Abstract:
A simplified assembly truss system rivets each power track inside one chord of each truss span so that the electrical components cannot be misaligned inside the chord during final assembly. The chord is slotted to receive lighting heads in its mid-sections, and short end slots allow interconnecting plugs to be inserted into matching power track ends. A stop captured by the rivets near each chord-end indexes the interconnecting plugs to ensure the final electrical assembly is correct.

Description:
RELATED APPLICATIONS 
     This Application claims benefit of, and is a continuation-in-part of, U.S. patent application Ser. No. 12/069,201, filed Feb. 09, 2008, titled, TRUSS WITH LIGHTING TRACK, and is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to lighting truss systems typically used in homes, offices, retail space, stages and trade shows. In particular, the present invention relates to trusses with electrical buss bars, insulator supports, and extruded aluminum carriers disposed in at least one steel truss chord and accessible for track light fixtures through slots. 
     2. Description of Related Art 
     Trusses are widely used to support overhead lighting units powered by electrical power cords dressed along the truss raceways. Truss systems for stages and tradeshow floors are available in I-beam, triangle, and square truss sections made from aluminum or steel. Steel trusses are strong enough to permit 40-foot spans, and aluminum trusses have the advantage that they can be made from extruded pieces. Extrusions allow the possibility of including power tracks inside for track lighting heads. 
     Trussing typically comes in ten-foot sections, and can be interconnected with 2, 3, 4, 5, and 6-way corners. The interconnections at the ends can be the tube-in-socket kind, or by butting together and bolting truss end plates. 
     Track lighting is another very flexible and adaptable lighting system, but more so for permanent installations. The power tracks themselves are usually very flimsy and need to be supported by bolting them to walls, ceilings, or support rods. 
     Line voltage track systems are dangerous and require large raceways that make the overall structures relatively large and clumsy. Low voltage systems enabled with step-down transformers permit much smaller and moderate structural piece sizes that make for easier and simplified installations. 
     SUMMARY OF THE INVENTION 
     Briefly, a simplified assembly truss system embodiment of the present invention rivets power tracks inside one chord of each truss span so that the power tracks cannot be misaligned inside the chord during final assembly. The chord is slotted to receive lighting heads in its mid-sections, and short end slots allow interconnecting plugs to be inserted into matching power track ends. A stop captured by the rivets near each chord-end indexes the inter-connecting plugs. 
     An advantage of the present invention is that a truss system is provided that does not allow incorrect or misaligned assembly by an installer. 
     Another advantage of the present invention is that a method is provided for the interconnection of low voltage power between truss sections. 
     The above and still further objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, especially when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective diagram of a stage lighting truss system embodiment of the present invention; 
         FIG. 2A  is a close up perspective exploded assembly view showing how typical truss sections are assembled together with interconnecting plugs for the low voltage power daisy-chaining; 
         FIG. 2B  is a close up perspective view showing how typical truss sections look after being assembled together; 
         FIG. 3A  is an end view of a truss section with one of its three main chords outfitted with power busses and slotting to accommodate lighting heads, transformers, and other devices, as in  FIG. 1 ; 
         FIG. 3B  is a perspective view of the truss section shown in  FIG. 3A ; 
         FIGS. 4A-4C  are end views and a perspective of a powered truss chord, as in  FIGS. 3A and 3B , which has aluminum extrusions and insulator supports for two-wire power bus bars and slotting in the steel truss chord tubing to accommodate lighting heads as in  FIG. 1 ; 
         FIGS. 4D-4F  are end views and a perspective of a powered truss chord, as in  FIGS. 3A and 3B , which has aluminum extrusions and insulator supports for four-wire power bus bars and slotting in the steel truss chord tubing to accommodate two circuits of lighting heads as in  FIG. 1 ; 
         FIGS. 5A-5C  are bottom, end, and top views of a 90-degree corner section that could be used with the parts shown in  FIGS. 1-3A  and  3 B, inside the power tracks are interconnected through the sharp turns by internal wiring; 
         FIGS. 5D-5F  are bottom, end, and top views of the 90-degree corner section like that of  FIGS. 5A-5C , but with a hard plastic conduit connecting the power chord together and enclosing the interconnecting wiring; 
         FIGS. 6A-6C  are bottom, end, and top views of a 45-45-degree corner section that could be used with the parts shown in  FIGS. 1-3A  and  3 B, the power tracks are interconnected through the 45-degree turns by internal wiring; 
         FIGS. 7A-7B  are perspective diagrams of a transformer power truss section to convert 110/220 VAC utility power into 12-VAC low voltage for the power tracks in  FIGS. 1-6A ,  6 B, and  6 C; 
         FIGS. 8A-8C  are perspective diagrams of a transformer power truss T-section to convert 110/220 VAC utility power into 12-VAC low voltage for the power tracks in  FIGS. 1-6A ,  6 B, and  6 C; 
