EP0295472B1 - Method of and installation for ramming mold material in foundry molding machines - Google Patents

Description

The invention relates to a method for compacting molding material in the molding box of foundry molding machines with a multi-die press plate, the individual punches of which are arranged at a distance from one another and penetrate into the back of the molding material at different depths according to the model height.

Basically, the aim is to achieve the same level of strength in the entire molding area. In practice, however, wall friction on box and model surfaces on the one hand, large differences in model heights or narrow, deep model contours on the other hand lead to different dimensional strengths. So there are differences in large model heights Molded parts are pressed over protruding model surfaces, whereas weakly compacted mold parts often occur in narrow and deep model contours and at the edge of the box.

In order to achieve a reasonably homogeneous compression of the mold with critical model contours, compression generally has to be carried out in two stages, the compression of the back of the molding material being able to be carried out with a multi-die press plate. The purpose of multi-stamp pressing is to automatically compensate for compression differences caused by the model during the compression process. It is known from DE-OS 29 36 173 to precompact the filled sand in the molding box first by means of a press plate approaching the back of the molding material and then to carry out the post-compaction in a second step by means of press dies stored in the press plate. The press rams are connected to a common pressure medium source and penetrate more or less deeply into the back of the molding material according to the model contour.

Likewise, it is known, for example from EP-AS 172 937, to carry out the predominant compaction first with a multi-die press plate and then to carry out post-compaction by pressing the model up with the mold box raised.

Finally, in the case of multi-die press plates, it is also known to support the dies on the outside with a higher pressure level than the dies on the inside, when the lifting table carrying the filled molding box is moved upwards against the punches. Although this results in a better stroke adjustment of the stamp to the model contour, the compression differences across the cross-section of the shape are still considerable. In most cases, this system must be combined with vibratory compaction.

Proceeding from this, the object of the present invention is to improve the method described at the outset in such a way that a consistently high compression quality is obtained even with difficult contours. In addition, a device is to be specified with which this method can be implemented inexpensively in practice.

This object is achieved in that at least the internal punches are each individually pressurized according to the contour of the model, that the press plate is then additionally used for compression and is moved up to about the upper edge of the molding box and that at the compression end a maximum stroke difference between individual Stamping of at least 30%, preferably at least 40% of the mold box height is observed.

These measures, in particular the individual pressure control and the stroke differences between the individual stamps which are forced until the end of the compression, result in surprisingly high compression values even in narrow and deep pockets of the model as well as in the model-free marginal area. This is probably due to the fact that, according to the invention, the compression end position of the pistons is largely reached over the entire model contour at the same time. This eliminates the relative movements that cause crack formation in areas of molding material that have already been compacted.

As has been shown, the stroke differences between the individual stamps are of crucial importance. These stroke differences, which are only 10 to 20% in the prior art, are expediently prescribed in the method according to the invention with over 40% and even with over 50% to about 80% of the mold box height. Surprisingly, the resulting strong depressions in the back of the mold do not have a negative, but on the contrary, an extremely positive effect on the compression.

Furthermore, it has been found that the described method produces particularly good results if the sum of the punch cross sections on the sand side is chosen to be 20% to 70%, in particular 20% to 50%, of the mold box area. It is particularly expedient to provide more specific stamp area in the inner area, that is to say above the model, than in the edge area, in that it amounts to 20% to 50% in the edge area 50% to 100% of the associated molding box area.

In addition, it has proven to be advantageous to carry out the compression process according to the invention with high lifting speeds of the press plate and the stamp. While the stamp speeds have hitherto been around 0.2 to 0.7 m / s, stamp speeds above 2.0 m / s are particularly recommended for the present method, particularly 3 to 10 m / s, values of 4 to 8 m / s being particularly preferred are cheap. At these high stamp speeds, the dynamic effects in the molding material are similar to those of gas pulse compression. The molding material particles are accelerated to such an extent that, when they strike the model or model plate surface, they are compressed to a greater extent than by mechanical slow pressing due to the impact impulse. The same applies to the molding material particles located under the pressing plate, if one expediently also moves the pressing plate towards the molding material at the same lifting speed.

However, if the kinetic energy of the punches and the press plate is transferred to the molding material undamped, there is an undesirable overpressure on high-lying model surfaces. According to the invention, this overpressure can be avoided in that the kinetic energy is predominantly absorbed only in those molding material areas which are not above high model parts but in model-free zones, that is to say at the box edge. For this purpose, the press batten is expediently provided on its edge and in the area between the outer punches with projections on the underside, for example with a circumferential bar that is only interrupted by the outer punches. As a result, the edge area of the mold acts as a damping device for the press plate and the individual punches connected to it, and at the same time this edge area experiences a desired additional compression.

