Tire curing mold with sealing elements

Abstract

A tire curing mold (2) is disclosed, comprising two shells (21) each for molding a sidewall of a tire, and a ring of sectors (22) for molding a tread of a tire, each sector (22) having an inner liner (23) and two segments (27) in the form of circular arcs, each segment (27) being arranged to fill a gap present at the interface between the inner liner (23) and a shell (21) and not coinciding with a molding surface (24) of the curing mold.

Description

Technical Field

[0001] This invention belongs to the field of tire manufacturing, and in particular relates to a sector-type tire curing mold. Background Technology

[0002] Tire manufacturing includes a curing step, during which the green tire is vulcanized and molded to obtain a tire with desired mechanical properties, geometry, and appearance. Curing takes place in a tire curing mold that includes molding elements. The molding elements together form an internal molded surface corresponding to the anterior portion (négatif) of the desired outer surface of the tire.

[0003] During the curing step, the green tire is pressurized and heated against the inner surface of the mold. The temperature conditions of the green rubber significantly reduce its viscosity, which, together with the pressure conditions, promotes the formation of rubber flash between the molded elements. To avoid flash formation, the gap between the molded elements, or in other words, the spacing, must be less than 0.03 mm.

[0004] In known methods, the molding elements of a sector-type mold include a sector for molding the tire tread and two housings for molding the tire sidewall. The sectors are arranged circumferentially to form an annulus, and the two housings are arranged axially on both sides of the annulus in a shroud-like manner. Each molding element is in contact with multiple other molding elements. Furthermore, the mold is subjected to considerable temperature differences, which often cause the molding elements to expand significantly. Under these conditions, it is difficult to achieve mold closure with gaps between molding elements less than 0.03 mm without very precise manufacturing of the molding elements, and the very precise manufacturing of molding elements is very expensive.

[0005] Application EP0522374, submitted in the applicant's name, proposes a sector-type mold 10, such as... Figure 1 and Figure 2As shown. The fan portion 11 has a liner 12 and a support member 14. The liner 12 forms part of the inner molded surface 13 of the curing mold, and is fastened to the support member 14. Furthermore, the fan portion includes two annular segments 15 made of steel, which are arranged laterally on the support member, such that in the closed position of the mold, the annular segments are located at the two interfaces between the liner and the housing 16. In the closed position of the mold, the annular segments 15 are in circumferential contact in pairs, and radial pressure is applied to them toward the inside of the mold, thus elastically compressing the annular segments 15 until the liner 12 turns to circumferentially contact in pairs. Therefore, the aluminum liner 12 is also elastically and / or plastically compressed. The circumferential compression of the assembly formed by the annular segments 15 and the liner element 12 tends to reduce the diameter of the assembly, which then radially contacts the housing. Therefore, due to the elastic and / or plastic deformation of the annular segment and the liner, it is possible for the mold to close with a gap of less than 0.03 mm between the molded elements.

[0006] However, the annular segments are precision components, requiring high-quality steel with good elastic properties. Their arrangement relative to other parts of the mold requires numerous adaptations, which complicates the mold design. Finally, mold assembly requires precise fit. Therefore, the production, adaptation, and assembly of such curing molds are very expensive.

[0007] Furthermore, these segments coincide with the internal molding surface. In other words, the segments have a molding surface that forms part of the internal molding surface of the mold. Therefore, it is very limited, or even impossible, to make or insert engravings on the portion of the internal molding surface formed by the annular segments, which are intended to form markings on the tire shoulder.

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a solution to avoid rubber overflow. Summary of the Invention

[0009] Therefore, the first subject of the present invention is a tire curing mold comprising two housings and a fan-shaped portion, each housing for molding the sidewall of a tire and the fan-shaped portion for molding the tread of a tire, each fan-shaped portion having an inner liner and two arcuate segments, characterized in that each segment is arranged to fill the gap at the interface between the inner liner and the housing, and does not coincide with the molding surface of the curing mold.

