Patent Application
20100000652
The present invention relates to a tire which is provided with a light weight bead core.
In particular, the present invention relates to a tire which is provided with a light weight bead core, said bead core contributing in decreasing the overall tire weight while ensuring a good anchoring thereof to a wheel rim on which the tire is mounted.
A tire generally comprises: a carcass structure comprising at least one carcass ply; a tread band in a position radially external to the carcass structure; a belt structure interposed between the carcass structure and the tread band. A tire generally further comprises a pair of sidewalls applied to the carcass structure in axially opposite positions. The ends of the at least one carcass ply are folded back or secured to two annular reinforcing elements, i.e. the so-called “bead cores”, and the tire region which comprises the bead core is known as “tire bead”.
Generally, in a position radially external to the bead core, the tire bead further comprises an elastomeric insert, conventionally called “bead filling” or “bead apex”, which has a substantially triangular cross-section and extends radially outwardly from the respective bead core.
A tire bead, and particularly the bead core thereof, is generally requested to perform a plurality of functions.
Firstly, a bead core performs the function of anchoring the tire carcass cords in the tire bead, the carcass cords being subjected to longitudinal stresses proportional to the tire inflation pressure and to the tire curvature ratio. The carcass cords are further subjected to longitudinal and torsional stresses which are due to the centrifugal force, the lateral thrusts and/or the torques acting on the tire during travelling thereof.
Furthermore, a bead core performs the function of anchoring the tire to a respective wheel rim thereby ensuring, in case of a tubeless tire, a sealing effect between the tire and the wheel rim, the latter being provided in correspondence of the bead mounting position and generally comprising two substantially conical coaxial surfaces which act as the supporting base for the tire beads. Said surfaces generally terminate in a flange, radially projecting outwardly, that supports the axially outer surface of the bead and against which the latter abuts by virtue of the tire inflation pressure. Proper positioning of the bead into its seat is ensured by the conical shape of the bead seat in cooperation with the bead core.
The bead core is requested to withstand relevant deformations that arise during the fitting operation of the tire on a respective wheel rim. In fact, the diameter of the radially internal annular surface of the bead core is smaller than the radially external diameter of the rim flange and is selected so that, once the tire bead has been positioned in the respective bead seat of the rim, after passing over the flange, it is pushed by the pressure of the tire inflating fluid along the diverging surface of the bead seat against the axially internal surface of the flange. Generally, the fitting of a tire on a respective rim starts with the deformation (ovalisation) of the tire bead so that a portion thereof is able to pass over the flange. Successively, the rest of the tire bead is caused to completely pass over the flange such that the bead is positioned in the closest bead seat. Then the bead is pushed axially towards the opposite bead seat so as to cause it to fall into the central groove of the rim. In this way, once the bead is located inside the abovementioned central groove, the equatorial plane of the tire may be inclined with respect to the equatorial plane of the rim so as to allow also the opposite bead to pass over the flange and be positioned in the corresponding bead seat, by means of ovalisation thereof (and hence of ovalisation of the respective bead core). Finally, the tire is inflated so that both the beads come into abutment against the axially internal surfaces of the flange. Owing to the rigidity of the bead core, the fitting/removal operations of the tire onto/from the rim require the use of levers with which it is possible to apply a force sufficient to deform the bead core, modifying the configuration from a substantially circular one to an oval one, so as to allow, as mentioned above, the bead to pass over the flange. However, the use of levers acting on the elongated elements forming the bead core may result in locally exceeding the elastic strain limits of said elements which is particularly undesirable since it may have a negative effect on the structural strength properties of the bead core during the travel of the tire and, in some cases, may also result in breakage of one or more of the elongated elements of the tire bead core.
Besides the above functions, the bead core is requested to ensure the transmission of torques (traction torques and braking torques) from the rim to the tire during the vehicle accelerations and decelerations. Therefore the anchoring of the tire to the rim is requested to be suitable so as to prevent the tire from sliding with respect to the mounting rim. This aspect, which is important for any vehicle (passenger cars, trucks, motorbikes), is particularly critical in the case of high performance (HP) and ultra high performance (UHP) tires, these tires being designed for high-powered cars which are generally involved in high operating speeds (e.g., higher than 200 km/h) and/or extreme driving conditions wherein swift and relevant accelerations/decelerations are generally caused to occur.
Usually bead cores are formed by steel wires or cords. However, alternative materials have been suggested in the art.
