Installation and method for a double-knife machining process for the recovery of rubber from bandages

Abstract

The present invention relates to a machining method for recovering the material constituting the outer layer (4) of a bandage (1) having a wall (3) comprising, on the one hand, at least one outer layer (4) based on elastomer, which has been shaped to present sculpted blocks (60) separated by grooves (61), and on the other hand, at least one reinforcing layer (5) located beneath said outer layer (4) and containing a plurality of reinforcing threads (6). The method in which the bandage (1) is rotated (R20) about itself, around said principal axis (Z20), in a chosen direction of rotation (R20+, R20-), and a first cutting tool (2) and a second cutting tool (2'), preferably one in each hemisphere (H1, H2) of the bandage, are simultaneously engaged in order to remove material from one or more areas of the outer layer (4) to a depth located between the bottom (61B) of the grooves (61) and the reinforcing layer (5). Figure 13

Description

Title of the invention: DOUBLE-KNIFE MACHINING INSTALLATION AND METHOD FOR RECOVERING RUBBER FROM TIRES

[0001] The present invention relates to the field of recycling of tires, in particular pneumatic tires.

[0002] More particularly, the invention aims to recover, in particular from a tire which is finally reaching the end of its life and whose carcass can therefore no longer be repaired or reused, the largest possible quantity of the rubber-based material which constitutes the external layer covering the carcass, and in particular the largest possible quantity of the material constituting the tread.

[0003] To reconcile the imperatives of industrial efficiency and respect for the environment, it is however desirable to have a process and an installation which make it possible to quickly and simply collect a significant part of the potentially recoverable material on each bandage, while only incurring the lowest possible energy expenditure.

[0004] The objects assigned to the invention therefore aim to propose an installation and a machining method which make it possible to efficiently remove a maximum of rubber-based material from tires while remaining energy-efficient.

[0005] The objects assigned to the invention are achieved by means of a method of machining a bandage, said bandage having a wall which comprises on the one hand at least one external layer based on elastomer, which has been shaped to present sculpture blocks separated by grooves, and on the other hand at least one reinforcing ply which is located under said external layer and which contains a plurality of reinforcing threads, said method comprising a step of removing material during which: - by means of a rotating support having an axis of rotation called the “main axis”, the bandage is driven in rotation on itself, around said main axis, in a chosen direction of rotation, and - while the bandage is rotating in the chosen direction of rotation, at least two cutting tools are simultaneously used which act simultaneously against the external layer to remove material therefrom, namely at least one first cutting tool which is carried by a first positioning system making it possible to position and move said first cutting tool relative to the main axis, so as to make the first cutting tool follow a first cutting path, and at least one second cutting tool which is carried by a second positioning system positioning for positioning and moving said second cutting tool relative to the main axis, so as to cause the second cutting tool to follow a second cutting path distinct from the first cutting path, said first and second cutting paths being defined so that they allow material to be removed, in one or more zones of the external layer, up to a depth which is located between the bottom of the grooves and the reinforcing ply.

[0006] Advantageously, the multiplication of cutting tools, and the fact that the cutting tools intervene simultaneously, at least partially hidden or even totally hidden from each other, makes it possible to machine the bandage quickly, by removing material from the external layer simultaneously in several working zones, which reduces the cycle time.

[0007] Furthermore, because the cutting tools are arranged so that they can all intervene in consideration of a single and same direction of rotation of the bandage, the entire step of removing material is carried out without it being necessary to stop the rotation of the bandage, or to reverse the direction of rotation of said bandage. The number and duration of the transient phases of acceleration and braking of the support and the bandage are therefore minimized, and therefore the losses of time as well as the corresponding losses of energy, linked in particular to inertial phenomena.

[0008] Finally, the independence of the positioning systems advantageously makes it possible to adapt the trajectory of each cutting tool to the area of ​​the bandage which is covered by said cutting tool, and in particular to differentiate the second cutting trajectory from the first cutting trajectory according to the layout pattern of the reinforcing wires specific to each bandage.Thus, it is possible in particular, when each of the first and second cutting tools is assigned to the machining of a hemisphere of the bandage distinct from the hemisphere assigned to the other cutting tool, to approach each cutting tool as close to the reinforcing ply as possible in the hemisphere of the bandage covered by said cutting tool, taking into account the direction of the bandage and the orientation of the reinforcing wires in the hemisphere concerned, without risking catching and tearing the reinforcing wires, and therefore without risking blocking the operation of the installation or damaging one and / or the other of the cutting tools.

[0009] 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:

[0010] [Fig.l] illustrates, in a perspective view, an example of an installation making it possible to implement a method according to the invention, here more particularly an installation comprising two robotic arms respectively carrying a first cutting tool and a second cutting tool which are here arranged on either side of the rotating support which carries the bandage to be machined.

[0011] [Fig.2] is a front view of the installation of [Fig.l], in a plane normal to the main axis.

[0012] [Fig. 3] illustrates, in a schematic perspective cutaway view, a tire that can be treated by the method according to the invention, said tire having a first layout diagram of its reinforcing threads, comprising in this case a first reinforcing ply, radially the outermost, which has a first set of reinforcing threads arranged parallel to each other, in a first oblique orientation relative to the equatorial circumferential direction of the tire, and a second reinforcing ply, radially more internal than the first reinforcing ply, which is partially covered by the first reinforcing ply and which extends axially beyond the axial limits of the first reinforcing ply, and which comprises a second set of reinforcing threads, arranged parallel to each other, and having a second oblique orientation of the same sign as the first orientation of the reinforcing threads of the first reinforcing ply.

[0013] [Fig. 4] is a sectional view, in a radial plane containing the main axis, and before any material removal operation, of a bandage which can be treated by the method according to the invention, preferably a bandage which has a first layout diagram according to [Fig. 3].

[0014] Figures 5A and 5B illustrate, in schematic views respectively in perspective and in section in a radial plane, the bandage of Figures 3 and 4 during a preliminary trench digging step, during which a circumferential trench is dug in the equatorial zone of the bandage by means of the first cutting tool, before proceeding to the material removal step which involves simultaneously the first cutting tool and the second cutting tool.

[0015] Figures 6A, 6B and 6C illustrate, respectively in a partial schematic view from above, a perspective view, and a schematic view in section in a radial plane, the principle of implementation of the first cutting path of the first cutting tool within the bandage of Figures 3, 4, 5A and 5B, which makes it possible to remove the external layer present in the first hemisphere of the bandage by axially moving the first cutting tool flush with the first reinforcing ply, from the equatorial trench towards a first axial end of the bandage, over a first axial cutting range which covers a first hemisphere of the bandage. For the sake of readability, the second cutting tool and the second cutting path do not appear in these figures.

[0016] Figures 7A and 7B illustrate, respectively in a partial schematic view from above and a schematic view in section in a radial plane, the bandage of Figures 3, 4, 5A and 5B, during the simultaneous implementation of the first cutting tool and the second cutting tool. While the bandage is rotating, according to a single and same direction of rotation, the first cutting tool executes the first cutting path detailed in Figures 6A, 6B, 6C in order to remove the outer layer in the first hemisphere, here by sliding in contact with the reinforcing threads, while the second cutting tool executes at the same time the second cutting path in order to remove the outer layer in the second hemisphere of the bandage, by moving axially towards the second axial end of the bandage, but by providing a centrifugal radial offset of the second cutting path relative to the first cutting path, which makes it possible to maintain said second cutting tool, at least in a part of the second hemisphere, at a radial distance from the main axis which is strictly greater than that used for the first cutting tool in the first hemisphere of the bandage, and this in order to preserve in at least a part or even in the whole of the second hemisphere, for safety,a residual thickness of external layer which protects the reinforcing threads of the second hemisphere from tearing, in particular at the corresponding edges of the reinforcing plies.

[0017] [Fig. 8] illustrates, in a perspective cutaway view, including an enlarged inset portion, another type of tire that can be treated by the method according to the invention. This tire has a second layout diagram which in this case comprises a first radially external reinforcing ply which has a first set of reinforcing threads which are arranged parallel to each other, and substantially or even exactly parallel to the equatorial circumferential direction of the tire. This first reinforcing ply, also called a "fret", thus forms a hoop which preferably covers the entire axial width of the top of the tire. Such a first reinforcing ply can in particular be obtained by winding around the main axis, on several consecutive contiguous turns, a continuous strip formed of a matrix, for example a rubber matrix, in which parallel and continuous reinforcing threads are embedded.This second layout scheme further provides a second reinforcing ply, which is located under the first reinforcing ply and which comprises a second set of reinforcing threads, preferably arranged obliquely relative to the equatorial circumferential direction, and the axial ends of which are located set back from the corresponding axial ends of the first reinforcing ply, so that the first reinforcing ply extends axially beyond the second reinforcing ply and completely covers said second reinforcing ply.

[0018] [Fig.9] is a sectional view, in a radial plane containing the main axis, and before any material removal operation, of a bandage which has a second layout diagram according to [Fig.8].

[0019] Figures 10A and 10B illustrate, respectively in a partial schematic view from above and a schematic view in section in a radial plane, the bandage of [Fig.9] during a preliminary stage of trench digging, during which a circumferential trench is dug in the equatorial zone of the tire using the first cutting tool, before proceeding with the material removal step which involves the first cutting tool and the second cutting tool simultaneously.

[0020] Figures 11A and 11B illustrate, respectively in a partial schematic view from above and a schematic view in section in a radial plane, the bandage of Figures 9 and 10A and 10B during a material removal step according to the invention during which the outer layer in the first hemisphere of the bandage is removed by means of a first cutting tool which is advanced axially in contact with the first reinforcing ply, from the equatorial trench to the first axial end of the bandage, and the outer layer in the second hemisphere of the bandage is simultaneously removed by means of a second cutting tool which is advanced axially in contact with the first reinforcing ply, from the equatorial trench to the second axial end of the bandage.

[0021] [Fig. 12] illustrates, in a detailed perspective view, the end of a robotic arm of the installation of figures 1 and 2 which carries a cutting tool formed by a rotating cylindrical knife as well as the sharpening system for maintaining the circular cutting edge of said knife.

[0022] [Fig. 13] illustrates, according to a schematic view in a radial plane, the principle of a material removal step, applicable in particular to a bandage having the first aforementioned layout diagram, a step during which a first cutting path and a second cutting path are executed which make it possible to axially move the first cutting tool and the second cutting tool at a radial distance from the main axis forming an intermediate distance strictly between the bottom of the grooves and the radially outermost surface of the reinforcing ply. Such cutting paths can be defined from knowledge of the radial position of the bottom of one or more grooves, and can, depending on the case, either follow the curve of the bandage, which corresponds to the imaginary line passing through the bottoms of the grooves, or be rectilinear and parallel to the main axis.

