Additive manufacturing device for a tire tread

Abstract

Device (10) for additive manufacturing all or part of a tread (6) of a tire (4) configured to deposit an extruded material forming the tread (6) onto a circumferential bearing surface of said tire (4) and comprising a drive element for rotating the tire capable of driving said tire (4) around a horizontal axis of rotation (XX), characterized in that it comprises: - a fixed base (11) fixed to the ground (S) and - a printing element (14) connected to the base (11) and comprising a support (16) movable in translation relative to said base (11) along a longitudinal axis (X), parallel to the axis of rotation (XX), and a plurality of printing modules (20, i), fixed on the support (16) arranged circumferentially around the tire (4), offset along the longitudinal axis (X) by a longitudinal pitch from each other,and extending each along a radial axis (Ai) perpendicular to the axis of rotation (XX) of the tire (4). Figure for the abbreviation: Fig 1,

Description

Title of the invention: Device for additive manufacturing of a tire tread

[0001] The present invention relates to the field of manufacturing a tire tread.

[0002] Conventional wheels are known, comprising a rim on which a tire is mounted, including a tread and two sidewalls. This type of wheel includes an inner tube inflated to the recommended nominal inflation pressure.

[0003] Another type of tubeless wheel known as "tubeless" in Anglo-Saxon terms is also known, comprising a layer of waterproof butyl rubber to replace the inner tube.

[0004] Integral wheels, known as "airless" wheels, are also known, comprising a radial load-bearing structure, generally made of glass-fiber-reinforced plastic, around which a solid tire is fixed, comprising a tread and two sidewalls. The solid tire is not subjected to internal pressure.

[0005] Such an integral wheel has the advantage of being flexible in the event of impacts, puncture-proof, and durable due to the materials from which it is made. Furthermore, once worn, it is known that the tread can be removed and recycled. Thus, such an integral wheel also helps to meet environmental requirements.

[0006] It is known to retread worn treads on conventional tires with inner tubes. Tires used on heavy-duty motor vehicles are particularly affected by any renewal process that extends their service life. Thus, it is known to remove the worn tread and replace it with a new one by wrapping and securing it onto the casing of the tire that no longer has a tread.

[0007] Other techniques are known for renewing tire treads. For example, document WO-A1-2013086577 describes an apparatus and a method for retreading a worn tire tread. The tread is made of a thermoplastic elastomer. The apparatus includes a heating device for heating the worn surface of the tread and a three-dimensional printer, known as a 3D printer, for applying one or more layers of thermoplastic elastomer to the heated surface. The 3D printer comprises a series of print heads arranged in a row.

[0008] However, such a process is specifically designed for retreading conventional wheel tire treads that include an inner tube. Furthermore, the heating steps for the receiving surface are energy-intensive and costly, and require suitable heating equipment.

[0009] Moreover, such a process only allows material to be deposited on flat surfaces and not on curved surfaces, and in a continuous and non-fractional manner.

[0010] Document FR-B1-3 067 281 proposes a simpler, less energy-intensive process that can be implemented anywhere. This document describes a system for manufacturing the tread of a tubeless, integral wheel tire. The device includes a construction robot with one or more nozzles for depositing material by addition. The nozzles are arranged side by side and are laterally movable so as to cover the entire tread to be constructed.

[0011] However, such a process is particularly slow since the tire is positioned at a given azimuth before the nozzle deposits material, and the operation is repeated until the entire tread is manufactured. Such a solution only allows for the deposition of a few tens of grams per hour, for example, 50 g / h per print head.

[0012] Furthermore, the slow manufacturing of the tread can generate seepage problems.

[0013] In order to reduce the manufacturing time of the tread, large extruders with material deposition nozzles of 5 mm to 10 mm could be used. However, in this case, although the material deposition rate is higher, on the order of 900 g / h / extruder used, the precision is much lower.

[0014] The proposed solutions are therefore not satisfactory since they require a choice between the speed of manufacturing the tread or the quality of the tread pattern.

[0015] Thus, there is a need to improve the manufacturing devices, in particular the recharging, of a tire tread.

[0016] The objective of the invention is to manufacture, in particular to recharge, quickly a tread of a tire while maintaining the quality of the tread pattern.

[0017] We therefore seek to manufacture a tread in a short period of time on the order of 10 to 20 minutes and which corresponds to a time of changing a conventional tire by an automotive professional.

[0018] The present invention relates to an additive manufacturing device for all or part of a tire tread or wheel band.

[0019] By “additive manufacturing”, we mean a manufacturing process by adding extraded material, called “fused deposition modeling”, acronym FDM in Anglo-Saxon terms.

[0020] By "pneumatic" we mean all types of toroidal elastic bandages subjected to internal pressure or not.

[0021] The term "tread" of a tire means a quantity of rubber material delimited by lateral surfaces and by two principal surfaces, one of which is called the tread surface, intended to come into contact with a road surface when the tire is in motion. The tread comprises a plurality of cuts or grooves extending onto at least one of the lateral surfaces.

[0022] The term "sidewall" of a tire refers to a portion of the tire's lateral surface located between the tire tread and a wheel support structure. In the case of a conventional wheel tire, the sidewall begins at the ends of the tread grooves and extends to a tire bead.

[0023] The additive manufacturing device is configured to deposit an extruded material forming the tread on a circumferential carrier surface or peripheral external contour of said tire and comprising a drive element for rotating the tire capable of driving said tire around a horizontal axis of rotation.

[0024] The additive manufacturing device comprises: - a fixed base attached to the ground and - a printing unit connected to the base and comprising a support that moves in translation relative to said base along a longitudinal axis parallel to the axis of rotation, and a plurality of printing or material deposition modules fixed to the support, with "i" being the number of printing modules, between 5 and 20, preferably equal to 10.

