PROCESS AND APPARATUS FOR BUILDING TYRES

Abstract

The invention is related to a process and an apparatus for building tyres. In the process a carcass sleeve (11) comprising at least one carcass ply (3) and a pair of annular anchoring structures (5) is transferred to a shaping drum (14) comprising flange elements (16a, 16h) that are each engageable to one of said annular anchoring structures (5). The carcass sleeve (11) is shaped according to a toroidal configuration by means of mutual axial approaching of the flange elements (16a, 16b). Before shaping, annular grip elements (36) respectively carried by the flange elements (16a, 16b) are radially expanded each inside one of the annular anchoring structures (5) in order to engage the carcass sleeve (11). The annular anchoring structures (5) are moved axially apart from each other before engaging the carcass sleeve (11) by means of the annular grip elements (36).

Claims

1. Process for building tyres comprising: transferring a carcass sleeve (11) comprising at least one carcass ply (3) and a pair of annular anchoring structures (5) to a shaping drum (14) comprising flange elements (16a, 16b) that are each engageable to one of said annular anchoring structures (5); shaping the carcass sleeve (11) according to a toroidal configuration by means of mutual axial approaching of the flange elements (16a, 16b); wherein, before shaping, annular grip elements (36) respectively carried by said flange elements (16a, 16b) are radially expanded, each inside one of said annular anchoring structures (5) in order to engage the carcass sleeve (11); wherein the annular anchoring structures (5) are moved axially apart from each other before engaging the carcass sleeve (11) by means of the annular grip elements (36).

2. Process as claimed in claim 1, wherein moving the annular anchoring structures (5) axially apart comprises: positioning at least one abutment member (37) against an axially inner side of each annular anchoring structure (5); axially moving the abutment members (37) respectively engaged with each annular anchoring structure (5).

3. Process as claimed in claim 2, wherein axially moving the abutment members (37) comprises translating the flange elements (16a, 16b) carrying said abutment members (37).

4. Process as claimed in claim 2 or 3, wherein positioning the abutment members (37) comprises: arranging the abutment members (37) according to a contracted condition, wherein each abutment member (37) defines a maximum diameter size (D2) less than an internal diameter (D1) of each annular anchoring structure (5); axially inserting, in the carcass sleeve (11), the abutment members (37) in the contracted condition; expanding the abutment members (37) to a radially expanded condition wherein each abutment member (37) defines a maximum diameter size (D2) greater than the internal diameter (D1) of each annular anchoring structure (5).

5. Process as claimed in one or more claims 2 to 4, wherein the axial insertion of the abutment members (37) in the carcass sleeve (11) occurs by axially translating the abutment members (37) in mutual approaching from the outside towards the interior of the annular anchoring structures (5).

6. Process as claimed in one or more preceding claims, wherein engaging the carcass sleeve (11) to the shaping drum (14) comprises positioning the carcass sleeve (11) substantially in axial alignment relation between the flange elements (16a, 16b), before moving the annular anchoring structures (5) axially apart.

7. Process as claimed in claim 6, wherein positioning the carcass sleeve (11) comprises radially translating the carcass sleeve (11) in order to insert it between the mutually spaced flange elements (16a, 16b).

8. Process as claimed in claim 7, wherein radially translating the carcass sleeve (11) is actuated by means of a carcass handling device (34) operating externally on the carcass sleeve (11).

9. Process as claimed in claims 2 and 8, further comprising retaining the carcass sleeve (11) by means of the carcass handling device (34) during the positioning of the abutment members (37) in the annular anchoring structures (5).

10. Process as claimed in claim 2 and 8 or 9, further comprising disengaging the carcass handling device (34) from the carcass sleeve (11) after the insertion of the abutment members (37) in the annular anchoring structures (5).

11. Process as claimed in claim 2 and one or more claims 8 to 10, further comprising disengaging the carcass handling device (34) from the carcass sleeve (11) before axially moving the abutment members (37) in order to actuate the axial moving apart of the annular anchoring structures (5).

12. Process as claimed in one or more claims 2 to 11, further comprising axially inserting the annular grip elements (36) in the annular anchoring structures (5) simultaneously with the axial insertion of the abutment members (37) in the carcass sleeve (11).

13. Process as claimed in one or more preceding claims, wherein before transferring the carcass sleeve (11), a toroidal forming drum (25) is engaged with the shaping drum (14), coaxially between said flange elements (16a, 16b).

