Laying head for thread winding unit

Abstract

The present invention relates to a method for manufacturing a spool comprising the steps of: k The laying head (8) for the roving is provided with a plurality of line roller pairs (10) for winding the roving from the bobbin. k , 12 k ), and each roller pair (10 k , 12 k ) is the number of times that one given roving (M k ) and is intended to be compatible with roving (M k ) in the unwinding direction of the upstream roller (10 k ) and the downstream roller (12 k ), and a roller (10 k , 12 k ) rotate independently of each other.

Description

[Technical Field]

[0001] The present invention relates to a laying head for a unit for winding at least one strand from a fiber bobbin. The bobbin may contain one to several fibers. These fibers are assembled to form strands deposited around an object, such as a hollow mandrel, which is intended to form a reservoir capable of receiving a pressurized fluid, particularly hydrogen gas. The present invention also relates to a thread winding unit. [Background technology]

[0002] Thread winding is a method of forming composite materials into the shape of a component with a rotating axis (such as a cylinder or cone). This method is suitable for mass production and is mainly used in the manufacture of components subjected to high mechanical stress (such as tanks and pipes).

[0003] Figure 1 shows a thread winding unit 10, according to known art, which includes a mandrel 12 rotatably mounted to a frame 14 around a substantially horizontal longitudinal axis A. The unit 10 includes a dispenser 16 that is translatably movable along the longitudinal axis A and supports a number of bobbins 17 that extend substantially perpendicularly to the panels of the dispenser and substantially horizontally. Each bobbin 17 includes strands 20 that are joined together adjacent to each other at a laying head 22 to form a sheet. The laying head 22 is fixed to the dispenser 16 via a carriage 24 that is translatably movable along the longitudinal axis A.

[0004] In some configurations (not shown), the laying head can also move transversely with respect to the axis of the mandrel, rotate around the transverse axis, pivot around the longitudinal axis, and possibly move along the vertical axis.

[0005] Before starting the thread winding unit, the sheet is attached to the mandrel. The dispenser's tensioner is activated to apply tension to the fibers, limiting shrinkage and compressing the deposited successive layers as much as possible. The layers are defined by windings, which allow the sheet to be deposited over the entire surface of the mandrel to be covered. To cover the entire surface of the cylinder and desired areas of the hemispherical bottom, it is possible to form helical-type layers with sheets deposited by forming helices. It is also possible to create circumferential-type layers in which the sheet is deposited over all or part of the cylindrical region of the mandrel, approximately perpendicular to the axis of the mandrel.

[0006] Thread winding structuring allows for the stacking of continuous helical and / or circumferential layers to achieve the desired mechanical properties of the object. Generally, the machine is controlled by numerical control, which is often programmed by the operator using software specifically designed for thread winding.

[0007] Contact laying machines are known that allow for the laying of short lengths of tape without the risk of spinning. However, these machines cannot lay and maintain long, continuous fibers under controlled tension or axial mechanical stress applied in the direction of the fibers.

[0008] Known processes of this type include ATL, which stands for "Automated Tape Layer," and AFP, which stands for "Automated Fiber Placement."

[0009] In the ATL process, very wide tapes (generally 100 - 300 mm) are used. This technology enables deposition onto surfaces with small radii of curvature and large dimensions, such as the wings of commercial aircraft. The AFP process performs the juxtaposition of tapes less than 10 mm wide and the assembly at the head outlet of up to 32 tapes.

[0010] The main applications are for creating flat parts and parts with large radii of curvature. The main idea is to replace manual labor in laying successive plies with a given fiber orientation.

[0011] All current systems use calibrated pre-impregnated (fiber / resin) tapes with separation films between the layers on storage bobbins. These calibrated tapes are obtained from the re-cutting of unidirectional pre-impregnated sheets, which involves the risk that the reinforcement on the edge is partially cut. Here, the material cost is high, and it is necessary to have a system for winding the separation film during the draping operation.

[0012] None of these systems use standard pre-impregnated fibers, i.e., they do not have a separation film between the layers for implementation by thread winding. Since the strands forming the sheet are cut at both ends of the manufactured part, continuous tension (or stress) in the fiber direction cannot be applied to the strands.

[0013] To date, most of the continuous development in the field of composite material implementation has focused on process automation. These developments are driven by the huge needs expressed in the automotive and aerospace sectors. The development of hydrogen storage technologies (e.g., at an operating pressure of 700 bar) with an increase in gravimetric capacity (i.e., the ratio of the amount of stored hydrogen to the mass of the container) pushes the limits of the use of composite materials.

