US2798108A - poland - Google Patents

Description

July 2, 1957 F. F. POLAND ELECTRIC FURNACES 3 SheetsSheet 1 Filed Aug. 9, 1955 FRANK F. POLAND 81 510 W Y W Arr atent 2,798,108 Patented July 2, 1957 fifice 1 ELECTRIC FURNACES Frank F. Poland, Rome, N. Y., assignor to Revere Copper and Brass Incorporated, Rome, N. Y., a corporation of Maryland Application August 9, 1955, Serial No. 527,313

14 Claims. (Cl. 13-61) My invention relates to electric furnaces, and particularly but not exclusively to high temperature tilting vacuum furnances of the resistor type for melting refractory metals such at titanium and zirconium.

The invention has among its objects the provision of an electric resistor type furnance mounted for tilting, with improved means for preventing shifting of the resistors and their supports when the furnace is tilted, in which respect it constitutes an improvement on the furnace disclosed in applicants Patent 2,697,127, issued December 14, 1954.

A further object of the invention is a resistor electric furnace having provision for melting metal in a pot or skull of the same metal. I

A still further object of the invention is the provision of a vacuum electric furnace having improved means for sealing the joint between the removable cover and body of the furnace.

The above and other objects of the invention will, however, be best understood from the following description when read in the light of the accompanying drawings of a specific embodiment of the invention selected for illustrative purposes, while the scope of the invention will be more particularly pointed out in the appended claims.

In the drawings;

Fig. 1 is a vertical medial section of a furnace and associated parts according to the invention;

Fig. 2 is a section on the line 2-2 of. Fig. l on an enlarged scale;

Fig. 3 is a plan of the furnace according to Figs. 1 and 2, with parts broken away;

Fig. 4 illustrates a detail; and

Fig. 5 is a section on the line 5-5 of Fig. 1, with parts omitted.

Referring to the drawings, the furnace illustrated comprises an open top metallic casing 1 having opposite side walls 3 and 5, opposite side walls 7 and 9, and a bottom wall 11, these walls being welded together along their adjacent edges to provide an air tight construction. As shown, the side walls are reinforced by horizontal channel-irons 13, and the bottom wall 11 by horizontal I-beams 15, the channel-irons and I-beams being welded to said walls.

Lying against the outer sides of the channeldrons 13 are plates 17 welded thereto at their abutting edges as indicated at 18 (Fig. 2). The lower edges of the lower plates 17 rest on the bottom wall 11 of the casing and are welded thereto, while the spaces between the upper edges of the upper plates and adjacent walls of the casing are closed by plates 19 welded thereto.

The spaces between the side walls of the casing 1 and plates 17 form a water jacket extending entirely about said casing. Cooling water may be supplied the water jacket so formed from flexible conduits 21 (Fig. 1) connected to the lower portions of said jacket and be discharged therefrom through flexible conduits 23 connected to their upper portions, the channel-irons 13 being formed with rows of spaced openings 25 for permitting upward flow of cooling water through them.

As shown, the furnace casing is supported on a tilting platform 27 comprising an upper plate 29 on which the lower flanges of the I-beams 15 rest and to which they are welded. The bottom wall 11 of the furnace casing and the plate 29 in conjunction with the I-beams 15 form longitudinally extending passageways 31 across the bottom of the furnace casing, which passageways attheir opposite ends are closed by channel-irons 33 welded to the ends of the I-beams 15, which latter are profiled to fit within the adjacent side openings of the channel-irons 33. Cooling water may be admitted to and discharged from these passageways 31 by manifold conduits formed by channel-irons 35 (Fig. 2) welded to the outer sides of the channel-irons 33, these'channel-irons 33 having openings 37 placing the manifolds so formed in communication with the ends of the passageways. Cooling water may besupplied the right hand manifold, as viewed in Fig. 2, by a flexible conduit 38 and be discharged from the left hand manifold by a like conduit 40.

