Vulcanization tool

Abstract

Vulcanization tool (1) for vehicle tires (2), which has at least two molded parts (3) which can be connected to one another and whose inner molding surfaces (4) form a cavity (5) with the negative mold of a vehicle tire (2) to be produced when assembled, wherein: -the forming surfaces (4) have negative profile elements for forming positive profile elements of the vehicle tyre (2) to be vulcanised, -venting means (7) are introduced into the mould surfaces (4), -a venting means (7) comprises a cylindrical venting channel (8) with a rigid, replaceable pin (9) inserted therein for discharging the air from the vulcanisation tool (1) and for preventing the penetration of liquid rubber material into the venting channel (8), -the pin (9) consists of two regions (10, 11) with respect to its longitudinal extent, of which the first region (10) on the mold surface side has a geometry that is complementary to a bearing surface (12) introduced into the mold surface (4), -this first region (10) of the pin (9) closes the venting channel (8) at the level of the molding surface (4) except for a venting slot (13) running through the pin (9) in the longitudinal direction, -the second region (11) adjoining the first region (10) comprises the remaining pin and has a smaller diameter than the venting channel (8), so that an annular gap (14) remains between the wall (15) of the venting channel (8) and the pin (9), -the venting slot (13) extends in the longitudinal direction of the pin (9) completely through the first region (10) and reaches into the second region (11), so that one end (16) of the venting slot (13) opens into the annular gap (14) of the venting channel (8), characterized in that the venting slot (13) is introduced into the pin (9) by means of a micro saw (17) and is designed as a cross-slot with three branches, the venting slot (13) having a width of between 30 and 150 µm.

Description

[0001] The invention relates to a vulcanization tool according to the preamble of patent claim 1.

[0002] A vulcanization tool for vehicle tires is known, comprising at least two interconnectable molded parts whose inner molding surfaces, when assembled, form a cavity with the negative mold of a vehicle tire to be produced. The molding surfaces comprise negative profile elements for forming positive profile elements of the vehicle tire to be vulcanized. The necessity of venting such a vulcanization tool for producing a vehicle tire during the vulcanization process arises from the fact that the air present in the cavity of the vulcanization tool is compressed during the vulcanization process and would lead to the formation of localized shrinkage points between the inner surface of the vulcanization tool and the outer contour of the green tire.The lack of direct contact between the inner surface of the vulcanization tool and the blank in such a case not only leads to a dent in the blank at such a location, but also to reduced heating due to the lower thermal conductivity of air compared to the metal of the vulcanization tool. This can also lead to insufficient sulfur crosslinking of the rubber material and cause material failure of the vehicle tire, resulting in inferior quality of a vehicle tire produced in this way or rendering the vehicle tire completely unusable.

[0003] Tire tread patterns are also highly detailed, featuring, for example, longitudinal and transverse grooves as well as numerous, sometimes even twisted, incisions, also referred to as "grooves," which define so-called "negative tread elements." From a pneumatic perspective, the numerous protrusions on the inner surface of the vulcanization tool divide the air volume to be discharged into mutually isolated chambers, each of which requires at least one venting device.

[0004] Some vulcanization molds for the production of vehicle tires have a large number of individual vent holes, with between 1,000 and 3,000 vent holes currently being the norm. In conventional vulcanization tools, the vent holes have a diameter of approximately 0.7 to 1.5 mm, depending on the required depth. A typical car summer tire mold has approximately 2,000 vent holes, while a typical car winter tire mold has approximately 3,000 vent holes.

[0005] However, a disadvantage is that during the vulcanization process, parts of the liquid rubber material can flow into the vent holes, resulting in the finished tire exhibiting small nubs or threads, so-called "sprouts," which either break off during use or must be mechanically removed after the tire is removed from the vulcanization tool. This process, also known as "trimming," represents additional effort during tire production.

