Drum for manufacturing a tire and associated process

Abstract

The invention relates to a drum (2) for manufacturing a tire, the drum comprising a shaft (4), a compressed-air flow channel (50) and two gripping modules (5) each provided with: - contact surfaces (16) and retaining grooves (18); - an expansion mechanism (22); and - an elastic membrane (20). The gripping modules (5) are axially movable between: - a folding position in which the contact surfaces (16) can enter into radial contact with the green tire (8), said contact surfaces being located axially between beads (40) of the green tire (8), and - a shaping position in which the retaining grooves (18) are capable of receiving the beads (40).

Description

[0001] DESCRIPTION

[0002] Title of the invention: Tire manufacturing drum and associated process

[0003] technical field

[0004] The invention relates to the manufacture of tires.

[0005] In particular, the invention relates to a tire manufacturing drum comprising axially movable gripping units between a folding position and a forming position, and a method for folding and forming a tire from a tire blank and such a manufacturing drum.

[0006] Previous techniques

[0007] A tire is divided into three distinct zones including a crown which includes a crown reinforcement and a tread intended to come into contact with the ground, beads intended to ensure the grip of the tire on the rim of a wheel, and sidewalls intended to connect the crown to the beads.

[0008] To manufacture a tire, elements in the form of beads, strips, or plies are successively and circumferentially arranged on a manufacturing drum to form a cylindrical tire blank. The element of a tire blank that forms the tire carcass reinforcement is called the carcass ply. The carcass ply is also folded around the beads on this manufacturing drum. This manufacturing drum is generally called a finishing drum. Such a finishing drum is described in document EP 0 953 434 B l.

[0009] Next, a step called bending is performed, which consists of folding or folding the tire beads to ensure a proper fit and seal when the tire is mounted on a rim. This step is carried out on a bending drum. Such a bending drum is described in document EP 1 798 022 A1. Then, the generally cylindrical tire blank is transformed into a toroidal tire blank on another manufacturing drum during a step called forming. During this transformation, the top of the blank is stretched to increase its diameter by pressurizing the volume enclosed by the blank and the drum with air, and the beads of the blank are brought together axially. This other manufacturing drum is generally called a finishing drum. Such a finishing drum is described in document WO 2020 / 128320 A1.

[0010] The invention aims to reduce the costs associated with the manufacture of a tire.

[0011] Description of the invention

[0012] The invention relates to a drum for manufacturing a tire from a tire blank which is provided with two ribs, two sides and a top, the manufacturing drum comprising a barrel extending axially and two tire blank gripping modules which are each movable in axial translation along the barrel, each gripping module being provided:

[0013] - of a tire blank gripping unit comprising a plurality of holding sectors which are arranged circumferentially with respect to each other and which are each provided with a contact surface and a holding groove;

[0014] - of an expansion mechanism configured to move the gripping unit of said gripping module between a position radially close to the barrel and at least one position radially far from the barrel; and

[0015] - of an elastic membrane disposed in the retaining grooves of the gripping unit of said gripping module.

[0016] The elastic membranes of the gripping modules are designed to partially form a sealed chamber through contact with the pneumatic blank. The manufacturing drum also includes at least one compressed air passage between a compressed air source external to the manufacturing drum and the sealed chamber.

[0017] According to a general characteristic, the gripping modules are axially mobile at least between:

[0018] - an axially close position known as the "folding" position, in which the contact surfaces of the gripping units in said radially distant position from the barrel are able to come into radial contact with one of the flanks and / or the top of the tire blank by being located axially between the ridges of the tire blank, and

[0019] - an axially distant position called "conforming" in which the retaining grooves of the gripping units in said radially distant position of the barrel are suitable for receiving the ridges of the tire blank, the axial distance between the retaining grooves of the gripping units being equal to the axial distance between the ridges of the tire blank.

[0020] The gripping units in the radially close position to the barrel allow the pneumatic blank to be placed around the gripping units.

[0021] The gripping units in said position radially away from the barrel allow the pneumatic blank whose inner diameter is equal to the outer diameter of the gripping units in said position radially away from the barrel to be held.