The cover 39 of the furnace casing comprises a horizontally extending plate 41 adapted to rest at its peripheral edge portion on the plates 19 at the upper edges of the water jackets for the side walls of the casing. Resting on and welded to the upper side of the plate 41 are laterally spaced, longitudinally extending channel-irons 43. On" the upper flanges of these channel-irons are positioned longitudinally extending plates 45 welded thereto at their abutting edges, as indicated at 46 (Fig. 1), so as to form a Water jacket 47 for the cover. Cooling water may be admitted to and discharged from this water jacket through pipe connections 49 connected to flexible water conduction conduits St the channel-irons 43 having openings 51 spaced longitudinally thereof for permitting passage of the cooling water through them. For holding the cover in position (when the furnace is tilted and is not under avacuum the usual hold down devices 53 may be provided.

As best shown by Figs. 3 and 4, the projecting peripheral portion of the cover plate 41 resting on the plates 19 at the top of the water jacket for the side walls of the furnace casing carries at its upper side bars 55 forming a raised surface extending continuously about the cover. Adjacent the outer edge of the cover plate 41 the plates 19 carry bars 57 which also form a raised surface ex tending continuously about the cover. These bars 55 and 57 are formed of material, such as copper, having good soldering properties, and are heremetically brazed to the plates 41 and 19, respectively. On the upper surfaces of these bars and bridging the space between them are placed strips 59, preferably of the same material as the bars, which strips form in substance a continuous strip extending entirely about the cover, this strip being hermetically soldered to the bars to seal the joint between the furnace casing and its cover. The bars, being of copper or the like, may be readily heated by use of a blow torch for soldering the strips 59 thereto and for softening the solder to permit the strips to be peeled off the bars when the cover is to be removed.

As shown, the furnace supporting platform 27 is itself pivotally supported at 61 on a bracket carried by a foundation pier 63. For tilting the platform for pouring the furnace is shown a pair of air cylinders 65 each pivotally supported at its lower end at 67 on a bracket 68 carried by a foundation pier 69, the piston rod 71 of each air cylinder projecting from the upper end of the latter and being pivotally connected at its upper end at 73 to the side of the furnace casing opposite the pivotal support for the platform. By use of the three-way valve 75 the flexible pipe 77 connected to the lower end of each air cylinder may be selectively connected to a pipe 79, leading from a source of compressed air supply, or to a port 81 in the casing of said valve communicating with the atmosphere, in this Way to raise the air cylinder pistons 83 for tilting the furnace to pour it, and at the completion of the pouring operation to cause the pistons to descend to place the parts in the position shown by Fig. 1. As above indicated, the various inlet and outlet connections to the water jackets of the furnace comprise lengths of flexible hose or the like for permitting such tilting.

As further shown, means are provided for rocking the platform .27, and parts carried by it, about the pivotal support 61 through a small angle for agitating a pool of molten metal, hereinafter described, adapted to be contained in the furnace chamber. In the illustrated embodiment of the invention such means comprises a rotary shaft 85 supported in suitable bearing brackets 87 carried by the foundation pier 69. Fixedly carried by the shaft is a cam 89 with which cooperates a roller 91 rotatably mounted in bearing brackets 93 carried at the under side of the platform. As shown, an electric motor 95 is provided for rotating the cam shaft 85, the shaft for this purpose having fixedly secured thereon a chain sprocket wheel 97 about which and a driving sprocket wheel 99 passesa chain 101. The sprocket wheel 99, as schematically shown in Fig. l, is driven by reduction gearing contained in the gearbox 103, this reduction gearing being driven by the motor 95. For stopping and starting the motor a suitable manually operated switch under the control of the operator may be provided, so that the furnace may be rocked through a small angle, when desired, for sloshing the above mentioned pool of metal to facilitate melting solid metal pieces added to such pool through the charging means hereinafter described.

