PNEUMATIC BAKE-OUT MOLD

Abstract

A pneumatic tire baking mold (10) comprising molding parts (11), wherein the mold includes heating elements arranged in at least one of said molding parts (11), and wherein the mold includes several insulating elements (40, 41a, 41b, 43, 44, 45), each insulating element being made of at least one thermally insulating material, said insulating elements being arranged on the external faces of said molding parts so as to thermally insulate them substantially completely from the other parts of the mold. Figure for the abbreviation: Fig. 1

Description

Title of the invention: COOKING MOLD FOR PNEUMATICS

[0001] The invention relates to the manufacture of tires and in particular to the baking or vulcanizing molds for tires and more particularly to the sector type molds.

[0002] The manufacture of a tire includes a curing step during which a raw tire blank is molded and vulcanized to obtain a tire with the desired mechanical characteristics, geometry, and appearance. Curing takes place in a tire curing mold comprising an upper and a lower molding assembly, axially movable relative to each other, and a ring of radially movable sectors. More specifically, a tire curing mold primarily comprises two molding shells for the tire sidewalls and two molding rings for the tire bead, which are located axially on either side of a ring having several circumferential molding sectors for the tire tread. The internal space defined by these parts in the closed position of the mold forms a molding cavity for the tire blank.Such a baking mold is arranged within a baking press comprising, among other things, mechanisms for opening and closing the baking mold on a tire blank and for opening it in order to extract the vulcanized tire and introduce a new blank.

[0003] The curing of a tire blank is carried out, in a known manner, with heat supplied both inside and outside the blank. Thus, a flexible curing membrane is deployed inside the blank using pressurized steam to press the tire blank against the walls of the mold cavity. The exterior of the mold is often placed in a steam environment, which provides heat to the outside of the tire blank. While functioning satisfactorily, it has been observed that the heat transfer efficiency with this type of conventional curing is very low, approximately 3% to 7%, because the entire mold, including the molding and structural parts, must be heated in order to transfer heat to the tire blank.The term "resistant parts" generally refers to parts that do not participate in the molding of the tire, but which support the molding parts when they are fixed, or even drive them in motion when the molding parts move between the opening and closing positions of the mold.

[0004] Document JP 2004-34652 proposes a solution to this problem. This document describes a vulcanizing mold comprising an upper ring, a lower ring, and a plurality of radially movable sectors. The radially outer surface of the sectors is inclined to cooperate with the radially inclined inner surface of an axially movable clamping ring. The radial movement of the sectors is thus ensured during the axial movement of the clamping ring. More specifically, according to this document, heat is supplied from outside the tire blank by equipping each sector with heating elements arranged so as to be close to the tire blank and by insulating the heating elements radially on the outside within each sector.While this does reduce heat loss to the outside of the sectors, it is nevertheless observed that, due to the fact that many metal parts are in contact during firing at the molding cavity, including at the sector level, heat still escapes to the outside of it, towards the resistant parts of the mold.

[0005] However, the need to improve the thermal efficiency of a tire vulcanization mold remains.

[0006] An objective of the invention is to remedy the aforementioned disadvantages and to provide a tire vulcanization mold capable of efficiently curing a tire blank, while reducing the risk of overcooking in areas with thin walls of the tire.

[0007] This objective is achieved by the invention, which provides a pneumatic cooking mold comprising molding parts formed by: - an upper molding shell for an upper sidewall of a tire, - a lower molding shell for a lower sidewall of a tire, - an upper molding ring for an upper bead of a tire; - a lower molding ring for a lower bead of a tire; - a ring of radially movable circumferential sectors for molding a tire tread, where each sector comprises a molding element for a portion of the tire tread, characterized in that the mold comprises heating elements arranged in at least one of said molding parts and in that the mold comprises several insulating elements where each insulating element is made of at least one thermally insulating material, said insulating elements being arranged on the external faces of said molding parts so as to thermally insulate them substantially completely from the other parts of the mold.

