EP1295655B1 - Venting valve assembly for casting moulds - Google Patents

Abstract

The valve plug (20) is held in the open position by friction, at the same time being biased to closure.

Description

The invention relates to a vent valve device for molds according to the preamble of claim 1.

In order to reliably prevent air pockets in the finished casting during casting, and in particular during die casting, the casting mold or the cavity of the casting mold must be vented during the casting process. Not only must it be possible for the air present in the cavities of the casting machine and the casting mold to escape, but it must also be ensured that the gases emerging from the liquid casting mass can likewise escape.

One problem with the venting of die casting molds is that the vent valve of the valve device should be closed as late as possible, so that the cavity is vented as far as possible to complete filling, but on the other hand to prevent liquid casting material from entering the vent valve.

In order to take this problem into account, basically two types of valve devices for die casting molds are known, both types having a bleed valve with a reciprocating closure member for closing the bleed channel. While in the first type the closure member is externally actuated, the closure member in the second type is operatively connected to a force transducer which is actuated directly by the casting material penetrating the cavity into the venting channel utilizing its kinetic energy.

Under externally operated valve devices is understood that the valve piston is not actuated by the penetrating from the cavity in the venting channel casting material, but by an external power source, the latter is designed as a majority pneumatically or hydraulically operating system. The timing for triggering the closing operation may be, for example, in these valve devices be determined by means of a fill level of the cavity monitoring sensor. A difficulty with such valve devices is that the actual closing process takes a relatively long time, since the signal initiating the closing process (electrical pulse) has to be converted into a mechanical movement, for example into the actuation of a servo valve. In addition, a certain system pressure must prevail for closing the venting valve or an actuating member operatively connected to the valve piston, so that the venting valve can be closed pneumatically or hydraulically within the required period of time. However, since the opening of a servo valve generally causes a pressure drop, after opening the servo valve, the system pressure required to close the vent valve must first be reestablished. Finally, usually still a locking mechanism that locks the valve piston in the open position, to be moved, which also leads to a delay in the closing process. It is understood that such valve devices require a high structural complexity and can react prone to certain operating parameters. In addition, such valve devices usually require at least about 10 ms from recognition of the mold filling to complete closure of the valve piston.

By contrast, very fast and reliable valve devices can be realized with the second type of valve devices. In order to be able to build up the dynamic pressure required for the closing process on the force transducer, the venting channel leading from the cavity to the force transducer has directional and cross-sectional changes. In addition, the venting channel between the force transducer and the actual valve body of the vent valve must have a certain minimum distance and be designed angled so that the vent valve is securely closed before the liquid casting material has reached the vent valve. To increase the efficiency of such vent valves, a vacuum pump is usually connected to the vent valve.

From EP 0 612 573 a generic valve device for venting of die casting molds is known, which with a vent channel, one in the vent channel arranged vent valve and an actuator for closing the vent valve is provided. The actuating device has a force transducer, which can be acted upon by the casting material protruding from the cavity into the venting channel and is in mechanical operative connection with the movable closure part of the venting valve. In this case, the force transducer is designed as a shock member whose working stroke is limited to a fraction of the closing path to be covered by the movable closure part of the venting valve. Furthermore, the closure part of the venting valve is free to move beyond the working stroke of the force transducer and the actuating device has a force transmission member for the transmission of the shock pulse from the force transducer to the movable closure part of the venting valve.

Although a vent valve designed in this way works very reliably in practice, it would be desirable for certain applications if the energy required for closing the valve would not have to be applied solely by the casting material. As can be seen from the general formula (E = m · v ^2/2 ) for calculating the kinetic energy, the energy available for closing the valve device depends on the mass and the speed of the casting material. In other words, in unfavorable conditions, namely with low casting weights and / or low casting material speeds, the available energy may not be sufficient to close the vent valve within the required time. On the other hand, in the case of large casting weights and / or at high speeds, a very high energy can act on the force transducer, which causes it to hit the end stop or the valve seat together with the closure part at a high speed, which of course also, in particular with regard to a limited Lifetime, is undesirable.

