EP0678611B1 - Needle head and machine for producing a plate-shaped armature for a piece of composite material - Google Patents

Description

The present invention relates to a tapping head which can be used in a machine for making a frame in plate form for a piece of composite material, formed of said reinforcement embedded in a hardened matrix, said reinforcement comprising overlapping plies of wire (in carbon, glass, boron, in particular), and a machine comprising such a stitching head.

More particularly, although not exclusively, such pieces of composite material are used in the fields aeronautics and space by virtue of their excellent properties of resistance to mechanical stress and / or thermal.

We know many processes and machines to obtain said pieces of composite material, and in particular their frame. Generally, we start by realizing the reinforcement from fibers (threads), in particular mineral, distributed in at least two directions, after what we introduce the material of the matrix in the reinforcement, and said material is hardened to form said matrix and, thus, said composite part.

• on réalise au moins certaines desdites nappes en déposant des tronçons de fil rectilignes faisant partie d'un fil continu sur un support, en tendant chaque tronçon de fil entre deux points de fixation en position des extrémités dudit tronçon, la nappe étant ainsi constituée de tronçons de fil s'étendant au moins sensiblement parallèlement les uns par rapport aux autres, et les tronçons de fil de ladite nappe s'étendant suivant une direction, soit parallèle, soit croisée par rapport à la direction des tronçons de fils d'une autre nappe quelconque de l'armature ; et
• on solidarise entre elles l'ensemble des nappes superposées par piquage sans nouage d'un fil continu traversant lesdites nappes.

For example, patent EP-B-0 284 497 of the applicant describes a method and a machine for producing a frame for a piece of composite material, formed of said frame embedded in a hardened matrix, said frame comprising plies superimposed wire, process according to which:

• at least some of said plies are produced by depositing straight sections of wire forming part of a continuous wire on a support, by stretching each section of wire between two fixing points in position of the ends of said section, the ply thus being made up of sections of wire extending at least substantially parallel to each other, and the sections of wire of said ply extending in a direction, either parallel or crossed with respect to the direction of sections of son of another ply any of the frame; and
• all of the superimposed sheets are joined together by stitching without knotting a continuous thread passing through said sheets.

In this case, to deposit the straight sections of wire constituting the corresponding layers, a particular device comprising a tube, open to its lower end and having an opening at its part upper, for the passage of a continuous wire. This head of removal allows each section of wire to be stretched between fixing points in position of its ends, materialized by pins temporarily installed in the support, made of a material that can be penetrated by said pins, like a foam of synthetic material. After formation of the superimposed layers of wire and joining of said plies together, the pins are removed of support.

As already indicated, the joining together of the whole superimposed sheets is made by stitching without knotting of a continuous thread crossing said plies and, this, using a stitching head, mounted on said machine, comprising a support carrying, on the one hand, means of binding to the machine and, on the other hand, a needle, as well that means for guiding the securing wire up to said needle.

However, in patent EP-B-0 284 497, it is a question of make reinforcements at least substantially cylindrical and, to do this, the support is in the form of a also cylindrical mandrel. So each tablecloth made up of straight wire sections is already compacted by the overlying tablecloth consisting of a length of wire continuous wound around said mandrel, which overlying ply also allows, if necessary, to compact and tamp all the underlying tablecloths already deposited on the mandrel. The joining together of the superimposed layers, by stitching without knotting a continuous through thread said layers, can therefore be carried out as illustrated by Figures 10a to 10f of patent EP-B-0 284 497, by simple introduction of the wire through the sheets, using the needle, the thread being retained therein in the form of loops of the even makes the tablecloths it crosses already construction, compacted. The connecting thread reinforces the effect of compaction and compaction, obtained beforehand when removing sheets made up of lengths of wire circumferential, and ensures the holding together of all the layers and the mechanical strength of the frame.

However, when it is desired to make reinforcements in form of plates (flat or curved), from sheets superimposed, each consisting of straight sections of wire, the problem of joining together overlapping tablecloths arises differently.

Indeed, in this case, if we disregard an intersection possible successive layers, which is not no longer desirable for other reasons, the tablecloths superimposed, by construction, no compaction. A solution to solve this problem is mentioned in patent EP-0 056 351. Here, the frame is made up tablecloths called "warp" and tablecloths called "de weft threads ", superimposed in parallel planes, the son of the tablecloths not being intertwined between them, and the upper and lower layers of all tablecloths being made up of "weft" tablecloths. The joining of said “warp” and “weft” plies is obtained by tying threads which cross the latter, bypassing the weft threads of the outer layers (upper and lower) so as to form with them a usual fabric trapping the webs and weft internal.

