US1357901A - Electric furnace - Google Patents

Description

R. R. REED.

ELECTRIC FURNACE.

APPLICATION FILED MAR. 2?. 1920.

1,357,901 Patented Nov. 2, 1920.

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@Ho z n m I and tain new and useful Improvements in Elec- U'Ni'rsn STATES ROBERT R. REED, 0F ITHACA, NEW YORK.

ELECTRIC FURNACE.

ASpefeicatioxi of` Letters Patent.

Patented Nov. 2, 1920.

LApplication led lI-arch 27, 1920. Serial No. 389,244.l

citizen of the United States of America, re-

sid at ithaca, in the county of rTompkins tate of New York, have invented 'cer-v tric Furnaces, of which the following is a specification. u 4

The primary object ofthe invention is the provision of means for protecting the'resstols of an electric furnace from oxidation, convection and deterioration, the method employed being one readily practised and easily as well as inexpensively installed.

A further object of the invention is to increase the life of an electric furnace substantially indefinitely bythe preservation of carbon on'other resistors employed in the furnace,j, a protective 'envelop being employed failingto give up oxygen to the carbon and also cutting oil' convection.

A still `further object of .the invention is to provide a carbon resistance furnace preventingdisintegration of the resistors due to oxidizing and 'the effect of air currents 'traveling along the 'face of the resistor disintegratingparticles thereof, the .invention providing yielding heat-insulation for the resistors' as well as mounting the latter yieldinglv'in the furnace.

Vith these general objects in view and others that will appear as the nature of the invention is better understood, the same consists of thefmethod hereinafter set forth which will be described in connection with one manner of carrying out the saine as illustrated in the accompanying drawing.

ln the drawing like reference characters designate corresponding parts throughout 'the several views, and

'Figure 1 is a vertical transverse sectional view of theinvention,

F ig. 2 is a top plan view thereof with the top' plate `removed, and

Figs.A 3., et, and 5 are detail views of different forms of resistors adaptable for employment with my furnace in carrying out the inventio'nfv My'mcthod and apparatus broadly consiste" in the protection of resistors in electric furnaces by means of liquid glass and l have herein-illustrated an electric furnace comprising an outer container 10 constructed of such material as fire brick or concrete and being a heat insulator for the mechanical protectionof the heating chamber therein. A lining 11 for the container 10 consists of magnesia (Mg.) or powdered brick dust and magnesia, thereby forming a heat insulating liner for the container. A crucible preferably formed of graphite of suitable dimensions' with an open mouth 13 is centrally mounted within the heating chamber 14 upon blocks or abutments 15 in such a manner as to allow for expansion and contraction. M olten glass 16l surrounds the crucible 12 within the chamber 14 and the magnesia lin'- ing 11 contacting the glass 18 forms a cushion orresilient heat insulator therefor. The glass 16 is first inserted in the chamber 14 in 'powdered form, a plurality of resistors ,17 being mounted in the chamber 14 with their lower ends resting upon small pedestals 18 of socket form permitting slight lateral movement to 'the resistors during the expansin and contraction of the glass 16.

The resistors 17 are preferably carbon, owing to the high resistance, which decreases as the' temperature rises, leading in' e1ectrodes 19 being connected to the upper ends of the resistors 17 and projecting outwardly of the furnace through the lining l1 and container'l() for connection with theelectrical service wires 20 leading from the generator, not shown. 'Any desired number of resistors 17 may be employed, it being understood that the powdered glass 16 is heated by the electrical current fiowing through the resistors 17, melting the glass `16 which 'flows around the resistors 17 'and ciucible 12 shutting oli' all air and oxygen. The glass 16 forms none of the chemical combination with the material of either tle resistors 17 or Crucible 12 andthe-glass wi l not appreciably partivith its oxygen content at any temperature less than 1800o C.

