Abstract:
A clip designed to retain a conductive strap to a circuit breaker case is disclosed. The clip comprises a main body portion and a flange. The main body portion includes a first edge and a second edge. The flange depends from the first edge of the main body portion and includes a first end and a second end. The first end of the flange is configured for attachment to the conductor strap and the second end of the flange and the main body portion configured to secure the conductor strap in mounting stability within the case and to prevent movement of the conductor strap relative to the case.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to clips and more particularly to a clip for attaching to a conductor (strap) in a rotary contact circuit breaker. 
     Circuit breakers are one of a variety of overcurrent protective devices used for circuit protection and isolation. The basic function of a circuit breaker is to provide electrical system protection whenever an electrical abnormality occurs in any part of the system. In a rotary contact circuit breaker, current enters the system from a power source. The current passes through a line strap to a fixed contact mounted on the line strap and then to a moveable contact. The moveable contact is fixedly attached to an arm, and the arm is mounted to a rotor that in turn is rotatably mounted in a cassette. As long as the fixed contact is in physical contact with the moveable contact, the current passes from the fixed contact to the moveable contact and out of the circuit breaker to downstream electrical devices. 
     In the event of an extremely high overcurrent condition (e.g. a short circuit), electromagnetic forces are generated between the fixed and moveable contacts. These electro-magnetic forces repel the movable contact away from the fixed contact. Because the moveable contact is fixedly attached to a rotating arm, the arm pivots and physically separates the fixed contact from the moveable contact. 
     Once activated, the circuit breaker operating mechanism separates a pair of main contacts to stop the flow of current in the protected circuit. Conventional trip units act directly upon the circuit breaker operating mechanism to activate the circuit breaker operating mechanism. 
     During an interruption event, such as a short circuit, high levels of energy travel through the load side strap (conductor). During these events, the load side conductor experiences forces causing undesirable rotational and translational movement of the conductor. Typically, load side conductor connections are fixedly supported within the circuit breaker case to absorb the energy passing through during interruption as well as during assembly when electrical connections are made to the load side conductors. However, to fixedly support the load side strap can require additional space in which to provide and mount a supporting structure for the load side conductors and connections. 
     SUMMARY OF THE INVENTION 
     The above discussed and other drawbacks and deficiencies are overcome or alleviated by a clip for retaining a conductive strap to a circuit breaker case is disclosed. The clip comprises a main body portion and a flange. The main body portion includes a first edge and a second edge. The flange depends from the first edge of the main body portion and includes a first end and a second end. The first end of the flange is configured for attachment to the conductor strap and the second end of the flange and the main body portion configured to secure the conductor strap in mounting stability within the case and to minimize movement of the conductor strap relative to the case. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will now be described, by way of example, with reference to the following FIGURES, in which: 
     FIG. 1 is a perspective view of a circuit breaker including a base; 
     FIG. 2 is an exploded view of the circuit breaker of FIG. 1; 
     FIG. 3 is a perspective view of the assembly of a clip attached to a load strap; 
     FIG. 4 is a perspective view of a circuit breaker cassette assembly; 
     FIG. 5 is a perspective view of the clip of FIG. 3; 
     FIG. 6 is perspective view of the base of the circuit breaker of FIG. 1 including the assembly of the clip, the load strap and a cross bar; 
     FIG. 7 is a perspective view of the base, the mid cover and the assembly of a cross bar; and 
     FIG. 8 is an exploded cut-away view of the base of the circuit breaker of FIG.  6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to FIG. 1, an embodiment of a molded case circuit breaker  10  is generally shown. Circuit breakers of this type generally an insulated case  12  having a cover  38  attached to a mid-cover  14  coupled to a base  32 . A handle  20  extending through cover  38  gives the operator the ability to turn the circuit breaker  10  “on” to energize a protected circuit (not shown), turn the circuit breaker “off” to disconnect the protected circuit (shown in FIG.  3 ), or “reset” the circuit breaker after a fault (not shown). A plurality of line and load straps (conductors)  18 ,  22 ,  34 ,  44  also extend through the case  12 . The circuit breaker  10  in FIG. 1 shows a typical three phase configuration, however, the present invention is not limited to this configuration but may be applied to other configurations, such as one, two or four phase circuit breakers. 
     Referring to FIGS. 2 and 3, the handle  20  is attached to a circuit breaker operating mechanism  24 . The circuit breaker operating mechanism  24  is coupled with a center cassette  26  and is connected with outer cassettes  28  and  30  by a drive pin  46 . The cassettes  26 ,  28 ,  30  along with the circuit breaker operating mechanism  24  are assembled into the base  32  and retained therein by the mid-cover  14 . The mid-cover  14  is connected to the base  32  by any convenient means, such as screws  36 , snap-fit (not shown) or adhesive bonding (not shown). Cover  38  is attached to the mid-cover  14  by screws  40 . 
