Additive manufacturing device for a tire tread

Abstract

A device (10) for the additive manufacturing of 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 vertical axis of rotation (RR). The device comprises: - a fixed base (12, 13) fixed to the ground (S) and on which the tire (4) is mounted; - a printing element (14) connected to the base (13) and comprising a support (16) and a plurality of printing modules (20; i), fixed to the support (16) arranged circumferentially around the tire (4), offset along a vertical axis (Z), parallel to the axis of rotation (RR), by a vertical pitch from each other, and each extending along a radial axis (Ai) perpendicular to the axis rotation (RR) 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, also known as "airless" wheels, are still known. They comprise a radial load-bearing structure, generally made of fiberglass-reinforced plastic, around which a solid tire is fixed, including 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 / 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 vertical axis of rotation.

[0024] The additive manufacturing device comprises: - a fixed base attached to the ground and on which the tire is mounted; - a printing unit connected to the base and comprising a support and a plurality of printing or material deposition modules, fixed to the support, with "i" the number of printing modules, between 5 and 30, preferably equal to 20.

[0025] The printing modules are arranged circumferentially, equally spaced or not, around the tire and offset along a vertical axis, parallel to the axis of rotation, by a vertical pitch, for example variable, from each other, 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 the 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 dispensing nozzle fed with a molten material stream by the corresponding extruder, comprising at least one distribution orifice and a chamber reception of the molten material 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. Preferably, the printing modules have no other mobility than this radial movement.

[0035] The tread is manufactured by depositing the extruded material, along the radial axis to the tire, layer by layer on the bearing 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 vertical axis of rotation.

[0038] Additive manufacturing on a substrate, for example the bearing surface of the tire, or more generally the tire, set in continuous rotation allows the tread to be manufactured or completely rebuilt around its entire circumference.

[0039] The extruders are mounted on the support and can move along the radial axis to the pneumatic with a variable distance along the vertical axis between each extruder, which allows helical laying or variation of section during circumferential and helical laying.

[0040] The molten material can thus be deposited on flat or curved surfaces by moving the curves up or down.

[0041] The helical layers can be laid in both directions, allowing for overlapping. Pocket printing is also possible (outlining then filling, or vice versa).

[0042] 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.

[0043] 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 preferably less than 15min and without a vulcanization step.

[0044] 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.

[0045] Advantageously, the base comprises: - a base fixed to the ground, - a guiding element extending from the base along the vertical axis parallel to the axis of rotation of the tire, and - a tire support platform, mounted to slide relative to the guide element along a translation axis parallel to the tire's rotation axis and rotating around said translation axis.

[0046] The tire comprises three degrees of mobility, namely around its axis of rotation, in translation along the vertical axis of translation and in rotation around said vertical axis of translation.

[0047] In other words, the tire is not mobile in translation along one of the axes X, Y.

[0048] For example, the base comprises a first base on which the pneumatic tire is mounted and a second base on which the printing element is mounted. The first and second bases may be separate or a single unit.

[0049] According to a first embodiment, each extruder extends along an extension axis, forming an angle with the radial axis, between 0° and 90°, for example equal to 45°.

[0050] Advantageously, each printing module includes a material deposit nozzle closure device comprising a closure means movable along the radial axis 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.

[0051] Thus, each nozzle includes its own sealing means configured to interrupt the flow of molten material through the distribution orifice of the corresponding nozzle.

[0052] 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.

[0053] Such a loading time corresponds to a material deposit rate of between 5kg / h and 15kg / h, preferably equal to 10kg / h.

[0054] 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.

[0055] 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.

[0056] By “continuous rotation”, we mean a rotation in a single direction of rotation, without interruption and at a constant speed.

[0057] By "discontinuous rotation" is meant a rotation in a single direction of rotation at variable speed during the deposition of material.

[0058] 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.

[0059] The needle stroke is preferentially dependent on the flow rate of material and is variable with the aim 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] The needle valve allows for clean stops of the flow of molten material, without burrs, and clean restarts of said flow.

