ASSEMBLY MACHINE FOR THE MANUFACTURE OF TIRES FOR VEHICLE WHEELS AND PROCESS OF REPLACING FORMING DRUMS IN AN ASSEMBLY MACHINE.

Abstract

At least one standby forming drum (22) is located at a storage station (23) on a bearing assembly (21) of an assembly machine (1), and a plurality of forming drums (22) are distinguished. To replace one of the standby forming drums (22) with the active forming drum (22), the distal end (30) of the central shaft (28) of the active forming drum (22) is engaged by means of a manipulator (18). The second half (26) of the active forming drum (22) is moved along the central shaft (28) to the immobilization position. The active forming drum (22) is then uncoupled from the bearing assembly (21), and the bearing assembly (21) is engaged with the standby forming drum (22) at the site of the active forming drum (22) that was previously removed from the bearing assembly (21).

Description

ASSEMBLY MACHINE FOR THE MANUFACTURE OF TIRES FOR VEHICLE WHEELS AND PROCESS OF REPLACING FORMING DRUMS IN AN ASSEMBLY MACHINE The present invention relates to an assembly machine for manufacturing vehicle tires, and a process for replacing forming drums in a vehicle tire assembly machine. 1C A vehicle wheel tire generally comprises a casing structure comprising at least one casing ply having fins at the respective opposite ends coupled with respective annular anchoring structures, integrated into the areas normally identified as heels, having an inner diameter that substantially corresponds to the so-called tire fitting diameter on a respective mounting rim. The casing structure is associated with a belt structure that may comprise one or more layers of belts, positioned radially overlapping each other and the casing ply, which has textile or metallic reinforcing cords with a cross orientation and / or orientation substantially parallel to the circumferential extension direction of the tire (at 0 degrees). A tread, also made of elastomeric material, is applied radially outside the belt structure as a semi-finished component of the tire. The respective sidewalls, made of elastomeric material, are also applied axially outside the lateral surfaces of the casing structure, each extending from one of the lateral edges of the tread to the respective anchoring ring at the beads. In tubeless tires, a sealed cover layer, generally called a liner, covers the inner surfaces of the tire. The manufacture of a green tire may essentially provide for the manufacture of the casing layer(s), anchoring ring structures and / or other casing structure components and / or, when previously manufactured as semi-finished products, their assembly together on a manufacturing drum to form the casing structure in the shape of a so-called casing liner having a substantially cylindrical shape. The casing lining is then molded according to a toroidal configuration, to be coupled with a so-called outer lining, previously obtained when manufacturing and / or assembling the belt strips, tread and / or other components. Following the manufacture of a green tire, a molding and vulcanization treatment is generally carried out to determine the structural stabilization of the tire by crosslinking the elastomeric compounds and also to imprint, if necessary, the desired tread pattern and any distinctive graphic markings on the sidewalls of the tire. The term elastomeric material refers to a composition comprising at least one elastomeric polymer and at least one reinforcing filler. This composition also includes additives such as, for example, a crosslinking agent 15 and / or a plasticizer. Due to the presence of the crosslinking agent, this material can be crosslinked by heating to form the final manufactured article. The term radial and the expression radially inside / outside are used with reference to the radial direction of the devices used (e.g., drums, machines) and / or the tire, i.e., a direction substantially perpendicular to the rotation or central axis of the device / devices used / tire. The term axial and the expression axially inside / outside are used with reference to the axial direction of the devices used (e.g., drums, machines) and / or the tire, i.e., a direction parallel to the rotation or central axis of the devices used / the tire. The terms circumferentially and circumferentially are used with reference to the annular extension of the devices used or of the tire. By forming drum is meant to indicate a drum arranged to receive the pre-built carcass liner, and provided with two half-parts, each arranged to fit with one of the heels and be axially accessible to shape the carcass liner according to a toroidal configuration. When referring to a central shaft of a forming drum, the expressions proximal end and distal end indicate the ends of the shaft respectively closest to and farthest from the bearing unit of an assembly machine that supports such forming drum. Document WO2010 / 070374, filed by the same Applicant, describes a plant for the production of tires of different sizes, comprising a casing manufacturing line and a crown structure manufacturing line, both converging at an assembly station. Along the casing manufacturing line, forming drums are sequentially transferred between a plurality of first workstations defined for applying the various casing structure components to each forming drum. Auxiliary drums are then sequentially transferred between a plurality of second workstations distributed along the crown structure manufacturing line for applying the various crown structure components to each forming drum.The assembly station comprises forming devices that can be directly coupled to the forming drum that carries the pre-formed housing liner on it, to toroidally shape the housing liner and couple it to the crown structure previously removed from the auxiliary drum. WO2015 / 181654 describes a tire manufacturing apparatus in which a pre-fabricated casing liner is transferred to a forming apparatus. The liner has two coaxially movable half-parts configured to engage the casing liner at their respective beads. A forming drum, which can expand within the casing liner during forming, is coupled between the half-parts. Once forming is complete, the forming drum carrying the casing liner is adapted to be removed from the forming apparatus for transfer to devices that create the crown structure by applying elementary components directly onto the formed casing liner. Document WO2005 / 011967, submitted by the same Applicant, describes a method for manufacturing a tire casing structure on a drum having a proximal and a distal half, mutually accessible for radial expansion of the casing layer against a belt structure supported by a transfer member. The proximal half is axially fixed to a support structure carried by a robotic arm of a motion group, which transmits axial motion to the proximal half, while the distal half travels along a path twice the length of the path transmitted by the robotic arm. The robotic arm transfers the drum to a unit for dispensing an elongated element to form a tread on the belt structure and / or a pair of sidewalls in positions axially outside the casing structure. In the field of tire production, the Applicant has noticed an increasing search to balance, on the one hand, the need to be able to vary production between different batches of medium / small tires and, on the other hand, the need to keep the cycle time and consequently the production costs at levels compatible with market needs. Production processes of the type illustrated in WO2015 / 181654 do not suggest solutions that are particularly advantageous in the case of the aforementioned frequent change in the size of the tires being processed, due to downtime for the replacement of the respective equipment. The production solution used in plants of