EP2238288A1

EP2238288A1 - Method and device for manufacturing a cable comprising two layers of the in situ compound type

Info

Publication number: EP2238288A1
Application number: EP08869079A
Authority: EP
Inventors: Thibaud Pottier; Henri Barguet
Original assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France; Societe de Technologie Michelin SAS
Current assignee: Compagnie Generale des Etablissements Michelin SCA; Michelin Recherche et Technique SA France
Priority date: 2007-12-28
Filing date: 2008-12-22
Publication date: 2010-10-13
Anticipated expiration: 2028-12-22
Also published as: BRPI0821476A2; CN101910507A; CN101910507B; WO2009083213A1; JP2011508109A; FR2925923A1; EA201070802A1; KR101526630B1; KR20100106539A; EP2238288B1; BRPI0821476A8; US8627696B2; JP5486509B2; EA016480B1; US20110011486A1; FR2925923B1

Abstract

Method for manufacturing a metal cable comprising two layers (Ci, Ce) of M+N construction, made up of an inner layer (Ci) consisting of M wires of diameter d1 wound together in a helix with a pitch p1, M varying from 2 to 4, and an outer layer (Ce) of N wires of diameter d2 wound together in a helix with a pitch p2 around the inner layer (Ci), said method comprising at least the following steps, carried out in line: an assembly step, in which the M core wires are twisted together so as to form the inner layer (Ci) at a point of assembly; downstream of said point of assembly of the M core wires, a sheathing step, in which the inner layer (Ci) is sheathed with a diene rubber composition called “filling compound” in the uncured state; an assembly step, in which the N wires of the outer layer (Ce) are twisted together around the inner layer (Ci) thus sheathed; and a final twist balancing step. Device for implementing such a method.

Description

METHOD AND DEVICE FOR MANUFACTURING A TWO-LAYER CABLE OF THE TYPE IN SITU GUM

The present invention relates to processes and devices for manufacturing two-layer metal cables, of M + N construction, used in particular for the reinforcement of rubber articles, in particular tires.

It is more particularly related to processes and devices for manufacturing metal cables of the type "gummed in situ", that is to say, gummed from the inside, during their manufacture, by rubber in the raw state, in to improve their resistance to corrosion and consequently their endurance especially in the belts of tires for industrial vehicles.

A radial tire comprises in known manner a tread, two inextensible beads, two flanks connecting the beads to the tread and a belt circumferentially disposed between the carcass reinforcement and the tread. This belt consists of various plies (or "layers") of rubber reinforced or not by reinforcing elements ("reinforcements") such as cords or monofilaments, metal or textile type.

The tire belt generally consists of at least two superimposed belt plies, sometimes called "working" plies or "crossed" plies, whose reinforcing cords, generally of metal, 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 rubber, of variable widths depending on the case, with or without reinforcements; examples of simple rubber cushions include so-called "protection" plies intended to protect the rest of the belt from external aggression, perforations, or so-called "hooping" plies comprising reinforcements oriented substantially along the circumferential direction (so-called "zero degree" plies), whether radially external or internal with respect to the crossed plies.

Such a tire belt must meet in a known manner to different requirements, often contradictory, including:

be as rigid as possible with low deformation, because it contributes in a substantial way to stiffen the crown of the tire; to have as low a hysteresis as possible, on the one hand to minimize rolling heating of the inner zone of the crown and on the other hand to reduce the rolling resistance of the tire, which is synonymous with fuel economy; finally possess a high endurance, vis-à-vis in particular the phenomenon of separation, cracking of the ends of the crossed plies in the shoulder area of the tire, known as "cleavage", which requires in particular metal cables which reinforce the belt plies to have a high resistance to compression fatigue, all in a more or less corrosive atmosphere.

The third requirement is particularly strong for tire casings for industrial vehicles such as heavy vehicles, designed to be retreaded once or more when the treads they comprise reach a degree of critical wear after prolonged rolling.

For the reinforcement of the belts above, generally used "steel cords" ("layered cords") consisting of a central core and one or more layers of concentric threads arranged around this soul. The most widely used layered cables are essentially M + N or M + N + P construction cables, formed of a core of M wire (s) surrounded by at least one layer of N wires which may itself be surrounded by an outer layer of P son, the M, N or P son having generally the same diameter for reasons of simplification and cost.

The availability of increasingly resistant and durable carbon steels means that tire manufacturers are moving as far as possible towards the use of cables having only two layers, in particular to simplify the manufacture of these cables. to reduce the thickness of the reinforcing composite sheets and thus the hysteresis of the tires, ultimately reduce the costs of the tires themselves and reduce the energy consumption of vehicles equipped with such tires.

For all the reasons set out above, the two-layer cables most used today in tire belts are essentially M + N construction cables consisting of an inner core or layer of M yarns (in particular of 3 or 4 wires) and an outer layer of N wires (e.g., from 6 to 12 wires). The outer layer is relatively desaturated due to the high diameter of the inner layer provided by the presence of M core son, especially when the diameter of the core son is chosen to be greater than that of the son of the outer layer.

This type of construction promotes, as is known, the external penetrability of the cable by the tire calendering rubber or other rubber article during the cooking of the latter, and consequently, it is possible to improve the endurance of the cables in fatigue and fatigue-corrosion, particularly with regard to the cleavage problem mentioned above.

Furthermore, good penetration of the cable by rubber allows in a known manner, thanks to a volume of air trapped in the cable which is less, to reduce the cooking time of the tires ("duration in press").