[0064] The 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.

[0065] 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.

[0066] For example, the actuator includes a piezoelectric device (not shown) for closing or opening the distribution orifice of the corresponding nozzle.

[0067] Alternatively, any other means of closure associated with each of the nozzles could be provided, such as for example a valve.

[0068] Advantageously, the pressure regulating member includes a worm screw movable along the extension axis, for example driven in rotation by a motor, in a conduit supplying the molten material rod to a chamber upstream of the molten material receiving chamber of the printing nozzle.

[0069] 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.

[0070] 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.

[0071] Thanks to the pressure regulating device associated with each extruder, independent pressure regulation from one extruder to another and variable distance along the axis The radial arrangement between the extruders allows for variations in cross-sections, enabling complex and more resilient stacking strategies.

[0072] According to another embodiment, each extruder extends along a radial axis.

[0073] In this embodiment, each printing module includes a material deposit nozzle closure device comprising a closure means movable along the radial axis, for example in the form of a needle actuated by the actuator to move the closure means in translation along the radial axis.

[0074] In this embodiment, the pressure regulating member comprises a worm screw movable about the radial axis, for example driven in rotation by a motor, in a duct supplying the molten material rod to a chamber upstream of the molten material receiving chamber of the printing nozzle.

[0075] In this embodiment, the displacement member comprises a base fixed to the support, a plate including a tapped hole and set in translation by an electric motor associated with a worm screw including a thread cooperating with the tapped hole of the plate and a fixing base integral with the extruder.

[0076] Thus, the rotation of the worm screw causes the extruder to move along the associated radial axis.

[0077] Preferably, the printing modules are distributed circumferentially not regularly on the support, i.e. the circumferential gap between two adjacent printing modules is different.

[0078] Alternatively, the printing modules could be regularly distributed circumferentially on the support.

[0079] For example, the support has the shape of an arch that can go up to 360°.

[0080] The support is preferably fixed relative to the base.

[0081] According to one embodiment, the moving member comprises a fixed base to the support, a worm screw rotated by an electric motor and a mounting base attached to the extruder and including a tapping that cooperates with the thread of the worm screw.

[0082] Thus, the rotation of the worm screw causes the extruder to move along the associated radial axis.

[0083] 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 1mm wide and preferably between 1mm and 1.6mm to make a material deposit 2mm wide.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] According to one embodiment, each printing module comprises at least one application roller disposed downstream of the associated printing nozzle along the vertical axis and rotatable about an axis parallel to the axis of rotation of the pneumatic tire. This roller is configured to apply pressure to the bead of molten material deposited on the carrier surface, particularly 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.

[0088] The application rollers also allow any air pockets to be drained, for example from degassing or bubbling at the interfaces between the layers.

[0089] Advantageously, the additive manufacturing device further includes a heating module connected to the wheel support platform, and fixed relative to the wheel support platform and concentric with the tire in a material deposition position.

[0090] 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.

[0091] 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.

[0092] This also prevents "crosslinking," or molecular-scale transformation of the surface layer, which would prevent inter-diffusion between the layers and cause decohesion. Prolonged exposure to excessively high temperatures leads to the degradation of the thermoplastic elastomer, for example, in the case of a temperature-controlled enclosure. Managing this temperature The interface and cooling rates are therefore an important factor in the performance of the resulting tread.

[0093] Advantageously, the additive manufacturing device further includes a machining module connected to the base and movable in translation relative to said base along the longitudinal axis X, said machining module including a machining tool configured to make a groove in the thickness of the tread in the circumferential direction.

[0094] The movement of the machining module allows it to traverse any curvature of the tire.

[0095] For example, the machining tool is a circular saw set in rotation by an electric motor.

[0096] 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.

[0097] This machining process generates a reference profile for the subsequent material deposition. The various print heads will thus follow a known and controlled profile.

[0098] 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.

[0099] It could also be envisaged that the additive manufacturing device would further include a three-dimensional vision module, 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.

