Abstract: A process of positioning a riser sleeve about a plug of a mold cavity pattern. The riser sleeve is positioned to engage the plug to prevent sand from entering the interstitial space between the riser sleeve and the plug. The riser sleeve may comprise a deformable annular lip for engagement with the perimeter of the plug. The riser sleeve may engage the plug in sealing relationship.

Abstract: A method and machine for forming an open riser in a mold includes a resiliently compressible plug received into the upper end of a riser sleeve, which projects above the riser sleeve and cope sand level so as to be advanced into the riser sleeve during squeezing of the mold sand. The plug is fixed to the upper squeeze plate to be withdrawn from the riser sleeve as the squeeze plates are separated, creating an open riser.

Abstract: The apparatus comprises a table (5), on which a pattern plate (6) is attached, a flask (7), the bottom surface of which can be fitted to the pattern plate (6), a filling frame (30), the bottom surface of which can be fitted to the upper surface of the flask (7), and in which the highest part of its opening is smaller than the lowest part of its opening, a blow head (17), which is used for blowing in molding sand, and for squeezing the blown-in molding sand, and which is placed above the table (5), and a thin plate body (20), which can be inserted into the blown-in molding sand and which is placed around a sand holder (12) that is a part of the blow head (17), in which the highest part of the opening of the filling frame (30) has such a size that the outer surface of the thin plate body (20) can contact the inner surface of the highest part of the filling frame (30), and in which the size and shape of the lowest part of the opening of the filling frame (30) are the same as those of the opening of the flask (7)

Abstract: A first quantity of all the molding sand necessary to produce a mold is fed in the mold space, the first quantity being one of at least two parts divided from the total molding sand. The mold space is evacuated and then air is introduced into the mold space at the air-pressure rising rate of 30--to 500 kg/cm.sup.2 /sec. Another quantity of the molding sand is fed into the mold space, the mold space is evacuated and then air is introduced into the mold space at the air-pressure rising rate of 30--to 500 kg/cm.sup.2 /sec. The apparatus includes a sand passage through which each quantity of sand is fed into the mold space, and a gate for closing the sand passage thereby closing the mold space to allow the mold space to be evacuated and then subjected to a pressure increase.

Abstract: Molding sand filled in a space defined by a pattern plate and a flask is pre-compacted before the molding sand is completely pressed. A pre-compacting member is inserted into the molding sand toward the pattern plate, and then is stopped based on a predetermined depth of the pre-compacting member in the molding sand or a predetermined pressure caused by the pre-compacting member in the molding sand.

Abstract: A space defined by inside surfaces of a main molding flask and lower auxiliary flask and the upper surface of a pattern plate where the upper surface of the pattern plate is retained at a predetermined level along the inside surfaces of the main molding flask and lower auxiliary flask is filled with an amount of molding sand. The molding sand is then squeezed in the space with upper and lower press heads in at least one of upward and downward directions to form at least one of first and second halves of a sand mold such that a lower surface of the first or second half of the sand mold is formed at a desired level along the inside surfaces of the main molding flask and lower auxiliary flask irrespective of edges of the main molding and lower auxiliary flasks. The desired level is determined by the level of the upper surface of the pattern plate at the time when the squeezing step has finished.

Abstract: A method and apparatus is provided for increasing the packing density and strength of sand for gas-hardening casting molds. The method is characterized by the steps of filling spaces defined by a pattern plate 1 and a mold frame with gas-hardening casting sand 4, depressurizing a closed container 3 after the filled assembly has been conveyed thereinto, introducing air into the container 3, applying a pressure to the upper surface of the casting sand to increase its packing density, and hardening the casting sand by a hardening gas.

Abstract: A method of filling a core cavity, wherein the entire core cavity is uniformly filled with highly compacted sand for molding the core without the need of providing many ventholes. The method is characterized in that sand for molding the core is drawn into the core cavity through an inlet to preparatorily fill the cavity, and then the thus prepared sand is repeatedly and sequentially compacted by impulsively pressurizing the sand, starting with the sand farthest from the inlet and ending with the sand nearest to the inlet.

Abstract: The machine includes a lifter table for lifting a pattern plate and flask which hold molding sand and a pre-compacting member and a pressing member disposed above the lifter table for horizontal movement and for being inserted into the flask when the lifter table lifts the flask. The pre-compacting member includes a thin-plate body to be positioned slightly spaced apart from an inner surface of the flask or inner and outer surfaces of a pattern when inserted into the molding sand held in the flask. The pressing member includes a squeezing body that presses the molding sand from above.