[0023] [Fig. 14] illustrates, according to a schematic view in a radial plane, the principle according to which, to ensure that the cutting tool comes into contact with the reinforcing ply and then slides along the reinforcing ply while remaining in contact with the reinforcing wires, and this in order to remove as much thickness as possible from the external layer, said cutting tool is brought to a starting position, here in the equatorial plane, which is radially closer to the main axis, by a value called the “nominal deflection value”, than is the reinforcing ply, the outermost face of which is located, in the absence of a cutting tool, at a radial distance from the main axis called the “radial envelope distance”. Thus, the cutting tool is advantageously prestressed against the reinforcing ply, locally creating a slight radial deformation centripetal bending of the reinforcing threads by elastic bending.

[0024] The present invention relates to a method of machining a bandage 1.

[0025] 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 used tread from the bandage, with a view to retreading said bandage, when the carcass of said bandage 1 is reusable.

[0026] However, preferably, the machining method according to the invention will be part of a method for recycling a rubber-based material present on the bandage 1, preferably a method 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.

[0027] Such a recycling process will find application in particular to end-of-life tires 1, the carcass of which can no longer be repaired or reused, and which must therefore be dismantled to recover the raw materials.

[0028] As can be seen in particular in figures 4, 9, 13 and 14, bandage 1 has a wall 3 which comprises on the one hand at least one external layer 4 based on elastomer, which has been shaped to have sculpture blocks 60 separated by grooves 61, and on the other hand at least one reinforcing ply 5 which is located under said external layer 4 and which contains a plurality of reinforcing threads 6.

[0029] Of course, the tread blocks 60 and the grooves 61 being initially shaped on the new or freshly retreaded tire 1, the method according to the invention can be applied equally well to worn tires 1, on which there will remain remnants of tread blocks 60 and grooves 61 which will depend on the degree of wear of the tire 1, or to new or almost new tires, discarded for quality considerations, and having intact tread blocks 60 and grooves 61.

[0030] Preferably, the grooves 61 taken into consideration for the purposes of the invention are circumferential grooves, which form the deepest hollows on the surface of the wall 3.

[0031] E4 will denote the thickness of the external layer 4, and in particular the residual thickness of said external layer, which separates the external surface of the wall 3 from the surface of the reinforcing ply 5, 5' closest to said external surface of the wall 3.

[0032] In a manner known per se, the reinforcing ply 5, 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, 6' are embedded.

[0033] In particular, it will be possible to have a reinforcing sheet 5, 5' whose matrix is ​​formed from an elastomer base, preferably from rubber, and containing reinforcing threads. 6 metallic, or possibly polymer such as aramid.

[0034] Alternatively, the reinforcing sheet 5, 5' may have a resin matrix reinforced by reinforcing threads 6, 6' made of fiberglass.

[0035] Within the same reinforcing ply 5, 5', the reinforcing threads 6, 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.

[0036] Said reinforcing threads 6, 6' are arranged according to an implantation pattern, which is specific to the bandage 1.

[0037] The layout diagram defines the layout of the reinforcing threads 6, 6' within the reinforcing ply 5, 5', and therefore in particular the orientation A6, A6' of said reinforcing threads 6, 6', or even the spacing between neighboring reinforcing threads 6, 6'.

[0038] By way of example, a first layout diagram may be considered, as illustrated in Figures 3, 4 and 7A, which in this case comprises a first reinforcing ply 5, radially the outermost, which has a first set of reinforcing threads 6, called “first reinforcing threads 6”, arranged parallel to each other, according to a first orientation A6 oblique relative to the equatorial circumferential direction of the tire 1, and a second reinforcing ply 5', radially more internal than the first reinforcing ply 5, which is partially covered by the first reinforcing ply 5 and which extends axially beyond the axial limits, or “selvages” 5_1, 5_2, of the first reinforcing ply 5, and which comprises a second set of reinforcing threads 6', called “second reinforcing threads 6'”, arranged parallel to each other, and having a second oblique orientation A6', forming here an angle A6'_ang in figure 6A,second orientation A6' which is of the same sign as the first orientation A6 of the reinforcing threads 6 of the first reinforcing ply 5.,

[0039] Such a first implantation scheme may in particular be frequently found within a tire 1 intended for heavy goods vehicles.

[0040] The first reinforcing wires 6 of the first reinforcing ply 5 implemented in accordance with this first layout diagram will preferably be metallic. Similarly, the second reinforcing wires 6' of the second reinforcing ply 5' implemented in accordance with this first layout diagram will preferably be metallic.

[0041] According to another example, a second layout diagram may be considered as illustrated in Figures 8 and 9, which comprises a first radially external reinforcing ply 5 which has a first set of reinforcing threads 6 which are arranged parallel to each other, and substantially or even exactly parallel to the equatorial circumferential direction of the bandage. This first reinforcing ply, also called a "collar", thus forms a hoop which preferably covers the entire axial width of the top of the bandage. Such a first reinforcing ply 5 may in particular be obtained by winding several consecutive contiguous turns around of the central axis of the tire, a continuous strip formed of a rubber matrix in which parallel and continuous reinforcing threads 6 are embedded. This second layout scheme further provides a second reinforcing ply 5', which is located under the first reinforcing ply 5 and which comprises a second set of reinforcing threads 6', preferably arranged obliquely relative to the equatorial circumferential direction, and the axial ends of which are located set back from the corresponding axial ends of the first reinforcing ply 5, so that the first reinforcing ply 5 extends axially beyond the second reinforcing ply 5' and completely covers said second reinforcing ply 5'.

[0042] The first reinforcing threads 6 used in the first reinforcing ply 5 according to this second implantation scheme, radially the outermost, may be made of a metallic material, for example steel, in a composite material comprising glass fibers embedded in a resin, or even in a textile material made of polymer such as polyamide (“Nylon”) or aramid.

[0043] The second implantation scheme described above may in particular, but not exclusively, be implemented within tires intended to equip passenger vehicles.

[0044] For convenience of description, when it is not necessary to distinguish specifically between the first reinforcing ply 5 and the second reinforcing ply 5', respectively between the first reinforcing threads 6 and the second reinforcing threads 6', and in particular when characteristics can be applied indifferently to a bandage 1 in which a single reinforcing ply would be concerned by the machining operation or to a bandage in which several reinforcing plies would be concerned by the machining operation, reference may be made generically to a "reinforcing ply 5, 5'" or to a "reinforcing ply 5", and respectively to "reinforcing threads 6, 6'" or "reinforcing threads 6".

[0045] Furthermore, it will be noted that the invention is applicable to very varied types of bandages, including toroidal bandages intended to equip vehicle wheels, among which pneumatic bandages, or airless bandages suspended by flexible spokes, but also bandages 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 the machining operations may of course be adapted according to the nature of the bandage 1 to be treated.

[0046] Preferably, the method may be applied to tires 1 intended for heavy goods vehicles, typically vehicles whose total authorized laden weight is greater than 3.5 tonnes, said tires being sized to be mounted on rims with dimensions between 16.5 inches and 24 inches.

[0047] The method may however also be applied to tires 1 intended for passenger vehicles, and therefore adapted to rims with a diameter between 13 inches and 24 inches.

[0048] The method according to the invention can of course be applied without restriction to tires of very varied dimensions, including very large tires, for example civil engineering tires intended to be mounted on rims of up to 63 inches.

[0049] Preferably, in a manner known per se, and as can be seen in particular in FIGS. 1, 2, 4, 9, 13 and 14, 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 (not shown), 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.

[0050] In a manner known per se, the first and second beads 7, 8 allow the tire to be mounted on a rim.

[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.

[0052] Preferably, the wall 3 of the tire has a toroidal revolution shape, curved outwards, and may more preferably delimit in this way, in the case where the tire 1 is a pneumatic tire, a cavity which makes it possible to contain the inflation gas of said pneumatic tire.

[0053] According to the invention, the method comprises a material removal step during which: - by means of a rotating support 20 having an axis of rotation called the “main axis” Z20, the bandage 1 is driven in rotation R20 on itself, around said main axis Z20, in a chosen direction of rotation R20+, R20-, and - while the bandage 1 is rotating R20 in the chosen direction of rotation R20+, R20-, at least two cutting tools 2, 2' are used which act simultaneously against the outer layer 4 to remove material therefrom, namely at least one first cutting tool 2 which is carried by a first positioning system 42 making it possible to position and move said first cutting tool 2 relative to the main axis Z20, so as to make the first cutting tool 2 follow a first cutting path T2_l, and at least one second cutting tool 2' which is carried by a second positioning system 42' making it possible to position and move said second cutting tool 2' relative to the main axis Z20, so as to make the second cutting tool 2' follow a second cutting path T2_2 distinct from the first cutting path T2_l, said first and second cutting paths cut T2_l, T2_2 being defined so that they allow material to be removed, in one or more zones of the external layer 4, up to a depth which is located between the bottom 61B of the grooves 61 and the reinforcing ply 5.

[0054] Advantageously, the method according to the invention makes it possible to remove the material from the external layer 4 to a significant depth, close to the reinforcing ply 5, 5' or even which coincides with the depth of implantation of the reinforcing ply 5, 5', and thus to maximize the quantity of material recovered, while avoiding tearing the reinforcing threads 6, 6'.

[0055] The simultaneous use of several cutting tools 2, 2', here two cutting tools 2, 2', makes it possible to simultaneously cover more volume of the external layer 4, and more particularly more axial surface of the external layer 4, and therefore to improve the efficiency of the process by reducing the necessary cycle time.

[0056] Furthermore, since the entire material removal operation takes place while maintaining the bandage 1 in a single direction of rotation, here a direction of rotation R20- which is negative by convention in FIGS. 2, 5A, 6A, 7A, 10A, 11A, the transient braking, stopping and acceleration phases which would otherwise be necessary to reverse the direction of rotation of the support 20 are saved; this limits energy consumption as well as the cycle time.

[0057] In practice, the main axis Z20 will coincide with the central axis of the bandage 1, around which the bandage 1 forms a toroidal ring, and which therefore corresponds to the axis around which the bandage rotates when said bandage 1 is in service on a vehicle wheel and rolling on the ground.

[0058] By convention, “axial” will designate a direction parallel to the axis considered, here more particularly a direction parallel to the axis of rotation Z20, and “radial” a direction perpendicular to said axis.

[0059] The term “circumferential” direction will be used to designate a direction of the tire which is orthoradial relative to the central axis of the tire, here therefore orthoradial relative to the main axis Z20, that is to say a direction which is contained in a plane normal to the central axis of the tire and which is, at a point considered on the tire, perpendicular to the radius which joins the central axis of the tire to said point considered, or even, in other words, a direction which, at a point considered on the tire, is normal to the radial plane which contains the central axis of the tire and which passes through said point considered.

