GB1303122A - - Google Patents

Abstract

1303122 Making multiple bore helically corrugated heat exchanger tubes; twisting; corrugating TURBOTEC Inc 16 March 1970 [8 Sept 1969] 12497/70 Headings B3A and B3E [Also in Divisions F2 and F4] A method of providing a double-walled tube element U as in Fig. 1, of steel, copper, or aluminium, where the outer tube 11 has helical corrugations 18-21 in its wall, consists in a forming in a tube 11 a plurality of helical indentations 43, Fig. 6, corresponding to the required number of helical corrugations, b inserting a thin-walled core tube 10 through the tube 11 and c applying a twisting torque to the tube 11 whereby the corrugations 18-21, initiated at said indentations 43, are formed in the tube wall and include inwardly directed portions engaging and locating the core tube 10, the latter having a thickness corresponding generally to that of the tube 11 so that the core tube becomes helically indented at 15 by the corrugations and located thereby. Fig. 4 shows apparatus for twisting the tube 11. One end of the tube is held by jaws 38 in a tail stock 37 and the other end of the tube is rotatably mounted in a headstock 39. The tailstock is controllably movable by hydraulic means 41, along the bed 34 as the tube 11 shortens during twisting. Alternatively the hydraulic means may be omitted. Centring collars (Figs. 5, 7, 8 and 10) may locate one or 'both ends of the core tube 10 within the tube 11. Alternatively no centring collars are provided (Fig. 9), alignment of the core tube being effected automatically by the helical corrugations in the tube 11 as they are formed.