DE69903980T2 - METHOD AND DEVICE FOR FEEDING MOLTEN METAL INTO A MOLD - Google Patents

Description

TECHNICAL AREA

The present invention relates to countergravity casting and, more particularly, to the delivery of molten metal to the molds in a plant in which the molds are filled by pumping the molten metal into the mold cavities via a filling head which is temporarily connected to a filling opening in the mold, the molds being held stationary and the filling head being moved axially and, if necessary, laterally/sideways to provide the temporary connection.

TECHNOLOGY BACKGROUND

When casting aluminium alloys and other similar light metal alloys in such an installation, it is known that the components in direct contact with the molten metal should be made of ceramic material in order to avoid deterioration of the material. Such material is difficult to machine and flexible joints are difficult to produce. However, in order to bring the filling head into and out of engagement with the filling opening and to move the filling head into alignment with the filling opening, it is necessary to be able to move the filling head axially and in a lateral direction respectively. Adjustment in the lateral direction may be required in some cases as a result of a change in the delivery position of the moulds, for example in a mould train. From EP-760 723 it is known to cast light metal alloys as described above and this document does indeed mention the above axial and lateral movement of the filling head, but is silent on the steps that must be taken to achieve these movements. Accordingly, it is assumed that the entire filling system is moved together to achieve these movements in relation to the need to seal the interior of the filling system from the ambient air to prevent oxidation of the molten metal.

A casting process of the type mentioned above normally involves melting raw material, for example aluminum, in a melting furnace. The molten metal is transferred to a buffer furnace, in which the molten metal is prepared for casting by temperature regulation, alloying, degassing, mixing, etc. From the buffer furnace, the molten metal is transferred to the pump furnace and pumped into the molds through the filling pipe and the filling head. In order to prevent heat loss from the furnaces and to provide a way to protect the molten metal from oxidation by using an inert gas over the molten metal, the furnaces are preferably designed as substantially closed vessels. In order to provide the above mentioned lateral and axial movement of the filling head without common movement of the entire filling system, it is necessary to provide a certain type of flexibility. This flexibility is difficult to provide due to the need to use ceramic materials - with inherently inflexible properties - for components in direct contact with the molten metal.

DISCLOSURE OF THE INVENTION

It is an object of the present invention to provide a method and a device for use in the method which enable the mentioned lateral and axial movement of the filling head to be carried out in an advantageous manner without moving the entire mass of the filling system, and this object is achieved with a method of the type which according to the present invention also comprises the features set out in the characterizing portion of claim 1. With this method the mass to be moved when carrying out the lateral and axial movement of the filling head is significantly reduced. Preferred embodiments of the method and the device for use in the method are set out in claims 2-10.

DRAWING SHORT DESCRIPTION

In the following detailed part of the present description, the invention will be explained in more detail with reference to exemplary embodiments of the apparatus for supplying molten metal to molds in a mold train according to the invention shown in the drawings, in which:

Fig. 1 is a schematic side view of a mold string and an apparatus for supplying molten metal to the mold string according to the invention;

Fig. 2 shows different positions of flexibility to provide the possibility of carrying out the lateral or axial movement of the filling head;

Fig. 3 shows a preferred embodiment of a device according to the invention;

Fig. 4 shows an arrangement with rotating movement of the filling head, the filling tube and the pump;

Fig. 5 shows an arrangement with tilting movement of the filling head, the filling pipe and the pump; and

Fig. 6 shows an arrangement with linear movement of the filling head, the filling pipe and the pump in a plane forming an angle with the horizontal plane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The moulding line shown in Fig. 1 is well known and will therefore not be explained in more detail. In the filling station, the mould cavities 1 are filled with molten metal to produce the desired moulded articles. To supply the molten metal, a filling head 2 is brought into engagement with a filling opening 3 in the mould and the molten metal is pumped into the mould through filling head 2. In order to bring the filling head 2 into tight engagement with the filling opening 3, it is necessary to be able to move the filling head 2 laterally, i.e. in the direction of transport of the moulds in the moulding line 4, so as to to compensate for varying delivery positions of the moulds, and to move the filling head axially, i.e. in a direction towards the moulds. After providing this engagement, the mould is filled by pumping the molten metal into the mould cavity and the filling opening 3 is closed in a conventional manner, as is known for example from EP-760 723. After closing the filling opening 3, the pressure of the pump 8 is reduced and the filling head 2 can be withdrawn from the mould and is ready for engagement with the next mould in the strand 4.

