Method, service drum and device for constructing a tire for a vehicle

Abstract

A carcass structure (2a) is connected to a crown structure (7), and the crown structure (7) is formed by one or more belt plies (8a, 8b) arranged around an auxiliary drum (22). A service drum (31) is arranged, and the service drum (31) includes fan segments (35) that are circumferentially distributed around a central geometric axis (X1) and are radially movable. Each fan segment has a radially outer surface (36) that has a curved profile in a radial plane relative to the central geometric axis (X1). The belt plies (8a, 8b) are transferred coaxially around the service drum (31), and the fan segments (35) are carried to an expanded state so as to shape the belt plies (8a, 8b) according to the curved profile. At least one insert (37) creating a sliding interface is interposed between the radially inner surface of the fan segments (35) and the belt plies (8a, 8b), and the insert (37) creating the sliding interface facilitates the circumferential sliding of the belt plies (8a, 8b) relative to the fan segments (35).

Description

Technical Field

[0001] The present invention relates to a method for constructing a tire for a vehicle wheel. The present invention also relates to a device that can be used to construct a tire according to the foregoing method, and a service drum that can be used in said device.

[0002] In particular, the present invention is specifically aimed at manufacturing ultra-high performance tires, especially for racing competitions. Background Art

[0003] A tire for a vehicle wheel generally includes a carcass structure that includes at least one carcass ply, each carcass ply having opposite end flanges that are joined to corresponding anchoring annular structures integrated in a region generally identified by the name "bead", which defines the radially inner circumferential edge of the tire.

[0004] The carcass structure is associated with a crown structure. The "crown structure" of a tire refers to at least one belt structure having one or more belt plies that are radially superimposed relative to each other and relative to the carcass ply, having textile or metallic reinforcing cords with a crosswise orientation and / or extending generally parallel to the circumferential direction of the tire. More preferably, the crown structure includes a belt structure having at least one belt ply and a tread made of an elastomeric material, the tread being applied to the crown structure in a radially outer position.

[0005] Corresponding sidewalls made of an elastomeric material are also applied in an axially outer position on the lateral surfaces of the carcass structure, each sidewall extending from one of the lateral edges of the tread until the corresponding anchoring annular structure. In a "tubeless" type of tire, an airtight covering layer generally referred to as a "liner" covers the inner surface of the tire.

[0006] The terms "radial" and "axial" and the expressions "radially inner / outer" and "axially inner / outer" are used with reference to the radial direction (i.e., the direction perpendicular to the central geometric axis with respect to the service drum and / or the annular tire component being processed) and the axial direction (i.e., the direction parallel to the central axis) of the service drum and / or the annular tire component being used. The terms "circumferential" and "circumferentially" are alternatively used with reference to the annular extension of the foregoing service drum and / or annular component.

[0007] In document WO 2012 / 146988, the applicant described the possibility of manufacturing a crown structure by a method in which an annular assembly is formed on a so-called auxiliary drum, the annular assembly comprising a first radially inner belt layer and at least one second radially outer belt layer. Then, the axially opposite end portions of the first belt layer are turned over onto the at least one second belt layer so as to at least partially superpose the end portions of the first belt layer on the at least one second radially outer belt layer.

[0008] Then, the belt layer is transferred to a service drum, the service drum comprising radially movable segments adapted to radially expand to engage the belt structure. In the radially expanded state, the service drum may have an outer surface shaped according to a curved cross-sectional profile so as to impart the desired shape to the belt layer engaged thereon.

[0009] A second part of the belt structure is made on the service drum by circumferentially winding at least one reinforcing element made of an elastomeric material longitudinally incorporating one or more continuous cords according to axially adjacent coils, thereby forming an additional belt layer, generally referred to as the "zero-degree layer" according to the orientation of the reinforcing cords relative to the circumferential direction, for the purpose of maintaining the desired cross-sectional profile of the belt structure, even under the action of the high centrifugal forces triggered during use.

[0010] Then, according to mutually adjacent coils, the deposition of a continuous elongate element made of an elastomeric material is actuated around the belt structure carried by the service drum so as to form a tread having the desired shape and thickness.

[0011] The applicant has observed that the expanding action (also referred to herein as "shaping") exerted by the service drum on the belt layer is useful for imparting a suitable curved cross-sectional profile to the belt structure, which curved cross-sectional profile matches or is close to the desired profile that the belt structure must assume within the mold employed during the subsequent tire vulcanization process, so as to limit its uncontrolled deformation and to be able to manage the selection of the material properties of the constituent of the tire, the management of the footprint area and the management of the tire response has a positive impact.

[0012] However, the applicant has observed that the shaping of the belt structure actuated according to the prior art encounters several difficulties, which are particularly evident when constructing tires for ultra-high performance sports use.

[0013] In such tires, especially if intended for racing competitions involving extreme working conditions, it may be required that one or more belt plies be made of a manufactured product in the form of strips, with a textile and / or metallic type of reinforcing cord having a high tensile strength and thus low extensibility. It may also be required that the axially opposite lateral edges of at least one of the belt plies be turned up to at least partially cover a radially more external belt ply, for example in order to confer greater responsiveness and response speed to the tire during cornering or for other performance purposes.

[0014] Referring to such above-described structural solutions for tires for racing competitions helps to increase the overall stiffness of the belt structure, preventing its deformability for shaping purposes. The use of reinforcing cords formed of or typically containing aromatic polyamide fibers and / or other non-extensible materials further exacerbates these difficulties.

[0015] A significant increase in the structural non-extensibility of the belt also counteracts the expansion of the segment of the service drum, with the risk of causing excessive stresses on the structural components of the service drum and / or on the same components of the belt structure.

