US1493731A - Electric furnace - Google Patents

Description

May 13 1924. v

C. A. CADWELL ELECTRIC FURNACE Filed July 3. 1920 2 Sheets-Sheet 1 v l 2 W 3, e e a 9. 3 /o /W m, mz //A W L o w f E 2 /N H M w nm/ w w a 1 D U o Z A Fu v. m 5 c 1 w. u J w. 1li A M w 3 c E n ..g\%l5 n n 4 4 x), Av MM z QV .www Q ,f I. .ll z o V ,o 2 u, l m M Patented May 13, 1924.

UNITED STATES y 1,493,731 PATENT OFFICE.

CHARLFSA. CADWELL, 0F CLEVELAND, OHIO, ASSIGNO'R TO THE ELECTRIC RAILWAY IMPROVEMENT COMPANY, OF CLEVELAND, OHIO, A CORPORATION 0F OHIO.

ELECTRIC FURNACE.

Application led July 3,

To all whom t may concern:

Be it known that I, CHARLES A. CADWELL, a citizen of the United States, and a resident of Cleveland, county of Cuyahoga, and State of Ohio, have invented a new and useful Improvement in Electricl Furnaces, of which the following is a specification, the principle of the invention being herein eX- plained and the best mode in which I have contemplated applying that principle, so as to distinguish it from other inventions.

In general the present improved furnace is of the type wherein a resistor of granular material is employed in conjunction with a plurality of electrodes by which the current is conducted to thefurnace. More particularly the object of the invention is to provide in a furnace of this general type a laterally enclosed chamber or else a crucible, which for the purpose in hand, may be regarded as the equivalent of such a chamber, in order that the articles to be heated or melted, as the case may be, may be placed in such chamber or crucible,

To the accomplishment of the foregoing and related ends, the invention, then, consists of the means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the followino; description setting forth in detail certain mechanism embodying the invention, such disclosed means constituting, however, but several of the various forms in which the principle of the invention vmay be car- P ried out.

In said annexed drawings Fig. 1 is a central longitudinal section of a crucible furnace embodying my present improvements; Fig. 2 is a transverse section of the same, the plane of the section being indicated by the line 2-2, Fig. 1; Fig. 3 is a plan view of said furnace; Fig. 4 is a broken sectional view corresponding to that of Fig. 1, but showing a muflie charnber in place of a crucible; and Fig. 5 is a section corresponding with that of Fig. 2, but showingr the same modification in construction as Fig. 4.

Referring to the construction of furnace shown in Figs. 1, 2 and 3, such furnace will be seen to comprise an outer casing 1 pref erably of sheet metal` and of any desired shape and size, the elongated rectangular form shown being merely illustrative. The sides and bottom of this casing are lined 1920. Serial No. 393,918.

with layers 2 of suitable heat non-conducting material, such as infusorial earth, the walls of the furnace chamber proper being .defined by plates or blocks?) of fire-clay or equivalent heat resisting material. The bot- 5 which is removably held therein. WVhen the crucible is in place its spout is designed to be directed towards one side of the furnace chamber` and the corresponding lateral wall 3 of the latter is provided with a channeled block 6 that forms in effect a continuation of such crucible spout. Accordingly, by tilting the furnace as a whole about its longitudinal central axis, the contents of thn crucible may be discharged over this spout extension without it being necessary to remove the crucible.

Two blocks 7 of the same material as the blocks 3`enclose the furnace chamber proper from above, and fit laterally about the upper projectinxr portion of the crucible 5. The opening 8 that is left between these blocks 7 is arranged to be cosed by means of a movable cover 9 that slidably rests on said blocks 7, being carried by a pair of rocker arms 10 connected at their upper ends to a, yoke 11 that is attached tosaid cover block 9.