Within the furnace chamber are heat refractory walls forming a furnace chamber 105, within the upper portion of which chamber is suspended a resistor grid comprising the elongated resistors 106 for radiating heat downward toward the bottom of the chamber. As shown, the bottom wall 107 and top wall 109 of the furnace chamber are each formed of an integral slab of heat refractory material such as hard carbon or graphite, preferably the latter. The side walls of the furnace chamber, as shown, are formed of upper slabs 111 and lower slabs 113 of the same material as the top and bottom walls. Between the upper and lower slabs 111 and 113 is positioned a body 115 which forms a flange 117 projecting into the furnace chamber above the bottom wall 107 and extending entirely about the chamber interiorly thereof. This body 115 i may be formed of an upper rectangular ring 119 (Fig. 2) resting on a lower rectangular ring 121. The upper ring 119 is preferably formed of heat refractory material of poor heat conductivity such as porous carbon, while the lower ring 121 is preferably formed of graphite. The composite structure formed by the rings 119 and 121 could be formed as an integral ring consisting wholly of porous carbon except that porous carbon is a poor structural material and is liable to failure. Hence the structure is formed in the way illustrated to provide for reinforcing the porous carbon with the graphite insert constituted by the ring 121. As shown, the top wall or roof slab 109 of the furnace chamber is formed at its lower side adjacent its periphery with a groove 123 extending entirely about it, in which groove are received the upper edge portions of the side wall slabs 111. Similarly, the bottom wall 107 is formed at its upper side with a peripheral groove 125 which receives the lower edge portions of the side wall slabs 113. The lower edge portions of the slabs 111 are received in a groove 127 formed in the upper side of the ring 119, while the upper edge portions of the slabs 113 are received in a groove 129 formed in the under side of the ring 121. The under side of the ring 119, as shown, is formed with a groove 131 extending entirely about it, and the ring 121 at its upper side is formed i being melted in the furnace chamber.

with a complementary tongue 133 received by such groove.

The several slabs 111 and 113 constituting part of the side walls of the furnace chamber abut each other at their end portions and are held in assembled relation by reason of said slabs being fitted into the grooves 123, 125, 127 and 129, while the rings 119 and 121 are held in assembled relation with each other and with the slabs 111 and 113 by reason of the tongue 133 on the ring 121 being fitted within the groove 131 and the slabs 111 and 113 being fitted into the grooves 127 and 129 respectively, in this way to form with the wall slabs 107 and 109 a boxlike structure. Exteriorly of the furnace chamber and within the furnace casing is a mass 135 which extends upward from the bottom of the furnace casing to a level indicated at 137 (Fig. 2), such mass preferably being formed of blocks of porous carbon, this mass acting to support the walls forming the furnace chamber. Resting on the mass 135 and surrounding the walls forming the upper portion of the furnace chamber is a mass 139 preferably formed of carbon beads or carbon beads mixed with a small proportion of broken charcoal, which mass extends upward to a level indicated at 141 (Fig. 2) or very slightly above it. These masses of porous carbon and carbon beads act as heat insulators for the walls of the furnace chamber and in conjunction with the water jackets above described prevent the metallic walls of the furnace casing from heating to above their softeningtemperature.

The continuous interior flange 117 at the interior of the furnace chamber acts to shieldthe slabs 113, and those peripheral portions of the bottom wall slab 107 which lie beneath it, from the heat radiated downward from the resistors 106, while the porous carbon of the ring 119 acts to minimize heat conduction from the slabs 111 to the slabs 113, so that the under side of the flange 117, the interior surfaces of the slabs 113, and the interior surface of the bottom wall slab 107 below the flange, are kept cool enough to be at a temperature below the melting point of the titanium, zirconium, or other metal The creation of this relatively low temperature is augmented by the heat conducted through the mass 135 to the water jacket surrounding the side walls of the furnace casing and the water jacket below the bottom wall of the furnace casing. The conduction of heat from the portions of the bottom wall of the furnace chamber to the water jacket below the bottom of the furnace casing also acts to keep that portion of the upper surface of the bottom wall slab 107 lying inwardly of the inner edge of the flange 117 at a temperature below the melting point of the metal. Initially there may be rammed into the space beneath the flange 117, and across the entire bottom of the furnace chamber inwardly of the inner edge of said flange, a mass of the metallic material like that to be melted, for example, a mass of sponge titanium or sponge zirconium or small pieces of titanium or zirconium scrap or a mixture of scrap and such sponge metal. The heat radiated downward from the resistors will melt down part of such mass to form an open top pot-like skull 143 of the solid metal having a bottom wall 145 and a rim or side walls 147, the portion of the mass forming the bottom wall of such pot-like receptacle ordinarily being thinner than the portions which form the rim of such receptacle because such bottom wall is exposed to direct radiation from the resistor grid, while the rim portions are shaded by the flange 117. In this way the metal charged to the furnace chamber may be melted to form a pool of molten metal in this pot-like receptacle, the solid metal of the receptacle protecting such molten metal from the carbonaceous material surrounding it, it being understood that metals such as zirconium and titanium and particularly the latter actively react with carbon, which reaction if permitted may undesirably contaminate the metal.

