Venting unit, vulcanisation mould, and pneumatic vehicle tyre

Abstract

The invention relates to a venting unit (3) to be inserted in a drilled hole (2), originating from an interior, of a mould part (1) of a vulcanisation mould for vulcanising a green tyre, wherein the venting unit (3) has a closed and an open position and comprises the following components: - a housing (6), - a valve core (7), - a valve disc (4), which is associated with the valve core (7) and, in the closed position of the venting unit (3), rests with a circumferential edge region (4a) on a seat face which extends annularly around the outer end of the housing (6), - a valve shaft (8), which is associated with the valve core (7) and has an outer cylindrical shaft portion (8a), and - a compression coil spring (10). The outer edge region (4a) of the valve disc (4) has a thickness (s1) of 0.10 mm to 0.40 mm, in particular 0.20 mm to 0.25 mm. The venting unit (3) should be pressed into the drilled hole (2) such that the seat face (13) extending around the outer end of the housing (6) is inwardly offset with respect to the mould part interior (1a) by 0.05 mm to 0.35 mm, in particular 0.10 mm to 0.15 mm.

Description

[0001] Description

[0002] Venting unit, vulcanization mold and pneumatic vehicle tires

[0003] The invention relates to a venting unit for insertion into a bore extending from the inside of a molded part of a vulcanization mold for vulcanizing a green tire, wherein the venting unit has a closed and an open layer and the following components:

[0004] - a largely circular-cylindrical, sleeve-shaped housing which can be pressed into the bore and has a largely constant inner diameter and a central axis,

[0005] - a valve insert inserted in the housing and movable relative to it in the axial direction,

[0006] - a valve disc belonging to the valve insert, which is circular in plan view and which, in the closed position of the venting unit, rests flatly on a seating surface which is ring-shaped at the outer end of the housing and oriented at right angles to the central axis, with a peripheral edge area of ​​constant thickness,

[0007] - a valve stem belonging to the valve insert and adjoining the valve disc, comprising an outer, cylindrical stem section, an inner stem section and a transition section between these stem sections,

[0008] - a helical compression spring which surrounds the inner shaft section and the transition section of the valve stem and is supported at one end on the housing and acts on the outer shaft section of the valve stem at its other end.

[0009] The invention further relates to a vulcanization mold with at least one molded part with venting holes, and to a pneumatic vehicle tire vulcanized in the vulcanization mold. In order to ensure venting of a tire vulcanization mold during molding of the green tire, a plurality of venting holes is provided in molded parts, in particular in mold segments that form the tread area, into each of which a venting unit is introduced. Such venting units have valve inserts with valve closures, for example valve plates, which close the venting holes when the green tire is molded in and at least largely prevent the formation of rubber extrusions during vulcanization of the tire. During molding of the green tire, the venting inserts ortheir valve closures are open and protrude from the inside of the molded parts, such as the mold segments, so that the necessary ventilation is ensured during the molding of the green tire.

[0010] A venting unit of the type mentioned above is known, for example, from WO 2020 / 211995 A1. The valve closure is stepped on the outside and, when the venting unit is closed, rests on a correspondingly stepped inner wall section of the housing. The dimensions and design of the steps are such that, when the venting unit is closed, an annular, circumferential gap remains between the corresponding step surfaces on the valve closure and those on the inner wall section of the housing, which has a width of 0.01 mm to 0.50 mm. All gaps are connected to one another and thus form a single, continuous, stepped gap running from the contact surfaces into the interior of the venting unit, which changes direction according to the number of steps.The aforementioned gaps act as labyrinth gaps and thus, in a known manner, act as a barrier against the penetration of liquid or low-viscosity media, especially particularly free-flowing rubber compounds, into the interior of the venting unit. The valve closure protrudes slightly beyond the inside of the molded part even when the venting unit is closed. The protrusion is in the range of 0.05 mm to 0.20 mm, supporting proper closure of the venting unit and the buildup of counterpressure in the gaps.

[0011] Another venting unit for a vulcanization mold of a pneumatic vehicle tire is known from WO 2017 / 211517 A1. This venting unit has a valve stem with a truncated cone-shaped, outwardly widening valve plate, which, when the venting unit is closed, rests against a conically shaped extension on the outer inner wall section of the housing. Adjacent to the valve plate, the valve stem has a cylindrical retaining section onto which a helical compression spring, which presses the valve stem and thus the valve plate into the open position, can be attached with at least two of its coils. This measure enables precise positioning and a secure fit of the helical compression spring on the valve stem.