[0025] The printing modules are arranged circumferentially, equally spaced or not, around the tire and offset along the longitudinal axis by a longitudinal pitch from each other, for example variable, each printing module extending along a radial axis perpendicular to the axis of rotation of the tire and each comprising: - an extruder configured to be regulated at a pressure between 100 bars and 300 bars, preferably between 180 bars and 220 bars, movable along a radial axis to the pneumatic and configured to produce a rod of molten material, for example from granules of material, preferably of plastic material, for example thermoplastic elastomer, acronym TPE, the granules of material being thus extruded hot; - a material deposit nozzle supplied with molten material by the corresponding extruder comprising at least one distribution orifice and a molten material receiving chamber from the associated extruder in fluidic communication with said distribution orifice; - an extruder displacement device along the corresponding radial axis; and - a pressure regulation device inside the extruder.

[0026] Such a manufacturing device makes it possible to manufacture, in particular to reload, quickly a tread of a tire while maintaining the quality of the tread pattern.

[0027] The extruders can be fed centrally or individually with another material, which makes it possible to vary the characteristics of the plastic material depending on its position in the tread. Multi-material treads can thus be obtained.

[0028] The material rod has, for example, a thickness of 0.7 mm and a width of 2 mm when deposited on the carrier surface. Indeed, before deposition, the material rod has a cross-section identical to that of the material dispensing nozzle. The material rod then has a circular cross-section when the material dispensing nozzle has a circular cross-section.

[0029] The extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0030] The high pressure in the extruder chambers makes it possible to obtain the highest possible application pressure of the molten material.

[0031] Such high pressures make it possible to obtain a high flow rate while maintaining a small extruded section, and thus obtain fine and precise patterns, a good level of filling, between 99.5% and 100% and good cohesion between the layers.

[0032] By "width" is meant the direction in the direction parallel to the axis of rotation of the tire.

[0033] By "thickness" we mean the direction along the radial direction to the axis of rotation of the tire.

[0034] The printing modules are mobile independently of each other along a radial axis specific to each printing module and simultaneously with the other modules along the longitudinal axis parallel to the axis of rotation of the tire.

[0035] The tread is manufactured by depositing the extruded material layer by layer onto the carrier surface of the tire.

[0036] The extruded material inter-diffused or heat-welded by inter-diffusion onto the previously deposited layer of material and solidified during the temperature drop.

[0037] Each of the nozzles is configured to deposit the molten material onto the carrier surface of the mobile tire rotating around a horizontal axis of rotation.

[0038] Additive manufacturing on a support, for example the carrier surface of the tire, or more generally the tire, set in continuous rotation makes it possible to manufacture or completely reconstitute the tread over its entire circumference.

[0039] The tire here comprises only one degree of freedom, namely around its axis of rotation. In other words, the tire is not free to move in translation along any of the X, Y or Z axes.

[0040] The extruders are mounted on the support and can move longitudinally with a variable distance along the radial axis between each extruder, which allows helical laying or variation of section during circumferential and helical laying.

[0041] The molten material can thus be deposited on flat or curved surfaces by moving up or down the curves.

[0042] The helical layers can be laid in both directions, allowing for overlapping. Pocket printing is also possible (outlining then filling, or vice versa).

[0043] This additive manufacturing device can be configured to deposit the material rods side by side or to create "walls" and then fill the spaces between these walls. In all cases, managing the deposited volume according to the available space allows us to achieve porosity rates of less than 0.5% and to correct any "out-of-roundness" defects in the envelope.

[0044] The device is also compact and autonomous and can deposit treads on new or retreaded tires as well as on "air-less" wheels in a short period of time between 10min and 20min and without a vulcanization step.

[0045] Such a device is preferably, but not exclusively, intended to equip automotive centers, car dealerships, fleet management centers or to be installed in small utility vehicles in order to be able to recharge tire treads anywhere, for example in a parking area, a motorway rest area, etc.

[0046] Advantageously, each printing module includes a material deposit nozzle closure device comprising a movable closure means between a closure position and a plurality of opening positions of the nozzle distribution orifice, and an actuator for controlling the movement of the closure means between the closure and opening positions, the closure means of all the printing modules being controllable independently of each other.

[0047] Thus, each nozzle includes its own sealing means configured to interrupt the flow of molten material through the distribution orifice of the corresponding nozzle.

[0048] Each of the nozzles can be interrupted independently and reactively, so as to generate any sculpture on the wheel in a short time, preferably less than 15 minutes.

[0049] Such a loading time corresponds to a material deposit rate of between 5kg / h and 15kg / h, preferably equal to 10kg / h.

[0050] The shutter frequency is between 0.05Hz and 20Hz, for example equal to 0.1Hz for a continuous undercoat and 10Hz on average for a sculpture featuring many blocks of gum.

[0051] Thus, each of the material depositing nozzles is configured to deposit molten material onto the tire, in particular its circumferential carrier surface, which can be driven in rotation continuously or discontinuously around an axis of rotation in a single direction of rotation.

[0052] By “continuous rotation”, we mean a rotation in a single direction of rotation, without interruption and at a constant speed.

[0053] By "discontinuous rotation" is meant a rotation in a single direction of rotation at variable speed during the deposition of material.

[0054] By "opening position" of said distribution orifice, we mean a fully open position of the distribution orifice, but also intermediate positions in which the distribution orifice is partially open.

[0055] The stroke of the needle is preferentially dependent on the flow rate of material and variable with the objective of matching the opening of the distribution orifice to the rheology of the thermoplastic material "TPE" in order to allow the pressure regulator to manage the transient phases.

[0056] This variable stroke advantageously limits the sudden pressure drop at needle opening, which results in over-extrusion followed by under-extrusion with each sealing cycle, a situation that is very detrimental to the fill rate and lateral cohesion between the rods. For example, this stroke can vary between 0.5 mm and 0.8 mm depending on the viscosity of the printed material and the desired flow rate.

