US1456893A - Electric-furnace wall construction - Google Patents

Description

May 29, 1923.. 1,456,893

7 G. M. LITTLE ELECTRIC FURNACE WALL CONSTRUCTION Filed May 24, 1.921

WITNESSES; INVENTOR Wm .v

ATTORNEY Patented May 29, 1923.

UNITED STATES PATENT OFFICE.

GEORGE E. LITTLE, OI PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

ELECTRIC-FURNACE WALL CONSTRUCTION.

Application filed lay 24, 1921. Serial No. 472,095.

To all whom it may concern:

Be it known that I, Gnonon M. Lima, a citizen of the United States, and a resident of Pittsburgh in the county of Allegheny 5 and State of lennsylvania, have invented a new and useful Improvement in Electrlc- Furnace Wall Construction, of which the following is a specification.

My invention relates to electric furnaces l and particularly to electric-resistance furnaces and it has for its object to provide means for "reducing leakage current between the current-conducting electrodes.

In my co-pending application, Serial No.

1 454,776, filed March 23, 1921, I have disclosed an electric-resistance furnace in which the heating element comprises two substantially parallel members, each of which is provided with an elongated electrode extendin through the furnace wall.

I have foun that, under certain conditions of operation of a furnace, of the character designated, there is a relatively large leakage of current between the two elec- 2 trodes, especially if the bricks of the wall engage the electrodes and especially so if the temperature of the furnace is raised to a relatively high value.

In practicing my invention, I build up a portion of the furnace wall immediately adjacent to, and surrounding a part of the electrodes with a plurality of thin plates of refractory high-temperature-resisting material which plates may be separated either by a layer of granular material between successive plates or by a plurality of integral projections on the plates themselves. The resistance to the passage of an electric current between successive plates is thus increased many times by the use of either the granular material or the small-area integral projections.

In the single sheet of drawings,-

Figure 1 is a view, in vertical section, of an electric-resistance furnace comprising the device embodying my invention;

Fig. 2 is a view, in vertical section, on the line II-II of Figure 1;

Fig. 3 is a view, in section, of a plurality of thin plates of refracto material surrounding a portion of the e ectrode, and

Fig. 4 is a top plan view of the group of platesillustrated in Fig. 3.

- All electric furnace 10 comprises a suitable metal framework or casing 11 provided with supporting members 12.

In the casing 11 are provided outer walls 13 of heat-insulating bricks or blocks and inner walls 14 of high-temperature-resisting bricks or blocks. The inner walls 14 are suitably spaced apart to provide a furnace hamber 15 of any suitable or desired contour and dimensions.

A heating element 16, located in the chamber 15 comprises a plurality of refractory carbonaceous elements, built up in two parallel parts, the whole heating element being substantially of the type described in the hereinbefore mentioned application.

A plurality of elongated electrodes 17 are provided, the inner end of each of the electrodes being, adapted to opera-tively engage a graphite end block 18. A water-cooled contact terminal 19 has a wedging engagement with the tapered outer end of the electrode 17. "Resilient compressing means to maintain the electrode 17 in engagement with the block 18, and the block 18 in engagement with the elements of the heating means 16, comprise a threaded rod 20, a helical spring 21, a nut 22 and a washer 23 located on the threaded rod 20. A suitable anchorage for the outer end of the resilient compressing means is provided in the shape of a bracket 24 of substantially L-shape sultably secured to the metallic casing 11 of the furnace. An insulating member 25 is placed between the enlarged inner end of the rod 20 and the outer surface of the contact terminal 19 to suitably insulate the two members from each other.

While I have illustrated a specific embodiment of a resilient compressing means, I desire it to be understood that this is schematic only and any suitable construction thereof may be employed.

An insulating member 26 of asbestos may be located in the outer face of the wall 13, surrounding the contact terminal 19 to effectively insulate it from the casing 11.

A plurality of relatively thin refractory plates 27 are provided, substantially as illustrated in Figs. 1 and 2 of the drawing, in order to not only operate with the resilient compression means to maintain the electrodes in proper operative position relatively to each other and to the other parts of the furnace but also to provide means for re- Bill ducing current lealrage from the two elec trodes,

It may be noted that there is not only a line contact between each electrode and any one of the plates immediately adjacent thereto but that there is a possibility of the area of contact becoming larger, by reason of the wear of the electrode caused by movement of the electrodes in the wall through which they pass. It is, of course, apparent that there will be some movement of the electrode l7 relatively to the wall, by reason of the heating and cooling of the furnace during operation.

In order to still further increase the contact resistance existing between the plates 27 having fiat surface engagemen ll may separate successive plates by means of a thin layer of granular material, as illustrated in Fig. 3 between the middle and the bottom plate. ll may provide each of the plates 27 with a plurality of integral projections on one or both surfaces, each projection being of relatively small area. Either of these means increases the contact resistance between successive plates and this increased resistance operates to substantially reduce leakage; current between the electrodes or between any one electrode and any other part of the furnace which is at a substantially difierent potential.

It may be noted that the use of the device embodying my invention provides relatively simple means for cooperating with the resilient compressing means to mainta n the electrodes in proper operative position rela tively to each other and to reduce leakage current between the electrodes or to other parts or the furnace.

Various modifications may be made in the device embodying my invention with out departing from the spirit and scope thereof and l desire that only such limitations shall be placed thereon as are imposed by the prior art or are specifically forth in the appended claims.

I claim as my invention:

1. An electric furnace comprising; plumesses rality of walls enclosing a furnace chamber, a resistor located in said chamber, a plurality of spaced parallel-extending electrodes operatively engaging said resistor to conduct current thereto and therefrom, a plurality of relatively thin plates located between said electrodes and parallel thereto and means for spacing said plates relatively small distances apart and for permitting only a relatively small area of contact between adjacent plate 2. An electric furnace comprising a plurality of current-conducting electrodes and means for reducing current leakage from said electrodes comprising a plurality of relatively thin parallel-extending refractory plates and means for permitting only a relatively small area of contact between adjacent lates.

3. An electric furnace comprising a plurality of "current-conducting electrodes and means for supporting said electrodes in operative position relatively to each other and for reducing current leakage from said electrodes, said means comprising a plurality of relatively thin refractory members spaced relatively small distances apart and having only a relatively small area of contact between adjacent plates.

An electric furnace comprising a plurality of wflls enclosing furnace chamher, a resistor located in said chamber and supported one end thereof by one of said walls a plurality of electrodes operatively engaging said resistor to conduct current to and from said resistor and means for reducing the current leakage between and from said electrodes said means comprising a plurality of space/depart refractory members surrounding said electrodes intermeditheir and having only a relatively small area of surface contact between adjacent plates.

In testimony whereof. 'l have hereunto subscribed name this 18th day of May,

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