Patent ID: 12194701

DETAILED DESCRIPTION

In the various figures, elements that are identical or similar have the same reference signs. They are not therefore systematically described again.

FIG.1schematically illustrates a curing mould10for a tyre used to mould and vulcanize a green tyre, in order to obtain a tyre having the desired geometry and appearance. The mould defines an internal space having a general symmetry of rotation about a central axis12. The curing mould comprises a frame, moulding elements, vulcanizing means, and means for opening and closing the mould. The opening and closing means are suitable for causing the moulding elements to move between an open position and a closed position. The open position corresponds to the step of removing a moulded, vulcanized tyre, and to the step of introducing a new green tyre. The closed position (FIG.1) corresponds to the step of moulding and vulcanizing the green tyre. The vulcanizing means are suitable for providing the heat energy and pressure respectively necessary for vulcanizing and moulding the green tyre. By way of example, the thermal energy and pressure are provided by pressurized water vapour circulating around the mould and inside the green tyre in an extendible membrane. In the closed position of the mould, the moulding elements form a moulding surface14that is the negative of the desired external surface of the tyre. The moulding elements more particularly comprise a lining16for moulding the tread of the tyre, two shells18for moulding the sidewalls of the tyre, and two rings20for moulding the beads of the tyre.

FIG.2illustrates a portion of the moulding surface14forming hollows or protrusions. The protrusions extend from the outside of the mould towards the inside of the mould. By way of example, the protrusions take the form of parallelepipeds, grooves24extending circumferentially and/or transversely, or blades26or spurs. The protrusions24,26define angular or rounded cavities28. By way of example, the cavities take the form of prisms, or extend circumferentially and/or transversely along a polygonal cross-section. The moulding surface14is circumscribed by a substantially cylindrical or toric external former, known as the “crown form”.

Hereinafter, unless otherwise stated, an axial or transverse direction denotes a direction parallel to the central axis12; the radial direction32denotes a direction perpendicular to the central axis and therefore intercepting it; and the circumferential direction denotes a direction perpendicular to a radial direction, and orthogonal to the central axis.

FIGS.3to5illustrate more particularly a cavity28comprising at least one blade26. The cavity28closes on a radially outermost bottom wall30of said cavity, and optionally tangent to the crown form.

The lining16is divided into a plurality of lining elements, each lining element including a plurality of blades26, a body32and optional inserts. A blade26is a thin moulding element the thickness of which generally varies between 0.2 and 2 mm. The blade26includes a moulding portion34that extends radially from the bottom wall30, and an anchoring portion36suitable for being submerged in the body32of the lining element. By way of example, a blade26is obtained using a method for removing material such as laser cutting, plastic deformation such as stamping, additive manufacturing such as consolidation by selective melting, or a combination of these methods. Preferably, a lining element is obtained using a casting method by overmoulding the body32of the lining element around the anchoring portion36of the blades, or by manufacturing the body32of the lining element using an additive manufacturing method, then assembling said body with the blades. The blades26can be assembled with the lining body32so as to produce a lining element using an assembly method by screwing, bonding, or welding, or any other appropriate assembly method. Finally, a lining element can be obtained by an additive manufacturing method in which the body32of the lining element and the moulding portion34of the blades are produced in one piece.

The curing mould10is provided with a venting device suitable for discharging the air trapped between the external surface of the green tyre and the moulding surface14. To this end, the venting device comprises vents38(FIG.4) that pass through the lining16, forming so many passages for the air to the outside of the mould. Each cavity28closes on one or more vents. By way of example, a vent38takes the form of a hole, or of the passage resulting from the assembly clearance between a blade26and the body32of a lining element.

At least one cavity28is divided into chambers40by at least one blade26. “Chamber” is not given to mean a hermetically sealed space formed by the division of the cavities by the blades; it is given to mean a space in which air might be trapped between the rubber entering the chamber and the last moulding zones of the chamber and, more particularly, the angular portions of the chamber. “Angular portion” is given to mean that the walls that make up the chamber or the cavity form intersections the radius or bevel of which is less than 5 mm.

At least one of said chambers40does not close on a vent38, thus preventing the air from a pocket from being discharged to the outside of the mould10. At least one duct42passes through the blade26so that the chamber that does not close on a vent38communicates through the duct42with a chamber that does close on a vent38. The air can thus flow from an air pocket located in a non-vented chamber to a vented chamber. By way of example, a cavity28can be divided into a series of chambers40, all of the chambers communicating with each other in a given network by means of ducts42, the number of vented chambers being greater than or equal to1, and strictly less than the total number of chambers of the cavity28.

