Weaving machine and method for producing shaped fabric

Abstract

The invention relates to a jacquard loom (10) for manufacturing a fabric (T) having a variable thickness (e1, e2, e3) across a width (L) of the fabric by means of knitting between a plurality of warp threads (30) and a plurality of weft threads (31), the loom comprising: a plurality of heddles (22) connected to a mechanism (11) capable of moving the heddles in a vertical direction (Dv) between a reference position (PH) and a first position for opening the warp threads, each harness wire is also provided with a hole (23), and warp yarns (30) penetrate through the holes (23); a rapier (40) arranged downstream of the harness wire (113) and capable of pulling the weft yarn (31) from the bobbin (50); and a device (90) arranged downstream of the plurality of heddles (22) and the rapier (40) for gripping the fabric, the device comprising two bearing surfaces (93, 94) arranged on both sides of the fabric (T) in order to compress the fabric between the bearing surfaces (93, 94); characterized in that at least the first bearing surface (93) is shaped to at least partially complement the surface of the fabric.

Description

Technical Field

[0001] The present invention relates to the manufacture of fabrics, in particular shaped three-dimensional fabrics, i.e. having a variable thickness over its width. Such fabrics can be used in particular as reinforcements or preforms in the manufacture of composite objects by resin transfer molding, in particular for aerospace applications. Background Art

[0002] Three-dimensional fabrics (3D) can be used as reinforcements or preforms in composite objects manufactured by resin transfer molding (RTM).

[0003] Depending on the geometry of the object, the reinforcement does not always have a constant thickness over its entire width. In particular, the surface of the mould on which the reinforcement is placed before the injection of the resin may not be flat. In this case, in order to avoid the formation of wrinkles during the placement of the reinforcement in the cavity of the mould, it is advantageous for the fabric to have a variable thickness, for example a thickness that is less at its edges than in its centre.

[0004] Such a fabric can be manufactured using a jacquard loom, in particular the one described in document FR 3 074 195 A1.

[0005] Figure 1 A jacquard loom 10 is shown for producing a three-dimensional fabric obtained by weaving together a plurality of warp yarns 30 and a plurality of weft yarns 31 in a plurality of layers.

[0006] The loom 10 is equipped with a jacquard mechanism 11 supported by a superstructure. Figure 1 Not shown in FIG.

[0007] The loom 10 also comprises a harness 20 consisting of a base plate 21 and heddles or harnesses 22 , each heddle 22 being connected at one end to a control hook 12 of the jacquard mechanism 11 and at the other end to one of the return springs 13 , wherein the return springs are fixed to the frame 14 of the loom 10 .

[0008] Each heald 22 comprises an eyelet 23 through which a warp thread 30 passes. Under the traction exerted by the control hook 12 and the return spring 13 respectively, the healds 22 and their associated eyelets 23 are driven in a substantially vertical oscillating movement indicated by the double arrow F.

[0009] The healds 22 make it possible to lift certain warp threads 30 and thus create a shed 15 , in other words an opening between the lower and upper sheets of warp threads 30 , making it possible to introduce a weft thread 31 by means of a rapier 40 .

[0010] The rapier 40 is provided at its end with a clamp 41 which grabs the weft yarn 31 from a bobbin 50 to pass the weft yarn 31 through the opening between the upper and lower sheets of the warp yarn 30 produced by the shed 15 , and the weft yarn 31 is cut using a knife 60 after it is positioned in the shed 15 .

[0011] The comb 70 present upstream of the rapier 40 is then folded downwards in order to compact the weft thread or threads introduced into the shed 15 .

[0012] The rapier 40 is then ready to take a new weft thread 31 from the bobbin 50 again and to place it again in the shed 15 or in a different shed, depending on the defined weaving pattern.

[0013] Thus, a 3D or multi-layer woven fabric T having the warp yarns 30 and the weft yarns 31 is gradually formed.

