Patent GB-479581-A (GB)
Title: Improvements in or relating to welding apparatus
IPC: B23K11/30
Filed: 1936-05-05
Abstract: 479,581. Making bellows; electric welding ; prizing - tools. LOOKWOOD, H.C. May 5, 1936, No. 14713/37. Divided out of 474,753, [Group XXVIII]. [Classes 83 (ii) and 83 (iv)] [Also in Group XXIII] In an electric resistance seam welding apparatus, one of the electrodes consists of a very small diameter rod supported throughout a considerable portion of its length by a massive electrode, which does not contact with the work or has a non-conducting tip, so as to avoid mechanical deformation of the rod and to minimize the volume of work through which the current passes. The current, which is alternating and continuously applied and of substantially constant mean effective value, is thus confined substantially to that volume wherein the heat generated in the work is no greater than can be dissipated without injury to the work or electrodes and a continuous and substantially unvarying seam weld is thus obtained. In welding bellows plates alternately adjacent their inner and outer edges to adjacent plates, the plates are placed one by one, after a previous weld has been effected, in a work holder 321 secured to a table 320 rotated at a number of constant speeds, on roller bearings 342 on a fixed table 318, through worm gear speed reducing mechanism 336. The work holder consists of a pair of rings 350, 351, slotted at intervals to leave projections 354, 355, Fig. 7, which are provided with horizontal notches 356 to receive lugs 90 on a pair of bevelled clamping members 86, 87 provided with insulating inserts. Screwed on these rings are contact rings 359, 362 with notched upper ends and also with toothed portions 361, 364 which are engaged by a pinion 367 on a removable tool 366 so as to raise or lower the rings. Under the plates is provided a backing-up member 368 which is engaged by posts 369 resting on a pressure plate 371, Fig. 2, so as to clamp the plates against the members 86, 87. The pressure plate is adjusted by a screw 373 and handoperated worm gear 80, 79. Between the plates to be welded and the previously welded plates is placed a thin soft copper gasket ring 99 which forms the stationary electrode and is supported by a split hardened steel ring 102 to provide a hard unyielding surface. Prior to performing an outer weld as between plates A<2>, A3, Fig. 7, a corresponding gasket 98 and ring 101 are placed under the plate A3 in readiness for the next inner weld. After the plates have been pressed against the clamps by the member 368, the ring 362 is screwed up to clamp the welding gasket 99, which is in electrical connection with the arm 317 leading to one of the terminals of a welding transformer through rings 362, 351, table 320, contact brushes 346 and fixed table 318. The movable electrode 316 is carried by a manually adjusted horizontal slide 109 carried by a counterweighted slide 315, which is pressed down to provide the welding pressure by a hand lever 322 or automatically. The electrode may consist of a copper, tungsten or tungsten tipped wire 124 of 0À095" diameter, Fig. 10, mounted in a copper member 121 and pushed down by a pneumatically operated rod 128 with sufficient pressure only to provide a good electric contact. The end of the member 121 is provided with a metal cap 122 or thin ferrule coated with insulating material such as hard enamel or a ferrule of nonconducting material. The rod 128 carries a piston 127 reciprocated in a cylinder by air supplied from port 145 through a valve 150 operated in one direction by a spring 160 and in the other direction bv a solenoid 156 connected by the contact 163 of a magnetic switch 162 in the control circuit 161, the switch being controlled by a push button 166. The switch 162 also carries the contacts 164, 165 of the welding circuit. The rear end of the rod 128 is enclosed in a glass tube 132 surrounded by a slotted metal tube so as to indicate the amount of wire 124 left in the member 121. Rotation of the table with the work in continuous contact with the end of the wire electrode effects the weld which is continuous due to the narrow contact furnished by the small diameter of the electrode. Cooling water may be flowed or sprayed between the clamps and is drained from the table through a pipe 105. For effecting an inner weld a member of similar shape to the member 87 forms the inner clamp and the outer clamp 87 is replaced by one similar to clamp 86. The gaskets, which are used for one welding operation only, are removed after welding by drawing them out until both edges at one point are exposed, whereupon they are cut radially and then spiralled out. The steel inserts 101, 102 are provided with holes 176, Fig. 13, and are removed, after first exposing one end, by pins 180 on a cylindrical member 179 carried by a handle 175. The movable electrode may alternatively consist of a wire 227, Fig. 22, carried by reels, one or both of which may be driven, and passing over a preferably grooved water cooled copper or like disc 225 mounted on the slide 315. The wire passes over a guide roll 232 on a forked slide 233 engaging the disc 225 so that it follows any axial adjustment of the disc. The insert of clamp 86 may have a projection 94 in the vicinity of the weld and the end of the insert of clamp 87 is recessed to receive the plates being welded. In a modification, the rings 359, 362 may be replaced by composite rings 203, 207, Fig. 15, insulated at 205, 208, and the steel inserts 209 may be insulated on their ends and on the side away from the plates being welded. The outer parts only of the rings are in contact with the gaskets. The backing up member may consist of two steel rings 200, 201 separated by insulation 202. In a further modification the gaskets may have strips of paper or other insulating material 191, 192 or paint on the parts under the clamps so that contact of the plate with the gasket is only made when the movable electrode is applied. In a father form the gaskets may be formed with integral or attached projections opposite the movable electrode or may have a folded end. Two continuous welds at 193 may be performed simultaneously. The clamps may have steel inserts 213, Fig. 19, separated by insulation 212 from the clamp body. For work of different size alternative work holders may be used. Specification 474,753 is referred to.