Ventilation unit, vulcanization mold and pneumatic vehicle tire

Abstract

The present invention relates to a ventilation unit (3) to be inserted into a borehole (2) originating from the inside of a mold part (1) of a vulcanization mold for vulcanizing green tires, the ventilation unit (3) having a closed position and an open position and including the following components: a housing (6), a valve core (7), a valve disc (4) connected to the valve core (7) and resting at its peripheral region (4a) on a seating surface extending annularly around the outer end of the housing (6) in the closed position of the ventilation unit (3), a valve shaft (8) connected to the valve core (7) and having an outer cylindrical shaft portion (8a), and a compression coil spring (10). The outer peripheral 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 vent unit (3) must be pressed into the bore (2) so that the seat (13) extending around the outer edge of the housing (6) is offset inwards by 0.05 mm to 0.35 mm, in particular 0.10 mm to 0.15 mm, relative to the interior of the mould part (1a).

Description

[Technical Field]

[0001] The present invention relates to a ventilating unit for insertion into a hole made in a mold part of a vulcanization mold for vulcanizing green tires and extending from the inside of the mold part, the ventilating unit having a closed position and an open position and comprising the following components: a housing in the form of a cylindrical sleeve that can be press-fit into the bore and has a generally constant inner diameter and central axis; - a valve insert inserted into the housing and axially movable relative to the housing; - a valve disc which is part of the valve insert, which is circular in plan view and which, in the closed position of the vent unit, extends circumferentially in the form of a ring around the outer end of the housing and which seats with a peripheral area of ​​constant thickness flat against a seating surface oriented at right angles to the central axis; - a valve stem that is part of the valve insert and is adjacent to the valve disc and has an outer cylindrical stem portion, an inner stem portion, and a transition portion between the stem portions; - a compression coil spring surrounding the inner stem portion and transition portion of the valve stem, the compression coil spring being supported by one end on the housing and acting at its other end on the outer stem portion of the valve stem; The present invention relates to a ventilation unit including:

[0002] The present invention also relates to a curing mold having at least one mold part with a vent hole and a pneumatic vehicle tire cured in the curing mold. [Background technology]

[0003] To provide ventilation for the tire curing mold during the molding of the green tire, a number of ventilation holes, each incorporating a ventilation unit, are provided in the mold parts, particularly mold segments, that define the tread area. Such ventilation units have a valve closure, e.g., a valve insert with a valve disc, which closes the ventilation hole when the green tire is molded, at least primarily to prevent flash during the curing of the tire. During the molding of the green tire, the ventilation insert or its valve closure is open and protrudes from the inside of the mold part, e.g., the mold segment, thereby ensuring the necessary ventilation during the molding of the green tire.

[0004] A ventilation unit of the type mentioned at the outset is known, for example, from WO 2020 / 211995 A1. The valve closure is stepped on the outside like a staircase and, in the closed position of the ventilation unit, is supported on a correspondingly stepped inner wall of the housing. The dimensions and design of the steps are such that, in the closed position of the ventilation unit, they extend circumferentially in the form of a ring, leaving gaps with widths of 0.01 mm to 0.50 mm between the corresponding stepped surfaces on the valve closure and the stepped surfaces on the inner wall of the housing. All of the gaps are connected to each other, thereby forming a single, continuous, step-shaped gap extending from the contact surface into the interior of the ventilation unit and changing direction depending on the number of steps. The gaps, known as labyrinth gaps and therefore as such, act as a barrier against the penetration and penetration of liquids or low-viscosity media, especially highly fluid rubber compounds, into the interior of the ventilation unit. Even when the vent unit is closed, the valve closure protrudes slightly beyond the inside of the mold part, the protrusion being approximately 0.05 mm to 0.20 mm, which contributes to good closure of the vent unit and to the build-up of back pressure in the gap.

