Thin-walled plastic corrugated, perforated drain pipes prodn. - by maaking holes -crrrorugations in pipe while stilll plastically deforme

摘要

Thin-walled plastic drain-pipes with an axially corrugated wall contg. water inlet holes are produced by (a) extruding a thermoplastic tube, (b) corrugating the tube while it is still in a warm deformable state, and (c) making the holes by piercing the corrugated tube while it is still in a warm deformable state. Method provides easy hole formation without damaging the wall of the pipe. Size of the holes can be controlled to give efficient drainage.