阅读说明：本技术 制造车轮轮胎的方法和设备以及由此获得的轮胎 (Process and apparatus for manufacturing tyres for vehicle wheels and tyres thus obtained ) 是由 C·E·阿穆里 C·德科尔 M·坎图 R·巴西利科 于 2020-05-26 设计创作，主要内容包括：在一种用于制造车轮轮胎的方法中,轮胎(2)的至少一个胎面带(9)或其他弹性体部件通过围绕成型鼓(15)沿多个匝(C)施加至少一个连续的细长元件(14)而制成,成型鼓(15)围绕其几何旋转轴线(X)旋转。连续细长元件(14)通过挤压第一材料通过挤压喷嘴(16)的动作制成,以形成从挤压喷嘴(16)的出口开口(18)离开的所述连续细长元件(14)的内芯(33)。在挤压过程中,不同于第一材料的第二材料在挤压喷嘴(16)处和出口开口(18)的上游围绕第一材料输送,以形成完全包围内芯(33)的涂层(32)。(In a process for manufacturing tyres for vehicle wheels, at least one tread band (9) or other elastomeric component of the tyre (2) is made by applying at least one continuous elongated element (14) along a plurality of coils (C) around a forming drum (15), the forming drum (15) being rotated about a geometric rotation axis (X) thereof. The continuous elongated element (14) is made by the action of extruding a first material through an extrusion nozzle (16) to form an inner core (33) of said continuous elongated element (14) exiting from an outlet opening (18) of the extrusion nozzle (16). During extrusion, a second material, different from the first material, is delivered around the first material at the extrusion nozzle (16) and upstream of the outlet opening (18) to form a coating (32) that completely surrounds the inner core (33).)

1. A process for manufacturing tyres for vehicle wheels, wherein at least one elastomeric component of the tyre (2) is manufactured by applying at least one continuous elongated element (14) along a plurality of coils (C) around a forming drum (15), said forming drum (15) being rotated about a geometric rotation axis (X) thereof;

wherein the continuous elongated element (14) is made by:

extruding a first material through an extrusion nozzle (16) to form an inner core (33) of the continuous elongated element (14) exiting from an outlet opening (18) of the extrusion nozzle (16);

delivering a second material different from the first material around the first material at the extrusion nozzle (16) and upstream of the outlet opening (18) during the extrusion process to form a coating (32) surrounding the inner core (33).

2. The method of claim 1, wherein the applying is performed simultaneously with the extruding.

3. The method of claim 1 or 2, further comprising the act of pressing the first material without the second material.

4. The method according to one or more of the preceding claims, further comprising the action of pressing said second material without said first material.

5. The method according to one or more of the preceding claims, further comprising the action of modulating the flow rate of said second material conveyed around said inner core (33) so as to modify the thickness of said coating (32) applied around said inner core (33).

6. The method according to claim 5, wherein the flow rate of the first material is modulated in combination with the flow rate modulation of the second material to keep the total flow rate of the first and second materials through the outlet opening (18) substantially constant.

7. A method according to one or more of the preceding claims, wherein, during the extrusion, at the extrusion nozzle (16) and upstream of the outlet opening (18), the action of conveying a third material, different from the first material and different from the second material, around the first material is further performed to form a coating (36) surrounding the inner core (33).

8. The method of claim 7, wherein the act of delivering the third material is performed without delivering the second material.

9. The method of claim 7 or 8, further comprising the act of modulating the flow rate of the third material delivered around the inner core (33) to modify the thickness of the coating (36) applied around the inner core (33).

10. The method according to claim 9, wherein the flow rate of the first material is modulated in combination with the flow rate modulation of the third material to keep the total flow rate of the first and third materials through the outlet opening (18) substantially constant.

11. An apparatus for manufacturing tyres for vehicle wheels, comprising:

an extrusion assembly (13) having an extrusion nozzle (16), the extrusion nozzle (16) being longitudinally traversed by an outlet channel (17) leading to an outlet opening (18);

a first supply unit (19) for introducing a first elastomeric material into a first supply conduit (20) axially converging into the outlet channel (17) of the extrusion nozzle (16);

a forming drum (15) rotatably operable in front of the outlet opening (18) of the extrusion nozzle (16);

wherein the extrusion assembly (13) further comprises an injection chamber (30) arranged around the outlet channel (17) of the extrusion nozzle (16) and flowing therein through a radial entry slit (31) extending along a closed line around the outlet channel itself;

a second supply unit (23) for introducing a second elastomeric material into a second supply conduit leading to said injection chamber (30).

12. Apparatus as claimed in claim 11, wherein said first supply unit (19) comprises a first mixing group (19a) operating on said first elastomeric material and a gear pump (21) operatively interposed between said first mixing group (19a) and said extrusion nozzle (16).

13. Apparatus according to claim 11 or 12, wherein said second supply unit (23) comprises a second mixing group (24) having a screw (25) rotatably operable in a mixing chamber (26).

14. Apparatus as claimed in claim 13, wherein said screw (25) is axially movable in said mixing chamber (26) to transfer said second elastomeric material into said injection chamber (30).

15. Apparatus as claimed in one or more of the claims from 11 to 14, wherein said first supply unit (19) and second supply unit (23) are operable independently from each other to selectively and controllably feed said first and/or second elastomeric material towards said outlet channel (17) of said extrusion nozzle (16).

