Method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels

Abstract

A method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels, comprises: i) dispensing a continuous elongated element (23) onto a forward branch of a conveyor belt (49) until a head of the continuous elongated element (23) is brought to said building drum (15); ii) stopping the head while continuing to dispense the continuous elongated element (23) and progressively deforming the forward branch into a zigzag shape, lengthening it, to accumulate the continuous elongated element (23) while the head remains still; iii) advancing the head, applying it on the building drum (15) and at least partially winding the continuous elongated element (23) on the building drum (15) by rotating the building drum (15). During winding, the continuous elongated element (23) is dispensed with a dispensing speed (Ve) lower than a peripheral speed (Vp) of the building drum (15) and the deformation of the forward branch is progressively reduced to at least partially compensate for a difference between the dispensing speed (Ve) and the peripheral speed (Vp).

Description

[0001] Method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels

[0002] DESCRIPTION

[0003] Technical field of the invention

[0004] The present invention refers to a method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels. In particular, the present invention refers to the deposition in one or more coils of a continuous elongated element made of elastomeric material onto a building drum for the purpose of making components of a green tyre.

[0005] Definitions

[0006] With the term “elastomeric material”, it is intended a composition comprising at least one elastomeric polymer and at least one reinforcement filler. Such composition can also comprise additives, such as crosslinking agents and / or plasticisers. Due to the presence of the crosslinking agents, the elastomeric material can be crosslinked by heating so as to form the final manufactured product.

[0007] By “elongated element” it is intended an element in which one dimension is greater than the remaining ones, i.e. a strip-shaped element preferably provided with a flattened section. Preferably said elongated element is only made of elastomeric material.

[0008] The terms “radial” and “axial” and the expressions “radially inner / outer” and “axially inner / outer” are used with reference to the radial direction of the tyre / of the building drum (i.e. to a direction perpendicular to the geometric rotation axis of the tyre / of the building drum) and to the axial direction of the tyre / of the building drum (i.e. to a direction parallel to the geometric rotation axis of the tyre / of the building drum).

[0009] The terms “circumferential” and “circumferentially” are used with reference to the annular extension of the tyre / of the building drum. A radial plane of the tyre / of the building drum contains the rotation axis thereof.

[0010] The expressions “low”, “under”, “lower” or “on the lower part”, and “high”, “above”, “upper” or “on the upper part” are used to indicate a relative position of one element with respect to another, respect to the level of the ground. State of the art

[0011] A tyre for vehicle wheels generally comprises a carcass structure associated with a belt structure. The carcass structure comprises at least one carcass ply having axially opposite end flaps engaged with respective anchoring annular structures integrated in zones normally identified with the name "beads". The carcass structure is associated with the belt structure which comprises one or more belt layers situated radially superimposed with respect to each other and with respect to the carcass ply. In radially outer position with respect to the belt structure, a tread band made of elastomeric material is applied, as are other semifinished products constituting the tyre. On the lateral surfaces of the carcass structure, each extended from one of the lateral edges of the tread band up to the respective anchoring annular structure, respective sidewalls are also applied, in axially outer position. The building of a green tyre is generally performed by assembly of respective semifinished products on one or more building drums in order to form the components of such tyre. Several of such components can be obtained by depositing a semifinished product defined by a continuous elongated element, e.g. dispensed by an extruder, in a circumferential sense and according to one or more coils onto a building drum while the latter is rotated around a respective rotation axis. Following the building of the green tyre, a moulding and vulcanisation treatment is executed aimed to determine the structural stabilisation of the tyre, by crosslinking the elastomeric material as well as imparting a desired tread design on the tread band.

[0012] The document EP1033236A2 illustrates, for example, an apparatus for manufacturing elastomeric tyre components. Such apparatus comprises an extruder for extruding green elastomeric material and forming an elongated element, a winding drum around which the elongated element made of elastomeric material is wound, a conveyor for conveying the elongated element made of elastomeric material towards the winding drum. The conveyor comprises a conveyor belt wound around rollers. The conveyor belt has a side on which the elongated element is positioned and transported. The conveyor comprises a storage section with variable capacity in which the conveyor belt is articulated. The document KR20200037992A illustrates an apparatus for forming a cover layer by winding a cord on a tyre structure arranged on a drum, in which the apparatus comprises a cord feeder, a buffer and a winder.

[0013] Documents US2009025857A1 , US2024190676A1 , US2009178757A1 illustrate devices for feeding materials in tapes or strips.

[0014] Summary

[0015] In such context, the Applicant has observed that the quality of the tyres produced by deposition of continuous elongated elements depends, among various factors, also on how the continuous elongated element is managed and manipulated (conveyed and possibly stored) after its manufacturing, before being placed on the building drum, i.e. during the continuous transport from a dispenser towards said building drum.

[0016] The Applicant has observed that, if the continuous elongated element is deformed during transport, the built tyre might not be in accordance with the design specifications and tyres of a same model produced in series may result different from each other.

[0017] The Applicant has in particular observed that the process of loading the continuous elongated element at the start of the building of a series of tyres or in the action that takes place between the building of one tyre and the next can be critical since an initial portion of the continuous elongated element (termed head) intended to be applied first on the building drum can be deformed due to the separation from the already-deposited elongated element and / or if it is retained by rollers placed downstream of the extruder, as can for example occur in the apparatus illustrated in EP1033236A2, during the machine stop and awaiting the start or restart of the production. The deformed head can in fact generate non-uniform ities in the component of the built tyre obtained by the subsequent section of continuous elongated element deposited on the building drum.

[0018] The Applicant has observed that the abovementioned drawbacks are more considerable if the continuous elongated element is formed by only elastomeric material.

[0019] In such context, the Applicant has then set as objective that of obtaining that the continuous elongated element possesses the design geometric characteristics once deposited on the building drum, therefore keeping such characteristics even during the transport from the dispenser to the building drum, thus obtaining the design characteristics in the finished tyre in a repeatable manner.

[0020] The Applicant has perceived that the use of a device for storing the continuous elongated element placed between a dispenser of the continuous elongated element and an applicator of the same onto a building drum and the action of loading the aforesaid storage device are rather important for the purpose of resolving the abovementioned problems.

[0021] More precisely the Applicant has perceived that the use of a storage device and a loading thereof lacking manipulations, allow attaining the solutions of the aforesaid problems with repeatability and efficiency.

