| 摘要 |
An extrusion die, particularly for double-walled corrugated thermoplastic pipes, including an extrusion head, a nozzle, two concentric hollow mandrels carrying die lips and a cooled and vacuumed third mandrel. The vacuum is maintained between the third mandrel and the inner wall of the pipe by means of groups of channels, each such group having an independent vacuum pressure to prevent retraction of the wall from the mandrel until the wall is set and to allow adjustment of the pressure along the length of the mandrel. |