[0014] The loom 10 further comprises means for clamping the fabric T, present downstream of the healds 22 and the rapier 40 .

[0015] The clamping device 80 comprises a lower jaw 81 and an upper jaw 82, each of which is connected to an actuating device (not shown). The clamping device makes it possible in particular to control the position of the opening point of the shed 15, in other words to control the position of the two warp threads separating from each other in the upstream direction.

[0016] During the weaving of three-dimensional fabrics, a difficulty encountered is the swelling of the fabric, in other words the phenomenon of swelling of the fabric due to the interweaving of the warp and weft yarns.

[0017] Due to this expansion, the three-dimensional fabric leaving the loom has a thickness that is greater than the intended thickness, which can cause defects during the implementation of the RTM method.

[0018] In particular, the reinforcements may form local protrusions which may cause squeezing of the fabric during closing of the mould, manifesting themselves in the final object as areas where the mechanical properties are not controlled.

[0019] Document WO 2021 / 048486 therefore describes a method for closing the mold aimed at preventing such extrusion. Summary of the invention

[0020] It is therefore an object of the present invention to design a weaving machine that makes it possible to control the expansion of a forming fabric, thereby improving the RTM process that can subsequently be carried out.

[0021] To this end, the present invention proposes a jacquard loom for manufacturing a fabric having a variable thickness across its width, in particular a two-dimensional or three-dimensional fabric, by weaving together a plurality of warp yarns and a plurality of weft yarns, the loom comprising:

[0022] - a plurality of heddles connected to a mechanism capable of moving said heddles in a vertical direction between a reference position and a first position for opening said warp threads, each heddle also being provided with an eyelet through which one of said warp threads passes;

[0023] a rapier, arranged downstream of the heald, capable of drawing the weft thread from the bobbin; and

[0024] - means for clamping the fabric, arranged downstream of the plurality of heddles and the rapier, the means comprising at least two bearing surfaces, including at least a first bearing surface and a second bearing surface arranged on both sides of the fabric to compress the fabric between the bearing surfaces.

[0025] The weaving machine is characterized in that at least the first supporting surface is shaped at least partially complementary to the surface of the fabric.

[0026] At least one surface of the fabric is non-planar due to variations in fabric thickness.

[0027] In this context, the term "shaped to be at least partially complementary" shall mean that the first bearing surface has a non-planar shape with its concavity oriented towards the surface of the fabric. Preferably, the bearing surface at least partially matches the non-planar surface of the fabric, in other words, when the first bearing surface is oriented towards the surface of the fabric in a vertical direction, the distance between the first bearing surface and the surface of the fabric is substantially constant at least over a portion of the width of the fabric.

[0028] In this context, the terms "upstream" and "downstream" extend in the advancing direction of the yarn weaving.

[0029] Advantageously, the clamping device comprises at least one clamping rod having said at least one first bearing surface.

[0030] In certain embodiments, the clamping rod includes a body and a removable portion carrying the first bearing surface, the removable portion being reversibly connected to the body of the clamping rod.

[0031] The removable portion may be in the form of a solid metal bar on which the first bearing surface is formed.

[0032] In certain embodiments, the clamping device includes a table having a second support surface, the second support surface being planar.

[0033] Particularly advantageously, the distance between the first bearing surface and the second bearing surface is selected to reduce the expansion of the fabric to reach a minimum expansion threshold.

[0034] Another object of the present invention relates to a method for manufacturing a fabric, in particular a 3D fabric, having a variable thickness over the width of the fabric, the method comprising:

[0035] - weaving a plurality of warp yarns and a plurality of weft yarns by means of a jacquard loom as described above to form said fabric; and

[0036] - Compression of the fabric is applied by means of said clamping means by means of said first and second supporting surfaces.

[0037] Particularly advantageously, the distance between the bearing surfaces is controlled to reduce the expansion of the fabric to reach a minimum expansion threshold.

[0038] In certain embodiments, the warp and weft yarns include carbon and / or glass.

