EP0922798A1 - Weaving device for making a structure for a composite article - Google Patents

Abstract

The composite fabric weaving has a longitudinal cam to move the warps, and a structured weft insertion system. The assembly for weaving a composite material has a system (5) to give different displacement movement speeds to the warps (FC) which rotates round a longitudinal axis (X-X). Its profile is set as a function of at least one lateral edge of the woven material, in a cam shape. The cam (5) has a flat surface and a profile which is defined by a variable lateral width, at right angles to the axis (X-X), where the axis is generally orthogonal to the direction (D) of the warps (FC). The cam profile is defined so that the lateral width (hi) is at a point (Pi) along the axis (X-X) to meet the equation: Li= n(Pj)+F1(hi,θ 2) - F2(hi,θ 1) where: Li is the required length of the warp in the woven fabric at the point (Pi) on the longitudinal axis (X-X); n is the number of wefts in the fabric; n Pj is the displacement of the warps in each step; F1 and F2 are the distance functions of the lateral width (hi) and the extreme rotation angles (θ 1, θ 2) of the cam. The weft insertion system gives a variable number of superimposed wefts of different weft thicknesses. The length of warp displacement, with longitudinal displacement by steps for the insertion of the wefts, is set for each step.

Description

The present invention relates to a woven structure for the production of a piece of composite material, as well as a method and a device for producing such a woven structure.

In known manner, to form a piece of composite material, we impregnates the woven structure with a resin which is then polymerized or otherwise hardened, for example by a rise in temperature or a electron bombardment.

More particularly, although not exclusively, such parts of composite material are used in aeronautics and space by virtue of their excellent resistance properties to mechanical and / or thermal stresses. Many applications in particular, thermal protections of bodies entering the atmosphere, powder rocket nozzles, aircraft brakes, helicopter rotor hubs, trains landing, wing root, leading edges, etc ...

However, as soon as the parts to be produced have a shape complex with a variation in shape and / or thickness, such as most of the aforementioned pieces, the realization becomes complicated. Indeed, it is then necessary to form, instead of a simple woven structure usual, appropriate specific reinforcements, intended to be drowned in the hardened resin.

Many processes and devices have been devised and implemented point for making such specific reinforcements, generally complicated, but the automated manufacturing of shaped parts complex encounters great difficulties, which lead to machines very complicated and therefore expensive, without the parts always obtained all the necessary qualities of homogeneity and resistance.

Also, it is often necessary, when the parts present very complicated and evolving forms, to make cuts or subsequent machining of prefabricated parts, which increases well heard the cost and decreases the mechanical strength.

In addition, such specific reinforcements cannot practically not be made by weaving, since in a known way a structure woven fabric which is usually produced by wrapping weft threads in chain wires moved longitudinally, always have a shape rectangular.

• d'une part, le tissage est souvent exclu et il est nécessaire de mettre en oeuvre des procédés complexes pour réaliser les armatures appropriées ; et
• d'autre part, des traitements ultérieurs à la fabrication, tels que des usinages, sont généralement nécessaires.

Consequently, the aforementioned known state of the art has a double drawback, when the parts to be produced have complex shapes:

• on the one hand, weaving is often excluded and it is necessary to implement complex processes to produce the appropriate reinforcements; and
• on the other hand, treatments subsequent to manufacture, such as machining, are generally necessary.

Note, however, that US-A-2,998,030 describes a weaving process, which implements means, such as a roller, to modify the speeds of movement of the different warp threads, in order to obtain a woven structure of curvilinear shape.

The object of the present invention is to improve such a process for weaving complex parts does not requiring little or no further treatment.

• des moyens pour déplacer longitudinalement les fils de chaíne ;
• des moyens pour enlacer les fils de trame dans lesdits fils de chaíne ; et
• des moyens pour engendrer des vitesses de déplacement différentes pour au moins certains desdits fils de chaíne,

est remarquable en ce que lesdits moyens pour engendrer des vitesses de déplacement différentes comportent une came profilée susceptible de tourner autour d'un axe longitudinal, dont le profil est déterminé en fonction du contour souhaité au moins d'un bord latéral de la structure tissée à réaliser, en ce que ladite came présente une forme sensiblement plane et un profil qui est défini par une longueur transversale variable, perpendiculairement audit axe longitudinal, et en ce qu'elle est agencée de sorte que ledit axe longitudinal est sensiblement orthogonal à la direction définie par les fils de chaíne.To this end, according to the invention, the weaving device for producing a woven structure which is intended for producing a piece of composite material and which comprises weft threads and warp threads, said device comprising in particular:

• means for longitudinally moving the chain son;
• means for entangling the weft threads in said warp threads; and
• means for generating different displacement speeds for at least some of said warp threads,

is remarkable in that said means for generating different displacement speeds comprise a profiled cam capable of rotating around a longitudinal axis, the profile of which is determined as a function of the desired contour at least of a lateral edge of the woven structure with realize, in that said cam has a substantially planar shape and a profile which is defined by a variable transverse length, perpendicular to said longitudinal axis, and in that it is arranged so that said longitudinal axis is substantially orthogonal to the defined direction by the sons of chain.

