Abstract:
A cable channel filler or spline ( 126 ) and a cable ( 40 ) containing the cable channel filler or spline in its core. The channel filler extends longitudinally and has a plurality of spaced longitudinally extending open pockets ( 128, 130, 132, 134 ) in which wires ( 42 ) or cables, such as unshielded twisted pair cables, are placed and form part of the core. The core containing the twisted pair cables in the pockets is jacketed. The channel filler has an imbedded shield ( 136 ) that extends into each of the channel filler pocket legs and is preferably prepared from a single tape. Alternatively when two tapes are used for the shield, the first tape has three shield legs and with one leg being a folded over leg and the second tape forms the fourth leg and has 20 to 50 percent or at least {fraction (1/16)} inches of one of its sides encased by the folded over leg of the first tape.

Description:
[0001]    This application claims priority from provisional application No. 60/177,068 filed on Jan. 19, 2000. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to a cable channel filler or spline and to a cable having the channel filler or spline. More particularly, the present invention relates to a cable channel filler having a shield, formed from a foil tape, embedded therein and having a plurality of shield legs with the shield legs forming a plurality of channel filler/cable pockets.  
         BACKGROUND OF THE INVENTION  
         [0003]    Electronic cables provide a highway through which much of today&#39;s digital information travels. Many of the cables which transmit digital information utilize a plurality of twisted pair cables. These twisted pair cables, to satisfy high-speed digital requirements, need to transmit information at high frequencies. Unfortunately, high frequencies, generally transmitted at extremely low voltages, are susceptible to electronic interference. For instance, near end cross-talk between twisted pairs within the same cable, referred to in the industry as NEXT, can interfere with high frequency signal transmission.  
           [0004]    To control NEXT in unshielded twisted pair (UTP) cables, the industry typically resorts to extremely short lay lengths and/or a central channel filler member that acts to physically separate the twisted pairs in order to improve crosstalk performance. The ultimate control for crosstalk is to individually shield the twisted pairs (ISTP) and electrically isolate them from one another by grounding the common shield plane. Though effective, these cables are typically quite expensive to purchase and install.  
           [0005]    U.S. Pat. Nos. 5,789,711, 5,969,295 and 5,519,173 each describe methods used to physically separate twisted pairs with a shaped central filler in UTP or screen twisted pair cables. These configurations provide some isolation due to physical separation of the UTP&#39;s, but do not provide the benefit of a conductive isolating member between the pairs.  
           [0006]    U.S. Pat. No. 5,952,615 describes the embodiment of an ISTP cable that utilizes a central rod filler surrounded with a shield, and an overall shield to fully isolate each twisted pair. This configuration typically requires that the shielding members be grounded and is contrary to my UTP invention. In addition, one embodiment proposes two metal tapes inside the fins of the central rod filler configures in a cruciform shape. This configuration of the two metal tapes is not desirable in that it allows the possibility of electromagnetic leakage between the joining point of the two tapes. In addition, the close proximity of the shield surrounding the entire circumference of the twisted pairs adversely affects the impedance and attenuation of the cable&#39;s twisted pairs. To maintain required impedance and attenuation values, the ISTP design requires that additional insulation material and copper volume be added to the twisted pairs, increasing the size and cost of the cable, both undesirable. Also, the proximity of the shield adversely affects the stability of electrical parameters such as impedance, attenuation and return loss.  
           [0007]    U.S. Pat. No. 3,819,443 describes a shielding member comprised of laminated strips of metal and plastic materials that are cut, bent and assembled to define radial branches of a shielding member. This configuration also has many of the same problems previously described. The assembly of the tapes allows a channel for electromagnetic leakage to be transmitted from opposite pairs.  
         SUMMARY OF THE INVENTION  
         [0008]    Our cable improves the isolation of a plurality of twisted pairs from each other by having a channel filler with a plurality of longitudinally extending tubular pockets and an internal metal shield. In some instances, it is preferred that the channel filler cable pockets have a cross-sectional area that is equal to or greater than the diameter of the envelope area of the wire(s) or cable(s) that are to be placed in each of the pockets. The metal shield is embedded in the channel filler to isolate each of the channel filler pockets. The channel filler shield is preferably a single tape that is folded to the conformity of the shape of the channel filler and extends into and is embedded by each of the pocket legs. The single shield tape is folded to provide a plurality of fins or legs so that there is a shield leg for each of the channel filler pocket legs. We also provide an improved two tape shield. In the two tape shield a first shield tape is folded to provide the plurality of shield legs and the second shield tape provides one shield leg. The second shield leg has 20-50% at least {fraction (1/16)} inch of one side thereof being encased by a folded over portion of one of the first shield tape legs.  