[0016] The applicant has also observed that, in addition to the corresponding radial expansion of the belt structure, the radial progressive expansion of the segment of the service drum also causes its circumferential dilation. This phenomenon typically begins near the axial midline plane of the belt structure, where there is the initial contact with the segment, and then progressively extends towards the axial outer edge. The reinforcing cords constituting the belt ply facilitate this radial and circumferential expansion by progressively changing their orientation with respect to the circumferential direction, resulting in a narrowing of the overall width of the belt structure.

[0017] The applicant has also observed that, at the end of the shaping of the belt ply, the belt structure has a non-constant degree of expansion along the radial section. This degree of expansion actually varies between a maximum degree of expansion near the axial midline plane and a minimum degree of expansion near the axial outer edge. Due to the above-described expansion difficulties, the minimum expansion may be zero or in any case insufficient.

[0018] The applicant has realized that the above kinetic characteristics impart relative sliding between the radially inner surface of the belt ply and the segment.

[0019] The applicant has found that during shaping, a reduction in the friction generated between the surfaces of the segment in contact with the radially inner surface of the belt structure can significantly reduce the stresses transmitted between the belt structure and the components of the shaping drum, facilitating the radial expansion of the belt itself.

[0020] The aforementioned friction reduction can be achieved by interposing at least one insert that creates a sliding interface between the fan segment and the radially inner surface of the belt layer. The insert that creates the sliding interface can move relative to both the belt structure and the fan segment. More particularly, by moving relative to the inner surface of the fan segment and the belt layer, the insert that creates such a sliding interface allows the friction generated by the relative movement between the parts to be eliminated or significantly reduced, thus significantly facilitating the optimal execution of shaping even when the belt structure being processed has a high deformation resistance. Summary of the Invention

[0021] In a first aspect, the present invention relates to a method for constructing a tire for a vehicle.

[0022] Preferably, a carcass structure including at least one carcass ply is provided, and the carcass ply has end flaps that are joined to corresponding anchoring annular structures.

[0023] Preferably, a crown structure is provided.

[0024] Preferably, the crown structure is joined to the carcass structure at a radially outer position.

[0025] Preferably, manufacturing the crown structure includes sequentially arranging one or more belt layers around an auxiliary drum.

[0026] Preferably, a service drum is provided, which includes fan segments circumferentially distributed around a central geometric axis, and the fan segments can move radially between a radially contracted state and a radially expanded state. In the radially contracted state, the fan segments approach the central geometric axis, and in the radially expanded state, the fan segments move away from the central geometric axis.

[0027] Preferably, each fan segment has a radially outer surface that has a curved profile in a radial plane relative to the central geometric axis.

[0028] Preferably, the belt layer is removed from the auxiliary drum and transferred coaxially around the service drum arranged in the contracted state.

[0029] Preferably, the fan segments of the service drum are expanded from the contracted state to the expanded state so as to shape the belt layer according to the curved cross-sectional profile of the radially outer surface of the fan segments.

[0030] Preferably, at least one insert that creates a sliding interface is interposed between the fan segment and the radially inner surface of the belt layer. During the expansion of the fan segment, the insert that creates the sliding interface moves relative to the fan segment and abuts against the radially inner surface so as to facilitate the circumferential sliding of the belt layer relative to the fan segment.

[0031] In a second aspect, the present invention relates to a service drum for manufacturing a vehicle tire.

[0032] Preferably, a plurality of fan segments are provided, which are circumferentially distributed around a central geometric axis, and these fan segments are radially movable between a radially contracted state and a radially expanded state. In the radially contracted state, these fan segments are close to the central geometric axis, and in the radially expanded state, these fan segments move away from the central geometric axis.

[0033] Preferably, each fan segment has a radially outer surface, which has a curved profile in a radial plane relative to the central geometric axis.

[0034] Preferably, the service drum further includes at least one insert for generating a sliding interface. The insert for generating the sliding interface is movable relative to the radially outer surface of the fan segment and is configured to operate in contact with the radially inner surface of one or more belt plies that can be applied around the service drum, so as to facilitate the circumferential sliding of the belt plies relative to the fan segment.

[0035] Another aspect of the present invention provides an apparatus for manufacturing a vehicle tire.

[0036] Preferably, a carcass building area for manufacturing a carcass structure is provided.

[0037] Preferably, a crown building area for manufacturing a crown structure is provided.

[0038] Preferably, an assembly station is provided, wherein each carcass structure is associated with one of the crown structures.

[0039] Preferably, the crown building area includes an auxiliary drum.

[0040] Preferably, at least one feeding group is provided, and the feeding group is configured to sequentially arrange one or more belt plies around the auxiliary drum.

[0041] Preferably, a service drum according to the second aspect of the present invention is provided.

[0042] Preferably, a transfer device is provided, which is configured to remove the belt plies from the auxiliary drum and transfer them coaxially around the service drum arranged in a contracted state.

[0043] The applicant believes that the presence of the insert eliminates or significantly reduces the friction generated between the radially inner surface of the belt ply and the outer surface of the fan segment, without the need to resort to the use of a lubricant layer in the form of a fluid or powder, which would undesirably migrate towards the belt ply and thus unacceptably change the properties of the material. The elimination of this friction significantly facilitates the expansion of the fan segment and promotes the optimal execution of belt ply forming, even when one or more of these belt plies include reinforcing cords made of a material with poor ductility and / or have turned-up end flaps.

[0044] In at least one of the foregoing aspects, convenient embodiments of the present invention may include one or more of the following preferred features.

