Abstract:
A wiring system for LED signs includes a plurality of coaxial cables in circuit relationship to a power supply and at least one light emitting diode within a letter box housing. A bushing connectable to the housing has two cylindrical longitudinal passageways therethrough, each passageway dimensioned to accommodate an outside diameter of a coaxial cable. The coaxial cables may be a predetermined length and the cables and bushing may come preassembled to the job site. Additional sets of coaxial cables may be connected to the circuit in series or parallel wiring arrangement by way of a splice connector that receives and fastens the threaded fitting at the end of each coaxial cable. The bushings and the splice connector provide strain relief for the coaxial cable and a safety ground path for the circuit.

Description:
REFERENCE TO PENDING APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/041,359, filed Apr. 1, 2008, and entitled “Wiring System for LED Signs”. 
     
    
     FIELD OF INVENTION 
       [0002]    The present invention relates generally to the use of light emitting diodes (LEDs) in signage and, more particularly, to wiring systems in LED signage applications. 
       BACKGROUND OF INVENTION 
       [0003]    Channel letters are commonly used in signage to advertise the name of the business. A housing in the shape of the letter and covered by a plastic translucent lens typically contains one or more neon light tubes arranged in the shape of the letter. Although neon lighting provides a bright, continuous light source, it is also fragile, experiences difficulty in cold starting, and high voltage is required. Because of these disadvantages, the sign lighting industry has witnessed major changes over the past five years as neon lighting is being replaced by light emitting diodes (LEDs) in channel letter applications. 
         [0004]    One of the basic assumptions driving the conversion to LEDs is that the low voltage LEDs are safer, less expensive, and more energy efficient than neon. However, a lack of knowledge concerning DC voltage transmission coupled with no adequate system for safety ground continuity, splice connections, and wiring designed for use with LEDs leaves a great many LED installations less safe, more expensive, and less energy efficient than anticipated. 
         [0005]    To date, a myriad of products and installation methods to properly connect power sources to LEDs have been introduced. Those methods include the use of (1) insulated speaker wire or other small diameter wire, which typically lack proper conductor size and insulation not designed for such use inside and outside of a building; (2) Class 2 wires designed for interior use only; (3) the combination of insulated speaker wire or class 2 wire with mechanical conduit and make-up boxes; (4) wire splicing with wire nuts, electrical tape, and bare twisted wire connections; (5) one or more large holes drilled through the sign-supporting substraight; (6) no secondary safety ground wiring; and (7) a hodgepodge of parts and pieces left to the discretion and knowledge of the installer to make a proper connection between the power source and the LEDs. All the above leaves electrical sign inspectors and field installation crews looking for a safe, practical, and National Electric Code-compliant method and system for connecting power sources to LEDs. 
       SUMMARY OF THE INVENTION 
       [0006]    A wiring system for a light emitting diode (LED) sign includes a wiring set and a system and method for connecting the wiring set to the LED sign. The wiring set includes a bushing with at least two cylindrical longitudinal passageways that is received by an opening in a letter box housing. Each passageway receives a portion of a coaxial cable and holds that portion of the cable securely within the bushing. A chamfered opening at an end of each passageway protects the portion of each cable extending from the bushing into the interior of the housing from becoming cut or bent. Each cable has a threaded fitting at one end that allows it to be spliced by a splice assembly connector to an opposing cable of a second wiring set. In a preferred embodiment, the coaxial cables are each predetermined length “L” with at least one of the coaxial cables in each set having a marking or band that indicates a proper polarity connection with an opposing coaxial cable of a second wiring set. 
         [0007]    A wiring system according to this invention includes two or more coaxial cables of a wiring set arranged in a circuit relationship to a power supply and at least one light emitting diode contained within a letter box housing. The power supply is preferably a 50V or less power supply. A knockout or opening in the housing receives a bushing having two substantially cylindrical longitudinal passageways. Each bushing passageway is preferably co-planar to the other passageway and sized so as to allow a portion of a coaxial cable to tightly pass therethrough. The coaxial cable may be a predetermined length of cable. 
         [0008]    The bushing connects to the housing by way of a locknut threaded onto the bushing and tightened so that a flange portion of the bushing seats to an exterior surface of the housing, thereby providing a ground and strain relief for the two coaxial cables. A chamfered opening at an end of each passageway also protects the portion of each cable extending from the bushing into the interior of the housing from becoming cut or bent. 
         [0009]    The wiring system may also include a coaxial cable splice connector. The splice connector may include a bushing with a receiver on each end that accommodates the threaded termination end of the coaxial cable and receives the conductive portion of the coaxial cable. A nut threads onto the termination end and secures the coaxial cable to the connector, thereby providing a strain relief as well as a ground path. 
