Tire for agricultural vehicle comprising a single-layer casing reinforcement.

Abstract

A tire for an agricultural vehicle comprising a single-layer casing reinforcement. The present invention relates to a tire for an agricultural vehicle (1), and in particular its casing reinforcement (4), and aims, for a tire that operates at low pressure on shifting soil, to reduce soil compaction and increase traction capacity by decreasing the structural rigidity of the tire. According to the invention, the casing armor (4) consists of a single casing layer (41) that has an average thickness E of at most 2 mm and a rupture resistance Fr, expressed in daN / cm, which satisfies the relation: Fr > = Fs = (Cs*Pmax*10-3)*((R2 ? ((R + Rj) / 2)2)2) / Rj, with - Fs: limit reference resistance (in daN / cm), - Cs: safety factor at least equal to 1, - Pmax: maximum recommended inflation pressure (in kPa), - R = D / 2: outer radius of the tire (in mm), - Rj = Dj / 2: nominal radius of the rim (in mm).

Description

1 / 30 “PNEUMATIC TIRE FOR AGRICULTURAL VEHICLE COMPRISING A SINGLE-LAYER CARCASS ARMOR”

[0001] The present invention relates to a tire for an agricultural vehicle, such as an agricultural tractor or an agro-industrial vehicle, and refers more specifically to its carcass assembly.

[0002] The dimensional specifications (section width, overall diameter, mounting rim diameter and width) and operating conditions (load, speed, pressure) of a tire for an agricultural vehicle are defined in standards, such as, for example, the standard of the “European Tyre and Rim Technical Organisation” or ETRTO in its “Standards Manual-2018”, in the section dedicated to “Agricultural equipment tyres”. As an example, a radial tire for the wheel of an agricultural tractor is intended to be mounted on a rim whose diameter is generally between 16 inches and 46 inches, and even 54 inches, and to equip an agricultural tractor that has a power between 50 hp and more than 250 hp (up to 550 hp) and that can travel up to 65 km / h.For this type of tire, the minimum inflation pressure in use, which corresponds to the specified load capacity, is most often a maximum of 400 kPa, but can drop to 240 kPa for an "Improved Flexion" or IF tire, and even 160 kPa for a "Very High Flexion" or VF tire.

[0003] A tire for an agricultural vehicle is designed to run on various types of soil, such as the more or less compacted soil of fields, unpaved access roads to fields, and paved road surfaces. Considering the diversity of use, in the field and on the road, a tire for an agricultural vehicle must offer a compromise in performance between, but not limited to, traction in the field on loose soil, resistance to tearing, resistance to wear on the road, resistance to rolling, and vibration comfort on the road.

[0004] A constant concern of vehicle tire manufacturers Petition 870220061654, dated 07 / 13 / 2022, p. 16 / 56 2 / 30 of the agricultural benefits, in relation to the use of tires in the field, is the improvement of traction on shifting soil while minimizing soil compaction caused by the tires, which can harm crops.

[0005] This is why, in the agricultural field, low-pressure, and therefore high-flexion, tires have been developed. The ETRTO standard thus distinguishes between IF (Improved Flexion) tires, with a minimum recommended inflation pressure generally equal to 240 kPa, and VF (Very High Flexion) tires, with a minimum recommended inflation pressure generally equal to 160 kPa. According to the standard, compared to a standard tire, an IF tire has a 20% increased load capacity, and an VF tire has a 40% increased load capacity, for an inflation pressure equal to 160 kPa.

[0006] It is known that the increase in traction on mobile ground and the decrease in soil compaction are mainly driven by the pressure in the contact area of ​​the tire with the ground, the pressure in the contact area itself being driven largely, but not solely, by the inflation pressure.

[0007] In fact, inflation pressure gives the tire a pneumatic stiffness that is added to its structural stiffness. Thus, the overall stiffness of the tire results from the combination of pneumatic stiffness and structural stiffness. Consequently, in low-pressure use where pneumatic stiffness becomes low, the structural stiffness of the tire makes a significant contribution to the pressure in the contact area.

[0008] Therefore, to reduce the pressure in the contact area of ​​a low-pressure tire, it is necessary to reduce the structural stiffness of the tire, and especially all bending stiffnesses that allow it to flatten, both in the circumferential direction, tangent to the circumference of the tire, and in the axial direction, parallel to the axis of rotation of the tire.

[0009] In a structural plan, like any tire, a tire for an agricultural vehicle comprises a tread, intended to come into contact with the ground by means of a tread surface, which corresponds to its Petition 870220061654, dated 07 / 13 / 2022, page 17 / 56 3 / 30 contact surface on a rigid ground, and of which the two axial ends are connected by means of two flanks to two beads that ensure the mechanical connection between the tire and the rim on which it is intended to be mounted.

[0010] In what follows, the circumferential (or longitudinal), axial (or transverse), and radial directions designate, respectively, a direction tangent to the tread surface and oriented according to the direction of rotation of the tire, a direction parallel to the axis of rotation of the tire, and a direction perpendicular to the axis of rotation of the tire. A radial (or meridian) plane is defined by a radial direction and an axial direction, and contains the axis of rotation of the tire. A circumferential plane is defined by a radial direction and a circumferential direction, and is therefore perpendicular to the axis of rotation of the tire. The circumferential plane that passes through the middle of the tread is called the equatorial (or median) plane.

[0011] The tread of an agricultural vehicle tire comprises raised elements, called tread patterns, which extend radially outward from a base surface to the tread surface, and which are separated from each other by voids.

[0012] The tread can be geometrically defined, according to the axial direction, by an axial width L, and, according to a radial direction, by a radial height H. The axial width L is the distance measured between the two axial end points of the tread that come into contact with a rigid ground when the tire, inflated to its nominal pressure Pn, is crushed under its nominal load Zn, these nominal values ​​being recommended service values ​​defined, for example, by the ETRTO standard. The axial width L can be defined as a percentage of the nominal section width B of the tire or “design section width” defined in the ETRTO standard. The radial height H of the tread, measured according to a radial direction, is the maximum height of the tread elements, or, equivalently, the maximum depth of the gaps separating the tread elements.The radial tread height H is at least 20 mm, frequently at least 50 mm, and most often at least 60 mm. Petition 870220061654, dated 07 / 13 / 2022, p. 18 / 56 4 / 30

[0013] The proportion of voids in the tread is usually quantified by an overall volumetric notching ratio TEV, defined as the ratio between the volume VC of voids and the total volume V of the assumed void-free tread, which corresponds to the geometric volume delimited by the tread surface and the bearing surface, parallel to the tread surface and tangent to the bottoms of the deepest voids. The radial distance between the tread surface and the bearing surface therefore defines the radial height H of the tread. As the tread surface varies with tread wear, the overall volumetric notching ratio TEV is generally, but not necessarily, variable with the level of wear. Thus, the overall volumetric notching ratio TEV can be defined for a new state or for a given state of wear.For example, a new agricultural tractor drive wheel tire has a volumetric notch ratio (VTR) of at least 30%, often at least 50%, and most often at least 60%. In what follows, the expression "volumetric notch ratio VTR" implicitly means "volumetric notch ratio VTR in the new condition".

