EP0937524A1 - Method for de-aerating of die casting moulds and valve apparatus for carrying out the process - Google Patents

Abstract

During filling, the die cavity (8) and/or the pressure chamber (1) is/are vented via a second venting valve (12) in addition to the first venting valve (11). The second valve (12) is closed before the die cavity is completely filled, after which the first valve (11) is closed by the casting material which enters into the venting channel (9) and powers an actuator connected in effect to the first valve. The valve arrangement (10) comprises two venting valves of which one (12) is operated by remote control, while the other (11) is connected in effect to an actuator powered by the casting material entering into the venting channel (9).

Description

The invention relates to a method for venting die casting molds according to the Preamble of claim 1 and a valve device for performing the Method according to the preamble of claim 6.

To reliably prevent air pockets in the finished casting during die casting To be able to, the die or the mold cavity of the die be vented during the die casting process. Not only that in the Any voids in the die casting machine and the die can escape can, but it must also be ensured that the gases emerging from the liquid casting compound can also escape.

One problem with venting die casting molds is that Bleed valve should be closed as late as possible to allow the mold cavity as far as possible until it is completely filled, but on the other hand Liquid pouring material should be prevented from entering the vent valve penetrates. In order to take this problem into account, valve devices are known the vent valve is operatively connected to a force transducer, of the casting material penetrating from the mold cavity into the ventilation duct is operated. With such valve devices can be very fast and reliable Realize valve devices. To the on the force transducer for the The venting channel shows that it can build up the necessary back pressure Changes in direction and cross-section. In addition, the ventilation duct between the force transducer and the actual valve body of the Breather valve have a certain minimum distance and are angled be so that the vent valve is closed before the liquid pouring material reached the vent valve. By an angled version of the Vent channel between the force transducer and the vent valve is also prevents the splashes of the Pour the casting compound into the vent valve and plug it. To efficiency It is customary to increase such vent valves on the vent valve a vacuum pump connected.

EP 0 612 573 describes a generic valve device for venting Die casting molds known, which have a vent channel, one in the vent channel arranged vent valve and an actuator for Closing the vent valve is provided. The actuator has one Force transducer, which through the from the mold cavity into the ventilation channel penetrating casting material can be acted upon and with the movable Closing part of the vent valve is in a mechanical operative connection. Here the force transducer is designed as a thrust member, its working stroke on one Fraction of that to be covered by the movable closure part of the vent valve Closing path is limited. Furthermore, the closure part of the vent valve can be moved freely over the working stroke of the force transducer, and the actuator has a power transmission member for the transmission of the shock pulse from the force transducer to the movable closure part of the vent valve.

Although such vent valves work very reliably in practice, would be it is particularly desirable for mold cavities with a large volume, if the ventilation performance could be increased. The maximum venting performance is particularly due to the changes in direction and cross-section limited in the ventilation duct, because of this the flow resistance for the gases escaping the mold cavity is increased significantly.

In order to deal with the problem described, it would now be obvious to To enlarge the cross section of the existing ventilation valve and the ventilation duct. However, tests have shown that an enlargement of the valve cross-section together with the ventilation duct not the desired success with it, since the flow resistance due to the angled Design of the ventilation duct for efficient ventilation still in the Way stands. An enlargement of the vent valve also means that the mass of the parts to be moved increases, which means that the parts to be applied automatically Closing forces increase and / or the closing time of the vent valve increases undesirably increased. In addition, an enlargement of the Valve cross section and the ventilation duct that the dimensions of the valve device increase, which is also undesirable.

It is therefore the object of the invention to provide a method for venting die casting molds to propose with which, with reliable functioning, higher ones Allow venting performance to be achieved.

This object is achieved by the method steps specified in the characterizing part of claim 1 solved.

The venting performance can be considerably increased with the proposed method increase because of a second vent valve, which is before full filling of the mold cavity is closed, on the one hand the average cross section of the for the venting channels can at least be doubled and also the vent duct section leading to the second vent valve in Regarding the flow resistance can be optimized.