         FIGS. 9-11  are perspective view diagrams of short, medium, and long lengths of straight truss sections, with two, three, and four power slots respectively; 
         FIGS. 12A-12C  are perspective view diagrams showing, in three steps, the assembly of a plastic elbow conduit and wiring for a corner truss section; 
         FIG. 13  is a perspective view diagram of a straight truss section with a utility line voltage powered pendulum lamp and strain relief support base; 
         FIG. 14  is a perspective diagram of a 4-transformer power truss 4-way cross connection to convert 110/220 VAC utility power into 12-VAC low voltage for the power tracks in adjoining truss sections; 
         FIGS. 15A and 15B  are perspective view diagrams of two lengths of straight truss sections, showing how slots can be used to thread a power cord; and 
         FIGS. 16A and 16B  are perspective view diagrams of two lengths of straight truss sections and a radius corner section, showing how slots can be used to thread a power cord through the corner. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  represents a stage lighting truss system embodiment of the present invention, and is referred to herein by the general reference numeral  100 . Truss system  100  may be arranged in many configurations suitable for the dimensions and uses of a floor  102 . In one configuration, truss system  100  is made primarily from steel and comprises a pair of vertical supports  104  and  106  with base footings  108  and  110 . A three-chord member, triangular construction is shown in  FIG. 1 , but 2-chord (I-beam), and 4-chord (square) truss pieces can also be used. A unique aspect is at least one of the chords has an electrical track and fixture slot within to accommodate and power low-voltage lighting heads. 
     Each section is terminated with a welded triangular flange, e.g.,  112  and  114 . These bolt together and allow the modular assembly needed to custom configure each application of the system. An interconnector, shown in later Figures, allows daisy-chaining of the electrical power from one powered truss chord to the next. 
     A pair of 90-degree corner connectors  116  and  118  provide mounts overhead for a span of three horizontal truss sections  120 ,  122 , and  124 . Typically, three such sections would provide a 30-foot span. For example, low-voltage lighting heads  130 - 135  can be installed anywhere along the powered truss chord  140 - 146  using a fixture slot in the steel tubing that provides mechanical support aloft and electrical contact access to the electrified power busses inside. 
     A step-down transformer  150  provides low-voltage, 12/24 VAC, power converted from a 120/240 VAC power line cord  152 . The low voltage connection from the step-down transformer can be detachable through the track fixture slot like the lighting heads, or wired-in for high amperage through a heavier feed cable connection. 
       FIG. 2A  shows a close-up of the connection between sections, e.g., between flanges  112  and  114  in  FIG. 1 , and is referred to by the general reference numeral  200 . Connection  200  requires an electrical interconnector  202  with opposite male plug ends. During on-site assembly, an insertion motion  204  puts this in place in one truss section end, as shown here by another interconnector  206 . 
     A riveted stop  207 , visible here only in the end of a powered truss chord  208  prevents the interconnector  206  from going in too deep. Its rivet prevents field personnel from assuming this piece can be adjusted or disassembled by them. 
     A matching female socket here aligns with a similar powered truss-chord  210  and female socket in an adjoining truss section. These two truss sections are joined by matching welded flanges  212  and  214 , and all are made of steel for strength. A typical machine bolt  216  passes through holes  218  and is threaded and tightened to a machine nut. Slots  224 - 227  provide access for lighting heads and transformers into the internal power tracks  228  and  230 . The internal power tracks  228  and  230  are disposed in each of the powered truss-chords  208  and  210  and are electrically bridged by interconnector  206 . 
     It&#39;s advantageous to have the longest fixture slots  224  and  226  possible, and these are most practical when the chords are comprised of steel. Slots  225  and  227  are each just a few inches long and are divided by webbings  232  and  234  from slots  224  and  226 . The webbings  232  and  234  help maintain the overall strength of the tube sections in which they are disposed. 
       FIG. 2B  shows the results of assembling connection  200 . 
       FIGS. 3A and 3B  represent a flange end of a three-chord truss  300 . In  FIG. 3B , three steel chords  301 - 303  are welded at their ends in a triangular pattern to a flange  304 . Bolt holes  306 - 308  are provided to fasten this end to another adjoining truss section. Truss chord  303  is a powered truss chord and can receive a lighting head  310  and track connector  312  through a near continuous fixture slot  314 . An end slot  315  allows for testing and inspection of any interconnecting plugs after assembly. 
     How much of the length of powered truss-chord  303  that can be slotted is limited by the weakening effects a continuous fixture slot would have. If steel were used for the tubing, the slotting would have less of an effect on the truss strength. Such slots can be cut from the steel tubing by industrial lasers, which allow for clean straight cuts of any shape. The slotting  314  and  315  in the steel tubing may be interrupted at the ends and every three or four feet to allow a web  316  to brace together the open pieces. Other metals, of course, can be used for the tubing and flanges. 
