| 摘要 |
PCT No. PCT/FR94/00646 Sec. 371 Date Jan. 5, 1996 Sec. 102(e) Date Jan. 5, 1996 PCT Filed Jun. 2, 1994 PCT Pub. No. WO94/29661 PCT Pub. Date Dec. 22, 1994Tube (1) internally grooved by helicoidal ribs (2) having a helix angle of 5 DEG to 50 DEG , an apex angle (alpha) of 30 DEG to 60 DEG . The tube is characterized in that the ribs (2) form a periodic profile comprising at least two ribs of different heights, one designated high (2h) of a height Hh, and the other designated low (2b) of a height Hb, with a ratio Hb/Hh of 0.40 to 0.97, each high rib being bordered by a flat-bottomed groove (3). |