[0014] Conventional thread winding processes (dedicated machines) and more robotic ones (general-purpose machines) did not take into account the significant impact on the process in terms of performance loss. In most cases, the bobbin support is far from the laying head, and the strand passes through a number of deflections and rollers before reaching the laying head. Each change in direction and / or rotation causes the strand to spin or bend on itself due to friction with the walls of the rollers, which can lead to degradation of the specific threads that make up the strand and / or premature failure of the material, resulting in a decrease in material performance. Additionally, due to changes in shape, it was possible for some layers to be layered, causing porosities or local excesses in the matrix and / or reinforcing fibers.

[0015] There are many types of laying heads made of different shapes and different materials. Generally, practitioners make a trade-off that allows them to lay the maximum amount of material per hour at the expense of the quality of the laid material. The laying head is a major component when laying composite materials on a mandrel. The impact on the overall performance of the manufactured object depends on the quality of the laying.

[0016] In this regard, a head as described previously with reference to FIG. 1 typically includes a release roller that ensures that the different strands emerging from each bobbin are brought together. This roller is integrally made and causes problems regarding the distance covered by each strand. During laying, each strand covers a unique and specific distance with respect to an immaterial line (the theoretical winding axis that defines the most ideal winding path according to the angle and shape of the object). In other words, each strand covers a different distance from the distances covered by other strands from other bobbins.

[0017] In a thread winding unit, a laying head, such as the one described with reference to FIG. 1 for example, should ensure the following functions: - Sheet index, i.e., juxtaposition of different strands, - Information on molded sheets, - Orienting the sheet according to the selected angle, - Maintaining tension in the strand while minimizing friction, - Maintaining the shape of each strand, and therefore the shape of the molded sheet. In most embodiments, the head is formed of a machined rotating roller, one or more grooves, made of either a plastic material (whether fluorinated or not) or a metal material (steel, stainless steel, or alloy). Each integral roller receives several strands.

[0018] However, the presence of a single roller is known to cause undulations in the sheet on the mandrel, and these undulations can result in significant defects in the carbon fiber coating, potentially drastically reducing the expected / desired mechanical strength of the final part. These undulations in the strands on the sheet or wound portion should be understood as one of the signs of loose laying or loss of tension at the sheet level. After compression, these undulations result in significant defects such as folds in the material and uneven areas where the fiber / matrix ratio can change considerably.

[0019] This problem can arise both when using so-called dry strands, i.e., when impregnation is required during unwinding, and when using strands impregnated with a partially polymerized matrix called a prepreg. In the latter case, each strand has a certain level of tackiness (allowing it to hold its folds together on the mandrel), which significantly limits, or even makes impossible, strand slippage. Note that the presence of an integrated roller at the exit of the laying head will further increase the unevenness.

[0020] Furthermore, it should be noted that using guide rollers for several strands on different bobbins does not address the aforementioned problem of different distances covered by each strand, and, when combined with a single exit roller, further exacerbates this problem.

[0021] Contact laying machines are the only ones that offer a partial solution to this technical problem. They can only use (higher-priced) pre-adjusted sheets. Because contact application does not allow for prior stressing (tensioning) of the material, the tension level is zero or very low (in contrast to screw-type techniques). [Prior art documents] [Patent Documents]

[0022] [Patent Document 1] International Publication No. 2017 / 203109 [Patent Document 2] UK Patent Application Publication No. 921138 [Patent Document 3] French Patent Application Publication No. 2882681 [Overview of the project] [Problems that the invention aims to solve]

[0023] The present invention relates to a laying head for laying a plurality of strands, each having a longitudinal axis originating from a bobbin, wherein the laying head comprises a plurality of pairs of line rollers for winding the strands from the bobbin, each pair of line rollers intended to operate in accordance with only one given strand, each pair of rollers comprises an upstream roller and a downstream roller with respect to the direction of unwinding of the strand, and the line rollers rotate independently of each other. [Means for solving the problem]

[0024] According to the present invention, rotational decoupling of each roller ensures the complete movement of each strand without being affected by the movement of other strands. In other words, each strand is moved independently of the other strands to the downstream end of the head for laying on the mandrel.

[0025] The roller may have an axis of rotation that is approximately perpendicular to the direction of the strand.

[0026] Each pair of line rollers may be associated with a release roller, which is coaxial and rotatable independently of each other. Thus, the two upstream and downstream rollers are associated with a given release roller that is different from the release rollers associated with other pairs of upstream and downstream rollers.

[0027] This prevents the formation of undulations in the sheet on the mandrel, ensuring optimal efficiency when laying the sheet on the mandrel.

