METHOD FOR CUTTING A THREE-DIMENSIONAL FABRIC WITH TWO FABRIC PANEL CONNECTED BY STRINGING TOGETHER

Description

[0001] The present invention relates to the field of fabric cutting.

[0002] It is known, notably from patent FR-3 088 238 filed by the applicant, to implement a so-called "three-dimensional" fabric which comprises, in superposition along a direction called "stacking direction", a first layer of fabric forming a lower layer, a second layer of fabric forming an upper layer which extends parallel to said lower layer, and a network of reinforcing threads called "stays" which are interposed between the lower layer and the upper layer and which each connect the lower layer to the upper layer in order to allow the upper layer and the lower layer to move apart from each other along the stacking direction, within the limit of a maximum separation distance which is determined by the length of the stays, and while remaining captive to each other.

[0003] Such a three-dimensional fabric can be used in particular for the manufacture of pneumatic tires for vehicle wheels, or in various other applications.

[0004] However, a difficulty arises in cutting such a three-dimensional fabric. Indeed, when the three-dimensional fabric is lying flat, the stays are compressed in a relatively disordered fashion between the lower and upper layers, so that it is not possible to make a cut through the thickness of the three-dimensional fabric without randomly severing one or more stays.

[0005] One solution is to manually separate the lower and upper layers to carefully make a cut using a cutting tool, taking care not to cut a stay. However, such a manual operation remains relatively delicate and is hardly suitable for the industrial-scale processing of three-dimensional fabric. A method for cutting a three-dimensional fabric according to the preamble of claim 1 is known from US 2020 / 238677 A1.

[0006] The objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and to propose a new cutting process which guarantees a precise, reliable and efficient cut of a three-dimensional fabric.

[0007] The objects assigned to the invention are achieved by means of a cutting process of a fabric called a "three-dimensional fabric" which comprises, superimposed along a direction called the "stacking direction", i) a first layer of fabric, called the "bottom layer", which extends lengthwise along a first direction called the "warp direction" which is perpendicular to the stacking direction, and widthwise along a direction called the "weft direction" which is perpendicular to the warp direction and to the stacking direction, ii) a second layer of fabric, called the "top layer", which is distinct from the bottom layer and which extends parallel to said bottom layer, and iii) a network of threads called "stays" which are interposed in the space called the "bonding space" included between the bottom layer and the top layer,and which each connect the lower layer to the upper layer in order to allow the upper and lower layers to move apart from each other along the stacking direction, within the limit of a maximum separation distance which is determined by the length of the stays, while remaining captive to each other, said method being characterized in that it comprises: , an opening step (a), during which a cutting tool is introduced into the connection space between two adjacent stays, and in a direction called the "introduction direction" which is perpendicular to the stacking direction, said cutting tool comprising a first flange, called the "lower flange", intended to slide in contact with the face of the lower layer which is oriented towards the connection space, and a second flange, called the "upper flange", intended to slide in contact with the face of the upper layer which is oriented towards the connection space, said lower and upper flanges together forming, successively along the introduction direction, first (i) a penetration point, along which the height separating the lower flange from the upper flange, considered along the stacking direction, gradually increases,so that said penetration tip can progressively separate, as the cutting tool progresses in the insertion direction, the upper and lower layers from each other, according to the stacking direction, until said lower and upper layers are placed in a configuration called the "fully open configuration" which corresponds to the maximum separation distance allowed by the stays, then ii) a stabilizing spacer whose height corresponds to the maximum separation distance allowed by the stays, in order to maintain the three-dimensional fabric in the fully open configuration, a cutting step (b) in which at least one of the lower and upper layers is cut, without cutting any stays, by means of a cutting blade which is associated with the corresponding sole, at the level of the stabilizing spacer.

[0008] Advantageously, the method according to the invention makes it possible to position the cutting tool reproducibly between two rows of stays, to progressively move the three-dimensional fabric from a loose or even flattened configuration to a fully open configuration, simply by the relative movement of the penetration tip with respect to the three-dimensional fabric along the direction of introduction, which will make it possible to tension the stays to align said stays all substantially perpendicular to the lower and upper layers, and to maintain said stays under tension, before the passage of the cutting blade and until after the passage of the cutting blade, so that the trajectory of the cutting blade never crosses the path of a stay, and that the cutting operation therefore preserves the integrity of said stays.

[0009] Other objects, features and advantages of the invention will become apparent in more detail from the following description, as well as from the accompanying drawings, which are provided for illustrative purposes only and are not intended to be limiting, including:

[0010] There figure 1 illustrates, according to a perspective view, a three-dimensional piece of fabric according to the invention, in a fully open configuration.

[0011] There figure 2 is a side view of the three-dimensional fabric of the figure 1 , in a projection plane containing the stacking direction and the chain direction.