[0008] A baking mold comprises molding parts that cooperate with resistant parts adapted to support or drive the molding parts in motion. According to the invention, at least one of the molding parts comprises a heating element and All molding parts are thermally insulated almost completely from the resistant parts. More specifically, elements made of a thermally insulating material are arranged on the external surface of all molding parts. The external surface of a molding part is understood to be the surface that does not participate in the molding process. Thus, the molding parts that come into direct contact with the tire can be heated to the desired curing temperature without heat loss to the tire blank due to thermal inertia, and without heat loss to the resistant parts. Indeed, the components of a tire curing mold are made of metallic materials for reasons of mechanical resistance under pressure and temperature. Such components come into contact during curing and readily conduct heat through thermal contact.However, with the solution of the invention, by interposing thermally insulating elements on the external faces of all the molding parts, it is possible to thermally decouple the molding parts, preventing metal-to-metal contact (for example, steel-to-steel or aluminum-to-steel contact) between the molding parts and the resistant parts of the mold. According to the invention, the ratio between the external surface area not thermally insulated and the thermally insulated surface area of ​​all the molding parts can be less than 1%. The 1% percentage can be attributed to the fastening of the insulators with metal screws.

[0009] The energy efficiency of a baking mold of the invention is between 70 and 75%, which is significantly higher than that of molds in the prior art.

[0010] According to advantageous and non-limiting features, taken alone or in combination where technically feasible: - the mold may include first insulating elements which can be made of a first thermally insulating material so as to ensure the transmission of mechanical forces to the molding parts which they thermally insulate; - said first thermally insulating material may be a composite material comprising glass fibers in an epoxy resin matrix; - the thermal conductivity of said first thermally insulating material of the first insulating elements can be between 0.2 and 0.4 W / mK; - the mold may include second insulating elements which may be made of a second thermally insulating material which may have a thermal conductivity of less than 0.03W / mK; - The surface area occupied by the first insulating elements can be no more than 30% of the surface area of ​​the molded parts with which they come into contact, and the second insulating elements can occupy the remainder of the external surface area of ​​said molded parts; thus, the surface area occupied is limited to a minimum. by the first insulating elements and this just enough so that they can withstand the stresses experienced during operation, the rest of the external surface of the molding parts being covered by the second insulating elements having better thermal insulation properties in order to obtain optimized thermal insulation of the molding parts compared to the resistant parts of the mold; - the mold may include electric heating elements which have the advantage of being able to provide better energy efficiency, compared to molds whose heating elements include a circulation of water vapor; - each molding part can include at least one electric heating element, which allows for differentiated heating of the molding parts from each other; differentiated heating means that the molding parts are heated to different temperatures relative to each other; - each molded part can include at least one temperature sensor, which allows the temperature of the heating element to be adapted to the area of ​​the tire blank; - the temperature sensors can be connected to a control unit capable of controlling said electric heating elements.

[0011] According to an advantageous aspect, the mold of the invention may include means for actuation in a radial movement of the sectors, said means comprising a shrink ring whose internal surface is inclined to cooperate with the inclined external surface of the sectors and where, for each sector, the shrink ring can transmit the clamping force to prismatic shims or insulating strips which can bear directly on the lining of the sector.

[0012] According to another advantageous aspect, the mold may include central actuation parts for a cooking membrane and the mold may include thermally insulating elements arranged axially outside said central parts.

[0013] The invention also relates to a method for molding a tire blank using a baking mold comprising molding parts according to one of the preceding claims, characterized in that at least one of said molding parts is heated by at least one heating element and in that all the molding parts are thermally insulated substantially completely from the other parts of the mold.

[0014] The heating elements can be electric heating elements to which temperature sensors are associated.

[0015] Each heating element can be controlled to a pre-established cooking temperature, at least two heating elements that can be controlled at different temperatures relative to each other

[0016] The invention will be better understood from the following description, which is based on the following figures: Fig. 1 is an axial cross-sectional view of a baking mold according to a first embodiment of the invention; [Fig.2] is a radial cross-sectional view of the mold of [Fig.1]; [Fig.3] is an enlarged scale view of part of the mold illustrated in [Fig.2]; [Fig.4] is an axial cross-sectional view of a circumferential sector of the mold of [Fig.1]; [Fig.5] is an exploded view of the area of ​​[Fig.4]; [Fig.6] is an axial cross-sectional view of a baking mold according to a second embodiment of the invention; [Fig.7] is a perspective view of a circumferential sector of the mold of [Fig.6]; [Fig.8] is a perspective view of the back of the trim in the [Fig.7] sector; [Fig.9] is a schematic top view of an upper flat ring which is part of the mold of [Fig.1].

[0017] In the various figures, identical or similar elements bear the same reference. Their description is therefore not systematically repeated.

