WO2015090921A1

WO2015090921A1 - Two-layer multi-strand metal cable

Info

Publication number: WO2015090921A1
Application number: PCT/EP2014/076119
Authority: WO
Inventors: Natacha PIRONNEAU; Emmanuel Clement; Thibault RAPENNE; Stéphane LAURENT
Original assignee: Compagnie Generale Des Etablissements Michelin; Michelin Recherche Et Technique S.A.
Priority date: 2013-12-16
Filing date: 2014-12-01
Publication date: 2015-06-25
Also published as: FR3014914B1; FR3014914A1

Abstract

The two-layer multi-strand cable (50) according to the invention comprises: - an inner layer (C1) made up of an inner strand (TI), - an outer layer (C2) made up of L>1 outer strands (TE). Each inner and outer strand (TI, TE) comprises: - an inner layer (12, 12') respectively made up of Q and Q' inner wires (F1, F'1), an intermediate layer (14, 14') respectively made up of M and M' intermediate wires (F2, F2'), and - an outer layer (16, 16') respectively made up of N and N' outer wires (F3, F3'). The diameter DI of the inner strand (TI) is larger than the diameter DE of each outer strand (TE). The outer layer (16') of the inner strand (TI) is unsaturated. The outer layer (16') of each outer strand (TE) is unsaturated.

Description

Two-layer multi-strand wire rope

[001] The invention relates to multi-strand 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 such as cables or monofilaments, of metal or textile type.

[003] The crown reinforcement generally comprises at least two superimposed vertex plies, sometimes called "working plies" or cross plies, whose reinforcement elements, generally metallic, are arranged substantially parallel to each other inside. a web, but crossed from one web to another, that is to say inclined, symmetrically or not, relative to the median circumferential plane, an angle which is generally between 10 ° and 45 ° The working plies generally comprise reinforcing elements having a very low elongation so as to ensure their function of guiding the tire.

[004] The crown reinforcement may also comprise various other layers or layers of auxiliary rubber, of varying widths depending on the case, with or without reinforcing elements. By way of example, mention may be made of so-called protection plies responsible for protecting the rest of the belt from external aggressions, perforations, or so-called shrinking plies comprising reinforcing elements oriented substantially in the circumferential direction (zero-plies). degree), whether radially external or internal to the working plies. The protective plies generally comprise reinforcing elements having a high elongation so as to be deformed under the effect of a stress exerted by an indenter, for example a rock.

It is known from the state of the art a reinforcing element of the working ply comprising a multi-strand wire rope with two layers of structure 189.23. This cable comprises an inner layer of the cable consisting of an inner strand and an outer layer of the cable consisting of 6 outer strands wound helically around the inner layer of the cable. Each inner and outer strand comprises an inner layer of the strand consisting of 3 internal son, an intermediate layer consisting of 9 son and an outer layer of the strand consisting of 15 external son. Each wire has a diameter equal to 0.23 mm.

[007] A tire of heavy industrial vehicle, including civil engineering, is subjected to many attacks. Indeed, the rolling of this type of tire is usually done on a rough surface sometimes leading to perforations of the tread. These perforations allow the entry of corrosive agents, for example air and water, which oxidize the metal reinforcing elements of the crown reinforcement, in particular crown plies, and considerably reduce the service life of the tire. .

[008] A solution to increase the life of the tire is to fight against the spread of these corrosive agents. It is thus possible to cover each inner and intermediate layer of rubber during the manufacture of the cable. During this process, the rubber present penetrates the capillaries present between each layer of each strand and thus prevents the propagation of corrosive agents. Such cables, generally called cables gummed in situ, are well known in the state of the art.

[009] Another solution to increase the life of the tire is to increase the breaking force of the cable 189.23. Generally, the breaking force is increased by increasing the diameter of the wires constituting the cable and / or the number of wires and / or the unit resistance of each wire. However, further increase the diameter of the son, for example beyond 0.50 mm, necessarily leads to a decrease in the flexibility of the cable which is not desirable, increase the number of son leads most of the time a drop in the penetrability of the strands by the rubber and increase the unit resistance of each wire requires significant investments in wire manufacturing facilities.

[010] The invention aims a cable having a breaking force and improved penetrability with respect to the cable 189.23.

[011] For this purpose, the subject of the invention is a two-layer multi-strand wire rope comprising:

an inner layer of the cable consisting of an internal strand,

an outer layer of the cable consisting of L> 1 external strands,

each inner and outer strand comprising:

an internal and external strand inner layer consisting respectively of Q and Q 'internal wire (s), an intermediate layer of the inner and outer strand respectively consisting of M and M 'intermediate wires, and

an outer layer of the inner and outer strand respectively consisting of N and N 'external wires,

in which :

the diameter D1 of the inner strand is greater than the diameter DE of each outer strand,

the outer layer of the inner strand is unsaturated, and

the outer layer of each outer strand is unsaturated.