[0012] THE figures 3A et 3B illustrate, respectively according to a perspective view and a front projection view in a plane normal to the direction of introduction, a cutting tool according to the invention, designed to make a cut of the upper layer only.

[0013] THE figures 4A, 4B, 4C et 4D are perspective views of the successive phases of a cross-sectional operation of three-dimensional tissue figures 1 et 2 by the tool of figures 3A et 3B , according to an introduction direction which is transverse, here perpendicular, to the warp direction, and therefore parallel to the weft direction.

[0014] THE figures 5A et 5B illustrate, respectively according to a perspective view and a front projection view in a plane normal to the direction of insertion, a variant of the cutting tool figures 3A, 3B which has a bulge to widen the bearing surface of the upper sole, in the part forming the stabilizing spacer.

[0015] THE figures 6A et 6B illustrate, respectively according to a perspective view and a front projection view in a plane normal to the direction of insertion, another variant of the cutting tool figures 3A, 3B whose section gradually widens from the lower sole to the upper sole so that the upper sole is wider than the lower sole in the part forming the stabilizing brace.

[0016] There figure 7 illustrates, according to a perspective view, a variant of three-dimensional fabric which presents, in its width, empty spaces of stays called "longitudinal corridors" which allow the insertion of cutting tools to make a longitudinal cut, according to an introduction direction which is this time parallel to the warp direction.

[0017] THE figures 8A et 8B illustrate, respectively, according to a side view in a plane containing the insertion direction and the stacking direction, and according to a front projection view in a plane normal to the insertion direction, a variant of a cutting tool according to the invention that allows for a simultaneous cut of the lower and upper layers, more particularly a longitudinal cut along an insertion direction parallel to the warp direction, for example when said cutting tool is inserted into a longitudinal channel of the three-dimensional fabric of the figure 7 .

[0018] THE figures 9A et 9B illustrate, respectively from a side view in a plane containing the insertion direction and the stacking direction, and from a top projection view in a plane normal to the stacking direction, a variant of the cutting tool figures 8A et 8B whose soles have a flattened shape, and therefore a low height footprint, to facilitate the passage of the penetration tip between the roots of the stays, as close as possible to the lower and upper layers of the three-dimensional fabric.

[0019] The present invention relates to a method for cutting a fabric 1 called "three-dimensional fabric" 1.

[0020] As is particularly visible on the figures 1, 2 And 7 , such a three-dimensional fabric 1 comprises, in superposition along a direction called the "stacking direction" DZ: (i) a first layer 2 of fabric, called the "lower layer" 2, which extends lengthwise along a first direction called the "warp direction" DX, which is perpendicular to the stacking direction, and widthwise along a direction called the "weft direction" DY, which is perpendicular to the warp direction DX and the stacking direction DZ, (ii) a second layer 3 of fabric, called the "upper layer" 3, which is distinct from the lower layer 2 and which extends parallel to said lower layer 2, and (iii) a network of threads 4 called "stays" 4, which are interposed in the space called the "bonding space" 5 between the lower layer 2 and the upper layer 3, and which each connect the lower layer 2 to the upper layer 3 in order to allow the upper layer 3 and the lower layer 2 to move apart from each other along the stacking direction DZ,within the limit of a maximum separation distance H5_max, which is determined by the length of the stays 4, and while remaining captive to each other.

[0021] The lower 2 and upper 3 layers are preferably each made of a woven textile, in which the warp yarns are oriented along the warp direction DX and the weft yarns are oriented along the weft direction DY.

[0022] The stays 4, which keep the lower layer 2 and the upper layer 3 attached to each other, are made of a flexible but substantially inextensible material, in order to allow the three-dimensional fabric 1 to adopt alternately a flattened configuration, in which the upper layer 3 is close to the lower layer 2, and the stays 4 sandwiched and lying between said layers 2, 3, and an open configuration, in which the stays are deployed and tensioned to accompany the upper layer 3 which moves away from the lower layer 2 in the stacking direction DZ until it reaches the maximum separation distance H5_max planned, at which said stays 4 stop the separation of the layers 2, 3 and oppose any further mutual separation of said lower layer 2 and upper layer 3 in the stacking direction DZ.

[0023] As an indication, the 4 stays can be made of polyamide, polyester, elastane, aramid, or a mixture of these materials.

[0024] The length of the stays 4, and consequently the maximum spacing distance H5_max, may be between 40 mm and 70 mm, more preferably between 45 mm and 65 mm, or even between 55 mm and 65 mm.

[0025] Preferably, the lower layer 2 and the upper layer 3 overlap exactly, in projection in a plane normal to the stacking direction DZ, and for this purpose both have the same length along the warp direction DX on the one hand, and the same width along the weft direction DY on the other.

