RU2818380C1 - Tire for agricultural vehicle comprising hybrid carcass reinforcing element - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: tire (10) contains at least one carcass layer (28), which contains one or more reinforcing elements (36). Tire (10) is obtained using a method comprising a step of manufacturing each carcass layer (28), in which one or more glued frame reinforcing elements (36) are immersed in the polymer composition to form each uncured frame layer (27), wherein the ratio of the tangent modulus at the equivalent force generated by the green layer at 7% elongation to the secant modulus at the equivalent force generated by the green layer at 1% elongation is greater than or equal to 2.00. Density of carcass reinforcing elements (36) in uncured carcass layer (27) is from 50 to 150 carcass reinforcing elements (36) per decimetre of uncured carcass layer (27), and each frame reinforcing element (36) forms an angle greater than or equal to 85°, with tire circumferential direction Z (10).

EFFECT: improved tire performance.

14 cl, 8 dwg, 4 tbl

Description

[001] The invention relates to a tire for an agricultural vehicle.

[002] A tire for agricultural vehicles is known from the prior art, sold under the Michelin brand and belonging to the AxioBib range, and the specified tire has the following dimensional characteristics: 710/70R42. Such a tire contains two beads, each of which contains at least one annular reinforcing structure and frame reinforcement fixed in each of the beads by bending around the annular reinforcing structure. Frame reinforcement contains three frame layers, each of which contains a plurality of frame reinforcing elements. Each frame reinforcement element contains a knot consisting of two multi-filament polyester strands wound together in a spiral around each other.

[003] An agricultural vehicle tire is produced by a method comprising the step of manufacturing each carcass ply, in which bonded carcass reinforcing elements are embedded in a polymer composition to form each uncured carcass ply.

[004] Due to the use of PET and the number of carcass plies, such a prior art tire is difficult to manufacture due to its green moldability and three carcass plies. In particular, the carcass reinforcement must, due to its properties in the uncured state, allow radial expansion and therefore elongation around the circumference of the tire in order to prevent radial and circumferential deformations imposed on the tire during its manufacture. Radial and circumferential strains are applied during tire curing, during which the tire expands radially and circumferentially, for example by pressurizing an inflatable membrane, to be pressed against the surfaces of the curing mold. These deformations are especially significant in agriculture due to the high tread height of the tire that must be molded.

[005] Moreover, the same prior art tire has, thanks to the use of PET, a cornering rigidity that is highly improveable. In particular, this problem is especially acute in the case of agricultural vehicle tires, which are lightly inflated during use in order to reduce compaction of loose soil in the field.

[006] The object of the present invention is to provide a tire for an agricultural vehicle that provides significant traction force by:

- improving formability in the uncured state, and

- improved cornering rigidity,

while providing the same characteristics as the prior art tire, namely the tire's tensile strength.

[007] To this end, an object of the invention is a tire for an agricultural vehicle comprising two beads, each of which has at least one annular reinforcing structure and a frame reinforcement secured in each of the beads by rotation around the annular reinforcing structure, the frame reinforcement comprising at least one frame layer containing one or more frame reinforcing elements, each frame reinforcing element comprising:

- a unit consisting of two multifilament threads of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide, the threads being wound together in a spiral to form a layer; or

- a knot consisting of one multifilament thread of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide,

moreover, the threads are wound together in a spiral around one another; or

- a core consisting of a first multifilament filament of an aliphatic polyamide, and a layer containing at least two second multifilament filaments of an aromatic polyamide or aromatic copolyamide, the second filament filaments of the layer being wound together in a spiral around the core;

wherein the tire is produced by a method comprising the step of manufacturing each carcass ply, in which carcass reinforcing element(s) bonded in a polymer composition are incorporated to form each uncured carcass ply, wherein the ratio of the tangent modulus at the equivalent force generated by the uncured ply at 7% elongation , to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation, greater than or equal to 2.00.

[008] Thus, the use of a hybrid carcass reinforcement element containing an assembly of one or two multifilament yarns made of an aromatic polyamide or aromatic copolyamide and a multifilament yarn made of an aliphatic polyamide will reduce the secant modulus at the equivalent force generated by the uncured layer, at 1% elongation relative to the breaking force of the carcass, compared with the breaking force of the prior art tire and thus will improve the formability of the tire in the uncured state.

[009] In addition, the use of this hybrid carcass reinforcement element will allow the tangential modulus at the equivalent force generated by the uncured ply at 7% elongation, relative to the carcass breaking force, to be relatively high compared to that of a prior art tire, thereby significantly improving cornering rigidity.

[010] Thus, above the selected ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation, the hybrid carcass layer of the tire according to the invention will improve its formability in the uncured condition and its cornering stiffness compared to a prior art tire, while providing the same characteristics as the latter, namely the tire's tensile strength.

[011] In FIG. 1 shows the force-elongation curve of uncured carcass layers containing tire carcass reinforcements of the prior art and uncured carcass layers of tire reinforcements according to the invention. This curve reflects what happens to an agricultural tire during its shaping when the carcass is under low load, i.e., subject to slight deformation, and when it is under the highest tensile load of the carcass when the tire is moving, i.e. has a significant elongation. One result of using a hybrid reinforcement element comprising an aromatic polyamide or aromatic copolyamide monofilament assembly and an aliphatic polyamide monofilament is to produce a bimodulus curve, that is, one that has a relatively low modulus at small strains and a relatively high modulus at large strains. In particular, the uncured carcass layer has a relatively low modulus at small deformations, in this case controlled by the modulus of the aliphatic polyamide filament, which provides good tire shape. In addition, the uncured carcass layer has a relatively high modulus under large deformations, in this case controlled by the modulus of the aromatic polyamide or aromatic copolyamide yarn(s), which allows for improved cornering rigidity of the tire at high loads.

[012] It should be recalled that, as is well known, a fiber made from an aromatic polyamide or an aromatic copolyamide is a fiber of linear macromolecules formed from aromatic groups held together by amide bonds, at least 85% of which are directly linked to the two aromatic cores, and more specifically poly(p-phenylene terephthalamide) (or PPTA) fibers, which have been manufactured for a very long time from optically anisotropic spinning compositions. Among the aromatic polyamides or aromatic copolyamides, mention may be made of polyarylamides (or PAA, in particular known under the trade name Ixef from Solvay), poly(methoxylylenadipamide), polyphthalamides (or PPA, in particular known under the trade name Amodel from Solvay), amorphous semi-aromatic polyamides (or PA 6-3T, in particular known under the trade name Trogamid from Evonik), meta-aramids (or poly(metaphenylene isophthalamide) or PA MPD-I, in particular known under the trade name Nomex from Du Pont de Nemours) or para-aramids (or poly(paraphenylene terephthalamide) or PA PPD-T, in particular known under the trade name Kevlar of Du Pont de Nemours or the trade name Twaron of Teijin).

[013] By fiber made from aliphatic polyamide is meant a fiber of linear macromolecules of polymers or copolymers containing amide functions, which do not have aromatic rings and can be synthesized by polycondensation between a carboxylic acid and an amine. Among the aliphatic polyamides, mention may be made of nylons PA4.6, PA6, PA6.6 or PA6.10, and in particular Zytel from DuPont, Technyl from Solvay or Rilsamid from Arkema.

