Break-resistant high-energy multi-strand cable with 1xN construction

Abstract

The extracted cord (60') has a 1xN structure comprising a single layer (61) of N spirally wound strands (62). Each strand (62) comprises two layers of metal wires (F1, F2) having diameters D1 and D2. The extracted cord 60' has a structural elongation As' ≥ 1.00% and a modulus of elasticity MC' ≤ 80 GPa. The mechanical resistance of at least 50% of the metal wires (F1, F2) having diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3,500-2,000 x D1 for the metal wires having diameter D1 and greater than or equal to 3,500-2,000 x D2 for the metal wires having diameter D2.

Description

[Technical field]

[0001] The present invention relates to cords and to tires including these cords. [Background technology]

[0002] A tire for a construction plant vehicle having a radial carcass reinforcement including a tread, two inextensible beads, two sidewalls connecting the beads to the tread, and a crown reinforcement arranged circumferentially between the carcass reinforcement and the tread is known from the prior art, in particular from document WO 2016 / 131862. This crown reinforcement includes a number of plies reinforced by reinforcing elements such as metal cords, the cords of one ply being embedded in the elastomeric matrix of the plies.

[0003] The crown reinforcement includes an operational reinforcement, a protective reinforcement, and potentially further reinforcements such as a hoop reinforcement.

[0004] The protective reinforcement comprises one or more protective plies, each of which comprises a plurality of protective filamentary reinforcing elements. Each protective filamentary reinforcing element is a cord exhibiting a 1×N structure. The cord comprises a single layer of N=4 strands wound in a spiral with a pitch p3=20 mm. Each strand comprises in part an inner layer of M=3 inner threads wound in a spiral with a pitch P1=6.7 mm and an outer layer of P=8 outer threads wound in a spiral around the inner layer with a pitch p2=10 mm. Each of the inner and outer threads has a diameter equal to 0.35 mm and a mechanical strength equal to 2765 MPa.

[0005] On the other hand, when the tire goes over obstacles, for example in the form of rocks, these obstacles present the risk of perforating the tire deep down to the crown reinforcement, these perforations allowing corrosive chemicals to penetrate into the crown reinforcement of the tire, shortening the life of the tire.

[0006] On the other hand, it has been found that the cords of the protective ply can exhibit breakage resulting from the relatively significant deformations and loads applied to the cords, especially when the tire goes over an obstacle. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] WO2016 / 131862 [Patent Document 2] EP0602733 [Patent Document 3] EP0383716 Summary of the Invention [Problem to be solved by the invention]

[0008] The object of the invention is a cord that makes it possible to reduce or even eliminate the number of breaks and perforations. [Means for solving the problem]

[0009] To this end, the subject of the invention comprises a single layer of N spirally wound strands, each strand having two layers of metal threads, an inner layer consisting of M ≥ 1 inner metal threads of diameter D1; an outer layer consisting of P>1 outer metal threads of diameter D2 wound around the inner layer; The cord according to the invention exhibits a structural elongation As determined by applying the standard ASTM D2969-04 of 2014 such that As≧3.00%. The cord according to the invention satisfies MC≦127, where MC=200×cos 4 (α) × [M × (D1 / 2) 2 ×cos 4 (β) + P × (D2 / 2) 2 ×cos 4 (γ)] / [M×(D1 / 2) 2 +P×(D2 / 2) 2], where: - D1 and D2 are expressed in mm, -α is the helix angle of each strand in the cord, -β is the helix angle of each internal metal thread in the internal layer; -γ is the helix angle of each outer metal thread in the outer layer.

[0010] The indicator MC represents the elastic modulus of the cord. In this formula, the modulus 200 represents the elastic modulus of steel, which is approximately 200 GPa. In the cord according to the invention, the mechanical strength of at least 50% of the metal threads of diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3500-2000 x D1 for the metal thread of diameter D1 and greater than or equal to 3500-2000 x D2 for the metal thread of diameter D2.

[0011] Due to the relatively high structural elongation and the indicator MC, which represents the relatively low elastic modulus of the cord, the cord according to the invention makes it possible to reduce punctures and therefore to extend the life of the tire. In particular, the inventors of the present invention have discovered that cords with lower stiffness than those of the prior art perform better against obstacles. The inventors have found that it is more effective to embrace an obstacle by using a cord with a lower stiffness than to try to stiffen and reinforce the cord as much as possible to counter the deformations imposed by the obstacle, as is generally taught in the prior art. Embracing an obstacle reduces the load set against the obstacle and therefore also reduces the risk of the tire being punctured.

[0012] Due to the relatively high structural elongation, the indicator MC representing the relatively low elastic modulus of the cord, and the relatively high mechanical strength of the majority of the metal threads of the cord, the cord according to the invention also makes it possible to reduce the number of breaks. In particular, the inventors involved in the present invention have discovered that the determining criterion for reducing cord breakage is not only the force at break, as is widely taught in the prior art, but the energy at break, represented in this application by an indicator equal to the product of the force at break and the elongation at break. In particular, the cords of the prior art either have a relatively high force at break but a relatively low elongation at break, or a relatively high elongation at break but a relatively low force at break. In both cases, the cords of the prior art break with a relatively low energy. Due to its relatively high structural elongation, the cord according to the invention necessarily exhibits a relatively high elongation at break. Synergistically, the relatively low elastic modulus makes it possible to retract the elongation at break due to the relatively low slope of the force-elongation curve in the elastic domain. Lastly and especially, the inventors have discovered that increasing the mechanical strength of the majority of metal threads, as will be demonstrated by comparative tests below, allows both to increase the structural elongation, making it possible to retract the elongation at break and therefore the energy indicator at break, as explained below, and also to increase the force at break, making it possible to increase the energy indicator at break.

[0013] The structural elongation As, a parameter known to those skilled in the art, is determined, for example, by applying the standard ASTM D2969-04 of 2014 to the cord tested to obtain a force-elongation curve. As is derived from the curve obtained as the elongation in % corresponding to the projection onto the elongation axis of the intersection point between the tangent to the structural part of the force-elongation curve and the tangent to the elastic part of the force-elongation curve. It will be recalled that the force-elongation curve comprises a structural part, an elastic part and a plastic part in the direction of increasing elongation. The structural part corresponds to the structural elongation of the cord resulting from the movement together of the different strands and metal threads that compose the cord. The elastic part corresponds to the elastic elongation resulting from the configuration of the cord, in particular the configuration of the various layer angles and thread diameters. The plastic part corresponds to the plastic elongation resulting from the plasticity of the metal threads (irreversible deformation beyond the elastic limit). The helix angle is defined by the following formula: α=arctan(2×π×R3 / p3), where R3 is the radius of the turns of the strand and p3 is the pitch at which the strand is wound. β=arctan(2×π×R1 / p1), where R1 is the radius of turns of the M internal metallic threads and p1 is the pitch with which the M internal metallic threads are assembled into a cord. The pitch p1 is such that 1 / p1=1 / p10+1 / p3, where p10 is the pitch of the M internal metallic threads in the strands before they are assembled to form the cord. When M=1, R1=0 and therefore β=0. γ=arctan(2×π×R2 / p2), where R2 is the radius of the turns of the N outer metallic threads and p2 is the pitch with which the N outer metallic threads are assembled into the cord. The pitch p2 is such that 1 / p2=1 / p20+1 / p3, where p20 is the pitch of the M outer metallic threads in the strands before they are assembled to form the cord.

[0014] The radius of turns R3 is measured on a cross-section perpendicular to the main axis of the cord and corresponds to the distance between the center of the helix represented by each strand and the center of the cord.Similarly, the radii of turns R1 and R2 are measured on a cross-section perpendicular to the main axis of each strand considered individually and correspond to the distance between the center of the helix represented by each inner and outer thread and the center of the strand, respectively.

[0015] In the present invention, a cord comprises a single layer of N strands, which means that it comprises an assembly of not more than one layer of strands, not less than one layer, which means that the assembly has only one layer of strands, not zero or two.

[0016] Each strand has two layers, which means that it includes an assembly composed of not more than two, not less than two layers of metal threads, and means that the assembly has not one, not three, but only two layers of metal threads. The outer layer of each strand is in contact with and wrapped around the inner layer of that strand.

[0017] The cord according to the invention as defined above is bare, meaning that it does not have any polymer composition, in particular the cord does not have any elastomeric composition.

