Airless tyre, in particular for an extraterrestrial vehicle, comprising an optimised tread, and method for manufacturing the airless tyre via additive manufacturing

Abstract

The invention relates to an airless tyre (1) for a vehicle, comprising, radially from the inside to the outside, a supporting structure (2) intended to co-operate with a rim (60) of a wheel (10), a shear strip (3) secured to the supporting structure (2) and a tread (4) secured to the shear strip (3). The tread (4) comprises at least one elastically deformable layer (40) comprising a plurality of consecutive patterns (41) distributed circumferentially along the perimeter of the tread (4).

Description

[0001] DESCRIPTION

[0002] TITLE: Airless tire, in particular for extraterrestrial vehicles, comprising an optimized tread and method for manufacturing the airless tire by additive manufacturing

[0003] Technical field of the invention

[0004] The present invention relates to the field of airless tires, in particular, but not exclusively, intended to equip an extraterrestrial exploration vehicle, in particular intended to move, for example, on the moon or on the planet Mars, in an environment subject to very strong temperature variations, which can reach very low temperatures down to -243°C and very high temperatures up to +130°C. Such a thermal gradient is notably measured at the South Pole of the moon.

[0005] The present invention relates more particularly to the tread of such an airless tire.

[0006] State of the prior art

[0007] A conventional tyre subjected to the internal pressure of an inflation gas, generally air, or a conventional solid or airless tyre, not subjected to the internal pressure of an inflation gas, are not suitable for such use, because the usual rubber-based materials from which they are made have mechanical properties incompatible with use in an environment which can reach very low temperatures, also called cryogenic temperatures.

[0008] It is known to have, as an alternative technical solution to a conventional tire, an airless tire, or more generally a tire without inflation gas, which carries the load thanks to structural components and which has performances comparable to those of a conventional tire. An airless tire, mounted on a hub, or a rim, is sometimes called a "non-pneumatic elastic wheel". In the following, the circumferential or longitudinal direction designates the direction of rotation of the tire, the axial or transverse direction designates a direction parallel to the axis of rotation of the tire and the radial direction designates a direction perpendicular to the axis of rotation of the tire.

[0009] The term "inner" element means the part closer to the axis of rotation of the tire compared to an "outer" element.

[0010] An airless tire generally comprises, radially from the inside to the outside:

[0011] - a carcass made up of structural elements and intended to cooperate with a rim or a hub; and

[0012] - a tread integral with the carcass and intended to transmit rolling forces to said carcass, to be worn and to guarantee the grip of the tire with the ground.

[0013] The carcass comprises, radially from the inside to the outside:

[0014] - a supporting structure, intended to structurally carry at least part of the load applied to the tire and secured to the rim or hub; and

[0015] - a shear strip, intended to transmit rolling forces by shear to the supporting structure and to contribute at least in part to carrying the load.

[0016] The supporting structure comprises, radially from the inside to the outside, means of connection with a rim or a hub, radial elements or spokes, and means of connection with the shear band.

[0017] However, the load-bearing structure does not usually delineate a sealed internal cavity to contain a pressurized gas, as in a conventional tire. Therefore, an airless tire does not need to have a sealed connection to a rim or hub.

[0018] The shear band comprises, radially from the inside to the outside:

[0019] - a first radially inner membrane, - a shear layer consisting of one or more shear elements, and

[0020] - a second radially outer membrane intended to receive the tread and connected to the radially inner membrane by the shear layer.

[0021] Generally, the first and second membranes have a modulus of elasticity in circumferential extension often significantly higher than the modulus of elasticity in shear of the shear layer of polymeric material, such that, under the applied load, the membranes do not elongate or elongate only slightly when the tire is flattened while rolling. The relative displacement of the membranes relative to each other occurs by shear in the shear layer. For example, the membranes, respectively inner and outer, comprise a layer or a superposition of layers of reinforcements coated in a polymeric material.

[0022] The shear layer of polymeric material is made, for example, of a polymeric material, such as a natural rubber or a synthetic rubber, or a polyurethane. Typically, the material of the shear layer has a shear modulus of at least 3 MPa and at most 20 MPa, which allows for easier flattening of the shear band under load.

[0023] Finally, the tread, which is the radially outer component of the tire, is most often made of a polymeric material, such as natural rubber or synthetic rubber.

[0024] Michelin North America has been marketing, for several years, a mounted assembly, consisting of an airless tire, as previously described, and a wheel, under the name MICHELIN® TWEEL®. This technical solution mainly comprises a tread, a shear band, a load-bearing structure, consisting of highly resistant polyresin spokes and a hub made of two reinforced steel parts. However, in very low temperature applications, the usual polymeric materials constituting an airless tire are incompatible with the specified temperature range.

[0025] Thus, the usual polymeric materials, used, in particular, for the shear band, have levels of rigidity which will generate high contact pressures, involving a risk of the tire sinking into soft ground, particularly as on the moon, and generate high rolling resistance, involving high energy consumption, which is detrimental to the energy autonomy of the extraterrestrial vehicle.

[0026] In addition, common polymeric materials, such as natural rubber or synthetic rubber, which generally make up the tread of an airless tire, are also incompatible with the specified temperature range.

[0027] Finally, treads known for such applications generally have a smooth outer surface, which greatly penalizes ground grip, especially on soft ground, especially on the moon.

[0028] Furthermore, methods for manufacturing airless tires, well known to those skilled in the art, consist of manufacturing, in a first step and independently, the different structural elements before assembling them together, in a second step, while respecting a precise assembly and positioning process. The different structural elements can be held in position using different processes such as, for example, gluing, riveting, bolting, crimping, or ultrasonic welding.

[0029] Such processes have disadvantages, linked in particular to the poor adhesion between the different elements which make up the airless tire.

[0030] Furthermore, the manufacturing quality of such airless tires is not always satisfactory, the variations in geometric dimensions linked to the manufacturing of each of the structural elements adding to the variations in positioning of the assembly process, which can consequently harm the overall quality of the airless tire and its performance.

[0031] Other methods of manufacturing airless tires using molding processes to produce the various elements are also known to those skilled in the art.

[0032] However, these molding manufacturing processes require the manufacture of expensive tools such as molds, and do not allow the production of complex geometries sometimes necessary for the manufacture of the elements of an airless tire.

[0033] Subsequently, there is a need to address the above-mentioned drawbacks.

[0034] Statement of the invention

[0035] The inventors aim to design an airless tire that can run in an extraterrestrial environment, at very low temperatures, typically in the range [-243°C; +130°C], and on various types of ground, which may be sandy or stony.

[0036] The invention aims in particular to improve the traction of the airless tire while protecting it from ground damage, in particular by choosing an appropriate tread, without impairing the flattening of the airless tire.

[0037] Another objective of the invention is to propose a manufacturing method which allows the simple and low-cost production of a tread of an airless tire, or more generally of the airless tire, making it possible to produce complex shapes, to guarantee excellent manufacturing reproducibility and perfect adhesion between the different structural elements during the manufacture of the airless tire.

[0038] The present invention relates to an airless tire for a vehicle, in particular an extraterrestrial vehicle, comprising radially from the inside to the outside, a supporting structure, intended to cooperate with a rim of a wheel, a shear band secured to the supporting structure and a tread secured to the shear band. The tread comprises at least one elastically deformable layer comprising a plurality of successive patterns distributed circumferentially around the perimeter of the tread.