         [0010]    A method of wiring the LED sign includes the steps of connecting a conductive portion of a first end of a first coaxial cable to a power supply and splicing a second end of the first coaxial cable to a first end of a second coaxial cable. A portion of the second coaxial cable passes tightly through a passageway in a first bushing that is connectable to the letter box housing. A conductive portion at a second end of the second coaxial cable is connected to a LED housed within the letter box housing. The bushing is then secured to the letter box housing and a safety ground path is provided. Additional letter boxes may be connected to the circuit by splicing a first end of a third coaxial cable that passes tightly through a second passageway of the first bushing to a first end of a fourth coaxial cable that passes tightly through a passageway in a second bushing connectable to a second letter box housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an isometric view of a junction box connector assembly for a single coaxial cable. A threaded fitting located on an end of the coaxial cable threads into a bushing and is secured to the junction box by a locknut. 
           [0012]      FIG. 2  is a reverse isometric view illustrating the relationship between the threaded fitting on the cable and the bushing. 
           [0013]      FIG. 3  is an isometric view of the assembled connector assembly. 
           [0014]      FIG. 4  is an isometric view of a splice assembly having a connector with a conductive bushing. 
           [0015]      FIG. 5  is a front view of the splice assembly. Each end of the connector receives the conductive portion of a coaxial cable. A nut provided with each cable secures the cable to the connector. 
           [0016]      FIG. 6  is a front view of the completed splice assembly. The assembly provides a path for current flowing in one cable to pass to the other cable. 
           [0017]      FIG. 7  is an isometric view of a dual-cable letter box connector assembly. 
           [0018]      FIG. 8  is a front view of the dual-cable letter box connector assembly. A bushing having two cylindrical passageways allows two coaxial cables to pass therethrough. A locknut threads onto the exterior threads of the bushing. 
           [0019]      FIG. 9  is a view taken along section line  9 - 9  of  FIG. 8 . 
           [0020]      FIG. 10  is a front view of the bushing used in the dual-cable junction box connector assembly. 
           [0021]      FIG. 11  is a view of the bushing taken along section line  11 - 11  of  FIG. 10 . 
           [0022]      FIG. 12  is a front view of the bushing without coaxial cable passing therethrough. 
           [0023]      FIG. 13  is a view of a letter box having a knockout and connected to the dual-cable junction box connector assembly. The coaxial cables supply current to an array of light emitting diodes (LEDs). 
           [0024]      FIG. 14  is a front view of a Z-shaped letter box containing LEDs arranged in a corresponding Z-shape. Coaxial cables provided by the dual-cable junction box connector assembly supply current to the LEDs. 
           [0025]      FIG. 15  is a view of the wiring system in a series arrangement and employing the single- and dual-cable junction box connector assemblies and the splice assembly. 
           [0026]      FIG. 16  is an alternate embodiment of the letter box connector assembly. 
           [0027]      FIG. 17  is a view of the letter box connector assembly taken along section line  17 - 17  of  FIG. 16 . Cylindrical passageways in the bushing allow coaxial cables to pass therethrough. 
           [0028]      FIG. 18  is an exploded view of the letter box connector assembly. 
           [0029]      FIG. 19  is a front view of the letter box connector assembly. The bushing may have two or four cylindrical passageways for receiving coaxial cable. 
           [0030]      FIG. 20  is a view of the letter box connector assembly configured for a parallel wiring arrangement. Four coaxial cables, each preferably 3 feet in length, pass therethrough. Two of the cables have a male connector at one end and two of the cables have a female fitting for attachment to a complementary preassembled letter box connector assembly. 
           [0031]      FIG. 21  is a view of the letter box connector assembly taken along section line  21 - 21  of  FIG. 20 . A locknut secures the connector assembly to the letter box, thereby providing a ground path and strain relief between coaxial cable and the letter box. 
           [0032]      FIG. 22  is a view of the wiring system connected in a parallel arrangement. 
           [0033]      FIG. 23  is a view of the letter box connector assembly with two coaxial cables passing therethrough for use in a series wiring arrangement. Color coding is used on the coaxial cables so that the proper splice connections are made throughout the wiring system. 
           [0034]      FIG. 24  is a view of a wiring set designed to connect to the wiring set illustrated in  FIG. 23 . 
           [0035]      FIG. 25  is a view of the wiring system connected in a series arrangement. 
           [0036]      FIG. 26  is a view of a 2-wire system connected in a split parallel wiring arrangement. The system includes one set of letter leads for each letter box, a set of jump leads to connect the sets of letter leads, and a transformer lead. All of the leads are color-coded to ensure that the proper splice connections are made throughout. 
           [0037]      FIG. 27  is a view of the 2-wire system of  FIG. 26  connected in a standard parallel wiring arrangement. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0038]    The invention described below is not limited in its application to the details illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or carried out in a variety of ways. The phraseology and terminology employed herein are for purposes of description and not limitation. Elements illustrated in the drawings are identified by the following numbers: 
         [0000]    
       