[0022] The Applicant has finally found that by providing for a blocking in position of one head of the continuous elongated element in proximity to the point of application of the same on the building drum, while the same continuous elongated element dispensed by the dispenser loads the storage device, non-uniform ities and twisting of the continuous elongated element itself are reduced, allowing the obtainment of design parameters of the continuous elongated element and of the components built therewith and hence of the entire tyre during the subsequent building steps.

[0023] In accordance with one aspect thereof, the present invention relates to a method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels.

[0024] The method comprises: i) dispensing a continuous elongated element onto a forward branch of a conveyor belt until a head of the continuous elongated element is brought to said building drum while the forward branch extends between a dispenser of the continuous elongated element and an applicator of said continuous elongated element on the building drum.

[0025] The method comprises: ii) stopping the head of the continuous elongated element at the applicator while continuing to dispense the continuous elongated element and progressively deforming the forward branch into a zigzag shape, lengthening it, to accumulate the continuous elongated element while said head remains still.

[0026] The method comprises: iii) advancing the head, applying it on the building drum and at least partially winding the continuous elongated element on said building drum by rotating the building drum.

[0027] During winding, the continuous elongated element is dispensed with a dispensing speed lower than a peripheral speed of the building drum and the deformation of the forward branch is progressively reduced to at least partially compensate for a difference between the dispensing speed and the peripheral speed.

[0028] The present description also illustrates an apparatus for depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels.

[0029] The apparatus comprises a dispenser configured for dispensing a continuous elongated element.

[0030] The apparatus comprises an applicator operatively active on the building drum and configured for applying the continuous elongated element on said building drum.

[0031] The apparatus comprises an variable capacity storage device interposed between the dispenser and the applicator and configured for supporting and guiding the continuous elongated element.

[0032] The variable capacity storage device comprises a plurality of rollers and a conveyor belt engaged with said rollers.

[0033] The conveyor belt defines a closed loop path comprising a forward branch provided between the dispenser and the applicator and a return branch provided between the applicator and the dispenser.

[0034] One face of the conveyor belt is configured for supporting and conveying the continuous elongated element along the forward branch and between an inlet and an outlet of said forward branch.

[0035] The variable capacity storage device comprises an actuator.

[0036] The variable capacity storage device comprises a support structure.

[0037] The variable capacity storage device comprises a carriage mounted on the support structure.

[0038] The actuator is connected to the carriage in order to move said carriage with respect to the support structure and along a translation direction.

[0039] The plurality of rollers comprises: a first fixed set of rollers mounted on the support structure, a second fixed set of rollers mounted on the support structure, a first movable set of rollers mounted on the carriage and a second movable set of rollers mounted on the carriage.

[0040] The conveyor belt defines the forward branch while passing in contact with the rollers of the first fixed set of rollers and with the rollers of the first movable set of rollers. The conveyor belt defines the return branch while passing in contact with the rollers of the second fixed set of rollers and with the rollers of the second movable set of rollers.

[0041] The carriage is movable between a first position, in which a straight line tangent to an upper lateral surface of the rollers of the first movable set of rollers lies on a side of a straight line tangent to a lower lateral surface of the rollers of the first fixed set of rollers opposite the second movable set of rollers, and at least one second position, in which both the first movable set of rollers and the second movable set of rollers are positioned between the first fixed set of rollers and the second fixed set of rollers.

[0042] The apparatus can be configured for actuating the method according to the invention.

[0043] The Applicant deems that the present invention allows improving the quality of the tyres produced, keeping the adherence to the design specifications and the uniformity of the characteristics of the tyres of a series and of a same model, so that by operating according to the present invention the elongated element keeps the design characteristics while it transits from the dispenser towards the building drum and once deposited on the building drum itself.

[0044] The present invention, in the aforesaid aspect, can have one or more of the preferred features which are described hereinbelow.

[0045] Preferably, once the deposition on the building drum has been completed, the method comprises: iv) stopping the rotation of the building drum and stopping a portion of the continuous elongated element placed at the applicator while continuing to dispense the continuous elongated element.

[0046] Preferably, the method comprises: progressively deforming the forward branch in said zigzag shape, lengthening it, to accumulate the continuous elongated element while said portion of the continuous elongated element remains still.

[0047] Preferably, once the deposition on the building drum has been completed, the method comprises: v) separating a segment of the continuous elongated element placed on the building drum from the rest of the continuous elongated element lying on the forward branch while said portion of the continuous elongated element is stopped and rotating said building drum in order to deposit the aforesaid segment. Preferably, after action v), actions iii), iv) and v) are repeated cyclically. The Applicant has verified that the above-described actions allow interrupting the deposition, in order to change the building drum or to deposit a segment of the continuous elongated element on another portion of the same building drum, without having to stop the dispensing of material from the dispenser. In this manner, accumulations of material downstream of the extruder are not formed, together with the consequent generation of non-uniform ities in the continuous elongated element produced.

[0048] Preferably, the conveyor belt is engaged with a plurality of rollers and defines a closed loop path comprising the forward branch between the dispenser and the applicator and a return branch between the applicator and the dispenser.

[0049] Preferably, progressively deforming the forward branch comprises: moving some of the rollers between a first configuration, in which the forward branch has a first length, and at least one second configuration, in which the forward branch has a zigzag shape and a second length greater than the first length.

[0050] Preferably, each of the rollers freely rotates around an axis thereof.

[0051] Preferably, the plurality of rollers comprises: a first fixed set of rollers mounted on a support structure, a second fixed set of rollers mounted on the support structure.

[0052] Preferably, the plurality of rollers comprises: a first movable set of rollers mounted on a carriage and a second movable set of rollers mounted on the carriage.

[0053] The first fixed set and the second fixed set of rollers are termed “fixed” in the sense that the axes of the rollers are fixed with respect to the support structure. The first movable set of rollers and the second movable set of rollers are termed “movable” in the sense that the axes of the rollers are fixed with respect to the carriage and thus are moved together with said carriage and with respect to the support structure. Preferably, each of the rollers of the first fixed set of rollers freely rotates around an axis thereof.

[0054] Preferably, each of the rollers of the second fixed set of rollers freely rotates around an axis thereof.

[0055] Preferably, each of the rollers of the first movable set of rollers freely rotates around an axis thereof.

[0056] Preferably, each of the rollers of the second movable set of rollers freely rotates around an axis thereof. Preferably, the conveyor belt defines the forward branch while passing in contact with the rollers of the first fixed set of rollers and with the rollers of the first movable set of rollers.