[0005] A further venting unit for a vulcanization mold for pneumatic vehicle tires is known from WO 2017 / 211517 A1. This venting unit has a valve stem with a frustoconical, outwardly expanding valve disc that rests against the inversely shaped expansion of the outer inner wall of the housing when the venting unit is closed. Adjacent to the valve disc, the valve stem has a cylindrical retaining portion into which a compression spring, which presses the valve stem and thus the valve disc into the open position, can fit by at least two of its turns. This measure allows for precise positioning and a good fit of the compression spring on the valve stem.

[0006] The unwanted penetration of modern rubber compounds, which are highly fluid for high-performance tires, into ventilation units due to additional heating during tire molding remains a problem that has not been adequately resolved. These particular rubber compounds leave visible traces of flash of various shapes and sizes around the ventilation unit. Furthermore, with known ventilation units, after a certain number of heating cycles, it is almost inevitable that the rubber compounds that have entered the ventilation unit will fill the ventilation unit with rubber material due to their fluidity, causing blockages in the ventilation unit, especially the compression coil springs. As a result, sufficient ventilation of the vulcanization mold is no longer guaranteed, affecting the quality of the vulcanized tire to the extent that it develops contraction points and must be rejected. The affected vulcanization mold must be removed from the tire heating press, and the ventilation unit removed and replaced with a new one. These measures force a production stop and therefore incur additional costs due to the need to install a new ventilation unit. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2020 / 211995A1 [Patent Document 2] International Publication No. 2017 / 211517A1 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention is based on the object of improving a ventilation unit of the type mentioned at the outset so as to ensure perfect ventilation over a significantly greater number of heating cycles than known ventilation units, by reliably avoiding the occurrence of flash and making the penetration of rubber compounds more difficult in particular and ensuring sufficient functioning of the compression coil spring over a large number of heating cycles. [Means for solving the problem]

[0009] The stated object is achieved according to the invention by an outer edge region of the valve disc, which seats on a seating surface in the closed position of the vent unit, having a thickness of 0.10 mm to 0.40 mm, in particular 0.20 mm to 0.25 mm, so that the vent unit can be press-fit into the bore such that the seating surface, which extends circumferentially around the outer edge of the housing, is offset inwardly relative to the inside of the mold parts by a distance of 0.05 mm to 0.35 mm, in particular 0.10 mm to 0.15 mm, and the radially outer stem part of the valve stem has an outer diameter which is 80% to 97% of the inner diameter of the housing.

[0010] According to the invention, these measures combined with one another ensure that sufficient functioning of the vent unit is guaranteed over a greater number of heating cycles than in known vent units, even in the case of rubber compounds that are significantly more fluid in the warm, unvulcanized state. Due to the corresponding adaptation of the distance between the seating surface on the housing and the inside of the mold and the thickness of the edge of the valve disc that rests on the seating surface in the closed position, the path of movement during opening and closing is very small, and when the vent unit is closed, the valve disc protrudes at most slightly beyond the inside of the mold parts, so that, on the one hand, the closing of the vent unit is optimally supported during the molding of green tires, and, on the other hand, the narrow gap that exists when the vent unit is open leaves almost no room for the intrusion of rubber material. Any intruding rubber material is prevented from advancing, still in a fluid state, into the sensitive area of ​​the compression coil spring by the equally small gap between the radially outer stem part of the valve stem and the inner wall of the housing.

[0011] Particularly preferred is a design in which the radially outer stem portion of the valve stem has an outer diameter that is 85% to 90% of the inner diameter of the housing.

[0012] In a particularly preferred embodiment, the radially outer stem portion of the valve stem has a length in a range such that the compression spring acts on this portion at a distance of 30% to 60% of the total length of the vent unit taken from the outer end of the vent unit, which also contributes to the effect that intruding rubber compound or material does not advance into the area of ​​the compression spring.