[0026] According to the invention, the process first comprises an opening step (a), which corresponds, for example, to figures 4A et 4B , during which a cutting tool 10 is introduced into the connection space 5, between two neighboring stays 4, and in a direction called "introduction direction" D10 which is perpendicular to the stacking direction DZ, said cutting tool 10 comprising a first base 11, called "lower base" 11, intended to slide in contact with the face of the lower layer 2 which is oriented towards the connection space 5 and a second base 12, called "upper base" 12, intended to slide in contact with the face of the upper layer 3 which is oriented towards the connection space 5.

[0027] As is particularly visible on the figures 3A , 5A , 6A , 8A And 9A , said lower soles 11 and upper soles 12 together form, successively along the direction of introduction D10, firstly (i) a penetration tip 13, along which the height H13 separating the lower plate 11 from the upper plate 12, considered in the stacking direction DZ, gradually increases, so that said penetration tip 13 can gradually separate, as the cutting tool 10 progresses in the insertion direction D10, the upper plate 3 and the lower plate 2 from each other, in the stacking direction DZ, as illustrated in the figure 4B , until the said lower 2 and upper 3 layers are placed in a configuration called the "fully open configuration" which corresponds to the maximum spacing distance H5_max allowed by the stays 4, then ii) a stabilizing spacer 14 whose height H14 corresponds to the maximum spacing distance H5_max allowed by the stays 4, in order to maintain the three-dimensional fabric 1 in a fully open configuration, as is the case on the figure 4C .

[0028] The opening step (a) thus includes a spreading phase, during which the cutting tool 10 spreads the layers 2, 3 apart in order to put the stays 4 under tension, then a stabilization phase during which the spacer 14 keeps the layers 2, 3 spread apart and the stays 4 under tension.

[0029] At the level of the stabilizing spacer 14, the lower 11 and upper 12 flanges preferably form flat and parallel surfaces, normal to the stacking direction DZ. Said flanges 11, 12 are therefore capable of maintaining, at least locally, the layers 2, 3 parallel to each other, at a distance from each other which is equal to the maximum spacing distance H5_max, and each of said layers 2, 3 substantially in a plane normal to the stacking direction DZ.

[0030] It should be noted that, for the sake of simple convenience of representation and for better readability, views 4A and 4B intentionally show the three-dimensional fabric 1 in a fully open configuration, whereas, in practice, the said three-dimensional fabric 1 is, until it has been pushed aside by the penetration point 13 and until it is effectively supported and stretched by the cutting tool 10, in a loose state, the stays 4 being more or less sagging.

[0031] Advantageously, the opening effect provided by the insertion of the cutting tool 10 between the lower 2 and upper 3 layers allows said layers 2, 3 to exert a pull on the stays 4, and thus to straighten and put the stays 4 into tension, according to the longitudinal extension direction of said stays 4, and then to maintain said stays 4 in tension as long as the stabilizing spacer 14 prevents said lower 2 and upper 3 layers from coming together under the tensile force exerted on said layers 2, 3, in reaction, by the stays 4.

[0032] The three-dimensional fabric 1 is thus advantageously opened by a wedge effect, thanks to the penetration point 13 which bears on the lower layer 2, by means of the lower sole 11, to separate the upper layer 3 from the lower layer 2, against which the upper sole 12 simultaneously bears to push back said upper layer 3. At the end of this opening phase, said three-dimensional fabric 1 is stabilized in a fully open configuration, which is stiffened by the stabilizing spacer 14 which includes the cutting tool 10.

[0033] The three-dimensional fabric 1 being thus stretched in the stacking direction DZ and stiffened, and the stays 4 being consequently clear of the path of the cutting tool 10 and ordered, here substantially aligned in rows with respect to each other, it is possible to easily cut the targeted layer(s) 2, 3, without risking accidentally cutting a stay 4.

[0034] According to the invention, the method therefore comprises, after the opening step (a), a cutting step (b), during which at least one of the lower 2 and upper 3 layers is cut, without cutting any stays 4, by means of a cutting blade 15 which is associated with the corresponding sole 11, 12, at the level of the stabilizing spacer 14, as illustrated for example in the figure 4C .

[0035] Advantageously, this simply requires continuing the movement of the cutting tool 10 relative to the three-dimensional fabric 1 along the introduction direction D10, which thus defines the orientation of the cutting line LC2, LC3 along which the layer 2, 3 concerned is cut ( figures 4C, 4D ), or where applicable the two cutting lines LC2, LC3 along which each of the two layers 2, 3 is respectively cut ( figure 7 ).

[0036] By preserving the stays 4, on each side of the cutting line LC2, LC3, we advantageously preserve the mechanical properties and the homogeneity of the structure of the three-dimensional fabric 1.

[0037] The cutting blade 15 may have any suitable shape. Preferably, said cutting blade 15 may have a concave, sickle-shaped, curved shape, as is particularly evident on the figures 3A , 5A , 6A , 8A And 9A . According to a particularly simple and compact arrangement, said cutting blade 15 can be fixed directly onto the relevant sole 11, 12.

