WO2006128633A1

WO2006128633A1 - Electrically conductive elastic composite yarn

Info

Publication number: WO2006128633A1
Application number: PCT/EP2006/005008
Authority: WO
Inventors: Pol Speleers
Original assignee: Nv Bekaert Sa
Priority date: 2005-06-02
Filing date: 2006-05-24
Publication date: 2006-12-07
Also published as: US20080282665A1; SI1885925T1; EP1885925A1; EP1885925B1; DE602006017360D1; CN101180423B; CN101180423A; ATE483835T1

Abstract

An electrically conductive elastic composite yarn comprises at least one elastic member having a ratio N being drafted length Ld over relaxed length Lr1 N being in the ränge of 1 to 10. The yarn further comprises more than one metal filament wrapped around the elastic member. The yarn is characterized in that each of the metal filaments is twisted with at least one other of the metal filaments.

Description

ELECTRICALLY CONDUCTIVE ELASTIC COMPOSITE YARN Background

The present invention relates to an electrically conductive elastic composite yarn, and a textile product comprising such yarn. The invention further relates to the use of such textile products.

Metal fibers and especially metal filaments are known as elements of an electrically conductive yarn. As an example, an electrically conductive yarn is used as a thermal fuse in US5927060, or for evacuation of electrostatic charges build up in a textile fabric such as described in US3288175.

Electrically conductive elastic composite yarns are known from WO2004/097089. This document, upon which the preamble of the present first claim is based, describes electrically conductive elastic composite yarns comprising at least one elastic member having a ratio N, this is the drafted length Ld over relaxed length Lr of this elastic member, being in the range of 1 to 8. This yarn may comprise more than one metal filament wrapped around the elastic member. The metal filaments have a length which is at least equal to the drafted length of the elastic member. The yarn has the advantage that, when being subjected to elongation, the metal filaments are not subjected to tensile stress.

The yarn may however suffer from some disadvantages. Because of the very large length of metal filaments in the yarn per linear meter of yarn, the metal filaments are very likely not to be in contact with the outer surface of the elastic member. Because of this, the metal filament has the liberty to displace randomly around the elastic member when the latter is not under tension. When this yarn is used to provide a textile product, some metal filament loops may tend to stick out of the textile product due to random deformation of the metal filaments. This phenomenon usually occurs when the textile product was stretched repetitively.

This freedom of movement of the metal filaments may as well cause some minor changes in electrical properties of the yarn, because after each stretching of the textile, in casu the yarn, there may occur a different number of contacting points between adjacent loops of the same filament, or between several filaments used to provide the same yarn.

The fact that metal filaments may lose contact with the underlying elastic member, may as well cause more frequent filament ruptures, or may disturb the production of the textile fabric in which the yarn is used, or may disturb the use of the textile product because of filaments pointing out of the surface of the textile product. The fact that the metal filaments are making contact with the underlying elastic member, may increase drastically the so-called flexlife of the electrically conductive elastic composite yarn.

Summary Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.

An aspect of the claimed invention provides an electrically conductive elastic composite yarn. An aspect of the present invention provides an electrically conductive elastic composite yarn which has stable electrical conductive properties over life time when repetitively stretched to a large extent. An aspect of the present invention provides an electrically conductive elastic composite yarn which can be repetitively stretched to a large extent, meanwhile not having metal filaments buckling out of the yarn or the textile product in which it is used. Another aspect of the present invention provides an electrically conductive elastic composite yarn of which the electrical resistance is easy to calculate. Another aspect of the present invention provides an electrically conductive elastic composite yarn which is easy to use for providing textile products such as woven, braided or knitted textile products, and garments comprising such textile products comprising an electrically conductive elastic composite yarn as subject of the invention.

A further aspect of the present invention provides a textile product comprising an electrically conductive elastic composite yarn, and a garment comprising a textile product comprising an electrically conductive elastic composite yarn.

A further aspect of the present invention provides a textile product and a garment, which has been incorporated in this product or garment, an electrically conductive elastic composite yarn serving as an operational safe antenna or resistive heating element, having stable and predictable electrical properties and a very high so-called flexlife.

