Double-layer multi-strand cable with improved bending durability

Abstract

The present invention relates to a multi-strand cable (50) comprising an inner layer (CI) of a cable made up of K=1 inner strands (TI) having three plies (C1, C2, C3), the inner ply (C1) being made up of Q inner metal threads (F1), the middle ply (C2) being made up of M intermediate metal threads (F2), and the outer ply (C3) being made up of N outer metal threads (F3); and an outer layer (CE) of a cable made up of L>1 outer strands (TE) wound on the inner layer (CI) of the cable having three plies (C1', C2', C3'), the inner ply (C1') being made up of Q' inner metal threads (F1'), the middle ply (C2') being made up of M' intermediate metal threads (F2'), and the outer ply (C3') being made up of N' outer metal threads (F3'). The cable (50) has a durability criterion SL≦40,000 MPa.mm, where SL=max(F), and an overall dimensional criterion Ec≧0.46, where Ec=Sc / Se.

Description

Technical Field

[0001] The present invention relates to cords, non-pneumatic tire types, conveyor belts or endless track reinforcing products, and tires provided with these cords.

Background Art

[0002] A tire for a construction vehicle having a radial carcass reinforcement, comprising a tread, two inextensible beads, two sidewalls connecting the beads to the tread, and a crown reinforcement circumferentially disposed between the carcass reinforcement and the tread, is known from the prior art. This crown reinforcement comprises a plurality of plies reinforced with reinforcing elements such as metal cords, and the cords of one ply are embedded in the elastomeric matrix material of the ply.

[0003] The crown reinforcement comprises a working reinforcement, a protection reinforcement, and optionally further reinforcements, such as hoop reinforcements.

[0004] The carcass reinforcement comprises, for a part thereof, at least one elastomeric ply called a carcass ply reinforced with reinforcing elements such as metal cords. A carcass ply reinforcement element with a two-layer multi-strand metal cord having a structure number of 189.23 is known from the prior art. This cord comprises an inner layer of the cord composed of one inner strand and an outer layer of the cord composed of six outer strands spirally wound around the inner layer of the cord. Each inner strand comprises an inner layer of the strand composed of three inner threads, an intermediate layer of the strand composed of nine intermediate threads, and an outer layer of the strand composed of fifteen outer threads. Each thread has a diameter equal to 0.23 mm. Each outer strand comprises an inner layer of the strand composed of three inner threads, an intermediate layer of the strand composed of nine intermediate threads, and an outer layer of the strand composed of fifteen outer threads. Each thread has a diameter equal to 0.23 mm.

[0005] Tires for large industrial vehicles, especially tires of the plant construction type, are subject to numerous attacks. Specifically, tires of this type usually travel on rough roads, and sometimes punctures occur in the tread. These punctures allow the ingress of corrosive agents such as air and water, which oxidize the metal reinforcing elements of the crown reinforcement and, in some cases, the metal reinforcing elements of the carcass reinforcement, significantly shortening the life of the tire.

[0006] Regarding the carcass reinforcement, the inventors of the present invention recognize that what is mainly required for the carcass reinforcement is durability under high loads. As a result, it is important to design a cord with a high level of breaking force, low bending stiffness, and very good penetration rate by the elastomer compound.

[0007] However, it is known that the cords of the prior art do not have very good permeability by the elastomer compound, and for this reason, their durability in a corrosive environment is low.

[0008] One solution to extend the life of the tire is to counteract the action of the corrosive agents within each strand. Thus, during the method of manufacturing the cord, each inner layer and intermediate layer of each strand can be covered with rubber. During this method, the deposited rubber penetrates into the capillaries existing between the layers of each strand, thereby preventing the spread of the corrosive agents. Such cords are generally called on-site rubber-coated cords and are well known from the prior art. However, in the method of manufacturing such on-site rubber-coated cords, it is necessary to be proficient in numerous industrial constraints, especially to avoid the overflow of rubber, particularly at the periphery of each strand.

[0009] Another solution for extending the life of a tire is to increase the breaking force of the prior art cords. Generally, the breaking force increases by increasing the diameter of the threads making up the cord and / or by increasing the number of threads and / or the individual strength of each thread. However, further increasing the diameter of the thread, for example beyond 0.50 mm, will necessarily lead to a decrease in the flexibility of the cord, which is not desirable for the cords used in carcass reinforcements. Increasing the number of threads generally results in a decrease in the ability of the elastomer compound to penetrate the strands. Increasing the individual strength of each thread requires a significant investment in the equipment used to manufacture the threads.

Prior art documents

Patent documents

[0010]

Patent Document 1

Patent Document 2

Summary of the invention

Problems to be solved by the invention

[0011] The object of the present invention is to provide a cord with improved bending durability compared to the prior art cords while avoiding the above-mentioned drawbacks.

Means for solving the problems

[0012] For this purpose, one subject of the present invention is a two-layer multi-strand cord, - an inner layer of the cord composed of three-layer inner strands with K = 1, - an inner layer composed of Q = 1, 2, 3 or 4 inner metal threads with a diameter d1, - an intermediate layer composed of M intermediate metal threads with a diameter d2 wound around the inner layer, - An inner layer comprising an outer layer composed of N external metal threads with a diameter d3 wound around the intermediate layer - An outer layer of the cord, which is composed of three-layer outer strands with L>1 wound around the inner layer of the cord - An inner layer composed of internal metal threads with a diameter d1’ and Q’ = 1, 2, 3, or 4 - An intermediate layer composed of M’ intermediate metal threads with a diameter d2’ wound around the inner layer - An outer layer comprising an outer layer composed of N’ external metal threads with a diameter d3’ wound around the intermediate layer. This cord has - Bending durability criteria When it is TIFF0007710473000001.tif8150, SL ≤ 40,000 MPa·mm, and - When the size criterion is Ec = Sc / Se, Ec ≥ 0.46, where - TIFF0007710473000002.tif6150 is the maximum bending stress per unit curvature found in the internal threads of the inner and outer strands or the intermediate threads of the inner and outer strands - TIFF0007710473000003.tif6150 is the maximum bending stress per unit curvature found in the outer threads of the inner and outer strands - M steel = 210,000 MPa is the elastic modulus of steel - d1, d1’, d2, d2’, d3, and d3’ are expressed in mm - TIFF0007710473000004.tif9150 - Cp is the penetration coefficient of the cord TIFF0007710473000005.tif6150 is the inter-strand penetration coefficient TIFF0007710473000006.tif6150 is the penetration coefficient of the outer strand - When the inter-strand distance E of the outer strands (TE) of the outer layer (CE) < 30 μm TIFF0007710473000007.tif6150 or - when E > 70 μm, TIFF0007710473000008.tif6170 or - when -30 μm ≤ E ≤ 70 μm, TIFF0007710473000009.tif6150, and TIFF0007710473000010.tif9150, and where CpC2’ is the penetration coefficient of the intermediate layer of the external strand, and CpC3’ is the penetration coefficient of the external layer of the external strand, and - when the thread pitch distance I2’ of the intermediate metal threads in the intermediate layer < 10 μm, TIFF0007710473000011.tif6150 or - when I2’ > 40 μm, TIFF0007710473000012.tif6150 or - when 10 μm ≤ I2’ ≤ 40 μm, TIFF0007710473000013.tif6150, and - when the thread pitch distance I3’ of the external metal threads in the external layer < 10 μm, TIFF0007710473000014.tif6150 or - when I3’ > 40 μm, TIFF0007710473000015.tif6157 or - when 10 μm ≤ I3’ ≤ 40 μm, TIFF0007710473000016.tif6150, and - Cr is the dimensionless performance coefficient of the code, TIFF0007710473000017.tif18170, where d3 and d3’ are expressed in mm, αf is the contact angle between the external metal threads of the internal strand and the external metal threads of the external strand, expressed in radians, αt is the helix angle of each external strand, expressed in radians, TIFF0007710473000018.tif15150 is the total breaking force (in Newtons) for the Q’ + M’ + N’ threads of the external strand Cste = 1500 N·mm -2 and D is the diameter of the cord (mm), Sc is the compression surface area (mm 2 ), and Sc = [Q × (d1 / 2) 2 + M × (d2 / 2) 2 + N × (d3 / 2) 2 + L × (Q’ × (d1’ / 2) 2 + M × (d2’ / 2) 2 + N’ × (d3’ / 2) 2 )] × π, and Se is the surface area of the cord (mm 2 ), and Se = π × (D / 2) 2 where Se is given by the formula above