The molten metal for filling the molds is provided by melting raw material metal in a melting furnace 5, from which the molten metal is transferred to a buffer furnace 6 in which the molten metal is prepared for pouring by temperature regulation, degassing, alloying, mixing, etc. From the buffer 6, molten metal is transferred to the pump furnace 7, which has a relatively low capacity and from which the molten metal is pumped 8 to the filling head 2 via a filling pipe 9. The pumping can be carried out by means of an electromagnetic pump 8 or a pressure-activated pump immersed in the molten metal and connected to the filling pipe 9 and the filling head 2. Another way for pumping the molten metal from the pump furnace 7 is to pressurize the interior of the pump furnace 7, causing the molten metal to rise into a submerged filling pipe 9 connected to the filling head 2. The latter pumping method requires that the pump furnace 7 can be completely closed in order to be able to generate sufficient overpressure within the pump furnace 7.

In principle, it is desirable that each of the furnaces 5, 6 and 7 is constructed as a closed vessel in order to be able to control the atmosphere above the molten metal. Moreover, the connections between the various furnaces are made of rigid materials due to the fact that all elements in contact with the molten metal must be made of ceramic material or the like capable of resisting the influences of the molten metal. The entire system of furnaces could be made gas-tight without flexible seals. However, this would require that, in order to provide the lateral and axial movement of the filling head 2, the entire system consisting of melting furnace 5, buffer furnace 6 and pump furnace 7 including pump 8 and filling pipe 9 would have to be moved both laterally and axially in order to provide the desired lateral and axial movement of the filling head 2. Due to the high weight of this system (up to about 100 tons), this solution is not preferred. It will be appreciated that the mobility required to provide lateral or axial movement of the filling head 2 can be provided between any two consecutive interconnected components, i.e. filling head 2 - filling pipe 9, filling pipe 9 - pump 8, pump 8 - pump furnace 7, pump furnace 7 - buffer furnace 6 and buffer furnace 6 - melting furnace 5. However, it must be stressed here that the mobility for the lateral movement need not be provided at the same location as the mobility for the axial movement. By splitting the mobility, the mobility can be designed as a purely linear mobility in each of the mobility points in the system. Since the axial movement is most commonly used, the mobility for this movement is preferably positioned as close as possible to the filling head 2 in order to reduce the mass to be moved. In a preferred embodiment, the axial movement by moving the pump 8, the filling pipe 9 and the filling head 2 as a unit relative to the pump furnace 7, and a possible seal 10 between the pump 8 and the pump furnace 7 is provided by securing the pump in a movable cover 11 to the pump furnace 7. In this embodiment, the lateral movement can be provided by moving the pump furnace 7, and a movable connection can be provided between the pump furnace 7 and the buffer furnace 6, for example by means of a connection 14.

Many other possibilities can be suggested. Among these is the embodiment in which both the lateral and axial movement is provided by movement of the pump 8 relative to the pump furnace 7. In this embodiment, the seal 10 between the pump 8 and the pump furnace 7 is preferably provided by mounting the pump 8 in a cover 11 which is slidably movable relative to the pump furnace 7, and the seal 10 between the cover 11 and the pump furnace 7 is provided in the form of a flexible fiber ceramic seal attached to one part and in sliding engagement with the other part.

An example of such a construction is shown in Fig. 3, in which the pump 8 is mounted in a pump cover 11 which is laterally and axially movable together with the pump 8. Two pump furnace covers 12, 13 are provided in the lateral sides of the pump cover 11, these pump furnace covers 12, 13 being movable only in the lateral direction.

In order to provide a seal 10 between the pump furnace 7 and the movable covers 11, 12, 13, the pump cover 11 is provided with flanges on the front and rear sides which slidably engage with flexible sealing elements 10 attached to the corresponding upper edges of the pump furnace 7. Furthermore, the side edges of the pump cover 11 are provided with vertical flanges which slidably engage with flexible sealing elements 10 attached to the corresponding adjacent vertical edges of the two pump furnace covers 12, 13. The two pump furnace covers 12, 13 are provided at the front and rear with flanges that slidably engage the above-mentioned flexible sealing elements 10 that are fixed to the respective upper edges of the pump furnace 7, and these covers are further provided with flexible sealing elements 10 along their edges opposite to the edges that engage the pump cover 11, the sealing elements 10 sealingly engaging a large surface area flange that is positioned toward the lateral sides of the pump furnace 7.

In order to relieve the sealing elements 10 from the weight of the pump furnace covers 12, 13, these covers 12, 13 are provided with rollers running on rails positioned along the front and rear edges of the pump furnace 7 on the outside of the sealing elements 10. The pump cover 11 is fixed to the pump 8, which is attached to a two-axis sliding system to provide the lateral and axial movement of the filling head 2, the filling pipe 9, the pump 8 and the pump cover 11 together, the covers 12, 13 of the pump furnace are connected to the part of the sliding system that provides the lateral movement.