It is thus seen that, in this case, the settlement of the warp and weft plies is only obtained by traction on the binding wires. Indeed, as they are arranged, the binding threads obviously require a shuttle for their removal, which implies that the tablecloths have a low "density" of the warp and weft (or a significant spacing of these wires), as well as a thin, which, therefore, requires exercise traction on the binding wires to maintain and pack the warp and weft threads. Such traction risk of course breaking the fragile binding threads by nature. In addition, the solution indicated above comes back, ultimately, to achieve, at least in part, a usual fabric by crossing the weft threads of the tablecloths external and binding threads, in fact equivalent to son of chain.

The object of the present invention is to avoid these drawbacks, and relates to a stitching head, usable in a machine for the realization of a plate-shaped reinforcement for a piece of composite material, thanks to which the holding mechanical reinforcement is ensured without the need for it, for this, to make a kind of "fabric" of threads of weft and interwoven binding threads.

For this purpose, the stitching head, usable in a machine for the realization of a plate-shaped reinforcement for a piece of composite material, formed of said frame embedded in a hardened matrix, said reinforcement comprising overlapping layers of thread, crossed by a thread of joining, said head comprising a support bearing, on the one hand, means of connection to the machine and, on the other hand, a needle, as well as means for guiding the thread of joining up to said needle, is remarkable, according to the invention, in that said stitching head comprises mechanical means for compacting said superimposed layers yarn associated with said needle.

Thus, the mechanical strength of the armature is only obtained by the friction of the securing wire on the sections of wire constituting the overlapping plies, without apply stress to said securing wire, and this thanks to the prior packing of the sheets superimposed to achieve a sufficient density of sections of wire which constitute them.

Said mechanical means of compaction include a presser foot operated in connection with the movement of said needle.

Said stitching head has a support rotary at the lower end of which is mounted said needle, associated with the presser foot.

According to a first embodiment, said needle is hollow and said rotary support is traversed by a channel of wire guide connected to said needle.

In this case, advantageously, said stitching head comprises a spring mechanism, controlling the presser foot, comprising a connecting bar, pushed down by a compression spring retained by a stop in contact of the needle holder.

According to a second embodiment, said needle has an oblique through eye and is associated with a thread guide comprising a body obliquely crossed by a wire passage channel, the lower end of which is flared.

In this case, preferably, said stitching head comprises a mechanism for actuating the presser foot assembly, thread guide and needle, consisting of a first actuating cylinder a plate on which said assembly is mounted, a axis carrying the wire guide and a second cylinder actuating the crowbar.

In particular, said needle can be held on said plate, by means of a support, using of conical pliers tightened by a nut.

In addition, the axis carrying the thread guide can be stressed by a tension spring and retained by a stop.

The figures in the accompanying drawing will make it clear how the invention can be realized. In these figures, references identical denote similar elements.

Figure 1 shows schematically in perspective an example machine for producing a frame in the form of plate for a piece of composite material.

Figure 2 is a schematic sectional view illustrating a first embodiment of a stitching head according to the invention.

Figures 3 and 4 are views in longitudinal section of two alternative embodiments of the needle used in the stitching head of the invention.

Figure 5 shows, in section, a thread guide for the needle in Figure 4.

Figure 6 schematically illustrates a second example of production of a stitching head according to the invention provided a wire guide according to figure 5.

Figures 7A to 7D schematically illustrate the process for joining the superimposed layers of the frame produced in accordance with the invention.

The machine 10 of FIG. 1, described in patent EP-B-0 284 497, includes a frame provided with a base 11 and vertical uprights 12, joined at their upper part by a horizontal cross 13.

Each vertical upright 12 has a slide 14, and a transverse bar 15 is fixed in the vicinity of its ends in slides 16 mounted in the slides 14 in which they can be immobilized by screws 17. With this arrangement, the bar 15 can be adjusted in height on the uprights 12.

On the bar 15, is mounted a carriage 18 on which is provided a horizontal arm 19 sliding transversely and adjustable relative to the bar 15.

At one of its ends, the horizontal arm 19 carries a vertical arm 20 also mounted sliding and adjustable.

At its lower end 21, the vertical arm 20 comprises fixing means adapted to receive a head stitching P.

The machine further comprises a base 22, supporting a support 6 for a frame 1, having a shape of convex plate. This frame 1 can advantageously be carried out, as described elsewhere, in the requests for French patent, in the name of the plaintiff, filed on 18 April 1994 under the headings "Process and machine for the making a frame for a piece of material composite "and" Method and machine for producing a plate-shaped frame for a piece of material composite".

It will be noted that, in FIG. 1, the layers have already been removed and the stitching head P is carrying out the joining of the superimposed layers.