[0039] Another object of the invention relates to a method for manufacturing a composite object comprising a fabric having a defined shape, in particular a two-dimensional or three-dimensional fabric, comprising:

[0040] - producing said fabric by the method as described above;

[0041] - winding a reinforcement formed by a portion of said fabric in a cavity (imprint) of a mould defining the outer surface of said object;

[0042] - closing the mould; and

[0043] - Introducing resin into the cavity to impregnate the reinforcement.

[0044] In certain embodiments, the object has a rotationally symmetric shape.

[0045] In particular, the object may be a fan casing, a turbine casing, a nozzle casing or a mixer casing for an aircraft engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Other features and advantages of the present invention will become apparent from the following detailed description made with reference to the accompanying drawings, in which:

[0047] Figure 1 An assembled view of a known jacquard loom is shown;

[0048] Figure 2A , Figure 2B and Figure 2C is a cross-sectional view of a three-dimensional fabric having a variable thickness across the width of the fabric;

[0049] Figure 3 yes Figure 2A A cross-sectional view of a three-dimensional fabric and a rod of a clamping device according to one embodiment;

[0050] Figure 4 yes Figure 2A A cross-sectional view of a three-dimensional fabric and a rod of a clamping device according to the prior art;

[0051] Figure 5 shows an assembly view of a jacquard loom according to one embodiment of the present invention; and

[0052] Figure 6 is a schematic diagram of the expansion variation as a function of the distance between the bearing surfaces of the clamping device.

[0053] For reasons of ease of drawing readability, the drawings are not necessarily drawn to scale.

[0054] The same reference numerals between the drawings indicate the same element or an element that performs the same function. DETAILED DESCRIPTION

[0055] The present invention relates to the manufacture of a forming fabric having controlled expansion.In the remainder of this document, reference will essentially be made to three-dimensional fabrics, but the description is equally applicable to two-dimensional fabrics.

[0056] Figure 2A An example of a shaped three-dimensional fabric seen in cross section is shown. In this example, the fabric has a flat lower surface, and the thickness gradually increases from its edge (thickness e1) to its center (thickness e3), with an intermediate thickness e2, thereby forming a non-planar upper surface. Of course, this thickness variation profile is given only by way of example and is not limiting.

[0057] Furthermore, both major surfaces of the fabric may have non-planar shapes.

[0058] Figure 2B A second example of a formed three-dimensional fabric is shown in cross-section.

[0059] Figure 2C A third example of a formed three-dimensional fabric is shown in cross-section.

[0060] Generally, shaped weaving consists in weaving a profile proportional to the internal profile of the composite object to be produced. In a manner known per se, this profile is obtained by differential take-off of the yarns by means of non-cylindrical take-off rollers which allow the yarns to have different lengths depending on the position of each yarn on the roller.

[0061] The expansion of such a fabric may be defined as the ratio between the total volume occupied by the fabric produced by the loom and a reference volume of the fabric, which corresponds, for example, to the minimum volume that can be reached by compressing the fabric.

[0062] In the present invention, expansion is controlled by using a clamping device having a bearing surface shaped at least partially complementary to the shape of the fabric surface facing it.

[0063] Figure 3 Shows Figure 2A A cross-sectional view of a fabric and a rod 92 of a clamping device according to one embodiment of the present invention.

[0064] The support surface 93 in contact with the fabric T makes it possible to compress the assembly of warp and weft yarns, thus reducing the expansion of the fabric.

[0065] In contrast, in known types of clamping devices, such as Figure 4 As shown, the surface of the jaws 82 facing the fabric is planar and therefore is not capable of contacting the entire surface of the fabric or compressing the fabric in a uniform manner.

[0066] Figure 5 A Jacquard weaving machine 10 comprising a clamping device according to the invention is shown.

[0067] In a manner known per se, the loom 10 is equipped with a jacquard mechanism 11 supported by a superstructure which is Figure 5 Not shown in FIG.

