FR3020714A1 - LOW RESISTANCE LINEIC COMMUNICATION CABLE - Google Patents

Abstract

The present invention relates to a communication cable comprising a plurality of twisted pairs of elongated electrically conductive elements insulated from each other, and an electrically insulating sheath surrounding said plurality of twisted pairs, and to a method of manufacturing said communication cable.

Description

The present invention relates to a communication cable comprising a plurality of twisted pairs of elongated electrically conductive elements insulated from each other, and an electrically insulating sheath surrounding said plurality of wires. twisted pairs, and to a method of manufacturing said communication cable. It typically applies to LAN or Local Area Network communication cables (network cables or LAN cables). The communication cables are mainly divided into two distinct groups: fiber-optic cables and metal-conductor cables that include coaxial and twisted-pair cables, each of which has its own parameters that affect the quality of the signal. communication.

The invention more particularly relates to twisted pair LAN communication cables having improved performance, particularly in terms of signal transmission and energy. A twisted pair LAN cable is mainly used for networking computers and telephony. It generally comprises at least eight insulated copper conductor wires forming four pairs of twisted copper conductors, and an electrically insulating sheath surrounding said four pairs of twisted copper conductors. A LAN cable may include shielded twisted pairs against electromagnetic radiation (well known as Shielded Twisted Pair or STP) to limit interference, or unshielded twisted pairs (well known as Unshielded Twisted Pair or UTP). ), that is, no protective shield or protective sheath exists between the twisted pairs of said cable. Theoretically, STP cables can carry the signal up to about 150 to 200 meters while UTP cables can carry the signal up to about 100 meters. LAN cables are standardized into various categories of signal integrity. For example, Category 5E can transmit up to 1000 Mbit / s of information while Category 7A can transmit up to 10 Gbit / s of information. The dimensional characteristics of a LAN cable, and in particular the diameter of the elongated electrically conductive members of the twisted pairs of said cable, vary according to the category to which said cable belongs. In addition, the evolution of LAN cables is characterized by a steady increase in bit rates, from a few MHz in the mid-1980s, to 100 MHz in the late 1990s, to 1500 MHz today, and more in the medium term.

An effective communication cable is characterized in particular by a skin effect and / or a reduced linear resistance (e) s. The skin effect or film effect is a phenomenon of electromagnetic origin, for which the current tends to flow only at the surface of the conductors at high frequencies. This phenomenon exists for all the conductors traversed by alternating currents and causes the decay of the current density within the conductor as one moves away from the periphery of said conductor. Moreover, it is known from the prior art that the depth of penetration of the current is even lower than the frequency is high. In particular, Table 1 below shows the current penetration depths for a metal such as copper at different frequencies: TABLE 1 Frequency (MHz) Depth of penetration (μm) 1 66 10 20.87 100 6.66 300 3.81 600 2.69 Thus, the penetration depth of the current in copper at a frequency of 1 MHz is 66 lm. In parallel, an electric current passing through a conductor dissipates part of its energy in the form of heat (Joule losses). This results in a decrease in the power of this signal. The higher the linear resistance of the conductor, the greater the joule loss (i.e., the heating). This heating is not without consequences on the conductor and especially on the electrically insulating layer of the cable, in particular that which is directly in contact with said conductor, and can be at the origin of a degradation of the cable, or even a 10 fire. Therefore, an international standard IEC 61156 today imposes to have a linear resistance of the conductor lower or equal to 95 ohm / km. Document US2010 / 0006321 proposes a communication cable comprising at least one pair of elongate electrically conductive elements insulated from each other, possibly twisted, a first electrically insulating layer surrounding said pair of elongate electrically conductive elements insulated from one another, and a second electrically insulating layer surrounding said first electrically insulating layer. Each of the elongated electrically conductive elements comprises a conductive core 20 of steel and an electrically conductive layer of copper or silver surrounding said steel conductive core. With this configuration, the communication cable has improved signal transmission, especially at high frequencies. However, the signal transmission properties and the energy of said cable are not optimized. The object of the present invention is to overcome the drawbacks of the techniques of the prior art by proposing in particular a cable with improved signal transmission and energy properties and thus, which can be used at frequencies ranging from 1 to 1500. MHz, while respecting the international standard I EC 61156 as defined above. The present invention therefore has as its first object a communication cable comprising: - a plurality of twisted pairs of elongate electrically conductive elements insulated from each other, and - an electrically insulating sheath surrounding said plurality of twisted pairs of isolated elongate electrically conductive elements between them, - said identical elongate electrically conductive elements being chosen from any one of the following metallic elements: an aluminum core and a copper layer surrounding said aluminum core, a steel core and a copper layer surrounding said steel core, and a hollow copper tube, said copper layer or said hollow copper tube having a copper thickness greater than or equal to the copper penetration depth at 1 MHz which is 66 μm. tm, said communication cable being characterized in that said copper thickness is sufficient to have a linear resistance of less than or equal to 95 ohm / km. In the present invention, the term "a plurality of twisted pairs" means at least one twisted pair or one or more twisted pair (s). In addition, when the metal element is an aluminum core (respectively steel) and a copper layer surrounds said aluminum core (respectively steel), then the aluminum core (respectively steel) is covered with a continuous layer of copper. The communication cable of the invention is distinguished from coaxial cables not belonging to the field of the invention, by distinct elongate electrically conductive elements insulated from one another, and by the small diameter of the elongated electrically conductive elements, less than one millimeter .

