TYRE FOR VEHICLE WHEELS

Abstract

A tyre for vehicle wheels comprises a support structure and a tread band arranged in a radially outer position with respect to the support structure. The support structure comprises at least one reinforcing layer including a plurality of hybrid reinforcing cords (10′) each having a metallic wire (21) twisted together with a multifilament textile yarn (22) comprising a plurality of filaments (23). In any cross section of each of said hybrid reinforcing cords (10′), the metallic wire (21) is at least partially embedded in the filaments (23) of the multifilament textile yarn (22).

Claims

1-15. (canceled)

16. A tyre for vehicle wheels comprising: a support structure and a tread band arranged in a radially outer position with respect to the support structure, wherein the support structure comprises at least one reinforcing layer, the at least one reinforcing layer comprising a plurality of hybrid reinforcing cords, wherein each hybrid reinforcing cord of the plurality of hybrid reinforcing cords comprises at least one first strand, the at least one first strand comprising at least one metallic wire twisted together with a first multifilament textile yarn comprising a plurality of filaments, and wherein, in any cross section of at least some of the plurality of hybrid reinforcing cords, the at least one metallic wire is at least partially embedded in the filaments of the first multifilament textile yarn.

17. The tyre according to claim 16, wherein at least some of the plurality of hybrid reinforcing cords comprise at least one portion of cord at which the at least one metallic wire is completely surrounded by the filaments of the first multifilament textile yarn.

18. The tyre according to claim 16, wherein at least some of the plurality of hybrid reinforcing cords comprise n first hybrid strands twisted together and each including x metallic wires, wherein n is a number ranging between 1 and 4 and x is a number ranging between 1 and 3.

19. The tyre according to claim 16, wherein the at least one first strand is twisted together with at least one second strand, wherein the at least one second strand comprises at least one monofilament textile wire twisted together with a second multifilament textile yarn comprising a plurality of filaments, wherein, in any cross section of the at least one second strand, the at least one monofilament textile wire is at least partially embedded in the filaments of the second multifilament textile yarn.

20. The tyre according to claim 19, wherein at least some of the plurality of hybrid reinforcing cords comprise m second strands twisted together with the at least one first strand, wherein and each of the m second strands comprises y monofilament textile wires, wherein m is a number ranging between 1 and 4 and y is a number ranging between 1 and 3.

21. the tyre according to claim 16, wherein the at least one metallic wire has a diameter ranging between 0.10 mm and 0.45 mm and the first multifilament textile yarn has a linear density ranging between 400 dtex and 4000 dtex.

22. The tyre according to claim 16, wherein the at least one metallic wire is made of steel.

23. The tyre according to claim 16, wherein the filaments of the first multifilament textile yarn are made of fibers chosen from fibers of aromatic polyamides, fibers of aliphatic polyamides, polyester fibers, polyketone fibers, polyvinyl alcohol fibers, cellulose fibers, glass fibers, carbon fibers, and mixtures thereof.

24. The tyre according to claim 16, wherein the plurality of hybrid reinforcing cords belongs to a fabric having a plurality of elongated weft elements and a plurality of elongated warp elements.

25. The tyre according to claim 24, wherein at least some of the plurality of hybrid reinforcing cords belong to the plurality of elongated warp elements.

26. The tyre according to claim 16, wherein the at least one reinforcing layer comprises a plurality of hybrid textile reinforcing cords, wherein each hybrid textile reinforcing cords of the plurality of hybrid textile reinforcing cords comprises at least one respective strand, wherein the at least one respective strand comprises at least one monofilament textile wire twisted together with a respective multifilament textile yarn comprising a plurality of filaments, wherein, in any cross section of at least some of the plurality of hybrid textile reinforcing cords, the at least one monofilament textile wire is at least partially embedded in the filaments of the respective multifilament textile yarn.

27. The tyre according to claim 26, further comprising a fabric having a plurality of elongated weft elements and a plurality of elongated warp elements, wherein at least some of the plurality of hybrid textile reinforcing cords belong to the plurality of elongated warp elements.

28. The tyre according to claim 27, wherein the fabric comprises at least one of the hybrid reinforcing cords every z hybrid textile reinforcing cords, wherein z is a number ranging between 1 and 30.

29. The tyre according to claim 16, wherein the support structure comprises: a carcass structure comprising at least one carcass layer having opposite end edges turned around respective annular anchoring structures to define, on opposite sides with respect to an equatorial plane (M-M) of the tyre, respective bead structures; a crossed belt structure arranged in a radially outer position with respect to the carcass structure and in a radially inner position with respect to the tread band; wherein the at least one reinforcing layer belongs to at least one of: the at least one carcass layer; at least one belt layer of the crossed belt structure; at least one stiffening layer associated with the at least one carcass layer at or close to a respective turned end edge.

30. A hybrid reinforcing cord comprising: at least one metallic wire and a multifilament textile yarn comprising a plurality of filaments, wherein, in any cross section of the hybrid reinforcing cord, the at least one metallic wire is at least partially embedded in filaments of the multifilament textile yarn.