[0022] The gripping units, simultaneously in the axially close folding position and in the radially distant position, are able to hold the tire blank so that the rims of the tire blank extend axially on either side of the gripping units. Thus, an external tool, separate from the manufacturing drum and dedicated to folding, can operate on the rims to perform a folding step.

[0023] This folding step specifically involves folding the carcass ply and a bead protector around the associated bead. This means folding the tire blank element that forms the tire carcass reinforcement and a layer of rubber or composite material around the associated bead to encase it. This step protects the associated bead and ensures a better bond between the different layers of the tire.

[0024] The gripping units, simultaneously in the axially distant shaping position and in the radially distant position, are also capable of holding the tire blank. The air circulation channel then allows the sealed chamber to be pressurized in order to perform a shaping step during which the gripping units move axially closer together to give the tire blank a toroidal shape.

[0025] The axial stroke and axial dimensions of the gripping units therefore make it possible to hold the tire blank, on the one hand, to perform a folding step and, on the other hand, to perform a shaping step, thus reducing the number of tools required for tire manufacturing.

[0026] In other words, with a single manufacturing drum, different steps necessary for the production of the tire can be carried out.

[0027] Advantageously, the axial movement of the gripping modules is symmetrical to each other.

[0028] Optionally, in the axially close folding position, the gripping units are axially in contact with each other.

[0029] Advantageously, the expansion mechanism of each gripping module is configured to move the gripping unit of said gripping module between the radially close position of the barrel and at least the first and second radially distant positions of the barrel, and configured to immobilize the gripping unit of said gripping module at each of the first and second radially distant positions of the barrel.

[0030] The diameter of the gripping unit of said gripping module in the second position radially distant from the barrel is greater than the diameter of the gripping unit of said gripping module in the first position radially distant from the barrel.

[0031] Thus, the manufacturing drum allows the folding and shaping steps to be carried out on tire blanks whose inner diameter is equal to the outer diameter of the gripping units in each of the first and second positions radially distant from the drum.

[0032] Advantageously, the expansion mechanism of each gripping module is configured to move the gripping unit of said gripping module between the position radially close to the barrel and a third position radially far from the barrel, and configured to immobilize the gripping unit of said gripping module in the third position radially far from the barrel, the diameter of the gripping unit of said gripping module in the third position radially far from the barrel being greater than the diameter of the gripping unit of said gripping module in the second position radially far from the barrel.

[0033] Thus, the manufacturing drum allows the folding and shaping steps to be carried out on tire blanks whose inner diameter is equal to the outer diameter of the gripping units in each of the first, second and third positions radially distant from the drum.

[0034] Optionally, the expansion mechanism of each gripping module includes a rotary selector equipped with rotating rings and stops, said rotating rings being capable of being at least in a first immobilizing position of the gripping unit of said gripping module in the first position radially away from the barrel and in a second immobilizing position of the gripping unit of said gripping module in the second position radially away from the barrel.

[0035] Optionally, the rotating rings are capable of being in at least one third immobilizing position of the gripping unit, with the gripping module in the third position radially distant from the barrel. Optionally, the elastic membrane of each gripping unit comprises polyurethane.

[0036] Polyurethane is particularly extensible and allows the chamber to be sealed when the gripping units are at least in the first and second positions radially away from the barrel, and in particular in the first, second and third positions radially away from the barrel.

[0037] Optionally, the expansion mechanism of each gripping module includes an annular cylinder that is mobile in axial translation along the shaft and a plurality of connecting rods that convert the axial movement of the annular cylinder into a radial movement communicated to the holding sectors of the gripping unit of said gripping module.

[0038] Thus, the expansion mechanism of each gripping module is compact, thereby facilitating the arrangement of the pneumatic blank around the gripping units in the radially close position to the barrel.

[0039] Preferably, the radial movement of the holding sectors of the gripping unit of said gripping module is a purely radial movement.

