Patent GB-1147439-A (GB)
Title: Pressure welding involving high frequency current heating
IPC: B23K13/04
Filed: 1966-11-29
Abstract: 1,147,439. Welding by pressure. AMERICAN MACHINE & FOUNDRY CO. 29 Nov., 1966 [30 Nov., 1965], No. 53284/66. Heading B3R. In welding a first metal member with opposed faces to a second metal member having a surface in contact with one face of the first member, a high frequency current is caused to flow between a pair of contacts on the face of the first member remote from the surface of the second member and to extend through the first member and at least partly through the second member to heat the members to welding temperature and the members are pressed together to produce a forged weld. The current is supplied by sliding or roller contacts. Two superposed metal sheets 25, 26, Fig. 1, are held in contact and current from a high frequency source 28 i.e. 3000- 1,000,000 cycles/sec. is supplied via a pulsing device if desired to spaced apart contacts 29, 30 engaging the upper sheet 25, a portion 34 of the supply conductor extending over the path of the heating current. The sheets are advanced in the direction of the arrow, are heated by the current which flows down through the sheet 25 into the sheet 26 and are passed between presure rollers 40, 41 which produce a forged type weld along the line 27. The pulsing device permits the welds to be formed in short lines or even spots. The workpieces may be stationary while the contacts are advanced. Members of different metals and of different thicknesses may be welded, the thinner member or the member of highest resistance being uppermost. The source 28 of current may be connected through rigid fluid cooled leads 45, 46, Fig. 6, the lead 45 carrying a roller contact 47 and the lead 46 being connected by a hollow fluid cooled proximity conductor to a support 50 for the other roller contact 51. A roller 51 may with the roller 52 apply the welding pressure and a support roller 56 may be arranged beneath roller 47. Magnetic elements 57, 58 of ceramic insulation material concentrate the current flow and are arranged above and/or below the workpieces. To weld along a number of bands 64, 65, 66, 67, Fig. 7, the current source is connected to contacts 68, 69 and a number of proximity conductor portions 70-76 which determine the path of the current. Bridge elements 77, 78, 79 may carry the current in its transverse paths. Radiator tube assemblies may be similarly welded from two plates having tube portions and web portions. The inner and outer walls of a multi-wall tube may be welded along two diametrically opposed lines by connected contacts to opposite sides of the outer tube wall and connecting these with proximity conductors extending axially and transversely of the tube. A flat sheet is welded to the ridges of a corrugated member by employing a U-shaped proximity conductor and two pressure rollers i.e. using part of an apparatus as shown in Fig. 7. The arrangement of Fig. 1 may be used to weld the interlocked edges of sheets, a horizontal strip to the upper edge of a vertical strip, a folded vertical strip to a horizontal sheet with the strip legs together or separated e.g. for radiating purposes and two superposed sheets with attached forwardly and rearwardly protruding lugs to permit welding to the very ends. To weld two members, one of which has been knurled, engraved, or decorated along the proposed weld line the proximity conductor is bent to overlie the line and to extend from contacts not on the line. To produce a weld of some width a proximity conductor of curved or zig-zag shape is employed. To weld two thin workpieces 150, 151, Fig. 17, along lines transverse to the movement of the workpieces the contacts 153, 154 are applied so that the current runs transversely to momentarily heat the workpieces, an upper pressure roller 156 of or with a rim of insulating material being arranged between the contacts. Where metal of different expansion coefficients are to be welded they may be curved before passing through the welding region. An upper workpiece may be held against a lower workpiece by gas pressure introduced into an enclosure over the workpieces or a magnet beneath the lower workpiece may be used. To spot weld workpieces which remain stationary relatively to the current applying contacts current is applied to flow across a small distance and then a hammer or pressure member is thrust down to effect a spot weld. Similarly a line weld may be made and if the hammer is of copper it will form a proximity conductor.