Vent valve to be used in venting bores of vulcanization moulds

Technical Field

The invention concerns a vent valve to be used in venting bores of vulcanization moulds for production of technical rubber products, especially for tyre production. Vent valves according to the present invention are particularly suitable to be used in vulcanization moulds for tyre production for the tread area to prevent forming depressions or lateral flow projections.

Background Art

Moulds for tyre vulcanization are equipped with venting bores, through which air escapes, so that semi-finished tyre placed in the mould by pressure acting from the side of mould cavity can acquire the shape corresponding to the tool inserted in the vulcanization mould. This unvulcanized semi-finished product moves the air to the mould circumference, where it escapes from the mould. At the same time the tyre material enters the venting bores and projecting excess rubber results, which must be removed following the vulcanization.

Insufficient removal of air from the vulcanization mould causes faults on the finished products, both depressions are formed in the tread area and the material may be insufficiently heated and thus vulcanization of the semi-finished product may be incomplete.

Vent valves and vulcanization forms equipped with vent valves are known from EP 0774 333 (CZ 291837), where the vent valve for venting bore of the vulcanization mould contains a movable valve insert with a valve shank and a disk, wherein the valve insert may be pushed into the closed position by pressure acting on that side of the disk, which is oriented to the cavity of the vulcanization mould, into which the vent valve is built-in, and vice versa, the valve insert can be moved by means of a spring into an open position, if no pressure acting from the cavity on the valve disk is present, wherein movement of the valve insert is delimited by a stop, arranged at the end of the vent valve oriented away from the cavity, for restricting the valve insert movement into the open position to a path shorter than 2 mm, wherein, for the purpose of a possibility to dismount the valve insert, the stop is realized as a snap connection provided with a clearance between the valve

shank at one hand and the valve body at the other hand. Delimitation of the vent valve path is ensured by the snap lock. The snap lock is preferably located on the valve shank or it is inserted into the valve body. A disadvantage of this solution is that the vent valve consists even of four components, namely of a valve body, a valve insert, a wound spring and a flexion spring, which represents the snap lock. Disassembly of some embodiments of the vent valve according to the invention is also problematic.

The aim of the present invention is to create such vent valve, which will provide for reliable air venting of a vulcanization mould, will consist of possibly the simplest parts, will be simply assembled and disassembled and simultaneously, its price will be acceptable.

Disclosure of Invention

The above aim is achieved by a vent valve intended for venting bores of vulcanization moulds, especially for the tread area, consisting of a valve sleeve, in which a valve insert and a wound spring are movably located, wherein the valve insert is formed by a valve shank, which is equipped at one end with a disk and at the other end with a conical surface changing into backwards oriented conical end, and the valve insert movement is delimited by a delimiter of opening the valve, the nature of which consists in that the inner surface of the valve sleeve is in its part further apart from the disk provided with conical surface, oriented away from the disk. Delimiter of the movement of the valve insert (of opening the valve) is formed by two mutually cooperating conical surfaces or parts of conical surfaces, wherein one of the conical surfaces is the above mentioned inner surface of the valve sleeve and the other conical surface is a conical surface created at the end of the valve shank of the valve insert, which is oriented against the mentioned conical surface or part of conical surface of the valve sleeve.

According to a preferred embodiment, the valve sleeve consists of a part, the outer diameter of which corresponds essentially to that of the bore of the vulcanization mould for embedding the valve, and of a part having a slightly smaller outer diameter. That part of the valve sleeve, the outer diameter of which corresponds essentially to that of the bore of the vulcanization mould for embedding the vent valve, is located more closely to the disk of the valve insert, while the disk of the valve insert extends into the inner space of the vulcanization mould. The second part of the valve sleeve, which has a smaller outer diameter than that of the bore for embedding the vent valve, is located further away from the disk of the valve insert, thus more closely to the outer space of the vulcanization

mould. This part of the valve sleeve having the smaller diameter is provided with at least two longitudinal openings or notch grooves.

The valve sleeve, as described above, may be formed as a single rotational component or it may be formed by connecting, for example by pressing together, a separately produced rotational part as the part having the greater outer diameter, and a part having the smaller outer diameter produced as a drawn piece.

Each of the longitudinal openings uniformly spaced along the circumference of the part of the valve sleeve having smaller outer diameter is provided with a springy shaped projection, oriented to the inner space of the sleeve, wherein each shaped projection contains a part of a conical surface on the inner wall of the valve sleeve for cooperation with the conical surface of the valve insert.

