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  
         [0001]    This invention relates generally to circuit breakers, and more particularly to circuit breakers for use with rotary contact assemblies.  
           [0002]    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.  
           [0003]    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.  
           [0004]    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  
         [0005]    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.  
           [0006]    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.  
           [0007]    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  
       [0008]    [0008]FIG. 1 is perspective view of an electrically isolating iso bearing.  
         [0009]    [0009]FIG. 2 is perspective view of a rotary contact assembly used with the iso bearing shown in FIG. 1.  
         [0010]    [0010]FIG. 3 is a perspective view of a circuit breaker used with the iso bearing shown in FIG. 1. 
     
    
     DETAILED DESCRIPTION  
       [0011]    [0011]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.  
         [0012]    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 .  
         [0013]    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).  
         [0014]    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).  
         [0015]    [0015]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).  
         [0016]    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 .  
         [0017]    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.  
         [0018]    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 .  
         [0019]    [0019]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.  
         [0020]    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 .  
         [0021]    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 .  
         [0022]    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.