[0057] Preferably, the conveyor belt defines the return branch while passing in contact with the rollers of the second fixed set of rollers and with the rollers of the second movable set of rollers.

[0058] Preferably, moving some of the rollers between the first configuration and said at least one second configuration comprises: translating the carriage with respect to the support structure.

[0059] Preferably, the carriage is translated along a vertical direction.

[0060] Preferably, the conveyor belt is engaged with a first motorised roller located at a mouth of the dispenser.

[0061] Preferably, the conveyor belt is engaged with a second motorised roller located at the applicator.

[0062] Preferably, action i) is performed by rotating the first motorised roller with a first angular speed corresponding to a first linear speed of the conveyor belt placed at the first motorised roller.

[0063] Preferably, action i) is performed by rotating the second motorised roller with a second angular speed corresponding to a second linear speed of the conveyor belt placed at the second motorised roller.

[0064] Preferably, the first linear speed is equal to the second linear speed.

[0065] Preferably, the first linear speed and the second linear speed are comprised between 0.01 m / s and 1 m / s.

[0066] Preferably, action ii) is performed by stopping the second motorised roller and continuing to rotate the first motorised roller.

[0067] Preferably, action ii) is performed by rotating the first motorised roller with a first angular speed corresponding to the first linear speed.

[0068] Preferably, the first linear speed is comprised between 0.01 m / s and 1 m / s.

[0069] Preferably, action iii) is performed by rotating the first motorised roller with a first angular speed and the second motorised roller with a second angular speed such that the first linear speed is less than the second linear speed.

[0070] Preferably, action iv) is performed by stopping the second motorised roller and keeping the first motorised roller rotating.

[0071] Preferably, during action iii), the dispensing speed is less than the first linear speed. Preferably, the dispensing speed is comprised between 0.001 m / s and 0.3 m / s.

[0072] Preferably, during action iii), a ratio between first linear speed and the dispensing speed is greater than 1 to generate a first stretching of the continuous elongated element.

[0073] Preferably, said ratio between first linear speed and the dispensing speed is comprised between 1 and 2.

[0074] Preferably, during action iii), the peripheral speed is greater than the second linear speed.

[0075] Preferably, the peripheral speed is comprised between 0.5 m / s and 4 m / s.

[0076] Preferably, during action iii), a ratio between the peripheral speed and the second linear speed is greater than 1 to generate a second stretching of the continuous elongated element.

[0077] Preferably, said ratio between the peripheral speed and the second linear speed is comprised between 0.8 and 1.5.

[0078] Preferably, the dispenser is an extruder.

[0079] Preferably, a mouth of the dispenser is positioned at the inlet on the forward branch and the applicator is positioned at the outlet of forward branch.

[0080] Preferably, a distance between two successive rollers of the first fixed set of rollers is greater than a diameter of the rollers of the first movable set of rollers.

[0081] Preferably, the distance between two successive rollers of the first fixed set of rollers is comprised between 0.03 m and 0.1 m.

[0082] Preferably, the diameter of the rollers of the first movable set of rollers is comprised between 0.02 m and 0.08 m.

[0083] Preferably, by moving the carriage between the first position and said at least one second position, the rollers of the first movable set of rollers at least partially pass between the rollers of the first fixed set of rollers.

[0084] Preferably, the support structure comprises a first support frame having a plurality of projections arranged along an edge thereof and directed towards the carriage. Preferably, the projections of the first support frame are directed downward.

[0085] Preferably, each of the rollers of the first fixed set of rollers is carried by a respective projection of the first support frame.

[0086] Preferably, the carriage has a plurality of projections arranged along an edge thereof and directed towards the first support frame.

[0087] Preferably, the projections of the carriage are directed upward. Preferably, each of the rollers of the first movable set of rollers is carried by a respective projection of the carriage.

[0088] Preferably, when the carriage is in the first position, the projections of the carriage are positioned between the projections of the first support frame.

[0089] Preferably, the support structure comprises a second support frame spaced from the first support frame and carrying the second fixed set of rollers.

[0090] Preferably, the support structure has the shape of a column provided with a guide and the carriage is engaged with said guide.

[0091] Preferably, at least part of the rollers of said plurality engaged with the forward branch has a lateral surface provided with a circumferential groove shaped for housing the continuous elongated element.

[0092] Preferably, the rollers of the first movable set of rollers have said circumferential groove.

[0093] The groove allows housing the continuous elongated element carried by the conveyor belt, keeping it in design conditions.

[0094] Preferably, each of the rollers of said plurality has two lateral shoulders for laterally retaining the conveyor belt.

[0095] Preferably, the groove is interposed between the two lateral shoulders.

[0096] Preferably, the groove is equidistant from said two lateral shoulders.

[0097] Preferably, the forward branch is positioned above the return branch.

[0098] Preferably, the face of the conveyor belt configured for supporting the continuous elongated element is directed upward while it moves along the forward branch.

[0099] Preferably, the continuous elongated element lies between the conveyor belt and each of the rollers of the first movable set of rollers.

[0100] Preferably, when the carriage is in the first position, the dispenser and the applicator are aligned with each other and with the forward branch.

[0101] Preferably, when the carriage is in the first position, the forward branch is rectilinear. Preferably, the variable capacity storage device comprises a first motorised roller located at the dispenser.

[0102] Preferably, the variable capacity storage device comprises a second motorised roller located at the applicator.

[0103] Preferably, the conveyor belt is partially wound around the first motorised roller and the second motorised roller.

[0104] Preferably, the first motorised roller is synchronised with the dispenser. Preferably, a dispensing speed of the continuous elongated element from the dispenser is correlated with a first linear speed of the conveyor belt placed at the first motorised roller.

[0105] Preferably, the second motorised roller is synchronised with the building drum.

[0106] Preferably, a peripheral speed of the building drum is correlated with a second linear speed of the conveyor belt placed at the second motorised roller.

[0107] Preferably, the dispensing speed is less than the first linear speed to generate a first stretching of the continuous elongated element.

[0108] Preferably, the peripheral speed is greater than the second linear speed to generate a second stretching of the continuous elongated element.

[0109] Preferably, the apparatus comprises a control unit.

[0110] Preferably, the control unit is operatively connected to the first motorised roller.

[0111] Preferably, the control unit is operatively connected to the second motorised roller. Preferably, the control unit is operatively connected to the actuator.

