| 摘要 |
PURPOSE: To produce a double-wall pipe by modifying the profile of a pipe made of a thermoplastic material by forming integrally a great number of ribs on the outer circumference of the pipe longitudinally with intervals and by bending and deforming the ribs to enable to make easily double walls having smooth surface. CONSTITUTION: By extruding a thermoplastic material parison from an extrusion die 22 through an extrusion nozzle 14 and expanded outlet channel into a space between a plug 32 and grooves 50 of an endlessly moving (rotating) mold tunnel 12, and at first under the cooperation with the adjoining mold tunnel 12, a ribbed tube having ribs 60 whose foot part is thicker than the top part formed on the outer circumference of the tube with equal pitches is mold formed successively. Next, after that the mold tunnel 12 is separated, the formed ribbed tube is passed through a sleeve 70, and the thinned top part of the ribs 60 is bent and deformed. Then, by overlaying the top part on the foot part of the rearward adjoining rib 60, the outer wall of the pipe is formed. |