[014] A reinforcing element in its natural state is an element in which the constituent material(s) of the reinforcing element are made without any coating having an adhesive function covering the material or materials. Thus, the reinforcing element in its natural state may be uncoated, which means that the constituent material(s) of the reinforcing element are not coated with any coating or possibly sized, that is, coated with a sizing composition having, in particular, lightweighting functions sliding of the constituent material(s) of the reinforcing element during its manufacture and preventing the accumulation of electrostatic charges.

[015] By bonded carcass reinforcement member, it is meant that during the manufacture of the carcass reinforcement member, the assembly consisting of the constituent multi-filament threads of the carcass reinforcement member is coated with a coating having a bonding function.

[016] Thus, in the first embodiment, the multifilament yarns are assembled to form a bobbin reinforcement member in the natural state, the bobbin reinforcement fiber member in the natural state is coated with an outer layer of a thermally cross-linkable adhesive composition, and the carcass reinforcement member in the natural state is coated with an outer layer , is heat treated to crosslink the adhesive composition to form a bonded frame reinforcement member.

[017] In a second embodiment of the invention, the native frame reinforcement member is coated with an intermediate layer of a first thermally cross-linkable adhesive composition, the native frame reinforcement member coated with the intermediate layer is thermally treated to crosslink the first adhesive composition to form a pre-bonded frame reinforcement member. , the pre-bonded frame reinforcement element is coated with an outer layer of a second thermally cross-linkable adhesive composition, and the pre-bonded frame reinforcement element coated with the outer layer is thermally treated to cross-link the second adhesive composition to form a bonded frame reinforcement element.

[018] In a preferred embodiment of the invention, this coating is an adhesive composition. Such an adhesive composition is, for example, of the RFL (resorcinol-formaldehyde-latex) type.

[019] By uncured framework layer is meant the composite formed when bonded framework reinforcement element(s) are embedded in a polymer composition. In other words, it is the composite that forms the carcass layer before molding the tire, and in it the polymer composition has not yet been cross-linked.

[020] By polymer composition is meant a composition comprising at least one elastomer, preferably a diene elastomer, for example natural rubber, and a reinforcing filler, for example carbon black and/or silica, and a crosslinking system, for example a vulcanizing system, preferably containing sulfur .

[021] The secant modulus at the equivalent force developed by the uncured layer at 1% elongation means the gradient of a straight line connecting the beginning of the force-elongation curve obtained under the conditions of ASTM D 885/D 885M - 10a of 2014 at the 1% abscissa point the same curve, which occurs immediately after a standard pre-stretch of 0.5 cN/tex on the reinforcing element. In the case of a bonded reinforcing textile fiber element, the secant modulus is measured immediately before the step of embedding the carcass reinforcing textile fiber element into the carcass layer, that is, without any other step that changes the properties of the secant module occurring between its final heat treatment step and the embedding step. Thus, the secant modulus measured before the step of manufacturing the frame layer is measured after one or more steps of coating the reinforcing textile fiber element in its natural state with one or more layers of one or more crosslinkable adhesive compositions and after one or more steps of heat treating the reinforcing textile fiber element in in its natural state, coated with one or more layers to cross-link the adhesive composition(s) to form a bonded reinforcing textile fiber element.

[022] By tangent modulus at the equivalent force developed by the uncured layer at 7% elongation, is meant the tangent modulus which is the result of calculating the derivative of the force-elongation curve obtained from the force-elongation curve obtained by applying ASTM D 885/D 885M - 10a from 2014 at 7% elongation. In the case of a bonded reinforcing textile fiber element, the tangent modulus is measured immediately before the step of embedding the frame reinforcing textile fiber element into the frame layer, that is, without any other step that changes the properties of the tangent modulus occurring between its final heat treatment step and the embedding step. Thus, the tangent modulus measured before the step of manufacturing the frame layer is measured after one or more steps of coating the reinforcing textile fiber element in its natural state with one or more layers of one or more crosslinkable adhesive compositions and after one or more steps of heat treating the reinforcing textile fiber element in in its natural state, coated with one or more layers to cross-link the adhesive composition(s) to form a bonded reinforcing textile fiber element.

[023] Preferably, after the embedding step, the method comprises the step of laying the framework layer so as to form the surface as substantially a cylinder of rotation about an axis, and then the step of shaping the framework layer, during which at least a portion of the framework layer is moved in a radial direction from the axis frame layer and extends around the circumference.

[024] In one preferred embodiment of the invention, the bonded carcass reinforcing element(s) of the uncured carcass layer are parallel to each other before the laying and molding step.

[025] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is less than or equal to 30.00, preferably less than or equal to 27.00 or more preferably less than or equal to 24.00.

[026] Thus, in this range of modulus ratios ranging from 2.00 to 30.00, the tire will have good formability and improved cornering rigidity.

[027] Preferably, the ratio of the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the force at break of the uncured framework layer is strictly less than 7.00, preferably less than or equal to 5.00, and more preferably less than or equal to 4.00 .

[028] Preferably, the ratio of the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the force at break of the uncured framework layer is greater than or equal to 0.50.

[029] Thus, in this range of ratios of secant modulus at the equivalent force developed by the uncured layer at 1% elongation to the force at rupture of the carcass layer, the small strain modulus is reduced compared to the small strain modulus of the prior art frame reinforcement element, containing two strands of polyester, due to the presence of an aliphatic polyamide strand in the hybrid, which allows the curvature of the force-elongation curve of the uncured carcass layer to be reversed compared to the force-elongation curve of the uncured carcass layer of the prior art and, therefore, to reduce the modulus, thereby thus ensuring good shaping of the tire. One skilled in the art will know how to select a ratio of secant modulus at the equivalent force developed by the uncured ply at 1% elongation to the breaking force of the uncured carcass ply that is high enough to facilitate placement of the uncured ply into the tire.

[030] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured carcass layer is strictly greater than 6.00 and preferably greater than or equal to 7.00.

[031] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured carcass layer is strictly less than 30.00, preferably less than or equal to 25.00, and more preferably less than or equal to 22.00.

[032] Thus, in this range of ratios of tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the force at break of the carcass layer, the modulus at large strains is relatively high compared to that of the prior art uncured carcass layer containing two strands of polyester, due to the presence of a hybrid, which allows for significantly improved cornering rigidity. With large deformations, the tire according to the invention turns. The ratio of the tangential modulus at the equivalent force generated by the uncured ply at 7% elongation to the breaking force of the uncured carcass must be high enough so that the tire does not deform excessively but rather rotates the vehicle under load.