[0112] Preferably, the control unit is configured for controlling the first linear speed and the second linear speed in an independent manner.

[0113] Preferably, the control unit is configured for commanding the actuator as a function of a difference between the first linear speed and the second linear speed.

[0114] Preferably, the apparatus comprises an inlet drive belt placed at the entrance of the forward branch.

[0115] Preferably, the inlet drive belt has a portion facing the forward branch in order to press the continuous elongated element exiting from the dispenser.

[0116] Preferably, the inlet drive belt is moved with a speed equal to the first linear speed. Preferably, the inlet drive belt forms a closed loop wound on two rollers.

[0117] Preferably, the apparatus comprises an outlet drive belt placed at the outlet of the forward branch.

[0118] Preferably, the outlet drive belt has a portion facing the forward branch in order to press the continuous elongated element before the deposition on the building drum. Preferably, the outlet drive belt is moved with a speed equal to the second linear speed.

[0119] Preferably, the outlet drive belt forms a closed loop wound on two rollers.

[0120] Preferably, the apparatus comprises a cutting device configured for cutting the continuous elongated element. Preferably, the cutting device is positioned at the outlet of the forward branch and upstream of the applicator.

[0121] Preferably, the cutting device is operatively connected to the control unit.

[0122] Preferably, a section of the forward branch close to the outlet is rectilinear both when the carriage is in the first position and when the carriage is in said at least one second position.

[0123] Preferably, the cutting device is located at said section of the forward branch close to the outlet.

[0124] Preferably, the applicator comprises a presser roller having a lateral surface facing a lateral surface of the building drum.

[0125] Preferably, the apparatus comprises a blower located at the outlet of the forward branch.

[0126] Preferably, the blower is oriented for accompanying the continuous elongated element towards the building drum.

[0127] Preferably, a section of the forward branch close to the inlet is rectilinear both when the carriage is in the first position and when the carriage is in said at least one second position.

[0128] Preferably, the apparatus also comprises a monitoring device configured for detecting at least one parameter of the continuous elongated element arranged on said section of the forward branch close to the inlet.

[0129] Preferably, the monitoring device comprises an optical sensor or ultrasound sensor. Preferably, in the first position of the carriage, the forward branch has a first length e, in said at least one second position of the carriage, the forward branch has a zigzag shape and a second length.

[0130] Preferably, the second length is greater than the first length.

[0131] Preferably, the return branch has a zigzag shape both in the first position of the carriage and in said at least one second position of the carriage.

[0132] Preferably, a length of the return branch in the first position is greater than a length of the return branch in said at least one second position.

[0133] Preferably, a total length of the conveyor belt is comprised between 4 m and 40 m. Preferably, in the first position of the carriage, the first length of the forward branch is comprised between 1 m and 3 m.

[0134] Preferably, in said at least one second position, the carriage is positioned between the first fixed set of rollers and the second fixed set of rollers. Preferably, in the first position, the first movable set of rollers lies at least partially on a side of the first fixed set of rollers opposite the second movable set of rollers. Preferably, in said first position, the first movable set of rollers lies completely on a side of the first fixed set of rollers opposite the second movable set of rollers.

[0135] Preferably, in the first position, the rollers of the first movable set of rollers at least partially lie between the rollers of the first fixed set of rollers.

[0136] Further characteristics and advantages will be more evident in the detailed description of preferred but not exclusive embodiments of a method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels, according to the present invention.

[0137] Description of the drawings

[0138] Such description will be set forth hereinbelow with reference to the enclosed drawings, provided only as a non-limiting example, in which: figure 1 illustrates a top schematic view of a plant for making tyres for vehicle wheels; figure 2 shows a schematic three-dimensional view of an apparatus for depositing a continuous elongated element onto a building drum according to the method of the present invention and belonging to the plant of figure 1 ; figure 3 is an enlarged view of a portion of the apparatus of figure 2; figures 4, 5 and 6 are side elevation views of the apparatus of figure 2 in respective operative configurations; figure 4A illustrates an enlarged view of a portion of figure 4; figure 7 illustrates an element of the apparatus pursuant to the preceding figures; figure 8 is a detail of the apparatus of figures 2 and 3; figure 9 shows a sectional perspective view of an example of a continuous elongated element; figure 10 is a radial half-section of a tyre for vehicle wheels attained with the plant of figure 1 .

[0139] Detailed description

[0140] With reference number 1 in figure 10, a tyre for vehicle wheels is overall indicated which essentially comprises a carcass structure 2 having two carcass plies 3a, 3b. A layer of impermeable elastomeric material or so-called liner 4 is applied inside the carcass plies 3a, 3b. Two anchoring annular structures 5, each comprising a so- called bead core 6a carrying an elastomeric filler 6b in radially outer position, are engaged with respective end flaps of the carcass ply or plies 3a, 3b. The anchoring annular structures 5 result integrated in proximity to zones normally identified with the name "beads" 7, at which there is normally the engagement between the tyre 1 with a respective mounting rim, not illustrated. A belt structure 8 comprising one or more belt layers 9a, 9b is circumferentially applied around the carcass plies 3a, 3b, and a tread band 10 is circumferentially superimposed on the belt structure 8. Associated with the belt structure 8 are so-called "under-belt inserts" 11 , each located between the carcass plies 3a, 3b and one of the axially opposite end edges of the belt structure 8. Two sidewalls 12, each extended from the corresponding bead 7 to a corresponding lateral edge of the tread band 10, are applied in axially opposite positions on the carcass plies 3a, 3b.

[0141] The abovementioned components of the tyre 1 are made in a building plant 13, schematically illustrated as an example in figure 1.

[0142] The plant 13 comprises a carcass building line 14, at which building drums 15 are moved between different semifinished product dispensing stations 16 arranged to form, on each building drum 15, a carcass sleeve comprising the carcass plies 3a, 3b, the liner 4, the anchoring annular structures 5, and possibly at least one part of the sidewalls 12.

[0143] Simultaneously, in an external sleeve building line 17, one or more auxiliary building drums 18 are sequentially moved between different work stations 19 arranged to form, on each auxiliary building drum 18, an external sleeve, comprising the underbelt inserts 11 , the belt structure 8, the tread band 10, and possibly at least one part of the sidewalls 12.

[0144] The plant 1 also comprises an assembly station 20 at which the external sleeve is coupled to the carcass sleeve, in order to define the built green tyre 1 .