For example, Great Britain Patent GB 1,072,277 discloses a light weight bead core for pneumatic tires. In particular, it discloses a tire bead reinforcement comprising a hoop shaped structure of continuously wound, epoxy resin dipped, continuous filament glass fiber, said structure containing 8% by weight to 40% by weight of epoxy resin and 60% by weight to 92% by weight of glass fiber. The abovementioned bead core is said to be particularly useful for airplain tires.
Japanese Patent Application JP 04/133807 discloses a pneumatic tire characterized in that it has a bead core manufactured by annularly winding a non-metallic fiber cord having a minimum tensile modulus of 350 g/D, a maximum bending force of at least 0.1 Kg and a melting point or a softening point of at least 170° C. Preferably, said non-metallic fiber is selected from: aramid fibers, carbon fibers, glass fibers, which may also be used as composite fibers. The abovementioned bead core is said to be advantageously used in light weight tire.
However, the above reported light weight bead core may show some drawbacks.
In particular, said light weight bead core may not ensure the bead mechanical resistance (structural integrity of the tire bead) and thus the safeness thereof during use of the tire, as well as the tire uniformity (e.g., the regularity of the tire geometrical dimensions, the rigidity of the tire in the radial direction and the uniform distribution of the tire masses along the circumferential direction). Moreover, said light weight bead core may not ensure a good anchoring of the tire bead to the rim so that the torques, which are generated by the vehicle (e.g., by the engine or the brakes thereof), may be transmitted from the rim to the tire causing substantial sliding of the tire on the rim.
The Applicant has faced the problem of providing a tire whose bead core structure contribute in decreasing the overall tire weight, fact which remarkably influences the tire performances such as rolling resistance, especially in case high-powered vehicles are considered, while ensuring tire bead mechanical resistance, stable anchoring of the tire to the rim, as well as tire uniformity.
The Applicant has found that the above aims may be achieved by providing the tire with bead cores which include both elongated elements of composite material and metal elongated elements.
According to a first aspect, the present invention relates to a tire comprising:
For the purpose of the present description and of the claims which follow, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term “about”. Also, all ranges include any combination of the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.
For the purpose of the present description and of the claims which follow, the term “elongated element” is used to indicate a single wire (i.e. a monofilament), or a yarn or a cord which is obtained by stranding at least two single wires.
Preferably, the ratio (% by volume) between the amount of metal material and the amount of composite material present in the bead core of the present invention is comprised from 3% by volume to 80% by volume with respect to the total volume of the bead core. More preferably, said ratio is comprised from 5% by volume to 60% by volume with respect to the total volume of the bead core. The ranges mentioned above are particularly preferred since they may ensure a satisfactory balance among hooping force of the tire bead on the rim, high tensile strength requested to the bead core and bead core weight.
Further features and advantages will become more apparent from the detailed description of preferred but non-exclusive embodiments of a bead core in accordance with the present invention. The present description should be taken with reference to the accompanying drawings, given by way of non limiting example.
In the drawings:
a and 1b show a first embodiment of a bead core strip element and a bead core, respectively, according to the present invention;
a and 2b show a second embodiment of a bead core strip element and a bead core, respectively, according to the present invention;
a and 3b show a third embodiment of a bead core strip element and a bead core, respectively, according to the present invention;
a and 4b show a fourth embodiment of a bead core strip element and a bead core, respectively, according to the present invention;
a and 5b show a fifth embodiment of bead core strip elements and a bead core, respectively, according to the present invention;
a shows a schematic cross section of a hybrid cord which is used in a bead core in accordance with the present invention;
b and 6c show a sixth embodiment of a bead core strip element and a bead core, respectively, according to the present invention;
a and 8b show an annular insert and a bead core, respectively, according to an eighth embodiment of the present invention;
a and 9b show an annular insert and a bead core, respectively, according to a ninth embodiment of the present invention;
a and 10b show an annular insert and a bead core, respectively, according to a tenth embodiment of the present invention;
a shows a twelfth embodiment of a bead core according to the present invention;
b shows a thirteenth embodiment of a bead core according to the present invention;
A typical bead core structure is the so-called “Alderfer” structure which has a configuration of the type “m×n”, where “m” indicates the number of axially adjacent wires or cords (obtained by stranding at least one pair of wires) and “n” indicates the number of radially superimposed layers of said cords. This structure is obtained by using a rubberized strip element comprising a predefined number of cords (usually, textile or metallic cords) and by winding (coiling) said rubberized strip element so as to form a desired number of layers arranged radially superimposed one to the other. This constructional method allows the formation of cross-sectional contours of the bead core which are of a substantially quadrangular type. Typical examples of Alderfer structures are 4×4, 5×5, 4×5 and 6×5 structures.
