Multi-strand cable having two multi-strand layers

Abstract

The invention relates to a multi-strand cable (50) having two multi-strand layers, the cable (50) comprising: - an inner cable layer (CI) consisting of X = 3 or 4 multi-strands (M1), the multi-strands (M1) comprising K = 2, 3 or 4 strands (T1) helically wound around an axis (B), each strand (T1) being a strand having at least two layers (C1, C3), and - an outer cable layer (CE) consisting of Y > 1 multi-strands (M2) wound around the inner cable layer (CI), each multi-strand (M2) comprising L = 2, 3 or 4 strands (T2) helically wound around an axis (A’), each strand (T2) being a strand having at least two layers (C1’, C3’), wherein the multi-strands (M1) of the inner layer and the multi-strands (M2) of the outer layer are helically wound around a main axis (A). The cable (50) has a structural elongation As, which satisfies As ≥ 1.0%.

Description

Technical Field

[0001] This invention relates to cords and tires comprising these cords. Background Technology

[0002] Cords with a structure of (1+6)×(3+8) are known from the prior art (as described in document FR2969181B). These cords consist of six strands spirally wound around the core with a twist pitch of 60 mm. Each strand comprises an inner layer with three inner threads spirally wound with a twist pitch of 7.7 mm and an outer layer with eight outer threads spirally wound around the inner layer with a twist pitch of 15.4 mm. The structural elongation of the cord is less than 2% and the breaking strength is 19600 N.

[0003] These cords are rigid cords, which have the advantage of reducing tension on the working ply, but greatly increase the circumferential stiffness of the structure. When these cords are placed in additional reinforcements, they can lead to increased sensitivity of the central crown block of the tread to impacts.

[0004] Currently, there is a growing demand for new types of cords used in tire tread ply (especially ply with a layup angle of less than 10°, such as additional reinforcements). The purpose of such reinforcements is to reduce tension on the working ply and improve tire durability, particularly crack resistance. Summary of the Invention

[0005] The object of the present invention is a cord that has a good trade-off between stiffness and flexibility: the flexibility is sufficient to reduce the stiffness of the tread block, but the breaking force is sufficient to withstand tensile stress loads.

[0006] Therefore, one aspect of the present invention is a multi-strand cord having two multi-strand element layers, wherein the cord comprises:

[0007] - Inner layer of the cord, the inner layer of the cord is composed of X=3 or 4 multi-strand elements, the multi-strand elements including K=2, 3 or 4 strands spirally wound around an axis, each strand having at least two layers, the at least two layers comprising:

[0008] - An inner layer composed of Q1 internal metal wires with a diameter of d1, and

[0009] - An outer layer consisting of Q3 outer metal wires with a diameter of d3 wound around the inner layer, and

[0010] - Outer layer of the cord, the outer layer of the cord is composed of Y>1 multi-strand elements wound around the inner layer of the cord, each multi-strand element including L=2, 3 or 4 strands spirally wound around the axis, each strand having at least two layers, the at least two layers including:

[0011] - An inner layer composed of internal metal wires with a diameter of d1' (Q1'), and

[0012] - An outer layer consisting of Q3' outer metal wires with a diameter of d3' wound around the inner layer.

[0013] Both the inner and outer multi-strand elements are spirally wound around the main axis, and

[0014] The cord has a structural elongation As, which satisfies As≥1.0%. The structural elongation As is determined by applying the 2014 standard ASTM D2969-04 to the cord to obtain a force-elongation curve. The structural elongation As is equal to the elongation, expressed as a percentage, corresponding to the intersection of the tangent to the elastic portion of the force-elongation curve at a point along its elastic portion and the elongation axis of the force-elongation curve.

[0015] Thanks to this multi-strand cord construction with two multi-strand element layers, the cord according to the invention can achieve cords with sufficient structural elongation (providing tensile flexibility) and sufficient metallic quality, while maintaining fine filaments to obtain bending flexibility, improving the trade-off between shear in the polymer matrix, flexibility and strength of the crown block, thereby improving the trade-off between cracking and attack performance.