[0145] Of course, plants of different configuration, not illustrated herein, can be employed for building the green tyre 1 .

[0146] The built green tyres 1 are finally transferred to at least one shaping, moulding and vulcanisation unit 21 .

[0147] In at least one of the work stations 16 of the carcass building line 14 an apparatus 22 is provided for depositing continuous elongated elements 23 on the building drums 15. Such apparatus 22 is illustrated in figures 2-8 and is used for example for depositing the “under-belt inserts” 11 , i.e. a segment of a continuous elongated element 23 wound at least once for 360° around the building drum 15 defines one of the two "under-belt inserts" 11 of figure 10.

[0148] The apparatus 22 comprises a dispenser 24 configured for dispensing a respective continuous elongated element 23. The dispenser 24 is for example an extruder, which can be of known type and therefore is not described in detail herein. The enclosed figures illustrate a head of the extruder 24 provided with a mouth 24A from which the continuous elongated element 23 is dispensed. The continuous elongated element 23, an exemplifying embodiment thereof being illustrated figure 9, is formed only by elastomeric material.

[0149] The apparatus 22 comprises an applicator 25 operatively active onto a building drum 15 and configured for applying the continuous elongated element 23 on the building drum 15 while said building drum 15 is supported and rotating around a rotation axis “X-X” thereof by a dedicated mechanism, e.g. a robotic arm, not illustrated. The illustrated applicator 25 comprises a presser roller 26 which has a lateral surface thereof facing a lateral surface 27 of the building drum 15. The presser roller 26 is carried by an actuator 28 configured for moving the presser roller 26 between a work position (figure 4), in which the presser roller 26 lies in proximity to the lateral surface 27 of the building drum 15 in order to press the continuous elongated element 23 against said lateral surface 27 while the building drum 15 rotates, and a wait position (figures 3, 5, 6, 8), in which the presser roller 26 is spaced from the building drum 15.

[0150] The apparatus 22 also comprises an variable capacity storage device 29 which lies interposed between the dispenser 24 and the applicator 25 and is configured for supporting and guiding the continuous elongated element 23 from the mouth 24A of the dispenser 24 up to the presser roller 26 and to the building drum 15.

[0151] The variable capacity storage device 29 comprises a support structure 30 which has, for example, the shape of a vertical column.

[0152] A carriage 31 is engaged with a guide of the support structure 30 and an actuator or motor, not illustrated, is connected to the carriage 31 in order to move said carriage 31 with respect to the support structure 30 and along a vertical translation direction “V”. The carriage 31 is shaped as a plate and has a face on which the following are mounted: a first movable set 32 of rollers 33 and a second movable set 34 of rollers 33. The rollers 33 of the first movable set 32 are arranged along a respective horizontal row. The rollers 33 of the second movable set 34 are arranged along a respective horizontal row located in a lower position with respect to the first movable set 32 of rollers 33.

[0153] Each of the rollers 33 of the first movable set 32 and of the second movable set 34 is free to rotate around an axis thereof “Y-Y” perpendicular to the abovementioned face of the carriage 31 . In particular, in the embodiment illustrated in figure 7, each of the rollers 33 of the first movable set 32 and of the second movable set 34 comprises a radially outer portion 35 mounted by bearings 37 on a small shaft 36 fixed to the face of the carriage 31 .

[0154] In addition, the carriage 31 has a plurality of projections 38 arranged along an upper edge thereof and each of the projections 38 carries one of the rollers 33 of the first movable set 32 (figure 4).

[0155] The variable capacity storage device 29 comprises a first support frame 39 and a second support frame 40 fixed to the support structure 30. The first support frame 39 is positioned higher than the second support frame 40 and is spaced from the second support frame 40.

[0156] The first support frame 39 is shaped as a plate and has a face on which a first fixed set 41 of rollers 42 is mounted. The first support frame 39 has a plurality of projections 43 arranged along a lower edge thereof and each of the projections 43 carries one of the rollers 42 of the first fixed set 41 . The projections 43 of the first support frame 39 are directed downward and towards the carriage 31 , the projections 38 of the carriage 31 are directed towards the first support frame 39. The rollers 42 of the first fixed set 41 are arranged along a respective horizontal row.

[0157] The second support frame 40 is shaped as a plate and has a face on which a second fixed set 44 of rollers 42 is mounted. The rollers 42 of the second fixed set 44 are arranged along a respective horizontal row.

[0158] Each of the rollers 42 of the first fixed set 41 and of the second fixed set 44 has a structure equal to or similar to that of the rollers 33 of the first movable set 32 and of the second movable set 34 and is therefore free to rotate around an axis thereof “Y-Y” perpendicular to the face of the respective first support frame 39 or second support frame 40.

[0159] The first fixed set 41 and the second fixed set 44 of rollers 42 are termed “fixed” in the sense that the axes “Y-Y” of the rollers 42 are fixed with respect to the support structure 30. The first movable set 32 of rollers 33 and the second movable set 32 of rollers 33 are termed “movable” in the sense that the axes “Y-Y” of the rollers 33 are fixed with respect to the carriage 31 and hence are vertically moved together with said carriage 31 and with respect to the support structure 30.

[0160] The variable capacity storage device 29 comprises a first motorised roller 45 (connected to and rotated by a motor, not illustrated) located at the mouth 24A of the dispenser 24 and interposed between said dispenser 24 and the first fixed set

[0161] 41 of rollers 42. The variable capacity storage device 29 comprises a second motorised roller 46 (connected and rotated by a motor, not illustrated) located at the applicator 25 and interposed between the first fixed set 41 of rollers 42 and said applicator 25. The variable capacity storage device 29 also comprises a first idle return roller 47 positioned at the first motorised roller 45 and a second idle return roller 48 positioned at the second motorised roller 46.

[0162] The variable capacity storage device 29 comprises a conveyor belt 49 engaged with the first motorised roller 45, the rollers 33 of the first movable set 32 and the rollers

[0163] 42 of the first fixed set 41 , the second motorised roller 46, the second idle return roller 48, the rollers 42 of the second fixed set 44, the rollers 33 of the second movable set 34, the first idle return roller 47, so as to define a closed loop path.

[0164] The conveyor belt 49 defines a forward branch while passing in contact with the first motorised roller 45, the rollers 42 of the first fixed set 41 of rollers, the rollers 33 of the first movable set 32 of rollers and the second motorised roller 46. The conveyor belt 49 defines a return branch while passing in contact with the second idle return roller 48, the rollers 42 of the second fixed set 44, the rollers 33 of the second movable set 34, the first idle return roller 47.