           [0009]    A communication cable manufactured using the channel filler of our invention generally has an unshielded twisted pair cable in each pocket. Then the twisted pair containing channel filler is jacketed.  
           [0010]    The present invention and the advantages thereof will become more apparent upon consideration of the following detailed description when taken in conjunction with the accompanying drawings 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    FIGS.  1 - 3  are enlarged cross-sectional views of the single tape shields each having four shield legs.  
         [0012]    [0012]FIG. 4 is an enlarged cross-sectional view of a two tape shield constructed according to our invention.  
         [0013]    [0013]FIG. 5- 8  are enlarged partial cross-sectional plan view of various channel fillers with our imbedded shield.  
         [0014]    [0014]FIG. 9 is an enlarged cross-sectional view of a cable having the channel filler of FIG. 6.  
         [0015]    [0015]FIGS. 10 and 11 are cross-sectional views of our elongated channel filler having a drain wire or strength member. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0016]    The following description taken in conjunction with the drawings will further explain the inventive features of our elongated channel filler and cables utilizing our elongated channel filler.  
         [0017]    Referring to FIG. 1, our elongated channel filler shield  20  has along its cross-sectional plane a first leg  21 , a second leg  22 , a third leg  23 , and a fourth leg  24 . The shield is made from a single tape having a width equal to about six times the width of each leg when all of the legs  21 - 24  have equal widths. The shield legs  22  and  24  are folded legs to provide a thickness double the thickness of shield legs  21  and  23 . The shield in FIG. 1 is formed by folding the tape 90 degrees at a first point  50  to form a first segment  52 , which is the first leg  23  of the shield. The first segment  52  is approximately ⅙ of the total width of the tape. The tape is then folded 180 degrees at a second point  54  to form a second segment  56  and a third segment  58 , which forms the second  24  leg of the shield. The second segment is approximately ⅙ and the third segment is approximately {fraction (2/6)} of the total width of the tape. The tape is then folded 180 degrees at a third point  60  to create a fourth segment  62 , completing the third leg  22  of the shield. Lastly, the tape is folded 90 degrees at a fourth point  64 , creating the fourth leg  21  of the shield. The second, third and fourth segments  56 ,  58  and  62  are compressed, eliminating gaps therebetween. The space between each leg creates pockets  66  adapted to accept the placement of twisted pair cables  42  as shown in FIG. 9. Each pocket  66  has a 90 degree inner edge and are defined by two legs of the shield and by a cable jacket  43 . Since there are no breaks in the one piece shield, frequency interference from each pocket is significantly reduced over previous shield designs.  
         [0018]    Referring to FIG. 2, our shield  25 , all four legs  26 , 27 ,  28  and  29  have a double layer of shield tape. The double layers are engaging each other when the shield tape is imbedded in a channel filler. By folding a single piece of shield tape into this configuration, it is possible to place a drain wire or strengthening member  45  at the converging point  68  of the four legs  26 , 27 ,  28  and  29 , shown in FIG. 10. With this configuration, each leg  26 , 27 ,  28  and  29  has a length approximately ⅛ of the total width of the tape. The benefit of the shield  25  is that each leg  26 , 27 ,  28  and  29  is comprised of two segments of tape, allowing the use of thinner tape.  
         [0019]    [0019]FIG. 3 another of our shields  30  made from a single tape folded to provide for double layer “T” shield legs  31 ,  32 ,  33  and  34 . The legs,  31 ,  32 ,  33  and  34 , and the top  70  of the “T”, are double layered and shaped to coincide with the shape of the side ends of the channel filler legs, as shown in FIG. 11. This design further reduces interference by partially closing off the pockets  72  that contain the twisted pair cables. By folding a single piece of shield tape into this configuration, it is possible to place a drain wire or strengthening member  45  at the converging point  74  of the four legs  31 ,  32 ,  33  and  34 .  
         [0020]    Referring to FIG. 4, there is shown another of our channel filler shield  35  made of two shield tapes and having shield legs  36 ,  37 ,  38  and  39 . Legs  36 ,  37  and  38  are made with a single shield tape with leg  37  being folded over to provide a double layered leg. Leg  39  is formed by the second tape and has 20-50% —at least {fraction (1/16)} inch of one side encased between the folded over portions of shield leg  37 . The at least {fraction (1/16)} in. encased portion is needed prevent the leg  39  from disengaging from between the folded portions of the leg  37 . When assembled, leg  39  is placed between the segments of the leg  37 . By utilizing a two tape shield of this design, electromagnetic leakage between the joining point of the two tapes is eliminated because of the overlap between the tapes.  