[0068] The loom 10 also comprises a harness 20 consisting of a bottom plate 21 and heddles or harnesses 22, each heddle 22 being connected at one end to a control hook 12 of the jacquard mechanism 11 and at the other end to one of the return springs 13 fixed to the frame 14 of the loom 10.

[0069] Each heald 22 comprises an eyelet 23 through which a warp thread 30 passes. Under the traction exerted by the control hook 12 and the return spring 13 respectively, the healds 22 and their associated eyelets 23 are driven in a substantially vertical oscillating movement indicated by the double arrow F.

[0070] The healds 22 make it possible to lift certain warp threads 30 and thus create a shed 15 , in other words an opening between the lower and upper sheets of warp threads 30 , making it possible to introduce a weft thread 31 by means of a rapier 40 .

[0071] The rapier 40 is provided at its end with a clamp 41 which grabs the weft yarn 31 from the bobbin 50 to pass the weft yarn 31 through the opening between the upper and lower sheets of the warp yarn 30 produced by the shed 15 , and the weft yarn 31 is cut using a knife 60 after it is positioned in the shed 15 .

[0072] The reed 70 present upstream of the rapier 40 is then folded downwards in order to compact the weft thread or threads introduced into the shed 15 .

[0073] The rapier 40 is then ready to take a new weft thread 31 from the bobbin 50 again and to place it again in the shed 15 or in a different shed, depending on the defined weaving pattern.

[0074] The weaving machine 10 further comprises a clamping device 90 for the fabric T, present downstream of the healds 22 and the rapier 40 .

[0075] According to the invention, said clamping device 90 comprises two bearing surfaces 93, 94 arranged on both sides of the fabric.

[0076] The support surface 93 facing the upper surface of the fabric has a surface complementary to the surface of the fabric, wherein the upper surface of the fabric is the forming surface of the fabric.

[0077] exist Figure 3 In the embodiment shown, the shape of the support surface is complementary to the surface of the fabric, provided that, at any point on the width of the fabric, the distance between the support surface and the surface of the fabric is constant (when the support surface is in contact with the fabric, the distance is zero). However, in other embodiments, the support surface may have a shape that is partially complementary to the shape of the surface of the fabric, in other words, the distance between the support surface and the fabric may be constant in a part of the width of the fabric (e.g., the central part), but may be different in another part of the width of the fabric (e.g., the edge part). In other embodiments, the shape of the support surface may not be completely consistent with the shape of the surface of the fabric, but may have an intermediate shape between the plane shape and the shape of the fabric surface, which intermediate shape has a concave portion oriented toward the fabric surface (in other words, if the surface of the fabric has a concave portion, the corresponding part of the support surface has a convex portion, and conversely, if the surface of the fabric has a convex portion, the corresponding part of the support surface has a concave portion). Typically, along the width of the fabric, the relative deviation of the distance between the support surface and the fabric surface is on average 30%, or even less than 10%.

[0078] Said bearing surface 93 belongs to a clamping rod 92. The clamping rod 92 can be integral with the frame 14 of the weaving machine 10.

[0079] Alternatively, the weaving machine may have a plurality of bearing surfaces, each bearing surface being arranged on a respective clamping rod, the clamping rods being arranged parallel to one another.

[0080] Furthermore, the bearing surface 93 does not have to be continuous. For example, the bearing surface can extend over at least two parallel clamping bars.

[0081] exist Figure 5In the embodiment shown, the support surface 94 , facing the lower surface of the fabric, is planar and belongs to a table 91 that is integral with the frame 14 .

[0082] Alternatively (not shown), if the reverse side of the fabric also has a non-planar shape, the workbench 91 can be replaced by one or more clamping rods, which also have a supporting surface complementary to the lower surface of the fabric and are arranged opposite to the supporting surface 93 of the clamping rod 92 in the direction Z, which is perpendicular to the main surface of the fabric.

