Abstract:
A bus joint assembly for use in switchgear equipment having bus bars joined together at a bus joint and for joining vertical and horizontal buses. The bus joint connector comprises a connector, nut plate, connecting and supporting pins as well as a splice bus connector. The bus joint connector with integrated fixture pins locates and supports horizontal buses to vertical buses during assembly.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 60/779,597 filed Mar. 6, 2006, entitled “Bus Joint Interface” is incorporated fully herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to the field of electrical switchboards and panel boards having bus bars, and more specifically to a bus joint connector for facilitating the assembly of bus bars generally found in switchgear assemblies. 
     BACKGROUND OF THE INVENTION 
     Switchgear assemblies, switchboards and panelboards are general terms which cover metal enclosures, housing switching and interrupting devices such as fuses, and circuit breakers, along with associated control, instrumentation and metering devices. Such assemblies typically include associated bus bars, interconnections and supporting structures used for the distribution of electrical power. Low voltage switchgear and switchboards operate at voltages up to 600 volts and with continuous currents up to 5000 amps or higher. Such devices are also designed to withstand short circuit currents ranging up to 200,000 amps (3 phase RMS symmetrical). 
     Typical switchgear equipment is composed of a lineup of several metal enclosed sections. Each section may have several circuit breakers stacked one above the other vertically in the front of the section with each breaker being enclosed in its own metal compartment. Each section has a vertical or section bus which supplies current to the breakers within the section via short horizontal branch buses. The vertical bus bars in each section are supplied with current by a horizontal main bus bar that runs through the lineup of metal enclosed sections. A typical arrangement includes bus bars for each electrical phase of a multiple phase system which may include three power phases and a neutral. 
     The bus bars typically are joined by bus bar joints in the switchgear line-up. Bus bar joints typically are assembled with bolts that must be accessible for routine maintenance, for example, tightening or replacing bus bars. Bus bar assemblies typically increase in thickness as the current rating of the switchgear equipment increases. It is also typical to provide insulation of various components within a switchgear enclosure including a cover of the bus bar joints. 
     Installation of bus bars are rather labor intensive and require careful assembly. A problem faced during installation is aligning and supporting the horizontal bus bars to the vertical bus bars in an efficient and expeditious manner. The present invention facilitates the installation process by provisioning a means of aligning and supporting adjacent horizontal bus bars as they are being installed on the vertical bus bars. 
     Thus, there is a need for a bus joint assembly for use in switchgear equipment that will align and support bus bars. There is a further need for a bus joint assembly that may be used with various bus bar configurations. There is an additional need for a bus joint assembly that can facilitate the installation process. 
     SUMMARY 
     In the installation of a bus joint assembly, a bus joint connector is used which facilities the installation process. Because of the use of supporting pins, horizontal bus bars are horizontally aligned and supported while being fastened to the vertical bus bar. 
     Horizontal buses connect to vertical buses through a bus joint assembly. A typical bus joint assembly is a bolted joint comprised of the following components: splice bus, bus joint connector and hardware. A horizontal bus is sandwiched between the splice bus and bus joint connector. The fixture pins are connected to the bus joint connector. The bus joint connector with connected fixture pins serves two functions: (1) to locate the horizontal bus on the bus joint connector; and (2) to support and align the horizontal bus. 
     The bus joint connector with fixture pins solves the assemblability issue of having to locate, align and support the horizontal bus while assembling the splice bus and hardware in the same step. The advantage of having the horizontal bus located, aligned and supported allows a single installer to focus on assembling just the splice bus and hardware. This greatly improves assembly process time. 
     A disadvantage of known main bus joint designs is the lack of horizontal support while splice buses are fastened. For the most part, current installation practices require that the installer locate, align, support, assemble and secure the main bus joint components in one step. This process is difficult and time consuming for a single installer. 
     Although the embodiments described herein focus on the use of a horizontal main bus” in the form of a channel shaped bus bar, it should be understood that other forms of horizontal bus bars may be used. More specifically, the bus joint connector with fixture pins described below can work with bus bars having other geometric shapes like flat bus bars. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of a nut plate and associated fixture pin and fin. 
         FIG. 1   a  is an illustration of an integral double nut plate and associated roll pins and fixture pins. 
