Reinforcement cord for tire for vehicle wheel and tire comprising said reinforcement cord

Abstract

Reinforcing cord (10) for tyres for vehicle wheels, comprising at least two elongated elements (11a, 1ib) made of a non-metallic material and twisted together, the reinforcing cord (10) extending along a non-linear longitudinal trajectory, in particular along a contoured longitudinal trajectory.

Description

Technical Field

[0001] This invention relates to reinforcing cords in tires used for vehicle wheels.

[0002] The present invention also relates to tires for vehicle wheels, said tires comprising such reinforcing cords.

[0003] The reinforcing cord of the present invention has a geometry suitable for achieving high partial load elongation. Background Technology

[0004] US10,618,353 B2 describes a fabric reinforcing cord comprising two or more yarns twisted together and made of aramid fibers. The high modulus of the aramid fibers imparts a desired stiffness to these reinforcing cords. To improve partial load elongation, during the manufacture of such reinforcing cords, the yarns are spaced apart and an RFL adhesive composition is inserted between them. When these reinforcing cords are pulled, the yarns move closer together, thereby compressing the adhesive composition and achieving the desired partial load elongation. As the load increases, the elongation is offset by the high modulus of the aramid fibers.

[0005] WO 2012 / 083148 A1, US 2017 / 0274706 A1 and US 4,155,394 A describe a fabric-reinforced cord comprising elongated elements made of a high-modulus, low-elongation material (aramid), said elongated elements being twisted to elongated elements made of a low-modulus, high-elongation material (nylon).

[0006] KR 20110061110 A describes a reinforcing cord comprising at least one elongated element with high elongation made of nylon, at least one elongated element with medium elongation made of a material selected from polyester, polyvinyl alcohol, polyvinyl acetate (PVA), rayon, lyocell, polyethylene naphthalate (PEN), and at least one elongated element with low elongation made of, for example, aramid, carbon fiber, or glass fiber. Summary of the Invention

[0007] In this specification and the appended claims, unless otherwise stated, when referring to certain angular values, these values ​​shall be regarded as absolute values, that is, positive and negative values ​​relative to a reference plane or direction.

[0008] Furthermore, unless otherwise stated otherwise, when referring to any range of values ​​between the minimum and maximum values, the aforementioned minimum and maximum values ​​are considered to be included within the aforementioned range.

[0009] Furthermore, all ranges include any combination of the stated minimum and maximum values, and include any intermediate ranges, even if not specifically stated otherwise.

[0010] Even if not explicitly stated, any numerical value should be assumed to be preceded by the term "about" to indicate any value that differs slightly from the stated value, for example, taking into account typical dimensional tolerances in the reference field.

[0011] The following definitions apply in the following text:

[0012] The term "green tire" is used to refer to tires that have been obtained through manufacturing processes but have not yet been molded and vulcanized.

[0013] The terms "tire" or "finished tire" are used to refer to tires obtained by molding and vulcanizing raw tires in a vulcanizing mold.

[0014] The term "tire footprint area" refers to the portion of a tire that comes into contact with the ground or road surface when the tire is mounted on a rim and a predetermined vertical load is applied to it.

[0015] The term "parallel" is used not only to indicate a state of perfect parallelism, but also to indicate a state that deviates slightly from perfect parallelism, for example, by an angle of deviation of no more than 5°.

[0016] The term "vertical" is used not only to indicate a state that is perfectly perpendicular or orthogonal, but also to indicate a state that deviates slightly from a perfectly perpendicular or orthogonal state, for example, by an angle of deviation of no more than 5°.

[0017] The term "equatorial plane" in tire refers to the centerline plane perpendicular to the tire's axis of rotation. The equatorial plane divides the tire into two generally symmetrical and equal parts.

[0018] The term "elastomer material" or "elastomer" is used to refer to a material comprising a vulcanizable natural or synthetic polymer and reinforcing fillers, wherein the material can be deformed under stress at room temperature and after vulcanization, and is able to rapidly and positively recover its basic original shape and dimensions after the deformation force is removed (as defined in ASTM D1566-11 Standard Terminology Relating To Rubber).

[0019] The terms "upstream" and "downstream" are used with reference to a predetermined direction and a predetermined reference. Thus, for example, assuming a left-to-right direction and a reference taken along said direction, the position "downstream" relative to that reference indicates a position to the right of said reference, while the position "upstream" relative to said reference indicates a position to the left of said reference.

[0020] When referring to tires, the terms "circumferential" and "circumferentially" are used with reference to the tire's rolling direction, which corresponds to a direction lying on a plane that coincides with or is substantially parallel to the tire's equatorial plane. When referring to reinforcing cords, the same terminology is used with reference to a direction that rotates about the center of the reinforcing cord in any cross-section of the reinforcing cord.

[0021] When referring to tires, the terms "radial," "inner radial," and / or "outer radial" are used with reference to a direction substantially parallel to the tire's equatorial plane, i.e., substantially perpendicular to the tire's axis of rotation. Alternatively, when referring to reinforcing cords, the same terms are used with reference to a direction substantially perpendicular to the longitudinal direction of the reinforcing cords.

[0022] When referring to tires, the terms "axial," "inward axial," and / or "outward axial" are used with reference to a direction substantially perpendicular to the tire's equatorial plane, i.e., substantially parallel to the tire's axis of rotation. Alternatively, when referring to reinforcing cords, the same terms are used with reference to a direction substantially parallel to the longitudinal direction of the reinforcing cords.

[0023] The terms "longitudinal trajectory" and "longitudinal direction" of reinforcing cords refer to the trajectory and direction followed by the centers of the circumcircles of all cross-sections of the reinforcing cord, respectively.

[0024] When a reference line is fixed at the outermost radial point of the reinforcing cord, tangent to the reinforcing cord and pointing along the longitudinal direction of the reinforcing cord, if the distance from the center of the circle to the reference line varies along the longitudinal direction of the reinforcing cord such that the difference between the maximum and minimum distances is greater than 150 μm, then the longitudinal trajectory is considered "non-linear".

[0025] The term "basic axial direction" is used to indicate a direction that is tilted at an angle between 70° and 90° relative to the equatorial plane of the tire.

[0026] The term "basic circumferential direction" is used to indicate a direction oriented at an angle between 0° and 10° relative to the tire's equatorial plane.

[0027] The term "reinforced cord" or simply "cord" is used to refer to an elongated element comprising several elongated elements, which may be coated with an elastomeric material or incorporated into an elastomeric material matrix.

[0028] The term "slender element" is used to refer to wire or yarn.

[0029] The term "wire" is used to refer to a long, thin component consisting of a single filament. Therefore, the term "monofilament" is also used to refer to "wire".

[0030] The term "yarn" is used to refer to an elongated element composed of an aggregate of multiple filaments twisted together. Therefore, the term "multifilament" is also used to refer to "yarn".

[0031] Each filament can also be called a "fiber".

[0032] Therefore, slender elements can be composed of a single wire, a single yarn, or several yarns twisted together.

[0033] In the case of yarns, elongated elements can be represented by abbreviations that represent the fabric material, the linear density of the fibers used, and the number of yarns forming the elongated element. For example, an elongated element made of polyethylene terephthalate (PET) and identified as PET 1672 represents an elongated element consisting of PET fibers with a linear density of 1670 dtex and formed by two yarns twisted together.

