Multi-core cable with two multi-core layers

Description

[0001] The invention relates to cables and a pneumatic system comprising these cables.

[0002] Cables with a 1xN structure, as described in document WO2016 / 131862, are known from the prior art. These cables comprise a single layer of N=4 strands wound helically with a pitch p3=20 mm. Each strand comprises, on the one hand, an inner layer of 3 inner wires wound helically with a pitch p1=6.7 mm and, on the other hand, an outer layer of 8 outer wires wound helically around the inner layer with a pitch p2=10 mm. The structural elongation of the cable is 2.8%, the cable diameter is 3.8 mm, the linear density is 36.4 g / m, and the endurance criterion is 3635 N x m / g.

[0003] These cables have the advantage of possessing a relatively high structural elongation, but the endurance criterion could be improved to increase the endurance of the reinforcements while reducing shear stress in the polymer matrix.

[0004] A two-layer multi-strand cable is described in document WO2013 / 174896A1.

[0005] Today, a need is emerging for the development of new cables for applications in apex plies, particularly zero-degree plies such as apex plies for shrink-fitting. These plies are designed to shrink-fit the tire, thereby reducing shear stress at the plies' edges and decreasing the rigidity of the apex block at the center against stresses.

[0006] The invention aims at a cable which has sufficient flexibility and structural elongation to allow the shaping of the tire and reduce the rigidity of the top block, with an improved endurance criterion to withstand cyclic tensile stresses.

[0007] To this end, the invention relates to a multi-strand cable with two layers of multi-strands, in which the cable comprises: an inner layer of the cable consisting of X=3 or 4 multi-strands comprising K=2, 3 or 4 strands wound helically around an axis, each strand having at least two layers comprising: an inner layer consisting of Q1 internal metal wire(s) of diameter d1, and an outer layer consisting of Q3 external metal wires of diameter d3 wound around the inner layer;and an outer layer of the cable consisting of Y>1 multi-strands wound around the inner layer of the cable, each multi-strand comprising L=2, 3 or 4 strands wound helically around an axis, each strand being at least two-layered comprising: an inner layer consisting of Q1' internal metallic wire(s) of diameter d1', and an outer layer consisting of Q3' external metallic wires of diameter d3' wound around the inner layer, with the multi-strands of the inner and outer layers being wound helically around a main axis, the cable has an endurance criterion V1 = Δ; σ bending / (M / D) < 3000 N xm / g; with - Δ σ flexion = Macier × Max di ; di ′ 2 in MPa.mm is the maximum bending stress per unit curvature seen by the inner and outer wires of the inner and outer strands, with di, di' being the diameter of the metal wires and i, i' ranging from 1 to 3, and with Macier = 200,000 MPa; M is the linear mass in g / m of the cable, M being the sum of the metal cross-sections of all the metal wires of the cable multiplied by the density of steel Ro, with Ro = 7.79 g / cm³; D is the diameter of the cable (50) in mm; and the cable has a structural elongation As such that As ≥ 1.0%, the structural elongation As being determined according to ASTM D2969-04 of 2014 to the cable so as to obtain a force-elongation curve, the structural elongation As being equal to the elongation, in %, corresponding to the intersection between the tangent to the elastic part of the force-elongation curve at any point of its elastic part and the axis of elongations of the force-elongation curve.

[0008] Thanks to this multi-strand cable configuration with two layers of multi-strand, the cable according to the invention makes it possible to obtain a cable with sufficient metal mass while keeping thin wires allowing to achieve increased endurance performance and thus improve the compromise between shear in the polymer matrix and the endurance of the cable and improve the cleavage performance.

[0009] On the one hand, thanks to its relatively low endurance criterion, the cable according to the invention makes it possible to reduce stress levels in the cable subjected to tensile stress and thus extend the tire's lifespan. Indeed, the inventors of the invention discovered that the primary determining criterion for improving the endurance performance of a cable in a corrosive environment was not solely the breaking strength, as is widely taught in the prior art, but the endurance criterion represented in this application by an indicator equal to a combination of bending stress, cable diameter, and cable metal mass: The bending stress per unit curvature seen by the inner and outer threads of the strands: Δ σ bendingbeing the maximum bending stress per unit curvature seen by the metal wires, on this type of cable, the inventors of the invention discovered that the tension stress on the cable simultaneously generated tensile and bending stresses at the scale of the individual wires; thus, reducing this bending stress criterion is therefore positive for the cable's tensile endurance performance by relieving the portion due to bending; the metal mass of the cable relative to the cable diameter, which, by increasing it, mainly relieves the tensile stresses of the cable: with M being the linear mass of the cable in g / m, which can be defined in a simplified way as the sum of the metal cross-sections of all the individual wires of the cable multiplied by the density of steel Ro = 7.79 g / cm3, with the sum of the cross-sections being determined by image processing on a cross-section of the cable and;with the cable diameter D is measured on the cable according to ASTM D2969-04. ;

[0010] By definition, the diameter of the cable is the diameter of the smallest circle in which the cable is circumscribed without the ferrule.

