Fiber coating machine with coating head equipped with tension limiting system

Abstract

The invention relates in particular to a fiber coating machine comprising a fiber coating head (2) comprising a fixed part (21) and a movable part (22) slidably mounted on the fixed part and biased by at least one compression cylinder (25). The movable part comprises a coating roller (23) and a guiding system for guiding at least one fiber (F1, F2) towards the coating roller in a guiding plane (P1, P2). The machine further comprises a tension limiting system (4) comprising at least one cylinder (41-44) on which each fiber can be wound at least partially, and drive means (29) capable of rotating the cylinder. The tension limiting system is mounted on the movable portion of the head upstream of the guide system.

Description

Technical Field

[0001] The present invention relates to a fiber coating machine equipped with a specific tension limiting system, and a method for manufacturing composite material parts by means of such a machine. Background Art

[0002] It is known, in particular from patent document WO2006 / 092514, that a fiber coating machine is used to automatically lay a wide band formed by more than one fiber, in particular flat continuous fibers of the ribbon type, usually called tow, in particular carbon fibers composed of a large number of carbon filaments or filaments, on a laying surface (such as the surface of a male or female mold).

[0003] These machines are generally called fiber placement machines and generally comprise a fiber coating head comprising a fixed part and a movable part, the movable part comprising a coating roller and a guide system, the coating roller being used to coat at least one fiber (in particular a band formed by more than one fiber) on a coating surface, the guide system being used to guide at least one fiber along a guide plane towards the coating roller and comprising for each fiber a fiber cutting system, a fiber rerouting system and a fiber clamping system. The movable part is slidably mounted on the fixed part and is biased by at least one hold-down jack. These machines also comprise fiber storage means, such as a remote creel, a conveying means for conveying the fibers from the storage means to the head, and a displacement system capable of, for example, displacing the head relative to the placement surface.

[0004] The conveying means can comprise flexible tubes, each of which can receive the fibers in its internal channel and which are preferably provided with at least one longitudinal flexible blade arranged substantially parallel to the plane of transport of the fibers received in the internal channel of the flexible tube. Such flexible tubes constitute a conveying means of simple design, compact dimensions and low cost, making it possible to achieve high movement speeds, offset the storage device from the displacement system, isolate the fibers from the outside and simplify the displacement system of the coating head, in particular using a displacement system such as a multi-jointed arm of the standard six-axis robot type.

[0005] In order to limit the tension in the fibers, it is proposed in the above-mentioned patent document to provide at least one tension limiting system, which is arranged between the fiber storage device and the coating head, the tension limiting system comprising at least two cylinders parallel to each other, on which a plurality of fibers can be partially wound, and drive means for driving the cylinders to rotate at substantially the same speed. The drive means are controlled by a mechanical control unit so that the peripheral speed of the cylinders is greater than the fiber movement speed at the coating roller, so as to exert a pulling force on the fibers coming from the storage device, thereby limiting the fiber take-up tension at the coating roller, regardless of the fiber movement speed. The tension limiting system is usually placed in the creel or at the creel outlet, or between the storage device and the head along the fiber path defined by the transport device. Such a tension limiting system makes it possible to unwind several spools or balls of fiber for fibers running at different speeds at the coating head using a single control system. The tension limiting system reduces the tension of the fiber at the coating roller, regardless of the fiber speed.

[0006] Currently available machines with such tension limiting systems enable one or more fibers to be coated at low tensions. However, such low residual tensions can adversely affect the quality of the layup, especially when the layup is performed at high speeds, and more particularly when cutting and redirecting the running fibers at high speeds. Summary of the invention

[0007] The purpose of the present invention is to provide a technical solution to overcome the above disadvantages.

[0008] To this end, the present invention proposes a fiber coating machine for manufacturing composite material parts, comprising: a fiber coating head, the fiber coating head comprising a support structure or a fixed part and a movable part, the movable part comprising

[0009] a compaction system comprising at least one coating roller for coating at least one fiber, in particular in the form of a strip formed of more than one fiber, on a coating surface,

[0010] a guide system for guiding at least one fiber along a guide plane towards the coating roller, and

[0011] - a fiber cutting system and a fiber redirecting system, and preferably a fiber clamping system,

[0012] The movable part is slidably mounted on the fixed part along a sliding plane and is biased by at least one hold-down jack mounted between the fixed part and the movable part.

