| 摘要 |
The present invention provides a multilayer synthetic resin pipe having spiral ribs, and an extrusion molding method and apparatus for manufacturing the same. The multilayer synthetic resin pipe (70) of the present invention includes a plurality of spiral ribs (74) and a plurality of through holes (73). The multilayer synthetic resin pipe (70) has increased strength and superior heat and noise insulation ability, considering the required amount of material. Furthermore, in the present invention, an inner layer (71) of the pipe (70) is thicker than an outer layer (72), so that the lifetime of the pipe is extended. As well, the through holes (73), defined in the inner and outer layers of the pipe, are disposed in a multilayered arrangement, so that, even if the multilayer pipe has a large diameter, spiral ribs do not buckle during a process of manufacturing the pipe. |
