Method for machining a tyre using a measurement of the deformation of the tyre in order to detect the arrival of the cutting tool near the reinforcing wires of the tyre

Abstract

The invention relates to a method for machining a tyre (1) having a wall (3) that comprises an outer layer (4) made of rubber and a reinforcing ply (5) located beneath the outer layer (4) and containing reinforcing wires (6), during which the tyre (1) is rotated (R20), the loaded position (P3_S1) is measured, the loaded position being the position occupied, in a working sector (S1), by the wall (3) of the tyre that is in contact with the cutting tool (2), the free position is measured (P3_S2), the free position being the position occupied by the wall (3) in a reference sector (S2), wherein the wall (3) is disengaged from the cutting tool (2), and the loaded position (P3_S1) is compared with the free position (P3_S2) in order to detect whether a predetermined deviation, referred to as the "characteristic deformation threshold" (Delta_thresh), has been exceeded, wherein the threshold is representative of the occurrence, in the working sector (S1), of a deformation (26) that signals that the cutting tool (2) has reached the reinforcing ply (5).

Description

METHOD FOR MACHINING A BANDAGE USING A MEASUREMENT OF THE DEFORMATION OF THE BANDAGE TO DETECT THE ARRIVAL OF THE CUTTING TOOL IN THE PROXIMITY OF THE REINFORCING THREADS OF THE BANDAGE

[0001] The present invention relates to the field of machining of tires, in particular rubber-based pneumatic tires, said machining having the aim of removing from the tire at least part of the material which constitutes it, for example with a view to retreading said tire and / or recycling said material when said tire reaches the end of its life.

[0002] Retreading processes have been known for a long time, during which the tread is removed from a used tire to recover the carcass of said tire and reuse said carcass by placing a new tread on it.

[0003] For example, the tread can be peeled off and the surface of the casing can then be worked with a grinding wheel to texture the layer of rubber covering the casing and thus ensure good grip for the new tread. During grinding, care is usually taken to maintain a certain thickness of the layer of rubber covering the casing, in order to minimize the amount of material needed to produce the new tread.

[0004] However, with a view to increasing the recycling rate of the raw materials that make up the bandages, the inventors wanted to develop a machining process that would enable the recovery of the maximum possible amount of rubber-based material, particularly from the tread, from a bandage that is finally reaching the end of its life and whose carcass can therefore no longer be repaired or reused.

[0005] However, this presents several difficulties.

[0006] A first difficulty is to achieve rapid material removal, in order to limit the cycle time and energy consumption required to carry out the machining operation.

[0007] A second difficulty is that, to facilitate the recycling of recovered materials, the machining process should allow for a certain selectivity, so that only the material based on desired rubber, of good quality, without mixing with said material foreign bodies, such as fragments of reinforcing threads from the carcass.

[0008] Furthermore, it is important not to damage the cutting tool, or more generally the machine, which is used to carry out the machining operation, in particular in order to reduce the frequency, duration, and costs of maintenance. Therefore, it is necessary to prevent the cutting tool from catching, cutting or tearing the reinforcing wires present in the carcass, in particular when it comes to metal reinforcing wires, which are particularly likely to blunt the cutting tool and / or block the machining operation by becoming entangled.

[0009] The objects assigned to the invention therefore aim to remedy the aforementioned drawbacks and to propose a machining method which makes it possible to quickly and safely recover a maximum of noble rubber-based material from a used tire, and which in particular makes it possible for this purpose to remove material as close as possible to the underlying carcass of the tire, without risking harmful interference with the reinforcing threads of said carcass.

[0010] The objects assigned to the invention are achieved by means of a method of machining a bandage, said bandage having a wall which comprises at least one external layer based on elastomer, preferably based on vulcanized rubber, and at least one reinforcing ply, located under said external layer and containing reinforcing threads, method during which: - the bandage is fixed on a rotating support having an axis of rotation, - said rotary support is rotated in order to rotate the bandage around said axis of rotation, - in a first azimuthal angular sector considered around the axis of rotation, called the "working sector", a cutting tool is pressed against the wall of the bandage, in a direction called the "penetration direction" which is directed towards the reinforcing ply, so that said cutting tool penetrates into the external layer and removes material from said external layer by gradually approaching the reinforcing ply, said method being characterized in that, while the bandage is rotated and the cutting tool is pressed against the wall of said bandage: - we measure a first position of the wall, called the “constrained position” which occupies, in the working area, the wall of the bandage which is in contact with the cutting tool, - a second corresponding position of the wall, called the "free position", is measured, which said wall occupies in a second azimuthal angular sector considered around the axis of rotation, which is called the "reference sector", which is angularly distant from the working sector, and in which the wall is clear of the cutting tool, - the constrained position is compared to the free position in order to detect the reaching or crossing of a predetermined difference, called the "characteristic deformation threshold", which is representative of the appearance, in the working sector, of a deformation of the wall which results from a flexural collapse of the reinforcing wires under the pressure exerted by the cutting tool when, due to proximity between the cutting tool and the reinforcing wires, the progression of the cutting tool in the direction of penetration is only incompletely accompanied, or no longer accompanied at all, in the working sector, by an effective reduction in the thickness of the external layer by removal of material.

[0011] Advantageously, the inventors have in fact observed that: - as long as the residual thickness of the outer layer is sufficient, the progression of the cutting tool through the outer layer, in the direction of penetration, over a given depth, in the angular working sector, is accompanied by a cutting, and therefore an effective removal, of the material constituting the outer layer over a substantially equivalent depth, so that the variation in the free position of the wall follows substantially, or even exactly, the variation in the position of the cutting tool, and therefore the variation in the constrained position of the wall, so that, by compensation effect, the difference observed between the measured free position and the measured constrained position is substantially constant, and more particularly substantially zero, - but that, on the other hand, when the residual thickness of the external layer which separates the cutting tool from the reinforcing wires belonging to the reinforcing ply becomes, under the effect of the removal of material, less than a predefined value, or more particularly becomes substantially zero, and therefore the cutting tool reaches a certain proximity to the reinforcing wires, and more particularly the cutting tool comes into contact with said reinforcing wires, in the angular working sector, that is to say in other words when the cutting tool has substantially or even totally exhausted the elastomeric material constituting the external layer, then the continuation of the progression of the cutting tool in the direction of penetration causes elastic bending deformation of the reinforcing wires, due to the fact that said cutting tool drives said reinforcing wires in its movement in the direction of penetration without being able to remove any more material from the wall, and therefore without modifying the free position of the wall in the reference angular sector; thus, the constrained position of the wall continues to evolve with the position of the cutting tool, under the constraint of said cutting tool, in the working angular sector, while the free position of the wall remains substantially or even exactly constant, in the reference angular sector. Due to this divergence, the difference observed between these two measured positions increases, in practice rapidly, until it crosses the fixed characteristic deformation threshold.

[0012] The invention advantageously makes it possible to detect the crossing of this characteristic deformation threshold, and therefore to detect the moment when the residual thickness of the external layer becomes too low to be able to absorb the progression of the cutting tool, which means that the cutting tool has reached the limit of the reinforcement layer, and therefore the limit of the depth of material that it is possible to recover with said cutting tool.

[0013] Concretely, when the residual thickness of the external layer, and therefore the distance which separates the cutting tool from the closest reinforcing wires located in the reinforcing ply, becomes less than a predefined value, the pressure exerted by the cutting tool during the continuation of the penetration movement of the cutting tool against the wall of the bandage causes a local deformation of said wall of the bandage, in the angular working sector, by elastically pushing in the reinforcing wires which support said wall, which locally creates a flat or even a hollow in relation to the curvature which the wall of the free bandage presents, in the absence of a cutting tool.

[0014] When the wall of the bandage thus collapses under the pressure of the cutting tool, said wall tends to give way to the cutting tool, so that said cutting tool is no longer able, despite the continuation of its movement in the direction of penetration, to effectively remove material, and therefore thickness, from said wall, in proportion to the amplitude of said movement.

[0015] The appearance of this local deformation therefore creates, as said above, a divergence between on the one hand the evolution of the value of the constrained position, which is by nature sensitive to said local deformation of the wall and varies in particular as a function of said local deformation of the wall, and on the other hand the value of the free position, which is considered in a zone not affected by the local deformation, and which therefore varies essentially as a function of the sole evolution of the effective residual thickness of the wall.

[0016] The inventors have discovered that by monitoring the occurrence of this local deformation induced by the cutting tool, and by quantifying the extent of this local deformation induced by the cutting tool, it is possible to reliably detect a proximity between the cutting tool and the underlying reinforcing wires, without the risk of the cutting tool perforating the reinforcing ply or tearing off reinforcing wires.

[0017] It then becomes possible to interrupt the machining operation before the cutting tool damages the reinforcing wires or perforates the reinforcing ply, and to adapt the cutting path so that the cutting tool can pass as close as possible to said reinforcing wires, without catching, tearing or cutting said reinforcing wires, or perforating the reinforcing ply. It is thus possible to optimize material removal, without putting the cutting tool or, more generally, the installation at risk.

[0018] Furthermore, the inventors have also found that such local deformation behavior due to a reduction in thickness is reproducible, in principle, from one bandage to another, so that the method is applicable to a wide variety of bandages, of different dimensions and structures, and is therefore very versatile.

