DATA CABLE WITH FREE STRIPPING WATER BLOCKING MATERIAL

Cross Reference to Related Application

[0001] This application claims priority to U.S. Provisional Patent Application No.

'5 60/895,584, filed March 19, 2007, the disclosure of which is incorporated herein by reference in its entirety.

Field of the Invention

[0002] The present invention relates to a data cable. In particular, the present invention0 relates to a data cable containing a free stripping water blocking material.

Backeround of the Invention

[0003] Several different types of data cables are in use today. Some data cables utilize optical fibers to transmit light signals, while others use conductors to convey electrical '3 data signals. To minimize potential incompatibility between data cables of the same general type, standards have been established. For conductive data cables, one such standard is known as TIA/EIA-568-B for eight-conductor, 100-ohm, balanced, twisted-pair cabling, such as category 5e conductive data cables. The most identifiable feature of category 5e data cables are their pin/pair assignments. The pin/pair assignment of category 5e cables is often 0 referred to as "eight position eight conductors," ("8P8C") or sometimes referred to as

"RJ45." Category 5e conductive data cables are often used in commercial settings where a spectrum of at least 100 MHz is required for data transmission. Typical applications include 10 base T, 100 base TX, token ring, 1000 base T gigabit Ethernet, 155 Mbps ATM, or 622 Mbps ATM.

[0004] To effectively convey data signals from one location to another, a conductive data cable must minimize or prevent moisture inside the data cable since high moisture levels can degrade conductivity and result in loss of data or data distortion. Depending on the construction of the particular data cable, the introduction of moisture can result in a short circuit, an increase in the data cable's capacitance, an increase in signal attenuation, or in the complete failure of the data cable.

[0005] Moisture can penetrate to the interior of the data cable in several different ways. Water may enter through a failure in a data cable's jacket. Water may also enter through a cable end, where a cable connector is attached. Mechanical impacts, electrical arcs, or lightning may breach the jacket that protects the data cable or the joint where one data cable joins another. Water may then flow through the breach towards the core of the data cable and longitudinally along the length of the data cable. Also, changes in ambient conditions may lead to differences in water vapor pressure between the interior and the exterior of the data cable. The difference in vapor pressure may then cause moisture to diffuse into the interior of the data cable. Eventually, there may be an undesirable level of moisture inside the cable. [0006] Since the data cable's ability to resist penetration by moisture may be a crucial characteristic in certain applications, the data cable must be tested and meet certain performance specifications to ensure that the presence of water will not significantly affect the data cable. Several different performance specifications pertain to waterproof data cables. The particular specification used depends on the proposed application and use. One such specification is MIL-DTL-24643/59, which is set by Naval Sea Systems Command. It prescribes the water blocking requirements for a conductive data cable to be used on a Navy

ship. To meet the requirements of MIL-DTL-24643/59, an open end of the data cable is subjected to a predetermined water pressure for a predetermined amount of time. Data cables that allow limited water migration to a specified length when subjected to the test are deemed "waterproof." [0007] Various methods have been used to block water. One method of protecting data cables against water penetration is to provide a layer of plastic or polymeric material. In a cable insulated by a polymeric material, water can travel by capillary action along the cable interstices, causing problems in conductivity. In most environments, it is desirable, if not essential, that the cable be more watertight than can be achieved with polymeric material alone. Some data cables may include a metal/plastic laminate foil beneath the outer protective jacket of the data cable. The metal/plastic laminate foil may become bonded to the polymeric material, normally when the polymer is extruded. However, it is difficult to design a jacket in which the laminate foil remains intact when the data cable is subjected to impact, as the laminate tends to be driven into gaps between conductors lying underneath the laminate and to split along resulting crease lines.

[0008] Another method of protecting a data cable against water penetration is to use water swellable materials. However, when water swellable materials are exposed to high humidity over a long period of time, they expand by as much as three times their original volume. Associated dielectric properties of water swellable materials, such as dissipation factor and dielectric constant, change as water swellable materials absorb moisture. The water swellable materials are generally in close proximity to the insulated conductors of the data cable. Thus, changes in the dielectric properties of the water swellable materials affect

the dielectric properties of conductive data cables, and changes in the dielectric properties of conductive data cables affect their data transmission capabilities. Therefore, when the dielectric properties of the water swellable materials change, the change affects the data transmission capabilities of conductive data cables. [0009] Filler materials are also commonly used in conductive data cables to prevent water penetration by capillary action along cable interstices. Filler materials are commonly synthetic polymers, petroleum based greases, oils, or silicone flooding compounds. Filler materials may be coated on components of the conductive data cable to prevent longitudinal movement of moisture. In addition, the interstices within the cable may be filled with the filler material to minimize water entry and migration. However, applying filler material in order to block water necessitates additional handling and processing steps in the manufacturing of the cable. The additional steps increase manufacturing time. Further, the addition of filler material significantly increases the weight of the electrical cable. Finally, conductive data cables with filler material cannot be terminated without peeling away or removing waterblocking material on the conductors.

