Patent GB-457013-A (GB)
Title: An improved process and machine for the electric welding of tubes
IPC: B23K11/06
Filed: 1936-05-29
Abstract: 457,013. Welding tubes. SCIAKY, D., 13, Rue Charles Fourier, Paris. May 29, 1936, No. 15259. Convention date, May 29, 1935. [Class 83 (iv)] [See also Groups XXXV and XXXVI] In a continuous process of resistance welding tubes, the tube passes first between a munber of roller electrodes before the welding point is reached so as to heat the entire cross - section of the tube and then under a roller electrode positioned over the seam gap so as to effect the weld. The greatest heating effect thus occurs at the position of the welding electrode and thick walled tubes may thus be welded throughout their thickness. Parallel concave roller electrodes 13 connected to one terminal of a transformer 22 are positioned at the sides of the tube, through which the tube passes to the welding electrode 15 connected to the other terminal of the transformer. This electrode is narrow but sufficiently wide to avoid too intense a concentration of heat and has a pressure applied thereto which may be about ¢ to <1>/3 that applied to the electrodes 13. An auxiliary electrode 19<1> may be mounted over the seam in transverse alignment with and electrically connected to the electrodes 13. The weld may be completed by pressure rollers 21. In order to vary the amount of heating of the portion 17 of the tube and to increase it at the welding point, the rollers 21 may be connected to one terminal of an auxiliary transformer 24 in parallel with transformer 22, the other terminal being connected to the electrodes 13 and also to the electrode 19<1> when used, the current being of a different voltage from the main current and being in the opposite direction. The transformers are both provided with taps 23, 25 so as to regulate their respective voltages. The contact pressure of the electrode 15 may be regulated automatically according to variations in current intensity due to fluctuations of supply voltage or inequalities in the tube surface so as to maintain a constant welding temperature. For this purpose the electrode is carried by a lever 29, Fig. 7, pivoted at 30 and pressed down by a spring 28, which may be adjusted by a hand wheel 31, or by counterweights. The pivot is carried by a rod 33 having a boss bearing on a stop 32 and a core 35 co-operating with a solenoid coil 36 connected to the electrical circuit through a rheostat. The coil may be inserted in either the primary or secondary of the transformer 22. The rod 33 may also be adjusted by a hand wheel 34 to remove the electrode from the work. The current in the coil 36 may also be controlled by an electronic or other relay influenced by a welding control member such as a photo- or thermo-electric cell, thermo-couple &c. The lever 29 may be connected to a rod, sliding in a support such as 40 but with a recessed lower end, and provided with a nut acting as a stop to prevent the electrode from dropping into the gap in the tube. The amount of compression of the spring may be indicated by a dial cooperating with a pointer integral with a pinion, which meshes with a rack vertically moved in correspondence with the hand wheel 31. The welding electrode 15 is secured to a hollow spindle 48, Fig. 9, having a portion 48a, rotating in a chamber 54 in a drum 53, to which mercury is supplied at 57. The mercury may be emptied out at 76. The spindle is of copper alloy and the surfaces in contact with the mercury are coated electrolytically with chromium. The bearing 58 which is in two parts, compresses a rubber ring 75 surrounding a band 73 of plaited asbestos to seal the joint at this end. A seal 56 is also provided at the other end. The welding leads are welded into thimbles 60 secured in recesses 59, 59a in the drum. The electrode is water cooled by passing water from a nozzle 62 in a fixed sleeve 63 through a tube 52 secured to the spindle, whence it emerges by channels 67 in the plug 49 into a chamber 68. The water is discharged through channels 69, space 70 and ports 71 into chambers 72 to cool the thimbles. A liquid seat 64-66 is provided in the sleeve 63. The electrodes 13 are carried by hollow spindles 79, Fig. 10, formed at 80 as mercury cups into which dip curved projections on a conductor member 81 clamped to a hollow rod 83. Cooling water passes through pipes 84, spindles 79 and exit apertures 87 in the electrodes. The electrodes 13 and pressure rolls 21 are carried by longitudinally adjustable slides and are adjustable relatively to each other by screws. The electrode 15 and its pressure applying mechanism are mounted on a slide longitudinally adjustable by a screw. The tube passes to the electrodes 13 under a guide roller and after welding it is guided first under an adjustable roller and then under an adjustable scraper for removing burr.