14. Process as claimed in claim 13, wherein concurrently with transferring the carcass sleeve (11), said carcass sleeve (11) is fit around the toroidal forming drum (25) in a first radially contracted operative condition.

15. Process as claimed in claim 13 or 14, wherein during the shaping of the carcass sleeve (11), the forming drum (25) is radially expanded inside the carcass sleeve (11).

16. Process as claimed in claim 15, wherein the expansion of the forming drum (25) occurs in the absence of contact with the carcass sleeve (11).

17. Process as claimed in one or more claims 13 to 16, wherein at the end of the shaping, the carcass sleeve (11) is released, radially contracting in order to couple inner surfaces thereof in contact relation on outer surfaces of the radially expanded forming drum (25).

18. Process as claimed in one or more claims 13 to 17, wherein at the end of the shaping, the carcass sleeve (11) is released, radially contracting by means of evacuation of an operative inflation fluid of the carcass sleeve (11).

19. Process as claimed in one or more preceding claims, further comprising associating a crown structure (6) in radially outer position with respect to the toroidally shaped carcass sleeve (11).

20. Process as claimed in one or more claims 13 to 19, wherein a crown structure (6) is built on a radially outer surface of said toroidally shaped carcass sleeve (11) associated with said expanded toroidal forming drum (25).

21. Apparatus for building tyres, comprising: carcass loading devices (33) for transferring, to a shaping drum (14), a carcass sleeve (11) comprising at least one carcass ply (3) and a pair of annular anchoring structures (5), wherein said shaping drum (14) comprises flange elements (16a, 16b) that are each engageable to one of said annular anchoring structures (5); shaping devices for shaping the carcass sleeve (11) according to a toroidal configuration by means of mutual axial approaching of the flange elements (16a, 16b); wherein each of said flange elements (16a, 16b) carries at least one radially expandable annular grip element (36) inside one of said annular anchoring structures (5) in order to engage the carcass sleeve (11), and an abutment member (37) that is radially movable with respect to the annular grip element (36) in axially inner position with respect to the latter.

22. Apparatus as claimed in claim 21, wherein said abutment members (37) are axially movable between a mutual approaching condition and a mutual moving-apart condition.

23. Apparatus as claimed in claim 21 or 22, wherein the flange elements (16a, 16b) are mutually interconnected by means of a support structure (17) that is axially outer with respect to the flange elements (16a, 16b) themselves.

24. Apparatus as claimed in one or more claims 21 to 23, wherein each flange element (16a, 16b) is axially movable on command of at least one respective actuator (21) operating between the support structure (17) and the flange element itself.

25. Apparatus as claimed in one or more claims 21 to 24, wherein each abutment member (37) is movable between a contracted condition, in which it defines a maximum diameter size (D2) less than an internal diameter (D1) of each annular anchoring structure (5), and an expanded condition in which it defines a diameter size greater than a diameter size of the respective annular grip element (36).

26. Apparatus as claimed in one or more claims 21 to 25, wherein each abutment member (37) comprises a plurality of circumferentially distributed sectors (38).

27. Apparatus as claimed in claim 26, wherein each sector (38) is slidably guided according to a radial direction with respect to a longitudinal symmetry axis (X-X) of the shaping drum (14).

28. Apparatus as claimed in one or more claims 21 to 27, wherein each flange element (16a, 16b) incorporates at least one fluid-dynamic actuator (40) for determining the radial movement of each abutment member (37) between a contracted condition and an expanded condition.

29. Apparatus as claimed in claim 28, wherein said fluid-dynamic actuator (40) comprises a piston (41) that is axially movable between a first and a second position in order to determine the radial movement of the respective abutment member (37).

30. Apparatus as claimed in claim 29, wherein said piston (41) is axially movable between the second position and a third position in order to carry the respective annular grip element (36) between a contracted condition and an expanded condition.

31. Apparatus as claimed in claim 29 or 30, further comprising first elastic members (49) in order to oppose the movement of the piston (41) from the first to the second position.

32. Apparatus as claimed in one or more claims 29 to 31, further comprising second elastic members (53) in order to oppose the movement of the piston (41) from the second to the third position.

33. Apparatus as claimed in claims 29 and 32, wherein the second elastic members (53) have an elastic constant greater than an elastic constant presented by the first elastic members (49).