[0165] The forward branch extends between an inlet close to the mouth 24A of the dispenser 24 and an outlet close to the applicator 25 and has a rectilinear section close to the inlet followed by an intermediate section engaged with the rollers 33 of the first movable set 32 and with the rollers 42 of the first fixed set 41 and a rectilinear section close to the outlet. The intermediate section of the forward branch is engaged in sequence and alternatively with an upper lateral surface of a roller 42 of the first fixed set 41 and then with a lower lateral surface of a roller 33 of the first movable set 32 and so forth, such to be able to define a zigzag shape when the carriage 31 takes on specific positions, described in more detail below. The return branch extends between said outlet before the applicator 25 and said inlet before the mouth 24A and has an intermediate section engaged with the rollers 33 of the second movable set 34 and with the rollers 42 of the second fixed set 44. The intermediate section of the return branch is engaged in sequence and alternating with a lower lateral surface of a roller 42 of the second fixed set 44 and then with an upper lateral surface of a roller 33 of the first movable set 34 and so forth, in a manner so as to define a zigzag shape.

[0166] The forward branch is extended above the return branch and a face of the conveyor belt 49 is configured for supporting and conveying the continuous elongated element 23 along the forward branch, between the dispenser 24 and the applicator 25.

[0167] The carriage 31 is movable between a first position and at least one second position. Figure 4 illustrates the carriage 31 in the first position. In the illustrated exemplifying embodiment, in the abovementioned first position, the first movable set 32 of rollers completely lies on the side of the first fixed set 41 of rollers opposite the second movable set 34 of rollers. As can be observed in fact, the rollers 33 of the first movable set 32 are positioned above, i.e. at a higher elevation, than the rollers 42 of the first fixed set 41. In addition, the projections 38 of the carriage 31 are positioned between the projections 43 of the first support frame 39.

[0168] In this configuration, the intermediate section of the forward branch of the conveyor belt 49 is horizontal rectilinear and is aligned with the rectilinear section close to the inlet and with the rectilinear section close to the outlet. The dispenser 24 and the applicator 25 are aligned with each other and with the forward branch. In addition, the forward branch has a first length “L1”. The intermediate section of the return branch of the conveyor belt 49 has a zigzag shape.

[0169] In other embodiments, not illustrated but still within the scope of the present invention, when the carriage 41 is in the first position, the first movable set 32 of rollers substantially lies on one side of the first fixed set 41 of rollers opposite the second movable set 34 of rollers, i.e. the rollers 33 of the first movable set 32 of rollers partially lie between the rollers 42 of the first fixed set 41 of rollers.

[0170] A distance between two successive rollers 42 of the first fixed set 41 of rollers is greater than a diameter of the rollers 33 of the first movable set 32 of rollers. For example, the distance between two successive rollers 42 of the first fixed set 41 of rollers is comprised between 0.030 m and 0.1 m and the diameter of the rollers 33 of the first movable set 32 of rollers is comprised between 0.02 m and 0.08 m. More generally, when the carriage 41 is in the first position, a straight line “R1” tangent to a upper lateral surface of the rollers 33 of the first movable set 32 of rollers lies on one side of a straight line “R2” tangent to a lower lateral surface of the rollers 42 of the first fixed set 41 of rollers opposite the second movable set 34 of rollers (figure 4A).

[0171] In the second positions (figures 2, 3, 5 and 6), the carriage 31 is positioned between the first fixed set 41 of rollers and the second fixed set 44 of rollers and both the first movable set 32 of rollers and the second movable set 34 of rollers are positioned between the first fixed set 41 of rollers and the second fixed set 44 of rollers. Figures 2, 3, 5 and 6 illustrate the carriage 41 in different second positions, in which the forward branch of the conveyor belt 49 has a zig-zag shape, as with the return branch. In the second positions, the forward branch has respective second lengths “L2” greater than the first length “L1”. In addition, a length of the return branch in the first position is greater than lengths of the return branch in the second positions. For example, a total length of the conveyor belt 49 is comprised between 4 m and 40 m. In the first position of the carriage 31 , the first length “L1” of the forward branch is comprised between 1 m and 3 m.

[0172] The continuous elongated element 23 dispensed from the mouth 24A of the dispenser 24 is deposited on the face of the conveyor belt 23 at the rectilinear section close to the inlet. As is visible in figure 3, at the rollers 33 of the first movable set 32, the continuous elongated element 23 remains interposed between the conveyor belt 49 and the lateral surface of each roller 33.

[0173] The radially outer portion 35 of each of the rollers 33 of the first movable set 32 therefore has (figure 7) two lateral shoulders 50 in order to laterally retain the conveyor belt 49 and a circumferential groove 51 made in an abutment surface 52 of the radially outer portion 35 delimited by two lateral shoulders 50. The circumferential groove 51 is equidistant from the two lateral shoulders 50 and allows housing the continuous elongated element 23 carried by the conveyor belt 49, and thus the continuous elongated element 23 maintains its design characteristics when it is situated between the conveyor belt 49 and the lateral surface of the rollers 33. The apparatus 22 comprises an inlet drive belt 53 placed at the entrance of the forward branch. The inlet drive belt 53 forms a closed loop wound on two rollers and has a portion facing the section of the forward branch close to the inlet in order to press the continuous elongated element 23 exiting from the dispenser 24. The apparatus 22 also comprises an outlet drive belt 54 placed at the outlet of the forward branch (figure 4). The outlet drive belt 54 forms a closed loop wound on two rollers and has a portion facing the section of the forward branch close to the outlet in order to press the continuous elongated element 23 before the deposition on the building drum 15.

[0174] A monitoring device 55 is operatively active on the section of the forward branch close to the inlet and downstream of the inlet drive belt 53. The monitoring device 55 comprises one or more sensors and is configured for detecting at least one parameter of the continuous elongated element 23 while the latter is arranged on the section of the forward branch close to the inlet. For example, the monitoring device 55 comprises an optical sensor or ultrasound sensor.

[0175] As is better visible in figure 8, a cutting device 56 is positioned at the outlet of the forward branch and upstream of the applicator 25. The cutting device 56 is configured for cutting the continuous elongated element that is situated on the section of the forward branch close to the outlet.

