| 摘要 |
PURPOSE:To obtain a pipe provided with fins whose surface area (radiating surface) is remarkably large and and at cost, by forming a wave-form continuous pleats whose pitch is enlarged inward gradually on the internal circumferential side of a spiral fin. CONSTITUTION:Steel strip is made into corrugated steel tape 13 by passing the steel strip through a gearing face of a gear 12 for wavy processing and forming. The corrugated steel tape 13 is led out through a guide slit 18 and a circular-arcform leading slit 19 so that the tape 13 is wound round a pipe 1 perpendicularly to its external surface, spot welding 20 between a starting edge of the inner circumference of the corrugated steel tape 13 and the external circumference of the pipe 1 is made, to begin with, then the external circumferential side of the corrugated steel tape 13 is extended in a plane state and the inner circumferential side of the same corresponding to the extended amount is contracted as pleats part through the rotation of the pipe 1 and movement of a mobile stand, while the corrugated steel tape 13 is wound securely round the pipe 1 gradually in a state standing upright perpendicularly to the external circumferential surface of the pipe 1, through which a fins 24 are formed. Then the spot welding between the terminal edge of the inner circumference of the corrugated steel tape 13 is made similarly to the case of the starting edge of the steel tape 13. |