The resistors 106, as shown, comprise the intermediate bars 149 (Fig. 5) and shorter end bars 151 all preferably formed of graphite. As shown, each bar 151 is provided with a reduced diameter portion 153 screw-'threadedly; received by a graphite sleeve 155 at one end portion .of such sleeve. Screw-threaded into the opposite ,end portion of said sleeve is a resistor extension 157 which extends to the exterior of the furnace casing where its end portion has screwed thereon a copper terminal 159 to which may be connected a flexible energizing cable (not shown) for the resistor grid. As indicated in Fig. 1, each resistor extension projects through an opening 161 in the side wall of the furnace chamber and through an aligned opening 163 formed in a block 165 supported by the mass 135 of porous carbon heat insulating material. A sleeve 167 extends from the block 165 through the adjacent side wall of the furnace casing, its outer end portion being received in and fitting the bore 169 of a sleeve 171, which bore forms an opening extending through the adjacent water jacket, the sleeve being welded to the opposite walls of the water jacket for making a water tight joint therewith. The block 165 and sleeve 167 preferably are formed of porous carbon, and the resistor extension projects through their bores and the opening 161 in out-ofcontacting relation with the Walls of such bores andopening so as to be in electrically insulated relation thereto.

As shown, the sleeve 171 has a portion 173 (Fig. 5) extending outwardly from the adjacent outer wall 17 of the water jacket of the furnace casing. The outer end of this portion 173 fits and is welded to a collar 175, preferably of steel, forming a radially extending outward peripheral flange on said sleeve. The terminal 159 extends through an opening 177 in a disc 179 preferably of copper, to which disc the terminal is welded. Between the flange or collar 175 and disc 179 is placed a flat ring 181 of heat refractory electric insulating material such as the material commercially known as formica which consists essentially of ureaand phenol-formaldehyde resins absorbed in the fibrous base. At the outer side of the disc 179 is placed a metallic ring 103, or material such as steel, which bears against said disc for stiffening it. Through each of a plurality of circumferentially spaced sets' of aligned openings in the flange or collar 175, ring 181, disc 179, and ring 183 is inserted a tube 185 of heat refractory electric insulating material, such as the above referred to formica, and through the bores of these tubes are passed bolts 187 carrying cooperating nuts 189 for holding the parts in assembled relation, washers 191 of heat refractory electric insulating material such as the formica, through which washers the bolts extend, being placed between the metal washers 193 which surround the portions of the bolts adjacent the bolt heads and nuts 189. By reason of the tubes 185 and washers 191 .the

bolts. are effectively insulated from the parts through which they extend so as to prevent the terminals 159 being in electrical communication with the sleeve 171 and the furnace casing. For preventing leakage of air between the insulating ring 181 and the flange 175 atone side of it, and between it and the disc 179 at its other side, said flange and disc are each provided with a circumferential groove 195 receiving a resilient gasket 197, preferably an Q-ring, these gaskets bearing against the opposite flat sides of the ring 181. It will be observed that by the construction just described the terminals 159 are rigidly mechanically connected to the adjacent side wall of the furnace casing, which acts to prevent shifting of the resistor grid relative to such wall when the furnace is rocked or tilted.

As shown, the ends of the intermediate resistor bars 149 have reduced diameter screw-threaded end portions 199 which extend through openings 201 in graphite plates 203 and are clamped to said plates by nuts 205 so as to place them in electrical communication therewith. Those end portions of the end resistor bars 151 which are remote from the extensions 157 are in a like manner connected to the adjacent plates 203. In this way the resistor bars and their extensions are connected for series flow of electric current from one terminal 159 of the resistor grid to its other terminal.