A further conventional bead core structure is the so-called “round cable” bead core. This type of bead core has a central core, for example obtained from a single wire which is welded end-to-end so as to form a circle, around which a further single wire is wound and finally joined to itself, preferably by means of a fastening element such as, for example a metallic (e.g., brass) clip or strip to form at least one sheath layer. Depending on the number of the sheath layer obtained, the “round cable” bead cores have different configuration such as, for example, the following: 1×1.5 mm+(6+12)×1.3 mm wherein digit “1” indicates the central core (e.g., obtained from a single wire having a diameter of 1.5 mm), digit “6” indicates that a further single wire having a diameter of 1.3 mm, is wound (for example, according to S winding direction) around the central core six times so as to form a first sheath layer, digit “12” indicates that the same further single wire is subsequently wound (for example, according to Z winding direction opposed to S winding direction) around said first sheath layer twelve times, so as to form a second sheath layer in a position radially external to said first sheath layer. Further configuration may be, for instance: 1×3.0 mm+(9)×1.5 mm, 1×3.0 mm+(8)×1.8 mm, 1×1.8 mm+(7)×1.4 mm.
A further conventional bead core structure is the so-called “single wire bead core”. This is formed from a single rubberized cord which is wound so as to form a first layer of axially adjacent turns (coils); then, the same cord, is further wound so as to form a second layer in a position radially external to said first layer, and so on, so as to form several radially superimposed layers. Therefore, by varying the number of turns in each layer, it is possible to obtain cross-sectional contours of the bead core with different geometrical forms, for example a hexagonal shaped cross-section. A regular hexagonal bead core may be formed, for example, by means of 19 windings arranged in the configuration: 3-4-5-4-3. This series of numbers indicates that the individual rubberized cord is wound so as to form firstly three turns axially adjacent to each other to form a first layer; then four turns axially adjacent to each other are provided in succession so as to form a second layer radially superimposed on the first layer, followed by five turns, axially adjacent to each other, so as to form a third layer radially superimposed on the second layer, then four turns axially adjacent to each other so as to form a fourth layer radially superimposed on the third layer and finally three turns axially adjacent to each other so as to form a fifth layer radially superimposed on the fourth layer. Further configurations may be, for instance, 4-5-4-3 and 5-6-5-4.
A further conventional bead core structure is obtained by using a plurality of rubberized cords, each individual cord being radially wound onto itself so as to form a stack (i.e. a series) of radially superimposed wound turns (coils). Several stacks of turns, possibly with a different vertical extension (namely different number of wound turns radially superimposed on each other), axially adjacent to each other, thus form the abovementioned bead core. Preferably, said wires have predetermined cross sections (e.g., a substantially hexagonal cross section) so that the wires of axially adjacent coils may be coupled together to form an assembly (i.e. the bead core) that is constituted by equal and distinct elements (modular elements) and that is provided with a compact cross section, i.e. the latter does not comprise hollow spaces or interferences and has an area corresponding to the sum of the section areas of said distinct elements.
The carcass structure CS comprises one or more carcass plies CP (only one being shown in
Tire TI further comprises a belt structure 7 interposed between the carcass structure CS and the tread band TB, said belt structure preferably comprising two belt layers, usually including metal cords that are parallel to each other in each layer and crossing over those of the adjacent layers. The metal cords in each layer are symmetrically inclined with respect to the tire equatorial plane Y-Y. Preferably, in a radially outermost position, the belt structure also comprises a third belt layer which is provided with rubberized cords, preferably textile cords, that are oriented circumferentially, i.e. with a disposition at substantially zero degrees with respect to the tire equatorial plane Y-Y.
a, 1b and 11 show a first embodiment of the present invention. In particular,
The term “adjacent”, as used in the present description and in the claims which follow, may or may not imply contact but always implies absence of anything of the same kind between. Two elongated elements are considered to be adjacent one to the other either if they are in contact (at least partially) or if they are not in contact (for instance, when rubber is provided in between). Two elongated elements are not considered to be adjacent one to the other if there is a third elongated element there between.
The bead core 51 shown in
The 6×4 bead core arrangement shown in
According to the embodiment shown in
According to the embodiment shown in
Therefore, the bead core 51 of
According to the present invention, the term “series” is used to indicate a stack of radially superimposed coils of a single elongated element.