the type described in document WO2010 / 070374 solves the aforementioned problem, but with overall unit costs per tire produced that are quite high and not always compatible with the business logic of the market. Implementing production methods of the type described in WO2005 / 011967 requires that each drum be equipped to perform the operations of constructing the casing structure and shaping the casing structure to match the belt structure. This entails relatively high production costs, also stemming from the need to employ particularly complex and bulky machinery for obtaining and applying the tire components and for moving the drums. The need to handle the forming drums, which are considerably heavy and bulky, also makes it difficult to achieve satisfactory accuracy in the coupling between the casing liner and the belt structure when the drum is supported and moved by the robotic arm. The Applicant has thus identified a way to balance the opposing needs of maintaining limited costs with consistent quality levels in the face of frequent changes in tire sizes being processed, limiting the impact of such changes on productivity and processing costs, by using an assembly machine equipped with an interchangeable molding drum configured to accommodate the pre-produced casing liner. In the Applicant's view, the use of a prefabricated casing liner also simplifies and lightens the forming drum structure, as the components required for the casing liner production operations do not need to be present in the molding drum. The Applicant has finally discovered that by configuring an assembly machine with two or more individually coupleable forming drums of different sizes using a single bearing assembly and a manipulator, the bearing assembly itself can be simplified and conveniently mounted on a stationary structure. Each forming drum can then be easily and quickly replaced, each time with drums of different sizes, without requiring any additional equipment beyond that already provided in the plant for production purposes. The structure of the forming drums and the bearing assembly will be simplified, and the positioning accuracy of the inner liner during coupling with the outer liner will be improved. More particularly, according to a first aspect, the invention relates to a process of replacing forming drums in a vehicle tire assembly machine. Preferably, each of said forming drums comprises a central shaft having a proximal end and a distal end. Preferably, each of said forming drums comprises a first half that is fixed close to the distal end or the proximal end. Preferably, each of said forming drums comprises a second half that is slidably coupled along the central axis and movable along the latter from an immobilized position at a minimum distance from the first half. Preferably, among these forming drums, at least one forming drum waiting at a storage station and one active forming drum in a bearing assembly of the assembly machine are distinguished. Preferably, the standby forming drum is replaced by the active forming drum, which is coupled by means of a manipulator to the distal end of the central shaft of the active forming drum. Preferably, the standby forming drum is replaced by the active forming drum by moving the second half of the active forming drum along the central axis to the immobilization position. Preferably, the standby forming drum is replaced with the active forming drum by disengaging the active forming drum from the bearing assembly. Preferably, the standby forming drum is replaced by the active forming drum that couples the bearing assembly to the standby forming drum, instead of the active forming drum previously removed from the bearing assembly. According to another aspect, the invention relates to the machine for manufacturing tires for vehicle wheels. Preferably, a set of bearings and a plurality of forming drums are provided, which can be individually and alternatively attached to the bearing set. Preferably, a storage station is provided which has a plurality of supports, each configured for the coupling of one of said forming drums. Preferably, in said plurality of forming drums, one or more standby drums can be distinguished at the storage station and an active forming drum in the bearing assembly. Preferably, at least one manipulator is provided, configured to pick up one of the waiting drums from the storage station and reposition the active forming drum in the storage station. Preferably, each of said forming drums comprises a central shaft having a proximal end and a distal end. Preferably, each of said forming drums comprises a first half that is fixed close to said proximal or distal end. Preferably, each of said forming drums comprises a second half slidably coupled along the central axis. Preferably, the active cantilever forming drum is fixed to the bearing assembly at the proximal end of its central shaft. Preferably, the manipulator is configured to couple with the distal end of the central shaft of the active forming drum. Preferably, the bearing assembly comprises a positioning actuator configured to operate on the active forming drum, to move the second half along the central axis. The Applicant believes that entrusting the drum replacement operation to a manipulator allows the bearing assembly to focus solely on transmitting the necessary axial movements to the drum halves, thus improving the accuracy of the shell liner's positioning relative to the outer liner during forming. The manipulator can also be conveniently used to interact with other parts of the plant, for example, during the coupling of the outer liner to an annular transfer member. The bearing assembly can be conveniently equipped with control members that can be interconnected with the various parts of the forming drum to determine its movement during the assembly cycle.Each drum can in turn integrate only the components defined to interact on the tire being processed, for the benefit of structural simplification and weight reduction, integrated into a uniform assembly, separable from the bearing assembly without the need to disassemble individual parts. The cantilevered mounting of the molding drum also provides ample maneuvering space around the distal end of the central shaft, facilitating the gripping and extraction of the molding drum, as well as its coupling to the mobile carriage. In at least one of the aspects mentioned above, at least one convenient embodiment of the invention may also comprise one or more of the following preferred features. Preferably, the action of moving the second half of the active forming drum along the central axis until the immobilization position is activated by a positioning actuator that is part of the bearing assembly. Preferably, the decoupling of the active forming drum from the bearing assembly comprises decoupling the positioning actuator from the second half of the active forming drum in the immobilized position. Preferably, decoupling the active forming drum from the bearing assembly comprises decoupling the proximal end of the active forming drum from the bearing assembly. Preferably, the positioning actuator is decoupled from the second half of the active forming drum before decoupling the proximal end of the central shaft of the active forming drum from the bearing assembly. Preferably, coupling the bearing assembly with the waiting forming drum comprises coupling, by means of said manipulator, the distal end of the central shaft of the waiting forming drum with the respective second half disposed in the immobilization position. Preferably, coupling the bearing assembly with the waiting forming drum comprises bringing the proximal end of the waiting forming drum closer to a coupling seat carried by the bearing assembly, using said manipulator. Preferably, coupling the bearing