EP4642628A1

EP4642628A1 - Apparatus for vulcanising and moulding tyres and method for pre-heating circumferential sectors in an apparatus for vulcanising and moulding tyres

Info

Publication number: EP4642628A1
Application number: EP23836595.1A
Authority: EP
Inventors: John Bottomley; Jordanis NASSOS
Original assignee: Pirelli SpA; Pirelli Tyre SpA
Current assignee: Pirelli and C SpA; Pirelli Tyre SpA
Priority date: 2022-12-28
Filing date: 2023-12-19
Publication date: 2025-11-05
Also published as: WO2024141857A1; CN120418073B; IT202200026979A1; CN120418073A

Abstract

An apparatus for vulcanising and moulding tyres comprises an annular container (16) engaging or configured to engage a plurality of circumferential sectors (10). The annular container (16) is movable between a raised position, in which the circumferential sectors (10) are circumferentially spaced from each other, and a lowered position, in which the annular container (16) surrounds the circumferential sectors (10) and the circumferential sectors (10) are circumferentially moved close to each other. A conduit (26) for circulating a heating medium is provided in the annular container (16). The conduit (26) surrounds the circumferential sectors (10) and has a wavy pattern that stretches towards the bottom (18) and towards the top (17) in a wavy pattern.

Description

“Apparatus for vulcanising and moulding tyres and method for pre-heating circumferential sectors in an apparatus for vulcanising and moulding tyres”

DESCRIPTION

Technical field of the invention

The present invention is situated in the context of processes and apparatuses for producing tyres for vehicle wheels.

The production cycles of a tyre for vehicle wheels provide for a building process in which various structure components of the tyre itself may be made and/or assembled on one or more drums to make a green tyre. The green tyres are then transferred to a moulding and vulcanising line where a moulding and vulcanising process is actuated. The moulding and vulcanising process is adapted to define the structure of the tyre according to a desired geometry and tread design.

The present invention relates to an apparatus for vulcanising and moulding tyres and to a method for pre-heating circumferential sectors in an apparatus for vulcanising and moulding tyres. The present invention in particular relates to the design of conduits of the apparatus for vulcanising and moulding tyres, said conduits carrying a heating medium employed to heat the mould housing a green tyre to be moulded and vulcanized.

State of the art

Assemblies for vulcanising and moulding tyres are known in the art.

The document US20090162460A1 provides a mould assembly comprising a plurality of segments which are arranged to form an annular ring when assembled together. Surrounding the segments are a plurality of slide blocks for receiving and supporting the segments. The slide blocks are slidable in a radial direction. The container housing further comprises an annular actuating ring. The inner radial surface of the actuating ring is angled for engagement with an outer angled surface of slide blocks. The tread mold segments have an outer radial surface having channels for receiving tubular members or an X shaped coupling for the passage of heating steam.

The document CN204196061 II illustrates a steam chamber guide ring for a tyre segmented mould. The steam chamber guide ring comprises a guide ring body, a steam inlet and a steam outlet, wherein one or multiple steam circulating grooves is or are formed in the inner conical surface of the guide ring body. The steam circulating grooves in the top end is communicated with the steam inlet, the steam circulating grooves in the bottom end is communicated with the steam outlet and a steam circulation hole is disposed between the two adjacent steam circulating grooves.

The document JP2015155151A discloses a container for a tyre vulcanizing machine. The container includes a cavity in which a steam piping for supplying steam to the cavity is disposed. The steam piping includes a plurality of steam inlet ports to be connected to an external piping for introducing steam and a steam discharge port from which the introduced steam is discharged into the cavity. The container includes a steam exhaustion port from which the steam discharged into the cavity is exhausted into an external piping at a position symmetrical to the steam discharge port. In the cavity, a plurality of baffle plates are further installed such that the steam introduced into the cavity runs meandering through the cavity. Further mold assemblies for moulding tyres comprising a container provided with annular channels for steam are disclosed in documents CN 104690856, CN204820080U and JP5036419B2.

Definitions

By “tyre”, when not otherwise specified, it is intended a green tyre or a moulded and vulcanised tyre.

The terms “radial” and “axial” and the expressions “radially inner/outer” and ’’axially inner/outer” are used with reference to the radial direction of an apparatus for vulcanising and moulding tyres or of a tyre to be vulcanised and moulded inside the same (i.e. to a direction perpendicular to the geometric axis of rotation of the apparatus or of the tyre inside the same, the two axes being substantially coincident) and to the axial direction of said apparatus and of said tyre (i.e. to a direction parallel to the geometric axis of rotation of the apparatus or of the tyre inside the same). A radial plane of the tyre contains the axis of rotation thereof.

The terms “circumferential” and “circumferentially” are used with reference to the annular extension of the apparatus and of the tyre inside the same. The expressions “low”, “below”, “lower”, “bottom” and “high”, “above”, “upper”, “top” are used for indicating a relative position with respect to the ground in the normal use of the reference element.

The Applicant has observed that the mold assemblies of the prior art described above involve criticalities in terms of: speed of the transient heating of the mould assembly, heat distribution all over the mould assembly, cycle time, set up time, heating losses and steam consumption.

The Applicant has observed that the segments of the mould are heated by heat conduction from the steam circulating through the annular ring to said segments. When the mould is closed and the annular ring surrounds the segments, the heat of the steam flowing through ducts fashioned in the annular ring moves by conduction through the walls of the annular ring and then to the segments which lie in contact with a radial inner face of said annular ring.

