Patent Publication Number: US-2011048767-A1

Title: Twisted Pairs Cable with Tape Arrangement

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/275,380, filed Aug. 27, 2009, which application is hereby incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to cables for use in the telecommunications industry. More particularly, this disclosure relates to a multi-pair cable for use in the telecommunications industry. 
     BACKGROUND 
     A wide variety of cable arrangements having twisted conductor pairs are utilized in the telecommunications industry. In some cable arrangements, the twisted conductor pairs are separated by one or more filler components. The filler components occupy a volume that adds to the overall diameter of the cable. 
     In other arrangements, the cable includes shielding that surrounds the twisted conductor pairs, and the one or more filler components. Cable shielding is commonly provided in the form of a conductive tape. The conductive tape is wound around the outer diameter of the cable core in an overlapping manner. 
     In general, improvement has been sought with respect to existing cable assemblies, generally to reduce size of twist pair cables, reduce costs associated with twisted pair cables, and improve signal transmission performance of twisted pair cables. 
     SUMMARY 
     The present disclosure relates to a multi-pair cable having a plurality of twisted conductor pairs and a tape arrangement. The tape arrangement includes foamed tape. In one aspect, the foamed tape both provides a dielectric barrier between the twisted conductor pairs and a jacket of the multi-pair cable, and defines at least two separate twisted pair regions in which the twisted conductor pairs lie. 
     A variety of examples of desirable product features or methods are set forth in part in the description that follows, and in part will be apparent from the description, or may be learned by practicing various aspects of the disclosure. The aspects of the disclosure may relate to individual features as well as combinations of features. It is to be understood that both the foregoing general description and the following detailed description are explanatory only, and are not restrictive of the claimed invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, cross-sectional view of a first multi-pair cable, shown with a first tape arrangement, according to the principles of the present disclosure; 
         FIG. 2  is cross-sectional view of a foamed tape piece, according to the principles of the present disclosure; 
         FIG. 3  is a schematic, cross-sectional view of a second multi-pair cable, shown with a second tape arrangement, according to the principles of the present disclosure; and 
         FIG. 4  is a schematic, cross-sectional view of a third multi-pair cable, shown with a third tape arrangement, according to the principles of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to various features of the present disclosure that are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 1  schematically illustrates a multi-pair cable  10  including one embodiment of a tape arrangement  12  that is an example of how inventive aspects of the present disclosure may be practiced. Preferred features of the cable  10  and tape arrangement  12  include the reduction of electrical coupling characteristics and improvement of signal transmission performance. 
     Referring to  FIG. 1 , in general, the multi-pair cable  10  includes a plurality of twisted conductor pairs  14 . Each of the twisted conductor pairs  14  includes two insulated conductors  16  twisted about one another along a longitudinal axis of the pair. The plurality of twisted conductor pairs generally defines a central cable core  18  of the cable  10 . A jacket  20  surrounds the plurality of twisted conductor pairs  14  or central cable core  18 . 
     In the illustrated embodiment, the jacket  20  is channeled to reduce material costs and/or provide a desired dielectric characteristic. In particular, internal channels  22  are formed on an inside diameter of the jacket  20 . The channels  22  improve upon the dielectric characteristics of the jacket by providing a location for air to reside. The channels  22  also reduce the amount of material utilized in manufacturing the cable, and accordingly reduce the cost of the cable. The reduced amount of jacket material further correspondingly reduces the amount or propagation of flames and smoke, thereby enhancing the flame retardant quality of the cable  10 . In one embodiment, the jacket  20  is made of a non-conductive material such as polyvinyl chloride (PVC), for example. Other types of non-conductive materials can also be used for the jacket, including other plastic materials such as fluoropolymers (e.g. ethylenechlorotrifluorothylene (ECTF) and flurothylenepropylene (FEP)), polyethylene, or other electrically insulating materials. In an alternative embodiment, the jacket can have a non-channeled construction. 
     While the cable  10  of  FIG. 1  is illustrated with a first embodiment of the tape arrangement (e.g.,  12 ), it is to be understood that the above general description of the cable  10  also applies to the cables having other tape arrangements described in detail hereinafter. 