[0040] Advantageously, the expansion mechanism of each gripping module includes a plurality of pneumatic supply channels, each comprising a pneumatic supply hose extending axially in a spiral inside the barrel.

[0041] Thus, the pneumatic supply lines do not clutter the volume outside the manufacturing drum and can follow the movement of the gripping modules.

[0042] The invention also relates to a method for folding and shaping a tire from a tire blank and a manufacturing drum as described above, the method comprising:

[0043] - the positioning of each gripping unit in the axially close folding position and the positioning of the tire blank around the drum so that the sides and / or the top of the tire blank are opposite the contact surfaces of the gripping units and so that the contact surfaces of the gripping units are located axially between the ridges of the tire blank;

[0044] - the displacement of each gripping unit in said position radially away from the barrel so that the contact surfaces of the gripping units are in contact with the sides and / or the top of the tire blank by being located axially between the ridges of the tire blank;

[0045] - the flattening of the tire blank, notably carried out with the external tool to the manufacturing drum which is dedicated to flattening

[0046] - the movement of each gripping unit into the position radially close to the barrel;

[0047] - the positioning of each gripping unit in the axially distant conformation position and the positioning of the tire blank so that the ridges of the tire blank are opposite the retaining grooves of the gripping units;

[0048] - the displacement of each gripping unit into said position radially away from the barrel so that the ridges of the pneumatic blank are in the retaining grooves of the gripping units; and

[0049] - the conformation of the tire blank.

[0050] Advantageously, the shaping of the pneumatic blank includes pressurizing the sealed chamber and axially bringing the gripping units together.

[0051] Optionally, a rotation of at least one of the ribs of the tire blank is carried out during the axial approach of the gripping units by sliding the elastic membrane concerned relative to the holding sectors of the gripping unit concerned.

[0052] Brief description of the drawings The present invention will be better understood upon study of the detailed description of an embodiment, taken by way of non-limiting example and illustrated by the accompanying drawings in which:

[0053] [Fig 1] is a longitudinal cross-sectional view of a manufacturing drum during a folding step according to an example of an embodiment of the invention;

[0054] [Fig 2] is a side view of the manufacturing drum of figure 1 on which the elastic membranes of the drum have not been shown;

[0055] [Fig 3], [Fig 4] and [Fig 5] are cross-sectional views of a rotary selector of the manufacturing drum along axis AA of Figure 1 when the gripping units are respectively in a first, second and third position radially away from the drum;

[0056] [Fig 6] is a cross-sectional view of one of the manufacturing drum gripping units along axis A-A' of Figure 1 when this gripping unit is in the second position radially away from the drum;

[0057] [Fig 7] is a side view of a gripping module of the manufacturing drum of figure 1 during the folding step;

[0058] [Fig 8] is a side view and partly longitudinal section of the manufacturing drum of figure 1 during a shaping step;

[0059] [Fig 9] schematically illustrates a method of folding and shaping a tire according to an example of an embodiment of the invention.

[0060] Detailed description

[0061] Figure 1 represents a longitudinal section of a manufacturing drum 2 of a tire.

[0062] The manufacturing drum comprises a frame (not shown), a drum 4 extending axially from the frame along a longitudinal axis X-X', and two gripping modules 5, each equipped with a gripping unit 6 for a pneumatic blank 8, and which are movable in axial translation along the drum 4. The drum 4 extends from the frame while being movable in rotation about the axis X-X' relative to the frame. Each gripping module 5 is fixed in rotation relative to the drum 4.

[0063] The manufacturing drum 2 also includes means for axially translating the gripping modules 5, for example a motor (not shown), a threaded rod 10 which is located in the barrel 4 and which is driven by the motor so as to be mobile in rotation relative to the frame, and nuts 12 which are provided with transmission fingers and which are capable of converting the rotational movement of the threaded rod 10 into a translational movement of the gripping modules 5.

[0064] Each gripping unit 6 is provided with a plurality of retaining sectors 14 which are arranged circumferentially with respect to each other and which are each provided with a contact surface 16 and a retaining groove 18 distinct from the contact surface 16. The retaining sectors 14 are arranged circumferentially so as to create a continuous ring of sectors in the circumferential direction.

