| 摘要 |
PURPOSE:To prevent extremely thin wall thickness from developing at the peripheral end of the bottom part and consequently form uniform wall thickness over the whole region of the bottom part by a method wherein a biaxially stretching blow molding is realized in a form with no reverse curving and, after that, the reverse curving of the central part of the bottom part is realized through the deformating by simple caving-in. CONSTITUTION:By axially stretching a primary molding S1 under the condition that the central part of the bottom part of the molding S1 is softly pinched between the tip of a bottom pin 3 and the tip of a stretching pin 5 and, after that, forcing pressure fluid in the molding S1, a secondary molding S2 is obtained. After the pressure in the molding S2 is brought to near atmospheric pressure by exhausting the pressure fluid forced in the molding S2, the bottom pin 3 is advanced by the desired amount so as to push the central part of the bottom part S2b inwards in order to obtain a tertiary molding S3. The tertiary processed item S3 is released from a mold 1 under the state being held by a holder 4 and uniformly heated by a heater 6 up to a temperature to develop heat shrinkage so as to be deformed through shrinking to a quaternary molding S4. During the state that the temperature of the quaternary molding S4 is still within the stretchable temperature range, the molding S4 is assembled under the state being held by the holder 4 to a secondary blowing mold 2 so as to realize the stretching of the quaternary processed molding S4 to a product S. |