However, the construction cables 3 + N or 4 + N have the disadvantage that they are not penetrable to the core because of the presence of a channel or capillary in the center of the three or four core wires, which remains vacuum after impregnation with rubber and therefore conducive, by a kind of "wicking" effect, to the propagation of corrosive media such as water. This disadvantage is well known, it has been disclosed for example in patent applications WO 01/00922, WO 01/49926, WO 2005/071157, WO 2006/013077.

To solve the problem above, it has been proposed to open the inner layer Ci, by removing its son, through a unit core wire (or "core wire") and remove a wire from the outer layer; thus, the cable obtained, for example of construction 1 + 3 + (N-I), becomes penetrable from the outside to its center. With respect to the wires of the inner layer, the core wire should be neither too thin, otherwise it does not produce the desaturation effect that is targeted, nor too big otherwise the wire does not stay in the center of the cable. Typically, for example, a 0.12 mm diameter core wire is used for 0.35 mm diameter C 1 and C 1 wire wires (see, for example, RD {Research Disclosure) August 1990, No. 316107, "Steel cord construction". ).

This first solution, relatively expensive since it requires adding a wire that does not otherwise contribute to the resistance of the cable, also faces a manufacturing problem: a high voltage on the core wire is necessary to maintain the wire at the center of the cable during wiring, which may in some cases approach the breaking force of the wire. Removing an external wire further reduces the resistance of the cable per section unit.

Still in order to solve this problem of penetrability to the core, patent application US 2002/160213 for its part proposed the production of M + N type cables gummed in situ, M ranging from 2 to 4. The method proposed here consists of to be sheathed individually (that is to say, singly, "wire to wire") with rubber in the green state, upstream of the assembly point of the M son (or torsion point), one or preferably each M son to obtain an inner layer sheathed rubber, before the subsequent introduction of N son of the outer layer by wiring around the inner layer and sheathed.

The process proposed above poses many problems. First of all the sheathing of a single thread on the M threads, for example of one thread out of three (as illustrated for example in FIGS. 11 and 12 of this application), does not make it possible to guarantee a sufficient filling by the eraser. of final cable, and thus to obtain satisfactory corrosion resistance. Then, the wire-to-wire cladding of each of the M wires (as illustrated for example in FIGS. 2 and 5 of this document), if it actually leads to a filling of the cable, leads to the use of too much rubber. The overflow of rubber at the periphery of the final cable then becomes unacceptable under industrial wiring and scrubbing conditions.

Due to the very strong adhesiveness of the rubber in the green state, the cable thus erased becomes unusable because of a parasitic sticky effect on the manufacturing tools or between the turns of cable during the winding of the latter on a reception coil, not to mention the final impossibility of properly calender the cable. It is recalled that calendering consists in transforming the cable, by incorporation between two layers of rubber in the green state, into a metal rubberized fabric used as a semi-finished product for any subsequent manufacture, for example for the manufacture of a tire.

Another problem posed by the insulated cladding of each of the M son is the large size imposed by the use of M extrusion heads. Because of such a bulk, the production of cylindrical layer cables (that is to say not pitch pi and p ₂ different from one layer to another, or footstep pi and p ₂ identical but with direction of torsion different from one layer to another) must necessarily be carried out in two discontinuous operations: (i) individual wrapping son then wiring and winding of the inner layer at first, (ii) wiring of the outer layer around the inner layer in a second time. Also because of the high stickiness of the rubber in the green state, the winding and the intermediate storage of the inner layer require, during the coil winding of the inner layer, the use of spacers and steps important slicing to prevent parasitic bonding between the wound layers and, for the same layer, between the turns.

All the above constraints are highly penalizing from the industrial point of view and antithetical to the search for high production rates.

Continuing their research, the Applicants have discovered a new process of twisting and scrubbing online and continuously, applicable to the manufacture of M + N cables gummed in situ, which overcomes the aforementioned drawbacks.

Accordingly, a first object of the invention is a method for manufacturing a two-layer (Ci, Ce) metal cable, of M + N construction, comprising an inner layer (Ci) consisting of M son of diameter d, coiled together in a helix according to a pitch pi, M ranging from 2 to 4, and an outer layer (Ce) of N son of diameter d ₂ wound together in a helix in a pitch p ₂ around the inner layer (Ci), said method comprising at least the following steps operated online: - A step of assembly by twisting the M core son, for forming the inner layer (Ci) at an assembly point; downstream from said assembly point of the M core wires, a step of sheathing the inner layer (Ci) with a diene rubber composition, called "filling rubber", in the green state; a step of assembly by twisting the N son of the outer layer (Ce) around the inner layer (Ci) and sheathed; a final balancing step of the twists.

The invention also relates to an assembly device and in-line scrubbing, usable for implementing the method of the invention, said device comprising upstream downstream, according to the direction of advancement of the cable being formed:

feeding means for the M core wires; first assembly means by twisting the M core son for forming the inner layer; means for sheathing the inner layer;

- Out of the cladding means, second assembly means by twisting the N outer son around the core and sheathed, for forming the outer layer; at the output of the second assembly means, torsion balancing means.

The invention as well as its advantages will be readily understood in the light of the description and the following exemplary embodiments, as well as FIGS. 1 to 7 relating to these examples which schematize, respectively:

an example of an in situ twisting and scrubbing device that can be used for implementing the method according to the invention (FIG.

in cross-section, a construction cable 3 + 9 of the compact type that can be manufactured by the method of the invention (FIG. in cross-section, a conventional 3 + 9 construction cable, also of the compact type (Fig. 3); in cross-section, a 3 + 9 construction cable of the cylindrical layer type which can be manufactured by the method of the invention (FIG 4); - in cross-section, a conventional 3 + 9 construction cable, also of the cylindrical layer type (Fig. 5);

- in cross-section, another conventional cable, of the type with cylindrical layers, of construction 1 + 3 + 8 with a core wire of very small diameter (Fig. 6); in radial section, a heavy-duty pneumatic tire with a radial carcass reinforcement (Fig. 7). I. DETAILED DESCRIPTION OF THE INVENTION

In the present description, unless expressly indicated otherwise, all the percentages (%) indicated are% by weight. Any range of values designated by the expression "between a and b" represents the range of values from more than a to less than b (i.e., terminals a and b excluded) while any range of values designated by the expression "from a to b" means the range from a to b (i.e., including the strict limits a and b).

