| 摘要 |
1,039,063. Rolling. CALUMET & HECLA Inc. May 27, 1965 [Dec. 28, 1964], No. 25026/65. Heading B3M. A rotating tubing T has a preferably localised fine pitch helical finning 26, Fig. 6 (not shown), produced thereon, by three rotating rolls, R which are fed radially towards the tube axis, the axes of the rolls being placed at a taper angle B1. Fig. 3 (not shown) and at a skew angle A 1 , Fig. 2 (not shown), relative to the tube axis at the start of the operation, and the angles being continuously decreased to the angle B 2 and increased to the angle A 2 , during rolling. Each roller comprises a plurality of discs 10, 12, 14, 16 &c., each of uniform thickness, but having peripheries which progressively increase in diameter and thickness. The tube is rotated and fed axially through the rolls by its engagement with the latter. The crests of the fins may be of the same, greater, or less diameter than the diameter of the unfinned tube portions, and during rolling a mandrel may be located within the tube. The fins may be of single start, two start or three start. |
