EP4058629A1

EP4058629A1 - Two-layer metal cables having a sheathed inner layer and an improved performance

Info

Publication number: EP4058629A1
Application number: EP20819811.9A
Authority: EP
Inventors: Alexandre GIANETTI; Pierre-Marie MICHON
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2019-11-15
Filing date: 2020-11-05
Publication date: 2022-09-21
Anticipated expiration: 2040-11-05
Also published as: EP4058629B1; AU2020382109A1; FR3103200A1; WO2021094674A1

Abstract

The invention relates to a two-layer cable (50) comprising: - an inner layer (C1) consisting of M>1 inner metal wires (F1); - a cable outer layer (C3) consisting of N outer metal wires (F3) wound around the inner layer (C1) of the cable. The cable (50) is obtained by a method involving a step of manufacturing the sheathed inner layer (CIG) in which the inner layer (CI) is surrounded by an elastomer composition having a thickness G and then by the N outer metal wires to form the outer layer (C3), with N being strictly greater than Nmax, which is the maximum number of outer metal wires (F3) that can be arranged on the theoretical outer layer (C3T) obtained when the inner layer (C1) is in direct contact with the theoretical outer layer (C3T).

Description

Two-layer wire rope with improved performance sheathed inner layer

The invention relates to metal cables which can be used in particular for reinforcing tires, particularly tires intended to equip vehicles carrying heavy loads and traveling at sustained speed, such as, for example, trucks, tractors, trailers or buses trucks, planes ...

A tire of the heavy-duty type with a radial carcass reinforcement comprises a tread, two inextensible beads, two sidewalls connecting the beads to the tread and a belt, or crown reinforcement, disposed circumferentially between the reinforcement carcass and tread. This vertex reinforcement includes several reinforcements with different functions.

The crown frame generally comprises a working frame comprising two working plies, or crossed plies, comprising wire working metal reinforcing elements arranged substantially parallel to each other in each working ply, but crossed by one ply to the other, that is to say inclined, symmetrically or not, with respect to the median circumferential plane, by an angle generally ranging from 15 ° to 40 °. This working reinforcement allows, among other functions, the at least partial transmission of the transverse forces exerted by the ground on the tire during the rolling of the latter in order to ensure the directionality of the tire, that is to say the capacity of the tire. tire to allow the vehicle on which it is mounted to turn.

[004] Certain current tires, called "road" tires, are intended to be driven at high speed and over increasingly long journeys, due to the improvement of the road network and the growth of the motorway network in the world. All the conditions under which such a tire is required to run undoubtedly allow an increase in the number of kilometers traveled, the wear of the tire being less; on the other hand, the endurance of the latter and in particular of the crown reinforcement is penalized. [005] The tire crown reinforcement must in a known manner meet various, often contradictory, requirements, in particular:

- be as rigid as possible with low deformation, because it contributes substantially to stiffening the crown of the tire;

- have as low a hysteresis as possible, on the one hand to minimize heating of the internal crown area during travel and on the other hand to reduce the rolling resistance of the tire, which is synonymous with fuel economy;

- finally have a high endurance, vis-à-vis in particular the phenomenon of separation, cracking of the ends of the crossed plies in the shoulder zone of the tire, known by the term "cleavage", which requires in particular metal cables which reinforce the working plies to present a high resistance to fatigue in compression, all in a more or less corrosive atmosphere.

[006] The third requirement is particularly strong for tire casings for industrial vehicles such as heavy goods vehicles, designed to be able to be retreaded one or more times when the treads which they comprise reach a critical degree of wear afterwards. prolonged taxiing.

For the reinforcement of the above working plies, so-called layered steel cables are generally used consisting of a central core and one or more layers of concentric son arranged around this core. The most used layered cables are essentially cables of M + N or M + N + P construction, formed of a core of M wire (s) surrounded by at least one layer of N wires possibly itself surrounded by an outer layer of P wires, the M, N or even P wires generally having the same diameter for reasons of simplification and cost.

For all the reasons explained above, the two-layer cables most used today in tire belts are essentially 3 + N construction cables made up of a core or internal layer of 3 internal metal wires. and an outer layer of N outer metal wires helically wound around the inner layer of the cable (eg 8 or 9 outer metal wires). The outer layer is relatively desaturated thanks to the large diameter of the inner layer provided by the presence of the three core threads, all the more so when the diameter of the core threads is chosen to be greater than that of the threads of the outer layer.