[0016] Structural elongation As is a parameter well-known to those skilled in the art, determined, for example, by applying the 2014 standard ASTM D2969-04 to the tested cord to obtain a force-elongation curve. As is derived from the obtained curve and is the elongation, expressed as a percentage, corresponding to the intersection of the tangent to the elastic portion of the force-elongation curve and the elongation axis of the force-elongation curve. It should be remembered that the force-elongation curve includes structural, elastic, and plastic portions in the direction of increasing elongation. The structural portion corresponds to the structural elongation of the cord resulting from the movement of the different strands and wires constituting the cord together. The elastic portion corresponds to the elastic elongation resulting from the construction of the cord (particularly the angles of the layers and the diameters of the wires). The plastic portion corresponds to the plastic elongation resulting from the plasticity of the wires (irreversible deformation beyond the elastic limit).

[0017] In this invention, the cord comprises two layers having multi-strand elements, which means that it comprises an assembly consisting of no more and no less than a layer of Y>1 multi-strand elements wound around a single layer having multi-strand elements. This means that the assembly has two multi-strand element layers, not one layer or three layers, but only two layers.

[0018] In this invention, a multi-strand element has a strand layer, meaning that it comprises a component consisting of one (no more and no less) strand layer, meaning that the component consists of one strand layer, not zero layers, not two layers, but only one layer.

[0019] In one embodiment, the inner multi-strand elements of the cord are surrounded by a polymer composition and then surrounded by an outer layer.

[0020] Advantageously, each strand has a cylindrical layer.

[0021] Advantageously, each strand in the multi-strand element has two layers, meaning it comprises an assembly consisting of two (no more, no less) layers of metal wire. This means the assembly has two layers of metal wire, not one or three layers, but only two. The outer layer of each strand is wound around the inner layer of the strand in contact with it.

[0022] Advantageously, each strand in the inner layer and each strand in the outer layer have a cylindrical layer. It should be recalled that this cylindrical layer is obtained when the different layers of the strand are wound with different twist pitches and / or when the winding directions of these layers differ from one layer to another. Strands with cylindrical layers are highly permeable, unlike strands with compact layers, where all layers have the same twist pitch and all layers are wound in the same direction, thus exhibiting much lower permeability.

[0023] Advantageously, each strand in the inner layer and each strand in the outer layer are unsaturated, which means that there is enough space between the outer layer strands to allow the elastomer compound to impregnate each strand.

[0024] Preferably, the strands are not pre-formed.

[0025] Advantageously, the cord as defined above is bare, meaning it does not contain any polymer composition; in particular, the cord does not contain any elastomer composition.

[0026] Metal wire is understood as a metal monofilament whose core is primarily (i.e., more than 50% of its weight) or entirely (100% of its weight) made of a metallic material (e.g., carbon steel). Metal wire may advantageously include a layer of metallic coating covering the core, said metallic coating being selected from zinc, copper, tin, and alloys of these metals, such as brass. Each wire is preferably made of pearlitic or ferritic-pearlitic carbon steel.

[0027] The values ​​of the characteristics of the exposed cords described in this application are measured or determined directly on the cords after they are made (i.e., before any step of embedding into the polymer matrix (especially the elastomer matrix)).

[0028] In this application, any numerical range expressed as "between a and b" represents a numerical range from greater than a to less than b (i.e., excluding endpoints a and b), while any numerical range expressed as "from a to b" means a numerical range from endpoint "a" to endpoint "b", i.e., including strictly endpoints "a" and "b".

[0029] Advantageously, As ≥ 1.5%, and preferably, As ≥ 2.0%.

[0030] Another subject of the present invention is a cord extracted from a polymer matrix, wherein the extracted cord comprises:

[0031] - Inner layer of the cord, the inner layer of the cord is composed of X=3 or 4 multi-strand elements, the multi-strand elements including K=2, 3 or 4 strands spirally wound around the main axis, each strand having at least two layers, the at least two layers including:

[0032] - An inner layer composed of Q1 internal metal wires with a diameter of d1, and

[0033] - An outer layer consisting of Q3 outer metal wires with a diameter of d3 wound around the inner layer, and

[0034] - Outer layer of the cord, the outer layer of the cord is composed of Y>1 multi-strand elements wound around the inner layer of the cord, each multi-strand element including L=2, 3 or 4 strands spirally wound around the axis, each strand having at least two layers, the at least two layers including:

[0035] - An inner layer composed of internal metal wires with a diameter of d1' (Q1'), and

[0036] - An outer layer consisting of Q3' outer metal wires with a diameter of d3' wound around the inner layer.

