| 摘要 |
A corrugated pipe manufacturing apparatus provided with a roller assembly consisting of a plurality of rollers rotatable at an equal speed and having a plurality of projecting rings respectively, each of which rollers forming a generally helical body due to the projecting rings and constituting a substantially one rotary shaft, and a synthetic resin supply unit for feeding synthetic resin in strips to the roller assembly, characterized in that the pitch, diameter and width of the projecting rings are reduced gradually in accordance with the coefficient of contraction of the synthetic resin strips, driven rings which can be rotated in accordance with peripheral speed of the outer edge portions of the projecting rings being provided in the roller valley portions between the projecting rings. Owing to such construction, the separation of the synthetic resin strips, which is ascribed to the contracting actions thereof, from the rollers and the vertical wrinkles (strain regarding the interior of the strips) which are liable to occur between the projecting rings and the valley portions can be prevented, and corrugated pipes having excellent molding stability, a high precision and a high durability can be manufactured.
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