Control system for retention of constant internal pressure in a blown tubular film includes a controler with a component portion and a control unit with proportion characteristics

摘要

Pressure difference between the air inside the tube(1) and the air outside is used as a control variable. A controler(4) with a component portion receives the measured variable and produces an appropriate control signal which is fed to a control unit(5) with proportional characteristics for varying the internal air pressure. An elastic gas storage unit(6) is located between the control unit and the tube blowing head(2). The control unit(5) may comprise a gas pump with a performance electronic circuit. Air is taken from the atmosphere to vary internal pressure in the blown tube(1). The control unit may alternatively be a control valve with a performance electronic circuit and in this case internal pressure is produced by compressed gas. The elastic gas storage unit(6) is a rubber bag. A set value may be created by the controler which enables the blown tube diameter to be finely controled.