[0039] In other words, the outer surface of the tread is corrugated, i.e. not cylindrical, unlike the outer surface of a tread of existing airless tires.

[0040] By "successive patterns" we mean a succession of patterns along the perimeter of the tread.

[0041] By "elastically deformable" we mean any element capable, by its shape or structure, of deforming during an external stress, for example during contact with the surface of the ground under the action of the load carried by the wheel, and of returning to its initial shape when the external stress stops. In fact, we play on the structure of the tread to give it elasticity.

[0042] This allows the tread to absorb external shocks without degrading the airless tire's run-flat, while remaining sufficiently rigid to prevent blistering of the outer shear membrane of the shear band interfacing with it. This blistering can occur in a treadless or smooth tread tire, due to the stresses generated by the shear elements of the shear band on the outer shear membrane of the shear band.

[0043] The tread patterns help increase grip on the ground.

[0044] Furthermore, thanks to the tread patterns, the contact pressure with the ground is minimized due to the maximization of the contact surface with the ground, which improves the traction of the airless tire without degrading it.

[0045] Such a tread also helps the tire lie flat on the ground without damaging it.

[0046] Each pattern of the tread comprises successively, in the circumferential direction, an anchoring section configured to be integral with the shear band, a first radial portion extending from the anchoring section in a substantially radial direction towards the outside of the tire, a support section configured to come into contact with the ground surface and a second radial portion extending from the anchoring section in a substantially radial direction towards the inside of the tire, the support section circumferentially connecting the first and second radial portions.

[0047] “Substantially radial direction” means a direction parallel to the radial direction or a direction inclined at an angle of between 0° and 25° to the radial direction.

[0048] The tread layer has a thickness of between 0.5 mm and 5 mm and a total height of between 1 mm and 30 mm, the total height being at least twice the thickness.

[0049] The tread support section is spaced from the outer shear membrane of the shear band by vacuum.

[0050] Preferably, the supporting structure, the shear band and the tread are each made of the same material.

[0051] For example, the supporting structure, the shear band and the tread are each made of at least one material, preferably thermoplastic, preferably high-performance, having the following mechanical characteristics, measured according to ASTM D638 standard of ASTM (“American Society for Testing and Materials”) International:

[0052] - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to - 196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and

[0053] - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to - 196°C, at least equal to 40 MPa and at most equal to 260 MPa. Such an airless tire is intended to equip an extraterrestrial vehicle and is capable of withstanding strong temperature gradients ranging from -243°C to + 130°C.

[0054] To enable an airless tire to roll in an extraterrestrial environment that can vary between very low temperatures and very high temperatures, typically in the range [-243°C; 130°C], and on soils of various types, which can be sandy or stony, the Applicant has selected materials having, essentially, a Young's modulus in tension E and a maximum tensile stress Sm within specific ranges both at room temperature, taken as 20°C, and at very low temperature, taken as -196°C.

[0055] The Young's modulus in tension E and the maximum tensile stress Sm are measured on a tensile curve "stress - elongation", established from a tensile test carried out on a standardized specimen, in accordance with the ASTM D638 standard ("Standard Test Method for Tensile Properties of Plastics"), developed by ASTM ("American Society for Testing and Materials") International. The standardized specimen has a length equal to 84 mm and a thickness equal to 2 mm, and includes a necking having a length equal to 25 mm and a width equal to 4 mm. The tensile speed applied to the specimen is equal to 500 mm / min. The Young's modulus in tension E is a tangent modulus measured at low strain.

[0056] The Young's modulus in traction E conditions the rigidities and the load capacity of the airless tire, at the target operating temperatures. The maximum tensile stress Sm conditions the endurance of the airless tire, at the target operating temperatures.

[0057] Consequently, the inventors have chosen materials whose aforementioned mechanical characteristics make it possible to guarantee a satisfactory compromise between the load capacity and the endurance required for the airless tire under the intended conditions of use. The airless tire must be capable of carrying a load typically between 5 daN and 200 daN, and is intended to be mounted on a vehicle which can typically travel up to a maximum speed of 20 km / h.

[0058] In the context of the present invention, the inventors have demonstrated, surprisingly, that such a high-performance thermoplastic polymeric material also makes it possible to achieve a satisfactory compromise between high structural rigidity, high endurance and low mass of the airless tire, at very low cryogenic temperatures, as shown by measurements carried out at - 196°C.

[0059] According to a preferred embodiment, the supporting structure, the shear band and the tread are each made of the same material. An identical material for all the components of an airless tire simplifies manufacturing and allows for easier adhesion between the different components.

[0060] Preferably, at least one material constituting the supporting structure, the shear band and the tread is a high-performance thermoplastic polymeric material. This type of material, which performs very well at room temperature, is known to retain good mechanical properties, in terms of mechanical strength and rigidity, at high temperatures, typically at least equal to 150°C. In the context of the present invention, the inventors have demonstrated, surprisingly, that such a high-performance thermoplastic polymeric material also makes it possible to achieve a satisfactory compromise between high structural rigidity, high endurance and low mass of the airless tire, at very low cryogenic temperatures, as shown by measurements carried out at -196°C.

[0061] According to a first advantageous embodiment, the at least one material constituting the supporting structure, the shear band and the tread is a polyaryletherketone (PAEK). The generic term "polyaryletherketones" (PAEK) designates a family of technical polymers with high thermomechanical properties, in particular at high temperature. A polyaryletherketone, such as, for example, the Victrex AM200TM material, marketed by the company Victrex®, is, in particular, easy to process and has good mechanical characteristics at very low temperature, as shown in Table 1 of this document.

[0062] According to a second advantageous embodiment, the at least one material constituting the supporting structure, the shear band and the tread is a polyetheretherketone (PEEK). A polyetheretherketone is a thermoplastic polymeric material belonging to the family of polyaryletherketones. A polyetheretherketone, such as, for example, the materials Victrex CT 100TM and Victrex 450GTM, marketed by the company Victrex®, have the required mechanical characteristics, in particular at cryogenic temperatures.

[0063] According to a third advantageous embodiment, the at least one material constituting the supporting structure, the shear band and the tread is a polyimide (PI). A polyimide, such as, for example, the Aurum PL500ATM material, has excellent mechanical characteristics at cryogenic temperatures, but is more difficult to implement than a polyetheretherketone, such as the Victrex CT 100TM material.

[0064] According to a fourth advantageous embodiment, the at least one material constituting the supporting structure, the shear band and the tread is a polyetherimide (PEI). A polyetherimide such as, for example, the Ultem 1010TM material, has mechanical properties comparable to those of a polyetheretherketone, such as the Victrex CT 100TM material, but with a lower elongation at break. It has the advantage of being more economical.

[0065] Preferably, the supporting structure, the shear band and the tread are each made of the same material. An identical material for all the constituents of an airless tire simplifies manufacturing and allows for easier adhesion between the different constituents. Preferably, the tread layer is connected to the shear band, in particular to its external shear membrane, by a plurality of connection points each located at an anchoring section of a pattern, all of said connection points forming an attachment surface of between 5% and 90% of the external surface of the shear band, in particular of its external shear membrane.