This type of construction promotes, as we know, the external penetrability of the cable by the calendering rubber of the tire or other rubber article during the curing of the latter, and consequently makes it possible to improve endurance. cables in fatigue and fatigue-corrosion, particularly vis-à-vis the problem of cleavage described above.

[010] The construction cables (M> 1) + N however have the drawback that they are not penetrable to the core because of the presence of a channel or capillary in the center of the N core wires, which remains empty after impregnation with the rubber and therefore conducive, by a sort of "wicking" effect, to the propagation of corrosive media such as water. This drawback of M + N construction cables is well known, it has been explained for example in patent applications WO 01/00922, WO 01/49926, WO 2005/071157, WO 2006/013077.

To solve the above problem, it has been proposed to open the inner layer, by separating its son, with a unitary core wire and to remove a wire from the outer layer; the cable thus obtained, of construction 1 + 3 + (P-1), becomes penetrable from the outside to its center. Relative to the wires of the inner layer, the core wire must be neither too thin, otherwise it does not produce the desired desaturation effect, nor too big without which the wire will not remain not in the center of the cable.

[012] This solution is first of all expensive since it requires adding a wire which does not otherwise contribute to the resistance of the cable; it also comes up against a manufacturing problem: a high tension on the core yarn is necessary to keep the yarn in the center of the cable during twisting, a tension which can in certain cases approach the breaking force of the yarn. Finally, the elimination of an external wire has the consequence of further reducing the resistance of the cable per unit of section.

[013] All of the above constraints are highly penalizing from an industrial point of view and contradict the search for high production rates.

[014] The aim of the invention is a cable with improved efficiency solving the problems mentioned above.

[015] CABLE ACCORDING TO THE INVENTION

[016] To this end, the invention relates to a two-layer cable, comprising:

- an internal layer made up of M> 1 internal metal wires,

- an outer layer of the cable consisting of N outer metal wires wound around the inner layer of the cable, in which: the cable is obtained by a process comprising a manufacturing step of the sheathed inner layer in which the inner layer is surrounded with an elastomeric composition having a thickness G then N external metal wires to form the external layer, with N being strictly greater than Nmax which is the maximum number of external metal wires that can be placed on the theoretical external layer obtained when the internal layer is directly in contact with the theoretical outer layer.

[017] Any interval of values designated by the expression “between a and b” represents the domain of values going from more than a to less than b (that is to say limits a and b excluded) while any interval of values designated by the expression “from a to b” signifies the range of values going from the limit “a” to the limit “b”, that is to say including the strict limits “a” and “b ".

[018] In the invention, the cable has two layers of son, that is to say it comprises an assembly consisting of two layers of son, no more and no less, that is to say that the assembly has two layers of wires, not one, not three, but only two.

[019] The inner layer of the cable is surrounded by an elastomeric composition having a thickness G and then it is surrounded by an outer layer.

[020] By directly in contact with the theoretical outer layer is meant that no sheath is arranged between the inner layer and the theoretical outer layer. The outer layer is thus placed as close as possible to the center in which the inner layer is circumscribed.

By elastomer composition or elastomeric composition is meant that the composition comprises at least one elastomer or one rubber (the two terms being synonymous) and at least one other component.

[022] The maximum number of outer wires having a diameter d3 which can be placed on the theoretical outer layer having a helix radius Rt and a helix angle at obtained when the inner layer is directly in contact with the theoretical outer layer, hereinafter referred to as Nmax is defined by the following formula:

Nmax = E (TÎ / arctan [(d3 / 2) ² / ((Rt ² - (d3 / 2) ² ) x cos ² at))] ^1/2 ) with, by definition, E is the integer value of the formula in parenthesis, the helix radius Rt of the theoretical outer layer of the cable is the radius of the theoretical circle passing through the centers of the outer wires of the theoretical outer layer in a plane perpendicular to the axis of the cable.

[023] The helix angle at is a quantity well known to those skilled in the art and can be determined by the following calculation at = Arctan [2p x Rt / P], formula in which P is the pitch expressed in millimeters to which each metallic wire element is wound and Rt is the helix radius of the theoretical outer layer of the cable expressed in millimeters and Arctan denoting the arctangent function.