[0013] The machine also comprises a tension limiting system comprising at least one cylinder on which each fiber can be at least partially wound and a drive device capable of driving the cylinder in rotation so that the peripheral speed of the cylinder is greater than the moving speed of the fiber in the head,

[0014] Characterized in that the tension limiting system is mounted on the movable part of the coating head upstream of the guide system with respect to the advancement direction of the fibers in the head.

[0015] According to the invention, a tension limiting system is mounted on the mobile part of the head, as close as possible to the redirection system, the cutting system and the compaction system, preferably without an intermediate return system inserted between the tension limiting system and the compaction system, so that the fiber tension during placement is as low as possible. This very low fiber tension in the head enables accurate positioning of the fiber ends at high placement speeds (e.g., more than 1 m / s), in particular during fiber cutting and / or fiber redirection in operation. Low fiber tension avoids problems such as slippage during fiber redirection and thus enables accurate positioning of the fiber ends. This low fiber tension also enables the fiber placement capabilities to be improved by high curvatures in the fiber plane (commonly referred to as "steering"). In the case of a head capable of coating fiber tapes, the tension limiting system located on the mobile part therefore enables approximately the same fiber tension for all fibers at the coating roller, thus ensuring an optimal tape placement quality.

[0016] According to an embodiment, said tension-limiting system is mounted on the movable part of the coating head such that the fibers exiting the tension-limiting system are arranged along said guide plane defined by the guide system.

[0017] According to an embodiment, in the case of a machine intended for coating a tape formed of several fibers, the guide system is suitable for guiding a plurality of fibers in the form of a tape towards a coating roller, the guide system comprises first and second guide means arranged in a staggered manner to guide the fibers in the form of two bundles towards the coating roller along two guide planes approaching each other from upstream to downstream, the tension limiting system comprises a first assembly of at least one cylinder (preferably at least two cylinders) through which a first bundle of fibers passes and a second assembly of at least one cylinder (preferably at least two cylinders through which a second bundle of fibers passes), the first bundle of fibers being preferably arranged at the outlet of the first assembly in the first guide plane and the second bundle of fibers being arranged at the outlet of the second assembly in the second guide plane. The tension limiting system according to the invention advantageously makes it possible to limit the tension differences between the fibers of the tape and thus ensure a good laying quality.

[0018] According to an embodiment, the guide device comprises a first channel and a second channel intended to separately receive the first and second bundles of fibers, respectively, preferably, the first channel is formed at the assembly interface between the first outer panel and the center panel, and the second channel is formed at the assembly interface between the center panel and the second outer panel.

[0019] According to an embodiment, for each fiber, the redirection system comprises a counter-roller, which is actuated by an actuation system (e.g. a pneumatic jack) between a rest position and an active position to press the fiber against at least one drive roller, said drive roller and the cylinder of the tension limiting system being rotatably driven by a common drive motor, preferably mounted on the mobile part, via a transmission system, so that the circumferential speed of the cylinder is greater than the circumferential speed of the drive roller, preferably at least 5%, for example about 20%. Mounting the tension limiting system on the mobile part advantageously enables the motor of the redirection system to be used for driving the cylinder by providing appropriate transmission means to obtain the desired circumferential speed of the cylinder and the drive roller. This technical solution makes it possible to simplify the speed control of the cylinder, avoid embedding a second motor on the mobile part, and thus provide a tension limiting system with small overall dimensions and reduced weight.

[0020] The transmission includes, for example, one or more belts and / or one or more gear systems, and optionally return rollers, wherein the one or more belts and / or one or more gear systems mesh with gears associated with each cylinder, with pinions associated with the drive rollers, and with one or more pinions associated with the shaft of the drive motor.

