Abstract:
A cable is provided containing one or o polymeric elements for reduction of crosstalk. The cable includes a plurality of unshielded twisted pairs, each of which is an insulated conductor pair twisted around one another, each having a different lay length. A jacket encloses the plurality of unshielded twisted pairs, where an unshielded twisted pair, has the longest lay length among the plurality of unshielded twisted pairs is positioned within the center of the jacket such that an axis of the twisted pairs that has the longest lay length substantially coincides with the central longitudinal axis of the cable. A plurality of bumper elements are disposed within the jacket in the interstices between said plurality of unshielded twisted pairs, where the bumper elements are profiled polymer structures.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to the field of cables. More particularly, the present invention relates to filler components used in communication cables. 
         [0003]    2. Description of Related Art 
         [0004]    Communication cables are broadly grouped into two arrangements, fiber optic cables and metal conductor cables, each of which has their own unique set of construction parameters that affect the quality of the communication signals carried therethrough. 
         [0005]    Regarding metal conductor cables, one typical arrangement is the LAN (Local Area Network) cable that is usually constructed of four pairs of twisted insulated copper conductors encased within a jacket. Other larger cables may employ more pairs of conductors. 
         [0006]    In this typical four pair LAN cable construction, in addition to protecting against external environmental interferences, in order to decrease cross talk between signals passing through one pair, and signals passing through adjacent pairs within the same LAN cable, the pairs of conductors are twisted. Moreover, as the signal interference between pairs is highest when conductors of adjacent pairs He parallel to one another, pairs are twisted around one another at different rates (i.e. at different lay lengths) to minimize the instances of parallel conductors in adjacent pairs. Other items such as tapes, fillers, or cross fillers may be added to even further reduce the amount of cross talk between pairs within the cable. 
         [0007]    For example, in prior art arrangements where four twisted pairs are included in one jacket it is common to use four different lay lengths, one for each of the four twisted pairs. These varied rates of twisting result in a reduced number of incidences where the wires in the pairs run parallel to one another, effecting a reduction in crosstalk. For example, in a typical four pair cable, arranged in a compact square/rectangle, there are six different crosstalk combinations that need to be addressed, as shown in prior art  FIG. 1  (labeled C 1 -C 6 ). 
         [0008]    It is typically known that the shorter the lay length of a particular pair in a multi-pair cable, the more crosstalk is reduced. However, shorter lay lengths obviously use more wire per length of cable, and thus there are limitations on how short the lay length can be in any given copper wire twisted pair. Therefore, it is ideal to have the longest lay length possible that meets the desired crosstalk threshold. 
         [0009]    One prior art manner for addressing such cross talk issues is to isolate the longest lay length pair in a four pair LAN cable, making it equidistant to the other three pairs in the same cable and as far as possible from other pairs in adjacent LAN cables. For example, as shown in U.S. Pat. No. 7,550,674, a plurality of unshielded twisted pairs are provided, each of which has a different lay length. The jacket encloses the plurality of unshielded twisted pairs, and the unshielded twisted pair that has the longest lay length among the plurality of unshielded twisted pairs positioned within the center of the jacket, substantially along the central longitudinal axis of the cable. See prior art  FIG. 2 . 
         [0010]    To maintain such geometry and its advantageous electrical characteristics, bumper elements are disposed around the central pair in between the outside pairs. The bumper elements are typically polymers formed as solid, foamed or hollow structures, however, alternative materials and structures may be used. These bumpers are advantageously of a dimension substantially equal to the diameter of a twisted pair, and are used for maintaining a regular geometry along the length of cable as shown in  FIG. 2 . 
         [0011]    However, the necessity of the bumpers to maintain the pair geometry in the cable necessarily leads to the drawback of using additional components in the cable, which is always a disadvantage in cable construction owing to added size, weight, cost and fuel load (fuel load affects the flame and smoke performance of cable constructions in flame tests). 
