WO2014090998A2 - Steel cord comprising cylindrical layers of structure 2+9+14 - Google Patents

Abstract

The invention relates to a steel cord (30) comprising cylindrical layers, said cord including: an inner layer (C1) formed by 2 wires, an intermediate layer (C2) formed by 9 wires helically wound around the inner layer (C1), and an outer layer (C3) formed by 14 wires helically wound around the intermediate layer (C2).

Description

 Wire rope with cylindrical layers of structure 2 + 9 + 14

 [001] The invention relates to cylindrical layer cables used in particular for the reinforcement of tires, particularly tires for heavy industrial vehicles.

 [002] A radial carcass reinforcement tire comprises a tread, two inextensible beads, two flanks connecting the beads to the tread and a belt, or crown reinforcement, arranged circumferentially between the carcass reinforcement and the band. rolling. This crown reinforcement comprises several layers of rubber, possibly reinforced by reinforcing elements or reinforcements such as cables or monofilaments, of metal or textile type.

 [003] The tire crown reinforcement generally consists of at least two superimposed layers, sometimes called working plies or crossed plies, whose reinforcing cables, generally metallic, are arranged substantially parallel to each other at the same time. interior of a web, but crossed from one web to another, that is to say inclined, symmetrically or otherwise, with respect to the median circumferential plane, of an angle which is generally between 10 ° and 45 ° depending on the type of tire considered. The crossed plies may be supplemented by various other plies or layers of auxiliary gum, of varying widths depending on the case, with or without reinforcements. By way of example, simple rubber cushions may be mentioned, so-called protective layers intended to protect the rest of the crown reinforcement from external aggressions, perforations, or so-called hooping plies comprising reinforcements oriented substantially according to the invention. circumferential direction (so-called zero-degree plies), whether radially external or internal with respect to the crossed plies.

[004] A tire of heavy industrial vehicle, including civil engineering, is subjected to many stresses and mechanical stresses, including compression. Indeed, the rolling of this type of tire is usually done on a rough coating mechanically soliciting the tread but also the crown reinforcement significantly. In addition, the rough coating sometimes leads to perforations of the tread. These perforations allow the entry of corrosive agents, for example air and water, which oxidize the metal reinforcements of the crown reinforcement and considerably reduce the life of the tire. [005] The working plies are generally reinforced by so-called strand cords ("strand cords") which have a high breaking force. In particular, the state of the art is known of a strand cable comprising a core strand and a plurality of strand strands, each strand comprising one or more core strands surrounded by an intermediate layer of N strands, optionally itself surrounded by an outer layer of P son, the assembly may be optionally shrunk by a hooping layer. Thus, strand cables of structure (1 + 6) + 6x (1 + 6) or (3 + 9) + 8x (1 + 6) are known.

 In order to improve the compressive strength of the cable, it has been proposed many modifications of the structure of the cable and the materials constituting the son of the different layers, in particular to increase the breaking force of the cable.

[007] In order to improve the corrosion resistance, it has been proposed to modify their construction in order to increase in particular their penetrability by the rubber, and thus to limit the risks due to fatigue corrosion. Indeed, it is sought that the cable is impregnated as much as possible by the rubber, that this material penetrates into all the spaces between the son constituting the cable. If this penetration is insufficient, then empty channels or capillaries are formed along the cable, and the corrosive agents capable of penetrating the tire, for example as a result of perforations or other attacks on the crown of the tire, travel along these channels through the crown reinforcement of the tire. The presence of this moisture plays an important role in causing corrosion and accelerating fatigue processes (so-called fatigue-corrosion phenomena), compared to use in a dry atmosphere.

 [008] However, these improvements in compressive strength and corrosion are often, if not always, incompatible or even contradictory with the other criteria specific to the use and manufacture of the cable, in particular industrial cost, uniformity, industrial feasibility or resistance to shocks and perforations.

 [009] Thus, most of the time, the characteristics of the stranded cable are chosen so as to favor a high-breaking force of the cable, with respect to the resistance to corrosion.

 [010] The invention therefore aims a cable both resistant to corrosion and compression.

 [011] For this purpose, the subject of the invention is a cylindrical wire rope comprising:

an inner layer consisting of 2 wires, an intermediate layer consisting of 9 wires wound helically around the inner layer,

 an outer layer consisting of 14 wires wound helically around the intermediate layer.

[012] The cable according to the invention has high compressive strengths and corrosion resistance.

 [013] Unlike the strand cables of the state of the art, the inventors at the origin of the invention discovered that the problems of resistance to compression and corrosion could be solved synergistically by a cable layer with high penetration by the gum having unsaturated intermediate and outer layers. Thus, the structure of the cable according to the invention is highly penetrable and has a higher compressive strength than a moderately or poorly penetrable cable and having comparable or even superior mechanical properties.

[014] Unlike strand cables of the state of the art in which it seeks to protect the cable essentially against the alteration of its mechanical properties, including its breaking strength, consecutive direct corrosion by corrosive agents, inventors at the origin of the invention have discovered that the high penetrability of the cable according to the invention on the one hand, to protect the cable against the action of corrosive agents and on the other hand, to increase the resistance compression thanks to a self-hoop conferred by the rubber having penetrated into the cable.

 [015] Indeed, the inventors at the origin of the invention have identified that the most detrimental effect of the corrosive agents was not so much the alteration of the mechanical properties of the cable, in particular its breaking force, that the loss of adhesion between the yarns and the adjacent gum subsequent to corrosion of the adhesion interface by these corrosive agents. When it occurs, this loss of adhesion leads to a separation of the cable of its adjacent eraser. Once disconnected, the cable then slides in a sheath formed by the adjacent rubber and no longer takes the forces exerted on the tire. It is therefore less resistant to compression. On the contrary, the cable according to the invention makes it possible to preserve the adhesion between the wires and the adjacent rubber. The cable according to the invention thus cooperates with the rubber to take up the forces exerted on the tire and is therefore more resistant to compression.

