Abstract:
A cable has a marking located at least partly within the cable. A method of manufacturing the cable includes a step of providing at least one marking at least partly within the cable.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority under 35 U.S.C. §119 to GB Patent Application No. 1208322.6, filed on May 11, 2012, entitled “Cable and Method of Manufacturing a Cable”, the content of which is incorporated by reference herein in its entirety. 
       BACKGROUND 
       [0002]    The present invention relates to a cable and a method of manufacturing a cable. 
         [0003]    The theft of cables, such as electrical cables, presents an increasing problem, fuelled by high demand for metal worldwide. Cables present an easy target for thieves, as it is often impractical to maintain vigilance over them, for example where the cables are located in geographically remote or covered areas, or simply because of the length of the cabling involved e.g. in a railway network. 
         [0004]    As a result, it is not uncommon for cables to be stolen, with the metal which they contain being extracted from the cabling and sold on to third parties. Such thefts present a number of problems, which can extend well beyond the direct economic loss to the owner of the cable. For example, where the cable in question is used to supply an electrical current e.g. to a railway network or to homes, parties other than the owner e.g. railway commuters, homeowners etc. are affected and will experience inconvenience and possible knock-on economic losses of their own before the cabling is replaced and the relevant power supply system restored to normal. 
         [0005]    It would be possible to mark the exterior of a cable to indicate ownership, in an attempt to dissuade theft, for example using commercially-available spray-on DNA-type markings sprayed onto the exterior of a cable. However, a thief need only strip the exterior sheath of a cable to readily remove the markings, and thus seek to avoid prosecution if caught with the stripped cable, as establishing ownership of the cable may then be rendered impossible. 
       SUMMARY 
       [0006]    Aspects of the invention are defined in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: 
           [0008]      FIG. 1  shows a first embodiment of a cable according to an aspect of the present invention; 
           [0009]      FIG. 2  is an enlarged view of a detail of the embodiment of  FIG. 1 ; 
           [0010]      FIGS. 3   a  and  3   b  show an identifier according to the first embodiment; 
           [0011]      FIG. 4  is a flow chart showing a method of manufacture of a cable according to an embodiment of an aspect of the present invention; 
           [0012]      FIG. 5  is a flow chart showing a step in the manufacture method of  FIG. 4  in greater detail; 
           [0013]      FIG. 6  shows a second embodiment of a cable according to an aspect of the present invention; 
           [0014]      FIG. 7  is a flow chart showing a method of manufacture of a cable according to another embodiment of an aspect of the present invention; and 
           [0015]      FIG. 8  is a flow chart showing a step in the manufacture method of  FIG. 7  in greater detail. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]      FIG. 1  shows a first embodiment of a cable  1  according to an aspect of the present invention. The cable  1  of the present embodiment is a low voltage electrical cable, intended to carry a current at a voltage of approximately 1000V, and which may for example be employed as a power or auxiliary control cable for use in applications such as in power networks, underground, outdoor and indoor applications and for use in cable ducting. 
         [0017]    The cable  1  of the present embodiment comprises a sheath  2 , armouring  3 , bedding  4 , insulation (shown generally at  5 ) and a conductor (shown generally at  6 ). 
         [0018]    In the present embodiment, the sheath  2  is formed from a suitable material such as a plastics material or elastomer, for example by extrusion. In the present embodiment, the sheath  2  is formed from Polyvinyl Chloride (“PVC”) and bears an exterior marking  2 A, which is described in further detail hereinafter. The sheath encloses the remaining components of the cable  2  (i.e. the armouring  3 , bedding  4 , insulation  5  and conductor  6  in the present embodiment) and provides mechanical and environmental protection to the cable  1 , as well as holding the remaining components of the cable  1  together. 
         [0019]    The armouring  3  is provided to protect the cable from mechanical damage as a result of external stresses being applied, either during or after installation of the cable  1 . The armouring  3  of the present embodiment comprises steel wire armour (“SWA”) formed from a plurality of individual steel wires, although other suitable braids or wrappings of metal (e.g. aluminium), or suitable non-metallic material, may be used in accordance with the intended use of the cable  1 . 