[0019] Other objects, characteristics and advantages of the invention will appear in more detail on reading the description which follows, as well as with the aid of the appended drawings, provided for purely illustrative and non-limiting purposes, among which:

[0020] Figure 1 illustrates, according to a schematic sectional view in a plane normal to the axis of rotation of the support, a sectional plane which here coincides with the equatorial plane of the bandage, a first phase of a method according to the invention, where the cutting tool, here formed by a rotating cylindrical knife, approaches the wall of the bandage, by the apparent surface, here the radially external face, of said wall. In this schematic view, the orientation of the cylindrical knife has been adapted for a better understanding of the representation.

[0021] Figure 2 is a detail view of Figure 1.

[0022] Figure 3 is a view of the first phase of the process of Figures 1 and 2 in a radial plane containing the axis of rotation, and which also corresponds to a plane containing the axis of rotation of the cylindrical knife. An enlarged partial view shows the reinforcing wires present within the reinforcing ply.

[0023] Figure 4 is a perspective view of the bandage and cutting tool of Figure 3.

[0024] Figure 5 is a view similar to Figure 1, during a second phase of the method during which, while the bandage is rotated, the cutting tool penetrates the outer layer in the direction of penetration and thus removes part of the material constituting said outer layer, consequently reducing the residual thickness of said outer layer and therefore, locally, the overall thickness of the wall of the bandage.

[0025] Figure 6 is a view similar to Figure 2, during the second phase illustrated in Figure 5.

[0026] Figure 7 is a view similar to Figure 3, during the second phase illustrated in Figure 5.

[0027] Figure 8 is a view similar to Figure 4, during the second phase illustrated in Figure 5.

[0028] Figure 9 is a view similar to Figures 1 and 5, during a third phase of the method during which, while the bandage is still rotated, the cutting tool penetrates further into the outer layer to the point of arriving in the immediate vicinity of the underlying reinforcing threads, and more particularly in contact with said reinforcing threads, the residual thickness of the outer layer thus being less than a predefined value, or even almost zero.

[0029] Figure 10 is a view similar to Figures 2 and 6, during the third phase illustrated in Figure 9.

[0030] Figure 11 is a view similar to Figures 3 and 7, during the third phase illustrated in Figure 9. As in Figure 3, an enlarged partial view shows the reinforcing threads present within the reinforcing ply.

[0031] Figure 12 is a view similar to Figures 4 and 8, during the third phase illustrated in Figure 9.

[0032] Figure 13 is a view similar to Figures 1, 5 and 9, during a fourth phase of the method during which, while the bandage is still rotated, the cutting tool continues its movement towards the reinforcing ply, in the direction of penetration, and, having exhausted the material constituting the external layer, no longer finds, or no longer finds enough, elastomer-based material to remove, so that the progression of the cutting tool is accommodated, in the working sector, by an elastic deformation in flexion of the reinforcing threads, the cutting tool pushing back the reinforcing threads and thus causing a local deformation of the wall of the bandage.In this way, the progression of the cutting tool creates and / or amplifies the difference between, on the one hand, the constrained position of the wall, considered in the working sector, and on the other hand the free position of the wall, which said wall finds by elastic return outside the working sector, and which is measured in the reference sector, to the point that this difference reaches and exceeds the characteristic deformation threshold which signals that the cutting tool has reached, or substantially reached, the reinforcement layer.

[0033] Figure 14 is a view similar to Figures 2, 6, and 10, during the fourth phase illustrated in Figure 13.

[0034] Figure 15 is a view similar to Figures 3, 7, and 11, during the fourth phase illustrated in Figure 13.

[0035] Figure 16 is a view similar to Figures 4, 10 and 12, during the fourth phase illustrated in Figure 13.

[0036] Figure 17 illustrates, using schematic curves, the evolution as a function of time t, of the constrained position of the wall in the working sector, of the free position of the wall in the reference sector, of the residual thickness of the external layer which separates the cutting tool from the nearest reinforcing wires, and of the difference which is observed between the constrained position and the free position. This difference begins to diverge significantly when, during the fourth phase mentioned above, the wall of the bandage collapses under the pressure of the cutting tool and thus eludes the cutting tool, when said cutting tool is no longer able, despite the continuation of its movement in the direction of penetration, to remove effectively of the material, and therefore of the thickness, to said wall, in proportion to the amplitude of said movement (typically here in proportion to the pitch which corresponds to the radial progression of the cutting tool between the third phase and the fourth phase). Said gap thus ends up crossing the characteristic deformation threshold which makes it possible to detect that the distance which separates the cutting tool from the reinforcing wires belonging to the reinforcing ply has become less than a predefined value, and more particularly that the cutting tool has reached the reinforcing ply.

[0037] Figure 18 illustrates, in a perspective view, a machining installation making it possible to implement a machining method according to the invention.

[0038] The present invention relates to a method of machining a bandage 1.

[0039] Machining allows the mechanical removal of material from the bandage 1, using a cutting tool 2.

[0040] It will be noted that, in absolute terms, it would be possible to consider using an abrasive tool, such as a grinding wheel, as the cutting tool 2. However, a cutting tool 2 having at least one sharp blade will be preferred. Such a cutting tool 2 having a sharp blade provides, in particular, a faster and more efficient cut than a grinding wheel, for less energy expenditure. In all cases, the cutting tool 2 chosen must be capable of removing material from the outer layer of the bandage 1, and more particularly of approaching the reinforcing threads present in an underlying reinforcing ply, without risking tearing said reinforcing threads.

[0041] The machining method according to the invention may be used, for example, for stripping a bandage 1, that is to say for removing the remains of a worn tread from the bandage, with a view to retreading said bandage, when the carcass of said bandage 2 is reusable.

[0042] However, preferably, the machining method according to the invention will be part of a method for recycling a rubber-based material present on said bandage 1, preferably for recycling the rubber-based material constituting the tread, and will therefore aim to recover the largest possible quantity of said material relative to the total quantity of said material which is present on said bandage 1.

[0043] Such a recycling process will be particularly applicable to end-of-life tires 1, whose carcass can no longer be repaired or reused, and which must therefore be dismantled to recover the raw materials.

[0044] As can be seen in particular in figures 2, 3, 4, 9 and 11, the bandage 1 has a wall 3 which comprises at least one external layer 4 based on elastomer, preferably based on vulcanized rubber, and at least one reinforcing ply 5, located under said external layer 4 and containing reinforcing threads 6.

[0045] In a manner known per se, and as is notably visible in Figures 9 and 11, such a reinforcing ply 5 is preferably formed by a thin layer of a material forming a matrix which extends in two main directions which define the surface of the reinforcing ply, and in the thickness of which the reinforcing threads 6 are embedded.

[0046] In particular, it will be possible to have a reinforcing sheet 5 whose matrix is ​​formed from an elastomer base, preferably from rubber, and containing metallic reinforcing threads 6, or possibly from a polymer such as aramid.

[0047] Alternatively, the reinforcing sheet 5 may have a resin matrix, reinforced by fiberglass reinforcing threads 6.

[0048] Within the same reinforcing ply 5, the reinforcing threads 6 will preferably be arranged side by side, parallel to each other, even if other arrangements are possible without departing from the scope of the invention.

[0049] Preferably, the reinforcing ply 5 will form a crown ply.

[0050] Preferably, in a manner known per se, and as can be seen in Figure 18, the bandage 1 has a first annular heel 7 and a second annular heel 8, provided respectively with a first bead wire and a second bead wire, and the wall 3 of the bandage forms a crown 10, radially external, as well as a first flank 11 which connects said crown 10 to the first heel 7 and a second flank 12 which connects the crown 10 to the second heel 8.

[0051] The outer layer 4 will preferably correspond to the tread of the bandage 1, which extends over the crown 10 of said bandage 1. This being the case, the invention is potentially applicable to any outer layer 4, regardless of its location.

[0052] Preferably, in a manner known per se, the first sidewall 11, the apex 10 and the second sidewall 12 will together form a toroidal wall 3, concave relative to the axis of rotation Z20. The tire 1 may thus preferably be a pneumatic tire whose wall 3 delimits the toroidal inflation cavity.

[0053] The bandage 1 will preferably be of a dimension allowing its mounting on a rim whose diameter is between 13 inches and 63 inches.

[0054] Preferably, the method may be applied to tires intended for heavy goods vehicles, typically vehicles with a total authorized laden weight greater than 3.5 tonnes, said tires being sized to be mounted on rims with dimensions between 16.5 inches and 24 inches.

[0055] During the process, the bandage 1 to be machined is first fixed on a rotating support 20 having an axis of rotation Z20.

[0056] By convention, "axial" will be used to designate a direction parallel to the axis considered, here more particularly a direction parallel to the axis of rotation Z20, and "radial" will be used to designate a direction perpendicular to said axis.

[0057] The term "circumferential" direction will be used to designate a direction of the tire which is orthoradial to the axis of the tire, that is to say which, at the point considered on the tire, is normal to the radial plane which contains the axis and which passes through the said point considered.

[0058] Preferably, the rotary support is arranged to hold the bandage 1 by the first heel 7 and second heel 8, while leaving the crown 10 free to deform elastically under the pressure of the cutting tool 2.