[0006] One improvement in this regard is valves that are inserted into the vulcanization tool and perform a venting function. Each of the valves is pressed into a closed position when the rubber compound comes into contact with the valve during the stamping of the green vehicle tire. It must be accepted that some of the valves close a little too late to completely expel all the air from the cavity of the vulcanization tool. However, this results in circular ring-like protrusions on the vehicle tire that are visually noticeable but usually so small that their presence is tolerated. When the vehicle tire is removed from the vulcanization tool, the valves are pressed into an open position by a weak spring on each valve.Such closable vent valves are disclosed in DE 195 43 276 A1 and are used, for example, as so-called "Eurovents." In one specific embodiment, a Eurovent comprises a metal sleeve in which a valve disc, which can be closed against the force of a spring, is arranged on a shaft (collectively referred to as a "pin") to seal the mold surface. This valve closes the sleeve end in the plane of the mold surface after the air has been released. This valve prevents blowouts on the vehicle tire because the valve disc is flush with the mold surface and completely seals the venting means, preventing liquid rubber from entering the vent channel. A disadvantage, however, is that the Eurovent, which has a complex design due to the use of a spring, is susceptible to contamination because, for example, rubber material that gets under the edge of the disc can contaminate the valve, stick to it, and thus render it unusable.This adverse effect is further exacerbated by modern rubber compounds that contain alternative plasticizers.

[0007] From DE 10 2013 225 280 A1, which constitutes subsequently published prior art pursuant to Section 3 (2) of the Patent Act (PatentG), a vulcanization tool for vehicle tires is known. The vulcanization tool comprises molded parts into which venting means with cylindrical venting channels, each with a replaceable pin, are introduced. The pin is formed from two regions in terms of its longitudinal extent: a first region, which forms the end of the pin facing the mold surface, approximately at the level of the mold surface, and at this end has approximately the same diameter as the venting channel formed in the opposite direction in this region; and a second region, which encompasses the remaining pin and in which the pin has a smaller diameter than the venting channel, such that an annular gap remains between the wall of the venting channel and the pin.The pin is rigidly and replaceably arranged in the venting channel and has a longitudinal venting slot that extends completely through the first region and into the second region, so that one end of the venting slot opens into the annular gap. The venting slot can be a single slot, a Phillips slot, or a curved slot. Furthermore, the venting slot has a width of 50 µm to 100 µm.

[0008] US 2009 / 0261509 A1 discloses another vulcanization tool for vehicle tires. The vulcanization tool comprises molded parts that have venting means, each of which comprises a cylindrical venting channel with a pin holder and a replaceable pin inserted therein. The pin consists of two regions along its longitudinal extent – ​​a first region with a larger diameter and a second region with a smaller diameter, so that an annular gap remains between the wall of the venting channel and the pin. The pin further comprises a venting slot that extends in the longitudinal direction of the pin through the first region and into the second region, so that one end of the venting slot opens into the annular gap.According to one embodiment, the venting slot is designed as a cross-slot with three branches and has a width of 0.02 mm to 0.5 mm, in particular of 0.02 mm to 0.1 mm. The first region, viewed in cross section, is conical in shape such that it has a seating surface which runs at a first angle relative to the pin's longitudinal axis. The pin holder has a seating surface (corresponding to a bearing surface) which, viewed in cross section, runs at a second angle to the pin's longitudinal axis, which is smaller than the first angle. If a green tire (blank tire) is positioned in the vulcanization mold, the vulcanization mold can be vented via the venting slots.When the green tire is pressed against the inside of the mold segment, for example, using a heating bladder, the first section of the pin is pushed into the venting channel, pressing the seating surfaces together and closing the venting slot. When the fully vulcanized tire is removed, the pin is relieved of pressure, so that the venting slot—due to the differently angled seating surfaces—is pushed out of the venting channel. The advantage is that after vulcanization is complete, no spring is required to push out the pin, which is no longer under pressure. This improves the durability of the pin and further prevents rubber extrusion.