Due to this sufficient thickness of copper, the cable of the invention has both better properties of signal transmission and energy. Further, depending on the metal element chosen for the elongate electrically conductive members of the twisted pairs, the cable of the invention has at least any of the following additional properties: improved breaking strength, decreased weight, and manufacturing cost decreased. In a particular embodiment, the cable of the invention complies with industry dimensional standards for at least one of the cables of category 5E, 6, 6A, 7 and 7A. In a particular embodiment of the invention, each of the elongated electrically conductive elements is isolated by means of an electrically insulating layer comprising at least one polymeric material. Thus, an electrically insulating layer comprising at least one polymeric material each surrounds elongate electrically conductive elements. The polymeric material may be selected from polyethylene (PE), polypropylene (PP), fluorinated ethylene propylene copolymer (FEP), ethylene tetrafluoroethylene copolymer (ETFE), terpolymer of ethylene and fluorinated ethylene-propylene (EFEP), polytetrafluoroethylene (PTFE), copolymer of ethylene and chlorotrifluoroethylene (ECTFE), copolymer of tetrafluoroethylene and perfluoromethylvinylether (MFA), copolymer of tetrafluoroethylene and perfluoropropylvinylether (PFA), Polyphenylene oxide (PPO), polyphenylene sulphide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA), polyetherimide (PEI), polyurethane (PU), thermoplastic elastomers (TPE), and crosslinked thermoplastics (TPV). Polyethylene (PE) may be selected from low density polyethylene (LDPE), medium density (MDPE), high density (HDPE), ethylene propylene rubber (EPR) and linear low density polyethylene (LLDPE) .