[0018] A metal thread is understood to be a metal monofilament comprising a core consisting mainly (i.e. more than 50% of its weight) or entirely (100% of its weight) of a metallic material, for example carbon steel. The metal thread may advantageously comprise a layer of a metallic coating covering the core, the metallic coating being selected from zinc, copper, tin and alloys of these metals, for example brass. Each thread is preferably made of pearlitic or ferritic-pearlitic carbon steel.

[0019] The characteristic values ​​described in this application with respect to bare cords are measured on or determined from the cords immediately after they have been manufactured, i.e. before any step of embedding in a polymer matrix, in particular an elastomeric matrix.

[0020] In this application, any range of values ​​expressed by the phrase "between a and b" refers to a range of values ​​from greater than a to less than b (i.e., excluding the endpoints a and b), whereas any range of values ​​expressed by the phrase "from a to b" refers to a range of values ​​from the endpoint "a" to the endpoint "b", i.e., strictly including the endpoints "a" and "b".

[0021] In one preferred embodiment, As≧3.10%, i.e. the energy-at-break indicator of the cord is further increased and therefore the risk of breakage is reduced.

[0022] Optionally, As≦4.00%, preferably As≦3.75%, more preferably As≦3.50%. Limiting the structural elongation ensures that the cord can nevertheless absorb sufficient load for relatively small deformations.

[0023] In an advantageous embodiment making it possible to achieve the abovementioned properties, α ranges from 13° to 39°, preferably from 16° to 27°, and more preferably from 21° to 27°.

[0024] In an advantageous embodiment making it possible to achieve the abovementioned properties, β ranges from 6° to 22°, and preferably from 8° to 15°.

[0025] In an advantageous embodiment making it possible to achieve the abovementioned properties, γ ranges from 13° to 30°, and preferably from 16° to 23°.

[0026] In one preferred embodiment, MC≦125. By further limiting the elastic modulus indicator MC, the elastic portion is further elongated and therefore the energy at break indicator is increased.

[0027] Advantageously, MC ≥ 100, preferably MC ≥ 110, more preferably MC ≥ 115. The use of a relatively high elastic modulus indicator MC ensures that the cord is nevertheless able to absorb sufficient loads for relatively small deformations.

[0028] Advantageously, the cord exhibits a force at break Fr such that Fr≧8500 N, preferably Fr≧9000 N, more preferably Fr≧9350 N, even more preferably Fr≧9600 N. The force at break is measured according to standard ASTM D2969-04.

[0029] Advantageously, the cord exhibits an elongation at break Ar such that Ar ≧6.50%, preferably Ar ≧6.75%, more preferably Ar ≧6.90%. The elongation at break is measured according to standard ASTM D2969-04.

[0030] Very preferably, the cord exhibits an energy at break indicator Er, which is equal to the product of the force at break Fr expressed in N and the elongation at break Ar expressed in %, such that Er≧60 000 N.%, preferably Er≧63 000 N.%, more preferably Er≧64 000 N.%.

[0031] Very advantageously, the cord presents an energy at break indicator Er equal to the product of the force at break Fr, expressed in N, and the elongation at break Ar, expressed in %, and a diameter D, expressed in mm, such that Er / D≧15 000, preferably Er / D≧15 800, more preferably Er / D≧16 000 and very preferably Er / D≧16 500. The cord thus presents an advantageous compromise between energy at break and bulk, in particular to reduce the thickness of the ply in which it is to be positioned and thus the weight of the tire.

[0032] Yet another subject of the invention is a cord extracted from a polymer matrix, the cord presenting a 1×N structure comprising a single layer of N strands wound in a spiral, each strand having two layers of metal threads; an inner layer consisting of M ≥ 1 inner metal threads of diameter D1; an outer layer consisting of P>1 outer metal threads of diameter D2 wound around the inner layer; The extracted cord according to the invention exhibits a structural elongation As' determined by applying the standard ASTM D2969-04 of 2014 such that As'≧1.00%. The extracted cord according to the invention exhibits an elastic modulus MC'≦80 GPa. In the extracted cord according to the invention, the mechanical strength of at least 50% of the metal threads of diameters D1 and D2, measured according to the standard ASTM D2969-04, is greater than or equal to 3500-2000×D1 for the metal threads of diameter D1 and greater than or equal to 3500-2000×D2 for the metal threads of diameter D2.

[0033] The extracted cord according to the present invention results from embedding a bare cord in a polymer matrix, as opposed to the bare cords mentioned above which do not exhibit any polymer matrix.

[0034] The structural elongation As' of the extracted cord is measured in a similar manner to the structural elongation As of the bare cord defined above.

[0035] The modulus of elasticity MC' of the extracted cord is calculated by measuring the slope of the elastic part of the force-elongation curve obtained by applying the 2014 standard ASTM D2969-04 to the tested extracted cord, and then distributing this slope to the metal cross-section of the cord, i.e. the sum of the cross-sections of the threads that make up the extracted cord. Alternatively, the metal cross-section can be determined by measuring the linear metal density of the extracted cord according to the 2014 standard ASTM D2969-04 and dividing this linear metal density by the density of the steel used.

[0036] Preferably, the polymer matrix is ​​an elastomeric matrix.

[0037] The extracted cord according to the invention is obtained without a polymer matrix as defined above by embedding the bare cord in a polymer matrix, preferably an elastomeric matrix, based on a polymer, preferably an elastomeric composition.

[0038] In the extracted cord according to the invention, the enclosure of the cord, corresponding to the volume bounded by the strands and bounded by a theoretical circle radially inside and tangent to each strand, is filled with a polymer matrix, preferably an elastomeric matrix.

[0039] A polymer matrix is ​​understood to be a matrix which comprises at least one polymer, i.e. is based on a polymer composition.

[0040] An elastomeric matrix is ​​understood to be a matrix having elastomeric behavior resulting from the crosslinking of an elastomeric composition. Preferred elastomeric matrices are thus based on elastomeric compositions.

[0041] The expression "based on" must be understood to mean that the composition comprises compounds of the various components used and / or products of in situ reactions of these components, some of which are at least partially reacted with one another and / or are intended to react with one another during the various phases of the preparation of the composition, i.e. the composition can be in a fully or partially crosslinked or non-crosslinked state.

[0042] A polymer composition is understood to mean that the composition comprises at least one polymer. Preferably, such polymer is a thermoplastic, such as a polyester or polyamide, a thermosetting polymer, an elastomer, such as natural rubber, a thermoplastic elastomer, or a combination of these polymers.

[0043] An elastomeric 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. The composition used in the above-mentioned plies is a conventional composition for skim coating of filamentary reinforcing elements, comprising a diene elastomer, for example natural rubber, a reinforcing filler, for example carbon black and / or silica, a crosslinking system, for example a vulcanization system, preferably comprising sulfur, stearic acid and zinc oxide, and optionally vulcanization accelerators, retarders and / or various additives. The adhesion between the metal threads and the matrix in which they are embedded is provided, for example, by a metal coating, for example a brass layer.

[0044] The values ​​of the characteristics described in this application for the extracted cords are measured on or determined from the cords extracted, for example, from the polymer matrix, in particular the elastomeric matrix, of the tire. Thus, for example, a strip of material radially outside the extracted cord on the tire is removed, so that the extracted cord can be seen to be radially flush with the polymer matrix. This removal can be done by peeling with a cutter or gripper or by planing. The ends of the extracted cord are then exposed using a knife. Then, using a relatively shallow angle so as not to plasticize the extracted cord, the cord is pulled from the matrix so as to remove it from the matrix. The extracted cord is then carefully cleaned, for example with a knife, taking care not to damage the surface of the metal thread, in order to peel off any residues of the polymer matrix that are locally adhered to it.

[0045] In one preferred embodiment, As' > 1.05%, more preferably As' > 1.10%, which further increases the energy at break indicator of the cord within the polymer matrix, thus reducing the risk of breakage.

[0046] Optionally, As'≦1.50%, preferably As'≦1.40%. Limiting the structural elongation ensures that the cords within the polymer matrix can nevertheless absorb sufficient load for relatively small deformations.

[0047] In one preferred embodiment, MC'≦77 GPa. By further reducing the elastic modulus indicator MC', the elastic portion is further elongated and therefore the energy at break indicator is increased.

[0048] Advantageously, MC'≧60 GPa, preferably MC'≧65 GPa, more preferably MC'≧68 GPa. The use of a relatively high modulus indicator MC' ensures that the cord in the polymer matrix is ​​nevertheless able to absorb sufficient loads for relatively small deformations.