An embodiment of the invention provides an electrically conductive elastic composite yarn having the features as set out in the characterizing portion of present claim 1. Use of such electrically conductive elastic composite yarn provides a textile product and/or a garment, wherein such electrically conductive elastic composite yarn is used e.g. as an antenna. Advantageous embodiments are set out in the dependent claims. Surprisingly, it was found that the fact that for each metal filament in the yarn, the metal filaments being twisted with at least one other metal filament reduces the risk on metal filaments displacing relatively freely during cycles of stretching and relaxing the yarn. Within the yarn substantially all of an elongating stress imposed on the composite yarn is carried by the elastic member. This is because the conductive covering filaments have a length that is at least equal to the drafted length of the elastic member. All of this results in electrical properties of the electrically conductive elastic composite yarn which are predictable at the start, and remain unchanged during repetitive stretching and relaxing cycles of the yarn. As the number of contacting points between the twisted filaments remain unchanged during stretching, and as, in case of more than two groups of twisted filaments being wound around the same elastic member, preferably in opposite direction, the number of contacting points between the groups of filaments remain unchanged during stretching and no significant deviation of electrical properties of the yarn is noticed.

The twisted filaments, or alternatively more than one group of twisted filaments, are wrapped around an elastic member.

The drafted length Ld of the elastic member is defined to be that length to which the elastic member may be stretched and return to within five per cent (5%) of its relaxed (stress free) unit length L.

The ratio N of the elastic member is defined as drafted length Ld over relaxed length Lr. For yarns as subject of the invention, N is in the range of 1 to 10, more preferably in the range 1.5 to 5, or even more preferred in the range 1.5 to 3.

Preferably this elastic member is provided out of elastic polymer or natural or artificial rubber.

As an example, polyurethane may be used. The elastic member may e.g. comprise only one elastic filament, or may comprise a number of elastic filaments, possibly twined to each other.

The filaments are metal filaments preferably having an equivalent diameter D being equal or more than 1 μm, and less or equal to 150μm. More preferred, the equivalent diameter ranges from 6μm to 65μm

The metal filaments used to provide a yarn as subject of the invention preferably comprises copper or copper-alloy, nickel or nickel-alloy, aluminium or aluminium-alloy, silver or silver alloy or steel such as stainless steel. Possibly each filament is provided out of a core metal, encompassed by one or more metal layers. As an example each filament may comprise a steel core such as a low carbon steel core being provided with a layer of an other metal, preferably a metal being more electrically conductive than the core, such as a copper-layer or a copper-alloy layer, an aluminium layer or an aluminium-alloy layer, a silver or a silver-alloy layer, a tin or a tin alloy layer. The layer is preferably provided by cladding. One can also provide an outer layer which leads to an improved resistance to galvanic corrosion because of e.g. sweat or salt liquids, such as a metal layer comprising nickel or a nickel-alloy, titan or a titan-alloy, silver or a silver-alloy or such as a polymer layer.

Most preferred, the metal filaments are provided by a metal fiber bundle drawing operation. The metal filaments, which obtain in that case a substantially polygonal, usually penta- or hexagonal cross section, are characterized by an equivalent diameter, which is the diameter of an imaginary circle, having the same surface area as the average surface area of a radial cross section of the metal filament.

According to the present invention, each of the metal filaments is twined with at least one other of the metal filaments of the yarn as subject of the invention. The total number of filaments used to provide a yarn as subject of the invention is preferably in the range of 2 to 1000. Possibly the metal filaments of the yarn as subject of the invention could be grouped in at least two groups of metal filaments, which metal filaments of each of said groups are twisted with each other. It was found that preferably each of said groups comprises M metal filaments, for which M being at least 2 and preferably less or equal than 550. More preferred, M ranging from 2 to 280 such as 2, 9, 10, 50, 125 or 275.

