Patent GB-103062-A (GB)
Title: Improvements in Electric Furnaces.
Inventor: KOHN MILTON MORRIS
IPC: H05B3/66
Filed: 1916-05-17
Abstract: 103,062. Kohn, M. M. May 17, 1916. Resistance furnaces.-Holders for removable heating-units are mounted in a housing made of diatomaceous material, such as infusorial earth, serving as heat insulation. In a small furnace, the housing may be in one piece; in a large furnace, blocks 17, Fig. 2 or Fig. 7, may be held in staggered relation within a metal casing by bolts 18 or otherwise. The housing may be lined with fire-proof cement. Heads closing the ends of the furnace are preferably made internally of fibrous material, such as asbestos, and externally of a mixture of fibrous material and cement. The permanent holders 20 for the removable resistance units are secured by divergent ribs 22 fitting into some of the housing-blocks In the rectangular furnace, each resistance unit comprises a row of blocks 28, Figs. 2 and 5, provided with flanges 31 fitting grooves in the holders, and with holes 32 to receive longitudinal bolts 34, which serve also as conductors. These bolts may extend through the rear head of the furnace, so that the resistance units are removable with the head; or they may be coupled by screw joints to bolts in the head, so that the units may be removed independently through the front end of the furnace. In some cases, the coils themselves may extend through the head tc the external connectors. Undercut parallel grooves for coil or other resistances are made at one or each of two opposite sides of the blocks; the sets of grooves on opposite sides may be parallel or at right-angles. Two sets of grooves of different depths may cross at right-angles in the same side of the block. Each resistance unit is reversible in position, to present one or other of the resistances towards the furnace chamber. Thus, the resistance unit can still be used when one resistance is burnt out or damaged. The outer resistance may serve for current-regulation. Regulating- resistances may also be placed in or on the housing, or in the closing-heads. In a cylindrical furnace, there may be two semi-cylindrical resistance units 74, 75, Fig. 7, with dovetailed flanges fitting in pairs in holders 79, 80 secured as above described; or an integral cylindrical resistance unit of equivalent form may be employed. Substances such as charcoal, or a mixture of charcoal and sodium bicarbonate, evolving gases which prevent oxidation or otherwise influence the material being heated, may be inserted in bores in the heating-unit supports. The heating-coils are preferably arranged so that they can be variously connected for use with different supply pressures. Fig. 4 represents regulating-resistances 67, connected to contact blocks 70 engaging by an arm on a slide 71. A second spring arm 72<1> is pivoted to the slide so that it can be turned into contact with a bar 71' parallel to the slide, to cut out of circuit an additional resistance 70<1>. An opening in one of the furnace heads is fitted with an horizontally-hinged door, having a weighted arm so that it can remain in either its open or closed position. The furnace may be supported on legs 93, Fig. 2, tied by cross-bars 94. Specification 2968/11 is referred to.