HEATING PRESS AND METHOD FOR VULCANIZING A VEHICLE TIRE IN THIS HEATING PRESS UNDER VACUUM

Description

[0001] The invention relates to a heating press for vulcanizing a vehicle tire, comprising a heating press upper part and a heating press lower part. A container comprising the molded parts of a vulcanizing mold and a cylindrical hood upper part enclosing the container are arranged on the heating press upper part. The heating press upper part and the heating press lower part are connected to the container in such a way that, when the heating press upper part is lowered by an axial stroke, the molded parts of the vulcanizing mold can be closed radially. The invention further relates to a method for vulcanizing a raw tire in this aforementioned heating press.

[0002] The heating press described above is a standard heating press for vulcanizing vehicle tires under atmospheric conditions.

[0003] The heating press comprises a container that houses the actual segmented vulcanizing mold, including the mold segments that give the tire its shape, sidewall shells, and bead rings. Heating chambers are also integrated for temperature control of the mold components. During vulcanization, the container is enclosed by a hood, which, in the prior art, primarily serves for temperature insulation during the vulcanization process.

[0004] To minimize defects on the tire surface, the air between the surface of the raw tire and the molding surface of the vulcanizing mold components must be removed. It is generally known that 1,000 to 5,000 vent valves are required in the mold components for this purpose. These vent valves allow air to escape radially and axially from the mold cavity through venting channels. However, the mold components of a new vulcanizing mold must be equipped with these valves. Furthermore, these valves tend to become clogged with rubber from the tire being vulcanized, necessitating time-consuming replacement or cleaning.

[0005] Patent specification US 5,145,688 A discloses a vulcanizing press with an upper and a lower part similar to that mentioned in the preamble of independent claim 1.

[0006] The invention is based on the objective of providing a heating press for vulcanizing a vehicle tire, with which vehicle tires can be reliably vulcanized in the vulcanizing mold without the need for venting valves. It is also an objective of the invention to provide a method for the time-efficient vulcanization of a vehicle tire using the aforementioned heating press.

[0007] The task is solved with regard to the heating press by The hood upper part and the heating press upper part are movable independently of each other and relative to each other in the axial direction; the cylindrical hood upper part has a length sufficient to form a closed hood interior with the heating press lower part and heating press upper part when the heating press upper part is open; at least one vacuum-tight seal is arranged on each of those surfaces where the hood upper part directly abuts the heating press upper part and – when the hood interior is closed – the heating press lower part, in order to make the closed hood interior vacuum-tight; the seals are preferably arranged on the heating press upper part and on the heating press lower part; during a first stroke, the hood upper part is movable independently of the heating press upper part in such a way that it forms a vacuum-tight hood interior with the heating press lower part.While the vulcanizing mold is still open to allow air in, a pump and a vacuum tank are arranged, by means of which a vacuum can be generated inside the hood after the first stroke, the vacuum tank and the pump being connected to the inside of the hood, and the vacuum tank and the pump being connected to each other, and in a second stroke the upper part of the heating press being movable axially independently of the upper part of the hood such that the vulcanizing mold can be completely closed under vacuum conditions inside the hood.

[0008] The key feature is that the heating press according to the invention vulcanizes vehicle tires under vacuum. The vulcanizing mold itself has no venting means for venting the mold cavity. Vacuum vulcanization eliminates the need for the 1000 to 5000 venting valves typically found in vulcanizing molds, which are used to radially expel air from the mold cavity. This eliminates the need for post-processing of the rubber protrusions on the tire caused by the venting means, as well as the replacement or cleaning of malfunctioning venting valves. This saves time and money. Furthermore, vacuum vulcanization gives the tire an external shape that is completely free of defects and therefore appears perfect.

[0009] The vacuum, which can be maintained within the closed interior of the hood after the first stroke of the hood's upper section, serves to remove air from the still-open vulcanizing mold, particularly between the outer surface of the tire and the forming surfaces of the mold's forming parts. After the second stroke of the heating press's upper section, which occurs under vacuum conditions within the hood's interior, the vulcanizing mold can be completely closed. The tire to be vulcanized is then produced to a high standard and without defects. To create the vacuum-tight interior of the hood, in one embodiment of the invention, the end face of the hood's upper section can move onto the lower section of the heating press, or in another embodiment, it can move over the lower section of the heating press, so that the end of the hood's upper section encloses the lower section of the heating press.

