Curing mold and method for curing green tire

Abstract

The invention relates to a curing mould (10) for tyres, comprising: an upper shell (16a) for moulding a tyre sidewall, a lower shell (16b) for moulding a tyre sidewall,-a ring (20) of circumferential sections for moulding a tyre tread, each section comprising an upper section part (20a) axially separable from the lower section part (20b), the curing mould being able to interact with a device, -said means are used to actuate the simultaneous radial movement of all section parts. Each lower segment part (20b) comprises a holding device (100) for holding the lower segment part (20b) in a radial position between a closed position of the mould and an open position of the mould, the elements of the holding device (100) belonging to the lower segment part and the lower housing (16b).

Description

Technical Field

[0001] The present invention relates to the manufacture of tires, and in particular to molds and methods for curing or vulcanizing green tires. The present invention particularly relates to the manufacture of tires including a tread pattern extending to the sidewalls, such as tires for all-terrain (or off-road) vehicles. Background Art

[0002] The manufacture of tires includes a curing step, during which the green tire blank is vulcanized and molded to obtain a tire with the desired mechanical properties, geometry and appearance. Curing is carried out in a tire curing mold, which includes an upper molding assembly and a lower molding assembly that can be axially moved relative to each other. The molding assembly includes molding elements that together define the internal tire molding surface. Therefore, the mold mainly includes two shells for molding the tire sidewalls and two rings for molding the tire beads, which are axially located on both sides of the crown ring, and the crown ring includes a plurality of circumferential sections for molding the tread of the tire. This curing mold is arranged in a curing press, which in particular includes a curing mold that can open and close the curing mold on the green tire and a mechanism that can open the curing mold to remove the vulcanized tire and insert a new green tire.

[0003] WO2014 / 044713 in the name of the applicant describes a curing mold for tires, which mainly includes an upper shell for molding the sidewall of the tire that can move with the upper plate of the press, and a lower shell for molding the sidewall of the tire fixed and held by the lower plate of the press. The mold also includes a crown ring for molding the circumferential segment of the tire tread, which can move radially between the open position and the closed position of the mold. Each segment is connected to the upper plate of the press to which the upper shell is fixed, so that it can move axially with the upper plate of the press, and can also move radially relative to the upper plate of the press. Therefore, each segment can slide radially relative to the upper shell, and can slide axially and radially relative to the lower shell. Although its operation is satisfactory, it is noted that this mold is not suitable for molding tires whose tread pattern of the tread extends to the sidewall, because the radial retraction of the segments of this mold is not sufficient to remove the vulcanized tire.

[0004] Furthermore, KR20140018710A discloses a curing mold, the mechanism of which is similar to that described in the aforementioned document, but in which the crown ring of the circumferential segment is divided into two parts, upper and lower, by a horizontal plane passing through the meridian of the tire, so as to facilitate the insertion of the green tire and the removal of the cured tire before curing. When the actuator translates the upper shell axially, the two crown rings of the segment are radially retracted, but only the upper crown ring of the segment is raised together with the upper shell, while the lower crown ring of the segment remains in contact with the lower shell. When the mold is closed, the guide fingers protruding at the radial interface of each upper segment in the mold open position interact with the orifices of the facing lower segment. The guide fingers push the spring-mounted rods located in the facing lower segment, which are arranged to guide the radial translation of the lower segment. Although it allows a greater radial retraction of the segments than the aforementioned document, the curing press must be modified, more specifically its lower plate or the tool for actuating the mold, so that they can receive the mold according to the document.

[0005] There remains a need to be able to use the same curing press and the same tooling for actuating the moulds without modification for different types of tyres including different types of tread patterns, and therefore to be able to receive different curing moulds. Summary of the invention

[0006] One object of the present invention is to overcome the drawbacks of the above-mentioned documents, thereby facilitating the moulding and demoulding of tyres in which the tread pattern of the tread extends to the sidewalls. Another object of the present invention is to improve the appearance of the moulded tyres.

