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 cable consisting of K=1 inner strands (TI) with two plies (C1, C3), the inner ply (C1) consisting of Q inner metal threads (F1) and the outer ply (C3) consisting of N outer metal threads (F3), and an outer layer (CE) of cable consisting of L>1 outer strands (TE) wound on the inner layer (CI) of the cable with two plies (C1', C3'), the inner ply (C1') consisting of Q' inner metal threads (F1') and the outer ply (C3') consisting 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 belt or endless track reinforcement 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 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 at least one elastomeric ply called a carcass ply, which is in part 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 68.23 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 eight outer strands helically wound around the inner layer of the cord. Each inner strand comprises an inner layer of the strand composed of three inner threads and an outer layer of the strand composed of nine outer threads. Each thread has a diameter equal to 0.26 mm. Each outer strand comprises an inner layer of the strand composed of one inner thread and an outer layer of the strand composed of six 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, this type of tire usually travels on a rough road surface, and sometimes perforations occur in the tread. These perforations allow the intrusion 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, the cords of the prior art are known to have poor 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 agent within each strand. Therefore, 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, thus preventing the spread of the corrosive agent. Such cords are generally called on-site rubber-coated cords and are well known from the prior art. However, in the manufacturing method of such on-site rubber-coated cords, it is necessary to be proficient in numerous industrial constraints, especially to avoid the overflow of rubber, especially 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 that make up the cord and / or by increasing the number of threads and / or the individual strength of each thread. However, increasing the diameter of the thread even further, for example beyond 0.50 mm, will necessarily lead to a decrease in the flexibility of the cord, which is not desirable for the cord used in carcass reinforcement. 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] An object of the present invention is to provide a cord with improved bending durability compared to 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 two inner strands with K = 1, - an inner layer composed of Q = 1, 2, 3 or 4 inner metal threads with a diameter d1, - an inner layer comprising an outer layer composed of N outer metal threads with a diameter d3 wound around the inner layer, - An outer layer of a cord composed of two outer strands with L > 1 wound around an inner layer of the cord, - An inner layer composed of internal metal threads with Q' = 1, 2, 3 or 4 and a diameter d1', - An outer layer composed of N' external metal threads with a diameter d3' wound around the inner layer, and an outer layer having the same, and this cord has, - Bending durability criteria When it is TIFF0007710472000001.tif8150, SL ≤ 40,000 MPa·mm, and - When the size criterion Ec = Sc / Se, Ec ≥ 0.46, where - TIFF0007710472000002.tif6150 is the maximum bending stress per unit curvature seen in the internal threads of the internal and external strands, - TIFF0007710472000003.tif6150 is the maximum bending stress per unit curvature seen in the external threads of the internal and external strands, - M steel = 210,000 MPa is the elastic modulus of steel, - d1, d1', d3 and d3' are expressed in mm, - TIFF0007710472000004.tif9150, - Cp is the penetration coefficient of the cord, TIFF0007710472000005.tif6150 is the inter-strand penetration coefficient, TIFF0007710472000006.tif6150 is the penetration coefficient of the external strand, - When the inter-strand distance E of the external strands of the outer layer < 30 μm, TIFF0007710472000007.tif6150 or - When E > 70 μm, TIFF0007710472000008.tif6150 or - When 30 μm ≤ E ≤ 70 μm, TIFF0007710472000009.tif is 6150, when the thread pitch distance I3’ of the external metal threads of the outer layer is < 10 μm, TIFF0007710472000010.tif is 6150 or when -I2’ > 40 μm, TIFF0007710472000011.tif is 6150 or when -10 μm ≤ I2’ ≤ 40 μm, TIFF0007710472000012.tif is 6150, - Cr is the dimensionless performance coefficient of the cord, TIFF0007710472000013.tif is 15150, where d3 and d3’ are expressed in mm, αf is the contact angle, in radians, between the external metal threads of the inner strand and the external metal threads of the outer strand (F3’), αt is the helix angle of each outer strand, in radians, TIFF0007710472000014.tif15150 is the total breaking force (in Newtons) for the Q’ + N’ threads of the outer 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 + N × (d3 / 2) 2 + L × (Q’ × (d1’ / 2) 2 + N’ × (d3’ / 2) 2 )] × π, and Se is the surface area of the cord (mm 2 ), and Se = π × (D / 2) 2 and

[0013] On the one hand, due to its relatively low bending durability standard, the cord according to the present invention can reduce the stress level of the cord subjected to bending stress load, and thus 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 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 found in the internal threads of the internal and external strands divided by the penetration coefficient of the cord, or - the bending stress per unit curvature found in the external threads of the internal and external strands divided by the penetration coefficient of the cord and the performance coefficient of the cord, is.

