METHOD FOR THE CONSTRUCTION OF TIRE BELT ASSEMBLIES FOR VEHICLE WHEELS.

Abstract

A method for manufacturing belt assemblies for vehicle tires is described. The method comprises constructing a cross-belt structure on a first substantially cylindrical forming drum (25). Depending on the type of tire to be produced, it is possible to choose whether to construct a belt assembly having a cylindrical shape or a belt assembly having a toroidal shape. To manufacture a belt assembly with a cylindrical shape, at least one zero-degree belt is formed on said first forming drum (25) in a radially external position relative to said cross-belt structure.To construct a belt assembly having a toroidal shape using this method, the cross-belt structure of the first forming drum (25) is adopted, the cross-belt structure having a toroidal shape, the toroidal cross-belt structure is transferred to a second forming drum (210), and at least one layer of zero-degree belts is deposited on the second forming drum (210) in a radially outward position relative to the toroidal cross-belt structure.

Description

METHOD FOR THE CONSTRUCTION OF TIRE BELT ASSEMBLIES FOR VEHICLE WHEELS DESCRIPTION The present invention relates to a method for constructing tire belt assemblies for vehicles. A vehicle wheel tire generally comprises a casing structure, a crown structure arranged in a radially external position with respect to the casing structure, and a pair of sidewalls that are the axially external surfaces of the tire, with respect to a median plane perpendicular to the axis of rotation of the tire. The casing structure comprises at least one casing layer formed by reinforcing yarns embedded in an elastomeric material matrix. The casing fabric has opposite end edges coupled to annular anchoring structures. These structures are arranged in areas of the tire generally identified as beads and typically each consists of a substantially circumferential annular insert or bead core onto which at least one filler insert is applied, radially outward, tapering radially away from the axis of rotation. Specific reinforcement inserts can be provided in the heels that have the function of improving the transmission of engine torque to the tire. In the case of tubeless tires, that is, tires without an air tube, a layer of elastomeric material, generally known as a liner, can also be placed radially inside the structure of the casing to provide the necessary impermeability for the air used to inflate the tire. Generally, the liner extends from one bead to the other. The crown structure comprises a belt structure and, in a radially external position relative to the belt structure, a tread made of elastomeric material. The belt structure comprises one or more belt layers arranged in radial juxtaposition to each other, comprising reinforcing cords that have an orientation substantially parallel to the direction of the circumferential extension of the tire (zero-degree belt layer), or, in the case of more belt layers, with a cross orientation. In the latter case, this zero-degree belt layer can be presented in a radially external position with respect to the belt layers that have a cross orientation. Longitudinal and transverse grooves are typically formed on the tread and arranged to define a desired tread pattern. Between the tread and the belt structure, a so-called under-tread layer made of elastomeric material with suitable properties can be placed to achieve a stable bond between the belt structure and the tread itself. The sidewalls are made of elastomeric material and define the axially external surfaces of the tire; that is, the surfaces positioned axially external to the annular anchoring structures, the casing ply(s), the belt ply(s), and possibly at least a portion of the tread. For example, each sidewall extends from one of the lateral edges of the tread to the corresponding annular anchoring structure of the beads. Throughout this description and in the claims, any numerical value is considered to be preceded by the term approximately to also indicate any numerical value that differs slightly from the one stated, for example to take into account the dimensional tolerances of the reference field. The term elastomeric material is used to describe a composition comprising at least one elastomeric polymer and at least one reinforcing filler. This composition may also include additives such as a crosslinking agent and / or a plasticizer. The crosslinking agent allows the material to be crosslinked by heating to form the final manufactured product. The term green tire is used to indicate a tire obtained from the manufacturing process and not yet molded and vulcanized. The term finished tire is used to indicate the tire obtained by subjecting a green tire to a molding and vulcanizing process. The term tire is used to indicate a finished tire or a green tire. The terms axially, axially, radially, radially, circumferentially, and circumferentially are used with reference to the tire or the forming drum used in the tire production process. In particular, the terms axially and axially are used to indicate references / parameters arranged / measured or extending in a direction substantially parallel to the axis of rotation of the tire or drum. The terms radial and radially are used to indicate references / parameters arranged / measured or extending in a direction substantially perpendicular to the axis of rotation of the tire or forming drum and lying in a plane comprising said axis of rotation. The terms circumferentially and circumferentially are used to indicate references / parameters arranged / measured or extending along a circumference that extends around the axis of rotation of the tire or forming drum. The term "structural component" of a tire is used to indicate any part of the tire capable of performing its function, or part thereof. Examples of tire structural components include: the casing structure, the crown structure or parts thereof, such as the liner, the underline, the abrasion-resistant inserts, the bead core, the bead filler inserts (and thus the annular anchoring structures defined by bead cores and their respective filler inserts), the casing ply(s), the belt ply(s), the underline belt ply, the underline tread ply, the sidewall inserts, the tread, textile or metallic reinforcement inserts, elastomeric reinforcement inserts, etc., or parts thereof. The term cross-belt structure is used to indicate a belt structure comprising at least two layers of belts arranged radially juxtaposed one above the other and each of which includes a plurality of parallel textile and / or metallic and / or hybrid reinforcing cords, inclined with respect to the circumferential extension direction of the tire (and therefore to an axial mid-plane of the tire), wherein the reinforcing cords of one belt layer are inclined with respect to said axial mid-plane of the tire at the same angle and on the opposite side to the reinforcing cords of another belt layer. The term belt assembly is used to denote an annular assembly comprising a cross-belt structure and a zero-degree belt layer arranged in a radially external position relative to the cross-belt structure. The term cylindrical forming of a belt assembly is used to indicate a construction cycle intended to obtain a belt assembly that has a substantially cylindrical shape. The term toroidal forming of a belt assembly is used to indicate a construction cycle intended to obtain a belt assembly having a substantially toroidal shape and a profile in a radial section close to the profile in a corresponding radial section of the finished tire. The term substantially toroidal forming drum is used to indicate a forming drum whose outer surface has a profile in a radial section so that whatever semi-finished product is placed on it during the construction of a tire being processed, the semi-finished product takes a shape similar to that of the finished tire. The term "tire in process" is used to indicate a tire at any stage of the production process, from the manufacture of at least one structural component to the production