Sand mold and apparatus for reduced pressure casting

A unitary, rigid, self supporting, gas permeable, low temperature bonded, sand grain mold having peripheral side surfaces extending between vertically spaced upper and lower surfaces with mold cavity means spaced therebetween and vertical gate passage means with its lower open end exposed at said lower surface, for use in a method of vacuum casting metal comprising:

• submerging said lower surface and said open end of said gate passage means beneath an underlying surface of molten metal while maintaining said upper surface and at least a portion of said side surfaces thereabove;
• applying a reduced pressure to the upper surface of said mold to simultaneously fill said gate passage means and said mold cavity means with molten metal;
• solidifying said molten metal throughout the transverse dimension of at least a portion of said gate passage means;
• and
• thereafter removing said mold and the submerged open end of said gate passage means from contact with said underlying surface of molten metal before said solidified metal in said gate passage means portion remelts due to contact with said underlying surface of molten metal,
• said mold comprising
• upper and lower low temperature bonded mold halves adhesively secured together in a generally horizontal mold parting plane with said upper and lower surfaces generally parallel to and vertically spaced on opposite sides of said mold parting plane
• mold cavity means extending to said generally horizontal mold parting plane and spaced between said upper and lower surfaces, and
• gate passage means extending vertically from said mold cavity means through said lower mold half to said lower mold half lower surface and terminating with its lower open end exposed at said lower surface,
• said gate passage means having a restricted portion having a maximum width in at least one dimension of 0.75 inches for said solidification of metal therein.

A unitary, rigid, self supporting, gas permeable, low temperature bonded, sand grain mold having peripheral side surfaces extending between vertically spaced upper and lower surfaces with mold cavity means spaced therebetween and a plurality of vertical gate passages with lower open ends spaced from one another exposed at said lower surface, for use in a method of vacuum casting metal, comprising:

• submerging said lower surface and said open ends of said gate passages beneath an underlying surface of molten metal while maintaining said upper surface and at least a portion of said side surfaces thereabove;
• applying a reduced pressure to the upper surface of said mold to simultaneously fill said gate passages and said mold cavity means with molten metal;
• solidifying said molten metal throughout the transverse dimension of at least a portion of said gate passages;
• and
• thereafter removing said mold and the submerged open ends of said gate passages from contact with said underlying surface of molten metal before said solidified metal in said gate passage portions remelts due to contact with said underlying surface of molten metal,
• said mold comprising
• upper and lower low temperature bonded sand grain mold halves adhesively secured together in a generally horizontal mold parting plane with said upper and lower surfaces generally parallel to and vertically spaced on opposite sides of said mold parting plane
• mold cavity means extending to said generally horizontal mold parting plane and spaced between said upper and lower surfaces, and
• a plurality of gate passages extending vertically from said mold cavity means through said lower mold half to said lower mold half lower surface and terminating in a generally horizontal plane with their lower open ends spaced from one another exposed at said lower surface,
• said gate passages each having restricted portions having a maximum width in at least one dimension of 0.75 inches for said solidification of metal therein.

A low temperature bonded, sand grain mold comprising a peripheral side surface extending between vertically spaced upper and lower surfaces, with mold cavity means spaced therebetween, said mold being characterized in that,

• said mold is unitary, rigid, and self supporting
• said lower mold surface and a portion of said side surface are external, unencumbered by mechanical support, and adapted to be submerged in molten metal to be cast in said mold,
• said mold comprises upper and lower mold halves adhesively secured together at a generally horizontal mold parting plane with said upper and lower surfaces generally parallel to and vertically spaced on opposite sides of said parting plane;
• said mold includes gate passage means extending vertically from said mold cavity means through said lower mold half to said lower mold surface, said gate passage means having at least one dimension small enough to solidify molten metal therein when said lower mold surface and said side surface portion are submerged in a molten metal reservoir,
• said gate passage means having a restricted portion having a maximum width in at least one dimension of 0.75 inches
• said mold has an upper peripheral sealing surface adapted to be sealed to a vacuum chamber,
• whereby, when said mold is sealed to said vacuum chamber, said lower surface and said side surface portion are submerged in a reservoir of molten metal, and said mold cavity means is filled by the application of a vacuum, said metal will solidify in said gate passage means and said mold can be removed from said molten metal before said metal in said gate passage means remelts.