ES2212664T3 - PROCEDURE AND DEVICE FOR THE MANUFACTURE OF A METAL ROPE TO REINFORCE ELASTOMERIC PRODUCTS, PARTICULARLY PNEUMATIC. - Google Patents

Abstract

Device for manufacturing metal cords to be used particularly for reinforcing composite elastomeric products, comprising: a supporting structure (100); a rotor (5) engaged with respect to said supporting structure (100) and rotatable according to a predefined axis; a cradle fastened to said supporting structure (100) according to an oscillation axis which coincides with the rotation axis of the rotor (5); feeding devices operatively fitted on said cradle to feed several elementary wires from the respective feeding spools (8), said elementary wires being driven onto said rotor (5) according to a stranding path with and sections (10A, 10C) coinciding with the rotation axis of the rotor (5) and with a central section (10B) distanced from said rotation axis; at least one preforming device (15) operatively engaged with the cradle and operating on one of said elementary wires in a section upstream with respect to the first end section (10A) of the stranding path. Furthermore, said at least one preforming device (15) is suitable for providing said elementary wire with a substantially sinusoidal deformation without sharp edges.

Description

Procedure and device for manufacturing of a metal rope to reinforce elastomeric products, particularly tires

The present invention relates to a device to preform one or more elementary wires that form a string Metal reinforcement. This rope is especially suitable for reinforce composite elastomeric matrix products, such as tires

In particular, the preforming device according to the present invention it is suitable for operating on wires of high carbon metal, which are preferred for manufacture high elongation strings.

The expression "high elongation" is used to indicate the ability of the reinforcing elements to stretch under tension, at least initially, to a considerable extent, thanks to the use of specific and / or certain materials geometric shapes specifically selected to meet the Particular manufacturing phases of tires and / or conditions of Tire use

In particular, these strings, defined as "HE" (High Elongation), present a final elongation between the 4% and 10%.

The wires that come out of this device preformation according to the invention are subsequently supplied to a conventional twisting station known in the art, where wires thus preformed are rotated about the longitudinal axis of the rope thus obtained.

Another object of the present invention is a process for manufacturing said rope, which comprises the following phases: preform one or more elementary wires that they form said rope by subjecting them to permanent deformation at along its longitudinal development; twist the elemental wires by a helical turn around the longitudinal axis of the rope.

In addition, the present invention relates to a metal rope, preferably a reinforcing rope, obtained through a preformation process and a subsequent twisting of the type previously mentioned.

This rope is specifically designed to be used in the manufacture of vehicle tire components motorized, but can easily be used to manufacture other articles, such as for example fluid conduits of high pressure, belts, belt conveyors, or any other product made of opposite material with elastomer base.

As is known, metal strings usually used to reinforce elastomeric products are generally made of several helically wound elemental wires around an axis that coincides with the longitudinal development of The ropes themselves.

Preferably, said strings are produced. by twisting machines comprising: a structure of support; a rotor coupled to said support structure which is swivel along a predefined axis; a tray attached to the support structure along an oscillation axis that coincides with the rotor rotation axis; feeding devices operatively mounted on said tray and / or outside, suitable for supplying one or more elementary wires that arrive from respective supply coils, said one or more being said elemental wires actuated along trajectories of suitable twisted; and preferably at least one device of preformation that works on one or more elementary wires in a section of the wires that precedes the twisting phase later.

This preformation device imposes on said one or more elementary wires a permanent bending deformation suitable to support and improve the subsequent disposition of wires according to a helical development that ensures that it is maintained the necessary structural compactness of the rope.

In addition, it is important to indicate that these strings, especially when used in tire manufacturing, they are generally required to be provided with a high mechanical resistance and allow good adhesion physicochemical with the elastomeric material in the that are embedded, as well as an efficient penetration of said material in the space surrounding each wire of said rope.

In fact, it is now that to eliminate the risk of that the strings suffer an unwanted corrosion phenomenon once introduced in a tire, or inside any product Made of elastomeric material, it is very important that the wires Elementals that form the strings are fully coated, for all its surface extension, through the material elastomeric in which the rope is embedded.

This result, which is harder to achieve when the more complex strings are considered, it is not achieved easily even when dealing with strings formed by a bass number of elementary wires.

