Pressing bladder for a vulcanisation mould, process for making a moulded and vulcanised tyre and moulded and vulcanised tyre

Abstract

A pressing bladder (103) for a vulcanisation mould (100) has a radially external surface (105) configured to adhere to a radially internal surface of a green tyre (5a) during a moulding and vulcanisation step of the green tyre to obtain a moulded and vulcanised tyre (5). The radially external surface (105) comprises reliefs (107) having the shape of ribs (110) or columns (111) and bridges (112).

Description

[0001] Pressing bladder for a vulcanisation mould, process for making a moulded and vulcanised tyre and moulded and vulcanised tyre

[0002] The present invention relates to a pressing bladder for a vulcanisation mould, a process for making a moulded and vulcanised tyre and a moulded and vulcanised tyre.

[0003] A tyre for vehicle wheels typically has a substantially toroidal structure concentric with respect to a rotation axis of the tyre itself during operation, and has a substantially concave internal surface, delimiting an internal cavity which, in operating conditions, is internally closed by a mounting rim. On the external surface of the tyre, a tread band may be identified, and a pair of sidewalls which extend radially from respective axially opposite edges of the tread band towards respective beads adapted to engage with the mounting rim.

[0004] Following the building of the green tyre by assembling the respective components, a moulding and vulcanisation step is generally carried out to determine the structural stabilisation of the tyre by cross-linking the elastomeric compositions.

[0005] The moulding and vulcanisation step is carried out in a vulcanisation mould comprising a vulcanisation chamber and, inside it, a pressing bladder. During the moulding and vulcanisation step, the pressing bladder is expanded inside the green tyre to compress it against the walls of the mould and imprint the desired tread pattern and any distinctive graphic marks on the tyre sidewalls.

[0006] The term "functional insert" means a support structure combinable or combined with at least one component, the support structure being able to also include part of said at least one component, said at least one component being adapted to perform a function when associated with a moulded and vulcanised tyre. Functional inserts include, for example, a sensor device configured to monitor and / or store operating parameters of the tyre or a means for generating and / or storing energy with the associated housing bodies.

[0007] The term "crown band" refers to a portion of the radially internal surface of the tyre, opposite the tread band.

[0008] The term "relief" means a portion protruding or projecting from a radially external surface of a pressing bladder configured to adhere to a radially internal surface of a green tyre during a moulding and vulcanisation step of the green tyre.

[0009] The term "height" of a relief means the distance between the plane tangent to the radially external surface of the pressing bladder, at the base of the relief, and the plane, parallel to the previous one, passing through the apical or radially most external part, of the relief itself.

[0010] The term "depression" refers to a hollow in the radial internal surface of a tyre.

[0011] The term "depth" of a depression means the distance between the plane tangent to the radially internal surface of a tyre, at the edge of the depression, and the plane, parallel to the previous one, passing through the radially innermost part of the depression itself.

[0012] The term "groove" refers to an elongated depression on the radially internal surface of a tyre along a prevailing longitudinal direction of development. The term "width" of a groove refers to the distance between the edges of the depression on the radially internal surface of the tyre.

[0013] The term "rib" refers to an elongated relief on the radially external surface of a pressing bladder along a prevailing longitudinal direction of development.

[0014] The term "width" of a rib refers to the distance between the edges of the rib on the radially external surface of the pressing bladder.

[0015] The term "parallel" in relation to ribs / grooves means ribs / grooves that do not intersect each other, whether rectilinear or curvilinear, and not necessarily at a constant distance from each other, whether parallel or perpendicular to the prevailing direction of development.

[0016] The term "distance" between two adjacent parallel ribs / grooves means the interval between two corresponding points of two adjacent ribs / grooves, measured parallel to the radially external surface of the pressing bladder or the radially internal surface of the tyre and perpendicular to the longitudinal direction of the rib or groove.

[0017] The term "cell" refers to a depression which, parallel to the radially internal surface of a tyre, does not have a prevailing development dimension.

[0018] The term "column" refers to a relief which, parallel to the radially external surface of a pressing bladder, does not have a prevailing development dimension.

[0019] The terms "radial" and "axial" and the expressions "radially internal / external" and "axially internal / external" are used with reference to the radial direction of the tyre / pressing bladder (i.e. a direction perpendicular to the geometric rotation axis of the tyre / the central axis of the pressing bladder) and to the axial direction of the tyre / pressing bladder (i.e. a direction parallel to the geometric rotation axis of the tyre / the central axis of the pressing bladder).

[0020] The terms "circumferential" and "circumferentially" are used in reference to the annular development of the tyre / pressing bladder. A radial plane of the tyre / pressing bladder contains the rotation axis of the tyre or the central axis of the pressing bladder.

