MANUFACTURE OF FLEXIBLE TUBE FOR EXHAUST PIPE

PURPOSE:To prevent deformation of a titled tube during using by attaching a combustible stringlike body on an outer face of a metallic tube, passing it through an outer layer tube, bulge forming a bellows on the laminated tube and burning off the stringlike body. CONSTITUTION:A stringlike body 13 made of combustible material is attached on the outer face of a metallic inner layer tube 11 in longitudinal direction, and passed through an outer layer tube 12. A laminated tube thus formed is fed to a bulge forming die to apply liquid pressure on the inner face. The laminated tube is deformed to the outside along undulation formed on the inner face of the die, and a bellows consisting of crest parts 15 and trough parts 16 is formed. Then, the laminated tube is heated to burn off the stringlike body between tubes 11, 12. Combustion gas is discharged from through holes 15 provided on both ends 18 of the tube 12 to obtain a cavity 17 in place of the stringlike body 13. Thus, the escape ways for residual air or oil are provided and the deformation of inner and outer tubes during using can be prevented.