[0010] It goes without saying that the hood or heating press may have additional seals to maintain a vacuum-tight interior. However, no modifications to the container or vulcanizing mold itself are to be made with regard to vacuum sealing measures.

[0011] The term vacuum refers to atmospheric pressure in the range of 950 mbar (abs) to 0.1 mbar (abs). The ring seal preferably has a round or rectangular cross-section.

[0012] It is advantageous to have a hydraulic, pneumatic or electric actuator that allows the upper part of the hood to be moved in an axial direction.

[0013] In a particular embodiment of the invention, a hood lower part in the form of a circular ring is arranged on the lower part of the heating press, wherein the circular ring of the upper hood part and the circular ring of the lower hood part have the same inner diameter and the same outer diameter and are arranged in alignment with each other in the heating press. This results in a very reliable seal of the hood interior.

[0014] It is advantageous if the seals are ring seals with round, square and / or flat cross-sections.

[0015] For reliable sealing performance, it is advantageous for the ring seal to be arranged in an annular groove, with the diameter of the ring seal being slightly larger than the depth of the groove. Slightly larger means that the seal, when installed in the groove and under seal, is compressed by a maximum of 40% compared to its compressionless geometry. Precise design of the groove in relation to the seal geometry further prevents damage to the seal(s) and improves its durability.

[0016] In one embodiment of the invention, the ring seal consists of solid material. This solid material can consist of one or more materials known for seals, such as FKM or FFKM. These seals are cost-effective and easy to handle.

[0017] In another embodiment of the invention, the ring seal is a hose whose diameter can be changed. This has the advantage that the ring seal is subjected to less stress and its diameter is only increased when the sealing effect is required.

[0018] It is advantageous if the ring seals are differentially pumped double ring seals. This has the advantage that any leaks can be compensated for with low pumping power.

[0019] It is advantageous for the vacuum tank to have a volume approximately 5 to 10 times larger than the volume of the closed hood (including mold, container, tire blank, and heating bellows). This ensures that a vacuum can be reliably generated within the hood. Furthermore, the time required to generate the necessary vacuum is significantly reduced. This can then take place during the normal loading and unloading process.

[0020] With regard to the method using the aforementioned heating press, the invention is solved by carrying out the following steps one after the other: a) Loading the open vulcanizing press by placing the raw tire to be vulcanized into the container, b) Moving the hood upper part by a first stroke in the axial direction towards the lower part of the vulcanizing press until a closed hood interior is obtained, consisting of the hood upper part, the upper part of the vulcanizing press, and the lower part of the vulcanizing press, while the vulcanizing mold is still open, c) only if the ring seal is a hose with a variable diameter: inflating the annular hose seal to create a vacuum-tight seal in the hood interior, d) opening the connection between the vacuum tank and the hood interior to create a partial vacuum in the vacuum-tight sealed hood interior by pressure equalization between the vacuum tank and the hood interior, e) upon maintaining the partial vacuum in the hood interior: closing the connection between the vacuum tank and the hood interior.Opening the connection between the hood interior and the pump and pumping out the remaining air from the hood interior to create a vacuum; f) Moving the heating press upper part by a second stroke, moving the container so that the vulcanizing mold is completely closed, and subsequently closing the connection between the hood interior and the pump; g) Vulcanizing the raw tire and opening the connection between the pump and the vacuum tank and creating a vacuum in the vacuum tank, with the connection from the pump to the hood interior and the connection from the vacuum tank to the hood interior each being closed; h) Opening the heating press by moving the hood interior and the heating press upper part and unloading the fully vulcanized tire. and to vulcanize each additional tire, repeat steps a) - h).

[0021] To facilitate step h), it is advantageous to first open and then close another valve located in the hood to break the vacuum in the hood.