The method of the invention is intended for the manufacture of a two-layer metal cable (Ci, Ce) of M + N construction, of the "gummed in situ" type, comprising an inner layer (Ci) consisting of M son of diameter di wound helically together in a pitch p _b M ranging from 2 to 4, and an outer layer (Ce) of N d ₂ diameter son wound helically in a pitch p ₂ around the inner layer (Ci), said method comprising at least the following steps operated online:

firstly, a step of assembly by twisting the M core son, for forming the inner layer (Ci) at an assembly point; then, downstream from said assembly point of the M core wires, a step of sheathing the inner layer (Ci) with a diene rubber composition called "filling rubber" in the green state (that is, say non-crosslinked); followed by a step of assembly by twisting the N son of the outer layer (Ce) around the inner layer (Ci) and sheathed; then a final balancing step of the twists.

It is recalled here that there are two possible techniques for assembling metal wires:

or by wiring: in such a case, the wires are not twisted around their own axis, due to a synchronous rotation before and after the assembly point; or by twisting: in such a case, the yarns undergo both a collective twist and an individual twist around their own axis, which generates a detorsion torque on each of the threads.

A first essential characteristic of the above method is to use, both for the assembly of the inner layer and for that of the outer layer, a twisting step.

During the first step, the M core wires are twisted together (direction S or Z) to form the inner layer Ci, in a manner known per se; the son are delivered by feeding means such as coils, a distribution grid, coupled or not to a joining grain, intended to converge the core son in a common point of torsion (or assembly point).

The M son of the inner layer have for example a diameter d between 0.20 and 0.50 mm, in particular in a range of 0.23 to 0.40 mm; their not twisting Pi is for example between 5 and 30 mm.

It will be recalled here that in a known manner the pitch "p" 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.

The inner layer (Ci) thus formed is then sheathed with filling gum in the green state, provided by an extrusion screw at an appropriate temperature. The filling rubber can thus be delivered at a fixed point, unique and compact, by means of a single extrusion head, without using an individual sheathing son upstream of the assembly operations, before forming the inner layer, as described in the prior art.

This method has the significant advantage of not slowing down the conventional assembly process. It enables the complete operation of initial twisting, scrubbing and final twisting in one line, irrespective of the type of cable produced (compact layer cable as a cylindrical layer cable), all at high speed. The method of the invention can be implemented at a speed (running speed of the cable on the twisting-scrub line) greater than 70 m / min, preferably greater than 100 m / min.

Downstream of the assembly point (that is to say between the assembly point and the extrusion head), the tension stress exerted on the M threads, substantially identical from one thread to the other, is preferably between 10 and 25% of the breaking force of the son.

The extrusion head may comprise one or more dies, for example an upstream guide die and a downstream die calibration. It is possible to add continuous measurement and control means of the diameter of the cable connected to the extruder. Preferably, the extrusion temperature of the filling rubber is between 60 ^° C. and 120 ° C., more preferably between 70 ^° C. and 110 ^° C.

The extrusion head thus defines a cladding zone having the shape of a cylinder of revolution whose diameter is of course adjusted to the specific construction of the cable manufactured. By way of example, in the case of a 3 + N construction cable, the extrusion diameter is preferably between 0.4 and 1.2 mm, more preferably between 0.5 and 1.0 mm. The extrusion length is preferably between 4 and 10 mm. Preferably, at the outlet of the extrusion head, the inner layer Ci, at any point of its periphery, is covered with a minimum thickness of filling rubber which is preferably greater than 5 μm, more preferably greater than 10 μm. for example between 10 and 50 microns.

The amount of filling gum delivered by the extrusion head is adjusted to a preferred range of 5 to 40 mg per gram of final cable (i.e., gummed in situ).

Below the indicated minimum, it is not possible to guarantee that the filling rubber is present in each of the interstices of the cable, while beyond the maximum indicated, one can expose oneself to the different problems previously described due to overflowing of the filling rubber at the periphery of the cable. For all these reasons, it is preferred that the amount of filling gum delivered be between 5 and 30 mg, more preferably still within a range of 10 to 25 mg per g of cable.

The diene elastomer of the filling rubber is preferably chosen from the group consisting of polybutadienes (BR), natural rubber (NR), synthetic polyisoprenes (IR), different copolymers of butadiene, the various copolymers of isoprene, and mixtures of these elastomers. A preferred embodiment consists in using an "isoprene" elastomer, that is to say a homopolymer or a copolymer of isoprene, in other words a diene elastomer chosen from the group consisting of natural rubber (NR). , the synthetic polyisoprenes (IR), the various isoprene copolymers and the mixtures of these elastomers.

The filling rubber is of the vulcanizable type, that is to say that it generally comprises a vulcanization system adapted to allow the crosslinking of the composition during its cooking, typically based on sulfur and one or more accelerators. The filling rubber may also comprise all or part of the usual additives intended for tire rubber matrices, such as, for example, reinforcing fillers such as carbon black or silica, antioxidants, oils, plasticizers, anti-eversion agents, resins, adhesion promoters, and cobalt salts. Preferably, the filling rubber has, in the crosslinked state, a secant modulus ElO extension (at 10% elongation) which is between 5 and 25 MPa, more preferably between 5 and 20 MPa.