[0021] Document WO2015 / 097645A1, on behalf of the same Applicant, describes an apparatus for the surface treatment of green tyres which comprises a support for a green tyre having at least one surface to be treated. A device for applying a semi-permanent treatment substance comprises a nozzle configured to spray the treatment substance at low pressure onto the surface to be treated and an applicator configured to distribute the sprayed treatment substance onto the same surface. A support element of the application device is configured to position the application device at a specified application distance from the surface to be treated of the green tyre. The surface treatment apparatus comprises devices for generating a controlled relative movement between the green tyre and the application device so as to apply the treatment substance to the surface to be treated according to a predefined path, by means of the application device.

[0022] As illustrated in WO2015 / 097645A1 before the moulding and vulcanisation step, surface treatments, such as the deposition of a treating substance or release agent on the radially internal surface of the tyre, may be carried out. The Applicant notes that the release agent is adapted to improve the interaction between the radially internal surface of the tyre and the pressing bladder, facilitating the removal of the tyre at the end of the moulding and vulcanisation step and preserving the integrity of the pressing bladder so as to prolong the operational life thereof.

[0023] The Applicant has however observed that during the moulding and vulcanisation operations, problems of excessive adhesion and / or poor smoothness may arise between the radially internal surface of the tyre and the pressing bladder even if the treatment substance or a release agent are deposited with care. Such phenomena may compromise the integrity of the pressing bladder which must be replaced frequently resulting in frequent maintenance interruptions.

[0024] In an attempt to overcome these drawbacks, the Applicant felt it was necessary to focus its attention on the interaction step between the tyre and the pressing bladder rather than on the deposition step of the release agent on the radially internal surface of the green tyre.

[0025] In particular, the Applicant observed that one of the factors influencing the distribution of the release agent between the radially internal surface of the tyre and the pressing bladder is the shape of the radially external surface of the pressing bladder. More precisely, the Applicant observed that the provision of reliefs on at least a portion of the radially external surface of the pressing bladder improves the distribution of the release agent.

[0026] The Applicant has finally found that providing reliefs, more preferably reliefs having the shape of parallel ribs, arranged on at least a portion of the radially external surface of the pressing bladder, more preferably at at least a central middle line band, improves the distribution of the release agent in the interaction between the radially internal surface of the tyre and the pressing bladder, generating corresponding depressions in the radially internal surface of the tyre during the moulding and vulcanisation step.

[0027] According to a first aspect, the invention relates to a pressing bladder for a vulcanisation mould.

[0028] Preferably, the pressing bladder has a radially external surface configured to adhere to a radially internal surface of a green tyre during a moulding and vulcanisation step of the green tyre itself to obtain a moulded and vulcanised tyre.

[0029] Preferably, said radially external surface comprises reliefs having the shape of ribs or columns and bridges.

[0030] The Applicant believes that the presence of reliefs on at least a portion of the radially external surface of the pressing bladder and more preferably at least at the central middle line band, improves the distribution of the release agent in the interaction between the radially internal surface of the tyre and the pressing bladder itself, thus preserving the integrity of the pressing bladder.

[0031] According to a second aspect, the invention relates to a process for making a moulded and vulcanised tyre.

[0032] Preferably, provision is made for building a green tyre.

[0033] Preferably, provision is made for applying a layer of release agent to a radially internal surface of the green tyre.

[0034] Preferably, provision is made for subjecting said green tyre to a moulding and vulcanisation step to obtain a moulded and vulcanised tyre.

[0035] Preferably, said moulding and vulcanisation step comprises placing the green tyre in a vulcanisation mould having an internal moulding surface and a pressing bladder according to the preceding aspect.

[0036] Preferably, said moulding and vulcanisation step comprises expanding the pressing bladder inside the green tyre.

[0037] Preferably, said moulding and vulcanisation step comprises providing heat inside the vulcanisation mould to obtain said moulded and vulcanised tyre.

[0038] Preferably, said moulding and vulcanisation step comprises extracting said moulded and vulcanised tyre from the vulcanisation mould.

[0039] According to a third aspect, the invention relates to a moulded and vulcanised tyre.

[0040] Preferably, said moulded and vulcanised tyre comprises a radially internal surface.

[0041] Preferably, said moulded and vulcanised tyre has depressions with respect to said radially internal surface.

[0042] Preferably, said depressions have the shape of grooves or cells and connecting channels.

[0043] The Applicant believes that the presence of said depressions, more preferably of parallel grooves at least at the crown band, improves any subsequent processing steps of the tyre which affect the radially internal surface of the tyre itself, for example by contributing to the evacuation of gas during the adhesion of a functional insert to the radially internal surface of the tyre.

[0044] In at least one convenient embodiment, the invention further comprises one or more of the following preferential features.

[0045] Preferably, said reliefs have a height between 0.01 mm and 1 mm. Preferably, said reliefs have a height of 0.04 mm.

[0046] Preferably, said reliefs are arranged at at least one central band located in a middle line area with respect to a central axis of the pressing bladder.