         
               
               
             
           
               
                   
               
             
             
               
                 10 
                 Wiring system 
               
               
                 12 
                 Coaxial cable 
               
               
                 14 
                 Junction box 
               
               
                 16 
                 Letter box 
               
               
                 18 
                 Light emitting diode 
               
               
                 20 
                 Junction box connector assembly 
               
               
                 22 
                 Threaded fitting 
               
               
                 24 
                 Bushing 
               
               
                 26 
                 Locknut 
               
               
                 27 
                 Flange portion 
               
               
                 28 
                 Central opening 
               
               
                 29 
                 Threaded portion 
               
               
                 30 
                 Splice assembly 
               
               
                 32 
                 Threaded fitting 
               
               
                 34 
                 Splice connector 
               
               
                 36 
                 Nut 
               
               
                 37 
                 Opening 
               
               
                 38 
                 Insulated bushing 
               
               
                 39 
                 Threaded portion 
               
               
                 40 
                 Letter box connector assembly 
               
               
                 42 
                 Bushing 
               
               
                 44 
                 Locknut 
               
               
                 46 
                 First cylindrical passageway 
               
               
                 47 
                 Interior wall 
               
               
                 48 
                 Second cylindrical passageway 
               
               
                 50 
                 Chamfered opening 
               
               
                 62 
                 Threaded fitting 
               
               
                 64 
                 Splice connector 
               
               
                 66 
                 Marking 
               
               
                 68 
                 Band 
               
               
                 70 
                 Wiring set 
               
               
                 82 
                 Bushing 
               
               
                 84 
                 Fitting 
               
               
                 86 
                 Passageway 
               
               
                 88 
                 Passageway 
               
               
                 90 
                 Passageway 
               
               
                 92 
                 Passageway 
               
               
                 110 
                 Conductor 
               
               
                 112 
                 Insulator 
               
               
                 114 
                 Outer insulator 
               
               
                 116 
                 First end 
               
               
                 118 
                 Second end 
               
               
                 120 
                 Pass-thru or letter box lead 
               
               
                 122 
                 Jumper lead 
               
               
                 124 
                 Transformer lead 
               
               
                 130 
                 Splice assembly 
               
               
                   
               
             
          
         
       
     