16. Apparatus as claimed in one or more of the claims from 11 to 15, and comprising a third supply unit (34) for introducing a third elastomeric material into a third supply duct (35) opening into said injection chamber (30).

17. Apparatus as claimed in one or more of the claims from 11 to 16, wherein said first supply duct (20) terminates in a distributor (50) associated with said extrusion nozzle (16), said distributor (50) having a conical annular shape with an internal passage for the passage of said first elastomeric material.

18. Apparatus as claimed in one or more of the claims from 11 to 16, wherein said radial slits (31) have a variable axial dimension along their circumferential extension.

19. A tyre for vehicle wheels, comprising:

a carcass structure (3) having at least one carcass ply (4), said carcass ply (4) having respective end flaps (4a) engaged in respective annular anchoring structures (6);

a belt structure (8) extending circumferentially around said carcass structure (3);

-elastomeric components (5, 6b, 9, 10, 11) applied to said carcass structure (3) and belt structure (8);

wherein at least one of said elastomeric components (5, 6b, 9, 10, 11) comprises a continuous elongated element (14), said continuous elongated element (14) being wound around turns (C) concentric to an axis of rotation (XI) of said tyre (2), wherein one or more of said turns (C) have an inner core (33) consisting of a first elastomeric material and a coating (32) consisting of a second elastomeric material different from said first elastomeric material, said coating surrounding said inner core (33).

20. A tyre as claimed in claim 19, wherein said elastomeric component formed by said continuous elongated element (14) is a tread band (9).

21. Tyre according to claim 19 or 20, wherein said second elastomeric material is electrically conductive.

22. Tyre according to one or more of claims 19 to 21, wherein in one or more of said turns (C) the thickness of said coating (32) is different from the thickness of the coating present in the other turns (C).

23. Tyre according to one or more of claims 19 to 22, wherein the turns (C) of the coating having different thicknesses each have equal cross-sectional dimensions.

24. Tyre according to one or more of claims 19 to 23, wherein a plurality of said turns (C) is free of coating (32).

25. Tyre according to one or more of claims 19 to 24, wherein the turns (C) without the coating (32) and the turns (C) provided with the coating (32) have respectively the same cross-sectional dimensions.

26. Tyre according to one or more of claims 19 to 24, wherein one or more of said coils (C) has a coating (36) surrounding said inner core (33), said coating (36) being constituted by a third elastomeric material different from said first elastomeric material.

27. The tire of claim 26, wherein the third elastomeric material is different from the second elastomeric material.

Technical Field

The present invention relates to a process and an apparatus for manufacturing tyres for vehicle wheels. The invention also relates to a tyre for vehicle wheels obtainable by the above method and/or apparatus.

In particular, the present invention may be conveniently used to improve the construction of tread bands and/or other elastomeric components used in the manufacture of tyres.

Background

A tyre for vehicle wheels generally comprises a carcass structure comprising at least one carcass ply having opposite end flaps respectively engaged with respective annular anchoring structures, integrated in the areas generally identified by the name of "beads", the internal diameter substantially corresponding to the so-called "fitting diameter" of the tyre on a respective mounting rim.

The carcass structure is associated with a belt structure, which may comprise one or more belt layers, arranged in radial superposed relationship with respect to each other and to the carcass ply, having textile or metallic reinforcing cords with crossed orientation and/or substantially parallel to the circumferential development direction (0 degrees) of the tyre. The tread band is applied at a position radially external to the belt structure and is also made of elastomeric material like other semifinished products constituting the tyre.

Respective sidewalls of elastomeric material are also applied at an axially external position on the lateral surfaces of the carcass structure, each extending from one of the lateral edges of the tread band up to the beads at the respective annular anchoring structure. In "tubeless" tires, an air-tight coating, commonly referred to as a "liner," covers the inner surface of the tire.

After the manufacture of the green tyre by assembling the respective components, a moulding and vulcanisation treatment is generally carried out in order to determine the structural stability of the tyre by cross-linking of the elastomeric composition and, if necessary, to impart thereon the desired tread pattern, as well as to impart any distinctive or informative graphic markings at the tyre sidewalls.

The terms "radial" and "axial" and the expressions "radially inner/outer" and "axially inner/outer" are used with reference to the radial direction of the tyre or the building drum (i.e. the direction perpendicular to the axis of rotation of the tyre or the building drum) and to the direction of the axis of rotation of the tyre or the building drum. The radial plane of the tyre or of the building drum contains the respective axis of rotation.

The term "elastomeric material" is used to indicate a composition comprising at least one elastomeric polymer and at least one reinforcing filler. Preferably, such compositions further comprise additives, such as cross-linking agents and/or plasticizers. Due to the presence of the cross-linking agent, this material can be cross-linked by heating, thus forming the final article.

The term "helical/spiral winding" refers to an operation in which at least one continuous elongated element made of elastomeric material, for example in the form of a strip, is wound circumferentially around a geometric axis to form a plurality of turns approaching in the axial direction and/or overlapping in the radial direction, respectively.

The term "structural component" refers to a tire component incorporating structural reinforcing elements, typically in the form of metal, textile or hybrid cords. For example, the carcass ply/plies, belts, bead cores and some fillers are structural components.