[0014] On the one hand, the inventors of the present invention assume the theory that, especially in the region between strands where the most stress is applied, the larger the surface area of the contact between the threads, that is, the larger 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 the tensile performance of the cord due to lateral weakening in the contact between the outer metal threads of the inner layer and the outer layer. 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 metal 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 either have a relatively low bending durability standard but an optimal size standard, or have an optimal size standard, i.e., a size standard exceeding 0.46, but a relatively high bending durability standard. The cords according to the present invention have a relatively low durability standard and a relatively high size standard due to their relatively high performance coefficient and relatively high penetration coefficient, thereby enabling an 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 end points 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 end point "a" to the end point "b", i.e., including the exact end points "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 horn is inscribed. Preferably, the cord has a diameter D such that D ≦ 6.0 mm, and 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 has 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 at different pitches and / or when the winding directions of these layers are different for each layer. The strand with a cylindrical layer has a very high permeability, unlike a strand with a dense layer where the pitch of all the layers is the same and the winding direction of all the layers is the same, resulting in a much lower permeability.

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

[0025] The outer strand is a two-layer strand. The outer strand comprises an assembly of threads consisting of two layers of threads, no more and no less, which means that the assembly of threads has two layers of threads, not one layer and not three layers, but only two 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 having this pitch makes one full revolution 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 the thread is located, and then the thread having this pitch makes one full revolution 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 made by the strand or the thread 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 thread and the strand are determined in accordance with ASTM standard D2969-04(2014).

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

[0030] The helix angle αt of each external 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. In this formula, pe is the pitch represented in millimeters around which each external strand is wound, and Re TE is the helix radius of each external 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 external strands is defined as the shortest distance that evenly separates the circular envelopes inscribed by two adjacent external 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 external strand from the distance between the two centers of two adjacent external 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 case where, according to a normal orthogonal two-dimensional reference system, that is, according to the cross-section of the cord, with O being the center of the cord, OA is taken in the direction of the horizontal axis, and 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 helix radius of each external strand expressed in millimeters.

[0036] The helix 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 (unit: 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 (unit: mm), and D TE is the diameter of the external strand (unit: mm).

[0037] The diameter of the external strand is calculated as follows: DTE = 2×Re1’ + d1’ + 2×d2’, 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 , and 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 and averages 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 regarding the outer layer of the outer strand is Re3’ = Re1’ + d1 / 2 + d3 / 2 and is calculated as such, 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, obtained by subtracting the thread diameter from the distance between the centers of two metal threads, and the calculation method is the same as that used for the external 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 external strand.

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

[0044] Preferably, the strand does not undergo preforming.

[0045] 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 entirely (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.

[0046] When advantageously using carbon steel, 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 threads.

[0047] ​ The metal or steel to be used can be coated with itself with a metal layer that improves the processing characteristics of, for example, the metal cord and / or its components, or the usage characteristics of the cord and / or the tire itself, such as adhesiveness, corrosion resistance, or aging resistance, regardless of whether it is carbon steel or stainless steel. According to a preferred embodiment, the steel to be used is coated with a layer of brass (Zn-Cu alloy) or zinc.

[0048] 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.

[0049] Another main subject of the present invention is the cord as described above, extracted from a polymer matrix.

[0050] Preferably, the polymer matrix is an elastomer matrix.

[0051] The polymer matrix, preferably the elastomer matrix, is based on a polymer composition, preferably an elastomer composition.

[0052] It is understood that the polymer matrix is a matrix containing at least one polymer. Accordingly, the polymer matrix is based on a polymer composition.

[0053] What an elastomer matrix means is a matrix containing at least one elastomer. Accordingly, a preferred elastomer matrix is based on an elastomer composition.