[0045] Preferably, forming the crown structure includes:

[0046] Applying a first belt layer around the outer surface of the auxiliary drum;

[0047] Applying a second belt layer around the first belt layer, the width of the second belt layer being less than the width of the first belt layer;

[0048] Turning up the terminal flaps of the first belt layer around the corresponding lateral edges of the second belt layer and superimposing them on the second belt layer.

[0049] According to the applicant, turning up the terminal flaps improves the performance characteristics of the tire.

[0050] Preferably, the turning up of the terminal flaps is performed before transferring the belt layer to the service drum.

[0051] Thus, the processing time on the service drum can be balanced with the time required to perform other operations upstream and / or downstream thereof.

[0052] Preferably, in the radially contracted state, the segment defines the outer diameter of the service drum, the size of which is smaller than the inner diameter of the at least one belt layer previously formed on the auxiliary drum.

[0053] Preferably, the size of the outer diameter of the service drum defined by the segment in the radially expanded state is larger than the inner diameter of the at least one belt layer previously formed on the auxiliary drum.

[0054] Preferably, the movement of the segment towards the radially expanded state determines the circumferential expansion of the elastic sleeve of the insert that constitutes the sliding interface.

[0055] Preferably, the movement of the segment towards the radially expanded state determines the reduction in the axial size of the elastic sleeve of the insert that constitutes the sliding interface.

[0056] Preferably, the movement of the segment towards the radially expanded state determines the rolling of the rolling elements of the insert that constitutes the sliding interface.

[0057] Preferably, at least one additional closed layer is also formed by winding one or more reinforcing cords around the belt layer carried by the service drum in axially side-by-side coils.

[0058] Preferably, the formation of the additional closed belt is performed after the segments of the service drum have expanded.

[0059] Preferably, a tread is also provided around the belt layer carried by the service drum in the expanded state.

[0060] Preferably, the insert for generating the sliding interface includes an elastic sleeve arranged around a sector segment.

[0061] The use of an elastically deformable elastic sleeve allows for easy expansion of the sector segment. In addition, during the circumferential expansion set by the sector segment, the elastic sleeve tends to narrow axially, thereby minimizing the relative sliding caused by the axial contraction of the belt layer.

[0062] Preferably, the elastic sleeve is mounted around the sector segment in an elastically expanded state.

[0063] Therefore, during the transition between the contracted state and the expanded state of the sector segment, the consistency between the diameter dimension of the elastic sleeve and the diameter dimension of the service drum is facilitated.

[0064] Preferably, the movement of the sector segment towards the radially expanded state determines the circumferential expansion of the elastic sleeve.

[0065] Preferably, the movement of the sector segment towards the radially expanded state determines the reduction in the axial size of the elastic sleeve.

[0066] Therefore, the axial contraction of the belt layer during molding is at least partially facilitated.

[0067] Preferably, the elastic sleeve is axially received in a centering recess formed in each of the sector segments.

[0068] Therefore, while the sector segment returns to the contracted state, the stability and repeatability of the axial positioning of the elastic sleeve are facilitated.

[0069] Preferably, the centering recess has two axial shoulders facing the axial outer edge of the elastic sleeve.

[0070] Preferably, the height of the axial shoulder is not greater than the thickness of the elastic sleeve.

[0071] Preferably, the height of the axial shoulder corresponds to the thickness of the elastic sleeve.

[0072] Therefore, satisfactory surface continuity is achieved between the elastic sleeve and the part of the sector segment that is axially external to the elastic sleeve itself.

[0073] Preferably, when in the contracted state, the height of the axial shoulder is lower than the thickness of the elastic sleeve.

[0074] The lower height of the axial shoulder compensates for the reduction in the thickness supported by the elastic sleeve after diameter expansion, promoting satisfactory surface continuity in the expanded state.

[0075] Preferably, the axial extension of the elastic sleeve is less than the axial extension of the radially inner surface of the belt layer.

[0076] The axial outer region of the belt layer tends to be more resistant to deformation due to the presence of the turn-up, so the axial outer region of the belt layer acts directly against the rigid surface of the segment. Thus, during segment expansion, the risk of applying excessive squeezing or cutting stress on the elastic sleeve is limited by the action of the axial outer edge of the belt layer.

[0077] Preferably, the axial extension of the elastic sleeve is greater than or equal to the axial extension of the radially inner surface of the belt layer.

[0078] Thus, greater surface continuity is obtained, reducing the risk of causing imprints and defects on the radially inner surface of the belt layer.

[0079] Preferably, the elastic sleeve is made of an elastomeric material, more preferably made of chloroprene.

[0080] Preferably, the elastic sleeve has an anti-friction coating, more preferably a "Milliken" layer.

[0081] Preferably, the radially outer surface of the segment has an anti-friction treatment, more preferably by "PlasmaCoat 25301 / 2008F".

[0082] Preferably, the insert that creates the sliding interface includes a plurality of rolling elements that are rotatably engaged with each segment and project from its radially outer surface.

[0083] Using a coupling member consisting of a rigid body in the production insert facilitates greater process repeatability and limits the effects of wear and aging, promoting greater reliability over time.

[0084] Preferably, the rolling elements include spheres.

[0085] Preferably, each of the spheres is rotatably received in a respective slot, and the respective slots are arranged in the respective segments.

[0086] The rolling freedom of the spheres facilitates relative sliding between the belt layer and the segments of the drum in both the axial direction and the circumferential direction.

[0087] Preferably, each of the spheres is rotatably received in a respective bushing, and the respective bushings are arranged in slots formed in the respective segments.

[0088] Preferably, at least one closing plate fixed to each segment holds the spheres in the respective slots and at least partially defines the radially outer surface of the segment.

