WO2022074225A1 - Filament winding device and method for producing an object made of composite material - Google Patents

Abstract

The invention relates to a device (10) for continuous filament winding around a mandrel (14) extending along a main axis (A1) the device (10) comprising: - a mandrel support (20); - a movable carriage (24); - at least one winding rotor (26) comprising a central orifice (28) intended to receive the mandrel (14) and rotatably mounted on the carriage (24) about an axis (A3) of rotation; - at least one spool support (38); characterized in that the winding rotor (26) is rotatably mounted about its axis (A3) of rotation with respect to the spool support (38), the winding rotor (26) comprising a mechanism (42) for accumulating an intermediate strand (12B) of the filament material (12) by winding said intermediate strand (12B) around the central orifice (28), the intermediate strand (12B) thus accumulated being capable of sliding relative to the accumulation mechanism (42).

Description

DESCRIPTION

TITLE: Filament winding device and method for producing an object made of composite material

Technical field of the invention

The invention relates to a device for continuous filament winding around a mandrel extending along a main axis the device comprising :

- a mandrel support;

- a movable carriage;

- at least one winding rotor comprising a central orifice intended to receive the mandrel and rotatably mounted on the carriage about an axis of rotation;

- at least one spool support.

The invention also relates to a method for producing an object made of composite material from such a filament winding device.

Technological background

It is known to produce pieces made of composite material by means of a filament winding method. Such a method involves winding a continuous and flexible filament material, for example wires, bands or fibers, helically around a mandrel which may form an integral part of the final product. The winding is carried out by several back and forth movements along the mandrel. A back and forth movement is usually called a "swing".

In order to secure the filament material and possibly provide additional mechanical properties to the composite material, it is known to embed the filament material thus wound in a matrix which is usually formed of resin.

The filament material may be impregnated with a resin just prior to its winding, for example by passing a strand of the filament material located between a spool and the mandrel in a bath. As it is wound around the mandrel, the filament material is pulled, causing the spool to unwind and the filament material to pass into the resin.

Alternatively, it is also known to dry-wind the filament material. The resulting intermediate object can then be impregnated with the matrix material, for example the resin.

The invention is applicable to both types of windings.

The known filament winding devices allow the filament material to be wound around mandrels with a straight main axis. The mandrel is, for example, rotationally shaped.

In this case, the mandrel is generally rotatably mounted on rotational drive means carried by a stationary support relative to the ground. A carriage comprising a fiber guide means is moved in two directions during the filament winding method.

The carriage is first moved in translation parallel to the main axis of the mandrel while the latter is rotating. A free end of the filament material has been previously secured to the mandrel. The rotation of the mandrel in relation to the carriage causes the filament material to be wound. This creates a tension in the filament material, which is thus automatically unwound from a supply spool arranged either in the carriage or on a stationary part in relation to the mandrel support.

The carriage is also moved in translation in a radial direction with respect to the main axis of the mandrel. This allows the distance between the carriage and the mandrel to be adjusted as the thickness of the filament material wound around it increases.

This solution is ideally suited to mandrels with a straight axis, for example when the mandrel is formed by a bottle or a pipe. However, when the mandrel has a curvilinear axis, this device is no longer applicable. The document DE 38 43 490 discloses a filament winding device which allows this solution to be adapted to certain mandrels having a non-rectilinear shape.

It is also known to arrange a rotor on the carriage. In this case, the supply spool of filament material is mounted on the rotor. The mandrel is then stationary in relation to its support. It is the rotation of the rotor that causes the winding of the filament material around the mandrel.

This solution is perfectly suited to mandrels with a straight or curvilinear axis, as long as the shape of the mandrel leaves enough space to allow the rotor equipped with its supply spool to turn. For example, such a device is adapted for toroidal mandrels which have a central opening large enough to allow the passage of the supply spool which rotates integrally with the rotor.

However, none of these filament winding devices are applicable to mandrels with a more complex shape, in particular to mandrels that do not allow the rotor equipped with its supply spool to pass through certain narrow section parts. For example, the production of medium-sized helical springs, such as springs intended for the motor vehicle suspension, is not possible.

The document WO 201 7/1 16320 discloses a device for continuous filament winding in one direction around a straight mandrel in which a radial strand of the filament material is guided to the mandrel by a conical deflector.

For this reason, such springs made of composite material are nowadays produced by winding around a straight mandrel which is then plastically deformed by helical winding around a forming cylinder. Such a spring is, for example, disclosed by the document DE 10 201 1 01 8217.

Such a method for producing a spring made of composite material, or any other object of complex shape, is unsatisfactory because the forming of the object after winding may cause a degradation of the composite material. Moreover, such a production method is expensive because it involves many additional steps, some of which are carried out manually.

In addition, it is usually necessary to invest in a forming mold that can only allow to produce one object geometry. Such a method is therefore not very flexible.

Summary of the invention

The invention proposes a continuous filament winding device around a mandrel extending along a main axis, straight or curvilinear, the device comprising:

- a mandrel support on which the mandrel is intended to be secured;

- a carriage which is slidably mounted in relation to the mandrel support along the main axis of the mandrel;

- at least one winding rotor which comprises a central orifice intended to receive the mandrel and which is rotatably mounted on the carriage about an axis of rotation which is generally coaxial with the central orifice;

- at least one spool support which is intended to receive a spool comprising a supply of filament material;

- a guide member equipped with a through opening for the passage of the filament material which is integral in rotation with the winding rotor and which allows to guide a strand of filament material, referred to as radial strand, which unwinds from the spool towards the central orifice tangentially to the mandrel in order to wind it around the mandrel by rotation of the winding rotor; characterized in that the winding rotor is rotatably mounted about its axis of rotation with respect to the spool support, the winding rotor comprising a mechanism for accumulating an intermediate strand of the filament material located directly upstream of the guide member for guiding said intermediate strand by winding it around the central orifice to form an accumulation reel, the accumulation reel being capable of sliding with respect to the accumulation mechanism in order to allow the radial strand to be wound around the mandrel.

According to another embodiment of the invention, the spool support is mounted on the carriage.

According to another embodiment of the invention, the spool support is fixedly mounted with respect to the mandrel support.

According to another embodiment of the invention, the accumulation mechanism comprises a plurality of rollers which are rotatably mounted on the rotor and which are distributed around the central orifice.

According to another embodiment of the invention, at least one of the rollers of the accumulation mechanism, referred to as tensioning roller, is mounted with a radial mobility on the rotor.

According to another embodiment of the invention, the radial displacements of the at least one tensioning roller are actively controlled.

