Near the other end of the wall flue P is shown an inlet pipe or passage 61, extending between an exterior point and the wall flue. The furnace and chamber are shown with downfeed, being arra,.nged upright, and the lowe@ end of the chamber tube is shown as being enlarged and discharging at some distance vertically above and on to a conical distributor or screen 8, wlach serves for distrl-'butiiig tl,.e material discharged from said chamber over a discharge table 9, and each of these parts 8 and 9 inay be secured to the splqdle or drive shaft 10 of the iinpeller screw 9, and tbus partake of the rotation of the screw. The spindle I 0 is shown driven at both ends, through the medium of resilient couplings or cushioning springs i 1, 92, by driving worms on shafts 13, 14 meshing with worm wlieels to vihich the spring couphngs are connected. The two shafts are adapted to be rotated, th.,-ough bevel gearin.a, from a common power shaft 15 with such reduction tb-at the speed of the shaft d 0 and feeder 4 is, for exa ipie; of the order of about one revol,dtion per minlite, b@,it naturally va@-ied aecordizig to the desired duration of treatir-ent in an,v particular case. F-eferring further to the feedip-g device or rotary screw 4, ',his is s'nown in its oreferr,- d form comprising a refractory and heat conductive stem or core 41, mouiited o,.n tne ck,.oerating shaft g 0, and feed ribs or screw t.-hreads,,Zb projecting from , the core substantially to the chat-,iber inner vtrall part 1. By this -.,,rrangement the ground mass does not fUl the chai-nbet, bub occupies only, the annular sdace or path A between tTie care @ia and the wall 2. By having th6 screw stem relatively twck and -the annular palh relatively thin, as show,n, the advancing mass between these hot parts, vihich itself may be a poor heat conductor, becomes rapidly, thoroughly and uniformly heated throughout the mass, to the great betterment of the reiiction or treatment. The outer wall part 2 of the chamber wall is shown surroiinded by a body 20-6'k' of electricalresistatice-heating matei-ial contained in a relatively wide space between the chamber ar@d a refractory casing or jocket iS of composition comprising asbestos, magnesia, aluminu-rn ozide or the lilee, said exterior casing showri resting o-,q a refractory base or slab 17, which itself is supported by P. steel frame-i-ork, -upon which also the bearings of tb-e drivin.- gearing are mounted. Electric current is introduced to the mass 23-21 by electrodes IS, of wi-Ach three are shovvn as extended throu,-h aoertures provided, at different le-vels, in the jacket 16. Sai-d electrodes are arranged to be radiauy slidable in suitabjy cooled sleeves or buslies 19, and the inn,,r end of each electrode is provided wit'n a readily renewable wearing piece or tip of reduced cross section, said piece preferably being screwed into the inner end of the body of the electrode. , The ample space between t-fie reaction chamber and the exterior jacket 16 Is filled ivlth resistance material, preferably granular and in graded arrangement. The Innermost layor 20', 1. e., the layer @,diacent to the chamber outer wall part 2, consists of relatively coarse granules,, as of coke, graphite, or the like. . The outermost layer 2 1, i. e., the layer adjacent to the casing or Jacket 16, consists of very fine or pulverized r@aterial sunh as sgot (lamp black, carbon black) affording an insulating function, and optionally it may be mixed with magnesia, aluminum oxide or the 22,274 instance, briquetted. The space interinediate said layers 20 and 21 is fllled with a layer 2011 of granular carbon or the like, the size of these granules decreasing, In outward direction, for example, from % size substantially corresponding to that of the granules of the inner layer 20, substantially to a size corresponding to that of the particles of the outer layer 2 1. The Inner portion of the body 20-201-- 21 of heating material, when sub10 Jected to a suitable current, generates and maintains the desired temperature in the tubular wall of chamber C, which is communicated to the advancing annulus Gf ore or.other mixture and to the cylindrical core of the feed device operating 15 in the chamber. The modus operandi of the described furnace is preferably as forows: First, the electrodes 18 are shifted or slid lnwq@rd, until t','Lieir inner ektremities o@- wear 'Llips 20 directly contact with the chaniber outer wall part 2, whereupon the current is switched on. The curreni; will thereupon flow between &Ie--trodes principally through the chamber wall, which is thus quickly heated to the required temperiture. 25 About then or thereafter the feeder or screw is begun to b-- ro@@ated, whereby the powdered ore or sl'bstance to be treated is caused slowly to adva@@,ice descendingly from the hopper 5 into and throudli the reaction char,,iber, each portion being So subject to the ho@@ treatmeiit for a orolonged p@Iriod untl' reaching the bottorr, or discharge ooening. 