[0012] The unintentional penetration of particularly flowable, modern rubber compounds for high-performance tires into venting units due to additional heating during tire molding remains an unsatisfactorily resolved problem. These special rubber compounds leave visible protrusions of various shapes and sizes around the venting units. Furthermore, after a certain number of heating cycles with conventional venting units, it is almost impossible to prevent the rubber compounds that have penetrated into the interior of the venting units due to their flowability from filling the venting units with rubber material and blocking the venting units, particularly the helical compression springs. This no longer ensures adequate venting of the vulcanization mold, and shrinkage spots form on the vulcanized tire, impairing the quality of the vulcanized tires, so that they may even have to be rejected.The affected vulcanization molds must be removed from the tire curing press, and the venting units removed and replaced with new ones. These measures require a production shutdown, thus incurring additional costs, the latter also due to the need to install new venting units.

[0013] The invention is based on the object of improving a venting unit of the type mentioned at the outset in such a way that the formation of shoots is reliably avoided and that it ensures perfect venting over a significantly larger number of heating cycles than the known venting units, in particular by making it more difficult for rubber mixture to penetrate and ensuring perfect function of the helical compression spring over a large number of heating cycles.

[0014] The stated object is achieved according to the invention in that the outer edge region of the valve disk, which rests on the seat surface in the closed position of the venting unit, has a thickness of 0.10 mm to 0.40 mm, in particular of 0.20 mm to 0.25 mm, wherein the venting unit is to be pressed into the bore in such a way that the seat surface running around the outer end of the housing is offset inwards by a distance of 0.05 mm to 0.35 mm, in particular of 0.10 mm to 0.15 mm, relative to the inside of the molded part, and wherein the radially outer shaft section of the valve stem has an outer diameter which is 80% to 97% of the inner diameter of the housing.

[0015] According to the invention, these measures in combination ensure that even with rubber compounds that are particularly free-flowing when warm and unvulcanized, the venting unit functions perfectly over a significantly greater number of heating cycles than with known venting units. By appropriately adjusting the distance between the seating surface on the housing and the inside of the mold to the thickness of the edge of the valve disk resting there in the closed position, the movement path during opening and closing is very small and the valve disk protrudes at most slightly beyond the inside of the molded part when the venting unit is closed. This not only optimally supports the closing of the venting unit when molding the green tire, but also ensures that the narrow gap that exists when the venting unit is open leaves hardly any room for rubber material to penetrate.Any rubber material that might penetrate is also prevented from penetrating the delicate area of ​​the helical compression spring while it is still flowable by the narrow gap between the radially outer section of the valve stem and the inner wall of the housing.

[0016] Particularly preferred is an embodiment in which the radially outer shaft section of the valve stem has an outer diameter which is 85% to 90% of the inner diameter of the housing.

[0017] In a further preferred embodiment, the radially outer shaft section of the valve stem has an extension length such that the helical compression spring acts on this section at a position located at a distance of 30% to 60% of the total length of the venting unit, determined from the outer end of the venting unit. This measure also supports the effect of preventing any penetrating rubber mixtures or rubber material from penetrating the area of ​​the helical compression spring.

[0018] Furthermore, the seat surface surrounding the outer end of the housing is advantageously the outer free edge of the housing, so that when a venting unit is pressed into a bore, only a section of the bore wall extending to the inside of the molded part is present outside the seat surface. This section of the bore wall has a height of 0.10 mm to 0.15 mm, measured in the direction of extension of the bore. The venting unit is therefore pressed only a short distance into the bore interior without risking damage to the housing.

[0019] An optimal fit of the valve disk on the seat surface of the housing is particularly supported by the fact that the outer edge area of ​​the valve disk has a width of 0.20 mm to 0.30 mm and overlaps with the seat surface on the outer edge of the housing in such a way that when the venting unit is closed, a gap with a width of 0.04 mm to 0.06 mm remains between the edge of the edge area of ​​the valve disk and the bore wall section.

[0020] An optimal fit of the valve disk on the seat surface of the housing with good mobility of the same is further preferably ensured in that the seat surface running around the inside of the molded part end of the housing runs around an opening in the housing which widens outwards in a funnel shape and is formed by a continuous decrease in the wall thickness of the housing, so that the seat surface has a width of 0.20 mm to 0.35 mm.

[0021] The mobility and stability of the valve disk are further supported by the fact that it has a disk base part which extends with a frusto-conical section with decreasing diameter to the adjoining outer shaft section, whereby this frusto-conical section has a thickness of 0.25 mm to 0.40 mm parallel to the central axis and the smallest diameter of the frusto-conical section is located adjacent to the outer shaft section and is 0.20 mm to 0.40 mm larger than the diameter of the outer shaft section.