[0066] The sum of the curvilinear distances between two consecutive connection points for all tread patterns is between 100% and 250% of the length of the shear band, including its external shear membrane.

[0067] For example, the outer surface of the bearing section of each pattern has a domed shape.

[0068] Alternatively, it could be provided that the external surface of the support section is flat.

[0069] It could be envisaged that the sections and radial portions of each pattern are connected to each other by connecting radii in order to limit stress concentrations.

[0070] Advantageously, the tread patterns are distributed circumferentially at a constant pitch.

[0071] According to one embodiment, the patterns of the elastically deformable layer of the tread extend over the same angular sector, that is to say that the patterns have the same circumferential width.

[0072] According to another embodiment, the patterns of the elastically deformable layer of the tread extend over a different angular sector, that is to say that the patterns may not have the same circumferential width.

[0073] According to one embodiment, each pattern is symmetrical with respect to a radial median plane passing through the axis of rotation of the wheel.

[0074] According to one embodiment, the tread patterns each extend transversely along an axis parallel to the axis of rotation of the wheel or along an axis forming an angle of between 0° and 15°, preferably between 0° and 5°, relative to the axis parallel to the axis of rotation of the wheel. Too great an angle could penalize the flattening of the wheel.

[0075] Preferably, the elastically deformable layer of the tread comprising a plurality of patterns extends transversely over the entire width of the tire.

[0076] It could also be provided that the tread comprises at least two elastically deformable layers each comprising a plurality of patterns, said two layers being joined in the transverse direction.

[0077] Generally, the elastically deformable layer of the tread comprising a plurality of patterns extends transversely over at least 20% of the width of the tire.

[0078] Advantageously, the patterns are identical to each other and are regularly distributed circumferentially around the perimeter of the tread.

[0079] According to one embodiment, the patterns are linked together and form a continuous circumferential distribution.

[0080] According to one embodiment, the first radial portion of each pattern comprises a first part extending in a substantially radial direction from the anchoring section and a second part circumferentially offset relative to the first part, extending towards the adjacent pattern, and connected to the support section. The first part and the second part of the first radial portion are connected by a circumferential part. The second radial portion comprises a first part extending in a substantially radial direction from the anchoring section and a second part circumferentially offset relative to the first part, extending towards the adjacent pattern, and connected to the support section.The first part and the second part of the second radial portion are connected by a circumferential part, said circumferential parts respectively of the first and second radial portions extending in an opposite circumferential direction. According to another embodiment, the first radial portion of each pattern comprises a first part extending in a substantially radial direction from the anchoring section and a second part circumferentially offset relative to the first part, extending opposite the adjacent pattern, and connected to the support section. The first part and the second part of the first radial portion are connected by a circumferential part.The second radial portion of each pattern comprises a first part extending in a substantially radial direction from the anchoring section and a second part circumferentially offset relative to the first part, extending opposite the adjacent pattern, and connected to the support section, the first part and the second part of the second radial portion being connected by a circumferential part, said circumferential parts respectively of the first and second radial portions extending in the same circumferential direction.

[0081] According to another embodiment, the patterns are not linked together and form a discontinuous circumferential distribution.

[0082] For example, the first radial portion of each pattern comprises at least one first convex portion and at least one second concave portion and the second radial portion comprises at least one first convex portion and at least one second concave portion.

[0083] By "concave" we mean a shape that curves towards the inside of the tire.

[0084] By "convex" we mean a shape that curves outward from the tire, as opposed to concave.

[0085] Each pattern here has the shape of an I.

[0086] Advantageously, the shear band comprises, radially from the inside to the outside, an internal shear membrane, a shear structure consisting of a plurality of circumferentially distributed shear elements and an external shear membrane, and the anchoring section of each pattern is tangential to the external surface of the external shear membrane of the shear band. For example, the number of patterns of the tread is a multiple of the number of shear elements of the shear band.

[0087] For example, the number of shear elements is 40 and the number of patterns is 80.

[0088] For example, the respective perimeters of the inner shear membrane and the outer shear membrane of the shear band are circular. Alternatively, it could be provided that the respective perimeters of the inner shear membrane and the outer shear membrane of the shear band are not circular.

[0089] In a non-limiting manner, each shear element comprises, for example, two opposite curvatures.

[0090] For example, the supporting structure consists of a plurality of spokes regularly distributed circumferentially.

[0091] In a non-limiting manner, the spokes of the supporting structure each comprise an internal end secured to the rim, for example by fixing means (not shown), such as screw means (screws / nuts) or by rivets (not shown), a concave portion and an external end secured to the shear band by screw means or by rivets (not shown).

[0092] It could also be provided that the tread comprises at least one additional layer radially external to the base layer in order to protect the latter from external aggressions. For example, the additional layer has a thickness of between 0.1 mm and 3 mm.

[0093] The additional layer is made of metal, for example, titanium, aluminum, steel, a nickel and titanium alloy known as nitinol®.

[0094] According to a second aspect, the invention relates to a wheel comprising an airless tire as described above mounted on a rim.

[0095] The invention also relates to a method for manufacturing a tread as previously described. A first method for manufacturing an airless tire uses extrusion technology. Such an extrusion manufacturing method consists of compressing a material forced to pass through a die having the section of the part to be obtained.

[0096] Another method of manufacturing a tread uses injection technology. Such an injection manufacturing process involves injecting the material(s) making up the tread or the entire airless tire into a mold.

[0097] Yet another method of manufacturing a tread uses additive manufacturing technology. An additive manufacturing method uses a three-dimensional printing machine depositing a malleable printing material in successive layers, by means of a nozzle. Such a three-dimensional printing machine generally comprises a chamber which forms an enclosure delimited by a wall, and inside which is a plate intended to support a part being printed, as well as a nozzle for supplying the material constituting said part. To be able to generate the shape of the part, drive systems are provided comprising an elevator for moving either the plate or the nozzle vertically, and translation tables crossed relative to each other to horizontally control either the plate or the nozzle responsible for delivering the material constituting the part.

[0098] According to a variant of the manufacturing process by implementing additive manufacturing technology, it includes a single stage of manufacturing the tire consisting of a unitary part.

[0099] Such a method for additive manufacturing of an airless tire allows the manufacturing of an airless tire forming a single-piece assembly as described above by additive manufacturing using an additive manufacturing machine comprising a manufacturing plate, perpendicular to the axis of revolution of the tire having an axial direction, and a nozzle, capable of moving in the axial direction and in any circumferential plane perpendicular to the axial direction. Said method for additive manufacturing of the airless tire comprises the following successive steps:

[0100] (a) manufacturing a first layer of the airless tire, extending in the axial direction, by depositing a printing material on the manufacturing plate by said nozzle, to form, in any order, cords as follows:

[0101] - a radially inner membrane cord intended for the manufacture of the radially inner membrane of the supporting structure;

[0102] - a radially intermediate membrane cord intended for the manufacture of an internal shear membrane of the shear band;

[0103] - a radially outer membrane cord intended for the manufacture of an external shear membrane of the shear band;

[0104] - a connecting structure bead for manufacturing spokes of the supporting structure connecting the radially inner membrane to the inner shear membrane of the shear band; said structure bead having a plurality of second zones interpenetrated with the radially intermediate membrane bead, said second interpenetrating zones and a plurality of fifth zones interpenetrated with the radially inner membrane bead;

[0105] - a joining structure bead for manufacturing shear elements of the shear band connecting the inner shear membrane of the shear band to the outer shear membrane of the shear band, said joining structure bead having a plurality of third zones interpenetrated with the radially intermediate membrane bead and a plurality of fourth zones interpenetrated with the radially outer membrane bead;

[0106] - a tread structure cord intended for the manufacture of the tread and having a plurality of first zones interpenetrated with the radially outer membrane cord;

[0107] (b) production of at least one additional layer produced according to step (a), the beads of the at least one additional layer being superimposed in an axial direction on the beads of the axially adjacent previous layer with reflow of the interface between the previous layer and the at least one additional layer.