[0034] The term "strand" is used to refer to an assembly consisting of at least two elongated elements. A strand may define a reinforcing cord on its own, or it may be intended to be twisted to at least another elongated element or at least another strand to create a reinforcing cord.

[0035] The term "hybrid strand" is used to refer to a strand consisting of at least two slender elements made of different materials.

[0036] In this specification and the following claims, any reference to a particular plastic material should be understood to extend both to fossil-derived plastic materials and, if any, to corresponding recycled or bio-based materials. Thus, for example, when PET is mentioned, it is foreseeable that such PET may be of fossil or recycled origin.

[0037] The term "recycled material" is used to refer to plastic materials that are obtained from waste or industrial waste made from corresponding plastic materials (usually, but not necessarily, fossil-derived) and subjected to appropriate mechanical and / or chemical and / or thermal treatment in order to obtain reusable products.

[0038] The term "non-recycled material" is used to refer to plastic materials derived from fossils.

[0039] The term "bio-based material" is used to refer to materials that are not of fossil origin and are not derived from waste or industrial waste, but are derived from renewable resources such as, for example, agricultural and forestry products grown and / or used by humans for purposes other than human or animal nutrition.

[0040] The term "diameter" in wire refers to the diameter measured according to the BISFA E10 method (International Bureau for Standardization of Man-made Fibers, internationally recognized test method for steel cord in tires, 1995 edition).

[0041] The “diameter” of a yarn is intended to represent the diameter of the ideal circumference of all the filaments that circumferentially define the yarn.

[0042] The term "breaking load" for reinforcing cord is used to describe the load at which a reinforcing cord breaks, as assessed according to the BISFA (International Bureau for Standardization of Man-made Fibers) standards associated with the test material, as defined below.

[0043] The term "partial load elongation" for reinforcing cords is used to express the difference between the percentage elongation a reinforcing cord gains when subjected to a 50 N traction force and the percentage elongation a reinforcing cord gains when subjected to a 2.5 N traction force. Partial load elongation is evaluated using the BISFA E7 method (International Bureau for Standardization of Man-Made Fibers, Internationally Recognized Test Method for Steel Cords in Tires, 1995).

[0044] The term "modulus" is used to represent the ratio between load (or force) and elongation measured at any point on a load-elongation curve according to BISFA standards. This curve is plotted by calculating the first derivative of the load-elongation function that defines the curve, normalized to a linear density in TeX. Therefore, the modulus is expressed as cN / Tex or MPa. In a load-elongation plot, the modulus is determined by the slope of the curve relative to the X-axis.

[0045] The term "initial modulus" is used to refer to the modulus calculated at the origin of the load-elongation curve (i.e., when the elongation is zero).

[0046] The term "final modulus" is used to refer to the modulus calculated near the fracture load, before any sudden failure occurs.

[0047] In the context of this invention, the term "high modulus" is used to refer to a modulus above 5 MPa, while the term "low modulus" is used to refer to a modulus below 5 MPa.

[0048] The term "linear density" or "count" for yarn is used to indicate the weight of a cord / slender element per unit length. Linear density can be measured in dtex (grams per 10 kilometers of length).

[0049] For the measurement of linear density and the determination of tensile properties (such as breaking load), the tests specified according to BISFA standards refer to flat yarns that are not twisted during the testing phase. Specifically:

[0050] - For aramid fibers (AR), refer to the test method for para-aramid yarns - 2002 edition.

[0051] • Determination of linear density - Chapter 6;

[0052] • Determination of tensile properties - Chapter 7 - Test procedures - Section 7.5 - Using the initial pre-stretching procedure;

[0053] - For nylon (NY), refer to BISFA - Test Methods for Polyamide Yarns - 2004 Edition.

[0054] • Determination of linear density - Chapter 6 - Procedure A;

[0055] • Determination of tensile properties - Chapter 7 - Procedure A;

[0056] • Preparation of laboratory samples: Preparation of relaxed samples - Section 7.4.1.1 => Preparation of samples on foldable spools;

[0057] • Preparation of laboratory samples and execution of tests: manual testing - Section 7.5.2.1 => c);

[0058] • Program start => e) Pre-stretch at the start of the program;

[0059] • Use a Zwick-Roell Z010 force gauge for traction;

[0060] - For polyester (PET), refer to BISFA - Test Methods for Polyester Yarn - 2004 Edition:

[0061] • Determination of linear density - Chapter 6 - Procedure A;

[0062] • Determination of tensile properties - Chapter 7 - Procedure A;

[0063] • Preparation of laboratory samples: Preparation of relaxed samples - Section 7.4.1.1 => Preparation of samples on foldable spools;

[0064] • Preparation of laboratory samples and execution of tests: manual testing - Section 7.5.2.1 => c);

[0065] • Program start => e) Pre-stretch at the start of the program;

[0066] • Use the Zwick-Roell Z010 force gauge for traction.

[0067] In the following text, when referring to the adhesion to the elastomeric material of the reinforcing cord or its elongated element, it refers to the adhesion ability of the reinforcing cord / elongated element solely by its shape or structure, and therefore does not take into account surface coating treatments by means of an adhesive composition, such as, for example, the resorcinol-formaldehyde-latex (RFL) composition commonly used in the tire manufacturing industry.

[0068] The term "structural component" for tire is used to refer to any tire ply or layer containing reinforcing cords, such as, for example, the carcass ply of a car or motorcycle tire, or the belt ply of a car tire, or the zero-degree reinforcement layer (or cross-belt structure) of a motorcycle tire, or a reinforcing layer connected to the carcass ply at or near the corresponding folded-up edge of the carcass ply, and the term "bead wrapping" and "wire bead wrapping" are also used below to refer to said reinforcing layer.

[0069] The term "mechanical properties" of a reinforcing cord or its elongated elements or strip elements incorporating the cord is used to indicate the response of the reinforcing cord / strip element when subjected to a load (or force). Under traction loads, such loads cause elongation, which varies based on the amount of load as a function of a specific load-elongation curve.

[0070] Tires used for vehicle wheels include a carcass structure comprising multiple reinforcing cords (typically fabric). These reinforcing cords may be incorporated into a single carcass ply or into multiple carcass ply layers stacked radially on top of each other (preferably no more than two carcass ply layers).

[0071] The tire carcass structure has: a crown portion extending on opposite sides relative to the equatorial plane, wherein reinforcing cords extend in a generally axial direction at the crown portion; and two side portions extending on opposite sides relative to the crown portion, each of the side portions being located near the corresponding sidewall of the tire.

[0072] A crown structure including a belt structure is provided at a radially outer position relative to the tire body structure, and a tread belt made of an elastomeric material is provided at a radially outer position relative to the belt structure.

[0073] The belt structure may include a cross belt structure and / or a zero-degree reinforcement layer.

[0074] A cross-belt structure typically found in automobile tires comprises several radially overlapping belt layers. Specifically, it may provide: a first belt layer comprising reinforcing cords (typically fabric or metal reinforcing cords) that are substantially parallel to each other and inclined at a predetermined angle relative to the tire's equatorial plane; and at least one second belt layer disposed radially outward relative to the first belt layer and comprising reinforcing cords (typically fabric or metal reinforcing cords) that are substantially parallel to each other but oriented at an inclination opposite to that of the reinforcing cords in the first belt layer relative to the tire's equatorial plane.

