Vent valve

Abstract

Vent valve for a moulded part, having a moulded-part inner face, of a vulcanisation mould for a vehicle tyre, the vent valve comprising: a circular-cylindrical housing (1), which can be pressed into a bore of the moulded part, is elongated in the bore longitudinal direction, and has a central axis (a); a helical compression spring (5), one end of which is supported at the housing-inner end of a valve-shaft portion (3a) that adjoins a valve head (4) in the direction of the interior of the housing (1) and the other end of which is supported on the housing (1) in the housing interior. The helical compression spring (5) is designed and installed under preloading in the closed state of the vent valve such that, in the closed state, it has a spring force F which is determined as follows: F = F D · (1+ r H ), where r H = 1 / 2D, F D is from 0.5 N / mm to 3.0 N / mm, and where D is the outer diameter of the housing (1) in the region of the valve-shaft portion (3a) that adjoins the valve head (4) in the direction of the interior of the housing (1).

Description

[0001] Description

[0002] vent valve

[0003] The invention relates to a vent valve for a molded part of a vulcanization mold of a vehicle tire, said mold having an inner mold part, comprising a housing that can be pressed into a vent bore of the molded part, is elongated in the longitudinal direction of the bore, is circularly cylindrical and has a central axis, and comprises a valve plunger located in the housing and movable relative to said housing in the axial direction, having a valve stem with a valve head that can close the housing on the inner mold part side, and having a helical compression spring surrounding the valve stem, which is supported with one end on the inner end of a valve stem section that adjoins the valve head towards the interior of the housing, and is supported with its other end on the housing inside the housing. The invention further relates to a vulcanization mold for a vehicle tire with at least one molded part with vent bores.

[0004] To ensure the venting of a tire vulcanization mold during the molding of the green tire, a plurality of vent holes is provided in molded parts, for example in mold segments that form the tread area of ​​the tire. Vent valves are typically incorporated into the vent holes. Known vent valves have valve inserts with valve heads, which, when green tires are molded into the mold, close the vent holes on the inside of the molded part and are intended to at least largely prevent the formation of rubber extrusions and the penetration of rubber compound into the interior of the vent valves during tire vulcanization. Before and at the beginning of the molding of the green tire, the valve caps are open and protrude slightly on the inside of the molded parts, ensuring the necessary venting during the molding of the green tire.A vent valve of the type mentioned at the outset is known, for example, from WO 2019 / 219304 A1. In the embodiment of a vent valve known from DE 10 2016 209 912 A1, the valve head is frustoconical and, in the closed position of the vent valve, contacts a seat surface provided on the inside of the housing pressed into the vent bore and adapted to the frustoconical shape of the valve head.

[0005] It frequently happens that when the green tire is molded into the vulcanization mold, small amounts of components of the rubber compound, especially in rubber compounds with particularly high flow rates, penetrate the vent valves and remain as a sticky coating on the undersides of the valve heads and on the valve housing. This prevents the vent valves from opening properly after the tire is removed from the mold. Defective, stuck vent valves lead to defects in the vulcanized tire, requiring the vulcanization process in the affected mold to be interrupted, the mold parts removed, and the valve stems replaced manually.

[0006] The invention is based on the object of ensuring, by means of a particularly simple measure, a permanent functionality of the vent valves, in particular in the case of rubber mixtures which promote sticking of the vent valves.

[0007] The stated object is achieved according to the invention in that the helical compression spring is designed in such a way and is installed under pretension in the closed state of the vent valve in such a way that it has a spring force F in the closed state, which is determined as follows: F = F D - (l + r H ') where r H = D >

[0008] F D from 0.5 mm to 3.0 mm and where D is the outer diameter of the housing (1) in the region of the valve stem section (3a) adjoining the valve head (4) towards the interior of the housing (1).

