Patent GB-1481471-A (GB)
Title: Welding apparatus
IPC: B23K15/04
Filed: 1975-05-23
Abstract: 1481471 Electron beam welding apparatus GEC MECHANICAL HANDLING Ltd 23 May 1975 [19 April 1974] 17266/74 Heading H1D [Also in Division B3] In external or internal electron beam welding together of tubes end-to-end, an electron beam gun is rotated with respect to stationary workpiece tubes and at least one electrode of the gun is slip-ring energized. As described, the gun is of the glow discharge type. In the external welding apparatus of Fig. 1, a gun support ring 4 is journalled, on rollers 5, in a casing 1a, 1b and rotatable by an electric motor 7 via gearing 6. The casing halves 1a, 1b are in use, clamped together about butted tube ends 2 and sealed thereto by inflatable members in chambers 3. The tube bores are also sealed, as by use of the internal welding apparatus of Fig. 2 described below. The ring 4 carries fast a cathode 9, first and second anodes and a magnetic focusing device 32. The cathode 9 comprises an aluminium cylindrical block fast in a ring 10 which is supported on the ring 4 via rods 11 and electrical insulator 12 and is electrically connected to a fixed insulated supply lead 13 via a spring-loaded brush 15. The first anode is formed by that part of an annular channel 17 surrounding an aperture 23 thereof, the channel 17 being supported on the ring 4 via tubes 18 and electrical insulators 19 and being closed by an annular brush 20 fast with a further fixed insulated supply lead 21. The ring 4 comprises annular ribs 26, 25 bounding, with the ring 4, a chamber 24 enclosing the cathode 9, channel 17 and brush 20, and a further annular rib 28 which together with the rib 25 and the ring 4 bounds a further chamber 30. The second anode is formed by that part of the rib 25 surrounding an aperture 27 thereof. A point of focus aperture 31 is provided in the rib 28. The chambers 24, 30 and the casing are evacuated respectively via ports 34 and, by a pump 37 and ports 35, 36. To assist evacuation isolation of the chambers 24, 30, the aperture 31 may be extended in length as by a narrow bore tube. A plurality of guns may be provided by further aluminium blocks 9 and corresponding apertures and focusing devices. In operation, the casing is evacuated continuously and argon admitted to a pressure of say 0À1 torr. The second anode is earthed and smaller and greater negative potentials (e.g. 20 kv. and 40-50 kv.) are applied to the first anode and the cathode. In the internal welding apparatus of Fig. 2, a gun support assembly 44, 45 is ball-journalled in a casing 41-43 and rotatable by an electric motor (not shown) via gearing 47. The casing 41-43 is, in use, sealed to butted tube ends 2 by inflatable members in peripheral annular channels 69 of the casing. The exterior of the tube ends is also sealed, as by use of the above described apparatus of Fig. 1. The support assembly 44, 45 carries fast a cathode 50, an anode and a magnetic focusing device 61 all aligned chordally of tubes 2. The cathode 50 comprises an aluminium cylindrical block provided with a flat 58 and carried on a ring 51 which is supported on the support assembly 44, 45 via insulated rods 53 and electrically connected to a fixed lead via a spring-loaded brush 54. The anode is formed by that part of a cathode-surrounding cylinder 56 surrounding an aperture 57 in said cylinder. The cylinder 56 is in turn surrounded by a cylinder 59 provided with a point of focus aperture 60. The chamber bounded by the cylinder 59 and the remainder of the casing are evacuated via a pipe 65 and, respectively, ports 62, 66. A typical cathode potential is 35 kw. The support assembly 44, 45 may carry a plurality of guns, and each gun may have more than one anode. External and internal welds are normally effected simultaneously. An annular inset may be placed between the workpiece tube ends. Reference has been directed by the Comptroller to Specification 1,370,442.