At the output of the preceding cladding step, during a third step, the final assembly is carried out, always by twisting (S or Z direction), of the N wires of the outer layer (Ce) around the inner layer (Ci) and sheathed. During the twisting, the N threads come lean on the filling rubber, embed itself in it. The filling rubber, moving under the pressure exerted by these external son, naturally has a tendency to fill, at least in part, each of the interstices or cavities left empty by the son, between the inner layer and the outer layer.

The number N of wires of the outer layer N is, of course, a function not only of the respective diameters di and d ₂ , but also of the number M of wires of the inner layer. For a value M preferably equal to 3 or 4, it varies preferably from 6 to 12. These N son have for example a diameter d ₂ of between 0.20 and 0.50 mm, in particular in a range of 0.23. at 0.40 mm, d ₂ can of course be identical to or different from the diameter di M soul son.

According to a particularly preferred embodiment, the inner layer comprises 3 or 4 wires, more preferably 3 wires, and the outer layer preferably comprises 8, 9 or 10 wires.

In the case of a 3 + N cable, the following relationships are preferably verified:

for N = 8: 0.7 <(di / d ₂ ) <1;

for N = 9: 0.9 <(di / d ₂ ) <1.2; for N = 10: 1.0 <(di / d ₂ ) <1.3.

According to a particularly preferred embodiment, the inner layer has 3 wires and the outer layer has 9 wires.

The twisting pitch p ₂ , identical to or different from the pitch pi, is preferably between 10 and 30 mm, more preferably in a range of 12 to 25 mm. Preferably, there is the relation 0.5 <pi / p ₂ <1 which is verified.

According to another preferred embodiment, the method of the invention is implemented with pi and p ₂ which are equal.

Preferably, the outer layer Ce has the preferred characteristic of being a saturated layer, that is to say that, by definition, there is not enough room in this layer to add at least one (N _max + l) th wire diameter d ₂ , N _max representing the maximum number of windable son in a layer around the inner layer Ci. This construction has the advantage of limiting the risk of overflow of filling rubber at its periphery and of offer, for a given diameter of the cable, a higher resistance.

The number N of wires can vary to a very large extent according to the particular embodiment of the invention, for example from 6 to 12 wires for an internal layer Ci of 3 wires, it being understood that the maximum number N _max of wires N will be increased if their diameter d ₂ is reduced compared to the diameter d of the M core wires, in order to preferentially preserve the saturated outer layer.

The M + N cable, like any layer cable, can be of two types, namely of the compact type or the type with cylindrical layers.

According to a particularly preferred embodiment of the invention, the son of the outer layer (Ce) are helically wound at the same pitch and in the same direction of torsion (that is to say in the direction S (provision "S / S"), or in the direction Z ("Z / Z" arrangement)) and the wires of the inner layer (Ci), for obtaining a layer cable of the compact type as schematized for example in Figure 2.

In such compact-layer cables, the compactness is such that virtually no distinct layer of wires is visible; As a result, the cross-section of such cables has an outline which is polygonal and non-cylindrical, as illustrated for example in Fig. 2 (compact cable 3 + 9 gummed in situ) and Fig. 3 (compact cable 3 + 9 conventional, c that is, not gummed in situ).

After twisting the outer layer around the inner layer sheathed with filling rubber, the cable M + N is not yet complete. The central channel delimited by the M core wires, when M is equal to 3 or 4, is not yet filled with filling rubber, in any case insufficiently to obtain a watertightness property. the air is acceptable. When M is equal to 2, the filling rubber surrounds the inner layer without sufficiently penetrating between the two wires which remain in contact with each other, which can be detrimental in particular with respect to the risks of wear. possible by fretting.

The next essential step is to route the cable through torsion balancing means. By "torsion balancing" is meant here in known manner the cancellation of the residual torsional torques (or of the detorsion springback) exerted on each wire of the cable, in the inner layer as in the outer layer.

Torsion balancing tools are well known to those skilled in the art of twisting; they may consist for example of "trainers" or "twisters" or "twister-trainers", consisting of either pulleys for twisters or small diameter rollers for trainers, pulleys and / or rollers through which circulates the cable.

It is assumed a posteriori that, when passing through the balancing tool, the detorsion exerted on the M core son, causing a reverse rotation, at least partial, of the latter around their axis, is sufficient to force, to train the eraser filling in the green state (Le., uncrosslinked, uncured), still hot and relatively fluid from the outside to the heart of the cable, even inside the central channel formed by the M son (For M = 3 or 4) or between the two wires themselves (for M = 2), ultimately offering the cable of the invention the excellent property of impermeability to air that characterizes it. The additional dressing function, provided by the use of a trainer tool, would have the advantage that the contact of the roller of the trainer with the son of the outer layer will exert additional pressure on the filling rubber further promoting its penetration between the M souls.

In other words, the method of the invention exploits the rotation of the M core wires, at the final stage of manufacture of the cable, to naturally distribute, homogeneously, the filling rubber inside and around the inner layer (Ci), while perfectly controlling the amount of filling compound provided.

Thus, unexpectedly, it has been found possible to penetrate the filling rubber into the heart of the cable of the invention, by depositing the rubber downstream of the assembly point of the M son and not upstream as described in FIG. the prior art, while controlling and optimizing the amount of filling gum delivered through the use of a single extrusion head.

After this final step of balancing the torsion, the manufacture of the cable of the invention is complete. This cable can be wound on a receiving reel, for storage, before being processed, for example, through a calendering installation, for preparing a metal / rubber composite fabric.