[0021] In the case of a machine intended for coating several fibers, the redirection system comprises a first redirection device comprising at least one first drive roller and a counter roller, which are actuated by an actuation system between a static position and an active position to press a first bundle of fibers individually onto the first drive roller, and a second redirection device comprising at least one second drive roller and a counter roller, which are actuated by an actuation system between a static position and an active position to press a second bundle of fibers individually onto the second drive roller, the drive rollers being driven by a common drive motor.

[0022] The machine may also comprise: a fiber storage device, such as a creel mounted remote from the head or on a support integral with a fixed part of the head; a delivery device for delivering the fiber from the storage device to the head; and a displacement system suitable for achieving a relative displacement of the head with respect to the deposition surface, in particular enabling displacement of the head. According to one embodiment, the delivery device comprises at least one flexible delivery tube, each delivery tube being capable of receiving a fiber in its internal passage.

[0023] In an embodiment, preferably when the storage device is remote from the head and the delivery device comprises more than one delivery tube, the machine comprises a second tension-limiting system arranged upstream of the delivery device capable of delivering more than one fiber from the storage device to the coating head. This second tension-limiting system makes it possible to effectively reduce the tension of the fibers before they enter the delivery tube and thus ensure efficient delivery of the fibers in the tube and low fiber tension at the outlet of the delivery tube. By means of a tension-limiting system according to the invention mounted on the mobile part of the head, in particular by means of a tension-limiting system of reduced overall dimensions (including a reduction in the number of cylinders, for example only two cylinders for each fiber), it is possible to effectively reduce the low fiber tension at the outlet of the tube and to make the fibers consistent with each other.

[0024] According to the embodiment described in application FR2114113 filed by the applicant on December 23, 2021, a belt is mounted around each cylinder for each fiber so that it is inserted between each fiber and said cylinder, each belt being able to adhere to the fiber and being driven more or less by the cylinder according to the pressure exerted by the fiber on the belt. In order to limit the corners of contact between the belt and the cylinder, preferably, each belt is mounted in a ring on a sliding path formed in part by said cylinder and a complementary part, which is crescent-shaped and fixedly mounted around the cylinder so that the ends of said complementary part are tangentially fitted to said cylinder. Preferably, a generally C-shaped guide flange is mounted on said cylinder and said intermediate part so that each fiber and each belt is guided between two flanges, each flange comprising at each end at least one tab capable of elastically snap-fitting into a recess of the intermediate part. In this embodiment, the flanges can be easily removed for replacement or to enable the belt to be replaced.

[0025] Another object of the present invention is a method for manufacturing a composite material part, comprising coating continuous fibers onto a coating surface, characterized in that the coating of the fibers is carried out by a fiber coating machine as described above, by relative displacement of the coating head relative to the laying surface according to a laying trajectory. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be better understood, and other objects, details, features and advantages will become more apparent, during the course of the following detailed description of a currently preferred specific embodiment of the invention, with reference to the accompanying schematic drawings, in which:

[0027] - Figure 1 is a schematic side view of a fiber coating machine according to the present invention, comprising a head equipped with a tension limiting system; and

[0028] - Figure 2 and Figure 3 for Figure 1An enlarged schematic side view of a coating head. DETAILED DESCRIPTION

[0029] Figure 1 The schematic diagram shows a fiber placement machine according to the invention, which enables placement by contacting a mold of a tape formed of several fibers. The coating machine comprises a displacement system 1 formed by a multi-jointed arm 11 of the six-axis robot type (known per se), movably mounted on a linear axis 12, a coating head 2 mounted at the end arm 11a of the multi-jointed arm, a fiber storage device 7 and a delivery device 8 for delivering the fibers from said storage device to the coating head.

[0030] The multi-jointed arm 11 is attached by its base 112 to a carriage 13 slidably mounted on a linear axis 12 consisting of two parallel rails 121 fixed to the floor. The carriage is equipped with drives, such as motorized rollers, controlled by a mechanical control unit for moving the placement head along these rails.