'For suspending the resistor grid theplates 203 connecting the ends of the resistor bars are shown as slidably resting on graphite plates 207 screw-threadedly secured to the '-lower ends of vertically extending graphite rods 209 which project upwardly through openings 211 (Fig. 1) formed in the top wall slab 109 of the furnace chamber in spaced relation to the walls of such openings so as to be in electrically insulated relation to said Walls. Aligned with the openings 211 are the cylindrical bores 213 of sleeves 215, through which bores the rods 209 extend in out-of-contacting relation to the walls thereof. These sleeves 215, which preferably are of exteriorly square cross-section, are preferably formed of heat refractory material of poor heat conductivity such as porous carbon. The sleeves at their upper ends carry electric insulating rings 217 of heat refractory electric insulating-material such as zirconia or fused alumina, the sleeves being of suificient length to keep the temperature of these rings below that at which they will soften. Resting on the top of the rings 217 are graphite washers 219, the rods 209 extending upwardly through these washers and at their upper ends screw-threadedly carrying'graphite nuts 221 resting on the washers. By reason of this construction the rods 209 are effectively electrically insulated from the sleeves 215 and the upper roof slab 109 on which such sleeves rest.

As shown, also resting on the upper side of the roof slab 109 of the furnace chamber is an upwardly extending tubular structure 222 having a bore 223 aligned with an opening 225 in said slab positioned centrally thereof, this tubular structure being exteriorly of square crossscction and preferably being formed of porous carbon so as to have poor heat conductivity.

At a level above the upper end of the tubular struc ture 222 just described the furnace casing interiorly thereof carries a peripheral flange 227 on which rest removable slabs 229, preferably of graphite, forming a layer which acts to insulate the cover 39 of the furnace. This layer is formed with an opening 231 in alignment with the bore 223 of the tubular structure 222, and aligned with the opening 231 is an upwardly extending metallic tube 233 carried by and projecting above the furnace cover 39. The upper end of this tube is normally closed in a fluid tight manner by a removable cover plate 235. Upon removal of the cover plate there may be attached to the upper end of the tube a charging device, of known kind, for from time to time charging the furnace chamber with metal, such as cut up scrap, by way of the bore of the tube and the opening 231, bore 223, and opening 225.

The layer formed by the slabs 229 at the top of the furnace casing is also formed with an opening 237 with which is aligned the bore of a metal tube 239 carried by and extending through the furnace cover 39. The upper end of this tube may be connected by a conduit 241 to a vacuum pump or the like for exhausting the furnace chamber and parts connected thereto, this conduit being flexible and of sufficient length to permit rocking and tilting of the furnace. Melting metal such as titanium or zirconium in a vacuum furnace having provision for continuously exhausting the portions of the furnace containing the molten metal acts to cause such metal to be free from absorbed gases.

Also carried by the platform 27 which supports the furnace is a casting chamber 243, of a known kind, adapted to contain a removable mold 245, which mold rests on a platform 246 having at opposite sides thereof upwardly extending arms 247, these arms'being swingingly and removable trunnioned at 249 on brackets 251 fixedly carried internally of the casting chamber by its side walls. The purpose of swingingly trunnioning the mold is to maintain it in vertical position when the furnace is rocked or tilted about the pivotal support 61.

For pouring the contents of the furnace into the mold 245,-when the furnace is tilted, there is shown a pouring conduit or spout 253 preferably formed of graphite. This conduit is shown as slidably extending through a heat refractory sleeve 255 also preferably formed of graphite, this sleeve extending through a metal sleeve 257 connecting the adjacent walls of the furnace casing and casting chamber. The conduit 253 also extends through the mass 135 of porous carbon and abuts at its inner end against the outer side of the body 115 which forms the interior flange 117 of the furnace chamber. Extending through the body 115 is shown a tube 259 having a pora tion projecting at its outer end from said body and screwthreaded into the end of the conduit 253 so as to connect the bore 261 of said tube to the bore 263 of said conduit.

As shown, the casting chamber has a removable water jacketed cover 265 normally resting thereon in fluid tight relation thereto. After the furnace is poured the metal in the mold 245 may be permitted to solidify, whereupon the cover 265 of the casting chamber may be removed, and the platform 246 by means of its side arms 247', together with the mold and its contents, may be lifted from said chamber, preferably the energization of the resistor grid being reduced to facilitate such solidification.