Therefore, the bead core 51 comprises at least one first series of the second elongated element 31 and at least one second series of the first elongated element 21. In detail, the bead core 51 comprises three first series of the second elongated elements 31 and three second series of the first elongated elements 21, said first and second series being arranged in an alternate configuration. More in detail, according to this first embodiment, each first series is axially adjacent to at least one second series.
The Applicant has found that the tire integrity, and thus the driving safeness, may be advantageously improved by arranging in the tire the bead core so as to have its side containing the metal elongated element(s) facing the rim flange. This means that it is particularly advantageous to provide a strip element wherein the metal elongated element(s) is (are) positioned at the strip element axial edge which, when integrated in the bead core, faces the rim flange. In detail, the Applicant has found that it is preferable to provide a bead core whose metal elongated element(s) are located in proximity of the rim flange and the elongated element(s) made of composite material are located in proximity of the inner surface of the tire. In that way, the bead core portion more resistant to mechanical stresses is positioned in correspondence of the rim flange where the most intense stresses are generated during travelling of the tire and during the mounting/demounting operations of the tire onto/from the rim.
According to the present invention, said first elongated elements 21 are made of composite material comprising a plurality of elongated fibers embedded in a polymeric material, said composite material having a flexural modulus, measured according to Standard ASTM D790-03, at 23° C., not lower than or equal to 10 GPa, preferably of from 20 GPa to 200 GPa.
According to a further preferred embodiment, said composite material has an ultimate tensile strength, measured according to Standard ASTM D3916-02, at 23° C., not lower than or equal to 600 MPa, preferably of from 1000 MPa to 2500 MPa.
According to a further preferred embodiment, said composite material has a tensile modulus, measured according to Standard ASTM D3916-02, at 23° C., not lower than or equal to 20 GPa, preferably of from 30 GPa to 200 GPa.
According to a further preferred embodiment, said composite material has a specific gravity, measured according to Standard ASTM D792-00, lower than or equal to 3.0 g/cm3, preferably of from 1.0 g/cm3 to 2.5 g/cm3.
According to one preferred embodiment, said polymeric material has a flexural modulus, measured according to Standard ASTM D790-03, at 23° C., not lower than or equal to 0.5 GPa, preferably of from 2.0 GPa to 25 GPa
According to a further preferred embodiment, said polymeric material has an ultimate tensile strength, measured according to Standard ASTM D638-03, at 23° C., not lower than or equal to 40 MPa, preferably of from 50 MPa to 200 MPa.
According to a further preferred embodiment, said polymeric material may be selected, for example, from thermoplastic resins, thermosetting resins, or mixtures thereof. Thermosetting resins are particularly preferred.
According to a further preferred embodiment, said thermoplastic resins may be selected, for example, from: nylon-6,6, nylon-6, nylon-4,6, polyester (such as, for example, polyethylene terephthalate, polyethylene naphthalate), polyether ether ketone, polycarbonate, polyacetal, or mixtures thereof. Polyethylene tetrephthalate is particularly preferred.
According to a further preferred embodiment, said thermosetting resins may be selected, for example, from: vinyl-ester resins, epoxy resins, unsaturated polyester resin (such as, for example, isophthalic polyester resins), phenolic resins, melamine resins, polyimide resins, bismaleimide resins, furan resins, silicone resins, allyl resins, or mixtures thereof. Vinyl ester resins, epoxy resins, or mixtures thereof, are particularly preferred.
According to one preferred embodiment, said elongated fibers have an ultimate tensile strength, measured according to Standard ASTM D885-03, not lower than or equal to 1500 MPa, preferably of from 1800 MPa to 4000 MPa.
According to a further preferred embodiment, said elongated fibers have a tensile modulus, measured according to Standard ASTM D885-03, not lower than or equal to 50 GPa, preferably of from 60 GPa to 250 GPa.
According to a further preferred embodiment, said elongated fibers may be selected, for example, from: glass fibers, aromatic polyamide fibers (for example, aramid fibers such as, for example, Kevlar®), polyvinyl alcohol fibers, carbon fibers, or mixtures thereof. Glass fibers are particularly preferred. Glass fibers of type “E” are still particularly preferred.
According to one preferred embodiment, said elongated fibers are present in the composite material in an amount of from 30% by weight to 95% by weight, preferably of from 50% by weight to 90% by weight, with respect to the total weight of the composite material.
