US1840247A

US1840247A - Induction electric furnace

Info

Publication number: US1840247A
Application number: US378036A
Authority: US
Inventors: Northrup Edwin Fitch
Original assignee: Ajax Electrothermic Corp
Current assignee: Ajax Electrothermic Corp
Priority date: 1929-07-13
Filing date: 1929-07-13
Publication date: 1932-01-05
Anticipated expiration: 1949-01-05

Description

' Jan. 5, 1932. E, F. No RTHRUP 1,840,247

INDUCTION ELECTRIC FURNACE Filed July 13. 1929 2 Sheets-Sheet 2 4 Patented .Ian. 5, 1932 UNITED srArEs PATENT orrics TBOTHERMIC CORPORATION, 01' MAI NEW JERSEY INDUCTION ELECTRIC FURNACE Application flledj'uly s, 1929. sema- 30,378,036.

My invention relates to induction electric furnaces and articularly to cooling the inductor coils 0 such furnaces.

The main purpose of my invention is to coolthe inductor of an induction electric furnace by vaporization of a liquid through the heat ofthe furnace inductor, applyin the latent heat of vaporization of the liqui to the cooling of the furnace inductor.

A further purpose is to electrically insulate an inductor furnace inductor against short circuiting by liquid application and to spray the liquid upon the insulated surface taking u the heat of the furnace in vaporiz-ation o the liquid.

A further urpose is to eatly reduce the amount of liquid require for cooling a furnace inductor.

, A further purpose is to use a liquid spraying coil outside of a furnace inductor for the double purpose of carrying liquid to spray upon the inductor and of eliminating the external field about the inductor.

A- further purpose is to use a liquid spraying coil outside of a furnace inductor for the I have preferred to illustrate one form only t among the various forms in which my invention may be practiced, selecting a form which is practicaheflicient and reliable and Figure 1 is a vertical central section through the pouring spout of a coreless -in-- duction electric furnace in connection with -which my invention is shown.

Figure 2 is a section'of Figure 1 taken upon 'line 22.

point at .which a'spraying outlet is attached.

In the drawings similar numeralsindicate like parts.

I a ply m invention to a form of inductlon e ectric urnace to which it is well suited but which for my broader disclosure must be broad invention to the inductors of furnaces.

frame and support of the furnace are not material to the broader disclosure which requires only that there be a furnace inductor upon WhlCh my cooling s ray may be directed.

Water cooling 0' furnace inductors is not new; but inthe past it has been customary to pass water through a hollow coil conductor in sufiicient quantity to keep the conductor temperature down. This has involved the supply of a large quantity of water since the water cannot take up much heat from the coil before it must be discharged from the coil.

nnwm FITCH. xoarrmur, orrnmcnr'ou, NEW JERSEY, as'smxoa'ro max unacmax. NEW many, a oonrom'rron 01' In the present case approximately 'a twentieth as much water is required as compared with the prior art and it can be supphed as a .small stream within thick pipe walls, thoroughly safeguarding the water used. Describmg in explanation and not in limitation In the furnace shown I have illustrated a crucible 5 surrounded by a finely divided refractory 6, which is tamped in, and aretaming shell such as micanite 7, for example.

Outside of the micanite and in engagement with the turns 8 of inductor 9 I provide an air-dried shell or lining 10 of molded'refractory for which I find quite acceptable a mlx- 'ture of 7 0% sand, 20% thermolith (chrome ore with a binder) and 10% sodium silicate. The finely divided refractory, micamte and air-dried lining represent one desirable form of; heat insulation,-which at the sametnne protects well'against enga' ment of the-coil by 'molten metal leakingv cm the melt and is suitable whether a crucible be used or, not.

material which is also desirably an electrical insulator and which will stand a temperature which higher voltages are permitted or c of several hundred degrees Fahrenheit. I have used a so-called white porcelain which is sprayed on and of which there are several on the market, one under the.name of Insalute. This insulation protects against leakage of liquid through the coil and also fully protects against current short-circuiting. The insulated coil is wound with a tape 13 which acts as a wick when liquid is sprayed upon it. As the most desirable liquid is water I will treat this liquid as water in the specification with the understanding that it is intended to cover any other liquid vaporizable to advantage for the purpose intended. For this tape 13 I find asbestos to be advantageous. The wick-like covering distributes water sprayed upon it so as to make practically the whole surface available as a vaporizing surface.