The Applicant has observed that, after each vulcanising and moulding cycle, when the mould is opened by raising the annular ring and radially opening the segments to remove a vulcanized and moulded tyre and to load a green tyre to be vulcanized and moulded, the segments cool down and have to be heated again by the annular ring once said annular ring is again coupled to the segments.

The Applicant has observed that the shape and position of the ducts of the annular rings belonging to the prior art are not able to heat the segments in effective and quick manner.

In particular, the Applicant has observed that the ducts of the annular rings belonging to the prior art allow to transfer a reduced amount of heat to the segments and this results in significant heat losses.

The Applicant has also observed that the ducts of the annular rings belonging to the prior art do not allow to provide an evenly distributed heat to the segments and generate cold spots which are detrimental to efficiency and performance of the apparatus and may also be detrimental to the quality of the manufactured tyres.

The Applicant has observed that the above drawbacks also negatively affect the set up time (time employed to heat up the mould once loaded and closed and before starting the vulcanising and moulding cycle) and the vulcanising and moulding cycle time. The Applicant has perceived the need to improve the effectiveness of the heating of the segments and of the overall mould in the process of vulcanising and moulding in order to improve quality of tyres, to reduce vulcanising and moulding cycle time and to reduce power consumption.

The Applicant has perceived the need that the abovementioned drawbacks could be resolved by designing the steam ducts inside the annular ring such as to maximize heat transfer from the steam to radially outer parts of the circumferential sectors.

The Applicant has finally found that the above-indicated objectives and still others can be obtained by bringing the ducts and the heating medium as close as possible to the circumferential sectors and by widening as soon as possible an inner surface of said ducts so as to spread over a prevailing part of the radially outer parts of the circumferential sectors.

In accordance with a first aspect, the present invention relates to an apparatus for vulcanising and moulding tyres.

Preferably, said apparatus for vulcanising and moulding tyres comprises a plurality of circumferential sectors arranged around a central axis, the circumferential sectors being movable between a first position, in which they are circumferentially spaced from each other and further from the central axis, and a second position, in which they are circumferentially moved close to each other and closer to the central axis.

Preferably, said apparatus for vulcanising and moulding tyres comprises an annular container having a top, a bottom, a radially inner face and a radially outer face; the annular container engaging or being configured to engage the circumferential sectors, the annular container being movable between a raised position, in which the circumferential sectors are in the first position, and a lowered position, in which the annular container surrounds the circumferential sectors and the circumferential sectors are in the second position; wherein, in the lowered position, the radially inner face of the annular container is in contact with a radially outer part of the circumferential sectors.

Preferably, when the annular container is in the lowered position and the circumferential sectors are in the second position, the apparatus delimits a vulcanization and moulding cavity for housing a tyre. Preferably, a conduit for circulating a heating medium is provided in the annular container, said conduit surrounding the circumferential sectors when the annular container is in the lowered position.

Preferably, the conduit stretches towards the bottom and towards the top in a wavy pattern.

In accordance with a second aspect, the present invention relates to a method for pre-heating circumferential sectors in an apparatus for vulcanising and moulding tyres.

Preferably, the method comprises: providing an annular container placed or configured to be placed around a plurality of circumferential sectors arranged around a central axis, the plurality of circumferential sectors delimiting a vulcanization and moulding cavity.

Preferably, the method comprises: making a heating medium flowing through a wavy pattern fashioned in the annular container, the wavy pattern stretching from a top to a bottom and from a bottom to a top of the annular container.

Preferably, a radially inner face of the annular container is in contact or is configured to be put in contact with a radially outer part of the circumferential sectors.

Preferably, the apparatus is the one of the first aspect.

The Applicant deems that the present invention allows to achieve the above listed objectives.

The Applicant believes that the invention achieves a more uniform temperature distribution over the entire annular container compared to what disclosed in the cited references (i.e. less cold spots).

The Applicant also believes that the assembly comprising the annular container of the invention and the circumferential sectors reaches a temperature steady state faster than disclosed in said cited references.

The Applicant also believes that the invention allows to reduce heat losses and steam consumption and therefore allows to decrease energy consumption with respect to what disclosed in said cited references.

The Applicant also believes that the present invention allows to reduce vulcanization and moulding cycle time and to reduce set up time.

The present invention may have one or more of the preferred features that are described herein below. Preferably, the heating medium is steam, preferably water steam.

Preferably, in a diametrical section of the annular container, at least some parts of the conduit are closer to the radially inner face than to the radially outer face of said annular container.

Preferably, it is provided for making the heating medium flowing closer to the radially inner face of the annular container than to a radially outer face of said annular container.

Preferably, the annular container comprises a drain channel connected to the conduit.

Preferably, it is provided for draining a condensed part of the steam from the wavy pattern or from the conduit.

Preferably, draining is performed while the steam is flowing through the wavy pattern or through the conduit.

The Applicant has verified that the drain channel allows to remove the condensed part of the steam and to make the steam drier and this improves heat transfer capabilities. Indeed, steam dryness has a direct effect on the total amount of transferable energy contained within the steam, which affects heating efficiency and quality. Supplying steam that is as close to being dry as possible enables greater heating efficiency.

Preferably, the drain channel is annular and surrounds the central axis.

Preferably, the drain channel is positioned below the conduit.

Preferably, the annular container comprises at least one drain hole connecting the conduit to the drain channel.