• Li est la longueur souhaitée du fil de chaíne de la structure tissée, qui est situé audit point Pi selon ledit axe longitudinal ;
• n est le nombre de fils de trame de la structure tissée ;
• les n Pj sont les pas de déplacement des fils de chaíne déplacés par pas ; et
• F1 et F2 sont des distances fonctions de ladite longueur transversale hi et respectivement d'angles extrêmes 1 et 2 de rotation de la came, lors du déplacement des fils de chaíne.

In addition, advantageously, said profile is defined so that its transverse length hi, at a point Pi along said longitudinal axis, satisfies the following relationship: Li = Σn (Pj) + F1 (hi, 2) - F2 (hi, 1), in which :

• Li is the desired length of the warp of the woven structure, which is located at said point Pi along said longitudinal axis;
• n is the number of weft threads of the woven structure;
• n Pj are the displacement steps of the chain son moved in steps; and
• F1 and F2 are distances as a function of said transverse length hi and respectively of end angles 1 and 2 of rotation of the cam, during the movement of the chain wires.

It will be noted that, thanks to the present invention, the structure woven fabric obtained can have a variable thickness, which can be freely select. Thus, thanks to the invention, it is possible to modify the shape of the woven structure, not only in one plane, but also transversely to this plane, which creates a structure three-dimensional in any shape.

• enlacer un nombre variable de fils de trame superposés ; et/ou
• enlacer des fils de trame présentant des diamètres variables ; et/ou
• modifier la longueur du pas de déplacement des fils de chaíne déplacés longitudinalement par pas, l'enlacement des fils de trame étant réalisé à chaque pas.

To modify the thickness of the woven structure, in the case of an embodiment of the multilayer type according to the invention, it is possible:

• entwining a variable number of superimposed weft threads; and or
• entwine weft threads having variable diameters; and or
• modify the length of the displacement step of the warp threads displaced longitudinally in steps, the interweaving of the weft threads being carried out at each step.

The figures in the accompanying drawing will make it clear how the invention can be realized. In these figures, identical references denote similar elements.

Figure 1 is a schematic top view of a device according to the invention.

Figure 2 is a schematic side view of a device according to the invention.

Figure 3 shows, in perspective, part of a device according to the invention.

Figure 4 schematically shows part of a structure woven according to the invention.

Figure 5 is a graphical representation allowing explain the determination of the profile of a cam according to the invention.

The weaving device 1 according to the invention and shown schematically in Figures 1 to 3 allows for a structure woven 2, of the tablecloth type, formed of FT weft threads and warp threads FC and intended for the production of a piece of composite material.

We know that such a piece of composite material is formed of usual way, by said woven structure which is embedded in a matrix hardened resin.

• des moyens 3A et 3B pour déplacer longitudinalement par pas, selon une direction D, les fils de chaíne FC. A cet effet, lesdits moyens 3A et 3B présentent des formes coopérantes, par exemple en gradins, pour maintenir, en particulier par coincement, lesdits fils de chaíne FC ; et
• des moyens 4, comprenant par exemple un peigne de frappe, pour enlacer lesdits fils de trame FT dans lesdits fils de chaíne FC.

In known manner, said device 1 comprises in particular:

• means 3A and 3B for longitudinally moving in steps, in a direction D, the FC chain son. To this end, said means 3A and 3B have cooperating shapes, for example in steps, to maintain, in particular by wedging, said FC chain son; and
• means 4, comprising for example a striking comb, for entangling said weft son FT in said chain son FC.

According to the invention, said device 1 further comprises a cam 5 to generate different movement speeds for at least some of said FC chain sons.

The set of elements 3A, 3B and 5 and of roller 8 specified below are integral and move together, and the cam 5 rotates regularly by an increment of rotation when the FC chain wires advance.

So, thanks to these differences in speed, we get a structure woven 2, at least one lateral edge 6A of which according to the weft threads FT is not perpendicular to the direction D defined by the FC chain wires, such as shown in figure 4.

Consequently, the woven structure 2 obtained by the device 1 has a non-rectangular shape, because although the longitudinal edges 7A and 7B according to the FC chain wires remain parallel, at least the lateral edge 6A is not perpendicular to said longitudinal edges 7A and 7B.

