| 摘要 |
<p>A cylindrical, perforated, land drainage pipe is fitted with an internal plaited sleeve, and when pulled, the sleeve narrows and elongates. The sleeve is made of an elastic threat of synthetic material, its unstretched dia, being the internal dia. of the pipe. The sleeve has ties by which another sleeve can be attached, to replace the existing one when that is pulled through the pipe to unclog it. For irrigation, the pipe has narrow pipes along its sides; the narrow pipes have perforations opening into the main pipe, and others opening into the ground. The main pipe may have a plaited sleeve. The narrow pipes have either plaited sleeves or wicks to conduct the irrigation water.</p> |