[0089] Preferably, each sphere projects from the outer surface of the respective segment by an amount less than its diameter.

[0090] Preferably, each sphere projects from the outer surface of the respective segment according to a size included between about 0.5 mm and about 3.5 mm, such as about 1 mm.

[0091] Preferably, each of the spheres has a diameter included between about 5 mm and about 20 mm, such as about 12 mm.

[0092] The lower limit reduces the risk of sphere wedging in the belt layer, especially between adjacent cords. The upper limit allows for an appropriate number of spheres to be accommodated without increasing the size of the segment.

[0093] Preferably, the spheres on each segment are spaced apart from each other according to a size included between about 6 mm and about 60 mm, such as about 25 mm.

[0094] Preferably, each of the spheres projects from the radial outer surface of the respective segment according to a size less than its diameter and is free to rotate about its center about any axis passing through its center.

[0095] The rotational freedom of the spheres allows for facilitating the sliding of the belt layer relative to the segment in both the circumferential and axial directions.

[0096] Preferably, the rolling elements include rollers.

[0097] Preferably, each of the rollers is rotatably engaged in a housing formed in the radial outer surface of the respective segment.

[0098] Preferably, each of the rollers is rotatable about an axis of rotation extending substantially parallel to the circumferential direction of the service drum.

[0099] Thus, the rollers are adapted to facilitate the relative axial sliding between the belt layer and the radial outer surface of the segment, facilitating the axial narrowing of the belt layer after its circumferential expansion on the segment.

[0100] Preferably, each of the rollers has a diameter included between about 5 mm and about 25 mm, such as about 16 mm.

[0101] Preferably, the rollers on each segment are spaced apart from each other according to a size included between about 6 mm and about 60 mm, such as about 19 mm.

[0102] Preferably, a turning-up device is also provided for turning up the end flap of the first belt layer around the respective lateral edge of the second belt layer and superimposing it on the second belt layer.

[0103] Preferably, the turning-up device operates at the auxiliary drum.

[0104] Preferably, the transfer device includes clamping elements that are circumferentially distributed and radially movable relative to the central geometric axis.

[0105] Preferably, the auxiliary drum has an external cylindrical forming surface.

[0106] Additional features and advantages will become more apparent from a detailed description of the preferred but non - exclusive embodiments of the method, apparatus, and service drum for constructing a tire for a vehicle wheel according to the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0107] These descriptions will be elaborated below with reference to the drawings, which are provided for illustrative purposes only and not for purposes of limitation, wherein:

[0108] Figure 1 An apparatus for manufacturing a tire according to the present invention is schematically shown in a plan view;

[0109] Figure 2 A service drum according to an embodiment of the present invention is shown in a perspective view;

[0110] Figure 3 One of the fan segments of the drum is schematically shown in a diametrical section, Figure 2 wherein the fan segment is in a contracted state;

[0111] Figure 4 The fan segment during belt layer forming in an expanded state is shown; Figure 3 of the fan segment;

[0112] Figure 5 Another embodiment of the service drum according to the present invention in an expanded state is shown in a perspective view;

[0113] Figure 6 An enlarged detail of is shown in a partial section; Figure 5 of;

[0114] Figure 7 The radially outer portion of a fan segment of a service drum according to another embodiment of the present invention is shown in a perspective view;

[0115] Figure 8 A tire obtainable according to the present invention is schematically shown in a radial semi - section. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0116] Referring to the above - mentioned drawings, reference numeral 1 generally indicates an apparatus for manufacturing a tire for a vehicle wheel, which is arranged to implement the method according to the present invention.

[0117] The apparatus 1 is set up for manufacturing a tire 2 ( Figure 8 ), which essentially comprises a carcass structure 2a having at least one or more carcass plies 3.

[0118] An impermeable elastomeric material layer, or so-called liner 4, can be applied inside the carcass ply 3. Two anchoring annular structures 5 are joined to the respective end flanges 3a of the carcass ply 3, each anchoring annular structure 5 including a so-called bead core 5a which carries an elastomeric filler 5b in a radially outer position. The anchoring annular structures 5 are integrated in the vicinity of the area generally identified by the name "bead" 6, where the joining of the tire 2 to the respective mounting rim normally takes place.

[0119] The crown structure 7 is applied circumferentially around the carcass structure 2a. The crown structure 7 includes a belt structure 8 and preferably a tread 9, the belt structure 8 having one or more belt plies 8a, 8b, and the tread 9 being circumferentially superimposed on the belt structure 8.

[0120] More particularly, in the illustrated example, a radially inner first belt ply 8a and at least one second belt ply 8b in a radially outer position are provided.

[0121] At least one belt ply, in the illustrated example the first belt ply 8a, has axially opposite end flanges 10 which are turned up in a radially outer position on a radially more outer second belt ply 8b. In the absence of one or more radially outer belt plies 8b, the end flanges 10 of the first belt ply 8a can be turned up on the same first belt ply.

[0122] The belt structure 8 can also include a pair of belt-like reinforcing inserts 8c, each reinforcing insert 8c being radially superimposed on the terminal edge 10a of one of the turned-up end flanges 10.

[0123] At least one additional reinforcing layer 11 of the so-called "zero-degree ply" type can also be radially superimposed on the belt plies 8a, 8b and possibly the belt-like reinforcing inserts 8c in order to impart to the belt structure 8 the desired resistance to circumferential and radial extensibility.

[0124] Two sidewalls 12 are applied in laterally opposite positions on the carcass ply 3, each sidewall extending from the corresponding bead 6 to the corresponding lateral edge of the tread 9.

