| 摘要 |
The pipe i.e. integrally rolled ribbed type pipe (1), has ribs (2) running helically on a pipe exterior. Primary grooves (6) are found between the adjacent ribs. An undercut secondary groove (8) is arranged in an area of a groove base (7) of the primary grooves. A pair of oppositely lying material edges (9) extends continuously along the primary grooves. A cross section of the secondary groove is varied in space intervals without influencing a shape of the ribs. A distance is formed between the edges such that the distance is varied in spaced intervals to form local cavities (10).
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