| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce weight and cost and to improve, for example, durability and smoothness of the surface in a hole by forming a duct with the foamed body of synthetic resin with a specific density. SOLUTION: The large hole of a duct 1 becomes an insertion hole 2 of a cable and a small hole becomes a PC steel rod insertion hole 3 for passing a PC steel rod. The duct 1 is made of foamed polystyrene and is formed by a mold with a core so that the inner surfaces of the holes 2 and 3 keep to be smooth. Therefore, when the cable is passed through, the friction is small to prevent the cable from being damaged. Even a long pipe 1 can be easily manufactured with a high dimension accuracy by a large mold. Also, by changing the core dimension, holes of various types of apertures can be easily and accurately formed and the number of holes can be freely selected. The pipe 1 is extremely light and can be operated and expanded easily and at the same time cannot be damaged. Also, it cannot be corroded even if it is buried under ground and is highly durable.</p> |