As illustrated, communicating with the charging tube 233 for the furnace is a valve controlled pipe 267 (Fig; 1) leading from a source of inert gas, such as argon, under pressure for initially flushing the furnace and casting chambers to remove air therefrom, the argon admitted through the pipe escaping from the furnace chamber into the casting chamber through the pouring spout 253, and from the casting chamber through a pipe (not shown) connected to an opening 269 in the walls of the casting chamber. This supply of argon may also be established when the cover plate 235 of the charging tube 233 is removed, so as to prevent entrance of air into the interior of the furnace by way of such tube. Likewise it may be established when the cover 265 of the casting chamber is removed while the cover plate 235 is in place for preventing entrance of air into the interior of the furnace by way of the pouring spout 253 and tube 259.

In the present embodiment of the invention because of the high temperatures employed the porous carbon sleeves 215 must be long to prevent heating of the insulators 217 to their softening temperature, and the tubular structure 222 must be correspondingly long to bring its upper end in proximity to the charging opening 231 in the layer formed by the slabs 229. For insuring against shifting of the sleeves 215 and the tubular structure 222 when the furnace is tilted they are shown as fitting recesses 270 in the upper side of the furnace chamber roof slab 109, which recesses receive their lowerend portions. For further insuring against such shifting, and for preventing their tilting relative to the slab 109, there is shown a plurality of rods 271, of heat refractory material such as hard carbon or graphite preferably the latter, extending horizontally from the walls of the furnace casing operatively to the sleeves 215, there being interposed between such sleeves and the adjacent ends of these rods plates 273 of heat refractory electric insulating material. Further, there is interposed between the two left hand sleeves 215, as viewed in Fig. 3, a spacing plate 275 of such material. Also there is interposed between the tubular structure 222 and adjacent plates 273 at the left of said structure, as viewed in Fig. 3, a like spacing plate 277. against which latter the right hand end ofthe spacing plate 275 bears. Still further, there is interposed between the opposite side of said tubular structure and the sleeve 215 at its right, as viewed in Fig. 3, a spacing plate 279. As shown, interposed between the left hand vertical edge of the plate 275, as viewed in Fig. 3, and the adjacent wall of the furnace casing is a further rod 281. The several rods and insulating plates just described are partially embedded in the upper surface of the mass 13S! of carbon beads so as to be supported thereby and held against lateral movement. As clearly indicated in Figs. -1 and 3,

the insulating plates which contact the sleeves 215 also contact the graphite washers 219 supported by said sleeves so as electrically to insulate said washers from the body of carbon beads, the tubular structure 222, and the walls of the furnace casing. The plates 275, 277 and 279 preferably are of the. same material as the plates 273, which material may be zirconia or fused alumina.

It will be understood that within the scope of the appended claims wide deviations may be made from the form of the invention described without departing from the spirit of the invention.

I claim:

1. An electric furnace comprising means forming a furnace chamber having top, bottom and side walls, a resistor grid in said chamber between its top and bottom walls in spaced relation thereto and to said side walls for radiating heat downward toward its bottom wall, means mounting said furnace for tilting movement, means comprising elongated heat refractory members for suspending said grid in said chamber, which members extend upward from said grid through said top wall, means carried by said top wall at the upper side thereof for supporting said members at their upper end portions against downward movement under the weight of said grid, and means above said top wall associated with the said means for so supporting said members and operatively extending from such supporting means laterally thereof adjacent the upper end portions of said members for bracing said supporting means against shifting when the furnace is tilted.

2. An electric furnace according to claim 1 in which the means for supporting the members which suspend the grid are tubular, said members extending through the bores of such tubular means, there being a heat insulating layer of granular material resting on the top wall of the chamber and surrounding said tubular means, and the means for bracing said tubular means against shifting being supported by said layer.

