| 摘要 |
A process for producing a plastic pipe having an oval crosssectional shape with a high dimensional precision, which comprises conducting a roughly shaped plastic pipe having an oval cross-sectional shape, which is in the softened state and composed of a large-diameter portion, a small-diameter portion and transitional portions connecting them to each other, to a cooling tank while its shape is adjusted by being passed through a forming tube with its large-diameter portion down; cooling the form-ad-justed plastic pipe in the cooling tank by dipping the large-diameter portion or both the large diameter portion and a part of the transitional portions contiguous thereto in a cooling bath, and subjecting that portion of the form-adjusted plastic pipe which is out of the cooling bath to a shower of a cooling liquid. This plastic pipe is useful for a drainage or sewage system. |
