ES2452520T3 - Cable element, cable for data transmission, procedure for the manufacture and use of the cable for data transmission - Google Patents

Abstract

Data transmission cable (20) comprising more than one cable element (10) for the transmission of high frequency data, each cable element (10) comprising a single twisted pair (1) of insulated electrical conductors, surrounded by a first shielding layer (4) thus forming a first space (5) comprised between said single braided pair (1) and an inner surface of said first shielding layer (4), in which, at least, part of said first space comprises a water barrier compound, characterized in that said first shielding layer (4) includes an electrically conductive material in which said cable elements (10) are surrounded by an extruded outer sheath (11), said outer sheath (11) defining a second space (13) comprised between an inner surface of the outer sheath (11) and an outer surface of the at least one cable element (10), further comprising a second shielding layer (12) surrounding the cab elements le (10), in which said second shielding layer (12) is surrounded by the outer sheath (11).

Description

Cable element, cable for data transmission, procedure for the manufacture and use of the cable for data transmission

[0001] The present invention relates to a cable for data transmission comprising more than one cable element for high frequency data transmission comprising a single twisted pair of insulated electrical conductors surrounded by a first shielding layer, forming a first space between said twisted pair of insulated electrical conductors and an inner surface of said first shielding layer.

[0002] EP 0572173 refers to a communication cable that has water barrier capabilities. Such a cable has a plurality of metallic conductors, and one of such cables comprising a plurality of individual copper conductors configured as twisted pairs. A plurality of these twisted pair conductors are closely packaged together to create a series of units, in which each unit is helically wrapped separately with a water-absorbing hydrophilic wire. The cable includes a core comprising one or more pairs of insulated metal conductors, in which a hydrophobic material is used as a filler compound to occupy any gaps or interstices that remain within the core.

[0003] EP 0586158 refers to a cable comprising a plurality of longitudinally extending transmission means that includes a core having a plurality of pairs of insulated metal conductors, in which the conductors can be grouped together into units and the units assembled together within the core. Linkages are used to jointly connect the conductors, in which the core is disposed within a plastic material that is wound. The core is filled with a super-absorbent polymer in powder form.

[0004] GB 2164198 refers to a fiber optic cable comprising a plurality of insulated wires stranded together and impregnated with a water repellent medium and having on its surface a sprinkling of a water barrier powder. The coated cable harness is in turn surrounded by an inner protective sheath of plastic materials extruded over the beam, a metal barrier strip and an outer sheath of extruded plastic around the barrier strip.

[0005] US 6,686,537 and US 6,815,611 disclose high performance data cables in which a laterally wound shielding tape is used on each twisted pair cable, whose shielding tape is attached with a fastener metallic or textile to meet impedance / RL, attenuation uniformity and capacitance imbalance. By using this side-wound shield, most of the trapped air that is normally found in shielded twisted pair cables is removed.

[0006] US 2005/0077066 describes a cable having a plurality of individually shielded twisted pairs, each individual shielded twisted pair including a shield consisting of multiple layers with a first surface and a second surface opposite the first surface. The shield has a first longitudinally extending side and a second longitudinal side. The shield is oriented around the twisted pair with a side fold or "cigarette bundle" fold. A portion of the side-wrapped shield is attached to itself. By joining a portion of the shield to itself, said shield forms a semi-rigid tube that encompasses the twisted pair.

[0007] WO 2005/073983 refers to fillers for use in communication cables, such as electrical and optical cables. An example of such electrical cables comprises two electrical conductors, typically twisted to form a pair. Around each electrical conductor is a polymeric insulator, and an outer cable structure encloses the twisted pair of electrical conductors and the filler material.

[0008] The space between the twisted pair of insulated electrical conductors and the first shielding layer of the cables according to the prior art is filled with air. When this type of prior art cables are used outdoors, water can diffuse or drip into this space between the twisted pair of insulated electrical conductors and the first shielding layer. As a result of the entry of water, data transmission, especially for high frequencies, may be disturbed or even lost. Disturbance

or loss of data transmission is attributed to a too high level of dielectric loss (L), defined as the product of the relative dielectric permittivity (E) and the dissipation factor (D). This dielectric loss depends on the frequency and temperature at which the cable element operates.