[0100] 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.

[0101] The wheel can be a wheel with or without an inner tube, called "tubeless" in Anglo-Saxon terms.

[0102] 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.

[0103] According to a first application example, each printing module is configured to deposit, along the radial axis to the tire, extruded material forming the tread on the tire, in particular its circumferential carrier surface, along a circumferential line of material Lj.

[0104] By material deposition along a "circumferential line of material" Lj, material is meant along a circular path of the tire, with j ranging from 1 to x, x being the total number of lines of material.

[0105] 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 layers of material to form the total thickness of the desired tread.

[0106] A layer of material C corresponds to a thickness of molten material deposit.

[0107] According to this first example, the lines Lj have a constant width and the layers Ch have a constant thickness.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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.

[0112] 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 moving the platform in translation along the axis of translation, from right to left and then from left to right, combined with the movement of the extruders along the radial axis and the rotation of the tire around its axis of rotation.

[0113] 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 platform is moved translationally along the axis of translation 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, an entire layer is produced with each complete rotation of the tire.

[0114] 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 with each complete rotation of the tire.

[0115] 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:

[0116] [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 in a wheel mounting position;

[0117] [Fig.2] represents the additive manufacturing device of [Fig.1] in a machining position of the bearing surface of the wheel;

[0118] [Fig.3] represents the additive manufacturing device of the [Fig.l] in a material depositing position on the bearing surface of the wheel;

[0119] [Fig.4] illustrates a material deposition module of the additive manufacturing device of the [Fig.l] according to a first embodiment;

[0120] [Fig.5] is a cross-sectional view of the material deposition module of [Fig.4] showing an example of a temporary sealing system for the dispensing orifice of a material deposition nozzle;

[0121] [Fig.6A], [Fig.6B] are views of a material deposition module of the additive manufacturing device of [Fig.1] according to a second embodiment;

[0122] [Fig.7A], [Fig.7B], [Fig.7C] are examples of reliefs printed by the additive manufacturing device of the [Fig. 1] ; and

[0123] [Fig.8A], [Fig.8B], and [Fig.8C] are examples of print line inclination by the additive manufacturing device of [Fig.1].

[0124] 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:

[0125] - a longitudinal axis X, horizontal and extending from back to front on the [Fig.l];

[0126] - a horizontal transverse axis Y, perpendicular to the longitudinal axis X and extending from left to right across [Fig. 1]; and

[0127] - a vertical axis Z, orthogonal to the longitudinal axis X and transverse axis Y and extending from bottom to top on the [Fig.l].

[0128] The radial axis Ai, with i the number of material deposition modules between 5 and 30, corresponds to the extension axis of each 20; i material deposition module.

[0129] The extension axis Bi corresponds to the extension axis of each extruder 21. The extension axis Bi forms an angle with the radial axis Ai between 0° and 90°, here 45°.

[0130] When the extension axis Bi is inclined with respect to the radial axis Ai at an angle equal to 0°, it is coincident with said radial axis Ai.

[0131] As illustrated in Figures 1 to 3, a wheel assembly 1 comprises a rim 2 including a mounting hub 3 and a tire 4 or pneumatic tire mounted on the rim 2. The tire 4 comprises a tread surface 5, a tread 6 and two sidewalls 7 surrounding on both sides and on the other hand the bearing surface 5 of tread, of which only one is visible on the [Fig.l].

[0132] Rim 2 is preferably the final rim intended to be mounted on a motor vehicle.

[0133] The fixing hub 3 forms the fixing interface between the wheel 1 and the vehicle.

[0134] The fixing hub 3 here defines a hollow fixing cylinder in which an axle of wheel (not referenced) can be housed.

[0135] The tire 4 is here subjected to internal pressure via an inner tube (not shown) inflated to a recommended or lower nominal inflation pressure.

[0136] Alternatively, the assembled unit 1 could be a tubeless wheel, also known as a "tubeless" wheel in Anglo-Saxon terms.