[0018] Figure 1 illustrates a curing mold 10 for a tire blank according to a first embodiment of the invention, a mold intended for curing a tire for a passenger vehicle. The curing mold 10 is intended to be inserted between the upper 2 and lower 4 platens of a curing press 1. A curing press comprises a frame forming a base, assumed to be stationary and fixed to the ground. The press also comprises, in a known manner, means for guiding and actuation (for example, hydraulic cylinders) of the drive mechanisms for opening and closing the mold, as well as an installation for providing the mold with the curing conditions (in terms of pressure and temperature of the heat transfer fluid) necessary for vulcanizing the tire.

[0019] The baking mold 10 for a tire blank comprises an upper molding assembly and a lower molding assembly, each molding assembly having an upper shell 16a, respectively a lower shell 16b for molding a sidewall of the tire, and an upper ring 18a, respectively a lower ring 18b for molding a bead of the tire. A ring of circumferential sectors 20 for molding the tire tread completes the upper and lower molding assemblies and, together with them, forms the molding portions 11 of the mold 10. In the closed position of the mold, the internal surfaces of the molding parts 11 together form a molding cavity intended to accommodate a tire blank.

[0020] In the example illustrated in figures 1 to 5, the mold is of the "container" type, the upper shell 16a is made to slide axially with the upper plate 2 of the press, to which it is rigidly fixed, the lower shell 16b being rigidly fixed to the lower plate 4 of the press which is, itself, fixed, and the circumferential sectors 20 are made to make movements in a radial direction during the opening and closing of the mold.

[0021] The baking mold 10 is substantially rotationally symmetric about its central axis X-X'. The central axis extends vertically. In the following description, "axial" or "axially" refers to a direction or displacement parallel to the central axis, and "radial" or "radially" refers to a direction or displacement perpendicular to the central axis X-X'. A circumferential direction is a direction tangent to the radial direction and corresponds to the circumferential direction of the tire.

[0022] The circumferential sectors 20 of the sector ring are arranged side-by-side in the circumferential direction. Each sector includes a molding 19 for the tire tread pattern, the molding being held by a sector support. Thus, the molding 19 of each sector extends from the interface with the upper shell 16a to the interface with the lower shell 16b.

[0023] The radially external surfaces 21 of the sector lining supports are conical, they all have the same inclination extending downwards and radially outwards.

[0024] The press further comprises a conical ring 14 whose radially internal surface 14a is inclined radially downwards and has the same inclination as the radially external surfaces 21 of the sectors 20. The conical ring 14 is connected to a first actuator of the baking press, for example a hydraulic cylinder, which allows it to perform an axial movement upwards and downwards. During the closing of the mold, the conical ring 14 descends, positions itself on the ring of sectors 20, brings the sectors radially inside the mold and applies a force on the sectors to keep the assembly closed during baking when the temperature and pressure values ​​inside the molding cavity increase. The conical ring 14 comprises a plurality of rods 12 having a T-shaped cross-section ([Fig.2] and 3) each rigidly fixed on the conical ring, each rod 12 being intended to slide in a rail 17 of a corresponding sector 20 of the ring of sectors. Stops (not illustrated) located between one end of each rod 12 and a notch on the external surface 21 of each sector limit the radial recoil of the sectors during the die. The conical ring is positioned upwards to open the mold. In this embodiment, the conical ring 14, the rods 12, and their connecting elements to the mold sectors and the upper platen of the press are of the type described in document WO 2014 / 044713.

[0025] The upper plate 2 of the press is connected to a second actuator, for example a hydraulic cylinder, which allows it to perform an axial movement up and down during the closing and opening operations of the mold, as will be explained later.

[0026] The conical ring 14, the upper plates 2 and lower plates 4 and the parts adjacent to the molding cavity, but not including any part coming directly into contact with the tire blank, form the resistant parts of the mold, as opposed to the molding parts which come directly into contact with the tire blank.

[0027] In the open position of the mold, the conical ring 14 and the molding parts located in the upper part of the mold: the upper shell 16a, the upper molding ring 18a and the sectors 20 are moved axially upwards together with the upper platen 2 of the press so as to clear the molding cavity (the molding cavity being understood as the space formed inside all the molding parts in the closed position of the mold) in order to be able to extract the cured tire and to introduce a new tire blank 3. Once the tire blank 3 is installed and centered on the molding components of the lower part of the mold, the upper platen 2 descends, under the action of the first actuator of the press, bringing the molding parts towards the lower platen 4.Next, the conical ring 14 descends in turn, under the action of the second actuator of the press, to close the firing cavity by moving the sectors 20 radially inwards, thus closing the mold for a new firing. The mold is opened by first raising the conical ring 14, followed by the raising of the upper plate 2.

