Double-layer multi-strand cable with improved bending endurance

Abstract

The invention relates to a multi-strand cable (50) comprising a cable inner layer (CI) consisting of K=1 inner strand (TI) having two plies (C1, C3) and a cable outer layer (CE) consisting of L>1 outer strands (TE) having two plies (C1', C3') wound around the cable inner layer (CI), the inner ply (C1) consisting of Q inner metallic filaments (F1) and the outer ply (C3) consisting of N outer metallic filaments (F3), the inner ply (C1') consisting of Q' inner metallic filaments (FT) and the outer ply (C3') consisting of N' outer metallic filaments (F3'). The cord (50) has: - a durability criterion SL≤ 40 000 MPa.mm, with SL = max: (F); and - an overall size criterion Ec≥ 0.46, with E = Sc / Se.

Description

Technical Field

[0001] This invention relates to cords, reinforced products of non-pneumatic tire types including such cords, conveyor belts or tracks, and tires. Background Technology

[0002] A tire for construction site vehicles is known from the prior art, having a radial carcass reinforcement and including a tread, two non-stretchable bead sections, two sidewalls connecting the bead sections to the tread, and a crown reinforcement arranged circumferentially between the carcass reinforcement and the tread. This crown reinforcement includes multiple ply layers reinforced with reinforcing elements (such as metal cords), with the cords of one ply layer embedded in an elastomeric matrix of the ply layer.

[0003] The crown reinforcement includes the working reinforcement, the protective reinforcement, and possible other reinforcements (such as the ring reinforcement).

[0004] The carcass reinforcement itself includes at least one elastomeric carcass ply reinforced by reinforcing elements (e.g., metal cords). A carcass ply reinforcement element is known from the prior art, comprising a double-layered multi-strand metal cord having a structure of 68.23. This cord comprises an inner cord layer and an outer cord layer, the inner cord layer consisting of inner strands, and the outer cord layer consisting of eight outer strands wound in a spiral around the inner cord layer. Each inner strand comprises an inner strand layer consisting of three inner strands and an outer strand layer consisting of nine outer strands. Each strand has a diameter equal to 0.26 mm. Each outer strand comprises an inner strand layer consisting of one inner strand and an outer strand layer consisting of six outer strands. Each strand has a diameter equal to 0.23 mm.

[0005] Tires on heavy-duty industrial vehicles (especially those used on construction sites) suffer from numerous attacks. Specifically, these types of tires are often driven on uneven road surfaces, sometimes resulting in punctures in the tread. These punctures allow corrosive agents (such as air and water) to enter, oxidizing the metal reinforcing elements of the tread reinforcement and sometimes the carcass reinforcement, thus significantly reducing tire life.

[0006] Regarding carcass reinforcements, the inventors of this invention have recognized that the primary requirement for carcass reinforcements is durability under high loads; therefore, it is important to design cords with high breaking strength levels, low flexural stiffness, and very good elastomer blend permeability.

[0007] However, it is known that existing cords are not very resistant to being permeated by elastomer blends, which makes them less durable in corrosive environments.

[0008] One solution to increase tire life is to combat the behavior of corrosive agents within each strand. This can be achieved by coating each inner and middle layer of each strand with rubber during the manufacturing process of the cord. During this process, the deposited rubber permeates the capillaries present between each layer of each strand, thus preventing the diffusion of corrosive agents. Such cords are commonly referred to as in-situ rubberized cords and are well known in the art. However, the methods for manufacturing these in-situ rubberized cords require the control of numerous industrial constraints, particularly to prevent rubber from overflowing from the periphery of each strand.

[0009] Another solution to increase tire life is to increase the breaking strength of existing cords. Typically, this is achieved by increasing the diameter of the filaments that make up the cord and / or by increasing the number of filaments and / or the individual strength of each filament. However, further increasing the filament diameter, for example, beyond 0.50 mm, inevitably leads to a reduction in cord flexibility, which is undesirable for cords used in carcass reinforcements. Increasing the number of filaments generally reduces the ability of the elastomer compound to penetrate the strands. Increasing the individual strength of each filament requires a significant investment in the equipment used to manufacture the filaments. Summary of the Invention

[0010] The object of the present invention is a cord that has improved bending durability compared with prior art cords, while avoiding the aforementioned disadvantages.

[0011] For this purpose, one aspect of the present invention is a double-layer multi-strand cord, comprising:

[0012] - An inner layer of cord composed of K=1 double-layered internal strands, wherein the double-layered internal strands include:

[0013] - An inner layer consisting of 1, 2, 3, or 4 internal metal wires with a diameter d1, and

[0014] - An outer layer consisting of N outer metal wires with a diameter d3 wound around the inner layer.

[0015] - An outer layer of the cord consisting of L>1 double-layered outer strands wound around the inner layer of the cord, wherein the double-layered outer strands include:

[0016] - An inner layer consisting of 1, 2, 3, or 4 internal metal wires with a diameter d1', and

[0017] - An outer layer consisting of N' outer metal wires with a diameter d3' wound around the inner layer, wherein:

[0018] Cords have:

[0019] - Bending durability standard SL≤40000 MPa.mm, where ,as well as

[0020] - Dimensional standard Ec≥0.46, where Ec=Sc / Se

[0021] in:

[0022] - in MPa.mm It is the maximum bending stress per unit of bending portion obtained through the internal threads of the internal and external strands;

[0023] - in MPa.mm It is the maximum bending stress per unit of bending portion obtained through the outer metal wire of the inner strands and outer strands;

[0024] - M 钢 =210000 MPa is the modulus of steel;

[0025] - d1, d1', d3 and d3' are represented in mm.

[0026] -

[0027] - Cp is the permeability coefficient of the cord, where It is the penetration coefficient between lines and It is the penetration coefficient of external line stocks, where:

[0028] - When the spacing E between the outermost strands of the outer layer is E < 30 μm, =0.4; or

[0029] - When E>70 µm =1.0; or

[0030] - When 30 µm ≤ E ≤ 70 µm

[0031] Furthermore, when the spacing I3' of the outer metal wires in the outer layer is I3' < 10 μm, =0.4; or

[0032] - When I3'>40 µm =1.0; or

[0033] - When 10 µm ≤ I3' ≤ 40 µm

[0034] - Cr is the dimensionless performance coefficient of the cord, where

[0035] in:

[0036] d3 and d3' are represented in mm.

[0037] αf is the contact angle, expressed in radians, between the outer metal wire of the inner strand and the outer metal wire (F3') of the outer strand.

