DE2843598A1 - METHOD AND DEVICE FOR COMPRESSING FOUNDRY SAND - Google Patents

Description

DR. ING. HANS LIGHTI DIPL.-ING. HEINER LICHTI DIPL.-PHYS. DR. KLAUS LEUTWEIN

PATE N TA N CHOICES

D-7500 KARLSRUHE 41 (GRÖTZINCEN) ■ DURLACHER STR. 31 CHOICE HOUSE) TELEPHONE (0721) 4Θ5Ι1 - TELEX 7825986 LIPA D

ARENCO-BMD 4615/78

Maschinenfabrik GmbH
Pfinztalstrasse 90

D-7500 Karlsruhe 41

Method and device for compacting foundry molding sand

The invention relates to a method for compacting foundry molding sand in the molding box by pressing excess sand from above into the molding box, as well as a device for carrying out the process.

There are a number of well-known ones for compacting foundry molding sand Procedure. Naturally, all processes aim to achieve the best possible compression of the molding sand in order to create one when the mold is later poured to get a flawless casting. The problems with compaction lie on the one hand in the relatively large cavity volume of the molding sand with loose bedding, on the other hand in the poor sliding properties of the Sand particles.

030016/0328

4615/78

In the known vacuum pressing, the molding sand is subjected to a negative pressure during pressing, which is intended to ensure that the air obtained in the molding sand SchüiLing faster and more completely escapes. This method only leads to satisfactory results with binder-free molding sand. In addition, methods are known at which, in addition to pressing, have a mechanical shaking movement in the molding sand is entered. This happens because the molding sand shaken before pressing, but if necessary also shaken during pressing. The shaking movement is caused by the impact of the Press table produced on an anvil, with a very strong impact delay up to over 200 g. The frequency here is approx. 10 Hz. With this method, a very good compression is achieved, however it is associated with a considerable amount of noise. With this method one can therefore hardly meet the environmental protection conditions today be more fair.

Finally, the so-called. Shooting methods are known in which the molding sand is suddenly shot into the molding box under excess pressure, in order to obtain a good pre-compression, especially in the area of the model. In addition, a pressing process then takes place. This shooting procedure have proven themselves well in practice, but then cause problems with itself when it comes to intricate models. An attempt has already been made to remedy this situation by removing the upper press plate, against which the mold is moved by means of the press table, as a profile plate is formed, the profile of the model contour is adapted. It is also known to use a so-called. Much punch press head So the press plate is replaced by a variety of stamps. In both cases the aim is to cover the entire depth of the To produce the most uniform possible compression of the molding sand depending on the model contour. This is more or less secure

Ü3flDi6 / 0328

4615Λ8

ensures that the molding sand penetrates into small and intricate cavities, overall, however, the degree of compaction is unsatisfactory.

As the most versatile process with a satisfactory degree of compaction The vibrating press method has proven itself in every model shape. Despite being diverse Efforts have not yet succeeded in finding a satisfactory solution to the noise pollution.

Starting from a method in which the molding sand in the molding box is compressed from above, the invention is based on the object of creating a method and a device that on the one hand allow precise contouring of even complex models and generate only a low level of noise.

This object is achieved according to a first basic idea of the invention in that before pressing from above the molding sand in the The molding box is pre-compressed from below, the amount of excess sand is dimensioned so that after the pressing is completed from below there is still a protrusion of molding sand above the molding box.

Although a method is known in which the molding sand instead of from above is compressed from below. But the excess sand that is in a filling frame arranged below the molding box, be dosed very precisely because the press plate is flush with the upper edge of the molding box. The amount of excess sand must be like this be dimensioned so that after pressing the part plane of the mold is flush with the lower edge of the molding box. If it is too low If the amount of excess sand is too soft, the mold will be over-pressed.

The method according to the invention essentially consists of a combination of the known pressing methods from above and below. Here

030016/0328

- ^ - 4615/78

the advantage is first achieved that during the pressing from below the molding sand in the area of the model is pre-compacted, there for a sharp-contoured impression is provided. During the subsequent pressing the final compression of the molding sand takes place from above above the model, so that the mold has a good and uniform degree of compression after both pressing operations have been completed. In the inventive Method, despite the pressing process from below, surprisingly, the disadvantage of this known pressing method of over or over Avoid underpressing the mold, as the excess sand for pressing from below is not precisely dosed, but only ensured it must be that there is still sufficient excess sand for the second process stage, the pressing from above. When pressing At the top it no longer matters whether there is still a protrusion of molding sand after pressing or whether the surface of the molding sand is present is below the top of the molding box.