[0011] Structural elongation (As), a quantity well known to those skilled in the art, is determined, for example, by applying the ASTM D2969-04 standard (2014) to a tested cable to obtain a force-elongation curve. The As on the resulting curve is the elongation, expressed as a percentage, corresponding to the intersection between the tangent to the elastic portion of the force-elongation curve and the elongation axis of the force-elongation curve. As a reminder, a force-elongation curve comprises, as we move towards increasing elongations, a structural portion, an elastic portion, and a plastic portion. The structural portion corresponds to the structural elongation of the cable resulting from the coming together of the various strands and wires constituting the cable. The elastic portion corresponds to the elastic elongation resulting from the cable's construction, particularly the angles of the different layers and the diameters of the wires.The plastic part corresponds to the plastic elongation resulting from the plasticity (irreversible deformation beyond the elastic limit) of the metal wires.

[0012] In the invention, the cable comprises two layers of multi-strand, that is to say, it comprises an assembly consisting of one layer of Y>1 multi-strand wound around a single layer of multi-strand, no more and no less, that is to say, the assembly has two layers of multi-strand, not one, not three, but only two.

[0013] In the invention, the multi-strand is a single-layer strand, that is to say, it comprises an assembly consisting of one strand layer, no more and no less, that is to say, the assembly has one strand layer, not zero, not two, but only one.

[0014] In one embodiment, the internal multi-strands of the cable are surrounded by a polymeric composition and then by the outer layer.

[0015] Advantageously, each strand has cylindrical layers.

[0016] Advantageously, each strand in the multi-strand is double-layered, meaning it comprises an assembly of two layers of metal wire, no more and no less; that is, the assembly has two layers of metal wire, not one, not three, but only two. The outer layer of each strand is wound around the inner layer of that strand, in contact with the inner layer of that strand.

[0017] Advantageously, each strand of the inner layer and each strand of the outer layer are cylindrical. Recall that such cylindrical layers are obtained when the different layers of strands are wound at different pitches and / or when the winding directions of these layers differ from one layer to another. A cylindrical strand is highly penetrable, unlike a tightly packed strand in which the pitches of all layers are equal and the winding directions of all layers are identical, which exhibits much lower penetrability.

[0018] Advantageously, each strand of the inner layer and each strand of the outer layer are desaturated, i.e. there is a space between the outer layer threads, allowing the elastomeric composition to impregnate each strand.

[0019] Preferably, the strands do not undergo pre-formation.

[0020] Advantageously, the cable as defined above is bare, that is to say, devoid of any polymeric composition, in particular the cable is devoid of any elastomeric composition.

[0021] A metal wire is defined as a metallic monofilament comprising a core made primarily (i.e., more than 50% of its mass) or entirely (100% of its mass) of a metallic material, for example, carbon steel. The metal wire may advantageously include a metallic coating covering the core, the metallic coating being selected from zinc, copper, tin, and alloys of these metals, for example, brass. Each wire is preferably made of pearlitic or ferritic-pearlitic carbon steel.

[0022] The values ​​of the characteristics described in this application for the bare cable are measured on or determined from the cables directly after manufacture, i.e. before any embedding step in a polymeric matrix, in particular an elastomeric one.

[0023] In this application, any range of values ​​designated by the expression "between a and b" represents the range of values ​​from more than a to less than b (i.e., excluding bounds a and b) while any range of values ​​designated by the expression "from a to b" means the range of values ​​from the bound "a" to the bound "b", i.e., including the strict bounds "a" and "b".

[0024] Advantageously, As ≥ 1.5% and preferably As ≥ 2.0%.