[0038] αt is the helix angle of each outer strand, expressed in radians;

[0039] It is the sum of the breaking forces in Newtons of the Q'+N' strands of the outer thread;

[0040] Cste = 1500 N.mm -2 ;

[0041] D is the diameter of the cord in mm;

[0042] Sc is based on mm 2 The compact surface area is calculated as Sc = [Q × (d1 / 2)]. 2 +N × (d3 / 2) 2 + L × (Q' ×(d1' / 2) 2 +N' × (d3' / 2) 2 )] × π, and Se is the value of the cord in mm 2 The surface area is calculated as Se = π × (D / 2). 2 .

[0043] On the one hand, the cords according to the present invention, due to their relatively low flexural durability criterion, allow for a reduction in stress levels within cords subjected to flexural stress loads, thereby extending tire life. Specifically, the inventors of the present invention have discovered that the primary determining criterion for improving the durability of cords in corrosive environments lies not only in the breaking force as widely taught in the prior art, but also in the flexural durability criterion, which in this application is represented by an index equal to the maximum value of the following:

[0044] - The bending stress per unit bending portion obtained by dividing the inner strands of the inner and outer strands by the permeability coefficient of the cord; or

[0045] - The bending stress per unit bending portion obtained by the outer threads of the inner and outer strands, divided by the cord's permeability coefficient and its performance coefficient.

[0046] On one hand, the inventors of this invention hypothesize that the larger the surface area of ​​the contact between the threads, especially in the region between strands where stress is greatest—that is, the larger the contact surface area between the outer metal wires of the inner strands and the outer metal wires of the outer strands—the more the weakened load is reduced at multiple contacts. To optimize these contacts, the inventors hypothesize that for the same load, lower stress is required due to tension in the cord, or good geometric characteristics are needed in the contact between the outer metal wires of the inner strands and the outer metal wires of the outer strands, or more specifically, in the contact angle, to increase the contact surface area. Under a given tension, the performance factor allows for taking into account the loss of tensile properties of the cord due to the lateral weakening of the contact between the threads in the inner and outer layers of outer metal wires. This performance factor depends on the number of outer metal wires in the inner layer, the contact angle between the outer metal wires of the inner strands and the outer metal wires of the outer strands, the corresponding diameters d3 and d3' of the outer metal wires in the inner and outer layers, the helix angle of the outer strands, and the breaking force of the outer strands. Therefore, strong cords have a performance coefficient close to 1, while weak cords have a suboptimal performance coefficient closer to 0.5.

[0047] On the other hand, the cords according to the invention, due to their sufficiently high dimensional standards, can have the maximum metallic mass on the smallest possible surface area, thereby contributing to improved bending durability. Specifically, the inventors of the invention have discovered that a second determining criterion for improving the durability of the cords in corrosive environments lies not only in the breaking force as widely taught in the prior art, but also in the dimensional standard, which in this application is represented by an index equal to the compact surface area of ​​the cord divided by the surface area of ​​the cord.

[0048] Specifically, existing cords have relatively low flexural durability standards but suboptimal dimensional standards, or optimal dimensional standards (i.e., exceeding 0.46) but relatively high flexural durability standards. Cords according to the present invention, due to their relatively high performance coefficient and relatively high permeability coefficient, have relatively low durability standards and relatively high dimensional standards, thereby improving flexural durability.

[0049] Any range of values ​​expressed as “between a and b” represents a range of values ​​from greater than a to less than b (i.e., excluding endpoints a and b), while any range of values ​​expressed as “from a to b” means a range of values ​​from endpoint “a” to endpoint “b”, i.e., including the strict endpoints “a” and “b”.

[0050] By definition, the diameter of a strand is the diameter of the smallest circle circumscribed within it and outside the strand.

[0051] Advantageously, the diameter of the cord is the diameter of the smallest circle circumscribed within it and the unwound cord. Preferably, the cord has a diameter D that satisfies D ≤ 6.0 mm, and more preferably 2.0 mm ≤ D ≤ 5.5 mm. The diameter D is measured on the cord according to standard ASTM D2969-04.

[0052] In this invention, the cord has two layers with strands, which means that it comprises an assembly consisting of no more and no less than two layers with strands. This means that the assembly has two layers with strands, not one layer or three layers, but only two layers.

[0053] In one embodiment, the inner strands of the cord are surrounded by a polymer composition and then by an outer layer.

[0054] Advantageously, the internal strands have cylindrical layers.

[0055] Advantageously, each outer strand has a cylindrical layer.

[0056] Highly advantageously, both the inner strands and each outer strand have cylindrical layers. It should be recalled that such cylindrical layers are obtained when the individual layers of the strand are wound with different twist pitches and / or when the winding directions of these layers differ from one layer to another. Strands with cylindrical layers are extremely permeable, unlike strands with compact layers, where all layers have the same twist pitch and all layers are wound in the same direction, thus exhibiting much lower permeability.

[0057] The internal strands are double-layered strands. The internal strands comprise a filament assembly consisting of no more and no less than two layers of filaments. This means that the filament assembly has two layers of filaments, not one layer, nor three layers, but only two layers.

[0058] The outer strands are double-layered strands. The outer strands comprise a filament assembly consisting of no more and no less than two layers of filaments. This means that the filament assembly has two layers of filaments, not one layer or three layers, but only two layers.

[0059] It should be recalled that, as is known, the twist pitch of a strand represents the length of that strand measured parallel to the axis of the cord, after which the strand with this twist pitch completes a full loop around the axis of the cord. Similarly, the twist pitch of a filament represents the length of that filament measured parallel to the axis of the strand in which the filament is located, after which the filament completes a full loop around the axis of the strand.

[0060] The winding direction of a layer with strands or threads refers to the direction in which the strands or threads are formed relative to the axis of the cord or strand. The winding direction is usually indicated by the letter Z or the letter S.

[0061] The twist pitch, winding direction, and diameter of the yarn and strands are determined according to the 2014 standard ASTM D2969-04.

[0062] The contact angle between the outer metal wires of the inner strand and the outer metal wires of the outer strand is... Figure 6 The angle αf is shown in the schematic diagram of the cord according to the invention. The cord axis A-A' is shown, around which the inner and outer layers of the cord are wound. In this diagram, only one wire from the outer layer of the inner strand and one wire from the outer layer of the outer strand are shown to better illustrate the angle αf, which is the contact angle between the outer wires of the inner and outer strands. This is one of the relevant parameters for determining the cord attenuation factor, because a smaller contact angle results in less cord attenuation.

[0063] The helix angle αt of each outer strand is a parameter well known to those skilled in the art and can be determined using the following formula: tan αt = 2 × π × Re TE / pe, where pe is the twist pitch (in millimeters) of each outer strand, Re TE Let α be the helix radius of each outer strand, expressed in millimeters, and tan be the tangent function. αt is expressed in degrees.