[0137] The assembled unit 1 could also be a so-called "airless" tire.

[0138] 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.

[0139] The tread 6 comprises a plurality of cutouts or carvings extending over at least one of its lateral surfaces.

[0140] The rim 2 here forms a radial load-bearing structure for the tire 4.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] The additive manufacturing device 10 comprises a first fixed base 12 fixed to the ground S, a second fixed base 13 fixed to the ground S and a printing element 14 attached to the second base 13, i.e. there is no relative mobility between the second base 13 and the printing element 14.

[0145] The first base 12 and the second base 13 are here separated. Alternatively, a single fixed base comprising two base parts could be provided.

[0146] The printing unit 14 comprises a support 16 and a plurality of printing modules 20; i, here twenty in number, fixed to the support 16 and arranged in circumferentially around the tire 4. “i” corresponds to the number of printing modules, between 5 and 30, here numbering 20.

[0147] The support 16 here extends over a circumferential range of 300°. Alternatively, the support 16 could be provided to extend over a circumferential range of up to 360°.

[0148] The support 16 is fixed relative to the base 13.

[0149] The printing modules 20; i are mounted on the support 16 and can move along the radial axis Ai variable between each printing module 20; i, which allows placement on a curve and in a helix or variation of section during circumferential and helical placements on a curved or non-curved surface.

[0150] The molten material rods can be deposited onto flat or curved surfaces by moving up or down the curves. Helical placement can be performed 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.

[0151] Each printing module 20; i extends along a radial axis Ai perpendicular to the axis of rotation RR of the tire 4.

[0152] The printing modules 20; i are distributed circumferentially on the support 16 with a different circumferential gap between two adjacent printing modules 20, i.

[0153] Alternatively, an identical circumferential gap could be provided between two adjacent printing modules 20, i.

[0154] The printing modules 20; i are offset along the vertical axis Z by a distance or vertical step from each other.

[0155] As illustrated in detail in Figures 4 and 5, each printing module 20; i comprises:

[0156] - an extruder 21 regulated at a pressure between 100 bars and 300 bars, of Preferably between 180 bar and 220 bar, movable along the radial axis Ai via pneumatic control 4 and configured to produce a molten material rod, for example from material granules, preferably made of plastic, for example thermoplastic elastomer (TPE). The material granules are thus hot-extruded. Each extruder 21 extends along an extension axis Bi, here inclined relative to the radial axis Ai, at an angle between 0° and 90°, here equal to 45°.

[0157] - a material dispensing nozzle 22 fed with a rod of molten material by The corresponding extruder 21. Each material deposition nozzle 22, or spray nozzle, comprises a receiving chamber 22a for 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 deposit, and preferably between 1 mm and 1.6 mm for a 2 mm wide material deposit. 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. Each material deposition nozzle 22 deposits material onto the bearing surface 5 of the tire along the associated radial axis Ai.

[0158] - a displacement member 23 of the extruder 21 along the radial axis Ai corresponding. The displacement member 23 here comprises a base 23a fixed to the support 16, a plate 23b comprising a tapped hole (not shown) cooperating with the thread of a worm screw (not shown) rotated by an electric motor 23c and a fixing base 23d integral with the extruder 21. Thus, the rotation of the worm screw causes the movement of the extruder 21 along the associated radial axis Ai.

[0159] - a pressure regulating device inside the extruder 21. The device Pressure regulation is not illustrated in detail here. However, reference can be made to Figures 6A and 6B, which illustrate another embodiment of the extruder. The regulating element may include a worm gear rotating about the extension axis Bi in a duct that feeds the molten material to a chamber upstream of the molten material receiving chamber of the printing nozzle, and a pressure sensor in the chamber. Increasing the rotational speed of the worm gear causes an increase in pressure inside said chamber. Conversely, decelerating the worm gear causes a decrease in pressure inside said chamber.

