Tyre vulcanizing mould provided with venting means

The invention relates to a vulcanization mold for the production of pneumatic tires with a variety between 1,000 and 3,000 of ventilation holes.

It is known that each tire vulcanization mold must be vented so that the green tire attaches itself to the shaping tools of the vulcanization mold by inflating from the inside. The blank drives air in front of it radially on the outside; where this air cannot flow out, it is compressed to a pressure just below the applied inflation pressure. Although the application of pressure leads to an increase in the air dissolving capacity in the rubber, the air dissolving capacity is still extremely small even then. The remains of air, which have neither been removed nor dissolved in the rubber, form local cushions between the inner contour of the vulcanization mold and the outer contour of the green tire.

The lack of direct contact at these locations between the vulcanization mold, hereinafter simply referred to as "mold", and the blank not only leads to the indentation of the blank at such a location, but also to a reduced heating due to the much lower thermal conductivity of air to the metal the form; this can lead to insufficient sulfur crosslinking and cause material failure in the company.

All tire manufacturers therefore take great care to deflate their molds.

Tread patterns of tires are usually very detailed with longitudinal and transverse grooves as well as numerous, sometimes even sinuous, cuts that separate different positives such as blocks and bars. From a pneumatic point of view, the generally numerous projections of the shape radially inward, which form the later tire negatives, divide the air volume to be discharged into chambers which are insulated from one another, each of which requires at least one ventilation channel.

According to the oldest and still predominant technology, a large number of thin bores, which run approximately perpendicular to the surface to be molded, are arranged in the molding tools for venting molds, which open into ventilation channels of the outer components of the mold. These holes have a diameter of approximately 0.7 to 1.5 mm depending on the required drilling depth and thus on the size of the tires. A typical car summer tire shape has about 1,500 vent holes, a typical car winter tire shape has about 2,500 vent holes.

These holes have a pleasantly low flow resistance for the air to be removed; However, even for the tougher rubber, their flow resistance is still so low that after the expansion pressure has been built up, significant amounts of rubber flow into the ventilation holes until crosslinking prevents further flow. As a rule, it is possible, by adjusting the speed of vulcanization (by means of temperature, accelerator dosage, sulfur dosage), diameter of the ventilation holes and crack resistance of the vulcanized bristle-like shoots, to ensure that the shoots do not tear off the tire when the tire is removed from the mold; if they tore off, they would get stuck in their respective ventilation hole and would prevent the correct ventilation of the tire subsequently to be vulcanized in this form.

There are many customers, especially in the upper price segment, who do not like the bristle or hedgehog-like appearance of the tires removed in this way with their many sprouts. This is the main reason why in many tire series the shoots are removed before delivery. Numerous techniques are known for this, some reminiscent of shaving, others reminding of planing and still others reminding of grinding. For the purpose of particularly attractive cutting edges, cold embrittlement of the shoots to be separated is also known. - However, all of these techniques involve considerable costs.

For this reason, there has long been the task of specifying devices and / or methods which lead to tires without a drive without expensive subsequent removal from the drive. Several proposals for solving this task have already become known:

From US Pat. No. 3,377,662 dated April 1968, it is known to insert a pin with a star-shaped cross-section in each of the ventilation holes known per se, the outer envelope circle of which is slightly larger than the inside diameter of the ventilation holes, so that each pin is held in its bore by an interference fit . The formerly one, relatively large, cross-section per bore thus becomes several channels, which are significantly smaller in cross-section, with even the sum of the cross-sectional areas of the individual channels thus produced being approximately 10 times below the cross-sectional area of ​​the vent hole thus throttled, the individual cross-sectional areas approximately the factor 100.

This proposal assumes that drills cannot exceed a certain degree of slenderness, i.e. a drill length in relation to the diameter, because otherwise they would buckle. Therefore, the diameter of a vent hole cannot be chosen to be as small as desired.

For the desired ventilation function, however, the flow cross-sections are likely to be significantly smaller than can be produced with a drill; the shoots would correspondingly become smaller. The main idea of ​​this document is to subsequently restrict a hole that is too wide for manufacturing reasons to some much narrower channels. EP-PS 0 518 899 is of almost identical content.