[016] The cable is of the tubular or cylindrical layer type. By cables with tubular or cylindrical layers is meant cables consisting of a core comprising an inner layer, and optionally a core or a core, and one or more concentric layers, here the intermediate and outer layers, each of cylindrical or tubular shape, arranged around this core, such that, at least in the cable at rest, the thickness of each intermediate and outer layer is substantially equal to the diameter of the son constituting it; As a result, the cross section of the cable has a substantially circular outline or envelope.

[017] The cables with cylindrical or tubular layers of the invention should in particular not be confused with so-called "compact" layer cables, wire assemblies wound at the same pitch and in the same direction of winding. In such compact cables, the compactness is such that virtually no separate layer of wires is visible; As a result, the cross-section of such cables has a contour that is no longer circular, but polygonal.

 [018] A cable with tubular or cylindrical layers, also called non-compact cable, is a cable in which at least two layers of son have a pitch or a direction of winding different from each other.

 In one embodiment, the wires of the inner layer are wound helically. In another embodiment, the wires of the inner layer are rectilinear, that is to say, has an infinite pitch.

 [020] By wire means, by definition a cable formed of son consist predominantly (that is to say, for more than 50% of these son) or integrally (for 100% son) of a metal material. The invention is preferably implemented using a steel cable, more preferably a carbon pearlitic (or ferritoclastic) steel, hereinafter referred to as "carbon steel", or else stainless steel (by definition, steel comprising at least one minus 11% chromium and at least 50% iron). But it is of course possible to use other steels or other alloys. The wires are preferably made of steel, more preferably of carbon steel.

 [021] When carbon steel is used, its carbon content (% by weight of steel) is preferably between 0.4% and 1.2%, especially between 0.5% and 1.1%. ; these levels represent a good compromise between the mechanical properties required for the tire and the feasibility of the wires. It should be noted that a carbon content of between 0.5% and 0.6% makes such steels ultimately less expensive because easier to draw. Another advantageous embodiment of the invention may also consist, depending on the applications concerned, of using steels with a low carbon content, for example between 0.2% and 0.5%, in particular because of a cost lower and easier to draw.

[022] The metal or steel used, whether it is in particular a carbon steel or a stainless steel, may itself be coated with a metal layer improving, for example, the setting properties. of the metal cable and / or its constituent elements, or the properties of use of the cable and / or the tire themselves, such as adhesion properties, corrosion resistance or resistance to aging.

 [023] According to a preferred embodiment, the steel used is covered with a layer of brass (Zn-Cu alloy) or zinc. It is recalled that during the manufacturing process of the son, the coating of brass or zinc facilitates the drawing of the wire, as well as the bonding of the wire with the eraser. But the son could be covered with a thin metal layer other than brass or zinc, having for example the function of improving the corrosion resistance of these son and / or their adhesion to the gum, for example a thin layer Co, Ni, Al, an alloy of two or more of Cu, Zn, Al, Ni, Co, Sn.

 [024] The skilled person knows how to manufacture steel son having such characteristics, in particular by adjusting the composition of the steel and the final work hardening rates of these son, according to his own particular needs, in for example using micro-alloyed carbon steels containing specific addition elements such as Cr, Ni, Co, V, or various other known elements (see for example Research Disclosure 34984 - "Micro-alloyed steel cord constructions for tires" - May 1993, Research Disclosure 34054 - "High tensile strength steel cord constructions for tires" - August 1992).

[025] The interleaf distance of a layer is defined, on a section of the cable perpendicular to the main axis of the cable, as the smallest distance separating, on average on said layer, two adjacent wires of said layer. Thus, channels allow the passage of the rubber, firstly through the outer layer and secondly through the intermediate layer to effectively penetrate the rubber in the cable during the vulcanization of the tire.

 [026] In one embodiment, the inter-wire distance D2 of the wires of the intermediate layer is greater than or equal to 25 μηη.

 [027] Thus, the cable has a relatively high interfilial distance D2, which improves the penetrability of the intermediate layer.

[028] Preferably, the interfering distance D2 of the wires of the intermediate layer is greater than or equal to 30 μηι, preferably 40 μηη and more preferably 50 μηι.

[029] By increasing the interfering distance D2, it is more favored the passage of the gum through the intermediate layer.

[030] In another embodiment, the inter-wire distance D3 of the wires of the outer layer is greater than or equal to 25 μηι. [031] Preferably, the interfilial distance D3 of the outer layer of the son is greater than or equal to 30 μηι, preferably 40 μηι and more preferably 50 μηι. By increasing the interfering distance D3, the passage of the gum through the outer layer is further promoted.

[032] Preferably, the inter-wire distance D2 of the wires of the intermediate layer is less than or equal to 100 μηη. Thus, it improves the strength and cohesion of the cable and its breaking force.

 [033] Preferably, the inter-wire distance D3 of the wires of the outer layer is less than or equal to 100 μηη. Thus, it also improves the strength and cohesion of the cable and its breaking force.

 [034] Preferably, the ratio D2 / D3 satisfies 0.5 <D2 / D3 <1.5, preferably 0.7 <D2 / D3 <1.3, more preferably 0.8 <D2 / D3 <1, 2 and even more preferably 0.9 <D 2 / D 3 <1.1.

 [035] The passage channels of the eraser comprise an external opening allowing the rubber to penetrate from the outside of the cable to the inside of the cable and an internal opening allowing the rubber to open into the heart of the cable, for example to contact of the inner layer. In order to ensure maximum penetration of the rubber, the outer and inner openings preferably have relatively close dimensions. Thus, the penetration of the rubber is optimized by avoiding that one of the external and internal openings of each passage channel limits the flow of gum.

 [036] Advantageously, the diameters d1 and d2 of the wires respectively of the inner and intermediate layers satisfy d1 / d2≥1, preferably d1 / d2> 1. Thus, in the case where d1 / d2> 1, the desaturation of the intermediate and external layers is increased, which favors the penetrability of the cable by the rubber. In the case where d1 = d2, it will be preferred to have d3 <d2 so as to increase the desaturation of the outer layer which promotes the penetrability of the cable by the rubber.