[0064] By definition, the helical radius Re of the outer layer of the cord is the radius of the theoretical circle, which passes through the center of the outer strands of the outer layer in a plane perpendicular to the cord axis.

[0065] By definition, on a cross-section of the cord perpendicular to the main axis of the cord, the spacing E between the outer strands of the outer layer is defined as the shortest distance between the average dividing circular envelope (where two adjacent outer strands are inscribed within the circular envelope).

[0066] The spacing E between the strands is the distance between the two centers of two adjacent outer strands (e.g., ...). Figure 8 The distance between points A and B shown in the diagram is minus the diameter of the outer line strand.

[0067] Preferably, all the threads in the same layer of the predetermined (inner or outer) strands have substantially the same diameter. Advantageously, all the outer strands have substantially the same diameter. "Substantially the same diameter" means that the threads or strands have the same diameter within industrial tolerances.

[0068] Therefore, in an orthogonal 2D reference frame, i.e., along the cross-section of the cord, with OA as the x-axis, where O is the center of the cord, and assuming all outer strands have substantially the same diameter, the coordinates of the centers A and B of the two strands are calculated: A = [Re TE , 0],B= [Re TE × cos (2π / L); ReTE × sin( 2π / L)], where L is the number of outer strands, Re TE The helix radius, expressed in millimeters, for each outer strand.

[0069] Calculate the spiral radius of each outer strand using the following formula: Re TE = max (Re_minTE; ReTE is unsaturated), where

[0070] Re minTE is the winding radius obtained under conditions of layer oversaturation. This is the minimum radius for all strand contacts.

[0071] Re_min TE = 1 / [( sin 2 (π / L) / D TE / 2) 2 - cos 2 (π / L) × (2π / pe) 2 ]

[0072] Where L is the number of outer strands, pe is the twist pitch (in millimeters) of each outer strand, and D... TE The diameter of the outer strands, measured in mm, and

[0073] Re TE不饱和的 Corresponding to unsaturated or strictly saturated structures, Re TE不饱和的 =D TI / 2 + D TE / 2, where DTI is the diameter of the internal strands in mm, D TE The diameter of the outer strand, measured in mm.

[0074] The diameter of the outer strand is calculated as follows:

[0075] D TE =2 × Re1' + d1' 2 × d2', where Re1' is the inner winding radius of the outer strand, where

[0076] - If the inner layer of the outer strand contains only one inner metal wire: Re1' = 0;

[0077] Otherwise, Re1' = 1 / [( sin 2 (π / Q') / d1' / 2)2 -cos 2 (π / Q') × (2π / p1') 2 ]

[0078] Where Q' is the number of inner metal wires in the outer strand, d1' is the diameter of the inner metal wires in the outer strand in mm, and p1' is the twist pitch in the inner layer of the outer strand in mm.

[0079] Next, calculate the distance AB in the reference frame using the following formula: AB = [(xb-xa)] 2 + (yb-ya) 2 ] 1 / 2 Then, the strand spacing in µm is obtained: E = AB - D TE / cos(αt) × 1000, where D TE Let αt be the diameter of the outer strand, and αt = atan (2π ReTE / pe) be the helix angle of the outer strand, where pe is the twist pitch in millimeters for each outer strand.

[0080] By definition, on a cross-section of the cord perpendicular to the main axis of the cord, the spacing between the strands of the layers is defined as the shortest distance between two adjacent strands in the average separating layer.

[0081] The wire spacing of the following calculation layers is as follows:

[0082] Calculate the outer winding radius of the outer strand: Re3'=Re1'+d1 / 2+d2 / 2

[0083] Where Re1' is the inner winding radius of the outer strand as defined above.

[0084] The wire spacing I3' is the distance between the centers of the two metal wires minus the wire diameter, such as in... Figure 8 As shown; the calculation method is the same as that for external lines:

[0085] A'= [Re 3' , 0]

[0086] B'= [Re 3' × cos (2π / N') ; Re3' × sin( 2π / N')]

[0087] A'B'=[ (xb'-xa') 2 + (yb'-ya') 2 ] 1 / 2

[0088] Therefore, we get I3' = A'B' - d3' / cos(αC3') × 1000, where αC3' = atan(2πR3' / p3') is the helix angle of the outer layer of the outer strand.

[0089] The sum SI3' is the sum of the spacing between each pair of adjacent outer threads in the outer layer.

[0090] Preferably, the strands are not pre-formed.

[0091] According to the invention, the cord is made of metal. The term "metallic cord" is understood by definition to mean a cord formed of cords primarily (i.e., more than 50% of the cords) or entirely (100% of the cords) of a metallic material. This metallic material is preferably made of steel, more preferably of pearlitic (or ferritic-pearlitic) carbon steel (hereinafter referred to as "carbon steel"), or of stainless steel (as defined, steel containing at least 11% chromium and at least 50% iron). However, it is of course possible to use other steels or other alloys.

[0092] When carbon steel is used advantageously, its carbon content (by weight of steel) is preferably between 0.4% and 1.2%, particularly between 0.5% and 1.1%; these contents represent a good trade-off between the mechanical properties required for the tire and the availability of yarn.

[0093] The metal or steel used, whether particularly carbon steel or stainless steel, may be coated with a metal layer that, for example, improves the processability of the metal cord and / or its components, or improves the performance of the cord and / or tire itself, such as adhesion, corrosion resistance, or aging resistance. According to a preferred embodiment, the steel used is coated with a brass (Zn-Cu alloy) layer or a zinc layer.

[0094] Advantageously, the outer strands are wound in a spiral around the inner strands with a twist pitch pe ranging from 30 mm to 100 mm, preferably from 50 mm to 90 mm.

[0095] Another subject of the present invention is the cord described above extracted from a polymer matrix.

[0096] Preferably, the polymer matrix is ​​an elastomer matrix.

[0097] The polymer matrix, preferably the elastomer matrix, is based on a polymer composition, preferably an elastomer composition.

[0098] A polymer matrix is ​​understood to be a matrix containing at least one polymer. Therefore, a polymer matrix is ​​based on a polymer composition.

[0099] An elastomeric matrix refers to a matrix containing at least one elastomeric element. Therefore, a preferred elastomeric matrix is ​​based on an elastomeric composition.

[0100] The term "based on" should be understood to mean that the composition comprises a mixture of various components used and / or in-situ reaction products, some of which are capable and / or intended to react with each other at least partially during various stages of the manufacture of the composition; thus the composition may be in a fully crosslinked or partially crosslinked state or in a non-crosslinked state.

[0101] The term "polymer composition" is understood to mean that the composition contains at least one polymer. Preferably, such polymer can be a thermoplastic such as polyester or polyamide, a thermosetting polymer, an elastomer such as natural rubber, a thermoplastic elastomer, or a combination of these polymers.

