FR2812465A1 - Supple woven sleeve for protecting cables, has metal incorporated in warp and/or weft threads to form screen against electromagnetic waves - Google Patents

Abstract

A sleeve (1) is made from woven weft (3) and warp (4) threads with the former possessing a shape memory effect to create a tube with edges (10, 11) that close over the cables (5). It has a coating or filaments of a metallic material in its warp and weft threads, which can be of a metal/textile material. The density of the weave mesh and the amount of metal incorporated depend on the range of electromagnetic frequencies to be attenuated.

Description

FLEXIBLE PROTECTIVE SHEATH

  The present invention relates to the general technical field of flexible sheaths for protecting bundles of cables carrying energy,

  information or even light or sound.

  The present invention relates more particularly to flexible protective sheaths formed of a woven material provided with weft threads and warp threads and which comprises, in the direction of the weft, thermoformable threads with shape memory making it possible to obtain an element of substantially tubular shape, this element comprising a first free longitudinal edge and a second free longitudinal edge, the sheath being reversibly openable to occupy an open position in which the two longitudinal edges are spaced apart from each other on at least a part of the length of the sheath, and a closed position in which the two longitudinal edges are mutually superimposed. Such opening sheaths are known in particular from US-A-5 143 149 and are usually shaped by heat treatment to be closable on themselves. We thus obtain a memory tube of

  form which can be opened longitudinally along a generator.

  By locally spreading the longitudinal free edges of the sheath, it is possible to access the cables whose sheath provides protection against external aggressions such as for example abrasion, water, fire or

still good oil.

  Even if such sheaths facilitate access to cables for maintenance, they do not effectively protect the cables they contain against electromagnetic waves while these

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  waves constitute an extremely important risk factor, in

particularly on board aircraft.

  An object of the present invention therefore aims to provide a new protective sheath which overcomes the various drawbacks listed above by protecting the cables contained in the sheath,

  against the negative effects of electromagnetic waves.

  Another object of the present invention is to propose a new protective sheath ensuring electromagnetic shielding while being flexible,

and economical.

  Yet another object of the present invention is to propose a new protective sheath against electromagnetic waves belonging to a

frequency range determined.

  Another object of the present invention is to propose a new protective sheath which makes it possible to protect the cables against electromagnetic waves belonging to the widest possible frequency range. Yet another object of the present invention is to propose a new protective sheath which protects the cables not only against electromagnetic waves, but also against the attacks caused

  in particular by water, abrasion, fire or even oil.

  The objects assigned to the present invention are achieved by means of a flexible protective sheath formed of a woven material provided with weft threads and warp threads and which comprises in the direction. of the weft, thermoformable son with shape memory making it possible to obtain an element of substantially tubular shape, this element comprising a first edge

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  free longitudinal and a second free longitudinal edge, the sheath being reversibly open to occupy an open position in which the two longitudinal edges are spaced apart from one another over at least part of the length of the sheath, and a closed position in which the two longitudinal edges are mutually superimposed. characterized in that at least one metallic material enters the composition of the flexible sheath in order to form a protective screen against

electromagnetic waves.

  Other aspects of the present invention will be explained in more detail in the

  reading of the description given below as well as in the attached drawings, given

  by way of purely illustrative and nonlimiting examples, in which: - Figure 1 illustrates, in a perspective view, the flexible sheath of

  protection according to the present invention, in normal closed position.

  - Figure 2 illustrates, in a perspective view, the flexible sheath of the

Figure 1, in the open position.

  - Figures 3 and 4 represent graphs showing the attenuation obtained as a function of the frequencies of the electromagnetic waves, for two types

of different fabrics.

  The flexible sheath 1 according to the present invention shown in Figures 1 and 2 is formed of a woven material 2 which is provided with weft threads 3 and

chain 4.

