Method for the manufacture of thin-walled shaped articles of thermoplastic material

A method of manufacturing thin-walled synthetic plastic articles which comprises the sequential steps of extruding a continuous hot plastic web of thermoplastic material at a temperature wherein said material is in substantially fluid condition and substantially immediately stabilizing said web by passing the opposite surfaces of said web in contact with heat exchange areas maintained at substantially constant cooling temperature materially below the extrusion temperature and below the temperature range in which said material is elastically deformable for precooling opposite surfaces of the web to provide therealong continuous relatively thin outer supportive layers while the core remains in hot fluid condition, allowing said outer layers to be partially reheated by heat conducted from the core so that said layers become sufficiently elastic and deformable to permit shaping, and subsequently subjecting said web to a shaping tool operation wherein said layers are positively displaced relative to each other while the hot plastic material between said layers remain sufficiently fluid for redistribution between said layers.

A method of manufacturing thin-walled synthetic plastic articles which comprises the sequential steps of forming as by extrusion a continuous hot plastic web of substantially fluid thermoplastic material and substantially immediately stabilizing said web by contacting opposite surfaces of the web with heat exchange surfaces maintained at a predetermined cooling temperature appreciably lower than the forming temperature to initially provide along the said web continuous cooled outer supportive layers that are not sufficiently deformable to permit their shaping in a subsequent shaping tool operation while the hot plastic material between said layers remains as a fluid core heated close to the extrusion temperature at forming;

• heating said layers to elastically deformable condition by heat derived from said core;
• and during said shaping tool operation displacing and stretching said layers relative to each other, and further cooling at least one of said layers by contact with a cooled shaping tool surface that corresponds with a desired end product;
• said fluid core being distributed between said two opposite shell-like outer surfaces in response to shaping pressure.