[0065] The retaining grooves 18 of each gripping unit 6 are axially offset on the side of the other gripping unit relative to the contact surfaces 16 of said gripping unit. The retaining grooves 18 of each gripping unit 6 are radially offset inwards relative to the contact surfaces 16 of said gripping unit.

[0066] Each gripping module 5 is equipped with an elastic membrane 20 arranged in the retaining grooves 18 of the gripping unit 6.

[0067] Each elastic membrane 20 is annular and conforms to the shape of the retaining grooves 18 of the associated gripping unit 6, in particular conforms to a bottom of the retaining grooves 18 of the associated gripping unit 6.

[0068] In the example shown, and with reference to Figure 2 on which the elastic membrane 20 and the pneumatic blank 8 have not been shown for reasons of clarity, each retaining sector 14 comprises a first part 14a which is provided with the contact surface 16 and a second part 14b which is provided with the retaining groove 18.

[0069] The retaining sectors 14 are nested together in the circumferential direction. In particular, the first parts 14a are nested together in the circumferential direction and the second parts 14b are nested together in the circumferential direction.

[0070] Alternatively, each retaining sector 14 could comprise a single piece provided with the contact surface 16 and the retaining groove 18.

[0071] Each gripping module 5 is equipped with an expansion mechanism 22 capable of modifying the diameter of the gripping unit 6 of the associated gripping module 5. Each expansion mechanism 22 is capable of moving the associated gripping unit 6 between a position radially close to the barrel 4 and at least one first position radially distant from the barrel 4, in particular between a position radially close to the barrel 4 and at least the first and second positions radially distant from the barrel 4, and more precisely between a position radially close to the barrel 4 and the first, second and third positions radially distant from the barrel 4.

[0072] The outside diameter of the gripping units 6 in the position radially close to the barrel 4 is strictly less than the outside diameter of the gripping units 6 in the first position radially far from the barrel 4, which is itself strictly less than the outside diameter of the gripping units 6 in the second position radially far from the barrel 4, which is itself strictly less than the outside diameter of the gripping units 6 in the third position radially far from the barrel 4.

[0073] Each expansion mechanism 22 is capable of radially immobilizing the associated gripping unit 6 in the radially close position of the barrel 4 and in the first radially distant position of the barrel 4, in particular in the radially close position of the barrel 4 and in the first and second radially distant positions of the barrel 4, and more precisely in the radially close position of the barrel 4 and in the first, second and third radially distant positions of the barrel 4.

[0074] Each expansion mechanism 22 includes an annular cylinder 24 which is arranged circumferentially around the shaft 4 and which is movable in axial translation along the shaft 4, and includes a plurality of connecting rods 26 each connected to the annular cylinder 24 of the associated expansion mechanism 22 and to one of the retaining sectors 14 of the associated gripping unit 6, the connecting rods 26 being able to convert the axial movement of the annular cylinder 24 of the associated expansion mechanism 22 into a purely radial movement communicated to the retaining sectors 14 of the associated gripping unit 6.

[0075] To achieve purely radial movement, each retaining sector 14 of the gripping unit 6 is connected to the annular cylinder 24 of the associated expansion mechanism 22 by a pair of connecting rods 26 of the same length, which are offset axially and radially from each other. One of the connecting rods 26 of the pair of connecting rods 26 is connected to a fixed point 27, which is located radially inside the associated retaining sector 14.

[0076] Each elastic membrane 20 comprises, for example, polyurethane so as to be extensible during the movement of the gripping unit 6 associated with the first, second and third positions radially distant from the barrel 4.

[0077] The ring cylinder 24 is, for example, a pneumatic ring cylinder.

[0078] The expansion mechanism 22 of each gripping module 5 includes at least one first pneumatic supply channel 28a, in particular at least of the first and second pneumatic supply channels 28a, 28b, and more specifically of the first, second and third pneumatic supply channels 28a, 28b, 28c.

