| 摘要 |
PURPOSE:To prevent shear of thickness at a product section of a parison in the longitudinal direction by stopping discharge of the parison after a lapse of time that the bottom end of the parison reaches a predetermined terminal position. CONSTITUTION:Discharging of a parison is started and the parison descends at a fixed descending speed. When the bottom end of the parison reaches a height of an optical sensor 20, the optical sensor 20 detects it and sends a signal to a control device. A pre-pinch device 30 is moved forward so as to pre-pinch the parison P and quantity of die gap of the parison thickness is controlled so as to change from a start point b1 till a terminal point b2 in sequence. At the time that the parison P reaches an entire length L, the discharging of the parison P is stopped. Thus, the parison P changes in thickness. In a stage of mold clamping, a length corresponding to a product section B among the thickness changes is pinched by a pair of right and left molds 8A, 8B for molding, so that an obtained product has a desired thickness change, thereby saving resources and improving yield. |