[0014] The tread pattern elements for agricultural vehicles are usually, but not necessarily, in the form of bars. A bar generally has an elongated, globally parallelepiped shape, continuous or discontinuous, consists of at least one straight or curved portion, and extends axially from a median zone of the tread to its axial ends or shoulders. A bar is separated from adjacent bars by gaps or grooves. The bars are distributed circumferentially with a constant or variable pitch and are generally arranged on either side of the equatorial plane of the tire, so as to form a V-pattern, also called a gallon pattern, the tip of the V-pattern being intended to be the first to enter the contact surface with the ground.The tread bars generally exhibit symmetry with respect to the equatorial plane of the tire, most often with a circumferential offset between the two rows of bars, obtained by rotating one half of the tread around the tire axis. Petition 870220061654, dated 07 / 13 / 2022, page 19 / 56 5 / 30 in relation to the other half of the tread.

[0015] A radial tire for an agricultural vehicle also comprises a reinforcing armor, consisting of a top armor, radially inside the tread, and a carcass armor, radially inside the top armor.

[0016] The top armor of a radial tire for agricultural vehicles comprises a superposition of top layers that extend circumferentially, radially on the outside of the carcass armor. Each top layer consists of reinforcements coated with an elastomer-based mixture and are parallel to each other. When the top layer reinforcements form an angle of at most 10° with the circumferential direction, they are said to be circumferential, or substantially circumferential, and provide a sealing function that limits the radial deformation of the tire. When the top layer reinforcements form an angle of at least 10° and most often at most 30° with the circumferential direction, they are called angle reinforcements and have a function of absorbing transverse forces, parallel to the axial direction, applied to the tire.Top layer reinforcements may consist of a combination of multifilament filaments made of textile-type polymeric materials, such as polyester, for example polyethylene terephthalate (PET), an aliphatic polyamide, for example nylon, an aromatic polyamide, for example aramid, or even rayon, or by a combination of wires made of metallic material, such as steel. As a non-limiting example, the top armor of a low-pressure agricultural vehicle tire often comprises between 4 and 6 top layers with polyester reinforcements.

[0017] The carcass armor of a radial tire for agricultural vehicles comprises at least one carcass layer connecting the two beads to each other. The reinforcements of a carcass layer are substantially parallel to each other and form, with the circumferential direction, an angle between 75° and 105°, preferably between 85° and 95°. A carcass layer comprises reinforcements that are mostly textile, coated with an elastomer-based polymer material. Petition 870220061654, dated 07 / 13 / 2022, page 20 / 56 6 / 30 is commonly called a coating mix. When the carcass reinforcement comprises several carcass layers, the respective reinforcements of two consecutive carcass layers, that is, adjacent to each other, are crossed from one carcass layer to the next.

[0018] A decrease in the structural rigidity of the tire, and consequently, an easier flattening of the tire's top, could be obtained by limiting the radial height H of the tread and by placing voids in the tread near its axial edges, these voids acting as hinges during the flattening of the tread. This type of design is classically used for a low-pressure tire tread.

[0019] A decrease in the structural stiffness of the tire, and consequently, an easier flattening of the tire's top, could also be achieved by reducing the number of top layers of the tire reinforcement, which allows for a reduction in the thickness of the tire reinforcement. To maintain the same tensile strength of the tire reinforcement, the reduction in the number of top layers required replacing the usual textile reinforcements made of PET or nylon with reinforcements with higher tensile strength, such as aramid or steel reinforcements. For example, a tire reinforcement consisting of 4 top layers with PET reinforcements could be replaced by a tire reinforcement of equivalent tensile strength consisting of 2 top layers with steel reinforcements.

[0020] The inventors set themselves the objective, for a low-pressure pneumatic tire such as an IF (Improved Flexion) or a VF (Very High Flexion) pneumatic tire on shifting ground, to reduce soil compaction and increase traction capacity by decreasing the structural rigidity of the tire.

[0021] This objective is achieved, according to the invention, by a tire for an agricultural vehicle, intended to be mounted on a rim having a nominal diameter Dj and to be inflated with a minimum recommended pressure of at most equal to 240 kPa, which has an outer diameter D and which comprises, radially from the outside Petition 870220061654, dated 07 / 13 / 2022, p. 21 / 56 7 / 30 inwards, a tread, a top armor and a carcass armor: - the tread comprising sculpted elements separated from each other by voids and having a radial height H of at least 20 mm and at most 60 mm, measured between a tread surface and a bearing surface parallel to the tread surface and tangent to the bottoms of the deepest voids, - the tread, which has an axial width L, comprising at least two axially external voids, each of which has a centerline that forms an angle of at most 45° with a circumferential direction of the tire, positioned on either side of an equatorial plane passing through the center of the tread and which are separated by an average axial distance L1 of at least 0.5*L, - the tread having an overall volumetric notch ratio TEV, defined as the ratio between the void volume VC and the total void volume V of the assumed void-free tread, comprised between the bearing surface and the tread surface, at least equal to 30% and at most equal to 60%, - the top armor comprising at least two top layers, each comprising reinforcements coated with an elastomer-based material, parallel to each other, crossed from one layer to the next, and forming, with the circumferential direction of the tire, an angle at least equal to 10°, - the carcass armor comprising at least one carcass layer, which comprises textile reinforcements coated with an elastomer-based material, parallel to each other, and which form, with the circumferential direction of the tire, an angle of at least 75° and at most 105°, - the carcass reinforcement being constituted by a single layer of carcass that has an average thickness E of at most equal to 2 mm and a tensile strength Fr, expressed in daN / cm, which satisfies the relationship: Fr > = Fs = (Cs*Pmax*10-3)*((R2- ((R + Rj) / 2)2)2) / Rj, with Petition 870220061654, dated 07 / 13 / 2022, page 22 / 56 8 / 30 - Fs: reference limit resistance (in daN / cm), - Cs: safety factor at least equal to 1, - Pmax: maximum recommended inflation pressure (in kPa), - R = D / 2: outer radius of the tire (in mm), - Rj = Dj / 2: nominal radius of the rim (in mm).

[0022] The invention is essentially characterized by the choice of a single-layer casing armor comprising textile reinforcements, which have a limited average thickness and a tensile strength Fr that guarantees an expected level of safety. Such a single-layer casing armor has low structural stiffness, allowing, for a pneumatic tire operating at low pressure on mobile ground, to reduce soil compaction and increase traction capacity.

[0023] Such a low structural stiffness carcass armor is even more effective in terms of compaction and traction if it is associated with a tread that preferably has the characteristics described below. The tread is not too thick, with a radial height H limited to at least 20 mm and at most 60 mm. The tread is open, with an overall volumetric notch ratio TEV of at least 30% and at most 60%. The tread has a flattening facilitated by the presence of at least two axially external voids, each of which has a centerline that forms, with a circumferential direction of the tire, an angle of at most 45°, positioned on either side of a median plane that passes through the middle of the tread and which are separated from each other by an average axial distance L1 of at least 0.5*L, said voids acting as hinges.In other words, the two axially outer voids are substantially longitudinal and axially distant from each other, on average, by a distance at least equal to 0.5*L.

[0024] Every carcass layer is radial or substantially radial, meaning it comprises textile reinforcements coated with an elastomer-based material, parallel to each other, and forming, with a circumferential direction of the tire, a Petition 870220061654, dated 07 / 13 / 2022, p. 23 / 56 9 / 30 angle at least equal to 75° and at most equal to 105°, and most often an angle at least equal to 85° and at most equal to 95°.

[0025] According to a first essential feature of the invention, the carcass armor consists of a single carcass layer having an average thickness E of at most equal to 2 mm.