34. Apparatus as claimed in one or more claims 21 to 33, wherein each flange element (16a, 16b) is removably fixed to the support structure (17).

35. Apparatus as claimed in one or more claims 28 to 33, wherein each flange element (16a, 16b) has at least one supply connector (42a, 42b) leading to the fluid-dynamic actuator (40).

36. Apparatus as claimed in claim 35, wherein said at least one supply connector (42a, 42b) is connectable to a supply duct (43) carried by the support structure (17).

37. Apparatus as claimed in one or more claims 29 to 36, wherein said piston (41) operates on at least one first thrust element (47) having at least one first thrust wall (47a) acting in abutment against said abutment member (37).

38. Apparatus as claimed in claim 37, wherein said first thrust wall (47a) acts against the abutment member (37) substantially according to a direction that is inclined with respect to a longitudinal symmetry axis (X-X) of the shaping drum (14).

39. Apparatus as claimed in one or more claims 29 to 38, wherein said piston (41) operates on at least one second thrust element (50) having a second thrust wall (50a) acting in abutment against a block (51) that is radially movable inside the respective annular grip element (36).

40. Apparatus as claimed in claim 39, wherein said second thrust wall (50a) acts against the abutment member (37) substantially according to a direction that is inclined with respect to a longitudinal symmetry axis (X-X) of the shaping drum (14).

Description

[0106] Further characteristics and advantages will be clearer from the detailed description of a preferred but not exclusive embodiment of a process and an apparatus for obtaining tyres, in accordance with the present invention. Such description will be set forth hereinbelow with reference to the set of drawings, provided only as a non-limiting example, in which:

[0107] FIG. 1 schematically shows a lay-out of a building apparatus in accordance with the present invention;

[0108] FIG. 2 schematically shows, in side view and in partial section, the loading of a carcass sleeve on a shaping station;

[0109] FIG. 3 schematically shows, in side view and in partial section, flange elements that are mutually approached in order to be arranged for the engagement with the carcass sleeve;

[0110] FIG. 4 shows one of the flange elements in greater detail, during the insertion of abutment members and annular grip elements inside the beads of the carcass sleeve;

[0111] FIG. 5 shows an action subsequent to that represented in FIG. 4, in which the abutment members are expanded inside the carcass sleeve, released in abutment relation against the annular grip elements;

[0112] FIG. 6 shows an action subsequent to that represented in FIG. 5, in which the flange elements are mutually moved apart in order to determine an axial tensioning of the carcass sleeve;

[0113] FIG. 7 shows an action subsequent to that represented in FIG. 6, in which the annular grip elements are radially expanded for determining the engagement of the carcass sleeve;

[0114] FIG. 8 schematically shows, in side view and in partial section, the execution of the shaping of the carcass sleeve;

[0115] FIG. 9 shows the application of a belt layer on the shaped carcass sleeve that is coupled to a forming drum;

[0116] FIG. 10 schematically shows, in radial half-section, a tyre obtainable in accordance with the present invention.

[0117] With reference to the abovementioned figures, reference number 1 overall indicates a plant for building tyres for vehicle wheels, arranged for actuating a process according to the present invention.

[0118] The plant 1 is set for obtaining tyres 2 (FIG. 10) essentially comprising at least one carcass ply 3 preferably internally covered with a layer of impermeable elastomeric material or so-called liner 4. Two annular anchoring structures 5, each comprising a so-called bead core 5a preferably carrying an elastomeric filler 5b in radially outer position, are engaged with respective end flaps 3a of the carcass ply/plies 3. The annular anchoring structures 5 are integrated in proximity to zones “B” normally identified with the term “beads”, at which occurs the engagement between the tyre 2 and a respective mounting rim (not depicted) normally occurs.

[0119] A crown structure 6 preferably comprising a tread band 8 circumferentially superimposed on a belt structure 7, is circumferentially applied around the carcass ply/plies 3.

[0120] Two sidewalls 9, each extended from the corresponding bead “B” to a corresponding lateral edge tread band 8, are applied in laterally opposite positions on the carcass ply/plies 3.