European patent application 0 311 550, published in April 89, teaches to insert in each of the known ventilation channels a pin with a circular cross section and a slightly smaller outside diameter than the inside diameter of the ventilation hole on the tire-shaping side. In a further outlying area, each ventilation channel has projections which hold the respective pin, probably through an interference fit.

Here, too, it is a matter of a subsequent narrowing to wide channels by using one pin each. Contrary to the previous document, this solution does not distribute the remaining flow cross-section of a vent hole over many small gaps lying on a ring, but results in a coherent, narrow, circular gap. While the star-like outer profile of pins according to the previous document can be obtained inexpensively by pulling a wire through a corresponding die, the wedge-hub-like inner profile of the ventilation channels according to EP-PA 0 311 550 requires the transition from drilling to more expensive shaping or milling.

EP-PA 0 591 745 proposes to use open-pore material at certain points of the mold which shape the tire and have a pore size of less than 0.05 mm. This porosity should be large enough to allow air to escape quickly enough and small enough to prevent rubber from penetrating into the pores with subsequent blockage.

However, our own experience suggests that too many pores clog after too few vulcanized tires. Pore ​​cleaning is almost impossible.

From European patent application 0 440 040, published in August 1991, it is known to separate shaped segments along such lines into sub-segments which connect locations with ventilation requirements to one another. Here, too, the idea is to keep the ventilation ducts narrower so that the increased flow resistance for the rubber allows only a very small inflow path.

Compared to the known state of the art, this measure allows the ventilation gaps to be cleaned, the shape segment concerned being broken down into its sub-segments. However, such shapes are very expensive due to the large number of mating surfaces, which, moreover, in most modern tire treads could not be flat but should be curved in accordance with the transverse groove course of the finished tire.

A special arrangement of such venting gaps, referred to there by reference number 18, is known from DE-OS 39 14 649, which is older and subsequently published compared to the above-mentioned document, and is located directly at the foot of the ribs (column 2, line 43).

The European patent application 0 451 832, which is somewhat younger in priority than the European patent application 0 440 040, also teaches the arrangement of ventilation gaps by means of the puzzle-like fine division of the mold segments. DE-OS 19 33 816 (see claim 6), JP-A-76 91 423, JP-A-51-119776 and US Pat. Nos. 4,691,431 and 4,708,609 also point in this direction.

It has also been repeatedly suggested to create a vacuum in the tire vulcanizing mold before the tread pattern is impressed. A much smaller number of ventilation channels could suffice for this, even a single one with sufficient time to evacuate; the tires to be removed from such a shape are therefore essentially free of sprouts and there is no need for cleaning.

Disadvantageously, however, given the size and the numerous parting levels of vulcanizing molds for tires, it is only possible to generate a vacuum under 0.1 bar with exorbitant effort; at 0.1 bar there are still residual air quantities that exceed the absorption capacity of the rubber through solution; However, you still cannot do without ventilation ducts. - The same is proposed in US Patents 4,573,894, 4,597,929, 4,881,881 and 5,283,022 as well as that of DE-OS 22 10 099 and European Patent Application 0 468 154. EP-PA 0 414 630 ties in with this and also teaches how to remove the fully vulcanized tire the opposite, that is, a gas injection into the mold through the "ventilation" channels. The latter - without vacuum application - is previously known from US Pat. No. 4,812,281.

The German laid-open documents 22 00 314 from July 1973, 25 24 538 from December 1976 and 31 42 288 from May 1983 disclose devices for the production of non-driven injection molded parts. A single ventilation channel is arranged concentrically to the axis of rotation of the cavity and opens into an evacuator, which creates a largely vacuum in the mold before the polymer mixture starts to be injected. The residual air pressure can be very low because there is only one sealing surface, which also has a short arc length. Shortly after the start of injection, i.e. before the cavity is completely filled with the polymer mixture, a valve with a conical valve disc closes the ventilation channel.

The valve closure is effected directly (DE-OS 22 00 314 and DE-OS 31 42 288) by the impact of the polymer mixture flow on the cavity-side surface of the valve plate or indirectly (DE-OS 25 24 538) by the delivery pressure acting on one side caused bending of a plate, which is transferred to the valve plate by a sliding mechanism. The very early closing of the valve ensures that none of the polymer mixture penetrates into the gap between the seat surface and the conical surface of the valve disc facing away from the cavity. In this way, complete freedom from streaking is achieved and a sticking problem of the valve is avoided from the outset; therefore, a weak coil spring is sufficient to open the valve when the finished vulcanized part, in particular the rubber sealing ring, is removed.