[0083] Thus, the support surface 93 is specifically shaped to at least partially match the shape of the non-planar surface of the fabric.

[0084] In order to manufacture 3D fabrics with different shapes, it is sufficient to replace one or more clamping rods with one or two clamping rods having a bearing surface complementary to the surface of the new fabric. It therefore involves a particularly simple modification of the weaving machine. In order to simplify this modification, the clamping rods can be in the form of an assembly of a body integral with the frame of the weaving machine and a removable part carrying the bearing surface. The removable part can, for example, be connected to the body by screws or any reversible connection means.

[0085] Furthermore, the distance d between the support surface 93 and the support surface 94 is chosen so that the support surfaces bear against the surface of the fabric and exert a compressive force on the fabric between the clamping bar 92 and the table 91 or, where applicable, between the two clamping bars.

[0086] The clamping bars and table are made in a sufficiently rigid structure to resist the compressive forces exerted on the fabric. For example, each clamping bar (or, in the case of a removable assembly, a removable portion of the clamping bar) may be in the form of a solid metal bar with a bearing surface machined.

[0087] Due to the complementarity of the contacting surfaces, this compression is substantially uniform over the entire contacting surface and preferably over the entire width L of the fabric. The compression has the effect of compacting the warp and weft yarns in the thickness direction (Z direction) of the fabric and thus reducing the expansion of the fabric.

[0088] During weaving, the distance d between the support surfaces is usually fixed, the clamping rod 92 and the table 91 being fixed relative to the frame. However, this distance can optionally be adjusted, in particular during fine tuning of the weaving, for example using shims of different thicknesses.

[0089] A person skilled in the art will be able to define the force applied as a function of the fabric structure to obtain a minimum expansion. For example, the expansion of the fabric can be measured without applying compression by a clamping device, and then gradually applying increasing compressive forces by reducing the distance between the support surfaces until the desired expansion is obtained.

[0090] In particular, the expansion of the fabric may be measured for a plurality of distances between the support surfaces.

[0091] therefore, Figure 6 Schematically shows Figure 2A The expansion F of a fabric of the type shown in , obtained empirically as a function of the distance d between the support surface of the clamping bar and the support surface of the table. It can be observed that the more the distance d decreases, the more the expansion decreases, until a limit (which may be non-zero) is reached, which corresponds to the minimum expansion F that can be obtained for this fabric min .

[0092] A person skilled in the art can therefore use simple tests to determine the distance between the support surfaces in order to obtain a determined (preferably minimum) expansion for a given fabric.

[0093] The clamping rod 92 is then fixed at a desired distance from the workbench 91 .

[0094] Thus, a fabric T is gradually formed: the fabric has 3D multiple layers of warp yarns 30 and weft yarns 31 woven together and has minimal expansion, in other words, the thickness of the fabric leaving the loom 10 is substantially equal to the expected thickness while conforming to the shape defined by the thickness variation.

[0095] In particular, in the case of a fabric intended for forming a preform or reinforcement for manufacturing a composite material object by an RTM method, the thickness of the fabric leaving the loom 10 is substantially equal to the thickness for which the mould has been designed.

[0096] To manufacture such a composite object, the weaving machine 10 provides a length of manufactured 3D fabric, which constitutes a preform or a reinforcement.

[0097] The reinforcement is placed in the cavity of a mold for the RTM process.

[0098] For example, in the case of a fan casing, the reinforcement is wound onto a mandrel.

[0099] Even if the mandrel has a shape that cannot be flattened, the reinforcement shape is adapted to minimize the formation of wrinkles or bulges due to variations in fabric thickness.

[0100] Furthermore, if the thickness of the reinforcement is the same as that expected by the mold design, closing of the mold will not result in squeezing of the fabric.

[0101] When the mold is closed again, resin is injected into the mold cavity. The resin impregnates the mesh of the fabric.

[0102] The molded composite object is maintained in the mold cavity for a duration sufficient to allow the resin to cure.