[033] The expression “twist balanced” in the first and second embodiments of the invention should be understood to mean that the multifilament yarns are wound with substantially identical twist and that the twist of the monofilaments of each multifilament yarn in the final assembly is substantially zero. In particular, the method of making these frame reinforcements, which is well known in the art, comprises a first step in which each monofilament yarn (more properly called a "strand of yarn") is first twisted individually on itself (with an initial twist of R1', R2' , R3', where R1'=R2'=R3') in a given direction D'=D1'=D2'=D3' (direction S or Z, respectively, according to generally accepted terminology denoting the orientation of the turns relative to the transverse rod S or Z) to form a thread or twist (more properly called a "thread") in which the monofilaments are deformed into a spiral about the axis of the thread. Next, in the second step, the yarns are then twisted together with a final twist R4 such that R4=R1'=R2'=R3' in the direction D4 opposite to the direction D'=D1'=D2'=D3' (Z or S direction, respectively) to obtain a reinforcing element (more correctly called a "cord"). This reinforcing element is then called twist balanced because the monofilament yarns exhibit the same residual twist in the final reinforcing element since R1'=R2'=R3' and this residual twist is zero or substantially zero since R4=R1' =R2'=R3' and the direction D'=D1'=D2'=D3' is opposite to the direction D4. The expression "substantially zero residual twist" means that the residual twist is strictly less than 2.5% of the twist of R4.

First embodiment of the invention

[034] Preferably, the tire according to the first embodiment of the invention comprises at least one carcass ply comprising one or more carcass reinforcing elements, said or each carcass reinforcing element comprising an assembly consisting of:

- two multifilament yarns of aromatic polyamide or aromatic copolyamide, and

- multifilament thread of aliphatic polyamide;

wherein the threads are wound together in a spiral to form a layer.

[035] The expression "knot consisting of" is understood to mean that the knot does not contain a multifilament yarn other than two multifilament yarns of an aromatic polyamide or an aromatic copolyamide and an aliphatic polyamide.

[036] Preferably, the frame reinforcing element is twist balanced.

[037] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 4.00.

[038] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is less than or equal to 10.00, preferably less than or equal to 7.00 or more preferably less than or equal to 5.00.

[039] Preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is less than or equal to 5.00 and preferably less than or equal to 4.00.

[040] Preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is greater than or equal to 1.00, preferably greater than or equal to 2.00, and more preferably greater than or equal to 3.00 .

[041] Preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured framework layer is greater than or equal to 8.00, preferably greater than or equal to 10.00, and preferably greater than or equal to 13.00.

[042] Preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured framework layer is less than or equal to 18.00 and preferably less than or equal to 17.00.

Second embodiment of the invention

[043] Preferably, the tire according to the second embodiment of the invention comprises at least one carcass ply comprising one or more carcass reinforcing elements, said or each carcass reinforcing element comprising an assembly consisting of:

- multifilament yarn of aromatic polyamide or aromatic copolyamide; And

- multifilament thread of aliphatic polyamide;

with the threads wound together in a spiral, one around the other.

[044] Preferably, the frame reinforcing element is twist balanced.

[045] An aromatic polyamide or aromatic copolyamide multifilament yarn and an aliphatic polyamide multifilament yarn are collected together and wound spirally around each other.

[046] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 2.20.

[047] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is less than or equal to 4.00 and preferably less than or equal to 3.50.

[048] Preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the force at break of the uncured framework layer is less than or equal to 4.00.

[049] Preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is greater than or equal to 1.00 and preferably greater than or equal to 2.00.

[050] Preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured framework layer is greater than or equal to 6.00 and preferably greater than or equal to 7.00.

[051] Preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured framework layer is less than or equal to 12.00 and preferably less than or equal to 10.00.

Third embodiment of the invention

[052] Preferably, the tire according to the third embodiment of the invention comprises at least one carcass ply comprising one or more carcass reinforcing elements, said or each carcass reinforcing element comprising:

- a core consisting of a first multifilament filament of aliphatic polyamide, and

- a layer containing at least two second multifilament yarns of an aromatic polyamide or an aromatic copolyamide, the second yarns of the layer being wound in a spiral around a core.

[053] Preferably, the layer consists of three second multifilament yarns of an aromatic polyamide or an aromatic copolyamide.

[054] Such a frame reinforcing textile fiber element is commonly referred to as a “core insert.” The manufacturing method is described in particular in WO2019122698. In this way, the central core is inserted into the middle of the second threads of the layer, which are therefore peripheral and adjacent to them. Every second layer thread is wound around another second layer thread(s) without wrapping the core around the layer threads.

[055] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 5.00 and preferably greater than or equal to 6.00.

[056] Preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is less than or equal to 24.00.

[057] Preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is less than or equal to 4.00 and preferably less than or equal to 3.00.

[058] Preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the force at break of the uncured framework layer is greater than or equal to 0.60.

[059] Preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the force at break of the uncured framework layer is greater than or equal to 8.00.

[060] Preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured framework layer is less than or equal to 22.00 and preferably less than or equal to 20.00.

[061] The preferred features described below apply equally to all three embodiments of the invention described above.

[062] Preferably, the twist factor K of the frame reinforcing element is strictly greater than 150 and preferably greater than or equal to 180.

[063] The twist factor K is related to the twist T according to the following known relationship:

K = T x [(Number / (1000.ρ)]1/2

in which the twist T of the filaments is expressed in turns per meter, the quantity is expressed in tex (the mass in grams of 1000 meters of reinforcement), and finally ρ represents the density or mass per unit volume (in g/cm ³ ) of the material (e.g. about 1.50 g/cm ³ for cellulose, 1.44 g/cm ³ for aramid, 1.38 g/cm ³ for polyester such as PET, 1.14 g/cm ³ for nylon); in the case of a hybrid cord, ρ is of course the average of the densities weighted by the corresponding reinforcing element material numbers. As an example, for the first embodiment of the invention, for a reinforcing element comprising an assembly consisting of two multifilament yarns made of an aromatic polyamide, each numbered 330 tex, and a filament made of an aliphatic polyamide, numbered 188 tex, and in which the twist of the reinforcing element is 270 turns per meter, K is calculated as follows:

K=270x[(330+330+188)/(1000x(330x1.44+330X1.44+188x1.14)/(330+330+188))]1/2

K= 212

[064] The twist T of the reinforcing element can be measured using any method known to one skilled in the art, for example, in accordance with ASTM D 885/D 885M - 10a of 2014.

[065] The number (or linear density) of each thread is determined in accordance with ASTM D1423. The number is given in tex (weight in grams of 1000 m of product - as a reminder: 0.111 tex is equal to 1 denier).

[066] Preferably, the reinforcing element has a twist factor K such that it has a value sufficient to provide a good compromise between tensile modulus and breaking strength on the one hand, and fatigue and compression resistance on the other hand. This way the tire will exhibit a good compromise between cornering stiffness and fatigue resistance.

[067] Preferably, the number of the aromatic polyamide or aromatic copolyamide multifilament yarn(s) is greater than or equal to 55 tex, preferably greater than or equal to 70 tex, more preferably greater than or equal to 90 tex, and even more preferably greater than or equal to 110 tex.

[068] Preferably, the number of aromatic polyamide or aromatic copolyamide multifilament yarn(s) is less than or equal to 500 tex, preferably less than or equal to 400 tex, and more preferably less than or equal to 340 tex.

[069] Preferably, the aliphatic polyamide multifilament yarn number is greater than or equal to 20 tex, preferably greater than or equal to 30 tex, and more preferably greater than or equal to 40 tex.

