Braiding machine with a reserve region

Abstract

The invention relates to a braiding machine comprising: - a plurality of yarn feed spindles (30) movable along a guide path (100) so as to participate in the braiding, - a reserve zone (20) capable of receiving at least one spindle (30) so as to interrupt its participation in the braiding.

Description

Technical Field

[0001] The present invention relates to braiding machines allowing the production of braided structures, and more particularly braided tubular structures having large variations in section. Prior art

[0002] A braiding machine conventionally comprises a plate having circuits, called guide paths, which intersect each other and along which are moved yarn feed spindles connected to a draw point of the machine. These yarn feed spindles therefore intersect regularly to produce a braid. Generally speaking, the formation of the braid can be carried out on a form, called a shaping mandrel, which moves during the formation of said braid: this is then referred to as "over-braiding". The movement of the spindles along the guide paths is conventionally carried out by means of notched wheels driven in rotation and preferably arranged in one or more concentric circles. Such braiding machines are for example described in documents FR 2 804 133 and US 8 347 772.

[0003] When it is desired to manufacture a braided structure having large variations in section with a machine of the prior art, it is found that the braided structure obtained does not have uniform braiding. Indeed, in the areas of the braid having a large section, the density of threads is lower or even insufficient, or the angles between the braided threads are greater, in comparison with the areas of the braid having a smaller section.

[0004] WO 2015 / 117148 A1 and EP 3 502 332 A1 disclose braiding machines. US 2 354 212 A discloses a machine for braiding tubular parts. JP H07 18548 A discloses a device for replacing an empty wire spool with a full wire spool. Statement of the invention

[0005] The present invention aims to overcome the aforementioned drawbacks by proposing a braiding machine capable of producing a uniform braided structure despite significant variations in section. To this end, according to a first aspect of the invention, the invention proposes a braiding machine comprising: a plurality of yarn feed spindles connected to guide supports and movable along a guide path so as to participate in braiding, all or part of the spindles being integral with a positioning element cooperating with a corresponding guide support and removable relative to the latter, a plurality of reserve supports located outside the guide path, said reserve supports being capable of receiving yarn feed spindles placed in reserve so as to interrupt their participation in braiding, the positioning elements being capable of cooperating with the reserve supports to carry out this placing in reserve.

[0006] Thus, the use of spindles capable of cooperating with guide supports movable along the guide path makes it possible to easily remove or add spindles to the braiding, without requiring complex operations such as dismantling the braiding machine plate.

[0007] Such a system of cooperation between the positioning elements and the guide supports therefore makes it possible to easily vary the number of yarn supply spindles participating in the braiding of the braided structure. Thus, the number of spindles participating in the braiding can be adapted to the section of the structure to be braided in order to obtain a constant yarn density and angle values ​​between the yarns despite variations in section.

[0008] Thus, when it is desired to reduce the section of the braided structure, spindles are removed from the guide path in order to interrupt their participation in the braiding, by separating the positioning elements of said spindles from the guide supports. Consequently, the number of braided threads is reduced, which makes it possible to avoid a significant increase in the density of threads, or an undesired reduction in the angles between the braided threads, at the level of the area of ​​smaller section. On the contrary, when it is desired to increase the section of the braided structure, spindles are added to the main guide path, by mounting the positioning elements of said spindles with the guide supports present on the guide path. Consequently, the number of braided threads is increased, which makes it possible to avoid a significant reduction in the density of threads, or an undesired increase in the angles between the braided threads, at the level of the area of ​​smaller section.The braiding weave therefore remains identical and uniform across the entire braided structure thus obtained.

[0009] The use of reserve holders makes it possible to easily store the spindles in a reserve area, in particular the spindles which have been removed from the guide path in order to interrupt their participation in braiding, and / or the spindles which are intended to be added to the guide path to participate in braiding.

[0010] According to a particular embodiment of the invention, the machine comprises a reserve support drive system capable of driving at least part of the reserve supports circumferentially to the guide path.

[0011] The backup supports go around the outside edge of the guide path, or go around the inside edge of the guide path.

[0012] The use of a reserve zone comprising at least one part that can rotate circumferentially to the guide path makes it possible to limit the appearance of singularities in the braiding. Indeed, when a spindle has just been removed from the guide path in order to interrupt the participation in the braiding of the yarn coming from said spindle, the yarn coming from said spindle is still being intertwined. When the yarn is being intertwined, it is neither braided and tightened with the other yarns, nor free. There is therefore a transition stage in which the yarn no longer participates in the braiding, but is still being intertwined, so that a part of the yarn is completely braided and tightened with the other yarns, a part of the yarn is being intertwined and a part of the yarn is free.This transition stage ends when the part of the yarn that was being intertwined is completely braided and tightened with the other yarns, that is to say, the yarn now only comprises a completely braided and tightened part, and a free part that is not braided and not intertwined.

[0013] If the spindle removed from the guide path is directly positioned on a reserve support fixed relative to the movable guide supports, the yarn coming from said spindle is abruptly stopped while it may be in the process of being intertwined, which may lead to unwanted tensions in the yarns or to singularities in the braiding. In order to accompany the yarn during the transition step, i.e. when it is still in the process of being intertwined but no longer participating in the braiding, the spindle from which said yarn comes can be positioned on a movable reserve support. Said movable reserve support thus makes it possible to extend the movement of the spindle in the clockwise or counterclockwise direction, until at least the end of the transition step. When the transition step is completed, the movement of the movable reserve support can be interrupted, the spindle can be moved to a fixed part of the reserve area and / or the yarn coming from said spindle can be cut.

[0014] According to another particular embodiment of the invention, the system for driving the reserve supports comprises at least a first circumferential crown on the guide path and capable of rotating in a first direction of rotation and at least a second circumferential crown on the guide path and capable of rotating in a second direction of rotation opposite to the first direction of rotation, each first or second crown carrying one or more reserve supports.

[0015] The first and second rings surround the outer edge of the guide path, or go around the inner edge of the guide path.

[0016] Thus, it is possible to simultaneously accompany in their transition stage threads from spindles that rotated clockwise on the guide path and threads from spindles that rotated counterclockwise.

[0017] According to another particular embodiment of the invention, the reserve supports are present around the guide path.

[0018] By placing the reserve area, and any reserve circumferential crowns, on the periphery of the guide path, access to the spindles present in the reserve area is facilitated.

[0019] According to another particular embodiment of the invention, the machine further comprises a shaping mandrel on which the braiding is intended to be carried out.

[0020] The presence of a shaping mandrel makes it easier to braid the structure, the shape of the shaping mandrel providing support on and around which the wires can be braided with the desired section.

[0021] According to another particular embodiment of the invention, the machine comprises a global drive system comprising the drive system of the reserve supports and a drive system of the guide supports, the global drive system being configured so that the angular speed of at least a portion of the reserve supports is a function of the angular speed of at least a portion of the guide supports so that the movement of at least a portion of the reserve supports accompanies the movement of at least a portion of the guide supports.

[0022] According to another particular embodiment of the invention, the overall drive system comprises a transmission system configured to transmit the movement of a drive system of the guide supports to the drive system of the reserve supports.

[0023] Preferably, the drive system for the reserve supports is a rack and pinion system. Preferably, the drive system for the guide supports is a system of notched wheels rotated by a gear train. Preferably, the transmission system is a belt system connecting the gear train of the guide support drive system to the rack and pinion system of the reserve support drive system. Indeed, this overall drive system has the advantage of being robust and allowing high braiding speeds.