In fact, to confer the required stability geometric and structural to the rope, the elementary wires that they form the rope they are compacted, that is, they are placed intimately in contact with each other, leading to the formation of one or more cavities closed inside said rope that extend along of the longitudinal development of the rope.

These cavities are closed and, in Consequently, they cannot be reached by the elastomeric material during the normal phases of rubber tapping and, as Consequently, corrosion can develop inside said cavities closed and spread along the wires Elementals that form the rope.

As a consequence, this means, for example, that regarding cuts and punctures in the structure of the tire, or for any other reason, moisture and / or external agents may penetrate these closed cavities inevitably starting a fast corrosion process of elementary wires, thus severely compromising the structural resistance of the rope and tire.

In addition, the presence of said closed cavities that cannot be reached by the elastomeric material implies reduced adhesion of the wires to the elastomer, which - about all if these ropes are used to make tires - in the practice can cause an unwanted tendency for wires separate from the elastomer.

An additional inconvenience due to rubber tapping insufficient of the wires, caused by the presence of said wires Closed cavities, is the development of wear of the wires in contact with each other. This generates an inevitable degeneration of the fatigue resistance of the wires and, consequently, of the rope.

An attempt to overcome this type of problem known in the art is to use the so-called strings "open", where the wires (usually between three and five) remain distant from each other throughout the entire phase of rubberized, performed according to known procedures that they consist of maintaining a tensile load that does not exceed five kilograms applied to the rope.

These strings are described, for example, in US Patent 4,258,543 in the name of the applicant. These ropes allow greater penetration of the rubber between the wires that form the ropes.

However, the strings obtained in this way they present several problems, especially in practice, since wires that form the strings tend to distance themselves too when subjected to considerable tensile stress during Tire manufacturing and tire use. This fact produces an unwanted geometric and structural instability of the ropes, which impairs the performance of the tire.

According to another embodiment of the prior art, it is they use the so-called double diameter ropes, that is, ropes with two pairs of wires, where the diameter of the wires of the first torque is properly differentiated from the diameter of the second pair.

It is also known (see patent EP 168,857) make a metal rope that has a first pair of wires elementals of equal diameter and a second pair of wires Elementals with a diameter smaller than the diameter of the first pair. Said first and second pairs are supplied to a machine of internal pickup twisted after going through a head circular preformation, where the wires of the first and second pair follow paths that ensure different preformation actions each.

The rope obtained in this way, in consequently, it presents the pair of wires with a larger diameter helically wound together while each wire of the second pair is interposed between the two wires of the first pair and extends parallel to the latter, being separated so proper of it.

In this way, the closed cavities cited previously removed from the cross section of the rope, ensuring total coverage of elementary wires by the elastomeric material used during the rubberizing phase.

However, the suggested technical solution involves that the wires with the smallest diameter are separated from those of larger diameter also when the rope is subject to stresses of traction in practice. This fact, as for the ropes "open" cited above, causes a certain geometric and structural instability of the rope that is not advantageous

In addition, it is very difficult to confer on the rope as well obtained a precise and regular geometric configuration in each point of its longitudinal development, since the reciprocal position constant of the wires in the rope is ensured by the type particular of preformation device used, but the distance between the wires with the smallest diameter and the wires with the largest diameter tends to vary randomly at various points of longitudinal development, both in resting conditions and in use of the rope

According to another known preformation procedure in the art and described in US Patent 4,258,543 cited formerly in the name of the applicant, a machine can be used roller preform. The roller is inactive and has several preforming seats, each located to engage operatively with a respective elementary wire of the rope.

These preformation seats are slots circumferential on the surface of the roller, whose width is substantially equal to the diameter of the corresponding wire elementary, with an end portion of semicircular profile that it has a coplanar axis to that of the end portions of the others circumferential grooves

In this way, the preformation can be varied adjusting the radius of curvature of said grooves or adjusting the tension applied to the wire. However, even this solution present problems, since the preformation action performed on the wire is often hindered by twisting tractions dynamic

To solve the problem of poor cauchutado of the wires of a given rope - a fact that can, as it has been mentioned, cause consequent corrosion problems not desired - a suggested solution consists of ropes usually formed with a low number of wires, where at least one of the elementary wires deforms during preforming to acquire a design that is no longer continuous, but presents a suitable dashed line.

This embodiment is described, for example, in the US 5,020,312, according to which at least one wire of a given rope is subjected to a zigzag design along the longitudinal direction of said rope.