[0028] The axis of rotation of the roller may be perpendicular to the longitudinal axis.

[0029] The upstream and downstream rollers of a pair of line rollers may be staggered relative to the upstream and downstream rollers of another pair of rollers in a plane perpendicular to the roller's axis of rotation and containing the longitudinal axis. The upstream and downstream rollers of a pair of line rollers may also be staggered relative to the upstream and downstream rollers of another pair of rollers in a plane parallel to the roller's axis of rotation. This parallel plane may contain the longitudinal axis.

[0030] This double-staggered arrangement allows the maximum number of strands to pass through a limited space.

[0031] Alternatively, the k upstream rollers of the k roller pairs may be arranged in a continuous line perpendicular to the longitudinal direction, so that the odd-numbered upstream rollers are supported by the first upstream pivot, and the even-numbered upstream rollers are supported by the second pivot located downstream of the first pivot.

[0032] Of the k roller pairs, the k downstream rollers may be arranged continuously along a direction perpendicular to the longitudinal direction L, with the odd-numbered downstream rollers supported by a third upstream pivot, and the even-numbered downstream rollers supported by a fourth pivot located downstream of the third pivot. The third pivot may also be located downstream of the second pivot.

[0033] At least two of the two pairs of rollers, the upstream rollers, can be arranged coaxially so as to rotate on the same upstream pivot.

[0034] At least two of the two pairs of rollers, the downstream rollers, can be arranged coaxially so as to rotate on the same pivot.

[0035] Each roller may include an annular groove for receiving strands, the annular groove having a concave bottom surface. The bottom of the annular groove may have a variable radius of curvature, in particular, a radius of curvature that increases from the center of the annular groove outwards.

[0036] The axes of the downstream rollers in each pair of rollers can be positioned so as to be outside the plane containing the rotation axis of the upstream roller and the rotation axis of the release roller.

[0037] The longitudinal axis of the laying head can be positioned such that there exists a plane where all the rotation axes of the rollers are located on the same side of the plane.

[0038] The bobbin strands may be associated with each pair of rollers, and the reinforcing fibers of each strand are impregnated with a curable matrix, which is preferably made of carbon fiber and may be made of a thermosetting or thermoplastic material in particular.

[0039] The present invention also relates to a device for laying a plurality of strands, each originating from a bobbin, comprising the aforementioned laying head, the laying head being rotatable and movable around a longitudinal axis.

[0040] The present invention also relates to a unit for winding at least one strand of fibers from at least one bobbin, the unit comprising the apparatus or laying head described above and a robot for moving an object intended to be completely or partially covered by the at least one strand of fibers from the bobbin. [Brief explanation of the drawing]

[0041] [Figure 1] This is a schematic perspective view of a thread winding unit using conventional technology. [Figure 2] This is a schematic perspective view of the laying head according to the present invention. [Figure 3] This is a top view of the laying head according to the present invention. [Figure 4] This is a side view of the laying head according to the present invention. [Figure 5] This is a schematic cross-sectional view of a roller intended for use with a laying head according to the present invention. [Figure 6] This is a schematic diagram of the four downstream rollers of the laying head according to the present invention. [Modes for carrying out the invention]

[0042] Other features, details, and advantages will become clear upon reading the detailed description below and analyzing the attached drawings.

[0043] Next, refer to FIGS. 2 to 4 showing a laying head 8 having a longitudinal axis L extending along a first longitudinal direction D1 and including two lateral arms B1, B2 spaced apart from each other along a second direction D2 perpendicular to the longitudinal direction D1. This second direction D2 is perpendicular to a third direction D3 which is also perpendicular to the first direction D1. The laying head can include a single lateral arm B1 or B2.

[0044] Upstream side 10 k , k ,

[0045] , , , k , k and downstream side 12 k A pair of rollers of k is arranged between the lateral arms B1, B2 and are independent of each other with respect to rotation, that is, paired. In the example shown in the figure, the laying head includes four upstream rollers 101, 102, 103, 104 and four downstream rollers 121, 122, 123, 124. Upstream side 10 k and downstream side 12 k Each roller on the upstream side 10 and downstream side 12 has a rotation axis extending along the second direction D2. Therefore, the axes of the rollers are perpendicular to the longitudinal direction D1 and the longitudinal axis L of the laying head 8. Upstream 10 k and downstream 12 k The rollers on the upstream side 10 and downstream side 12 are so-called line rollers for guiding along the line of the strand M k k , and this line is parallel to the longitudinal axis L. Nevertheless, it is possible to recognize them as rollers for guiding the strand. In the example shown in the figure, there are four strands M1, M2, M3, M4, each related to a pair of rollers on the upstream side 10 k and downstream side 12 k It can be seen that they are related to the pairs of rollers. In the present disclosure, it should be understood that all configurations where the number k of pairs of rollers [10 k , 12 k is 2 or more are covered. It should be clearly understood that the present invention is more particularly interesting when the number of pairs of rollers is large, for example 4 or more.