[0009] In this regard, it should be noted that this loss or alteration of the data transmission does not necessarily mean that the cable can no longer carry electric current.

[0010] A further problem associated with weathering of the cables according to the prior art is that the performance of the cable can be jeopardized due to the application of external forces or movements.

 [0011] An object of the present invention is to provide an improved data transmission cable comprising cable elements that can be used outdoors, preferably without impairing the data transmission performance of the cable.

[0012] Another object of the invention is to provide a cable for data transmission that is resistant to deformation.

[0013] The present invention is characterized by the characterization portion of claim 1.

[0014] The presence of the water barrier compound in the first space blocks the penetration of water in the first space of the cable element. Similarly, even in circumstances where water is introduced in part of the first space, the water barrier compound will prevent further penetration into the cable element in the longitudinal direction thereof.

[0015] The present inventors have surprisingly found that a certain increase in dielectric loss, whose increase in loss is the result of the presence of water barrier compound in the first space between the twisted pair of insulated electrical conductors and a surface inside the first shielding layer, will not result in a significant loss of data transmission performance.

[0016] Due to the presence of the water barrier compound, the present inventors have also found that a cable element according to the present invention is more resistant to mechanical deformation.

[0017] Both of these properties make the cable elements suitable for use for both indoor and outdoor data transmission cables.

[0018] In a preferred embodiment, the relative dielectric permittivity of the water barrier compound is less than or equal to 4 and even more preferably less than or equal to 3 for the frequency and temperature at which the water is operated. element. Working temperatures can be specified to be between -40 ° and 70 ° Celsius.

[0019] When the relative dielectric permittivity is less than or equal to 3, compared to the cable elements according to the prior art, there is no need to adjust the thickness of the insulation layer surrounding the electrical conductors.

[0020] In a further preferred embodiment, the dissipation factor of the water barrier compound is less than or equal to 0.001 for the frequency and temperature at which the cable element is operated. If the dissipation factor of the water barrier compound is greater than 0.001, the transmission losses increase to an unacceptable level. The water barrier compound may be in the form of a gel, such as, for example, a petroleum-based gel or a silicone-based gel, or in the form of a hot melt.

[0021] As hereafter used a hot melt material, it is defined as a material that at room temperature is a solid, while it can flow at elevated temperatures, for example temperatures above 80 °

or even above 100 ° Celsius.

[0022] In a preferred embodiment the water barrier compound is a hot melt material and more preferably a hot melt adhesive. A hot melt adhesive joins both of the insulated electrical conductors of the twisted pair and the first shielding layer.

[0023] In a further preferred embodiment, the hot melt adhesive is an elastomer based adhesive. Preferably, the hot melt material is a polyurethane or a polyacrylate-based material.

[0024] Such an embodiment allows the cable element to be even more resistant to mechanical deformation, resulting in a more reliable data transmission behavior, that is, data transmission disturbances or losses resulting from mechanical loads applied to the Data transmission cable are reduced to a minimum.

[0025] An additional advantage of a hot melt material is that such a material is relatively easy to handle when compared to, for example, gels. This is particularly relevant for the worker who has to splice or connect a cable in the field. The worker can remove the hot melt material from the twisted pair relatively easily without having the risk of getting his hands dirty, or getting his tools or clothes dirty.

[0026] Yet another advantage of using a hot melt material is that such a material can be processed relatively easily and allows production speeds comparable to those of conventional unfilled cable elements.

[0027] In this regard, it is noted that the water barrier compound of the cable element of the present invention should not be confused with a water-swellable material. More particularly, the present water barrier material is not a water inflatable material.

[0028] A water-swellable material swells under the influence of water and thereby effectively blocks the penetration of water in both a radial and longitudinal direction of a cable or cable element. When first applied to a cable element during its manufacturing process, such water-swellable materials may not result in disturbances or loss of data transmission for the operating frequency and temperature. However, when used, the water swellable material can absorb water and as a result the overall composition of the water swellable material thus obtained contains water.

[0029] Consequently, the relative dielectric permittivity of the therefore swollen water-swellable materials increases which results in an increase in dielectric losses to an unacceptable level, more particularly, to values significantly greater than 0.01. Such values are too high in practice and may result in disturbance or loss of signal.

