US1626263A

US1626263A - Furnace and method of operating the same

Info

Publication number: US1626263A
Application number: US593793A
Authority: US
Inventors: Frank W Brooke
Original assignee: WILLIAM SWINDELL AND BROTHERS
Current assignee: WILLIAM SWINDELL AND BROTHERS
Priority date: 1922-10-11
Filing date: 1922-10-11
Publication date: 1927-04-26
Anticipated expiration: 1944-04-26

Description

1927. Apnl 26 F. w. BROOKE FURNACE AND METHOD OF OPERATING THE SAME Filed Octv 11, 1922 5 Sheets-Sheet l April 26 1927' F. w. BROOKE FURNACE AND METHOD OF OPERATING THE SAME Filed Oct. 11, 1922 s Sheets-Sheet 2 INVENTOR 1,626,263 F. W. BROOKE FURNACE AND METHOD OF OPERATING THE SAME Filed OCt. ll, 1922 5 Sheets-Sheet 3 mvsmon April 26, 1927.

F. W. BROOKE FURNACE AND METHOD OF OPERATING THE SAME April 26, 1927.

Filed Oct. 11, 1922 5 Sheets-Sheet 4 lskoov INVENTOR W @171 L 1 5626526 3 April 26 1927 F. w. BROOKE FURNACE AND METHOD OF OPERATING THESAME Filed 0m. 11, 1922 s Sheets-Sheet 5 INVHENTOR Patented Apr. 26, 1927.

UNITED STATES PATENT OFFICE.

FRANK W. BROOKE, OF PITTSBURGH. PENNSYLVANIA, ASSIGNOB. TO WILLIAM SWIN- DELL AND BROTHERS. OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

FURNACE AND METHOD OF OPERATING THE SAME.

Application filed October 11, 1922. Serial No. 593,793.

The present invention relates broadly to electric furnaces, and more particularly to improvements in electric furnace installations and methods of operating the same.

It has heretofore been customary to provide electric melting furnaces, each with its own electrical equipment. Such an in stallationis objectionable for several dif ferent reasons, although it is effective for the purpose intended.

In the first place, where a single furnace is used with a single electrical equipment, it has been customary to support at least a portion of the equipment from some portion of the furnace body. During the tilting of the furnace to discharge the same, the added weight of ,the electrode equipment has required additional operatin power, and has imposed a load on the furnace structure tending to dis'ort the same and thereby crack or spall the refractory lining. Ob-

viously, also, such a construction makes it necessary to design the furnace with respect to the electrical equipment, thereby making it impossible tolocate the doors, jambs and the like in accordance with the requirements for maximum efficiency.

During the operation of such a furnace, the electrode equipment has materially interfered with the maintenance of uniform heat conditions in the furnace body by preventing uniform heat radiation. This has resulted in unequal wear and burning away of portions of the furnace, thereby necessitating frequent repair.

In addition .to these practical obiections from a constructional standpoint, there is a serious objection inherent in the furnace operation. This operation, with res ect to the electrical equipment, may be into two periods, the first period representing that during which the electricalequi J; ment is operating, for the purpose of me ting down or refining a charge, while the second period represents that during which the electrical equipment is idle to permit discharging the furnace, repairing the same or recharging. During the second period, the electrical equipment which usually represents the most expensive part of the furnace installation has not been capable of any use. This represents a high overhead, and by ivided reason of the uneven load factor, the cost of the electrical energy has accordingly been unnecessarily high.

Attempts have been-made to devise a continuously operating electrical furnace, but this is obviously impractical. It has also been attempted to use'two sets of electrical heating means on two hearths placed on an open turntable, but such an arrangement has not been adaptable to the making of steel.

Other attempts have been made to reduce the period during which. the electrical equipment is out of actual use by so constructing the furnace that it is possible to reduce the period required for charging. One method of accomplishing this has been to removably' support the furnace roof. This is objectionable as it reduces the thermal elficiency of the furnace by permitting large heat losses during the time the furnace is uncovered, and also for the reasons that it destroys the neutral atmosphere within the furnace as well as resulting in damage to the refractory.

