Patent Publication Number: US-6664469-B1

Title: Neutral bar assembly and method of making assembly

Description:
FIELD OF THE INVENTION 
     This invention relates generally to neutral bar assemblies made up of several neutral bars electrically and mechanically coupled together and the method of making such neutral bar assemblies. 
     BACKGROUND OF THE INVENTION 
     Electrical enclosures, such as breaker boxes, commonly have only one neutral bar mounted therein for the purpose of referencing and/or grounding distribution circuits. In recent times, the use of electronic devices has expanded significantly, both commercially and in our homes. Consequently, the number of neutral or grounding outlets necessary to accommodate these additional electronic devices has increased. One solution to this problem is to expand or increase the size of the electrical enclosure to accommodate additional neutral bars. Customers such as home owners resist this solution because either: 1) it is too costly or 2) there is insufficient space for a larger electrical enclosure. Consequently, there is a need to add additional neutral or grounding outlets in an electrical enclosure of a fixed size. 
     Previous attempts to electrically couple multiple neutral bars together efficiently in a fixed space or volume have included mounting multiple neutral bars on a stepped bracket, such as is disclosed in U.S. Pat. No. 2,909,757. This method of mounting multiple neutral bars requires additional screws and mounting brackets and is therefore costly. In addition, the limited space within an electrical enclosure may not allow an electrician or an original equipment manufacture (OEM) to add additional neutral bars in this manner. Furthermore, the spacing between adjacent neutral bars in such an assembly may be insufficient so that an electrician may be unable to see into which hole he or she is inserting a wire. 
     Another drawback with existing neutral bar assemblies is that in order for the neutral bars to receive neutral conductors or wires of different diameters, additional equipment is required. U.S. Pat. No. 3,594,710 discloses such a neutral bar assembly which requires nuts and bolts to secure neutral bars having different hole spacings and different wire range holes together in an assembly. Again, this method of mounting neutral bars together is costly because of the additional equipment required. 
     The most common current method of securing additional neutral bars to a mounted neutral bar in an electrical enclosure is to independently mount each additional neutral bar in the electrical enclosure and connect the bars with a single wire. This method is costly and provides only a single electrical connection between the neutral bars. 
     Another less common method of electrically joining neutral bars in an electrical enclosure has been to bend a copper wire into a Z shape and secure the ends of the copper wire in wire-receiving holes of the neutral bars with wire binding screws. However, this method does not allow the neutral bars to be placed close enough together to maximize the space inside the electrical enclosure. In addition, this method is not practical because the neutral bars are not rigidly mounted together. Therefore, when an electrician tightens a wire binding screw to secure a wire into one of the openings in one of the neutral bars, the z-shaped copper wire may bend or deflect, jeopardizing the electrical connection between the neutral bars. 
     Consequently, there is a need to electrically and structurally connect several neutral bars together in a compact, efficient, and cost-effective manner, without increasing the size of the electrical enclosure. There is also a need for a method of connecting adjacent neutral bars structurally and electrically such that the wire-binding screws may be torqued properly without disturbing the electrical connection and spacing between the neutral bars. Further, there is a need for a neutral bar assembly through which an electrician may see to put the correct wire in the correct hole or bore. There is also a need for a method of structurally and electrically joining adjacent neutral bars having different hole spacings and different wire range holes. Finally, there is a need for a relatively inexpensive and convenient method to use expanders for structurally and electrically interconnecting two or more neutral bars together to form a spatially compact multi-bar assembly. 
     SUMMARY OF INVENTION 
     The present invention overcomes the foregoing and other shortcomings and drawbacks of neutral bar expanders and assemblies heretofore known. While the invention will be described in connection with certain embodiments, it will be understood that the invention is not limited to these embodiments. On the contrary, the invention includes all alternatives, modifications, and equivalents as may be included within the spirit and scope of the present invention. 
     The present invention comprises a neutral bar assembly in which at least two neutral bars are electrically and mechanically secured together with a pair of expanders to form a spatially compact multi-bar assembly. In one preferred embodiment of the present invention, first and second neutral bars are coupled together with a pair of generally U-shaped expanders, each having spaced-apart, generally parallel legs which are received in respective wire-receiving bores of the two neutral bars being assembled to each other. In an alternative preferred embodiment of the present invention, three neutral bars are electrically and mechanically joined together with a pair of expanders, which are each generally shaped like a staircase, each having three spaced-apart, generally parallel legs which are received in respective wire-receiving bores of the neutral bars being assembled to each other. Although the expanders of the present invention preferably secure together two or three neutral bars, any number of neutral bars may be joined together in accordance with the present invention. 
