EP2964825B1 - Method and machine for spreading a fabric-type textile sheet - Google Patents

Description

The present invention relates to the technical field of machines for homogenizing the thickness of fibrous webs and / or spreading such fibrous webs, in order to obtain lower surface weights. In particular, the invention relates to a method and a machine for homogenizing the thickness of such sheets, as well as fabrics obtainable by the implementation of such a method.

In the field of composite materials, the Applicant has been interested in providing textile webs having the most homogeneous thicknesses possible, so as to obtain parts with final mechanical properties mastered. In the case of fabrics, conventionally constituted by an interweaving of warp threads and weft threads, this is particularly difficult.

Composite reinforcements are exclusively used with the addition of resin by different processes. The geometry of the final composite part therefore directly results from the thicknesses of the reinforcement used. It is clear that the use of thinner reinforcements will offer lighter composite parts and also more efficient because having their fibers oriented better with less ripples. What is less obvious but also true is that these reinforcements are also used in sometimes large stack, it is necessary to minimize their thickness variations to make more reliable and robust geometry of the composite part obtained. The individual variabilities of the folds going to add up, a great variability of the thickness of the reinforcement will inevitably lead to a high variability of thickness in the final part when using processes such as vacuum infusion.

Various documents are concerned with the spreading of tissues, without mentioning the impact that the spreading applied on the thickness may have and in particular on the differences in thicknesses that the spreading textile plies obtained have. We can mention the documents US 4932107 , US 5732748 , EP 670921 , WO2005 / 095689 and WO 94/12708 . It is important note that a fabric does not come out of a loom with a thickness and an opening factor homogeneous over its width. Indeed, the very principle of weaving induces a withdrawal phenomenon well known to those skilled in the art. This shrinkage is a decrease in the width of the warp ply before and after weaving. It is due to the interlacing action of the warp and weft threads. They travel a final distance lower because of their undulations on and under the warp threads. This results in a decrease in the width of the web at the exit of the comb of a loom. As this shrinkage is related to the corrugations of the weft threads, it is not homogeneous over the width of the fabric in that the weft threads are more free close to the edges and less held by smaller neighboring warp threads. Being less blocked and freer, these edge wires thus wave more, resulting in a greater thickness and generally a larger opening factor. The difference in thickness between the edges and the medium increases with the mass per unit area of the fabric.

It should also be noted that the phenomenon of edge allowance is accentuated very locally by the use of generally thermoplastic selvedge threads used on the edges of the fabric to block the last warp threads.

All the fabrics proposed in the prior art, which are spread after weaving, because of the spreading technique used necessarily have significant thickness variations. In particular, in the document US 4,932,107 there is no mention whatsoever of any width of the fabric, the average width of the warp and weft yarns after spreading and the homogeneity of the aperture factor on the fabric. Now, all these elements determine the more or less homogeneous thickness of the tissue obtained after plating. If one considers the examples proposed in this patent, if one applies a tension of 200g / cm on a fabric of 1.5m of width, the value of the tension on the roll will be 150x200 = 30000 is 30000g. This value is sufficient to create a bending rollers preventing a parallelism between the axes of the rollers and therefore a homogeneous pressure on the fabric, due to a greater pressure on the edges. he This results in a limitation of the width of the fabric to be treated in relation to the diameter of the rolls and their length. To try to circumvent this difficulty, it could be envisaged to increase the diameter of the rollers to limit the bending, but in this case the inertia of these would then become important and the energy necessary to obtain the amplitude and the frequency would increase in proportion. Moreover, it can be noted that the patent US 4,932,107 has implemented in its example 3B, 2 rollers 125mm in diameter with a single vibratory upper roller diameter 60mm, which does not allow to obtain on the one hand, satisfactory spreading and on the other hand, a homogenization of thickness. More generally, all the tissue spreading techniques described in the prior art do not make it possible to adapt to the initial differences in thickness that the tissue exhibits and therefore do not make it possible to obtain a spread and a homogenization of the satisfactory thickness.

There are also fabrics made in two steps, the first step being the constitution of low weight webs consolidated via a polymeric binder, and then making the interlacing to form a fabric. Such fabrics due to the prior consolidation of the webs offer less opportunities in terms of deformability during their implementation. In addition, the polymeric binders used may not be compatible with the specifications hygrothermal solicitation of the final composite part.

In this context, the invention proposes to respond to the problems mentioned above and encountered in the prior art and to provide a new method and a new machine for controlling, in a simple manner, the thickness of the textile web obtained. following a spreading operation, so as to obtain a small variability in thickness, even on large widths of web.

• on amène la nappe à défiler entre au moins deux rouleaux rotatifs dont les axes s'étendent parallèlement entre eux et sensiblement perpendiculairement au sens de défilement de la nappe,
• on fait passer la nappe sous pression entre au moins une génératrice de pression des rouleaux entraînés en oscillation axiale et en opposition de phase.

In this context, the invention relates to a method of spreading a textile web comprising at least warp threads, according to which:

• the web is brought to scroll between at least two rotary rollers whose axes extend parallel to each other and substantially perpendicular to the direction of travel of the web,
• the web is passed under pressure between at least one pressure generator of the rollers driven in axial oscillation and in opposition of phase.

According to the invention, at least one pressure generator of the rollers is produced with adjustable pressure values along said generator to spread the sheet with a small thickness variability.

In the context of the invention, it is thus possible to ensure the application of a uniform pressure on the web to obtain a uniform thickness regardless of the width of the web. The rollers thus modulate the pressure applied between the center and the ends of the web, taking into account the different thicknesses of the web so as to apply a uniform pressure on the material along the pressure generator. Typically, the pressure applied to the center of the web is greater than that applied on its edges to account for the upper thickness of the web on its edges relative to its central part.

According to a preferred embodiment, one of the rollers, which is flexible and the other rigid, is made and is carried on this flexible roll, substantially perpendicular to its axis, localized supports distributed along the axis of the roll and with adjustable values. to realize the generator with adjustable pressure values. The flexible roller can thus self-position without stress and thus modulate the pressure applied to the web. In this case, the method preferably consists, among other things, in adjusting the position of the localized supports along the axis of the flexible roller and / or in distributing the localized supports regularly along the axis of the flexible roller.

According to a preferred embodiment that can be combined with the previous one, the method consists, among other things, in distributing the localized supports at most over the entire width of the textile web.

According to another preferred embodiment that can be combined with the above, the method consists, among other things, in bringing the textile web to passing on the periphery of the flexible roller between two pressure generators with adjustable localized pressure values of two rigid rollers driven in synchronism, rotation and oscillation. In this case, preferably, the method consists in causing the textile sheet to pass between 1/6 and 1/3 of the periphery of the flexible roll. It is thus possible to overcome the tension applied to the moving textile web. In addition, this makes it easier to obtain an adjustable pressure on the textile ply throughout the two pressure generators between the textile ply and the rigid rolls, since this mode of passage of the textile ply which no longer wraps the rolls. as in the patent US 4,932,107 This makes it possible to add a series of rigid supports to the two rigid rollers thus avoiding any bending. On the other hand, this mode of passage also facilitates the positioning of localized supports on the flexible roller.