[0038] In practice, the stacking direction DZ will preferably be vertical, so that layers 2 and 3 will form horizontal surfaces when subjected to the cutting action, which itself will occur along a horizontal insertion direction D10. In accordance with the chosen naming convention, the lower layer 2 will then preferably be positioned below the upper layer 3, that is, at a lower altitude than the upper layer 3.

[0039] Preferably, as can be seen in particular on the figures 3A , 5A , 6A , 8A et 8B , 9A et 9B , the penetration tip 13 of the cutting tool 10 has, in projection in a plane normal to the stacking direction DZ, a first bevel 16 allowing the cutting tool 10 to make its way between two neighboring stays 4, and, in projection in a plane containing the introduction direction D10 and the stacking direction DZ, a second bevel 17 which allows the penetration tip 13 to separate the lower 2 and upper 3 layers from each other until reaching the fully open configuration.

[0040] Advantageously, the same penetration point 13 thus ensures clearance of the passage for the cutting tool 10 in both directions transverse to the penetration direction D10, namely in the width of the cutting tool 10 thanks to the first bevel 16, and in the height of the cutting tool 10 thanks to the second bevel 17.

[0041] The bevels 16, 17 can, without going out of the scope of the invention, form straight ramps, and therefore appear in projection as straight segments arranged in broken lines, or they can form curved ramps, which follow curved lines.

[0042] The first and second bevels 16, 17 can meet and coexist at the front end of the sole(s) 11, 12 under consideration, to form a point, for example a polyhedral point as is the case on the figures 3A , 5A, 6A , or a rounded point, as is the case on the figures 9A et 9B .

[0043] In all cases, the penetration point 13 advantageously forms a bow which precedes the stabilizing spacer 14 to separate the layers 2, 3 and the shrouds 4.

[0044] The variation in the height H13 of the penetration tip induced by the second bevel 17 will preferably represent at least 5%, preferably at least 10%, or even at least 30%, and possibly up to 100% (case of the figures 3A , 5A, 6A ) of the height H14 of the stabilizing spacer 14, and therefore of the maximum spacing distance H5_max. Thus, the progressive increase in height provided by the penetration tip 13 will be sufficient to allow the penetration tip 13 to engage an unstretched three-dimensional fabric 1 and then to bring said three-dimensional fabric 1, and more particularly the stays 4, into tension along the stacking direction DZ.

[0045] Regarding the variants illustrated on the figures 3A , 5A et 6A , the variation in height of the penetration tip induced by the second bevel 17 is equal to the height footprint H12 of the upper sole 12, since said second bevel 17 is here supported exclusively by said upper sole 12.

[0046] Regarding the variants illustrated on the figures 8A, 8B And 9A et 9B , the variation in height of the penetration tip induced by the second bevel is equal to the sum of the respective height footprints H11, H12 of the lower footing 11 and the upper footing 12, since the second bevel 17 is distributed between these two footings 11, 12.

[0047] If a small variation in the height H13 of the penetration tip 13 is chosen, for example representing 5% to 10% of the maximum spacing distance H14, relatively flat base plates 11, 12 can be used for this purpose, i.e., having a small height H11, H12 along the stacking direction DZ, as illustrated in the figures 9A et 9B .

[0048] Such relatively flat soles 11, 12 will be particularly suitable for engaging said soles 11, 12 as close as possible to the "roots" of the stays 4, that is to say, as close as possible to the point where said stays 4 emerge from the lower layer 2, respectively upper layer 3, in the connection space 5, according to the stacking direction DZ. This can be advantageous for engaging the cutting tool 10 between two rows of stays 4 which are of considerable length and which, when not yet tensioned, tend to be disordered and intertwine in the central portion of the connection space 5.

[0049] Indeed, to prevent such stays 4 from passing to the "wrong" side of the first bevel 16 and the base 11, 12, and therefore to prevent the penetration tip 13 from being trapped and hindered by said stays 4 and from destroying said stays 4 during its progression in the direction of introduction D10, it is desirable to position and keep the tips of the bases 11, 12 in the immediate vicinity of the layers 2, 3 and therefore of the roots of the stays 4, at a distance from the central part of the connection space 5 (considered according to the stacking direction DZ), by limiting the height H11, H12 of each base 11, 12.

[0050] Preferably, as is clearly visible on the figures 1 et 2 , the three-dimensional fabric 1 comprises a plurality of continuous reinforcing yarns 20 which are oriented along the warp direction DX and arranged side by side, parallel to each other, according to a predetermined repetition pitch P20 in the weft direction DY.

[0051] Preferably, each reinforcing wire 20 then forms, along the DX warp direction, and as illustrated on the figure 2 , a crenellated undulation which includes a succession of periods which each include a first segment 21 called "upper segment" 21, where the reinforcing wire 20 is interlaced with the upper layer 3, then a second segment 22 forming a stay 4 called "descending" which connects said upper segment 21, and therefore the upper layer 3, to the lower layer 2, then a third segment 23 called "lower segment" 23, where the reinforcing wire 20 is interlaced with the lower layer 2, then a fourth segment 24 forming a stay 4 called "ascending" which connects said lower segment 23, and therefore the lower layer 2, to the upper layer 3.