[0102] The term "elastomer composition" is understood to mean that the composition comprises at least one elastomer and at least one other component. Preferably, a composition comprising at least one elastomer and at least one other component comprises an elastomer, a crosslinking system, and a filler. As a reminder, the ply layers in a tire are formed from the aforementioned cords embedded in the elastomer composition. Compositions that can be used for these ply layers are conventional compositions for calendering filamentary reinforcing elements and comprise diene elastomers (e.g., natural rubber), reinforcing fillers (e.g., carbon black and / or silica), crosslinking systems (e.g., vulcanization systems, preferably vulcanization systems containing sulfur, stearic acid, and zinc oxide), and possibly vulcanization accelerators and / or retarders and / or various additives. Adhesion between the metal wires and the matrix in which they are embedded is provided, for example, by a metallic coating (e.g., a brass layer).

[0103] The values ​​of the characteristics described for the extracted cord in this application are measured or determined in cords extracted from, for example, a polymer matrix, particularly an elastomer matrix, of a tire. Thus, for example in a tire, a strip of material located radially outside the cord to be extracted is removed to expose the cord to be extracted, radially flush with the polymer matrix. This removal can be accomplished by peeling using a cutter and jig, or by planing. Next, the end of the cord to be extracted is exposed using a tool. The cord is then pulled to extract it from the matrix, with a relatively shallow angle applied to avoid plasticizing the cord. The extracted cord is then carefully cleaned, for example, using a tool, to separate any polymer matrix residue locally adhering to the cord, while taking care not to damage the surface of the wire.

[0104] The advantageous features described below also apply to the cords and extracted cords as defined above.

[0105] Advantageously, SL≤37500 MPa.mm, preferably SL≤35000 MPa.mm.

[0106] The lower the SL standard, the better the bending durability of the cord.

[0107] Advantageously, SL ≥ 25000 MPa.mm, preferably SL ≥ 27500 MPa.mm.

[0108] Preferably, SL is greater than 25000 MPa.mm, because a fairly large size is sought by maximizing the metal mass.

[0109] Advantageously, Ec ≥ 0.47, preferably Ec ≥ 0.48.

[0110] Advantageously, Ec ≤ 0.65, preferably Ec ≤ 0.55.

[0111] Specifically, within these dimensions of standard Ec, the maximum metallic mass can be achieved within the smallest possible surface area while maintaining good permeability of durability standard SL. Specifically, the greater the metallic mass, the lower the tensile stress in the cord for the same load; conversely, if the dimensions are too large to have the same metallic mass, the cord is larger and the elastomeric composite material including the cord is thicker, leading to greater heating risks and dimensional issues with the final object.

[0112] Preferably, αf is greater than or equal to 0°, and more preferably greater than or equal to 3°.

[0113] Preferably, αf is less than or equal to 25°, and more preferably less than or equal to 20°.

[0114] Within this range of 0° to 25° of contact angle, the contact area is maximized, and the polymer composition penetrates the cord relatively well.

[0115] Preferably, αt is greater than or equal to 0°, and more preferably greater than or equal to 3°.

[0116] Preferably, αt is less than or equal to 20°, more preferably less than or equal to 15°, and even more preferably less than or equal to 10°.

[0117] Within this spiral angle range, the contact load between the outer and inner strands is minimized when tension is applied to the cord.

[0118] To calculate the bending durability standard, angles αf and αt are expressed in radians, which is the value in degrees multiplied by π and divided by 180°.

[0119] In one embodiment, at least 50% of the metal wires in the cord, preferably at least 60%, more preferably at least 70%, and highly preferably each metal wire includes a steel core having a composition conforming to the standard NFEN 10020 of September 2000 and a carbon content of C ≤ 0.80%.

[0120] In another embodiment, at least 50% of the metal wires in the cord, preferably at least 60%, more preferably at least 70%, and highly preferably each metal wire includes a steel core having a composition conforming to the September 2000 standard NF EN 10020 and a carbon content of C > 0.80%, preferably C ≥ 0.82%. Such a steel composition combines non-alloy steel (points 3.2.1 and 4.1 of the September 2000 standard NF EN 10020), stainless steel (points 3.2.2 and 4.2 of the September 2000 standard NF EN 10020), and other alloy steels (points 3.2.3 and 4.3 of the September 2000 standard NF EN 10020). The relatively high carbon content allows for the achievement of the mechanical strength of the metal wires in the cord according to the invention. Advantageously, at least 50% of the wires in the cord, preferably at least 60%, more preferably at least 70%, and highly preferably each wire includes a steel core having a composition conforming to the September 2000 standard NF EN 10020 and a carbon content of C ≤ 1.20%, preferably C ≤ 1.10%. Using excessively high carbon content is relatively expensive on the one hand, and on the other hand, leads to a decrease in the fatigue-corrosion durability of the wires.

[0121] Preferably, the ranges of d1, d1', d3, and d3' are independently from each other from 0.12 mm to 0.38 mm, more preferably from 0.15 mm to 0.35 mm.

[0122] In one embodiment, when Q>1, the cord satisfies that each inner layer of each outer strand is wound in a winding direction opposite to the winding direction of the cord and the inner and outer layers of the inner strands, and the outer layer of each outer strand is wound around the inner layer of the outer strand in a winding direction opposite to the winding direction of the cord and the inner and outer layers of the inner strands. In this embodiment, the winding direction of each outer filament of the outer strand opposite to the winding direction of each outer filament of the inner strand allows for the formation of a relatively wide contact area rather than a point-like pattern, thereby benefiting the coefficient of performance.

[0123] In another embodiment, when Q>1, the cord satisfies that each layer of the inner and outer layers of each outer strand is wound in the same winding direction as the cord and the inner and outer layers of the inner strands. In this other embodiment, a more point-like and less linear contact area is formed, which is less advantageous for the coefficient of performance, but allows for easier industrial implementation because all layers are wound in the same direction, thus the cord is assembled in the same direction.

[0124] In yet another implementation, when Q>1, each inner layer of each outer strand is wound in a winding direction opposite to the winding direction of the cord, the inner and outer layers of the inner strands, and the outer layer of each outer strand.

[0125] In another implementation, when Q>1, the inner layer of the inner strand is wound in a winding direction opposite to the winding direction of the cord, the inner and outer layers of each outer strand, and the outer layer of the inner strand.

[0126] In another implementation, when Q>1, the inner layer of the inner strand and the inner layer of each outer strand are wound in a winding direction opposite to the winding direction of the cord, the outer layer of each outer strand and the outer layer of the inner strand.

[0127] Advantageously, when Q > 1, various combinations of winding directions organized in Table 1 can be specifically envisioned.