This produces a continuous contact between at minus two adjacent wires along the longitudinal development of the impossible rope, thus causing the formation of a zone of separation between said two wires, that is, inlet openings which allow the introduction of rubber material in each curve Zigzag wire.

According to the subject described in this document, one or more suitable wires to form a given rope are unwound of respective storage coils and are supplied in a pair of opposite sprockets, through which the one or more wires mentioned above and are preformed according to the direction axial conferred to the zigzag design cited above.

This type of preformation is described. exhaustively and is also represented in detail in US Pat. 5,581,990.

However, the biggest problem with ropes manufactured according to this operating procedure reside in a remarkable breakage of the external fibers of the wires that form a string given at the apex of the fold. This fact implies a unavoidable and undesirable decrease in resistance values fatigue of said rope and, consequently, a decrease in the level qualitative of the tire in which said procedure is used.

In addition, it is known to use devices preformation provided with preformation heads for printing an axial deformation to one or more of said wires. More in In particular, US Patent 5,319,915 describes the positioning of a flat surface, which extends parallel to the axis of a wire, before twisting. Said flat surface is provided with preformation heads consisting of several pins positioned perpendicularly with respect to this flat surface to a regular distance from each other.

As depicted in US Pat. 5,722,226, said pins can be placed on a structure of support that can also be conical or cylindrical (i.e. not necessarily flat) and can be aligned or properly alternated to provide that the wire is preformed with the desired zigzag trajectory

This device, accordingly, is placed so that said wire alternately passes over and over under said head sequence, while all the device is rotated around its axis, which is parallel to the axis of the wire.

EP-A-0 patent 791 682 describes a device for manufacturing ropes of metal that are particularly used for elastomeric products reinforcing compounds according to claim 1, comprising a support structure, a rotor coupled with respect to said structure support and swivel according to a predefined axis, a tray held to said support structure along an oscillation axis that matches the axis of rotation of the rotor, devices feed operatively placed on said tray to supply several elementary wires of respective coils of feeding, said elementary wires being activated on said rotor according to a twisting path with sections of end that coincide with the axis of rotation of said rotor and with a separate central section of said axis of rotation; and that too It comprises at least one preforming device (15) operatively coupled with the tray and operative on the elementary wires in a previous section with respect to the first end section (10a) of the twisting path, thereby said at least one preforming device is suitable for providing said elementary wire of a deformation that is substantially a helical fold without sharp edges. Because internal torsional stresses that deform said wires are induced to them a helical configuration.

This device, however, has the drawback that the preforming device couples the least one elementary wire individually and thus produces a substantially sinusoidal deformation arranged on a flat.

US-A-5 patent 213 652 describes a steel cord that is used to reinforce composite elastomeric products comprising a pair of individually preformed interlocking filaments on a pin type preformer in a sinusoidal shape that is arranged on a plane. No device details mentioned for the manufacture of this rope.

The applicant has surprisingly found a twisting system for the manufacture of a metal rope provided with a good penetration of the elastomeric material between the wires that form said metal cord, as well as provided with good fatigue resistance compared to similar ropes known in the art.

In particular, the applicant has found that applying a gentle preforming action - substantially sinusoidal - to one or more metal wires that form a rope given, the rope has a better fatigue resistance, for example, with respect to the strings obtained by a process of preformation that uses sprockets.

More particularly, the applicant has found surprisingly, a rope according to the invention has a increased final elongation while string penetration in the elastomeric material it is considerably increased with respect to the wires mentioned above of the prior art.

A first aspect of the present invention is refers to a device according to claim 1.

Preferably, the device according to the invention comprises a preforming device for each wire Elemental of the rope.

More particularly, said at least one device preformation device according to the invention it comprises a first and a second pulley fixed to a structure of adequate support and free to rotate around its axis, each pulley having several opposite pins suitable for reciprocally penetrate each other a predefined distance to induce sinusoidal deformation without sharp edges on a wire passing through the space between the pins of the first pulley and the corresponding pins of the second pulley.

Another aspect of the present invention relates to to a method according to claim 6.

Another aspect of the present invention relates to to a tire for vehicle wheels according to claim 8.