According to another preferred embodiment that can be combined with the above, the method comprises heating the textile web during its passage between the pressure generator or generators.

According to another preferred embodiment that can be combined with the above, the method consists in providing, as textile web, a fabric comprising warp threads and weft threads each consisting of a set of filaments able to move freely relative to one another. the others within said wire, the spread being made on the warp son and weft son.

• au moins deux rouleaux rotatifs dont les axes s'étendent parallèlement entre eux et perpendiculairement à une génératrice de pression, délimitée entre les deux rouleaux,
• une motorisation en rotation pour au moins un rouleau,
• et un système d'entrainement des rouleaux en oscillation axiale en opposition de phase.

The present invention also relates to a machine for spreading a textile web composed of at least warp threads, comprising:

• at least two rotary rollers whose axes extend parallel to each other and perpendicular to a pressure generator defined between the two rollers,
• a motorization in rotation for at least one roll,
• and a system for driving the rollers in axial oscillation in opposition to the phase.

According to the invention, the machine comprises a system for creating the pressure generator with distributed adjustable pressure values according to said generator, for spreading the textile web with a small thickness variability.

• le système pour créer la génératrice de pression comporte parmi les rouleaux rotatifs, un rouleau flexible et une série d'appuis localisés à pression réglable, répartis selon l'axe du rouleau flexible et agissant sur le rouleau flexible supporté par au moins un rouleau rigide,
• les appuis localisés sont équipés d'un dispositif de réglage de leur position le long de l'axe du rouleau flexible,
• les appuis localisés exercent leur pression sur le rouleau flexible, via des organes de roulement à débattement axial,
• le rouleau flexible délimite avec deux rouleaux rigides dont les axes s'étendent parallèlement entre eux, deux génératrices de pression avec des valeurs de pression localisées réglables, ces deux génératrices étant écartées entre 1/6 et 1/3 de la périphérie du rouleau flexible,
• les rouleaux possèdent un diamètre compris entre 30 mm et 60 mm,
• la machine comporte pour chaque rouleau rigide, une série de supports rigides comportant chacun un berceau fixé à un châssis et présentant deux branches d'appui équipées chacune d'un organe de roulement pour un rouleau rigide, possédant un mouvement de rotation et un mouvement de translation selon l'axe des rouleaux rigides,
• le système d'entrainement des rouleaux en oscillation axiale et en opposition de phase comporte un moteur entraînant en synchronisme à l'aide d'une transmission, deux arbres à came décalés à 180° dont l'un agit sur l'une des extrémités du rouleau flexible et dont l'autre agit sur l'une des extrémités du ou des rouleaux rigides, l'autre extrémité des rouleaux étant sollicitée par un système élastique ; ceci permet d'assurer un contrôle parfait de l'amplitude et du fonctionnement en opposition de phase entre le rouleau flexible et les deux rouleaux rigides,
• la machine comporte un système de relevage du rouleau flexible dont les extrémités sont pourvues de plaques sur l'une desquelles agit le système élastique et sur l'autre desquelles agit l'arbre à came,
• la machine comporte un système de chauffage de la nappe textile lors du passage de la nappe textile entre les génératrices de pression.

The machine according to the invention comprises one or the other, or all the characteristics below, when they do not exclude each other:

• the system for creating the pressure generator comprises, among the rotary rollers, a flexible roller and a series of adjustable pressure localized supports, distributed along the axis of the flexible roller and acting on the flexible roller supported by at least one rigid roller,
• the localized supports are equipped with a device for adjusting their position along the axis of the flexible roller,
• the localized supports exert their pressure on the flexible roller, via axially-running rolling members,
• the flexible roller defines with two rigid rollers whose axes extend parallel to each other, two pressure generators with adjustable localized pressure values, these two generators being spaced between 1/6 and 1/3 of the periphery of the flexible roller,
• the rollers have a diameter of between 30 mm and 60 mm,
• the machine comprises for each rigid roller, a series of rigid supports each having a cradle fixed to a frame and having two bearing branches each equipped with a rolling member for a rigid roller, having a rotational movement and a movement of translation along the axis of the rigid rollers,
• the drive system of the rollers in axial oscillation and in opposition of phase comprises a motor driving in synchronism with the aid of a transmission, two camshafts offset by 180 °, one of which acts on one end of the flexible roller and the other of which acts on one end of the rigid roll or rollers, the other end of the rollers being biased by an elastic system; this makes it possible to ensure perfect control of amplitude and operation in phase opposition between the flexible roller and the two rigid rollers,
• the machine comprises a lifting system of the flexible roller whose ends are provided with plates on one of which acts the elastic system and on the other of which acts the camshaft,
• the machine comprises a heating system of the textile web during the passage of the textile web between the pressure generators.

• une masse surfacique supérieure ou égale à 40 g/m² et inférieure à 100 g/m² et un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 35 µm,
• une masse surfacique supérieure ou égale à 100 g/m² et inférieure ou égale à 160 g/m² et un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 50 µm,
• une masse surfacique supérieure à 160 g/m² et inférieure ou égale à 200 g/m² et un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 60 µm, ou
• une masse surfacique supérieure à 200 g/m² et inférieure ou égale à 400 g/m² et un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 90 µm.

With such methods and devices, it is possible to produce fabrics composed of warp yarns and weft yarns, having a small variation in thickness, characterized by one or other of the following combinations of characteristics:

• a basis weight greater than or equal to 40 g / m ² and less than 100 g / m ² and a standard deviation of thickness measured on a stack of three identical tissues deposited on each other and in the same direction which is less than or equal to equal to 35 μm,
• a basis weight greater than or equal to 100 g / m ² and less than or equal to 160 g / m ² and a standard deviation of thickness measured on a stack of three identical tissues deposited on top of one another and in the same direction which is less than or equal to 50 μm,
• a basis weight greater than 160 g / m ² and less than or equal to 200 g / m ² and a standard deviation of thickness measured on a stack of three identical tissues deposited on top of one another and in the same direction which is less than or equal to equal to 60 μm, or
• a basis weight greater than 200 g / m ² and less than or equal to 400 g / m ² and a standard deviation of thickness measured on a stack of three identical tissues deposited on top of one another and in the same direction which is less than or equal to equal to 90 μm.

In such fabrics, the warp threads and / or the weft threads consist of a set of filaments, said filaments being able to move freely relative to each other within a single thread. Therefore, such fabrics can be obtained by the method according to the invention. According to the prior art, the method according to the invention allows access to such fabrics having such a combination of characteristics. Obtaining such fabrics with a width of at least 100cm, especially with a width of 100 to 200cm, is possible. The fabrics according to the invention can therefore have a large width and a very great length, for example approximately equivalent to the length of the available threads, namely several hundreds or thousands of meters.

