Abstract:
An electrical cable comprises a cable core comprising at least one electrical conductor, at least one polymeric inner layer enclosing the cable core, and at least one polymeric outer layer enclosing the cable core and the inner layer to form the electrical cable, the outer layer operable to maintain integrity of the cable within a predetermined temperature range.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is entitled to the benefit of, and claims priority to, provisional patent application U.S. 60/933,932 filed Jun. 8, 2007, the entire disclosure of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to cables and, in particular, to an enhanced electrical cable. 
       SUMMARY OF THE INVENTION 
       [0003]    An embodiment of a cable comprises a cable core comprising at least one electrical conductor, at least one polymeric inner layer enclosing the cable core; and at least one polymeric outer layer enclosing the cable core and the inner layer to form the electrical cable, the outer layer operable to maintain integrity of the cable within a predetermined temperature range. Alternatively, the predetermined temperature range is from about −60° Celsius to about 80° Celsius. Alternatively, the outer layer comprises one of polyamide, thermoplastic polyurethane, thermoplastic vulcanizate, a hard grade thermoplastic elastomer, ethylene chlorotrifluoroethylene, ethylene-tetrafluoroethylene copolymer, and combinations thereof. Alternatively, the inner layer comprises one of polyolefin, fluoropolymer, thermoplastic elastomer, thermoplastic vulcanizate and combinations thereof. Alternatively, the electrical conductor comprises a plurality of conductors helically wound about a central electrical conductor. Alternatively, the electrical cable further comprises at least one shield layer disposed adjacent at least one of the cable core, the inner layer, and the outer layer. The shield layer may comprise one of interlocking metallic tape and metallic mesh tape. 
         [0004]    Alternatively, the cable further comprises an intermediate tie layer disposed between the inner layer and the outer layer and operable to bind with both the inner layer and the outer layer. The intermediate tie layer may comprise one of modified polyethylene, modified fluoropolymer, modified polypropylene, modified ethylene-propylene copolymer, modified poly(4-methyl-1-pentene), modified thermoplastic vulcanizate, modified thermoplastic elastomer, modified ethylene-tetrafluoroethylene copolymer, modified ethylene fluorinated ethylene-propylene, modified polychlorotrifluoroethylene, modified ethylene chlorotrifluoroethylene, expanded-Polytetrafluoroethylene (ePTFE) and combinations thereof. 
         [0005]    In another embodiment, an electrical cable assembly comprises a cable core comprising at least one filler rod, a plurality of conductors arranged about the filler rod to form the cable core, the conductors having internal interstices therebetween filled by the filler rod, each of the conductors comprising a conductor core comprising at least one electrical conductor, at least one polymeric inner layer enclosing the conductor core, and at least one polymeric outer layer enclosing the conductor core and the inner layer to form the conductor, the outer layer operable to maintain integrity of the conductor within a predetermined temperature range, wherein the cable core is enclosed by a filler layer of elastomeric material that fills external interstices between the conductors to form the fiber optic cable assembly. 
         [0006]    Alternatively, the conductors forming the cable core comprise one of a triad configuration, a quad configuration, and a hepta configuration. Alternatively, the cable assembly further comprises a jacket layer enclosing the filler layer and the cable core. A plurality of strength members may be embedded in the jacket layer. Alternatively, the cable assembly further comprises at least one layer of strength members disposed within the outer layer. At least one of the strength members may be formed from Kevlar material and may be oriented at a zero lay angle with respect to the cable core. Alternatively, the cable assembly further comprises at least one shield layer enclosing the filler layer. Alternatively, the filler rod is formed from one of a soft polymeric material, a hard TPE coated rod, and a hard TPE coated rod yarn. 
         [0007]    In another embodiment, a method for forming a cable comprises providing at least one filler rod, cabling a plurality of conductors about the filler rod to form a cable core, the filler rod filling internal interstices between the conductors, wherein each of the conductors comprise a conductor core comprising at least one electrical conductor, at least one polymeric inner layer enclosing the conductor core, and at least one polymeric outer layer enclosing the conductor core and the inner layer to form the conductor, the outer layer operable to maintain integrity of the conductor within a predetermined temperature range, and enclosing the cable core with a filler layer of elastomeric material that fills external interstices between the conductors to form the fiber optic cable assembly. 
         [0008]    Alternatively, the method further comprises enclosing the cable core and filler layer in a jacket layer. Alternatively, the method further comprises disposing at least one strength member in the jacket layer. Alternatively, the method further comprises heating the filler rod to assist in cabling the conductors about the filler rod. Alternatively, the filler rod and the filler layer are extruded. Alternatively, the method further comprises disposing at least one shield layer adjacent at least one of the cable core, the inner layer, and the outer layer. 