         [0039]    Referring to the drawings and first to  FIGS. 1 to 3 , a coaxial cable  12  connects to a junction box connector assembly  20  that includes a threaded fitting  22 , a threaded bushing  24 , and a locknut  26 . Coaxial cable  12  is of a type well-known in the art and typically includes a conductor  110 , inner insulation  112 , a wire mesh (ground), and outside insulation or jacket  114 . Threaded fitting  22  may be a crimp fitting, a compression fitting, or a screw-type fitting. An end of coaxial cable  12  receives threaded fitting  22 . A threaded central opening  28  in bushing  24  threads onto fitting  22  and allows the conductor  110  and insulation  112  of coaxial cable  12  to pass through the opening  28 . Locknut  26  then threads onto an external threaded portion  29  of bushing  24 . To maintain the ground connection, a fold-over crimp of the wire mesh is preferred. 
         [0040]    In a preferred embodiment, an electrical box (not shown) having either a knockout or fabricated opening receives bushing  24 . A flange portion  27  of bushing  24  contacts the exterior surface of the electrical box and locknut  26  threads onto the exposed threads  29  of bushing  24  within the electrical box, thereby providing a ground path and strain relief between coaxial cable  12  and the electrical box. A portion of the shield  112  of coaxial cable  12  may be stripped away so that a required electrical connection can be made. 
         [0041]    Referring now to  FIGS. 4 to 6 , coaxial cable  12  connects to a splice assembly  30 . Splice assembly  30  includes threaded fitting  32 , splice connector  34 , and nut  36 . Threaded fitting  32  is preferably the same as threaded fitting  22  to provide connectivity to either junction box connector assembly  20  or splice assembly  30 . Splice connector  34  contains an insulated conductive bushing  38  with an opening  37  at each end that receives the conductive portion of coaxial cable  12 . A reduced inside diameter shoulder portion of nut  36 , which is slightly smaller than an outside diameter of the threaded portion of fitting  22 , serves to contain nut  36  on coaxial cable  12 . Nut  36  then threads onto the exterior threaded portion  39  of splice connector  34  and secures coaxial cable  12 , thereby providing a strain relief as well as a ground path. Splice connector  34  may also be configured in a tee-shaped arrangement (not shown) to connect three coaxial cables  12  in the same manner as described above. 
         [0042]    Referring now to  FIGS. 7 to 12 , two coaxial cables  12  connect to a letter box (see  FIGS. 13 and 14 ) through a dual-cable letter box connector assembly  40 . Connector assembly  40  comprises a threaded bushing  42  having two cylindrical, co-planar passageways  46 ,  48  passing therethrough. The central longitudinal axis of each passageway  46 ,  48  is preferably substantially parallel to the central longitudinal axis of bushing  42 . Each passageway may be separated from the other passageway by an interior wall  47  having a rectangular-shaped cross-section. The inside diameter of each passageway  46 ,  48  is preferably sized so that a jacketed coaxial cable  12  may pass tightly through each passageway  46 ,  48 . Force is then required to remove cable  12  from the passageway  46 ,  48 . Bushing  42  is preferably sized to be received by the same knockout or opening as that of bushing  24 . Locknut  44  is preferably interchangeable with locknut  26 . Bushing  42  connects to an electrical box in the same manner as bushing  24  and provides an equipment ground path from coaxial cables  12  and a strain relief pass for the coaxial cables  12 . 
         [0043]    Referring to  FIGS. 13 and 14 , in a preferred embodiment connector assembly  40  connects to a letter box  16  that has a knockout or fabricated opening. One of the two coaxial cables  12  provided by connector assembly  40  carries a positive charge and the other carries a negative charge. Letter box  16  is of a type well-known in the art and may comprise any number of geometrical configurations typically found in commercial signage. One or more light emitting diodes (LEDs)  18  are arranged within an interior space of letter box  16  to produce a predetermined letter, symbol, image, or word. Because of their low current draw, the LEDs  18  may be arranged in series without an observer perceiving any loss in lighting intensity across the series. The conductive portion  110  of each coaxial cable  12  is then placed in communication with the LEDs  18  to provide sufficient current to light the LEDs  18 . 
         [0044]    Referring now to  FIG. 15 , wiring system  10  may include different arrangements of junction box connector assemblies  20  and  40  and splice assemblies  30 . Connector assembly  30  provides coaxial cable  12  to a junction box  14  and a power supply (see  FIGS. 22 and 25 ). The power supply is preferably less than a  50 V AC or DC power supply. Connector assembly  40  provides coaxial cable  12  to the letter boxes  16 . System  10  supplies a complete wiring system that maintains mechanical and electrical protection without the use of standard conduit and electrical fittings. In addition, the unique configuration of connector assemblies  20  and  40  allows an installer to drill a smaller hole through the letter box  16  or other attachment holding the LED  18  than the hole required by standard conduit or electrical fittings. 
