Loom and method for manufacturing a shaped fabric

Abstract

The invention relates to a Jacquard loom (10) for manufacturing a fabric (T) having a variable thickness (e1, e2, e3) across its width (L) by means of weaving between a plurality of warp yarns (30) and a plurality of weft yarns (31), the loom comprising: a plurality of heald wires (22), which are connected to a mechanism (11) capable of moving the heald wires in a vertical direction (Dv) between a reference position (PH) and a first position for opening the warp yarns, each heald wire being further provided with an eye (23) through which a warp yarn (30) passes, a rapier (40) arranged downstream of the heald wires (113), capable of drawing a weft yarn (31) from a bobbin (50), a device (90) for holding the fabric arranged downstream of the plurality of heald wires (22) and of the rapier (40), comprising two bearing surfaces (93, 94) arranged on either side of the fabric (T) to compress the fabric between the bearing surfaces (93, 94), characterised in that at least a first bearing surface (93) is shaped so as to be at least partially complementary to a surface of the fabric.

Description

[0001] LOOM AND METHOD FOR MANUFACTURING A SHAPED FABRIC

[0002] Technical field

[0003] The invention relates to the manufacture of a fabric, in particular a three-dimensional fabric, in shape, that is to say having a variable thickness across its width. Such a fabric can in particular serve as reinforcement or preform in the manufacture of composite objects by resin transfer molding, in particular for applications in aeronautics.

[0004] State of the art

[0005] Three-dimensional (3D) fabrics can be used as reinforcements or preforms in composite objects manufactured by resin transfer molding (RTM).

[0006] Depending on the geometry of the object, the reinforcement does not always have a constant thickness across its entire width. In particular, the mold surface on which the reinforcement is placed before the resin is injected may not be developable. In this case, to avoid the formation of folds when placing the reinforcement in the mold cavity, it may be advantageous for the fabric to have a variable thickness, for example, a lower thickness at its edges than in its center.

[0007] Such a fabric can be manufactured using a Jacquard type loom, which is described in particular in document FR 3 074 195 A1.

[0008] Figure 1 illustrates a Jacquard type loom 10 used for producing a three-dimensional fabric obtained by multi-layer weaving between a plurality of layers of warp threads 30 and a plurality of layers of weft threads 31.

[0009] The loom 10 is equipped with a Jacquard mechanism 11 supported by a superstructure not shown in figure 1.

[0010] The loom 10 also comprises a harness 20 consisting of a weaving board 21 and control threads or heddles 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 weaving loom 10.

[0011] Each heddle 22 comprises an eyelet 23 crossed by a warp thread 30. The heddles 22 and their associated eyelet 23 are driven by a substantially vertical oscillating movement represented by the double arrow F under the tensile forces exerted respectively by the control hooks 12 and the return springs 13.

[0012] The heddles 22 make it possible to lift certain warp threads 30 and thus create a shed 15, that is to say an opening between lower and upper layers of warp threads 30 allowing the introduction of weft threads 31 by means of a lance 40.

[0013] The lance 40 is provided at its end with a clamp 41 which grips a weft thread 31 from a spool 50 to place it through the opening between the layers of warp threads 30 created by the shed 15, the weft thread 31 being cut using a knife 60 after its positioning in the shed 15.

[0014] A comb 70 present upstream of the lance 40 is then folded down in order to pack the weft thread(s) introduced into the shed 15.

[0015] The lance 40 is then ready to pick up a new weft thread 31 from the bobbin 50 and place it either again in the shed 15 or in a different shed depending on the defined weave.

[0016] A fabric T is thus gradually formed having a 3D or multi-layer weave between the warp threads 30 and the weft threads 31.

[0017] The loom 10 further comprises a device for holding the fabric T present downstream of the heddles 22 and the rapier 40.

[0018] The holding device 80 comprises a lower jaw 81 and an upper jaw 82 each connected to an actuating means (not shown). Said holding device makes it possible in particular to control the position of the opening point of the shed 15, that is to say the location from which two layers of warp threads move away from each other upstream.

[0019] One difficulty encountered when weaving a three-dimensional fabric is the swelling of the fabric, that is to say the phenomenon of swelling of the fabric due to the interlacing of the warp and weft threads.

[0020] Because of this swelling, the three-dimensional fabric coming out of the loom has a thickness greater than the expected thickness, which can cause defects when implementing the RTM process.