Description

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0188] Further characteristics and advantages of the tyre of the present invention will become clearer from the following detailed description of preferred embodiments thereof, made with reference to the attached drawings. In such drawings:

[0189] FIG. 1 is a schematic partial half-cross-sectional view of a portion of a tyre according to an embodiment of the present invention;

[0190] FIG. 2 is a schematic side view of a segment of an embodiment of a hybrid reinforcing cord used in the tyre of FIG. 1;

[0191] FIG. 3 is an enlarged schematic view of a cross-section of a first strand belonging to the hybrid reinforcing cord of FIG. 2;

[0192] FIG. 4 is an enlarged schematic view of a cross-section of a first embodiment of the hybrid reinforcing cord of FIG. 2 comprising two first strands like those of FIG. 3, such a cross section being taken on the section plane S-S drawn in FIG. 2;

[0193] FIG. 5 is an enlarged schematic view of a cross-section of a second strand belonging to an alternative embodiment of the hybrid reinforcing cord of FIG. 2;

[0194] FIG. 6 is an enlarged schematic view of a cross-section of a second embodiment of the hybrid reinforcing cord of FIG. 2 comprising a first strand like that of FIG. 3 and a second strand like that of FIG. 5, such a cross section being taken on the section plane S-S drawn in FIG. 2;

[0195] FIG. 7 is an enlarged schematic view of a cross-section of a third embodiment of a hybrid reinforcing cord used in the tyre of FIG. 1;

[0196] FIG. 8 is an enlarged schematic view of a cross-section of a fourth embodiment of a hybrid reinforcing cord used in the tyre of FIG. 1;

[0197] FIG. 9 is a schematic side view of a segment of an embodiment of a hybrid textile reinforcing cord which can be used in the tyre of FIG. 1;

[0198] FIG. 10 is an enlarged schematic view of a cross-section of the hybrid reinforcing cord of FIG. 9, such a cross section being taken on the section plane S-S drawn in FIG. 9;

[0199] FIG. 11 is a schematic perspective view of the hybrid textile reinforcing cord of FIG. 9, in which part of its components have been removed to show other components that otherwise would be hidden;

[0200] FIG. 12 is a schematic perspective view of an alternative embodiment of the hybrid textile reinforcing cord of FIG. 9, in which part of its components have been removed to shown other components that otherwise would be hidden;

[0201] FIG. 13 is a schematic plan view of a preferred embodiment of a fabric comprising hybrid reinforcing cords like for example that of FIG. 2 and hybrid textile reinforcing cords like for example that of FIG. 9.

[0202] For the sake of simplicity, FIG. 1 shows only a part of an exemplary embodiment of a tyre 100 in accordance with the present invention, the remaining part, which is not shown, being substantially identical and being arranged symmetrically with respect to the equatorial plane M-M of the tyre.

[0203] The tyre 100 shown in FIG. 1 is, in particular, an exemplary embodiment of a tyre for four-wheeled vehicles.

[0204] Preferably, the tyre 100 is an HP or UHP tyre for sports and/or high or ultra-high-performance vehicles.

[0205] In particular, the tyre 100 carries one of the following speed codes: “T”, “U”, “H”, “V”, “Z”,“W”, “Y”, according to the E.T.R.T.O. standard.

[0206] In FIG. 1 “a” indicates an axial direction, “c” indicates a radial direction, “M-M” indicates the equatorial plane of the tyre 100 and “R-R” indicates the rotation axis of the tyre 100.

[0207] The tyre 100 comprises at least one support structure 100a and, in a radially outer position with respect to the support structure 100a, a tread band 109 made of elastomeric material.

[0208] The support structure 100a comprises a carcass structure 101, which in turn comprises at least one carcass layer 111.

[0209] Hereinafter, for the sake of simplicity of presentation, reference will be made to an embodiment of the tyre 100 comprising a single carcass layer 111. However, it is understood that what is described has an analogous application in tyres comprising more than one carcass layer.

[0210] The carcass layer 111 has axially opposite end edges engaged with respective annular anchoring structures 102, called bead wires, possibly associated with an elastomeric filler 104. The area of the tyre 100 comprising the bead wire 102 and the possible elastomeric filler 104 forms an annular reinforcing structure 103 which is called “bead structure” and which is intended to allow the tyre 100 to be anchored on a corresponding mounting rim, not shown.

[0211] The carcass layer 111 comprises a plurality of reinforcing cords 10a coated with elastomeric material or embedded in a matrix of cross-linked elastomeric material.

[0212] The carcass structure 101 is of the radial type, i.e. the reinforcing cords 10a are arranged on planes comprising the rotation axis R-R of the tyre 100 and substantially perpendicular to the equatorial plane M-M of the tyre 100.

[0213] Each annular reinforcing structure 103 is associated with the carcass structure 101 by folding back (or turning) the opposite end edges of the at least one carcass layer 111 about the bead wire 102 and the possible elastomeric filler 104, so as to form the so-called turns 101a of the carcass structure 101.

