METHOD FOR ENHANCING THE WEAVING OF A WARP YARN FABRIC HAVING A HIGH MODULUS OF ELASTICITY

5 The invention relates to the field of weaving fabric, and more specifically to a method for improving the weaving of a fabric of warp yarns high modulus.

10 As is known, in a conventional weaving machine, the warp yarns are unwound from a warp beam, and then moved over a whip roll. Downstream thereof, depending on the weave chosen, the different parallel warp threads are pulled alternately upward and downward for shedding. The different yarns occurs 15 then unified at the point [...], where the comb comes beat the tissue after each weft insertion.

Within the shed, wires are pulled upwards and downwards by means of smooth. It is not surprising that these warp threads thus drawn 20 mechanical stresses to each opening of the shed. These constraints apply very strongly the wires on their guides successive (grommets, eyelets of the heddles, comb...) generating [...] and inducing to the cases of wires that cause stoppages of the weaving machine, thereby slowing the speed of actual production and the regularity of the resulting fabric.

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Some manufacturers of looms seek to decrease stress on wires in imparting a reciprocating at whip roll, in synchronism with the opening of the shed. Unfortunately, the great weight of the roll back rest and therefore its 30 high inertia reduces its mobility, and the more so as the beat frequency is high.

By designing from mechanical wires are subjected are even more important when the speeds beat are important. Thus, it has been found that for fast looms, [...] to say mainly those in which the weft yarn is driven by water jet 5 or air jet, it is difficult to exceed the speed of 1000 to 1200 beats per minute without observing a strong degradation of warp ends and many cases, and particularly as the modulus of elasticity of the warps is high.

10 This phenomenon, much steeper than the warp yarns are steeper, especially brings incidents more frequent when weaving polyester that for the polyamide.

The invention therefore seeks to overcome the problem of broken wires 15 consecutive chain's high mechanical stresses undergone by the wires at the time of opening of the shed and [...] increasing the beating rate machines while maintaining a same quality of weaving.

The invention provides a method for enhancing the weaving of a fabric comprising warp yarns to high modulus, wherein:

is unwound continuously, from a beam, a warp sheet parallel;

25 - passed said web on a roll back rest;

forming a shed, using smooth, defined in the advancing direction of the chain, to the input by an opening point of [...] and on the other side by a [...] point;

inserting a weft thread in the shed in the vicinity of the point 30[...] to form a fabric;

and finally, the tows and is wound regularly the fabric thus formed.

This method is characterized in that, adjacent the point of shedding, heating is created warp yarns to a temperature sufficient to induce a local reduction of the modulus of elasticity of the warp threads, followed by cooling of the wires 5 chain in the shed before it reach the smooth.

In the following description and claims, the term elastic modulus (or Young's modulus) the directional coefficient (or the slope at the origin) of the curve giving the tractive power and ordered 10 in abscissa the elongation than the force results. This module is expressed in Newtons/tex or in [...] (GPa at). By way of example, the elastic modulus of the polyester yarns cold is of the order of 10 GPa for textile yarns to strong residual elongation or elongation at break (greater than 35%). H can reach 15 GPa for leads to high 15 tenacity low residual elongation (of the order of 15%). For comparison, the Young's modulus polyamide yarns is of the order of 5 GPa or more. In the two cases -, a heating beyond the second order transition temperature causes a decrease in modulus of elasticity when stretching then the wire. Typically, the module 20 hot elasticity modulus may decrease to reach in some cases the tenth module's cold.

In other words, the invention involves heating the warp yarns at the opening point of the shed, to provide decreased 25 modulus of elasticity to make them more flexible, and more specifically to allow them to absorb, in the inlet region in the shed, the impulse voltage increases due to movement of the heddles.

30 In general, for the low rate of progression of, cooling occurs by natural convection, but the invention also covers the variants for the use of additional means of any kind to facilitate cooling.

Further, in the case where the warp yarns are thermoplastic and 5 therefore exhibit a softening temperature (rpm) and a melting point (Tm), is heated advantageously the warp yarns at a temperature between the softening temperature (rpm) and the melting point (Tm) of the warp yarns. Thus, the heating of the warp threads is possible in some cases cause stretching while limiting 10 the voltage to which are subjected the wires upon opening of the shed, thereby reducing the chances of breakage.

Thus, according to the invention, said warp threads is stretched in the heated zone due to the traction jerky that imparts the 15 movement of smooth, combined with the regular call of the rolling up the fabric. Surprisingly, the stretching saccadic wires thus produced does not produce as would be assumed of the, irregularities in the warp threads and leaving, in the tissue. Much to the contrary, there is an improvement in the regularity of the wires thus treated, both in like manner as in 20 dyeing affinity.

In practice, the heating is carried out either by convection, or by radiation or by contact.

25 In a practical embodiment, the heating performed by touching, by means of a heater pad protected from abrasion by a coating of chrome or ceramic. In other words, before entering the shed, or right at the inlet thereof, the warp threads rub by sliding on a heating element whose length, counted in the direction 30 passage of the thread, is calculated to cause the temperature increase desired to core wires, depending upon the length of the progression rate and size of the wires.

Advantageously in practice, the pad is associated with means for away from the yarn sheet on stopping of the loom 5 weaving. Thus, as soon as the warp threads are stopped, the heater pad is warp threads to avoid in causing degradation, or even merging in the extreme case.

Advantageously, the heater pad is located above the chain 10 to avoid heating the remanent by convection during the ignoring of the skate.