[0047] Preferably, said central band corresponds to a crown band of the radially internal surface of the moulded and vulcanised tyre.

[0048] Preferably, said reliefs have the shape of columns and bridges, with two adjacent columns connected by at least one bridge.

[0049] Preferably, said bridges have a width between 0.05 mm and 1 mm.

[0050] Preferably, said bridges have a width of 0.7 mm.

[0051] Preferably, said reliefs have the shape of ribs and said ribs have a width between 0.05 mm and 1 mm.

[0052] Preferably, said ribs are arranged according to a grid pattern.

[0053] Preferably, said ribs arranged according to a grid pattern have a width of 0.5 mm.

[0054] Preferably, said ribs are parallel to each other.

[0055] Preferably, said parallel ribs have a width of 0.2 mm.

[0056] Preferably, a distance between two adjacent parallel ribs is between 0.1 mm and 5 mm.

[0057] Preferably, the distance between two adjacent parallel ribs is 0.7 mm.

[0058] Preferably, the distance between two adjacent parallel ribs is constant along a direction parallel to a prevailing development direction of the ribs.

[0059] Preferably, the distance between two adjacent parallel ribs is constant along a direction perpendicular to a prevailing development direction of the ribs.

[0060] Preferably, the set of ribs is elongated on the radially external surface along a single prevailing longitudinal development direction oriented in a direction parallel to a central axis of the pressing bladder.

[0061] Preferably, the pressing bladder comprises evacuation channels obtained at two respective lateral evacuation bands and configured to channel the fluids placed between a green tyre and the pressing bladder itself during the moulding and vulcanisation step towards the environment outside the vulcanisation mould. Preferably, the central band comprising said reliefs extends along the entire axial section between the two lateral evacuation bands.

[0062] Preferably, the ribs are rectilinear.

[0063] Preferably, the ribs are curvilinear.

[0064] Preferably, said depressions have a depth between 0.01 mm and 1 mm with respect to said radially internal surface of the tyre. Preferably, said depressions have a depth of 0.04 mm.

[0065] Preferably, said depressions have the shape of grooves and said grooves have a width between 0.05 mm and 1 mm.

[0066] Preferably, said grooves are arranged according to a grid pattern.

[0067] Preferably, the grooves arranged according to a grid pattern have a width of 0.5 mm.

[0068] Preferably, said grooves are parallel to each other.

[0069] Preferably, said parallel grooves have a width of 0.2 mm. Preferably, a distance between two parallel and adjacent grooves is between 0.1 mm and 5 mm.

[0070] Preferably, a distance between two adjacent parallel grooves is 0.7 mm.

[0071] Preferably, the distance between two parallel and adjacent grooves is constant along a direction parallel to a prevailing direction of development of the grooves.

[0072] Preferably, the distance between two parallel and adjacent grooves is constant along a direction perpendicular to a prevailing direction of development of the grooves.

[0073] Preferably, the set of grooves is elongated on the radially internal surface along a single prevailing longitudinal development direction oriented in a direction parallel to the rotation axis of the tyre.

[0074] Preferably, said depressions have the shape of cells and connecting channels, wherein two adjacent cells are connected by at least one connecting channel.

[0075] Preferably, said connecting channels have a width between 0.05 mm and 1 mm.

[0076] Preferably, said connecting channels have a width of 0.7 mm.

[0077] Preferably, said depressions are arranged at at least one crown band of the radially internal surface.

[0078] Further features and advantages will become more apparent from the detailed description of preferred, but not exclusive, embodiments of a pressing bladder for a vulcanising mould, a process for making a moulded and vulcanised tyre, and a moulded and vulcanised tyre. Such description is given hereinafter with reference to the accompanying drawings, provided only for illustrative and, therefore, non-limiting purposes, in which:

[0079] - Figure 1 illustrates a schematic plan view of a functional insert for a tyre;

[0080] - Figure 2 illustrates the functional insert of Figure 1 in section according to the trace II-II of Figure 1; - Figure 3 schematically illustrates a tyre arranged with its rotation axis parallel to the plane of Figure 3 and sectioned along a radial plane;

[0081] - Figure 4 illustrates a portion of a radially internal surface of a tyre or a radially external surface of a pressing bladder in a first embodiment;

[0082] - Figures 4A and 4B illustrate respective enlarged portions of Figure 4;

[0083] - Figure 5 shows an enlarged section along the line A-A of Figure 4 of the tyre and the relevant pressing bladder;

[0084] - Figure 6 shows an enlarged section along the line B-B of Figure 4 of the tyre and the relevant pressing bladder;

[0085] - Figure 7 illustrates a portion of a radially internal surface of a tyre or a radially external surface of a pressing bladder in a second embodiment;

[0086] - Figure 7A illustrates an enlarged portion of Figure 7;

[0087] - Figure 8 shows an enlarged section along the line C-C of Figure 7 of the tyre and the relevant pressing bladder;

[0088] - Figure 9 illustrates a portion of a radially internal surface of a tyre or a radially external surface of a pressing bladder in a third embodiment;

[0089] - Figure 9A illustrates an enlarged portion of Figure 9;

[0090] - Figure 10 shows an enlarged section along the line D-D of Figure 9 of the tyre and the relevant pressing bladder;

[0091] - Figures 11, 12 and 13 show schematically in diametrical section one half of a vulcanisation mould in successive operating moments of a moulding and vulcanisation step. With reference to the accompanying figures, reference numeral 1 indicates a functional insert (Figures 1-3) i.e. an element adapted to perform a function inside a tyre.