         FIG. 1   b  is an illustration of a U-shaped bus joint connector having a removal fastener. 
         FIG. 1   c  is an illustration of a grooved pin. 
         FIG. 1   d  is an illustration of the grooved pin of  FIG. 1   c  depicting a cross-section having grooves and raised portions. 
         FIG. 1   e  is an illustration of a fixture pin with fin. 
         FIG. 2  is an illustration of a U-shaped bus joint connector, nut plates, fixture pins and roll pins. 
         FIG. 3  is an illustration of a step in the assembly of horizontal bus bars on the fixture pins. 
         FIG. 3   a  is a close-up of a notch on one end of a horizontal bus bar. 
         FIG. 4  is an illustration of the use of a splice assembly with associated horizontal bus bars. 
         FIG. 5  is an illustration of an L-shaped bus joint connector and associated nut plates, fixture pins and roll pins. 
         FIG. 6  is an illustration of the installation of horizontal bus bars using an L-shaped bus joint connector and splice plate on a single vertical bus bar. 
         FIG. 7  is an illustration of a double horizontal bus bar configuration. 
     
    
    
     DETAILED DESCRIPTION 
     Shown in  FIG. 1  is a nut plate  15  for use with the bus joint connector  24  shown in  FIG. 2 . The nut plate  15  is preferably made of metal such as steel although other supportive materials such as, cooper, aluminum, or an alloy may be used. Steel is an often preferred material since it is very strong and performs very well in maintaining thread integrity. 
     The nut plate arrangement is preferred over a single bolt-single nut design arrangement since there are fewer parts to handle, and it is easier to assemble when access is near impossible. The nut plate  15  is shown in a rectangular form for illustration purposes only. The shape of the nut plate  15  may take whatever form is most economical or structurally appropriate. For example the nut plate  15  may be made in a circular disk shaped form when stamping is used to mass produce nut plate  15 . 
     The nut plate  15  in its preferred form comprises at least one hole  12  through which a fixture pin  14  may be engaged. As will be discussed in more detail below, the nut plate  15  and roll pin  22   b  function to align and support the layers  24   a ,  24   b  of the bus joint connector  24 . The nut plate  15  and the fixture pin  14  function to align and provide structural support to the horizontal bus bars  34 ,  36  during installation. In one embodiment of the present invention, the fixture pin  14  is mateably inserted and held in place in a friction fit within hole  12 . Fixture pin  14  mates with hole  12  and passes through clearance hole  25  with approximately a 1/16 inch tolerance. To better secure the fixture pin  14  with the nut plate  15 , the fixture pin  14  may have one or more raised fins  10  as shown in  FIG. 1   e . Moreover, the longitudinal cross-section may increase towards fin  10  so as provide a more secure friction fit. The raised fin(s)  10  is used to enhance the friction fit when the fixture pin  14  is inserted into the hole  12 . It should be understood that reference to fin, does not limit the fin to any particular form or structure. The term fin should be understood to mean, a raised portion on the surface of fixture  14  so as to enhance a friction fit in hole.  12 . 
     Alternatively, fixture pin  14  may be configured as a grooved pin  14   c  formed by a swaging operation in which one or more tools penetrate the nominal diameter of the surface of metal pin  14   c . For example and as shown in  FIGS. 1   c  and  1   d , three tools may be use at predetermined 120° intervals. The penetration displaces a controlled amount of metal to each side of the grooving tool, forming a raised or expanded portion  6  along the side of each groove  5  causing the outer circumference at the grooved portion to slightly increase. In this manner, the insertion of the grooved pin within the hole  12  of the nut plate  15  will result in a friction fit. Moreover, it should be understood that the fixture pin  14  may or may not contain a fin  10  or groove  5 . Fixture pin  14  may only have a tapered longitudinal surface such that insertion of the narrower end through hole  12  will result in a friction fit when inserted. Fixture pin  14 , may have a uniform cross-sectional area, provided that it provides a friction fit with hole  12 . Other means of fastening the fixture pin  14  may be readily apparent to those skilled in the art without departing from the spirit and scope of the present invention. 