[0049] Advantageously, the extracted cord exhibits a force at break Fr' such that Fr'≧8500 N, preferably Fr'≧9000 N. This force at break is measured on the extracted cord according to standard ASTM D2969-04.

[0050] Advantageously, the extracted cord exhibits an elongation at break Ar' such that Ar'≧3.70%, preferably Ar'≧3.80%, more preferably Ar'≧3.90%, said elongation at break being measured on the extracted cord according to standard ASTM D2969-04.

[0051] Very preferably, the extracted cord exhibits an energy at break indicator Er', which is equal to the product of the force at break Fr' of the extraction cord expressed in N and the elongation at break Ar' of the extraction cord expressed in %, such that Er'≧33 000 N.%, preferably Er'≧35 000 N.%, more preferably Er'≧36 000 N.%.

[0052] Very advantageously, the extracted cord presents an energy at break indicator Er' equal to the product of the force at break Fr' of the extracted cord expressed in N and the elongation at break Ar' of the extracted cord expressed in %, and a diameter D expressed in mm such that Er' / D≧8500, preferably Er' / D≧8800, more preferably Er' / D≧9000 and very preferably Er' / D≧9100. The extracted cord thus presents an advantageous compromise between elongation at break and bulk in order to reduce the thickness of the ply in which it is to be positioned and thus the weight of the tire.

[0053] The advantageous features described below apply to both the bare code and the extracted code described above.

[0054] Preferably, at least 60%, preferably 70%, more preferably each of the metal threads of diameters D1 and D2, measured according to standard ASTM D2969-04, has a mechanical strength greater than or equal to 3500-2000×D1 for the metal threads of diameter D1 and greater than or equal to 3500-2000×D2 for the metal threads of diameter D2.

[0055] Advantageously, at least 50%, preferably at least 60%, more preferably at least 70%, and very preferably, of the metal threads of diameters D1 and D2, measured according to standard ASTM D2969-04, the mechanical strength of each metal thread is greater than or equal to 3600-2000×D1 for the metal threads of diameter D1 and greater than or equal to 3600-2000×D2 for the metal threads of diameter D2.

[0056] In a preferred configuration, N=3 or N=4, preferably N=4.

[0057] In preferred configurations, M=3, 4, or 5, preferably M=3.

[0058] In preferred configurations, P=7, 8, 9, 10 or 11, preferably P=8.

[0059] In a preferred configuration, where M>1 internal threads are helically wound with a pitch p1, p1 ranges from 3 mm to 11 mm, preferably from 5 mm to 9 mm.

[0060] In a preferred configuration, where the P outer thread is helically wound with a pitch p2, p2 ranges from 6 mm to 14 mm, preferably from 8 mm to 12 mm.

[0061] In a preferred configuration, where the strand is helically wound with a pitch p3, p3 ranges from 10 mm to 30 mm, preferably from 15 mm to 25 mm, more preferably from 15 mm to 19 mm.

[0062] In a highly preferred embodiment, the outer layer of each strand is unsaturated, preferably fully unsaturated.

[0063] By definition, an unsaturated thread layer is one in which there is sufficient space between the threads to allow the polymer composition, e.g., elastomeric composition, to pass through. Thus, an unsaturated layer means that there is no contact between the threads in this layer, and there is sufficient space between two adjacent threads in the layer to allow the polymer composition, e.g., elastomeric composition, to pass through the layer. In contrast, a saturated thread layer is one in which there is not sufficient space between the threads in the layer to allow the polymer composition, e.g., elastomeric composition, to pass through, for example, due to the threads in the layer being paired and contacting each other.

[0064] Advantageously, the interthread distance of the outer layer of each strand is greater than or equal to 5 μm. Preferably, the interthread distance of the outer layer of each strand is greater than or equal to 15 μm, more preferably greater than or equal to 35 μm, and even more preferably greater than or equal to 50 μm.

[0065] The unsaturation of the outer layer of each strand advantageously facilitates the penetration of the polymer composition, e.g., elastomeric composition, deep into the center of the strand, thus making the strand less susceptible to corrosion.

[0066] By definition, a fully unsaturated thread layer is one in which there is enough room in the layer to incorporate at least one (P+1)th thread having the same diameter as the P thread of the layer, so that the threads may or may not be in contact with each other. The fully unsaturated state of the outer layer of each strand allows for maximum penetration of the polymer composition, e.g., elastomeric composition, into each strand, and therefore makes each strand less susceptible to corrosion. Advantageously, therefore, the sum of the inter-thread distances SI2 of the outer layers of each strand is such that SI2≧D2. The sum SI2 is the sum of the inter-thread distances between each pair of adjacent threads in the layer. The inter-thread distance of a layer is defined as the average shortest distance between two adjacent threads of this layer in the cross section of the cord perpendicular to the main axis of the cord. The inter-thread distance is therefore calculated by dividing the sum SI2 by the number of thread spacings in the intermediate layer.

[0067] Advantageously, in tyres intended to equip construction plant vehicles, the diameter D1, D2 of each metal thread ranges from 0.25 mm to 0.50 mm, preferably from 0.30 mm to 0.45 mm, and more preferably from 0.32 mm to 0.40 mm.

[0068] In a preferred embodiment, each internal thread has a diameter D1 greater than or equal to the diameter D2 of each external thread. The use of diameters such that D1>D2 makes it possible to promote the permeation of the polymer composition, for example the elastomeric composition, through the external layer. The use of diameters such that D1=D2 makes it possible to limit the number of different threads managed in the manufacture of the cord.

[0069] Advantageously, the layer of N strands is unsaturated, preferably incompletely unsaturated.

[0070] By definition, an unsaturated strand layer is such that there is sufficient space between the strands to allow the polymeric composition, preferably the elastomeric composition, to pass through. An unsaturated strand layer means that there is no contact between the strands and there is sufficient space between two adjacent strands to allow the polymeric composition, preferably the elastomeric composition, to pass deep into the enclosure. In contrast, a saturated strand layer is such that there is not sufficient space between the strands of the layer to allow the polymeric composition, preferably the elastomeric composition, to pass through, for example due to the strands of the layer contacting each other in pairs.

[0071] Advantageously, the interstrand distance of the strand layer, defined as the average shortest distance between the circular envelopes inscribed by two adjacent strands on a cross section of the cord perpendicular to the main axis of the cord, is greater than or equal to 30 μm in the desaturated strand layer. Preferably, the average interstrand distance E between two adjacent strands is greater than or equal to 70 μm, more preferably greater than or equal to 100 μm, even more preferably greater than or equal to 150 μm and very preferably greater than or equal to 200 μm.

[0072] A strand layer that is incompletely saturated is one in which there is not enough space in the layer to allow the addition of at least one (N+1)th strand having the same diameter as the N strands in the layer.

[0073] According to the invention, each strand is of the type that is not rubberized in situ, meaning that each strand consists of various layers of threads and does not present any polymeric composition, in particular an elastomeric composition, before the strands are assembled together.

[0074] Advantageously, at least 50%, preferably at least 60%, more preferably at least 70% of the metal threads of the cord, very preferably each metal thread of the cord, comprises a steel core having a composition according to the NF EN 10020 standard of September 2000 and a carbon content C>0.80%, preferably C≧0.82%. Such steel compositions are a combination of non-alloy steels (sections 3.2.1 and 4.1 of the NF EN 10020 standard of September 2000), stainless steels (sections 3.2.2 and 4.2 of the NF EN 10020 standard of September 2000) and other alloy steels (sections 3.2.3 and 4.3 of the NF EN 10020 standard of September 2000). The relatively high carbon content makes it possible to provide the mechanical strength of the metal threads of the cord according to the invention. It is believed that the method of manufacturing the metal threads could be modified to increase the mechanical strength of the metal threads, in particular by further work-hardening each metal thread. Modifying the method of manufacturing the metal threads would require relatively significant industrial investment, whereas the use of a relatively high carbon content does not require any investment. Moreover, unlike methods where further work-hardening the metal threads would appreciably reduce the bending-compression durability of the metal threads, the use of a relatively high carbon content makes it possible to maintain this bending-compression durability.

[0075] Advantageously, C≦1.10%, preferably C≦1.00%, more preferably C≦0.90%. The use of excessively high carbon contents is not only relatively expensive, but also leads to a decrease in the fatigue-corrosion resistance of the metal thread.