[0007] The present invention achieves this object by providing a curing mold for a tire, comprising:

[0008] - an upper shell, which is used to mold the tire sidewalls,

[0009] - a lower shell, which is used to mold the tire sidewalls,

[0010] - a crown ring of circumferential segments for molding a tire tread, each segment comprising an upper segment part suitable for axial separation from a lower segment part, a curing mold suitable for interacting with the device,

[0011] - said means for actuating, during the operation of opening and closing the mould, the simultaneous radial movement of all the sector parts and the axial movement of the upper part of each sector relative to the lower part of the same sector,

[0012] Characterized in that each lower sector part comprises a holding device for holding the lower sector part in a radial position between a closed position of the mould and an open position of the mould, the elements of the holding device belonging to the lower sector part and to the lower shell.

[0013] The curing mould of the invention comprises a crown ring of circumferential segments which, in the closed position of the mould, form a closed ring, the crown ring of circumferential segments being cut along horizontal radial planes so that during the opening of the mould, the upper and lower parts of the segments of the crown ring can be separated from each other axially and circumferentially. This makes the opening of the mould cavity larger, making it easier to remove the tire whose tread pattern extends to the sidewalls.

[0014] The invention proposes a device made so as to keep the lower part of each segment in a radial position so as to limit the risk of relative movements between the upper and lower parts of the segment during the movements of opening and closing the mould. Moreover, this device for keeping the lower segment part in position prevents any accidental displacement thereof that could occur when the mould is opened (e.g. by falling objects, actions of the press operator, etc.). The lower segment part is thus kept radially in position and can interact correctly with the upper segment part during the movements of opening and closing the mould. Keeping the lower segment part in position means that it is kept in the stable position it maintains, as long as no predetermined force is applied to it to displace it from this holding position.

[0015] Also according to the invention, since all elements of the holding device belong to the lower part and the lower shell of the segment, the mold of the invention can be mounted on any suitable press without modifying elements of the press, such as the plates.

[0016] Furthermore, since the holding device is connected to each lower segment part, the solution can be applied to any type of mould, regardless of the number of segments or their position in the mould.

[0017] The holding device can be made so as to hold the lower segment part in an axial position. This makes it possible to hold the lower segment part in a stable axial position and to hold it in a stable radial position so as to ensure satisfactory operation of the mould without damaging the tyre, for example when the mould is opened to remove the cured tyre, which has a tendency to adhere to the walls of the curing mould.

[0018] The holding device may comprise a slide extending in radial direction, said slide interacting with a pusher made to exert a radial force on the slide during radial movement of the lower segment part between the open position and the closed position of the mould. Still according to the invention, the pusher exerting an axial force in the direction of the slide is thus also able to hold the lower segment part in a stable axial position in its two end positions: a first radially inner position when the mould is closed and a second radially outer position when the mould is open.

[0019] In a first embodiment of the present invention, the slide member can move together with the lower section component, and the push member can be fixed to the lower housing through a bottom plate.

[0020] The slide may comprise rollers which, during radial movement of the lower section part, interact with two notches arranged on either side of the pusher in the base plate.

[0021] In a second embodiment of the present invention, the slide member may be fixed to the lower housing, and the push member may be movable together with the lower section member.

[0022] The slide may comprise two notches which are able to interact with the balls of the pusher during radial movement of the lower section component.

[0023] The pusher may include a return spring.

[0024] The return spring can be calibrated so that it can keep the lower section part in a predetermined position when the force exerted on the pusher is less than the force it is subjected to when the mould is closed.

[0025] The slide may have a dovetail-shaped cross section. This dovetail shape makes it possible to satisfactorily guide the radial translation of the lower segment part and to maintain it in axial position, particularly in the case of tires with a sticky composition or a complex tread pattern, which therefore tend to adhere to the inner wall of the molded part of the mold.

