Control of tubular film size.

摘要

An apparatus for gauging and controlling the circumference of extruded thin-film tube (14) in an extruder system in which thin-film is extruded as a tube from an annular die (11) and pulled along a predetermined path. The apparatus includes one or more ultrasonic-ranging-transducers (60) spaced around the tube exterior oriented to transmit and receive sonic pulses along paths generally normal to the tube surface, energizing means for each transducer to transmit sonic pulse to and receive a return pulse from the tube surface, means associated with each transducer for generating a range signal representative of the time required for the pulse to travel to and from the tube, and means (51, 58, 58') responsive to the range signals for varying the quantity of air within the tube to control tube diameter.