assembly with the standing forming drum comprises fixing said proximal end to the coupling seat. Preferably, coupling the bearing assembly with the standby forming drum comprises coupling the positioning actuator with the second half of the standby forming drum. Preferably, coupling the bearing assembly to the standby forming drum comprises uncoupling the manipulator from the distal end of the standby forming drum's central shaft. Preferably, by means of said positioning actuator, a displacement action of the second half along the central axis from the immobilization position is performed. Preferably, the manufacture of a casing sleeve is foreseen comprising at least one casing canvas having axially opposed end fins coupled with the respective reinforcing annular structures. Preferably, an outer lining comprising at least one strap structure is planned. Preferably, a housing liner is provided to be attached to an active forming drum. Preferably, the outer liner is provided for coupling with a stationary annular transfer member, positioned coaxially to the active forming drum. Preferably, the axial movement of the active forming drum is provided to insert the carcass liner into a position axially centered with respect to an axial centerline plane of the outer liner carried by the stationary annular transfer member. Preferably, the second half of the active forming drum is provided with a rearward displacement along the central axis towards the axial centerline plane, while the central axis is displaced axially to move the first half towards the axial centerline plane. Preferably, the second half is displaced relative to the central axis by axial displacements twice the range of the displacement of the first half. In this way, the housing liner maintains its axially centered position relative to the outer sleeve during the mutual approach of the halves. Preferably, the first half is fixed in the vicinity of the distal end of the central axis. This feature facilitates positioning the second half at an appropriate distance from the proximal end, so that space is freed around the latter to facilitate the maneuvers of hooking and unhooking the forming drum with respect to the bearing assembly. Preferably, the proximal end and the distal end of the central axis are firmly fixed together. Preferably, the second half is axially interposed between the proximal end and the distal end. Preferably, the bearing assembly comprises a linear guide and a movable carriage along the linear guide and is configured to couple with the central shaft of the active forming drum at the respective proximal end. The mobility provided by the carriage and positioning actuator allows for the axial insertion of the forming drum into a stationary annular transfer member that carries an outer liner. This insertion then determines the coupling of the outer liner with a casing liner carried by the forming drum after a symmetrical axial approach of the forming drum halves, without requiring any axial movement of the stationary annular transfer member. The assembly machine is therefore compatible with the use of a stationary annular transfer member, improving the accuracy of the coupling between the casing liner and the outer liner. Preferably, the positioning actuator is fixed to the carriage. Preferably, the linear guide is extended along a sliding direction parallel to the central axis. Preferably, the cart is moved along the direction of sliding. Preferably, a motorized drive is also provided that acts between the carriage and the linear guide to move the carriage along the linear guide. Preferably, the configured carriage is set up to position the active forming drum in a working position axially centered with respect to a stationary annular transfer member. Preferably, said stationary annular transfer member is stationary with respect to said assembly machine. Preferably, said stationary annular transfer member is configured to couple to an outer liner that can be coupled around a casing liner carried by the forming drum. Preferably, the manipulator is configured to engage an auxiliary drum and place it in a coaxially centered position within the stationary annular transfer member. The same manipulator used to couple the outer liner to the stationary annular transfer member is also conveniently used to perform the replacement of the forming drums. Preferably, the central axis of each forming drum carries a distal flange that engages tightly with the first half. Preferably, the proximal end of each forming drum can be engaged with a mandrel operatively housed in the bearing assembly. Preferably, the central shaft of each forming drum carries a proximal flange that is strongly coupled with the bearing assembly. Preferably, the proximal end of the central shaft is coupled to the bearing assembly by means of first threaded members distributed circumferentially and operating through the proximal flange. Preferably, each of the first threaded elements has a head that defines a stop seat against the proximal flange, and a stem rotatably coupled in a through hole arranged through the proximal flange. Preferably, each of the first threaded elements is housed in a defined cavity between the proximal flange and a locking disc that is attached to the proximal flange itself. Preferably, each of the first threaded elements has an operating seat accessible through an access opening obtained in the locking disc. Preferably, each of the first threaded elements can be engaged with a fastening element carried by some mandrel and axially movable towards a working position in contrast to the elastic return elements, after the action of the respective first threaded member. Preferably, it is also foreseen that at least one sensor carried by the bearing assembly will interact with an extension of the head of each fastening element to emit an alarm signal in the absence of the extension of the head in the working position. Preferably, the central shaft has pneumatic activation channels connected to the proximal end and operatively coupled with fluid dynamic couplings carried by the bearing assembly. Preferably, the positioning actuator comprises a coupling member configured to engage the second half of the active forming drum to move it along the central axis. Preferably, the coupling member can be moved relative to the carriage, parallel to the linear guide. Preferably, the coupling member has a tubular body that is slidably guided along a cylindrical support that cantilevers out from the carriage. Preferably, the mandrel of the bearing assembly is operatively housed in the cylindrical support. Preferably, the coupling member comprises a terminal counter flange operatively connectable by means of a coupling with a coupling ring carried by the second half of the active forming drum. Preferably, the coupling ring is rotatably coupled to the second half. Preferably, said coupling comprises second threaded elements distributed circumferentially and operating through the respective through openings arranged in one of said end counter flanges and coupling ring. Preferably, each through opening has a flared portion and an arched slot extending from the flared portion along a circumference concentric to the central axis. Preferably, each of said second threaded elements comprises a head that can be inserted axially through the enlarged portion of one of said through openings. Preferably, each of said second threaded members comprises a stem that can be coupled through the arched groove following an angular rotation of the coupling ring. Preferably, the proximal ridge has a larger diametral dimension than the distal ridge. The larger dimensions of the proximal flange allow for a stronger coupling of the forming drum with the bearing assembly and facilitate the installation of the mechanical and