[0059] The inventors have in fact found that it is thus possible to hold the bandage 1, in particular in the case of a bandage for a heavy goods vehicle, by the beads 7, 8, while maintaining sufficient firmness of said bandage 1 for the machining operation, without it being necessary to inflate said bandage 1 or to support said bandage 1 by tiles which would be placed under the top 10 of said bandage 1.

[0060] It is therefore advantageous to machine bandages 1 which are no longer watertight, because they have perforations or lacerations, which is common on bandages which have reached the end of their life.

[0061] In this respect, it will be noted that the method can preferably be implemented on a non-inflated tire 1, that is to say a tire 1 whose radially internal face of the wall 3 is at ambient atmospheric pressure, without overpressure relative to said ambient atmospheric pressure which bathes the support 20 and more generally the workshop in which the installation 40 which makes it possible to carry out the method is installed. The support 20 therefore preferably serves to hold by the first and second beads 7, 8, and drive in rotation R20, a non-inflated tire 1.

[0062] Advantageously, the fact of not having to inflate the bandage 1 to implement the method according to the invention makes it possible to use a particularly simple support 20, capable of adapting to numerous dimensions of bandage 1, since it is not necessary to provide means which would make it possible to ensure sealing of the cavity of the bandage 1, and which would therefore be very dependent on the dimensions of each bandage.

[0063] The retention by the heels 7, 8 also makes it possible to maintain, in the parts of the bandage intended to be subjected to the action of the cutting tool 2, a compromise between, on the one hand, sufficient initial rigidity which is necessary to allow the cutting tool 2 to engage and cut the outer layer 4, and on the other hand, sufficient flexibility, once the thickness of the outer layer 4 has been reduced, to allow the appearance of the local deformation which is necessary, in accordance with the method according to the invention, to detect that the cutting tool 2 has arrived in the vicinity of the reinforcing threads 6.

[0064] Furthermore, the support by the heels 7, 8 allows the same support 20 to easily adapt to bandages 1 of very varied dimensions, and in particular to bandages 1 having internal diameters which are very different from one bandage 1 to another.

[0065] In this respect, it will be noted that, as illustrated in Figure 18, the rotary support 20 could for example be formed by a radially expandable drum 21, having jaws 22 which are capable of alternately deploying in a radially centrifugal manner to engage the heels 7, 8, thus adopting a diameter corresponding to the internal diameter of the bandage 1, and retracting in a radially centripetal manner to release the bandage 1 after the machining operation.

[0066] It should be noted that any suitable drum variant may be used, for example a cylindrical drum provided with an inflatable membrane which comes into radial contact sealing of the heels 7, 8, which possibly allows the cavity between the membrane and the wall of the bandage to be slightly inflated to improve the rigidity of the bandage during machining, or a drum comprising two axially movable flanges, each engaging one of the heels.

[0067] According to the process: - the rotating support 20 is rotated in order to drive the bandage 1 in rotation R20 around the axis of rotation Z20, and - in a first azimuthal angular sector SI considered around the axis of rotation Z20, called the “working sector” SI, a cutting tool 2 is pressed against the wall 3 of the bandage, in a direction FWD called the “penetration direction” FWD which is directed towards the reinforcement ply 5, so that said cutting tool 2 penetrates into the external layer 4 and removes material from said external layer 4 while gradually approaching the reinforcement ply 5.

[0068] It will be noted that the penetration movement of the cutting tool 2 may be sequential, the cutting tool 2 approaching the reinforcing ply, and therefore penetrating more deeply into the wall 3, by successive increment steps, each increment step corresponding to a desired depth of pass, and each movement over an increment step being followed by a temporary stop of the penetration movement, while the bandage 1 continues its rotation R20, to allow the machining of the wall to the depth of pass thus defined, before carrying out the next step.

[0069] Alternatively, the penetration movement of the cutting tool 2 may be continuous, and only stop once the cutting tool 2 has reached the maximum possible penetration depth, i.e. the limit of proximity to the reinforcing wires 6 of the reinforcing ply 5.

[0070] In all cases, a machining operation by turning will preferably be carried out.

[0071] As an indication, the rotation speed of the support 20, and therefore of the bandage 1, during the material removal operations, may be between 1 rpm and 5 rpm, for example equal to 3 rpm. Higher rotation speeds could of course be considered, for example of the order of 10 rpm. The speeds The aforementioned methods, however, present an advantageous compromise between the power required for acceleration and braking of the support 20, reliability of the detection of the arrival of the cutting tool 2 on the reinforcement layer 5, and cycle time.

[0072] Preferably, and as can be seen in figures 1 to 16, the cutting tool 2 is formed by a cylindrical knife 25 with a circular base, driven in rotation R25 around its generating axis Z25, and of which a circular edge 25A forms the cutting edge which engages the wall 3 of the bandage.

[0073] Such a cylindrical knife 25 advantageously provides a precise, clean and regular cut, which makes it possible to remove the constituent material of the external layer 4 in the form of shavings or even strips.

[0074] The speed of rotation R25 of the knife 25 around its generator axis Z25 will for example be between 1 rpm and 1.5 rpm.

[0075] The generator axis Z25, around which said cylindrical knife 25 rotates in rotation R25 on itself while the bandage 1 is itself driven in rotation R20 by its support 20, is advantageously oriented so that said cylindrical knife 25, and more particularly its edge 25A, is presented in a manner substantially tangent to the visible surface, in movement, of the wall 3, and more preferably slightly obliquely relative to said visible surface.

[0076] Thus, more preferably, in order to promote the penetration of the edge 25A of the cylindrical knife 25 into the wall 3 and to clear the space necessary for a robotic arm 44 responsible for positioning and moving the knife 25 relative to the support 20 and the bandage 1, the generator axis Z25 of the cylindrical knife will have, in a plane normal to the axis of rotation Z20, and more particularly in a plane normal to the axis of rotation Z20 passing through the point of the edge 25A which is in contact with the wall 3 and which is closest to the axis of rotation Z20, a non-zero angle of inclination relative to the tangent to the perimeter of the wall 3, for example an angle of inclination of the order of 15 degrees.

[0077] The cylindrical knife 25 will preferably be provided with a sharpening system, comprising for example a sharpening wheel, which will allow the cutting edge to be automatically sharpened during or after the cutting operation.

[0078] The edge 25A forming the cutting edge will preferably be a smooth edge 25A which is in the form of a continuous wall, like the knife 25 shown to the right of the bandage 1 in figure 18. Such a smooth edge 25A will in fact have the advantage of not having any roughness likely to accidentally catch a reinforcing wire 6, and will therefore be able to approach without risk as close as possible to the reinforcing ply 5.

[0079] Preferably, the cylindrical knife 25 will have a diameter between 100 mm and 300 mm.

[0080] According to the invention, while the bandage 1 is driven in rotation R20 and the cutting tool 2 is pressed against the wall 3 of said bandage: - we measure a first position of the wall P3 S1, called the “constrained position” P1 S1, which is occupied, in the working sector SI, by the wall 3 of the bandage which is in contact with the cutting tool 2, - a second corresponding position P3 S2 of the wall is measured, called the “free position” P3 S2, which said wall 3 occupies in a second azimuthal angular sector S2 considered around the axis of rotation Z20, which is called the “reference sector” S2, which is angularly distant from the working sector SI, and in which the wall 3 is clear of the cutting tool 2, - the constrained position P3 S1 is compared to the free position P3 S2 in order to detect the reaching or crossing of a deviation called the predetermined “characteristic deformation threshold” Delta thresh.

[0081] In this case, said deviation called “characteristic deformation threshold” Delta thresh predetermined is representative of the appearance, in the working sector SI, of a deformation 26 of the wall 3 which results from a flexural collapse of the reinforcing wires 6 under the pressure exerted by the cutting tool 2 when, due to a proximity between the cutting tool 2 and the reinforcing wires 6, the progression of the cutting tool 2 in the penetration direction FWD is only incompletely accompanied, or no longer accompanied at all, in the working sector SI, by an effective reduction in the thickness of the external layer 4 by removal of material.

[0082] As an indication, we can choose, in particular depending on the bandage 1 to be treated, a characteristic deformation threshold value Delta thresh between 5 mm and 30 mm, for example equal to 10 mm.

[0083] It will be noted that, in view of the sign convention used in particular in figure 17, where the comparison between the constrained position P3 S1 and the free position P3 S2 is carried out by calculating the difference, which will be noted “Delta”, corresponding to a subtraction between the constrained position P3 S1 and the free position P3 S2, i.e. Delta = P3_S1 - P3 S2, then the characteristic strain threshold value Delta thresh mentioned above is, strictly speaking, of negative sign, and therefore preferably included, algebraically, between -5 mm and -30 mm, for example equal to -10 mm. For convenience of description, however, reference may preferably be made to the absolute value of said Delta deviation and in particular of said characteristic strain threshold Delta thresh.

[0084] In practice, the distance which separates said cutting tool 2 from the reinforcing wires belonging to the reinforcing ply 5 corresponds to the smallest residual thickness E4 of the external layer 4 which remains between on the one hand the cutting tool 2, here more particularly the edge 25A of the knife, which is in contact with the wall 3, and on the other hand the reinforcing wires present in the reinforcing ply 5 which are located closest to said cutting tool 2. It will therefore be possible, for convenience of description, to designate under the same reference said distance and the thickness E4 of the external layer 4.