[0025] The invention also relates to a cable extracted from a polymer matrix, in which the extracted cable comprises: an inner layer of the cable consisting of X=3 or 4 multi-strands comprising K=2, 3 or 4 strands wound helically around an axis, each strand having at least two layers comprising: an inner layer consisting of Q1 internal metallic wire(s) of diameter d1, and an outer layer consisting of Q3 external metallic wires of diameter d3 wound around the inner layer;and an outer layer of the cable consisting of Y>1 multi-strands wound around the inner layer of the cable, each multi-strand comprising L=2, 3 or 4 strands wound helically around an axis, each strand being at least two-layered comprising: an inner layer consisting of Q1' internal metallic wire(s) of diameter d1', and an outer layer consisting of Q3' external metallic wires of diameter d3' wound around the inner layer, with the multi-strands of the inner and outer layers being wound helically around a main axis, the extracted cable (50') has an endurance criterion V1 = Δ; σ bending / (M / D) < 3000 N xm / g; with Δ σ flexion = Macier × Max di ; di ′ 2 in MPa.mm is the maximum bending stress per unit curvature seen by the inner and outer wires of the inner and outer strands, with di, di' being the diameter of the metal wires and i, i' ranging from 1 to 3, and with Macier = 200,000 MPa; M is the linear mass in g / m of the cable, M being the sum of the metal cross-sections of all the metal wires of the cable multiplied by the density of steel Ro, with Ro = 7.79 g / cm³; D is the diameter of the cable in mm; and the cable has a structural elongation As' such that As' ≥ 0.3%, the structural elongation As' being determined according to ASTM D2969-04 of 2014 to the cable so as to obtain a force-elongation curve, the structural elongation As' being equal to the elongation, in %, corresponding to the intersection between the tangent to the elastic part of the force-elongation curve at any point of its elastic part and the axis of elongations of the force-elongation curve.

[0026] Preferably, the polymer matrix is ​​an elastomeric matrix.

[0027] The polymeric matrix, preferably elastomeric, is based on a polymeric composition, preferably elastomeric.

[0028] A polymer matrix is ​​defined as a matrix comprising at least one polymer. The polymer matrix is ​​thus based on a polymer composition.

[0029] An elastomeric matrix is ​​defined as a matrix comprising at least one elastomer. The preferred elastomeric matrix is ​​thus based on the elastomeric composition.

[0030] The expression "based on" means that the composition includes the mixture and / or the in situ reaction product of the different constituents used, some of these constituents being able to react and / or being intended to react with each other, at least partially, during the different phases of manufacturing the composition; the composition can thus be in a totally or partially crosslinked state or in a non-crosslinked state.

[0031] By polymeric composition, we mean that the composition comprises at least one polymer. Preferably, such a polymer can be a thermoplastic, for example a polyester or a polyamide, a thermosetting polymer, an elastomer, for example natural rubber, a thermoplastic elastomer or a mixture of these polymers.

[0032] An elastomeric composition is defined as a composition comprising at least one elastomer and at least one other component. Preferably, a composition comprising at least one elastomer and at least one other component includes an elastomer, a crosslinking system, and a filler. Suitable compositions for these webs are conventional compositions for calendering reinforcing wire elements and include a diene elastomer, for example, natural rubber; a reinforcing filler, for example, carbon black and / or silica; a crosslinking system, for example, a vulcanizing system, preferably comprising sulfur, stearic acid, and zinc oxide; and optionally, a vulcanization accelerator and / or retarder and / or various additives. Adhesion between the metal wires and the matrix in which they are embedded is ensured, for example, by a metallic coating, such as a layer of brass.

[0033] The values ​​of the characteristics described in this application for the extracted cable are measured on, or determined from, cables extracted from a polymer matrix, particularly an elastomeric one, for example, from a tire. Thus, for example, on a tire, the outer layer of material is removed radially from the outside of the cable to be extracted so that the cable is exposed radially from the polymer matrix. This removal can be done by peeling with pliers and knives or by planing. Then, the end of the cable to be extracted is exposed using a knife. Finally, the cable is pulled from the matrix at a relatively shallow angle to avoid damaging it.The extracted cables are then carefully cleaned, for example with a knife, so as to detach the remains of polymer matrix attached locally to the cable and taking care not to degrade the surface of the metal wires.

[0034] To determine the linear mass of the extracted cable, a cross-section of the cable is performed in the elastomeric matrix, determining the steel surface area by image processing and multiplying by the density of the steel.

[0035] To measure the linear mass of the extracted cable, one can also, following the operation described above, weigh one meter of cleaned cable to determine the average linear mass of cleaned cable over 10 measurements.

[0036] The advantageous characteristics described below apply equally to bare cable and to cable extracted from a polymer matrix.

[0037] Advantageously, criterion V1 is greater than or equal to 1000 N xm / g, preferably greater than or equal to 1500 N xm / g.

[0038] Advantageously, criterion V1 is less than or equal to 2500 N xm / g.

[0039] Advantageously, M ranges from 30 to 180 g / m, preferably from 50 to 130 g / m.

[0040] Preferably, the cable has a cable diameter such that the diameter D of the cable goes from 4 mm to 9.5 mm, preferably from 5 mm to 7.5 mm.

[0041] By definition, the diameter of a strand is the diameter of the smallest circle in which the strand is circumscribed.