         [0012]    Another problem with these bumpers is that their proximity to the pairs that they separate disturbs the signal&#39;s electromagnetic field and reduces the effectiveness of the transmission signal through the pair owing to the detrimental dielectric properties of the polymers from which they are constructed. Although foaming the polymers used to make these bumpers is a possible solution and in theory could yield improved electrical performance, foaming is generally a non-preferred option owing to its added processing/extrusion difficulties versus solid profile extrusion. 
       OBJECTS AND SUMMARY 
       [0013]    The present arrangement overcomes certain drawbacks with the prior art by providing a low cost and effective bumper for maintaining proper spacing geometry of the twisted pairs within a communications/LAN cable without requiring the use of foamed polymers. 
         [0014]    Such improved bumpers are profiled so as to maintain a sufficient cross sectional diameter at any point along the length of the cable, while simultaneously significantly reducing polymer consumption making use of a profiled shape. Moreover, the profiled shapes of the bumpers include significant airspace reducing the overall negative dielectric effects on the signals in the pairs adjacent the bumpers. 
         [0015]    To this end the present arrangement is directed to a cable containing one or more polymeric elements for reduction of crosstalk. The cable includes a plurality of unshielded twisted pairs, each of which is an insulated conductor pair twisted around one another, each having a different lay length. A jacket encloses the plurality of unshielded twisted pairs, where an unshielded twisted pair, having the longest lay length among the plurality of unshielded twisted pairs is positioned within the center of the jacket such that an axis of the twisted pairs has the longest lay length substantially coincides with the central longitudinal axis of the cable. 
         [0016]    A plurality of bumper elements are disposed within the jacket in the interstices between said plurality of unshielded twisted pairs, where the bumper elements are profiled polymer structures. 
         [0017]    In another arrangement, a cable containing one or more polymeric elements for reduction of crosstalk is provided having a plurality of unshielded twisted pairs, each of which is an insulated conductor pair twisted around one another, the plurality of unshielded twisted pairs having different lay lengths. 
         [0018]    A central spacing element is provided around which the unshielded twisted pairs are arranged. One or more peripheral spacing elements are arranged within the unshielded twisted pairs to maintain the spacing of the unshielded twisted pairs. 
         [0019]    A jacket is provided enclosing the plurality of unshielded twisted pairs and central and peripheral spacing elements, where the spacing elements are profiled polymer structures. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]    The present invention can be best understood through the following description and accompanying drawings, wherein: 
           [0021]      FIGS. 1-2  show prior art LAN cable constructions; 
           [0022]      FIG. 3  shows the basic components of the communications cable according to one embodiment using the prior art geometry/arrangement as a model; 
           [0023]      FIG. 4A  shows a profiled bumper for the communications cable according to one embodiment; 
           [0024]      FIG. 4B  shows a profiled bumper for the communications cable according to the prior art; 
           [0025]      FIG. 5  shows the communications cable with the bumper of  FIG. 4A  according to one embodiment; 
           [0026]      FIGS. 6A and 6B  show a finned bumper for the communications cable according to one embodiment; 
           [0027]      FIG. 7  shows the communications cable with the bumper of  FIGS. 6A and 6B  according to one embodiment; 
           [0028]      FIGS. 8A and 8B  show a finned bumper for the communications cable according to one embodiment; 
           [0029]      FIG. 9  shows the communications cable with the bumper of  FIGS. 8A and 8B  according to one embodiment; 
           [0030]      FIGS. 10A and 10B  show a finned bumper for the communications cable according to one embodiment; 
           [0031]      FIG. 11  shows the communications cable with the bumper of  FIGS. 10A and 10B  according to one embodiment; 
           [0032]      FIG. 12  shows a shaped bumper for the communications cable according to one embodiment; 
           [0033]      FIG. 13  shows the communications cable with the bumper of  FIG. 12  according to one embodiment; 
           [0034]      FIG. 14  shows a shaped bumper for the communications cable according to one embodiment; 
           [0035]      FIG. 15  shows the communications cable with the bumper of  FIG. 14  according to one embodiment; 
           [0036]      FIG. 16  shows an exemplary prior art twenty five (25) pair cable; and 