[0075] The "zero-degree reinforcement layer" comprises multiple fabric reinforcement cords arranged in a generally circumferential winding direction on the belt structure (in the case of automobile tires) or on the crown portion of the carcass structure (in the case of motorcycle tires). In motorcycle tires, the zero-degree reinforcement layer itself may define the "belt structure" of the tire, or it may be replaced by two overlapping reinforcement layers defining a cross-belt structure.

[0076] Typically, the reinforcing cords of the zero-degree reinforcement layer are incorporated into a rubberized woven strip element. This strip element is spirally wound from one end to the other on the crown portion of the tire carcass structure with a predetermined laying tension.

[0077] The production cycle of tires for vehicle wheels typically begins with a process for building a raw tire, in which the various structural components of the tire are built and assembled. The raw tire thus formed then undergoes molding and vulcanization processes designed to define the structure of the finished tire according to the desired geometry and tread design.

[0078] Typically, the various structural components of a tire are built and assembled on a specialized molding drum that is roughly cylindrical in shape. These drums can contract / expand radially.

[0079] Specifically, a body structure is constructed on a first forming drum, which is known to be a first-stage drum, while a crown structure is constructed on a second forming drum, which is known to be an auxiliary drum or a second-stage drum.

[0080] The assembly of the carcass structure and the crown structure can be performed on a first forming drum, in which case the first-stage drum is referred to as a single-stage or "one-phase" drum. Alternatively, the assembly can be performed on different forming drums known as forming drums. This assembly involves positioning the crown structure coaxially and radially outward relative to the carcass structure, and then forming the green tire by radially expanding the first-stage drum and / or the forming drum. This forming allows the radially outer surface of the carcass structure to align with the radially inner surface of the crown structure, resulting in a toroidal configuration for the green tire.

[0081] The applicant has observed that during the forming of a green tire, the elongation experienced by the reinforcing cords in the zero-degree reinforcing layer located at the axial central portion of the drum (hereinafter referred to as the "central portion" of the drum) is greater than the elongation of the reinforcing cords located at the opposite shoulder portion of the drum (hereinafter referred to as the "shoulder" of the drum). In other words, during the forming of a green tire, the strip element incorporating the aforementioned reinforcing cords experiences greater elongation at the portion around the central portion of the drum (hereinafter referred to as the "central portion" of the strip element), and less elongation at the opposite side portion around the shoulder of the drum (hereinafter referred to as the "shoulder portion" of the strip element).

[0082] Therefore, after forming, the strip element is stretched to a greater extent in its central portion, and thus has greater stiffness, while it is stretched to a lesser extent in its relative shoulder portion, and thus has lower stiffness. In particular, the applicant has found that the difference in elongation and therefore stiffness between the central portion and the shoulder portion of the strip element is approximately 2%-3%.

[0083] The applicant has observed that, on the contrary, it is desirable for the strip element to have substantially uniform stiffness in the axial direction after molding, so as to avoid undesirable mechanical property inhomogeneities in the zero-degree reinforcement layer in the tire track area in the axial direction.

[0084] The applicant has considered that a suitable measure to limit the aforementioned elongation or stiffness differences, thereby achieving the desired stiffness uniformity in the axial direction, is to wrap the strip element around the drum using a varying laying tension between the shoulder and the center of the drum. Specifically, a greater laying tension can be applied at the shoulder of the drum, and a smaller tension at the center. In this way, after the strip element has been laid on the drum and before the green tire is formed, the strip element is pulled more at the shoulder of the drum and therefore has greater stiffness, while it is pulled less at the center of the drum and therefore has lower stiffness.

[0085] However, the applicant has found that the fabric reinforcing cords used in tire strip elements currently on the market have limited elongation under low loads (e.g., the load the strip element bears due to the aforementioned laying tension). Therefore, providing a lower laying tension at the center of the drum and a higher laying tension at the shoulder of the drum only allows for a partial reduction of the stiffness difference that typically exists between the central and shoulder portions of the strip element after molding.

[0086] Therefore, the applicant has conceived of manufacturing reinforcing cords with high partial load elongation so that when the strip element is wound onto the drum using a laying tension that is greater at the shoulder and smaller at the center, the shoulder portion of the strip element can achieve significant elongation. In this way, before the green tire is formed, the strip element is subjected to a greater degree of tension at its shoulder portion (and therefore higher stiffness) and a smaller degree of tension at its center portion (and therefore lower stiffness), thereby compensating for the unavoidable elongation differences in the axial direction that occur during the green tire forming process. Thus, after the green tire forming is completed, the desired uniformity of stiffness of the strip element in the axial direction will be achieved.

[0087] In order to reduce rolling resistance of its tires and thus reduce carbon dioxide emissions into the atmosphere, the applicant has been working to manufacture the lightest possible reinforcing cords and has therefore decided to use slender elements made of non-metallic materials.

[0088] The applicant has discovered that, in order to achieve a high partial load elongation, the reinforcing cords can be configured such that they extend along a non-linear longitudinal trajectory, preferably a wavy trajectory. In this way, when subjected to traction and before such stress is offset by the resistance provided by the material made into the elongated element, the reinforcing cords can elongate until they straighten. This initial elongation allows the desired high partial load elongation to be achieved.

[0089] The applicant has verified that non-linear reinforcing cords can be manufactured by twisting elongated elements of reinforcing cords in conventional twisting equipment typically used for twisting metal wires or fabric elongated elements, and by properly controlling the twisting process performed in such twisting equipment, either by twisting the elongated elements individually or after a semi-finished product has been formed by twisting two or more elongated elements together into strands. Such control includes, for example, feeding the elongated elements appropriately into the twisting device and arranging the twisting device such that, during twisting, each of the elongated elements is arranged in a desired position relative to the other elongated elements (e.g., such that some elongated elements are arranged radially inward relative to the other elongated elements, and the other elongated elements are wound around these elongated elements along a corresponding helical path, or such that all elongated elements are wound around each other along a corresponding helical path, without some elongated elements being arranged radially inward relative to the other elongated elements); adjusting the twisting pitch (the twisting pitch corresponds to the pitch in the reinforcing cord); adjusting the force pulling the individual elongated elements or semi-finished products; applying a predetermined braking force to the individual elongated elements or semi-finished products; and, if possible, applying a predetermined degree of deformation to the reinforcing cord (through measures known as preforming or pleating, which are typically provided in wire twisting devices to space the wires apart from each other).

[0090] Therefore, in a first aspect of the invention, the present invention relates to a reinforcing cord for a tire used in a vehicle wheel, the reinforcing cord comprising at least two elongated elements made of a non-metallic material.

[0091] Preferably, the at least two elongated elements are twisted together.

[0092] Preferably, the reinforcing cord extends along a non-linear longitudinal trajectory.

[0093] In a second aspect of the invention, the invention relates to a tire for a vehicle wheel, the tire comprising a plurality of cords according to a first aspect of the invention.