[0013] On the other hand, due to its relatively low bending durability criteria, the cord according to the present invention reduces the stress level of the cord subjected to bending stress load, and thus makes it possible to extend the life of the tire. Specifically, the inventors of the present invention have found that the first criterion for improving the durability performance of the cord in a corrosive environment is not only the breaking force widely taught in the prior art, but also a bending durability criterion expressed by an index equal to the maximum value among the following in the present application. That is - the bending stress per unit curvature seen in the inner threads of the inner and outer strands and in the intermediate threads of the inner and outer strands divided by the penetration coefficient of the cord, or - the bending stress per unit curvature seen in the outer threads of the inner and outer strands divided by the penetration coefficient of the cord and the performance coefficient of the cord where Se is given by the formula above

[0014] On the one hand, the inventors of the present invention assume the theory that, especially in the inter-strand region where the most stress is applied, the greater the surface area of the inter-thread contact, that is, the greater the contact surface area existing between the outer metal threads of the inner strand and the outer metal threads of the outer strand, the more the weakening load is weakened over the number of contacts. In order to optimize these contacts, the inventors of the present invention assume the theory that it is necessary to have a lower stress due to the tension in the cord for the same load, or to have good geometric properties at the contact, more specifically at the contact angle between the outer metal threads of the inner strand and the outer metal threads of the outer strand, in order to increase the contact surface area. At a given tension, the coefficient of performance makes it possible to take into account the loss of tensile performance of the cord due to lateral weakening in the inter-thread contact at the level of the outer metal threads of the inner and outer layers. This coefficient of performance depends on the number of outer metal threads of the inner layer, the contact angle between the outer metal threads of the inner strand and the outer metal threads of the outer strand, the respective diameters d3 and d3' of the outer metal threads of the inner layer and the outer layer, the helix angle of the outer strand, and the force at break of the outer strand. Therefore, a robust cord has a coefficient of performance close to 1, and a weakened cord will have a sub-optimal weakening coefficient, rather close to 0.5.

[0015] Furthermore, on the other hand, thanks to its sufficiently high size criterion, the cord according to the present invention makes it possible to have the maximum metallic mass on the smallest possible surface area, and thus to contribute to the improvement of the bending durability. Specifically, the inventors of the present invention have found that a second criterion for improving the durability performance of the cord in a corrosive environment is not only the force at break, which is widely taught in the prior art, but also a size criterion expressed by an index equal to the compressed surface area of the cord divided by the surface area of the cord in the present application. Specifically, the prior art cords have either suboptimal size criteria with relatively low bending durability criteria or relatively high bending durability criteria with optimal size criteria, i.e., size criteria exceeding 0.46. The cords according to the present invention have relatively low durability criteria and relatively high size criteria due to their relatively high performance coefficient and relatively high penetration coefficient, thereby enabling improvement in bending durability.

[0016] The range of values indicated by the expression "between a and b" represents a range of values that extends from greater than a to less than b (i.e., excluding the endpoints a and b), whereas the range of values indicated by the expression "from a to b" means a range of values that extends from the endpoint "a" to the endpoint "b", i.e., including the exact endpoints "a" and "b".

[0017] By definition, the diameter of a strand is the diameter of the smallest circle in which the strand is inscribed.

[0018] Advantageously, the diameter of the cord is the diameter of the smallest circle in which the cord without a bellows is inscribed. Preferably, the cord has a diameter D such that D ≤ 6.0 mm, and more preferably 2.0 mm ≤ D ≤ 5.5 mm. The diameter D is measured on the cord in accordance with ASTM standard D2969-04.

[0019] In the present invention, the cord has two layers of strands, which means that it comprises an assembly composed of two layers of strands, neither more nor less, and the assembly has only two layers of strands, neither one layer nor three layers.

[0020] In one embodiment, the inner strands of the cord are surrounded by a polymer composition, followed by an outer layer.

[0021] Advantageously, the inner strands have a cylindrical layer.

[0022] Advantageously, each outer strand has a cylindrical layer.

[0023] Very advantageously, the inner strand and each outer strand have a cylindrical layer. It will be recalled that such a cylindrical layer can be obtained when the various layers of the strand are wound with different pitches and / or when the winding directions of these layers are different for each layer. The strands with cylindrical layers have a very high permeability, unlike the strands with a dense layer with the same pitch for all layers and the same winding direction for all layers, which results in a much lower permeability.

[0024] The inner strand is a three-layer strand. The inner strand comprises an assembly of threads consisting of three layers of threads, no more and no less, which means that the assembly of threads has three layers of threads, not two or four layers, but only three layers.

[0025] The outer strand is a three-layer strand. The outer strand comprises an assembly of threads consisting of three layers of threads, no more and no less, which means that the assembly of threads has three layers of threads, not two or four layers, but only three layers.

[0026] As is known, the pitch of a strand represents the length of this strand measured parallel to the axis of the cord, and then it will be recalled that the strand with this pitch makes one full turn around the said axis of the cord. Similarly, the pitch of a thread represents the length of this thread measured parallel to the axis of the strand in which this thread is located, and then the thread with this pitch makes one full turn around the said axis of the strand.

[0027] The winding direction of a layer of a strand or a layer of a thread is the direction that the strand or thread makes with respect to the axis of the cord or the strand. The winding direction is generally designated by the letters Z or S.

[0028] The pitch, winding direction, and diameter regarding the threads and strands are determined in accordance with ASTM standard D2969-04(2014).