The term "elastomeric component" refers to a tire component made of elastomeric material without cords or other structural reinforcing elements. However, the elastomeric material may incorporate a binding or reinforcing filler, for example in the form of dispersed fibres. The elastomeric component is for example a tread band, sidewalls, under-layer, liner, under-layer liner, wear elements, filler inserts or other components of the elastomeric material of the tyre.

WO 02006/046259, representative of the applicant, describes a tyre for vehicle wheels in which the tread band, sidewalls and/or other structural elements of elastomeric material have a layered structure comprising at least a first component and at least a second component made of a material having a composition different from that of the first component. The first and second parts have corrugated interface profiles defining elements that mechanically engage one another.

WO 02006/046162, representative of the applicant, describes the building of tyres for motor vehicles in which one or more structural elements of elastomeric material, such as tread bands provided with respective substrates, are manufactured by laying on a carcass structure or other forming support a continuous elongated element longitudinally divided into first and second reciprocally coupled portions, obtained by extruding two different elastomeric materials coming from respective extruders belonging to a common extrusion nozzle. The deposition of the turns causes the first material and the second material to form a first layer and a second layer, respectively, overlying the first layer.

Us patent 2006/0096697 proposes a method for producing tyres wherein the tread band is configured so that a cylindrical top portion is formed on a substantially cylindrical forming drum by simultaneous helical winding of a continuous elongated element made of a first non-conductive elastomeric material and of an elongated insert made of a second conductive elastomeric material by means of respective applicators, each comprising a belt conveyor. Each belt conveyor feeds in succession a respective elongated element or insert to a predetermined winding position on the surface of the forming drum. After the insertion of the hanger, the elongated element and the insert each come in succession from a respective dispenser, in particular an extruder or a calender located upstream of the belt conveyor, through which the exit speed from the dispenser is controlled. The applicator is supported by the moving unit and is alternatively moved at least in an axial direction relative to the building drum.

Us patent 2013/0133811 provides for the manufacture of tread bands by simultaneous helical winding of two continuous strip-like elements delivered by respective extruders directly onto the deposition surface of a rotationally actuated forming drum. One of the extruders comprises two distinct mixing units for processing a first non-conductive elastomeric material and a second conductive elastomeric material, respectively, flowing into the same extrusion nozzle. The mixing unit for processing the second conductive elastomeric material can be selectively activated and deactivated during the processing to determine when the dispensing of the strip-like conductive inserts coupled side by side along the respective strip-like elements coming out of the extrusion head is required.

Indeed, in the production of some elastomeric components, the coupling of two or more different elastomeric materials may be required. Typically, an elastomeric base material is provided, the composition of which is designed to impart certain basic properties to the respective elastomeric component, and one or more inserts made of additional elastomeric material are provided, the composition of which is designed to impart desired additional properties to the same elastomeric component.

For example, for the construction of the tread band, it is known to use an elastomeric base material comprising silica fillers, in order to meet the requirements of obtaining certain basic properties, such as high friction coefficient, wear resistance, low hysteresis, etc. Since such base material is generally electrically non-conductive, it is generally necessary to insert at least one insert made of an additional electrically conductive elastomeric material in order to satisfy the requirements of imparting to the tread band the capacity to discharge electrostatic charges towards the ground.

It may be necessary to use one or more further inserts made of a third elastomeric material different from the elastomeric base material and/or from an additional elastomeric material, for example at each of the axially opposite ends of the tread band and/or at the radially outer vertices of each sidewall, in order to promote the correct coupling between the sidewalls, generally made of respective elastomeric materials, and the tread band (mutual coupling during the subsequent manufacturing steps may be difficult).

The applicant has observed, however, that in the manufacture of tyres by helical winding of continuous elongated elements, the additional properties sought by the use of additional inserts may be compromised due to the deformations and displacements undergone by the individual turns formed by the continuous elongated elements, for example under the effect of the high pressures induced on the whole structure of the tyre during the moulding and vulcanisation processes.

The applicant has further observed that the greater the amount of additional elastomeric material introduced into the elastomeric component in order to impart the desired additional properties, the greater its negative impact on the performance of the same elastomeric component with respect to the other basic properties desired.

The applicant has therefore perceived that by implementing suitable measures to optimize the quantity and distribution of the additional elastomeric material in the continuous elongated element, it is possible to obtain an improvement in the quality of the product and to achieve a simplification of the machines for manufacturing and/or applying the continuous elongated element itself, as well as a convenient reduction of the time required for manufacturing the tyre.

In particular, the applicant has found that by producing, in an extrusion process, a coating or covering layer extending along the continuous elongated element, surrounding the profile of the continuous elongated element in a cross-sectional view, it is possible to impart to the elastomeric component subsequently obtained by spiral winding desired additional properties determined by specific design requirements, without significantly affecting other basic properties normally required by the elastomeric component itself. Furthermore, the coating or covering layer can be made with a reduced amount of additional elastomeric material, according to a suitably limited thickness. In addition to reducing the impact on other basic properties of the obtained elastomeric component, the reduced amount of additional elastomeric material required allows the extrusion equipment to be significantly simplified and the production costs to be reduced.

Disclosure of Invention

More specifically, in a first aspect thereof, the present invention relates to a process for manufacturing tyres for vehicle wheels.

