Mould Element Comprising A High-Contrast Texture

Abstract

A mould element (18) intended to be attached in a mould (10) for vulcanizing tires, the mould element (18) having the form of a skin with a thickness (E) comprised between 0.25 and 6 mm and comprising a bearing surface (20) with, on the opposite side, a moulding surface (22) intended to form all or part of the external surface of the tire. The mould element comprises a pattern (30) comprising a plurality of recessed (19, 21, 112) or protruding (106, 107) elements, formed as integral parts of the mould element (18).

Claims

1. A mould element adapted to be attached in a mould for vulcanizing tires, the mould element having the form of a skin with a thickness comprised between 0.25 and 6 mm, the said skin comprising a bearing surface and, on the opposite side, a moulding surface intended to form all or part of the external surface of the said tire, comprising a pattern provided with a plurality of recessed or protruding elements formed as integral parts of the said mould element, wherein the pattern comprises an organised arrangement of a plurality of elements, all or some of these elements being the repeat of one and the same basic element, the pattern present on the mould making it possible to obtain a particular texture on a tire vulcanized using the mould.

2. The mould element according to claim 1, wherein the depth of the recessed elements is less than or equal to 30% of the thickness of the mould element or the height of the protrusions is less than or equal to 30% of the thickness of the mould element.

3. The mould element according to claim 1, wherein the depth of the recessed elements is less than or equal to 15% of the thickness of the mould element or the height of the protrusions is less than or equal to 15% of the thickness of the mould element.

4. The mould element according to claim 1, wherein the pattern is arranged on a bar or a sipe blade of the mould element.

5. The mould element according to claim 1, wherein all or part of the pattern is formed by conical cavities distributed through the pattern with a density at least equal to one conical recess per square millimetre (mm.sup.2), each conical recess having a mean cross section comprised between 0.0005 mm.sup.2 and 1 mm.sup.2.

6. The mould element according to claim 1, wherein all or part of the pattern are substantially mutually parallel striations, the spacing of the striations in the pattern being at most equal to 0.5 mm, each striation having a mean width comprised between 0.02 mm and 0.5 mm.

7. The mould element according to claim 1, wherein all or part of the pattern forms recessed forms of parallelepipeds of a side length comprised between 0.05 mm and 0.5 mm, of a height comprised between 0.05 mm and 0.5 mm, the distance between two adjacent parallelepipeds in the texture being comprised between 0.05 mm and 0.5 mm.

8. The mould element according to claim 1, wherein the protruding elements form strands, said strands being distributed through the pattern with a density at least equal to one strand per square millimetre (mm.sup.2), each strand having a mean cross section S comprised between 0.0005 mm.sup.2 and 1 mm.sup.2.

9. The mould element according to claim 1, wherein the protruding elements form mutually parallel strips, the spacing of the strips in the pattern being at most equal to 0.5 mm, each said strip having a mean width comprised between 0.02 mm and 0.5 mm.

10. The mould element according to claim 1, wherein the recessed or protruding elements have mutually variable shapes and distances between them.

11. The mould element according to claim 1, configured for moulding a tire sidewall region.

12. The mould element according to claim 1, configured for moulding a region of a tire tread.

13. The mould element according to claim 1, produced by laser sintering.

14. A segmented mould for vulcanizing tires, each segment comprising a solid support block provided with a support surface and a set of linings attached to the support block, the set of linings comprising at least one mould element according to claim 1, arranged against a support surface of a support block.