In a preferred exemplary embodiment, it is proposed that the criterion for Close the second vent valve since the start of the filling process elapsed time, the position of the plunger, the distance traveled by the plunger Path, the level of the pressure chamber or the level of the mold cavity to use. This can ensure that the second vent valve is closed when the casting material has reached this.

Another object of the invention is to provide a valve device with which the method according to the invention can advantageously be carried out.

This object is achieved by means of a valve device which has the characteristics indicated in the license plate of claim 6 features listed.

Preferred developments of the valve device are in the dependent claims 7 to 14 circumscribed.

Fig. 1 eine schematisch dargestellte Druckgiessmaschine mit einer Druckgiessform und einer daran angeordneten Ventilvorrichtung im Ausgangszustand;

Fig. 2 die Druckgiessmaschine gemäss Fig. 1 in einer ersten Phase;

Fig. 3 die Druckgiessmaschine gemäss Fig. 1 in einer zweiten Phase;

Fig. 4 die Druckgiessmaschine gemäss Fig. 1 in einer dritten Phase;

Fig. 5 die Druckgiessmaschine gemäss Fig. 1 in einer vierten Phase;

Fig. 6 die detailliert dargestellte Ventilvorrichtung in einer Draufsicht;

Fig. 7 einen ersten Querschnitt durch die detailliert dargestellte Ventilvorrichtung entlang der Linie A-A in Fig. 6;

Fig. 8 einen zweiten Querschnitt durch die detailliert dargestellte Ventilvorrichtung entlang der Linie B-B in Fig. 6, und

Fig. 9 die in einer Druckgiessform eingebaute Ventilvorrichtung in einem Querschnitt gemäss der Fig. 7.

The method according to the invention and an exemplary embodiment of a valve device for carrying out the method are explained in more detail below with reference to drawings. In these drawings:

1 shows a schematically illustrated die casting machine with a die casting mold and a valve device arranged thereon in the initial state;

FIG. 2 shows the die casting machine according to FIG. 1 in a first phase;

3 shows the die casting machine according to FIG. 1 in a second phase;

4 shows the die casting machine according to FIG. 1 in a third phase;

5 shows the die casting machine according to FIG. 1 in a fourth phase;

6 shows the valve device shown in detail in a top view;

7 shows a first cross section through the valve device shown in detail along the line AA in FIG. 6;

Fig. 8 shows a second cross section through the valve device shown in detail along the line BB in Fig. 6, and

9 shows the valve device installed in a die casting mold in a cross section according to FIG. 7.

1, the basic structure and the principle of operation a die casting machine in the starting position and the one according to the invention Valve device explained in more detail, with only related to with the invention essential features and method steps becomes.

The essential components of the die casting machine are in the present example a pressure chamber 1 and a hydraulically actuated casting piston arranged therein 2 drawn. The pressure chamber 1 is used to fill the liquid casting material provided with a filling opening 4. At the outlet end of the pressure chamber 1 a die-casting mold 5 is arranged, which consists of two mold halves 5a, 5b. A connecting channel 6 leads from the pressure chamber 1 into the mold cavity 8 Die casting mold 5. On the top of die casting die 5 is the valve device 10 arranged, which is connected to the mold cavity 8 via a ventilation channel 9 is. The valve device 10 has two vent valves 11, 12, which are connected to a vacuum pump 18 via two connecting lines 14, 15. A check valve A, B is arranged in each of the two connecting lines 14, 15. The right ventilation valve 11 is not visible from this illustration Force transducer in operative connection, which from the mold cavity 8 in the Vent channel 9 penetrating casting material is actuated. The left bleed valve 12 is operated externally, which is indicated by an interrupted line 16 Is indicated, via which the vent valve 12 with a control device 19th connected is. In order to detect the position of the casting piston 2, there is a sensor 17 provided, which is also connected to the control device 19.

Figures 2 to 5 show the die casting machine and the valve device in four different phases.

In the first phase, the pressure chamber 1 becomes the liquid via the filling opening 4 Casting material G fed. Then the filling process is started by the piston 2 is shifted to the right in the direction of the die 5. After the Has pushed the piston 2 in front of the filling opening 4 (FIG. 3), the vacuum pump 18 put into operation and the two shut-off valves A and B opened. This allows the gases located in the pressure chamber 1 and in the mold cavity 8 via the both open valves 11, 12 of the valve device 4 escape or suction become.

