EP0055210B1 - Apparatus and process for low-pressure casting - Google Patents

Abstract

With low-pressure or die-casting methods there frequently occur leaks during the transfer of the molten metal from the metal containing basin or vessel to the mold. These leaks often lead to serious accidents and related operating interruptions. According to the invention these problems are solved by a casting method, wherein all movements of the mold occur in a vertical plane. With a preferred embodiment of apparatus for the performance of the method the mold is placed in a positive or form-locking manner with its casting or pour opening upon the casting hole of the metal containing vessel or basin and pressed against the latter in a fluidtight fashion by means of a pneumatic lifting cylinder. This affords the advantage of a simple connection of the mold with the basin and without requiring a coupling mechanism, and, additionally, the heating of the riser or up tube and/or immersion tube can be omitted, which otherwise conventionally was performed by gas heating.

Description

The invention relates to a low-pressure casting device according to the preamble of claim 1 and a low-pressure casting method according to the preamble of claim 4.

Mold casting has been made by hand for many years. Here, melt is poured directly from a melting furnace into the mold using a ladle, which is carefully set up (pulled up) by hand to prevent voids from forming during the filling process. The mold, cooling and sizing are also done by hand. This work requires a lot of practice and concentration from the founder and poses a considerable safety risk.

Accordingly, attempts have been made to mechanize the casting process, i. H. The timely installation of the mold during casting was carried out by a machine, as was the shaping, cooling and sizing. The melt was again filled by hand with a ladle, which is still a corresponding source of danger.

Subsequently, the mechanization was continued by means of a rotary table, the mold was placed on the furnace via a gas-heated coupling system and the melt was pressed out of the furnace into the mold using compressed air. By turning the rotary table further, the other work steps known from manual casting were carried out partly automatically, partly manually in corresponding stations.

It has been shown that with such a casting device, sealing problems occur on the coupling system. Under the known particularly tough requirements of a foundry, a rotary table can only be guided precisely for a very limited period of time. As a result, business interruptions and serious accidents very often occur as the melt flows out or is squeezed out.

A low pressure casting device forming the preamble of claim 1 is also known from GB-A-1 180370, which is intended to solve these problems. However, it is very complicated, so that malfunctions and accidents can also occur in this case.

It is accordingly an object of the invention to provide a low-pressure casting device of the type mentioned above and a low-pressure casting method with this device, which are less susceptible to faults and have high performance. In addition, the security risk compared to known systems is to be reduced. The construction of the device should be economical and have as few moving components as possible, the economy of the casting process being increased.

To achieve this object, the characterizing features of claim 1 are proposed in a device according to the preamble of claim 1.

The advantage of the invention is the fact that the low-pressure casting device is very simple and that the hydraulic and / or pneumatic lifting and swiveling device can operate economically with sufficient safety.

By precisely positioning the mold over the pouring hole of the crucible, there is a short, form-fitting connection which allows the omission of a coupling system; this eliminates the need to heat the riser pipe.

According to a further development of the device according to claim 2, the lifting and swiveling device has at least one pneumatic lifting cylinder which is arranged between the undercarriage and the mold and contains two swiveling cylinders acting on a two-armed lever, the two-armed lever with the mold via its mold holders or whose frame is connected.

The two-armed lever swivels the mold safely and with simple means during certain phases of the casting process.

According to a further development, a locking cylinder is provided on mold holders of the mold halves of the mold, each of which is connected at one end to a mold half. This construction enables easy and safe closing of the mold halves.

The low-pressure casting method with the low-pressure casting device according to claim 1 consists in that the mold halves of the mold are rotated by 90 ° in the vertical plane and their cut surfaces are lowered and immersed frontally in a cooling-sizing emulsion of the washing station.

It is expedient if, in a first process step with the mold halves open, the mold is turned into an inclined position, a casting core is inserted, the mold is closed and then turned back into its horizontal position. The inclined position thus facilitates manipulation and enables a casting core to be inserted easily without tools when the mold is open.

