| 摘要 |
1,240,380. Making tubes; drawing. NIPPON KOKAN K.K. 11 July, 1969 [13 July, 1968], No. 34949/69. Headings B3A and B3P. A longitudinally finned metal tube 2, Fig. 6, is made from a tube blank by forming a thickened portion on the tube at the region where each fin is to be formed and cold drawing the formed tube through a fin-forming die 5 using a cylindrical plug 11. The tube is formed with the thickened portions by rolling or drawing. In the latter case a circular die 8, Fig. 3, is used with a shaped plug 7, the plug may have an elliptical, generally rectangular or sector crosssection. |