[0022] An exemplary embodiment of a heating press and the method for vacuum vulcanizing a vehicle tire, along with further advantages, are described with reference to the following two schematic figures. These show: Fig. 1 a heating press according to the invention with container in the open state, Fig. 2 the heating press of the Fig. 1 in the closed state.

[0023] The Fig. 1 Figure 1 shows a heating press 1 according to the invention with a container 2 in the open position. The hood upper part is in its starting position. The tire blank can be inserted into the heating press 1.

[0024] The heating press 1 comprises a heating press lower part 6 and a heating press upper part 3 with a cylindrical hood upper part 4 and has the corresponding mechanisms for positioning the tire to be vulcanized, for actuating the components of the vulcanization mold, for introducing the heating media and for removing the finished vulcanized tire. Inside the hood upper part 4, a container 2 is arranged on the heating press upper part 3 such that, when the heating press upper part 3 is moved in the axial direction P1, the mold components of the vulcanization mold arranged in the container are movable in the radial direction P2.

[0025] A central mechanism 8 is arranged, to which a heating bellows (not shown) is attached, which can be inserted into the tire blank (not shown). Nozzles (not shown) are also arranged on the central mechanism 8, through which a heating medium can be introduced into the heating bellows (not shown).

[0026] The hood upper part 4 and the heating press upper part 3 are movable independently of each other and relative to each other in the axial direction P1. The cylindrical hood upper part 4 has a length 23, which is sufficient to form a closed hood interior 12 with the heating press lower part 6 and heating press upper part 3 when the vulcanizing mold is still open, i.e., when the heating press upper part 3 has not been fully moved onto the heating press lower part 6.

[0027] The hood upper part 4 is airtight or vacuum-tight and, when closed, forms a vacuum-tight hood interior 12. To create a vacuum-tight seal around the end face 7 of the hood upper part 4 when closed, a flat-section ring seal 5 is positioned on the lower part 6 of the heating press where the end face 7 of the hood upper part 4 rests on the lower part 6 when the hood is closed. Another ring seal 5 is attached to the upper part 3 of the heating press where the hood upper part 4 directly abuts the upper part 3. Further ring seals 9 provide a vacuum-tight seal, at least for the central mechanism 8, against the hood interior 12.

[0028] Container 2 is a standard Container 2, already known in the prior art.

[0029] Container 2 contains the segmented vulcanizing mold with a lower heating plate 13, a lower side wall shell 14, an upper heating plate 15, an upper side wall shell 16, a lower bead ring 17, and an upper bead ring 18. The components of the vulcanizing mold that are moved vertically (= axially) (arrow P1) to open and close include the segment ring 19, consisting of seven to nine segment shoes 20 and the attached profile / mold segments 21, as well as the upper side wall shell 16 with the upper bead ring 18. The segment shoes 20 are moved apart radially, in the direction of arrow P2, to open and close the vulcanizing mold.A locking ring 22 is arranged on the upper heating plate 15. This locking ring has a chamfered inner surface that interacts with the chamfered outer surfaces of the segment shoes 20 of the segment ring 19 such that, when the vulcanization mold closes, the segment shoes 20 are drawn together radially towards the closed segment ring 19. Heating chambers are contained in the lower heating plate 13, the upper heating plate 15, and the locking ring 22. At least one heating medium, in particular saturated steam (water vapor), is introduced into these chambers for vulcanizing the tire. In this way, the raw tire (not shown) is heated externally via the segment shoes 20, the sidewall shells 14, 16, and the bead rings 17, 18. This heating process is commonly referred to as external heating.

[0030] A conventional heating bellows (not shown) is arranged in a known manner and filled under pressure with at least one heating medium to center the raw tire from the inside, thereby shaping the heating bellows into a tire-like torus form. Since the raw tire is heated from the inside via the heating bellows, this type of heating is referred to as internal heating.

[0031] In a first stroke Hi - not shown in the figures - the hood upper part 3 can be moved in axial direction P1 independently of the heating press upper part 3 by means of an actuator 24 such that it forms a vacuum-tight hood interior 12 with the heating press lower part 6, while the vulcanizing mold is still open to allow air to pass through.