[012] The cable according to the invention has a breaking force and improved penetrability with respect to the cable 189.23. These two goals are achieved synergistically as explained below.

[013] Beforehand, it is necessary to remember that, in the cable 189.23 of the state of the art, the outer strands are contiguous and thus form a vault around the inner strand giving the cable a relatively high breaking force. Breaking this vault usually results in a drop in the breaking force. Indeed, by removing the vault around the inner strand, the outer son of each outer strand come, during the traction of the cable, exert a radial force directed towards the inside of the cable on the outer son of the inner strand while the arch allowed a distribution of this force both in a longitudinal component between the outer strands and in a radial component between the outer strands and the inner strand.

[014] In the invention, thanks to the characteristic DI> DE, the cable according to the invention has spaces between the outer strands for the passage of the eraser. Although the vault described above is broken, in the cable according to the invention, the high penetrability of the outer strands made possible by the unsaturation of the outer layer of the outer strands allows the gum having penetrated, on the one hand, between external strands and, secondly, between the outer strands and the inner strand, to at least partially restore the vault and thus limit the loss of breaking strength of the cable. In addition, this feature allows the gum to infiltrate between the outer layers of the inner and outer strands so as to create a gum mattress at least partially absorbing the radial component of the force between the inner and outer strands.

[015] By definition, an unsaturated layer of son is such that there is sufficient space in this layer to add at least one (P + 1) th thread of the same diameter as the P son of the layer, several son can then be in contact with each other. [016] In addition, thanks to the unsaturation of the outer layer of the inner strand, it promotes the penetrability of the inner strand by the rubber while maintaining a satisfactory rupture force. Indeed, the outer layer of the inner strand being unsaturated, it might be feared that the pressures exerted on each wire of this outer layer are too high and reduce the breaking strength of the cable. However, the gum mattress described above strongly limiting these pressures and do not alter or that very little breaking strength compared to the gain in corrosion resistance provided by the high penetrability of the inner strand.

[017] Moreover, as already described above, the unsaturation of the outer layer of the outer strands and the DI> DE characteristic of the cable according to the invention, ensure excellent penetrability of the gum through the strands external strands and which allows to obtain a strongly penetrated inner strand. The cable according to the invention is therefore less subject to the propagation of these corrosive agents.

[018] The propagation of the corrosive agents of the cable according to the invention is also improved thanks to the characteristic according to which the inner layer of each inner and outer strand consists of only one wire. Indeed, the three son of the inner layer of the cable of the state of the art delimit a central capillary greatly promoting the propagation of corrosive agents.

[019] The diameter of each strand and each wire can be measured by microscopic observation. The diameter of each strand is equal to the diameter of the circle circumscribing the corresponding strand.

[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.

[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. [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. implementation of the wire rope 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. According to a preferred embodiment, the steel used is covered with a layer of brass (Zn-Cu alloy) or zinc.

[023] Advantageously, the intermediate layer of the inner strand is unsaturated.

[024] Thus, it further promotes the penetrability of the inner strand and protects the cable against the propagation of corrosive agents. This feature is particularly advantageous when the inner strand has a central capillary delimited by the inner layer of the wires, that is to say when Q> 1 and more preferably when Q> 2.

[025] In a preferred embodiment, the inner wire of each outer strand has a diameter d1 'greater than the diameter d2' of each intermediate wire of said outer strand.

[026] In an even more preferred embodiment, the inner wire of each outer strand has a diameter d1 'greater than the diameter d3' of each outer wire of said outer strand.

[027] Thus, in these two preferred embodiments, the unsaturation of the outer layer of each outer strand is obtained by using different diameters of the son according to the layer of each outer strand. This increases the penetrability of the rubber through the outer strands. The restoration of the vault is amplified and thus the breaking force of the cable is increased. This better penetration also makes it possible to further limit the propagation of corrosive agents.

[028] Preferably, DI / DE≥1, 05 and more preferably DI / DE≥1, 10. Thus, it promotes more the passage of the gum. Preferably DI / DE <1, 20. This limits the outer diameter of the cable and thus maximizes the metal mass that can be put in a sheet. On the other hand, it reduces the thickness of the sheet and thus warming, the rolling resistance and the mass of the tire.

[029] Preferably, the son of the same layer of a predetermined strand (internal or external) are substantially all identical. Advantageously, the outer strands are substantially all identical. By "substantially identical" is meant that the wires and strands are identical to the industry tolerances. [030] In a preferred embodiment, the assembly constituted by the inner and outer layers of the cable has a diameter D less than or equal to 6 mm, preferably 5 mm and more preferably 4.3 mm.

[031] In a preferred embodiment, the ratio of the diameter D of the assembly constituted by the inner and outer layers of the cable to the average inter-strand distance E of the outer layer is less than or equal to 500, preferably to 100 and more preferably 40.