[0029] The contact angle between the external metal threads of the inner strand and the external metal threads of the outer strand is the angle αf shown in FIG. 6. In this schematic depiction of the cord according to the present invention, the axis A-A' of the cord around which the inner layer of the cord and the outer layer of the cord are wound is shown. In this depiction, only one metal thread of the outer layer of the inner strand and one metal thread of the outer layer of the outer strand are fixed so that the angle αf, which is the contact angle between the external metal threads of the inner strand and the external metal threads of the outer strand, can be better seen. Since the smaller the contact angle, the smaller the weakening of the cord, this is one of the parameters related when determining the weakening coefficient of the cord.

[0030] 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 calculation formula: tan αt = 2×π×Re TE / Pe. In this formula, pe is the pitch represented in millimeters around which each outer strand is wound, Re TE is the helix radius of each outer strand represented in millimeters, and tan refers to the tangent function. αt is represented in degrees.

[0031] By definition, the helix radius Re of the outer layer of the cord is the radius of the theoretical circle passing through the centers of the outer strands of the outer layer in a plane perpendicular to the axis of the cord.

[0032] By definition, the strand spacing between the strands of the outer layer of the outer strand is defined as the shortest distance that evenly separates the circular envelope inscribed by two adjacent outer strands on the cross-section of the cord perpendicular to the main axis of the cord.

[0033] The strand spacing E is obtained by subtracting the diameter of the outer strand from the distance between the two centers of two adjacent outer strands, points A and B shown in FIG. 8.

[0034] Preferably, all the threads of the same layer of a given (internal or external) strand have substantially the same diameter. Advantageously, all the external strands have substantially the same diameter. What "substantially the same diameter" means is that the threads or strands have the same diameter within the range of industrial tolerances.

[0035] For this purpose, in a two-dimensional orthonormal reference system, that is, following the cross-section of the cord, with O as the center of the cord, when OA is taken in the direction of the horizontal axis, in the case where all the external strands have substantially the same diameter, the coordinates of the centers of two strands A and B are calculated: A = [Re TE , 0], B = [Re TE × cos(2π / L), Re TE × sin(2π / L)], where L is the number of external strands, and Re TE is the spiral radius of each external strand expressed in millimeters.

[0036] The spiral radius of each external strand is calculated according to the following formula: Re TE = max(Re_minTE; Re TEunsaturated ), where Re_minTE is the winding radius obtained when the layer is supersaturated. This is the minimum radius when all the strands are in contact. Re_minTE = 1 / [(sin2(π / L) / DTE / 2)2 - cos2(π / L)×(2π / pe)2], where L is the number of external strands, pe is the pitch expressed in millimeters by which each external strand is wound, D TE is the diameter of the external strand (in mm), Re TEunsaturated corresponds to an unsaturated or strictly saturated structure, and Re TEunsaturated = D TI / 2 + D TE / 2, where D TI is the diameter of the internal strand (in mm), and D TE is the diameter of the external strand (in mm).

[0037] The diameter of the external strand is calculated as follows: DTE = 2×Re1’ + d1’ + 2×d2’ + 2×d3’, where Re1’ is the winding radius of the inner layer of the outer strand, - When the inner layer of the outer strand contains only one inner metal thread, Re1’ = 0, - Otherwise, Re1’ = 1 / [(sin 2 (π / Q’) / d1’ / 2) 2 - cos 2 (π / Q’) × (2π / p1’) 2 , where Q’ is the number of metal threads in the inner layer of the outer strand, d1’ is the diameter of the metal thread in the inner layer of the outer strand (unit: mm), and the pitch p1’ is the pitch of the inner layer of the outer strand (unit: mm).

[0038] Next, the distance AB is calculated in the reference system by the following formula: AB = [(xb - xa) 2 + (yb - ya) 2 , 1 / 2 and then the inter-strand distance is found in μm units as E = AB - D TE / cos(αt) × 1000, where D TE is the diameter of the outer strand, αt = atan(2πRe TE / pe) is the helix angle of the outer strand, and pe is the pitch of each outer strand expressed in millimeters.

[0039] By definition, the inter-thread distance of a layer is defined as the shortest distance that separates the average of two adjacent threads of the layer in a cross-section of the cord perpendicular to the main axis of the cord.

[0040] The inter-thread distance of a layer is calculated as follows: The winding radius for the outer layer of the outer strand is Re3’ = Re1’ + d1 / 2 + d2 + d3 / 2 where Re1’ is the winding radius of the inner layer of the outer strand as defined previously.

[0041] The thread pitch I3’ is, as shown in Fig. 8, the distance between the centers of two metal threads minus the thread diameter, and the calculation method is the same as that used for the outer strands: A’ = [Re3’, 0] B’ = [Re3’ × cos(2π / N’), Re3’ × sin(2π / N')] A'B' = [(xb' - xa') 2 + (yb' - ya') 2 1 / 2

[0042] Thus, I3’ = A’B’ - d3’ / cos(αC3’) × 1000 is obtained, where αC3’ = atan(2πR3’ / p3’) is the helix angle of the outer layer of the outer strands.

[0043] The total SI3’ is the sum of the thread pitches separating each pair of adjacent outer strands in the outer layer.

[0044] The thread pitch I2’ is the distance between the centers of two intermediate metal threads minus the thread diameter. The calculation method is the same as described above.

[0045] The total SI2’ is the sum of the thread pitches separating each pair of adjacent intermediate threads in the outer layer.

[0046] Preferably, the strands do not undergo pre-forming.

[0047] According to the present invention, the cord is made of metal. The term “metal cord” is understood, by definition, to mean a cord formed of threads mainly (i.e., more than 50% of these threads) or completely (100% of the threads) composed of a metallic material. Such a metallic material is preferably implemented using steel, more preferably pearlite (or ferrite - pearlite) carbon steel, hereinafter referred to as “carbon steel”, or stainless steel (by definition, stainless steel contains at least 11% chromium and at least 50% iron). However, it is of course possible to use other steels or other alloys. ​

[0048] When carbon steel is advantageously used, its carbon content (by weight of the steel) is preferably between 0.4% and 1.2%, particularly between 0.5% and 1.1%, and these contents represent a good compromise between the mechanical properties required for the tire and the feasibility of the thread.

[0049] The metal or steel used, regardless of whether it is carbon steel or stainless steel in particular, can be coated itself, for example, with a metal layer that improves the processing properties of the metal cord and / or its components, or the service properties of the cord and / or the tire itself, such as adhesiveness, corrosion resistance, or aging resistance. According to a preferred embodiment, the steel used is coated with a layer of brass (Zn-Cu alloy) or zinc.

[0050] Advantageously, the outer strands are wound helically around the inner strands with a pitch pe in the range from 30 mm to 100 mm, preferably in the range from 50 mm to 90 mm.

[0051] Another main subject of the present invention is the cord described above, extracted from a polymer matrix.

[0052] Preferably, the polymer matrix is an elastomer matrix.

