Plastic underdrainage tube

摘要

A plastic underdrainage tube of generally reticular configuration formed by integrally extruding a plastic material is disclosed. The tube is basically composed of axially spaced apart annular bands having relatively greater thicknesses to reinforce or impart to the tube a high stability against surrounding pressures, and circumferentially disposed longitudinal strands in thicknesses less than those of said annular bands. These longitudinal strands are closely spaced apart along the circumference of the tube to form drainage openings between the circumferentially adjacent strands, the openings being disposed across the entire periphery and lengthwise of the tube to allow the water inflow over the entire wall portion thereof. Each of said strands is blended into or integrally joined at its intersections to the annular bands so as to be mechanically supported by said annular bands of reinforcing members, thus improving the overall strength of the tube to withstand the surrounding pressure while maintaining the amount of plastic material to be used at a low level. In another version, longitudinal strands are formed in sinuously corrugated configuration and blend at their valley portions into the annular bands to define the drainage openings between the ridge portions of the adjacent strands. The external forces acting on the ridge portions can be spreaded or decentralized by the corrugation of the strands and supported by the adjacent annular bands of reinforcing member.