of the finished tire. For example, a tire in process is one that has just left the workstation dedicated to belt manufacturing and is now being moved to the workstations dedicated to applying the belt assembly, the possible underlayer of the tread, any reinforcing inserts, and the tread itself. The term functionally independent is used to indicate the ability of a member or device to perform the function for which it is intended autonomously, that is, without interacting or cooperating with other members or devices provided to perform the same function. The term normal operation is used to indicate the normal operating conditions of a tire production plant, thus excluding possible periods of start-up or shutdown of the plant itself, for example linked to a change in the production batch. The term cycle time of a manufacturing device is used to indicate the time that elapses between the exit of one work-in-process tire from a manufacturing device and the exit of the next work-in-process tire from the same plant, under normal operating conditions. Therefore, the cycle time of a manufacturing device is given by the sum of the time required to load the work-in-process tire into the manufacturing device, the time required to perform the manufacturing activity, and the time required to unload the work-in-process tire from the manufacturing device. The term total cycle time of a manufacturing plant is used to indicate the time that elapses between the exit of one in-process tire from a manufacturing plant and the exit of the next tire from the same plant, under stable operating conditions. The terms downstream / head and upstream are used with reference to a direction of movement. Therefore, assuming, for example, a direction of movement from left to right, a downstream or head position relative to any reference point indicates a position to the right of that reference point, and an upstream or tail position indicates a position to the left of that reference point. The production cycles of a tire foresee that, after a manufacturing process of a green tire in which the various structural components of the tire itself are built and assembled, the green tires are transferred to a molding and vulcanization line 25 where a molding and vulcanization process is adapted to define the structure of the finished tire according to a desired geometry and a tread pattern is achieved. The construction and subsequent assembly of tire structural components is carried out on suitable forming drums. For example, the casing structure can be built on a first forming drum, known as the first-stage drum, and the crown structure can be built on a second forming drum, known as the auxiliary or second-stage drum. The assembly of the casing structure to the crown structure can occur on the first forming drum, in which case the first-stage drum is called the single-stage drum, or on a different forming drum, known as the forming drum. WO2010 / 070374 describes an example of a plant for producing green tires. This plant comprises: at least one manufacturing line for manufacturing the housing structure on a first forming drum, wherein said manufacturing line comprises a plurality of workstations arranged in a sequential series; at least one manufacturing line for manufacturing the crown structure on at least a second forming drum, wherein the manufacturing line comprises a plurality of workstations arranged in a sequential series; and - at least one in-process tire forming and assembly station adapted to form the casing structure on the first forming drum that assembles it for the in-process tire crown structure. WO2008 / 152453 and US2012 / 0318460 describe examples of first and / or second stage forming drums that can be used in a tire production process such as that described in WO2010 / 070374 mentioned above. In both cases, they are radially shrinkable / expandable forming drums that are substantially cylindrical in shape. The forming drums described in the cited documents are widely used in tire production cycles where cylindrical forming of belt assemblies takes place. The Applicant has observed that, for example, in the production cycles of racing or high-performance tires, it is necessary to be able to adequately control the deformations to which the green tire is subjected during the molding and vulcanization process in order to give the tire the desired responsiveness and driving precision. To achieve this, it is advisable, before starting the molding and vulcanization process, to provide a toroidal shape that gives the belt assembly a substantially toroidal form as close as possible to the shape of the finished tire. In order to make a technologically and operationally flexible production plant, so as to reduce the manufacturing costs of the plant and its devices and apparatus and the spaces occupied by said devices and apparatus, the Applicant has considered it convenient to identify a suitable solution to carry out, by means of the same belt assembly manufacturing device, both a cylindrical conformation of the belt assembly and a toroidal conformation of the belt assembly, in which each time it is chosen which of the two types of conformation should be carried out according to the type of tire to be manufactured. The Applicant has noted that this solution could provide for the manufacture of the belt assembly on a substantially cylindrical forming drum when a cylindrical forming of the belt assembly has to be carried out, and on a substantially toroidal forming drum when a toroidal forming of the belt assembly has to be carried out. However, according to the Applicant, it would be extremely difficult to automatically (i.e., not manually) join the end parts of the belt layers of the cross-belt structure if said belt layers (each of which is defined by a semi-finished product in the form of a substantially flat strip cut to size) are deposited on a substantially toroidal forming drum. Therefore, the Applicant considered it preferable to identify an alternative solution that would allow the cross-belt structure to be built on a substantially cylindrical forming drum, not only in the case of cylindrical belt assemblies but also in the case of toroidal belt assemblies. This would involve using the same forming drum for the subsequent deposition of the zero-degree belt layer in the case of cylindrical belt assemblies and a different forming drum for the subsequent deposition of the zero-degree belt layer in the case of toroidal belt assemblies. Indeed, this latter operation can be performed on a forming drum of any shape, including toroidal, as no joints are required. The Applicant has finally found that it is possible to foresee a manufacturing cycle for the belt assembly having a first part of the cycle, dedicated to manufacturing the cross-belt structure, in which a substantially cylindrical forming drum is used both when cylindrical forming of the belt assemblies is carried out and when toroidal forming of the belt assemblies is to be carried out, and a second part of the cycle, dedicated to depositing the zero-degree belt layer, in which when cylindrical forming of the belt assemblies has been carried out, the aforementioned substantially cylindrical forming drum is still used, while when toroidal forming of the belt assemblies is carried out, the cross-belt structure is picked up from the substantially cylindrical forming drum and transferred to another forming drum after having been toroidally formed,then proceed with the deposition of the zero-degree belt layer onto the toroidal cross-belt structure. Therefore, the present invention relates to a method for manufacturing tire belt assemblies for vehicles. Preferably, a cross-belt structure is expected to be manufactured on a first drum of substantially cylindrical shape. Preferably, depending on the type of tire to be produced, a selection is made between a belt assembly that has a cylindrical shape or a belt assembly that has a toroidal shape. Preferably, to manufacture a belt assembly with a cylindrical shape, the method involves depositing at least one layer of zero-degree