Method of blow-moulding a flat container having portions with differing wall thicknesses

• Main Authors: MORISIGE, KOZO, TANAKA, HIROSI
• Format: Patent
• Language: English; French; German
• Published: 07.12.1994
• Edition: 5
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULARARTICLES; INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

A process for producing a blow moulded container from molten resin, said process comprising the steps of: extruding the molten resin from a die head (1) to form a parison (2); closing the bottom of said parison by pinching; preforming part of the parison into a thick-walled portion (10) while forcing a fluid into the parison at a sufficient pressure to prevent contact between the inner surfaces of the parison; drawing the remainder of the parison longitudinally to a length (li) at least 1.1 times its original (lo) length while the parison is at a temperature not lower than the melting point of the resin; expanding said parison to form a thin-walled portion (11) with a differential pressure being created across the wall of the parison; confining the expanded parison in a split mould (7) having a cavity of a shape conforming to that of said container, with the outer edge of the parison extending beyond that of said mould cavity (7b), so that the edge portions are fused together; and forcing a pressurised fluid into the parison confined in said mould (7) so that the parison is forced into close contact with the inside surfaces of the mould cavity.