Process of stretch-blow molding

摘要

The process and apparatus of stretch-blow molding a preform in the axial and radial directions into a biaxially oriented container by the use of a stretching rod assembly and a blowing of pressurized fluid. In the axially stretching step, the surface area of the working end of the stretching rod assembly is changed. The axially stretching step is carried out through a plurality of stages each of which provide a different surface area of the working end of the stretching rod assembly. The apparatus preferred to carry out this process has a plurality of concentrically disposed stretching rods and an tip piece fixedly mounted on the working end of each of the stretching rods and having an external diameter at the surface area different from those of the other stretching rods. When such stretching rods are driven independently or in combination, the bottom surface area of the stretching rod assembly to be engaged by the inner bottom wall of the preform can be easily changed.