     In each of the preferred embodiments of the present invention, the neutral bars are preferably die cast of aluminum, as is conventional; however, the neutral bars may be made of any electrically conductive material and stamped or extruded. Each of the neutral bars is generally elongated in overall shape with a rectangular transverse cross-section, having generally planar, parallel front and rear surfaces, generally planar, parallel top and bottom surfaces, and generally planar, parallel end surfaces. 
     A plurality of spaced bores extend through the neutral bar from the front surface to the rear surface. These bores are typically not threaded, although they may be threaded. The bores are sized and adapted to receive grounding wires from the rear thereof, as is conventional. The bores within each of the neutral bars are typically the same diameter and have a defined pitch, i.e. the distance between the centers of adjacent bores. The neutral bars are generally less than a foot long, however, may be three or four feet long depending upon the size of the breaker box or electrical enclosure which contains them. One common size bore for a neutral bar is approximately a quarter inch in diameter, accommodating wire gauges from 14 to 4, increasing in wire diameter. In addition, the bores may be of a larger diameter as to accommodate larger gauge wires, e.g. 2 to 0 gauge wires. One of the advantages of the present invention is that neutral bars made from different manufacturers, having different pitches may be joined together. In addition, neutral bars having different lengths and bores of different diameters may be joined together in accordance with the present invention. 
     In order to secure the wires inside the bores, a plurality of spaced, threaded holes extend downwardly from the top surface of the neutral bar into the bores of the neutral bar. A plurality of wire-binding screws are engaged in the threaded holes and when rotated advance into the bores of the neutral bar, thereby trapping or securing the grounding wires between the bores and the bottoms of the wire-binding screws. 
     Each of the expanders of the present invention is a unitary member made from an electrically conductive material. The expanders are preferably made of aluminum, but may be made of bronze, copper, or any other conductive material. Each of the expanders is preferably cast from aluminum, but may be manufactured via other methods, such as welding multiple pieces together. In addition, the expanders may be made by extruding a length of electrically conductive material such as aluminum in the desired shape and then cutting that extruded length in a transverse direction so that each expander has a desired width. 
     Each of the expanders has a body portion and at least two legs extending forwardly from the body portion. In one preferred embodiment of the present invention, each expander is generally U-shaped, having two spaced, parallel legs extending forwardly from a body portion. In another preferred embodiment of the present invention used to connect three or more neutral bars, each of the expanders is generally staircase-shaped, having three spaced, parallel legs extending forwardly from a body portion. In accordance with the present invention, the expanders may assume other configurations and shapes, as will be described in more detail below. 
     In each of the embodiments of the present invention, the legs of the expanders are inserted into the bores of the neutral bars and the wire-binding screws tightened in order to secure the legs of the expanders in the bores of the neutral bars. No additional brackets, bolts or hardware is necessary to secure the expanders to the neutral bars. 
     One method of making the neutral bar assembly of the present invention comprises adding at least one neutral bar to a neutral bar already mounted in an electrical enclosure. In this method, one of the legs of each of the expanders is inserted into one of the bores of each neutral bar to be added. Then the remaining legs of each of the expanders are inserted into the bores of the already mounted neutral bar and secured therein by tightening the appropriate wire-binding screws. Another method of making the neutral bar assembly of the present invention is the join all the neutral bars together into an assembly before the assembly is mounted in the electrical enclosure. 
    
    
     These and other objects and advantages of the present invention will be more readily apparent from the following drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate embodiments of the invention and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the invention. 
