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The peripheral portion of a flat, molecularly orientable material stock of substantially uniform thickness having a temperature below the upper limit of the molecularly orientable temperatures of the plastic material is clamped, and the central portion of the plastic material stock is introduced int

The peripheral portion of a flat, molecularly orientable material stock of substantially uniform thickness having a temperature below the upper limit of the molecularly orientable temperatures of the plastic material is clamped, and the central portion of the plastic material stock is introduced into a die cavity while compressing the central portion with an upper plunger and a lower plunger, thereby forming a hollow preform having a sidewall portion made from the plastic material which has been forced out from between the upper plunger and the lower plunger, while the sidewall portion is kept in contact with the side surface of the upper plunger kept at about molecularly orientable temperature. Thereafter, while the upper plunger is returning, a fluid under pressure is supplied into the hollow preform to expand radially the sidewall portion, so that the sidewall portion is brought into contact with the inner surface of the die cavity kept at a temperature below the lower limit of the molecularly orientable temperatures for cooling and solidifying. Thus, the sidewall portion of a plastic hollow article is formed from the sidewall portion of the hollow preform, and a plastic hollow article having a flange portion, the sidewall portion which is molecularly oriented, and a bottom wall portion is made.

대표청구항 ▼

A method of making a plastic hollow article having a flange portion, a sidewall portion and a bottom wall portion, at least said sidewall portion being molecularly oriented, which comprises clamping a peripheral portion corresponding to said flange portion of a flat, molecularly orientable plastic m

A method of making a plastic hollow article having a flange portion, a sidewall portion and a bottom wall portion, at least said sidewall portion being molecularly oriented, which comprises clamping a peripheral portion corresponding to said flange portion of a flat, molecularly orientable plastic material stock of substantially uniform thickness having a temperature below the upper limit of the molecularly orientable temperatures of said plastic material, such that the material of the peripheral portion will not flow radially, inwardly; thereafter introducing the central portion of said plastic material stock substantially corresponding to said bottom portion into a die cavity by moving a first plunger and a second plunger in said die cavity while compressing said central portion between said first plunger and said second plunger, said first and second plungers being moveable between an original position and a second position, said die cavity having a straight, axially extending inside surface with a clearance between said inside surface and a side surface of said first plunger being larger than the thickness of a sidewall portion of a hollow preform to be formed, such that the compressing force by the first plunger and the second plunger is kept comparatively high in a beginning stage of introducing the plastic material stock into the die cavity, thereby causing the plastic material forced out to substantially fill the space between the first plunger and the inside surface of said die cavity, and thereafter the compressing force is reduced and said introducing is continued to said position thereby permitting the filled plastic material to be drawn in the axial-direction, to form a hollow preform having a sidewall portion made from the plastic material which has been forced out from between the first plunger and the second plunger, said sidewall portion being kept in contact with the side surface of the first plunger kept at about molecularly orientable temperature; withdrawing the first plunger from said second plunger to said original position thereof and supplying a fluid under pressure, during said withdrawing, into said hollow preform to expand radially said sidewall portion, so that said sidewall portion is brought into contact with the inside of said die cavity kept at a temperature below the lower limit of said molecularly orientable temperatures for cooling and solidifying, whereby said sidewall portion of said plastic hollow article is formed from said sidewall portion of said hollow preform.