[0094] According to the applicant, the reinforcing cord of the present invention allows for desired stiffness uniformity of the strip element in the axial direction after the green tire forming is completed. This is achieved due to the fact that when the strip element is wound around the drum using a laying tension that is greater at the shoulder of the drum and lower at the center of the drum, the shoulder portion of the strip element can be significantly elongated, resulting in greater tension and higher stiffness than the central portion of the strip element, and thus compensating for the greater elongation / tension of the central portion of the strip element relative to the shoulder portion during the green tire forming process.

[0095] The increased stiffness of the shoulder portion of the strip element before the tire is formed results in increased stiffness of the entire tire crown portion, and thus causes uniform and efficient force transmission between the tire and the road surface in the tire track area, which is beneficial to tire performance and rolling resistance.

[0096] Furthermore, the high partial load elongation of the reinforcing cord of the present invention allows the strip element incorporating the reinforcing cord to withstand higher tensile forces during the forming of the green tire, thereby enabling the strip element to be laid on a drum with a diameter smaller than that typically provided, without any risk of damaging the belt structure to which the strip element is wound.

[0097] The applicant has observed that, depending on the type of elongated element used in the reinforcing cord (wire, yarn, and / or any combination of one or more wires and one or more yarns) and the non-metallic material (low-modulus material, high-modulus material, or any combination of such materials), a reinforcing cord according to the invention and having such characteristics can be manufactured to make the reinforcing cord suitable for use in structural components of automobile and motorcycle tires, in addition to zero-degree reinforcing layers. Specifically:

[0098] - Given the same material and diameter, wire is better suited than yarn to withstand compressive stress and reduce hysteresis caused by friction between wire and / or yarn filaments, while yarn is better suited than wire to withstand bending stress and adhere to the surrounding elastomeric material.

[0099] - For the same type of slender element and diameter, high modulus materials allow for increased stiffness and / or breaking load, while low modulus materials allow for maximum partial load elongation and / or breaking elongation.

[0100] According to the applicant, when the reinforcing cord of the present invention is used in the cross-belt structure of a tire or the reinforcing structure of the bead (hereinafter referred to as "bead wrapping" and "bead wrapping") or the carcass structure of a tire, it is preferable to maximize stiffness and / or breaking load, and when the reinforcing cord of the present invention is used in the zero-degree reinforcement layer, it is preferable to maximize partial load elongation and / or breaking elongation.

[0101] In at least one of the foregoing aspects, the present invention may have at least one of the following preferred features.

[0102] Preferably, the longitudinal trajectory is substantially wavy. In this way, the desired partial load elongation can be achieved by limiting the radial dimension of the reinforcing cord, thereby limiting the thickness of the strip element (and thus the structural component) incorporating the reinforcing cord.

[0103] Preferably, the basically wavy longitudinal trajectory has a basic periodicity that can be measured by the corrugation pitch, which is greater than 2 mm, more preferably greater than 3 mm, and even more preferably greater than 4 mm.

[0104] Preferably, the corrugation pitch is less than 25 mm, more preferably less than 20 mm, and even more preferably less than 12.5 mm.

[0105] In a preferred embodiment, the corrugation pitch is between 2 mm and 25 mm, preferably between 3 mm and 20 mm, and even more preferably between 4 mm and 12.5 mm.

[0106] In some preferred embodiments, at least one of the at least two elongated elements, a first elongated element, extends along a helical path with a predetermined pitch around at least one of the at least two elongated elements, a second elongated element.

[0107] In this configuration, a core portion disposed in a radially inner position and a crown portion disposed in a radially outer position and extending around the core portion can be identified within the reinforcing cord. At least one second elongated element is disposed in the core portion, while at least one first elongated element extends along the helical path and at the predetermined pitch at the crown portion and thus around the at least one second elongated element.

[0108] In other preferred embodiments, at least one of the at least two elongated elements, a first elongated element, extends along a corresponding helical path with a predetermined pitch, and at least one of the at least two elongated elements, a second elongated element, extends along a corresponding helical path with the predetermined pitch.

[0109] In this configuration, at least two slender elements of the reinforcing cord are spirally wound around each other and arranged side by side.

[0110] Preferably, the at least one second elongated element is twisted to the at least one first elongated element at the predetermined pitch. In this case, the at least two elongated elements define at least one first strand.

[0111] Preferably, the predetermined pitch is greater than 2 mm, more preferably greater than 3 mm, and even more preferably greater than 4 mm.

[0112] Preferably, the predetermined pitch is less than 25 mm, more preferably less than 20 mm, and even more preferably less than 12.5 mm.

[0113] In a preferred embodiment, the predetermined pitch is between 2 mm and 25 mm, preferably between 3 mm and 20 mm, and more preferably between 4 mm and 12.5 mm.

[0114] The applicant has discovered that, under these conditions, all other parameters being equal, the partial load elongation and breaking elongation of the reinforcing cord can be maximized.

[0115] In these embodiments, the predetermined pitch substantially corresponds to the aforementioned corrugated pitch of the wavy trajectory of the cord.

[0116] Preferably, the at least one first elongated element is defined by at least one yarn.

[0117] Preferably, the at least one first elongated element comprises one, two, or three yarns.

[0118] In some embodiments, the two or three yarns are twisted together.

[0119] Preferably, the at least one second elongated element is defined by at least one wire or yarn.

[0120] In some preferred embodiments, the at least one second elongated element comprises a single wire or two wires twisted together.

[0121] In other preferred embodiments, the at least one second elongated element comprises a single yarn.

[0122] In some preferred embodiments, the reinforcing cord comprises a single first strand.

[0123] Preferably, the individual strand comprises a single strand twisted into a single yarn.

[0124] In other preferred embodiments, the reinforcing cord comprises two first strands twisted together and extending along a corresponding helical path with a corresponding pitch.

[0125] The two first-line stocks may be the same as each other or different from each other.

[0126] Preferably, the two first-line strands are identical to each other.

[0127] The corresponding pitch may be equal to or different from the predetermined pitch.

[0128] Preferably, the corresponding pitch is equal to the predetermined pitch.

[0129] Preferably, each of the two first strands comprises at least one corresponding thread, which is twisted into at least one corresponding yarn.

[0130] More preferably, each of the two first strands comprises a single strand twisted into a single yarn.

[0131] In some embodiments, both the at least first elongated element and the at least second elongated element are made of the same non-metallic material.

[0132] In this case, preferably, the at least two elongated elements are defined by at least one wire and at least one yarn, or by at least two wires with the same or different diameters, or by corresponding yarns with the same or different linear densities.

[0133] In a preferred embodiment, the at least one first elongated element is made of a first non-metallic material, and the at least one second elongated element is made of a second non-metallic material different from the first material. In this case, the at least two elongated elements define at least one first hybrid strand when twisted together.

[0134] In a preferred embodiment, the first material and the second material are selected from: nylon, rayon, PET, aramid, and glass.

[0135] Preferably, the first material is selected from nylon, rayon, PET, aramid, and glass.

[0136] Preferably, the second material is selected from nylon, rayon, and PET.

[0137] Preferably, one elongated element is made of a low-modulus material, and the other elongated element is made of a material with a modulus higher than that of the former elongated element.

