| 摘要 |
PROBLEM TO BE SOLVED: To provide a method, which is rational and versatile, for applying a stripe or a spiral pattern to the inner surface of a plastic bottle by means of a blow molding. SOLUTION: A helical groove 3b is carved on a side of a core 3. A molten resin pressed out of an extruding machine is given a shape loosely by the groove 3b so that the whole of the resin advances, in the helical form, along the groove 3b, and hence a spiral pattern supplementary to the groove 3b is successively formed on the inner surface of a parison 6 so that a plastic bottle having a spiral pattern on the inner surface thereof can be obtained.
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