EP2808104B1 - Casting valve with a final compression piston - Google Patents

Description

The invention relates to a pouring valve for supplying melt of a casting device with a valve housing, which has a melt channel connection as inlet and a valve outlet as outlet, with a valve cell for receiving the melt and with a closing means for changing the Ventilauslassquerschnittsfläche. The invention further relates to a casting apparatus with such a casting valve and a casting method for producing castings with this casting apparatus.

From the prior art numerous measures are known to influence the mold filling process of casting cavities. For each type of melt, certain gate speeds and gate systems are suitable. Since a maximum gate speed must not be exceeded, it is necessary to dimension the cross-section of the gate surface and thus the part of the gate system, which allows the separation of the gate from the die after casting, sufficiently large. This requirement leads in flat and thin-walled castings to a high proportion of circulating material, the mass of which may be in the order of the casting material itself. The circulating material is then melted again, which requires a considerable external energy supply.

To reduce the amount of circulating material, the teaches DE 10 2011 050 149 A1 , a pouring valve in the form of a die-casting nozzle directly at the sprue of the To arrange die casting mold. By a resistance heater, the pouring valve is initially kept open. Turning off the heater leads to plug formation and thus to closing of the pouring valve. Controlled or temperature-independent closing of the valve is not possible. To open the plug must be reliably melted again, which prolongs the process duration and due to the temperature fluctuations requires a higher total energy input per casting.

Another controllable pouring valve for metallic melts is in DE 34 27 940 A1 disclosed. Inductively, the amount of melt is metered fed through the pouring valve, and in conjunction with room boundary elements is a barrier.

DE 10 2007 047 545 A1 discloses a pouring valve which is closable by means of a piston. The piston is axially movable in a valve housing. This gap accuracy due to concentricity errors of the piston does not lead to inhomogeneous mass flows and a reliable closing of the pouring valve is ensured, the piston skirt surface has a larger angle to the valve main axis than the valve housing in the outlet region. In the closed state, the piston thus forms an annular bearing surface with the housing wall.

Both latter casting valves can be used to reliably fill a casting cavity with a predetermined amount of melt. In order to compensate for the shrinkage of material during the solidification of the casting, however, melt must continue to be supplied. Either The above-mentioned pouring valves can not close until the shrinking process has been completed, which requires heating at least until they close and makes precise metering more difficult. Or a second mechanism is required which fills and recompresses the hollow volume resulting from the shrinkage process by means of a melt replenishment. The pouring valve and the Nachverdichtungsmechanismus must be coordinated with each other, which is complex, the caster can be built expansively and thus increases the energy required for heating.

A die casting machine according to DE 195 08 867 A1 has at least one movable and one stationary mold part, which are divided along a parting plane, and a mold cavity enclosed by these mold parts. In this mold cavity, a metal to be cast is injected via a runner of the mold with the aid of a casting piston. The casting piston is displaceable in a casting chamber, into which the metal can be introduced, by means of a drive along the longitudinal axis of the casting chamber. Furthermore, at least one Nachverdichterkolben acting on the injected metal is provided, which can be moved out of a cavity receiving it on the metal. At least one Nachverdichterkolben is hineinbewegbar in a staggered to the longitudinal axis of the casting chamber position in the runner.

After DE 195 33 447 C1 is used for filling a casting mold with a molten metal, the molten metal fed to the mold cavity of the casting tool via an annular chamber, which opens into its outer periphery of the mold cavity over its entire circumference. The supply of the molten metal into the annular chamber is interrupted by a piston displaceably mounted in the annular chamber. The molten metal can over a large feed cross section be supplied, resulting in a low filling rate, a short filling time.

Object of the present invention to improve the prior art and in particular to provide a pouring valve for a casting apparatus, which avoids the disadvantages mentioned above. Furthermore, it is a particular object of the invention to provide a die-casting method for metallic melts, which enables rapid casting while minimizing the supply of heat.