Preferably, the polymeric material is high density polyethylene. The electrically insulating sheath surrounding the plurality of twisted pairs of elongate electrically conductive elements can be conventionally made from suitable thermoplastic materials such as HDPE, MDPE or LLDPE; or else materials retarding the propagation of the flame or resistant to the propagation of the flame. In particular, if they do not contain halogen, it is called cladding type HFFR (for the Anglicism "Halogen Free Flame Retardant"). The electrically insulating sheath of the cable of the invention is preferably halogen-free, and comprises high-density polyethylene. In a particular embodiment, the cable of the invention comprises four twisted pairs of elongated electrically conductive elements insulated from each other. According to a preferred embodiment of the invention, each of the elongated electrically conductive elements has an outer diameter of from about 0.45 to about 0.7 mm, and preferably from about 0.5 to about 0.6 mm. According to a first variant, the metallic element of the elongated electrically conductive elements is a hollow copper tube. According to this first variant, the hollow copper tube may have a thickness ranging from about 100 μm to about 210 μm, and preferably from about 120 μm to about 195 μm. When the thickness is less than 100 μm, the elongated electrically conductive element may have insufficient mechanical strength. When the thickness is greater than 210 μm, the elongated electrically conductive member may exhibit an increased skin effect and the loss in mass becomes negligible. Thus, with respect to an elongated electrically conductive element made of solid copper (ie non-hollow) or an elongated electrically conductive element comprising a core of steel or aluminum covered with a layer of copper, the hollow copper tube presents the advantage of having a decreased weight (loss in mass of at least 8%) and a decreased cost. Moreover, it makes it possible to avoid the galvanic corrosion that may be encountered when the elongated electrically conductive element comprises a core of steel or aluminum covered with a copper layer, induced by the difference in galvanic potential between the copper and aluminum or copper and steel. Galvanic corrosion generally occurs in the event of a penetrating wound on the surface of the elongated electrically conductive element and / or on the end of the elongated electrically conductive element in the presence of moisture.

According to a second variant, the metal element of the elongated electrically conductive elements is a steel core and a copper layer surrounds said steel core. According to this second variant, the copper layer surrounding the steel core may have a thickness ranging from about 110 μm to about 190 μm.

When the thickness is less than 110 μm, the elongated electrically conductive element may have a linear resistance greater than 95 ohm / km, inducing heating of the cable and degradation of the transmission of energy. When the thickness is greater than 190 μm, the elongate electrically conductive member may exhibit an increased skin effect and the gain in strength becomes negligible. Thus, when the elongated electrically conductive element comprises a steel core covered with a copper layer, it has excellent breaking strength, that being about 1.5 times greater than that of an elongated electrically conductive element. solid copper only. The use of a steel core is particularly advantageous, especially when a large pulling force (ie greater than the breaking limit of the elongated electrically conductive element) must be applied to the elongated electrically conductive element during the first phase. installation of the communication cable, thereby avoiding any risk of damaging said elongated electrically conductive element.

According to a third variant, the metal element of the elongated electrically conductive elements is an aluminum core and a copper layer surrounds said aluminum core. According to this third variant, the copper layer surrounding the steel core may have a thickness ranging from about 70 μm to about 140 μm. When the thickness is less than 70 μm, the elongate electrically conductive element may have a linear resistance greater than 95 ohm / km, inducing heating of the cable and degradation of the transmission of energy. When the thickness is greater than 140 μm, the elongate electrically conductive member may exhibit an increased skin effect and the loss in mass becomes negligible. Thus, when the elongated electrically conductive member comprises an aluminum core coated with a copper layer, it has the advantage of having a decreased weight (mass loss of at least 15%) and a decreased cost per relative to a solid elongated electrically conductive element solely of copper. The communication cable of the invention may further comprise between the electrically insulating sheath and the plurality of twisted pairs of elongated electrically conductive elements insulated from each other, a first metal screen. Then, the electrically insulating sheath surrounds the first metal screen, and said first metal screen surrounds the plurality of twisted pairs of elongate electrically conductive elements insulated from each other. This first metal screen may be a so-called "wired" screen composed of a set of copper or aluminum conductors, a so-called "ribbon" screen composed of one or more conductive metal strips of copper or aluminum placed ) optionally helical, or a so-called "waterproof" screen type metal tube optionally composed of lead or lead alloy. This last type of screen makes it possible in particular to provide a moisture barrier that tends to penetrate the electric cable in a radial direction.

Said first metal screen is preferably made of aluminum. All types of metal screens can act as grounding of the cable and can thus carry fault currents, for example in the event of a short-circuit in the network concerned.

