Apparatus for measuring and controlling the wall thickness of plastic pipes

摘要

In the manufacture of plastic pipes by the extrusion process, the inside diameter of the pipe and, therefore, the wall thickness of the pipe is controlled by the takeaway speed at which the molten plastic pipe is removed from the sizing sleeve. An ultrasonic transducer is disposed at the upstream end of a sizing sleeve to provide signals representative of the thickness of the molten pipe advancing in the sizing sleeve. These signals are sent to devices for comparing the measured thickness of the molten plastic pipe with the desired thickness of the molten plastic pipe for producing a correction signal. The correction signal is employed for correcting the takeaway speed at which the molten plastic pipe is removed from the sizing sleeve.