[0060] The term "radial plane" or "meridian plane" will be used to designate a plane which contains the central axis of the tire, here therefore which contains the main axis Z20, and which therefore extends on the one hand along the central axis of the tire, and on the other hand along a radius of the tire, perpendicular to the central axis.

[0061] By analogy with the terrestrial globe, we will conventionally designate by "equatorial plane" P_EQ the plane normal to the central axis of the bandage, here therefore normal to the axis main Z20, which passes through the middle of the axial range W1 occupied by the bandage 1, and which thus divides said bandage into a first hemisphere H1 and a second hemisphere H2, said second hemisphere H2 being located opposite the first hemisphere H1 with respect to said equatorial plane P_EQ.

[0062] The axial width W1 of the bandage corresponds to the distance which separates two fictitious gauge planes which are normal to the central axis of the bandage, here the main axis Z20, and which are each tangent to the wall 3, respectively at a first axially outermost point of the wall 3, generally located at the outer surface of the first flank 11, and forming a first axial end 1_1 of the bandage, and at a second axially outermost point of the wall 3, located axially opposite the first point, and generally located at the surface of the second flank 12, and forming a second axial end 1_2 of the bandage 1. The axial range occupied by the bandage 1, which can also be noted “W1” for convenience, will correspond to the portion of the space delimited axially by, and therefore included between, the two aforementioned fictitious gauge planes.

[0063] By convention, the term “equatorial zone” will be used to designate an axial range of the tire 1 which, on the one hand, represents less than 35% of the axial range W1 covered by the tire 1, preferably less than 30% of the axial range W1 covered by the tire 1, more preferably less than 25% of the axial range W1 covered by the tire 1, or even less than 20%, less than 15% or even less than 10% of the axial range W1 covered by the tire 1, and which, on the other hand, contains the equatorial plane P_EQ of the tire.

[0064] By convention, the direction of rotation R20- will be considered negative when it corresponds to a clockwise direction in Figures 1 and 2, and is therefore oriented from bottom to top in Figures 6A, 7A, 10A and 11A.

[0065] Conversely, the direction of rotation R20+ would be positive by convention if it corresponded to a counterclockwise direction of rotation, or “trigonometric direction”, in Figures 1 and 2. However, the installation 40 allowing the implementation of the method, as illustrated in Figures 1 and 2, and more particularly the cutting tools 2, 2', are here specifically configured to operate with a negative direction of rotation R20-, so that such a negative direction of rotation R20- will be considered exclusively in what follows.

[0066] Preferably, 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 top 10 free.

[0067] The inventors have in fact found that it is thus possible to hold the bandage 1 by the heels 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.

[0068] 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.

[0069] Preferably, the method, and more particularly the material removal step, will therefore 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.

[0070] 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.

[0071] In this respect, it will be noted that, as illustrated in Figures 1 and 2, the rotary drive support 20 may 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.

[0072] 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 aforementioned speeds, however, present an advantageous compromise between the power required for acceleration and braking of the support 20, reliability of process control, and cycle time.

[0073] Preferably, in order to facilitate the evacuation of the material removed from the outer layer 4, and in order to avoid interference of the second cutting tool 2' with the first cutting tool 2, or more generally interference of the second positioning system 42' with the first positioning system 42, and this in particular in the equatorial zone of the bandage 1, the first cutting tool 2 and the second cutting tool 2' will be offset in azimuth relative to each other around the main axis Z20, in order to each occupy a distinct angular sector around the main axis Z20.

[0074] The first cutting tool 2 and the second cutting tool 2', and more particularly their respective points of contact with the wall 3 of the bandage 1, may thus preferably be distant from each other in azimuth by at least 30 degrees, preferably by at least 90 degrees, or even by at least 120 degrees, and for example by 180 degrees + / - 20 degrees.

[0075] A positioning at 180 degrees + / - 20 degrees will allow the first and second cutting tools 2, 2' to be substantially diametrically opposed, as illustrated in Figures 1 and 2.

[0076] Preferably, as can be seen in Figures 1, 2, 12 and 14, the first cutting tool 2 and the second cutting tool 2' are formed respectively by a first cylindrical knife 25 and a second cylindrical knife 25', the respective circular edges 25A, 25'A of which form the cutting edges and are oriented so as to engage the wall 3 in opposition to the chosen direction of rotation R20+, R20-.

[0077] Such cylindrical knives 25, 25' advantageously provide a precise, clean and regular cut, which makes it possible to remove the material constituting the external layer 4 in the form of shavings or strips, potentially right up to the reinforcing wires 6.

[0078] The generator axis Z25, Z25', around which each cylindrical knife 25, 25' considered 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, 25', and more particularly its edge 25A, 25'A, 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.

[0079] Thus, more preferably, in order to promote the penetration of the edge 25A, 25'A of the cylindrical knife 25, 25' into the wall 3 and to clear the space necessary for the corresponding positioning system 42, 42', the generating axis Z25, Z25' of the cylindrical knife will have, in a plane normal to the main axis Z20, and more particularly in a plane normal to the main axis Z20 passing through the point of the edge 25A, 25'A which is in contact with the wall 3 and closest to the main axis Z20, an 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, as can be seen in [Fig.2],

[0080] In order to be able to work simultaneously in consideration of a single and same direction of rotation R20-, the first and second cylindrical knives 25, 25' each point in the same circumferential direction, so that, here, in Figures 1 and 2, the first cylindrical knife 25, located to the right of the main axis Z20, points upwards, against the negative direction of rotation R20-, while the second cylindrical knife 25', diametrically opposite, located to the left of the main axis Z20, points downwards.

[0081] Furthermore, each of the first and second cylindrical knives 25, 25' will preferably be provided with a sharpening system 45, 45', comprising for example a sharpening wheel, which will automatically sharpen the edge during or after the cutting operation.

[0082] The edge 25A, 25'A forming the cutting edge will preferably be smooth, in the form of a continuous wall, without indentations, as illustrated in Figures 1, 2 and 12. Such a smooth edge 25A, 25'A will have in particular the advantage of not having any roughness likely to accidentally catch a reinforcing wire 6.

[0083] Preferably, the cylindrical knife 25, 25' will have a diameter of between 100 mm and 300 mm.

[0084] Each of the first and second cylindrical knives 25, 25' may also be associated with a chip evacuation chute 46, 46', as illustrated in FIGS. 1 and 12, which chute 46, 46' will guide the material removed from the bandage 1 towards a recovery system, comprising for example a discharge conveyor which may itself open directly above a recovery tank into which said conveyor will discharge the material extracted from the external layer 4 of the bandage 1.

[0085] The first cutting path T2_l causes the first cutting tool 2, opposite the bandage, to travel a first predetermined axial range W2_l along the main axis Z20, called the “first axial cutting range” W2_l.

[0086] We note Kl the starting point of the first cutting trajectory T2_l, and Ml the arrival point.

[0087] The second cutting path T2_2 causes the second cutting tool 2', opposite the bandage, to travel a second predetermined axial range W2_2 along the main axis Z20, called the “second axial cutting range” W2_2.

[0088] We note K2 the starting point of the second cutting trajectory, and M2 the corresponding arrival point.

[0089] The term “axial travel direction” S2_l, S2_2 denotes the direction in which the cutting tool 2, 2' in question travels, preferably monotonically, the axial range W2_l, W2_2 during the material removal step, on the abscissa along the main axis Z20, and therefore moves across the width of the bandage, transversely to the circumferential direction of the bandage 1, starting from a starting axial abscissa, which corresponds to the end of the axial cutting range where the cutting path begins, to arrive at an ending axial abscissa, which corresponds to the other end of the axial cutting range, where the cutting path ends.

[0090] By convention, it may be considered that the axial travel direction S2_l is positive, and therefore that the cutting tool moves along the increasing abscissas along the main axis Z20, when the cutting tool moves from the second flank 12 to the first flank 11, which corresponds to a direction of movement from the background to the foreground in FIGS. 1 and 2. For convenience, the positive direction of the increasing abscissas of the main axis Z20 may be noted Z20+.

[0091] In absolute terms, it could be envisaged that the first cutting tool 2 is used to make a first pass, at a first given depth, and that the second cutting tool 2' is used to follow in the wake of the first cutting tool 2' in order to make a second pass, at a second depth greater than the first depth; the second axial cutting range W2_2 would then be superimposed on the first axial cutting range W2_1.

[0092] However, in a particularly preferential manner, the first axial cutting range W2_1 and the second axial cutting range W2_2 will not be superimposed, but at most partly axially overlapping, and therefore not totally axially overlapping, or even not axially overlapping.

[0093] In a particularly preferential manner, the second axial cutting range W2_2 is complementary to said first axial cutting range W2_1 so that said first and second axial cutting ranges cover as a whole the entire axial range W1 occupied by the bandage 1. Thus, it will be possible to cover the entire axial width of the bandage, during the same material removal step, by the accumulation of the axial cutting ranges assigned respectively to the first cutting tool 2 and to the second cutting tool 2'.

[0094] Preferably, the bandage 1 being axially divided into a first hemisphere H1 and a second hemisphere H2 each located on a different side of the equatorial plane P_EQ of the bandage which is normal to the main axis Z20 and passes through the middle of the axial range W1 occupied by the bandage 1, the first cutting tool 2 is assigned to the removal of material in the first hemisphere H1 of the bandage 1 while the second cutting tool 2' is assigned to the removal of material in the second hemisphere H2 of the bandage 1.

[0095] The machining work is thus advantageously distributed substantially equally between the two cutting tools 2, 2'.

[0096] This makes it possible in particular to balance the wear of the cutting tools 2, 2'.

[0097] Above all, this makes it possible to optimize the overall cycle time since each of the first and second cutting tools 2, 2' operates on an individual cycle time which is substantially equal to the individual cycle time of the other cutting tool 2', 2, so that the two cutting tools 2, 2' can work in time that is totally masked, or almost totally masked, with respect to one another.

[0098] The first cutting tool 2 and the second cutting tool 2' will preferably work respectively in a first axial direction of travel S2_l and a second axial direction of travel S2_2 which are of opposite signs, preferably mirrored relative to the equatorial plane P_EQ, and more preferably each in an axial direction of travel which goes from the equatorial plane P_EQ towards the pole of the hemisphere Hl, H2 covered by the cutting tool 2, 2' considered.

[0099] By way of example, the first cutting tool 2 follows a first positive axial travel direction S2_l, here going from left to right, in Figures 6A, 7B, 1 1A and 13, while the second cutting tool 2' follows a second negative axial travel direction S2_2, going from right to left in Figures 7B, 1 1A and 13.

