US1412512A - Electric furnace - Google Patents

Description

0. A. COLBY.

ELECTRIC FURNACE.

APPLICATION FILED APR. 23, 1920.

l ,4 1 2,5 1 2. I Patented Apr. 11, 1922.

WITNESSES: INVENTOR gm/zco/b 4/ /M% ATTORNEY i be easily and quickly renewed.

umrsn s'rarss PATENT OFFICE.

I ORA. A. GOLBY, 0F IRWIN, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

' ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Apr. 11,1922.

To all whom it may concern:

Be it known that I, QRAIA. COLBY, a citizen of the United States, and a resident of Irwin, in the county of Westmoreland'and State of Pennsylvania, have invented a newand. useful Improvement in Electric F urnaces, of which the following is a specification.

My invention relates to electric furnaces and particularly to high-temperature furnaces of the electric-resistance type and it has for oneof its objects to provide an electric-resistance furnace adapted to operate for comparatively long periods of time. at relatively high temperature for annealing and heat treating of metal objects.

Another object is to provide a furnace of this type that shall employ solid blocks of refractory electrical conducting material for the resistor and that shall embody improved means for conducting current to and from the resistor.

Another object is to provide a furnace so constructed that the block resistors shall support thereof of the chamber, whereby a lower dontact resistance is obtained between the resistor and the terminal elec trodes which operatively engage the re-.

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Another object is to still further reduce the contact resistance between. the electrodes and the resistor by providing an auxiliary current path of relatively low resistance there-between, which current path may Another object is to provide a resistor which shall comprise a plurality of solid blocks ofelectrical conducting refractory material, such as may be purchasedin the open market so that the possibility of failure of the complete resistor is slight.

In practicing my invention, I provide a chamber in a refractory casing, the solid blocks oi refractory electrical-conducting material. comprising the resistor forming the side walls of the chamber. I provide [auxiliary recesses inthe casing adjacent the ends of the resistor blocks and locate therein solid terminal electrodes and a mass of granular electrical material operatively connecting the electrodes and the resistor blocks. I provide means whereby the granular electrical-conducting material may be easily and quickly renewed when it has been consumed during the operation of the fun nace.

In the single sheet of drawings, Figure 1' is a cross-sectional view of the furnace embodying my invention on the line I-I of Fig. 2, and Fig. 2 is a cross-sectional view on the line II-II of Fig. 1.

The supporting structure of the furnace comprises an exterior metal casing or frame 1, which encloses an outer shell 2 of heatinsulating brick and an inner shell 3 of fire brick. The vertical parts of the shell 3 are spaced apart to form a chamber 4:. A resistor 5 comprises a plurality of bricks or slabs of carborundum or silicon carbid, these blocks being in substantially a vertical position at the sides of the chamber a and forming the side walls thereof. A terminal electrode 6 is placed beneath the lower end of the resistor blocks 5, and a similar electrode 7, of slightly difi'erent form of crosssection, is placed above the upper end of the resistor blocks 5, both of the terminal electrodes operatively engaging the ends of the resistor blocks. A substantially horizontal.

'9' of finely divided electrical-conducting granular material, such as graphite or coke. The material 9 is thoroughly packed or ta'mped into place so that it will carry a relatively large portion of the current which may flow through the resistor blocks 5 and owing to its relatively low resistance and owing to the fact that it provides a large number of contact members with. the lower end ofthe resistor blocks 5, the energy loss in this granular material will be relatively small. An opening 10 is- .provide d-at the rear end of the furnace, coaxial with each of the recesses 8, to permit of access to the recess so that the granular material may be retamped whenever necessary or be entirel withdrawn and renewed whenever desire. A suitable covermember 11 is provided for the opening 10 to'retain the granular material in lace in the recess 8.

' Simi ar recesses 12 are provided outside of, and adjacent to, the upper end of the resistor blocks 5 and the terminal electrodes 7, these recesses being filled with granular electrical-conducting material 9, the same as used in the recess 8 and for the same pur pose. The recess 12 may extend to the upper surface of the furnace and, in this way, provide ready access to the recess and the granular material contained therein so that it may be tamped or renewed Whenever this becomes necessary.

A roof 13, formed of bricks or slabs of highly refractory material, is provided for the chamber l and is so formed that it rests upon theupper terminal electrodes 7, forcing these into close operative engagement with the upper ends of the resistor blocks and also forcing the lower ends of the resistor blocks 5 into close operative engag ment with the terminal electrodes 6. This provides a means for reducing the contact resistance between the electrodes and the resistor blocks but, as the resistor blocks may not expand and contract equally during repeated heating and cooling of the furnace, the contact between the carbon electrodes 6 and 7 and the resistor blocks 5 vary and, therefore, the granular material 9 is provided so that proper contact may be made, irrespective of the variations of length of the individual resistor blocks 5. A lifting member 1% is suitably secured to the roof 13 to permit of removing and re placing the roof l3 Whenever desired.

