FR2821632A1 - NEEDLE MACHINE HAVING A PENETRATION MEASURING DEVICE - Google Patents

Abstract

The invention concerns a needle-punching machine for a textile structure consisting of a plurality of superposed layers (12) comprising a vertically mobile needle-punching table (10), a needle-punching head including s specific number of barbed needles (18) and arranged in line with said needle-punching table, and means for driving the needle-punching head to impart thereto a reciprocating vertical movement defining a maximum needle penetration low point, wherein are provided measuring means (36), arranged at said needle-punching head to measure the position of an upper surface of the textile structure at the maximum needle penetration low point. Said measuring means are preferably arranged in a median plane of the needle-punching head perpendicular to a forward moving direction of the textile structure.

Description

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Field of the invention
The present invention relates to the production of needled textile structures intended to be used in the manufacture of protective parts used at high temperatures, of structural parts of rocket motors or else of very high performance brake discs for aviation or land vehicles.

Prior art
It is known that the brake discs must withstand braking forces which create particularly high shear forces. This phenomenon is accentuated in aircraft due to the significant constraints applied to the brake discs.

 To resist these shear forces which generate a delamination effect, the discs must be manufactured so as to minimize structural heterogeneities. Indeed, a non-uniform disc has local stress zones with heterogeneous characteristics which considerably increase the risks of tearing.

Conventionally, the brake discs are made from a reinforcing textile structure, formed from a plurality of superimposed layers and needled by a set of barbed needles penetrating in the z direction, that is to say transversely to the layers. After cutting, the textile structure is carbonized, densified using a material forming a matrix and is then optionally subjected to a heat treatment. The layers are superimposed on a support.
A step-down movement is generally imposed on the support as the different layers are superimposed and needled. The mechanical characteristics of the final product thus obtained strongly depend on the real density of needling chosen for the textile reinforcement structure. By real needling density is meant a function of the number of needle barbs per cm 3 seen by an elementary volume of the textile structure, which therefore includes the needling density per unit area, the penetration rate in z , the step of

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 downhill movement and the functional characteristics of the hands.

eux apportent des résultats intéressants, notamment en agissant sur le pas de descente. On peut citer le brevet US 4 790 052 qui propose d'accroître pour chaque couche superposée, la distance entre le support des couches et les aiguilles d'une distance égale à l'épaisseur d'une couche aiguilletée. On peut citer aussi le brevet EP 0 736 115 qui, pour assurer une épaisseur constante des différentes couches superposées, propose d'adopter un pas de déplacement du support de couches variable selon une loi de réduction prédéterminée. However, the current needling processes make it difficult to obtain this perfect uniformity sought although some of

they bring interesting results, in particular by acting on the step of descent. Mention may be made of US Pat. No. 4,790,052 which proposes increasing for each superposed layer, the distance between the support of the layers and the needles by a distance equal to the thickness of a needled layer. Mention may also be made of patent EP 0 736 115 which, in order to ensure a constant thickness of the various superimposed layers, proposes to adopt a pitch of displacement of the support for layers variable according to a predetermined reduction law.

 The imperfection of these methods stems from the fact that this step of downward movement of the layer support is generally calculated beforehand theoretically, in particular as a function of the number of layers which must form the textile structure to be obtained, without taking the depth into account. actual needle penetration. Now, knowledge of this parameter is essential to guarantee a uniform needling density, which guarantees perfect uniformity of the final textile structure.

 Patent application EP 0 695 823 sought to improve knowledge of the penetration depth of the needles by means of feeler rollers measuring the position of the upper surface of the textile structure between the needling operations and arranged laterally relative to the needle working area.

évidence. Cette absence de prise en compte de la déformation de la structure textile interdit en fait une connaissance exacte de la pénétration réelle des aiguilles. However, such a solution does not appear satisfactory because, under the action of the needling forces, there is a crushing of the textile structure which the measurement carried out does not allow to put in

evidence. This failure to take into account the deformation of the textile structure prohibits in fact an exact knowledge of the real penetration of the needles.

Object and definition of the invention
The present invention therefore provides a needling machine and its associated method which overcomes this drawback by allowing a measurement of the actual penetration of the needles in the textile structure to

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 needling taking into account its deformation during the needling operations of the different layers which compose it.