[0138] Preferably, one elongated element is made of a low-modulus material and the other elongated element is made of a high-modulus material, so as to achieve high stiffness under higher loads in addition to the desired partial load elongation.

[0139] This results in the unique "bimodulus" mechanical properties typical of hybrid reinforced cords. In the load-elongation curve, these unique "bimodulus" mechanical properties are converted into a curve defined by two segments separated by a connecting inflection point. In this curve, the segment to the left of the inflection point (representing partial load elongation, which is particularly high for the reinforced cord of this invention) has a much smaller inclination relative to the horizontal axis than the segment to the right of the inflection point (representing stiffness). Under partial load, the mechanical properties of the reinforced cord are affected by the tension of the reinforced cord (which initially extends along a non-linear trajectory) and are also regulated by the response provided by the low-modulus material. Under high load, however, the mechanical properties of the reinforced cord are primarily regulated by the response provided by the high-modulus material.

[0140] Preferably, the at least one first elongated element is defined by at least one aramid, glass, or PET yarn.

[0141] Preferably, the at least one second elongated element is defined by at least one nylon, rayon, or PET thread.

[0142] In some specific embodiments, at least one first elongated element and at least one second elongated element are both defined by nylon yarn. In this case, a greater partial load elongation is obtained only by stretching the reinforcing cord, which initially extends along a non-linear trajectory, compared to a conventional reinforcing cord defined by two nylon elongated elements.

[0143] In some specific embodiments, at least one first elongated element and / or at least one second elongated element are defined by PET wire or yarn. Compared to conventional reinforcing cords defined by nylon elongated elements, PET imparts higher stiffness to the reinforcing cord.

[0144] In some preferred embodiments, the reinforcing cord includes at least one third elongated element made of a non-metallic material and twisted to the at least one first elongated element.

[0145] In this case, at least one first elongated element and at least one third elongated element define at least one strand of wire, which is wound around at least one second elongated element at the predetermined pitch.

[0146] Preferably, the at least one third elongated element is arranged together with the at least one first elongated element at the crown portion of the reinforcing cord.

[0147] The at least one third elongated element may be made of the same or different non-metallic material as the at least one first elongated element.

[0148] Preferably, the at least one third elongated element is made of a non-metallic material different from the at least one first elongated element.

[0149] Preferably, the at least one third elongated element is made of a material selected from nylon, rayon, or PET.

[0150] Preferably, the at least one third elongated element is made of the same material as the at least one second elongated element.

[0151] In some embodiments, the at least one third elongated element is defined by at least one wire.

[0152] In some preferred embodiments, the at least one third elongated element comprises a single wire or two wires twisted together.

[0153] In some preferred embodiments, the reinforcing cord includes at least one fourth elongated element made of a non-metallic material and arranged at a radially inward position relative to the at least one first elongated element and (if present) also relative to the at least one third elongated element.

[0154] Preferably, the at least one fourth elongated element is twisted to the at least one second elongated element.

[0155] Therefore, the reinforcing cord of such embodiments has at least two elongated elements at the corresponding radial inner or core portion, and at least two elongated elements at the corresponding radial outer or crown portion when at least one third elongated element is also present.

[0156] The at least one fourth elongated element may be made of the same or different non-metallic material as the at least one second elongated element.

[0157] Preferably, the at least fourth elongated element is made of a nonmetallic material different from the nonmetallic material of the at least second elongated element.

[0158] In this case, the at least one second elongated element and the at least one fourth elongated element define at least one second hybrid strand, which is preferably arranged at a radially inward position relative to the first hybrid strand.

[0159] Preferably, the at least fourth elongated element is made of the same material as the at least first elongated element.

[0160] The second hybrid strand may be the same as or different from the first hybrid strand.

[0161] Preferably, the second hybrid strand is the same as the first hybrid strand.

[0162] In some preferred embodiments, the reinforcing cord includes a single second hybrid strand.

[0163] Preferably, the single second hybrid strand comprises a single strand twisted into a single yarn.

[0164] Preferably, the at least one fourth elongated element is made of a material selected from nylon, rayon, PET, aramid, and glass.

[0165] Preferably, the at least one fourth elongated element is defined by at least one yarn.

[0166] Preferably, the at least one third elongated element is defined by at least one nylon, rayon, or PET thread, and the at least one fourth elongated element is defined by at least one aramid or glass yarn.

[0167] More preferably, the at least one third elongated element is defined by a single nylon, rayon, or PET thread, and the at least one fourth elongated element is defined by a single aramid or glass yarn.

[0168] Preferably, the reinforcing cord has an initial modulus and a final modulus such that the ratio between the final modulus and the initial modulus is greater than or equal to 9.

[0169] Preferably, the ratio between the final modulus and the initial modulus is greater than or equal to 12, even more preferably greater than or equal to 20, or even more preferably greater than or equal to 30.

[0170] Preferably, the diameter of each wire is greater than or equal to 0.10 mm, more preferably greater than or equal to 0.16 mm, and even more preferably greater than or equal to 0.23 mm.

[0171] Preferably, the diameter of each wire is less than or equal to 0.8 mm, more preferably less than or equal to 0.5 mm, and even more preferably less than or equal to 0.35 mm.

[0172] In a preferred embodiment, the diameter of each wire is between 0.10 mm and 0.8 mm, more preferably between 0.16 mm and 0.5 mm, and even more preferably between 0.23 mm and 0.35 mm.

[0173] Preferably, the linear density of each yarn is greater than or equal to 235 dtex, more preferably greater than or equal to 500 dtex, and even more preferably greater than or equal to 940 dtex.

[0174] Preferably, the linear density of each yarn is less than or equal to 3300 dtex, more preferably less than or equal to 2700 dtex, and even more preferably less than or equal to 2200 dtex.

[0175] Preferably, the linear density of each yarn is between 235 dtex and 3300 dtex, more preferably between 500 dtex and 2700 dtex, and even more preferably between 940 dtex and 2200 dtex.

[0176] Preferably, the reinforcing cord of the present invention is used in the zero-degree reinforcing layer of a tire. Attached Figure Description

[0177] Further features and advantages of the tire of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention with reference to the accompanying drawings. In such drawings:

[0178] - Figure 1 This is a schematic partial half-sectional view of a portion of an embodiment of a tire including reinforcing cords according to the present invention;

[0179] - Figure 2-5 These are segmented photographs of various embodiments of the reinforcing cord according to the present invention;

[0180] - Figures 2a-5a yes Figure 2-5 The reinforcing cord in Figure 2-5 A schematic sectional view taken at section AA as indicated in the diagram;

[0181] - Figure 6 and Figure 7 Two load-elongation curves are shown: one for conventional fabric reinforced cord and the other for reinforced cord made according to the present invention. Detailed Implementation

[0182] For the sake of simplicity, Figure 1 Only a portion of an exemplary embodiment of the tire 100 according to the invention is shown; the remaining portions, not shown, are substantially the same and are arranged symmetrically with respect to the equatorial plane MM of the tire.

[0183] Figure 1 The tire 100 shown is an exemplary embodiment, particularly for a tire used in a four-wheeled vehicle.

