Method for controlling the geometry of a forming drum for producing tyres for vehicle wheels

Abstract

14. The folding mechanism according to claim 13, wherein the cam is arranged so as to move the adjusting shaft relative to the central axis and the adjusting shaft is moved relative to the central axis so as to move the adjusting shaft towards the cam. The cam is arranged so as to move the adjusting shaft towards the cam and the adjusting shaft is moved relative to the central axis. The cam is arranged so as to move the adjusting shaft towards the cam.

Description

[0001] This application is a divisional application of the Chinese invention patent application No. 202080084328.X, which entered the Chinese national phase of the international application PCT / IB2020 / 061722 with the invention name "Forming drum for producing wheel tires and method for controlling the geometric shape of a forming drum for producing wheel tires" and the international application date of December 10, 2020. Technical Field

[0002] The invention relates to a method for controlling the geometry of a shaping drum for producing tyres for vehicle wheels and to a shaping drum for producing tyres for vehicle wheels. Background Art

[0003] A tyre for vehicle wheels generally comprises a carcass structure, a crown structure arranged in a radially outer position with respect to the carcass structure and a pair of sidewalls representing the axially outer surfaces of the tyre with respect to a median plane perpendicular to the same axis of rotation of the tyre.

[0004] The carcass structure comprises at least one carcass ply formed from reinforcing cords embedded in a matrix of elastomeric material. The carcass ply has opposite end edges, each of which is joined to annular anchoring structures. The annular anchoring structures are arranged in the region of the tire generally identified by the name "bead" and are generally each formed by a substantially circumferential annular insert, known as a "bead core", onto which is applied at least one filling insert, which radially tapers away from the axis of rotation in a radially outer position.

[0005] At the beads, specific reinforcement structures may be provided which have the function of improving the transmission of torque to the tire.

[0006] In the case of a "tubeless" tire, i.e. one without an air chamber, a layer of elastomeric material, usually called an "inner liner", may also be provided in a radially inner position relative to the carcass structure to provide the necessary impermeability to tire inflation. Typically, the inner liner extends from one bead to the other.

[0007] The crown structure comprises a belt structure and a tread band made of elastomeric material in a radially outer position with respect to the belt structure.

[0008] The belt structure comprises one or more belt layers arranged radially juxtaposed on one another, the belt layers having textile or metallic reinforcing cords substantially parallel to the direction of circumferential extension of the tire (zero-degree layers) and / or having a cross orientation.

[0009] Between the carcass structure and the belt structure there may be provided a layer of elastomeric material, called "underbelt", the function of which is to make the radially external surface of the carcass structure as uniform as possible for the subsequent application of the belt structure.

[0010] Longitudinal and transverse grooves arranged to define the desired tread pattern are usually formed on the tread band. Between the tread band and the belt structure, a so-called "underlayer" made of an elastomeric material with suitable properties can be interposed to obtain a stable bond of the belt structure to the tread band itself.

[0011] The sidewalls are made of elastomeric material and represent the axially outer surface relative to the annular anchoring structure, the carcass ply(s), the belt(s) and possibly at least a portion of the tread band. For example, the sidewalls each extend from one of the lateral edges of the tread band to the respective annular anchoring structure of the bead.

[0012] The term "elastomeric material" is intended to mean a composition comprising at least one elastomeric polymer and at least one reinforcing filler. This composition may also contain additives, such as a crosslinking agent and / or a plasticizer. Due to the presence of the crosslinking agent, this material can be crosslinked by heating to form the final manufactured product.

[0013] The term "green tire" is intended to mean a tire obtained from a building process that has not yet been molded and cured.

[0014] The term "finished tire" is intended to mean a tire obtained by molding and vulcanizing a green tire.

[0015] The term "tire" is intended to mean a finished or green tire.

[0016] The terms "axial", "in the axial direction", "radial", "in the radial direction", "circumferential" and "circumferentially" are used with reference to the forming drum used in the tire production process.

[0017] In particular, the terms "axial" and "in the axial direction" are intended to mean references / quantities arranged / measured or extending in a direction substantially parallel to the geometrical axis of rotation of the forming drum.

[0018] The terms "radial" and "radially" are intended to mean references / values arranged / measured or extending in a direction substantially perpendicular to the geometrical axis of rotation of the forming drum and lying in a plane including such geometrical axis of rotation.

[0019] The terms "radially inner / outer" are intended to denote a position which is respectively closer to or further away from the above-mentioned geometrical axis of rotation of the forming drum.

[0020] The terms "axially inner / outer" are intended to denote positions respectively closer to and further away from a mid-plane perpendicular to the geometrical axis of rotation of the forming drum.

[0021] The terms "circumferential" and "circumferentially" are intended to mean a reference / value arranged / measured or extending along a circumference extending around the geometric axis of rotation of the forming drum.

[0022] The term "structural member" of a tire is intended to denote any part thereof or component thereof that is capable of performing its function. For example, the following members are structural members of a tire: the carcass structure, the crown structure or components thereof, such as the innerliner, the underliner, the wear-resistant insert, the bead core, the filling insert in the bead region (and thus the annular anchoring structure defined by the bead core and the respective filling insert), the carcass ply(s), the belt(s), the belt sublayer, the tread band sublayer, the sidewalls, the sidewall inserts, the tread band, textile or metal reinforcements, reinforcing elements made of elastomeric material, etc. or components thereof.

[0023] The term "tyre being processed" is intended to denote a tyre that is at any step of the relevant production process, starting from the shaping of at least one structural element constituting the carcass structure and / or the crown structure, up to the point at which the finished tyre is obtained. For example, a tyre being processed is a tyre that enters or leaves a work station dedicated to applying annular anchoring structures to the opposite end edges of the carcass ply(s) previously deposited on a forming drum, and dedicated to turning up these end edges around the aforementioned annular anchoring structures.

