PROTECTIVE SHEATH, IN PARTICULAR FOR ELECTRICAL CABLES, AND METHOD FOR MANUFACTURING SAME

Abstract

The invention relates to a protective sheath comprising an assembly of at least one electrically non-conductive thread, referred to as a core thread, which contributes to the final shape given to the sheath, and electrically conductive threads, as well as at least one protective film combined with all or part of one of the surfaces of the sheath, and characterized in that the protective film is combined by welding. Such assembly of the film by welding and not sewing ensures that the sheath is not damaged during its manufacturing.

Description

The invention relates to a protective sheath, in particular for electrical cables, wires or the like, comprising an assembly of at least one electrically non-conductive thread, referred to as a core thread, contributing to the final shape of the sheath, and electrically conductive threads, as well as at least one protective film covering all or part of at least one of the surfaces of the sheath.

The invention also relates to the method for manufacturing such a sheath.

The invention will be particularly described in the context of a protective sheath designed to accommodate electrical threads/cables, but shall not be limited thereto.

The protective sheath of the invention is preferably open over its length and is of the so-called self-closing type, wherein one edge of the sheath overlaps and goes beyond the other edge. Thus, the sheath can be opened easily by spreading the edges so as to place it around a strand of cables, and it closes automatically around the cables with an overlapping area.

Protective sheaths for electrical bundles are used in many areas, such as aeronautics, aerospace, automotive and other industries, so as to safely route such cable bundles carrying electrical signals among others.

The sheaths are very diverse depending on the field of application and type of protection required. The sheaths may simultaneously or otherwise have properties that protect them from outside attacks of the mechanical or chemical type or those relating to the outer temperature.

Some of these protective sheaths are further electromagnetically shielded in order to protect the electrical bundles from all electromagnetic interference and/or have electrically conductive elements designed to allow the electrical continuity of the assembly in which the sheaths are used.

Sheaths made from an assembly of woven threads are thus known, some of which are not electrically conductive, of the plastic type, and others are made of electrically conductive material, such as metal threads. The non-conductive threads form the weft, while metal threads form the warp, and possibly the weft. It must be remembered that warp threads extend lengthwise in relation to the sheath and weft threads extend crosswise to the warp threads, radially in relation to the sheath (depending on the width of the manufactured sheath, the width is the dimension transverse to the length of the sheath).

Non-conductive weft threads are advantageously made of plastic, for example PPS (polypropylene sulfide) in order to thermoform a flat ribbon made up by assembling threads and thus making a sheath with a tubular shape. This type of sheath remains split as explained above.

The inside of such sheaths is sometimes coated with protective film to avoid direct contact between the cables to protect and the threads of the sheath, particularly metal threads which unfortunately have abrasive properties.

That protective film is now made integral with the assembled ribbon of threads by sewing. Seams are made using so-called sewing threads along the length of the sheath, close to the two free edges of the film and possibly along the median line of the sheath for greater widths.

However, sewing can lead to cutting through or at least damaging the metal and/or other threads of the sheath, damaging the protective properties of the sheath, particularly in respect of its strength in hostile environments where some parameters could play a harmful role, for example temperature, very high humidity and/or salinity rate, such as salt spray. That is because the metal thread of the fabric of the sheath has a copper core and protective nickel coating. If the nickel is scratched or removed during the sewing step, the risk of corrosion is initiated; the copper core is no longer protected and will oxidize very quickly, damaging the sheath, which will no longer offer optimal protection to the electrical cables.

An excessively large number of cut metal threads could then deteriorate the electrical characteristics of the sheath, such as for example continuity and/or electromagnetic protection and damage the cables running inside said sheath.

Further, it is sometimes necessary to remove the protective film over a certain length of the sheath in order to provide electrical continuity between the metal threads of the two sheaths to connect to make a bypass over a strand of electrical threads, with possible metal or metal-coated mechanical interface parts. This operation of removing the film can damage the sheath in which the sewing threads that mechanically link the film to the thread ribbon are sewn.