In a particular embodiment, said first metal screen is a ribbon screen composed of an outer ribbon of aluminum and an inner ribbon of aluminum and polyester. The communication cable of the invention may further comprise a second metal screen surrounding each of the twisted pairs of elongated electrically conductive members insulated from each other, said second metal screen having the same definition as that of the first metal screen. The communication cable of the invention may further comprise a star ring for separating the twisted pairs. Said star ring is preferably made of plastic. When the metallic element of the electrically conductive elements of the communication cable of the invention is a steel core (respectively an aluminum core) covered with a layer of copper (second and third variants), it does not preferably comprise of intermetallic diffusion layer between the copper layer and the steel core 20 (respectively the aluminum core). This intermetallic diffusion layer can be formed during the production of the electrically conductive elements and results from the diffusion of the iron atoms of the steel core (respectively aluminum atoms of the aluminum core) in the copper layer. . The absence of an intermetallic diffusion layer in the elongated electrically conductive elements of the cable of the invention makes it possible to improve the quality of the signal transmission, the resistance to overheating and the mechanical properties (eg when bending) of said cable. The invention also relates to a method of manufacturing a cable as defined in the first and second variants of the first subject of the invention, said method comprising at least: i) a step of preparing at least two elongated electrically conductive members insulated from each other comprising at least one wire sub-step i-1) of two blank wires comprising a steel core and a copper layer surrounding said steel core or an aluminum core and a layer of copper surrounding said aluminum core, ii) a step of twisting said elongated electrically conductive elements insulated from each other to obtain at least one twisted pair, and iii) a step of applying the electrically insulating sheath around said at least one pair twisted, in particular by extrusion, said method being characterized in that step i) of preparing at least two elongated electrically conductive elements Isolated from each other further comprises, after the sub-step i-1) of drawing, a sub-step i-2) of heat treatment with the aid of an electric current of the drawn strands 15. The sub-step i-1) of drawing makes it possible to obtain an electrically conductive element with the desired shape and dimensions. Sub-step i-2) of heat treatment makes said electrically conductive member more flexible and provides an elongation of at least about 8%. Sub-step i-2) can provide an elongation of at most about 20%, and preferably at most about 35%. Moreover, the inventors of the present application have discovered that the sub-step i-2) of heat treatment with the aid of an electric current (also called joule annealing sub-step) makes it possible to avoid the intermetallic diffusion of aluminum and steel in the copper layer, and thus to obtain a cable having a better quality of signal transmission, and better resistance to heating and folding. Indeed, the examples of the present application which will be described below show that when the heat treatment is carried out in a conventional furnace, a diffusion of iron atoms of the steel core or aluminum atoms of the Aluminum core in the copper layer occurs, which has the effect of decreasing the electrical resistivity of the copper and thus, degrade the signal transmission. In a particular embodiment, the diameter of the blank wires 5 is from about 1.8 mm to about 15 mm. When the diameter of the roughing wires is approximately 1.8 to 2.7 mm, the step i) for preparing the elongate electrically conductive elements comprises a sub-step i-1) of drawing and a sub-step i- 2) heat treatment using an electric current, these two substeps 10 being sufficient to obtain said elongated electrically conductive elements with the desired shape and dimensions and an elongation of at least about 8%. When the diameter of the roughing wires is from 2.71 to 15 mm, the step i) of preparing the electrically conductive elements may comprise several sub-steps of wire drawing and heat treatment using an electric current. to obtain said elongate electrically conductive elements with the desired shape and dimensions and an elongation of at least about 8%. The Joule annealing step (sub-step i-2)) is to heat the drawn wire by imposing an electric current. To do this, the drawn roughing wire 20 is placed between two frets (specific pulleys for the reefs) distant of a variable length which depends on the apparatus used. A voltage difference is then applied between these two frets. The applied voltage can range from about 1 to about 50 volts. Step i) may further comprise after heat treatment sub-step i-2), a sub-step i-3) of insulation of the heat-treated drawn and drawn strands to form at least two elements. Electrically elongated conductors isolated from each other. When step ii) makes it possible to form several twisted pairs, the method may furthermore comprise, between steps ii) and iii), a step ii-1) of assembling said twisted pairs.