According to a preferred further development of this method, the Molding sand at least during the pressing from below a harmonic or a superimposed oscillation. Here a mechanical movement is thus entered into the molding sand, which - in contrast to the well-known vibration process - no compaction caused by a very strong impact delay, but rather sliding the sand particles on each other and on the adjacent molding box and The model surface promotes settlement with the result that the pore air escapes from the sand pack as the compaction progresses of the molding sand in the molding box and, last but not least, the required pressing force is reduced. This swinging movement is at least during the pressing process from below into the molding sand

the sand particles

wear so that the sliding movement / under the steadily increasing pressing pressure he follows.

0 34) 50-1 6/0328

- JB "- 4615/78

Practical vasuche have shown that an oscillation of approx. 50-100 Hz is particularly favorable for compacting the molding sand. In contrast to the conventional vibration method with its strong Mass deceleration and sudden destruction of energy is the development of the noise in the case of a harmonic or superimposed oscillation, it is far lower and more bearable. In addition, the Attenuate sound radiation much easier.

The vibration can be generated by conventional means or else can also be transmitted via the hydraulic medium generating the pressing pressure.

To carry out the method, the invention is based on a known one Device with a press table, egg ner with this associated model plate, a molding box, a receiving the excess sand Filling frame and a press plate arranged above it, against which the mold is moved by means of the press table. Devices of this type are known in a variety of embodiments for pure press compaction and for press vibration. Here the excess sand is from above displaced forth from the filling frame in the molding box.

According to the invention, such a device is now characterized in that that the clear cross section of the molding box is slightly larger than the outline the model plate is and that the molding box and filling frame are on hydraulic pistons support on the one hand on the model plate on the other hand on the pressure plate, the hydraulic pistons being acted upon or controlled in such a way that that when pressing from below the lower piston in their assigned Immerse the cylinder with the upper piston at a standstill, then upper and lower pistons are moved upwards synchronously until the molding box with its lower edge is again flush with the top of the model plate, and finally, when pressing from above, the upper piston in

030016/032 8

- tS - 4615/78

immerse the cylinders assigned to them with the lower piston stationary.

The first part feature of this device according to the invention ensures that the model plate can dip into the molding box from below during pressing, that is to say presses the molding sand upwards against the press plate, with in particular, the molding sand is compacted in the area of the model. During this work phase, the molding box and filling frame remain in place the second part is characterized by the fact that it is supported by the hydraulic pistons in their starting position. When the hydraulic pistons subsequently move upwards together, the filling frame and molding box become taken along, so moved up. You will be facing as long as the molding sand until the lower edge of the molding box is in the partial plane of the model, i.e. flush with the top of the model plate concludes. Then the compression then takes place from above, in that the press table pushes the molding sand further against the press plate, so that further excess sand from the filling frame is displaced and compacted in the molding box. The hydraulic pistons are controlled so that the molding box and the filling frame follow the movement of the model plate, i.e. the lower edge of the molding box in the parting plane of the model remains.

A preferred embodiment of the device described is characterized is characterized by the fact that on the model plate, on the press table, the press plate or the molding box vibration generators are arranged, which are excited at least during the pressing taking place from below. This vibration generator can, for example, in a corresponding Be accommodated cavity of the model plate or the press table. They are advantageously designed in such a way that the oscillation occurs at one frequency of approx. 50 - 100 Hz still has an amplitude despite the pressure applied

-7- 4615/78

/ IO

between 0.4 and 1 mm. Due to the pressure applied, the press table can undergo the further compression achieved during oscillation of the molding sand into the molding box, i.e. the vibratory movement occurs during the pressure rise to the set Press pressure. Such vibrations result in accelerations or decelerations of approx. 5 to 20 g, the effects of which on the sound development can be mastered without difficulty.