[0053] The polymer matrix, preferably the elastomer matrix, is based on a polymer composition, preferably an elastomer composition.

[0054] It is understood that the polymer matrix is a matrix containing at least one polymer. Therefore, the polymer matrix is based on a polymer composition.

[0055] What the elastomer matrix means is a matrix containing at least one elastomer. Therefore, a preferred elastomer matrix is based on an elastomer composition.

[0056] The expression "based on ~" should be understood to mean that the composition comprises a mixture of the various components used and / or the products of in-situ reactions, some of these components being at least partially reactive with each other and / or reaction being contemplated during the various stages of compound manufacture, so that the composition can be in a fully or partially cross-linked state, or in an uncross-linked state.

[0057] The polymer composition is understood to mean that the composition contains at least one polymer. Preferably, such a polymer can be a thermoplastic material, such as a polyester or a polyamide, a thermosetting polymer, an elastomer, such as natural rubber, a thermoplastic elastomer or a combination of these polymers.

[0058] The elastomer composition is understood to mean that the composition contains at least one elastomer and at least one other component. Preferably, a composition containing at least one elastomer and at least one other component contains an elastomer, a cross-linking system and a filler. Note that the ply in a tire is formed from the aforementioned cords embedded in the elastomer composition. The compositions that can be used for these plies are conventional compositions for calendering fibrous reinforcing elements and contain a diene elastomer, such as natural rubber, a reinforcing filler, such as carbon black and / or silica, a cross-linking system, such as a vulcanization system, preferably sulfur, stearic acid and zinc oxide, and optionally a vulcanization accelerator and / or retarder and / or various additives. The adhesion of the metal threads to the matrix in which they are embedded is imparted, for example, by a metal coating, such as a brass layer.

[0059] The characteristic values described in the present application for the extracted cords are measured or determined on the cords extracted from the polymer matrix material, particularly the elastomer matrix material, for example, with respect to a tire. Therefore, for example, in the case of a tire, a piece of material outside the cord in the radial direction is removed so that the cord extracted at the same height in the radial direction as the polymer matrix material can be examined. This removal can be performed by peeling using a cutter and a gripper or by planing. Next, the ends of the cord to be extracted are exposed with a knife. Then, the cord is pulled out from the matrix material while applying a relatively shallow angle so that the cord to be extracted does not become plasticized. Next, the extracted cord is carefully cleaned, for example, using a knife, and the remaining polymer matrix material locally attached to the cord is cut off while taking care not to damage the surface of the metal thread.

[0060] The advantageous features described below apply equally to the cords defined above and the extracted cords.

[0061] Advantageously, SL ≤ 37,500 MPa·mm, preferably SL ≤ 35,000 MPa·mm.

[0062] The lower this SL criterion, the better the bending durability of the cord.

[0063] Advantageously, SL ≥ 25,000 MPa·mm, preferably SL ≥ 27,500 MPa·mm.

[0064] It is preferable that SL is greater than 25,000 MPa·mm, which is for seeking a rather large size by maximizing the metal mass.

[0065] Advantageously, Ec ≥ 0.47, preferably Ec ≥ 0.48.

[0066] Advantageously, Ec ≤ 0.65, preferably Ec ≤ 0.55.

[0067] Specifically, within these ranges of the size criterion Ec, it is possible to obtain the maximum metal mass with the least possible surface area while maintaining a good penetration rate with respect to the durability criterion SL. Specifically, the greater the metal mass, the smaller the tensile stress in the cord for the same load. Conversely, if the size is too large for the same metal mass, the cord becomes larger, the elastomer composite containing the cord becomes thicker, leading to an increased risk of heat generation and problems related to the sizing of the final object.

[0068] Preferably, αf is 0° or more, and preferably 3° or more.

[0069] Preferably, αf is 25° or less, and preferably 20° or less.

[0070] In this range where the contact angle ranges from 0° to 25°, the contact area is maximized and the polymer composition penetrates the cord relatively well.

[0071] Preferably, αt is 0° or more, and preferably 3° or more.

[0072] Preferably, αt is 20° or less, preferably 15° or less, more preferably 10° or less.

[0073] In this range of the helix angle, the contact load between the outer strands and the inner strands when tension is applied to the cord is minimized.

[0074] To calculate the bending durability criterion, the angles αf and αt are expressed in radians, that is, the value in degrees obtained by multiplying the value in degrees by π and dividing by 180°.

[0075] In one embodiment, at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably each metal thread of the cord has a steel core having a composition compliant with the NF-EN standard 10020 (September 2000) and a carbon content C ≦ 0.80%.

[0076] In another embodiment, at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably each metal thread of the code comprises a steel core having a composition compliant with NF-EN standard 10020 (September 2000), with a carbon content C > 0.80%, preferably C ≥ 0.82%. Such steel compositions combine non-alloy steels (clauses 3.2.1 and 4.1 of NF-EN standard 10020 (September 2000)), stainless steels (clauses 3.2.2 and 4.2 of NF-EN standard 10020 (September 2000)), and other alloy steels (clauses 3.2.3 and 4.3 of NF-EN standard 10020 (September 2000)). The relatively high carbon content makes it possible to achieve the mechanical strength of the metal threads of the code according to the invention. Advantageously, at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably each metal thread of the code comprises a steel core having a composition compliant with NF-EN standard 10020 (September 2000), with a carbon content C ≤ 1.20%, preferably C ≤ 1.10%. The use of an overly high carbon content is on the one hand relatively expensive and on the other hand leads to a reduction in the corrosion fatigue durability of the metal threads.

[0077] Preferably, d1, d1’, d2, d2’, d3, d3’ are, independently of each other, in the range from 0.12 mm to 0.38 mm, preferably from 0.15 mm to 0.35 mm.

[0078] In one embodiment, the code is such that each outer layer of the outer strands is wound in a winding direction opposite to the winding direction of the code, and the outer layer of the inner strands is wound in the same winding direction as the winding direction of the code. In this embodiment, by making the winding direction of each outer thread of the outer strands opposite to the winding direction of each outer thread of the inner strands, it is possible to form a contact area that is not so punctiform and extends over a relatively wide range, which is advantageous for the performance coefficient.

[0079] In another embodiment, the cords are such that each outer layer of each outer strand and the outer layer of the inner strand are wound in the same winding direction as the winding direction of the cords. In this other embodiment, a more punctiform and less linear contact area is formed, which is less advantageous for the coefficient of performance, but since all the layers are wound in the same direction and the cords are assembled in the same direction, easier industrial implementation is possible.

[0080] In an alternative, when Q > 1, each inner layer and intermediate layer of each outer strand are wound in a winding direction opposite to the winding direction of the cords, and the inner layer and intermediate layer of the inner strand are wound in the winding direction of the cords.

[0081] In another alternative, when Q > 1, each inner layer and intermediate layer of each outer strand and the inner layer and intermediate layer of the inner strand are wound in the winding direction of the cords.

