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 short mouldings in the mould.

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 un-vulcanized 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 plate, wherein the valve insert may be pushed into the closed position by pressure acting on that side of the plate, 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 plate is present, wherein the 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 lock provided with a clearance between the valve shank at one hand and the valve body at the other hand. Delimitation of the valve insert 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 of even 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 problematic.

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

Disclosure of Invention

The above aim is achieved by a vent valve to be used in venting bores of vulcanization moulds, especially for the tread area, consisting of a valve sleeve, a valve insert, formed by a shank and equipped with a plate, wherein opening the valve is delimited by a delimiter, the nature of which consists in that the valve sleeve has a hollow cylinder shape with its bottom equipped with an opening for draining the air off, and the valve insert consists of an elastic (resilient) shank, formed by a bent flat spring with a shape resembling an inverted letter U, which is at one end equipped with a surface on which the plate is attached and the free ends are shaped to elastic arms, which are changing to a clamping part formed by two incomplete half circles, which are pressed apart from each other by the flat spring of the elastic shank and of the elastic arms to form the valve opening delimiter. The length H of the valve insert with the plate in a state with no pressure load is greater by the displacement p than the length h of the valve sleeve.

According to one embodiment, the valve sleeve consists of two undetachably joined parts. The sleeve is formed by a cylinder and a drawn sheet part, which form cavities for fixation and movement of the valve. They are undetachably joined by compression moulding. The valve insert is formed by a flat

spring and a plate, which are undetachably joined. Movement of the plate is allowed by elastic deformation of the flat spring.

The valve insert according to a further embodiment can be produced as a single rotational component.

The space between the incomplete half circles is necessary when assembling the valve, where both incomplete half circles are pressed against each other and the valve insert is inserted from the side of the vulcanization mould into the valve sleeve.

The vent valve consists of only two basic components, namely the valve sleeve and the valve insert, formed by shaping a flat spring. The valve insert can be pushed into a closed position by pressure acting on the outer side of the plate, wherein the valve insert is not moved, but it is only deformed in the area of the elastic shank and elastic arms. The movement into the position of open valve, when no pressure is acting in the direction from the cavity of the vulcanization mould, is ensured by the flat spring, of which the valve insert is created. The amount of displacement (p) is given by a difference of lengths (h, H) of parts of the valve sleeve (h) and the valve insert (H).

After pressing-in such valves into the vulcanization mould, each of the valves is pushed into closed position when the rubber mixture is entering while creating the pattern of tire-tread of the tyre semi-finished product, and vice versa, each of the valves is pushed into its open position when removing the finished tyre by the action of the flat spring, from which the elastic shank and elastic arms of the valve insert are formed.

To further improve cleanness and functionality of the cooperating elements, it is possible to furnish certain surfaces with an antiadhesive or anticorrosive layer.

As dismounting of valves 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 valve opening delimiter, 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 inserting the valve

insert into the sleeve under pressing the two incomplete half circles of the clamping part against each other.

An overview of figures in the drawings

Fig. 1 shows a longitudinal section through the vent valve according to the present invention.

Fig. 2 shows a view of the valve insert without the plate in a perspective representation.

Examples of invention embodiments

Example 1

The vent valve, shown in Fig. 1 , consists of a valve sleeve (5), which has cylindrical shape and is provided with a cavity. Valve sleeve (5) consists of a cylindrical part (5-1 ) and a drawn (metal) sheet part (5-2), which has an opening in the bottom (5-5) for draining air off. These parts are undetachably joined by pressing and form the valve sleeve (5), equipped at the side, which will be in use oriented into the mould cavity, by a conical surface (5-3). The opening in the bottom (5-5) allows the air to escape from the mould. In the cavity of the valve sleeve (5), there is located a valve insert (4), which is formed by bending a flat spring and consists of an elastic shank (4-3) having a shape of letter U, which is in the bent part equipped with a surface for attaching the plate (4-1 ). Free ends are shaped and form elastic arms (4-6), which change into the clamping part (4-5), formed as two incomplete half circles, abutting the inner wall of the part (5-2) and bottom (5-5) of the valve sleeve (5).

Plate (4-1 ) of the valve insert (4) is equipped with a conical surface, which is after embedding the valve into the vulcanization mould oriented to its inner space. This conical surface of the plate (4-1 ) can be pressed against the conical surface (5-3), formed in the corresponding part of the valve sleeve (5), whereby both the elastic shank (4-3) and elastic arms (4-6) will deform, thus closing the vent valve. The other way round, when pressure in the inner part of vulcanization mould on

plate (4-1 ) is released, elastic shank (4-3) and arms (4-6) of the valve insert (4) straighten and plate (4-1 ) is displaced into the open position of the valve.

Opening the valve is delimited by the fact that the clamping part of the valve insert is pressed by the force of the bent spring of elastic shank (4-3) against the inner wall of part (5-2) of the valve sleeve (5). If no pressure from the inner space of the vulcanization mould is acting on the plate (4-1 ), the valve is open and air may escape from the vulcanization mould through an opening existing between the conical surface (5-3) and the corresponding conical surface, created at the bottom part of the plate (4-1 ). During opening or closing the valve insert (4) is not moving in the valve sleeve (5), but it is deformed in the area of the elastic shank (4-3) and elastic arms (4-6). The length of the valve insert (4) including the plate (4-1 ) in the unloaded state is somewhat longer than the length of the valve sleeve (5).

The upper surface of the clamping part (4-5) at the elastic arms (4-6) may be equipped with a conical surface to facilitate dismounting of the valve insert (4).

Dismounting of the valve insert (4) is performed by knocking the valve insert (4) out into the inner space of the vulcanization mould.