Furthermore, it is recommended that the different pressurization of the individual stamps take place with discretely specified pressures, i.e. that instead of the previously used balancing pressure compensation, a certain support pressure is built up in each stamp, for example, in such a way that the stamps are completely moved out of the press plate before compacting and then are supported according to the model height with different levels of back pressure - especially pneumatically. The press plate is then pressed together with the stamps which move relative to it against the molding material.

Instead, the stamps can also be set to different levels from the start according to the model profile and then - in particular hydraulic - are supported or fixed so that they essentially maintain their level relative to one another during the subsequent compaction.

The method according to the invention is carried out in such a way that at least the pressure medium cylinders for the stamps located within the outer stamp are each connected to a pressure source via their own pressure medium lines and via valves. As a result, the individual stamps can either be pneumatically preloaded to a specific support pressure which is selected in accordance with the model contour, or the stamps are set hydraulically to different level positions in accordance with the model contour.

For different pressurization or for setting the different stroke positions, the pressure medium cylinders of the punches can each be connected to the pressure source via their own switching valves. In order to keep the expenditure on valves lower, the pressure medium cylinders can be row-by-row at their one end and column-by-row at their other end. be connected column-wise pressure medium line, these lines are each connected to the supply or discharge line via valves and the control of these valves is carried out by a microprocessor according to the desired stroke positions of the punches.

It is within the scope of the present invention to combine the mechanical compression described above with the action of a pressure gas pulse. The compressed gas pulse can be generated in a manner known per se by compressed air or by explosive gas mixtures.

Such a multi-stage compression offers the advantage that the compressed gas flowing through the molding material, on the one hand, brings about fluidization and, on the other hand, pre-compression of the molding material. Both effects improve the compression properties of the mold.

The pressure gas pulse can be brought into effect before and / or during pressing. Depending on the desired results, the pressure level and the pressure curve can be as high as, or significantly below, that of pure pulse compression. It is also within the scope of the invention to allow gas to escape from the molding box, in particular via the model plate, or to actively aspirate it during compression.

In order to carry out such a combined compression process, the press head can either be installed in a pressure vessel, which adjoins the filling frame. In this case, the press head expediently has a valve plate which interacts with a corresponding valve seat of the pressure container in order to open or shut off the connection of a pressure source which is under pressure to the molding box. So that the gas pulse can communicate to the molding material without large flow losses, it is recommended that the compressed gas not only between the press head and the filling frame, but also through corresponding openings of the press head can flow through it.

Instead, the press head itself can also be designed as a pressure vessel and connected to a pressure source. In this case, a tight connection of the press head to the filling frame must be ensured, for example by means of a sliding seal between the two parts.

Fig. 1

einen teilweisen Vertikalschnitt des Oberteils einer Formmaschine zu Beginn der Verdichtung;

Fig. 2

den entsprechenden Vertikalschnitt am Ende der der Verdichtung;

Fig. 3

ein Schaltungsschema für die Druckmittelzylinder;

Figur 4

einen teilweisen Vertikalschnitt des Oberteils einer Formmaschine mit zusätzlicher Impulsverdichtung zu Beginn der Verdichtung;

Figur 5

einen teilweisen Vertikalschnitt einer anderen Formmaschine mit zusätzlicher Impulsverdictung zu Beginn der Verdichtung;

Figur 6

einen Vertikalschnitt entsprechend Figur 5 bei fortgeschrittener Verdichtung und

Figur 7

einen entsprechenden Vertikalschnitt am Ende der Verdichtung.

Further details on this as well as on the other aspects of the invention follow from the following description of exemplary embodiments with reference to the drawing; shows.

Fig. 1

a partial vertical section of the upper part of a molding machine at the start of compression;

Fig. 2

the corresponding vertical section at the end of the compression;

Fig. 3

a circuit diagram for the pressure cylinder;

Figure 4

a partial vertical section of the upper part of a molding machine with additional pulse compression at the beginning of the compression;

Figure 5

a partial vertical section of another molding machine with additional pulse compression at the start of compaction;

Figure 6

a vertical section corresponding to Figure 5 with advanced compression and

Figure 7

a corresponding vertical section at the end of compression.

Figures 1 and 2 first show a model plate 1 with model 2 and a molding box 3 placed on the model plate 1 and a filling frame 4 placed thereon. The loosely poured molding sand is designated by 5.