According to another embodiment of the invention, the rotor has a closed ring shape.

According to another embodiment of the invention, the rotor has an ring shape opened by a segment intended to allow the radial insertion of the mandrel into the central orifice.

According to another embodiment of the invention, the filament winding device comprises controlled means for driving the rotor in rotation in both directions about its axis of rotation.

According to another embodiment of the invention, the filament winding device comprises two rotors arranged one after the other along the axis of rotation.

According to another embodiment of the invention, the carriage comprises a ring for guiding the filament material from the spool to the rotor, the guide ring being integral in rotation with the carriage about the axis of rotation.

The invention also proposes a method for producing an object made of composite material implementing the filament winding device according to any one of the preceding claims, comprising a filament winding phase during which the carriage moves successively back and forth along the axis of the mandrel which is received in the central orifice of the rotor, characterized in that the filament winding phase comprises at least one cycle comprising:

- an accumulation step during which the rotor is rotated in a first direction to wind a strand of the filament material helically in said first direction around the mandrel, an intermediate strand being simultaneously wound in said first direction around the central orifice by the accumulation mechanism ;

- a step of restitution of the accumulated intermediate strand during which the rotor is rotated in a second direction to wind the strand of filament material accumulated by the accumulation mechanism around the mandrel.

According to another embodiment of the method, the restitution step is triggered based on the number of revolutions of the rotor performed during the first accumulation step.

Another embodiment of the method is that it comprises a switching step between the two steps of the cycle.

According to another embodiment of the method, during the switching step, the filament material delivered by said rotor is secured to the mandrel.

According to another embodiment of the method, when the carriage is located at one end of the mandrel, the rotor located closer to said end, referred to as proximal rotor, changes its direction of rotation, while the rotor further from said end, referred to as distal rotor, maintains the same direction of rotation so that the filament material delivered by the distal rotor secures the filament material delivered by the proximal rotor by clamping it against the mandrel.

According to another embodiment of the method, it comprises a heating phase which is carried out after the filament winding phase, the filament material having previously been impregnated with a resin, the heating phase comprising a heating operation at a treatment temperature greater than or equal to a cross-linking temperature of the resin, for example of the order of 150°C.

According to another embodiment of the method, the mandrel is produced of a material having a melting temperature lower than the treatment temperature.

The invention also relates to a helical spring produced by the implementation of the method according to the teachings of the invention, the spring having a tubular wire forming the coils of the spring, the wire being produced solely of a tubular shell made of composite material obtained by winding filament material around a helically shaped mandrel and by a matrix material, such as the resin, the mandrel having been extracted during the heating phase.

Brief description of figures

Further characteristics and advantages of the invention will become apparent from the following detailed description, for the understanding of which reference is made to the appended drawings in which :

- Figure 1 is a side view showing a filament winding device produced according to the teachings of the invention in which a mandrel shaped like a helical spring is arranged.

- Figure 2 is a top view showing a carriage of the winding device of Figure 1 produced according to a first embodiment of the invention, the carriage being equipped with a rotor within which the mandrel is received.

- Figure 3 is a cross-sectional view according to the sectional plane 3-3 of Figure 2, which shows the carriage and its rotor at the beginning of the winding method.

- Figure 4 is a view similar to that of Figure 3 which shows the carriage and its rotor at the beginning of a restitution step of the filament winding method. - Figure 5 is a view similar to that of Figure 3 which shows the carriage and its rotor during a restitution step of the filament winding method.

- Figure 6 is a view similar to that of Figure 3 which shows the carriage and its rotor at the end of the restitution step.

- Figure 7 is a view similar to that of Figure 3 which shows an alternative embodiment of the carriage and its rotor.

- Figure 8 is a detail view showing a segment of the guide disc of the rotor equipped to the carriage and, in dashed lines, a cam disc for controlling the radial sliding of a tensioning roller shaft.

- Figure 9 is a side view showing an alternative embodiment of a switching step of the filament winding method implementing a filament winding device produced according to a second embodiment of the invention, with Figure 9 showing the carriages just prior to an operation for clamping the filament material of a carriage.

- Figure 1 0 is a view similar to that of Figure 9 which shows the carriages during the operation for fastening the filament material of a carriage.

- Figure 1 1 is a view similar to that of Figure 9 which shows the carriages after the operation for fastening the filament material of a carriage.

- Figure 1 2 is a block diagram which represents the filament winding method carried out according to the teachings of the invention.

- Figure 1 3 is a perspective view of a coil portion of a spring at the end of a filament winding phase of the method carried out according to the teachings of the invention.

- Figure 14 is a view similar to that of Figure 1 3 which shows the coil portion of the spring after a heating phase of the composite material.

Detailed description of the invention For the remainder of the description, elements with identical structure or similar functions will be designated by a same reference.

For the remainder of the description, an axial orientation which is directed parallel to the axis "A1 " of the mandrel 14, radial orientations which extend orthogonally to the axis "A1 " of the mandrel 14 from the axis "A1 " of the mandrel 14, inside, outwardly away from the axis "A1 " of the mandrel 14 will be adopted in a nonlimiting manner. Tangential orientations that are directed orthogonal to the axial and radial directions will also be adopted.

Shown in Figure 1 is a device 1 0 for continuous filament winding of a filament material 12 around a mandrel 14 extending along a main axis "A1 ".

The filament material 1 2 is, for example, formed by a wire, by a band or by any long, continuous and flexible material which is suitable to be wound continuously around a mandrel 14. In the example shown in the figures, the filament material 12 is formed of a wire, made for example of carbon fibers, glass fibers, or any other material having suitable mechanical characteristics. A supply of filament material 12 is stored here by winding around a spool 16.

The mandrel 14 may have a straight or curvilinear main axis "A1 ". This is here a mandrel 14 formed by a helical spring which thus has a curvilinear main axis "A1 " extending more precisely helically about an axis "A2" of revolution. The mandrel 14 thus extends helically around a central cylindrical well 1 8, shown in dashed lines, having an internal diameter "D1 ". In addition, two adjacent coils of the mandrel 14 are here spaced apart, in a direction parallel to the axis "A2" of revolution, by a distance "D2". The distance "D2" here is smaller than the internal diameter "D1 ".

The filament winding device 10 comprises a mandrel support 20 intended to fixedly receive the mandrel 14. Here, the mandrel support 20 comprises two jaws 22 which are each arranged at one axial end of the mandrel 14. Each jaw 22 is secured to the mandrel 14, for example by means of fastening brackets. The mandrel 14 is thus held stationary relative to the support 20. The support 20 is itself carried by a stationary frame 21 , shown schematically in Figure 1 , which rests on the ground.