Preferably, the conduit comprises a plurality of top portions and a plurality of bottom portions that follow one another in an alternating fashion.

Preferably, the drain channel is connected to at least one of the bottom portions.

Preferably, the drain channel is connected to all the bottom portions.

Preferably, the drain hole comprises a radial portion and an axial portion.

Preferably, the drain channel is connected to an outlet opening to discharge the condensate.

The Applicant has verified that, by connecting the drain channel to one or all the bottom portions, drainage of condensate, which tends to fall and settle downwards, is facilitated. Preferably, the annular container comprises a ring connected to the bottom of the annular container, the ring having a groove delimiting the drain channel.

Preferably, the ring follows the circumferential outline of the annular container.

Preferably, each of said parts of the conduit has a flat shape.

Preferably, each of said parts of the conduit has two dimensions much larger than a third dimension.

Preferably, the third dimension is perpendicular to the radially inner face of the annular container.

Preferably, each of said parts is delimited by a first inner surface parallel to the radially inner face of the annular container, by a second inner surface facing the first inner surface and by an edge inner surface connecting the first inner surface and the second inner surface.

Preferably, the first inner surface and the second inner surface are parallel to each other

Preferably, the first inner surface and the second inner surface are identical to one another.

Preferably, the first inner surface is further from the radially inner face of the annular container than the second inner surface.

Preferably, a ratio “A1/g” of an area “A1” of the first inner surface to a gap “g” between the first inner surface and the second inner surface is equal to or greater than 1000 mm.

Preferably, a ratio “A1/g” of an area “A1” of the first inner surface to a gap “g” between the first inner surface and the second inner surface is equal to or less than 2000 mm.

Preferably, a ratio “A1/C” of an area “A1” of the first inner surface to a width “C” of the vulcanization and moulding cavity is equal to or greater than 80 mm.

Preferably, a ratio “A1/C” of an area “A1” of the first inner surface to a width “C” of the vulcanization and moulding cavity is equal to or less than 100 mm.

Preferably, a ratio “A1/d1” of an area “A1” of the first inner surface to a first distance “d1” from the first inner surface to the radially inner face of the annular container is equal to or greater than 1000 mm.

Preferably, a ratio “A1/d1” of an area “A1” of the first inner surface to a first distance “d1” from the first inner surface to the radially inner face of the annular container is equal to or less than 2000 mm. Preferably, the first distance “d1” is measured perpendicular to the first inner surface.

Preferably, a ratio “A1/d2” of an area A1” of the first inner surface to a minimum radial distance “d2” from the second inner surface to the radially outer face of said annular container is equal to or greater than 100 mm.

Preferably, a ratio “A1/d2” of an area A1” of the first inner surface to a minimum radial distance “d2” from the second inner surface to the radially outer face of said annular container is equal to or less than 200 mm.

Preferably, a ratio “D/d2” of a maximum inner diameter “D” of the vulcanization and moulding cavity to a minimum radial distance “d2” from the second inner surface to the radially outer face of said annular container is equal to or greater than 10 mm.

Preferably, a ratio “D/d2” of a maximum inner diameter “D” of the vulcanization and moulding cavity to a minimum radial distance “d2” from the second inner surface to the radially outer face of said annular container is equal to or less than 20 mm.

Preferably, a ratio “d2/d1” of a minimum radial distance “d2” from the second inner surface to the radially outer face of said annular container to a first distance “d1” from the first inner surface to the radially inner face of the annular container is equal to or greater than 5.

Preferably, a ratio “d2/d1” of a minimum radial distance “d2” from the second inner surface to the radially outer face of said annular container to a first distance “d1” from the first inner surface to the radially inner face of the annular container is equal to or less than 20.

Preferably, a ratio “h/C” of a height “h” of the first inner surface to a width “C” of the vulcanization and moulding cavity is equal to or greater than 0.7.

Preferably, a ratio “h/C” of a height “h” of the first inner surface to a width “C” of the vulcanization and moulding cavity is equal to or less than 0.9.

Preferably, the height “h” is measured in a diametrical cross section of the annular container and parallel to the first inner surface.

Preferably, a ratio “w/C” of a width “w” of the first inner surface to a width “C” of the vulcanization and moulding cavity is equal to or greater than 0.4.

Preferably, a ratio “w/C” of a width “w” of the first inner surface to a width “C” of the vulcanization and moulding cavity is equal to or less than 0.6. Preferably, the width “w” is measured along a circumferential direction of the annular container.

Preferably, in a view along a radial direction, each of said parts is a U-shaped section of the conduit.

Preferably, a low bend of the U-shaped section is one of the bottom portions of the conduit.

Preferably, each of two upper ends of the U-shaped section is connected to an adjacent U-shaped section through one of the top portions.

Preferably, each top portion comprises a connection hole having an end connected to the upper end of one of the U-shaped sections and another end connected to the upper end of another of the U-shaped sections.

Preferably, each of said parts of the conduit is delimited by one groove fashioned in the radially inner face of the annular container.

Preferably, each of said parts of the conduit is delimited by a plate closing the groove.

Preferably, the first distance “d1” is a thickness of the plate.

Preferably, a radially inner working surface of the plates defines part of the inner face of the annular container.

Preferably, the radially inner working surface of the plates is flush with the remaining parts of the inner face of the annular container.

Preferably, each plate has a rectangular or trapezoidal outline.

Preferably, in the lowered position, the plates engage the radially outer parts of the circumferential sectors.