[0010] Therefore, the gap at the interface between the liner and the shell is filled by the segment, or in other words, the gap is zero or less than 0.03 mm. This avoids the formation of rubber overflow. Furthermore, since the segment does not coincide with the molding surface, it is easy to create or insert engravings for forming marks on the tire shoulder.

[0011] Advantageously, the segment is accommodated in a recessed groove on the contact surface. This design is simple and inexpensive compared to existing designs.

[0012] Preferably, in the closed position of the mold,

[0013] - The liner contacts the shell only through the aforementioned section.

[0014] - The fan sections make circumferential contact in pairs through the liner.

[0015] In other words, in the closed position of the mold, the segment is in radial contact with the shell, and radial pressure is applied to the segment, causing it to be elastically and / or plastically compressed until the liner is in circumferential contact with the adjacent liner. Thus, through the elastic and / or plastic deformation of the segment, the mold closes, wherein the gap between the molded elements is zero or less than 0.03 mm.

[0016] According to a variant of one implementation, in the closed position of the mold,

[0017] - The liner contacts the shell through the section and at the interface between the liner and the shell, via the contact surface of the liner.

[0018] - The fan sections make circumferential contact in pairs through the liner.

[0019] Therefore, in the closed position of the mold, the segment is in radial contact with the shell, and radial pressure is applied to the segment, causing it to be elastically and / or plastically compressed until the liner is in circumferential contact with the adjacent liner, and until the liner contacts the shell via the contact surface. Thus, through the elastic and / or plastic deformation of the segment, the mold closes, wherein the gap between the molding elements is zero or less than 0.03 mm.

[0020] Preferably, the segment is spaced apart from the molding surface, more preferably, by 0.1 mm to 10 mm. Therefore, the molding surface of the liner is not weakened by being too close to the groove and the segment. Furthermore, through radial compression, the segment widens axially and can be flush with or exceed the molding surface. Therefore, sufficient distance is required between the molding surface and the segment. Conversely, excessive distance related to insufficient radial compression of the segment in the closed position of the mold increases the risk of overflow. Therefore, it is necessary to limit this distance. In summary, such a design improves the forming quality of the tire.

[0021] Advantageously, the liner material has an allowable contact pressure of 350 MPa or greater, preferably greater than 400 MPa, known as the Brinell hardness test pressure. Therefore, the contact surfaces between the liners exhibit good wear resistance and Brinell hardness test resistance. The service life of the mold is thus improved. Preferably, the liner material is selected from materials including ferrous alloys (e.g., steel).

[0022] Preferably, the liner is obtained by a process of selective melting and solidification.

[0023] Advantageously, the material of the segment has an allowable contact pressure of less than 350 MPa, preferably less than 300 MPa, known as the Brinell hardness test pressure. Therefore, the segment can be more easily subjected to localized deformation, or even flattening, to achieve a tight seal between the housing and the liner. Preferably, the material of the segment is selected from materials including aluminum alloys.

[0024] The second subject of the present invention is a method for manufacturing a tire, which includes the step of curing the tire in a mold according to the first subject of the present invention.

[0025] Finally, the subject of the invention is a tire for mounting on the rim of a wheel, characterized in that it is obtained by a manufacturing method according to a second subject of the invention. Attached Figure Description

[0026] The invention will be better understood from the remainder of the description based on the following figures:

[0027] - Figure 1 The radial cross-sectional view of the curing mold, which has already been described, is based on the prior art.

[0028] - Figure 2 It has already been described as Figure 1 Axial cross-sectional view of the mold in the middle;

[0029] - Figure 3 This is a radial cross-sectional view of certain components of the curing mold according to the present invention;

[0030] - Figure 4 yes Figure 3 An axial cross-sectional view of certain components of the mold in an intermediate position between the open and closed positions;

[0031] - Figure 5 yes Figure 3 An axial cross-sectional view of certain components of the mold in the closed position of the mold. Detailed Implementation

[0032] In the various figures, the same or similar elements are labeled with the same reference numerals. Therefore, they are not described systematically again.

