| 摘要 |
A plastic material is fed through an extruder into a pipe moulding space (12) defined by an extrusion sleeve (4), a mandrel (9) and chill moulds (1, 2) moving in the direction of the central axis of the mandrel. When the pressure of the moulding space (12) deviates from a desired value, a gap is formed between the chill moulds (1, 2), and plastic material is squeezed into the gap, or grooves (13) of the chill moulds are filled up incompletely. In order to restore the pressure to the proper value, it is known to observe the produced pipe and adjust the speed of the extruder or the chill moulds on the basis of the deformations of the pipe. According to the invention, this slow and unreliable method is replaced by directly measuring the pressure of the material contained in the moulding space by means of a pressure sensor (14) which adjusts the speed of the extruder or the chill moulds. |