[037] The penetrability of the cable is amplified for cables that preferentially use wires for which, independently of each other, each diameter d1, d2, d3 of each wire respectively of each inner, intermediate and outer layer satisfies 0.15 mm < d1, d2, d3 <0.5 mm, preferably 0.22 mm <d1, d2, d3 <0.5 mm, more preferably 0.25 mm <d1, d2, d3 <0.5 mm and even more preferentially 0.30 mm <d1, d2, d3 <0.4 mm. These diameters make it possible to obtain an optimized compromise of compressive strength and endurance when the cable is used in particular in a crown reinforcement. To obtain an optimized compromise of compressive strength and endurance when the cable is used in particular in a carcass reinforcement, use will be made of preferably wires such as 0.15 mm <d1, d2, d3 <0.30 mm and more preferably such as 0.15 mm <d1, d2, d3 <0.26 mm.

 [038] Preferably, the diameters d1 and d2 of the wires respectively of the inner and intermediate layers satisfy 1, 05 <d1 / d2 <1, 3, preferably 1, 10 <d1 / d2 <1, 3 mm and more preferably 1 , <D1 / d2 <1, 3 mm. The d1 / d2 ratio should not be too small as this will reduce the penetrability of the cable. The ratio d1 / d2 must not be too big or it will unduly saturate the cable and thus adversely affect the good distribution of the wires. Thus, the ratio d1 / d2 makes it possible to obtain inter-wire distances D2, D3 that are not very dispersed, that is to say a homogeneous desaturation over the entire circumference of the cable. In addition, inner layer wires of too large diameter would cause an increase in the rigidity of the cable which would impair its ability to flex under tension.

 [039] In a preferred embodiment, each diameter d1, d2, d3 of each wire respectively of each inner, intermediate and outer layer verifies d1> d2 and / or d1> d3 which makes it possible to easily allow the passage of the eraser. between the wires of the intermediate and outer layers.

 [040] Even more preferably, each diameter d2, d3 of each wire of each intermediate and outer layer respectively d2 = d3 check which allows a simple cable design and therefore a manufacturing process easy to implement.

 [041] It is recalled here that, in a known manner, the pitch represents the length, measured parallel to the axis of the cable, at the end of which a wire having this pitch performs a complete revolution about said axis of the cable.

 [042] According to optional features independent of each other relating to the pitch of each wire of each layer:

 The wires of the inner layer are wound at a pitch p1 which satisfies <p1 <1 1 mm, preferably 7 <p1 <9 mm.

 The wires of the intermediate layer are wound at a pitch p2 which satisfies 8 <p2 <20 mm, preferably 12 <p2 <18 mm.

 The strands of the outer layer are wound at pitch p3 which satisfies 12 <p3 <30 mm, preferably 20 <p3 <28 mm.

[043] The steps of the different layers thus make it possible to obtain a cable having a relatively high tensile strength but having an elasticity adapted to its use, in particular as a reinforcement of the crown reinforcement or carcass of the tire. [044] Advantageously, the winding steps p1 and p2 of the wires of the inner and intermediate layers respectively, satisfy 0.4 <p1 / p2 <0.8 and preferably 0.5 <p1 / p2 <0.7. Such a ratio of steps p1 / p2 makes it possible to increase the number of gum passage channels between the inner and intermediate layer yarns while ensuring that each inner and intermediate layer has a contribution substantially equivalent to the breaking force of the cable. Indeed, not too close, that is to say for a p1 / p2 ratio greater than 0.8, lead to a compact cable having no gum passage channel. On the other hand, relatively different steps, that is to say for a ratio p1 / p2 of less than 0.4, would lead to the premature rupture of the strands of the layer having the highest pitch, which would make the layer presenting the least useless step to the resistance of the cable at break.

 [045] Advantageously, the winding steps p2 and p3 of the strands respectively of the intermediate and external layers satisfy 0.5 <p2 / p3 <0.9 and preferably 0.6 <p2 / p3 <0.8. In a similar manner to the above, such a ratio of p2 / p3 steps makes it possible to increase the number of gum passage channels between the yarns of the intermediate and external layers while ensuring that each intermediate and external layer has a substantially equivalent contribution. the breaking force of the cable.

[046] Preferably, the cable comprises a hooping layer comprising a hoop wire wrapped around the outer layer.

 [047] In the case where it is desired to confer on the cable, in addition to the self-locking properties described above, a further improved compressive strength, a shrinking layer is added which relieves the inner, intermediate layers. and external vis-à-vis the compression and thus improves the endurance of the cable.

[048] Such a hooping layer consists for example of a single wire, metallic or not. It is advantageous to choose a stainless steel hoop wire in order to reduce fretting wear of the wires of the outer layer in contact with the stainless steel hoop, the stainless steel wire possibly being replaced, in an equivalent manner, by a composite wire of which only the skin is made of stainless steel and the carbon steel core.

 [049] Optionally, the hoop wire is wound in pitch pf which verifies pf <10 mm, preferably pf <8 mm and more preferably pf <6 mm. Preferably, the direction of winding of the yarn of the hooping layer is different from the winding direction of the yarns of the outer layer.

[050] In one embodiment, the winding directions of the inner, intermediate and outer layer wires are all identical. Coiling in the same direction of the layers advantageously makes it possible to reduce the contact pressures between the wires of the different layers thus to obtain a cable with a high breaking strength. Thus, in this embodiment, all the layer son are wound either in the direction S (arrangement denoted "S / S / S"), or in the direction Z (arrangement denoted "Z / Z / Z").

[051] The winding in the same direction of the layers is made possible in particular by the high penetrability of the cable by the rubber which gives the cable auto-hooping properties described above.

 [052] In another embodiment, the winding direction of the outer layer son is different from that of the son of the intermediate layer. In the case where it is desired to promote the penetration of the rubber, it crosses the winding directions of the intermediate and outer layers which has the effect of increasing the number of passage channels. As explained above, the high penetrability of the cable of this embodiment makes it possible to effectively recover the forces due to its excellent adhesion to the adjacent rubber, which largely offsets a lower breaking force than in the previous embodiment. Thus, in this embodiment, the cable has an S / S / Z, Z / Z S, S / Z / S or Z / S / Z layout.