'vvhen the furnqcd chamber and the mL-,turL- therein have once reached the desired treatme7-it temperature, sj that from that mo35 me7lt onward the electrical energy supplied througli the electrodes 13 serves only for maintaining such teml>o-rature, tne electrgdes are readjusted and retracted a little from the charnber, whereo@, the current will thereafter pass for the 40 greater part through the coarse carbon granules 20, which by that time'have already assumed a high temperature. As a consequence, small. electric arcs will be formed between said granules. generating heat thus and by resistance, and the 15 total strength of the needed current will be con- siderably reduced. The extent of retraction of the electrodes and therefore their degree of immersion in the resistance mass may be varied at will by way'of control of the electric flow and generation of temperature. As stated, the very fine carbon powder or soot in the outermost layer in the space between the chainber wall and Jacket 06 aets as 9, heat @nsulator, so that the Jacket or casing remains rela55 tively --obl, minimizing heat loss. Besides, said fine material also acts as an elc-ctric insulp-tor, especially when magnesia or the like has been adrrixed therewith. If desired, the electrodes can be adjusted in posltion by automatic mears, as under the con00 trol of a suitable. thermos@tat, by way of controling the heating action to maintain a desired temperature. The separate vessel or receiving chamber 7 can be used for collecting and condensing gaseous 65 products that may be formed in the 'reaction chamber, for Instance, vapors of metals, as Mne. The increasing pitch of screw 4 in downward direction towards discharge may in some cases 70 be useful to prevent the s(>Iids undertreatment from clogging the reaction chamber. What is cl@Limed.1s: 1. An electric fumace comprising E@ base, a reaction chamber witli gi hollow waR structur6 surlike, aiid this layer may be suitably compressed, for @5 rounding said cliamber, said structure consisting

22)274 3 of Inner and outer wall parts,.with Inclined chtnnels in the inner wall part of said hollow vaU connecting the reartion chamber interior with the interspace or :ftue in the hoilow waH, a condenser connected to said chamber wall interspace,.an outer casing encircling said chamber waU structure with a space between said chamber waH and casing, means for introducing supplies of solid sizbstances into said chamber for treatment, means for discharging the treated io substances from the chamber, an insulating layer located adjacent to the inner face of said outer casing and occupying the outer portion of said space, a plurality of concentric layers of resistance lieati3ig material constituting a heatin.9 15 zone between said insulating layer and the outer face of said chamber wall structu're, said concentric layers or zone forming the main furnace heating means and consisting of durrent conducting particles of which the size graduary in- 20 creases in the direction from said insulating layer towards said chamber wall structure, and displaceable electrodes supported by s9Ad outer casing and protruding through said heat insulating layer into said heating zone. 25 2. An electric furnace comprising a base, a re-, action chamber with a houow wall structure surrounding said chamber, said structure consisting . of Inner and outer waH parts, with Inclined channels in the inner waU part of said hollow 30 wall connecting the reaction chamber Interior with the interspace or flue in the horow wall, a condenser connected to said chamber waR interspace, an outer casing encircling said chamber wafl structure with a space between said cham- 35 ber wall and cas@ng, means for introducing supplies of solid substances inio said chamber for treatment, a screw conveyor within the chamber for feeding the substances through the same, the pitch of sWd conveyor increasing from Its upper 40 to Its lower end, and means for discharging the treated substances from the chamber, an insulating layer located adjacent to the inner surface of said outer casing and occupying the outer portion of said space, a plurality of concentric 45 layers of,resistance heating material constituting a hezting zone between said insulating lay I er and the outer face of said chamber wall structure, . said concentric layers or zone forming the main fumace heating means and consisting @of current 50 oonducting particles . of which the size gradually increases In the direction from said Insulating layer towards said chamber waU structure, and displaciable electrodes silpported bi said outer casing and protruding through said heat Insulat- 5,5 ing layer into said heating zone, said electrodes being provided with exchangeable tips. 3. An electric furnace comprising a base, a tubular reaction chamber, a chamber waU struc- ' ture enclosing the chamber, an outer casing en- 60 circling said chamber wall structure, means for feeding the substances to be treated to said chamber from above anci for discharging the same from below, an insulating layer located next to the Inner surface -of said. outer casing, a 65 plurauty qf concentric layers of current conducting particles-@in a zone between said insiiIaUng layer and said chamber wall-structu're form@ ing the heating means of the furnace, the particle size of said layers gradually increasing In 70, the direction fro , m said insulating layer - inwardly towards said chamber wall s . tructure, and displaceable electrodes supported by said outer casIng. 