EP0129210A2 - Apparatus for compacting foundry moulding material - Google Patents

Abstract

A device for compressing foundry molding material by means of pressurized gas consists of a pressure vessel (5) for the pressurized gas, which forms a pre-pressure chamber, a mold space arranged underneath it, formed from a molding box (3) and filling frame (4), and a model plate (1) which closes the molding box below. with model (2) onto which the molding material is loosely poured before compression, and a valve arranged between the pressure vessel and the molding space, the closure member (11) of which is guided inside the pressure vessel and its opening movement under the effect of the pressure in the pressure vessel at least largely into the molding space is set up. The closure member can be designed as a rigid valve plate (11) with a plurality of slots (12) which cooperate with non-congruent slots (8) in a stationary plate (7) forming the valve, or as a flexible, thin valve plate (30 ), which is clamped on the edge and, after loosening the edge-side clamping (32) under the action of the compressed gas and opening the opening (29), is folded into the mold space.

Description

The invention relates to a device for compressing foundry molding material by means of pressurized gas, consisting of a pressure vessel for the pressurized gas forming a pre-pressure chamber, a mold chamber arranged below it from a mold box with filling frame and a model plate with a model that closes the mold box below, onto which the molding material is compressed is loosely heaped up, and a valve arranged between the pressure vessel and the mold space, the closure member of which releases the opening cross-section of the valve predominantly under the effect of the pressure in the pressure vessel.

A device of the aforementioned structure is the subject of earlier patent application No. 82 11 0996.4. There is a method and an apparatus for compacting foundry molding material, in particular molding sand, by means of compressed gas, e.g. Compressed air or compressed gas generated by explosive combustion, in which the compressed gas is suddenly released from a pressure vessel into the mold space, thereby acting on the free molding material surface and compressing the molding material particles with mutual impulse exchange and by delaying the accelerated molding material mass on the model top and the model plate , with additional fluidization effects occurring while reducing particle friction. What is essential here is a high gas mass throughput with the fastest possible pressure increase in the molding space. These parameters must be higher, the lower the outlet pressure in the pressure vessel, whereby outlet pressures are aimed at which are in the area of the pressure of operational compressed air networks, in order not to have to undertake too much constructive effort on the one hand for the production of compressed gas, and on the other hand for the structural control of the pressure. This means that the device must have a closure member which on the one hand closes the largest possible cross section for overflowing the compressed gas and on the other hand has the lowest possible mass in order to release the cross section as quickly as possible. This also requires opening drives which bring the closure member into the open position in a few milliseconds and thus release the cross section. The aforementioned requirements cannot be achieved with conventional valve designs.

The older patent application describes some embodiments of valve constructions that meet these requirements. The compressed gas itself is used to initiate at least the opening stroke of the valve and thus one as quickly as possible To achieve pressure equalization on both sides of the closure member so that any further opening movement does not have to be carried out against the pressure. In all these embodiments, the closure member is arranged so that it is substantially moved into the pressure vessel. This in turn requires a special structure of the closure member.

Building on the principle disclosed in the earlier patent application of utilizing the pressure drop between the pressure vessel and the molding space to open the valve, the present invention is based on the object of proposing improved embodiments in which the opening cross section is released solely under the action of the compressed gas.

This object is achieved in that the closure member is guided within the pressure vessel and its opening movement is at least largely directed into the mold space.

Deviating from the embodiments of the device described in the earlier patent application, in which the closure member is arranged completely in the pressure vessel and also opens within the same, the closure member is opened in the invention in the direction of the compressed gas flowing into the mold space. On the one hand, this leads to a more effective way of working, and on the other hand, the closure member can be kept in the closed position with simpler constructional means.

A preferred embodiment following the principle according to the invention is that the closure member is a valve plate provided with a plurality of openings, preferably slots, which interacts with a fixed plate arranged above it and between the pressure vessel and the mold space and having a multiplicity of openings, the openings of the valve plates and the fixed plate being offset relative to one another to form a tight seal, and that the valve plate is fixed in the closed position and after the fixing has been released can be accelerated into the mold space by means of the compressed gas.

The valve plate and the stationary plate are each designed in the manner of a grate, the openings of both plates not overlapping in the closed position. So the openings of the fixed plate are closed by the valve plate and their holes by the fixed plate. As soon as the valve plate is lowered even by a small amount, the compressed gas can flow into the molding space through the large number of openings in the stationary plate and the valve plate. This has the advantage that for the expansion of the compressed gas into the mold space, the closure member only has to carry out a very small stroke in order to release the largest possible overflow cross section.

Since the mold box and filling frame are generally of rectangular design, the valve plate advantageously has a rectangular cross section which is adapted to the rectangular cross section of the molding space, in order also to achieve the largest possible opening cross section and a uniform distribution of the compressed gas over the molding material surface.

