The invention is based on the use of circumferentially-heat-shrinkable multi-lumen sheaths of woven fabric for holding and separating adjacent conduits and includes fabric sheaths suitable for such use. Additional protection may also be provided by the sheath, for example abrasion resistance, impact protection or cut-through protection.

The fabric of these sheaths comprises filaments extending substantially circumferentially around the sheath (hereinafter"hoop filaments"), at least some of which hoop filaments are heat-shrinkable, and filaments extending substantially along the sheath (hereinafter"length filaments"), and it is mentioned that some degree of longitudinal shrinkage, to avoid the problem of wrinkling of the sheath at bends in the conduits, may be provided by incorporating heat-shrinkable fibres extending in the longitudinal direction. The spacers between the lumens are woven and flexible.

WO-A-95/11400 discloses a method of holding two or more fluid conduits together at a predetermined lateral distance, for example, a vehicle or domestic appliance, by means of a tubular solid polymeric heat shrink article. A circular shrink-to-fit product does not grip the substrate and allow temporary positioning of the product on the conduits prior to shrinkage. It is therefore difficult to accurately align complex shaped conduits, for example hoses, during the shrink process. Accurate alignment of the conduit assembly is important in a high volume production environment for efficient fitment to mounting points in a vehicle or appliance.

Misalignment of conduits, for example complex shaped vehicle hoses, in a finished assembly will require either costly rework or discard of the assembly. Use of a polymeric fixture having an inflexible spacer does not allow repositioning of misaligned conduits once shrinkage is completed.

US-A-5700528 discloses a solid heat-shrinkable ring in a non-circular configuration which has the advantage that it can grip the conduit prior to heat recovery and maintain any orientation during shrinkage. The disadvantage of this approach is that a unique product of the correct dimensions is required to provide grip for each conduit size. Use of a polymeric fixture having an inflexible spacer again does not allow repositioning following any misalignment, which can result in costly rework or discard of the assembly.

According to the current invention a novel means of coupling conduits has been discovered which offers all the benefits of heat shrinkable coupling components but which overcomes the inconvenient and costly problem of conduit misalignment in a finished fixture by use of a heat shrinkable, woven multi-lumen sheath having a flexible spacer between the lumens. A further advantage of the current invention over the prior art may also include a lower profile conduit assembly due to the reduced thickness of both the heat shrinkable spacer and the fabric surrounding the conduit. The lower cost of a woven solution is an added advantage..

One aspect of this invention provides a method of holding two or more conduits, preferably electrical or fluid conduits, together at a selected lateral distance from one another, comprising the steps of: (a) providing a holding article composed of a woven, multi-lumen sheath (preferably containing at least one crosslinked filament) comprising at least two dimensionally heat- recoverable portions of the sheath connected together by a flexible connecting portion of the sheath substantially integral with the recoverable portions, (b) placing the said heat-recoverable portions of the holding article around the conduits to be held together, and (c) recovering the heat-recoverable portions to grip the conduits, thereby holding the conduits at the selected distance from one another.

Methods according to this invention are especially useful for holding fluid conduits side-by- side but separated from one another, and are especially advantageous for holding fuel lines and flexible hoses, or other fluid conduits for a vehicle or for a domestic appliance, at a distance corresponding to the spacing of connection points carried by the vehicle or appliance.

The ends of the conduits so held may then be conveniently aligned with and connected to the connection points. For such purposes, the holding articles used according to this invention will preferably be applied near the ends of the hoses or other elongate conduits, although additional holding articles may be applied at one or more positions between the conduit ends to enhance stability. Separation of conduits at a distance from one another may be important to prevent abrasion or rattle, for example.

One preferred form of holding article for use in the method of this invention comprises a circumferentially-heat-shrinkable woven fabric sheath, capable of use on conduits, having at least two lumens separated by flexible spacers, extending longitudinally within the tubing.