In another Ausführungsforrn the apparatus in which the plunger is acted upon hydraulically, the invention provides ₃ that a hydraulic pulse generator is disposed in the hydraulic circuit of the press piston so that the vibration is transmitted via the hydraulic column.

The invention is illustrated below with reference to in the drawing Embodiments and phase images described. In the drawing demonstrate:

Figure 1 is a schematic longitudinal section through the for

Invention of relevant machine parts in the area of the molding box;

Figure 2 four phase images a), b), c) and d) showing the process sequence reproduce;

FIG. 3 shows a view similar to FIG. 2 of an embodiment with vibration excitation and

Figure 4 is a view similar to Figure 3 of another

guidance form with vibration excitation.

o 3 omi-ε / ο j 2 8

- β - 4615/78

Α \

Since to carry out the method according to the invention an essentially conventional compression molding machine can be used in the drawing only the machine parts relevant to the invention shown. In particular, the machine frame and the sand supply are missing and the flask conveyor. Reference is first made to Figure 1:

The molding machine has a plunger 1 in a conventional manner, which is guided in a stationary press cylinder 2 and in general is pressurized with compressed air. The plunger 1 carries a press table 3 on which a model plate carrier 4 is attached. On the model plate carrier 4, in turn, the model plate 5 is fixed with the model 6, which is surrounded by a molding box 7. A filling frame 8 is arranged between the molding box 7 and a press plate 9. The molding sand is swiveled out via a feed device, not shown, for example The press plate 9 is filled into the molding box until the molding sand is approximately flush with the upper edge of the filling frame 8.

The clear width of the molding box 7 is, as can be seen from Figure 1, slightly larger than the outline of the model plate 5. The molding box can therefore not be supported on the model plate. As a support for molding boxes Rather, 7 and filling frame 8 serve lower hydraulic pistons 10 and upper hydraulic pistons 11. The lower hydraulic pistons 10 run in Cylinders 12 on the model plate carrier and grip over their piston rods 13 on the underside of the molding box 7. The upper hydraulic pistons 11 run in cylinders 14 of the press plate 9 and engage over their Piston rods 15 on the top of the filling frame 8.

The phase diagrams in FIG. 2 show the process when compressing the Molding sand. The phase diagram according to FIG. 2 a) gives the starting position

0 3 0-Φ1-6 / 0328

- f - 4615/78

again, which corresponds to the position shown in FIG. Molding box and filling frame 8 are filled with molding sand up to the upper edge thereof and the pressing plate 9 has been brought into position. First of all (Fig. 2 b) pre-pressing, i.e. pressing from below. Due to the pressing stroke of the press table 3, model plate carriers 4 with model plate 5 and penetrate Model I6 into the molding box 7 from below. The pressing pressure is from the Fixed press plate 9 was added in this phase. With this pre-pressing, the molding sand is mainly in the contour of the model near area, which is indicated with 16, condensed. The lower and upper hydraulic pistons 10, 11 are with one another during the pre-pressing locked so that they maintain their original position, but the lower pistons 10 due to the movement of the model plate carrier 4 immerse in their cylinder 12. At this stage it will be natural also the molding sand in the area 17 below the press plate 9, which Forms abutment for the pressing pressure, pre-compressed.

In the subsequent phase according to FIG. 2 c), molding boxes 7 and filling frame 8 raised by synchronous lifting movement of the lower and upper pistons 10, 11 until the lower edge of the molding box 7 with the top of the model plate 5 is flush.

In the final phase according to Figure 2 d) the lower and upper plunger 10, 11 controlled so that they follow the further pressing movement of the ModelIplatteenträgers 4 synchronously, the flush finish between the lower edge of the molding box 7 and the top of the pattern plate 5 is thus retained. This is followed by a further compression, the Final compression of the molding sand in the molding box 7.

The height of the filling frame 8 or the filling height of the molding sand is dimensioned in the starting position according to Figure 2 a) if possible so,

- 10 -

030016/0328

4615/78

that after the final compression according to FIG. 2 d) the molding sand is approximately flush with the upper edge of the molding box 7. A minor one Molding sand excess is not harmful and can be stripped off if necessary.