Advantageously, said composite material may be manufactured continuously by pultrusion. This is a known technique which comprises unwinding continuous fibers from a reel, and dipping them into a polymeric material (i.e. a resin) bath to impregnate them. For example, when thermosetting resins are used, the fibers are passed through a liquid resin, or through a liquid mixture of its monomers and/or oligomers, and the thus impregnated fibers are passed through a die to give a desired shape to the composite material and to remove excessive uncured resin liquid and bubbles entrapped in the bundle. Then, the obtained composite material is passed through a tubular mold where it is heated to form a semi-cured composite material. Subsequently, the obtained semi-cured composite material is subjected to a further curing by means, for example, of UV radiation, or heating, to complete the curing reaction. When thermoplastic resins are used, the composite material may be produced according to the same manner as in the case of using the thermosetting resins, in which a bath of fused resins may be used as a liquid bath. Optionally, resin powder may be previously sprinkled around the fibers to promote the impregnation. Optionally, a further coating layer of thermoplastic resin, preferably selected from those above disclosed, may be applied to the obtained composite material. To this aim, the composite material is passed through a bath of fused resin and the thus impregnated composite material is passed through a die to obtain said coating layer.
Examples of composite materials which may be used according to the present invention and are available commercially are the products known by the name of Glassline® Getev from Tecniconsult S.p.A., Twintex® from Saint-Gobain Vetrotex.
Optionally, in order to improve its adhesion to the elastomeric material 41, said first elongated elements 21 may be surface-treated by immersing them into a solution containing a mixture of resorcinol-formaldehyde resin and a rubber latex (this mixture being commonly denoted by the expression “resorcinol-formaldehyde latex RFL”), and subsequently drying them. The latex used may be: vinylpyridine/styrene-butadiene (VP/SBR), styrene-butadiene (SBR); latex of natural rubber (NR); carboxylated and hydrogenated acrylonitrile-butadiene (X-HNBR); hydrogenated acrylonitrile (HNBR); acrylonitrile (NBR), ethylene-propylene-diene monomer (EPDM), chlorosulfonated polyethylene (CSM); or a mixture thereof.
Optionally, said first elongated elements 21 may be impregnated with an adhesive in a solvent medium for obtaining an additional layer covering the fibers. Preferably, the adhesive in a solvent medium is a blend of polymers, possibly halogenated polymers, organic compounds, such as isocyanates, and mineral fillers, such as carbon black. The additional layer, forming a ring around said elongated elements, is particularly advantageous for ensuring good adhesion to certain types of rubber, such as acrylonitrile (NBR), hydrogenated acrylonitrile (HNBR), carboxylated hydrogenated acrylonitrile (X-HNBR), vulcanizable hydrogenated acrylonitrile (ZSC), chlorosulfonated polyethylene (CSM), alkylated chlorosulfonated polyethylene (ACSM), or ethylenepropylene-diene monomer (EPDM).
According to one preferred embodiment, said first elongated elements have a diameter of from 0.2 mm to 3.0 mm, preferably of from 0.6 mm to 2.5 mm.
According to the present invention, said second elongated elements 31 are made of metal.
According to one preferred embodiment, said second elongated elements have a diameter of from 0.2 mm to 3.0 mm, preferably of from 0.6 mm to 2.5 mm.
According to a further preferred embodiment, said second elongated elements 31 are made of steel or an alloy thereof. The steel may be a standard NT (normal tensile) steel whose breaking strength ranges from 2600 N/mm2 (or 2600 MPa) to 3200 N/mm2, a HT (High Tensile) steel whose breaking strength ranges from 3000 N/mm2 to 3600 N/mm2, a SHT (Super High Tensile) steel whose breaking strength ranges from 3300 N/mm2 to 3900 N/mm2, a UHT (Ultra High Tensile) steel whose breaking strength ranges from 3600 N/mm2 to about 4200 N/mm2. Said breaking strength values depend in particular on the quantity of carbon contained in the steel.
According to a further preferred embodiment, said second elongated elements 31 consist of a metal monofilament, i.e. of a single metal wire.
Alternatively, said second elongated elements 31 are obtained by stranding at least two metal wires.
a and 2b show a perspective view of a portion of a bead core strip element 12 and of a bead core 52, respectively, according to a second embodiment of the present invention.
The bead core strip element 12 shown in
As schematically represented in
The bead core 52 shown in
According to the second embodiment shown in
Therefore, according to this second embodiment, the bead core 52 is provided with second elongated elements 32 that form a portion of the bead core and with first elongated elements 22 that form the remaining portion of the bead core.