[0100] Preferably, the starting points K1, K2 of the cutting trajectories T2_1, T2_2 will be located axially in the equatorial plane P_EQ, or at least in the vicinity of the equatorial plane, for example in the equatorial zone which contains the axial abscissa of the equatorial plane P_EQ and whose axial width is less than 35%, 30%, 25%, 20%, 15% or even 10% of the axial range W1 occupied by the tire 1.

[0101] According to a preferred implementation possibility, called “machining in contact with the reinforcing ply”, the first cutting trajectory T2_l is executed by bringing the first cutting tool 2 into contact with the reinforcing ply 5 and then axially moving the first cutting tool 2 so as to slide the first cutting tool 2 into contact with the reinforcing ply 5, or successive reinforcing plies 5, 5', along the reinforcing wires 6, 6', in at least a part or even the whole of a chosen hemisphere, here in at least a part or even the whole of the first hemisphere H1 in FIGS. 6A, 6B, 6C, 7B and 11A.

[0102] Thus, advantageously, in at least a part of this chosen hemisphere, and preferably in the entirety of said hemisphere, the entire thickness E4 of external layer 4 will be removed, and the maximum amount of available material will therefore be recovered.

[0103] Of course, in order not to tear the reinforcing threads 6, the first cutting tool 2 will have to travel along the chosen hemisphere in the correct direction in consideration of the orientation A6, A6' of the reinforcing threads, that is to say in the direction which tends to press against the reinforcing ply 5, 5' and the carcass of the tire the points formed by the ends of said reinforcing threads 6, 6' at the level of the selvedge(s) 5_1, 5'_1 of the reinforcing ply(ies) 5, 5' concerned, when the cutting tool 2 crosses said selvedge(s) 5_1, 5'_1 in the selected axial cutting range W2_l, here in our example in the first hemisphere H1, and this in such a way that the first cutting tool 2 does not take said reinforcing threads 6, 6' against the grain, and therefore does not tear the reinforcing threads 6, 6', in particular at the ends of the reinforcing threads which form the selvedge(s) 5_1, 5' 1 of the reinforcing plies 5,5' that the cutting tool 2 successively crosses by axially traversing the hemisphere considered.

[0104] This is why the method according to the invention will preferably comprise a step of identifying the orientation of the reinforcing threads 6, 6', during which the orientation A6, A6' of said reinforcing threads 6, 6' is identified relative to a reference direction called the "equatorial circumferential line" L_EQ which corresponds to the intersection of the radially external surface of the reinforcing ply 5 with the "plane equatorial » fictitious P_EQ which, as indicated above, is normal to the main axis Z20, and therefore to the central axis of rotation of the bandage, and passes through the middle of the axial range W1 occupied by said bandage 1.

[0105] More particularly, the orientation A6 may correspond to the angle called “ply angle” A6_ang that the reinforcing threads 6 of a reinforcing ply 5 located in the crown 10 of the tire 1 form, with respect to the equatorial circumferential line L_EQ, i.e. the angle at which each reinforcing thread 6 is oriented in a lace around an imaginary radial line that is perpendicular to the main axis Z20 and that passes through the intersection of said reinforcing thread 6 with the equatorial circumferential line, as illustrated in FIG. 6A.

[0106] The orientation A6, A6' of the reinforcing wires 6, 6' may typically be defined by means of two parameters, namely the sign of the layer angle A6_ang, A6'_ang and the value of said layer angle A6_ang, A6'_ang, taking for example as reference the equatorial circumferential line L_EQ, the orientation of which is considered to be zero degrees. By convention, it may be considered that the sheet angle A6_ang, A6'_ang is negative when, as is the case in Figure 6A, it deflects the reinforcing wire 6, 6' at an acute angle to the left, and therefore in the trigonometric, anti-clockwise, yaw direction, relative to the equatorial circumferential line L_EQ, and that the sheet angle A6_ang, A6'_ang is, on the other hand, positive when it deflects the reinforcing wire 6 at an acute angle to the right, and therefore in the clockwise yaw direction.

[0107] The identification of the orientation A6, A6' of the reinforcing threads may be carried out for each bandage 1 by any appropriate means, for example by querying a database pre-established by the manufacturer of the bandage and which contains information on the structure of the bandage 1 associated with an identifier of the bandage or of the batch of manufacture of the bandage, or by carrying out an X-ray of the bandage, or by carrying out a survey according to which the bandage 1 is locally dug, preferably in the equatorial zone, for example by digging an annular trench using one of the cutting tools 2, 2', until the reinforcing threads 6 are visible, the orientation A6 of which may then be identified, for example, by means of a laser profilometer or a camera associated with an image analysis system.

[0108] It is considered that the cutting tool 2 travels along the reinforcing wires 6 “in the right direction” when the relative movement of the cutting tool 2 with respect to the reinforcing ply 5, which can be represented for convenience in the form of a speed vector V2 in FIG. 6A, presents: - on the one hand a circumferential displacement component V2_circ, induced by the rotation R20 of the bandage 1, which is of the same sign as the circumferential component A6_circ of the orientation A6 of the reinforcing threads 6, considered when traveling through said reinforcing threads 6 from the equatorial plane P_EQ towards the pole of the hemisphere considered, here therefore, with regard to the first hemisphere Hl, towards the first axial end 5_1 of the reinforcing ply 5, and more generally towards the first axial end 1_1 of the bandage 1, - and on the other hand an axial displacement component V2_ax, which corresponds to the chosen axial travel direction S2_l, which axial displacement component V2_ax has the same sign as the axial component A6_ax of the orientation A6 of the reinforcing threads 6, considered when said reinforcing threads 6 are traveled from the equatorial plane P_EQ towards the pole of the hemisphere considered, here therefore, in the case of the first hemisphere Hl, towards the first axial end 5_1 of the reinforcing ply 5, and therefore more generally towards the first axial end 1_1 of the bandage 1.

[0109] Thus, if we consider at a given instant, in a plane reference frame whose origin corresponds to the point of contact of the cutting tool 2, and more particularly of the cutting edge of the cutting tool 2, with the reinforcing ply 5, and more particularly with a reinforcing wire 6, at the instant considered, and whose base is defined by an axial vector, parallel to the main axis Z20, and a circumferential vector, perpendicular to the axial vector, then the speed vector V2 of the cutting tool 2 which characterizes, at the point of contact between the cutting tool 2 and the reinforcing ply 5, the displacement of the cutting tool 2 relative to the surface of the reinforcing ply 5, is located in the same quadrant of said reference frame as the direction vector tangent to the reinforcing wire 6 passing through the origin of the reference frame at the instant considered, for example in the South-East quadrant in FIG. 6A, and points in the same direction as said direction vector tangent to the reinforcing wire 6,for example to the right and down in Figure 6A. ,

[0110] More particularly, the invention will make it possible, by a judicious choice of the cutting parameters, and more particularly by a judicious selection of the hemisphere and therefore of the axial direction of travel S2_l, taking into account on the one hand the direction of rotation R20-, which direction of rotation R20- is generally imposed, and on the other hand the identified orientation A6 of the reinforcing wires 6, to ensure that the circumferential components V2_circ and respectively axial components V2_ax of the speed vector V2 representative of the movement of the cutting tool 2 relative to the reinforcing ply 5 are, at the moment when said cutting tool 2 axially crosses the axial end 5_1 of the reinforcing ply 5 located in the hemisphere considered, and therefore crosses the free ends of the reinforcing wires 6, of the same signs as the circumferential components A6_circ, respectively axial components A6_ax, of the direction vector, tangent to the reinforcing wires 6,which characterizes the orientation A6 of said reinforcing wires at the axial end 5_1 of said reinforcing ply 5.,

[0111] In the part of the description which follows and which concerns the implementation of the machining in contact with the reinforcing ply, it will be considered, for convenience of description, that the machining in contact with the reinforcing ply is carried out by the first cutting tool 2 in the first hemisphere H1, here located on the right in Figures 6A, 6B, 6C, 7B and 1 IA.

[0112] It will be understood that when the reinforcing threads 6 have an oblique orientation A6 and are presented in the right direction in the first hemisphere H1, here for example at the level of the first selvedge 5_1 of the first reinforcing ply 5, taking into account the direction of rotation R20- chosen, here a negative direction of rotation R20-, then these same reinforcing threads 6 will be presented in the wrong direction in the second opposite hemisphere H2, here for example at the level of the second selvedge 5_2 of said first reinforcing ply, with respect to said direction of rotation R20- chosen.

[0113] This is why it will be appropriate to avoid sliding the second cutting tool 2' in contact with the reinforcing ply 5 in the second hemisphere H2, at least in the axial range which contains the second edge 5_2 of said reinforcing ply 5.

[0114] For this purpose, the second cutting path T2_2 preferably has, at least over a portion of the second hemisphere H2, a centrifugal radial offset Delta_T2 relative to the first cutting path T2_l, so as to preserve a certain residual excess thickness Delta_4 of external layer 4 in the second hemisphere H2 relative to the first hemisphere Hl, as can be seen in FIGS. 7A and 7B.

[0115] Advantageously, it is thus possible to preserve a residual safety thickness in the second axial cutting range W2_2, and therefore more particularly here in the second hemisphere H2, where the second cutting tool 2' will travel the reinforcing wires 6, 6' against the grain, so that the cutting tool 2' remains at a distance from said reinforcing wires 6, 6' in the risk zone(s), in particular when crossing the axial position of the ends of said reinforcing wires 6, 6', while, conversely, the first cutting tool 2 will be able to slide in contact with the reinforcing wires 6, 6' in the other axial cutting range, here the first axial cutting range W2_1, and therefore in the first hemisphere H1, where said reinforcing wires 6, 6' are oriented in the correct direction taking into account the direction of rotation R20- and the direction of axial travel S2_l.

[0116] In other words, it will thus be possible, in order to maintain the benefit provided in terms of time savings and energy savings by machining using a single direction of rotation, to take more precautions in hemisphere H2 where the reinforcing wires 6, 6' are run against the grain than in hemisphere H1 where the reinforcing wires 6, 6' are run in the correct direction, by machining the external layer 4 less deeply in the second hemisphere H2 than in the first hemisphere H1.

[0117] This may result in exposing the reinforcing ply 5, and more particularly the reinforcing threads 6, in the first hemisphere H1, and in maintaining a slight residual thickness E4 of external layer 4 which covers the reinforcing ply 5 over at least part or even all of the portion of the reinforcing ply 5 which extends into the second hemisphere H2, as can be seen in FIGS. 7A and 7B.

[0118] As an indication, the centrifugal radial offset Delta_T2 will preferably be included between 1 mm and 3 mm.