[0054] The expression "based on" should be understood to mean that the composition comprises a mixture of various components used and / or the product of an in-situ reaction, and some of these components are at least partially reactive with each other and / or a reaction is contemplated during various stages of compound production, and thus the composition can be in a fully or partially cross-linked state or in an uncross-linked state.

[0055] The polymer composition is understood to mean that the composition contains at least one polymer. Preferably, such a polymer can be a thermoplastic, 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.

[0056] 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 includes an elastomer, a crosslinking 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 include diene elastomers, such as natural rubber, reinforcing fillers, such as carbon black and / or silica, a crosslinking 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 between the metal threads and the matrix in which they are embedded is imparted, for example, by a metal coating, such as a brass layer.

[0057] The characteristic values described in this application for the extracted cords are measured on or determined from the cords extracted from a polymer matrix, particularly an elastomer matrix, for example, with respect to a tire. Thus, for example, in the case of a tire, a piece of material outside the extracted cord in the radial direction is removed so that the cord extracted at the same height in the radial direction as the polymer matrix can be examined. This removal can be carried out by peeling using a cutter and gripper, or by planing. Next, the ends of the extracted cord are exposed with a knife. Then, the cord is pulled out of the matrix while applying a relatively shallow angle so that the extracted cord does not become plasticized. Next, the extracted cord is carefully cleaned, for example, using a knife, and the remaining polymer matrix locally attached to the cord is separated while taking care not to damage the surface of the metal thread.

[0058] The advantageous features described below apply equally to the codes and the extraction codes defined above.

[0059] Advantageously, SL ≤ 37,500 MPa·mm, preferably SL ≤ 35,000 MPa·mm.

[0060] The lower this SL criterion, the better the bending durability of the code.

[0061] Advantageously, SL ≥ 25,000 MPa·mm, preferably SL ≥ 27,500 MPa·mm.

[0062] It is preferred that SL is greater than 25,000 MPa·mm, which is to obtain a relatively large size by maximizing the metal mass.

[0063] Advantageously, Ec ≥ 0.47, preferably Ec ≥ 0.48.

[0064] Advantageously, Ec ≤ 0.65, preferably Ec ≤ 0.55.

[0065] 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 code for the same load. Conversely, if the size is too large for the same metal mass, the code becomes large, the elastomer composite containing the code becomes thick, leading to an increase in the risk of heat generation and problems related to the sizing of the final object.

[0066] Preferably, αf is 0° or more, preferably 3° or more.

[0067] Preferably, αf is 25° or less, preferably 20° or less.

[0068] 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.

[0069] Preferably, αt is 0° or more, and preferably 3° or more.

[0070] Preferably, αt is 20° or less, preferably 15° or less, more preferably 10° or less.

[0071] 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.

[0072] To calculate the flexural 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°.

[0073] In one embodiment, at least 50%, preferably at least 60%, more preferably at least 70%, and most preferably each metal thread of the cord comprises a steel core having a composition compliant with the NF-EN standard 10020 (September 2000), with a carbon content C ≦ 0.80%.

[0074] 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 (Articles 3.2.1 and 4.1 of NF-EN standard 10020 (September 2000)), stainless steels (Articles 3.2.2 and 4.2 of NF-EN standard 10020 (September 2000)), and other alloy steels (Articles 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 excessively 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.

[0075] Preferably, d1, d1’, d3, d3’ are, independently of one another, in the range from 0.12 mm to 0.38 mm, preferably from 0.15 mm to 0.35 mm.

[0076] In one embodiment, when Q > 1, the code is such that each inner layer of each outer strand is wound in a winding direction opposite to the winding direction of the code, and the winding direction of the outer layer of each outer strand around the inner layer of the outer strand is in a winding direction opposite to the winding direction of the code and the inner and outer layers of the inner strand. In this embodiment, by making the winding direction of each outer thread of the outer strand opposite to the winding direction of each outer thread of the inner strand, 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.

[0077] In another embodiment, when Q > 1, the code is such that each inner and outer layer of each outer strand is wound in the same direction as the code and the inner and outer layers of the inner strands. In this other embodiment, a more punctiform and less linear contact area is formed, which is not very advantageous for the coefficient of performance, but since all the layers are wound in the same direction and the code is assembled in the same direction, easier industrial implementation is possible.