[0121] The plant 1 comprises a carcass building line 10 having one or more building stations 10a where the arrangement of a carcass sleeve 11 having substantially cylindrical shape is executed, for example according to known modes. The carcass sleeve 11 comprises said at least one carcass ply 3, preferably internally covered by the liner 4, and having the respective end flaps 3a engaged, e.g. by means of turning up, with the respective annular anchoring structures 5. If necessary, the carcass sleeve 11 can also comprise the sidewalls 9 or first portions thereof, each extended from a respective bead “B”. The obtainment of the carcass sleeve 11 along the building line 10 can provide for the use of at least one building drum 12 provided with axially spaced shoulders 12a, which act as mechanical reference for the correct positioning of the annular anchoring structures 5, according to a predetermined mutual axial distance “Q”. The carcass building line 10 leads to a shaping station 13 comprising a shaping drum 14 equipped with shaping devices 15, upon whose action the carcass sleeve 11 is shaped according to a toroidal configuration.

[0122] The shaping drum 14 for example comprises a first flange element 16a and a second flange element 16b, coaxially facing each other and which in operation are each engageable at one of the annular anchoring structures 5 respectively carried by the axially opposite ends of the carcass sleeve 11

[0123] The flange elements 16a, 16b are mutually interconnected by means of a support structure 17 that is axially outer with respect thereto. In other words, the support structure 17 supports the flange elements 16a, 16b across from each other, without the axially interposed space between them being occupied by structural elements dedicated to supporting one or both flange elements themselves.

[0124] The support structure 17 can comprise at least one carriage 18 carrying the first flange element 16a. The carriage 18 is movable along one or more linear guides 19, parallel to a geometric axis of mutual alignment between the flange elements 16a, 16b. In the illustrated example, said geometric axis coincides with a longitudinal symmetry axis X-X of the shaping drum 14. The linear guides 19 are preferably integral with respect to a fixed base 20, carrying the second flange element 16b. The movement of the carriage 18 along the linear guides 19 causes the switching of the shaping station 13 between a loading/unloading condition and a work condition. In the loading/unloading condition (FIG. 2), the first flange element 16a is spaced from the second flange element 16b to a greater extent, approximately at least double, with respect to an axial size of the non-shaped carcass sleeve 11, coming from the carcass building line 10. In the work condition, the flange elements 16a, 16b are mutually spaced to an extent equal to about the axial size of the carcass sleeve 11.

[0125] The shaping devices 15 can for example comprise a fluid-dynamic circuit (not illustrated) for introducing pressurized air or another operative inflation fluid between the flange elements 16a, 16b, inside the carcass sleeve 11. The shaping devices 15 can also comprise one or more actuators, preferably linear actuators 21, operating on one or preferably both flange elements 16a, 16b in order to move them axially towards each other starting from the aforesaid work condition.

[0126] In the illustrated example, the linear actuators 21 operate on respective tubular interconnection elements 22 coaxial with each other and slidably engaged respectively with the carriage 18 and with the base 20, and each carrying one of the flange elements 16a, 16b. The flange elements 16a, 16b can be removably fixed to the support structure 17. For example, each flange element 16a, 16b is removably fixed to one of the tubular interconnection elements 22, at a respective attachment collar 23 radially projecting with respect to a cylindrical base body 24.

[0127] The mutual approaching of the flange elements 16a, 16b upon action of the linear actuators 21 determines a mutual approaching of the annular anchoring structures 5 so as to allow the shaping of the carcass sleeve 11 according to a toroidal configuration, assisted by the simultaneous introduction of the pressurized operative fluid into the carcass sleeve 11. In the shaping station 13, the shaped carcass sleeve 11 can be coupled to a toroidal forming drum 25, rigid and expandable, arranged inside the carcass sleeve 11 itself.

[0128] The forming drum 25 (not illustrated in figures from 4 to 7), is expandable between a first radially contracted operative condition (FIGS. 2 and 3), and a second radially expanded operative condition (FIGS. 8 and 9). For such purpose, the forming drum 25 can comprise a plurality of drum sectors 26 circumferentially distributed around a central shaft 27. The drum sectors 26 are movable, preferably simultaneously with each other, from the aforesaid first operative condition in which they are close to the central shaft 27, to the second operative condition in which said drum sectors 26 are moved away from the central shaft 27. The movement of the drum sectors 26 can be achieved by means of transmission mechanisms 28 driven by a threaded bar 29 extended along the central shaft 27 and carrying two axially opposite threads 30a, 30b, respectively right hand and left hand threads.

[0129] The rotation of the threaded bar 29 in the central shaft 27, for example actuatable by means of a rotary driver 31 operating inside one of the tubular interconnection elements 22, causes a radial movement of the drum sectors 26, towards the first or the second operative condition according to the rotation sense imparted to the threaded bar 29.