The invention is thus aimed at offering a protective sheath made of multiple materials wherein the inner protective film is made integral so that the aforementioned drawbacks do not occur. In particular, the invention provides a sheath that protects the inner cables from abrasion and/or offers mechanical protection and/or electromagnetic shielding for the cables, wherein the sheath is made up of an assembly of metal and other non-conductive threads that are exposed to no risk of damage during manufacturing or the use of the sheath.

According to the invention, the protective sheath comprises an assembly of at least one electrically non-conductive thread, referred to as a core thread, which contributes to the final shape given to the sheath, and electrically conductive threads, as well as at least one protective film combined with all or part of at least one of the surfaces of the sheath, and is characterized in that the protective film is combined with the thread assembly by welding.

The thread assembly forms a ribbon on which the protective film is thus applied by making it integral by welding.

Thus, no sewing is required for making it integral. The sheath does not risk having the drawbacks of the prior art relating to fastening by sewing.

The film may be welded over only part of one of the surfaces of the sheath.

The film is welded along one or more continuous and/or discontinuous surfaces.

The thread assembly (ribbon) comprises at least one material adapted to allow the welding of the protective film.

Thus, the presence in the thread assembly (ribbon) of material that allows fastening by welding, such as the presence of one or more specific so-called welding threads made of material compatible with that of the protective film to allow joining by welding and not by a seam, avoids piercing and therefore the risk of damaging the conductive and non-conductive threads making up the ribbon.

The ribbon threads that are used for joining by welding to the protective film may be the core thread or a combination of the core thread and other threads included in the thread assembly of the ribbon.

In a preferred embodiment, the film is welded discontinuously, particularly along at least several welding points.

In one embodiment, the sheath comprises at least one additional non-conductive thread that is distinct from the core thread, designed for welding, which is integrated in the assembly of threads (ribbon) during the manufacture of said assembly. That additional thread may or may not be made in material distinct from the material of the core thread. The additional thread allows joining by welding, particularly discontinuously along a number of welding points.

The material of the welding thread or threads is preferably different from that of the core thread of the ribbon so that the steps of welding the film and then thermoforming the ribbon coated with the film can be carried out successively, and joining by welding does not modify the flat shape of the ribbon before or after it is shaped. The sheath is shaped before or after the film is fixed to the thread ribbon.

The thread assembly (ribbon) is achieved by weaving and/or knitting and/or braiding.

The thread assembly (ribbon) is advantageously woven by weaving at least one weft thread in non-conductive material corresponding to the core thread, and warp threads formed by conductive threads and possibly other threads in conductive or non-conductive material, wherein at least one of the threads in non-conductive material used for welding is incorporated as the weft or warp thread. The weft threads can comprise conductive threads and/or threads in different non-conductive threads.

The sheath may comprise functional threads, for example threads that serve the function of identification or marking. Thus, the thread ribbon may comprise colored threads that make it possible to identify the type of sheath (its type of protection). The ribbon may in a known manner comprise at least one thread that makes it possible to identify the maximum filling rate accepted by the sheath in use, wherein that thread is placed away from the edges of the sheath and only becomes visible when the overlap of the sheath in the closed position is insufficient because it contains an excessively large volume of cables that tends to open the sheath.

Preferably, the non-conductive welding thread is incorporated into the thread assembly (ribbon) as the warp thread.

The non-conductive core thread (which may be welding thread) and the welding threads have single or multiple filaments.

The non-conductive core thread is preferably made of thermoformable material.

The non-conductive core thread is particularly made of plastic or composite material.

The non-conductive core thread may be made of one or a combination of plastics selected particularly from: polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyamide (PA), polypropylene (PP), polyoxymethylene (POM), polyetheretherketone (PEEK), polyester, polyphenylene sulfide (PPS), polysulfone (PSU), polyimide (PI), polyamide-imide (PAI), polyvinylidene fluoride (PVDF), polyaryletherketone (PAEK) et polyetherimide (PEI).

The non-conductive core thread may for example have a diameter below 10 mm.