[0021] In particular, the reinforcement can form localized bumps, which can lead to pinching of the fabric when the mold is closed, resulting in areas in the final object whose mechanical properties are not controlled.

[0022] Document WO 2021 / 048486 thus describes a method for closing a mold intended to avoid such pinching.

[0023] Brief description of the invention

[0024] One aim of the invention is therefore to design a loom making it possible to control the expansion of the fabric in shape and thus improve the RTM process which may be implemented subsequently.

[0025] For this purpose, the invention proposes a Jacquard type loom for manufacturing a fabric, in particular a two-dimensional or three-dimensional fabric, having a variable thickness across its width by weaving between a plurality of warp threads and a plurality of weft threads, said loom comprising: - a plurality of control threads, connected to a mechanism capable of moving the control threads in a vertical direction between a reference position and a first opening position of the warp threads, each control thread being further provided with an eyelet through which one of the warp threads passes,

[0026] - a lance arranged downstream of the control threads, capable of pulling a weft thread from a bobbin,

[0027] - a fabric holding device arranged downstream of the plurality of control wires and the lance, comprising at least two bearing surfaces, including at least a first bearing surface and a second bearing surface arranged on either side of the fabric to compress the fabric between said bearing surfaces.

[0028] Said weaving loom is characterized in that at least the first support surface is shaped in a manner at least partially complementary to a surface of the fabric.

[0029] Due to the variation in thickness of the fabric, at least one surface of the fabric is non-flat.

[0030] By "conformed in an at least partially complementary manner" is meant in the present text that the first bearing surface has a non-planar shape whose concavity is oriented towards the surface of the fabric. Preferably, the bearing surface at least partially matches the non-planar surface of the fabric, that is to say that, when the first bearing surface is brought towards the surface of the fabric in the vertical direction, the distance between the first bearing surface and the surface of the fabric is substantially constant at least in part of the width of the fabric.

[0031] In this text, the terms "upstream" and "downstream" are understood to mean the progress of the weaving of the threads.

[0032] Advantageously, the holding device comprises at least one holding bar having said at least one first support surface.

[0033] In some embodiments, said holding bar comprises a body and a removable portion carrying the first bearing surface, the removable portion being reversibly connected to the body of the holding bar.

[0034] Said removable portion may be in the form of a solid metal bar, in which the first bearing surface is formed.

[0035] In some embodiments, the holding device comprises a table having the second bearing surface, said second bearing surface being planar.

[0036] Particularly advantageously, the distance between the first and second bearing surfaces is chosen so as to reduce the expansion of the fabric to achieve a minimum expansion threshold.

[0037] Another subject of the invention relates to a method for manufacturing a fabric, in particular a 3D fabric, having a variable thickness across its width, comprising: - weaving a plurality of warp threads and a plurality of weft threads using a Jacquard type loom as described above, so as to form said fabric, and

[0038] - the application, by the holding device, of compression of the tissue via said first and second support surfaces.

[0039] Particularly advantageously, the distance between the support surfaces is controlled so as to reduce the fabric swelling to achieve a minimum swelling threshold.

[0040] In some embodiments, the warp yarns and weft yarns comprise carbon and / or glass.

[0041] Another subject of the invention relates to a method for manufacturing a composite object comprising a fabric, in particular a two-dimensional or three-dimensional fabric, having a determined shape, said method comprising:

[0042] - the manufacture of said fabric by the process as described above;

[0043] - winding a reinforcement formed from a portion of said fabric into an imprint of a mold defining an exterior surface of the object;

[0044] - closing the mold;

[0045] - the introduction of a resin into the impression to impregnate the reinforcement.

[0046] In some embodiments, the object has a form of revolution.

[0047] The object may in particular be a fan casing, a turbine casing, a nozzle casing or a mixer casing for an aircraft engine.

[0048] Brief description of the figures

[0049] Other characteristics and advantages of the invention will emerge from the detailed description which follows, with reference to the appended drawings, in which:

[0050] - Figure 1 shows an overview of a known Jacquard type loom;

[0051] - Figures 2A, 2B and 2C are sectional views of a three-dimensional fabric having a variable thickness across its width;

[0052] - Figure 3 is a sectional view of the three-dimensional fabric of Figure 2A and of a bar of the holding device according to one embodiment;

[0053] - Figure 4 is a sectional view of the three-dimensional fabric of Figure 2A and of a bar of the holding device according to the state of the art;

[0054] - figure 5 shows an overall view of a Jacquard type loom according to one embodiment of the invention;

[0055] - Figure 6 is a basic graph of the evolution of the expansion as a function of the distance between the support surfaces of the holding device. For reasons of readability of the figures, the drawings have not necessarily been represented to scale.

