GB526527A - Improvements in and relating to electric vacuum annealing and melting furnaces - Google Patents

Abstract

526,527. Electric vacuum melting and annealing furnaces. BERGHAUS, B. March 18, 1939, No. 8739. Convention date, March 24, 1938. [Class 39 (iii)] [Also in Group XXXVI] In an annealing or melting furnace in which heating is effected in a metallic vacuum chamber by an electric gas discharge, the insulating and sealing medium between the vacuum chamber and the electric lead in conductor is protected from damage by electric discharge by a relatively long and narrow gap between said conductor and a member surrounding it. In Fig. 1, the conductor 3 is hollow and cooled by a medium passing through pipes 4, 5, and is surrounded by a metallic covering 6; ceramic &c. insulation 7 is spaced from the wall 2 of the vessel and a flange 10 on the conductor by packing rings 8, 9, of Ph, A1, Cu &c. and is clamped by insulation 11 and screws 12. In other forms an insulating cap extends from the conductor to the inner end of the covering 6 and the annular space within said covering extends into the insulation, or a cap on the conductor overhangs the end of the covering 6. In Fig. 4, the conductor 21 and a metallic screen 22 are in stepped form leaving a labyrinthine gap 23; the screen 22 may be omitted, the outer steps then being formed in the wall of the furnace. In Fig. 5, the screening sleeve 31 is hollow for circulation of cooling medium, while in a further form, the screen is formed of a coiled cooling pipe. In Fig. 7 the gap is formed between the conductor 43 and the furnace wall 2 which has a cooling chamber 40. In Fig. 8, the conductor 3 is surrounded by spaced metal sleeves 6a, 6b, 6d with flanges separated by insulation 7a, 7b, 7c, 7d, and connected through fixed or adjustable resistances 59 . . . . . 62 and condensers 63 ..... 66 to the electric lead 14. In Fig. 9, a furnace comprises an upper part 95 with a cooling jacket 98, and a lower part 94 with cooling space 118, packings 96, 97 being interposed; parts 94, 95 may form an anode together or separately, or be neutral. A vacuum pump is connected at 102, while a connection 103 is provided for a pressure gauge and admission of inert or reducing gases. An anode 108 is spaced and insulated from the part 94, and a cathode 109 is spaced and insulated from the anode and carries a plate 113 supporting the material under treatment. In Fig. 11, the gap is formed by an insulator 25 of quartz &c. surrounded by a cooling jacket 26; in other forms, the jacket 26 is omitted and the quartz &c insulator contacts or is spaced from the furnace wall. In Fig. 13, the conductor 4 is surrounded by a porcelain &c insulator 8 and is held by insulating and packing means 13, 14, 15 and a nut 16, gaps 9, 12 being provided. Specifications 526,526, [Group XL], and 526,528 are referred to.