| 摘要 |
<p>PROBLEM TO BE SOLVED: To realize a long span for handhole laying interval, by providing a plurality of projected strips extending on the outer peripheral surface of pipe in the pipe shaft direction, thereby reducing resistance when inserting a cable protection pipe to the inside of a conducting passage. SOLUTION: Many projected strips A, C extending in the pipe axis direction are provided on the outer peripheral surface of a cable protection pipe 1. Therefore, when pulling the cable protection pipe 1 to the inside of a conducting passage, the top of projected strips A, C may contact with the inner wall of the conducting passage, for example, and the inner wall of the conductive passage may contact with the outer peripheral surface of the cable protection pipe 1 at the top portion of the projected strips A, C. By a decrease in the contact area, the frictional resistance decreases greatly, and forces for pushing or pulling the cable protection pipe 1 can be reduced. As a result, if the pushing force or pulling force is almost identical, the unit length of a cable protection pipe 1 can be increased. Further, the span of the handhole laying interval can be increased.</p> |