     In addition, nut plate  15  may contain one or more retention holes  18 ,  19  through which retention hardware such as screws, bolts, washers and other fastening hardware may be inserted and used to attach switchgear equipment. Nut plate  15  may also have a hole  17  to accommodate fastening hardware such as roll pin  22 . In the embodiment shown in  FIG. 1 , the roll pin  22  is used to secure the nut plate  15  to the bus joint connector  24 . 
     As shown in  FIG. 2 , the fixture pin  14  and the roll pin  22  are inserted in corresponding holes within the bus joint connector  24 . The bus joint connector  24  is preferably made of any electrically conductive material such as cooper or aluminum. Although, the bus joint  24  is preferably made as a singular piece, the bus joint  24  as shown in  FIG. 2 , may be constructed of two correspondingly similar layers nested  24   a ,  24   b  whenever manufacturing equipment availability and/or the costs associated with such manufacture render a one piece design, unfeasible. For illustrative purposes, the bus joint connector  24  will be shown as a two piece design. A two piece design facilitates the manufacturing of bus joint connector  24  since a thinner gauge metal may be used which is more malleable. 
     The two layers  24   a ,  24   b  of the bus joint connector  24  are layered on top of each other (nested) and are connected to the nut plate  15  by roll pin  22 . In the present embodiment, the two layers  24   a ,  24   b  are U-shaped so as to substantially wrap-around and electrically connect vertical bus bars  30   a ,  30   b . In assembling the bus joint connector  24  and the nut plate  15 , roll pin  22  is inserted in hole  27  of the bus joint connector  24  and fixture pin  14  passes through hole  25 . The same structural configurations applicable to fixture pin  14  are applicable to roll pin  22 . As shown in  FIG. 2 , the center face  26   b  of bus joint  24  comprises two sets of holes ( 25   a ,  25   b ,  27   a ,  27   b ,  28   a ,  28   b ,  29   a ,  29   b ) so as to accommodate a pair of nut plates  15   a ,  15   b  with associated fixture and roll pins  14 ,  22  as well as associated fastening hardware  45   a ,  45   b.    
     In  FIG. 2 , two nut plates  15   a ,  15   b  are attached to the bus joint connector  24  by inserting corresponding fixture pins  14   a ,  14   b  and roll pins  22   a ,  22   b . Nut plate  15   a  is shown already in position and against the back center face  26   b  of layer  24   b  while fixture pin  14   a  is shown extending through hole  25   a . Once the bus joint  24  is fastened to the vertical bus bars  30   a ,  30   b , fixture pins  14   a  &amp;  14   b  are used to support and align horizontal bus bars  34 ,  36 . Alternatively, one larger nut plate  15  as shown in  FIG. 1   b  comprising an integrated version of two nut plates  15   a ,  15   b  may be used. Each side of nut plate  15  comprises corresponding holes  17   a ,  17   b ,  12   a ,  12   b ,  19   a ,  19   b  and associated fixture and roll pins  14   a ,  14   b ,  22   a ,  22   b . The use of a single larger nut plate  15  will facilitate assembly and better align and support the other assembly components. 
     Alternatively and as shown in  FIG. 1   b , the bus joint connector  24  may use removable fixture pins  8   a ,  8   b  such as slot head set screws, and other fastening means. The removable fixture pins  8   a ,  8   b  pass through holes  25   a ,  25   b  and engage holes  12   a ,  12   b  of the nutplate(s)  15 . The holes  12   a ,  12   b  are in this embodiment threaded to facilitate removal. It should be understood however, that fixture and roll pins  14 ,  22  and holes  25   a ,  25   b  and holes  12   a ,  12   b  as described above may also be used in other bus joint connector forms such as the L-shaped bus joint connector shown in  FIG. 5  without departing from the scope of the invention. 
     As shown in  FIG. 3 , the horizontal main bus bars  34 ,  36  have at each end a notch  38  for receiving the fixture pin  14 . During installation, each end of the horizontal bus bars  34 ,  36  is supported by each of the fixture pins  14  at different vertical buses. In  FIG. 3 , the left bus bar  34  is supported by the fixture pin  14   a  as well as a corresponding bus joint connector  24 . The horizontal bus bar  34  is also supported by a fixture pin  14   b  (not shown) on an adjacent vertical bus bar (not shown) on the left side of horizontal bus bar  34 . Corresponding holes on the ends of each horizontal bus are provided which are aligned by the fixture pins  14  and which extend from the nut plate  15  and the two layers  24   a ,  24   b  of the bus joint connector  24 . To secure the bus joint connector  24  to the vertical bars, fasteners  31 ,  33  of the type already disclosed above may be used. 