[0026] A carcass layer is a composite structure consisting of a juxtaposition of parallel reinforcements coated with an elastomer-based material, called a casing mixture. The carcass layer connects the two beads of the tire, anchoring itself in each bead to a circumferential reinforcement element, most often consisting of a union of metal wires called a cord. The thickness of the carcass layer varies according to the zone of the tire, due to the geometric conformation to which the carcass layer is subjected during tire manufacturing. In a given meridian section of the tire, this thickness is maximum radially inside the cord and minimum radially inside the top reinforcement. It is usual to measure the thickness of the carcass layer radially inside the cord, that is, the maximum thickness.On the other hand, the measured thickness is a so-called leveled thickness, which corresponds substantially to the diameter of the reinforcements, without taking into account the thicknesses of the coating mixture present radially on either side of the reinforcements. Furthermore, this thickness, commonly called the thickness under the cord, can vary according to the circumferential direction of the tire. In practice, this thickness can be measured in several meridian planes distributed around the circumference of the tire, for example in 4 equally distributed meridian planes around the circumference of the tire. It is this average thickness, measured under the cord, that must remain less than 2 mm within the scope of the invention.

[0027] According to a second essential feature of the invention, the carcass armor consists of a single carcass layer that has a tensile strength Fr, expressed in daN / cm, which satisfies the relationship: Fr >= Fs = (Cs*Pmax*10-3)*((R2- ((R + Rj) / 2)2)2) / Rj, with - Fs: limit reference resistance (in daN / cm), Petition 870220061654, dated 07 / 13 / 2022, page 24 / 56 10 / 30 - Cs: safety factor of at least 1, - Pmax: maximum recommended inflation pressure (in kPa), - R = D / 2: outer radius of the tire (in mm), - Rj = Dj / 2: nominal radius of the rim (in mm).

[0028] The composite material constituting the carcass layer can be mechanically characterized by a tensile behavior law, which represents the tensile stress (in daN / cm) applied to the composite material as a function of the tensile strength Fr of said composite material. According to the invention, the tensile strength Fr thus determined must be at least equal to a limit reference strength Fs equal to (Cs*Pmax*10-3)*((R2- ((R + Rj) / 2)2) / 2) / Rj.

[0029] In the expression of this limit reference resistance Fs, Pmax represents the maximum recommended inflation pressure, expressed in kPa. In fact, to have a correct connection between the tire and the air, which guarantees in particular the absence of rotation of the tire on its rim under the action of torque, it is necessary to have a correct tightening of the bead of each tire bead on the rim. An agricultural tire having a relatively low inflation pressure in use, it is necessary, to properly position the beads when mounting the tire on its rim, to use an inflation pressure generally higher than the operating pressure. Due to this, for obvious safety reasons, that is, to avoid a tire blowout during mounting, it is necessary to limit the inflation pressure during mounting to a maximum permissible value Pmax, recommended by tire manufacturers.For example, for an IF (Improved Flexion) tire, tire manufacturers may recommend a maximum inflation pressure Pmax of 250 kPa to ensure proper mounting of the tire on its rim. The inflation pressure is then adjusted depending on the application. The safety factor CS, at least equal to 1, is chosen by the tire designer based on the desired level of safety. R is the outer radius of the tire, expressed in mm and equal to half the outer diameter D of the tire, defined as the "Design Overall Diameter". Petition 870220061654, dated 07 / 13 / 2022, p. 25 / 56 11 / 30 total design) in the section dedicated to “Agricultural equipment tyres” of the “Standards Manual-2018” of the ETRTO standard. Finally, the term “(R+Rj) / 2” is the average radius of the tyre, defined as the average of the outer radius of the tyre and the nominal radius of the rim.

[0030] Preferably, Cs*Pmax is at least equal to 1000 kPa in the expression for the limiting reference resistance Fs. In this case, the value of Cs*Pmax is at least equal to the maximum inflation pressure that can be supplied by a typical compressor used for inflating a tire for an agricultural vehicle.

[0031] Even more preferably, Cs*Pmax is at least equal to 1500 kPa in the expression for the limiting reference resistance Fs. In this case, the value of Cs*Pmax is at least equal to 1.5 times the maximum inflation pressure that can be supplied by a typical compressor used for inflating a tire for an agricultural vehicle. Consequently, the limiting reference resistance Fs is increased by at least 50% compared to the previous case.

[0032] Advantageously, the average thickness E of the carcass layer is at most equal to 1.2 mm. The more this average thickness is limited, the lower the structural stiffness of the carcass reinforcement.

[0033] Most of the time the textile reinforcements of the single carcass layer form, with the circumferential direction of the tire, an angle of at least 85° and at most 95°. In other words, the carcass armor is almost perfectly radial.

[0034] Preferably the textile reinforcements of the single carcass layer comprise a bond consisting of at least one multifilament filament made of aromatic polyamide or aromatic copolyamide and / or made of aliphatic polyamide and / or made of polyester and / or made of cellulose.

[0035] A multifilament filament made of aromatic polyamide or aromatic copolyamide is itself constituted by a union of filaments made of aromatic polyamide or aromatic copolyamide. A filament made of aromatic polyamide or aromatic copolyamide is, in a known way, a filament of linear macromolecules formed by aromatic groups linked together by amide bonds of Petition 870220061654, dated 07 / 13 / 2022, p. 26 / 56 12 / 30 of which at least 85% are directly linked to two aromatic cores, and more specifically a fiber made of poly(p-phenylene terephthalamide) (or PPTA), manufactured from optically anisotropic fiber-forming compositions.Among the aromatic polyamides or aromatic copolyamides, we can mention polyarylamides (or PAA, notably known under the trade name Ixef from the company Solvay), poly(metaxylene adipamide), polyphthalamides (or PPA, notably known under the trade name Amodel from the company Solvay), amorphous semi-aromatic polyamides (or PA 6-3T, notably known under the trade name Trogamid from the company Evonik), meta-aramids (or poly(metaphenylene isophthalamide or PA MPD-1, notably known under the trade name Nomex from the company Du Pont de Nemours) or para-amides (or poly(paraphenylene terephthalamide or PA PPD-T, notably known under the trade name Kevlar from the company Du Pont de Nemours or Twaron from the company Teijin).

[0036] A multifilament filament made of aliphatic polyamide consists of a union of filaments made of aliphatic polyamide. By aliphatic polyamide filament, we mean a filament of linear macromolecules of polymers or copolymers containing amide functions that do not have aromatic rings and that can be synthesized by polycondensation between a carboxylic acid and an amide. Among the aliphatic polyamides, we can mention the nylons PA4.6, PA6, PA6.6 or even PA6.10, and notably Zytel from DuPont, Technyl from Solvay or Rilsamid from Arkema.

[0037] Even more preferably the textile reinforcements of the single carcass layer are hybrid textile reinforcements comprising a bond consisting of at least one multifilament filament made of aromatic polyamide or aromatic copolyamide and at least one multifilament filament made of aliphatic polyamide.

[0038] In the case where the textile reinforcements of the single carcass comprise a bond consisting of at least one multifilament filament made of aromatic polyamide or aromatic copolyamide and / or made of aliphatic polyamide and / or made of polyester and / or made of cellulose, or, even more preferably, are textile reinforcements Petition 870220061654, dated 07 / 13 / 2022, p. 27 / 56 13 / 30 hybrids comprising a union consisting of at least one multifilament filament made of aromatic polyamide or aromatic copolyamide and at least one multifilament filament made of aliphatic polyamide, the carcass layer, in its vulcanized state and extracted from the tire, has a law of behavior in extension that has a secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation, such that the ratio M1 / Fr of the secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation over the tensile strength Fr of the carcass layer is strictly less than 7, preferably less than or equal to 5, and more preferably less than or equal to 4.