         [0020]    The bedding  4  acts to protect the core of the cable from mechanical stress; in the present embodiment, the bedding  4  is formed from PVC although other materials suitable for this purpose may be employed. 
         [0021]    The conductor  6  is provided to carry the electric current for the cable  1  and is, in the present embodiment, provided as a plurality of stranded conductors in the form of three copper wires  7 , each comprising a plurality of copper strands twisted together to form the wires  7 . However, any suitable type and material of conductor may be used; for example, aluminium may be used as the material for the conductor  6  of the cable  1  and the conductor  6  may be provided in forms other than a plurality of stranded conductors. 
         [0022]    The insulation  5  of the cable  1  is provided to electrically insulate the conductor  6 . In the present embodiment the insulation  5  is provided in the form of three insulating sleeves  8 , each being fitted over a respective one of the wires  7 . The insulating sleeves  8  may be formed of any suitable insulating material, which in the present embodiment is Cross-Linked Polyethylene (“XPLE”). 
         [0023]      FIG. 2  is an enlarged view of a detail of  FIG. 1 , from which it may be seen that a plurality of identifiers  9  are present on the wires  7 ; in the present embodiment, these identifiers  9  are adhered to the metal conductor  6 , as described in greater detail hereinafter. 
         [0024]    Identifiers suitable for the present embodiment are manufactured by DataDot Technology Ltd. of New South Wales, Australia. It is however emphasised that the identifiers  9  of the present embodiment are merely exemplary and that other forms of identifier may be used according to the present invention. In another embodiment, for example, the identifiers can instead be provided as chemical or biological identifiers. For example, the identifiers can be made of elements which when combined in specific proportions make the compound unique. 
         [0025]    For ease of illustration, the identifiers  9  are only shown on the exposed sections of the wires  7 , but it will be understood that these identifiers  9  are present along the entire length of the wires  7  and in particular are present on the sections of the wires  7  enclosed within the sheath  2  of the cable  1 . 
         [0026]      FIGS. 3   a  and  3   b  show one of these identifiers  9  in greater detail; in the present embodiment, the remaining identifiers  9  are substantially identical to that shown in  FIGS. 3   a  and  3   b  and accordingly only one of these identifiers  9  will now be described. 
         [0027]    The identifier  9  shown in  FIGS. 3   a  and  3   b  takes the form of a discrete plate-like element  10 , of which the front side is shown in  FIG. 3   a  and the reverse is shown in  FIG. 3   b.    
         [0028]    In the present embodiment, both the front and rear sides of the discrete plate-like element  10  bear respective indicia  11   a,    11   b.  However, according to further embodiments, identical indicia may be provided on both the front and rear sides of the discrete plate-like elements  10 , or on only a single side of the discrete plate-like elements  10 , as desired. 
         [0029]    As shown in  FIG. 3   a , the indicia  1  la on the front side of the discrete plate-like element  10  comprises a unique identification code in the form of a ten-character alphanumeric string. This unique identification code  11  corresponds to an entry on a secure database, and accordingly allows the cable  1  on which the identifier  9  is provided to be identified using information stored on that secure database, which may for example comprise details such as the owner and/or manufacturer of the cable  1 , installation location of the cable  1  (e.g. GPS position), date of installation of the cable  1  and the like. 
         [0030]    As shown in  FIG. 3   b , the indicia  11   b  on the reverse side of the discrete plate-like element  10  directly indicates the registered owner of the cable  1 . 
         [0031]    The discrete plate-like element  10  is preferably of a size visible to the naked eye and may for example be between 0.3 mm and 0.5 mm across. In the present embodiment, the discrete plate-like elements  10  are formed from a metallic material, such as nickel, which can withstand the manufacturing process for the cable  1  described in greater detail below. 
         [0032]    The indicia  11   a,    11   b  may be provided in any suitable fashion. For example, the indicia may be etched, by laser or otherwise, into the material of the discrete plate-like elements  10 , may be provided as a hologram or multiple holograms on the discrete plate-like elements  10 , or by any other suitable means. 
         [0033]    In the present embodiment, each of the identifiers  9  on a given cable  1  are substantially identical and in particular bear the same indicia  11   a,    11   b.  Thus, inspection of any one of the plurality of identifiers  9  of the cable  1  will permit the cable  1  to be identified, for example by reference to the owner, manufacturer etc., as described above. Thus, any thief wanting to be sure of avoiding detection would need to remove all of the identifiers  9  from the cable. 