[0028] The heat transfer fluid arrives inside the molding cavity from an internal cooking device 25 located in the central part of the cooking cavity, said device comprising a cooking membrane which presses the tire blank onto the internal parts of the mold during cooking, as well as means for communicating the cooking membrane with a heat transfer fluid and for diffusing and increasing the pressure and temperature of the heat transfer fluid inside the cooking membrane.

[0029] According to the invention, the mold comprises heating elements arranged in all or part of the molding parts, and all the molding parts are insulated from the resistant parts of the mold by means of insulating elements, each insulating element being made in a thermally insulating material, said insulating elements being arranged on the external sides of said molding parts so as to thermally insulate the molding parts radially and axially from the resistant parts.

[0030] Advantageously, according to the invention, the sectors 20 each comprise at least one electric heating element 31. More specifically, several electric heating elements 31, four of which are shown in [Fig. 5], are inserted into the trim 19 of each sector 20 and receive electrical power via a power cord 35. Each molding ring, in particular the upper ring 18a and the lower ring 18b, comprises an annular electric heating element 32. In the example shown, the shells 18a and 18b do not have a heating element, but in an alternative embodiment of this first mode, each shell comprises one or more annular heating elements, preferably electric. Furthermore, a temperature sensor is preferably associated with each heating element 31, 32, also arranged in the molding portion near the heating element whose temperature the sensor is to measure.The various temperature sensors are connected to a programmable logic controller (PLC) that manages the power supply and therefore the temperature of the respective heating elements.

[0031] The lining 19 comprises, on its inner face facing the tire blank, recessed or protruding patterns constituting the negative of the reliefs or sculptures of the tire. It is produced in a known manner using metal additive manufacturing or by molding, for example, using a plaster-aluminum process.

[0032] The other components of a circumferential sector 20 are more clearly visible in [Fig. 5]. Thus, a circumferential sector 20 also includes a gasket support 22 and two prismatic shims 43 whose role is to transmit the compressive force from the conical ring 14. The gasket 19 is held by its support 22 by sandwiching a sheet 40 of thermal insulation. The sheet 40 includes two axial cutouts 40a communicating with two opposing axial cutouts 28 made in the thickness of the gasket support 22. The axial cutouts 40a and 28 are through cutouts and form passages for the prismatic shims 43.The gasket support 22 is metallic, for example made of steel for greater robustness, and has a jaw-shaped profile, including two axial rims 22a and 22b which project radially inwards from the main body which extends circumferentially along the same line as the gasket 19. Cords 41a and 41b, each made of a DELTHERM® type thermal insulating material, are provided between each axial rim of the gasket 19a, respectively 19b, and the axial rims 22a, respectively 22b, of the gasket support 22. The gasket 19 is fixed to its support 22 by means of screws 29 located at the axial rims 22a, 22b of the latter, so as to sandwich the sheet 40 and the cords 41a, and 41b. Furthermore, to connect everything. Having thus obtained the conical ring 14, the prismatic shims 43 are fixed to the two circumferential ends of the lining support 19. For this purpose, each prismatic shim 43 is fixed using flanges 25 on the upper face, flanges 26 on the lower face, and flanges 27 on the outer face, and the fixing screws provided for this purpose. The flanges 25, 26, and 27 are metallic. The flange 27 defines the outer surface 21 of the circumferential sector 20.

[0033] Two triangular lateral profile fins 24 complete the circumferential sector 22 by fixing them, using fixing screws, opposite each other to the support 22 and at a pre-established distance which thus determines the rail 17 in which the rod 12 attached to the conical ring 14 is made to slide.

[0034] As can be seen more clearly in Figures 2 and 3, the circumferential length of a support 22 with a circumferential sector 20 is less than that of a seal 19. The support 22 is thus designed to have the dimensions strictly necessary for the mechanical stresses to which it is subjected, while also optimizing the thermal insulation capacity offered by the thermal insulation sheet 40, which covers substantially the entire surface of the seal 19. Furthermore, this solution also makes it possible to produce sectors with standardized dimensions and to use them with seals of several different dimensions, which reduces the cost of manufacturing the mold.

