Patent GB-251634-A (GB)
Title: Improvements in and relating to electric welding apparatus
IPC: B23K11/11
Filed: 1926-04-28
Abstract: 251,634. British Thomson-Houston Co., Ltd., (Assignees of Weed, J. M.). April 28, 1925, [Convention date]. Void [Published under Sect. 91 of the Acts]. Welding.-In electrically welding heavy metal parts, the area over which the current is transmitted from the inner surface of one part to that of the other is limited by interposing a coating of insulation between the parts except over the area where the weld is to be effected. In spot welding thick plates, spring clips 37, Fig. 3, provided with discs 36 at one end and rings 38 at the other, are first applied to each plate, so that the discs 36 cover the welding spots on inner surfaces of the plates, while the insulating coating of whitewash or mineral paint is applied. The entire surfaces may previously have been provided with a high resistance coating to localize and intensify the heat of the weld. The outer surfaces of the plates are marked at the rings so as to fix the position at which the electrodes are to be applied. These portions may be finished with a conductive coating such as a metallic paint so as to reduce the contact resistances between the work and the electrodes and so to reduce the heating of and deformation of the electrodes. The plates, 16, 17, Fig. 1, are then arranged between hollow electrodes 2, 1, having flanges 21 which are received in U-shaped members 18, 25 secured to terminals 11, 26 connected to the current leads 6, 15. The terminals are secured to slotted plungers 12, 27, which are pressed by springs 13, 29 against screws on the members 8, 28. The member 8 is rigidly fixed in a socket 7 and the member 28 is connected to a sliding head operated by a hinged member 30 through a link 33. The electrodes receive headed pressure members 22, 24 of area equal to the uncoated area on the inner surfaces of the plates. When the head is operated the member 24 is forced against the work and the member 22 is thus forced against the reduced end 9 of the member 8 and a rigid pressure is thus applied to the parts to he welded. The electrodes are pressed through their springs against the work with sufficient pressure only to conduct the current, so further preventing deformation of the electrodes. The members 22, 24 may consist of a material such as high speed tool-steel, having a high compressive strength at high temperatures. In step-bystep line welding, the outer surfaces of the plates are provided with a conductive coating 44, Fig. 6, and the inner surfaces are each provided with two parallel strips of insulating coating separated preferably by a strip of a high resistance coating. The electrodes 40, 41 are placed slightly in advance of the pressure members 42, 43 so that the current is transmitted through the new areas rather than through the completed weld. In a continuous line welding machine, a pair of disc electrodes 51, Fig. 10, are connected to one terminal of a transformer and co-operate with a similar pair 47 connected to the other terminal. These electrodes are arranged slightly in advance of the pressure rolls 52, 53. The electrodes 51 are carried on opposite sides of the roll 52'on members 58 resiliently mounted by springs 63, 64 and bolts 62, 61 on the mounting 54 of the roll 52. The electrodes 47 are similarly carried by the mounting of the roll 53.