[0009] According to the invention, the vent valves contain helical compression springs whose spring force ensures that, even if the valve heads or valve stems and the interior of the housing become contaminated, the resulting adhesion force is overcome by the helical compression spring, ensuring that the valve opens after the fully vulcanized tire has been removed. The spring force is selected depending on the flowability of the potentially penetrating rubber compound or on certain components of the rubber compound, the previously determined degree of contamination, preferably within the specified range, and the outer diameter of the housing. The invention therefore also takes into account that stronger springs are advantageous in vent valves with a larger outer diameter.The invention therefore avoids production interruptions by preventing non-functioning vent valves and the removal of tire molds for cleaning outside of the scheduled intervals.

[0010] In a preferred embodiment, the helical compression spring has a spring force F in the closed state, where n is from 0.75 to 1.60. A spring force in this range has proven particularly suitable and advantageous for vent valves with conventional housing outer diameters, so that in most cases, even with heavy contamination from rubber material, the vent valve reliably opens after the tire has been removed.

[0011] The valve stem section adjacent to the valve head is specifically designed to have an outer diameter that is 85% to 90% of the inner diameter of the housing at that point. This design ensures a narrow gap between the valve stem section and the housing and reduces the likelihood of rubber material penetrating the area of ​​the helical compression spring.

[0012] A further advantageous measure in this regard is that the valve stem section adjoining the valve head has a height of 1.50 mm to 2.50 mm, determined parallel to the central axis.

[0013] In a further advantageous embodiment, a circumferential, in particular 0.20 to 0.60 mm wide, circular support surface is provided on the inner end face of the valve stem section, oriented perpendicular to the central axis, on which one end of the helical compression spring rests. Further valve stem sections with a smaller diameter adjoin the valve stem section, thus ensuring the required mobility of the helical compression spring.

[0014] The invention further relates to a vulcanization mold for a vehicle tire having at least one front part with vent holes into which vent valves are inserted, which are designed according to one or more of claims 1 to 6.

[0015] Further features, advantages and details of the invention are described in more detail with reference to the schematic drawing, which shows an embodiment of a vent valve.

[0016] Fig. 1 is a greatly enlarged view, partly cut away, of a vent valve in the closed state,

[0017] Fig. 2 a view of a valve stem of the vent valve.

[0018] Fig. 1 shows an exemplary embodiment of a vent valve that is inserted into a bore of a molded part, such as a mold segment, of a vulcanization mold for a vehicle tire, in particular for a pneumatic vehicle tire. The following description of an exemplary embodiment of the vent valve describes the design and arrangement of its components with reference to their installation position in the molded part, which has an inner side facing the mold cavity and an outer side facing the mold cavity.

[0019] The main components of the vent valve are an elongated housing 1, which is a largely circular-cylindrical component with a central axis a and by means of which the vent valve is press-fitted into a bore in the molded part, and a likewise elongated valve stem 2, which is inserted into the housing 1 along the central axis a. The valve stem 2 has a valve head 4 facing the inside of the mold and a valve stem 3 consisting of several sections, which is surrounded by a helical compression spring 5. The valve head 4 is designed, for example, in the shape of a flat truncated cone, with an outside facing the inside of the mold and an inside to which the valve stem 3 is connected.In the open position of the vent valve, the outer side of the valve head 4 protrudes beyond the inner side of the molded part under the pressure of the helical compression spring 5, creating a gap between the valve head 4 and the housing 1 through which air can enter the vent valve and be discharged via a bore section of the molded part. A green tire molded into the vulcanization mold presses the valve head 4 against a seat surface surrounding the housing 1, thereby closing it.

[0020] As shown in Fig. 1 and Fig. 2, a valve stem section 3a adjoins the valve head 4 centrally in the direction of the interior of the housing 1, which valve stem section is in particular circular-cylindrical and has an outer diameter di which is 85% to 90% of the inner diameter of the housing 1 at this point, so that a gap with a width of preferably 0.07 mm to 0.17 mm remains between the outer side of the valve stem section 3a and the inside of the housing 1. In the area of ​​the valve stem section 3a, the housing 1 has an outer diameter D, which is indicated in Fig. 1. The height h of the valve stem section 3a, determined parallel to the central axis a, is in particular 1.50 mm to 2.50 mm, in particular on the order of 2.00 mm. The valve stem section 3a is followed by further stem sections, which are not designated except for an end section 3b and each have a smaller diameter than the valve stem section 3a.The design is such that at the end of the valve stem section 3a inside the housing, a circumferential, in particular 0.20 mm to 0.60 mm wide, annular support surface 6 remains on the outside, on which one end of the helical compression spring 5 is supported.