[0130] In the second operative condition, the set of drum sectors 26 defines, along the circumferential extension thereof, a toroidal radially outer surface “S”, not necessarily continuous, shaped according to the internal configuration that at least one part of the carcass sleeve 11 must assume at completed shaping. Advantageously, provision can be made such that the forming drum 25 in the second operative condition has a curvature ratio comprised between about 0.15 and about 0.45, typically suitable for obtaining tyres for motorcycles or other two-wheel vehicles. If necessary, however, curvature radiuses can be employed with values lower than those indicated above, e.g. suitable for producing tyres for cars or trucks. Preferably, the forming drum 25 is positioned in the shaping station 13 before the respective carcass sleeve 11, e.g. still being processed along the carcass building line 10, reaches the shaping station 13 itself.

[0131] More particularly, provision is preferably made for the forming drum 25 to be projectingly supported in the shaping station 13. For example, a first end of the central shaft 27 can for such purpose be retained by a mandrel 32 coaxially housed in the first flange element 16a and carrying said rotary driver 31.

[0132] The forming drum 25 can therefore be arranged in the first operative condition by means of the rotary driver 31, if it was not already in such condition upon reaching the shaping station 13.

[0133] By means of carcass loading devices 33, the carcass sleeve 11 coming from the carcass building line 10 is then transferred into the shaping station 13 in order to be coaxially arranged in radially outer position around the forming drum 25 arranged in the first radially contracted operative condition.

[0134] The carcass loading devices 33 can for example comprise a carcass handling device 34 operating preferably on an external surface of the carcass sleeve 11.

[0135] The carcass handling device 34 is radially movable with respect to the flange elements 16a, 16b, in order to reach a release position in which the carcass sleeve 11 is inserted between the flange elements 16a, 16b arranged in the loading/unloading condition (FIG. 2), substantially in axial alignment relation with the flange elements 16a, 16b themselves and with the forming drum 25. The carcass sleeve 11 is subsequently arranged around the forming drum 25, preferably following an axial translation movement of the forming drum 25 itself. More particularly, with a movement of the carriage 18 along the linear guides 19, the forming drum 25 is coaxially inserted in the carcass sleeve 11. Preferably, the translation of the carriage 18 and the forming drum 25 terminates with the engagement of a second end of the central shaft 27 with a tailstock 35, situated inside the second flange element 16b (dashed line in FIG. 2). For the purpose of the engagement of the carcass sleeve 11, each flange element 16a, 16b comprises a radially expandable annular grip element 36, and an abutment member 37 that is radially movable with respect to the annular grip element 36, in an axially inner position with respect to the latter.

[0136] In the illustrated example, each abutment member 37 comprises a plurality of circumferentially distributed sectors 38. Each sector 38 is slidably guided according to a radial direction with respect to the longitudinal symmetry axis X-X of the shaping drum 14. More particularly, in the illustrated example each sector 38 has a base portion 38a slidably guided along a first guide column 39 radially projecting from the cylindrical base body 24. One end of the base portion 38a, axially inner with respect to the respective flange element 16a, 16b, carries an abutment plate 38b oriented according to a plane that is substantially radial with respect to the longitudinal symmetry axis X-X.

[0137] Each flange element 16a, 16b incorporates at least one fluid-dynamic actuator 40. The fluid-dynamic actuator 40 can for example comprise a piston 41, preferably annular, engaged around the cylindrical base body 24 and axially slidable with respect to the latter. The piston 41 delimits, inside the respective flange element 16a, 16b, a first chamber 40a and a second chamber 40b, preferably annular, respectively leading to a first and a second supply connector 42a, 42b separately connectable to a supply duct 43, carried by the support structure 17, for example as schematically indicated in FIG. 5.

[0138] At least one selector 44 switchable between a first and a second operative condition operates on the supply duct 43, in order to selectively connect the latter to a first fluid-dynamic supply line 45a and a second fluid-dynamic supply line 45b, respectively having different supply pressures. For example, the second fluid-dynamic supply line 45b can have a greater supply pressure than the supply pressure of the first fluid-dynamic supply line 45a.

[0139] An auxiliary selector 46 provides to selectively connect the first and the second supply connector 42a, 42b with the supply duct 43, and therefore with one of the fluid-dynamic supply lines, for example the first fluid-dynamic supply line 45a.

