Related Application

[0001] This application claims the benefit of U.S. Provisional Application No. 61/505,772, filed July 8, 201 1 and entitled Shielding for Cable Components, and U.S.

provisional application no. 61/513,220, filed July 29, 201 1, and entitled Method For Shielding A Substrate.

Field of the Invention

[0002] The present invention provides a shielding for cable components that uses a conductive or semi-conductive coating to reduce or eliminate internal and external cable crosstalk as well as other EMI/RF from sources outside of the cable. The present invention also relates to a method for applying the shielding to a substrate, such as a cable component.

Background of the Invention

[0003] A conventional communication cable typically includes a number of insulated conductors that are twisted together in pairs and surrounded by an outer jacket. Crosstalk or interference often occurs because of electromagnetic coupling between the twisted pairs within the cable or other components in the cable, thereby degrading the cable's electrical performance. Also, as networks become more complex and have a need for higher bandwidth cabling, reduction of cable-to-cable crosstalk (alien crosstalk) becomes increasingly important.

[0004] Shielding layers are often used to reduce crosstalk. Conventional shielding layers for communication cables typically include a continuous solid conductive material, such as aluminum or copper foil bonded to a plastic substrate. The substrate being provided for durability as the foil itself is not suitable for processing in a manufacturing environment. The shielding layer is wrapped around the cable's core of twisted wire pairs to isolate electromagnetic radiation from the core and also protect the core from outside interference. The conductive materials that can be used in this arrangement, however, are limited to those specific conductive foils that can be processed into a foil sheet. Other shielding applications rely on materials that highly absorb and dissipate interference. Shielding formed of such materials, however, is not advantageous in high performance communication cables, because the materials tend to attenuate the signal causing excessive power loss.

[0005] Typically in UTP (unshielded twisted pair) data communication cables, fillers made from dielectric materials are often used to provide physical separation between the pairs, effectively isolating their signals from one another. In UTP cables, the increased NEXT (near end crosstalk) performance required by 10 gigabit Ethernet applications necessitates the use of very large fillers, which in turn increases the size of the overall cable. In addition, the relatively large quantities of dielectric materials used in these large fillers often adversely affect the flame and smoke performance required to meet the plenum and riser ratings required for use in commercial installations.

[0006] Conventional STP (shielded twisted pair) and FTP (foil shielded twisted pairs) type cables often require shielding material to be placed around the individual pairs of conductors. Cable constructions of STP and FTP cables typically include pairs wrapped in foil tapes backed with polyester substrates to shield the pairs. These tapes are often rigid and do not effectively conform to the shape of the pair, thus adding extra radial dimension to the

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i overall cable construction. The polyester backer or substrate material also adversely affects the flame and smoke performance required to meet the plenum and riser ratings needed for use in commercial installations.

[0007] Additionally, it is often advantageous to make the shield discontinuous to avoid the need for grounding. Conventional discontinuous shields, however, are difficult to manufacture and require application of separate segments onto a substrate or laser ablation to cut the shield foils to make the shield discontinuous.

[0008] Therefore, a need exists for a shielding that can be easily applied to any cable component, such as a separator, that improves both electrical and flame/smoke performance, reduces the radial size of the cable, and increases flexibility of the cable. Moreover, a need exists for easily making the shielding discontinuous.

Summary of the Invention

[0009] Accordingly, the present invention provides a shielded cable component and method that comprises a main body that has an outer surface and the main body is formed of a dielectric material and a coating that is applied to the outer surface of the main body where the coating includes a conductive or semi-conductive shielding material. An outer layer is disposed on the coating that completely encapsulates the coating and the main body and the outer layer is formed of a dielectric material. In one exemplary embodiment, the cable component is a crossweb separator. In another exemplary embodiment, the coating is made of graphene.