[0024] The term "machine downtime" is intended to mean the time during which a tire production plant stops operating due to format change operations for production batches.

[0025] The production cycle of a tire provides that, after a green tire forming process in which the various structural components of the tire itself are formed and assembled, the green tire is transferred to a molding and vulcanization line in which molding and vulcanization processes are carried out that are suitable for defining the structure of the finished tire according to the desired geometry and tread pattern.

[0026] The shaping of the tire structural components and their subsequent assembly are carried out on suitable shaping drums. For example, the carcass structure may be shaped on a first shaping drum, referred to as the first-stage drum, while the crown structure may be shaped on a second shaping drum, referred to as the auxiliary or second-stage drum. The assembly of the carcass structure to the crown structure may be carried out on the first shaping drum, in which case the first-stage drum is referred to as a "single-stage" drum, or on a different shaping drum, referred to as a calibrating drum.

[0027] WO 2007 / 096629 describes a forming drum for manufacturing tires, comprising a plurality of segments defining the outer circumference of the forming drum, wherein the segments are divided into two series, one series located on each opposite side of a transverse center plane of the forming drum. The two series of segments are configured to be actuated by a hub assembly that rotates between a collapsed state, in which the tire carcass can be removed from the forming drum, and an expanded position, in which the tire carcass can be formed on the forming drum. The forming drum also includes mountings for actuating each of the two series of segments for selective relative axial positioning, and a device arranged outside the drum's axis of rotation for adjusting the drum's total working width. Preferably, one series of segments is associated with an inner hub located on one side of the transverse center plane, while the other series of segments is associated with an outer hub located on the opposite side of the transverse center plane. The device for adjusting the total working width of the drum includes a first series of inner worms associated with the inner hub and a second series of outer worms associated with the outer hub, the first and second series of worms being configured to rotate relative to each other so that rotation of the outer worms causes relative movement of the inner worms and controls axial separation of the inner hub from the outer hub.

[0028] US 4,151,035 describes a forming drum mounted axially on a hollow shaft. A plurality of arched segments are positioned around the drum by means of a plurality of stems. A shoulder, preferably provided at each end portion of the forming drum, is coaxially and slidably secured to the hollow shaft of the drum. During the tire building operation, each shoulder is axially retained by a plurality of sets of tie rods, each set comprising tie rods arranged around a hollow shaft having threaded ends. The tie rods are rigidly secured to the outside of the hollow shaft at the end portions by mounting holes and bolts at the right end and flanges and bolts at the left end. The tie rods are in turn secured to the holes and flanges by lock nuts. When axial resetting is required, the lock nuts are unscrewed from the end portions of the tie rods, allowing the tie rods to slide freely axially through the holes and flanges.

[0029] WO 2008 / 099236, filed by the same applicant, describes a forming drum having two halves supported by a central shaft extending along the geometric axis of the drum. The halves can be moved axially toward each other, for example, under the control of a threaded rod operatively disposed within the central shaft and provided with two threaded sections, one right-hand and one left-hand, each engaging one of the halves. Upon applying rotation to the threaded rod via an actuator operatively coupled to one end of the central shaft, the halves of the forming drum are thereby simultaneously displaced in opposite directions along the central axis.

[0030] The Applicant has observed that the space in the axial direction on the forming drum required for manufacturing the tread band is different depending on the width of the tread band and the height of the sidewalls of the finished tyre. In particular, the Applicant has observed that as the width of the tread band and the height of the sidewalls increase, the axial space on the forming drum required for manufacturing the tyre model increases.

[0031] The Applicant has observed that, in theory, every combination of tread band width and sidewall height requires a forming drum of predetermined axial dimensions.

[0032] Although it is possible to use the same forming drum for two or more combinations of tread band width and sidewall height, the Applicant has observed that it is necessary to manage forming drums with different extensions in the axial direction and to provide specific stores for the various drums.

[0033] The Applicant felt the need to manage the forming drums without having to provide specific stores of larger dimensions, while still ensuring the possibility of selecting the forming drum according to the combination of tread band width and sidewall height of the tyre to be manufactured.

[0034] The Applicant has observed that the forming drum described in document WO 2008 / 099236 makes it possible to use the same forming drum to build tyres having different combinations of tread band width and sidewall height, since the axial extension of the forming drum can be varied by exerting a rotation on a threaded rod arranged inside the central shaft.

[0035] The Applicant has demonstrated that, by rotating a threaded rod arranged inside the central shaft, an axial movement of the two halves of the forming drum is actuated, the size of which is proportional to the angular rotation undergone by the threaded rod.

[0036] The Applicant has noticed that it is possible to make the forming drum substantially continuously widen and narrow axially (between a maximum and a minimum), in other words without a discrete passage between the possible axial extension achievable by the forming drum and the previous or next axial extension reached or achievable.

[0037] The Applicant has demonstrated that this effectively enables the use of the same building drum to build tyres having any combination of maximum and minimum values falling within the range between tread band width and sidewall height.

[0038] However, the Applicant has observed that a "continuous" adjustment of the axial extension of the forming drum requires a precise and reliable control of the dimensions achieved; moreover, the mechanism envisaged for such adjustment must keep the axial extension fixed in every condition of use, without allowing "reversible" movements of the components constituting such a mechanism, for example in the event of an accidental or sudden impact during the processing cycle.

[0039] More precisely, the Applicant has demonstrated that the continuous measurement of the axial extension gradually occupied by the forming drum may require the use of complex measuring tools which, if not used correctly, may provide inaccurate indications; moreover, the axial adjustment may be slightly reversible due to the loss of axial position of the sectors during use, after the application of axial stress on the sectors, owing to vibrations or small shocks experienced in the movement of the drum itself.