     The load straps  22 ,  34 ,  44  connect the circuit breaker to load side wiring such as a lead  42  from electrical equipment. Line straps  18  connect to line-side wiring (not shown) in an electrical distribution circuit. 
     Referring to FIG. 4, a circuit breaker cassette assembly, generally shown at  50 , comprises a rotary contact assembly, shown generally at  52 , in a first electrically-insulative cassette half-piece  54  of cassette  30  intermediate a line strap  18 , and a load-side contact strap  58 . Although only a single circuit breaker cassette assembly  50  is shown, a separate circuit breaker cassette assembly is employed for each pole of a multi-pole circuit breaker and operates in a manner similar to that of circuit breaker cassette assembly  50 . 
     Electrical transport through rotary contact assembly  52  of circuit breaker cassette assembly  50  occurs from line strap  18  to an associated first fixed contact  64 , through first and second movable contacts  66 ,  68  secured to the ends of a movable contact arm, shown generally at  72 , and to an associated second fixed contact  70  on load-side contact strap  58 . Movable contact arm  72  is pivotally arranged between two halves of a rotor  74  and moves in conjunction with rotor  74  upon manual articulation of rotor  74 . Rotor  74  is rotatably positioned on a rotor pivot axle  73 , the ends of which are supported by inner parallel walls of first electrically-insulative cassette half-piece  54 . 
     Arc chute assemblies  60 ,  62  are positioned in the first electrically insulative cassette half piece  54  adjacent the respective pairs of first fixed and first moveable contacts  64 ,  66  and second fixed and second moveable contacts  70 ,  68 . The first and second movable contacts  66 ,  68  and moveable contact arm  72  move through a passageway provided by the arc chute assemblies  60 ,  62  in order to engage and disengage from the respective first and second fixed contacts  64 ,  70 . Each arc chute assembly  60 ,  62  is adapted to interrupt and extinguish the arc which forms when the circuit breaker  10  is tripped and the first and second moveable contacts  66 ,  68  are suddenly separated from the first and second fixed contacts  64 ,  70 . 
     Referring back to FIG. 3, it is understood circuit breaker cassettes  26 ,  28  within circuit breaker  10  are similarly constructed to circuit breaker cassette assembly  50  including rotary contact assembly  52  described herein. 
     A perspective view of cassettes  26 ,  28 ,  30  is shown along with the operating mechanism  24  and load side connections. Further, a clip  80  is shown mounted to load strap  22 . More specifically, load strap  22  is connected to a conductor  78  that is in turn connected to the load side contact strap  58 . Load straps  34 ,  44  are similarly configured for attachment to conductors  82 ,  252 , respectively. It is understood that the following description applies equally to all poles in circuit breaker  10 . 
     A trip unit, such as a thermal magnetic trip unit (not shown) enclosed within case  12  preferably attaching to load side contact straps  48 ,  58 ,  76  of cassette  26 ,  28 ,  30  with mechanical fasteners or other methods commonly used in circuit breaker manufacture are contemplated, such as brazing. The trip unit is assembled into the base  32  along with the cassettes  26 ,  28 ,  30 . Load straps  22 ,  34 ,  44  conduct current from the power source to the protected circuit. A current transformer (not shown) for an electronic trip unit (not shown) may be disposed around conductors  78 ,  56 ,  252 , respectively. 
     Load strap  22  has a first end  84 , a second end  86 , an edge  88  and an opposing edge  90 . First end  84  includes two apertures  92  spaced apart. Although two apertures  92  are preferred, load strap  22  may employ a single aperture  92  or more than two apertures  92 . Load strap  22  includes a surface  94  facing the exterior of the circuit breaker  10  and a surface  96  facing the interior of the circuit breaker  10 . Edge  88  and opposing edge  90  are located between the first end  84  and the second end  86 . Load strap  22  further includes a first section  98  and a second section  100 . First section  98  and second section  100  are integrally joined at an edge  102 . First section  98  is located between the first end  84  and edge  102 . Second section  100  is located between second end  86  and edge  102 . Located within the first section  98  proximate the first end  84  is a circular aperture  104 , preferably two circular apertures  104  aligned cross-wise and spaced apart, for accepting a mechanical fastener  82 , preferably a screw or rivet. In this way, mechanical fasteners  82  are inserted through apertures  104 , through corresponding apertures  106  located longitudinally through conductor  78  and finally through corresponding apertures  108  located in the load side contact strap  58 . 
