Patent Application
20230347608
The present invention relates to the manufacture of tyres and more particularly to the field of curing moulds that are used during a step of curing a tyre.
The manufacture of a tyre comprises a curing step, during which a green tyre is moulded and vulcanized so as to obtain a tyre having given mechanical characteristics, geometry and appearance. The tyre is cured in a curing mould. The green tyre is pressed against the mould so as to mould the internal surface of the mould on said green tyre and thus to form the external surface of the tyre. In particular, the mould comprises a lining intended to form a tread pattern on the tread of the tyre.
The radially internal surface of the lining has recessed and protruding patterns. In a known way, the protruding patterns have closely packed or longitudinal shapes. By way of example, the patterns of longitudinal shape are formed by sipe blades with a thickness greater than 2 mm that are intended to mould furrows in the tread pattern of the tyre, or by sipe blades with a thickness less than or equal to 2 mm of various shapes that are intended to mould voids. Said patterns extend circumferentially and/or transversely over the radially internal surface of the lining.
The protruding patterns of longitudinal shape sometimes extend in a curved manner and intersect regularly over the lining at various incidences. The intersections thus formed have complex and singular shapes. Some of these intersections partially delimit a recessed pattern in which rubber of the green tyre is moulded and vulcanized. This results in a tyre in which the tread pattern has protruding patterns that are not very advantageous. By way of example,
An objective of the invention is to overcome the drawbacks of the prior art and to provide an original solution for making it possible to improve the moulding quality of a tyre, while improving the performance thereof.
To this end, the invention provides a lining element of a curing mould for a tyre, forming a moulding surface, the moulding surface comprising recessed and protruding patterns, a first protruding pattern delimiting a first recessed pattern, and a second protruding pattern forming an intersection with the first protruding pattern, the intersection partially delimiting at least one second recessed pattern, the second recessed pattern protruding with respect to the first recessed pattern. According to the invention, the lining element has a moulding element designed to fill the second recessed pattern.
Thus, the second recessed pattern is filled by a moulding element. Consequently, the tread pattern of the tyre does not have a shape that is not very advantageous or useless, such as thin rubber tongues.
Preferably, the first protruding pattern and the first recessed pattern have a longitudinal shape.
Advantageously, the first protruding pattern is formed by a first sipe blade with a cross section in the form of a fork.
Preferably, the second protruding pattern is formed by a second sipe blade and by a bulge extending along a radially internal contour of the second sipe blade.
The invention is particularly advantageous for a lining element comprising the intersection of a Y-shaped sipe blade and of a sipe blade comprising a bulge.
According to a first variant, said moulding element is integral with the first sipe blade. Such a design is easy to manufacture and mount.
Preferably, the second sipe blade and the bulge have assembly means in the form of a slot into which the first sipe blade is intended to be inserted.
According to a second variant, said moulding element is integral with the second sipe blade and the bulge.
Preferably, the second recessed pattern forms a tongue, the thickness of which at the middle of the tongue is less than 5 mm and more preferably less than 2.5 mm.
According to a second subject, the invention provides a method for manufacturing a tyre, comprising a step of curing in a curing mould for a tyre having a lining element according to a first subject of the invention.
According to a third subject, the invention provides a tyre intended to be mounted on the rim of a wheel, characterized in that it is obtained by a manufacturing method according to the second subject of the invention.
The invention will be understood better from the remainder of the description, which is based on the following figures:
In the various figures, elements that are identical or similar bear the same reference signs. Their description is therefore not systematically repeated.
The lining 16 bears on a ring 22 of the mould with its radially external surface. The lining generally comprises a plurality of circumferentially disposed lining elements. By way of example, a lining element has a plurality of sipe blades, a body and possible inserts. A sipe blade is a thin moulding element. The sipe blade has a moulding part, the thickness of which varies generally from 0.2 to 2 mm for a tyre intended to be mounted on a passenger vehicle, and an anchoring part that is able to be submerged in the body of the lining element. By way of examples, a sipe blade is obtained by a material removing process such as laser cutting, a plastic deformation process such as pressing, an additive manufacturing process such as consolidation by selective melting, or by a combination of these processes.