[0042] Preferably, the diameters of the metal wires go independently of each other, from 0.15 mm to 0.50 mm, preferably from 0.18 mm to 0.35 mm and more preferably from 0.20 mm to 0.30 mm.

[0043] Preferably, the wires in the same layer of a predetermined strand all have substantially the same diameter. Advantageously, the outer strands all have substantially the same diameter. By "substantially the same diameter," we mean that the wires or strands have the same diameter within industry tolerances.

[0044] Advantageously, Y is equal to 8, 9, 10 or 11, preferably Y=9 or 10 and more preferably Y=9.

[0045] In a first embodiment, each strand of the inner layer is two-layered.

[0046] Advantageously, each strand of the outer layer is two-layered.

[0047] Advantageously, in this first embodiment, in a preferred variant, each strand of the inner and outer layers is two-layered.

[0048] In a second embodiment, each strand of the inner layer has three layers and comprises: an intermediate layer consisting of Q2 intermediate metal wires wound around the inner layer, and an outer layer consisting of Q3 external metal wires wound around the intermediate layer.

[0049] Advantageously, each strand of the outer layer is three-stranded and comprises: an intermediate layer consisting of Q2' intermediate metal wires wound around the inner layer, and an outer layer consisting of Q3' external metal wires wound around the intermediate layer.

[0050] Advantageously, in this second embodiment, in a preferred variant, each strand of the inner and outer layers has three layers.

[0051] Advantageously, each strand is of the non-gummed in situ type. By non-gummed in situ, we mean that before the strands are assembled together, each strand consists of the threads of the different layers and is devoid of polymeric composition, in particular elastomeric composition. Strands of the internal multi-strands of the cable according to the invention

[0052] Advantageously, Q1=1, 2, 3 or 4, preferably Q1=1, 2 or 3 and more preferably Q1=1 or 3.

[0053] Advantageously, Q3=5, 6, 7, 8, 9 or 10, preferably Q3=6, 7, 8 or 9 and more preferably Q3 =6 or 9.

[0054] In one embodiment, Q1=1.

[0055] Advantageously, Q3 = 5, 6 or 7 and preferably Q3 = 6.

[0056] In another preferred embodiment, Q1>1, preferably Q1=2, 3 or 4.

[0057] Advantageously, Q3 = 7, 8, 9 or 10 and preferably Q3 = 7, 8 or 9.

[0058] In a first variant, Q1=2 and Q3=7 or 8, preferably Q1=2, Q3=7.

[0059] In a second variant, Q1=3 and Q3=7, 8 or 9, preferably Q1=3, Q3=8.

[0060] In a third variant, Q1=4 and Q3=7, 8, 9 or 10, preferably Q1=4, Q3=9. Strands of the external multi-strands of the cable according to the invention

[0061] Advantageously, Q1'=1, 2, 3 or 4, preferably Q1'=1, 2 or 3 and more preferably Q1'=1 or 3.

[0062] Advantageously, Q3'=5, 6, 7, 8, 9 or 10, preferably Q3'=6, 7, 8 or 9 and more preferably Q3' = 6 or 9.

[0063] In one embodiment, Q1'=1.

[0064] Advantageously, Q3' = 5, 6 or 7 and preferably Q3' = 6.

[0065] In another preferred embodiment, Q1'>1, preferably Q1'=2, 3 or 4.

[0066] Advantageously, Q3'=7, 8, 9 or 10 and preferably Q3'=7, 8 or 9.

[0067] In a first variant, Q1'=2 and Q3'=7 or 8, preferably Q1'=2, Q3'=7.

[0068] In a second variant, Q1'=3 and Q3'=7, 8 or 9, preferably Q1'=3, Q3'=8.

[0069] In a third variant, Q1'=4 and Q3'=7, 8, 9 or 10, preferably Q1'=4, Q3'=9.

[0070] Advantageously, Q1=1 and Q3=6, Q1'= 1 and Q3'=6. REINFORCED PRODUCT ACCORDING TO THE INVENTION

[0071] Another object of the invention is a reinforced product comprising a polymer matrix and at least one cable or extracted cable as defined above.

[0072] Advantageously, the reinforced product comprises one or more cables according to the invention embedded in the polymer matrix, and in the case of several cables, the cables are arranged side by side along a main direction. PNEUMATIC ACCORDING TO THE INVENTION

[0073] Another object of the invention is a tire comprising at least one extracted cable or a reinforced product as defined above.

[0074] By pneumatic including an extracted cable, we mean a pneumatic including a cable whose properties, measured after extraction of the pneumatic, are those of the extracted cable, this cable being, prior to its incorporation into the pneumatic, a cable such as the cable described previously.