Thus prepared, the cable M + N can be qualified as airtight or impermeable to air: in the air permeability test described in paragraph II-1-B which follows, it is characterized by a flow rate average air less than 2 cm ³ / min, preferably less than or equal to 0.2 cm ³ / min.

The method of the invention makes possible the manufacture of M + N cables which may be advantageously free (or virtually free) of filling gum at their periphery. By such an expression, it is meant that no particle of filling compound is visible, with the naked eye, at the periphery of the cable, that is to say that the person skilled in the art does not make any difference at the output of manufacture, with the naked eye and at a distance of two or three meters, between a coil of M + N cable gummed in situ prepared according to the invention and a conventional M + N cable coil (that is, ie not erased in situ).

This method of the invention naturally applies to the manufacture of compact type cables

(for recall and by definition, those whose layers Ci and Ce are wound at the same pitch and in the same direction) as cables of the type with cylindrical layers (for recall and by definition, those whose layers Ci and Ce are wound either in different steps, or in opposite directions, or in different steps and in opposite directions).

An assembly device and scrub according to the invention, usable for the implementation of the method of the invention described above, comprises upstream downstream, according to the direction of advancement of a cable being formed:

means for feeding the M son of the soul;

- Means assembling by twisting the M core son for forming the inner layer; means for sheathing the inner layer; at the outlet of the cladding means, means for assembling by twisting of N external threads around the core thus sheathed, for forming the outer layer; finally, torsion balancing means.

FIG. 1 shows an exemplary device (10) for assembly by twisting, of the fixed feed and rotary receiving type, which can be used for the manufacture of a cable of the compact type (p ₂ = p ₃ and the same direction). of the layers Ci and Ce) as illustrated for example in FIG. 2. In this device, supply means (110) deliver M (for example three) core wires (11) through a grid ( 12) of distribution (axisymmetrical distributor), coupled or not to an assembly line (13), beyond which the M core wires converge at a point of assembly or point of twisting (14), for formation of the inner layer (Ci).

The inner layer Ci, once formed, then passes through a cladding zone consisting for example of a single extrusion head (15) through which is intended to circulate the inner layer. The distance between the point of convergence (14) and the sheathing point (15) is for example between 50 cm and 1 m. Around the inner layer Ci thus gummed (16), progressing in the direction of the arrow, are then assembled by twisting the N son (17) of the outer layer (Ce), for example nine in number, delivered by means power supply (170). The final cable M + N thus formed is finally collected on a rotary reception (19), after passing through the torsion balancing means (18) consisting for example of a twister-trainer.

It will be recalled here that, in a manner well known to those skilled in the art, for the manufacture of a cable of the type with cylindrical layers as illustrated for example in Figure 4 (not p ₂ and p ₃ different and / or sense different torsion of the layers Ci and Ce), use a device comprising two members (supply or reception) rotating, and not a single as described above (Figure 1) by way of example. FIG. 2 schematizes, in section perpendicular to the axis of the cable (assumed rectilinear and at rest), an example of a preferred cable 3 + 9 gummed in situ, obtainable by means of the method according to the invention. previously described invention.

This cable (noted CI) is of the compact type, that is to say that its inner layers Ci and external Ce are wound in the same direction (S / S or Z / Z according to a recognized nomenclature) and moreover to the same not (P ₁ = p ₂ ). This type of construction has the consequence that the internal (20) and external (21) wires form two concentric layers which each have a substantially polygonal contour (represented in dotted lines) (triangular for the Ci, hexagonal layer for the Ce layer), and not cylindrical as in the case of cables with cylindrical layers which will be described later.

The filling rubber (22) fills the central capillary (23) (symbolized by a triangle) formed by the three core wires (20) by spreading them very slightly, while completely covering the inner layer Ci formed by these three wires. (20). It also fills each interstice or cavity (also symbolized by a triangle) formed either by a core wire (20) and the two external wires (21) which are immediately adjacent to it, or by two core wires (20) and the outer wire (21) adjacent thereto; in total, 12 interstices (helical capillaries, also symbolized by a triangle) are thus present in this cable 3 + 9, to which is added the central channel or capillary (23).

According to a preferred embodiment, in this 3 + N cable, the filling rubber extends in a continuous manner around the layer Ci it covers.

For comparison, Figure 3 recalls the section of a cable 3 + 9 (noted C-2) conventional (i.e., not gummed in situ), also of the compact type. The absence of filling gum means that virtually all the threads (30, 31) are in contact with each other, which leads to a particularly compact structure, very difficult to penetrate (not to say impenetrable) of the outside by rubber. The characteristic of this type of cable is that the three core wires (30) form a channel or central capillary (33) which is empty and closed and thus conducive, by "wicking" effect, to the propagation of corrosive media such as that water.

FIG. 4 schematizes another example of a preferential cable 3 + 9 according to the invention.

This cable (noted C-3) is of the type with cylindrical layers, that is to say that its internal layers Ci and external Ce are either wound at the same pitch (pi = p ₂ ) but in a different direction (S / Z or Z / S), or wound at a different pitch (pi # p ₂ ) regardless of the torsion directions (S / S or Z / Z or S / Z or Z / S). In known manner, this type of construction has the consequence that the wires are arranged in two adjacent and concentric layers (Ci and Ce), tubular, giving the cable (and the two layers) an outline (shown in dotted lines) cylindrical and not polygonal.

The filling rubber (42) fills the central capillary (43) (symbolized by a triangle) formed by the three core wires (40) slightly apart, while completely covering the inner layer Ci formed by the three wires ( 40). It also fulfills, at least in part (here, in this example, totally) each interstice formed either by a core wire (40) and the two external wires (41) which are immediately adjacent to it (the nearest), or by two core wires (40) and the adjacent outer wire (41); in total, 12 interstices or capillaries are thus present in this cable 3 + 9, to which is added the central capillary (43).