[032] Thus, it further promotes the passage of the rubber between the outer strands and thus the restoration of the cable vault.

[033] The average inter-strand distance E of the outer strands is defined, on a section of the cable perpendicular to the main axis of the cable, as the smallest distance separating, on average on the outer layer, two adjacent strands of the layer. external.

[034] Optionally, the intermediate layer of each outer strand is saturated.

[035] The saturation of the intermediate layer of each outer strand ensures that each outer strand includes sufficient intermediate son and thus a maximum breaking force possible.

[036] By definition, a saturated layer is such that there is not enough room in this layer to add at least one (P + 1) th thread of the same diameter as the P son of the layer.

[037] Preferably, the intermediate layer of each outer strand is non-compact which, despite the saturation of this layer, the passage of the gum.

[038] By definition, a non-compact layer is such that there are spaces for the passage of the eraser between the son of the layer.

[039] In one embodiment, each inner wire of the inner strand has a diameter d1 equal to the diameter d2 of each intermediate wire of the inner strand.

[040] In one embodiment, each inner wire of the inner strand has a diameter d1 equal to the diameter d3 of each outer wire of the inner strand.

[041] In one embodiment, each intermediate wire of each outer strand has a diameter d2 'equal to the diameter d3' of each outer wire of said outer strand.

[042] Advantageously, Q> 1 and preferably Q> 2.

[043] In one embodiment, Q = 3, M = 8 or 9 and N = 13 or 14 and preferably Q = 3, M = 8 and N = 13. [044] Preferably M -6 and N-11.

[045] Advantageously, the diameter of the inner, intermediate and outer wires of each inner and outer strand is from 0.15 mm to 0.50 mm, preferably from 0.20 mm to 0.45 mm and more preferably from 0, 25 mm to 0.40 mm. Such diameters are compatible with use in a tire.

[046] In a preferred embodiment allowing a reduction of the contact pressures between the outer layers of the inner and outer strands and thus a breaking force gain, the outer layers of each inner and outer strand are wound in torsion directions different. Alternatively, the outer layers of each inner and outer strand are wound in the same direction of torsion.

[047] In one embodiment for increasing the penetrability of each strand, the intermediate and outer layers of each strand are wound in different directions of torsion. In another embodiment for increasing the breaking force of each strand, the intermediate and outer layers of each strand are wound in the same direction of torsion.

[048] For the following, it is recalled 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.

[049] The interleaf distance I 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.

[050] According to optional features that are independent of each other:

The ratio d2 / l2 of the diameter d2 of the M intermediate wires of the inner strand to the mean inter-wire distance 12 between the M intermediate wires of the inner strand is such that 2 <d2 / l2 <10 and preferably 3 <d2 / l2 < 7.

The ratio d3 / 13 of the diameter d3 of the N external wires of the inner strand to the mean inter-wire distance 13 between the N external wires of the inner strand is such that 2 <d3 / 13 <10 and preferably 3 <d3 / 13 < 7.

The d2VI2 'ratio of the diameter d2' of the M 'intermediate threads of each outer strand to the mean inter-wire distance 12' between the M 'intermediate threads of each outer strand is such that <d2VI2' <15 and preferably 5 < d2VI2 '<10.

The ratio d3VI3 'of the diameter d3' of the N 'external wires of each outer strand to the mean inter-wire distance 13' between the N 'outer wires of each outer strand is such that 3 <d37l3'<10 and preferably 4 < d37l3 '<6. [051] Another object of the invention is a tire comprising at least one cable as defined above.

[052] Preferably, 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 flanks, said crown reinforcement comprises less a cable as defined above.

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

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

[055] Preferably, the tire is for civil engineering type vehicle. Thus, the tire has a dimension in which the diameter, in inches, of the seat of the rim on which the tire is to be mounted is greater than or equal to 40 inches.

[056] 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;

FIG. 2 is a detailed view of zone I of FIG. 1;

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

Figure 4 is a photograph of the actual cable according to the invention embedded in a rubber matrix, in a section similar to that of Figure 3; and

- Figures 5 to 8 are photographs similar to those of Figure 3 control cables.

[057] EXAMPLE OF PNEUMATIC ACCORDING TO THE INVENTION

[058] Any range of values designated by the expression "from a to b" means the range of values going from the terminal "a" to the terminal "b", that is to say including the strict limits " a "and" b ". [059] In the figures, there is shown a reference X, Y, Z corresponding to the usual orientations respectively axial (X), radial (Y) and circumferential (Z) of a tire.

[060] There is shown in Figures 1 and 2 a tire according to the invention and designated by the general reference 10.

[061] The tire 10 is heavy vehicle type civil engineering, for example of the type "dumper". Thus, the tire 10 has a dimension of 53 / 80R63 type.