[0128] [Table 1]

[0129]

[0130] Advantageously, the permeability coefficient Cp of the cord is greater than or equal to 0.60, preferably greater than or equal to 0.70. Specifically, sufficient space is left between the threads or strands to allow the polymer composition (preferably an elastomer composition) to pass through.

[0131] Advantageously, the outer layer of the cord is unsaturated.

[0132] By definition, an unsaturated layer satisfies the condition that there is sufficient space between the filaments to allow the polymer composition (preferably an elastomer composition) to pass through. An unsaturated layer means that the filaments are not in contact, and there is sufficient space between two adjacent filaments to allow the polymer composition (preferably an elastomer composition) to pass through. Conversely, a saturated layer satisfies the condition that there is insufficient space between the filaments of the layer to allow the polymer composition (preferably an elastomer composition) to pass through, for example because the two filaments in each pair in the layer are in contact with each other.

[0133] By definition, the unsaturated layer of the cord satisfies a strand spacing of greater than or equal to 30 μm for the outer strands. On a cross-section of the cord perpendicular to its main axis, the strand spacing of the outer layer with the outer strands is defined as the shortest distance between the average dividing circular envelope (where two adjacent outer strands are inscribed within the circular envelope). Therefore, this structure of the cord ensures good permeability of the elastomer composition to the outer layer.

[0134] Advantageously, the outer layer of the inner strands is unsaturated.

[0135] Advantageously, the spacing between the outer strands of the inner strands is greater than or equal to 10 μm. Preferably, the spacing between the outer strands of the inner strands is greater than or equal to 15 μm.

[0136] Preferably, the spacing between the outer strands of the inner strands is less than or equal to 100 μm.

[0137] Advantageously, the sum of the spacing I3 of the outer layer of the inner strands SI3 is greater than the diameter d3 of the outer outer strands.

[0138] Advantageously, each strand is of the non-in-situ rubberized type. Non-in-situ rubberization means that before the strands are assembled together, each strand consists of layers of filaments without any polymer composition, and in particular without any elastomer composition.

[0139] Advantageously, the outer layer of each outer strand is unsaturated.

[0140] Advantageously, the spacing between the outermost strands of each outer strand is greater than or equal to 10 μm. Preferably, the spacing between the outermost strands of each outer strand is greater than or equal to 15 μm.

[0141] Preferably, the spacing between the outermost strands of each outer thread is less than or equal to 100 μm.

[0142] Advantageously, the sum of the outer layer wire spacing I3' of each outer strand is greater than or equal to the diameter d3' of the outer outer wire.

[0143] Preferably, the outer layer of the inner strand is wound around the inner layer of the inner strand in such a way that it contacts the inner layer of the inner strand.

[0144] Preferably, the outer layer of the outer strand is wound around the inner layer of the outer strand in such a way that it contacts the inner layer of the outer strand.

[0145] Advantageously, L=6, 7 or 8, preferably L=6 or 7, more preferably L=6.

[0146] Preferably, K=1 and L=6. In a cord with K=1, the strongest lateral load is the lateral load exerted by the outer strands on the inner strands.

[0147] Inner strands of cords according to the application

[0148] In one implementation, Q=1.

[0149] Advantageously, N=5, 6 or 7, preferably N=6.

[0150] In another preferred embodiment, Q>1, preferably Q=2, 3 or 4.

[0151] Advantageously, N=7, 8, 9 or 10, preferably N=8 or 9.

[0152] In the first alternative form, Q=2 and N=7 or 8, preferably Q=2 and N=7.

[0153] In the second alternative form, Q=3 and N=7, 8 or 9, preferably Q=3 and N=8.

[0154] In the third alternative form, Q=4 and N=7, 8, 9 or 10, preferably Q=4 and N=9.

[0155] Highly advantageously, the diameter d1 of each inner filament of the inner strand is equal to the diameter d3 of each outer filament of the inner strand. Therefore, it is preferable to use the same filament diameter in both the inner and outer layers of the inner strand, thereby limiting the number of different filaments that need to be managed during the manufacturing process of the cord.

[0156] Outer strands of cords according to the application

[0157] In one implementation, Q'=1.

[0158] Advantageously, N' = 5, 6 or 7, preferably N' = 6.

[0159] In another preferred embodiment, Q'>1, preferably Q'=2, 3 or 4.

[0160] Advantageously, N' = 7, 8, 9 or 10, preferably N' = 8 or 9.

[0161] In the first alternative form, Q'=2 and N'=7 or 8, preferably Q'=2 and N'=7.

[0162] In the second alternative form, Q'=3 and N'=7, 8 or 9, preferably Q'=3 and N'=9.

[0163] In the third alternative form, Q'=4 and N'=7, 8, 9 or 10, preferably Q'=4 and N'=9.

[0164] Advantageously, each inner filament of the outer strand has a diameter d1' greater than the diameter d3' of each outer filament of the outer strand.

[0165] Highly advantageously, each inner wire of the inner strand has a diameter d1 equal to the diameter d3 of each outer wire of the inner strand and equal to the diameter d1' of each inner wire of the outer strand.

[0166] Advantageously, Q=4 and N=9, Q'=3 and N'=9, d1=d3=d1' and d3'≤d1'. Specifically, the capillary in each outer strand TE is smaller than the capillary in the inner strand, thereby reducing the spread of corrosion in the event of perforation.

[0167] Reinforced product according to the application

[0168] Another subject of the invention is a reinforced product comprising a polymer matrix and at least one cord as defined above.

[0169] Advantageously, the reinforcing product comprises one or more cords according to the invention embedded in a polymer matrix, wherein in the case of multiple cords, the cords are arranged side by side along the main direction.

[0170] Tire according to the application

[0171] Another subject of the invention is a tire comprising at least one cord as defined above.

[0172] In one embodiment, the tire has a carcass reinforcement anchored in two beads and radially covered by a crown reinforcement, which itself is covered by the tread, and the carcass reinforcement has at least one cord as defined above.

[0173] In another embodiment, the tire has a carcass reinforcement anchored in two beads and radially covered by a crown reinforcement, which is itself covered by the tread and is joined to the beads via two sidewalls and includes at least one cord as defined above.

[0174] Preferably, the tread reinforcement includes a protective reinforcement and a working reinforcement, the working reinforcement including at least one cord as defined above, and the protective reinforcement being radially inserted between the tread and the working reinforcement.

[0175] In yet another embodiment, the tire has a carcass reinforcement anchored in two beads and radially covered by a crown reinforcement, the crown reinforcement itself being covered by the tread, the crown reinforcement being joined to the beads via two sidewalls and having at least one cord as defined above, the carcass reinforcement having at least one cord as defined above.