[024] Unlike the state of the art in which the cables have an N = Nmax, the cable according to the invention has N> Nmax wires thus making it possible to increase the breaking force of the cable by adding at least minus one extra thread. The inventors behind the invention put forward the hypothesis that the presence of the sheath makes it possible, on the one hand, to create a sufficient arch around the internal layer making it possible to add an additional thread and, on the other hand, to relieve the contact pressures by a cushion effect between the inner layer and the outer layer thereby improving the performance of each of the son of the cable.

[025] It will be recalled that, in a known manner, the pitch of a wire represents the length of this wire, measured parallel to the axis of the cable in which it is located, at the end of which the wire having this pitch makes one turn. complete around said axis of the wire.

[026] The direction of winding of a layer of wires is understood to mean the direction formed by the wires relative to the axis of the cable. The direction of winding is commonly designated by the letter either Z or S.

[027] The pitches, winding direction and diameters of the wires are determined in accordance with ASTM D2969-04 of 2014.

[028] Advantageously, the cable is metallic. The term “metallic cable” is understood to mean by definition a cable formed of wires consisting mainly (that is to say for more than 50% of these wires) or entirely (for 100% of the wires) of a metallic material. Such a metallic cable is preferably implemented with a steel cable, more preferably made of pearlitic (or ferrito-pearlitic) carbon steel hereinafter referred to as "carbon steel", or even stainless steel (by definition, steel comprising at least 11% chromium and at least 50% iron). But it is of course possible to use other steels or other alloys.

[029] When a carbon steel is advantageously used, its carbon content (% by weight of steel) is preferably between 0.05% and 1.2%, in particular between 0.4% and 1.1. %; these contents represent a good compromise between the mechanical properties required for the tire and the feasibility of the cords.

[030] The metal or steel used, whether it is in particular a carbon steel or a stainless steel, can itself be coated with a metal layer improving, for example, the setting properties. use of the metallic cable and / or its constituent elements, or the properties of use of the cable and / or the tire themselves, such as the properties of adhesion, resistance to corrosion or even resistance to aging. According to a preferred embodiment, the steel used is covered with a layer of brass (Zn-Cu alloy) or of zinc.

[031] Preferably, the wires of the same layer (internal or external) all have substantially the same diameter. Advantageously, the outer cords all have substantially the same diameter. By “substantially the same diameter” is meant that the wires have the same diameter within industrial tolerances.

[032] Advantageously, the outer threads are wound helically around the inner thread at a pitch ranging from 10 to 30 mm.

[033] Preferably, the threads do not undergo preformation.

[034] Advantageously, N = Nmax + 1 or Nmax + 2 and preferably N = Nmax + 1. In order to limit the external diameter of the cable, those skilled in the art will be able to adapt the thickness G of elastomeric composition necessary for a good compromise between contact pressure and improved breaking strength. The outer layer comprises a relatively high number of outer threads and therefore exhibits a relatively high breaking strength.

[035] Advantageously, the ratio of the diameter d1 of the or each internal metal wire to the diameter d3 of each external metal wire ranges from 0.9 to 1.2.

[036] Advantageously, the diameter d1 of the or each internal metal wire is equal to the diameter d3 of each external metal wire. Thus, the same diameter is preferably used for the internal metal wire (s) and for the external metal wires, which limits the number of different diameters to be managed during the manufacture of the cable.

[037] Advantageously, the outer layer of the cable is saturated so that the inter-wire distance of the outer metal wires is strictly less than 20 μm.

[038] By definition, a saturated cable layer is such that the inter-wire distance of the outer metal wires is strictly less than 20 μm. The inter-wire distance of the outer layer of outer wires is defined, on a section of the cable perpendicular to the main axis of the cable, as the shortest distance that separates, on average, two metallic wires external adjacent. Thus, this construction of the cable makes it possible to ensure good architectural stability of the outer layer and the saturation of the outer layer makes it possible to ensure that the outer layer comprises a relatively high number of outer metal wires and therefore has a breaking force. relatively high.

[039] Preferably, the inter-wire distance of the outer metal wires is less than or equal to 100 μm. In contrast, a desaturated cable layer is such that the inter-wire distance of the outer metal wires is greater than or equal to 20 μm.