The winding device 1 0 also comprises at least one carriage 24. In the example shown in Figure 1 , a winding device 10 comprising a single carriage 24 has been shown.

Alternatively, the winding device 10 comprises two carriages 24 which are identical here. The second carriage 24 is shown as a dashed lines in Figure 1 .

The carriage 24 carries at least one winding rotor 26 which comprises a central orifice 28 of axis "A3". The central axis "A3" of the orifice 28 is intended to be arranged generally coaxial with the axis "A1 " of the mandrel 14 during filament winding operations. The rotor 26 is rotatably mounted on the carriage 24 about its central axis, hereinafter referred to as axis "A3" of rotation. The terms "generally coaxial" mean that the axis "A3" of rotation of the rotor 26 may be slightly eccentric, for example of the order of 1 mm or less, with respect to the main axis "A1 " of the mandrel 14, at least occasionally, for example, to pass over a bend formed by the main axis "A1 " of the mandrel 14, the axis "A3" of rotation remaining, however, parallel to the portion of the mandrel 14 which passes through the rotor 26.

It is provided that the rotation of the rotor 26 can be controlled in both directions relative to the carriage 24. To this end, the filament winding device 1 0 comprises controlled means for driving the rotor 26 in rotation in both directions about its axis "A3" of rotation. For example, it is an electric motor (not shown), referred to as a winding motor, which can transmit its rotational energy by any transmission means, such as a roller and/or a gear and/or a belt or any other known means. Shown here is a belt 27 which cooperates with a pulley 25. As shown in Figure 2, the carriage 24 here comprises two identical parallel flanges 24A, 24B which extend in a plane orthogonal to the axis "A3" of rotation of the rotor 26. The flanges 24A, 24B are secured at a given distance from each other. Each flange 24A, 24B comprises an arm 32 which extends in a direction orthogonal to that of the axis "A3" of rotation of the rotor 26. At a free end of the arm 32 a ring 29 is arranged. The rings 29 are coincident with each other along the axis "A3" of rotation.

In particular, the rotor 26 is rotatably mounted on the rings 29. The rotor 26 is, for example, rotatably guided on the rings 29 by means of roller bearings (not shown).

The rotor 26 comprises, for example, at least two ring discs 26A, 26B, referred to as guide discs 26A, 26B, each of which is rotatably mounted on the ring 29 of one of the associated flanges 24A, 24B. The two guide discs 26A, 26B are secured to each other by means which will be detailed later.

The assembly of the rings 29 and the rotor 26 delimits a central eye 30 which is of sufficient size to contain each section part of the mandrel 14 around which a winding is intended to be performed. The eye 30 is here delimited by the inner edge of the rings 29 of the carriage 24.

In a variant of the invention not shown, the eye 30 is delimited at least partly by an inner edge of the rotor 26.

In a first embodiment shown in Figures 3 to 6, each disc 26A, 26B for guiding the rotor 26 has a closed ring shape. The rings 29 also have a closed circle shape. In this case, the mandrel 14 is inserted into the central eye 30 by one of its axial ends. Such an embodiment thus requires that the mandrel 14 has, at least at one of its axial ends, dimensions compatible with the dimensions of the central eye 30.

In a second embodiment shown in Figure 7, the discs 26A, 26B of the rotor 26 have a ring shape opened by a segment 34. The rings 29 have an identical opening 36. Thus, when the segment 34 and the opening 36 are aligned, the central eye 30 has an opening, preferably directed away from the arm 32, intended to allow radial insertion of the mandrel 14 into the eye 30. This allows windings to be produced around mandrels 14 having areas at their ends that do not allow axial insertion into the eye 30. These end areas are not, of course, intended to receive windings of the filament material 1 2.

The carriage 24 and the mandrel support 20 are mounted so that they can move relative to each other along the main axis "A1 " of the mandrel 14. The carriage 24 is thus capable of performing several back and forth movements, or "swings", along the mandrel.

The carriage 24 moves so that the section of the main axis "A1 " of the mandrel 14 received in the central eye 30, said current section, and the axis "A3" of rotation of the rotor 26 are generally coaxial. The term "coaxial" here includes the case where the axis "A3" of rotation is tangent to the main axis "A1 " when the current section is curvilinear.

More particularly, the carriage 24 is slidably movable relative to the mandrel 14, i.e., the carriage 24 does not rotate about the main axis "A1 " of the current section of the mandrel 14 during its displacement. Only the rotor 26 is rotated about the axis "A3" of rotation to allow the winding of the filament material 1 2. It will be understood that, depending on the shape of the main axis "A1 " of the mandrel 14, the carriage 24 may need to pivot punctually about the axis "A1 " of the mandrel 14 solely in order to be able to continue its sliding along the mandrel 14 and without this pivoting being assimilated as a rotation aimed at winding the filament material 12 around the mandrel 14.

The carriage 24 is also mobile in translation orthogonally to the main axis "A1 " of the mandrel "14" as indicated by the arrows "Fc" in figure 1 .

The mandrel support 20 is here rotatably mounted about the axis "A2" of revolution of the spring with respect to the frame 21 , as shown by the arrows "Fr" in Figure 1 , while the carriage 24 is slidably mounted in translation along a direction parallel to the axis "A2" of revolution of the spring with respect to the frame, as indicated by the arrows "Ft" in Figure 1 .

In a variant of the invention not shown, the support 20 is here fixedly mounted with respect to the frame 21 of the filament winding device 1 0. The carriage 24 is slidably mounted along the axis "A1 " of the mandrel 14, without rotation about said axis "A1 " so that displacement of the carriage 24 does not cause the filament material 12 to wind around the mandrel 14.

In a variant of the invention not shown, the support 20 is movably mounted with respect to the frame while the carriage 24 is stationary with respect to the frame. As shown in Figure 1 , the filament winding device 1 0 comprises at least one spool support 38 which is intended to receive the spool 1 6 comprising a supply of filament material. This is, for example, a rod allowing rotation of the spool 1 6, in particular when the filament material 1 2 is unwound from the outside. Alternatively, it may be another type of support 38 that allows the filament material 12 to be unwound from the inside of the spool 1 6.

The rotor 26 comprises a guide member 40 which is integral in rotation with said rotor 26 and which allows to guide a strand of the filament material which unwinds from the spool 1 6, referred to as tangential strand 12A, towards the interior of the central eye 30 tangentially up to the mandrel 14 in order to wind it around the mandrel 14 by rotation of the winding rotor 26. With reference to Figure 2, the guide member 40 is here formed by a plate extending from one guide disc 26A, 26B to the other and secured to said guide discs 26A, 26B. The plate is equipped with a through opening that allows the fiber to pass radially into the eye 30.