Preferably, the plates are made of a material having a thermal conductivity between 100 W/(m*K) and 180 W/(m*K).

Preferably, the plates are made of a material having a hardness between 40 HB and 210 HB.

Preferably, the plates are made of a material chosen in the group comprising: brass or an alloy comprising copper, nickel and silicon or an alloy comprising copper, tin, zinc, lead.

Preferably, when the annular container is in the lowered position, each circumferential sector is coupled to a plurality of said parts.

Preferably, the conduit has an inlet and an outlet. Preferably, the inlet and the outlet are fashioned on the radially outer face of the annular container.

Preferably, the inlet and the outlet are close to each other.

Preferably, the radially inner face of the annular container has a frusto-conical shape.

Preferably, the plates are disposed on the radially inner face of the annular container.

Preferably, the radially outer parts of the circumferential sectors are disposed on a fictional frusto-conical surface.

Preferably, an average speed of the heating medium in the wavy pattern or inside the conduit is between 15 m/s and 25 m/s, optionally of 20 m/s.

Preferably, a flow rate of the heating medium across the wavy pattern or through the conduit is between 4 m³/s and 8 m³/s.

Preferably, the annular container is made of structural steel.

Preferably, the ring is made of structural steel.

Preferably, the circumferential sectors are carried by the annular container.

Preferably, the annular container comprises a plurality of guides positioned on the radially inner face and the circumferential sectors are coupled to said guides so to slide along said guides.

Preferably, each guide is placed between two adjacent plates.

Preferably, when the annular container moves between the raised position and the lowered position, the circumferential sectors slide along said guides between the first position and the second position.

Preferably, each of the circumferential sectors comprises a supporting block and a working segment.

Preferably, the working segments are positioned radially inside with respect to the supporting blocks.

Preferably, the supporting block comprises the radially outer part.

Preferably, the supporting blocks slide along said guides between the first position and the second position

Preferably, the working segment is mounted on the supporting block.

Preferably, the working segment comprises a working surface configured to engage the tyre placed in the vulcanization and moulding cavity.

Preferably, said surface is configured to engage a radially outer portion of the tyre. Preferably, each working segment is removably connected to the respective supporting block so that said working segment can be replaced by another working segment.

Preferably, when the working segment is mounted on the respective supporting block, the working segment and the supporting block are integral to each other and move together between the first position and the second position.

Preferably, the apparatus further comprises a first sidewall plate and a second sidewall plate that are axially opposite, the first sidewall plate and the second sidewall plate each having a work surface arranged to operate on beads and on sidewalls of the green tyre.

Further features and advantages will be clearer from the detailed description of preferred but not exclusive embodiment of an apparatus for vulcanising and moulding tyres and to a method for pre-heating circumferential sectors in an apparatus for vulcanising and moulding tyres according to the present invention.

Description of the drawings

Such description will be set forth here below with reference to the enclosed drawings, provided only as a non-limiting example, in which:

- figure 1 shows, in diameter section view, a vulcanisation mould belonging to an apparatus for vulcanising and moulding tyres according to the present invention;

- figure 2 is a 3D view of an element of the apparatus of figure 1 with some parts in transparency to better display other parts;

- figure 3 is an enlarged portion of the element of figure 2 with some parts removed;

- figure 4 shows a 3D view of a portion of the apparatus of figure 1 ;

- figure 5 shows a steam flow path inside the element of figure 2;

- figure 6 is a diametrical section view of a part of the apparatus of the previous figures;

- figure 7 is a sectioned part of the apparatus of the previous figures;

- figure 8 is a different sectioned part of the apparatus of the previous figures; figure 9 is another different sectioned part of the apparatus of the previous figures; figure 10 is a chart showing a temperature - time development related to the apparatus of the invention and an apparatus of the prior art.

Detailed description

In figure 1, a diametrical section of a vulcanisation mould 1 belonging to an apparatus for vulcanising and moulding tyres 2 is illustrated.

A tyre 2 is only schematically illustrated in figure 1 and essentially comprises a carcass structure having one or more carcass plies. An impermeable elastomeric material layer or so-called “liner” is applied inside the carcass ply/plies. Two anchoring annular structures, each comprising a so-called bead core carrying an elastomeric filler in radially outer position, are engaged with respective terminal flaps of the carcass ply/plies. The anchoring annular structures are integrated in proximity to zones normally identified with the name “beads” 3, at which the engagement between the tyre and a respective mounting rim usually occurs. A belt structure comprising belt layers is circumferentially applied around the carcass ply/plies and a tread band 4 is circumferentially superimposed on the belt structure. Two sidewalls 5, each extended from the corresponding bead 3 to a corresponding lateral edge of the tread band 4, are applied in laterally opposite positions on the carcass ply/plies.

The vulcanisation mould 1 comprises a lower portion 6 and an upper portion 7 that are mutually coupleable.

Each of said lower portion 6 and upper portion 7 comprises a respective first sidewall plate 8 and second sidewall plate 9. The first sidewall plate 8 and the second sidewall plate 9 are axially opposite. Each of said first sidewall plate 8 and second sidewall plate 9 comprises a work surface arranged to operate on the beads 3 and on the sidewalls 5 of the green tyre 2. The lower portion 6 and the upper portion 7 are axially movable between a first position, in which they lie mutually spaced, and a second position, in which they lie coupled to each other.