Based on the known prior art, the object of the invention is to improve a vent valve device referred to in the preamble of claim 1 type such that it is universally applicable by their closure member regardless of the operating parameters of the casting device and the casting material, can be moved very quickly and reliably from the open to the closed position regardless of the process.

This object is achieved by the features cited in the characterizing part of claim 1.

With such a vent valve device, the closure member can be closed externally operated very quickly, in particular the time to cancel the frictional connection compared to conventional latches of the closure member is very short, especially since the closure member can already be biased in the closing direction or biased.

Preferred developments of the valve device are described in the dependent claims 2 to 16.

In a preferred embodiment of the vent valve device, a vent valve is provided with a hydraulically or pneumatically loadable chamber, which is provided with a vaultable in the direction of the closure member, the closure member frictionally fixable chamber wall. The chamber wall is so far deflected within the elastic limit of the material (steel), that it automatically bulges after the reduction of the pressure prevailing in the chamber in the release position releasing the closure member. Compared to conventionally designed vent valves, a pressure does not first have to be built up and / or a closure member has to be moved from a locking position into an unlocked position, so that the closure member can be moved from the open position to the closed position, but only the pressure in the locking position has to be increased Chamber are reduced so far that the chamber wall bulges back so that the prestressed closure member is released and can suddenly move from the open to the closed position. This pressure reduction can be done for example by opening a relief valve. The entire closing time from the recognition of the mold filling to the complete Closing the closure member can be significantly shortened in this way.

Fig. 1

einen Längsschnitt durch das Entlüftungsventil;

Fig. 2

eine Detailansicht des Entlüftungsventils gemäss Fig. 1;

Fig. 3

einen Querschnitt durch das Entlüftungsventil entlang der Linie A-A in Fig. 1;

Fig. 4

einen Querschnitt durch das Entlüftungsventil entlang der Linie B-B in Fig. 1;

Fig. 5

eine Blockschaltbild der gesamten Entlüftungsventileinrichtung;

Hereinafter, an embodiment of the valve device will be explained in more detail with reference to drawings. In these drawings shows:

Fig. 1

a longitudinal section through the vent valve;

Fig. 2

a detailed view of the vent valve according to FIG. 1;

Fig. 3

a cross section through the vent valve along the line AA in Fig. 1;

Fig. 4

a cross section through the vent valve along the line BB in Fig. 1;

Fig. 5

a block diagram of the entire vent valve device;

With reference to Figure 1, which shows the vent valve 1 in a longitudinal section, the structure of the vent valve is explained in detail. The vent valve 1 has a round valve housing 2, which is provided with a central valve channel 3 for receiving and guiding a closure member 20. On the front side of the valve housing 2 acting as an extension of a vent channel 7 venting chamber 6 is arranged, which is connected via a valve seat 9 with the valve channel 3. The venting chamber 6 is arranged between a first venting duct section 7a leading into the cavity to be vented and a second venting duct section 7b leading from the top of the valve housing 2 on the upper side. This second vent channel section 7b opens radially into a valve chamber 4 arranged in front of the valve channel 3 and adjacent to the valve seat 9. On the rear side of the valve housing 2, a pneumatic chamber 10 is inserted, which is closed by means of a cover 11. Furthermore, a valve chamber 3 enclosing hydraulic chamber 13 is inserted into the valve housing 2. This hydraulic chamber 13 is provided with a relatively thin, adjacent to the valve channel 3 chamber wall 14, which under the action of a in the hydraulic chamber 13 producible overpressure in the direction of the valve channel 3 is elastically herausölbbar, as can be seen from Fig. 2 in an enlarged and in favor of a good recognizability greatly exaggerated representation. For certain applications, it may also make sense to provide a gaseous medium for applying the hydraulic chamber instead of a liquid. In this sense, the term "hydraulic chamber" is not to be understood as limiting.