[0026] The present invention also relates to a method for molding a tire using the mold, comprising:

[0027] - an upper shell, which is used to mold the tire sidewalls,

[0028] - a lower shell, which is used to mold the tire sidewalls,

[0029] - a crown ring of circumferential segments for moulding a tyre tread, each segment comprising an upper segment part adapted to be axially separated from a lower segment part, the mould being adapted to interact with the device,

[0030] - said means for actuating, during the operation of opening and closing the mould, the simultaneous radial movement of all the sector parts and the axial movement of the upper part of each sector relative to the lower part of the same sector,

[0031] The method comprises the step of removing the tire at the end of curing, when all the sectors are simultaneously moved radially outwards and the upper part of each sector is moved axially upwards, causing the lower part of the sector to switch from a first radially inner holding position to a second radially outer holding position.

[0032] The molding method of the invention comprises a step of closing the empty mold, followed by a step of opening the mold without radial retraction of the sectors, in order to insert a new green tire into the mold.

[0033] The molding method of the present invention may comprise the step of axially closing the mold only on the green tire inserted into the mold. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be better understood through the remainder of the description based on the following drawings:

[0035] Figure 1 is a radial cross-sectional view of a curing mold according to a first embodiment of the present invention;

[0036] Figure 2a For the closed position Figure 1 An enlarged radial cross-section of the lower portion of the mold, Figure 2b for Figure 2a A detailed schematic diagram of the apparatus for holding the segments in position, wherein the mold is in an open position;

[0037] Figures 3a to 3i A simplified radial cross-sectional view showing the Figure 1 The mold in

[0038] Figure 4 is a radial cross-sectional view of a curing mold according to a second embodiment of the present invention;

[0039] Figure 5a For the closed position Figure 4 An enlarged radial cross-section of the lower portion of the mold, Figure 5b for Figure 5a A detailed schematic diagram of the apparatus for holding the segments in position, wherein the mold is in an open position;

[0040] Figure 6 is an enlarged cross-sectional view along plane AA;

[0041] Figures 7a to 7i A simplified radial cross-sectional view showing the Figure 4 The mold in. DETAILED DESCRIPTION

[0042] In the various drawings, the same or similar elements are provided with the same reference numerals, and therefore a systematic repeated description thereof will not be given.

[0043] Figure 1A mould 10 for curing a green tyre according to a first embodiment of the invention is shown. The curing mould 10 is intended to be inserted between an upper plate 2 and a lower plate 4 of a curing press 1. The curing press comprises a frame forming a mould base, which is assumed to be stationary and fixed to the ground. The press also comprises means for guiding and actuating the mechanism for opening and closing the mould (for example hydraulic cylinders), and means capable of providing the mould with the curing conditions (in terms of pressure and temperature of the heat transfer fluid) required for vulcanising the tyre.

[0044] The mold 10 for curing a green tire comprises an upper molding assembly and a lower molding assembly, each of which comprises an upper shell 16a and a lower shell 16b, respectively, for molding the tire sidewalls, an upper ring 18a and a lower ring 18b, respectively, for molding the beads of the tire, and a crown ring 20 for molding the circumferential segment of the tire tread. In the example shown in the accompanying drawings, the mold is of the "container" type, in which the upper shell 16a is axially slidable with the upper plate 2 of the press, and the lower shell 16b is rigidly fastened to the lower plate 4 of the press and moves the circumferential segment in the radial direction during the opening and closing of the mold.

[0045] The curing mould 10 exhibits substantially rotational symmetry about a central axis XX'. The central axis extends vertically. In the remainder of the description, "axial" or "axially" refers to a direction or movement parallel to the central axis, while "radial" or "radially" refers to a direction or movement perpendicular to the central axis XX'. The circumferential direction is a direction tangential to the radial direction and corresponds to the circumferential direction of the tyre.

