| 摘要 |
1400066 Perforated pipe F KIRCHNER and A KIRCHNER [trading as FRANKISCHE ISOLIERROHR-U METALLWARENWERKE GEBRUDER KIRCHNER] 20 July 1972 [20 July 1971] 34000/72 Heading F2P A perforated corrugated plastics pipe 1 has a sheet 5 of plastics film secured thereto by engagement of both the film 5 and a locking cord 6 in a series of undercut depressions 3, each depression 3 being formed in an external crest 4 of the corrugations. The depressions are conveniently in line in the longitudinal direction of the pipe-line. Preferably each crest 4 bears a depression 3, the depth of which is substantially the same as the depth of the corrugations and the bases of the depressions as coplanar. The plastics is preferably P.V.C. and the pipe is preferably extruded as smooth tube and subsequently corrugated and depressed in travelling moulds. |