pneumatic connection elements. Preferably, each forming drum also comprises at least one locking bolt that can be operatively activated to hold the second half in the immobilization position. Preferably, the locking latch comprises a fluid dynamic actuator acting on a radially moving insert about the central axis, between an operating position in which it engages in a coupling seat arranged on the central axis and a rest position in which it is disengaged from the coupling seat. Preferably, the fluid dynamic actuator is attached to the second half. Preferably, the fluid dynamic actuator is operationally connected to one of these pneumatic conduits. Preferably, an electronic control unit is also provided, configured to operate the motor drive and the positioning actuator simultaneously, in order to move the second half along the central axis according to axial displacements of double extension and opposite direction to the displacements imposed on the carriage along the linear guide. Other features and advantages will become clearer from the detailed description of a preferred, but not exclusive, embodiment of a process for replacing forming drums in a vehicle tire assembly machine, and of an assembly machine for manufacturing vehicle tires, according to the present invention. This description will be given below with reference to the accompanying drawings, presented as non-limiting examples, in which: - Figure 1 schematically shows, in plan view, the tire manufacturing plant that is part of the present invention; - Figure 2 schematically shows, in side view, an assembly machine according to the present invention, with the drum halves approximated to each other in an immobilization position; Figure 3 shows, in perspective, a forming drum decoupled from the assembly machine; - Figure 4 shows, in cross-section, a detail of the proximal end of the forming drum coupled to a mandrel of the assembly machine; Figure 5 shows, in perspective, a detail of the coupling for attaching the second half of the 10 forming drum to the coupling member of the assembly machine; - Figure 6 shows, in cross section, a detail of a bolt arranged in the vicinity of the proximal end of the 15 forming drum; Figure 7 shows, in half cross-section, a tire that can be obtained according to the present invention. With reference to the aforementioned figures, reference number 1 generally indicates an assembly machine for manufacturing vehicle tires, according to the present invention. The assembly machine 1 operates within a plant 2 for the manufacture of vehicle tires, an example of which is shown in Figure 7 and generally denoted by 3. The tire 3 comprises a casing structure 4 having at least one casing layer 5. A layer of the elastomeric waterproof material or the so-called lining 6 may be applied within the casing layer(s) 5. Two annular reinforcing structures 7 are coupled, each comprising a so-called bead core 7a carrying an elastomeric filler 7b in a radially external position, with the respective end flanges 5a of the casing layer(s) 5.The annular reinforcement structures 7 are integrated in the vicinity of areas normally identified as heels 8, where the coupling between the tire 3 and the respective mounting rim normally occurs. A belt structure 9 comprising one or more of the belt layers 9a extends circumferentially around the housing structure 4 and juxtaposes it circumferentially over a belt structure 9. Two sidewalls 11 are applied in laterally opposite positions on the casing layer(s) 5. Each sidewall has a radially inward vertex lia attached to the corresponding bead 8 and a radially outward end portion 11b attached to an axially outward edge 10a of the tread 10. In order to obtain the tire 3, it can be foreseen that, 5 in a casing manufacturing area 12, the lining 6, the layer / layers and / or other components such as at least a part of the sidewalls 11 are deposited according to known methods on at least one construction drum 13, to obtain at least one casing liner 14 in which the reinforcing annular structures 7 are coupled with the respective fins at the ends 5a of the casing layer / layers 5, wrapped around them. In an outer lining manufacturing area 15, in at least one auxiliary drum 16, the following can be done: at least one outer lining 17 comprising at least the belt structure 9 and possibly the tread 10 applied thereto and at least a portion of the side walls 11. A manipulator 18, operatively associated with the assembly machine 1, takes the auxiliary drum 16 from an output station in the outer liner construction area 15 and places it in a coaxially centered position within a stationary annular transfer member 19, preferably stationary relative to the assembly machine itself, configured to engage the outer liner 17 and hold it in a fixed position. At the control of the manipulator 18, the auxiliary drum 16 is radially retracted and decoupled from the liner with an axial movement, then reintroduced into the outer liner manufacturing area 15 to begin the construction of a new outer liner 17. For the purpose of coupling with the outer liner 17 retained by the stationary annular transfer member 19, the casing liner 14 is adapted in turn to be removed from the manufacturing drum 13 by means of a gripping device 20, which allows it to be transferred to the assembly machine 1. The assembly machine 1 essentially comprises a set of bearings 21 to which a plurality of forming drums 22 can be individually coupled. Preferably, two or more forming drums 22 are provided. Each forming drum 22 is arranged to process tires 3 having different structural characteristics from those of the tires 3 that can be achieved by the other forming drums 22. In particular, the tires 3 that can be obtained respectively by one or the other forming drum 22 may differ from each other at least in relation to the mounting diameter, i.e., the inner diameter to be detected at the beads 8. A storage station 23 is located near the bearing assembly 21, which has a plurality of supports 24, each configured for coupling one of the forming drums 22. During processing, an active forming drum 22 is located in the bearing assembly 21, and one or more standing forming drums 22 are distinguished in the storage station 23 within the plurality of forming drums 22. The standing forming drums 22 are individually interchangeable with the active forming drum 22, whenever it is necessary to switch to the production of tires 3 of a different type than the one being produced up to that point.For this purpose, the same manipulator 18 used to put the individual auxiliary drums 16 into coupling with the stationary annular transfer member 19, or possibly another manipulator dedicated for this purpose, is adapted to pick up the active forming drum 22 from the bearing assembly 21 to transfer it to the storage station 23, and to pick up one of the standby forming drums 22 from the storage station 23 to arrange it to be coupled with the bearing assembly 21, instead of the same active forming drum that was previously removed. Each forming drum 22 comprises a first half 25 and a second half 26 substantially facing each other, each of which carries a radially expandable annular gripping element 27, located on an axially internal and radially external edge thereof. Each annular gripping element 27, which is not described in detail as it is not relevant to the purposes of the invention, can be expanded radially to engage, preferably in a self-centering manner, with the respective heel 8 of the housing liner 14 carried by the gripping device 20. The housing liner 14 can thus be detached by the gripping device 20 and held firmly on the heels 8 thereof during the execution of a forming cycle in order to engage with the outer liner 17. The halves 25 and 26 are transported coaxially by a central shaft 28, which has a