Abstract:
A cable jacket that comprises first and second jacket layers each formed of a jacket material. At least one shielding tape is embedded between the first and second jacket layers. The shielding tape is formed of a substrate material and the substrate material has at least one conductive segment.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a jacket for a cable that includes an embedded shield and the method for making the jacket. More specifically, the jacket includes a shield that is a shielding tape with discontinuous conductive shielding segments. The shielding tape is embedded with the jacket by co-extruding the shielding tape with the jacket. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional communications cables typically include a core of twisted pairs of insulated conductors that are enclosed in a protective jacket. To avoid crosstalk with other cables, often referred to as alien crosstalk, conventional cables often include at least one shielding layer disposed around the core of twisted pairs of conductors. A non-conductive barrier layer between the shielding layer and the pairs must also be provided to insulate the core of pairs of the cable. 
         [0003]    Such cables, however, are often bulky because of the requirement of both a shielding layer and a barrier layer. Therefore, a need exists for a cable that protects against alien crosstalk and that is not bulky. 
       SUMMARY OF THE INVENTION 
       [0004]    Accordingly, the present invention may provide a cable jacket that comprises first and second jacket layers each formed of a jacket material. At least one shielding tape may be embedded between the first and second jacket layers. The shielding tape is formed of a substrate material and the substrate material has at least one conductive segment. In a preferred embodiment, the substrate material and the jacket material are the same, although different materials may be utilized. In another embodiment, the substrate material includes a plurality of conductive segments disposed in a spaced discontinuous arrangement. In yet another embodiment, a plurality of shielding tapes are embedded between the first and second jacket layers. 
         [0005]    The present invention may also provide a cable that comprises at least one twisted pair of insulated conductors and a jacket that encloses the twisted pair of insulated conductors. The jacket is formed of a jacket material. A shielding tape may be embedded in the jacket. The shielding tape is formed of a substrate material that has at least one conductive segment. The cable does not include a barrier layer. 
         [0006]    The present invention may further provide a cable assembly that comprises a plurality of cables that are bundled together. Each of the plurality of cables includes at least one twisted pair of insulated conductors, a jacket enclosing the at least one twisted pair of insulated conductors where the jacket is formed of a jacket material, and at least one shielding tape embedded in the jacket. The at least one shielding tape is formed of a substrate material and the substrate material has at least one conductive segment, whereby the cable does not include a barrier layer enclosed by the jacket. 
         [0007]    The present invention may also provide a method for making a cable jacket that comprises the steps of providing at least one shielding tape that has a substrate formed of a substrate material where the substrate includes at least one conductive segment; inserting the at least one shielding tape between first and second jacket layers of the cable jacket and each of the layers is formed of a jacket material; and co-extruding the shielding tape with the first and second jacket layers, wherein the substrate material of the shielding tape and the jacket material of the first and second jacket layers are the same such that during the co-extrusion step, the substrate and the first and second jacket layers bond together. 
         [0008]    Other objects, advantages and salient features of the invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses a preferred embodiment of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
           [0010]      FIG. 1  is a cross-sectional view of a cable having a jacket according to an exemplary embodiment of the invention, showing the jacket with a plurality of shields embedded therein; 
           [0011]      FIG. 2  is a plan view of a shield of the cable jacket illustrated in  FIG. 1 , showing the shield as a tape with a plurality of conductive segments; and 
           [0012]      FIG. 3  is a cross-sectional view of a cable assembly according to an embodiment of the invention, showing a plurality of the cables bundled together. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring to  FIGS. 1 and 2 , a jacket  100  for a cable C, such as a communications cable, according to an exemplary embodiment of the present invention minimizes noise coming from external cable sources, i.e. alien crosstalk, without the need for grounding the cable C. The jacket  100  of the present invention accomplishes the above by combining at least one discontinuous shield  200  with the jacket material. 