[0009] JP S61 252 110 A discloses a vulcanization tool with molded parts featuring cylindrical venting channels with inserted pins. Each pin comprises a first region that closes the venting channel at the level of the mold surface except for a venting slot running longitudinally through the pin, and a second region that has a smaller diameter than the venting channel, so that an annular gap remains between the wall of the venting channel and the pin. The venting slot extends completely through the first region and into the second region, so that one end of the venting slot opens into the annular gap. The pin is designed to be quickly replaceable and, above all, to have a central seat in the respective venting channel.

[0010] The invention is based on the object of providing a vulcanization tool that enables the production of vehicle tires with consistently high quality by improving the venting of the vulcanization tool, whereby its manufacture and design should be simple.

[0011] The invention solves this problem with the features of patent claim 1. Further embodiments of the invention are the subject of the subsequent subclaims.

[0012] A vulcanization tool for vehicle tires, which has at least two molded parts that can be connected to one another, the inner molding surfaces of which, when assembled, form a cavity with the negative mold of a vehicle tire to be produced, wherein: - the forming surfaces have negative profile elements for forming positive profile elements of the vehicle tyre to be vulcanised, - venting agents are incorporated into the mould surfaces, - a venting means comprises a cylindrical venting channel with a replaceable pin inserted therein for discharging air from the vulcanisation tool and preventing the penetration of liquid rubber material into the venting channel, - the pin consists of two areas in terms of its longitudinal extension, of which the first area, on the mould surface side, has a geometry that is designed to be complementary to a bearing surface incorporated in the mould surface, - this first area of ​​the pin closes the venting channel at the level of the moulding surface except for a venting slot running lengthwise through the pin, - the second region adjoining the first region comprises the remaining pin and has a smaller diameter than the vent channel, so that an annular gap remains between the wall of the vent channel and the pin, - the venting slot extends in the longitudinal direction of the pin completely through the first region and reaches into the second region, so that one end of the venting slot opens into the annular gap of the venting channel, is characterized according to the invention in that the venting slot is introduced into the pin by means of a micro saw and is designed as a cross slot with three branches, the venting slot having a width between 30 and 150 µm.

[0013] The particular advantage of the solution according to the invention is that the pins inserted into the venting channel do not have springs, and the valves formed thereby are considerably simpler in design than previously known systems. Furthermore, such a valve ensures reliable sealing of the venting channel, with only the venting slot created by the micro-sawing process forming a continuous opening to the open atmosphere and thus venting the vulcanization tool. This slot can be made so narrow with the micro-saw that no liquid rubber material penetrates the venting slot during the vulcanization process. This significantly improves the overall quality and appearance of the vehicle tire being produced. Complex reworking can be completely eliminated. Micro-saws of the type used here are typically only known for surgical applications.The use of this type of micro-saw in a vulcanization tool for a vehicle tire therefore represents a completely new application area for this type of micro-saw. Venting slots with such small dimensions reliably vent the air present in the vulcanization tool without the liquid rubber material being sucked or forced into the venting slot. The venting agent thus does not clog and can be used maintenance-free over a long period of time, which significantly reduces the maintenance costs of such a vulcanization tool.

[0014] Furthermore, a ventilation slot width of between 50 µm and 100 µm has proven to be particularly advantageous.

[0015] Since a vulcanization tool utilizes a multitude of such venting channels with inserted pins, ease of assembly also plays a crucial role. A further proposal of the invention is that, for the assembly of the pin, the first area of ​​the pin has a screw head shape with a conical sealing surface complementary to the bearing surface incorporated into the mold surface. Furthermore, such a sealing surface has proven to provide optimal sealing of the venting channel.

[0016] In order to secure the valve according to the invention, consisting of the venting channel and the pin, within the venting channel, it is further advantageous if the second region of the pin has a fixing section with which it can be inserted into a corresponding part of the wall of the venting channel. This fixing section can, for example, consist of a barb-like area that engages behind a correspondingly shaped contour of the venting channel. A clamping area, for example, is also conceivable.