[053] In another embodiment, the winding direction of the inner layer of son is different from that of the son of the intermediate layer.

[054] In a similar manner to the previous embodiment, it increases the number of passage channels between the inner and intermediate layers and therefore the compressive strength. Thus, in this embodiment, the cable has an S / Z / S, Z / S / Z, S / Z / Z or Z / S / S layout.

 [055] Note that the winding direction has no influence on the values of D2 and D3.

[056] Preferably, the wires of the inner layer are non-preformed. Thus, the cable manufacturing process is simplified without altering the properties of the cable and its performance in the tire.

 [057] In one embodiment, the inner layer is compact. By compact is meant that each wire of the inner layer is in contact with the inner layer of son adjacent thereto.

[058] In another embodiment, the inner layer is non-compact. By non-compact means that each wire of the inner layer is remote from the inner layer of wires that are adjacent thereto. Thus, each wire of the inner layer is not in contact with the son of the inner layer which are adjacent thereto. It facilitates the penetration of the rubber between the inner layer son, especially in the central capillary delimited by the son of the inner layer. [059] In order to separate the wires from the inner layer of each other, the cable preferably comprises a core wire between the wires of the inner layer. The diameter d0 of the core wire is between 0.05 mm and 0.12 mm inclusive.

[060] The invention also relates to a multistrand cable comprising, as elementary strand, at least one metal cable with cylindrical layers as described above.

 [061] The invention also relates to the use of a cable as defined above as reinforcing element of a rubber matrix.

[062] Another object of the invention is a tire comprising at least one cylindrical wire rope as defined above or a multistrand cable as defined above.

 [063] Preferably, the tire is intended for industrial vehicles chosen from light trucks, heavy vehicles such as "heavy goods vehicles" - ie, metro, buses, road transport vehicles (trucks, tractors, trailers), off-road vehicles. -route -, agricultural or civil engineering machinery, aircraft, other transport or handling vehicles. More preferably, the tire is intended for a vehicle of the civil engineering type or road transport equipment. Even more preferentially, the tire is intended for a vehicle of the civil engineering type.

 [064] In one embodiment, the tire comprising a carcass reinforcement anchored in two beads and radially surmounted by a crown reinforcement itself surmounted by a tread which is joined to said beads by two sidewalls, said armature of vertex has at least one cable as defined above.

 [065] Advantageously, the cable according to the invention is intended to be used as reinforcing element of a protective ply. Alternatively, the cable according to the invention is intended to be used as reinforcing element of a working ply.

 [066] In the case where the cable is used in a protective layer, the protective layer is more enduring and more resistant to corrosion because of the high penetrability of the cables that compose it.

[067] In the case where the cable is used in a working or crossed web, thanks to its high mechanical strength, in particular its compressive strength, the cable according to the invention makes it possible to confer on the tire a high endurance, in particular, the phenomenon of separation / cracking of the ends of the crossed plies in the shoulder area of the tire, known as "cleavage". [068] In another embodiment, the tire having a carcass reinforcement anchored in two beads, said carcass reinforcement comprises at least one cable as defined above.

 [069] Another object of the invention is a track comprising at least one cylindrical wire rope as defined above or a multistrand cable as defined above.

 [070] The invention will be better understood on reading the description which follows, given solely by way of example and 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 perpendicular to the axis of the cable (assumed rectilinear and at rest) of a cable according to one embodiment of the invention. [071] PNEUMATIC ACCORDING TO THE INVENTION

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

 [073] The tire 10 has a vertex 12 reinforced by a crown reinforcement 14, two sidewalls 16 and two beads 18, each of these beads 18 being reinforced with a rod 20. The top 12 is surmounted by a tread represented in this schematic figure. A carcass reinforcement 22 is wound around the two rods 20 in each bead 18 and comprises a turn-up 24 disposed for example towards the outside of the tire 10 which is represented here mounted on a rim 26. The carcass reinforcement 22 is known per se consists of at least one sheet reinforced by so-called radial cables, that is to say that these cables are arranged substantially parallel to each other and extend from one bead to the other so as to forming an angle of between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is situated midway between the two beads 18 and passes through the middle of the crown reinforcement 14) .

[074] The tire 10 is preferably intended for industrial vehicles chosen from vans, heavy vehicles such as "heavy goods vehicles" - ie, metro, buses, road transport vehicles (trucks, tractors, trailers), off-the-road vehicles. road -, agricultural or civil engineering machinery, aircraft, other transport or handling vehicles. In this case, the tire is intended for a vehicle of the civil engineering type. [075] The crown reinforcement 14 comprises at least one crown ply whose reinforcement cables are metal cables in accordance with the invention. In this crown reinforcement 14 schematized in a very simple manner in FIG. 1, it will be understood that the cables of the invention may, for example, reinforce all or part of the working crown plies, or plies (or half plies) triangulation crown. and / or protective crown plies, when such crown triangulation or protection plies are used. In addition to the working plies, those of triangulation and / or protection, the crown reinforcement 14 of the tire of the invention may of course comprise other crown plies, for example one or more crown plies.

 [076] Of course, the tire 10 further comprises, in a known manner, a layer of rubber or inner elastomer (commonly called "inner liner") which defines the radially inner face of the tire and which is intended to protect the carcass reinforcement of air diffusion from the interior space to the tire. Advantageously, in particular in the case of a truck tire, it may further comprise an intermediate reinforcing elastomer layer which is located between the carcass reinforcement and the inner layer, intended to reinforce the inner layer and, therefore, the carcass reinforcement, also intended to partially relocate the forces suffered by the carcass reinforcement.

 [077] In this crown ply, the density of the cables according to the invention is preferably between 15 and 80 cables per dm (decimetre) of the included terminal ply, more preferably between 25 and 65 cables per dm of ply included terminals, the distance between two adjacent cables, axis to axis, preferably being between about 1, 2 and 6.5 mm inclusive, more preferably between about 2 and 4 mm included terminals.