[0125] The apparatus 1 preferably has a carcass building area 13 in which the carcass structure 2a of the tire being processed is formed.

[0126] The crown structure 7 is built in a crown building area which is generally indicated by 14 in Figure 1 as a whole.

[0127] In an assembly station 15, the joining of each carcass structure 2a to the corresponding crown structure 7 is actuated.

[0128] More particularly, in the illustrated example, the assembly station 15 is operatively integrated in the carcass building area 13.

[0129] Alternatively, according to an embodiment not shown, the assembly station 15 is located outside the crown building area 14 and outside the carcass building area 13 and is operatively associated therewith.

[0130] According to Figure 1 the embodiment illustrated in, the carcass building area 13 includes at least one main drum 17 on which the carcass structure 2a of the tire 2 is built. The main drum 17 can be operatively supported by a mandrel 18 or another device which, if required, allows the main drum to be actuated to rotate and / or to be moved appropriately between one or more working units 19 during the application of the components of the carcass structure 2a.

[0131] In the crown building area 14, the following areas can preferably be identified: at least one first working area 20 and at least one second working area 21. At the first working area 20, the belt structure forming device 26 operates on at least one auxiliary drum 22 for building the belt structure 8 or at least a first part thereof.

[0132] The auxiliary drum 22 can be rotatably supported by a carriage 23 which is preferably movable parallel to the geometric rotation axis X of the auxiliary drum itself so as to selectively position the auxiliary drum in front of at least one first work station 24 and a second work station 25 which are spaced apart accordingly.

[0133] The belt structure forming device 26 preferably includes means for forming at least a first belt ply 8a by operating, for example, at the first work station 24 through a first feed group 27 to distribute at least a first product in the form of a strip made of elastomeric material cut to size, the elastomeric material including, for example, cords of a textile type which are parallel and close to each other and are oriented at a predetermined angle with respect to the longitudinal extension of the product itself, the predetermined angle preferably being included between approximately 30° and approximately 60°. The first product distributed by the first feed group 27 is applied around the auxiliary drum 22 and is actuated to rotate to form the first belt ply 8a, the application of the first belt ply 8a causing it to rotate once around the outer surface of the auxiliary drum 22 itself and having a cylindrical shape. At the end of the winding, the ends of the first belt ply 8a thus formed are butted against each other.

[0134] A second feed group 28 can also be provided for distributing a second product in the form of a strip made of elastomeric material cut to size, the width of the second product preferably being smaller than the width of the first product. The second product can include parallel textile or metal cords which are close to each other and are oriented at a predetermined angle with respect to the longitudinal extension of the product itself, the predetermined angle preferably being included between approximately 30° and approximately 60° and having a cross orientation with respect to the cords of the first product.

[0135] The second article is preferably applied around the first belt layer 8a in a manner similar to that of the first belt layer 8a, so as to form a second belt layer 8b that winds around the auxiliary drum 22 for a full turn. At the end of the winding, the ends of the second belt layer 8b thus formed are joined end to end, and the width of the second belt layer 8b is preferably smaller than the width of the first belt layer 8a.

[0136] Once the deposition of the belt layers 8a, 8b has been completed, the axially opposite terminal flaps 10 of the at least one first belt layer 8a that axially project relative to the second belt layer 8b are flipped around the terminal edges of the second belt layer 8b, so as to be radially superimposed outside the second belt layer itself. This operation can be carried out when the carriage 23 carrying the auxiliary drum 22 moves near the flipping station 29, where suitable flipping devices, which are not described and not illustrated in detail, can be obtained in a manner known per se, for example by means of inflatable chambers and / or suitable deformable chambers and / or mechanical thrust elements, which are partially or fully integrated in the same auxiliary drum 22.

[0137] In the first working area 20, for example at the aforementioned second workstation 25, the third feed group 30 is also operatively arranged for applying pairs of belt-shaped reinforcing inserts 8c, each belt-shaped reinforcing insert 8c being obtained in strip form and made of an elastomeric material incorporating longitudinally extending cords, preferably a textile, such as a nylon-based one.

[0138] Once the processing in the first working area 20 has been completed, the construction of the crown structure 7 continues in the second working area 21, operated by at least one service drum 31, which is preferably engaged with a robotic arm 32, preferably of anthropomorphic type.

[0139] For this purpose, the auxiliary drum 22 is preferably carried, for example by the axial movement of the carriage 23, into the first transfer station 33, where a transfer device group 34 operates, which is configured to transfer the belt structure 8 from the auxiliary drum 22 to the service drum 31.

[0140] In a preferred embodiment, such a transfer device group 34 includes at least one first transfer member 34a, which is substantially fixed in the crown construction area 14 and is configured to alternately engage with the auxiliary drum 22 carried by the carriage 23 and the service drum 31 carried by the robotic arm 32.

[0141] Once inserted into the first transfer member 34a, the auxiliary drum 22, which consists of radially movable fan segments (not shown), radially contracts so as to disengage from the belt structure 8, which remains held by the first transfer member 34a itself. To this end, the first transfer member 34a is equipped with clamping elements (not shown), which are circumferentially distributed and radially movable so as to be borne in contact with the belt structure 8.

[0142] As can be better seen in Figures 2 to 5 , the service drum 31 includes a plurality of fan segments 35 circumferentially distributed about a central geometric axis X1 and is equipped with actuator means. Since the actuator means can be implemented in any convenient manner and is not relevant to the purpose of the present invention, the actuator means is not described in detail. The actuator means allows the fan segments themselves to move selectively and preferably simultaneously between a radially contracted state ( Figure 3 ) and a radially expanded state ( Figure 4 ). In the radially contracted state, they approach the central geometric axis X1, and in the radially expanded state, the fan segments 35 move radially away from the central geometric axis X1. In the radially contracted state, the fan segments 35 define an outer diameter Dc of the service drum 31, the size of which is smaller than the inner diameter Di of the belt structure 8 previously formed on the auxiliary drum 22.

