PURPOSE: To enhance the safety and efficiency for the work of mending the inner surface of a large-bore duct by constructing a mending device from a cylindrical body made from an elastic material with a drain pipe, a passage pipe, and a fixing rope which are located respectively at the lower part, center part, and each side of the cylindrical body, and mounting a guard sponge plate on its outer periphery.
CONSTITUTION: Air is injected from an air suction hole 16 in a mending device 11 made of an elastic rubber material, so that the device 11 is formed into a cylindrical body. A drain pipe 12 is provided therein to force water in a duct through the drain pipe 12 so as to perform operations safely. Next, a communicating passage pipe 13 is provided in the center of the inside to allow easy passage from each side. Further, safety valves 17 are provided on each side 14 of the cylindrical body to keep safety. A guard sponge plate 24 is mounted on the outer peripheral surface 15. The plate 24 is 10 to 50mm thick and 10 to 50 degrees in hardness. Subsequently, at the stage of air injection, glass fibers and floss-silk-like glass are stacked, impregnated with a resin, and bonded to the plate 24. A mending material is pressed against the inner surface of the duct by the plate 24. Air for mending is vented by means of linear elements 25. Therefore, the mending work can be completed in a short time.