[0024] According to another particular embodiment of the invention, the machine further comprises a robotic arm configured to move at least one spindle between a guide support and a reserve support.

[0025] According to another particular embodiment of the invention, the machine further comprises a cutting device configured to cut a wire coming from a supply spindle whose positioning element cooperates with a reserve support.

[0026] The invention also relates to a method of braiding a braided structure comprising a first zone having a first section and a second zone having a second section different from the first section, the method implementing a machine according to the first aspect of the invention and comprising: braiding the first area of ​​the braided structure with a first number of wire feed spindles movable along the guide path, and braiding the second area of ​​the braided structure with a second number of wire feed spindles movable along the guide path, the second number of spindles being different from the first number of spindles by moving spindles between the guide supports and the reserve supports by cooperation of the positioning element of said moved spindles with the guide or reserve supports.

[0027] The invention also proposes, according to a second aspect of the invention, a braiding machine comprising: a plurality of yarn feed spindles movable along a main guide path so as to participate in braiding, characterized in that it further comprises: a reserve zone adjacent to the main guide path and comprising at least one secondary guide path capable of receiving at least one spindle and holding it in the reserve zone so as to interrupt its participation in the braiding, each secondary guide path being associated with at least one switching element which is movable between a first position preventing communication between the main guide path and the secondary guide path, and a second position allowing this communication and configured to allow passage of at least one spindle between the main guide path and the secondary guide path.

[0028] The reserve area may be located on the outer edge side of the main guide path, or on the inner edge side of the main guide path. In one example, the reserve area may surround the outer edge of the main guide path, or go around its inner edge.

[0029] The presence of the reserve zone makes it possible to vary the number of yarn supply spindles participating in the braiding of the braided structure. Thus, the number of spindles participating in the braiding can be adapted to the section of the structure to be braided in order to obtain a constant yarn density and angle values ​​between the yarns despite variations in section.

[0030] Thus, when the section of the braided structure is to be reduced, some spindles are removed from the main guide path in order to interrupt their participation in the braiding. Consequently, the number of braided threads is reduced, which makes it possible to avoid a significant increase in the density of threads, or an unwanted reduction in the angles between the braided threads, at the area of ​​the smallest section. On the contrary, when the section of the braided structure is to be increased, some spindles present in the reserve area are moved in order to add them to the main guide path. Consequently, the number of braided threads is increased, which makes it possible to avoid a significant reduction in the density of threads, or an unwanted increase in the angles between the braided threads, at the area of ​​the smallest section. The braiding weave therefore remains identical and uniform over the entire braided structure thus obtained.

[0031] According to a particular embodiment of the invention, the machine further comprises a shaping mandrel on which the braiding is intended to be carried out.

[0032] The presence of a shaping mandrel makes it easier to braid the structure, the shape of the shaping mandrel providing support on and around which the wires can be braided with the desired section.

[0033] According to another particular embodiment of the invention, the reserve zone is formed by a plurality of reserve regions distributed along the main guide path, each reserve region comprising a secondary guide path separated from the secondary guide paths of the other reserve regions.

[0034] According to another particular embodiment of the invention, the machine comprises a plurality of main notched wheels configured to be driven in rotation in order to circulate the feed spindles along the main guide path, said machine further comprising one or more secondary notched wheels in the reserve area, each secondary guide path of the reserve area being associated with at least one secondary notched wheel configured to be driven in rotation in order to circulate at least one feed spindle along said secondary guide path.

[0035] According to another particular embodiment of the invention, the machine comprises at least one rotation decoupling system configured to make the rotation of at least one secondary notched wheel independent of the rotation of the main notched wheels.

[0036] According to another particular embodiment of the invention, at least part of the switching elements is movable in translation to move from the first to the second position.

[0037] According to another particular embodiment of the invention, at least part of the switching elements can be moved in rotation to move from the first to the second position.

[0038] According to another particular embodiment of the invention, the machine further comprises a control unit configured to actuate the switching element.

[0039] According to another particular embodiment of the invention, the machine further comprises a cutting device configured to cut a wire coming from a supply spindle present in the reserve zone.

[0040] The invention also relates to a method of braiding a braided structure comprising a first zone having a first section and a second zone having a second section different from the first section, the method implementing a machine according to the second aspect of the invention and comprising: braiding the first area of ​​the braided structure with a first number of wire feed spindles movable along the main guide path, and braiding the second area of ​​the braided structure with a second number of wire feed spindles movable along the main guide path, the second number of spindles being different from the first number of spindles by virtue of the passage of spindles between the main guide path and the reserve area by actuation of the switching element. Brief description of the drawings

[0041] [ Fig. 1 ] There Figure 1is a three-dimensional view of a braiding machine according to the first aspect of the invention. Fig. 2 ] There Figure 2 is a top view detail of the braiding machine of the Figure 1 . [ Fig. 3 ] There Figure 3 is an exploded schematic view of a spindle cooperating with a guide support. Fig. 4 ] There Figure 4 is a schematic view of the mechanisms of operation of the braiding machine Figures 1 and 2 . [ Fig. 5 ] There Figure 5 is a schematic view of the machine of the Figures 1 and 2 when braiding a section of braid with a large section. Fig. 6 ] There Figure 6 is a schematic view of the machine of the Figures 1 and 2 when braiding a part of a progressive section braid. Fig. 7 ] There Figure 7 is a schematic view of the machine of the Figures 1 and 2 when braiding a small section of braid. Fig. 8 ] There figure 8is a schematic view of a braiding machine according to the second aspect of the invention when braiding a large section braid portion. Fig. 9 ] There Figure 9 is a schematic view of the braiding machine of the figure 8 when braiding a part of a braid with a small section. Fig. 10 ] There Figure 10 is a schematic view of a portion of the bed of the braiding machine figures 8 and 9 including notched wheels. Fig. 11 ] There Figure 11 is a schematic view of a switching element movable in translation in its second position according to a first embodiment. Fig. 12 ] There Figure 12 is a schematic view of a switching element movable in translation in its first position according to a second embodiment. Fig. 13A ] There Figure 13A is a schematic view of a switching element movable in translation in its second position according to a third embodiment. Fig. 13B ] There Figure 13B is a schematic view of the switching element of the Figure 13A in its first position. Fig. 14 ] There Figure 14 is a schematic view of a rotating movable switch element according to a fourth embodiment. Fig. 15 ] There Figure 15 is a schematic view of a rotating movable switch element according to a fifth embodiment. Fig. 16 ] There figure 16 is a schematic view of a rotating movable switch element according to a sixth embodiment. Description of the embodiments

[0042] A first aspect of the invention is presented in relation to the figures 1 to 7 .

[0043] THE Figures 1 and 2 schematically illustrate an example of a braiding machine according to the first aspect of the invention making it possible to produce a braided structure.

[0044] The braiding machine comprises a plate 1 and a plurality of wire feed spindles 30. The plate 1 is preferably horizontal, in order to facilitate its maintenance and that of the wire feed spindles 30. However, it does not depart from the scope of the invention if the plate 1 is vertical or inclined.

[0045] The plate 1 comprises a braiding zone 10. The braiding zone 10 comprises a guide path 100 and a plurality of guide supports 51 capable of cooperating with said guide path 100, and consequently capable of moving along the guide path 100. Preferably, the guide path 100 is machined in the mass of the plate 1 in the form of grooves, having for example a substantially rectangular section, open towards the outside, and inside which the guide supports 51 move.