Above it is a compression unit 6 in the form of a Veil stamp press head. Its individual punches 7 are distributed relatively evenly over the cross section of the molding box, expediently have a round cross section and are spaced apart from one another by an amount corresponding to their diameter. They traverse a horizontal press plate 8, which forms the lower end of a box-shaped compression head 9. At least the lower cross section of the compression head 9 is dimensioned so that it fits into the filling frame 4. The outer edge of the press plate 8 is formed by downwardly projecting strips 8a, which at the same time form elongated guide bushes for the external punches.

For each stamp 7, a pressure medium cylinder 10 is arranged within the compression head 9, each of which is connected to a pressure source 12 via a line 11.

In order to bring about the compression, either a lifting table (not shown in the drawing) is provided for raising the molding box against the compression head 9 or, what is more expedient, the compression head 9 can be moved hydraulically into the filling frame 4 which remains at rest via a press cylinder 13 arranged above.

It is now essential that the individual pressure medium cylinders 10 are prestressed with different pneumatic pressures, specifically with discrete values that are prescribed as a function of the model contour. For example, the external punches above the model-free space are pre-stressed with 4 bar, the neighboring punches with about 1 bar and the inner punches arranged above the model recess with about 3 bar compressed air. The individual prestressing of the individual cylinders 10 takes place by means of a schematically indicated electrical individual control 14, which can be program-controlled depending on the model.

If the hydraulic cylinder 13 is now triggered in the compression direction, the entire compression head 9 is accelerated to a speed of about 7 m / s, the individual punches 7 first penetrating into the back of the molding material. By overtaking the subsequent press plate 8, by its spaced arrangement and by its high lifting speed ensures that the prescribed maximum stroke difference ΔH / H of at least 30% is set at the end of the compression process.

The gaps between the individual stamps are compressed by the pressure plate 8, which more or less overtakes the above stamps 7 during the compression stroke. In spite of the steeply sloping model outer walls and the recess in the middle, a shape produced in this way was distinguished by extremely uniform dimensional strengths of 18 to 20 N / cm².

After the compression stroke, the hydraulic cylinder 13 is again pressurized with oil. When the compression head 9 is then pulled out of the molding box 3 or filling frame 4, the overpressure present in the cylinders 10 automatically ensures that the punches 7 are advanced to the position shown in FIG. 1.

Known monitoring units can automatically bring the pressure in individual cylinders 10 back to the prescribed level.

So that the sprue pin used for the production of the sprue is not acted upon by the punches, it is expedient to leave the punches in their retracted position above the pouring position. Since the pouring position depends on the model and therefore changes, different stamps must be held in their retracted position. In terms of control technology, this can be achieved according to the invention in that all cylinders 10 are connected via openings 10 a on the underside to a common pressure chamber 18 within the compression head 9, which is in turn connected via a connection 19 to a pneumatic pressure source. As a result, all punches 7 are resiliently biased upwards and the punches located above the pouring position remain in this position, whereas the other punches are individually subjected to counterpressure via the respective lines 11.

Fig. 2 shows an alternative to the pressure supply to the cylinders 10 compared to Fig. 1, in that each cylinder 10 has its own, electrically operated inlet valve 15 and in which all these valves open into a common pressure chamber 16 within the compression head 9. The pressure chamber 16 stands over an on or. Outlet valve 17 with a pressure medium source 12 or with the atmosphere in connection.

In order to apply the prescribed pre-pressure to the individual cylinders 10, the valves 15 are connected to an electrical selection device 20. It allows to close those valves 15, the cylinders 10 of which have reached the desired preload pressure, during the pressure increase in the pressure chamber 16.

While the above-described loading of the cylinders 10 is primarily intended for pneumatic pressure medium, the system shown in FIG. 3 is particularly suitable for a hydraulic loading of the cylinders in such a way that the punches 7 are set to different height positions before compression and more or less can be fixed. For this purpose, the individual cylinders as a two-dimensional matrix with a field arrangement of several columns, for example 1, 2, 3 and 4 several rows, for example A, B, C and D. The series-connected cylinder connections of the columns are located at the upper end of the cylinder and lie at right angles to the cylinder connections of the series connected in series at the lower cylinder ends. Each column ^S and each row R can be hydraulically switched on and off with a two-way valve V₁, V₂ ... or V _A , V _B ... As a result, only (S + R) valves are required for (SxR) cylinders; in the design according to FIG. 1 with 8 cylinders in a row and 7 rows in a row, only 7 + 8 = 15 individual valves are required for 56 cylinders.

