JPS57187111A - Manufacture of double-bend pipe - Google Patents

Abstract

PURPOSE:To easily manufacture a double-bend pipe by passing and inner pipe through an outer pipe, and by inserting the inner pipe into the outer pipe having straightly cylindrical parts respectively at both the ends of a 90 deg. bent cylindrical part, and pressing the outer pipe from both sides to deform the pipe into ''Koban''(an old Japanese coin having an elliptical shape) shape against the elasticity fo the pipe. CONSTITUTION:Stays 3 are fixed to the positions near to cylindrically bent part (b) of the outer circumference of a straightly cylindrical part 2 at the side of large-sized end part, at equal intervals in the circumferential direction, before passng an inner pipe through an outer pipe. At this time, a bend of a lower bent part 3(b), perpendicularly connecting a lower step piece 5 of the stay 3 and the bottom end of a stay piece 3', is bent reversely and strecthed to make the stay 3 lie down around the part 2. Next, a small-sized straightly cylindrical part 2' of the inner pipe is inserted into a large-sized straight part 1 of the outer pipe to press the part 1 from both sides and deform it into an elliptic shape or ''Koban'' shape against its elasticity in order to force the inner pipe into the outer pipe and to pass it through the latter by expanding the width W of the inner surface at the inside of 90 deg. bent outer pipe and the inner surface at the outside of the part 1. Next, the upper step piece 4 is fixed to the inner circumference of the part 1 after raising up the laying piece 3' to back it into an original form.