EP0118373A1 - Open-work textile structure and its method of manufacture - Google Patents

Abstract

Open-work textile structure of the type constituted by a warp knit fabric produced with yarns coated with a thermoplastic material, the coating being partly melted and bonding the yarns together in those areas where they are in contact. According to said structure, the open-work takes in the form of regular polygons of which some of the edges at least are slanted with respect to the length of said structure, the stitches of said knitted fabric imprisoning a weft yarn which extends in substantially a straight line parallel to the edges of the formed open-work.

Description

The present invention relates to a new type of openwork textile articles, produced on knitted looms; it also relates to a method for obtaining such an openwork article.

Knitted items e. discarded knits having a structure similar to a net are well known to technicians and have been the subject of numerous publications such as those which appeared in the review "Knitted Outerwear Times" of July 1968 pages 37 to 40.

Compared to threads conventionally produced by knotting, such articles have the advantage of being able to be produced at high speed, which considerably reduces their costs.

However, such knitted nets have the drawback of being able to be produced only in relatively small widths, depending on the knitting loom used. In addition, except when using complex armor and looms with a very large number of guide bars, they have a tendency to deform easily and not to exhibit homogeneous resistance in all directions. Finally, it is well known that certain threads such as glass threads, carbon threads, etc. which have very high tensile strength and are therefore particularly advantageous for certain applications, cannot be easily used on knitting looms, given their fragile flexion. However, the formation of meshes implies the creation of such constraints.

It has also been proposed in the French utility certificate published under No. 2,250,497 to make knitted articles, more particularly of the knitted type from yarns covered with a thermoplastic material. After knitting, the fabric is subjected to a heat treatment in order to give it a better hold and to ensure the cohesion of the assembly to avoid the unraveling. These articles used for the manufacture of curtains, that is to say for applications in which the mechanical stresses are low and / or are exerted in a preferential direction of the article (longitudinally or transversely) cannot be successfully used in other fields in which it is necessary to have balanced mechanical characteristics both in length and in width, or even at an angle as is the case for protective nets, safety nets, breeze nets -winds or fall arresters, laminate reinforcements .....

In addition, if one wants to obtain non-deformable articles, this implies the formation of a structure blocked on the loom itself and therefore limits the width of the article to the width of the loom.

However, we have found, and this is what is the subject of the present invention, a new type of openwork textile structure constituted by a knitted knitted fabric which, not only has great stability but also has mechanical characteristics balanced in almost all directions (long, cross and bias).

Furthermore, the openwork structure according to the invention has the characteristics of having a width that is significantly greater - than the knitting width, which can reach two to three times the latter and this, while exhibiting the aforementioned properties.

The invention also relates to a method for obtaining such an openwork textile structure.

In general, the openwork textile structure according to the invention is of the type constituted by a knitted fabric knitted made from yarns comprising a sheath of thermoplastic material, said sheath being partially melted and binding the threads together in the areas where they are in mutual contact and they are characterized by the fact that said knitted fabric is based on a weave comprising at least three bars and that the days are in the form of polygons regular, at least some of the sides of which are oriented at an angle with respect to the length of the structure and that the stitches of said knit trap a woven thread which extends in a substantially straight line parallel to the sides of the days formed.

Various textures can be envisaged without departing from the scope of the invention, depending on the final mechanical characteristics which it is desired to obtain.

Thus, according to an embodiment of the invention, the days of the structure have a hexagonal shape, which makes it possible to obtain practically identical resistances as well in the direction of the length, in the transverse direction and in the bias direction .

Alternatively, the days have a diamond shape, which gives perfectly balanced properties in the bias direction.

As yarns allowing a material according to the invention to be obtained, conventional coated yarns will be used, the core of which may be based on any textile material. However, the invention is particularly suitable for being implemented with high modulus wires which can be used for industrial applications, such as glass wires, high resistance chemical wires such as those sold. under the brand KEVLAR and this, even if these threads have a brittleness in bending because it has been observed that thanks to the process of implementation to obtain articles in accordance with the invention, such threads could be knitted without difficulty, then that this was not possible until now.

Of course, depending on the desired results, it is possible without departing from the scope of the invention, to use different types of weave provided that these weaves make it possible to obtain an openwork structure which can be deformed after knitting; similarly, the wires constituting the structure according to the invention can be either identical for all the guide bars, or possibly based on different materials and this, as regards both the core and the sheath.

As said previously, the invention also relates to a method for obtaining an openwork textile structure as defined above.