Abstract: Molding sand (S) is put in a mold space defined by a pattern plate (2), having a pattern (2A) on it, and a flask (3). The apparatus includes a thin-plate body (9) and/or a rod (11) to be inserted into the molding sand. It is pre-compacted at a part of it near the inner and outer surfaces of the pattern (2A) and the inner surfaces of the flask (3) by the thin-plate body and rod. The apparatus also has a pressing plate (8) to press all the molding sand after it is pre-compacted.

Abstract: Molding sand (S) is put in a mold space defined by a pattern plate (2), having a pattern (2A) on it, and a flask (3). The apparatus includes a thin-plate body (9) and/or a rod (11) to be inserted into the molding sand. It is pre-compacted at a part of it near the inner and outer surfaces of the pattern (2A) and the inner surfaces of the flask (3) by the thin-plate body and rod. The apparatus also has a pressing plate (8) to press all the molding sand after it is pre-compacted.

Abstract: Molding sand (5) is fed into a space defined by a pattern plate (2) and a flask (3) mounted on the pattern plate (2), and the space is enclosed at the upper part of the flask (3) by a cover (6). The air in the enclosed space is evacuated to reduce the air pressure between the grains of the molding sand in the enclosed space to 1 Torr to 150 Torr, and then air is introduced into the enclosed space from the upper part of the space so that the pressure in the space can increase at the rate of 15 atm/s to compress the molding sand (5). The method eliminates the need for vent holes and enables the mold to be crack-free since the air flow is not reflected.

Abstract: The invention relates to a process for the compression of molding sand in casting molds having a pattern plate with a pattern arranged therein. The molding sand is introduced loosely into the molding space located above the pattern plate and is thereafter fluidized to a final pressure of 20 bar maximum by means of a compressed-air surge acting on the molding sand followed by compression, by mechanical pressing. The process of the present invention provides a smooth pressure surge which is subdivided into at least a two part gradient in its pressure-rise time curve, so that the first part of the pressure-rise gradient takes place from 0.3 to 18 bar/sec to a pressure P.sub.1 and the second part has an increased pressure-rise gradient which takes place from 18 to 95 bar/sec. to a pressure P.sub.2 where P.sub.1 <P.sub.2 .ltoreq.20 bar. Subsequently, the P.sub.2 pressure is reduced in an essentially controlled manner, with a pressure-reduction gradient of a minimum of 3 bar/sec.

Abstract: A method for manufacturing a resin pattern, which does not break films in a vacuum sealed molding process and does not have secular deterioration even after repeated usages wherein a covering film is tightly contacted to an original pattern by vacuum suction, an amount of particle bodies are packed onto the covering film in a flask under the above described condition, upper portion of the flask is covered by another covering film, the tight contact of the covering film to the original pattern is released by returning the reduced pressure to normal pressure, internal pressure of the packed particle bodies is reduced, a mold cavity is formed by removing the original pattern from the packed particle bodies, a predetermined number of double solid bodies are set up in the mold cavity in the packed particle bodies which is previously turned reversely so as to be the cavity at upper side, molding resin is poured into the mold cavity, cores in the double solid bodies are withdrawn for forming through holes after hard

Abstract: A sand mold forming machine has a cope frame aligned above a drag frame with a pattern arranged between, and within, the frames. A sand filling is positioned in each of the frames. The sand fillings are compacted by squeeze plates overlaying the open, upper and lower ends of the cope and drag respectively. The squeeze plates are moved towards each other to compress the sand within the frames and against the pattern. Each of the squeeze plates is made of numerous, separate sections that are mounted upon a movable platten. The sections, of each plate, may move together as a group by moving the plattens or, the sections may be individually moved, relative to the plattens. Thus, pre-selected area of the sand fillings may be compacted more or less, as desired, than adjacent areas by separately moving opposing sections relative to the overall squeezing movements of the squeeze plate.

Abstract: A compressed air blowing apparatus for supplying compressed air to molding sand placed in a flask is arranged in such a manner that its compressed air reservoir tank is constituted by a surface-plate frame and a cover, the frame having a compressed-air outlet port which can be opened/closed by a sectioning device and a piston which can be vertically moved. The sectioning device is constituted by concentrically disposed large and small cylindrical members by a cover member secured to the large and small cylindrical members having air feed holes formed between the large cylindrical member and the small cylindrical member and by connecting duct for communicating the outside of the cylindrical member with the inside of the small cylindrical members.

