Method of producing a foamed, molded article

Claim 1

A method of producing a foamed, molded article, comprising the steps of: (a) accumulating in an accumulator a molten mass of an expandable thermoplastic resin while maintaining said molten mass at a temperature and a pressure so that said molten mass is prevented from foaming; (b) ejecting a predetermined quantity of the accumulated thermoplastic resin rapidly from said accumulator, into an atmosphere maintained at a pressure lower than the pressure within said accumulator so that the ejected thermoplastic resin commences foaming; (c) placing the ejected, molten thermoplastic resin in a mold cavity before the expansion thereof has been completed, said cavity being defined by a mold having a male mold section and a female mold section movable relative to each other, said mold sections having complementary-shaped configurations defining the mold cavity, the volume of said cavity being changeable by changing the position of said mold sections relative to each other; (d) compressing the molten thermoplastic resin placed in the mold cavity by changing the position of said mold sections relative to each other to change the volume of said cavity, the molten thermoplastic resin being compressed between said mold sections before the completion of the expansion to improve the expansion ratio of the resin; and (e) completing the expansion and molding of the thermoplastic resin in the mold cavity while controlling the compression pressure by moving said mold sections relative to each other, thereby to obtain a foamed, molded article.

Claim 2

A method of producing a foamed, molded article, comprising the steps of: (a) accumulating in an accumulator a molten mass of an expandable thermoplastic resin while maintaining said molten mass at a temperature and a pressure so that said molten mass is prevented from foaming; (b) ejecting a predetermined quantity of the accumulated thermoplastic resin rapidly from said accumulator, into an atmosphere maintained at a pressure lower than the pressure within said accumulator so that the ejected thermoplastic resin commences foaming; (c) placing the ejected, molten thermoplastic resin in a mold cavity before the expansion thereof has been completed, said cavity being defined by a mold having a male mold section and a female mold section movable relative to each other, said mold sections having complementary-shaped configurations defining the mold cavity, the volume of said cavity being changeable by changing the position of said mold sections relative to each other; (d) compressing the molten thermoplastic resin placed in the mold cavity by changing the position of said mold sections relative to each other to change the volume of said cavity, the molten thermoplastic resin being compressed between said mold sections before the completion of the expansion to improve the expansion ratio of the resin; and (e) completing the expansion and molding of the thermoplastic resin in the mold cavity while controlling the compression pressure by moving said mold sections relative to each other, thereby to obtain a foamed, molded article.