[0108] Repeating step (a) will produce a single-piece airless tire, with a height in the axial direction. The height of the airless tire will be adjusted to the tread width of the airless tire.

[0109] Remelting the interface between two adjacent layers allows for a very strong bond between each layer, thus making it possible to manufacture single-piece airless tires with high mechanical strength.

[0110] The creation of interpenetration zones during the deposition of the printing material allows, on the one hand, the spokes to adhere perfectly to the radially inner membrane of the supporting structure and to the inner shear membrane of the shear strip, and on the other hand, the shear elements to also adhere perfectly to the inner shear membrane of the shear strip and to the outer shear membrane of the shear strip.

[0111] This perfect adhesion between the structural elements of the airless tire makes it possible to obtain very high mechanical resistance and very good fatigue resistance of the said airless tire during operating stresses.

[0112] Obtaining, for each of the layers of the airless tire, junction zones located according to different horizontal azimuths for the cords delimiting closed zones makes it possible to reinforce the mechanical resistance of the airless tire by avoiding the propagation of possible cracks in said junction zones. The additive manufacturing process of the monobloc tire makes it possible to obtain an airless tire by implementing a unique process of depositing a printing material in the form of cords coming out of a nozzle and without having to assemble several parts together to constitute said tire. Each element of the tire is thus constituted by an axial superposition of layers, each layer being constituted by a single cord or "mono-cord", said "mono-cord" making it possible to save time and improve the quality of manufacturing of the airless tire, while improving the mechanical resistance of said tire.

[0113] Therefore, such an additive manufacturing process makes it possible to eliminate the assembly process of the various structural elements necessary for the manufacture of an airless tire, which saves manufacturing time and improves the quality of the airless tire.

[0114] In addition, this additive manufacturing process results in a lower manufacturing cost for the tire, as no tools are required to manufacture the various structural elements.

[0115] Thanks to the interpenetration of the beads of material deposited by the nozzle of the additive manufacturing machine in the connection zones of the different structural elements, the adhesion between them of said different structural elements is improved, thus making it possible to obtain better mechanical resistance properties and / or fatigue limit of the tire.

[0116] Brief description of the drawings

[0117] Other aims, characteristics and advantages of the invention will appear on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings in which:

[0118] [Fig. 1] represents an overall perspective view of a wheel comprising an airless tire comprising a tread according to a first embodiment of the invention; [Fig. 2] illustrates a detail view of the wheel of Figure 1;

[0119] [Fig.2A] represents a detail of figure 2;

[0120] [Fig.3] represents a table summarizing, for a wheel width of 300mm, under a load of 100daN, the length of the contact area of ​​the wheel measured, the average contact pressure, the deflection corresponding to the radial crushing of the tire and different maximum stresses;

[0121] [Fig.4] illustrates a detail view of Figure 2 with an additional layer; [Fig.5] represents an airless tire comprising a tread according to a second embodiment of the invention;

[0122] [Fig.6] represents an airless tire comprising a tread according to a third embodiment of the invention;

[0123] [Fig.7] represents an airless tire comprising a tread according to a fourth embodiment of the invention;

[0124] [Fig.8] represents an overall perspective view of a wheel comprising an airless tire comprising a tread according to another embodiment of the invention, in which the entire tire is produced by an additive manufacturing process;

[0125] [Fig.9] very schematically represents a device for additive manufacturing of the airless tire of figure 8;

[0126] [Fig. 10] is an overall and top view of the first layer deposited on the manufacturing plate of the carcass of the airless tire of Figure 8; [Fig. H] is a circumferential sectional view of a first interpenetration zone;

[0127] [Fig. 12] is a circumferential sectional view of a second interpenetration zone; and

[0128] [Fig. 13] is a circumferential sectional view of a third and fourth interpenetration zone.

[0129] Detailed description of at least one embodiment

[0130] In the following description, the terms "circumferential", "axial" and "radial" are defined relative to the axis of rotation XI - XI of the tire 1.

[0131] The "circumferential" direction means a direction of a plane perpendicular to the axis of rotation X l -Xl tangent to the tread of the tire 1, the "axial" direction is the direction of the axis of rotation Xl -Xl of the tire 1 and a "radial" direction means a direction perpendicular to the axis of rotation Xl -Xl of the tire 1.

[0132] Figure 1 is an overall perspective view of a mounted assembly or wheel 10 comprising a rim 60 and an airless tire 1 mounted on said rim 60.

[0133] By “rim” is meant a structure connecting to the vehicle and centrally supporting the tire 1.

[0134] The airless tire 1 is, for example, intended to equip an extraterrestrial vehicle and is capable of withstanding strong temperature gradients ranging from -243°C to +130°C.

[0135] The airless tire 1 comprises, radially from the inside to the outside, a supporting structure 2, intended to cooperate with the rim 60 or a hub, a shear band 3 secured to the supporting structure 2 and a tread 4 secured to the shear band 3.

[0136] The supporting structure 2 is constituted, here, by a plurality of spokes 21 regularly distributed circumferentially. In a non-limiting manner, the spokes 21 each comprise here an internal end 21a secured to the rim 60, for example by fixing means (not shown), such as screw means (screws / nuts) or by rivets (not shown), a concave portion 21b and an external end 21c secured to the shear band 3 by screw means or by rivets (not shown).

[0137] By way of non-limiting example, said fixing means could be configured to fix both a spoke 21 of the tire 1 and the rim 60.

[0138] The shear band 3 comprises, radially from the inside to the outside, a radially inner membrane 31, integral with the supporting structure 2, a shear structure 32 and a radially outer membrane 33.

[0139] As illustrated, the shear structure 32 is constituted by a plurality of shear elements 32a, here distributed circumferentially according to a regular pitch and extending radially between the radially inner membrane or internal shear membrane 31 and the radially outer membrane or external shear membrane 33.

[0140] In a non-limiting manner, each shear element 32a here comprises two opposite curvatures.

[0141] The supporting structure 2 is made of a thermoplastic polymer material, said to be high-performance.

[0142] The material constituting at least the supporting structure 2 has the following mechanical characteristics, measured according to ASTM D638 standard of ASTM (“American Society for Testing and Materials”) International:

[0143] - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to - 196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to - 196°C, at least equal to 40 MPa and at most equal to 260 MPa.

[0144] As illustrated in detail in Figures 1 and 2, the respective perimeters of the radially inner membrane 31 and the radially outer membrane 33 of the shear band 3 are circular.

