| 摘要 |
PROBLEM TO BE SOLVED: To manufacture a pleat part, whose cross sectional shape is optional, with a simple equipment by arranging the same number of first, second pressing boards in a peripheral direction alternately on an outer periphery in a pleat part molding section of a pipe material, while the first pressing boards are deeply pushed and driven in a centripetal direction and the second pressing boards are shallowly pushed and driven in the centripetal direction. SOLUTION: A pipe material 1, whose both end parts are contracted in advance, is positioned and fixed. Each of a first pressing board 8 is deeply pushed in a centripetal direction till almost a center point of the pipe material and, simultaneously, each of a second pressing board 9 is shallowly pushed in the centripetal direction. A hollow part 10 is formed at a pipe material part 3 of the pipe material 1 by the first pressing board 8. An arc shape peak part 11 is formed at a pipe material part 3 between the first pressing boards 8, 8 by the second pressing board 9. A transverse sectional shape of the pipe material part 3 becomes a petal shape likely to be a triangle shape and forms a channel 14 being constituted with the petal shape pleat part 12. The first, second pressing boards 8, 9 are arranged in a peripheral direction at an equal interval and it is preferable that a pressing face of the second pressing board 9 is formed longer in peripheral direction than that of the first pressing board 8.
|