[0085] As indicated above, the more the cutting tool 2 advances relative to the support 20, in the penetration direction FWD, and therefore in the direction of the reinforcement ply 5, the more said cutting tool 2 digs into the external layer 4 by removing the material constituting said external layer 4, at least as long as the residual thickness E4 of the external layer 4 offers sufficient material in engagement with the cutting tool 2.

[0086] On the other hand, when the cutting tool 2 comes close to the reinforcing wires 6, and more particularly reaches the reinforcing ply 5, the reinforcing wires 6 provide it with much greater cutting resistance than the elastomer-based material which constitutes the outer layer 4.

[0087] Continuing to move the tool in the penetration direction FWD then has the effect of pushing the reinforcing wires 6 and driving them in the penetration direction FWD, thereby elastically bending said reinforcing wires 6, and therefore more generally the wall 3, in the working sector SI, and this all the more easily as the reducing the thickness of wall 3 in the area considered reduces the bending rigidity of wall 3.

[0088] The wall 3 is then locally subject, in the working sector SI, to a deformation 26 in elastic bending induced by the cutting tool 2, which, by progressing in the penetration direction FWD, pushes in said wall 3, and therefore modifies the curvature of said wall 3 in the working sector 1, compared to the curvature that this same wall 3 naturally presents when it is removed from the influence of the cutting tool 2.

[0089] The deformation 26 can take the form of a flat, which breaks the natural curve of the wall 3, or even, more markedly, as can be seen in figures 13 to 16, of a depression at the level of which the wall presents a local inversion of the sign of its curvature, compared to its natural curve.

[0090] This deformation 26 is advantageously detectable by comparing on the one hand the natural shape of the wall 3, here characterized by the free position P3 S2, such that this natural shape is considered outside the zone of influence of the cutting tool 2, here more particularly in the reference sector S2, to on the other hand the artificial shape, characterized here by the constrained position P3 S1, which the wall 3 adopts in the zone subjected to the influence, here to the support force, of the cutting tool 2, in this case in the working sector SL

[0091] It will be noted that taking as a reference the actual shape of the wall 3, and therefore the corresponding free position P3 S2, on the bandage 1 which is the subject of the current method, and while said bandage 1 is rotating, allows the process of detecting the deformation not to be affected by centering, shape or curvature defects which may affect the bandage 1.

[0092] Indeed, it is for example possible to measure over at least one complete revolution of the bandage 1, the distance at which the wall 3 located in the reference sector S2 is from the axis of rotation Z20, and to take into account possible variations in radius, due for example to out-of-roundness, in the process of measuring the deformation, so that possible defects in shape, roundness or centering will not distort the process of measuring deformation and, in particular, will not create false positives during the analysis of the deformation with a view to detecting the characteristic deformation threshold Delta thresh.

[0093] For example, it will thus be possible, during a step of acquiring the profile of the bandage 1, to measure and record, at each azimuth of the bandage 1, for example every 1 degree of angle, the radius of the wall 3, for example before engaging the cutting tool 2 in the external layer 4, or after having made a first pass of the cutting tool 2 in the external layer 4, and thus to know, at each azimuth of the bandage, in a reference frame attached to the bandage 1, the deviation of the real radius from the average radius, then to correct for this deviation the values ​​of constrained position P3 S1 and free position P3 S2 measured respectively in the working sector 1 and the reference sector S2, according to the azimuth of the bandage which is present in each of said working sectors SI and reference S2 at the instant when the measurement of the position of the wall 3 is carried out.

[0094] Of course, the reference sector S2 must be chosen sufficiently far from the working sector SI so that the wall 3 located in said reference sector S2 is outside the zone of influence of the cutting tool 2, and more particularly in such a way that said wall 3 has been able to straighten, by elastic return, and thus have regained its natural shape, at the moment when it reaches said reference sector S2, after having been previously deformed by the pressure of the cutting tool 2 in the working sector SI.

[0095] For this purpose, the azimuthal distance d azim which separates, around the axis of rotation Z20, the azimuthal position at which the free position P3 S2 of the wall 3 is measured from the azimuthal position at which the constrained position P3 S1 of the wall 3 is measured is preferably greater than or equal to 30 degrees, preferably equal to or greater than 45 degrees, for example equal to or greater than 80 degrees.

[0096] In addition or as an alternative to these angle values, the azimuthal distance d azim which separates the azimuthal position at which the free position P3 S2 of the wall is measured from the azimuthal position at which the constrained position P3 S1 of the wall is measured may preferably be equal to or greater than 20 cm of arc length, for example between 20 cm and 100 cm of arc length.

[0097] The characteristic deformation threshold Delta thresh is of course chosen so that it corresponds to the occurrence of a deformation 26 of which it will have been determined that, when said deformation 26 occurs, the residual thickness E4 of the external layer is within a predefined, particularly fine range, which is such that, when the cutting tool is no longer separated from the reinforcing wires 6 by more than a residual thickness E4 included in said range, it is considered that a satisfactory degree of proximity has been reached between the cutting tool 2 and the reinforcing wires 6, so that it can be considered that the cutting tool 2 has reached the reinforcing ply 5, and more particularly the surface of the reinforcing wires 6.

[0098] This predefined value of residual thickness E4 can be substantially zero if, in view of the circumstances and in particular in view of the structure of the bandage 1 and the quality of the sharpening of the cutting tool 2, the cutting tool 2 can reach the surface of the reinforcing wires 6, without leaving any external layer 4 remaining, and slide over the reinforcing wires 6 without damaging the latter.

[0099] For information purposes, it may be considered that sufficient proximity has been reached between the cutting tool 2 and the reinforcing wires 6, and more particularly that the cutting tool 2 has reached the reinforcing ply 5, when the residual thickness E4 of the external layer is between 0 mm and 2 mm, or even between 0 mm and 1 mm.

[0100] The invention can be applied to bandages 1 whose reinforcing threads 6 closest to the outer layer 4, and therefore to the cutting tool 2, are made of any suitable material, including, where appropriate, a textile material, for example obtained from natural plant fibers or from polymer fibers such as aramid or PolyEthylene Terephthalate.

[0101] However, preferably, the method can be applied to a bandage 1 whose reinforcing threads 6 closest to the outer layer 4 in the FWD penetration direction are metallic, or in a “glass-resin” composite material which combines glass fibers in a resin matrix.

[0102] Such reinforcing wires 6, in particular metal wires, for example steel, will in fact have both good robustness, in particular to abrasion, and good elastic flexibility.

[0103] Such metallic reinforcing wires 6 are frequently found in the radially outermost crown plies within the tires 1 intended for heavy goods vehicles, or even for civil engineering machinery.

[0104] According to a preferred implementation possibility, the cutting tool 2 approaches the wall 3 and penetrates into said wall 3 in a penetration direction FWD which is transverse to the axis of rotation Z20, more preferably in a penetration direction FWD which is radial to the axis of rotation Z20.

[0105] Advantageously, by approaching the wall 3 with a centripetal radial approach movement, it is thus possible to machine the crown 10 of the bandage, with a view to recovering the material constituting the tread. Furthermore, the appearance of the deformation 26 is particularly easily detectable when this deformation has the effect of a centripetal radial bending of the crown 10, due to the marked change in the curvature of the circumference of the bandage that said deformation 26 induces locally, in the working sector S21, in consideration in a plane normal to the axis of rotation Z20, as can be seen in Figures 13, 14 and 15.

[0106] More preferably, the cutting tool 2 engages the wall 3 of the bandage via the top 10, in a radial FWD penetration direction.

[0107] This will maximize the speed of appearance and the amplitude of the deformation 26, which will improve the sensitivity and precision of the detection of the crossing of the characteristic deformation threshold Delta thresh. It will thus be possible to control the approach of the cutting tool 2 and bring the latter as close as possible to the reinforcement ply 5 and the reinforcement wires 6, while being able to react very quickly to prevent the cutting tool 2 from penetrating too deeply and attacking the reinforcement wires 6.

[0108] Furthermore, the contact between the cutting tool 2 and the wall 3 occupies, in the working sector SI, an axial range W2, considered on the abscissa along the axis of rotation Z20, which is called the “axial working range” W2.

[0109] The constrained position of the wall P3 S1 as well as the free position of the wall P3 S2 are then preferably measured within this same axial working range W2.

[0110] In other words, the constrained position P3 S1, and more particularly the deformation 26, on the one hand, and the free position P3 S2, and therefore the natural reference shape of the wall 3, on the other hand, are preferably measured in different angular positions in azimuth, namely respectively at the azimuthal position of the working sector SI and at the azimuthal position of the reference angular sector S2, but located approximately or even exactly at the same axial abscissa.

[0111] Thus, the free position P3 S2 will faithfully correspond to the natural position which is that of the wall 3 located on the circumferential trajectory of the cutting tool 2, and which the wall 3 therefore finds after leaving the working sector SI under the effect of the rotation R20, so that the comparison between the constrained position P3 S1 and the position P3 S2 will be particularly relevant and representative of the deformation 26 which is effectively attributable to the collapse of the wall 3, freed or almost freed locally of its external layer 4, under the pressure, here preferably the centripetal radial pressure, exerted by the cutting tool 2.