[0119] It is possible to implement a progressive, and more preferably progressive, centrifugal radial offset Delta_T2, for example which will be zero at the abscissa of the equatorial plane P_EQ, at the starting point K2 of the second cutting path T2_2, and which will become positive from a certain axial distance from the equatorial plane P_EQ, which in this case precedes the axial position of the second edge 5_2 of the reinforcing ply 5 in the second axial direction of travel S2_2, so that the second cutting tool 2' will move away from the reinforcing wires 6, in order to create the excess thickness Delta_4, and therefore to leave a residual thickness of external layer 4, only when the second cutting tool 2' approaches the second edge 5_2 of the reinforcing ply 5 located in the second hemisphere H2 and exceeds said second edge 5_2.

[0120] Preferably, the first positioning system 42 forms a master positioning system which executes a first cutting trajectory T2_l according to which said first positioning system 42 axially moves the first cutting tool 2 from the equatorial plane P_EQ by sliding said first cutting tool 2 in contact with the reinforcing ply 5, along the reinforcing wires 6, while the second positioning system 42' forms a slave positioning system within which the execution of the second cutting trajectory T2_2 is delayed in time, according to which said second positioning system 42' axially moves the second cutting tool 2' from the equatorial plane P_EQ, relative to the execution of the first cutting trajectory T2_l.

[0121] Thus, although the first and second cutting paths T2_l, T2_2 take place essentially simultaneously, over the same period of time, the first cutting path T2_l preferably benefits from a slight advance, which in particular allows the first cutting tool 2 to reveal any notable elements present in the first hemisphere H1, such as first edges 5_1, 5'1 of reinforcing plies 5, 5', before the second cutting tool 2', in turn, reaches similar notable elements, such as second edges 5_2, 5'_2, which are located in the second hemisphere H2, mirroring the notable elements of the first hemisphere H1 with respect to the equatorial plane P_EQ.

[0122] When the bandage 1, and more particularly the outermost reinforcing ply 5, has a symmetry of arrangement with respect to the equatorial plane P_EQ, as is frequently the case in practice, such a precaution makes it possible to anticipate the crossing, in the second hemisphere H2, of possible obstacles, such as edges or projections of the reinforcing ply 5, at the level of which the reinforcing threads 6, due to their orientation A6, have, in said second hemisphere H2, an increased vulnerability to tearing compared to these same reinforcing threads 6 considered in the first hemisphere H1. The invention therefore makes it possible to take, in good time, the necessary steps to adapt the second cutting trajectory T2_2 in order to avoid tearing of the reinforcing wires 6 in the second hemisphere H2.

[0123] Thus, preferably, a crossing by the first cutting tool 2 of a first edge 5_1 of the reinforcing ply 5 in the first hemisphere H1 is detected, and the second positioning system 42' is controlled so as to introduce into the second cutting trajectory T2_2 a centrifugal radial offset Delta_T2 which allows the second cutting tool 2' to pass radially at a distance from the reinforcing ply 5 when said second cutting tool 2' passes, in the second hemisphere H2, through an abscissa which is the mirror image, with respect to the equatorial plane P_EQ, of the abscissa of the first edge 5_1 crossed by the first cutting tool 2.

[0124] In this way, the second cutting path T2_2 can keep the second cutting tool 2' as close as possible to the reinforcing ply 5, the second positioning system 42' first adopting a following behavior according to which it reproduces a mirror image of the first cutting path T2_l and therefore slides the second cutting tool 2' into contact with the reinforcing ply 5, then an adjusted behavior, according to which it deviates from the mirror image of the first cutting path T2_l by slightly moving the cutting tool back, by the chosen centrifugal radial offset value Delta_T2, relative to the mirror image of the first cutting path T2_l, at the moment of crossing the second edge 5_2 located in the second hemisphere H2, and this in order to move the second cutting tool 2' away from the reinforcing ply 5 to an extent necessary and sufficient to maintain an excess thickness of protective material Delta_4 and thus not to catch the reinforcing threads 6.

[0125] The centrifugal radial offset Delta_T2 may be introduced in the form of a step or several successive steps, at a given axial abscissa or respectively successive axial abscissas, or in progressive form, for example by means of a ramp which extends over a given axial range.

[0126] The second positioning system 42' will advantageously control the second cutting tool 2' in radial position, from the radial positions identified along the first cutting trajectory T2_l, where appropriate corrected by the applicable centrifugal offset value Delta_T2.

[0127] Any appropriate means may be used to delay the start of execution of the second cutting trajectory T2_2 relative to the start of execution of the first cutting trajectory T2_1.

[0128] For example, for this purpose, it will be possible to trigger the axial movement of the second cutting tool 2' in the second hemisphere H2 along the second cutting trajectory T2_2: - when the first cutting tool 2 crosses, in the first hemisphere Hl, a predetermined axial abscissa threshold away from the equatorial plane P_EQ, - or at the end of a predetermined time delay from the triggering of the axial movement of the first cutting tool 2 along the first cutting path T2_l.

[0129] The detection of the crossing of a remarkable element, here of an edge 5_1, 5' 1 of reinforcement ply 5,5' in the first hemisphere H1 during the passage of the first cutting tool 2 at the axial abscissa of said remarkable element, or just after the passage of said cutting tool 2 at the axial abscissa of said remarkable element, may be carried out by any appropriate means, in particular by an optical detection device 50 such as a laser rangefinder which measures the distance of the wall 3 relative to the main axis Z20, a profilometer or a camera associated with an image analysis tool.

[0130] Preferably, the first cutting trajectory T2_l is executed by bringing the first cutting tool 2 into contact with the reinforcing ply 5 and then by controlling the first cutting tool 2 in radial force while the first cutting tool 2 is moved axially, so as to slide the first cutting tool 2 into contact with the reinforcing ply 5, along the reinforcing wires 6, in the first hemisphere Hl.

[0131] Such radial force control allows the first cutting tool 2 to remain permanently in contact with the wall 3, and in compression against said wall 3, and more particularly in contact with the reinforcing ply 5, during the rotation R20 of the bandage 1, even in the event of irregularities in curvature or centering causing out-of-roundness, and further allows the first cutting tool 2 to automatically accommodate, by dynamically adapting its radial position, the variations in the surface of the reinforcing ply 5, in particular the possible curvature of said reinforcing ply 5 as well as the projections formed by the edge(s) 5_1, 5'_1 of the reinforcing ply(s) 5 traversed by the first cutting tool 2.

[0132] For example, the first cutting tool 2 may be controlled by radial force so that the first cutting tool 2 exerts against the wall 3, and more particularly against the reinforcing ply 5, 5', a centripetal radial force of constant intensity, while said first cutting tool moves along the main axis Z20.

[0133] To achieve radial force control, it is possible, for example, to use a pneumatic cylinder which radially presses the first cutting tool 2 against the wall 3, and more particularly against the reinforcing ply 5, 5', with the desired radial force intensity. A pneumatic cylinder in fact ensures both good control of the force intensity and a flexible, floating pneumatic suspension of the first cutting tool 2, which allows the latter to remain permanently in contact with the wall 3, and more particularly with the reinforcing ply 5, 5'.

[0134] The radial positions adopted by the first cutting tool 2 along the first cutting path T2_l controlled by radial force, when said first cutting tool 2 follows the surface of the reinforcement ply 5 and moves axially, can advantageously serve as a reference to determine the corresponding radial positions of the second cutting tool 2', and thus construct a second adapted cutting path T2_2, from the first effective cutting path T2_l, integrating, if necessary, the corrections provided by the applicable centrifugal radial offset(s) Delta_T2, to control the second cutting tool 2' in radial position.

[0135] In this respect, preferably, during the execution of the first cutting path T2_l, radial positions are measured which are successively adopted by the first cutting tool 2 controlled in radial force, along the first cutting path T2_l in contact with the reinforcing ply 5, and the second cutting tool 2' is controlled in radial position, from the measured radial positions of the first cutting tool 2, so as to be able to introduce a centrifugal radial offset Delta_T2 in the second cutting path T2_2 if, in the first hemisphere H1, a variation in the radial position of the first cutting tool 2 is detected which is representative of the axial crossing, by the first cutting tool 2, of an edge 5_1 of the reinforcing ply 5.

[0136] Thus, it is the first cutting tool 2 itself which will be used to detect the crossing by the first cutting tool 2 of a first edge 5_1, 5'_1 of a reinforcing ply 5, 5' in the first hemisphere H1, by acting as a feeler whose radial position is monitored in order to detect the variations in radial position induced by the arrangement of the reinforcing ply(ies) 5, 5'.

[0137] The correction of the second cutting trajectory T2_2 will then be triggered in response to the detection of an edge 5_1 in the first hemisphere H1 to preserve the integrity of the reinforcement ply 5, and of the second cutting tool 2', when crossing the equivalent edge 5_2 in the second hemisphere H2.

[0138] Furthermore, the method according to the invention preferably comprises a preliminary step of analyzing the bandage during which the radial distance called the “envelope radial distance” D0_ply is evaluated at which the radially external limit of the reinforcing wires 6 of the reinforcing ply 5 which is located immediately under the outer layer 4 is located, relative to the main axis Z20, in the absence of radial stress exerted on the wall 3 by the cutting tools 2, 2', then a step of defining the cutting trajectory during which the first cutting trajectory T2_l, and preferably also the second cutting trajectory T2_2, is defined from the envelope radial distance D0_ply, by fixing the radial position of the starting point K1 of the first cutting trajectory T2_l, and preferably also the radial position of the starting point K2 of the second cutting trajectory T2_2,at a radial distance from the main axis Z20 which is less than the radial envelope distance D0_ply by a non-zero value called the “nominal deflection value” D_bend, as illustrated in [Fig. 14].,

[0139] Said nominal deflection value D_bend is preferably between 1 mm and 5 mm, more preferably between 2 mm and 5 mm, for example equal to 3 mm.

[0140] As illustrated in [Fig.14], the application of a nominal value of deflection D_bend allows the cutting tool 2, 2' to cause a radial depression of the wall 3 by elastic deformation in centripetal radial bending of the reinforcing wires 6, 6', and thus creates a prestress in radial compression of the cutting tool 2 against the external layer 4 supported by the reinforcing wires 6, 6', which makes it possible to scrape the external layer 4 as close to the reinforcing wires 6, 6' as possible, and more preferably in contact with said reinforcing wires 6, 6', taking into account, where appropriate, the degree of sharpening of the cylindrical knife 25, 25' forming the cutting tool 2, 2'.

[0141] Such prestressing also makes it possible to compensate for any defects in centering or roundness of the bandage 1, and therefore allows the cutting tool 2, 2' to reach the reinforcing ply 5 over the entire circumference of said bandage 1.

[0142] Preferably, the starting points K1, K2 of the cutting trajectories are located in the equatorial zone of the bandage 1, preferably at the axial abscissa of the equatorial plane P_EQ, so that the nominal value of deflection D_bend applies in practice to the radially outermost crest line of the reinforcing ply 5 and the reinforcing wires 6.