[0176] In addition, a blower 57 (figure 8) is located at the outlet of the forward branch. The blower 57 has a nozzle oriented in a manner such to accompany the continuous elongated element 23 which leaves the conveyor belt 49 towards the building drum 15. The blower is operatively connected for example to a compressed air source, not illustrated.

[0177] The apparatus 22 comprises a control unit 58, schematically illustrated in figure 5, which is operatively connected to the dispenser 24, to the first motorised roller 45, to the second motorised roller 46, to the actuator or motor connected to the carriage 31 , to the actuator 28, to the robotic arm that rotates the building drum 15, to the monitoring device 55, to the cutting device 56 and to the blower 57.

[0178] The control unit 58 and configured for commanding and controlling the apparatus 22 in accordance with a method of depositing the continuous elongated element 23 on the building drum 15 according to the present invention.

[0179] In an initial action (action i)), while the conveyor belt 49 is situated in a first configuration, corresponding to the first position of the carriage 31 illustrated in figure 4, and the forward branch is entirely rectilinear, the dispenser 24 starts to dispense and deposit a head of the continuous elongated element 23 onto the face directed upward of the forward branch, i.e. between the rectilinear section close to the inlet and the inlet drive belt 53. The first motorised roller 45 is synchronised with the dispenser 24, in the sense that a dispensing speed “Ve” of the continuous elongated element 23 from the dispenser 24 is correlated with a first angular speed of the first motorised roller 45 and hence a first linear speed “V1” of the conveyor belt 49 placed at the first motorised roller

[0180] 45. In particular, the dispensing speed “Ve” is less than the first linear speed “V1” to generate a first stretching of the continuous elongated element 23 proportional to a ratio “V17“Ve”, between said first linear speed “V1” and the dispensing speed “Ve”. The inlet drive belt 53 is moved with a speed equal to the first linear speed “V1” since, for example, it is driven by the same conveyor belt 49 or since one of the two rollers on which it is wound is connected to the motor of the first motorised roller 45. While the carriage 31 is maintained in the first position, the second motorised roller 46 is made to rotate with a second angular speed corresponding to a second linear speed “V2” of the conveyor belt 49 placed at the second motorised roller 46. Also the outlet drive belt 54 is moved with a speed equal to the second linear speed “V2” since, for example, it is driven by the same conveyor belt 49 or since one of the two rollers on which it is wound is connected to the motor of the second motorised roller

[0181] 46.

[0182] The first linear speed “V1” is equal to the second linear speed “V2”. In this manner, the forward branch of the conveyor belt 49 translates with “V1” = “V2” and carries the head of the continuous elongated element 23 up to the outlet of the forward branch and to the building drum 15. For example, the first linear speed “V1 ” and the second linear speed “V2” are comprised between 0.01 m / s and 1 m / s.

[0183] At this point (action ii)), the second motorised roller 46 is stopped, so as to stop the head of the continuous elongated element 23 on the rectilinear section close to the outlet, while the dispenser 24 continues to dispense and the first motorised roller 45 continues to rotate and maintain the rectilinear section moving, close to the inlet, with the first linear speed “V1 ”. For example, in this action, the first linear speed “V1 ” is comprised between 0.01 m / s and 1 m / s. Indeed, the control unit 58 is configured for controlling the first linear speed “V1” and the second linear speed “V2” in an independent manner.

[0184] Simultaneously, the carriage 31 is translated downward (figure 5) in a manner such to lengthen the forward branch, progressively deforming it according to a zig-zag shape. In this manner, the continuous elongated element 23 is accumulated on the forward branch while the head remains still on the rectilinear section close to the outlet. While the carriage 31 is moved starting from the first position of figure 4, the rollers 33 of the first movable set 32 of rollers pass between the rollers 42 of the first fixed set 41 of rollers in order to then be further lowered up to reaching the position of figure 6. In this action, the control unit 58 commands the actuator so that it moves the carriage 31 downward with a respective speed, as a function of the first linear speed “V1” (“V2” = 0).

[0185] Once the carriage 31 has reached the lower position of figure 6, the control unit 58 commands the second motorised roller 46 which advances the head of the continuous elongated element 23 up to bringing it onto the building drum 15, with the help aid of the blower 57. The control unit 58 also commands the robotic arm, which rotates the building drum 15, and the applicator 25 which presses the continuous elongated element 23 against the lateral surface 27 of the building drum 15 or against elements of the tyre 1 already deposited on the building drum 15, in a manner so as to wind the continuous elongated element 23 on the building drum 15 (action iii)).

[0186] During winding, the continuous elongated element 23 is dispensed by the dispenser 24 with a dispensing speed “Ve” lower than a peripheral speed “Vp” of the building drum 15 and the deformation of the forward branch is progressively reduced, lifting the carriage 31 , to at least partially compensate for a difference between the dispensing speed “Ve” and the peripheral speed “Vp”.

[0187] More particularly, the dispensing speed “Ve” is less than or equal to the first linear speed “V1”, to generate the possible first stretching. The second linear speed “V2” is greater than the first linear speed “V1” and the difference between “V1” and “V2” is compensated for by moving the carriage 31 upward with a speed “V” proportional to the difference between “V2” and “V1”.

[0188] The second motorised roller 46 is synchronised with the building drum 15 such that the peripheral speed “Vp” of the building drum 15 is greater than or equal to the second linear speed “V2” in order to confer a possible second stretching to the continuous elongated element 23 just before the deposition (generally “Vp” > “V2” > “V1” > “Ve”). If stretching is not desired, Vp = V2.

[0189] The second stretching of the continuous elongated element 23 is proportional to a ratio “Vp7“V2”, between the peripheral speed “Vp” and the second linear speed For example, the dispensing speed “Ve” is comprised between 0.001 m / s and 0.3 m / s . The peripheral speed “Vp” is comprised between 0.5 m / s and 4 m / s. A ratio between first linear speed and the dispensing speed is comprised between 1 and 2. A ratio between the peripheral speed “Vp” and the second linear speed “V2” is comprised between 0.8 and 1.5 .

[0190] The continuous elongated element 23 is for example wound in at least one single coil for 360° around the building drum 15.

[0191] Once the deposition on the building drum 15 has been completed, the rotation of the building drum 15 is stopped, and also the second motorised roller 46 is stopped so as to stop a portion of the continuous elongated element 23 placed on the rectilinear section close to the outlet. The dispenser 24 continues to dispense and the first motorised roller 45 is maintained rotating with “V1” > “Ve”. Simultaneously, the carriage 31 is once again lowered in order to accumulate the continuous elongated element 23 while the portion of the continuous elongated element 23 on the rectilinear section close to the outlet remains still (action iv)).