belts onto said first forming drum in a radially external position relative to said cross-belt structure. Preferably, to manufacture a belt assembly having a toroidal shape, the method involves picking up said cross-belt structure from the first forming drum. Preferably, to manufacture a belt assembly having a toroidal shape, the method involves toroidally shaping said crossed belt structure. Preferably, to manufacture a belt assembly having a toroidal shape, the method involves transferring said toroidal-shaped belt structure into a second forming drum. Preferably, to manufacture a belt assembly with a toroidal shape, the method involves depositing at least one layer of zero-degree belts onto said second forming drum in a radially external position relative to said toroidally crossed belt structure. The Applicant believes that the method according to the invention makes it possible to perform both cylindrical and toroidal belt assemblies using the same manufacturing device, thereby minimizing the number of devices and apparatus used and the space they occupy. This is due to the fact that the cross-belt structure is manufactured on a substantially cylindrical forming drum, whether performing cylindrical or toroidal belt assembly formation. Furthermore, thanks to the fact that when a toroidal conformation of the belt assembly is carried out, the zero-degree reinforcing layer is deposited on a cross-belt structure that had been previously formed toroidally, it is possible to automatically (i.e., non-manually) and easily join the end parts of the belt layer of the cross-belt structure. The present invention may have at least one of the preferred features described below. Preferably, this cross-belt structure is manufactured on the first substantially cylindrical drum in a first working area. This applies both when the belt assembly is cylindrically shaped and when it is toroidally shaped. Once the cross-belt structure has been built on the first forming drum, different arrangements are provided depending on whether a cylindrical or toroidal belt assembly is to be formed. Preferably, at least said zero-degree belt layer is deposited on said first forming drum (to manufacture a belt assembly having a cylindrical shape) or on said second forming drum (to manufacture a belt assembly having a toroidal shape) in a second working area. Preferably, the second work area is located downstream of the first work area with reference to the first direction of movement. Preferably, when a toroidal formation of the belt assembly is to be carried out, the cross-belt structure is formed toroidally in the first service area. Preferably, the first work area is located downstream of the second work area with reference to the first direction of movement. Preferably, to manufacture a belt assembly having a cylindrical formation, the first forming drum is moved along the first direction of movement from the first working area to the second working area. Preferably, to manufacture a belt assembly having a cylindrical formation, the first forming drum is moved along the first direction of movement from the second working area to the second service area. Preferably, said second service area is located downstream of said first service area with reference to said first direction of movement. Preferably, when a belt assembly having a cylindrical shape is to be manufactured, during the movement of said second working area towards said second service area, the first confirmation drum passes through said first service area without stopping. Preferably, to manufacture a belt assembly having a toroidal formation, the first forming drum is moved along the first direction of movement towards the first service area, passing through the second working area without stopping. Preferably, when manufacturing a toroidal belt assembly, the second forming drum can be moved from a first service area to the second working area along a second direction of movement opposite to the first. This movement follows a path partially identical to that of the first forming drum, thus optimizing space utilization. Preferably, after having moved said second forming drum from said first service area to said second working area, said second forming drum is moved from said second working area along said first direction of movement passing through said first service area without stopping. Preferably, before moving said second forming drum from said first service area to said second working area, said second forming drum is moved from a second service area to said first service area along said second feed direction. Preferably, said second service area is located downstream of said first service area with reference to said first direction of movement. Preferably, the toroidal formation of said cross-belt structure comprises transferring said cross-belt structure from the first forming drum to an annular clamping element. Preferably, said annular fastening member is located in said first service area. Preferably, the toroidal formation of said cross-belt structure comprises arranging said second forming drum in a radially interior position with respect to said annular clamping member. Preferably, the toroidal formation of said cross-belt structure comprises, after having arranged said second forming drum in a radially internal position with respect to said annular clamping member, radially expanding said second forming drum until it is in an expanded condition. Preferably in said expanded condition said second forming drum comes into contact with said cross-belt structure and deforms said cross-belt structure until it acquires a toroidal shape. Preferably, transferring said cross-belt structure from said first forming drum to said annular clamping member comprises arranging said first forming drum in a radially internal position with respect to said annular clamping member. Preferably, transferring said cross-belt structure from said first forming drum to said annular clamping member comprises radially contracting said annular clamping member until it comes into contact with said cross-belt structure. Preferably, transferring said cross-belt structure from said first forming drum to said annular clamping member comprises radially contracting said first forming drum, after having radially contracted said annular clamping member, leaving said cross-belt structure associated with said annular clamping member. Preferably, said second forming drum is substantially toroidal. In preferred embodiments, the first forming drum is radially contractible / expandable. In the aforementioned preferred embodiments or in other preferred embodiments, the second forming drum is radially contractible / expandable. In the aforementioned preferred embodiments or in other preferred embodiments, the annular clamping member is radially contractible / expandable. Other features and advantages of the present invention will become clearer from the following detailed description of the preferred embodiment thereof, according to the attached drawings. In those drawings: - Figure 1 is a schematic radial half-section view of a tire that can be manufactured by a process and a plant, where the method of the invention is carried out; - Figure 2 is a schematic top view of a plant for producing vehicle tires where a modality of the method of the invention is carried out; - Figures 3-17 are schematic top views of a belt assembly manufacturing line of the plant in Figure 2 in various operating configurations thereof during the toroidal formation of the belt assembly according to the method of the invention; - Figure 18 is a schematic front view of an annular clamping member provided in the manufacturing line of Figures 3-17; - Figures 19-20 are schematic perspective views of a manipulator arranged on the manufacturing line of Figures 3-17, in two different operating configurations of the same; - Figures 21 and 22 are schematic top views of a belt assembly manufacturing line of the plant in Figure 2 in various operating configurations thereof adopted during the cylindrical formation of the belt assembly according to