EP0084627B1 - Device for compacting foundry moulding material - Google Patents

Description

The invention relates to a device for compressing foundry molding material, which is loosely heaped over a model in a closed molding space, consisting of a molding box with filling frame and a model plate, by means of compressed gas acting on the molding material surface, which comes from a high pre-pressure chamber Pressure-generating pressure vessel is suddenly released into the mold space via a valve arranged between it and the mold space.

A large number of mechanical, pneumatic and combined compression methods are known for the compression of foundry molding material, only the pneumatic methods being of interest in connection with the invention. These can essentially be divided into two categories. In the first category, the molding material is placed under gas pressure in a pre-pressure chamber and, after opening a valve, is blown or injected into the molding chamber together with the air. In any case, this process requires mechanical re-pressing of the molding material in the molding box with significant press forces (e.g. DE-B-26 53 788).

In the other category, the molding material is poured onto the model loosely and then pressurized with compressed air from the back of the mold (e.g. DE-B-28 44 464, DE-B-1 961 234). Essentially two variants are known. In the first variant (DE-B-28 44 464), compressed air up to 7 bar is blown in once or more times over a period of time between 0.2 and 1 s via openings in a hollow end plate of the molding space, the air flowing through the molding sand should flow out through openings in the model plate. Mechanical repressing is also necessary here, on the one hand to compress the back of the mold, and on the other hand to squeeze out the residual air that is still present in the molding material due to the fluidization effect, the squeezing also being to be supported by a vacuum. This process does not achieve a noticeable reduction in design effort compared to the shooting and blowing processes.

In the other process variant (DE-B-1 961 234), work is carried out in the high pressure range, which is to say here that the pressure in the upstream pressure chamber is appreciably above the operating pressure of a conventional internal compressed air network of up to 7 bar. In the known case, a pre-pressure between 20 and 100 bar is proposed. This pressure should then be released into the mold space within a maximum of 0.15 s.

It should be possible to dispense with the usual re-pressing. As a further prerequisite for the effectiveness of this process, a certain ratio of gas throughput on the one hand and molding material mass on the other hand is required, this ratio should be between 5: 1 and 40: 1, which at the same time gives a dependency between gas throughput and mold box size. A molding machine for carrying out the method is described (DE-B-1 961 234 and DE-A1-2151 949), in which a pressure vessel forming the pre-pressure space is arranged above the molding box, which is closed downwards by the model plate, or a filling frame arranged above it, which can be connected to the molding space via a mechanically moved valve. With a reasonable size, a pre-pressure of 100 bar is proposed for mold boxes of customary size in order to achieve a satisfactory compression there after relaxation in the mold space. Such a high pressure easily leads to irregularities in the surface of the molding material when the compressed gas impinges on the back of the mold, as well as to a considerable design effort in order to generate such high pressures and to achieve the necessary compressive strength in the molding space. The valve of the known device is a poppet valve which has a combined pneumatic-mechanical auxiliary drive and closes an opening of a relatively small cross-section between the pressure vessel and the molding box. In order to prevent the compressed gas from striking the surface of the molding material in a radial manner, a distributor cone is further provided under the valve opening and above it is a perforated floor extending over the entire surface of the molding space or, in another variant, an adjustable slot floor (DE-A1-2151 949).

Furthermore, a plurality of openings are provided in the model plate (DE-B-1961 234) through which the compressed gas can flow out. These openings naturally represent a constant source of interference, since they clog with molding material after a short period of operation.

In an older proposal (EP-A1-0062331), the required high pressure gradient, which should be around 100 bar / s, and the gas mass flow rate required for the exchange of impulses to the molding material particles are already at relatively low outlet pressures, which are in the range of the operating pressure of conventional compressed air networks lie, reached. Flat or Laval nozzles with their own opening drives are provided.

In all of the above-mentioned embodiments, the closure member of the valve is opened into the pre-pressure space. This means that the opening drive must work against the form. With the required high pressure gradient, a correspondingly high opening speed must also be ensured. These circumstances require extremely complex drives and also a small mass for the closure member, thus a small valve cross section, which in turn, however, is not sufficient gas mass throughput is possible.

On the basis of this prior art, the object of the invention is to develop the device mentioned at the outset in such a way that a high pressure gradient and gas mass throughput can be achieved with little effort for the valve drive.

This object is achieved in that the valve has an elastically deformable, membrane-like closure member which releases the opening cross section of the valve predominantly under the effect of the pressure in the pressure vessel in a few milliseconds. According to the invention, the high potential energy of the compressed gas is thus used to open the valve, wherein elastically deformable closure members have the advantage of a low mass and can therefore be accelerated quickly. The holding force for such an elastic closure member can be applied in various ways, for example by inherent stability, by control air or the like ...