Other features and advantages of this invention will be better explained by the following description detailed of some preferred embodiments thereof, reproduced with reference to the attached drawings, where:

- Figure 1 represents, in side view, a known twisting machine, where the device is used preformation according to the present invention;

- Figures 2a and 2b represent in detail a preforming device according to the present invention, in a top floor view and a partial side view, respectively;

- Figure 3 represents a tire, in section partial straight, provided with constituent elements comprising reinforcing ropes according to the invention.

With reference to the cited figures previously, numerical reference 1 generally indicates a string metal reinforcement that is particularly used in products Composite elastomers, especially vehicle tires motor, according to the present invention.

In a way known to itself, the rope 1 It comprises several elementary wires, made of steel with content carbon between 0.65% and 0.98% and with a diameter between 0.10 mm and 0.50 mm, helically wound around the axis of the longitudinal extension of the rope.

However, steel, which is the material preferred thanks to its mechanical properties, presents the inconvenient that its adheres sufficiently to the material vulcanized elastomeric. Consequently, to get a good adhesion to the elastomeric material, the steel is generally coated with a layer of a suitable material. This material of Coating is preferably brass. However, they can be used other coating materials, such as alloys that contain Cu, Zn, Ni, Co, Mn. In the preferred case of coating brass, adhesion is favored by deformation during vulcanization of bisulfide bonds (-S-S-) between the elastomeric matrix and copper which - being a component of brass - Covers the metal reinforcement element.

The known procedures for coating a Metal element with a brass layer can be divided into two families: metallization and diffusion. The first includes the electrolytic metallization of copper and zinc, while the second comprises the electro-metallization of one or more layers of copper on steel, followed by the electro-metallization of a zinc layer and by a heat treatment with the purpose of spreading zinc in the copper layers, thus forming a layer of brass.

These wires are then coated, preferably, brass with a metal composition consisting by 30% to 40% by weight of zinc and between 70% and 60% by weight of copper, more preferably 32.5% by weight in zinc and 67.5% in copper weight, to form a brass layer equal to approximately 0.25 µm ± 0.05.

The specific characteristics and construction characteristics of the rope 1 according to the invention are they will understand better by the following description, both in what refers to the device used as the procedure for its manufacturing.

Figure 1 represents an example of a machine twisted, particularly suitable to form a rope constituted by 5 elementary wires.

The machine for the production of a rope metal reinforcement 1 comprises, in a known configuration, a support structure 100 to which a rotatably coupled rotor 5, turning the latter by means of a motor or devices similar (not represented). In addition, a tray (not shown in the figure) is connected to said support structure and can oscillate around the axis of rotation of the rotor 5. Several coils of Feed 8 are operatively coupled on the tray. By at least one elementary wire of said rope 1 is wound on Each of the coils.

In addition, suitable unwinding devices (not represented because they are known for themselves and conventional) are coupled to the coils 8, which are placed on the tray to properly guide the wires elementals that come from the coils 8.

In a known way, elementary wires at the exit of the tray they are actuated on the rotor 5 according to a predefined twisting path, along which the rope 1 is formed through the rotation effect imposed on the rotor 5 by said motor or equivalent device, in combination with the drive produced on the rope by means of devices collection (not represented because they are known and not relevant in the scope of the invention).

More particularly, the twisted path comprises a first end section 10a that matches essentially with the axis of rotation of the rotor 5 and delimited by a first transmission device of rotation 12, solidly fixed to rotor 5, and a mounting unit 11 that it consists, in a known way, of a plate with five holes, solidly attached to the tray and, consequently, stationary

Along this first end section 10a the wires are subjected to a first helical twist around the axis of rotation of the rotor 5 through the effect of the rotational traction that the rotor imposes on the first device of rotation transmission 12.

After the first rotating roller 12, the wires follow a central section 10b of the twisting path that extends to the rotor 5 and is radially offset with respect to the axis of rotation of the rotor to jump the tray 7 and reach a second transmission device 13 solidly coupled to the rotor on the end axially
opposite.

Finally, the twisted trajectory presents a second end section 10c substantially coinciding with the axis of rotation of the rotor 5 and extending beyond the second rotation transmission device 13. In this second end section, through the traction effect of rotation imposed by the rotor 5 on the second device of transmission of rotation 13, a second twist of the Elementary wires, thus completing the formation of the rope 1 that stretches progressively away from the devices of Collection cited above.