[0035] The insulating sheet 40 is preferably made of a flexible thermally insulating material with a thermal conductivity of approximately 0.03 W / mK. Such a material is, for example, BASOTECT® V3012 type insulating foam from BASF, or glass wool.

[0036] The prismatic shims 43 are made of a rigid, thermally insulating material that has very good mechanical strength properties and very low thermal conductivity of approximately 0.3 W / mK. Such a material is, for example, a composite material made from a glass fiber-reinforced epoxy resin, such as DELTHERM®. Thus, the prismatic shims 43 are able to withstand the compressive stresses from the conical ring 14 during mold closure, while also thermally insulating the seal 19 from the ring 14. This same material is preferably used to make the upper 41a and lower 41b beads that withstand axial stresses.

[0037] These insulating materials perform their functions well at the cooking temperature of the tire blank, which is between 120 and 180°C.

[0038] The prismatic wedges made of insulating material that resists mechanical stresses occupy 20% of the total surface area of ​​the back of the lining 19, while the insulating sheet 40, made of insulating foam, having thermal insulation properties superior to those of the resin strips, occupies the remaining 80%.

[0039] Figure 4 illustrates, by means of an axial cross-sectional view through a prismatic wedge 43, a circumferential sector 20 assembled as previously described. Figure 1 illustrates a cross-sectional view of the baking mold 1 in the closed position, obtained with an axial cross-sectional plane passing through a prismatic wedge 43. It can thus be seen in Figure 1 that the lining 19 is insulated in the radial direction by the thermally insulating material of the wedge 43 and in the axial direction by that of the cords 41a and 41b. It can also be seen in Figure 1 that the other molding parts, which consist of the shell 16a and the upper ring 18a in the upper molding assembly, and of the lower shell 16b and the lower ring 18b in the lower molding assembly, are also thermally insulated, in the axial direction, from the resistant parts of the mold.More specifically, an upper flat ring 44 is arranged directly in contact with the outer faces of the upper shell 16a and the upper ring 18a, and is sandwiched between these two molded parts and the upper plate 2 of the mold. Similarly, a lower flat ring 45 is arranged directly in contact with the outer faces of the lower shell 16b and the lower ring 18b, and is sandwiched between these two molded parts and the lower plate 4 of the mold. Furthermore, since the various parts are made of a thermally insulating material and have shapes of revolution, the thermal insulation of the molded parts with respect to the resistant parts also occurs in the radial direction of the mold.Preferably, the external diameter of the upper flat ring 44 and the lower flat ring 45 is extended so that they also thermally insulate the parts of the central part of the internal cooking device 25 supporting the cooking membrane. This allows the internal cooking cavity to be insulated for greater cooking efficiency inside the pneumatic blank.

[0040] The upper flat ring 44 and lower flat ring 45 are made from a disc 4a made of a thermally insulating material such as insulating foam, for example BASOTECT® V3012 from BASF. Several rectangular cutouts are made in the disc, oriented radially from its center, and strips 4b made of a glass fiber reinforced epoxy resin, such as DELTHERM®, are inserted into these cutouts ([Fig. 9]). [Fig. 9] illustrates, by way of example, an upper flat ring 44 with four strips 4b. The number of strips 4b and their dimensions can vary depending on the dimensions of the flat ring. The lower flat ring is made similarly to the upper flat ring, using a disc 4a and strips 4b.Since the upper flat rings 44 and lower flat rings 45 are subjected to significant axial mechanical stresses during mold closure, the aforementioned bars 4b are preferably made of a material with good mechanical strength properties and low thermal conductivity. This is preferred, as in the case of the shims. Materials 43, a composite material made from a glass fiber reinforced epoxy resin, such as DELTHERM®, with a thermal conductivity of approximately 0.3 W / mK. Thus, the glass fiber reinforced epoxy resin strips are able to withstand axial pressure stresses, while the rest of the disc provides excellent thermal insulation between the molded parts and the resistant parts of the mold. The insulating material strips, which resist mechanical stresses, occupy 20% of the total surface area of ​​the upper flat rings 44 and lower flat rings 45, while the insulating foam, having superior thermal insulation properties compared to the resin strips, occupies the remaining 80%.