[062] 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 radially surmounted by a tread 22 is joined to the beads 18 by the flanks 16. A carcass reinforcement 24 is anchored in the two beads 18, and is here wound around the two rods 20 and comprises a reversal 26 disposed towards the outside of the tire 20 which is shown here mounted on a rim 28. The carcass reinforcement 24 is radially surmounted by the crown reinforcement 14.

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

[064] The tire 10 also comprises a sealing ply 32 made of an elastomer (commonly called inner liner) which defines the radially inner face 34 of the tire 10 and which is intended to protect the carcass ply 30 from the diffusion of air from the interior space to the tire 10.

[065] The crown reinforcement 14 comprises, radially from the outside towards the inside of the tire 10, a protective reinforcement 36 arranged radially inside the tread 22, a working reinforcement 38 arranged radially at the inside of the protective armature 36 and an additional armature 40 arranged radially inside the armature 38. The armature 36 is thus radially interposed between the tread 22 and the armature of the armature. work 38.

[066] The protective armature 36 comprises first and second protective plies 42, 44 comprising protective metal reinforcing elements, the first ply 42 being arranged radially inside the second ply 44. Optionally, the protective metal reinforcing elements make an angle of at least 10 °, preferably from 10 ° to 35 ° and preferably from 15 ° to 30 ° with the circumferential direction Z of the tire.

[067] The working reinforcement 38 comprises first and second working plies 46, 48, the first ply 46 being arranged radially inside the second ply 48. Each ply 46, 48 comprises at least one metallic reinforcement element working comprising a cable 50 according to the invention. Optionally, the metal reinforcing elements of work are crossed from one working ply to another and make an angle at most equal to 60 °, preferably ranging from 15 ° to 40 ° with the circumferential direction Z of the tire .

[068] The additional reinforcement 40, also called limiter block, whose function is to partially recover the mechanical stresses of inflation, comprises, for example and in a manner known per se, additional metal reinforcing elements, for example such as described in FR 2 419 181 or FR 2 419 182 making an angle at most equal to 10 °, preferably ranging from 5 ° to 10 ° with the circumferential direction Z of the tire 10.

[069] EXAMPLE OF CABLE ACCORDING TO THE INVENTION

[070] There is shown in Figure 3 a cable 50 according to the invention.

[071] The cable 50 is metallic and is of the multi-strand type with two cylindrical layers. Thus, it is understood that the strand layers constituting the cable 50 are two in number. The layers of strands are adjacent and concentric. The cable 10 is devoid of rubber when it is not integrated with the tire.

[072] The cable 50 comprises an inner layer C1 of the cable 50 and an outer layer C2 of the cable 50. The inner layer C1 consists of a single inner strand T1. The outer layer C2 consists of L> 1 strands. external, that is to say several external strands TE wound helically around the inner layer C1 in a p-step. The cable 50 also comprises a band F consisting of a single wire wound helically around the outer layer C2 in a pitch pf.

[073] The inner strand T1 has an infinite pitch. The outer strands TE are wound helically in a winding direction of the outer strands, for example the direction S. The pitch p of the outer strands is such that 40 mm <p <100 mm and preferably 50 mm <p <90 mm . Here p = 70 mm.

[074] The hoop F is wound helically in a winding direction of the hoop different from the winding direction of the outer strands. Thus, for example, the outer strands TE are wound in the direction S around the inner strand Tl and the band F is The pitch pf of the band F is such that 2 mm <pf <10 mm and preferably 3 mm <pf <8 mm. Here mp = 5.1 mm.

[075] The assembly constituted by the inner C1 and outer C2 layers, that is to say the cable without the band F, has a diameter D greater than or equal to 4 mm and less than or equal to 6 mm, preferably at 5 mm and more preferably at 4.3 mm. The mean inter-strand distance E between two adjacent outer TE strands is greater than or equal to 30 μηι, preferably 45 μηη and more preferably 75 μηη and even more preferably 100 μηη. The ratio D / E is less than or equal to 500, preferably 100 and more preferably 40. Here, D = 4.23 mm, E = 121 μηη and D / E = 34.95.

[076] The inner strand T1 has a diameter D1 greater than the diameter DE of each outer strand TE. Preferably, DI / DE≥1, 05 and more preferably DI / DE≥1, 10. Preferably DI / DE <1, 20. In this case, D1 = 1.85 mm, DE = 1.58 mm and DI / DE = 1.17. Thus, the outer layer C2 of the cable 50 is non-compact. By definition, a non-compact layer of strands is such that there are spaces for the gum to pass between the strands of the layer.

[077] The inner strand T1 comprises an inner layer 12 of the strand Tl consisting of Q internal thread (s) F1, an intermediate layer 14 of the strand Tl consisting of M intermediate threads F2 wound helically around the inner layer 12 in a pitch p2, and an outer layer 16 of the strand Tl consisting of N external wires F3 wound helically around the intermediate layer 14 in a step p3. Q> 1, preferably Q> 2. The Q inner wires F1 are helically wound in a pitch p1. Here, Q = 3, M = 6 and N = 11.