For comparison, Figure 5 recalls the section of a cable 3 + 9 (noted C-4) conventional (i.e., not gummed in situ), also of the type with two cylindrical layers. The absence of filling rubber causes the three wires (50) of the inner layer (Ci) to come into close contact with each other, which leads to an impenetrable, closed and impenetrable central capillary (53). on the outside by rubber and propitious on the other hand to the propagation of corrosive media.

The method of the invention also applies advantageously to 2 + N construction cables. Thanks to an optimized penetration of the cable, from the inside, by the filling rubber, it is no longer necessary to desaturate the outer layer to improve its penetrability from the outside, in particular by rubber. At identical wire diameters between the layers Ci and Ce, this advantageously makes it possible, for example, to replace 2 + 7 construction cables with 2 + 8 construction cables, which are more resistant for the same size.

By way of preferred examples, the process of the invention is used for the manufacture of construction cables 2 + 6, 2 + 7, 2 + 8, 3 + 7, 3 + 8, 3 + 9, 4 + 8, 4 + 9, 4 + 10, in particular, of the latter, those consisting of yarns having substantially the same diameter from one layer to another

The method of the invention is of course not limited to the manufacture of preferential cables whose son have diameters between 0.20 and 0.50 mm, as indicated above. For example, the process of the invention can be used for the manufacture of cables whose M and N wires have diameters di and d ₂ smaller, for example in a range from 0.08 to 0, 20 mm, such cables being used, for example, for reinforcing parts of tires other than their crown reinforcement, in particular for reinforcing the carcass reinforcement of tires for industrial vehicles such as heavy goods vehicles. II. EXAMPLES OF CARRYING OUT THE INVENTION

The following tests demonstrate the ability of the method of the invention to provide cables whose tire endurance is significantly increased thanks to an excellent property of imperviousness to air in the cable axis.

H-I. Measurements and tests used

A) Dynamometric measurements

For metal wire and cable, the breaking force measurements denoted Fm (maximum load in N), tensile strength Rm (in MPa) and elongation at break denoted At (total elongation in %) are made in tension according to ISO 6892 of 1984.

With regard to the rubber compositions, the modulus measurements are carried out in tension, unless otherwise indicated according to ASTM D 412 of 1998 (test piece "C"): it is measured in second elongation (ie after one cycle). accommodation) the secant modulus "true" (i.e., reduced to the actual section of the specimen) at 10% elongation, denoted ElO and expressed in MPa (normal conditions of temperature and hygrometry according to ASTM D 1349 of 1999).

B) 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 here carried out either on cables extracted from tires or rubber sheets that they reinforce, so already coated with rubber in the cooked state, or on raw manufacturing cables.

In the second case, the raw cables must be previously embedded, coated from the outside by a so-called coating gum. For this, a series of 10 cables arranged in parallel (inter-cable distance: 20 mm) is placed between two skims (two rectangles of 80 x 200 mm) of a rubber composition in the raw state, each skim having a thickness 3.5 mm; the whole thing is then locked in a mold, each of the cables being kept under tension sufficient (for example 2 daN) to ensure its straightness when placed in the mold, using clamping modules; then the vulcanization (baking) is carried out for 40 min at a temperature of 140 ^° C. and under a pressure of 15 bar (rectangular piston of 80 × 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 composition for tires based on natural rubber (peptized) and carbon black N330 (65 phr), comprising the following usual additives: sulfur (7 phr), sulfenamide accelerator, is used as a coating rubber. (1 phr), ZnO (8 phr), stearic acid (0.7 phr), antioxidant (1.5 phr), cobalt naphthenate (1.5 phr); the ElO module of the coating gum is approximately 10 MPa.

The test is carried out on 2 cm of cable length, thus coated by its surrounding rubber composition (or coating gum), 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; a preliminary seal check of the seal is made using a solid rubber specimen, ie, without a cable.

The measured flow rate is lower as long as the longitudinal imperviousness of the cable is high. As the measurement is made with an accuracy of ± 0.2 cm ³ / min, measured values equal to or less than 0.2 cm ³ / min are considered to be zero; they correspond to a cable that can be described as airtight along its axis (ie, in its longitudinal direction).

C) Filling rate

The amount of filling compound is measured by difference between the weight of the initial cable (thus erased in situ) and the weight of the cable (and therefore that of its threads) whose filling rubber has been eliminated by a suitable electrolytic treatment.

A sample of cable (length 1 m), wound on itself to reduce its bulk, constitutes the cathode of an electrolyzer (connected to the negative terminal of a generator), while the anode (connected to the positive terminal ) consists of a platinum wire. The electrolyte consists of an aqueous solution (demineralized water) comprising 1 mole per liter of sodium carbonate. L ¹ specimen, completely immersed in the electrolyte, is turned on for 15 min at a current of 300 mA. The cable is then removed from the bath, rinsed thoroughly with water. This treatment allows the rubber to be easily detached from the cable (if this is not the case, we continue the electrolysis for a few minutes). The eraser is carefully removed, for example by simply wiping with an absorbent cloth, while detaching one by one the son of the cable. The threads are again rinsed with water and then immersed in a beaker containing a mixture of deionized water (50%) and ethanol (50%); the beaker is immersed in an ultrasonic tank for 10 minutes. The threads thus devoid of any trace of gum are removed from the beaker, dried under a stream of nitrogen or air, and finally weighed.

From the calculation, the rate of filling rubber in the cable is calculated, expressed in mg of filling rubber per gram of initial cable, and averaged over 10 measurements (10 meters of cable in total).