           [0037]      FIG. 17  shows a communications cable with a profiled bumper according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0038]    In one embodiment of the present invention, shown using prior art  FIG. 3  as an exemplary structural model, a cable  10  is provided having four twisted pairs  12   a - 12   d  of unshielded copper wire within an outer extruded jacket  14 . 
         [0039]    For the purposes of illustrating the salient features of the present invention cable  10  is shown to have four twisted pairs  12 . However, the invention is not limited in this respect. The present invention may also be applied to cables having larger or smaller counts of twisted pairs  12  as desired. 
         [0040]    Twisted pairs  12   a - 12   d  are described as copper, but any desired conductive metal may be substituted as desired. Furthermore, the copper in pairs  12  are coated with typical polymer coatings, such as PE (Polyethylene) or FEP (Fluoronated Ethylene Polymer) or other insulators based on the desired cost and fire safety standards. Jacket  14  is also an extruded polymer as well, formed from PVC (Poly Vinyl Chloride) or FRPVC (Flame Resistant PVC), or other such polymer compositions. 
         [0041]    As with standard four pair cables each of twisted pairs  12   a - 12   d  has a different rate of rotational twisting resulting in different lay lengths. In the present illustration, twisted pair  12   a  is presumed to have the shortest lay length and pair  12   d  has the longest lay length. For example a typical cable  10  may employ lay lengths in the ranges of 0.3″ to 0.55″ (0.3″, 0.325″, 0.35″ and 0.55″). Obviously, these lay lengths for pairs  12  are by way of illustration only, with the invention being equally applicable to any desired lay lengths depending on the desired crosstalk tolerance and desired mechanical (weight etc. . . . ) specifications. 
         [0042]    As shown in  FIG. 3 , pairs  12   a - 12   d  are arranged in a three spoked wheel arrangement with pair  12   d,  having the longest lay length, being centrally located substantially along the center longitudinal axis of cable  10 . The three pairs  12   a - 12   c  having the shorter lay lengths are disposed apart from one another, outwards towards the inside diameter of jacket  14 . Ideally, pairs  12   a - 12   c  are disposed substantially 120° apart. 
         [0043]    In one embodiment of the present invention, bumper elements  16  are disposed around central pair  12   d  and in between pairs  12   a,    12   b  and  12   c  respectively. As described in full detail below bumper elements  16  are typically polymers formed using specialized shapes to simultaneously maintain the geometry of pairs  12   a - 12   d  while reducing the amount of polymer used and maximizing the amount of open space/air to reduce any dielectric interference in the signals in pairs  12   a - 12   d.    
         [0044]    A reduction of polymer content can be achieved by the introduction of contoured/shaped bumpers  16  as described in more detail below. The shapes for contoured bumpers  16  can differ, but, regardless of the shape, should retain its structural integrity against crushing, bending, puffing, and normal abuse of cable  10 . In General, the polymer materials used for bumpers  16  may be selected from, but are not limited to high temperature materials such as FEP, PTFE, PFA, ETFE, etc. and low temperature materials such as PVC, FRPVC, PE, FRPE, PP, FRPP, LSZH compounds, etc. . . . 
         [0045]    Turning to details of the present invention, replacing the prior art bumpers shown in  FIG. 3 , a profiled shape for bumper  16  is shown in  FIG. 4A , where a profiled bumper  16  is provided, with a comparison to prior art bumpers such as that shown in  FIG. 4B . As shown in  FIG. 4B , the normal bumper of prior art (4 pair LAN cable such as that in  FIG. 2 ) may have an ID (Inner Diameter) of 0.035″ and an OD (Outer Diameter of 0.070″).  FIG. 4A  shows the present bumper  16  with eight (8) grooves  20 , but otherwise having the same ID and OD. 
         [0046]    In  FIG. 4A , the exemplary bumper  16  is formed as a hollow structure having eight (8) grooves  20  disposed substantially equally around the outer circumference, with  FIG. 4A  giving the dimensions of grooves  20 . 
         [0047]    As shown in  FIG. 4A , the exemplary groove  20  width is 0.004″, where the wall depth is 0.0175″ and the groove  20  depth is 0.0125.″ The groove to wall ratio is 0.71 with a substantially 20% reduction in surface area. 
         [0048]    Given the size and shapes of grooves  20  as disclosed in  FIG. 4A , the following table expresses the weight reduction advantages of the arrangement in  FIG. 4A  relative to the prior art arrangement of  FIG. 4B , Table 1 also shows the weight reduction that can be achieved with certain modifications to bumper  16  by adding 1-3 additional grooves  20  beyond the eight (8) grooves shown in  FIG. 4A . 
       Weight Reduction Examples 
       [0049]      
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Reduction in 
               