[0033] Figure 1 and Figure 2 A tire curing mold 10, known in the prior art, is schematically shown. The mold defines a cavity 17 that is generally rotationally symmetrical about a central axis 18.

[0034] Throughout the following text, unless otherwise indicated, the axial direction refers to the direction parallel to the central axis 18, the radial direction 19 refers to the direction perpendicular to and intersecting the central axis 18, and the circumferential direction refers to the direction perpendicular to both the radial direction 19 and the central axis 18.

[0035] Figure 3 This is a partial radial cross-sectional view of a tire curing mold 20 according to the invention in its closed position. The curing mold includes two housings 21 and a ring of fan-shaped sections 22, each housing for molding the tire sidewall and the fan-shaped sections 22 for molding the tire tread. Each fan-shaped section 22 has a liner 23 and a support 25, the liner 23 forming an internal molding surface 24 together with the housing. The liner 23 of the fan-shaped section 22 is monolithic or may be composed of multiple liner elements. The liner 23 is arranged on the radially inner surface 26 of the support 25 and is fixed to the radially inner surface 26 of the support 25 by any suitable means. The radially inner surface 26 of the support is generally in the form of an axially extending cylinder. For example, the surface may also have a truncated conical shape. The fan-shaped sections 22 are in circumferential contact in pairs through their side surfaces, and the fan-shaped sections 22 and the housings 21 are spaced apart by a gap J.

[0036] According to one embodiment of the invention, the mold 20 includes two arcuate segments 27. Each segment 27 is arranged to fill the gap J at the interface between the liner 23 and the housing 21, and does not coincide with the molding surface 24 of the cured mold. For example, all segments 27 located at the upper interface, for example, between the housing 21 and the fan 22, form an annular ring with a smaller cross-section compared to the cross-section of the adjacent element. For example, the radially inner surface of the housing 21, i.e., the surface abutted by the segments 27, typically takes the form of an axially extending cylinder.

[0037] Section 27 is accommodated in a recessed groove 28 on the contact surface of the liner at the interface between the liner and the shell. The section has a rectangular cross-section. Figure 3 However, it can also have, for example, a circular or triangular cross-section. The cross-section of the groove is complementary to the cross-section of the segment to ensure good distribution of contact pressure, and / or the cross-section of the groove extends axially to a much greater extent than the cross-section of the segment, so that the segment is inserted into the groove and flattened when the segment is radially compressed.

[0038] The segment 27 is spaced apart from the molded surface 24 of the liner 23, more preferably, by 0.1 mm to 10 mm. Therefore, the molded surface is not weakened by being too close to the groove 28 and the segment 27. Furthermore, through radial compression, the segment 27 widens axially and can be flush with or beyond the molded surface 24. Therefore, a minimum distance is required between the molded surface and the segment. Conversely, in the closed position of the mold, excessive distance related to insufficient radial compression of the segment increases the risk of flash. Therefore, it is necessary to limit this distance.

[0039] The material of the liner 23 has an allowable contact pressure (referred to as the Brinell hardness test pressure) greater than or equal to 350 MPa, preferably greater than 400 MPa. Therefore, the sides of the liner 23 exhibit good abrasion resistance and Brinell hardness test resistance. The material of the liner 23 is selected from materials including ferrous alloys. For example, the liner is made of steel, and more specifically, of steel suitable for a manufacturing process that allows for solidification by selective melting.

[0040] The material of section 27 has an allowable contact pressure (referred to as Brinell hardness test pressure) of less than 350 MPa, preferably less than 300 MPa. Therefore, the section can be more easily subjected to localized deformation, or even flattening, to achieve a tight seal between the housing 21 and the liner 23. The material of section 27 is selected from materials including aluminum alloys.

[0041] Figure 4 The mold 20 is shown in an intermediate position between the open and closed positions. The fan portion 22 abuts radially against the housing 21 via the liner 23 (not via the support member 24), and the liner 23 itself abuts radially against the housing 21 via the segment 27. The fan portions 22 are close in the circumferential direction, but still do not make contact.