It will thus be seen my preferred inductor is composite comprising not only the coil pro r but the insulation and wicking by oser spacings of the turns can be used without short-circuiting and the moisture sprayed can be'distributed to the best advantage.

Outside of the inductor I provide a vapor space 14 between the coil and spraying nozzles 15. These nozzles are supplied with water for spraying purposes from a pipe 16 which most -desii"abl forms a spiral surrounding the inner coil. It is short-circuited to'permit flow of current by induction within the outer (sprayingze coil to act as an elminator of stray field yond this coil. This eliminator action takes place because this induced current being opposite to that in the inductor it sets up magnetic lines outside of the (spraying) coil opposing the field at this point from the furnace inductor. These opposing lines can be made to equalize the field from the inductor.

The coil 16, considered as a stray field eliminator may be short-circuited directly as by connection of both ends with a metal furnace casin or frame of which a part only is shown at 1 18, 19 or can be short-circuited through condensers.

In practice it is quite common to use a voltage between inductor turns of the order of 30 volts. At this voltage the electrical lication of the water directly, if preferred, ut much more desirably through a wick- .like covering. The functions can be performed separately or together as desired. The inductor of course must be much hotter than the vaporizing temperature of the water and thus has a tendency to maintain dry the portion of insulation immediately adjoining it. I prefer not to rest upon any such action, however, and form a complete water-proof insulation between the wicklike material and the coil. However, this need not be formed as one material as the insulation if deisred can be effected by an insulating tape and the water-proofing function can be performed directly or outside of the tape by a coating which need not be an insulator.

If asbestos tape be used for the insulating function the requirements of the coating upon it become less stringent and require water-proofing only to prevent short-circuiting by water which is carried by the outer wick-like covering.

a I distribute the nozzles 15 close enough to gether circumferentially and vertically to secure 'ood' distribution of the water over the surface. The nozzles spray directly upon the inductor surface, which in my best form, therefore, means directly upon the covering of the inductor coil and are intended to spray just sufiicient Water so that the spray will be fully vaporized. However, the variation in the furnace performance by which the furnace current may be cut down at times may result in the spray slightly exceeding that which is required; and for this reason the lower part of'the space 14 isformed to guide any water present into an outlet or drain 20 by which it is drawn away from the furnace.

The spraying nozzles 15 .are anchored firmly in the coil by any suitable means which I recognize may be greatly varied. For purpose of illustration only I show in Figure 3 one excellent way for effecting this anchorage.

Because of the small amount of total water flow required I am able to use quite heavy, preferably copper, tubing for thewater-carrymg coil. This provides thick tube Walls 21 without unduly restricting the quantity of water flowing through the tubing, The nozzle stems 22 pass through openings 23 in one wall and are seated in sockets 24 formed in the opposite wall. They may be soldered in position and their outlet heads 25 are also "soldered on the nozzle stems. This against both of these and permits 'ree aping medium 27 which fi ls the spaces between the'coils and covers the inside and outside of the coils. I find that the so-called white porcelain insalute is quite effective for this purpose.

As stated the frame support for the 0 erating parts of the furnace may be wi ely varied. No attempt has been made to ,indi-.

cate any exact form other than to suggest that it may be made up of structural shapes and metal plate in one convenientform. The elimination of stray fields outsideof the water-supplying coil permits the frame to be built without regard to possible magnetic leakage.

The furnace shown rests upon a brick base 28 which may conveniently be of silocel or other form and which is supported by a metal plate bottom 29. The aying coil and inductor rest upon heat ins ion and at the top are protected by heat insulation both of which may also be electrically insulating and which is shown as comprising asbestos lumber 30, 31, 32 and 33 and a filling of asbestos lumber is shown at 34. The upper part of the crucible is protected by an airdried insulating covering 35 and the spout 36 may conveniently be molded from the same material using a -20-10 mixture such as has been described above.

The inductor is supplied with current by conductors 37 and'38 of which 37 is broken away to clear the illustration. Both are insulated by sleeves 39. i

These conductors receive their current from corresponding supply conductors of which one only, 40, is shown. It is insulated gom the bottom of the furnace by a strip To prevent the formation of moisture upon the conductors 37 and'38 and to avoid the consequent loss in insulation these conductors may be insulated in any suitable way such as by incasing them in a porcelain; or enamel coating.