In Figure 3, a first embodiment is shown in which during the Pressing from below the molding sand is exposed to a harmonic or superimposed vibration. In this embodiment has the ModelIplatteträger 4 above the press table 3 a HohlraurrrB on. On the press table conventional counter-rotating unbalance exciter 19 are attached, of which the vibration on the press table 3, the Transfer the model plate carrier 4 and the model plate 5 into the molding sand will. In this embodiment, the plunger 2 must be on one Be mounted damping spring, which is indicated schematically at 20. This can be - this should be emphasized - a mechanical, but it can also be a pneumatic spring.

In the embodiment according to FIG. 4, the model plate 5 is not on Model plate carrier 4 attached, but via damping springs 21 this or is supported on the press table 3. The vibration exciter 22 sit on the underside of the model plate 5 in this case these vibrate, which is then transmitted from the pattern plate 5 into the molding sand. In this embodiment, the pressing pressure of the plunger 2 or the press table 3 is initially transferred to the pattern plate 5 via the springs 21 during the pre-pressing. In the case of m final compaction according to FIG. 2 d), the model plate carrier 4 runs with stops 23 against the underside of the modal plate 5 so that the pressure is transferred directly to the model plate.

Instead of the exemplary embodiments shown, the vibration exciters of course also on the molding box 7 or on the press plate

030q _i 16/0328

- I / - 4515/78

be arranged. It is also possible to operate the plunger 2 hydraulically to act on and to set the hydraulic fluid in oscillation by means of a conventional pulse generator α In In this case the oscillation is carried out directly via the press table, model plate carrier and transfer the pattern plate onto the molding sand.

030016/0328

-45 -

Blank page

Claims (8)

2843588 DR. ING. HANS LICHT! · DIPL.-ING. HEINER LICHTI DIPL.-PHYS. DR.KLAUS LEUTWEIN PATENTANWÄLTE D-7S00 KARLSRUHE 41 (GRÖTZINGEN) DUR LAC H ER STR. 31 (HOCH H AUS) TELEPHONE (0721) 48511 TELEX 7825986 LIPA D ARENCO-BM D 4615/78 Maschinenfabrik GmbH Pfinztalstr. 90 05: October 1978 D-7500 Karlsruhe 41 PATENT CLAIMS 1. Process for compacting foundry molding sand in molding boxes, by pressing excess sand from above into the molding box, thereby denying that before pressing from above the molding sand is compacted in the molding box from below, the amount of excess sand being measured in such a way that that after completion of the pressing from below there is still a protrusion of molding sand above the molding box. 2. The method according to claim 1, characterized in that the molding sand at least during the pressing from below a harmonic or superimposed vibration. 3. The method according to claim 2, characterized in that the ■ Molding sand exposed to vibration of at least 50 Hz willo 03 0 016/0328 - 2 - 4615/78 4. The method according to any one of claims 1 to 3 _3, characterized in that the vibration is transmitted via a hydraulic medium. 5. The method according to claim 4, characterized in that the vibration via the hydraulic means generating the pressing pressure is entered. 6. Apparatus for performing the method according to claim 1 with a press table, a model plate connected to it, a molding box with a filling frame receiving the excess sand and a pressing plate arranged above it against which the mold is moved by means of the press table, thereby marked, that the clear cross section of the molding box (7) is slightly larger than the outline of the model plate (5) and that the molding box (7) and filling frame (8) on the one hand on the model plate via hydraulic pistons (10) (5) or the model plate carrier (4), on the other hand, on the pressure plate (9), with the hydraulic piston being applied in this way or are controlled that when pressing from below the lower piston (10) in the cylinder (12) assigned to them blocked Immerse the upper piston (11), then move the upper and lower piston (10, 11) synchronously upwards until the molding box (7) is flush with the upper edge of the model plate (5) again with its lower edge, and I close the from above while pressing upper piston (11) in their associated cylinder (14) when blocked immerse the lower piston (10). 7. Apparatus according to claim 6 for performing the method according to Claim 2 or 3, characterized in that on the model plate (5), or on the press table (3), the molding box (7) / on the press plate (9) Vibration generators (19 or 22) are arranged, which are excited at least during the pressing from below. - 3 - 4615/78 8. Apparatus according to claim 6 with a hydraulically applied Compression piston for carrying out the method according to claim 4 or 5, characterized in that the hydraulic circuit of the A hydraulic pulse generator is arranged on the plunger (2). 030016/0328