[0145] Alternatively, it could be provided that the respective perimeters of the radially inner membrane 31 and the radially outer membrane 33 of the shear band 3 are not circular.

[0146] In the example illustrated in Figures 1, 2 and 2A, the tread 4 comprises a single elastically deformable layer 40 comprising a plurality of successive patterns 41 distributed circumferentially around the perimeter of the tread 4.

[0147] In other words, the outer surface of the tread 4 is corrugated, therefore not cylindrical, unlike the outer surface of a tread of existing tires.

[0148] By "successive patterns" we mean a succession of patterns along the perimeter of the tread.

[0149] As illustrated, the elastically deformable layer 40 of the tread 4 extends transversely across the entire width of the tire 1.

[0150] It could also be provided that the tread 4 comprises at least two elastically deformable layers 40 each comprising a plurality of patterns, said two layers 40 being joined in the transverse direction.

[0151] Generally, the elastically deformable layer 40 of the tread 4 extends transversely over at least 20% of the width of the tire 1.

[0152] The patterns 41 are here identical to each other and are regularly distributed circumferentially around the perimeter of the tread.

[0153] As illustrated in detail in FIG. 2A, each pattern 41 of the tread 4 successively comprises, in the circumferential direction, an anchoring section 42 configured to be secured to the external shear membrane 33 of the shear band 3, a first radial portion 43 extending from the anchoring section radially outwards, a support section 44 configured to come into contact with the ground surface and a second radial portion 45 extending from the anchoring section radially inwards.

[0154] The support section 44 circumferentially connects the first and second radial portions 43, 45.

[0155] As illustrated in Figures 1, 2 and 2A, the anchoring section 42 is tangential to the outer surface of the outer shear membrane 33 of the shear band 3.

[0156] The external surface of the support section 44 here has a curved shape. Alternatively, it could be provided that the external surface of the support section 44 is flat.

[0157] The different sections 42, 44 and portions 43, 45 of each pattern 41 are connected to each other by connecting radii in order to limit stress concentrations.

[0158] The layer 40 of the tread is connected to the external shear membrane 33 of the shear band 3 by a plurality of connection points P each located at an anchoring section 42 of a pattern 41. The attachment surface formed by the anchoring sections 42 is between 5% and 90% of the external surface of the external shear membrane 33 of the shear band 3.

[0159] The sum of the curvilinear distances between two consecutive connection points P for all the patterns 41 of the tread 4 have a curvilinear length between the connection points P is between 100% and 250% of the length of the shear band 3.

[0160] The patterns 41 of the tread are periodic, that is to say they are distributed circumferentially according to a constant pitch.

[0161] Each pattern 41 is here symmetrical with respect to a radial median plane passing through the axis of rotation Xl -Xl of the wheel 10. The layer 40 of the tread 4 is elastically deformable, that is to say that it is configured to deform during an external stress, for example during contact with the surface of the ground under the action of the load carried by the wheel 1 and to return to its initial shape when the external stress stops.

[0162] This allows the tread 4 to absorb external shocks without degrading the flattening of the airless tire, while remaining sufficiently rigid to prevent blistering of the external shear membrane of the wheel, which can occur in a tire without a tread or with a smooth tread, due to the stresses generated by the shear elements on the external shear membrane.

[0163] The layer 40 of the tread 4 has a thickness el of between 0.5 mm and 5 mm and a total height H 1 of between 1 mm and 30 mm. Generally, the total height H 1 is at least greater than twice the thickness el , that is to say that there is a space not filled with material between the support section 44 and the external shear membrane 33 of the shear band 3.

[0164] As illustrated, the patterns 41 each extend transversely along an axis parallel to the axis of rotation Xl -X l of the wheel 1.

[0165] Alternatively, it could be provided that the patterns 41 extend transversely each along an axis forming an angle of between 0° and 15°, preferably between 0° and 5°, relative to the axis parallel to the axis of rotation Xl -Xl of the wheel 1. Too large an angle could penalize the flattening of the wheel.

[0166] The number of patterns 41 depends on the number of shear elements 32a.

[0167] In the illustrated example, the number of shear elements 32a is equal to 40 and the number of patterns 41 is equal to 80.

[0168] Alternatively, a number of patterns 41 could be provided that is identical to the number of shear elements 32a. Preferably, the number of patterns 41 is a multiple of the number of shear elements 32a greater than two. As illustrated, the patterns 41 of the elastically deformable layer 40 of the tread 4 extend over the same angular sector, that is to say that the patterns 41 have the same circumferential width.

[0169] Alternatively, it could be provided that the patterns 41 of the elastically deformable layer 40 of the tread 4 extend over a different angular sector, that is to say that the patterns may not have the same circumferential width.

[0170] In the example illustrated in Figures 1, 2 and 2A, the patterns 41 are linked together and form a continuous circumferential distribution of the tread.

[0171] Alternatively, it could be provided that the patterns 41 are not linked together and are spaced circumferentially from each other.

[0172] Figure 3 represents a table summarizing, for a wheel width of 300 mm, with forty shear elements, under a load of 100daN, the circumferential length of the contact area measured, the average contact pressure, the deflection corresponding to the radial crushing of the tire and different maximum stresses compared to a control, that is to say a tire without tread or with a smooth surface tread, without patterns.

[0173] In the tire according to the invention, a deflection similar to the witness is observed with a larger circumferential length of contact area, increased here by approximately 8%, which makes it possible to reduce the ground pressure.

[0174] Such an optimized tread pattern makes it possible to increase grip on the ground without increasing the maximum stress generated in the structural elements of the wheel (rim, supporting structure, shear band) and thus to obtain the lowest possible average contact pressure of the tire with the ground.

[0175] In the embodiment illustrated in Figure 4, in which the same elements bear the same references, the tread 4 comprises a layer 40 comprising a plurality of successive patterns 41 distributed circumferentially over the perimeter of the tread 4 and not linked together. In a similar manner to the previous embodiment, each pattern 41 of the tread 4 successively comprises, in the circumferential direction, an anchoring section 42 configured to be integral with the external shear membrane 33 of the shear band 3, a first radial portion 43' extending from the anchoring section 42 in a substantially radial direction towards the outside, a support section 44 configured to come into contact with the ground surface and a second radial portion 45' extending from the anchoring section in a substantially radial direction towards the inside.

[0176] The support section 44 circumferentially connects the first and second radial portions 43', 45'.

[0177] The anchoring section 42 is tangential to the outer surface of the outer shear membrane 33 of the shear band 3.

[0178] The external surface of the support section 44 here has a curved shape. Alternatively, it could be provided that the external surface of the support section 44 is flat.

[0179] In this example, the first radial portion 43' comprises a first convex portion 43a' and a second concave portion 43b' and the second radial portion 45' comprises a first convex portion 45a' and a second concave portion 45b'.

[0180] By "concave" we mean a shape that curves towards the inside of the tire.

[0181] By "convex" we mean a shape that curves outward from the tire, as opposed to concave.

[0182] Each pattern 41 here has the shape of an I.

[0183] The different sections 42, 44 and portions 43', 45' of each pattern 41 are connected to each other by connecting radii in order to limit stress concentrations.

[0184] The patterns 41 of the tread are periodic, that is to say they are distributed circumferentially according to a constant pitch.