Much of the description above-hasbeen included for the sake of completeness only and is not'necessary for my invention except that the various functions performed must be performed by some corresponding structure or be omitted. My invention resides primarily in the provision of a vapor s ray using a liquid which vaporizes effectively insulation covered or carr a moisture distributor or have both provlsions and utillzes the latent heat of vaporization for the coolin of the furnace. The insulation of the coil andthe wick covering are auxiliary to the main purpose. I take advantage also of the need of llquid supply for this vaporization to apply it in the form of a short-circuited mechanically and magnetically protective coil.

Obviously the invention is not restricted to melting furnaces as distinguished from heating or heat-treating furnaces in which the charge is not melted. Nor is the invention restricted in its usefulness even with furnaces having a molten charge to such as have a conducting charge but applies also to furnaces in which the heating is effected in a supplemental electrically conducting secondary which may be a crucible or auxiliary resistor.

All of these furnaces haveinductors and the inductors if they transmit much energy may desirably be or must be artificially cooled.

In operation the furnace may be heated by the inductor and the operations in it may be handled in the same manner as in other furnaces. The coil, however, whether coated and/ or covered or not is permitted to attain a much higher temperature than with interiorly water-cooled coils. I

The water is sprayed against What for cooling purposes is effectively the exterior of the coil; and that it is not actually the exterior of the coil is due to the need of protection against leakage, requiring a thin insulation, and to the desirabllity of distributing the vaporizing function over a larger area of the inductor than would be true if the wick feedingof the Water were omitted. The moist wick takes up the water quickly and reduces the tendency of the sprayed water to splash. In order to conveniently cover the invention whether the spraying take place directl upon the coil or not, I have used the wor inductor to'cov'er the unit of bare coil or insulated coil or insulated and wickcoated coil.

The amount of water sprayed may be con trolled not only by the size of the spray outlets but by the resistancemet by the water in other parts of the water circuit and by determination or adjustment of the'pressure of the water. This last control makes regulation of the water flow easy. I

It is desirable-"to spray the water at a rate as near to the water vaporizing rate of the inductor as may be, securing a maximum cooling effect from the heating of the water and from the latent heat of vaporization.

Excess spraying may be detected quickly and surely'by the discharge of water through the drain, keeping in mind that some water va-.

porized by the inductor will recondense in the space surrounding the inductor and discharge as water-as distinguished from steamthrou h the drain unless the temperature of the in uctor be kept high enough to maintain the inductor capacity for vaporization.

Since the water is vaporized normally as rapidly as it is fed to the space surrounding the inductor the rate of vaporization cannot rise much higher than normal even if molten metal leak'from the pool into this space; and

the inductor with its insulation forms amechanical guard against such a contingency.

I appreciate that the method and apparatus are effective to cool heated inductors without regard to the character of the charge to which they are applied.

In view of my invention and disclosure variations and modifications to meet individ-' ual whim or particular need will doubtless become evident to others' skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I, therefore, claim all such in so far as they fall within the reasonable spirit and scope of my invention.

Having thus described my invention, what I-claim as new and desireto secure by Let- I over the surface of the inductor an tors Patent is 1. The method of cooling a heating inductor, which consists in spraying a vaporizable liquid about the inductor.

2. The method of cooling a heating inductor, which consists in distributin -a liquid in utlliz ing the latent heat of vaporization of the liquid to reduce the temperature of the inductor.

3. The methodof cooling a heatinginductor, which consists in spraying a liquid u n the inductor in such limited quantit t atsubstantially all of it is vaporized y the heat of the inductor and in thus protecting against the presence of free water for engagement by leaka furnace charge.

4. The methodp cooling a heating inductor, which consists in sprayin the inductor with a vaporizable liquid an distributing the liquid by capillary action over the sur face of the inductor for purposes of vaporization. a

5. The method of cooling a heating inducwater-carrying coil f about the adapted to reduce the stray'mag'netic. field outside the coil and connections from the coil upon the inside adapted to spray the tor, which consists in protecting the inductor against water leakage between the turns, in distributing a li uid over the surface of the inductor by capi lary action and vaporizing theliquid so distributed by the heat of the inductor utilizing the latent heat of vaporization to cool the inductor.

6. The method of cooling a furnace inductor and at the same time protecting from stray field about the inductor, which consists in spraying a vaporizable liquid upon the surface of the inductor and utilizing the path of supply of the sprayed liquid to set up a magnetic field outside of it 1n opposition to the field there set up by the current in the furnace inductor.