[0046] Each guide support 51 comprises a guide face 51a and a mounting face 51b opposite the guide face 51a. The guide face 51a is capable of cooperating with the guide path 100. In particular, the guide face 51a of the guide support 51 comprises a protruding relief configured to move inside the groove of the guide path 100. Preferably, all the guide supports 51 present in the braiding zone 10 are identical.

[0047] Preferably, the braiding machine comprises a shaping mandrel 5, which is a form on which the intertwined threads rest to form the tight braid. The braiding machine in this case makes it possible to carry out so-called "over-braiding" processes. The braiding machine according to the invention is particularly advantageous in the case where it is desired to produce a braid having significant variations in section, and more precisely a braid whose perimeter of the section varies significantly. Unless otherwise stated, the sections are taken perpendicular to a longitudinal axis of the braided structure. Consequently, the advantages provided by the braiding machine according to the invention are particularly remarkable when said braiding machine comprises a shaping mandrel 5 whose shape has significant variations in thickness.

[0048] The braiding machine further comprises at least one drawing point located at a distance from the plate 1, and to which the threads coming from the supply spindles 30 movable along the guide path 100 are connected.

[0049] The braiding machine also includes a reserve area 20 circumferential to the braiding area 10, which includes a plurality of reserve supports 52. In the example illustrated in the Figures 1 and 2 , the reserve zone 20 is present around the outer edge of the braiding zone 10, which allows easy access to said reserve zone 20. However, it does not go beyond the scope of the invention if the reserve zone 20 goes around the inner edge of the braiding zone 10. Preferably, the reserve zone 20 is located in the same plane as the braiding zone 10. Preferably, the reserve zone 20 is adjacent to the guide path 100.

[0050] The reserve zone 20 is here in the form of several circumferential and concentric rings 21, 22, 23. Each ring 21, 22, 23 comprises at least one reserve support 52. Each reserve support 52 comprises a mounting face 52b. Preferably, all the reserve supports 52 present in the reserve zone 20 are identical.

[0051] As illustrated on the Figure 3, each wire feed spindle 30 comprises a holding portion 34 intended to accommodate a spool of wire, extended by a positioning element 35. The positioning element 35 is integral with the spindle 30. The positioning element 35 is configured to cooperate with the guide supports 51 and with the reserve supports 52. In particular, the positioning element 35 comprises a mounting face 35b opposite the holding portion 34, which is configured to cooperate with the mounting face 51b of the guide supports 51 and with the mounting face 52b of the reserve supports 52.

[0052] In particular, the mounting face 35b of the positioning element 35 may comprise a groove, and the mounting faces 51b and 52b of the guide supports 51 and reserve 52 may comprise a projecting relief, the groove of the mounting face 35b of the positioning element 35 being configured to cooperate with the projecting relief of the mounting faces 51b and 52b of the guide supports 51 and 52. The reverse is also possible.

[0053] Thus, each spindle 30 can be mounted on a guide support 51, by making the mounting face 35b of said spindle 30 cooperate with the mounting face 51b of said guide support 51, and can be mounted on a reserve support 52, by making the mounting face 35b of said spindle 30 cooperate with the mounting face 52b of said reserve support 52. Preferably, all the spindles 30 can be mounted on all the guide supports 51 and on all the reserve supports 52. Preferably, the mounting faces 51b of the guide supports 51 and the mounting faces 52b of the reserve supports 52 are identical.

[0054] The spindles 30 mounted on the guide supports 51 in the braiding zone 10 can participate in the braiding, that is to say that the thread(s) coming from the spools of said spindles 30 mounted on the guide supports 51 can be braided.

[0055] Thus, the spindles 30 mounted on the guide supports 51 are movable along the guide path 100.

[0056] The guide path 100 is configured to be traveled in a first direction of rotation, for example clockwise, by a first plurality of spindles 30 and in a second direction of rotation, for example counterclockwise, by a second plurality of spindles 30 in order to carry out the braiding. Thus, a first plurality of the guide supports 51 is configured to be movable at least in the clockwise direction and a second plurality of guide supports 51 is configured to be movable at least in the counterclockwise direction.

[0057] In the example illustrated on the Figures 1 and 2, the guide path 100 comprises two sub-guide paths 110 and 120 which regularly intersect, the first sub-guide path 110 being configured to be traveled by the first plurality of guide supports 51 on which the first plurality of spindles 30 are mounted and the second sub-path 120 being configured to be traveled by the second plurality of guide supports 51 on which the second plurality of spindles 30 are mounted. It is of course not outside the scope of the invention if the guide path comprises more than two sub-paths, for example if it is desired to produce a braided structure comprising several layers or having a complex binding weave, such as for example an interlock braid.

[0058] The braiding machine according to the invention comprises, in a well-known manner, a system for driving the guide supports 51. Preferably and in a well-known manner, the braiding zone 10 of the plate 1 comprises a plurality of notched wheels 11 configured to be driven in rotation in order to circulate the yarn supply spindles 30 along the guide path 100, as illustrated in the Figures 1 and 2 . Each notched wheel 11 preferably comprises four notches. The notched wheels 11 are preferably rotated in a well-known manner by means of gear trains controlled by one or more motors, the gear trains preferably being located on the face of the plate 1 opposite the face comprising the guide path 100 and the notched wheels 11. For example, the reserve area 20 does not comprise notched wheels, and the reserve supports 52 are not driven by notched wheels.

[0059] The braiding machine according to the invention preferably comprises a system for driving the reserve supports 52, capable of driving at least a portion of the reserve supports 52 circumferentially to the guide path 100. In the example illustrated in the figures 1 to 4 , the rotational drive system of the reserve supports 20 comprises at least one circumferential crown 21, 22 movable in rotation circumferentially to the braiding zone 10, that is to say movable in rotation along the inner or outer edge of the guide path 100. The reserve zone 20 further preferably comprises at least one fixed circumferential crown 23.

[0060] Preferably, the reserve zone 20 comprises at least one first circumferential crown 21 movable in a first direction of rotation, for example movable in the clockwise direction, and at least one second circumferential crown 22 movable in a second direction of rotation opposite to the first direction of rotation, for example movable in the counterclockwise direction.

[0061] The first circumferential crown(s) 21 movable in the clockwise direction can accompany the movement of the first plurality of guide supports 51 movable on the guide path 100 in the clockwise direction, and consequently the movement of the first plurality of spindles 30 mounted on the first plurality of guide supports 51 and therefore movable in the clockwise direction. Consequently, if it is desired to remove from the braiding a spindle 30 movable in the clockwise direction to place it in the reserve zone 20, for example to produce a portion of the braided structure of smaller section, but without risking that the thread coming from said movable spindle 30 creates a singularity in the braiding or an undesired tension, it is possible to place said spindle 30 on the first crown 21 movable in the clockwise direction by making the positioning element 35 of said spindle 30 cooperate with a reserve support 52 present on the first crown 21.Thus, the thread from said spindle 30 will remain mobile in a clockwise direction in order to accompany the end of its braiding to the braided structure being produced, even if the spindle 30 has been removed from the braiding zone and no longer participates in the braiding.