• - que le tricot ajouré réalisé est à base d'une armure comportant au moins trois barres, au moins deux de ces barres étant enfilées à disposition et travaillant de manière à former un filet dont les jours sont déformables et sont de forme polygonale et sont susceptibles d'être déformés transversalement, la troisième-barre distribuant un fil tramé ;
• - qu'après réalisation du tricot, on l'étire transversalement lors de l'opération de traitement thermique de manière à orienter en biais par rapport à la longueur dudit tricot au moins une partie des jours qu'il comporte et a, amener les fils tramés dans une position sensiblement rectiligne parallèlement aux côtés des jours formés.

In general, the method according to the invention consists in making a knitted fabric, on a warp loom, Rachel or the like, from yarns comprising a sheath of thermoplastic material and then heat treating the perforated textile structure obtained, so as to partially melt the thermoplastic sheathing material in order to bond the wires together in the areas where they are in mutual contact, and the method according to the invention being characterized by the fact

• - that the openwork knitting produced is based on a weave comprising at least three bars, at least two of these bars being threaded at disposal and working so as to form a net whose days are deformable and are of polygonal shape and are susceptible to be deformed transversely, the third bar distributing a screened wire;
• - that after knitting, it is stretched transversely during the heat treatment operation so as to orient at an angle with respect to the length of said knitting at least part of the days it comprises and to bring the threads screened in a substantially straight position parallel to the sides of the days formed.

Preferably, when knitting, the loom is adjusted so as to have a decontextured structure, the stitches being loose, this being obtained, for example, by increasing the flow and / or the felling to a value higher than that used for the production of knitted nets proposed to date.

Thanks to such a process, it is therefore possible to obtain, on a loom of determined width, articles having a much greater width, of the order of two to three times the knitting width, on the days of the article finished. being, unexpectedly, perfectly stabilized while the untreated knit is by its eminently deformable structure, said article also having mechanical characteristics balanced in all directions (length, width, bias) and therefore good isotropy.

The invention and the advantages which it brings will however be better understood thanks to the exemplary embodiments given below by way of indication but not limitation and which are illustrated by the attached diagrams, diagrams which are conventional representations of knitted articles with knits discards and which, for a person skilled in the art, allow without particular difficulty, to reproduce them.

For the four exemplary embodiments which will be described in more detail below and which all relate to an openwork textile structure in accordance with the invention, a Rachel loom of gauge 12 is used as a loom (that is to say having twelve needles in 25, 4 mm) the food threads being coated threads comprising. a core based on high tenacity polyester, 1100 decitex, coated with PVC at a rate of 30% polyester and 70% PVC by weight.

Example 1:

This example illustrated by FIG. 1 illustrates a perforated textile structure in accordance with the invention obtained from a three bar weave knit.

The front bars (I and II) are threaded at disposal, a full, a vacuum, and work so as to form a net whose days are likely to be deformed if the knitting is pulled. By itself, such a type of openwork structure is not industrially usable taking into account this possibility of deformation.

• - barre (I) : 4.6/4.2/4.6/4.2/4.6/6.4/6.8/6.4/6.8/ 6.4
• - barre (II): 4.2/4.6/4.2/4.6/4.2/2.4/2.0/2.4/2.0/ 2/4

In the present case, the wires of the bars (I) and (II) work according to the following armours:

• - bar (I): 4.6 / 4.2 / 4.6 / 4.2 / 4.6 / 6.4 / 6.8 / 6.4 / 6.8 / 6.4
• - bar (II): 4.2 / 4.6 / 4.2 / 4.6 / 4.2 / 2.4 / 2.0 / 2.4 / 2.0 / 2/4

Regarding the bar (III), it is threaded full and works in a weft weave 2.2 / 0.0. The knitted fabric obtained is then treated on a ream where it is widened by approximately 2.5 times and subjected to a temperature of approximately 135 ° C for one minute, making it possible to cause a partial melting of the PVC sheath which causes the bond. wires between them at their point of contact.

This passage on the ream allows to give the knitting days a hexagonal, regular configuration. The sides formed by the parts corresponding to the area A of FIG. 1 are arranged in the lengthwise direction of the fabric, while the sides corresponding to the areas referenced B and C are oriented at an angle relative to the length of the article. . Furthermore, the wires of bar III which work in the weft on a needle are brought in a substantially straight line with respect to the sides of the formed day.

In this way, an article is obtained which has excellent stability while the starting knitted fabric is, by itself, highly deformable, this article having balanced mechanical characteristics. both long and wide and across.