[040] Advantageously, the thickness G of the sheath of elastomeric composition is strictly greater than 10 μm, preferably greater than or equal to 12 μm and more preferably greater than or equal to 15 μm. The greater the thickness G of the elastomeric composition, the more metallic threads can be added to the outer layer and the capillaries between the threads filled.

[041] Advantageously, the thickness G of the sheath of elastomeric composition is less than or equal to 300 μm, preferably less than or equal to 250 μm and more preferably less than or equal to 230 μm. This thickness makes it possible to optimize the relatively high number of external metal wires and therefore to have a relatively high breaking force while limiting the external diameter of the cable.

[042] Advantageously, the elastomeric composition comprises an elastomer chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, isoprene copolymers, and mixtures of these elastomers.

[043] Preferably, the elastomeric composition comprises an elastomer chosen from the group consisting of natural rubber, synthetic polyisoprenes, isoprene copolymers, and mixtures of these elastomers.

[044] Preferably, the elastomer composition also comprises a vulcanization system, a filler. More preferably, the elastomer is diene.

[045] Preferably, the elastomeric composition comprises carbon black as reinforcing filler.

[046] Advantageously, M = 2, 3 or 4 and preferably M = 3 or 4. The most severe transverse forces exerted in the cable when the latter is placed in tension are the transverse forces exerted between internal metal wires.

[047] In the state of the art, cables are known having an architecture in which M> 1 and comprising a number of external metal wires such that the external layer of the cable is saturated so as to maximize the breaking force by adding a maximum number of external metal wires. Here, for the cable according to the invention having an architecture in which M> 1, thanks to the formation of a cushion of elastomer composition at least partially absorbing the transverse forces exerted between the internal metal wires, the cable exhibits a markedly improved breaking strength.

[048] Advantageously, N = 9, 10, 11 or 12, preferably N = 10 or 11.

[049] Advantageously, each metal wire respectively has a diameter d 1, d3 ranging from 0.22 mm to 0.60 mm and preferably from 0.22 mm to 0.50 mm.

[050] In a first variant, M = 2 and N = 9 or 10.

[051] In a second variant, M = 3 and N = 10.

[052] In a third variant, M = 4 and N = 11.

[053] In these three cable variants according to the invention, the transverse forces exerted between the internal metal wires are absorbed by the sheath and the cable has an improved breaking force due to the presence of an external metal wire. additional while limiting its external diameter.

[054] REINFORCED PRODUCT ACCORDING TO THE INVENTION

[055] Another object of the invention is a reinforced product comprising an elastomeric matrix and at least one cable as defined above.

[056] Advantageously, the reinforced product comprises one or more cables according to the invention embedded in the elastomeric matrix, and in the case of several cables, the cables are arranged side by side in a main direction.

[057] PNEUMATICS ACCORDING TO THE INVENTION

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

[059] Preferably, the tire comprises a carcass reinforcement anchored in two beads and surmounted radially 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 cable as defined above.

[060] In a preferred embodiment, the crown frame comprises a protective frame and a working frame, the working frame comprising at least one cable as defined above, the protective frame being radially interposed between the tread and the working reinforcement.

[061] The cable is particularly intended for industrial vehicles chosen from heavy vehicles such as "Heavy goods" - ie, metro, bus, road transport vehicles (trucks, tractors, trailers), off-road vehicles - , agricultural or civil engineering machinery, other transport or handling vehicles.

[062] Preferably, the tire is for a heavy vehicle type vehicle. [063] The invention will be better understood on reading the examples which follow, given solely by way of non-limiting examples and made with reference to the drawings in which:

- Figure 1 is a sectional view perpendicular to the circumferential direction of a tire according to the invention;

- Figure 2 is a sectional view of a reinforced product according to the invention;

- Figure 3 is a schematic sectional view perpendicular to the cable axis (assumed rectilinear and at rest) of a cable (50) according to a first embodiment of the invention;

- Figure 4 is a view similar to that of Figure 3 of a cable (50 ’) according to a second embodiment of the invention;

- Figure 5 is a view similar to that of Figure 3 of a cable (50 ") according to a third embodiment of the invention.