[0057] Such a device makes it possible to deposit material onto curved surfaces continuously or in fragments with precise control over the volume and its distribution on the tread. In other words, such a device makes it possible to deposit the right amount of material in the right place.

[0058] Preferably, the sealing means is in the form of a needle actuated by the actuator to move the sealing means in translation along the radial axis.

[0059] The needle valve allows for clean stops in the flow of molten material, without burrs, and clean restarts of said flow.

[0060] Variable stroke sealing needles make it possible to guarantee the section of the rods laid during transient phases, i.e. the opening and closing of the distribution orifice, depending on the printing pressure, the viscosity of the deposited material and the thickness of the layers.

[0061] Having individual modules, each comprising an extruder and a sealing needle, allows for control of the material deposition rate at variable speeds. Complex shapes can also be created.

[0062] For example, the actuator includes a piezoelectric device (not shown) for closing or opening the distribution orifice of the corresponding nozzle.

[0063] Alternatively, any other means of closure associated with each of the nozzles could be provided, such as for example a valve.

[0064] Advantageously, the pressure regulating member includes a worm screw that rotates about the radial axis, for example driven in rotation by a motor, in a conduit for supplying the molten material rod to a chamber upstream of the molten material receiving chamber of the printing nozzle.

[0065] Accelerating the rotational speed of the worm screw causes an increase in pressure inside said chamber. Conversely, decelerating the worm screw causes a decrease in pressure inside said chamber.

[0066] Said chamber is dimensioned to serve as a buffer space and thus dampen the impact of pressure variations related to the plugs on the section of the deposited rod.

[0067] Thanks to the pressure regulating device associated with each extruder, the independent pressure regulation from one extruder to another and the variable distance along the radial axis between the extruders allows for variations in cross-sections enabling complex and more resilient stacking strategies.

[0068] Preferably, the printing modules are distributed circumferentially not regularly on the support, i.e. the circumferential gap between two adjacent printing modules is different.

[0069] Alternatively, the printing modules could be regularly distributed circumferentially on the support.

[0070] For example, the support has the shape of an arch extending over an angular range of up to 360°.

[0071] The shape of an arch allows a "gravity" type feeding at the inlet of the extrusion screw.

[0072] The support is mobile in translation relative to the base along the longitudinal axis, for example, on two parallel longitudinal guide rails.

[0073] According to one embodiment, the displacement member comprises a base fixed to the support, a worm screw rotated by an electric motor and a fixing lug integral with the extruder and comprising a tapping cooperating with the thread of the worm screw.

[0074] Thus, the rotation of the worm screw causes the extruder to move along the associated radial axis.

[0075] For example, the distribution orifice of each material depositing nozzle has a dimension between 0.6mm and 1.6mm, preferably between 0.6mm and 0.8mm to make a material deposit of 1mm wide and preferably between 1mm and 1.6mm to make a material deposit of 2mm wide.

[0076] For example, the distribution orifice of each of the nozzles has a rectangular or circular cross-section. A rectangular cross-section improves the level of detail in the carving and the quality of the breaks.

[0077] The material depositing nozzles may be identical to each other or different, in their dimensions, such as the diameter of the distribution orifice, the length of the conduit located after the needle seat or their external dimension.

[0078] For example, the rotating drive element is in the form of a rotating drum or cylinder cooperating with the wheel hub and configured to drive the tire in rotation via the wheel hub.

[0079] According to one embodiment, each printing module comprises at least one movable application roller rotating about an axis parallel to the axis of rotation of the tire and configured to apply pressure to the bead of molten material deposited on the carrier surface, in particular to optimize the infill rate, smooth imperfections on the upper surface of the bead to facilitate the printing of the next layer, and maximize cohesion between the sub-layers and the deposited bead of molten material. It is preferable to apply the roller between each layer immediately after the bead has been deposited.

[0080] For example, each printing module includes two parallel application rollers arranged on either side of the printing nozzle along the longitudinal axis.

[0081] The application rollers also allow any air pockets to be drained, for example from degassing or bubbling at the interfaces between the layers.

[0082] Advantageously, the additive manufacturing device further comprises a heating module connected to the base and movable relative to the base via a motor / screw-nut and connecting rod system combining translation along the transverse Y-axis and rotation along an axis parallel to the longitudinal X-axis to position itself concentrically with the pneumatic tire. This combination of movement makes it possible to adapt to the entire targeted dimensional range by optimizing the distance to the interface to be heated. It allows also to clear the heating ramp for tire loading / unloading operations.

[0083] Preferably, the heating module includes a heating element, for example by infrared radiation, pulsed hot air, laser or any other heating means, the temperature of which is regulated with a measurement of the surface temperature of the tire by a temperature sensor, for example a pyrometer.

[0084] The heating module allows for local heating of the printing interface to ensure good interdiffusion between the layers. Unlike the conventional strategy of printing in a temperature-controlled chamber, only the interface is heated before the molten material is deposited. This results in very short heating times and avoids reversion phenomena, particularly over-curing of other parts of the rebuilt tire casing, which leads to losses in performance and tire durability.

[0085] This also prevents "crosslinking," or molecular-scale transformation of the surface layer, which would inhibit interdiffusion between the layers and cause decohesion. Prolonged exposure to excessively high temperatures leads to the degradation of the thermoplastic elastomer, for example, in a temperature-controlled environment. Therefore, managing this interface temperature and cooling rates is a crucial factor in the performance of the resulting tread.

[0086] Advantageously, the additive manufacturing device further comprises a machining module connected to the base and movable in translation relative to said base along the longitudinal axis and along a radial axis to the tire, said machining module comprising a machining tool configured to make a groove in the thickness of the tread in the circumferential direction.

[0087] The movement of the machining module allows it to traverse any curvature of the tire.