[0143] Taking into account the above, if we opt for the implementation possibility called “machining in contact with the reinforcement ply”, we can in particular envisage one or other of the scenarios among the four scenarios below, designated respectively by “scenario 1”, “scenario 2”, “scenario 3”, and “scenario 4”.

[0144] SCENARIO 1

[0145] The starting point Kl of the first cutting path T2_l is fixed at an axial position contained in the equatorial zone, preferably in the equatorial plane P_EQ, and at a radial distance from the main axis Z20 which, as illustrated in [Fig. 14], is less than the radial envelope distance D0_ply, by a value called the “nominal deflection value” D_bend chosen to be between 2 mm and 5 mm, for example equal to 3 mm, so that the first cutting tool 2 causes a radial depression of the wall 3 by elastic deformation in bending of the reinforcing wires 6 and is thus prestressed radially against the external layer 4 supported by the reinforcing wires 6.

[0146] We then opt for a first rectilinear cutting path T2_l, the path of which forms, from the starting point Kl, a straight line parallel to the main axis Z20. Thus, the first cutting tool 2 moves axially while remaining at a constant radial distance from the main axis Z20.

[0147] Advantageously, when the wall has a curved shape and the reinforcing ply 5, 5' tends to be folded back towards the main axis Z20 at the shoulders of the bandage 1, a such a scenario makes it possible to recover a maximum of material in the equatorial zone, while passing the first cutting tool 2 at a radial distance from the edge of the reinforcement ply 5, 5', in particular at the shoulders.

[0148] Preferably, the second cutting path T2_2 is also rectilinear and parallel to the main axis Z20, a mirror image of the first cutting path T2_l with respect to the equatorial plane P_EQ, starting from a starting point K2 which is located radially at a distance from the main axis which is either, preferably, identical to that of the starting point Kl of the first cutting path or, possibly, offset by a centrifugal radial offset value Delta_T2. The second cutting tool 2' is controlled in radial position.

[0149] The second cutting trajectory T2_2 therefore has, in the second hemisphere H2, the same effects and the same consequences as the first cutting trajectory T2_l in the first hemisphere HL.

[0150] Such a scenario 1 is particularly suitable for the machining of a bandage which has the first layout diagram mentioned above and illustrated in Figures 3, 4, and 6A.

[0151] Such a scenario 1 would also be well suited to the machining of a bandage which would have a (third) layout diagram according to which, unlike the layout diagram, the second reinforcing threads 6' of the second reinforcing ply 5' would have an orientation A6' of opposite sign to the orientation A6 of the first reinforcing threads 6, so that, in the first hemisphere, the first selvedge 5_1 of the first reinforcing ply 5 would be presented in the correct direction facing the first cutting tool 2 while the first selvedge 5'_1 of the second reinforcing ply 5' would be presented against the grain.Indeed, a rectilinear trajectory, executed opposite a wall 3 whose top 10 is radially more protruding than the shoulders, allows the first cutting tool 2 to pass into contact with the edge 5_1 of the first reinforcing ply 5, in the right direction, and at a slight radial distance from the edge 5'_1 of the second reinforcing ply 5', while avoiding catching the second reinforcing wires 6'.

[0152] SCENARIO 2

[0153] Identical to scenario 1, except that the first cutting path T2_l is curved, according to a predetermined curvature, the first cutting tool 2 being controlled in radial position.

[0154] The second cutting tool 2' is also controlled in radial position according to a second cutting path T2_2 also curved, and which integrates, if necessary, with respect to the first cutting path, a centrifugal offset value Delta_T2.

[0155] SCENARIO 3

[0156] As in scenario 1, the starting point Kl of the first cutting trajectory T2_l is fixed at an axial position contained in the equatorial zone, preferably in the equatorial plane P_EQ, and at a radial distance from the main axis Z20 which is less than the radial envelope distance, of a value called the “nominal deflection value” D_bend chosen which is between 2 mm and 5 mm, for example equal to 3 mm, so that the first cutting tool 2 causes a radial depression of the wall 3 by elastic deformation in bending of the reinforcing wires 6 and is thus prestressed radially against the reinforcing ply 5.

[0157] On the other hand, this time we opt for a first cutting trajectory T2_l which, unlike scenario 1, implements a servocontrol of the first cutting tool 2 in radial force, and no longer in radial position, while the first cutting tool moves axially.

[0158] Thus, the first cutting tool 2 slides in contact with the reinforcing ply 5, and more particularly in contact successively with the first reinforcing ply 5 then with the second underlying reinforcing ply 5', in the first hemisphere H1, as illustrated in FIGS. 6A, 6B and 6C.

[0159] This maximizes material recovery by exposing the reinforcing ply 5, 5' and the reinforcing threads 6, 6'.

[0160] The second cutting tool 2' is controlled in radial position, and executes a second cutting path T2_2 which is calculated, and more preferably mirrored, from the first cutting path T2_l, in particular from the radial positions of the first cutting path T2_l, and adjusted when necessary by the introduction of a centrifugal radial offset Delta_T2, on all or part of the second hemisphere H2, as illustrated in FIGS. 7A and 7B. In practice, such a centrifugal radial offset Delt_T2 is introduced at least at the abscissas which correspond to crossings of edges 5_2, 5'_2 in the second hemisphere H2.

[0161] Thus, a maximum of available material is also recovered in the second hemisphere H2, while avoiding taking the corresponding edges 5_2, 5'_2 against the grain.

[0162] Such a scenario 3 is particularly well suited to the machining of a bandage 1 having the first layout diagram of FIGS. 3, 4 and 6A, since it allows in particular the first cutting tool 2 to slide successively in contact with the first reinforcement ply 5 then the second reinforcement ply 5', and to successively cross the edge 5_1 of the first reinforcement ply then the edge 5'_1 of the second reinforcement ply, since these edges 5_1, 5'_1 are both in the right direction.

[0163] SCENARIO 4

[0164] This is a variant of scenario 3, applied to a bandage presenting the second implantation diagram described above with reference to figures 8 and 9, a variant according to which the centrifugal radial offset Delta_T2 is added simply towards the end of the second cutting path T2_2, just to allow the second cutting tool 2' to cross the second end 5_2 of the first reinforcing ply 5 while leaving, as indicated in dotted lines in Figure 11B, a very slight excess thickness Delta_4 of outer layer material 4 which covers the axial end, and therefore the second selvedge 5_2, of the first reinforcing ply 5. Thus, the second cutting tool 2 does not risk peeling the reinforcing threads 6 at the end of the continuous strip wound in a spiral, and therefore at the second selvedge 5_2, where said continuous strip, although the angle A6_ang of the reinforcing threads 6 is small or even substantially zero, is, in absolute terms, taken in the wrong direction due to the direction of rotation R20- negative.

[0165] The first cutting tool 2 approaches the first reinforcement ply 5 in the right direction, it is possible for it to remain in contact with said first reinforcement ply 5 throughout the first hemisphere H1, and to cross the first edge 5_1 of said first reinforcement ply 5 without damage.

[0166] According to a preferred implementation possibility, called “machining under the bottoms of the grooves”, the cutting paths T2_1, T2_2 will be defined in such a way that the cutting tools 2, 2' reach, in the external layer 4, intermediate depths, closer to the main axis Z20 than are the bottoms 61B of the grooves 61, but in centrifugal radial withdrawal from the reinforcing ply or plies 5, 5', and in particular from the first radially outermost reinforcing ply 5, in order to avoid any contact between the cutting tool 2, 2' and the reinforcing wires 6, 6', as illustrated in [Fig. 13],

[0167] Such an implementation is particularly suitable for situations in which it is desired to machine a bandage 1 provided with a first reinforcing ply 5 that is relatively fragile, because it is relatively thin and / or provided with reinforcing threads 6 made of polymer material, or in situations in which the architecture of the bandage 1, and in particular of the reinforcing ply 5, is not known, or poorly identified, so that there remains a doubt as to how to machine the bandage 1 without risk to the installation 40.

[0168] Thus, such an implementation could be of particular interest for machining certain tires used by passenger vehicles and whose reinforcing ply 5 forms a textile band which it is desired to avoid cutting or perforating.

[0169] Such machining under the bottoms of the grooves may use as a reference, to fix the cutting paths T2_l, T2_2, the radial envelope distance D0_ply, provided that this can be determined without damaging the reinforcement ply 5. The cutting tools 2, 2' may then be positioned in centrifugal radial withdrawal by the radial envelope distance D0_ply, for example from 1 mm to 3 mm in centrifugal radial withdrawal by the radial envelope distance D0_ply.

[0170] However, preferably, the depth of the groove bottoms 61B will be taken as a reference, because the grooves 61 and their bottoms 61B are advantageously visible di directly on the apparent surface of the wall 3, and therefore their characteristics measurable without it being necessary to dig the external layer 4.

[0171] Thus, preferably, the method comprises a preliminary step of analyzing the tire during which the radial distance, called the “radial groove bottom reference” D0_groove, is evaluated, at which the bottom 61B of at least one of the grooves 61 is located, relative to the main axis Z20, in the absence of radial stress exerted on the wall 3 by the cutting tools 2, 2', then a step of defining the cutting trajectory, during which the first cutting trajectory T2_1, and preferably also the second cutting trajectory T2_2, are defined from the radial groove bottom reference D0_groove.

[0172] More particularly, the cutting trajectories T2_l, T2_2, and more particularly their respective starting points Kl, K2, can be fixed at a radial distance from the main axis Z20 which is less than the radial reference of the groove bottom D0_groove, by a chosen offset value D_in.

[0173] Said offset value D_in is, in absolute value, non-zero, to force the cutting tool 2, 2' to penetrate into the external layer 4 under the bottoms 61B of the grooves, and strictly less than the difference between the groove bottom reference D0_groove and the radial envelope distance D0_ply, so that the cutting tool 2, 2' cannot reach the reinforcing ply 5, and therefore leaves a slight thickness E4 of protective external layer on the reinforcing ply 5.

[0174] The offset value D_in can be for example between 1 mm and 3 mm.

[0175] The radial reference of the groove bottom D0_groove can be measured by any suitable device, in particular an optical detection device 50, such as a profilometer, a laser rangefinder, etc. which scans the wall 3 and whose position relative to the main axis Z20 is known.

[0176] More particularly, to implement machining under the bottoms of the grooves, one can choose a scenario from the three scenarios below, noted respectively “scenario 5”, “scenario 6”, and “scenario 7”.

[0177] SCENARIO 5

[0178] The starting point Kl of the first cutting path T2_l is fixed, preferably at an axial position contained in the equatorial zone, more preferably in the equatorial plane P_EQ, at a radial distance from the main axis Z20 which is less than the radial groove bottom reference D0_groove, by a chosen offset value D_in which is non-zero, offset value D_in which can be for example between 1 mm and 3 mm, and a first straight cutting path T2_l is opted for, the path of which forms, from the starting point Kl, a straight line parallel to the main axis Z20.