The fabric of the sheath comprises filaments extending substantially circumferentially around the sheath (hereinafter"hoop filaments"), at least some of which hoop filaments are heat- shrinkable, and filaments extending substantially along the sheath (hereinafter"length filaments"), and it is mentioned that some degree of longitudinal shrinkage, to avoid the problem of wrinkling of the sheath at bends in the conduits, may be provided by incorporating heat-shrinkable fibres extending in the longitudinal direction. The spacers between the lumen will be filamentary and substantially integral with the lumen. In a preferred form spacers will comprise one or more longitudinal filaments interlaced with the hoop filaments in a non- tubular weave construction.

Various fabric designs may be employed in the present invention, but a weave is preferred, in particular a plain weave, although other weaves such as a 2/2 twill would be suitable. When using a weave, it is preferred that one set of fibres runs substantially parallel to the length of the sheath, and another set of fibres runs substantially circumferentially of the sheath. If the sheath is to be made continuously in line, it will be desirable (at least when using a narrow fabric loom) for the warp fibres to become the longitudinal fibres of the sheath, and the weft fibres to become the circumferential fibres of the sheath. The spacer may be woven as a tubular section but will more preferably be a flat section which could be a plain weave, 2/2 twill or any other no-tubular structure. Multiple layers, especially doule or triple layers may be incorporated using suitable weave designs and techniques. The number of warps ends in the spacer will be at least one and preferably two or more. One or more spacers may be included which may be central or offset.

By using a fabric, it is possible to select as circumferential fibres those that are ideal for the provision of heat-shrink properties, and to select for the longitudinal fibres those which are ideal for provision of other properties, for example, abrasion-resistance, toughness, resistance to notch propagation, low coefficient of friction, impact resistance, and high temperature performance. Such fibres preferably predominate on an external surface of the sheath. Thus, it is preferred to use high density polyethylene (HDPE) or linear low density (LLDPE) as the circumferential fibres and to use a polyester, such as polyethylene. terephthalate, or a nylon in the warp direction. Other suitable circumferential fibres include polyolefins such as low density polyethylene, medium density polyethylene, polypropylene/polyethylene copolymers and fluoropolymers such as polyvinylidene difluoride (PVDF) and ethylene chlorotrifluoroethylene (E-CTFE). Other suitable longitudinal fibres include polyacryonitrile and copolymers thereof, polyphenylene sulphide, cellulose acetate, aromatic polyamides, eg Kevlar, natural fibres and fluoro polymers. The longitudinal fibres are preferably able to flatten-out and/or to move under the influence of an adjacent surface. This ability to flatten- out or to move results in that surface causing less damage to the fibres. To this end it is preferred that the longitudinal fibres comprise multi-filament bundles since the filaments within each bundle will be able to move slightly with respect to one another. At present it is preferred to use a co-mingled yarn. A further advantage of multifilament bundles is that cut- through of any filament results in less overall damage to the product. The circumferential, heat-shrinkable, fibres may comprise simple monofilaments.

Various preferred characteristics of the product can be achieved by suitable selection of the weave density, weave design, and weaving process. For example, the spacer between the lumens may vary in dimension depending on requirements. If coupling only is required in a low profile assembly without complete physical separation then a minimum number of longitudinal filaments will be woven in to the spacer. If a physical barrier between the hoses is required, for example for noise or abrasion suppression, then more longitudinal filaments may be included. Alternative weaves, such as a 2/2 twill, may also be employed for the flexible spacer depending on requirements. Alternative fibre types may also be employed to increase separation. Other elongate materials such as small ropes or yams of high tex may also be woven or stitched in as spacers. Some of the possible configurations of spacer are shown diagrammatically in Figure 1.