     The second section  100  of load strap  22  is angled inward toward surface  94 . Preferably, the second section  100  is angled to be substantially perpendicular to the first section  98 . Centrally located within the second section  100  is a circular aperture  110 . In this way, the second section  100  is angled and extends outward from base  32  of circuit breaker  10  such that circular aperture  110  provides an accessible connection to the end user such as to connect to lead  42  from electrical equipment. It is understood that load straps  34 ,  44  are similarly configured to load strap  22 . 
     Referring to FIG. 5, clip  80  generally includes a main body portion  112 , a flange  114  and an arm  116 . Preferably, clip  80  is made of a metal, although any material of suitable strength may be used. The main body portion  112  includes a first end  118 , a second end  120 , a first edge  122  and a second edge  124 . First and second edges  122 ,  124  extend longitudinally from the first end  118  to the second end  120 . Also, main body portion  112  has a first surface  126  and an opposing second surface  128 . First and second surfaces  126 ,  128  extend lengthwise between first and second ends  118 ,  120  and are bounded by the first and second edges  122 ,  124 . The main body portion  112  is generally rectangular in shape extending lengthwise between first end  118  and second end  120 . Proximate to the first end  118  and located within the main body portion  112  and extending through first and second surfaces  126 ,  128  is a circular aperture  130 . Extending outward from the main body portion  112  is flange  114 . Flange  114  is integral with the main body portion  112  and extends between the first end  118  and the second end  120  of the main body portion  112 . Flange  114  has a first end  132  and a second  134  and is preferably bent towards first surface  126 . Most preferably, the flange  114  is bent such that it is substantially perpendicular to the main body portion  112 . Extending outward from the flange  114  proximate to the first end  132  is arm  116 . Arm  116  extends outward along a portion of the flange  114 . Preferably, the arm  116  is angled inwards towards first surface  126  of main body portion  112  forming a base section  136  extending from the flange  114  and a free section  138 . Preferably, the arm  116  is continuous with the flange  114 . The free section  138  includes a circular aperture  140 . Preferably, the free section  138  is angled parallel to the main body portion  112  such that the circular aperture  140  of the free section  138  is aligned with the circular aperture  130  of the main body portion  112 . Most preferably, the free section  138  is substantially perpendicular to the base section  136  such that the arm  116 , the portion of the flange  114  adjacent to arm  116  and the portion of the main body portion  112  adjacent to arm  116  collectively form a U-shaped member shown generally at  142 . 
     Referring back to FIG. 3 as well as FIG. 5, clip  80  is shown assembled onto the load strap  22  prior to assembly of the load strap  22  with the clip  80  attached onto base  32  (FIG.  1 ). The manner in which clip  80  is assembled onto the load strap  22  will now be described. 
     To fasten clip  80  onto the load strap  22 , the arm  116 , the portion of the flange  114  adjacent to arm  116  and the portion of the main body portion  112  adjacent to arm  116  is slidably inserted over edge  88  of the first section  98  of the load strap  22  such that circular apertures  130 ,  140 ,  146  are aligned. Next, a rivet  148  or other similar mechanical fastener is inserted, preferably through circular aperture  140 , through circular aperture  146  and finally through circular aperture  130  to securely fasten clip  80  onto load strap  22 . Although a mechanical fastener is used to effect the connection, any convenient method used in circuit breaker manufacture can be used. 
     Referring to FIG. 6, the assembly of load strap  22  with attached clip  80  to base  32  is shown. Referring also to FIG. 8, an exploded cut away view of the base  32  is shown. 
     Base  32  includes a floor section  164  having an end  152  located at the line side, and an end  154  located at the load side. Located between ends  152 ,  154  is an edge  156  and an opposing edge  166  (shown in phantom). Opposing sidewalls  158 ,  160  extend upward from floor section  164 . Each sidewall  158 ,  160  has a top edge  162  and join with the floor section  164  at edges  156 ,  166 , respectively. Each sidewall  158 ,  160  also includes a first end  168  at the load side and a second end  170  at the line side. Located proximate the first end  168  on the top edge  162  of sidewall  158  are two notches  198  spaced apart. Located proximate the first end  168  on the top edge  162  of sidewall  160  are two notches  200  spaced apart. 
     Partitions  172 ,  174  are located between sidewalls  158 ,  160  on the load side and extend upward from floor section  164 , preferably perpendicular to floor section  164 . Partition  172  and partition  174  define an opening  176  corresponding to a second pole of the circuit breaker  10 . Partition  174  and sidewall  158  from an opening  178  corresponding to the first pole of the circuit breaker. Partition  172  and sidewall  160  form an opening  180  corresponding to the third pole of the circuit breaker  10 . All openings are generally the same size. 