This ventilation technology lives with the problem that the amount of residual air still present in the mold can no longer escape from the - early - closing time of the valve, but is compressed. This disadvantage is acceptable in good injection molds because very small amounts of residual air can be reached. In addition, the extruders that deliver the polymer mixture reach between 100 and 400 bar, usually around 300 bar, depending on the type of delivery pressure. As a result, the extremely small amount of residual air in injection molds can be compressed enormously, so that the residual air volume has shrunk to practically zero from here at the end of the filling process. This also increases the air absorption in the rubber through solution.

Because such small amounts of residual air in tire molds are not possible due to the larger volumes of approx. Three orders of magnitude and the numerous, sometimes abutting sealing surfaces, and because the inflation pressures for car and motorcycle tires are only around 10 bar, for heavy truck Tires are around 15 bar, this non-expanding injection molding is not transferable to the manufacture of pneumatic tires.

From DE-OS 36 22 598 the arrangement of vent holes in a mold for multi-component plastics on a manually pushable plunger is known.

In conclusion, the overview of the prior art is that some of the proposals cited above have brought small improvements, but no all-round satisfactory solution for venting tire shapes has been given, which is most clearly shown by the fact that most tires are still used today show disruptive shoots after removal from the mold.

Therefore, the inventors have made it their task to create a vulcanization mold that enables the production of practically non-driven pneumatic tires without machining.

The object is achieved in that each vent hole contains a valve which is designed so that it is closed by the approach of the blank surface and is opened again during demolding, so that the next blank to be vulcanized is embossed again with the valves open. Each of the valves to be arranged in a vent hole according to the invention preferably has a movable valve insert with a shaft and a plate arranged thereon, which is designed as a truncated cone on the side facing away from the cavern and with an at least substantially flat surface on the side facing the cavern, the truncated surface the valve disc with an adapted surface of the relevant segment of the vulcanization mold or of a valve housing cooperates.

Each of the valves is pressed into the closed position when the polymer mixture strikes while embossing the green tire, which is preferably a pneumatic tire, but conversely a weak spring pushes each of the valves into the open position when the finished tire is removed.

While in the case of the injection molds evacuated via a single valve, which is about twice to three times as large, the valve closes "too early", in the solution presented here for preferably evacuator-free ventilation of tire vulcanization molds, the numerous tiny valves close much more precisely - in particular not too early, which is the rule Safety is extremely important - because they are each arranged at the end of a polymer flow branch and not near the beginning. It is accepted that some of the valves close a shade too late for a 100% prevention of drive-out. The toroidal shoots accepted in this way have had an average ring diameter of 2.8 mm, a ring width of approx. 0.3 mm and a height of approx. 0.25 mm in previous attempts; the shoots are so small that, at least in most market segments, a subsequent shoot removal is unnecessary.

This results in savings in working time, space requirements and expensive waste of rubber to dispose of; these savings exceed the cost of increased capital requirements due to valve costs. In particular, the saving in working time surprised internal critics of the invention, who initially feared that the working time saved on the old grinding machines would be more than compensated for by the maintenance outlay for the valves, which were used in an insanely high number. Surprisingly, however, the first test form did not show any need for maintenance on any of the approximately 1,600 small valves.

In comparison to the previously prevailing, nail-like shoots, which have become much less inconspicuous by the invention, their appearance corresponds to those which remain on the tire in accordance with EP-PA 0 311 550 discussed on page 4.

In contrast to the many previous proposals with narrow but rigid ventilation gaps, no cumulative rubber or rubber or charring residues are observed on the device according to the invention. The surprising cleanliness of the interacting valve seat and valve disk surfaces seems to be due to the fact that, on the one hand, the amount of rubber that has penetrated into the valve gap leads to a rapid and almost complete sealing against further rubber flow due to the valve closing movement, so that the amount of rubber that has penetrated per gap length is much smaller than in the case of the previous proposals for ventilation via rigid gaps and, secondly, that the outlets of the shoots, which at first appear to be particularly at risk of being torn due to their delicacy, do not tear off, because after the vulcanization, the opening of the valve, best driven by a spring, is no longer trapped by any shoots; in particular, the rubber compression due to the expansion pressure no longer has an effect - with the otherwise usual clamping action.

