Method for forming hollow articles

Claim 1

The method of forming a hollow article from moldable settable material by molding the material about a mandrel in a segmental pressure mold and comprising: charging with raw moldable material a mold having a cavity shaped to impart a predetermined exterior configuration to the article and in which cavity is disposed a removable mandrel having a shape to impart a predetermined interior configuration to the article; the mold comprising two segments, each segment having a first molding part and a second molding part; said first parts having complementary first parting surfaces, respectively, and the second parts having complementary second parting surfaces, respectively; the first and second parting surfaces of each segment forming a continuous parting surface of the associated segment in the closed position of the segments, the second part of each segment being movable relative to the first part of the associated segment in a direction toward and away from the parting surface of the associated first part so that the parting surfaces of the first parts can be juxtaposed while the second parts are juxtaposed against a portion of the mandrel and held thereby in spaced face to face relation to each other, and the parting surfaces of the second parts can be juxtaposed after removal of the mandrel; and said portion of the mandrel being shaped to impart to the article, while said second parts are juxtaposed against said portion, aligned spaced mateable edges, respectively, from between which the mandrEl can be withdrawn from the article while the second parts are opened sufficiently and while, concurrently therewith, the molding pressure is relieved on the first parts, and at least one of which edges, at each aligned unit of the length of said edges, is disposed beyond the adjacent complementary parting surfaces of said second parts after removal of the mandrel, a distance sufficient so that the spaced mateable edges can be juxtaposed in face to face relation under pressure by movement of the second mold parts to closed positions; closing said first mold parts against each other and the second mold parts against the mandrel, under pressure, so as to confine the material under predetermined pressure in the space between the mandrel and mold segments, and maintaining the first mold parts in closing relation to each other and the material under setting conditions from the instant of initial closure and throughout the entire setting operation, except for an instant while the closing pressure is relieved for withdrawal of the mandrel; and maintaining the second mold parts juxtaposed against the mandrel, and the material under setting conditions from the instant of initial closure and until the material is partially set to a degree such that the material maintains its molded shape and remains in partially set fusible condition and in contact with the mold cavity walls of the segments; relieving the pressure on the first mold parts and opening the second mold parts sufficiently to permit withdrawal of the mandrel through the space between said mateable edges, from the partially set material while the material remains so partially set and fusible and in firm contact with the cavity walls; promptly thereupon withdrawing the mandrel from the cavity through the space between said aligned mateable edges; promptly thereafter reapplying the pressure to the first mold parts, and closing the second mold parts against each other under pressure and thereby causing them to move said mateable edges into said face to face contact under sufficient pressure to cause said mateable edges to engage and fuse together and the material to assume the final shape of the article; retaining the mold segments in closed condition and maintaining controlled setting conditions for a period to fully set the material and permanently fuse and bond the adjacent strata of said mateable edges together in sealing relation while all portions of the article are held in said final molded position in the cavity; and after the material is set, opening the mold and removing the article therefrom.

Claim 2

The method of forming a hollow article from moldable settable material by molding the material about a mandrel in a segmental pressure mold and comprising: charging with raw moldable material a mold having a cavity shaped to impart a predetermined exterior configuration to the article and in which cavity is disposed a removable mandrel having a shape to impart a predetermined interior configuration to the article; the mold comprising two segments, each segment having a first molding part and a second molding part; said first parts having complementary first parting surfaces, respectively, and the second parts having complementary second parting surfaces, respectively; the first and second parting surfaces of each segment forming a continuous parting surface of the associated segment in the closed position of the segments, the second part of each segment being movable relative to the first part of the associated segment in a direction toward and away from the parting surface of the associated first part so that the parting surfaces of the first parts can be juxtaposed while the second parts are juxtaposed against a portion of the mandrel and held thereby in spaced face to face relation to each other, and the parting surfaces of the second parts can be juxtaposed after removal of the mandrel; and said portion of the mandrel being shaped to impart to the article, while said second parts are juxtaposed against said portion, aligned spaced mateable edges, respectively, from between which the mandrEl can be withdrawn from the article while the second parts are opened sufficiently and while, concurrently therewith, the molding pressure is relieved on the first parts, and at least one of which edges, at each aligned unit of the length of said edges, is disposed beyond the adjacent complementary parting surfaces of said second parts after removal of the mandrel, a distance sufficient so that the spaced mateable edges can be juxtaposed in face to face relation under pressure by movement of the second mold parts to closed positions; closing said first mold parts against each other and the second mold parts against the mandrel, under pressure, so as to confine the material under predetermined pressure in the space between the mandrel and mold segments, and maintaining the first mold parts in closing relation to each other and the material under setting conditions from the instant of initial closure and throughout the entire setting operation, except for an instant while the closing pressure is relieved for withdrawal of the mandrel; and maintaining the second mold parts juxtaposed against the mandrel, and the material under setting conditions from the instant of initial closure and until the material is partially set to a degree such that the material maintains its molded shape and remains in partially set fusible condition and in contact with the mold cavity walls of the segments; relieving the pressure on the first mold parts and opening the second mold parts sufficiently to permit withdrawal of the mandrel through the space between said mateable edges, from the partially set material while the material remains so partially set and fusible and in firm contact with the cavity walls; promptly thereupon withdrawing the mandrel from the cavity through the space between said aligned mateable edges; promptly thereafter reapplying the pressure to the first mold parts, and closing the second mold parts against each other under pressure and thereby causing them to move said mateable edges into said face to face contact under sufficient pressure to cause said mateable edges to engage and fuse together and the material to assume the final shape of the article; retaining the mold segments in closed condition and maintaining controlled setting conditions for a period to fully set the material and permanently fuse and bond the adjacent strata of said mateable edges together in sealing relation while all portions of the article are held in said final molded position in the cavity; and after the material is set, opening the mold and removing the article therefrom.