Abstract: Green sand is packed as molding sand into a compression mold and the green sand is precompacted in the mold using a hydraulic press and thereafter is finally compacted after the precompaction wherein prior to precompaction recesses formed in the molding tools are subjected to a vacuum for drawing the molding sand into the recesses. In this way, even complicated mold cores can be produced satisfactorily and efficiently from green sand.

Abstract: A forming press, such as a foundry squeeze press, includes an axially movable bolster having locking hooks for engaging trunnions on a replaceable forming tool, such as a foundry sand squeeze board, to releasably secure the tool against the bolster and yet permit quick change-over from one forming tool to another to accommodate production of different workparts (e.g., mold copes or drags). The hooks are pivoted by a linear screw device to first positions wherein they are engaged with the trunnions. The hooks have pivot axes offset from the trunnion axes in such a manner as to impart such a component of motion along the bolster axis to the hooks when they are pivoted to the first positions as to tightly clamp the tool against the bolster. The hooks are pivotable by the linear screw device to second positions disengaged from the trunnions to free the forming tool for removal from the bolster.

Abstract: A forming apparatus for the manufacture of casting molds made from sand or another moldable mixture by means of a pressure shock wave from a gaseous medium is proposed. The forming apparatus comprises a structural frame constructed from columns, cross beams, and longitudinal beams, a forming combination within the structural frame, and a pressure vessel for producing the pressure shock wave. The pressure vessel is located above the forming combination and is supported by the cross beams of the structural frame. The forming apparatus also includes a filling vessel containing a supply of sand or other moldable mixture for delivery to the forming combination. The filling vessel is located above the forming combination and is supported by the cross beams of the structural frame is such manner that the topmost edges of these cross beams lie in substantially the same plane as the bottom of the filling vessel.

Abstract: To improve the accuracy of making a casting pattern from a casting model or mold (2, 2') in a molding material (M) retained in a foundry form, a single pressure pulse (P) is applied to the molding material which, however, has two phases of pressure gradient, namely a first or initial phase (1) of low pressure gradient extending up to about 1 to 3 bar during between about 10-100 m/sec, for example about 50 m/sec, to initiate fluidization of the molding material. The then fluidized and still fluidized molding material is compacted by raising the pressure from the initial low pressure pulse abruptly at a second and much higher pressure gradient to the customary compaction pressure of between 3 to 6 bar. The two-phase pressure pulse can be applied, selectively, only in a region above the model or throughout the entire mold.

Abstract: A motor is mounted on a support positioned under a sand-supplying hopper. The motor is provided with sand-stirring vanes and has a protective plate to protect the motor from sand discharges. An air discharge valve is provided annularly outside the hopper and includes an annular plunger which has a dihedral-shaped front face for closing a correspondingly-shaped annular aperture connected to an air source and is displaceably positioned within an annular chamber provided in a support ring of the valve.

Abstract: A sand mold forming machine has a cope frame aligned above a drag frame with a pattern arranged between, and within, the frames. A sand filling is positioned in each of the frames. The sand fillings are compacted by squeeze plates overlaying the open, upper and lower ends of the cope and drag respectively. The squeeze plates are moved towards each other to compress the sand within the frames and against the pattern. Each of the squeeze plates is made of numerous, separate sections that are mounted upon a movable platten. The sections, of each plate, may move together as a group by moving the plattens or, the sections may be individually moved, relative to the plattens. Thus, pre-selected areas of the sand fillings may be compacted more or less, as desired, than adjacent areas by separately moving opposing sections relative to the overall squeezing movements of the squeeze plate.

Abstract: The machine includes a compressed air bell-shaped ejector, a sand supplying hopper positioned above a diffuser located over a molding box receiving sand from the hopper. The sand supplying hopper is arranged axially inside the compressed air bell-shaped ejector so that an annular mouth is defined, which surrounds a sand discharge mouth of the hopper. The mouth of the hopper and the mouth of the ejector both face the diffuser which closes the top of the molding chamber. A valve for closing the bell-shaped ejector includes a tubular membrane which is adapted and fixed at its edges to the internal surface of the diffuser, at a coaxial portion thereof which faces the hopper.

Abstract: An airvessel for molding articles comprises a tank, a highly elastic membrane formed as a valve element and fixed in the tank by flanges to a support plate to form an annular chamber which may be pressurized via an air supply conduit to deform the membrane towards a closure position in which the membrane falls upon a valve seat. An opening is established in the center of the membrane-support plate assembly to which is axially coupled an outlet conduit for release of residual air which is present in a diffuser positioned below the membrane and coupled to a mold box.