According to one embodiment, it is provided that the closure member designed as a membrane lies in the closed position sealingly against the edge of the opening in the pressure vessel. The entire free cross section of the opening is accordingly closed by the membrane. Some embodiments of the type of closure and its release are explained below.

A tried and tested embodiment is characterized in that the membrane is clamped on the edge above the opening and inside the pressure vessel to form an annular flow cross-section for the compressed gas and in the closed position under the effect of control air acting on its inside while shutting off the flow cross-section and plant on Opening edge of the pressure vessel is bulged like a balloon.

The flow cross-section between the edge-side clamping of the membrane and the opening of the pressure vessel should be equal to or larger than the free cross-section of the opening, so that a rapid overflow of the compressed gas is possible. The control air is only used for balloon-like inflation of the membrane and is blown off for the purpose of releasing the flow cross-section, for example by only opening one blow-off valve in the control air circuit. The pressure of the compressed gas acting on the membrane in the area of the flow cross section forces the membrane out of the area of the flow cross section in the shortest possible time.

The space on the inside of the membrane is expediently connected to a control air line which can be closed by means of a pinch valve. This pinch valve can have a cross-sectional area that allows the control air to be blown off quickly and easily.

According to a modified embodiment, the closure member consists of a plurality of elastic membranes arranged parallel to one another and parallel to the axis of the opening, of which two each delimit a part of the opening cross section and can be brought into the closed position by means of compressed air in which they abut one another. This closure member works similarly to several pinch valves arranged side by side.

According to another embodiment of the invention, the membrane is designed as a tear membrane and clamped between the molding box and the pressure vessel. It is designed in such a way that it is either opened arbitrarily or involuntarily when the pressure in the pressure vessel rises when the desired pre-pressure is reached.

In a preferred embodiment, the tear membrane is weakened for the purpose of opening the opening in defined areas which are arranged such that when the membrane is torn open under the action of the compressed gas, the membrane is retained as a coherent part. This avoids, in particular, that parts of the membrane are thrown onto the molding material surface when tearing open and thereby either interfere with the compression process at this point or lead to disturbances in further processes to which the mold is subjected after compression.

In one embodiment of this basic design, the tear membrane in the area of the opening of the pressure vessel is supported by a grid with a large grid dimension. Before opening the opening in the area of each grating opening, it is weakened or separated on only three sides. On the one hand, the grating prevents the membrane from bulging too much in the mold space and the resulting excessive load, on the other hand, the grille gives the possibility of weakening or separating the tear membrane only at defined points, so that the membrane also after tearing is present in a coherent part and can be removed from the area of the opening without residue after the work cycle.

The invention provides several variants for weakening or separating the tear membrane. According to a first embodiment, a cutting device is arranged above the tear membrane, the cutting tools of which are arranged in the grid of the grid such that, for example, only three sides of each grid opening are assigned a cutting tool. The cutting tools can be arranged on a lattice frame movably guided in the pressure vessel, which does not or not appreciably impedes the flow of the compressed gas. The cutting device, the cutting tools of which act as a base against the individual lattice bars, has the advantage that a defined sectional view is obtained, that is, the membrane is always torn open at the same points by the action of the compressed gas.

In another embodiment, the the grid-forming rods on their top heating conductors, which are arranged, for example, on three sides of each grid opening and can be switched on to release the opening of the pressure vessel. In this and the aforementioned embodiment, a crosswise arrangement of the cutting tools or the heating conductor can also be provided as long as only the torn open membrane is retained as a coherent part.

In the latter embodiment, the material of the membrane is caused to melt or flow by the action of heat, so that there is no complete cut, but only a weakening of the membrane on the corresponding lattice bars. The membrane is then torn open by the compressed gas at these weakening points and the full cross section is released.

Instead of this design, it can also be provided that heating conductors are embedded in the tear membrane, which can be switched on to release the opening of the pressure vessel. These heating conductors are also arranged so that the membrane is retained in coherent parts.

According to a preferred exemplary embodiment, the tear membrane is part of an elastic endless web which can be pulled off a supply spool on one side of the molding box in the working cycle of the device by means of a reel arranged on the other side of the molding box. After each work cycle and opening of the valve, a new section of the endless web is thus pulled over the molding space and then clamped between the molding box and the filling frame by moving it to the opening edge of the pressure vessel.

Another embodiment of the valve is that the membrane-like closure member is a hose arranged coaxially with the opening, the cross section of which is adapted or adaptable to the cross section of the opening of the pressure container, which is clamped at one end at a distance above the opening of the pressure container within the same and which projects into this opening with its other end and can be pressed against the opening edge by means of a closing mechanism acting on its peripheral edge.

The hose is accordingly stretched as a cylindrical structure within the pressure vessel and closes the opening of the pressure vessel at its periphery. By loosening the closing mechanism, which can act on the hose from the inside or outside, the hose collapses inwards and releases the flow cross-section previously closed by it to the opening of the pressure vessel. In particular, plastics or rubber provided with reinforcing inserts are considered as materials, which are nevertheless sufficiently flexible. The flexibility is supported by the extensive training.