[0078] In yet another embodiment, when Q > 1, each inner layer of each outer strand is wound in a winding direction opposite to that of the code, the inner and outer layers of each inner strand, and the outer layer of each outer strand.

[0079] In yet another embodiment, when Q > 1, the inner layer of the inner strand is wound in a winding direction opposite to that of the code, the inner and outer layers of each outer strand, and the outer layer of the inner strand.

[0080] In yet another embodiment, 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 that of the code, the outer layer of each outer strand, and the winding direction of the inner strand.

[0081] Advantageously, when Q > 1, various combinations of winding directions as specifically tabulated in Table 1 below can be envisaged.

[0082]

Table 1

[0083] Advantageously, the penetration coefficient Cp of the code is 0.60 or more, preferably 0.70 or more. Specifically, sufficient space is left between the threads or strands to allow the passage of the polymer composition, preferably an elastomer composition.

[0084] Advantageously, the outer layer of the code is made unsaturated.

[0085] By definition, an unsaturated layer is one in which sufficient space is left between the threads to allow a polymer composition, preferably an elastomer composition, to pass through. An unsaturated layer means that the threads do not touch 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 of the layer are in contact with each other, so that there is no sufficient space between the threads of the layer to allow a polymer composition, preferably an elastomer composition, to pass through.

[0086] 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 equally 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.

[0087] Advantageously, the outer layer of the inner strands is unsaturated.

[0088] 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.

[0089] Preferably, the inter-strand distance of the outer layer of the inner strands is 100 μm or less.

[0090] Advantageously, the sum SI3 of the inter-strand distances I3 of the outer layer of the inner strands is greater than the diameter d3 of the outer strands of the outer layer.

[0091] Advantageously, each strand is of a type that does not undergo on-site rubber drawing. Not undergoing on-site rubber drawing 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.

[0092] Advantageously, the outer layer of each outer strand is unsaturated.

[0093] Advantageously, the distance between the threads of the outer layer of each outer strand is 10 μm or more. Preferably, the distance between the threads of the outer layer of each outer strand is 15 μm or more.

[0094] Preferably, the distance between the threads of the outer layer of each outer strand is 100 μm or less.

[0095] Advantageously, the sum SI3' of the distances I3' between the threads of the outer layer of each outer strand is equal to or greater than the diameter d3' of the outer threads of the outer layer.

[0096] Preferably, the outer layer of the inner strand contacts and wraps around the inner layer of the inner strand.

[0097] Preferably, the outer layer of the outer strand contacts and wraps around the inner layer of the outer strand.

[0098] Advantageously, L = 6, 7 or 8, preferably L = 6 or 7, more preferably L = 6.

[0099] 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 strand on the inner strand.

[0100] Internal strands of the cord according to the present invention

[0101] In one embodiment, Q = 1.

[0102] Advantageously, N = 5, 6 or 7, preferably N = 6.

[0103] In another preferred embodiment, Q > 1, preferably Q = 2, 3 or 4.

[0104] Advantageously, N = 7, 8, 9 or 10, preferably N = 7, 8 or 9.

[0105] In a first alternative form, Q = 2, N = 7 or 8, preferably Q = 2, N = 7.

[0106] In a second alternative form, Q = 3, N = 7, 8 or 9, preferably Q = 3, N = 8.

[0107] In a third alternative form, Q = 4, N = 7, 8, 9 or 10, preferably Q = 4, N = 9.

[0108] Most advantageously, each internal thread of the internal strand has a diameter d1 equal to the diameter d3 of each external thread of the internal strand. Thus, threads of the same diameter are preferably used for the internal and external layers of the internal strand, thereby limiting the number of different threads that need to be managed during the manufacture of the cord.

[0109] External strands of the cord according to the present invention

[0110] In one embodiment, Q' = 1.

[0111] Advantageously, N' = 5, 6 or 7, preferably N' = 6.

[0112] In another preferred embodiment, Q' > 1, preferably Q' = 2, 3 or 4.

[0113] Advantageously, N' = 7, 8, 9 or 10, preferably N' = 8 or 9.

[0114] In a first alternative form, Q' = 2, N' = 7 or 8, preferably Q' = 2, N' = 7.