[0088] For example, the machining tool is a circular saw set in rotation by an electric motor.

[0089] Machining of the layer which will receive the molten material ring could also be carried out by gouging, that is to say by removing material by turning with a hot gouge, by micro-milling, by turning, with cold or hot tools, or any means of removing material.

[0090] This machining process generates a reference profile for the subsequent material deposition. The various print heads will thus follow a known and controlled profile.

[0091] Another major advantage of having a machining module integrated into the additive manufacturing device is the ability to rework parts in case of printing defects.

[0092] It could also be envisaged that the additive manufacturing device would further include a vision module and a three-dimensional scanner, for example a Light Detection and Ranging (LIDAR) sensor coupled with artificial intelligence (AI), such as deep learning, for the automatic detection and correction of defects. This vision module also enables print traceability.

[0093] For example, the tire can be configured to be mounted on a so-called "conventional" wheel comprising a rim with a mounting hub. The tire, or pneumatic tire, is mounted on the rim. The tire comprises a circumferential tread-bearing surface, a tread, and two sidewalls surrounding the tread-bearing surface on either side. The rim is preferably the final rim intended for mounting on a motor vehicle. The mounting hub forms the attachment interface between the wheel and the vehicle. The tire is subjected to internal pressure, either directly or indirectly, via an inner tube inflated to a recommended or lower nominal inflation pressure.

[0094] The wheel can be a wheel with or without an inner tube, called "tubeless" in Anglo-Saxon terms.

[0095] Alternatively, the tire can be configured to be mounted on an "integral" type wheel comprising a radial support structure around which the tire or solid tire is fixed. The support structure includes a support radially external to the support structure. The support extends over the entire circumference of the support structure and includes an external peripheral contour forming a circumferential tread-bearing surface. The tread is structurally integrated into the support structure by means of a tread-bearing surface. The solid tire is not subjected to internal pressure. The radial support structure includes a mounting hub for attaching the wheel to a vehicle.

[0096] According to a first application example, each printing module is configured to deposit extruded material forming the tread on the tire, in particular its circumferential carrier surface, along a circumferential line of material Lj.

[0097] By material deposition along a "circumferential line of material" Lj, we mean the deposition of material along a circular trajectory of the tire, with j ranging from 1 to x, x being the total number of lines of material.

[0098] By "layer of material" Ch, we mean the set of circumferential lines of material Lj side by side over the entire width of the tread to be manufactured, with h ranging from 1 to y, y being the total number of material layers to form the desired total tread thickness.

[0099] A layer of material C corresponds to a thickness of molten material deposit.

[0100] According to this first example, the lines Lj have a constant width and the layers Ch have a constant thickness.

[0101] According to a second application example, each printing module is configured to deposit extruded material forming the tread onto the tire, specifically its circumferential carrier surface, along a circumferential line of material L, by varying the pressure inside the printing nozzle chamber to obtain variable line widths Lj. Thus, the lines Lj have a variable width and the layers Ch have a constant thickness.

[0102] According to a third application example, each printing module is configured to deposit extruded material forming the tread onto the tire, specifically its circumferential carrier surface, along a circumferential line of material L, by varying the radial distance between the extruder and the carrier surface in order to obtain variable layer thicknesses Ch. Thus, the lines Lj have a constant width and the layers Ch have a variable thickness.

[0103] Preferably, the start of each line Lj is offset along the transverse axis, in order to avoid stress concentrations. According to one example, the material is deposited in circumferential lines Lj parallel to the direction of movement of the tire.

[0104] According to another example, the material is deposited in lines Lj inclined relative to the direction of travel of the tire. In other words, the material is deposited in a helix by displacement of the support along the longitudinal axis combined with the displacement of the extruders along the radial axis and the rotation of the tire around its axis of rotation.

[0105] According to another example, the material is deposited in inclined and intersecting lines Lj relative to the direction of travel of the tire. In other words, the material is deposited in a crossed helix by displacement of the support along the longitudinal axis, from right to left and then from left to right, combined with the displacement of the extruders along the radial axis and the rotation of the tire around its axis of rotation.

[0106] For example, during a complete rotation of the tire, the material deposition nozzles of each printing module are actuated simultaneously to deposit material along a circumferential line of material on the lower material line. Then, the support is moved longitudinally along the axis of rotation of the tire after each complete rotation of the tire, so that the material deposition nozzles deposit material along the adjacent material line, and so on until the desired tread pattern is obtained. Thus, a portion of The layer dependent on the number of extruders used is produced at each complete rotation of the tire.

[0107] If the number of lines to be printed exceeds the number of printing modules, the substrate is offset along the tire's axis of rotation by the width of the entire set of printing modules in order to continue depositing the material on the subsequent circumferential lines. In this case, an entire layer is produced during several complete rotations of the tire.

[0108] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0109] [Fig.1] represents very schematically an additive manufacturing device for a tread according to the invention configured to manufacture a tread on a tire of a wheel according to a first embodiment;

[0110] [Fig.2] is a rear view of the additive manufacturing device in [Fig.1]; [YES] [Fig.2A] is a detailed view of an example of a machining module of the additive manufacturing device of [Fig.1];

[0112] [Fig.3] illustrates a detail of a material deposition module of the additive manufacturing device of the [Fig.l];

[0113] [Fig.4] is a cross-sectional view of the material deposition module of [Fig.3] showing an example of a temporary sealing system for the dispensing orifice of a material deposition nozzle;

[0114] [Fig.5A], [Fig.5B], [Fig.5C] are examples of reliefs printed by the additive manufacturing device of [Fig. 1]; and

[0115] [Fig.6A], [Fig.6B], and [Fig.6C] are examples of print line inclination by the additive manufacturing device of [Fig.1].

