Method of blow-molding hollow vessel and blow air cylinder

摘要

The present invention relates tn a method of blow-molding a hollowvessel, wherein when a nozzle (1) for blowing air is thrust into a parisonextruded from an extruder to thereby blow the air thereinto, the airis blown at least downward into the parison, an opening (8) is formed inthe parison in the vicinity of a blow nozzle thrust-in portion (7) orthere-above after the hollow vessel is shaped by the blown air, and the blownair is circulated in the hollow vessel and then discharged therefrom. Theinvention also relates to a blow air cylinder suitably used for said methodand has a particular construction wherein there is provided the blownozzle (1) having an opening capable of blowing air at least downwardlyat a rate of 30 % or above of the whole flow quantity of the blownair. The invention makes it possible to shorten the cooling time of themolded itean after blow-molding and produce molded items excellent inaccuracy of dimensions effectively.