               
                   
                   
                 gms/1″  
                 weight 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Round (standard - prior art) 
                 0.04502828 
                   
               
               
                   
                 Profile Fillers 
                   
                   
               
               
                   
                 8 Groove Outside 
                 0.03874255 
                 13.96% 
               
               
                   
                 9 Groove Outside 
                 0.03795683 
                 15.70% 
               
               
                   
                 10 Groove Outside 
                 0.03717112 
                 17.45% 
               
               
                   
                 11 Groove Outside 
                 0.0363854 
                 19.19% 
               
               
                   
                 8 Groove Inside and Outside 
                 0.03405532 
                 24.37% 
               
               
                   
                   
               
             
          
         
       
     
         [0050]      FIG. 5  shows cable  10  using three bumpers  16  as defined in  FIG. 4A . As shown in  FIG. 5 , a helical twist may be applied to bumpers  16  which may have either a constant or varied lay length along the length of bumper  16  and may be either helical (left or right handed) or SZ (periodic reversals). 
         [0051]    In another embodiment, as shown in  FIGS. 6A and 63 , instead of a round bumper  16  with profiles/grooves  20 , a “fin” bumper  30  may be used in cable  10  to create a similar effect.  FIGS. 6A and 6B  illustrate one exemplary design having a two (2) fin shaped bumper  30 . The two (2) fins are defined “two” splines extending from a center point (although such a bumper  30  appears to be a single helically would strip. However, for consistency, as outlined below, additional three (3) and four (4) spline designs for bumper  30  are within the contemplation of the present arrangement. The selection of one of such designs over the other may be based on, among other things, the desired material selection, required crush resistance, required electrical properties, etc. . . . and other such cable  10  construction requirements. 
         [0052]    Returning to the two (2) fin design, in  FIG. 6A , the exemplary bumper  30  is formed as a 0.015 polymer strip (with each end extending from the center being defined as one of the “fins”) having a width of 0.070″ as with the prior described bumper  16 . In the example shown, the helical twist rate is 0.250″ (per full rotation), but it is understood that other forms and rates of twisting may be used.  FIG. 6B  illustrates shows bumper  30  from  FIG. 6A  in profile. 
         [0053]      FIG. 7  shows cable  10  using three bumpers  30  as defined in  FIG. 6A . 
         [0054]    In another embodiment, as shown in  FIGS. 8A and 8B , instead of a round bumper  16  with profiles/grooves  20 , another fin bumper  32  may be used in cable  10  to create a similar effect.  FIGS. 8A and 8B  illustrate a three (3) fin shaped bumper  32 . In  FIG. 8A , the exemplary bumper  32  is formed as a 0.012″ three finned polymer strip (with each of the three fins extending from the center) having an overall circumference of width of 0.070″ as with the prior described bumper  16 . In the example shown, the helical twist rate is 0.250″ (per full rotation), but it is understood that other forms and rates of twisting may be used.  FIG. 8B  shows the exemplary three (3) fin bumper  32  from  FIG. 8A  in profile. 
         [0055]      FIG. 9  show cable  10  using three bumpers  32  as defined in  FIG. 8A . 
         [0056]    In another embodiment, as shown in  FIGS. 10A and 10B , instead of a round bumper  16  with profiles/grooves  20 , another fin bumper  34  may be used in cable  10  to similar effect.  FIGS. 10A and 10B  illustrate a four (4) fin shaped bumper  34 . In  FIG. 10A , the exemplary bumper  34  is formed as a 0.010″ four finned polymer strip (with each of the four fins extending from the center) having an overall circumference of width of 0.070″ as with the prior described bumper  16 . In the example shown, the helical twist rate is 0.250″ (per full rotation), but it is understood that other forms and rates of twisting may be used.  FIG. 10B  illustrates the exemplary four (4) fin bumper  34  from  FIG. 10A  in profile. 
         [0057]      FIG. 11  shows cable  10  using four bumpers  34  as defined in  FIG. 10A . 
         [0058]      FIGS. 12 and 13  illustrate another embodiment which, instead of a round bumper  16  with profiles/grooves  20 , a shaped triangle bumper  36  may be used in cable  10  to create a similar effect. 
         [0059]      FIGS. 14 and 15  illustrate another embodiment which, instead of a round bumper  16  with profiles/grooves  20 , a star shaped bumper  38  may be used in cable  10  to create a similar effect. 
         [0060]    As with the profiled bumper  16  shown in  FIGS. 4A ,  43  and  5 , each of the bumpers  30 ,  32 ,  34 ,  36  and  38  may employ a helical twist which may have either a constant or varied lay length along the length of the bumper(s) that can be either helical (left or right handed) or SZ (periodic reversals). The lay length of bumpers  30 ,  32 ,  34 ,  36  and  38  may employ a helical twist rate of substantially 1.00″ but ranging from 0.010″ to 10.00.″ 
         [0061]    As with the weight reduction advantages discussed above in table 1, the finned and shaped bumpers  30 ,  32 ,  34 ,  36  and  38  ( FIGS. 6 ,  8 ,  10 ,  12  and  14  respectively) also provide weight reduction advantages relative to the prior art arrangement of  FIG. 4B  as shown in the following Table 2. 
       Weight Reduction Examples 
       [0062]      
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Reduction in 
               