[0037] Both the inner and outer multi-strand elements are spirally wound around the main axis, and

[0038] The cord has a structural elongation As', which satisfies As'≥0.3%. The structural elongation As' is determined by applying the 2014 standard ASTM D2969-04 to the cord to obtain a force-elongation curve. The structural elongation As' is equal to the elongation, expressed as a percentage, corresponding to the intersection of the tangent to the elastic portion of the force-elongation curve at a point along its elastic portion and the elongation axis of the force-elongation curve.

[0039] Preferably, the polymer matrix is ​​an elastomer matrix.

[0040] The polymer matrix (preferably an elastomer matrix) is based on a polymer (preferably an elastomer) composition.

[0041] A polymer matrix is ​​understood to be a matrix containing at least one polymer. Therefore, a polymer matrix is ​​based on a polymer composition.

[0042] An elastomeric matrix refers to a matrix containing at least one elastomeric element. Therefore, a preferred elastomeric matrix is ​​based on an elastomeric composition.

[0043] The term "based on" should be understood to mean that the composition contains a mixture of the various components used and / or in-situ reaction products, some of which are capable of reacting and / or intended to react with each other at least partially during various stages of the manufacture of the composition; thus, the composition can be in a fully cross-linked or partially cross-linked state or a non-cross-linked state.

[0044] The term "polymer composition" is understood to mean that the composition contains at least one polymer. Preferably, such polymer can be a thermoplastic polymer (e.g., polyester or polyamide), a thermosetting polymer, an elastomer (e.g., natural rubber), a thermoplastic elastomer, or a combination of these polymers.

[0045] The term "elastomer composition" is understood to mean that the composition comprises at least one elastomer and at least one other component. Preferably, the composition comprising at least one elastomer and at least one other component comprises an elastomer, a crosslinking system, and a filler. Compositions that can be used for these ply layers are conventional compositions for surface coatings of filamentary reinforcing elements and comprise diene elastomers (e.g., natural rubber), reinforcing fillers (e.g., carbon black and / or silica), crosslinking systems (e.g., vulcanization systems, preferably comprising sulfur, stearic acid, and zinc oxide, and optionally vulcanization accelerators and / or retarders), and / or various additives. Adhesion between the metal wires and the matrix in which the metal wires are embedded is achieved, for example, by a metal coating (e.g., a brass layer).

[0046] The characteristic values ​​of the extracted cords described in this application are measured or determined in cords extracted from, for example, a polymer matrix (particularly an elastomer matrix) of a tire. Therefore, for example in a tire, a strip of material located radially outside the cord to be extracted is removed to expose the cord to be extracted, which is radially flush with the polymer matrix. This removal can be accomplished by peeling using a tool and jig or by planing. Next, the end of the cord to be extracted is peeled off using a tool. The cord is then pulled to extract it from the matrix, applying a relatively shallow angle to avoid plasticizing the cord. The extracted cord is then carefully cleaned, for example using a tool, to separate any polymer matrix residue locally adhered to the cord, while taking care not to damage the surface of the wires.

[0047] The advantages described below apply to both the cords defined above and the extracted cords.

[0048] Preferably, the cord has a cord diameter D that is in the range of 4 mm to 10 mm, and more preferably 5 mm to 8 mm.

[0049] By definition, the diameter of a strand is the diameter of its smallest circumscribed circle.

[0050] Preferably, the diameter of the independent metal wires ranges from 0.15 mm to 0.50 mm, more preferably from 0.18 mm to 0.35 mm, and even more preferably from 0.20 mm to 0.30 mm.

[0051] Preferably, the threads in the same layer of the predetermined strands all have substantially the same diameter. Advantageously, the outer strands all have substantially the same diameter. "Substantially the same diameter" means that the threads or strands have the same diameter within industrial tolerances.

[0052] Advantageously, Y is equal to 6, 7, 8, 9 or 10, preferably Y = 6, 7 or 8, and more preferably Y = 6.

[0053] Advantageously, K = 2, 3 or 4, preferably K = 3 or 4.

[0054] Advantageously, L = 2, 3 or 4, and preferably, L = 3 or 4.

[0055] In the first embodiment, each strand of the inner layer has two layers.

[0056] Advantageously, each strand of the outer layer has two layers.

[0057] Advantageously, in this first embodiment, in a preferred variant, each strand of the inner layer and each strand of the outer layer have two layers.

[0058] In the second embodiment, each strand of the inner layer has three layers and includes:

[0059] The intermediate layer consists of Q2 intermediate metal wires wound around the inner layer, and

[0060] The outer layer consists of Q3 outer metal wires wound around the middle layer.

