Abstract: Apparatus for producing plastic pipes by an extrusion process in which the wall thickness of the plastic pipe is controlled by the takeaway speed at which a soft plastic pipe is removed from a metal sizing sleeve. To measure the wall thickness of the soft plastic pipe advancing through the sizing sleeve for regulating the takeaway speed, a transducer emits ultrasonic sound through a plastic transmission line mounted in or on the sizing sleeve and interposed between the transducer and the plastic pipe. The time interval between the emission of a sonic pulse by the transducer and the detection of a reflected sonic pulse from the inner wall of the advancing soft plastic pipe is a function of the wall thickness of the plastic pipe in a soft plastic state.

Abstract: 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.

Abstract: 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.