[0112] For information purposes, in the case where the cutting tool 2 machines the top 10 of the bandage, the axial distance separating the measurement point of the free position P3 S2 from the measurement point of the constrained position P3 S1 will preferably be less than or equal to 50 mm, preferably less than or equal to 30 mm, preferably less than 20 mm, and for example less than or equal to 10 mm, or even ideally substantially zero.

[0113] Furthermore, by measuring the constrained position P3 S1 within the axial working range W2, and preferably in the center of said axial working range W2, the deformation 26 is captured in the zone where this deformation 26 has the greatest speed of appearance and the greatest amplitude, here the maximum deflection of the wall 3 in the working sector SI, which optimizes the sensitivity and speed of the detection.

[0114] In the case where a cylindrical knife 25 is used, the measurement point of the constrained position P3 S1 will preferably coincide, in particular on the abscissa along the axis of rotation Z20, but also preferably in azimuth around the axis of rotation Z20, with the extreme point of the edge 25A which, at the instant considered, is located closest to the reinforcing wires 6, here therefore preferably which is located radially closest to the axis of rotation Z20.

[0115] The bandage 1 has, along the axis of rotation, an overall width W1 called “axial width” W1.

[0116] This axial width W1 corresponds to the distance which separates two fictitious gauge planes which are normal to the axis and which are each tangent to the wall, respectively in a first axially outermost point of the wall 3, generally located on the external surface of the first flank 11, and at a second axially outermost point of the wall 3, located axially opposite the first point, and generally located on the surface of the second flank 12.

[0117] Preferably, the axial range W2 called the “working range” W2, which is occupied on the abscissa along the axis of rotation by the contact between the cutting tool and the wall, in the working sector, is located within an axial range called the “equatorial range” which represents less than 50% of the axial width W1, preferably less than 35% of the axial width W1, or even less than 30% of the axial width W1, and which contains the abscissa of the fictitious plane called the “equatorial plane” P_EQ, which is normal to the axis of rotation Z20 and which passes through the middle of the axial width W1.

[0118] Thus, preferably, the cutting tool 2 removes thickness from the outer layer 4, and therefore from the wall 3, by digging an equatorial circumferential trench, in a central portion of the crown 10 which forms an equatorial band of the bandage 1.

[0119] This has the first advantage of removing thickness from the wall 3, and of carrying out the measurements of the constrained position P3 S1 and the free position P3 S2 in an area of ​​the bandage 1 which is particularly sensitive, and therefore reactive, to the reduction in the thickness of the wall 3, and which will therefore flex and sink rapidly and with a large radial amplitude as soon as the cutting tool 2 has reached the reinforcement ply 5, or at the very least the degree of proximity expected with the reinforcement ply 5. This will therefore provide rapid, precise and reliable detection of the crossing of the characteristic deformation threshold Delta thresh.

[0120] A second advantage is that the arrangement of the reinforcing threads 6 in the equatorial range is generally such, regardless of the model of bandage 1, that said reinforcing threads are the least vulnerable to accidental peeling.

[0121] In this respect, and in particular when it is decided to engage the cutting tool 2 in the apex 10, in the equatorial range, in a radial FWD penetration direction, while the bandage 1 is held by its heels 7, 8 and driven in rotation R20, the reinforcing wires 6 located in said apex and the closest radially to the cutting tool 2, here therefore the reinforcing wires 6 of the radially outermost reinforcing ply 5 of the bandage 1, will preferably form, with respect to the circumferential direction of the bandage 1, an angle called the “ply angle” which is between + 45 degrees and -45 degrees.

[0122] The reinforcing ply 5 may correspond to a crown ply, within which the reinforcing threads 6 extend parallel to each other and are therefore all oriented obliquely relative to the circumferential direction according to a non-zero ply angle which is preferably between 5 degrees and 45 degrees in absolute value.

[0123] Alternatively, the reinforcing ply 5 may correspond to a reinforcing strapping, called a “fret” or “zero-degree band”, obtained by winding onto the carcass of the tire 1 a band containing continuous and mutually parallel reinforcing threads 6, so that said band forms several juxtaposed or even superimposed turns around the axis of rotation Z20. In this case, the ply angle formed by the threads depends on the axial winding pitch of said turns, and is generally close to zero degrees, for example strictly less, in absolute value, than 5 degrees, preferably between zero degrees and 3 degrees, or even between zero degrees and 2 degrees, that is to say that the reinforcing threads 6 are almost parallel to the circumferential direction.

[0124] In order to evaluate the deviation in shape of the wall 3 between the constrained shape imposed by the cutting tool 2 in the working sector SI and the natural shape observable outside the working sector SI, here in the reference sector S2, the position, and more particularly the variations in position, of the wall 3, here of the apparent surface of the external layer 4, will preferably be measured in directions which will correspond: - for the measurement of the constrained position P3 S1 in the working sector SI, in the penetration direction FWD; - for the measurement of the free position P3 S2, in the reference sector S2, to the fictitious direction which is obtained by the transformation of the penetration direction FWD by rotation centered on the rotation axis Z20 and of an angle equal to the azimuthal distance d azim which separates the azimuthal position where the free position P3 S2 is measured from the azimuthal position where the constrained position P3 S1 is measured.

[0125] Thus, if the penetration direction FWD is radial, perpendicular to the axis of rotation Z20, as is preferably the case when it is desired to machine the top 10 of the bandage 1, then the measurement of the constrained position P3 S1 will be carried out according to said radial penetration direction FWD in the working sector SI, while the measurement of the position free P3 S2 will be carried out in another radial direction, in the reference sector S2, and which will form with the penetration direction FWD an angle equal to the azimuthal distance d azim.

[0126] Preferably, the measurement of the constrained position P3_S 1 is carried out by measuring the position of the cutting tool 2 relative to the axis of rotation Z20.

[0127] In the preferred case of machining the vertex 10, it will thus be possible to measure the radial position of the cutting tool 2, and more particularly the changes in the radial position of the cutting tool 2, and therefore measure the value and changes in the shortest distance, called the “tool distance” D tool, which separates the cutting tool 2 from the rotation axis Z20.

[0128] Such a measurement of the radial position of the cutting tool 2 will be easy and quick to acquire, because it is deduced directly from the data, and in particular from the measurements, used by the servo system which controls the positioning and movement of the cutting tool 2 relative to the support 20 according to the penetration direction FWD.

[0129] The measurement of the free position P3 S2 can be carried out by any appropriate means, in particular by means of a mechanical probe equipped with a roller which will roll in contact with the wall 3.

[0130] However, preferably, the measurement of the free position P3 S2 is carried out by means of a non-contact measuring tool.

[0131] Indeed, compared to other possible means, such as a mechanical probe, such a non-contact measuring tool allows rapid acquisition which does not disturb the measurement by avoiding creating a parasitic deformation of the wall 3.

[0132] Preferably, the measurement of the free position P3 S2 is carried out by means of a laser rangefinder 32 whose beam is pointed at the wall 3 in the reference sector S2.

[0133] Such a laser rangefinder 32 is in fact simple and reliable, and can advantageously be offset at a distance from the bandage 1, protected from any shavings or strips of material, or even from any debris of reinforcing wires 6 or fragments of cutting tool 2 which could be accidentally generated by machining and driven or ejected by the rotation R20 of the bandage.

[0134] The term “laser distance” D laser will designate the measurement which is taken by the laser rangefinder 32, and which therefore corresponds to the distance which separates the wall 3, such that this wall 3 is configured in the reference sector S2, of the reference point formed by said rangefinder 32, which is preferably fixed on the frame 30.

[0135] The beam of the laser rangefinder 32 is preferably aligned with the desired measurement direction, located in the reference sector S2.

[0136] In the case of machining of the vertex 10, the measurement direction will preferably be radial.

[0137] In the case of machining in a radial FWD penetration direction, the measurement of the free position P3 S2 makes it possible to know the distance which separates the radially external surface of the vertex 10 from the axis of rotation Z20, and therefore to know the evolution of the residual radial thickness E4 of the external layer 4, as the cutting tool 2 progresses in the FWD penetration direction.

[0138] The measurement of the constrained position P3 S1, the measurement of the free position P3 S2 and the comparison between these positions are advantageously carried out in real time by a control unit 33, such as an electronic control unit 33.

[0139] It is thus possible to detect the characteristic Delta thresh deformation threshold almost instantly, as soon as deformation 26 appears, and to immediately take appropriate reaction decisions.

[0140] This being the case, preferably, the detection of the characteristic deformation threshold Delta thresh is validated on condition that said characteristic deformation threshold Delta thresh remains reached or crossed for a duration which corresponds to at least one complete rotation of the bandage 1 on itself.

[0141] For this purpose, a time delay can be provided, which will depend on the rotation speed R20, and which can typically be understood, and preferably adjustable, between 300 milliseconds, or even 500 milliseconds, low value, and 2000 milliseconds, high value.

[0142] This time delay will be triggered when the control unit 33 perceives that the difference between the constrained position P3 S1 and the free position P3 S2 reaches the characteristic deformation threshold Delta thresh, and reset if the difference falls back, in absolute value below said characteristic deformation threshold Delta thresh.

[0143] Advantageously, such a time delay will in particular make it possible to avoid false positives linked to slight centering or curvature defects of the bandage 1 which result, on the circumference of the bandage 1, in slight local variations in the apparent radius of the wall 3, variations which could cause the apparent difference between the constrained P3 S1 and free P3 S2 positions to temporarily cross the characteristic deformation threshold Delta thresh, although the cutting tool 2 has not yet reached the reinforcement ply 5.

