초록 ▼

A method of forming a foamed plastic article, comprising the steps of: injecting pressurized gaseous bubbles into a stream of heated liquid plastic; feeding the heated liquid, with entrained gas bubbles, into a mold cavity without expanding the bubbles; slowly expanding the mold cavity to permit the

A method of forming a foamed plastic article, comprising the steps of: injecting pressurized gaseous bubbles into a stream of heated liquid plastic; feeding the heated liquid, with entrained gas bubbles, into a mold cavity without expanding the bubbles; slowly expanding the mold cavity to permit the gas bubbles to expand and thereby produce a foamed plastic article; controlling the temperature of the mold cavity surfaces so that the plastic material is in a viscous liquid state during at least the major part of the bubble expansion process; and cooling the mold cavity surfaces to a temperature less than the melt point of the plastic.

대표청구항 ▼

A method of forming a foamed plastic article, comprising the steps of: (a) injecting gaseous bubbles at a pressure between 700 psi and 1200 psi into a matrix of heated liquid plastic; (b) providing a mold having a variable volume cavity and an expansion wall bounding one side of the the cavity, the

A method of forming a foamed plastic article, comprising the steps of: (a) injecting gaseous bubbles at a pressure between 700 psi and 1200 psi into a matrix of heated liquid plastic; (b) providing a mold having a variable volume cavity and an expansion wall bounding one side of the the cavity, the wall movable to a first position wherein the cavity has a relatively lower volume, the mold having a compressing means to urge the wall toward the first, lower-volume position; (c) introducing the heated liquid plastic with entrained gas bubbles into the variable-volume mold cavity without expanding the bubbles; (d) permitting the gaseous bubbles to expand so as to force the moveable wall at a gradual, selected rate to a second, relatively higher volume position in the mold cavity; (e) controlling the rate of bubble expansion by gradually reducing the force which the compression means applies to the moveable wall of the mold; (f) controlling the temperature of the mold cavity surfaces to maintain the plastic material in a viscous state during at least a major part of the bubble expansion process.