[0061] Advantageously, each strand of the outer layer has three layers and includes:

[0062] The intermediate layer consists of Q2' intermediate metal wires wound around the inner layer, and

[0063] The outer layer is composed of Q3' outer metal wires wound around the middle layer.

[0064] Advantageously, in this second embodiment, in a preferred variant, each strand of the inner layer and each strand of the outer layer have three layers.

[0065] Advantageously, each strand is of the non-in-situ rubberized type. Non-in-situ rubberization means that each strand consists of individual layers of filaments before the strands are assembled together, and does not contain any polymer composition (especially any elastomer composition).

[0066] The internal multi-strand element of the cord according to the present invention

[0067] Advantageously, Q1 = 1, 2, 3 or 4, preferably, Q1 = 1, 2 or 3, and more preferably, Q1 = 1 or 3.

[0068] Advantageously, Q3 = 5, 6, 7, 8, 9 or 10, preferably, Q3 = 6, 7, 8 or 9, and more preferably, Q3 = 6 or 9.

[0069] In one implementation, Q1 = 1.

[0070] Advantageously, Q3 = 5, 6 or 7, and preferably, Q3 = 6.

[0071] In another preferred embodiment, Q1>1, and preferably, Q1=2, 3 or 4.

[0072] Advantageously, Q3 = 7, 8, 9 or 10, and preferably, Q3 = 7, 8 or 9.

[0073] In the first variant, Q1 = 2 and Q3 = 7 or 8, and preferably, Q1 = 2 and Q3 = 7.

[0074] In the second variant, Q1 = 3 and Q3 = 7, 8 or 9, and preferably Q1 = 3 and Q3 = 8.

[0075] In the third variant, Q1 = 4 and Q3 = 7, 8, 9 or 10, and preferably Q1 = 4 and Q3 = 9.

[0076] The strands of the outer multi-strand element of the cord according to the present invention

[0077] Advantageously, Q1' = 1, 2, 3 or 4, preferably, Q1' = 1, 2 or 3, and more preferably, Q1' = 1 or 3.

[0078] Advantageously, Q3' = 5, 6, 7, 8, 9 or 10, preferably, Q3' = 6, 7, 8 or 9, and more preferably, Q3' = 6 or 9.

[0079] In one implementation, Q1' = 1.

[0080] Advantageously, Q3' = 5, 6 or 7, and preferably, Q3' = 6.

[0081] In another preferred embodiment, Q1'>1, and preferably, Q1'=2, 3 or 4.

[0082] Advantageously, Q3' = 7, 8, 9 or 10, and preferably, Q3' = 7, 8 or 9.

[0083] In the first variant, Q1' = 2 and Q3' = 7 or 8, and preferably, Q1' = 2 and Q3' = 7.

[0084] In the second variant, Q1' = 3 and Q3' = 7, 8 or 9, and preferably, Q1' = 3 and Q3' = 8.

[0085] In the third variant, Q1' = 4 and Q3' = 7, 8, 9 or 10, and preferably, Q1' = 4 and Q3' = 9.

[0086] Advantageously, Q1 = 1 and Q3 = 6, Q1' = 1 and Q3' = 6.

[0087] Enhanced product according to the present invention

[0088] Another subject of the invention is a reinforced product comprising a polymer matrix and at least one cord or extracted cord as defined above.

[0089] Advantageously, the reinforcing product comprises one or more cords according to the invention embedded in a polymer matrix, and in the case of several cords, the cords are arranged side by side in the main direction.

[0090] Tires according to the present invention

[0091] Another subject of the invention is a tire comprising at least one extracted cord or reinforcing product as defined above.

[0092] A tire that includes extracted cords means a tire that includes cords whose properties are measured prior to extraction from the tire and which, prior to being bonded to the tire, are, for example, cords described above.

[0093] Preferably, the tire has a carcass reinforcement anchored in two beads and radially covered by a crown reinforcement, which is itself covered by the tread and is attached to the beads via two sidewalls and includes at least one cord as defined above.

[0094] In a preferred embodiment, the crown reinforcement includes a protective reinforcement, a working reinforcement, and an additional reinforcement, the additional reinforcement including at least one cord as defined above, the additional reinforcement forming an angle of at most 10° with the circumferential direction Z of the tire, preferably ranging from 5° to 10°, and being radially inserted between the working reinforcement and the carcass reinforcement.