Other features and advantages of the present invention will appear in light of the examples which follow with reference to the annotated figures, said examples and figures being given for illustrative and not limiting.

Figure 1 schematically shows a structure of a twisted pair of a communication cable according to the invention. Figure 2 schematically shows a structure, in cross-section, of an elongated electrically conductive element isolated from a twisted pair of a communication cable according to the invention.

Figure 3 schematically shows a structure, in cross section, of a communication cable according to the invention. FIG. 4 represents a view, using an optical microscope sold under the trade name Nikon Epiphot, in cross section, of an electrically conductive element of a communication cable manufactured according to the process according to the invention (FIG. 4a), and an electrically conductive element of a communication cable manufactured according to a method of the prior art (FIG. 4b). For the sake of clarity, the same elements have been designated by identical references. Likewise, only the essential elements for the understanding of the invention have been shown schematically, and this without respect of the scale. FIG. 1 represents a twisted pair of elongated electrically conductive elements 1 insulated from one another by an electrically insulating layer 2, of a communication cable according to the invention. FIG. 2 shows one of the electrically conductive elements isolated from the twisted pair of FIG. 1, seen in cross-section. It comprises a conductive core 1-1 made of steel or aluminum, and a copper layer 1-2 surrounding said steel or aluminum core. The thickness of the copper layer is indicated by the arrow and the reference e.

FIG. 3 represents a communication cable according to the invention, comprising four twisted pairs of elongated electrically conductive elements 1, each of the elongated electrically conductive elements 1 being isolated by means of an electrically insulating layer 2, said four twisted pairs being surrounded by a metal screen 3, and said metal screen 3 being surrounded by an electrically insulating sheath 4. Examples Example 1: Characteristics of a cable according to the first subject of the invention comprising hollow copper tubes as elongated electrically conductive elements Table 2 below shows, according to the category of the cable (5E, 6, 6A, 7 or 7A), the dimensional characteristics of the hollow copper tube as an elongated electrically conductive element of the invention: outer diameter (Dext), inner diameter (Dint) , thickness of copper (e), the mass characteristics of the hollow copper tube : linear density, loss in mass with respect to a solid electrically conductive element only in copper, and the electrical characteristics of the hollow copper tube: linear resistance (FIL). TABLE 2 Category of Dext Dint cable RL Linear Loss (mm) (mm) (mm) (ohm / km) (kg / km) by mass (%) Cat. 5E 0.511 0.146 0.182 91.02 1.6729 9 Cat. 6 0.541 0.216 0.163 87.95 1.7312 16 Cat. 6A 0.56 0.245 0.158 85.33 1.7843 19 Cat. 7 0.562 0.267 0.147 89.28 1.7054 23 Cat. 7A 0.598 0.328 0.135 86.93 1.7516 Thus, the cables of the invention comprise a thickness of the copper (e) sufficient to have a linear resistance of less than 95 ohm / km, and this thickness (e) also makes it possible to guarantee the transport of the surface current of the elongated electrically conductive element since it is always greater than the minimum penetration depth of copper at 1 MHz which is 66 i..tm whatever the category of the cable of the invention. Finally, the cables have a loss in mass ranging from 9 to 30% relative to a solid electrically conductive elongated element only copper. Example 2: Characteristics of a cable according to the first subject of the invention comprising aluminum cores coated with a copper layer as elongated electrically conductive elements Table 3 below shows, according to the category of the cable (5E, 6, 6A, 7 or 7A), the dimensional characteristics of the elongated electrically conductive element of the invention (ie aluminum core covered with a copper layer): outer diameter (Dext), inside diameter (ie diameter of the core aluminum) (Dint), thickness of the copper (e), the mass characteristics of the elongated electrically conductive element: linear density, loss in mass with respect to a solid electrically conductive element only in copper, and the electrical characteristics of the elongated electrically conductive element: linear resistance (R [).