[0082] Advantageously, especially when Q > 1, various combinations of winding directions tabulated in Table 1 below can be envisaged.

[0083]

Table 1

[0084] Advantageously, the penetration coefficient Cp of the cords is 0.60 or more, preferably 0.70 or more. Specifically, sufficient space is left between the threads or strands to allow passage of the polymer composition, preferably the elastomer composition.

[0085] Advantageously, the outer layer of the cords is made unsaturated.

[0086] By definition, an unsaturated layer is one in which sufficient space remains between the threads to allow a polymer composition, preferably an elastomer composition, to pass through. The unsaturated layer means that the threads do not contact each other and there is sufficient space between two adjacent threads to allow a polymer composition, preferably an elastomer composition, to pass through. In contrast, a saturated layer is one in which, for example, each pair of two threads in the layer is in contact with each other, so that there is no sufficient space between the threads in the layer to allow a polymer composition, preferably an elastomer composition, to pass through.

[0087] By definition, the unsaturated layer of the cord is one in which the inter-strand distance with respect to the outer strands is 30 μm or more. The inter-strand distance of the outer layer of the outer strands is defined as the shortest distance that averages and separates the circular envelopes inscribed by two adjacent outer strands on a cross-section of the cord perpendicular to the main axis of the cord. Therefore, this structure of the cord can guarantee good permeability by the elastomer composition of the outer layer.

[0088] Advantageously, the outer layer of the inner strands is unsaturated.

[0089] Advantageously, the inter-strand distance of the outer layer of the inner strands is 10 μm or more. Preferably, the inter-strand distance of the outer layer of the inner strands is 15 μm or less.

[0090] Preferably, the inter-strand distance of the outer layer of the inner strands is 100 μm or less.

[0091] Advantageously, the total SI2 of the inter-strand distances I2 of the intermediate layer of the inner strands is greater than the diameter d2 of the intermediate strand of the intermediate layer.

[0092] Advantageously, the total SI3 of the inter-strand distances I3 of the outer layer of the inner strands is greater than the diameter d3 of the outer strand of the outer layer.

[0093] Advantageously, each strand is of a type where on-site rubber drawing is not performed. By "on-site rubber drawing is not performed", it means that before combining the strands with each other, each strand is composed of threads of various layers and does not contain any polymer composition, especially any elastomer composition.

[0094] Advantageously, the outer layer of each outer strand is unsaturated.

[0095] Advantageously, the thread pitch of the outer layer of each outer strand is 10 μm or more. Preferably, the thread pitch of the outer layer of each outer strand is 15 μm or more.

[0096] Preferably, the thread pitch of the outer layer of each outer strand is 100 μm or less.

[0097] Advantageously, the total SI2' of the thread pitches I2' of the intermediate layer of each outer strand is greater than the diameter d2' of the intermediate thread of the intermediate layer.

[0098] Advantageously, the total SI3' of the thread pitches I3' of the outer layer of each outer strand is equal to or greater than the diameter d3' of the outer thread of the outer layer.

[0099] Preferably, the outer layer of the inner strand contacts and wraps around the intermediate layer of the inner strand, and the intermediate layer of the inner strand contacts and wraps around the inner layer of the inner strand.

[0100] Preferably, the outer layer of the outer strand contacts and wraps around the intermediate layer of the outer strand, and the intermediate layer of the outer strand contacts and wraps around the inner layer of the outer strand.

[0101] Advantageously, L = 6, 7 or 8, preferably L = 6 or 7, more preferably L = 6.

[0102] Preferably, K = 1 and L = 6. In the code where K = 1, the most severe lateral load is the lateral load exerted by the outer strands on the inner strands.

[0103] Internal strands of the cord according to the present invention

[0104] In one embodiment, Q = 1.

[0105] Advantageously, M = 3, 4, 5 or 6, and preferably M = 3 or 4.

[0106] Advantageously, N = 9, 10 or 11, and preferably N = 9.

[0107] In another preferred embodiment, Q> 1, preferably Q = 2, 3 or 4.

[0108] Advantageously, M = 7, 8, 9 or 10, and preferably M = 7, 8 or 9.

[0109] Advantageously, N = 12, 13, 14 or 15, and preferably N = 12, 13 or 14.

[0110] In the first alternative, Q = 2, M = 7 or 8, N = 12 or 13.

[0111] In the second alternative, Q = 3, M = 8 or 9, N = 13 or 14.

[0112] In the third alternative, Q = 4, M = 9 or 10, N = 12, 13 or 14, and preferably Q = 4, M = 9, N = 14.

[0113] Very advantageously, each inner thread of the inner strand has a diameter d1 equal to the diameter d2 of each intermediate thread of the inner strand and equal to the diameter d3 of each outer thread of the inner strand. Thus, threads of the same diameter are preferably used for the inner, intermediate and outer layers of the inner strand, thereby limiting the number of different threads that need to be managed during the manufacture of the cord.

[0114] External strands of the cord according to the present invention

[0115] In one embodiment, Q' = 1.

[0116] Advantageously, M' = 3, 4, 5 or 6, and preferably M' = 3 or 4.

[0117] Advantageously, N' = 9, 10 or 11, and preferably N' = 9.

[0118] In another preferred embodiment, Q' > 1, and preferably Q' = 2, 3 or 4.

[0119] Advantageously, M' = 7, 8, 9 or 10, and preferably M' = 7, 8 or 9.

[0120] Advantageously, N' = 12, 13, 14 or 15, and preferably N' = 12, 13 or 14.

[0121] In the first alternative, Q' = 2, M' = 7 or 8, and N' = 12 or 13.

[0122] In the second alternative, Q' = 3, M' = 8 or 9, and N = 13 or 14, and preferably Q' = 3, M' = 9, N' = 14.

[0123] In the third alternative, Q' = 4, M' = 9 or 10, and N' = 12, 13 or 14.

[0124] Most advantageously, each intermediate thread of the outer strand has a diameter d2' equal to the diameter d3' of each outer thread of the outer strand. Thus, threads of the same diameter are preferably used for the intermediate layer and the outer layer of the outer strand, thereby limiting the number of different threads that need to be managed during the manufacture of the cord.

[0125] Advantageously, Q = 4, M = 9 and N = 14, Q' = 3, M' = 9 and N' = 14, and d1 = d2 = d3 = d1', d2' = d3' and d3' ≤ d1'. Specifically, the capillary at the center of each external strand is smaller than the capillary at the center of the internal strand, which makes it possible to reduce the spread of corrosion in case of perforation.

[0126] Reinforcement product according to the present invention

[0127] Another subject of the present invention is a reinforcing product comprising a polymer matrix and at least one cord as defined above.

[0128] Advantageously, the reinforcing product comprises one or more cords according to the invention embedded in the polymer matrix, and in the case of a plurality of cords, the cords are arranged side by side in the main direction.

[0129] Tire according to the present invention

[0130] Another subject of the present invention is a tire comprising at least one cord as defined above.