     FIG. 1 is a perspective view of a neutral bar assembly, comprising first and second identical neutral bars secured together with a first embodiment of expander; 
     FIG. 2 is a cross-sectional view taken along the line  2 — 2  of FIG. 1; 
     FIG. 3 is a perspective view of one preferred embodiment of the expander used in the neutral bar assembly of FIG. 1; 
     FIG. 4 is an alternative preferred embodiment of a neutral bar assembly having three identical neutral bars in accordance with the present invention; 
     FIG. 5 is a cross-sectional view taken along the line  5 — 5  of FIG. 4; 
     FIG. 6 is a perspective view of a second preferred embodiment of expander used in the embodiment of FIGS. 4 and 5; 
     FIG. 7 is a perspective view of an alternative embodiment of neutral bar assembly incorporating different neutral bars designed to connect different gauge wires in accordance with the present invention; 
     FIG. 8 is a perspective view of an alternative embodiment of expander; 
     FIG. 9 is a perspective view of a still further preferred embodiment of expander; 
     FIG. 10 is a perspective view of yet another preferred embodiment of expander; 
     FIG. 11 is a perspective view of another preferred embodiment of expander; 
     FIG. 12 is a perspective view of still another preferred embodiment of expander. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings, and particularly to FIGS. 1-3, there is illustrated a neutral bar assembly  10  comprising a first neutral bar  12  and a second neutral bar  14  secured together with a pair of expanders  16 . Each of the expanders  16  is illustrated in more detail in FIGS. 2 and 3 and will be described in more detail below. Due to the configuration of the expanders  16 , the second neutral bar  14  is positioned and secured generally above and behind the first neutral bar  12 . The neutral bars  12 ,  14  are positioned relative to each other such that an electrician may see therebetween in order to see which wire is going in which hole. 
     Each of the neutral bars  12 ,  14  has a pair of opposed end surfaces  18  (only one being show) which define a length L of the neutral bar. Each of the neutral bars  12 ,  14  also has a generally planar front surface  20  and a parallel, generally planar rear or back surface  22  which define the width W of the neutral bar. Lastly, each of the neutral bars  12 ,  14  has a top surface  24  and a bottom surface  26 , which define the height H of the neutral bar. See FIG.  2 . 
     Although the first and second neutral bars  12 ,  14  are illustrated in FIG. 1 as having an identical height, width, and length, they may have different lengths, widths, or heights from each other in accordance with the present invention. This feature of the present invention will be described in more detail below and is shown in FIG.  7 . 
     As is conventional, each of the neutral bars  12 ,  14  has a plurality of spaced bores  28  extending through the neutral bar from the front surface  20  to the rear surface  22 . Each of these bores  28  is generally circular in nature, although the bores may assume other configurations in accordance with the present invention. Within a neutral bar, each of the bores  28  is typically the same diameter; however, the diameters may vary within a neutral bar. Wires  30  (only one being shown) pass through the rear surface  22  of the neutral bar into the bores  28  of the neutral bar. Thus, each neutral bar may hold as many wires as there are bores within the neutral bar, minus the two bores in which a portion of each expander  16  is located. 
     In addition, each of the neutral bars  12 ,  14  has a plurality of spaced, threaded holes  32  extending downwardly from the top surface  24  of the neutral bar into one of the bores  28 . Each of the threaded holes  32  has a wire-binding screw  34  threadedly engaged therein. Although one configuration of wire-binding screw is illustrated, the wire-binding screw may assume other configurations in accordance with the present invention. 
     As best illustrated in FIG. 3, each of the expanders  16  in accordance with this embodiment of the present invention is a unitary member preferably cast from aluminum, having a generally L-shaped body portion  36  including a first portion  38  and a second portion  40 . The second portion  40  extends upwardly from the rear of the first portion  38  in a substantially L-shape. The first portion  38  of the body portion  36  has a front surface or shoulder  39  which functions to provide a stop preventing the first neutral bar  12  from moving rearwardly. 
     The expander  16  has a generally planar top surface  42 , a generally planar bottom surface  44 , and a pair of generally planar side surfaces  46 , which define the width of the expander  16 . Extending forwardly from the first portion  38  of the body portion  36  is a first leg  48  and extending forwardly from the second portion  40  of the body portion  36  is a second leg  50 . The first leg  48  is located in front of the second leg  50  and below the second leg  50 . Between the second leg.  50  and the first portion  38  of the body portion  36  is a slot  51  in which a lower portion  15  of the second neutral bar  14  is located, as shown in FIG.  2 . In this embodiment of the present invention, the expander  16  is of a uniform width and each of the first and second legs  48 ,  50  has a generally rectangular cross-sectional configuration, as best shown in FIG.  3 . 
     The configuration of the expanders  16  functions to position the neutral bars  12 ,  14  relative to each other such that an electrician may see therebetween in order to see which wire is going in which hole. More particularly, the front surface  39  abuts the rear surface  22  of the first neutral bar  12 , thereby preventing the first neutral bar from moving rearwardly and ensuring adequate spacing between the first and second neutral bars  12 ,  14 . 