The fabrics proposed in the context of the invention, because of their lower variability in thickness, will give composite parts to better controlled geometry and lead to a more robust overall manufacturing process.

avec:

• n = nombre de valeurs de mesures de l'épaisseur d'un empilement de trois tissus identiques et orientés dans la même direction, c'est-à-dire que les fils de chaînes d'une part, et les fils de trames d'autre part, sont orientés dans la même direction au sein de l'empilement,
• xi= une valeur de mesure de l'épaisseur de l'empilement des trois tissus identiques,
• x = moyenne arithmétique des mesures d'épaisseurs de l'empilement des trois tissus identiques.

The standard deviation of thickness is the root mean square of deviations from the mean, namely: $$\sqrt{\frac{1}{\mathrm{not}}{\displaystyle \underset{i}{\overset{}{\Sigma }}}{\left(x_i-\tilde{x}\right)}^2}$$

with:

• n = number of measurement values of the thickness of a stack of three identical tissues oriented in the same direction, that is to say that the warp threads on the one hand, and the warp son of on the other hand, are oriented in the same direction within the stack,
• xi = a measurement value of the thickness of the stack of the three identical tissues,
• x arithmetic mean of thickness measurements of the stack of the three identical tissues.

As the measured fabric unit folds became so thin, it became more representative to measure the standard deviation of thickness on a 3-ply stack.

In the context of the invention, the standard deviation can be obtained on a stack of three folds of the same fabric deposited on one another and oriented in the same direction and placed under pressure of 972mbar +/- 3mbar, and in particular, from 25 point thickness measurements distributed over an area of 305 x 305 mm, with for example one of the sides of the square which extends parallel to the warp threads of the fabric. The method described in the examples can be used.

Advantageously, the fabrics defined in the context of the invention consist of identical warp threads and weft threads identical to each other, and preferably of all identical warp and weft threads. In particular, the fabrics defined within the scope of the invention consist, preferably at least 99% by weight, or even consist exclusively of multi-filament reinforcing threads, in particular glass, carbon or aramid threads, carbon being preferred. Examples of fabrics according to the invention include those having a canvas-type architecture (otherwise known as taffeta), twill, braided, or satin.

• de tissus qui présentent une masse surfacique supérieure ou égale à 40 g/m² et inférieure à 100 g/m², un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 35 µm et un facteur d'ouverture moyen de 0 à 1%. De manière avantageuse, de tels tissus présentent une variabilité de facteur d'ouverture de 0 à 1 %. Dans le cadre de l'invention, l'étalement obtenu permet d'obtenir de tels tissus avec des fils, et en particulier des fils de carbone, présentant un titre de 200 à 3500 Tex, et de préférence de 200 à 800 Tex,
• de tissus qui présentent une masse surfacique supérieure ou égale à 100 g/m² et inférieure ou égale à 160 g/m², un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 50 µm et un facteur d'ouverture moyen de 0 à 0,5%. De manière avantageuse, de tels tissus présentent une variabilité de facteur d'ouverture d'au plus 0,5%. Dans le cadre de l'invention, l'étalement obtenu permet d'obtenir de tels tissus avec des fils, et en particulier des fils de carbone, présentant un titre de 200 à 3500 Tex, et de préférence de 400 à 1700 Tex,
• de tissus qui présentent une masse surfacique supérieure à 160 g/m² et inférieure ou égale à 200 g/m², un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 60 µm et un facteur d'ouverture moyen de 0 à 0,5%. De manière avantageuse, de tels tissus présentent une variabilité de facteur d'ouverture d'au plus 0,5%. Dans le cadre de l'invention, l'étalement obtenu permet d'obtenir de tels tissus avec des fils, et en particulier des fils de carbone, présentant un titre de 200 à 3500 Tex, et de préférence de 400 à 1700 Tex,
• de tissus qui présentent une masse surfacique supérieure à 200 g/m² et inférieure ou égale à 400 g/m², un écart type d'épaisseur mesuré sur un empilement de trois tissus identiques déposés les uns sur les autres et selon la même direction qui est inférieur ou égal à 90 µm et un facteur d'ouverture moyen de 0 à 0,1%. De manière avantageuse, de tels tissus présentent une variabilité de facteur d'ouverture d'au plus 0,1%. Dans le cadre de l'invention, l'étalement obtenu permet d'obtenir de tels tissus avec des fils, et en particulier des fils de carbone, présentant un titre de 200 à 3500 Tex et de préférence de 800 à 1700 Tex.

In particular, the invention allows the manufacture of:

• of fabrics having a basis weight greater than or equal to 40 g / m ² and less than 100 g / m ² , a standard deviation of thickness measured on a stack of three identical fabrics deposited on one another and in the same direction which is less than or equal to 35 μm and an average opening factor of 0 to 1%. Advantageously, such fabrics have an opening factor variability of 0 to 1%. In the context of the invention, the spread obtained makes it possible to obtain such fabrics with yarns, and in particular carbon threads, having a titre of 200 to 3500 Tex, and preferably 200 to 800 Tex,
• of fabrics having a basis weight greater than or equal to 100 g / m ² and less than or equal to 160 g / m ² , a standard deviation of thickness measured on a stack of three identical tissues deposited on each other and according to the same direction which is less than or equal to 50 μm and an average opening factor of 0 to 0.5%. Advantageously, such fabrics exhibit an aperture factor variability of at most 0.5%. In the context of the invention, the spread obtained makes it possible to obtain such fabrics with yarns, and in particular carbon threads, having a titre of 200 to 3500 Tex, and preferably 400 to 1700 Tex,
• of fabrics having a basis weight greater than 160 g / m ² and less than or equal to 200 g / m ² , a standard deviation of thickness measured on a stack of three identical tissues deposited on each other and according to the same direction that is less than or equal to 60 μm and an average opening factor of 0 to 0.5%. Advantageously, such fabrics exhibit an aperture factor variability of at most 0.5%. In the context of the invention, the spread obtained makes it possible to obtain such fabrics with yarns, and in particular carbon threads, having a titre of 200 to 3500 Tex, and preferably 400 to 1700 Tex,
• of fabrics having a basis weight greater than 200 g / m ² and less than or equal to 400 g / m ² , a standard deviation of thickness measured on a stack of three identical fabrics deposited on one another and in the same direction which is less than or equal to 90 μm and an average opening factor of 0 to 0.1%. Advantageously, such fabrics exhibit an opening factor variability of at most 0.1%. In the context of the invention, the spread obtained makes it possible to obtain such fabrics with yarns, and in particular carbon yarns, having a titre of 200 to 3500 Tex and preferably of 800 to 1700 Tex.

The aperture factor can be defined as the ratio between the area not occupied by the material and the total area observed, the observation of which can be made from the top of the fabric with illumination from beneath it. The opening factor (OF) is expressed as a percentage. It can, for example, be measured according to the method described in the examples.