 This object is achieved by a needling machine of a textile structure formed of a plurality of superposed layers comprising a needling table movable vertically, a needling head comprising a determined number of barbed needles and arranged at the plumb of said needling table, and means for driving the needling head to give it a vertical reciprocating movement defining a low point of maximum penetration of the needles in said textile structure, characterized in that it comprises in addition to measuring means, arranged at said needling head, for measuring the position of an upper surface of said textile structure at said low point of maximum needle penetration.

 Thus, with this integration of the measurement means in the needle board allowing the crushing of the textile structure to be taken into account under the effect of needling forces, it is possible to precisely determine the actual penetration depth of the needles.

 Preferably, these measuring means are arranged in a median plane of said needling head perpendicular to a direction of advance of said textile structure.

 According to a preferred embodiment, these means for measuring the position of the upper surface of said textile structure comprise an optical assembly for contactless measurement. Preferably, it is a wide beam type laser transmitter / receiver.

 According to an alternative embodiment, these measurement means may include a mechanical contact measurement probe.

 Advantageously, a sensor is provided, preferably of the inductive or optical type, for determining said low point of maximum penetration of the needles and processing means for controlling the vertical movement of said needling table as a function of the measurement of the position. of the upper surface of the textile structure made at said low point of maximum penetration of the needles by said measuring means.

 The invention also relates to the process implemented in the aforementioned machine as well as the textile structure obtained by this process.

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Preferably, the measurement of the position of the upper surface of the textile structure is carried out by means of instantaneous measurements taken in real time over the entire length of the textile structure.

Brief description of the drawings
The characteristics and advantages of the present invention will emerge more clearly from the following description, given by way of non-limiting illustration, with reference to the appended drawings in which: FIG. 1 is a schematic view of a first embodiment of a machine for needling textile structures according to the invention, - Figure 2 is a schematic view of a second embodiment of a machine for needling textile structures according to the invention, and - Figure 3 is a side view of the machine of Figure 2, its right part being shown in a position of maximum insertion of the needles.

Detailed description of preferred embodiments
Two embodiments of a machine allowing the needling of a flat textile structure are shown in FIGS. 1 and 2. Of course, it should be considered that the invention is not limited to the sole manufacture of flat structures and that that of forming a structure by winding a fibrous web also finds application with the present invention, whether it is an annular winding of a web or helical fabric in turns superimposed flat, or a winding of a sheet of turns superimposed on a mandrel.

 The machine conventionally comprises a so-called needling table 10 intended to support layers 12 or plies of width and length determined according to the final structure to be produced, and which will be brought one after the other to be superimposed in successive layers . The table is placed directly above a needling head 14 comprising, mounted on a needle board 16, a determined number of barbed needles 18 of known type, and which can be driven by a vertical reciprocating movement by one or more rod-crank assemblies 20 motorized by a single motor or not. A breaker 22

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fixé sur un bâti 24 de la machine est monté au dessus de la table d'aiguilletage pour empêcher que la structure textile ne soit entraînée lors de la remontée des aiguilles. Bien entendu, la table comme le débourreur sont percés respectivement de trous 26,28 pour le passage des aiguilles.

fixed on a frame 24 of the machine is mounted above the needling table to prevent the textile structure from being entrained when the needles are raised. Of course, the table as the stripper are respectively drilled with holes 26,28 for the passage of the needles.

The table is movable vertically by means of a drive device 30 consisting for example of a motorized worm. Several series of drive rollers 32, 34 (also called input / output presses) arranged upstream and downstream of the machine ensure horizontal transport of the textile structure towards the needling head.

 According to the invention, means 36 for measuring the position of an upper surface of the textile structure are provided, disposed at the level of the needling head 14 and intended to determine the actual penetration of the needles into this textile structure, a low point of maximum needle penetration. Indeed, the stroke of the needles being constant relative to the frame to which they are connected and the needling table being positioned at a known distance from this frame, it is easy to show that the distance of penetration of the needles into the material textile directly depends on the thickness of material existing between the needling table and the upper surface measured.

 To this end, the measuring means 36 are fixed on the frame 24 and it is provided that the needle board 16 (and the stripper 22) is pierced with an orifice 38 (respectively a passage orifice 40) to allow cooperation of these measuring means with the upper surface of the textile structure.