As at least 2 and preferably more than 2 metal filaments are used, which are twisted to each other, the yarn, when subjected to a stretching operation, is less vulnerable to filament ruptures, because of the twisting of the filaments. The tension which may be imposed on the metal filaments, are not to be born by only one metal filament, but are substantially equally divided amongst all the filaments present. An additional advantage is that, in case one filament is broken, the electrical properties of the yarn itself is few or not influenced due to the numerous contacts between the filaments being twisted together, and between the different groups of filaments in case such different groups are present. It was found that the electrical properties of the yarn are not influenced as long as not more than 80% of the filaments are broken. It was found that for each representative section of the yarn as subject of the invention having a relaxed length S, preferably the shortest metal filament in this section has a length F for which F being larger or equal to S, and F being smaller or equal to 5^*S, more preferred smaller than 3.5^*S. Further it was found that for each representative section of the yarn as subject of the invention having a relaxed length S, preferably the length of each of the metal filaments in this section is smaller or equal to 3^*S.

Each of the metal filaments is twisted with at least one other metal filament. Preferably a number of turns per meter between 10 and 200 is used.

Possibly at least two groups of metal filaments, which filaments are twisted with each other, are used to provide a yarn as subject of the invention. It was found that when at least two groups of metal filaments are present, the number of contacting points between the groups of filaments remain unchanged during stretching, resulting in no significant deviation of electrical properties of the yarn. This was especially the case when at least one group is wrapped around the elastic member in a first direction, whereas at least one of the other groups of metal fibers is wrapped in the opposite direction around the elastic member. This also contributes to a reduction of the liveliness of the yarn as subject of the invention. Possibly the groups of metal filaments are provided around the elastic member by braiding, which is also to be understood as wrapping in the spirit of the present invention.

In order to further reduce the liveliness of the yarn as subject of the invention, so providing a yarn which is more suitable and easy to process in textile production processes such as braiding, weaving or knitting, preferably the direction of twisting is opposite to the direction used to wrap the group of fibers around the elastic element.

Most preferred, the number of groups of filaments being wrapped in on direction around the elastic member, say the S-direction, is equal to the number of groups of filaments being wrapped in the opposite, say the Z-direction around the elastic member. Possibly a group of metal filaments comprises two or more subsets, each subset comprising at least two metal filaments being twisted with each other. The subsets are then twined with each other in order to provide the group of metal filaments, which on its turn is wrapped around the elastic member.

The number of turns per linear meter of relaxed yarn of the filaments wrapped around the elastic member, or in case of more than one group of metal filaments, the number of turns per linear meter of relaxed yarn of each of the groups wrapped around the elastic member is preferably between 150 and 1400. The numbers or turns per linear meter of yarn may be equal for each of the groups of metal filaments in case the yarn comprises more than one group of metal filaments.

According to the present invention, the electrically conductive elastic composite yarn as subject of the invention may be used to provide a textile product, e.g. a braided, woven or knitted textile product. The electrically conductive elastic composite yarn has the advantage that there are few or no metal filaments pointing out of the yarn, which enabled a smooth and trouble free incorporation of the yarn in the textile product.

Preferably, the electrically conductive elastic composite yarn is used to provide an elastic tape like woven fabric, in which the electrically conductive elastic composite yarn is present as a warp element. Possibly, the woven tape is woven so-to-say around the electrically conductive elastic composite yarn, which are present as non interwoven warp elements in a pocket. The other warp elements may comprise elastic yarns as well.

A tape-like woven structure with incorporated electrically conductive elastic composite yarns as subject of the invention may so be obtained. It was found that such tapes, when subjected to repetitive elongation, has no tendency to show metal filaments sticking out of the surface of the woven textile product.

A similar property was found for braided and knitted textile products.

The textile product as subject of the invention may have an elongation at rupture in the range of 100% to 400%, more preferred in the range of 200% to 350%. This elongation is measured by subjecting a textile sample with a given length to an elongation until rupture of one of the yarns comprised in the fabric. The length at rupture divided by the length of the textile fabric prior to elongation, and expressed in percentages is understood as the above-mentioned elongation at rupture.

It was found that the textile product may be used to provide a garment, wherein the electrically conductive elastic composite yarn, incorporated in the textile product, is used as e.g. an antenna. It was found that preferably a electrically conductive elastic composite yarn, being present in a loop shape in the garment, may function very well as a loop antenna. Especially tape-like woven textile products are suitable for such use. By integrating the electrically conductive elastic composite yarn into a woven tape and by connecting the two ends of the yarn, by means of e.g. electrical conductive snap fasteners, this tape could work as loop antenna when worn around e.g. the body of a person.