Variability of aperture factor means the maximum difference in absolute value obtained between a measured aperture factor and the average aperture factor. The variability is therefore expressed in% as the opening factor.

The average Aperture Factor can be obtained, for example, from 60 measurements of aperture factor spread over an area of 305 x 915mm of tissue. For example, the distribution can be made by distributing 1/3 of the opening factor measurements over a first third of the fabric width, 1/3 of the opening factor measurements on the second third of the fabric width. corresponding to its central part and 1/3 of the opening factor measurements on the third third of the fabric width.

Average Aperture Factor means the arithmetic mean of the 60 measured Opening Factor (FO) values. $$\mathrm{Factor}\text{'}\mathrm{Medium\; opening}=\left(\mathrm{FO}1+\mathrm{<figure-callout\; id="2"\; label="FO"\; filenames="imgf0002.png,imgf0004.png"\; state="\{\{state\}\}">FO</figure-callout>}2+\mathrm{FO}3+...+\mathrm{FO}60\right)/60$$

• La Figure 1 est une vue schématique de face, d'une machine d'étalement conforme à l'invention.
• La Figure 2 est une vue en coupe transversale de la machine d'étalement illustrée à la Fig. 1 .
• La Figure 3 est une vue schématique de face, d'une machine d'étalement conforme à l'invention, en position relevée du rouleau flexible.
• La Figure 4A et 4B sont des vues en plan d'un exemple d'un tissu illustré respectivement avant et après étalement.
• La Figure 5 est une vue permettant d'illustrer schématiquement le principe d'étalement mis en oeuvre par la machine d'étalement conforme à l'invention.

The detailed description which follows, with reference to the appended figures, makes it possible to better understand the invention.

• The Figure 1 is a schematic front view of a spreading machine according to the invention.
• The Figure 2 is a cross-sectional view of the spreading machine illustrated in FIG. Fig. 1 .
• The Figure 3 is a schematic front view of a spreading machine according to the invention, in the raised position of the flexible roller.
• The Figure 4A and 4B are plan views of an example of a fabric illustrated respectively before and after plating.
• The Figure 5 is a view to diagrammatically illustrate the principle of spreading implemented by the spreading machine according to the invention.

The Fig. 1 to 3 illustrate schematically an embodiment of a spreading machine 1 according to the invention, adapted to spread with low variability in thickness, a textile web 2 comprising at least 3 warp son. Conventionally, a textile web is understood to mean a sheet material consisting of threads and warp threads extending along the axis of travel of the web on the machine. The textile webs can be unidirectional or fabrics. In the example shown in Fig. 4A and 4B , The sheet 2 is a fabric comprising warp and weft 3 son son of 4, each warp yarn 3 and weft threads 4 being constituted by a filament array t. According to a preferred example of implementation, the spreading machine 1 according to the invention is placed at the output of a loom and at the entrance of a winding system of the web. It could also be expected that the sheet to be spread is from a unwinding system and is not directly positioned in line with a loom.

The spreading machine 1 comprises at least a first 5 and a second 6 rotating rollers and, in the illustrated example, a third rotary roll 7 . The rotary rollers 5, 6 and 7 have axes A extending parallel to each other and perpendicular to the direction of travel f1 of the ply 2 or perpendicular to the warp threads 3 . The first roller 5 and the second roller 6 delimit between them a first pressure generator G1 for the web 2 passing between the first and second rollers 5 , 6 . Similarly, in the example illustrated in the drawings, the first roller 5 and the third roller 7 delimit between them a second pressure generator G2 for the web 2 passing between the first and third rollers 5, 7 . Of course, the length of the rollers is adapted to the width of the sheet 2 to be spread so as to have a length greater than the width of the sheet 2 . Typically, the length of the rolls is between 1m and 2m.

According to an advantageous characteristic of the invention, the rollers 5, 6 and 7 are positioned so that the two pressure generators G1 and G2 are spaced between 1/6 and 1/3 of the periphery of the first roll 5 . In other words, the web 2 is in contact with the first roll 5 only between 1/6 and 1/3 of its periphery.

According to a preferred embodiment, the second 6 and third rollers 7 are positioned side by side in a horizontal plane, while the first roll 5 is positioned in the middle and above the second 6 and third roll 7 .

The spreading machine 1 according to the invention also comprises a motorization device 10 for ensuring the synchronized drive in rotation about their axes A and in the same direction of rotation, the second 6 and third rollers 7 . In the example illustrated, the motorization device 10 comprises an electric motor 11 controlled to drive in a synchronized manner, the speed of rotation of the second 6 and third rollers 7 . The output shaft of the electric motor 11 cooperates with a transmission belt 12 which rotates pulleys 13 supported by mounted shafts 14 axially secured to the first end of the second 6 and third rollers 7 .

In the example illustrated, the first roll 5 is not rotated by the motorization device 10 . The first roll 5 is rotated by the traveling force of the web 2 and by the rollers 6 , 7 . Of course, it can be envisaged that the motorization 10 also causes the first roll 5 to rotate.

The spreading machine 1 according to the invention also comprises a system 15 for driving the rollers 5 , 6 and 7 in axial oscillation each along its axis A. More specifically, the drive system 15 allows the axial oscillation of the first roller 5 in phase opposition with respect to the second and third rollers 6 and 7 which are perfectly synchronized in axial oscillation. In the example illustrated in the drawings, the drive system 15 comprises an electric motor 16 driving in synchronism with a transmission 17 such as a belt, a first 19 and a second 20 camshafts allowing exert an axial force on the rollers. As is clear from the Fig. 1 the cams of the cam shafts 19 and 20 are angularly offset from each other by a value equal to 180 °.

The first camshaft 19 acts on the second end of the first roller 5 and more precisely on the transverse face of a shaft 21 extending axially from the first roller 5 . According to an advantageous variant embodiment, the first cam shaft 19 acts on the shaft 21 , via a plate 21a carried by the shaft 21 . Thus, even when the first roller 5 is moved vertically, the cam shaft 19 continues to exert an axial force on the shaft 21 as will be explained in more detail in the following description.

The second camshaft 20 acts on the second end of the second roller 6 and in the illustrated example, the third roller 7 also. According to this illustrated variant, the second and third rollers 6 and 7 are equipped axially, at their second end, with shafts 22 in contact, by their transverse face, with the camshaft 20 which ensures the synchronized axial oscillation of the second and third rollers 6 and 7 . Thus, the second and third rollers 6 and 7 have a perfectly synchronized axial oscillation.

The first ends of the first, second and third rollers 5, 6 and 7 are biased by an elastic system 25 compensating for the action exerted by the cam shafts 19 , 20 on the second ends of the first, second and third rollers 5 , 6 and 7 . In the exemplary embodiment illustrated, the elastic system 25 comprises stacks of Belleville washers interposed between on the one hand, a support 28 and on the other hand, each shaft 14 and a shaft 29 extending axially from the first end of the first roll 5 . According to an advantageous variant embodiment, a stack of Belleville washers 25 acts on the shaft 29 via a plate 29a carried by the shaft 29 . Thus even when the first roller 5 is moved vertically, the stack of Belleville washers 25 continues to exert an axial force on the shaft 29 as will be explained in more detail in the following description.

