Patent Publication Number: US-7717750-B1

Title: Kit for converting N class bus plug to a J class bus plug

Description:
BACKGROUND OF THE INVENTION 
   I. Field of the Invention 
   The present invention relates generally to bus plugs. 
   II. Description of Related Art 
   Modern day factories are typically equipped with electrical bus for supplying three phase electrical power to the machinery in the factory. The electrical bus typically includes three main conductors and occasionally has a neutral phase and an integral ground bar. The supply voltage may be either 240 or with 600 volts being the maximum rating. 
   In order to electrically connect the electrical bus with the machinery, conventionally a bus plug is attached to the preexisting ports along a length of bus. The bus plug contains three fuses, one for each phase bar of the electrical bus. Consequently, once the bus plug is attached to the electrical bus, one end of each of the electrical fuses is electrically connected to the electrical bus (line side). The other ends of the fuses (load side) are then connected to the machinery which is powered through the electrical bus plug. 
   Electrical equipment of the type used in factories is typically powered by either 240 or 480 volts. Conventionally, an N class bus plug is employed with a 240 volt electrical bus and N class fuses are conventionally used with the N class bus plug. Such N class fuses are rated to operate at 240 volts. 
   Conversely, an R class bus plug is conventionally employed with electrical buses maintained at 480 volts. Such R class bus plugs accept R class fuses which are rated at 600 volts maximum. Such R class fuses are significantly longer than the N class fuses utilized in the 240 volt bus plug. 
   Since the R class fuses for 600 volts are longer in size than the N class fuses for 240 volts, the housing for an R class bus plug is also longer in size than the N class bus plug. This, in turn, increases the overall cost of an R class bus plug. Furthermore, R class bus plugs are much rarer than the N class bus plugs and thus more costly to obtain for the reconditioning and refurbishing business for such bus plugs. 
   There is a J class fuse which is essentially the same in size as the N class fuse, but the J class fuse is rated up to 600 volts. It is not possible, however, to simply replace the N class fuse in an N class bus plug with a J class fuse since the J class fuse uses a different electrical connection than the N class fuse. Consequently, where a 600 volt bus plug has been required, it has been necessary previously to use the larger size and more expensive R class bus plug with its larger housing. 
   SUMMARY OF THE PRESENT INVENTION 
   The present invention overcomes the above-mentioned disadvantages of the previously known bus plugs by providing a kit to convert an N class bus plug to accept J class fuses. As such, the kit of the present invention allows a relatively inexpensive 240 volt N class bus plug to be converted inexpensively to a 600 volt bus plug while maintaining nationally recognized safety standards. 
   In brief, the kit of the present invention comprises a plurality of Z-shaped electrical conductive strips which are preferably made of copper or a copper alloy. One Z-shaped conductive strip is associated with each fuse terminal in the N class bus plug. 
   A first fastener is associated with each strip. This first fastener secures the bottom of the conductive strip to its associated fuse terminal. 
   Thereafter, a J class fuse is associated with each pair of fuse terminals. The J class fuse includes a flat conductive electrical contact extending outwardly from each end. One electrical contact from the J class fuse overlies and flatly abuts against the top of one of the conductive strips. 
   Thereafter, a second fastener electrically connects each electrical contact of the class fuse with the top of its associated conductive strip. This second fastener preferably comprises a bolt and nut. 
   A third fastener, solder, is applied with heat to solidify the connection of the Z bracket to the copper conductors in the existing plug mechanism. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     A better understanding of the present invention will be had upon reference to the following detailed description when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which: 
       FIG. 1  is a sectional view taken substantially along line  1 - 1  in  FIG. 2 ; 
       FIG. 2  is a plan view of an N class bus plug converted to 600 volt operation utilizing the kit of the present invention; and 
       FIG. 3  is a fragmentary exploded elevational view illustrating a portion of the present invention. 
   

   DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
   With reference first to  FIGS. 1 and 2 , a bus plug  10  is shown having an N class housing  12 . The housing  12  also includes a cover which has been removed in the drawing for clarity. 
   The bus plug  10  includes three electrical connectors  14  which protrude outwardly from a back  16  of the housing  12 . Each electrical connector  14  is adapted for connection with one line  18  ( FIG. 1 ) of an electrical bus  20  of the type found in factories. Such electrical bus includes three separate lines, and together they supply three phase electrical power. The electrical bus  20  illustrated in  FIG. 1  is rare at 600 volts maximum. 
   For safety, the electrical bus  20  is contained within and separated by insulators from the housing  22 . The housing  22  includes access plates (not shown) which are removed to allow the electrical connectors  14  to engage the electrical contacts  18  of the electrical bus  20 . The bus plug housing  12  is then secured to the bus housing  22  in any conventional fashion, such as by screws. 
   Still referring to  FIGS. 1 and 2 , the bus plug  10  includes three pairs of spaced apart fuse terminals  24  and one electrical fuse  26  is associated with each pair of electrical terminals  24 . Consequently, as best shown in  FIG. 2 , the upper three fuse terminals  24  are electrically connected to the bus  14  while the lower three electrical terminals are adapted to be connected to the electrical powered machinery in the factory. 
   The fuses  26  illustrated in the patent drawing are J type fuses for a 600 volt application. Each J class fuse  26  includes a flat electrical contact  28  extending outwardly from each end of the fuse  26 . However, these electrical contacts  28  are not compatible with and, therefore, cannot be used with a standard N class bus plug since the standard electrical terminals  24  in a standard N class bus plug are not dimensioned to receive the J class fuse  26 . 
   Consequently, with reference to  FIGS. 1 and 3 , the present invention provides a conversion kit to convert a standard N class bus plug to accept J class fuses. In doing so, the standard N class bus plug and its housing may be used with a 600 volt electrical system. 
   With reference then to  FIGS. 1 and 3 , the kit of the present invention includes six Z-shaped conductive strips  30  which are made of an electrically conductive material and formed from flat metal bar stock. Each conductive strip  30  is preferably made of copper or a copper alloy and one conductive strip  30  is associated with each of the six fuse terminals  24 . 
   Each Z-shaped conductive strip  30  includes a generally flat bottom  32  and a generally flat top  34 . The flat bottom  32  is positioned flatly against its associated fuse terminal  24  and is secured to its associated fuse terminal  24  by a first fastener  36 , such as a bolt which engages a threaded hole  37  in the terminal  24 . In doing so, the Z-shaped conductive strip is electrically connected to its associated fuse terminal  24 . However, to enhance the electrical connection between the Z-shaped conductive strip and its associated fuse terminal  24 , the bottom  32  of the Z-shaped conductive strip  30  is also preferably soldered to its associated fuse terminal  24  by solder  38  ( FIG. 3 ) after the Z-shaped strip  30  is bolted to the terminal  24 . 
   After all six Z-shaped conductive strips have been attached to their associated fuse terminals  24 , the J class fuses  26  are positioned within the fuse box housing  12  so that the flat electrical contacts  28  overlie and flatly abut against the top  34  of the Z-shaped conductive strips  30 . The electrical contacts  28  of the fuses  26  are then secured to the top of their associated Z-shaped conductive strips  30  at each end of the fuse  26  by second fasteners  42 , such as a nut and bolt, thus electrically connecting the fuse contacts  28  to their associated electric terminals  24  through the Z-shaped conductive strip  30 . These second fasteners  34  are preferably a bolt and nut in which the bolt extends through registering holes in the fuse contact  28  and top  34  of the conductive strip  30 . 
   As can be seen from the foregoing, the present invention enables a conventional N class bus plug with its conventional size housing  12  to be converted to a 600 volt bus plug using T class fuses  26 . This results in substantial savings in the reconditioning/refurbishing business since housings  12  for N class bus plugs are not only more plentiful, but much less expensive, than the previously used R class bus plugs. 
   Having described my invention, many modifications thereto will become apparent to those skilled in the art to which it pertains without deviation from the spirit of the invention as defined by the scope of the appended claims.