In order to further increase the cleanliness of the two interacting, preferably conical, surfaces on the valve seat and plate, it is possible to coat these surfaces with an anti-adhesive coating; As an antiadhesive, for example, as is known from DE-OS 39 03 899 and EP-PA 0 228 652, polytetrafluoroethylene or polydimethylsiloxane are recommended.

Instead of the forced opening (ie not by pulling out by means of the adhesion between the finished tire and valve plate but by means of a valve drive) by a spring, a pneumatic drive by blowing air into the ventilation channels would also be possible as an equivalent, but appears more complex. Although EP-PA 0 414 630 and US Pat. No. 4,812,281 already show air blowing in during demolding, there are no valves there, and consequently there is no valve drive, and no pneumatic drive support either.

For the rational production of vulcanization molds according to the invention and for the purpose of simple valve replacement, should a valve fail, it is recommended that, according to claim 3, each valve has its own, preferably cylindrical, housing, against which all movable components of the valve are held captive. In this context, "captive" means that no individual parts can be lost when shipping from the valve manufacturer or when screwing in or screwing out; this does not mean that the valve can no longer be dismantled. At least in the ongoing testing stage, it has proven useful that the valve disk can be easily dismantled for regular (although so far unexamined) inspection, for example via a snap lock, as detailed in claims 7 to 13 and in two exemplary embodiments.

The valve housings (12) preferably have an outer diameter between 2.0 and 6.0 mm, more preferably between 2.0 and 4.5 mm for car tires, and more preferably between 3.0 and 6.0 mm for heavy trucks.

Since disassembly is rarely required, it is recommended that the valves are fastened in the mold segments less so than a pair of threads rather a press fit; For this purpose, the outer diameter of the valve housing should be larger than the inner diameter of the associated vent hole in the mold segment when the valve is removed. With a housing outer diameter of 3.5 mm, the oversize should be 50 to 150 µm compared to the bore, correspondingly more with a larger housing diameter and less with a smaller housing diameter. These dimensions refer to the material pairing of steel for the valve housing and aluminum for the segments with the receiving bores; the expert knows that he stiff material pairing, z. B. steel / steel, the oversize has to choose correspondingly smaller.

Preferably, according to claim 5, each valve of the vulcanization mold according to the invention has a stop on the side of the valve stem facing away from the cavern, which limits the movement of the valve insert into the open position, more preferably for valves in the form of passenger car tires in a path between 0.3 and 1, 2 mm and for molds for heavy truck tires in a path between 0.5 and 2.0 mm. The extent to which the valve opening movement is limited is also referred to below as the valve lift. By means of this travel limitation - in cooperation with a tension-free spring length greater than the installation length of the spring in the most open position possible - it can be achieved that the spring is always under tension or force at its force introduction surfaces There is pressure, which avoids a spring rattle, as it would occur with a spring attachment with play, in a simple and effective way. In addition, if the valve closing path were too large, the valve closure would occur with a delay and cause an excessive expulsion between the cooperating, preferably frustoconical, sealing surfaces.

Assuming that all test heaters on all valves have so far been successful, at least so far an easy inspection and, if necessary, replacement option for the valve inserts still seems desirable. Therefore the valve insert should come out of the valve housing or - With a housing-free arrangement of the valve inserts directly in the respective mold segment - be removable from the mold segment, even when using a stop to limit the valve closing path; just such a stop stands in the way of dismantling in the direction of the cavern.

As a solution to this problem, it is proposed to make the attachment of the stop on the valve stem detachable, for example by a thread pairing. For this purpose, an external thread could be arranged on the end of the valve stem facing away from the cavern. The disk serving as a stop could be pushed over this thread with a through hole and subsequently clamped with a nut at the end of the shaft; To reduce the number of parts, it would also be possible to arrange the internal thread that matches the external shaft thread directly in the bore of the stop disk.

