Double tube with petal shape and method of manufacturing the same

Abstract

A double tube includes an inner tube having a corrugated petal shape in a wave form in an outer tube. The double tube is manufactured by a method including: inserting the inner tube into the outer tube and coaxially disposing the inner tube and the outer tube; inserting a plurality of petal forming bars into a space between the outer tube and the inner tube and arranging the petal forming bars along a circumferential direction at predetermined intervals; disposing an assembly of the outer tube, the inner tube, and the petal forming bars in a mold of a hydroforming machine; supplying a fluid in the inner tube while applying a pressure to the inner tube in an axial direction to expand the inner tube; and separating the petal forming bars from the space between the outer tube and the inner tube.

Dependencies are inferred from the claim text.