[0062] In a comparable manner, the second circumferential crown(s) 22 movable in the counterclockwise direction can accompany the movement of the second plurality of guide supports 51 movable on the guide path 100 in the counterclockwise direction, and consequently the movement of the second plurality of spindles 30 mounted on the second plurality of guide supports 51 and therefore movable in the counterclockwise direction.Consequently, if it is desired to remove from the braiding a spindle 30 movable in the counterclockwise direction to place it in the reserve zone 20, for example to produce a portion of the braided structure of smaller section, but without risking that the thread coming from said movable spindle 30 creates a singularity in the braiding or an undesired tension, it is possible to place said spindle 30 on the second ring 22 movable in the counterclockwise direction by making the positioning element 35 of said spindle 30 cooperate with a reserve support 52 present on the second ring 22. Thus, the thread coming from said spindle 30 will remain movable in the counterclockwise direction in order to accompany the end of its braiding to the braided structure being produced, even if the spindle 30 has been removed from the braiding zone and no longer participates in the braiding.

[0063] Thus, preferably, the movable circumferential rings 21 and 22 are preferably intended to accommodate the spindles 30 temporarily and for a short period, before said spindles 30 are arranged on the fixed ring(s) 23 for a longer period. The movable circumferential rings 21 and 22 then correspond to a transition zone between the braiding zone 10 and the fixed parts of the reserve zone 20. Preferably, the arrangement of a spindle 30 on one of the movable rings 21, 22 is therefore only temporary, for a period preferably corresponding to the time necessary for the thread from said spindle, which is being intermingled with the other threads at the time when said spindle is removed from the braiding zone, to be entirely braided into the braided structure to be produced. This greatly reduces the risk of singularities in the final braided structure.

[0064] As illustrated in the example of the Figure 4, the machine according to the invention preferably comprises a global drive system which comprises on the one hand the drive system 71 of the guide supports 51 and on the other hand the drive system 73, 74, 76, 21, 22 of the reserve supports 52.

[0065] In the example illustrated on the figures 1 to 4 , the rotational drive system of the movable crowns 21 and 22, which belongs to the drive system of the reserve supports 52, can be mechanically linked to the rotational drive system of the notched wheels 11, which belongs to the drive system of the guide supports 51. For example, as illustrated in the Figure 4, the rotational drive system 71 of each notched wheel 11, preferably in the form of gears, is connected by a belt 72 to a pinion 73 belonging to the reserve zone 20. The movable crowns 21, 22 each comprise a circumferential rack 74, 76 actuated directly or indirectly by the pinion 73. Thus, in the example illustrated on the Figure 4 , the movement of the drive system 71 of the guide supports 51 is transmitted to the drive system 21, 22, 73, 74, 76 of the reserve supports 52 by means of a movement transmission system in the form of a belt 72.

[0066] Preferably, in order to further limit the risk of singularity in the braiding following a change in the number of spindles 30 participating in the braiding, the overall drive system is configured so that the angular speed of at least a portion of the reserve supports 52 is a function of the angular speed of at least a portion of the guide supports 51, so that the movement of at least a portion of the reserve supports 52 accompanies the movement of at least a portion of the guide supports 51. Preferably, the angular speed of at least a portion of the reserve supports 52 is equal to the angular speed of at least a portion of the guide supports 51, that is to say that at least a portion of the reserve supports 52 travels the same angular extent relative to the central axis of the machine as at least a portion of the guide supports for a given duration.The central axis of the machine can be defined for example as the axis passing through the draw point or through the center of the shaping mandrel of the machine, and passing through the center of the main guide path. The angular velocity is expressed in radians per second and the angular extent in radians, the reference center being a point on the central axis of the braiding machine.

[0067] Thus, at least a portion of the guide supports completes a full revolution along the guide path 100 when at least a portion of the guide supports 51 completes a full revolution of the guide path 100.

[0068] In the example illustrated on the figures 1 to 4, the movable crowns 21, 22 make a complete revolution around the guide path 100 when at least a part of the spindles 30 make a complete revolution of the guide path 100. Thus, the spindles 30 present on the first crown 21 movable in the clockwise direction follow the movement of the spindles 30 movable in the clockwise direction on the guide path 100, and the spindles 30 present on the second crown 22 movable in the counterclockwise direction follow the movement of the spindles 30 movable in the counterclockwise direction on the guide path 100. The reduction ratio between the rotation of the notched wheels 11 and the rotation of each circumferential crown 21, 22 must therefore preferably correspond to half the value of the number of notched wheels 11 per circumferential row. In the example illustrated in the Figure 1, the braiding machine comprises a single row of notched wheels 11 comprising sixteen notched wheels 11. Thus, the value of the reduction ratio between the rotation of each gear 71 of said notched wheels 11 and the rotation of the rack 74, 76 of each movable crown 21, 22 will be eight.

[0069] The transfer of the spindles 30 between the braiding zone 10 and the reserve zone 20, or between the different parts or circumferential crowns 21, 22, 23 of the reserve zone 20, can be carried out manually or by one or more robotic arms 8 comprising a hooking and unhooking clamp. These robotic arms 8 are for example fixed around the braiding zone 10 and the reserve zone 20.

[0070] The braiding machine may also comprise a cutting system 9 configured to cut the threads coming from the spindles 30 arranged in the reserve zone 20, and in particular the threads coming from the spindles 30 arranged in the fixed parts of the reserve zone 20, in order to avoid any risk of tangling of one of the threads not participating in the braiding with the threads participating in the braiding.

[0071] We will now describe in relation to the schematic figures 5 to 7 an example of a braiding method according to the first aspect of the invention for producing a braided structure 300 having significant variations in section, and more precisely significant variations in the perimeter of the section. Thus, the braided structure 300 to be produced comprises in its length a first zone having a first section perimeter, a transition zone, and a second zone having a second section perimeter, the second perimeter being different from the first perimeter. In the example illustrated in the figures 5 to 7 , the first perimeter is greater than the second perimeter and the transition zone has a section whose perimeter decreases regularly between the first zone and the second zone.

[0072] In the example illustrated on the figures 5 to 7, the braiding is carried out on a shaping mandrel 5 which generally has the shape of the braided structure 300 to be produced. It is of course not outside the scope of the invention if the braiding is not carried out on a shaping mandrel. The threads coming from the spools of the thread supply spindles are fixed to a drawing point.

[0073] We begin by producing the first zone of the braided structure 300 by circulating a first number of yarn supply spindles 30 along the guide path 100, inside the braiding zone 10. Thus, the yarns 31 from the bobbins carried by this first number of spindles 30 intertwine around the shaping mandrel 5 so as to produce the first zone of the braided structure 300, as illustrated in the Figure 5 .

[0074] In order to produce the transition zone of the braided structure 300 whose section perimeter decreases while maintaining a density of threads and angles between the threads similar to the density of threads and angles between the threads of the first zone of the braided structure 300, thread supply spindles 30 are gradually removed from the braiding zone 10 to place them in the reserve zone 20. Thus, these supply spindles 30 are removed from the guide path 100 manually, or automatically. Preferably, as illustrated in the Figure 6, a robotic arm 8 as previously described grasps a spindle 30 to be removed from the guide path 100 and separates it from the guide support 51 on which it was mounted by separating the positioning element 35 of said spindle 30 from the mounting surface 51b of the guide support 51. Then, the robotic arm 8 moves the spindle 30 to the reserve area 20, to mount it with one of the reserve supports 52 present in the reserve area 20 by assembling the positioning element 35 of said spindle 30 with the mounting face 52b of said reserve support 52.

