US Patent 7296612 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 the molten metal in the pressure riser will maintain an 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.