[0076] Preferably, the bare code or the extracted code has a diameter D such that D ≦ 4 mm, preferably 3.5 mm ≦ D ≦ 4 mm. The diameter D is measured on the bare code or the extracted code in accordance with the standard ASTM D2969-04.

[0077] Advantageously, the bare code or the extracted code is - in time series during one stage, - when M > 1, M internal metal threads are spirally wound to form an inner layer, - P external metal threads are spirally wound around the inner layer to form an outer layer, - the step of individually assembling each of the N strands, - the step of collectively assembling by twisting the N strands that are spirally wound at a pitch p3 during the stage, obtained by a method including

[0078] Advantageously, the step of individually assembling each of the N strands is performed by twisting.

[0079] In this advantageous embodiment, during the individual assembly step, the M internal metal threads are spirally wound at a pitch p10 in the range of 5 mm to 15 mm, preferably 8 mm to 12 mm.

[0080] Furthermore, in this advantageous embodiment, during the individual assembly step, the P external metal threads are spirally wound at a pitch p20 in the range of 12 mm to 27 mm, preferably 17 mm to 23 mm.

[0081] In one particularly preferred embodiment, the bare code or the extracted code, after the collective assembly step, - overtwist the N strands to change from pitch p3 to a temporary overtwist pitch p3' such that p3' < p3, - reverse twist the N strands to change from the temporary overtwist pitch p3' to an intermediate pitch p3'' such that p3'' > p3', obtained by a method including the step of aerating the code.

[0082] In certain preferred embodiments, p3″≧p3.

[0083] The aeration stage makes it possible to shorten the pitch p3 by additional twisting to a temporary overtwist pitch p3' and to implicitly shorten each pitch p1 and p2 to a temporary overtwist pitch p1' and p2', respectively. The countertwist stage makes it possible to relieve the additional twisting and to obtain the intermediate pitch p3'' and to implicitly obtain the intermediate pitches p1'' and p2''. The sequence and sequence of the overtwist stage and the subsequent countertwist stage makes it possible to plastically deform the metal threads and to provide a relatively effective aeration on the cord, for example facilitating the permeation of the cord by the polymer composition, in particular the elastomeric composition.

[0084] Very preferably, the bare cord or extracted cord is subjected to aeration of the cord after the step of aerating the cord, - countertwisting the N strand so as to change the intermediate pitch p3'' to a temporary equilibrium pitch p3''' such that p3''''>p3 and p3''''>p3'; - twisting the N strand so that it changes from equilibrium pitch p3''' to pitch p3; It is obtained by a process which includes an equilibration step.

[0085] The aeration stage generates a residual torsional torque in the cord. The reverse twisting stage makes it possible to extend the intermediate pitch p3'' to a temporary equilibrium pitch p3''' by reverse twisting, and to implicitly extend each intermediate pitch p1'' and p2'' to a temporary equilibrium pitch p1'''' and p2'' respectively. The twisting stage makes it possible to eliminate the reverse twist and return to the initial pitch p3, and also to the initial pitches p1 and p2, implicitly. The succession and sequence of the reverse twisting stage and the subsequent twisting stages makes it possible to eliminate the residual torsional torque. The cord obtained at the end of the balancing stage therefore exhibits a substantially zero residual torsional torque. A substantially zero residual torsional torque corresponds to the cord being in torsional balance so that it can be used in the subsequent stages of its use. The residual torsional torque is expressed in meters per revolution, is measured according to standard ASTM D2969-04, and corresponds to the number of revolutions that a cord of a predetermined length can make around its main axis when it is allowed to move freely.

[0086] Advantageously, p3 / p3'>p3'' / p3. Thus, the magnitude of the additional twist is greater than the magnitude of the countertwist to allow for a balance and at the same time have as little as possible a detrimental effect on the aeration of the cord.

[0087] Another subject of the invention is a tyre for a construction plant vehicle comprising at least one filamentary reinforcing element formed by an extracted cord as defined above after extraction from the tyre.

[0088] Yet another subject of the invention is a tire for a construction plant vehicle comprising at least one filamentary reinforcing element obtained by embedding in a polymer matrix a bare cord as defined above, said bare cord embedded in a polymer matrix forming a cord which, after being extracted from the tire, forms an extracted cord according to the invention.

[0089] Another subject of the invention is a tire for a construction plant vehicle comprising at least one filamentary reinforcing element formed by an extracted cord as defined above after extraction from the tire and obtained by embedding the bare cord as defined above in a polymer matrix.

[0090] In one preferred embodiment, the tire comprises: a crown including a tread and a crown reinforcement; -Two side walls; -Two beads, each sidewall connects each bead to a crown, the tire comprising a carcass reinforcement anchored in each of the beads and extending in the sidewalls and the crown, the crown reinforcement being sandwiched in the radial direction between the carcass reinforcement and the tread, the crown reinforcement comprising at least one filamentary reinforcing element formed by an extracted cord as defined above after extraction from the tire and / or obtained by embedding a bare cord as defined above in a polymer matrix.

[0091] In one embodiment, the carcass reinforcement comprises at least one carcass ply, the carcass ply comprising carcass filamentary reinforcing elements and extending from one bead to the other so as to form an angle with the circumferential direction of the tire in the range of 80° to 90°.

[0092] In this embodiment, the crown reinforcement preferably extends circumferentially around the entire circumference of the tire.

[0093] Advantageously, the crown reinforcement comprises a protective reinforcement arranged radially outside the crown reinforcement, i.e. the crown reinforcement does not comprise any other reinforcement reinforced by filamentary reinforcing elements arranged radially outside the protective reinforcement.

[0094] Preferably, the protective reinforcement comprises at least one filamentary reinforcing element formed by an extracted cord as defined above after extraction from the tire and / or obtained by embedding a bare cord as defined above in a polymer matrix.

[0095] More preferably, the protective reinforcement comprises at least one protective ply comprising one or more protective filamentary reinforcing elements forming an angle with the circumferential direction of the tire that is greater than or equal to 10°, preferably ranging from 10° to 45°, more preferably from 15° to 40°, the or each protective filamentary reinforcing element being formed by an extracted cord as defined above after extraction from the tire and / or by at least one filamentary reinforcing element obtained by embedding a bare cord as defined above in a polymer matrix.

[0096] In one preferred embodiment, the protective reinforcement comprises two protective plies each comprising one or more protective filamentary reinforcing elements forming an angle with the circumferential direction of the tire that is greater than or equal to 10°, preferably ranging from 10° to 45°, more preferably from 15° to 40°, the or each protective filamentary reinforcing element being formed by an extracted cord as defined above after extraction from the tire and / or by at least one filamentary reinforcing element obtained by embedding a bare cord as defined above in a polymer matrix.

[0097] Preferably, the orientation of the angle between the protective filamentary reinforcing elements in one protective ply and the circumferential direction of the tire is opposite to the orientation of the angle between the protective filamentary reinforcing elements in the other protective ply and the circumferential direction of the tire, in other words the protective filamentary reinforcing elements in one protective ply cross the protective filamentary reinforcing elements in the other protective ply. The orientation of the angle means the clockwise or counterclockwise direction in which it is necessary to rotate from a reference line that defines this angle to reach the other line that defines this angle, in this case the circumferential direction of the tire.

[0098] In certain preferred embodiments, the crown reinforcement includes a hoop reinforcement disposed radially inward of the protective reinforcement.

[0099] Advantageously, the hoop reinforcement comprises at least one filamentary reinforcing element formed by an extracted cord as defined above after extraction from the tire and / or obtained by embedding a bare cord as defined above in a polymer matrix.

[0100] In one preferred embodiment, the protective reinforcement and the hoop reinforcement each comprise at least one metallic filamentary reinforcing element formed by the extracted cord defined above after extraction from the tire and / or obtained by embedding the bare cord defined above in a polymer matrix.

[0101] Advantageously, the hoop reinforcement comprises at least one hooping ply comprising one or more hooping filamentary reinforcing elements that form an angle with the circumferential direction of the tire of less than or equal to 10°, preferably less than or equal to 5° and more preferably substantially zero°, the or each filamentary hooping filamentary reinforcing element being formed by an extracted cord as defined above after extraction from the tire and / or by at least one filamentary reinforcing element obtained by embedding a bare cord as defined above in a polymer matrix. The use of the cord according to the invention in the hoop reinforcement ensures the absorption of the loads associated with the inflation pressure and makes it possible to limit the radial expansion of the tire. This absorption and limitation is even more effective when the angle between the hooping filamentary reinforcing element and the circumferential direction of the tire is small, given the relatively high flexibility of the at least one metallic filamentary reinforcing element.