[0022] For a long-lasting function of the helical compression spring, it is advantageous according to a further embodiment if an annular circumferential support surface is formed on the outer shaft section of the valve stem at the transition section, on which the helical compression spring is supported and thus presses the valve stem and thus the valve plate into the open position.

[0023] The vulcanization mold according to the invention comprises at least one molded part with venting holes, into which venting units according to one or more of claims 1 to 8 are inserted. It is particularly advantageous if the molded parts are mold segments that form a segmented ring for shaping the tread of the pneumatic vehicle tire. With such a vulcanization mold, tires whose treads are made of a rubber compound that is super-soft in the warm and unvulcanized state and therefore particularly flowable can be vulcanized over a large number of heating cycles without significant growth of the tread.

[0024] The pneumatic vehicle tire according to the invention has been vulcanized in a vulcanization mold according to claim 9 or 10.

[0025] Further features, advantages and details of the invention will now be described in more detail with reference to the drawing, which shows an embodiment.

[0026] Fig. 1 is an enlarged view, partially cut away, of a ventilation unit in the closed state,

[0027] Fig. 2 is an enlarged sectional view (longitudinal section) of a housing of the venting unit inserted into a molded part and

[0028] Fig. 3 is an enlarged view of a valve stem.

[0029] Fig. 2 shows a sectional view of a housing 6 of a venting unit 3 inserted into a bore 2 of a molded part 1, such as a mold segment, of a vulcanization mold for a pneumatic vehicle tire. The molded part 1 has an inner side 1a facing the mold cavity and a molded part outer side (not shown). Typically, a number of mold segments form a mold segment ring for forming a profiled tread of a green tire inserted into the vulcanization mold.

[0030] In the following description of an embodiment of a venting unit 3, the design and arrangement of its components is considered with reference to their installation position in a molded part 1, for example a mold segment of a segment ring forming the tread, wherein designations such as "outside", "outside", "outside" and the like refer to positions on or near the inside of the molded part 1a, and designations such as inside, inside, inside and the like refer to positions further inside the molded part 1 or the venting unit 3.

[0031] As shown in particular in Fig. 1, the main components of each venting unit 3 are the elongated housing 6 and a likewise elongated valve insert 7 inserted into the housing 6. The housing 6 is a largely cylindrical component with a central axis a. The valve insert 7 has a valve stem 8, the valve disk 4 sitting on the outside of the latter with a disk base part 9 and a helical compression spring 10. The central axis a is also the central longitudinal axis of the valve insert 7, which is largely rotationally symmetrical. In the open position of the venting unit 3, at least the upper side of the valve disk 4 projects beyond the molded part inner side 1a such that air can penetrate into the venting unit 3 and be discharged. A green tire molded into the vulcanization mold presses the valve disk 4 into its closed position.

[0032] The housing 6 shown in Fig. 2, which is sleeve-shaped and rotationally symmetrical with respect to the axis a, has an outer housing section 6a with a specially designed end section 6ai and an inner housing section 6b with a specially designed end section 6bi. Between the two end sections 6ai, 6bi, the housing sections 6a and 6b have an equally large, constant inner diameter di of 1.60 mm to 2.20 mm. The outer housing section 6a has a constant outer diameter d2, the inner housing section 6b a constant outer diameter ds, wherein the outer diameter d2 is 0.10 mm to 0.40 mm, preferably 0.15 mm to 0.30 mm, larger than the outer diameter da, so that the wall thickness of the housing 6 in the outer housing section 6a is greater than the wall thickness of the housing 6 in the inner housing section 6b.In the end section 6ai, which, viewed parallel to the axis a, extends over 0.40 mm to 0.50 mm, a funnel-shaped opening 11 is formed by a continuous decrease in the wall thickness of the housing 6 and a continuous increase in the inner diameter. This opening 11 is surrounded by an inclined surface 11a that runs at a constant angle a of 20° to 24° to the central axis a. The opening 11 is surrounded on the outside by an annular, flat seating surface 13 oriented at a right angle to the axis a, with a constant width b of 0.20 to 0.35 mm and an inner diameter d4 of 1.90 mm to 2.70 mm. The seating surface 13 forms the outer free edge of the housing 6.

[0033] In the end section 6bi of the inner housing section 6b, a projection 12 is formed on the inner wall, which projection 12 leaves a circular opening which has a diameter ds which is 0.50 mm to 0.80 mm smaller than the inner diameter di of the housing 6.