The vulcanisation mould 1 comprises a circumferential portion defined by a plurality of circumferential sectors 10 all arranged around a central axis “Y-Y” of the vulcanisation mould 1. The circumferential sectors 10 are movable between a first position, in which they are circumferentially spaced from each other and further from the central axis “Y-Y”, and a second position, in which they are circumferentially moved close to each other and closer to the central axis “Y-Y”. In the second position, the circumferential sectors 10 together with the first sidewall plate 8 and second sidewall plate 9 delimit a vulcanization and moulding cavity 11 for housing the tyre 2 (figure 6). The vulcanization and moulding cavity 11 has a shape corresponding to an external shape to be conferred to the tyre 2 once it is moulded and vulcanised.

In the non-limiting example shown in the attached figures, each circumferential sector 10 comprises a supporting block 12 and a working segment 13 (figures 1 and 6). With respect to the central axis “Y-Y”, the working segment 13 is positioned radially inside the respective supporting block 12 and is mounted on the respective supporting block 12 through connecting devices, not shown, which allow to disengage and replace the working segment 13 with another working segment 13. This way, the working segments 13 may be replaced to vulcanize and mould tyres of different size and/or different shape and/or different tread pattern.

When the working segment 13 is mounted on the respective supporting block 12, the working segment 13 and the supporting block 12 are integral to each other and move together between the first position and the second position.

In other embodiments, not shown, each circumferential sector 10 may be made of one piece only.

Each working segment 13 comprises a working surface 14 (figures 1 and 6) radially facing inwards towards the central axis “Y-Y” and configured to engage a radially outer portion of the tyre 2 when the tyre 2 is placed in the vulcanization and moulding cavity 11. In the second position, the mutually-approached working surfaces of the circumferential sectors 10 define a circumferential surface arranged for operating against the tread band 4 of the green tyre 2 to be vulcanised.

In the non-limiting embodiment illustrated in the figures, the circumferential sectors 10 are carried by the upper portion 7. In particular, the circumferential sectors 10 are mounted on guides 15 belonging to the upper portion 7 and are configured for being moved between the first position and the second position.

Indeed, the upper portion 7 comprises an annular container 16 having a top 17, a bottom 18, a radially inner face 19 and a radially outer face 20. The annular container 16 is co-axial to the central axis “Y-Y” and carries the circumferential sectors 10. The guides 15 are positioned on the radially inner face 19 and are fashioned as T-shaped ribs slidably engaged in respective T-shaped grooves 21 made in a radially outer part 22 of the circumferential sector 10 (figure 7).

The radially outer parts 22 of the circumferential sectors 10 are disposed on a fictional frusto-conical surface and the radially inner face 19 of the annular container 16 has a frusto-conical shape. Both the fictional frusto-conical surface and the radially inner face 19 taper upward and the T-shaped ribs and T-shaped grooves 21 are slanted and converge towards the central axis “Y-Y”.

The annular container 16 is movable between a raised position and a lowered position. The guides 15 slide inside the grooves 21 when the annular container 16 moves between the raised position and the lowered position.

In the raised position, the circumferential sectors 10 are in the first position, the annular container 16 is located above the circumferential sectors 10 and the circumferential sectors 10 hang from the annular container 16.

In the lowered position, the annular container 16 surrounds the circumferential sectors 10, the circumferential sectors 10 are in the second position and the radially inner face 19 of the annular container 16 is in contact with the radially outer parts 22 of the circumferential sectors 10 (figures 1 and 6). In the lowered position, the circumferential sectors are in the second position and the apparatus delimits the vulcanization and moulding cavity 11.

Devices, that are per se known and not illustrated, are configured for moving the abovementioned parts of the apparatus between the above-indicated positions.

A flexible and elastic membrane 23, for example made with a compound with butyl rubber base, is installed on the mould 1. The elastic membrane 23 has a pair of radially inner circumferential edges 24 provided with anchoring appendages anchored to a part of the apparatus, as illustrated in figure 1, and internally delimits an expandable chamber 25. A generator and/or a tank of a hot and pressurised fluid, not illustrated since of known type, is/are operatively connected to the expandable chamber 25 in order to inflate the elastic membrane 23. A vacuum pump, not illustrated since of known type, is operatively connected or connectable to the expandable chamber 25, in order to bring a pressure inside the expandable chamber 25 below a pressure outside said expandable chamber 25 and to collapse/contract the membrane 23.

The apparatus also comprises devices operatively associated with the vulcanising and moulding cavity 11 and configured for administering heat, also through the hot and pressurised fluid, to the tyre 2 contained in said vulcanising and moulding cavity 11.

In order to pre-heat the circumferential sectors 10 just before the vulcanising and moulding step and also to heat said circumferential sectors 10 during the vulcanising and moulding step, a conduit 26 for circulating a heating medium is provided in the annular container 16. The conduit 26 surrounds the circumferential sectors 10 when the annular container 16 is in the lowered position and has a wavy pattern that stretches from the top 17 to the bottom 18 and from the bottom 18 to the top 17 of the annular container 16.

In a diametrical section of the annular container 16 (figures 1 , 5, 6 and 7), some parts 27 of the conduit 26 are closer to the radially inner face 16 than to the radially outer face 20 of said annular container 16.

