Patent Publication Number: US-11393610-B2

Title: Ethernet cable cross-filler with notches

Description:
BACKGROUND 
     Field of the Invention 
     This invention relates to LAN cables. More particularly, the present invention relates to an improved cross filler construction for separating the pairs within a LAN cable. 
     Description of Related Art 
     LAN (Local Area Network) cables are common communication cables that are typically constructed of eight copper conductor wires in the form of four twisted pairs within a jacket. Owing to increases in signal throughput the electrical and communication performance of such cables is under an ever-increasing demand. There are several ways to improve the electrical performance of such cables including varied pair placement, shielding and other techniques. 
     One such component typically added to LAN cables is a cross filler which is a cross shaped extruded polymer that physically separates the four pairs within the jacket from one another. The purpose of the cross filler is to reduce the internal cross talk between the pairs within the cable by simply keeping a physical distance barrier between the pairs along the length of the cable. Prior art  FIG. 1  shows a basic cross filler in a LAN cable and  FIG. 2  shows the same cross filler in perspective view. 
     Such cross fillers may be used on their own or in combination with other LAN cable materials (i.e. shields) etc. . . . , to eventually meet the desired electrical characteristics. However, apart from such electrical characteristics there is always the concern that the added components will interfere with meeting the required physical requirements of the cable. For example, an exemplary industry standard is TIA 568.2-D that requires a bend radius of 4× cable OD (outside Diameter) for UTP (Unshielded Twisted Pair LAN cables) and 8× cable OD for screened horizontal cable constructions. 
     Another of the most basic of the physical requirements/demands is that the cable and its components are made as small and light as possible, and using the least amount of material in order to reduce costs. Also, bending, flexing, fire/smoke safety standards etc. . . . favor a smaller and simpler construction for LAN cables as added materials increase fuel for fire and otherwise make such LAN cables heavier and more costly. Additionally, stiff cables cause installation problems because they are more likely to get tangled and kinked when being pulled from a box and they are likewise more difficult to pull through conduits. 
     In prior art solutions, to address the issue of flexibility, the use of softer materials may help. Likewise, changing the design parameters such as twist lay length or eliminating or reducing the size of the cross filler can also improve flexibility. However, these solutions have tradeoffs: softer materials may not perform as well in flame tests, may cost more, or may have degraded electrical attributes. Changing the design parameters can also negatively impact the electrical performance of the cable or increase the cost. 
     OBJECTS AND SUMMARY 
     As such, there is a need for an improved cross filler with notches that avoids the problems with the prior art. The present invention thus looks to improve on prior art cross fillers by making them lighter and more flexible than prior art versions, while avoiding tradeoffs associated with prior art cross filler flexibility solutions. Such cables with improved flexibility are more resistant to tangles and snags when being pulled from a box. Additionally, flexible cables allow for an increased packaging density, which leads to smaller box sizes (lower packaging costs, potential for lower shipping costs, less jobsite trash for installer to deal with). 