[0013] Furthermore, advantageously, the seating surface extending circumferentially around the outer end of the housing is an outer free edge of the housing, so that when the vent unit is pressed into the hole, only a portion of the wall of the hole outside the seating surface reaches the inside of the mold part. This portion of the wall of the hole has a height determined in the direction of the hole, in particular between 0.10 mm and 0.15 mm. Therefore, the vent unit is only pressed slightly inside the hole without risking damage to the housing.

[0014] Optimal seating of the valve disc on the seating surface of the housing is aided by an outer edge region of the valve disc overlapping the seating surface on the outer edge of the housing so that a gap having a width of 0.20 mm to 0.30 mm and a width of 0.04 mm to 0.06 mm remains between the edge of the edge region of the valve disc and part of the wall of the hole when the vent unit is closed.

[0015] Optimal seating of the valve disc on the seating surface of the housing, together with good mobility of the valve disc, is preferably also ensured by a seating surface that extends circumferentially around the end of the housing inside the mold part, widening outwards in a funnel-like shape and extending around the outside of the opening in the housing, formed by a continuous reduction in the wall thickness of the housing, whereby the support surface has a width of 0.20 mm to 0.35 mm.

[0016] Mobility and stability of the valve disc are also supported by the valve disc having a disc base that terminates adjacent the outer stem section with a frustoconical section of decreasing diameter, the frustoconical section having a thickness of 0.25 mm to 0.40 mm parallel to the central axis a, and the smallest diameter of the frustoconical section is after the outer stem section and is 0.20 mm to 0.40 mm greater than the diameter of the outer stem section.

[0017] For the durable functioning of the compression coil spring, it is advantageous if, according to a further configuration, a circumferentially extending support surface in the form of a ring is formed at the transition on the outer stem part of the valve stem, on which the compression coil spring is supported and in this way presses the valve stem and thus the valve disc into the open position.

[0018] The vulcanization mold according to the invention has at least one mold part with a ventilation hole into which a ventilation unit according to one or more of claims 1 to 8 is inserted. It is particularly advantageous if the mold part is a mold segment forming a segment ring for molding the tread of a pneumatic vehicle tire. Such a vulcanization mold can be used to vulcanize tires with treads made from extremely soft and therefore highly fluid rubber compounds in the warm, unvulcanized state over multiple heating cycles without a significant amount of flash occurring on the tread.

[0019] The pneumatic vehicle tire according to the present invention is vulcanized in the vulcanization mold according to claim 9 or 10.

[0020] Further features, advantages and details of the invention will now be described in more detail on the basis of the drawings which represent exemplary embodiments. [Brief explanation of the drawings]

[0021] [Figure 1] 1 shows an enlarged, partially cut-away view of the ventilation unit in a closed state. [Figure 2] 1 shows an enlarged cross-sectional representation (longitudinal section) of the housing of the ventilation unit inserted into the mold part. [Figure 3] An enlarged view of the valve stem is shown. DETAILED DESCRIPTION OF THE INVENTION

[0022] 2 shows a cross-sectional representation of a housing 6 of a vent unit 3 inserted into a hole 2 made in a mold part 1, e.g., a mold segment, of a curing mold for a pneumatic vehicle tire. Mold part 1 has an inner mold part 1a facing the mold cavity and an outer mold part, not shown. Typically, multiple mold segments form a mold segment ring for molding a profiled tread of a green tire inserted into the curing mold.

[0023] In the following description of exemplary embodiments of the ventilation unit 3, the configuration and arrangement of its components are considered with respect to their mounting position on the mold part 1, e.g., the mold segments of a segment ring for molding the tread, and designations such as "outside," "external side," and "outside" refer to positions on or near the inner mold part 1a, while designations such as "inside," "inner side," and "inside" refer to positions further inside the mold part 1 or of the ventilation unit 3.