               
                   
                   
                 gms/1″ 
                 weight 
               
               
                   
                   
               
             
             
               
                   
                 Round (standard - prior art) 
                 0.04502828 
                   
               
               
                   
                 Shaped Fillers 
                   
                   
               
               
                   
                 2 fin 0.015″ wall with .25″ lay 
                 0.01637222 
                 63.64% 
               
               
                   
                 length 
                   
                   
               
               
                   
                 3 fin 0.012″ wall with .25″ lay 
                 0.01840088 
                 59.13% 
               
               
                   
                 length 
                   
                   
               
               
                   
                 4 fin 0.010″ wall with .25″ lay 
                 0.01520377 
                 66.24% 
               
               
                   
                 length 
                   
                   
               
               
                   
                 Triangle 0.010″ wall with .25″ 
                 0.02026457 
                 55.00% 
               
               
                   
                 lay length 
                   
                   
               
               
                   
                 Star .25″ lay length 
                 0.02545299 
                 43.47% 
               
               
                   
                   
               
             
          
         
       
     
         [0063]    Moreover, as shown in the following Table 3 the finned bumpers  30 ,  32  and  34  ( FIGS. 6 ,  8  and  10 ) additionally provide surface area reduction relative to the prior art arrangement of  FIG. 4B  as shown in the following Table 3. These reductions in surface area relative to the prior art bumpers provide an added advantage in that they reduce the dielectric interference with the signals in the adjacent pairs  12 . 
       Surface Area Reduction Examples 
       [0064]      
         [0000]    
       
         
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 1″ Long 
                   
               
               
                   
                   
                 Surface Area 
                 Reduction in 
               
               
                   
                   
                 (in {circumflex over ( )}2) 
                 Surface Area 
               
               
                   
                   
               
             
             
               
                   
                 Standard Round Filler 
                 0.21991149 
                   
               
               
                   
                 0.070″ OD 
                   
                   
               
               
                   
                 2 Fin Sprial with 0.25″ 
                 0.03017138 
                 86.28% 
               
               
                   
                 Lay Length 
                   
                   
               
               
                   
                 3 Fin Sprial with 0.25″ 
                 0.03613513 
                 83.57% 
               
               
                   
                 Lay Length 
                   
                   
               
               
                   
                 4 Fin Sprial with 0.25″ 
                 0.03007738 
                 86.32% 
               
               
                   
                 Lay Length 
               
               
                   
                   
               
             
          
         
       
     
         [0065]    It is noted that in the examples shown in  FIGS. 4-15 , each of cables  10  have the basic four (4) pairs  12  in typical LAN cables. However, as noted above, there is no restriction on using the bumpers  16  (or  30 - 38 ) in other twisted pair type LAN cables for similar geometric/shape retention. 
         [0066]    For example,  FIG. 16  shows an exemplary prior art twenty five (25) pair cable  100  which, among other components (pairs 12), includes a central spacing element  102  and peripheral spacers  104  that are used for maintaining the desired position of pairs  12  within the larger space enclosed by jacket  14  of cable  100 . 
         [0067]    In one embodiment shown in exemplary  FIG. 17 , the same cable  100  may utilizes the bumpers  16  (and/or  30 - 38 ) as described above. For example, in  FIG. 17 . For example, spacing element  102  and peripheral spacers  104 , rather than being solid fillers, employ profiled bumpers  102 ,  104  (or shaped helical twisted fillers—not shown), conferring the same advantages outlined above, including reduction in weight material and dielectric interferences. It is understood that this larger twenty five (25) pair  12  LAN cable  100  is likewise a non-limiting example and that such profiled/shaped bumper elements  102  and  104  can equally be applied to small, midsized and even larger (25+) pair LAN cables as desired. 
         [0068]    While only certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes or equivalents now occur to those skilled in the art. It is therefore, to be understood that this application is intended to cover all such modifications and changes that fall within the true spirit of the invention.