Alternatively, the textile product comprising an electrically conductive elastic composite yarn as subject of the invention may function as a heatable textile product, wherein the electrically conductive elastic composite yarn functions as a resistive heating element. For the intended applications, the textile product may be part of a garment. Especially garments being seat upholstery, e.g. car seat upholstery, benefits from the stable and reliable electrical properties of the yarn as subject of the invention under any stretched condition. Further it was noticed that the so-called flex-life of the resistive element was significantly improved. Flex-life is to be understood as the resistance to rupture of the yarn under repetitive bending conditions. As an alternative, the textile product or the yarn as subject of the invention itself may be part of a heating device which is integrated in the car seat as such, usually between the foamed part of the seat and the upholstery.

As further alternative used, the yarn as subject of the invention or a textile product as subject of the invention may be used as part of an electrode for detection and/or measuring the presence of body liquids such as sweat or urine, or as a part of a sensor for measuring and detecting hart beat or respiration monitoring.

As further alternative, the yarn as subject of the invention or a textile product as subject of the invention may be used as leadwire which connects different electronic devices to each other such as batteries, PCB's, monitoring devices.

Brief description of the drawings

The invention will now be described hereinafter, by way of example only, with reference to the accompanying drawings wherein

• FIGURE 1 , FIGURE 2, FIGURE 3, FIGURE 4 and FIGURE 5 show schematically a yarn in accordance with examples of the invention; • FIGURE 6 shows schematically a tape-like woven structure in accordance with an example of the invention;

• FIGURE 7 shows schematically a garment comprising a textile product in accordance with an example of the invention;

• FIGURE 8 shows schematically a car seat comprising a textile product in accordance with an example of the invention as resistance heating element. Description of the particular embodiments

FIGURE 1 shows schematically a yarn 101 in accordance with an example of the invention, which yarn comprises an elastic member 110, which is wrapped with mutually twisted metal filaments, together indicated 120. As an example, elastic member 110 is a natural rubber filament, whereas the metal filaments 120 comprise 275 filaments of alloy stainless steel AISI 316L, and having an equivalent diameter of 12μm. They are twisted to each other using 100 turns per meter in Z direction, and subsequently are wrapped in S direction around the elastic member 110 using 1100 turns per meter. The ratio N of drafted length Ld over relaxed length Lr of the elastic member is 1 ,4. For a relaxed length S being 100mm of the yarn 101 , the length of each of the filaments is substantially equal, thus is the same as the shortest length F of a metal filament. In this embodiment F is 140mm. The electrical resistance of this yarn 101 is 21 ohm/meter.

Alternatively, the metal filaments 120 comprise 90 filaments of alloy stainless steel AISI 316L, and having an equivalent diameter of 14μm. They are twisted with each other using 100 turns per meter in Z direction, and subsequently are wrapped in S direction around the elastic member 110 using 1000 turns per meter.

An alternative yarn 201 in accordance with an example of the invention is shown schematically in FIGURE 2. The yarn 201 comprises an elastic member 210, which is wrapped with two groups 221 and 222 of mutually twisted metal filaments. As an example, elastic member 210 is natural rubber filament, whereas each of the groups 221 and 222 of metal filaments comprises 550 filaments of alloy 316L having an equivalent diameter of 12μm. The first group 221 is twisted to each other using 175 turn per meter in S direction, and subsequently is wrapped in Z direction around the elastic member 210 using 1000 turns per meter. The second group 222 is twisted to each other using 175 turns per meter in Z direction, and subsequently is wrapped in S direction around the elastic member 210 using 1000 turns per meter.