Preferably, at least one elastomeric component of the tyre is made by applying at least one continuous elongated element along a plurality of turns around a building hub, which rotates about its geometric rotation axis.

Preferably, the continuous elongated element is made by the action of the extrusion nozzle of extruding the first material to form an inner core of said continuous elongated element exiting from the outlet opening of the extrusion nozzle.

Preferably, the continuous elongated element is made by the action of delivering a second material, different from the first material, around the first material at the extrusion nozzle and upstream of the outlet opening during said extrusion to form an over-coating (completely) surrounding the inner core.

According to another aspect thereof, the present invention relates to an apparatus for manufacturing tyres for vehicle wheels.

Preferably, an extrusion assembly is provided having an extrusion nozzle longitudinally traversed by an outlet passage leading to an outlet.

Preferably, a first supply unit is provided for introducing the first elastomeric material into a first supply conduit axially converging into the outlet channel of the extrusion nozzle.

Preferably, a building drum is provided, which is rotatably operable in front of the outlet opening of the extrusion nozzle.

Preferably, the extrusion assembly comprises an injection chamber arranged around the outlet channel of the extrusion nozzle and flowing therein through a radial entry slit extending along a closed line around the outlet channel itself.

Preferably, the extrusion assembly comprises a second supply unit for introducing a second elastomeric material into a second supply conduit leading to the injection chamber.

According to another aspect thereof, the present invention relates to a tyre for vehicle wheels.

Preferably, a carcass structure is provided having at least one carcass ply having respective end flaps engaged in respective annular anchoring structures.

Preferably, a belt structure is provided, extending circumferentially around the carcass structure.

Preferably, elastomeric components applied to the carcass structure and belt structure are provided.

Preferably, at least one of said elastomeric components comprises a continuous elongated element wound according to concentric turns around the rotation axis of the tyre.

Preferably, one or more of said turns have an inner core of a first elastomeric material and a coating of a second elastomeric material different from the first elastomeric material, which (integrally) surrounds the inner core.

The applicant believes that the outer surface of the elastomeric component so formed may exhibit additional properties brought about by the elastomeric material constituting the coating or covering of the helical elongated element. At the same time, the elastomeric material that makes up the core of the continuous elongated element imparts the essential properties required for the elastomeric component.

The applicant believes that this can be exploited in a particularly convenient manner when, during the building and/or use of the tyre, the desired additional properties must be manifested in the behaviour of the elastomeric component with respect to the other elements with which it must come into contact.

For example, in the tread band, it may be provided that at least a portion of the elongated element has a high electrical conductivity as an additional property, so as to be able to discharge to the ground the electric charges accumulated while the vehicle is running. By arranging the coating cover layer or having a minimum or sufficiently small thickness, the static charge dissipation can also be effectively promoted without significantly affecting basic properties such as road grip, low hysteresis, wear resistance, etc.

Furthermore, the cross-sectional area of the coating or cladding and the cross-sectional area of the inner core can be easily modulated relative to each other as required during extrusion of the elongate element.

It is also possible to obtain a tread band or other elastomeric component of a tyre having several portions made of respectively different compounds, and to obtain more elastomeric components made of respectively different compounds, for example by gradually or almost instantaneously reducing the thickness and therefore the cross-sectional area of the coating or covering layer and/or the core to a value of zero during the extrusion process, and at the same time integrating the reduction in area of one with the corresponding increase in area of the other.

In particular, it is possible to integrate axially opposite ends of the tread band portion of the radially outer side wall having contact surfaces with the remaining portion of the sidewalls, made of an elastomeric material compatible with or identical to the elastomeric material normally used for manufacturing the aforesaid remaining portion of the sidewalls of the tyre, so as to facilitate a satisfactory coupling between the sidewalls and the tread band during the manufacture of the tyre and the subsequent moulding and vulcanisation steps.

In at least one convenient embodiment, the invention may further comprise one or more of the following preferred features.

Preferably, the applying is performed simultaneously with the pressing.

Preferably, said application comprises the transmission of a transverse distribution movement between the forming drum and the extrusion nozzle for distributing said coils in mutual approaching relationship.

Preferably, the action of pressing the first material without the second material is also provided.

Preferably, the act of pressing the first material in the absence of the second material precedes the act of conveying the second material.

Preferably, the action of pressing the first material without the second material is performed after the action of conveying the second material.

Preferably, the action of interrupting the delivery of the second material is also provided to compress the first material in the absence of the second material.

Preferably, there is also provided the act of pressing the second material in the absence of the first material.

Preferably, the act of pressing the second material in the absence of the first material precedes the act of conveying the first material.

Preferably, the action of pressing the second material without the first material is performed after the action of conveying the first material.

Preferably, the action of interrupting the delivery of the first material is also provided to squeeze the second material in the absence of the first material.

Preferably, the act of modulating the flow of the second material delivered around the inner core is provided to modify the thickness of the coating applied around the inner core. Preferably, the flow rate of the first material is modulated in combination with the flow rate modulation of the second material to keep the total flow rate of the first and second materials through the outlet opening substantially constant.

Preferably, there is further provided the act of increasing or decreasing the flow rate of the first material in conjunction with a decrease or increase in the flow rate of the second material, respectively.