[0079] Each of the first, second and third pneumatic supply routes 28a, 28b, 28c includes a pneumatic supply pipe extending axially in a spiral inside the barrel 4. The first pneumatic supply route 28a supplies the annular cylinder 24.

[0080] The second and third pneumatic supply channels 28b, 28c are located radially inside the first pneumatic supply channel 28a.

[0081] With reference to Figures 3 to 5, each expansion mechanism 22 comprises a rotary selector 30 equipped with first and second rotary rings 32, 34 that are axially adjacent and free to rotate relative to each other. The first and second rotary rings 32, 34 each comprise a plurality of stops 32b, 32c, 34a, 34c, respectively, which are of different axial lengths and are suitable for blocking the movement of the associated ring cylinder 24 according to the angular positions of the rotary rings 32, 34, thus preventing radial movement of the associated gripping unit 6. The first and second rotary rings 32, 34 are suitable for being in first, second, and third angular positions.

[0082] In the first angular position (figure 4), the first and second rotating rings 32, 34 immobilize the associated gripping unit 6 in the first position radially away from the barrel 4 by preventing its expansion beyond the first position radially away from the barrel 4. More specifically, the stops 34a of the second rotating ring 34 of the associated rotary selector 30 block the axial movement of the associated annular cylinder 24 when the first and second rotating rings 32, 34 are in the first angular position.

[0083] In the second angular position (figure 3), the first and second rotating rings 32, 34 immobilize the associated gripping unit 6 in the second position radially away from the barrel 4 by preventing its expansion beyond the second position radially away from the barrel 4. More specifically, the stops 32b of the first rotating ring 32 of the associated rotary selector 30 block the axial movement of the associated annular cylinder 24 when the first and second rotating rings 32, 34 are in the second angular position.

[0084] The stops 32b, 32c, 34a, 34c of the first and second rotating rings 32, 34 are arranged in pairs of stops which are radially opposed to each other in order to distribute circumferentially the forces when blocking the axial movement of the associated annular cylinder 24.

[0085] Each rotary selector 30 includes two springs 36 which each act on one of the first and second rotating rings 32, 34 of the associated rotary selector 30 to return them to the second angular position.

[0086] Each rotary selector 30 includes a pneumatic cylinder 37 which is supplied by the second pneumatic channel 28b, and which is capable of acting on the first rotary ring 32 to position the first and second rotary rings 32, 34 of the associated rotary selector 30 in the first angular position, one of the two springs 36 of the associated rotary selector 30 acting against the movement of this pneumatic cylinder 37 so that the first and second rotary rings 32, 34 of the associated rotary selector 30 return to the second angular position when this pneumatic cylinder 37 is no longer supplied by the second pneumatic channel 28b.

[0087] In the third angular position (figure 5), the first and second rotating rings 32, 34 immobilize the associated gripping unit 6 in the third position radially away from the barrel 4 by preventing its expansion beyond the third position radially away from the barrel 4. More specifically, the stops 32c, 34c of the first and second rotating rings 32, 34 of the associated rotary selector 30 block the axial movement of the associated annular cylinder 24 when the first and second rotating rings 32, 34 are in the third angular position.

[0088] Each rotary selector 30 includes another pneumatic cylinder 38 which is supplied by the third pneumatic channel 28c, and which is capable of acting on the second rotary ring 34 to position the first and second rotary rings 32, 34 of the associated rotary selector 30 in the third angular position, the other of the two springs 36 of the associated rotary selector 30 acting against the movement of this other pneumatic cylinder 38 so that the first and second rotary rings 32, 34 of the associated rotary selector 30 return to the second angular position when this other pneumatic cylinder 38 is no longer supplied by the third pneumatic channel 28c.

[0089] Figure 6 illustrates one of the gripping modules 5 of the manufacturing drum 2 whose associated gripping unit 6 is immobilized in the second position radially away from the barrel 4. The associated expansion mechanism 22 includes a plurality of stops 39 (also visible in Figures 1 and 2) distributed circumferentially which are able to come into axial contact with the stops 32b, 32c, 34a, 34c of the first and second rotating rings 32, 34 according to their angular position so as to limit the axial stroke of the associated annular cylinder 24.