[0046] The circumferential segments of the crown ring 20 are arranged side by side in the circumferential direction and each segment of the crown ring is divided into two parts, upper and lower, preferably divided by a radial plane, which in the example shown is the median plane M, i.e. a plane passing equidistantly from the tire bead and therefore also from the molding rings 18a and 18b. More specifically, each segment comprises an upper segment part 20a and a lower segment part 20b, the upper part 20a and the lower part 20b being located on either side of the plane M so that they are in contact when the mold is closed and they move away from each other when the mold is open, as will be explained below. Each segment part comprises an inner lining for molding the tread pattern of the tire held by the segment support. Thus, the upper segment part 20a comprises an inner lining 19a extending from the interface with the lower part 20b to the interface with the upper shell 16a. Similarly, the lower section component 20b includes a liner 19b extending from an interface with the upper portion 20a to an interface with the lower shell 16b. Figure 1 As shown, the inner liners 19a, 19b extend beyond the tread and are intended to mold the tread pattern of the tread to the tire on the sidewalls.

[0047] The radially outer surfaces 21a and 21b of the supports of the liners of the upper and lower section parts 20a, 20b are conical and have the same inclination extending downwardly and radially outwardly.

[0048] The press further comprises a conical ring 14, whose radially inner surface 14a is inclined radially downwards and has the same inclination as the radially outer surfaces 21a and 21b. The conical ring is connected to an actuator of the curing press, for example a hydraulic cylinder, which enables it to perform an axial movement up and down. During the closing of the mold, the conical ring 14 moves downwards, it is positioned on the crown ring 20 of the segment, it brings the segment radially inside the mold, and during the curing process at the increased temperature inside the mold cavity, it exerts a force on the segment to keep the assembly closed. The conical ring 14 comprises a plurality of slides 12, each rigidly fastened to the conical ring, each slide intended to slide in the track of a corresponding segment of the crown ring 20. A stopper located between one end of the slide 12 and a notch in the outer surface 21a of each segment makes it possible to limit the radial retraction travel of the segment during the upward movement of the conical ring to open the mold. In this embodiment, the conical ring 14, the slide 12 and the elements for connecting them to the segments of the mould and the upper plate of the press are as described in WO 2014 / 044713.

[0049] The upper plate 2 of the press is connected to another actuator, such as a hydraulic cylinder, which enables the upper plate 2 to move axially up and down during the operation of closing and opening the mold, as will be explained below.

[0050] In the open position of the mold, the conical ring 14 and the upper molded parts (i.e., the upper segment part 20a, the upper shell 16a and the upper mold ring 18a, which are rigidly connected to the upper plate 2 of the press) move axially upwards, thereby clearing the mold cavity so that the cured tire can be removed and a new green tire can be inserted. During the mold closing process, the upper plate moves downwards and the upper segment part 20a is retracted radially outwards, and the conical ring 14 moves downwards to close the curing cavity, thereby closing the mold for curing. The heat transfer fluid reaches the interior of the mold cavity from a device 25 located in the central part of the curing cavity, which device includes, for example, a curing bladder, which presses the green tire against the interior of the mold during the curing process.

[0051] According to the invention, each lower section part 20b is provided with a device 100 for maintaining the lower section part 20b in a radial position between the closed position of the mould and the open position of the mould.

[0052] In a first embodiment, this Figure 1 , Figure 2a and Figure 2bAs can be seen most clearly in Figure 1 , the elements of the holding device 100 belong to the lower segment part 20b and the lower shell 16b. More specifically, the holding device 100 comprises a slide 101 adapted to move in a cavity 102, having an elongated shape extending in the radial direction and located at the bottom of the lower segment part 20b, which interacts with a pusher 108 arranged in a bottom plate 110 of the lower shell 16b. The slide 101 is rigid; it has the shape of an elongated beam extending between the lower shell 16b and the lower segment part 20b and has, for example, a dovetail cross section. In another example (not shown), the slide has a T-shaped cross section or has any suitable shape that simultaneously enables it to guide the radial translation of the lower segment part and prevents its axial movement when subjected to forces having an axial component. The bottom plate 110 is rigidly fastened to the lower shell 16b, for example using fastening screws. More specifically, the bottom plate 110 comprises a hole 107 in which a pusher 108 and a return spring 109 for pushing the pusher axially outward are arranged, the substantially circular axial lower end 108' of the pusher 108 protruding relative to the end of the bottom plate 110. The axial lower surface 110' of the bottom plate 110 is provided with two cavities 112 and 114 located on either side of the pusher 108. The slide 101 comprises a roller 105, which is mounted so as to be free to rotate about its central axis, located at the axial outer end of the slide and interacting with the recesses 112 and 114 during the radial movement of the lower segment part 20b. The bottom plate 110 further comprises a stopper 115 which positions the roller in the recess 114 in a stable manner. The slide 101 is rigidly connected to the lower section part 20b and is fastened to the lower section part 20b by means of a pin 116 inserted into a hole 117, the axis of which is transverse to the longitudinal direction of the slide 101 and the lower section part 20b and to a fastening screw which is transverse to the axis of the hole 117 (not shown).