[0095] Cords are most specifically designed for use in heavy vehicles such as "heavy-duty vehicles"—i.e., subways, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles, agricultural vehicles or construction site vehicles, or other transport or handling vehicles.

[0096] Preferably, the tire is used on construction site type vehicles. Therefore, the tire has a size in which the base diameter of the rim intended to mount the tire is greater than or equal to 40 inches.

[0097] The present invention also relates to a rubber article comprising, or comprising, components impregnated according to the invention. A rubber article means any type of article made of rubber, such as a ball, a non-pneumatic object (e.g., a non-pneumatic tire), a conveyor belt, or a track. Attached Figure Description

[0098] The invention will be better understood by reading the following embodiments, which are given by way of non-limiting example only, and with reference to the accompanying drawings, in which:

[0099] - Figure 1 A cross-sectional view perpendicular to the circumferential direction of the tire according to the present invention;

[0100] - Figure 2 for Figure 1 Detailed view of area II;

[0101] - Figure 3 A cross-sectional view of the reinforced product according to the present invention;

[0102] - Figure 4 This is a schematic diagram of a cross-section of the cord (50) according to a first embodiment of the present invention, perpendicular to the cord axis (assuming the cord is straight and stationary).

[0103] - Figure 5 A schematic diagram of a cross-section of the extracted cord (50') perpendicular to the cord axis (assuming the cord is straight and stationary) according to a first embodiment of the present invention; and - Figure 6 To and Figure 4 A similar diagram of the cord (60) according to a second embodiment of the present invention. Detailed Implementation

[0104] Embodiments of tires according to the present invention

[0105] Figure 1 and Figure 2 Reference frames X, Y, and Z are shown, corresponding to the tire's usual axial direction (X), radial direction (Y), and circumferential direction (Z), respectively.

[0106] The tire's "central circumferential plane" M is a plane perpendicular to the tire's axis of rotation and equidistant from the annular reinforcement structure of each bead.

[0107] Figure 1 and Figure 2 The tire according to the invention is shown, indicated by the overall designation 10.

[0108] Tire 10 is used on heavy vehicles in construction site types (such as "dump truck" types). Therefore, tire 10 has a size of 53 / 80R63.

[0109] Tire 10 has a crown 12, two sidewalls 16, and two beads 18. The crown 12 is reinforced by crown reinforcements 14, and each of the beads 18 is reinforced using a ring-shaped structure (bead threads 20 in this example). The crown reinforcements 14 are radially covered by a tread 22 and connected to the beads 18 via the sidewalls 16. A carcass reinforcement 24 is anchored in the two beads 18 (wound around the two bead threads 20 in this example) and includes a flange 26 arranged toward the outer side of the tire 20, which is shown here mounted on a wheel rim 28. The carcass reinforcement 24 is radially covered by the crown reinforcements 14.

[0110] The carcass reinforcement 24 includes at least one carcass ply 30, which is reinforced by radial carcass cords (not shown). The carcass cords are arranged substantially parallel to each other and extend from one bead 18 to the other, thus forming an angle between 80° and 90° with the central circumferential plane M (a plane perpendicular to the axis of rotation of the tire, located between the two bead 18s and passing through the center of the crown reinforcement 14).

[0111] The tire 10 also includes an airtight ply 32 (commonly referred to as a “liner”) made of an elastomer, which defines the radial inner surface 34 of the tire 10 and is designed to protect the carcass ply 30 from air diffusion from the interior space of the tire 10.

[0112] The tread reinforcement 14, radially extending from the outer to the inner side of the tire 10, includes: a protective reinforcement 36 radially disposed inside the tread 22; a working reinforcement 38 radially disposed inside the protective reinforcement 36; and an accessory reinforcement 40 radially disposed inside the working reinforcement 38. Therefore, the protective reinforcement 36 is radially inserted between the tread 22 and the working reinforcement 38. The working reinforcement 38 is radially positioned between the protective reinforcement 36 and the accessory reinforcement 40.

[0113] The protective reinforcement 36 includes a first protective ply 42 and a second protective ply 44, both of which include protective metal cords. The first ply 42 is radially disposed inside the second ply 44. Optionally, the protective metal cords form an angle of at least 10° with respect to the tire's circumferential direction Z, preferably between 10° and 35°, and more preferably between 15° and 30°.

[0114] The working reinforcement 38 includes a first working fabric layer 46 and a second working fabric layer 48, wherein the first fabric layer 46 is arranged radially inside the second fabric layer 48.