H-2. Cable manufacturing

Two types of cables were first manufactured, 3 + 9 layered cables (referenced CI) and 1 + 3 + 8 layered cables (referenced C-5), the respective constructions of which correspond to the schematic representations of the cables. Figures 2 and 6 attached, and whose mechanical properties are given in Table 1 below.

Table 1

CI cables as schematized in Figure 2 were manufactured according to the method according to the invention, using a device as described above and shown schematically in Figure 1. The filling rubber was a rubber composition conventional tire crown reinforcement, having the same formulation as that of the belt rubber web that the CI cable is intended to reinforce in the tire test that follows. This composition was extruded at a temperature of 90 ^° C. through a calibration die of 0.700 mm.

Each CI cable is made up of 12 wires in total, all 0.30 mm in diameter, which have been wound at the same pitch (pi = p ₂ = 15.4 mm) and in the same direction of twist (S) for the obtaining a cable of the compact type. The rate of filling rubber, measured according to the method previously indicated in paragraph II-1C, is 16 mg per g of cable. This filling gum fills the channel or central capillary formed by the three core wires slightly apart, while completely covering the inner layer Ci formed by the three son. It also fills, at least partially if not totally, each of the twelve interstices or empty channels formed either between a core wire and the two external wires which are immediately adjacent to it, or between two core wires and the external wire which is adjacent.

C-5 cables, as shown schematically in Figure 6 were manufactured according to a conventional method. They are free of filling gum. Each C-5 cable comprises a core wire (65) of very small diameter (0.12 mm); the three inner wires (60) and the eight outer wires (61) each have a diameter of 0.35 mm. The 3 wires of the inner layer are wound together in a helix (direction S) with a pitch pi equal to 7.7 mm, this layer Ci being in contact with a cylindrical outer layer of 8 wires themselves wound together in a helix ( direction S) around the core in a pitch p ₂ equal to 15.4 mm. The core wire (65), by removing the wires (60) of the inner layer Ci and filling in some way the central channel formed by these three core wires (60), makes it possible to desaturate (by increasing the diameter of the inner layer Ci) the outer layer Ce (with identical thread diameters from one layer to another) and thereby increase the external penetrability of the cable (C-5) by rubber. Thanks to this construction, the C-5 cable becomes penetrable from the outside to its center.

All the wires used for the manufacture of these cables are fine carbon steel wires, manufactured according to known methods, the properties of which are given in Table 2 below.

Table 2

The C-I and C-5 layered cords are then calendered to rubber skims made of a conventional rubber composition for use in the manufacture of radial heavyweight tire belt plies. This composition is based on natural rubber (peptized) and N33O carbon black (55 phr), it also comprises the following usual additives: sulfur (6 phr), sulfenamide accelerator (1 phr), ZnO (9 phr), stearic acid (0.7 phr), antioxidant (1.5 phr), cobalt naphthenate (1 phr); the ElO module of the filling rubber is approximately 6 MPa.

II-3. Test of pneumatic crown reinforcement cables The cables CI and C-5 were then tested in a truck tire belt as shown schematically in FIG. 7.

This radial tire 1 comprises an apex 2 reinforced by a crown reinforcement or belt 6, two sidewalls 3 and two beads 4, each of these beads 4 being reinforced with a rod 5. The crown 2 is surmounted by a tread represented in this schematic figure. A carcass reinforcement 7 is wound around the two rods 5 in each bead 4, the upturn 8 of this armature 7 being for example disposed towards the outside of the tire 1 which is shown here mounted on its rim 9. The carcass reinforcement 7 is in known manner constituted by 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 a bead to the other so as to form an angle of between 80 ° and 90 ° with the median circumferential plane (plane perpendicular to the axis of rotation of the tire which is located halfway between the two beads 4 and passes through the middle of the crown frame 6). Of course, this tire 1 also comprises, in a known manner, an inner rubber or elastomer layer (commonly called "inner rubber") which defines the radially inner face of the tire and which is intended to protect the carcass ply from the diffusion of the tire. air from the interior space to the tire.

The crown reinforcement or belt 6 is in known manner constituted by two triangulation half-plies reinforced by metal cables inclined by 65 degrees, surmounted by two sheets called "working plies" superimposed crossed. These working plies are reinforced by metal cables arranged substantially parallel to each other and inclined by 26 degrees (radially internal ply) and 18 degrees (radially external ply). The two working plies are furthermore covered by a protective ply reinforced with conventional metal cables (high elongation) inclined at 18 degrees. All angles of inclination indicated are measured relative to the median circumferential plane of the tire.

In the tests that follow, the two "webs" webs above use either the C-I cables or the C-5 cables manufactured previously.

Two series of truck tire tests (denoted PI and P-5 respectively) of dimensions 315/70 R22.5 are carried out, with in each series of tires intended for driving, others for pneumatic shelling. new. The tires PI and P-5 are identical with the exception of the cables that strengthen their belt 6. The tires PI are reinforced by CI cables manufactured according to the method of the invention, the tires P-5 are reinforced by the cables C -5 which, because of their recognized performance, are particularly comparable to conventional 3 + 9 cables (wireless core unit), a witness of choice for this test.

These tires are subjected to a severe rolling test, in overload, intended to test their resistance to the so-called "cleavage" phenomenon (separation of the ends of the belt plies), by subjecting the tires (on an automatic rolling machine) to sequences of very strong drift and put in severe compression of their summit block in the shoulder zone.

The test is conducted until the forced destruction of the tires.

It is then noted that the tires PI reinforced by the cables resulting from the process of the invention, under the very severe conditions of rolling imposed on them, have a significantly improved endurance: the average distance traveled is increased by 20% compared with the tires. witnesses already showing an excellent performance.