The relationship between the rotation speed of rotor 5, preferably between 2000 and 6000 rpm, and the speed of pulling of the rope 1 - and, consequently, of the wires elementals that form it, preferably between 60 and 250 m / min - define a twisted step value, that is, the step according to which said elementary wires are helically wound on the finished rope 1.

In a preferred embodiment of the invention, said twisting pitch is maintained between 3 mm and 50 mm, preferably between 6 mm and 30 mm, more preferably equal to 16 mm

The following items are arranged operationally in sequence for each elementary wire along of the path of the elementary wires inside the tray, and more precisely before the mounting unit 11: a rotation transmission device 14, a device of preformation 15 according to the invention (shown in detail in the Figure 2) and a rotation transmission device 16 which It consists of a pulley rotated 90º with respect to the pulley pair of the invention; said rotated pulley has the purpose of driving the wire leaving the preforming device 15, to the unit of assembly 11.

With reference to figure 2a, the device preformation 15 according to the present invention comprises a pair of pulleys 200 and 201, preferably a pair of steel plates, fixed to a suitable support structure 202 and free to rotate around its axes. Each pulley has several opposite pins 203 and 204 suitable for reciprocally penetrating an extension predefined to cause axial deformation and deformation by bending at the same time on a wire that crosses the space between the pins of the first pulley 200 and the corresponding pins of the second pulley 201, during the penetration cited above obtained by the movement of the pair of pulleys mentioned above driven and rotated by means of the wire.

More particularly, the longitudinal axis of the support structure cited above is advantageously located perpendicular to the direction of advance of the wire that is submits to the desired preformation operation.

The pulleys 200 and 201 mentioned above are fixed to said support structure 202 and opposite, so that the first pulley 200 is held in a fixed position with respect to said support structure 2002, but is free to rotate around from its axis perpendicular to the longitudinal axis L of the structure of support.

The second pulley 201 of this pair, by the On the contrary, it is advantageously movable along a guide line 205 on the support structure and is located in parallel to the longitudinal axis L of the support structure to allow a fine adjustment of the second pulley 201, using a graduated scale 206 appropriate, with respect to the first and to approximate well or separate The pair mentioned above.

In addition, as mentioned above, each pulley 200 and 201 of the preforming device according to the The present invention is provided with a plurality of pins 203 and 204 of suitable length, located perpendicular to the surface of the pulley plate and placed consecutively each other to follow the peripheral profile of the pulley according to one step default defined by the distance between the axes of two consecutive pins.

With reference to Figure 2b, which represents a partial side view of the preforming device 15 according to the invention, to allow reciprocal penetration of the pins having said pair of pulleys, it is necessary that they be separated from way different from the longitudinal axis L of the support structure, that is, the surfaces of the plates of said pulleys belong to two different planes P1 and P2 parallel to each other and parallel to the plane containing the longitudinal axis L of the support structure 202.

In addition, to ensure the mentioned penetration previously, the pins 203 and 204 provided in the first pulley 200 and the second pulley 201 must be placed on surfaces of opposite plates so that, during the rotation of said pulleys, the respective pins are in reciprocal positions opposite.

More particularly, the penetration of pulleys of the pair of pulleys is variable and adjusted by the movement of the second movable pulley 201 closer or further by the straight guide 205 cited above. This setting is performed using a graduated scale 206 that is calibrated to define the level of penetration of the pins and, consequently, the resulting degree of preformation on the wire after with respect to the preformation device according to the present invention.

The level of penetration of the pins represents, the consequence, the change - longitudinal with respect to the support structure 202 - made by the second mobile pulley 201 in the direction of the first pulley 200, which is fixed.

In particular, said level of penetration represents the distance D between the axis of a first pin 203 that it has the fixed pulley 200 and the shaft of a second pin 204 in the mobile pulley 201. Said second pin 204 is in a position consecutive with respect to the first, so that the distance D cited above is measured in the penetration area of said First and second pin. This area defines the trajectory of preformation of said wire.

Finally, the twisting machine comprises a stretching device (winch), a device for collecting the rope produced and the usual reinforcement devices of the wires, such as the false club, to eliminate tension residual in the finished rope. These devices are not represented as they are known, conventional and not particularly relevant for the purposes of the invention.

According to another embodiment of the invention, the twisting operation is such as to ensure that at least one wire of a given rope is subject to preforming according to the present invention, while the rest of the wires of said Rope are treated as described in the prior art. By For example, said remaining wires can be subjected to preforming using a roller preforming machine, such as that described in US Patent 4,258,543 cited above in the name From applicant.