The object is achieved by a pouring valve for supplying melt of a pouring device, wherein the pouring valve comprises a valve housing having a melt channel connection as inlet and a valve outlet as outlet, a valve cell for receiving the melt and a closing means for changing the Ventilauslassquerschnittsfläche and wherein the valve cell can be connected via a melt channel connection with a melt channel, which can be prestressed by means of casting pressure, and the casting valve has a recompression piston for recompressing the melt after the mold has been filled.

The integration of the recompression piston as squeeze pin in the pouring valve space-saving arrangement is created, which emits relatively little heat due to their compactness. Due to the fact that the melt for the filling of the casting cavity and the melt for recompression come from the same valve cell or according to the valve outlet downstream of the valve cell, the number of required heating means and pipelines can also be kept low.

The valve cell of the casting valve can be connected to a melt reservoir or a casting chamber via the melt channel connection. If the pouring valve is part of a die casting device, the melt channel connection, the valve cell and the valve outlet are pressure-resistant. The valve cell can also have a plurality of melt channel connections, via which the melt can flow.

If the valve cell has a plurality of melt channel connections, it can be provided that the melt flows out again during casting via at least one channel. The valve cell thus does not form the end of the melt channel, but is also flowed through by melt during the casting process, which does not leave the pouring valve via the valve outlet. As a result, a continuous heat input is ensured during the casting, and the heating means, which is arranged in or on the casting valve can be made smaller or possibly omitted entirely.

In one embodiment, the pouring valve may be integrated into the die-cast channel such that the valve cell passes through a part of the melt channel can be prestressed by means of casting pressure. The valve cell may have a storage volume, which is advantageously completely enclosed by the valve housing, so that it can be heated as located in the casting valve hot cell. An unwanted solidification can be easily avoided.

It is not necessary that the valve cell occupies a certain volume; The pouring valve can be integrated in a melt channel particularly well if the cross-sectional area of the valve cell corresponds to the sum of the cross-sectional areas of the feeding melt channel connections. In this case, it is not enlarged in diameter compared to the melt channel and thus provides no additional volume

The pouring valve preferably has as closing means a valve piston which is movable axially in the direction of the valve outlet and can close it. The valve housing and the valve piston are preferably designed so that the diameter of the effective Ventilauslassquerschnittsfläche is steadily reduced when ancestors of the valve piston. The effective Ventilauslassquerschnittsfläche is the surface which is flowed through during the casting vertically from the melt. When closing the pouring valve, the Ventilauslassquerschnittsfläche is reduced at least after an initial phase, so that also reduces the flowing amount of melt due to the constant pressure. Finally, the passage is narrowed so that the melt stream breaks off or decreases so that the Melt cooled and another flow is prevented without external temperature supply.

The valve piston and the valve piston enclosing housing portion preferably form a conical valve seat. At least one of the two components valve piston or housing wall thus has a chamfer or a chamfer in such a way that the Ventilauslassquerschnittsfläche tapers in the direction of the valve outlet. As a result, when the valve piston approaches the housing bottom, the melt flow can take place through an annular opening which allows a relatively vortex-free melt flow. The effect is exacerbated when both components, the valve piston lateral surface and the housing bottom are seen in the sectional view provided with bevels.

The bevels do not necessarily have to be conical. Thus, the housing inner wall or the piston skirt surface may be partially conical or curved in the axial direction. If the piston skirt surface or the valve seat are crowned, concentricity errors of the valve piston can be compensated particularly well, so that despite possible gap dimensions, the mass flow in the closed state is minimized. Advantageously, the crown also causes a line contact to form between these components when closing. Jamming of the valve piston can be reliably prevented by the thus lack of surface contact and possibly remaining between the surfaces solidifying melt material, which prevents damage to the valve piston and the valve housing. In the valve gap may have penetrated melt material due to the temperature gradient to the environment cool down and melted at the valve opening for the next casting process again.