[0090] With reference to Figures 7 and 8, the gripping modules 5 are axially mobile between an axially close position, referred to as the "folding" position, and an axially distant position, referred to as the "forming" position. These two positions are defined relative to the tire blank 8, which is equipped with two ridges 40, two sidewalls 42, and a vertex 44. In the axially close folding position, the gripping modules 5 are further apart axially than in the axially distant forming position. The axial movement of the gripping modules 5 is symmetrical to each other.

[0091] The tire blank 8 is generally cylindrical in shape. The inter-bead distance d40 of the tire blank 8 is the axial distance between the two beads 40 of the tire blank 8. The inter-sidewall distance d42 of the tire blank 8 is the axial distance between the two sidewalls 42 of the tire blank 8.

[0092] The seat of the tire blank 8 is the inside diameter of the tire blank 8 measured at the heels of the tire blank 8. The outside diameter of the gripping modules 5, in particular the gripping units 6, when the gripping units 6 are in one of the first, second and third positions radially away from the barrel 4 is equal to the seat of the tire blank 8.

[0093] In the axially close folding position (Figure 7), the contact surfaces 16 of the gripping units 6 in the radially distant position of the barrel 4, whose outer diameter corresponds to the seat of the tire blank 8, are able to come into radial contact with the flanks 42 and / or the top 44 of the tire blank 8 by being located axially between the ridges 40 of the tire blank 8. In particular, in the axially close folding position, the axial distance between the axially outer ends of the contact surfaces 16 of the gripping units 6 is less than the inter-ridge distance d40, and here equal to the inter-flank distance d42, of the tire blank 8.Alternatively, in the axially close folding position, the axial distance between the axially outer ends of the contact surfaces 16 of the gripping units 6 could be less than the inter-sidewall distance d42 of the tire blank 8.

[0094] In the axially close folding position, an external folding tool 46 can perform a folding step on the beads 40. During the folding step, the carcass ply and a bead protector, which notably consists of a layer of rubber or composite material, are folded with the external tool 46 around beads located in the beads 40 of the tire blank 8.

[0095] In the axially distant conformation position (Figure 8), the retaining grooves 18 of the gripping units 6 in the radially distant position of the barrel 4, whose outer diameter corresponds to the seat of the tire blank 8, are able to come into radial contact with the ridges 40 of the tire blank 8, the ridges 40 of the tire blank 8 then fitting into the retaining grooves 18 of the gripping units 6. In particular, in the axially distant conformation position, the axial distance between the retaining grooves 18 of the gripping units 6 is equal to the inter-ridge distance d40 of the tire blank 8.

[0096] When the ridges 40 of the pneumatic blank 8 are arranged in the retaining grooves 18 of the gripping units 6, the elastic membranes 20 form in part a sealed chamber 48 by contact with the pneumatic blank 8, the elastic membranes 20 forming the sealed chamber 48 jointly with the pneumatic blank 8, the surfaces of the gripping modules 5 and the surfaces of the barrel 4.

[0097] The manufacturing drum 2 further includes a compressed air passage 50 between a compressed air source external to the manufacturing drum 2 (not shown) and the sealed chamber 48. The compressed air passage 50 allows the circulation of compressed air from the compressed air source to the chamber 48. The sealed chamber 48 is suitable for retaining the compressed air during the shaping of the tire blank 8.

[0098] Figure 9 represents a folding and shaping process of a tire from the tire blank 8 and the manufacturing drum 2.

[0099] We begin with a step SI of positioning the gripping units 6 in the axially close folding position. During the step SI, the tire blank 8 is also positioned around the barrel 4 so that the contact surfaces 16 of the gripping units 6 are opposite the flanks 42 and / or the top 44 of the tire blank 8 and so that the gripping units 6 are located axially between the ridges 40 of the tire blank 8.