According to the invention, the cross-section of a duct28has an area of between 0.0001 mm2and 0.25 mm2and, more preferably, 0.01 mm2and 0.1 mm2. The cross-section of a duct is therefore small and weakens the blade less. The blade includes a plurality of ducts42arranged in alignment or in any other appropriate arrangement, and the ducts are 0.01 mm to 2 mm apart and, more preferably, 0.1 mm to 0.5 mm apart. The density of the ducts is up to 100 ducts per mm2and, more preferably, up to 25. The ducts are arranged secant or adjacent to, or at most 5 mm and, more preferably, 2 mm from a contour44defining the intersection between the moulding portion34of the blade and the bottom wall30of said cavities. The ducts42are adjacent to or at most 5 mm and, more preferably, at most 2 mm, from the last moulding zones and, in particular, from the angular parts of a chamber40.

According to one variant embodiment, when the blade26is produced separately from the body32of the lining element, the ducts42are arranged on the anchoring portion36of the blade, adjacent to or at most 2 mm from the contour44.

The blade26includes a stiffener along the contour44having a height, along the extension of the blade towards the inside of the mould, of up to 2 mm and, preferably, between 0.6 and 1.4 mm. “Stiffener” is given to mean an additional thickness across the contour of the moulding portion34preventing the blade from being elastically or plastically deformed during the moulding step or the mould removal step.

By way of example, the axial cross-section of a duct has a circular outline having a diameter of between 0.01 mm and 0.5 mm and, more preferably, 0.05 mm and 0.3 mm; a polygonal outline, for example triangular, having a base or height of between 0.1 and 0.7 mm and a curvature at the vertices of between 0.01 mm and 0.2 mm; or an outline in the form of a slot with a width of between 0.1 and 0.3 mm.

In the example illustrated inFIG.3, ducts42pass through the blade, arranged in an alignment, on the moulding portion34of the blade. In the example illustrated inFIG.5, a duct42is adjacent to the contour44. The ducts have a circular cross-section having a diameter equal to 0.2 mm, and the ducts are spaced at least 0.2 mm apart.

According to a first variant embodiment, during the manufacturing of a curing mould according to the invention, a blade26is manufactured using a method or combination of methods selected from the following group: removal of material such as laser cutting, plastic deformation such as stamping, or additive manufacturing and, more preferably, selective consolidation by melting. The duct(s)42is/are then produced by means of a laser piercing method. A laser piercing method is particularly suitable for producing ducts42with an axial cross-section having a circular outline with a diameter of between 0.05 mm and 0.3 mm, through a thin blade with a thickness of between 0.2 mm and 2 mm. The blade16is then assembled with the body of the lining element.

“Additive manufacturing” is given to mean a manufacturing method in which material is added.

“Selective consolidation by melting” is given to mean an additive manufacturing method with the aim of gradually and selectively aggregating or agglomerating additional input work material so as to obtain an output work material. The input work material takes the form of and/or is included in the composition of a powder, a wire or a solution/bath. The input work material is generally added by depositing a powder on a substrate so as to form a layer. The substrate takes the form of a plate or a previously agglomerated layer. Agglomeration is generally obtained by solidification of the input work material that has been fully or partially melted (sintered) by a localized or generalized energy input, then cooled. The energy input is generally provided by a laser or an electron beam, although it can be provided by induction or infrared radiation. In the case of a laser or an electron beam, the energy input is localized by means for orienting the energy input, such as optical or electromagnetic means respectively. The method gives the input work material a predetermined shape and mechanical properties. Said shape and said properties depend on the material of the input work material and the parameters of the method. Said shape is generally a one-piece solid, although it can consist of a plurality of one-piece solids.

According to a second variant embodiment, the blade26is manufactured and the duct(s)42is/are produced simultaneously using an additive manufacturing method. An additive manufacturing method is particularly suitable for producing ducts42with an axial cross-section having a circular outline with a diameter of between 0.01 mm and 0.5 mm. The blade26is then assembled with the body32of the lining element.

According to a third variant embodiment, the body32of a lining element, the moulding part34of the blade(s) and the duct(s)42are manufactured in one piece, using an additive manufacturing method.

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