Of course, the lateral and longitudinal adjectives are defined by in relation to the weft and warp threads, and not in relation to the structure woven 2 final, the latter may have a longer length important according to the weft threads than according to the warp threads.

• soit une ligne rectiligne de manière à obtenir une structure tissée de forme trapézoïdale ;
• soit une ligne courbe quelconque, comme représenté sur la figure 4.

According to the invention, said lateral edge 6A or the two lateral edges can have:

• either a rectilinear line so as to obtain a woven structure of trapezoidal shape;
• or any curved line, as shown in FIG. 4.

Furthermore, according to the invention, the profiled cam 5 is capable of rotate, at least partially around an axis X-X orthogonal to the direction D, and is arranged upstream of the means 3A and 3B, in the direction E of movement or advancement of the FC chain wires, near said means 3A and 3B.

As can be seen in Figures 1 to 3, the device 1 according to the invention further comprises the roller 8 of axis L-L parallel to the X-X axis and arranged at a distance d upstream from the X-X axis, such that shown in Figure 5.

Said profiled cam 5 of generally planar shape has a profile adapted to the shape of the lateral edge 6A which it is desired to obtain, as specified below. Said profile is defined by a transverse length h variable, perpendicular to said longitudinal axis X-X, as shown in Figure 5.

• , l'angle de rotation de la came 5, de valeur comprise entre deux valeurs limites 1 et 2 non représentées ;
• r, le rayon du rouleau 8, ainsi que des extrémités arrondies 5A et 5B de la came profilée 5, qui présentent le même rayon ;
• l, la longueur entre l'axe L-L du rouleau 8 et l'axe de l'extrémité arrondie 5A de la came profilée 5 ; et
• α, un angle qui est défini par les conditions de tangence du fil de chaíne FC.

In this FIG. 5, there is also shown:

• , the angle of rotation of the cam 5, of value between two limit values 1 and 2 not shown;
• r, the radius of the roller 8, as well as the rounded ends 5A and 5B of the profiled cam 5, which have the same radius;
• l, the length between the axis LL of the roller 8 and the axis of the rounded end 5A of the profiled cam 5; and
• α, an angle which is defined by the tangency conditions of the chain wire FC.

• Li est la longueur souhaitée du fil de chaíne FCi de la structure tissée 2, qui est situé audit point Pi selon ledit axe longitudinal X-X ;
• n est le nombre de fils de trame FT de la structure tissée 2 ;
• P est le pas de déplacement des fils de chaíne FC sous l'action des moyens 3A, qui a lieu à chaque fois que l'on met en place un fil de trame FT et qui est supposé constant ; et
• F1 et F2 sont des distances précisées ci-dessous et fonctions de ladite longueur transversale hi et respectivement desdits angles extrêmes 1 et 2 de rotation de la came 5.

According to the invention, said profile of the cam 5 is defined so that its transverse length hi, at a point Pi along the longitudinal axis XX, as shown in FIG. 3, checks the following relationship: Li = Pn + F1 (hi, 2) - F2 (hi, 1) in which :

• Li is the desired length of the chain wire FCi of the woven structure 2, which is located at said point Pi along said longitudinal axis XX;
• n is the number of weft threads FT of the woven structure 2;
• P is the pitch of movement of the chain son FC under the action of the means 3A, which takes place each time that a weft thread FT is put in place and which is assumed to be constant; and
• F1 and F2 are distances specified below and functions of said transverse length hi and respectively of said extreme angles 1 and 2 of rotation of the cam 5.

Of course, the length obtained by the product P.n can be determined differently if the displacement or advancement step P of the FC chain wires is not constant, namely by a simple summation of the lengths of the different steps.

According to the invention, the parameters h, d, r, 1 and 2 above are optimized to have the best possible distribution uniformity of the wires of weft FT between the lateral edges 6A and 6B of the woven structure 2.

The mode of calculation of the functions F1 and F2 is specified below. As the calculation is the same for the two functions, it is explained on a function F depending on an angle . To get F1 and F2, just replace  respectively by 1 and 2, in this function F.

• la structure tissée 2 ne glisse pas de la came 5 selon la direction X-X ;
• les fils de chaíne FC présentent une élasticité nulle ; et
• l'épaisseur de la structure tissée 2 est constante et indépendante de la tension et de la pression,

on déduit facilement l'expression : F = r + r(π2 -) + h + r(α + ) + I + rα, qui s'écrit F = r(1 + π2 + 2α) + h + I. From geometric relations and the representation of Figure 5, and assuming that:

• the woven structure 2 does not slip from the cam 5 in the direction XX;
• the FC chain son have zero elasticity; and
• the thickness of the woven structure 2 is constant and independent of the tension and the pressure,

we easily deduce the expression: F = r + r ( π 2 -) + h + r (α + ) + I + rα, which is written F = r (1 + π 2 + 2α) + h + I.