It is advantageous if the riser pipe is heated by the melt by means of heat conduction and heat radiation. It is therefore not necessary to keep the riser pipe at the required temperature, either electrically or with gas. The ceramic of the riser works as a heat store, so that the necessary temperature of the riser is maintained even after a long time.

According to a further development, the pouring opening of the mold is pressed directly onto the pouring hole of the crucible. It is therefore not necessary to use additional coupling systems that used to cause leaks and possibly also accidents during the casting process.

• Fig. 1 eine an einer Laufschiene aufgehängte Gießvorrichtung über der zentralen Ausformstation einer Gieß-Einheit,
• Fig. 2 die Gießvorrichtung Fig. 1 in geneigter Lage mit eingelegtem Gießkern,
• Fig. 3 die Gießvorrichtung Fig. 1 in einer Seitenansicht,
• Fig. 4 eine Gieß-Einheit in einer vereinfachten Ansicht von oben, ohne eingezeichnete Gießvorrichtung,
• Fig. 5 einen Schmelztiegel mit zwei Kammern in Schnittdarstellung,
• Fig. eine Teilansicht der Gießvorrichtung Fig. 1 während des Kühl- und Beschlichtungsvorgangs und
• Fig. 7 einen charakteristischen Operationsablauf bei der Herstellung von Formteilen mit Hohlräumen.

In the following the invention is based on simplified, exemplary drawings explained here. It shows

• 1 a casting device suspended from a running rail above the central shaping station of a casting unit,
• 2 the casting device FIG. 1 in an inclined position with the casting core inserted,
• 3 shows the casting device of FIG. 1 in a side view,
• 4 shows a casting unit in a simplified view from above, without the casting device shown,
• 5 shows a crucible with two chambers in a sectional view,
• Fig. A partial view of the casting device Fig. 1 during the cooling and sizing process and
• Fig. 7 shows a characteristic operational sequence in the production of molded parts with cavities.

In Fig. 1, the running rail is indicated by 1 over a casting unit. This running rail 1 forms a yoke 4 by means of supports (not shown here). A carriage 2 is arranged in a known manner so as to be movable on the running rail 1 in the arrow directions indicated. On the chassis 2, a suspension 5 is attached consisting of two double T-beams with support plates. A _' lifting cylinder 6 is located vertically in the center of the suspension 5, which is fixed on the one hand to a suspension plate 15 and on the other hand acts on a lowerable support plate 14 by means of a piston. Four vertical column guides 8 arranged concentrically to the lifting cylinder 6 are likewise attached to the carrier plate 14 and the suspension plate 15.

A mold holder 11 with a lock cylinder 12, a horizontal column guide 13 and a flange 13 'is arranged on a frame 16, shown partially cut away. In the center of the frame 16 there is an axis of rotation 10 with a two-armed lever 9, on each of which two pivot cylinders 7 act at the ends - in push-pull.

A mold 17, designed in a known manner, with a separation point 17 'and a pouring opening 30 is flanged to the mold holder 11 and drawn in dashed lines.

The casting device Fig. 1 is shown above its molding station A with the side facing away from the operator. On the left is a cooling and sizing bath 28, on the right a melting pot 25 with double chambers.

The casting device is limited in its movement sequence by the running rail 1 with the undercarriage 2 and its supports in the x direction and by a foundation 20 in the z direction. All movements take place in a vertical plane V (board level). The frame 16 with mold 17 is aligned parallel to a horizontal plane H.

In the following figures, the same parts are provided with the same reference numbers.

2 shows the casting device in FIG. 1 in a position inclined by approximately 20 ° with respect to the horizontal plane H. This was achieved by controlling the swivel cylinder 7 in opposite directions with corresponding rotation of the two-armed lever 9 and its axis of rotation 10 which is firmly connected to the frame 16.

This position serves to insert a casting core 31 into one of the two mold halves 17a and 17b.

Furthermore, 16 pivot axes 16 'can be seen on the frame, the function of which will be described later.

The side view according to FIG. Shows further details of the casting device and its suspension.

The two running rails 1 shown here are welded at the end to a running rail support 23 with struts 24.