We understand that, thanks to the arrangement of the bar 15 and arms 19 and 20, the end 21 can be adjusted in any desired position relative to support 6, according to three orthogonal axes X, Y and Z by means of motors M1, M2 and M3 which are shown, for example, mounted on the bar 15 and at the ends of the arms 19 and 20 and entrain these along these three axes through systems known suitable for pinion and rack, worm or other.

A first example of embodiment of a stitching head P is shown in Figure 2. To allow movement back and forth of the needle 33 relative to the support 6 (to deposit the successive sections of wire of a tablecloth), there is provided, as seen in Figure 2, a support 40, mounted on the block 29 linked to the machine 10, in which is arranged a guide 41, which can rotate on bearings 42 thanks to drive means not shown, guide which is crossed by a longitudinal channel 41A for the passage of the wire F, unwound from the coils 37 (FIG. 1), and of which the lower end 41B carries the needle 33. In addition, as still shown in this figure 2, a crowbar 43 is associated with needle 33, which can be animated with a movement parallel to the longitudinal extension of the needle using a spring mechanism 44. More particularly, the spring mechanism 44, controlling the presser foot 43, includes link bar 45, push downwards by a compression spring 44A and retained by a stop 44B in contact with the support 40 of the needle 33, when the needle is outside the tablecloths deposited. When the needle 33 goes down, the presser foot 43 is retained by the plies and the spring 44A exerts an effort of compression on them.

As illustrated in FIG. 3, the needle 33 can be a hollow needle, crossed by an axial channel 46, for the passage of the wire, and comprising a non-through eye 47, into which the canal opens laterally and obliquely 46.

However, the needle 33 can advantageously be as represented in FIG. 4, that is to say that it comprises an oblique through eye 48 opening into a groove longitudinal 49 of section in an arc, the depth gradually decreases away from the tip 34 of the needle and in which the thread is intended to spend.

When using the latter needle, a thread guide particular can be expected, as shown in figure 5. The thread guide has a body 50, substantially in the form of L, crossed obliquely by a channel 51 for the passage of wire F, the lower end 51A of which is flared for allow the wire to be guided, either substantially vertical or substantially horizontal (wire F shown in dashed lines), as will be seen more in detail later. A roller 52 releases the wire F while advancing in the channel 51, and jams it while moving back in the said channel. Indeed, it is the sliding of the wire which, by pulling towards the bottom, roll the roller 52 by opening the channel 51, then that a backward movement ("raising" of the wire) is blocking again the thread.

In FIG. 6, a second example of embodiment is shown. a stitching head comprising the presser foot assembly 43, thread guide 50 and needle 33 (Figure 4). On a circular flange 53 which can be fixed on the tool holder of the machine 10, is screwed a pneumatic cylinder 54 which actuates a plate 55. Furthermore, the flange 53 carries a ball bush 56 for guiding an axis 57. The plate 55 as for it carries a support 58 of the needle 33, a jack auxiliary 59, and a second sliding ball bearing 60 on axis 57. The auxiliary cylinder 59 carries the presser foot 43 and a wire clamp 61 (similar to the wire guide 50) for the wire F, while the guide pin 57 carries the thread guide or wire clamp 50, being stressed by the tension spring 62 and retained by a stop 63. The needle 33 is held on the support 58 using a conical clamp 64 tightened by a nut 65.

For joining together superimposed layers 2.3 of the frame 1, as shown on the Figures 7A to 7D, a branch in the Z direction. For this during the introduction of needle 33 into the plies 2,3, the thread F is driven by said needle through the plies 2,3 (figure 7B), the thread clamp (not shown in Figures 7A to 7D) being tight and the stroke of the needle being adjusted so that it enters the support 6. During the withdrawal of the needle 33 out of the ply 2,3, the thread clamp is loose and the needle removes by releasing the wire F as it goes through the plies 2,3, thereby forming an unclosed loop 8 which is only retained by the foam from which the support is formed and by the friction of the wire in plies 2 and 3 (figures 7C, 7D).

Thus, it is thanks to the elastic pressure of the foam closing on the loop after removing the needle from a part, and friction and tightening in the plies 2,3 on the other hand, that, during the withdrawal of the needle, the thread F, which flows freely through the needle during this withdrawal, is retained to form the open loop 8.

After having come out of the layers 2 and 3, we bring up the needle above the surface of said plies, of a distance equal to the thickness to be stitched increased by the pitch of branch 7, i.e. the desired spacing between two bites (Figure 7A).

We then operate the wire clamp to lock the wire in the needle, we move the stitching head one step, and we operate the device again to restart the cycle in order to continuously form a large amount of curls with the same wire F, that is to say to form the points of stitching 8 in a row. The next row of loops is performed after relative movement of the needle 33 by relative to reinforcement 1.