[0131] In one embodiment, the tire has a carcass reinforcement radially surrounded by a crown reinforcement fixed to two beads and itself surrounded by a tread, and the carcass reinforcement has at least one cord as defined above.

[0132] The cord is more particularly intended for industrial vehicles selected from "large vehicles", i.e. subway trains, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles, agricultural vehicles or plant construction vehicles, or other transport or handling vehicles.

[0133] Preferably, the tire is for a vehicle of the plant construction type. Thus, the tire has a diameter of the seat portion of the rim intended to receive the tire of 25 inches or more, preferably between 39 and 63 inches, in inches.

[0134] Furthermore, the present invention relates to an assembly according to the present invention, or a rubber article provided with the impregnated assembly according to the present invention. What the rubber article means is any kind of article made of rubber such as a ball, a non-pneumatic object such as a non-pneumatic tire casing, a conveyor belt or an endless track. The present invention should be better understood from the following examples, which are described in connection with the drawings as merely non-limiting examples.

Brief Description of the Drawings

[0135]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0136] Example of a tire according to the present invention

[0137] Reference systems X, Y, Z corresponding to the normal axial direction (X), radial direction (Y), and circumferential direction (Z) of the tire are illustrated in FIGS. 1 and 2.

[0138] The "median circumferential surface" M of the tire is a plane perpendicular to the rotation axis of the tire and located equidistant from the annular reinforcing structures of each bead.

[0139] Figures 1 and 2 represent a tire, generally designated by reference numeral 10, according to the present invention.

[0140] The tire 10 is for large vehicles of the plant construction type, for example the "dump truck" type. Thus, the tire 10 has dimensions of size 53 / 80R63.

[0141] The tire 10 has a crown 12 reinforced by a crown reinforcement 14, two sidewalls 16, and two beads 18, each of these beads 18 being reinforced using an annular structure, in this example a bead wire 20. The crown reinforcement 14 is radially surrounded by a tread 22 and is connected to the bead 18 by the sidewall 16. A carcass reinforcement 24 is fixed to the two beads 18, in this example wound around the two bead wires 20 and provided with a turn-up portion 26 positioned towards the outside of the tire 20, the turn-up portion 26 being shown here fitted to a wheel rim 28. The carcass reinforcement 24 is radially surrounded by the crown reinforcement 14.

[0142] The carcass reinforcement 24 comprises at least one carcass ply 30 reinforced by a radial carcass cord 50 (not shown) according to the present invention. The carcass cords 50 are positioned substantially parallel to each other and extend from one bead 18 to the other at an angle comprised between 80° and 90° with respect to the median circumferential surface M (a plane perpendicular to the rotation axis of the tire, located in the middle between the two beads 18 and passing through the center of the crown reinforcement 14).

[0143] The tire 10 also comprises a sealing ply 32, made of elastomer (commonly known as the "innerliner"), which defines the radially inner surface 34 of the tire 10 and is intended to protect the carcass ply 30 from the diffusion of air coming from the internal space of the tire 10.

[0144] The crown reinforcement 14 includes a protection reinforcement 36 disposed radially inward of the tread 22 from the outside to the inside of the tire 10, a working reinforcement 38 disposed radially inward of the protection reinforcement 36, and an additional reinforcement 40 disposed radially inward of the working reinforcement 38. Thus, the protection reinforcement 36 is radially sandwiched between the tread 22 and the working reinforcement 38. The working reinforcement 38 is radially sandwiched between the protection reinforcement 36 and the additional reinforcement 40.

[0145] The protection reinforcement 36 includes first and second protection plies 42, 44 provided with protection metal cords, and the first ply 42 is disposed radially inward of the second ply 44. Optionally, the protection metal cords form an angle of at least equal to 10°, preferably in the range from 10° to 35°, more preferably in the range from 15° to 30° with respect to the circumferential direction Z of the tire.

[0146] The working reinforcement 38 includes first and second working plies 46, 48, and the first ply 46 is disposed radially inward of the second ply 48.

[0147] The additional reinforcement 40, also called a limiting block, aims to partially absorb the mechanical stress of inflation and, for example, as is also known per se, includes additional metal reinforcement elements and forms an angle of at most equal to 10°, preferably in the range from 5° to 10° with respect to the circumferential direction Z of the tire 10, as described in, for example, French Patent No. 2419181 or French Patent No. 2419182.

[0148] Example of the reinforcement product according to the present invention

[0149] Figure 3 represents a reinforcing product, generally designated by reference numeral 100, according to the invention. The reinforcing product 100 includes at least one cord 50, in this example a plurality of cords 50, embedded in a polymer matrix 102.

[0150] Figure 3 represents the polymer matrix 102 and the cords 50 in a reference system X, Y, Z, where the direction Y is the radial direction and the directions X and Z are the axial and circumferential directions, respectively. In Figure 3, the reinforcement product 100 comprises a plurality of cords 50 arranged side by side in the main direction X, extending parallel to each other within the reinforcement product 100, and collectively embedded in the polymer matrix 102. In this example, the polymer matrix 102 is an elastomeric matrix based on an elastomer composition.

[0151] Cord according to the first embodiment of the present invention

[0152] Figures 4 and 5 represent, respectively, the cord 50 and the cord 50' according to the first embodiment of the present invention.

[0153] The cords 50 and 50' have the same geometric structure. The cord 50' is obtained after being extracted from the tire 10

[0154] Figure 7 is a photograph of the cord 50.

[0155] The cords 50 and the extracted cord 50' are made of metal and are of the multi-strand type with two cylindrical layers. Thus, it should be understood that the strands constituting the cord 50 or 50' are two layers, neither more nor less.

[0156] The cord 50 or cord 50' comprises an inner layer CI of a cord composed of inner strands TI with K = 1. The outer layer CE is composed of outer strands TE with L>1 wound around the inner layer CI of the cord. In this specific example, L = 6, 7 or 8, preferably L = 6 or 7, more preferably L = 6, and here L = 6.

[0157] This cord has a bending durability standard TIFF0007710473000020.tif13150.

[0158] TIFF0007710473000021.tif13150 and, TIFF0007710473000022.tif is 20150.

[0159] Since the inter-strand distance E = 80μm > 70μm, TIFF0007710473000023.tif is 7150.

[0160] Since the thread distance I3’ = 43μm, in the case of 40μm, TIFF0007710473000024.tif is 7150.

[0161] Since the thread distance I2’ = 36μm, TIFF0007710473000025.tif is 7150.

[0162] CpTe = (1 + 0.92) / 2 = 0.96

[0163] Cp = (0.96 + 1.00) / 2 = 0.98

[0164] TIFF0007710473000026.tif is 20150

[0165] TIFF0007710473000027.tif becomes 20150, which will be considerably lower than 40,000 MPa.mm. SL ≦ 37500 MPa.mm, preferably SL ≦ 35000 MPa.mm, SL ≧ 25,000 MPa.mm, preferably SL ≧ 27,500 MPa.mm.