[0214] In an embodiment, the coupling between carcass structure 101 and annular reinforcing structure 103 can be made through a second carcass layer (not shown in FIG. 1) which is applied in a radially outer position with respect to the carcass layer 111.

[0215] An anti-abrasion strip 105 is arranged at each annular reinforcing structure 103 so as to wrap around the annular reinforcing structure 103 along the axially inner, axially outer and radially inner areas of the annular reinforcing structure 103, thus being placed between the latter and the rim of the wheel when the tyre 100 is mounted on the rim. However, such an anti-abrasion strip 105 may not be provided.

[0216] The support structure 100a comprises, in a radially outer position with respect to the carcass structure 101, a crossed belt structure 106 comprising at least two belt layers 1061, 1062 arranged radially juxtaposed with respect to one another.

[0217] The belt layers 1061, 1062 respectively comprise a plurality of reinforcing cords 10b, 10c. Such reinforcing cords 10b, 10c have an orientation inclined with respect to the circumferential direction of the tyre 100, or to the equatorial plane M-M of the tyre 100, by an angle comprised between 15° and 45°, preferably between 20° and 40°. For example, such an angle is equal to 30°.

[0218] The support structure 100a can also comprise a further belt layer (not shown) arranged between the carcass structure 101 and the radially innermost belt layer of the aforementioned belt layers 1061, 1062 and comprising a plurality of reinforcing cords having an orientation inclined with respect to the circumferential direction of the tyre 100, or to the equatorial plane M-M of the tyre 100, by an angle equal to 90°.

[0219] The support structure 100a can also comprise a further belt layer (not shown) arranged in a radially outer position with respect to the radially outermost belt layer of the aforementioned belt layers 1061, 1062 and comprising a plurality of reinforcing cords having an orientation inclined with respect to the circumferential direction of the tyre 100, or to the equatorial plane M-M of the tyre 100, by an angle comprised between 20° and 70°.

[0220] The reinforcing cords 10b, 10c of a belt layer 1061, 1062 are parallel to one another and have a crossed orientation with respect to the reinforcing cords 10c, 10b of the other belt layer 1062, 1061.

[0221] In ultra-high-performance tyres, the belt structure 106 can be a turned crossed belt structure. Such a belt structure is made by arranging at least one belt layer on a support element and turning the opposite lateral end edges of said at least one belt layer. Preferably, at first a first belt layer is deposited on the support element, then the support element is radially expanded, then a second belt layer is deposited on the first belt layer and finally the opposite axial end edges of the first belt layer are turned onto the second belt layer to at least partially cover the second belt layer, which is the radially outermost one. In some cases, it is possible to arrange a third belt layer on the second belt layer. Advantageously, the turning of the axially opposite end edges of a belt layer on another belt layer arranged in a radially outer position of the first one provides the tyre with a greater reactivity and responsiveness when tackling a bend.

[0222] The support structure 100a comprises, in a radially outer position with respect to the crossed belt structure 106, at least one zero degrees reinforcing layer 106c, commonly known as “zero degrees belt”. It comprises reinforcing cords 10d oriented in a substantially circumferential direction. Such reinforcing cords 10d thus form an angle of a few degrees (typically lower than 10°, for example comprised between 0° and 6°) with respect to the equatorial plane M-M of the tyre 100.

[0223] The reinforcing cords 10a, 10b, 10c, 10d are coated with an elastomeric material or embedded in a matrix of cross-linked elastomeric material.

[0224] The tread band 109 made of elastomeric material, as well as other semi-finished products constituting the tyre 100, is applied in a radially outer position with respect to the zero degrees reinforcing layer 106c.

[0225] Respective sidewalls 108 made of elastomeric material are also applied on the lateral surfaces of the carcass structure 101, in an axially outer position with respect to the carcass structure 101 itself. Each sidewall 108 extends from one of the lateral edges of the tread band 109 up to the respective annular reinforcing structure 103.

[0226] The anti-abrasion strip 105, if provided, extends at least up to the respective sidewall 108.

[0227] In some specific embodiments, like the one shown and described here, the rigidity of the sidewall 108 can be improved by providing a stiffening layer 120, generally known as “flipper” or additional strip-like insert, which has the function of increasing the rigidity and integrity of the annular reinforcing structure 103 and of the sidewall 108.

[0228] The flipper 120 is wound around a respective bead wire 102 and the elastomeric filler 104 so as to at least partially surround the annular reinforcing structure 103. In particular, the flipper 120 wraps around the annular reinforcing structure 103 along the axially inner, axially outer and radially inner areas of the annular reinforcing structure 103.

[0229] The flipper 120 is arranged between the turned end edge of the carcass layer 111 and the respective annular reinforcing structure 103. Usually, the flipper 120 is in contact with the carcass layer 111 and the annular reinforcing structure 103.

[0230] In some specific embodiments, like the one shown and described here, the bead structure 103 can also comprise a further stiffening layer 121 that is generally known by the name “chafer”, or protective strip, and which has the function of increasing the rigidity and integrity of the annular reinforcing structure 103.