         [0034]    It will however be appreciated that any such removal is greatly hindered according to the present embodiment. 
         [0035]    In particular, the identifiers  9  are provided within the construction of the cable  1  itself, rather than simply on the exterior of the cable. Thus, simply treating the exterior of the cable  1  in some way will not remove the identifiers  9 , which are instead located within the cable  1  itself. Similarly, simply stripping the sheath  2  will not result in the identifiers  9  being removed. 
         [0036]    Rather, it would be necessary to fully strip the cable down to its metal content i.e. the metal conductor  6  before an attempt could even be made at removing the identifiers  9 . 
         [0037]    A significant theft deterrent is thereby provided, as any thief seeking to steal the cable  1  would need to either fully strip the cable  1  down to the conductor  6 , and then take action to remove the many identifiers  9 , at the installation location of the cable itself, or alternatively would need to risk detection in moving the cable to another location to perform this process, but with the identifiers  9  still present. As will be appreciated, either option would render theft of the cable  1  greatly undesirable to a thief, as compared to theft of a cable having only exterior markings. 
         [0038]    What is more, as the identifiers  9  are applied to the (valuable and hence desirable) metal content of the cable  1  itself, specifically, to the metal conductor  6  in the present embodiment, separating the identifiers from the cable  1  and its desirable metal content cannot be performed easily, and thus provides a further deterrent to theft of the cable  1 . 
         [0039]    In the present embodiment, the marking  2 A on the sheath  2  draws attention to the fact that the metal content of the cable  1  is marked by identifiers  9  in accordance with the present embodiment, to deter theft of the cable  1 . 
         [0040]    A method of manufacturing the cable  1  according to the above embodiment of the present invention will now be described with reference to  FIG. 4 . 
         [0041]    In a first step  401  of the manufacturing process, the conductor  6  is formed by twisting copper strands together to form the copper wires  7 . 
         [0042]    In a second step  402 , the identifiers  9  are applied to the conductor  6 . 
         [0043]    In a third step  403 , the conductor  6  is provided with the insulation  5 , for example by extrusion. 
         [0044]    In a fourth step  404 , the insulated conductor  6  is located within the bedding  4 . 
         [0045]    In a fifth step  405 , the armouring  3  is provided around the bedding  4 . 
         [0046]    In a sixth step  406 , the conductor  6 , insulator  5 , bedding  4  and armouring  3  are enclosed within the sheath  2 . 
         [0047]    In a seventh step  407 , the sheath  2  is provided with the exterior marking  2 A to communicate the presence of the theft deterrent to third parties. 
         [0048]    It will be noted that, according to the present embodiment, the conductor  6  is marked with the identifiers  9  before the conductor  6  is enclosed within the sheath  2 . As a result, the identifiers  9  are located within the sheath  2 , and are not merely provided externally. This internal provision of the identifiers  9  greatly provides a significant theft deterrent, as described above. 
         [0049]    The step  402  of applying the identifiers to the conductor  6  will now be described in further detail in conjunction with  FIG. 5 . 
         [0050]    In step  501 , the identifiers  9  are mixed with a carrier medium with adhesive properties. 
         [0051]    In step  502 , the carrier medium containing the identifiers  9  is applied to the metal conductor  6 , which in the case of the present embodiment comprises the three wires  7 , such that the identifiers  9  are adhered to the metal conductor  6 . 
         [0052]    A second embodiment of a cable according to an aspect of the present invention will now be described with reference to  FIG. 6 . 
         [0053]    The cable  12  of the present embodiment is a medium voltage electrical cable, rated to carry a current at a nominal voltage of approximately 33 kV, and which may for example be employed to distribute three phase alternating current electrical power supplies at nominal system voltages of 33 kV to traction substations on D.C. electrified lines. 
         [0054]    The cable  12  of the present embodiment comprises a sheath  13 , a separator  14 , a screen (shown generally at  15 ), bedding tape  16 , an insulation screen  17 , insulation  18 , a conductor screen  19  and a conductor  20 . 