In a further embodiment of this embodiment, a sealing seat which widens towards the molding box is arranged at the opening edge and the closing mechanism has a clamping ring which can be raised against it and clamps the end of the hose between itself and the sealing seat. This clamping ring leaves a sufficiently free passage cross section for the compressed gas and only needs to be lowered in the millimeter range in order to give the hose the opportunity to collapse. A stroke drive arranged in the pressure container can be provided as the drive for the clamping ring.

In order to convert the collapsed hose back into its shape in the absence of its own restoring force, it is provided according to one embodiment that a scraper ring is arranged above and inside the hose, which can be lowered into the area of the sealing seat after each opening of the opening. When the scraper ring has reached its end position, the clamping ring is lifted back into its position which grips the end of the hose and presses against the sealing seat.

In a modified embodiment, the membrane-like closure member is a bellows which is attached at one end to the pressure vessel, locked at its other end above the opening edge and closed at this end.

The bellows acts as a piston due to its frontal closure. By arranging its one end above the opening edge, the compressed gas can come into effect on the bellows at this end, so that after releasing the locking of the bellows, the compressed gas is suddenly raised or compressed, the compressed gas acting on the entire piston surface. Such bellows can be made from thin-walled sheet metal or from flexible materials and have great fatigue strength. They are therefore particularly suitable for the purpose according to the invention. The opening movement is preferably supported in that the bellows is under tension in the closed position, so that it contracts at the moment of unlocking and the compressed gas can quickly come into effect as a further accelerating force.

In a special embodiment, the bellows can have a flange at its end facing the opening, on which a locking device engages on the outside, the bellows being closed at this end by a membrane. Such a membrane has the advantage of a relatively low mass, which is favorable in terms of high acceleration.

In order to move the bellows into its closed position and to generate the pretension, a lifting drive can be provided which, after the locking device engages, returns to its starting position, thus not influencing the opening movement of the valve.

According to a further feature of this embodiment, the bellows stands on the inside the atmosphere. This enables resistance-free compression of the bellows during the opening process.

Finally, support tubes can be provided within the bellows, one of which is connected to the end facing the opening, that is to say it is carried along when the bellows moves. Instead of the bellows described above, a hose can also be provided, which is arranged, fastened, pretensioned, locked and accelerated in the same way.

With compression devices for foundry molding material, it is often desirable to be able to fill the molding material centrally and directly into the molding box. Such devices have a central molding material filling shaft, which can be locked with a slide or the like relative to the molding box or filling frame located below. For such a known device, the invention proposes that the valve has an annular opening surrounding the filling shaft, which creates the connection between the pressure vessel and a space arranged between the slide and the filling frame, on the inner wall of which a corresponding annular sealing seat is arranged and on the outer wall of which is arranged against the sealing seat and can be pressed as a diaphragm-like sealing member.

Here, the compressed gas is not released directly from the pressure vessel through the opening onto the free surface of the molding material, but rather via the ring opening into the space above the molding space. The advantage of this device is that the molding material can be filled in centrally. The valve closure and its acceleration can also easily take place within the required limit data, since, due to the large diameter of the ring opening, a relatively small stroke of the closure member is sufficient. The closure member is either designed as a bellows, which is acted upon on the outside with control compressed air and bulges inwards until it rests on the sealing seat, or as a hose, which then inflates with one half into the ring opening. To open the valve, only a blow-off valve in the control air circuit is opened, so that the annular bellows or the hose are pushed back under the action of the compressed gas and release the ring opening.

In this embodiment, the pressure vessel expediently surrounds the filling shaft in an annular manner and opens out into the annular opening of the valve via an annular opening.

The invention is described below with reference to some exemplary embodiments shown in the drawing.

• Figur 1 eine schematische Ansicht der Vorrichtung mit dem Druckbehälter und dem Ventil im Schnitt in einer ersten Ausführungsform ;
• Figur 2 eine der Figur 1 ähnliche Ansicht einer zweiten Ausführungsform ;
• Figur 3 eine ähnliche Ansicht einer dritten Ausführungsform ;
• Figur 4 eine der Figur 1 ähnliche Ansicht einer vierten Ausführungsform ;
• Figur 5 eine Draufsicht auf die Reißmembran der Ausführungsform gemäß Figur 4 ;
• Figur 6 einen Längsschnitt durch zwei weitere Ausführungsformen ;
• Figur 7 eine weitere Variante im Längsschnitt ;
• Figur 8 eine der Figur 1 ähnliche Ausführungsform im Längsschnitt und
• Figur 9 eine weitere Ausführungsform nach Art von Schlauchquetschventilen.