The ratio N of drafted length Ld over relaxed length Lr of the elastic member 210 is 1 ,4. For a relaxed length S of 100mm of the yarn 201 , the length of each of the filaments either from the first group 221 or second group 222 is substantially equal, thus is the same as the shortest length F of a metal filament. In this case, F is 140mm. The electrical resistance of this yarn 201 is 10 ohm/meter. An alternative yarn 301 in accordance with an example of the invention is shown schematically in FIGURE 3. The yarn 301 comprises an elastic member 310, which is wrapped with eight groups 321 , 322, 323, 324, 325, 326, 327 and 328 of mutually twisted metal filaments. As an example, elastic member 310 is natural rubber filament, whereas each of the groups 321, 322, 323, 324, 325, 326, 327 and 328 of metal filaments comprises 550 filaments of alloy AISI 316L, and having an equivalent diameter of 12μm. The groups 221 , 323, 325 and 327 are twisted to each other using 175 turns per meter in S direction. The groups 322, 324, 326 and 328 are twisted to each other using 175 turns per meter in Z direction. The eight groups are then braided around the elastic member 310 in such a way that the groups 321 , 323, 325 and 327 follow substantially a path as if they would be wrapped in Z direction around the elastic member 310. The groups 322, 324, 326 and 328 follow substantially a path as if they would be wrapped in S direction around the elastic member 310. All groups 321 , 322, 323, 324, 325, 326, 327 and 328 make 1000 turns per meter of yarn. The ratio N of drafted length Ld over relaxed length Lr of the elastic member 310 is 1 ,5. For a relaxed length S of 100mm of the yarn 301 , the length of each of the filaments either from the groups 321 , 322, 323, 324, 325, 326, 327 and 328 is substantially equal thus is the same as the shortest length F of a metal filament. In this case, F is 150mm. The electrical resistance of this yarn 301 is 5 ohm/meter.

An alternative yarn 401 in accordance with an example of the invention is shown schematically in FIGURE 4. The yarn 401 comprises an elastic member 410, which is wrapped with two groups 421 and 422 of mutually twisted metal filaments. The elastic member 410 comprises more than one, e.g. three elastic monofilaments 411 , 412 and 413, being natural rubber filaments, whereas each of the groups 421 and 422 of metal filaments comprises 180 filaments of alloy 316L having an equivalent diameter of 14μm. The first group 421 is twisted around each other using 100 turns per meter in S direction, and subsequently is wrapped in Z direction around the elastic member 410 using 1000 turn per meter. The second group 422 is twisted around each other using 175 turns per meter in Z direction, and subsequently is wrapped in S direction around the elastic member 410 using 1100 turns per meter. The ratio N of drafted length Ld over relaxed length Lr of the elastic member 410 is 1 ,5. For a relaxed length S of 100mm of the yarn 401 , the length of each of the filaments either from the first group 421 or second group 422 is substantially equal thus is the same as the shortest length F of a metal filament. F is 150mm. The electrical resistance of this yarn 401 is 22ohm/meter. An alternative yarn 501 in accordance with an example of the invention is shown schematically in FIGURE 5. The yarn 501 comprises an elastic member 510, which is wrapped with two groups 521 and 522 of mutually twisted metal filaments. The elastic member 510 comprises more than one, e.g. three elastic monofilaments 511 , 512 and 513, being provided out of natural rubber, whereas each of the groups 521 and 522 of metal filaments comprises 7 filaments of copper clad steel, and having an equivalent diameter of 63μm. The first group 521 is twisted to each other using 60 turns per meter in Z direction, and is wrapped in Z direction around the elastic member 510 using 850 turns per meter. The second group 522 is twisted to each other using 60 turns per meter in Z direction, and is wrapped in S direction around the elastic member 510 using 700 turns per meter.

The ratio N of drafted length Ld over relaxed length Lr of the elastic member 510 is 3,0. For a relaxed length S of 100mm of the yarn 501 , the length of each of the filaments from the first group is the shortest length F of a metal filament, being 300mm. The electrical resistance of this yarn 501 is 5 ohm/meter.

Each of the above mentioned yarns in accordance with the examples of the invention may be used to provide a textile product. Such a textile product may, as an example, be a woven textile product 601 as schematically shown in FIGURE 6. The woven fabric 601 has a warp direction 610 and a weft direction 611. A number of elastic electrically conductive yarns 620 in accordance with an example of the invention are present as elements in warp direction 610. The woven fabric has substantially three zones, being two side zones 630 and 631, between which a pocket-like zone 640 is located. The yarns 620 are provided in the interior of the pocket-like zone. In order to make electrical contact with an electronic device with which the woven textile product is to be connected, two snap fasteners 650 are provided, preferably in stainless steel.