[0192] The control unit 58 commands the cutting device 56 that separates a segment of the continuous elongated element 23 placed on the building drum 15 from the rest of the continuous elongated element 23 lying on the forward branch, a brief subsequent rotation of the same building drum 15 allows the deposition of the aforesaid segment (action v)). Optionally, the deposition of the aforesaid segment can also be facilitated by a brief rotation of the second motorised roller 46.

[0193] At this point, the above-described actions iii), iv) and v) can be repeated in order to apply a subsequent segment of the continuous elongated element 23 on a different portion of the same building drum 15 or on a different building drum 15.

Claims

CLAIMS1 . Method of depositing a continuous elongated element onto a building drum in a process for building tyres for vehicle wheels, comprising: i) dispensing a continuous elongated element (23) onto a forward branch of a conveyor belt (49) until a head of the continuous elongated element (23) is brought to said building drum (15) while the forward branch extends between a dispenser (24) of the continuous elongated element (23) and an applicator (25) of said continuous elongated element (23) on the building drum (15); ii) stopping the head of the continuous elongated element (23) at the applicator (25) while continuing to dispense the continuous elongated element (23) and progressively deforming the forward branch into a zigzag shape, lengthening it, to accumulate the continuous elongated element (23) while said head remains still; iii) advancing the head, applying it on the building drum (15) and at least partially winding the continuous elongated element (23) on said building drum (15) by rotating the building drum (15); wherein, during winding, the continuous elongated element (23) is dispensed with a dispensing speed (Ve) lower than a peripheral speed (Vp) of the building drum (15) and the deformation of the forward branch is progressively reduced to at least partially compensate for a difference between the dispensing speed (Ve) and the peripheral speed (Vp).

2. Method according to claim 1 , wherein, once the deposition on the building drum (15) has been completed, the method comprises: iv) stopping the rotation of the building drum (15) and stopping a portion of the continuous elongated element (23) placed at the applicator (25) while continuing to dispense the continuous elongated element (23) and progressively deforming the forward branch into said zigzag shape, lengthening it, to accumulate the continuous elongated element (23) while said portion of the continuous elongated element (23) remains still; v) separating a segment of the continuous elongated element (23) placed on the building drum (15) from the rest of the continuous elongated element (23) lying on the forward branch while said portion of the continuous elongated element (23) is stationary and rotating said building drum (15) for depositing said segment.

3. Method according to claim 2, wherein after action v), actions iii), iv) and v) are repeated cyclically.

4. Method according to one of the preceding claims, wherein the conveyor belt (49) is engaged with a plurality of rollers (33, 42) and defines a closed loop path comprising the forward branch between the dispenser (24) and the applicator (25) and a return branch between the applicator (25) and the dispenser (24); wherein progressively deforming the forward branch comprises: moving some of the rollers (33) between a first configuration, in which the forward branch has a first length (L1 ), and at least one second configuration, in which the forward branch has a zigzag shape and a second length (L2) greater than the first length (L1 ).

5. Method according to claim 4, wherein the plurality of rollers (33, 42) comprises: a first fixed set (41 ) of rollers mounted on a support structure (30), a second fixed set (44) of rollers mounted on the support structure (30), a first movable set (32) of rollers mounted on a carriage (31 ) and a second movable set (34) of rollers mounted on the carriage (31 ); wherein the conveyor belt (49) defines the forward branch while passing in contact with the rollers (42) of the first fixed set (41 ) of rollers and with the rollers (33) of the first movable set (32) of rollers and wherein the conveyor belt (49) defines the return branch while passing in contact with the rollers (42) of the second fixed set (44) of rollers and with the rollers (33) of the second movable set (34) of rollers; wherein moving some of the rollers (33) between the first configuration and said at least one second configuration comprises: translating the carriage (31 ) with respect to the support structure (30).

6. Method according to one of the preceding claims, wherein the conveyor belt (49) is engaged with a first motorised roller (45) located at a mouth (24A) of the dispenser (24) and a second motorised roller (46) located at the applicator (25) and wherein: action i) is performed by rotating the first motorised roller (45) with a first angular speed corresponding to a first linear speed (V1 ) of the conveyor belt (49) placed at the first motorised roller (45) and by rotating the second motorised roller (46) with a second angular speed corresponding to a second linear speed (V2) ofthe conveyor belt (49) placed at the second motorised roller (46), wherein the first linear speed (V1 ) is equal to the second linear speed (V2); action ii) is performed by stopping the second motorised roller (46) and continuing to rotate the first motorised roller (45); action iii) is performed by rotating the first motorised roller (45) with a first angular speed and the second motorised roller (46) with a second angular speed such that the first linear speed (V1 ) is less than the second linear speed (V2).

7. Method according to claim 6 when dependent on claim 2, wherein action iv) is performed by stopping the second motorised roller (46) and keeping the first motorised roller (45) rotating.

8. Method according to one of the preceding claims, wherein during action iii), the dispensing speed (Ve) is less than the first linear speed (V1 ) and a ratio (V1 / Ve) of the first linear speed (V1 ) to the dispensing speed (Ve) is greater than 1 to generate a first stretching of the continuous elongated element (23); and / or wherein the peripheral speed (Vp) is greater than the second linear speed (V2) and a ratio (Vp / V2) of the peripheral speed (Vp) to the second linear speed (V2) is greater than 1 to generate a second stretching of the continuous elongated element (23).

9. Method according to any one of claims 6 to 8, wherein the first linear speed (V1 ) and the second linear speed (V2) are comprised between 0.01 m / s and 1 m / s.

10. Method according to any one of the preceding claims, wherein the dispensing speed (Ve) is comprised between 0.001 m / s and 0.3 m / s.11 . Method according to claim 6, wherein a ratio (V1 / Ve) of first linear speed (V1 ) to the dispensing speed (Ve) is comprised between 1 and 2.

12. Method according to any one of the preceding claims, wherein said peripheral speed (Vp) is comprised between 0.5 m / s and 4 m / s.

13. Method according to claim 6, wherein a ratio (Vp / V2) of the peripheral speed (VP) to the second linear speed (V2) is comprised between 0.8 and 1 .5.

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