The valve insert, formed by a shank, which is provided at one end with a disk and at the other end with a conical surface changing into backwards oriented conical end, may be produced as a single rotational component or the valve insert disk may be produced separately and afterwards detachably attached to the valve insert shank.

The vent valve consists of three basic components, namely of a valve sleeve, a valve insert and a wound spring. The valve insert may be pushed into the closed position by pressure acting on the outer side of the disk, and the movement into the open position of the valve, when no pressure is acting in the direction from the inner of the vulcanization mould, is ensured by the wound spring, acting on the lower side of the disk. The displacement range (p) is given by the difference of the lengths (h, H) wherein the length of the valve sleeve is h and the length of the valve insert is H.

The part of the valve sleeve, which is oriented to the cavity of the vulcanization mould, has greater outer diameter than the part of the valve sleeve, which is located more closely to the outer side of the vulcanization mould, and the part of the valve sleeve having smaller diameter is provided with longitudinal notch grooves or openings provided with shaped projections extending into the inner part of the sleeve. Openings or notch grooves in this part of the sleeve serve for better escape of air from the vulcanization mould and for creation of the necessary elasticity of the valve sleeve, which is needed when mounting and dismounting the vent valve into and out of the mould.

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The outer surface of the part of the valve sleeve with smaller diameter (the narrower part) is formed by a conical surface or rotational surface having profile of a parabola curve.

Movements of the valve insert are delimited by a delimiter, arranged at the end of the vent valve, wherein the delimiter restricts the movement of the valve insert into the open position. Delimiter of opening the valve (displacement of the valve insert) is meant as abutment of two conical surfaces or parts of conical surfaces facing each other, wherein one of them is a part of the inner surface of the valve sleeve and the other is a part of the valve insert.

Bending of the valve sleeve when mounting and dismounting the valve insert is allowed by the notch grooves (at least 2) on the circumference of the valve sleeve mantle or deformation of the shaped projections (at least 2), containing parts of conical surface, in the longitudinal openings of the mantle, if this part has been produced as a drawn piece according to another embodiment of the present invention.

After pressing such valves into the vulcanization mould, each of the valves is pushed into the closed position by the rubber mixture of the tyre semi-finished product when pressure is applied, and vice versa, each of the valves is pushed into its open position by means of a wound spring when the finished tyre is removed.

For further improvement of cleanness and functionality of the cooperating elements, it is possible to furnish certain surfaces with anti-adhesive or anticorrosive layer.

As dismounting of venting valves from the mould is necessary only rarely, it is always sufficient to fix the valves in the segments of the vulcanization mould by pressing them in. For that purpose, diameter of the valve in dismounted state should always be slightly greater than the inner diameter of the respective venting bore.

An advantage of the vent valves according to the present invention is that the valve insert can be, despite the delimiter of the opening movement, easily dismantled by a force acting in the direction of the valve insert axis into the cavity of the vulcanization mould, and the valve can be easily assembled by acting of a force in the opposite direction.

An overview of figures in the drawings

The attached drawings show vent valves according to the present invention in various embodiments.

Figs. 1.1 , 1 .2 and 1.3 show the vent valve according to Example 1 , where Fig. 1.1 shows a section through the vent valve, Figs. 1.2 and 1 .3 are the outside views of the vent valve, wherein in Fig. 1 .2 the broken lines indicate the parts located inside the valve sleeve, which are not visible from outside.

Figs. 2.1 and 2.2 show the vent valve according to Example 2, where Fig. 2.1 shows a section through the vent valve, Fig. 2.2 is the outside view of the vent valve.

Figs. 3.1 and 3.2 show the vent valve according to Example 3, where Fig. 3.1 shows a section through the vent valve, Fig. 3.2 is the outside view of the vent valve.