TABLE 3 Dext Dint e RL cable category Mass Mass loss (mm) (mm) (mm) (ohm / km) linear (%) (kg / km) Cat. 5E 0.511 0.252 0.129 92.11 1.5119 17 Cat. 6 0.541 0.370 0.086 89.92 1.3892 32 Cat. 6A 0.56 0.406 0.077 86.62 1.3917 37 Cat. 7 0.562 0.408 0.077 86.06 1.3995 37 Cat. 7A 0.598 0.443 0.078 76.48 1.5549 38 Thus, the cables of the invention comprise a thickness of the copper (e) sufficient to have a linear resistance of less than 95 ohm / km, and this thickness (e) also makes it possible to guarantee the transport of the surface current of the elongated electrically conductive element since it is always greater than the minimum penetration depth of copper at 1 MHz which is 66 i..tm whatever the category of the cable of the invention. Finally, the cables have a mass loss ranging from 17 to 38% with respect to a solid electrically conductive elongated element solely made of copper. By way of comparison, the dimensional, mass and electrical characteristics of an elongated electrically conductive element of the prior art sold under the trade name CCA15% by the company FushiCopperweld or the company Commscope, comprising an aluminum core covered with a layer of Copper and used in Category 5E, 6, 6A, 7 and 7A cables of the prior art are listed in Table 4 below: TABLE 4 Loss Class Dem Dint RL en of the cable (mm) (mm) (mm) (ohm / km) linear mass (kg / km) (%) Cat. 5E (*) 0.511 0.471 0.0200 106.37 0.851 53 Cat. 6 (*) 0.541 0.497 0.0220 94.11 0.967 53 Cat. 6A (*) 0.56 0.515 0.0224 88.15 1.0306 53 Cat. 7 (*) 0.562 0.517 0.0225 87.51 1.0383 53 Cat. 7A (*) 0.598 0.520 0.0390 67.7 1.4545 42 (*) Cable not forming part of the invention Table 4 shows that the cables of the prior art (categories 5E and 6) do not have a thickness (e) sufficient to have a linear resistance of less than 95 ohm / km, and this thickness (e) also does not guarantee the transport of current on the surface of the elongated electrically conductive element since it is always lower at the minimum penetration depth of copper at 1 MHz which is 66 lm regardless of the category of the cable.

Example 3: Characteristics of a cable according to the first subject of the invention comprising copper-coated steel cores as elongated electrically conductive elements Table 5 below shows according to the category of the cable (5E , 6, 6A, 7 or 7A), the dimensional characteristics of the elongate electrically conductive element of the invention (ie steel core coated with a copper layer): outer diameter (Dext), inner diameter (ie diameter of the steel core) (Dint), copper thickness (e), and the electrical and mechanical characteristics of the elongated electrically conductive element: linear resistance (R [), mechanical strength (R), gain in strength with respect to a solid electrically conductive element only of copper. TABLE 5 Category of Dext Dint cable RL R, Gain (mm) (mm) (ohm / km) (MPa) in force (%) Cat. 5E 0.511 0.158 0.177 90.02 322 41 Cat. 6 0.541 0.231 0.155 87.49 407 77 Cat. 6A 0.56 0.262 0.149 84.68 442 92 Cat. 7 0.562 0.285 0.138 87.86 480 108 Cat. 7A 0.598 0.349 0.124 85.10 562 143 Thus, the cables of the invention comprise a copper thickness (e) sufficient to have a linear resistance of less than 95 ohm / km, and this thickness (e) also makes it possible to guarantee the transporting current at the surface of the elongate electrically conductive element since it is always greater than the minimum penetration depth of copper at 1 MHz which is 66 i..tm regardless of the category of the cable of the invention. Finally, the cables have a gain in strength ranging from 41 to 143% compared to a solid elongated electrically conductive element only copper. By way of comparison, the dimensional and electrical characteristics of an elongate electrically conductive element of the prior art sold under the trade name CCS40`) 01ACS by the company FushiCopperweld or the Commscope company comprising a copper coated steel core. and used in prior art Category 5E, 6, 6A, 7 and 7A cables are listed in Table 6 below: TABLE 6 Gain Category Dext Dint e RL R, Cable en (mm) (mm) ) (mm) (ohm / km) (MPa) force (%) Cat. 5E (*) 0.511 0.409 0.0511 136.30 903.60 393 Cat. 6 (*) 0.541 0.433 0.0541 121.60 903.60 393 Cat. 6A (*) 0.56 0.448 0.0560 113.49 903.61 393 Cat. 7 (*) 0.562 0.450 0.0562 112.68 903.61 393 Cat. 7A (*) 0.598 0.478 0.0598 99.52 903.61 393 (*) Cable not forming part of the invention Table 6 shows that the cables of the prior art do not have a sufficient thickness (e) to have a linear resistance less than 95 ohm / km, and this thickness (e) also does not guarantee the transport of the current on the surface of the elongated electrically conductive element since it is always less than the minimum penetration depth copper at 1 MHz which is 66 i..tm whatever the category of the cable.