[078] The cables according to the invention are preferably arranged in such a way that the width (denoted L) of the rubber bridge, between two adjacent cables, is between 0.1 and 3.0 mm inclusive. This width L represents, in known manner, the difference between the calendering pitch (no laying of the cable in the rubber fabric) and the diameter of the cable. Below the indicated minimum value, the rubber bridge, which is too narrow, risks being mechanically degraded during the working of the sheet, in particular during the deformations undergone in its own plane by extension or shearing. Beyond the maximum indicated, there is a risk of occurrence of penetration of objects, by perforation, between the cables. More preferably, for these same reasons, the width L is chosen between 0.4 and 1, 6 mm inclusive. [079] Preferably, the composition used for the fabric of the crown ply has, in the vulcanized state (ie, after curing), a secant modulus in extension E10 which is between 5 and 25 MPa inclusive, more preferably between 5 and 20 MPa limits included, especially in a range of 7 to 15 MPa limits included, when the fabric is intended to form a sheet of the top, for example a working sheet. It is in such areas of modules that we have recorded the best compromise of endurance between the cables of the invention on the one hand, and the reinforced fabrics of these cables on the other hand. [080] EXAMPLES OF CABLES ACCORDING TO THE INVENTION

 [081] There is shown in Figure 2 an example of an embodiment of a cable according to the invention and designated by the general reference 30. The cable 30 is metallic and is of the type with cylindrical layers. The cable 30 is of the non-compact type, that is to say that each of the son layers constituting it has a pitch and / or a winding direction different from that of at least one other layer.

 [082] The cable 30 is of the three-layer type, regardless of the presence or absence of a hooping layer. The layers of wires are adjacent and concentric. The cable 30 is devoid of rubber when it is not integrated with the tire.

[083] The cable 30 comprises an inner layer C1 comprising, here consisting of 2 inner wires helically wound at pitch p1 between 5 and 11 mm included terminals and preferably between 7 and 9 mm included terminals, here p1 = 8 mm . The inner layer C1 is compact, that is to say that each wire of the inner layer C1 is in contact with the inner layer of wires C1 which are adjacent thereto. The wires of the inner layer C1 are non-preformed.

[084] The cable 30 also comprises an intermediate layer C2 comprising, here consisting of 9 intermediate son helically wound around the inner layer C1 at pitch p2 between 8 and 20 mm inclusive terminals and preferably between 12 and 18 mm terminals included, here p2 = 16 mm.

[085] The cable 30 comprises an outer layer C3 comprising, here consisting of 14 external wires helically wrapped around the intermediate layer C2 at pitch p3 between 12 and 30 mm included terminals and preferably between 20 and 28 mm included terminals here p3 = 24 mm. The cable 30 comprises a shrinking layer Cf comprising, here consisting of a wire hoop wound helically around the outer layer C3 pitch pf. The pitch pf is less than or equal to 10 mm, preferably 8 mm and more preferably 6 mm. Here, mp = 4 mm. [086] Each layer C1, C2, C3, Cf has a substantially tubular envelope giving to the corresponding layer C1, C2, C3, Cf respectively its contour E1, E2, E3, cylindrical Ef of respective radius R1, R2, R3 corresponding to actual radius measured on the cable.

[087] The ratio p1 / p2 is between 0.4 and 0.8 included terminals and preferably between 0.5 and 0.7 included terminals. Here p1 / p2 = 0.67. The ratio p2 / p3 is between 0.5 and 0.9 inclusive and preferably between 0.6 and 0.8 included terminals. Here p2 / p3 = 0.75.

 [088] In this example, the winding directions of the son of the layers are all identical, that is to say either in the S direction ("S / S / S" arrangement) or in the Z direction (disposition "Z / Z / Z"). The winding direction of the wire of the shrinking layer Cf is different from the winding direction of the wire of the outer layer C3.

[089] Each wire of the layers C1, C2, C3 respectively has a diameter d1, d2, d3 of between 0.15 and 0.50 mm inclusive, preferably between 0.22 and 0.50 mm inclusive, more preferably between 0.25 mm and 0.5 mm and even more preferably between 0.3 and 0.4 mm inclusive.

 [090] Preferably, all the son of the same layer C1, C2, C3 have the same diameter. Alternatively, at least two son of the same layer has two different diameters. Each diameter d1, d2, d3 of each wire respectively of each inner layer C1, intermediate C2 and outer C3 verifies d1> d2, d1> d3 and d2 = d3. Thus, each diameter d1, d2, d3 is such that d1 = 0.35 mm, d2 = d3 = 0.30 mm. The diameter df of the wire of the shrinking layer Cf is between 0.10 and 0.26 mm inclusive, here df = 0.15 mm.

 [091] Preferably, the ratio d1 / d2 is greater than or equal to 1. In this case, d1 / d2 is between 1.05 and 1.3 inclusive, preferably between 1.10 and 1.3 included and more preferably between 1, 15 and 1, 3 inclusive. Here, d1 / d2 = 1, 17.

[092] In each intermediate layer C2 and external C3, on a section of the cable perpendicular to the main axis of the cable, at least two adjacent son are respectively separated by a channel P2, P3 for the passage of the eraser. Two adjacent wires of the same layer C2, C3 are separated, on average on each layer C2, C3, by an inter-wire distance D2, D3 defined as the smallest distance separating these two adjacent wires. D2 is greater than or equal to 25 μηη. Advantageously, D2 is greater than or equal to 30 μηι, preferably 40 μηη and more preferably 50 μηι. D3 is greater than or equal to 25 μηι. Advantageously, D3 is greater than or equal to 30 μηι, preferably 40 μηη and more preferably 50 μηι. In addition, each inter-son distance D2, D3 is less than or equal to 100 μηη. [093] The number n of son by layer (here n = 9 or n = 14), the interfil distance Di, the real radius Ri of the envelope of the considered layer (intermediate or external) and the diameter di of the son of the considered layer (d2 or d3) satisfies for each layer considered (i = 2 or 3) the following relation: Di = (2. (1 -cos (2n / n)) ^{0 5.} (Ri-di / 2) Preferably, the value Ri is the average of 10 measurements made on different parts of the cable.

