GROOVED TUBE, DOUBLE TUBE, AND ITS MANUFACTURING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a grooved tube 162 of new structure, a double tube 160 and its manufacturing method. SOLUTION: The grooved tube 162 used as an inner tube of the double tube 160 has a grooved part M having a spiral groove 162a extending along the axial direction of the tube, and an enlarged tube part K gradually enlarged into a circular cross section from the grooved part M. The enlarged tube part K gradually enlarged into the circular cross section from the grooved part M so as not to be smaller than the outer diameter of the grooved part M is provided on the end-side of the grooved part M to form the grooved tube 162 stable in the formed range of the spiral groove 162a in the axial direction of the tube. Further, the outer diameter (the maximum diameter part) as the grooved tube 162 is stabilized. COPYRIGHT: (C)2008,JPO&INPIT