[0075] In the example illustrated on the Figure 6, in order to produce the transition zone and then the second zone of the braided structure 300, the robotic arms 8 gradually remove a portion of the spindles 30 movable in the clockwise direction on the guide path 100 and a portion of the spindles 30 movable in the counterclockwise direction on the guide path 100. The spindles 30 movable in the clockwise direction which are removed are then arranged on the reserve supports 52 of the first ring 21 movable in the clockwise direction and the spindles 30 movable in the counterclockwise direction which are removed are then arranged on the reserve supports 52 of the second ring 22 movable in the counterclockwise direction.When a portion of the spindles 30 is arranged on the movable crowns 21 and 22, the threads 32 coming from said spindles 30 arranged on the movable crowns 21 and 22 no longer participate in the braiding but are in a transition stage, that is to say they are still being intermingled with other threads without yet being completely braided and tightened. The rotation of the movable crowns 21, 22 makes it possible to accompany this transition stage of the threads 32 coming from the spindles 30 leaving the guide path 100 and the braiding zone 10.

[0076] When the yarn 32 from a spindle 30 arranged on a movable crown 21 or 22 has completed the transition step, i.e. it is no longer being intertwined, the spindle 30 can be removed from the movable crown 21 or 22 to be arranged on the fixed circumferential crown 23, manually or automatically. Preferably, as illustrated in the Figure 7, the robotic arm 8 grasps a spindle 30 to be removed from a movable crown 21 or 22 and separates it from the reserve support 52 on which it was mounted by separating the positioning element 35 of said spindle 30 from the mounting surface 52b of the reserve support 52. Then, the robotic arm 8 moves the spindle 30 towards the fixed crown 23, to mount it with one of the reserve supports 52 present on said fixed crown 23 by assembling the positioning element 35 of said spindle 30 with the mounting face 52b of said reserve support 52 of the fixed crown 23. The threads 33 from the spindles arranged on the fixed crown 23 can be cut by the cutting device 9, in order to avoid any risk of tangling of one of the threads 33 not participating in the braiding with the threads 31 participating in the braiding.

[0077] When the braiding of the transition zone of the structure 300 is completed, there remains only a second number of spindles 30 movable along the guide path 100, inside the braiding zone 10. In the example illustrated in the figures 5 to 7 , the second number of 30 movable spindles is less than the first number of 30 movable spindles when braiding the first zone.

[0078] The second number of spindles 30 movable on the guide path 100 then makes it possible to braid the second zone of the braided structure 300, the threads 31 coming from the bobbins carried by this second number of spindles 30 intertwining around the shaping mandrel 5 as illustrated in the Figure 7 to create the 300 braided structure.

[0079] In a variant not illustrated, a braided structure can be produced having along its length a first zone having a first section perimeter, a transition zone and a second zone having a second section perimeter, as in the example illustrated in the figures 5 to 7 , but further comprising a second transition zone and a third zone having a third section perimeter. The third perimeter of the third section is here greater than the second perimeter of the second section, and may also be less than or greater than the first perimeter of the first section. It is of course not outside the scope of the invention if the third section perimeter is less than the first and second section perimeters.

[0080] In this variant, the first zone, the transition zone and the second zone are produced as described above. In order to produce the second transition zone of the braided structure, located in the extension of the second zone and whose cross-sectional perimeter increases, while maintaining a yarn density and angles between the yarns similar to the yarn density and angles between the yarns of the first zone and the second zone already braided, yarn supply spindles present in the reserve zone are gradually transferred to the braiding zone to make them participate in the braiding.

[0081] Thus, these feed spindles are removed from the fixed ring of the reserve area manually, or automatically. Preferably, a robotic arm as described previously grips a spindle to be removed from the fixed ring and separates it from the reserve support on which it was mounted by separating the positioning element of said spindle from the mounting surface of the reserve support. Then, the robotic arm moves the spindle to one of the movable parts of the reserve area, to mount it with one of the reserve supports present on the first or second movable ring by assembling the positioning element of said spindle with the mounting face of said reserve support.In our example variant, in order to create the second transition zone and then the third zone of the braided structure, the robotic arms place part of the spindles present on the fixed crown on the mobile crown in a clockwise direction and part of the spindles present on the fixed crown on the mobile crown in an anticlockwise direction.

[0082] When the threads from the spindles positioned on the movable crowns accompany the movement of the threads being braided, the robotic arm(s) progressively move the spindles arranged on the movable crown clockwise on the sub-guide path(s) traveled by clockwise guide supports, and the spindles arranged on the movable crown counterclockwise on the sub-guide path(s) traveled by counterclockwise guide supports, by mounting the positioning element of said spindles with the mounting faces of said guide supports not carrying spindles. Thus, the threads from the spindles mounted on the guide supports participate in the braiding.

[0083] The prior passage of the yarn feed spindles over moving parts of the reserve area before their participation in the braiding makes it easier to introduce the yarns from the said added spindles into the braiding.

[0084] When the braiding of the second transition zone of the structure is completed, there is therefore a third number of spindles, greater than the second number of spindles, movable along the guide path, inside the braiding zone.

[0085] The third number of movable spindles on the guide path then allows the third zone of the braided structure to be braided, the threads from the bobbins carried by this third number of spindles intertwining around the shaping mandrel.

[0086] The term "yarn" as used in this application may refer to a single yarn or a single fiber, but may also refer to a strand or a braid.

[0087] In particular, the threads may be carbon fibers, ceramic fibers, or a mixture of carbon fibers and ceramic fibers. The braided structure according to the method of the invention may be a fibrous structure, which may optionally be consolidated or densified by a matrix in order to form the fibrous reinforcement of a composite material part. The braided structure according to the method of the invention may thus form, for example, all or part of the fibrous reinforcement of a composite material part for the automotive, aeronautical or space industries. In particular, the braided structure obtained may form, for example, the fibrous reinforcement of a divergent part or a rocket engine nozzle.

[0088] The braided structure according to the method of the invention can also allow the formation of straps or ropes.

[0089] A second aspect of the invention is presented in relation to the figures 8 to 16 .

[0090] THE figures 8 and 9 schematically illustrate an example of a braiding machine according to the second aspect of the invention for producing a braided structure. The braiding machine comprises a plate 61 and a plurality of yarn feed spindles 63. The plate 61 is preferably horizontal, in order to facilitate its maintenance and that of the yarn feed spindles 63. However, it does not depart from the scope of the invention if the plate 61 is vertical or inclined.

[0091] The plate 61 comprises a braiding zone 610 and a reserve zone in the form of several reserve regions 620 distributed along the outer edge of the braiding zone 610, and separated from each other or not. It is of course not outside the scope of the invention if the reserve zone does not belong to the plate comprising the braiding zone.

[0092] It is of course not beyond the scope of the invention if the braiding machine has only one continuous reserve zone circumferential to the braiding zone. It is also not beyond the scope of the invention if the circumferential reserve zone is mobile in rotation around the braiding zone, for example in the case where the reserve zone is a continuous crown mobile in rotation around the braiding zone.

[0093] The reserve zone, whether or not in the form of several disjointed regions, is preferably located on the outside of the braiding zone 610, i.e. around the main guide path 6100, in order to facilitate its accessibility. However, it does not depart from the scope of the invention if the reserve zone, whether or not in the form of several disjointed regions, is located on the inside of the braiding zone 610.

