Patent GB-150756-A (GB)
Title: Improvements in and relating to methods of and apparatus for electric welding
IPC: B23K11/10
Filed: 1918-10-15
Abstract: 150,756. British Thomson - Houston Co., (General Electric Co.). Oct. 15, 1918. Heating by electricity.-In electric line or seam welding, particularly for thick plates or sheets, the electrode is traversed step by step over the work and current is applied only when the electrode is moving, so that after each movement, time is allowed for the portion last welded to cool under pressure, and thus overheating and consequent burning of this portion are prevented when the next portion is being welded. The alternating current being applied for a short time only is governed by the reactance of the circuit rather than by the resistance of the parts being welded, and a large impedance is therefore included in the welding circuit. In the machine shown, a horizontally-traversed roller electrode 22 co-operates with a bar electrode 17 for line welding, and a vertically-reciprocated electrode 23 co-operates with an electrode 19 for spot welding. One terminal of a single-turn transformer secondary 13 is connected by bolts to a yoke 15 separated by insulation 29 from the casing 28 and by insulation 30 from the other terminal 24 which is connected by flexible cables to the electrodes 22, 23. At one end of the yoke is secured, by a bolt 21, the support 18 for the electrode 19 and at the other end is similarly secured the bar 16 for the electrode 17. A fly-wheel mounted on a shaft 89 is rotated by a motor 33, the mechanism being controlled by a treadle-operated clutch. An eccentric and rod 36 on the shaft 89 reciprocate a hollow ram 35, Fig. 4, sliding in adjustable guides. To the ram is connected by bolts the frame 38, Fig. 2, carrying the electrode 23, which is carried by the screw 40 and is adjustably secured in the guide 41 by a nut 42, and is provided with a sleeve 54 and adjustable collar 54a between which and the guide is a spring 44 compressed when the electrode is forced against the work. The ram is also connected by a pin 50 and slot to a lever 48, Fig. 4, pivoted at 49 and connected by a link 47 to a bell-crank lever 46, which carries a pivoted member 9 having a pair of pawls 62, 61, one of which according to the direction of movement rotates a ratchet wheel 45 carried on the same shaft as a pinion 56, which engages a rack 57 on the slide 31 carrying the roller electrode so as to traverse it in either direction. The pawl member 9 is moved and held in either of two positions, so that either the pawl 62 or the pawl 61 may operate, by a pin 63 connected by two springs 69 to the lever and passing through a slot in the lever and through a slotted member 64 on a sliding rod 65. This rod is moved by a stop 76 on the slide engaging either of the two of the stops 73, 74, 75. The roller electrode is carried by a sleeve 124, Fig. 6, and is pressed against the work by a spring 125, but may be held out of contact therewith by a hand-operated cam 128. The spindle 60 of the electrode carries a pinion 59 engaging a rack 58 on the framing 32 so as to rotate the electrode positively. The gear ratios of the racks and pinions may be the same or different, in which latter case the roller is caused to slip on the work. The pawl member 9 carries two forked contacts 78, 79 which engage with contacts 79, 100 on the lever 46, Figs. 2 and 8, according to the direction of motion. When a switch blade 88. Fig. 8, carried by the shaft 89, Fig. 2, connects the segments 85, 86, current passes from mains 90, through the circuit 82, 83, 84, energizes the control magnets 80, 81, and so connects the contacts 93, 94, thus completing the primary circuit 95, 96 of the transformer. When the blade leaves the segments 85, 86, the current is cut off for the rest of the revolution. The contacts 99, 100 and segments 101, 102 are operative in the other direction of motion of the slide so that welding may be performed in both directions. The current may be regulated by varying the number of turns of the primary winding 12 by a hand-operated controller 106, contact being established successively between the segments 108 and contacts 109 connected by conductors 110 to different taps on the primary winding. The roller electrode may consist of a replaceable welding annulus 114, Fig. 7, secured by screws 117 to side members 115 116. The electrode may be removed from its holder 118 by taking out the screws 119, Fig. 6. It is hollow to contain cooling fluid such as water, supplied through a brass or other metal tube 120 fastened to the holder 118, and discharged from the shaft 60 through a gutter 122 and spout 123. The line welding mechanism may be disconnected by removing the link 47 and the machine used for spot welding only. In this case, the contacts on the pawl member and lever are connected by manual operation of the rod 65. When used for line welding only, the frame 38 may be raised out of contact with the work by a screw 52<b> after loosening the clamping-bolts.