[0056] Identical reference signs from one figure to another designate identical elements or elements fulfilling the same function.

[0057] Detailed description of embodiments

[0058] The invention relates to the manufacture of a shaped fabric having controlled expansion. In the following text, reference will be made mainly to a three-dimensional fabric, but the description also applies to a two-dimensional fabric.

[0059] Figure 2A illustrates an example of a shaped three-dimensional fabric, seen in section. In this example, the fabric has a flat lower surface and a thickness increasing successively from its edge (thickness ei) towards its center (thickness es) with an intermediate thickness e2, thus forming a non-flat upper surface. Naturally, this thickness variation profile is given for illustrative purposes only and is not limiting.

[0060] Furthermore, the two main surfaces of the fabric may have a non-planar shape.

[0061] Figure 2B illustrates a second example of a shaped three-dimensional fabric, seen in cross-section.

[0062] Figure 2C illustrates a third example of a shaped three-dimensional fabric, seen in cross-section.

[0063] Generally speaking, shaped weaving consists of 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 a differential call of threads by means of a non-cylindrical call roller which allows for different lengths of threads depending on the location of each thread on the roller.

[0064] The expansion of such a fabric can be defined as the ratio between the total volume occupied by the fabric, as produced by the loom, and a reference volume for this fabric, corresponding for example to the smallest volume to which this fabric could be brought by compressing it.

[0065] In the invention, the expansion is controlled by the use of a holding device which has a support surface shaped in a manner at least partially complementary to the shape of the surface of the facing fabric.

[0066] Figure 3 illustrates a sectional view of the fabric of Figure 2A and a bar 92 of the holding device according to one embodiment of the invention.

[0067] The bearing surface 93, which comes into contact with the fabric T, makes it possible to compress the assembly of the warp and weft threads and thus to reduce the swelling of the fabric. On the contrary, in a holding device of known type, as illustrated in FIG. 4, the surface of the jaw 82 facing the fabric is flat and therefore cannot come into contact with the entire surface of the fabric or compress the fabric uniformly.

[0068] Figure 5 illustrates a Jacquard type loom 10 comprising a holding device according to the invention.

[0069] In a manner known per se, the loom 10 is equipped with a Jacquard mechanism 11 supported by a superstructure not shown in figure 5.

[0070] The loom 10 also comprises a harness 20 consisting of a weaving board 21 and control threads or heddles 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 weaving loom 10.

[0071] Each heddle 22 comprises an eyelet 23 crossed by a warp thread 30. The heddles 22 and their associated eyelet 23 are driven by a substantially vertical oscillating movement represented by the double arrow F under the tensile forces exerted respectively by the control hooks 12 and the return springs 13.

[0072] The heddles 22 make it possible to lift certain warp threads 30 and thus create a shed 15, that is to say an opening between lower and upper layers of warp threads 30 allowing the introduction of weft threads 31 by means of a lance 40.

[0073] The lance 40 is provided at its end with a clamp 41 which grips a weft thread 31 from a spool 50 to place it through the opening between the layers of warp threads 30 created by the shed 15, the weft thread 31 being cut using a knife 60 after its positioning in the shed 15.

[0074] A comb 70 present upstream of the lance 40 is then folded down in order to pack the weft thread(s) introduced into the shed 15.

[0075] The lance 40 is then ready to pick up a new weft thread 31 from the bobbin 50 and place it either again in the shed 15 or in a different shed depending on the defined weave.

[0076] The loom 10 further comprises a device 90 for holding the fabric T present downstream of the heddles 22 and the rapier 40.

[0077] According to the invention, said holding device 90 comprises two support surfaces 93, 94 arranged on either side of the fabric.

[0078] The bearing surface 93 facing the upper surface of the fabric, which is a shaped surface of the fabric, has a shape complementary to the surface of the fabric.