[0010] Thus, there is a need in the art for an invention to provide better protection of data cables against water penetration. Particular need remains for water blocking protection that does not change the transmission properties of the data cable. Also, the water blocking protection must allow the cable to be terminated without peeling away or removing it from the conductors. Furthermore, the water blocking protection must allow the cable to meet the requirements of MIL-DTL-24643/59.

Summary of the Invention

[0011] Accordingly, it is an object of the invention to provide protection against water penetration of a data cable that is capable of both blocking water and maintaining transmission properties of the data cable. Another object is to provide water blocking protection that allows the data cable to be easily terminated without peeling away or removing it from the conductors. Yet another object is to provide a data cable that meets the requirements of the specification MIL-DTL-24643/59.

[0012] An exemplary embodiment of the present invention provides a data cable. The data cable includes conductors, a filler material, a shielding member, a water swellable tape, and a jacket. The conductors are substantially placed within the filler material. The shielding member is placed substantially around the filler material, and the water swellable tape is placed substantially around the shielding member. The jacket is placed substantially around the water swellable tape. [0013] Another embodiment of the present invention provides a data cable. The data cable includes conductors, a foam placed substantially around each of the conductors, a filler material, a shielding member, a water swellable tape, and a jacket. The conductors and the foam are substantially placed within the filler material. The shielding member is placed substantially around the filler material, and the water swellable tape is placed substantially around the shielding member. The jacket is placed substantially around the water swellable tape.

[0014] Yet another embodiment of the present invention provides a data cable. The data cable includes conductors, a foam placed substantially around each of the conductors, a solid

coat placed substantially around the foam, a filler material, a shielding member, a water swellable tape, and a jacket. The conductors, the foam, and the solid coat are substantially placed within the filler material. The shielding member is placed substantially around the filler material, and the water swellable tape is placed substantially around the shielding member. The jacket is placed substantially around the water swellable tape.

[0015] 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

[0016] 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 drawing, wherein:

[0017] FIG. 1 is a partial perspective view of a data cable according to an exemplary embodiment of the present invention, various layers of the cable being exposed for the purposes of illustration; and

[0018] FIG. 2 is a sectional view taken substantially along line 2-2 of the data cable illustrated in FIG. 1.

Detailed Description of the Invention

[0019] Referring to FIGS. 1-2, the present invention relates to a data cable 100 that substantially prevents penetration of water. The data cable 100 has water blocking protection that includes water swellable materials, but the water swellable materials are isolated and separated from the conductors 102 of the data cable 100. By isolating and separating the water swellable materials from the conductors 102, expansion of the water swellable materials does not substantially affect the transmission properties of the data cable 100. Also, the construction of the data cable 100 allows for simpler termination by avoiding the removal or peeling away of any water blocking protection. Furthermore, the data cable 100 substantially meets or exceeds the requirements of MIL-DTL-24643/59, which specifies the requirements for water blocking data cable used aboard Navy ships.

[0020] Referring to FIG. 1, a partial perspective view of the data cable 100 according to an embodiment of the invention is shown. The data cable 100 includes one or more conductors 102, a foam 104 substantially around each of the conductors 102, and a solid coat 106 substantially around the foam 104. In the embodiment of FIG. 1, the conductors 102 substantially surrounded by the foam 104 and the solid coat 106 are placed within a filler material 108. The filler material 108 is substantially wrapped with a corewrap 110 which is itself substantially surrounded by a shielding member 112. The shielding member 112 is substantially wrapped with a water swellable tape 118, and finally, a jacket 120 substantially covers an outermost surface of the data cable 100.

