SECTIONED BAKING MOLD FOR PNEUMATICS

Abstract

Cooking mold with radially moving sectors for pneumatics comprising: a lower shell (5), an upper shell (3), a closing ring (8) having an inclined inner face, a sectored ring (7) having a plurality of adjacent sectors distributed circumferentially, slides (12) integral with the inner surface of the closing ring (8) adapted to cooperate with grooves (14) present on the outer face of the sectors, each groove having a stop (21) adapted to cooperate with a stroke limiting device (24) of each slide.According to the invention, said stroke limiting device (24) comprises a pusher (30) located at the end of a rod (25) adapted to be actuated from the external face of said closing ring so that said pusher (30) can be moved between two positions: a first position in which it protrudes and a second position in which it is retracted relative to the internal surface of the closing ring. Figure for the abbreviation: Fig. 2.

Description

Title of the invention: SECTIONAL BAKED MOLD FOR PNEUMATICS

[0001] The invention relates to the manufacture of tires and in particular sector curing molds for the vulcanization of a tire blank.

[0002] The manufacture of a tire includes a curing stage during which a raw tire blank is molded and vulcanized to obtain a tire with the desired mechanical characteristics, geometry, and appearance. Curing molds ensure the vulcanization of the tire by applying pressure and heat to a tire blank. Sector vulcanization molds comprise several radially movable circumferential sectors for curing the tread and two shells for curing the sidewalls of the tire. A curing mold thus comprises several parts assembled and driven by appropriate kinematics in relation to a curing press.

[0003] Devices used to radially close the sectors on the tire blank often employ a sliding closure of the sectors along the inner surface of a conical closing ring. Among vulcanizing devices using such a conical closing ring, those with so-called "container" molds are preferred for ease of access to the molding space during tire loading and unloading. In these molds, the lower shell is fixed, and the molding cavity is closed by first bringing the upper sidewall molding shell, set in motion by the container's upper platform, into contact with the unmolded tire, followed by the sectors. When the mold is opened, the sectors move with the upper shell as it lifts.

[0004] The container molds are therefore composed of a sectored ring with several circumferential sectors, the external surface of the sectors being conical and the internal surfaces or linings of the sectors forming a toroidal cavity when the mold is closed. The radial movement of the sectors allows the mold to be opened for loading the tire blanks and unloading the cured tires, as well as closed during the curing of the tire blank.

[0005] During cooking, to maintain the fillings of the sectors in circumferential contact with each other, a complementary conical one-piece closing ring is positioned on the sectored ring, the inner surface of which has the same inclination as the outer surface of the sectors. The closing ring applies force to the sectors of the sectored crown to keep the assembly closed when the internal pressure of the tire increases.

[0006] To drive the sectors in a radial movement, the closing ring has a plurality of slides fixed vertically in the conical inner surface of the ring and which are distributed circumferentially so as to come into alignment with the grooves present on corresponding elements of the sectored ring.

[0007] When the press opens, pressure is exerted vertically on the segmented ring while the closing ring rises. The effect of the slides fixed to the closing ring, cooperating with the opposing grooves on each sector of the segmented ring, generates a radial force on each sector. The sectors are then driven radially until the stop of each sector, materialized by a part fixed to them or by a machined form, comes into contact with the travel limiter of the closing ring of the container mold. In this position, the closing ring drives the sectors of the segmented ring vertically, leaving space for the vulcanized casing extraction device and for the introduction of a raw blank.

[0008] In the case of existing container molds, the stroke limiter is fixed to the closing ring by an added part, assembled with a through screw. The installation of this stroke limiter is carried out manually with or without a pre-positioning tool, an operation that is not ergonomic and presents risks for the operator during maintenance phases, particularly during mold disassembly or assembly.

[0009] Moreover, it is not possible to replace an element of the sectorized ring in a cooking press under ergonomic conditions.

[0010] An objective of the invention is to remedy the disadvantages of the aforementioned documents and thus to make the operation of assembling and disassembling the parts of a container mold ergonomic, even when the mold is inside a baking press, while remaining reliable in operation.