[0184] Preferably, tire 100 is an HP or UHP tire for sport and / or high-performance and ultra-high-performance vehicles. This tire allows speeds above 190 km / h, up to and exceeding 300 km / h, and holds one of the following speed codes according to ETRTO standards (European Tyre and Rim Technology Organization): “T”, “U”, “H”, “V”, “Z”, “W”, “Y”. Its section width is equal to or greater than 185 mm, preferably between 195 mm and 385 mm, more preferably between 195 mm and 355 mm, and is designed to be mounted on rims with a mounting diameter equal to or greater than 13 inches, preferably not exceeding 24 inches, more preferably between 16 inches and 23 inches.

[0185] Figure 1 In the diagram, "a" represents the axial direction, "c" represents the radial direction, "MM" represents the equatorial plane of tire 100, and "RR" represents the axis of rotation of tire 100.

[0186] The tire 100 includes a carcass structure 101, which in turn includes at least one carcass ply 111.

[0187] In the following description, for the sake of simplicity, reference will be made to an embodiment of a tire 100 comprising a single carcass ply 111. The same applies to tires comprising more than one carcass ply.

[0188] The axially opposite end edges of the carcass ply 111 engage with corresponding annular anchoring structures 102 (referred to as bead cores), which may be associated with elastomeric filler 104. The region of the tire 100 including the bead core 102 and possibly the elastomeric filler 104 forms an annular reinforcing structure 103 (referred to as a “bead structure”) and is configured to allow the tire 100 to be anchored to a corresponding mounting rim (not shown).

[0189] The carcass ply 111 includes a plurality of reinforcing cords 10', which are coated with an elastomeric material or incorporated into a matrix of a cross-linked elastomeric material.

[0190] The tire carcass structure 101 is radial, that is, the reinforcing cords 10' are arranged on a plane including the axis of rotation RR of the tire 100 and are substantially perpendicular to the equatorial plane MM of the tire 100.

[0191] Each annular reinforcement structure 103 is associated with the carcass structure 101 by folding (or turning up) the opposite end edges of at least one carcass ply 111 around the bead core 102 and possibly the elastomeric filler 104 to form a so-called flange 101a of the carcass structure 101.

[0192] The crown structure is located radially outward relative to the carcass structure 101. The crown structure includes a cross-belt layer structure 106 and a zero-degree reinforcement layer 106c, commonly known as a "zero-degree belt".

[0193] The cross-belt structure 106 includes at least two radially overlapping belt layers 106a and 106b.

[0194] The belt layers 106a and 106b each include a plurality of reinforcing cords 10'' and 10'''. These reinforcing cords 10'' and 10''' are oriented at an angle between 15° and 45°, preferably between 20° and 40°, relative to the circumferential direction of the tire 100 or the equatorial plane MM of the tire 100. For example, the angle is equal to 30°.

[0195] The reinforcing cords 10'', 10''' of one belt layer 106a, 106b are parallel to each other and are cross-oriented relative to the reinforcing cords 10'', 10''' of the other belt layer 106b, 106a.

[0196] The zero-degree reinforcement layer 106c includes reinforcing cords oriented in a generally circumferential direction. Therefore, these reinforcing cords form an angle of a few degrees (typically less than 10°, for example, between 0° and 6°) with respect to the equatorial plane MM of the tire 100.

[0197] A tread strip 109 made of an elastomeric material is applied at a radially outer position relative to the zero-degree reinforcement layer 106c.

[0198] A corresponding sidewall 108 made of an elastomeric material is also applied to the side surface of the carcass structure 101, at an axially external position relative to the carcass structure 101 itself. Each sidewall 108 extends from one of the side edges of the tread strip 109 to the corresponding annular reinforcement structure 103.

[0199] In some specific embodiments, such as those shown and described herein, the stiffness of the sidewall 108 can be increased by providing a reinforcing layer 120, which is typically known as a “wire loop overlaid fabric” or an additional strip insert and functions to increase the stiffness and integrity of the annular reinforcement structure 103 and the sidewall 108.

[0200] The outer sheath 120 of the steel wire bead wraps around the corresponding bead core 102 and the elastomeric filler 104 to at least partially surround the annular reinforcement structure 103. In particular, the outer sheath 120 of the steel wire bead wraps around the annular reinforcement structure 103 along the axially inner, axially outer, and radially inner regions of the annular reinforcement structure 103.

[0201] The outer sheath 120 of the steel wire bead is arranged between the raised edge of the carcass ply 111 and the corresponding annular reinforcement structure 103. Typically, the outer sheath 120 of the steel wire bead is in contact with the carcass ply 111 and the annular reinforcement structure 103.

[0202] In some specific embodiments, such as those shown and described herein, the bead structure 103 may also include another reinforcing layer 121, which is generally known as the term "bead wrap" or protective strip and functions to increase the stiffness and integrity of the annular reinforcing structure 103.

[0203] The bead wrap 121 is connected to the corresponding raised end edge of the carcass ply 111 at an axially external position relative to the corresponding annular reinforcement structure 103 and extends radially toward the sidewall 108 and the tread strip 109.

[0204] The outer sheath 120 of the bead and the outer sheath 121 of the tire include reinforcing cords 10* (in the attached drawings, the reinforcing cords of the outer sheath 120 of the bead are not visible).

[0205] exist Figure 1 In the tire shown, at least some of the reinforcing cords of the zero-degree reinforcing layer 106c (preferably all the cords of the zero-degree reinforcing layer 106c) are reinforcing cords 10 according to the invention.

[0206] Figure 2 and Figure 2a A first embodiment of this reinforced cord 10 is shown.

[0207] The reinforcing cord 10 includes two elongated elements 11a at its crown portion (i.e., at the radially outer position), which are made of a non-metallic material and twisted together, and two elongated elements 11b at its core portion and therefore at the radially inner position, which are also made of a non-metallic material and twisted together and are of a different type from the two elongated elements 11a.

[0208] An elongated element 11a is twisted onto an elongated element 11b and extends along a helical path around the elongated element 11b at a predetermined pitch E. Figure 2 The individual elongated elements 11a and thus the longitudinal extension direction L of the reinforcing cord 10 are indicated in the diagram.

[0209] The reinforcing cord 10 extends along the longitudinal direction L in a non-linear, preferably wavy, trajectory. This trajectory has a periodicity that can be measured by the corrugation pitch.

[0210] The pitch E and the corrugated pitch are between 2 mm and 25 mm, preferably between 3 mm and 20 mm, and more preferably between 4 mm and 12.5 mm.

[0211] Preferably, the pitch E is approximately equal to the corrugated pitch.

[0212] exist Figure 2 and Figure 2a In the embodiment of the reinforcing cord 10 shown, each of the two elongated elements 11a is defined by a corresponding yarn, while each of the two elongated elements 11b is defined by a corresponding wire.

[0213] The diameter of each wire is between 0.10 mm and 0.8 mm, preferably between 0.16 mm and 0.5 mm, and more preferably between 0.23 mm and 0.35 mm.

[0214] The linear density of each yarn is between 235 dtex and 3300 dtex, preferably between 500 dtex and 2700 dtex, and more preferably between 940 dtex and 2200 dtex.

[0215] Each wire is made from materials selected from nylon, rayon, and PET.

[0216] Each yarn is made from materials selected from nylon, rayon, PET, aramid, and glass.