The elongation at rupture of the textile woven product is 310%

FIGURE 7 shows schematically a garment comprising a textile product in accordance with an example of the invention.

The garment, either e.g. a vest or as shown in FIGURE 7, a shirt 701 , may comprise one or more textile products 711 , 712, 713, 714 in accordance with examples of the invention for serving multiple purposes such as sweat detection, heart beat detection or monitoring, blood pressure measurement, or any other known application of electrically conductive textiles in garments. The textile products 711 , 712, 713, 714 may serve as well as an antenna for receiving or sending EM-waves. Preferably in this case, the textile products 711 , 712, 713 are used as they are provided in the shape of a loop antenna, since both ends of the tape, and both ends of the yarn in accordance with an example of the invention are approaching each other in such a way that the yarn or yarns are present according to a loop-shape. Preferably the textile products 711 , 712, 713, 714 are similar to the tape like woven fabric 601 as shown in FIGURE 6. The electronic device such as a transducer or receiver, is coupled to the two snap fasteners 650.

Alike, the garment being pants 702 may comprise a textile product 721 in accordance with an example of the invention comprising yarns in accordance with an example of the invention. Preferably the textile product 721 is similar to the tape like woven fabric 601 as shown in FIGURE 6. The textile product 721 may serve as well as a loop antenna for receiving or sending EM-waves. The electronic device such as a transducer or receiver, is coupled to the two snap fasteners 650, and in this case may easily be carried in the pocket 722 by the person wearing the pants. The snap fastener or alike coupling element may extend from the textile product 721 to the inner side of the pocket.

As an other alternative, the garment being a belt 703, may comprise a textile product 731 in accordance with an example of the invention comprising yarns in accordance with an example of the invention. Also in this case, the textile product 731 may be used as a loop antenna.

Another use is shown in FIGURE 8. A car seat 801 may be provided with a textile product 810 in accordance with an example of the invention, comprising yarns in accordance with an example of the invention serving as electrically heating yarns 812 by means of resistance heating. The yarns 812 in accordance with an example of the invention may be coupled to an electrical device providing the necessary current for use in the heatable textile, by means of two cables 813, each being coupled to an electrode 811 to which the yarns 812 are coupled. The electrodes 811 itself may as well comprise yarn in accordance with an example of the invention, being it with a smaller electrical resistance as the yarns 812.

The textile product 810 may be provided as a device being located between the foamed part 820 of the seat, or as an integrated part of the upholstery of the car seat.

An aspect of the invention can provide an electrically conductive elastic composite yarn which comprises at least one elastic member having a ratio N being drafted length Ld over relaxed length Lr, N being in the range of 1 to 10. The yarn further comprises more than one metal filament wrapped around the elastic member. The yarn is characterized in that each of the metal filaments is twisted with at least one other of the metal filaments.

Claims

1. An electrically conductive elastic composite yarn comprising at least one elastic member having a ratio N being drafted length Ld over relaxed length Lr₁ said N being in the range of 1 to 10, said yarn further comprising more than one metal filament wrapped around said at least one elastic member, said metal filament having a length that is equal to or greater than the drafted length Ld, characterized in that each of said metal filaments is twisted with at least one other of said filaments.

2. An electrically conductive elastic composite yarn as in claim 1 , wherein said metal filaments are wrapped around said at least one elastic member using a number of turns per meter of said yarn in the range of 150 turns per meter to 1400 turns per meter.

3. An electrically conductive elastic composite yarn as in any one of the claims 1 to 2, wherein said metal filaments are twisted in a direction of twist, said filaments are wrapped around said at least one elastic element in the opposite direction of said direction of twist.

4. An electrically conductive elastic composite yarn as in any one of the claims 1 to 3, wherein said yarn comprising at least a first group of metal filaments being twisted with each other and a second group of metal filaments being twisted with each other, said first group and said second group being wrapped around said at least one elastic member.

5. An electrically conductive elastic composite yarn as in any one of the claims 1 to 4, wherein said yarn comprising more than 2 groups of metal filaments being twisted with each other.