[0032] However, with the first stroke Hi, which is carried out with the hood top part 4, the heating press top part 3 can also be moved simultaneously - however, the vulcanizing mold must remain open after the first stroke Hi.

[0033] A pump 10 and a vacuum tank 11 are arranged, by means of which a vacuum can be generated in the interior 12 of the hood after the first stroke Hi. The vacuum tank 11 and the pump 10 are connected to the interior 12 of the hood, and the vacuum tank 11 and the pump 10 are connected to each other. Due to a vacuum in the interior of the hood 12, especially during the molding and vulcanization of the tire, the usual venting valves arranged in the mold surface of the vulcanizing mold are completely unnecessary.

[0034] The Fig. 2 shows the heating press 1 of the Fig. 1in a closed state, which is obtained after a second stroke H 2, in which the heating press upper part 3 is movable independently of the hood upper part 4 in the axial direction P1, so that the vulcanizing mold is completely closed under vacuum conditions in the interior 12 of the hood. The connection between the vacuum tank 11 and the hood interior 12 is closed. Subsequently, the connection between the hood interior 12 and the pump 10 is closed. The vulcanization of the raw tire then takes place.

[0035] Vulcanizing a passenger car tire takes approximately 15 minutes. During this time, the connection between pump 10 and vacuum tank 11 is opened to create a vacuum in the vacuum tank 11, while the connection between pump 10 and the hood, as well as the connection between the vacuum tank 11 and the hood, remain closed. After the tire has been vulcanized, the volume of the hood interior 12 is vented via a valve (not shown), and the heating press 1 is opened to unload the fully vulcanized tire from the container 2, which contains the vulcanizing mold. For this purpose, the upper part of the heating press 3, along with the container 2 and the upper part of the hood 4, moves upwards, and the tread segments 21 are simultaneously moved outwards in the radial direction P2. The tire is then released. Reference symbol list (Part of the description)

[0036] 1 Heating press 2 Container 3 Heating press upper part 4 Hood upper part 5 Ring seal 6 Heating press lower part 7 End face of hood upper part 8 Center mechanism 9 Ring seal 10 Pump 11 Vacuum tank 12 Hood interior 13 Lower heating plate 14 Lower side wall shell 15 Upper heating plate 16 Upper side wall shell 17 Lower bead ring 18 Upper bead ring 19 Segment ring 20 Segment shoe 21 Profile segment / Form segment 22 Locking ring 23 Length of hood upper part 24 Actuator First stroke H 2 Second stroke P1 Axial direction P2 Radial direction

Claims

1. Heating press (1) for vulcanizing a vehicle tyre under a vacuum, - comprising a heating press upper part (3) and a heating press lower part (6), wherein a container (2) having the mould parts (14, 16, 17, 18, 21) of a vulcanizing mould and a cylindrical hood upper part (4) enclosing said container are arranged on the heating press upper part (3), and wherein the heating press upper part (3) and the heating press lower part (6) are connected to the container (2) in such a way that, when the heating press upper part (3) is being lowered through a stroke that takes place in the axial direction (P1), the mould parts (14, 16, 17, 18, 21) of the vulcanizing mould can be closed in the radial direction (P2), - wherein the hood upper part (4) and the heating press upper part (3) can be moved independently of one another and relative to one another in the axial direction (P1), - wherein the cylindrical hood upper part (4) has a length (23) which is sufficient to form a closed hood interior space (12) with the heating press lower part (6) and heating press upper part (4) when the heating press upper part (3) is open, - wherein at least one respective vacuum-tight seal (5) is arranged on those surfaces at which the hood upper part (4) directly adjoins the heating press upper part (3) and - when the hood interior space (12) is closed - the heating press lower part (6), in order to make the closed hood interior space (12) sealable in a vacuum-tight manner, wherein the seals (5) are preferably arranged on the heating press upper part and on the heating press lower part, - wherein, in the course of a first stroke (H1), the hood upper part (4) can be moved independently of the heating press upper part (3) in the axial direction P1 in such a way that said hood upper part forms a vacuum-tight hood interior space (12) with the heating press lower part (6), although the vulcanizing mold remains open in an air-permeable manner, - wherein a pump (10) and a vacuum tank (11), by means of which a vacuum can be generated in the interior space of the hood (12) after the first stroke (H1), are provided, wherein the vacuum tank (11) and the pump (10) are connected to the interior space (12) of the hood (4), and wherein the vacuum tank (11) and the pump (10) are connected to one another, and - wherein, in the course of a second stroke (H2), the heating press upper part (3) can be moved independently of the hood upper part (4) in the axial direction P1 in such a way that the vulcanizing mould can be completely closed under vacuum conditions in the interior space of the hood (12).