[0030] In a further preferred embodiment, the first shielding layer is, at least partially, in contact with the single twisted pair of insulated electrical conductors. The first single shielding layer thus surrounds the single twisted pair in a relatively tight manner, however, a first space is still formed between an inner surface of the first shielding layer and an outer surface of the single twisted pair of insulated electrical conductors. The first shielding layer is applied around the single twisted pair of insulated electrical conductors for the purpose of electrical shielding, more particularly, in order to reduce crosstalk phenomena.

The present invention is restricted to a cable element in which the two insulated electrical conductors are twisted together and in intimate mutual contact in the longitudinal direction. Such construction further comprises a shielding layer, said shielding layer surrounding only a single twisted pair of insulated electrical conductors.

[0032] Preferably, the first shield layer consists of or comprises a metal.

[0033] The embodiments of suitable shield layers are plastic sheets laminated in aluminum. Other exemplary embodiments of the shielding layer are represented by the shielding sheet as described in US 2006/004896 or the shielding system disclosed in WO 2006/105166. All these embodiments are specifically incorporated by reference.

[0034] In yet another preferred embodiment, the water barrier compound completely fills the first space along the length of the cable element, thus making it impossible at any location for water entry into the first space along the length of the cable element length.

[0035] The present invention relates to a cable for data transmission comprising at least one cable element according to the present invention in which said at least one cable element is surrounded by an extruded outer sheath. said outer sheath defining a second space comprised between an inner surface of the outer sheath and an outer surface of at least one cable element, further comprising a second shielding layer surrounding the at least one cable element wherein said second shielding layer is surrounded by the outer sheath.

[0036] In a specific embodiment the cable for data transmission according to the invention consists of four cable elements.

[0037] The second shield layer should not be confused with the first shield layer that surrounds the twisted pair of insulated electrical conductors. The second shielding layer should not be considered as a part of the cable element and also does not directly surround the single twisted pair of insulated electrical conductors. In the embodiment in which the data transmission cable comprises more than one cable element, the second shielding layer surrounds all the cable elements.

[0038] In the second space, at least one water-swellable material and / or at least one water barrier material may be present. The present inventors found that with the presence of such additional water swellable materials and / or water barrier materials an even more robust and water resistant cable is obtained.

[0039] The cable for data transmission and consequently the cable elements according to the invention operate at high relative frequencies of at least 1 MHz preferably in a range of 1 to 1000 MHz more preferably 100 to 1000 MHz.

[0040] For example, the data transmission cable according to the invention can be of the type Cat. 5, Cat. 5e, Cat. 6, Cat. 6a, Cat. 7, Cat. 7a as defined in the standard International IEC 61156-5.

[0041] Typically, the data transmission cable according to the invention does not contain resistant or reinforcing elements such as longitudinal dielectric resistant members, aramid wires, glass reinforced rods and the like.

[0042] The data transmission cable according to the invention can be used as such, that is, it does not require additional circumferential layers or envelopes.

[0043] The data transmission cable according to the invention allows the use, at least partially, in weather conditions, that is, in conditions where the cable may be exposed to water or moisture at varying temperatures.

[0044] The present invention will now be described by means of the following figures that should not be construed as limiting in any way.

Figure 1 shows a cable element for data communication.

Figure 2 shows an embodiment of a cable for data communication according to the present invention.

Figure 3 shows a schematic representation of a production line for the manufacture of cable element according to the present invention.

[0045] Figure 1 shows a schematic representation of a cable element 10, comprising a single twisted pair of two insulated electrical conductors 1, hereinafter referred to as twisted pair 1. Each of the two insulated electrical conductors of the twisted pair 1 it comprises a conductive core 2 covered by an insulating layer 3. The two insulated electrical conductors of the twisted pair 1 pair are twisted together and consequently, in mutual intimate contact in the longitudinal direction. Not forming part of the twisted pair 1 other conductors or elements.