The drawing shows:

• Figure 1 is a schematic view of the device with the pressure vessel and the valve in section in a first embodiment;
• Figure 2 is a view similar to Figure 1 of a second embodiment;
• Figure 3 is a similar view of a third embodiment;
• Figure 4 is a view similar to Figure 1 of a fourth embodiment;
• FIG. 5 shows a top view of the tear membrane of the embodiment according to FIG. 4;
• FIG. 6 shows a longitudinal section through two further embodiments;
• Figure 7 shows another variant in longitudinal section;
• 8 shows an embodiment similar to FIG. 1 in longitudinal section and
• Figure 9 shows a further embodiment in the manner of pinch valves.

In the drawing, only the parts of a compression device necessary for understanding the invention are shown. In particular, the machine stand, the devices for lifting and lowering the molding box and filling frame and, if appropriate, for ejecting the finished mold from the molding box are not shown. Likewise, the devices for bringing the model up and for filling the molding sand - with the exception of FIG. 2 - are not shown, since all of the aforementioned components are known in foundry mechanical engineering.

A mold box 2 sits on a model plate 1 with the model (not shown) and a filling frame 3 on this. These parts form the mold space. Above the molding space there is a pressure vessel 4 for receiving pressurized gas up to 20 bar, which is fed via a nozzle 5 from a pressure accumulator or - at low admission pressure from the compressed air network.

The pressure vessel has an opening which is arranged centrally in the exemplary embodiment according to FIG. 1 and whose inside width corresponds approximately to the free horizontal cross section of the filling frame 3. Attached to the pressure vessel 4 is an extension 38 which extends the opening 6 downward, against which the unit consisting of fashion plate 1, molding box 2 and filling frame 3 can be pressed from below.

The opening edge 7 of the opening 6 forms a sealing seat for a valve denoted overall by 8, which has an elastic closure member 9. In this embodiment, the elastic closure member 9 is designed as a membrane 10 which is inflatable like a balloon and, when inflated, lies tightly against the opening edge 7 in the pressure vessel 4. Furthermore, a plurality of support strips 11 are arranged within the extension 38, against which the membrane 10 bears in the inflated state.

The membrane 10 is clamped with its edge 12 at a distance above the bottom of the pressure vessel 4. For this purpose, a ring 13 supported on the ground and a plate 14 are used, which are clamped together by means of screws while clamping the edge 12 of the membrane 10.

The plate 14 is held by a centrally arranged tube 15, which in turn is fastened in the lid 16 of the pressure vessel 4. This pipe establishes the connection between the inside of the membrane 10 and a compressed gas source, not shown, which supplies the control air for closing the valve 8. Between this compressed gas source, not shown, and the membrane 10, a pinch valve 17 is arranged, which can be closed or vented via a three-way valve 18. In the lower mouth area of the tube 15, a fitting with soft transitions is arranged, against which the membrane 10 can bear.

Under the action of the control air supplied via the pipe 15, the membrane 10 bulges outwards and lies sealingly against the opening edge 7. In this state, the pressure vessel 4 is filled with compressed gas up to 20 bar. The molding unit consisting of molding box and filling frame is pressed against the lower edge of attachment 38 on pressure vessel 4. The hose pinch valve 17 is closed at the latest during the filling process of the pressure container 4. By suddenly blowing off the control air to hold the hose pinch valve 17, the hose pinch valve 17 opens automatically under the effect of the pressure prevailing in the tube 15, so that the compressed gas in the pressure vessel 4 suddenly pushes back the membrane 10 via the annular flow cross-section 19 between the ring 13 and the bottom of the pressure vessel , so that it bears against the contour of the fitting at the lower end of the tube 15. The compressed gas can then relax through the opening 6 into the molding space and have a compressing effect on the molding material surface. The compression effect is based on a combined piston-like pressurization and a fluidization process with dynamic pressure development.

The opening times of the membrane 10 are in the millisecond range, provided only the cross section of the tube 15 and the pinch valve 17 is large enough to suddenly blow off the locking air. Likewise, the outflow cross section for the control air of the pinch valve must be correspondingly large. With this construction, a pressure gradient of greater than 300 bar / s can be achieved within the molding space.

While in the embodiment according to FIG. 1 the molding material has to be poured into the molding space outside the compression station, FIG. 2 shows an embodiment in which a filling shaft 20 with a filling funnel 21 for the molding material is arranged above the molding space consisting of molding box 2 and filling frame 3 is. The filling shaft 20 can be closed relative to the molding space by means of a slide 52 or the like. Between the slider 52 and the filling frame 3, an enlarged housing extension 38 is arranged in the axial direction. In this exemplary embodiment, the pressure vessel 4 is annular and surrounds the filling shaft 20 which passes through it centrally.

The pressure vessel 4 has an annular opening 22 which is concentric with the filling shaft 20 and which connects to an annular opening 23 in the region of the slide 52. This ring opening 23 surrounds the filling shaft 20 or the extension 38 only on a part of its circumference, which, however, should be as large as possible. For example, the ring opening 23 is only missing on the side on which the slide 52 is extended. The ring opening 23 opens into the shoulder 38 via a conical section 24.