[0021] The conductors 102 provide pathways for data signals. In the embodiment shown, eight conductors 102 are intertwined so as to form four twisted pairs of conductors 102. The

conductors 102 are made of copper and are 24 American Wire Gauge ("AWG") per ASTM B 8 Class B. The twisting lay is between approximately one-half inch to approximately one inch. Each pair of conductors 102 are twisted with a different lay length. In other embodiments, the conductors 102 may be made of another material, be of another gauge or AWG, or have a different twisting lay. The number, material, gauge, and the twisting lay of the conductors 102 is not meant to be limiting but meant to illustrate one particular embodiment to describe the data cable 100. For example, the conductors 102 can be made of other electrically conductive materials such as, but not limited to, aluminum, silver, gold, or some other electrically conductive metal or alloy. The conductors 102 can also be plated with another electrically conductive material, such as tin, silver, nickel, or other suitable plating material. Furthermore, although each of the conductors 102 may be a solid conductor, each of the conductors 102 may alternatively be made up of several conductive strands. [0022] Referring to FIG. 2, the conductors 102 are arranged longitudinally adjacent to one another to provide the cable 100 with a substantially circular cross-section. Also, in the embodiment depicted, although two adjacent conductors 102 are intertwined with each other to form a twisted pair, the conductors 102 may be intertwined in the same direction, or the conductors 102 may be intertwined in a direction different from the intertwining of other conductors 102. Furthermore, the conductors 102 may be intertwined to form a helical braid or a helical spiral.

[0023] The conductors 102 shown are substantially covered with a foam 104. The foam 104 provides electrical insulation and water blocking. Bubbles in the foam 104 and the foam

104 itself provide electrical insulation. Also, the foam 104 should have good dielectric properties and should be extrudable. In the embodiment shown, the foam 104 is made from high density polyethylene (HDPE) which provides electrical insulation, has good dielectric properties, and is extrudable. In the depicted embodiment, the foam 104 is approximately 6-7 mils thick. The thickness of the foam 104 is exemplary only, and is not intended to be limiting to the invention; the optimal thickness of the foam 104 may be less than 6 mils or more than 7 mils.

[0024] The solid coat 106 substantially surrounds the foam 104 and provides mechanical support for the foam 104. The solid coat 106 can be made of any material that provides rigid support. In the embodiment shown, the solid coat 106 is made of HDPE and is about 5 mils thick. The thickness of the solid coat 106 is exemplary only to describe one embodiment of the invention.

[0025] A layer of insulation (not shown) may be placed around the foam 104, in which case the solid coat 106 would then be placed over the insulation. The insulation may be made of an appropriate dielectric material. Also, the insulation may be colored, coded, marked, or otherwise processed to provide identification. In one embodiment, the insulation is made of HDPE.

[0026] The conductors 102 substantially surrounded by the foam 104 and the solid coat 106 are disposed within the filler material 108. The filler material 108 blocks water. To meet the requirements of MIL-DTL-24643/59, the filler material 108 is preferably a free stripping material or made of a material with a substantially solid consistency. In the embodiment shown, the filler material 108 is made from commercially available

"UNIB LOC™," which is manufactured by Unigel. The filler material 108 can include a super absorbent polymer (SAP). The filler material 108 can also be a polymer impregnated with SAP.

[0027] The filler material 108 may be substantially surrounded with the corewrap 110. The corewrap 110 provides support to the filler material 108 while the conductors 102 are disposed within the filler material 108. In the depicted embodiment, the corewrap 110 is made of mylar which is helically wrapped with about 25% or greater overlap. [0028] The shielding member 112 substantially surrounds the corewrap 110. The shielding member 112 provides electrical shielding. In the embodiment shown, the shielding member 112 includes an aluminum/mylar tape 114 helically applied and a copper braid 116. The aluminum/mylar tape 114 is a tape with aluminum on one side and mylar on the other with a coat of water swellable material on at least one side. The depicted embodiment has the aluminum side facing outward and water swellable material on the mylar side. Also, the aluminum/mylar tape 114 has about 25% overlap or greater. The copper braid 116 is made from 36 AWG copper wires with approximately 65% coverage.

[0029] The water swellable tape 118 is placed around the shielding member 112. The water swellable tape 118 is made of any soft, fibrous, gauze-like material that can absorb moisture or that contains water swellable material. The water swellable tape 118 can be made of a super absorbent polymer tape impregnated with a powder-like water swellable material. The water swellable tape 118 can also be made of super absorbent powder laminated between non-woven materials. In the embodiment shown, the water swellable tape

118 is one manufactured by Scapa.

[0030] Because the shielding member 112 is disposed between the conductors 102 and the water swellable tape 118, if the water swellable tape 118 expands, the water swellable tape 118 does not affect either the electrical or the transmission properties of the data cable 100. Thus, the embodiment shown provides water blocking protection and maintains the '5 transmission properties of the data cable 100.