[0034] The venting unit 3 is press-fitted into the venting bore 2 of the mold segment 1, such that the annular seating surface 13 on the outside of the housing 6 is located within the molded part interior 1a, offset inwardly from the latter by a distance c of 0.05 mm to 0.35 mm, in particular 0.10 mm to 0.15 mm. In the closed position of the venting unit 3, the valve disk 4 rests on the annular seating surface 13.

[0035] As shown in particular in Fig. 3, the valve disk 4, which is circular in plan view, has on its outer side a diameter de which is 0.30 mm to 0.60 mm larger than the inner diameter d4 of the seat surface 13, and an edge region 4a surrounding the disk base part 9, which edge region has a constant thickness si of 0.10 mm to 0.40 mm, in particular of 0.20 mm to 0.25 mm, and a constant width of 0.20 to 0.30 mm. A circumferentially narrow gap with a width of approximately 0.04 mm to 0.06 mm remains to the wall of the venting bore 3. This ensures that the valve disk 4 rests flat on the seat surface 13 at the edge when the venting unit 3 is in the closed position. Due to its thickness si, the valve plate 4 projects beyond the inner side 1a of the molded part by approximately 0.10 mm in this position.The plate base part 9 has a frustoconical section which has a decreasing diameter towards the interior of the housing 6, with a largest diameter dz which is 0.40 mm to 0.60 mm smaller than the diameter de on the outside of the valve plate 4, and a thickness S2 of 0.25 mm to 0.40 mm. The inclination of the outer surface of the plate base part 9 relative to the central axis a is selected such that the plate base part 9 does not come into contact with the inner wall of the housing 6 when the venting unit 3 is in the closed position.

[0036] The valve stem 8 is connected to the plate base part 9 with a cylindrical outer shaft section 8a, which is followed by a transition section 8b and, on this, an inner shaft section 8c with an end section 8ci. The outer shaft section 8a has an outer diameter ds which is 80% to 97%, in particular 85% to 90%, of the inner diameter di of the housing 6. The outer shaft section 8a has a minimum length of 2.50 mm and preferably extends over 30% to 50%, in particular 38% to 43%, of the total length Ls of the valve stem 8. The valve stem 8 has its largest diameter in the outer shaft section 8a and its smallest diameter in the inner shaft section 8c.The transition section 8b has diameters which are smaller than the diameter in the outer shaft section 8a and larger than the diameter in the inner shaft section 8c, such that an annular circumferential support surface 8ai remains on the outer shaft section 8a at the transition section 8b, on which support surface one end of the helical compression spring 10, which is positioned around the inner shaft section 8c and around the transition section 8b, is supported. The outer shaft section 8a is preferably designed with an extension length such that the helical compression spring 10 acts on this section at a position which is located at a distance of 30% to 60% of the total length L (Fig. 1) of the venting unit 3, determined from the outer end of the venting unit 3. A slot 14 is formed in the inner shaft section 8c and extending over the end section 8ci along the central axis a.The end section 8ci, thus divided into two by the slot 14, has a projection 15 on each side, so that when the valve stem 8 is inserted into the housing 6, the projections 15 engage below the projection 12 surrounding the inner end of the housing 6. The helical compression spring 10 positioned on the inner shaft section 8c rests with its second end on the surrounding projection 12 on the inside of the housing.

[0037] List of reference symbols

[0038] 1 molded part 2 vent hole

[0039] 1a molded part inside

[0040] 3 Ventilation unit

[0041] 4 valve plates

[0042] 4a Edge area 5 Tread

[0043] 6 housings

[0044] 6a outer housing section

[0045] 6b inner housing section

[0046] 6ai, 6bi end section 7 valve insert

[0047] 8 valve stem

[0048] 8a outer shaft section

[0049] 8ai support surface

[0050] 8b transition section 8c inner shaft section

[0051] 8ci final section

[0052] 9 Plate base part

[0053] 10 helical compression spring

[0054] 11 Opening 11a Inclined surface

[0055] 12 lead

[0056] 13 ring-shaped seat

[0057] 14 slot

[0058] 15 projection a central axis a angle (slant surface 11a) di inner diameter of the housing 6 d2 outer diameter of the outer housing section 6a da outer diameter of the inner housing section 6b d4 inner diameter of the seat surface 13 ds diameter of the opening on the projection 12 de diameter of the valve disc 4 d? largest diameter of the frusto-conical section of the disc base part 9 ds outer diameter of the stem section 8a si thickness of the valve disc 4 S2 thickness of the frusto-conical section of the disc base part b width of the seat surface 13

