Casting method and mold for implementing same

Abstract From the Canadian patent

A casting mold filled with free-flowing particulate matter such as sand, in which there is imbedded a vaporizable pattern of foam plastic conforming to the shape of the desired casting, has at least two of its walls formed by flexible membranes exposed to the atmosphere for creating a more or less isobaric pressure upon the application of suction to its interior. One membrane may span the open top of a four-sided rigid shell whose perforated bottom is overlayed by another such membrane; alternatively, with the sidewalls of the shell also perforated and/or vertically ribbed or fluted five membranes, may be combined into an open-topped bag lining the interior of the shell, the top of the bag …