The drive system 15 as described above makes it possible to ensure perfect control of the amplitude of operation in phase opposition between the first roller 5 on the one hand and the second and third rollers 6, 7 on the other go. Moreover, this solution makes it possible to guarantee the desired movement of the rollers despite wear phenomena due to the elimination of the mechanical clearance between the cam shafts and the rollers.

Of course, the axial vibration frequency is adjustable for example from 5 to 50 Hz via the adjustment of the electric motor 16 . Typically, the amplitude of the axial oscillation of the rollers is of the order of 0.5 mm.

The spreading machine 1 also comprises for the second and third rollers 6 and 7 , a series of rigid supports 31 for supporting without bending, the rollers while allowing their movements of rotation and oscillation. In the illustrated example, each rigid support 31 comprises a fork or cradle 32 rigidly fixed to a frame 33 preferably rigidly anchored to the ground. Each fork or cradle 32 presents and two support legs 34 each equipped with a rolling member 35 for a roller 6 , 7 , which can receive both the rotational movement and the oscillation movement. In the example shown on the Fig. 1 four rigid supports 31 support the rollers. Of course, the number of rigid supports 31 may be different depending in particular on the length of the rollers.

According to the invention, the spreading machine 1 comprises a system 40 for creating the first pressure generator G1 and in the example illustrated, also the second pressure generator G2 , with adjustable pressure values distributed according to the one or more generatrices, to spread the sheet 2 with a small variability of thickness. In other words, the system 40 makes it possible to modulate the pressure at will, along these pressure generators G1 , G2 to apply a uniform pressure on the sheet taking into account the initial differences in thickness of the sheet, in order to to spread the sheet with a small variability of thickness.

According to a preferred embodiment, the system 40 comprises as a first roll 5 , a flexible roll and a series of localized supports 42 with adjustable pressure, distributed along the axis of the flexible roll 5 and acting on the flexible roll 5 . As is more particularly apparent from the Fig. 2 , the first roller 5 is flexibly mounted along its axis A in the sense that it is free of any guide bearing at both ends. The flexible roller 5 can thus self-position, without any stress, between the two other rollers 6 and 7 . Conversely, the second and third rollers 6 and 7 are rigid because they are supported without bending by the frame 33 . Each localized support 42 exerts its pressure on the flexible roller 5, via rolling members 43 with axial displacement. Thus, each localized support 42 is able to exert a substantially vertical pressure force perpendicular to the axis of the flexible roller 5 while accepting the rotational movement and axial oscillation of the flexible roller 5 . For example, each localized support 42 is a pressure cylinder 44 whose rod is equipped with a rolling member 43 . Each pressure cylinder 44 is connected to a control unit not shown but known per se, for adjusting the pressure exerted on the flexible roller 5 . In the example shown on the Fig. 1 , the spreading machine 1 comprises four pressure cylinders. Of course, the number of pressure cylinders 44 may be different.

According to an advantageous variant embodiment, the localized supports 42 are equipped with a device 46 for adjusting their position along the axis of the flexible roller 5 . Thus, the localized supports 42 can be moved independently of each other, along the axis of the flexible roller 5 so as to be able to exert their pressure force in all selected locations of the web 2 . In the illustrated example, the jacks 44 are slidably mounted along a gantry 45 which overhangs the flexible roller 5 at a distance. Each cylinder 44 is placed in a fixed position by means of a locking system of the cylinder body on the frame, not shown but of all types known per se.

According to an advantageous variant of embodiment, the spreading machine 1 according to the invention comprises a lifting system 48 of the flexible roll 5 to allow the operations of setting up the sheet 2 between the flexible roll 5 and the rigid rollers 6 , 7 . In the example shown, the lifting system 48 comprises two jacks 49 fixed by their body on the gantry 45 and whose rods 49a act on the shafts 21 and 29 extending from the two ends of the flexible roller 5 . It should be noted that the elastic system 25 acts on the shaft 29 of the flexible roller 5 while the cam shaft 19 continues to exert an axial force on the shaft 21 , even during lifting operations of the flexible roller 5 because of the presence of end plates 21a and 29a , as shown in FIG. Fig. 3 .

According to an advantageous characteristic of embodiment, the spreading machine according to the invention comprises a heating system 51 of the web and rollers during the passage of the web between the pressure generators. The heating system 51 comprises a nozzle 52 for supplying hot air produced by a hot air production unit that is not shown but is known per se. This feed nozzle 52 opens between the two rigid rollers 6 and 7 directing the flow of hot air to the flexible roller 5 according to its portion between the two pressure generators G1 and G2 . Typically, a Leister type heating unit is used to heat the web 2 and rolls to a temperature of 80 ° C.

In the foregoing description, the spreading machine 1 comprises a flexible roll 5 and two rigid rollers 6,7 defining two pressure generators G1 , G2 . Of course, the spreading machine 1 according to the invention may have a similar operation by implementing a single rigid roller 6 defining with the flexible roller 5, a single pressure generator G1 . Furthermore, the spreading machine 1 described above comprises, as localized supports 42 , cylinders exerting a pressure force on the flexible roller 5 . Other solutions can be envisaged for creating pressure generators with adjustable pressure values.

The spreading machine 1 according to the invention is particularly suitable for spreading the warp threads 3 and also the weft threads 4 when the web 2 is a fabric.

The implementation of a spreading method follows directly from the foregoing description.

• on amène la nappe 2 à défiler entre au moins deux rouleaux rotatifs 5, 6-7 dont les axes A s'étendent parallèlement entre eux et sensiblement perpendiculairement au sens de défilement de la nappe,
• on fait passer la nappe sous pression entre au moins une génératrice de pression G1 des rouleaux entraînés en oscillation axiale et en opposition de phase,
• et on réalise au moins une génératrice de pression G1 des rouleaux 5, 6-7 avec des valeurs de pression réglables le long de ladite génératrice pour étaler la nappe 2 avec une faible variabilité d'épaisseur.

According to the method of spreading a sheet 2 :

• the web 2 is brought to scroll between at least two rotary rollers 5, 6-7 whose axes A extend parallel to each other and substantially perpendicular to the direction of travel of the web,
• the web is passed under pressure between at least one pressure generator G1 of the rollers driven in axial oscillation and in opposition of phase,
• and at least one pressure generator G1 of the rollers 5, 6-7 is made with adjustable pressure values along said generator to spread the sheet 2 with a small variability in thickness.

It should be understood that it is thus possible to modulate the pressure between the center and the edges of the web 2 so that the flexible roll 5 applies a uniform pressure on the sheet 2 given the differences in the thickness of the sheet. Of course, it can be envisaged that the pressures are identical along the contact generator.