[0075] Preferably, the tire comprises a carcass reinforcement anchored in two beads and radially surmounted by a crown reinforcement itself surmounted by a tread, the crown reinforcement being joined to said beads by two sidewalls and comprising at least one cord as defined above.

[0076] In a preferred embodiment, the top reinforcement comprises a protective reinforcement and a working reinforcement and a clamping reinforcement comprising at least one cable as defined above, the protective reinforcement being radially intercalated between the tread and the working reinforcement and the clamping reinforcement being preferably intercalated between the two layers of working reinforcement.

[0077] The cable is particularly intended for industrial vehicles chosen from among heavy vehicles such as "Heavy Goods Vehicles" - i.e., metro, bus, road transport vehicles (trucks, tractors, trailers), off-road vehicles -, agricultural or civil engineering vehicles, other transport or handling vehicles.

[0078] Preferably, the tire is for construction equipment type vehicles. Thus, the tire has a dimension in which the diameter, in inches, of the rim seat on which the tire is intended to be mounted is greater than or equal to 40 inches.

[0079] The invention also relates to a rubber article comprising an assembly according to the invention, or an impregnated assembly according to the invention. By rubber article, we mean any type of rubber article such as a balloon, a non-pneumatic object such as a non-pneumatic bandage, a conveyor belt, or a track. The invention will be better understood upon reading the following examples, given solely by way of non-limiting illustration and made with reference to the drawings in which: there figure 1 is a cross-sectional view perpendicular to the circumferential direction of a tire according to the invention; the figure 2is a detailed view of zone II of the figure 1 ; there figure 3 is a cross-sectional view of a reinforced product according to the invention; the figure 4 is a schematic cross-sectional view perpendicular to the cable axis (assumed to be straight and at rest) of a cable (50) according to a first embodiment of the invention; the figure 5 is a schematic cross-sectional view perpendicular to the cable axis (assumed to be straight and at rest) of an extracted cable (50') according to a first embodiment of the invention; and the figure 6 is a view analogous to that of the figure 4 of a cable (60) according to a second embodiment of the invention. EXAMPLE OF A PNEUMATIC TIRE ACCORDING TO THE INVENTION

[0080] In the Figures 1 And 2 , we have represented a coordinate system X, Y, Z corresponding to the usual orientations respectively axial (X), radial (Y) and circumferential (Z) of a tire.

[0081] The "circumferential median plane" M of the tire is the plane that is normal to the axis of rotation of the tire and that is equidistant from the annular reinforcement structures of each bead.

[0082] We have represented on the Figures 1 And 2 a tire according to the invention and designated by the general reference 10.

[0083] Tire 10 is for heavy-duty vehicles such as construction equipment, for example, dump trucks. Tire 10 has a size of 53 / 80R63.

[0084] The tire 10 comprises a crown 12 reinforced by a crown reinforcement 14, two sidewalls 16, and two bead 18, each bead 18 being reinforced with an annular structure, here a bead 20. The crown reinforcement 14 is radially surmounted by a tread 22 and joined to the bead 18 by the sidewalls 16. A carcass reinforcement 24 is anchored in the two bead 18 and is here wrapped around the two beads 20. It includes a gusset 26 facing outwards from the tire 20, which is shown here mounted on a rim 28. The carcass reinforcement 24 is radially surmounted by the crown reinforcement 14.

[0085] The carcass reinforcement 24 comprises at least one carcass layer 30 reinforced by radial carcass cables (not shown). The carcass cables are arranged substantially parallel to each other and extend from one bead 18 to the other so as to form an angle between 80° and 90° with the median circumferential plane M (plane perpendicular to the axis of rotation of the tire which is located midway between the two bead 18 and passes through the middle of the apex reinforcement 14).

[0086] The tire 10 also includes a sealing layer 32 made of an elastomer (commonly called inner rubber) which defines the radially inner face 34 of the tire 10 and which is intended to protect the carcass layer 30 from air diffusion from the space inside the tire 10.

[0087] The crown reinforcement 14 comprises, radially from the outside to the inside of the tire 10, a protective reinforcement 36 arranged radially inside the tread 22, a working reinforcement 38 arranged radially inside the protective reinforcement 36 and a reinforcing reinforcement 40 radially interposed between the two plies 48, 46 of the working reinforcement 38. The protective reinforcement 36 is thus radially interposed between the tread 22 and the working reinforcement 38.

[0088] The protective frame 36 comprises first and second protective layers 42, 44 comprising protective metal cables, the first layer 42 being arranged radially inside the second layer 44. Optionally, the protective metal cables make an angle of at least 10°, preferably from 10° to 35° and preferably from 15° to 35° with the circumferential direction Z of the tire.