[0143] Under the command of the robotic arm 32, the service drum 31 in the radially contracted state is adapted to translate along its central geometric axis X1 so as to be coaxially inserted into the first transfer member 34a carrying the belt structure 8.

[0144] Thus, the belt layers 8a, 8b previously removed from the auxiliary drum 22 are transferred coaxially around the service drum 31 and are engaged after the subsequent radial movement of the fan segments 35 towards the radially expanded state.

[0145] Each fan segment 35 of the service drum 31 has a radially outer surface 36, which has a curved profile in a radial plane relative to the central geometric axis X1. Thus, when they move radially away from the contracted state, the fan segments 35 initially contact the radially inner surfaces of the belt layers 8a, 8b at the axial midline plane P.

[0146] The size of the outer diameter De defined by the fan segments 35 in the radially expanded state is larger than the inner diameter Di of the belt structure 8 previously formed on the auxiliary drum 22. As the movement of the fan segments 35 towards the radially expanded state progresses, the belt layers 8a, 8b thus radially expand and are shaped along the radially outer surface 36 of the fan segments 35 according to a curved cross-sectional profile.

[0147] In this case, the belt plies 8a, 8b undergo an increase in the circumferential extension, having a maximum size near the axial midplane P and gradually decreasing in the direction of the axial edges. The change in the inclination angle of the cords constituting the belt plies 8a, 8b facilitates the increase in the circumferential extension of the belt plies 8a, 8b, and this inclination angle tends to decrease with respect to the circumferential extension direction and the simultaneous contraction of the size of the axial extension of the belt plies themselves.

[0148] These adjustments create a relative movement between the radially inner surface of the belt plies 8a, 8b and the radially outer surface 36 of the segment 35.

[0149] Between the segment 35 and the radially inner surface of the belt plies 8a, 8b, at least one insert 37 creating a sliding interface is interposed, and during the expansion of the segment 35, the insert 37 creating a sliding interface moves relative to the segment itself and abuts against the radially inner surface of the belt plies 8a, 8b to facilitate the above relative sliding and eliminate or significantly reduce friction.

[0150] In Figures 2 to 4 the preferred embodiment represented, the insert 37 creating a sliding interface includes at least one elastic sleeve 38, and the elastic sleeve 38 is arranged around the segment 35 of the service drum 31.

[0151] At least when the segment 35 is in the expanded state, the elastic sleeve 38 is preferably mounted around the segment 35 in an elastically expanded state. When the segment 35 is in the contracted state, the elastic sleeve 38 can in any case maintain a desired degree of tension in the circumferential direction to maintain a constant contact against the radially outer surface of the segment 35. The translation of the segment 35 in the radially expanded state causes the circumferential expansion of the elastic sleeve 38. Corresponding to this circumferential expansion, there may be a decrease in the axial size of the elastic sleeve 38 and / or its radially detectable thickness with respect to the central geometric axis X1.

[0152] The elastic sleeve 38 can conveniently be made of an elastomeric material. For example, such an elastomeric material can have a polychloroprene base (a polymeric form of chloroprene commercialized by "Du Pont Performance Elastomers" under the name "neoprene") in order to achieve satisfactory dimensional stability, repeatability of deformation caused by stress, and structural integrity over time.

[0153] At least the outer surface and / or the inner surface of the elastic sleeve 38 can be coated with an anti - friction layer to improve the slidability with respect to the radially inner surface at the belt ply and / or the outer surface of the segment 35, for example by coating with "milli ken" (code of Milliken Europe B.V.B.A.: "2700 / 070 31 + solvent").

[0154] In order to improve the slidability, it may be provided that the radially outer surface 36 of the fan segment 35 is at least partly provided with an anti-friction treatment, such as an anti-friction treatment carried out by "PlasmaCoat 25301 / 2008F" of Impreglon Italia S.r.l..

[0155] Preferably, the elastic sleeve 38 is axially received in the centering recess 39, which is defined on each of the fan segments 35 by two axial shoulders 39a facing the axial outer edge of the elastic sleeve 38. The axial shoulders 39a may conveniently have a radial extension corresponding to the thickness of the elastic sleeve 38. The radial extension of the axial shoulders 39a corresponds to the depth of the centering recess 39. Alternatively, it may be provided that at least in the contracted state, the radial extension of the axial shoulders 39a is less than the thickness of the elastic sleeve 38, so as to correspond to said thickness when the fan segment 35 is in the radially expanded state.

[0156] It may be conveniently provided that at least at their radially inner surfaces, the axial extension of the elastic sleeve 38 is less than the axial extension detectable on the belt plies 8a, 8b. Thus, in the contracted state, as the fan segment 35 moves towards the radially expanded state, the axial opposite ends of the belt plies 8a, 8b directly abut against the outer surface of the fan segment 35. Thus, a high expansion force can be transmitted to the belt plies 8a, 8b without the risk of subjecting the elastic sleeve 38 to excessive stress at the opposite ends of the belt plies themselves.

[0157] Alternatively, in the case where there is preferably greater continuity on the abutment surfaces of the belt plies 8a, 8b, the axial extension of the elastic sleeve 38 may be greater than or equal to the axial extension of the radially inner surface of the belt plies themselves. In other words, the entire width of the radially inner surface of the belt plies 8a, 8b abuts against the elastic sleeve 38, thus being beneficial to surface continuity.