During this spreading operation, the sheet 2 is kept under a substantially constant low value voltage, by means of appropriate systems of tension of the sheet 2 , located on its path upstream and downstream of the pressure rollers and designed to compensate for the forces likely to appear for example upstream at the exit of the loom and, downstream, at the reel of the web.

According to a preferred embodiment, one of the flexible rollers 5 and the other 6-7 rigid and is carried on the flexible roller, substantially perpendicular to its axis, localized supports 42 distributed along the axis of the roller and with adjustable values to make the generator with adjustable pressure values. Thus, pressures of different values are exerted in different places of the pressure generator to ensure the correct spreading of the son of the sheet 2 .

According to an advantageous characteristic of the invention, the method consists in adjusting the position of the localized supports 42 along the axis of the flexible roller so as to selectively choose the places where the pressures are to be applied. For example, it is possible to distribute the localized supports 42 regularly along the axis of the flexible roller. However, the adjustment consists of distributing the localized supports 42 at most over the entire width of the sheet 2 . Indeed, it should be that, whatever the width of the web, the localized supports 42 always act inside the delimited area overhanging the width of the web 2 . In other words, the localized supports 42 must not act on an area of the flexible roll which is never in contact with the sheet 2 . According to a preferred example of implementation, the position of the cylinders which are adjacent to the edges of the sheet are positioned to be at least 50mm distant from these edges. Typically, the cylinders that are adjacent to the edges of the sheet are positioned to be spaced 150mm from these edges. The cylinders located between these two cylinders adjacent to the edges are positioned so that all the cylinders are spread regularly. For example, the number of cylinders is chosen so that the distance between two adjacent cylinders is at least 300mm. According to a preferred embodiment, the sheet 2 is caused to pass over the periphery of the flexible roller 5 between two pressure generators G1 , G2 with adjustable localized pressure values. These two generators are delimited between the flexible roller 5 and two rigid rollers 6 , 7 driven in synchronism, rotation and oscillation. Advantageously, the web 2 is caused to pass over the flexible roll 5 , between 1/6 and 1/3 of the periphery of the flexible roll 5 .

According to one characteristic of the invention, the sheet 2 and the rollers are heated during its passage between the pressure generator or generators.

It follows from the foregoing description that the invention enables the warp yarns of a unidirectional web of warp yarns or warp yarns and / or weft yarns interlaced with a fabric to be spread out. The spread textile webs will be at least partially made of reinforcing threads of the carbon, glass or aramid type which conventionally consist of a set of filaments extending in the direction of the thread.

Advantageously, in the context of the invention, the textile sheet to be spread out will consist either exclusively of a unidirectional sheet of warp yarns, or of a fabric consisting of an intertwining of warp yarns and yarns. frame. Of course, in all cases, the son are not secured to each other by any binder or mechanical bonding mode of the type stitching or knitting that would hinder their movement relative to each other and would not allow their spreading. In the case of a fabric, the warp threads and the weft threads are held together only by the weaving. In particular, in the case of a textile web consisting of a unidirectional sheet of warp son, the latter will consist of carbon son, glass or aramid. In the case of a fabric consisting of an intertwining of warp and weft yarns, it is possible either to spread the only weft yarns which, in this case, will be interlaced with yarns playing the role of such as son of thermoplastic material, or to spread both warp son and weft son. In all cases, the son intended to be spread in the process according to the invention consist of a set of filaments freely movable relative to each other, and in particular carbon son. Such son may initially have a circular section or, preferably, rectangular, but at the output of the method according to the invention, they will present a rectangular section following the application of pressure forces. In order to allow their spreading, the son to be spread will be neither impregnated, nor coated, nor associated with any polymeric binder that would hinder the free movement of the filaments relative to each other. The yarns to be spread are, nevertheless, most often characterized by a mass content of standard size that can represent at most 2% of their mass.

A carbon yarn consists of a set of filaments and generally has from 1,000 to 80,000 filaments, preferably from 12,000 to 24,000 filaments. In a particularly preferred manner, in the context of the invention, carbon threads of 1 to 24 K, for example 3K, 6K, 12K or 24K, and preferably 12 and 24K, are used. For example, the carbon threads present in the unidirectional sheets have a title of 60 to 3800 Tex, and preferably 400 to 900 tex. The unidirectional sheet can be made with any type of carbon son, for example, High Strength (HR) son whose tensile modulus is between 220 and 241GPa and whose tensile strength is between 3450 and 4830MPa, Intermediate Module (IM) wires whose tensile modulus is between 290 and 297GPa and whose tensile breaking stress is between 3450 and 6200MPa and High Module Wires (HM) whose tensile modulus is between 345 and 448GPa and whose tensile strength is between 3450 and 5520Pa (according to ASM Handbook, ISBN 0-87170-703-9, ASM International 2001 ).

The Fig. 4A schematically shows a fabric before spreading consisting of an interlacing of warp son and weft son width slightly different due to weaving. This may include, but is not limited to 3K carbon. Each of the warp yarns and weft yarns consist of a set of filaments. Initially, the opening factor of the textile web is 4%.

The Fig. 4B illustrates the tissue obtained after the implementation of the spreading method according to the invention. This fabric has an OF content of 0% and warp and weft threads of different widths.

In the context of the invention, it is possible that the textile web before being subjected to the process according to the invention has a zero or non-zero opening factor. When initially the opening factor is not zero, the application of the method according to the invention causes a decrease in the opening factor that accompanies the obtaining of the homogenization of the thickness of the textile web. That initially the opening factor is zero or not zero, the application of the method according to the invention causes a decrease in the thickness of the fabric by homogenization of the thickness of the son constituting it.

The invention is not limited to the examples described and shown because various modifications can be made without departing from its scope.

Examples of carbon yarn fabrics obtained by the process according to the invention are described in the examples below.

MEASURING METHODS USED Thickness measurements I. The following equipment is used:

• ➢ Vacuum pump Leybold systems vacuum reference 501902
• ➢ Three-dimensional Tesa machine "micro-hite DCC 3D"
• ➢ Glass plate tempered glass, thickness 8mm
• ➢ Vacuum tarpaulin ref 818260F 205 ° C green nylon 6 from Umeco, Aerovac.
• ➢ Bidim AB1060HA 380gsm 200 ° C polyester uncompressed nominal thickness 6mm, supplier Umeco Aerovac.
• ➢ PC with PC-Dmis V42 software
• ➢ Ball probe ø3 with a maximum tripping of 0.06 N
• ➢ Cutting wheel type Robuso
• ➢ Cutting template 305x305 mm
• ➢ Vacuum outlet
• ➢ Vacuum seal SM5130 from the supplier Umeco Aerovac.