For the purpose of faster handling, claim 7 proposes to realize the path limitation by means of a snap closure, which is designed with play, between the valve stem and the valve housing or the respective molded segment. All valve inserts can be dismantled without loosening hundreds of screw connections; the snap lock of each valve insert should be designed so that a strong pull in the direction of the cavern is sufficient for disassembly and a strong push in for assembly. Further details can be found in the exemplary embodiments and claims 8 and 9 and 10 to 13.

To explain the invention, some exemplary embodiments are described below with reference to figures. It shows:<dl id="dl0001"><dt>Fig. 1a</dt><dd>in longitudinal section, the left half of a mold segment from the area forming the tread area of ​​the tire with a valve in each vent hole, without a blank,</dd><dt>Fig. 1b</dt><dd>in longitudinal section the same half of the mold segment, but with an adjacent blank, which leads all vent valves to the closed position,</dd><dt>Fig. 2</dt><dd>in the same section plane on a scale of 20: 1, a single vent valve with a screwed-on stop on the side facing away from the cavern to limit the valve opening path,</dd><dt>Fig. 3</dt><dd>in the same sectional plane on a scale of 20: 1, a single vent valve with a limitation of the valve opening path through a defined play in a snap lock, which includes a spiral spring to be inserted as a separate component,</dd><dt>Fig. 4a</dt><dd>on the same scale, in the top view, in the disassembled state, the spiral spring installed in FIG. 3</dd><dt>Fig. 4b</dt><dd>in an analogous representation, another embodiment of the spiral spring which can be installed in FIG. 3 and</dd><dt>Fig. 5</dt><dd>analogous to Figure 3, a single vent valve with a limitation of the valve opening path by a defined play in a snap lock, but here the deflection necessary for a snap lock is not achieved as a bend of a separate spiral spring but the lower slotted end of the valve stem.</dd></dl>

FIG. 1a shows in longitudinal section the left half of a mold segment 10 of a vulcanization mold 1 according to the invention; In this example, the vulcanization mold 1 is divided radially in the tread area as usual - but not necessary for the invention - the segments 10 are therefore radially movable. This segment 10 originates from the area which forms the tread area of ​​the tire. Radially divided shapes usually have 7 to 13 segments 10 in the tread area, mostly 7 or 9 in car tire shapes, mostly 9 or 11 in light truck tire shapes and 11 or 13 in heavy truck tire shapes.

Deviating from the later functional position of the finished tire with an approximately horizontal position of the axis of rotation, vulcanization molds are generally operated in a flat arrangement, that is to say with the axis of rotation in a vertical position; the blanks are easier to insert and the vulcanized tires are easier to demold. The two side parts of the mold are accordingly called the top and bottom of the mold.

There is a need for ventilation both for the radially movable segments 10 and for the two side parts, not shown here; however, the number of ventilation openings 2 required per area is smaller in the side parts than in the segments 10 because the shape to be molded is not so complicated there. The venting in the axially movable side parts 10 is preferably carried out by means of the same valves 3 as in the radially movable segments 10; Because, apart from the less dense arrangement of the ventilation openings 2, there are no differences between the ventilation of the radially movable segments 10 and the axially movable side parts 10, the reference symbol 10 applies to both types of segments.

It is essential that a valve 3 is arranged in each vent hole 2. The mold segment is shown in Fig. 1a without a blank; as a result, all vent valves 3 are opened in conjunction with a weak compression spring 11, as can be seen more clearly in the larger figure 2. As can also be seen in FIG. 2, the valve plates 6 protrude into the cavern.

The return spring to reach the opening position should be as weak as possible and as strong - taking into account weight, friction and manufacturing tolerances - as necessary; In order to reach the opening position safely, it has been sufficient according to previous tests if the pre-tension (more precisely: the pre-compression) is 1.5 times the sum of the weight of the valve insert and half the spring weight.

In such a mold 1, as shown in FIG. 1a, with open ventilation channels 2 as a result of opened valves 3, the blank of a tire 14 is now to be inserted in a manner known per se.