4. A continuously-operable electric fumace for 75 treating solid substances or mixtures, havim a furnace support or ba-se and an outer enclosure or casing, and substance infeeding and discharging means, and comprising in combination therewith, a refractory-walled tubular reaction chamber. arranged longitudinally between the furnace infeed Rnd point of discharge of the substances to be treated, said chamber wiU being elbsed but of horow structure to provide gas or vapor interspaces constituting a longitudinal wall :due, with an extension passage leading from such flue to a separate place of disposal as to a condensing vessel, and said chamber waU having perforations in its inner face- for outflow of gases or vapors from the chamber interior to the wall flue, a body of electrical-res istance-heating material arranged surrounding the chamber waR in heating relation thereto,. and provided with current-supplying or electrode members, and an interior mechanical feed device as a rotatable screw of refractory material occupying and relatively operable within the chamber adapted progressively to convey or cause the advancing feed of the ma,ss of substances uncter treatnient. 5. A contiriuously-operable high-temperature, metallurgical electric fumace for treating ore substances, and distilling metals therefrom, having a fumace, support or base and an outer enclosure or casing, and substance Infeeding and discharging means, and 6ompridng a combina-. tion therewith, a refractorywalled tubular reaction chamber arranged between the fumace infeed and discharge, sWd chamber wall being closed but of hollow structure to provide lnterspaces constituting a wau,fiue, with an extension passage adapted to conduct -vapors froni such flue to a separate 4condensing vessial, and said "chamber wall having perforations In Its Inner face adapted for outflow. of vapors from the chamber interior to the waR flue, a body.of eleetrical-resistance-heating material arranged surrounding the chamber waH -in - heaung relation thereto adapted to generate temperatures sUMclent to vaporize n3:etals froin such ore substances, aiid provided with current-supplying or el6ctrode members, and,an Interior mechanical feed device as a rotatable screw of refractory ma occupying and relativ'ely operable, within the chamber adapted progressively, to convey or cause the advancing- feed therethrough of th6 mass of substances under treatment. 6.. A continuously-operable electric furnace for treating solid substances or mixtures, havlng a furnace. support or base and an outer enclosure or casing, and substance infeeding and dischargIng means, and comprising In combination therewith, a refractory-walled tubular reaction chamber arranged between a higher famace tnfeed means and A lower discharge means for the substances treated, said chamber wall being closed but of hollow structure to provide gas Inter-. spaces constituting aii upwardly extending wall flue, with an extension passage leading from the upper end of such flue to a separate place of dtsposali and said chamber waU hgving perforations in Its Inner face for o,utflow of gases or vapors from the chamb,er'interior to the wall flue, a body Of electrical-resistance-heating material arranged surrounding the chamber wall In heating relation thereto and with @electrgdes to conduct current thereto, and an Interior mechwcal feed device comprising a rotatable screw of refractory niaterial occupying and relatively operable withIn ttie chamb6r adapted progresdvely to convey or cause the advancing downfeed of the mass of

4 22,274 substances under treatment, at 9 predetermained re,te of screw rotation rnd speed of downfeed. 7. An electric furnace as in claimli and w, hereIn the body of electrical-resistenee-l-ieating nip--terial Is in subdivided or granulax Llorni confined between the chamber i,@all and thLouter casing, such material being 6f gradeci &it--s of particles methodically arranged with th-e coarser particles adjacent to the thamber and the flner particles adjacent to the casing. 8. An electric furnace Es In claizil 4 and v@herein the body of electrical-re-sistance-heating material is in subdivided or granuler form car-flned between the chamber waeu and the outer casing, such material being of -g-rp-ded sizes of particles methodically arranged vyith the coarser part-leles adjacent t-- the chamber end the f-iner particles adjacent to the cesing; the layer v,7hich is neor.@ est to tiie casing being composed of pexticles of such fineness es afford insulation proteet',ing the outer casing. 9. An electric furnace as in elpiin 4. and wherein the body of electrical-resistance-heeting material is in subdivided or granular form con:ftned between the chamber wall tlnd the outer casing, such material being of graded sizes of particles meth odically arranged wita the coarser particles adjacent to the chamber and the finer particles adjacent. to the casing; and wherein are electrodes extending through the casing Into th@-, mass of granlar material and shiftable into and out of substahtial cor-tact witn the chamber waH and io bodily removable for renewal and adjustable as to the-degree of extensi(>ii into the granular mass. 10. An electric fumace as in claim 4 and whereiri the mechanical feed device or screw ,omprises a refractory central stem or core of 'substantial 15 dism6ter thereby with the chamber wall definIng ari annular path for the advancing solids, wherein rapid, thorough and uniform heating of the solids occurs. 11. An electric furnace as in claim 6,9,nd where20 iia the feed ,,crew pitch varies along its length with increase of pitch toward the furnace discharge. DANIP-.L GARDNER.