[0089] The working frame 38 comprises first and second working layers 46, 48, the first layer 46 being arranged radially inside the second layer 48.

[0090] The shrink-fit armature 40, also called the limiting block, includes at least one cable 50 making an angle of no more than 10°, preferably from 0° to 5° with the circumferential direction Z of the tire 10. EXAMPLE OF A REINFORCED PRODUCT ACCORDING TO THE INVENTION

[0091] We have represented on the figure 3 a reinforced product according to the invention and designated by the general reference 100. The reinforced product 100 comprises at least one cable 50, in this case several cables 50, embedded in the polymeric matrix 102.

[0092] On the figure 3 The polymer matrix 102 and the cables 50 were represented in an X, Y, Z coordinate system in which the Y direction is the radial direction and the X and Z directions are the axial and circumferential directions. On the figure 3, the reinforced product 100 comprises several cables 50 arranged side by side along the main direction X and extending parallel to each other within the reinforced product 100 and collectively embedded in the polymer matrix 102. Here, the polymer matrix 102 is an elastomeric matrix based on an elastomeric composition. CABLE ACCORDING TO A FIRST EMBODIMENT OF THE INVENTION

[0093] We have represented on the figure 4 cable 50 according to a first embodiment of the invention.

[0094] With reference to the figure 5 Each marginal reinforcement element is formed, after extraction of the tire 10, by an extracted cable 50' as described below. The cable 50 is obtained by embedding it in a polymer matrix, in this case in a polymer matrix forming each polymer matrix of each working layer.

[0095] The 50 cable and the 50' extracted cable are metallic and of the multi-strand type with two cylindrical layers. Thus, it is understood that the layers of multi-strands constituting the 50 or 50' cable are two in number, no more, no less.

[0096] At least 50% of the metal wires, preferably at least 60%, more preferably at least 70% of the metal wires, and most preferably each metal wire of the cable comprises a steel core having a composition conforming to standard NF EN 10020 of September 2000 and a carbon content C > 0.80% and preferably C ≥ 0.82%, and at least 50% of the metal wires, preferably at least 60%, more preferably at least 70% of the metal wires, and most preferably each metal wire of the cable comprises a steel core having a composition conforming to standard NF EN 10020 of September 2000 and a carbon content C ≤ 1.20% and preferably C ≤ 1.10%. Here, each metal wire comprises a steel core having a composition conforming to standard NF EN 10020 of September 2000 and a carbon content C = 0.86%.

[0097] Each wire has a tensile strength, denoted Rm, such that 2500 ≤ Rm ≤ 3100 MPa. The steel used for these wires is said to be SHT grade ("Super High Tensile"). Other wires can be used, for example, lower grade wires, such as NT grade ("Normal Tensile") or HT grade ("High Tensile"), as well as higher grade wires, such as UT grade ("Ultra Tensile") or MT grade ("Mega Tensile"). METHOD FOR MANUFACTURING THE CABLE ACCORDING TO THE INVENTION

[0098] We will now describe an example of a manufacturing process for 50-strand multi-strand cable.

[0099] Each internal strand T1 described above is manufactured according to known processes comprising the following steps, preferably carried out in-line and continuously: First, a first assembly step by wiring or twisting the 6 external wires F3 around the internal wire F1 of the internal layer C1 at a pitch of p3 and in the direction S to form the external layer C3 at a first assembly point; preferably a final balancing step of the twists. Each previously described outer strand T2 is manufactured using known processes comprising the following steps, preferably carried out in-line and continuously: First, a first assembly step by wiring or twisting the 6 external wires F3' around the internal wire F1' of the internal layer C1' at the pitch p3' and in the S direction to form the external layer C3' at a first assembly point; preferably a final balancing step of the twists.

[0100] By "torsional balancing", we mean here, in a way well known to those skilled in the art, the cancellation of residual torsional couples (or elastic torsional return) acting on each wire of the strand, in the outer layer.

[0101] After this final twist balancing stage, the strand manufacturing process is complete. Each strand is wound onto one or more receiving reels for storage, before the subsequent assembly operation by re-twisting the elementary strands to obtain the multi-strand cable.

[0102] For the manufacture of the multi-strands of the invention, the process is carried out in a manner well known to those skilled in the art, by twisting the strands previously obtained, using twisting machines sized to assemble strands.

[0103] In a manufacturing step of a multi-strand M1, the K=3 internal strands T1 are assembled by wiring at the pitch P1 and in the direction S to form a multi-strand M1 of the internal layer CI at a first assembly point.

[0104] In a manufacturing step of the inner layer CI, the X=3 multi-strands M1 are assembled by wiring at a pitch of pi and in the Z direction to form the inner layer CI at a first assembly point.