[0217] Preferably, each wire is made of a low-modulus material, particularly nylon, rayon, or PET, and each yarn is made of a high-modulus material, particularly aramid or glass.

[0218] In cases where each thread is made of nylon, rayon, or PET, each yarn can be made of PET.

[0219] The reinforcing cord 10 is intended to be incorporated into a strip-shaped element made of an elastomeric material and is intended to be used in the manufacture of the zero-degree reinforcing layer 106c of the tire 100.

[0220] In all the reinforcing cords 10 according to the invention, preferably, at least one elongated element made of a low-modulus material and at least one elongated element made of a high-modulus material are provided. In particular, the ratio between the final modulus and the initial modulus is greater than or equal to 9.

[0221] Figure 2 and Figure 2a The example of the reinforcing cord 10 of the type shown has the following construction:

[0222] 2 × 0.28 NY + 1 × AR 1672

[0223] The reinforcing cord includes two elongated elements 11b, which are defined by corresponding nylon yarns with a diameter of 0.28 mm, and are twisted to two elongated elements 11a defined by corresponding aramid yarns with a linear density of 1670 dtex.

[0224] exist Figure 3 and Figure 3a Another example of the reinforcing cord 10 according to the present invention is shown in the figure.

[0225] The reinforcing cord 10 and Figure 2 and Figure 2a The reinforcing cord shown differs only in that, at its crown portion, the reinforcing cord comprises strand 11 instead of two elongated elements 11a, the strand comprising elongated elements 11a made of a nonmetallic material, which are twisted to elongated elements 11c made of a nonmetallic material different from that of the elongated elements 11a.

[0226] The thread 11 extends along the helical path around the two elongated elements l1b at a predetermined pitch E.

[0227] The slender element 11a of strand 11 is the same as the one mentioned above. Figure 2 , Figure 2a It is the same as the slender element described.

[0228] The elongated element 11c of the strand 11 is defined by a corresponding wire with a diameter between 0.10 mm and 0.8 mm, preferably between 0.16 mm and 0.5 mm, and more preferably between 0.23 mm and 0.35 mm.

[0229] The elongated element 11c is made of a material selected from nylon, rayon, and PET.

[0230] Figure 3 and Figure 3a The example of the reinforcing cord 10 of the type shown has the following construction:

[0231] 2 × 0.23 NY + 1 × (AR1680 + NY 0.23)

[0232] The reinforcing cord includes two elongated elements 11b, each defined by a corresponding nylon thread with a diameter of 0.23 mm and twisted to a strand 11 (hereinafter referred to as the "crown strand"). The strand includes an elongated element 11a defined by an aramid yarn with a linear density of 1680 dtex, which is twisted to an elongated element 11c defined by a nylon thread with a diameter of 0.23 mm. Furthermore, in this configuration, both elongated elements 11b are arranged in the core portion of the reinforcing cord 10, while the strand 11 is arranged at the crown portion of the reinforcing cord 10.

[0233] An example of the reinforcing cord 10 according to the invention (not shown) Figure 3 and Figure 3a The only difference in the example shown is that the elongated element 11b provided in its core portion is twisted to another elongated element to form a strand (hereinafter referred to as the "core strand"), which is then twisted to the aforementioned crown strand to form the reinforcing cord 10.

[0234] Preferably, the core strands are the same as the crown strands.

[0235] Another example of the reinforcing cord according to the invention (not shown) Figure 2 and Figure 2a The only difference in the example shown is that the reinforcing cord includes conventional hybrid strands at its crown portion, instead of two elongated elements 11a. These conventional hybrid strands consist of two aramid yarns, each with a linear density of 1330 dtex, twisted together to form a nylon yarn with a linear density of 1400 dtex. This conventional hybrid strand corresponds to the reinforcing cord described below. Figure 6 and Figure 7 In the description, the reinforcing cord is represented by STD and has the following construction: 2 × AR1330 / NY1400.

[0236] exist Figure 4 and Figure 4a Another example of the reinforcing cord 10 according to the invention is shown in the figure.

[0237] This reinforced cord 10 and Figure 2 and Figure 2a The only difference of the reinforcing cord shown is that the reinforcing cord includes a single elongated element 11b in its core portion, rather than two elongated elements 11b. In a specific example, the single elongated element is defined by a yarn made of a material selected from nylon, rayon, PET, aramid, and glass.

[0238] The elongated element 11a is a reference Figure 2 , 2a The types described above.

[0239] Figure 4 and Figure 4a The example of the reinforcing cord 10 of the type shown has the following construction:

[0240] 1 × NY1400 + 2 × AR1670

[0241] This reinforcing cord 10 includes elongated elements 11b defined by nylon yarn with a linear density of 1400 dtex and twisted to two elongated elements 11a defined by corresponding aramid yarns with a linear density of 1670 dtex. The elongated elements 11b are arranged in the core portion of the reinforcing cord 10, while the two elongated elements 11a are arranged in the crown portion of the reinforcing cord 10.

[0242] Therefore, the reinforcing cords in the examples discussed above have at least one elongated element in the core portion and at least one elongated element in the crown portion. These reinforcing cords are manufactured by feeding the aforementioned elongated element into a twisting device typically used for twisting metal wires and appropriately controlling the twisting process.

[0243] In the specific case where there are several elongated elements in the core portion and / or crown portion, the twisting process first involves forming one or more semi-finished products, wherein all the elongated elements in the core portion (hereinafter referred to as "first elongated elements") and / or all the elongated elements in the crown portion (hereinafter referred to as "second elongated elements") have been pre-twisted. These semi-finished products and the possible individual elongated elements are fed into a twisting device, where they are twisted together by arranging the first elongated elements in a radially inward position relative to the second elongated elements.

[0244] The twisting process is controlled by adjusting the force applied to the elongated elements / semi-finished products, applying a predetermined braking force only to some of these elongated elements / semi-finished products, and applying a predetermined degree of deformation (preforming or pleating) to the reinforcing cord. Applying the braking force allows some elongated elements / semi-finished products to be braked relative to others, thus creating a margin for certain elongated elements relative to others within a unit length of the reinforcing cord. Specifically, to first operate elongated elements made of lower stiffness materials under traction to obtain the desired high partial load elongation, and subsequently operate elongated elements made of higher stiffness materials under traction to achieve sufficient stiffness even under higher loads, the elongated elements made of higher stiffness materials create a margin relative to those made of lower stiffness materials. The desired degree of deformation (preforming or pleating) can be achieved by passing the elongated elements with a predetermined tension through multiple small-diameter (e.g., 1 to 5 mm) cylinders. This allows for the provision of reinforcing cords with high curvature and therefore the desired wavy shape.

[0245] After twisting the semi-finished product, the resulting reinforced cord undergoes an adhesion treatment in order to maintain the desired geometry.

[0246] Figure 5 , Figure 5a Another example of the reinforcing cord 10 according to the invention is shown.

[0247] The reinforcing cord 10 and Figure 4 and Figure 4a The only difference in the reinforcing cord shown is that, in this example, the various elongated elements 11a, 11b constituting the reinforcing cord 10 are not separated between the core portion and the crown portion, but are all twisted together so as to be arranged side by side along the respective helices with the same pitch.