[0039] A carcass layer consisting of a juxtaposition of textile reinforcements coated with an elastomer-based material, parallel to each other and distributed according to a pitch P, the secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation is defined as the ratio MC1 / P between the secant modulus MC1 with the equivalent force developed by a textile reinforcement at 1% elongation, expressed in daN%, and the pitch P, expressed in cm. More precisely, the pitch P is the distance between the respective middle fibers of two consecutive reinforcements. In the usual case of a carcass layer that wraps around a circumferential reinforcement element or cord, to form a twist, the pitch P is measured at the level of the portion of the carcass layer radially interior to the cord, the latter having an almost zero conformation in manufacturing, that is, without significant variation of the pitch in relation to the initial state.The secant modulus M1 is therefore expressed in daN / cm / %. The secant modulus MC1 with the equivalent force developed by a textile reinforcement at 1% elongation is the slope of the line connecting the origin of the "Out-of-Elongation" curve obtained, for a single textile reinforcement, under the conditions of the ASTM D 885 / D 885M - 10a of 2014 standard to the 1% abscissa point of that same layer.

[0040] The tensile strength Fr of the carcass layer, expressed in daN / cm, is defined as the ratio FCr / P between the tensile strength FCr of a textile reinforcement, expressed in daN, and the pitch P, expressed in cm. The tensile strength FCr of a reinforcement Petition 870220061654, dated 07 / 13 / 2022, page 28 / 56 14 / 30 textile is the limit strength of the "Force-Elongation" curve of the textile reinforcement, obtained under the conditions of the ASTM F 885 / D 885M - 10a standard of 2014.

[0041] The M1 / Fr ratio advantageously allows quantifying the stiffness of the carcass layer as a function of its resistance to rupture with the aid of a dimensionless criterion, valid across the set of dimensions of tires commonly used in the agricultural field.

[0042] An M1 / Fr ratio greater than 7 would make the carcass layer difficult to form during tire molding before the tire cooking stage, with a risk of carcass layer disorganization due to the textile reinforcements passing through the coating mixture of said textile reinforcements.

[0043] Advantageously, the ratio M1 / Fr of the secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation over the tensile strength Fr of the carcass layer is greater than or equal to 0.5.

[0044] An M1 / Fr ratio of less than 0.5 would make handling the carcass layer difficult during tire manufacturing, due to the excessively low rigidity of said carcass layer.

[0045] According to a first embodiment, the hybrid textile reinforcements of the carcass layer comprise a bond consisting of two multifilament filaments made of aromatic polyamide or aromatic copolyamide, and a single multifilament filament made of aliphatic polyamide, the filaments being wound together in a helically.

[0046] This first embodiment variant allows for a good compromise between breaking strength and industrial cost. High breaking strength is achieved thanks to the use of a reinforcement comprising 75% aromatic polyamide, usually aramid, allowing the formation of high-tenacity multifilament filaments. On the other hand, from an economic standpoint, the first embodiment variant has a joining structure that allows for correct productivity in the manufacture of textile reinforcement twisting machines.

[0047] According to a second embodiment, the textile reinforcements Petition 870220061654, dated 07 / 13 / 2022, page 29 / 56 15 / 30 hybrid carcass layer fabrics comprise a bond consisting of a single multifilament filament made of aromatic polyamide or aromatic copolyamide, and a single multifilament filament made of aliphatic polyamide, the filaments being wound together in a helix.

[0048] This second embodiment, which contains only 60% aromatic polyamide or aramid instead of 75%, has lower performance than the first embodiment in terms of tear resistance. On the other hand, it has a lower material cost than the first embodiment. Furthermore, due to the structure of its bonding, it allows for high manufacturing productivity on textile reinforcement twisting machines, hence a lower manufacturing cost. Consequently, the overall industrial cost of this second embodiment is lower than that of the first embodiment.

[0049] According to a third embodiment, the hybrid textile reinforcements of the carcass layer comprise a bond consisting of a core consisting of a first multifilament filament made of aliphatic polyamide, and a core comprising at least two second multifilament filaments made of aromatic polyamide or aromatic copolyamide, the second layer filaments being wound together in a helically around the core.

[0050] This third variant is a hybrid textile reinforcement usually called a hybrid textile reinforcement with “Core Insertion”, meaning with the insertion of a core within a layer of multifilament filaments. The construction of such a reinforcement is flexible and versatile and allows, in particular, adjusting the secant modulus M1 by an appropriate choice of twisting parameters and sizing heat treatment. On the other hand, due to the structure of the joint, the manufacture of a hybrid textile reinforcement is more expensive than the two previously described embodiments.

[0051] Advantageously, each top layer having a behavior law in extension characterized by a secant modulus at rupture M'=F'r / A'r (in daN / cm / %), F'r being the rupture strength of the top layer (in daN / cm) and A'r Petition 870220061654, dated 07 / 13 / 2022, page 30 / 56 16 / 30 its elongation at break (in %), the top reinforcement, comprising at least two top layers, each having a secant modulus at break M', has a resultant modulus at break M's, defined as the sum of the secant moduli at break M' of the set of top layers, at least equal to 150 daN / cm / %, preferably at least equal to 300 daN / cm / %.

[0052] A sufficiently rigid top armor, with a secant modulus at rupture M's at least equal to 150 daN / cm / %, ensures correct transverse tire thrust and, consequently, satisfactory field behavior, despite a low tire inflation pressure.

[0053] Preferably, the reinforcements of at least the top two layers of the top armor are metallic.

[0054] The use of metal reinforcements for the top layers makes it easy to achieve the minimum transverse stiffness required for the top reinforcement, thus minimizing the number of top layers and therefore the structural bending stiffness in relation to tread flatness.

[0055] Even more preferably, the metallic reinforcements of at least the two top layers of the top reinforcement have a bielastic behavior law comprising a first portion having a first extension modulus MG1 at most equal to 30 GPa, and a second portion having a second extension modulus MG2 at least equal to 2 times the first extension modulus MG1, said extension behavior law being determined for a metallic reinforcement coated with an elastomeric mixture having an extension modulus at 10% elongation MA10 at least equal to 5 MPa and at most equal to 15 MPa, and all top layer metallic reinforcement has a compression behavior law characterized by a critical buckling strain in compression E0 at least equal to 3%,The aforementioned law of behavior under compression is determined in a test specimen consisting of a reinforcement placed at its center and covered by a parallelepiped volume of elastomeric mixture that has a modulus of elasticity in extension at 10% elongation MA10 at least equal to 5 MPa and at most equal to 15 MPa. Petition 870220061654, dated 07 / 13 / 2022, page 31 / 56 17 / 30

[0056] This preferred variant of top reinforcement with at least two top layers with metallic reinforcements is therefore characterized by the use of elastic metallic reinforcements whose behavior laws have specific characteristics in both extension and compression.

[0057] With regard to its tensile behavior law, a metallic reinforcement is mechanically characterized, usually in a bare state, that is, not coated with an elastomeric material, by a curve that represents the tensile force (in N) applied to the metallic reinforcement as a function of its relative elongation (in %), called the force-elongation curve. From this force-elongation curve, mechanical characteristics in extension of the metallic reinforcement are deduced, such as the structural elongation As (in %), the total elongation at rupture At (in %), the force at rupture Fm (maximum load in N) and the tensile strength Rm (in MPa), these characteristics being measured, for example, according to the ISO 6892 standard of 1984 or the ASTM D2969-04 standard of 2014.