the method of the invention. Figure 1, reference number 2, shows an example of a tire that can be produced in a vehicle tire manufacturing plant. This tire can be produced using the method of the present invention. Tire 2 has a median plane A perpendicular to its axis of rotation R (Figure 2 shows the position of the axis of rotation R relative to the cross-section of tire 2 in an indicative and schematic way). The median plane A divides tire 2 into a first axial half 2a and a second axial half. For the sake of simplicity, Figure 2 shows only the first axial half 2a of tire 2, the other half being substantially a mirror image of the first axial half 2a (except for the tread pattern, which may not be symmetrical with respect to the aforementioned median plane Ά). The tire 2 substantially comprises a casing structure 3 having one or two casing plies 4a, 4b. A layer of the elastomeric waterproof material or so-called lining 5 is applied in a radially internal position relative to the casing ply(s) 4a, 4b. Two annular anchoring structures 6 (only the axial half 2a shown in Figure 2) are attached, in axially opposite positions (with respect to the median plane A), to the respective end edges of the casing layer(s) 4a, 4b. Each of the two annular anchoring structures 6 comprises a so-called bead core 6a carrying an elastomeric filler 6b in a radially external position. The two annular anchoring structures 6 are integrated near areas normally identified as beads 7 (only the axial half 2a of which is shown in Figure 2), where the coupling between the tire 2 and a corresponding mounting rim occurs. A crown structure 9' is arranged in a radially external position with respect to the housing structure 3, wherein the crown structure 9' comprises a belt assembly 8' and a tread 9 that is arranged in a radially external position with respect to the belt assembly 8'. The belt assembly 8' comprises a cross-belt structure 8 comprising two layers of radially juxtaposed belts 8a, 8b and a zero-degree belt layer 8c arranged in a radially external position relative to the cross-belt structure 8. The structure of the cross belts 8 may be associated with the so-called underbelt inserts, placed, each between the casing layers 4a / 4a, 4b and one of the axially opposite end edges of the belt structure 8. Two sidewalls 11, each extending from the corresponding bead 7 to a corresponding lateral edge of the tread 9, are applied in axially opposite positions (with respect to the median plane A) on the casing layer / layers 4a, 4b. The assembly of the portion of each sidewall 11 near the respective lateral edge of the tread 9 and of each portion of the tread 9 near the respective sidewall 11 is known as the shoulder 12 of the tire 2. Figure 2 shows a plant 1 for producing tires 2 for vehicles where a modality of the method of the invention is carried out. Plant 1 comprises a casing structure construction line 100, a crown structure construction line 200, a forming and assembly machine 300 to obtain a green tire 2' and a molding and vulcanizing station 400 to obtain the finished tire 2. In a normal operation of plant 1, the shell structure building line 100 comprises a plurality of workstations (such as the one below with reference number 125) comprising respective construction devices configured to build a plurality of shell structures on respective forming drums 110 collected from a first drum storage area 111. Similarly, the crown structure manufacturing line -200 comprises a plurality of workstations (such as, for example, the one illustrated in Figures 3-17) comprising corresponding manufacturing devices configured to build a plurality of crown structures on corresponding forming drums 210 taken from a second drum storage area 211. Preferably, 110 forming drums are substantially cylindrical. In contrast, with regard to the 210 forming drums, they are substantially cylindrical in the case where a cylindrical forming of the belt assembly is to be carried out, or substantially toroidal in the case where a toroidal forming of the belt assembly is to be carried out. Henceforth, reference will always be made to the configuration of 210 drums that have a substantially toroidal shape, unless expressly stated otherwise. The casing structure construction line 100 comprises a first run 120 comprising manufacturing devices configured to deposit onto the forming drum 110 a first part of the structural components of the casing structure. The first run 120 of the casing structure manufacturing line 100 comprises, for example: - a station configured to apply a coating; a station configured to apply an undercoat; - at least one station configured to apply a casing layer; - an optional station configured to apply metal and / or textile reinforcements; - an optional station configured to apply inserts under the straps. The casing structure construction line 100 also comprises a second run 130 comprising the manufacturing devices configured to manufacture on the forming drum 110 a second part of the structural components of the casing structure. The second run 130 of the housing structure manufacturing line 100 comprises, for example, a station configured to apply anti-abrasive inserts by wrapping a continuous elongated element around the forming drum of the first stage 110; an optional station configured to apply at least a portion of the side walls by spirally wrapping a continuous elongated element around the forming drum 110. Preferably, the first run 120 of the manufacturing line for the housing structures 100 is substantially rectilinear. Preferably, the first run 130 of the housing structure manufacturing line 100 is substantially rectilinear and perpendicular to the first run 120. In a corner area between the first run 120 and the second run 130 of the casing structure manufacturing line 100, a workstation 125 is arranged, configured to form the tire beads. The housing structure manufacturing line 100 also comprises a first transfer device 121 configured to transfer the forming drum 110 from the first path 120 to the heel forming station 125 and a second transfer device 122 configured to transfer the forming drum 110 from the heel forming station 125 to the second path 130. Each of these transfer devices 121, 122 may comprise an anthropomorphic robot (for example, a robotic arm having at least 6 axes of movement) or a non-anthropomorphic Cartesian motion device, enabling movement about three Cartesian axes X, Y, Z and , preferably with rotation about at least one, more preferably two, of said Cartesian axes X and Y. The Cartesian axes X and Y are shown in Figure 2, where the Z axis is perpendicular to the X and Y axes. Preferably, each forming drum 110 can be moved between said several workstations of the casing structure manufacturing line 100 in a sequence that is the same as or different from the spatial sequence of said plurality of workstations. Preferably, each forming drum 110 is moved by a carriage (not shown) along the first run 120 of the casing structure building line 100. Preferably, the carriage can be moved along suitable guides, by means of a suitable motor (preferably rectilinear) in two opposite directions of travel. The manufacture of the first part of the casing structure components is preferably carried out along the first run 120 of the casing structure manufacturing line 100 while the forming drum 110 is associated with a pair of axially opposed support rings (not shown). The aforementioned support drum is separated from the heels 125 and along the forming structure manufacturing 110 of the pair of rings in the second stroke forming station 130 of the casing line 100. The crown structure manufacturing line 200 comprises a first run 220 comprising manufacturing devices configured to manufacture on the forming drum a first part of the structural components of the crown structure. The first run 220 of the crown structure manufacturing line 200 includes, for example: - an optional station configured to apply lower belt inserts (this station is intended to be included unless it is already included in the first run 120 of the housing