[0102] In one preferred embodiment, the hoop reinforcement comprises two hooping plies each comprising one or more hooping filamentary reinforcing elements forming an angle with the circumferential direction of the tire of less than or equal to 10°, preferably less than or equal to 5° and more preferably substantially zero°, the or each filamentary hooping filamentary reinforcing element being formed by an extracted cord as defined above after extraction from the tire and / or by at least one filamentary reinforcing element obtained by embedding a bare cord as defined above in a polymer matrix.

[0103] In one embodiment, the two layers are formed by a continuous circumferential ply, where the ply is wound for at least two complete circumferential turns, each complete circumferential turn forming a layer.

[0104] Preferably, when the angle of the hooping filamentary reinforcing elements is substantially non-zero, the orientation of the angle between the hooping filamentary reinforcing elements and the circumferential direction of the tire in one hooping ply is opposite to the orientation of the angle between the hooping filamentary reinforcing elements and the circumferential direction of the tire in the other hooping ply, in other words, the hooping filamentary reinforcing elements in one hooping ply cross the hooping filamentary reinforcing elements in the other hooping ply.

[0105] In a preferred embodiment, the crown reinforcement comprises an actuation reinforcement disposed radially inwardly of the protective reinforcement.

[0106] Advantageously, the operational reinforcement comprises at least one operational ply comprising one or more operational filamentary reinforcing elements forming an angle with the circumferential direction of the tire that is less than or equal to 70°, preferably less than or equal to 60°, and more preferably ranging from 15° to 40°.

[0107] In one preferred embodiment, the operational reinforcement comprises two operational plies, each comprising one or more operational filamentary reinforcing elements forming an angle with the circumferential direction of the tire that is less than or equal to 70°, preferably less than or equal to 60°, and more preferably ranging from 15° to 40°.

[0108] Preferably, the orientation of the angle between the operative filamentary reinforcing elements and the circumferential direction of the tire in one working ply is opposite to the orientation of the angle between the operative filamentary reinforcing elements and the circumferential direction of the tire in the other working ply, in other words, the operative filamentary reinforcing elements in one working ply cross the operative filamentary reinforcing elements in the other working ply. The orientation of the angle means the clockwise or counterclockwise direction in which it is necessary to rotate from a reference line that defines this angle to reach the other line that defines this angle, in this case the circumferential direction of the tire.

[0109] In one embodiment, when the actuation reinforcement includes two actuation plies, the hoop reinforcement is radially disposed between the two actuation plies.

[0110] In one embodiment, the tire has a size of the WRU type, U≧35, preferably U≧35, more preferably U≧57. This tire size designation is the nomenclature of the ETRTO ("European Tire and Rim Technical Organization").

[0111] The invention will be better understood on reading the following description, given purely as a non-limiting example, with reference to the drawings in which: [Brief description of the drawings]

[0112] [Figure 1] 1 is a schematic cross-sectional view of a tire according to the present invention; [Diagram 2] FIG. 2 is a detailed view of portion II of the tire of FIG. 1. [Diagram 3] FIG. 1 is a schematic cross-sectional view perpendicular to the cord axis (assumed to be straight and at rest) of an extraction cord according to the invention. [Figure 4] FIG. 4 shows the force-elongation curve of the extraction cord of FIG. 3. [Diagram 5] 4 is a schematic cross-sectional view perpendicular to the cord axis (assumed to be straight and at rest) of the cord of FIG. 3 according to the invention in its bare state; [Figure 6] FIG. 6 shows the force-elongation curve of the extraction cord of FIG. 5. [Figure 7] FIG. 1 is a schematic diagram of an installation and method for producing bare cords and extraction cords according to the present invention. [Figure 8] FIG. 1 is a schematic diagram of an installation and method for producing bare cords and extraction cords according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0113] These figures show a coordinate system X, Y, Z which corresponds to the usual axial, radial and circumferential orientations of the tire.

[0114] The circumferential median plane M of the tire is a plane perpendicular to the tire's axis of rotation, equidistant from the annular reinforcing structures of each bead, and passing through the center of the crown reinforcement.

[0115] 1 and 2 show a tire for a construction plant type vehicle, for example of the "dumper" type, designated by the general reference number 10. The tire 10 thus has a size of, for example, 40.00 R 57 or 59 / 80 R 63 WRU type.

[0116] In a manner known to those skilled in the art, W is - when in H / B configuration, represents the nominal aspect ratio H / B as defined by the ETRTO, where H is the height of the tire's section and B is the width of the tire's section, -H.00 or B.00, where H=B, H and B are as defined above. U represents the diameter in inches of the rim seat on which the tire is intended to be mounted, and R represents the type of carcass reinforcement of the tire, in this case radial. U≧35, preferably U≧49, more preferably U≧57.

[0117] The tire 10 includes a crown 12 that includes a tread 22 and a crown reinforcement 14. The tread 22 is disposed radially outwardly of the crown reinforcement 14. The crown reinforcement 14 extends circumferentially about the tire 10, around the entire circumference of the tire 10.

[0118] The tire 10 further includes two sidewalls 16 and two beads 18, each of which is reinforced with an annular structure, in this case a bead wire 20. Each sidewall 16 connects each bead 18 to the crown 12.

[0119] The tire 10 further comprises a carcass reinforcement 24 fastened to each of the two beads 18, in this case wound around the two bead wires 20, and including turn-ups 26 arranged towards the outside of the tire 20, shown in this figure mounted on a wheel rim 28. The carcass reinforcement 24 extends within the sidewall 16 and the crown 12. The crown reinforcement 14 is sandwiched radially between the carcass reinforcement 24 and the tread 22.

[0120] The carcass reinforcement 24 includes at least one carcass ply 30, which includes carcass filamentary reinforcing elements 31 and extends from one bead 18 to the other bead 18 so as to form an angle with the circumferential direction Z of the tire 10 that is in the range of 80° to 90°.

[0121] The tire 10 further includes a sealing ply 32 (commonly known as an "inner liner") made of elastomer, which defines the radially inner surface 34 of the tire and is intended to protect the carcass ply 30 from the diffusion of air emanating from the space inside the tire 10.

[0122] The crown reinforcement 14 includes a protective reinforcement 36 disposed radially inward of the tread 22, a working reinforcement 38 disposed radially inward of the protective reinforcement 36, and a hoop reinforcement 50 disposed radially inward of the protective reinforcement 36. The protective reinforcement 36 is thus sandwiched radially between the tread 22 and the working reinforcement 38. The protective reinforcement 36 is thus also disposed radially outward of the crown reinforcement 14.

[0123] The protective reinforcement 36 comprises a first and a second protective ply 42, 44, the first ply 42 being arranged radially inside the second ply 44. Each of the first and second protective plies 42, 44 comprises in each of them, respectively, a first and a second protective filamentary reinforcing element 43, 45 arranged substantially parallel to each other. Each of the first and second protective filamentary reinforcing elements 43, 45 forms an angle with the circumferential direction Z of the tire 10 that is greater than or equal to 10°, preferably ranging from 10° to 45°, desirably from 15° to 40°. Optionally, the first and second protective filamentary reinforcing elements 43, 45 are crossed from one protective ply to the other protective ply. In this case, each of the first protective filamentary reinforcing elements 43 forms an angle with the circumferential direction Z of the tire 10 that is equal to +33°, and each of the second protective filamentary reinforcing elements 45 forms an angle with the circumferential direction Z of the tire 10 that is equal to -33°.

[0124] The working reinforcement 38 includes first and second working plies 46, 48, the first ply 46 being arranged radially inward of the second ply 48. Each of the first and second working plies 46, 48 includes first and second working filamentary reinforcement elements 47, 49, respectively, arranged substantially parallel to each other within each of the first and second working plies 46, 48. Each of the first and second working metal filamentary reinforcement elements 47, 49 forms an angle with the circumferential direction Z of the tire 10 that is less than or equal to 70°, preferably less than or equal to 60°, and more preferably ranging from 15° to 40°. Optionally, the first and second working filamentary reinforcement elements 47, 49 are crossed from one working ply to the other working ply. In this case, each first working metal filamentary reinforcing element 47 forms an angle equal to +19° with the circumferential direction Z of the tire 10 and each second working filamentary reinforcing element 49 forms an angle equal to -33° with the circumferential direction Z of the tire 10. Examples of working reinforcing elements are described in documents EP 0602733 as well as EP 0383716.