[0040] The Applicant has also observed that, in modern highly automated building lines, it is highly advantageous to be able to change the axial dimensions of the building drum as quickly as possible in order to reduce machine downtimes (and "line downtimes"), but without compromising the possibility of being able to use the same building drum to build tyres with different combinations of tread band widths and sidewall heights falling within a range of maximum and minimum values.

[0041] The Applicant finally observes that, in current use, a continuous variation of the possible axial extensions actuable by the forming drum, within the range of maximum and minimum values of axial extension, is unnecessary, since the actual number of possible axial extensions required to shape the tyre is limited, albeit high.

[0042] The Applicant has in fact demonstrated that there is a tolerance between the axial extension of the forming drum and the axial extension actually occupied by the tyre being worked, making it possible to form, on a forming drum having the same axial extension, two combinations of tread band width and sidewall height of the finished tyre, which differ from each other but whose difference falls within the tolerances quoted.

[0043] The Applicant has therefore found that by providing a threaded rod in the central shaft that can only be rotated in discrete predetermined steps, it is possible to correlate each discrete predetermined step of rotation of the threaded rod with an axial displacement of the two halves of the forming drum in a deterministic and predetermined manner. Depending on the discrete rotation steps chosen, it is also possible to predetermine the minimum increase or decrease in the axial extension of the forming drum. Summary of the Invention

[0044] The present invention therefore relates in a first aspect to a forming drum for producing tyres for vehicle wheels.

[0045] Preferably, the central shaft is arranged concentrically with the geometrical axis of rotation of the forming drum.

[0046] Preferably, two lateral deposition surfaces are provided, which are radially outside the central axis and axially opposite each other, wherein the two lateral deposition surfaces are driven in rotation about the geometrical axis of rotation by the central axis.

[0047] Preferably, an adjustment linkage is provided which is configured to move the two lateral deposition surfaces axially towards and away from each other, comprising an adjustment shaft coaxial with the central axis, wherein relative rotation between the adjustment shaft and the central axis actuates the adjustment linkage.

[0048] Preferably, at least one actuating device is provided which is fixedly connected to the adjusting shaft.

[0049] Preferably, at least one locking device is provided, which operates on the actuating device between a first state in which the locking device prevents rotation of the actuating device relative to the central axis and a second state in which relative rotation between the actuating device and the central axis is permitted.

[0050] Preferably, when the locking device is in the first state, it defines a plurality of locking positions for the actuating device.

[0051] Preferably, starting from a previous locking position, the actuating device can reach any locking position with a relative and predetermined angular rotation between the actuating device and the central axis with the locking device in the second state.

[0052] The applicant believes that the forming drum according to the invention makes it possible to minimize machine downtimes, since the actuating device can be rotated relative to the central shaft, preferably without removing the forming drum from the forming line. The applicant has verified that it is sufficient to lock the adjustment shaft and rotate the central shaft (possibly using the same actuator used during normal operation of the forming drum for this purpose) or to keep the central shaft stationary (in this case also possible using the same actuator used during operation of the forming drum) and rotate the adjustment shaft to change the axial dimension of the drum.

[0053] The applicant has also demonstrated that the locking device and the relative locking position it establishes make it possible to interrupt the relative rotation between the central shaft and the adjustment shaft after a predetermined relative rotation and, therefore, to avoid the need to continuously measure the axial extension gradually taken up by the drum during the relative rotation between the central shaft and the adjustment shaft after a predetermined relative axial displacement between the two lateral deposition surfaces. According to the applicant's experience, this not only minimizes machine downtime but also improves the accuracy of determining the axial dimension taken up by the drum.

[0054] The Applicant has verified that, in a forming drum according to the invention, it may be sufficient to carry out static measurements of the forming drum in the new configuration of the axial dimensions (in other words without moving parts) just to verify that the new axial dimensions are actually achieved.

[0055] In a second aspect thereof, the present invention relates to a method of controlling the geometry of a forming drum for producing tyres for vehicle wheels.

[0056] Preferably, provision is made for the central axis to be arranged concentrically with the geometrical axis of rotation of the forming drum.

[0057] Preferably, it is provided that the two lateral deposition surfaces are arranged radially outside the central shaft and axially opposite to each other, and the central shaft is rotatably coupled to the two lateral deposition surfaces.

[0058] Preferably, it is provided that the adjustment shaft is arranged coaxially with the central shaft and rotatable relative to the central shaft, and the two lateral deposition surfaces are coupled to the adjustment shaft.

[0059] Preferably, it is provided that the adjustment shaft is configured such that a rotation of the adjustment shaft relative to the central axis corresponds to an axial displacement of the two lateral deposition surfaces.

[0060] Preferably, provision is made for arranging at least one plurality of predetermined locking positions between the adjustment shaft and the central shaft, wherein the adjustment shaft is rotationally constrained to the central shaft, and wherein each locking position corresponds to a relative predetermined angular position between the adjustment shaft and the central shaft.

[0061] Preferably, provision is made for the adjustment shaft to be rotated relative to the central shaft, wherein the rotation of the adjustment shaft relative to the central shaft takes place from a locking position until a further locking position is reached.

[0062] The Applicant believes that in this way, a predetermined rotation of the adjustment shaft relative to the central shaft corresponds to a predetermined axial movement of the two deposition surfaces and thus to a predetermined axial dimension of the forming drum.

[0063] In at least one of the above aspects, the present invention may have at least one of the following preferred features.

[0064] Preferably, the locking device comprises at least one first locking element connected to the actuating device and at least one second locking element connected to the central shaft.