[0100] Then, in step S2, the gripping units 6 are moved to a position radially away from the barrel 4, the outer diameter of which corresponds to the seat of the tire blank 8, so that the contact surfaces 16 of the gripping units 6 are in contact with the flanks 42 and / or the top 44 of the tire blank 8, and so that the gripping units 6 are located axially between the ridges 40 of the tire blank 8. In step S2, the radial movement of the gripping units 6 is interrupted by the rotary selectors 30, the axial movement of the annular cylinders 24 being interrupted by the stops 32b, 32c, 34a, 34c of the first and second rotary rings 32, 34.

[0101] Next, a step S3 is performed to fold down the tire blank 8 with the external folding tool 46.

[0102] Then, during an S4 step, the gripping units 6 are moved into the radially close position of the barrel 4.

[0103] Next, a step S5 is performed to position the gripping units 6 in their axially distant conformation position. During step S5, the tire blank 8 is also positioned so that the ridges 40 of the tire blank 8 are aligned with the retaining grooves 18 of the gripping units 6.

[0104] Then, in step S6, the gripping units 6 are moved to a position radially away from the barrel 4, the outer diameter of which corresponds to the seat of the tire blank 8, so that the ridges 40 of the tire blank 8 are in the retaining grooves 18 of the gripping units 6. During step S6, the radial movement of the gripping units 6 is interrupted by the rods in the ridges 40 of the tire blank 8. The force exerted by the retaining grooves 18 of the gripping units 6 on the rods of the ridges 40 of the tire blank 8 then ensures the sealing of the sealed chamber 48.

[0105] Finally, during a step S7, the shaping of the pneumatic blank 8 is carried out. During the shaping, the sealed chamber 48 is pressurized and the gripping units 6 are brought together axially so that the pneumatic blank 8 takes on a toroidal pneumatic shape.

[0106] Optionally, a rotation is carried out around the X-X' axis of at least one of the ridges 40, in particular of the two ridges 40, of the pneumatic blank 8 relative to the barrel 4 during the axial approach of the gripping modules 5 by sliding of the elastic membrane 20 concerned relative to the holding sectors 14 of the gripping unit 6 concerned, the pneumatic blank 8 remaining fixed in rotation relative to the elastic membrane 20 concerned.

Claims

DEMANDS 1. A manufacturing drum (2) for a tire from a tire blank (8) which is provided with two ribs (40), two sidewalls (42) and a crown (44), the manufacturing drum (2) comprising a barrel (4) extending axially and two gripping modules (5) for the tire blank which are each movable in axial translation along the barrel (4), each gripping module (5) being provided: - of a gripping unit (6) of the pneumatic blank (8) comprising a plurality of retaining sectors (14) which are arranged circumferentially with respect to each other and which are each provided with a contact surface (16) and a retaining groove (18); - of an expansion mechanism (22) configured to move the gripping unit (6) of said gripping module (5) between a position radially close to the barrel (4) and at least one position radially far from the barrel (4); and - of an elastic membrane (20) disposed in the retaining grooves (18) of the gripping unit (6) of said gripping module (5); manufacturing drum (2) in which the elastic membranes (20) of the gripping modules (5) are intended to partially form a sealed chamber (48) by contact with the pneumatic blank (8), the manufacturing drum (2) further comprising at least one compressed air passage (50) between a compressed air source external to the manufacturing drum (2) and the sealed chamber (48); characterized in that the gripping modules (5) are axially movable at least between: - an axially close position called "folding down" in which the contact surfaces (16) of the gripping units (6) in said position radially away from the barrel (4) are able to come radially into contact with one of the sides (42) and / or the top (44) of the tire blank (8) by being located axially between the ridges (40) of the tire blank (8), and - an axially distant position called "conforming" in which the retaining grooves (18) of the gripping units (6) in said radially distant position of the barrel (4) are suitable for receiving the ridges (40) of the pneumatic blank (8), the axial distance between the retaining grooves (18) of the gripping units (6) being equal to the axial distance between the ridges (40) of the pneumatic blank (8).