In addition to the ring opening 23, the valve 8 has an annular bellows 25 which delimits a control air channel 26 to the ring opening 23. In the area of the slide there is also a sealing seat 27 which surrounds the filling shaft 20 and which cooperates with the closure member in the form of the annular bellows 25. By means of the control air supplied in the channel 26, the bellows 25 bulges into the ring opening 23 and lies against the seat 27 in a sealing manner.

During the compression process, the control air is blown out of the channel 26, so that the annular bellows 25 is pushed back under the action of the pressure gas present in the pressure vessel 4 and turned inside out.

The entire cross section of the ring opening 23 is thus free for the expansion of the compressed gas. As a result, the compressed gas suddenly arrives in the attachment 38 or in the molding space.

FIG. 3 shows another embodiment in which the section of a pressure-resistant hose 28 is clamped in the axial direction within the container 4. One end is clamped between a ring 29 and the flange 30 of a support tube 31, while its lower end hangs into the opening 6 of the pressure vessel 4. In the area of the opening 6, an annular sealing seat 32 is attached, which widens conically downwards. A clamping ring 33 is arranged inside the hose 28 and can be raised and lowered by means of a lifting drive 34. In the lowered position, the hose 28 can hang into the opening 6. When the clamping ring 33 is raised, the hose is then clamped between it and the sealing seat 32.

To initiate the compression of the molding material, the clamping ring 33 is slightly lowered. The pressure gas contained in the pressure vessel 4 then compresses the hose 28 inwards and the pressure gas can suddenly escape into the mold space 2, 3 via the clamping ring 33. In order to bring the collapsed hose 28 back into the desired shape, a scraper ring 53 is provided, which is arranged concentrically within the hose 28 and is lowered after relaxation, so that the hose 28 is pushed outwards again and with its lower end in the opening 6 protrudes. Then the clamping ring 33 is raised again so that the hose 28 can be clamped again.

FIGS. 4 and 5 show an exemplary embodiment in which the closure member 9 is formed from a tear membrane 35, ie is destroyed during the opening process. This tear membrane 35 is part of an endless belt 36, which is wound on one side of the molding space formed from the filling frame 3 and the molding box 2 on a supply spool 37 and is pulled off by a reel 39 by one membrane length in each working cycle. The endless web 36 moves between an attachment 40 on the filling frame 3 and a sealing ring 41 in the region of the opening 6 of the pressure vessel 4. The gap is sealed against the endless web when the molding box 2 is pressed by pressing the attachment 40.

A grating 42 is arranged within the attachment 40, the grating bars 43 of the membrane resting on the top side. As can be seen from Figure 5, the grid 42 has a wide grid dimension.

Above the opening 6, a cutting device 44 is arranged inside the pressure vessel 4, which consists of a grid frame 45 which serves as a carrier for a plurality of cutting tools 46. The cutting tools 46 are arranged in such a grid that they weaken or split the tear membrane 35 on three sides of a grid opening. These dividing lines are designated by 47 in FIG. 5 and drawn out a little more strongly. On the other hand, such a cutting tool is missing on each side 48 of each grid opening, so that the parts of the membrane corresponding to the grid grid remain there as continuous tabs on the endless web 36. As can be seen from FIG. 5, there is no separation of the membrane in the area of the lattice bars 43, so that the webs of material remaining there keep the flaps formed in connection with the endless web 36.

The lattice girder 45 of the cutting device 44 is guided on rods 49 within the pressure vessel 4 and can be raised and lowered by means of a pusher drive 50, so that the cutting knives can be lowered onto the tear membrane 9 from the rest position shown in FIG.

Before each compression process, an undamaged section of the endless web 36 is drawn in between the mold space and the pressure container by means of the winding reel 39. Subsequently, model plate 1, molding box 2, filling frame 3 and attachment 40 are started against the sealing ring 41 by clamping the endless web or the tear membrane 35 against the pressure vessel 4, and then the pressure vessel 4 is filled with compressed gas. Once the required form has been reached, the lattice frame 45 is lowered with the cutting tools 46 until they meet the tear membrane 35 and weaken it at least to such an extent that it tears open at these points to form the tabs indicated in FIG. The entire cross section of the opening 6 is thus suddenly available for the pressure increase in the molding space. After this compression process, the molding space is lowered with the attachment 40 and an undamaged section of the endless web 36 is drawn over the attachment 40.