[0058] In practice, a metallic reinforcement, extracted from the tire, is coated with a vulcanized elastomer-based material. It is possible to determine the behavior law of this metallic reinforcement extracted from the tire, and therefore coated, based on the ISO 6892 standard of 1984 as for a bare metallic reinforcement. By way of example, and in a non-exhaustive manner, the vulcanized elastomeric coating material is a rubber-based composition that has a secant extension modulus of elasticity at 10% elongation MA10 of at least 5 MPa and at most 15 MPa, for example 6 MPa, this extension modulus of elasticity being determined from tensile tests carried out in accordance with the French standard NF T 46-002 of September 1988.

[0059] From the force-elongation curve, which characterizes the extension behavior of the reinforcement, it is possible to define a stress-strain curve, where stress is equal to the ratio between the tensile force applied to the reinforcement and the surface area of ​​the reinforcement section, and strain is the relative elongation of the reinforcement. For a bimodule elastic behavior law comprising a first portion and a second portion, it is thus possible to define a first extension modulus MG1, which Petition 870220061654, dated 07 / 13 / 2022, page 32 / 56 18 / 30 represents the slope of the secant line passing through the origin of the reference, where the behavioral law is represented, and the transition point between the first and second portions. Similarly, it is possible to define a second extension module MG2, which represents the slope of a line passing through two points positioned in a substantially linear part of the second portion.

[0060] In the preferred variant of metallic reinforcements considered, every metallic reinforcement of the top layer, extracted from the tire, thus has a law of elastic behavior in extension, called bimodule, which comprises a first portion that has a first extension modulus MG1 at most equal to 30 GPa, and a second portion that has a second extension modulus MG2 at least equal to 2 times the first extension modulus MG1.

[0061] With regard to its behavior in compression, a metallic reinforcement is mechanically characterized by a curve that represents the compressive force (in N) applied to the metallic reinforcement as a function of its compressive deformation (in %). Such a compression curve is especially characterized by a limit point, defined by a critical buckling force Fc and a critical buckling deformation E0, above which the reinforcement is subjected to compressive buckling, which corresponds to a state of mechanical instability characterized by large deformations of the reinforcement with a decrease in compressive stress.

[0062] The law of behavior in compression is determined, with the aid of a Zwick or Instron type testing machine, on a specimen with dimensions 12 mm x 21 mm x 8 mm (width x height x thickness).The test specimen consists of a reinforcement, placed in its center and covered by a parallelepiped volume of elastomeric mixture that defines the volume of the test specimen, the axis of the reinforcement being positioned according to the height of the test specimen. In the context of the invention, the elastomeric mixture of the test specimen has a secant modulus of elasticity at 10% elongation MA10 at least equal to 5 MPa and at most equal to 15 MPa, for example equal to 6 MPa. The test specimen is compressed in the vertical direction, at a speed of 3 mm / min, until a compression deformation, that is, a crushing of the test specimen equal to 10% of its original size, is achieved. Petition 870220061654, dated 07 / 13 / 2022, pp. 33 / 56 19 / 30 initial height, at room temperature. The critical buckling force Fc and the corresponding critical buckling strain E0 are reached when the applied stress decreases while the strain continues to increase. In other words, the critical buckling force Fc corresponds to the maximum compressive force Fmax.

[0063] In the preferred variant of metallic reinforcement considered, every top layer metallic reinforcement has a behavior law in compression, characterized by a critical buckling strain in compression E0 at least equal to 3%.

[0064] The inventors have shown that metallic reinforcements described as elastic, characterized by laws of behavior in extension and compression as previously described, have a fatigue strength limit, during repeated cycles alternately in extension and compression, that is higher than that of usual metallic reinforcements.

[0065] In fact, when a tire for an agricultural vehicle comprising a tread with raised elements, such as bars, is worn, the tilting of the raised elements under torque (engine or brake) causes a tilting of the top layers, positioned radially inside the raised elements. This tilting results in alternately positive and negative curvatures of the top layers, and correlatively in the alternately compression / extension cycles of the metallic reinforcements of the top layers.

[0066] It should also be noted that the top layers of an agricultural vehicle tire frequently exhibit initial curvatures, both circumferentially and axially, resulting from the movements of the various elastomeric components and reinforcements during manufacturing, during the molding and curing of the tire. These initial deformations add to the deformations resulting from the tilting of the tread blocks and therefore also contribute to the compression / extension cycles of the metallic reinforcements of the top layers during tire wear.

[0067] Thus elastic metallic reinforcements of top layers according to Petition 870220061654, dated 07 / 13 / 2022, page 34 / 56 20 / 30 This preferred variant is designed to better withstand the compression / extension cycles described above, resulting in improved resistance of the tire's top reinforcement and, therefore, an increase in tire lifespan.

[0068] According to a special embodiment of the previously described preferred variant, the entire top layer metallic reinforcement is a 1xN structure multistrand cable comprising a single layer of N helically wound strands, each strand comprising an inner layer of M helically wound inner strands and an outer layer of P helically wound outer strands around the inner layer.

[0069] According to an initial variant of low-pressure tires, the agricultural vehicle tire is an IF (Improved Flexion) tire within the meaning of the ETRTO standard, in its “Standards Manual-2018”, in the section dedicated to “Agricultural equipment tyres”.

[0070] According to a second variant of low-pressure tires, the agricultural vehicle tire is a VF (Very High Flexion) tire within the meaning of the ETRTO standard, in its “Standards Manual-2018”, in the section dedicated to “Agricultural equipment tyres”.

[0071] The features of the invention are illustrated by schematic figures 1 to 8 and are not shown to scale: Figure 1: Half meridian section of a tire for an agricultural vehicle according to the invention. Figure 2: Perspective view of a tire for an agricultural vehicle according to the invention. Figure 3: Cross-sectional view of a portion of the carcass layer. Figure 4: Law of behavior in typical extension of a carcass layer comprising hybrid textile reinforcements according to a preferred embodiment of the invention. Figure 5: Section of a hybrid textile reinforcement for a carcass layer according to a first variant of the preferred embodiment of the invention. Petition 870220061654, dated 07 / 13 / 2022, pp. 35 / 56 21 / 30 Figure 6: Section of a hybrid textile reinforcement for a carcass layer according to a second variant of the preferred embodiment of the invention. Figure 7: Section of a hybrid textile reinforcement for a carcass layer according to a third variant of the preferred embodiment of the invention. - Figure 8: Respective laws of behavior in extension of a carcass layer comprising hybrid textile reinforcements according to two variant embodiments of the invention, and of a carcass layer comprising textile reinforcements of the prior art taken as a reference.

