PRODUCTION OF BENT PIPE

PURPOSE:To improve the dimensional accuracy of an inner diameter or a radius of curvature by mutually opposing one set of mutually symmetric split bent pipe main bodies each formed by bending a recessed groove part of which the inner peripheral surface has a semicircular cross-sectional shape to bond them. CONSTITUTION:One set of upper and lower split bent pipe main bodies 1, 1a having the same shape and a pair of left and right flange pipe bodies 2, 2a are preliminarily produced. Each of the bent pipe main bodies 1 is provided in such a state that its recessed groove part of which the inner peripheral surface 10a has a semicircular cross sectional shape is curved so as to have a radius R of curvature. Since this recessed groove part 10 is opened upwardly, the processing thereof is easy and becomes highly accurate. Circular arc ribs 12, 12a are provided to both left and right end surfaces 11, 11a of the recessed groove part 10 so as to extend outwardly and a plurality of bolt inserting holes 13... are bored in the recessed groove part 10 on both sides thereof and both bent pipe main bodies are fixed by bolts 14. Finally, the flange pipe main bodies 2, 2a are externally fitted to the protruding ribs 12, 12a.