[0160] - a sealing device 25 for the material depositing nozzle 22. The device The sealing mechanism 25 comprises a sealing means 25a movable about the radial axis Ai between a sealing position and an opening position of the distribution orifice 22b, and an actuator 25b for controlling the movement of the sealing means 25a between the sealing and opening positions. The sealing means 25a can be controlled independently of each other.

[0161] 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.

[0162] Each of the nozzles 22 can be interrupted independently and reactively, so as to generate any sculpture on the wheel 1 and in a short time, preferably less than 15 minutes, preferably less than 8 minutes.

[0163] Such a loading time corresponds to a material deposition rate of between 10kg / h and 20kg / h, preferably equal to 12kg / h.

[0164] 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.

[0165] In the example illustrated in [Fig.5], the sealing means 25a is in the form of a needle actuated by the actuator 25b to move the sealing means in translation along the axis of the extruder Bi.

[0166] The actuator 25b includes, for example, a piezoelectric device (not shown) for closing or opening the distribution orifice 22b of the corresponding nozzle 22.

[0167] The needle gate 25a allows for clean stops of the flow of molten material, without burrs, and clean restarts of said flow.

[0168] 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.

[0169] Alternatively, any other means of closure associated with each of the nozzles could be provided, such as for example a valve.

[0170] The terms “downstream” and “upstream” are defined by considering the direction of flow of matter.

[0171] 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.

[0172] 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.

[0173] The extruder is configured to deposit molten material with a flow rate of 1000g / h.

[0174] The high pressure in the extruder chambers makes it possible to obtain the highest possible application pressure of the molten material.

[0175] 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.

[0176] 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.

[0177] By "width" is meant the direction in the direction parallel to the axis of rotation RR of the tire 4.

[0178] By "thickness" is meant the direction along the radial direction to the axis of rotation RR of the tire 4.

[0179] The printing modules 20; i are mobile independently of each other along a radial axis Ai specific to each printing module.

[0180] The wheel 1 is mounted on the first base 12 comprising a base 12a fixed to the ground S and a guide member 12b extending from the base 12a along the vertical axis parallel to the axis of rotation RR of the tire 4.

[0181] The base 12 further comprises a support platform 12c for the wheel 1. The support platform 12c is mounted to slide relative to the guide member 12b along a translational axis Zl-Zl parallel to the axis of rotation RR of the tire 4 and to rotate about said translational axis Zl-Zl. Thus, the tire 4 mounted on the base 12 can perform a rotation RI about the translational axis Zl-Zl, a translation DI along the translational axis Zl-Zl, and a rotation about its own axis of rotation RR.

[0182] The tread 6 is manufactured by depositing the extruded material along the radial axis Ai layer by layer on 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.

[0183] Each of the nozzles 22 is configured to deposit, along the corresponding radial axis Ai, the molten material onto the carrier surface 5 of the tire 4 which is mobile and rotates around a vertical axis of rotation RR.

[0184] 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.

[0185] For this purpose, the additive manufacturing device 10 includes a drive element (not visible in the figures) for rotating the tire 4 around the axis of rotation RR.

[0186] The rotating drive element is, for example, in the form of a rotating drum or cylinder cooperating with the wheel hub 3 and configured to drive the tire 4 in rotation via the wheel hub 3.

[0187] The tire 4 here comprises three degrees of mobility, namely around its axis of rotation RR, in translation along the vertical axis Zl-Zl and in rotation around said vertical axis Zl-Zl.

[0188] As illustrated in [Fig. 4], and in no way limitingly, each printing module 20; i comprises an application roller 26 disposed downstream of the associated printing nozzle 22 along the vertical axis Z. Each application roller 26 is movable in rotation about an axis parallel to the axis of rotation RR of the pneumatic 4.

[0189] Each application roller 26 is 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.

[0190] The application rollers 26 also allow any air pockets to be drained, for example from degassing or bubbling at the interfaces between the layers.

[0191] The additive manufacturing device 10 further includes a heating module 30 connected to the base 12, in particular to the wheel support platform 12c, and fixed relative to the base 12, in particular to the wheel support platform 12c, and concentric with the tire 4 in the material deposition position, visible in [Fig.3].

