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 under vacuum with a heating press upper part and a heating press lower part, wherein a circular hood upper part with a container containing the mold parts of a vulcanizing mold is arranged on the heating press upper part, and wherein the heating press upper part is movable in the axial direction such that the hood upper part can be moved onto the heating press lower part to form a closed hood interior, wherein the heating press upper part, the heating press lower part and the press plate are connected to the container such that when the heating press upper part and the press plate are lowered over a total stroke in the axial direction, during which the open end of the hood upper part moves onto the heating press lower part, the mold parts of the vulcanizing mold can be closed in the radial direction, wherein at least one vacuum-tight seal is arranged at least in the end face of a hood part,wherein, during a first stroke, the upper part of the hood is movable such that it rests on the lower part of the heating press and the interior of the hood can be closed in a vacuum-tight manner by the seal(s), while the vulcanizing mold, however, is still open and permeable to air, and wherein a pump and a vacuum tank are arranged, by means of which a vacuum can be generated in the interior of the hood after the first stroke, wherein the vacuum tank and the pump are connected to the interior of the hood and wherein the vacuum tank and the pump are connected to one another, and wherein, during a second stroke, the press plate is movable such that the vulcanizing mold can be completely closed under vacuum conditions in the interior of the hood.

[0002] The upper part of the heating press and the lower part of the heating press are connected to the container in such a way that the molded parts of the vulcanizing mold can be closed in the radial direction via a total stroke in the axial direction.

[0003] The invention further relates to a process for vulcanising a green tyre in the aforementioned heating press under vacuum, comprising the following successive steps: a) Loading the opened curing press by placing the green tire to be vulcanized into the container b) Moving the upper part of the curing press by the first stroke in the axial direction towards the lower part of the curing press until the front face of the hood upper part rests on the lower part of the curing press in order to obtain a vacuum-tight, closed hood interior, while the vulcanizing mold is only partially closed c) Only in the case where the ring seal is a hose with an adjustable diameter: Inflating the annular hose seal in order 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, closed hood interior by equalizing the pressure between the vacuum tank and the hood interior e) When the partial vacuum is maintained in the hood interior: Closing the connection between the vacuum tank and the hood interiorOpening the connection between the hood interior and the pump and pumping out the remaining air from the hood interior to create the vacuum f) Moving the container in such a way that the vulcanisation mould is completely closed and then closing the connection between the hood interior and the pump g) Vulcanisation of the green tyre and opening the connection between the pump and the vacuum tank and creating a vacuum in the vacuum tank, whereby the connection of the pump to the hood interior and the connection of the vacuum tank to the hood interior are each closed h) Opening the heating press and unloading the fully vulcanised tyre and repeating steps a) - h) to vulcanise each additional tyre.

[0004] A heating press and a method of the type mentioned above are known, for example, from DE 10 2018 216 754 A1. The heating press has a press plate below the container, which is movable in the axial direction.

[0005] The heating press described above is a standard heating press for vulcanizing vehicle tires under atmospheric conditions.

[0006] The curing press comprises a so-called container, which contains the actual segmented vulcanizing mold with the tire-shaping mold segments, sidewall shells, and bead rings. Heating chambers are also provided for tempering the molded parts. During vulcanization, the container is surrounded by a closed hood, which, in the prior art, primarily serves to insulate the temperature during vulcanization.

[0007] To minimize imperfections on the tire surface, the air between the surface of the green tire and the molding surface of the vulcanizing mold parts must be removed. For this purpose, it is generally known that 1,000 to 5,000 vent valves must be provided in the mold parts. These vent valves discharge the air from the mold cavity radially and axially outward through vent channels. However, the mold parts of a new vulcanizing mold must be equipped with these valves. Furthermore, these valves tend to become dirty due to rubber from the tire being vulcanized penetrating them, so they must be replaced or cleaned at great expense.

[0008] The invention is based on the object of providing a heating press for vulcanizing a vehicle tire under vacuum, with which vehicle tires can be reliably vulcanized under vacuum and without the need for vent valves in the vulcanizing mold. It is also the object of the invention to provide a method for the time-efficient vulcanization of a vehicle tire under vacuum.

