281458 Castonguay et al. Aug 2001 B1
6281461 Doughty Aug 2001 B1
6326868 Kranz et al. Dec 2001 B1