[070] Preferably, the aliphatic polyamide multifilament yarn number is less than or equal to 300 tex, preferably less than or equal to 250 tex, more preferably less than or equal to 220 tex, and even more preferably less than or equal to 210 tex.

[071] Preferably, the twist of the frame reinforcing element (36) is from 240 to 500 turns per meter, and preferably from 260 to 480 turns per meter.

[072] For a given number, in this twist range, the tire of the invention has sufficient cornering rigidity for use in an agricultural vehicle tire.

[073] In the above range of twist ratios, when using numbers lower than the ranges described above, the carcass reinforcing elements will exhibit relatively high twist, resulting in a burst force that is too low and therefore a risk of burst pressure. Thus, the modulus will be too low, which will lead to a drop in cornering rigidity. Conversely, when using numbers above the ranges described above, the carcass reinforcement will exhibit relatively low twist and this will result in a risk of compressive fatigue. Thus, the number ranges described above for aromatic polyamide or aromatic copolyamide and aliphatic polyamide multifilament yarns provide a good compromise between breaking strength and cornering stiffness.

[074] According to the invention, the density of frame reinforcements in the uncured frame layer is from 50 to 150 frame reinforcements per decimeter of uncured frame layer.

[075] Preferably, the density of frame reinforcements in the uncured frame layer is from 60 to 140 frame reinforcements per decimeter of uncured frame layer.

[076] The density of bonded frame reinforcement elements in the uncured framework layer is the number of bonded frame reinforcement elements included in one decimeter of the uncured framework layer in a direction perpendicular to the direction in which the bonded framework reinforcement element(s) run parallel to each other.

[077] In these carcass reinforcement density ranges, the carcass layer exhibits relatively high tensile strength, allowing it to be used in agricultural vehicle tires.

[078] Preferably, the diameter d of the frame reinforcing element is less than or equal to 2.0 mm, preferably less than or equal to 1.8 mm, more preferably less than or equal to 1.5 mm, and even more preferably less than or equal to 1.2 mm. The reinforcing element extends in the general direction G, and the diameter of the reinforcing element is the diameter at which the reinforcing element is inscribed in a section plane perpendicular to the direction G.

[079] Preferably, the thickness E of the uncured carcass layer is less than or equal to 3.00 mm, preferably less than or equal to 2.50 mm, and more preferably less than or equal to 2.00 mm. The thickness of the uncured framework layer is the shortest distance between the two outer surfaces of the uncured framework layer, namely the distance measured in a direction perpendicular to the two outer surfaces of the uncured framework layer.

[080] Preferably, the d/E ratio is strictly less than 0.65 and preferably less than or equal to 0.62. In this way, the thickness of the uncured carcass layer and hence the hysteresis of the tires are reduced so as to reduce the energy consumption of vehicles equipped with such tires.

[081] Preferably, the breaking force of the frame reinforcing element is greater than or equal to 70 daN, preferably greater than or equal to 110 daN.

[082] Preferably, the tensile strength of the carcass layer is greater than or equal to 500 daN/cm.

[083] The force at break of the layer is calculated from the force-elongation curve obtained by applying ASTM D 885/D 885M - 10a from 2014 to the frame reinforcement element. The tensile strength of the carcass layer is determined by multiplying the tensile strength of the carcass reinforcing element by the number of carcass reinforcing elements per 1 cm of carcass layer, this number being determined in a direction perpendicular to the direction in which the carcass reinforcing elements extend in the carcass layer.

[084] According to the invention, the frame reinforcement consists of one or two frame layers.

[085] One skilled in the art will know how to select the number of carcass plies in accordance with the breaking force of the carcass reinforcement that is required depending on the size of the agricultural vehicle tire.

[086] Preferably, the frame reinforcement is made of a frame layer.

[087] According to the invention, each carcass reinforcing element forms an angle greater than or equal to 85° with the circumferential Z direction of the tire.

[088] Preferably, each carcass reinforcing element forms an angle in the range of 85° to 95° with the circumferential Z direction of the tire.

[089] In the specification and claims, any range of values denoted by the expression "between a and b" is a range of values extending from more than a to less than b (that is, excluding the end points a and b), whereas any range values denoted by the expression "a to b" means the range of values extending from the end point "a" to the end point "b", that is, including the strict end points "a" and "b".

[090] The expression "axial direction" means a direction substantially parallel to the axis of rotation of the tire.

[091] The expression "circumferential direction" means a direction that is substantially perpendicular to both the axial direction and the radius of the tire (in other words, tangent to a circle centered on the axis of rotation of the tire).

[092] The expression "radial direction" means a direction along the radius of the tire, namely any direction that intersects the axis of rotation of the tire and is substantially perpendicular to that axis.

[093] The expression "median plane" (denoted M) means a plane perpendicular to the axis of rotation of the tire, which is located midway between the two beads and passes through the middle of the crown reinforcement.

[094] The invention will be better understood in light of the following description, which is given solely by way of non-limiting example and with reference to the drawings, in which:

- fig. 1 illustrates the force-elongation curves of a prior art carcass reinforcement element and a tire according to the invention;

- fig. 2 is a radial sectional view of a tire for an agricultural vehicle according to the invention;

- fig. 3 is a detailed cross-sectional view of zone II of the tire of FIG. 2;

- fig. 4 illustrates an uncured carcass layer to produce the tire carcass layer of FIG. 2;

- fig. 5 is a sectional view in the V-V' plane of the uncured carcass layer of FIG. 4;

- fig. 6 is an enlarged cross-sectional view of a reinforcing element in accordance with the first embodiment of the invention;

- fig. 7 is an enlarged cross-sectional view of a reinforcing element in accordance with a second embodiment of the invention; And

- fig. 8 is an enlarged cross-sectional view of a reinforcing member in accordance with a third embodiment of the invention.

EXAMPLE OF A TIRE IN ACCORDANCE WITH THE FIRST EMBODIMENT OF THE INVENTION

[095] In FIG. 2 and 3 show the X, Y, Z directions corresponding to the axial (X), radial (Y) and circumferential (Z) orientation of the tire.

[096] In FIG. 2 and 3 show an example of a tire according to the invention, generally designated 10. The tire 10 is intended for an agricultural vehicle. In this particular case, the tire 10 is for a tractor.

[097] Tire 10 has a nominal rim diameter, defined by ETRTO, between 24 and 54 inches, including the end points (between 60.96 and 137.16 cm). The nominal height to width ratio of the tire 10, as defined by ETROC, is between 0.7 and 0.9, including the end points.

[098] The tire 10 has a crown 12 containing a crown reinforcement 14 containing one or more crown layers 16 of reinforcing elements. The crown reinforcement 14 is surmounted by the tread 18. The crown reinforcement 14 is located radially on the inner side of the tread 18. Two side walls 20 extend the crown 12 radially inward. The tire 10 has two beads 22 radially on the inner side of the side walls 20, each of which has an annular reinforcing structure 24.

