EP4117899A1

EP4117899A1 - Lining element of a curing mould for a tyre comprising sipe blades

Info

Publication number: EP4117899A1
Application number: EP21717138.8A
Authority: EP
Inventors: Damien BARDIN; Aleksander ROMAN; Dariusz KONOBROCKI; Paul LACOSTE
Original assignee: Compagnie Generale des Etablissements Michelin SCA
Current assignee: Compagnie Generale des Etablissements Michelin SCA
Priority date: 2020-03-10
Filing date: 2021-03-08
Publication date: 2023-01-18
Also published as: FR3108059B1; US20230166468A1; FR3108059A1; WO2021181036A1; CN115279577A

Abstract

Lining element (16) of a curing mould (10) for a tyre, forming a moulding surface (14), the moulding surface comprising recessed and protruding patterns, at least one first protruding pattern (30) being formed by a first sipe blade (32) with a fork-shaped section (34), and at least one second protruding pattern (36) being formed by a second sipe blade (38), and a bulge (40) extending along a contour (42) radially on the inside of the second sipe blade, at least one recessed pattern which is substantially in the form of a parallelepiped being delimited by at least one first protruding pattern (30) and a pair of second protruding patterns (36), wherein the first protruding pattern intersects, at each end thereof, a second protruding pattern.

Description

BAKING MOLD TRIM FOR PNEUMATICS

INCLUDING SLATS

[0001] The present invention relates to the manufacture of tires and, more particularly, to the field of baking molds used during a baking step of a tire.

[0002] The manufacture of a tire comprises a curing step, during which a tire blank is molded and vulcanized in order to obtain a tire of given mechanical characteristics, geometry and appearance. The tire is baked in a baking mold. The tire blank is pressed against the mold so as to mold the internal surface of the mold on said blank, and thus form the external surface of the tire. In particular, the mold comprises a lining intended to form a sculpture on the tread of the tire.

[0003] The molding surface of the lining comprises recessed and protruding patterns. The protuberance patterns are generally formed by blades intended to form grooves greater than 2 mm thick on the tire tread. The grooves in particular allow good evacuation of water when the tire is rolling on wet ground. In a known manner, the blades extend circumferentially and / or transversely over the radially internal surface of the lining, and intersect so as to form and delimit, on the tire tread, protuberance patterns of parallelepiped shape, generally called "Breads".

[0004] In order to improve the performance of the tire, the lining comprises molding elements in the form of strips up to 2 mm thick. The lamellae form notches on the tire tread, severing part or all of a bar. A notch thus makes it possible to improve the grip of the tire while maintaining good rigidity of the tread, which makes it possible in particular to limit energy dissipation.

[0005] From application WO2010039148, in the name of the applicants, is known a tire whose tread comprises notches in the form of a fork. In other words, a notch extends radially from the ground contact surface of the tread, towards the inside of the tread, then splits in two. The forked part of the notch is intended to emerge on the surface in contact with the ground of the tread when the latter has reached a certain level of wear. Such a notch makes it possible to restore the grip of the tire when the latter has reached a certain level of wear, while limiting the number of notches in new condition which makes it possible to maintain good rigidity of the tread. .

[0006] However, the so-called "Y" slats, which make it possible to obtain such notches, have strong undercuts making their release problematic, in particular because of the risk of tearing the loaves of the sculpture. The problem is all the more delicate as, in order to restore adhesion effectively, the forked part of the notch must have sufficient spacing, which increases the risk of the loaves of the sculpture tearing off.

[0007] An objective of the invention is to remedy the drawbacks of the state of the art and to provide an original solution to facilitate the release of a lining comprising Y sipes while improving the performance of the tire.

[0008] To this end, the invention provides a tire baking mold liner forming a molding surface, the molding surface comprising recessed and protruding patterns. At least a first protrusion pattern is formed from a first fork-shaped section sipe. At least a second protrusion pattern is formed of a second sipe and a bead extending along a radially inner contour of the second sipe. At least one recessed pattern is delimited in part by at least a first protruding pattern and at least a second protruding pattern.

