| 摘要 |
1,237,097. Extruded irrigation pipe. F. BUTRUILLE. 19 June, 1968 [22 June, 1967], No. 29138/68. Heading B5A. [Also in Divisions C3 and F2] An irrigation, or soaking, conduit 5 has a wall structure of intercommunicative cellular plastics material, e.g. formed ethylene polymers and copolymers, and an outer surface which, at normal operative pressures, is impervious to water, the wall having at least one score line 9 which penetrates the outer surface and destroys its water impervious nature. As shown, the conduit has four longitudinal score lines 9. Alternatively, a single helical score line, or a number of axially-spaced, ring-shaped, score lines, may be provided. The conduit is formed by extruding a hot hollow conduit from a foamable thermoplastic resin, e.g. polyethylene, with an alkali metal bicarbonate gas-releasing agent and a small amount of naphthylenic-type pail oil, the extruding taking place at about 300- 360‹ F. Air is then forced through the extruded conduit to expand it as it passes through the extrusion die and into a cooled sizer which cools, sizes, and hardens the conduit to form a water impervious external wall surface. The air injection also aids in connecting the cells of the foamed plastics. Each score line is then made in the external wall surface. |