[0094] The braiding zone 610 comprises a main guide path 6100. The yarn supply spindles 63 movable along this main guide path 6100 participate in the braiding of the braided structure. The main guide path 6100 is therefore configured to be traveled in the clockwise direction by a first plurality of spindles 63, and in the counterclockwise direction by a second plurality of spindles 63. In the example illustrated in the figures 8 and 9, the main guide path 6100 comprises two sub-guide paths 6110 and 6120 which regularly intersect, the first sub-guide path 6110 being configured to be traveled by the first plurality of spindles 63 and the second sub-path 6120 being configured to be traveled by the second plurality of spindles 63. It is of course not outside the scope of the invention if the main guide path comprises more than two sub-paths, for example if it is desired to produce a braided structure comprising several layers or having a complex binding weave, such as for example an interlock braid.

[0095] The reserve regions 620 each comprise a secondary guide path 6200. Unlike the yarn supply spindles 63 present in the braiding zone 610, the yarn supply spindles 63 present in the secondary guide path 6200 of these reserve regions 620, or more generally of the reserve zone, do not participate in the braiding of the braided structure. Each secondary guide path 6200 is therefore configured to maintain one or more supply spindles in one of the reserve regions 620, that is to say outside the braiding zone 610 and the main guide path 6100. Preferably, there is no direct communication between the different secondary guide paths.

[0096] Each yarn feed spindle 63 carries a spool of braiding yarns and comprises a guide support capable of moving along the main 6100 and secondary 6200 guide paths. In a well-known manner, each spool of braiding yarns is connected to a yarn tension and return management system.

[0097] The braiding machine further comprises at least one drawing point located at a distance from the plate 61, and to which the threads from the bobbins carried by the supply spindles 63 movable along the main guide path 6100 are connected.

[0098] Preferably, the braiding machine comprises a shaping mandrel 65, which is a form on which the intertwined threads rest to form the tight braid. The braiding machine in this case makes it possible to carry out so-called "over-braiding" processes. The braiding machine according to the invention is particularly advantageous in the case where it is desired to produce a braid having significant variations in section, and more precisely a braid whose perimeter of the section varies significantly. Consequently, the advantages provided by the braiding machine according to the invention are particularly remarkable when said braiding machine comprises a shaping mandrel 65 whose shape has significant variations in thickness.

[0099] Preferably, the main guide paths 6100 and secondary guide paths 6200 are machined in the mass of the plate 61 in the form of grooves, having for example a substantially rectangular section, open towards the outside, and inside which the guide supports of the feed spindles 63 move.

[0100] Preferably and in a well-known manner, the braiding area 610 of the tray 61 comprises a plurality of main notched wheels 611 configured to be rotated in order to circulate the yarn feed spindles 63 along the main guide path 6100, as illustrated in the Figure 10 .

[0101] Preferably, each reserve region 620 of the tray 61 also comprises at least one secondary notched wheel 622 configured to be rotated in order to circulate one or more yarn supply spindles 63 in the secondary guide path 6200 of said reserve region 620, as illustrated in the Figure 10 . Preferably, each reserve region 620 and each secondary guide path 6200 comprises a single secondary notched wheel 622. Preferably, each secondary notched wheel 622 is adjacent to a primary notched wheel 611. When a spindle 63 is held in the reserve region 620, on a secondary guide path 6200, there is preferably no passage of the spindle 63 from one notched wheel 622 to another. Thus, preferably, the spindle can travel along the secondary guide path 6200, but only over a region of limited angular extent.

[0102] As illustrated on the Figure 10, each main 611 or secondary 622 notched wheel preferably comprises four notches. The main 611 or secondary 622 notched wheels are preferably driven in rotation in a well-known manner by means of gear trains controlled by one or more motors.

[0103] Preferably, each secondary notched wheel 622 of the braiding machine is linked to a rotation decoupling system, configured to make the rotation of said secondary notched wheel 622 independent of the rotation of the adjacent main notched wheel 611.

[0104] Each secondary guide path of the reserve zone is connected to the braiding zone 610 by means of a switching element. This switching element is movable between a first position making it possible to isolate the secondary guide path 6200 of said reserve zone 620 from the main guide path 6100, and a second position making it possible to connect the secondary guide path 6200 of said reserve zone 620 to the main guide path 6100, in order to allow the passage of at least one feed spindle 63 between the main guide path 6100 and the secondary guide path 6200. Thus, two branches 6101 and 6102 of the main guide path 6100 and two branches 6201 and 6202 of the secondary guide path 6200 open onto each switching element.

[0105] Several types of switching element are possible within the framework of the present invention.

[0106] According to a first embodiment of the invention, the switching element is movable in translation, in accordance with the examples illustrated in the figures 10 to 12 .

[0107] In the example illustrated on the Figures 10 and 11 , the switching element 641 is in the form of a flat solid movable in translation in a translation direction D T1 tangent to the junction between the reserve zone 620 and the braiding zone 610. The switching element 641 comprises grooves 6411, 6412, 6413 and 6414 of substantially rectangular section, open towards the outside, and configured to allow the passage of a feed spindle guide support 63.

[0108] The switching element 641 comprises a first groove 6411, a second groove 6412, a third groove 6413 and a fourth groove 6414. As illustrated in Figures 10 and 11, the first groove 6411 and the second groove 6412 do not have a common intersection, so that when the switching element 641 is in its first position, the first groove 6411 belongs entirely to the main guide path 6100 and the second groove 6412 belongs entirely to the secondary guide path 6200. Thus, when the switching element 641 is in its first position, the first groove 6411 connects the two branches 6101 and 6102 of the main guide path 6100 and the second groove 6412 connects the two branches 6201 and 6202 of the secondary guide path 6200.

[0109] As illustrated on the Figures 10 and 11 , the third groove 6413 and the fourth groove 6414 of the switching element 641 intersect, so that when the switching element 641 is in its second position, illustrated in the Figure 11, the third groove 6413 connects the first branch 6101 of main guide path 6100 to the second branch 6202 of secondary guide path 6200 and the fourth groove 6414 connects the second branch 6102 of main guide path 6100 to the first branch 6201 of secondary guide path 6200.

[0110] Preferably, the first and second grooves 6411 and 6412 have a curved path, while the third and fourth grooves 6413 and 6414 have a straight path.

[0111] In the example illustrated on the Figure 12, the switching element 642 is in the form of a flat solid movable in translation in a translation direction D T2 perpendicular to the junction between the reserve zone 620 and the braiding zone 610. The switching element 642 comprises grooves 6421, 6422, 6423 and 6424 of substantially rectangular section, open towards the outside, and configured to allow the passage of a feed spindle guide support 63.

[0112] The switching element 642 comprises a first groove 6421, a second groove 6422, a third groove 6423 and a fourth groove 6424. As illustrated in the Figure 12 , the first groove 6421 and the second groove 6422 are isolated from each other and do not have a common intersection, so that when the switching element 642 is in its first position, illustrated in the Figure 12, the first groove 6421 belongs entirely to the main guide path 6100 and the second groove 6422 belongs entirely to the secondary guide path 6200. Thus, when the switching element 642 is in its first position, the first groove 6421 connects the two branches 6101 and 6102 of the main guide path 6100 and the second groove 6422 connects the two branches 6201 and 6202 of the secondary guide path 6200.