[0065] Preferably, when the locking device is in the first state, the first locking element and the second locking element engage with each other.

[0066] Preferably, when the locking device is in the second state, the first locking element and the second locking element do not engage with each other.

[0067] Preferably, the relative rotation between the adjustment shaft and the central shaft occurs by the same angular amount between two mutually consecutive locking positions.

[0068] In this way, the central shaft and the adjusting shaft always reach any two consecutive locking positions with the same relative rotation.

[0069] Preferably, the at least one first locking element and the at least one second locking element are mutually engageable at least once after a rotation of 360° between the actuating device and the central axis.

[0070] Preferably, starting from the locking position, another locking position is reached when the adjustment shaft and the central shaft are relatively rotated 360°.

[0071] Preferably, said locked position is actuated by said at least one first locking device.

[0072] Preferably, said further locking position is actuated by the same at least one first locking device.

[0073] In this way, starting from a stable axial dimension occupied by the forming drum, each mutual rotation through 360° between the actuating device and the central shaft corresponds to a new predetermined axial dimension of the forming drum.

[0074] Preferably, the actuating device is provided with at least two first locking elements angularly spaced 180° apart.

[0075] Preferably, the central shaft is provided with at least two second locking elements spaced 180° apart.

[0076] Preferably, at least two locking positions intercept each 360° relative rotation between the adjustment shaft and the central shaft.

[0077] In this embodiment, starting from a stable axial dimension occupied by the forming drum, each 360° mutual rotation between the actuating device and the central shaft corresponds to two mutually consecutive and increasing (or decreasing depending on the relative rotation direction) predetermined axial dimensions of the forming drum.

[0078] Preferably, the adjustment linkage is configured so that a 180° relative rotation between the actuating device and the central shaft corresponds to a predetermined relative displacement between the two lateral deposition surfaces. This relative displacement preferably defines a minimum axial expansion / contraction step of the forming drum.

[0079] Preferably, a relative rotation of 180° between the actuating device and the central axis corresponds to a displacement of the two lateral deposition surfaces of greater than about 1 mm.

[0080] Preferably, a relative rotation of 180° between the actuating device and the central axis corresponds to a displacement of the two lateral deposition surfaces of less than about 10 mm.

[0081] Preferably, a 180° relative rotation between the actuation device and the central axis corresponds to a displacement of the two lateral deposition surfaces comprised between approximately 1 mm and approximately 10 mm, inclusive.

[0082] Preferably, a relative rotation of 180° between the actuating device and the central axis corresponds to a displacement of the two lateral deposition surfaces of greater than about 2 mm.

[0083] Preferably, a relative rotation of 180° between the actuating device and the central axis corresponds to a displacement of the two lateral deposition surfaces of less than about 5 mm.

[0084] Preferably, a 180° relative rotation between the actuation device and the central axis corresponds to a displacement of the two lateral deposition surfaces comprised between approximately 2 mm and approximately 5 mm, inclusive.

[0085] Preferably, a relative rotation of 180° between the actuating device and the central axis corresponds to a displacement of the two lateral deposition surfaces of approximately 2.5 mm.

[0086] Preferably, the second locking element comprises a pin movable relative to the central axis between a detent state in which the second locking element engages the first locking element and a released state in which the second locking element does not engage the first locking element.

[0087] Preferably, the pin is slidable in a first direction in the axial direction between the stopped state and the released state and in a second direction opposite to the first direction between the released state and the stopped state.

[0088] Preferably, the second locking element further comprises an elastic element connected to the pin and acting between the pin and the central axis; the elastic element axially pushes the pin in the stopped state.

[0089] Preferably, the central shaft comprises a housing seat for a pin; the pin is axially slidable within the housing seat.

[0090] Preferably, the first locking element comprises a seat in the actuating device, the seat being engageable by the head of the pin when in the resting condition.

[0091] Preferably, the actuating device is arranged at a first axial end of the central shaft; and a supporting device fixedly connected to the central shaft and rotatable relative to the adjustment shaft of the adjustment linkage is arranged at a second axial end of the central shaft opposite to the first axial end.

[0092] Preferably, the supporting device comprises at least a first pair of coupling elements configured to be engaged by a moving device external to the forming drum.

[0093] Preferably, the actuating device comprises at least a second pair of coupling elements configured to be engaged by a moving device external to the forming drum.

[0094] Preferably, the adjustment shaft includes a first threaded portion having a right-handed or left-handed helical thread and a second threaded portion having a helical thread opposite to that of the first threaded portion.

[0095] Preferably, at least one first carriage connected to one of the two lateral deposition surfaces is mounted on the first threaded portion and at least one second carriage connected to the other of the two lateral deposition surfaces is mounted on the second threaded portion.

[0096] Preferably, the central shaft comprises an opening extending in the axial direction and passed through in the radial direction by respective brackets connected to the first and second carriages; each bracket connecting the respective first or second carriage to the respective lateral deposition surface.

[0097] Preferably, a central deposition surface is provided which is arranged between the two lateral deposition surfaces; the central deposition surface is located radially outside the central shaft and is rotatably coupled to the central shaft.

[0098] Preferably, the two lateral deposition surfaces comprise end portions axially facing the central deposition surface and configured to be radially inserted into the central deposition surface.

[0099] Preferably, rotating the adjustment shaft relative to the central axis includes releasing the adjustment shaft from a locked position.

[0100] Preferably, the relative rotation between the adjustment shaft and the central shaft is actuated by locking the adjustment shaft and rotating the central shaft.

[0101] Preferably, it is provided to provide at least one first locking device, which operates on the adjustment shaft between a first state and a second state, in which the first locking device prevents the adjustment shaft from rotating relative to the central axis and in which the first locking device allows the adjustment shaft to rotate relative to the central axis. BRIEF DESCRIPTION OF THE DRAWINGS

[0102] Further features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the present invention with reference to the accompanying drawings.