For example, to adjust the cylinder D3 in the stroke, only the two valves V _D and V₃ are opened. Now the piston can be lowered to a lower position by supplying pressure oil via line S and all the other cylinders in this row and in this column remain blocked despite their connection in series because one of their two valves always remains closed.

Because of the variety of model-related single stroke settings, it is advisable to control the valves via a programmable microprocessor. For this purpose, the image of the model height contour is entered into the control program in a model-coded stroke data record and is available for the duration of the model impressions for individual control of the individual stamps. When changing models, only the model-coded stroke data record needs to be changed.

In order to make the stroke adjustment practicable, it is advisable to carry it out in batches using successive metering levers of the same size, that is, the desired one Approach stroke position in certain individual steps. This means that you can no longer move to an infinite number of lifting positions. In practice, however, it is sufficient if each stamp can be gradually adjusted by about two to three centimeters.

Due to the features of claims 18 and 19, which are not shown in the drawing, there is the advantage that, instead of several manually exchangeable exchangeable frames, only the projection 8a or the projections need to be adjusted in terms of their projection in order to optimally match them to different ones Adapt model sizes or model contours.

FIGS. 4 to 7 show molding machines with which the previously described method is carried out in combination with an air pulse acting on the molding material. Depending on its strength, this air pulse causes fluidization, but preferably also pre-compression of the molding material.

For this purpose, in the embodiment according to FIG. 4, the entire press head 6 with the compression head 9 and the press cylinder 13 is installed in a pressure container 21. The pressure vessel 21 has a valve seat 22 which interacts with a head plate 23 of the compression head 9, which acts as a valve disk, with the interposition of a seal 22a. As a result, the pressure container 21 can enter a closed upper chamber 21a, which is connected to a compressed air source 24, and a lower chamber 21b, which is in airtight connection with the molding space formed by molding box 3 and filling frame 4, can be divided.

The function is as follows: First, the chamber 21a is filled with compressed gas, in particular compressed air, the top plate 23 of the compression head 9 sealing the chamber 21a via appropriate sealing surfaces. Then the hydraulic cylinder 13 is reversed so that the compression head 9 moves down. The chamber 21 opens and the compressed gas in it flows with simultaneous downward movement of the compression head 9 and reaches both along the outer edge gap between the compression head and the pressure vessel 21 and through gaps between the individual punches 7 and the pressure plate 8 to the first still loose molding material 5. The molding material 5 is fluidized by and when the plunger 7 is immersed there is first the positive effect of a reduction in friction. Furthermore, the compressed gas flowing through the molding material effects a pre-compression in a manner known per se. The final compression takes place in the manner already described by the punches 7 penetrating into the molding material at different depths and finally by the press plate 8.

If no value is placed on the rinsing of the individual punches 7 within the compression head 9, the compressed gas can of course also be supplied outside the compression head 9 in the molding space. The compressed gas can also be moved laterally via valves, not shown be introduced into the lower region of the pressure container 21 above the filling frame 4.

Figures 5 to 7 show another design that works with combined compression. In contrast to FIG. 4, the press head 6, that is to say its compression head 9, is itself designed as a pressure vessel. For this purpose, a chamber 9a is formed in the compression head 9, which on the one hand is to be pressurized via a pressurized gas connection 24 and, on the other hand, can be opened to the molding space via numerous valves 25, only one of which is shown in the drawing. In addition, the compression head 9 is provided on the outer edge of the press plate 8 formed by the strips 8a with sealing lips 26 which seal it against the full frame 4.

The chamber 9a is connected via connections 27 to the underside of all pressure medium cylinders 10, so that it is not only responsible for the generation of the pressure gas pulse, but also for the lifting of the stamps 7. In the exemplary embodiment, the pressure medium cylinders 10 are accommodated directly in the chamber 9a, therefore simple cross bores at the lower end of the cylinders 10 are sufficient for the connections 27.

Figure 5 shows the beginning of the compression process. The compression head 9 is just so far immersed in the filling frame that the sealing lips 26 seal it against the filling frame 4. The pressure medium cylinders 10 are depressurized from above, whereas the chamber 9a has an overpressure via the external pressure gas source 24. This excess pressure is transferred via the connections 27 to the lower displacement of the cylinders 10 and holds all the individual stamps 7 in the upper stroke position shown.