The glass 16 to be emploved in my method and apparatus has a high Si()2 content` such as glass having over eighty per cent. of SiQ2 in its make-up with the i'en'iainder chemically substantially equally resistant in deoxygenation. Suchv glass as Pyrex (('orning Glass Company) or any glass having a high silicon oxid content may be employed. The `crucible 12 is of any standard make such as Dixon X' Cofs Crucible. i'i the mechanical side. the low coefficient of expansion (.0000063) prevents destructive pressure between the crucible 12 and the electrodes 17-19 und the surrounding walls 11-'-10,

the heat insulation 11 being of a yielding na-v ture as well as the shiftable mounting of the resistors 17 and theY crucible 12 also-'guard against such pressures of expansion and contraction efforts.

A cap or plate 21 covers the chamber 1e being formed of such material as concrete, soapstone or other refractory material with a heat insulating lining 22 of such material. as magnesia. Dierent forms of resistors 1T may be employed such as perforated plate resistors shown in lig. 3 and cylindrical as shown in Fig. 5. The resistor in Fig. 5 comprises a refractory tube 23 containing molten glass 241` and a central resistor 25, the same being used in special cases where the glass bath 16 for all resistors 17 in common, appears to be unsatisfactory. Whichever form of resistors is employed, the same are preferably spaced lequal distances yapart around the Crucible 12 within the molten .glass 16. ein opening 26 is provided in the cap 21 for gaining access to the Crucible mouth 13 therebeneath, the construction of container being substantially that usually employed in electric furnaces. Suitable arrangement may be made for withdrawing the electrodes 19 so thatthe glass 16 after the first heat run forms a solid Aenvelop for cooling which contains the resistors 1'4" which can be replaced in the same form and is serviceable as a repair element.

My invention including' the method of einployiiig liquid glass for the protection of electric furnace resistors is not limited to the construction of apparatus herein illustrated and while an embodiment thereof has ,electric furnaces from disintegration consisting in surrounding the resistors with liquid glass.

5. The method of protecting electric fur? nace elements from disintegration consisting in surrounding such elements with pulverized glass whereby al rise in temperature ofthe resistors`produces a molten glass envelop therefor.

6. A. method for protecting the resistors of an electric furnace consisting in surrounding the resistors with powdered glass in the heating chamber of the furnace and raising the temperature of the resistors Learner above the melting point of the glass forming a molten glass envelop surrounding the rel sisters.' V

7. A method for protecting the resistors of an electric furnace consisting in surrounding the resistors with powdered glass in the heating chamber of the furnace and raising the temperature of -the resistors above the melting point of the glass forming a molten glass envelop surrounding the resisters, and yieldingly mounting the resis pensating for the eripansion and contraction of the glass.

10. The method of protecting the. resistors of an electric furnace consisting inthe pro- 1vision of a resilient heat insulating lining lfor the heating chamber of the furnace and providing molten glass surrounding the resistors in contact with said lining whereby expansion and contraction is equalizcd.

11. rllhe method of protecting the Crucible and resistors of electric furnaces consisting in providing a resilient heat insulating lining for the chamber of the furnace with the crucible and resistors positioned therein and the provision of molten glass surrounding the crucible and resistors within and in contact with said lining.

12. The method4 of protecting resistors for electric furnaces consisting in the provision ofa resilient lining ofl magnesia for the heating chamber of the furnace andlproviding molten glass contacting said lining surrounding the resistors and Crucible.

13. The method of protecting resistors for electric furnaces consisting in the-provision of a resilient lining of magnesia for the heating chamber of the furnace and provid ing molten lass contacting said lining sui'- rounding t e resistor and Crucible and yieldingly mounting tie Crucible and resistors Within the molten glass of the heat-- ing chamber.

i 14. An electric furnace comprising a' container, a resilient heatl insulating lui'ing therefor providing aheating chamber within the furnace, electrically connected resistors within the heating chamber and molten glass within said chamber surrounding said resistors.

sev

10' eating for expansion and contraction.

16. An electric furnace comprising a container of refractory material, a resihentheat insulating lining therefor formed of brick dust and magnesia, electrically connected resistors inwardly of the lining, powdered glass surrounding.. the resistors adapted for assuming a molten mass upon raising the temperature of the resistors in the furnace. In testimony whereof I afix my si nature.

ROBERT R. R ED.

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