[0103] In these figures:

[0104] Figure 1 is a schematic perspective view of a forming drum for wheel tyres according to the present invention;

[0105] Figure 2 yes Figure 1 Schematic side view of the drum, with some parts removed to better highlight other parts;

[0106] Figure 3 yes Figure 1 a schematic perspective view of some parts of the drum;

[0107] Figure 4 yes Figure 1 a schematic perspective view of some parts of the drum;

[0108] Figure 5 yes Figure 1 a schematic perspective view of some parts of the drum;

[0109] Figure 6 yes Figure 5 an enlarged schematic perspective view of some details of

[0110] Figure 7 yes Figure 1 A schematic perspective view of some components of the drum. DETAILED DESCRIPTION

[0111] exist Figure 1-Figure 7 In the drawing, reference numeral 1 denotes as a whole a forming drum for tyres for vehicle wheels according to the invention.

[0112] The drum 1 comprises a central shaft 2 having an axial extension that intersects a geometrical axis X about which the drum 1 is rotatable.

[0113] In a radially outer position relative to the central axis 2 , there are two lateral deposition surfaces 3 , 4 , essentially cylindrical, axially opposite each other and driven in rotation by the central axis 2 .

[0114] The lateral deposition surfaces 3, 4 each comprise a respective first sector 5 and a second sector 6. The radially outer surfaces 5a of the first sectors 5 are arranged relative to one another, at least in the deposition state of the drum 1, so as to create a substantially continuous surface defining the lateral deposition surface 3. Similarly, the radially outer surfaces 6a of the second sectors 6 are arranged relative to one another, at least in the deposition state of the drum 1, so as to create a substantially continuous surface defining the lateral deposition surface 4.

[0115] In a preferred embodiment of the present invention, the lateral deposition surfaces 3, 4 can be positioned relative to the central axis 2 in the deposition state (eg Figure 1 and Figure 2 In particular, in the deposition state, the first sector 5 and the second sector 6 are moved radially away from the central axis 2, while in the maintenance state, the first sector 5 and the second sector 6 are moved radially closer to the central axis 2. The maintenance state can be activated, for example, to remove a carcass structure, a belt structure or a tyre processed by the forming drum 1.

[0116] In a preferred embodiment of the present invention, Figure 1 and Figure 2 As shown, a central deposition surface 7 is provided which is arranged axially between the two lateral deposition surfaces 3 , 4 .

[0117] The central deposition surface 7 comprises a third sector 8. At least in the deposition state of the drum 1, the radially outer surfaces 8a of the third sector 8 are arranged relative to each other so as to create a substantially continuous surface defining the central deposition surface 7. The central deposition surface 7 can be moved relative to the central axis 2 in the deposition state (e.g. Figure 1 and 2 The central deposition surface 7 and the two lateral deposition surfaces 3, 4 are substantially radially aligned with each other in the maintenance state.

[0118] The third sector 8 is axially connected in a sliding manner to the first sector 5 and the second sector 6. The third sector 8 is rigidly radially connected to the first sector 5 and the second sector 6, so that a radial movement of the third sector 8 causes an identical radial movement of the first sector 5 and the second sector 6, and so that a radial movement of the first sector 5 and the second sector 6 causes an identical radial movement of the third sector 8. The third sector 8 is rigidly rotatably connected to the first sector 5 and the second sector 6, so that a rotation of the third sector 8 about the geometric axis X causes an identical rotation of the first sector 5 and the second sector 6 about the geometric axis X, and so that a rotation of the first sector 5 and the second sector 6 about the geometric axis X causes an identical rotation of the third sector 8 about the geometric axis X.

[0119] like Figure 1 As shown, the auxiliary support elements 9 are arranged in an axially outer position relative to the two deposition surfaces 3, 4. The auxiliary support elements 9 are preferably annular and comprise radially outer surfaces 9a which, when in the deposition state, are substantially aligned with the lateral deposition surfaces 3, 4. Each auxiliary support element 9 is axially constrained to the respective lateral deposition surface 3, 4 in a removable manner.

[0120] In order to allow the lateral deposition surfaces 3, 4 and the central deposition surface 7 to contract and expand radially, an expansion linkage 10 is provided (at Figure 3 and 4 The third sector 8 is a first sector 5 and a second sector 6.

[0121] For example, the expansion linkage 10 may include a steering shaft (not shown) operatively associated with the central shaft 2. The steering shaft is fixedly connected to the steering ring 12 (e.g., Figure 4), the steering ring 12 is rotatably mounted on the central shaft 2 and axially positioned at the third sector 8. The third sector 8 is connected to the steering ring 12 by a linkage mechanism (not shown), which is configured to convert the rotational movement of the steering ring 12 into a radial displacement of the third sector 8. Each of the first sector 5 and the second sector 6 is connected to a first end of a telescopic support 13, which is connected to a second end of a crown 14 slidably mounted on the steering shaft. By rotating the steering shaft in a first angular direction relative to the central shaft 2 from the maintenance state, radial expansion of the third sector 8 is actuated until the deposition state is reached. The radial movement of the third sector 8 also pulls the first sector 5 and the second sector 6 into the deposition state. By rotating the steering shaft in a second angular direction relative to the central shaft 2 from the deposition state, radial contraction of the third sector 8 is actuated until the maintenance state is reached. The radial movement of the third sector 8 also pulls the first sector 5 and the second sector 6 into the maintenance state.