     Still referring to  FIG. 1 , the tape arrangement  12  includes foamed tape  24 . The foamed tape  24  is generally planar (see  FIG. 2 ) but has a flexible construction. The foamed tape  24  completely surrounds the circumference of the cable core  18  such that the foamed tape  24  is located between the jacket  20  and each twisted pair  14 . The foamed tape  24  provides a dielectric barrier between the twisted pairs  14  and the jacket  20  to aid in reducing cross-talk between cables. 
     In one embodiment, the foamed tape  24  is a flurothylenepropylene tape. In another embodiment, the foamed tape  24  is a polypropylene tape. In still another embodiment, the foamed tape  24  is a polyethylene tape. In some embodiments, the foamed tape  24  has a dielectric constant of about 1.7. Other electrically insulating materials can also be used. Referring to  FIG. 2 , the foamed tape  24  has a thickness T of about 0.005 inches to 0.010 inches. The air content of the foamed tape  24  generally ranges between about 15% and 35%; in one embodiment, the air content is about 25%. The tape arrangement  12  is preferably a non-conductive tape arrangement. In particular, no portion of the tape arrangement  12 , i.e., the foamed tape  24 , is conductive. The foamed tape  24  has instead the same uniform foam construction throughout the cross-section of the foamed tape. 
     In addition to providing a dielectric barrier between the twisted pairs and the jacket, the foamed tape  24  wraps around the twisted pairs  14  so as to define at least two separate twisted pair regions in which the twisted pairs lie. Separating or spacing apart the twisted pairs aids in reducing cross-talk between twisted pairs. 
     The tape arrangement  12  in  FIG. 1  includes only the single piece of foamed tape  24 . The single piece of foamed tape  24  has a width W ( FIG. 2 ) extending from a first end  30  to a second end  32 . The width W of the foamed tape  24  wraps around the twisted pairs in an S-shaped configuration. In  FIG. 1 , the S-shaped configuration of the single piece of foamed tape  24  separates a first set  26  of two twisted pairs from a second set of two twisted pairs. The width W of the foamed tape in  FIG. 1  is between about 0.625 inches and 0.875 inches. 
     Each of the twisted conductor pairs  14  has a lay length, that is, a twist rate at which the two insulated conductors of the pair are twisted about one another. The plurality of twisted pairs  14  includes twisted pairs having longer lay lengths and twisted pairs having shorter lay length. For example, first and second twisted pairs  14  can have a longer lay length, and third and fourth twisted pairs  14  can have a shorter lay length. The longer and shorter lay lengths of the twisted pairs range between about 0.3 and 0.4 twists per inch. In one embodiment, the foamed tape  24  is arranged such that the first set  26  of two twisted pairs  14  includes one longer lay length twisted pair and one shorter lay length twisted pair, and the second set  28  of two twisted pairs also includes one longer lay length twisted pair and one shorter lay length twisted pair. 
     Referring now to  FIG. 3 , a second embodiment of a tape arrangement  112  is illustrated. In this embodiment the tape arrangement includes two pieces of foamed tape  124  that completely surround the cable core  18  and that define at least two separate twisted pair regions in which the twisted pairs  14  lie. 
     Similar to the previous embodiment, the two pieces of foamed tape  124  are each generally planar, and are flexible in construction. The pieces of foamed tape  124  each have a width that wraps around two twisted pairs  14  in an S-shaped configuration. The foamed tapes  124  wrap around the twisted pairs  14  to separate or divide the twisted pairs. 
     More specifically and referring to  FIGS. 3 and 4 , the two pieces of foamed tape  124  define four twisted pair regions that separate each twisted pair  14  from the other twisted pairs. In  FIG. 3 , the width of each foamed tape  124  is provided so as to completely surround the cable core  18  and completely surround two of the twisted pairs  14 ; in  FIG. 4 , the width of each foamed tape  124  is provided so as to completely surround the cable core  18  and completely surround all four of the twisted pairs  14 . The width of each foamed tape  124  in  FIGS. 3 and 4  is between about 0.375 inches and 0.625 inches. 
     The presently disclosed foamed tape arrangements provide for separation of the twisted pairs while reducing the overall diameter of the cable in comparison to conventional fillers. The reduced overall diameter is accomplished in part by the low profile (e.g., flatness) of the flexible foamed tape. In addition to providing separation, the flexible foamed tape also surrounds the cable core to function as a dielectric barrier having a significantly lower dielectric constant than that of conventional conductive shielding tape. 
     The above specification provides a complete description of the present invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, certain aspects of the invention reside in the claims hereinafter appended.