Description

DESCRIPTION OF THE FIGURES

[0027] All the embodiment details are given in the description which follows which is supplemented by FIGS. 1 to 8, given solely by way of non-limiting examples and in which:

[0028] FIG. 1a is a perspective view of a first example of a mould element comprising a pattern according to the invention;

[0029] FIG. 1b is a perspective view of the mould element of FIG. 1a placed on a support block;

[0030] FIG. 2a is a front view of a second exemplary embodiment of the mould element with support block according to the invention;

[0031] FIG. 2b is a side view of the mould element of FIG. 2a placed on a support block;

[0032] FIG. 3 shows a mould element comprising a pattern formed of striations recessed into the mould;

[0033] FIG. 4 shows a mould element in which the striations of the pattern have a pyramid-like cross section;

[0034] FIG. 5 depicts a pattern comprising a plurality of holes;

[0035] FIG. 6 is an enlarged view of the pattern of FIG. 5;

[0036] FIG. 7 shows a mould element comprising a pattern formed of strands protruding from the mould;

[0037] FIG. 8 shows a mould element comprising a pattern formed of strips.

DETAILED DESCRIPTION OF THE INVENTION

[0038] A pattern on a mould means an organized arrangement of a plurality of elements (striations, holes, strands, strips), all or some of these elements being a repeat of one and the same basic element, the pattern present on the mould making it possible to obtain a particular texture on a tire.

[0039] In the description which will follow, elements that are substantially identical or similar will be denoted by identical references.

[0040] FIG. 1 illustrates a portion of a segmented mould 10 for vulcanizing tires. This mould 10 comprises a body 12 advantageously made of aluminium alloy and notably comprising a plurality of support surfaces 16 intended to accept a plurality of inserts 18. Each insert adopts the form of a thin skin, on which are arranged networks of tire tread pattern elements 24. Included among the tread pattern elements 24 there are notably sipe blades 26 which are intended to form circumferential slits in the tread of the tire or circumferential bars 28 which are intended to form a longitudinal groove in the tread of the tire. The various bars 28 may be connected by axial sipe blades 29 to form the network of tread pattern elements 24.

[0041] Each of the inserts 18 comprises a first 20 and a second 22 surface which are opposite surfaces, the first surface 20 being intended to be in contact with the support surface 16 of the mould. The inserts are specifically designed to allow patterns 30 used to produce textures on the tires and which will be moulded with the mould to be incorporated into the body 12. For that, at least some of the inserts 18 comprise a pattern 30 which comprises a plurality of recessed or protruding elements, the said pattern being formed as an integral part of the inserts. In other words, each insert 18 including the patterns 30 is produced as a single piece. The thickness of each insert 18 is comprised between 0.25 and 6 millimetres or even more.

[0042] In order to produce such an insert 18, the procedure advantageously involves selective laser sintering of a metallic powder. During manufacture of the insert, care is taken to ensure that the shape of the first surface 20 is the complement of the shape of the support surface 16 of the body 12 so that the insert 18 can engage correctly with the body.

[0043] The mould element 18 comprises one or several patterns 30. According to the exemplary embodiments, the patterns 30 are provided between the bars and sipe blades, and/or on portions of bars and/or on portions of sipe blades. In the example of FIG. 1b, patterns 30 defining profiles of substantially square shapes are provided between certain sipe blades. Depending on the desired appearance, a near-infinite number of pattern shapes or profiles may be provided. A longitudinal pattern is moreover provided along a bar 31. This example also includes textures on the flanks of the sipe blades 29. The patterns 30 are also formed as an integral part of the mould element. The mould elements, including the patterns 30, are advantageously produced by laser sintering, this method of manufacture affording the advantage of making it possible to create very fine and/or highly complex patterns, as described hereinafter.

[0044] FIG. 2a illustrates another exemplary embodiment in which patterns 30 are provided between each of the sipe blades 24.

[0045] The extent of the patterned regions, the profiles and the positionings of the patterned regions vary according to the embodiment, the examples illustrated being provided only by way of nonlimiting illustration. Furthermore, the patterns may adopt striated shapes, as depicted for example in FIG. 3, which shows square-wave striations 19, or in FIG. 4, which shows pyramid-shaped striations 21.

[0046] FIG. 5 illustrates the pattern according to a non-limiting first alternative form of the first embodiment. In this alternative form, the pattern is formed by a plurality of cavities 112. The cavities 112 here are in the shape of cones which extend into the depth of the mould and open onto the mould in the form of circular openings 111. The cavities 112 thus have a cross section which decreases into the depth of the mould. It will be noted that, in this alternative form, the openings 111 of the cavities 112 do not touch. The openings 111 are separated by intermediate regions 113.