[0024] As FIG. 1 particularly shows, the main components of each vent unit 3 are an elongated housing 6 and a similarly elongated valve insert 7 inserted into the housing 6. The housing 6 is a primarily cylindrical element having a central axis a. The valve insert 7 includes a valve stem 8, a valve disc 4 seated externally on the housing and having a disc base 9, and a compression coil spring 10. The central axis a is also the central longitudinal axis of the valve insert 7, which has a primarily rotationally symmetrical design. In the open position of the vent unit 3, at least the upper side of the valve disc 4 protrudes beyond the inner mold part 1a to allow air to enter and be conveyed into the vent unit 3. The green tire being molded in the vulcanization mold presses the valve disc 4 into its closed position.

[0025] The housing 6, shown in FIG. 2, is sleeve-shaped and rotationally symmetrical about axis a. It has an outer housing portion 6a with a specially designed end 6a1 and an inner housing portion 6b with a specially designed end 6b1. Between the two ends 6a1 and 6b1, the housing portions 6a and 6b have an equally large, constant inner diameter d1 between 1.60 mm and 2.20 mm. The outer housing portion 6a has a constant outer diameter d2, and the inner housing portion 6b has a constant outer diameter d3, which is 0.10 mm to 0.40 mm, preferably 0.15 mm to 0.30 mm, greater than the outer diameter d3, such that the wall thickness of the housing 6 at the outer housing portion 6a is greater than the wall thickness of the housing 6 at the inner housing portion 6b.

[0026] At the end 6a1 of the housing 6, which extends from 0.40 to 0.50 mm when considered parallel to the axis a, the continuous decrease in wall thickness and the continuous increase in inner diameter form a funnel-shaped, outwardly flaring opening 11 around which extends an inclined surface 11a that extends at a constant angle α of 20 to 24° relative to the central axis a. A ring-shaped, flat seat 13 extends circumferentially around the opening 11 on the outside, is oriented perpendicular to the axis a, has a constant width b of 0.20 to 0.35 mm, and an inner diameter d4 of 1.90 to 2.70 mm. The seat 13 forms the outer free edge of the housing 6.

[0027] At the end 6b1 of the inner housing part 6b, a protrusion 12 is formed on the inner wall, extending circumferentially around the end 6b1 and leaving a circular opening having a diameter d5, the diameter d5 being 0.50 mm to 0.80 mm smaller than the inner diameter d1 of the housing 6.

[0028] The press fit has the effect that the vent unit 3 seats in the vent hole 2 of the mould segment 1 in such a way that the seating surface 13, which extends circumferentially in the form of a ring around the outside of the housing 6, is offset inwards relative to and lies within the mould part inner side 1a 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 vent unit 3, the valve disc 4 comes into abutment against the seating surface 13, which extends circumferentially in the form of a ring.

[0029] As shown in FIG. 3, the valve disc 4, which is circular in plan view, has an outer diameter d6 that is 0.30 to 0.60 mm larger than the inner diameter d4 of the seating surface 13. It extends circumferentially around the disc base 9 and has a peripheral region 4a with a constant thickness s1 of 0.10 to 0.40 mm, in particular 0.20 to 0.25 mm, and a constant width of 0.20 to 0.30 mm. A narrow peripheral gap with a width of approximately 0.04 to 0.06 mm remains against the wall of the vent hole 3. This ensures that, in the closed position of the vent unit 3, the valve disc 4 rests with its edge flat against the seating surface 13. As a result of its thickness s1, the valve disc 4 in this position protrudes beyond the inner mold part 1a by approximately 0.10 mm. The disc base 9 has a frustoconical portion with a diameter that decreases towards the interior of the housing 6, with a maximum diameter d7 that is 0.40 mm to 0.60 mm smaller than the outer diameter d6 of the valve disc 4, and a thickness s2 of 0.25 mm to 0.40 mm. The inclination of the outer surface of the disc base 9 relative to the central axis a is selected so that the disc base 9 does not come into contact with the inner wall of the housing 6 when the vent unit 3 is in the closed position.