         [0055]    In the present embodiment, the sheath  13  is formed from graphite coated Medium Density Polyethylene (MDPE) and bears an exterior marking  13 A. The sheath  13  encloses the remaining components of the cable  12  (i.e. the separator  14 , screen  15 , bedding tape  16 , insulation screen  17 , insulation  18 , conductor screen  19  and conductor  20  in the present embodiment) and provides mechanical and environmental protection to the cable  12 , as well as holding the remaining components of the cable  12  together. 
         [0056]    The separator  14  of the present embodiment is provided in the form of water swellable tape. 
         [0057]    The screen  15  is a conducting layer of the cable  12  which has the function of providing an earth fault path. In the present embodiment, the screen is provided as a copper wire screen  15 A helically wound with equalising copper tape  15 B. A plurality of identifiers  21 , which are described in greater detail hereinafter, are present along the length of the screen  15  (although, for convenience, they are only illustrated on the exposed parts of the screen  15  in the Figure). In particular, a plurality of identifiers  21  are provided along both the copper wire screen  15 A and the copper tape  15 , in particular on portions thereof to be enclosed within the sheath  13 . 
         [0058]    The bedding tape  16  provides a smooth transition to the underlying layer, and in the present embodiment is provided as water swellable semi-conducting tape. 
         [0059]    The insulation screen  17  of the present embodiment is provided as solidly bonded, extruded semi-conducting Cross-Linked Polyethylene. 
         [0060]    The insulation  18  of the present embodiment is provided as a layer of suitable electrically insulating material e.g. Cross-Linked Polyethylene. 
         [0061]    The conductor screen  19  of the present embodiment is provided as solidly bonded, extruded semi-conducting Cross-Linked Polyethylene. 
         [0062]    The conductor  20  of the present embodiment is provided to carry the electric current for the cable  12  and is, in the present embodiment, provided as a compact circular stranded plain copper conductor. However, any suitable type and material of conductor may be used; for example, a circular solid aluminium conductor maybe be used as the conductor  20 . 
         [0063]    Except that the indicia  11   a,    11   b  of the identifiers  21  will relate to the cable  12  of the present embodiment, the identifiers  21  are of exactly the same form as the identifiers  9  of the first embodiment, and accordingly the identifiers  21  are not described further here. Similarly, the sheath  13  of the present embodiment is marked at  13 A in the same way as the sheath  2  of the first embodiment is marked at  2 A, to communicate the theft deterrent of the cables to third parties, in particular by referring to the presence of the indicators  21  contained within the construction of the cable  12 . 
         [0064]    As will be appreciated, the present embodiment thus enjoys similar theft-deterrent benefits as the first embodiment. In particular, in the present embodiment, each of the identifiers  21  located within the cable  12  are substantially identical and in particular bear the same indicia  11   a,    11   b.  Thus, inspection of any one of the plurality of identifiers  21  of the cable  12  will permit the cable  12  to be identified, for example by reference to the owner, manufacturer etc., as described above. Thus, any thief wanting to be sure of avoiding detection would need to remove all of the many identifiers  21  from the cable  12 . 
         [0065]    It will however be appreciated that any such removal is greatly hindered according to the present embodiment. 
         [0066]    In particular, the identifiers  21  are provided within the construction of the cable  12  itself, rather than simply on the exterior of the cable  12 . Thus, simply treating the exterior of the cable  12  in some way will not remove the identifiers  21 , which are instead located within the cable  12  itself. Similarly, simply stripping the sheath  13  will not result in the identifiers  21  being removed. 
         [0067]    Rather, it would be necessary to strip the cable  12  down to access the metal content presented by the screen  15  before an attempt could even be made at removing the identifiers  21 . 
         [0068]    A significant theft deterrent is thereby provided, as any thief seeking to steal the cable  12  would need to expend significant time in stripping the cable  12  to access the screen  15 , and then take action to remove the many identifiers  21 , at the installation location of the cable itself before removing the metal content presented by the screen  15 , or alternatively would need to risk detection in moving the cable  12  to another location to perform this process, but with the identifiers  21  still present. As will be appreciated, either option would render theft of the cable  12  greatly undesirable to a thief, as compared to theft of a cable having only exterior markings. 