In the valve channel 3, the displaceable between an open and a closed position closure member 20 is received, wherein the closure member 20 is shown in the present example in the open position. The closure member 20 has a valve stem 21 with a valve head 22 arranged at the end and designed as a conical valve. With this valve head 22, the vent channel 7 can be closed at the valve seat 9, if necessary, so that no casting material from the first vent channel section 7a can penetrate into the valve channel 3 and the second vent channel section 7b. On the side opposite the valve head 22, a valve plate 23 is connected to the valve stem 21 by means of a screw 27. The valve disk 23 has a peripheral collar 25 serving as a stop and an elastic deflectable center plate part 24. The valve plate 23 is received in the pneumatic chamber 10, wherein the valve plate 23, and thus also the closure member 20, can be moved pneumatically both to the right in the open position shown as well as to the left in the closed position. For this purpose, two channels 28, 29 are provided, which open frontally before and behind the valve disk 23 into the pneumatic chamber 10.

3 shows a cross section through the venting valve along the line AA in FIG. 1. As can be seen from this illustration, both the valve channel 3 and the valve stem 21 have a polygonal cross section. This has the advantage, inter alia, that the valve disk 23 can be easily removed from the valve stem 21 by releasing the valve disc 23 fixing the valve stem 21 without fixing the valve stem since the valve stem 21 in the valve channel 3 can not rotate (FIG . 1). A polygonal design of the valve channel 3 also favors a clamping, frictional locking of the closure member 20th

From FIG. 4, which shows a cross-section through the venting valve along the line B-B in FIG. 1, the venting duct section 7b leading from the housing 2 on two sides can be seen.

Based on the block diagram according to Figure 5, the basic structure and operation of the entire vent valve device, with partial reference to Figure 1, will be explained in more detail. In addition to the actual venting valve, the venting valve device has a sensor 30 preferably arranged in the first venting duct section 7a, by means of which the casting material penetrating into the venting duct can be detected. In addition, a control and monitoring unit 32 is provided which comprises a hydraulic unit 33 and a pneumatic unit 34. The hydraulic unit 33 is connected via a feed 36 and a return 37 to the hydraulic chamber 13. In addition, a relief valve assembly 38 is provided, which u.a. a relief valve 39 arranged in the return 37, by means of which a rapid reduction of the prevailing in the hydraulic chamber 13 overpressure can be initiated. The actuation of this relief valve 39, i. the opening, by means of the sensor signal, which is indicated by the leading from the sensor 30 to the discharge valve 39 line 40.

For the pneumatic actuation of the valve disk 23, two lines 41, 42 leading from the pneumatic source 34 to the pneumatic chamber 10 are provided. Via a third line 43 of the prevailing in the vent passage vacuum can be measured. As a pneumatic source 34 is in most cases an in-house pressure connection, of course, a separate pressure source can be provided. Furthermore, a vacuum source for forcibly venting the cavity is connected to the second vent channel section 7b.

