| 摘要 |
<p>PURPOSE:To prevent firmly generation of cracks in a bottom part which is molded in a self-standing form by a method wherein on an outer surface of the bottom part in an incompletely oriented area, many stress gathering reducing parts are provided in the form of small recesses and projections, linear protrusions, grooves or the like. CONSTITUTION:A bottom part 4 is constituted of an incompletely extended area 8 which includes an unoriented area 7 where an orientation center is positioned, a leg piece 5, a reverse area 6 which is a valley wall and rising parts of the unoriented area 7 and the leg piece 5 and is surrounded by a sufficiently oriented area, and further the incompletely oriented area 8 is added with stress gathering reducing parts 9. The stress gathering reducing parts 9 provided on the bottom part 4 of a bottle 1 may be of various forms and constitutions. Each stress gathering reducing part 9 is designed to have a height of the incompletely oriented area 8 from an outer surface of 0.2mm and a diameter of a skirt part in the outer surface of 1.6mm. But only the outside part 9 indicated by double circles is formed to have a height of 0.1mm, so that degree of generation of local stress due to a formation of stress gathering reducing parts 9 is reduced in a peripheral part.</p> |