In this last expression, r, h,  and d are parameters variables to choose, and I and α are unknowns, which we can calculate, as detailed below.

By performing a double projection respectively on a horizontal axis and a vertical axis not shown, we obtain the following two relationships: d = -rsin + hcos + rsin + rsinα + Icosα + rsinα O = r + rcos + hsin + r (1-cos) -r (1-cosα) -lsinα-r (1-cosα) which are simplified by: Icosα + 2rsinα = d-hcos lsinα-2rcosα = hsin

By calculating the expression (1) ² + (2) ² , we obtain I 2 + 4r 2 = d 2 + h 2 -2dhcos, that is to say : I = d 2 + h 2 -4r 2 -2dhcos.

Furthermore, from the expression (1) sinα + (2) cosα, we obtain: 2r = (d-hcos) sinα-hsincosα, that is to say : α = arcsin ( 2r d 2 + h 2 -2dhcos ) + arcsin ( hsin d 2 + h 2 -2dhcos ).

From the above, we are able to calculate I and α, and therefore to form the function F from the parameters r, h, d and .

Consequently, by taking determined values of r, d, 1 and 2 and using said function F and the above expression (EO), we arrive to deduce the distance hi for each point Pi considered, that is to say at determine the profile of the cam 5.

It will also be noted that, on the weaving device 1 used according to the invention, each FC chain wire is wound on a independent coil not shown so as to deliver different lengths of wire as specified and required by said device 1.

The device 1 according to the invention also makes it possible to modify the thickness of the woven structure 2, in particular in the case of realization of a multilayer type structure.

• on enlace, à chaque pas de déplacement du dispositif 1, des fils de trame FT superposés présentant un nombre et/ou un diamètre variables ; et/ou
• on varie la longueur du pas P de déplacement ou d'avancement des fils de chaíne FC.

To do this, that is to say to obtain a variable thickness, according to the invention:

• we wrap, at each movement step of the device 1, superimposed weft son FT having a variable number and / or diameter; and or
• we vary the length of the pitch P of movement or advancement of the chain son FC.

To do this, it suffices to form in correspondence in particular the means 4 above.

Thus, thanks to the invention, it is possible to produce woven structures 2 of variable shape and thickness. We are therefore able to preform the woven structures 2 according to the pieces of composite material to manufacture, which considerably reduces subsequent processing, of machining type, to which said parts are then subjected.

In addition, the device 1 according to the invention is simple to achieve and implement and it is inexpensive.

Claims (5)

Weaving device for producing a woven structure which is intended for producing a piece of composite material and which comprises weft threads (FT) and warp threads (FC), said device (1) comprising in particular: means (3A, 3B) for longitudinally moving the chain wires (FC); means (4) for entangling the weft threads (FT) in said warp threads (FC); and means (5) for generating different displacement speeds for at least some of said chain threads (FC), characterized in that said means (5) for generating different displacement speeds comprise a profiled cam (5) capable of rotating around a longitudinal axis (XX), the profile of which is determined according to the desired contour at least a lateral edge (6A) of the woven structure (2) to be produced, in that said cam (5) has a substantially planar shape and a profile which is defined by a variable transverse length (h), perpendicular to said longitudinal axis (XX ), and in that it is arranged so that said longitudinal axis (XX) is substantially orthogonal to the direction (D) defined by the chain threads (FC). Device according to claim 1,
characterized in that said profile is defined so that its transverse length hi, at a point Pi along the longitudinal axis (XX), satisfies the following relationship: Li = Σn (Pj) + F1 (hi, 2) - F2 (hi, 1), in which : Li is the desired length of the warp thread (FCi) of the woven structure (2), which is located at said point Pi along said longitudinal axis (XX); n is the number of weft threads (FT) of the woven structure (2); the n Pj are the displacement steps of the chain son (FC) moved in steps; and F1 and F2 are distances as a function of said transverse length hi and respectively of end angles 1 and 2 of rotation of the cam (5). Device according to any one of the preceding claims, for producing a woven structure having a variable thickness,
characterized in that said means (4) for interweaving weft yarns (FT) entwine a variable number of superimposed weft yarns (FT). Device according to any one of the preceding claims, for producing a woven structure having a variable thickness,
characterized in that said means (4) for interweaving weft yarns (FT) entwine weft yarns (FT) having variable diameters. Device according to any one of the preceding claims, for producing a woven structure having a variable thickness,
characterized in that it is formed so as to be able to modify the length of the displacement step of the warp threads (FC) displaced longitudinally in steps, the interweaving of weft threads (FT) being produced at each step.

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