In order to vent the cavity of a mold (not shown) via the vent valve 1, the latter must be brought into the open state according to FIG. For this purpose, via the line 41 and the bore 29 in the left part 10 a of Pneumatic chamber 10 constructed an overpressure, so that the valve plate 23 moves together with the closure member 20 to the right in the open position. Thereafter, an overpressure of about 100 bar in the hydraulic chamber 13 is constructed via the line 36, so that the chamber wall 14 bulges under the action of this overpressure in the direction of the valve stem 21 and the closure member 20 is fixed in the open position frictionally. Now, the other, right side of the valve disk 23 is acted upon by the line 42 and the bore 28 with pressure, so that the valve plate 23 is biased together with the closure member 20 pneumatically in the closing direction. It is understood that the entire elements are coordinated so that the closure member 20, even with full pressurization of the valve disk 23 in the closing direction, is frictionally held by the bulged chamber wall 14 in the open position. In this state, the vent valve 1 is in the venting position, in which via the vent channel 7 before and during the actual casting process continuously air / gases can be sucked out of the cavity / can. As soon as the casting material reaches the sensor 30, the latter generates an electrical signal which is used directly or indirectly to open the relief valve 38. By opening the relief valve 38, the pressure in the hydraulic chamber 13 is abruptly reduced, since only a very small volume of hydraulic fluid must flow out of the hydraulic chamber 13, so that the bulged chamber wall 14 curves back automatically. By the backward arching of the chamber wall 14, the frictional connection to the closure member 20 is released and the pneumatically biased closure member 20 moves very quickly from the open to the closed position. In this case, the valve plate 23 helps to absorb the kinetic energy of the closure member 20 in terms of a resilient end stop by first serving as a stop collar 25 of the valve plate 23 on the lid 11 applies and the kinetic energy is trapped by the elastic plate middle part 24. For this purpose, the valve plate 23 is made of an elastic material with a high internal damping, wherein the elastic plate middle part 24 is designed such that it is deflected only within the elastic limit of the material. As a material for the valve plate 23, in particular composite fiber materials offer, since they are lightweight and their properties can be selectively influenced by These are specifically provided with a high internal damping. The arrangement valve plate-closure member is designed and dimensioned so that the valve head 22 has not yet applied sealingly on the valve seat 9 when the collar 25 of the valve plate 23 on the lid 11 of the pneumatic chamber 10 comes to rest. The transmitted during the closing movement of the closure member 20 kinetic energy is therefore intercepted controlled by the valve disk 23. After the valve plate 23 has applied with its collar 25 on the lid 11 of the pneumatic chamber 10, the valve plate 23 is deflected so far elastically by the inherent in the closure member 20 kinetic energy until the valve head 22 rests sealingly on the valve seat 9. This deflected state of the valve disk 23, in which the valve seat 9 is closed by the valve head 22, remains in existence as long as a minimum overpressure, for example 5 bar, is maintained in the pneumatic chamber 10.

Instead of pneumatic means for biasing the closure member 20, it could also offer to bias this by means of a spring. In addition, instead of a hydraulically deflectable chamber wall 14, piezoelectric crystals could also be used, for example, which frictionally fix the closure member 20 under the influence of an applied electrical voltage. It is understood that a vent valve device may be provided which comprises more than one vent valve. In addition, instead of a poppet valve, for example, a cylindrical or flat valve can be used.

• Das Entlüftungsventil ist universell einsetzbar, da das Schliessen des Verschlussorgans prozessunabhängig erfolgt, d.h. unabhängig von den Betriebsparametern der Giesseinrichtung sowie des Giessmaterials;
• Das Verschlussorgan wird zuverlässig und sehr schnell, d.h. in der Grössenordnung von ca. 1-2 ms, von der Offen- in die Schliessstellung bewegt. Dadurch kann mit dem Schliessen des Entlüftungsventils bis zum vollständigen Füllen der Kavität gewartet werden;
• Das Entlüftungsventil ist sehr einfach aufgebaut und besitzt sehr wenig bewegte Teile. Zudem brauchen keine Dichtungen, Federn etc. vorgesehen zu werden. Dadurch ist es sehr kompakt, wartungsarm, zuverlässig und kostengünstig in der Herstellung. Zudem steht ein grosser Absaugquerschnitt zur Verfügung.
• Das Verschlussorgan wird kontrolliert abgebremst, was die Lebensdauer des gesamten Entlüftungsventils erhöht.
• Der runde Aufbau bietet zahlreiche Vorteile beim Einbau.

The main advantages of the shown vent valve device and in particular of the vent valve can be summarized as follows:

• The vent valve can be used universally, since the closure of the closure member is independent of the process, that is, regardless of the operating parameters of the casting device and the casting material;
• The closure member is reliably and very quickly, ie in the order of about 1-2 ms, moved from the open to the closed position. This can be waited until the filling of the cavity with the closing of the vent valve;
• The vent valve is very simple and has very few moving parts. In addition, no seals, springs, etc. need to be provided. This makes it very compact, low-maintenance, reliable and cost-effective to manufacture. In addition, a large suction cross section is available.
• The closure member is braked controlled, which increases the life of the entire vent valve.
• The round construction offers many advantages during installation.