Instead of the cutting tools, it can also be provided to embed heating conductors on the upper side 51 of the bars 43 in accordance with the grid of the cutting tools 46. Since the tear membrane 35 rests tightly under the action of the compressed gas on the top of the bars 43, heat is transferred quickly, so that the elastic membrane at the points of the heating conductors is quickly weakened by melting, vaporization or burning of the material and in accordance with the sectional view of FIG Figure 5 tears open. The heating conductors can in particular be designed as PTC elements, the limit temperature of which is only slightly above the melting temperature of the tear membrane, so that a thermally self-regulating device of robust construction is provided. In both embodiments, deviating from the described arrangement of the cutting tools or the heating conductor, a crosswise arrangement can also be provided, only sufficiently wide material webs having to be retained in all directions between the individual arrangements.

Instead of the aforementioned design, the heating conductors can also be embedded within the endless web 36, it being possible for the current to be supplied via the supply reel 37 or the winding reel 39.

FIG. 6 shows two further embodiments which have a structure similar to that according to FIG. 3. In the left half of the drawing, a bellows 55 is arranged within the pressure vessel 4, which is attached at one end 56 to the cover 16 of the pressure vessel 4 by a ring 57. At the other end, the bellows 55 has a flange 58. It is also closed at this end by a membrane 59 or the like. The interior 60 of the bellows 55 is in free communication with the atmosphere via an opening 61 in the cover 16 of the pressure container 4.

Between the flange 58 and the edge of the opening 6, a sealing ring 62 is inserted, which is firmly connected to one of the two parts. At this end of the bellows, a support tube 63 is also attached. Likewise, in the upper region of the bellows 55 there is a support tube 64 fastened to the cover 16 of the pressure container 4.

In the open position, the flange 58 of the bellows 55 is approximately at the level 65, from which it can be moved by means of a lifting drive 66 into the closed position shown in the pulled-out position, while at the same time being set under tension. In this position, a locking device acts on the flange 58, of which only two bolts 67 are shown. Before the start of a work cycle, the latches 67 are released so that the bellows rises under the effect of the pretension and is then accelerated into the position indicated by 65 under the action of the compressed gas on the membrane 59, as a result of which the entire cross section of the opening 6 is suddenly released.

In the embodiment shown in the right half of FIG. 6, the bellows 55 is replaced by a hose 68, which is at least partially applied to a support tube 69 and which is pushed together after opening the latch 67 under the action of the elastic prestress and the gas pressure. Otherwise, the other structure is the same as in the bellows shown in the left half. Only the lower support tube 63 is missing.

FIG. 7 shows an exemplary embodiment in which the desired rapid release of the entire cross section of the opening 6 takes place with the aid of an electrical surge discharge. The high forces and accelerations that can be achieved in this way are used, for example, when shaping metals (transploder technology) to produce high air velocities (plasma wind tunnel) and the like. Like. Used. Since this technique is known, only those details which relate directly to the invention are dealt with here. The circuit essentially has a capacitance, an inductance and an interrupter switch. The capacitor is charged when the switch is open. Closing the switch creates an induction flow.

In FIG. 7, the inductance is arranged as a primary coil 70 around the opening 6 of the pressure vessel 4. On the primary coil 70 is - optionally with the interposition of a sealing ring - a valve plate 71 acting as a secondary coil made of electrically conductive but non-magnetic material, which at the lower end of an elastic holder, for. B. a rolling membrane 72 is attached. This in turn is attached to an open support tube 73. The sealing force of the valve is generated by the pressure present in the pressure vessel 4 and acting on the back of the valve plate 71. When the capacitor is suddenly discharged, a high induction flow arises in the secondary coil 70, which generates an induction voltage in the secondary coil, the valve plate 71. This leads to the formation of eddy currents in the windingless secondary coil, the force of the secondary field being opposite to that of the primary field, as a result of which the valve disk 71 is repelled. The magnitude of the repulsive force is proportional to the change in the induction flow over time. When the valve disk 71 is lifted or pushed off, the entire opening cross section is suddenly released, the opening movement being supported by the pressure acting on the underside of the valve disk. Due to the open design of the support tube, the movement of the valve plate 71 is not hindered.

3, 6 and 7, the actual closure member for the opening cross-section to be released is formed by the tubular structures 28, 68 and 71, respectively, which are formed by means of a further component (33 in FIGS. 3, 58, 67 in FIG. 6 and 71 in Fig. 7) held in the closed position and either only under the action of the compressed gas (Fig. 3) or with its supportive action (Fig. and 7) with an initially effective auxiliary drive (55 in Fig. 6 or internal stress of 68 in Fig. 6, 70, 71 in Fig. 7). Figures 3, 6, 7 only show exemplary embodiments of this principle.

