METHOD OF PREPARING MOULDS FOR LARGE CASTINGS IN PITS Russian patent published in 1995 - IPC

FIELD: foundry practice. SUBSTANCE: the method is based on vacuum moulding. Accordingly, a gas-tight film is applied to the surface of the pit and that of the pattern. A ventilation means is lowered into the pit and so is the pattern, being placed on a layer of moulding sand there. The pattern is vacuum degassed, and the rest of the sand is dumped into the pit. The ventilation means and the pattern are set to vibrate with the result that the sand becomes compact. The mould is sealed off at the parting line and subjected to vacuum degassing. The degassing of the pattern is ended, and the pattern is removed from the mould cavity. To ensure effective sand compacting, shock-absorbers are placed under the ventilation means inside the mould at the pit bottom. EFFECT: increased productivity of the process and improved quality of castings. 2 cl, 1 dwg