Figure 1b shows in an analogous representation to Figure 1a the moment when - towards the end of the "residual lifting" - the blank of the tire 14 to be embossed and vulcanized, precisely in the groove bases of the form 1, which mold the resulting areas of the tread pattern and where Most ventilation channels 2 open on the cavern side, comes to the system. As a result of this application, the rubber, which already has a certain dimensional stability, presses the valves 3 against the only weak resistance of the respective compression spring into the closed position shown here.

"Residual lifting" is understood in the tire technical language to mean the small remainder of the entire elevation or bombage, which is achieved by flatulence within the vulcanization mold and by which the profile shaping is achieved or - in the case of very deep profiles and / or very rigid reinforcements - is at least completed.

FIG. 2 shows in the same sectional plane as FIG. 1 on a 20: 1 scale a single vent valve 3 with a valve insert 4. The valve insert 4 comprises at least one valve plate 6 and a valve stem 5. The spring 11 is centered on a shoulder of the valve plate 6. To limit the valve opening path, a stop 13 with an internal thread is screwed onto the side facing away from the cavern, cooperating with an external thread on the corresponding end of the valve stem 5.

The valve plate 6 has an end face 8 which is adapted to the shape of the cavity and is therefore essentially flat. The green tire attaches itself to this during the remaining lifting. The valve disc 6 is also designed as a truncated cone 7 suitable in diameter and in the cone angle to the inner conical surface 9. The cone angle to the dash-dotted longitudinal axis of the valve insert should be between 15 ° and 60 °; The angle of 22 ° shown here has proven itself.

For better logistics in mold manufacturing, e.g. B. for the purpose of outsourcing the entire valve production to a valve manufacturer, it is recommended, as shown here, to arrange each valve insert 4 in a separate, essentially cylindrical housing 12. Together with the compression spring 11 and the stops 13, this results in a structural unit which captively summarizes all the individual parts of the valve 3; Such a valve 3 can be obtained completely pre-assembled from the valve manufacturer and can be used by the mold maker in appropriately prepared ventilation holes from the cavern.

The insertion is preferably carried out by driving into a narrow hole; an interference fit is achieved. In order to obtain a sufficiently secure hold on the one hand and on the other hand a disassembly option which does not violate the segment, it has proven useful to provide an inner bore diameter d (see FIG. 1a) of 3.35 mm with an outer housing diameter D of 3.5 mm. To facilitate hammering, the housing 12 advantageously has a taper at the end facing away from the cavern.

The spring 11 is preferably designed as a wire coil spring with about 10 free turns and one turn resting on a block at both ends; with a steeper winding of the spring, it appears possible to achieve a small twist of the valve insert around the dash-dotted longitudinal axis each time it opens and closes. In this way, a closing action that is particularly uniform over the circumference of the valve plate could be achieved even longer.

If, in contrast to FIG. 2, the valve 3 is designed without a housing, the inner-conical surface 9 must of course be drilled or milled directly at the appropriate point on the shaped segment.

Figure 3 shows in the same sectional plane as Figure 2 and on the same scale 20: 1, a single vent valve 3 with a limitation of the valve stroke h by a defined play in a snap lock, which includes a spiral spring 16 to be inserted as a separate component. In the position as open as possible, which is shown here, the valve stem 5 with the frustoconical surface 18.1 of the collar 18 facing the cavern, which is arranged at the end of the valve stem 5 facing away from the cavern, strikes the end face 16.3 of the spiral spring 16 facing away from the cavern.

Fig. 4a shows this spiral spring 16 individually on the same scale in plan view with an external C-shaped part 16.2, which can be bent so far that the spring 16 from the side facing away from the cavern, so in Figure 3 from below, are inserted can snap into the shaft of the housing and then into the groove 15 which is on the inside of the valve housing 12 or - In the case of a housing-free version - is arranged in the bore in the segment in a plane perpendicular to the longitudinal axis of the valve 3. The spiral spring 16 also has inwardly pointing, elastically flexible legs 16.1, which are dimensioned such that they engage in the groove 17 of the valve stem 5 shown in FIG. 3 after their deflection, that is to say tightly enough that after the cavern facing surface 18.1 has been applied of the federal government 18 on the surface 16.3 of the spring 16 facing away from the cavern, resistance to further pulling out of the valve insert 4 occurs; on the other hand, the legs 16.1 should preferably stand so far that the valve insert 4 can move between the stops 18.1 and 17.1 without jamming along its dash-dotted longitudinal axis.