       FIGS. 4A-4F  provide more details of what&#39;s inside a powered truss chord  400 . It includes a steel outer tubing  402  in which is disposed an aluminum extrusion  404 . Such, in turn, provides for two insulator supports  406  and  408  as seen in  FIGS. 4A-4C . These can be made of any good electrical insulating material that is also mechanically strong and able to resist breaking and cracking, e.g., polyvinyl chloride (PVC) and other plastics. A pair of copper bus bars  410  and  412  carry a low voltage current to power track lighting and other devices. The electrical contact can be made directly inside anywhere along the exposed bars. An access fixture slot  414  in extrusion  404  allows a lighting head connector, e.g.,  312  in  FIGS. 3A and 3B , to be inserted through to make contact with power buss bars  410  and  412 . A similar, matching fixture slot  416  is cut into the adjacent section of the steel main truss chord  402 . 
     The aluminum extrusion  404  is permanently secured inside powered truss-chord  402  with a rivet  420  and square nut stop  421  through a hole  422 .  FIGS. 4C and 4F  use drawing cutaways in tubing  402  to better show the details of rivet  420  and square nut stop  421 . 
       FIGS. 4D-4F  include instead a 4-wire bus bar extrusion  430 , a first pair of insulators  432  and  434 , a top pair of copper buss bars  436  and  438 , a second pair of insulators  440  and  442 , and a bottom pair of copper buss bars  444  and  446 . 
       FIGS. 5A-5C  represent one kind of 90-degree corner section that could be used with the parts shown in  FIGS. 1-3A  and  3 B, and is referred to herein by the general reference numeral  500 . Corner  500  comprises three main chords  501 - 503  and end-plate flanges  504  and  506 , e.g., made of steel. Slots  507 - 510  are respectively cut in the outer edge of powered truss chord  502 . Power busses are aligned with slots  508  and  510  and connected by a pair of wires through a plastic elbow  512 . Male-male interconnectors  518  and  520  provide for power connections to the adjoining truss sections. 
       FIGS. 5D-5F  are bottom, end, and top views of a 90-degree corner section  540  like those of  FIGS. 5A-5C , but with a hard plastic conduit  542  enclosing interconnecting wiring. Slots  507 - 510  are disposed in the power chord  502  which provide access to power busses inside. End slots  507  and  510  allow for the inspection and testing of respective interconnectors  518  and  520 . 
       FIGS. 6A-6C  represent a 45-45-degree corner section that could be used with the parts shown in  FIGS. 1-3A  and  3 B, and is referred to herein by the general reference numeral  600 . Corner  600  comprises three main chords  601 - 603  and end-plate flanges  604  and  606 , e.g., made of steel. Slots  608 - 612 , are cut into the corresponding straight runs of powered truss chord  602 . Slot  610  allows a power cord to be threaded in the tubing to the outside. Power busses, like that shown in  FIG. 4 , are aligned and connected through the sharp turns by wire pairs. Male-male interconnectors  624  and  626  provide for power connections to the adjoining truss sections through matching female sockets. 
       FIGS. 7A-7B  represent a transformer power truss section  700  to convert 120VAC or 220VAC utility power into 12VAC low voltage for the power tracks in  FIGS. 1-6A  and  6 C. The power truss section  700  comprises three truss chords  701 - 703 , of which chord  702  carries the low voltage wiring and lighting tracks. A utility power supply pigtail  704  leads in through a slot  705  in chord  701  and has a ground connection  706 . Two step-down transformers  708  and  710  convert, e.g., 120VAC to 12VAC and are respectively protected by circuit breakers  712  and  714 . These each have a pushbutton reset (shown for  714 ) that a user can get to easily on the outside. A low voltage output from step-down transformer  708  connects through a wire lead  716  to an interconnector  718 . Similarly, another low voltage output from step-down transformer  710  connects through a wire lead  720  to an interconnector  722 . These respectively plug into a power track accessible through slots  723 - 726 .  FIG. 7B  shows how the electrical components can be enclosed. 