[0116] In the following description, we consider an orthonormal basis X, Y, Z, defined with respect to the additive manufacturing device 10 in which we find:

[0117] - a longitudinal axis X, horizontal and extending from back to front on the [Fig.l];

[0118] - a horizontal transverse axis Y, perpendicular to the longitudinal axis X and extending from left to right across [Fig. 1]; and

[0119] - a vertical axis Z, orthogonal to the longitudinal axis X and transverse axis Y and extending from bottom to top on the [Fig.l].

[0120] The axis Ai, with i the number of material deposit modules between 5 and 20, corresponds to the extension axis of each 20, i material deposit module.

[0121] As illustrated in Figures 1 and 2, a mounted assembly 1 or wheel comprises a rim 2 including a fixing hub 3 and a tire 4 or pneumatic tire mounted on the rim 2. The tire 4 comprises a tread carrier surface 5, a tread 6 and two sidewalls 7 surrounding the tread carrier surface 5 on either side, only one of which is visible in [Fig. 1].

[0122] Rim 2 is preferably the final rim intended to be mounted on a motor vehicle.

[0123] The fixing hub 3 forms the fixing interface between the wheel 1 and the vehicle.

[0124] The fixing hub 3 here defined as a hollow fixing cylinder in which an axle of wheel (not referenced) can be housed.

[0125] The tire 4 is here subjected to internal pressure via an inner tube (not shown) inflated to a recommended or lower nominal inflation pressure.

[0126] Alternatively, the assembled unit 1 could be a tubeless wheel, also known as a "tubeless" wheel in Anglo-Saxon terms.

[0127] The assembled unit 1 could also be a so-called "airless" tire.

[0128] The tread 6 comprises two lateral surfaces (not referenced), an internal surface (not visible) integral with the tread carrier surface 5 and a tread surface 6a opposite the internal surface and intended to come into contact with a roadway S when the wheel 1 rolls.

[0129] The tread 6 comprises a plurality of cutouts or carvings extending over at least one of its lateral surfaces.

[0130] The rim 2 here forms a radial load-bearing structure for the tire 4.

[0131] As illustrated in [Fig.1], an additive manufacturing device 10 for a tread 6 is configured to deposit an extruded material forming the tread 6 onto a circumferential carrier surface 5 of the tire 4 of the wheel 1.

[0132] In general, the additive manufacturing device 10 for a tread 6 is configured to deposit an extruded material forming the tread 6 on a tire 4. Indeed, it would be possible to manufacture the tread 6 on a tire 4 not mounted on a wheel.

[0133] It is also possible to provide for the resurfacing of a new tread 6 over a worn tread. In this case, the bearing surface 5 corresponds to the worn tread.

[0134] The additive manufacturing device 10 includes a fixed base 11 fixed to the ground S and a printing element 14 connected to the base 11 by a sliding link, i.e. movable in translation relative to the base 11 along the longitudinal axis X.

[0135] The printing element 14 includes a support 16, here in the form of an arch extending over an angular range of 165°. Generally, the support 12 extends over an angular range of up to 360°.

[0136] The printing unit 14 further comprises a plurality of printing modules 20, i, here ten in number, fixed on the support 16 and arranged circumferentially around the tire 4. “i” corresponds to the number of printing modules, between 5 and 20.

[0137] The support 16 is mobile in translation relative to the base 11 along the longitudinal axis X, here on two parallel longitudinal guide rails lia.

[0138] The extruders 21 are mounted on the arch-shaped support 16 and can move longitudinally with a variable distance along the radial axis Ai between each extruder, which allows helical laying or variation of section during circumferential and helical laying.

[0139] The molten material rods can be deposited onto flat or curved surfaces by moving up or down the curves. Helical placements can be made in both directions, allowing for overlapping layers. Pocket printing (contouring then filling, or vice versa) is also possible, but in a degraded mode (reduced speed and without continuous heating of the interface). This additive manufacturing device can be configured to deposit the material rods side by side or to create "walls" and then fill between these walls. In all cases, managing the deposited volume according to the available space allows us to achieve porosity levels of less than 0.5% and to correct any "out-of-roundness" defects in the surface.

[0140] Each printing module 20, i extends along a radial axis Ai perpendicular to the axis of rotation XX of the tire 4.

[0141] The printing modules 20, i are distributed circumferentially on the support 16 with a different circumferential gap between two adjacent printing modules 20, i.

[0142] Alternatively, an identical circumferential gap could be provided between two adjacent printing modules 20, i.

[0143] The printing modules 20, i are offset along the longitudinal axis X by a distance or not longitudinal from each other.

[0144] As illustrated in detail in Figures 3 and 4, each printing module 20, i comprises:

[0145] - an extruder 21 regulated at a pressure between 100 bars and 300 bars, of Preference between 180 bar and 220 bar, movable along a radial axis Ai to the pneumatic 4 and configured to produce a molten material rod, for example from material granules, preferably made of plastic, for example thermoplastic elastomer, acronym TPE. The material granules are therefore hot extruded.

[0146] - a material dispensing nozzle 22 fed with a rod of molten material by The corresponding extruder 21. Each material deposition nozzle 22, or jet, comprises a chamber 22a for receiving the molten material from the associated extruder 21 and a distribution orifice 22b communicating with the chamber 22a. The distribution orifice 22b has a dimension between 0.6 mm and 1.6 mm, preferably between 0.6 mm and 0.8 mm for a 1 mm wide material deposition, and preferably between 1 mm and 1.6 mm for a 2 mm wide material deposition. The distribution orifice 22a of each nozzle has a rectangular or circular cross-section. A rectangular cross-section improves the level of detail in the sculpting and the quality of the discontinuities.

[0147] - a displacement member 23 of the extruder 21 along the radial axis Ai corresponding. The displacement element 23 here comprises a base 23a fixed to the support 16, a worm gear 23b rotated by an electric motor 23c and a mounting bracket 23d integral with the extruder 21 and comprising a threaded hole cooperating with the thread of the worm gear 23b. Thus, the rotation of the worm gear causes the movement of the extruder 21 along the associated radial axis Ai.