     Partition  172  has a first end  182  and a second end  184  where the second end  184  is integral with floor section  164 . Partition  174  has a first end  244  and a second end  246  where the second end  246  is integral with floor section  164 . Located at the first end  244  of partition  174  is an opening  234 . Located at the first end  182  of partition  172  is an opening  150 . Partitions  172 ,  174  are parallel to each other. FIG. 6 shows base  32  suitable for use in a three pole circuit breaker and thus has three openings  176 ,  178 ,  180 . It is noted that the number of openings correspond to the number of poles in the circuit breaker  10  (FIG.  1 ). 
     Further, partition  172  has a first side  186  and a second side  188 . First side  186  faces outward and second side  188  faces inward. Located within the floor section  164  of base  32  and proximate the first side  186  of partition  172  is a projection  190  extending upward from floor section  164 . Partition  174  has a first side  248  and a second side  250 . First side  248  faces outward and second side  250  faces inward. Located within the floor section  164  of base  32  and proximate the first side  248  of partition  172  is a projection  192  extending upward from floor section  164 . Projections  190 ,  192  extend generally parallel to partitions  172 ,  174  respectively. Preferably, projections  190 ,  192  are integrally molded with the floor section  164  and protrude outward therefrom. Projection  190  and first side  186  of partition  172  form a slot  194  extending outward from the floor section  164 . Similarly, projection  192  and first side  186  of partition  172  form a slot  196  extending outward from the floor section  164 . 
     Located on the top edge  162  of sidewall  158  proximate to the load side end and integrally molded therein is a notch  198 , preferably two notches. Located on the top edge  162  of sidewall  160  proximate to the load side end and integrally molded therein is a notch  200 , preferably two notches. 
     A cross bar  202  is also shown. The cross bar  202  provides additional structural support for the sidewalls  158 ,  160  as well as providing support and attachment for the load straps  22 ,  34 ,  44 . Cross bar  202  is preferably molded of a plastic material such as a bulk molding compound with a sufficient dielectric strength to provide sufficient electrical insulation between the phases (poles). 
     Referring to FIGS. 7 and 8, the cross bar  202 , the base  32  and the midcover  14  assembly is shown. The cross bar  202  will be described in further detail. Further, although a cross bar  202  is shown being utilized in a three pole circuit breaker, it is understood that the cross bar  202  may be employed in a single pole circuit breaker as well as a multi pole circuit breaker. 
     Cross bar  202  includes a body  204  having first end  206 , a second end  208 , a top surface  210  and a bottom surface  212 . Extending inward towards the interior of the circuit breaker  10  from the bottom surface  212  and located proximate the first end  206  is a projection  214 , preferably two projections  214  spaced apart from one another at first end  206 . Extending inward towards the interior of the circuit breaker  10  from the bottom surface  212  and located proximate the second end  208  is a projection  218 , preferably two projections  218  spaced apart from one another at second end  208 . Cross bar  202  also includes a first section  224 , a second section  226  and a third section  228 . First, second and third sections  224 ,  226 ,  228  are integral sections each including an aperture, preferably two,  242  for connection to respective load straps  22 ,  34 ,  44  for each of the respective poles. It is noted that the number of apertures provided for in the cross bar  202  may be less than or greater than two. Located within the body  204  of the cross bar  202  is an opening  230  located between the load strap  22  and the load strap  34 . An opening  232  is also located between the load strap  34  and the load strap  44 . Openings  230 ,  232  extend from the top surface  210  to the bottom surface  212  and are adapted to accept a mechanical fastener (not shown) to secure the circuit breaker (FIG. 1) to a mounting member (not shown) such as, but not limited to, a panel and align with corresponding openings  150 ,  234  located within the respective partitions  172 ,  174  thereby connecting the cross bar  202  to the base  32  using a mechanical fastener  216 , preferably a screw. The openings  230 ,  232  mechanically lock all three straps  22 ,  34 ,  44  together by securing the first, second and third sections  224 ,  226 ,  228 . The openings  230 ,  232  also aid in over surface and through air spacing. Air spacing is desirable to reduce the risk of a short circuit. 
     Referring to FIGS. 6 and 7, the load strap  22  with the clip  80  attached is shown assembled within base  32 . The assembly will be described in reference to load strap  22 . However, it is understood that clip  80  may also be utilized to mount load straps  34 ,  44 , corresponding to the respective second and third poles of the circuit breaker  10 , within base  32 . 