2. Heating press (1) according to Claim 1, characterized in that a hydraulic, pneumatic or electric actuator (24), which can move the hood upper part (4) independently of the heating press upper part (3) in the axial direction (P1), is provided.

3. Heating press (1) according to Claim 1 or 2, characterized in that a hood lower part in the form of a circular ring is arranged on the heating press lower part (6), wherein the circular ring of the hood upper part (3) and the circular ring of the hood lower part have the same inside diameter and the same outside diameter and are arranged in line with one another in the heating press (1).

4. Heating press (1) according to one or more of the preceding claims, characterized in that the seals are ring seals (5, 9) with circular, polygonal and / or flat cross sections.

5. Heating press (1) according to Claim 4, characterized in that the ring seal (5, 9) is arranged in a circular-ring-shaped groove, wherein the diameter of the ring seal (5, 9) is slightly greater than the depth of the groove.

6. Heating press (1) according to Claim 4 or 5, characterized in that the ring seal (5, 9) consists of solid material.

7. Heating press (1) according to Claim 4 or 5, characterized in that the ring seal (5, 9) is a hose of variable diameter.

8. Heating press (1) according to one or more of Claims 4 to 7, characterized in that the ring seal (5, 9) is a differentially inflated double ring seal.

9. Heating press (1) according to one or more of the preceding claims, characterized in that the vacuum tank (11) has a volume that is approximately 5 to 10 times greater than the volume of the closed hood(s) (4).

10. Method for vulcanizing a pneumatic vehicle tyre under a vacuum in a heating press (1) according to one or more of Claims 1 to 9, characterized in that the following steps are performed in succession: a) loading the opened heating press (1) by placing the green tyre for vulcanization into the container (2), b) moving the hood upper part (4) through a first stroke (H1) in the axial direction (P1) towards the heating press lower part (6), until a closed hood interior space (12) composed of hood upper part (4), heating press upper part (3) and heating press lower part (6) is obtained, while the vulcanizing mould remains open, c) only if the ring seal (5, 9) is a hose of variable diameter: inflating the circular-ring-shaped hose seal in order to seal off the hood interior space (12) in a vacuum-tight manner, d) opening the connection between the vacuum tank (11) and the hood interior space (12) in order to generate a partial vacuum, by way of pressure equalization between the vacuum tank (11) and the hood interior space (12), in the hood interior space (12) that has been closed in a vacuum-tight manner, e) when the partial vacuum is obtained in the hood interior space (12): closing the connection between the vacuum tank (11) and the hood interior space (12), opening the connection between the hood interior space (12) and the pump (10), and pumping the remaining air out of the hood interior space (12) in order to generate the vacuum, f) moving the heating press upper part (3) through a second stroke (H2), in the course of which the container (2) is moved in such a way that the vulcanizing mould is completely closed, and subsequently closing the connection between the hood interior space (12) and the pump (10), g) vulcanizing the green tyre and opening the connection between the pump (10) and the vacuum tank (11) and generating a vacuum in the vacuum tank (11), wherein the connection of the pump (10) to the hood interior space (12) and the connection of the vacuum tank (11) to the hood interior space (12) are each closed, h) opening the heating press (1) by moving the hood upper part (4) and the heating press upper part (3) and removing the fully vulcanized tyre and repeating the steps a) - h) in order to vulcanize each further tyre.

11. Method for vulcanizing a pneumatic vehicle tyre according to Claim 10, characterized in that, to facilitate step h), this is preceded by a further valve arranged in the hood (4) being opened in order to deplete the vacuum and subsequently being closed again.