[0046] The conductive core 2 may have a diameter ranging from about 400 mm to 700 mm, depending on the application. The conductive core 2 can be of the solid type, that is, it consists of a single wire of conductive material. In an alternative embodiment conductive core 2 is of the twisted type, in which several wires of conductive material are twisted. For example, conductive core 2 may consist of seven strands where six strands extend around a central strand.

[0047] Conductive core 2 sometimes referred to as core wire or wire is made of an electrical conductive material, preferably a metal such as copper, coated copper, copper or aluminum alloy.

[0048] The insulation layer 3 may be made of a polymer material or a polymer compound comprising a polymer material such as polyethylene, polypropylene, ethylene-propylene copolymers, polyvinyl chloride, fluorinated plastics such as polytetrafluoroethylene. A polymer compound in this context should be understood in the sense of a polymer material where one or more additives are added. Examples of such additives are UV stabilizers, antioxidants, pigments, dyes, flame retardant additives and fillers such as talc and molten silica.

[0049] The insulating layer 3 may be solid or spongy, that is, contain small air pockets. The wall thickness of the insulating layer 3 can be between 200 and 600 mm depending on the application. The insulation layer 3 can be applied to the conductive core 2 by means of extrusion, completely surrounding it and is preferably in direct contact with said conductive core 2.

[0050] The twisted pair 1 is surrounded by the first shielding layer 4 defining a first space 5 comprised between the first shielding layer 4 and the twisted pair 1. From Figure 1 it is clearly apparent that said first space 5 basically consists of two distinct zones and, that the space 5 corresponds to the space enclosed by the shield layer 4 minus the space occupied by the twisted pair 1. In the embodiment of Figure 1, it is appreciated that the shield layer 4 is surrounding directly the single twisted pair 1.

[0051] According to the present invention, a water barrier compound (not shown) is present in the first space 5. In an exemplary embodiment the water barrier compound, is a hot melt adhesive marketed under the brand INSTANTE-FLEX X47 of National Starch & Chemical This hot melt material has been shown to effectively block the water and provide mechanical stability to the cable element 10. In addition, this hot melt material is relatively easy to peel manually when one end of the cable element 10 has to be spliced or connected in the ground, not being necessary solvent

[0052] Figure 2 shows a cable 20 for data transmission consisting of four cable elements 10 which according to the present invention are surrounded by a second shield layer 12. The cable elements 10 may extend in parallel or may be twisted around each other, either in the form of a propeller or in an SZ configuration as is known per se. The data transmission cable 20 is not limited to the specific number of four cable elements 10, but any number can be used, for example, two, four or even up to twenty cable elements 10 may be present within said second shielding layer 12. Additionally, cable 20 can be grouped together with other cables for data transmission 20, forming a communication cable (not shown). Such a communication cable may comprise a central reinforcing member in which several data transmission cables 20 are wound around in the form of a propeller or in an SZ configuration, and finally surrounded by an outer plastic sheath. Within such a communication cable the number of cable elements 10 present in these cables for data transmission 20 may differ from one cable for data transmission 20 to another cable for data transmission 20.

[0053] The second shield layer 12 may be in the form of a tape that has been wrapped around the elements of the cable 10. In an alternative embodiment the second shield layer 12 in the form of a tape may be folded in the longitudinal direction to form a tube-like structure The second shielding layer 12 comprises a conductive material, such as a metal and may be in the form of a braid of relatively thin metal wires, for example made of copper.

[0054] The second shielding layer 12 and the cable elements 10 are surrounded by the outer sheath 11. The outer sheath 11 may be of a polymer material or a polymer compound comprising a polymer material such as polyethylene, polypropylene , ethylene-propylene copolymers, polyvinyl chloride, polyurethane. In the embodiment shown in Figure 2, the second shielding layer 12 is fitted tightly to the inner surface of the outer sheath 11. It should be understood that other configurations may also be provided whose embodiments allow a certain radial separation between the second shielding layer 12 and the inner wall of the outer sheath 11.

[0055] The outer sheath 11 defines a second space 13 comprised between an inner surface of said outer sheath 11 and an outer surface of the cable elements 10. This second space 13 corresponds to the space enclosed by the outer sheath 11 minus the space occupied by the elements of the cable 10 minus the space occupied by second shield layer 12, when present.