[0113] As illustrated on the Figure 12, the third groove 6423 and the fourth groove 6424 of the switching element 642 intersect, so that when the switching element 642 is in its second position, the third groove 6423 connects the first branch 6101 of the main guide path 6100 to the second branch 6202 of the secondary guide path 6200 and the fourth groove 6424 connects the second branch 6102 of the main guide path 6100 to the first branch 6201 of the secondary guide path 6200.

[0114] Preferably, the first and second grooves 6421 and 6422 have a curved path, while the third and fourth grooves 6423 and 6424 have a straight path.

[0115] In the example illustrated on the Figures 13A And 13B, the switching element 643 is in the form of two flat solids 643a, 643b movable in translation in a translation direction perpendicular to the junction between the reserve zone 620 and the braiding zone 610, the first solid 643a translating in a direction opposite to the second solid 643b. Each solid 643a, 643b of the switching element 643 has a rounded edge opposite a straight edge.

[0116] When the switching element 643 is in the first position, the straight edge of the first solid 643a is in contact with the straight edge of the second solid 643b, such that the rounded edge of the first solid 643a defines a portion of the main guide path 6100 by connecting the two branches 6101 and 6102 of the main guide path 6100 and such that the rounded edge of the second solid 643b defines a portion of the secondary guide path 6200 by connecting the two branches 6201 and 6202 of the secondary guide path 6200.When the switching element 643 is in the second position, the rounded edge of the first solid 643a is in contact with one of the walls of the main guide path 6100 and the rounded edge of the second solid 643b is in contact with one of the walls of the secondary guide path 6200, so that the gap generated between the straight edge of the first solid 643a and the straight edge of the second solid 643b allows the passage of a feed spindle 63 from the first branch 6101 of the main guide path 6100 to the second branch 6202 of the secondary guide path 6200, and from the second branch 6102 of the main guide path 6100 to the first branch 6201 of the secondary guide path 6200.

[0117] According to a second embodiment of the invention, the switching element is movable by rotation, in accordance with the examples illustrated in the figures 14 to 16 .

[0118] In the example illustrated on the Figure 14, the switching element 644 is in the form of a solid circular plate movable in rotation about an axis of rotation perpendicular to the plate 61. The switching element 644 comprises grooves 6441, 6442, 6443 and 6444 of substantially rectangular section, open towards the outside, and configured to allow the passage of a feed spindle foot 63.

[0119] The switching element 644 comprises a first groove 6441, a second groove 6442, a third groove 6443 and a fourth groove 6444. As illustrated in the Figure 14, the first groove 6441 and the second groove 6442 do not have a common intersection, so that when the switching element 644 is in its first position, the first groove 6441 belongs entirely to the main guide path 6100 and the second groove 6442 belongs entirely to the secondary guide path 6200. Thus, when the switching element 644 is in its first position, the first groove 6441 connects the two branches 6101 and 6102 of the main guide path 6100 and the second groove 6442 connects the two branches 6201 and 6202 of the secondary guide path 6200.

[0120] As illustrated on the Figure 14 , the third groove 6443 and the fourth groove 6444 of the switching element 644 intersect, so that when the switching element 644 is in its second position, illustrated in the Figure 14, the third groove 6443 connects the first branch 6101 of main guide path 6100 to the second branch 6202 of secondary guide path 6200 and the fourth groove 6444 connects the second branch 6102 of main guide path 6100 to the first branch 6201 of secondary guide path 6200.

[0121] Preferably, the first and second grooves 6441 and 6442 have a curved path, while the third and fourth grooves 6443 and 6444 have a straight path.

[0122] In the example illustrated on the Figure 15, the switching element 645 is in the form of a flat solid of generally triangular shape connected by a pivot connection to the plate 61 and movable in rotation about an axis of rotation perpendicular to the plate 61. When the switching element 645 is in the first position, the tip of the flat solid is positioned between the main guide path 6100 and the secondary guide path 6200, so that a first edge of the flat solid defines a part of the main guide path 6100 by connecting the two branches 6101 and 6102 of the main guide path 6100 and a second edge of the flat solid, opposite the first edge of said solid, defines a part of the secondary guide path 6200 by connecting the two branches 6201 and 6202 of the secondary guide path 6200.When the switching element 645 is in the second position, the tip of the flat solid is positioned in contact with one of the walls of the main guide path 6100, or in contact with one of the walls of the secondary guide path 6200 as illustrated in the . Figure 15 . When the tip of the flat solid is positioned in contact with one of the walls of the main guide path 6100, the gap created between said flat solid and the secondary guide path 6200 allows the passage of a feed spindle 63 between the first branch 6201 of the secondary guide path 6200 and the second branch 6102 of the main guide path 6100. When the tip of the flat solid is positioned in contact with one of the walls of the secondary guide path 6200, as illustrated in the Figure 15, the gap cleared between said flat solid and the main guide path 6100 allows the passage of a feed spindle 63 between the second branch 6202 of the secondary guide path 6200 and the first branch 6101 of the main guide path 6100.

[0123] In the example illustrated on the figure 16 , the switching element 646 is in the form of four flat solids 646a, 646b, 646c, 646d of generally triangular shape and movable in rotation about an axis of rotation perpendicular to the plate 61. The first solid 646a is present on the second branch 6102 of the main guide path 6100. The second solid 646b is present on the second branch 6202 of the secondary guide path 6200. The third solid 646c is present on the first branch 6201 of the secondary guide path 6200. The fourth solid 646d is present on the first branch 6101 of the main guide path 6100.

[0124] Thus, when the switching element 646 is in the first position, the first solid 646a and the fourth solid 646d each define a wall of the main guide path 6100 by blocking the passage to the secondary guide path 6200. When the switching element 646 is in the second position, according to a first mode, the first solid 646a pivots to connect the second branch 6102 of the main guide path 6100 to the first branch 6201 of the secondary guide path 6200, the second solid 646b and the third solid 646c being positioned so as to allow this connection, as illustrated in the figure 16 . According to a second mode, the fourth solid 646d pivots to connect the first branch 6101 of the main guide path 6100 to the second branch 6202 of the secondary guide path 6200, the second solid 646b and the third solid 646c being positioned so as to allow this connection.

[0125] In each of the preceding examples, the switching element may be controlled manually, for example by means of a joystick, or automatically, for example by means of a control unit configured to actuate said switching element.

[0126] The switching element(s) may be connected to the gear system enabling the movement of the feed spindles 63, for example to the gear train driving the rotation of the notched wheels 611 or 622. The use of a rotating switching element is particularly advantageous in this case, this configuration allowing a simplified mechanism for actuating the switching element and easy integration under the plate 61 of the braiding machine.

[0127] We will now describe in relation to the figures 8 and 9an example of a braiding method according to the second aspect of the invention for producing a braided structure 6300 having significant variations in section, and more precisely significant variations in the perimeter of the section. Thus, the braided structure 6300 to be produced comprises in its length a first zone having a first section perimeter, a transition zone, and a second zone having a second section perimeter, the second perimeter being different from the first perimeter. Unless otherwise stated, the sections are taken perpendicular to a longitudinal axis of the braided structure. In the example illustrated in the figures 8 and 9 , the first perimeter is greater than the second perimeter and the transition zone has a section whose perimeter decreases regularly between the first zone and the second zone.