By. the present invention the practical constructional and operating disadvantages of electrical furnaces as heretofore used are obviated and there is provided a furnace installation having long operating life, a high thermal efiiciency, a decreased operation and installation cost and an increased output. These advantages are obtained by the use of a plurality of furnaces with one electrical equipment, the installation being such that it is possible to produce'a relative movement between the electrical equipment and the furintact, and then the electrodes are substantially immediately utilized with another furnace.

The present invention also lends itself admirably to the use of two different voltages or stages of varying electrical capacity as may be required in some furnace installations.

In the accompanying drawings, there are shown for purposes of illustration only, certain embodiments of the present invention, it being understood that the drawings do not define the limits of my invention, as changes may be made in the construction and operation without departing from the Spirit or scope of the broader claims.

In the drawings:

Figure 1 is a plan view of a complete installation in accordance with one form of the present invention;

Figure 2 illustrates this installation, partly in vertical section and partly in elevation, and shows diagrammatically one method of charging;

Figure 3 is a vertical sectional view on an enlarged scale showing one of the furnaces;

Figure 1 is a side elevation of one form of locking means for the furnace turntable;

Figure 5 is a top plan view of the construction shown in Figure 4:;

Figures 6 and 7 are diagrammatic views showing operating curves for the electrical equipment, and

Figure 8 illustrates diagrammatically a modified embodiment of this invention.

A furnace installation embodying the present invention may comprise a turntable 1 carrying a plurality of furnaces of similar construction. In Figures 1 and 2 the turntable is illustrated as carrying two

similar furnaces

2 and 3. These furnaces are pref erably mounted on diametrically opposite sides of the turntable whereby the turntable is counterbalanced. This turntable is mounted to rotate about its center as will be explained in detail hereinafter.

Positioned at'one side of the turntable, and supported independently of the turntable or furnace structures. is the electrical equipment for the furnaces. This equipment may comprise a step-down transformer 4 from which are taken three

sets

5, 6 and 7 of secondary conductors. These conductors need only be of a length sufiicient to reach from the transformer to the electrodes. As most commercial electric arc melting furnaces operate with a three-phase current, the transformer is preferably of.the threephase type having each set of the secondary conductors connected with

different electrodes

8, 9 and 10. It will be obvious, however, that the construction of the transformer and the number of electrodes may be'varied in accordance with demands of the particular furnace design or operation. The conductors and electrodes are supported from a suitable frame work 11 permitting the electrodes to be raised and lowered by These )i es circulate water throu h coolin D b devices 19 and Y20 surrounding the openings in the roofs through which the electrodes pro ect. When the electrodes are removed from a particular furnace, refractory blocks 21, as illustrated in Figures 2 and 3, may be inserted in the electrode openings to restrict heat radiation from the interior of the furnace and retain the desired neutral atmosphere therein.

The turntable 1 may be constructed in any desired manner as, for instance, from channels andangles of sufficient strength to support the furnaces, and is so mounted upon a foundation 22 as to be easily rotatable. Anti-friction rollers 23 may be provided on the foundation in supporting engagement with the turntable. A ball bearing raceway 2t on the foundation may be provided to cooperate with a similar raceway 25 on the bottom of the turntable toreceive balls 26 permitting easy rotation of the turntable.

For supplying the desired cooling water to the pipes 17 and 18 irrespective of the position of the turntable, a water supply pipe 27 extends through the center of the turntable and is provided with a coupling permitting the pipes 17 and 18 to rotate with the furnaces, while water is being supplied to the

cooling devices

19 and 20. The discharge pipes from these cooling devices may empty into a funnel 29 conducting the water to any desired point.

