Stock material or miscellaneous articles – Structurally defined web or sheet – Including grain – strips – or filamentary elements in...
Patent
1998-03-30
2000-12-26
Ahmad, Nasser
Stock material or miscellaneous articles
Structurally defined web or sheet
Including grain, strips, or filamentary elements in...
156178, 156179, 428107, 428110, 428111, B29C 7022, B32B 512
Patent
active
061655864
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a flat strip, in particular for reinforcing ducts, and to ducts reinforced by such strips.
An expedient use of the flat strip according to the invention is in the production of the reinforcements of a hose used in the oil industry.
BACKGROUND OF INVENTION
Strips or bands for specific uses are provided in the literature and in industry, each strip or band consisting of filamentary rovings made of synthetic or natural material, which are connected to one another either by means of a binding material, whatever the degree of impregnation of the said rovings, or by means of woven, braided, lapped or twisted textile threads.
The technique for the first category has the disadvantage of requiring a large proportion of material in order to ensure that the rovings are bound to one another. At the present time, the proportion of material is of the order of 50% by volume, even when the fibres within the rovings are impregnated only partially or not at all. This results in a limited performance in terms of maximum permissible resistance per unit of cross-section. This is especially the case with regard to profiles made of the composite material FRP (Fibre Reinforced Plastic), such as a composite consisting of glass fibre or aramide fibre and thermosetting or thermoplastic resin, and as regards strips consisting of a lap of juxtaposed parallel rovings (for example, made of aramide) which are contained in a thermoplastic mass, such as polyamide, the said mass being longitudinally and transversely continuous.
Other disadvantages described below have been encountered in the use of this technique, depending on the type of binding material. When the material is deformable, such as a thermoplastic, for example a polyamide, it does not ensure that the radial position of the rovings or their position in relation to one another is maintained sufficiently firmly when the strip is subjected to high traction, such as when it is wound around a duct. It has been found, in fact, that the tensioned filaments, while bearing on a curved support, tend to approach the supporting surface and to push the lower filaments radially and laterally in spite of the binding material. This results in the material experiencing a creeping effect under the influence of contact pressure exerted by the filaments. By contrast, when the material is not deformable, such as a thermosetting resin, for example epoxy resin, the strip is rigid and is therefore unsuitable for being wound around a duct.
With regard to the technique of the second category, there have been improvements in assembling longitudinal rovings more efficiently. Thus, in weaving, it has been proposed to add to or substitute for the weft threads threads which comprise heat-meltable material, the heat-sealing property of this material being revealed after weaving. The function of the heat-meltable material is to ensure the stability of the rovings relative to one another after the fabric has been cut, as described in the FR 2,577,946.
The FR 2,677,047 is also known, this describing a textile reinforcement in the form of a plane band intended for the production of complex laminated structures. The reinforcement comprises spaced longitudinal threads forming a unidirectional structure and a flattened tubular braiding forming a bi-directional structure which surrounds the longitudinal threads. It likewise comprises threads comprising heat-meltable material for binding the longitudinal threads in the manner of a loose woven weft. After thermal treatment, the heat-meltable material ensures that the longitudinal threads are held relative to one another and are connected to the tubular braiding.
The products described in the above patents are intermediate reinforcing products involved in the composition of a complex laminated structure, for example tubes made of the composite material FRP. They are put to use by being embedded in a thermosetting resin and forming the reinforcing element of the latter after the resin has been cured. As such, they must have bare warp
REFERENCES:
patent: 2129110 (1938-09-01), Weaver
patent: 4664961 (1987-05-01), Vees
patent: 5885685 (1999-03-01), Tingley
Do Anh Tuan
Le Nouveau Joel
Ahmad Nasser
Coflexip
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