Examples of invention embodiments

Example 1

The vent valve, shown in Fig. 1.1 , consists of a valve sleeve (5), which has cylindrical shape and is provided with a cavity. The outer diameter of that part (5-1 ) of the valve sleeve (5), which, when used in the venting bore of a vulcanization mould, is located more closely to the inner space of the mould, is essentially the same as diameter of the bore in the vulcanization mould for embedding the valve, and is greater than the outer diameter of the second part (5-4) of the sleeve (5), which is oriented outwards of the mould. This part (5-4) of the sleeve (5) having smaller outside diameter is provided with at least two longitudinally oriented notch grooves (5-5) (Fig. 1.3), running from the sleeve end to its part (5-1 ) having greater outer diameter. These notch grooves allow air to escape from the vulcanization mould into the space created between the cylindrical bore in the vulcanization mould and the tapered part (5-4) of the valve sleeve (5) and further away from the vulcanization mould. This space is necessary when replacing the valve insert (4). The valve insert (4) is located in the cavity of the valve sleeve (5). The valve insert is a rotational component formed by a disk (4-1 ), shank (4-3) and conical surface (4-2). When pressure is acting from the cavity of the vulcanization mould, disk (4-2) abuts that edge of the valve sleeve (5), which oriented inwards the vulcanization mould. This edge of the valve sleeve (5) is equipped with conical surface (5-3). The valve sleeve (5) is at its inner surface in the lower part provided with a stop surface (5-6) for the wound spring (6) and

an inner conical surface (5-2), which together with the conical surface (4-2) of the valve insert (4) forms the delimiter for opening the valve.

On the shank (4-3) of the valve insert (4), there is located the wound spring (6), which ensures open position of the vent valve, if there is no pressure acting in the vulcanization mould. The wound spring (6) bears with one end against the stop surface (5-6) and with the other end against the lower part of the disk (4-1 ). The lower part of the disk (4-1 ), abutting the conical surface (5-3) of the valve sleeve (5), is provided with a corresponding conical surface. The valve insert (4) is provided with a conical surface (4-2), changing into a backwards oriented conical end, and the valve sleeve (5) is in the tapered part (5-4) provided with a facing inner conical surface (5-2), abutting the conical surface (4-2) of the valve insert (4), to prevent pushing the valve insert (4) out of the valve insert (5) by the wound spring (6), so that the delimiter of movement of the valve insert (4) is created. The inner conical surface (5-2) of the sleeve (5) is interrupted only at the positions of the longitudinal notch grooves (5-5).

The disk (4-1 ) of the valve insert (4) is provided with a conical surface, which, when pressure is acting on the disk (4-1 ) which is after building it in the vulcanization mould oriented into its inner space, can be forced against the conical surface (5-3), created in the corresponding part of the valve sleeve (5), thus closing the vent valve, and vice versa, if pressure in the inner part of the vulcanization mould acting on the disk (4-1 ) is released, the valve insert (4) is displaced by the wound spring (6) into the open position.

Movements of the valve insert are delimited by the valve delimiter, created by cooperation of the conical surface (4-2) of the valve insert (4), arranged at the end of the shank (4-3), which is further away from the inner space of the vulcanization mould, with the inner conical surface (5-2) of the valve sleeve (5).

Longitudinal notch grooves (5-5) allow in cooperation with the valve insert (4), the wound spring (6) and the space in the bore of the vulcanization mould for air better to escape from the inner space of the vulcanization mould and they ensure elasticity and opening

(releasing) of this tapered part (5-4) of the valve sleeve (5) to facilitate the valve dismantling when replacing the valve insert (4) and spring (6). Valve insert (4), possibly with the wound spring (6), is removed from the valve sleeve (5) by knocking it out inwards the vulcanization mould.

Example 2

The vent valve, shown in Fig. 2.1 , consists of a valve sleeve (5) of cylindrical shape, which is provided with a cavity. The valve sleeve (5) is formed by tight connection, for example by pressing together two hollow cylindrical parts, namely a machined rotational body as part (5-1 ) having greater outer diameter, and a drawn piece (tapered part (5-4)) having at least in a part of it smaller outer diameter in comparison with the above part. Outer diameter of that part of the valve sleeve (5), which when used in the venting bore of the vulcanization mould is located more closely to the inner space of the mould, is essentially the same as diameter of the bore for embedding the vent valve of the vulcanization mould, so it has greater diameter than the outer diameter of the second part (5-4) of the valve sleeve (5), which is located closer to the outer space. This part (5-4) of the valve sleeve (5) having smaller outer diameter is provided with two longitudinal openings, while material of the sleeve wall extends into the inner space of the valve sleeve (5) and creates a shaped projection (5-7). This shaped projection (5-7) contains at the inner side the inner part of the conical surface (5-2) to cooperate with the conical surface (4-2) of the valve insert (4), thus creating the delimiter for opening the vent valve. Longitudinal openings (shown in Fig. 2.2) allow air to escape from the vulcanization mould into the space created between the cylindrical bore of the vulcanization mould and the tapered part (5-4) of the valve sleeve (5) and further away from the vulcanization mould. In the cavity of the valve sleeve (5), there is located the valve insert (4). The valve insert is a rotational component formed by the disk (4-1 ), shank (4-3) and conical surface (4-2). When pressure is acting from the vulcanization mould cavity, disk (4-1 ) abuts that edge of the valve sleeve (5), which is oriented inwards the vulcanization mould. On the shank (4-3) of the valve insert (4), there is located the wound spring (6), which ensures open position of the vent valve, if no pressure is acting inside the vulcanization mould. The wound spring (6) bears with one end against the stop surface (5-6) of the spring and with the other end against the lower part of the disk (4-1 ).