7. The method of cooling an electric furnace inductor, which consists in spraying a vaporizable liquid about the inductor while limiting the uantity of said liquid applied to, substantial y the quantity vapori'za e by the inductor.

8. The method of cooling an electric furnace inductor, which consists in spraying a vaporizable liquid about the inductor while limiting the quantity of said liquid a plied to substantially the quantity vaporizable by the inductor and draining any excess liquid applied from the inductor.

9. The method of cooling an electric furnace inductor, which consists in applying water to the surface of the inductor and draining excess of water applied by gravity from the inductor.

10. A furnace inductor and means for spraying the vapor of a liquid upon the surface of the inductor to cool the inductor.

11. A furnace inductor insulated to protect from ShO'rt eircuiting, a source of liquid supplythereabout and connections from the source adapted to spray the liquid upon the furnace inductor to cool the inductor by vaporizations of the liquid.

12. In a cooling mechanism for furnaces an inductor coil, a wick-like covering upon the coil and means for spraying liquid upon the covering to distribute it over the inductor by capillary action.

13. In an inductor type electric furnace, ,a'coreless furnace inductor, a source of alternating current therefor, a mechanically protective water-carrying coil surrounding the inductor coil and spray connections from the water coil adapted to spray the surface of the, inductor to cool the inductor by reaision odf the latent heat of vaporization of the 14. In an inductor type electric furnace, a coreless furnace-inductor, a source of alternating current therefor, a short-circuited inductor water from the coil upon the inductor.

.15. In an inductor type electric furnace, a coreless furnace inductor coil, a source of alternating current therefor, a water-carrying coil outside of the inductor, connections coreless furnace inductor coil, a source of alternating current therefor, a heat-conducting insulator upon the inductor coil, 9. shortcircuited water-carrying coil about the inductor coil adapted to reduce the stray magnetic field outside the coil and connections I 'from the coil upon the inside adapted to spray the water from the coil toward the inductor coil.

' 17. In an inductor type electric furnace, a coreless furnace inductor, a source of alternating current therefor, 21. water-carrying coil spaced from the inductor and having a drain between it and the inductor and spraying connections from the water-carrying coil directed toward the inductor.

18. In an inductor type electric furnace, a coreless furnace inductor, a source of alternating current therefor, a short-circuited water-carrying coil concentric with and spaced from the inductor adapted to reducethe stray magnetic field outside the coil, a filling between the turns of the coil cl the spacesbetween the turns of the coil, a 5 connections from the coil upon the inside adapted to spray the water from the coil upon the inductor.

19. In. an inductor type electric fu a coreless furnace inductor coil, a source of alternating current therefor, a water-proofing insulating coating on the inductor coil, a source of water supply outside the inductor coil and spraying evices connected with the source for spra g the insulated surface of the inductor coil 20. In an inductor type electric furnace, a

coreless furnace inductor coil, a source of alternating current therefor, a short-circuited water-carrying coil about the inductor coil from the water adapted to reduce the stray magnetic field outside the water-carrying coil, an insulatwater-proofing coating upon the inductor c'oil, a capillary covering upon the and connections from the water-carrying co ing water -proofing coating upon the inductor 0011, a capillary covering upon the coat and connections from the water-car? coi g upon the inside adapted to spray t 0 water from the water-carrying coil upon the cover;

ing of the inductor coil.

22. In an inductor type electric furnace, a coreless furnace inductor. coil, a source of alternating current. therefor, an insulatin water-proofing covering on the inductor co a capillary water spreader about the covering and means for spraying Water upon thespreader.

23. In an inductor type electric furnace;

a coreless furnace inductor coil,"a source 0 alternatin current therefor, a crucible within the in uctor coil, a sinterable finely di-. vided refractory about the crucible, an air dried sinterable refractory 'linin the inductor and about the finely divde refractory,

a water-carryin g coil outside of the inductor coil, an insulating water-proofing coating on the inductor coil, means for spraying water toward the inductor coil from the outside to vaporize the water and a drain freeing the space about the inductor coil from excess water.

EDWIN F. NORTIIRUP.

upon the inside adapted to spray the water coil upon the covering of the inductor coil.

- 21. In an inductor type-electric furnace, a

coreless furnace inductor coil, a source of al-.

ternating current therefor, a short-circuited water adapted to reduce the stray magnetic field outside the water-carrying coil, an insulatcoil about the inductor coil