BLOW MOLDING OF HOLLOW MOLDED PRODUCT

摘要

PROBLEM TO BE SOLVED: To uniformly perform cooling within a short time by blowing air having pressure higher than the set pressure held in a parison at a time of a cooling process in a blow process. SOLUTION: Blow air is blown in a parison 1 from the air supply passage 13 of an air supply and discharge nozzle 12 to perform blow molding to bring the parison 1 into contact with the inner surface of a mold 11. At this time, blown-in air is set to pressure higher than the air pressure held in the parison at a time of cooling. As a result, the molding of the parison is quickly performed. A pressure detector 17 detects that the pressure in the parison reaches a predetermined pressure to stop the blow-in of blow air. In a next cooling process, mist is sprayed into the parison from a mist nozzle 14 to quench the inner surface of the parison. Subsequently, high pressure cooling air is blown in from the air supply and discharge nozzle 12 and the parison is opened to the atmosphere through a relief valve 16 at the same time. An air circulating stream is generated while the inner pressure of the parison is held to the predetermined pressure by the relief valve 16 and mist is spread to the inner surface of a molded product to further uniformly cool the molded product.