[0059] L Total length of the ventilation unit 3

[0060] Ls Total length of the valve stem 8 c Distance

Claims

Patent claims 1 . A venting unit (3) for insertion into a bore (2) extending from an inner side of a molded part (1) of a vulcanization mold for vulcanizing a green tire, the venting unit (3) having a closed and an open layer and the following components: - a housing (6) which can be pressed into the bore (2), is largely circular-cylindrical and sleeve-shaped and has a largely constant inner diameter (di) and a central axis (a), - a valve insert (7) inserted in the housing (6) and movable relative to it in the axial direction, - a valve disc (4) belonging to the valve insert (7) which is circular in plan view and which, with a peripheral edge region (4a) of constant thickness (si), rests flatly on a seating surface which is annularly circumferential at the outer end of the housing (6) and oriented at right angles to the central axis and remains within the seating surface (13) in the closed position of the venting unit (3), - a valve stem (8) belonging to the valve insert (7) and adjoining the valve plate (4) with an outer, cylindrical stem section (8a), an inner stem section (8c) and a transition section (8b) between these stem sections (8a, 8c), - a helical compression spring (10) which surrounds the inner shaft section (8c) and the transition section of the valve stem (8) and is supported with one end on the housing (6) and with its other end acts on the outer shaft section (8a) of the valve stem (8), characterized in that the outer edge region (4a) of the valve disk (4) which rests on the seat surface (13) in the closed position of the venting unit (3) has a thickness (si) of 0.10 mm to 0.40 mm, in particular of 0.20 mm to 0.25 mm, wherein the venting unit (3) is to be pressed into the bore (2) in such a way that the seat surface (13) running around the outer end of the housing (6) is opposite the The inside of the molded part (1a) is offset inwards by a distance (c) of 0.05 mm to 0.35 mm, in particular of 0.10 mm to 0.15 mm, and wherein the radially outer shaft section (8a) of the valve stem (8) has an outer diameter (ds) which is 80% to 97% of the inner diameter (di) of the housing (6).

2. Ventilation unit (3) according to claim 1, characterized in that the radially outer shaft section (8a) of the valve stem (8) has an outer diameter (ds) which is 85% to 90% of the inner diameter (di) of the housing (6).

3. Ventilation unit (3) according to claim 1 or 2, characterized in that the radially outer shaft section (8a) of the valve stem (8) has an extension length such that the helical compression spring (10) acts on this section (8a) at a position which is located at a distance of 30% to 60% of the total length (L) of the venting unit (3) determined from the outer end of the venting unit (3).

4. Ventilation unit (3) according to one or more of claims 1 to 3, characterized in that the seat surface (13) running around the outer end of the housing (6) is the outer free edge of the housing (6), so that when the ventilation unit (3) is pressed into a bore (2), there is a bore wall section extending to the inside of the molded part outside the seat surface (13).

5. Ventilation unit (3) according to one or more of claims 1 to 4, characterized in that the outer edge region (4a) of the valve plate (4) has a width of 0.20 mm to 0.30 mm and overlaps with the seat surface (13) on the outer edge of the housing (6) in such a way that when the ventilation unit (3) is closed, a gap with a width of 0.04 mm to 0.06 mm remains between the edge of the edge region (4a) of the valve plate (4) and the bore wall section.

6. Ventilation unit (3) according to one or more of claims 1 to 5, characterized in that the seat surface (13) running around the inside end of the housing (6) of the molded part runs around an opening (11) of the housing (6) which widens outwards in a funnel shape and is formed by a continuous decrease in the wall thickness of the housing (6) such that the seat surface (13) has a width (b) of 0.20 mm to 0.35 mm.

7. Ventilation unit (3) according to one or more of claims 1 to 6, characterized in that the valve plate (4) has a plate base part (9) which extends with a frusto-conical section with decreasing diameter to the adjoining outer shaft section (8a), wherein the frusto-conical section has a thickness (S2) of 0.25 mm to 0.40 mm parallel to the central axis and its smallest diameter is at the connection to the outer shaft section (8a) and is 0.20 mm to 0.40 mm larger than the diameter (ds) of the outer shaft section (8a).

8. Ventilation unit (3) according to one or more of claims 1 to 7, characterized in that an annular circumferential support surface (8ai) remains on the outer shaft section (8a) of the valve stem (8) at the transition section (8b), on which the helical compression spring (10) is supported.

9. Vulcanization mold for a pneumatic vehicle tire with at least one molded part with venting holes into which venting units according to one or more of claims 1 to 8 are inserted.

10. Vulcanization mold according to claim 9, wherein the mold parts are mold segments which form a segment ring for molding the tread of the vehicle pneumatic tire.

11. A pneumatic vehicle tire which has been vulcanized in a vulcanization mold according to claim 9 or 10.

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