Advantageously, but not necessarily, the displacements in a plane orthogonal to the main axis "A1 " of the mandrel 14 allows in particular to maintain a reduced distance between the guide member 40 and the surface of the mandrel 14, including the wound layers of filament material. For example, the displacements of the carriage 24 in the plane orthogonal to the axis "A1 " are controlled so that the distance between the guide member 40 and the surface of the mandrel 14 is substantially constant throughout the filament winding method. In this case, the axis "A3" of rotation of the rotor 26 may be slightly eccentric, for example of the order of 1 mm or less, relative to the main axis "A1 " of the mandrel 14.

The winding rotor 26 is rotatably mounted about its axis "A3" of rotation relative to the spool support 38. In other words, the spool support 38 is not integral in rotation with the winding rotor 26.

According to the embodiment shown in Figure 1 , the spool support 38 is fixedly mounted on the carriage 24. This embodiment is particularly suitable when the carriage 24 is movable relative to the ground. In particular, this allows to prevent entanglement of the filament material 1 2 in the event of complex movements of the carriage 24. The spool support 38 is here intended to receive the spool 1 6 along an axis parallel to the axis "A3" of rotation of the rotor 26.

The spool support 38 is also fixedly mounted with respect to the ground.

To enable the filament material 12 to be guided from the spool 1 6 to the rotor 26, the arm 32 of the carriage comprises at least one guide ring 41 which is formed by a perforated plate similar to that of the guide member 40. The guide ring 41 is integral in rotation with the carriage 24 about the axis A3 of rotation. Thus, the guide ring 41 allows the filament material to be distributed to the rotor 26 during its rotation about the axis "A3" of rotation in both directions of rotation.

The guide ring 41 extends from one flange 24A, 24B to the other. Here it is secured to said flanges 24A, 24B to form a fastening tie rod.

By prejudice, such an arrangement is avoided in the prior art because upon the rotation of the rotor 26, the guide member 40 creates a movable bearing point which causes a part of the filament material 12 to become entangled around the guide member 40 and the mandrel 14. The invention allows to turn what appears to be a prohibitive disadvantage into an advantage, allowing to obtain a filament winding carriage 24 with a small overall size which allows windings to be carried out around mandrels 14 of complex shape.

Indeed, such a carriage 24 whose rotor 26 does not carry the spool 16 has a reduced overall size. More particularly, a segment of the ring 29 and the rotor 26, located opposite the arm 32, has a maximum radial dimension "D3" which is much smaller than the internal diameter "D1 " of the mandrel 14 as well as the distance "D2" between two coils.

To this end, the winding rotor 26 also comprises a mechanism 42 for accumulating an intermediate strand 12B of the filament material 1 2 located upstream of the guide member 40 by winding said intermediate strand 1 2B around the central eye 30 to form an accumulation reel 43. The intermediate strand 12B thus accumulated forms the accumulation reel 43 which is susceptible to slide as a monobloc with respect to the accumulation mechanism 42 when the radial strand 12A is pulled under the effect of its winding around the mandrel 14. Thus, the length of filament material 12 which unwinds from the spool 1 6 is greater than that required for the winding around the mandrel 14 alone, since it also comprises a length that comes to be wound around the accumulation mechanism 42.

The accumulation mechanism 42 comprises a plurality of bearing points distributed on the rotor 26 around the central eye 30. These bearing points allow to produce an accumulation of filament material 1 2 which can subsequently be used in the form of the accumulation reel 43 by polygonal coil winding of the intermediate strand 12B of filament material at a distance around the mandrel 14 and the guide member 40 as shown, for example, in Figures 4 and 5. The accumulation reel 43 is thus wound around the axis "A3" of rotation of the rotor. When the rotor 26 is rotated in a first direction, the intermediate strand 1 2B is wound by being tensed between the guide ring 41 of the arm 32 and successively each bearing point.

The sliding of the filament material 12 relative to the accumulation mechanism 42 is necessary to allow the pursuit of the winding around the mandrel 14 of the radial strand 1 2B concurrently with the accumulation operation by winding an increasing length of intermediate strand 1 2B around the accumulation mechanism 42. In order to promote the sliding of the filament material 12 relative to the bearing points of the accumulation mechanism 42, the bearing points of the accumulation mechanism 42 are here formed by rollers 42A, 42B which are rotatably mounted on the rotor 26 about axes parallel to the axis "A3" of rotation of the rotor 26.

Each bearing point is thus formed by a roller 42A, 42B having a rotation shaft 44 extending from one guide disc 26A, 26B to the other. The rollers 42A, 42B are distributed around the central eye 30.

At least one of the rollers of the accumulation mechanism 42, referred to as tensioning roller 42A, comprises a shaft 44 which is mounted with a radial mobility on the rotor 26. In the embodiment shown in the figures, the rotor 26 here comprises five tensioning rollers 42A. The tensioning rollers 42A are controlled between a radial inner position, i.e. closest to the axis "A3" of rotation of the rotor 26, as illustrated in Figures 3 and 6, and a radial outer position, i.e. further from the axis "A3" of rotation of the rotor 26, as illustrated in Figures 4 and 5.

Only two rollers of the accumulation mechanism 42, referred to as stationary rollers 42B, here have an axis that is fixedly mounted on the rotor 26. More particularly, each end of the shaft 44 of each stationary roller 42B is secured to either of the guide discs 26A, 26B. The two stationary rollers 42B are arranged next to each other, so as to delimit a tangential space which is arranged radially in line with the guide member 40.

In a variant of the invention not shown, the winding of the filament material 12 around the rollers 42A, 42B is, for example, controlled by means of a fiber winding mechanism known per se and which will therefore not be described in further detail hereinafter. For example, the guide ring 41 is mounted movable along a direction parallel to the axis "A3" of rotation of the rotor 26 with respect to the arm 32 so as to allow the filament material to be evenly distributed around the accumulation mechanism 42.

As shown in Figure 8, the tensioning rollers 42A are guided in radial translation by means of grooves 46 which extend radially in each guide disc 26A, 26B. Each groove 46 receives a section of the rotation shaft 44 of a tensioning roller 42A.

The radial displacement of the tensioning rollers 42A is actively controlled as their speed and/or the amount of radial displacement is likely to vary as a function of the thickness of filament material 12 wound around the mandrel 14.