II. Description of the measure

• ➢ Put the glass plate with the stack of three pieces of the same fabric, as well as the environment, in order from bottom to top:
  • ∘ Bidim (felt known to those skilled in the art)
  • ∘ Stack of fabrics in the same direction, with the warp threads extending in the direction parallel to an edge of the square of 305 x 305mm
  • ∘ Vacuum tarpaulin
  Ensure a good vacuum level (vacuum less than 15 mbar).
  • ➢ Establish a reduced pressure of at least 15 mbar in the vacuum cover, so as to place the stack under a pressure of 972mbar +/- 3mbar.
  • ➢ It is necessary to achieve a dimensional stabilization of the stack of tissues under reduced pressure.
  • ➢ Leave the stack under this reduced pressure at least 30 minutes before taking the points.
• ➢ Take a physical point on the table in manual mode (white point top left of the table) thanks to the joystick ( joy on the joystick), to validate then to pass in auto mode ( auto on handle):
  • ➢ Switch to automatic mode and wait for the measurement to take place.

The program takes 25 measurement points thanks to its trigger probe.

The measurement of 25 "empty" points is repeated, that is to say without the stacking of the three tissues in order to measure the thickness of the vacuum cover and the window.

Thus by difference in altitude measurement between, with and without stacking, we have a thickness average of 25 points, on the stack.

Opening factor measurements

The opening factors were measured according to the following method.

The device consists of a SONY brand camera (model SSC-DC58AP), equipped with a 10x objective, and a Waldmann brand light table, model W LP3 NR, 101381 230V 50HZ 2x15W. The sample to be measured is placed on the light table, the camera is fixed on a bracket, and positioned at 29cm from the sample, then the sharpness is adjusted.

The measurement width is determined according to the textile web to be analyzed, using the ring (zoom), and a rule: 10 cm for open textile sheets (OF> 2%), 1.17 cm for loosely opened textile sheets (OF <2%).

With the aid of the diaphragm and a control plate, the brightness is adjusted to obtain a value of OF corresponding to that given on the control plate.

The Videomet contrast measuring software from Scion Image (Scion Corporation, USA) is used. After image capture, the image is processed in the following way: using a tool, a maximum area corresponding to the chosen calibration is defined, for example for 10 cm - 70 holes, and comprising a number of integer patterns. We then select an elementary surface in the textile sense of the term, that is to say a surface that describes the geometry of the fabric by repetition.

As the light of the light table passes through the openings of the fabric, the percentage OF is defined by a hundred times the ratio of the white surface divided by the total area of the elementary pattern: 100 * (white surface / elementary surface).

It should be noted that the brightness adjustment is important because diffusion phenomena can change the apparent size of the holes and therefore the OF. An intermediate brightness will be retained, so that no phenomenon of saturation or diffusion too important is visible.

127cm wide fabrics with surface weights, standard thickness deviations, aperture factor, factor variability opening and presented in Table 2 below, were obtained using the method according to the invention, using the parameters as defined in Table 1 .

The machine used complies with Fig. 1 and 2 , with rollers of 60 mm diameter and a length of 1700 mm, the cylinders being spaced apart from each other by 320 mm, both located at the ends being spaced 155 mm from the edge of the fabric. Table 1 gives, by way of example, for the fabrics presented in Table 2 , the pressing force of the 4 pressure cylinders 44 (Nos. 1 to 4) taken from one edge to the other of the fabric, with a speed of travel of the textile web (mm / min), a frequency (Hz) and a temperature (° C). According to these exemplary embodiments, greater forces are applied in the central zone of the fabric 2 allowing good spreading of the fabric 2 , compensating for the thickness difference initially existing between the center and the edges of the fabric, as illustrated in FIG. Fig. 5 .

The AS4 3K yarns supplied by Hexcel Corporation (Stamford USA) are high tensile stress tensile yarns of 4433 MPa, tensile modulus of 231 GPa have a titer of 200 TEF with filaments of 7.1 microns.

The AS4 12K yarns supplied by Hexcel Corporation (Stamford USA) are high tensile strength tensile yarns of 4433 MPa, tensile modulus of 231 GPa have a titer of 800 TEX with filaments of 7.1 microns.

The AS7 12K yarns supplied by Hexcel Corporation (Stamford, USA) are high tensile stress tensile yarns of 4830Mpa, tensile modulus of 241GPa, and have a titer of 800Tex with filaments of 6.9 microns.

The IM7 6K yarns supplied by Hexcel Corporation (Stamford, USA) are 5310Mpa Intermediate Tensile Stress modulus yarns, with 276Gpa tensile modulus and have a 223Tex titer with 5.2 micron filaments.

The IM7 12K yarns supplied by Hexcel Corporation (Stamford, USA) are Intermediate Stress at Breakage modulus yarns. 5670Mpa, tensile modulus of 276Gpa and have a titer of 446Tex with 5.2 micron filaments.

For example, 199g / m ² AS4 3K tissue before plating has an average Aperture Factor of 10.5% (12.5% at the edges of the tissue, 6.5% at the center of the tissue) or a variation of 6% of the opening factor between center and edge, and an average thickness of 0,191mm (0,201mm on the edges of the fabric, 0,187mm on the center of the fabric) is a variation of thickness of 12% between center and edge. The standard deviation of the thickness of the stack of three folds of the non-spread fabric is 0.055mm.

After plating, the opening factor of this same tissue increases to an average of 0.1%, a reduction of 99% compared to the non-spread tissue, with a maximum variation of 0.5%, which is not not due to an increase in values at the edges, the average opening factor of the edges and the center being equal to 0.1%. A large part of the measured openness factors are close to 0%, and a small population above 0.1% up to 0.5% in rare cases, inducing a 0.1% average with variation maximum of 0.5%. The thickness of the tissue after spreading is 0.177mm, which is 8% less than the non-spread fabric. The standard deviation of the stack of three folds of the spread fabric is 0.030mm, a gain of 45% over the non-spread fabric. This information is collated in Table 3 below.

As another example, a fabric of 75 g / m ² in AS4C 3K will have an average opening factor before spreading of 45%, and a mean opening factor after spreading of 0.8%, a gain of 98%. %.

In all cases, the implementation of the method according to the invention causes a significant decrease in the standard deviation of the thickness, the average thickness, the opening factor and its variability. In particular,