 [094] Preferably, the ratio D2 / D3 is between 0.5 and 1.5 inclusive, preferably between 0.7 and 1.3, inclusive, more preferably between 0.8 and 1, inclusive, and even more preferably between 0.9 and 1, 1 limits included.

[095] The son of the layers C1, C2, C3 and Cf are preferably brass-coated carbon steel. The carbon steel wires are prepared in a known manner, for example starting from machine wires (diameter 5 to 6 mm) which are first cold-rolled, by rolling and / or drawing, to a neighboring intermediate diameter. of 1 mm. The steel used for the cable 10 is a steel whose carbon content is about 0.92% and having about 0.2% chromium, the remainder being made of iron and the usual unavoidable impurities related to the manufacturing process of steel. Alternatively, a steel with a carbon content of 0.7% is used. The intermediate diameter son undergo a degreasing treatment and / or pickling, before further processing. After deposition of a brass coating on these intermediate son, is carried on each wire a so-called "final" work hardening (ie, after the last patenting heat treatment), by cold drawing in a moist medium with a drawing lubricant which is for example in the form of an emulsion or an aqueous dispersion. The brass coating that surrounds the son has a very small thickness, significantly less than a micrometer, for example of the order of 0.15 to 0.30 μηη, which is negligible compared to the diameter of the steel son. Of course, the composition of the wire steel in its various elements (eg C, Cr, Mn) is the same as that of the steel of the starting wire.

 [096] The characteristics of the embodiment described above are summarized in Table 1 below.

 Table 1

[097] On a rassemblé dans le tableau 2 ci-dessous certaines caractéristiques du câble 30 selon le mode de réalisation (Exemple 1 ) décrit ci-dessus et de variantes de ce câble, les autres caractéristiques étant égales par ailleurs.

[097] The following are shown in Table 2 below certain characteristics of the cable 30 according to the embodiment (Example 1) described above and variants of this cable, the other characteristics being equal elsewhere.

 Table 2

[098] METHOD OF MANUFACTURING THE CABLE AND PNEUMATIC ACCORDING TO THE INVENTION

 [099] We will now describe a method of manufacturing the cable according to the invention.

 [0100] Beforehand, it is recalled that there are two possible techniques for assembling wires or metal strands:

 or by wiring: in such a case, the son or strands do not undergo torsion around their own axis, due to a synchronous rotation before and after the point of assembly;

 or by twisting: in such a case, the son or strands undergo both a collective twist and an individual twist around their own axis, which generates a torque of untwisting each of the son or strands.

 In a first assembly step by twisting the two son of the inner layer C1, is formed at a first point called "first assembly point" the first layer C1. The son are delivered by supply means such as coils, a distribution grid, coupled or not to a connecting grain, intended to converge the two son to the first assembly point.

 In a second assembly step by twisting the 9 son of the intermediate layer C2 around the inner layer C1, a second point called "second assembly point" is formed by an intermediate cable C1 + C2 of structure 2 9. As previously for the two son of the inner layer C1, the 9 son of the intermediate layer C2 are delivered by supply means for converging around the inner layer C1, the 9 son at the second assembly point.

In a third assembly step by twisting the 14 son of the outer layer C3 around the intermediate layer C3, a third point is formed. "Third assembly point" means an intermediate cable C1 + C2 + C3 of structure 2 + 9 + 14. As a variant, the third step uses a wiring assembly of the 14 wires of the outer layer C3 around the intermediate layer C3. As previously for the 2, 9 son of the inner and intermediate layers C1, C2, the 14 son of the outer layer C3 are delivered by feeding means intended to converge around the intermediate layer C2, the 14 son to the third assembly point.

 In a fourth preferred step, the twists are balanced in the cable 30. During this step, the cable 30 is passed through torsion balancing means to obtain a so-called balanced cable in torsion (c). i.e., practically without residual torsion); "Torsional balancing" here means, in a known manner, the cancellation of the residual torsional torques (or of the detorsional springback) exerted on each wire of the cable in the twisted state, in its respective layer. The torsion balancing means are known to those skilled in the art of twisting. These means comprise rotating balancing means, for example twisters, twister-trainers, or non-rotating, for example trainers, consisting of either pulleys for twisters, or small diameter rollers for trainers, pulleys or rollers through which the cable runs, in a single plane for rotating means or in at least two different planes for non-rotating means.

 Finally, in a fifth assembly step, the wire of the frettage layer Cf is wound around the intermediate cable C1 + C2 + C3.

 Alternatively, the first, second and third steps can be performed by wiring.

The previously described cable 30 may be obtained by the method described above.

 We will now describe a method of manufacturing the tire according to the invention.

The cable 30 is incorporated by calendering to a known composition based on natural rubber and carbon black as reinforcing filler, conventionally used for the manufacture of the working plies in the crown reinforcement of radial tires. This composition essentially comprises, in addition to the elastomer and the reinforcing filler (carbon black), an antioxidant, stearic acid, an extension oil, cobalt naphthenate as adhesion promoter, finally a vulcanization system (sulfur, accelerator, ZnO). Composite fabrics comprising one or more cables 30 embedded in a rubber matrix are thus formed. The rubber matrix is formed of two thin layers of rubber which are superposed on both sides of the cables and which respectively have a thickness of between 0.3 mm and 1.4 mm inclusive. The calender pitch (no laying of the cables in the rubber matrix) is between 2 mm and 4 mm inclusive.

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

MEASUREMENTS AND COMPARATIVE TESTS

An example of a cable according to the invention was compared with a stranded cable of the state of the art called structure 49.23FR (1 + 6) x0.23 + 6x (1 + 6) x0.23 comprising a hooping layer comprising a hoop wire of diameter df = 0.15 mm.

 The cable according to the invention of Example 1 'differs from the cable of Example 1 according to the invention only by the winding direction of the intermediate and outer layers.

[0114] Dynamometric measurements

 The measure of force at break noted Fr (maximum load in N) is performed in tension according to ISO 6892 of 1984. Table 3 below shows the results obtained from breaking force Fr. The force at Fr fracture is indicated in relative unit (UR) with respect to the cable breaking force of the state of the art. When Fr is greater than 1 U.R, the breaking force of the tested cable is greater than that of the cable of the state of the art. Conversely, when Fr is less than 1 U.R, the breaking strength of the tested cable is lower than that of the cable of the state of the art.

