Patent GB-1393461-A (GB)
Title: Process and apparatus for making metal tubing continuously from a metal strip
IPC: G02B6/44
Filed: 1972-04-21
Abstract: 1393461 Making metal tubing; skelping; swaging; drawing; welding by fusion J VALDECK 21 April 1972 [21 April 1971] 18665/72 Headings B3A B3E B3H B3P and B3R A method of making metal tubing continuously from strip 13 comprises passing the strip through an aligned series of mating, forming rolls 27, 28, 32, 33, 36, 37, to form it into a tube, passing the formed tube into an inert gas chamber 56 and between a pair of pincher rolls 57, Fig. 4, positioned within the chamber, welding the formed tube downstream of the rolls 57 and quenching the welded tube downstream of the welding point prior to further working. The tubing is suitable for making hypodermic needles. Tube forming, Fig. 1.-Stainless steel strip is fed from a rotary table 12 to a wiping unit 15 where it is cleaned with solvent by a pad 17 and wiped dry by a pad 18. A roll 21 aligns the strip horizontally and rolls 23, 24, 26 centre it with respect to the forming rolls. The strip passes through three pairs of horizontally mounted forming rolls 27, 28, 32, 33, 36, 37, and stabilizing guide rolls 31, 34, between the forming roll pairs. An internal gas lance 42 enters the partially formed tube as it passes through rolls 41, 41. The formation of the tube is continued by forming roll pairs 46, 46, 49, 52 and guide rolls 43, 44, 47, 48, and a final pair of forming rolls 53, 54 bring the edges of the tube into abutment. The roll 49 is fitted with a spring steel blade 51 which aligns the seam for welding. Welding and quenching. Fig. 4.-The formed tube passes through a bush 55 into the gas chamber 56. The pincher rolls 57, 57, are horizontally adjustable by a knob 59 and are electrically insulated by thrust washers (61), (61<SP>1</SP>) and bearings (58), Fig. 5 (not shown), which may be of nylon. Welding is performed by a D.C. heli-arc welder 74 having a tungsten electrode 76 and shield 77 through which a helium-argon mixture is passed, the same mixture being fed to the interior of the tube by the lance 42. Eddy currents are substantially eliminated by the insulation of the rolls 57, 57, and by a carbon brush 63 bearing on the tube immediately downstream of the welding point. The gas chamber 56 is earthed at 79 and it is cooled by passing water through channels 78. The water passes to a quenching chamber 66 via a pipe 123, channel 71 and openings 72. The tube is welded at 2425 F. and is rapidly cooled through the carbide precipitation range of 900- 1400 F. in the chamber 66. The quenched tube is wiped by a bush 67, the surplus water falling into a drip box 68 and passing to a drain 73. The welded tube then passes through pairs of sizing rolls 81, 82, 83, 83, 84, 86, Fig. 1, and is cut to length on a rack 88. Tube drawing, Fig. 8.-The welded tube 64 is held in a clamp (226) or (227) of a drawing unit (200), Fig. 10 (not shown), and a mandrel (201) is inserted into the tube by a puller unit (229). The mandrel is recessed a short distance in the tube, e.g. 2 inches in a 0À25 inch O/D tube, and the recessed end is reduced in diameter. The reduced end of the tube 64 is passed through a bush 217, between oiler rolls 218, 219, through a guide tube 222 and then through a die 224. The roll 219 picks up oil from a chamber 216 and it is evenly distributed over the tube surface by a brush 221. The tube end is secured between serrated jaws of a gripper 204 mounted in a drum 203 thereby depressing a plunger 211 against a spring 248 and the end of the plunger engages in a slot 209 of a rotating side plate 208, to cause rotation of the drum. The gripper which is pivotably mounted on a shaft 245, and the plunger 211 are held down by the tension load imposed by the drawn tube 242. When the end of the tube 242 clears the die 224, the spring 248 lifts the plunger clear of the slot 209, to stop rotation of the drum. The free end of the tube may be inserted in a notch 246, to retain it on the drum. The drawing process is repeated until the tube has been reduced to a predetermined diameter, there being a plurality of drums provided. Mandrel removal and tube sinking. Fig. 22.- The drawn tube is next passed through a derodding unit (300), Fig. 14 (not shown), for the removal of the mandrel (201). The unit (300) comprises a number of pairs of rolls and an entry guide (301). The pairs of rolls loosen the tube on the mandrel and they are arranged so as to act in different planes on the tube. The mandrel is manipulated manually to free it completely in the tube, which is then returned to the drawing unit, Fig. 10, and secured in one of the clamps (226), (227). The mandrel is engaged by the puller unit (229) withdrawn from the tube (242) and inserted in a further tube (64). The reduced tube end is inserted in guide 402 and die 404 of a sinking unit. The tube is fed on to one of a plurality of drums (412), Fig. 17 (not shown), and the sinking unit is traversed by a fluid pressure cylinder 435 along the length of the drum. Oil is supplied from a reservoir 411 by a pump 442 and it passes through openings 408 into the tube 282. It is returned via a tube 431 which is telescopically mounted over the supply pipe 409. The travel of the unit is controlled by a collar 439 on the pipe 431 which engages a limit switch 440. The pipe is passed through a plurality of sinking units and finally coiled on a reel (473), Fig. 17. Straightening and swaging the pipe, Fig. 32.- The reel (473) is placed in a tank of cleaning solvent (524), Fig. 27 (notshown), and the tube is unreeled through wiping pads (510) prior to passing through a rotary frame (509). The frame has four centering pegs (511) and one off-set peg (512), the latter stretching the tube beyond its elastic limit as it is drawn through the frame (509). The tube is pulled by belts (517), (517) of a puller unit (520), which engage opposite sides of the tube, and from the unit (520) it passes to a cutter (515) where it is cut into desired lengths. The cut tube lengths are then passed through rotating dies 614, which are moved inwardly by stationary opposed rollers 610 engaging hardened dowels 611 on the dies and returned by centrifugal force. The stroke of the dies is adjusted by fitting rings 613 of different thicknesses in a groove 618 cut in the end face of the die drive shaft. The ring 613 also passes through grooves in the dies and the outward throw of the die is limited by the gap between the radially inward face of the groove and the inner diameter of the ring 613, Fig. 31 (not shown).