WO2001070432A1

WO2001070432A1 - Method and apparatus for producing two-part moulds

Info

Publication number: WO2001070432A1
Application number: PCT/DK2000/000130
Authority: WO
Inventors: Søren Erik KNUDSEN
Original assignee: Georg Fischer Disa A/S
Priority date: 2000-03-20
Filing date: 2000-03-20
Publication date: 2001-09-27
Also published as: AU2000232748A1

Abstract

The method and apparatus for producing two-part moulds using a moulding machine comprising two co-axially positioned moulding chambers (1, 2) separated by a pattern plate (15), two squeeze plates (5, 6), one at each outwardly positioned end of each moulding chamber (1, 2), actuator means (22) for applying a compacting force to the squeeze plates (5, 6) and a compression of frame (18) for transmission of the compacting force from one squeeze plate (6) to the other (5), comprises application of a supplementary force to at least one of the squeeze plates (5, 6) during the compacting of the mould material, thereby increasing or decreasing the compacting force applied to one of said squeeze plates (5, 6) and the corresponding mould parts relative to the other. By this feature, it is achieved that the mould material in the two mould parts are provided with different compactness and corresponding different porosity for escape of gas(es) and stability towards erosion by the metal to be cast in the mould cavity, in correspondence with desired parameters.

Description

METHOD AND APPARATUS FOR PRODUCING TWO-PART MOULDS

TECHNICAL FIELD

The present invention relates to a method and an apparatus for producing two-part moulds of the kind set forth in the preamble of claims 1 and 4, respectively.

BACKGROUND ART

EP-0,468,355 discloses a moulding machine of the above-mentioned type. This moulding machine produces flaskless moulds using a cope flask, a pattern plate and a drag flask, and uses two squeeze plates for compacting the mould material in the cope and drag flasks. The force for compacting the mould material is provided by means of a drive means and a compression frame moving the squeeze plates towards each other, thereby applying equal and oppositely directed forces to the squeeze plates. By this procedure for compacting, the mould material in the two mould parts are provided with approximately the same compactness and corresponding porosity for escape of gas(es) and stability towards erosion by the metal to be cast in the mould cavity.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to provide a method and an apparatus for producing two-part moulds of the kind referred to above, with which it is possible to produce mould parts with different compactness and correspondingly different porosity for escape of air and stability against erosion. The inventors have realised that the demands for the two parts of the mould are different due to the fact that air escape is demanded primarily through the top part and erosion stability is primarily demanded in the bottom part. This object is achieved by a method of said kind, which according to the present invention also comprises the features as set forth in the characterizing clause of claim 1 , and an apparatus of said kind, which according to the present invention also comprises the features set forth in the characterizing clause of claim 4. With this method and apparatus, the compacting forces applied to the two individual parts of the mould can be controlled in order to achieve appropriate parameters of compactness for these parts. In accordance with a preferred embodiment, the supplementary force is applied by means of actuators, possibly already present for other purposes, whereby the costs for implementing the method are minimised.

Preferably the control of the supplementary force is performed simply by controlling the fluid pressure applied to a fluid-driven actuator, which in its simplest form may be performed by using a simple pressure relief valve in one line from said actuator.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed part of the present description, the invention will be explained in more detail with reference to the exemplary embodiment of an apparatus for providing two-part moulds according to the invention shown in the drawings, in which Figure 1 schematically shows an apparatus suited for performing the method in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 shows diagrammatically an apparatus, in which the present invention may be implemented. The apparatus comprises two moulding chambers 1 ,2 positioned coaxially and separated by a pattern plate 15. The moulding chamber 1 is defined by a cope flask 3 closed at one end by the pattern plate 15 and at the other end by a squeeze plate 5. The moulding chamber 2 is defined by a drag flask 4 closed at one end by the pattern plate 15 and at the other end by a squeeze plate 6. In Figure 1 , the apparatus is shown in the compacting position, in which compacting of mould material is performed by moving the squeeze plates 5,6 towards each other, said movement being provided by means of an actuator 22 and a compression frame 18. During the compacting step, the two flasks 3,4 and the pattern plate 15 are locked in position by means of the corresponding moving actuators. Activating the actuator 22 will move the squeeze plate 6 into the moulding chamber 2 and the reaction force is transmitted from the actuator 22 via the compression frame 18 to the squeeze plate 5 which is moved into the moulding chamber 1. In this way, equal and oppositely directed forces are applied to the squeeze plates 5,6 and accordingly, approximately identical compacting is performed onto the mould material inside the two moulding chambers 1 ,2. However, in accordance with the present invention, a supplementary force is applied to one of the squeeze plates 5,6. In the apparatus shown in Figure 1 , this supplementary force is applied by means of one of the actuators 7,13a, which apart from being used for applying this supplementary force are present in order to be able to move the squeeze plates 5,6 relative to the moulding chambers 1 ,2 and corresponding cope and drag flasks 3,4. As an alternative, the actuators 7,13a for applying the supplementary force may be provided as separate actuators not used for the movement of the squeeze plates 5,6, in which case the actuators 7,13a may act between the compression frame 18, as indicated by the dotted lines at 8 and 9, and the moulding chambers 1 ,2, as indicated by the connection between the actuators 7,13a and the cope flask 3.

Performing the compacting of the mould material in the two moulding chambers 1 ,2, using the actuator 22 for applying equal forces to the two squeeze plates 5,6 and applying a supplementary force by means of one of the actuators 7, 13a, two mould parts are formed with different compactness and accordingly different properties.

