GB554815A - Improvements in or relating to the manufacture of finned tublar members for heat exchangers and other purposes - Google Patents

Abstract

554,815. Making finned tubes &c. THORNTON, A. A. (Brown Fintube Co.). Sept. 2, 1942, No. 12373. [Classes 83 (ii) and 83 (iv)] [Also in Group XIII] Angular bending; welding.- Finned tubes for heat exchangers, boiler or furnace walls or other structures consist of one or more channel members first secured to the exterior of a tube and thereafter deformed so that each member forms a single hollow fin. As shown in Fig. 1 tubes 10 with fins 11 which are streamlined to transverse flow of fluids, are made by joining to the tubes preferably by resistance welding, the bases of a pair of channel fin members at a series of spots as described in Specification 554,813, and then bending the flanges and preferably welding the edges either continuously or at a number of spots 15. The operations may be performed by passing the tube and fin elements through rolls 20, 22, 24 for guiding the tube and rolls 21, 25 for aligning the fin members with electrode rolls 23 for welding the bases of the fins to the tubes. The electrodes may be connected to opposite terminals of the electric circuit. The welded assembly then passes through rolls 26, having tapered portions 28 and cylindrical portions 29 for forcing together the flanges, and then through electrode rolls 30 for welding the edges of the flanges together and is discharged from the machine through guide rolls 31. The rolls 23, 26, 30 are driven for feeding the tube through the machine. In a modified assembly the flanges are flattened together throughout most of their area leaving a hollow at 37, Fig. 4. A series of such members welded together at their edges may form the wall of a boiler. In another form with a greater degree of streamlining, the base of the fins may be secured as shown in Fig. 5 over about 90 degrees of the circumference of the tube and may be intermittently resistance welded thereto along three lines 43, 44, 45 either in a single or a series of traverses. In order to prevent strains in the structures due to expansion of the edges of the fin due to higher temperature thereof than the base portions, the fin may be slotted at 49 from the outer edges towards the base to a depth depending on the service for which the tube is intended. The slots may be cut either before or after the fin is secured to the tube.