[0052] And so on, the fourth segment 24 forming the ascending stay 4 connects the lower segment 23 of the period concerned to the first segment, namely the upper segment 21, of the following period, etc.

[0053] Advantageously, the use of such reinforcing threads 20 which are uninterrupted over the entire length of the three-dimensional fabric 1, and which each pass alternately from the upper layer 3 to the lower layer 2 and vice versa, simplifies the manufacture of the three-dimensional fabric, and guarantees a solid anchoring, and therefore great robustness, of the stays 4.

[0054] Preferably, the segments 21, 22, 23, 24, and therefore more particularly the corresponding stays 4, of the different reinforcing wires 20 which follow one another along the weft direction DY, are aligned in rows according to said weft direction DY, so as to delimit within the bond space 5, between each row of stays 4, transverse corridors 25 empty of stays and oriented according to said weft direction DY.

[0055] According to a first possible implementation, which corresponds to figures 4A à 4D , and which we will call "transverse cutting", the introduction direction D10 is transverse to the warp direction DX, and more preferably perpendicular to the warp direction DX and therefore parallel to the weft direction DY.

[0056] The penetration tip 13 of the cutting tool 10 is then engaged in the so-called "transverse corridor" 25, which is comprised between, on the one hand, a row of descending stays 4, 22 distributed along the weft direction DY and corresponding to the plurality of reinforcing wires 20, and, on the other hand, the immediately following row of ascending stays 4, 24, as can be seen on the figure 4B .

[0057] According to this first possible implementation, the lower sole 11 is without a cutting blade 15 and is arranged to slide on the row of lower segments 23 which are integrated into the lower layer 2 above the transverse channel 25, without cutting said lower segments 23, while the upper sole 12 is provided with a cutting blade 15 which cuts the upper layer 3, in the space between two successive rows of upper segments 21, and consequently without cutting the reinforcing wires 20, as can be seen on the figures 4C et 4D .

[0058] Advantageously, the lower sole 11 is used here to retain the lower layer 2, and the lower segments 23 of the reinforcing wires 20, which form the floor of the transverse corridor 25, against the tensile stress exerted in the stacking direction DZ by the tensioning of the stays 4 and by the cutting operation, while the upper sole 12 tensions the upper layer 3 and cuts the latter in an interval where said upper layer 3 is devoid of reinforcing wires 20, and which here corresponds to the ceiling of the transverse corridor 25. This avoids any damage to the three-dimensional fabric 1, and in particular any tearing of the stay 4, during the cutting operation.

[0059] Preferably, the lower plate 11 will rest, according to the stacking direction DZ, on the lower layer 2, and therefore on the corresponding lower segments 23, while the lower layer 2 and the lower segments 23 will themselves rest on an underlying rigid support, such as an anvil or table. The lower layer 2, and more generally the three-dimensional fabric 1, will thus be guided with particular precision and fluidity between the lower plate 11 and the underlying support during the cutting operation.

[0060] Advantageously, making cuts in only one of the two layers 2, 3 allows the three-dimensional fabric 1 to remain in one piece, thanks to the intact, uncut layer 2, while increasing the ability of said three-dimensional fabric 1 to conform to fit a curved surface, since the cutting lines LC3 allow the different portions of the cut layer 3 to move freely away from each other in order to accommodate an increase in length induced by the curvature of said surface.

[0061] According to a preferred arrangement of the cutting tool 10, the width W12 of the upper sole 12, considered perpendicular to the feed direction D10, is greater than the width W11 of the lower sole 11, as can be seen in the figures 5B et 6B .

[0062] Such an arrangement allows us to take into account the fact that the stays 4 are generally not, even when under tension in the fully open configuration, strictly perpendicular to the layers 2, 3, particularly due to the transitions between segments 21, 23 integrated into said layers 2, 3 and segments 22, 24 emerging from the stays 4, so that said segments 21, 22, 23, 24 of the same reinforcing wire 20 do not exactly form a rectangular crenellation, but rather follow, along the warp direction DX, a trapezoidal crenellation, the shorter bases of which correspond to the segments 21, 23 integrated into the layers 2, 3, and the longer bases correspond to the gaps, empty of reinforcing wires 20, which separate, within the same layer 2, 3, and along the same reinforcing wire 20, two segments successive layers of the same nature integrated into said layer 2,3 (that is, two successive upper segments 21 of the same reinforcing wire 20, or respectively two successive lower segments 23 of the same reinforcing wire).