       FIG. 3   a  shows one end of a horizontal bus bar  36  having a notch  38  on its end. The notch  38  is preferably made such that the opening will accommodate fixture pin  14   a  with a clearance of about 1/16″. Holes  52 ,  54  on the horizontal bus bar  36  are aligned with the holes  28   b  and  29   b  so as to accommodate fastening hardware. 
     In  FIG. 4 , the horizontal bus bars  34 ,  36  have been mounted on fixture pins  14   a ,  14   b  and are ready for fastening. As previously discussed, the mounting of horizontal bus bars  34 ,  36  on fixture pins  14   a ,  14   b  significantly enhances the assembly process by allowing the horizontal bus bars  34 ,  36  to be horizontally aligned and supported while splice bus assembly  43  is mounted. Splice bus assembly  43  is preferably a one piece C-shaped bracket insertable between the upper and lower flanges of horizontal bus bars  34 ,  36 . Fixture pins  14   a ,  14   b  extend through corresponding holes in the splice bus assembly  43  so as to align the splice bus assembly  43  while assembly is performed. Hardware such as socket head cap screws  45   a  and  45   b  are used to secure splice bus assembly  43  to the horizontal bus bars  34 ,  36  and the vertical bus bars  30   a ,  30   b . Holes through the front and back sides of the splice bus assembly  43  align with corresponding holes  52 ,  54  as well as holes  29 ,  28  in the bus joint  24  and holes  19 ,  18  in the nut plate(s)  15 . 
     In an alternate embodiment, an L-shaped bus joint connector  24  is shown in  FIG. 5 . The L shaped bus joint connector  24  is likewise preferably nested or double layered and comprises layers  24   a ,  24   b  as in the U shaped bus joint connector  24  shown in  FIG. 2 , although a single piece configuration may also be used. The same type of removable fixture pin  8  may also be used in the L shaped configuration of the L-shaped bus joint connector  24 . In this removable configuration, holes  12   a ,  12   b  may be threaded. The L-shaped bus joint  24  may be used in circumstances when for example, a single vertical bus bar  30   a  is used (see  FIG. 6 ). The L-shaped bus joint  24  is similar to the U-shaped bus joint  24  as shown in FIG.  2 ,—more specifically, it includes faces  26   a ,  26   b  and excludes face  26   c.    
     Shown in  FIG. 6  are horizontal bus bars  34 ,  36  supported in place by fixture pins  14   a ,  14   b . The L-shaped bus joint  24  is mounted on a single vertical bus  30   a  by fasteners  31 ,  33 . To secure the horizontal bus bars  34 .  36 , to the bus joint  24 , a splice plate  60  is attached to the horizontal bus bars  34 ,  36  and fastened by fasteners  45   a ,  45   b.    
       FIG. 7  shows a horizontal double-bar design which uses the components of  FIG. 4  and adds a horizontal bar  34   b , nut plate  72  and associated screws or fastening means  74 . In this double-bar design, horizontal bus bar  34  comprises a front  34   a  and a back  34   b  bus bar. The additional horizontal bus bar  34   b  (back bar) is fastened to splice assembly  43  by a nut plate (not shown) within splice assembly  43  and by using fastening means such as screws or bolts through the splice plate  72 , the corresponding holes in bus bar  34   b , splice assembly  43 , bus joint connector  24  and nut plate  15 . The same double-bar design may also be used on the adjoining bus bar  36 . 
     While the embodiments illustrated in the figures and described above are presently disclosed, it should be understood that these embodiments are offered by way of example only. The bus joint assembly is not intended to be limited to any particular embodiment, but is intended to extend to various modifications that nevertheless flow within the scope of the intended claims. For example, the bus joint assembly can be used with one or two vertical bus bars. The nut plate can be made of a single or two piece design. Moreover, the bus joint assembly can be configured to facilitate use with different shaped bus bars. Other modifications will be evident to those with ordinary skill in the art.