[0092] The functional insert 1 may be a sensor means comprising, for example, a housing body 2 and a sensor 3 mounted on the housing body 2 optionally in a single body, or it may be the housing body 2 alone for a sensor 3 which may be mounted subsequently on the housing body 2 or another element adapted to perform a function inside a tyre.

[0093] In the case of the sensor means, the housing body 2 is preferably made of elastomeric material.

[0094] As illustrated for example in Figure 2, the functional insert 1 has an adhesive surface 4a and an exposed surface 4b facing away from the adhesive surface 4a. If the functional insert 1 is a sensor means or a housing body 2 of a sensor means, the adhesive surface 4a and the exposed surface 4b are preferably surfaces of the housing body 2.

[0095] The adhesive surface 4a and the exposed surface 4b preferably represent the surfaces of greatest extension of the functional insert 1. In other words, the functional insert 1 has, in a direction perpendicular to the adhesive surface 4a and the exposed surface 4b, a thickness smaller than the dimensions of the adhesive surface 4a and the exposed surface 4b.

[0096] X indicates an axis of the functional insert 1, perpendicular to the adhesive surface 4a.

[0097] The adhesive surface 4a and in general the housing body 2 can have a circular shape around the axis X as illustrated in the accompanying figures or another shape. Figure 3 shows a schematic example of a tyre 5 subjected to a moulding and vulcanisation step. In other words, Figure 3 shows a moulded and vulcanised tyre 5.

[0098] The tyre 5 has a substantially toroidal structure concentric with respect to a rotation axis Y which corresponds to the axis around which the tyre itself rotates during operation.

[0099] The tyre 5 has a substantially concave radial internal surface 6 delimiting an internal cavity which, in operating conditions, is closed by a mounting ring. A portion of the radially internal surface 6 to which, externally, the tread band 7 corresponds defines a crown band 6a of the radially internal surface 6.

[0100] With reference to a radially external surface of the tyre, a tread band 7 and a pair of sidewalls 8 may be identified which extend radially from respective axially opposite edges of the tread band 7 towards respective beads 9 suitable for engagement on the mounting rim.

[0101] The radially internal surface 6, preferably the crown band 6a, has depressions 10 with respect to the radially internal surface 6 of the tyre 5.

[0102] The depressions 10 have a depth "P" preferably between 0.01mm and 1mm, even more preferably 0.04 mm, with respect to the radially internal surface 6 of the tyre 5.

[0103] According to a possible embodiment, for example illustrated in Figure 3, the depressions 10 may cover the entire circumferential extension of the tyre 5, preferably the entire circumferential extension of the crown band 6a.

[0104] In a process for creating the moulded and vulcanised tyre 5, provision is made for building a green tyre 5a and for subjecting the green tyre 5a to a moulding and vulcanisation step to obtain the moulded and vulcanised tyre 5.

[0105] According to a possible embodiment, provision is made for applying a layer of release agent to the radially internal surface of the green tyre before subjecting it to the moulding and vulcanisation step.

[0106] The depressions 10 are made during or after the moulding and vulcanisation step.

[0107] As illustrated for example in Figure 3, the tyre 5 may comprise the functional insert 1 attached to the radially internal surface 6, preferably to the crown band 6a, of the tyre 5 at an application area "A". In particular, the adhesive surface 4a is adhered to the radially internal surface 6 of the tyre, preferably to the crown band 6a, at the application area "A". In this case, the depressions 10 cover at least the application area "A", preferably the entire circumferential extension of the tyre 5, even more preferably the entire circumferential extension of the crown band 6a. In order to attach the functional insert, the depressions 10 may only cover the application area "A".

[0108] In a process for attaching the functional insert 1 to the tyre 5, provision is made for creating the moulded and vulcanised tyre 5. Provision is also made for arranging the functional insert 1 and for making the adhesive surface 4a of the functional insert 1 adhere to the radially internal surface 6 of the tyre 5, preferably to the crown band 6a, at the application area "A". During or after the moulding and vulcanisation step, provision is made for creating, at least on the application area, a plurality of gas escape routes configured to evacuate, in the subsequent adhesion step between the adhesive surface 4a of the functional insert 1 and the radially internal surface 6 of the tyre, a gas (air) interposed between these two surfaces. In fact, the process for attaching the functional insert 1 to a tyre 5 involves evacuating the gas placed between the adhesive surface 4a of the functional insert 1 and the radially internal surface 6 of the tyre 5 through the plurality of gas escape routes created on the application area "A", while the adhesive surface 4a of the functional insert 1 is made to adhere to the application area itself.