         [0014]    As seen in  FIG. 1 , the cable C includes the jacket  100 , one or more twisted pairs of insulated conductors  102 , and an optional separator  104  disposed between the pairs  102  to isolate the same. The jacket  100  includes inner and outer layers  110  and  120  that, when combined with one or more of the shields  200 , form a single jacket. Preferably, the inner and outer layers  110  and  120  are extruded with the shields  200 , such that the layers and shields melt together to form the jacket. Alternatively, the layers  110  and  120  and the shields  200  may be bonded to one another by any known method, such as adhesive and the like. The inner and outer layers  110  and  120  may be formed of any known jacket material for communication cabling, such as PVC, HDPE, FEP, flame retardant PE, or the like. Because the one or more shields  200  are incorporated in the jacket  100 , a separate shielding layer surrounding the conductor pairs  102  is not required. Also, the inner layer  110  acts as a barrier between the one or more shields  200 , thereby eliminating the need for a separate barrier layer. The overall diameter of the cable is reduced because less jacket material is required for the jacket  100  and both the shielding and barrier layers have been eliminated. 
         [0015]    The shield  200  may be a shielding layer or tape made up of a substrate  202 , as seen in  FIG. 2 , that is preferably of the same type and chemical nature of the material of the jacket  100 . For example, if the material of the jacket  100  is PVC, then the substrate of the shielding tape is also PVC. That allows the jacketing material to properly bond with the substrate material of the shielding tape  200  to form the single jacket  100 . 
         [0016]    The shielding tape  200  may include a plurality of conductive segments  204 , such as aluminum, copper, ferrite, or any other conductive bricks. The segments  204  may be applied to the surface of the substrate  202  by adhesive, heat pressing, laser ablation, vapor deposition, or by spraying conductive particles onto the substrate  202  to form the segments. Alternatively, the conductive segments  204  can be sandwiched between two layers of the substrate  200 . The conductive segments  204  are preferably spaced from each other, thereby forming a discontinuous shield, as seen in  FIG. 2 . Although the conductive segments  204  are shown as having a substantially rectangular shape, the segments  204  may have other shapes, such as square, trapezoidal, diamond, and the like. Additionally, the segments  204  may all be substantially the same size or may have various sizes. The conductive segments  204  may also be placed in a random pattern along the substrate. 
         [0017]    According to an exemplary method of the present invention, one or more of the shielding tapes  200  is inserted into the jacket  100  during the jacket extrusion process. Specifically, the shielding tape  200  is pulled through the actual die/crosshead or tooling for the jacket  100  in between the inner and outer layers  110  and  120  of the jacket. Thus, one or more shielding tapes  200  may be sandwiched by the inner and outer jacket layers  110  and  120 . During that co-extrusion process, the material of the jacket layers  110  and  120  is in a molten or near molten state. When the shielding tape or tapes  200  come into contact with the molten jacket material, bonding/melting of the shielding tape or tapes occurs within the jacket material. Alternatively, the two jacket layers may be preformed materials (not in a molten state) that are bonded together. 
         [0018]    Preferably, the material of the jacket  100  and its layers  110  and  120  are the same as the substrate  202  of the shielding tapes  200 , so that the materials readily mix and bond to each other. This creates a near seamless dispersing of the shielding tape  200  within the jacket  100 . Alternatively, the jacket layers  110  and  120  may be formed of a different material than the substrate  202  of the shielding tapes  200 . In that case, the jacket layers  110  and  120  may be bonded to the substrates  202  of the shielding tapes by any know method, such as adhesive bonding, high pressure, or the like. On the other hand, the outer jacket layer  120  may suffice as a barrier to hold the shielding tape  200  and the inner jacket layer  110  in place. 
         [0019]    During the co-extrusion process, the conductive segments  204  are encased in the jacket  100  while also maintaining the original orientation of the segments on the shielding tape  200 . That orientation of the segments insures consistent electrical properties of the cable, such as return loss and attenuation. Thus, the method of the present invention allows conductive shielding segments  204  to be inserted into the jacket  100  without negatively impacting the physical properties of the jacket, such as tensile strength and elongation. That is because the near continuous material of jacket  100  (incorporated with one or more shielding tapes  200 ) maintains its original tensile strength as well as elongation properties. 
         [0020]    Referring to  FIG. 3 , a plurality of the cables C may be bundled together. An optional outer jacket  300  may be provided that encloses the bundle cables C. Each cable C includes the jacket  100 , as described above. 
         [0021]    While particular embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.