With reference to Figure 8, the rotor 26 here comprises at least one cam disc 48 which is arranged against one of the guide discs 26A. Here, the rotor 26 comprises two cam discs 48 each of which is arranged against an associated guide disc 26A, 26B. The cam disc 48 comprises cams, here in the form of oblique grooves 50, receiving a section of the rotation shaft 44 of an associated tensioning roller 42A. The rotation of the cam disc 48 relative to the guide discs 26A, 26B about the axis "A3" of rotation allows the shafts 44 of the tensioning rollers 42A to slide radially in either direction in the grooves.

The rotation of the cam disc 48 is, for example, controlled by means of an electric motor, for example by means of the mechanical drive means, here a belt 52 and a pulley 54. By regulating the rotation of the motors relative to each other, it is thus possible to cause the cam disc 48 to rotate only a fraction of a revolution during a full revolution of the rotor 26 relative to the guide disc 26A.

In a variant not shown, the rotation of the cam disc can also be driven by the winding motor. In this case, a device allowing to change the speed transmitted to the cam disc is interposed between the winding motor and the cam disc. This is, for example, a differential gear mechanism or a continuously variable transmission which is, for example, driven by an electric motor separate from the winding motor.

The winding device 1 0 also comprises a tensioning mechanism 56 for allowing to maintain a constant tension in the strand 12C of the filament material extending between the spool 16 and the guide member 41 . In the example shown in Figure 1 , the device comprises at least one stationary pulley 58 and at least one movable pulley 60. The tensioning mechanism 56 comprises six stationary pulleys 58 and three movable pulleys 60. The stationary pulleys 58 are aligned in a first row on a stationary support 62. The movable pulleys 60 are aligned along a second row parallel to the first row of stationary pulleys 58. The movable pulleys 60 are rotatably mounted on a ramp 64 movable between a proximal position in which the spacing between the first row and the second row is minimal and a distal position in which the spacing between the first row and the second row is maximal. The strand 1 2C of filament material is arranged in a zigzag pattern extending alternately around a stationary pulley 58 and then a movable pulley 60. By moving the movable pulleys 60 away towards their distal positions, the tension in the strand 1 2 of filament material can thus be increased, while by moving closer the movable pulleys 60 towards their proximal positions, the tension can be reduced. Such a tensioning mechanism 56 has the advantage that it allows to absorb a release of the tension in the filament material during a restitution step as will be explained later. Such a tensioning mechanism 56 may be associated with a device (not shown) for breaking the filament material which acts, for example, by friction with a strand of filament material or with the spool 16.

In a variant of the invention not shown, the tensioning mechanism may be replaced and/or assisted by a motor which drives the rotation of the spool 1 6. Such a device is particularly advantageous and with a small overall size when the spool is mounted on the arm. In this case, the rotation of the spool is controlled by a motor which allows the tension to be maintained, or even to rewind a part of the strand during a restitution step as will be explained in more detail later.

According to a first embodiment of the invention shown in Figures 1 to 7, the filament winding device 1 0 comprises a single carriage 24 equipped with its rotor 26 as previously described.

A method for producing an object made of composite material implementing the winding device 10 carried out according to the first embodiment of the invention with reference to Figure 1 2 is now described.

This method comprises in particular a filament winding phase „P1 „

Prior to the start of the filament winding phase "P1", the mandrel 14 is mounted on the support 20 and inserted inside the eye 30. A free end strand of filament material 1 2 is pulled from the spool 16, previously installed on its support 38, and passed through the tensioning mechanism 56 and through the guide ring 41 . The strand is received in the space delimited between the two stationary rollers 42B from the outside inwards before being inserted into the guide member 40 after angular return around one of the stationary rollers 42B. The free end strand is pulled and secured to one end of the mandrel 14 as shown in Figure 3. Then, the filament winding phase "P1" is started. During this phase "P1 " of filament winding, the carriage 24 moves successively back and forth, or swings, along the main axis "A1 " of the mandrel 14 from one end of the mandrel 14 to the other.

The filament winding phase "P1 " comprises at least one cycle comprising a first accumulation step "E1 " and a restitution step "E2". These cycles are intended to be repeated until the desired amount of filament material 1 2 has been wound around the mandrel 14.

During these cycles, the rotor 26 is rotated in one direction or the other by the winding motor simultaneously with the displacement of the carriage 24 by swings. The rotation of the rotor 26 causes the filament material 1 2 to be wound around the mandrel 14, while the displacement of the carriage 24 allows to carry out an helical winding of the filament material 1 2 around said mandrel 14. The ratio of the rotational speed of the rotor 26 to the speed of displacement of the carriage 24 allows to determine the helix angle of the winding.

During the first accumulation step "E1 ", the rotor 26 is rotated in a first direction, here counterclockwise, with reference to Figure 3, to wind a strand of the filament material 1 2 helically in said first direction, indicated by the arrow "F1 ", around the mandrel 14. This winding causes a tension in the filament material 12 which automatically unwinds from the spool 16. The tension of the filament material is controlled by means of the tensioning mechanism 56. An intermediate strand 12B of the filament material 1 2 is simultaneously wound in said first direction around the eye 30 by the accumulation mechanism 42.

At the beginning of the accumulation step "E1 ", the tensioning rollers 42B occupy their internal position.

The length of filament material 1 2 required to be wound around the mandrel 14 and to be accumulated by the accumulation mechanism 42 is simultaneously drawn from the spool 1 6. The intermediate strand 12B wound around the accumulation mechanism 42 then forms the accumulation reel 43. The sliding of the filament material 12 relative to the accumulation mechanism 42, in particular by rolling of the rollers 42A, 42B allows to continue the winding around the mandrel 14 during the accumulation. More particularly, the entire accumulation reel 43 formed by the winding of the intermediate strand 1 2B slides fixedly around the rollers 42A, 42B, without sliding of one coil of said accumulation reel 43 with respect to another. In particular, the filament material 1 2 continues to slide freely in the guide member 40 due to the position of the stationary rollers 42A which allow to prevent the filament material 1 2 from becoming entangled around the guide member 40.

The accumulation reel 43 formed by the winding of the intermediate strand 12B around the accumulation mechanism 42 is thus unwound from the inside to be wound around the mandrel 14. As a result, the internal diameter of the accumulation reel 43 increases as its external diameter increases with the number of revolutions performed by the rotor 26. However, the inner diameter increases at a lower speed than the outer diameter. To keep the intermediate strand 12B tensed around the rollers 42A, 42B the tensioning rollers 42B are therefore progressively displaced to their outer position during the accumulation step "E1 ".

When the length of the accumulated intermediate strand 12B is sufficient or when the external diameter of the accumulation reel 43 is sufficient, for example after a determined time, or after a determined number of revolutions, the accumulation step "E1 " is stopped.