[0053] In operation, when the mould is in the closed position, the roller 105 of the slide 101 is positioned in the notch 112. During the opening of the mould, the lower segment part 20b moves radially outwards, the roller 105 of the slide 110 follows the movement of the segment and actuates the pusher 108 against the return spring 109. At the end of the radial retraction movement of the lower segment part 20b, the roller 105 reaches the second notch 114 and is held by the protrusion 108' of the pusher 108, which returns to its position under the action of the spring 109, and the stop 115.

[0054] The slide 110 adopts two stable positions when it moves: a first position corresponds to the closed position of the mold, when the roller 105 is positioned in the notch 112; a second position corresponds to the open position of the mold, when the roller 105 is housed in the notch 114 of the bottom plate 110 under the latching action of the pusher 108. This enables the lower segment part 20b to be maintained in the axial and radial position and prevents it from moving in the open position of the mold.

[0055] Now refer to Figures 3a to 3i The operation of the mold according to the first embodiment is described. Figure 3a The curing mould 10 is shown in a closed or curing position for obtaining a tyre P, with the roller 105 being located in the recess 112 of the base plate 110 . Figure 3b It is shown that the step of opening the mould begins when a force is applied in the axial direction on the conical ring 14, which force causes the upper and lower segment parts to retract radially at the same time. Means (not shown, such as fingers protruding on the upper segment part 20a, which interact with holes in the lower segment part 20b at the interface of said parts) make it possible to synchronize the upper and lower parts 20a, 20b of each segment. The rollers 105 have left the notches 112. Once the radial retraction of the segments has taken place, the upper segment part 20a is separated from the lower segment part 20b along the radial plane M.

[0056] Figure 3c The fully open position of the mould is shown, in which the upper moulding part is axially moved apart so that the cured tyre can be taken out. In this position, the roller 105 interacts with the recess 114 of the base plate 110 and the lower section part 20b is held in place.

[0057] Figure 3d and Figure 3e The step of closing the empty mould is shown. The mould is closed by lowering the upper plate 2 and the conical ring 14 axially.

[0058] Figure 3f The step of opening the mould is shown, but only axially (or vertically) without radial retraction of the segments, in particular the upper and lower segment parts 20a, 20b. The lower segment part 20b is held against the lower shell 16b due to the force of the spring 109 of the pusher 108, which applies a force to the rollers 105 of the slide 101. The actuator for moving the upper segment parts 20a holds them against the upper shell 16a. A new green tyre E can be inserted into the mould cavity, as Figure 3g Then, the mold is closed only axially (or vertically), as shown in Figure 3h When the mold is fully closed, curing can be performed, as shown in Figure 3i shown.

[0059] This additional step of closing the empty mold before axially (or vertically) opening the mold is only to return the upper and lower segment parts to their radial positions before inserting a new green tire and thus prevent rubber extrusion at the interface between the radially outer end of each upper part 20a and lower part 20b and the upper shell 16a and lower shell 16b, respectively. As a result, the appearance of the cured tire is improved.