The bead core 52 of
Preferably, the second metal elongated elements 32 form the axially outer portion of the bead core 52, i.e. the bead core portion which is close to the rim flange.
Preferably, the first elongated elements 22 made of composite material form the axially inner portion of the bead core 52, i.e. the bead core portion which is close to the inner surface of the tire and thus to the cylindrical central groove of the rim.
Preferably, the elongated elements 22 and 32 of this embodiment have the same characteristics of the elongated elements 21 and 31 of the first embodiment, respectively.
a and 3b show a perspective view of a portion of a bead core strip element 13 and of a bead core 53, respectively, according to a fourth embodiment of the present invention.
The bead core strip element 13 shown in
As schematically represented in
The bead core 53 shown in
According to the fourth embodiment shown in
Therefore, according to this fourth embodiment, the bead core 53 is provided with second elongated elements 33 that form the axially inner and outer portions of the bead core and with first elongated elements 23 that form the central portion of the bead core.
Preferably, the elongated elements 23 and 33 of this embodiment have the same characteristics of the elongated elements 21 and 31 of the first embodiment, respectively.
a and 4b show a perspective view of a portion of a bead core strip element 14 and of a bead core 54, respectively, according to a fourth embodiment of the present invention.
The bead core strip element 14 shown in
As schematically represented in
The bead core 54 shown in
According to the fourth embodiment shown in
Therefore, according to this fourth embodiment, the bead core 54 is provided with first elongated elements 24 that form the axially inner and outer portions of the bead core and with second elongated elements 34 that form the central portion of the bead core.
Preferably, the elongated elements 24 and 34 of this embodiment have the same characteristics of the elongated elements 21 and 31 of the first embodiment, respectively.
a and 5b show a perspective view of a portion of a bead core strip elements 15a and 15b and of a bead core 55, respectively, according to a fifth embodiment of the present invention.
The bead core 55 is obtained by using two bead core strip elements 15a, 15b. In detail, the first bead core strip element 15a comprises only second metal elongated elements 35 while the second bead core strip element 15b comprises only first elongated elements 25 made of composite material.
As schematically represented in
The bead core 55 shown in
Therefore, according to this fifth embodiment, the bead core 55 is provided with second elongated elements 35 that form the radially inner portion of the bead core and with first elongated elements 25 that form the radially outer portion of the bead core.
Alternatively (this embodiment being not shown), the bead core 55 is provided with first elongated elements 25 that form the radially inner portion of the bead core and with second elongated elements 35 that form the radially outer portion of the bead core.
Preferably, the elongated elements 25 and 35 of this embodiment have the same characteristics of the elongated elements 21 and 31 of the first embodiment, respectively.
b and 6c show a perspective view of a portion of a bead core strip element 16 and of a bead core 56, respectively, according to a sixth embodiment of the present invention.
a shows a cross-sectional view of a cord 26 which is used for producing the bead core 56 partially shown in
As indicated in
According to this embodiment, the second elongated element 36 is made of metal. Preferably, the second elongated element 36 is made of steel or an alloy thereof.
According to this embodiment, the further elongated element 26 is a cord which comprises at least one second metal elongated element 26s and at least one first elongated element 26c which is made of composite material, the at least one second metal elongated element 26s being stranded together with the at least one first elongated element 26c.
As shown in
Preferably, the second elongated element 26s is made of metal. Preferably, the second elongated element 26s is made of steel or an alloy thereof.
Preferably, the diameter of the cord 26 is of from 0.8 mm to 2.5 mm. More preferably, the diameter of the cord 26 is of from 1.5 mm to 2.0 mm.
Preferably, the number of the second elongated elements 26s, which are stranded around the elongated element 26c, is of from 3 to 8.
Preferably, the twisting pitch of the second elongated elements 26s is of from 12 mm to 22 mm.
Alternatively (this embodiment being not shown), the further elongated element 26 comprises a second metal elongated element which is surrounded by a crown of first elongated elements. In other words, the further elongated element 26 is obtained by stranding a plurality of second elongated elements around a second elongated element, the latter being the cord core.
As schematically represented in
The bead core 56 shown in
Preferably, the elongated elements 26c and 36 and 26s of this embodiment have the same characteristics of the elongated elements 21 and 31 of the first embodiment, respectively.
