WO1992009844A1

WO1992009844A1 - Improvements in and relating to tubing

Info

Publication number: WO1992009844A1
Application number: PCT/GB1991/002071
Authority: WO
Inventors: Hubert Andrieu; Daniel Caudron
Original assignee: Textilver SA; T&N PLC
Current assignee: Textilver SA; T&N PLC
Priority date: 1990-11-28
Filing date: 1991-11-26
Publication date: 1992-06-11
Anticipated expiration: 1993-05-28
Also published as: GB2250934A; GB9124884D0; GB9025923D0

Abstract

A braided or knitted flexible textile tube (4) is provided with a flexible foamed polymeric lining (17) over the inner surface thereof, preferably of a silicone elastomer. The tube (4) is preferably made of glass or polyester fibre and, optionally, has a further flexible textile tube (12) as a liner, the flexible foamed polymeric material (17) being enclosed between the outer (4) and inner (12) tubes.

Description

Improvements in and relating to tubing

This invention relates to flexible tubing and in particular to tubing made by braiding, knitting or weaving filamentary material. Such material will hereinafter be referred to as textile tube.

Textile tube especially when made from glass fibre/filament, is -commonly used for thermal protection of fluid conduits. For example, brake and fuel pipes often require protection against radiant heat from an internal combustion engine exhaust system. Known methods of enhancing the .thermal protection performance of textile tube include coating with a reflective layer such as aluminium foil or a resin composition incorporating aluminium flakes. More severe thermal conditions can be overcome by increasing the wall thickness of the textile tube. However, there are practical limits to the thickness of filament which can be economically processed into tube, especially for glass filaments. A possible solution to this is to make several overlaid concentric tubes into a single tube, but this is expensive.

An object of the present invention is to provide a novel textile tube which can be made in a single operation.

According to this invention, a flexible textile tube comprises a -knitted or braided fabric tube provided with a flexible foamed polymeric lining over the inner surface thereof. The foamed polymeric lining is preferably a silicone elastomer. The textile tube is preferably made from glass fibres/filaments, although for some end uses, it may be satisfactory to employ other fibres/filaments- such as polyester. Optionally, the foamed polymeric lining may be formed around the outer surface of a further flexible -textile tube which serves as a liner, the further tube having a smaller diameter than the outer or main flexible tube. In such a case, the flexible foamed polymeric lining preferably fills the annular space between the two tubes.

It is also possible to produce a tube in which the foamed polymeric lining fills substantially the whole of the textile tube. Such a product with a minimal or even no central bore may be used as a gasket material, for example as an oven door gasket of the kind used to prevent leakage of hot gases .

The outer surface of the textile tube may be treated to reduce heat absorption, for example by any of the methods described earlier.

The invention further includes a method of producing a flexible textile tube by the steps of braiding or knitting a tube from a plurality of textile filaments, introducing a curable foamed polymeric composition into said tube to form a flexible lining over the inner surface thereof and thereafter curing the composition in situ in the tube. The polymeric composition may be caused to foam before, after or during its introduction into the textile tube.

The method preferably includes the step of braiding or knitting the tube around a hollow mandrel through which the curable polymeric material is introduced into the tube. Preferably, the method further comprises the step of forcing the curable polymeric material around an extrusion die in the mandrel which cause the composition to adhere to the inside of the tube prior to the curing step. Curing is preferably carried out by subjecting the newly lined tube to heat, for example by passing the newly made tube through a heating zone. The composition may be foamed before or during its introduction to the tube. However, it is preferred to use the heating step to both cause the composition to foam and to cure it in situ.

Optionally, the method includes the step of introducing a further textile tube through the mandrel to form an inner textile liner for the foamed polymeric composition.

The invention also includes apparatus for carrying out the invention, the apparatus comprising a hollow mandrel provided with an inlet at one end thereof for a curable polymeric composition and at or adjacent the opposite end, an extrusion die adapted to cause the polymeric composition to flow from said opposite end as a tubular or cylindrical mass which adheres to the inner surface of a textile ube formed by knitting or braiding on said mandrel. The extrusion die may include a feed aperture for an inner textile tube, so that the curable polymeric material adheres to both tubes to form a final composite tube in which the inner and outer textile tubes are separated by a foamed polymeric layer.