[0140] Following the introduction of air or another pressurized operative fluid into the first chamber 40a or into the second chamber 40b of the fluid-dynamic actuator 40, the piston 41 of each flange element 16a, 16b is axially movable between a first position, represented in FIG. 4, and a second position, represented in FIGS. 5 and 6 for determining the radial expansion and contraction movement of the respective abutment member 37. For such purpose, the piston 41 carries first circumferentially distributed thrust elements 47, axially movable upon action of the fluid-dynamic actuator 40 and each having at least one first thrust wall 47a acting in abutment against the abutment member 37, substantially according to a direction that is inclined with respect to the longitudinal symmetry axis X-X of the shaping drum 14. More particularly, each first thrust element 47 carries the respective first thrust wall 47a, substantially wedge-shaped, against a first inclined abutment surface 38c obtained on the base portion 38a of the respective sector 38 of the abutment member 37. The first inclined abutment surface 38c is preferably directed to the side opposite the abutment plate 38b of the respective sector 38.

[0141] Upon action of the respective fluid-dynamic actuators 40, the sectors 38 radially translate, guided by the respective first guide columns 39, switching the abutment members 37 between a contracted condition and an expanded condition. In the contracted condition, each abutment member 37 defines a maximum diameter size “D2” less than an internal diameter “D1” of each annular anchoring structure 5 of the carcass sleeve 11. In the radially expanded condition, the maximum diameter size “D2” of each abutment member 37 is greater than the internal diameter “D1” of each annular anchoring structure 5.

[0142] First elastic members 49, for example comprising traction springs operating between each first guide column 39 and the base portion 38a of the respective sector 38, oppose the movement of each piston 41 from the first to the second position. The elastic reaction exerted overall by the first elastic members 49 is less than the thrust action exerted by the first thrust elements 47 following the supply of the first chamber 40a with the fluid coming from the first fluid-dynamic supply line 45a.

[0143] The piston 41 also carries circumferentially distributed second thrust elements 50, preferably in alternated sequence with respect to the first thrust elements 47. In other words, each second thrust element 50 is circumferentially arranged between two first contiguous thrust elements 47.

[0144] The second thrust elements 50 have respective second thrust walls 50a that are adapted to act against respective blocks 51 that are radially movable inside the annular grip element 36 of the respective flange element 16a, 16b.

[0145] In the illustrated example, the blocks 51 are slidably guided along respective second guide columns 52 radially projecting from the cylindrical base body 24, and each circumferentially inserted between two contiguous sectors 38 of the abutment member 37.

[0146] Each of the second thrust walls 50a can have substantially wedge-shaped configuration, so as to act substantially according to a direction that is inclined with respect to the longitudinal symmetry axis X-X of the shaping drum 14, each against a second inclined abutment surface 51a obtained on the respective block 51.

[0147] The second thrust walls 50a, preferably arranged in axially retreated position with respect to the first thrust walls 47a, are adapted to come into contact against the respective blocks 51 upon reaching the radially expanded condition of the sectors 38 of the abutment member 37, when the piston 41 is in the second position as exemplified in FIGS. 5 and 6.

[0148] With a further axial advancement of the piston 41 from the second position, the second thrust elements 50 cause a simultaneous radial moving apart of the blocks 51.

[0149] Each annular grip element 36, made of elastomeric material and substantially counter-shaped with respect to the respective annular anchoring structure 5 carried by the carcass sleeve 11, has a continuous circumferential extension, and circumscribes the blocks 51 preferably in contact relation therewith.

[0150] The radial movements of the blocks 51 following the axial translation of the piston 41 between the second position and a third position, carry the respective annular grip elements 36 between a radially contracted condition, in which they have a maximum diameter size smaller than internal diameter “D1” of each annular anchoring structure 5, and a radially expanded condition, in which they are adapted to act in thrust relation, each against one of the annular anchoring structures 5, as exemplified in FIG. 7.

[0151] Preferably, the movement of the piston 41 from the second to the third position occurs in contrast to second elastic members 53. Such second elastic members 53 can for example be obtained from the same annular grip elements 36. In the illustrated example, the second elastic members 53 comprise second traction springs operating between each second guide column 52 and the respective block 51.

[0152] Provision is made for the second elastic members 53 to have an elastic constant greater than the elastic constant presented by the first elastic members 49. More particularly, the elastic resistance produced by the second elastic members 53 is greater than the action exerted by the first thrust elements 47 following the supply of the first chamber 40a with the fluid coming from the first fluid-dynamic supply line 45a.