In order to achieve a hermetic seal in the closing days, the valve plate or the stationary plate are provided with a sealing strip surrounding all openings on the surfaces facing each other. This sealing layer is preferably seated on the valve plate. According to another embodiment of the invention, the closure member is designed as a thin valve plate made of a flexible material, which covers an opening between the pressure vessel and the molding space, is tightly fixed at the edges in the closed position and after releasing the fixation under the effect of the compressed gas towards the center and down in the mold space is displaced.

This valve plate can for example consist of rubber, rubber-elastic plastic or a plastic with a different elasticity behavior, it is only important that the cross-section and material are selected so that the valve plate is folded into the mold space as quickly as possible after the release of the pressure gas and while doing so as much as possible ichen cross section of the opening. Here, too, the opening movement is carried out exclusively under the action of the compressed gas if the edge fixing of the valve plate is released.

This embodiment gives the possibility that the opening between the pressure vessel and the mold space corresponds to the free cross-section of the mold space, the valve plate being arranged in the closed position in the pressure vessel and resting on the edge of the bottom thereof delimiting the opening. Due to the large opening cross-section that is possible as a result, and its sudden release by folding down the valve plate, the desired gas mass throughput and the rapid increase in pressure in the molding space can be achieved in a particularly simple manner.

The flexible valve plate can be held in the closed position by means of a ring or frame, which acts on its peripheral edge from above and to which the fixation is assigned. This ring or frame, which is also under the action of the compressed gas, presses the edge of the Ven tilplatte against the opening of the bottom of the pressure vessel. This ring or frame can have a relatively small mass, so that it can also be lifted off with a low driving force in order to initiate the opening movement of the valve plate.

In a further preferred embodiment, the material of the valve plate has a resilience which brings it into a position approximately corresponding to its closed position. The valve plate, which is displaced into the mold space due to its flexibility during the opening movement, straightens itself up after the pressure equalization has been reached and reaches a position in which it is again located within the pressure container and pressed against the edges again by means of a closing drive which acts on the ring or frame can be.

In the aforementioned embodiments it is further provided that the valve plate is arranged on a central guide rod, by means of which it can be brought from the open position into the closed position, and which can be fixed in the closed position of the valve plate by means of a clamping device forming the fixation.

The valve plate is thus brought from the open position into the closed position by means of the guide rod. Then the guide rod is fixed by means of the clamping device so that the pressure vessel can be filled with the compressed gas. By releasing the clamping device, the valve plate is released and is suddenly accelerated into the open position by the pressure gas applied to it. Due to its radial action on the guide rod, the clamping device provided according to the invention has the advantage that only very short distances are required for loosening are necessary so that this process can also take place in the shortest possible time.

A pressure medium cylinder acting on the guide rod can serve as the closing drive for the closure member, and is decoupled from the guide rod after the guide rod has been fixed by means of the clamping device, at least at the beginning of the opening movement. The drive connection is then re-established and the valve plate is brought back into the closed position by means of the guide rod.

If the valve plate is formed from a flexible material, the ring or frame pressing the valve plate on the edge sits on the lower part of a two-part guide rod, which is guided so as to be axially displaceable relative to the upper part. The ring or frame is provided with spring brackets which are supported at the opening edge and are pretensioned during the closing movement, while after loosening the clamping device they accelerate the ring or frame with the lower part of the guide rod upwards, releasing the valve plate edge. Under the action of the compressed gas, the valve plate pulls out of the gap between the ring or frame on the one hand and the bottom of the pressure vessel delimiting the opening on the other and folds into the mold space.

• Fig. 2 einen der Fig. 1 entsprechenden Längsschnitt mit der Ausführungsform einer flexiblen Ventilplatte.

Further details and advantages of the invention will become apparent from the following description of the drawing, which shows two embodiments of the device. The drawing shows:

• Fig. 2 is a longitudinal section corresponding to FIG. 1 with the embodiment of a flexible valve plate.

In the drawing, only the parts of the compression device of a foundry molding machine necessary for understanding the invention are shown. In particular, the machine stand, the device for lifting and lowering the molding box and filling frame and, if necessary, for ejecting the finished mold from the molding box are not shown. The facilities for bringing up the model and for filling the molding sand are also not shown, since these components are known in foundry mechanical engineering.

On a model plate 1 with a model 2 sits a molding box 3 and on this a filling frame 4. Above the molding space is a pressure vessel 5 - in the embodiment shown for receiving compressed air - which is connected via a connection 6 from a pressure accumulator or - at low admission pressure - is fed from the company's compressed air network.