[0185] Each pattern 41 is here symmetrical with respect to a radial median plane passing through the axis of rotation Xl-Xl of the wheel 10. In the embodiment illustrated in FIG. 5, in which the same elements bear the same references, the tread 4 comprises a layer 40 comprising a plurality of successive patterns 41 distributed circumferentially over the perimeter of the tread 4 and are linked together and form a continuous circumferential distribution.

[0186] In a manner similar to the previous embodiment, each pattern 41 of the tread 4 successively comprises, in the circumferential direction, an anchoring section 42 configured to be secured to the external shear membrane 33 of the shear band 3, a first radial portion 46 extending from the anchoring section 42 in a substantially radial direction towards the outside, a support section 44 configured to come into contact with the surface of the ground and a second radial portion 47 extending from the anchoring section in a substantially radial direction towards the inside.

[0187] The support section 44 circumferentially connects the first and second radial portions 46, 47.

[0188] The anchoring section 42 is tangential to the outer surface of the outer shear membrane 33 of the shear band 3.

[0189] The external surface of the support section 44 here has a curved shape. Alternatively, it could be provided that the external surface of the support section 44 is flat.

[0190] In this example, the first radial portion 46 comprises a first part 46a extending in a substantially radial direction from the anchoring section 42 and a second part 46b circumferentially offset relative to the first part 46a, extending towards the adjacent pattern 41, and connected to the support section 44. The first part 46a and the second part 46b of the first radial portion 46 are connected by a circumferential part 46c.

[0191] The second radial portion 47 here comprises a first part 47a extending in a substantially radial direction from the anchoring section 42 and a second part 47b circumferentially offset relative to the first part 47a, extending towards the adjacent pattern 41, and connected to the support section 44. The first part 47a and the second part 47b of the second radial portion 47 are connected by a circumferential part 46c. The circumferential parts 46c, 47c of the first and second radial portions 46, 47 here extend in an opposite circumferential direction.

[0192] The patterns 41 of the tread are periodic, that is to say they are distributed circumferentially according to a constant pitch.

[0193] Each pattern 41 is here symmetrical with respect to a radial median plane passing through the axis of rotation Xl-Xl of the wheel 10.

[0194] In the embodiment illustrated in Figure 6, in which the same elements bear the same references, the tread 4 comprises a layer 40 comprising a plurality of successive patterns 41 distributed circumferentially around the perimeter of the tread 4 and are linked together.

[0195] In a similar manner to the previous embodiment, each pattern 41 of the tread 4 successively comprises, in the circumferential direction, an anchoring section 42 configured to be secured to the external shear membrane 33 of the shear band 3, a first radial portion 48 extending from the anchoring section 42 in a substantially outward direction, a support section 44 configured to come into contact with the ground surface and a second radial portion 49 extending from the anchoring section 42 in a substantially inward direction.

[0196] The support section 44 circumferentially connects the first and second radial portions 48, 49.

[0197] The anchoring section 42 is tangential to the outer surface of the outer shear membrane 33 of the shear band 3.

[0198] The external surface of the support section 44 here has a curved shape. Alternatively, it could be provided that the external surface of the support section 44 is flat.

[0199] In this example, the first radial portion 48 comprises a first part 48a extending in a direction substantially from the anchoring section 42 and a second part 48b offset circumferentially relative to the first part 48a, extending opposite the adjacent pattern 41, and connected to the support section 44. The first part 48a and the second part 48b of the first radial portion 48 are connected by a circumferential part 48c.

[0200] The second radial portion 49 here comprises a first part 49a extending in a direction substantially from the anchoring section 42 and a second part 49b offset circumferentially relative to the first part 49a, extending opposite the adjacent pattern 41, and connected to the support section 44. The first part 49a and the second part 49b of the second radial portion 49 are connected by a circumferential part 49c. The circumferential parts 48c, 49c of the first and second radial portions 48, 49 extend here in the same circumferential direction.

[0201] The patterns 41 of the tread are periodic, that is to say they are distributed circumferentially according to a constant pitch.

[0202] Each pattern 41 is not here symmetrical with respect to a radial median plane passing through the axis of rotation X l -Xl of the wheel 10.

[0203] Generally speaking, the shape of the patterns is unlimited. The patterns can be linked together or spaced circumferentially from each other.

[0204] In all the embodiments described, it could also be provided that the tread 4 comprises an additional layer 50 integral with the layer 40 in order to protect the latter from external attacks.

[0205] For example, the additional layer has a thickness between 0.1 mm and 3 mm.

[0206] The additional layer is made of metal, for example, titanium, aluminum, steel, a nickel and titanium alloy known as nitinol®.

[0207] The 41 patterns of the tread 4 allow for increased grip on the ground.

[0208] Furthermore, thanks to the patterns 41 of the tread 4, the contact pressure with the ground is minimized due to the maximization of the contact surface with the ground, which makes it possible to improve the traction of the airless tire without degrading it. Such a tread 4 also promotes the flattening of the tire on the ground.

[0209] The tread 4 as described in the embodiments illustrated in FIGS. 1, 2, 2A, 4, 5 and 6 can be produced by extrusion of a plastic material, such as polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyimide (PI), polyetherimide.

[0210] Extrusion is a mechanical manufacturing process by which a compressed material is forced through a die having the cross-section of the part to be obtained.

[0211] Alternatively, it could be envisaged to produce such a tread by injecting a plastic material, such as polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyimide (PI), polyetherimide, in a molding process.

[0212] It could also be envisaged to produce such a tread 4 using an additive manufacturing process.

[0213] Additive manufacturing processes use three-dimensional printing machines to manufacture airless tires by depositing a malleable printing material in successive layers, using a nozzle.

[0214] The tread could also be manufactured by an additive manufacturing process simultaneously with the manufacture of the shear strip 3 and the supporting structure 2, as seen in the example illustrated in Figure 8 and in which the same elements bear the same references.

[0215] The airless tire 1 illustrated in Figure 8, in the form of a single-piece assembly, is produced by an additive manufacturing process using an additive manufacturing machine 100', an example of which is illustrated in Figure 9.

[0216] The additive manufacturing machine 100 ' comprises a nozzle 1 10 ', a manufacturing plate 101 ', a horizontal displacement system 102 ' in any circumferential plane YZ, and an axial displacement system 103 ' in an axial direction X, parallel to the axis of rotation Xl-Xl of the tire 1 and perpendicular to any circumferential plane YZ.

[0217] The horizontal movement system 102' and the axial movement system 103' make it possible to control a relative movement of the nozzle 110' with respect to the manufacturing plate 101' so that said nozzle 110' can deposit a molten printing material 104' in the form of preferably continuous beads 105'.

[0218] Any other type of additive manufacturing machine by depositing a bead 105' of a malleable printing material 104' is suitable, such as, for example, machines in which the relative movement of the nozzle 110' with respect to the manufacturing plate 101' is achieved by the movement of said manufacturing plate 101'.

[0219] According to a first step of the method of the invention, a first layer of said tire 1, extending in the axial direction X, will be produced by depositing a printing material 104' on the manufacturing plate 101' by the nozzle 110', to form, in any order, cords C1', C2', C3', C4', C5'.