Whatever the density of the fabric and the yarn used, thanks to the application of the method according to the invention, the gain in standard deviation of thickness of 3 folds under a pressure of 972 mbar is equal to at least 20%, and in most cases, is greater than 30%. <b> Table 1 </ b> Density Chain and weft Designation Matter Title thread Support force cylinders (N) Speed Frequency Temperature son / cm Tex # 1 # 2 # 3 # 4 mm / min Hz ° C 75g / m ² - IM7 6K - Canvas 1.88 IM7GP 6K HSCP5000 223 200 400 400 200 420 17 55 75g / m ² - AS4 3K - Canvas 1.88 AS4GP 3K HSCP5000 200 200 400 400 200 420 17 55 98g / m ² - IM7 6K - Canvas 2.2 IM7GP 6K HSCP6000 223 200 400 400 200 340 17 55 98g / m ² - AS4 3K - Canvas 2.45 AS4GP 3K HSCP5000 200 200 400 400 200 340 17 55 160g / m ² IMA 12 K - Canvas 1.79 IMAGS 12K HSCP6000 446 400 500 500 400 417 27 55 199g / m ² AS4 3K - Canvas 4.98 AS4GP 3K HSCP5000 200 200 400 400 200 500 17 55 199g / m ² - AS4 12K - Canvas 1.24 AS4GP 12K HSCP3000 800 200 400 400 200 600 40 55 300g / m ² - AS7 12K - Twill 2/2 1.24 AS7GP 12K HSCP4000 800 200 400 400 200 600 40 55 Thickness (mm) Opening Factor (%) Average stack of 3 folds Standard deviation of the 3-ply stack Average thickness per fold Average Variability 75g / m ² - IM7 6K - Canvas 0.169 0,023 0,056 0.2 0.5 75g / m ² - AS4 3K - Canvas 0,145 0,028 0.048 0.8 0.8 98g / m ² - AS4 3K - Canvas 0.232 0,025 0.077 0.6 0.6 98g / m ² - IM7 6K - Canvas 0.222 0,024 0.074 0.1 0.5 160g / m ² IMA 12 K - Canvas 0.340 0,046 0.113 0.4 0.4 199g / m ² AS4 3K - Canvas 0.531 0,030 0.177 0.1 0.5 199g / m ² - AS4 12K - Canvas 0.446 0,038 0.149 0 0.1 300g / m ² - AS7 12K - Twill 2/2 0.742 0.078 0.247 0 0.1 Thickness (mm) Opening factor (%) Average thickness per fold measured on a stack of 3 folds Standard deviation of the 3-ply stack Before spreading After spreading Gain Before spreading After spreading Gain Average Maximum variability Gain Before spreading After spreading 199g / m ² AS4 3K - Canvas 0.191 0.177 8% 0,055 0,030 45% 10.5 0.1 99%

Claims (20)

1. A method for spreading a textile sheet (2) including at least warp yarns (3), according to which:

   - the sheet (2) is caused to run between at least two rotary rollers (5), (6-7) the axes A of which extend parallel to one another and substantially perpendicular to the direction of travel of the sheet,

   - the sheet is caused to pass under pressure between at least one pressure generator (G1) of the rollers driven into axial oscillation and in phase opposition,

   characterized in that at least one pressure generator (G1) of the rollers (5), (6-7) is produced with adjustable pressure values along said generator for spreading the sheet (2) with a low thickness variability.
2. The method according to claim 1, characterized in that one of the rollers (5) is made flexible and the other one rigid (6-7) and localized supports (42) distributed along the axis of the roller and with adjustable values are exerted on this flexible roller, substantially perpendicular to its axis in order to produce the generator with adjustable pressure values.
3. The method according to claim 2, characterized in that it consists of adjusting the position of the localized supports (42) along the axis of the flexible roller.
4. The method according to claim 2 or 3, characterized in that it consists of regularly distributing the localized supports (42) along the axis of the flexible roller.
5. The method according to one of claims 1 to 4, characterized in that it consists of distributing the localized supports (42) at most over the whole of the width of the sheet (2).
6. The method according to one of claims 1 to 5, characterized in that it consists of causing the sheet (2) to pass over the periphery of the flexible roller between two pressure generators (G1, G2) with adjustable localized pressure values of two rigid rollers (6, 7) synchronously driven in rotation and in oscillation.
7. The method according to claim 6, characterized in that it consists of causing the sheet (2) to pass between 1/6 and 1/3 of the periphery of the flexible roller (5).
8. The method according to one of claims 1 to 7, characterized in that it consists of heating the sheet (2) upon its passing between the pressure generator(s).
9. The method according to one of claims 1 to 8, characterized in that it consists of bringing as a sheet (2), a fabric including warp yarns (3) and weft yarns (4) each consisting of a set of filaments which may move freely relatively to each other within said yarn, the spreading being achieved on the warp yarns and on the weft yarns.
10. The method according to one of claims 1 to 9, characterized in that it consists of adjusting the pressure values along the pressure generator(s) (G1, G2) in order to apply a uniform pressure on the sheet (2) taking into account of the initial thickness differences of the sheet.
11. A machine for spreading sheets (2) consisting of at least warp yarns (3), including:

    - at least two rotary rollers (5), (6-7), the axes of which extend parallel to each other and perpendicular to a pressure generator (G1), (G2) delimited between both rollers,

    - a rotating motor drive (10) for at least one roller,

    - and a system (15) for driving the rollers in axial oscillation in phase opposition,

    characterized in that it includes a system (40) for creating the pressure generator (G1, G2) with adjustable pressure values distributed along said generator, in order to spread the sheet (2) with a low thickness variability.
12. The spreading machine according to claim 11, characterized in that the system (40) for creating the pressure generator includes from among the rotary rollers, a flexible roller (5) and a series of localized supports (42) with adjustable pressure, distributed along the axis of the flexible roller and acting on the flexible roller (5) supported by at least one rigid roller (6, 7).
13. The spreading machine according to claim 12, characterized in that the localized supports (42) are equipped with a device (46) for adjusting their position along the axis of the flexible roller.
14. The spreading machine according to claim 12 or 13, characterized in that the localized supports (42) exert their pressure on the flexible roller (5), via rolling members with axial displacement (43).
15. The spreading machine according to one of claims 12 to 14, characterized in that the flexible roller (5) delimits with two rigid rollers (6, 7), the axes of which extend parallel to each other, two pressure generators (G1, G2) with adjustable localized pressure values, both of these generators (G1, G2) being spaced apart between 1/6 and 1/3 of the periphery of the flexible roller (5).
16. The spreading machine according to one of claims 11 to 15, characterized in that the rollers (5, 6, 7) have a diameter comprised between 30 mm and 60 mm.
17. The spreading machine according to one of claims 12 to 16, characterized in that it includes for each rigid roller a series of rigid supports (31) each including a cradle (32) attached to a chassis (33) and having two supporting branches (34) each equipped with a rolling member (35) for a rigid roller, having a movement of rotation and a movement of translation along the axis of the rigid rollers.
18. The spreading machine according to claim 11, characterized in that the system (15) for driving the rollers into axial oscillation and in phase opposition includes a motor (16) synchronously driving by means of a transmission (17), two camshafts (19, 20) shifted by 180°, one (19) of which acts on one of the ends of the flexible roller (5) and the other one acts on one of the ends of the rigid roller(s) (6, 7), the other end of the rollers being urged by an elastic system (25).
19. The spreading machine according to one of claims 11 to 18, characterized in that it includes a system (48) for raising the flexible roller (5), the ends of which are provided with plates (21a, 29a) on one of which acts the elastic system (25) and on the other one of which acts the camshaft (19).
20. The spreading machine according to one of claims 11 to 19, characterized in that it includes a system (51) for heating the sheet (2) upon passing of the sheet between the pressure generators.

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