In the case of a glass fibre braided tube with a lining of a foamed silicone elastomer, the additional heat insulation achievable by virtue of the foam layer is indicated by the relative thermal conductivities. Thus K for glass braid is typically 0.12 w/m/°C whilst for silicone elastomer foam, it is 0.035 w/m/°/c. Accordingly, a textile tube with a foamed polymeric lining can offer very significantly improved protection.

In order that the invention be better understood, preferred embodiments of it will now be described with reference to the accompanying drawing in which:-

Figure 1 is a schematic view of an apparatus adapted to produce textile tube according to the invention, and

Figure 2 is a cross-sectional side view of part of the apparatus of Figure 1, and

Figure 3 is a cross-sectional side view of part of Figure 2 illustrating a modified or further embodiment of the invention.

Like parts in all three Figures bear like reference numerals, in the interests of clarity. In Figure 1, a ^•conventional textile braiding machine comprises a supporting frame 1 provided with a plurality of bobbins 2 supported for motion around the circumference of the frame 1 in the usual way under the control of drive means (not shown). By virtue of the interweaving motion of the bobbins the filaments 3 from the individual bobbins are assembled as a conventional tubular braid 4 around a hollow mandrel 5, the latter being more clearly illustrated in Figures 2 and 3. At the top of the hollow mandrel there is an extrusion die 6 (Figures 2 and 3 show this in more detail). The die 6 is supplied with a curable, foamable silicone elastomer composition through a tube 7 from a mixing station comprising a supply drum 8, a mixer 9 and a pump 10.

Projecting from the top of the mandrel 5 there is an inner, fixed tube 11, or in the case of Figure 3, a further braid 12 of smaller diameter than the braid 4.

Surrounding the braid path above the extrusion die and around the fixed tube 11 (or braid 12) there is a tubular heat treatment oven 15 from which the braid 4 emerges, passes around a pulley 16 and is then taken to a winding station (not shown) where it is collected on a spool in the usual way.

Referring firstly to Figures 2 and 3, the actual braiding operation is entirely conventional in that the bobbins circle the frame 1 following the usual sinusoidal path relative to one another. The textile tube 4 produced by this is braided around the hollow mandrel 5 where the individual filaments 3 are brought together forming an interwoven (braided) structure. As the braid thus formed passes upwards past the extrusion die 6, it is internally coated with silicone elastomer composition 17 (Figures 2/3). This internal coating 18 has its inner diameter determined either by the inner fixed tube 11, or (in Figure 3) by the further braid 12 which is introduced through the centre of the extrusion die, from the bottom of the machine.

It will be appreciated that the further braid 12, if used, must be previously prepared. Normally this will be done by using a separate braiding machine to form a spool of the further braid. The use of a further braid will necessitate some minor modification of the extrusion die, as shown in Figure 3. In this case, the die is constructed with a centrally disposed inner aperture 20 through which the further braided tube 12 can pass. The die itself is thus tubular with an outwardly directed annular orifice 21 at the top, (as is also seen in Figure 2). The elastomer supply tube 7 is in the case of Figure 3 parallel to the further braid 12 although in the Figure 2 embodiment, this is not necessary.

The effect of the tubular heat treatment oven 15 on the silicone elastomer coating 18 is to cause the composition to foam and cure in situ on the inner surface of the braided tube 4, the inner diameter of the foam layer being determined by the fixed tube 11.

It will be appreciated that if the inner tube 11 is omitted and the rate of supply of composition is increased, the cured foam may fill the braided tube. As previously mentioned, this is within the scope of the present invention, as is the use of different diameter of braid, extrusion die and inner tube, in order to produce products of different sizes and characteristics. The same basic apparatus may be used to produce foam lined or foam filled textile tubes for many different end uses, since the kind an^'d number of filaments used and the polymeric material can be altered as appropriate.