[0158] In Figures 5 to 7 Another preferred embodiment illustrated in, it is provided that the insert 37 creating the sliding interface includes a plurality of rolling elements 40, 41, which are rotatably engaged with each fan segment 35 and project from its radially outer surface 36. During the expansion of the fan segment 35, the rolling elements 40, 41 contact the radially inner surfaces of the belt plies 8a, 8b and are adapted to be driven to rotate so as to facilitate the relative sliding between the belt plies themselves and the fan segments.

[0159] In Figure 5 and Figure 6In the example, the rolling elements include spheres 40 which are distributed on the radially outer surface 36 of each segment 35 with a mutual distance preferably included between about 6 mm and about 60 mm, for example about 25 mm. Preferably, each sphere 40 having a diameter approximately included between about 5 mm and about 20 mm, for example about 12 mm, is rotatably received in a respective bushing 40a which in turn is received in a slot 40b arranged in the segment 35. One or more closing plates 35a fixed to each segment 25 hold the bushing 40a and thus the sphere 40 within the respective slot 40b. The closing plate 40 at least partially defines the radially outer surface 36 of the segment 35. Through the closing plate 35a, each sphere 40 projects from the outer surface 36 with a size less than its diameter, approximately included between about 0.5 mm and about 3.5 mm, for example about 1 mm. Each sphere 40 can freely rotate about its center according to any axis passing through its center, but it cannot perform a spontaneous detachment of the sphere 40 from the respective slot 40a.

[0160] In Figure 7 the example, the rolling elements include rollers 41 which are distributed on the radially outer surface 36 of each segment 35 with a mutual distance preferably included between about 6 mm and about 60 mm, for example about 19 mm. Preferably, each roller 41 has a diameter approximately included between about 5 mm and about 25 mm, for example about 16 mm, and each roller 41 is rotatably engaged in a respective housing 41a formed in the radially outer surface 36 of the segment 35 and projects from the radially outer surface 36 of the segment 35 with a size less than its diameter. Each roller 41 is rotatably engaged in the respective housing 41a about its axis of rotation which is preferably parallel to the circumferential extension direction of the service drum 31 and of the belt structure 8 arranged on the service drum 31, so as to facilitate the relative sliding in the axial direction between the belt plies 8a, 8b and the segments 35 of the drum itself.

[0161] When the segment 35 has reached the expanded state, the aforementioned radially movable element of the first transfer member 34a moves radially away from the belt structure 8 which remains engaged with the service drum 31.

[0162] Thus, through the robotic arm 32, the service drum 31 can be axially translated so as to be removed together with the formed belt structure 8 from the first transfer member 34a.

[0163] The robotic arm 32 (for example of the type having six or more axes of rotation) is able to support, actuate the rotation of and suitably move the service drum 31 in the second working area 21 in order to obtain the tread strip 9 and, if necessary, at least a second part of the belt structure 8.

[0164] This second part of the belt structure 8 can, for example, comprise the aforementioned additional closure layer 11, which can be applied as a supplement or alternative to the belt-like reinforcement insert 8c by means of a winding device 42 operating in a third work station 43 preferably installed in the second work area 21.

[0165] Once the formation of the possible additional closure layer 11 has been completed, the robot arm 32 carries the service drum 31 at at least one fourth work station 44, where the device 45 provided for the formation of the tread band 9 operates, preferably by depositing a continuous elongate element made of elastomeric material in accordance with side-by-side and / or radially superposed coils.

[0166] Once the production of the tread band 9 has been completed, the service drum 31 can be carried by means of the robot arm 32 in a relationship engaging with the second transfer station 16, where the joining of the crown structure 7 to the carcass structure 2a is carried out in a manner not described as it is not relevant to the object of the present invention.

[0167] After carrying out possible additional processing, for example in order to improve the adhesion of the crown structure 7 to the carcass structure 2a, and / or in order to apply the sidewalls 12 to the laterally opposite surfaces of the tyre 2 being processed, the constructed tyre 2 can be removed from the main drum 17 in order to carry out the final vulcanization process and / or other processing provided for in the production cycle.

Claims

1. A method for constructing a tire for a vehicle, the method comprising: Manufacturing a carcass structure (2a), the carcass structure including at least one carcass ply (3), the carcass ply having end flaps (3a) that are joined to respective anchoring annular structures (5); Manufacturing a crown structure (7); Connecting the crown structure (7) to the carcass structure (2a) at a radially outer position; wherein manufacturing the crown structure (7) includes: Successively arranging one or more belt plies around an auxiliary drum (22); Arranging a service drum (31), the service drum including fan segments (35) that are circumferentially distributed around a central geometric axis (X1) and are capable of moving radially between a radially contracted state and a radially expanded state, in the radially contracted state, the fan segments approach the central geometric axis (X1), and in the radially expanded state, the fan segments (35) move away from the central geometric axis (X1), wherein each fan segment (35) has a radially outer surface (36) that has a curved profile in a radial plane relative to the central geometric axis (X1); Removing the one or more belt plies from the auxiliary drum (22) and transferring the belt plies coaxially around the service drum (31) arranged in the radially contracted state; Expanding the fan segments (35) of the service drum (31) from the radially contracted state to the radially expanded state so as to shape the one or more belt plies along the radially outer surface of the fan segments (35) according to a curved cross-sectional profile; wherein at least one insert (37) creating a sliding interface is interposed between the fan segments (35) and the radially inner surface of the one or more belt plies, the insert (37) creating the sliding interface moving relative to the fan segments (35) and abutting against the radially inner surface during expansion of the fan segments (35) so as to facilitate circumferential sliding of the one or more belt plies relative to the fan segments (35).