The pressure vessel has a stationary plate as the bottom 7, which is provided with a plurality of slots 8 in a rust-like manner in the area above the molding space. A frame 9 is flanged to the underside of the base 7, to which in turn an exhaust air line with a valve 10 is connected. The pressure vessel 5 with the frame 9 on the one hand and the model plate 1 with model 2, molding box 3 and filling frame 4 can be moved relative to one another in order to be able to fill the molding space with molding material. Before compression, these two assemblies are brought together and pressed tightly together at their interface.

A closure element in the form of a rigid plate 11, which likewise has a multiplicity of slots 12, interacts with the bottom 7 or its area having the slots 8. Furthermore, on the upper side of the valve plate, within the area of the slots 12, as well as the slots 8 in the base 7, there is a sealing coating 13. As can be seen from the left half of the illustration, the slots 8 in the bottom 7 and the slots 12 in the valve plate 11 are offset from one another in such a way that they do not overlap in the skiing position.

The valve plate 11 is seated on a guide rod 14 which can be lifted from the open position of the valve plate shown on the right into the closed position shown on the left by means of a sliding piston 15 sliding thereon. Damping cylinders 17, with which a crosshead 18 fastened on the guide rod 14 cooperates, sit on the cylinder 16 for the reciprocating piston 15, which cylinder is fixed within the pressure container 5. The upper end face of the lifting piston 15 acts against this crosshead 18 during its upward movement. Furthermore, the guide rod 14 is assigned a clamping device, designated as a whole by 19, of which one clamping part 20 is axially movable within a housing 21 supported on the floor and the other clamping part 22 sits on the guide rod. The clamping parts can be wedges or the like.

Finally, there is a support body 23 on the floor 7, which delimits an overflow space 24 between it and the floor 7. The support body has circumferentially coaxial slots 25, which are rotated on the outside by a rotatable ring 26, which in turn has slots 27.

• In der in Fig. 1 wiedergegebenen Schließlage des Ventils, in der auch die Schlitze 25 des Tragkörpers 23 von dem Ring 26 verschlossen sind, wird der Druckbehälter 5 über den Anschluß 6 mit Druckgas gefüllt.

The operation of the device is described below:

• 1, in which the slots 25 of the support body 23 are also closed by the ring 26, the pressure vessel 5 is filled with compressed gas via the connection 6.

The clamping device 19 is in the clamping position, so that the valve plate 11 is pressed tightly against the bottom 7. Molding box 3 and filling frame 4 are loosely filled with molding sand. To initiate the opening stroke, the ring 26 is first rotated in such a way that its slots 27 come into coincidence with the slots 25 of the supporting body 23 (see right half of the illustration), so that the compressed gas can reach the overflow chamber 24. A mechanical safety latch 28 is subsequently extended and the reciprocating piston 15 is lowered when the clamping device 19 is blocked, and it slides down on the guide rod 14. Then the clamping device 19 is released hydraulically and the guide rod 14 and the valve plate 11 are released. The pressure gas present via the slots 8 on the valve plate 11 suddenly accelerates it downward, so that the pressure gas can relax in the molding space via the slots 12 and over the edge region. During the opening stroke, the guide rod 14 is braked when the crosshead 18 strikes the damper 17. The valve plate reaches the position shown on the right. In the meantime, the molding sand is accelerated and at the same time braked on model plate 1 and model 2 and compacted in the process. After completion of the opening stroke, the ring 26 is rotated again to secure it, so that a new filling process can begin without the compressed gas being able to overflow. By means of the ring 26, moreover, the gas mass throughput can be preset and the shape hardness can thereby be determined. By means of the lifting piston 15, the guide rod 24 with the valve plate 11 is then raised again via the crosshead 18 and fixed in the closed position (I inke half of the illustration) by means of the clamping device. The safety latch 28 is retracted. During this process, the compressed gas still present in the molding space is blown off via the valve 10.

In the embodiment according to FIG. 2, the bottom 7 of the pressure vessel 5 is provided with an opening 29 which corresponds approximately to the inside width of the filling frame, that is to say is rectangular or has the largest possible circular opening 29. This opening 29 is overlapped by a flexible valve plate 30, which is clamped in its center on the lower part 14 'of the two-part guide rod 14 here. In the closed position, the valve plate 30 runs approximately horizontally and. is pressed with its edge 31 by means of a ring or frame 32 sealingly against the bottom 7 of the pressure vessel 5 delimiting the opening. The ring or frame 32 is also seated on the lower part 14 'of the guide rod 14 and is axially displaceable therewith, the axial stroke being limited by dampers 33 which are fastened to the upper part 14 "of the guide rod 14. Furthermore, the guide rod 1, associated with a clamping device 19. Finally, the guide rod 14 has a lifting drive 34, which has the same function as the lifting piston 15 according to FIG of the ring 32 on the valve plate edge 31 or the base 7, which extends down to the spring and engages the bolt 36, which is supported on the base 7 of the pressure vessel 5.