Preferably, a lining element is obtained by a casting process involving overmoulding the body of the lining element about the anchoring part of the sipe blades, or by manufacturing the body of the lining element by way of an additive manufacturing process, after which said body is joined to the sipe blades. The joining of the sipe blades to the lining body so as to produce a lining element may be effected by a screwed assembly process, an adhesive bonding process, a welding process, or by any other suitable joining process. Lastly, a lining element may be obtained by an additive manufacturing process in which the body of the lining element and the moulding part of the sipe blades are produced integrally.
The moulding surface of the lining 16 has recessed patterns 24 and protruding patterns 26. A “pattern” means the shape of a part of the moulding surface of the lining, or the shape corresponding to a part of the tread pattern of a tyre. A pattern has a technical and/or aesthetic function.
The moulding surface of the lining is circumscribed by an exterior template of substantially cylindrical or toric shape, known as a “crown form”. The protruding patterns extend radially from the crown form towards the interior of the mould. A radial direction 28 is a direction perpendicular to the central axis 12 of the mould. By way of example, the protruding patterns are in the form of parallelepipeds, circumferentially and/or transversely extending furrows, or are in the form of sipe blades or of spikes. The protruding patterns entirely or partially delimit, on the moulding surface, recessed patterns. By way of example, the recessed patterns have prismatic shapes or extend circumferentially and/or transversely along a polygonal section.
The first sipe blade, known as a Y-shaped sipe blade, comprises two moulding parts. A first part with a section in the form of a stem 44 extends from the crown form 46 towards the interior of the mould, and a second part, extending and dividing the stem, with a section in the form of arms 34. By way of example, the second part has two arms. 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 bulge 40 is arranged along the radially internal contour 42 of the second sipe blade 38. The section of the bulge has various shapes and is delimited by a contour of rounded, polygonal, convex or concave shape. By way of example, the bulge is integral with the second sipe blade 38. The height of the second sipe blade is between 2 mm and 20 mm and preferably between 2 mm and 14 mm. The thickness of the bulge is understood as being the section of the bulge which is comprised 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 bulge 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 bulge 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 bulge 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.
At least one recessed pattern of the lining 16 is substantially in the form of a parallelepiped or, in other words, of a 6-faced polyhedron, the opposite faces of which are substantially parallel. Preferably, the moulding surface 14 comprises a plurality of said recessed patterns, which are distributed uniformly over the entirety of said moulding surface. At least 20% of said recessed patterns and preferably at least 50% of said recessed patterns are partially delimited by at least one first protruding pattern 30 and at least one second protruding pattern 36. Preferably, the first protruding pattern and the second protruding pattern intersect. Preferably, said recessed patterns are delimited by at least one first protruding pattern and a pair of second protruding patterns, the first protruding pattern intersecting a second protruding pattern at each of its ends.
The protruding patterns 26 may form intersections 48. In a radial view of the lining, an intersection is delimited by a contour surrounding the superposed parts of each protruding pattern. Consequently, the expression “intersection of protruding patterns” is not understood to mean the regular parts, or parts outside said contour, of the intersecting protruding parts, but is understood to mean at least the singular parts and the superposed parts of said patterns. The regular parts of the protruding patterns are the parts in which the radial profile thereof is not impacted by the intersection of the protruding patterns.
The first protruding pattern 30 delimits a first recessed pattern 50, and the second protruding pattern 36 forms an intersection 48 with the first protruding pattern. The first protruding pattern 30 and the first recessed pattern 50 have a longitudinal shape. The intersection 48 partially delimits at least one second recessed pattern (not shown). The second recessed pattern protrudes with respect to the first recessed pattern and forms a tongue 52 (
According to a first variant illustrated in
According to a second embodiment variant illustrated in
Further variants and embodiments of the invention may be envisaged without departing from the scope of these claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002357 | Mar 2020 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/055739 | 3/8/2021 | WO |