[0045] As shown in FIG. 3, each upstream roller is associated with a downstream roller so as to form a pair of line rollers for guiding a given strand, and the other strands are guided by a separate pair of line rollers.

[0046] The terms "upstream" and "downstream" should be understood to refer to rollers located upstream or downstream of each other with respect to the direction of unwinding or laying of strands M1, M2, M3, and M4, i.e., with respect to the unwinding direction of the strands. In this case, the unwinding direction of strands M1, M2, M3, and M4 is from left to right along the first direction D1.

[0047] Upstream 10 k and downstream 12 k Each pair of line rollers is a release roller 14 k Related to this, the release rollers are coaxial with the shaft 15. Here, they are mounted on the same pivot 19. In the illustrated example of the laying head 8, there are four release rollers 101, 102, 103, and 104. Each upstream and downstream roller pair is in a plane P including the first longitudinal direction D1 and the third longitudinal direction D3. k Symmetrical strand M k It has a surface that supports it. A pair of line rollers 10 k , 12 k The liberation roller related to Strand M k It has a surface to support plane P, and this surface is also plane P k It is symmetrical with respect to this. Please note that the aforementioned support surface is an annular surface and has a circular cross-section, but the support itself is not annular.

[0048] Upstream 10 k and downstream 12 k The support surfaces 17 of the line roller are formed at the bottom of the annular groove 19. These support surfaces 17 are shown to be substantially flat, but may have a cross-section with a concave curved shape. These bottom surfaces 17 of the annular groove 19 may have a variable radius of curvature, and in particular may have a radius of curvature that increases from the center of the annular groove toward the outside of the annular groove 19. Upstream 10 k and downstream 12 k Each line roller may include two ball bearings 21 to ensure perfectly centered rotational motion.

[0049] In the configuration described here, k rollers are arranged in a continuous line along direction D2. Roller 10 where k is an odd number k The roller 10 is supported by the same pivot 16 and k is even. k It is supported by another pivot 18. Pivot 16 is located upstream of pivot 18. Roller 12 where k is odd k The roller 12 is supported by the same pivot 20, and k is an even number. k It is supported by another pivot 22. Pivot 20 is located upstream of pivot 22. Pivot 18 is located upstream of pivot 20. Pivots 16, 18, 20, and 22 are supported by the release roller 14 k It is located upstream of pivot 19. Pivots 16, 18, 20, and 22 extend in a second direction D2 and are therefore perpendicular to the longitudinal axis L. A person skilled in the art will understand that pivots 16, 18, 20, and 22 are perpendicular to the axes 161, 162, 163, and 164 of pivots 16, 18, 20, and 22 and are arranged alternately along a plane containing the longitudinal axis L (Figure 4). Similarly, a person skilled in the art will understand that the upstream and downstream even-numbered line rollers and the upstream and downstream odd-numbered line rollers are arranged alternately in a plane parallel to the axis of the line rollers or the axis of rotation of rollers 10k, 12k.

[0050] The k upstream rollers are arranged in a continuous line D2 perpendicular to the longitudinal direction L, so that the odd-numbered upstream rollers are supported by the first upstream pivot 16, and the even-numbered upstream rollers are supported by the second pivot 18 located downstream of the first upstream pivot 16.

[0051] The k downstream rollers may be arranged continuously along a direction D2 perpendicular to the longitudinal direction L, with odd-numbered downstream rollers supported by a third upstream pivot 20, and even-numbered downstream rollers supported by a fourth pivot 22 located downstream of the third pivot 20. The third pivot 20 may also be located downstream of the second pivot 18.

[0052] In Figure 4, a person skilled in the art will understand that the axes 201, 221 of the downstream rollers 121, 122, 123, 124 of each pair of rollers are located off-plane from the axis of rotation of the associated upstream rollers 101, 102, 103, 104 and the axis of rotation 15 of the release roller 14k. Furthermore, a person skilled in the art will understand that the strand M located between the upstream and downstream rollers k Part 24 is a strand M located between the downstream roller and the release roller. k It can be understood that it forms an angle substantially equal to 90° with portion 26. This angle can be between 70° and 110°, preferably between 80° and 100°.