[0060] In a second embodiment, this Figure 4 , Figure 5a , Figure 5b and Figure 6 As can be seen most clearly in Figure 1 , all the elements of the holding device 100 also belong to the lower segment part 20b and the lower shell 16b. More specifically, the holding device 100 comprises a slide 121 comprising two notches 124 and 126 which interact with the pusher 103 belonging to the lower segment part 20b. The slide 121 is rigidly fastened to the lower shell 16b by its radially outer end 121 ' in any suitable manner, for example using screws (not shown), the other end of the slide being free. The slide 121 is rigid; it has the shape of an elongated beam extending between the lower shell 16b and the lower segment part 20b and has a cross section, for example, of a dovetail shape. The lower segment part 20b comprises, at its bottom, an elongated hole 122, the shape of which is complementary to that of the slide 121; more specifically, the elongated hole 122 has a cross section of the same shape as that of the slide, a dovetail shape in the example shown in the figures, but with greater dimensions to allow the lower segment part 20b to slide radially relative to the slide 121. The lower segment part 20b comprises a pusher 103 of the type comprising a ball 118 pushed downwardly by a return spring 119.

[0061] In operation, when the mold is in the closed position, the ball 118 of the pusher 103 is positioned in the notch 124. During the opening of the mold, the lower segment part 20b moves radially outwards, and the ball 118 of the pusher 103 follows the movement of the segment by rolling on the slide 121 while compressing the return spring 119. At the end of the radial retraction movement of the lower segment part 20b, the ball 118 of the pusher 103 arrives in the second notch 126, where it is retained under the action of the expanded return spring 119. The stop 128 prevents any radial movement of the lower segment part 20b beyond this position.

[0062] The lower segment part 20b adopts two stable positions when it moves: a first position corresponds to the closed position of the mold, when the pusher 103 is positioned in the notch 124; a second position corresponds to the open position of the mold, when the pusher 103 is housed in the notch 126 of the slide 121 under the action of the latch. This allows the lower segment part 20b to be maintained in the axial and radial position and prevents it from moving in the open position of the mold.

[0063] Now refer to Figures 7a to 7i The operation of the mold according to the second embodiment of the present invention is described. Figure 7a The curing mould 10 is shown in the closed or curing position for obtaining the tyre P, the ball 118 of the pusher 103 being located in the recess 124 of the slide 121 . Figure 7b The step of opening the mould is shown starting when a force is applied in the axial direction on the conical ring 14, which force causes the upper and lower segment parts to retract radially at the same time. Means (not shown, such as fingers protruding on the upper segment part 20a, which interact with holes in the lower segment part 20b at the interface of said parts) make it possible to synchronize the upper and lower parts 20a, 20b of each segment. The ball 118 of the pusher 103 has left the notch 124. Once the radial retraction of the segments has taken place, the upper segment part 20a is separated from the lower segment part 20b along the radial plane M.

[0064] Figure 7c Shown is the fully open position of mould, in this position, upper moulding part axially moves away, makes it possible to take out cured tyre.In this position, the ball 118 of pusher 103 interacts with the notch 126 of slide 121, and lower section part 20b is maintained in proper position.

[0065] Figure 7d and Figure 7e The step of closing the empty mould is shown. The mould is closed by lowering the upper plate 2 and the conical ring 14 axially.

[0066] Figure 7f The step of opening the mould is shown, but only axially (or vertically) without radial retraction of the segments, in particular the upper and lower segment parts 20a, 20b. The lower segment part 20b is held against the lower shell 16b due to the force of the spring 119 of the pusher 103, which presses the ball into the recess of the slide 121. The actuator for moving the upper segment parts 20a holds them against the upper shell 16a. A new green tyre E can be inserted into the mould cavity, as Figure 7g Then, the mold is closed only axially (or vertically), as shown in Figure 7h When the mold is fully closed, curing can be performed, as shown in Figure 7i shown.