[0166] Compression surface area Sc = [4×(0.26 / 2) 2 +9×(0.26 / 2) 2 +14×(0.26 / 2) 2 +6×(3×(0.26 / 2) 2 +9×(0.23’ / 2) 2 +14×(0.23 / 2) 2 ×π = 8.10

[0167] Surface area Se = π×(4.6 / 2)2 = 16.88

[0168] Ec = Sc / Se = 8.10 / 16.88 = 0.48, and Ec ≥ 0.47, Ec ≥ 0.48, Ec ≤ 0.65, preferably Ec ≤ 0.55.

[0169] The penetration coefficients of cords 50 and 50' are equal to 0.98, which is 0.60 or more, preferably 0.70 or more.

[0170] The outer layers of cords 50 and 50' are unsaturated. Therefore, the strand - to - strand distance E of the outer strands strictly exceeds 20 μm. Here, E = 80 μm.

[0171] αf is 0° or more, preferably 3° or more, and 25° or less, preferably 20° or less. Here, αf = 6.6°.

[0172] αt is 0° or more, preferably 3° or more, and 20° or less, preferably 15° or less, more preferably 10° or less. Here, αt = 8.1°.

[0173] Internal strands TI of cords 50 and 50'

[0174] Each internal strand TI is a three - layer strand, comprising an inner layer C1 composed of internal metal threads F1 with Q = 2, 3 or 4, an intermediate layer C2 composed of M external metal threads F2 wound around the inner layer C1, and an outer layer C3 composed of N external metal threads F3 wound around the intermediate layer C2.

[0175] Here, Q = 4.

[0176] M = 7, 8, 9 or 10, preferably M = 7, 8 or 9. Here, M = 9.

[0177] N = 12, 13, 14 or 15, preferably N = 12, 13 or 14. Here, N = 14.

[0178] The outer layer C3 of each internal strand TI is unsaturated. The thread pitch of the outer layer of the internal strand is 30 μm or more, and in this case, it is equal to 46 μm. The total SI3 of the thread pitches I3 of the outer layer C3 is larger than the diameter d3 of the outer thread F3 of the outer layer C3. Here, the total SI3 = 0.046 × 14 = 0.64 mm, which is a value larger than d3 = 0.26 mm.

[0179] d1, d2, and d3 are, independently of each other, in the range from 0.12 mm to 0.38 mm, preferably from 0.15 mm to 0.35 mm. Here, d1 = d2 = d3 = 0.26 mm.

[0180] External strands TE of cords 50 and 50'

[0181] Each outer strand TE is a three-layer strand and includes an inner layer C1' composed of Q' = 2, 3, or 4 internal metal threads F1', an intermediate layer C2' composed of M' external metal threads F2' wound around the inner layer C1', and an outer layer C3' composed of N' external metal threads F3' wound around the intermediate layer C2'.

[0182] Here, Q' = 3.

[0183] M' = 7, 8, 9, or 10, preferably M' = 7, 8, or 9. Here, M' = 9.

[0184] N' = 12, 13, 14, or 15, preferably N' = 12, 13, or 14, and here, N' = 14.

[0185] The outer layer C3' of each outer strand TE is unsaturated. Since it is unsaturated, the thread pitch I3' of the outer layer C3' that separates the N' outer threads on average is 10 μm or more. The thread pitch I3' of the outer layer of the outer strand is 30 μm or more, and in this case, it is equal to 43 μm. The total SI3' of the thread pitch I3' of the outer layer C3' is larger than the diameter d3' of the outer thread F3' of the outer layer C3'. Here, the total SI3' = 0.043 × 14 = 0.60 mm, which is a value larger than d3' = 0.23 mm.

[0186] Each outer layer C3' of the outer strand TE is wound in a winding direction opposite to the winding direction of the cord, and the outer layer C3 of the inner strand TI is wound in the same winding direction as the winding direction of the cord. Each inner layer C1' and intermediate layer C2' of each outer strand TE are wound in a winding direction opposite to the winding direction of the cord, and the inner layer C1 and intermediate layer C2 of the inner strand TI are wound in the winding direction of the cord. In this case, the winding directions of the layers C1, C2, C3 and the cord are Z, and the winding directions of the layers C1', C2' and C3' are S.

[0187] Manufacturing method of the cord according to the present invention

[0188] Here, an example of the manufacturing method of the multi-strand cord 50 will be described.

[0189] Each of the above-mentioned inner strands is manufactured according to a known method including the following steps, and is preferably continuously executed in-line. - First, a first assembly step of forming the inner layer C1 at the first assembly point by twisting or winding the Q = 4 inner threads F1 of the inner layer C1 in the Z direction with a pitch p1; - Subsequently, a second assembly step of forming the intermediate layer C2 at the second assembly point by twisting or winding M = 9 intermediate threads F2 around the Q inner threads F1 of the inner layer C1 in the Z direction with a pitch p2; - Subsequently, a third assembling step of twisting or winding an external strand F3 with N = 14 in the Z direction around M intermediate strands F2 of the intermediate layer C2 at a pitch p3 to form an external layer C3 at a third assembling point; - Preferably, a final twist balancing step.

[0190] Each of the above-mentioned external strands is manufactured according to a known method including the following steps, preferably continuously and inline. - A first assembling step of twisting or winding an internal strand F1' with Q' = 3 of the internal layer C1' in the S direction at a pitch p1' to form an internal layer C1' at a first assembling point; - A second assembling step of twisting or winding M' = 9 intermediate strands F2' around Q' internal strands F1' of the internal layer C1' in the S direction at a pitch p2' to form an intermediate layer C2' at a second assembling point; - A third assembling step of twisting or winding an external strand F3' with N' = 14 around M' intermediate strands F2' of the intermediate layer C2' in the S direction at a pitch p3' to form an external layer C3' at a third assembling point; - Preferably, a final twist balancing step.

[0191] What "twist balancing" means here is well known to those skilled in the art, but it is the elimination of the residual torque (or elastic recovery of twist) applied to each thread of the strand in the intermediate layer as in the external layer.

[0192] After this final twist balancing step, the manufacture of the strand is completed. Each strand is wound onto one or more receiving reels for storage prior to the operations after twisting and combining the basic strands to obtain a multi-strand cord.

[0193] To manufacture the multi-strand cord of the present invention, as is well known to those skilled in the art, the method involves twisting or combining the previously obtained strands using a twisting or twining machine that has been evaluated for assembling the strands.

[0194] Thus, the external strands TE with L = 6 are combined around the internal strand TI with a pitch pe and in the Z direction to form the cord 50. Perhaps, in the final combining step, the wrapper F is wound around the previously obtained assembly in the S direction with a pitch pf.

[0195] Next, the cord 50 is incorporated by calendering into a composite stock formed from a known composition based on natural rubber and carbon black as reinforcing fillers, which has been conventionally used in the manufacture of the crown reinforcement of radial tires. This composition essentially contains, in addition to an elastomer and a reinforcing filler (carbon black), an antioxidant, stearic acid, extender oil, cobalt naphthenate as an adhesion promoter, and finally a vulcanization system (sulfur, accelerator, and ZnO).