     As best illustrated in FIG. 2, the first or lower leg  48  of the expander  16  is received in the outermost bore  28 ′ of the first neutral bar  12  and secured therein with one of the wire-binding screws  34 ′. In addition, the second leg  50  of the expander  16  is located in the outermost hole  28 ″ of the second neutral bar  14  and secured therein with wire-binding screw  34 ″. 
     Although the legs  48 ,  50  of each of the expanders  16  are illustrated as being secured in the outermost bores  28 ′,  28 ″ of the first and second neutral bars  12 ,  14 , respectively; they may be located in any of the bores of the first and second neutral bars  12 ,  14  without departing from the spirit or scope of the present invention. Although two expanders  16  are illustrated and described, the neutral bars  12 ,  14  may be secured together with more than two expanders  16 . 
     FIGS. 4-6 illustrate an alternative preferred embodiment of the present invention. In this embodiment of the present invention, a neutral bar assembly  10   a  is illustrated comprising a first neutral bar  12   a , a second neutral bar  14   a , located generally above and behind the first neutral bar  12   a , and a third neutral bar  52  located generally above and behind the second neutral bar  14   a . Each of the first, second, and third neutral bars is identically configured, having the same length, width, and height. However, neutral bars of different lengths may be used in accordance with the this embodiment of the present invention. 
     Each of the three neutral bars  12   a ,  14   a  and  52  are identically configured, each having a plurality of bores  28   a , a plurality of threaded holes  32   a  and a plurality of wire binding screws  34   a . The neutral bars  12   a ,  14   a  and  52  are identically configured to the first and second neutral bars  12 ,  14  described hereinabove. 
     Referring to FIGS. 5 and 6, the first, second and third neutral bars  12   a ,  14   a  and  52  are electrically and mechanically joined by a pair of expanders  54 . Each of the expanders  54  is generally staircase shaped having a body portion  56  including a first step portion  55  having a front surface  61 , a second step portion  57  having a front surface  63  and a top portion  59 . A first leg  58  extends forwardly from the first step portion  55 , a second leg  60  located above said first leg  58  extends forwardly from the second step portion  57  and a third leg  62  located above said second leg  60  extends forwardly from the top portion  59 . Thus, each of the legs  58 ,  60  and  62  extend generally forwardly from the body portion  56 . Each expander  54  has a pair of opposed side surfaces  64  defining the width of the expander  54 , a generally planar upper surface  66  and a generally planar lower surface  68 . Each leg  58 ,  60  and  62  has a generally rectangular cross-sectional configuration. 
     The configuration of the expanders  54  functions to position the three neutral bars  12   a ,  14   a  and  52  relative to each other such that an electrician may see therebetween in order to see which wire is going in which hole. More particularly, as best illustrated in FIG. 5, the front surface  61  of the first step portion  55  abuts the rear surface  22   a  of the first neutral bar  12   a , thereby preventing the first neutral bar  12   a  from moving rearwardly and ensuring adequate spacing between the first and second neutral bars  12   a ,  14   a . Similarly, the front surface  63  of the second step portion  57  abuts the rear surface  22   a  of the second neutral bar  14   a , thereby preventing the second neutral bar  14   a  from moving rearwardly and ensuring adequate spacing between the secondhand third neutral bars  14   a ,  52 . 
     Like the expanders  16  of the embodiment described hereinabove, each of the expanders  54  is a unitary member, preferably cast from aluminum, although the expanders could be stamped from sheet material having a thickness equal to the width of the expander, or extruded from bar stock and cut-off in increments of a desired width. However, the expanders  54  may be made of any electrically conductive material. 
     Referring to FIG. 5, the first leg  58  of the expander  54  is located inside the outermost bore  28   a ′ of the first neutral bar  12   a  and secured therein with wire binding screw  34   a ′. Similarly, the second leg  60  of the expander  54  is located inside the outermost bore  28   a ″ of the second neutral bar  14   a  and secured therein with wire binding screw  34   a ″. Additionally, the third leg  62  of the expander  54  is located inside the outermost bore  28   a ″′ of the third neutral bar  52  and secured therein with wire binding screw  34   a″′.    