The preforming devices 15 according to the present invention are applicable to all types of currently known twisting systems, for example a double turn system or an arrangement system. More particularly, a double-turn system may have internal collection (if the collection coil of the finished product is inside the tray, between the rotors) or external collection (if the supply coils are inside the tray while the pickup coil of the finished product is out of the tray). The arrangement system, finally, differs from the double-turn system in that in the arrangement machines each turn of the rotor corresponds to a single twist step, while in the double-turn machines each turn of the rotors corresponds to an advance Equal two twisting steps. Consequently, the difference between these two systems is in their
productivity.

According to a preferred embodiment of the invention, the pulleys used in the preforming device are identical in set, that is, they have equal diameter, an equal number of pins and pins used in both pulleys have the same diameter.

With the preformation machine 15 - thanks to its structure - it is possible to obtain a wire with a deformation in substantially sinusoidal wave on a plane that is parallel and intermediate to planes P1 and P2 containing the surfaces of pulley plate. Said wire has no sharp edges, tips or cuts on its surface. The elementary wire that passes to through the pins of the two pulleys is subjected to a alternating deformation defined by the circular shape of the pins, and does not present, consequently, sections with the edges, tips or cuts cited above that are found, by example, on the outer surface of the wires that pass to through a pair of sprockets according to the prior art. From in fact, said cogwheels, due to their geometric conformation, inevitably cut the surface of the wire during the action collection that occurs during the preformation advance of the wire. As mentioned earlier, this action of Pickup causes wire strains.

Table I represents the parameters main technical-construction of a embodiment of the preformation device 15 according to the present invention. According to this embodiment, the pulleys of the device according to the invention has the same diameter, an equal number of pins and pins of equal diameter. However, others are possible embodiments, for example, pulleys having pins with Different diameters

TABLE I

1

The most appropriate selection of values to be attribute to machine parameters is to define them specifically according to, for example, the desired degree of preformation of the wire, the diameter of the wire (between 0.10 and 0.50 mm) and the desired value of the final characteristics of the rope. Further, It is important to emphasize that the traction exerted on the rope it also depends on the precise choices of the parameters of the process according to the characteristics of the machines used, by example, torsion angles, rotor speed, pitch distorted.

It is also important to indicate that, to produce a rope, and consequently a rubberized fabric that contains said rope, which has high elasticity characteristics, is it is preferable to submit all the wires that form said rope to the preformation process according to the invention.

However, if the main requirement resides in the penetration of the rubber inside the rope, it can be enough to preform a limited number of the wires that form rope. This number can be defined based on the number total wires forming the rope and the degree of penetration wanted.

Figure 3 represents a generic tire that comprises rubberized fabrics provided with reinforcement ropes according to the invention. With reference to this figure, the tire to which relates the invention comprises a housing 100, preferably covered internally with an air-tight sheet of rubber 110, a tread 120 located on the periphery of this housing, a pair of axially facing flanks 130 that end with heels 140 reinforced with heel wires 150 and respective heel padding elements 160 for fixing said tire to a corresponding mounting rim 170. The tire may include additionally reinforcing edges 190 and, in the case of radial casing tires, also a waist structure 210 interposed between the housing and the tread.

The housing 100 comprises one or more fabrics of housing attached to said heel wires 150, for example, folded around said heel wires from the inside outward. The fabric or shell fabrics can be formed by sections of rubberized fabric reinforced with ropes textile or metal embedded in the fabric rubber.

The waist structure 210 comprises two bands waist 230 and 240, radially overlapped, and a third band of waist 250 in a radially outermost position.

Waist bands 230 and 240 are formed through sections of rubberized fabric that incorporate ropes of metal, parallel to each other in each band and crossed with respect to of adjacent bands, preferably inclined in a manner symmetric with respect to the equatorial plane of the tire according to an angle between 10º and 30º, while the waist band 250 is provided of strings that are circumferentially oriented, that is, at 0º regarding said equatorial plane. This band 250 can be performed, in particular for truck tires and the like, by means of a pair of symmetrically located bands with respect to the equatorial plane of tire. For truck tires, a band can be used auxiliary (not shown in the figure) in a radial position external with respect to the waist structure 210, provided with ropes of reinforcement inclined with respect to the equatorial plane by means of a angle between 10º and 70º, usually called “layer breaker. "

In a similar way, others can be formed construction elements of the tire through tissue sections rubberized with reinforcing ropes properly inclined with respect to the axial, radial and / or circumferential directions of the tire, as required. For example, the reinforcing edge 190 cited previously used inclined ropes according to an included angle between 30º and 60º with respect to the axial direction.