As can be seen in FIG. 3, these limbs 16.1 are spread from the cavern when the valve stem 5 is mounted by means of a leading conical surface 18.2 which is arranged at the end facing away from the cavern and which forms a collar-like thickening 18 of the valve stem 5 at the end of the valve stem 5 facing away from the cavern heard. After overcoming the thickest area of ​​the collar 18, the legs 16.1 - sliding on the inversely oriented conical surface 18.1 - narrow again so that the valve stem 5 only with great force in the direction of the cavern (in particular with a greater force than that of the spring 11 ) could be pulled out in the opposite direction. In order to secure the spring 16 against being pressed out of the groove 15 during assembly of the valve insert 4, a sleeve can be pressed or screwed in from the side facing away from the cavity up to the spring.

The inwardly facing legs 16.1 engage in a groove 17 of the valve stem 5, which (17) is delimited to the side facing away from the cavern by the conical surface 18.1 and to the side facing the cavern by the preferably flat surface 17.1. The groove width w17 of the groove 17 is larger by an amount than the spring width 16; this amount is somewhat larger than the valve stroke h, so that in the closed position of the valve 3, the groove end face 17.1, which participates in the closing movement, does not penetrate as far as the end face 16.4 of the spiral spring 16 facing the cavern, thereby avoiding overdetermination in the travel limitation of the valve insert 4 and thus it is possible to insert the outer conical surface 7 of the valve disk 6 into the inner conical surface 9, which causes a perfect closing of the valve 3 and freedom from misalignment between the end face 8 of the valve plate 6 and the surrounding cavern surface. - This could theoretically also be achieved with a smaller slot width w17 if the slot width w15 were correspondingly larger, in short:<maths id="math0001" num=""><math display="block"><mrow><mtext>w17 + w15 - 2w16&gt; h.</mtext></mrow></math><img file="EP0774333A2_D0001.tif" /></maths>

However, the outer part 16.2 would then also have to be displaceable relative to the housing 12, but this also leads to a play addition in the radial direction of the valve and to a tendency to tilt with correspondingly scattering friction coefficients. Therefore, w16 is preferably only slightly smaller than w15 that the clearance of approx. 20 µm required for insertion is reached. The above requirement is then simplified to:<maths id="math0002" num=""><math display="block"><mrow><mtext>w17 - w16&gt; h.</mtext></mrow></math><img file="EP0774333A2_D0002.tif" /></maths>

FIG. 4b shows, in an analogous representation to FIG. 4a, such a variant of the spiral spring 16, in which legs which are denoted here by 16.6 are connected to the C-shaped part, here 16.5, not inwards but outwards. The legs 16.6 should engage in the housing groove 15 and the C-shaped part 16.5 in the groove 17 of the valve stem 5.

Figure 5 shows, in an analogous representation to Figure 3, a single vent valve 3 with a limitation of the valve opening path by a defined play in a snap lock, the deflection required for a snap lock being achieved here as a bend, but not as a bend of a separate spiral spring, but as a bend of the slotted end of the valve stem 5 facing away from the cavern, ie appearing at the bottom of the drawing.

To save costs, the slitting is achieved by only one slit 19, as shown here. Then, the slot 19 must be quite wide, as shown, in order not only to allow a sufficient spring deflection of the two remaining tongues towards one another during assembly and disassembly through the opening 12.1 of the housing 12 facing away from the cavity, but also in the perpendicular one further longitudinal sectional plane through the valve 3. (The latter cutting plane would be referred to as a cross-sectional plane for the entire form 1.) However, a narrower slot design would also be possible if the collar 18 were leveled near the slot, i.e. less protruding from the remaining surface of the shaft 5, or if instead of one Slot 19 two intersecting slots would be arranged on the end of the shaft 5 facing away from the cavern.

The collar 18 at the end of the valve stem 5 facing away from the cavern has a boundary surface 18.1 facing the cavern. It serves as a stop surface to limit the valve opening and is placed in such a way that it should correspond to a valve stroke of about 0.5 mm in the desired opening position - which with a valve disc diameter of approximately 2.8 mm and a cone angle to the longitudinal axis of 22 ° shown here - on the surface of the housing 12 facing away from the cavern - or an equivalent surface in the case of a housingless design. The opening stroke is limited by this striking.