         [0009]    Embodiments of cables and cable assemblies may be advantageously utilized as land seismic cables and/or may be utilized alone or in combination to create land seismic cables with some or all of the following characteristics lower cost, easy manufacturing, water blocking capabilities, the ability to perform well at arctic and tropical temperatures, and minimize damage from animal biting. The potential for bonding between all materials in the cable core significantly increases the cable&#39;s resistance to water infiltration. The conductor insulation&#39;s three-layered bonded design is also easily potted to various potting compounds 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein: 
           [0011]      FIG. 1  is a radial cross-sectional view of an embodiment of a cable; 
           [0012]      FIGS. 2   a - 2   c  are radial cross-sectional views, respectively, of steps for forming a cable assembly; 
           [0013]      FIGS. 3   a - 3   f  are radial cross-sectional views, respectively, of alternate steps for forming a cable assembly; 
           [0014]      FIGS. 4   a - 4   c  are radial cross-sectional views, respectively, of embodiments of a cable assembly; 
           [0015]      FIGS. 5   a  and  5   b  are an end view and plan view, respectively, of an extruder for forming a cable; 
           [0016]      FIGS. 6   a  and  6   c  are axial and radial cross-sectional views, respectively, of a shield layer and cable including a shield layer of an embodiment of a cable and  FIG. 6   b  is a side view of a shield layer; 
           [0017]      FIG. 7   a  is a side view and  FIG. 7   b  is a radial cross-sectional view of an embodiment of a shield layer and cable including a shield layer; and 
           [0018]      FIG. 8  is a side view of an embodiment of a cable having a shield layer. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring now to  FIG. 1 , there is shown an embodiment of a cable, indicated generally at  100 . The cable  100  includes a cable core  102  comprising a plurality of electrical conductors  104  (only one indicated). The electrical conductors  104  preferably comprise a plurality of conductors cabled helically around a central conductor  105 . Preferably, the electrical conductors  106  are formed from a copper material or similarly electrically conductive material. 
         [0020]    An inner layer  108  formed from a polymer material, for example, encases the electrical conductors  104  of the cable core  102 . An outer layer  110  formed from a polymer material, for example, encases the inner layer  108  and an optional tie layer  112  is disposed between the inner layer  108  and the outer layer  110 . 
         [0021]    The inner layer  108  may comprise a polyolefin (such as polyethylene (PE), ethylene-propylene copolymer (EPC), Poly(4-methyl-1-pentene) (TPX), or another suitable polyolefin) that provides good electrical insulation properties. The inner layer  108  may comprise a fluoropolymer (such as ETFE [Tefzel®] or ECTFE [Halar®]). The inner layer  108  may also comprise a thermoplastic elastomer (TPE) or thermoplastic vulcanizate (TPV), such as, but not limited to, Santoprene™, Engage™, Elexar™ or Infuse™. 
         [0022]    The outer layer  110  may comprise polyamide (Nylon) or thermoplastic polyurethane (TPU) or other suitable polymer. The outer layer  110  may comprise a hard grade thermoplastic elastomer (TPE) or thermoplastic vulcanizate (TPV), such as, but not limited to, Santoprene™ Engage™, Elexar™ or Infuse™. The outer layer  110  may comprise ethylene chlorotrifluoroethylene (ECTFE) such as Halar™, ethylene-tetrafluoroethylene copolymer (ETFE) such as Tefzel™, or any other suitable TPE, TPV or thermoset rubber. The outer layer  110  preferably comprises a material that is durable, flexible, can bond to the tie layer  112  (discussed in more detail below), can bond to TPE interstitial filler materials, TPV interstitial filler materials or potting materials, and perform well by maintaining its material properties and thus the integrity of the cable in temperatures ranging from about −60° Celsius to about 150° Celsius or from about −60° Celsius to about 80° Celsius or from about −20° Celsius to about 80° Celsius, thereby allowing electrical power to be transmitted through the cable  100 . 