FIG. 6 shows the following compression section: Individual cylinders 10 were subjected to discrete counterpressures, preferably gas pressures, on their upper side via their connecting line 11, so that individual punches 7 immersed in the molding material to different depths according to the contour of the model 2.

At the same time, the valves 25 in the chamber 9a were opened, as a result of which the gas under pressure flows into the lower part of the compression head 9, flows around the punches 7 and penetrates into the molding material. This leads to the fluidization already described and the easier penetration of the punches 7 into the molding material surface and to a certain pre-compression of the molding material.

However, it is also within the scope of the invention to trigger this fluidization and precompression only after the punches 7 have already reached the default setting shown in FIG. 6 in accordance with the model contour.

At particularly deep or narrow places in the model or model plate area, exhaust air nozzles 28 can discharge the gas originating from the pressure pulse and the shaped air of the molding material liberated during the subsequent mechanical compression. This air discharge can additionally by active air extraction before and / or during the Compressed are supported by connecting the exhaust air nozzles 28 to a vacuum source.

FIG. 7 shows the arrangement after the compression has ended, that is to say after the compression head 9 has been pressed into its lower end position by the hydraulic cylinder 13 in the manner described at the outset, a maximum stroke difference of at least 30% based on the mold box height being maintained between the individual stamps 7 becomes.

The fluidization and pre-compression effect by the gas pulse is effective due to the high stamp speeds at least during the main part of the stroke movement of the compression head 9. The duration of action of the gas pulse can be optimally adapted to the other process parameters by corresponding control of the valves 25. It may also be expedient to make the air pulse relatively weak, so that it only leads to fluidization of the molding material without pre-compression.

The above exemplary embodiments have each been described with a lowerable compression head 9. Of course, the reversal of the movement conditions is also within the scope of the present invention, that is to say to keep the compression head 9 at a constant height while omitting the hydraulic cylinder 13 and to raise the model plate 1 against the compression head by means of a lifting table (not shown).

In summary, the advantage of the described invention is that the individual control of the individual punches or their different preload in the sense of a high maximum stroke difference between the individual punches results in a much more homogeneous compression than before, even with problematic model contours.

The invention also extends to boxless molding, the molding box being stripped or disassembled after compression. The invention is also suitable for combination with other precompression processes.

Claims (31)