[0041] It is clear from what has been described with reference to Figures 1 to 5 that a baking mold 10 thus constructed makes it possible to completely isolate the molding parts 19, 16a, 16b, 18a and 18b from the surrounding resistant parts (conical ring 14, upper plate 2, lower plate 4), so that there is substantially no longer any metallic contact, and therefore no heat loss, between the molding parts and the resistant parts of the mold. By substantially, it is understood that the ratio between the surface area of ​​the contact area that could cause heat loss and the surface area of ​​the thermal insulation that envelops the molding parts is less than 10% and preferably less than 5%. The difference, up to 100% coverage of the molding parts by thermal insulation, can be due to the fastening of the parts made of thermally insulating material using metal screws, such as screws 29.

[0042] During operation, when the curing mold 10 is closed on the tire blank, the electric heating elements 31 are regulated, all or individually, to at least a first setpoint temperature, which is the desired curing temperature to ensure the curing of the tread or a portion thereof. The annular electric heating elements 32 are also powered and regulated to a predetermined temperature, desired for curing the tire bead. The thermal insulators surrounding the molding parts on all their external sides prevent heat from diffusing towards the resistant parts of the mold, thus ensuring that each area of ​​the tire is cured at the correct temperature and efficiently.

[0043] Furthermore, a sleeve 50 made of insulating material, such as a BASF BASOTECT® V3012 type insulating foam mattress, allows the baking mold 10 to be isolated from the external environment, the sleeve 50 being arranged around the resistant parts of the baking mold. This limits heat exchange outside the mold.

[0044] Figures 5 and 6 illustrate a baking mold 100 according to a second embodiment of the invention, a mold intended for baking a very large tire dimensions, such as a tire for a construction vehicle. The 100 baking mold exhibits rotational symmetry around a vertical axis Y-Y'.

[0045] The baking mold 100 is intended to be inserted between the upper 2' and lower 4' plates of a baking press 1'. The lower plate supports a lower shell 160b, made in several pieces or elements for large molds, as well as a ring 180b. The lower shell elements 160b and the lower ring 180b are rigidly fixed to a lower insulation support plate 4”, which is itself rigidly fixed to the lower plate 4' by sandwiching insulation 501 between the two plates. Similarly, the press includes an upper plate 2' to which is fixed an upper shell 160a composed of several parts or elements, as well as an upper ring 180a. The upper shell elements 160a and the ring 180a are rigidly fixed to an upper insulation support plate 2”, which is itself fixed to the upper plate 2' by sandwiching insulation 502 between the two plates.The upper plate 2' and the lower plate 4' are mounted to slide vertically along the Y-Y' axis. The mold also includes circumferential sectors 200 that extend peripherally to form a ring when the mold is closed. Such a sector 200 is shown in [Fig. 7]. Each sector includes an inner front face having a molded portion or lining 190 extending in a vertical and a circumferential direction.

[0046] The mold also includes a clamping ring 150 actuated by a movable ring 145, which is itself connected to one of the press actuators. This ring ensures that the sectors 200 are held in position when the molding cavity is pressurized. The clamping ring 150 includes a conical inner face adapted to cooperate with the conical outer face 224 of the sectors 200.

[0047] Each sector 200 comprises a flat lower face 220b adapted to rest on the flat surface of the upper face of the lower plate 4' and a flat upper face 220a adapted to come into contact with the flat lower face of the upper plate 2'. The components of an assembly forming a sector 200 are held by attachment to a support 220 located at the rear, on the side opposite the axis Y-Y'. Similar to the first embodiment, the circumferential length of the support 220 is less than that of the fitting 190. The support 220 is provided in the lower part of its lateral sides 223, with two plates 221 parallel to each other and spaced apart by the width of the support 220. Each plate has a through hole 222 in its lower part, which is intended to receive a tilting pin 146. More particularly with reference to [Fig.[6], it is noted that the tilting pin 146 is able to travel along a ramp 147 inclined outwards (relative to the Y-Y' axis) of a cam 148 rigidly fixed to the frame 6 of the press 1'. .

[0048] The baking mold 100 of [Fig. 6] is shown in the closed position, the parts The molding elements 11' formed by the linings 190, the upper shell 160a, the lower shell 160b, the upper ring 180a, and the lower ring 180b are brought into contact to close around the tire blank 3, thus ensuring its curing. At the end of the curing process, during demolding, the upper plate 2' and the lower plate 4' slide upwards relative to the frame 6. The movable ring 145 drives the clamping ring 150 upwards, moving it away from the sectors 200. As the clamping ring 150 moves upwards, the sectors 200 undergo a radial sliding and outward rotational movement around the axis of the tilting pin 146, which allows the mold to open completely for the removal of the cured tire.