The welding thread is preferably in plastic, for example of the type polytetrafluoroethylene (PTFE), perfluoroalkoxy alkane (PFA), polyamide (PA), polypropylene (PP), polyoxymethylene (POM), polyetheretherketone (PEEK), polyester, polyphenylene sulfide (PPS), polysulfone (PSU), polyimide (PI), polyamide-imide (PAI), polyvinylidene fluoride (PVDF), polyaryletherketone (PAEK) et polyetherimide (PEI). It may for example have a diameter below 10 mm.

The welding thread may have one or more filaments The non-conductive welding thread (which may be the core thread or any other thread) may for example have a diameter below 10 mm. It may also take the form of a narrow strip, for example 2 mm wide and less than 10 mm thick.

Conductive threads are made of metal or are metal-coated. They comprise metal material that may be selected, particularly, without limitation, from nickel-plated copper, tin-plated copper, silver-plated copper, nickel, stainless steel. Alternatively, they may be formed with metal-coated polymer, wherein the polymer is the core of the thread and is coated with metal.

The conductive threads preferably have diameters below 10 mm.

A conductive thread preferably takes the form of a single filament or a twisted or untwisted assembly of multiple filaments.

The protective film is preferably in plastic. It may comprise composite material. It may be made from a thread assembly that takes the form of an unwoven strip or woven strip or knitted strip. It may also be extruded material. It may for example be made of polytetrafluoroethylene (PTFE), PFA, meta-aramid, PPS, PEEK, etc.

Preferably, the sheath thread assembly comprises at least two parallel welding threads extending longitudinally in relation to the sheath and spaced close to the two free longitudinal edges of the protective film. The welds are for example arranged at a distance of about 10 mm from the longitudinal edges of the protective film.

Several other welding threads may be added to the edge welding threads, particularly at least a third additional thread is integrated along the median longitudinal line of the sheath.

According to one characteristic, the film is made integral with (welded to) the non-conductive welding threads for example by heat transfer, ultrasound or any other usual means that allows said thread to fuse with the film.

The protective film is preferably less than 10 mm thick, particularly less than 1 mm, preferably about 0.05 mm.

The protective film is preferably made integral only in the longitudinal direction of the sheath, because of the presence of welding threads in the longitudinal direction. The protective film is preferably welded at several welding points aligned longitudinally with the sheath or extending in a general direction along the longitudinal axis of the sheath.

Preferably, at least on some parts of the sheath, no weld is made transverse to the axis of the sheath, which makes it easier to hold the film at its free ends in order to separate it if required. That is because when the sheath is used, it is useful to peel off the protective film over a certain length so that the electrical sheath with its metal threads can act as an electrical connection interface, for example between two sheaths to connect and/or with metal or metal-coated mechanical connecting parts.

Once the protective film is peeled off over a certain length, it is cut transverse to the longitudinal axis of the sheath or turned over on itself.

Further, the absence of a thread associated mechanically (by sewing as in the prior art) with the ribbon of assembled threads avoids the risk of damaging the threads making up the ribbon/sheath during the life of the sheath (when the film must be removed).

As a result, the removal of the protective film is made significantly easier because one only needs to pull the film to peel it off, since there is no mechanical assembly part between film and ribbon, which further ensures that the sheath is not damaged.

The width of the thread assembly ribbon is adapted to the required sheath diameter.

The protective sheath in the invention is particularly used for electromagnetic shielding and applies to all areas: aeronautics, aerospace, automotive, maritime, construction etc.

The invention also relates to a method for manufacturing the sheath in the invention.

The method comprises a step of assembling several threads including electrically conductive threads to form a ribbon, a step of associating a protective film over all or part of at least one of the surfaces of the ribbon, and is characterized in that the step of associating the protective film is achieved by welding.

The assembly step is achieved by weaving and/or knitting and/or weaving the threads.

If the assembly step does not in itself constitute also a step for shaping the sheath, the method comprises an additional step of shaping the sheath, preferably by thermoforming, before or after the protective film is made integral. Advantageously, thermoforming is achieved thanks to the presence of ribbon threads in thermoformable material.