[0122] The crown 14 has a plurality of openings 15 and is operatively associated with the central shaft 2, each opening 15 being passed through by a bracket 16 connected to the crown 14 and the central shaft 2 ( Figure 3 ). The opening 15 allows the steering shaft to rotate without rotating the bracket 16 and thus the central shaft 2.

[0123] Rotation of the drum 1 about its geometric axis X is achieved by rotating the central shaft 2, which rotates the support 16 and, along with it, the crown 14. The support 16 is positioned symmetrically with respect to the geometric axis X of the drum 1. The rotation of the crown 14 determines the rotation of the first and second sectors 5, 6, which in turn rotates the third sector 8. The rotation of the third sector 8 rotates the steering ring 12, which in turn rotates the steering shaft. In this way, the central shaft 2 and the steering shaft rotate together as a unit, and the lateral and central deposition surfaces 3, 4, and 7 remain in their respective radial positions.

[0124] Drum 1 includes an adjustment linkage 17 (e.g. Figure 5 ), the adjustment linkage 17 is configured to move the two lateral deposition surfaces 3 , 4 axially towards and away from each other and to define different axial dimensions for the forming drum 1 .

[0125] Adjusting the linkage 17 has no effect on the central deposition surface 7 , in other words it does not change the axial position of the central deposition surface 7 .

[0126] When the two lateral deposition surfaces 3, 4 are axially directed towards each other, they are configured to be at least partially inserted under the central deposition surface 7, thereby reducing the axial dimension of the forming drum 1, keeping its radially outer surface substantially continuous.

[0127] The adjustment linkage 17 is actuated by an adjustment shaft 18, which is coaxial with the central shaft 2, arranged inside the central shaft 2 and rotatable about the geometric axis x. A rolling bearing 19 is radially interposed between the adjustment shaft 18 and the central shaft 2 to allow relative rotation between the adjustment shaft 18 and the central shaft 2.

[0128] The adjustment shaft 18 includes a first threaded portion 20 and a second threaded portion 21 having respective threads with opposite threads (one right-handed and the other left-handed). The two threaded portions each extend from a middle portion of the adjustment shaft 18 and extend axially away from the middle portion ( Figure 5 ).

[0129] A corresponding internally threaded first and second carriages 22, 23 engage on each of the two threaded sections 20, 21. Rotation of the adjustment shaft 18 relative to the carriages 22, 23 results in screwing the first carriage 22 into the corresponding threaded section and screwing the second carriage 23 out of the corresponding threaded section, and subsequently in displacement of the two carriages 22, 23 in opposite axial directions. The corresponding lateral deposition surfaces 3, 4 are connected to the first and second carriages 22, 23. Thus, the first and second sectors 5, 6 are connected to the first and second carriages 22, 23, respectively, so as to be able to move axially together with the carriages 22, 23.

[0130] In particular, a respective bracket 16 connected to a respective crown 14 is mounted on each carriage 22, 23. As described above, a respective series of first sectors 5 or second sectors 6 is connected to each crown 14.

[0131] In order to allow the carriages 22 , 23 to move axially without interfering with the central shaft 2 , the central shaft 2 comprises an opening 24 for each bracket 16 . Figure 4 The openings 24 and the brackets 16 are shown. As shown, the openings 24 have an axial extension and are radially penetrated by the brackets 16, so that the brackets 16 emerge from the openings 24 and can be constrained to the corresponding crown 14. The openings 24 also function to lock the relative rotation between the carriages 22, 23 and the threaded portions 20, 21 of the adjustment shaft 18. To this end, the circumferential dimension of each opening 24 is substantially equal to the circumferential dimension of the bracket portion 16 that passes through the opening 24 itself.

[0132] As can be seen above, by rotating the adjustment shaft 18 relative to the central axis 2 in a first angular direction, the two carriages 22, 23 are axially displaced towards each other by the threaded portions 20, 21 of the adjustment shaft 18 and are forced not to rotate with the adjustment shaft 18 by the engagement of the respective brackets 16 in the openings 24. The two carriages axially move the crown 14 to which the first and second sectors 5, 6 are constrained, moving them towards each other and reducing the axial dimension of the forming drum 1.

[0133] By rotating the adjustment shaft 18 in a second angular direction relative to the central axis 2, opposite to the first angular direction, the two carriages 22, 23 are displaced axially away from each other by the movement of the threaded portions 20, 21 of the adjustment shaft 18 and are forced not to rotate with the adjustment shaft 18 by the engagement of the respective brackets 16 in the openings 24. The two carriages axially move the crown 14 to which the first and second sectors 5, 6 are constrained, moving them away from each other and increasing the axial dimension of the forming drum 1.

[0134] The forming drum 1 comprises an actuating device 25 fixedly connected to the adjusting shaft 18. As shown in the figures, the actuating device 25 is arranged at an axial end of the adjusting shaft 18 and projects axially from the central shaft 2. The actuating device 25 has the purpose of allowing a rotational movement to be transmitted to the adjusting shaft 18. In a preferred embodiment of the invention, the actuating device 25 has a substantially conical shape so as to be engageable by an external moving device, such as a spindle.

[0135] On the axially opposite side with respect to the actuating device 25, the forming drum comprises a supporting device 40. The supporting device 40 is rotatably constrained to the central shaft 2 and is configured to transmit a rotational movement to the central shaft 2. In this connection, the supporting device has a substantially conical shape so as to be engageable by an external moving device, such as a spindle.

[0136] The support device 40 comprises at least one first pair of coupling elements 41, which are preferably diametrically opposed and are configured to be engaged by an external mobile device. As an example, the first pair of coupling elements 41 can be made of grooves configured to be engaged by keys of an external mobile device.

[0137] Similarly, the actuating device 25 includes at least one second pair of coupling elements 42, preferably diametrically opposed, configured to be engaged by an external mobile device. As an example, the second pair of coupling elements 42 can be made of grooves configured to be engaged by a key of an external mobile device.