[0011] This objective is achieved by the invention, which proposes a pneumatic cooking mold with radially moving sectors comprising: - a lower molded tire sidewall shell, - an upper molded tire sidewall shell, - an axially movable closing ring having an inclined inner face, - a sectorized tire tread molding ring comprising a plurality of circumferentially arranged adjacent sectors whose internal radial faces comprise the tread molding liners of the tire and the external radial faces are inclined so as to be able to cooperate with the internal face of said sealing ring by means of - slides attached to the inner surface of the closing ring, capable of cooperating with grooves on the outer face of the sectors so that the axial movement of the closing ring moves the sectors radially, each groove having a stop capable of cooperating with a stroke limiting device for each slide in the open position of the mold, characterized in that said stroke limiting device is an assembly made up of parts formed so as not to be elastically deformable comprising a pusher located at the end of a rod, the rod being able to be actuated from the external face of said closing ring so that said pusher can be moved between at least two positions: a first position in which it protrudes from the internal surface of said closing ring and a second position in which it is retracted from the internal surface of the closing ring.

[0012] The baking mold of the invention is a container-type mold. It comprises a ring of circumferential sectors that form a closed ring when the mold is closed. The circumferential sectors are radially movable, actuated by a conical closing ring to open and close the mold. The closing ring has a shape of revolution and is coaxial with the axis of revolution of the mold. The closing ring includes slides that move in grooves in the sectors and a travel limiting device on each slide that is adapted to contact a stop in each groove at the end of the mold's opening stroke.

[0013] The invention provides a retractable stroke limiting device comprising an actuating rod extended by a pusher, the rod being designed so as to be actuated from the outer face of said closing ring so that said pusher can be moved between at least two positions: a first position in which it protrudes from the inner surface of said closing ring and a second position in which it is retracted from the inner surface of the closing ring. Thus, when the pusher protrudes from the inner surface of the closing ring, it can come into contact with the stop of the groove and limit the opening stroke of the sectors. When the pusher is in the retracted position, the ring is disengaged from the sectors and these can be removed, replaced, cleaned, etc.This allows the operator to carry out maintenance operations safely, even when the mold is in the baking press.

[0014] Moreover, such a stroke limiting device is made up of parts formed so as not to be elastically deformable, it is understood that it does not include any spring-type parts, which ensures increased robustness and reliability in harsh operating conditions due to temperature and contamination with cooking vapors.

[0015] Said rod and said pusher can be arranged in a housing passing through said closing crown at the level of a slide.

[0016] Said housing may be an orifice having a shape of revolution extending in a radial direction with respect to the axis of revolution of the mold.

[0017] Said orifice may include at least one shoulder. Such a shoulder makes it possible to form an axial stop for the rod in one of the limit positions of the pusher.

[0018] Said rod can be actuated by a rotational movement about its longitudinal axis. In another embodiment, the rod can be actuated by a translational movement, a locking device being able to hold it in the protruding position of the pusher.

[0019] Said rod may include a threaded portion cooperating with a tapped portion of said orifice. In one embodiment, the threaded rod may include a cam track formed on its external surface which can cooperate with a lug integral with the inner wall of the rod housing within the closing ring. The rotational movement of the rod thus induces a radial translational movement of the pusher located at the end of the rod.

[0020] Said pusher can be fixed to said rod by means of a fixing pin. In one embodiment, the pusher and the rod are one piece.

[0021] Said pusher passes through said orifice with an operating clearance of less than 0.05 mm. Such sliding clearance between the two parts thus makes it possible to limit the bending stresses exerted on the pusher.