[078] We have p1 such that 4 mm <p1 <15 mm and preferably 6 mm <p1 <10 mm. The Q F1 son are helically wound in a direction of inner layer 12 of the Tl strand. Here p1 = 8 mm.

[079] We have p2 such that 7 mm <p2 <30 mm and preferably 10 mm <p2 <25 mm and more preferably 10 mm <p2 <18 mm. The M son F2 are helically wound in an intermediate layer direction 14 of the Tl strand. Here p2 = 14 mm.

[080] There is also p3 such that 10 mm <p3 <40 mm and preferably 15 mm <p3 <35 mm and more preferably 15 mm <p3 <25 mm. The N son F3 are helically wound in an outer layer direction 16 of the Tl strand. Here p3 = 20 mm.

[081] Preferably, the outer layer direction 16 of the strand T1 is identical to the intermediate layer direction 14 of the strand T1, for example the direction S. Alternatively, these directions are different.

[082] Each inner, intermediate and outer wire of the inner strand Tl respectively has a diameter d1, d2 and d3. Each wire has a resistance to rupture, denoted Rm, such that 2500 <Rm <3500 MPa. The steel of these threads is said to be of grade SHT ("Super High Tensile"). Each diameter of the inner wires d1, intermediate d2 and external d3 of the inner strand T1 is from 0.15 mm to 0.50 mm, preferably from 0.20 mm to 0.45 mm and more preferably from 0.25 mm to 0. , 40 mm. Here d1 = 0.38 mm and d2 = d3 = 0.35 mm.

[083] The intermediate layer 14 of the inner strand T1 is unsaturated and non-compact. Indeed, the average inter-wire distance 12 between the intermediate M son F2 is here equal to 55 μηι.

[084] The ratio d2 / l2 is such that 2 <d2 / l2 <10 and preferably 3 <d2 / l2 <7. Here, d2 / l2 = 5.45.

[085] The outer layer 16 of the inner strand T1 is unsaturated. Indeed, the average inter-son distance 13 between the N external son F3 is here equal to 60.5 μηη.

[086] The ratio d3 / 13 is such that 2 <d2 / l2 <10 and preferably 3 <d2 / l2 <7. Here, d3 / l3 = 4.96.

[087] Each outer strand TE comprises an inner layer 12 'of the strand TE consisting of Q' internal thread (s) F1 ', an intermediate layer 14' of the strand TE consisting of M 'intermediate threads F2' wound helically around the inner layer 12 'in a pitch p2', and an outer layer 16 'of the strand TE consisting of N' external wires F3 'wound helically around the intermediate layer in a pitch p3'. Here, Q '= 1, M' = 6 and N '= 11.

[088] For each outer strand TE, considered unwound from around the inner layer C1, p2 'such that 7 mm <p2' <30 mm and preferably 10 mm <p2 '<25 mm and more preferably 10 mm < p 2 '<18 mm. The M 'son F2' are helically wound in an intermediate layer direction 14 'of the TE strand. Here p 2 '= 14 mm.

[089] Also p3 'such that 10 mm <p3' <40 mm and preferably 15 mm <p3 '<35 mm and more preferably 15 mm <p3' <25 mm. The N 'son F3' are helically wound in an outer layer direction 16 'TE strand. Here p3 '= 20 mm.

[090] Preferably, the outer layer direction 16 'of the strand TE is identical to the intermediate layer sense 14' of the strand TE, for example the direction Z. In a variant, these directions are different.

[091] In a particularly preferred embodiment, the winding directions of the outer layers 16 and 16 'are different.

[092] Each inner, intermediate and outer wire of each outer strand TE has a diameter d1 ', d2' and d3 ', respectively. Each wire has a breaking strength, denoted Rm, such that 2500 <Rm <3500 MPa. The steel of these threads is said to be of grade SHT ("Super High Tensile"). Each diameter of the wires The internal diameter d1 'and external d3' of each outer strand TE is from 0.15 mm to 0.50 mm, preferably from 0.20 mm to 0.45 mm and more preferably from 0.25 mm to 0, 40 mm. Here d '= 0.38 mm and d2' = d3 '= 0.30 mm.

[093] The intermediate layer 14 'of the TE strand is saturated and non-compact. Indeed, the average inter-son distance 12 'between the intermediate M' son F2 'is here equal to 38 μηι.

[094] The ratio d2VI2 'is such that <d2VI2' <15 and preferably 5 <d2VI2 '<10. Here d272' = 7.90.

[095] The outer layer 16 'of the TE strand is unsaturated. Indeed, the mean inter-wire distance 13 'between the N' external wires F3 'is here equal to 55.4 μηη.

