| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a boot precisely in its small diameter portion and large diameter portion. SOLUTION: Parison is extruded from a blow die head 30, and the parison is held in its tip end by an insert 40 and a first split die 50 so as to form the small diameter portion of a boot along with an annular inward protrusion. Air is blown in the parison from the blow die head 30 so as to preform the parison substantially spherically in the proximity of the blow die head, then the parison is cut for forming an inverted conical upper end portion of the parison. In the next place, an air blowing nozzle 80 in common use with a large diameter portion forming insert is put therein from the upper end portion of the parison, after that, between the air blowing nozzle 80 and the second split die 70, the parison is held in its upper end portion for forming an annular inward protrusion to subsequently be subjected to blow forming operation by blowing air in the inner portion of the parison, thereby forming the middle portion of the boot into a bellows-form and inverted conical body in conformity with the cavity of the first split die 50. |