The valve piston and the housing wall may be formed in the axial direction specific to the casting so that the tapered valve outlet cross-sectional area formed by the two components is designed so that the desired mold filling speed can be influenced by moving the valve piston. Thus, at the start of casting a large flow cross-section may be provided, which is required for the rapid filling of the casting cavity and to avoid trapped air, which is reduced with increasing degree of filling according to the shape of the casting cavity. If the valve piston has a variable diameter over its axial length, with a correspondingly shaped valve housing, only a temporary reduction in the flow cross-section can take place, which is widened again before the final closing of the pouring valve.

The valve piston and the valve outlet are preferably arranged centrally in the valve housing. As a result, the pouring valve builds compact. Axially on the valve piston, the valve piston drive can connect to the side facing away from the valve outlet and be integrated into the housing of the pouring valve. If the secondary compression piston can be moved via a separate drive, this can also be integrated into the valve housing.

In order to prevent a temperature drop of the melt and thus unwanted crystallization processes, can the melt channel connection, the valve outlet or other melt-contacting areas can be made heatable in the pouring valve. Each melting section is preferably heated separately. An electrically operated heater has a low inertia behavior and allows good control or regulation of the heating power. For example, the channel walls themselves may be heated or covered by coils. The valve cell can also be heated.

In one embodiment of the invention, the valve piston also takes over the function of Nachverdichtens. The same component then forms both the closing piston and the Nachverdichtungskolben. For this purpose, the valve piston is designed, for example, as a circular cylinder which forms a valve seat with a valve housing wall. The valve housing wall may initially have a conical shape and then be tubular, so that the valve piston initially throttles the melt inflow during the process in the tubular section, closes the valve upon reaching the tubular section and then recompresses during the process within the tubular section.

In another embodiment, the casting valve on two pistons, which are at least temporarily movable relative to each other. The first piston is formed by the valve piston, with which the pouring valve is closable, and the second piston is designed as a secondary compression piston separately from the valve piston. Preferably, the two pistons are arranged coaxially with each other, wherein the Nachverdichtungskolben is located inside. The housing wall is designed so that the valve piston in this Can move arrangement on the valve wall, is prevented from further movement and due to the smaller diameter of the Nachverdichtungskolbens whose further movement still possible.

The secondary compression piston may have its own piston drive for the relative movement to the valve piston. As a result, it can be controlled separately from the valve piston, and it can be matched in its performance to the recompression. As piston actuators for the Nachverdichtungskolben and the valve piston, for example, hydraulic drives or electric spindles come into question. The two piston drives can also be formed by different drive types.

A particularly compact pouring valve can be achieved if both pistons are movable by the same drive. Via drive valves or other control mechanisms it can be provided that only one of the pistons or both pistons are displaced simultaneously at a certain point in time. If a relative displacement is undesirable, at least in phases, as in the closing of the pouring valve, both pistons can also be connected to one another by suitable coupling means, so that they can only be moved together.

In another variant, the two pistons are coupled to each other and can only be moved to each other by increased effort. As long as the valve piston has not moved to block and thus closes the valve seat on the valve, then move both pistons together. By the then leaps and bounds increasing force dissolves the Nachverdichtungskolben of the valve piston and can then be moved alone. A piston drive is sufficient for this variant. A complex control unit is not required in this embodiment.

The piston drive is preferably carried out hydraulically and is arranged for thermal reasons on the opposite side of the valve outlet. In order not to expose the drive unit to the high temperatures of the hot melt, the pouring valve may have the pressure force transmitting decoupling means. The decoupling means are disposed between the piston heads and the piston drives and may be formed by ceramic layers or other sufficiently strong thermal insulators.

In addition or instead, the heat transfer can be reduced by a suitable mechanical structure. Compared to the piston diameter, thin-walled intermediate bolts which connect the piston head to the piston drive, transmit less total heat and allow the arrangement of coolants in the spaces thus created.

The pouring valve according to the invention is preferably installed in a die casting apparatus for metallic melts, but can also be used in other casting methods, such as in continuous casting or casting of non-metallic melts.