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[0010] The present invention also provides a cable that comprises a plurality of wire pairs and a separator that is disposed between the pairs. The separator includes a main body that has an outer surface and the main body is formed of a dielectric material. A coating is applied to the outer surface of the main body. The coating includes a conductive or semi- conductive shielding material. An outer layer is disposed on the coating completely encapsulating the coating and the main body. The outer layer is formed of a dielectric material. In one embodiment, the coating is discontinuous.

[OOl1] The present invention further provide a method for applying a shielding to a substrate the comprises the steps of providing a dielectric substrate that has a surface; coating the surface of the substrate with a conductive or semi-conductive shielding layer; and extruding a dielectric outer layer over the shielding layer such that the outer layer completely encapsulates the shielding layer and the substrate.

[0012] The present invention yet further provides a method for applying shielding to a substrate that comprises the steps of providing a substrate having a surface; applying at least one discrete amount of masking solution on the surface of the substrate; coating the surface of the substrate with a conductive or semi-conductive shielding layer such that the at least one discrete amount of masking solution is covered by at least one portion of the shielding layer; and removing the at least one discrete amount of masking solution and the at least one portion of the shielding layer from the substrate to create an electrically discontinuous shield on the surface of the substrate.

[0013] The present invention may also provide a method for applying shielding to a cable component that comprises the steps of providing a dielectric cable component and the

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1 cable component has a surface; applying at least one discrete amount of masking solution on the surface of the cable component; coating the surface of the cable component with a conductive or semi-conductive shielding layer such that the at least one discrete amount of soluble solution is covered by at least one portion of the shielding layer; and removing the at least one discrete amount of masking solution and the at least one portion of the shielding layer to create an electrically discontinuous shield on the surface of the cable component.

[0014] 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.

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1 Brief Description of the Drawings

[0015] 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:

[0016] FIG. 1 is a cross-sectional view of a cable including a cable component with a shielding in accordance with an exemplary embodiment of the present invention;

[0017] FIG. 2 is a perspective view of a cable component according to a first step of the method of applying a shielding in accordance with an exemplary embodiment of the present invention;

[0018] FIG. 3 is a perspective view of a cable component according to a second step of the method of an exemplary embodiment of the present invention; and

[0019] FIG. 4 is a perspective view of a cable component according to a third step of the method of an exemplary embodiment of the present invention;

[0020] FIG. 5 is a perspective view of a cable component according to a fourth step of the method of an exemplary embodiment of the present invention;

[0021] FIG. 6 is a perspective view of a cable component according to a fifth step of the method of an exemplary embodiment of the present invention, showing the cable component with the shielding applied thereto;

[0022] FIG. 7 is a perspective view of a cable component similar to FIG. 6 with a shielding applied thereto according to a second embodiment of the present invention; [0023] FIG. 8 is a perspective view of a cable component according to a third embodiment of the method of the present invention; and

[0024] FIG. 9 is a cross-sectional view of a cable including the cable component of FIG. 8.

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Detailed Description of Exemplary Embodiments

[0025] Referring to FIGS. 1 -9, a cable component 100 of a cable C includes a shielding 120 according to an exemplary embodiment of the present invention. The cable component 100 may be a separator, for example, that isolates one or more pairs of insulated wires 102 in the core of the cable C. The separator may be a cross-web (FIG. 1) or a tube (FIG. 8), for example. By using shielding 120 with the component 100, the size of the component 100 may be reduced, thereby reducing the overall radial size of the cable C, and the flexibility of the cable C is increased. Moreover, the need for a shielding layer wrapped around the core of the cable is eliminated. The shielding 120 is also easily applied to the component 100 and improves both electrical and flame/smoke performance. The shielding 120 is preferably discontinuous to eliminate the need for grounding.