[0072] Figure 1 is a meridian half-section, in a YZ meridian plane, of an agricultural vehicle tire 1 according to the invention. The agricultural vehicle tire 1 is intended to be mounted on a rim 5 having a nominal diameter Dj and to be inflated to a recommended minimum pressure of at most 240 kPa. It has an outer diameter D and comprises, radially from the outside to the inside, a tread 2, a top armor 3 and a carcass armor 4. The tread 2 comprises sculpted elements 22 separated from each other by voids 23 and have a radial height H of at least 20 mm and at most 60 mm, measured between a tread surface 25 and a bearing surface 24 parallel to the tread surface 25 and tangent to the bottoms of the deepest voids.Tread 2 has an axial width L and comprises two substantially longitudinal axially external voids 231, positioned on either side of an equatorial plane XZ that passes through the middle of tread 2 and which are separated by an average axial distance L1 at least equal to 0.5*L. In the cross-section of the figure, only half the axial width L and half the distance L1 / 2 between an axially external longitudinal void 231 and the equatorial plane XZ are represented. On the other hand, tread 2 has an overall volumetric notch ratio TEV, defined as the ratio between the volume VC of voids and the total volume V of the tread 2 assumed without voids, comprised between the support surface 24 and the tread surface 25, at least equal to 30% and at most equal to 60%. Top reinforcement 3 comprises two top layers (31, 32), each comprising reinforcements coated with a material based on. Petition 870220061654, dated 07 / 13 / 2022, pp. 36 / 56 22 / 30 elastomer, parallel to each other, crossed from one layer to the next, and forming, with the circumferential direction XX' of the tire, an angle at least equal to 10°. The carcass reinforcement 4 comprises a single carcass layer 41, which comprises textile reinforcements coated with an elastomer-based material, parallel to each other, crossed from one layer to the next, and forming, with the circumferential direction XX' of the tire, an angle at least equal to 85° and at most equal to 95°.

[0073] Figure 2 is a perspective view of a tire 1 for an agricultural vehicle according to the invention. The tread 2 comprising sculpted elements 22 separated from each other by voids 23 and having a radial height H at least equal to 20 mm and at most equal to 60 mm, measured between a tread surface 25 and a support surface 24 parallel to the tread surface 25 and tangent to the bottoms of the deepest voids. In the embodiment shown, the embossed elements are grouped in five circumferential rows of blocks. The blocks 22 are separated from each other by voids 23 that are either substantially longitudinal, in the circumferential direction, or substantially transverse, in the axial direction.Tread 2 comprises at least two circumferential distributions of substantially longitudinal, axially exterior voids231 that act as hinges and facilitate tread crushing. Finally, tread 2 has an open tread pattern with an overall volumetric notching ratio TEV, defined as the ratio between the void volume VC 23 and the total void volume V of the assumed void-free tread 2, comprised between the bearing surface 24 and the tread surface 25, at least equal to 30% and at most equal to 60%.

[0074] Figure 3 is a cross-sectional view of a portion of carcass layer 41, the cut being made perpendicular to the direction of the reinforcements 411. The carcass layer 41 comprises textile reinforcements coated 41 with an elastomer-based material 412. It has a total thickness Et and a leveled thickness E which corresponds to the diameter of the reinforcements. An average value of this leveled thickness E is... Petition 870220061654, dated 07 / 13 / 2022, pp. 37 / 56 23 / 30 which, according to the invention, must be at least equal to 2 mm. This leveled thickness E is measured in the cut of the carcass layer portion. Figure 2 also shows the pitch P, the distance between the centerlines of two consecutive reinforcements.

[0075] Figure 4 is a typical tensile behavior law of a carcass layer comprising hybrid textile reinforcements according to a preferred embodiment of the invention. This behavior law represents the unit tensile force F, expressed in daN / cm, applied to the carcass layer as a function of its relative elongation A, expressed in %. In the example shown, the tensile strength Fr is equal to 775 daN / cm. Furthermore, the secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation is such that the ratio M1 / Fr of the secant modulus M1 to the tensile strength Fr is equal to 3.5, and therefore less than 4.

[0076] Figure 5 represents a section of a hybrid textile reinforcement for the carcass layer according to a first variant of the preferred embodiment of the invention. In this first variant, the hybrid textile reinforcements of the carcass layer comprise a joint (A / A / N) consisting of two multifilament filaments made of aramid (A), and a single multifilament filament made of nylon (N), the filaments being wound together in a helically.

[0077] Figure 6 represents a section of a hybrid textile reinforcement for the carcass layer according to a second variant of the preferred embodiment of the invention. In this second variant of the preferred embodiment of the invention, the hybrid textile reinforcements of the carcass layer comprise a joint (A / N) consisting of a single multifilament filament made of aramid (A), and a single multifilament filament made of nylon (N), the filaments being wound together in a helically.

[0078] Figure 7 represents a section of a hybrid textile reinforcement for a carcass layer according to a third variant of the preferred embodiment of the invention. In this third variant, the hybrid textile reinforcements of the carcass layer comprise a (N+A / A / A) bond consisting of a core consisting of a Petition 870220061654, dated 07 / 13 / 2022, pp. 38 / 56 24 / 30 first multifilament filament made of nylon (N), and may be a layer comprising three secondary multifilament filaments made of aramid (A), the secondary filaments of the layer being wound together in a helix around the core. This type of hybrid textile reinforcement is usually called “Core Insertion” reinforcement.

[0079] Figure 8 represents the respective laws of behavior in extension of a carcass layer comprising hybrid textile reinforcements according to the embodiment variants shown in Figures 5 and 7, and of a carcass layer comprising prior art textile reinforcements taken as a reference. Each law of behavior represents the unit extension force F, expressed in daN / cm, applied to the carcass layer as a function of its relative elongation A, expressed in %. The law of behavior I1 relates to a carcass layer comprising hybrid textile reinforcements comprising a bond (A / A / N) consisting of two multifilament filaments made of aramid (A), and a single multifilament filament made of nylon (N), the filaments being wound together in a helix.Behavior law I2 relates to a carcass layer comprising hybrid textile reinforcements comprising a (N+A / A / A) bond consisting of a core made of a first multifilament filament made of nylon (N), and a layer comprising three second multifilament filaments made of aramid (A), the second layer filaments being wound together helically around the core. Behavior law E relates to a carcass layer comprising textile reinforcements comprising a (PET / PET) bond of two multifilament filaments made of PET (polyethylene terephthalate) type polyester of the reference state of the art.For the respective laws of behavior I1 and I2, the secant moduli M1 with the equivalent force developed by the carcass layer at 1% elongation are such that the ratios M1 / Fr of the secant modulus M1 to the tensile strength Fr of the carcass layer are respectively equal to 3.5 and 0.8, and therefore less than 4. The tensile strengths Fr are respectively equal to 775 daN / cm for I1 and 641 daN / cm for I2. The preceding values ​​should be compared with the reference state of the art for which the ratio M1 / Fr is equal to 7.7, for a tensile strength Fr equal to . Petition 870220061654, dated 07 / 13 / 2022, pp. 39 / 56 25 / 30 213 daN / cm. Thus, the carcass layers according to the invention have a secant modulus M1 at 1% lower elongation than the reference, and a higher tensile strength Fr, the latter being achieved for a relative elongation at break Ar at least 50% lower than that of the reference.

[0080] The invention was more specifically studied for an agricultural vehicle tire with dimensions 710 / 70R42 VF, meaning that, according to the ETRTO standard definitions, it has a section width S = 210 mm, a section height to section width ratio H / S = 70%, and a mounting rim with a diameter Dj = 42 inches = 166.8 mm. This tire is, moreover, a “VF” (Very High Flexion) tire. From the preceding characteristics, it is possible to deduce the outer radius of the tire R = Rj + H, with Rj, the rim radius, equal to Dj / 2 = 533.4 mm and H = 0.7*S ​​= 497 mm. With these assumptions, R is equal to 533.4 + 497 = 1030.4 mm. Taking Cs*Pmax equal to 1000 kPa, the limiting reference resistance Fs is equal to Fs = (Cs*Pmax*10-3)*((R2- ((R + Rj) / 2)2) / 2) / Rj = 103*10-3*((1030.42-((1030.4 + 533.4) / 2)2) / 2)533.4 = 422 daN / cm.Therefore, the reinforcement cage, consisting of a single layer of casing, must have a measured thickness E of at most 2 mm and a tensile strength Fr of at least Fs = 422 daN / cm.