[0125] The hoop reinforcement 50, also called limiting block, comprises a first and a second hoop ply 52, 54, each of which comprises a first and a second hoop filamentary reinforcing element 53, 55 arranged substantially parallel to each other in its respective interior. Each of the first and the second hoop filamentary reinforcing elements 53, 55 forms an angle with the circumferential direction Z of the tire 10 that is less than or equal to 10°, preferably less than or equal to 5°, and more preferably substantially zero. In this case, each of the first and the second hoop filamentary reinforcing elements 53, 55 forms an angle with the circumferential direction Z of the tire 10 that is substantially zero.

[0126] In the illustrated embodiment, the hoop reinforcement 50 is advantageously positioned radially between the two working plies 46,48.

[0127] With reference to Figure 3, each protective reinforcing element 43, 45 and each hooping reinforcing element 53, 55 is formed by an extracted cord 60' after extraction from the tire 10 as explained below. As for the cord 60', this cord is obtained by embedding a bare cord 60 shown in Figure 5 in a polymer matrix, in this case an elastomeric matrix, which respectively forms each of the elastomeric matrices of each protective ply 42, 44 and each of the hooping layers 52, 54 in which the protective reinforcing elements 43, 45 and each of the hooping reinforcing elements 53, 55 are embedded, respectively.

[0128] The bare cord 60 and the extraction cord 60' present a 1xN structure comprising a single layer 61 of N strands 62 wound in a spiral to define an internal enclosure 64 of the cord. Within the cord 60', the internal enclosure 64 is filled with a filler material 66 for filling it. The filler material 66 is based on a polymer composition, in this case an elastomeric composition, equal to the composition of the elastomeric matrix of each protective reinforcement element 43, 45 and hooping reinforcement element 53, 55, in this case each protective ply 42, 44 and each hooping ply 52, 54 in which each cord 60 is embedded, respectively.

[0129] Each strand 62 has two layers of metal threads, including an inner layer C1 of M>1 inner metal threads F1 of diameter D1 and an outer layer C2 of P>1 outer metal threads F2 of diameter D2 wound around the inner layer C1.

[0130] In this case, the bare cord 60 and the extraction cord 60' have a diameter D such that D≦4 mm, preferably 3.5 mm≦D≦4 mm. In this case, D=3.89 mm.

[0131] Similarly, N=3 or N=4, in which case N=4 is preferred. Furthermore, M=3, 4, or 5, in which case M=3 is preferred. Furthermore, P=7, 8, 9, 10, or 11, in which case P=8 is preferred.

[0132] The respective diameters D1, D2 of each metal thread F1, F2 range from 0.25 mm to 0.50 mm, preferably from 0.30 mm to 0.45 mm, more preferably from 0.32 mm to 0.40 mm. In this case D1=D2=0.35 mm. Each metal thread F1, F2 comprises a steel core exhibiting a non-alloy steel composition according to the NF EN 10020 standard of September 2000 and a carbon content such that C>0.80%, preferably C≧0.82% and C≦1.10%, preferably C≦1.00%, more preferably C≦0.90%. In this case C=0.86%. According to the invention, the mechanical strength Rm of at least 50% of the metal threads F1, F2 with diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3500-2000 x D1, preferably 3600-2000 x D1 for each metal thread with diameters D1, D2, respectively, and is greater than or equal to 3500-2000 x D2, preferably 3600-2000 x D2. In this case, each metal thread F1, F2 exhibits a mechanical strength Rm, measured according to standard ASTM D2969-04, greater than or equal to 3600-2000 x D1 and greater than or equal to 3600-2000 x D2 for each metal thread with diameters D1, D2, respectively. In this case, the mechanical strength Rm of each thread F1, F2 is equal to 2960 MPa.

[0133] The layer 61 of N strands is preferably incompletely saturated. The distance between two adjacent strands 62 is equal to 200 μm.

[0134] The outer layer C2 of each strand 62 is unsaturated, preferably in a fully unsaturated state, in this case the distance between two adjacent outer threads F2 is equal to 60 μm.

[0135] Within the bare cord 60 and the extraction cord 60', M>1 internal metal threads F1 are helically wound with a pitch p1 ranging from 3 to 11 mm, preferably from 5 to 9 mm, in this case p1=6.4 mm. The corresponding helix angle β of each internal metal thread F1 within the internal layer C1 ranges from 6° to 22°, preferably from 8° to 15°, in this case β=11.2°.

[0136] In the bare cord 60 and in the extraction cord 60', the P outer metal threads F2 are wound helically with a pitch p2 ranging from 6 mm to 14 mm, preferably from 8 mm to 12 mm, in this case p2=9.5 mm. The corresponding helix angle γ of each outer metal thread F2 in the outer layer C2 ranges from 13° to 30°, preferably from 16° to 23°, in this case γ=20.0°.

[0137] The strands 62 are helically wound with a pitch p3 ranging from 10 mm to 30 mm, preferably from 15 mm to 25 mm, more preferably from 15 mm to 19 mm, in which case p3=18 mm. The helix angle α of each strand 62 in the bare cord 60 and the extraction cord 60' ranges from 13° to 39°, preferably from 16° to 27°, more preferably from 21° to 27°, in which case α=23.2°.

[0138] The cord 60' exhibits a force at break Fr' such that Fr'≧8500 N, preferably Fr'≧9000 N, in this case Fr'=9133 N. The cord 60' exhibits an elongation at break Ar' such that Ar'≧3.70%, preferably Ar'≧3.80%, more preferably Ar'≧3.90%, in this case Ar'=3.96%. The cord 60' exhibits an energy indicator Er' at break equal to the product of the force at break Fr' expressed in N and the elongation at break Ar' expressed in %, such that Er'≧33 000 N.%, preferably Er'≧35 000 N.%, more preferably Er'≧36 000 N.%, in this case Er'=36 137 N.%. The ratio of the energy at break indicator Er' to the diameter D, expressed in mm, is such that Er' / D > 8500, preferably Er' / D > 8800, more preferably Er' / D > 9000, very preferably Er' / D > 9100. In this case Er' / D = 9297.

[0139] According to the invention, as shown in Figure 4, the cord 60' has a structural elongation As' greater than or equal to 1.00%, preferably As'≧1.05%, more preferably As'≧1.10%. Furthermore, As'≦1.50%, preferably As'≦1.40%. In this case, As'=1.20%.

[0140] According to the invention, as shown in Figure 4, the cord 60' has a modulus of elasticity MC' ≦ 80 GPa, preferably MC' ≦ 77 GPa. Furthermore, MC' ≧ 60 GPa, preferably MC' ≧ 65 GPa, more preferably MC' ≧ 68 GPa. In this case, MC' = 74 GPa.

[0141] With reference to figure 6, the cord 60 presents a force at break Fr such that Fr ≥ 8500 N, preferably Fr ≥ 9000 N, more preferably Fr ≥ 9350 N, even more preferably Fr ≥ 9600 N, in this case Fr = 9835 N. The cord 60 presents an elongation at break Ar such that Ar ≥ 6.50%, preferably Ar ≥ 6.75%, more preferably Ar ≥ 6.90%, in this case Ar = 6.99%. The cord 60 presents an energy indicator Er at break equal to the product of the force at break expressed in N and the elongation at break expressed in %, such that Er ≥ 60 000 N.%, preferably Er ≥ 63 000 N.%, more preferably Er ≥ 64 000 N.%, in this case Er = 68 747 N.%.

[0142] The cord 60 exhibits a ratio of the energy at break indicator Er to the diameter D, expressed in mm, such that Er / D≧15 000, preferably Er / D≧15 800, more preferably Er / D≧16 000, very preferably Er / D≧16 500, in this case Er / D=17 673.

[0143] According to the invention, MC≦127, preferably MC≦125. Furthermore, MC≧100, preferably MC≧110, more preferably MC≧115. In this case, MC=117. The elastic modulus indicator MC is given by MC=200×cos 4 (α) × [M × (D1 / 2) 2 ×cos 4 (β) + P × (D2 / 2) 2 ×cos 4 (γ)] / [M×(D1 / 2) 2 +P×(D2 / 2) 2 ], where D1 and D2 are expressed in mm, α is the helix angle of each strand 62 in the cord 60, β is the helix angle of each inner metal thread D1 in the inner layer C1, and γ is the helix angle of each outer metal thread D2 in the outer layer C2.