[064] EXAMPLE OF A TIRE ACCORDING TO THE INVENTION

[065] In Figure 1, there is shown a reference X, Y, Z corresponding to the usual respectively axial (X), radial (Y) and circumferential (Z) orientations of a tire. [066] The “median circumferential plane” M of the tire is the plane which is normal to the axis of rotation of the tire and which is located equidistant from the annular reinforcing structures of each bead.

[067] There is shown in Figure 1 a tire according to the invention and designated by the general reference 10.

[068] The tire 10 is for a heavy-duty vehicle. Thus, the tire 10 has a dimension of the 315/80 R 22.5 type.

[069] This tire 10 comprises a crown 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a bead wire 5. The crown 2 is surmounted by a strip of bearing not shown in this schematic figure. A carcass reinforcement 7 is wound around the two bead wires 5 in each bead 4, the upturn 8 of this reinforcement 7 being for example disposed towards the outside of the tire 10 which is shown here mounted on its rim 9. The carcass reinforcement 7 is in a manner known per se consisting of at least one ply reinforced by so-called "radial" cables, that is to say that these cables are arranged practically parallel to each other and extend from one bead to the other. the other so as to form an angle of between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is located midway between the two beads 4 and passes through the middle of the 'crown reinforcement 6).

[070] The tire according to the invention is characterized in that its belt 6 comprises at least, as reinforcement of at least one of the belt plies, a two-layer metal cable according to the invention. In this belt 6, it will be understood that the cables of the invention can for example reinforce all or part of the so-called working belt plies. Of course, this tire 10 also comprises, in a known manner, an inner layer of rubber or elastomer (commonly called "inner rubber") which defines the radially internal face of the tire and which is intended to protect the ply from casing of the air diffusion coming from the space inside the tire.

[071] EXAMPLE OF A REINFORCED PRODUCT ACCORDING TO THE INVENTION [072] There is shown in Figure 2 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 the species several cables 50, embedded in the elastomeric matrix 102.

[073] In Figure 2, there is shown the elastomeric matrix 102, the cables 50 in an X, Y, Z frame in which the Y direction is the radial direction and the X and Z directions are the axial and circumferential directions. In Figure 3, the reinforced product 100 comprises several cables 50 arranged side by side in the main direction X and extending parallel to each other within the reinforced product 100 and collectively embedded in the elastomeric matrix 102.

[074] CABLE ACCORDING TO A FIRST EMBODIMENT OF THE INVENTION

[075] There is shown in Figure 3 the cable 50 according to a first embodiment of the invention.

[076] The cable 50 is metallic and has two layers. Thus, it is understood that the layers of metal son constituting the cable 50 are two in number, no more, no less.

[077] The cable 50 comprises an internal layer C1 of the cable consisting of M> 1 internal metal wires F1. In this case, M = 2, 3 or 4 and preferably M = 3 or 4, here M = 2. The internal layer C1 is surrounded by an elastomeric composition having a thickness G then forming the internal sheathed layer CIG. The outer layer C3 consists of N> Nmax outer metal wires F3 wound around the internal sheathed layer CIG of the cable.

Nmax = E (n / arctan [(d3 / 2) ² / ((Rt ² - (d3 / 2) ² ) x cos ² at))] ^1/2 ) = E (n / arctan [(0.30 / 2) ² / ((0.47 ² - (0.30 / 2) ² ) x cos ² (3.14x10.9 / 180)))] ^1/2 ) = E (9.58) = 9. In this case, N = 9,10, 11 or 12, preferably N = 10 or 11 and N = Nmax + 1 = 9 + 1 = 10.

[078] Each internal metal wire F1 and each external metal wire F3 respectively has a diameter d1 and d3. The diameter d1 of each inner metal wire F1 is preferably equal to the diameter d3 of each outer metal wire F3.lci d1 = d3 = 0.30 mm.

[079] The outer layer C3 of the cable is saturated. The inter-wire distance of the outer wires is strictly less than 20 μm and here is equal to 0 μm.

[080] Each wire has a tensile strength, denoted Rm, such that 2500 <Rm <3100 MPa. The steel of these wires is said to be of SHT (“Super High Tensile”) grade. Other yarns can be used, for example lower grade yarns, for example of grade NT ("Normal Tensile") or HT ("High Tensile"), such as higher grade yarns, for example of UT grade (" Ultra Tensile ”) or MT (“ Mega Tensile ”). [081] CABLE MANUFACTURING PROCESS ACCORDING TO THE INVENTION

[082] The cable according to the invention is manufactured using a process comprising steps well known to those skilled in the art.

