| 摘要 |
A perforated corrugated tube of thermoplastic or like material in which the tube is made with radially inwardly extending blisters in the valleys thereof which are sheared off to provide perforations through the valleys of the corrugations, the apparatus and method being characterized in that the perforated corrugated tube is made in a continuous manner by molding the tube with the blisters in a traveling mold and shearing the blisters as the tube emerges from the traveling mold. A further characterizing feature of the perforated corrugated tube herein rendering it useful as for highway drainage and frostproofing purposes, is that it is formed with a smooth walled channel-like bottom portion having upwardly diverging side walls merging with the remaining perforated corrugated portion of the tube.
|