According to this embodiment, the single elongated element 27, which is used for obtaining the bead core 57, is that shown in
In detail, the bead core 57 is obtained by winding the single elongated element 27 (which is embedded in an elastomeric material 47) so as to form a first layer of axially adjacent turns (coils); then, in a position radially external to said first layer, the same elongated element is further coiled so as to form a second layer in a position radially external to the first layer, and so on, so as to form several radially superimposed layers. Therefore, by varying the number of turns in each layer, it is possible to obtain cross-sectional contours of the bead core with different geometrical forms. For example, it is possible to obtain a bead core with a hexagonal shaped cross-section as shown in
a and 8b show, respectively, a perspective view of an annular insert 68 and of a bead core 58, said bead core comprising two or more annular inserts 68, according to a eighth embodiment of the present invention.
In detail, the bead core 58 is described, for instance, in European Patent EP 928,680 mentioned above, according to which a tire bead comprises an annular structure which includes at least one annular insert, the latter being substantially in the form of a circle ring concentric with the geometric axis of rotation of a toroidal support on which the tire is manufactured and located close to a corresponding inner circumferential edge of a tire first carcass ply. According to this document, the annular insert is made of at least one elongated element which is wound up to form a plurality of substantially concentric coils. Generally, combined with a first annular insert is a second annular insert substantially extending in the form of a respective circle ring and coaxially disposed in side by side relationship with the first annular insert. Interposed between the first and second annular inserts is at least one filling body made of elastomeric material. Moreover, a third annular insert may be combined with the second annular insert by interposing a further filling body between the second and the third annular inserts.
According to the embodiment shown in
In detail, the elongated element 28, which is used for obtaining the annular insert 68, corresponds to the elongated element 26 of
Alternatively (this embodiment being not shown), the elongated element 28 comprises a second metal elongated element which is surrounded by a crown of first elongated elements. In other words, the elongated element 28 is obtained by stranding a plurality of first elongated elements around a second elongated element, the latter being the cord core.
Preferably, the bead core 58 is formed of more than one annular insert 68. According to the embodiment shown in
Preferably, the second annular insert 68′ is identical to the first annular insert 68, i.e. the second annular insert is made of the elongated element 28 described above. Alternatively (this embodiment being not shown), the second annular insert 68′ may be obtained by winding a rubberized metal elongated element (e.g., the second metal elongated element 31 described with reference to the first embodiment). Alternatively (this embodiment being not shown), the second annular insert 68′ may be obtained by winding a rubberized elongated element made of composite material (e.g., the second elongated element 21 described with reference to the first embodiment).
Preferably, the second annular insert 68′ is associated to a third annular insert 68″, a second filling body 78′ being interposed therebetween. The third annular insert 68″ is identical to the first annular insert 68, i.e. the third annular insert is made of the elongated element 28 described above. Alternatively (this embodiment being not shown), the third annular insert 68″ may be obtained by winding a rubberized metal elongated element (e.g., the second metal elongated element 31 described with reference to the first embodiment). Alternatively (this embodiment being not shown), the third annular insert 68″ may be obtained by winding a rubberized elongated element made of composite material (e.g., the first elongated element 21 described with reference to the first embodiment).
The filling bodies are preferably made of an elastomeric material having a hardness included between 70° and 92° Shore A.
a and 9b show, respectively, a perspective view of an annular insert 69 and of a bead core 59, said bead core comprising two or more annular inserts 69, according to a ninth embodiment of the present invention.
As described with reference to the eighth embodiment, the bead core 59 may be obtained as disclosed, for instance, in European Patent EP 928,680 mentioned above.
According to the embodiment shown in
According to this embodiment, the further elongated element 29 corresponds to the elongated element 26 of
Alternatively (this embodiment being not shown), the further elongated element 29 comprises a second metal elongated element which is surrounded by a crown of first elongated elements. In other words, the further elongated element 29 is obtained by stranding a plurality of first elongated elements around a second elongated element, the latter being the cord core.
According to this embodiment, the elongated element 39 is preferably made of metal. Preferably, said metal material is steel or an alloy thereof.
Alternatively (this embodiment being not shown), the elongated element 39 is made of composite material.
Preferably the bead core 59 comprises more than one annular insert 69. According to the embodiment shown in
Preferably, the second annular insert 69′ is identical to the first annular insert 69, i.e. the second annular insert is obtained by winding the strip element 19 described above. Alternatively (this embodiment being not shown), the second annular insert 69′ may be obtained by winding a rubberized metal elongated element (e.g., the second metal elongated element 31 described with reference to the first embodiment). Alternatively (this embodiment being not shown), the second annular insert 69′ may be obtained by winding a rubberized elongated element made of composite material (e.g., the first elongated element 21 described with reference to the first embodiment).