A. metal terminal plate 15 is provided for each of the terminal electrodes 6 and 7, being located below the electrode e and above the electrode 7. The electrodes 6 and 7 may consist of graphite or of amorphous carbon, and suitable connecting means may be used to connect the metal terminal plates thereto. A dead-air space 16 is provided adjacent to the outside of the resistor blocks 5 to reduce the amount of heat which is conducted aWay from the outside of the resistor blocks 5.

While I have indicated that each of the sets of resistor blocks 5 is in a separate cir-v cuit, it is, of course, to be understood that the two sets of blocks may be connected in series if it is desired to apply a relatively higher voltage to the terminals'of the fun nace.

I thus provide a furnace of relatively high capacity in which the resistor comprises a relatively large number of individual blocks of refractory material. I provide, also, means for conducting the current from these resistor blocks Which shall insure a current flowing through all of, the resistors in parallel, even though the individual blocks expand and contract difilerent amounts. l provide also means for readily renewing the granular current-conducting means, thus insuring that the furnaces may be operated for relatively long periods of time Without torn down and reassembled. hile I have shown a specific embodiment of my invention, various changes may be bein arnets made therein without departing from the spirit and scope of my invention, and I desire that only such limitations shall be placed thereon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invention:

1. in an electric furnace, the combination with a chamber, of a resistor adjacent said chamber and forming the side Wall thereof, electrodes operatively engaging the ends of said resistor, terminal members connected to said electr'odes,and masses of electrical-conducting granularmaterial operatively engaging the ends of said resistor and said electrodes.

2. ln' an electric furnace, the combination With a chamber, of a resistor comprising solid bricks or blocks of refractory electrical-conducting material forming the side WtLllS'Ol said chamber, solid carbonaceous terminal electrodes operatively engaging the ends of said resistor, and a mass of electri cal-conducting granular material operatively engaging each of the electrodes and the adjacent resistor-end.

3. in an electric furnace, the combination with a chamber, of a resistor comprising solid bricks of refractory electrical-conducting material forming the side Walls of said chamber, terminal electrodes adjacent the ends of said resistor, granular electrical-conducting material operatively engaging the ends of the resistor and the adjacent electrode, and a cover member for said chamber adapted to cause said electrodes and said resistor to operatively engage each other.

l. In an electric furnace, the combination with a chamber, of a resistor comprising solid bricks or bloclrs of refractory electrical-conducting material forming the side Walls of said chamber, terminal electrodes adjacent the ends of said resistor, and a roof for said chamber, said resistor blocks and said electrodes being adapted to support said roof in its operative position.

5. In an electric furnace, the combination with a heating chamber, of aresistor comprising solid blocks or bricks of refractory electrical-conducting material forming the side Walls of said chamber, terminal electrodes adjacent the ends of said resistor, masses of electrical conducting granular material operatively engaging the ends of said resistor and the adjacent electrodes, and a roof for said chamber, said roof being supported by said resistor and said terminal electrodes.

6. Iii an electric furnace, the combination with a chamber and av roof for said cham- 1535 her, of a resistor comprising solid bricks of refractory electrical-conducting material forming the side Walls of said chamber, terminal electrodes adjacent to the ends of said resistor, said electrodes and said resistor being adapted to support Said roof in its operative position and means for reducing the amount of heat conducted away from-the sides of said reisistor and said chamber.

7. In anelectrical furnace, the combination With a chamber, and aroof for said chamber, of a resistor comprising bricks of refractory material forming the side Walls of the chamber, solid carbonaceous terminal electrodes adjacent the ends of said resistor bricks, said resistor and said electrodes being adapted to support said roof-in its operative position, a mass of electrical-conducting granular materialoperatively engaging the ends of said resistor blocks and said electrodes, and jacketing means adjacent said resistor blocks for reducing the amount of heat conducted away from the sides of said resistor and said chamber.

electrodes adjacent to, and operatively engaging the ends of said resistor blocks,

masses of electrical-conducting granular material located in the sides of said resistorblocksaway from said chamber and operatively engaging the ends of said resistor blocks and the adjacent electrodes and a roof for said chamber, said roof being supported "by said resistor and 'said' electrodes.

In testimony whereof, I have hereunto subscribed my name this 1st day of April,

ORA A. COLBY.

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