METHOD AND DEVICE FOR BLOW MOLDING OF HOLLOW ARTICLE

摘要

PURPOSE: To increase strength and to reduce the amt. of a thermoplastic resin material by stretching a parison up to the predetermined partial length of a blow mold by a tensile rod and supplying blowing-in air to hold the tensile rod to the contact state with the bottom part of the parison to expand the parison by the blowing-in air. CONSTITUTION: The parison V sealed in the gap between blow mold parts 11, 12 is placed on a blow mandrel 10. Compressed air is supplied to an inside cylinder 18 to displace a piston 19 to an upper position. A tensile rod 15 is extended into the parison V to stop at the bottom part of the parison V. The rotor 20 connected to the inside cylinder 18 comes into contact with a cam 21 and the tensile rod 15 is moved upwardly by the rotor 20 tumbling along the cam 21 and the parison V is mechanically prestretched. When the parison V reaches a predetermined position, blowing-in air enters the parison V through the gap between the tensile rod 15 and the mandrel 10 to expand the parison V not only in the axial direction thereof but also in the diameter direction thereof and the parison V is brought into contact with the inside walls of the blow mold parts 11, 12 to form a finish product.