[0115] In a second alternative form, Q' = 3, N' = 7, 8 or 9, preferably Q' = 3, N' = 9.

[0116] In a third alternative form, Q' = 4, N' = 7, 8, 9 or 10, preferably Q' = 4 and N' = 9.

[0117] Very advantageously, each internal thread of the external strand has a diameter d1' greater than the diameter d3' of each external thread of the external strand.

[0118] Very advantageously, each internal thread of the internal strand has a diameter d1 equal to the diameter d3 of each external thread of the internal strand and equal to the diameter d1' of each internal thread of the external strand.

[0119] Advantageously, Q = 4 and N = 9, Q' = 3 and N' = 9, and d1 = d3 = d1', d3' ≤ d1'. Specifically, the capillaries within each external strand TE are smaller than the capillaries within the internal strand, making it possible to reduce the spread of corrosion in the event of perforation.

[0120] Reinforcement product according to the present invention

[0121] Another subject of the present invention is a reinforced product comprising a polymer matrix and at least one cord as defined above.

[0122] Advantageously, the reinforced 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.

[0123] Tire according to the present invention

[0124] Another subject of the present invention is a tire comprising at least one cord as defined above.

[0125] 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.

[0126] In another embodiment, the tire has a carcass reinforcement radially surrounded by a crown reinforcement fixed to two beads and itself surrounded by a tread, the crown reinforcement being joined to the beads by two sidewalls and comprising at least one cord as defined above.

[0127] Preferably, the crown reinforcement comprises a protection reinforcement and a working reinforcement, the working reinforcement comprising at least one cord as defined above, and the protection reinforcement being arranged radially between the tread and the working reinforcement.

[0128] In yet another embodiment, the tire has a carcass reinforcement radially surrounded by a crown reinforcement fixed to two beads and itself surrounded by a tread, the crown reinforcement being joined to the beads by two sidewalls and having at least one cord as defined above, and the carcass reinforcement having at least one cord as defined above.

[0129] The cords are in particular intended for industrial vehicles selected from "large vehicles", i.e. underground trains, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles, agricultural vehicles or plant construction vehicles, or other transport or handling vehicles.

[0130] Preferably, the tire is for a plant construction type vehicle. 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 25 and 57 inches, in inches.

[0131] The present invention also relates to an assembly according to the invention, or a rubber article comprising the impregnated assembly according to the invention. Rubber article means any kind of article made of rubber, such as balls, non-pneumatic objects such as non-pneumatic tire casings, conveyor belts or endless tracks. The present invention should be better understood from the following examples, described in connection with the drawings by way of non-limiting example only.

Brief Description of the Drawings

[0132]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Modes for Carrying Out the Invention

[0133] Examples of tires according to the present invention

[0134] The 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.

[0135] The "median circumferential plane" M of the tire is a plane perpendicular to the rotation axis of the tire and equidistant from the annular reinforcing structures of each bead.

[0136] FIGS. 1 and 2 represent a tire, generally designated by reference numeral 10, according to the present invention.

[0137] The tire 10 is for large vehicles of the plant construction type, for example the "loader" type. Accordingly, the tire 10 has dimensions of type 35 / 65R33.

[0138] 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 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 26 positioned towards the outside of the tire 20, the turn-up 26 being shown here fitted to a wheel rim 28. The carcass reinforcement 24 is radially surrounded by the crown reinforcement 14.

[0139] The carcass reinforcement 24 comprises at least one carcass ply 30 reinforced by a radial carcass cord 50 (not shown) according to the invention. The carcass cords 50 are positioned substantially parallel to one another and extend from one bead 18 to the other so as to form an angle comprised between 80° and 90° with respect to the median circumferential plane M (a plane perpendicular to the axis of rotation of the tire, located in the middle between the two beads 18 and passing through the center of the crown reinforcement 14).

[0140] The tire 10 also comprises a sealing ply 32 (generally known as an "innerliner") made of an elastomer, which defines the radially inner face 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.

[0141] 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 sandwiched radially between the tread 22 and the working reinforcement 38. The working reinforcement 38 is sandwiched radially between the protection reinforcement 36 and the additional reinforcement 40.

[0142] The protection reinforcement 36 includes first and second protection plies 42, 44 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.