     The load strap  22  is slidably received within opening  180  such that the second end  134  of the flange  114  of the clip  80  is slidably inserted into slot  196  such that flange  114  is accepted within slot  196 . When the load straps  22 ,  34 ,  44  are fully inserted into the respective openings  176 ,  178 ,  180 , the projections  214  located on the cross bar  202  are captively received within notches  198  located on the top edge  162  of sidewall  158  and the projections  218  located on the cross bar  202  are captively received within notches  200  located on the top edge  162  of sidewall  160 . 
     When assembled, second surface  96  of load strap  22  faces inward towards base  32  and first surface  94  faces outward. In this way, clip  80  rivets towards the inside of the circuit breaker  10  (FIG. 1) providing for maximum support of load strap  22 . 
     When the clip  80  engages slot  196 , load strap  22  is provided additional structural support to assist in the prevention of translational and rotational movement of load strap  22  during assembly and interruption (e.g. short circuit) events. During an interruption event, load strap  22  tends to rotate about a centrally located point A (FIG. 6) towards the exterior of circuit breaker (FIG.  1 ). That is to say, load strap  22  rotates counterclockwise when viewed from the exterior of circuit breaker  10 . During assembly, force is also applied to load strap  22  to effect the connections to the load side wiring such as the load sided contact strap  58  and lead  42  from electrical equipment as described hereinabove. The clip  80  is placed over the edge  88  to stabilize the load strap  22  during rotational and translational movement exerted on the load strap  22  during interruption as well as translational and rotational forces acting on the load strap  22  during end user connection of various electrical equipment to load strap  22 . In this way, clip  80  is forced against the partition  172  thereby providing additional support for load strap  22  to assist in the prevention of its translational and rotational movement. 
     Once the load strap  22  is assembled into the base  32  as described hereinabove, the cross bar  202  is attached to the load straps  22 ,  34 ,  44  and connected to the sidewalls  158 ,  160  as follows. 
     The first section  224  of the cross bar  202  is securely located onto the first end  84  of the load strap  22  by inserting mechanical fasteners  240  through apertures  242  located within the first section  224  of the cross bar  202  and through apertures  92  located in the first end  84  of the load strap  22 . The second section  226  of the cross bar  202  is securely located onto the first end  84  of the load strap  34  by inserting mechanical fastener  240  through apertures  242  located within the second section  226  of the cross bar  202  and through apertures  92  located in the first end  84  of the load strap  34 . The third section  228  of the cross bar  202  is securely located onto the first end  84  of the load strap  44  by inserting mechanical fastener  240  through apertures  242  located within the third section  228  of the cross bar  202  and through apertures  92  located in the first end  84  of the load strap  44 . 
     As described herein, the cross bar  202  securely locks the load straps  22 ,  34 ,  44  within base  32 . Cross bar  202  is advantageously employed in base  32  that is employed in a modular circuit breaker design where size must be optimized. Further, cross bar  202  is also advantageously used within circuit breakers where overall space requirements can be kept to a minimum thus not requiring the internal structure of base to be made larger for increase load strap support. 
     As described herein, the clip  80  provides support for load strap  22  thus limiting load strap  22  movement during assembly and interruption events thus decreasing the stresses exerted on the base  32  from the load strap  22  during these events. Clip  80  is advantageously employed in base  32  employed in a modular circuit breaker design where size must be optimized. Further, clip  80  is also advantageously used within circuit breakers where overall space requirements can bee kept to a minimum thus not requiring the internal structure of base to be made larger for increase load strap support. 
     Further, by using clip  80 , the load strap  22  is able to extend from base  32 , as opposed to being secured within the base  32 . This configuration for the load strap  22  is preferred over being secured within the base  32  since the end user is now provided top and bottom access to circular aperture  110 . The clip  80  also provides additional support to ensure the integrity of base  32  during assembly of the electrical connections to the circuit breaker as well as during interruption events. 
     It is understood that although FIG. 8 is an exploded view, in part, of the projection  190  and slot  194 , the projection  192  and slot  196  are similarly configured and disposed within the floor section  164  of base  32  as identified in FIG.  6 . 
     Finally, it is understood that multiple clips  80  may be utilized as shown in FIG.  3 . In a preferred embodiment, and as shown in FIG. 3, clips  80  are mounted to load straps  22  and  44 . In this way, movement of the load straps  22 ,  44 , which correspond to the outermost poles of the multi-pole circuit breaker  10  (FIG.  1 ), is minimized during an interruption event and assembly, thereby ensuring increased structural integrity to the sidewalls  158 ,  160 . 
     While this invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.