[0231] The chafer 121 is associated with a respective turned end edge of the carcass layer 111 in an axially outer position with respect to the respective annular reinforcing structure 103 and extends radially towards the sidewall 108 and the tread band 109.

[0232] The flipper 120 and the chafer 121 comprise reinforcing cords 10e (in the attached figures those of the flipper 120 are not visible) coated with an elastomeric material or embedded in a matrix of cross-linked elastomeric material.

[0233] The tread band 109 has, in a radially outer position thereof, a rolling surface 109a intended to come into contact with the ground. Circumferential grooves (not shown in FIG. 1) are formed on the rolling surface 109a, such grooves being connected by transversal notches (not shown in FIG. 1) so as to define on the rolling surface 109a a plurality of blocks of various shapes and sizes (not shown in FIG. 1).

[0234] A sub-layer 107 is arranged between the crossed belt structure 106 and the tread band 109.

[0235] In some specific embodiments, like the one shown and described herein, a strip 110 consisting of elastomeric material, commonly known as “mini-sidewall”, can possibly be provided in the connection area between the sidewalls 108 and the tread band 109. The mini-sidewall 110 is generally obtained through co-extrusion with the tread band 109 and it allows an improvement of the mechanical interaction between the tread band 109 and the sidewalls 108.

[0236] Preferably, an end portion of the sidewall 108 directly covers the lateral edge of the tread band 109.

[0237] In the case of tubeless tyres, a layer of rubber 112, generally known as “liner”, can also be provided in a radially inner position with respect to the carcass layer 111 to supply the necessary air tightness to the inflation air of the tyre 100.

[0238] At least some of the reinforcing cords 10a (preferably all of the reinforcing cords 10a provided in the carcass layer 111) and/or of the reinforcing cords 10b, 10c (preferably all of the reinforcing cords 10b provided in the belt layer 1061 and all of the reinforcing cords 10c provided in the belt layer 1062, also in the case in which the crossed belt structure 106 is a turned crossed belt structure) and/or of the reinforcing cords 10e of the flipper 120 and/or of the chafer 121 are hybrid reinforcing cords 10′ of the type shown in FIGS. 2-6 and described below.

[0239] The reinforcing cords 10d are, on the other hand, preferably, non-hybrid reinforcing cords, i.e. made of a single textile material, preferably aramid or nylon.

[0240] With reference to FIGS. 2-4, the hybrid reinforcing cord 10′ comprises two strands 20 twisted to one another.

[0241] Preferably, the two strands 20 are identical. Therefore, only one of them, shown in FIG. 3, will be described hereinafter.

[0242] The strand 20 comprises a single metallic wire 21 twisted together with a multifilament textile yarn 22 defined by a plurality of filaments 23.

[0243] The twisting pitch of the metallic wire 21 and of the multifilament textile yarn 22 is preferably the same as the twisting pitch P1 of the two strands 20. Such a twisting pitch P1 is preferably comprised between 1 mm and 20 mm, more preferably between 2 mm and 15 mm, for example equal to 12.5 mm.

[0244] As can be seen in the cross sections shown in FIGS. 3 and 4, in at least some of the cross sections of the strand 20 and of the hybrid reinforcing cord 10′ the metallic wire 21 is completely embedded in the filaments 23 of the multifilament textile yarn 22.

[0245] The strand 20 can comprise more than one metallic wire 21 embedded in the filaments 23 of the multifilament textile yarn 22.

[0246] In particular, it is possible to provide up to three metallic wires 21 for each strand 20, preferably up to two metallic wires 21, even more preferably a single metallic wire 21 for each strand 20.

[0247] In the embodiment shown in FIGS. 2-4, the metallic wire 21 is, in at least some of the cross sections of the strand 20 and of the hybrid reinforcing cord 10′, completely embedded in the filaments 23 of the multifilament textile yarn 22 and, therefore, the aforementioned filaments 23 are arranged around the metallic wire 21 so as to completely surround the metallic wire 21.

[0248] Therefore, the hybrid reinforcing cord 10′ of FIG. 2 has at least one portion of cord (or segment of cord) in which the metallic wire 21 is not visible since it is entirely covered, or completely surrounded, by the filaments 23 of the multifilament textile yarn 22.

[0249] Although the embodiment of FIGS. 2-4 in which the metallic wire 21 is, in at least some of the cross sections of the hybrid reinforcing cord 10′, completely embedded in the filaments 23 of the multifilament textile yarn 22 is particularly preferred, embodiments in which, in any cross section of the hybrid reinforcing cord 10′, the metallic wire 21 is only partially embedded in the filaments 23 of the multifilament textile yarn 22, and in particular those in which at least 50% of the outer surface of the metallic wire 21 is embedded in the filaments 23 of the multifilament textile yarn 22 are deemed equally preferred.