[0031] The fiber coating head 2 (also referred to as the fiber placement head) comprises a coating roller or a pressure roller 23 capable of contacting the mold to coat, for example, a tape formed by a number of fibers pre-impregnated with resin. The machine is designed to coat flat continuous ribbon fibers, such as carbon fibers packaged in the form of spools. The storage device consists of a creel for receiving a fiber spool 9, which is schematically shown by the mark 7. The creel is also mounted on a follower bracket 71, which is arranged on a track 121 and mechanically connected to the bracket 13 carrying the manipulator. The machine is intended to lay eight fiber tapes in this article, and the creel comprises eight mandrels 72, which can be motorized to receive eight fiber spools 9. In a manner known per se, the creel can include a vibrating roller or pulley through which the fiber passes, so that the rotation of the mandrel can be controlled according to the position of the vibrating roller. Similarly, a secondary mandrel can be associated with each mandrel for rewinding any separator as the fiber is unwound.

[0032] The conveying device 8 comprises flexible conveying tubes equipped with flexible reinforcing blades, as described, for example, in patent WO 2012 / 160270. The fibers are conveyed individually from the creel 7 to the head 2 in these conveying tubes. Figure 1 As schematically shown at 80 in FIG. 8 , the tubes are gathered into a bundle and placed in an inner channel of a flexible protective sheath 81 which can be cooled, thereby cooling the fibers.

[0033] Reference Figure 2 and Figure 3The head 2 comprises a supporting structure or fixed part 21 by which the head is mounted on a multi-jointed arm and on which a movable part 22 is mounted which can be moved in translation. The fixed part 21 comprises a supporting plate 211 arranged on a first upper face, with a bracket 212 for attachment to the end wrist of the multi-jointed arm along the assembly axis A. The supporting plate 211 carries two mounting plates 213 extending spaced apart and vertically on its second main face opposite to the first main face, and the movable part 22 is slidably mounted on the front edge of the mounting plates. The movable part 22 comprises, in a manner known per se: a coating roller 23; a guide system 24 for guiding the fibers in two batches or bundles along two guide planes P1, P2 towards the roller; a cutting system for cutting each fiber individually; a redirection system for redirecting each fiber that has just been cut individually so as to be able to stop and restart the coating of the fibers at any time and to be able to select the width of the wire web; and a clamping system for clamping each fiber that has just been cut. By way of example, the guiding system and the cutting, diverting and clamping systems are similar to those described in patent WO2008 / 132299. The mobile part 22 comprises two flanges 221 interconnected by a crosspiece and between which are mounted pressure rollers, a guiding system, a cutting system, a diverting system and a clamping system. The rear edge of the flange is equipped with a bracket 214 which slides in a plane parallel to the axis A on complementary rails 214 mounted on the front edges of the two mounting plates. The movable part is connected to the fixed part by at least one clamping jack 25 (preferably a pneumatic jack, for example two clamping jacks), which defines the clamping force applied to the fiber to the mold by the clamping roller 23. Each jack is mounted on the fixed part by its jack body 25a and its rod 25b extends parallel to the sliding plane and is connected to the upper edge of the flange 221. In Figure 2 In the configuration shown, the jack pushes the moving part in the direction opposite to the support plate, ie vertically downwards. The hold-down jack, for example of the double-acting pneumatic type, is pressure controlled to adjust the hold-down force.

[0034] The guide system comprises a first and a second channel, which are positioned in a staggered arrangement along two guide planes P1, P2, approaching each other from downstream to upstream, so as to guide the fibers to the roller in the form of two bundles of fibers. The first and the second channels are designed to receive the first and the second bundles of fibers F1, F2, respectively, separately. The guide system comprises, for example, three plates, preferably metal plates, which are mounted flat against each other to define a first guide channel and a second guide channel between them, through which the first and the second bundles of fibers pass respectively to feed them tangentially to the coating roller. The first channel is formed at the assembly interface between the first outer plate and the center plate, having a triangular cross section, and the second channel is formed at the assembly interface between the center plate and the second outer plate.