As a reference, Table 7 below presents, according to the category of the cable (5E, 6, 6A, 7 or 7A), the dimensional characteristics of the elongated electrically conductive solid element in copper only: external diameter (Dext), the mass characteristics of the solid elongated electrically conductive element in copper only: linear density, and the electrical and mechanical characteristics of the elongated electrically conductive solid copper element only: linear resistance (R [) and mechanical resistance (Rm).

TABLE 7 Dext Mass category RL R, cable (mm) linear (ohm / km) (MPa) (kg / km) Cat.

5E (*) 0.511 1.8293 83.27 230 Cat. 6 (*) 0.541 2.0505 74.29 230 Cat.

6A (*) 0.56 2.1970 69.33 230 Cat. 7 (*) 0.562 2.2127 68.84 230 Cat.

7A (*) 0.598 2.5053 60.80 230 (*) Cable not forming part of the invention The values of mass density and mechanical strength made it possible to determine the loss in mass when the elongate electrically conductive element is a hollow copper tube and when the elongate electrically conductive member is an aluminum core covered with a copper layer with respect to a solid elongated electrically conductive element made of copper only (Examples 1 and 2 respectively); and the gain in strength when the elongated electrically conductive member is a copper-coated steel core with respect to a solid elongated copper-only electrically conductive member (Example 3). Example 4: Manufacture of an Elongated Electrically Conductive Element According to Step i) of the Process According to the Invention A 30 mm outer diameter roughing wire comprising an aluminum core and a copper layer surrounding said aluminum core was drawn according to sub-step i-1) to form a drawn extruded wire of approximately 1.8 mm outside diameter. Then, the drawn extruded wire was annealed by the Joule effect according to sub-step i-2) by passing said wire between two frets about 1.5 meters apart, and imposing a voltage on it. about 20 volts. The speed of passage of the drawn wire between the two frets was of the order of 10 meters / second. An elongated electrically conductive member according to the invention has thus been obtained. Figure 4a shows a cross-sectional view through microscopy (magnification × 400) of the wire obtained at the end of the process of the invention. FIG. 4a shows that said wire does not comprise an intermetallic diffusion layer. For comparison, a 30 mm outer diameter blank wire comprising an aluminum core and a copper layer surrounding said aluminum core was drawn to form a drawn wire of approximately 1.8 mm outside diameter. Then, the drawn wire was annealed in the oven at a temperature of about 300 ° C for 3 hours. An elongated electrically conductive element not in accordance with the invention has thus been obtained. FIG. 4b shows a microscopic view (magnification x 400), in cross-section, of the wire obtained at the end of the process not according to the invention. FIG. 4b shows that said wire comprises an intermetallic diffusion layer having a thickness of approximately 4 μm.