A sample of the rope (5 x 0.35, step 16 mm, that is, a string formed by concatenating five wires with a diameter equal to 0.35 mm) were made according to the method of the invention The wires that form said rope they were made of steel with a carbon content equal to 0.7%. In addition, said wires were advantageously coated with brass, with a deposit coating equal to 3.74 g of brass in relation to 1 kg of steel; the percentage of copper in the brass is preferably equal to 64.4%. The preformation device 15 according to the invention used to obtain said sample of the rope presented pins with a diameter of 1.5 mm to get a wire with a shape in wave (sinusoidal) with a width equal to 0.75 mm and a pitch equal to 3.25 mm

Table II below represents the results achieved by the applicant in the tests comparisons between a 5 x 0.35 string undergoing preforming according the known procedure of cogwheels and the same rope preformed according to the process of the invention as it has been described above in detail. The values shown in the Table II are the average values obtained by performing of an arithmetic average between a plurality of values resulting from the tests performed by the applicant.

TABLE II

two

The ultimate tensile strength and tests final elongation were performed both on a bare string as on a rope embedded in the elastomeric matrix and subjected to vulcanization according to the procedures not described here because They are typically known in the prior art.

The flexion fatigue test, known as FFF test (Firestone Flexion Fatigue) or Wallace test, was performed on a band of rubberized fabric. That band suffered a series of bending cycles done alternately by moving the band of fabric around a properly sized roller with a properly selected preload related to dimensions of the reinforcement ropes in the tissue sample.

The test cited above was conducted on a rubberized rubber band reinforced with metal ropes arranged having a thickness equal to 100 strings / decimeter by applying to the roller a preload of 150 pounds (68 kg) using a lever mechanism and using a roller with a diameter equal to 50 mm. This lever mechanism caused on the roller, and consequently on the sample, an opposite force e equal to that weight. The sample was placed and the test consisted of count the traction cycles performed by the alternate movement above. The test ended when the sample was broke up

The test related to penetration into the tissue consisted of measuring the degree of penetration of rubber between the wires that form said rope and identify, accordingly, the quality of the elastomeric coating around each of said wires. A suitable funnel advantageously made of glass was invested on the bottom of a bowl containing alcohol ethyl. This funnel had a scale along the stem cylindrical and ended, at the free end of this stem, with a suction device generally operated by the operator. He actuation of the suction device made the alcohol ethyl will rise in the cylindrical rod to reach a level predefined, called level zero. In this phase, the sample that has been to examine, which consists of a band of the type described previously with dimensions equal to 5 cm x 5 cm, it was submerged in the bowl and placed at the entrance of the funnel. Ethyl alcohol it has the property of expelling the air that can be contained in The elastomer matrix and take its place. This fact caused a decrease with respect to the zero level mentioned above of the level of the ethyl alcohol on the stem with scale. This measurement allowed define the volume of air processed by the material elastomeric in which the wires are embedded and, in consequently, the degree of penetration of the rubber between the wires They form the rope. This test was performed on the raw sample and in the vulcanized sample.

Analyzing the figures indicated in Table II, it seems obvious that a given string obtained according to the procedure of the invention has characteristics physicochemical remarkably better than an equal rope obtained according to a twisting process comprising a preforming device with gear wheels.

In the case of the invention, the final elongation of the rope is considerably greater, as well as the fatigue of flexion, which is greatly increased. This produces a rope with improved mechanical characteristics with respect to the technique previous.

In addition, the results achieved confirm the obtaining a greater rubber penetration and a final elongation considerably higher, which produces a greater elasticity than rope. This aspect is particularly desired when these strings They are used as reinforcement ropes for elastomers used for manufacture tires

From the results achieved by the Applicant arises that: a greater degree of penetration of pins, and consequently a greater degree of preformation of the wires that form a rope, corresponds to greater elongation reached by the rope.