[0115] The additional reinforcement 40 (also known as a restraining unit) (one of its purposes is to partially absorb the mechanical stress of inflation) includes at least one cord 50, and the additional reinforcement forms an angle of at most 10° with respect to the circumferential direction Z of the tire 10, preferably in the range of 5° to 10°.

[0116] Embodiments of the enhanced product according to the present invention

[0117] Figure 3 The illustration depicts a reinforced product according to the invention, designated by the overall designation 100. The reinforced product 100 includes at least one cord 50 (in this example, multiple cords 50) embedded in a polymer matrix 102.

[0118] Figure 3 The polymer matrix 102 and the cord 50 are illustrated using reference frames X, Y, and Z, where direction Y is the radial direction, and directions X and Z are the axial and circumferential directions, respectively. Figure 3 In this process, the reinforcing product 100 includes a plurality of cords 50 arranged side by side in the main direction X, extending parallel to each other within the reinforcing product 100, and together embedded in the polymer matrix 102.

[0119] Here, polymer matrix 102 is an elastomeric matrix based on an elastomeric composition.

[0120] Cord according to the first embodiment of the present invention

[0121] Figure 4A cord 50 according to a first embodiment of the present invention is illustrated.

[0122] Reference Figure 5 After extraction from tire 10, each reinforcing element of the additional reinforcement is formed from the extracted cord 50' as described below. The cord 50' is obtained by embedding in a polymer matrix, in this example, in a polymer matrix that forms each working ply layer.

[0123] Both cord 50 and extracted cord 50' are made of metal and are of the multi-strand type with two multi-strand cylindrical layers. Therefore, it will be understood that cord 50 or 50' consists of two (no more and no less) multi-strand element layers.

[0124] The cord comprises at least 50% metal wires, preferably at least 60%, more preferably at least 70% metal wires, and the steel core of each metal wire preferably has a composition according to the standard NF EN 10020 of September 2000, with a carbon content C > 0.80%, preferably C ≥ 0.82%. The cord comprises at least 50% metal wires, preferably at least 60%, more preferably at least 70% metal wires, and the steel core of each metal wire preferably has a composition according to the standard NF EN 10020 of September 2000, with a carbon content C ≤ 1.20%, preferably C ≤ 1.10%. Here, the steel core of each metal wire has a composition according to the standard NF EN 10020 of September 2000, with a carbon content C = 0.86%.

[0125] Each wire has a breaking strength expressed as Rm, satisfying 2500 ≤ Rm ≤ 3100 MPa. The steel used in these wires is designated as SHT (“Super High Tensile”). Other wires can be used, such as lower grades like NT (“Normal Tensile”) or HT (“High Tensile”), or higher grades like UT (“Ultra Tensile”) or MT (“Mega Tensile”).

[0126] Method for manufacturing the cord according to the invention

[0127] An embodiment of a method for manufacturing multi-strand cord 50 will now be described.

[0128] Each of the aforementioned internal strands T1 is manufactured according to a known method, the method comprising the following steps, preferably performed sequentially:

[0129] - First, the first step is assembly, which involves cabling or twisting six outer threads F3 in the S direction with a twist pitch p3 around the inner thread F1 of the inner layer C1, thereby forming the outer layer C3 at the first assembly point.

[0130] - Preferably, the final twisting balancing step.

[0131] Each of the aforementioned outer strands T2 is manufactured according to a known method, the method comprising the following steps, preferably performed sequentially:

[0132] - First, the first step is assembly, which involves cabling or twisting six outer threads F3' in the S direction with a twist pitch p3' around the inner layer C1', thereby forming the outer layer C3' at the first assembly point;

[0133] - Preferably, the final twisting balancing step.

[0134] As is known to those skilled in the art, “twist balance” here means eliminating residual torque (or elastic recovery of twist) applied to each strand in the outer layer.

[0135] After this final twisting and balancing step, the manufacturing of the strands is complete. Before subsequent operations involving assembling the basic strands through cable bonding to obtain multi-strand cords, each strand is wound onto one or more receiving spools for storage.

[0136] In order to manufacture the multi-strand cord of the present invention, as is known to those skilled in the art, the method uses a cable-binding machine with specifications matching the assembled strands to bind the previously obtained strands together.

[0137] In the step of manufacturing the multi-strand element M1, K=3 inner strands T1 are assembled by cabling in the S direction with a twist P1, thereby forming the multi-strand element M1 of the inner layer CI at the first assembly point.

