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. An apparatus for use in the method is made up of a pressure vessel, a mold flask placed thereunder having a filling frame and a pattern plate. The opening cross section of the valve is 50 to 150% of the horizontal cross section of the mold flask and is opened in a short time of the order of milliseconds.

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: 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.