[0250] The metallic wire 21 is made of steel, whereas the filaments 23 of the multifilament textile yarn 22 are made of fibers of aromatic polyamides, or of fibers of aliphatic polyamides, for example Nylon 6, Nylon 6.6, Nylon 4.6, Nylon 4.10, Nylon 10.10, Nylon 11, Nylon 12, Nylon 6.10, Nylon 6.12, or of polyester fibers, for example polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), or of polyketone fibers, or of polyvinyl alcohol fibers, or of cellulose fibers, for example rayon or lyocell), or of glass or carbon fibers, or any mixture of the aforementioned fibers, or assemblies of mixed fibers comprising two or more of the materials listed above. In the case of commingled fibers, the fibers of the filaments 23 can for example comprise: [0251] 50% Aramid with linear density equal to 1100 dtex and 50% PET with linear density equal to 1100 dtex; [0252] 43% Aramid with linear density equal to 840 dtex and 57% PET with linear density equal to 1100 dtex; [0253] 33% Aramid with linear density equal to 550 dtex and 67% PET with linear density equal to 1100 dtex.

[0254] Irrespective of the specific type of textile material used for the filaments 23 of the multifilament textile yarn 22, such a material is suitably made adhesive on its surface so as to offer an adequate adhesivity to the surrounding elastomeric material. Typically, the adhesive treatment can be carried out by coating with an adhesive substance or by a chemical or physical treatment.

[0255] For example, the adhesive treatment is carried out through immersion of the hybrid reinforcing cord 10′, after having twisted together the two strands 20, in a solution comprising the adhesive substance. In this case even possible portions of metallic wire 21 that are directly exposed to the surrounding elastomeric material are made adhesive.

[0256] The metallic wire 21 preferably has a diameter comprised between 0.10 mm and 0.45 mm, more preferably between 0.15 mm and 0.40 mm depending on the area of the tyre 100 in which the hybrid reinforcing cords 10′ are arranged and how much it is preferred for the performance of the tyre 100 to be prioritized with respect to its weight.

[0257] The multifilament textile yarn 22 preferably has a linear density comprised between 400 dtex and 4000 dtex, preferably between 800 dtex and 2500 dtex, depending on the material from which it is made and the area of the tyre 100 in which the hybrid reinforcing cords 10′ are arranged.

[0258] In some preferred embodiments, the metallic wire 21 has a diameter equal to 0.22 mm and the linear density of the multifilament textile yarn 22 is equal to 1680 dtex.

[0259] FIGS. 2 and 4 show a hybrid reinforcing cord 10′ comprising only two strands 20. However, alternative embodiments are foreseen in which the hybrid reinforcing cord 10′ comprises a single strand 20 (in which case the hybrid reinforcing cord 10′ will coincide with the strand 20 shown in FIG. 3) or more than two strands 20, for example up to four strands 20.

[0260] The strands 20 can be equal to each other, as shown in FIG. 4. In this case, in at least some of the cross sections of the hybrid reinforcing cord 10′ the metallic wire 21 of each strand 20 is at least partially embedded in the filaments 23 of the respective multifilament textile yarn 22.

[0261] Alternatively, as shown in FIG. 6, one of the two strands of the hybrid reinforcing cord 10′ is the same as the strand 20 described above, whereas the other strand is a strand 30 made entirely of textile material, of the type for example shown in FIG. 5.

[0262] With reference to FIGS. 5 and 6, the strand 30 comprises a monofilament textile wire 31 twisted to a multifilament textile yarn 32 so that, in at least some of the cross sections of the strand 30 and of the hybrid reinforcing cord 10′, the monofilament textile wire 31 is partially embedded in the filaments 33 of the multifilament textile yarn 32.

[0263] The twisting pitch of the monofilament textile wire 31 and of the multifilament textile yarn 32 is preferably the same as the twisting pitch P1 of the two strands 20 and 30. Such a twisting pitch P1 is preferably comprised between 1 mm and 20 mm, more preferably between 2 mm and 15 mm, for example equal to 12.5 mm.

[0264] As can be seen in the cross sections shown in FIGS. 5 and 6, in at least some of the cross sections of the strand 30 and of the hybrid reinforcing cord 10′ the monofilament textile wire 31 is completely embedded in the filaments 33 of the multifilament textile yarn 32.

[0265] The strand 30 can comprise more than one monofilament textile wire 31 embedded in the filaments 33 of the multifilament textile yarn 32.

[0266] In particular, it is possible to provide up to three monofilament textile wires 31 for each strand 30, preferably up to two monofilament textile wires 31, even more preferably a single monofilament textile wire 31 for each strand 30.

[0267] In the embodiment shown in FIGS. 5 and 6, the monofilament textile wire 31 is, in at least some of the cross sections of the strand 30 and of the hybrid reinforcing cord 10′, completely embedded in the filaments 33 of the metallic yarn 32 and, therefore, the aforementioned filaments 33 are arranged around the monofilament textile wire 31 so as to completely surround the monofilament textile wire 31.

[0268] Therefore, the hybrid reinforcing cord 10′ of FIG. 6 has at least one portion (or segment) of cord in which the monofilament textile wire 31 is not visible since it is entirely covered, or completely surrounded, by the filaments 33 of the multifilament textile yarn 32.