[0138] Operating on the actuating device 25 is at least one locking device 26 (at Figure 5 and 6 ), the locking device 26 can be moved between a first state and a second state, in which the locking device 26 prevents the actuating device 25 from rotating relative to the central axis 2 and in which the locking device 26 allows relative rotation between the actuating device 25 and the central axis 2.

[0139] When the locking device 26 is in the first state, the central shaft 2 rotates together with the adjustment shaft 18, preventing the possibility of an axial movement of the two lateral deposition surfaces 3, 4.

[0140] In a preferred embodiment of the present invention, when the locking device 26 is in a first state, the locking device 26 rotatably couples the adjustment shaft 18 and the central shaft 2. In the first state of the locking device 26, the forming drum 1 generally rotates about the geometric axis X during the tire building process. When the locking device 26 is in a second state, the central shaft 2 rotates relative to the adjustment shaft 18, actuating the axial movement of the two lateral deposition surfaces 3, 4. In the second state of the locking device 26, the forming drum 1 is in the process of changing its axial dimension.

[0141] When in the first state, the locking device 26 defines a plurality of locking positions for the actuating device 25, in each of which the central shaft 2 is locked from rotation relative to the adjustment shaft 18. In each of the locking positions, the adjustment shaft 18 occupies a predetermined angular position relative to the central shaft 2. Thus, depending on the locking position reached, the carriages 22, 23 occupies a predetermined axial position along the adjustment shaft 18, the predetermined axial position corresponding to a predetermined axial dimension of the forming drum 1.

[0142] The locking positions are angularly spaced apart by a predetermined and constant angular distance, so that any two consecutive locking positions are angularly spaced apart by the same angular distance. Thus, two positions of the carriages 22, 23 along the adjustment shaft 18 corresponding to two consecutive locking positions are axially spaced apart by a predetermined amount. In other words, two consecutive locking positions correspond to two axial dimensions of the forming drum that are separated from each other by a predetermined amount.

[0143] Specifically, the distance separating the position of the first carriage 22 in one locked position from the position of the first carriage 22 in the next locked position is proportional to the thread pitch of the first threaded portion 20 of the adjustment shaft 18 and is proportional to the relative rotation of the rotary shaft 18 relative to the central shaft 2. Similarly, the distance separating the position of the second carriage 23 in one locked position from the position of the second carriage 23 in the next locked position is proportional to the thread pitch of the second threaded portion 21 of the adjustment shaft 18 and is proportional to the relative rotation of the rotary shaft 18 relative to the central shaft 2. The distance between the position of the first carriage 22 in one locked position and the position of the first carriage 22 in the next locked position is equal to the distance between the position of the second carriage 23 in one locked position and the position of the second carriage 23 in the next locked position. The distance between the position of the first carriage 22 in any locked position and the position of the first carriage 22 in the next locked position is always the same. In a preferred embodiment of the invention, the distance separating the position occupied by the first carriage 22 in any locking position from the position occupied by the first carriage 22 in the next locking position is between 2 and 5 mm, even more preferably 2.5 mm.

[0144] In order to transfer between the two locking positions, the locking device 26 must be arranged in the second state, so as to allow a relative rotation between the central shaft 2 and the adjusting shaft 18 .

[0145] like Figure 6 As shown, the locking device 26 comprises at least one first locking element 27 connected to the actuating device 25 and at least one second locking element 28 connected to the central shaft 2 .

[0146] The first locking element 27 and the second locking element 28 are configured to interact with each other to allow the adjustment shaft 18 to rotate relative to the central shaft 2 and to prevent the adjustment shaft 18 from rotating relative to the central shaft 2. Specifically, when the locking device 26 is in the first state, the first locking element 27 and the second locking element 28 engage with each other, and when the locking device 26 is in the second state, the first locking element 27 and the second locking element 28 do not engage with each other.

[0147] In a preferred embodiment of the present invention, the second locking element 28 comprises a pin 29 which is constrained to rotate with the central shaft 2. The pin 29 is axially movable relative to the central shaft 2 between a stopped state in which the pin 29 engages the first locking element 27 and a released state in which the pin 29 does not engage the first locking element 27. The pin 29 is partially inserted into a housing seat 30 formed in the central shaft 2. The housing seat 30 is formed by a blind axial hole 30a open at the axial end of the central shaft 2 ( Figure 7 ).

[0148] like Figure 6 As shown, pin 29 includes a head 31 connected to a rod 32. Head 31 is disposed at a first axial end of rod 32, and a resilient element 33 is provided at a second axial end of the rod. Resilient element 33 is, for example, a linear spring. Rod 32 and resilient element 33 are inserted into housing seat 30 of central shaft 2, with head 31 axially exposed from housing seat 30. The resilient element 33 axially pushes rod 32 toward the outlet of housing seat 30. Head 31 is equipped with an appendage 31a extending radially inward.

[0149] The first locking element 27 comprises a seat 34 in the actuating device 25, which seat 34 can be engaged by the head 31 of the pin 29. Figure 6 As shown, a seat 34 is formed on the annular portion 35 of the actuating device 25. The shape of the seat 34 in the actuating device 25 matches the appendage 31a of the head 31 so that the appendage 31a can be received in the seat 34.

[0150] In the preferred embodiment of the present invention, there are two locking devices 26, each equipped with a first locking element 27 and a second locking element 28. Figure 6As shown, the two second locking elements 28 are spaced 180° apart, in other words, they are arranged at diametrically opposite positions on the central axis 2. Similarly, the two first locking elements 27 are spaced 180° apart, in other words, they are arranged at diametrically opposite positions on the actuating device 25.

