| 摘要 |
PURPOSE:To control not only the discharging amount of cooling air but also the suction amount of the same and stabilize cooling effect by a method wherein an opening and closing signal for the discharge control valve of cooling air is fed back to the feeding valve of the cooling air to control the opening and closing of the feeding valve. CONSTITUTION:A product diameter detecting sensor 12 is equipped immediately above a frost line 11, whereat whitening of a transparent film is started, in order to control the width of film by passing cooling air between a guide tube 3 and the film. The output of the product diameter detecting sensor 12 becomes an opening and closing input for a control motor 16 for controlling the opening and closing of the discharging side valve through an operator 17. The control motor 16 is provided with a sensor 19 for detecting the opening degree of the valve and feedback of the output to a feed air side valve opening and closing control motor 15 is effected through another operator 18 to control the air feeding valve 5. Accordingly, perfect correction with respect to external turbulence is effected and, whereby, nonuniformity in thickness of inflation film, fluctuation of width of the film, generation of wrinkles or the like may be prevented. |