In the non-limiting embodiment of the attached figures, each of these parts 27 is flat and is defined by a respective U-shaped section. The U-shaped section has two dimensions much larger than a third dimension and the third dimension is perpendicular to the radially inner face 19 of the annular container 16. As shown in figure 3, each of the U-shaped sections is a groove or pocket fashioned in the radially inner face 19 of the annular container 16. Said groove may be milled in the annular container 16. The groove is closed by a rectangular or trapezoidal plate 28 (which in figure 3 has been removed). A radially inner working surface of the plates 28 defines part of the inner face 19 of the annular container 16 and is flush with the remaining parts of the inner face 19 of the annular container 16. As shown in figure 7, each guide 15 is placed between two adjacent plates 28.

The annular container 16 is made of structural steel, for instance unalloyed structural steel, and the the plates 28 are made of a material having a thermal conductivity between 100 W/(m*K) and 180 W/(m*K) and a hardness between 40 HB and 210 HB. For instance, the plates 28 are made of brass or an alloy comprising copper, nickel and silicon, like CuNi2Si, or an alloy comprising copper, tin, zinc and lead, like CuSn7Zn4Pb7. The plates 28 allow heat transfer from the heating medium to the circumferential sectors 10.

Each U-shaped section comprises a low bend and two upper ends connected by two straight sections (figure 3). Each of two upper ends of the U-shaped section is connected to an adjacent U-shaped section through a connection hole 29 having an end connected to the upper end of one of the U-shaped sections and another end connected to the upper end of another of the U-shaped sections. In figure 7, the connection holes 29 are fashioned through a thickness of the annular container 16. As shown in figure 5, the wavy pattern of the conduit 26 comprises the sequence of U-shaped sections and connection holes 29 that follow one another in an alternating fashion starting from an inlet 30 and terminating to an outlet 31. In other words, the conduit 26 comprises a plurality of top portions and a plurality of bottom portions that follow one another in an alternating fashion. The top portions are defined by the connection holes 29, the bottom portions are defined by the low bends of the U-shaped sections and said top and bottom portions are connected by the straight sections of the U-shaped sections. The inlet 30 and the outlet 31 are fashioned on the radially outer face 20 of the annular container 16 and are close to each other (figures 2, 5 and 7).

As shown in figure 3 and in the diametrical cross section of figure 6, each U- shaped section is delimited by a first inner surface 32 parallel to the radially inner face 19 of the annular container 16, by a second inner surface 33 facing the first inner surface 32 and by an edge inner surface 34 connecting the first inner surface 32 and the second inner surface 33. In the illustrated embodiment, each of the first inner surface 32 and second inner surface 33 is U-shaped. The first inner surface 32 and the second inner surface 33 are parallel to each other and identical to one another. The first inner surface 32 is further from the radially inner face 19 of the annular container 16 than the second inner surface 33. In the illustrated embodiment, the second inner surface 33 is part of the respective plate 28.

The first inner surface 32 and the second inner surface 33 are spaced by a gap “g” (measured perpendicular to the first inner surface 32 and to the second inner surface 33). A first distance “d1” from the second inner surface 33 to the radially inner face 19 of the annular container 16 (measured perpendicular to the first inner surface 32 and the second inner surface 33) is a thickness of the plate 28. The first inner surface 32 has an area “A1” equal to an area of the second inner surface 33. The first inner surface 32 has a height “h” measured parallel to said first inner surface 32 and in a diametrical cross section of the annular container 16 (figures 3 and 6). The first inner surface 32 has a width “w” measured parallel to said first inner surface 32 or along a circumferential direction of the annular container 16 and orthogonal to the height “h” (figures 3 and 6). The first inner surface 32 is spaced from the radially outer face 20 of the annular container 16 of a minimum radial distance “d2”. The conduit 26 has an average cross section area, measured perpendicular to an average direction of flow of the heating medium inside the conduit 26. The vulcanization and moulding cavity 11 has a maximum inner diameter “D” and a width “C” (figure 1).

The parts 27 and related elements may be dimensioned as follows. A ratio “A1/g” of the area “A1” of the first inner surface 32 to the gap “g” is between 1000 mm and 2000 mm. A ratio “A1/C” of the area “A1” of the first inner surface 32 to the width “C” of the vulcanization and moulding cavity 11 is between 80 mm and 100 mm. A ratio “A1/d1” of the area “A1” of the first inner surface 32 to the first distance “d1” is between 1000 mm and 2000 mm. A ratio “A1/d2” of the area A1” of the first inner surface 32 to the minimum radial distance “d2” is between 100 mm and 200 mm. A ratio “D/d2” of the maximum inner diameter “D” of the vulcanization and moulding cavity 11 to the minimum radial distance “d2” is between 10 mm and 20 mm. A ratio “d2/d1” of the minimum radial distance “d2” to the first distance “d1” is between 5 and 20. A ratio “h/C” of the height “h” of the first inner surface 32 to the width “C” of the vulcanization and moulding cavity 11 is between 0.7 and 0.9. A ratio “w/C” of the width “w” of the first inner surface 32 to the width “C” of the vulcanization and moulding cavity 11 is between 0.4 and 0.6.

Thanks to the above dimensions, an average speed of the heating medium inside the conduit 26 may be limited to 15 m/s to 25 m/s, optionally to 20 m/s, and a flow rate of the heating medium across the conduit may be limited to 4 m³/s and 8 m³/s. The annular container 16 of the vulcanisation mould 1 further comprises a ring 35 connected to the bottom 18 of the annular container 16 o defining said bottom 18. The ring 35 may be of structural steel, for instance unalloyed structural steel, follows the circumferential outline of the annular container 16 and has a groove fashioned in an upper part thereof. The groove of the ring 35 and the bottom 18 of the annular container 16 delimit together an annular drain channel 36 that surrounds the central axis “Y-Y” and is positioned below the conduit 26. Cross sections of the ring 35 and of the drain channel 36 are depicted in figures 1 , 6, 8 and 9.