Claims (12)

REVENDICATIONS1. A communication cable comprising: - a plurality of twisted pairs of elongated electrically conductive members insulated from each other, and - an electrically insulating sheath surrounding said plurality of twisted pairs of elongated electrically conductive members insulated therebetween, said elongated electrically conductive members, identical, being chosen from any one of the following metallic elements: an aluminum core and a copper layer surrounding said aluminum core, a steel core and a copper layer surrounding said steel core, and a hollow copper tube, said copper layer or said hollow copper tube having a copper thickness greater than or equal to the copper penetration depth at 1 MHz which is 66 μm, said communication cable being characterized in that said copper thickness is sufficient to have a linear resistance less than or equal to 95 ohm / km. 20 2. Cable according to claim 1, characterized in that it complies with dimensional standards of the industry for at least one of the cables of category 5E, 6, 6A, 7 and 7A. Cable according to claim 1 or claim 2, characterized in that each of the elongate electrically conductive elements is insulated by means of an electrically insulating layer comprising at least one polymeric material. 4. Cable according to claim 3, characterized in that the polymeric material is selected from polyethylene (PE), polypropylene (PP), fluorinated ethylene propylene copolymer (FEP), ethylene and tetrafluoroethylene copolymer (ETFE). ), fluorinated ethylene-propylene terpolymer (EFEP), polytetrafluoroethylene (PTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), tetrafluoroethylene-perfluoromethylvinylether copolymer (MFA), copolymer of tetrafluoroethylene and perfluoropropylvinylether (PFA), polyphenylene oxide (PPO), polyphenylene sulphide (PPS), polyetheretherketone (PEEK), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyamide (PA) , polyetherimide (PEI), polyurethane (PU), thermoplastic elastomers (TPE), and crosslinked thermoplastics (TPV). Cable according to any one of the preceding claims, characterized in that the electrically insulating sheath surrounding the plurality of twisted pairs of elongate electrically conductive elements is made from suitable thermoplastic materials or materials which retard the propagation of the flame or resistant to the propagation of the flame. 6. Cable according to any one of the preceding claims, characterized in that it comprises four twisted pairs of elongate electrically conductive elements insulated from each other. Cable according to any one of the preceding claims, characterized in that each of the elongated electrically conductive elements has an outer diameter ranging from 0.45 to 0.7 mm. 8. Cable according to any one of the preceding claims, characterized in that the metal element of the elongated electrically conductive elements is a hollow copper tube and the hollow copper tube has a thickness ranging from 100 i..tm to 210 iim . 25 Cable according to any one of claims 1 to 7, characterized in that the metal element of the elongated electrically conductive elements is a steel core and a copper layer surrounds said steel core, and the copper layer surrounding the steel core has a thickness ranging from 110 i..tm to 190 i..tm. 30 Cable according to any one of claims 1 to 7, characterized in that the metallic element of the elongated electrically conductive elements is an aluminum core and a copper layer surrounds said aluminum core, and the copper layer surrounding the Steel core has a thickness ranging from 70 μm to 140 μm. Cable according to claim 9 or claim 10, characterized in that it does not include an intermetallic diffusion layer between the copper layer and the steel or aluminum core. 12. A method of manufacturing a cable as defined in claim 11, said method comprising at least: i) a step of preparing at least two elongate electrically conductive elements insulated from each other comprising at least one substep i -1) of drawing two blanks comprising a steel core and a copper layer surrounding said steel core or an aluminum core and a copper layer surrounding said aluminum core, ii) a step of twisting said elements electrically elongate conductors insulated together to obtain at least one twisted pair, and iii) a step of applying the electrically insulating sheath around said at least one twisted pair, said method being characterized in that step i) of Preparation of at least two elongate electrically conductive elements insulated from each other further comprises, after the drawing sub-step i-1), a line sub-step i-2). thermally by means of an electric current of the drawn roughing wires.