[0143] 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. Each ply 46, 48 includes at least one cord 50. Optionally, the working metal cords 50 cross from one working ply to the other and form an angle of at most equal to 60°, preferably in the range from 15° to 40° with respect to the circumferential direction Z of the tire.

[0144] The additional reinforcement 40, also called a restraint 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.

[0145] Example of the reinforcement product according to the present invention

[0146] Figure 3 represents a reinforcing product, generally designated by reference numeral 100, according to the present invention. The reinforcing product 100 includes at least one cord 50, and in this example a plurality of cords 50, embedded in a polymer matrix 102.

[0147] 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 reinforcing product 100 is arranged side-by-side in the main direction X and includes a plurality of cords 50 that extend parallel to each other within the reinforcing product 100 and are collectively embedded in the polymer matrix 102. In this example, the polymer matrix 102 is an elastomeric matrix based on an elastomeric composition.

[0148] Cord according to the first embodiment of the present invention

[0149] Figures 4 and 5 represent a cord 50 and a cord 50', respectively, according to the first embodiment of the present invention.

[0150] The cords 50 and 50' have the same geometric structure. The cord 50' is obtained after being extracted from the tire 10

[0151] Figure 7 is a photograph of the cord 50.

[0152] 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 is to be understood that the strands forming the cord 50 or 50' are two layers and neither more nor less.

[0153] The cord 50 or cord 50' includes an inner layer CI of the cord composed of an inner strand 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 particular example, L = 6, 7 or 8, preferably L = 6 or 7, more preferably L = 6, and here L = 6.

[0154] This cord meets the bending durability criteria It has TIFF0007710472000016.tif13150.

[0155] It has TIFF0007710472000017.tif7150 and, It has TIFF0007710472000018.tif10150.

[0156] Since the inter-strand distance E = 58μm, It is TIFF0007710472000019.tif10150.

[0157] Since the fine wire distance I3’ = 36μm, when 10μm ≦ I3’ ≦ 40μm, It is TIFF0007710472000020.tif7150.

[0158] Cp=(0.82 + 0.92) / 2 = 0.87

[0159] It is TIFF0007710472000021.tif21163

[0160] It becomes TIFF0007710472000022.tif13150, which will be much lower than 40,000MPa.mm. SL ≦ 37500MPa.mm, preferably SL ≦ 35000MPa.mm, SL ≧ 25,000MPa.mm, preferably SL ≧ 27,500MPa.mm.

[0161] The compression 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

[0162] The surface area Se = π×(3.2 / 2)2 = 8.04

[0163] Ec = Sc / Se = 3.89 / 8.04 = 0.48, and Ec ≧ 0.47, Ec ≧ 0.48, Ec ≦ 0.65, preferably Ec ≦ 0.55.

[0164] The penetration coefficients of Codes 50 and 50' are equal to 0.87, which is 0.60 or more, preferably 0.70 or more.

[0165] The outer layers of Codes 50 and 50' are unsaturated. Therefore, the strand - to - strand distance E of the outer strands is strictly more than 20 μm. Here, E = 58 μm.

[0166] αf is 0° or more, preferably 3° or more, and 25° or less, preferably 20° or less. Here, αf = 5.1°.

[0167] αt is 0° or more, preferably 3° or more, and 20° or less, preferably 15° or less, more preferably 10° or less. Here, αt = 6.5°.

[0168] Internal strands TI of cords 50 and 50'

[0169] Each internal strand TI is a two - layer strand, comprising an inner layer C1 composed of internal metal threads F1 with Q = 2, 3, or 4, and an outer layer C3 composed of N external metal threads F3 wound around the inner layer C1.

[0170] Here, Q = 4.

[0171] N = 7, 8, 9, or 10, preferably N = 8 or 9. Here, N = 9.

[0172] The outer layer C3 of each internal strand TI is unsaturated. The strand - to - strand distance of the outer layer of the internal strand is 30 μm or more, and in this case, it is equal to 38 μm. The total SI3 of the strand - to - strand distances I3 of the outer layer C3 is larger than the diameter d3 of the outer threads F3 of the outer layer C3. Here, the total SI3 = 0.038×9 = 0.34 mm, which is a value larger than d3 = 0.26 mm.

[0173] d1 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 = d3 = 0.26 mm.