[083] The cable described above is manufactured according to known processes comprising the following steps, preferably carried out online and continuously:

- first, a first assembly step by twisting the M> 1 internal threads F1 of the internal layer C1 at the pitch p1 and in the S direction to form the internal layer C1 at a first assembly point;

- followed by a second manufacturing step of the internal sheathed layer CIG, the internal layer C1 is surrounded with an elastomeric composition having a thickness G then the N external metal wires F3 are assembled by twisting around the internal layer CIG at the pitch p3 and in the S direction to form the assembly of the CIG and C3 layers, with N being strictly greater than Nmax which is the maximum number of external metal wires F3 that can be placed on the theoretical external layer C3T obtained when the internal layer C1 is directly in contact with the theoretical outer layer C3T;

- preferably a final torsion balancing step.

[084] The term "torsional balancing" is understood here to mean, in a manner well known to those skilled in the art, the cancellation of the residual torsional torques (or of the elastic torsional return) exerted on each wire, in the layer. intermediate as in the outer layer.

[085] After this final torsion balancing step, cable manufacturing is complete.

[086] In this case, N> Nmax = 9, here N = 10.

[087] The thickness G of the sheath of elastomeric composition is strictly greater than 10 μm, preferably greater than or equal to 12 μm and more preferably greater than or equal to 15 μm and the thickness G is less than or equal to 300 μm, preferably less than or equal to 250 μm and more preferably less than or equal to 230 μm. Here, G = 71 µm.

[088] The elastomeric composition comprises a vulcanization system, a filler and a diene elastomer.

[089] As elastomeric composition, use is made of a composition of diene elastomer (s) conventional for tires, based on natural rubber (peptized) and carbon black N330 (65 phr), further comprising the usual additives. following: sulfur (7 pce), sulfenamide accelerator (1 pce), ZnO (8 pce), stearic acid (0.7 pce), antioxidant (1.5 pce), cobalt naphthenate (1.5 pce) (pce meaning parts by weight per hundred parts of elastomer); the E10 modulus of the elastomeric coating composition is approximately 10 MPa.

[090] Optionally, in a final assembly step, the hoop F is wound at the pitch pf in the Z direction around the assembly obtained previously.

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

[092] The composite fabrics reinforced by these cables comprise a matrix of elastomeric composition formed of two thin layers of elastomeric composition which are superimposed on either side of the cables and which respectively have a thickness ranging from 0.6 and 1.5. mm. The calendering pitch (laying of cables in the fabric of elastomeric composition) ranges from 1 mm to 4 mm.

[093] These composite fabrics are then used as a working ply in the crown reinforcement during the tire manufacturing process, the steps of which are also known to those skilled in the art.

[094] CABLE ACCORDING TO A SECOND EMBODIMENT OF THE INVENTION [095] FIG. 4 shows a cable 50 ’according to a second embodiment of the invention. Elements similar to the first embodiment are designated by identical references.

[096] Unlike the first embodiment described above, the cable 50 ’according to the second embodiment is such that M = 3 and L = 10.

[097] CABLE ACCORDING TO A THIRD EMBODIMENT OF THE INVENTION [098] FIG. 5 shows a cable 50 ”according to a third embodiment of the invention. Elements similar to the first embodiment are designated by identical references.

[099] Unlike the first embodiment of the cable 50 described above, the cable 50 ”according to the third embodiment is such that M = 4 and L = 11.

[0100] Table 1 below summarizes the characteristics for the different cables 50, 50 'and 50 ".

[0101] Table 1

[0102] COMPARATIVE TESTS

[0103] Variation of the NMAX as a function of the diameter of the wires

[0104] Tables 2, 3 and 4 below have summarized the characteristics for the variations in diameter for the various cables 50, 50 'and 50 "and the Nmax was calculated.

[0105] Table 2

[0106] Table 3

[0107] Table 4 [0108] TESTS OF RESISTANCE TO RUPTURE

[0109] This test makes it possible to determine the breaking strength of the cables tested, by measuring the breaking force noted Fm (maximum load in N) carried out in tension according to the ISO 6892-1 standard of October 2009.

[0110] Table 5 summarizes the characteristics of the indicator cable T1, of comparative cables C1 and C2 not in accordance with the invention.