[0021] The helical compression spring 5 rests with its second end on the inside of the housing against a projection 7 formed on the inner end of the housing 1 and on the inside, in particular a circumferential projection 7, which leaves an opening in the center. The aforementioned end section 3b of the valve stem 3 is divided into two parts by a slot 8; the two parts each have a projection 9 on the outside, so that when the valve stem 3 is inserted into the housing 1, the projections 9 engage below the projection 7 circumferentially extending at the inner end of the housing 1.

[0022] In preferred embodiments, the helical compression spring 5 has six to eight coils and consists of a metal wire with a diameter of, for example, 0.20 mm to 0.25 mm. The inner and outer diameters of the helical compression spring 5 are such that it is optimally supported inside the housing on the support surface 6 of the valve stem section 3a and on the projection 7 of the housing 1, while maintaining good compressibility and mobility. The helical compression spring 5 is designed and installed in the vent valve in such a way that, when the vent valve is closed, it exerts a spring force F, which is determined as follows:

[0023] F = F D • (1 + r H ) where r H = -D and

[0024] F D from 0.5 — mm to 3.0 — mm , in particular F Dfrom 0.75 mm to 1.60 mm. Therefore, in the closed state of the vent valve, the pre-tensioned helical compression spring 5 has such a spring force that even in the case of sticky residues of rubber material on the housing 1 and / or on the conical underside of the valve head 4 after demolding of the tire, the vent valve reliably returns to its open position.

[0025] List of reference symbols

[0026] 1 housing

[0027] 2 valve stems

[0028] 3 valve stem

[0029] 3a, 3b valve stem section

[0030] 4 valve head

[0031] 5 helical compression spring

[0032] 6 Support surface

[0033] 7 lead

[0034] 8 slot

[0035] 9 Projection a central axis h height di outer diameter of the valve stem section 3a

[0036] D Outer diameter of the housing 1

Claims

Patent claims 1. A vent valve for a molded part of a vulcanization mold of a vehicle tire, said vent valve comprising a housing (1) which can be pressed into a bore of the molded part, is elongated in the longitudinal direction of the bore, is circularly cylindrical and has a central axis (a), and has a valve stem (2) located in the housing (1) and movable relative to it in the axial direction, has a valve stem (3) with a valve head (4) which can close the housing (1) on the inside of the molded part, and has a helical compression spring (5) surrounding the valve stem (3), which is supported with one end on the inside end of a valve stem section (3a) adjoining the valve head (4) towards the inside of the housing (1), and is supported with its other end on the housing (1) inside the housing, characterized in thatthat the helical compression spring (5) is designed in such a way and is installed under pretension in the closed state of the vent valve in such a way that it has a spring force F in the closed state which is determined as follows: F = F D - (l + r H ) where F D from 0.5 — to 3.0 — mm and where D is the outer diameter of the housing (1) in the region of the valve stem section (3a) adjoining the valve head (4) towards the interior of the housing (1).

2. Vent valve according to claim 1, characterized in that the helical compression spring (5) in the closed state has a spring force F at which F D of 0.75 amounts.

3. Vent valve according to claim 1 or 2, characterized in that the valve stem section (3a) adjoining the valve head (4) has an outer diameter (di) which is 85% to 90% of the inner diameter of the housing (1) at this point.

4. Vent valve according to one of claims 1 to 3, characterized in that the valve stem section (3a) adjoining the valve head (4) has a height (h) of 1.50 mm to 2.50 mm, determined parallel to the central axis (a).

5. Vent valve according to one of claims 1 to 4, characterized in that at the housing-inner end of the valve stem section (3a) there is an externally circumferential, in particular 0.20 mm to 0.60 mm wide, circular ring-shaped support surface (6) on which one end of the helical compression spring (5) is supported.

6. Vulcanization mold for a vehicle tire with at least one molded part with vent holes in which vent valves are inserted, which are designed according to one or more of claims 1 to 5.

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