Table 3

[0116] Le câble selon l'invention présente une force à rupture bien plus élevée que le câble de l'état de la technique et donc améliore l'endurance du pneumatique. Γ01171 Test de perméabilité à l'air

The cable according to the invention has a breaking force much higher than the cable of the state of the art and thus improves the endurance of the tire. Γ01171 Air permeability test

 This test makes it possible to determine the longitudinal permeability to the air of the cables tested, by measuring the volume of air passing through a specimen under constant pressure for a given time. The principle of such a test, well known to those skilled in the art, is to demonstrate the effectiveness of the treatment of a cable to make it impermeable to air; it has been described for example in ASTM D2692-98.

 The test is performed here on specimens comprising raw manufacturing cables previously coated from the outside by a so-called coating gum. For this, a series of 10 cables arranged in parallel is placed between two layers or "skims" (two rectangles of 80 x 200 mm) of a diene rubber composition in the green state, each skim having a thickness of 3.5 mm; the whole is then locked in a mold, each of the cables being kept under a sufficient tension (for example 2 daN) to ensure its straightness during the establishment in the mold, using clamping modules; then the vulcanization (baking) is carried out at a temperature of 130 ° C for a period of between 100 min and 10 hours and under a pressure of 15 bar (rectangular piston 80 x 200 mm). After which, the assembly is demolded and cut 10 pieces of cables thus coated, in the form of parallelepipeds of dimensions 7x7x20 mm, for characterization.

A conventional rubber diene rubber composition based on natural rubber (peptized) and carbon black N330 (65 phr), comprising the following usual additives: sulfur (7 phr), is used as a coating rubber. ), sulfenamide accelerator (1 phr), ZnO (8 phr), stearic acid (0.7 phr), antioxidant (1.5 phr), cobalt naphthenate (1.5 phr) (phr parts per hundred parts) elastomer); the E10 module of the coating gum is approximately 10 MPa.

The test is carried out on 4 cm of cable length, thus coated by its surrounding rubber composition (or coating gum) in the fired state, in the following manner: air is sent to the cable inlet, under a pressure of 1 bar, and the volume of air at the outlet is measured using a flow meter (calibrated for example from 0 to 500 cm3 / min). During the measurement, the cable sample is locked in a compressed seal (eg a dense foam or rubber seal) in such a way that only the amount of air passing through the cable from one end to the other, along its longitudinal axis, is taken into account by the measure; seal tightness Waterproof itself is checked beforehand with the help of a solid rubber test tube, that is to say without cable.

 The average air flow measured Dm (average of 10 specimens) is even lower than the longitudinal imperviousness of the cable is high. The measurement is made with an accuracy of ± 0.2 cm3 / min.

The cables are subjected to the air permeability test described above, by measuring the volume of air (in cm ³ ) passing through the cables in 1 minute (average of 10 measurements). The results are summarized in Table 4 below. The flow Dm is indicated in relative unit (UR) with respect to the cable flow of the state of the art. When Dm is greater than 1 UR, the rate of the tested cable is higher than that of the cable of the state of the art. Conversely, when Dm is less than 1 UR, the rate of the tested cable is lower than that of the cable of the state of the art.

 Table 4

[0124] La saturation de chaque toron du câble de l'état de la technique ainsi que la saturation du câble de l'état de la technique lui-même entraine une pénétration limitée de la gomme et donc la création de nombreux capillaires externes situés entre chaque couche interne et externe de chaque toron de couche et entre chaque toron de couche. L'air, et donc les agents corrosifs, peuvent donc facilement y circuler.

The saturation of each cable strand of the state of the art and the saturation of the cable of the state of the art itself leads to a limited penetration of the rubber and therefore the creation of many external capillaries located between each inner and outer layer of each strand and between each strand. Air, and therefore corrosive agents, can therefore easily circulate.

The strand cable of the state of the art also comprises internal capillaries present between the son of the core strand. These communicate easily with the external capillaries which favors the passage of air, and therefore corrosive agents, between the different capillaries.

 Due to their high desaturation, the cables according to the invention have little or no capillary between the layers C1 and C2 and no capillary between the layers C2 and C3 so that the air flow is relatively low. which makes it possible to improve the non-propagation of the corrosive agents with respect to the cable of the state of the art. [0127] Adhesion-corrosion test

This test is performed in accordance with ASTM D2229. Test specimens similar to those made for the air permeability test are produced. One end of the test tube is immersed in a salt water bath for a period of predetermined, here 21 days. Then, it measures the adhesion force Fa necessary to tear the cable coating rubber. The more the adhesion interface has been altered by the corrosive agent, here salt water, the lower the measured force. The results are summarized in Table 5.

The initial Fa forces of the tested cables are indicated in relative unit (U.R) with respect to the initial force Fa of the cable of the state of the art. When Fa of the tested cable is greater than 1 U.R, the initial force Fa of the tested cable is greater than the initial force Fa of the cable of the state of the art.

 The forces Fa at 21 days of the tested cables are indicated in relative unit (U.R) with respect to the initial force Fa of the tested cable. When the 21-day force Fa is less than 1 U.R, the 21-day force FA of the cable under test is less than the initial force Fa of the cable under test.

 Table 5

[0131] Le câble selon l'invention présente une force d'adhésion Fa bien supérieure à celle du câble de l'état de la technique. Les câbles selon l'invention sont protégés contre l'action directe des agents corrosifs et présentent une résistance à la compression et une endurance accrue grâce au confinement des agents corrosifs. Γ0132Ί Masse des câbles et des nappes de renfort

The cable according to the invention has an adhesion force Fa much greater than that of the cable of the state of the art. The cables according to the invention are protected against the direct action of the corrosive agents and have a compressive strength and an increased endurance thanks to the confinement of the corrosive agents. Γ0132Ί Mass of cables and reinforcing plies

For a value of predetermined breaking strength of web, here 1700 daN / cm, was calculated the mass of cable contained in 1 m ² of a reinforcing ply and the mass of this reinforcing ply. The gains in mass of cable and in mass of reinforcement ply are then deducted for 1 m ² of ply compared to a reinforcing ply of 1 m ² comprising cables of the state of the art. These gains are summarized in Table 6 below.