[0063] Indeed, the increased width W12 of the upper sole 12 thus makes it possible to maximize the bearing surface of the laying tool 10 which supports the upper layer 3 during the cutting operation, at the level of the large base of the trapezoid, that is to say, in the example retained here, between two successive upper segments 21, at the level of the ceiling of the transverse corridor 25. The upper layer 3 is thus stabilized even more effectively during the cutting operation.

[0064] The additional width W12 of the upper sole 12 can be achieved by any suitable modification, for example by providing a local bulge or an added piece 26 as an additional thickness of the cutting tool 10 in the area of ​​the stabilizing spacer 14, as illustrated in the figures 5A et 5B , or alternatively by providing a cutting tool 10 whose cross-section is, in the area of ​​the stabilizing spacer 14, flared so as to widen continuously, according to a predetermined opening angle A14, between the lower flange 11 and the upper flange 12, as can be seen on the figure 6B .

[0065] According to a second possible implementation, which we will call "longitudinal cutting", the introduction direction D10 is, this time, parallel to the chain direction DX.

[0066] The penetration tip 13 of the cutting tool 10 is then engaged in the space called "longitudinal corridor" 27 which is contained between two immediately adjacent parallel reinforcing wires 20.

[0067] Preferably, according to this second possible implementation, the lower sole 11 and the upper sole 12 are each provided with a cutting blade 15, as illustrated in the figures 8A, 8B And 9A, in order to simultaneously cut the lower layer 2 and the upper layer 3 along the warp direction DX, between the two reinforcing wires 20, as schematically represented by the cutting lines LC2, LC3 which appear as dotted lines on the figure 7 .

[0068] Such a possibility of implementation will in particular make it possible to precisely cut a desired width of three-dimensional fabric 1.

[0069] The cutting lines LC2, LC3 may, but not necessarily, be located approximately in the center of the longitudinal channel 27 along the weft direction DY. Preferably, the cutting lines LC2, LC3 will be located at a distance of between 2 mm and 4 mm from the last stay 4 belonging to the three-dimensional fabric strip 1 that is to be retained. This is so that the cut can be made as close as possible to the stay 4 while preserving some intact warp threads between said stay 4 and the cutting line LC2, LC3, and therefore between said stay 4 and the selvedge of the strip thus cut, in order to prevent said stay 4, which is closest to said selvedge of the strip, from detaching from said strip during the implementation of said strip.

[0070] It should be noted that an enlarged longitudinal corridor 27 can be provided by locally increasing the distance separating, in the weft direction DY, the immediately adjacent reinforcing wires 20 that laterally delimit said longitudinal corridor 27, relative to the distance separating the other reinforcing wires 20 from each other. That is to say, at the reinforcing wire 20 placement iteration corresponding to the longitudinal corridor 27, the spacing P20 between the reinforcing wires 20 can be locally increased compared to the "normal" spacing P20 used outside the longitudinal corridor 27, as can be seen on the figure 7 .

[0071] An enlarged longitudinal corridor 27 will indeed facilitate the introduction and progression of the cutting tool 10 relative to the three-dimensional fabric 1, and will considerably limit the risks of snagging a stay 4 or cutting a stay 4 by a sole 11, 12. It will also allow the use of relatively wide soles 11, 12, which will offer a large bearing surface to the layers 2, 3, and will thus ensure a particularly stable holding of the layers 2, 3, especially during the cutting operation.

[0072] However, with a suitable cutting tool 10, in particular a cutting tool 10 whose soles 11, 12 have a low height footprint H11, H12 as described above, it will be possible to cut the three-dimensional fabric 1 along a "narrow" longitudinal corridor 27, that is to say, whose width corresponds for example to the "normal" distribution pitch P20, constant, of the stays 4 according to the weft direction DY.

[0073] According to a particularly preferred variant of the second possible implementation of the aforementioned process, two cutting tools 10 are simultaneously engaged in two distinct parallel longitudinal channels 27, so that the simultaneous cutting operation of the lower 2 and upper 3 layers in each of the two longitudinal channels 27 allows the three-dimensional tissue 1 to be subdivided into a central band 28, contained between the two longitudinal channels 27, and two lateral bands 29, 30, as shown in the figure 7 .

[0074] Such a process, which simultaneously involves four soles 11, 12 and four corresponding cutting blades 15, makes it possible in particular to produce a central band 28 of suitable width, for example adapted to the dimensions of the pneumatic tire which said central band 28 will equip, and to eliminate the edges corresponding to the lateral bands 29, 30, in order to produce a precise, clean and burr-free delimitation of the central band 28.

[0075] Such a process can in particular be implemented downstream of a manufacturing station where a three-dimensional fabric 1 is produced continuously over very long lengths, exceeding one hundred meters or even one thousand meters, in order to carry out a longitudinal cut, and therefore an adaptation in width of the three-dimensional fabric 1, on the fly, as said three-dimensional fabric comes out, in its raw state, from the manufacturing station.