[0220] As seen in Figures 10 to 13, the nozzle 110' will deposit:

[0221] - a radially inner membrane cord Cl', intended for the manufacture of the radially inner membrane 2d of the supporting structure 2 and having a first width RI',

[0222] - a radially intermediate membrane cord C2', intended for the manufacture of the internal shear membrane 31 of the shear band 3 and having a second width R2',

[0223] - a radially outer membrane cord C3', intended for the manufacture of the external shear membrane 33 of the shear strip 3 and having a third width R3',

[0224] -a connecting structure cord C4', intended for the manufacture of the spokes 21 of the supporting structure 2 connecting the radially inner membrane 2d to the inner shear membrane 31 of the shear strip 3, said connecting structure cord C4' having a fourth width R4', -a junction structure cord C5', intended for the manufacture of the shear elements 32a of the shear strip 3 connecting the inner shear membrane 31 of the shear strip 3 to the outer shear membrane 33 of the shear strip 3, said junction structure cord C5' having a fifth width R5'; and

[0225] - a tread structure cord C6' intended for the manufacture of the tread 4, said tread structure cord C6' having a sixth width R6'.

[0226] As illustrated in detail in Figure 11, the radially outer membrane cord C3' has a plurality of first interpenetrating zones ZI with the tread structure cord C6', said first interpenetrating zones ZI each having a first arc length L1' and, in a radial direction, a first maximum thickness E1.

[0227] As illustrated in detail in Figure 12, the structural bead C4' has a plurality of second interpenetrating zones Z2 with the radially intermediate membrane bead C2', said second interpenetrating zones Z2 each having a second arc length L2' and, in a radial direction, a second maximum thickness E2.

[0228] As seen in Figure 13, the junction structure bead C5' has a plurality of third interpenetrating zones Z3 with the radially intermediate membrane bead C2', said third interpenetrating zones Z3 each having a third arc length L3' and, in a radial direction, a third maximum thickness E3.

[0229] The junction structure bead C5' also has a plurality of fourth interpenetrating zones Z4 with the radially outer membrane bead C3', said fourth interpenetrating zones Z4 each having a fourth arc length L4' and, in a radial direction, a fourth maximum thickness E4.

[0230] The connecting structure bead C4' also has a plurality of fifth interpenetrating zones (not shown) with the radially inner membrane bead C1', said fifth zones each having a first arc length and, in a radial direction, a fifth maximum thickness.

[0231] According to the additive manufacturing process of the tire, the nozzle 110' will then produce at least one additional layer following step (a), the beads (C1', C2', C3', C4', C5', C6') of the at least one additional layer being superimposed in an axial direction, here vertical Z to the beads (C1', C2', C3', C4', C5', C6') of the previous axially adjacent layer with remelting of the interface between the previous layer and the at least one additional layer.

[0232] As can be seen in Figure 8, repeating step (a) will make it possible to produce a single-piece airless tire 1, of height H in the axial direction X. The height H of the airless tire 1 will be adjusted to the width of the tread 4 of the airless tire 1.

[0233] Remelting the interface between two adjacent layers allows for a very strong bond between each layer, thus making it possible to manufacture one-piece airless tires with high mechanical strength.

[0234] The creation of interpenetration zones Z1, Z2, Z3, Z4 during the deposition of the printing material 104' allows, on the one hand, the spokes 21 to adhere perfectly to the radially inner membrane 2d of the supporting structure 2 and to the internal shear membrane 31 of the shear strip 3, and on the other hand, the shear elements 32a to also adhere perfectly to the internal shear membrane 31 of the shear strip 3 and to the external shear membrane 33 of the shear strip 3.

[0235] This perfect adhesion between the structural elements of the airless tire 1 makes it possible to obtain very high mechanical resistance and very good fatigue resistance of said airless tire 1 during operating stresses.

[0236] Obtaining, for each of the layers of the airless tire 1, junction zones located according to different horizontal azimuths for the cords delimiting closed zones makes it possible to reinforce the mechanical resistance of the airless tire 1 by avoiding the propagation of possible cracks in said junction zones.

[0237] The additive manufacturing process described with reference to Figures 8 to 13 makes it possible to obtain an airless tire by implementing a unique process for depositing a printing material in the form of cords emerging from a nozzle and without having to assemble several parts together to constitute said tire. Each element of the tire is thus constituted by an axial superposition of layers, each layer being constituted by a single cord or "monocord", said "monocord" making it possible to save time and improve the quality of manufacturing of the airless tire, while improving the mechanical resistance of said tire.

[0238] Therefore, such an additive manufacturing process makes it possible to eliminate the assembly process of the various structural elements necessary for the manufacture of an airless tire, which saves manufacturing time and improves the quality of the airless tire.

[0239] In addition, this additive manufacturing process results in a lower manufacturing cost for the tire, as no tools are required to manufacture the various structural elements.

[0240] Thanks to the interpenetration of the beads of material deposited by the nozzle of the additive manufacturing machine in the connection zones of the different structural elements, the adhesion between them of said different structural elements is improved, thus making it possible to obtain better mechanical resistance properties and / or fatigue limit of the tire.

Claims

vehicle, in particular extraterrestrial, comprising, radially from the inside to the outside, a supporting structure (2), intended to cooperate with a rim (60) of a wheel (10), a shear band (3) integral with the supporting structure (2) and a tread (4) integral with the shear band (3), the tread (4) comprising at least one elastically deformable layer (40) comprising a plurality of successive patterns (41) distributed circumferentially on the perimeter of the tread (4), characterized in that - each pattern (41) of the tread (4) successively comprises, in the circumferential direction, an anchoring section (42) configured to be integral with the shear strip (3), a first radial portion (43, 43', 46, 48) extending from the anchoring section (42) in a substantially radial direction towards the outside of the tire, a support section (44) configured to come into contact with the ground surface and a second radial portion (45, 45', 47, 49) extending from the anchoring section (42) in a substantially radial direction towards the outside of the tire, the support section (44) circumferentially connecting the first and second radial portions (43, 45; 43', 45'; 46, 47; 48, 49) and in that - the layer (40) of the tread (4) has a thickness (el ) of between 0.5 mm and 5 mm and a total height (H l ) of between 1 mm and 30 mm, the total height (H l ) being at least greater than twice the thickness (el ), the support section (44) of the tread being spaced from an external shear membrane (33) of the shear band (3) by a vacuum.

2. Airless tire (1) according to claim 1, wherein the supporting structure (2), the shear band (3) and the tread (4) are each made of at least one material, preferably thermoplastic, having the mechanical characteristics following, measured according to ASTM D638 standard of ASTM (“American Society for Testing and Materials”) International: - a Young's modulus in tension E, measured at a temperature equal to 20°C, at least equal to 1 GPa and at most equal to 6 GPa, and, measured at a temperature equal to - 196°C, at least equal to 1.2 GPa and at most equal to 9 GPa, and - a maximum tensile stress Sm, measured at a temperature equal to 20°C, at least equal to 25 MPa and at most equal to 150 MPa, and, measured at a temperature equal to - 196°C, at least equal to 40 MPa and at most equal to 260 MPa.

3. Airless tire (1) according to any one of the preceding claims, wherein the layer (40) of the tread (4) is connected to the shear band (3) by a plurality of connection points (P) each located at an anchoring section (42) of a pattern (41), all of said connection points (P) forming an attachment surface of between 5% and 90% of the external surface of the shear band (3).

