Method for molding hollow plastic articles

A method for producing a hollow synthetic resin molded article having a general configuration corresponding to two trays joined at their bottoms with a hollow portion formed at their periphery, said article including at least one non-hollow first portion resulting from joining of the bottoms of the two trays and at least one hollow second portion resulting from joining of the bottoms of the two trays and being isolated from said peripherally located hollow portion;

• said method comprising
• opening a split mold having mold cavities with a contour conforming to said tray-like configuration of the desired article,
• feeding a heated parison of a thermoplastic synthetic resin in the form of a tube or two parallel-laid sheets extruded from a die into a space between the opposing mold members of the split mold,
• applying negative pressure to vacuum suction holes provided in the cavities of said split mold and to vacuum suction holes provided in parting surfaces surrounding said cavities, the positions of said latter vacuum suction holes relative to said cavities being determined according to the depth of said cavities,
• simultaneously blowing heated compressed air against the inside surface of that portion of the parison which corresponds to said parting surfaces in the direction facing said parting surfaces to facilitate attaching of the parison to said parting surfaces,
• closing said split mold, while applying said negative pressure, to join the parison at its portions corresponding to the periphery and said first portion to thereby form the parison into a crude hollow moleded article, and
• blowing pressurized air into the hollow portion of said crude molded article with said split mold being kept closed to thereby form the parison into a desired final configuration.