[0035] The redirection system comprises a first redirection device and a second redirection device, wherein the first redirection device comprises a first drive roller 26 and a reverse roller, the first drive roller 26 being rotatably mounted in a transverse hole of a central plate, the reverse roller being actuated by an actuation system between a static position and an active position to press the first bundle of fibers F1 alone against the first drive roller, and the second redirection device comprises a second drive roller 27 and a reverse roller, the second drive roller 27 being rotatably mounted on a second outer plate, the reverse roller being actuated by an actuation system between a static position and an active position to press the second bundle of fibers F2 alone against the second drive roller. The two drive rollers 26, 27 are driven to rotate via a belt by a motor 29 mounted on a mobile part. Each drive roller is equipped at its end with a pinion 26a, 27a, a first belt 28, the first belt 28 meshes with the pinion of the drive roller and meshes with a first pinion 29a mounted on the shaft of the motor 29. To facilitate maintenance operations, the tension of the first belt is adjusted by a belt tensioning system 30 comprising a tensioning roller mounted at the end of a pivoting arm actuated by a jack.

[0036] The cutting system, known per se, comprises first cutting means for cutting each first bundle of fibers F1 and second cutting means for cutting each second bundle of fibers F2. Similarly, the clamping system comprises first clamping means for clamping each first bundle of fibers and second clamping means for clamping each second bundle of fibers.

[0037] According to the invention, the head is equipped with a tension-limiting system 4, mounted on the moving part 22, upstream of the guide system 24 with respect to the direction of movement of the fibers in the head, through which the fibers F1, F2 entering the head pass, in order to limit or even eliminate the tension in the fibers exerted by the compaction rollers. The tension-limiting system 4 comprises a first set of two rollers 41, 42 for the first bundle of fibers F1, and a second set of two rollers 43, 44 for the second bundle of fibers F2.

[0038] At the head inlet, the head comprises a row of first pulleys 31 mounted to rotate on a first axis, thereby directing a first bundle of fibers F1 coming from the tube to the tension limiting system, and a row of second pulleys 32 mounted to rotate on a second axis for a second bundle of fibers F2, these pulleys 31, 32 being mounted on a support 33 fixed to the fixed part 21. A delivery tube 80 is mounted at its ends to said support 33, upstream of the two rows of pulleys, in two parallel rows via a fastening system 34, for example in the form of a box, so as to form two bundles of fibers. A sheath 81 is fixed to said support 33 by its ends.

[0039] At the exit of the conveying tube, the first bundle of fibers F1 passes through the first pulley 31, then through the first cylinder 41 and the second cylinder 42. At the exit of the second cylinder 42, the fibers F1 are arranged in the plane P1 and directly enter the first guide channel of the guide system 24. The second web fibers F2 pass through the second pulley 32, then through the first cylinder 43 and the second cylinder 44. At the exit of the second cylinder 44, the fibers F2 are arranged in the plane P2 and directly enter the second guide channel. Each fiber is in direct or indirect contact with the first main face against the first cylinder and then with the second main face against the second cylinder.

[0040] The first and second groups of rollers 41-44 are rotatably mounted on a support plate 45 assembled to the moving part in a cantilevered manner, the rotation axes C of the rollers 41-44 are parallel to each other and to the rotation axis B of the pinch roller 23, and the rollers extend vertically from the first main face of the support plate. The rollers 41-44 can be driven to rotate in the positive direction by the drive motor 28 of the diversion system. Each cylinder is equipped with a gear 46 at its end located on the second main face side of the carrier plate 45. The cylinder is rotated by a second belt 47 (for example, a double toothed belt), which is meshed with a second pinion 29b on the shaft of the drive motor 28 and each gear 46 of the cylinder, and the second belt also passes through a return roller 48 to define a belt path for driving all cylinders. A tensioning roller system can also be provided to adjust the tension of the second belt. The diameters of the drive rollers 26, 27 and their pinions 26a, 26b and the diameters of the rollers 41-44 and their gears 46 are defined so that the circumferential speed of the rollers 41-44 is greater than the circumferential speed of the drive rollers, for example, about 20% greater. Alternatively, a single belt may be provided to drive the drive roller and cylinder in rotation.