[0176] Cords are most specifically designed for use in industrial vehicles, agricultural vehicles, or construction site vehicles selected from heavy vehicles (e.g., “heavy-duty vehicles”, i.e., subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles), or other transport or handling vehicles.

[0177] Preferably, the tire is used on construction site type vehicles. Therefore, the tire has a size in which the base diameter of the rim intended to mount the tire is greater than or equal to 25 inches, preferably 25 to 57 inches.

[0178] The present invention also relates to rubber articles comprising components according to the invention or impregnated components according to the invention. Rubber articles are defined as any type of article made of rubber, such as balls, non-pneumatic objects (e.g., non-pneumatic tires), conveyor belts, or tracks. Attached Figure Description

[0179] The invention will be better understood by reading the following embodiments, which are given by way of non-limiting example only and with reference to the accompanying drawings, wherein:

[0180] - Figure 1 A cross-sectional view perpendicular to the circumferential direction of the tire according to the invention;

[0181] - Figure 2 for Figure 1 Detailed view of area II;

[0182] - Figure 3 A cross-sectional view of the reinforced product according to the present invention;

[0183] - Figure 4 A schematic diagram of a cross section perpendicular to the cord axis (assuming it is straight and stationary) of the cord (50) according to the first embodiment of the present invention;

[0184] - Figure 5 A schematic diagram of a cross section perpendicular to the cord axis (assuming it is straight and stationary) of the extracted cord (50') according to the first embodiment of the present invention;

[0185] - Figure 6 for Figure 4 A schematic diagram of the angle αf of the cord (50);

[0186] - Figure 7 A photograph of the cord (50) according to the first embodiment of the present invention, and

[0187] - Figure 8 This is a schematic diagram showing the various geometric parameters of the cord. Detailed Implementation

[0188] Embodiments of tires according to the present invention

[0189] exist Figure 1 and Figure 2 The reference frames X, Y, and Z are shown, which correspond to the tire's usual axial direction (X), radial direction (Y), and circumferential direction (Z), respectively.

[0190] The tire's "circumferential midplane" M is a plane that is perpendicular to the tire's axis of rotation and equidistant from the annular reinforcement structure of each bead.

[0191] Figure 1 and Figure 2 A tire according to the invention, indicated by the overall designation 10, is shown.

[0192] Tire 10 is used on heavy-duty vehicles of the construction site type, such as "forklift" type heavy-duty vehicles. Therefore, tire 10 has a size of 35 / 65 R 33.

[0193] Tire 10 has a crown 12 reinforced by crown reinforcement 14, two sidewalls 16, and two bead 18, each of which is reinforced by an annular structure, in this case by bead lines 20. Crown reinforcement 14 is radially covered by tread 22 and connected to the bead 18 via the sidewalls 16. Carcass reinforcement 24 is anchored in the two bead 18, in this case wrapped around the two bead lines 20, and includes a flange 26 disposed towards the outer side of tire 20, which is shown here as being mounted on a wheel rim 28. Carcass reinforcement 24 is radially covered by crown reinforcement 14.

[0194] The carcass reinforcement 24 includes at least one carcass ply 30 reinforced by radial carcass cords 50 (not shown) according to the invention. The carcass cords 50 are arranged substantially parallel to each other and extend from one bead 18 to the other, thereby forming an angle between 80° and 90° with the circumferential midplane M (a plane perpendicular to the axis of rotation of the tire, located between the two beads 18 and passing through the center of the crown reinforcement 14).

[0195] The tire 10 also includes a sealing ply 32 (commonly referred to as the “liner”) made of an elastomer, which defines the radial inner surface 34 of the tire 10 and is designed to protect the carcass ply 30 from air diffusion from the interior space of the tire 10.

[0196] The tread reinforcement 14, radially extending from the outer side to the inner side of the tire 10, includes: a protective reinforcement 36 radially disposed within the tread 22; a working reinforcement 38 radially disposed within the protective reinforcement 36; and an additional reinforcement 40 radially disposed within the working reinforcement 38. Thus, the protective reinforcement 36 is radially inserted between the tread 22 and the working reinforcement 38. The working reinforcement 38 is radially inserted between the protective reinforcement 36 and the additional reinforcement 40.

[0197] The protective reinforcement 36 includes a first protective ply 42 and a second protective ply 44, both of which include protective metal cords. The first ply 42 is radially disposed inside the second ply 44. Optionally, the protective metal cords form an angle of at least 10° with respect to the tire's circumferential direction Z, preferably between 10° and 35°, and more preferably between 15° and 30°.

[0198] The working reinforcement 38 includes a first working ply 46 and a second working ply 48, the first ply 46 being arranged radially inside the second ply 48. Each ply 46, 48 includes at least one cord 50. Optionally, the working metal cord 50 crosses from one working ply to the other and forms an angle with the circumferential direction Z of the tire of up to 60°, preferably in the range of 15° to 40°.

[0199] The additional reinforcement 40, also known as a restraining block, is intended to partially absorb the mechanical stress of inflation. The additional reinforcement 40 includes, for example, additional metal reinforcement elements known per se (e.g., as described in FR 2 419 181 or FR 2 419 182), forming an angle with the circumferential direction Z of the tire 10 at a maximum of 10°, preferably in the range of 5° to 10°.

[0200] Embodiments of the enhanced product according to the present invention

[0201] Figure 3 The reinforced product according to the invention is shown, indicated by the overall designation 100. The reinforced product 100 includes at least one cord 50 embedded in a polymer matrix 102, in this case, a plurality of cords 50.

[0202] Figure 3The polymer matrix 102 and cord 50 are shown in reference frames X, Y, and Z, where direction Y is the radial direction and directions X and Z are the axial and circumferential directions, respectively. Figure 3 In this process, the reinforcing product 100 includes a plurality of cords 50 arranged side by side in the main direction X, which extend parallel to each other within the reinforcing product 100 and are collectively embedded in the polymer matrix 102.

[0203] In this case, the polymer matrix 102 is an elastomeric matrix based on an elastomeric composition.

[0204] Cord according to the first embodiment of the present invention

[0205] Figure 4 and Figure 5 Cord 50 and cord 50' according to a first embodiment of the present invention are shown respectively.

[0206] Cords 50 and 50' have the same geometry. Cord 50' is obtained after being extracted from tire 10.

[0207] Figure 7 A photo of tire 50 is shown.

[0208] The cord 50 and the extracted cord 50' are made of metal and are of a multi-strand type with two cylindrical layers. Therefore, it will be understood that there are exactly two strand layers that make up cord 50 or 50'.

[0209] Cord 50 or cord 50' comprises an inner cord layer CI consisting of K=1 inner strands TI. The outer cord layer CE consists of L>1 outer strands TE wound around the inner cord layer CI. In this particular case, L=6, 7 or 8, preferably L=6 or 7, more preferably L=6, and here L=6.