         [0021]    Referring to FIGS.  5 - 8 , there are shown different shapes of channel fillers having embedded therein any one of the shields of FIGS. 1, 2, and  4 . Since the foil tape is flexible, it is possible to bend the legs into a position that conforms with the shape of the channel fillers. By using the shields of FIGS. 1, 2 and  4 , it is possible to form the shield from the tape and apply the filler in a continuous operation, eliminating steps need for other cable designs.  
         [0022]    The preferred material for the elongated channel filler is any suitable polymer or copolymer depending on the needs of the user for crush resistance, breaking strength, gel fillings, safety, and the need for flame and smoke resistance. In many applications the material will be a flame retardant polyethylene or polyvinyl chloride. Since the filler is a polymer material, it is possible to apply the filler in various shapes to accommodate cable design requirements. The filler is designed to follow the contours of the shield and to further insulate the pockets and add overall strength to the finished cable. The cross section of the filler  86  with the embedded shield  88 , shown in FIG. 5, illustrates a plus-symbol shaped filler that has four legs  76 ,  78 ,  80  and  82  that define the pockets  84 . The cross section of the filler  90  with the embedded shield  92  in FIG. 6 illustrates the shield  92  with the legs  94 ,  96 ,  98  and  100  in a perpendicular orientation. The filler  90  surrounds the shield  92 . The tips of the legs  94 ,  96 ,  98  and  100  are rounded, which conforms to the shape of the cable. The inner edges  102  are also rounded to create a curved pocket  104 . FIG. 7 illustrates a shield  106  and a filler  108  with curved tips  110  that conform with certain cable design requirements. Since the shield  106  is flexible, it is possible to form it into the desired shape. FIG. 8 illustrates a shield  112  and a filler  114  that is formed so that pockets  116  and  118  have an interior angle  120  smaller than pockets  122  and  124 . This filler design is used in cables having an oval or rectangular cross-section.  
         [0023]    Referring to FIG. 9, there is shown a cable  40 , having as its core our elongated channel filler  126  with first pair of diametrically opposed pockets  128  and  130  each containing an unshielded twisted pair cable  42 , and second pair of pockets  132  and  134  each also containing an unshielded twisted pair cable  42 . The core  136  which contains our elongated channel filler  126  has an embedded shield  138 , and the cables  42 , in its pockets. The core is surrounded by a jacket  43  which was extruded thereover. The jacket  43  can be any suitable jacket material normally utilized such as foamed on non-foamed polyvinyl chloride, fluorinated polymers, polyethylene, the flame retardant compositions, etc.  
         [0024]    Each unshielded twisted pair cable  42  has a pair of conductors with appropriate insulation  140 . The conductors are generally copper, tinned copper, or any other appropriate conductor. The conductor insulation  140  is a foamed or non-foamed insulation of polyethylene, polypropylene, fluorinated ethylene propylene, tetrafluoroethylene, polyvinyl chloride, etc.  
         [0025]    Referring to FIG. 10, there is shown a channel filler  150  having an embedded shield  152  and a drain wire  45  located in opening  68 . The channel filler has the same shield construction as the shield of FIG. 2. In this embodiment, the drain wire  45  is between double layers of the channel filler shield  152 .  
         [0026]    Generally for a communication cable having four twisted pair cables, all of the same size with or without different lays, uses our shield channel filler. The channel filler has a diameter of about 0.150 inches to about 0.350 inches. The size of the twisted pair cables  42  are generally about 24 AWG to about 22 AWG. For other applications, the channel filler will have as many pockets or pocket legs as needed. For instance, in a four pair cable, the channel filler will have four pocket legs, in a 10 pair cable, the channel filler would have 10 pocket legs. Likewise, the embedded shield would have 4 and 10 shield legs respectively.  
         [0027]    The shields may be any suitable shield such as an aluminum or copper tape, BELDFOIL, DUOFOIL, or any suitable metal tape. The shield which uses a polymer base can have aluminum or copper on one of both sides of the polymer base. The thickness of the metal on the shield is about 0.0003 to 0.001 inches.  
         [0028]    Referring to FIG. 11, there is shown a channel filler  142  having an embedded shield  144  and a drain wire or strengthening member  45 . The channel filler has the same shield construction as the shield of FIG. 3. In this embodiment, the drain wire is between the double layers of the channel filler shield.  
         [0029]    The drain wire, is generally made with tinned copper, tinned aluminum, etc. the strength member is generally made from polyethylene.  
         [0030]    It will, of course, be appreciated that the embodiments which have just been described have been given by way of illustration, and the invention is not limited to the precise embodiments described herein. Various changes and modifications may be effected by one skilled in the art at without departing from the scope or spirit of the invention as defined in the appended claims.