GB1532075A - Electric arc heating vacuum apparatus - Google Patents

Abstract

1532075 Direct arc heating V N KARINSKY 24 Aug 1976 35239/76 Heading H5H A D.C. direct arc vacuum furnace has a D.C. source 13 connected between a conductive workpiece support 3 and a thermionic emissive cathode 5 which comprises a plurality of rods 6 mounted in a conductive support 7 and arranged to define a space 8 deeper than its width and open towards the workpiece support; a gas source 40 delivers gas to the space 8. The rods may be arranged in a ring (Figs. 4, 5, 14 not shown) or in parallel lines (Figs. 6, 8, 9, 15 not shown) they may tend to converge away from the support (Figs. 7, 13, 14, 15 not shown) or be parallel. To prevent electric discharge to the walls 2 of the vacuum chamber and splashes from the workpiece reaching the cathode, the cathode may be shrouded by a jacket that extends to the ends of the rods, (Figs. 12, 13, 16 not shown) or stop short of the ends of the rods (Fig. 10, not shown) or project beyond them (Fig. 11 not shown). The jacket may be watercooled, and may be integral with or extended by a conductive (e.g. graphite) sheath (cf. Figs. 10-13). The gas supply may open directly into the space defined by the rods as in Fig. 1, 10 or at one side within the jacket (Figs. 11-13) or at both sites (Fig. 16). The workpiece support may be a "table" as shown in Fig. 1, a crucible (Figs. 10, 12) or a watercooled ingot mould (Fig. 16). Movement of the cathode towards and away from the workpiece is permitted by insulating bushes 17 (and 25, Figs. 10, 12, 16).