Preferably, the second annular insert 69′ is associated to a third annular insert 69″, a second filling body 79′ being interposed therebetween. Preferably, the third annular insert 69″ is identical to the first annular insert 69. Alternatively (this embodiment being not shown), the second annular insert 69″ may be obtained by winding a rubberized metal elongated element (e.g., the second metal elongated element 31 described with reference to the first embodiment). Alternatively (this embodiment being not shown), the second annular insert 69″ may be obtained by winding a rubberized elongated element made of composite material (e.g., the first elongated element 21 described with reference to the first embodiment).
a and 10b show, respectively, a perspective view of an annular insert 610 and of a bead core 510, said bead core comprising two or more annular inserts 610, according to a tenth embodiment of the present invention.
As described with reference to the eighth embodiment above, the bead core 510 is obtained as disclosed, for instance, in European Patent EP 928,680 mentioned above.
Bead core 510 comprises three annular inserts 610, 610′, 610″ and two filling bodies 710, 710′ interposed therebetween. Each of the annular inserts 610, 610′, 610″ is substantially in the form of a circle ring and is located close to a corresponding inner circumferential edge of a tire carcass ply.
According to this embodiment, the annular inserts 610, 610′, 610″ are made of a single rubberized elongated element which is wound to form a plurality of substantially concentric coils.
According to the preferred embodiment shown in
Preferably, the annular insert 610 that is obtained by winding the elongated element 210 made of composite material is arranged at the axially inner portion of the bead core 510, i.e. the bead core portion that is close to the inner surface of the tire.
The “round cable” bead core 17 shown in
The “round cable” bead cores shown in
The central core shown in
Preferably, the elongated elements 30 and 40 of this embodiment are the same as, and have the same characteristics of, respectively, the elongated elements 21 and 31 of the first embodiment.
a shows a perspective view of a portion of a “round cable” bead core according to a twelfth embodiment of the present invention.
The “round cable” bead core 17a shown in
The “round cable” bead cores shown in
Preferably, the elongated element 40 of this embodiment is the same as, and has the same characteristics of, the elongated element 31 of the first embodiment.
The further elongated element 26 corresponds to the elongated element 26 of
Alternatively (said embodiment being not shown), said first sheath layer may be made of a second elongated element 40.
Alternatively (said embodiment being not shown), said second sheath layer may be made of a second elongated element 40.
b shows a perspective view of a portion of a “round cable” bead core according to a thirteenth embodiment of the present invention.
The “round cable” bead core 17b shown in
The “round cable” bead cores shown in
Preferably, the elongated elements 30 and 40 of this embodiment are the same as, and have the same characteristics of, respectively, the elongated elements 21 and 31 of the first embodiment.
Alternatively (said embodiment being not shown), said first sheath layer may be made of a second elongated element 40 and said second sheath layer may be made of a first elongated element 30.
For further description of the invention, some illustrative examples are given below.
A bead core (bead core A) similar to those described with reference to the first embodiment of the present invention shown in
A bead core (bead core B) having the same 5×5 Alderfer structure of bead core A, was manufactured with conventional steel wires.
The characteristics of the obtained bead cores are given in Table 1 below.
The bead core A according to the present invention was obtained by using a strip element in which the sequence of the axially adjacent elongated elements was the following: “MCMCM”, where “M” was the metal elongated element and “C” was the composite material elongated element.
Table 1 shows that the weight of the bead core A according to the present invention is remarkably lower (<30%) than the weight of a conventional bead core B which is made of steel elements only.
Furthermore, Table 1 shows that, in spite of the remarkable reduction of the overall bead core weight, the minimum theorical breaking load of the bead core A has not been negatively affected.
A bead core (bead core C) similar to those described with reference to the eleventh embodiment of the present invention shown in
A “round cable” bead core (bead core D) having the same configuration 1×1.5 mm+(6S+12Z)×1.3 mm of bead core C, was manufactured with conventional steel wires.
The characteristics of the obtained bead cores are given in Table 2 below.
92.7
Table 2 shows that the weight of the bead core C according to the present invention is remarkably lower (<60%) than the weight of a conventional bead core D which is made of steel elements only.
Moreover, Table 2 shows that the flexional stiffness of the bead core C according to the present invention has not been negatively affected.
Furthermore, Table 2 shows that, in spite of the remarkable reduction of the overall bead core weight, the minimum theorical breaking load of the bead core C has not been negatively affected.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/011160 | 11/22/2006 | WO | 00 | 8/26/2009 |