  In order to conform the woven material 2 into a substantially cylindrical shape, at least some of the weft threads 3 comprise a material

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  thermoformable which, after heat treatment, makes it possible to obtain a

shape memory element.

  The weft threads 3 thus extend transversely along the smallest dimension of the sheath 1, and the warp threads 4 extend along the length of this sheath. The cross section of the thermoformed sheath depends on the objects which are intended to be protected by this sheath. These objects are for example cables 5. The section can be square, rectangular or else

  still annular as shown in the figures.

  The weft threads 3 are for example made of thermoplastic material with

shape memory.

  The sheath 1 according to the present invention can be opened reversibly according to a generator. It has a first longitudinal edge 10 and a

  second longitudinal edge 11 which are both free.

  The sheath 1 thus has a closed position in which the two free edges 10 and 11 are mutually superimposed, the free edge 11 is for example in abutment on the free edge 10 (FIG. 1), and an open position in which a user has moved aside the two edges of each other (Figure 2) to access the cables 5. Generally, the two edges are mutually spaced over only part of the length of the sheath in order to have local and momentary access to the cables 5. The closed position is the normal position of the sheath in which the sheath internally delimits

  a closed volume to protect the cables contained therein.

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  According to an essential characteristic of the present invention, at least one metallic material enters into the composition of the flexible sheath in order to

  form a shield against electromagnetic waves.

  For the purposes of the invention, the term composition of the sheath made of metallic materials means the overall amount of this or these materials present in the sheath. The metallic material (s) are present up to a certain predetermined amount in the form of a metallic deposit produced on one (inner face or outer face) or both sides of the fabric 2, or even in the form of a deposit produced at at least some of the threads before weaving these threads, or even by entering into the intrinsic composition of at least some of the weft threads and warp threads. According to a preferred embodiment of the invention, at least one metallic material is used in the composition of at least some of the weft threads 3 and in the composition of at least some of the warp threads 4. These weft threads 3 and chain 4 are intertwined to form a screen with electromagnetic waves. The sheath 1 according to the present invention makes a sort of Faraday cage, which can be opened locally by taking back its own

initial form.

  The density of the meshes formed by the metallic or partially metallic weft 3 and warp 4 son is a function of the attenuation of the electromagnetic waves to be obtained between the outside and the inside of the sheath 1. The tighter the meshes, the more the frequency range of the stopped waves is large. In general, the density of the meshes and the quantity of metallic material incorporated in the fabric 2 are functions of

  the electromagnetic frequency range to be attenuated.

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  The meshes thus constitute a metallic network whose nodes make it possible to conduct the electromagnetic waves from one mesh to another, along the length of the sheath 1. These waves are conducted on the surface of the sheath, without penetrating inside. of this sheath and therefore do not reach the cables 5 and conversely, the waves emitted by the cables remain trapped inside the sheath and do not disturb the environment of

sheath.

  The network constituted by the meshes with metallic or partially metallic wires can be supported by a matrix which ensures the cohesion of

lI'ensemble.

  In a preferred form of the invention, the weft 3 comprises threads of thermoplastic material and metallic threads and the warp 4 comprises

  textile threads and metallic threads.

  As a variant, metallo-textile threads can replace or be added to the metallic threads of the weft and the warp. Such metallo-textile yarns may consist of 80% polyester and 20%

stainless steel.

  When these metallo-textile threads are crossed in weft and warp to form, for example, meshes of 3 mm on a side, the sheath then forms a screen against electromagnetic waves over a range of frequencies.

  between 0.7 and 2.3 GigaHertz.