[0041] In operation, the drive motor 29 is controlled by the machine control unit to drive the drive rollers 26, 27 so that the peripheral speed of the redirecting roller is equal to the peripheral speed of the hold-down roller 26 pressed against the deposit surface, the peripheral speed of the hold-down roller corresponding to the speed of the TCP (Tool Center Point) on the deposit surface S, the TCP being the midpoint of the intersection line between the hold-down roller and the deposit surface. It is also possible to redirect each fiber end from the cutting system to the hold-down roller by controlling the drive motor and the redirecting reversing roller associated with said fiber when the head is not in contact with the deposit surface, for example during a connecting track between two deposit tracks.

[0042] Some fibers cannot be in direct contact with the rotating cylinder because they are fragile, elastic or light. To achieve these fibers, as described in the aforementioned documents, a belt can be mounted around each cylinder so that the belt is between each fiber and the cylinder, each belt being able to adhere to the fiber and be driven more or less by the cylinder according to the pressure exerted by the fiber on the belt, which pressure is proportional to the tension of the fiber.

[0043] In order to limit the tension of the fibers before entering the delivery tube, the machine comprises a tension limiting system 104 placed in the creel, as described in the aforementioned patent document, preferably a system corresponding to the one described in patent application FR2114113.

[0044] Although the invention has been described with respect to specific embodiments, it is obvious that the invention is by no means restricted thereto and that it comprises all technically equivalent alternatives to the means described as well as combinations thereof, if these fall within the scope of the invention.

Claims

1. A fiber coating machine for manufacturing composite material parts, the fiber coating machine comprising a fiber coating head (2), the fiber coating head comprising a fixed part (21) and a movable part (22), the movable part comprising - a pressing system comprising at least one coating roller (23), a guide system for guiding at least one fiber (F1, F2) along a guide plane (P1, P2) towards the coating roller, and -Fiber cutting system and fiber redirection system, The movable part (22) is slidably mounted on the fixed part (21) and is biased by at least one pressing jack (25) mounted between the fixed part and the movable part. The machine also comprises a tension limiting system (4), comprising at least one cylinder (41-44) on which each fiber can be at least partially wound, and a drive device (29) capable of driving the cylinder in rotation, It is characterized in that The tension limiting system (4) is mounted on the movable part (22) of the coating head upstream of the guide system (24).

2. The machine according to claim 1, characterized in that: The tension limiting system (4) is mounted on the movable part (22) of the coating head so that the fibers (F1, F2) leaving the tension limiting system are arranged in the guide plane (P1, P2).

3. The machine according to claim 1 or 2, characterized in that: The guide system (24) is capable of guiding a plurality of fibers (F1, F2) in the form of a belt toward the coating roller (23), the guide system (24) comprising a first and a second guide device, the first and the second guide device being used to guide the fibers in the form of two bundles along two guide planes (P1, P2) toward the coating roller, the tension limiting system (4) comprising a first group of at least one cylinder (41, 42) and a second group of at least one cylinder (42, 43), the first bundle of fibers (F1) passing through the first group of at least one cylinder, and the second bundle of fibers (F2) passing through the second group of at least one cylinder.

4. The machine according to claim 1, characterized in that For each fiber, the redirection system comprises a reversing roller, which is actuated by an actuation system between a static position and an active position to press the fiber onto at least one drive roller (26, 27), wherein the drive roller and the cylinder (41-44) of the tension limiting system (4) can be driven to rotate by a common drive motor (29) mounted on the mobile part via a transmission system (28, 29a, 29b, 47, 46, 47, 48) so that the circumferential speed of the cylinder is greater than the circumferential speed of the drive roller.

5. The machine according to one of claims 1 to 4, characterized in that It comprises a second tension-limiting system (104) arranged upstream of a conveying device (8) capable of conveying more than one fiber from a storage device (7) to the coating head (2).

6. A method for manufacturing a composite material component, comprising applying continuous fibers to a coating surface, characterized in that The coating of the fibers is carried out by a fiber coating machine according to one of claims 1 to 5 by a relative displacement of the coating head with respect to the deposition surface according to a deposition trajectory.

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