2. Manufacturing drum (2) according to claim 1, wherein the expansion mechanism (22) of each gripping module (5) is configured to move the gripping unit (6) of said gripping module (5) between the radially close position of the drum (4) and at least the first and second radially distant positions of the drum (4), and configured to immobilize the gripping unit (6) of said gripping module (5) at each of the first and second radially distant positions of the drum (4).

3. Manufacturing drum (2) according to claim 2, wherein the expansion mechanism (22) of each gripping module (5) is configured to move the gripping unit (6) of said gripping module (5) between the radially close position of the drum (4) and a third radially distant position of the drum (4), and configured to immobilize the gripping unit (6) of said gripping module (5) in the third radially distant position of the drum (4), the diameter of the gripping unit (6) of said gripping module (5) in the third radially distant position of the drum (4) being greater than the diameter of the gripping unit (6) of said gripping module (5) in the second radially distant position of the drum (4).

4. Manufacturing drum (2) according to claim 3, wherein the expansion mechanism (22) of each gripping module (5) comprises a rotary selector (30) provided with rotating rings (32, 34) and stops (32b, 32c, 34a, 34c, 39), said rotating rings (32, 34) being capable of being at least in a first immobilizing position of the gripping unit (6) of said module. gripping (5) in the first position radially away from the barrel (4), in a second immobilizing position of the gripping unit (6) of said gripping module (5) in the second position radially away from the barrel (4), and in a third immobilizing position of the gripping unit (6) of said gripping module (5) in the third position radially away from the barrel (4).

5. Manufacturing drum (2) according to any one of claims 1 to 4, wherein the elastic membrane (20) of each gripping module (5) comprises polyurethane.

6. Manufacturing drum (2) according to any one of claims 1 to 5, wherein the expansion mechanism (22) of each gripping module (5) comprises an annular cylinder (24) which is movable in axial translation along the barrel (4) and a plurality of connecting rods (26) which convert the axial movement of the annular cylinder (24) into a radial movement communicated to the retaining sectors (14) of the gripping unit (6) of said gripping module (5).

7. Manufacturing drum (2) according to any one of claims 1 to 6, wherein the expansion mechanism (22) of each gripping module (5) comprises a plurality of pneumatic supply channels (28a, 28b, 28c) each comprising a pneumatic supply hose extending axially in a spiral inside the drum (4).

8. A method for flattening and shaping a tire from a tire blank (8) and a manufacturing drum (2) according to any one of claims 1 to 7, comprising: - the positioning of each gripping unit (6) in the axially close folding position and the positioning of the tire blank (8) around the barrel (4) so ​​that the sides (42) and / or the top (44) of the tire blank (8) are opposite the contact surfaces (16) of the gripping units (6) and so that the contact surfaces (16) of the gripping units (6) are located axially between the ridges (40) of the tire blank (8); - the displacement of each gripping unit (6) in said position radially away from the barrel (4) so ​​that the contact surfaces (16) of the gripping units (6) are in contact with the sides (42) and / or the top (44) of the tire blank (8) by being located axially between the ridges (40) of the tire blank (8); - the folding of the pneumatic blank (8); - the displacement of each gripping unit (6) into the radially close position of the barrel (4); - the positioning of each gripping unit (6) in the axially distant conforming position and the positioning of the pneumatic blank (8) so that the ridges (40) of the pneumatic blank (8) are opposite the retaining grooves (18) of the gripping units (6); - the displacement of each gripping unit (6) into said position radially away from the barrel (4) so ​​that the ridges (40) of the pneumatic blank (8) are in the retaining grooves (18) of the gripping units (6); and - the conformation of the pneumatic blank (8).

9. Folding and shaping method according to claim 8, wherein the shaping of the tire blank (8) comprises pressurizing the sealed chamber (48) and axially bringing together the gripping units (6), a rotation of at least one of the ridges (40) of the tire blank (8) being carried out during the axial bringing together of the gripping units (6) by sliding the elastic membrane (20) concerned relative to the retaining sectors (14) of the gripping unit (6) concerned.

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