Abstract: A process for compacting powdery materials is initiated by a pressure surge in which a surge G.sub.1 acts at a time t.sub.1 on the surface of the powdery material and, at the same time, a surge G.sub.2 is applied at a time t.sub.2 to a region of the material at a distance from the surface in the direction of the pattern so that friction between the sides of the mold housing and the compacting material is reduced. The time relationship is such that the air introduced into the material by surge G.sub.2 has time to escape before the surge G.sub.1 reaches the pattern plate. For this purpose, openings 9 are provided in the pattern plate between the mold box wall 3 and pattern 2. These openings can be arranged around the marginal areas of the pattern plate and can vary in size and number depending upon the distance between the wall 3 and pattern 2 or on the shape of the pattern. The openings can be vented to the atmosphere or connected to a suction source.

Abstract: To permit close matching of compaction pressure being applied to foundry mold making material, such as foundry sand, to the shape of a mold pattern (2) in a pattern box (3, 4), individual fluid pressure is applied to a plurality of press plungers (7) located on a pressure plate which is moved towards the sand in the mold box at a high rate of speed, the press plungers being biassed by fluid pressure to have a maximum difference (.DELTA.H) in stroke of penetration depth of at least 30% of the height (H) of the mold box; individual valves (14) can apply compressed air to individual cylinders under control, for example, of a microprocessor; the valves can be located in a matrix arrangement (FIG. 3). The method and apparatus can be used in combination with explosion or pressure impulse compaction and fluidizing of the foundry sand.

Abstract: An apparatus for compacting granular materials comprises a rack having a pedestal for supporting the mold which contains the granular material to be compacted. A compacting mechanism for applying a compacting force to the granular material is mounted for vertical movement above the mold and is provided with a seal for sealing the mold when applying a compacting force to the granular molding material.

Abstract: An apparatus for the compression of foundry moulding material by compressed gas, which comprises a pressure tank for the compressed gas forming an inlet pressure zone, a moulding zone positioned beneath the same constituted by a moulding box with filling frame and pattern plate with pattern, onto which the moulding material is loosely poured prior to compression, and a large-area valve arranged between the pressure tank and the moulding zone. The closure member thereof frees the valve opening in the pressure tank in a few milliseconds and moves into the inlet pressure zone. The closure member is driven by a pressure cylinder, whose piston on the lift side forms the moveable termination of a gas-pressurized pressure reservoir and by its opposite side is connected to a high pressure source.

Abstract: A flaskless sand mold is formed in vertically aligned, sand-filled cope and drag flasks having a pattern board arranged between them so that pattern portions mounted upon the board extend upwardly into the cope and downwardly into the drag. The sand in the drag flask is supported upon a vertically guided platen which covers the bottom of the drag flask, and the cope is covered with a squeeze plate. The sand fillings are compressed against the pattern board and the pattern portions by the platen and squeeze plate to form compacted cope and drag sand molds with aligned cavities. Then the platen, supporting the drag sand mold, is lowered a short distance while the drag flask is held immovably against the cope flask. Thereafter, while the platen, with the drag sand mold, continues to lower, the drag frame is simultaneously lowered into a rest position upon a track-like support.

Abstract: Molten metal is poured from a melt container to a mold cavity defined by a molding material wherein the molding material in the region of the runner gate is of a higher density with respect to the rest of the molding material. A pouring lip protruding from the melt container seals in the region of the runner gate for delivering molten metal from the melt container to the mold cavity.

Abstract: Granular material is selectively compressed in a molding box by a series of pressure surges applied over the granular material.

Abstract: A method of producing a mold core from green sand, wherein green sand is blown into a mold cavity which is sized to be greater than the size of the mold core to be obtained, so that a preformed mold body is prepared. The preformed mold body is then compacted by a compacting die having a cavity recess which is sized in conformity with the size of the mold core to be obtained, until the preformed mold body size is reduced to the final stage. In consequence, the green sand is compacted to develop uniform distributions of strength and hardness over the entire portion of the mold core as the product.