[0022] The object of the invention is also achieved with a method for molding a tire blank using a baking mold comprising: - a lower molded tire sidewall shell, - an upper molded tire sidewall shell, - an axially movable closing ring having an inclined inner face, - a sectorized tire tread molding ring comprising a plurality of circumferentially arranged adjacent sectors, the internal radial faces of which comprise tire tread molding liners and the external radial faces of which are inclined to cooperate with the internal face of said closing ring by means of - slides attached to the inner surface of the closing ring, capable of cooperating with grooves on the outer face of the sectors so that the axial movement of the closing ring moves the sectors radially, each groove having a stop capable of cooperating with a stroke limiting device for each slide in the open position of the mold,characterized in that said stroke limiting device is an assembly made up of parts formed so as not to be elastically deformable, comprising a pusher located at the end of a rod capable of being actuated from the external face of said closing ring so that said pusher can be moved between at least two positions: a first position in which it protrudes from the internal surface of said closing ring and a second position in which it is retracted from the internal surface of the closing ring.

[0023] The molding process of the invention may include a step of placing the pusher in the position in which it protrudes from the internal surface of said closing ring before baking.

[0024] The invention will be better understood from the following description, which is based on the following figures: Figure 1a is an axial cross-sectional view of a baking mold according to the prior art; [Fig.lb] is an enlarged scale view of detail A of figure la; [Fig.2] is an axial cross-sectional view of a baking mold comprising a stroke limiting device according to the invention; [Fig.3] is an exploded view of the stroke limiting device of [Fig.2]; Figures 4 and 5 are axial section views illustrating the mold incorporating the stroke limiting device of [Fig.2] in two operating positions.

[0025] In the various figures, identical or similar elements bear the same reference. Their description is therefore not systematically repeated.

[0026] Figure 1a illustrates a curing mold 10' for a prior art tire prototype. The curing mold 10' comprises upper plates 2' and lower plates 4' intended to be inserted between the plates (not shown) of a curing press. A curing press includes a frame forming a base for the mold, assumed to be stationary and fixed to the ground. The press also includes means for guiding and actuation (e.g., 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.

[0027] The baking mold 10' for a tire blank comprises an upper shell 3' and a lower shell 5' for molding a sidewall of the tire, as well as a sectored ring 7' of circumferential sectors for molding the tread of the tire. The mold includes, in a known manner, an upper ring and a lower ring for molding a bead of the tire. In the example illustrated in the figures, the mold is of the "container" type. The upper shell 3' slides axially with the upper platen 2' of the press, the lower shell 5' is rigidly fixed to the lower platen 4' of the press, and the circumferential sectors of the sectored ring 7' move radially during the opening and closing of the mold.

[0028] The baking mold 10' is substantially rotationally symmetric about its central axis Y-Y'. 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 Y-Y'. A circumferential direction is a direction tangent to the radial direction and corresponds to the circumferential direction of the tire.

[0029] The radially external surfaces of sectors of the sectorized crown 7' are conical, they have the same inclination extending downwards and radially outwards.

[0030] The mold further comprises a conical closing ring 8' whose radially internal surface is inclined radially downwards and has the same inclination as the radially external surfaces of the sectors of the segmented ring 7'. The closing ring 8' is connected to an actuator of the firing press, for example a hydraulic cylinder, which allows it to perform an axial movement up and down. During mold closure, the closing ring 8' descends, positions itself on the segmented ring 7', brings the sectors radially inside the mold, and applies force to the sectors to keep the assembly closed during firing as the temperature inside the mold cavity increases.The closing ring 8' comprises a plurality of slides 12' each rigidly fixed to the inner face of the ring, each slide 12' being designed to slide in a groove 14' of a corresponding sector of the closing ring 8'. A shoulder 21' located in the axially upper part of each sector limits the radial recoil stroke of the sectors when the shoulder 21' comes into contact with a stroke limiter 24' of the closing ring 8' during mold opening.

[0031] As more clearly seen in [Fig. 1b], the travel limiter 24' is fixedly mounted on the closing ring 8'. More precisely, a through screw 25' is screwed in from the outside of the closing ring 8' and holds the limiter 24' in place by screwing it into a threaded hole 26' made inside the limiter 24'. This travel limiter is installed manually with or without a pre-positioning tool, and the limiter 24' must be held in place while the screw is rotating. This is not ergonomic and poses risks to operators during mold maintenance, especially when the mold is hot. Therefore, with this solution, it is not possible to replace an element of the segmented ring in a baking press under ergonomic conditions.