[0030] The disk base 9 is adjacent to a valve stem 8 having a cylindrical outer stem portion 8a followed by a transition portion 8b, which is followed after the inner stem portion 8c having an end portion 8c1. The outer stem portion 8a has an outer diameter d8 that is 80% to 97%, particularly 85% to 90%, of the inner diameter d1 of the housing 6. The outer stem portion 8a has a minimum length of 2.50 mm and preferably extends over 30% to 50%, particularly 38% to 43%, of the total length L8 of the valve stem 8. The valve stem 8 has its largest diameter at the outer stem portion 8a and its smallest diameter at the inner stem portion 8c. The transition portion 8b has a diameter smaller than that of the outer stem portion 8a and larger than that of the inner stem portion 8c, so that a support surface 8a1 extending circumferentially in the form of a ring remains on the outer stem portion 8a against the transition portion 8b, and one end of a compression coil spring 10 positioned around the inner stem portion 8c and the transition portion 8b is supported on the support surface 8a1. The outer stem portion 8a is preferably designed to have a length in a range such that the compression coil spring 10 acts on this portion at a distance of 30% to 60% of the total length L (FIG. 1) of the ventilation unit 3 taken from the outer end of the ventilation unit 3.

[0031] A slit 14 is formed along the central axis a in the inner stem portion 8c and extending across the end 8c1. The end portions 8c1, which are divided into two by the slit 14, have respective protrusions 15 on their outer sides so that, when the valve stem 8 is inserted into the housing 6, the protrusions 15 engage under protrusions 12 that extend circumferentially around the inner end of the housing 6. A compression coil spring 10 positioned on the inner stem portion 8c is supported by its second end inside the housing on the peripheral protrusions 12. [Explanation of symbols]

[0032] 1. Mold parts 2 ventilation holes 1a Inside of mold part 3 Ventilation unit 4-valve disc 4a Edge region 5 Tread 6. Housing 6a Outer housing part 6b Inner housing part 6a1, 6b1 ends 7 Valve Inserts 8 Valve stem 8a outer stem 8a1 support surface 8b Transition 8c inner stem 8c1 end 9 Disk base 10 Compression coil spring 11 Aperture 11a Slope 12 Protrusion 13 circumferentially extending bearing surface in the form of a ring 14 Slit 15 Protrusion a Center axis α angle (slanted surface 11a) d1 Inner diameter of housing 6 d2: outer diameter of the outer housing part 6a d3: outer diameter of the inner housing part 6b d4 seat 13 inner diameter d5 Diameter of the opening of the protrusion 12 d6 diameter of valve disc 4 d7 Maximum diameter of the frustum of the disc base 9 d8 Outer diameter of stem part 8a S1 Valve Disc 4 Thickness s2 Thickness of the truncated cone at the base of the disc b Width of seat 13 L Overall length of ventilation unit 3 L8 valve stem length 8 c distance

Claims

1. A ventilation unit (3) for insertion into a hole (2) made in and extending from the inside of a mold part (1) of a vulcanization mold for vulcanizing green tires, said ventilation unit having a closed position and an open position and comprising the following components: - a hole (2) that can be press-fitted and has a substantially constant inner diameter (d １ a housing (6) in the form of a cylindrical sleeve, having a central axis (a) and a a valve insert (7) inserted in said housing (6) and axially movable relative to said housing (6); a valve disc (4), which is part of the valve insert (7), is circular in plan view and which, in the closed position of the vent unit (3), extends circumferentially in the form of a ring around the outer end of the housing (6) and is of a constant thickness (s) so that it lies flat against a seating surface oriented at right angles to the central axis and that the valve disc (4) remains within the seating surface (13); １ a valve disc (4) seated at the peripheral region (4a) of the valve; a valve stem (8) that is part of the valve insert (7), that adjoins the valve disc (4) and that has an outer cylindrical stem portion (8a), an inner stem portion (8c) and a transition portion (8b) between the stem portions (8a, 8c); a compression coil spring (10) surrounding the inner stem portion (8c) and the transition portion of the valve stem (8), the compression coil spring (10) being supported by one end on the housing (6) and acting at its other end on the outer stem portion (8a) of the valve stem (8); In the ventilation unit (3) comprising the valve disc (4), the outer edge region (4a) of the valve disc (4) which rests on the seat surface (13) in the closed position of the ventilation unit (3) has a thickness (s) of 0.10 mm to 0.40 mm, in particular 0.20 mm to 0.25 mm. １ ), the vent unit (3) can be press-fit into the hole (2) so that the seating surface (13), which extends circumferentially around the outer end of the housing (6), is offset inwards with respect to the inner side of the mould part (1a) by a distance (c) of 0.05 mm to 0.35 mm, in particular 0.10 mm to 0.15 mm, and the radially outer stem portion (8a) of the valve stem (8) is offset from the inner diameter (d) of the housing (6) by a distance (c) of 0.05 mm to 0.35 mm, in particular 0.10 mm to 0.15 mm. １ ) is 80% to 97% of the outer diameter (d ８ ) A ventilation unit (3).

