US1555259A - High-frequency-corona-discharge furnace - Google Patents

Description

C. T. ALLCUTT HIGH FREQUENCY CORONA DISCHARGE FURNACE Filed Oct. 27. 1923 F/y n INVENTOR Ueser Z'H//ca' ATTORNEY .Sept 29, 1925.

WITN EsSEs:

lPatented Sept. 29, 1925.

UNITED STATES asma PATENT OFFICE.

CHESTER T. ALLCUTT, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T WESTING- HOUSE ELECTRIC l&z MANUFACTURING COMPANY, A CORPORATION O'F PENNSYL- VANIA.

HIGH-FREQUENCY-CQRCNA-IDISCHARGE FURNACE.

Application filed October 27, 1923, Serial No. 671,1.

To all whom z't may concern.'

Be it known that I, CHESTER T. ALLCU'rr,

a citizen of the United States, and a resident of Pittsburghf in the county of Allegheny 6 and State of Pennsylvania, have invented a new and useful Improvement in High-Frequency Corona Discharge Furnaces, of which the following is a specification.

My invention relates to electric heating and it has for its object to provide a method of and means for heating bya high-frequency corona discharge.

In practicing my invention, I provide a source of high-frequency current supply of suiiiciently high voltage to produce a corona discharge between a pair of co-operating electrodes and adjacent to a mass of mat-erial to be heated thereby.

In the single sheet of drawings,

Figure 1 is a schematic View of a heating system embodying my invention, the furnace part thereof being shown in section,

Fig. 2 is a schematic view of a modified form of heating system embodying my in- 25 vention,

Fig. 3 is a view in vertical section of an electric furnace for use with my system, and

Fig. 4 is a top plan view thereof.

Referring more particularly to Fig. 1 of the drawing, a container 11 for a mass of material 12 to 4be heated, may be built up of any suitable refractory material that will resist a relatively high temperature. The container is preferably composed of conducting refractory material, such as graphite, although a non-conductingl material may beemployed, particularly if the'.charge 12 is of conducting material. A circular electrode 13 surrounds the container 11 and is spaced therefrom a suitable distance. The inner peripheral surface of the electrode 13 may be provided with a plurality of inwardly projecting points 14.

The electrode 13, which is of a suitable electric-'conducting material, is connected to one terminal of the secondarywinding of a transformer 15, the other terminal of which is connected to the crucible 11 and also to the charge 12 placed therein. The transformer 15 is intended to schematically represent a source of sustained electric current of high voltage and of high frequency, and I have included a condenser 16y in parallel circuit relation to the secondary winding of the transformer and the furnace constituted by the container 11 and thelelectrode 13 to neutralize the inductive reactance of the transformer 15.

If the source of supply 15 is suitably energized, a relatively high-frequency and high-voltage electric current is delivered to the electrodes constituted by the member 13 and the member 11 and if the voltage is sufficiently high, the air becomes ionized and .a corona discharge is produced at the points 14. This discharge is of relatively high temperature and the heat therefrom Will be radiated or otherwise transmitted through the crucible 11 to the mass 12 of material located thereon, which is to be heated.

It is desirable, in heating systems of this kind, to stabilize the discharge as otherwise the electrical discharge may take the form of a s ark discharge between a relatively few mts on the surface of the lelectrodes and t ereby cause local heating.

In Fig. 2 of the drawing, I have illustrated a construction comprising a container 11 with a mass of material 12 located therein. An electrode 17 of metal may be located closely adjacent to and around the outer surface of a crucible 18 of a dielectric material, such as quartz and spaced from the outer surface of the crucible 11. j

The quartz crucible acts as a condenser in series with the ionized air gap between it and the container 11. The action of the condenser is such as to prevent a spark discharge being established over any individual portion of the electrode or of the material-containing crucible. The prevent1on of a spark discharge is desirable, since such a discharge would occurl between a few points Y only on the opposing surfaces of the electrodes-and would cause localized heating.