[0151] In order to change the axial dimension of the forming drum 1 , the rotation of the drum is stopped and the forming drum is preferably not moved from the position it occupies on the production line.

[0152] In this case, the locking device 26 is in a locked position in the first state, in other words in a state in which the adjustment shaft 18 rotates with the central shaft 2 as a unit.

[0153] The locking device 26 is thus arranged in the second state, in which the adjustment shaft 18 can be rotated relative to the central shaft 2 .

[0154] In order to bring the locking device 26 into the second state, a force is exerted on the head 31 of the second locking element 28, causing the corresponding pin 29 to increase its penetration into the housing seat 30 compared to the elastic element 33. The appendage 31 a of the head 31 thus disengages from the seat 34 of the first locking element 27 formed in the actuating device 25, releasing the adjustment shaft 18 from rotating as a unit with the central shaft 2.

[0155] At this point, the adjustment shaft 18 (or central shaft 2) is rotated and the rotation of the central shaft 2 (or adjustment shaft 18) is locked, thereby obtaining relative rotation between the adjustment shaft 18 and the central shaft 2. The force applied to the head 31 can be stopped 179° before the final angular position of the mechanism because the head 31 is no longer aligned with the seat 34 and therefore cannot reengage the seat 34 and lock the mutual rotation between the adjustment shaft 18 and the central shaft 2.

[0156] As described above, the rotation of the adjustment shaft 18 relative to the central shaft 2 determines the axial displacement of the two carriages 22, 23, which are moved towards or away from each other (depending on the relative direction of rotation between the adjustment shaft 18 and the central shaft 2) by the threaded portions 20, 21 of the adjustment shaft 18 and are forced not to rotate with the adjustment shaft 18 by the engagement of the corresponding brackets 16 in the openings 24. The two carriages 22, 23 axially move the crown 14 to which the first and second sectors 5, 6 are constrained, moving them apart and increasing (or decreasing) the axial dimension of the forming drum 1.

[0157] The relative rotation between the adjustment shaft 18 and the central shaft 2 continues until the head 31 is again aligned with the seat 34. When alignment occurs, the elastic element 33 returns the appendix 31a of the head 31 to engagement in the seat 34 of the actuating device 25, locking the adjustment shaft 18 in rotation with the central shaft 2 in the new and subsequent locked position.

[0158] In the preferred embodiment described, the new and subsequent locking position is reached after a relative rotation of 180° between the adjustment shaft 18 and the central shaft 2. This relative rotation corresponds to a displacement of the two lateral deposition surfaces 3, 4 towards each other (or apart) by 2.5 mm.

[0159] Obviously, the number of locking devices 26 and their mutual positioning can be chosen according to the specific operating requirements of the forming drum, just as the amount of movement of the two lateral depositing surfaces 3, 4 together and apart between two consecutive locking positions can be chosen according to the specific operating requirements of the forming drum.

[0160] The invention has been described with reference to some preferred embodiments. Various modifications may be made to the embodiments described above while still falling within the scope of protection of the invention as defined by the appended claims.

Claims

1. A method for controlling the geometry of a forming drum (1) for producing wheel tyres, comprising: Arranging the central shaft (2) concentrically with the geometric axis of rotation (X) of the forming drum; Arranging two lateral deposition surfaces (3, 4) radially outside the central shaft (2) and axially opposite to each other, and rotatably coupling the central shaft (2) to the two lateral deposition surfaces (3, 4); Arranging an adjustment shaft (18) coaxially with the central shaft (2) and rotatable relative to the central shaft (2), and coupling the two lateral deposition surfaces (3, 4) to the adjustment shaft (18); constructing the adjustment shaft (18) such that a rotation of the adjustment shaft (18) relative to the central axis (2) corresponds to an axial displacement of the two lateral deposition surfaces (3, 4); at least one set of a plurality of predetermined locking positions is arranged between the adjustment shaft (18) and the central shaft (2), wherein the adjustment shaft (18) is rotationally constrained to the central shaft (2), and wherein each locking position corresponds to a relative predetermined angular position between the adjustment shaft (18) and the central shaft (2); The adjustment shaft (18) is rotated relative to the central shaft (2), wherein: The rotation of the adjustment shaft (18) relative to the central shaft (2) is actuated from a locked position until another locked position is reached.

2. The method according to claim 1, wherein The relative rotation between the adjustment shaft (18) and the central shaft (2) occurs by the same angular amount between two successive locking positions.

3. The method according to claim 1 or 2, wherein: Starting from the locking position, when the adjusting shaft (18) and the central shaft (2) are relatively rotated 360 degrees, another locking position is reached.

4. The method according to claim 1 or 2, wherein: Each 360° relative rotation between the adjustment shaft (18) and the central shaft (2) is blocked in at least two locking positions.

5. The method according to claim 1 or 2, wherein: Rotating the adjustment shaft (18) relative to the central shaft (2) includes releasing the adjustment shaft (18) from the locked position.

6. The method according to claim 1 or 2, wherein: Relative rotation between the adjustment shaft (18) and the central shaft (2) is achieved by locking the adjustment shaft (18) and rotating the central shaft (2).

7. The method according to claim 1 or 2 includes arranging at least one first locking device (26) operating on the adjusting shaft (18) between a first state and a second state, wherein in the first state, the first locking device prevents the adjusting shaft (18) from rotating relative to the central shaft (2), and in the second state, the first locking device allows the adjusting shaft (18) to rotate relative to the central shaft (2).

8. The method according to claim 7, wherein: Starting from a locking position performed by the at least one first locking device (26), upon a relative rotation of 360° between the adjustment shaft (18) and the central shaft (2), another locking position performed by the same at least one first locking device (26) is reached.

Images