[0269] Although the embodiment of FIGS. 5-6 in which the monofilament textile wire 31 is, in at least some of the cross sections of the hybrid reinforcing cord 10′, completely embedded in the filaments 33 of the multifilament textile yarn 32 is particularly preferred, embodiments in which, in any cross section of the hybrid reinforcing cord 10′, the monofilament textile wire 31 is only partially embedded in the filaments 33 of the multifilament textile yarn 32, and in particular those in which at least 50% of the outer surface of the monofilament textile wire 31 is embedded in the filaments 33 of the multifilament textile yarn 32 are deemed equally preferred.

[0270] The monofilament textile wire 31 is made of fibers of aliphatic polyamide, for example Nylon 6, Nylon 6.6, Nylon 4.6, Nylon 4.10, Nylon 10.10, Nylon 11, Nylon 12, Nylon 6.10, Nylon 6.12, or polyester fibers, for example polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyethylene isophthalate (PEI), or polyaryletherketone fibers, for example polyetheretherketone (PEEK), or mixtures thereof.

[0271] The filaments 33 of the multifilament textile yarn 32 are preferably made of a material selected among those indicated above with reference to the filaments 23 of the multifilament textile yarn 22 of the strand 20.

[0272] The filaments 33 of the multifilament textile yarn 32 are also suitably treated with an adhesive on the surface so as to offer an adequate adhesivity to the surrounding elastomeric material. If the adhesive treatment is carried out through immersion of the hybrid reinforcing cord 10′ in a bath containing an adhesive substance after having twisted together the two strands 20 and 30, possible portions of monofilament textile wire 31 that are directly exposed to the surrounding elastomeric material are also made adhesive.

[0273] The monofilament textile wire 31 preferably has a diameter comprised between 0.10 mm and 0.70 mm, more preferably between 0.15 mm and 0.50 mm, depending also on the material from which it is made and on the area of the tyre 100 in which the hybrid reinforcing cords 10′ are arranged.

[0274] The multifilament textile yarn 32 preferably has a linear density comprised between 400 dtex and 4000 dtex, preferably between 800 dtex and 2500 dtex, depending also on the material from which it is made and on the area of the tyre 100 in which the hybrid reinforcing cords 10′ are arranged.

[0275] In some preferred embodiments, the monofilament textile wire 31 has a diameter equal to 0.40 mm and the linear density of the multifilament textile yarn 32 is equal to 1680 dtex.

[0276] Preferably, the multifilament textile yarn 32 of the strand 30 is identical to the multifilament textile yarn 22 of the strand 20.

[0277] The monofilament textile wire 31 may or may not be twisted on itself before being twisted to the multifilament textile yarn 32. If twisted on itself, the twist pitch of the monofilament textile wire 31 is preferably the same as the twisting pitch of the monofilament textile wire 31 and of the multifilament textile yarn 32.

[0278] The multifilament textile yarn 32 may or may not be twisted on itself before being twisted to said at least one monofilament textile wire 31. If twisted on itself, the twist pitch of the multifilament textile yarn 32 is also preferably the same as the twisting pitch of the monofilament textile wire 31 and of the multifilament textile yarn 32.

[0279] Although FIGS. 5 and 6 show a hybrid reinforcing cord 10′ comprising two strands 20 and 30, alternative embodiments are foreseen in which the hybrid reinforcing cord 10′ comprises a single strand 20 and more than one strand 30, or a single strand 30 and more than one strand 20, or many strands 20 and many strands 30.

[0280] For example, FIG. 7 shows an embodiment of a hybrid reinforcing cord 10′ comprising two strands 20 twisted together to a strand 30, whereas FIG. 8 shows a different embodiment of a hybrid reinforcing cord 10′ comprising two strands 30 twisted together to a strand 20. The empty space at the center of the hybrid reinforcing cord 10′ shown in FIGS. 7 and 8 in reality will be occupied by the filaments 23 and 33 of the multifilament textile yarns 22 and 32.

[0281] In the case in which the hybrid reinforcing cord 10′ comprises more than one strand 30, the strands 30 can be equal to each other, as shown in FIG. 8. In this case, in at least some of the cross sections of the hybrid reinforcing cord 10′ the monofilament textile wire 31 of each strand 30 is at least partially embedded in the filaments 33 of the respective multifilament textile yarn 32.

[0282] In specific embodiments, only the reinforcing cords 10a, and not also the reinforcing cords 10b, 10c and 10e, or vice-versa, are hybrid reinforcing cords 10′ of the type described above.

[0283] In other specific embodiments, only the reinforcing cords 10b, and not also the reinforcing cords 10a, 10c, 10e or vice-versa, are hybrid reinforcing cords 10′ of the type described above.

[0284] In some embodiments, only the reinforcing cords 10b and/or 10c, and not also the reinforcing cords 10a and 10de, are hybrid reinforcing cords 10′ of the type described above.

[0285] In yet other embodiments, only the reinforcing cords 10e, and not also the reinforcing cords 10a, 10b and/or 10c, are hybrid reinforcing cords 10′ of the type described above.