4 shows the die casting machine in a third phase, in which the piston 2 has moved so far to the right that the piston has moved to the right 2 remaining part of the pressure chamber 1 completely filled with the casting material G. is, the latter has not yet penetrated into the mold cavity 8. In this Phase, the left vent valve 12 is now closed. The closure of the Left valve 12 is pneumatic via line 16.

As a criterion for closing the left vent valve 12 is in the present Example used the absolute position of the casting piston 2, because of the Position of the piston 2, the level of the pressure chamber 1 is known or determined can be. Since the filling of the mold cavity 8 with the casting material G in the Usually happens within about 20 to 80 milliseconds, the left vent valve 12 closed before the casting material G entered the mold cavity 8 is. Of course, the left vent valve 12 must be immediately before that Casting material G this can be closed. This is the case if the mold cavity 8 is completely filled and the casting material G in the vent channel penetrates. In this case, however, there is a risk that the actual Pour casting compound G ahead of splash into left vent valve 12 and add this. By closing the left vent valve early 12 this fact is taken into account. An early closing of the left Vent valve 12 also has the advantage that principle-related fluctuations of certain operating variables, for example the one filled into the pressure chamber Volume of the casting material, uncritical in terms of a reliable Operation of the valve device are and also a proportionate simple control can be used. However, the exact time the closing of the vent valve 12 the prevailing general conditions be adjusted.

Instead of the absolute position of the piston 2, the relative position of the Piston can be used as a criterion for closing the vent valve 12. Other variations are that since the start of the filling process elapsed time, the fill level of the pressure chamber 1 or the fill level of the mold cavity 8 are used, but this list is by no means exhaustive is to be considered.

After the left vent valve 12 has been closed, the check valve can also A of the vacuum pump 18 are closed. Which is still in the mold cavity 8 gases can now escape via the right vent valve 11 or suctioned off. The right vent valve 11 remains open as long as until the casting material penetrating into the venting channel 9 comes out of this Representation has not reached visible force transducer. Through the kinetic The force transducer and the valve body generate the energy of the casting material of the right vent valve 12 moved and the latter closed, such as will be explained in more detail below.

6 shows a plan view of the valve device 10 in a detailed illustration. The ventilation channel leading into the valve device 10 is identified by the reference symbol 9 provided, during which the channel section leading to the first vent valve 11 with the reference numeral 9b and leading to the second vent valve 12 Channel section is provided with the reference number 9a. The second vent valve 12 leading ventilation duct section 9a is straight, so that the flow resistance for the escaping gases is kept as low as possible can be. The to the force transducer 20 and the valve body 30 of the first Ventilation channel section 9b leading ventilation valve 11 is angled. The angled design of the ventilation duct section 9b serves to to intercept the splashes leading the actual casting compound G and the Flow of the casting material after reaching the force transducer 20 in such a way delay that the valve body 30 has reached its closing position in time, before the casting material has reached valve body 30. The force transducer 20 is arranged at the end of a side arm 9c of the channel section 9b. In addition, a storage space 9d is provided in the area of the force transducer 20 in which that for the closing movement of the force transducer 20 and that in operative connection with it necessary elements can be built up. in the further two plungers 38, 39 are shown, which are used to tension one of them Representation not visible spring package are provided.

Fig. 7 shows a first cross section through the one in the starting position Valve device along the line A-A in Fig. 6, the two plungers 38, 39 for a better understanding of how it works than in a common vertical plane are drawn horizontally.