1. Method for ramming mould material in moulding boxes of foundry moulding machines with a multi-stamp press plate, individual stamps being arranged spaced apart from one another and penetrating to different depths into the mould material corresponding to the model height, and ramming initially being effected only by the stamps forced in the ramming direction by a pressure medium, characterised in that at least the internally situated stamps (7) are in each case individually impacted with pressure medium corresponding to the contour of the model (2), the press plate (8) is then additionally used for the ramming and is driven roughly to the upper edge of the moulding box, and that a maximum stroke difference between individual stamps (7) of at least 30%, preferably at least 40% of the moulding box height, is maintained at the end of ramming.
2. Method according to claim 1, characterised in that a maximum stroke difference between individual stamps of at least 50% of the moulding box height is maintained.
3. Method according to claim 1 or 2, characterised in that the sum of the sand-side stamp cross-sections is chosen to be 20% to 70%, particularly 20% to 50%, of the moulding box area.
4. Method according to any one of the preceding claims, characterised in that the sum of the sand-side stamp cross-sections in the internal region is chosen to be 20% to 50%, and in the edge region to be 50% to 100%, of the relevant moulding box area.
5. Method according to any one of the preceding claims, characterised in that the stroke rate of a ramming head (9) containing the stamps (7) and the press plate (8) is more than 2.0 m/sec., particularly 3 to 10 m/sec., preferably 4 to 8 m/sec.
6. Method according to any one of the preceding claims, characterised in that the kinetic energy of the press plate (8) and its stamps (7) at the end of the ramming stroke is absorbed, at least mainly at the edge of the moulding box (3), by the mould material.
7. Method according to any one of the preceding claims, characterised in that the variable pressure impact of the stamps (7) is effected with discretely predetermined pressures.
8. Method according to any one of the preceding claims, characterised in that the stamps (7) are completely disengaged from the press plate (8) before the ramming and are then supported by a varyingly strong counterpressure, in particular pneumatic counterpressure, corresponding to the model height, following which the press plate (8) together with the stamps (7) displaced relative thereto is pressed onto the mould material (5).
9. Method according to one of claims 1 to 7, characterised in that the stamps (7) are on the one hand subjected to a constant pressure in the ramming direction, and on the other hand are supported by predetermined counterpressures discretely corresponding to the model contour.
10. Method according to one of claims 1 to 7, characterised in that the stamps (7) are set at different levels corresponding to the model height and are supported by an equally strong counterpressure, particularly hydraulic pressure, so that the stamps essentially maintain their positions relative to one another during ramming.
11. Installation for implementing the method according to one of claims 1 to 10, with a press head (6) containing a plurality of stamps (7) distributed over the moulding box cross-section and that are individually guided in pressure medium cylinders (10) and can be disengaged from the press plate (8) forming the lower closure of the press head (6), characterised in that at least the pressure medium cylinders (10) for the stamps (7) lying within the outer stamps are in each case connected via their own pressure medium lines and valves to a pressure source (12).
12. Installation according to claim 11, characterised in that the pressure medium cylinders (10) are in each case connected via their own pilot valve (15) to the pressure source (12).
13. Installation according to claim 11, characterised in that the pressure medium cylinders (10) are connected at one end in a row-type arrangement and at their other end in a column-type arrangement to pressure medium lines arranged respectively in rows and columns, the said lines being connected in each case via valves (V₁, V₂, V₃...; V_A, V_B, V_C...) to a pressure medium feed line and to a pressure medium removal line.
14. Installation according to one of claims 11 to 13, characterised in that the afore-mentioned valves (14; 15; V₁...; V_A...) are controlled by a microprocessor corresponding to the desired preset pressures and stroke positions of the stamps (7).
15. Installation according to one of claims 11 to 14, characterised in that the desired stroke positions are set in a stepwise manner by successive, equally large metering strokes.
16. Installation according to one of claims 11 to 15, characterised in that the press plate (8) has underneath, on its edge and in the region between the external stamps, a surrounding protuberance or several individual protuberances (8a).
17. Installation according to claim 16, characterised in that the protuberance or protuberances (8a) have a width of 50 to 100 mm and a height of 50 to 130 mm.
18. Installation with a press plate (8) which has underneath its edge a surrounding protuberance or several individual protuberances (8a), according to claim 16 or 17, characterised in that the protuberance or protuberances (8a) are mounted vertically adjustable relative to the press plate (8) so as to project by different amounts.
19. Installation according to claim 18, characterised in that the protuberance or protuberances (8a) are adjusted pneumatically.
20. Method according to one of claims 1 to 10, characterised in that the mechanical ramming by compresion described there is combined with the action of a compressed gas pulse produced by compressed air or by explosion of ignitable gas mixtures.
21. Method according to claim 20, characterised in that the compressed gas pulse is employed before and/or during the compression.
22. Method according to claim 20 or 21, characterised in that during the ramming gas is evacuated from the moulding box (3), especially via the model plate (1).
23. Installation for implementing the method according to claims 20 or 21, with a press head (6) containing a plurality of stamps (7) distributed over the moulding box cross-section, which stamps are in each case guided in pressure medium cylinders (10) and can be disengaged from the press plate (8) forming the lower closure of the press head (6), characterised in that the press head (6) is incorporated in a pressure vessel (21) that can be connected in a leakproof manner to the filling frame (4).
24. Installation according to claim 23, characterised in that the press head (6) has a valve head (23) that co-operates with a valve seat (22) of the pressure vessel (21) in order to open or close the connection of a pressure source, under excess pressure, to the moulding box (3).
25. Installation according to claim 23 or 24, characterised in that the press head (6) has flow openings in the region of its ramming head (9).
26. Installation for implementing the method according to claims 20 or 21, with a press head (6) containing a plurality of stamps distributed over the moulding box cross-section, which stamps are in each case guided in pressure medium cylinders (10) and can be disengaged from the press plate (8) forming the lower closure of the press head (6), characterised in that the press head (6) contains a pressure vessel (9a) and is connected to a pressure source (24).
27. Installation according to claim 26, characterised in that the pressure vessel (9a) is arranged in a region of the press head (6) containing the pressure medium cylinders (10).
28. Installation according to claim 26 or 27, characterised in that the pressure vessel (9a) communicates via valves (25) with the moulding space formed by moulding boxes (3) and filling frame (4).
29. Installation according to any one of claims 26 to 28, characterised in that the press head (6) can be connected in a leakproof manner to the filling frame (4).
30. Installation according to claim 29, characterised in that the press head (6) dips into the filling frame (4) via sealing lips (26) along the inner wall of said frame.
31. Installation according to one of claims 23 to 30, characterised in that vent channels (28) are arranged in the model plate (1) and/or in the model (2).

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