[0109] The depressions 10 represent an embodiment of the aforementioned plurality of gas escape routes. In this case, during or after the moulding and vulcanisation step, provision is made for creating the depressions 10 at least on the application area "A", preferably on the entire circumferential extension of the tyre 5, even more preferably on the entire circumferential extension of the crown band 6a.

[0110] According to a possible embodiment illustrated for example in Figures 7-10, the depressions 10 have the shape of grooves 11. According to a possible embodiment, the grooves 11 are arranged according to a grid pattern (Figures 7-8).

[0111] In the case of the arrangement according to a grid pattern, the grooves 11 are rectilinear and form a grid defined by contiguous regular or irregular polygons as illustrated in Figures 7-8. According to an alternative not illustrated, the grooves 11 are curvilinear and form a grid defined by contiguous areas having non-rectilinear contours.

[0112] In the case of the arrangement according to a grid pattern, the grooves 11 have a width "L" preferably between 0.05mm and 1mm, even more preferably 0.5 mm.

[0113] According to a possible embodiment, the grooves 11 are arranged parallel to each other (Figures 9-10).

[0114] In the case of the parallel groove arrangement, the grooves 11 may be rectilinear or curvilinear. Furthermore, also in this case, the grooves 11 have a width "L" preferably between 0.05 mm and 1 mm. Preferably, in the case of the parallel groove arrangement, the width "L" is 0.2 mm.

[0115] In the case of the parallel groove arrangement, a distance DI between two adjacent grooves is preferably between 0.1 mm and 5 mm, even more preferably 0.7 mm. The distance DI between two adjacent grooves is preferably constant along a direction parallel to the prevailing direction of development of the grooves 11. The distance DI between two adjacent grooves is preferably constant along a direction perpendicular to the prevailing direction of development of the grooves 11, i.e. the distance DI between two adjacent grooves remains constant along all the grooves.

[0116] In the case of the parallel groove arrangement, in which the set of grooves 11 is elongated on the radially internal surface 6 of the tyre 5 along a single prevailing longitudinal direction of development Yl, such single prevailing longitudinal direction of development Yl is preferably oriented in a direction parallel to the rotation axis Y of the tyre, as for example illustrated in Figure 3.

[0117] According to a possible embodiment illustrated for example in Figures 4-6, the depressions 10 have the shape of cells 12 and connecting channels 13, in which two adjacent cells 12 are connected by at least one connecting channel 13. A cell is a depression which, parallel to the radially internal surface of a tyre, does not have a prevailing development dimension. The cells 12 are delimited by ribbings 14 arranged according to a grid pattern. The ribbings 14 may be rectilinear and form a grid defined by contiguous regular or irregular polygons as illustrated in Figure 4. According to an alternative not illustrated, the ribbings 14 may be curvilinear and form a grid defined by contiguous areas having non-rectilinear contours.

[0118] A connecting channel 13 interrupts a ribbing 14 between two adjacent cells 12. The connecting channels 13 have a width LI preferably between 0.05 mm and 1 mm, even more preferably 0.7 mm. The width LI is measured along the prevailing direction of development of the respective ribbing 14. The ribbings 14 have a width L2 preferably between 0.05 mm and 1 mm, even more preferably 0.5 mm. The width L2 is measured perpendicular to the prevailing direction of development of the respective ribbing 14.

[0119] With reference to Figures 11, 12 and 13, 100 indicates a vulcanisation mould overall.

[0120] The vulcanisation mould 100 has a cavity 101 having a shape and in particular an internal moulding surface 102 corresponding to the external shape to be given to the moulded and vulcanised tyre 5. The cavity 101 and the internal moulding surface 102 extend around a central axis Z which corresponds to the rotation axis Y of the tyre 5 housed in the vulcanisation mould 100.

[0121] The vulcanisation mould 100 includes a pressing bladder 103 or expandable air chamber which also extends around the central axis Z. The pressing bladder 103, of substantially toroidal shape, has two radially internal circumferential edges carrying respective anchoring appendages 104, which may be sealingly engaged in the mould 100 to operationally associate the pressing bladder 103 with the mould itself. The anchoring appendages 104 are connected to the mould 100 at areas adapted to receive the beads of the green tyre 5a.

[0122] The pressing bladder 103 has a radially external surface 105 configured to adhere to a radially internal surface of the green tyre 5a during the moulding and vulcanisation step of the green tyre.