[0128] In the example illustrated on the figures 8 and 9, the braiding is carried out on the shaping mandrel 65 which generally has the shape of the braided structure 6300 to be produced. It is of course not outside the scope of the invention if the braiding is not carried out on a shaping mandrel. The threads coming from the spools of the thread supply spindles 63 are fixed to a drawing point.

[0129] The first zone of the braided structure 6300 is produced by circulating a first number of yarn supply spindles 63 along the main guide path 6100, inside the braiding zone 610. Thus, the yarns 631 from the bobbins carried by this first number of spindles 63 intertwine around the shaping mandrel 65 so as to produce the first zone of the braided structure 6300, as illustrated in FIG. figure 8 .

[0130] In order to produce the transition zone of the braided structure 6300 whose section perimeter decreases while maintaining a density of threads and angles between the threads similar to the density of threads and angles between the threads of the first zone of the braided structure 6300, thread supply spindles 63 are gradually removed from the braiding zone 610 to place them in the reserve zone 620. Thus, these supply spindles 63 leave the main guide path 6100 by means of a switching element to be held in a secondary guide path 6200, so as to no longer participate in the braiding of the structure 6300. Consequently, the threads 632 coming from the spools carried by the spindles 63 held in the reserve zone 620 are no longer braided.

[0131] These threads 632 can be cut by a cutting device (not shown) configured to cut the thread 632 coming from a supply spindle 63 present in the reserve zone 620 while the braiding operation continues, in order to avoid any risk of tangling of one of these threads 632 not participating in the braiding with the threads 631 participating in the braiding.

[0132] When the braiding of the transition zone of the structure 6300 is completed, there remains only a second number of yarn supply spindles 63 movable along the main guide path 6100, inside the braiding zone 610. In the example illustrated in the figures 8 and 9 , the second number of movable feed spindles 63 is less than the first number of movable spindles 63 when braiding the first zone.

[0133] The second number of wire feed spindles 63 movable on the main guide path 6100 then makes it possible to braid the second zone of the braided structure 6300, the wires 631 coming from the bobbins carried by this second number of spindles 63 intertwining around the shaping mandrel 65 as illustrated in the figure 9 .

[0134] In a variant not illustrated, a braided structure can be produced having along its length a first zone having a first section perimeter, a transition zone and a second zone having a second section perimeter, as in the example illustrated in the figures 8 and 9, but further comprising a second transition zone and a third zone having a third section perimeter. The third perimeter of the third section is here greater than the second perimeter of the second section, and may also be less than or greater than the first perimeter of the first section. It is of course not outside the scope of the invention if the third section perimeter is less than the first and second section perimeters.

[0135] In this variant, the first zone, the transition zone and the second zone are produced as described above. In order to produce the second transition zone of the braided structure, located in the extension of the second zone and whose cross-sectional perimeter increases, while maintaining a yarn density and angles between the yarns similar to the yarn density and angles between the yarns of the first zone and the second zone already braided, yarn feed spindles present in the reserve zone are gradually transferred to the braiding zone to make them participate in the braiding. Thus, these feed spindles leave, by means of a switching element, the secondary guide path in which they were held to be introduced onto the main guide path, in order to participate in the braiding of the structure.Therefore, the threads from the bobbins carried by the added spindles on the main guide path are braided with the threads from the bobbins carried by the second number of spindles already present on the main guide path.

[0136] When the braiding of the second transition zone of the structure is completed, a third number of yarn feed spindles are movable along the main guide path, within the braiding zone. The third number of yarn feed spindles movable on the main guide path 6100 then allows the third zone of the braided structure to be braided, the yarns from the bobbins carried by this third number of spindles intertwining around the shaping mandrel.

[0137] The term "yarn" as used in this application may refer to a single yarn or a single fiber, but may also refer to a strand or a braid.

[0138] In particular, the threads may be carbon fibers, ceramic fibers, or a mixture of carbon fibers and ceramic fibers. The braided structure according to the method of the invention may be a fibrous structure, which may optionally be consolidated or densified by a matrix in order to form the fibrous reinforcement of a composite material part. The braided structure according to the method of the invention may thus form, for example, all or part of the fibrous reinforcement of a composite material part for the automotive, aeronautical or space industries. In particular, the braided structure obtained may form, for example, the fibrous reinforcement of a divergent part or a rocket engine nozzle.

[0139] The braided structure according to the method of the invention can also allow the formation of straps or ropes.

Claims

1. Braiding machine comprising: - a plurality of yarn feed spindles (30) connected to guide supports (51) and movable along a guide path (100) so as to participate in the braiding, all or part of the spindles (30) being integral with a positioning element (35) cooperating with a corresponding guide support (51) and removable relative to the latter, - a plurality of reserve supports (52) located outside the guide path (100), said reserve supports (52) being able to receive yarn feed spindles (30) placed in reserve so as to interrupt their participation in the braiding, the positioning elements (35) being able to cooperate with the reserve supports (52) to carry out this placing in reserve, the braiding machine being characterized in thatit comprises a drive system (73, 74, 76, 21, 22) for the reserve supports (52) capable of driving at least a portion of the reserve supports (52) circumferentially to the guide path (100).

2. Machine according to claim 1, in which the drive system (73, 74, 76, 21, 22) of the reserve supports (52) comprises at least one first crown (21) circumferential to the guide path (100) and capable of rotating in a first direction of rotation and at least one second crown (22) circumferential to the guide path (100) and capable of rotating in a second direction of rotation opposite to the first direction of rotation, each first or second crown (21, 22) carrying one or more reserve supports (52).

3. Machine according to claim 1 or 2, wherein the reserve supports (52) are present around the guide path (100).

4. Machine according to any one of claims 1 to 3, said machine comprising a global drive system comprising the drive system (73, 74, 76, 21, 22) of the reserve supports (52) and a drive system (71) of the guide supports (51), the global drive system being configured so that the angular speed of at least a part of the reserve supports (52) is a function of the angular speed of at least a part of the guide supports (51) so that the movement of at least a part of the reserve supports (52) accompanies the movement of at least a part of the guide supports (51).

5. Machine according to claim 4, wherein the overall drive system comprises a transmission system (72) configured to transmit the movement of a drive system (71) of the guide supports (51) to the drive system (73, 74, 76, 21, 22) of the reserve supports (52). ​6. Machine according to any one of claims 1 to 5, said machine further comprising a shaping mandrel (5) on which the braiding is intended to be carried out.

7. Machine according to any one of claims 1 to 6, said machine further comprising a robotic arm (8) configured to move at least one spindle (30) between a guide support (51) and a reserve support (52).

8. Machine according to any one of claims 1 to 7, said machine further comprising a cutting device (9) configured to cut a wire (32, 33) coming from a supply spindle (30) whose positioning element (35) cooperates with a reserve support (52).

9. A method of braiding a braided structure (300) comprising a first zone having a first section and a second zone having a second section different from the first section, the method implementing a machine according to any one of claims 1 to 8 and comprising: - braiding the first zone of the braided structure (300) with a first number of yarn feed spindles (30) movable along the guide path (100), and - braiding the second zone of the braided structure (300) with a second number of yarn feed spindles (30) movable along the guide path (100), the second number of spindles being different from the first number of spindles by virtue of the movement of spindles (30) between the guide supports (51) and the reserve supports (52) by cooperation of the positioning element (35) of said moved spindles with the guide supports (51) or reserve supports (52).