proximal end 29 and a distal end 30 firmly fixed to each other and angularly offset. The first half 25—being an integral part of either the proximal end 29 or the distal end 30—is integral to both ends, as these are integral to each other. For this purpose, the central shaft 28 carries at its distal end 30 a distal flange 31, tightly coupled to the first half 25. The distal end 30 is preferably in the form of a tapered stem, which can be operatively coupled by a gripping member 32 carried by the manipulator 18 or by another manipulator dedicated to this purpose. The second half of part 26 is axially interposed between the proximal end 29 and the distal end 30 and is slidably coupled along the central axis 28. For this purpose, the second half 26 can be fixed to a tubular liner 33 slidably engaged around the central axis 28. The bearing assembly 21 comprises a linear guide 34 and a carriage 35 movable along the linear guide 34. The carriage 35 is configured to engage the central shaft 28 of the active forming drum 22 at the respective proximal end 29, to support it in a coaxial cantilever with respect to the stationary annular transfer member 19. The stationary linear guide 34 extends along a sliding direction parallel to the central axis 28 of the active forming drum 22. A motorized drive 36 acts between the linear guide 34 and the carriage 35 to move the latter, together with the active forming drum 22, along the sliding direction. The bearing assembly 21 also comprises a positioning actuator 37 configured to operate on the active forming drum 22, to move the second half 26 along the central axis 28. The positioning actuator 37 is preferably fixed to the carriage 35 and may comprise, for example, a pair of electric cylinders driven by a servomotor (not illustrated), fixed on opposite sides of the carriage 35 and operating on a coupling member 38 that is movable relative to the carriage 35, parallel to the linear guide 34. The coupling member 38 is preferably a tubular body guided by sliding along a cantilevered cylindrical support 40 extending from the carriage 35, parallel to the sliding direction. The coupling member 38 carries a counter-end flange 39, operatively connectable with the second half 26 of the active forming drum 22, for movement along the central axis. 28. Within the cylindrical support 40 of the carriage 35, a mandrel 41 can be operatively housed, which can be driven in rotation by a motor 42. The engagement of the proximal end 29 with the bearing assembly 21 preferably occurs in the mandrel 41. For this purpose, the proximal end 29 can be provided to be made in the form of a tapered stem, operatively coupled for axial insertion into the corresponding coupling seat 41a arranged in the mandrel 41, to facilitate the relative centering of the parts in the coupling stage. At the proximal end 29 of the central axis 28, a proximal rim 43 is installed, which preferably has a larger diametral dimension than the distal rim 31. Preferably, the proximal end 29 of the central shaft 28 is adapted to be fixed to the bearing assembly 21 by means of the first threaded members 44 distributed circumferentially and working through the proximal flange 43. Preferably, each of the first threaded elements 44 has a head 44a defining a stop space against the proximal flange 43, and a stem 44d rotatably coupled in a through hole disposed through the proximal flange 43. At least the head 44a is housed, preferably with some axial play, in a cavity 45 defined between the proximal flange 43 and a locking disc 46, 5 movably fixed to the proximal flange 43 itself. Access openings 47 are made in the closing disc 46, which are preferably flared; through each of these openings, it is possible to insert an Allen key or other suitable tool 10 that fits with an operating seat made in the head 44a of the respective first threaded member 44, for the purpose of tightening and loosening operations. Each of the first threaded elements 44 can be operatively engaged with a respective locking element 48 operatively carried by the mandrel 41. By the action of the respective first threaded member 44, each locking element 48 can be axially moved towards the proximal flange 43, 20 opposing the action of one or more cup-shaped springs or other elastic return elements 49, which operate between a bearing surface 50 carried by the mandrel 41 and a head extension 48a of the same locking element 48. More particularly, when the respective first threaded element 44 is screwed on, the locking element 48 is movable to a working position in which the head extension 48a of the same moves close to the proximal flange 43, and the latter is stably pressed against the mandrel 41. At least one sensor 51 carried by the bearing assembly 21, for example fixed within the tubular body of the coupling member 38, is adapted to interact with the head extension 48a of each fastening element 48, to emit an alarm signal in the absence of the head extension 48a in the working position, and / or an approval signal in the presence of the head extension 48a in the working position. The proximal end 29 connects to one or more pneumatic conduits 52, made within the central shaft 28 to supply an operating fluid that also manages the activation of the annular gripping elements 27 carried by the first and second halves 26. Preferably, the pneumatic conduits 52 lead to an axial outer surface of the proximal flange 43. With the coupling of the proximal end 29 to the mandrel 41, the connection of the pneumatic conduits 52 with respective fluid dynamic couplings arranged in the mandrel itself is determined. Preferably, the engagement between the second half 26 of the active forming drum 22 and the coupling member 38 is effected by means of a coupling 53 that operates between the end counter flange 39 and a coupling ring 54 terminally supported by the second half 26 of the active forming drum 22. Preferably, the coupling ring 54 is rotatably coupled to the second half 26. The coupling 53 may comprise second threaded elements 55 circumferentially distributed and operating through respective through openings 56 arranged in the terminal counter flange 39 or, as in the illustrated example, in the coupling ring 54. Each through opening 56 has an enlarged portion 57, from which extends an arched slot 58, extending along a circumference concentric to the central axis 28. Each of the second threaded elements 55 has a respective head 55a that can be inserted axially through the flared portion 57 of the respective through opening 56, and a threaded stem 55b that screws into the end flange 39. The stem 55b of each of the second threaded elements 55 is adapted to fit into the arched groove 58 after an angular rotation of the coupling ring 54, after the respective head 55a has passed through the flared portion 57. Upon completion of the rotation, the second threaded members 55 are adapted to tighten for a stable locking of the second half 26 to the coupling member 38. The execution of a forming cycle for assembling the casing liner 14 with the outer liner 17 provides that the same casing liner, carried by the gripping device 20, is engaged in the active forming drum 22. To this end, the gripping device 20 coaxially positions the casing liner 14 between the stationary annular transfer member 19 and the active forming drum 22, while the carriage 35 holds the latter in a loading position, preferably at a maximum distance from the stationary annular conveyor member 19 itself. With an axial movement of the carriage 35, the active forming drum 22, arranged with the half parts 25, 26 in a parking position with a pre-set mutual axial distance, and with the respective annular gripping elements 27 in a radial contact condition, is inserted axially into the housing liner 14. Through the pneumatic ducts 52, the radial expansion