PURPOSE: To provide hollow tubes for greenhouses which can be inexpensively produced using a conventional hollow tube manufacturing facility, has various couplings, such as a cross, with high restraint capability, and additionally is easily bendable.CONSTITUTION: A hollow curved tube having an octagonal cross section which is a curved portion in which an intermediate portion is curved in an arcuate shape with an eaves portion having a straight end at one end and with a roof portion having a substantially straight end at the other end, a curved outer surface positioned on the outermost side of the curved portion and a curved inner surface positioned on the innermost side of the curved portion being flat surfaces. The surface of at least a part of the hollow curved tube and the hollow straight tube is satin processed to form a roughened surface to have an increased friction coefficient.SELECTED DRAWING: Figure 2【目的】従来の中空管製造設備を利用して安価に製造可能で、十字等の各種接手の緊締強度が高く、しかも曲げ加工容易な温室用中空管を提供すること。【構成】長さ方向全体に亘って直線状の断面八角形の中空直管と、一方端が直線状の軒部で他端が略直線状の屋根部で中間部が円弧状に湾曲した湾曲部である断面八角形の中空湾曲管と、の組み合わせからなる温室用中空管であって、中空湾曲管は、湾曲部の最も外側に位置する湾曲外面と最も内側に位置する湾曲内面が平坦面とされている。また、中空湾曲管と中空直管の少なくとも一部の表面は、梨地加工されて粗面が形成され摩擦係数が増大されている。【選択図】図２