structure manufacturing line 100); - at least one belt assembly manufacturing station; an optional station configured to apply a lower coating; The crown structure construction line 200 also comprises a second run 230 comprising the manufacturing devices configured to manufacture a second part of the crown structure structural components. The second run 230 of the crown structure manufacturing line 200 comprises, for example: - at least one station configured to apply a tread that spirally wraps around a continuous elongated element around the forming drum 210; - an optional station configured to apply at least a portion of the side walls by spirally wrapping a continuous elongated element around the forming drum 210. This latter station is provided for at least in said second run 130 of the casing structure manufacturing line 100 or in said second run 230 of the crown structure manufacturing line 200. The crown structure manufacturing line 200 also comprises a drum transfer device 221 configured to transfer the forming drum 210 from the first run 220 to the second run 230. The drum transfer device 221 may comprise an anthropomorphic robot (e.g., a robotic arm having at least 6 axes of movement) or a non-anthropomorphic Cartesian motion device, which allows movement along three Cartesian axes X, Y, Z and, preferably, rotation about at least two of said Cartesian axes X and Y. Preferably, each forming drum 210 can be moved between said several workstations of the crown structure manufacturing line 200 in a sequence that is the same as or different from the spatial sequence of said plurality of workstations. Preferably, the first 220 run of the crown structure manufacturing line 200 is substantially rectilinear. More preferably, the first run 220 of the crown structure manufacturing line 200 is substantially parallel to the first run 120 of the housing structure manufacturing line 100. Preferably, the second run 230 of the manufacturing line of the crown structures 200 is substantially rectilinear and perpendicular to the first run 220. The forming and assembly machine 300 is configured to sequentially form, one at a time, the casing structures arriving from the casing structure manufacturing line 100, and to assemble them to the corresponding crown structures, which arrive progressively from the crown structure manufacturing line 200, in order to produce the corresponding green tires. In the specific example illustrated here, the forming and assembly machine 300 is configured to form the casing structures and to assemble them to the respective crown structures on a forming drum 330. Therefore, it operates on casing structures and crown structures that have been detached from the corresponding forming drums 110 and 210. These forming drums 110 and 210 are then moved back to their respective storage areas 111 and 211. The manufactured green tires 2' that come out of the forming and assembly machine 300 are transferred to the molding and vulcanizing station 400 where a molding and vulcanizing process is carried out which is configured to define the tire structure according to a desired geometry and tread pattern, for obtaining the finished tires 2. With regard to Figures 3-17, the crown structure manufacturing line 200 comprises a belt assembly manufacturing device 201. Preferably, said device 201 is arranged on the first run 220 of the crown structure manufacturing line 200. The belt assembly manufacturing device 201 comprises a carriage 21 movable on a substantially straight track 21a. The track 21a is arranged to obtain a movement of the carriage 21' along a straight direction of movement A', which is preferably parallel to the first path 220 of the crown structure manufacturing line 200, and along a direction of movement B opposite to the direction of movement A. As described below, during its movement, the carriage 21 supports a substantially cylindrical forming drum 25 to manufacture on it a set of belts or only a part of it, depending on whether a cylindrical forming of the belt set is to be carried out (in which case the carriage 21 always supports only the substantially cylindrical forming drum 25) or a toroidal forming of the belt set is to be carried out (in which case the carriage 21 supports the substantially cylindrical forming drum 25 during a first part of the manufacturing process of the belt set and the substantially toroidal forming drum 210 for the remaining part of the manufacturing process of the belt set). Forming drums 25 and 210 are radially contractible / expandable. Both comprise a plurality of angular sectors that are radially movable in a synchronous manner. The angular sectors of forming drum 25 are shaped to give forming drum 25 a substantially cylindrical geometry regardless of its radial dimension, while the angular sectors of forming drum 210 are shaped to give forming drum 210 a substantially toroidal geometry regardless of its radial dimension. The belt assembly manufacturing device 201 comprises a first working area W1 arranged downstream of an initial position P0 of the carriage 21 with reference to the direction of movement A and a second working area W2 arranged downstream of the first working area W1 with respect to the direction of movement A. The initial position PO can also be defined on the first working area W1. The first working area Wl comprises a device for manufacturing the cross-belt structure 22. For this purpose, the first working area Wl comprises a first operating station Wla comprising a deposition apparatus 22a configured to deposit a first layer of belts having a plurality of first reinforcing cords inclined with a first orientation and a second operating station Wlb arranged downstream of the first operating station Wla with respect to the direction of movement A and comprising a deposition apparatus 22b configured to deposit a second layer of belts having a plurality of second reinforcing cords inclined with a cross orientation with respect to the orientation of the aforementioned first cords. The second work area W2 comprises a deposit device 23 configured to deposit a layer of zero 20 degree straps. The belt assembly manufacturing device 201 comprises, downstream of the second working area W2 with reference to the direction of movement A, a first service area S1. With reference to Figures 3-17, the belt assembly manufacturing device 201 also comprises, downstream of the first service area SI with reference to the direction of movement A, a second service area S2. Two support members, 41 and 45, are provided in the second service area S2. Support member 41 is configured to support a first forming drum (for example, forming drum 25 shown in Figures 19 and 20), while support member 45 is configured to support a second forming drum (for example, forming drum 210 shown in Figures 19 and 20). In the particular modality shown in figures 19 and 20, the two support members 41, 45 are part of a single manipulator 40. The manipulator 40 is placed without moving in a second service area S2, meaning that when it is used, it always remains in the same position relative to the ground. The manipulator 40 comprises a base frame 40a that is stably positioned on the ground and a mobile assembly 40b that rotates relative to the base frame 40a about a rotation axis R that is oblique to the ground. In particular, the rotation axis R is inclined at an angle of 45° to the ground. Mobile group 40b is service 44 of the base frame 40a. inclined by an angle equal to associated with a surface of Said service surface is 45° with respect to the ground. The two support members 41, 45 are fixedly associated with the movable group 40b, such that the rotation of the movable group 40b about the base frame 40a around the rotation axis R causes the support members 41, 45 to rotate around the rotation axis R. This rotation can be driven by a motor assembly not visible in the figures. The rotation angle can be configured as desired. Each support member 41, 45 comprises a corresponding support arm 42, 46 and a respective mounting shaft. When the support member 42, 46 supports a corresponding