of the annular gripping elements 27 is driven to cause the engagement of the housing liner 14 on the heels 8. The gripping device 20 can be detached and moved away from the housing liner 14 retained by the active forming drum 22. Another change of carriage 35 towards the stationary annular transfer member 19 generates an axial movement of the active forming drum 22, to insert the carcass liner 14 into an axially centered position with respect to an axial centerline plane in plane M of the outer liner 17 carried by the stationary annular transfer member 19. At this point, the first half 25 and the second half 26 of the forming drum 22 are moved axially, simultaneously with the insufflation of air or other operating fluid into the housing liner 14, to give it a toroidal shape and couple it to the outer liner 17. This approach is conveniently achieved by simultaneously activating the positioning actuator 37 and the drive motor 36 of the bearing assembly 21, so that the second half 26 of the active forming drum 22 moves along the central axis 28 towards the axial centerline plane M, while the entire central axis 28 moves axially to move the first half 25 towards the same axial centerline plane M. An electronic control unit (not illustrated) manages the drive of the motorized drive 36 and the positioning actuator 37, and possibly other parts of the assembly machine 1, so that the displacement completed by the second half 26 with respect to the central axis 28 has double the extension and opposite direction with respect to the displacement simultaneously imposed on the carriage 35 with respect to the linear guide 34. This feature facilitates maintaining the housing liner 14 in an axially centered position with respect to the outer liner 17 held by the stationary annular transfer member 19, preventing mutual axial movements of the two throughout the forming action, thus improving the accuracy of the coupling. Once the coupling is complete, the stationary annular transfer member 19 can be disengaged from the outer liner 17. As the carriage 35 moves away from the stationary annular transfer member 19, the tire 3, which is being processed and held by the forming drum 22, is axially extracted from the same stationary annular transfer member and brought to a roller device 60. This device performs a rolling operation to consolidate the coupling between the outer liner 17 and the casing liner 14, while the tire 3 rotates under the action of the motor 42 operating on the mandrel 41. Upon completion of the rolling operation, the tire 3 can be removed from the active forming drum 22 by the radial contraction of the gripping annular elements 27, allowing the active forming drum 22 to be positioned for a new work cycle. When it is requested to replace the active forming drum 22 with one of the forming drums 22 waiting at the storage station 23, the manipulator 18 coaxially positions its gripping member 32 with the active forming drum 22, and the latter is moved to an exchange position by a movement of the carriage 35 along the linear guide 34. In the exchange position, the active forming drum 22 engages its distal end 30 with the gripping member 32 of the manipulator 18. When the active forming drum 22 is firmly held by the manipulator 18 at its distal end 30, the positioning actuator 37 moves the second half 26 along the central axis 28, bringing it to a minimum distance immobilization position from the first half 25. Each forming drum 22 can be conveniently associated with at least one locking bolt 61 that can be operatively activated to hold the second half 26 in the immobilized position. This locking bolt 61 can comprise a fluid dynamic actuator 62 that is fixed to the second half 26 and operates on an insert 63 that is radially movable about the central axis 28, between an operative position in which the insert 63 is engaged in a locking seat 64 arranged on the central axis 28, and a rest position in which the insert 63 is withdrawn from the locking seat 64, releasing the axial mobility of the second half 26. The fluid dynamic actuator 62 can be conveniently connected to one of said pneumatic conduits 52 arranged on the central axis 28, so that its activation occurs simultaneously with the radial contraction of the annular gripping elements 27. After the locking bolt 61 is activated, the active forming drum 22 can be decoupled from the bearing assembly 21. To do this, the positioning actuator 37 must first be decoupled from the second half 26. This operation requires loosening the second threaded elements 55 using the aforementioned Allen wrench or another suitable hand tool. Once loosening is complete, a slight angular rotation of the coupling ring 54, which can be performed manually by an operator, causes axial alignment of the flared portions 57 of the through openings 56 with the heads 55a of the second threaded elements 55. The coupling member 38 is then adapted to move away from the second half 26 by the action of the positioning actuator 37, to facilitate access to the proximal end 29 of the central axis 28. The operator can therefore easily reach the first threaded elements 44 and cause them to detach from the fastening elements carried by the mandrel 41. Once the decoupling is complete, the active forming drum 22 is disconnected from the bearing assembly 21 and can be moved away from it by the manipulator 18, which places it in one of the supports 24 provided in the storage station 23. The locking bolt 61 keeps the second half 26 in the immobilized position, preventing unwanted displacements of it along the central axis 28 even when the forming drum 22 is oriented along an inclined or vertical axis, to facilitate its movement by the manipulator 18. The same manipulator 18 is responsible for retrieving one of the forming drums 22 waiting from the storage station 23 by hooking it at its respective distal end 30, allowing it to be engaged in the bearing assembly 21 to replace the one previously removed. When retrieving it, the second half of the forming drum 22 will be secured in the immobilized position by means of the locking pin 61. This ensures that the center of gravity of the forming drum 22 is close to its distal end 30, conveniently limiting the stress on the manipulator 18. The operation of hooking the waiting forming drum 22 onto the bearing assembly 21 will be executed with an operating sequence that is the reverse of that described above for the unhooking of the preceding active forming drum 22. After the proximal end 29 of the standby forming drum 22 has been brought close and axially inserted into the coupling seat 41a by means of the manipulator 18, the first threaded elements 44 are tightened. Once the fastening is complete, the rotation of the forming drum around its axis, which can be done manually or by means of the mandrel 41 motor 42, allows the sensor 51 to detect the presence in the correct operating position of the head extensions 48a of each fastening element 48, and gives permission for the continuation of the assembly sequence. The positioning actuator 37 carries the terminal counter flange 39 adjacent to the coupling ring 54 to allow mechanical connection of the same with the second half 26 by means of the coupling 53. At the command of the positioning actuator 37, by uncoupling the locking bolt 61, the second half 26 can be moved along the central axis 28 from the immobilization position 5. Once the central shaft 28 and the second half 26 have been secured to the bearing assembly 21, the manipulator 18 can be decoupled from the distal end 30 of the central shaft 28. The appropriate movement of the carriage 35 and / or the positioning actuator 37, managed by the electronic control unit, places the halves 25, 26 in a locked position at a predetermined axial distance from each other, to begin a new forming cycle.