[0148] - a pressure regulating device 24 inside the extruder 21. The device 24 pressure regulation includes a worm screw 24a movable about the radial axis Ai in a conduit 24b supplying the molten material rod to a chamber 24c upstream of the chamber 22a receiving the molten material from the printing nozzle 22 and a pressure sensor 24d in the chamber 24c.

[0149] Accelerating the rotational speed of the worm screw 24a causes an increase in pressure inside said chamber 24c. Conversely, decelerating the worm screw 24a causes a decrease in pressure inside said chamber 24c.

[0150] - a sealing device 25 for the material depositing nozzle 22. The device The sealing mechanism 25 comprises a movable sealing means 25a between a closed position and an open position of the distribution orifice 22b, and an actuator 25b for controlling the movement of the sealing means 25a between the closed and open positions. The sealing means 25a can be controlled independently of each other.

[0151] Thus, each nozzle 22 includes its own sealing means 25 configured to interrupt the flow of molten material through the distribution orifice 22b of the corresponding nozzle.

[0152] Each of the nozzles 22 can be interrupted independently and reactively, so as to generate any sculpture on the wheel 1 in a short time, preferably less than 15 minutes.

[0153] Such a loading time corresponds to a material deposit rate of between 5kg / h and 15kg / h, preferably equal to 10kg / h.

[0154] The shutter frequency is between 0.05Hz and 20Hz, for example equal to 0.1Hz for a continuous undercoat and 10Hz on average for a sculpture featuring many blocks of gum.

[0155] In the example illustrated in [Fig.4], the obturating means 25a is in the form of a needle actuated by the actuator 25b to move the obturating means in translation along the radial axis Ai.

[0156] The actuator 25b includes, for example, a piezoelectric device (not shown) for closing or opening the distribution orifice 22b of the corresponding nozzle 22.

[0157] The needle gate 25a allows for clean stops of the flow of molten material, without burrs, and clean restarts of said flow.

[0158] The needle stroke is preferentially dependent on the material flow rate and is variable in order to match the opening of the dispensing orifice to the rheology of the TPE, thus allowing the pressure regulator to manage the transient phases. This variable stroke advantageously limits the sudden pressure drop at needle opening, which results in over-extrusion followed by under-extrusion with each sealing cycle (very detrimental to the fill rate and lateral cohesion between the rods). For example, this stroke can vary between 0.5 mm and 0.8 mm depending on the viscosity of the printed material and the desired flow rate.

[0159] Alternatively, any other means of closure associated with each of the nozzles could be provided, such as for example a valve.

[0160] The terms "downstream" and "upstream" are defined by considering the direction of flow of matter.

[0161] The extruders 21 can be fed centrally or individually with another material, which makes it possible to vary the characteristics of the plastic material depending on its position in the tread. This allows for the production of multi-material treads.

[0162] The material bead has, for example, a thickness of 0.7 mm and a width of 2 mm when deposited on the carrier surface. Indeed, before deposition, the material bead has a cross-section identical to that of the material dispensing nozzle. The material bead then has a circular cross-section when the material dispensing nozzle has a circular cross-section.

[0163] The extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0164] The high pressure in the extruder chambers makes it possible to obtain the highest possible application pressure of the molten material.

[0165] Such high pressures make it possible to obtain a high flow rate while maintaining a small extruded section, and thus obtain fine and precise patterns, a good level of filling, between 99.5% and 100% and good cohesion between the layers.

[0166] Thanks to the pressure regulating organ 24 associated with each extruder 21, the independent pressure regulation from one extruder to another and the variable distance along the radial axis Ai between the extruders allows for variations in cross-sections enabling complex and more resilient stacking strategies.

[0167] By "width" is meant the direction in the direction parallel to the axis of rotation XX of the tire 4.

[0168] By "thickness" is meant the direction along the radial direction to the axis of rotation XX of the tire 4.

[0169] The printing modules 20, i are mobile independently of each other along a radial axis Ai specific to each printing module and simultaneously with the other modules along the longitudinal axis X parallel to the axis of rotation XX of the tire 4.

[0170] The tread 6 is manufactured by depositing the extruded material layer by layer onto the carrier surface 5 of the tire 4. The extruded material melts on the layer of material previously deposited and solidifies when the temperature drops.

[0171] Each of the nozzles 22 is configured to deposit the molten material onto the carrier surface 5 of the tire 4 which is mobile and rotates around a horizontal axis of rotation XX.

[0172] Additive manufacturing on a support, here the carrier surface 5 of the tire 4, or more generally the tire 4, set in continuous rotation, makes it possible to manufacture or completely reconstitute the tread 6 over its entire circumference.

[0173] For this purpose, the additive manufacturing device 10 includes a drive element 15 for rotating the tire 4 around the axis of rotation X-X'.

[0174] As illustrated in [Fig.2], the rotational drive member 15 is in the form of a rotating drum or cylinder cooperating with the wheel hub 3 and configured to rotate the tire 4 via the wheel hub 3.

[0175] These variants are interesting in the case where it is necessary to manufacture the tread 2 without removing the wheel 1 from the vehicle.

[0176] The tire 4 here comprises only one degree of freedom, namely around its axis of rotation XX. In other words, the tire 4 is not mobile in translation along any of the axes X, Y or Z.

[0177] As illustrated in [Fig.3], and in no way limitingly, each printing module 20, i comprises two parallel application rollers 26 arranged on either side of the printing nozzle 22 along the longitudinal axis X. Each application roller 26 is movable in rotation about an axis parallel to the axis of rotation XX of the tire 4.