[0103] The composite object is then demoulded and any finishing processes are performed, which are conventional and will not be described herein.

[0104] Reference may be made in particular to document EP 1 961 923, which describes a method for producing a gas turbine casing made of a composite material.

[0105] The quality of the composite object is significantly improved relative to an object made from a fabric whose expansion during weaving is not controlled. In particular, the absence of wrinkles or bulges makes it possible to maintain the structure of the fabric at any point on the object during placement in the mold cavity, thus avoiding variations in local mechanical properties.

[0106] The invention is applicable for producing any type of housing or housing element having a rotationally symmetrical shape, in particular for aircraft engines, such as a fan housing, a turbine housing, a nozzle housing or a mixer housing.

Claims

1. A jacquard loom (10) for manufacturing a fabric (T) by weaving together a plurality of warp yarns (30) and a plurality of weft yarns (31), the fabric having a variable thickness (e1, e2, e3) across a width (L) of the fabric, the loom comprising: a plurality of heddles (22) connected to a mechanism (11) capable of moving said heddles in a vertical direction (Dv) between a reference position (PH) and a first position for opening said warp threads, each heddle also being provided with an eyelet (23) through which one of said warp threads (30) passes; a rapier (40), arranged downstream of the heald (113), capable of pulling the weft thread (31) from the bobbin (50); as well as a device (90) for clamping the fabric, arranged downstream of the plurality of heddles (22) and the rapier (40), the device comprising at least two supporting surfaces, the supporting surfaces comprising at least a first supporting surface (93) and a second supporting surface (94) arranged on both sides of the fabric (T) to compress the fabric between the first and second supporting surfaces (93, 94); Characterized in that at least the first bearing surface (93) is shaped at least partially complementary to the surface of the fabric.

2. The loom according to claim 1, wherein: The clamping device comprises at least one clamping rod (92) having the at least one first bearing surface (93).

3. The loom according to claim 2, wherein: The clamping rod comprises a body and a removable portion carrying the first bearing surface, the removable portion being reversibly connected to the body of the clamping rod.

4. The loom according to claim 3, wherein: The removable portion is in the form of a solid metal bar on which the first bearing surface is formed.

5. A loom according to any one of claims 1 to 4, wherein: The clamping device comprises a workbench (91) having the second support surface (94), the second support surface (94) being planar.

6. A loom according to any one of claims 1 to 5, wherein: The distance (d) between the first and second bearing surfaces is selected to reduce the expansion (F) of the fabric (T) to achieve a minimum expansion threshold (F min ).

7. A weaving machine according to any one of claims 1 to 6, configured for producing three-dimensional fabrics.

8. A method for manufacturing a fabric, in particular a three-dimensional fabric (T), having a variable thickness (e1, e2, e3) over its width (L), comprising: Weaving a plurality of warp yarns (30) and a plurality of weft yarns (31) by means of a jacquard loom according to any one of claims 1 to 7 to form the fabric; as well as Compression of the fabric is applied by means of the clamping device by means of the first and second bearing surfaces (93, 94).

9. The method according to claim 8, wherein: The distance (d) between the first and second support surfaces is controlled to minimize expansion of the fabric.

10. The method according to any one of claims 8 or 9, wherein: The warp yarns and the weft yarns include carbon and / or glass.

11. A method for producing a composite object comprising a fabric having a defined shape, in particular a three-dimensional fabric, the method comprising: Manufacturing the fabric by the method according to any one of claims 8 to 10; winding a reinforcement formed from a portion of the fabric into a cavity of a mold defining an outer surface of the object; closing the mold; and Resin is introduced into the cavity to impregnate the reinforcement.

12. The method according to claim 11, wherein: The object has a rotationally symmetrical shape.

13. The method according to any one of claims 11 or 12, wherein: The object is a fan casing, a turbine casing, a nozzle casing or a mixer casing for an aircraft engine.

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