Claims

1. A method for replacing forming drums in a vehicle tire assembly machine (1), wherein each of said forming drums (22) comprises: a central shaft (28) having a proximal end (29) and a distal end (30); a first half (25) fixed in close proximity between the distal end (30) and the proximal end (29); a second half (26) slidably coupled along the central shaft (28) and movable along the latter from a fixed position at a minimum distance from the first half (25); at least one standing forming drum (22) in a storage station (23), and an active forming drum (22) in a bearing assembly (21) of the assembly machine (1), said forming drums (22) being distinguished from one another;wherein the standby forming drum (22) is replaced with the active forming drum (22) by: engaging the distal end (30) of the central shaft (28) of the active forming drum (22) by means of a manipulator (18); moving the second half (26) of the active forming drum (22) along the central shaft (28) to the immobilization position; uncoupling the active forming drum (22) from the bearing assembly (21); and coupling the standby forming drum (22) to the bearing assembly (21), in place of the active forming drum (22) previously removed from the bearing assembly (21).

2. The process according to claim 1, wherein the action of 20 displaces the second half (26) of the active forming drum (22) along the central axis (28) until the immobilization position is achieved by means of a positioning actuator (37) that is part of the bearing assembly (21).

3. The process according to claim 1 or 2, wherein the decoupling of the active forming drum (22) from the bearing assembly (21) comprises: disengaging the positioning actuator (37) from the second half (26) of the active forming drum (22) in the immobilization position; decoupling the proximal end (29) of the active forming drum (22) from the bearing assembly (21).

4. The process according to claim 3, wherein said positioning actuator (37) is released from the second half (26) of the active forming drum (22) before decoupling the proximal end (29) of the central shaft (28) of the active forming drum (22) from the bearing assembly (21).

5. The process according to one or more of the preceding claims, wherein coupling the standby forming drum (22) of the bearing assembly (21) comprises: engaging, by means of said manipulator (18), the distal end (30) of the central shaft (28) of the standby forming drum (22) with the respective second half (26) disposed in the immobilization position; by said manipulator (18), bringing the proximal end (29) of the standby forming drum (22) close to a coupling seat (41a) carried by the bearing assembly (21); securing said proximal end (29) to the coupling seat (41a); coupling the positioning actuator (37) to the second half (26) of the standby forming drum (22); disengaging the manipulator (18) from the distal end (30) of the central shaft (28) of the standby forming drum (22).

6. The process according to claim 5, wherein the action of displacing the second half (26) along the central axis (28) from the immobilization position is achieved by means of said positioning actuator (37).

7. The process according to one or more of the preceding claims, further comprising: i) manufacturing a casing liner (14) comprising at least one casing layer (5) having axially opposed end fins (5a) coupled with respective reinforcing annular structures (7); ii) manufacturing an outer liner (17) comprising at least one strap structure (9); iii) fitting the casing liner (14) into the active forming drum (22); iv) coupling the outer liner (17) with a stationary annular transfer member (19) positioned coaxially to the active forming drum (22); v) axially moving the active forming drum (22) to insert the casing liner (14) into a position axially centered with respect to an axial centerline plane (M) of the outer liner (17) carried by the annular transfer member (19);20 v) subsequently moving the second half (26) of the active forming drum (22) along the central axis (28) towards the axial centerline plane (M), while the central axis (28) is axially displaced to move the first half (25) towards the axial centerline plane (M); wherein the second half (26) is displaced relative to the central axis (28) according to axial displacements of double range relative to the displacement of the first half (25).; 8. An assembly machine for manufacturing vehicle tires comprising: a bearing assembly (21); a plurality of forming drums (22), individually and alternatively attachable to the bearing assembly (21); a storage station (23) with a plurality of supports (24), each configured for attaching one of said forming drums (22); the plurality of forming drums (22) can be distinguished from one or more standby drums in the storage station (23) and an active forming drum (22) in the bearing assembly (22); at least one manipulator (18), configured to pick up one of the standby drums from the storage station (23) and reposition the active forming drum (22) in the storage station (23); wherein each of said forming drums 5 (22) comprises: a central shaft (28) having a proximal end (29) and a distal end (30);10 a first half (25) fixed in proximity to one of the proximal (29) and distal (30) ends; a second half (26) slidably engaged along the central axis (28); wherein the active forming drum (22) is cantilevered and fixed to the bearing assembly (21) at the proximal end (29) of its central axis (28); 20 wherein the manipulator (18) is configured to engage with the distal end (30) of the central axis (28) of the active forming drum (22); wherein the bearing assembly (21) also comprises a 25 positioning actuator (37) configured to operate on the active forming drum (22) to move the second half (26) along the central axis (28).

9. The machine according to claim 8, wherein said first half (25) is fixed in the vicinity of the distal end (30) of the central axis (28).

10. The machine according to claim 8 or 9, wherein the proximal end (29) and the distal end (30) of the central shaft (28) are strongly connected to each other.

11. The machine according to one or 10, wherein the second half between the proximal end (29) and the distal end (30) of claims 8 to (26) is axially interposed.

12. The machine according to one or more of claims 8 to 11, wherein the bearing assembly (21) comprises: a linear guide (34); a carriage (35) movable along the linear guide (34) and configured to engage the central shaft (28) of the active forming drum (22) at the respective proximal end (29).