[0210] Cords have bending durability standards

[0211] = 210000 × 0.26 / 2 = 27300 MPa.mm and =210000 × 0.26 / 2= 27300 MPa.mm.

[0212] The strand spacing E = 58 µm, therefore =0.82.

[0213] The wire spacing I3' = 36 µm, therefore, when 10 µm ≤ I3' ≤ 40 µm... =0.92.

[0214] Cp = (0.82+0.92) / 2= 0.87.

[0215] =0.98.

[0216] SL = max( ; = max (31379; 32019) = 32019 MPa.mm, which is much lower than 40000 MPa.mm. SL≤37500 MPa.mm, preferably SL≤35000 MPa.mm and SL≥25000 MPa.mm, preferably SL≥27500 MPa.mm.

[0217] Compact surface area Sc = [4 ×(0.26 / 2)] 2 +9 × (0.26 / 2) 2 + 6 × (3 × (0.26 / 2) 2 +9× (0.23 / 2) 2 ] × π = 3.89.

[0218] Surface area Se = π × (3.2 / 2) 2 = 8.04.

[0219] Ec=Sc / Se=3.89 / 8.04=0.48, Ec≥0.47, Ec≥0.48 and Ec≤0.65, preferably Ec≤0.55.

[0220] The permeability coefficients of cords 50 and 50' are equal to 0.87, which is greater than or equal to 0.60, and preferably greater than or equal to 0.70.

[0221] The outer layer CE of cords 50 and 50' is unsaturated. Therefore, the strand spacing E of the outer strands is strictly greater than 20 µm. Here, E = 58 µm.

[0222] αf is greater than or equal to 0°, preferably greater than or equal to 3° and less than or equal to 25°, preferably less than or equal to 20°. Here, αf = 5.1°.

[0223] αt is greater than or equal to 0°, preferably greater than or equal to 3° and less than or equal to 20°, preferably less than or equal to 15°, and more preferably less than or equal to 10°. Here, αt = 6.5°.

[0224] Inner strands of cords 50 and 50'

[0225] Each internal strand TI is a double-layered strand, consisting of an inner layer C1 composed of Q=2, 3 or 4 internal metal wires F1 and an outer layer C3 composed of N external metal wires F3 wound around the inner layer C1.

[0226] Here, Q=4.

[0227] N = 7, 8, 9 or 10, preferably N = 8 or 9, and in this case N = 9.

[0228] The outer layer C3 of each inner strand TI is unsaturated. The spacing between the outer strands of the inner strands is greater than or equal to 30 μm, and in this case, it is equal to 38 μm. The sum SI3 of the spacing I3 of the outer strands C3 is greater than the diameter d3 of the outer strand F3 of the outer layer C3. Here, the sum SI3 = 0.038 × 9 = 0.34 mm, which is greater than the value of d3 = 0.26 mm.

[0229] The ranges of d1 and d3 are independent of each other, from 0.12 mm to 0.38 mm, preferably from 0.15 mm to 0.35 mm. Here, d1 = d3 = 0.26 mm.

[0230] Outer strands of cords 50 and 50'

[0231] Each outer strand TE has two layers, including an inner layer C1' consisting of 2, 3 or 4 inner metal wires F1' and an outer layer C3' consisting of N' outer metal wires F3' wound around the inner layer C1'.

[0232] Here, Q'=3.

[0233] N' = 7, 8, 9 or 10, preferably N' = 8 or 9, and in this case N' = 9.

[0234] The outer layer C3' of each outer strand TE is unsaturated. Because it is unsaturated, the average spacing I3' between the N' outer strands of the outer layer C3' is greater than or equal to 10 µm. The spacing I3' of the outer layer of each outer strand is greater than or equal to 30 μm, and in this case, equal to 37 μm. The sum SI3' of the spacing I3' of the outer layers C3' is greater than the diameter d3' of the outer strand F3' of the outer layer C3'. Here, the sum SI3' = 0.036 × 9 = 0.32 mm, which is greater than d3' = 0.23 mm.

[0235] Each inner layer C1' of each outer strand TE is wound in a winding direction opposite to the winding direction of the inner layer C1 and outer layer C3 of the cord and the inner strand TI, and the outer layer C3' of each outer strand TE is wound around the inner layer C1' of the outer strand TE in a winding direction opposite to the winding direction of the inner layer C1 and outer layer C3 of the cord and the inner strand TI. In this case, the winding direction of layers C1, C3 and the cord is Z, while the winding direction of layers C1' and C3' is S.

[0236] Method for manufacturing the cord according to the invention

[0237] An embodiment of a method for manufacturing multi-strand cord 50 is now described.

[0238] Each of the aforementioned internal strands is produced according to a known method comprising the following steps, preferably performed sequentially:

[0239] - The first step of assembly is to form the inner layer C1 at the first assembly point by cable or twisting the Q=4 inner filaments F1 of the inner layer C1 in the Z direction with a twist pitch p1.

[0240] - Next is the second step of assembly, in which the outer layer C3 is formed at the second assembly point by weaving or twisting N=9 outer threads F3 in the Z direction with a twist pitch p3 around the inner layer C1 by Q inner threads F1.

[0241] - Preferred final twisting balance step.

[0242] Each of the aforementioned outer strands is produced according to a known method comprising the following steps, preferably performed sequentially:

[0243] - The first step of assembly is to form the inner layer C1' at the first assembly point by cable or twisting the Q'=3 inner filaments F1' of the inner layer C1' in the S direction with a twist pitch p1';

[0244] - Next is the second step of assembly, in which the outer layer C3' is formed at the second assembly point by cable or twisting N'=9 outer threads F3' in the S direction with a twist pitch p3' around the inner layer C1'.

[0245] - Preferred final twisting balance step.

[0246] As is known to those skilled in the art, “twist balance” here means the elimination of residual torque (or elastic reset of twist) on each filament of the strands in the intermediate layer, as is done in the outer layer.

[0247] After this final twisting and balancing step, the strand manufacturing is complete. Before the subsequent operation of assembling the basic strands by cable bonding to obtain multi-strand cords, each strand is wound onto one or more receiving spools for storage.

[0248] In order to manufacture the multi-strand cord of the present invention, the previously obtained strands are cabled or twisted together by means of methods known to those skilled in the art using a cable-jointing or twisting machine that is compatible with the assembly strands.

[0249] Therefore, L=6 outer strands TE are assembled around the inner strand TI with a twist pitch pe in the Z direction to form a cord 50. Alternatively, in the final assembly step, the covering material F is wound around the previously obtained assembly with a twist pitch pf in the S direction.