[0053] In Figure 3, a person skilled in the art can see that the strand M k However, upstream line roller 10 k , downstream line roller 12 k and release roller 14 k Therefore, line P k It will be understood that the wires are guided in the rewinding direction along this line. In this example, a person skilled in the art will understand the presence of four wires: P1, P2, P3, and P4.

[0054] The upstream line roller is a first series of upstream rollers 10, where k is an odd number and is supported by the same pivot 16. k And, where k is an even number, a second series of upstream rollers 10 supported by the same pivot 18 k The downstream line rollers include a first series of downstream rollers 12, where k is odd and supported by the same pivot 20. k And, where k is an even number, a second series of downstream rollers 12 are supported by the same pivot 22.k This includes the pivots 16, 18, 20, and 22, which are distinguished in pairs. Along the longitudinal direction L and along the unwinding direction, those skilled in the art will see that the pivots are a first series of upstream rollers 10 where k is odd. k Pivot 16, second series of upstream rollers 10 where k is an even number k Pivot 18, first series of downstream rollers 12 where k is odd k Pivot 20, followed by a second series of downstream rollers 12 where k is an even number. k It can be understood that the strand M is positioned from upstream to downstream, having pivot 22. k It works in cooperation with the upstream roller of a series of upstream rollers and the downstream roller of a series of downstream rollers. More specifically, the strand M where k is odd. k It cooperates with the upstream roller of the first series of upstream rollers and the downstream roller of the first series of downstream rollers, and the strand M where k is even. k It cooperates with the upstream rollers of the second series of upstream rollers and the downstream rollers of the second series of downstream rollers. The roller arrangement is a strand M where k is an even number. k And, a strand M where k is an odd number k These are arranged alternately along the second direction D2.

Claims

1. A laying head (8) for laying multiple strands (Mk), each of the strands originating from a bobbin, the laying head (8) having a longitudinal axis (L) and comprising multiple pairs of line rollers (10k, 12k) for winding the strands from the bobbin, each pair of line rollers (10k, 12k) intended to operate in accordance with only one given strand (Mk), comprising an upstream roller (10k) and a downstream roller (12k) with respect to the unwinding direction of the strand (Mk), the line rollers (10k, 12k) rotating independently of each other, A laying head in which the upstream roller (10 k) and downstream roller (12 k) of a pair of line rollers are arranged alternately with respect to the upstream roller (10 k) and downstream roller (12 k) of another pair of rollers in a plane parallel to the rotation axis of the upstream roller (10 k) and the rotation axis of the downstream roller (12 k).

2. The laying head according to claim 1, wherein each pair of line rollers (10k, 12k) is associated with a release roller (14k), the release rollers (14k) being coaxial and rotatable independently of each other.

3. The laying head according to claim 1 or 2, wherein the rotation axis of the roller (10k, 12k, 14k) is perpendicular to the longitudinal axis (L).

4. The laying head according to claim 3, wherein the upstream roller (10k) and downstream roller (12k) of a pair of line rollers are arranged alternately with respect to the upstream roller (10k) and downstream roller (12k) of another pair of rollers in a plane perpendicular to the rotation axis of the rollers (10k, 12k) and parallel to the longitudinal axis (L).

5. The laying head according to any one of claims 1 to 4, wherein at least two of the two pairs of rollers, the upstream rollers (10k), are arranged coaxially so as to rotate on the same upstream pivot (16, 18).

6. The laying head according to any one of claims 1 to 5, wherein at least two of the two pairs of rollers, the downstream rollers (12k), are arranged coaxially so as to rotate on the same pivot (20, 22).

7. The laying head according to any one of claims 1 to 6, wherein each roller is provided with an annular groove for receiving strands, and the annular groove (17) has a concave, curved bottom surface.

8. The laying head according to any one of claims 1 to 6, wherein the axis of the downstream roller (12k) of each pair of rollers is positioned off-plane from the plane including the rotation axis of the upstream roller (10k) and the rotation axis of the release roller (14k).

9. A laying head according to any one of claims 1 to 8, wherein strands of bobbins are associated with each pair of rollers, and the reinforcing fibers of each strand are impregnated with a curable matrix.

10. The laying head according to claim 9, wherein the reinforcing fiber is made of carbon fiber.

11. A device for laying multiple strands, wherein each of the strands is a laying head (8) according to any one of claims 1 to 10, and each strand is a bobbin and is rotatable and movable around a longitudinal axis (L).

12. A unit for winding at least one strand from a bobbin, comprising: an apparatus according to claim 11 or a laying head according to any one of claims 1 to 10; and a robot for moving an object intended to be completely or partially covered by the at least one strand of the bobbin.

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