GB787965A - Improvements in electric furnaces - Google Patents

Abstract

787,965. Electric furnaces. JERU, H. Jan. 12, 1656 [Jan. 13, 1955], No. 1099/56. Class 39(3) A furnace for baking food, for metallurgical treatments, for producing glass, or serving as a kiln or drier has a vault-comprising an inner metal wall 2 lining the furnace chamber and a metal band 1 extending along the length of the hearth, these elements 1, 2 forming resistance heaters connected together at one or both ends and fed in series with current. The wall 2 bounds and supports insulating fillings around it. Thus the walls may be sheets of mild steel, cast iron or of refractory metal, the wall 2 forming the vault, and the sheet 1, which has upturned edges, forming the hearth and resting on brickwork 7. The furnace is embedded in sand 8 held by side walls 10 of concrete or sheet metal supported by spaced iron uprights 11 interconnected at their tops by stays 12 and rests on a concrete base 9. The heating elements 1, 2 are connected electrically at one end 3 by a metal plate 16 welded thereto and having an aperture for entry of material to be treated, said aperture having an external sash door 13 of concrete. The other ends of the elements which may be in sections of different cross sections, are connected by leads 4 to a transformer 6. If a 3 phase transformer is used, it may be connected in star or deeta formation to the elements, different phases being connected to the elements at separate points along their lengths. In order to adjust the temperature distribution along the furnace, successive portions of the elements may be short-circuited by copper blades 28 which are moved against or from the elements by screws 29 operated by wheels 30. Pyrometers 26 may extend through tubes 27 in the roof. Articles 22 to be heated may be laid on asbestos plates 23 on a carriage 20 having wheels 21 running on the hearth 1, said articles being secured to the carriage by clamps 24 with the interposition of an insulating plate 24.. A table for the articles to be loaded may be placed in a pit before the door 13.