[0049] According to the invention, the baking mold 100 comprises electric heating elements arranged in the molding sections. Since this is a very large baking mold, at least one electric heating element is arranged in each of the molding sections 190, 160a, 160b, 180a, 180b, such as annular electric heating elements 132 arranged in the molding shells or rings ([Fig. 6]) or coil-shaped heating elements 131 arranged in a groove 191 of the lining 190 of a sector 200 ([Fig. 8]). A temperature sensor is also preferably associated with each heating element, also arranged in the molding section near the heating element whose temperature the sensor is to measure. The various temperature sensors are connected to a controller that manages the power supply and therefore the temperature of the respective heating elements.In order to make the cooking of the tire efficient with a cooking mold 100, all the molding parts 190, 160a, 160b, 180a, 180b are thermally insulated from the resistant parts of the mold.

[0050] Thus, with regard to the insulation of the seals 190, strips of thermal insulation are arranged on the back of each seal, attaching them to the seal 190 of each sector 200. More specifically, first strips 140 are used alternately with second strips 143 arranged side-by-side, one extending from the other in the vertical direction of a seal 190 in order to completely cover its rear face. The second strips 143 have good mechanical strength and are capable of withstanding the compressive stresses from the clamping ring 150. In one embodiment, the shape of the strips 143 is limited to that of the imprint of the support 220; in other words, the second strips 143 are replaced by shorter second strips, their length being that of the width of a sector support 220.In order to ensure good thermal insulation of the trim 190, the part left free by the strips 143 of the surface of the back of the trim 190 is covered with a sheet of thermal insulation having better thermal insulation capacity.

[0051] An upper cord 141a and a lower cord 141b, each made of a thermally insulating material, are fixed between the upper, respectively lower edge of the trim 190, and the upper face 220a, respectively lower face 220b of each sector 200.

[0052] The first 140 strips are made of a flexible thermally insulating material with a thermal conductivity of approximately 0.03 W / mK. Such a material is, for example, BASOTECT® V3012 type insulating foam from BASF, or glass wool.

[0053] The second strips 143 are made of a rigid, thermally insulating material that has very good mechanical strength properties and very low thermal conductivity of approximately 0.3 W / mK. Such a material is, for example, a composite material made from a glass fiber-reinforced epoxy resin, such as DELTHERM®. Thus, the strips 143 are able to withstand the compressive stresses from the clamping ring 150 during mold closure, while also thermally insulating the seal 190 from the ring 150. This same material is preferably used to make the upper 141a and lower 141b cords that bear axial stresses.

[0054] It is also noted in [Fig. 6] that the other molding parts, which are formed by the shell 160a and the upper ring 180a in the upper molding part, and by the lower shell 160b and the lower ring 180b in the lower molding part, are also thermally insulated in the axial direction from the resistant parts of the mold. More specifically, a first upper flat ring 44' is arranged directly in contact with the external faces of the upper shell 160a and a second upper flat ring 44" is arranged directly in contact with the upper ring 180a, the rings 44' and 44" being sandwiched between these two molding parts and the upper plate 2' of the mold.Similarly, a first lower flat ring 45' is arranged directly in contact with the outer faces of the lower shell 160b, and a second lower flat ring 45" is arranged directly in contact with the lower ring 180b. Rings 45' and 45" are sandwiched between these two molded parts and the lower 4" insulating support plate of the mold. Furthermore, since the various parts are made of a thermally insulating material with shapes of revolution, the thermal insulation of the molded parts from the resistant parts also occurs in the radial direction of the mold. As seen in [Fig. 6], flat rings 44' and 45' may have a stepped cross-section to better conform to the mold parts between which they are inserted.Each of the upper flat rings 44', 44" and lower 45', 45" are made from a disc made of a thermally insulating material of the insulating foam type, for example of the BASOTECT® V3012 type from the BASF company, disc in. Several rectangular cutouts are made radially from the center of the disc, and strips of glass fiber reinforced epoxy resin, such as DELTHERM®, are inserted into these cutouts, similarly to ring 44 illustrated in [Fig. 9], adapting the dimensions and sizing of the rings and strips according to the loads they will bear. Since these parts are subjected to significant axial mechanical stresses during mold closure, they are preferably made of a material with good mechanical strength and low thermal conductivity. Therefore, as in the case of prismatic shims 43, a composite material made from glass fiber reinforced epoxy resin, such as DELTHERM®, with a thermal conductivity of approximately 0.3 W / mK, is preferred.Thus, the fiberglass-reinforced epoxy resin strips are able to withstand axial pressure stresses, while the rest of the disc provides excellent thermal insulation between the molded parts and the resistant parts of the mold. The insulating material strips, which resist mechanical stresses, occupy 20% of the total surface area of ​​the upper 44', 44" and lower 45', 45" flat rings, while the insulating foam, having superior thermal insulation properties compared to the resin strips, occupies the remaining 80%.