[0009] The task is solved with regard to the heating press by arranging a press plate above the container in the upper part of the hood in such a way that this press plate and thus the container can be moved in the axial direction.

[0010] The vacuum created within the closed hood interior after the first stroke serves to remove the air from the not yet fully closed vulcanizing mold, particularly between the outer surface of the tire and the molding surfaces of the mold's forming parts. After the second stroke, which occurs under vacuum conditions within the hood interior by the additional press plate running axially within the hood interior between the top of the container and the hood upper section, the vulcanizing mold can be completely closed. The seal located in the end face of the hood upper section is only subjected to pressure and thus provides a reliable and durable seal. The tire to be vulcanized is manufactured to a high quality and without defects.

[0011] Another important aspect is that the vulcanizing mold itself does not have any venting devices for venting the mold cavity. Vulcanization under vacuum eliminates the need for the 1,000 to 5,000 venting valves typically found in the vulcanizing mold, which are used in the prior art to radially vent the air from the mold cavity. This eliminates the need to rework the rubber vents on the tire created by the venting devices, nor does it require the replacement or cleaning of deflated vent valves. This saves time and money. Furthermore, vacuum vulcanization gives the vulcanized tire an outer shape that is completely free of defects and therefore appears perfect. It goes without saying that the hood or heating press can be equipped with additional seals to ensure a vacuum-tight interior.There should be no changes to the container or the vulcanization mold itself with regard to airtightness measures.

[0012] The term vacuum refers to air pressure in the range from 950 mbar (abs) to 0.1 mbar (abs). The ring seal preferably has a round, square, or flat cross-section.

[0013] It is useful if a hydraulic, pneumatic or electric actuator is arranged by which the press plate can be moved in the axial direction.

[0014] In a specific embodiment of the invention, a hood lower part in the shape of a circular ring is arranged on the heating press lower part. The circular ring of the hood upper part and the circular ring of the hood lower part have the same inner and outer diameters and are arranged flush with each other in the heating press. This ensures a very reliable seal in the interior of the hood.

[0015] It is useful if the seal is a ring seal.

[0016] For reliable sealing performance, it is advisable to arrange the ring seal in a circular groove, with the diameter of the ring seal slightly larger than the depth of the groove. Slightly larger means that when installed in the groove and in the sealed state, the seal is compressed by a maximum of 40% compared to the compression-free geometry of the seal. The precise design of the groove in relation to the seal geometry further prevents damage to the seal(s) and improves durability.

[0017] In one embodiment of the invention, the ring seal is made of solid material. The solid material can be made of one or more materials known for sealing, such as FKM or FFKM. These seals are cost-effective and easy to handle.

[0018] In another embodiment of the invention, the ring seal is a hose with an adjustable diameter. 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.

[0019] It is advantageous if the ring seals are differentially pumped double ring seals. This has the advantage that any leaks can be compensated with low pumping power.

[0020] It is advisable for the vacuum tank to have a volume approximately 5 to 10 times larger than the volume of the closed hood (including mold, container, press plate, green tire, and bladder). 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 be done during the normal loading and unloading process.

[0021] With regard to the method using a heating press mentioned above, the object is achieved in that, for step f), the press plate in the upper part of the heating press is moved by the second stroke.

[0022] To facilitate step h), it is advantageous to first open another valve located in the hood to break the vacuum in the hood and then close it again.

[0023] An embodiment of a heating press and the method for vacuum vulcanization of a pneumatic vehicle tire, including further advantages, are shown in the following schematic Figures 1 to 4. They show: Fig. 1 shows a heating press according to the invention with a container in the open state; Fig. 2 shows the heating press of the Fig. 1 in the closing phase after a first stroke; Fig. 3 the heating press of the Fig. 1 and the Fig. 2 in closed position after a second stroke.

[0024] The Fig. 1shows a heating press 1 according to the invention with a container 2 in the open state. The green tire can be inserted into the heating press 1.

[0025] The heating press 1 comprises a heating press upper part 3, which is connected to a circular hood upper part 4, and a heating press lower part 6, which is connected to a circular hood lower part 7. The heating press 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 fully vulcanized tire. In the hood upper part 4, a press plate 23 is arranged above the container 2 such that this press plate 23, and thus the container 2, can be moved in the axial direction P1. The container 2 is enclosed by the hood 4, 7 during the vulcanization process. The annular hood upper part 4 and the annular hood lower part 7 have the same inner diameter and the same outer diameter and are arranged with their end faces 24, 25 aligned in the heating press 1.