Although it will depend on the tex value of the fibres, for most purposes the following weave densities will be suitable: 10-50, particularly 15-40 warp ends per cm, and 3-20, particularly 10-15 weft picks per cm. As mentioned above, the circumferential fibres are preferably monofilaments, and the longitudinal fibres preferably comprise multifilament bundles. More particularly, the longitudinal fibres comprise five to ten fold (particularly about six fold) bundles, each of the fibres within each bundle again comprising a bundle of very fine filaments. Each of the folds is preferably 10-20 tex, preferably about 17 tex (tex being the ISO standard for linear density of textile strands and is the weight in grams of 1000 m) and each of those filaments preferably comprises 30-40 very fine filaments. Damage to any one filament will not of course be catastrophic. The circumferential fibres preferably have a tex value of 5- 200, more preferably 20-100, especially 40-70.

The sheath may comprise two or more lumens of similar or different sizes. The number and shape of the interior lumens are not critical, although fewer than 10, preferably fewer than 8, more preferably fewer than 6, lumens may be convenient for many purposes. It may also be preferable for the lumens to be of reasonably uniform shape and reasonably symmetrical distribution, for example, as shown in the accompanying Figure 1. Other configurations will readily occur to persons familiar with weaving technology.

The sheath may be produced in long lengths, cut to length, slid over the conduits and then heat-shrunk around the hose to locate it in position. The desired shrinkage ratio for this purpose is from 1.2 : 1 to 5: 1. The lower value will be suitable where the hose to be protected is straight and where installation at low tolerances is simple. Shrink ratios greater than, say, 5: 1 might be difficult to achieve in practice and might result in instability or uneven shrinkage during installation. In general a shrink ratio between 1.5 : 1 and 3: 1 is preferred. Where the sheath is to be installed around a shaped, non-linear hose it may be desirable to provide some longitudinal shrinkage to avoid wrinkling at the bends in the hose. To this end heat-shrinkable fibres can be included in the longitudinal direction. A longitudinal shrinkage ratio of from 1- 20%, more preferably 5-15%, will generally be suitable. Shrinkage when expressed as a ratio means a dimension before shrinkage compared to the dimension after shrinkage. When expressed as a percentage it means the change in the original dimension.

Where the sheath is produced in long lengths it will usually require cutting before installation.

This can be done with a guillotine. Preferably the sheath will be coated in manufacture, either in continuous or discrete lengths, with a binder and then dried. The binder prevents fraying of the cut ends and makes mounting on the substrate easier. The cut length will vary depending on the requirements of the application. In some instances one or more short lengths of, for example, 10mm may be used where in other cases a single longer length of, for example 300mm may be used.

Some degree of cross-linking of at least some of the fibres of the sheath may be desirable to render the sheath heat-shrinkable. The circumferential fibres, which by virtue of their heat- shrinkability, drive shrinkage of the overall product, are preferably cross-linked and stretched before weaving of the fabric. They may be cross-linked and then stretched at an elevated temperature and then cooled, or the heating, stretching and cooling may precede the cross- linking. Generally it will be desirable to weave the fabric from heat-shrinkable fibres, although in some circumstances it may be preferred to produce the fabric from heat-stable fibres, and then stretch the fabric. Depending on the temperature performance of the product it may be desirable to cross-link the fibres which are, or are to become, heat-shrinkable before weaving in order that the longitudinal fibres may remain uncross-linked. Where higher temperature performance is required it may be desirable to cross-link the overall fabric (either by cross-linking separately all of the fibres from which it is to be made, or by cross-linking the woven fabric) in order to ensure that all of the fibres retain their integrity at high temperatures.

The sheath may be produced in the form of a multi-lumen tube, or other structure closed in cross-section or it may be woven as a sheet and later formed into tubes either before or during installation. A product formed into a tube during installation, known as a"wraparound sleeve" may be provided with a so-called closure mechanism to hold it in the wrapped around configuration around the hose. Alternatively the product may be woven as a single tube and then stitched in a subsequent process to produce a multi-lumen construction. One or more separating portions between the lumens may be formed by weaving or by stitching together two sides of the tube or by stitching in an additional yarn, possibly of higher tex, of the type described above. It will be understood that the additional yarn forming the spacer will often be a relatively narrow yarn, preferably of diameter less than 3 mm, more preferably less than 2 mm or less than 1 mm. However, thicker carriers, for example of diameter 4 or 5 mm or more, may also be useful, as may be flexible carriers of this diameter made up of multiples of thinner carriers.