 Depending on the embodiment envisaged, this cooperation can be carried out without contact (with a remote measurement of the position of the upper surface of the textile structure) or with contact (by the descent of a mechanical probe on the upper surface of the textile structure).

 FIG. 1 illustrates a preferred embodiment of the invention in which these non-contact measurement means consist of an optical measurement assembly such as a laser transmitter / receiver 42. The transmitter directs a laser beam, through the needle board, towards the upper surface of the textile structure (after passing through the stripper) which then reflects it towards the receiver. The transmitter / needling table distance being assumed to be known by a prior measurement,! a distance determination

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 emitter / upper surface of the textile structure, by analyzing the return path of the laser beam, then suffices to accurately assess the thickness of the textile structure supported by the needling table. In addition, to overcome the relief of the textile structure, this laser assembly is preferably of the wide beam type (because this laser model by allowing measurements over the entire length of the beam ensures an integration effect) . Of course, the use of an infrared optical measurement assembly is entirely possible without however being preferred.

 FIG. 2 illustrates an alternative embodiment in which the measuring means consist of a mechanical feeler formed by an internal piston 44 fixed to the frame 24 and on which an external sleeve 46 can slide, the slightly rounded end of which is intended to come into direct contact with the textile structure (after crossing the needle board and the stripper). This sliding of the sleeve is ensured by the controlled injection of a fluid, preferably compressed air, into the piston from a control module 48 fixed on the frame 24. The pressure of the fluid is adjusted according to the nature of the textile structure to be needled (hardness, rebound reaction) and adjusted so as to avoid any rebound of the sleeve on this textile structure. The sleeve also comprises at its upper part a reflective collar 50 intended to cooperate with an optical measurement assembly such as a laser or infrared transmitter / receiver 52 also fixed on the frame. The emitter directs its radiation towards the collar of the sleeve which then reflects it towards the receiver. The transmitter / receiver distance, when the end of the probe is in contact with the needling table, being assumed to be known by a prior measurement, the determination of the transmitter / receiver distance when this end is in contact with the upper surface of the textile structure (by analyzing the return path of the radiated beam) here again suffices to accurately assess the thickness of the textile structure supported by the needling table.

 In the two abovementioned embodiments, the measuring means 36 are preferably arranged in a median plane of the needling head 14 perpendicular to a direction of advance of the textile structure (it is of course not prohibited to s '' deviate significantly). They

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 can be split, when this textile structure is in the form of two adjacent plates advancing parallel to each other under the needling head. In this configuration illustrated in FIG. 3, the needling head generally comprises two boards with independent needles arranged side by side, the measurement means then being placed substantially in the center of each of these boards. To make it easier to understand, this figure shows the machine, for the alternative embodiment of FIG. 2, in two distinct positions, one (left part of this figure) corresponding to a rest position, the needling head. being in the raised position, and the other (right part) corresponding to a position of this head at a low point of maximum needle penetration.

une détermination de la pénétration réelle moyenne des aiguilles à partir de laquelle le dispositif d'entraînement de la table d'aiguilletage 30 relié aux moyens de traitement 58 pourra commander de façon automatique le déplacement vertical de la table d'aiguilletage en vue du passage suivant, le pas de descente de cette table étant géré de façon que les aiguilles pénètrent d'une distance déterminée dans la structure textile. The determination of the low point of maximum penetration of the needles is carried out in real time by a sensor 54, for example of the inductive or optical type, integral with the frame and cooperating for example with a determined cam profile 56 of the rod-crank assembly 20 control of the vertical reciprocating movement of the needling head. This cam profile makes it possible to define a period of time (and not just a single instantaneous measurement instant) during the descent of the needle board, preferably in the vicinity of the low point, during which the measurement means 36 will be active and will be able to acquire several measurements from which will be determined, at the level of a processing module 58 connected on the one hand to the sensor 54 and on the other hand to the measurement means 36, a first average value of the thickness needled layers. These measurements will then be repeated for each horizontal advance of the textile structure, the set of values obtained after a given passage allowing

a determination of the average actual penetration of the needles from which the needling table drive device 30 connected to the processing means 58 can automatically control the vertical movement of the needling table for the next passage , the step of descent of this table being managed so that the needles penetrate a determined distance into the textile structure.