[0105] In a manufacturing step of the M2 multi-strands of the outer CE layer, the L=3 outer strands T2 are assembled by wiring at the P2 pitch and in the S direction to form the M2 multi-strands of the outer CE layer at a first assembly point.

[0106] Then, in a subsequent manufacturing step, the Y=9 external multi-strands M2 are assembled by wiring around the inner layer CI at a pitch pe and in the Z direction to form the CI and CE layer assembly. Optionally, in a final assembly step, the F ring is wound at a pitch pf in the S direction around the assembly previously obtained.

[0107] The 50 cable is then incorporated by calendering into composite fabrics made of a known composition based on natural rubber and carbon black as a reinforcing filler, conventionally used for manufacturing the crown reinforcements of radial tires. This composition essentially comprises, in addition to the elastomer and the reinforcing filler (carbon black), an antioxidant, stearic acid, an expanding oil, cobalt naphthenate as an adhesion promoter, and finally a vulcanization system (sulfur, accelerator, ZnO).

[0108] The composite fabrics reinforced by these cables have an elastomeric matrix composed of two thin layers of elastomeric material superimposed on either side of the cables, with thicknesses ranging from 1 mm to 4 mm respectively. The calendering pitch (the spacing of the cables within the elastomeric fabric) ranges from 4 mm to 8 mm.

[0109] These composite fabrics are then used as a working layer in the crown reinforcement during the tire manufacturing process, the steps of which are otherwise known to those skilled in the art. CABLE ACCORDING TO A SECOND EMBODIMENT OF THE INVENTION

[0110] We have represented on the figure 6 a cable 60 according to a second embodiment of the invention.

[0111] Unlike the first embodiment described above, cable 60 according to the second embodiment is such that Q1=Q1'=1; Q2=Q2'=5 and Q3=Q3'=10.

[0112] Table 1 below summarizes the characteristics for the different 50, 50' and 60 cables.

[0113] Table 2 below summarizes the characteristics for the cable of the state of the art described in document WO2016 / 131862. [Table 2] Cable EDT K / sens cable 4 / S strand direction S Q1 3 Q3 8 p1 (mm) 6,7 p2 (mm) 10 Pe (mm) 20 At % 6,0 As % 2,8 D (mm) 3,80 M (g / m) 36,4 M / D (kg.m 2< ) 9,5 Board bending ( MPa. mm ) 34800 V1(N xm / g) 3635

[0114] It is observed that the 50, 50' and 60 cables according to the invention make it possible to obtain a cable exhibiting sufficient flexibility and structural elongation to allow the shaping of the tire and reduce the rigidity of the top block, with an improved endurance criterion to withstand cyclic tensile stresses compared to the cable of the prior art.

[0115] The invention is not limited to the embodiments described above.

Claims

1. Multi-strand cord (50) with two multi-strand layers, characterized in that the cord (50) comprises: - a cord internal layer (CI) made up of X=3 or 4 multi-strand elements (M1) comprising K=2, 3 or 4 strands (T1) wound in a helix about an axis (B), each strand (T1) having at least two layers (C1, C3) comprising: an internal layer (C1) made up of Q1 internal metal thread(s) (F1) of diameter d1, and - an external layer (C3) made up of Q3 external metal threads (F3) of diameter d3 wound around the internal layer (C1), and - a cord external layer (CE) made up of Y>1 multi-strand elements (M2) wound around the internal layer (CI) of the cord, each multi-strand element (M2) comprising L=2, 3 or 4 strands (T2) wound in a helix about an axis (A'), each strand (T2) having at least two layers (C1', C3') comprising: - an internal layer (C1') made up of Q1' internal metal thread(s) (F1') of diameter d1', and - an external layer (C3') made up of Q3' external metal threads (F3') of diameter d3' wound around the internal layer (C1'), the multi-strand elements of the internal layer (M1) and of the external layer (M2) being wound in a helix about a main axis (A), the cord (50) having an endurance criterion V1 = Δσbending / (M / D) < 3000 N x m / g; where - Δ σ bending = Msteel × Max di ; di ′ 2 in MPa.mm is the maximum bending stress per unit curvature experienced by the internal and external threads of the internal and external strands, where di and di' are the diameter of the metal threads and i and i' range from 1 to 3 and where Msteel=200 000 MPa; - M is the linear mass of the cord (50) in g / m, M being the sum of the cross sections of metal of all the metal threads in the cord multiplied by the density of steel, Rho, where Rho=7.79 g / cm3; - D is the diameter of the cord (50) in mm; and the cord (50) has a structural elongation As such that As ≥ 1.0%, the structural elongation As being determined by applying the standard ASTM D2969-04 of 2014 to the cord (50) so as to obtain a force-elongation curve, the structural elongation As being equal to the elongation, in %, corresponding to the intersection between the tangent to the elastic portion of the force-elongation curve at some point along the elastic portion thereof and the elongation axis of the force-elongation curve.

