| 摘要 |
PURPOSE:To apply a convex mark on the outer surface of a tube simultaneously with an expansive molding thereof by expanding the tube by a vacuum method using an expansive tube molding cylinder having holes or flutes shaping a character, a symbol and other patterns. CONSTITUTION:An expansive tube molding cylinder 6 having flutes 12 shaping a numeral, character, symbol and the other patterns along with a number of tiny holes 11 is used to perform an expansive tube molding of a raw pipe 1 in a vacuum molding unit. After the expansive tube molding of a tube 7, an electromagnetic valve 8 is opened and a cooling water 9 is fed into a vacuum layer 5 to cool the tube 7. Thus, a specified marking is made possible during the expansive tube molding. |