6. An electrically conductive elastic composite yarn as in any one of the claims 4 to 5, wherein said first group is wrapped around said at least one elastic element in S-direction, said second group being wrapped around said at least one elastic member in Z-direction.

7. An electrically conductive elastic composite yarn as in any one of the claims 4 to 6, wherein the number of groups being wrapped around said at least one elastic member in S-direction is equal to number of groups being wrapped around said at least one elastic member in Z-direction.

8. An electrically conductive elastic composite yarn as in any one of the claims 4 to 7, wherein each of said groups comprises a number of metal filaments M, said M being equal or more than 2, said M being less or equal to 550

9. An electrically conductive elastic composite yarn as in claim 8, wherein said M is identical number for each of said groups of metal filaments.

10. An electrically conductive elastic composite yarn as in any one of the claims 1 to 9, wherein said yarn comprises 1000 or less metal filaments.

11. An electrically conductive elastic composite yarn as in any one of the claims 1 to 10, wherein each of said metal filaments are twisted with at least one other of said filaments using between 10 and 200 turns per meter.

12. An electrically conductive elastic composite yarn as in any one of the claims 1 to 11 , wherein for each section of the yarn having a relaxed length S, the shortest of said metal filaments in said section having a length F, said F being equal or larger than S, said F being less or equal than 5^*S.

13. An electrically conductive elastic composite yarn as in any one of the claims 1 to 12, wherein for each section of the yarn having a relaxed length S, the length of each of said metal filaments is less or equal than 3*S.

14. An electrically conductive elastic composite yarn as in any one of the claims 1 to 13, wherein said N being in the range of 1.5 to 5.

15. An electrically conductive elastic composite yarn as in any one of the claims 1 to 14, wherein said at least one elastic element being a polyurethane member of a natural or artificial rubber member.

16. An electrically conductive elastic composite yarn as in any one of the claims 1 to 15, wherein each of said metal filaments have an equivalent diameter D, said D being equal or more than 1μm, said D being less or equal to 150μm.

17. An electrically conductive elastic composite yarn as in any one of the claims 1 to 16, wherein each of said metal filaments is provided by metal fiber bundle drawing operation.

18. An electrically conductive elastic composite yarn as in any one of the claims 1 to 17, wherein each of said metal filaments comprises copper or copper-alloy, steel, nickel or nickel-alloy, aluminium or aluminium-alloy or stainless steel.

19. A textile product comprising at least one electrically conductive elastic composite yarn as in any one of the claims 1 to 18.

20. A textile product as in claim 19, wherein said textile product is a woven fabric.

21. A textile product as in claim 20, wherein said yarn is present as a weft or warp yarn.

22. A textile product as in any one of the claims 19 to 21 , wherein said textile product having an elongation at rupture of 100 % to 400 %.

23. A garment comprising a textile product as in any one of the claims 19 to 22.

24. A garment as in claim 23, wherein said yarn is present as a loop.

25. A garment as in claim 23, wherein said garment being a seat upholstery.

26. An electrically heating device comprising at least one electrically conductive elastic composite yarn as in any one of the claims 1 to 18.

27. An electrically heating device comprising a textile product as in any one of the claims 19 to 22.

28. The use of an electrically conductive elastic composite yarn as in any one of the claims 1 to 18 as an antenna.

29. The use of an electrically conductive elastic composite yarn as in any one of the claims 1 to 18 as a resistive heating element.

30. The use of a textile product as in any one of the claims 19 to 22, wherein said yarn being used as an antenna.

31. The use of a textile product as in claim 30, wherein said yarn being present as a loop- antenna.

32. The use of a textile product as in any one of the claims 19 to 22, wherein said yarn being used as a resistive heating element.

33. The use of a garment as in any one of the claims 23 to 25, wherein said yarn being used as an antenna.

34. The use of a garment as in claim 33, wherein said yarn being present as a loop-antenna.

35. The use of a garment as in any one of the claims 23 to 25, wherein said yarn being used as a resistive heating element.

36. The use of a garment as in claim 33, wherein said garment being a seat upholstery.