In addition to the force transducer 20, the valve body received in a valve channel 34 30 and the two plungers 38, 39 are from this illustration by means of a Spring 25 loaded working piston 24, a poppet valve 27, a drive plate 23, a pressure plate 35 and a spring assembly 36 can be seen. The valve body 30 has a collar 32 which is provided with axial recesses 33, via which the gases from the vent passage portion 9b into one above the valve body 30 arranged outlet channel 41 can reach the vacuum pump connected is. The force transducer 20 has a collar 21 which is in the reverse direction directional movement engages frictionally on the drive plate 23. The Driving plate 23 engages the valve body 30 at the upper end, during this it engages in the working piston 24 at the lower end. On the back side the drive plate 35, the spring assembly 36 is arranged, which by means of Pressure plate 35, the force transducer 20 and the valve body 30 and the working piston 24 Press forward in the starting position shown here. About the the spring plunger becomes the two plungers 38, 39 which penetrate the drive plate 23 freely 36 compressed when installing the valve device 10, so that the force transducer 20 by the kinetic energy of the casting compound can be moved backwards, as will be explained later. Of the The closing path of the force transducer 20 is a fraction of the closing path of the Valve body 30 and the working piston 24 limited. This allows the of the Pouring mass transferred to the moving parts 20, 23, 24, 30 kinetic energy be kept within certain limits. To the valve body 30 from here Moving the open to the closed position shown must be done by the force transducer 20 only a shock pulse can be transmitted. Through this shock pulse the drive plate 23 together with the valve body 30 and the working piston 24 in Freewheel moved to its end position. To support the closing movement and / or around the working piston 24, the drive plate 23 and the valve body To hold 30 in the end position, the working piston 24 can pass through the channel 28 pneumatically. As soon as the working piston 24 from the poppet valve 27 has lifted, the entire end face of the working piston 24 from the pressure medium acts, which supports the closing movement or the working piston 24 is held in its end position.

8 shows a cross section through the second vent valve 12 of the valve device. This consists essentially of a closing piston 45, one Driving plate 48, a pressure plate 49, two springs 50, 51 and the one in one Valve channel 54 received valve body 52. The movable closing piston 45 is in turn provided with a collar 46 which is non-positively attached to the Driving plate 48 attacks. The drive plate 48 is operatively connected to the valve body 52 by engaging the valve body 52 at the upper end. About the two springs 50, 51, the drive plate 48 together with the Valve body 52 and the closing piston 45 pressed forward. Around the valve body 52 to move from the open to the closed position shown here is about a channel 44 leading to the closing piston 45 is supplied with a pressure medium the end face of the closing piston 45 and this together with the drive plate 48 and the valve body 52 against the spring force moved against an end stop at the rear. The one immersed in the valve channel 54 Head 53 of valve body 52 seals valve channel 54.

Because the second vent valve 12 is actuated externally, the second one Vent valve 12 leading vent duct section 9a designed in a straight line become, which is reflected in a very low flow resistance. However, it must be ensured that the second vent valve 12 is closed is before the casting material has reached this.

FIG. 9 shows the cross section taken along the line A-A in FIG valve device built into a die-casting mold consisting of two halves 5a, 5b 10. When installed, the spring assembly 36 is on by the two the one half 5b of the die 5, the plungers 38, 39 pressed together. The valve body 30 is under the action of the closing spring 25 of the working piston 24 still in the open position, so that the gases from the Mold cavity via the ventilation channel 9 and the valve channel 34 into the outlet channel 41 can flow, as indicated by arrows 57. As soon as the Casting compound has reached the force transducer 20, this is under the force of pouring pouring material suddenly moved to its end stop. The Bund 21 on the force transducer 20 transmits this force pulse to the drive plate 23, which is under the effect of the kinetic mediated by the force transducer 20 Energy takes off from the force transducer 20 after it reaches its end position has, and together with the valve body 30 and the working piston 24 the return force of the closing spring 25 is moved further. The vent valve 11 closed by the head 31 of the valve body 30 in the valve channel 34 dips. The closing movement of the vent valve 11 is supported by the pressure of a pressure medium applied to the working piston 24, which after lifting the working piston 24 from the control valve 27, the entire end face of the working piston 24. However, it should be mentioned that the vent valve 11 normally without the support of the working piston 24 can be closed, because the closing movement of the vent valve 11 necessary energy from the mold cavity 8 into the ventilation channel 9 penetrating liquid casting material G is applied.