[0111] Table 5 the indicator cable T1, the comparative cables C1 and C2 and the cable 50 ′ according to the invention. The results of these tests are given in base 100. Thus, a result greater than 100 for one or other of these tests means that the cable tested has a breaking force greater than the control cable. In the same table, we also compared the breaking force related to the diameter of the cable.

[0113] Table 6

[0114] It is noted that the cable 50 ’according to the invention has a breaking force of the same order as that of the comparative cable C2 and better compared to the control cable T1 and the comparative cable C1.

It is noted that the breaking force reduced to the diameter of the cable is significantly greater than that of the control cable T1 and that of the comparative cables C1 and C2 with improved penetrability. The cable according to the invention has a better arrangement of the wires in the same space. This test clearly demonstrates that the presence here of the sheath of elastomeric composition making it possible to put two additional threads on the outer layer in accordance with the invention makes it possible to obtain an arching effect and thus a more effective participation of each thread in the breaking force. of the cable compared to the T1 cable and thus solve the problems mentioned in the preamble.

Of course, the invention is not limited to the embodiments described above.

For reasons of industrial feasibility, cost and overall performance, it is preferred to implement the invention with linear threads, that is to say straight, and of conventional circular cross section.

It is also possible to combine the characteristics of the various embodiments described or envisaged above, provided that they are compatible with one another.

Claims

1. Two-layer wire rope (50), characterized in that it comprises:

- an internal layer (C1) made up of M> 1 internal metal wires (F1),

- an outer layer (C3) of the cable consisting of N outer metal wires (F3) wound around the inner layer (C1) of the cable, in which: the cable (50) is obtained by a process comprising a step of manufacturing the sheathed internal layer (CIG) in which the internal layer (Cl) is surrounded by an elastomeric composition having a thickness G then N external metal wires to form the external layer (C3), with N being strictly greater than Nmax which is the maximum number of outer metal wires (F3) that can be placed on the theoretical outer layer (C3T) obtained when the inner layer (C1) is directly in contact with the theoretical outer layer (C3T).

2. Cable (50) according to the preceding claim, wherein N = Nmax + 1 or Nmax + 2 and preferably N = Nmax + 1.

3. Cable (50) according to any one of the preceding claims, wherein the diameter d1 of each inner metal son (F1) is equal to the diameter d3 of each outer metal son (F3).

4. Cable (50) according to any one of the preceding claims, wherein the outer layer (C3) of the cable is saturated so that the inter-wire distance of the outer metal wires (F3) is strictly less than 20 µm.

5. Cable (50) according to any one of the preceding claims, in which the thickness G of the sheath of elastomeric composition is strictly greater than 10 μm, preferably greater than or equal to 12 μm and more preferably greater than or equal to 15. pm.

6. Cable (50) according to any one of the preceding claims, in which the thickness G of the sheath of elastomeric composition is less than or equal to 300 μm, preferably less than or equal to 250 μm and more preferably less than or equal to 230 pm.

7. Cable (50) according to any one of the preceding claims, in which the sheath of elastomeric composition comprises an elastomer chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, copolymers. of isoprene, and mixtures of these elastomers.

8. Cable (50) according to the preceding claim, wherein the elastomeric composition sheath comprises an elastomer selected from the group consisting of natural rubber, synthetic polyisoprenes, isoprene copolymers, and mixtures of these elastomers.

9. Cable (50) according to any one of the preceding claims, in which the sheath of elastomeric composition comprises carbon black as reinforcing filler.

10. Cable (50) according to any one of the preceding claims, wherein M = 2, 3 or 4 and preferably M = 3 or 4.

11. Cable (50) according to any one of the preceding claims, wherein N = 9,10, 11 or 12, preferably N = 10 or 11.

12. Cable (50) according to any one of the preceding claims, wherein each metal wire (F1, F3) respectively has a diameter d 1, d3 ranging from 0.22 mm to 0.60 mm and preferably from 0, 22 mm to 0.50 mm.

13. Reinforced product (100), characterized in that it comprises an elastomeric matrix (102) and at least one cable (50) according to any one of claims 1 to 12.

14. A tire (10), characterized in that it comprises at least one cable (50) according to any one of claims 1 to 12 or a reinforced product according to claim 13.