A plurality of drain holes 37 connect the low bend of the U-shaped sections to the drain channel 36. The drain channel 36 shown in figure 8 comprises a radial portion 38 connected to the low bend and an axial portion 39 connecting the radial portion 38 to the drain channel 36. An outlet opening 40 in the ring 35 allows to discharge the condensate from the drain channel 36 (figures 8 and 9).

The annular container 16 may also be provided with an insulation layer 41 applied to the radially outer face 20 thereof (figures 1 and 6).

In use, a green tyre 2 is placed in the open vulcanisation mould 1 while the circumferential sectors 10 are in the first position and the annular container 16 is in the raised position. The vulcanisation mould 1 is then closed by lowering the annular container 16 and bringing the circumferential sectors 10 to the second position. In the lowered position of the annular container 16, the plates 28 engage the radially outer parts 22 of the circumferential sectors 10 and each circumferential sector 10 is coupled to a couple of said U-shaped sections.

According to a method of pre-heating according to a method of the present invention, a source of the heating medium, for instance steam, preferably water steam, is connected to the conduit 26 and the steam is circulated inside the conduit 26. The steam flows close to the circumferential sectors 10 when it crosses the U-shaped sections. The heat of the steam is transferred from the U- shaped sections to the circumferential sectors 10 through the plates 28 and heat up the circumferential sectors 10. A condensed part of the steam is drained from the conduit 26 through the drain holes 37 and the annular drain channel 36 and leaves the drain channel 36 through the outlet opening 40.

The chart of figure 10 shows the history over time t (min) of the temperature T (°C) of the supporting blocks 12 of the circumferential sectors 10 of the apparatus of the invention (line A) and of an apparatus according to the prior art (line B). As the invention, the annular container of the prior art is provided with conduit fashioned in the wall and close to a radially outer face of the annular container. Differently from the invention, the conduit of the prior art is a single toroidal conduit and it is closer to a radially outer face than to a radially inner face of the annular container. The parameters of the following Table 1 apply to the apparatus of the invention (line A) and to an apparatus according to the prior art (line B). The parameters of Table 2 refer to the apparatus of the invention (line A). The parameters of Table 3 refer to the apparatus of the prior art (line B).

Table 1

Heat transfer in still air

Table 2

Table 3

Figure 10 shows that the circumferential sectors 10 of the apparatus according to the prior art (B) reaches a final constant temperature (of 180°C) in 30 minutes while the circumferential sectors 10 of the apparatus of the invention (A) reach the final temperature (of 185°C) in only 13 minutes. The following Table 4 shows the computed simulated steam consumptions of the apparatus of the invention and of the apparatus according to the prior art to reach the respective steady temperatures. The reduction of steam consumption is about 57%. Table 4

Claims

1. Apparatus for vulcanising and moulding tyres, comprising: a plurality of circumferential sectors (10) arranged around a central axis (Y-Y), the circumferential sectors (10) being movable between a first position, in which they are circumferentially spaced from each other and further from the central axis (Y- Y), and a second position, in which they are circumferentially moved close to each other and closer to the central axis (Y-Y); an annular container (16) having a top (17), a bottom (18), a radially inner face (19) and a radially outer face (20); the annular container (16) engaging or being configured to engage the circumferential sectors (10), the annular container (16) being movable between a raised position, in which the circumferential sectors (10) are in the first position, and a lowered position, in which the annular container (16) surrounds the circumferential sectors (10) and the circumferential sectors (10) are in the second position; wherein, in the lowered position, the radially inner face (19) of the annular container (16) is in contact with a radially outer part (22) of the circumferential sectors (10); wherein, when the annular container (16) is in the lowered position and the circumferential sectors (10) are in the second position, the apparatus delimits a vulcanization and moulding cavity (11) for housing a tyre (2); wherein a conduit (26) for circulating a heating medium is provided in the annular container (16), said conduit (26) surrounding the circumferential sectors (10) when the annular container (16) is in the lowered position; wherein the conduit (26) stretches towards the bottom (18) and towards the top (17) in a wavy pattern.

2. The apparatus of claim 1 , wherein, in a diametrical section of the annular container (16), at least some parts (27) of the conduit (26) are closer to the radially inner face (19) than to the radially outer face (20) of said annular container (16).

3. The apparatus of claim 1 or 2, wherein the annular container (16) comprises a drain channel (36) connected to the conduit (26).

4. The apparatus of claim 3, wherein the drain channel (36) is annular and surrounds the central axis (Y-Y).

5. The apparatus of claim 3 or 4, wherein the drain channel (36) is positioned below the conduit (26).

6. The apparatus of one of claims 3 to 5, wherein the annular container (16) comprises at least one drain hole (37) connecting the conduit (26) to the drain channel (36).

7. The apparatus of one of claims 1 to 6, wherein the conduit (26) comprises a plurality of top portions and a plurality of bottom portions that follow one another in an alternating fashion.

8. The apparatus of claim 7 when depending on one of claims 3 to 6, wherein the drain channel (36) is connected to at least one of the bottom portions.