[0042] Figure 5 The mold 20 is shown in the fully closed position. In other words, the mold's closing mechanism applies a radial clamping pressure from the outside to the inside of the mold to the fan 22, causing the segment 27 to be elastically and / or plastically compressed radially until the fan 22 is in paired circumferential contact through its liner 23.

[0043] According to a variant of the first embodiment, in the closed position of the mold,

[0044] - The liner 23 contacts the housing 21 only through the section 27.

[0045] - The fan section 22 makes circumferential contact with the inner liner 23 in pairs.

[0046] According to a variant of the second embodiment, in the closed position of the mold,

[0047] - Liner 23 contacts housing 21 through the contact surface of liner 27 at the interface between liner and housing.

[0048] - The fan sections make circumferential contact in pairs through the liner.

[0049] The lining is obtained through a process of selective melting and solidification. "Selective solidification by melting" is understood as an additive manufacturing process designed to progressively and selectively polymerize or agglomerate an input processing material to obtain an output processing material. The input processing material is used in the form of powder, filament, or solution / bath, and / or in combinations of powder, filament, or solution / bath. The input processing material is generally introduced by depositing powder onto a support to form a layer. The support is in the form of a plate or a previously agglomerated layer. Agglomeration is typically achieved through the solidification of the input processing material, wherein the input processing material is completely or partially melted (sintered) by a localized or generalized energy input, and then cooled. The energy input is generally achieved by a laser or electron beam, although it can be achieved by infrared radiation or induction. In the case of lasers and electron beams, the positioning of the energy input is achieved by means of directional energy input (e.g., optical or electromagnetic means), respectively. This process gives the input processing material a predetermined shape and mechanical properties. The shape and characteristics depend on the raw materials and process parameters of the input processing material. The shape is typically a monomeric solid, although it can be composed of multiple monomeric solids.

Claims

1. A tire curing mold (20) comprising two housings (21) and a fan-shaped portion (22), each housing (21) for molding the sidewall of the tire, the fan-shaped portion (22) for molding the tread of the tire, each fan-shaped portion (22) having an inner liner (23) and two arc-shaped segments (27). Its features are, Each segment (27) is arranged to fill the gap at the interface between the liner (23) and the shell (21), and does not coincide with the molding surface (24) of the curing mold, the segment (27) being arranged to be spaced 0.1 mm to 10 mm from the molding surface (24). The material of the liner (23) has an allowable contact pressure greater than or equal to 350 MPa, referred to as the Brinell hardness test pressure, and the material of the section (27) has an allowable contact pressure less than 350 MPa, referred to as the Brinell hardness test pressure. The material of the liner (23) is selected from iron alloys, and the material of the section (27) is selected from aluminum alloys.

2. The mold according to claim 1, wherein, The segment (27) is accommodated in a recessed groove (28) on the contact surface of the liner at the interface between the liner and the housing.

3. The mold according to claim 1 or 2, wherein, In the closed position of the mold, - The liner (23) contacts the shell (21) only through the section (27), - The fan (22) makes circumferential contact in pairs through the liner (23).

4. The mold according to claim 1 or 2, wherein, In the closed position of the mold, - The liner (23) contacts the shell (21) through the section (27) and the contact surface of the liner at the interface between the liner and the shell. - The fan (22) makes circumferential contact in pairs through the liner (23).

5. The mold according to claim 1 or 2, wherein, The material of the liner (23) has an allowable contact pressure greater than 400 MPa, known as the Brinell hardness test pressure.

6. The mold according to claim 1 or 2, wherein, The liner (23) is obtained by a process of selective melting and solidification.

7. The mold according to claim 1 or 2, wherein, The material of section (27) has an allowable contact pressure of less than 300 MPa, known as the Brinell hardness test pressure.

8. A method for manufacturing a tire, comprising the step of curing the tire in a mold (20) according to any one of claims 1 to 7.

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