[0144] Preferably, the control unit 33 is arranged to cause, when the characteristic deformation threshold Delta thresh is reached or exceeded, and more particularly once the detection of said characteristic deformation threshold Delta thresh has been validated at the end of the aforementioned time delay, a recoil of the cutting tool 2, in order to release the cutting tool 2 from the wall 3, and / or a stoppage of the rotation R20 of the rotary support 20.

[0145] In other words, the method according to the invention makes it possible to stop the penetration of the cutting tool 2 into the wall 3, and more particularly the penetration of the cutting tool 2 into the external layer 4, and therefore to stop the cutting operation, as soon as said cutting tool 2 reaches the reinforcing ply 5, and more particularly the reinforcing wires 6, so that damage to said reinforcing wires 6 or the cutting tool 2 or even to pollute the elastomer-based material that is collected by machining with fragments of foreign bodies is avoided.

[0146] The recoil of the cutting tool 2 can advantageously be carried out in the penetration direction FWD, by making said cutting tool 2 turn back in order to move it away from the wall 3 in the same penetration direction FWD as that which said cutting tool 2 took to approach the reinforcement ply 5 and remove material from the external layer 4.

[0147] Preferably, after having detected the reaching or crossing of the characteristic deformation threshold Delta thresh, which amounts to implementing, in accordance with what has been described above, a method that could be designated as a “method for detecting the arrival of a cutting tool 2 at a reinforcement ply 5”, the removal of material from the external layer 4 is resumed by moving the cutting tool 2 relative to the rotary support 20 along a cutting path that is defined as a function of the free position P3 S2, called “radial envelope distance”, noted “D0_ply”, which the wall 3 relative to the rotating support 20 at the time when the characteristic deformation threshold Delta thresh was detected.

[0148] The cutting path thus defined will advantageously make it possible to carry out a complementary machining step, aimed at removing and recovering additional material constituting the external layer 4, after the first machining step which has made it possible not only to detect the position of the reinforcing ply 5, but also to remove and recover part of the material constituting the external layer.

[0149] The radial envelope distance D0_ply corresponds to the radial position, considered relative to the axis of rotation Z20, and more particularly to the outermost radial position, considered relative to the axis of rotation Z20, of the apparent surface of the reinforcing ply 5, and more particularly of the reinforcing wires 6, which have been exposed by the cutting tool 2.

[0150] Thus, the first machining operation, by which the cutting tool 2 is made to penetrate the outer layer in order to hollow out the outer layer 4, preferably in the equatorial page of the bandage 1, until it substantially reaches the reinforcing ply 5, can constitute a preliminary survey making it possible to determine the effective radial position of the reinforcing ply 5 relative to the axis of rotation Z20, here the radial envelope distance D0_ply.

[0151] This radial envelope distance D0_ply being known, a cutting path can be defined for the cutting tool 2, so that the cutting tool 2 can cover the entire axial width W1 of the tire, and more particularly the entire axial width of the crown 10, so as to recover the largest possible quantity of material constituting the tread, said cutting path being such that it allows the cutting tool 2 to pass as close to the reinforcing ply 5 as possible, or even preferably to slide in contact with the reinforcing ply 5, along the reinforcing threads 6, without catching, damaging or tearing the reinforcing threads 6.

[0152] For example, we can provide a cutting path for this purpose in which: - the cutting tool 2 is placed at a radial distance from the rotation axis Z20, called the “starting radial distance”, which is slightly less than the envelope radial distance D0_ply, of a chosen value, for example lower by a value between 2 mm and 5 mm, for example equal to 3 mm, so that the starting radial distance is slightly closer to the axis of rotation Z20 than the envelope radial distance D0_ply. Thus, the cutting tool 2 slightly pushes the reinforcing ply 5 at the start of the cutting path, and if necessary along part or even all of said cutting path, which in particular makes it possible to compensate for any out-of-roundness, and, thanks to the prestress thus exerted by the cutting tool 2, to maximize the quantity of material recovered by favoring a cutting of the external layer 4 as close as possible to the reinforcing threads 6, - then, while the bandage 1 is driven in rotation R20 by the support, the cutting tool 2 is moved axially, parallel to the axis of rotation Z20, preferably over the entire axial width W1 of the bandage 1, at a radial distance equal to the starting radial distance, in order to machine by turning the external layer 4 forming the tread, preferably over the entire width of said tread.

[0153] Advantageously, the adjustment and optimization of the cutting path according to the radial envelope distance D0_ply allows each bandage 1 to be machined safely, and in a way that is individually optimized for each bandage, which allows the recovery of as much material as possible.

[0154] The invention also relates as such to a recycling process, during which elastomer-based material, preferably vulcanized rubber-based material, more preferably vulcanized rubber-based material constituting a tread, is recovered in the form of chips or strips by subjecting one or more tires 1 to a machining process as described above, then this material is reused by incorporating it into the formulation of new elastomer mixtures, preferably into the formulation of new mixtures which are then used to manufacture new treads.

[0155] Of course, the invention also relates to an installation 40 making it possible to implement a machining method according to the invention.

[0156] Such an installation 40, an example of arrangement of which is illustrated in FIG. 18, and more particularly its control unit 33, is arranged to detect the reaching or crossing of the characteristic deformation threshold, in accordance with the method above-mentioned, to deduce therefrom a radial envelope distance D0_ply, then to define an appropriate cutting path, depending on the radial envelope distance D0_ply thus identified, and to apply said cutting path, preferably automatically.

[0157] Thus, the invention preferably relates to an installation 40 intended to machine a bandage 1, said bandage 1 having a wall 3 which comprises at least one external layer 4 based on elastomer, preferably based on vulcanized rubber, and at least one reinforcing ply 5, located under said external layer 4 and containing reinforcing threads 6, said installation 40 comprising: - a rotary support 20 which is arranged to receive the bandage 1, which rotary support 20 is mounted in rotation on a frame 30 around an axis of rotation Z20 and associated with a drive system 41 which makes it possible to drive said rotary support, and therefore the bandage, in rotation R20 on itself around said axis of rotation Z20, - a cutting tool 2, - a positioning system 42 which makes it possible to move the cutting tool 2 relative to the frame 30 and to the rotary support 20, while the rotary support 20 carrying the bandage 1 is driven in rotation R20, so as to be able to press the cutting tool 2 against the wall 3 of the bandage, in a first azimuthal angular sector SI considered around the axis of rotation Z20, called the “working sector” SI, in a direction called the “penetration direction” FWD which is directed towards the reinforcing ply 5, so that said cutting tool 2 can penetrate into the external layer 4 and remove material from said external layer 4 by gradually approaching the reinforcing ply 5.

[0158] The rotary support 20 may be in the form of a drum 21 carrying radially expandable jaws 22, and which is carried by the frame 30, itself preferably fixed, on which said drum 20 is articulated in rotation by at least one bearing.

[0159] The drive system 41 will comprise a motor, preferably an electric motor 43, controlled by the control unit 33 and making it possible to drive the drum 22 in rotation R20 relative to the frame 30.

[0160] The positioning system 42 may comprise a motorized arm 44, such as a robotic arm, which carries the cutting tool 2 at its free end. The control unit 33 is capable of automatically controlling said positioning system 42.

[0161] Said motorized arm 44 may also incorporate a sharpening system 45 for sharpening the cutting tool 2. The control unit 33 is advantageously capable of automatically controlling said sharpening system 45.

[0162] According to the invention, the installation 40 comprises: - a first measuring device 47, arranged to measure a first position of the wall, called the “constrained position” P3 S1 which, in the working sector SI, the wall 3 of the bandage which is in contact with the cutting tool 2 occupies, - a second measuring device 48, arranged to measure a second corresponding position of the wall, called “free position” P3 S2, which said wall 3 occupies in a second azimuthal angular sector S2 considered around the axis of rotation Z20, which is called “reference sector” S2, which is angularly distant from the working sector SI, and in which the wall 3 is disengaged from the cutting tool 2, - a control unit 33, arranged to compare the constrained position P3 S1 with the free position P3 S2 in order to detect the reaching or crossing of a deviation called the predetermined “characteristic deformation threshold” Delta thresh, which is representative of the appearance, in the working sector, of a deformation 26 of the wall which results from a flexural collapse of the reinforcing wires 6 under the pressure exerted by the cutting tool 2 when, due to a proximity between the cutting tool 2 and the reinforcing wires 6, the progression of the cutting tool 2 in the penetration direction FWD is only incompletely accompanied, or no longer accompanied at all, in the working sector SI, by an effective reduction in the thickness of the external layer 4 by removal of material.

[0163] As explained above, the appearance of the deformation 26, and therefore the crossing of the characteristic deformation threshold Delta thresh, signals that the residual thickness E4 of the external layer 4 which defines the distance which separates the cutting tool 2 from the reinforcing wires belonging to the reinforcing ply 5 has become less than the predefined value, or, in other words, signals that the cutting tool 2 has reached the reinforcing ply 5.