[0026] A "center mechanism" 8 is provided. This is also equipped with ring seals 9, where necessary, to create a vacuum seal between the center mechanism 8 and the heating press upper and lower parts 3, 6. A heating bladder (not shown) is attached to the center mechanism 8 and can be inserted into the green tire (not shown). Nozzles (not shown) are also arranged on the center mechanism 8 through which a heating medium can be introduced into the heating bladder (not shown).

[0027] The hood upper part 4 and the hood lower part 7 are designed to be airtight or vacuum-tight, respectively, and when closed, form a vacuum-tight hood interior 12. To ensure a vacuum-tight seal between the end faces 24, 25 of the two hoods 4, 7 when closed, an annular seal 5 is arranged in the end face 24 of the hood upper part 4. Additional annular seals 9 provide a vacuum-tight seal between the center mechanism 8 and the travel mechanism / actuator 26 of the press plate 23.

[0028] A vacuum can be generated in the hood interior (= interior of the hood) 12 by means of a pump 10 and a vacuum tank 11, wherein the vacuum tank 11 and the pump 10 are connected to the interior 12 of the hood, and wherein the vacuum tank 11 and the pump 10 are connected to one another. By creating a vacuum in the hood interior 12, particularly during the molding and vulcanization of the tire, the need for vent valves conventionally arranged in the molding surface of the vulcanizing mold is completely eliminated.

[0029] Container 2 is a conventional container 2 that is already known in the state of the art.

[0030] The 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. Those components of the vulcanization mold that are moved in the vertical (= axial) direction (arrow P1) for opening and closing include the segment ring 19 consisting of seven to nine segment shoes 20 and the profile / mold segments 21 attached to it 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 the arrow P2 for closing and opening the vulcanization mold.A locking ring 22 is arranged on the upper heating plate 15. The locking ring has a beveled inner surface that interacts with beveled outer surfaces of the segment shoes 20 of the segment ring 19 such that, when the vulcanization mold is closed, the segment shoes 20 are moved together in the radial direction to form the closed segment ring 19. The lower heating plate 13, the upper heating plate 15, and the locking ring 22 contain heating chambers into which at least one heating medium, in particular saturated steam (steam), is introduced to vulcanize the tire. In this way, the green tire (not shown) is heated from the outside via the segment shoes 20, the sidewall shells 14, 16, and the bead rings 17, 18, so that this heating is usually referred to as external heating.

[0031] A conventional heating bladder (not shown) is arranged in a known manner and is filled with at least one heating medium under pressure to center the green tire in the mold from the inside, whereby the heating bladder is formed into a torus shape appropriate for the tire. Since the green tire is heated from the inside via the heating bladder, this type of heating is referred to as internal heating.

[0032] In the Fig. 2 is the heating press 1 of the Fig. 1 in the closing phase after a first stroke H 1.

[0033] The heating press upper part 3 has been moved by the first stroke H 1 so that the end face 24 of the hood upper part 4 rests on the end face 25 of the hood lower part 7. The press plate 23 in the hood upper part 3 is still in its original position and thus has not yet been moved. A closed, vacuum-tight hood interior 12 is maintained, while the vulcanizing mold is only partially closed. If the ring seal 5 is a hose with an adjustable diameter, this is inflated to create a vacuum-tight seal between the hood 4, 7. The connection between the vacuum tank 11 and the hood interior 12 is opened to generate a partial vacuum in the vacuum-tight hood interior 12 by equalizing the pressure between the vacuum tank 11 and the hood interior 12.When the partial vacuum is maintained in the hood interior 12, the connection between vacuum tank 11 and hood 4, 7 is closed, the connection between the hood interior 12 and pump 10 is opened and the remaining air is pumped out of the hood interior 12 to generate the vacuum.