In general, the accumulation step "E1 " is stopped when the carriage 24 reaches a point on the mandrel 14 for which the properties of the composite material are not sought. This will be, for example, a section of the mandrel 14 which can be cut off later or which will not be subject to such high mechanical stresses as the rest of the section which has undergone the filament winding. Typically, the accumulation step "E1 " is stopped at the end of a back or a forth movement, when the carriage 24 is at either end of the mandrel 14, as is the case here.

Alternatively, the accumulation step "E1 " is stopped at an intermediate section of the mandrel 14.

A switching step "Eb" is then initiated. During this switching step "Eb", the end of the tangential strand 12B of the filament material that is in contact with the mandrel 14 is secured to the mandrel 14. According to this first embodiment, the fastening is here performed by gluing the filament material 12, for example, by means of a glue point 58. The fastening operation is performed manually, for example. In order to carry out this fastening operation, the displacement of the carriage 24 and the rotation of the rotor 26 are temporarily interrupted.

At the end of the switching step "Eb", a step "E2" of restitution of the intermediate strand 1 2B accumulated during the first accumulation step "E1 " is triggered. During this restitution step, the carriage 24 resumes its displacements by successive back and forth movements. When the switching step "Eb" has been performed on an end section of the mandrel 14, the carriage 24 resumes its displacements in an opposite direction with respect to the direction it was following just before its stop, whereas when the switching step "Eb" has been performed on an intermediate section of the mandrel 14, the carriage 24 can continue its displacement in the same direction with respect to the direction it was following just before its stop.

The rotor 26 is rotated in a second direction, opposite to the first direction, to wind the intermediate strand 12B of filament material accumulated by the accumulation mechanism 42 during the accumulation step "E1 " around the mandrel 14 in said second direction, as represented by the arrow "F2" in Figures 4, 5 and 6. The fastening of the radial strand 12B to the mandrel 14 during the switching step "Eb" allows the mandrel 14 to retain the filament material 1 2 during the rotation of the rotor 26 in the other direction creating an anchor point necessary for the winding.

During this restitution step "E2", substantially no filament material 12 is pulled from the spool 16. Only the accumulated intermediate strand 12B unwinds from the inside. Thus, the accumulation reel 43 formed by the winding of the intermediate strand 1 2B around the accumulation mechanism 42 is thus unwound from the inside to come to be wound around the mandrel 14.

However, due to the difference in dimensions between the inner diameter and the outer diameter of the accumulation reel 43, a part of the intermediate strand 1 2B unwinds from the outside of the accumulation reel 43. To maintain the tension upstream of the accumulation reel 43, the tensioning mechanism 56 is controlled to absorb the part of fiber unwound from the accumulation reel 43. As a result, the internal diameter of the accumulation reel 43 increases, while its external diameter decreases based on the number of revolutions performed by the rotor 26.

During this restitution step "E2", the tensioning rollers 42B are progressively controlled to pursue their displacement towards their outer position, as represented by the arrows "F3" in Figure 5, so as to maintain the accumulated intermediate strand 1 2B under tension at all times.

When the entire accumulated intermediate strand 1 2B has been unwound, as shown in Figure 6, the cycle is complete. The switching step "Eb" is repeated before the start of a new cycle. The rotation of the rotor 26 may be performed in the first direction during the accumulation step "E1 " and then in the second direction during the restitution step "E2" as previously described. Alternatively, the new cycle may be repeated by reversing the directions of rotation of the rotor 26 in each step "E1 " and "E2". Thus, the rotor 26 will be able to rotate in the second direction during the accumulation step "E1 " and then in the first direction during the restitution step "E2".

As indicated by the reference "C", the cycle is repeated in this order until the desired amount of filament material 1 2 has been wound around the mandrel 14.

At the end of the filament winding phase "P1 ", an intermediate object formed by a winding of filament material 12 around the mandrel 14 is thus obtained.

According to a second embodiment of the invention shown in Figures 9 to 13 and in dashed lines in Figure 1 , the filament winding device 1 0 comprises a first rotor 26-1 and a second rotor 26-2. The two rotors 26-1 and 26-2 are each carried by a carriage 24 as previously described. Although not shown for the second rotor 26- 2, each rotor 26-1 and 26-2 is associated with its own spool 16 with the same structure and the same arrangement as described for the rotor 26 of the first embodiment.

The two carriages 24 move together. In this case, the two rotors 26-1 and 26-2 are arranged at a fixed distance from each other. They are arranged one after the other along the axis "A1 " of the mandrel 14. The rotation of each of the rotors 26-1 and 26-2 is independently controlled so that the rotors 26-1 and 26-2 can rotate in the same direction or in two opposite directions.

The winding phase "P1 " for each of the rotors 26-1 , 26-2 is similar to the filament winding phase "P1 " carried out according to the first embodiment of the invention. Thus, each rotor 26 operates in a cycle comprising an accumulation step "E1 " and a restitution step "E2". A switching step "Eb" is interposed between each accumulation and restitution step "E1 , E2" as shown in Figure 1 2.

However, unlike the previously described the filament winding phase "P1 ", the switching step "Eb" here consists of locking the filament material 1 2 delivered by one of the rotors 26 onto the mandrel 14 by means of the filament material 12 delivered by the other rotor 26. For this purpose, the cycles of each of the rotors 26- 1 , 26-2 are out of phase.

Thus, as shown in Figure 9, initially the two rotors 26-1 and 26-2 rotate synchronously in the same direction indicated by the arrows "F4-1 , F4-2".

When the length of intermediate strand 1 2B accumulated on one of the rotors 26, for example the first rotor 26-1 , is sufficient, the switching step for this first rotor 26-1 starts when said rotor 26- 1 is located at the corresponding end 60, here on the right, of the mandrel 14 with reference to Figure 10. Said first rotor 26-1 is then located closest to said end 60. It will therefore be referred to as proximal rotor 26-1 to describe the remainder of the switching step "Eb". The second rotor 26-2, further from said end, will therefore be referred to as distal rotor 26-2.

When the proximal rotor 26-1 reaches the end of its stroke, as shown in Figure 1 0, the carriage 24 temporarily stops. The proximal rotor 26-1 then temporarily stops rotating, while the rotor 26-2 continues to rotate, as indicated by the arrow "F4-2", to wind the filament material 12-2 around the strand of filament material 1 2-1 which has just been wound around the mandrel 14 by the proximal rotor 26-1 . This operation allows to lock the filament material strand 12-1 of the proximal rotor 26-1 to the mandrel 14 to form an anchor point 62.