9. The apparatus of claim 8, wherein the drain channel (36) is connected to all the bottom portions.

10. The apparatus of claim 2 or of one of claims 3 to 9 when depending on claim 2, wherein each of said parts (27) of the conduit (26) has a flat shape.

11. The apparatus of claim 2 or of one of claims 3 to 10 when depending on claim 2, wherein each of said parts (27) is delimited by a first inner surface (32) parallel to the radially inner face (19) of the annular container (16), by a second inner surface (33) facing and parallel to the first inner surface (32) and by an edge inner surface (34) connecting the first inner surface (32) and the second inner surface (33); wherein the first inner surface (32) is further from the radially inner face (19) of the annular container (16) than the second inner surface (33).

12. The apparatus of claim 11 , wherein a ratio of an area (A1) of the first inner surface (32) to a gap (g) between the first inner surface (32) and the second inner surface (33) is between 1000 mm and 2000 mm.

13. The apparatus of claim 11 or 12, wherein a ratio of an area (A1) of the first inner surface (32) to a width (C) of the vulcanization and moulding cavity (11) is between 80 mm and 100 mm.

14. The apparatus of any of claims 11 to 13, wherein a ratio of an area (A1) of the first inner surface (32) to a first distance (d1) from the first inner surface (32) to the radially inner face (19) of the annular container (16) is between 1000 mm and 2000 mm; the first distance (d1) being measured perpendicular to the first inner surface (32).

15. The apparatus of any of claims 11 to 14, wherein a ratio of an area (A1) of the first inner surface (32) to a minimum radial distance (d2) from the second inner surface (33) to the radially outer face (20) of said annular container (16) is between 100 mm and 200 mm.

16. The apparatus of any of claims 11 to 15, wherein a ratio of a maximum inner diameter (D) of the vulcanization and moulding cavity (11) to a minimum radial distance (d2) from the second inner surface (33) to the radially outer face (20) of said annular container (16) is between 10 mm and 20 mm.

17. The apparatus of any of claims 11 to 16, wherein a ratio of a height (h) of the first inner surface (32) to a width (C) of the vulcanization and moulding cavity (11) is between 0.7 and 0.9; the height (h) being measured in a diametrical cross section of the annular container (16) and parallel to the first inner surface (32).

18. The apparatus of any of claims 11 to 17, wherein a ratio of a width (w) of the first inner surface (32) to a width (C) of the vulcanization and moulding cavity (11) is between 0.4 and 0.6; the width (w) being measured along a circumferential direction of the annular container (16).

19. The apparatus any of claims 11 to 18 when claim 11 depends on one of claims 7 to 9, wherein, in a view along a radial direction, each of said parts (27) is a U-shaped section of the conduit (26); wherein a low bend of the U-shaped section is one of the bottom portions of the conduit (26), wherein each of two upper ends of the U-shaped section is connected to an adjacent U-shaped section through one of the top portions.

20. The apparatus of claim 2 or of one of claims 3 to 19 when depending on claim 2, wherein each of said parts (27) of the conduit (26) is delimited by one groove fashioned in the radially inner face (19) of the annular container (16) and by a plate (28) closing the groove; wherein, in the lowered position, the plates (28) engage the radially outer part (22) of the circumferential sectors (10).

21. The apparatus of claim 20, wherein the plates (28) are made of a material having a thermal conductivity between 100 W/(m*K) and 180 W/(m*K) and a hardness between 40 HB and 210 HB.

22. The apparatus of claim 2 or of one of claims 3 to 21 when depending on claim 2, wherein, when the annular container (16) is in the lowered position, each circumferential sector (10) is coupled to a plurality of said parts (27).

23. The apparatus of one of claims 1 to 22, wherein the conduit (26) has an inlet (30) and an outlet (31), the inlet (30) and the outlet (31) being fashioned on the radially outer face (20) of the annular container (16) and being close to each other.

24. The apparatus of one of claims 1 to 23, wherein each of the circumferential sectors (10) comprises a supporting block (12) and a working segment (13), the supporting block (12) comprising the radially outer part (22), the working segment

(13) being mounted on the supporting block (12) and comprising a working surface

(14) configured to engage the tyre (2) placed in the vulcanization and moulding cavity (11).

25. A method for pre-heating circumferential sectors in an apparatus for vulcanising and moulding tyres, the method comprising: providing an annular container (16) placed or configured to be placed around a plurality of circumferential sectors (10) arranged around a central axis (Y-Y), the plurality of circumferential sectors (10) delimiting a vulcanization and moulding cavity (11); making a heating medium flowing through a wavy pattern fashioned in the annular container (16), the wavy pattern stretching from a top (17) to a bottom (18) and from a bottom (18) to a top (17) of the annular container (16); wherein a radially inner face (19) of the annular container (16) is in contact or is configured to be put in contact with a radially outer part (22) of the circumferential sectors (10).

26. The method of claim 25, comprising: making the heating medium flowing closer to the radially inner face (19) of the annular container (16) than to a radially outer face (20) of said annular container (16).

27. The method of claim 25 or 26, wherein an average speed of the heating medium in the wavy pattern is between 15 m/s and 25 m/s.

28. The method of any of claims 25 to 27, wherein a flow rate of the heating medium across the wavy pattern is between 4 m³/s and 8 m³/s.

29. The method of any of claims 25 to 28, wherein the heating medium is steam and the method further comprises: draining a condensed part of the steam from the wavy pattern.

30. The method of claim 29, wherein draining is performed while the steam is flowing through the wavy pattern.