This invention will now be described with reference to examples that are merely illustrative and not limitative of the scope of the invention, and from the accompanying drawings, wherein:

FIG. 1 is a schematic perspective view of the sheath of the invention with a view to use;

FIG. 2 is a schematic sectional side view of the flat thread ribbon of the sheath along its longitudinal axis, coated in part with the protective film;

FIG. 3 is a schematic top view of the thread ribbon of the sheath;

FIG. 4 is a schematic perspective top view of FIG. 2.

The protective sheath 1 illustrated in FIG. 1 is presented with a view to use. It is designed to accommodate electrical cables to protect them from abrasion, mechanically and electromagnetically, and act if required as the electrical connection interface between two other sheaths and/or with metal or metal-coated mechanical parts.

The protective sheath 1 is cylindrical in shape and has a circular or other section.

The protective sheath 1 is longitudinally split and is closed on itself, wherein one of the longitudinal edges 10 is folded over and beyond the opposite longitudinal edge 11. That so-called self-closing sheath is easy to place around cables, especially when the cables are already installed. It also makes it easier to repair or remove cables already installed inside the sheath or add cables to a strand already in place in the sheath.

The sheath is placed by spreading the longitudinal edges 10 and 11 in order to open the sheath and place it around the cables. When the edges are released, the sheath closes automatically.

The diameter of the sheath and the edge overlap portion are adapted to the size of the cable bundle to protect.

The sheath 1 is obtained from a flat ribbon 2 as visible in FIGS. 2 to 4 which is designed to be thermoformed to give it a tubular or other shape.

The sheath firstly comprises a thread assembly ribbon 2 constituting the structure of the sheath and comprising metal threads for electromagnetic shielding, thermoplastic threads for shaping and other threads for identifying the sheath and the minimum overlap rate acceptable in use, and secondly a protective film 3 covering all or part of the surface accommodating the cables and serving the purpose of protecting the cables from the abrasion of the metal threads. The use of another film that is made integral using the same method in the invention on the opposite side of the sheath is not ruled out.

The ribbon 2 has (FIG. 2) an outer side 20 designed to be in contact with the outside environment once the sheath is shaped, and an opposite inner surface 21 with which the protective film 3 is associated.

By reference to FIGS. 2 to 4, the ribbon 2 is a woven assembly comprising a weft thread 4 in thermoformable and non-conductive material (forming the core thread of the ribbon), unreferenced textile threads and metal threads 5 forming the warp threads. Metal and non-metal threads can also be incorporated as weft threads.

The weft thread 4 has a single filament or multiple filaments.

The metal threads 5 have a single or multiple filaments. They are preferably derived from a braided metal ribbon.

The weft thread 4 is woven with metal threads 5 to intertwine and form the ribbon 2.

According to the invention, the thread assembly comprises at least one thread designed to make the film 3 integral by welding. The thread may be the core thread 4 made up of the weft thread in the woven assembly or one or more other distinct threads of the core thread 4 and conductive threads 5. This thread or these threads that allow welding are referred to as the welding threads.

In a particular embodiment, the ribbon 2 comprises additional threads 6 that form the welding threads. These welding threads 6 are arranged in warp threads and are introduced in the ribbon during the weaving step.

The welding threads 6 are compatible with the material of the protective film 3 to be made integral therewith by welding. The welding threads are in the exemplary embodiment in material distinct from the material of the weft thread 4. However, they may be in the same material as the weft thread,

The welding threads 6 are preferably in plastic, for example PTFE, PFA, PA, PP, POM, PEEK, polyester, PSU, PPS, PI, PAI, PVDF, PAEK or PEI.

The welding threads 6 preferably extend in the longitudinal direction of the sheath.

The sheath preferably comprises at least two welding threads 60 and 61 parallel and spaced, and arranged close to the two free longitudinal edges 30 and 31 respectively of the film 3. The welding threads are preferably integrated at a distance less than 10 mm from said edges.

Other welding threads may be distributed in the textile extending as warp threads.

The protective film 3 is applied against the ribbon 2 and is not at all associated therewith by mechanical assembly.