[0123] A duct 106 formed in the vulcanisation mould 100 flows inside the pressing bladder 103, so as to allow the expansion of the latter following the introduction of steam, or other operating fluid, under pressure.

[0124] With reference to Figures 4, 7 and 9 which represent a schematic illustration of both the radially internal surface 6 of the tyre 5 and the radially external surface 105 of the pressing bladder 103, the references in brackets are those relating to the pressing bladder 103.

[0125] Preferably, the radially external surface 105 of the pressing bladder 103 comprises reliefs 107 (Figures 5, 6, 8, 10). In particular, the reliefs 107 are configured to create 5 corresponding depressions 10 in the tyre.

[0126] According to a possible embodiment, the reliefs 107 of the pressing bladder 103 are arranged in an area of the radially external surface 105 corresponding at least to the application area "A". In particular, the reliefs 107 of the pressing bladder 103 are arranged so that the gas escape routes are created at least at the application area "A".

[0127] According to a possible embodiment, irrespective of the attachment of the functional insert 1 or the position of the application area "A", the reliefs 107 of the pressing bladder 103 extend along the entire circumferential extension of the pressing bladder 103. In particular, the reliefs 107 of the pressing bladder 103 are arranged so that the depressions 10 are arranged over the entire circumferential extension of the radially internal surface 6 of the tyre 5, preferably of the crown band 6a.

[0128] With particular reference to the creation of the depressions 10 at the crown band 6a, the reliefs 107 of the pressing bladder 103 are arranged at a central band 108 located in a middle line area with respect to the central axis Z. The central band 108 preferably corresponds to the crown band 6a of the radially internal surface 6 of the moulded and vulcanised tyre 5.

[0129] The pressing bladder 103 may have, at each side of the tyre, a lateral evacuation band 109 in which evacuation channels are obtained on the radially external surface 105 configured to channel the fluids placed between the green tyre and the pressing bladder itself towards the environment outside the mould during the moulding and vulcanisation step.

[0130] When both the central band 108 featuring the reliefs 107 and the two lateral evacuation bands 109 are present, the central band 108 preferably extends along the entire axial section between the two lateral evacuation bands 109.

[0131] Preferably, the reliefs 107 of the pressing bladder 103 have a height "H" between 0.01 mm and 1 mm, even more preferably 0.04 mm. In particular, such dimension is suitable for creating depressions having a depth "P" preferably between 0.01 mm and 1 mm, even more preferably 0.04 mm, with respect to the radially internal surface 6 of the tyre 5.

[0132] According to a possible embodiment illustrated for example in Figures 7-10, the reliefs 107 of the pressing bladder 103 are shaped as ribs 110. In particular, the reliefs 107 of the pressing bladder 103 are shaped in such a way as to create corresponding depressions 10 having the shape of grooves 11.

[0133] According to a possible embodiment, the ribs 110 are arranged according to a grid pattern (Figures 7-8). In particular, the ribs 110 are shaped so as to create grooves 11 arranged according to a grid pattern (Figures 7-8).

[0134] In the case of the arrangement according to a grid pattern, the ribs 110 may be rectilinear and form a grid defined by contiguous regular or irregular polygons as illustrated in Figures 7-8. According to an alternative not illustrated, the ribs 110 may be curvilinear and form a grid defined by contiguous areas having non-rectilinear contours.

[0135] In the case of the arrangement according to a grid pattern, the ribs 110 have a width "L" between 0.05 mm and 1 mm, even more preferably 0.5 mm. In particular, such dimension is adapted to make grooves 11 having a width "L" preferably between 0.05 mm and 1 mm, even more preferably 0.5 mm.

[0136] According to a possible embodiment, the ribs 110 are arranged parallel to each other (Figures 9-10). In particular, the ribs 110 are shaped so as to create grooves 11 arranged parallel to each other (Figures 9-10).

[0137] In the case of the parallel rib arrangement, the ribs 110 may be rectilinear or curvilinear. In particular, the ribs 110 are shaped so as to create grooves 11 that are respectively rectilinear or curvilinear. Furthermore, the ribs 110 have a width "L" preferably between 0.05 mm and 1 mm, even more preferably 0.2 mm. In particular, such dimension is adapted to make grooves 11 having a width "L" preferably between 0.05 mm and I mm, even more preferably 0.2 mm.

[0138] In the case of the parallel rib arrangement, a distance DI between two adjacent ribs 110 is preferably between 0.1 mm and 5 mm, even more preferably 0.7 mm. In particular, such dimension is adapted to create corresponding adjacent grooves

[0139] II arranged at a distance DI preferably between 0.1 mm and 5 mm, even more preferably 0.7 mm. The distance DI between two adjacent ribs 110 is preferably constant along a direction parallel to the prevailing direction of development of the ribs. In particular, such arrangement is adapted to create corresponding grooves 11 in which the distance DI between two adjacent grooves is preferably constant along a direction parallel to the prevailing direction of development of the grooves. The distance DI between two adjacent ribs 110 is preferably constant along a direction perpendicular to the prevailing direction of development of the ribs 110 i.e. where the distance between two adjacent ribs 110 remains constant along all the ribs. In particular, this arrangement is suitable for creating corresponding grooves 11 in which the distance DI between two adjacent grooves is preferably constant along a direction perpendicular to the prevailing direction of development of the grooves 11, i.e. in which the distance between two adjacent grooves 11 remains constant at all the grooves.