Then, the carriage 24 resumes its displacement towards the other end of the mandrel 14 as shown in Figure 1 1 . The proximal rotor 26-1 changes its direction of rotation, as indicated by the arrow "F4-1 ", while the distal rotor 26-2 keeps the same direction of rotation "F4-2". The proximal rotor 26-1 can therefore continue the winding operation around the mandrel 14 in the opposite direction without the risk of loosening the filament material 1 2-1 already wound on the mandrel 14 due to the anchor point 62.

The transition from one step of the cycle to the other for the second rotor 26-2 will be performed in the same manner at a later time when the second rotor 26-2 is in proximity to the other end of the mandrel 14. The first rotor 26-1 will then form the distal rotor while the second rotor 26-2 will form the proximal rotor.

After the filament winding phase "P1 ", a heating phase "P2" is started. During this heating phase "P2", the intermediate object is subjected to a thermal treatment operation.

Prior to this heating phase "P2", the filament material 12 of the intermediate object obtained at the end of the filament winding phase "P1 " is impregnated with a material in the liquid state serving as matrix. This is a thermosetting material such as resin, for example a thermosetting epoxy resin. As previously explained, the impregnation of the filament material 1 2 may be carried out prior to its winding around the mandrel 14 by passing a strand of the filament material 1 2 through a bath of material serving as matrix, or after its winding around the mandrel 14 by infusing the intermediate object into a bath of material serving as matrix, for example by a well-known vacuum impregnation method.

The heating phase comprises a heating operation which consists of exposing the intermediate object to a treatment temperature equal to or higher than a cross-linking temperature of the resin, for example in the range of 150°C.

During this heating operation, the intermediate object is first subjected to a first gelling temperature during which the material serving as matrix, in this case the resin, is gelled, i.e. it takes on a much more viscous consistency than when it was impregnated around the filament material 1 2. The gelling temperature is, for example, around 80°C. After sufficiently long exposure to this gelling temperature, the filament material 1 2 is likely to maintain its wound shape, even in the absence of a mandrel 14.

Then, the intermediate object is subjected to a second treatment temperature which corresponds to a temperature equal to or higher than a cross-linking temperature of the material serving as matrix, in this case the resin. After sufficient exposure to this treatment temperature, the material serving as matrix is hardened by polymerization. The cross-linking temperature is, for example, about 1 50°C. The composite material formed by the filament material 1 2 and the material serving as matrix is then rigid and strong. The object is thus finished.

The object obtained by this method can integrate the mandrel 14. In this case, the mandrel 14 is made of a material that remains solid at the treatment temperature of the heating phase "P2". The object thus comprises the mandrel 14 covered by a tubular shell 70 made of composite material formed by the filament material 12 wound during the method and the hardened material of the matrix.

The object obtained by this method may also be made solely of a composite material formed from the filament material 12 and the material serving as a matrix. In this case, the mandrel 14 must be removed from the object. The object thus comprises only a tubular shell 70 of composite material formed by the filament material 1 2 wound during the method and the hardened material of the matrix.

When the mandrel 14 has a shape that does not allow it to be extracted in the solid state, the mandrel 14 is advantageously made of a material having a melting temperature below the treatment temperature. Advantageously, the melting temperature of the material forming the mandrel 14 is higher than the gelling temperature so that the material serving as matrix is sufficiently viscous to maintain the shape of the wound filament material 12 even when the mandrel 14 passes into the liquid phase. The mandrel 14 is, for example, made of wax or a metallic material with a melting temperature between the gelling temperature and the cross-linking temperature.

Such a filament winding device 1 0 carried out according to one or other of the embodiments of the invention advantageously allows windings to be produced around mandrels having complex shapes that do not allow the passage of carriages with greater overall size. Furthermore, it is possible to produce such a winding without the need to change the spool 16 frequently since the spool 16 can contain as much filament material 1 2 as required, the overall size of the spool 1 6 not being a limiting factor for the passage of the carriage 24 along the mandrel 14.

The winding device 10 and the associated production method are capable of being used to produce a spring made of composite material. It is a compression spring whose coils are not joined. The coils are formed by a helically wound wire as shown in Figure 1 . In particular, the invention makes it possible to obtain a spring with a tubular wire. It has been found that the main mechanical characteristics of a spring are provided by a peripheral part of the wire. Since a central part of the wire is of no interest in terms of strength and elasticity, producing a spring with a tubular wire allows to obtain a lighter spring with mechanical characteristics equivalent to those of a spring of the same dimensions produced with a solid wire.

To produce such a spring, a tubular mandrel 14 can be provided, as shown in Figures 3 to 6. In this case, the mandrel 14 can be integrated into the final spring obtained at the end of the production method. The tubular wire forming the spring 66 is thus formed from the tubular mandrel 14 and its tubular shell 70 made of composite material.

According to a variant shown in Figures 13 and 14, the spring 66 is made solely of composite material, the composite material being formed of filament material 12 bound by means of a matrix. The tubular wire forming the spring 66 is then formed solely by the tubular shell 70 of composite material, the mandrel 14 having been removed.

The matrix here is formed of thermosetting resin by heating, for example the thermosetting epoxy resin.

The filament material 1 2 is, for example, formed by a high mechanical strength carbon fiber, such as the T300 or T700 products produced by the company Toray or the products AS4 or AS7 produced by the company Hexcel.

Alternatively, the filament material 1 2 is formed by a high mechanical strength glass fiber.

The spring 66 is formed of a wire made of composite material forming a hollow helical tube. More particularly, the wire is formed by the shell 70 made of composite material obtained by the production method of the invention. To allow the tubular shape of the wire to be produced, the mandrel 14 is advantageously made of a material having a melting temperature between the gelling temperature of the resin, for example about 80°C, and its crosslinking temperature, for example about 1 50°C.

Advantageously, the mandrel 14 is made of a material which has a solid phase at room temperature, for example around 25°C, during the winding method, and has a liquid phase during the heating step to harden the matrix of the composite material, for example at a temperature between 80°C and 150°C, for example between 1 00°C and 1 20°C.

Advantageously, the mandrel 14 is made of metallic material. Thus, it is possible to obtain the mandrel 14 by deforming a straight wire of said metallic material, for example by helically winding it around a cylinder with the desired helical pitch.

Represented in figure 1 3 is an intermediate object corresponding to a portion of coil of the spring 66 obtained after the filament winding phase "P1 " and before the heating phase "P2". Shown is the shell 70 made of composite material arranged around the mandrel 14. However, the resin is not yet hardened.