Claims (16)

1. Venting valve assembly for casting moulds, with a venting valve (1), which has a valve housing (2), provided with a venting channel (7), and a closing member (20), intended for closing the venting channel (7) and movable between an open position and a closed position, characterized in that the closing member (20) can be held in the open position by friction and at the same time can be biased in the closing direction.
2. Venting valve assembly (1) according to Claim 1, characterized in that first means for frictionally fixing the closing member (20) in the open position and second means for biasing the closing member (20) that is fixed in the open position in the closing direction are provided.
3. Venting valve assembly according to Claim 2, characterized in that the first means have a hydraulically or pneumatically operable chamber (13), which is provided with a chamber wall (14) which can curve convexly in the direction of the closing member (20) and can frictionally fix the closing member (20).
4. Venting valve assembly according to Claim 3, characterized in that the chamber wall (14) can be deflected within the elastic limit of the material in such a way that, after the positive pressure prevailing in the chamber (13) is reduced, it automatically curves back into the starting position, releasing the closing member (20).
5. Venting valve assembly according to one of Claims 2 to 4, characterized in that the second means comprises a chamber (10) which can be pneumatically subjected to positive pressure, in which a valve plate (23) arranged on or in operative connection with the closing member (20) and pneumatically operable in the closing direction of the closing member (20) is arranged.
6. Venting valve assembly according to Claim 2, characterized in that the second means comprises a spring biasing the closing member (20) in the closing direction.
7. Venting valve assembly according to Claim 3 or 4, characterized in that the closing member (20) is displaceably accommodated in a valve channel (3) in the valve housing (2) and in that the chamber (13) at least partially encloses the valve channel (3).
8. Venting valve assembly according to one of Claims 3, 4 or 7, characterized in that a relief valve (39) is provided for reducing the positive pressure prevailing in the hydraulically operable chamber (13) and for overcoming the frictional connection between the chamber wall (14) and the closing member (20) within a predetermined time.
9. Venting valve assembly according to Claim 8,
   characterized in that at least one sensor (30) is provided for detecting the casting material penetrating into the venting channel (7), which sensor serves for directly or indirectly activating the relief valve (39).
10. Venting valve assembly according to one of the preceding claims, characterized in that the closing member (20) has a valve stem (21) with a valve head (22) arranged at its end and acting as a closing part.
11. Venting valve assembly according to Claim 10, characterized in that the venting channel (3) let into the valve housing (2) has a cross section other than that of a circle, preferably a polygonal cross section, and in that the valve stem (21) of the closing member (20) is of a form corresponding to the form of the valve channel (3) while the valve head (22) is of a round form.
12. Venting valve assembly according to Claim 10 or 11, characterized in that the valve housing (2) is provided with a first and a second venting channel portion (7a, 7b), a valve seat (9), which can be closed by the valve head (22), being arranged between the first and second venting channel portions (7a, 7b).
13. Venting valve assembly according to Claim 5, characterized in that the valve plate (23) is arranged on the valve stem (21) on the side opposite from the valve head (22), the valve plate (23) being pneumatically operable in the opening and closing directions.
14. Venting valve assembly according to Claim 13, characterized in that the valve plate (23) is provided with a collar (25), serving as a stop, and also a central cup part (24), which can be resiliently deflected and absorbs the kinetic energy of the closing member (20) during the closing movement.
15. Venting valve assembly according to Claim 14, characterized in that the valve plate (23) is produced from a material provided intrinsically with a great damping effect, preferably from a composite fibrous material.
16. Venting valve assembly according to one of Claims 13 to 15, characterized in that the valve plate (23) is detachably connected to the closing member (20).

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