In a casting apparatus with a pouring valve according to the invention, the amount of circulating material is thereby reduces filling and recompression via the same pouring valve. A casting device preferably has the pouring valve according to the invention directly on the gate area of the casting or on the casting itself. By spatially very close arrangement of the casting then the proportion of Sprue and the amount of circulating material can be further reduced. In particular, in the case of planar structural parts, casting compositions of less than 20% of the casting mass can be achieved thereby. At the same time, the sprue system can be compact. The sprue material can be reused as circulating material. The fact that less sprue material must be melted and the hot melt in the loop is always close to the mold cavity available, less time is required for the casting cycle, so that the timing is improved.

The invention also relates to a method for die casting with a die casting device and a casting valve having a valve piston, which provides the following steps: providing a cleaned and prepared for a mold filling casting cavity with a closed pouring valve, opening the pouring valve for pouring, closing the pouring valve after Formfüllende, removing the Casting and re-compression during the cooling process and before the removal of the casting by means of a built-in the pouring valve piston.

The proposed method allows the filling and the recompression via the same gate opening, so that the number of gate areas is reduced compared to separately arranged to the casting valve squeeze pins. The required post-processing of the casting is thus reduced. The fact that the Nachverdichtungskolben and the Valve piston are arranged close to each other to space, the heat losses occurring are minimized and facilitates the coordination between the phases in which the two pistons are actuated.

Figur 1

einen Teil einer erfindungsgemäßen Gießvorrichtung mit einer Gießkammer und einem Gießventil im Längsschnitt in schematischer Darstellung,

Figur 2

einen Längsschnitt eines erfindungsgemäßen Gießventils mit zwei konzentrischen Kolben sowie

Figur 3a

das erfindungsgemäße Verfahren zum Betreiben des Gießventils durch eine schematischen Darstellung der Stellung des Ventilkolbens zum Zeitpunkt der Reinigung der Gussteilformkavität,

Figur 3b

eine schematische Darstellung der Stellung des Ventilkolbens vor dem Gießvorgang,

Figur 3c

eine schematische Darstellung der Stellung des Ventilkolbens während des Gießens,

Figur 3d

eine schematische Darstellung der Stellung des Ventilkolbens nach Formfüllende,

Figur 3e

eine schematische Darstellung der Stellung des Ventilkolbens während des Abkühlens und

Figur 3f

eine schematische Darstellung der Stellung des Ventilkolbens unmittelbar vor der Gussteilentnahme.

Hereinafter, the pouring valve and the working method for operating the pouring valve in a casting apparatus will be described with reference to drawings. The individual figures show:

FIG. 1

a part of a casting device according to the invention with a casting chamber and a pouring valve in longitudinal section in a schematic representation,

FIG. 2

a longitudinal section of a pouring valve according to the invention with two concentric pistons and

FIG. 3a

the method according to the invention for operating the pouring valve by a schematic representation of the position of the valve piston at the time of cleaning the casting mold cavity,

FIG. 3b

a schematic representation of the position of the valve piston before the casting process,

Figure 3c

a schematic representation of the position of the valve piston during casting,

3d figure

a schematic representation of the position of the valve piston after Formfüllende,

FIG. 3e

a schematic representation of the position of the valve piston during cooling and

FIG. 3f

a schematic representation of the position of the valve piston immediately before the casting removal.

FIG. 1 schematically shows a part of a casting apparatus 1 for die casting of metallic melts 2 such as magnesium or aluminum melts. The casting apparatus 1 has a casting chamber 4, which can be filled from a melt reservoir, not shown, via a melt valve 19. The melt 2 is conveyed from the horizontally oriented casting chamber 4 by a hydraulically moved, in the horizontal advancing casting piston 6 in a melt channel 11 and pressurized.