[0081] Table 1 below presents the characteristics of the respective textile reinforcements of the compared carcass layers, which correspond to that of which the laws of behavior are presented in Figure 8, namely the reference carcass layer with textile reinforcements comprising a bond of 2 filaments made of PET, a carcass layer according to a first embodiment I1 with hybrid textile reinforcements comprising a bond consisting of two multifilament filaments made of aramid, and a single multifilament filament made of nylon, and a carcass layer according to the second embodiment I2 with hybrid textile reinforcements comprising a bond consisting of a core consisting of a first multifilament filament made of nylon, and a layer comprising three second multifilament filaments made of aramid. Petition 870220061654, dated 07 / 13 / 2022, pp. 40 / 56 26 / 30 [TABLE 1] Carcass layer E 11 I2 Filament nature PET / PET Aramid / Aramid / Nylon Nylon / 1 + Aramid / 3 Filament counts (tex) 144 / 144 330 / 330 / 188 47 + 167 / 167 / 167 Filament twists T (turns / m) 420 / 420 270 / 270 340 + 315 / 315 Twist factor K 192 212 196 Density (number of reinforcements / dm) 120 67 81 Reinforcement diameter d (mm) 0.62 mm 1.11 mm 0.92 mm Layer thickness Et (mm) 1.41 mm 1.90 mm 1.80 mm d / Et ratio 0.44 0.58 0.51

[0082] Definition of the characteristics of table 1: - Filament count (tex): mass in g of a multifilament filament with a length of 10000 m (1 tex = 1 g / 10000 m). - Filament twist T (turns / m): number of twist turns applied. The 1st value is the twist applied to a multifilament filament according to a first twist direction S, and the 2nd value is the twist applied to the joining of elementary multifilament filaments according to a second twist direction Z, the inverse of the preceding one. - Twist factor K: the twist factor K is defined by the relation K = T x [(Title / (1000.p)]1 / 2, in which the twist T of the joining of elementary multifilament filaments, i.e., of the reinforcement, is expressed in number of turns per meter, the title of the reinforcement is expressed in tex (mass in g of a reinforcing element that has a Petition 870220061654, dated 07 / 13 / 2022, pp. 41 / 56 27 / 30 length equal to 10000 m), and finally p is the density or volumetric mass (in g / cm3) of the material (for example: approximately 1.50 g / cm3 for cellulose, 1.44 g / cm3 for aramid, 1.38 g / cm3 for polyester such as PET, 1.14 g / cm3 for nylon). In the case of a hybrid reinforcement, p is an average of the densities weighted by the respective counts of the reinforcing element materials. - Density (number of reinforcements / dm): Number of reinforcements per dm of carcass layer; It is the inverse of the P pitch, which separates the centerlines of two consecutive reinforcements. - Reinforcement diameter d (mm): Diameter of the circle circumscribed around the junction of multifilament strands that constitutes the reinforcement. - Layer thickness Et (mm): Total thickness of the carcass layer, equal to the sum of the reinforcement diameter and the thicknesses of the elastomeric mixture, known as the calendering thickness, that coats the reinforcements on both sides. The leveled thickness E of the carcass layer is equal to the diameter d of the reinforcement.

[0083] Table 2 below presents, for a carcass layer according to reference E, as well as for the respective carcass layers according to embodiments I1 and I2 of the invention, the following mechanical characteristics: [TABLE 2] Carcass layer E 11 I2 Tensile strength Fr of a carcass layer (daN / cm) 213 daN / cm 775 daN / cm 641 daN / cm Ratio M1 / Fr of secant modulus M1 at 1% elongation versus tensile strength Fr of the carcass layer 7.70 3.53 0.82

[0084] The reference pneumatic tire, comprising a casing armature with three casing layers, each casing layer having the characteristics of Petition 870220061654, dated 07 / 13 / 2022, pp. 42 / 56 Reference 28 / 30 E from Tables 1 and 2 is compared with two pneumatic tires comprising a single-layer casing armor, which exhibits the characteristics of variants I1 and I2 from Tables 1 and 2. Table 3 below presents this comparison: [TABLE 3] Pneumatic E 11 I2 Number of carcass layers 3 3 1 Total thickness of carcass reinforcement 4.23 mm 1.90 mm 1.80 mm Level thickness E of single-layer carcass reinforcement (mm) Without object 1.11 mm 0.92 mm Total rupture strength of carcass reinforcement (daN / cm) 638 daN / cm 775 daN / cm 641 daN / cm

[0085] Table 3 shows that the carcass reinforcements of variants I1 and I2 satisfy well the two essential characteristics of the invention: an average thickness E of less than 2 mm, and even less than 1.2 mm, and a tensile strength Fr greater than the limit reference strength Fs = 422 daN / cm.

[0086] Table 4 below presents the combined top armor and sculpture characteristics with the carcass armor characteristics, for reference E and embodiment variant I1. [TABLE 4] Features Reference E (710 / 70R42 IF 179D Michelin AXIOBIB) Invention 11 (710 / 70R42 VF179D) Number of carcass layers 3 1 Petition 870220061654, dated 07 / 13 / 2022, pp. 43 / 56 29 / 30 Nature of the carcass reinforcements PET / PET Aramid / Aramid / Nylon Number of top layers 6 2 Nature of the top layer reinforcements Bonding of 3 rayon wires, each with a diameter of 0.94 mm Elastic metallic reinforcement 24.26, consisting of 24 steel wires, each with a unit diameter of 26 / 100 mm, divided into 4 cords of 6 wires Overall volumetric notching ratio TEV of the tread > 65% < 50% Average radial height H of the tread 65 mm 45 mm Tread pattern type Bar pattern Block pattern comprising 4 longitudinal voids, axially positioned on either side of the median equatorial plane of the tire, the two intermediate longitudinal voids being spaced axially 370 mm apart and the two longitudinal voids axially exterior being spaced a distance apart Petition 870220061654, dated July 13, 2022, pp. 44-56 30 / 30 axial igual a 568 mm

[0087] The reduction in structural rigidity of the tire, aimed at by the inventors and obtained thanks to a single-layer carcass reinforcement as proposed by the invention, can be further enhanced by combining said single-layer carcass reinforcement with a top reinforcement and a tread of smaller thicknesses than those of the reference tire. Thus, the top reinforcement advantageously comprises two top layers with elastic metal reinforcements, instead of six layers of textile reinforcements made of rayon. On the other hand, the traditional tread with a bar pattern also advantageously comprises a pattern with blocks of lower radial height (45 mm instead of 65 mm), and therefore thinner, but with a lower volumetric notch ratio (less than 50% instead of greater than 60%), and therefore more closed.This block sculpture finally comprises two longitudinally axially external voids sufficiently spaced apart (568 mm) to ensure a hinge function that guarantees the facilitated flattening of the tread. Petition 870220061654, dated 07 / 13 / 2022, pages 45 / 56