[0140] In the case of the parallel rib arrangement, the set of ribs 110 is elongated on the radially external surface 105 of the pressing bladder 103 along a single prevailing longitudinal direction of development Yl.

[0141] This single prevailing longitudinal direction of development Yl is preferably oriented to obtain a set of grooves 11 elongated on the radially internal surface 6 of the tyre 5 along a single prevailing longitudinal direction of development Y1 oriented in a direction parallel to the rotation axis Y of the tyre 5, as for example illustrated in Figure 3.

[0142] According to a possible embodiment illustrated for example in Figures 4-6, the reliefs 107 of the pressing bladder 103 have the shape of columns 111 and bridges 112, with two adjacent columns 111 connected by at least one bridge 112. In particular, the reliefs 107 are shaped so as to create depressions 10 having the shape of cells 12 corresponding to the columns 111 and connecting channels 13 corresponding to the bridges 112, with two adjacent cells 12 connected by at least one connecting channel 13. A column is a relief which, parallel to the radially external surface of a pressing bladder, does not have a prevailing development dimension.

[0143] The columns 111 are delimited by incisions 113 arranged according to a grid pattern. In particular, the incisions 113 are shaped in such a way as to create corresponding ribbings 14 in the tyre 5. The incisions 113 may be rectilinear and form a grid defined by contiguous regular or irregular polygons as illustrated in Figure 4. According to an alternative not illustrated, the incisions 113 may be curvilinear and form a grid defined by contiguous areas having non-rectilinear contours.

[0144] A bridge 112 crosses an incision 113. In particular, the bridge 112 is adapted to create a corresponding connecting channel 13 which interrupts a ribbing 14 between two adjacent cells 12. The bridges 112 have a width LI preferably between 0.05 mm and 1 mm, even more preferably 0.7 mm. In particular, such dimension is adapted to create corresponding connecting channels 13 having a width LI preferably between 0.05 mm and 1 mm, even more preferably 0.7 mm. The width LI is measured along the prevailing direction of development of the respective incision 113. The incisions 113 have a width L2 preferably between 0.05 mm and 1 mm, even more preferably 0.5 mm. In particular, such dimension is adapted to make corresponding ribbings 14 having a width "L2" preferably between 0.05 mm and 1 mm, even more preferably 0.5 mm. The width L2 is measured perpendicular to the prevailing direction of development of the respective incision 113.

[0145] In use, the green tyre 5a is placed in the vulcanisation mould 100 to undergo the moulding and vulcanisation step. The pressing bladder 103 is inside the radially internal cavity delimited by the green tyre 5a.

[0146] In the moulding and vulcanisation step, provision is made for expanding the pressing bladder 103 inside the green tyre 5a to press the green tyre towards the internal moulding surface 102 of the vulcanisation mould 100 as illustrated in sequence in Figures 11-13.

[0147] In the moulding and vulcanisation step, provision is finally made for supplying heat inside the vulcanisation mould 102 to obtain the moulded and vulcanised tyre 5 and for extracting the moulded and vulcanised tyre 5 from the vulcanisation mould 102. The heat applied determines the cross-linking of the elastomeric material of which the tyre itself is composed.

[0148] According to an embodiment in which the depressions 10 are made during the moulding and vulcanisation step, preferably provision is made for exploiting the expansion of the pressing bladder 103 so as to impress the reliefs 107 against the radially internal surface of the green tyre to create, in the moulded and vulcanised tyre 5, the corresponding depressions 10.

Claims

CLAIMS1. Pressing bladder (103) for a vulcanisation mould (100) having a radially external surface (105) configured to adhere to a radially internal surface of a green tyre (5a) during a moulding and vulcanisation step of the green tyre itself to obtain a moulded and vulcanised tyre (5), wherein said radially external surface (105) comprises reliefs (107) having the shape of ribs (110) or columns (111) and bridges (112).

2. Pressing bladder (103) for a vulcanisation mould (100) according to claim 1, wherein said reliefs (107) have a height (H) between 0.01 mm and 1 mm.

3. Pressing bladder (103) for a vulcanisation mould (100), according to claim 1 or 2, wherein said reliefs (107) are arranged at at least a central band (108) arranged in a middle line area with respect to a central axis (Z) of the pressing bladder (103).

4. Pressing bladder (103) for a vulcanisation mould (100) according to claim 3, wherein said central band (108) corresponds to a crown band (6a) of the radially internal surface (6) of the moulded and vulcanised tyre (5).