The running rail support 23 is also welded to a support plate 21 and a support 22. The whole is detachably connected to a foundation plate 20 fixed in a foundation 18 by anchors 19.

Four rollers 3 with side guides 3 'are arranged above the chassis 2. Below this is a control block S, which is used for the electro-pneumatic control of all cylinders.

The casting device is shown while the mold 17 is being lowered onto a cover plate 33 of the crucible 25. The pouring hole 27 of the crucible 25 and the pouring opening 30 of the mold 17 are shown schematically Flap shown.

After the mold 17 has been completely lowered onto the cover plate 33, the lifting cylinder 6 exerts a vertically downward pressing force K, which creates a positive connection between the pouring hole 27 and the pouring opening 30 of the mold. Now the casting process can take place.

The overview of the entire casting unit 32, FIG. 4, in turn shows the foundation plates 20, supports 22, the two slide rail supports 23 and a slide rail 1 shown in simplified form connected, notoriously known cooling and sizing bath 28 with a sizing emulsion 42. One edge - designated 0-0 - of the crucible 25 represents the zero point of the coordinate system in the horizontal plane. The pouring hole 27 is measured from this zero point, also the corresponding control functions of the casting device.

The space between the melting crucible 25 and a part of the cooling and sizing bath 28 designated W = washing station is a shaping station A. Here, the corresponding casting core is inserted by hand when the casting device is inclined (cf. FIG. 2); likewise the casting is removed here when the mold is opened again.

• Der Schmelztiegel 25 ist als gasdicht abgeschlossener Doppelkammer-Ofen ausgebildet. Schmelze 37 wird hier durch eine elektrische Heizung 36 über dem Schmelzpunkt des Gießmaterials, im vorliegenden Fall ein Buntmetall, erhitzt. Eine keramische Ausmauerung 35 dient dabei der Wärmeisolation. Eine metallische Abdeckplatte 33 ist auf ihrer Unterseite mit einer Feinkeramik 34 ebenfalls als Wärmeisolation belegt. Ein Steigrohr 27' ebenso aus einer Feinkeramik bestehend, taucht in die Schmelze 37 und ist an seiner Oberseite mittels eines Flansches bündig in die Abdeckplatte 33 eingelassen. Über dem Gießloch 27 befindet sich die Eingießöffnung 30 der Kokille 17. Die beiden Kokillenhalterungen 11 erfahren dabei eine Anpreßkraft K', welche sich auf die angeflanschte Kokille 17 überträgt und formschlüssig einen flüssigkeitsdichten Übergang zwischen der Kokille und dem Schmelztiegel ergibt.

5, the actual Explain the casting process in more detail:

• The crucible 25 is designed as a gas-tight double chamber furnace. Melt 37 is heated here by an electric heater 36 above the melting point of the casting material, in the present case a non-ferrous metal. A ceramic lining 35 is used for thermal insulation. A metallic cover plate 33 is also covered on its underside with a fine ceramic 34 as thermal insulation. A riser pipe 27 'also consisting of a fine ceramic, dips into the melt 37 and is flush with the cover plate 33 on its upper side by means of a flange. The pouring opening 30 of the mold 17 is located above the pouring hole 27. The two mold holders 11 experience a contact pressure K 'which is transmitted to the flanged mold 17 and results in a fluid-tight transition between the mold and the crucible.

A supply line 39 connects the left chamber of the crucible 25 with a compressed air source, not shown, which emits an excess pressure p. A controllable solenoid valve 38, which controls the casting cycle, is interposed. A drain 40 for the residual pressure p 'is closed by a drain valve 41.

During the casting process, the solenoid valve 38 is opened, so that the pressure p builds up in the gas space G located above the melt 37, which presses the melt 37 into the second chamber of the crucible 25. As a result, the gas space G located on this side is compressed and the melt is pressed into the cavity of the mold 17 through the riser pipe 27 ', the opening 27 and the pouring opening 30. The casting core 31, here a hemisphere, is located half in the mold halves divided by the separation point 17 '.