When producing flaskless moulds, which is the case with the apparatus shown in Figure 1 , the resulting two-part moulds are used in a position where the cope produced in the moulding chamber 1 is positioned on top of the drag produced in the moulding chamber 2. In this situation, it is advantageous to have a cope which is more porous than the drag and accordingly, the supplementary force is applied in order to reduce the compacting force provided by the squeeze plate 5, e.g. by using the actuator 7 to apply a force directed to the right, as seen in Figure 1 , or by applying a force to the squeeze plate 6 by means of the actuator 13a, said force being directed to the right as seen in Figure 1. The resulting less compact cope provides better possibilities for the gas(es) to escape from the moulding cavity up through the cope and the corresponding drag is produced with a higher compactness and accordingly higher resistance against erosion of the drag during pouring of the material to be moulded in the mould cavity. The apparatus shown in Figure 1 is intended to produce horizontally divided flaskless moulds in the form of a cope and a drag. After compacting, the whole system consisting of cope flask 3, drag flask 4, pattern plate 15, squeeze plate 5 and possibly squeeze plate 6 is rotated 90 degrees in order to position the cope flask 3 on top of the drag flask 4, whereafter the two moulding chambers, i.e. cope flask 3 and drag flask 4, are separated in order to take out the pattern plate 15, after which the cope flask 3 and the drag flask 4 are moved towards each other in order to position the cope and drag on top of each other, whereafter cope and drag are moved out of the cope flask 3 and the drag flask 4 by means of the squeeze plate 5, using e.g. the actuator 7. In order to be able to release the cope and drag from the cope flask 3 and the drag flask 4, the cope flask 3 and the drag flask 4 are provided with draft. Due to this draft, the area of the squeeze plate 5 is smaller than the area of the squeeze plate 6, whereby the normal situation, in which no supplementary forces are applied to the squeeze plates 5,6, will provide a higher compacting of the cope than of the drag due to equal forces acting on different areas. In this situation, the cope will have a higher compactness than the drag, whereby the escape of gas(es) from the cope will be hampered.

The above described different pressures in the cope and drag flasks 3,4, when applying equal forces to the two squeeze plates 5,6 will provide a certain bending of the pattern plate 15 and this bending can be reduced to zero, or even reversed to a bending in the opposite direction, by applying the supplementary force in accordance with the present invention. If the supplementary force is applied to an extent giving rise to such bending, it is preferred to dimension the pattern plate relatively stronger in order to minimize the bending. Reducing the bending to zero by balancing the forces has the advantage of minimizing the risk of tear off and deformation of the resulting mould surfaces.

Although the invention has been described above in connection with a specific embodiment thereof, it will be evident for a man skilled in the art that the present invention can be used in connection with other types of moulding machines for producing two-part moulds, without departing from the scope of the following claims.

Claims

1. Method for producing two-part moulds in a moulding machine comprising two coaxially positioned moulding chambers (1,2), separated e.g. by a pattern plate (15), two squeeze plates (5,6), one at each outwardly positioned end of each moulding chamber (1,2), actuator means (22) for applying a compacting force to the squeeze plates (5,6), and a compression frame (18) for transmission of the compacting force from one squeeze plate (6) to the other (5), said method comprising the steps of a) filling the two moulding chambers (1 ,2) with compressible mould material, b) compacting said mould material by moving said squeeze plates (5,6) towards each other, using said actuator means (22) and compression frame (18), thereby applying equal and oppositely directed forces to said squeeze plates (5,6), characterized by further comprising the steps of c) applying a supplementary force to at least one of said squeeze plates (5,6) during said compacting step b), thereby increasing or decreasing the compacting force applied to one of said squeeze plates (5,6) and corresponding mould parts relative to the other.

2. Method in accordance with claim 1, characterized by comprising the step of applying said supplementary force in a continuously adjustable manner.

3. Method in accordance with claim 1 or 2, where said moulding machine comprises separate moving actuators (7,13a) for moving at least one of said squeeze plates (5,6), characterized by comprising the step of applying said supplementary forces by means of said moving actuators (7,13a).

4. Method in accordance with claim 3, where said separate moving actuators (7,13a) are fluid-driven actuators, characterized by comprising the step of applying said supplementary forces by controlling the fluid pressure applied to said separate moving actuators (7,13a) during the compacting step b).

5. Apparatus for performing the method in accordance with claim 1, said apparatus comprising a moulding machine comprising - two coaxially positioned moulding chambers (1,2) separated by a pattern plate (15),

- two squeeze plates (5,6), one at each outwardly positioned end of each moulding chamber (1,2), - a compacting actuator means (22) positioned to apply a compacting force (2) to the squeeze plates (5,6), and

- a compression frame (18) positioned to transmit the compacting force from one squeeze plate to the other, characterized by further comprising separate means (7,13a) for applying a supplementary force to at least one of the squeeze plates (5,6) during the application of the compacting force by means of the compacting activator means (22).

6. Apparatus in accordance with claim 5, characterized by comprising means for continuously controlling the applied supplementary force.

7. Apparatus in accordance with claim 5 or 6, characterized by said separate means (7,13a) for applying said supplementary force to said squeeze plates being present in the form of separate control means for controlling the forces applied by separate moving actuators (7,13a) for moving the squeeze plates (5,6).

8. Apparatus in accordance with claim 7, characterized by comprising separate moving activators (7,13a) for the squeeze plates (5,6) in the form of fluid- driven actuators and the control means for controlling the forces applied by said moving actuators (7,13a) comprising pressure control means controlling the fluid pressure applied to said moving actuators (7,13a).

9. Apparatus in accordance with claim 8, c h a ra c t e r i z e d by the pressure control means being implemented in the form of a continuously adjustable pressure relief valve connectable to one of the fluid lines to said moving actuators (7, 13a).