         [0069]    What is more, as the identifiers  21  are applied to (valuable and hence desirable) metal content of the cable  12  itself, specifically the metal presented by the copper screen  15 , separating the identifiers  21  from the cable  12  and this desirable metal content of the cable  12  cannot be performed easily (it would be almost impossible for the thieves to ensure that all of the indicia have been removed) and thus provides a further deterrent to theft of the cable  12 . 
         [0070]    In the present embodiment, identifiers  21  are not provided on the metal conductor  20 . This is primarily for safety considerations, as in the present embodiment the identifiers  21  comprise plate-like elements  10  and are preferably metallic, e.g. of nickel, as described above in conjunction with the first embodiment. As the cable  12  of the present embodiment is intended to carry current at a higher voltage than the cable  1  of the first embodiment, the identifiers  21  are not provided on the metal conductor  20  as if any of the plate-like elements  10  comprising the identifiers  21  were to be affixed to the metal conductor  20  standing proud from the surface of the conductor  20 , damage to the remainder of the cable  12  could occur given the magnitude of voltage carried, possibly causing the cable  12  to fail. 
         [0071]    However, if a different type of identifier  21  were used, which did not present such safety concerns, it is conceivable that the identifiers  21  could also be applied to the conductor  20 , in addition to the screen  15 . 
         [0072]    Further, it will be appreciated that the present invention is widely applicable to allow any desired component, e.g. any component formed from or containing metal, metal alloy or any other valuable material, of a cable to be provided with indicia e.g. by means of identifiers such as the identifiers  9 ,  21 . 
         [0073]    A method of manufacturing the cable  12  according to the above-described second embodiment of the present invention will now be described with reference to  FIG. 7 . 
         [0074]    In a first step  701  of the manufacturing process, the conductor  20  is formed by twisting copper strands together to form the copper wire. 
         [0075]    In a second step  702 , the conductor  20  is located within the conductor screen  19 . 
         [0076]    In a third step  703 , the conductor  20  and conductor screen  19  are located within the insulation  18 . 
         [0077]    In a fourth step  704 , the insulation screen  17  is provided over the insulation  18 . 
         [0078]    In a fifth step  705 , the bedding tape  16  is provided over the insulation screen  17 . 
         [0079]    In a sixth step  706 , the screen  15  is provided over the bedding tape  16 . 
         [0080]    In a seventh step  707 , the identifiers  21  are applied to the metal screen  15 . 
         [0081]    In an eighth step  708 , the separator  14  is applied over the screen  15 . 
         [0082]    In a ninth step  709 , the conductor  20 , conductor screen  19 , insulation  18 , insulation screen  17 , bedding tape  16 , screen  15  and separator  14  are enclosed within the sheath  13 . 
         [0083]    In a tenth step  710 , the sheath  13  is provided with the exterior marking  13 A to communicate the presence of the theft deterrent to third parties. 
         [0084]    In an eleventh step  711 , a graphite coating is applied to the sheath  13 . 
         [0085]    It will be noted that, according to the present embodiment, the metal screen  15  is marked with the identifiers  21  before the metal screen  15  is enclosed within the sheath  13 . As a result, the identifiers  21  are located within the sheath  13 , and are not merely provided externally of the cable. This internal provision of the identifiers  21  provides a significant theft deterrent, as described above. 
         [0086]    The step  707  of applying the identifiers  21  to the screen  15  will now be described in further detail in conjunction with  FIG. 8 . 
         [0087]    In step  801 , the identifiers  21  are mixed with a carrier medium with adhesive properties. 
         [0088]    In step  802 , the carrier medium containing the identifiers  21  is applied to the metal screen  15 , which in the case of the present embodiment comprises the copper wire screen  15 A and copper tape  15 B, such that the identifiers  21  are adhered to the metal screen  15 . 
         [0089]    According to embodiments, the present invention may be applied to many other types of cable, for example to signalling cable, telecommunications cable and the like, as well as power cables. 
         [0090]    It will be understood that embodiments of the present invention are described herein by way of example only, and that various changes and modifications may be made without departing from the scope of the invention. In particular it is emphasised that the types of cable of the first and second embodiments described above have been selected for exemplary illustration purposes only, and that the present invention is by no means limited to the specific types of cable described above.