[0153] Consequently, following the activation of the fluid-dynamic actuator 40 with the pressurized fluid coming from the first fluid-dynamic supply line 45a, the piston 41 translates from the first position, being stopped in the second position when the second thrust elements 50 abut against the respective blocks 51.

[0154] The movement of the piston 41 towards the third position only occurs following the introduction of the operative fluid at greater pressure, coming from the second fluid-dynamic supply line 45b.

[0155] As is visible in FIGS. 3 and 4, at the end of the axial movement of the carriage 18, the flange elements 16a, 16b are each positioned close to one of the annular anchoring structures 5 integrated in the beads “B”, in axially outer position with respect to the latter, while the carcass sleeve 11 is retained by the carcass handling device 34.

[0156] The annular grip elements 36 and the abutment members 37 of both flange elements 16a, 16b are arranged in radially contracted condition, with the respective pistons 41 in the first position.

[0157] Upon action of the linear actuators 21, the flange elements 16a, 16b are axially moved close to each other, translating the abutment members 37 in mutual approaching, until an axial insertion of the abutment members 37 themselves in the carcass sleeve 11 is determined, each from the outside towards the interior of the respective annular anchoring structure 5. Simultaneously, the annular grip elements 36 are inserted inside the annular anchoring structures 5, substantially in radial alignment relation with the same.

[0158] Upon action of the selector 44, the first chamber 40a of each fluid-dynamic actuator 40 is placed in communication with the first fluid-dynamic supply line 45a. Consequently each piston 41 translates from the first to the second position, carrying the respective abutment member 37 in the expanded condition. The stop of the second thrust elements 50 against the respective blocks 51, retained in contracted position by the second elastic members 53, stops the travel of the piston 41 in the second position.

[0159] When the abutment members 37 have reached the expanded condition, the carcass handling device 34 can disengage the carcass sleeve 11 and be moved away from the shaping station 13. The carcass sleeve 11 is then released in abutment relation against the abutment members 37.

[0160] In this situation, the difference between the internal diameter D1 of each annular anchoring structure 5 and the minimum diameter of the respective annular grip element 36 is lower than the difference detectable between the maximum diameter size “D2” of the abutment member 37 and said internal diameter D1. Consequently, the abutment plates 38b of each abutment member 37 face opposite the axially inner sides of the respective annular anchoring structures 5, along the entire circumferential extension thereof.

[0161] A new action of the linear actuators 21 causes a mutual axial moving apart of the flange elements 16a, 16b and therefore of the abutment members 37.

[0162] The abutment plates 38b of the abutment members 37 come into contact against the axially inner sides of the respective annular anchoring structures 5, along the entire circumferential extension thereof. With the continuation of the action of the linear actuators 21, the action of the abutment members causes a mutual axial moving apart of the annular anchoring structures 5, with consequent axial extension of the carcass sleeve 11, while the annular grip elements 36 remain in contracted condition.

[0163] Preferably, the action of the linear actuators 21 is controlled such that the axial moving apart of the abutment members 37 terminates upon reaching an axial distance between the annular anchoring structures 5 corresponding to the mutual axial distance “Q” defined on the building drum 12. In other words, at the end of the action of axial moving apart, the mutual distance between the abutment members 37, and more precisely between the respective abutment plates 38b, is equal to the distance between the shoulders 12a arranged on the building drum 12.

[0164] By means of the selector 44 operating on the supply duct 43, the first chamber 40a of the fluid-dynamic actuator 40 in each of the flange elements 16a, 16b is then placed in fluid communication with the second fluid-dynamic supply line 45b.

[0165] The consequent introduction of operative fluid at greater pressure overcomes the resistance offered by the second elastic members 53, enabling the translation of the piston 41 towards the third position.

[0166] Consequently, the blocks 51 radially translate away from the longitudinal symmetry axis X-X causing the radial expansion of the respective annular grip elements 36. Each annular grip element 36 is therefore carried in engagement relation with the carcass sleeve 11, inside the respective annular anchoring structure 5. More particularly, the annular grip element 36 hermetically and sealingly engages the respective annular anchoring structure 5, exerting a radial thrust action from the interior towards the outside.

[0167] The carcass sleeve 11 is thus stably constrained to the flange elements 16a, 16b.