[0009] The second pattern molds a channel embedded in the tread of the tire, and a notch opening into said channel. The channel improves the performance of the tire. For example, the channel is intended to emerge on the surface of the tread when the latter has reached a certain level of wear, and makes it possible to restore the water drainage capacity of the tire. It is then possible to reduce the depth or the number of grooves when new. In addition, the notches make it possible, in new condition, to maintain good rigidity of the tread, which in particular allows to limit energy dissipation. Finally, the channel into which the notch opens makes it possible to eliminate the stress concentrations in the bottom of the notch, and thus, to reduce the risks of tearing of the blocks of rubber when the tire is rolling.

[0010] Furthermore, combining a first pattern and a second pattern to mold blocks of a tire tread also makes it possible to improve the performance of said tire, in particular when its tread has reached a certain level of wear. The channel provides flexibility to the tread and helps maintain tire grip. For example, the designers have observed that a tire thus molded made it possible to obtain a performance compromise that is more advantageous in terms of grip and drainage, than a tire in which the bars only have single notches or notches in the form of a fork. .

[0011] Finally, achieving such a performance compromise makes it possible to reduce the spacing of the forked part of the first sipe and thus to reduce the undercuts of the molding surface of the lining. The risk of the bars tearing off the tire tread during its release from the mold is then limited.

Preferably, the first protruding pattern and the second protruding pattern intersect. The thus molded tread is softer, and the risk of the tire tread strips tearing off when it is released from the mold is then limited. Advantageously, the hollow pattern substantially takes the form of a parallelepiped delimited by at least a first protruding pattern and a pair of second protruding patterns, the first protruding pattern intersecting at each of its ends a second protruding pattern. protuberance. Such an arrangement makes it possible to improve the drainage performance of the tire. In addition, the risk of the bars tearing off the tire tread during its release from the mold is limited.

Preferably, the thickness of the bead of the second protruding pattern is less than 60% of the thickness of the fork of the first protruding pattern, more preferably less than 50% and, even more preferably, less than 40 %. Thus, the undercuts of the molding surface of the trim are limited, and the risk of the bars tearing off from the tire tread during demolding is also limited.

Advantageously, the height of the bead of the second protruding pattern is between 50% and 200% of the height of the fork of the first protruding pattern and, more preferably, between 70% and 150%.

Preferably, the bead of the second protruding pattern and the fork of the first protruding pattern overlap radially at most over 50% of their height and, more preferably, at most over 30% of their height. Such an arrangement makes it possible to reduce the lamination of the vulcanized rubber when the lining element withdraws from the tread of the tire. Thus, the risk of the bars tearing off the tire tread during its release from the mold is limited.

Advantageously, the first protruding pattern delimits a first hollow pattern, and the second protruding pattern forms an intersection with the first protruding pattern, the intersection partly delimiting at least one second hollow pattern, the second pattern recessed protruding from the first recess pattern, the trim member including a molding member adapted to fill the second recess pattern.

Preferably, said molding element is integral with the first strip. [0019] According to a second object, the invention provides a method of manufacturing a tire comprising a baking step in a baking mold for a tire comprising a lining element according to the invention.

[0020] According to a third object, the invention provides a tire intended to be mounted on the rim of a wheel, characterized in that it is obtained by a manufacturing process according to the second object of the invention.

The invention will be better understood from the remainder of the description, which is based on the following figures: FIG. 1 is a view in radial section of certain elements of a baking mold; FIG. 2 is a perspective view of certain elements of the lining of the mold of FIG. 1; FIG. 3 is a perspective view of a part of the tread of a tire having reached a certain level of wear, said part having been molded by the elements of FIG. 2; FIG. 4 is a perspective view of certain elements of the lining of the mold of FIG. 1, according to a first variant of the invention; FIG. 5 is a perspective view of certain elements of the lining of the mold of FIG. 1, according to a second variant of the invention; FIG. 6 is a perspective view of certain elements of the lining of the mold of FIG. 1, according to a second variant of the invention.

In the various figures, identical or similar elements bear the same reference. Their description is therefore not systematically repeated.