Claims

1 / 5 CLAIMS 1. A tire (1) for an agricultural vehicle, intended to be mounted on a rim (5) having a nominal diameter Dj, defined as the “nominal rim diameter” in the section dedicated to “Agricultural Equipment Tires” in the “Standards Manual - 2018” of the ETRTO standard, and to be inflated to a minimum recommended pressure of at most 240 kPa, having an outer diameter D, defined as the “total design diameter” in the section dedicated to “Agricultural Equipment Tires” in the “Standards Manual - 2018” of the ETRTO standard, and comprising, radially from the outside to the inside, a tread (2), a top reinforcement (3) and a carcass reinforcement (4): - the tread (2) comprising tread elements (22) separated from each other by voids (23) and having a radial height H of at least 20 mm and at most 60 mm,measured between a tread surface (25) and a bearing surface (24) parallel to the tread surface (25) and tangent to the bottoms of the deepest voids, - the tread (2), which has an axial width L, comprising at least two axially external voids (231), each of which has a centerline that forms with a circumferential direction (XX') of the tire an angle of at most 45°, positioned on either side of an equatorial plane (XZ) that passes through the middle of the tread (2) and which are separated by an average axial distance L1 at least equal to 0.5*L, - the tread (2) having an overall volumetric notch ratio TEV, defined as the ratio between the volume VC of voids (23) and the total volume V of the tread (2) assumed without voids, comprised between the bearing surface (24) and the surface of running (25), at least equal to 30% and at most equal to 60%,- the top armor (3) comprising at least two top layers (31, 32), each comprising reinforcements coated with an elastomer-based material, parallel to each other, crossed from one layer to the next, and forming, with the circumferential direction (XX') of the tire, an angle by Petition 870250110600, of 02 / 12 / 2025, page. 11 / 20 2 / 5 less than or equal to 10°, - the carcass reinforcement (4) comprising at least one carcass layer (41), comprising textile reinforcements coated with an elastomer-based material, parallel to each other, and forming, with the circumferential direction (XX') of the tire, an angle at least equal to 75° and at most equal to 105°, characterized in that the carcass reinforcement (4) is constituted by a single carcass layer (41) that has an average thickness E at most equal to 2 mm and a rupture resistance Fr, expressed in daN / cm, which verifies the relation: Fr >= Fs = (Cs*Pmax*10-3)*((R2 - ((R + Rj) / 2)2)2) / Rj, with - FCr / P,FCr being the breaking strength, expressed in daN, of a textile reinforcement, and defined as the limit strength of the "Force-Elongation" curve of the textile reinforcement, obtained under the conditions of the ASTM D 885 / D 885M - 10a standard of 2014, and P being the spacing between the distance between the respective neutral axes of two consecutive reinforcements, - Fs: limit reference resistance (in daN / cm), - Cs: safety factor at least equal to 1, - Pmax: maximum recommended inflation pressure (in kPa), - R = D / 2: outer radius of the tire (in mm), - Rj = Dj / 2: nominal radius of the rim (in mm).

2. Pneumatic (1) according to claim 1, characterized in that Cs*Pmax is at least equal to 1000 kPa.

3. Pneumatic (1) according to claim 1 or 2, characterized in that Cs*Pmax is at least equal to 1500 kPa.

4. Pneumatic (1) according to any one of claims 1 to 3, characterized in that the average thickness E of the carcass layer (41) is at most equal to 1.2 mm.

5. Pneumatic (1) according to any one of claims 1 to 4, characterized in that the textile reinforcements of the single carcass layer (41) comprise a joint consisting of at least one multifilament filament made of aromatic polyamide or aromatic copolyamide and / or made of aliphatic polyamide Petition 870250110600, dated 02 / 12 / 2025, page 12 / 20 3 / 5 and / or made of polyester and / or made of cellulose.

6. Pneumatic (1) according to any one of claims 1 to 5, characterized in that the textile reinforcements of the single carcass layer (41) are hybrid textile reinforcements comprising a bond consisting of at least one multifilament filament made of aromatic polyamide or aromatic copolyamide and at least one multifilament filament made of aliphatic polyamide.

7. Tire (1) according to claim 5 or 6, characterized in that the carcass layer (41), in its vulcanized state and extracted from the tire, has a behavior law in extension that has a secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation, such that the ratio M1 / Fr of the secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation over the tensile strength Fr of the carcass layer is strictly less than 7, preferably less than or equal to 5, and more preferably less than or equal to 4.

8. Pneumatic (1) according to claim 7, characterized in that the ratio M1 / Fr of the secant modulus M1 with the equivalent force developed by the carcass layer at 1% elongation over the tensile strength Fr of the carcass layer is greater than or equal to 0.

5.

9. Pneumatic (1) according to any one of claims 5 to 8, characterized in that the hybrid textile reinforcements of the carcass layer (41) comprise a joint consisting of two multifilament filaments made of aromatic polyamide or aromatic copolyamide, and a single multifilament filament made of aliphatic polyamide, the filaments being wound together in a helically.

10. Pneumatic (1) according to any one of claims 5 to 8, characterized in that the hybrid textile reinforcements of the carcass layer (41) comprise a bond consisting of a single multifilament filament made of aromatic polyamide or aromatic copolyamide, and a single multifilament filament made of aliphatic polyamide, the filaments being wound together in a helically. Petition 870250110600, dated 02 / 12 / 2025, p. 13 / 20 4 / 5 11. Pneumatic (1) according to any one of claims 5 to 8, characterized in that the hybrid textile reinforcements of the carcass layer (41) comprise a joint consisting of a core consisting of a first multifilament filament made of aliphatic polyamide, and a layer comprising at least two second multifilament filaments made of aromatic polyamide or aromatic copolyamide, the second layer filaments being wound together helically around the core.

12. Pneumatic (1) according to any one of claims 1 to 11, each top layer (31, 32) having a behavior law in extension defined by a secant modulus at rupture M'=F'r / A'r (in daN / cm / %), F'r being the rupture strength of the top layer (in daN / cm) and A'r its elongation at rupture (in %), characterized in that the top reinforcement (3) comprising at least two top layers (31, 32), each having a secant modulus at rupture M', has a resultant modulus at rupture M's, defined as the sum of the secant moduli at rupture M' of the set of top layers, at least equal to 150 daN / cm / %, preferably at least equal to 300 daN / cm / %.

13. Pneumatic (1) according to claim 12, characterized in that the reinforcements of at least two top layers (31, 32) of the top armor (3) are metallic.

14. Pneumatic (1) according to claim 13, characterized in that the metallic reinforcements of at least two top layers (31, 32) of the top reinforcement (3) have a bielastic behavior law comprising a first portion having a first extension modulus MG1 at most equal to 30 GPa, and a second portion having a second extension modulus MG2 at least equal to 2 times the first extension modulus MG1, said extension behavior law being determined, based on ISO 6892 of 1984, for a metallic reinforcement coated with an elastomeric mixture having an extension modulus of elasticity at 10% elongation MA10, determined from tensile tests performed in accordance with French standard NF T 46-002 of September 1988, at least equal to 5 MPa and at most equal to 15 MPa, and in which all metallic reinforcement of Petition 870250110600, of 02 / 12 / 2025, page.14 / 20 5 / 5 top layer (31,32) has a compression behavior law, defined by a critical buckling strain in compression E0 at least equal to 3%, said compression behavior law being determined on a test specimen consisting of a reinforcement placed in its center and covered by a parallelepiped volume of elastomeric mixture that has a modulus of elasticity in extension at 10% elongation MA10 at least equal to 5 MPa and at most equal to 15 MPa.

15. Pneumatic (1) according to claim 14, characterized in that the entire top layer metallic reinforcement (31, 32) is a 1xN structure multi-strand cable comprising a single layer of N strands, each strand comprising an inner layer of M helically wound inner strands and an outer layer of P helically wound outer strands around the inner layer. Petition 870250110600, dated 02 / 12 / 2025, page 15 / 20

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