More specifically, as seen in Figures 7A-7D, in starting from the initial (and final) position shown on the FIG. 7A, in which the presser foot 43 comes from go back up, we lower the pricking head (in the way described below with reference to FIG. 6) to form a loop of thread 8 when lowering needle 33 to through the superimposed layers 2.3. Note that at this moment, the thread guide 50 is stopped in contact with the lap more superior (Figure 7B). The needle 33 being in its lowest position (Figure 7C), presser foot 43 in turn presses on the uppermost layer superimposed layers 2,3 by trapping the loop 8. It is this combined action of pressing the wire guide 50 and especially presser foot 43 which compresses the superimposed layers then having a density of the sections of wire which constitute them sufficient to retain by friction of the tablecloth securing wire. The crowbar 43 remaining in contact with the uppermost layer, during the ascent of the needle 33 (FIG. 7D), the thread slides into the eye of the needle while remaining in place.

Now also considering FIG. 6, the descent of the needle 33 is provided by the jack 54 which descends in driving the plate 55 and therefore all the fixed parts on this one. At the start of this descent, i.e. before the penetration of needle 33 into the superimposed layers 2,3, the wire F is held by the wire clamp 61 and the wire guide 50, also playing the role of wire clamp, and forms a loop (Figure 7A).

When the needle 33 enters the plies 2,3, the wire guide 50 comes into contact with these layers, immobilizing the axis 57, and the wire F slides in the wire guide 50, while that the previously formed wire loop is pressed into the tablecloths (Figure 7B). The needle 33 having arrived in its lowest position (Figure 7C), presser foot 43 is brought into contact with the uppermost layer by actuator of the jack 59 to bring it down, which ensures the compaction of the superimposed layers, then we order the raising of the jack 54 and thus of the needle 33 (FIG. 7D).

When the needle 33 rises through the plies 2,3, the presser foot 43 remains pressed against them under the pushing of the associated jack 59. The wire is then trapped by the wire clamp. When the stop 63 returns to contact with the sleeve 60, the thread guide 50 rises with the needle 33 and the wire slides into it. The end of the needle rise 33 controls the presser foot 43. The thread is caught by the thread guide 50 and slides in the thread clamp higher 61.

Claims (8)

1. Stitching head for a machine for producing a reinforcement in the form of a sheet for a composite component formed by the said reinforcement embedded in a cured matrix, the said reinforcement comprising superposed plies of thread through which passes a consolidating thread, the said head including a support carrying, on the one hand, means of linkage to the machine and, on the other hand, a needle as well as means for guiding the consolidating thread right to the said needle and, associated with the said needle (33), mechanical means (43, 50) for compacting the said superposed piles of thread,
   characterized:

   in that it comprises a rotary support (41, 53) at the lower end of which the said needle (33) is mounted;

   in that the said mechanical compaction means include a presser-foot (43), associated with the said needle (33) and actuated in conjunction with the movement of the latter; and

   in that means (44, 59) are provided to allow a rotary movement of the said presser-foot (43) in relation to the said needle (33).
2. Stitching head according to Claim 1, characterized in that the said needle (33) is hollow and in that a thread-guiding channel (41A) connected to the said needle passes through the said rotary support (41).
3. Stitching head according to Claim 2, characterized in that the said stitching head (P) comprises a spring mechanism (44), controlling the presser-foot (43), including a linkage bar (45) pushed downwards by a compression spring (44A) and retained by a stop (44B) in contact with the support (40) of the needle (33).
4. Stitching head according to Claim 1, characterized in that the said needle (33) has an oblique through-eye (48) and is associated with a thread-guide (50) comprising a body through which passes obliquely a channel (51) for passage of the thread, the lower end (51A) of the said channel being flared.
5. Stitching head according to Claim 4, characterized in that the stitching head (P) comprises a mechanism for actuating the presser-foot (43)/thread-guide (50)/needle (33) assembly, consisting of a first cylinder actuator (54) actuating a plate (55) on which the said assembly is mounted, a spindle (57) carrying the thread-guide (50) and a second cylinder actuator (59) actuating the presser-foot (43).
6. Stitching head according to Claim 5, characterized in that the said needle (33) is held in position on the said plate (55) by means of a support (58), using a conical clamp (64) tightened by a nut (65).
7. Stitching head according to Claim 5 or Claim 6, characterized in that the spindle (57) carrying the thread-guide (50) is stressed by a tensioning spring (62) and retained by a stop (63).
8. Machine for producing a reinforcement in the form of a sheet for a composite component, characterized in that it includes a stitching head (P) according to any one of Claims 1 to 7.

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