Whilst the arrangements thus far described result in a textile tube which can be used for many applications, there are some applications where it is desirable to apply an external heat reflective coating. Figure 2 illustrates in simplified form how this may be accomplished by using an annular coating die 30 located below the oven 15. The coating die 30 is conventional; it comprises an annular trough 31 whose inner edge 32 is closely spaced from the braid 4 so as to apply a coating layer of controlled thickness. The coating material itself in curable liquid or semi-liquid form is supplied to the trough 31 through a feed pipe 33 from conventional mixing/compounding apparatus (not shown). A typical coating material might be a silicone or acrylic polymer composition filled with aluminium flakes, the oven 15 then serving to cure both the lining material and the coating layer. Examp l e 1

As a further illustration of the invention, a 48 carrier braiding machine of the Figure 1 type was set up with a bobbin of 320 tex glass fibre yarn on each carrier- The machine was operated to form a braided tube on a mandrel 20 mm in diameter at a take-up speed of 1.2 m/minute, thereby giving a braid angle of about 60°. A silicone elastomer composition comprising a material sold under the trade designation RTF 762 A/B and a foaming agent was pumped" up the inside of the mandrel to an extrusion die 19 mm in diameter. The die formed a compacted layer about 0.5 mm thick on the inside of the braid. The mandrel 11 in this case -had an outside diameter of 1.1 mm. The coated product was passed through the oven 15 at 300°C, the length of the oven being in this case 450 mm. The heat treatment caused the silicone elastomer to f am, expanding on the order of ten times, to yield a braided textile tube with a silicone elastomer foam lining about 5 mm thick. The final product had thus a 20 mm outside diameter and a 10 mm insi^'de diameter.

Example 2

The above procedure was repeated using a further braid instead of the tube 11. The further braid was of outside diameter 11 mm and was made from 544 tex yarns braided on a 96 carrier machine at a braid angle of about 47°. The final product was a braided textile tube 20 mm in outside diameter with an approximately 10 mm central bore lined with braid, the annular space between the two braids being filled with cured silicone elastomer foam.

Both products exhibited excellent insulation performance.

Claims

CLA IMS

1. A flexible textile tube comprising a knitted or braided tubular structure with a flexible foamed polymeric lining.

2. A textile tube according to claim 1 wherein the flexible foamed polymeric lining comprises a cured silicone elastomer.

3. A textile tube according to claim 1 or claim 2 comprising glass fibres/filaments.

4. A textile tube according to claim 1 or claim 2 comprising polyester filaments.

5. A textile tube according to any preceding claim provided with a further flexible textile tube as a liner, the foamed polymeric lining being formed on the outer surface of said further tube to fill the annular space between said tubes.

6. A textile tube according to any of claims 1-4 where the flexible foamed polymeric lining fills substantially the whole of the tube.

7. A textile tube according to any of claims 1-6 wherein the outer surface of the tube is treated to reduce heat absorption.

8. A method of producing a flexible textile tube according to any of claims 1-7, the method comprising the steps of knitting or braiding a tube from a plurality of textile yarns or filaments, introducing a curable polymeric composition into said tube to form a flexible foamed lining over the inner surface thereof and thereafter curing the composition as a foam in situ in the tube.

9. A method according to claim 8 wherein said composition is caused to foam _before, during or after introduction into the textile tube.

10. A method according to claim 8 or claim 9 including the further step of forcing said composition through an extrusion die whereby the composition is formed into a layer on the inner surface of the tube.

11. A method according to any of claims 8-10 including the step of forming said tube around a hollow mandrel.

12. A method according to claim 11 including the step of introducing a further textile tube through said mandrel to constitute a liner for the tube, the flexible foamed polymeric lining filling the annular space between the inner surface of the tube and the outer surface of the further tube.

13. Apparatus for producing a flexible textile tube according to claim 1, comprising a hollow mandrel provided with an inlet at one end thereof for a curable foamed or foamable polymeric composition, an extrusion die at or adjacent the opposite end adapted to cause said composition to flow from said opposite end as a flexible tubular or cylindrical mass which adheres to the inner surface of a textile tube formed by knitting or braiding around said mandrel.

14. Apparatus according to claim 13 further including in said extrusion die a feed aperture for an inner textile tube, so that the polymeric material adheres to both tubes to form a composite tube in which the inner and outer textile tubes are separated by a flexible foamed polymeric layer.

15. Apparatus according to any of claims 13-14 further comprising an oven operable to foam and/or cure the polymeric material.

16. A method of making a textile tube substantially as herein described with a foamed polymeric lining reference to and as illustrated by the accompanying drawings or by Examples 1 and 2.

17. Apparatus for making a textile tube with a foamed polymeric lining substantially as described with reference to and as illustrated by the accompanying drawings.