 Table 6

[0134] En raison d'une force à rupture plus élevée que le câble de l'état de la technique, on peut augmenter le pas de pose, réduire le nombre de câble dans la nappe et donc diminuer simultanément la masse de câble et la masse de la nappe.

Due to a higher breaking force than the cable of the state of the art, it is possible to increase the laying pitch, reduce the number of cables in the sheet and thus simultaneously reduce the cable mass and the mass of the tablecloth.

In addition, because of a higher compactness than the strand cable of the state of the art, it is possible to reduce the thicknesses of calendering rubber and thus lighten the sheet.

 Thus, the weight of the tire is significantly reduced, in particular in web mass, which reduces the hysteresis of the tire, therefore its rolling resistance and therefore the fuel consumption. In addition, the industrial costs of the cable and the ground are reduced.

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

For example, some son could be non-circular section, for example plastically deformed, including a substantially oval or polygonal section, for example triangular, square or rectangular. In this case, the diameter of each wire should be interpreted as the diameter of the circle in which the wire section is inscribed.

In another embodiment, the son of the inner layer are rectilinear, that is to say, has an infinite pitch.

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

It is also possible to envisage cables in which the winding direction of the inner layer wires is different from that of the wires of the intermediate layer, for example S / Z / S, Z / S / Z layout cables, S / Z / Z or Z / S / S.

 In a non-illustrated embodiment, the inner layer is non-compact.

 In another embodiment not illustrated, d2 = d1 and d3 <d2.

In addition, the cable according to the invention may be used in a tire for road transport equipment, for example in the crown reinforcement, in particular in a working crown ply.

 In addition, the cable according to the invention may reinforce a carcass reinforcement. Thus, it will also be possible to use cables with wires such as 0.15 mm <d1, d2, d3 <0.30 mm and more preferably such as 0.15 mm <d1, d2, d3 <0.26 mm.

The cable according to the invention may reinforce rubber matrices other than those intended for the manufacture of a tire, for example a matrix of rubber for the manufacture of a caterpillar. Thus, it will be possible to envisage using a track comprising the cable according to the invention.

 It is also possible to combine the characteristics of the different embodiments described or envisaged above provided that they are compatible with each other.

 It is possible to envisage a multi-strand cable comprising, as elementary strand, at least one layered metal cable as described above.

Claims

1. Cable (30) with cylindrical layers, characterized in that it comprises:  an inner layer (C1) consisting of 2 wires,  an intermediate layer (C2) consisting of wires wound helically around the inner layer (C1),  an outer layer (C3) consisting of 14 wires wound helically around the intermediate layer (C2).  2. Cable (30) according to the preceding claim, wherein the interfering distance D2 son of the intermediate layer (C2) is greater than or equal to 25 μηη.  3. Cable (30) according to the preceding claim, wherein the interfering distance D2 of the son of the intermediate layer (C2) is greater than or equal to 30 μηη, preferably 40 μηη and more preferably 50 μηη.  4. Cable (30) according to any one of the preceding claims, wherein the interfering distance D3 son of the outer layer (C3) is greater than or equal to 25 μηι.  5. Cable (30) according to the preceding claim, wherein the interfering distance D3 son of the outer layer (C3) is greater than or equal to 30 μηι, preferably 40 μηη and more preferably 50 μηη.  6. Cable (30) according to any one of the preceding claims, wherein the interfering distance D2 of the son of the intermediate layer (C2) is less than or equal to 100 μηη.  7. Cable (30) according to any one of the preceding claims, wherein the interfering distance D3 of the son of the outer layer (C3) is less than or equal to 100 μηη.  Cable (30) according to any one of the preceding claims, wherein the ratio D2 / D3 satisfies 0.5 <D2 / D3 <1.5, preferably 0.7 <D2 / D3 <1.3, plus preferably 0.8 <D2 / D3 <1, 2 and even more preferentially 0.9 <D2 / D3 <1.1. 9. Cable (30) according to any preceding claim, wherein each diameter d1, d2, d3 of each wire respectively of each inner layer (C1), intermediate (C2) and outer (C3) checks 0.15 < d1, d2, d3 <0.5 mm, preferably 0.22 <d1, d2, d3 <0.5 mm, more preferably 0.25 <d1, d2, d3 <0.5 mm and even more preferably 0, <D1, d2, d3 <0.4 mm. 10. Cable (30) according to any preceding claim, wherein each diameter d1, d2 of each wire respectively of each inner layer (C1) and intermediate (C2) verifies d1 / d2> 1, preferably 1, 05 <d1 / d2 <1, 3, more preferably 1, 10 <d1 / d2 <1, 3 mm and even more preferably 1, 15 <d1 / d2≤1, 3 mm.  1 1. Cable (30) according to any one of the preceding claims, wherein each diameter d1, d2, d3 of each wire respectively of each inner (C1), intermediate (C2) and outer (C3) layer satisfies d1> d2 and / or d1> d3.  12. Cable (30) according to any one of the preceding claims, wherein each diameter d2, d3 of each wire each wire respectively of each intermediate layer (C2) and external (C3) verifies d2 = d3.  13. Cable (30) according to any one of the preceding claims, wherein the winding direction of the outer layer son (C3) is different from that of the intermediate layer son (C2).  14. Cable (30) according to any one of the preceding claims, wherein the son of the inner layer (C1) are non-preformed.  15. Multistrand cable, characterized in that it comprises, as elementary strand, at least one wire (30) with cylindrical layers of metal according to any one of the preceding claims.  16. Pneumatic tire (10), characterized in that it comprises at least one cylindrical metal cable (30) according to any one of claims 1 to 14 or a multistrand cable according to claim 15.  Chenille, characterized in that it comprises at least one cylindrical metal cable (30) according to any one of claims 1 to 14 or a multistrand cable according to claim 15.