[0056] The second space 13 may also contain water barrier and / or water inflatable materials (not shown).

[0057] Figure 3 schematically shows a production line to be used in a process for manufacturing the cable elements according to the present invention.

[0058] The first shield layer 4 in the form of a belt is joined with a single twisted pair 1 and fed to the matrix 30. By means of this matrix 30, on the first shield layer 4 and the twisted pair gathered together apply a water barrier compound. After the application of the water barrier compound in the matrix 30, the assembly of the first shield layer 4, the twisted pair 1 and the water barrier compound is supplied to a folding device or folded matrix 31. In the folding device 31, the tape forming the first shield layer 4 is folded in such a way that a cable element 10 is obtained, in which twisted pair 1 and the water barrier compound are surrounded by first shield layer 4 , where the water barrier compound is present in the first space created by the first protective layer 4 and the twisted pair 1. It should be understood that the present invention is not limited to a first shield layer manufactured in this manner and that other procedures known in the art can be applied.

[0059] Several production lines, such as the one described above, can be operated in parallel for the simultaneous manufacture of several cable elements 10. The cable elements 10 manufactured in this way can then be assembled in parallel, in a helix or in a configuration. SZ, optionally provided with a second shield layer 12, water barrier materials and / or water-swellable materials and, finally, provide them by extrusion of the outer sheath 11 in order to form a cable for data transmission 20.

Claims (13)

one.

Data transmission cable (20) comprising more than one cable element (10) for high frequency data transmission, each cable element (10) comprising a single twisted pair (1) of insulated electrical conductors, surrounded by a first shielding layer (4) thus forming a first space (5) comprised between said single twisted pair (1) and an inner surface of said first shielding layer (4), in which at least part of said The first space comprises a water barrier compound, characterized in that said first shielding layer (4) includes an electrically conductive material in which said cable elements (10) are surrounded by an extruded outer sheath (11), said outer sheath defining (11) a second space (13) comprised between an inner surface of the outer sheath (11) and an outer surface of the at least one cable element (10), further comprising a second shielding layer (12) that surround the element s of cable (10), wherein said second shielding layer (12) is surrounded by the outer sheath (11).

2.

Data transmission cable (20) according to claim 1 wherein the water barrier compound has a relative dielectric permittivity E less than or equal to 4, preferably less than or equal to 3, for the frequency and temperature at that the cable element works (10).

3.

Cable for data transmission (20) according to one or more of the preceding claims 1 and 2, wherein the water barrier compound has a dissipation factor D less than or equal to 0.001, for the frequency at which the cable element (10) works.

Four.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 3, wherein the water barrier compound is a hot melt material, more preferably a hot melt adhesive.

5.

Data transmission cable (20) according to claim 4 wherein the hot melt adhesive is an elastomer-based hot melt adhesive.

6.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 5, wherein the shielding layer (4) is, at least partially, in contact with the single twisted pair (1) of conductors electrical insulated.

7.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 6 wherein the first shielding layer (4) includes metal.

8.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 7 wherein the water barrier compound completely fills the first space (5) along the length of the cable element ( 10).

9.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 8, wherein at least one water-swellable material and / or at least one water barrier material is present in said second space (13).

10.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 9 operating at a frequency of at least 1 MHz.

eleven.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 10 operating at a frequency in a range of 100 to 1000 MHz.

12.

Cable for data transmission (20) according to one or more of the preceding claims 1 to 11, wherein the cable (20) does not contain reinforcing elements.

13.

Use of the cable for data transmission (20) according to one or more of the preceding claims 1 to 12 for the transmission of data in outdoor conditions.

 REFERENCES CITED IN THE DESCRIPTION This list of references cited by the applicant is solely for the convenience of the reader. It is not part of the European patent document. Although great care has been taken in the compilation of references, errors or omissions cannot be excluded and the EPO disclaims all responsibility in this regard.  Patent documents cited in the description

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EP 0572173 A [0002] • US 20050077066 A [0006]

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EP 0586158 A [0003] • WO 2005073983 A [0007]

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GB 2164198 A [0004] • US 2006004896 A [0033]

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US 6686537 B [0005] • WO 2006 105166 A [0033]

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US 6815611 B [0005]