MOUTH CYLINDRICAL PART OF SYNTHETIC RESIN BOTTLE BODY

摘要

A mouth cylindrical part of a synthetic resin bottle body capable of providing high pressure resistance and heat resistance and stably providing high sealability and resources-saving by maximally uniformizing the effect of a thread formed portion on the crystallization of a molten resin material along the circumferential direction of the mouth cylindrical part. Threads (3) formed by extending gradually downsized start end extension parts (5) and terminal end extension parts (6) from the body part start end (a) and the body part terminal end (b) of a body part (4) are formed on the outer periphery of the cylindrical wall (2) of the mouth cylindrical part (1) in the form of a multiple thread screw. The start end extension parts (5) and the terminal end extension parts (6) of the other threads (3) having an approximately same length are positioned overlappingly with each other in the vertical direction, and the entire part of the mouth cylindrical part (1) is whitened by thermal crystallization. Thus, shrinkage (h) can be eliminated from the upper end surface of the cylindrical wall (2) irrespective of an increase in bore of the mouth cylindrical part (1) and an increase in heat resisting temperature. Accordingly, an increase in height dimension due to an increase in bore of the mouth cylindrical part (1) can be suppressed.