| 摘要 |
<p>A plastics corrugated pipe (1) provided with wave crests (3) and wave valleys (2) comprising apertures (4). A water permeable surrounding covering (13) engaging the tops of the wave crests (3) is heat-shrunk onto the plastics pipe (1), said surrounding covering (13) consisting of a foil layer 5 supporting air filled cushions (6). An outer foil layer (7) engages the tops (14) of the cushions. Two layers of air filled cushions (6, 6a) may be connected with each other. The outer foil layer (7) and the inner foil layer (5) are provided with perforations (8, 9). Perforations (11, 17) may also be present in the top (14) and bottom of the cushions (6).</p> |