[0179] The first cutting tool 2 thus travels the first hemisphere at a constant distance, here worth DO_groove - D_in, of the main axis Z20.

[0180] The second cutting path T2_2 is then preferably also rectilinear and parallel to the main axis Z20, and is preferably carried out at the same radial distance from said main axis Z20 as the first cutting path T2_1.

[0181] SCENARIO 6

[0182] As for scenario 5, the starting point Kl of the first cutting trajectory T2_l is fixed, preferably at an axial position contained in the equatorial zone, more preferably in the equatorial plane P_EQ, at a radial distance from the main axis Z20 which is less than the radial groove bottom reference D0_groove, by a chosen offset value D_in which is non-zero, offset value D_in which can be for example between 1 mm and 3 mm.

[0183] On the other hand, this time we opt for a first curved cutting path T2_l presenting a predetermined curved path which, in a radial plane containing the main axis Z20, presents a concave shape relative to the main axis Z20.

[0184] This scenario 6 makes it possible to improve the recovery of material at the shoulders, while maintaining, compared to the reinforcing plies 5, 5', a safety thickness E4 at any point along the width of the bandage.

[0185] The same applies to the second cutting path T2_2, which is the mirror image of the first cutting path T2_l with respect to the equatorial plane P_EQ.

[0186] SCENARIO 7

[0187] According to a preferred characteristic which may constitute an invention in its own right, a fictitious curved interpolation line is determined which passes through the respective bottoms 61B of several grooves 61, preferably through the bottoms of all the grooves distributed axially in the zone of the external layer 4 concerned by the cutting path T2_l, T2_2 considered, and a first curved cutting path T2_l is opted for which is parallel to the fictitious curved interpolation line, and closer to the main axis Z20 than said fictitious interpolation curve by a chosen offset value D_in which is non-zero, an offset value D_in which may be for example between 1 mm and 3 mm.

[0188] The cutting paths T2_1, T2_2 thus faithfully follow the actual path of the groove bottoms 61B of the bandage 1 concerned, while passing just below the groove bottoms 61B, in the solid part of the external layer 4, and remaining radially at a safe distance from the reinforcing plies 5, 5'.

[0189] In this way, the quantity of recovered material is optimized on a case-by-case basis for each bandage, while guaranteeing the absence of interference between the reinforcing threads 6, 6' and the tools, and therefore the preservation of the integrity of the reinforcing plies 5, 5' and the cutting tools 2, 2'.

[0190] Preferably, one opts for the possibility of implementation according to which at at least one of the cutting tools 2, 2', or even each of the first and second cutting tools 2, 2', slides in contact with the reinforcing ply 5, or for the implementation possibility according to which each of the cutting tools 2, 2' is held back, at a radial distance from the reinforcing ply 5, the method comprises, prior to the material removal step during which the first and second cutting tools 2, 2' act simultaneously, a trench digging step, during which the first cutting tool 2 is axially positioned at an axial abscissa included in an axial range which on the one hand represents less than 35% of the axial range W1 covered by the bandage 1, preferably less than 30% of the axial range W1 covered by the bandage 1, or even less than 25%, less than 20%, less than 15% or even less than 10% of the axial range W1 covered by the bandage 1, and which on the other hand contains the equatorial plane P_EQ of bandage 1,that is to say that the first cutting tool 2, and more particularly the central axis Z25 of the first knife 25, is positioned in the equatorial zone, more preferably the first cutting tool 2 is positioned axially at the axial abscissa of the equatorial plane P_EQ, then, while the bandage 1 is driven in rotation R20 around the main axis Z20, here in this case in the direction of rotation R20- negative, the first cutting tool 2 is engaged in the internal layer 4, according to a centripetal radial penetration movement, so as to dig a circumferential trench 27 located at the chosen axial abscissa.

[0191] Advantageously, the starting point Kl of the first cutting trajectory T2_l followed by the first cutting tool 2 and the starting point K2 of the second cutting trajectory T2_2 followed by the second cutting tool 2' are then preferably both located inside said trench 27.

[0192] Advantageously, the material extracted from the external layer 4 during the digging of the trench 27 can be advantageously recovered, in the same way as the material which will then be removed during the execution of the first and second cutting trajectories T2_1, T2_2, and can even represent up to 30% or even 35% of the total material recovered by the method according to the invention.

[0193] Furthermore, by fixing the starting points Kl, K2 in the trench 27, and therefore in the equatorial zone, the cutting tools 2, 2' are allowed to be pre-positioned from the outset at the appropriate axial abscissa, and at the appropriate depth of cut, and to effectively attack the external layer 4, during their respective axial movements in the hemispheres Hl, H2.

[0194] Furthermore, the trench 27 can advantageously be dug until the first cutting tool 2 reaches the reinforcing layer 5, and thus makes the reinforcing wires 6 visible.

[0195] In this case, it will be possible to advantageously detect the orientation A6 of the reinforcing threads 6 by observing the apparent surface of the reinforcing ply 5, which forms the bottom of the exploration trench 27, for example by means of an optical detection device 50.

[0196] Similarly, we can thus determine the radial envelope distance D0_ply.

[0197] Furthermore, preferably, during braking phases aimed at slowing the rotation speed of the support 20, energy is recovered by means of a converter, such as an alternator, coupled to said support 20.

[0198] More particularly, for simplicity of design, it will be possible, during braking phases, to use in generator mode the electric motor which is provided to drive the support 20 in rotation R20.

[0199] This will advantageously make it possible to achieve energy savings, by converting the kinetic energy of the support 20 and the bandage 1 into electrical energy.

[0200] Of course, the invention also relates to an installation 40 making it possible to implement a method as described above.

[0201] The installation 40 thus comprises, as can be seen in Figures 1 and 2, 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 a main axis Z20, here horizontal, and associated with a drive system 41, preferably comprising an electric motor, which makes it possible to drive said rotary support 20, and therefore the bandage 1, in rotation R20 on itself around said main axis Z20, in a determined direction of rotation R20+, R20-, here by convention a negative direction of rotation R20-.

[0202] The installation 40 also comprises a first cutting tool 2, preferably formed by a first cylindrical knife 25, and a second cutting tool 2', distinct from the first cutting tool 2, and preferably formed by a second cylindrical knife 25'.

[0203] The installation 40 further comprises a first positioning system 42 which carries the first cutting tool 2, preferably at the end of a first robotic arm 44, and which makes it possible to position and move said first cutting tool 2 relative to the frame 30, and more particularly relative to the main axis Z20, so as to make the first cutting tool 2 follow a first cutting trajectory T2_l while the support 20 drives the bandage 1 in rotation R20, so as to remove material from the external layer 4 of the bandage 1.

[0204] Similarly, the installation 40 comprises a second positioning system 42' which carries the second cutting tool 2', preferably at the end of a second robotic arm 44', and which makes it possible to position and move said second cutting tool 2' relative to the frame 30, and more particularly relative to the main axis Z20, so as to make the second cutting tool 2' follow a second cutting path T2_2, distinct from the first cutting path T2_1, while the support 20 drives the bandage 1 in rotation R20, so as to remove material from the external layer 4 of the bandage 1.

[0205] As indicated above, the first and / or the second positioning system 42, 42', and more particularly one and / or the other of the first and second robotic arms 44, 44', may comprise a pneumatic cylinder for radially pressing the corresponding cutting tool 2, 2' against the wall 3 of the bandage 1, and where appropriate controlling said cutting tool in radial force.

[0206] Each positioning system 42, 42' will preferably be provided with a sharpening system 45 for sharpening the cutting edge of the cylindrical knife 25, 25' mounted on the robotic arm 44, 44', as well as a chute 46, 46' for guiding and facilitating the evacuation of the shavings or strips of material which are detached from the external layer of the bandage 4 by the corresponding cutting tool 2, 2'.

[0207] The installation 40 also comprises a control unit 51 making it possible to automatically control the installation 40.

[0208] Said control unit 51 comprises a piloting unit 52 arranged to pilot the drive system 41 in order to implement the rotation R20 of the support 20 and to pilot and coordinate the first and second positioning systems 42, 42' in order to execute the first and second cutting trajectories T2_l, T2_2.

[0209] Advantageously, the control unit 52 makes it possible to simultaneously implement the two cutting tools 2, 2', and therefore to execute the two cutting trajectories T2_l, T2_2 at least in part, or even in full, in time masked with respect to each other, with, where appropriate, a slight advance given to the first cutting trajectory T2_l, as explained above.

[0210] The control unit 51 also comprises a bandage analysis system 53 which makes it possible to identify, for example by means of an optical detection device 50 which may include a profilometer, a laser rangefinder, and / or a camera associated with image processing, the radial envelope distance D_ply, the radial groove bottom reference D_groove, and / or the orientation A6 of the reinforcing threads, as explained above.

[0211] The control unit 51 further comprises a unit 54 for adapting the cutting paths, which is arranged to define the first cutting path T2_1 and the second cutting path T2_2, and in particular to ensure that the combination of said cutting paths, and more preferably each of said cutting paths T2_1, T2_2, makes it possible to remove material, in one or more zones of the external layer 4, here more particularly each in the hemisphere H1, H2 which is allocated to it, up to a depth which is located between the bottom 61B of the grooves 61 and the reinforcing ply 5.

[0212] In particular, the unit 54 for adapting the cutting trajectories is capable of defining a first and / or a second cutting trajectory T2_l which presses the corresponding cutting tool 2, 2' against the reinforcing ply 5, 5', to slide said cutting tool 2, 2' into contact with the reinforcing wires 6, 6', and to include, if necessary, a radial offset. centrifugal Delta_T2 for radially moving back the cutting tool 2, 2' concerned in the portions of one and / or the other of the first and second cutting trajectories T2_l, T2_2 in which the reinforcing threads 6, 6' are presented against the grain relative to the action of the cutting tool 2, 2', and more particularly in which the circumferential component A6_circ of the direction vector along which the reinforcing threads 6, 6' extend is of opposite sign to the circumferential component V2_circ of the speed vector V2 along which the cutting tool 2, 2' moves relative to the wall 3 of the bandage, and therefore in particular relative to the corresponding reinforcing ply 5, 5'.

[0213] The control unit 52, the bandage analysis system 53 and the unit 54 for adapting the cutting sequence will preferably be electronic or computer-based, and will allow automatic performance of the steps of bandage analysis, adaptation of the cutting trajectories, and coordinated execution of the cutting trajectories.

[0214] The control unit 52, the bandage analysis system 53 and the unit 54 for adapting the cutting sequences may advantageously be grouped within the control unit 51, which is for example formed by a computer or an industrial programmable automaton.