[0192] 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, for example of the pyrometer type (not shown).

[0193] 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.

[0194] This also avoids the crosslinking or transformation at the molecular scale of the surface layer which would prevent inter-diffusion between the layers, which would cause decohesion. Prolonged exposure to excessively high temperatures leads 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.

[0195] The additive manufacturing device 10 further includes a machining module 50 connected to the base 12 and movable in translation relative to said second base 13 along the longitudinal axis X.

[0196] As illustrated, the machining module 50 is mounted to slide on a guide rail 53.

[0197] The movement of the machining module 50 combined with the vertical movement along the Zl-Zl axis of the base 12 allows any curve of the tire 4 to be traversed.

[0198] 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.

[0199] Figures 1 to 3 show an example where the machining tool is a two-size milling cutter 51 rotated by an electric motor 52.

[0200] Machining the layer that will receive the molten material rod could also be carried out by a circular saw, by gouging, i.e. by removing material by turning with a hot gouge, by micro-milling, by turning, or any other means of material removal

[0201] 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.

[0202] 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.

[0203] The additive manufacturing device 10 further includes a vision module (not shown) comprising 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.

[0204] Figures 6A and 6B, in which the same elements bear the same references, illustrate another embodiment of each extruder extending along the extension axis Bi coinciding with the radial axis Ai.

[0205] In this embodiment, each printing module 20; i comprises a nozzle 22 material deposition closing device 25 comprising a closing means 25a movable about the radial axis Ai, for example in the form of a needle actuated by the actuator to move the sealing means in translation along the radial axis Ai.

[0206] In this embodiment, the pressure regulating member 24 includes a worm screw 24a movable about the radial axis Ai, for example driven in rotation by a motor, 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.

[0207] In this embodiment, the extruder 21 movement element 23 along the corresponding radial axis Ai is not a rail but 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 including a threaded hole cooperating with the thread of the worm gear 23b. Thus, the rotation of the worm gear causes the extruder 21 to move along the associated radial axis Ai.

[0208] In this example, the pressure regulating member 24 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.

[0209] 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.

[0210] A first example of material deposition is illustrated with reference to [Fig.7A].

[0211] In this example, each printing module 20; i is configured to deposit, along the radial axis Ai to the tire 4, extruded material forming the tread 6 on the tire 4, in particular its circumferential carrier surface 5, along a circumferential line of material Lj.

[0212] 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.

[0213] 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.

[0214] A layer of material C corresponds to a thickness of molten material deposit.

[0215] The lines Lj have a constant width and the layers Ch have a constant thickness.

[0216] A second example of material deposition is illustrated with reference to [Fig.7B].

[0217] 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.

[0218] The lines Lj have a variable width and the layers Ch have a constant thickness.

[0219] A third example of material deposition is illustrated with reference to [Fig. 7C].

[0220] 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.

[0221] The lines Lj have a constant width and the layers Ch have a variable thickness.

[0222] Figures 8A, 8B, and 8C 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 to avoid stress concentrations.

[0223] In the example illustrated in [Fig.8A], the material is deposited in circumferential lines Lj parallel to the direction of travel D of the tire 4.

[0224] In the example illustrated in [Fig.8B], 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 platform 12c in translation along the translation axis Zl-Zl combined with the displacement of the extruders 21 along the radial axis Ai and the rotation of the carrier surface 5.

[0225] In the example illustrated in [Fig.8C], 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 moving the platform 12c in translation along the translation axis Zl-Zl, from right to left and then from left to right, combined with the movement of the extruders 21 along the radial axis Ai and the rotation of the carrier surface 5.

[0226] During a complete rotation of the tire, the material depositing nozzles 22 of each printing module 20; i are actuated simultaneously to deposit material along a circumferential line of material on the lower material line, then the platform 12c is moved in translation along the translation axis Zl-Zl 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 is obtained.

