US Patent 7134479 Apparatus and method for low pressure sand casting

A process for counter gravity sand casting including providing precision cores in a sand mould supported in a casting machine for rotation about a horizontal axis through the center of the mould, providing primary casting risers fed by a launder section, a pressure riser connected to the launder section and the primary risers, rising upwardly beside the mould, whereby on rotation a the molten metal in the pressure riser will maintain a internal constant pressure in the mould until the casting risers are upper most, so as to maintain the internal pressure during the cooling of the mould.