[0168] During the shaping, when the carcass sleeve 11 starts to be radially expanded, the radial expansion of the forming drum 25 can be driven by means of rotation of the threaded bar 30 upon action of the rotary driver 31.

[0169] The shaping of the carcass sleeve 11 is preferably executed in the absence of contact between the latter and the forming drum 25, at least until the forming drum 25 itself has reached the maximum radial expansion, upon reaching the second operative condition thereof.

[0170] Upon reaching a predetermined maximum value of the diameter size of the carcass sleeve 11, the introduction of the operative fluid inside the carcass sleeve 11 is interrupted, along with the axial approaching of the flange elements 16a, 16b upon action of the linear actuators 21, immediately before or at the same time as the completion of the radial expansion of the forming drum 25.

[0171] Hence the coupling is enabled between the carcass sleeve 11 and the forming drum 25. Such coupling occurs by carrying an inner surface of the carcass sleeve 11 in contact relation against the radially outer toroidal surface “S” of the forming drum 25.

[0172] The coupling can be actuated following a slight radial contraction of the carcass sleeve 11, for example obtained due to an elastic contraction thereof following the evacuation of the preceding operative fluid introduced during the shaping.

[0173] Upon completed coupling, the flange elements 16a, 16b disengage the carcass sleeve 11, leaving it on the forming drum 25.

[0174] For such purpose, upon action of the auxiliary selector 46, in each flange element 16a, 16b the second chamber 40b of the fluid-dynamic actuator 40 is connected to the supply duct 43, and consequently to one of the first and second fluid-dynamic supply line 45a, 45b, in order to drive the axial retreat of the piston 41 towards the first position. The abutment members 37 and the annular grip elements 36 are consequently carried back into respective contracted conditions.

[0175] Carcass sleeve 11 and forming drum 25 in mutual coupling relation are adapted to be transferred to a crown building area 54, which is remote with respect to the shaping station 13, in order to form or apply the crown structure 6 in radially outer position with respect to the shaped carcass sleeve 11. For such purpose, while the forming drum 25 remains supported by the mandrel 32, the tailstock 35 is disengaged from the central shaft 27. With a retreat of the first flange element 16a, the shaping station 13 is carried back into the loading/unloading condition, freeing the access to an anthropomorphous first robotic arm 55 or other suitable transfer devices, which in turn engage the forming drum 25 at the second end of the central shaft 27, previously freed from the tailstock 35.

[0176] The first robotic arm 55 transfers the forming drum 25 from the shaping station 13 to the crown building area 54. The first robotic arm 55 is also adapted to suitably move the forming drum 25 in front of the belt layer building device 56, which for example can comprise a distributor that supplies at least one rubber-covered cord or another continuous elongated reinforcement element made of textile or metallic material. A belt layer 7a is therefore obtained by winding said continuous elongated element according to circumferential coils 57 axially approached around the radially outer surface of the carcass sleeve 11 coupled to the forming drum 25, while the latter is driven in rotation and suitably moved by the first robotic arm 55.

[0177] In the crown building area 54, devices 58 can if necessary operate for building auxiliary layers 7b, to be applied on the carcass sleeve 11 before or after the application of said at least one belt layer 7a. In particular, such auxiliary layers 7b can comprise parallel textile or metal cords, arranged according to an inclined orientation with respect to the circumferential extension direction of the carcass sleeve 11, respectively crossed between auxiliary layers 7b that are adjacent to each other.

[0178] The transfer of the forming drum 25 between the auxiliary layer building devices 58 and the belt layer building device 56 can be assigned to the same first robotic arm 55, or to an anthropomorphic second robotic arm or to a handling device of another type.

[0179] The forming drum 25 is then transferred to tread band obtainment devices 59.

[0180] The tread band obtainment devices 59 can for example comprise a first spiralling unit configured to wind at least one continuous elastomeric elongated element according to circumferential coils, that are axially adjacent in mutual contact, in radially outer position around the belt structure 7, while the forming drum 25 is driven in rotation and suitably moved in order to distribute the circumferential coils according to a predefined scheme.

[0181] The plant 1 can finally comprise devices for obtaining sidewalls (not illustrated) against axially opposite lateral portions of the carcass sleeve 11.

[0182] The built green tyre 2 is adapted to be removed from the forming drum 25 in order to be moulded and vulcanised in a moulding and vulcanising unit.