If desired the sheath may be provided with some form of visual marking either for identifying it or as a means of determining when it has been subjected to abrasion. For example, a logo of distinguishing colour may be woven into the sheath using for example a Jaquard mechanism on a narrow fabric or other weaving machine. Such a logo may serve to identify the product as that of a particular company, it may be provided for aesthetic reasons, or it may be provided to indicate the nature of the fluid that the underlying hose is carrying. For example, hoses containing dangerous fluids or hoses that will become hot during use may be provided with a marking in red etc. by way of a warning.

Various other characteristics may be built into the design of the sheath depending on the nature of the conduits to be coupled. For example, the materials may be chosen to ensure high temperature performance, oil resistance, acid resistance, and resistance to a variety of other chemicals.

EXAMPLE A heat-shrinkable bi-lumen fabric sheath was provided as follows. A narrow fabric loom was used to produce a heat-shrinkable fabric sheath comprising two tubes of 40 mm diameter in a plain weave having lengthwise warp and circumferential weft. The weft was a cross-linked linear low density polyethylene monofilament of 65 tex and the warp fibres consisted of six fold polyethylene terephthalate multifilaments, each of the six filaments itself consisting of thirty four very fine filaments. Each of the six multifilaments had a tex value of 16.7. The warp density was 27 ends per cm and the weft density was 11 picks per cm. The bulk of the fabric was made as a tubular plain weave design using four shafts. The flat spacer section was produced in the center of the fabric as a flat plain weave using four warp ends on an extra two shafts. The multilumen tube was coated with an aqueous disperion of an ethylene copolymer, dried and crosslinked by electron beaming. A section of sheath of length 25 cm was cut by means of a guillotine and slid over two rubber hoses of 23mm diameter and was then shrunk in place.

It will be understood that the reference to circumferentially-heat-shrinkable sheaths does not necessarily limit the invention to tubular sheaths of substantially circular cross-section.

Sheaths of square, triangular, hexagonal, or any other desired tubular cross-section, whether woven as tubes or formed by wrapping around and fastening a fabric originally woven as a sheet, may be included, provided that they are heat-shrinkable in the direction of the perimeter so as to narrow the tube, thus enabling them to contract around and grip the conduits to which they provide coupling in use.

The hoop filaments in this aspect of the present invention extend substantially circumferentially around the sheath, as distinct from the helical filaments of a braid, which extend very noticeably along the sheath as well as around it. The length filaments of the fabric according to the present invention extends substantially along the sheath, preferably substantially parallel with the sheath tubular axis, although a certain amount of helical curvature of these length filaments may be tolerable in practice and is to be understood as included within the expression"substantially along the sheath". It is generally preferred, though not essential, that the hoop filaments are provided by the weft of the fabric and the length filaments are provided by the warp of the fabric.

The invention also includes a method of making the sheaths hereinbefore described by weaving with the length (preferably warp) filaments held under sufficiently high tension and the hoop (preferably weft) filaments under sufficiently low tension. The length filaments are preferably multi-filament yarns, especially substantially-untwisted tows.. The spreading and flexibility of multi-filaments yams may also produce advantageous softness and noise- deadening impact insulation effects to reduce rattling in vehicles and other end uses. Mono- filaments or tape-like length filaments could nevertheless be used, provided they are flexible enough. The exact degree of flexibility is not readily quantifiable, but will generally be greater than that of relatively brittle materials such as glass fibre and can readily be tested by trial and error in practice. Lower flexibility may to some extent be better tolerated as the diameter of the filaments decreases.