[0017] To improve the fixation of the pin in the venting channel, it is further proposed that the fixation section be divided into at least two elastically deformable parts by at least one slot. The elastic design of part of the pin allows for significantly simplified assembly, which is particularly advantageous in conjunction with the previously mentioned barb-like engagement contour. Should this actually become necessary, the pin can also be disassembled due to its elastic deformability.

[0018] The vehicle tires produced with the vulcanization tool according to the invention can be all-season tires, summer tires, winter tires, or studded tires. Examples of producible vehicle tires include, but are not limited to, industrial tires, passenger car tires, truck tires, and bicycle tires.

[0019] The invention is explained in more detail below with reference to the accompanying drawings. The exemplary embodiments shown do not represent a limitation to the variants shown, but serve merely to illustrate a principle of the invention.

[0020] Identical or similar components are always designated by the same reference numerals. To illustrate the functionality of the invention, the figures show only highly simplified schematic diagrams, omitting components that are not essential to the invention. However, this does not mean that such components are not present in a solution according to the invention.

[0021] It shows: Fig. 1: a simplified, spatial representation of a vulcanization tool, Fig. 2: a section through a ventilation duct with a pin inserted, Fig. 3: a special version of a pen, Fig. 4: an example of a design variant for a micro saw and Fig. 5: four different exemplary embodiments of a venting slot in a pin (only variant b is in accordance with the invention).

[0022] The Fig. 1 shows an example of a spatial representation of a vulcanization tool 1 for a vehicle tire 2. The vulcanization tool 1 consists of several mold parts 3, the inner mold surfaces 4 of which form a cavity 5 when assembled. The cavity 5 forms the negative mold of the vehicle tire 2 to be produced, wherein the mold surfaces 4 in the Fig. 1 have negative profile elements not shown for forming positive profile elements of the vehicle tire 2 to be vulcanized. In addition, the forming surfaces 4 are Fig. 1 venting means 7, also not shown, is introduced.

[0023] From the Fig. 2 shows, by way of example, a venting means 7 which, in the present case, consists of a venting channel 8 which is introduced into the mold surfaces 4 of a molded part 3 of the vulcanization tool 1. Located in the venting channel 8 is a pin 9 which consists of a first, screw-head-like, i.e. conically tapered, region 10 and a second region 11 which directly and integrally adjoins this first region 10. The outer surface of the first region 10 of the pin 9 lies in sealing contact with a complementarily shaped bearing surface 12 which is introduced into the mold surface 4. The special feature of the illustrated embodiment of the venting means 7 is that a venting slot 13 which is introduced with a micro saw 17 is present in the pin 9, said venting slot 13 forming a connection between the cavity 5 of the vulcanization tool 1 and the free atmosphere.For this purpose, the venting slot 13 has a length that extends from its first region 10 into the second region 11. Consequently, the end 16 of the venting slot 13 projects into the second region 11 of the pin 9. In this region 11, the pin 9 has, at least in sections, a diameter that is smaller than the diameter of the venting channel 8. This has the result that an annular gap 14 remains between the outer surface of the pin 9 in its second region 11 and the wall 15 of the venting channel 8, which forms a transition to the free atmosphere and thus discharges the air from the vulcanization tool 1 via the venting slot 13.A further special feature of the illustrated embodiment is that the end piece of the second region 11 of the pin 9 is provided with a slot 19, which results in the fixing section 18 formed thereby having two elastically deformable legs which, after insertion of the pin 9 into the venting channel 8, engage behind corresponding counter-contours and thus releasably fix the pin 9 in the venting channel 8.

[0024] The Fig. Figure 3 shows a further, special design variant of a pin 9, as it can be inserted into a venting channel 8. In contrast to the design variant, which is described in connection with the Fig. 2, this pin 9 has a fixing section 18, which only has a contour complementary to the venting channel 8 in this area and is inserted into the venting channel 8 with the fixing section 18 in a clamping manner. Consequently, this pin 9 is not elastically deformable in the area of ​​the fixing section 18.

