| 摘要 |
1,162,137. Welding by fusion; making thermocouples. UNITED KINGDOM ATOMIC ENERGY AUTHORITY. 21 Oct., 1966 [4 Nov., 1965], No. 46871/65. Headings B3A and B3R. [Also in Divisions H2 and H5] In welding the casing 7 of a thermocouple 1 by the heating effect of electrons derived from a plasma arc generator 3; the sealing of the casing 7 stops current flowing through a circuit ineluding a wire 6 of the thermocouple and the arc plasma and this is detected and automatically causes the welding to be stopped. Six thermocouples are mounted in one end of a glass enclosure 2 connected through a buffer volume 10 to a vacuum pump 11. The plasma arc generator 3 using argon is located at the other end of the enclosure 2 and the plasma is directed towards a steel deflector 4 having a concave end 5. Flow of electrons to the workpieces is controlled by the voltage applied to them. The wires 6 are connected in turn through switch 36 to a battery 44 which provides a preheating current and charges a condenser 42 which provides the welding current. The casings 7 are welded by connecting them in turn by a switch 37 to a generator 46 producing a steadily increasing voltage. A checking circuit from a source 47 through a wire 6 and the plasma to the anode 12 of the plasma generator 3 is broken when the end of the casing closes due to fusion, whereupon a trip device 48 disconnects the generator 46 after a predetermined delay. The thermocouple cables are prepared for welding by drilling out the magnesium oxide insulation and the wires 6 to a depth of 1 mm., removing a further 0.5 mm. of the oxide insulation and bending the wires towards each other. The plasma arc generator consists of an insulating block 21, Fig. 2, mounting a conductive insert 25 carrying a tungsten cathode 14. An annular silver anode 12 is held by a threaded boss 13 against an alumina sleeve 20 surrounding the cathode 14. Cooling water inlet and outlet pipes 18, 19 are provided and argon is fed through a tube 27. A starting electrode is located downstream of the anode 12. |