[0286] When the reinforcing cords 10e are hybrid reinforcing cords 10′ of the type described above, such hybrid reinforcing cords 10′ can be used only in the flipper 120 (if provided and when the chafer is not provided or is provided and comprises non-hybrid reinforcing cords), only in the chafer 121 (if provided and when the flipper is not provided or is provided and comprises non-hybrid reinforcing cords), or both in the flipper 120 and in the chafer 121 (if both of them are provided).

[0287] In particularly preferred embodiments, the hybrid reinforcing cords 10′ are used at least in the belt layers 1061, 1062 of the crossed belt structure 106.

[0288] In some embodiments, the reinforcing layers in which the hybrid reinforcing cords 10′ are provided comprise only hybrid reinforcing cords 10′.

[0289] In other embodiments, the reinforcing layers in which the hybrid reinforcing cords 10′ are provided are mixed reinforcing layers that comprise, in addition to the aforementioned hybrid reinforcing cords 10′, hybrid textile reinforcing cords 10″ of the type for example described below with reference to FIGS. 9-12.

[0290] In the specific example shown in FIGS. 9 and 10, the hybrid textile reinforcing cord 10″ comprises only textile strands. In particular, the hybrid textile reinforcing cord 10″ comprises two strands 30 identical to the strands 30 described above with reference to FIGS. 5-8. Therefore, what has been described above with respect to the strands 30 of the hybrid reinforcing cords 10′ of FIGS. 5-8 is also valid for the strands 30 of the hybrid textile reinforcing cords 10″.

[0291] The two strands 30 are twisted to one another with a twisting pitch P2 that preferably is identical to the twisting pitch P1 described above.

[0292] Preferably, the two strands 30 are identical to one another.

[0293] FIG. 10 shows an embodiment of a hybrid textile reinforcing cord 10″ in which the monofilament textile wires 31 of the two strands 30 are not twisted on themselves.

[0294] FIG. 11 shows an embodiment of a hybrid textile reinforcing cord 10″ in which the monofilament textile wires 31 of the two strands 30 are twisted on themselves with a predetermined twist pitch T.

[0295] Preferably, the twist pitch T is the same as the twisting pitch P2.

[0296] The direction of the twisting of the monofilament textile wires 31 can be the same as or opposite to the twisting direction of the two strands 30.

[0297] FIGS. 9-12 show a hybrid textile reinforcing cord 10″ comprising only two strands 30. However, alternative embodiments are foreseen in which the hybrid textile reinforcing cord 10″ comprises a single strand 30 (in which case the hybrid textile reinforcing cord 10″ will coincide with the strand 30 shown in FIG. 5) or more than two strands 30, for example up to four strands 30.

[0298] The reinforcing layer in which the hybrid reinforcing cords 10′ and possibly the hybrid textile reinforcing cords 10″ are provided preferably has a thread count comprised between 50 cords/dm and 100 cords/dm, more preferably between 60 cords/dm and 85 cords/dm.

[0299] Such a reinforcing layer preferably has a thickness comprised between 0.7 mm and 1.6 mm, more preferably between 0.9 mm and 1.3 mm.

[0300] The hybrid reinforcing cords 10′ and the hybrid textile reinforcing cords 10″ can form part of a fabric 50, like for example the one shown in FIG. 13.

[0301] The fabric 30 comprises a plurality of elongated weft elements 51 (schematized by vertical lines in FIG. 13) and a plurality of elongated warp elements 52 (schematized by horizontal lines in FIG. 13).

[0302] The elongated weft elements 51 are made of nylon or cotton.

[0303] The elongated warp elements 52 can be defined solely by the aforementioned hybrid reinforcing cords 10′ or, as shown in FIG. 13, by both the aforementioned hybrid reinforcing cords 10′ and the aforementioned hybrid textile reinforcing cords 10″, to define a “mixed” fabric 50 in this case.

[0304] In particular, in the embodiment shown in FIG. 13 a hybrid reinforcing cord 10′ is provided every nine hybrid textile reinforcing cords 10″. However, fabrics 50 are foreseen in which every hybrid reinforcing cord 10′ is interposed between two hybrid textile reinforcing cords 10″ or is arranged after a predetermined number of hybrid textile reinforcing cords 10″ that can be lower than or equal to 30.

[0305] The fabric 50 is intended to be embedded in an elastomeric material in a subsequent calendaring step to define the aforementioned reinforcing layer.

[0306] In a preferred embodiment of the fabric 50, each of the hybrid reinforcing cords 10′ comprises three strands twisted together, and in particular: [0307] two strands 30 each comprising a monofilament textile wire 31 of PET having a diameter equal to 0.40 mm and a multifilament textile yarn 32 of PET having a linear density equal to 1680 dtex; [0308] a strand 20 comprising a metallic wire 21 of steel having a diameter equal to 0.22 mm and a multifilament textile yarn 22 of PET having a linear density equal to 1680 dtex.

[0309] Such hybrid reinforcing cords 10′ thus have a construction of the type (Steel 0.22+PET 1680)+(PET 0.40 mm+PET 1680)×2. The diameter of such hybrid reinforcing cords 10′ is equal to about 0.93 mm. Hereinafter, such a cord is indicated as CORDINV1.