     In accordance with one embodiment, this is achieved by a cross filler for arrangement within a LAN cable having a plurality of twisted pair conductors. The cross filler has a body and a plurality of radially extending arms from a center point. Each of the arms has a plurality of spaced apart notches cut into the arms, the notches spaced apart along the length of the arms. Each of the notches are dimensioned allowing bending of the LAN cable without physical breakdown of the cross filler. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention can be best understood through the following description and accompanying drawings, wherein: 
         FIG. 1  shows a prior art cross filler for a LAN cable; 
         FIG. 2  shows the prior art cross filler for a LAN cable of  FIG. 1  in perspective view; 
         FIG. 3  illustrates a notched cross filler for a LAN cable, in accordance with one embodiment; 
         FIG. 4  illustrates the notched cross filler for a LAN cable of  FIG. 3  in perspective view, in accordance with one embodiment; 
         FIG. 5  illustrates the notched cross filler for a LAN cable of  FIG. 3  in perspective view and in a bent position, in accordance with one embodiment; and 
         FIG. 6  illustrates the notched cross filler for a LAN Cable of  FIG. 3  within a jacket of the cable and with spaced notches, in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In one embodiment of the present arrangement, as shown in  FIGS. 3 and 4 , the present arrangement includes a LAN cable  10  having four twisted pairs  12   a - 12   d  and a cross filler  20 . Although the present example is shown for a four twisted pair LAN cable, the features of the present cross filler  20  described herein may be equally employed in other cable arrangements requiring internal spacing as well as LAN cables including more or fewer twisted pairs. In one example, cross filler  20  may be constructed by pressure or drawdown extrusion using a shaped die and made from any one of FRPVC (Flame retardant Poly Vinyl Chloride), FRPE (Flame retardant Poly Ethylene), FRPP (Flame retardant Poly Propylene), PE (Poly Ethylene), PP (Poly Propylene), FEP (Fluorinated Ethylene Co-Polymer), PFA (Perfluoroalkoxy alkanes) and other polymers commonly used in the construction of LAN cables. 
     As shown in  FIGS. 3-4 , cross filler  20  includes a central region  21  and four radically extending arms  22 A- 22 D. Each of arms  22  has a given length from the center of filler  20  as well as a plurality of notches  26  or cuts disposed along the longitudinal length of the cable. Standard cross filler designs such as those in  FIGS. 1 and 2  naturally resist being bent or curved because of their geometry. Adding perpendicular notches or cuts  26  to arm  22  of cross filler  10  alleviates this resistance and allows the cables to bend and flex easier as shown in  FIG. 5 . 
     In one embodiment, notches/cuts  26  can be as small as small as a width of zero (0) (in other words just a cut in the arm without removal of material). In another embodiment larger widths for notches/cuts  26  may be used as long as such cuts  26  do not allow twisted pairs  12  to pass through notches  26  and move, even partially, across arm  22  into an area for adjacent pair  12 . As an example, in this embodiment with wider notches/cuts  26  would be less than ½ the lay length of the tightest lay of an adjacent pair  12 . In one example, such notches  26  may be made by a rotary cutting wheel either during the extrusion operation, or during the cabling operation (or wherever cross filler  20  is being pulled into cable  10 . 
     In one embodiment, regarding the depth of cuts/notches  26  into arms  22 , a maximum depth could be set to equal to the dimension of the arm  22  (in other word down to the center point of the cross), as long as it does not go past the center axis. 
     Regarding the longitudinal spacing of cuts  26  along the length of arms  22  of cross filler  20 , such spacing is a function of a desired bend radius of cable  10 . In this case, bend radius refers to the tightest bend radius around which cable  10  can be wound without destroying the cable or resulting in an unacceptable level of attenuation relative to the desired standards of the cable construction. The tighter/smaller the bend radius the closer the spacing of notches  26 . In one embodiment, as shown in  FIG. 6  notches  26  are spaced for at least one (1) notch  26  per quadrant of bend radius, which equates to a maximum notch spacing of 2π×OD (Outside Diameter) for UTP (Unshielded Twisted Pair) or 4π×OD (Outside Diameter) for screened cables. For example, for a UTP cable  10  with an OD of 0.225″, spacing would be at a maximum of 1.41″ between successive notches  26 . 
     In another embodiment, it is noted that a regular periodic notch  26  spacing results in a return loss spike that may modulate and create a crosstalk spike in the signals passing through pairs  12 . As such, in this arrangement, aside from the basic notch spacing advised above, the actual placement is varied slightly, from notch  26  to notch  26  about an average of the calculated distance to avoid precise repetitions. For example, if the calculated spacing is 1.41″ per notch  26 , a first spacing may be 1.40, then a second spacing may be 1.42″ for an average of 1.41″. 
     While only certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes or equivalents will 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.