[0025] The Fig. 4 illustrates an example of a micro saw 17 used to create the venting slot 13 in the pin 9 of the venting means 7. The saw blade of such a micro saw 17 is equipped with a cross-section that allows a venting slot 13 having a width between 50 µm and 100 µm to be sawn into the pin 9.

[0026] In the picture parts a), b), c) and d) of the Fig.Figure 5 shows four different exemplary embodiments of the venting slot 13 in a pin 9. Thus, the venting slot 13 can be designed in a straight line, as can be seen in image part a) (not according to the invention). The inventive possibility is shown in image part b), where the venting slot 13 is designed as a cross-slot with three branches. As can also be seen from image part c), it is also possible to create a winding sectional shape of the venting slot 13 (not according to the invention). Finally, image part d) shows yet another variant of a cross-slot as a non-inventive possibility for a venting slot 13. List of reference symbols 1 vulcanization tool 2 vehicle tires 3 molded part 4 Form surface 5 Cavity 7 Venting agents 8 Ventilation duct 9 pin 10 first area 11 second area 12 Bearing surface of the mold surface 13 Ventilation slot 14 Annular gap 15 wall 16 End of the vent slot 17 Micro saw 18 Fixation section 19 slot

Claims

[1] Vulcanization tool (1) for vehicle tires (2), which has at least two molded parts (3) which can be connected to one another and whose inner molding surfaces (4) form a cavity (5) with the negative mold of a vehicle tire (2) to be produced when assembled, wherein: -the forming surfaces (4) have negative profile elements for forming positive profile elements of the vehicle tyre (2) to be vulcanised, -venting means (7) are introduced into the mould surfaces (4), -a venting means (7) comprises a cylindrical venting channel (8) with a rigid, replaceable pin (9) inserted therein for discharging the air from the vulcanisation tool (1) and for preventing the penetration of liquid rubber material into the venting channel (8), -the pin (9) consists of two regions (10, 11) with respect to its longitudinal extent, of which the first region (10) on the mold surface side has a geometry that is complementary to a bearing surface (12) introduced into the mold surface (4), -this first region (10) of the pin (9) closes the venting channel (8) at the level of the molding surface (4) except for a venting slot (13) running through the pin (9) in the longitudinal direction, -the second region (11) adjoining the first region (10) comprises the remaining pin and has a smaller diameter than the venting channel (8), so that an annular gap (14) remains between the wall (15) of the venting channel (8) and the pin (9), -the venting slot (13) extends in the longitudinal direction of the pin (9) completely through the first region (10) and into the second region (11), so that one end (16) of the venting slot (13) opens into the annular gap (14) of the venting channel (8), characterized by that the venting slot (13) is introduced into the pin (9) by means of a micro saw (17) and is designed as a cross slot with three branches, wherein the venting slot (13) has a width between 30 and 150 µm. [2] Vulcanization tool according to claim 1, characterized by that the vent slot (13) has a width between 50 and 100 µm. [3] Vulcanization tool according to one of the preceding claims, characterized by that the first region (10) of the pin (9) has a screw head shape with a conical sealing surface designed complementary to the bearing surface (12) introduced into the shaped surface (4). [4] Vulcanization tool according to one of the preceding claims, characterized by that the second region (11) of the pin (9) has a fixing section (18) with which it can be inserted into a corresponding part of the wall (15) of the venting channel (8). [5] Vulcanization tool according to claim 4, characterized by that the fixing section (18) is divided into at least two elastically deformable parts by at least one slot (19). [6] Vulcanization tool according to one of the preceding claims, characterized by that the vehicle tyres (2) produced with the vulcanisation tool are all-season tyres, summer tyres, winter tyres or studded vehicle tyres.

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