[0227] Thus, a portion of the layer dependent on the number of extruders used is produced at each complete revolution of the tire.

[0228] In the case where the number of lines to be printed is greater than the number of printing modules 20; i, the platform 12c is moved in translation along the translation axis Zl-Zl of the width of the set of printing modules 20; i in order to continue the deposition of the material on the following circumferential lines.

[0229] In this case, an entire layer is made during several complete revolutions of the tire.

[0230] 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 of all or part of a tread (6) of a tire (4) configured to deposit an extruded material forming the tread (6) on a circumferential carrier surface (5) of said tire (4), characterized in that it comprises a drive element for rotating the tire capable of driving said tire (4) around a vertical axis of rotation (RR), and that it comprises: - a base (12, 13) fixed to the ground (S) and on which the tire (4) is mounted; - a printing unit (14) attached to the base (13) and comprising a support (16) and a plurality of printing modules (20; i) fixed to the support (16), with "i" being the number of printing modules, between 5 and 30, arranged circumferentially around the pneumatic (4), and offset along a vertical axis (Z), parallel to the axis of rotation (RR), by a vertical pitch from each other, each printing module (20;(i) extending along a radial axis (Ai) perpendicular to the axis of rotation (RR) 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 rod; - a material dispensing nozzle (22) supplied with a molten material rod 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); - a device (23) for moving 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 the base (12) comprises: - a base (12a) fixed to the ground (S), - a guide element (12b) extending from the base (12a) along the vertical axis parallel to the axis of rotation (RR) of the tire (4), and - a platform (12c) for supporting the tire (4), mounted to slide relative to the guide element (12b) along a translation axis (Zl-Zl) parallel to the axis of rotation (RR) of the tire (4) and rotating around said translation axis (Zl-Zl).

3. Device (10) according to claim 1 or 2, wherein each extruder (21) extends along an extension axis (Bi), forming an angle with respect to the radial axis (Ai) between 0° and 90°.

4. Device (10) according to claim 3, wherein each printing module (20; i) comprises a sealing device (25) for the material depositing nozzle (22) comprising a sealing means (25a) movable about the radial axis (Ai) between a sealing position and a plurality of opening positions of the distribution orifice (22b) of the nozzle (22), and an actuator for controlling the movement of the sealing means (25a) between the sealing and opening positions, the sealing means (25a) of all the printing modules (20; i) being controllable independently of each other.

5. Device (10) according to claim 4, 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).

6. Device (10) according to any one of the preceding claims, wherein the pressure regulating member (24) comprises a worm screw (24a) rotatable about the extension axis (Bi) 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).

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

8. 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°.

9. Device (10) according to any one of the preceding claims, wherein the support (16) is fixed relative to the base (12; 13).

10. 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 plate (23b) comprising a tapped hole and set in translation by an electric motor (23c) associated with a worm screw comprising a thread cooperating with the tapped hole of the plate (23b) and a fixing base (23d) integral with the extruder (21).

11. 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 make a material deposit 1mm wide and preferably between 1mm and 1.6mm to make a material deposit 2mm wide.

12. Device (10) according to any one of the preceding claims, wherein each printing module (20; i) comprises at least one application wheel (26) disposed downstream of the associated printing nozzle (22) along the vertical axis (Z) and movable in rotation about an axis parallel to the axis of rotation (RR) of the tire (4) and configured to apply pressure to the bead of molten material deposited on the carrier surface (5).

13. Device (10) according to claim 2 taken in combination with any of the preceding claims, further comprising a heating module (30) connected to the wheel support platform (12c) and fixed relative to the wheel support platform (12c) and concentric with the tire (4) in a material depositing position.

14. Device (10) according to claim 13, 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.

15. A device (10) according to any one of the preceding claims, further comprising a machining module (50) connected to the base (13) and movable in translation relative to said base (13) along the longitudinal axis (X), said machining module (50) comprising a machining tool (51) configured to perform a groove in the thickness of the tread (6) in the circumferential direction.

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