       FIGS. 8A-8C  represent a transformer power truss T-section  800  to convert 120VAC or 220VAC utility power into 12VAC low voltage, e.g., for the power tracks in  FIGS. 1-6A ,  6 B, and  6 C. The power truss T-section  800  comprises three truss chords  801 - 803  which T-intersect with three other truss chords  804 - 806 . Chords  802  and  805  carry the low voltage wiring and lighting tracks. A utility power supply pigtail  807  leads in through chord  804  and has a ground connection  808 . Three step-down transformers  810 - 812  convert, e.g., 110-VAC to 12-VAC, and are respectively protected by circuit breakers  814 - 816 . These each have a pushbutton reset on the corresponding arm&#39;s flange plate  818 - 820  that a user can get to easily on the outside. A low voltage output from step-down transformer  810  connects through a wire lead to a power bus under an end slot  821 , a fixture slot  822  and interconnector  824 . Similarly, another low voltage output from step-down transformer  811  connects through a wire lead to a power bus under an end slot  825 , a fixture slot  826  and to an interconnector  828 . A third low voltage output from step-down transformer  812  connects through a wire lead to a power bus under an end slot  829 , a fixture slot  830  and then to interconnector  832 . 
       FIGS. 9-11  represent a short, a medium, and a long length of straight truss sections, referred to herein by the general reference numerals  900 ,  1000 , and  1100 . For example, these could be four, six, and eight feet long. In  FIG. 9 , straight truss section  900  has slots  901 - 904 . In  FIG. 10 , straight truss section  1000  has slots  10001 - 1006 . In  FIG. 11 , straight truss section  1100  has slots  1101 - 1108 . The slots keep enough webbing between them to provide the structural strength necessary for the truss to provide good support without bending or flexing. For this reason, the longer lengths of straight truss sections need to be broken up in more slots, such that the webbing between them can be spaced no more than a few feet apart. For example, in  FIG. 9 , the maximum length of slots  902  and  903  would be several inches. 
       FIGS. 12A-12C  provide more detail on the wiring and interconnection of corner truss sections, like that shown in  FIGS. 5D-5F . A corner truss  1200  has two plastic elbow sections  1202  and  1204  that clamp over and join the ends of intersecting power truss chords and electric tracks  1206  and  1208 . A pair of screws  1210  and  1212  holds them together. Inside, a pair of electrical wires  1214  connect respective ends  1216  and  1218  of the electric tracks  1206  and  1208 . 
       FIG. 13  represents a straight truss section  1300  that does not include an electric track or power chord. Instead, three truss chords  1302 ,  1304 , and  1306 , are used to support a pendulum lamp  1308 . A clamp on support base  1310  provides a decorative base and strain relief for a power cord  1312 . This feeds into a slot in chord  1302  and out one end, emerging as a pigtail  1314  for connection to a power source and/or junction box. 
       FIG. 14  represents a 4-way truss connecting section  1400  that includes four arms  1401 - 1404  and a power chord with slots  1405 - 1408 . Other chords  1411 - 1416  are welded together from tubing to form the basic three-chord structural member with 4-way intersection. Interconnectors  1421 - 1424  provide for electrical, low voltage connections to other truss sections. Each has a respective circuit breaker  1431 - 1434  that can be easily reset with a pushbutton by a user if a circuit fault occurred. Four step-down transformers are represented by  1440  and  1444 , and receive utility power through a slot  1444  using a power cord and pigtail  1446 . Cover screens would normally be installed to protect workers from electric shock, and are not shown here so the internal components can be understood and described. End slots  1451 - 1454  provide access and inspection of interconnectors  1421 - 1424 . 
       FIGS. 15A and 15B  represent a truss section  1500  that illustrates how the utility power cords can be dressed inside the truss chords. A first straight truss has three chords  1501 - 1503  that join with a second straight truss section with three matching truss chords  1504 - 1506 . These all have open ends that allow cords and other wiring to pass inside between them, and the truss sections bolt together with end flanges like  1507  and  1508  using fasteners like  1509 . A first power plug and cord  1510  passes up inside chords  1504  and  1501  through a slot  1512 . A pigtail  1514  appears at the open end of chord  1501 . Another power plug and cord  1516  similarly passes up inside chords  1506  and  1503 , but exits through a slot  1520  to appear as pigtail  1522 . 
       FIG. 16  represents a corner assembly  1600  that uses a radius elbow section to join straight truss sections. The way the utility power wiring is threaded in the truss chord tubing members is the focus of this illustration. A first straight truss section has straight chords  1601 - 1603  that align with three corresponding radius chord members  1604 - 1606  in an elbow truss. These, in turn, connect to respective chords  1607 - 1609  in a second straight truss section. A detail B shows how flanges  1610  and  1611  mate and are bolted together. A power plug and cord  1620  threads into a slot  1622  in chord  1607  and runs up along inside chords  1604  and  1601 . It is seen in a cutaway as cord  1624  and exits a slot  1626  with a pigtail end  1628 . Standard twist-on wire connections can be used to complete the electrical connection, e.g., to a step-down transformer or line-voltage lamp. Cord  1624  is shown passing through a butt-joint  1630 . 
     Although particular embodiments of the present invention have been described and illustrated, such was not intended to limit the invention. Modifications and changes will no doubt become apparent to those skilled in the art, and it was intended that the invention only be limited by the scope of the appended claims.