[0055] Furthermore, a sleeve 500 made of insulating material, such as bagged rock wool, insulates the baking mold 100 from the ambient temperature outside the mold. The sleeve 500 is arranged around the resistant parts of the baking mold. Insulating rings 501 in the upper part and 502 in the lower part of the mold, made of the same material as the sleeve 500, further insulate the mold thermally from the upper trays 2' and lower trays 4', respectively. This limits heat exchange outside the mold.

[0056] Other variants and embodiments of the invention may be envisaged within the scope of the invention as claimed.

Claims

Claims

1. Curing mold (10, 100) for a tire comprising molding parts (11) formed by: - ​​an upper shell (16a, 161a) for molding an upper tire sidewall, - a lower shell (16b, 161b) for molding a lower tire sidewall, - an upper ring (18a, 181a) for molding an upper tire bead; - a lower ring (18b, 181b) for molding a lower tire bead; - a crown of radially movable circumferential sectors (20, 200) for molding a tire tread, where each sector comprises a lining (19, 190) for molding a portion of the tire tread, characterized in that the mold comprises heating elements arranged in at least one of said molding portions (11, 11') and in that the mold comprises several insulating elements (40, 41a, 41b, 43, 44, 45;44', 44”, 45', 45”, 140, 141a, 141b, 143) where each insulating element is made of at least one thermally insulating material, said insulating elements being arranged on the external faces of said molding parts so as to thermally insulate them substantially completely from the other parts of the mold.;

2. Mold according to one of the preceding claims, characterized in that it comprises first insulating elements made of a first thermally insulating material so as to ensure the transmission of mechanical forces to the molding parts which they thermally insulate.

3. Mold according to the preceding claim characterized in that said first thermally insulating material is a composite material comprising glass fibers in an epoxy resin matrix.

4. Mold according to one of claims 2 or 3, characterized in that the thermal conductivity of said first thermally insulating material is between 0.2 and 0.4 W / mK.

5. Mold according to one of the preceding claims, characterized in that it comprises second insulating elements made of a second thermally insulating material having a conductivity thermal less than 0.03W / mK.

6. Mold according to the preceding claim, characterized in that the surface occupied by said first insulating elements is at most 30% of the surface of the molding parts with which they come into contact and that said second insulating elements occupy the remainder of the external surface of said molding parts.

7. Mold according to one of the preceding claims, characterized in that said heating elements are electric heating elements (31, 32, 131, 132).

8. Mold according to one of the preceding claims, characterized in that each molding part comprises at least one electric heating element (31, 32, 131, 132).

9. Mold according to one of claims 7 or 8, characterized in that each molding part comprises at least one temperature sensor.

10. Mold according to the preceding claim, the temperature sensors are connected to a control unit capable of controlling said electric heating elements.

11. Mold according to one of the preceding claims, characterized in that it comprises means for actuating the sectors (20, 200) in a radial movement, said means comprising a hooping ring (14, 150) whose internal surface is inclined to cooperate with the inclined external surface of the sectors (20, 200) and in that, for each sector, the hooping ring transmits the clamping force to prismatic shims (43) or to insulating strips (143) bearing directly on the lining (19, 190) of the sector (20, 200).

12. Mold according to one of the preceding claims, characterized in that the mold comprises central parts for actuating a cooking membrane and in that the mold comprises thermally insulating elements arranged axially outside said central parts.

13. Method of molding a tire blank using a curing mold comprising molding parts according to one of the preceding claims, characterized in that at least one of said molding parts is heated by at least one heating element and in that all the molding parts are thermally insulated substantially completely from the other parts of the mold.

14. Molding method according to the preceding claim, characterized in that said heating elements are electric heating elements. to which temperature sensors are associated.

15. Molding method according to the preceding claim, characterized in that each heating element is controlled at a pre-established cooking temperature, at least two heating elements being controlled at different temperatures relative to each other.

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