The melt channel 11 is surrounded by heating means 5 in the form of coils, which prevent cooling of the melt 2. From the heated melt channel 11, the melt 2 passes through a melt channel connection 12 into the valve cell 8 (FIG. FIG. 2 ) of the pouring valve 7 and from there via the valve outlet 10 into the casting cavity 3. The casting cavity 3 itself is formed by two half-molds 15, 16 and is formed in a known manner by the enlarged by the Schwindmaß negative mold of the casting to be produced. The half-molds 15, 16 are separable from each other at a parting surface 9, so that the finished casting can be removed.

FIG. 2 shows a pouring valve 7 with a valve housing 13 which has a fillable via the melt channel connection 12 valve cell 8, which is part of the melt channel 11 itself and in comparison to this and the melt channel connection 12 has no enlarged cross-section. Centrally in the valve housing 13, the valve piston 14 is arranged, via which the valve outlet 10 is closed. On the end face 17 of the valve piston 14, a convex lateral surface 18 of the valve main cone connects, which merges axially into a subsequent cylinder section 20. The inner wall 21 of the valve housing 13, which adjoins the Ventilauslass 10 has an inclination relative to the main valve axis 22, which is greater than that of the lateral surface 18. When closing the Gießventils 7 of the valve piston 7 and inner wall 21 of the valve housing 13 therefore form an annular gap and in the closed state due to the crowning a circular line contact as a valve seat.

The valve piston 14 is driven by a first piston drive 24, which operates hydraulically and is arranged axially offset from the valve piston 14. Since the valve piston 14 is in contact with the hot melt 2, decoupling means 26 are provided in the form of intermediate bolts as spacers mechanically and thus thermally decouple the piston drive 24 with the piston plate 28 from the piston head 29 of the valve piston 14, but the pressure force on the Nevertheless, piston head 29 is transferred.

The valve piston 14 is formed as a hollow cylinder and has co-axial to the direction of a Nachverdichtungskolben 23. In the same way as the valve piston 14, the recompression piston 23 has a second piston drive 25 which is operable independently of the first piston drive 24. Its hydraulic chambers 30 are connected axially to those of the first piston drive 24.

The operation of the in the Figures 1 and 2 illustrated pouring valve 1 is divided into six different phases. In the in FIG. 3a shown, the initial position, which is reached after the removal of the casting of the previous casting cycle ', the valve piston 14 and the Nachverdichtungskolben 23 are closed and as far as possible in the direction of the valve outlet 10 driven. The melt channel 11 is therefore separate from the casting cavity 3, which therefore can be cleaned and prepared by a spray process for the next casting.

Before the next casting process, the casting cavity 3 is closed so tightly that it withstands the melt pressure of the subsequent die casting process. In this second phase, the inner recompression piston 23 returns to its starting position, which is set back so far from the valve piston 14 closing the valve outlet 10 that a blind hole 27 is created between the inner walls of the valve piston 14. The blind hole depth corresponds approximately to the stroke of the valve piston 14th

By retracting the valve piston 14, the actual casting process is initiated as a third phase. The valve piston 14 releases from its annular valve seat, and by the now flowing, hot melt 2 is possibly at this point cooled material melted. Due to the ring-line contact and any heating located on the pouring valve 7, the solidified amount of melt is so small that it is completely melted and does not make opening the valve piston 14 difficult or only insignificantly difficult. The valve outlet 10 is opened to the maximum, and the melt 2 can flow annularly between the pistons 14, 23 and the inner wall 21 of the valve housing 13 in the Gussteilkavität 3. The envisaged for filling amount of melt is pushed by the advancing casting piston 6 via the melt channel 11.

Upon completion of the mold filling operation, the pouring valves 7, of which in FIG. 1 only one is shown, closed by ancestors of the valve piston 14 (fourth phase, Figure 4). Due to the relative movement of the valve piston 14 and the non-moving Nachverdichtungskolbens 23 again forms the end-side blind hole 27, and the casting can cool. Since, due to the closed valve piston 14, the melt pressure can no longer be applied through the casting piston 6 of the casting chamber 4, the required casting pressure is now generated by the secondary compression piston 23.

