| 摘要 |
<p>Page 10 An apparatus for producing helically wound double-walled fused thermoplastic pipes, corrugated outside and smooth inside. The apparatus includes extrude means forming two bands of a thermoplastic material, a former shaping the corrugated configuration of and helically winding the first extruded band, a cooled element pressing the second band to the inside of the corrugations and having passages communicating with the second band and with a vacuum means.</p> |