[0076] According to one possible implementation, it would of course be possible to supply a large-width raw three-dimensional fabric 1, and simultaneously produce, continuously, several parallel central strips 28, distributed side by side in the width of the raw three-dimensional fabric 1, by means of several cutting tools 10 acting in parallel with each other to cut the three-dimensional fabric 1 on the fly along as many parallel cutting lines LC2, LC3.

[0077] An example of a cutting tool 10 particularly suited to longitudinal cutting is shown schematically on the figures 8A et 8B .

[0078] According to this preferred example, the lower sole 11 and the upper sole 12 each have a ski shape with a curved tip 31, and are joined in a mirror image by their respective tips 31 to form the penetration tip 13.

[0079] The presence of spatulas 31 arranged substantially symmetrically with respect to a plane of symmetry normal to the stacking direction DZ can in particular allow, if the height H11, H12 of said spatulas, and therefore of the soles, is sufficiently large, to place the top of the penetration tip 13 substantially at mid-height of the bond space 5, and allows the two layers 2, 3 to distribute and flow in a substantially symmetrical and homogeneous way along the cutting tool 10, each on a different side of the plane of symmetry, which avoids cutting irregularities between the lower layer 2 and the upper layer 3.

[0080] For this purpose, the cutting tool 10 will preferably be mounted at a height and in a fixed position, so that the lower 2 and upper 3 sheets which pass in contact with the soles 11, 12 are floating, that is to say that they are not pressed by the cutting tool 10 against any support such as a table or an anvil, and that their trajectory is not constrained by such a support which would be placed opposite the soles 11, 12. The said sheets 2, 3 therefore circulate freely on each of the opposite faces of said cutting tool 10, such as these faces are materialized by a sole 11, 12.

[0081] The spatulas 31 can advantageously form the double bevel 16, 17 mentioned above. Furthermore, the curved profile of the spatulas 31 will facilitate the smooth insertion and progression of the penetration tip 3, and more generally of the cutting tool 10, within the three-dimensional tissue 1.

[0082] The variant of the embodiment illustrated on the figures 9A et 9B presents a cutting tool 10 whose soles 11, 12 have "quasi-flat" spatulas 31 and which therefore advantageously have a low height footprint H11, H12. Such a variant will be particularly suitable for cutting a three-dimensional fabric 1 whose stays have a large length, typically on the order of 55 mm to 65 mm, and whose longitudinal channels 27 have a small width (considered at the root of the stays 4 formed by two neighboring reinforcing wires 20), typically between 15 mm and 25 mm, in particular on the order of 20 mm.

[0083] Advantageously, the implementation of relatively narrow longitudinal corridors 27 will maximize the useful width of the central band 28, and thus reduce the drops represented by the lateral bands 29, 30.

[0084] Moreover, preferably, and in particular in the case where a longitudinal cut is made, the cutting movement is generated by moving the three-dimensional tissue 1, along the introduction direction D10, relative to the cutting tool 10 which is held fixed.

[0085] Such an option makes it possible in particular to manage a continuous flow of three-dimensional fabric 1, in the case of a longitudinal cut.

[0086] The three-dimensional fabric 1, and more particularly the central band 28 and the lateral bands 29, 30 which originate from it, can be pulled by motorized reels located downstream of the cutting tool 10 and on which the said bands 28, 29, 30 are wound, as they are cut.

Claims

1. Method for cutting a fabric referred to as "three-dimensional fabric" (1) which comprises, placed one on top of another in a direction referred to as "stacking direction" (DZ): i) a first fabric ply (2), referred to as "lower ply" (2), which extends lengthwise in a first direction referred to as "warp direction" (DX) which is perpendicular to the stacking direction (DZ), and widthwise in a direction referred to as "weft direction" (DY) which is perpendicular to the warp direction (DX) and to the stacking direction (DZ); ii) a second fabric ply (3), referred to as "upper ply" (3), which is separate from the lower ply (2) and which extends parallel to said lower ply; and iii) a network of threads referred to as "stays" (4) which are positioned in the space referred to as "connecting space" (5) comprised between the lower ply (2) and the upper ply (3) and which each connect the lower ply (2) to the upper ply (3) in order to allow the upper ply (3) and the lower ply (2) to move away from one another in the stacking direction (DZ), within the limit of a maximum separation distance (H5_max) which is determined by the length of the stays (4), while remaining captive relative to one another, said method being characterized in that it comprises: - an opening step (a), during which a cutting tool (10) is inserted into the connecting space (5), between two adjacent stays (4), and in a direction referred to as "insertion direction" (D10) which is perpendicular to the stacking direction (DZ), said cutting tool (10) comprising a first sole (11), referred to as "lower sole" (11), intended to slide in contact with that face of the lower ply (2) that faces towards the connecting space (5) and a second sole (12), referred to as "upper" sole (12), intended to slide in contact with that face of the upper ply (3) that faces towards the connecting space (5), said lower sole (11) and upper sole (12) together forming, in succession along the insertion direction (D10), firstly i) a penetration end (13), along which the height (H13) which separates the lower sole (11) from the upper sole (12), as considered in the stacking direction (DZ), increases gradually, such that said penetration end (13) can gradually move the upper ply (3) and the lower ply (2) away from one another in the stacking direction (DZ) as the cutting tool (10) advances in the insertion direction (D10), until said lower ply (2) and upper ply (3) are placed in a configuration referred to as "fully open configuration" which corresponds to the maximum separation distance (H5_max) allowed by the stays (4); and then ii) a stabilizing spacer (14) of which the height (H14) corresponds to the maximum separation distance (H5_max) allowed by the stays (4), in order to keep the three-dimensional fabric (1) in the fully open configuration, - a cutting step (b), during which at least one of the lower ply (2) and upper ply (3) is cut, without cutting any stays (4), by means of a cutting blade (15) which is associated with the corresponding sole (11, 12), at the stabilizing spacer (14).

