| 摘要 |
PURPOSE:To provide a method of productively manufacturing a synthetic resin pipe with spiral inner surface ribs or grooves and an extrusion mold used for the manufacture without causing any deformation such as distortion or the like after piping and adversely affecting the spiral ribs so that they are reduced in size by hot drain or the like flowing therein, and further without impairing the drainage capacity semipermanently. CONSTITUTION:The mold is characterized in that a support shaft is extended from the core 21f of an extrusion mold, and a tip end ring 23 or tip end core as a diameter-enlarged member is supported on the support shaft, and further parison 5a extruded by the reaming member is expanded from its inner part to be pre-molded into an outer diameter approximately equal to the inner diameter of an inlet of forming means or slightly larger than the diameter, and thereafter the parison is passed through the forming means. |