Figure 8 shows a variant of the embodiment shown in Fig. 1. Therefore, only the differences are dealt with here. Here, the control air line consists of a simple compressed air hose 74 which is passed through the pressure vessel 4 and opens out via a connection piece in the space behind the membrane 3. A ventilation nozzle 75 is also connected to this space and is closed with a valve of any type - here a valve flap 76. The ventilation nozzle 75 opens behind the valve flap with an opening 77 in the pressure vessel. The space behind the membrane is filled with compressed gas at a higher pressure than the pressure vessel 4 via the compressed air hose 74 and the membrane 9 is thus kept closed. By opening the valve flap, pressure equalization occurs between the pressure vessel 4 and the space behind the membrane 9, which at the same time lifts off from the sealing seat 7. With this design, the great advantage is achieved that the not insignificant amount of control air and its energy is supplied to the gas expansion process and is thus used for the compression. A similar variant is also possible for the embodiment according to FIG. Since the elastic closure members are components that are subject to wear, a quick replacement should be possible. It is therefore in the embodiment of FIG. 8, the entire valve 8 with the parts 7, 9, 12, 13, 14, 75, 76 and optionally 11 combined to form a structural unit which is releasably attached to the pressure vessel 4 by means of a quick-change flange 78 and if the Membrane 9 can be exchanged for another unit.

In the embodiment according to FIG. 9, the closure member 9 consists of a plurality of membranes 80 arranged side by side, which in the opening position shown in broken lines run approximately parallel to the axis of the opening 6. Two membranes 81, 82 are stretched between lower strips 83, which pass through the opening 6 of the pressure vessel 4, and upper strips 84, which are arranged in alignment over the lower strips 83, by connecting them to the strips 83 at their longitudinal edges by means of clamping strips 85 or 84 are attached. A sufficiently large opening cross section remains between the strips 83 and 84, respectively. Between two membranes 81, 82, chambers 86 are formed, which are connected to one another and connected to a control compressed air line 87. Furthermore, the chambers 86 are connected to a flap valve 88, via which the control compressed air in the compressed air container 4 can be relieved. The mode of operation is essentially the same as in the embodiment according to FIG. 8, but the closed position is produced by abutment of diaphragms 81, 82 which lie opposite one another.

Claims (31)

1. Apparatus for compacting foundry mold making material, wherein said material is heaped on a pattern is a closed mold space consisting of a mold flask (2) with a filling frame (3) and a pattern plate (1), and said material is compacted by a pressure gas acting on the surface of the material, said pressure gas being expanded suddenly from a high pressure vessel (4) through a valve (8) into the mold space, characterised in that the valve (8) comprises an elastically deforming diaphragm-like closing member (9) adapted to be moved clear of the opening cross section of the valve in a few milliseconds mostly by the effect of the pressure in the pressure vessel (4). 2. Apparatus according to claim 1, wherein said closing member (10) is a diaphragm designed in a shut position thereof to rest upon the edge (7) of the opening (6) in the pressure vessel (4) in a sealing manner.

3. Apparatus as claimed in claim 1 or 2 wherein said diaphragm (10) is gripped at its edge by part of said apparatus to be in a position over the said opening (6) within said pressure vessel (4) so that a ring-like flow cross section for the pressure gas is formed, said diaphragm being designed to be bulged outwards in a shut position thereof by driving air acting on an inner side of the diaphragm, said outwardly bulged diaphragm then resting against the edge (7) of the opening of the pressure vessel (4).

4. Apparatus as claimed in claim 3 wherein the space on the inner side of the diaphragm (10) is connected to a driving air line (15) and is provided with a valve for shutting off said air line, for example a pinch valve (17).

5. Apparatus as claimed in claim 4 wherein said closing member (9) is made up of a a number of elastic diaphragm panels (80) placed paralle! to each other and to an axis of said opening (6), two of said panels (81, 82) in each case limiting a part of the cross section of the opening and able to be moved by compressed air into a position shutting off said opening.

6. Apparatus as claimed in claim 5 wherein in said opening (6) a number of parallel narrow bars (83) and with distance thereabove a further group of corresponding bars (84) are placed, the diaphragms being placed in pairs (81, 82) between two superposed bars and forming a chamber (86), in which said compressed air may be run.

7. Apparatus as claimed in claim 6 wherein said chambers (86) between such pairs of diaphragms (81, 82) are joined together and to a common compressed air line (87).

8. Apparatus as claimed in claim 1 wherein said diaphragm (10) is a rupture (bursting) diaphragm and is stretched between the mold flask (2) and the pressure vessel (4).

9. Apparatus as claimed in claim 8 wherein the said rupture diaphragm (35) has areas of weakness for the purpose of uncovering the opening (7), said areas of weakness being placed at defined positions (47) so that on rupture of said areas of weakness under the effect of the compressed gas the diaphragm is kept in one piece.

10. Apparatus as claimed in claim 8 or 9 wherein a grating (42) with widely spaced grating bars is provided for supporting the rupture diaphragm (35) in the opening (6) of the pressure vessel (4) and wherein the rupture diaphragm (35) is only weakened along three sides of each opening of the grating for uncovering said opening (6) by separating at said three sides.

11. Apparatus as claimed in claim 10 wherein over the rupture diaphragm (35) there is a cutting tool (44), whose cutting edges (46) are so placed in line with the bars of the grating (42) that only at three sides of each grating opening edges are provided.