[0032] The invention aims to remedy this problem and proposes a cooking mold 10 for pneumatic with radially moving sectors and comprising a stroke limiting device 24, as seen in figures 2 to 5.

[0033] The baking mold 10 of the invention is also of the container type, it is substantially rotationally symmetric with central axis X-X', and it comprises, similarly to that described with reference to [Fig. 1a], an upper shell 3 and a lower shell 5 for molding a sidewall of the tire, as well as a sectored ring 7 of circumferential sectors for molding the tread of the tire. The upper shell 3 is made to slide axially with the upper platen 2 by being actuated by a cylinder of the press, the lower shell 5 is rigidly fixed to the lower platen 4 of the baking press, and the circumferential sectors of the sectored ring 7 are made to move in a radial direction during the opening and closing of the mold by means of a closing ring 8 with a conical internal surface.

[0034] The closing ring 8 comprises a plurality of slides 12 each rigidly fixed on the inner face of the closing ring, each slide 12 being intended to slide in a groove 14 of a corresponding sector of the closing ring 8. A shoulder 21 located in the axially upper part of each sector allows the radial recoil stroke of the sectors to be limited when the shoulder 21 comes into contact with the end of a stroke limiting device 24 of the closing ring 8 during the opening of the mold.

[0035] Figure 3 illustrates the stroke limiting device in its exploded position. It comprises a rod 25, which is a stepped screw in the example shown in the figures, consisting of a threaded portion 29, which cooperates with a tapped hole 28 in the locking ring 8, a head 31, and an end 26 designed to receive a pusher 30. The head 31 has a prismatic end, male, for example, a hexagonal head, or female, for example, a round-head bolt, the head 31 coming cooperate with a key allowing the screw 25 to be screwed and unscrewed. The end 26 of the stepped screw or rod 25 is crossed by a smooth open orifice 27.

[0036] The pusher 30 is a hollow cylindrical end adapted to receive the end 26 of the rod 25. It has a smooth through orifice 31 adapted to coincide with the orifice 27 of the rod 25 during their assembly. The limiting device 24 is assembled by securing the end 26 of the rod 25 inside the pusher 30 using a pin 32. The pin 32 allows the pusher 30 to be fixed and axially positioned on the rod 25. In one embodiment, the pusher 30 may have a prismatic shape.

[0037] The stroke limiting assembly 24 is inserted into a through hole 40 formed through the closing ring 8 at the level of the slide 12, several through holes 40 being distributed circumferentially to allow the stroke limiting devices 24 to cooperate with the stops 21 of the sectors of the sectored ring 7. Each through hole 40 has, along its longitudinal axis, a recess for the screw head 31 delimited by a counterbore, a threaded portion 28 intended to cooperate with the threaded portion 29 of the rod 25 and a smooth portion 42 which opens towards the inner face of the closing ring 8. The diameter of the smooth portion 42 of the hole 40 is larger than that of the threaded portion 28. The pusher 30 passes through the hole 40 with a functional sliding clearance.

[0038] In operation, when the rod 25 is rotated, the retractable stroke limiter assembly 24 translates in the orifice 40 between a deployed or folded position inside it.

[0039] Fig. 4 illustrates the mold of the invention comprising the stroke limiting device 24 in a position in which it protrudes from the inner face of the closing ring 8. In this position, which is that corresponding to the firing, the closing ring 8 drives the sectors in their radial movement until the pusher 30 comes to rest against the shoulder 21 of the groove 14 of each sector.

[0040] Fig. 5 illustrates the mold of the invention comprising the stroke limiting device 24 in a position in which it is recessed from the internal surface of the closing ring 8. In this position, corresponding to that of the maintenance operation, the closing ring 8 can be lifted and detached from the sectors of the sectorized ring 7, thus giving the operator free access to the mold sectors for maintenance or replacement operations.