     FIG. 7 illustrates yet another preferred embodiment of the present invention. In this embodiment, a neutral bar assembly  10   c  is created from neutral bars of different sizes and lengths. The neutral bar assembly  10   c  comprises a first neutral bar  12   c  similar to the neutral bars  12  and  12   a  described hereinabove, a second neutral bar  66  and a pair of expanders  16  identical to those shown in FIG.  3  and described hereinabove. The length of neutral bar  66  exceeds that of neutral bar  12   c . The first neutral bar  12   c  has generally planar front and rear surfaces  20   c ,  22   c , generally planar top and bottom surfaces  24   c ,  26   c  along with end surfaces  18   c . The second neutral bar  66  has generally planar front and rear surfaces  68 ,  70 , generally planar top and bottom surfaces  72 ,  74  along with end surfaces  76 . Due to the difference in size each of the surfaces of the second neutral bar  66  is larger than the corresponding surface of the first neutral bar  12   c.    
     The second neutral bar  66  has a plurality of bores  78  of a diameter greater than the diameter of the bores  28   c  of the first neutral bar  12   c  which are adapted to receive wires  30   c . In addition, the second neutral bar  66  has a plurality of threaded holes  80  of a diameter greater than the diameter of the threaded holes  32  of the first neutral bar  12   c  and a plurality of wire binding screws  82  which are larger than the wire binding screws  34   c  of the first neutral bar  12   c.    
     The configuration of the expanders  16  allows neutral bars of different lengths and transverse cross-sectional sizes such as neutral bars  66  and  12   c  to be electrically and mechanically connected. 
     FIG. 8 illustrates an alternative embodiment of expander  84  having a body portion  86 , a first leg  88  and a second leg  90  located above the first leg  88 . Each of the legs  88 ,  90  has a circular cross-sectional configuration. 
     FIGS. 9 and 10 illustrate additional alternative embodiments of expanders. FIG. 9 illustrates a generally U-shaped expander  92  having a curved body portion  94 , a first leg  96  and a second leg  98  located above the first leg  96 . First leg  96  is longer than second leg  98 . Each of the legs  96 ,  98  along with the body portion  94  has a square cross-sectional configuration. 
     FIG. 10 illustrates a generally U-shaped expander  92   a  having a curved body portion  94   a , a first leg  96   a  and a second leg  98   a  located above the first leg  96   a . First leg  96   a  is longer than second leg  98   a . Each of the legs  96   a ,  98   a  along with the body portion  94   a  has a circular cross-sectional configuration. 
     FIGS. 11 and 12 illustrate additional alternative embodiments of expanders which may be used in accordance with the present invention. FIG. 11 illustrates an expander  100  having a straight body portion  102 , a first leg  104 , a second leg  106  located above the first leg  104  and a third leg  108  located above the second leg  106 . Each of the legs  104 ,  106 ,  108  extend forwardly from the body portion  102 . Each of the legs  104 ,  106 ,  108  along with the body portion  102  have a square cross-sectional configuration. The legs  104 ,  106 ,  108  are preferably welded to the body portion  102  but may be secured via other means. 
     FIG. 12 illustrates an expander  100   a  having a straight body portion  102   a , a first leg  104   a , a second leg  106   a  located above the first leg  104   a  and a third leg  108   a  located above the second leg  106   a . Each of the legs  104   a ,  106   a ,  108   a  extend forwardly from the body portion  102   a . Each of the legs  104   a ,  106   a ,  108   a  along with the body portion  102   a  have a circular cross-sectional configuration. The legs  104 ,  106 ,  108  are preferably welded to the body portion  102  but may be secured via other means. 
     One method of making the expanders of the present invention and particularly those embodiments shown in FIGS. 3,  6 ,  9  and  11 , is to extrude a length of electrically conductive material from bar stock through an extruder, as is conventional. Once the length of electrically conductive material has been extruded such that the result has the desired shape, the length is cut in a transverse direction such that the resultant expanders have a desired width. 
     Regarding the embodiments of expander shown in FIGS. 3,  6 ,  9  and  11 , the legs of each of these expanders have a rectangular cross sectional configuration. Hence, the screws of the neutral bars engage a flat surface of the expander, typically the top surface of the expander legs. Hence, the configuration of the legs of the expander are helpful in preventing the neutral bars from moving relative to each other in a direction parallel to their respective lengths. 
     While the present invention has been illustrated by a description of various embodiments and while these embodiments have been described in considerable detail, it is not the intention of applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. The invention in its broader aspects is therefore not limited to the specific details, representative apparatus and method, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of applicant&#39;s general inventive concept.