[0174] External strands TE of cords 50 and 50'

[0175] Each external strand TE is a two-layer strand and includes an inner layer C1' composed of internal metal threads F1' with Q' = 2, 3 or 4, and an outer layer C3' composed of N' external metal threads F3' wound around the inner layer C1'.

[0176] Here, Q' = 3.

[0177] N' = 7, 8, 9 or 10, preferably N' = 8 or 9. Here, N' = 9.

[0178] The outer layer C3' of each external strand TE is unsaturated. Since it is unsaturated, the thread pitch I3' of the outer layer C3' that separates the N' external threads on average is 10 μm or more. The thread pitch I3' of the outer layer of the external strand is 30 μm or more, and in this case, it is equal to 37 μm. The total SI3' of the thread pitches I3' of the outer layer C3' is larger than the diameter d3' of the external threads F3' of the outer layer C3'. Here, the total SI3' = 0.036 × 9 = 0.32 mm, which is a value larger than d3' = 0.23 mm.

[0179] Each inner layer C1' of each external strand TE is wound in a winding direction opposite to the winding directions of the inner layer C1 and the outer layer C3 of the cord and the inner strand TI, and the winding direction of the outer layer C3' of each external strand TE around the inner layer C1' of the external strand TE is in a winding direction opposite to the winding directions of the inner layer C1 and the outer layer C3 of the cord and the inner strand TI. In this case, the winding directions of layers C1, C3 and the cord are Z, and the winding directions of layers C1' and C3' are S.

[0180] Manufacturing method of the cord according to the present invention

[0181] Here, an example of a method for manufacturing the multi-strand cord 50 will be described.

[0182] Each of the above-described inner strands is manufactured according to a known method including the following steps, and is preferably continuously executed inline. - First, a first assembling step of forming the inner layer C1 at a first assembling point by twisting or winding the inner threads F1 of Q = 4 of the inner layer C1 in the Z direction at a pitch p1; - Subsequently, a second assembling step of forming the outer layer C3 at a second assembling point by twisting or winding N = 9 outer threads F3 around the Q inner threads F1 of the inner layer C1 in the Z direction at a pitch p3; - Preferably, a final twist balancing step.

[0183] Each of the above-described outer strands is manufactured according to a known method including the following steps, and is preferably continuously executed inline. - First, a first assembling step of forming the inner layer C1' at a first assembling point by twisting or winding the inner threads F1' of Q' = 3 of the inner layer C1' in the S direction at a pitch p1'; - Subsequently, a second assembling step of forming the outer layer C3' at a second assembling point by twisting or winding N' = 9 outer threads F3' around the Q' inner threads F1' of the inner layer C1' in the S direction at a pitch p3'; - Preferably, a final twist balancing step.

[0184] What "twist balancing" means here is well known to those skilled in the art, but it is the elimination of the residual torque (or the elastic recovery of the twist) applied to each thread of the strand in the intermediate layer as in the outer layer.

[0185] After this final twist balancing step, the manufacture of the strand is completed. Each strand is wound around one or more receiving reels for storage prior to the operation of twisting and combining the basic strands to obtain the multi-strand cord.

[0186] To manufacture the multi-strand cord of the present invention, as is well known to those skilled in the art, the method is to twist or twine the previously obtained strands using a twisting machine or a twining machine that has been evaluated for gathering the strands.

[0187] 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 last combining step, the wrapper F is wound around the previously obtained assembly in the S direction with a pitch pf.

[0188] 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 a reinforcing filler, 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).

[0189] 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.

[0190] 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 in another way.

[0191] Cord according to the second embodiment of the present invention

[0192] Unlike the first embodiment described above, the code 60 according to the second embodiment is such that Q = 3, N = 8, Q' = 3, and N' = 8.

[0193] Cord according to the third embodiment of the present invention

[0194] Unlike the first embodiment described above, the code 70 according to the third embodiment is such that K = 1, L = 7, Q = 3, N = 8, Q' = 1, and N' = 5.

[0195] Table 2 below summarizes the characteristics of various codes 50, 50', 60, and 70 according to the present invention.

[0196]

Table 2

[0197] Comparative test

[0198] Evaluation of bending durability criteria and dimensional criteria

[0199] Various control codes and prior art codes were simulated.