2. The radially outer stem portion (8a) of the valve stem (8) is located at the inner diameter (d １ ) is 85% to 90% of the outer diameter (d ８ 2. A ventilation unit (3) according to claim 1, characterized in that it comprises:

3. 3. The ventilation unit (3) of claim 1 or 2, characterized in that the radially outer stem portion (8a) of the valve stem (8) has a length in a range such that the compression coil spring (10) acts on said portion (8a) at a distance of 30% to 60% of the total length (L) of the ventilation unit (3) taken from the outer end of the ventilation unit (3).

4. The ventilation unit (3) according to any one of claims 1 to 3, characterized in that the seating surface (13) extending circumferentially around the outer end of the housing (6) is an outer free edge of the housing (6), whereby when the ventilation unit (3) is pressed into the hole (2), outside the seating surface (13) there is a part of the wall of the hole that reaches to the inside of the mold part.

5. A ventilation unit (3) according to any one of claims 1 to 4, characterized in that the outer edge region (4a) of the valve disc (4) has a width of 0.20 mm to 0.30 mm and overlaps the seat surface (13) on the outer edge of the housing (6) so that, when the ventilation unit (3) is closed, a gap having a width of 0.04 mm to 0.06 mm remains between the edge of the edge region (4a) of the valve disc (4) and the part of the wall of the hole.

6. 6. The ventilation unit (3) according to any one of claims 1 to 5, characterized in that the seating surface (13), which extends circumferentially around the end of the housing (6) inside the mold part, widens outward in a funnel shape and extends around the outside of an opening (11) in the housing (6) formed by a continuous reduction in the wall thickness of the housing (6), whereby the support surface (13) has a width (b) of 0.20 mm to 0.35 mm.

7. The valve disc (4) has a disc base (9) which reaches the adjacent outer stem portion (8a) by a frustoconical portion of decreasing diameter, the frustoconical portion having a thickness (s) of 0.25 mm to 0.40 mm parallel to the central axis a. ２ ) and its minimum diameter is behind the outer stem portion (8a) and is smaller than the diameter (d ８ 7. A ventilation unit (3) according to any one of claims 1 to 6, characterized in that it is 0.20 mm to 0.40 mm larger than the diameter of the slit 1.

8. On the outer stem portion (8a) of the valve stem (8), there is provided a circumferentially extending support surface (8a) in the form of a ring. １ 8. The ventilation unit (3) according to claim 1, wherein a spring (10) is formed in the transition portion (8b) on which the compression coil spring (10) is supported.

9. A vulcanization mold for pneumatic vehicle tires, having at least one mold part with a ventilation hole into which a ventilation unit according to any one of claims 1 to 8 is inserted.

10. 10. The vulcanization mold of claim 9, wherein the mold parts are mold segments that form segment rings for molding the tread of the pneumatic vehicle tire.

11. A pneumatic vehicle tire vulcanized in the vulcanization mold according to claim 9 or 10.

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