[0250] The cord 50 is then incorporated into a composite fabric formed by calendering from a known composition based on natural rubber and carbon black (as reinforcing filler), which is typically used to manufacture the crown reinforcement of radial tires. In addition to the elastomer and reinforcing filler (carbon black), the composition essentially contains antioxidants, stearic acid, extender oil, cobalt naphthenate as a adhesion promoter, and a final vulcanization system (sulfur, accelerator, and ZnO).

[0251] The composite fabric reinforced by these cords has an elastomeric composition matrix formed by two thin layers of elastomeric composition, each layer stacked on either side of the cord and having a thickness ranging from 1 mm to 4 mm. The calendering pitch (the spacing between the cords laid in the elastomeric composition fabric) ranges from 4 mm to 8 mm.

[0252] These composite fabrics are then used as carcass ply layers in a method of manufacturing tires, the steps of which are otherwise known to those skilled in the art.

[0253] Cord according to a second embodiment of the present invention

[0254] Unlike the first embodiment described above, the cord 60 according to the second embodiment satisfies Q=3 and N=8, and Q'=3 and N'=8.

[0255] Cord according to a third embodiment of the present invention

[0256] Unlike the first embodiment described above, the cord 70 according to the third embodiment satisfies K=1, L=7, Q=3 and N=8, and Q'=1 and N'=5.

[0257] Table 2 below summarizes the features of various cords 50, 50', 60 and 70 according to the present invention.

[0258] [Table 2]

[0259]

[0260] Comparative Test

[0261] Evaluation of the bending endurance criterion and of the size criterion

[0262] Various control cords and existing technology cords were simulated.

[0263] Table 3 summarizes the characteristics of the control cord C1 and the prior art cord EDT (68.23 cord).

[0264] [Table 3]

[0265]

[0266] Tables 2 and 3 show that, compared to the prior art cord EDT and control cord C1, cords 50, 50', 60, and 70 have relatively low flexural durability standards while maintaining sufficient dimensional standards. Specifically, cords EDT and C1 have relatively high flexural durability standards, which makes it difficult to effectively reduce stress in the cord during flexural stress loading. Therefore, the cords according to the invention have a low flexural durability standard SL ≤ 40000 MPa·mm sufficient to compensate for these deficiencies, while maintaining satisfactory dimensions.

[0267] The present invention is not limited to the above-described embodiments.

Claims

1. Double-layer multi-strand cord (50), comprising: - An inner layer (CI) of cord composed of K=1 double-layer (C1, C3) inner strands (TI), wherein the inner strands (TI) include: - An inner layer (C1) consisting of 1, 2, 3, or 4 internal metal wires (F1) with a diameter d1, and - The outer layer (C3) consists of N outer metal wires (F3) with a diameter d3 wound around the inner layer (C1). - An outer cord layer (CE) consisting of L>1 double-layered (C1', C3') outer cord strands (TE) wound around the inner cord layer (CI), wherein the outer cord strands (TE) include: - An inner layer (C1') consisting of 1, 2, 3, or 4 internal metal wires (F1') with a diameter d1', and - An outer layer (C3') consisting of N' outer metal wires (F3') with a diameter d3' wound around the inner layer (C1'). Its features are: The cord (50) has: - Bending durability standard SL≤40000 MPa.mm, where ,as well as - Dimensional standard Ec≥0.46, where Ec=Sc / Se, in: - in MPa.mm It is the maximum bending stress per unit of bending portion obtained through the internal threads (F1, F1') of the internal and external strands; - in MPa.mm It is the maximum bending stress per unit of bending portion obtained through the outer metal wires (F3, F3') of the inner and outer strands; - M 钢 =210000 MPa is the modulus of steel; - d1, d1', d3 and d3' are represented in mm. - - Cp is the permeability coefficient of the cord, where Cp IT is the penetration coefficient between line stocks and Cp TE is the penetration coefficient of external line stocks, where: - When the spacing E of the outer strands (TE) of the outer layer (CE) is E < 30 μm, Cp IT =0.4; or - When E > 70 µm, Cp IT =1.0; or - When 30 µm ≤ E ≤ 70 µm Furthermore, when the wire spacing I3' of the outer metal wires (F3') of the outer layer (C3') is I3' < 10 μm, Cp TE = 0.4; or - When I3' > 40 µm, Cp TE = 1.0; or - When 10 µm ≤ I3' ≤ 40 µm - Cr is the dimensionless performance coefficient of the cord (50), where in: d3 and d3' are represented in mm. αf is the contact angle, expressed in radians, between the outer metal wire (F3) of the inner strand (TI) and the outer metal wire (F3') of the outer strand (TE). αt is the helix angle of each outer strand (TE) in radians; It is the sum of the breaking forces in Newtons of the Q'+N' strands of the outer thread; Cste=1500 N.mm -2 ; D is the diameter of the cord in mm; Sc is based on mm 2 The compact surface area is calculated as Sc = [Q × (d1 / 2)]. 2 +N × (d3 / 2) 2 + L × (Q' ×(d1' / 2) 2 +N' × (d3' / 2) 2 )] × π, and Se is the length of the cord (50) in mm 2 The surface area is calculated as Se = π × (D / 2). 2 .

2. The cord (50) according to claim 1, wherein, SL≤37500 MPa.mm.

3. The cord (50) according to claim 1, wherein, SL≥25000 MPa.mm.

4. The cord (50) according to claim 1, wherein, Ec≥0.

47.

5. The cord (50) according to claim 1, wherein, Ec≤0.

65.

6. The cord (50) according to claim 1, wherein, αf is greater than or equal to 0°.

7. The cord (50) according to claim 1, wherein, αf is less than or equal to 25°.

8. The cord (50) according to claim 1, wherein, αt is greater than or equal to 0°.

9. The cord (50) according to claim 1, wherein, αt is less than or equal to 20°.

10. The cord (50) according to claim 1, wherein, The outer layer (CE) of the cord is unsaturated, such that the spacing between the outer strands is greater than or equal to 30 µm. On the cord cross section perpendicular to the main axis of the cord (50), the spacing between the strands is defined as the shortest distance that averages the distance between two adjacent outer strands (TE) inscribed in the circular envelope.

11. The cord (50) according to claim 1, wherein, The outer layer (C3') of each outer strand (TE) is unsaturated.

12. The cord (50) according to claim 1, wherein, The permeability coefficient Cp of the cord is greater than or equal to 0.

60.

13. The cord (50) according to claim 1, which is extracted from a polymer matrix.

14. An enhanced product (100), characterized in that, The reinforcing product (100) comprises a polymer matrix (102) and at least one cord (50) according to claim 1.

15. A tire (10), characterized in that, The tire (10) includes at least one cord (50) according to claim 1 or a reinforcement product according to claim 14.

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