Textiles: weaving – Fabrics – Materials
Reexamination Certificate
2002-04-24
2003-12-02
Calvert, John J. (Department: 3765)
Textiles: weaving
Fabrics
Materials
C139S4260TW, C139S42000D, C139SDIG001, C442S268000, C442S301000
Reexamination Certificate
active
06655416
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a novel type of textile material in sheet form that can be used for technical purposes, such as reinforcing structures for composites, laminated complexes, complexes for sealing in the building field, or in public works, complexes intended for repairing pipes and, more generally, for any type of structure comprising a resin-based matrix, made of polyester or other resin, reinforced by a textile reinforcing sheet.
PRIOR ART
The use of textile sheets, especially those based on glass fibers, has been proposed for decades for reinforcing a plastic in the manufacture of laminated or molded structures with a plane or shaped, as is apparent, for example, from patents FR-A-1 469 065, FR-A-1 394 271, U.S. Pat. No. 3,930,091, FR-A-2 034 787 and FR-A-2 568 275.
Such textile structures have also been proposed for the purpose of being used in the building field and in public works for the production of impermeable membranes, especially reinforced bitumen membranes (FR 2 409 338) for producing complexes that can be used to repair pipes or similar structures, whether buried or not (EP-A-542 639).
From all these documents, it is apparent that the reinforcing structure must be tailored according to the various applications.
The base structures that have been proposed for decades for producing such reinforcements, especially since the appearance of glass yarns, are, on the one hand, mats which consist of discontinuous fibers and are in the form of a structure similar to a “felt”, and, on the other hand, warp-and-weft fabrics consisting of yarns or roving assemblies based on glass yarns consisting of continuous filaments.
Apart from these types of structure, “unidirectional” sheets have also been proposed in which the glass yarns are arranged in the same longitudinal direction, these yarns being linked together either chemically (French patent 1 394 271) or by means of stitching (French patent 1 469 065).
It has also been proposed in U.S. Pat. No. 3,930,091 to produce a sheet which, unlike the previous ones, consists predominantly of glass fibers extending transversely with respect to the length of said sheet, these yarns being bound together by a binding warp thread, which is loose and consists of yarns coated with a heat-meltable or similar material, making it possible, especially after a heat treatment, to keep the weft yarns parallel to one another.
Compared with balanced warp-and-weft fabrics, such unidirectional sheets do not, however, allow articles reinforced both longitudinally and transversely to be produced.
Moreover, for many applications, the problem arises of how to have a reinforcing structure which can deform upon installing it, especially when articles molded to a shape are produced.
In the case of a reinforcement in the form of a unidirectional sheet, it is possible to obtain such “deformability” in the transverse direction with respect to the orientation of the yarns, for example by using elastic yarns as binding yarns.
In the case of a balanced warp-and-weft fabric, it may be envisioned to obtain deformability by selecting the weave.
This is because it is well known that certain weaves, of the satin or twill type, result in deformable woven structures. However, the amount of deformation possible is limited to a few percent.
Such a problem of limited possible deformability of the reinforcement also arises within the context of the use of complex structures consisting of a combination of a nonwoven mat and of bidirectional or unidirectional woven structures, which are used especially for repairing pipes using a technique consisting in covering the internal surface of the structure to be renovated with a tubular structure made from a flexible complex comprising a fluid-impermeable membrane and a fibrous base structure which is impregnated with an uncured synthetic resin and, after said complex has been pressed against the surface of the structure to be repaired, in causing the resin to cure so as to form an internal “sleeving”.
As regards putting such a tubular structure in place inside the pipe to be renovated, two main techniques have been used hitherto.
The first, which stems more particularly from British patent 1 357 355, consists in introducing the tubular material produced beforehand into the pipe to be renovated in such a way that the fibrous structure is positioned so as to face the surface to be renovated and the impermeable surface layer itself is located on the inside, facing the flow region.
After it has been put into place along the entire length of the pipe, the sleeve is put under pressure so that it is pressed against the internal surface. The resin is then caused to cure.
Another technique, called the “inside-out” technique, consists, as is apparent from British patent 1 449 455, in introducing the preformed sleeve with the impermeable surface lying on the outside and then, upon introduction into the pipe, in turning said sleeve inside out so that the fibrous structure comes into contact with the internal surface of the pipe and the impermeable layer lies on the inside.
Such a procedure allows the fibrous structure to be impregnated with uncured resin progressively as it is put into place inside the pipe.
Moreover, the curing may also be carried out continuously, for example by light radiation.
These two techniques, and more particularly the turning-inside-out installation technique, means having a base material which has sufficiently high mechanical properties in the length direction to ensure that it is installed.
Moreover, it is desirable that the tubular structure be able also to be deformable under the action of the stresses exerted in the transverse direction so as to allow the sleeve to rest perfectly against the surface of the wall to be renovated when the structure is pressurized, and to do so so that it follows perfectly the surface of the work to be renovated.
Consequently, in all uses involving textile reinforcements in sheet form, the problem may arise of having the possibility of deformation both in the machine direction and in the cross direction, while maintaining, in the final product (laminated article, molded article, impermeable membrane, complex for pipe repair), high mechanical properties in all directions.
SUMMARY OF THE INVENTION
What has now been found, and it is this which forms the subject of the present invention, is a novel type of fabric that can be used either by itself or combined with other structures, such as nonwoven fibrous webs, reinforcing meshes, etc., so as to constitute a complex which not only makes it possible, upon installing it, to retain good mechanical properties, especially tensile strength, both in the warp direction and in the weft direction, while still permitting deformation in the other direction, thereby ensuring in the final product mechanical properties equivalent to those conferred by a nondeformable fabric.
The invention also relates to a process and to a plant for producing such a type of fabric, as well as to the use of the latter to produce complexes such as built-up roofing membranes and pipe-repair structures.
In general, the material according to the invention consists of a warp-and-weft fabric made from twist-free roving assemblies of continuous technical filaments (glass, carbon, aramid, etc.), which roving assemblies will, in the rest of the description, be referred to by the generic term “yarns”. Such a fabric is characterized in that:
the fabric is made in a plain weave or derivative thereof, the density of the warp and the weft preferably being balanced;
the warp yarns or weft yarns are weakened or cut individually at predetermined intervals without any appreciable deterioration in the characteristics of the weft or warp yarns lying beneath the weakening or cutting area; and
the areas in which a series of yarns of the fabric are weakened or cut are produced with a lateral and vertical step between two consecutive yarns or groups of yarns.
In the present description, the expression “two consecutive yarns or groups of yarns” is understood to mea
Etablissement les Fild d'Auguste Chomarat et Cie
Heslin Rothenberg Farley & & Mesiti P.C.
Muromoto Jr. Robert H.
Pietrangelo John
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