Patent GB-522102-A (GB)
Title: A method of and apparatus for the manufacture of metal tubing
IPC: B23K11/06
Filed: 1938-12-01
Abstract: 522,102. Making tubes. BRITISH BUNDYTUBING CO., Ltd. Dec. 1, 1938, No. 34968. Convention date, Sept. 8. [Classes 83 (ii) and 83 (iv)] Soldering. In making metal tubes from strip stock the tube after formation is fed longitudinally and electric current is passed longitudinally through successive sections of the tube to melt a separate bonding metal at the contiguous surfaces and is also passed longitudinally through the successive heated sections to maintain the bonding metal at this temperature so that time is provided for establishing an interfacial connection with the strip by diffusion or alloying and for flowing the bonding metal into the joints by capillarity. The tubes may consist of steel, copper, brass or coppernickel alloy and may be single ply with lap, lock or butt seams, or may be double ply tubes formed from one or two strips. The bonding metal may consist of copper, brass, bronze or tin-lead alloy. The bonding metal may consist of an electrolytic coating on the strip or may be disposed loosely in the tube in wire, strip or powder form or in a recess between the plies of a double ply tube. A steel tube may also have an external electro-deposited coating of copper when a copper coated tube is desired. The tube may be fed direct from the forming mill through rollers 2, so as to pass successively into contact with three electrodes 7-8, 33, 46, the electrodes 7-8 and 46 being connected by conductors 25, 27 and bus bar 5 to one terminal of the secondary of a transformer 6, and the electrode 33 by conductor 26 to bus bar 4 connected to the other terminal. The electrodes 7-8 consist of metallic rollers, the electrode 7 being carried by a spring-pressed arm. Co-operating with the metal roller electrodes 33, 46 are spring pressed carbon or graphite rollers 40, 47. The bonding metal is melted during the passage of the tube from electrodes 7-8 to electrode 33, and is maintained at this temperature between electrodes 33 and 46, whereupon the tube passes through a quenching bath 55. A reducing or non-oxidizing gas may be introduced through pipe 60 to tubular casings of heat insulating material 56, 54, 53, 52, 32 surrounding the tube, particularly when using cuprous metal for bonding. When a lead-tin alloy is used a flux may be used instead. The electrodes 7-8 are idle, but the electrodes 33, 46 are driven at a peripheral speed slightly greater than the speed of traverse of the tube so as to effect a wiping action on the tube. The grooves in the rolls 46, 47 may be of slightly smaller diameter than the outside diameter of the tube so that pressure is applied to the tubes at the seams &c. The electrodes 33, 46 are driven by a belt 65 from a shaft 64 which is driven by a belt or chain 63 from an electric motor 62. The belt 65 is kept taut by a pulley 70 on a slide controlled by a cable 73 and weight 72. A set of pulling rolls 50 in a housing 51 may be driven, if necessary, by a belt or chain 75. The electrodes are carried by separate slides, 13, 33<SP>1</SP>, 46<SP>1</SP>, adjustable in guides 14 on the bed. The slides 13, 33<SP>1</SP> are adjusted relatively to the slide 46<SP>1</SP> by a handle 19 which through mitre gears 18, 17 rotates a screwed shaft 16, Fig. 4, passing through a nut 31 on the slide 33<SP>1</SP> and through a screwed bush rotatably mounted in the slide 13. The slide 13 may also be adjusted relatively to the slide 33<SP>1</SP> by a handle 23 which rotates the screwed bush through spur gears 22, 21, 20. The housing of the electrode 33 has a removable face plate and a mica plate is clamped on the top which bursts in the event of an explosion or excessive pressure in the housing. In a modification, Fig. 7, the electrode 33 may be replaced by a pair of electrodes 33a, 33b. In a modification of this form the electrodes 33a and 7-8, Fig. 8, are connected to the opposite terminals of a different transformer from that of the electrodes 46, 33b. This form may be further modified by replacing the electrodes 33a, 33b by a single electrode. In a further form, Fig. 10, a magnetic element 86 is disposed round the tube between the second and third electrode so as to set up a reactance which may be varied to govern the current density in this section.