The reverse movement, the closing movement, is in no way limited by the collar 18, but solely by the impact of the outer-conical surface 7 of the valve disk 6 on the inner-conical surface 9.

To remove such a valve insert 4, a strong pull on the valve plate 6 in the direction of the cavern is sufficient due to the shown and preferred conical design of the stop surface 18.1; otherwise, the remaining tongues of the valve stem would have to be bent together by hand so far that they can pass through the opening 12.1 of the housing 12 with the other hand .

For the assembly, a conical design of the other boundary surface 18.2 of the federal government 18 is also expedient; then a strong push in is enough.

The depth of the slot 19 or of the slots on the end of the shaft 5 facing away from the cavern is small enough to provide sufficient resistance to unintentional removal of the valve insert in combination with the tongue stiffness thus maintained, and on the other hand large enough to make the tongues so flexible that disassembly is tolerably easy.

The detailed exemplary embodiments are intended to give the person skilled in the art extensive knowledge of the invention; however, the scope of protection is not restricted by these details. The essence of the invention alone is to insert a valve into each of the hundreds of ventilation bores of a tire vulcanization mold, each valve being closed by the approaching of the blank surface and being opened again during demolding.

The following list of reference symbols is part of the description:

Reference symbol list:

<dl id="dl0002" compact="compact"><dt>1</dt><dd>Vulcanization form</dd><dt>2</dt><dd>Vent holes in 1</dd><dt>3</dt><dd>Valve, to be used in 2</dd><dt>4</dt><dd>Valve insert from 3</dd><dt>5</dt><dd>Shaft of 4</dd><dt>6</dt><dd>Plate at the end of the cavern facing 4</dd><dt>7</dt><dd>Truncated cone on the side of 6 facing away from the cavern</dd><dt>8</dt><dd>essentially flat surface on the side of FIG. 6 facing the cavern</dd><dt>9</dt><dd>internal conical surface in 10 or 12 suitable for 7</dd><dt>10</dt><dd>Segment of 1</dd><dt>11</dt><dd>weak spring, pushing insert 4 of valve 3 into the open position</dd><dt>12</dt><dd>Housing of 3</dd><dt>13</dt><dd>Stop to limit movement of 4</dd><dt>14</dt><dd>Pneumatic tire 15 groove in the inside of the housing 12 on the side facing away from the cavern</dd><dt>16</dt><dd>Bending spring for snap lock<ul id="ul0001" list-style="none" compact="compact"><li>16.1 inward leg of 16 (4a)</li><li>16.2 outer, C-shaped part of the spiral spring 16 (4a)</li><li>16.3 end face facing away from the cavern of 16</li><li>16.4 end face facing the cavern of 16</li><li>16.5 inner, C-shaped part of other spiral spring 16 (4b)</li><li>16.6 outward leg of 16 (4b)</li></ul></dd><dt>17</dt><dd>Groove on the outside of the valve stem 5 near the end facing away from the cavern<ul id="ul0002" list-style="none" compact="compact"><li>17.1 End face to limit 17 on the side facing the cavern</li></ul></dd><dt>18</dt><dd>Collar at the end of the valve stem facing away from the cavern 5<ul id="ul0003" list-style="none" compact="compact"><li>18.1 boundary surface of the collar 18 facing the cavern, at the same time the boundary surface of the groove 17 facing away from the cavern, serving as a stop surface</li><li>18.2 boundary surface of the collar 18 facing away from the cavern, preferably designed as a truncated cone as an insertion aid</li></ul></dd><dt>19</dt><dd>Slot (e) through the end of the valve stem 5 facing away from the cavern in order to allow deflection of the waist width</dd><dt>D</dt><dd>Outside diameter of the valve housing 12</dd><dt>d</dt><dd>Inside diameter</dd><dt>H</dt><dd>Valve lift</dd><dt>w15</dt><dd>Width of the groove 15</dd><dt>w16</dt><dd>Width or thickness of the spiral spring 16</dd><dt>w17</dt><dd>Width of the groove 17</dd></dl>