The function of the vent valve according to the embodiment, shown in Figs. 2.1 and 2.2, is the same as described in Example 1 for the embodiment according to Figs. 1.1 to 1 .3.

The tapered part (5-4) of the valve sleeve is provided with two oblong openings, in which shaped projection (5-7) is created from the sleeve wall material, which projection includes a part of conical surface (5-2). Movements of the valve insert are delimited by cooperation of the conical surface (4-2), arranged at the end of the shank (4-3), which is further away

from the inner space of the vulcanization mould, with parts of the conical surfaces (5-2), created on the shaped projections (5-7), created in the longitudinal openings of part (5-4) of the valve sleeve (5).

Openings, provided with the shaped projection (5-7), in the tapered part (5-4) of the valve sleeve (5) allow in cooperation with the valve insert (4), the wound spring (6) and the space in the bore of the vulcanization mould air better to escape from the inner space of the vulcanization mould and the shaped projection (5-7) ensures elasticity of this part of the valve sleeve (5) to facilitate the valve dismantling when replacing valve insert (4) and spring (6). The valve insert, possibly with the wound spring, can be removed from the valve sleeve (5) by knocking it out inwards the vulcanization mould.

Example 3

Fig. 3.1 shows a further embodiment of the vent valve, which consists of a valve sleeve (5) of cylindrical shape, which is provided with a cavity. Outer diameter of that part (5-1 ) of the valve sleeve (5), which, when used in the venting bore of a vulcanization mould, is located more closely to the inner space of the mould, is essentially the same as diameter of the bore in the vulcanization mould for embedding the valve, and is greater than the outer diameter of the second part (5-4) of the sleeve (5), which is oriented outwards of the mould. This part (5-4) of the valve sleeve (5) having smaller outside diameter is provided with at least two longitudinal notch grooves (5-5) (Fig. 3.2), running from the lower (outer) end of the sleeve (5) to its part (5-1 ) having greater outer diameter. These notch grooves (5-5) allow air to escape from the vulcanization mould into the space created between the cylindrical bore in the vulcanization mould and the tapered part (5-4) of the valve sleeve (5) and further away from the vulcanization mould. This space is also necessary when replacing the valve insert (4).

In the cavity of the valve sleeve (5), there is located the valve insert (4). The valve insert is a rotational component, which is in this embodiment formed by the disk (4-1 ) as a separately produced part, attached to the upper part of the shank (4-3) and conical surface (4-2), which changes to backwards oriented conical end. When pressure is acting from the vulcanization mould cavity, disk (4-1 ) abuts that edge of the valve sleeve (5), which is oriented inwards the vulcanization mould. This edge of the valve sleeve (5) is equipped with inner conical surface (5-3). The valve sleeve (5) is at its inner surface in the lower part provided with a stop surface (5-6) for the wound spring (6), and an inner conical

surface (5-2), which together with the conical surface (4-2) of the valve insert (4) forms the delimiter for opening the valve.

The function of the vent valve according to this embodiment is the same as already described function of the valve according to Example 1 , with the difference that when opening or closing the valve, only disk (4-1 ) is moving, which is made as a separate part of the valve insert (4). In the open position, there is space created between the lower part of the disk and the end of the shank (4-3), wherein the height of this space corresponds to the amount of displacement p, i. e. to the valve travel. During the action of the valve, the shank (4-3) of the valve insert stays in this case at rest.