[0178] The application rollers 26 are configured to apply pressure to the deposited molten bead in order to optimize the infill rate, smooth imperfections on the top surface of the bead to facilitate the printing of the next layer, and maximize cohesion between the sub-layers and the deposited molten bead. It is preferable to apply the rollers 26 between each layer immediately after the bead has been deposited.

[0179] The application rollers 26 also allow any air pockets to be drained, for example from degassing or bubbling at the interfaces between the layers.

[0180] The additive manufacturing device 10 further comprises a heating module 30 connected to the base 12, and movable relative to the base 12 via a motor / screw-nut and connecting rod system (not shown) combining translation along the transverse axis Y and rotation about an axis parallel to the longitudinal axis X to position itself concentrically with the tire. This combination of movement allows adaptation to the entire targeted dimensional range by optimizing the distance to the interface to be heated. It also allows the heating ramp to be cleared for tire loading / unloading operations.

[0181] The heating module 30 includes a heating element 30a, for example by infrared radiation, pulsed hot air, laser or any other heating means, the temperature of which is regulated with a measurement of the surface temperature of the tire 4 by a temperature sensor (not shown), such as for example a pyrometer.

[0182] The heating module 30 allows for local heating of the printing interface to ensure good interdiffusion between the layers. Unlike the conventional strategy of printing in a temperature-controlled chamber, only the interface is heated before the molten material is deposited. This results in very short heating times and avoids reversion phenomena, particularly over-curing of other parts of the rebuilt tire casing, which leads to losses in performance and tire durability.

[0183] This also prevents "crosslinking" or molecular-scale transformation of the surface layer, which would prevent interdiffusion between the layers and cause decohesion. Excessive exposure to Excessive temperatures lead to the degradation of the thermoplastic elastomer, for example, in the case of a temperature-controlled chamber. Managing this interface temperature and cooling rates is therefore a crucial factor in the performance of the resulting tread.

[0184] The additive manufacturing device 10 further includes a machining module 50 connected to the base 12 and movable in translation relative to said base 12 along the longitudinal axis X and along a radial axis to the pneumatic 4.

[0185] As illustrated, the machining module is mounted to slide on a guide rail 53.

[0186] The movement of the machining module 50 allows it to traverse any curve of the tire 4.

[0187] The machining module 50 includes a machining tool 51 configured to make a groove in the thickness of the tread 6 in the circumferential direction.

[0188] Fig. 2A shows an example where the machining tool is a circular saw 51 rotated by an electric motor 52.

[0189] Machining the layer that will receive the molten material ring could also be carried out by gouging, that is to say by removing material by turning with a hot gouge, by micro-milling, by turning, or any other means of material removal

[0190] This machining process generates a reference profile for the subsequent material deposition. The various print heads 22 will thus follow a known and controlled profile.

[0191] Another major advantage of having a machining module 50 integrated into the additive manufacturing device 10 is the ability to rework parts in case of printing defects.

[0192] The additive manufacturing device 10 further includes a vision module 60 comprising a three-dimensional scanner, for example a Light Detection and Ranging (LIDAR) type sensor (not shown), coupled with artificial intelligence (AI), of the deep learning type, for the automatic detection and correction of defects. This vision module also enables print traceability.

[0193] A first example of material deposition is illustrated with reference to [Fig.5A].

[0194] In this example, each print module 20, i is configured to deposit the extruded material forming the tread 6 on the tire 4, in particular its circumferential bearing surface 5, along a circumferential line of material Lj.

[0195] By material deposition along a "circumferential line of material" Lj, material is meant along a circular path of the tire 4, with j ranging from 1 to x, x being the total number of lines of material.

[0196] By "layer of material" Ch, we mean the set of circumferential lines of material Lj side by side over the entire width of the tread 6 to be manufactured, with h ranging from 1 to y, y being the total number of layers of material to form the total thickness of the desired tread 6.

[0197] A layer of material C corresponds to a thickness of molten material deposit.

[0198] The lines Lj have a constant width and the layers Ch have a constant thickness.

[0199] A second example of material deposition is illustrated with reference to [Fig. 5B].

[0200] In this example, each printing module 20, i is configured to deposit extruded material forming the tread 6 onto the tire 4, in particular its circumferential carrier surface 5, along a circumferential line of material L, by varying the pressure inside the chamber 22a of the printing nozzle 22 in order to obtain variable line widths Lj.

[0201] The lines Lj have a variable width and the layers Ch have a constant thickness.

[0202] A third example of material deposition is illustrated with reference to [Fig. 5C].

[0203] In this example, each printing module 20, i is configured to deposit extruded material forming the tread 6 onto the tire 4, in particular its circumferential carrier surface 5, along a circumferential line of material L, by varying the radial distance Ai between the extruder 21 and the carrier surface 5 in order to obtain variable layer thicknesses Ch.

[0204] The lines Lj have a constant width and the layers Ch have a variable thickness.

[0205] Figures 6A, 6B, and 6C are examples of the inclination of the printing lines by the additive manufacturing device of [Fig. 1]. In all the illustrated examples, the starting point of each line Lj is offset along the transverse axis Y, in order to avoid stress concentrations

[0206] In the example illustrated in [Fig.6A], the material is deposited in circumferential lines Lj parallel to the direction of travel D of the tire 4.

[0207] In the example illustrated in [Fig.6B], the material is deposited in lines Lj inclined with respect to the direction of travel D of the tire 4. In other words, the material is deposited in a helix by displacement of the support 16 along the longitudinal axis X combined with the displacement of the extruders 21 along the radial axis Ai and the rotation of the carrier surface 5.

[0208] In the example illustrated in [Fig.6C], the material is deposited in inclined and crossed lines Lj with respect to the direction of travel D of the tire 4. In other words, the material is deposited in a crossed helix by displacement of the support 16 along the longitudinal axis X, from right to left and then from left to right, combined with the displacement of the extruders 21 along the radial axis Ai and the rotation of the carrier surface 5.

