| 摘要 |
PURPOSE:To make it possible to seal securely the ends of a ripple fin tube at the time of a leak test by a method wherein the inner surface of each end of the ripple fin tube provided with grooves in the inner surface thereof is made smooth. CONSTITUTION:To make smooth the inner surface 3a of each end of the ripple fin tube provided with grooves in the inner surface thereof, one end of a pipe 8 having a smooth inner surface is expanded and a groove forming punch 9a is inserted into the flared section 8a of the expanded end of the pipe 8 so as to form a plurality of grooves in the inner surface of the pipe 8 with the exception of the flared section 8a. After that, the flared section 8a is swaged or drawn to have the same diameter as the original part of the pipe 8. |