[0047] Furthermore, the openings 111 are evenly distributed across the mould so that the distance d between each opening of the pattern is roughly similar.

[0048] FIG. 6 is an enlarged view of the pattern of FIG. 5. All or some of the cavities here have at least one wall 114 which, when viewed in section, makes an angle comprised between 10 and 60 with respect to a direction Z perpendicular to the pattern.

[0049] FIG. 7 illustrates an embodiment in which the pattern 30 comprises a plurality of strands 106, the strands 106 being distributed through the pattern with a density at least equal to one strand per mm.sup.2, each strand having a mean cross section S comprised between 0.0005 mm.sup.2 and 1 mm.sup.2.

[0050] It will be noted that the mean cross section of each strand corresponds to the mean of the cross sections S measured at regular intervals from the base of the strand. The strands 106 have a conical overall shape with a cross section decreasing along the height Hb of these strands.

[0051] FIG. 8 illustrates one embodiment in which the pattern 30 comprises a plurality of mutually parallel strips 107, the spacing of the strips 107 in the pattern 30 being at most equal to 0.5 mm, each strip 107 having a mean width comprised between 0.02 mm and 0.5 mm. It will be noted that the mean width corresponds to the mean of the widths 1 measured at regular intervals along the height Hl of the strip, the height of each strip being comprised between 0.05 and 0.5 mm. In another alternative form of embodiment, the pattern comprises a combination of strands 106 and/or of strips 107.

[0052] The invention is not restricted to the examples described and depicted and various modifications can be made thereto without departing from its scope. Thus, according to another nonlimiting alternative form of embodiment, the strips 107 of FIG. 8 may be discontinuous. They have a planar part between them. They may further have differences in cross section from one another. In addition, the strips may have curvatures or corners, notably along their length. They may furthermore be of variable length.

[0053] Thus, according to another nonlimiting alternative form of embodiment, the cavities 112 may have a parallelepipedal cross section of side length C comprised between 0.05 mm and 0.5 mm, of height Hp comprised between 0.05 mm and 0.5 mm, the distance between two adjacent cavities in the texture being comprised between 0.05 mm and 0.5 mm. As an alternative, the cross section of the cavities may be circular, polygonal (for example hexagonal). With square or polygonal structures it is possible to organize the openings 111 more easily in relation to one another so as to limit the surface area of the intermediate regions 113 between these openings. With such shapes of opening it is possible more easily to achieve high levels of occupancy of the openings on the mould.

[0054] In order to adapt a mould for manufacturing a new type of tire, all that is required is the removal of the mould elements 18 arranged on the body 12, which correspond to the old type of tire manufactured, then the addition, advantageously in a single operation, of the new mould elements 18 onto the surface 16 of the body 12. Because the various lining elements 24 and the patterns 30 are borne by one and the same single skin 18, it is possible to add all the lining elements of one and the same segment to a support block 12 in a single operation, something which proves to be particularly swift.

[0055] The invention has been described in conjunction with a mould of the segmented type. It may also be implemented in relation to a mould of some other type.

NUMERICAL REFERENCES USED IN THE FIGURES

[0056] 10 Mould [0057] 12 Body [0058] 16 Support surface [0059] 18 Mould element [0060] 19 Square-wave striation [0061] 20 Bearing surface [0062] 21 Pyramid-shaped striation [0063] 22 Moulding surface [0064] 24 Network of tire tread pattern elements [0065] 26 Sipe blades [0066] 28 Circumferential bars [0067] 29 Axial sipe blades [0068] 30 Patterns [0069] 31 Bar [0070] 106 Strands [0071] 107 Strips [0072] 111 Circular opening [0073] 112 Cavity [0074] 113 Intermediate region [0075] 114 Wall