[0200] Table 3 summarizes the characteristics of the control code C1 and the prior art code EDT (68.23 code).

[0201]

Table 3

[0202] Tables 2 and 3 show that codes 50, 50', 60, and 70 have relatively low bending durability criteria while having sufficient size criteria compared to the prior art code EDT and the control code C1. 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 maintaining a satisfactory size.

[0203] The present invention is not limited to the above-described embodiments.

Explanation of Reference Numerals

[0204] Code 50 Inner layer of the inner strand of C1 Inner layer of the outer strand of C1' Outer layer of the inner strand of C3 Outer layer of the outer strand of C3' Outer layer of the CE code Inner layer of the CI code Distance between strands E Inner metal thread of the inner strand of F1 Inner metal thread of the partial strand of F1' Outer metal thread of the inner strand of F3 Outer metal thread of the outer strand of F3' Distance between threads of the outer layer of the outer strand of I3' Outer strand TE Inner strand TI

Claims

1. A two-layer multi-strand cord (50), comprising an inner layer (CI) of said cord composed of inner strands (TI) of two layers (C1, C3) with K = 1, said inner layer (CI) being,[[]]END]] an inner layer (C1) composed of inner metal threads (F1) of Q = 1, 2, 3 or 4 with a diameter d1, and an outer layer (C3) composed of N outer metal threads (F3) with a diameter d3 wound around said inner layer (C1), having,[[]]END]] said cord (50) being,[[]]END]] provided with an outer layer (CE) of said cord composed of outer strands (TE) of two layers (C1’, C3’) with L > 1 wound around said inner layer (CI) of said cord, said outer layer (CE) being,[[]]END]] an inner layer (C1’) composed of inner metal threads (F1’) of Q’ = 1, 2, 3 or 4 with a diameter d1’, and an outer layer (C3’) composed of N’ outer metal threads (F3’) with a diameter d3’ wound around said inner layer (C1’), having,[[]]END]] said cord (50) being,[[]]END]] when, a bending durability criterion SL of SL ≤ 40,000 MPa·mm, and when a size criterion Ec = Sc / Se, a size criterion Ec of Ec ≥ 0.46, where is the maximum bending stress per unit curvature seen in said inner threads (F1; F1’) of said inner and outer strands, is the maximum bending stress per unit curvature seen in said outer metal threads (F3; F3’) of said inner and outer strands, M steel = 210,000 MPa is the elastic modulus of steel, d1, d1’, d3 and d3’ are expressed in mm units, being,[[]]END]] Cp is the penetration coefficient of said cord, is the inter-strand penetration coefficient, is the penetration coefficient of said outer strands, - when the inter-strand distance E of said outer strands (TE) of said outer layer (CE) is < 30 μm or - when E > 70 μm, or - when 30 μm ≤ E ≤ 70 μm, being,[[]]END]] when the inter-strand distance I3’ of said outer metal threads (F3’) of said outer layer (C3’) is < 10 μm, or when I3’ > 40 μm, or when 10 μm ≤ I3’ ≤ 40 μm, being,[[]]END]] Cr is the dimensionless performance coefficient of said cord (50), being, where d3 and d3’ are expressed in mm units, αf is the contact angle in radians between said outer metal threads (F3) of said inner strands (TI) and said outer metal threads (F3’) of said outer strands (TE). αt is the helix angle of each outer strand expressed in radians, is the total of the breaking forces (in Newtons) for the Q'+N' threads of the outer strand Cste = 1500 N·mm -2 and D is the diameter (mm) of the cord, Sc is the compression surface area (mm 2 ), and Sc = [Q × (d1 / 2) 2 + N × (d3 / 2) 2 + L × (Q' × (d1' / 2) 2 + N' × (d3' / 2) 2 )] × π, and Se is the surface area of the code (mm 2 ), and Se = π × (D / 2) 2 . 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 25° or less.

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

7. The strand pitch of the outer strand is defined as the shortest distance that evenly separates the circular envelopes in which two adjacent outer strands (TE) are inscribed on the cross-section of the cord perpendicular to the main axis of the cord (50), and 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 penetration coefficient Cp of the cord is 0.60 or more.

9. A reinforcing 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 cord (50) according to claim 1 or the reinforcing product according to claim 9.

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