Preferably, during said extrusion, the action of conveying a third material, different from the first material and different from the second material, around the first material is further performed, at the extrusion nozzle and upstream of the outlet opening, to form a coating (completely) surrounding the inner core.

Preferably, the act of conveying the third material is performed without conveying the second material.

Preferably, the action of pressing the first material without conveying the second material and the third material is also provided.

Preferably, there is also provided the act of pressing the third material in the absence of the first material.

Preferably, the act of pressing the third material in the absence of the first and second materials is also provided.

Preferably, the act of modulating the flow of the third material delivered around the inner core is provided to modify the thickness of the cover layer applied around the inner core. Preferably, the flow rate of the first material is modulated in combination with the flow rate modulation of the third material to keep the total flow rate of the first material and the third material through the outlet opening substantially constant.

Preferably, there is further provided the act of increasing or decreasing the flow rate of the first material in conjunction with a decrease or increase in the flow rate of the third material, respectively. Preferably, the first supply unit comprises a first mixing group operating on the first elastomeric material and a gear pump operatively interposed between the first mixing group and the extrusion nozzle.

Preferably, the second supply unit comprises a second mixing group having a screw rotatably operable in the mixing chamber. Preferably, said screw is axially movable in the mixing chamber to transfer the second elastomeric material into the injection chamber.

Preferably, the first and second supply units are operable independently of each other for selectively and controlled feeding of the first material and/or the second material towards the outlet channel of the extrusion nozzle.

Preferably, a third supply unit is also provided for introducing a third elastomeric material into a third supply conduit leading to the injection chamber.

Preferably, the third supply unit comprises a respective mixing group having a screw, rotatably operable in the mixing chamber and axially movable in the mixing chamber, for transferring the third elastomeric material into the injection chamber.

Preferably, said first supply conduit terminates in a distributor associated with said extrusion nozzle, said distributor having a conical annular shape with an internal passage for the passage of said first elastomeric material.

Preferably, said radial slits have a variable axial dimension along their circumferential extension.

Preferably, the elastomeric component formed by said continuous elongated element is a tread band.

Preferably, the second elastomeric material is electrically conductive.

Preferably, the second elastomeric material has the same composition as the elastomeric material used for producing the tyre sidewalls.

Preferably, in one or more of said turns, the thickness of the coating is different from the thickness of the coating present in the other turns.

Preferably, the turns of the coating, respectively having different thicknesses, have respectively equal cross-sectional dimensions. Preferably, a plurality of said turns are uncoated.

Preferably, the turn without coating and the turn provided with coating each have equal cross-sectional dimensions.

Preferably, one or more of the turns has a cover layer (completely) surrounding the core, the cover layer being composed of a third elastomeric material different from the first elastomeric material.

Preferably, the third elastomeric material is different from the second elastomeric material.

Preferably, the third elastomeric material has the same composition as the elastomeric material used for producing the tyre sidewalls.

Drawings

Further features and advantages will become apparent from the detailed description of a preferred but not exclusive embodiment of a process and an apparatus for producing tyres for vehicle wheels according to the present invention, and of a tyre for vehicle wheels obtainable by the aforementioned method and/or apparatus. This description is given below with reference to the accompanying drawings, which are provided for illustrative and therefore non-limiting purposes only, and in which:

figure 1 shows a perspective view of an apparatus for manufacturing tyres for vehicle wheels according to the present invention;

FIG. 2 shows the apparatus of FIG. 1 in a longitudinal sectional view;

FIG. 3 shows an enlarged detail of FIG. 2, highlighting a variant embodiment;

figure 4 shows a detail of a variant of the embodiment of figure 3 according to a longitudinal section with respect to the orthogonal plane of figure 3;

FIG. 5 shows a detail of FIG. 2 on an enlarged scale, highlighting the continuous elongated element dispensed by the extrusion nozzle;

FIG. 6 is an enlarged cross-sectional view of the elongated member;

figure 7 schematically shows a radial section of a tyre for vehicle wheels according to the invention;

fig. 8 schematically shows the tread band of the tyre of fig. 7.

Detailed Description

With reference to the above figures, numeral 1 indicates an apparatus for manufacturing tyres for vehicle wheels according to the present invention.

The apparatus 1 can be conveniently used for manufacturing tyres 2 (fig. 7), the tyre 2 substantially comprising a carcass structure 3, the carcass structure 3 having at least one carcass ply 4. An airtight layer or so-called liner 5 of elastomeric material may be applied internally of the carcass ply or plies 4. Two annular anchoring structures 6 are associated to respective end flaps 4a of one or more carcass plies 4, each annular anchoring structure 6 comprising a so-called bead core 6a, the bead core 6a carrying an elastomeric filler 6b in a radially external position. The annular anchoring structures 6 are integrated in proximity of the region generally identified by the name of "beads" 7, where the engagement between the tyre 2 and the respective mounting rim generally takes place.

A belt structure 8 comprising one or more belt layers 8a, 8b extends circumferentially around the carcass structure 3, a tread band 9 being circumferentially superposed on the belt structure 8.

The belt structure 8 may be associated with so-called "under-belt inserts" 10, each under-belt insert 10 being placed between one or more carcass plies 4 and one of the axially opposite end edges of the belt structure 8.