[099] The tire 10 also has a radial carcass reinforcement 26. The carcass reinforcement 26 extends from the beads 22 through the sidewalls 20 to the crown 12. The carcass reinforcement 26 has one or more carcass layers 28 containing a plurality of carcass reinforcing elements 36, with at least one of these carcass layers 28 is secured in each of the beads 22 by folding 30 around the annular reinforcing structure 24 so as to form in each of the beads 22 a warp thread 32 extending radially between each bead 22 through the side walls 20 and the crown 12 and thread a fold 34 extending radially from each bead 22 through each side wall 20, with the radially outer end 36 of the fold strand 34 located radially on the outer side of the annular reinforcing structure 24 and axially on the outer side of the warp thread 32. In this case, the frame reinforcement 26 contains one frame layer 28, which means that the frame reinforcement 26 consists of a frame layer 28.

[0100] Each frame reinforcement member 36 forms an angle greater than or equal to 85°, and preferably in the range of 85° to 95°, with the circumferential Z direction of the tire 10.

[0101] The tire 10 also includes an inner liner 38 located radially and axially on the inner side of the carcass reinforcement 26. The inner layer 38 extends between each bead 22, extending through the sidewalls 20 and the crown 12.

[0102] Each bead 22 contains, in addition to the annular reinforcing structure 24, a mass of filler rubber 40 located in the space defined by the main thread 32 and the fold thread 34. Each bead 22 also contains a first mass 42 of protective rubber for the bead 22 after bending 30 of the frame reinforcement 26.

[0103] Each annular reinforcing structure 24 includes an annular bead wire 52 coated with a coating mass 54, for example, containing rubber. A bead wire 52 is located radially on the inner side of the filler rubber mass 40.

EXAMPLE OF FRAMEWORK LAYER

[0104] The uncured carcass layer 27 according to the first embodiment of the invention from which the carcass layer 28 is produced will be described with reference to FIG. 4 and 5.

[0105] The carcass layer 27 is produced in a manner in which bonded carcass reinforcement element(s) 36 are embedded in a polymer composition. The frame reinforcing element is coated with an RFL adhesive composition.

[0106] The uncured carcass layer 27 contains a plurality of carcass reinforcing elements 36. The reinforcing elements are located side by side and parallel to each other along a general direction D substantially perpendicular to the general direction G in which the reinforcing elements of the uncured carcass layer 27 extend, the general direction G forms an angle greater than or equal to 85°, and preferably in the range of 85° to 95°, with the circumferential direction Z of the tire 10 once the uncured carcass ply 27, which forms the carcass ply 28, is positioned within the tire 10. In this particular case the general direction G forms an angle of substantially 90° with the circumferential direction Z of the tire 10 once the uncured carcass layer that forms the carcass layer 28 is positioned within the tire 10.

[0107] The ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than 2.00; it is less than or equal to 30.00, preferably less than or equal to 27.00, and more preferably less than or equal to 24.00. More preferably, the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 4.00; it is less than or equal to 10.00, preferably less than or equal to 7.00, and more preferably less than or equal to 5.00. In this case it is 4.76.

[0108] The ratio of the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the force at break of the uncured framework layer is strictly less than 7.00, preferably less than or equal to 5.00, and more preferably less than or equal to 4.00; and it is greater than or equal to 0.50. More preferably, the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is less than or equal to 5.00 and preferably less than or equal to 4.00 and it is greater than or equal to 1.00, preferably greater or equal to 2.00 and more preferably greater than or equal to 3.00. In this case it is 3.53.

[0109] The ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the force at break of the uncured framework layer is strictly greater than 6.00 and preferably greater than or equal to 7.00; and it is less than or equal to 30.00, preferably less than or equal to 25.00, and more preferably less than or equal to 22.00. More preferably, the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured carcass layer is greater than or equal to 8.00, preferably greater than or equal to 10.00, and preferably greater than or equal to 13.00 and less than or equal to 18.00 and preferably less than or equal to 17.00. In this case it is equal to 16.78.

[0110] The frame reinforcement member 36 and the corresponding assembly 37 will be described below.

The nature of the threads of the frame reinforcing element

[0111] As schematically shown in FIG. 5, the carcass reinforcing element 36 includes a unit 37 consisting of two multifilament yarns made of an aromatic polyamide or aromatic copolyamide 46, 47, and a multifilament yarn made of an aliphatic polyamide 48, the three yarns 46, 47 and 48 wound together in a spiral with layer formation. The frame reinforcing element 36 is torsionally balanced. For accuracy of description in FIG. 6 is a cross-sectional view of the reinforcing member 36 in accordance with the first embodiment of the invention, in which the monofilaments of each of the threads can be seen.

[0112] The aromatic polyamide selected in this case is preferably a para-aramid known under the trade name Kevlar 1K1380 type 956 from Maydown.

[0113] The aliphatic polyamide is nylon, known under the trade name Nylon T728 from Kordsa.

[0114] In some embodiments not shown, the frame reinforcement 36 includes, in addition to the assembly 37, a layer of adhesive composition covering the assembly 37.

Number of frame reinforcing elements 36

[0115] In the carcass reinforcing element 36, the thread number 46 or 47 is greater than or equal to 55 tex, preferably greater than or equal to 70 tex, more preferably greater than or equal to 90 tex, and even more preferably greater than or equal to 110 tex.

[0116] In the carcass reinforcing element 36, the thread number 46 or 47 is less than or equal to 360 tex and preferably less than or equal to 340 tex.

[0117] In this case, thread number 46 is equal to thread number 47, which is 330 tex.

[0118] In the carcass reinforcing member 36, the number of multifilament yarn 48 made from an aliphatic polyamide is greater than or equal to 20 tex, preferably greater than or equal to 30 tex, and more preferably greater than or equal to 40 tex.

[0119] In the carcass reinforcing member 36, the aliphatic polyamide multifilament yarn number is less than or equal to 300 tex, preferably less than or equal to 250 tex, more preferably less than or equal to 220 tex, and even more preferably less than or equal to 210 tex.

[0120] In this case, thread number 48 is 188 tex.

[0121] The twist factor K of the frame reinforcing element 36 is strictly greater than 150 and preferably greater than or equal to 180. In this case, it is 212.

Twisting the frame reinforcing element

[0122] In the frame reinforcing element 36, the twist of the reinforcing element is from 240 to 500 turns per meter, and preferably from 260 to 480 turns per meter. In this particular case, the twist of the reinforcing element 36 is equal to 270 turns per meter.

Geometric characteristics of the uncured framework layer 27

[0123] With reference to FIG. 5, the uncured carcass layer 27 has a thickness E, and the carcass reinforcement 36 has a diameter d. In this fig. 5, the illustration of each thread is deliberately schematic to simplify the description. In fig. 6 shows the frame reinforcing element 36 as it looks in reality.

[0124] The diameter of the frame reinforcement element 36 is less than or equal to 2.0 mm, preferably less than or equal to 1.8 mm, more preferably less than or equal to 1.5 mm, and even more preferably less than or equal to 1.2 mm. In this case, the frame reinforcing element 36 has a diameter d=1.11 mm.

[0125] The thickness E of the uncured carcass layer 27 is less than or equal to 3.00 mm, preferably less than or equal to 2.50 mm, more preferably less than or equal to 2.00 mm. The frame reinforcing element 36 has a thickness E=1.90 mm.