[0138] In the manufacturing step of the inner layer CI, X=3 multi-strand elements M1 are assembled by cabling in the Z direction with a twist pitch pi, thereby forming the inner layer CI at the first assembly point.

[0139] In the step of manufacturing the multi-strand element M2 of the outer CE, L=3 outer strands T2 are assembled by cabling in the S direction with a twist pitch P2, thereby forming the multi-strand element M2 of the outer CE at the first assembly point.

[0140] Then, in subsequent manufacturing steps, Y=9 outer multi-strand elements M2 are assembled by winding around the inner layer CI in the Z direction with a twist pitch pe, thereby forming an assembly of layers CI and CE. Alternatively, in the final assembly step, an outer winding wire F is wound around the previously obtained assembly in the S direction with a twist pitch pf.

[0141] The cords 50 are then bonded to a composite fabric by calendering. This composite fabric is formed from a known composition commonly used in the manufacture of crown reinforcements for radial tires. The known composition is based on natural rubber and carbon black as a reinforcing filler. In addition to the elastomer and reinforcing filler (carbon black), the composition essentially includes an antioxidant, stearic acid, a binder oil, cobalt naphthenate as a adhesion promoter, and a final vulcanization system (sulfur, accelerator, and ZnO).

[0142] The composite fabric reinforced by these cords has an elastomeric composition matrix formed by thin layers of two elastomeric compositions stacked on both sides of the cords, each having a thickness ranging from 1 mm to 4 mm. The calendering pitch (the distance between the cords laid in the elastomeric composition fabric) ranges from 4 mm to 8 mm.

[0143] Then, in the process of manufacturing the tire, these composite fabrics are used as working cord layers in the tread reinforcement, the steps of which are known to those skilled in the art.

[0144] Cord according to a second embodiment of the present invention

[0145] Figure 6 A cord 60 according to a second embodiment of the present invention is shown.

[0146] Unlike the first embodiment described above, the cord 60 according to the second embodiment satisfies Q1=Q1'=1; Q2=Q2'=5 and Q3=Q3'=10.

[0147] Table 1 below summarizes the characteristics of various cord types 50, 50', and 60.

[0148] To determine the breaking force of the cord, the cord was extracted, and then multi-strand elements M1 and M2 were extracted, with each multi-strand element subjected to a tensile test individually. The breaking forces of all multi-strand elements were summed and then multiplied by a 90% correction factor to account for performance losses during assembly.

[0149] [Table 1]

[0150]

[0151]

[0152] Table 2 below summarizes the characteristics of the prior art cords described in FR2969181B.

[0153] [Table 2]

[0154] (1+6) / Direction of the cord (1+6) / S The direction of the stock S Q1 3 Q3 8 p1(mm) 7.7 p2(mm) 15.4 Pi(mm) inf Pe(mm) 60 At% 2 As% 0.1 Fracture force (daN) 19 600

[0155] It has been found that, compared with cords in the prior art, the cords 50, 50' and 60 according to the present invention can obtain cords with sufficient elongation, sufficient metallic mass and sufficient breaking force, with the aim of obtaining cords that have a good trade-off between stiffness and flexibility; the flexibility is sufficient to reduce the stiffness of the crown block, but the breaking force is sufficient to withstand tensile stress loads.

[0156] The present invention is not limited to the embodiments described above.

Claims

1. A multi-strand cord (50) having two multi-strand layers, characterized in that, The cord (50) includes: - The inner layer CI of the cord, wherein the inner layer CI is composed of X=3 or 4 multi-strand elements M1, wherein the multi-strand element M1 includes K=2, 3 or 4 strands T1 spirally wound around axis B, each strand T1 having at least two layers (C1, C3), wherein the at least two layers (C1, C3) include: - The inner layer C1 is composed of Q1 internal metal wires F1 with a diameter of d1, and - The outer layer C3 consists of Q3 outer metal wires F3 with a diameter of d3 wound around the inner layer C1, and - Outer layer CE of the cord, wherein the outer layer CE is composed of Y>1 multi-strand elements M2 wound around the inner layer CI of the cord, each multi-strand element M2 including L=2, 3 or 4 strands T2 spirally wound around axis A', each strand T2 having at least two layers (C1', C3'), wherein the at least two layers (C1', C3') include: - The inner layer C1' is composed of internal metal wires F1' with diameter d1' of Q1', and - The outer layer C3' is composed of Q3' outer metal wires F3' with a diameter of d3' wound around the inner layer C1'. Both the inner multi-strand element M1 and the outer multi-strand element M2 are spirally wound around the main axis A, and The cord (50) has a structural elongation As that satisfies As ≥ 1.0%, which is determined by applying the 2014 standard ASTM D2969-04 to the cord (50) to obtain a force-elongation curve. The structural elongation As is equal to the elongation, expressed as a percentage, corresponding to the intersection of the tangent to the elastic portion of the force-elongation curve at a point along its elastic portion and the elongation axis of the force-elongation curve.