[0164] Preferably, the first measuring device 47 uses the information supplied to the control unit 33 by the positioning system 42 which maneuvers the cutting tool 2 to know the position of said cutting tool 2 in the frame of reference of the frame 30, and more particularly to know the radial distance, called “tool distance” and noted D tool, in this case the minimum radial distance, which separates said cutting tool 2 from the axis of rotation Z20. This tool distance D tool is in fact equal to the radial distance from the axis of rotation Z20 at which the portion of the wall 3 of the bandage is located which is situated in the working sector SI, and against which the cutting tool 2 bears, so that this tool distance provides a value representative of the constrained position P3 S1.

[0165] Preferably, the second measuring system 48 uses a laser rangefinder 32, which is carried by the frame 30, and therefore preferably located at a predetermined fixed distance from the axis of rotation Z20, the beam of which makes it possible to measure the distance, here the radial distance, called "laser distance" and noted D laser, which is measured by the laser rangefinder 32, and which therefore corresponds to the distance, here radial, which separates the wall 3, such that this wall 3 is configured in the reference sector S2, from the fixed reference point formed, on the frame 30, by said rangefinder 32. This laser distance D laser is therefore representative of the free position P3 S2, either by considering said laser distance D laser directly as such, or by considering the difference between on the one hand the distance which separates the rangefinder 32 from the axis of rotation Z20 and on the other hand said laser distance D laser.

[0166] The control unit 33 is preferably capable of calculating, in real time, the difference, noted “Delta”, between the constrained position P3 S1 and the free position P3 S2, for example by simple subtraction of the values ​​of radial distance from the axis of rotation Z20 that the wall 3 presents respectively in its constrained form, in the working sector SI, and in its free natural form, in the reference sector S2.

[0167] We can thus ask: Delta = P3_S1 - P3 S2

[0168] In practice, according to an implementation variant which allows a simplified and particularly rapid calculation, and is therefore well suited to real-time monitoring, it can be considered that the Delta deviation can be estimated directly from the tool position D tool and the laser position D laser, and more particularly by considering the difference between, on the one hand, the evolution, decreasing as the machining progresses, of the tool position D tool in the work sector SI and, on the other hand, the concomitant, and increasing, evolution of the laser distance D laser in the reference sector S2, as the residual thickness E4 of the external layer 4 decreases under the effect of the machining.

[0169] According to this variant, we can pose: Delta = (D tool - D tool start) + (D laser - D laser start) where D tool represents the tool position measured at the instant considered D tool start represents the tool position measured at the start of the machining operation, preferably at the instant when the cutting tool 2 comes into contact with the wall 3 of the bandage 1 D laser represents the laser position measured at the instant considered D laser start represents the laser position measured at the start of the machining operation, preferably at the instant when the cutting tool 2 comes into contact with the wall 3 of the bandage 1 so that, in the above expression, the term (D tool - D tool start) is in practice negative, and constitutes a decreasing function with respect to time, while the term (D laser - D laser start) is in practice positive, and constitutes an increasing function with respect to time.

[0170] When the cutting tool 2 approaches sufficiently close to the reinforcing ply 5, and therefore the value of the residual thickness E4 of the external layer 4 becomes sufficiently thin, a divergent behavior of the evolution of the tool position D tool is observed with respect to the evolution of the laser position D laser, due to the fact that the cutting tool 2 continues its movement of displacement in the penetration direction FWD, causing a depression of the wall 3 by bending of the reinforcing wires in the working sector SI, while, due to the lack of external layer 4, the wall 3 escapes the cutting action of the cutting tool 2, and its apparent radius no longer decreases, so that the laser position D laser no longer increases, and is therefore no longer proportional to the evolution of the tool position D tool.

[0171] This divergence causes a rapid increase, in absolute value, of the Delta deviation, which the control unit 33 detects when said Delta deviation crosses the characteristic deformation threshold Delta thresh.

[0172] Immediately, and more preferably as soon as the time delay has made it possible to verify that the characteristic deformation threshold Delta thresh has been crossed over a complete revolution of the bandage 1, the control unit 33 automatically commands the stopping of the machining, by stopping the rotation of the support 20 and / or by moving the cutting tool 2 away from the wall 3.

[0173] The control unit 33 also identifies, as the radial envelope distance D0_ply, the free position P3 S2 that the wall 3 occupied when crossing the characteristic deformation threshold Delta thresh.

[0174] Preferably, the control unit 33 then calculates a cutting path which takes into consideration the radial envelope distance D0_ply, and resumes machining in order to remove, by turning, more preferably by turning, the material constituting the external layer 4.

[0175] An example of operation of the installation 40, and therefore of the successive phases of the machining process, will now be described with reference to figures 1 to 16, and to the curves of the graph in figure 17.

[0176] In a first phase Phi, called the “preliminary approach phase”, the drum 22 carrying the bandage 1 is rotated R20 around the axis of rotation Z20, while the cutting tool 2 is at a distance from the wall 3. During this first phase, the cutting tool 2 is set in motion, preferably in the direction of penetration FWD, here in a centripetal radial direction, until said cutting tool 2 comes into contact with the wall 3, here by the apparent radially external face of said wall 3, and in this case in the equatorial range of the apex 10 of the bandage 1, as illustrated in FIGS. 1 to 4. In doing so, the tool distance D tool decreases.

[0177] On the other hand, as long as the cutting tool 2 has not engaged the external layer 4, the thickness E4 of said external layer does not vary, so that the laser distance D laser and more generally the free position P3 S2 remain constant during this first phase Phi.

[0178] In a second phase Ph2, which forms an engagement phase, the movement of the cutting tool is continued, in the penetration direction FWD, here in a centripetal radial movement, which can be executed continuously or in successive incremental steps, while the bandage 1 is rotating Z20, so that said cutting tool 2 engages the wall 3 and penetrates into it, gradually sinking into the external layer 4 which is thus machined by turning and sees its thickness progressively reduced accordingly, as illustrated in Figures 5 to 8.

[0179] In doing so, the tool distance D tool continues to decrease, because the cutting tool 2 gradually approaches the axis of rotation Z20. Simultaneously, the thickness E4 of the outer layer decreases due to the removal of material by the cutting tool 2. This reduction in the thickness E4 is perceptible in the reference sector S2, because it results in the radially outer surface of the wall 3 approaching the axis of rotation Z20, and therefore moving away from the rangefinder 32, so that the free position P3 S2 decreases, while, conversely, the laser distance D laser increases, by a value equal to the thickness removed from the outer layer 4.

[0180] Then comes a third phase Ph3, forming a progression phase, during which the cutting tool 2 continues its advance movement in the penetration direction FWD, and thus penetrates deeper and deeper into the outer layer 4, the thickness E4 of which continues to decrease. This third phase ends when the cutting tool 2 substantially reaches the reinforcing ply 5, leaving only a very small residual thickness E4 of the outer layer between the cutting tool 2 and the underlying reinforcing wires 6, which is less than a predefined value, and more preferably zero, as illustrated in FIGS. 9 to 12.

[0181] During this third phase Ph3, the tool distance D tool and the residual thickness E4 progress, in this case decrease, in a substantially proportional way, and even in a substantially equal way. Consequently, the same applies to the constrained position P3 S1 and the free position P3 S2 which decrease proportionally, here equally, to each other.

[0182] The Delta deviation therefore remains substantially constant, if necessary substantially zero, as was already the case during the second phase Ph2.

[0183] Then comes a fourth phase Ph4, called the “reinforcement ply deformation phase”, during which the cutting tool 2 continues to move in the penetration direction 2, towards the reinforcement ply 5, and therefore here towards the rotation axis Z20.

[0184] In doing so, the cutting tool 2 no longer having or having almost no more material constituting the external layer 4 to remove, said wall 3 collapses, in the working sector SI, under the thrust of the cutting tool 2, undergoing a local deformation 26 which accompanies and absorbs the displacement component of the cutting tool 2 carried by the penetration direction FWD, as seen in Figures 13 to 16.

[0185] As a result, the thickness E4 hardly varies any more, or even not at all, so that the laser distance D laser actually measured, and more generally the free position P3 S2, stabilize at a substantially constant value, while the tool distance D tool continues to decrease.

[0186] This divergence is indicated by a variation in the Delta deviation which increases in absolute value, here which decreases in algebraic value on the graph in figure 17 due to the sign convention used, until it crosses the characteristic deformation threshold Delta thresh.

[0187] This crossing is detected and allows the control unit 33 to establish the radial envelope distance D0_ply which will in turn allow a cutting path to be defined, and more particularly to set a limit for approaching the cutting tool 2 relative to the rotation axis Z20 which should not be exceeded during subsequent machining operations.

[0188] It will be noted that, even taking into account a possible time delay aimed at confirming the crossing of the characteristic deformation threshold Delta thresh, the duration of the fourth phase Ph4 can be very short, for example less than 3 seconds, or even less than one second, insofar as the deformation 26 of the wall 3 can occur in a very short time from the moment when a critical value of the residual thickness E4 has been reached.

[0189] Of course, the invention is in no way limited to the embodiment variants described above, the person skilled in the art being able to isolate or freely combine one or other of the aforementioned characteristics, or to substitute equivalents for them.

[0190] In particular, it will be noted that the invention is applicable to very varied types of tires, including toroidal tires intended to equip vehicle wheels, among which pneumatic tires and airless tires suspended by flexible spokes, but also tires forming tracks intended for example for construction machinery, agricultural machinery or snowmobiles, or even bandages forming reinforced belts such as transmission belts or conveyor belts. The support 20 intended to receive the bandage 1 for machining operations may of course be adapted according to the nature of the bandage 1 to be treated.