H-4. Air permeability tests

The CI cables, manufactured with the method of the invention, were further subjected to the air permeability test (paragraph II-1B), by measuring the volume of air passing through the cables in 1 min (average of 10 measurements for each cable tested).

For each CI cable tested and for 100% of the measurements (ie ten test pieces out of ten), a flow rate of zero or less than 0.2 cm ³ / min was measured; the CI cables are therefore impervious to air, they can be qualified as airtight along their axis in the sense of the test of paragraph II-IB, this thanks to an optimal penetration rate by the rubber (filling rubber ).

In situ control gummed cables, of the same 3 + 9 construction as the CI cables, were also manufactured by individually sheathing either a single wire or each of the three wires of the inner layer Ci. This sheathing was made using extrusion dies of variable diameter (320 to 420 microns) arranged this time upstream of the assembly point (sheathing and in-line twisting) as described in the prior art (US 2002/160213 application cited above); for a rigorous comparison, the amount of filling gum delivered was adjusted in such a way that the rate of filling rubber in the final control cables (ie between 6 and 25 mg per g of cable, as measured according to the method of II-1C), which is close to that of the cables of the invention.

In the case of single wire cladding, regardless of the cable tested, it was observed that 100% of the measurements (ie, 10 out of 10 test pieces) indicated an air flow rate greater than 2 cmVmin; the measured average flow rate varied from 16 to 62 cm ³ / min depending on the operating conditions used, in particular the diameter of the extrusion die tested.

In the case of the individual cladding of each of the three yarns, even though the measured average flow rate (ranging from 0.2 to 4 cm ³ / min) was lower than the previous values, it was observed that:

- in the worst case (320 μm die), 90% of the measurements (ie 9 out of 10 test pieces) had a flow rate greater than 2 cnrVmin, with an average flow rate of 4 cm ³ / min; - in the best case (420 μm die), 10% of the measurements (ie 1 specimen on

10) still had a flow rate of about 2 cm ³ / min, with an average flow rate close to 0.2 cm ³ / min.

In other words, none of the above test leads can be qualified as an airtight cable along its longitudinal axis.

In addition, it was noted that among these control cables, those with the lowest air permeability (as a reminder, those obtained by individually wrapping each of the 3 son through a 420 micron die) had a relatively large amount filling rubber at their periphery, rendering them unsuitable for a calendering operation in industrial conditions.

In summary, the method of the invention allows the manufacture of M + N construction cables gummed in situ which, thanks to an optimal penetration rate by rubber, on the one hand can be implemented effectively under conditions industrial, especially without the difficulties associated with excessive overflowing of rubber during their manufacture, on the other hand have a tire belt endurance which is significantly improved compared to the best control cables known to date for such an application.

Claims

1. A method of manufacturing a two-layer metal cable (Ci, Ce) of M + N construction, comprising an inner layer (Ci) consisting of M son of diameter d, wound together in a helix in a pitch p ,, M ranging from 2 to 4, and an outer layer (Ce) of N son of diameter d ₂ wound together helically in a pitch p ₂ around the inner layer (Ci), said method comprising at least the following steps operated online :

- A step of assembly by twisting the M core son, for forming the inner layer (Ci) at an assembly point; downstream from said assembly point of the M core wires, a step of sheathing the inner layer (Ci) with a diene rubber composition, called "filling rubber", in the green state; a step of assembly by twisting the N son of the outer layer (Ce) around the inner layer (Ci) and sheathed; a final balancing step of the twists.

2. The method of claim 1, wherein the diameter d1 is between 0.20 and 0.50 mm and the pitch pitch pi is between 5 and 30 mm.

3. The method of claim 1 or 2, wherein the tensile stress exerted on the M son, downstream of the assembly point, is between 10 and 25% of their force at break.

4. Process according to any one of claims 1 to 3, in which the diene elastomer of the filling compound is chosen from the group consisting of polybutadienes, natural rubber, synthetic polyisoprenes, butadiene copolymers, copolymers of isoprene, and mixtures of these elastomers.

The process of claim 4, wherein the diene elastomer is natural rubber.

6. Method according to any one of claims 1 to 5, wherein the extrusion temperature of the filling rubber is between 60 ^° C and 120 ° C.

7. A method according to any one of claims 1 to 6, wherein the amount of filling gum delivered during the cladding is between 5 and 40 mg per gram of final cable.

8. Method according to any one of claims 1 to 7, wherein the inner layer, after sheathing, is covered with a minimum thickness of filling rubber greater than 5 microns.

9. A method according to any one of claims 1 to 8, wherein the diameter d ₂ is between 0.20 and 0.50 mm and the pitch p ₂ is greater than or equal to pi.

10. A method according to any one of claims 1 to 9, wherein the son of the outer layer are helically wound at the same pitch and in the same direction of torsion as the son of the inner layer.

The method of any one of claims 1 to 10, wherein M is 3 and N is 8, 9 or 10.

The method of any one of claims 1 to 11, wherein the outer layer Ce is a saturated layer.

13. Online assembly and scrubbing device, usable for the implementation of a method according to any one of claims 1 to 11, said device comprising upstream downstream, in the direction of advancement of the cable. training courses :

means for feeding the M son of the soul; first assembly means by twisting the M core son for forming the inner layer; means for sheathing the inner layer;

- Out of the cladding means, second assembly means by twisting the N outer son around the core and sheathed, for forming the outer layer;

- At the output of the second assembly means, torsion balancing means.

14. Device according to claim 13, comprising a fixed power supply and a rotary reception.

15. Device according to claim 13 or 14, wherein the cladding means are constituted by a single extrusion head comprising at least one calibration die.

16. Device according to any one of claims 13 to 15, wherein the son of torsion balancing means comprise a trainer or a twister or a twister-trainer.