2. The method according to claim 1, wherein, Forming the crown structure (7) includes: Applying a first belt ply (8a) around the outer surface of the auxiliary drum (22); Applying a second belt ply (8b) around the first belt ply (8a), the width of the second belt ply (8b) being smaller than the width of the first belt ply (8a); Turning up terminal flaps (10) of the first belt ply (8a) around respective terminal edges of the second belt ply (8b) and superimposing them on the second belt ply (8b).

3. The method according to claim 2, wherein, Performing the turning up of the terminal flaps (10) of the first belt ply (8a) before transferring the one or more belt plies onto the service drum (31).

4. The method according to any one of claims 1 to 3, wherein In the radially contracted state, the outer diameter (Dc) of the service drum (31) defined by the fan segments (35) is smaller than the inner diameter (Di) of the one or more belt plies previously formed on the auxiliary drum (22).

5. The method according to any one of claims 1 to 3, wherein, In the radially expanded state, the outer diameter (Dc) of the service drum (31) defined by the fan segment (35) is greater than the inner diameter (Di) of the one or more belt plies previously formed on the auxiliary drum (22).

6. The method according to any one of claims 1 to 3, wherein The movement of the fan segment (35) towards the radially expanded state determines the circumferential expansion of the elastic sleeve (38) that forms the insert (37) creating the sliding interface.

7. The method according to any one of claims 1 to 3, wherein, The movement of the fan segment (35) towards the radially expanded state determines a reduction in the axial dimension of the elastic sleeve (38) that forms the insert (37) creating the sliding interface.

8. The method according to any one of claims 1 to 3, wherein The movement of the fan segment (35) towards the radially expanded state determines the rolling of the rolling elements of the insert (37) creating the sliding interface.

9. A service drum for manufacturing a tire for a vehicle, the service drum comprising: a plurality of fan segments (35) circumferentially distributed about a central geometric axis (X1) and capable of moving radially between a radially contracted state and a radially expanded state, in the radially contracted state, the fan segments are close to the central geometric axis (X1), and in the radially expanded state, the fan segments (35) move away from the central geometric axis (X1); wherein each fan segment (35) has a radially outer surface (36) that has a curved profile in a radial plane relative to the central geometric axis (X1); wherein the service drum (31) further comprises at least one insert (37) creating a sliding interface, the insert creating the sliding interface being movable relative to the radially outer surface (36) of the fan segment (35) and configured to operate in contact against the radially inner surface of one or more belt plies that can be applied around the service drum (31) so as to support the circumferential sliding of the one or more belt plies relative to the fan segment (35).

10. The service drum according to claim 9, wherein, The insert (37) creating the sliding interface comprises an elastic sleeve (38) arranged around the fan segment (35).

11. The service drum according to claim 10, wherein, The elastic sleeve (38) is axially received in a centering recess (39) formed in each of the fan segments (35).

12. The service drum according to claim 11, wherein, The centering recess (39) has two axial shoulders (39a) towards the axial outer edge of the elastic sleeve (38), and the height of the axial shoulders (39a) is not greater than the thickness of the elastic sleeve (38).

13. The service drum according to claim 12, wherein, When in the radially contracted state, the height of the axial shoulders (39a) is lower than the thickness of the elastic sleeve (38).

14. The service drum according to any one of claims 10 to 13, wherein, The axial extension of the elastic sleeve (38) is less than the axial extension of the radially inner surface of the one or more belt plies.

15. The service drum according to any one of claims 10 to 13, wherein The axial extension of the elastic sleeve (38) is greater than or equal to the axial extension of the radially inner surface of the one or more belt plies.

16. The service drum according to claim 9, wherein, The insert (37) creating the sliding interface comprises a plurality of rolling elements that are rotatably engaged with each fan segment (35) and project from the radially outer surface (36) of the fan segment.

17. The service drum according to claim 16, wherein, The rolling elements comprise spheres (40).

18. The service drum according to claim 17, wherein, Each of said spheres (40) is rotatably received in a slot (40a) arranged in said radially outer surface (36) of the respective segment (35).

19. The service drum according to claim 18, wherein, Each of said spheres (40) projects from the radially outer surface (36) of the respective segment (35) by an amount less than its diameter and is free to rotate about its center about any axis passing through its center.

20. The service drum according to claim 16, wherein, Said rolling elements include rollers (41).

21. The service drum according to claim 20, wherein, Each of said rollers (41) is rotatably engaged in a housing (41a) formed in the radially outer surface (36) of the respective segment (35).

22. The service drum according to claim 20 or 21, wherein, Each of said rollers (41) is capable of rotating about an axis of rotation that is substantially parallel to the circumferential extension direction of said service drum (31).

23. An apparatus for manufacturing a tire for a vehicle, said apparatus comprising: A carcass building area (13) for manufacturing a carcass structure (2a); A crown building area (14) for manufacturing a crown structure (7); An assembly station (15) in which each carcass structure (2a) is associated with one of said crown structures (7); Wherein said crown building area (14) comprises: An auxiliary drum (22); At least one feed group (30) configured to sequentially arrange one or more belt plies around said auxiliary drum (22); A service drum (31) according to any one of claims 9 to 22; A transfer device (34) configured to remove said one or more belt plies from said auxiliary drum (22) and transfer said belt plies coaxially around the service drum (31) arranged in a radially contracted state.

24. The apparatus according to claim 23, further comprising a turning-up device (29) for turning up the end flaps (10) of a first belt ply (8a) around the respective lateral edges of a second belt ply (8b) and superimposing them on said second belt ply (8b).

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