FIG. 1 schematically illustrates a curing mold 10 of a tire used to mold and vulcanize a tire blank, with a view to obtaining a tire of the desired geometry and appearance. The mold delimits a generally symmetrical interior space by revolution of central axis 12. The baking mold comprises a frame, molding elements, vulcanization means, and means for opening and closing the mold. The opening and closing means are able to set the molding elements in motion between an open position and a closed position (FIG. 1). The open position corresponds to the step of extracting a molded and vulcanized tire, as well as to the step of introducing a new tire blank. The closed position corresponds to the step of molding and vulcanizing the tire blank. The vulcanization means are able to supply the thermal energy and the pressure necessary, respectively, for the vulcanization and the molding of the tire blank. By way of example, the supply of thermal energy and pressure is provided by pressurized water vapor circulating around the mold, and inside the tire blank in an expandable membrane. In the closed position of the mold, the molding elements form a molding surface 14 corresponding in negative to the desired external surface of the tire. The elements of moldings more particularly comprise a lining 16 intended to mold the tread of the tire, two shells 18 intended to mold the sidewalls of the tire, and two rings 20 intended to mold the beads of the tire.

The lining 16 is supported by its radially outer surface on a crown 22 of the mold. The packing generally includes a plurality of packing elements disposed circumferentially. For example, a trim element comprises several slats, a body and possible inserts. A lamella is a fine molding element. The lamella comprises a molding part, the thickness of which generally varies from 0.2 to 2 mm for a tire intended to be mounted on a passenger vehicle, and an anchoring part suitable for being immersed in the body of the element. of garnish. For example, a lamella is obtained by a material removal process such as laser cutting, plastic deformation such as stamping, additive manufacturing such as selective melting consolidation, or by a combination of these methods. Preferably, a packing element is obtained by a foundry process by overmolding the body of the packing element around the anchoring part of the lamellae, or by manufacturing the body of the packing element by a manufacturing process additive, then assembly of said body with the lamellae. The assembly of the slats with the trim body so as to produce a trim element can be achieved by a screwed assembly process, by gluing, by welding, or by any other suitable assembly process. Finally, a packing element can be obtained by an additive manufacturing process in which the body of the packing element and the molding part of the lamellae are made in one piece.

The molding surface of the lining 16 comprises recessed patterns 24 and protruding patterns 26. By "pattern" is meant the shape of a part of the molding surface of the lining, or the corresponding shape part of the tread pattern of a tire. A pattern has a technical and / or aesthetic function.

The molding surface of the lining is circumscribed by an outer jig of substantially cylindrical or toric shape, called "crown shape". The protruding patterns extend radially from the crown shape towards the interior of the mold. A radial direction 28 is a direction perpendicular to the central axis 12 of the mold. For example, the protruding patterns take the form of parallelepipeds, grooves extending circumferentially and / or transversely, or else take the form of lamellae or spikes. The protruding patterns delimit totally or in part, on the molding surface, the recessed patterns. By way of example, the recessed patterns take prismatic shapes, or else extend circumferentially and / or transversely in a polygonal section.

Figure 2 illustrates part of the molding surface of the lining 16. According to the invention, at least a first protrusion pattern 30 is formed of a first blade 32 of fork-shaped section 34, and at at least a second protrusion pattern 36 is formed of a second sipe 38 and a bead 40 extending along a radially inner contour 42 of the second sipe.

The first said Y strip comprises two molding parts. A first part of section in the form of a trunk 44 extends from the crown form 46 towards the interior of the mold, and a second part, extending and dividing the trunk, of section in the form of branches 34. By way of example, the second part has two branches. The height, measured in the radial direction 28, of the first part is less than 10 mm and, preferably, less than 7 mm. The height of the second part is between 2 mm and 10 mm and, preferably, between 2 mm and 7 mm. The thickness, measured in a circumferential or transverse direction, of the second part or, in other words, of the fork, is between 2 mm and 10 mm and, preferably, between 2 mm and 7 mm. A circumferential or transverse direction is perpendicular to the radial direction 28 and, respectively, orthogonal or parallel to the central axis 12.

The bead 40 is arranged along the radially inner contour 42 of the second strip 38. The section of the bead takes various shapes, and is delimited by a contour of rounded, polygonal, convex or concave shape. For example, the bead is integral with the second sipe 38. The height of the second sipe is between 2 mm and 20 mm and, preferably, between 2 mm and 14 mm. The thickness of the bead is understood as the section of the bead which is included in a circular template with a diameter of between 2 mm and 20 mm and, preferably, between 2 mm and 7 mm.