forming drum, its mounting shaft coincides with the rotation axis of the corresponding forming drum. The two support arms 42, 46 extend along substantially perpendicular directions to each other and are configured to support the forming drums so that the mounting axis of one of the two support members 41, 45 (and therefore the axis of rotation of one of the two forming drums) is arranged along a substantially horizontal direction and the mounting axis of the other support member 41, 45 (and therefore the axis of rotation of the other forming drum) is arranged along a substantially vertical direction. In the operating configuration shown in Figure 19, the support arm 42 supports the substantially cylindrical forming drum 25 such that the support member 41 is in a loading / unloading position and the rotation axis of the forming drum 25 (and therefore the mounting axis of the support member 41) is arranged along a horizontal direction, while the support arm 46 supports the substantially toroidal forming drum 210 such that the support member 45 is in a standby position and the rotation axis of the forming drum 210 (and therefore the mounting axis of the support member 45) is arranged along a vertical direction. In the operating configuration shown in Figure 20, the mobile group 40b has been rotated 180° about the rotation axis R. In this configuration, the support members 41, 45 have exchanged positions, so that the support arm 42 supports the forming drum 25 with the support member 41 in the aforementioned standby position and the rotation axis of the forming drum 25 arranged along the aforementioned vertical direction, while the support arm 46 supports the substantially toroidal forming drum 210 with the support member 45 in the loading / unloading position mentioned above and the rotation axis of the forming drum 210 arranged along the aforementioned horizontal direction. Each forming drum 25, 210 is supported by the respective support arm 42, 46 by means of a corresponding damping device 43, 47 capable of compensating for possible axial movements of the forming drum 25, 210. Preferably, each damping device 43, 47 comprises a plurality of pneumatic cylinders, at least some of which are functionally independent of each other to allow a different degree of compensation depending on whether the forming drum 25, 210 is arranged with its axis of rotation extending along a horizontal or vertical direction. As already stated, the 201 belt assembly manufacturing device allows for both cylindrical and toroidal belt assembly shaping. When toroidal forming of the belt assembly has to be carried out, the belt assembly manufacturing device 201 is configured to adopt the operating configuration shown in Figure 4, where the carriage 21 is in its first position P0 (or in the first working area W1 in the case where the starting position P0 is defined in the first working area W1) and supports a substantially cylindrical forming drum 25.In this operating configuration, the support arm 42 of the manipulator 40 is oriented so that the support member 41 is in the aforementioned loading / unloading position (and therefore the mounting axis of the support member 41 is oriented along a horizontal direction), while the support arm 46 is oriented so that the support member 45 is in the aforementioned waiting position (and therefore the mounting axis of the support member 45 is oriented along a vertical direction) and supports a substantially toroidal shaped drum 210, as shown in Figure 19. Next, the carriage 21 with the forming drum 25 is moved along the direction of movement A until the forming drum 25 is brought to the first working area Wl. This movement is not activated when the initial position PO is defined in the first work area Wl. As shown in Figure 4, the carriage 21 stops when the forming drum 25 is at the first operating station Wla, where the depositing apparatus 22a deposits a first layer of belts, such as the belt layer 8a of tire 2 in Figure 1, onto the forming drum 25. As shown in Figure 5, the carriage 21 is subsequently moved along the direction of movement A and is stopped when the forming drum 25 is at the second operating station Wlb, where the depositing apparatus 22b deposits a second layer of belts, such as the belt layer 8b of tire 2 in Figure 1, onto the forming drum 25 in a radially external position relative to the first layer of belts, thus building on the forming drum 25 a cross-belt structure, such as the cross-belt structure 8 of tire 2 in Figure 1. As shown in Figure 6, the carriage 21 is subsequently moved along the direction of movement A and is stopped when the forming drum 25, which carries the cross-belt structure, reaches the first service area SI and is positioned radially inside the annular clamping member 30. The cross-belt structure is then transferred from the forming drum 25 to the annular clamping member 30. This transfer comprises first the radial contraction of the annular clamping member 30 through a synchronous radial movement of the angular sectors 35 until the angular sectors 35 make contact with the cross-belt structure and subsequently the radial contraction of the forming drum 25 through a synchronous radial movement of the corresponding angular sectors. At this point, the cross-belt structure remains fixedly connected to the annular clamping member 30 and the carriage 21 is moved along the direction of movement A to carry the forming drum 25, without the cross-belt structure on it, to the second service area S2, where it is transferred to the first support member 41, as shown in Figure 7. Subsequently, as shown in Figure 8, cart 21 is moved along the direction of movement B to move away from the second service area S2. As shown in Figure 9, at this point the mobile group 40b of the manipulator 40 rotates about the rotation axis R through an angle of 180°. This rotation causes the support member 41 to rotate about the rotation axis R until it is brought to the waiting position originally occupied by the support member 45 and, simultaneously, the support member 45 to rotate about the rotation axis R until it is brought to the loading / unloading position originally occupied by the support member 41. The forming drum 25 thus has its rotation axis oriented along a vertical direction and the forming drum 210 has its axis oriented along a horizontal direction, as shown in Figure 20. Subsequently, as shown in Figure 10, the carriage 21 is moved along the direction of movement A to lift the forming drum 210 from the support member 45. Subsequently, as shown in Figure 11, the carriage 21 is moved along the direction of movement B until the forming drum 210 is positioned in the first service area SI, in a radially internal position relative to the annular clamping member 30. The cross-belt structure is then transferred from the annular clamping member 30 to the forming drum 210. This transfer comprises the radial expansion of the forming drum 210 through a synchronous radial movement of its angular sectors until said angular sectors bring the forming drum 210 to an expanded condition in which the aforementioned angular sectors are in contact with the cross-belt structure supported by the annular clamping member 30. To facilitate the aforementioned transfer, a radial expansion of the annular clamping member 30 may be provided when the forming drum 210 has reached the aforementioned expanded condition. The radial expansion of the annular clamping member 30 may also be at least partially simultaneous with the radial expansion of the forming drum 210. Preferably, the forming drum 210 remains in the aforementioned expanded state until the end of the crown structure manufacturing cycle. Once the cross-belt structure has been transferred to the forming drum 210, as shown in Figure 12, carriage 21 is moved along the direction of movement B to carry the forming drum 210, with the cross-belt structure on it, to the second working area W2. Here, the zero-degree belt layer, such as the zero-degree belt layer 8c of tire 2 in Figure 1, is deposited onto the forming drum 210, radially outward from the