[0067] As explained above, this additional step of closing the empty mold before axially (or vertically) opening the mold is only to return the upper and lower segment parts to their radial positions before inserting a new green tire and thus prevent rubber squeezing at the interface between the radially outer end of each upper portion 20a and lower portion 20b and the upper shell 16a and lower shell 16b, respectively. This makes it possible to avoid the appearance of burrs on the cured tire.

[0068] Other variants and embodiments of the invention are conceivable within the scope of the claimed invention.Thus, the upper and lower segment parts may be axially separated along a radial plane other than the median plane or along a non-radial plane.

Claims

1. A mold (10) for curing a tire, comprising: - an upper shell (16a) for molding the tire sidewalls, - a lower shell (16b) for molding the tire sidewalls, - a crown ring (20) of circumferential segments for molding a tire tread, each segment comprising an upper segment part (20a) suitable for axial separation from a lower segment part (20b), a curing mold suitable for interacting with the device, - said device is used to actuate, during the operation of opening and closing the mould, the simultaneous radial movement of all the segment parts and the axial movement of the upper part (20a) of each segment relative to the lower part (20b) of the same segment, Characterized in that each lower section part (20b) comprises a holding device (100) for holding the lower section part (20b) in a radial position between a closed position of the mould and an open position of the mould, the elements of the holding device (100) belonging to the lower section part and the lower shell (16b).

2. The mold according to claim 1, characterized in that: The device is made so as to be able to hold the lower section part (20b) in an axial position.

3. A mould according to any one of the preceding claims, characterised in that The holding device (100) comprises a slide (101, 121) extending in radial direction, the slide (101, 121) interacting with a pusher (103, 108) made to exert an axial force on the slide during radial movement of the lower segment part (20b).

4. The mold according to claim 3, characterized in that: The sliding member (101) can move together with the lower section component (20b), and the pushing member (108) is fixed on the lower housing (16b) through the bottom plate (110).

5. The mould according to the preceding claim, characterized in that The slide (101) comprises a roller (107) which, during the radial movement of the lower section part (20b), interacts with two notches (112, 114) arranged on either side of a pusher (108) in the bottom plate (110).

6. The mold according to claim 3, characterized in that: The sliding member (121) is fixed on the lower housing (16b), and the pushing member (103) can move together with the lower section component (20b).

7. The mold according to the preceding claim, characterized in that The slide (121) comprises two notches (124, 126) which interact with the ball (118) of the pusher (103) during radial movement of the lower section part (20b).

8. The mold according to any one of claims 3 to 7, characterized in that The pushing member (103, 108) comprises a return spring (109, 119).

9. The mold according to the preceding claim, characterized in that The return spring (109, 119) can be calibrated so that when the force applied to the pusher (103, 108) is less than the force it is subjected to when the mold is closed, the return spring (109, 119) can keep the lower section part (20b) in a predetermined position.

10. The mold according to any one of claims 3 to 9, characterized in that The sliding member (101, 121) has a dovetail-shaped cross section.

11. A method for molding a green tire using a curing mold, comprising: - an upper shell (18a) for molding the tire sidewalls, - a lower shell (18b) for molding the tire sidewalls, - a crown ring (20) of circumferential segments for moulding a tyre tread, each segment comprising an upper segment part (20a) adapted to be axially separated from a lower segment part (20b), said curing mould being adapted to interact with the device, - said device is used to actuate, during the operation of opening and closing the mould, the simultaneous radial movement of all the segment parts and the axial movement of the upper part (20a) of each segment relative to the lower part (20b) of the same segment, The method comprises the step of removing the tire at the end of curing, when all the segments are simultaneously moved radially outwards and the upper part (20a) of each segment is moved axially upwards, so that the lower part (20b) of the segment is switched from a first radially inner holding position to a second radially outer holding position.

12. Moulding method according to the preceding claim, characterised in that It comprises a step of closing the empty mould, followed by a step of opening the mould without radial retraction of the sectors, in order to insert a new green tyre into the mould.

13. Moulding method according to the preceding claim, characterised in that The mould is closed axially only on the green tyre inserted into the mould.

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