Preferably, the thickness of the bead of the second protruding pattern is less than 60% of the thickness of the fork of the first protruding pattern, more preferably, less than 50% and, even more preferably, less than 40%. The height of the bead of the second protruding pattern is between 50% and 200% of the height of the fork of the first protruding pattern and, more preferably, between 70% and 150%. The bead of the second protruding pattern and the fork of the first protruding pattern overlap radially at most over 50% of their height and, more preferably, at most over 30% of their height.

[0031] At least one hollow pattern of the liner 16 takes substantially the form of a parallelepiped or, in other words, of a polyhedron with 6 faces, the opposite faces of which are substantially parallel. Preferably, the molding surface 14 comprises several of said recessed patterns, distributed homogeneously over the whole of said molding surface. At least 20% of said recessed patterns and, preferably, at least 50% of said recessed patterns, are delimited in part by at least a first protruding pattern 30 and at least one second protruding pattern 36. Preferably, the first protrusion pattern and the second protrusion pattern intersect. Preferably, said recessed patterns are delimited by at least a first protruding pattern and a pair of second protruding patterns, the first protruding pattern intersecting at each of its ends a second protruding pattern.

The protruding patterns 26 can form intersections 48. According to a radial view of the trim, an intersection is delimited by a contour including the superimposed parts of each protruding pattern. Therefore, by "intersection of protruding patterns", we do not mean the regular parts, or outside said contour, of the protruding patterns intersecting, we mean at least the singular parts and the superimposed parts of said patterns. The regular parts of the protruding patterns are the parts whose radial profile is not impacted by the intersection of protruding patterns.

The first protrusion pattern 30 defines a first hollow pattern 50, and the second protrusion pattern 36 forms an intersection 48 with the first protrusion pattern. The first protrusion pattern 30 and the first indentation pattern 50 take a longitudinal shape. The intersection 48 partially delimits at least one second hollow pattern (not shown). The second recessed pattern protrudes relative to the first recessed pattern, and forms a tongue 52 (FIG. 3), the thickness of which in the middle of the tongue is less than 5 mm and, more preferably, less than 2.5 mm. The trim element has a molding element adapted to fill the second recess pattern. According to a first variant illustrated in Figure 4, the molding element 54 is integral with the first strip 32. The second strip 36 and the bead 38 comprise assembly means 54 taking the form of a slot 56 in which the first strip is intended to be inserted (FIG. 5).

[0035] According to a second variant embodiment illustrated in Figure 6, the molding element 52 is integral with the second strip 38 and the bead 40.

[0036] Other variants and embodiments of the invention can be envisaged without departing from the scope of these claims.

Claims

1. A tire baking mold (10) trim element (16) forming a molding surface (14), the molding surface comprising recessed and protruding patterns, at least a first protrusion pattern (30) being. formed by a first strip

(32) of fork-shaped section (34), and at least one second protrusion pattern (36) being formed of a second sipe (38) and a bead (40) extending along a radially internal contour (42) of the second sipe, at least one hollow pattern taking substantially the form of a parallelepiped being delimited by at least a first protruding pattern (30) and a pair of second protruding patterns (36), the first protruding pattern intersecting at each of its ends a second protruding pattern.

2. A trim element according to the preceding claim wherein the thickness of the bead (40) of the second protruding pattern is less than 60% of the thickness of the fork (34) of the first protruding pattern, more preferably less than 50% and, even more preferably, less than 40%.

3. Trim element according to one of the preceding claims wherein the height of the bead (40) of the second protruding pattern is between 50% and 200% of the height of the fork (34) of the first protruding pattern and, more preferably , between 70% and 150%.

4. A trim element according to one of the preceding claims wherein the bead (40) of the second protruding pattern and the fork (34) of the first protruding pattern overlap radially at most over 50% of their height and, more preferably, at the bottom. over 30%. 5. A trim element according to one of the preceding claims wherein the first protrusion pattern (30) defines a first recess pattern (50), and the second protrusion pattern (36) forms an intersection (48) with the first pattern in protrusion, the intersection partially defining at least a second recess pattern, the second recess pattern projecting from the first recessed pattern, the trim member including a molding member (52) adapted to fill the second recessed pattern.

6. A trim element according to the preceding claim wherein said molding element is integrally formed with the first strip (32). 7. A method of manufacturing a tire comprising a baking step in a baking mold (10) for a tire comprising a lining element according to one of claims 1 to 6.

8. A tire intended to be mounted on the rim of a wheel, characterized in that it is obtained by a manufacturing process according to claim 7.