[0031] The jacket 120 wraps the outermost peripheral area of the cable 100. In the embodiment shown, the jacket 120 is made of a fire retardant, substantially halogen free polyolefin with cross link agents. With the described construction, the jacket 120 meets the standards delineated in MIL-DTL-24643/59. The jacket 120 emits little smoke, minor 0 amounts of toxic fumes when the jacket 120 is combusted, and contains substantially no halogens.

[0032] The embodiment of the data cable 100, as described above, substantially meets or exceeds the standards of MIL-DTL-24643/59. Also, with the above described construction, the data cable 100 has a weight per length of approximately 28.6 kg per 304.8 meters or 63 5 pounds per 1,000 feet nominally. The data cable 100 also has the following electrical characteristics.

[0033] A method of manufacturing the data cable 100 begins with providing conductors 102 The conductors 102 are pulled through a foam and insulation extruder The foam and insulation extruder places insulation around each conductor 102 and the foam 104 around the insulation The insulation may be colored, coded, marked, or otherwise processed to provide identification Then, a solid coat 106 is placed around the foam 104 In one embodiment, pairs of the conductors 102 are twisted together where the twisting lay is between approximately one-half mch to approximately one inch Next, the conductors 102 which are

substantially surrounded by the foam 104 and the solid coat 106 are placed in the filler material 108. Corewrap 110 made of mylar contains the filler material 108 while the conductors 102 are placed in the filler material 108. Then, the shielding member 112 is placed around the corewrap 110. In one embodiment, the aluminum/mylar tape 114 is pulled around the filler compound 108 and then a copper braid 116 is weaved around the aluminum/mylar tape 114. Water swellable tape 118 may be wrapped around the shielding member 112. Finally, the jacket 120 is placed around the shielding member 112. In one embodiment, the jacket 120 is extruded around the shielding member 112. If the jacket 120 is made of a material containing cross link agents, then the data cable 100 undergoes cross linking. The cross linking can be completed by electron beam exposure.

[0034] As is apparent from the above description, the present invention provides a data cable 100 that is capable of blocking water while substantially maintaining transmission properties. The data cable 100 has water blocking protection that includes water swellable materials whose dielectric properties change as the water swellable material expands. However, the water swellable materials are separated from the conductors 102 by, at least, the shielding member 112, which prevents the water swellable material from affecting the transmission properties of the conductors 102. Furthermore, the data cable 100 substantially meets or exceeds the requirements of MIL-DTL-24643/59, which specifies the requirements for water blocking data cable used aboard Navy ships. [0035] While a particular embodiment has 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.

[0036] For instance, while the conductors 102 are placed longitudinally to provide the data cable 100 with a substantially circular cross-section, each of the conductors 102 may also be placed longitudinally adjacent to each other to form a substantially triangular, rectangular, trapezoidal, or polygonal cross-section. [0037] Also, although the embodiment described has HDPE as the insulation covering the conductors 102, the dielectric material covering the conductors 102 may also be, but not limited to, thermoset, thermoset polyethylene, thermoplastic, thermoplastic fluoropolymer, fluorocarbon-based polymer, polyethylene, polyvinyl chlorides (PVC), polyvinylidene fluoride (PVDF), ethylene tetrafluoroethylene (ETFE), ethylene propylene rubber (EPR), silicone, silicone tape, rubber tape, glass tape, combinations of the aforementioned materials, or other electrically insulating material.

[0038] Furthermore, other than HDPE, the foam 104 can also be made of propylene, thermoplastic polymer, PVC, fluoropolymer, polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene (FEP), perfluoroalkoxy polymer resin (PFA), combinations of the above materials, or other similar materials. Fluoropolymers include fully fluorinated fluorocarbon polymers and partially fluorinated polymers such as polychlorotrifluoroethylene (PCTFE), ETFE, ethylene chlorotrifluoroethylene (ECTFE), and PVDF.

[0039] As for the solid coat 106 surrounding the foam 104, the solid coat 106 can be made of propylene, thermoplastic polymer, PVC, PTFE, FEP, PFA, combinations of the aforementioned materials, or other similar materials, instead of HDPE. In an alternative embodiment, the solid coat 106 can be disposed substantially on each of the conductors 102

without the foam 104 so that the solid coat 106 provides both insulation and mechanical support.

[0040] Additionally, the shielding member 112 may be aluminum, aluminum foil, aluminum braid, combinations of the aforementioned materials, or any other electrically shielding material. And, the jacket 120 may be made of a non-conductive material, such as, but not limited to, a polymer or a plastic.