Two sidewalls 11 are applied in laterally opposite positions on the carcass ply/plies/4. Each side has a radially inner vertex 11a joined to the respective bead 7 and a radially outer end portion 11b possibly joined to a radially outer vertex 12 which the tread band 9 has at its axially outer end 9 a.

With reference to the above definitions, in the example of tyre shown, the carcass ply/plies 4, the belt layers 8a, 8b and the bead cores 6a represent the structural components, while the sidewalls 11, the liner 5, the filler 6a, the under-belt insert 10 and the tread band 9 with any radially external apex 12 represent the elastomeric components applied to the carcass structure 3 and/or to the belt structure 8.

In the preferred embodiment example described herein, the apparatus 1 is used for making a tread band 9. However, the present invention may be conveniently used to spiral wind any other elastomeric component, such as the sidewalls 11, the liner 5, the filler 6a, the under-belt insert 10 and/or other elastomeric components required for manufacturing the tire 2.

The apparatus 1 comprises a pressing assembly 13, the pressing assembly 13 being arranged to dispense at least one continuous elongated element 14, preferably in proximity to the outer surface S of the forming drum 15. The forming drum 15 is substantially supported near the pressing device, for example by a robotized arm 15 a. The robotized arm 15a suitably supports and moves the forming drum 15 so as to determine the application of the continuous elongated element 14 according to the turns around the outer surface S of the forming drum 15 itself, while the forming drum 15 rotates about its geometric rotation axis X. The extrusion assembly 13 has at least one extrusion nozzle 16, an outlet channel 17 leading to an outlet opening 18 passing longitudinally through the extrusion nozzle 16, the continuous elongated element 14 being dispensed through the outlet opening 18.

Upstream of the extrusion nozzle 16, a first supply unit 19 is arranged, which first supply unit 19 is configured to introduce a first elastomeric material into a first supply conduit 20, which first supply conduit 20 axially converges into the outlet channel 17 of the extrusion nozzle 16.

Preferably, the first supply unit 19 comprises a first mixing group 19a operating on the first elastomeric material, the first mixing group 19a being only schematically illustrated, since it can be configured in a known manner. A gear pump 21 is operatively interposed along the first supply duct 20 between the first mixing group 19a and the extrusion nozzle 16. The use of the gear pump 21, the actuation speed of which can be suitably adjusted by means of a Programmable Logic Controller (PLC) associated with the actuator unit 22, allows to instantaneously control the flow rate of the first elastomeric material sent to the extrusion nozzle 16 with a suitable accuracy.

The extrusion assembly 13 further comprises a second supply unit 23, the second supply unit 23 being configured to introduce a second elastomeric material, different from the first elastomeric material, into the outlet channel 17 of the extrusion nozzle 16.

More specifically, the second supply unit 23 preferably comprises a second mixing group 24, which second mixing group 24 has a screw 25 operatively housed in a mixing chamber 26 and can be operated in rotation by a motor 27. Preferably, the screw 25 is also axially movable in the mixing chamber 26, for example on command of the axial movement unit 28, to promote the transfer of the second elastomeric material into a second supply duct 29, the second supply duct 29 extending in a radial direction with respect to the outlet channel 17 and opening into the injection chamber 30. The injection chamber 30 preferably has an annular configuration, is arranged around the outlet channel 17 of the extrusion nozzle 16 and flows therein through a radial entry slit 31, the radial entry slit 31 extending along a closed line around the outlet channel 17 itself, completely surrounding the outlet channel 17 (fig. 2). The supply conduit 20 may terminate in a distributor 50 associated with the extrusion nozzle 16. The distributor 50 has a conical annular shape with an internal passage for the passage of the above-mentioned first elastomeric material, which terminates in an outlet section 51. The outlet section 51 is slightly spaced from the inlet section 52 of the extrusion nozzle 16. The radial slit 31 is axially defined between an outlet section 51 of the distributor 50 and an inlet section 52 of the extrusion nozzle 16. The outlet section 51 may have a substantially elliptical or in any case geometrically similar, but possibly greater circumferential profile with respect to the profile of the outlet opening 18 and therefore of the continuous elongated element 14 coming out therefrom. As illustrated in the embodiment variants shown in fig. 3 and 4, the outlet section 51 of the distributor 50 and/or the inlet section 52 of the extrusion nozzle may have a concave profile or be uneven in a different manner, for example, in a plane orthogonal to their longitudinal axes coinciding with the longitudinal axes of the channel 20 and the extrusion nozzle 16. As a result of this non-planar profile, a variable distance is created between the distributor 50 and the extrusion nozzle 16 along the circumferential extension of the outlet section 51 and the inlet section 52. In other words, the radial slits 31 may have a variable axial dimension along their circumferential extension. During operation of the apparatus 1, the first supply unit 19 and the second supply unit 23 are adapted to operate independently of each other to cause selective and controlled feeding of the first material and/or the second material towards the outlet channel 17 of the extrusion nozzle 16.