[0026] A method according to an exemplary embodiment of the present invention generally includes the steps of applying a coated shielding layer 122 to a substrate, such as cable component 100, and encapsulating or completely covering the same with an outer layer 130. The outer layer 130 completely encapsulates the cable component 100 and its shielding layer 122 such that there are not openings or gaps in the outer layer 130. More specifically, the method may include the steps of: extruding the substrate or cable component 100 (FIG. 2); applying discrete amounts of a masking solution 1 10 to the substrate (FIG. 3); coating the cable component 100 and masking solution 1 10 with a conductive shielding layer 122 (FIG. 4); removing the discrete amounts of masking solution 1 10 and the portions of the conductive shielding layer 122 in contact with the masking solution (FIG. 5); and extruding the outer layer 130 over the conductive shielding layer 122 to encapsulate the same (FIG. 6). [0027] As seen in FIGS. 1 and 2, the substrate or cable component 100 preferably has a main body 1 12 with an outer surface 114. The main body 112 may be formed of any dielectric material like polyolefins, such as polypropylene or polyethylene, or a

fluoropolymers, such as FEP, ECTFE, MFA, PFA and the like.

[0028] After extruding the cable component 100, discrete amounts of the masking solution 1 10 may be applied to the outer surface 114 of the component 100. The discrete amounts of masking solution 110 are preferably applied as spaced apart concentric circumferential bands around the outer surface 1 14 of the component 100, as seen in FIG. 3. In a preferred embodiment, the component 100 may have a substantially cross-web shape in cross-section and the bands of masking solution 110 conform to the shape of the component's outer surface 1 14. The masking solution 1 10 is preferably a solution that is brittle when dried or poorly adheres to the outer surface 1 14 and therefore is easily removed, such as water based inks for cable band marking, pigment based coatings, UV curable coatings, temporary adhesives and/or a soluble solution, such as masking ink, for example, that is water soluable.

[0029] After application of the discrete amounts of masking solution 1 10, the component outer surface 1 14 and the bands of masking solution 1 10 may be coated with the conductive shielding layer 122 of the shielding 120, as seen in FIG. 4. The bands of masking solution 1 10 prevent the coated shielding layer 122 from adhering to the outer surface 1 14 of the component 100 where the masking solution has been applied. The coating layer 122 may be applied to the outer surface 1 14 in any known matter, such as by spraying, wiping, electrostatic deposition, chemical deposition, vacuum deposition, and the like. The coated shielding layer 122 is preferably formed of a conductive material, such as graphene or graphite. The coated shielding layer 122 may also be formed of a semi-conductive material.

[0030] Alternatively, the shielding layer 120 may be formed by conductive particles suspended in a non-conductive substrate, as disclosed in commonly owned currently pending U.S. Application Serial No. 13/246,183, filed September 27, 201 1 and entitled Shielding for Communication Cables Using Conductive Particles, and commonly owned currently pending U.S. Application Serial No. 13/045,000, filed March 10, 201 1 and entitled Cable Having Insulation With Micro Oxide Particles, the subject matter of each of which is herein incorporated by reference. For example, the conductive particles may be selected from aluminum, copper, iron oxides, silicone dioxide, nickel, zinc, silver, carbon nano fibers, graphene, or graphite, and the substrate may be an ink or adhesive.

[0031] To make the coated shielding layer 122 discontinuous, the circumferential bands of the masking solution 1 10 are removed, thereby taking with it any residual shielding layer 122 or portions of the shielding layer 120 covering the circumferential bands of the masking solution, as seen in FIG. 5. The bands of masking solution 1 10 and the shielding layer portions covering those bands may be removed in several ways, such as by using pressurized air or water to flake off or wash off the masking solution 1 10 and residual shielding layer 122. Alternatively, a solution may be used to dissolve the bands of masking solution 1 10, such that the portions of the shielding layer 122 covering the bands can be removed. By removing the masking solution 1 10 and consequently the conductive material adhered to the masking solution, gaps 550 shaped as spaced circumferential bands in the coated shielding layer 122 are created, thereby defining discrete segments 560 of the 12 045570

shielding layer 122, as seen in FIG. 5. The discrete segments 560 create an electrically discontinuous shield along the length of the cable component 100.