The arrangement shown has the further function of allowing removal of the pump 8 and the pump cover 11 from the pump furnace 7, whereupon the two pump furnace covers 12, 13 can be brought together to close off the pump furnace 7 from the environment. This represents an advantage in connection with starting and shutting down/shutting down the system.

The flexible sealing elements 10 are preferably made of fiber-ceramic material.

Fig. 4-6 show different ways of providing the axial movement of the filling head.

Fig. 4 shows how a pivoting movement of the pump 8, the filling pipe 9 and the filling head 2 in conjunction with a suitable design of the filling pipe 9 provides an axial movement of the filling head 2. Furthermore, Fig. 4 shows a connection 14 between the buffer furnace 6 and the pump furnace 7 in order to provide the required flexibility between these two parts and therefore be able to move the pump furnace 7 in the lateral direction and to keep the buffer furnace 6 stationary.

Fig. 5 shows a corresponding arrangement in which the pivoting movement of the pump 8, the filling pipe 9 and the filling head 2 is carried out in a vertical plane, i.e. with a tilting of these parts relative to the pump furnace 7.

Fig. 6 shows a linear movement of the same components, where the movement is carried out in a plane forming an angle with the horizontal plane.

Many other types of movement can be considered by those skilled in the art. Depending on the type of movement to be performed, the seal 10 between the moving and stationary parts must be designed according to the required movement.

List of reference symbols

1 mold cavity

2 filling head

3 Filling opening

4 mold line

5 Melting furnace

6 buffer furnace

7 Pump furnace

8 Pump

9 Filling tube

10 seals

11 Pump cover

12 Cover of the pump furnace

13 Cover of the pump furnace

14 Connection

Claims (10)

1. A method of supplying molten metal to a mold in a plant by a supply system in which the molds are filled by pumping the molten metal into mold cavities via a filling head (2) which is temporarily connected to a filling opening (3) in the mold, the molds being held stationary and the filling head (2) being moved axially and optionally laterally to provide the temporary connection, the supply system comprising a pump furnace (7), a pump (8), a filling pipe (9) and a filling head (2) for alignment with the filling opening (3) of the mold and optionally a melting furnace (5) and a buffer furnace (6), with the steps that: - the filling head (2) is moved sideways to match the lateral position of the filling opening (3) of the mold, and - the filling head (2) is moved axially to match the axial position of the filling opening (3) of the mold, characterized that at least one of the elements melting furnace (5), buffer furnace (6), pump furnace (7), pump (8) and filling pipe (9) present in the delivery system is held stationary in at least one of the lateral or axial directions during the movement of the filling head (2). 2. Method according to claim 1, characterized in that suitable movable connections (14)/seals (10) are provided between these parts (5-8), which are moved relative to one another during the lateral or axial movement of the filling head (2). 3. Method according to claim 1 or 2, characterized in that the axial movement of the filling head (2) is provided by movement of the filling head (2), the filling pipe (9) and the pump (8) relative to the rest of the system. 4. Method according to one of claims 1 or 2, characterized in that that the axial movement of the filling head (2) is provided by an axial movement of the filling head (2) and the filling tube (9) relative to the rest of the system. 5. Method according to one of claims 1 or 2, characterized in that the axial movement of the filling head (2) is provided by a pivoting movement of the filling head (2) and the filling pipe (9), possibly together with the pump (8), the pivoting movement providing an axial component of the movement for the filling head (2). 6. Method according to claim 5, characterized in that the pivoting movement is carried out in a horizontal plane (rotating) or in a vertical plane (tilting). 7. Method according to one of claims 1 or 2, characterized in that the axial movement of the filling head (2) is provided by a linear movement of the filling head (2) and the filling pipe (9), possibly together with the pump (8), the linear movement providing an axial component of movement for the filling head (2). 8. Method according to claim 7, characterized in that the linear movement is provided at an angle relative to the axial direction. 9. Sealing system for use in a method according to any one of the preceding claims, in which at least one of the lateral and axial movements is provided by movement of the pump (8) and the filling pipe (9) together with the filling head (2), characterized in that the pump (8) is positioned in a cover (11) positioned at the upper portion of the pump furnace (7), the cover (11) being in pressure contact with a corresponding flange on the pump furnace (7), a sealing material (10) being provided between the cover (11) and the flange of the pump furnace (7). 10. Sealing system according to claim 9, characterized in that the sealing material (10) is provided in the form of a flexible fiber ceramic material.