[096] The ratio d3VI3 'is such that 3 <d37l3' <10 and preferably 4 <d37l3 '<6. Here, d3VI3' = 5.42.

[097] Each internal wire F1 of the inner strand T1 has a diameter d1 equal to the diameter d2 of each intermediate wire F2 of the inner strand T1.

[098] Each intermediate wire F2 of the inner strand T1 has a diameter d2 equal to the diameter d3 of each outer wire F3 of the inner strand T1.

[099] Each intermediate wire F2 'of each outer strand TE has a diameter d2' equal to the diameter d3 'of each outer wire F3' of said outer strand TE.

The inner wire F1 'of each outer strand TE has a diameter d1' greater than the diameter d2 'of each intermediate wire F2' and the diameter d3 'of each outer wire F3' of said outer strand TE.

The cable according to the invention is manufactured using a method comprising steps that are well known to those skilled in the art. Thus, 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.

The cable 50 is incorporated by calendering with composite fabrics formed of a known composition based on natural rubber and carbon black as reinforcing filler, conventionally used for the manufacture of radial tire crown reinforcement. 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 and finally a vulcanization system (sulfur, accelerator, ZnO).

The composite fabrics reinforced by these cables comprise a rubber matrix formed of two thin layers of rubber which are superimposed on either side of the cables and which respectively have a thickness of between 1 and 4 mm inclusive. The calender pitch (no laying of the cables in the rubber fabric) is between 4 mm and 8 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

The cable 50 according to the invention was compared with several control cables T1, T2, T3 and T4.

The cable 50, shown in FIG. 4, is a cable 132.30 FR according to the invention with structure [(3 + 8 + 13) x0.30) + 6x (0.38+ (6 + 11) x0.30) ] +0.28 and whose sons are of grade SHT.

The cable T1, shown in FIG. 5, is the cable 189.23 FR described in the preamble of the present application and of structure [(3 + 9 + 15) x0.23 + 6x (3 + 9 + 15) x0 .23] +0.26 and whose sons are of grade NT (for "Normal Tensile").

The cable T2, shown in FIG. 6, is a cable 77.35 FR of [(3 + 8) x0.35 + 6x (3 + 8) x0.35] +0.23 structure and whose wires are of HT grade. (for "High Tensile").

The breaking strength, denoted Rm, of the son of the cables T1 and T2 is such that 2500 MPa <Rm <3000 MPa.

The cable T3, represented in FIG. 7, is a cable 126.35 FR of structure [(0.39+ (6 + 11) x0.35) + 6x (0.39+ (6 + 11) x0.35)] + 0.28 and whose sons are of grade SHT.

The cable T4, shown in FIG. 8, is a 126.30 FR cable of structure [(0.38+ (6 + 11) x0.30) + 6x (0.38+ (6 + 11) x0.30)] + 0.28 and whose sons are of grade SHT.

The tensile strength, denoted Rm, of the son of the cables T3, T4 and 50 is such that Rm> 3000 MPa. [0114] Measurement measurements

The measure of force at break noted Fm (maximum load in N) is performed in tension according to ISO 6892 of 1984. Table 1 below shows the results obtained by force at break Fm.

The breakage force before aging Fi is measured on a manufactured cable having been stored under normal conditions of pressure and temperature for a period of less than or equal to 4 months.

The breaking force after aging Fr is measured on a manufactured cable having been heated at 150 ° C. for 1 hour.

The breaking force of the gummed cable Fg is measured on a non-aged gummed cable (storage for a period of less than or equal to 4 months).

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 cables from manufacturing and not aged. The raw cables are previously coated from the outside with a so-called coating gum. For this, a series of 10 cables arranged in parallel (interchangeable distance: 20 mm) is placed between two layers or "skims" (two rectangles of 80 x 200 mm) of a diene rubber composition in the raw state, each skim having a thickness of 5 mm; the whole is then locked in a mold, each of the cables being kept under a sufficient tension (for example 3 daN) to ensure its straightness during the establishment in the mold, using clamping modules; then the vulcanization (baking) is carried out for about 10 to 12 hours at a temperature of about 120 ° C and 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 7x7x60 mm, for characterization.

A conventional diene rubber composition for a tire 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) (parts by weight) percent elastomer); the E10 module of the coating gum is approximately 10 MPa.

The test is carried out on 6 cm of cable length, thus coated by its surrounding rubber composition (or coating gum) in the cooked state, as follows: 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 cm ³ / 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; the tightness of the seal itself is checked beforehand with the aid of a solid rubber specimen, that is to say without cable.

The average air flow measured (average of the 10 test pieces) is even lower than the longitudinal imperviousness of the cable is high. As the measurement is made with an accuracy of ± 0.2 cm3 / min, measured values less than or equal to 0.2 cm3 / min are considered to be zero; they correspond to a cable which can be described as airtight (totally airtight) along its axis (i.e., in its longitudinal direction).