Reissued Feb. 23, 1943 Re. 22,274 UNITED STATES 'PATENT OFFICE -22,274 ELECTRIC FURNACE Daniel Gardner, New York, N. Y., assignor, by mesne assignmentr,, to Cirdner Thermal Corporation, a corpomtion of Delawam original N6. 2,195,453, dated April 2,.1940, Serial No. 234,099, October 10, 1938. Application for reissue Februu7 17, 1942, Serial No.. 431,229 11 Claims. This invention relatc-,s to electric fumaces of the class adapted for carrying out chemical, metallurgical or heat-treatment operations, at suitable high tempei@atures according to the treatment in hand. Particularly the invention per- 5 tains to an electric furnace with tubular type of reaction chamber, which thus Is continuously operable, the ores or other mixtures or substances progress ing longitudinally from.furnace Inlet to discharg e through the chamber, e. g. with down- 10 ward trend to cooperate with gravii@. The general objects are to afford Increased rate of output, with improved effteiency and thoroughness, of reaction, and with reliable maintenance and cont,r.-I of treatment temperature and, duration" 15 and further advantages will appear from the following disclosure of an Mustrative embodiment of the invention, including durability of apparatus, continuous relief of generated gases and econom y as to heat losst-s and current consump- 20 tion. In a furnace according to the prdsent invention, the reaction chamber is refractory wared, its waU being closed against air entrance to the chamber , but of hollow structure or double - 23 walled to provide gas interspapes constituting a longitudi nally extending wall flue, @from which flue leads an extension passage or conduit to a separate place of disposal or reception, as t,6 a vapor condensing vessel; the inner wall part or 30 face being perforated for gas outflow from the chamber; space to the flue; there being a body of electrical-resistance-heating mate al ri arrange d surrounding the outer waU part of the chamber wall and In heating relation thereto axid- 35 adapted to have suita-ble current supplied to it; . and cooperative.therewith an interior mechani-. Cal feed device as a screw, 'of refractory ma;terial, occupyin g the chamber and operable or relatively rotatable therein progressively to eonvey or cause 40 the advancing feed Gf the mass of substances under treatment. By designating as refractory the chamber wala and the feed screw this term Is intended in Its broad sense of being reslstant to the high temperat-ures of treatment, and prefer- 45 ably also to corro.-,ion from the substances contacted; and these parts should be heat c'onductive as well. The term gas isused in the broad sense of including vapors. As rega.rds the iesist(CL 13--23) generated between t-he coamer particles of -material, into wmeh the electrodes project. Bad material surrounds the -tumace chamber, in which the treatment is to be carried out, in such a preferred arrangement that the size of the granules or particles decreases, from the inside Or chamber wall towards the outside or casing, to on. an exceedingly fine conditi , so that the outer layer of . the granular materw is formed by a fine powder which, by virtue of the very high intem&l resistance between its particles, actuaw f=ctions as an lnqijlator, both electrically and ther mally; the granules of the inner layer of Wd material, however, having a relatively large size. for example of about 3 to 8 m-., so that electric arcs can be fo=ed between the same. . . I In order that the above statements may be more readfly understood, reference is had to the annexed drawing, in which the alwe ft'ure,iUustrates, la a vertical sectional elevation, one embodiment of an electric furnace constructed in aceordance with the Invention. The furnace cbamber C has it interior space enclosed byitsre@fractory wall 1-2 which Is holand shown composed of a@ first WaU Part Or low Inner rylinder I of graphite, petroleum coke. smcon -@earbide, zirconiii- carbide or other conduetive material swtable for the PurPOses' andsurroundiiig the I=er cylinder, with a narrow lnterspace or flue r between, an outer cylii2qer, or wan part 2 of similar material. The fumace, chamb,er C has its innei waH -part I i@rovided with upwardly inclined perforations or narrow passages 3, constituting exits L for the escape of gases such as metal vapors to the wall flue P. Interiorly the cham-ber is fitted Lwith a mechanical feed device or impeuer screw 4. of refractory material such as graphite br petroleum coke. This driven feed device of screw, rotatable relatively to the chamber, occupies i@@y the cham,.ber space so as to.act directly onthe solid supstances under treaiinexit and progressively, convey or cause the advancing feed of the m and the -pitch of said screw is shown as varyft, namely, increasing from the infeed or.upper end to the discharge or lower end of the fumace.' The screw @ feeder extends upwardly and into a hopper 6 wlUch serves for,supplying the material to be treated, for-instance suitably ground ore ance h4ating material this is preferably in sub- 50 'in mixture with any required agents, as fluxes. divided or gr&nular form, and the generation of At one end, in this case the upper end, the tn@ heat Is effected in one or both of two ways, nameterspace P bet,@veen the chamber waU parts or cyl. ly, partly by the resistance encountered by the inders I and 2 communicates, through a conduit. electric current In its. passage through. the fur- or extension passage 6, with a sepamte place of nace or material. PartlY bY small electric arcs 43 disposal as a condensing vessel or chamber 7.@