3. An electric furnace comprising a metallic casing containing heat refractory material defining a furnace chamber having top, bottom and side walls, a resistor grid in said chamber between its top and bottom walls in spaced relation thereto and to said side walls for radiating heat downward toward its bottom wall, means mounting said furnace for tilting movement, means comprising elongated heat refractory electrically conductive rods for suspending said grid in said chamber, which rods extend from said grid through openings formed in said top wall in spaced relation to the walls of such openings, sleeves supported by said top wall at the upper side thereof through which said rods extend in out-of-contacting relation to the walls of such sleeves, which sleeves are of electrically conductive material of relatively poor heat conductivity, heat refractory electric insulators carried by said sleeves adjacent their upper end portions for supporting said rods against downward movement under the weight of said grid, and means comprising elongated members operatively extending from said sleeves to said casing at the upper end portions of said sleeves for bracing said sleeves against shifting when the furnace is tilted.

4. An electric furnace according to claim 3 in Which a heat insulating body of granular material rests on the top wall of the furnace chamber and surrounds the sleeves, the elongated members which brace said sleeves against shifting being supported by said body.

5. An electric furnace comprising means forming a furnace chamber having top, bottom and side walls, a resistor grid in said chamber between its top and bottom walls in spaced relation thereto and to said side walls for radiating heat downward toward its bottom wall, said grid having end extensions projecting through said side walls to the exterior of said furnace, means mounting said furnace for tilting movement, means restraining said grid against lateral shifting when said furnace is tilted, means comprising elongated heat refractory members for suspending said grid in said chamber, which members extend upward from said grid through said top wall, means carried by said top wall at its upper side for supporting said members at their upper end portions against downward movement under the weight of said grid, and means above said top wall associated with the said means for so supporting said members and operatively extending from such supporting means adjacent the upper end portions of said members in the directions of the lengths of said end extensions for bracing said supporting means against shifting when the furnace is tilted.

6. An electric furnace comprising a metallic casing, means mounting said casing for tilting movement from a generally horizontal to an inclined position in such wise as to raise and lower at least one lateral side thereof, heat refractory material within said casing defining a furnace chamber having top, bottom and side walls, a resistor grid in said chamber intermediate its bottom and top walls for radiating heat downward toward said bottom wall, which grid has end extensions projecting through the side walls of said chamber and casing at said side of said casing which is so raised and lowered, means at the exterior of said casing for securing said extensions to said casing in electrically insulated relation thereto acting to prevent lateral shifting of said grid when said casing is tilted, means suspending said grid in said chamber comprising elongated graphite rods extending through openings formed in said top wall of said chamber in spaced relation to the walls of such openings, upwardly extending sleeves of porous carbon supported on the upper side of said top wall, through the bores of which sleeves said rods extend in spaced relation to the walls of said bores, heat refractory electric insulators carried by said sleeves at their upper end portions, means supporting said rods at their upper end portions on said insulators, and means in electrically insulated relation to said rods operatively extending from said sleeves adjacent their upper end portions to the side walls of said casing acting to brace said sleeves against shifting when the furnace is tilted.

7. An electric furnace comp-rising a casing containing means forming a furnace chamber having top, bottom and side walls, means mounting said furnace for tilting movement, means for charging said chamber with material to be treated therein comprising an opening formed in the top wall of said chamber and a sleeve supported by such wall at its upper side having a bore in registry with said opening, a resistor grid in said chamber, means for suspending said grid in said chamber comprising elongated suspension members extending from said grid through openings formed in the top wall of said chamber, sleeves having bores in registry with the last mentioned openings resting on said top wall at its upper side, through the bores of which last mentioned sleeves said suspension members extend in spaced relation to the walls of such bores and those of said openings registering therewith, these last mentioned sleeves being positioned at opposite sides of the first mentioned sleeve, elongated members extending laterally of the sleeves through which said suspension members extend for bracing such sleeves operatively against said casing for restraining them against shifting when the furnace is tilted, and means between those sides of the first mentioned sleeve which face the sides of the said sleeves through which the suspension members extend for bracing said first mentioned sleeve against shifting relative to said sleeves through which said suspension members extend.

8. An electric furnace according to claim 7 in which the suspension members and the sleeves through which they extend are of electrically conductive material, and said suspension members are supported by electrical insulators carried by said sleeves adjacent the upper end portions of the latter.

9. An electric furnace according to claim 7 in which the suspension members and the sleeves through which they extend are of electrically conductive material, and

said suspension members are supported by electrical insulators carried by said sleeves adjacent the upper end portions of the latter, there being a body of granular heat insulating material resting on the top wall of the furnace chamber and surrounding said sleeves, the means which braces the several sleeves against shifting relative to each other and the elongated members which extend laterally of those sleeves for bracing them against shifting relative to the furnace casing being supported by said body.