13. The machine according to claim 12, er. in which the positioning actuator (37) is fixed to the carriage (35).

14. The machine according to claim 12 or 13, wherein the linear guide (34) extends in the sliding direction parallel to the central axis (28).

15. The machine according to one or more of claims 12 to 14, wherein the carriage (35) moves along the sliding direction.

16. The machine according to one or more of claims 12 to 15, further comprising a motorized drive (36) operating between the carriage (35) and the linear guide (34) to move the carriage (35) along the linear guide (34).

17. The machine according to one or more of claims 12 to 16, wherein the carriage (35) is configured to position the active forming drum (22) in a working position axially centered with respect to an annular transfer member (19).

18. The machine according to one or more of claims 8 to 17, wherein said annular transfer member (19) is stationary with respect to said assembly machine (1).

19. The machine according to one or more of claims 8 to 18, wherein said annular transfer member (19) is configured to couple to an outer liner (17) that can be coupled around a housing liner (14) carried by the forming drum (22).

20. The machine according to one or more of claims 8 to 19, wherein the manipulator (18) is configured to couple an auxiliary drum (16) and place it in a coaxial position centered within the annular transfer member (19).

21. The machine according to one or more of claims 8 to 20, wherein the central shaft (28) of each forming drum (22) carries a distal flange (31) that is tightly coupled to the first half (25).

22. The machine according to one or more of claims 8 to 21, wherein the proximal end (29) of each forming drum (22) can be engaged with a mandrel (41) operatively housed in the bearing assembly (21).

23. The machine according to one or more of claims 8 to 22, wherein the central shaft (28) of each forming drum (22) carries a proximal flange (43) that is tightly coupled to the bearing assembly (21).

24. The machine according to claim 23, the proximal end (29) of the central shaft (28) is adapted to couple with the bearing assembly (21) by means of the first threaded members (44) circumferentially distributed and which operate through the proximal flange (43).

25. The machine according to claim 24, wherein each of the first threaded members (44) has a head (44a) defining a stop seat against the proximal flange (43), and a rotatably coupled stem (44b) in a through hole arranged through the proximal flange (43).

26. The machine according to one or more of claims 23 to 25, wherein each of the first threaded members (44) is located in a cavity (45) defined between the proximal flange (43) and a locking disc (46) that is fixed to the proximal flange (43).

27. The machine according to one or more of claims 24 to 26, wherein each of the first threaded members (44) has an operating seat accessible through an access opening obtained in the locking disc (46).

28. The machine according to one or more of claims 24 to 27, wherein each of the first threaded members (44) is coupled with a fastening element (48) carried by some mandrel (41) and axially movable to a working position in contrast to the elastic return elements (49), after the action of the respective first threaded member (44).

29. The machine according to claim 28, further comprising at least one sensor (51) carried by the bearing assembly (21), which interacts with a head extension (48a) of each fixing element (48) to emit an alarm signal in the absence of the head extension (48a) in the working position.

30. The machine according to one or more of claims 8 to 29, wherein the central shaft (28) has pneumatic activation channels (52) connected to the proximal end (29) and operatively coupled with fluid dynamic couplings carried by the bearing assembly (21).

31. The machine according to one or more of claims 8 to 29, wherein the positioning actuator (37) comprises a coupling member (38) configured to engage the second half (26) of the active forming drum (22) to move it along the central axis (28).

32. The machine according to claim 31 when dependent on one or more of claims 12 to 30, wherein the coupling member (38) can be moved relative to the carriage (35), parallel to the linear guide (34).

33. The machine according to claim 31 when dependent on one or more of claims 12 to 31, wherein the coupling member (38) has a tubular body slidably guided along a cylindrical support (40) cantilevering out from the carriage (35). 15 34. The machine according to claim 33 when dependent on one or more of claims 22 to 31, wherein the mandrel (41) of the bearing assembly (21) is operatively housed in the cylindrical support (40). 20 35. The machine according to one or more of claims 31 to 34, wherein the coupling member (38) comprises a terminal counter flange (39) operatively connectable by means of a coupling (53) with a coupling ring (54) carried by the second half (26) of the active forming drum (22).

36. The machine according to claim 35, wherein the coupling ring (54) is rotatably coupled to the second half (26).

37. The machine according to claim 35 or 36, wherein said coupling (53) comprises circumferentially distributed second threaded members (55) operating through the respective through openings (56) arranged in one of said end flanges (39) and the coupling ring (54).

38. The machine according to claim 37, wherein each through opening (56) has an enlarged portion (57) and an arched slot (58) extending from the enlarged portion (57) along a circumference concentric to the central axis (28).

39. The machine according to claim 37 or 38, wherein each of said second threaded members (55) comprises: a head (44a) axially insertable through the enlarged portion (57) of one of said through openings (56); and a stem (44b) attachable through the arched groove (58) following an angular rotation of the coupling ring (54).

40. The machine according to claim 21 and one or more of claims 23 to 39, wherein the proximal flange (43) has a diametral dimension greater than the diametral dimension of the distal flange (31).

41. The machine according to one or more of claims 8 to 40, wherein each forming drum (22) also comprises at least one locking bolt (61) that can be operatively activated to hold the second half (26) in the immobilized position.

42. The machine according to claim 41, wherein the locking latch (61) comprises a fluid dynamic actuator (62) acting on an insert (63) movable radially about the central axis (28), between an operating position in which it engages in a coupling seat (64) arranged on the central axis (28) and a rest position in which it is extracted from the coupling seat (64).

43. The machine according to claim 42, wherein the positioning actuator (62) is fixed to the second half (26). X 44. The machine according to claim 42 or 43, wherein the fluid dynamic actuator (62) is operatively connected to one of said pneumatic conduits (52).

45. An assembly machine according to one or more of claims 16 to 44, further comprising an electronic control unit configured to simultaneously operate the motor drive (36) and the positioning actuator 10 (37), in order to move the second half (26) along the central axis (28) according to axial displacements of double entities and opposite direction to the displacements imposed on the carriage (35) along the linear guide (34).

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