5. Pressing bladder (103) for a vulcanisation mould (100) according to claim 3 or 4, comprising evacuation channels obtained at two respective lateral evacuation bands (109) and configured to channel towards the environment external to the vulcanisation mould (100) the fluids interposed between a green tyre (5a) and the pressing bladder itself during the moulding andvulcanisation step, wherein the central band (108) comprising said reliefs (107) extends along the entire axial section interposed between the two lateral evacuation bands (109).

6. Pressing bladder (103) for a vulcanisation mould (100) according to one or more of the preceding claims, wherein said reliefs (107) have the shape of ribs (110) and said ribs (110) have a width (L) between 0, 05mm and 1mm.

7. Pressing bladder (103) for a vulcanisation mould (100) according to claim 6, wherein said ribs (110) are arranged according to a grid pattern.

8. Pressing bladder (103) for a vulcanisation mould (100) according to claim 6, wherein said ribs (110) are parallel to each other.

9. Pressing bladder (103) for a vulcanisation mould (100) according to claim 8, wherein a distance (DI) between two parallel and adjacent ribs (110) is between 0.1 mm and 5 mm.

10. Pressing bladder (103) for a vulcanisation mould (100) according to claim 9, wherein the distance between two parallel and adjacent ribs (110) is constant along a direction parallel to a prevailing direction of development of the ribs.

11. Pressing bladder (103) for a vulcanisation mould (100) according to claim 9 or 10, wherein the distance between two parallel and adjacent ribs (110) is constant along a directionperpendicular to a prevailing direction of development of the ribs.

12. Pressing bladder (103) for a vulcanisation mould (100) according to one or more of claims 8 to 11, wherein the set of ribs (110) is elongated on the radially external surface (105) along a single prevailing longitudinal direction of development (Yl) oriented in a direction parallel to a central axis (Z) of the pressing bladder (103).

13. Pressing bladder (103) for a vulcanisation mould (100) according to one or more of claims 1 to 5, wherein said reliefs (107) have the shape of columns (111) and bridges (112), with two adjacent columns (111) connected by at least one bridge (112).

14. Process for making a moulded and vulcanised tyre (5), comprising: building a green tyre (5a); applying a layer of release agent to a radially internal surface of the green tyre (5a); subjecting said green tyre (5a) to a moulding and vulcanisation step to obtain a moulded and vulcanised tyre (5); wherein said moulding and vulcanisation step comprises:• placing the green tyre (5a) in a vulcanisation mould (100) having an internal moulding surface (102) and a pressing bladder (103) according to one or more of the preceding claims;• expanding the pressing bladder (103) inside the green tyre(5a);• providing heat inside the vulcanisation mould (100) to obtain said moulded and vulcanised tyre (5);• extracting said moulded and vulcanised tyre (5) from the vulcanisation mould (100).

15. Moulded and vulcanised tyre (5) comprising a radially internal surface (6) and having depressions (10) with respect to said radially internal surface (6) having the shape of grooves (11) or cells (12) and connecting channels (13).

16. Tyre (5) according to claim 15, wherein said depressions (10) have a depth (P) between 0.01 mm and 1 mm with respect to said radially internal surface (6) of the tyre (5).

17. Tyre (5) according to claim 15 or 16, wherein said depressions have the shape of grooves (11) and said grooves have a width (L) between 0.05 mm and 1 mm.

18. Tyre (5) according to claim 17, wherein said grooves (11) are arranged according to a grid pattern.

19. Tyre (5) according to claim 17, wherein said grooves (11) are parallel to each other.

20. Tyre (5) according to claim 19, wherein a distance (DI) between two parallel and adjacent grooves (11) is between 0.1 mm and 5 mm.

21. Tyre (5) according to claim 20, wherein the distance between two parallel and adjacent grooves (11) is constant along a direction parallel to a prevailing direction of development of the grooves.

22. Tyre (5) according to claim 20 or 22, wherein the distance between two parallel and adjacent grooves (11) is constant along a direction perpendicular to a prevailing direction of development of the grooves.

23. Tyre (5) according to one or more of claims 19 to 22, wherein the set of grooves (11) is elongated on the radially internal surface (6) along a single prevailing longitudinal direction of development (Yl) oriented in a direction parallel to a rotation axis (Y) of the tyre (5).

24. Tyre (5) according to claim 15 or 16, wherein said depressions (10) have the shape of cells (12) and connecting channels (13), wherein two adjacent cells (12) are connected by at least one connecting channel (13).

25. Tyre (5) according to claim 24, wherein said connecting channels (13) have a width (LI) between 0.05 mm and 1 mm.

26. Tyre (5) according to one or more of claims 15 to 25, wherein said depressions (10) are arranged at at least one crown band (6a) of the radially internal surface (6).

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