The use of the first material is arranged such that when the building drum 15 is rotated and suitably moved in front of the outlet opening 18, the first supply unit 19 is activated to feed the first material into the outlet channel 17 of the extrusion nozzle 16. The first material is thus extruded through the extrusion nozzle 16, out of the outlet opening 18 without the second material, while being applied around the outer surface of the building drum 15. The rotation imparted to the forming drum 15 about its geometric rotation axis X determines the formation of successive coils C, while the transverse movement imposed to the forming drum 15 by the robotized arm 15a determines the distribution of the coils C according to a predetermined scheme, for example in mutually approached relationship along the axial extension of the outer surface S of the forming drum 15.

At any desired moment during the extrusion process, the second supply unit 23 is adapted to be activated, for example by axial movement of the respective screw 25, for pushing the second material into the injection chamber 30. At the extrusion nozzle 16 and upstream of the outlet opening 18, the second material pushed into the injection chamber 30 is conveyed through the radial slits 31 around the first material coming from the first supply conduit 20, preferably through said distributor 50. Thus, the second material is distributed around the first material to be extruded through the extrusion nozzle 16. Thus, the second material forms said coating 32 on the outside of the continuous elongated element 14 dispensed by the outlet opening 18, said coating 32 completely surrounding the inner core 33 defined by the first material. By using the aforementioned concave or non-planar shape of the outlet section 51 of the distributor 50 and/or of the inlet section 52 of the extrusion nozzle 16, it is possible to initially produce a variable layer thickness, i.e. in the vicinity of the radial slits 31 of the coating 32, which then becomes substantially constant in the vicinity of the aforementioned outlet opening 18, due to the transverse displacement undergone by the second elastomeric material (and/or a third elastomeric material, as will be understood below) along the cross-sectional variations in the path of the extrusion nozzle 16. For the purpose of making the coating 32, the dispensing of the second material may be maintained for a period of time necessary to form the desired number of turns C around the building drum 15. The second supply unit 23 can then be deactivated in order to interrupt the delivery of the second material and, in the absence of the second material, to continue to build up the other part of the elastomeric component to be manufactured by dispensing the first material.

Additionally or alternatively, deactivation of the first supply unit 19 may be provided, if desired, to compress the second material without the first material. This technical measure can be used, for example, to obtain turns C made of the second material only in certain areas of the elastomer component to be manufactured, or to make parts of the above-mentioned elastomer component using the second material only.

The act of extruding the first material or the second material without the other material may be preceded or followed by the act of extruding the same other material, depending on the requirements.

It may be advantageous to provide the action of modulating the flow rate of the second material conveyed around the inner core 33, for example by adjusting the axial movement speed of the screw 25, so as to modify the thickness of the coating 32 applied around the inner core itself.

By adjusting the actuation speed of the gear pump 21, it is also advantageously possible to modulate the flow rate of the first material, possibly in combination with a variation of the flow rate of the second material. More specifically, the flow rate of the first material may be increased or decreased, respectively, in combination with a decrease or increase, respectively, in the flow rate of the second material. For example, an increase in the flow rate of the second material may correspond to an equal decrease in the flow rate of the first material, so as to maintain the total flow rate, i.e. the sum of the flow rates, of the first and second materials through the outlet opening 18, and therefore the cross-sectional dimension of the continuous elongated element 14, substantially constant.

Flow modulation may also be used to gradually change from a state in which only one material is extruded without another material to an operating state in which only another material is extruded.

According to a possible preferred variant, the device 1 may further comprise a third supply unit 34, which third supply unit 34 is configured to introduce a third material, different from the first material and preferably, but not necessarily, also from the second material, into a third supply duct 35 leading to the injection chamber 30.

The third supply unit 34, schematically shown in dashed lines in fig. 2, can be made substantially identical to the second supply unit 23.

The third supply unit 34 may be enabled selectively and independently of the enablement of the first supply unit 19 and the second supply unit 23. Preferably, the activation of the third supply unit 34 is performed when at least the second supply unit 23 remains inactive.

During the pressing of the first material, the activation of the third supply unit 34 causes the third material to be delivered to the injection chamber 30, preferably without the second material being delivered, to form a covering layer 36, which covering layer 36 completely surrounds the inner core 33 formed by the first material itself.

By operating the third supply unit 34 in a manner similar to that described with reference to the second supply unit 23, it may be advantageous to provide the action of modulating the flow rate of the third material delivered around the inner core 33 to modify the thickness of the cover layer 36 formed of the third material.

The act of pressing the first material may also be performed without conveying the second material and/or the third material, and the act of pressing the second material/the third material in the absence of the first material and/or the third material/the second material.

The flow rate of the first material may be modulated in combination with the flow rate modulation of the third material by increasing or decreasing the flow rate of the first material in combination with a decrease or increase, respectively, in the flow rate of the third material. For example, an increase in the flow rate of the third material may correspond to an equal decrease in the flow rate of the first material, so as to maintain the total flow rate, i.e. the sum of the flow rates, of the first and third materials through the outlet opening 18, and therefore the cross-sectional dimension of the continuous elongated element 14, substantially constant.

In a preferred embodiment of providing a second material equal to the third material, it is possible, if necessary, to form a continuous coating around the inner core 33, up to the desired number of turns, and to alternate the operation of the second supply unit 23 and the third supply unit 34, one in the operating (injection) step and the other in the material loading step, throughout the helical winding step of the continuous elongated element 14.