[0209] During a complete rotation of the tire, the material depositing nozzles 22 of each printing module 20, i are actuated simultaneously to deposit the material along a circumferential line of material on the lower material line, then the support 16 is moved in longitudinal translation along the axis of rotation XX of the tire 4 after each complete rotation of the tire, so that the material depositing nozzles deposit material along the adjacent material line and so on until the desired tread pattern is obtained.

[0210] Thus, a portion of the layer dependent on the number of extruders used is produced at each complete revolution of the tire.

[0211] In the case where the number of lines to be printed is greater than the number of printing modules 20, i, the support 16 is offset along the axis of rotation XX of the tire 4 by the width of the set of printing modules 20, i in order to continue the deposition of the material on the following circumferential lines.

[0212] In this case, an entire layer is made during several complete revolutions of the tire.

[0213] The additive manufacturing device is compact and autonomous and can print treads on new or retreaded tires as well as on "air-less" wheels in a short period of time between 10min and 20min and without a vulcanization step, while allowing the deposition of an extruded material on a carrier surface of any curve.

Claims

Demands

1. Device (10) for additive manufacturing all or part of a tread (6) of a tire (4) configured to deposit an extruded material forming the tread (6) onto a circumferential bearing surface (5) of said tire (4) and comprising a rotating drive element (15) of the tire capable of driving said tire (4) around a horizontal axis of rotation (XX), characterized in that it comprises: - a fixed base (11) fixed to the ground (S) and - a printing element (14) connected to the base (11) and comprising a support (16) movable in translation relative to said base (11) along a longitudinal axis (X), parallel to the axis of rotation (XX), and a plurality of printing modules (20, i), fixed to the support (16), with "i" being the number of printing modules, from 5 to 20, arranged circumferentially around the pneumatic (4), and offset along the longitudinal axis (X) by a longitudinal pitch from each other,each printing module (20,i) extending along a radial axis (Ai) perpendicular to the axis of rotation (XX) of the pneumatic (4) and comprising: - an extruder (21) configured to be regulated at a pressure between 100 bars and 300 bars, preferably between 180 bars and 220 bars, movable along a radial axis (Ai) to the pneumatic (4) and configured to produce a molten material bead; - a material depositing nozzle (22) supplied with a molten material bead by the corresponding extruder (21) comprising at least one distribution orifice (22b) and a molten material receiving chamber (22a) from the associated extruder (21) in fluidic communication with said distribution orifice (22b); - an extruder (23) displacement element for the extruder (21) along the corresponding radial axis (Ai); and - a pressure regulating device (24) inside the extruder (21).

2. Device (10) according to claim 1, wherein each printing module (20, i) comprises a nozzle (22) material deposition closing device (25) including a closing means (25a) movable between a closing position and a plurality of nozzle dispensing orifice (22b) opening positions (22), and an actuator to control the movement of the shuttering means (25a) between the shuttering and opening positions, the shuttering means (25a) of the set of printing modules (20, i) being controllable independently of each other.

3. Device (10) according to claim 2, wherein the sealing means (25a) is in the form of a needle actuated by the actuator (25b) to move the sealing means (25b) in translation along the radial axis (Ai).

4. Device (10) according to any one of the preceding claims, wherein the pressure regulating member (24) comprises a worm screw (24a) rotatable about the radial axis (Ai) in a conduit (24b) supplying the molten material rod to a chamber (24c) upstream of the molten material receiving chamber (22a) from the printing nozzle (22).

5. Device (10) according to any one of the preceding claims, wherein the printing modules (20, i) are regularly distributed circumferentially on the support (16).

6. Device (10) according to any one of the preceding claims, wherein the support (16) has the shape of an arch extending over an angular range of up to 360°.

7. Device (10) according to any one of the preceding claims, wherein the support (16) is movable in translation relative to the base (11) along the longitudinal axis (X) on two parallel longitudinal guide rails (lia).

8. Device (10) according to any one of the preceding claims, wherein the displacement member (23) comprises a base (23a) fixed to the support (16), a worm screw (23b) rotated by an electric motor (23c) and a fixing lug (23d) integral with the extruder (21) and comprising a tapping cooperating with the thread of the worm screw (23b).

9. Device (10) according to any one of the preceding claims, wherein the distribution orifice (22b) of each material depositing nozzle (22) has a dimension between 0.6mm and 1.6mm, preferably between 0.6mm and 0.8mm to achieve a material deposit 1mm wide and preferably between 1mm and 1.6mm to achieve a material deposit 2mm wide.

10. Device (10) according to any one of the preceding claims, wherein each printing module (20, i) includes at least one application roller (26) movable in rotation about an axis parallel to the axis of rotation (XX) of the tire (4) and configured to apply pressure on the bead of molten material deposited on the carrier surface (5).

11. Device (10) according to claim 10, in which each printing module (20, i) comprises two application rollers (26) parallel to each other and arranged on either side of the printing nozzle (22) along the longitudinal axis (X).

12. Device (10) according to any one of the preceding claims, further comprising a heating module (30) connected to the base (12), and movable relative to the base (12) via a motor / screw nut and connecting rod system combining a translation along a transverse axis (Y) and a rotation along an axis parallel to the longitudinal axis (X) to position itself concentrically to the tire (4).

13. Device (10) according to claim 12, wherein the heating module (30) comprises a heating element (30a), the temperature of which is regulated with a measurement of the surface temperature of the tire (4) by a temperature sensor.

14. Device (10) according to any one of the preceding claims, further comprising a machining module (50) connected to the base (12) and movable in translation relative to said base (12) along the longitudinal axis (X) and along a radial axis to the pneumatic (4), said machining module (50) comprising a machining tool (51) configured to make a groove in the thickness of the tread (6) in the circumferential direction.