Patent GB-244476-A (GB)
Title: An improved method of and apparatus for producing highfrequency electric welds and the product resulting therefrom
IPC: B23K13/04
Filed: 1925-12-10
Abstract: 244,476. Pancoast, D. F. Dec. 11, 1924, [Convention date]. Tubes.-Longitudinal seams of tubes &c. are electrically butt-welded by an alternating current of a frequency over 100 cycles per second and less than 1000 cycles per second, flowing across the seam progressively of the length thereof, in order to obtain metal texture and density with reduction of the size of the burr and so to avoid the necessity of subsequent machining. A current of from 12000 to 15000 amperes at 1¢ volts may be used at a frequency of 300 cycles per second. The stock is fed past the electrodes at a high speed, viz. :-60 feet per min., so that the heating effect of each impulse overlaps that of a previous impulse and so maintains progressively along the seam a substantially constant temperature, thus producing a weld of substantially the tube gauge. The current is supplied from a single phase alternator to the primary of a transformer having a secondary, which is connected to the primary of a second transformer and is balanced so as to maintain a constant current at the electrodes, which are carried by the secondary of the second transformer. A preformed tube is passed through the welding- machine by a pair of power-driven feed rolls at each side thereof, the pair on the exit side also preventing opening of the seam during cooling. The tube passes under seam guides 93, 94 arranged on each side of a tapered rotary file 87, which forms radial faces on the blank adjacent the seam cleft which abut over substantially their whole area when subjected to welding pressure. The file is driven by chain gear preferably in the opposite direction to that of the tube and at a slightly greater linear speed. The guides and file are mounted in a laterally adjustable slide. The welding-throat consists of a pair of electrode rolls 57 of copper alloy and a supporting roll 34. The electrode rolls have stub shafts 63 rotating in insulating-bushes in upper and lower pairs of plates 52, 53 secured to and insulated from the frame 25. They are separated from the plates 52 by ball thrust bearings 66 and have circular ribs 71 dipping in mercury baths 72, which are formed integral with the terminal plates 33 of the transformer and rest on the plates 53. The upper surfaces have channels 64 supplied from a valved pipe 95 with a cooling fluid such as water, which passes through apertures 68 into depressions 67 and thence through ducts 69. The terminal plates have a series of slots 74 to receive the separate spaced bars of the one turn secondary 14 which passes through a slot 29 in the transverse frame member 28 and over the rear portion of the upper limb of the laminated core 31. The core is centrally secured by two pairs of brackets 32 to the member 28 and its vertical sides carry the transformer primary 12. The supporting roll 34, which has a groove of slightly greater radius than that of the tube, is trunnioned in ball bearings in a slide 37 vertically adjusted by a screw 44 through worm gear, in guides 38, which are bolted together with blocks 42 to the member 28. The tube after welding passes between a pair of weld-retaining rolls 78 mounted in slides adjustable by a right and left-hand screw 79. Specifications 30544/97, [Class 83, Metals, Cutting], and 188,690 are referred to.