In the fifth cooling phase, the casting solidifies and the casting chamber 4 is prepared for a new mold filling operation. During cooling, the consequent shrinkage of material is compensated for by the secondary compression piston 23 which presses the melt 2 located in the blind hole 27 and the immediately adjacent region into the casting cavity. If the amount of melt required for the re-compaction 2 the Blind hole volume corresponds, the adjoining the valve outlet 10 runner can be particularly short or possibly even eliminated. As in FIG. 3e shown moves in this embodiment, the Nachverdichtungskolben 23 beyond the end face 17 of the valve piston 14 out into the Gussteilkavität 3 into it. The solidification process can be accelerated by supplying cooling power via cooling channels.

Prior to the opening of the casting cavity 3 and the removal of the casting, in the last phase ( FIG. 3f ) a retraction of the recompression piston 23; the valve piston 14 remains closed.

LIST OF REFERENCE NUMBERS

1

caster

2

melt

3

Gussteilkavität

4

casting chamber

5

heating

6

casting plunger

7

casting valve

8th

valve cell

9

interface

10

valve outlet

11

melt channel

12

Melt channel connection

13

valve housing

14

plunger

15

Mold half shell

16

Mold half shell

17

front

18

lateral surface

19

melt valve

20

cylinder section

21

inner wall

22

Valve main axis

23

Nachverdichtungskolben

24

first piston drive

25

second piston drive

26

decoupling means

27

blind

28

piston plate

29

piston head

30

hydraulic chamber

Claims (10)

1. A casting valve (7) for supplying melts (2) to a casting device (1), comprising:

   - a valve housing (13) comprising a melt channel connection (12) as an inlet and a valve outlet (10) as a run-out,

   - a valve compartment (8) for receiving the melt (2) ;

   - a closing means for modifying a cross-sectional surface of the valve outlet, wherein

   - the valve compartment (8) is connectable via the melt channel connection (12) with a melt channel (11) that is pressurizable by means of a casting pressure; and

   - the casting valve (7) comprises a post-compression piston (23) configured to post-compress the melt (2) after completion of a mold filling.
2. The casting valve according to claim 1, characterized in that the closing means is designed as a valve piston (14) and forms a cone-shaped valve seat together with a part of the inner wall (21) of the valve housing (13).
3. The casting valve according to claim 2, characterized in that the cone-shaped part of the inner wall (21) is conical and the valve piston (14) has a crowned piston lateral surface (18), which forms a linear contact with the inner wall (21) during closing.
4. The casting valve according to claim 2 or 3, characterized in that the casting valve (7) has a post-compression piston (23), which is disposed coaxially with the valve piston (17) and is movable relative to it.
5. The casting valve according to claim 4, characterized in that the casting valve (7) has separate piston drives (24, 25) for the pistons (17, 23).
6. The casting valve according to claim 5, characterized in that one of the piston drives (24, 25) is designed as a hydraulic drive.
7. The casting valve according to claim 1, characterized in that the casting valve (7) has a heating means (5) for heating the valve compartment (8).
8. The casting valve according to claim 1, characterized in that the casting valve (7) has insulation means (26) for thermal insulation of the valve piston (17) from the piston drive (24).
9. A casting device (1) for die casting with a mold cavity (3) and a casting valve (7) according to one of the afore-mentioned claims, characterized in that the casting valve (7) is disposed directly on the gate area or directly on the cast part cavity (3).
10. A method for die casting with a casting device (1) and a casting valve (7) having a valve piston (14), which comprises the following steps:

    - providing a mold cavity (3), which is cleaned and prepared for a mold filling process, with the casting valve (7) in a closed position;

    - opening the casting valve (7) for casting;

    - closing the casting valve (7) after filling the mold;

    - removing the cast part, characterized in that

    - a post-compression is carried out by means of a post-compression piston (23) integrated in the casting valve (7) during the cooling process and before removing the cast part.

Images