vIn Figs. 3 and 4, I have illustrated a relatively simple electric furnace structure that may be employed in the system embodying my invention. The inner cruclble and electrode 11 containing the mass 12 of material to be heated is made relatively small in lateral cross-section and may be made relatively deep to receive the desired amount of material at one time. An Vouter electrode 19 is formed in the shape of a crucible and is of much larger area of cross-section than the container 11. A mass 21 of porous re` fractory electric-insulating material, such as pared to the dimensions of the outer electrode 19, the corona discharge will be established upon the surface of the inner electrode container 11 when the terminals of a suitable source of supply of high-frequency and high-voltage electric energy is connect-v ed to the respective electrodes. This condition exists for the reason that the electric stress at any point on the surface ofthe inner electrode container 11 vis very much greater than that on a corresponding and co-operating surface portion of the outer electrode 19. Hence, the corona discharge will be established on substantially the outer surface of the container 11 and the4 heat generated thereby will be transmitted through the walls of the container to the mass of material to lbe heated that is located therein.

That portion of the air path lying between the electrode 19 and the outer limits of the corona discharge formed on the outer surface of the crucible 11 is substantially unionized and hence acts as a relatively perfect condenser dielectric for stabilizing the corona discharge. v

Where I have referred 'to a high frequency alternating current, I desire it to be understood that reference is made to frequencies not less than those usually employed in radiotelegraphy and radiotelephonyy and such higher frequencies as may be commercially produced for such applications. An alternating current of sustained high frequency is particularly a plicable for my purpose, as the discharges rom a series of high frequency wave trains, such as produced by an oscillatory spark discharge will not effect the desired heating.

Various modications and changes may be made without departing from the spirit and scope of the invention, I desire, therefore, that only such limitations shall be placed thereon as are imposed by the prior art or are set forth in the appended claims.

I claim as my invention:

1. In a heating system, in combination, a` crucible for containing a. charge to he heated, and means for producing a corona discharge adjacent to said crucible to heat the same.

2. In a heating system, in combination, a crucible for containing a charge to be heated, and means for producing a high-frequency corona discharge adjacent to said crucible' to heat the saine.V

3. An electric furnace comprising a charge to be heated and means for producing a corona discharge adjacent thereto to heat the same.

4. An electric furnace comprising a charge to be heated and means for producing a high-frequency corona discharge adjacent thereto to heat the'same.

5. In a heating system, in combination, a crucible for containing a charge to be heated, an electrode adjacent Ato said crucible and spaced therefrom, and means electrically connected to said crucible and said electrode for producing a corona discharge adjacent to said crucible for heating the same.

6. In a heat-ing' system, in combination, a

'material container of relatively small external dimensions; an electrode, of relatively large dimensions, surrounding said container, and means for producing an alternating electric field of high potential between said container and said electrode.

7. The method of heating material which comprises the vproduction of a corona discharge adjacent to a crucible containing said material.

8. The method of heating m'aterial which comprises placing a crucible containing the same in a high-frequency electric field of sufficiently high voltage to produce a corona discharge adjacent to said crucible.

9. In a heating system, in combination, a crucible for containing a charge to be heated, means for producing a corona discharge from said crucible to heat the same and means for stabilizing said corona discharge- 10. In a heating system, in combination, a crucible for containing a charge to be heated, means for producing a corona discharge from said crucible to heat the same and means for insuring a substantially uniform ditribution of heating ei'ect over said cruci le.

11. In a heating system, in combination, a crucible for containing a charge to be heated, means for producing a corona discharge from' said crucible to heat the same and means comprising a condenser for insuring a substantially uniform distribution of current over said crucible.

12. In a heating system, in combination, a crucible for containing a charge to be heated, an electrode adjacent to said crucible and spaced therefrom, means electrically connected to said crucible and said electrode for producing a corona discharge adjacent to said crucible for heating the same, and means located between said crucible and electrode for stablizing said corona discharge.

In testimony whereof, I have hereunto subscribed my name this 22nd day of October, 1923. a

CHESTER T. ALLCUTT,

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