10. An electric furnace having a water jacketed casing, heat refractory material within said casing in heat conductive relation to the walls thereof defining a furnace chamber having top, bottom and side walls, a resistor grid in said chamber between its top and bottom walls for radiating heat downward toward said bottom wall, said side walls between said grid and said bottom wall having a circumferential interior flange for shading the peripheral portion of said bottom wall beneath said flange and the portions of the side walls between said flange and bottom wall from heat radiated downward from said grid, means for charging to said chamber above said flange metal to be melted by heat radiated downward from said grid, whereby, by reason of such shading and conduction of heat to the water jacket from said bottom wall and from the portions of the side walls between said flange and bottom wall, .to maintain a solid layer of such metal on said bottom wall and a peripheral rim of solid metal extending upward from the periphery of such layer in contact with the portions of said side walls beneath said flange, which bottom layer and rim form a pot-like receptacle for receiving the metal charged to said chamber and in which such metal may be melted.

11. An electric furnace according to claim 10 in which the circumferential interior flange of the side walls of the furnace chamber is formed as part of a body of heat refractory material of relatively poor heat conductivity operatively interposed between the portions of the side walls above and below said flange for minimizing conduction of heat from the portions of said side walls above said flange to the portions thereof below said flange.

12. An electric furnace according to claim 10 in which the circumferential interior flange of the side walls of the furnace chamber is formed as part of a body of porous carbon operatively interposed between the portions of the side walls above and below said flange for minimizing conduction of heat from the portions of said side walls above said flange to the portions thereof below said flange.

13. An electric furnace having a water jacketed casing, heat refractory material within said casing in heat conductive relation to the walls thereof defining a furnace chamber having top, bottom and side walls, a resistor grid in said chamber between its top and bottom walls for radiating heat downward toward said bottom wall, said side walls between said grid and said bottom wall having a circumferential interior flange for shading the peripheral portion of said bottom wall beneath said flange and the portions of the side walls between said flange and bottom wall from heat radiated downward from said grid, means for charging to said chamber above said flange metal to be melted by heat radiated downward from said grid, whereby, by reason of such shading and conduction of heat to the water jacket from said bottom wall and from the portions of the side walls between said flange and bottom wall, to maintain a solid layer of such metal on said bottom wall and a peripheral rim of solid metal extending upward from the periphery of such layer in contact with the portions of said side walls beneath said flange, which bottom layer and rim form a pot-like receptacle for receiving the metal charged to said chamber and in which such metal may be melted, said flange being formed of porous carbon having a reinforcing insert of graphite and being interposed between the portions of the side walls at the upper and lower sides of said flange for minimizing conduction of heat from such upper portions to such lower portions. 7

14. An electric furnace having a water jacketed casing, heat refractory material within said casing in heat conductive relation to the walls thereof defining a furnace chamber having top, bottom and side walls, a resistor grid in said chamber between its top and bottom walls for radiating heat downward toward said bottom wall, said side walls between said grid and said bottom wall having a circumferential interior flange for shading the peripheral portion of said bottom wall beneath said flange and the portions of the side walls between said flange and bottom wall from heat radiated downward from said grid, means for charging to said chamber above said flange metal to be melted by heat radiated downward from said grid, whereby, by reason of such shading and conduction of heat to the water jacket from said bottom wall and from the portions of the side walls between said flange and bottom wall, to maintain a solid layer of such metal on said bottom wall and a peripheral rim of solid metal extending upward from the periphery of such layer in contact with the portions of said side walls beneath said flange, which bottom layer and rim form a pot-like receptacle for receiving the metal charged to said chamber and in which such metal may be melted, said flange. being formed of porous carbon having a reinforcing insert of graphite and being interposed between the portions of the side walls at the upper and lower sides of said flange for minimizing conduction of heat from such upper portions to such lower portions, the porou carbon constituting the portion of the flange exposed to heat radiated downward from the grid.

References Cited in the file of this patent UNITED STATES PATENTS

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