         [0045]    Referring now to  FIGS. 16 to 19 , an alternate embodiment of letter box connector  40  is illustrated. Similar to bushing  42  (see  FIG. 7 ), bushing  82  is located at a second end  118  of cable  12  (see  FIG. 20 ). Bushing  82  has an external threaded portion  83  that is received by and threads into threaded fitting  84 . Bushing  82  has cylindrical passageways  86 ,  88 ,  90  and  92 . The central longitudinal axis of each passageway  86 ,  88 ,  90  and  92  is preferably substantially parallel to the central longitudinal axis of bushing  82 . 
         [0046]    The inside diameter of each passageway  86 ,  88 ,  90 ,  92  is preferably sized so that a portion of jacketed coaxial cable  12  may pass tightly through each passageway  86 ,  88 ,  90 ,  92 . In other words, the second end  118  of each cable  12  is received by the respective passageway  86 ,  88 ,  90 ,  92  and then passes through the respective passageway so that a portion of the coaxial cable  12  residing between the first end  116  and second end  118  is tightly held by the respective passageway. Force is then required to remove cable  12  from each passageway  86 ,  88 ,  90 ,  92 . A locknut  44  (see  FIG. 21 ) threads onto the threaded portion  84  and secures the connector assembly  40  to the letter box  16 , thereby providing a ground path and strain relief between coaxial cable  12  and the letter box  16 . 
         [0047]    Junction box connector  20  may also be similarly constructed using bushing  82  with one passageway  86 , two passageways  86 ,  88 , or four passageways  86 ,  88 ,  90  and  92  with all of the passageways being used or one or more of the passageways being unused. 
         [0048]      FIGS. 20 to 22  illustrate fitting  40  as part of a wiring set  70  configured for a parallel wiring arrangement. Four coaxial cables  12 A-D pass through fitting  40 . Wiring set  70  is preferably preassembled and delivered to the job site with each cable  12  being a predetermined length L, preferably  3  feet in length. Splice assembly  30  includes a threaded fitting  62  and a nut  64  that threads onto fitting  62 . Coaxial cables  12  are preferably color coded with a marking  66 , such as a line drawn on the outer surface of outer insulator  114 , or band  68  to ensure proper polarity connections to an opposing set of cables (see  FIG. 22 ). Marking  66  or band  68  may be color-coded. A variable length run of cable  12  connects the first wiring set  70  to a transformer. 
         [0049]      FIGS. 23 to 25  illustrate fitting  40  as part of a wiring set  70  that is configured for a series wiring arrangement. Two coaxial cables  12 A-D, again preferably of a predetermined length L, pass through fitting  40 . Fitting  40  may have two passageways  86  and  88  or four passageways  86 ,  88 ,  90  and  92  (with two of the four passageways unused). Coaxial cables  12 A and  12 C may be spliced together by connecting connector  62 A to nut  64 C of coaxial cable  12 C. Similarly, cables  12 B and  12 D may be spliced together by connecting nut  64 B to connector  62 D. Color bands  68 B and  68 D help ensure the proper polarity connections. A variable length run V of cable  12  connects the first and last wiring set  70  to a transformer. 
         [0050]      FIGS. 26 and 27  illustrate a 2-wire wiring system  10  arranged in a split parallel and a standard parallel wiring arrangement, respectively. (Wiring system  10  may also be wired according to a serial wiring arrangement but a parallel wiring arrangement is preferred because it is easier to troubleshoot.) Wiring system  10  ensures safe, correct and proper wiring installation by providing the proper conductor to move  5  amps, a safety ground path, and visual cues that ensure red-to-red and black-to-black wiring connections throughout. Each wiring system  10  includes, for a specified signage application, the required number of pass-thru or letter box leads  120  and jumper leads  122 , and a transformer lead  124 . 
         [0051]    Letter box lead  120  includes a letter box assembly connector  40  and a pair of coaxial cables  12 . Jumper lead  122  includes a coaxial cable  12  with a threaded fitting  62  at one end and a splice assembly connector  130  at the other end. Two jumper leads  122  may be secured to one another by way of a cable tie in order provide a pair of jumper leads  122 . Transformer lead  124  includes a junction box assembly connector  20  and two coaxial cables  12  each having a splice assembly connector  130  at one end. The leads  120 ,  122 , and  124  are preferably color-coded to indicate polarity. In a preferred embodiment, splice connector assembly  130  is a 3-way splice connector with no resistor. The coaxial cables  12  of leads  120 ,  122  and  124  may include a colored jacket  114  with appropriate color markings  66  on one or both cables  12  to indicate polarity and ensure red-to-red and black-to-black connections throughout wiring system  10 . 
         [0052]    While a wiring system for LED signs has been described with a certain degree of particularity, many changes may be made in the details of construction and the arrangement of components without departing from the spirit and scope of this disclosure. The wiring system, therefore, is not limited to the embodiments set forth herein for purposes of exemplification, but is to be limited only by the scope of the attached claim or claims, including the full range of equivalency to which each element thereof is entitled.