2. Method according to Claim 1, characterized in that the penetration end (13) of the cutting tool (10) has, in projection in a plane normal to the stacking direction (DZ), a first bevel (16) allowing the cutting tool (10) to clear a passage between two adjacent stays (4), and, in projection in a plane containing the insertion direction (D10) and the stacking direction (DZ), a second bevel (17) which allows the penetration end (13) to move the lower ply (2) and upper ply (3) away from one another until the fully open configuration is reached.

3. Method according to Claim 1 or 2, characterized in that the three-dimensional fabric (1) comprises a plurality of continuous reinforcing threads (20) which are oriented in the warp direction (DX) and disposed side by side, parallel to one another, at a predetermined repeat pitch (P20) in the weft direction (DY), each reinforcing thread (20) forming, along the warp direction (DX), a crenellated undulation which comprises a succession of periods which each comprise a first segment (21) referred to as "upper segment", the reinforcing thread (20) being interlaced with the upper ply (3), then a second segment (22) forming a stay (4) referred to as "top-down" which connects said upper segment (21), and thus the upper ply (3), to the lower ply (2), then a third segment (23) referred to as "lower segment", the reinforcing thread (20) being interlaced with the lower ply (2), and then a fourth segment (24) forming a stay (4) referred to as "bottom-up" which connects said lower segment (23), and thus the lower ply (2), to the upper ply (3).

4. Method according to Claim 3, characterized in that the insertion direction (D10) is transverse to the warp direction (DX), and more preferably perpendicular to the warp direction (DX) and thus parallel to the weft direction (DY), in that the penetration end (13) of the cutting tool (10) is fitted into the space referred to as "transverse corridor" (25) which is comprised between on one side a row of top-down stays (4, 22), which are distributed along the weft direction (DY) and correspond to the plurality of reinforcing threads (20), and on the other side the row of immediately following bottom-up stays (4, 24), and in that the lower sole (11) is devoid of a cutting blade and is arranged in such a way as to slide on the row of lower segments (23) which are integrated in the lower ply (2) vertically in line with the transverse corridor (25), without cutting said lower segments (23), whereas the upper sole (12) is provided with a cutting blade (15) which cuts the upper ply (2), in the space comprised between two successive rows of upper segments (21), and consequently without cutting the reinforcing threads (20).

5. Method according to Claim 4, characterized in that the width (W12) of the upper sole (12), considered perpendicularly to the insertion direction (D10), is greater than the width (W11) of the lower sole (11).

6. Method according to Claim 3, characterized in that the insertion direction (D10) is parallel to the warp direction (DX), in that the penetration end (13) of the cutting tool (10) is fitted into the space referred to as "longitudinal corridor" (27) which is comprised between two immediately adjacent parallel reinforcing threads (20), and in that the lower sole (11) and the upper sole (12) are each provided with a cutting blade (15) in order to simultaneously cut the lower ply (2) and the upper ply (3) along the warp direction (DX), between said two reinforcing threads (20).

7. Method according to Claim 6, characterized in that two cutting tools (10) are fitted simultaneously into two separate parallel longitudinal corridors (27) such that the operation of simultaneously cutting the lower ply (2) and upper ply (3) in each of the two longitudinal corridors (27) makes it possible to subdivide the three-dimensional fabric (1) into a central strip (28), comprised between the two longitudinal corridors (27), and two lateral strips (29, 30).

8. Method according to Claim 6 or 7, characterized in that the lower sole (11) and the upper sole (12) each have the form of a ski provided with an inwardly curved tip (31), and are butt-joined in a mirror image of one another via their respective tips (31) such that the penetration end (13) is formed.

9. Method according to one of the preceding claims, characterized in that the cutting movement is generated by displacing the three-dimensional fabric (1), in the insertion direction (D10), relative to the cutting tool (10) which is kept fixed in place.