Within the furnace chamber, adjacent the respective ends thereof, are two graphite blocks 12 that constitute the electrodes through which the current is conducted to said chamber. The inwardly directed faces of these electrodes are preferably curved, as best shown in Fig. 3, to correspond with the curvature of the crucible holder 4, and the space between such blocks and crucible holder is packed with granular carbon 13 or some similar conducting material of relatively high resistance.

The current accordingly in passing lengthwise through the material composing such resistor generates heat due to the resistance encountered. Ordinarily, with a resistor of the` character described, it is found. that the heat generated by the passage of the Current is greatest along the bottom of the furnace chamber, which is objectionable, not only because it tends to burn out such bottom, but also because there is a Corresponding loss in efficiency. Without entering upon a detail explanation of this condition, I have found that by embedding in such granular material a transversely eX- tending graphite body of the general form of the Crucible holder 4, the electrical resistance for the passage of the current is decreased in a plane spaced above the floor of the furnace chamber. As a result the path of greatest current density will include such holder and the Crucible/held therein, instead of being deflected along the fioor or the side Walls of the furnace chamber Where it would be relatively ineffective.

For the purpose of oscillatorily supporting the furnace, trunnions are provided, one at each end, said trunnions being tubular in order to permit graphite rods 16 to extend therethrough. The inner ends of these rods are threaded or otherwise firmly attached to the electrode blocks 12 while in order to conduct the current to said rods respectively, collars 17, carefully insulated from the trunnions 15, are attached to said rods. As shown in Figs. 1 and 3, flexible conductors 18 are in turn attached to said Collars.

In the modified form of furnace shown in Figs. 4 and 5, instead of utilizing a vertically disposed graphite body of the form of Crucible holder 4, I substitute a horizontally disposed hollow graphite or carbon block 20, preferably of the cylindrical shape illustrated, and of such size as to provide an adequate interior space for the reception of the article or articles to be heated. In other words, this form of furnace is primarily adapted for use as a muftle furnace, the open ends of the chamber being closed by removable plugs 21 of fire-clay or the like. Preferably the chamber is lined with a layer 22 of alundum or similar plaster. The main body of the hollow block is embedded in a mass of granular material 23 that constitutes a resistor of the same character as that shown and described in connection with the first form of furnace; and just as in the case of the crucible holder 4, so said chamber 2O serves to decrease the electrical reiaea'rei sistance for the passage 'of tric current in a plane spaced above the floor of the furnace chamber.

Other modes of applying the principle of my invention may be employed instead of the one explained, Change being made as regards the lnechanism herein disclosed, provided the means stated by any of the following claims or the equivalent of such stated means be employed.

I therefore particularly point out Yand distinctly claim as my invention 1. In anvelectric resistance furnace, the combination of a suitable chamber provided with hollow trunnions, electrodes extending into said chamber through such trunnions, a vertically disposed Crucible holder of graphite positioned centrally of said chamber, and a resistor of granular Conducting material lying about said electrodes and between the same and said Crucible holder.

2. In an electric resistance furnace, the combination of a suitable chamber provided with hollow trunnions, electrodes extending into said chamber through such trunnions, a vertically disposed Crucible holder of graphite positioned Centrally of said chamber, a resistor of granular Conducting material lying about said electrodes and between the same and said Crucible holder, and a block-of heat-resisting material provided on its upper face with a downwardly and outwardly directed channel positioned against said Crucible adjacent its upper edge and projecting from said Chamber so as to form a spout adapted to discharge the contents of the Crucible in said holder when said furnace is oscillated about such trunnions,

3. In an electric resistance furnace, the combination of a suitable Chamber provided with hollow trunnions, electrode rods eX- tending into said chamber through such trunnions, electrode blocks secured to the ends of said electrode rods andpositioned parallel to the respective ends of said chamber, a vertically disposed Crucible holder of graphite positioned Centrally of said chamthe heating eleci ber, and a resistor of granular conducting material positioned about said'crucible and between t e. same and said electrode blocks.

Signed by me, this 1st day of July, 1920.

CHARLES A. CADWELL.

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