cross-belt structure. This creates the desired toroidal shape of the belt assembly, such as the belt assembly 8' of tire 2 in Figure 1. Next, as shown in Figure 13, the carriage 21 is moved along the direction of movement A to carry the forming drum 210, with the belt assembly thus formed on it, to the second service area S2, where it is transferred to the second support member 45. Subsequently, car 21 moves along the direction of movement B to move away from the second service area S2, as shown in Figure 14. As shown in Figure 15, at this point the mobile group 40b of the manipulator 40 rotates about the rotation axis R through an angle of 180°. This rotation causes the support member 45 to rotate about the rotation axis R until it is brought to the waiting position previously occupied by the support member 41 and, simultaneously, causes the support member 41 to rotate about the rotation axis R until it is brought to the loading / unloading position previously occupied by the support member 45. The forming drum 210 thus has its rotation axis oriented along a vertical direction and the forming drum 25 has its axis oriented along a horizontal direction, as shown in Figure 19. Subsequently, as shown in Figure 16, the carriage 21 is moved along the direction of movement A to lift the forming drum 25 from the support member 41. Next, as shown in Figure 17, the carriage 21 with the forming drum 25 moves in the direction of movement B until it returns to its initial position P0 (or to the first working area W1 if the initial position P0 is defined in the first working area W1). During this movement, the forming drum 25 passes in a radially inside position with respect to the annular clamping member 30 without stopping in the first service area SI, in the second working area W2, and, if the initial position P0 is not defined in the first working area W1, in that first working area W1. Shortly before, during or just after the movement of carriage 21 to carry the forming drum 25 from the second service area S2 to the initial position PO (or to the first working area Wl in the case where the initial position PO is defined in the first working area Wl), the drum transfer device 221, shown in Figure 2, picks up the forming drum 210 from the support member 45 to send it to the route 230 of the crown structure manufacturing line 200 and a new substantially toroidal forming drum 210', shown in Figure 17, is placed on the support member 45, preferably again by means of the drum transfer device 221. The manufacturing device 201 of the belt assembly described above can thus proceed with a new manufacturing cycle of a belt assembly having a toroidal shape, repeating the actions described above. From the above description it is clear that in a normal operation of the plant in Figure 2, a plurality of substantially toroidal forming drums 210, 210' enter / exit in succession from the belt assembly manufacturing device 201, while the forming drum 25 always remains inside said manufacturing device 201. Preferably, in the plant of figure 2 there are 5 or 6 substantially toroidal forming drums that circulate simultaneously in the manufacturing line of the crown structures 200. These forming drums have diameters, in their contracted configuration, preferably between 500 mm and 900 mm and allow a maximum radial expansion of 300 mm. Therefore, the annular clamping member 30 must also be able to have a similar radial expansion. When cylindrical forming of the belt assembly is required, the belt assembly manufacturing device 201 is configured to adopt an operating configuration that differs from that shown in Figure 3 only because the support member 45 also supports a substantially cylindrical forming drum, which is fully equivalent to the forming drum 25 described above. A forming drum 250 is shown in Figure 21. Next, carriage 21 with forming drum 25 is moved along the direction of movement A until forming drum 25 is brought to the first working area W1. Analogously to that shown in figure 4, car 21 stops when the forming drum 25 is located at the first operating station Wla, where the deposit apparatus 22a deposits a first layer of belts onto the forming drum 25. Analogously to that shown in Figure 5, the carriage 21 is subsequently moved along the direction of movement A and is stopped when the forming drum 25 is at the second operating station Wlb, where the depositing apparatus 22b deposits the second layer of belts onto the forming drum 25, in a radially external position relative to the first layer of belts, thus building a structure of crossed belts over the forming drum 25. From then on, as shown in Figure 21, the carriage 21 is subsequently moved along the direction of movement A and stops when the forming drum 25 reaches the second working area W2, where the deposition device 23 deposits the zero-degree belt layer onto the forming drum 25, in a radially external position relative to the cross-belt structure, thus obtaining the desired cylindrical shape of the belt assembly. Next, as shown in Figure 22, the carriage 21 moves along the direction of movement A until the forming drum 25, having passed through the first service area SI, without stopping there and passing in a radially interior position with respect to the annular clamping member 30, reaches the second service area S2, where it is transferred to the support member 41. Subsequently, carriage 21 is moved along the direction of movement B to move away from the second service area S2, in a manner analogous to that shown in Figure 8 (where, however, it should be understood that instead of forming drum 210, there is a forming drum 250). At this point, the mobile group 40b of the manipulator 40 is rotated around the rotation axis R by an angle of 180°, analogously to what is illustrated in Figure 9 (it being understood here that instead of the forming drum 210, the forming drum 250 is present). This rotation brings the forming drum 25 to the position originally occupied by the forming drum 250, and the latter to the position originally occupied by the forming drum 25. The forming drum 25 thus has its axis of rotation oriented along a vertical direction, and the forming drum 250 has its axis oriented along a horizontal direction. Subsequently, carriage 21 is moved along the direction of movement A to lift the forming drum 250 from the support member 45, in a manner analogous to that illustrated in figure 10 (it being understood here that instead of the forming drum 210, there is the forming drum 250). Next, carriage 21 with forming drum 250 moves in the direction of movement B until it returns to its initial position P0 (or to the first working area Wl if the initial position P0 is defined in the first working area Wl). During this movement, the forming drum 250 passes in a radially inside position with respect to the annular clamping member 30 without stopping in the first service area Si, the second working area W2, and the first working area Wl. Shortly before, during, or just after moving carriage 21 to carry forming drum 250 from the second service area S2 to the initial position P0 (or to the first working area W1 if the initial position P0 is defined in the first working area W1), the drum transfer device 221, shown in Figure 2, picks up forming drum 25 from the support member 41 for routing 230 of the crown structure manufacturing line 200 and places on the support member 41, preferably again by means of the drum transfer device 221, another substantially cylindrical forming drum, also fully equivalent to the substantially cylindrical forming drum 25 described above, in the case where a new belt assembly is to be cylindrically shaped, or a substantially toroidal forming drum, such as forming drum 210,210' shown in figures 35 and 17, in the event that a toroidal shaping of the belt assembly has to be carried out. The present invention has been described with reference to some preferred embodiments. Various modifications may be made to the embodiments described above, while still remaining within the scope of protection of the invention, as defined by the following claims.