         [0023]    The tie layer  112  may comprise the same polymer used in the inner layer  108  modified with maleic anhydride, acrylic acid, or another suitable material. The tie layer  112  facilitates bonding of the inner layer(s)  108  and the outer layer  110 , thereby creating a continuous bonded insulation system for the cable  100 . The tie layer  112 , may comprise polyethylene (PE) modified with a suitable functional chemical group such as maleic anhydride, acrylic acid, etc., (Bynel® by Dupont, Polybond® by Crompton Corporation etc.). The tie layer  112  may comprise polypropylene (PP) modified with a suitable functional chemical group such as maleic anhydride, acrylic acid, etc., (ADMER® by Mitsui Chemicals, Polybond® by Crompton Corporation etc.). The tie layer  112  may comprise ethylene-propylene copolymer (EPC) modified with a suitable functional chemical group such as maleic anhydride, acrylic acid, etc., (ADMER® by Mitsui Chemicals etc.). The tie layer  112  may comprise poly(4-methyl-1-pentene) (TPX) modified with a suitable functional chemical group maleic anhydride, acrylic acid, etc. (ADMER® by Mitsui Chemicals). The tie layer  112  may comprise maleic-anhydride modified or acrylic-modified TPV (such as Santoprene™) or any other TPE. 
         [0024]    The tie layer  112  may comprise ethylene-tetrafluoroethylene copolymer (ETFE) modified with a suitable functional chemical group maleic anhydride, acrylic acid, etc. (Tefzel® HT 2202 by Dupont, NEOFLON™ ETFE EP-7000 by Daikin), ethylene fluorinated ethylene-propylene (EFEP) terpolymers (NEOFLON™ EFEP by Daikin), polychlorotrifluoroethylene (PCTFE) modified with a suitable functional chemical group (such as, but not limited to, maleic anhydride, acrylic acid), ethylene chlorotrifluoroethylene (ECTFE) modified with a suitable functional chemical group (such as, but not limited to, maleic anhydride, acrylic acid), expanded-Polytetrafluoroethylene (ePTFE) adhered to the inner insulating layer(s)  108 ,  308 ,  408 ,  608 ,  808 ,  1008 , or  1214  (specially manufactured process such as high temperature heat-applied sintering and taping), or any type of modified fluoropolymer that can adhere to the inner layer  108  or the outer layer  110 . Preferably the tie layer  112  bonds to each of the inner layer  108  and the outer layer  110 . 
         [0025]    The electrical conductors  106  are preferably in communication with, for example, a source of electrical power (not shown) and an electrical tool or device (not shown) and are operable to transmit electrical power between the electrical power source and the electrical tool or device. 
         [0026]    Referring now to  FIG. 2   a - 2   c , there is shown a method for manufacturing a cable assembly or core  200 . The cable assembly  200  includes a soft elastomer-coated filler yarn or rod  202  that is preferably extruded as shown in  FIG. 2   a . At least one and preferably a plurality of cables or conductors  204  such as, but not limited to, the cable  100  shown in  FIG. 1  are cabled helically around the rod  202  as shown in  FIG. 2   b . As the conductors  204  compress against the rod  202 , the elastomeric material of the rod  202  deforms to fill any interstitial voids between the rod  202  and the conductors  204 . An additional filler layer of an elastomeric material  206  is extruded over the rod  202  and the conductors  204  to complete the cable assembly  200 , as shown in  FIG. 2   c.    
         [0027]    Referring now to  FIG. 3   a - 3   e , there is shown a method for manufacturing a cable assembly or core  300 . The cable assembly  300  includes a solid polymer rod  302  ( FIG. 3   a ) or hard TPE coated rod or yarn  303  ( FIG. 3   d ) is provided as shown in  FIG. 3   a  and  FIG. 3   d . The rod or yarn  302  or  303  is then heated to soften the polymer. At least one and preferably a plurality of cables or conductors  304  such as, but not limited to, the cable  100  shown in  FIG. 1  are cabled helically around the rod  302  as shown in  FIGS. 3   b  and  3   e . As the conductors  304  compress against the rod  302 , the elastomer of the rod  302  deforms to fill any interstitial voids between the rod  302  and the conductors  304 . An additional filler layer of preferably soft elastomeric material  306  such as, but not limited to a TPE or TPV material, is extruded over the rod  302  and the conductors  304  to fill any outer interstitial voids and complete the cable assembly  300 , as shown in  FIGS. 3   c  and  3   f . The cable assembly  200  or  300  is advantageously completely filled and requires no liquid rubber fillers. The elastomeric material  206  or  306  may be a TPE or TPV material such as, but not limited to, Santoprene™, Engage™, or Infuse™. To further minimize the potential for water flow along the conductors  204  or  304 , the insulated conductors  204  or  304  and extruded elastomeric void filler  206  or  306  may be chemically bonded and/or physically compressed together during cabling or in the extruder. 