After the mold 17 has been formed, it is moved over the cooling and size bath 28 by means of the casting device. Here, the two mold halves 17a, 17b together with their locking cylinders 12 and the four column guides 13 are rotated 90 ° downward about their pivot axis 16 'by means of two further pneumatic pivoting cylinders (not shown for reasons of clarity).

By lowering the lifting cylinder 6, the two mold halves 17a, 17b are immersed in the emulsion 42 consisting of cooling water and size, as in FIG. 6, a.

The operational sequence characteristic of casting hollow bodies can be followed with the aid of FIG. 7:

As the first operation, a mold core 31 is inserted into the mold half 17a when the mold 17 is rotated about a = 20 ° with respect to the horizontal plane H; Operation 1. The mold halves 17a, 17b are closed by an electrical switching pulse triggered by the operator; Op. 2. Then the mold 17 is rotated into its horizontal position and locked; Op. 3rd

By moving horizontally in the direction of the arrow, the pouring opening 30 is positioned over the pouring hole 27 of the crucible 25; Op. 4. The mold 17 is then lowered and pressed onto the pouring hole 27; Op. 5. Then the melt is pressed into the mold 17 in the manner described above; Op. 6. After a solidification time adapted to the casting, the mold 17 is lifted vertically from the casting hole 27; Op. 7. This is followed by a horizontal displacement of the casting device up to the molding station A; Op. 8. The casting is here manually removed from the mold 17; Op. 9. The mold 17 is brought to the washing, drying and sizing station W by a further manually triggered switching pulse, the mold halves 17a, 17b are rotated and lowered by 90 ° as mentioned above; Op. 10, 11. After the two mold halves 17a, 17b have dried, the mold is again moved into its starting position; Op. 12.

The process sequences described using the example of the manufacture of brass fittings can be adapted to other castings and materials in almost any way. Of course, the operations of turning the mold and inserting the core can be omitted when producing full castings.

Claims (8)

1. Low-pressure casting apparatus for cast pieces in a movably mounted mould (17), having a melting crucible (25) which is closed in a pressure-tight manner and which has a casting aperture (27) on its top, the gas cavity (G) in the melting crucible (25) being connected to a gas pressure line, and the mould (17) being indirectly secured by way of a travelling mechanism (2) to a guide rail (1), characterized in that an hydraulic and/or pneumatic lifting and pivoting device (6, 7,9, 10) is interposed between the travelling mechanism (2) and the mould (17), the lifting and pivoting device (6,7,9, 10) holding the mould (17) which is guided over the melting crucible (25), a demoulding station (A) and a washing, drying, and smoothing station (W), and an ascending pipe (27') which is immersed into the level of the melt (37) is provided (fig. 1).

2. Apparatus according to claim 1, characterized in that the lifting and pivoting device (6-10/13-15) comprises at least one pneumatic lifting cylinder (6) which is disposed between the travelling mechanism (2) and the mould (17), and comprises two pivoting cylinders (7) acting upon a two-armed lever (9), the two-armed lever (9) being connected to the mould (17) by way of its mould fastenings (11) or its frame (16) (fig. 1).

3. Apparatus according to claim 2, characterized in that one closing cylinder (12), which is connected at each end to a mould half (17a, 17b), is provided in each case on mould fastenings (11) of the mould halves (17a, 17b) (fig. 1, 2).

4. A low-pressure casting process with the low-pressure casting apparatus according to claim 1, characterized in that the mould halves (17a, 17b) of the mould (17) are each rotated through 90" in the vertical plane (V) and are lowered and immersed with their cut surfaces towards the front into a cooling smoothing emulsion (42) of the washing station (28) (fig. 6).

5. A process according to claim 4, characterized in that in a first method step the mould (17) is rotated into an oblique position, with the mould halves (17a, 17b) opened, a casting core

(31) is inserted, and the mould (17) is closed and rotated back into its horizontal position (H) (fig. 2).

6. A process according to claim 4, characterized in that the ascending pipe (27') is heated only by the melt (37).

7. A process according to claim 4, characterized in that the pouring aperture (30) of the mould (17) is pressed directly on to the casting aperture (27) of the melting crucible (25).

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