[0144] According to the present invention, as shown in FIG. 6, the cord 60 has a structural elongation As ≧ 3.00%, preferably As ≧ 3.10%. Further, As ≦ 4.00%, preferably As ≦ 3.75%, more preferably As ≦ 3.50%. In this case, As = 3.20%.

[0145] Each bare cord 60 and extracted cord 60' is first in the range of 5 mm to 15 mm, preferably 8 mm to 12 mm, in time series during the step, and in this case p10 = 10 mm, and the internal metal thread F1 is spirally wound around each of the N strands 62 at a pitch p10 to form an internal layer C1 by a method including the step of individually assembling each of the N strands 62 by twisting. Then, the external metal thread F2 is spirally wound around the internal layer C2 at a pitch p20 in the range of 12 mm to 27 mm, preferably 17 mm to 23 mm, and in this case p20 = 20 mm to form the external layer C2. This method further includes the step of spirally winding the N strands 62 at the above-mentioned pitch p3 during the step and collectively assembling the pre-formed N strands 62 by twisting. During this collective assembly step, the pitches of the internal metal thread F1 and the external metal thread F2 change from p10 and p20 to the above-mentioned pitches p1 and p2, respectively.

[0146] After the collective assembly step, the method includes the step of aerating the bare cord 60 in which the N strands 62 are overtwisted so as to change from the pitch p3 to a temporary overtwist pitch p3' < p3, and in this case p3' = 10 mm. Then, in the aeration step, the N strands 62 are reverse-twisted so as to change from the temporary overtwist pitch p3' to an intermediate pitch p3'' > p3' and p3'' ≧ p3, and in this case p3'' = p3 = 18 mm.

[0147] After the aeration stage, the method first includes a balancing stage in which the N strands are counter-twisted to change from the intermediate pitch p3'' to a temporary equilibrium pitch p3''' such that p3'''>p3 and p3'''>p3', in this case p3''''=23 mm. Then, in the balancing stage, the N strands are twisted to change from the temporary equilibrium pitch p3'''' to pitch p3. In this case, advantageously p3 / p3'>p3'''' / p3.

[0148] For its part, the tire 10 is obtained by a manufacturing method that includes, in addition to the above-mentioned steps of the method for manufacturing the cords, a step of embedding the cords 60 in a polymer matrix, in this case an elastomeric matrix, for example by skim coating, to form at least one ply or layer comprising the cords embedded in the matrix. The method for manufacturing the tire 10 then includes a step of assembling this ply or layer with at least other products to form the tire in an uncrosslinked, green form. The method for manufacturing the tire 10 then includes a crosslinking step in which the uncrosslinked green form is crosslinked, in this case by vulcanization.

[0149] 7 and 8 show an installation 68 for manufacturing the bare cord 60 described above.

[0150] The equipment 68 includes equipment 70 for individually assembling each strand 62, shown in FIG. 7, and equipment 72 for collectively assembling the strands 62, shown in FIG.

[0151] - cabling where the metal thread or strand is not subjected to twisting about its own axis due to synchronous rotation near the assembly point; or by twisting in which the metal threads or strands undergo both collective and individual twisting about their own axes, thereby generating a counter-torsional torque on each of the metal threads and strands or on the cord itself, It will be recalled that there are two possible techniques for assembling the metal threads, one of which is:

[0152] The method of manufacturing bare cord 60 uses twisting rather than cabling.

[0153] The equipment 70 for individually assembling each strand 62 includes, from upstream to downstream in the direction in which the strand 62 passes, a means 74 for feeding the M inner metal thread F1, a means 76 for assembling the M inner metal thread F1 by twisting, a means 77 for setting the assembled M inner metal threads in a rotating state, a means 78 for feeding the P outer metal thread F2, a means 80 for assembling the P outer metal thread F2 around the inner layer C1 by twisting, a means 81 for setting the strand 62 in a rotating state, a means 83 for tensioning the strand 62, and a means 84 for storing the strand 62.

[0154] The assembly 72 for collectively assembling these strands 62 includes, from upstream to downstream in the direction in which the bare cord 60 passes, a means 86 for feeding the N strands 62, a means 88 for assembling the N strands 62 together by twisting, a means 90 for setting the bare cord 60 in a rotated state, a means 92 for aerating the bare cord 60, a means 94 for balancing the bare cord 60, a means 96 for tensioning the bare cord 60, and a means 98 for storing the bare cord 60.

[0155] 7, the means 74 for feeding the M internal metal threads F1 includes a reel 102 for unwinding each internal metal thread F1. The means 76 for assembling the M internal metal threads F1 by twisting includes a distributor 104 and an assembly guide 106 that defines an assembly point P1. The means 77 for setting in a rotating state includes two flywheels 107 arranged downstream of the assembly point P1.

[0156] The means 78 for feeding the P external metal threads F2 include a reel 108 for unwinding each external metal thread F2. The means 80 for assembling the P external metal threads F2 include a distributor 110 and an assembly guide 112 that defines an assembly point P2. The means 81 for setting in rotation include two flywheels 113 arranged downstream of the assembly point P2.

[0157] The means 83 for tensioning the strands 62 includes one or more winches 118 and the means 84 for storing the strands 62 includes a reel 120 for winding up each strand 62 .

[0158] The strands 62 are assembled, in this case by twisting.

[0159] 8, the means 86 for feeding the N strands 62 includes a reel 122 for unwinding each strand 62. The means 88 for assembling the N strands 62 together by twisting includes a distributor 124 and an assembly guide 126 that defines an assembly point P3. The means 90 for setting the bare cord 60 in a rotating state includes two flywheels 128 arranged downstream of the assembly point P3. The aeration means 92 includes a twister 130. The balancing means 94 includes a twister 132. The means 96 for tensioning the bare cord 60 includes one or more winches 134, and the means 98 for storing the bare cord 60 includes a reel 136 for winding the bare cord 60.

[0160] Comparative Test

[0161] A comparison is made below between the prior art cord T0, six control cords T1 to T6, and two cords I1 and I2 according to the invention, as disclosed in WO2016 / 131862. For each of these cords, certain characteristics were measured in its bare state and when extracted from the tire. It is noted that cord I2 corresponds in its bare state to cord 60 mentioned above, and corresponds when extracted from the tire to cord 60' mentioned above.

[0162] Codes T0, T2, T3, T5 and I1 were each produced by a process that did not implement the aeration step described above, in contrast to codes T2, T4, T6 and I2 that were each produced by a process that implemented the aeration step described above.

[0163] Each of the cords was tested in an air permeability test. Such a permeability test is known to those skilled in the art and makes it possible to determine the longitudinal air permeability of the cord tested by measuring the volume of air passing along the test sample under a constant pressure for a given period of time. The principle of such a test, known to those skilled in the art, is to reveal the effectiveness of a treatment that makes the cord impermeable to air and is described, for example, in the ASTM D2692-98 standard. Such a test is carried out on freshly manufactured, unaged cords. The raw cords are previously coated on the outside with an elastomeric composition, called the coating composition. For this purpose, a series of 10 parallel cords (distance between cords: 20 mm) is placed between two layers or "skims" (two rectangles with dimensions of 80 mm x 200 mm) composed of a diene elastomer composition in the untreated state, each having a thickness of 5 mm, then all of them are fixed in a mold and kept under sufficient tension (for example 3 daN) using a crimping module to ensure that each of the cords lies straight when placed in the mold, and then vulcanized (cured) at a temperature of around 120°C and under a pressure of 15 bar (rectangular pistons with dimensions of 80 mm x 200 mm) for about 10 to 12 hours. The whole is then extracted from the mold and a test sample of 10 cords thus coated is cut into a rectangular parallelepiped shape with dimensions of 7 mm x 7 mm x 60 mm for characterization. The coating elastomer composition used is a diene elastomer composition conventionally used in tyres based on natural (deflocculated) rubber and carbon black N330 (65 phr), further containing the usual additives: sulphur (7 phr), sulphenamide accelerator (1 phr), ZnO (8 phr), stearic acid (0.7 phr), antioxidants (1.5 phr), cobalt naphthenate (1.5 phr) (phr means parts by weight per 100 parts by weight of elastomer), and the E10 modulus of this coating elastomer composition is around 10 MPa.Thus, the test is performed on a 6 cm length of cord coated with a surrounding elastomeric composition (or coating elastomeric composition) in the cured state by injecting air into the intake end of the cord at a pressure of 1 bar and measuring the volume of air at the exhaust end using a flow meter (e.g., 0 cm). 3 / min to 500cm 3 The measurement was carried out using a method in which the air flow rate was measured using a compression airtight seal (calibrated to 100 / min). During the measurement, a sample of the cord was fixed in a compressed airtight seal (e.g. a seal made of dense foam or rubber) so that only the amount of air passing along the cord from one end to the other along the longitudinal axis of the cord was taken into account in the measurement, and the airtight seal itself was previously checked for airtightness using a solid test sample of the elastomeric composition, i.e. without the cord. The higher the longitudinal impermeability of the cord, the lower the average measured air flow rate (averaged over 10 test samples). Code T0 is indicated with a relative measurement value "=". Codes that are more permeable and therefore less permeable than code T0 are indicated with a relative measurement value "-", and codes that are even more permeable and therefore very less permeable than code T0 are indicated with a relative measurement value "--". In contrast, codes that are less permeable and therefore more permeable than code T0 are indicated with a relative measurement value "+", and codes that are even less permeable and therefore very much more permeable than code T0 are indicated with a relative measurement value "++". The results of this test are given in the line designated "APA." The results of all of these comparative tests are collated in Table 1 below.