In the closed position shown on the left in FIG. 2, the part 14 'of the guide rod 14 is in its lower position. The valve plate 30 is pressed tightly against the bottom 7 in the region of its edge 31 by means of the ring 32. The spring accumulators 35 are preloaded. The guide rod 14 is fixed by means of the clamping device 79. To initiate the opening movement, first the clamping device and thereby the spring accumulator 35 are released, so that the ring or frame 32 suddenly lifts upwards and runs against the damper 33. At the same time, the entire guide rod 14 is raised by means of the lifting drive 34. Under the action of the compressed gas present on the valve plate 30, the latter can pull out between the ring 32 and the base 7. It is then displaced by the pressurized gas to the center and downwards into the position shown on the right in FIG. 2, so that most of the opening cross section is released. During this opening process, the molding sand in the molding box 3 and filling frame 4 is compressed. As soon as there is complete pressure equalization, the valve plate straightens up again and, due to its resilience, comes into contact with the ring 32 (see upper position of the valve plate in the right-hand illustration in FIG. 2). Then the guide rod 14 moves down together with the ring 32 until the bolts 36 of the spring accumulator 35 hit the floor 7 and are prestressed in the process. Finally, the ring 32 in turn clamps the edge 31 of the valve plate 30 tightly against the bottom 7. The upper part 14 "of the guide rod is raised somewhat again by means of the lifting drive, so that the ring or frame 32 again has the necessary play with respect to the dampers 33.

Claims (10)

1.Device for compressing foundry molding material by means of compressed gas, consisting of a pressure vessel forming a pre-pressure chamber for the compressed gas, a molding space arranged underneath, consisting of a molding box with filling frame and a model plate with a model that closes the molding box below, onto which the molding material is loosely poured before compression is, and a angeord Neten valve between the pressure vessel and the mold space, the closure member of the opening cross-section of the valve suddenly releases mainly under the effect of the pressure in the pressure vessel, characterized in that the closure member (11, 30) inside the pressure vessel (5) and his Opening movement is at least largely directed into the mold space (3, 4). 2. Device according to claim 1, characterized in that the closure member is a with a plurality of openings, preferably slots (12) provided valve plate (11) with one above it and between the pressure vessel (5) and the mold space (3, 4th ) arranged stationary plate (7) cooperates with a plurality of openings (8), the openings (12, 8) of the valve plate (11) and the stationary plate (7) being offset from one another to form a tight seal, and that the valve plate ( 11) fixed in the closed position and after releasing the fixation (19) by means of the compressed gas in the mold space (3, 4) can be accelerated. 3. Apparatus according to claim 2, characterized in that the valve plate (11) has a rectangular cross section adapted to the rectangular cross section of the molding space (3, 4). 4. Apparatus according to claim 2 or 3, characterized in that the valve plate (11) or the fixed plate (7) on the mutually facing surfaces with all openings (8, 12) surrounding the sealing coating (13) is provided. Apparatus according to claim 1, characterized in that the closure member is designed as a thin valve plate (30) made of a flexible material, which covers an opening (29) between the pressure vessel (5) and the molding space (3, 4), tightly fixed at the edge in the closed position is and after loosening the fixation (19,32) under the action of the compressed gas towards the center and down into the mold space (3,4). - 6. Device according to claim 5, characterized in that the opening (29) between the pressure vessel (5) and the mold space (3, 4) corresponds to the free cross section of the mold space, the valve plate (30) is arranged in the closed position in the pressure vessel (5) and lies on the edge of the bottom of the opening (7). 7. Apparatus according to claim 5 or 6, characterized in that the flexible valve plate (30) by means of a ring or frame (32) which acts from above on its peripheral edge and which is associated with the fixation (19), held in the closed position is. 8. Device according to one of claims 5-7, characterized in that the material of the valve plate (30) has a resilience which brings them into a position approximately corresponding to their closed position. 9. Device according to one of claims 1-8, characterized in that the valve plate (11,30) is arranged on a central guide rod (14) by means of which it can be brought from the open position into the closed position and which forms the fixation by means of a Clamping device (19) can be fixed in the closed position of the valve plate. 10. Device according to one of claims 1-9, characterized in that serves as a closing drive on the guide rod (14) acting pressure medium cylinder (15, 16 or 34) which after fixing the guide rod (14) by means of the clamping device (19) is uncoupled from the guide rod (14) at least at the beginning of the opening movement. 11. The device according to any one of claims 5-10, characterized in that the valve plate (30) on the edge pressing ring or frame (32) on the lower part (14 ') of a two-part guide rod (14) opposite the upper part ( 14 '') is guided axially displaceable to a limited extent, sits and is provided with spring brackets (35) which are supported on the opening edge of the base (7) and are pretensioned during the closing movement, while after loosening the clamping device (19) the ring or Accelerate the frame (32) with the lower part (14 "), releasing the valve plate edge (31).

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