[0215] Of course, the invention is in no way limited to the embodiment variants described above, the person skilled in the art being able in particular to isolate or freely combine one or other of the aforementioned characteristics, or to substitute equivalents for them.

[0216] In particular, the provisions applicable to machining under the groove bottoms 61B, and more particularly with the use of a fictitious interpolation line as described in scenario 7, could possibly be applied to machining of the bandage 1 which would implement a single cutting tool 2 rather than two cutting tools 2, 2', which single cutting tool 2 would process the entire width of said bandage 1, either in one pass covering the two hemispheres H1, H2, or in two successive passes each covering, preferably from the trench 27 dug in the equatorial zone, a separate hemisphere H1, H2.

Claims

Claims

1. Method for machining a tire (1), said tire (1) having a wall (3) which comprises on the one hand at least one outer layer (4) based on elastomer, which has been shaped to have sculpture blocks (60) separated by grooves (61), and on the other hand at least one reinforcing ply (5) which is located under said outer layer (4) and which contains a plurality of reinforcing threads (6), said method comprising a material removal step during which: - by means of a rotating support (20) having an axis of rotation called the "main axis" (Z20), the tire (1) is driven in rotation (R20) on itself, around said main axis (Z20), in a chosen direction of rotation (R20+, R20-), and - while the bandage (1) is rotating (R20) in the chosen direction of rotation (R20+, R20-), at least two cutting tools (2, 2') are used which act simultaneously against the outer layer (4) to remove material therefrom, namely at least one first cutting tool (2) which is carried by a first positioning system (42) making it possible to position and move said first cutting tool (2) relative to the main axis (Z20), so as to make the first cutting tool (2) follow a first cutting path (T2_l), and at least one second cutting tool (2') which is carried by a second positioning system (42') making it possible to position and move said second cutting tool (2') relative to the main axis (Z20), so as to make the second cutting tool (2') follow a second cutting path (T2_2) distinct from the first cutting path (T2_l), said first and second cutting paths (T2_l,T2_2) being defined so that they allow material to be removed, in one or more areas of the external layer (4), up to a depth which is located between the bottom (61B) of the grooves (61) and the reinforcing ply (5).,

2. Method according to claim 1 characterized in that, the bandage (1) being axially divided into a first hemisphere (Hl) and a second hemisphere (H2) each located on a different side of the equatorial plane (P_EQ) of the bandage which is normal to the main axis (Z20) and passes through the middle of the axial range (Wl) occupied by the bandage (1), the first cutting tool (2) is assigned to the removal of material in the first hemisphere (Hl) of the bandage (1) while the second cutting tool (2') is assigned to the removal of material in the second hemisphere (H2) of the bandage (1).

3. Method according to claim 2 characterized in that the first cutting path (T2_l) is executed by bringing the first cutting tool (2) into contact with the reinforcing ply (5) then axially moving the first cutting tool (2) so as to slide the first cutting tool (2) into contact with the reinforcing ply (5) along the reinforcing wires (6), in at least a part or even the whole of the first hemisphere (H1), and in that the second cutting path (T2_2) has, at least on a part of the second hemisphere (H2), a centrifugal radial offset (Delta_T2) relative to the first cutting path (T2_l), so as to preserve a certain residual excess thickness (Delta_4) of external layer (4) in the second hemisphere (H2) relative to the first hemisphere (H1).

4. Method according to claim 2 or 3 characterized in that the first positioning system (42) forms a master positioning system which executes a first cutting trajectory (T2_l) according to which it axially moves the first cutting tool (2) from the equatorial plane (P_EQ) by sliding said first cutting tool (2) in contact with the reinforcing ply (5), along the reinforcing wires (6), in that the second positioning system (42') forms a slave positioning system within which the execution of the second cutting trajectory (T2_2) is delayed in time, according to which said second positioning system (42') axially moves the second cutting tool (2') from the equatorial plane (P_EQ), relative to the execution of the first cutting trajectory (T2_l),in that a crossing by the first cutting tool (2) of a first edge (5_1) of the reinforcing ply (5) in the first hemisphere (H1) is detected, and in that the second positioning system (42') is controlled so as to introduce into the second cutting path (T2_2) a centrifugal radial offset (Delta_T2) allowing the second cutting tool (2') to pass radially at a distance from the reinforcing ply (5) when said second cutting tool (2') passes, in the second hemisphere (H2), by an abscissa which is the mirror image, with respect to the equatorial plane (P_EQ), of the abscissa of the first edge (5_1) crossed by the first cutting tool (2).,

5. Method according to claim 4 characterized in that the axial movement of the second cutting tool (2') is triggered in the second hemisphere (H2) along the second cutting path (T2_2) when the first cutting tool (2) crosses, in the first hemisphere (Hl), a predetermined axial abscissa threshold away from the equatorial plane (P_EQ), or at the end of a predetermined time delay from the triggering of the axial movement of the first cutting tool (2) along the first cutting path (T2_l).

6. Method according to one of claims 2 to 5 characterized in that the first cutting path (T2_l) is executed by bringing the first cutting tool (2) into contact with the reinforcing ply (5) then by controlling the first cutting tool (2) in radial force while the first cutting tool (2) is moved axially, so as to slide the first cutting tool (2) into contact with the reinforcing ply (5), along the reinforcing wires (6), in the first hemisphere (Hl).

7. Method according to claim 6 and one of claims 4 or 5, characterized in that, during the execution of the first cutting path (T2_l), radial positions are measured which are successively adopted by the first cutting tool (2) controlled in radial force, along the first cutting path (T2_l) in contact with the reinforcing ply (5), and the second cutting tool (2') is controlled in radial position, from the measured radial positions of the first cutting tool (2), so as to be able to introduce a centrifugal radial offset (Delta_T2) in the second cutting path (T2_2) if, in the first hemisphere (Hl), a variation in the radial position of the first cutting tool (2) is detected which is representative of the axial crossing, by the first cutting tool (2), of an edge (5_1) of the reinforcing ply (5).

8. Method according to one of claims 2 to 7 characterized in that it comprises a preliminary step of analysis of the bandage during which the radial distance called "radial envelope distance" (D0_ply) is evaluated at which the radially external limit of the reinforcing threads (6) of the reinforcing ply (5) which is located immediately under the outer layer (4) is located, relative to the main axis (Z20), in the absence of radial stress exerted on the wall (3) by the cutting tools (2, 2'), then a step of definition of the cutting trajectory during which the first cutting trajectory (T2_l), and preferably also the second cutting trajectory (T2_2), is defined from the radial envelope distance, by fixing the radial position of the starting point (Kl) of the first cutting trajectory (T2_l), and preferably also the radial position of the starting point (K2) of the

9. second cutting path (T2_2), at a radial distance from the main axis (Z20) which is less than the radial envelope distance (D0_ply) by a non-zero value called “nominal deflection value” (D_bend), said nominal deflection value (D_bend) preferably being between 1 mm and 5 mm, more preferably between 2 mm and 5 mm, for example equal to 3 mm. Method according to one of claims 1 or 2, characterized in that it comprises a preliminary step of analyzing the tire during which the radial distance, called the "radial groove bottom reference" (D0_groove), at which the bottom (61B) of at least one of the grooves (61) is located relative to the main axis (Z20), in the absence of radial stress exerted on the wall (3) by the cutting tools (2, 2'), is evaluated, then a step of defining the cutting path, during which the first cutting path (T2_l), and preferably also the second cutting path (T2_2), is defined from the radial groove bottom reference (D0_groove), by choosing one scenario from: - “scenario 5”: the starting point Kl of the first cutting path T2_l is fixed at a radial distance from the main axis Z20 which is less than the radial reference of the groove bottom (D0_groove), by a chosen offset value (D_in) which is non-zero, an offset value which can be for example between 1 mm and 3 mm, and a first straight cutting path (T2_l) is opted for, the path of which forms, from the starting point (Kl), a straight line parallel to the main axis (Z20); - “scenario 6”: the starting point (Kl) of the first cutting path (T2_l) is fixed at a radial distance from the main axis (Z20) which is less than the radial groove bottom reference (D0_groove), by a chosen offset value (D_in) which is non-zero, an offset value which can be for example between 1 mm and 3 mm, and a first curved cutting path (T2_l) is opted for, having a predetermined curved path which, in a radial plane containing the main axis (Z20), has a concave shape relative to the main axis (Z20); - “scenario 7”: a fictitious curved interpolation line is determined which passes through the respective bottoms (61B) of several grooves (61), preferably through the bottoms (61B) of all the grooves distributed axially in the area of ​​the external layer (4) concerned by the tra- cutting path (T2_l, T2_2) considered, and we opt for a first curved cutting path (T2_l) which is parallel to the fictitious interpolation curved line, and closer to the main axis (Z20) than said fictitious interpolation curve by a chosen offset value (D_in) which is non-zero, an offset value which can be for example between 1 mm and 3 mm.

10. Method according to one of the preceding claims, characterized in that the first cutting tool (2) and the second cutting tool (2') are distant from each other, in azimuth around the main axis (Z20), by at least 30 degrees, preferably by at least 90 degrees, or even by at least 120 degrees, and for example by 180 degrees + / - 20 degrees.

11. Method according to one of the preceding claims, characterized in that the first cutting tool (2) and the second cutting tool (2') are formed respectively by a first cylindrical knife (25) and a second cylindrical knife (25'), the circular edges (25A, 25'A) of which form the cutting edges and are oriented so as to engage the wall (3) in opposition to the direction of rotation (R20+, R20-) chosen.

12. Method according to one of the preceding claims, characterized in that it comprises, prior to the material removal step during which the first and second cutting tools (2, 2') act simultaneously, a trench digging step, during which the first cutting tool (2) is axially positioned at an axial abscissa included in an axial range which, on the one hand, represents less than 35% of the axial range (W1) covered by the bandage (1), preferably less than 30% of the axial range (W1) covered by the bandage (1), or even less than 25%, less than 20%, less than 15% or even less than 10% of the axial range (W1) covered by the bandage (1), and which, on the other hand, contains the equatorial plane (P_EQ) of the bandage (1), more preferably the first cutting tool (2) is axially positioned at the axial abscissa of the plane equatorial (P_EQ), then, while the bandage (1) is rotated (R20) around the main axis (Z20),the first cutting tool (2) is engaged in the internal layer (4), according to a centripetal radial penetration movement, so as to dig a circumferential trench (27) located at the chosen axial abscissa, and in that the starting point (Kl) of the first cutting path (T2_l) followed by the first cutting tool (2) and the starting point (K2) of the second cutting path (T2_2) followed by the second cutting tool (2') are both located inside, said trench (27).

13. Method according to one of the preceding claims, characterized in that, during the braking phases aimed at slowing the rotation speed of the support (20), energy is recovered by means of a converter, such as an alternator, coupled to said support (20).

Images