[0164] (Table 1) JPEG0007644710000001.jpg174170

[0165] It should be noted that the use of a relatively short pitch p3 in the cords I1 and I2 makes it possible to increase the As of these cords compared to the control cords. Such an increase increases the elongation at break Ar, as described above, and therefore increases the energy indicator at break of the cord, while allowing the absorption of deformations caused by obstacles. Furthermore, the relatively short pitch p3 obtains a relatively modest elastic modulus, thus extending the elastic part of the force-elongation curve, which further makes it possible to increase the elongation at break Ar of the cord, as described above, and therefore increases the energy indicator at break Er, while allowing the absorption of deformations caused by obstacles.

[0166] Comparing codes T0 and T3 as well as codes T2 and I1, it should be noted that the use of metal threads with a relatively high mechanical strength (2960 MPa) instead of metal threads with a lower mechanical strength (2765 MPa) does not cause an increase in the energy at break indicator corresponding to the increase in mechanical strength in the bare cord. In the case of codes T2 and I1, even this change in the energy at break indicator is not observed. The inventor explains this by the fact that the metal threads and strands in the bare cable are in contact with each other and that the higher the mechanical strength for a given method for manufacturing the metal threads, the more susceptible the metal threads are to contact loads, thereby reducing the elongation at break Ar and / or the force at break Fr of the cord despite the increase in the mechanical strength of each metal thread. Nevertheless, with the cord filled with the polymer composition, the filler, in this case the polymer matrix, prevents contact between the metal threads and between the strands and makes it possible to increase the energy indicator at break Er' of the cord by increasing the elongation at break Ar' and / or the force at break Fr' due to the use of metal threads with a relatively high mechanical strength (2960 MPa).

[0167] Finally, it is noted that, all things being equal, the implementation of the method including an aeration step significantly improves the permeability of the cord with the polymer composition, in this case the elastomeric composition.

[0168] The present invention is not limited to the above-described embodiments.

[0169] In particular, it is considered that cords having a carbon content C of at least 50%, preferably at least 60%, more preferably at least 70%, such that C>0.80%, preferably C≧0.82% and such that C≦1.10%, preferably C≦1.00%, more preferably C≦0.90% can be used without departing from the scope of the invention.

[0170] Likewise, it is considered that cords in which the mechanical strength of at least 50%, preferably at least 60%, more preferably at least 70% of the metal threads of diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3500-2000×D1 for metal threads of diameter D1, preferably greater than or equal to 3600-2000×D1 for metal threads of diameter D1 and greater than or equal to 3500-2000×D2 for metal threads of diameter D2, preferably greater than or equal to 3600-2000×D2, may be used without departing from the scope of the invention.

[0171] This is because it is sufficient that a sufficient number of the metal threads of the assembly have a sufficiently high mechanical strength to make it possible to achieve the desired properties, in particular the energy at break properties.

Claims

1. A cord (60) presenting a 1×N structure comprising a single layer (61) of N spirally wound strands (62) each having two layers of metal threads (F1, F2) and including an inner layer (C1) of M≧1 inner metal threads (F1) of diameter D1 and an outer layer (C2) of P>1 outer metal threads (F2) of diameter D2 wound around said inner layer (C1), The cord (60) exhibits a structural elongation As determined by application of the 2014 standard ASTM D2969-04 such that As≧3.00%, The code (60) satisfies MC≦127, where MC=200×cos 4 (α)×[M×(D1 / 2) 2 ×cos 4 (β)+P×(D2 / 2) 2 ×cos 4 (γ)] / [M×(D1 / 2) 2 + P × (D2 / 2) 2 ], where: D1 and D2 are expressed in mm, α is the helix angle of each strand (62) in the cord (60); β is the helix angle of each internal metal thread (F1) in said internal layer (C1); and γ is the helix angle of each external metal thread (F2) in said external layer (C2), the mechanical strength of at least 50% of said metal threads (F1, F2) of diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3500-2000 x D1 for metal threads of diameter D1 and greater than or equal to 3500-2000 x D2 for metal threads of diameter D2, A code (60).

2. It exhibits a breaking force Fr such that Fr ≧ 8500 N; The cord (60) of claim 1.

3. exhibit an elongation at break Ar such that Ar ≧ 6.50%; A cord (60) according to claim 1 or 2.

4. exhibiting an energy-at-break indicator Er equal to the product of the force at break of the cord, expressed in N, and the elongation at break of the cord, expressed in %, such that Er≧60,000 N. A cord (60) according to any one of claims 1 to 3.

5. A cord (60') exhibiting a 1xN structure comprising a single layer (61) of N spirally wound strands (62), each strand (62) having two layers of metal threads (F1, F2) and including an inner layer (C1) of M > 1 inner metal thread (F1) of diameter D1 and an outer layer (C2) of P > 1 outer metal thread (F2) of diameter D2 wound around said inner layer (C1), the enclosure of the cord, corresponding to a volume bounded by each of the strands and bounded by a theoretical circle radially inside and tangent to each of the strands, is filled with a thermoplastic polymer matrix having elastomeric behavior resulting from crosslinking of an elastomeric composition; The cord (60') exhibits a structural elongation As', determined by applying the 2014 standard ASTM D2969-04, such that As' ≥ 1.00%, The cord (60') exhibits an elastic modulus MC'≦80 GPa; The elastic modulus MC' is calculated by measuring the slope of the elastic part of the force-elongation curve obtained by applying the 2014 standard ASTM D2969-04 to the cord, then dividing this slope by the metal cross-section of the cord, i.e. by the cross-section of the threads that make up the cord; the mechanical strength of at least 50% of the metal threads (F1, F2) of diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3500-2000 x D1 for metal threads of diameter D1 and greater than or equal to 3500-2000 x D2 for metal threads of diameter D2; A cord (60') characterized in that

6. exhibit a breaking force Fr' such that Fr'≧8500N; A cord (60') according to claim 5.

7. exhibit an elongation at break Ar′ such that Ar′≧3.70%; A cord (60') according to claim 5 or 6.

8. exhibiting an energy-at-break indicator Er' equal to the product of the force at break of the cord, expressed in N, and the extracted elongation at break of the cord, expressed in %, such that Er'≧33000 N. A cord (60') according to any one of claims 5 to 7.

9. the mechanical strength of at least 50% of said metal threads (F1, F2) of diameters D1 and D2, measured according to standard ASTM D2969-04, is greater than or equal to 3600-2000 x D1 for metal threads of diameter D1 and greater than or equal to 3600-2000 x D2 for metal threads of diameter D2, A cord (60, 60') according to any one of the preceding claims.

10. A tire (10) for a construction plant vehicle, comprising: and / or formed by a cord (60') according to any one of claims 5 to 8; Obtained by embedding a cord (60) according to any one of claims 1 to 4 and 9 in a polymer matrix, At least one filamentous reinforcing element (43, 45, 53, 55), A tire (10) comprising:

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