[0032] It is preferable that the segments 560 be sized relative to the lay length of the individual pairs 102 and lay length of the cable's core. This is due to the fact that the segments 560 act as antennas that retransmit electromagnetic energy. Also the gaps 550 are preferably sized to effectively block the range of frequencies most likely to impinge on the shielding 120 to accommodate any cable component design. These gaps 550 in the coating 122 provide another method to tune the shielding characteristics to the specific cable design by spacing them at intervals to avoid interference with the pair and or cable lay lengths. Although it is preferable that the shielding 120 be made discontinuous, the shielding 120 may be made continuous by eliminating the steps of applying and removing the masking solution 1 10 before applying the coating 122.

[0033] To protect the coated shielding layer 122, the outer layer 130 is extruded over the coated shielding layer 122, as seen in FIG. 6, such that the outer layer 130 encapsulates the layer 122 by completely covering the layer 122. Thus, the shielding 120 of the component 100 includes inner and outer layers, the inner coated shielding layer 122 and the outer layer 130. The outer layer 130 is preferably thicker than the shielding layer 122. For example, the shielding layer 122 may have a thickness of less than about 0.001 inches and the outer layer 130 may have a thickness of about 0.003 - 0.005 inches. The outer layer 130 preferably has a thickness that is at least twice that of the shielding layer 122 and more preferably a thickness that is three times larger than the shielding layer thickness. The outer layer 130 is preferably formed of the same material as the main body 1 12 but may be formed of a different material. For example, the outer layer 130 may be formed of a dielectric material such as olefins, such as polypropylene or polyethylene, or fiuoro-polymers, such as FEP, ECTFE, MFA, PFA, and the like.

[0034] FIG. 7 illustrates an alternative embodiment of a shielding 720 for the cable component 100. The shielding 720 is the same as the shielding 120 of the first embodiment, except that longitudinal gaps 750 are provided in the coated shielding layer 722 alone or in addition to the circumferential or radial gaps 550. The addition of circumferential or radial gaps allows another degree of shield tuning and isolation between cable components. The method of applying the shielding 720 is the same as the first embodiment with the additional step of adding masking solution to create the longitudinal gaps 750. More specifically, the method may include the steps of: extruding the cable component 100; applying discrete amounts of a masking solution to the cable component in longitudinal strips or both circumferential bands and longitudinal strips; coating the cable component 100 and masking solution with the conductive shielding layer 722; removing the discrete amounts of masking solution and the portions of the conductive shielding layer 722 in contact with the masking solution to create the gaps 550 and 750 in the shielding, thereby increasing the number of segments 560 in the shielding; and extruding the outer layer 130 over the conductive shielding layer 122 to encapsulate the same.

[0035] FIGS. 8 and 9 illustrate a cable component of the present invention as a tube 100' in accordance with a third embodiment instead of a cross-web separator of the first and second embodiment. The tube 100' preferably encloses at least one of the pairs 102 in the cable core, as seen in FIG. 9. The tube 100' includes shielding 820 that is applied using the same steps described above with respect to the first and second embodiments. The main body 812 of the tube 100' is first extruded, similar to the step shown in FIG. 2 and discrete amounts of a masking solution are then applied to the tube's main body 812, similar to the step shown in FIG. 3. The tube 100' is then coated with a conductive shielding layer 822, similar to the step shown in FIG. 4 and the discrete amounts of masking solution are then removed along with portions of the conductive shielding layer 122 in contact with the masking solution, to create circumferential gaps 850 in the shielding, similar to the step shown in FIG. 5. Finally, an outer layer 830 is extruded over the conductive shielding layer 822, similar to the step shown in FIG. 6.

[0036] 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. For example, the separators of the above exemplary embodiments may have any cross-sectional shape, and is not limited to a crossweb or tube. Moreover, the shielding of the exemplary embodiments may be applied to any component of a cable and not just the separator.