Abstract: Foundry molding material is poured or pneumatically infed into a mold frame arrangement containing at least one pattern, a molding frame and a filling frame. Subsequently, the foundry molding material is compacted by a compacting arrangement containing, for example, any one of a compressed-air surge compacting device, a combustion-force surge compacting device, a pressure compacting device, a vibrational compacting device or a combined pressure-and-vibrational compacting device. Also during such compacting operation at least the predominant portion of the foundry molding material contained in the filling frame is displaced into the molding frame. During such compacting operation a preselected expanding gas is infed into predetermined local regions of the foundry molding material while such material is being compacted. As a result, there are formed zones of reduced packing density in the foundry molding material.

Abstract: A method and apparatus for producing flaskless foundry molds made up of copes and drags of wet casting foundry sand, which is blasted into a cavity to form the mold with the use of vacuum. The sand is pressed mechanically while aspirating air therefrom. The gap coming into existence between the pressing plate and the back side of a mold during pneumatic impact compaction is filled with sand before pressing so that a flat back side is produced on the mold so that when casting takes place later there is not danger of the bottom of the mold fracturing or of deformation taking place.

Abstract: An ultra-light structure is produced by continuously molding a greensand core, forming a material in the mold pattern in the core which solidifies to form a solidified framework, and removing the greensand core.

Abstract: An apparatus and method for making cores from green sand continuously and automatically. The method comprises blowing the green sand together with compressed air into a die cavity formed by a pair of dies, stabbing the green sand filled in the die cavity by stabbing rods to compact the green sand thereby to form a core, and applying a surface stabilizing agent to the surface of the core taken out from the dies, followed by drying of the core. Disclosed also is an apparatus suitable for carrying out this method.

Abstract: In an apparatus for compressing foundry moulding material by pressure gas comprising a pressure vessel for the pressure gas forming an inlet pressure chamber, a moulding chamber positioned below it formed from moulding boxes with sand frames and a pattern plate with pattern on which the moulding material is loosely heaped up prior to compression and a large-area valve arranged between the pressure vessel and the moulding chamber, its closure member frees the valve opening in a few milliseconds, accompanied by the joint action of the pressure in the pressure vessel and thereby moves into the moulding chamber.

Abstract: In a process for the compaction of foundry mold making material, more specially foundry sand, using a pressing plate placed directly on the material and accelerated to a speed of up to 20 meters per second, an efficient and even compaction of the material over the full height thereof is made possible by accelerating the pressing plate in an initial phase lasting for up to 50% of the total duration of the compaction stroke progressively up to the maximum speed, then moving it in an ensuing main phase at a more or less constant speed and finally slowing it down degressively in a terminal phase, lasting for up to 30% at the most of the overall stroke time, the driving force being preferably supplied by a captive gas volume under high pressure and opposed by a hydraulic counter force, the effect of said counter force as an opposing load decreasing during the compaction stroke by rapid discharge of a hydraulic liquid.

Abstract: An ultra-light structure is produced by continuously molding a green sand core, forming a material in the mold pattern in the core which solidifies to form a solidified framework, removing the green sand core and wrapping the resultant solidified framework structure in a material.

Abstract: In a method of preparing a sand mold in which mold sand within a mold frame is squeezed from an upper side opposite to a lower side of the frame at which a pattern is embedded and also from said lower side, the squeezing from the lower side is made only after the squeezing from the upper side has been completed by about or more than 95% of a total squeezing stroke. The sand mold thus prepared comes to have a desired hardness particularly at casting surfaces thereof.

Abstract: In an apparatus for the compaction of foundry sand by the impact of pressurized gas on the foundry sand as filled into a flask over a pattern plate with a pattern therein, a specially designed diaphragm is used to get an even and constant hardness of the mold in every horizontal plane thereof and/or to put an end to the formation of shear cracks in the mold between different parts of the volume of the sand. This diaphragm is placed over the so far uncompacted surface of the foundry sand and it has a permeability to gas varying with the height of the sand to be compacted so that such permeability is less in the parts with high and/or plateau-like pattern contours than in parts where there is no pattern on the pattern plate.

Abstract: An apparatus for the compaction of foundry sand using a pressurized gas method is made up of a conventional flask closed by a pattern plate with a pattern and has a filling frame and a chamber over the foundry sand heaped on the pattern. A high-speed filling of the chamber is carried out by gas under pressure in a matter of milliseconds so that the foundry sand is compacted while at the same time the pressure falls. In order to be certain of an even and reproducible compacting effect on the sand whatever way of producing the gas pressure is used, i.e. with or without an explosion of a gas mixture to get a gas pressure wave, use is made of a piston plate that is placed a small distance over the surface of the sand filling for separating the sand from the gas pressure space at least at the beginning of the action of the gas, such piston plate being freely movable and having an outline generally the same as the free cross section of the filling frame and the flask.