The protective film 3 is only joined to the ribbon 2 by welding points 62 preferably extending longitudinally in relation to the textile when flat or axially in relation to the sheath.

The protective film 3 is added to the ribbon 2 preferably before the sheath is thermoformed.

Alternatively, the protective film 3 may be made integral after the sheath is thermoformed, also by welding. This alternative is however less convenient as it makes it necessary to open the sheath and keep it flat, and then close it again.

The protective film 3 is made of non-abrasive material, preferably in plastic or an assembly of composite textile threads. It may for example take the form of a woven or knitted strip. It may for example be made of PTFE, PFA, meta-aramid, PPS or PEEK.

The thickness of the protective film 3 is preferably less than 10 mm. The film is made functional with the aforementioned materials for thickness of about 0.05 mm.

The protective film 3 is made integral by welding against the welding threads 6 of the ribbon 2.

Welding is achieved by any known technique, such as thermal welding (heat transfer) or by ultrasound.

The protective film 3 is adapted to be detached from the ribbon 2 after it is made integral, merely by pulling it off to peel it. This operation may in a way be assimilated with the manner in which the protective film is peeled off a yogurt container.

The film may advantageously be peeled off before the sheath is thermoformed or during its use, over a certain length, and can be cut or turned over.

Thus, the protective sheath in the invention provides the required mechanical and shielding protection, allows electrical continuity and protects the electrical cables to be accommodated therein from abrasion; such protection is durable and there is no risk of its properties being affected over time.

Claims

1. A protective sheath comprising an assembly of at least one electrically non-conductive thread, referred to as a core thread, which contributes to the final shape given to the sheath, and electrically conductive threads, as well as at least one protective film combined with all or part of at least one of the surfaces of the sheath, wherein the protective film is combined with the thread assembly by welding.

2. The protective sheath according to claim 1, wherein the thread assembly comprises at least one material adapted to allow the welding of the protective film.

3. The protective sheath according to claim 1, wherein the protective film is welded along one or more continuous and/or discontinuous surfaces.

4. The protective sheath according to claim 1, wherein the thread assembly comprises at least one additional non-conductive thread that is distinct from the core thread and designed for welding, particularly made in material distinct from the material of the core thread.

5. The protective sheath according to claim 1, wherein the thread assembly is obtained by weaving at least one weft thread formed by the core thread in non-conductive material and warp threads formed by the conductive threads, and possibly other threads in non-conductive material, wherein at least one of the threads in non-conductive material used for welding is incorporated as the weft or warp thread.

6. The protective sheath according to claim 1, wherein the protective film is less than 10 mm thick, particularly less than 1 mm, preferably about 0.05 mm.

7. The protective sheath according to claim 1, wherein the welding of the protective film is made by heat transfer or ultrasound.

8. The protective sheath according to claim 1, wherein the protective film is welded at several welding points extending in a general direction along the longitudinal axis of the sheath, particularly at a distance of about 10 mm from the longitudinal edges of the protective film.

9. The protective sheath according to claim 1, wherein the thread assembly comprises functional threads, for example threads that serve the function of identification or marking.

10. The method for manufacturing a sheath according to claim 1, comprising a step of assembling several threads including electrically conductive threads to form a ribbon, a step of associating a protective film over all or part of at least one of the surfaces of the ribbon, wherein the step of associating the protective film is achieved by welding.

11. The protective sheath according to claim 1, wherein the protective film is welded over only part of one of the surfaces of the sheath.

12. The protective sheath according to claim 1, wherein the threads in the thread assembly that are used for joining by welding to the protective film are the core thread or a combination of the core thread and other threads included in the thread assembly, wherein each thread may have single or multiple filaments.

13. The protective sheath according to claim 1, wherein the thread or threads that are used for joining by welding are made of thermoformable material, particularly of plastic or composite material.

14. The protective sheath according to claim 1, wherein the protective film is made of plastic material, and may comprise composite material.

15. The use of a sheath according to claim 1, to safely route, particularly for electromagnetic shielding, cable bundles carrying electrical signals among others, especially in the following areas: aeronautics, aerospace, automotive, maritime, construction.