Example 2.

This example illustrated by FIG. 2 is comparable to the previous example, but differs from it in that the weave ratio is 32 rows instead of 10. An openwork textile structure is also obtained, the days having a hexagonal shape, the sides extending both in the long direction and at an angle and in which, the wires of the bar (III) which form the wefts, are substantially aligned with respect to the sides of said days.

Example 3.

This example illustrated by FIG. 3 shows an openwork textile structure according to the invention produced in a four-bar weave.

As for the previous examples, the bars (I) and (II) form the openwork mesh structure of the knitted fabric while the bars (III) and (IV) are threaded at disposal and work in a woven weave.

Compared to the articles obtained in accordance with Examples 1 and 2, this openwork textile structure appears, after widening and heat treatment, with diamond-shaped days, the weft threads extending substantially rectilinearly inside the knitted fabric. .

Example 4.

This example illustrated in FIG. 4 is a variant making it possible to obtain an openwork textile structure having diamond-shaped days.

In this armor, the bars (I) and (II) form the mesh structure while the bars (III), (IV) (V) and (VI) work in a screened armor. After widening the knit and heat treatment, a perfectly stable and balanced article is obtained.

The articles obtained in accordance with the invention can find numerous applications and be used as is, for example, as a safety net, windbreak nets, fall protection, geotextile articles.

They can also be used as reinforcing elements for laminated or laminated articles, etc.

Of course, the invention is not limited to the embodiments described above, but it covers all the variants produced in the same spirit.

Thus, if in the previous examples, knitting is obtained on a Rachel loom with a needle bed, it could possibly be envisaged to produce tubular knits on Rachel looms with two needle beds, the article obtained being either kept in the form of a tube, or possibly cut according to a generator, which allows to double the width of the finished product.

Furthermore, such articles could also be made on any other loom, such as chain looms or hook looms.

In addition, it is possible by combining different armors, to obtain days of different shape from each other, for example an alternation of days of hexagonal shape and of diamond shape.

Furthermore, if it is preferable to produce articles made up entirely of wires comprising a heat-bonded sheath, it could be envisaged to have only some of these wires having such a property, for example to have only woven wires. or that two bars working in opposition and which form meshes.

Furthermore, in addition to the particular characteristics resulting from the very structure of the article according to the invention, the presence of a thermoplastic sheath makes it possible to obtain very good protection against bad weather, ultraviolet radiation,. Or even coloring effects.

Finally, if the material used is wires of which only the outer periphery is based on a thermoplastic material, it could be envisaged to use any other equivalent type of son, or even wires entirely based on thermoplastic material. Similarly, if the heat treatment to which the article is subjected is such that there is only a partial melting of the thermoplastic sheath, and this in order to keep it a certain flexibility, it could be envisaged to carry out a treatment much more thermal depending on the desired stiffness.

Claims (5)

1 / Openwork textile structure of the type consisting of a knitted fabric, made from threads comprising a sheath of thermoplastic material, said sheath being partially melted and binding the threads together in the areas where they are in mutual contact, characterized by the fact that said knit is based on a weave comprising three bars and that the days are in the form of regular polygons, at least some of the sides of which are oriented obliquely to the length of the structure and that the stitches of said knit trapping a screened yarn which extends in a substantially straight line parallel to the sides of the days formed. 2 / textile structure according to claim 1, characterized in that the days have the shape of a hexagon whose two sides are parallel to the lengthwise direction of the fabric, the others being arranged at an angle to said fabric. 3 / Openwork textile structure according to claim 1, characterized in that the days are in the form of a diamond. 4 / A method for obtaining an openwork textile structure according to one of claims 1 to 3 which consists in making a knitted fabric knitted from threads comprising a sheath of thermoplastic material, then that the heat is treated openwork textile structure obtained so as to partially melt the thermoplastic sheathing material in order to bond the threads together in the areas where they are in mutual contact, characterized by the fact: - that the openwork knitting produced is based on a weave comprising at least three bars, at least two of these bars being threaded at disposal and working so as to form a net, the days of which are deformable and are of polygonal shape and are liable to be deformed transversely, the third bar distributing a screened wire; - that after knitting, it is stretched transversely during the heat treatment operation so as to orient at an angle relative to the length of said knitting at least part of the days it comprises and to bring the wefted threads in a substantially straight position parallel to the sides of the days formed. 5 / A method according to claim 4, characterized in that the loom is adjusted so as to have a decontextured structure, the meshes being loose.

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