2. Cord (50) according to the preceding claim, wherein As ≥ 1.5% and preferably As ≥ 2.0%.

3. Multi-strand cord (50') with two multi-strand layers, extracted from a polymer matrix (102), characterized in that the extracted cord (50') comprises: - a cord internal layer (CI) made up of X=3 or 4 multi-strand elements (M1) comprising K=2, 3 or 4 strands (T1) wound in a helix about an axis (B), each strand (T1) having at least two layers (C1, C3) comprising: an internal layer (C1) made up of Q1 internal metal thread(s) (F1) of diameter d1, and - an external layer (C3) made up of Q3 external metal threads (F3) of diameter d3 wound around the internal layer (C1), and - a cord external layer (CE) made up of Y > 1 multi-strand elements (M2) wound around the internal layer (CI) of the cord, each multi-strand element (M2) comprising L=2, 3 or 4 strands (T2) wound in a helix about an axis (A'), each strand (T2) having at least two layers (C1', C3') comprising: - an internal layer (C1') made up of Q1' internal metal thread(s) (F1') of diameter d1', and - an external layer (C3') made up of Q3' external metal threads (F3') of diameter d3' wound around the internal layer (C1'), the multi-strand elements of the internal layer (M1) and of the external layer (M2) being wound in a helix about a main axis (A), the extracted cord (50') having an endurance criterion V1 = Δσbending / (M / D) < 3000 N x m / g; where - Δ σ bending = Msteel × Max di ; di ′ 2 in MPa.mm is the maximum bending stress per unit curvature experienced by the internal and external threads of the internal and external strands, where di and di' are the diameter of the metal threads and i and i' range from 1 to 3 and where Msteel=200 000 MPa; - M is the linear mass of the cord (50') in g / m, M being the sum of the cross sections of metal of all the metal threads in the cord multiplied by the density of steel, Rho, where Rho=7.79 g / cm3; - D is the diameter of the cord (50') in mm; and the cord (50') has a structural elongation As' such that As' ≥ 0.3%, the structural elongation As' being determined by applying the standard ASTM D2969-04 of 2014 to the cord (50') so as to obtain a force-elongation curve, the structural elongation As' being equal to the elongation, in %, corresponding to the intersection between the tangent to the elastic portion of the force-elongation curve at some point along the elastic portion thereof and the elongation axis of the force-elongation curve.

4. Cord (50; 50') according to any one of the preceding claims, wherein the criterion V1 is greater than or equal to 1000 N x m / g and preferably greater than or equal to 1500 N x m / g.

5. Cord (50; 50') according to any one of the preceding claims, wherein the criterion V1 is less than or equal to 2500 N x m / g.

6. Cord (50; 50') according to any one of the preceding claims, wherein M ranges from 30 to 180 g / m, preferably from 50 to 130 g / m.

7. Cord (50; 50') according to any one of the preceding claims, wherein the diameter D of the cord ranges from 4 mm to 9.5 mm, preferably from 5 mm to 7.5 mm.

8. Cord (50; 50') according to any one of the preceding claims, wherein the diameters of the metal threads (F1; F3; F1'; F3') range, independently of one another, from 0 15 mm to 0.50 mm, preferably from 0.18 mm to 0.35 mm, and more preferentially, from 0.20 mm to 0.30 mm.

9. Cord (50; 50') according to any one of the preceding claims, wherein Y is equal to 8, 9, 10 or 11, preferably Y=9 or 10 and more preferentially Y=9.

10. Cord (50; 50') according to any one of Claims 1 to 9, wherein each strand (T1) of the internal layer (CI) has two layers (C1, C3).

11. Cord (50; 50') according to any one of Claims 1 to 9, in which each strand (T2) of the external layer (CE) has two layers (C1', C3').

12. Cord (50; 50') according to any one of the preceding claims, wherein each strand (T1; T2) of the internal and external layers (Cl; CE) has two layers (C1, C3, C1', C3').

13. Reinforced product (100), characterized in that it comprises a polymer matrix (102) and at least one cord (50') such that the properties of this cord, measured after extraction, are those of the extracted cord (50') according to any one of Claims 3 to 12.

14. Tyre (10), characterized in that it comprises at least one cord (50') such that the properties of this cord, measured after extraction, are those of the extracted cord (50') according to any one of Claims 3 to 12, or a reinforced product according to Claim 13.