Method of molding hollow bodies

In a method of molding a hollow body by:

• (a) continuously extruding downwardly into free space a melt of synthetic resin from a die thereby forming a moving tubular parison having a free end;
• (b) closing and sealing the free end with a means for forming a bottom thereby forming a closed end on the parison;
• (c) holding the parison with a means for holding;
• (d) cutting the parison with a means for cutting thereby forming a cut-off tube with the closed end;
• and
• (e) blowing a fluid into the cut-off tube retained in a mold thereby forming said hollow body;
• the improvement wherein:
• (1) steps b-d are performed in a successive order of (c) holding, (d) cutting, and (b) sealing;
• (2) the die accommodates a mandrel extendable in the direction of extrusion to provide a mandrel extension having an end;
• (3) the means for forming a bottom comprises a frame surrounding the path of movement of the parison, sealing members circumferentially spaced about the frame and radially movable, and means for moving said sealing members, and the step of closing and sealing comprises moving said sealing members from outside the parison toward its center, bringing said sealing members into contact with each other while filling the resin of the free end into a space provided between said end of said mandrel extension and said sealing members to form the closed end which is a bottom;
• (4) the means for holding holds the portion of the moving parison which becomes the cut-off tube by its outside surface and is positioned at a distance away from the die in the direction of extrusion, the means for cutting is positioned between the die and the means for holding, and the means for forming a bottom is positioned between the means for cutting and the die;
• and
• (5) the method further comprises during the steps of cutting and sealing, moving the means for forming a bottom, the means for cutting, the means for holding, and said mandrel extension at substantially the same speed and in substantially the same direction as the movement of the parison extruded from the die.