| 摘要 |
The invention relates to a method for continuously producing plastic tubes by biaxial drawing consisting in producing a blank (E) by extrusion, heating said blank to a molecular condensation temperature, radially dilating it by the internal pressure of a fluid applied between two axially distant obturator rings ( 7, 11 ) and in carrying out a calibration ( 8 ) and cooling ( 9 ) associated with an axial tension produced on a tube at the output thereof. A pressure opposite to the internal pressure is applied to the blank wall from the outside in at least one area which is exposed to the radial dilation. Said opposite pressure is selected such that it is lower than the internal pressure, thereby preventing a counteraction to said dilation and remaining sufficient in order to control the dilation growth in such a way that it is possible to ensure a substantially constant material thickness on the same circumference. |