[0041] At the end of the maintenance or sector replacement operation, the operator repositions the sectors of the circular sectorized ring in order to reconstitute the baking mold. He then repositions the closing ring 8 onto the sectors of the sectorized ring 7 to move them horizontally until they reach the closed mold position. The operator then... rotation the rod by rotating the screw head 31 of the stroke limiter device 24 until the cooking position illustrated in [Fig.4].

[0042] Other variants and embodiments of the invention may be envisaged within the scope of the invention as claimed.

Claims

1. Demands Baking mold (10) with radially moving sectors for pneumatic use comprising: - a lower shell (4) for molding the tire sidewall, - an upper shell (2) of tire sidewall molding, - an axially movable closing ring (8) having an inclined inner face, - a sectorized ring (7) for molding the tire tread, said ring comprising a plurality of circumferentially arranged adjacent sectors, the internal radial faces of which comprise molding linings for the tire tread and the external radial faces of which are inclined so as to cooperate with the internal face of said closing ring by means of - slides (12) integral with the inner surface of the closing ring (8) adapted to cooperate with grooves (14) present on the outer face of the sectors so that the axial movement of the closing ring (8) moves the sectors in a radial movement, each groove (14) having a stop (21) adapted to cooperate with a stroke limiting device (24) of each slide (12) in the open position of the mold, characterized in that said stroke limiting device (24) is an assembly made up of parts formed so as not to be elastically deformable, comprising a pusher (30) located at the end of a rod (25) capable of being actuated from the external face of said closing ring (8) so that said pusher (30) can be moved between at least two positions: a first position in which it protrudes from the internal surface of said closing ring (8) and a second position in which it is retracted from the internal surface of the closing ring (8).

2. Mold according to the preceding claim, characterized in that said rod (25) and said pusher (30) are arranged in a housing passing through said closing ring (8) at the level of a slide (12).

3. Mold according to the preceding claim, characterized in that said housing is an orifice (40) having a shape of revolution extending in a radial direction.

4. Mold according to the preceding claim, characterized in that said orifice (40) comprises at least one counterbore (43).

5. Mold according to the preceding claim, characterized in that said rod (25) is actuated in a rotational movement around its longitudinal axis.

6. Mold according to the preceding claim, characterized in that said rod (25) comprises a threaded part (29) cooperating with a tapped part (28) of said orifice (40).

7. Mold according to any one of the preceding claims, characterized in that said pusher (30) is fixed to said rod (25) by means of a fixing pin (32).

8. Mold according to any one of claims 2 to 7, characterized in that said pusher (30) passes through said orifice (40) with a functional clearance of less than 0.05mm.

9. A method for molding a tire blank using a baking mold comprising: - a lower shell (4) for molding the tire sidewall, - an upper shell (2) for molding the tire sidewall, - an axially movable closing ring (8) having an inclined inner face, - a sectored ring (7) for molding the tire tread having a plurality of circumferentially arranged adjacent sectors, the inner radial faces of which have tire tread molding liners and the outer radial faces of which are inclined so as to cooperate with the inner face of said closing ring (8) by means of

10. - slides (12) integral with the inner surface of the closing ring (8) adapted to cooperate with grooves (14) present on the outer face of the sectors so that the axial movement of the closing ring (8) moves the sectors in a radial movement, each groove (14) having a stop (21) adapted to cooperate with a stroke limiting device (24) of each slide (12) in the open position of the mold, characterized in that said stroke limiting device (24) is an assembly made up of parts formed so as not to be elastically deformable comprising a pusher (30) located at the end of a rod (25) which is actuated from the external face of said closing ring so as to move said pusher (30) between at least two positions: a first position in which it protrudes from the internal surface of said closing ring (8) and a second position in which it is retracted from the internal surface of the closing ring (8). Molding method according to the preceding claim, characterized in that it includes a step of placing the pusher (30) in the position in which it protrudes from the internal surface of said closing ring (8) before baking.

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