[0079] In the embodiment illustrated in Figure 3, the shape of the bearing surface is complementary to the surface of the fabric insofar as, at any point along the width of the fabric, the distance between the bearing surface and the surface of the fabric is constant (this distance being zero when the bearing surface is in contact with the fabric). However, in other embodiments, the bearing surface could have a shape partially complementary to that of the surface of the fabric, i.e. the distance between the bearing surface and the fabric could be constant in one part of the width of the fabric (e.g. a central part), but different in another part of the width of the fabric (e.g. a peripheral part).In other embodiments, the shape of the bearing surface might not perfectly match the shape of the fabric surface, but have an intermediate shape between a plane shape and the shape of the fabric surface, this intermediate shape having a concavity oriented towards the fabric surface (in other words, if the fabric surface has a hollow, the corresponding part of the bearing surface has a bump and conversely, if the fabric surface has a bump, the corresponding part of the bearing surface has a hollow). Generally speaking, the relative deviation in distance between the bearing surface and the fabric surface depending on the fabric width is on average less than 30%, or even less than 10%.

[0080] Said support surface 93 belongs to a holding bar 92. The holding bar 92 may be secured to the frame 14 of the weaving loom 10.

[0081] Optionally, the loom may have several support surfaces each arranged on a respective holding bar, said holding bars being arranged parallel to each other.

[0082] Furthermore, the support surface 93 is not necessarily continuous. For example, said support surface may extend over at least two parallel support bars.

[0083] In the embodiment illustrated in Figure 5, the support surface 94 facing the lower surface of the fabric, which is flat, belongs to a table 91 secured to the frame 14.

[0084] Alternatively (not shown), if the opposite surface of the fabric also has a non-planar shape, the table 91 may be replaced by one or more holding bars also having a supporting surface complementary to the lower surface of the fabric, and arranged opposite the supporting surface 93 of the holding bar 92 in a Z direction perpendicular to the main surface of the fabric.

[0085] The bearing surface 93 is therefore specifically shaped to at least partially match the shape of the non-planar surface of the fabric.

[0086] To produce a 3D fabric with a different shape, it is sufficient to replace the support bar(s) with one or two support bars having a support surface complementary to that of the surface of the new fabric. This is therefore a particularly simple modification of the loom. To simplify such a modification, the support bars can be in the form of an assembly of a body secured to the frame of the loom and a removable portion carrying the support surface. The removable portion can, for example, be connected to the body by screws or any reversible connection means.

[0087] Furthermore, the distance d between the support surfaces 93 and 94 is chosen so as to apply the support surface against the surface of the fabric and to exert a compressive force on the fabric between the holding bar 92 and the table 91, or, where appropriate, between the two holding bars.

[0088] The support bar and the table are made in the form of structures sufficiently rigid to withstand the compressive force exerted on the fabric. For example, each support bar (or, in the case of a demountable assembly, the removable portion of the support bar) may be in the form of a solid metal bar, in which the bearing surface is machined.

[0089] Due to the complementarity of the contact surfaces, this compression is substantially uniform over the entire contact surface, and preferably over the entire width L of the fabric. The compression has the effect of compacting the warp and weft threads in the direction of the thickness of the fabric (Z direction) and thus reducing the bulge of the fabric.

[0090] The distance d between the support surfaces is generally fixed during weaving, the holding bar 92 and the table 91 being fixed relative to the frame. However, this distance can possibly be adjusted, in particular when setting up the weaving, for example using shims of different thicknesses.

[0091] The skilled person is able to define the force to be applied depending on the structure of the fabric to obtain minimal expansion. For example, the expansion of the fabric can be measured without applying compression by the holding device, then gradually applying an increasing compression force by decreasing the distance between the support surfaces until the required expansion is obtained.

[0092] In particular, it is possible to measure the expansion of the fabric for different distances between the support surfaces.

[0093] Figure 6 thus schematically illustrates the expansion F for a fabric of the type shown in Figure 2A, obtained empirically as a function of the distance d between the support surface of the holding bar and the support surface of the table. It can be seen that the more the distance d is reduced, the more the expansion is reduced until a limit (which may be non-zero) is reached corresponding to the minimum expansion Fmin that can be obtained for this fabric. A person skilled in the art is therefore able, using simple tests, to determine the distance between the support surfaces to obtain a determined expansion (preferably minimal) for a given fabric.

[0094] The holding bar 92 is then fixed at the desired distance from the table 91.

[0095] A fabric T is thus gradually formed having a 3D or multi-layer weave between the warp threads 30 and the weft threads 31 and having minimal expansion, that is to say that the thickness of the fabric leaving the loom 10 is substantially equal to the intended thickness, while respecting the shape defined by the variations in thickness.

[0096] In particular, in the case where the fabric is intended to form a preform or reinforcement for the manufacture of a composite object by the RTM process, the thickness of the fabric leaving the loom 10 is substantially equal to the thickness for which the mold was designed.