[0126] Thus, the d/E ratio is strictly less than 0.65, preferably less than or equal to 0.62. The frame reinforcing element 36 has a d/E ratio of 0.58.

[0127] The density of the frame reinforcement 36 in the uncured frame layer 27 is from 50 to 150 frame reinforcements 36 per decimeter of the frame layer 28, preferably from 60 to 140 frame reinforcements 36 per decimeter of the frame layer 28. In this case, the density of the frame reinforcements 36 is equal to 67 frame reinforcing elements 36 per decimeter of uncured frame layer 27.

[0128] In FIG. 5 shows the pitch P, which is the distance, expressed in mm, between two similar points of two adjacent reinforcing elements 36. The pitch P is generally referred to as the laying pitch in which the reinforcing elements are laid into the uncured carcass layer. The pitch P and the density of reinforcing elements per decimeter of uncured framework layer are such that the density of reinforcing elements per decimeter of uncured framework layer is 100/P.

[0129] The above-described reinforcement density and thickness are, as explained above, the density of the carcass reinforcements 36 and the thickness E of the uncured carcass layer 27. In the tire 10, when the carcass layer 28 is obtained from the uncured carcass ply 27 by molding the green tire, the density of the reinforcements and the thickness of the carcass ply 28 are different from the density of the uncured carcass ply and vary depending on their distance from the axis of rotation of the tire. These variations largely depend on the degree of shaping of the green tire, as well as its geometry. One skilled in the art will be able, in particular, based on the degree of forming of the green tire and its geometry, to determine the characteristics of the corresponding uncured carcass ply.

METHOD FOR MANUFACTURING REINFORCING ELEMENT

[0130] As described above, the bobbin reinforcement element 36 is twist balanced, which means that the two multifilament yarns are wound with substantially identical twist, and the twist of the monofilaments in each multifilament yarn is substantially zero. In the first stage, each monofilament yarn (more correctly called a "thread") is first spun individually on itself with an initial twist of 270 turns per meter in a given direction, in this case the Z direction, to form a thread or twist (more correctly called " thread"). Next, in the second stage, the three strands are then twisted together with a final twist of 270 turns per meter in the S direction to produce a reinforcement assembly (more properly called a "cord").

[0131] In subsequent steps, each assembly is coated with an adhesive composition, such as an RFL (resorcinol-formaldehyde-latex) type adhesive composition, and subjected to heat treatment steps to at least partially cross-link the adhesive composition.

METHOD FOR MANUFACTURING UNCURED FRAMEWORK LAYER

[0132] The uncured framework layer 27 is made by incorporating a plurality of reinforcing elements 45 into the elastomeric composition, such as by calendering. During this calendering step, which is well known to those skilled in the art, the reinforcing elements are moved along and two strips made of an elastomeric composition called skims are inserted, one on each side of the reinforcing elements, so that the reinforcing elements are sandwiched between the two skims. Thus, the reinforcing elements are built into the elastomeric composition.

METHOD FOR MANUFACTURING A TIRE ACCORDING TO THE INVENTION

[0133] The tire manufacturing method is a method commonly used by those skilled in the art. During this method, as already described above, during the first series of tire manufacturing steps, various layers are sequentially laid down, including an uncured carcass layer 27 to form the carcass layer 28 of the tire 10. The green mold thus obtained is then molded. Next, other layers are laid down to form the crown 12 of the tire 10. Finally, the green mold thus obtained is vulcanized to form the tire 10.

TIRE ACCORDING TO THE SECOND EMBODIMENT OF THE INVENTION

[0134] Unlike the tire 10 according to the first embodiment of the invention, the tire 10-2 according to the second embodiment includes a carcass reinforcing element containing an assembly consisting of one multifilament yarn of an aromatic polyamide or an aromatic copolyamide and one multifilament yarn of an aliphatic polyamide, wherein the threads are wound together in a spiral around each other. For accuracy of description in FIG. 7 is a cross-sectional view of the reinforcing member 36-2 of the uncured carcass layer 27-2 according to the second embodiment of the invention, in which the monofilaments of each of the threads are visible.

[0135] The ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 2.20 and less than or equal to 4.00 and preferably less than or equals 3.50.

[0136] The secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is less than or equal to 4.00 and greater than or equal to 1.00 and preferably greater than or equal to 2.00.

[0137] The tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured carcass layer is greater than or equal to 6.00 and preferably greater than or equal to 7.00 and less than or equal to 12.00 and preferably less or equal to 10.00.

[0138] The characteristics of the tire 10-2 and the carcass layer 27-2 are shown in Tables 2, 3 and 4 below.

TIRE ACCORDING TO THE THIRD EMBODIMENT OF THE INVENTION

[0139] Unlike the tire 10 according to the first embodiment of the invention, the tire 10-4 according to the third embodiment includes a carcass reinforcing element comprising a core consisting of a first multifilament filament of an aliphatic polyamide and a layer containing three second multifilament filaments of an aromatic polyamide or aromatic copolyamide, wherein every second layer thread is wound around other second layer threads without winding the core around the layer threads. For accuracy of description in FIG. 8 is a cross-sectional view of the reinforcing member 36-4 of the uncured carcass layer 27-4 according to the third embodiment of the invention, in which the monofilaments of each of the strands are visible.

[0140] The ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 5.00 and preferably greater than or equal to 6.00 and less or equal to 24.00.

[0141] The secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured framework layer is less than or equal to 4.00 and preferably less than or equal to 3.00, and the secant modulus at the equivalent force generated by the uncured layer at 1% elongation, to the breaking force of the uncured framework layer, greater than or equal to 0.60.

[0142] The tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured framework layer is greater than or equal to 8.00 and less than or equal to 22.00 and preferably less than or equal to 20.00.

[0143] The characteristics of the tire 10-4 and the carcass ply 27-4 are shown in Tables 2, 3 and 4 below.

MEASUREMENTS AND COMPARATIVE TESTS

[0144] As a comparative example, two prior art carcass layers, respectively designated by the general references NEDT1 and NEDT2, from a prior art tire were taken. The carcass layers NEDT1 and NEDT2, respectively, contain carcass reinforcing elements, each of which contains a knot consisting of two multifilament threads made of polyester, which are collected together and wound in a spiral around each other with a twist of 420 turns per meter and 335 turns per meter, respectively. Each frame reinforcing element is twist balanced and each thread of each frame reinforcing element has a number equal to 144 tex and 220 tex respectively.

[0145] Also used were two control carcass layers C1 and C2 containing control reinforcing elements, each of which contains an assembly consisting of an aromatic polyamide or aromatic copolyamide multifilament yarn and a polyester multifilament yarn, which are collected together and wound in a spiral around each other friend with a twist of 380 turns per meter and 270 turns per meter, respectively. Each carcass reinforcement element is twist balanced, and the multi-filament yarn of aromatic polyamide or aromatic copolyamide, in this case para-aramid, is numbered 167 tex for C1 and 330 tex for C2. The polyester multifilament thread, in this case PET, has a number equal to 144 tex for C1 and 334 tex for C2.