4. Airless tire (1) according to claim 3, wherein the sum of the curvilinear distances between two consecutive connection points (P) for all the patterns (41) of the tread (4) is between 100% and 250% of the length of the shear band (3).

5. Airless tire (1) according to any one of the preceding claims, wherein the external surface of the support section (44) of each pattern (41) has a curved shape.

6. Airless tire (1) according to any one of the preceding claims, wherein the sections (42, 44) and radial portions (43, 45; 43', 45'; 46, 47; 48, 49) of each pattern (41) are connected to each other by connecting spokes.

7. Airless tire (1) according to any one of the preceding claims, in which the patterns (41) of the tread are distributed circumferentially at a constant pitch.

8. Airless tire (1) according to any one of the preceding claims, in which each pattern (41) is symmetrical with respect to a median radial plane passing through the axis of rotation (Xl -X l) of the wheel (10).

9. Airless tire (1) according to any one of the preceding claims, in which the patterns (41) of the tread (4) each extend transversely along an axis parallel to the axis of rotation (Xl-Xl) of the wheel (1) or along an axis forming an angle of between 0° and 15°, preferably between 0° and 5°, relative to the axis parallel to the axis of rotation (Xl-Xl) of the wheel (1).

10. Airless tire (1) according to any one of the preceding claims, in which the patterns (41) are identical to each other and are regularly distributed circumferentially around the perimeter of the tread (4). 1 1 . Airless tire (1) according to any one of the preceding claims, in which the patterns (41) are linked together and form a continuous circumferential distribution.

12. Airless tire (1) according to claim 10 taken in combination with any one of claims 1 to 5, wherein the first radial portion (46) of each pattern (41) comprises a first part (46a) extending in a substantially radial direction from the anchoring section (42) and a second part (46b) circumferentially offset relative to the first part (46a), extending towards the adjacent pattern (41), and connected to the support section (44), the first part (46a) and the second part (46b) of the first radial portion (46) being connected by a circumferential part (46c), and wherein the second radial portion (47) comprises a first part (47a) extending in a substantially radial direction from the anchoring section (42) and a second part (47b) offset circumferentially ... circumferentially relative to the first portion (47a), extending towards the adjacent pattern (41), and connected to the support section (44),the first part (47a) and the second part (47b) of the second radial portion (47) being connected by a circumferential part (46c), said circumferential parts (46c, 47c) respectively of the first and, the second radial portions (46, 47) extending in an opposite circumferential direction.

13. An airless tire (1) according to claim 10 taken in combination with any one of claims 1 to 5, wherein the first radial portion (48) of each pattern (41) comprises a first part (48a) extending in a substantially radial direction from the anchoring section (42) and a second part (48b) circumferentially offset relative to the first part (48a), extending opposite the adjacent pattern (41), and connected to the support section (44), the first part (48a) and the second part (48b) of the first radial portion (48) being connected by a circumferential part (48c), and wherein the second radial portion (49) of each pattern (41) comprises a first part (49a) extending in a substantially radial direction from the anchoring section (42) and a second part (49 ... portion (49b) circumferentially offset relative to the first portion (49a), extending opposite the adjacent pattern (41),and connected to the support section (44), the first part (49a) and the second part (49b) of the second radial portion (49) being connected by a circumferential part (49c), said circumferential parts (48c, 49c) respectively of the first and second radial portions (48, 49) extending in the same circumferential direction., 14. Airless tire (1) according to any one of the preceding claims, in which the patterns (41) are not linked together and form a discontinuous circumferential distribution.

15. Airless tire (1) according to claim 13 taken in combination with any one of claims 1 to 5, wherein the first radial portion (43') of each pattern (41) comprises at least one first convex portion (43a') and at least one second concave portion (43b') and wherein the second radial portion (45') comprises at least one first convex portion (45a') and at least one second concave portion (45b').

16. Airless tire (1) according to any one of the preceding claims taken in combination with any one of claims 1 to 5, wherein the shear band (3) comprises, radially from the inside to the outside, an internal shear membrane (31), a shear structure (32) constituted by a plurality of shear elements (32a) distributed circumferentially and an external shear membrane (33), and in which the anchoring section (42) of each pattern is tangential to the external surface of the external shear membrane (33) of the shear band (3).

17. Airless tire (1) according to claim 18, wherein the number of patterns (41) of the tread (4) is a multiple of the number of shear elements (32a) of the shear band (3).

18. Airless tire (1) according to any one of the preceding claims, in which the patterns (41) of the elastically deformable layer (40) of the tread (4) extend over the same angular sector.

19. Airless tire (1) according to any one of claims 1 to 17, wherein the patterns (41) of the elastically deformable layer (40) of the tread (4) extend over a different angular sector.

20. Wheel (10) comprising an airless tire (1) according to any one of the preceding claims mounted on a rim (60).

21. A method of manufacturing an airless tire (1) in the form of an airless tire (1) according to any one of claims 1 to 19 in the form of a single-piece assembly by additive manufacturing using an additive manufacturing machine (100') comprising a manufacturing plate (101'), perpendicular to the axis of revolution of the tire (1) having an axial direction (X), and a nozzle (110'), capable of moving in the axial direction (X) and in any circumferential plane (YZ) perpendicular to the axial direction (X), said additive manufacturing method comprising the following successive steps: (a) manufacturing a first layer of the airless tire (1), extending in the axial direction (X), by depositing a material printing (104') on the manufacturing plate (101') by said nozzle (110'), to form, in any order, beads (Cl', C2', C3', C4', C5', C6') as follows: - a radially inner membrane cord (Cl') intended for the manufacture of the radially inner membrane (2d) of the supporting structure (2); - a radially intermediate membrane cord (C2') intended for the manufacture of an internal shear membrane (31) of the shear band (3); - a radially outer membrane cord (C3'), intended for the manufacture of the outer shear membrane (33) of the shear strip (3); - a connecting structure bead (C4'), intended for the manufacture of spokes (21) of the supporting structure (2) connecting the radially inner membrane (2d) to the internal shear membrane (31) of the shear strip (3), said structure bead (C4') having a plurality of second interpenetrating zones (Z2) with the radially intermediate membrane bead (C2') and a plurality of fifth interpenetrating zones with the radially inner membrane bead (Cl'); - a joining structure bead (C5'), intended for the manufacture of shear elements (32a) of the shear band (3) connecting the inner shear membrane (31) of the shear band (3) to an outer shear membrane (33) of the shear band (3), said joining structure bead (C5') having a plurality of third interpenetrating zones (Z3) with the radially intermediate membrane bead (C2') and a plurality of fourth interpenetrating zones (Z4) with the radially outer membrane bead (C3'); and - a tread structure cord (C6') intended for the manufacture of the tread (4) and having a plurality of first interpenetrating zones (Zl) with the radially outer membrane cord (C3'); (b) production of at least one additional layer produced according to step (a), the beads (Cl', C2', C3', C4', C5', C6') of the at least one additional layer being superimposed in an axial direction (X) on the beads (Cl', C2', C3', C4', C5', C6') of the axially adjacent preceding layer with reflow of the interface between the preceding layer and the at least one additional layer.

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