The procedure is similar to measure the flow rate of each inner and outer strand. The inner and outer strands are obtained by separating the inner and outer strands from each other.

The results of tests carried out on the control cables T1 to T4 and 50 according to the invention are summarized in Table 1 below. The word "NM" means that the test has not been carried out and no measurement has been made.

The diameter is indicated in base 100 relative to the cable T1. Thus, for a cable T of diameter D (T), the value of D in base 100 D (T, 100) is given by the relation D (T, 100) = D (T) / D (T1).

The decay Dv breaking force due to the aging of the cable is equal to the ratio (Fi-Fr) / Fi in which Fi is the breaking force before aging and Fr is the breaking force after aging.

The decay force Dg breaking force due to the exfoliation of the cable is equal to the ratio (Fi-Fg) / Fi in which Fi is the breaking force before aging and Fg is the breaking force after scrubbing the cable.

The breaking force of the web Fm is measured by considering the breaking force of the gummed cable Fg. This breaking force Fm is indicated in base 100 with respect to a sheet comprising the cable T1. Thus, for a sheet comprising T-force breaking-edge cables Fm (T), the value of Fm in base 100 Fm (T, 100) is given by the relation Fm (T, 100) = Fm (T) / Fm (T1). For each cable, the breaking strength of the web was calculated for the same inter-cable distance. Those skilled in the art will be able to choose the inter-cable distance corresponding to the desired level of reinforcement.

Table 1

Cable T1 T2 T3 T4 50

189.23 EN 77.35 EN 126.35 EN 126.30 EN 132.30 EN

Denomination

NT HT SHT SHT SHT

E (μιη) 0 0 0 0 121

12 (μιη) 66 15 19 38 55

I3 (μιη) 11/53 55 60.5

I2 '(μιη) 66 15 19 38 38

Ι3 '(μιη) 11/53 55 55

Cable diameter (base

100 94 121 104 103 100) without fret F

Breaking force (N) without

20297 18231 32085 26794 24380 Aging Fi

Breaking force (N)

20003 16676 NM 23363 22444 after aging Fr

Breaking force (N) of the

20608 18126 31466 26845 24059 cable gummed Fg

Lapse Dv (%) 1, 4 8.5 NM 12.8 7.9

Lapse Dg (% -1, 5 0.6 1, 9 -0, 19 1, 3

Breaking force tablecloth

100 92 132 126 110 Fm (base 100)

Internal strand

Flow rate (cm ³ min ^-1 ) 100 50 80 64 37

Number of points to

0% 0% 0% 0% 0% debit

External strand

External strand flow

> 100 1 20 9 1 (cm ³ min- ¹ )

Number of points to

0%> 25% 0% 0% 40% nil

Cable

Average flow (cm ³ min ^-1 ) 400 35 120 50 33 Regarding the penetrability of the cables tested, it is noted that the cable 50 according to the invention has an average rate much lower than those of the control cables T1, T3 and T4 and substantially equal to that of the control cable T2. Thus, the cable 50 according to the invention has improved penetrability. The inter-strand spaces made possible by the DI> DE feature allow the rubber to access, on the one hand, the inner strand (the flow of the inner strand of the cable according to the invention 50 is much lower than that of the control cables T1 to T4) and, secondly, at the junction between each outer strand and the inner strand which allows to penetrate integrally each outer strand (the rate of each outer strand of the cable according to the invention 50 is much lower than those T1, T3 and T4 control cables). These results are observable in the photographs of FIGS. 4 to 8 on which it is observed that: the cable 50 according to the invention (FIG. 4) is almost completely penetrated with rubber;

the cable T1 (FIG. 5) has capillaries in each inner and outer strand and between each outer strand and the inner strand;

T2 cable (Figure 6) is relatively well penetrated with gum except the inner strand having capillaries;

the cable T3 (Figure 7) has many capillaries in the inner strand but also in some outer strands; and

the cable T4 not according to the invention (Figure 8) has many capillaries in the inner strand and between some outer strands and the inner strand.

Regarding the breaking forces of the cables tested, it will be noted that the cables T2, T3, T4 and 50 have a significant decrease in the breaking force after aging (breaking force Fr) and an increase in this breaking force after exfoliation (breaking force Fg) contrary to the T1 cable for which the breaking force remains substantially constant after aging and after scrubbing. As explained above, the very high penetrability of the cable 50 according to the invention makes it possible on the one hand to at least partially restore the vault and on the other hand to create rubber cushions between the inner and outer strands so that the gummed cable has a breaking force Fr close to the breaking force without aging Fi.

