MOLD APPARATUS FOR BIAXIAL STRETCHING BLOW MOLDING

摘要

PROBLEM TO BE SOLVED: To hold a preform so that the stretching center of the bottom part thereof is not displaced by providing an elastic material exerting elastic action on a support pin in the advance direction thereof in the vicinity of the retreat limit of a blow process in a cylinder chamber and forming the leading end surface of the support pin into a circumference-of-circle edge having a recessed cross-sectional shape. SOLUTION: A support pin 6 is inserted into the cylinder chamber 3a formed to the bottom mold 3 of a blow mold in a freely advancing and retreating manner to be arranged in order to prevent the wall thickness irregularity of a product subjected to blow molding and the leading end surface 6a of a support pin is formed into a circumference-of-circle edge having a recessed cross-sectional shape so that resistance of a degree preventing the slide of the bottom part 4a of a perform 4 is provided but the deformation of the preform is not obstructed at a time of the stretching blow molding of the preform 4. Further, the support pin is brought to an energizing state in an advance direction at a retreat position by an elastic material 3c and the stretching center part of the bottom part 4a of the preform is held by the leading end surface 6a of the support pin and the leading end surface 5a of the stretching rod 5 provided to a blow core mold 2 to prevent the displacement of the stretching center of the preform.