| 摘要 |
PURPOSE: A multi pipe is provided to increase durability and restoring force to external force and to reduce manufacturing cost by integrally forming a reinforce pipe outside an inner pipe as to be filled with a concrete material or a junction material. CONSTITUTION: A multi pipe comprises an inner pipe(2) formed of circular or rectangular shape and on whose outer peripheral a spiral outer rib(6) is formed, a reinforce pipe(4) integrally filled on an outer peripheral of the inner pipe. The spiral outer ribs are vertically formed on the outer peripheral of the inner pipe in a certain interval so as to extend one direction along the entire outer peripheral with constant pitch and lead angle, thereby forming spiral shape. To increase coupling force between the inner pipe and the reinforce pipe, a coupling protrusion(8) is integrally formed on a leading end of the outer rib.
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