 Thus, the needling process implemented in the machine of the invention can be summarized as follows. First, superimpose a second layer thickness on a first layer thickness

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 laid on the needling table and bind by needles with barbs of a needling head, and according to predetermined conditions, the thicknesses of the two layers thus superimposed, then relatively move the needling table relative to the head of needling of a determined displacement pitch as a function of the position of an upper surface of the two superimposed layers measured at a low point of maximum penetration of the needles by appropriate measurement means, and finally superimposing a third layer thickness on the two previous and tie this third layer thickness on the previous two according to the same predetermined conditions. These steps will then be repeated for the following layers until the desired thickness for the textile structure is obtained.

 The method implemented in the machines described above consists in placing on the table 10 first of all one or even two superposed layers which are then linked by needling by means of the needle board 16 while being moved horizontally over the whole length of the textile structure by feed rollers 32,34. The table is then lowered by a determined displacement pitch in order to be able to superimpose a third layer which is in turn needled with the other two and so on until the desired thickness is obtained.

 According to the invention, this determined displacement step is not fixed or subject to a predefined law of descent, but it results from the actual penetration of the needles into the preceding layers of the textile structure measured at the low point of maximum penetration of the needles in order to obtain the actual needling density desired for this textile structure, constant or changing density in the thickness of the textile structure. Thus, the position of the upper surface of this textile structure is measured at the center of the needles to manage the pitch of descent of the needling table, so that these needles penetrate the textile structure from a determined distance.

Claims (11)

 1. A needling machine for a textile structure formed of a plurality of superimposed layers (12) comprising a needling table (10) movable vertically, a needling head (14) comprising a determined number of needles to barbs (18) and arranged directly above said needling table, and means for driving said needling head to give it a vertical reciprocating movement defining a low point of maximum penetration of the needles in said textile structure, characterized in that it further comprises measuring means (36), disposed at said needling head, for measuring the position of an upper surface of said textile structure at said low point of maximum penetration of the needles.  2. Machine according to claim 1, characterized in that said measuring means are arranged in a median plane of said needling head perpendicular to a direction of advance of said textile structure.  3. Machine according to claim 1 or claim 2, characterized in that said means for measuring the position of the upper surface of said textile structure comprise an optical assembly (42) for non-contact measurement.  4. Machine according to claim 1 or claim 2, characterized in that said optical assembly comprises a laser transmitter / receiver.  5. Machine according to claim 4, characterized in that said laser transmitter / receiver is of the wide beam type.  6. Machine according to claim 1 or claim 2, characterized in that said means for measuring the position of the upper surface of said textile structure comprise a mechanical feeler (44-52) for contact measurement.  7. Machine according to any one of claims 1 to 6, characterized in that it further comprises a sensor (54), preferably of the inductive or optical type, for determining said low point of maximum penetration of the needles.  8. Machine according to claim 7, characterized in that it further comprises processing means (58) for controlling the <Desc / Clms Page number 10>  vertical displacement of said needling table as a function of the measurement of the position of the upper surface of the textile structure carried out at said low point of maximum penetration of the needles by said measuring means.  9. Method for producing a textile structure formed from a plurality of superimposed layers (12), comprising the following steps: a) superimposing a second layer thickness on a first layer thickness placed on a needling table (10 ), b) bonding by needles with barbs (16) a needling head (14), and according to predetermined conditions, the thicknesses of the two layers thus superimposed, c) relatively moving said needling table with respect to said needling head with a displacement pitch determined as a function of the position of an upper surface of the two superimposed layers measured, at the level of the needling head, at a low point of maximum penetration of the needles, d) superimposing a new layer thickness on the previous ones, e) binding said new layer thickness on the previous ones according to said predetermined conditions, and f) repeating steps c), d) and e) for thick next layer, the displacement of step c) being determined as a function of the position of the upper surface of the textile structure in progress, measured at the level of the needling head, at a low point of maximum penetration needles.  10. Method according to claim 9, characterized in that said measurement of the position of the upper surface of the textile structure is carried out by means of instantaneous measurements taken in real time over the entire length of the textile structure.  11. Textile structure formed from a plurality of superimposed layers obtained according to the method of claim 9.