This intermediate object undergoes the heating phase "P2" to produce the hardening of the resin. The mandrel 14 changes from a solid phase to a liquid phase. When the material forming the mandrel 14 has passed into the liquid phase during the heating phase "P2", it may be evacuated from the interior of the tubular shell 70 made of composite material through one of its ends by gravity and/or by injection of a pressurized fluid at one end of the tubular spring 66 which flushes said material through the other end of the tubular spring.

Figure 14 shows a portion of the coil of the spring 66 obtained at the end of the heating phase "P2". It can be seen that the mandrel 14 has been removed and the wire of the spring 66 is formed solely from the shell 70 made of composite material.

Such a spring 66 is advantageously light while having mechanical properties of elasticity and strength particularly adapted to the use of the spring, for example to form a shock absorber spring for a motor vehicle.

Claims

1 . A device (1 0) for continuous filament winding around a mandrel (14) extending along a main axis (A1 ), straight or curvilinear, the device (1 0) comprising :

- a mandrel support (20) on which the mandrel (14) is intended to be secured;

- a carriage (24) which is slidably mounted in relation to the mandrel support (20) along the main axis (A1 ) of the mandrel (14);

- at least one winding rotor (26) which comprises a central orifice (28) intended to receive the mandrel (14) and which is rotatably mounted on the carriage (24) about an axis (A3) of rotation coaxial with the central orifice (28);

- at least one spool support (38) which is intended to receive a spool (16) comprising a supply of filament material (1 2) ;

- a guide member (40) equipped with a through opening for the passage of the filament material which is integral in rotation with the winding rotor (26) and which allows to guide a strand of the filament material, referred to as radial strand (12A), which unwinds from the spool (16) towards the central orifice (28) tangentially to the mandrel (14) in order to wind it around the mandrel (14) by rotation of the winding rotor (26); characterized in that the winding rotor (26) is rotatably mounted about its axis (A3) of rotation with respect to the spool support (38), the winding rotor (26) comprising a mechanism (42) for accumulating an intermediate strand (1 2B) of the filament material (1 2) located directly upstream of the guide member (40) for guiding said intermediate strand (12B) by winding it around the central orifice (28) to form an accumulation reel (43), the accumulation reel (43) being capable of sliding with respect to the accumulation mechanism (42) in order to allow the radial strand (12A) to be wound around the mandrel (14).

2. The device (1 0) according to the preceding claim, characterized in that the spool support (38) is mounted on the carriage (24).

3. The device according to claim 1 , characterized in that the spool support (38) is fixedly mounted with respect to the mandrel support (20).

4. The device (1 0) according to any of the preceding claims, characterized in that the accumulation mechanism (42) comprises a plurality of rollers (42A, 42B) which are rotatably mounted on the rotor (26) and which are distributed around the central orifice (28).

5. The device (1 0) according to the preceding claim, characterized in that at least one of the rollers of the accumulation mechanism (42), referred to as tensioning roller (42B), is mounted with a radial mobility on the rotor (26).

6. The device (1 0) according to the preceding claim, characterized in that the radial displacements of the at least one tensioning roller (42B) are actively controlled.

7. The device (1 0) according to any one of the preceding claims, characterized in that the rotor (26) has a closed ring shape.

8. The device (1 0) according to any one of claims 1 to 6, characterized in that the rotor (26) has an ring shape opened by a segment (34) intended to allow the radial insertion of the mandrel (14) into the central orifice (28).

9. The device (1 0) according to any one of the preceding claims, characterized in that it comprises controlled means for driving the rotor (26) in rotation in both directions about its axis (A3) of rotation.

10. The device (1 0) according to any of the preceding claims, characterized in that it comprises two rotors (26-1 , 26-2) arranged one after the other along the axis (A1 ) of the mandrel (14).

1 1 . The device (1 0) according to any of the preceding claims, characterized in that the carriage (24) comprises a ring (41 ) for guiding the filament material from the spool (16) to the rotor (26), the guide ring (41 ) being integral in rotation with the carriage (24) about the axis (A3) of rotation.

1 2. A method for producing an object made of composite material implementing the filament winding device (1 0) according to any one of the preceding claims, comprising a filament winding phase (P1 ) during which the carriage (24) moves successively back and forth along the axis (A1 ) of the mandrel (14) which is received in the central orifice (28) of the rotor, characterized in that the filament winding phase (P1 ) comprises at least one cycle comprising :

- an accumulation step (E1 ) during which the rotor (26) is rotated in a first direction to wind a strand of the filament material (12) helically in said first direction around the mandrel (14), an intermediate strand (1 2B) being simultaneously wound in said first direction around the central orifice (28) by the accumulation mechanism (42);

- a step (E2) of restitution of the accumulated intermediate strand (1 2B) during which the rotor (26) is rotated in a second direction to wind the strand (12B) of filament material accumulated by the accumulation mechanism (42) around the mandrel (14).

13. The method according to the preceding claim, characterized in that the restitution step (E2) is triggered based on the number of revolutions of the rotor (26) performed during the first accumulation step (E1 ).

14. The method according to any one of claims 1 2 or 1 3, characterized in that it comprises a step (Eb) of switching between the two steps (E1 , E2) of the cycle.

15. The method according to any one of claims 1 2 to 14, characterized in that during the switching step (Eb), the filament material (1 2) delivered by said rotor (26) is secured on the mandrel (14).

16. The method according to the preceding claim taken in combination with claim 10, characterized in that when the carriage (24) is located at one end of the mandrel (14), the rotor (26-1 , 26- 2) located closer to said end, referred to as proximal rotor, changes its direction of rotation while the rotor (26-1 , 26-2) further from said end, referred to as distal rotor, maintains the same direction of rotation so that the filament material (1 2) delivered by the distal rotor secures the filament material delivered by the proximal rotor by clamping it against the mandrel (14).

17. The method according to any one of claims 1 2 to 1 6, characterized in that it comprises a heating phase (P2) which is carried out after the filament winding phase (P1 ), the filament material (12) having previously been impregnated with a resin, the heating phase (P2) comprising a heating operation at a treatment temperature greater than or equal to a cross-linking temperature of the resin, for example of the order of 150°C.

18. The method according to the preceding claim, characterized in that the mandrel (14) is made of a material having a melting temperature lower than the treatment temperature.

19. A helical spring (66) produced by the implementation of the method according to claim 18, the spring (16) having a tubular wire forming coils of the spring (66), the wire being produced solely of a tubular shell (70) made of composite material obtained by winding filament material (12) around a helically shaped mandrel (14) and by a matrix material, such as the resin, the mandrel (14) having been extracted during the heating phase.