[0034] The Fig. 3 shows the heating press of the Fig. 1 and the Fig. 2 in the closed state after a second stroke H 2 . After the interior 12 of the closed hood 4, 7 of the Fig. 2 a vacuum is generated, the airless vulcanizing mold is now completely closed and the connection between vacuum tank 11 and hood 4, 7 is closed by executing a second stroke H 2 , in which the press plate 23 moves the container 2 in the axial direction P1 by means of an actuator 26.

[0035] The connection between the hood interior 12 and the pump 10 is then closed. The green tire is vulcanized.

[0036] Vulcanizing a 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 hood 4, 7 and the connection between vacuum tank 11 and hood 4, 7 are both closed. After the tire has been vulcanized, the volume of the hood interior 12 is ventilated via a valve (not shown) and the heating press 1 is opened to unload the fully vulcanized tire from the container 2 containing the vulcanization mold. To do this, the press plate 23 with the container 2 first moves upwards and the tread segments 21 are simultaneously moved outwards in the radial direction P2. The hood upper part 4 then moves up and the tire is released. List of reference symbols (part of the description)

[0037] 1 Heating press 2 Container 3 Heating press upper part 4 Hood upper part 5 Ring seal 6 Heating press lower part 7 Hood lower part 8 Center mechanism 9 Ring seal 10 Pump 11 Vacuum tank 12 Hood interior = 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 / mold segment 22 Locking ring 23 Press plate 24 End face of the hood upper part 25 End face of the hood lower part 26 Actuator H 1 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, - having a heating press upper part (3) and a heating press lower part (6), wherein a circular-ring-shaped hood upper part (4) with a container (2) having the mould parts (14, 16, 17, 18, 21) of a vulcanizing mould is arranged on the heating press upper part (3), and wherein the heating press upper part (3) can be moved in an axial direction (P1) in such a way that the hood upper part (3) can be moved onto the heating press lower part (6) to form a closed hood interior space (12), - wherein the heating press upper part (3), the heating press lower part (6) and the press plate (23) are connected to the container (2) such that, when the heating press upper part (3) and the press plate (23) are being lowered through a total stroke that takes place in an axial direction (P1), in the course of which total stroke the open end of the hood upper part (4) moves onto the heating press lower part (6), the mould parts (14, 16, 17, 18, 21) of the vulcanizing mould can be closed in a radial direction (P2), - wherein at least one vacuum-tight seal (5) is arranged at least in the end face (24) of a hood part (4), - wherein, in the course of a first stroke (H1), the hood upper part (3) can be moved in such a way that it rests on the heating press lower part (6) and the hood interior space (12) can be closed in a vacuum-tight manner by the seal(s) (5, 9) although the vulcanizing mould is still open in an air-permeable manner, and - wherein a pump (10) and a vacuum tank (11), by means of which a vacuum can be generated in the hood interior space (12) after the first stroke (H1), are provided, wherein the vacuum tank (11) and the pump (10) are connected to the hood interior space (12), 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 press plate (23) can be moved in such a way that the vulcanizing mould can be completely closed under vacuum conditions in the hood interior space (12), characterized in that - a press plate (23) is arranged above the container (2) in the hood upper part (4) such that this press plate (23) and thus the container (2) can be moved in the axial direction (P1).

2. Heating press (1) according to Claim 1, characterized in that a hydraulic, pneumatic or electric actuator (26), which can move the press plate in the axial direction (P1), is provided.

3. Heating press (1) according to Claim 1 or 2, characterized in that a hood lower part (7) 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 (7) 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 seal is a ring seal (5, 9).

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, 7).

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, wherein 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 heating press upper part (3) through the first stroke (H1) in the axial direction (P1) toward the heating press lower part (6), until the end face (24) of the hood upper part (4) rests on the heating press lower part (6), in order to obtain a hood interior space (12) which is closed in a vacuum-tight manner, while the vulcanizing mould is only closed to some extent, 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 container (2) such 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) and removing the fully vulcanized tyre and repeating steps a) - h) in order to vulcanize each further tyre, characterized in that for step f), the press plate (23) in the heating press upper part (3) is moved through the second stroke (H2).

11. Method for vulcanizing a pneumatic vehicle tyre according to Claim 10, characterized in that, to facilitate step h), this is preceded by opening a further valve arranged in the hoods (4, 7) in order to deplete the vacuum and subsequently closing it again.