12. Apparatus as claimed in claim 11 wherein the cutting edges (46) are placed on a grating frame (45) being guided for sliding motion in the pressure vessel (4).

13. Apparatus as claimed in one of the claims 8 to 10 wherein the bars (43) of the grating (42) have heating conductors at their top sides being placed at three sides of each grating opening and being able to be electrically turned on for uncovering said opening (6) of the pressure vessel (4).

14. Apparatus as claimed in one of the claims 8 to 10 wherein heating conductors are embedded in the rupture diaphragm (35) which may be electrically turned on for uncovering the opening (4).

15. Apparatus as claimed in one of the claims 8 to 14 wherein the rupture diaphragm (35) is a part of an endless elastic web (36), that is taken from a supply roll (37) on one side of the mold flask (2) in step with operation of the apparatus by pulling it by means of a winch (37) on an opposite side of the apparatus.

16. Apparatus as claimed in claim 1 wherein said diaphragmlike closure member (9) is a flexible hose (28) whose axis corresponds to the axis of the opening (6) and whose cross section is designed to be in line with the cross section of said opening (6) of the pressure vessel (4), one end of said hose (28) being fixed with distance over and within the opening of the pressure vessel whereas an opposite end of the said hose is placed for projecting into the opening (6) and having a closing mechanism (33, 34) for pressing it against the edge (32) of the opening (6).

17. Apparatus as claimed in claim 16 wherein on the edge of the opening (6) there is sealing seat (32) becoming wider towards the mold flask (2) said closing mechanism having a gripping ring (33) movable upwards for gripping the end of the hose (28) against the sealing seat (32).

18. Apparatus as claimed in claim 16 or 17 wherein the gripping ring (33) can be moved upwards and downwards by a lifting drive (34) being placed in said pressure vessel (4).

19. Apparatus as claimed in one of the claims 16 to 18 wherein a stripping ring is placed above and within the hose (28) which is able to be lowered to a position near the sealing seat (32) after the opening (6) has been uncovered.

20. Apparatus as claimed in claim 1 wherein the diaphragmlike valve closing member is in the form of a folding bellows (55) having its axis lined up with the axis of the opening (6) and having one end thereof fixed in the pressure vessel (4) whereas the other end thereof is locked in the shut position of the valve over the edge (7) of the opening (6) and is shut off.

21. Apparatus as claimed in claim 20 wherein said bellows (55) has a flange (58) at its end nearest to the opening (6) and has a locking system (67) for acting against the outside of the flange, the said end of the bellows being closed by a diaphragm.

22. Apparatus as claimed in claim 20 or 21 wherein a lifting drive (66) is provided for moving the bellows (55) into its closed position.

23. Apparatus as claimed in one of the claims 20 to 22 wherein the inside of the bellows (55) is joined up with the outside atmosphere.

24. Apparatus as claimed in one of the claims 20 to 23 wherein support tubes (63, 64) are provided within the bellows (55), one (63) of such tubes being joined up with that end of the bellows that is nearest to the opening (6).

25. Apparatus as claimed in one of the claims 20 to 24 wherein instead of the bellows (55) a flexible hose (58) is provided.

26. Apparatus as claimed in one of the claims 20 to 25 wherein the bellows (35) and the hose (68) resp. are pre-stressed into the shut position of the valve.

27. Apparatus as claimed in claim 1 having a middle filling passage (20) for mold making material, a slide for shutting the passage off from the mold flask and the filling frame resp. that is placed thereunder, wherein the valve has a ring-like opening (23) round the passage for providing the connection between the pressure vessel (4) and a space between the slide (52) and the filling frame (3), and a ring-like seat means (27) on an inner wall face of the ring-like opening, and a ring-like bellows (25) or hose able to be pressed against the outer wall of the ring-like opening at the seat means.

28. Apparatus as claimed in claim 27 wherein the pressure vessel (4) is placed like a ring round the filling passage (20) and opens by way of a ring-opening (22) into the said ring-like opening (23) of the valve (8).

29. Apparatus as claimed in claim 27 or 28 wherein the ring-like bellows (25) is kept in the shut position by driving air.

30. Apparatus as claimed in one of the claims 2 to 7 and 27 to 29 wherein the driving air for the diaphragm (10, 80) and for the ring-like bellows (25) resp. for starting its opening motion undergoes expansion into the pressure vessel (4).

31. Apparatus as claimed in claim 1 wherein the valve (8) has a valve plate (71) forming the secondary coil of a highrate discharge circuit, whose primary coil (70) is placed round the opening (6) of the pressure vessel (4) and is formed with a sealing seat for the valve plate (71) and wherein the valve plate (71) is supported elastically by a coaxial flexible pipe-like structure, a roll diaphragm (72) or the like forming the diaphragm-like closure member.

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