PURPOSE: To produce a pipe of high quality without waste, by controlling the heat treatment by a heating position signal from an outer diameter measuring apparatus in case the outer diameter of an extruded synthetic resin pipe exceeds the reference value.
CONSTITUTION: The pipe P extruded from an extruder 1 is passed via an outer diameter limiting apparatus 4, a cooler 3 and a drawing apparatus into a heater 7 and is then passed through the automatic outer diameter measuring apparatus 8 to a cutter 6. If the part of the pipe passing through the automatic outer diameter measuring apparatus is strained to deform its cross section to an ellipse having a major axis in the vertical direction, the upper part and lower part of the pipe P passing through the heater 7 is heated by infrared heaters 21, 21 respectively that are operated by the outputted heating position signal, so that the internal stress can be eliminated and the roundness is substantially restored. In this manner, an abnormal outer diameter section that should be corrected can be finely controlled electrically to save manhours in comparison to the prior art.
HORIMA YUKIO
IMAMURA NOBUO
NAKAJIMA TOSHIAKI