In a preferred embodiment, the expander device heater pad operates by default, [...] to say it automatically retracts 15 the skate as soon as the progress of the wire stops, either consecutively to a thread breakage downstream, or following a failure of supplying electricity or compressed air of different organs of the plant.

In a preferred embodiment, the heater pad is disposed 20 in a region between the whip roll and lease guides disposed in proximity to the whip roll, defining the points of opening of the shed. Thus, the heating is achieved uniformly for all wires joined in a planar region where they are all parallel.

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This method can process many wires chemical, for example polyamides, polyester and advantageously partially oriented yarns, commonly called "roughing" ., especially such as disclosed in U.S. patents to-3 771,162 and US-to-3 772,872. In effect, the 30 weaving method according to the invention yields a yarn stretching and thus provides in a single step the two drawing operations saccadic characteristic and weaving whereas hitherto, for producing a fabric-based roughing, is resulted in prior to drawing regular traditional then a fully independent manner, at the time of weaving.

Π also permits processing of wires used in technology such as the glass strands or steel.

The way of realizing the invention, as well as concomitant advantages shall become apparent much of the description of the embodiment that follows, in support of the single figure herewith, which represents schematically the circuit paths of the warp yarns, within a loom.

As already said, the invention provides a method for enhancing the warp yarn weaving high modulus. This method can be implemented on a conventional loom, on which added elements for performing the function characteristic of the process.

Thus, the conventional loom ' has in the direction of the thread course, a warp beam (1) mounted on a shaft (2), and on which are wound parallel all the warp. These warp threads (3), from the warp beam (1) are unwound to a whip roll (4) from which they take a substantially horizontal direction. In a particular embodiment, said warp threads (3) then pass between two waveguides lease (5, 6). From these waveguides lease (5, 6), they are supported by stringers (7, 8) the object of which is apart upwardly or downwardly the different warp yarns (3) for shedding (9) and the insertion of the weft thread (16). After the smooth (7, 8) the warp threads are brought together at the point [...] (10) on which beat the comb (11), after each re-opening of the shed. From the point of [...], the tissue (12) thus formed passes different deflection rollers (13) give the end winding system (14).

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As already said, the invention includes heating the warp threads, adjacent the point of shedding, to decrease their modulus of elasticity and possibly their separation-of by the action of the machine, a stretching jerky just prior to weaving itself. As 20 already said, drawing jerky results in a regularity of the fabric, thus providing an unexpected effect, which explains the fact that it does not have hitherto been searched.

Thus, various means can be adjusted to ensure that 25 heating. In the illustrated form, it is a heater pad (20) present on the entire width of the set of warp yarns, and engageable with the warp sheet, between the roller (4) back rest and the guides lease (5, 6). More specifically, it is a transverse heating element whose bottom face is covered with a material 20 to very high surface hardness and low friction to avoid being abraded by the warp yarns which disturbances subsequent deterioration of the warp threads themselves. It includes in particular an outer layer (24) chromium plating or ceramic.

25 Of course, the invention covers all types of heating the shoe, and including those using electrical energy, by means of connections (22) appropriate.

As already said, the skate (20) may be associated with means (21) 30 engage the cutting position the pad (20) contact with warp yarns (3), and in particular remove the skate in the event of stopping of the machine, and this to avoid causing degradation or even melting of the wires in the extreme case. It may be purely mechanical means, or preferably by means of hydraulic cylinders acting, or even of electromechanical systems. Most preferably, the position 5 the rest of the pad is spaced apart from the thread layer so that in case of failure of the spacer means, the pad does not contact with the wires but instead automatically moves away therefrom.

Most preferably, the pad is positioned above the web 10^wires ·

Of course, the invention is not limited to the shape shown wherein the heating is carried out upstream guides lease (5, 6), but it also covers the variants in 25 which heating occurs near or just after them.

Furthermore/the method may be performed by a heater pad which contact area with the wires is a few centimeters, but also by means operating by radiation, or by 20 convection in which the heating element does not directly contact with the warp yarns.

As already said, the invention consists in the particular case of thermoplastic strands to raise the temperature of the wire beyond its temperature 25 transition, but below the melting point. Thus, it has been observed, for treating the polyamide (6-6), that the result was interesting if the temperature was in the range of to C. For 180° 200° polyamide 6, this temperature is 170° 190° to C. Concerning the polyester, this temperature is close 200° c to c-220°.

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Tests have been completed on [...] warp threads [...], a cloth made from one hand, according to the method, and on the other hand, without effecting the heating characteristic of the invention. Thus, it is observed that the tenacity treated yarns according to the invention is significantly increased, typically 10 % for the wires already drawn and 5 more than 100% for the roughing. Additionally, there is a regularity of the wires, as in like manner as in dyeing affinity.

In addition, the elongation at break is reduced, and can for example from 40% to 60 for wires previously drawn. In the case 10 particular a roughing, the elongation at break (or residual elongation) can pass from 50% to 400% before stretching after drawing. Finally, the dispersion regarding this elongation at break is extremely reduced, a factor 5, which corresponds to a homogenization of the qualities of the warp yarns. This homogenization is observed also in 15 dyeing affinity of which is improved.

It spring of the above that the method according to the invention proves advantageous in different planes. Thus, the processing of the yarn being woven allows an increase in the speed of 20 operation greater than 20%, for [...] to say typically pass from 1000 strokes per minute to more than 1200. Furthermore, the [...], [...] i.e. yield is increased, and 95% to 97 typically pass or even 98%, the increase in yield is complicated that it combines with the fact that the beating rate is also 25 increased.

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