2. The cord (50) according to the preceding claim, wherein, As ≥ 1.5%.

3. A multi-strand cord (50') having two multi-strand layers, extracted from a polymer matrix (102), characterized in that, The extracted cord (50') includes: - The inner layer CI of the cord, wherein the inner layer CI is composed of X=3 or 4 multi-strand elements M1, wherein the multi-strand element M1 includes K=2, 3 or 4 strands T1 spirally wound around the main axis B, and each strand T1 has at least two layers (C1, C3), wherein the at least two layers (C1, C3) include: - The inner layer C1 is composed of Q1 internal metal wires F1 with a diameter of d1, and - The outer layer C3 consists of Q3 outer metal wires F3 with a diameter of d3 wound around the inner layer C1, and - Outer layer CE of the cord, wherein the outer layer CE is composed of Y>1 multi-strand elements M2 wound around the inner layer CI of the cord, each multi-strand element M2 including L=2, 3 or 4 strands T2 spirally wound around axis A', each strand T2 having at least two layers (C1', C3'), wherein the at least two layers (C1', C3') include: - The inner layer C1' is composed of internal metal wires F1' with diameter d1' of Q1', and - The outer layer C3' is composed of Q3' outer metal wires F3' with a diameter of d3' wound around the inner layer C1'. Both the inner multi-strand element M1 and the outer multi-strand element M2 are spirally wound around the main axis A, and The cord (50') has a structural elongation As', which satisfies As' ≥ 0.3%. The structural elongation As' is determined by applying the 2014 standard ASTM D2969-04 to the cord (50') to obtain a force-elongation curve. The structural elongation As' is equal to the elongation, expressed as a percentage, corresponding to the intersection of the tangent to the elastic portion of the force-elongation curve at a point along its elastic portion and the elongation axis of the force-elongation curve.

4. The cord (50; 50') according to any one of the preceding claims, wherein, The diameter D of the cord ranges from 4 mm to 10 mm.

5. The cord (50; 50') according to claim 1 or 3, wherein, The diameters of the independent metal wires (F1; F3; F1'; F3') range from 0.15 mm to 0.50 mm.

6. The cord (50, 50') according to claim 1 or 3, wherein, Y equals 5, 6, 7, 8, 9, or 10.

7. The cord (50, 50') according to claim 1 or 3, wherein, K = 2, 3 or 4.

8. The cord (50, 50') according to claim 1 or 3, wherein L = 2, 3 or 4.

9. The cord (50; 50') according to claim 1 or 3, wherein, Each line T1 of the inner CI layer has two layers (C1, C3).

10. The cord (50; 50') according to claim 1 or 3, wherein, Each strand T2 of the outer CE layer has two layers (C1', C3').

11. The cord (60) according to claim 1 or 3, wherein, Each strand T1 of the inner CI layer has three layers (C1, C2, C3) and includes: The intermediate layer C2 is composed of Q2 intermediate metal wires F2 wound around the inner layer C1, and The outer layer C3 is composed of Q3 outer metal wires F3 wound around the middle layer C2.

12. The cord (60) according to claim 1 or 3, wherein, Each strand T2 of the outer CE layer has three layers (C1', C2', C3') and includes: The intermediate layer C2' is composed of Q2' intermediate metal wires F2' wound around the inner layer C1', and The outer layer C3' is composed of Q3' outer metal wires F3' that are wound around the middle layer C2'.

13. The cord (50; 50') according to claim 1 or 3, wherein each strand (T1; T2) of the inner and outer layers (CI; CE) has two layers (C1, C3, C1', C3').

14. A cord reinforcement product (100), characterized in that, The cord reinforcement product (100) comprises a polymer matrix (102) and at least one cord (50') according to claim 3.

15. A tire (10), characterized in that, The tire (10) includes at least one cord (50') according to claim 3, or a cord reinforcement product according to claim 14.

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