[0310] In the aforementioned embodiment of the fabric 50, each of the hybrid textile reinforcing cords 10″ comprises three strands 30 twisted together, each of them comprising a monofilament textile wire 31 of PET having a diameter equal to 0.40 mm and a multifilament textile yarn 32 of PET having a linear density equal to 1680 dtex.

[0311] Such hybrid textile reinforcing cords 10″ thus have a construction of the type (PET 0.40 mm+PET 1680)×3. Hereinafter, such a cord is indicated as CORD2.

[0312] The Applicant has verified that the increase of weight of the tyre due to the provision in the crossed belt structure 106 of a fabric 50 as described above with respect to a corresponding tyre having, in the belt structure 106, monofilament textile yarns instead of metallic wires, does not exceed 10 gr. and therefore is absolutely acceptable in cases in which an improvement of the performance is sought and it is wished to achieve the processability in current industrial tyre production plants.

Comparative Tests

[0313] The Applicant has carried out comparative tests between a cord CORDINV1, a cord CORD2, a conventional metallic reinforcing cord comprising two steel wires of 0.28 mm, used in the crossed belt structures of sports tyres commercialized by the Applicant (hereinafter indicated as CORD1), a hybrid reinforcing cord 10′ that differed from CORDINV1 only in that it comprises two strands 20 and a strand 30 (hereinafter indicated as CORDINV2) and a hybrid reinforcing cord 10′ that differed from cord CORDINV1 only in that it comprises three strands 20 and no strand 30.

[0314] Table 1 below shows the diameter and the weight of the aforementioned reinforcing cords.

TABLE-US-00001 TABLE 1 CORD 1 CORD2 CORDINV1 CORDINV2 CORDINV3 Cord diameter 0.60 1.15 0.16 1.06 0.90 [mm] Cord weight 0.96 1.08 1.20 1.34 1.43 [g/m]

[0315] It has been possible to note how as the number of metallic wires (CORDINV1, CORDINV2 and CORDINV3) increases compared to the number of monofilament textile wires present in the hybrid reinforcing cord 10′, the diameter of such reinforcing cords decreases. This is due to the fact that the metallic wires used have a diameter (equal to 0.22 mm) smaller than the diameter of the monofilament textile wires (equal to 0.40 mm). In any case, the diameter of the hybrid reinforcing cords 10′ (CORDINV1, CORDINV2 and CORDINV3) remains substantially equal to or lower than that of the hybrid textile reinforcing cords 10″ (CORD2). Therefore, a fabric 50 comprising both hybrid reinforcing cords 10′ and hybrid textile reinforcing cords 10″ does not have noticeable irregularity caused by the presence of different reinforcing cords.

[0316] It has also been possible to note how as the number of metallic wires in the hybrid reinforcing cords 10′ (CORDINV1, CORDINV2 and CORDINV3) increases compared to the conventional metallic reinforcing cords (CORD1) the weight of the reinforcing cord increases. Such an increase in weight nevertheless remains extremely small and is therefore totally acceptable, particularly in the case in which it is preferred to prioritize the performance of the tyre with respect to a more limited increase in weight, like that which would be obtained in the case in which only hybrid textile reinforcing cords 10″ (CORD2) are used.

[0317] In order to evaluate the suitability of the hybrid reinforcing cords 10′ described above for their use in the belt structure, the reinforcing cords described above were subjected to traction tests (to evaluate the breaking load) and bending or vertical rigidity tests (to evaluate the ability to withstand to bending stresses).

[0318] The traction tests were carried out according to method BISFA E6 (The International Bureau For The Standardization Of Man-Made Fibres, Internationally Agreed Methods For Testing Steel Tyre Cords, 1995 edition).

[0319] In the rigidity tests, all of the reinforcing cords described above were subjected to a ring compression test as follows: the reinforcing cords were treated with an adhesive substance and subsequently folded so as to join the opposite ends to create respective rings having a diameter of 80 mm. Such rings were subjected to an initial pretensioning of 0.5 N and to a crushing of 25 mm, with a compression speed of 100 mm/min.

[0320] The results of such tests are given in Table 2 below.

TABLE-US-00002 TABLE 2 CORD1 CORD2 CORDINV1 CORDINV2 CORDINV3 Breaking load 405 450 380 400 470 [N] Rigidity 0.13 0.06 0.09 0.10 0.11 [N]

[0321] It has been possible to note how the hybrid reinforcing cords 10′ (CORDINV1, CORDINV2, CORDINV3) have values of breaking load and rigidity that are absolutely comparable with those of the conventional metallic reinforcing cords (CORD1), approaching the values of the latter as the number of metallic wires provided in the hybrid reinforcing cords 10′ increases.

[0322] The aforementioned tests therefore have confirmed the suitability of the hybrid reinforcing cords 10′ of the present invention to being used in the belt structures of the tyres.

[0323] The present invention has been described with reference to some preferred embodiments. Different modifications can be made to the embodiments described above, still remaining within the scope of protection of the invention which is defined by the following claims.