         [0028]    Those skilled in the art will appreciate that the cable assemblies  200  or  300  may be formed from any number of cables and any combination of cables or conductors including, but not limited to, the cable  100 . The cable assemblies  200  or  300  may be assembled utilizing three cables or conductors  100  to form a triad cable assembly  200  or  300 . The cable assemblies  200  or  300  may be assembled utilizing four cables or conductors  100  to form a quad cable assembly  200  or  300 . The cable assemblies  200  or  300  may be assembled utilizing seven cables or conductors  100  to form a hepta cable assembly  200  or  300 . 
         [0029]    Referring now to  FIG. 4   a - 4   c , the cable assemblies, such as the cable assemblies  200  or  300  shown in  FIGS. 2 and 3  may then be encased in an outer layer  400  formed from a polymeric material. The outer layer  400  may include a plurality of strength members  402  embedded therein. The strength members  402  may be formed from any suitable material including, but not limited to, steel wire, high carbon steel, Kevlar, Vectran yarn or the like. The strength members  402  may be oriented at a zero lay angle with respect to the cable core or cable assemblies  200  or  300  or the strength members  402  may be cabled helically about the cable core or cable assemblies  200  or  300 . The strength members  402 , when constructed from Kevlar or Vectran yarn, may be formed from a single yarn or from a plurality of yarns twisted together to form the strength member  402 . 
         [0030]    As shown in  FIG. 4   a , a cable assembly  408  includes seven cables or conductors  100  arranged in a hepta configuration and enclosed by the outer layer  400  and an outer shell  410  and including strength members  402  embedded in the outer layer  400 . 
         [0031]    As shown in  FIG. 4   b , a cable assembly  408  includes four cables or conductors  100  arranged in a quad configuration about a hard TPE coated rod or yarn  303  and enclosed by the outer layer  400  and an outer shell  410  and including strength members  402  embedded therein. The assembly  418  includes four smaller diameter cables or conductors  100  arranged in the interstices of the larger diameter cables or conductors  100 . 
         [0032]    As shown in  FIG. 4   c , a cable assembly  412  includes four cables or conductors  100  arranged in a quad configuration about a hard TPE coated rod or yarn  303  and enclosed by the outer layer  400  and an outer shell  414  and including strength members  402  embedded in the outer layer  400 . 
         [0033]    The outer layer  400  may be a soft matrix such as TPE or TPV and the outer shells  406 ,  410 , and  412  may be formed from nylon or any suitable material to provide a tough jacket to prevent damage from field abuse and to provide rigidity to the cable assemblies  404 ,  408 , or  412 . 
         [0034]    Referring now to  FIG. 5   a , there is shown an end view of an extruder  500  that comprises a plurality of apertures  502  for threading strength members, such as the strength members  402 , therethrough to allow for placing the strength members  402  at a zero lay angle with respect to the cable core or cable assembly  200  or  300 .  FIG. 5   b  shows a side cross-sectional view of the extruder  500  with a cable  504  passing therethrough and including an inner layer  506  and an outer layer or jacket  508  being extruded over the strength members  402  and inner layer  506 . 
         [0035]    Referring now to  FIGS. 6   a - 8 , the cable, such as the cable  100  include a shield or armor layer between the inner layer and outer layer of the cable  100 . As shown in  FIG. 6   a - 6   c , the shield layer may comprise an interlocking metallic tape  600  disposed between an inner layer  602  and an outer layer or jacket  604  of a cable assembly  606 . The tape  600  may include holes  601  extending therethrough to allow the outer jacket  604  to bond with the inner layer  602 . As shown in  FIGS. 7   a - 7   b , the shield layer may comprise an interlocking metallic tape  700  disposed between an inner layer  702  and an outer layer or jacket  704  of a cable assembly  706 . The metallic tape  700  may be folded over to form a locked edge  708 , as shown in  FIG. 7   b . As shown in  FIG. 8 , the shield layer may comprise an overlapping or cigarette-wrapped metallic tape  800  disposed between an inner layer  802  and an outer layer or jacket  804  of a cable assembly  806 . Placement of the shield layer  600 ,  700 , or  800  between the core  602 ,  702 , or  802  and the jacket  604 ,  704 , or  804  may be preferable because its smaller diameter will requires less material for the shield layer  600 ,  700 , or  800 , resulting in a lower weight cable than if the shield layer  600 ,  700 , or  800  is placed over the outer jacket  604 ,  704 , or  804 . 
         [0036]    The preceding description has been presented with reference to presently preferred embodiments of the invention. Persons skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structures and methods of operation can be practiced without meaningfully departing from the principle, and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.