In another preferred embodiment (not shown), providing the second supply unit 23 and the third supply unit 34 with respective injection chambers, each axially distanced from each other along the longitudinal development of the outlet channel 17, the second supply unit 23 and the third supply unit 34 can be operated simultaneously, making two coatings of the second material and the third material, respectively, around the inner core 33 defined by the first material, providing specific physical characteristics to the elastomeric component of the tyre formed by the continuous elongated element 14.

The construction of the tread band 9 or other elastomeric component may require the use of only the first material, typically for a substantial portion of the elastomeric component itself. However, in some portions of elastomeric component, for example in an axially central portion a (fig. 6) adjacent to the axial centre line Y of the tread band 9, it may be necessary to use a second material, for example to determine a desired electrical conductivity between the belt structure 8 and the radially outer surface 9b of the same tread band 9, which is intended to be in contact with the ground during use of the tyre 2.

The preferential use of the third delivery unit 34 during the construction of the tread band 9 may be aimed at realising said radially external vertices 12. In this regard, the third supply unit 34 is adapted to be activated during the deposition of the turns C close to the axially external portion B (fig. 6) of each of the respective opposite axial ends 9a of the tread band 9. In these cases the continuous elongated element 14 dispensed will be provided with a covering layer 36 made of a third material.

The thickness of the covering layer 36 and the overall cross-sectional dimensions of the continuous elongated element 14 may be modified during deposition, for example by gradually reducing the size of the core 33 formed only of the first material during deposition of the turns C closer and closer to the axial ends 9a of the tread band 9, possibly until the distribution of the first material is completely interrupted, so that the turns C closest to the axial ends 9a are constituted only of the third material.

In the tyre 2 obtained according to the invention, at least one of the elastomeric components, in the case described the tread band 9, will be formed by a continuous elongated element 14, the continuous elongated element 14 being wound according to concentric turns C around the geometric rotation axis X of the tyre itself.

In one or more of the turns C, an inner core 33 made of a first elastomeric material is completely surrounded by a coating 32 made of a second elastomeric material or by a covering layer 36 made of a third elastomeric material, such inner core 33 being identifiable.

For making the tread band 9, the first elastomeric material may for example comprise a relatively large amount of silica, for example greater than 30 parts by weight in 100 parts by weight of compound.

For manufacturing the tread band 9, the second elastomeric material may for example comprise a sufficient amount of carbon black, for example more than 50 parts by weight in 100 parts by weight of compound, to obtain a sufficient electrical conductivity.

To make said radially external vertices 12, the third elastomeric material will have substantially the same composition and physicochemical properties as those of the elastomeric material used in the construction of the sidewalls 11, so as to achieve an optimal coupling between the radially external vertices 12 of the sidewalls 11 and the axial end 9a of the tread band 9 during the manufacture of the tyre 2.

For example, the turns C near the axial centerline Y of the tread band 9 may be covered by a coating 32 formed of a second conductive material, the turns C placed at the axial ends 9a of the tread band 9 to form the radially outer vertices 12 may in turn be covered by a covering layer 36 made of a third material, this covering layer 36 being substantially identical to that of the sidewalls 11, and finally the turns C distributed between the radially outer vertices 12 and the region close to the axial centerline Y of the tread band 9 may be formed of the first material only, without the coating 32 and/or the covering layer 36.

In one or more of the turns C, the thickness of the coating 32 or the cover layer 36 may be different from the thickness of the coating 32 or the cover layer 36 present in the other turns C.

The turns C of the coating 32 or the covering layer 36, respectively, having different thicknesses, may have cross-sectional dimensions equal to each other and/or equal with respect to the turns C without the coating 32 or the covering layer 36. Since it completely surrounds the core 33, the coating 32 formed of the second material can advantageously be made thin without risk of, for example, interrupting the electrical continuity through the tread band 9, nor of the turns C subsequently undergoing any deformation during vulcanization or in other processing steps after manufacture.

The same applies to the covering layer 36 formed of the third material, which ensures an effective covering of the core 33 also after any deformation or crushing imposed on the individual turns C.

The deposition pattern of the turns C of the continuous longitudinal element 14 may not (and does not have to) be carried out as shown in fig. 8, for example in the manufacture of the tread band 9, a single turn C having both a radially outer portion exposed to the radially outer surface of the tread and a radially inner portion in contact with the structural component in the electrically conductive material, for example the belt strips 8a, 8 b.

In general, the single turns C may be positioned above the other turns C, so that, for example in the manufacture of the tread band 9, the coating 32 that completely covers the outer surface of each single turn C allows contact and electrical conduction between the turn C positioned in contact with the structural component (the belt strips 8a, 8b) in the electrically conductive material and the turns radially external thereto (and so on up to the radially outer surface of the tread), promoting maximum flexibility of the manufacturing operations, rather than being forced to comply with specific schemes to favour, for example, electrical conduction.

The use of a smaller amount of the second material and/or the third material allows to reduce its impact on the essential performance characteristics required of the elastomeric component.

Furthermore, the reduced amount of the second material allows to advantageously limit the size and cost of the second supply unit 23 and of the entire apparatus.

The need for continuous supply of the second material and/or the third material to the second supply unit 23 is also eliminated for operational purposes. In fact, the standby period of the second supply unit 23 and/or the third supply unit 34 can be used to resume the supply of the second material and/or the third material inside the mixing chamber 26 without having to interrupt the manufacturing.