Comparison of wireframe layers

[0146] Geometric characteristics of reference frame layers C1 and C2, prior art frame layers (NEDT1 and NEDT2) and frame layers according to the first (27 and 27-1), second (27-2 and 27-3) and third ( 27-4 to 27-6) embodiments of the invention are set forth in Tables 1 and 2 below.

[Table 1] Frame layer NEDT1 NEDT2 C1 C2 Character of threads PET/PET PET/PET Aramid/PET Aramid/PET Thread number (tex) 144/144 220/220 167/144 330/334 Thread twist (revolutions/m) 420/420 335/335 380/380 270/270 K 192 189 178 185 Density (threads/dm) 120 96 113 74 d (mm) 0.62 0.75 0.66 1 E (mm) 1.41 1.72 1.46 1.8 d/E 0.44 0.44 0.45 0.56

[Table 2] Frame layer 27 27-1 27-2 27-3 27-4 27-5 27-6 Frame reinforcing element 36 36-1 36-2 36-3 36-4 36-5 36-6 Character of threads Aramid/Aramid/Nylon Aramid/Aramid/Nylon Aramid/nylon Aramid/nylon Nylon/1+Aramid/3 Nylon/1+Aramid/3 Nylon/1+Aramid/3 Thread number (tex) 330/330/188 167/167/140 110/94 167/140 47/1 + 167/3 47/1 + 167/3 47/1 + 167/3 Thread twist (revolutions/m) 270/270 330/330 470/470 380/380 340+ 315/315 340+ 315/315 340+ 315/315 K 212 195 186 184 196 196 196 Density (threads/dm) 67 90 133 109 81 77 76 d (mm) 1.11 0.83 0.56 0.68 0.92 0.97 0.98 E (mm) 1.90 1.63 1.36 1.08 1.80 1.37 1.38 d/E 0.58 0.51 0.41 0.46 0.51 0.55 0.55

[0147] Data regarding elongation and strength at break of the inventive framework layers, control framework layers and prior art framework layers are shown in Table 3 below.

[Table 3] Frame layer NEDT1 NEDT2 C1 C2 27 27-1 27-2 27-3 27-4 27-5 27-6 Layer breaking force (daN/cm) 213 266 356 459 775 576 314 397 641 578 573 Secant modulus at 1% elongation to force at layer rupture 7.70 7.82 8.38 7.22 3.53 3.37 2.82 3.10 0.82 0.63 2.29 Tangent modulus at 7% elongation to force at layer rupture 5.27 4.88 14.19 14.26 16.78 13.64 9.33 7.45 19.16 8.67 15.67 Tangent modulus at 7% elongation / secant modulus at 1% elongation 0.68 0.62 1.69 1.97 4.76 4.05 3.30 2.40 23.44 13.77 6.83

Tire comparison

[0148] Tires in accordance with the invention were then compared with control tires PC1 and PC2 and with prior art tires PEDT1 and PEDT2 containing one or more carcass plies described above in Tables 1-3 with respect to their tensile strength, their shape in the uncured state, their cornering stiffness and the trade-off between shaping and cornering stiffness.

[0149] The tensile strength of tires PEdT1, PEdT2, PC1, PC2 and 10 to 10-6 were compared with each other by designing the number of carcass plies to achieve a breaking strength suitable for a tire for agricultural use; then the uncured forming of PEdT1, PEdT2, PC1, PC2 and 10 to 10-6 tires was compared by forming a relationship with the secant modulus descriptors at 1% carcass layers NdT1, NdT2, C1, C2 and 27 to 27-6, and then the cornering stiffness of tires PEdT1, PEdT2, PC1, PC2 and 10 to 10-6 were compared by forming a relationship with the tangent modulus descriptor at 7% carcass layers NdT1, NdT2, C1, C2 and 27-6, and finally obtained from this best compromise between green formability and cornering stiffness for PEdT1, PEdT2, PC2 and 10-6 tires.

[0150] The results are summarized in Table 4 below.

[0151] The tensile strength of the tested tires is listed in Table 4. Good tensile strength is indicated by a "+" sign. Very good tensile strength is indicated by a “++”.

[0152] Likewise, uncured formability, cornering stiffness, and the tradeoff between formability and cornering stiffness are indicated, with poor value indicated by a “-”, good by a “+” and very good by a “++”.

[Table 4] Tire PEDT1 PEDT2 PC1 PC2 10 10-1 10-2 10-3 10-4 10-5 10-6 Number of frame layers 3 3 2 2 1 1 2 2 1 1 1 Breaking force of layer/layers (daN/cm) 638 798 712 918 775 576 629 794 641 578 573 Tensile strength + + ++ ++ ++ + + ++ + + + Shaping in uncured state - - - - + + + + ++ ++ + Cornering rigidity - - + + ++ + + + ++ + ++ Compromise between shaping and cornering rigidity - - - - + + + + ++ ++ +

[0153] These results demonstrate that tires 10 to 10-6 according to the present invention exhibit both tensile strength equivalent to or greater than prior art tires PEdT1 and PEdT2 and, furthermore, uncured formability that is significantly better , and a cornering rigidity that is significantly higher than that of the prior art PEdT1 and PEdT2 tires.

[0154] Additionally, compared to control tires PC1 and PC2, tires 10 to 10-6 were noted to have uncured formability that was significantly better. This very good formability in the uncured state is the result of the use, in particular, of multifilament aliphatic polyamide yarn. At equivalent cornering stiffness, it is noted that the PC1 tire does not have good forming in the uncured state, while the 10-1 tire meets all the criteria and, in particular, the trade-off between forming and cornering stiffness.

[0155] Thus, the tires of the present invention exhibit very good green shape and better cornering rigidity while maintaining very good tensile strength.

[0156] Thus, as shown by the above results, the invention clearly consists of a tire containing one or more carcass reinforcing elements, each carcass reinforcing element comprising:

- a unit consisting of two multifilament threads of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide, the threads being wound together in a spiral to form a layer; or

- a knot consisting of one multifilament thread of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide,

moreover, the threads are wound together in a spiral around one another; or

- a core consisting of a first multifilament filament of an aliphatic polyamide, and a layer containing at least two second multifilament filaments of an aromatic polyamide or aromatic copolyamide, the second filament filaments of the layer being wound together in a spiral around the core;

characterized in that the tire is produced by a method comprising the step of manufacturing each carcass ply, in which carcass reinforcing element(s) bonded in a polymer composition are incorporated to form each uncured carcass ply, wherein the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7 % elongation, to secant modulus at the equivalent force generated by the uncured layer at 1% elongation, greater than or equal to 2.00.

[0157] The invention is not limited to the above-described embodiments.

[0158] It may also be possible to combine features of the various embodiments and variations described or provided for above, provided that they are compatible with each other and consistent with the invention.