Claims

1. A method for manufacturing tire belt assemblies for vehicles comprising: - constructing a cross-belt structure (8) on a first forming drum of substantially cylindrical shape (25); - selecting, according to the type of tire (2) to be produced, whether to manufacture a belt assembly (8') having a cylindrical shape or a belt assembly (8') having a toroidal shape; wherein, to manufacture a belt assembly (8') having a cylindrical shape, said method comprises: - depositing at least one layer of zero-degree belts (8c) on the first forming drum (25) in a radially external position with respect to said cross-belt structure (8); wherein, to manufacture a belt assembly (8') having a toroidal shape, said method comprises: - lifting said cross-belt structure (8) from said first forming drum (25); toroidally shaping said cross-belt structure (8);- transferring said toroidally formed cross-belt structure (8) to a second forming drum (210); - depositing at least one layer of zero-degree belts (8c) onto the second forming drum (210) in a radially external position relative to said toroidally formed cross-belt structure (8).; 2. The method according to claim 1, wherein said cross-belt structure (8) is constructed on said first substantially cylindrical forming drum (25) in a first working area (Wl), at least said zero-degree belt layer (8c) is deposited on said first forming drum (25) or on said second forming drum (210) in a second working area (W2) disposed downstream of said first working area (Wl) with respect to a first direction of movement (A), and said cross-belt structure (8) has a toroidal shape in a first service area (SI) disposed downstream of said second working area (W2) with respect to said first direction of movement (A).

3. The method according to claim 2, wherein, in order to manufacture a belt assembly (8') having a cylindrical shape, said first forming drum (25) is moved along said first direction of movement (A) from said first working area (W1) to said second working area (W2) and from said second working area (W2) to a second service area (S2) disposed downstream of said first service area (S1) with reference to said first direction of movement (A), wherein during the movement from said second working area (W2) to said second service area (S2), the first forming drum (25) passes through said first service area (S1) without stopping there.

4. The method according to claim 2, wherein to manufacture a belt assembly (8') having a toroidal formation, said first forming drum (25) is moved along said first direction of movement (A) towards said first service area (SI) passing through said second working area (W2) without stopping.

5. The method according to claim 4, wherein, in order to manufacture a belt assembly (8') having a toroidal shape, said second forming drum (210) is moved from said first service area (SI) to said second working area (W2) along a second direction of movement (B) opposite to said first direction of movement (A).

6. The method according to claim 5, wherein, to manufacture a belt assembly (8') having a toroidal shape, after having moved said second forming drum (210) from said first service area (SI) to said second working area (W2), said second forming drum (210) is moved from said second working area (W2) along said first direction of movement (A) passing through said first service area (SI) without stopping.

7. The method according to claim 5 or 6, wherein, in order to construct a belt assembly (8') having a toroidal shape, before moving said second forming drum (210) from said first service area (SI) to said second working area (W2), said second forming drum (210) is moved from a second service area (S2) to said first service area (SI) along said second feed direction (B), wherein said second service area (S2) is disposed downstream of said first service area (SI) with reference to said first movement direction (A).

8. The method according to any of the preceding claims, wherein the toroidal shaping of said cross-belt structure (8) comprises: - transferring said cross-belt structure (8) from said first shaping drum (25) to an annular clamping element (30).

9. The method according to claim 8 when dependent on any of claims 2 to 7, wherein said annular fastening element (30) is disposed in said first service area (SI).

10. The method according to claim 9, wherein the toroidal formation of said cross-belt structure (8) comprises: - arranging said second forming drum (210) in a radially interior position with respect to said annular clamping member (30).

11. The method according to claim 10, wherein the toroidal formation of said cross-belt structure (8) comprises, after having arranged said second forming drum (210) in a radially interior position with respect to said annular clamping member (30): - radially expanding said second forming drum (210) until it adopts an expanded condition in which it comes into contact with said cross-belt structure (8) and deforming said cross-belt structure (8) until the latter adopts a toroidal shape.

12. The method according to any of claims 8 or 11, wherein said cross-belt structure (8) from said first forming drum (25) to an annular clamping member (30) comprises: - arranging said first forming drum (25) in a radially interior position with respect to said annular clamping member (30).

13. The method according to claim 12, wherein said cross-belt structure (8) from said first forming drum (25) to an annular clamping member (30) comprises: - radially contracting said annular clamping member (30) until it comes into contact with said cross-belt structure (8).

14. The method according to claim 13, wherein said cross-belt structure (8) from said first forming drum (25) to an annular clamping member (30) comprises, 5 after having radially contracted said annular clamping member (30): - radially contracting said first forming drum (25) leaving said cross-belt structure (8) associated 10 with said annular clamping member (30).

15. The method according to any of the preceding claims, wherein said second forming drum (210) is substantially toroidal.

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