[0097] To make such a composite object, we have a certain length of 3D fabric made using loom 10, which constitutes a preform or reinforcement.

[0098] The reinforcement is placed in the mold cavity of the RTM process.

[0099] For example, in the case of a fan casing, the reinforcement is wound onto a mandrel.

[0100] Even though the mandrel has a non-developable shape, the shape of the reinforcement, due to variations in fabric thickness, is adapted to minimize the formation of folds or bumps.

[0101] Furthermore, since the thickness of the reinforcement is identical to the thickness planned for the mold design, closing the mold does not cause any pinching of the fabric.

[0102] Once the mold is closed, a resin is injected into the mold cavity. The resin impregnates the mesh of the fabric.

[0103] The molded composite object is held in the impression for a sufficient time to allow the resin to harden.

[0104] Then, the composite object is demolded and any finishing treatments are carried out, which are conventional and will therefore not be described in this text.

[0105] Reference may be made in particular to document EP 1 961 923 which describes a method for manufacturing a gas turbine casing from composite material.

[0106] The quality of the composite object is significantly improved compared to that of an object manufactured from a fabric whose expansion has not been controlled during weaving. In particular, the absence of folds or bumps during placement in the imprint makes it possible to preserve the structure of the fabric at every point of the object, and thus avoid localized changes in mechanical properties. The invention finds application for the manufacture of any type of casing or casing element having a shape of revolution, in particular for an aeronautical engine, such as a fan casing, a turbine casing, a nozzle casing or a mixer casing.

Claims

Claims 1. Jacquard type loom (10) for manufacturing a fabric (T) having a thickness (ei, e2, es) variable over its width (L) by weaving between a plurality of warp threads (30) and a plurality of weft threads (31), said loom comprising: - a plurality of control threads (22), connected to a mechanism (11) capable of moving the control threads in a vertical direction (Dv) between a reference position (PH) and a first opening position of the warp threads, each control thread being further provided with an eyelet (23) crossed by one of the warp threads (30), - a lance (40) arranged downstream of the control threads (113), capable of pulling a weft thread (31) from a bobbin (50), - a device (90) for holding the fabric arranged downstream of the plurality of control threads (22) and the lance (40), comprising at least two bearing surfaces, including at least a first bearing surface (93) and a second bearing surface (94) arranged on either side of the fabric (T) to compress the fabric between said first and second bearing surfaces (93, 94), characterized in that at least the first bearing surface (93) is shaped in a manner at least partially complementary to a surface of the fabric.

2. Weaving loom according to claim 1, wherein the holding device comprises at least one holding bar (92) having said at least one first bearing surface (93).

3. A loom according to claim 2, wherein said holding bar comprises a body and a removable portion carrying the first bearing surface, the removable portion being reversibly connected to the body of the holding bar.

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

5. Weaving loom according to one of claims 1 to 4, in which the holding device comprises a table (91) having the second bearing surface (94), said second bearing surface (94) being flat.

6. Weaving loom according to one of claims 1 to 5, in which the distance (d) between the first and second support surfaces is chosen so as to reduce the expansion (F) of the fabric (T) to reach a minimum expansion threshold (Fmin).

7. Loom according to one of claims 1 to 6, configured to manufacture a three-dimensional fabric.

8. Method for manufacturing a fabric, in particular a three-dimensional fabric (T), having a thickness (ei, e2, es) which varies over its width (L), comprising: - weaving a plurality of warp threads (30) and a plurality of weft threads (31) by means of a Jacquard type loom according to one of claims 1 to 7, so as to form said fabric, and - the application, by the holding device, of compression of the tissue via said first and second support surfaces (93, 94).

9. The method of claim 8, wherein the distance (d) between the first and second bearing surfaces is controlled so as to minimize the swelling of the fabric.

10. Method according to one of claims 8 or 9, in which the warp threads and the weft threads comprise carbon and / or glass.

11. Method for manufacturing a composite object comprising a fabric, in particular a three-dimensional fabric, having a specific shape, comprising: - the manufacture of said fabric by the method according to one of claims 8 to 10; - winding a reinforcement formed from a portion of said fabric into an imprint of a mold defining an exterior surface of the object; - closing the mold; - the introduction of a resin into the impression to impregnate the reinforcement.

12. Method according to claim 11, in which the object has a shape of revolution.

13. Method according to one of claims 11 or 12, in which the object is a fan casing, a turbine casing, a nozzle casing or a mixer casing for an aeronautical engine.

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