After the casting compound has hardened, the right half of the die 5b away. The riser is activated by the two under the action of the spring assembly 36 standing plungers 38, 39 ejected.

The venting performance can be achieved with a valve device 10 configured in this way significantly increase compared to conventional vent valves without the valve device is much larger. Thanks to the two-stage ventilation process, in which one vent valve 12 is closed externally, before the mold cavity 8 is completely filled and in which the other vent valve 11 actuated by the casting material penetrating into the mold cavity 8 reliable operation can also be ensured.

Claims (14)

Process for venting die casting molds (5) from die casting machines, which are provided with a casting piston (2) arranged in a pressure chamber (1) for injecting the liquid casting material (G) into the mold cavity (8), the die casting mold (5) having at least a ventilation channel (9, 9b) leading out of the mold cavity (8) is provided, in which a ventilation valve (11) is arranged, which is in operative connection with a force transducer (20) which extends from the mold cavity (8) into the ventilation channel ( 9) advancing casting material (G) is acted upon and shifted, characterized in that the mold cavity (8) and / or the pressure chamber (1) is / are vented during the filling process in addition to the first vent valve (11) via a second vent valve (12) , wherein the second vent valve (12) is closed before the mold cavity (8) is completely filled, and wherein the first vent valve (11) thereafter from that in the vent ventilation channel (9, 9b) penetrating and the force transducer (20) acting casting material (G) is closed. A method according to claim 1, characterized in that the second vent valve (12) is closed by a third-party operation, using as a criterion to close the second vent valve (12) since the start of the filling process elapsed time, the position of the plunger (2), that of the plunger (2) distance traveled, the level of the pressure chamber (1) or the level of the Mold cavity (8) is used. A method according to claim 1 or 2, characterized in that the second Vent valve (12) is closed before the mold cavity (8) to more than Half is filled with the casting material (G), preferably before the casting material (G) penetrates from the pressure chamber (1) into the mold cavity (8). Method according to one of the preceding claims, characterized in that that a vacuum in the ventilation duct to support the ventilation process (9) is generated. Method according to one of the preceding claims, characterized in that that the second vent valve (12) is closed hydraulically or pneumatically becomes. Valve device (10) for performing the method according to one of the preceding Claims, characterized in that the valve device (10) first vent valve (11), which is operatively connected to a force transducer (20), which extends from the mold cavity (8) into the ventilation channel (9, 9b) penetrating casting material (G) and that the valve device (10) has a second, externally operated vent valve (12). Valve device according to claim 6, characterized in that the valve device (10) a substantially rectilinear vent duct section (9a), at the end of which the second vent valve (12) is arranged is. Valve device according to claim 6 or 7, characterized in that a a further, angled ventilation duct section (9b) is provided in which the first vent valve (11) is arranged. Valve device according to claim 7 and 8, characterized in that the further, angled ventilation duct section (9b) and essentially straight ventilation duct section (9a) into a common Vent channel (9) open. Valve device according to claim 8, characterized in that the cross section of the straight ventilation duct section (9a) is greater than the middle cross section of the angled ventilation duct section (9b). Valve device according to one of claims 6 to 10, characterized in that that the force transducer (20) in the angled ventilation duct section (9b) is arranged, and that the force transducer (20) in the flow direction of the Casting material (G) seen before the first vent valve (11) is arranged. Valve device according to claim 11, characterized in that the force transducer (20) is designed as a thrust member, the working stroke of a fraction of the valve body (30) of the first vent valve (11) to be covered Way is limited, and that the valve body (30) over the working stroke of the force transducer (20) is also free to move. Valve device according to one of claims 6 to 12, characterized in that the valve device (10) consists of two device halves (10a, 10b) that the two valve bodies (30, 52) of the two vent valves (11, 12) by means of springs (25, 51) are biased and that the springs (25, 51) on one half of the device (10a) are supported. Valve device according to one of claims 6 to 13, characterized in that that means for detecting the position of the casting piston (2), that of the casting piston (2) distance traveled, the time elapsed since the start of the filling process, the level of the pressure chamber (1) or the level of the mold cavity (8) are provided.

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