[0248] Figure 5 and Figure 5a The example of the reinforcing cord 10 of the type shown has the following construction:

[0249] 1 × NY940 + 2 × AR1670

[0250] The reinforcing cord 10 includes elongated elements 11b, which are defined by nylon yarn with a linear density of 940 dtex and twisted to two elongated elements 11a defined by corresponding aramid yarn with a linear density of 1670 dtex. The two elongated elements 11a and 11b are spirally wound around each other.

[0251] Figure 5 and Figure 5a The reinforcing cord can be manufactured by feeding the aforementioned elongated elements into a twisting device typically used for twisting fabric yarns and appropriately controlling the twisting process. No semi-finished or pre-twisted elongated elements are required. The parallel filaments of the individual elongated elements 11a, 11b are fed directly into the twisting device, which twists them together in a single stage. First, each elongated element is twisted in one direction; then, after the elongated elements have been twisted, the resulting reinforcing cord is twisted, resulting in the untwisting of the individual elongated elements.

[0252] In this case, the twisting process is controlled by adjusting the force pulling the elongated elements and applying a predetermined braking force only to some of the elongated elements, similar to the method discussed above.

[0253] After the individual elongated elements are twisted, the reinforcing cord undergoes an adhesion treatment to maintain the desired geometry.

[0254] The applicant has conducted some comparative tensile tests on various reinforcing cords according to the present invention and conventional reinforcing cords commonly used in the zero-degree reinforcement layer of tires, in accordance with the BISFA standard.

[0255] The standard reinforcing cord comprises two aramid yarns, both having a linear density of 1330 dtex and twisted to a linear density of 1400 dtex. This cord is referred to herein as STD and is constructed as follows: 2 × AR1330 / NY1400.

[0256] The reinforcing cord according to the present invention has the following structure:

[0257] -2 × 0.28 NY + 1 × AR 1672, denoted here as INV1 (this is from the reference above). Figure 2 and Figure 2a (Example of the description);

[0258] -2 × 0.23 NY + 1 × (AR1680 + NY 0.23), denoted here as INV2 (this is from the reference above). Figure 3 and Figure 3a (Example of the description);

[0259] -2 × NY 0.23 + 2 × AR1330 / NY1400, referred to here as INV3 (this is the example described above, in which a conventional hybrid strand constructed of 2 × AR1330 / NY1400 is set at the crown portion of the reinforcing cord).

[0260] -1 × NY1400 + 2 × AR1670, denoted here as INV4 (this is from the reference above). Figure 4 and Figure 4a (Example described).

[0261] The results of these comparative tests are as follows: Figure 6 As shown.

[0262] It is noteworthy that, with other parameters being equal, the partial load elongation of the reinforcing cord according to the present invention is much greater than that of conventional reinforcing cords, and it also possesses unique "bimodulus" mechanical properties. Therefore, in addition to the desired load elongation, it can also guarantee high stiffness under higher loads. In particular, the reinforcing cord INV3 has mechanical properties designated herein as "trimodulus," characterized by: firstly, a high partial load elongation, which is a result of both the stretching of the initially non-linear reinforcing cord and the reaction provided by the nylon yarn present in the core portion of the reinforcing cord; then (after the first inflection point), a slight increase in stiffness (with a corresponding slight decrease in elongation), which is a result of the reaction provided by the nylon yarn present in the crown portion of the reinforcing cord; subsequently (after the second inflection point), a significant increase in stiffness (with a corresponding significant decrease in elongation), which is a result of the reaction provided by the aramid yarn present in the crown portion of the reinforcing cord.

[0263] The applicant has, in accordance with BISFA standards, described another reinforcing cord according to the present invention and the above reference. Figure 6 The conventional reinforced cord was subjected to further comparative tensile testing.

[0264] The reinforcing cord according to the present invention has the following structure:

[0265] -1 × NY1400 + 2 × AR1670, here identified as INV5 (referencing the above). Figure 5 and Figure 5a (The example mentioned).

[0266] exist Figure 7 The results of these comparative tests are shown in the figure.

[0267] Similarly, in this case, it can be noted that, with other parameters being equal, the partial load elongation of the reinforcing cord according to the invention is much greater than that of the conventional reinforcing cord, and it also has the unique “bimodulus” mechanical properties discussed above.

[0268] The present invention has been described with reference to some preferred embodiments. Various modifications can be made to the above embodiments while remaining within the scope of protection of the invention as defined by the following claims.

Claims

1. A reinforcing cord (10) for a tire for a vehicle wheel, the reinforcing cord comprising at least two elongated elements (11a, 11b) made of a non-metallic material and twisted together, wherein the reinforcing cord (10) extends along a non-linear longitudinal trajectory.

2. The reinforcing cord (10) according to claim 1, wherein, The longitudinal trajectory is basically wavy.

3. The reinforcing cord (10) according to claim 1 or 2, wherein, At least one of the at least two elongated elements (11a, 11b) is a first elongated element (11a) that extends along a helical path with a predetermined pitch (E) around at least one of the at least two elongated elements (11a, 11b) is a second elongated element (11b).

4. The reinforcing cord (10) according to claim 1 or 2, wherein, At least one of the at least two elongated elements (11a, 11b) is a first elongated element (11a) extending along a corresponding helical path with a predetermined pitch (E), and at least one of the at least two elongated elements (11a, 11b) is a second elongated element (11b) extending along a corresponding helical path with the predetermined pitch (E).

5. The reinforcing cord (10) according to claim 3 or 4, wherein, The at least one first elongated element (11a) is defined by at least one yarn, and the at least one second elongated element (11b) is defined by at least one wire or yarn.

6. The reinforcing cord (10) according to any one of claims 3 to 5, wherein, The at least one first elongated element (11a) is made of a non-metallic first material, and the at least one second elongated element (11b) is made of a non-metallic second material different from the first material.

7. The reinforcing cord (10) according to claim 6, wherein, The first material and the second material are selected from: nylon, rayon, PET, aramid, and glass.

8. The reinforcing cord (10) according to claim 6 or 7, wherein, The first material is selected from nylon, rayon, PET, aramid, and glass, and the second material is selected from nylon, rayon, and PET.

9. The reinforcing cord (10) according to claim 3 or any one of claims 5 to 8 when dependent on claim 3, the reinforcing cord further comprising at least one third elongated element (11c), the third elongated element being made of a non-metallic material and twisted to the at least one first elongated element (11a).

10. The reinforcing cord (10) according to claim 9, wherein, The at least one third elongated element (11c) is defined by at least one wire.

11. The reinforcing cord (10) according to claim 9 or 10, wherein, The at least one third elongated element (11c) is made of a material different from that of the at least one first elongated element (11a).

12. The reinforcing cord (10) according to any one of claims 9 to 11, wherein, The at least one third elongated element (11c) is made of a material selected from nylon, rayon, and PET.

13. The reinforcing cord (10) according to any one of claims 9 to 12, wherein, The at least one third elongated element (11c) is made of the same material as the at least one second elongated element (11b).

14. The reinforcing cord (10) according to any one of the preceding claims, wherein, The reinforcing cord (10) has an initial modulus and a final modulus such that the ratio between the final modulus and the initial modulus is greater than or equal to 9.

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