Abstract: A process for making an investment mold wherein a paste composition is used as the separating layer between the investment mould of refractory material and the surface of the metal container in which the investment mould itself is located. The composition is constituted by an organic component which can be eliminated by thermal degradation at temperatures above 200.degree. C. and a refractory mineral component which is stable at the casting temperature of the alloy used in the casting process. In a preferred embodiment, the composition comprises vaseline, talc and kaolin.

Abstract: The apparatus has a valve arrangement which opens rapidly due to priming or prestressing of the valve plate by the pressure in the pressure chamber. When the valve is closed, pressure, built up in the pressure chamber space closed by the valve, applies a force to the valve member in the direction of its open position. The valve member is held closed by a holder arrangement. Following the development of a predetermined pressure in the pressure chamber, the holder arrangement releases the valve member such that the pressure in the pressure chamber forces the valve member to its open position opening the pressure chamber passage and permitting the pressure medium to surge onto the surface of the molding material. This apparatus is suitable for all high-stressed gases which must be released suddenly.

Abstract: Loosely poured granular material is compacted by a burst of air under pressure which is built up in a space Q1 and is abruptly released through the outlet end of a passageway Q3 which opens toward the material surface. While the pressure in Q1 is being built up and until released, it is restrained by a sealing member which concurrently covers the outlet side of Q1, the input end of passage Q3 and an accelerating space Q2. The sealing member is held in place by a counterpressure in a space Q4 acting on a larger surface area than Q1. The pressure is suddenly decreased in Q4, abruptly unbalancing the pressures and releasing the pressurized gas from Q1 into Q3 and against the surface.

Abstract: The apparatus has a plurality of tubular hollow members arranged between the pressure chamber and the molding units, in the pressure surge flow direction, for conducting the gaseous medium to the top of the molding material. With distribution of the pressure medium flow through a plurality of independent and different cross sections, the lifting force required to open the packing element is greatly reduced and the packing element can be opened rapidly.

Abstract: In order to make castings from casting sand or another moldable mixture, a pressure surge wave is used which has upper and lower limit values which values have been established by an optimal selection of a pattern of pressures. The other moldable mixture comprises particles of raw material, binder, water, and, if need be, additives. The rise in pressure takes place with an increasing pressure gradient, dp/dt, of at least 50 atmospheres (absolute)/second. A minimum pressure of at least 2 atmospheres (absolute) is maintained for at least 0.01 second. The pressure drop takes place at a decreasing pressure gradient, -dp/dt, of up to about 2.0 atmospheres (absolute)/second. The disclosed values represent an optimalization, in view of a simple design and economy of operation, with a surprisingly good compacting.

Abstract: In a process for compacting foundry mold making material, and more specially wet foundry sand, by the violent effect of gas pressure on the free surface of the mold material heaped on to the pattern, the compacting effect may be made better and the height of extra material on the pattern may be better controlled by placing a gas-permeable further or auxiliary mass on the free surface of the mold material. The further material is made up of separate pieces of material that may be moved in relation to the surface of the mold material, the gas pressure taking effect on the free surface of the further mass. The further mass may be used in compaction processes in which the pressure wave is produced by expansion of gas from a receiver and processes in which the wave is produced by an explosion.

Abstract: In a process for compacting foundry mold making material, that is loosely heaped in a closed mold space over a pattern, the surface of the material is acted on by a compressed gas with a pressure of at the most 8 bar. This gas is caused to undergo expansion out of an inlet space through a valve in an opening at a gas flow rate of over 50 kg/sec and with a pressure increase rate of over 300 bar/sec, into the mold space. The maximum pressure in the inlet space or antichamber is 20 bar.

Abstract: In order to make casting sand or another moldable mixture, a pressure surge wave is used which has upper and lower limit values which values have been established by an optimal selection of a pattern of pressures. The other moldable mixture comprises particles of raw material, binder, water, and, if need be, additives. The rise in pressure takes place with an increasing pressure gradient, dp/dt, of at least 50 atmospheres (absolute)/second. A minimum pressure of at least 2 atmospheres (absolute) is maintained for at least 0.01 second. The pressure drop takes place at a decreasing pressure gradient,--dp/dt, of up to about 2.0 atmospheres (absolute)/second. The disclosed values represent an optimalization, in view of a simple design and economy of operation, with a surprisingly good compacting.