[0159] It is also possible to provide, independently of an agricultural vehicle tire, comprising two beads, each of which has at least one annular reinforcing structure and a carcass reinforcement secured in each of the beads by rotation about the annular reinforcing structure, the carcass reinforcement comprising at least one frame layer containing one or more frame reinforcing elements, each frame reinforcing element comprising:

- a unit consisting of two multifilament threads of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide, the threads being wound together in a spiral to form a layer; or

- a knot consisting of one multifilament thread of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide,

moreover, the threads are wound together in a spiral around one another; or

- a core consisting of a first multifilament filament of an aliphatic polyamide, and a layer containing at least two second multifilament filaments of an aromatic polyamide or aromatic copolyamide, the second filament filaments of the layer being wound together in a spiral around the core;

wherein the tire is produced by a method comprising the step of manufacturing each carcass ply, in which carcass reinforcing element(s) bonded in a polymer composition are incorporated to form each uncured carcass ply, wherein the ratio of the tangent modulus at the equivalent force generated by the uncured ply at 7% elongation , to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation, greater than or equal to 2.00;

tire for an agricultural vehicle, containing two beads, each of which has at least one annular reinforcing structure and carcass reinforcement fixed in each of the beads by rotating around the annular reinforcing structure, and the carcass reinforcement contains at least one carcass ply containing one or more frame reinforcing elements, each frame reinforcing element comprising:

- a unit consisting of two multifilament threads of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide, the threads being wound together in a spiral to form a layer; or

- a knot consisting of one multifilament thread of an aromatic polyamide or aromatic copolyamide and one multifilament thread of an aliphatic polyamide,

moreover, the threads are wound together in a spiral around one another; or

- a core consisting of a first multifilament filament of an aliphatic polyamide, and a layer containing at least two second multifilament filaments of an aromatic polyamide or aromatic copolyamide, the second filament filaments of the layer being wound together in a spiral around the core;

wherein the tire is produced by a method comprising the step of manufacturing each carcass ply, in which carcass reinforcing element(s) bonded in a polymer composition are incorporated to form each uncured carcass ply, wherein the ratio of the secant modulus at the equivalent force generated by the uncured ply at 1% elongation , to the breaking force of the uncured layer is strictly less than 7.00, preferably less than or exactly 5.00, and more preferably less than or exactly 4.00.

[0160] All of the advantageous and preferred features described herein can be provided with this tire.

Claims (23)

1. A tire (10) for an agricultural vehicle, containing two beads (22), each of which has at least one annular reinforcing structure (24) and frame reinforcement (26) fixed in each of the beads (22) by bending around an annular reinforcing structure (26), wherein the frame reinforcement (26) consists of one or two frame layers (28) containing one or more reinforcing elements (36), and each frame reinforcing element (36) contains: - a unit (37) consisting of two multifilament filaments of an aromatic polyamide or aromatic copolyamide and one multifilament filament of an aliphatic polyamide, the filaments being wound together in a spiral to form a layer; or - a unit (37) consisting of one multifilament yarn of aromatic polyamide or aromatic copolyamide and one multifilament yarn of aliphatic polyamide, wherein the threads are wound together in a spiral around each other; or - a core consisting of a first multifilament filament of an aliphatic polyamide, and a layer containing at least two second multifilament filaments of an aromatic polyamide or aromatic copolyamide, the second filament filaments of the layer being wound together in a spiral around the core; characterized in that the tire (10) is produced by a method comprising the step of manufacturing each carcass ply (28), in which carcass reinforcing element(s) (36), coated with a coating having an adhesive function in the polymer composition, is embedded to form each uncured carcass ply (27), and the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is greater than or equal to 2.00, and the tangent and secant moduli are obtained from force-elongation curve obtained by applying ASTM D 885/D 885M - 10A from 2014; wherein the density of frame reinforcing elements (36) in the uncured frame layer (27) ranges from 50 to 150 frame reinforcing elements (36) per decimeter of uncured frame layer (27); And each frame reinforcing element (36) forms an angle greater than or equal to 85° with the circumferential Z direction of the tire (10). 2. The tire (10) as claimed in any one of the preceding claims, wherein the ratio of the tangential modulus at the equivalent force generated by the uncured layer at 7% elongation to the secant modulus at the equivalent force generated by the uncured layer at 1% elongation is less than or equal to 30.00 , preferably less than or equal to 27.00 and more preferably less than or equal to 24.00. 3. The tire (10) as claimed in any one of the preceding claims, wherein the ratio of the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured carcass layer is strictly less than 7.00, preferably less than or equal to 5.00 and more preferably less than or equal to 4.00. 4. The tire (10) as claimed in any one of the preceding claims, wherein the ratio of the secant modulus at the equivalent force generated by the uncured layer at 1% elongation to the breaking force of the uncured carcass layer is greater than or equal to 0.50. 5. The tire (10) as claimed in any one of the preceding claims, wherein the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured carcass layer is strictly greater than 6.00 and preferably greater than or equal to 7.00 . 6. The tire (10) as claimed in any one of the preceding claims, wherein the ratio of the tangent modulus at the equivalent force generated by the uncured layer at 7% elongation to the breaking force of the uncured carcass layer is less than or equal to 30.00, preferably less than or equal to 25, 00 and more preferably less than or equal to 22.00. 7. Tire (10) according to any one of the preceding paragraphs, in which the twist coefficient K of the carcass reinforcing element (36) is strictly greater than 150 and preferably greater than or equal to 180, and K is determined by the formula: K=T × [(Number / (1000.ρ)] ^1/2 where T is the twist of the frame reinforcing element (36), expressed in turns per meter, Number is the sum of the numbers of the multi-fiber threads of the frame reinforcing element in tex, ρ is the average mass per unit volume of multi-fiber threads in g/cm ³ , weighted by the corresponding numbers of the constituent materials multi-filament threads. 8. Tire (10) according to any one of the preceding claims, wherein the number of multifilament thread(s) of aromatic polyamide or aromatic copolyamide is greater than or equal to 55 tex, preferably greater than or equal to 70 tex, more preferably greater than or equal to 90 tex, and even more preferably greater or equal to 110 tex. 9. Tire (10) according to any one of the preceding claims, wherein the number of multifilament thread(s) of aromatic polyamide or aromatic copolyamide is less than or equal to 500 tex, preferably less than or equal to 400 tex, and more preferably less than or equal to 340 tex. 10. Tire (10) according to any one of the preceding claims, wherein the number of multifilament thread(s) of aliphatic polyamide is greater than or equal to 20 tex, preferably greater than or equal to 30 tex, and more preferably greater than or equal to 40 tex. 11. Tire (10) according to any one of the preceding claims, wherein the number of multifilament thread(s) of aliphatic polyamide is less than or equal to 300 tex, preferably less than or equal to 250 tex, more preferably less than or equal to 220 tex and even more preferably less than or equal to 210 tex. 12. Tire (10) according to any one of the preceding claims, wherein the twist of the carcass reinforcing element (36) is from 240 to 500 turns per meter and preferably from 260 to 480 turns per meter. 13. The tire (10) as claimed in any one of the preceding claims, wherein the density of carcass reinforcements (36) in the uncured carcass layer (27) is from 60 to 140 carcass reinforcements (36) per decimeter of uncured carcass layer (27). 14. The tire (10) as claimed in any one of the preceding claims, wherein each carcass reinforcing element (36) forms an angle in the range of 85° to 95° with the circumferential Z direction of the tire (10).