Claims

CLAIMS 1. Method for machining a bandage (1), said bandage (1) having a wall (3) which comprises at least one external layer (4) based on elastomer, preferably based on vulcanized rubber, and at least one reinforcing ply (5), located under said external layer (4) and containing reinforcing threads (6), method during which: - the bandage (1) is fixed on a rotating support (20) having an axis of rotation (Z20), - said rotary support (20) is rotated in order to drive the bandage (1) in rotation (R20) on itself around said axis of rotation (Z20), - in a first azimuthal angular sector (SI) considered around the axis of rotation (Z20), called the "working sector" (SI), a cutting tool (2) is pressed against the wall (3) of the bandage, in a direction called the "penetration direction" (FWD) which is directed towards the reinforcing ply (5), so that said cutting tool (2) penetrates into the external layer (4) and removes material from said external layer (4) by gradually approaching the reinforcing ply (5), said method being characterized in that, while the bandage (1) is driven in rotation (R20) and the cutting tool (2) is pressed against the wall (3) of said bandage: - a first position (P3 S1) of the wall, called the “constrained position” (P3 S1), is measured, which is occupied, in the working sector (SI), by the wall (3) of the bandage which is in contact with the cutting tool (2), - a second corresponding position (P3 S2) of the wall is measured, called the “free position” (P3 S2), which said wall (3) occupies in a second azimuthal angular sector (S2) considered around the axis of rotation (Z20), which is called the “reference sector” (S2), which is angularly distant from the working sector (SI), and in which the wall (3) is clear of the cutting tool (2), - the constrained position (P3 S1) is compared to the free position (P3 S2) in order to detect the reaching or crossing of a predetermined difference, called the “characteristic deformation threshold” (Delta thresh), which is representative of the appearance, in the working sector (SI), of a deformation (26) of the wall (3) which results from a flexural collapse of the reinforcing wires (6) under the pressure exerted by the cutting tool (2) when, due to proximity between the cutting tool (2) and the reinforcing wires (6), the progression of the cutting tool (2) in the penetration direction (FWD) is only incompletely accompanied, or no longer accompanied at all, in the work sector (SI), by an effective reduction in the thickness of the external layer (4) by removal of material.

2. Method according to claim 1 characterized in that the cutting tool (2) approaches the wall (3) and penetrates into said wall in a penetration direction (FWD) which is transverse to the axis of rotation (Z20), preferably radial to the axis of rotation (Z20).

3. Method according to claim 1 or 2 characterized in that the contact between the cutting tool (2) and the wall (3) occupies, in the working sector (SI), an axial range (W2), considered on the abscissa along the axis of rotation (Z20), which is called the “axial working range” (W2), and in that the constrained position of the wall (P3 S1) as well as the free position of the wall (P3 S1) are measured within this same axial working range (W2).

4. Method according to one of the preceding claims, characterized in that the bandage (1) has, along the axis of rotation (Z20), an overall width (Wl) called "axial width" (Wl), and in that the axial range (W2) called "working range" (W2), which is occupied on the abscissa along the axis of rotation (Z20) by the contact between the cutting tool (2) and the wall (3), in the working sector (SI), is located within an axial range called "equatorial range" which represents less than 50% of the axial width (Wl), preferably less than 35%, of the axial width (Wl), and which contains the abscissa of the fictitious plane called "equatorial plane" (P_EQ), which is normal to the axis of rotation (Z20) and which passes through the middle of the axial width (Wl).

5. Method according to one of the preceding claims, characterized in that the measurement of the constrained position (P3 S1) is carried out by measuring the position of the cutting tool (2) relative to the axis of rotation (Z20).

6. Method according to one of the preceding claims, characterized in that the measurement of the free position (P3 S2) is carried out by means of a non-contact measuring tool (31), preferably by means of a laser rangefinder (32) whose beam is pointed at the wall (3) in the reference sector (S2).

7. Method according to one of the preceding claims, characterized in that the azimuthal distance (d azim) which separates the azimuthal position at which the free position (P3 S2) of the wall is measured from the azimuthal position at which the constrained position (P3 S1) of the wall is measured is greater than or equal to 30 degrees, preferably equal to or greater than 45 degrees, for example equal to or greater than 80 degrees.

8. Method according to one of the preceding claims, characterized in that the cutting tool (2) is formed by a cylindrical knife (25) with a circular base, driven in rotation (R25) around its generating axis (Z25), and of which a circular edge (25 A) forms the cutting edge which engages the wall (3) of the bandage.

9. Method according to one of the preceding claims, characterized in that the reinforcing threads (6) closest to the outer layer (4) in the penetration direction (FWD) are metallic, or in a “glass-resin” composite material which combines glass fibers in a resin matrix.

10. Method according to one of the preceding claims, characterized in that the bandage (1) has a first annular heel (7) and a second annular heel (8), provided respectively with a first bead wire and a second bead wire, in that the wall (3) of the bandage forms a radially external crown (10), as well as a first flank (11) which connects said crown (10) to the first heel (7) and a second flank (12) which connects the crown (10) to the second heel (8), and in that the rotating support (20) is arranged to hold the bandage (1), preferably not inflated, by the first heel (7) and second heel (8), while leaving the crown (10) free to deform elastically under the pressure of the cutting tool (2).

11. Method according to claim 10 characterized in that the cutting tool (2) engages the wall (3) of the bandage via the top (10), in a radial penetration direction (FWD), and in that the reinforcing wires (6) located in said top (10) and closest radially to the cutting tool (2) form, with respect to the circumferential direction of the bandage (1), an angle called "ply angle" between + 45 degrees and -45 degrees.

12. Method according to one of the preceding claims, characterized in that the measurement of the constrained position (P3 S1), the measurement of the free position (P3 S2) and the comparison between these positions are carried out in real time by a control unit (33), and in that said control unit (33) is arranged to cause, when the characteristic deformation threshold (Delta thresh) is reached or exceeded, a recoil of the cutting tool (2) in order to release the cutting tool from the wall (3), and / or a stoppage of the rotation (R20) of the rotating support (20).

13. Method according to one of the preceding claims, characterized in that the detection of the characteristic deformation threshold (Delta thresh) is validated on condition that said characteristic deformation threshold (Delta thresh) remains reached or crossed for a duration which corresponds to at least one complete rotation of the bandage (1) on itself.

14. Method according to one of the preceding claims, characterized in that, after having detected the reaching or crossing of the characteristic deformation threshold (Delta thresh), the removal of material from the external layer (4) is resumed by moving the cutting tool (2) relative to the rotating support (20) along a cutting path which is defined as a function of the free position (P3 S2), called “radial envelope distance” (D0_ply), which the wall (3) occupied relative to the rotating support (20) at the time when the characteristic deformation threshold (Delta thresh) was detected.

15. Installation (40) intended for machining a bandage (1), said bandage (1) having a wall (3) which comprises at least one external layer (4) based on elastomer, preferably based on vulcanized rubber, and at least one reinforcing ply (5), located under said external layer (4) and containing reinforcing threads (6), said installation comprising: - a rotary support (20) which is arranged to receive the bandage, which rotary support is mounted in rotation on a frame (30) around an axis of rotation (Z20) and associated with a drive system (41) which makes it possible to drive said rotary support (20), and therefore the bandage (1), in rotation (R20) on itself around said axis of rotation, - a cutting tool (2), - a positioning system (42) which makes it possible to move the cutting tool (2) relative to the frame (30) and the rotating support (20), while the rotating support carrying the bandage is driven in rotation (R20), so as to be able to press the cutting tool (2) against the wall (3) of the bandage, in a first azimuthal angular sector (SI) considered around the axis of rotation (Z20), called "working sector" (SI), in a direction called "penetration direction" (FWD) which is directed towards the reinforcement ply (5), so that said cutting tool (2) can penetrate into the external layer (4) and remove material from said external layer (4) by gradually approaching the reinforcement ply (5), said installation (40) being characterized in that it comprises: - a first measuring device (47), arranged to measure a first position of the wall, called the “constrained position” (P3 S1), which is occupied, in the working sector (SI), by the wall (3) of the bandage which is in contact with the cutting tool (2), - a second measuring device (48), arranged to measure a second corresponding position of the wall, called "free position" (P3 S2), which said wall (3) occupies in a second azimuthal angular sector (S2) considered around the axis of rotation (Z20), which is called "reference sector" (S2), which is angularly distant from the working sector (SI), and in which the wall (3) is disengaged from the cutting tool (2), - a control unit (33), arranged to compare the constrained position (P3 S1) with the free position (P3 S2) in order to detect the reaching or crossing of a predetermined deviation called "characteristic deformation threshold" (Delta thresh), which is representative of the appearance, in the working sector (SI), of a deformation (26) of the wall (3) which results from a flexural collapse of the reinforcing wires (6) under the pressure exerted by the cutting tool (2) when, due to a proximity between the cutting tool (2) and the reinforcing wires (6), the progression of the cutting tool (2) in the penetration direction (FWD) is only incompletely accompanied, or no longer accompanied at all, in the working sector (SI), by an effective reduction in the thickness of the external layer (4) by removal of material.

Images