| 摘要 |
PURPOSE:To permit elimination of an internal stress or distribute the same to a condi tion coping with a molded shape by a method wherein a forming area is processed plastically once so as to have a shape much smaller than the final shape thereof and, thereafter, the synthetic resin material in this area is heated to the softening condition thereof while fitting it into a mold coped with the final configuration of the area. CONSTITUTION:The diameter of the mouth 11 of a cylindrical vessel 1, whose necking process is effected by employing molds 3, 4, becomes smaller than the diameter of a cylindrical section 12 while the mouth 11 and the cylindrical section 12 are continued through a curved surface. A split mold 2, equipped when an annular protuberance 21 coinciding with the profile of the mouth 11, is mounted on the mouth 11 of the vessel and the whole of the vessel is heated to the softening point of a synthetic resin material constituting the vessel 1. According to this method, the area of necking process is deformed to a direction of expanding the diameter thereof, the mouth 11 is formed with a flange section 14 at the upper end thereof, a recessed groove 13 is continued to the lower side thereof and a sectional shape, in which the lower part of the recessed groove is continued to the cylindrical section 12 through a convex arced section 15, is formed while wavings in the arced section 15 can be eliminated. |
