| 摘要 |
PURPOSE:To manufacture inexpensively a differential thickness pipe having a stepless inner surface and a wall-thickness difference to its outer surface direction at its thick-walled part by pushing out the thick part of a sheet to the pipe outer-surface direction and forming a titled pipe at the same time by a die having a target step difference. CONSTITUTION:A sheet material having thickness differences in its both surfaces is inserted between a punch 7 and a die 9, and is bent in proportion to the lowering of the punch 7. The lower surface of a thin sheet-part is first brought into contact with a part 10 of die 9 corresponding to a thin-walled part of pipe; and successively the inner diam. side of a thick-walled part is pushed out to the outer diam. side of pipe by a pressing part 8 of punch 7, and the sheet material is bent to a target radius of curvature at the same time. In this way, the sheet material is transferred by degrees in the circumferential direction to bend a tubular body stepwise; then a differential thickness pipe having no step in its inner surface and step differences at its outer-surface side, is obtained. |
