| 摘要 |
PROBLEM TO BE SOLVED: To provide a riser which forms a bottom structure resistant to the load and impact of a sewage flow, and which is equipped with durability high enough to make sewage stably flow down without a deterioration in its functionality, even on the occurrence of the risk of the intrusion of groundwater into the bottom of the riser or the action of groundwater pressure. SOLUTION: A spiral guide passage is provided inside a riser body 11, so that the sewage spirally flowing down can be discharged from an outflow port which is provided in the lateral side of the bottom of the riser body. In the bottom 20 of the riser body 11, an inside surface layer 21 with abrasion resistance and impact resistance, and a substrate layer 22 inside the layer 21 are laminated, and connected together for integration by a fixing implement 30; and a reinforced resin layer 23 is superposed on the outside of the substrate layer 22. COPYRIGHT: (C)2007,JPO&INPIT
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