The applicant performed the tests especially on a 1 x 5 x 0.35 string obtained by a process of twisted according to the invention. That rope seemed particularly suitable for use to form, for example, the so-called layer of rupture in the waistlines for heavy-duty tires and the like, advantageously used in "off-road" paths.

It is important to indicate that the strings obtained according to the invention can be used as reinforcing ropes for any type of elastomeric structure that is used for the manufacture of tires, with particular preference for elastomers that require a high elongation string, for example at the reinforcing edges 190 shown in Figure 3.

The applicant, in fact, has observed that the final elongation of a 1 x 5 x 0.35 string is clearly better regarding the final elongation of a 3 x 4 x 0.22 string, widely used in practice. Said rope consists of three wires, each of which consists of four 0.22 wires of diameter.

More particularly, the final elongation of a 3 x 4 x 0.22 naked string is equal to 5.5% and this value falls to approximately 3% after vulcanization. In the case of invention, on the other hand, the 5 x 0.35 string has a final elongation of approximately 6% also after vulcanization. This fact, as mentioned above, allows an advantageous use in rupture layers for tires of heavy load, which must absorb accidental shocks that can be produce on roads of type "OFF".

In addition, this aspect appears particularly advantageous also in terms of costs, production time and productivity of the process according to the invention, since they are required necessarily two work cycles with very crooked steps limited (in particular equal to 3.15 mm for each thread and equal to 6.3 for the final rope) to make a 3 x 4 x 0.22 rope, while the rope according to the invention is obtained in a single duty cycle and presents a greater twisting step (in particular equal to 16 mm).

Also, make a 5 x 0.35 string instead of a 3 x 4 x 0.22 string allows a withdrawal process smoother, with the consequent savings in terms of times of work and wear of used machines.

Claims (8)

1. Device for the manufacture of ropes metal (1) that are particularly used for elastomeric products reinforcing compounds, comprising: - a support structure (100); - a rotor (5) coupled with respect to said support and swivel structure along a predefined axis; - a tray fixed to said structure of support along an oscillation axis that coincides with the axis of rotor rotation; - power devices (8) adjusted operatively on said tray to supply several wires elementary from respective feeding coils, being said elementary wires actuated on said rotor according to a twisting path with end sections (10a, 10c) that coincide with the axis of rotation of said rotor and with a section central (10d) separated from said axis of rotation; characterized by the fact that - comprises at least one device preformation (15) operatively coupled with the tray and that works on at least one of said elementary wires in an earlier section with respect to the first end section of the twisted path; and - said at least one device preformation (15) provides said elementary wire with a substantially sinusoidal wave deformation arranged on a flat. 2. Device according to claim 1, characterized in that it comprises a preforming device (15) for each elementary wire of said metal ropes (1). Device according to claim 1, characterized in that said at least one preforming device comprises a first (200) and a second pulley (201) fixed to a suitable support structure (202) free to rotate around its axis, each pulley having a plurality of opposite pins (203, 204) suitable for reciprocal penetration at a predefined distance (D) to induce a sinusoidal deformation without sharp edges on a wire passing through the space between the pins (203 ) of the first pulley (200) and the corresponding pins (204) of the second pulley (201). Device according to claim 3, characterized in that said first and second pulleys (200, 201) are rotated by means of the wire. 5. Device according to claim 3, characterized in that said distance (D) is variable. 6. Procedure for the manufacture of a metal rope (1), particularly for elastomeric products reinforcing compounds, comprising at least two wires elementary, with a diameter preferably between 0.10 and 0.50 mm, said procedure comprising the following phases: - permanent deformation of at least one of said elementary wires by wave deformation substantially sinusoidal arranged on a plane; - twisting said elementary wires together by double helical bending around the longitudinal axis of said rope. 7. Metal rope (1), particularly for composite elastomeric reinforcement products, which comprises at least two elementary wires, of which at least one is preform according to the method of claim 6. 8. Tire for vehicle wheels, comprising a bull-shaped carcass (100), a tread (120) located on the periphery of said carcass, a pair of axially facing flanks (130) ending with heels (140 ) reinforced with heel wires (150) and respective heel padding elements (160) to fix said tire to a corresponding mounting rim (170), said tire comprising rubberized reinforced fabrics with metal reinforcing ropes (1), which they comprise at least two elementary wires helically wound together and around the axis of the longitudinal extension of the rope, characterized in that at least said elementary wires are obtained according to the method of claim 6.