  In a first example, the sheath according to the present invention consists of weft son 3 comprising a metallo-textile yarn (polyester / stainless steel) for four textile yarns (polyester), and of warp son 4 comprising a metallo-textile yarn ( polyester / stainless steel) for three textile threads (polyester). Electromagnetic attenuation for electromagnetic waves emitted at forty

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  centimeters of the sheath 1, as a function of the frequency of these waves, is represented by the graph in FIG. 3. The values of this attenuation at certain points of the curve are: Frequencies (MHz) Attenuation (dB)

A 11,000,000 - 48,727

B 12997000 - 45.409

C 14999000 - 47.503

D 18009000 - 42,765

E 20998000 - 48.169

F 23,000,000 - 49.599

G 24995000 - 53.784

H 26997000 - 60.349

  In a second example, the sheath according to the present invention consists of weft threads 3 comprising a metal-textile thread (polyester / stainless steel) for four textile threads (polyester), and warp threads 4 comprising a thread

  metallo-textile (polyester / stainless steel) for four textile yarns (polyester).

  The electromagnetic attenuation for electromagnetic waves emitted at forty centimeters from the sheath 1, as a function of the frequency of these waves, is represented by the graph of figure 4. The values of this attenuation at certain points of the curve are:

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Frequencies (MHz) Attenuation (dB)

K 11000000 - 49.578

L 12997000 - 45.103

M 14999000 - 45.338

N 18009000 - 42.157

O 20998000 - 42,729

P 23,000,000 - 41.518

Q 24995000 - 49.184

R 26997000 - 51.486

  It will be noted that each time that the value of the waves is reduced by 3dB, the propagation of these waves is halved. The attenuations obtained with the sheath 1 according to the present invention therefore make it possible to reduce by

  very importantly the propagation of these waves.

  It is understood that the variations in the mesh density and in the composition of the metallo-textile threads allow a variation in the frequency range of the attenuated or stopped waves according to criteria determined by the user, depending on the cables to be protected and the environment in

which these cables are placed.

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  In addition, the sheath may also have characteristics of resistance to fire, water, oil or even abrasion by subjecting it to

  appropriate treatments or by choosing a suitable type of textile yarn.

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Claims (7)

  1 - Flexible protective sheath formed of a woven material (2) provided with weft threads (3) and warp threads (4) and which comprises, in the direction of the weft, thermoformable threads with shape memory allowing '' obtain an element of substantially tubular shape, this element comprising a first free longitudinal edge (10) and a second free longitudinal edge (11), the sheath (1) being reversibly openable to occupy an open position in which the two edges longitudinal (10, 11) are spaced from each other over at least part of the length of the sheath (1), and a closed position in which the two longitudinal edges (10, 11) are mutually superimposed, characterized in that at least one metallic material enters the composition of the flexible sheath (1) in order to form a protective screen to electromagnetic waves.   2 - Sheath according to claim 1, characterized in that the flexible sheath (1)   comprises at least one deposit of at least one metallic material.   3- sheath according to claim 1, characterized in that at least one metallic material enters into the composition of at least some of the threads of the weft (3) and into the composition of at least some of the threads of the warp ( 4), said weft (3) and warp (4) threads being intertwined in order to form a screen for protection against electromagnetic waves. 4 Sheath according to claim 3, characterized in that the weft threads   (3) include metallic wires. 11 2812465   - Sheath according to claim 3 or 4, characterized in that the wires of the   weft (3) comprise metallo-textile yarns.   6- sheath according to any one of claims 3 to 5, characterized in   that the warp threads (4) further include textile threads and metallic threads.   7- sheath according to any one of claims 3 to 6, characterized in   that the warp threads (4) include textile threads and metallo-textile threads.   8- sheath according to claims 5 and 7, characterized in that the son   metallo-textiles contain polyester and at least 20% stainless steel.   9- Sheath according to any one of claims 3 to 8, characterized in   that the mesh density and the amount of metallic material incorporated into the fabric (2) are a function of the frequency range electromagnetic to be attenuated.   -Sheath according to any one of claims I to 9, characterized in   in that at least one chemical and / or mechanical treatment is applied to the sheath (1) in order to obtain at least one of the properties chosen from the water-repellent, flame-retardant, oil-repellent and resistance to Abrasion.