[0196] The composite stock reinforced by these cords has an elastomer composition base material formed from two thin layers of an elastomer composition that are overlapped on both sides of the cords and have a thickness in the range of 1 mm to 4 mm. The calendering pitch (the interval at which the cords are laid in the elastomer compound stock) ranges from 4 mm to 8 mm.

[0197] Next, these composite stocks are used as carcass plies in the carcass reinforcement during the method of manufacturing a tire, and the steps are known to those skilled in the art by other methods.

[0198] Cord according to the second embodiment of the present invention

[0199] Unlike the first embodiment described above, the cord 60 according to the second embodiment is such that Q = 1, M = 4, and N = 9, Q’ = 1, M’ = 3, and N’ = 9.

[0200] The following Table 2 summarizes the characteristics of various codes 50, 50' and 60 according to the present invention.

[0201] [Table 2] Comparative test

[0202] Evaluation of bending durability criteria and dimensional criteria

[0203] Various control codes and prior art codes were simulated.

[0204] Table 3 summarizes the characteristics of control code C1 and prior art code EDT (189.23 code).

[0205] [Table 3]

[0206] Tables 2 and 3 show that codes 50, 50' and 60 have relatively low bending durability criteria compared to prior art code EDT and control code C1, while having sufficient size criteria. Specifically, codes EDT and C1 have relatively high bending durability criteria that cannot effectively reduce the stress within the code during bending stress loading. Thus, the code according to the present invention has a bending durability criterion SL≤40,000 MPa·mm that is low enough to improve these drawbacks, while being able to maintain a satisfactory size.

[0207] The present invention is not limited to the above-described embodiments. [Explanation of Reference Numerals]

[0208] Code 50 C1 Inner layer of the inner strand C1' Inner layer of the outer strand C2 Intermediate layer of the inner strand Intermediate layer of the C2' outer strand Outer layer of the C3 inner strand Outer layer of the C3' outer strand Outer layer of the CE code Inner layer of the CI code Distance between E strands Inner metal thread of the F1 inner strand Inner metal thread of the F1' partial strand Outer metal thread of the F2 inner strand Outer metal thread of the F2' outer strand Outer metal thread of the F3 inner strand Outer metal thread of the F3' outer strand Distance between threads in the outer layer of the I3' outer strand TE outer strand TI inner strand

Claims

1. A two-layer multi-strand cord (50) comprising: an inner layer (CI) of the cord composed of three layers (C1, C2, C3) of inner strands (TI) with K = 1, wherein the inner layer (CI) has an inner layer (C1) composed of Q = 1, 2, 3, or 4 inner metal threads (F1) with diameter d1, an intermediate layer (C2) composed of M intermediate metal threads (F2) with diameter d2 wound around the inner layer (C1), and an outer layer (C3) composed of N outer metal threads (F3) with diameter d3 wound around the intermediate layer (C2), and the cord (50) has an outer layer (CE) of the cord composed of three layers (C1’, C2’, C3’) of outer strands (TE) with L > 1 wound around the inner layer (CI) of the cord, wherein the outer layer (CE) has an inner layer (C1’) composed of Q’ = 1, 2, 3, or 4 inner metal threads (F1’) with diameter d1’, an intermediate layer (C2’) composed of M’ intermediate metal threads (F2’) with diameter d2’ wound around the inner layer (C1’), and an outer layer (C3’) composed of N’ outer metal threads (F3’) with diameter d3’ wound around the intermediate layer (C2’), and the cord (50) has a bending durability criterion such that when considering the bending durability criterion SL, SL ≤ 40,000 MPa·mm, and a size criterion Ec = Sc / Se such that when considering the size criterion Ec, Ec ≥ 0.46, where is the maximum bending stress per unit curvature seen in the inner threads (F1; F1’) of the inner and outer strands or the intermediate threads (F2; F2’) of the inner and outer strands, is the maximum bending stress per unit curvature seen in the outer metal threads (F3; F3’) of the inner and outer strands, M steel = 210,000 MPa is the elastic modulus of steel, d1, d1’, d2, d2’, d3, and d3’ are expressed in mm units, and Cp is the penetration coefficient of the cord, is the inter-strand penetration coefficient, is the penetration coefficient of the outer strands, - when the inter-strand distance E of the outer strands (TE) of the outer layer (CE) is < 30 μm or - when E > 70 μm, or - when 30 μm ≤ E ≤ 70 μm, and where Here, CpC2’ is the permeability coefficient of the intermediate layer (C2’) of the external strand (TE), and CpC3’ is the permeability coefficient of the external layer (C3’) of the external strand (TE), where when the thread pitch distance I2′ of the intermediate metal thread (F2’) of the intermediate layer (C2’) < 10 μm, or when I2’ > 40 μm, or when 10 μm ≤ I2’ ≤ 40 μm, or, - when the thread pitch distance I3’ of the external metal thread (F3’) of the external layer (C3’) < 10 μm, or - when I3’ > 40 μm, or when 10 μm ≤ I3’ ≤ 40 μm, and Cr is the dimensionless performance coefficient of the cord, where d3 and d3’ are expressed in mm, αf is the contact angle between the external metal thread (F3) of the internal strand (TI) and the external metal thread (F3’) of the external strand, expressed in radians, αt is the helix angle of each external strand (TE), expressed in radians, is the total breaking force (in Newtons) for the Q’ + M’ + N’ threads of the external strand, Cste = 1500 N·mm -2 and D is the diameter (in mm) of the cord, Sc is the compression surface area (mm 2 ), and Sc = [Q × (d1 / 2) 2 + M × (d2 / 2) 2 + N × (d3 / 2) 2 + L × (Q' × (d1' / 2) 2 + M × (d2' / 2) 2 + N' × (d3' / 2) 2 )] × π, and Se is the surface area of the code (mm 2 ), and Se = π × (D / 2) 2 is satisfied. The code (50) is characterized by this.

2. The cord (50) according to claim 1, wherein SL ≤ 37,500 MPa·mm.

3. The cord (50) according to claim 1, wherein SL ≥ 25,000 MPa·mm.

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

65.

5. The cord (50) according to claim 1, wherein αf is 0° or more and αf is 25° or less.

6. The cord (50) according to claim 1, wherein αt is 0° or more and αt is 20° or less.

7. The external layer (CE) of the cord is defined as the shortest distance that evenly separates the circular envelopes inscribed by two adjacent external strands (TE) on the cross-section of the cord perpendicular to the main axis of the cord (50), and the strand pitch distance of the external strand is unsaturated so as to be 30 μm or more. The cord (50) according to claim 1.

8. The cord (50) according to claim 1, wherein the permeability coefficient Cp of the cord is 0.60 or more.

9. A reinforced product (100) comprising an elastomer base material (102) and at least one cord (50) according to claim 1.

10. A tire (10) comprising at least one code (50) according to claim 1 or a reinforcing product according to claim 9.

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