Also concerning the breaking forces, the cable 50 according to the invention has fracture forces Fi and Fg much higher than the T1 and T2 cables thus providing better reinforcement. In addition, the cable 50 according to the invention has a significantly smaller diameter than the cable T3 and substantially equal to that of the cable T4, which maximizes the metal mass that can be put in a sheet. It is also possible to reduce the thickness of the sheet and therefore the heating, the rolling resistance and the mass of the tire.

In conclusion, the cable 50 according to the invention has the best compromise between breaking force, penetrability, efficiency and ease of use in a web.

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, in particular substantially oval section or polygonal, for example triangular, square or rectangular.

The son, of circular section or not, for example a corrugated wire, can be twisted, twisted helical or zig-zag. In such cases, it must of course be understood that the diameter of the wire represents the diameter of the cylinder of imaginary revolution which surrounds the wire (space diameter), and no longer the diameter (or any other transverse size, if its section is not circular) of the core wire itself.

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.

The characteristics of the various embodiments described or envisaged above may also be combined provided that they are compatible with each other.

Claims

1. Multi-strand wire (50) with two layers, characterized in that it comprises:

- an inner layer (C1) of the cable (50) consisting of an inner strand (Tl), - an outer layer (C2) of the cable (50) consisting of L> 1 outer strands

(YOU),

each inner and outer strand (T1, TE) comprising:

an internal and external strand inner layer (12, 12 ') (T1, TE) respectively consisting of Q and Q' internal thread (s) (F1, F1 '),

an intermediate layer (14, 14 ') of the inner and outer strand (T1, TE) respectively consisting of M and M' intermediate wires (F2, F2 '), and

an outer layer (16, 16 ') of the inner and outer strand (Tl, TE) respectively consisting of N and N' external wires (F3, F3 '),

in which :

the diameter D1 of the inner strand (Tl) is greater than the diameter DE of each outer strand (TE),

the outer layer (16) of the inner strand (Tl) is unsaturated, and

the outer layer (16 ') of each outer strand (TE) is unsaturated.

2. Cable (50) according to the preceding claim, wherein the intermediate layer (14) of the inner strand (Tl) is unsaturated.

3. Cable (50) according to any one of the preceding claims, wherein the inner wire (F1 ') of each outer strand (TE) has a diameter d1' greater than the diameter d2 'of each intermediate wire (F2') of said outer strand (TE).

4. Cable (50) according to any one of the preceding claims, the inner wire (F1 ') of each outer strand (TE) has a diameter d1' greater than the diameter d3 'of each outer wire (F3') of said outer strand (YOU).

5. Cable (50) according to any one of the preceding claims, wherein the ratio of the diameter D of the assembly constituted by the inner (C1) and outer (C2) layers of the cable (10) over the distance E average strands of the outer layer (C2) is less than or equal to 500, preferably 100, more preferably 50 and even more preferably 40.

The cable (50) according to any one of the preceding claims, wherein the intermediate layer (14 ') of each outer strand (TE) is saturated.

7. Cable (50) according to any preceding claim, wherein each inner wire (F1) of the inner strand (T1) has a diameter d1 equal to the diameter d2 of each intermediate wire (F2) of the inner strand (Tl) .

8. Cable (50) according to any one of the preceding claims, wherein each intermediate wire (F2) of the inner strand (T1) has a diameter d2 equal to the diameter d3 of each outer wire (F3) of the inner strand (Tl) .

9. Cable (50) according to any one of the preceding claims, wherein each intermediate wire (F2 ') of each outer strand (TE) has a diameter d2' equal to the diameter d3 'of each outer wire (F3') of said outer strand (TE).

Cable (50) according to any one of the preceding claims, wherein Q> 1 and preferably Q> 2.

1 1. Cable (50) according to any one of the preceding claims, wherein Q = 3, M = 8 or 9 and N = 13 or 14 and preferably Q = 3, M = 8 and N = 13.

12. Cable (50) according to any one of the preceding claims, wherein M '= 6 and N' = 1 1.

13. Cable (50) according to any one of the preceding claims, wherein the outer layers of each inner and outer strand are wound in different directions of torsion.

14. Cable (50) according to any one of the preceding claims, wherein the intermediate and outer layers of each strand are wound in the same direction of torsion.

15. Pneumatic tire (10), characterized in that it comprises at least one cable (50) according to any one of claims 1 to 14.

16. Pneumatic tire (10) according to the preceding claim, comprising a carcass reinforcement (24) anchored in two beads (18) and radially surmounted by a crown reinforcement (14) itself surmounted by a tread (22). which is joined to said beads (18) by two flanks (16), said crown reinforcement (14) comprises at least one cable (50) according to any one of claims 1 to 14.

17. A tire (10) according to the preceding claim, wherein the crown reinforcement (14) comprises a protective armature (38) and a working armature (36), the armature (36) comprising at least one cable (50) according to any one of claims 1 to 14, the protective armature (38) being radially interposed between the tread (22) and the working armature (36).