Wherrthe turntable is in such position that one of the furnaces is in cooperative engagement with the electrical equipment, it is desirable for obvious reasons to lock the turntable against movement. While this may be accomplished in a number of different ways, I have illustrated in Figures 1 and 5 one convenient form of locking mechanism. This may comprise a locking \mernher 30 carried by and movable radially of the turntable. An operating member 31 is also carried by the turntable on a pivotal mounting 32. This operating member has a pin operating in a slot in the locking member so that swinging movement of the operating member in a clockwise direction, as viewe in Figure 4, will move the locking member to the dotted line position and thereby withdraw the end 34 from engagement with a casting 35 placed at any. suitable point around the turntable. When the parts ing material. This contactor closes contacts 38 in the operating circuit of a motor 39 operative as will be explained hereinafter,

, for tilting the furnaces. A spring 40 surrounding the rod 36 normally urges the same to switch opening position.

After the contents of a furnace have been melted and refined and the furnace moved out of engagement withthe electrodes, the contents may be discharged in several ways well known to the art.

One method which will be described here is to tilt the furnace body so that the molten metal will discharge itself through the door opening provided for that purpose. The tilting is accomplished by raisin the rear end of the furnace by means 0 a screw geared to a motor as willnow be explained.

The motor 39 drives the shaft 41. (Figure 1) through suitable gearing 42. This shaft carries a bevel pinion43 (Figures 2 and cooperating with a bevel pinion 44 having an interiorly screw threaded hub en-. gaging screw threads on a lifting member 45. 'When the gears 43- and 44 are operated, the member'45 is raised or lowered, depend" ing on the direction of rotation of the shaft 41. The lifting member is prevented from rotational movement withjthe gear 44 by a pin 46/which enters an opening in a fixed portion 47 on the foundation. This in is of such length that it will remain in the opening in the portion 47, during the time the lifting member is being raised, until the oblong head 48 of the lifting member, as shown in Figure 5, enters a groove 49 in the bottom of the furnace structure. Engagement between the head 48 and the groove 49 is then effective for preventing rotational movement of the lifting member. The member 45 may continue to rise and swing the furnace about its pivotal mounting .50 until the parts occupy the position shown in dotted lines in Figure 3. i

For purposes of safety, it may be deemed advisable under certain circumstances to provide a safety interlock between the lifting mechanism and the locking mechanism to prevent; untimely operation of the turntable. In Figures 4 and 5, such a means is illustrated as comprising aseries of links so arranged that when the pin 46 is in the position illustrated in Figure 4, a pin 51 is withdrawn from the casting 35' a suflicient' distance to allow movement of the locking member 30 to unlocking position, thus permitting movement of the turntable. At the same time, switch member 37 is disengaged from contacts 38, opening the control circuit of motor 39 thus preventing operation of the tilting'mechanism. \Vhen the turntable is again in proper position for tilting, locking member 30 is again moved to position shown in Figure 4, re-establishing conditions for tilting. As soon as the lifting member 45 is raised, the pin 46 is moved away from the link 52 thereby permitting a spring 53 to operate the linkage and move the pin 51 upwardly through an opening in the end 34 of the locking member, thus holding the parts in locking position, preventing movement of the turntable.

The furnaces may be of any desired general construction. As is customary in this art", they'may be formed with a frame work 54 lined withthe usual refractory material 55. As the electrode equipment is supported independently of the furnaces, it will'be apparent that the furnace structure may be designed without regard to interfering liniitations, such as exist where the electrode equipment is in part or entirely supported by the furnace. This permits the doors 56 and 57to be so located with respect to the electrodes as to reduce the action of the heat from the arcs on the door jambs and arches to a minimum, and at the same time insure substantially uniform heat radiation from the furnace walls. This also prevents Severe mechanical strains on the furnace shell during the tilting operation. thereby saving the comparatively fragile refractory lining and insuring a furnace structure which is easy, to tilt as it is not top heavy or over-balanced. This construction enables the roof. to be easily removedas may be desired for repairs, it only being necessary to swing the same to charging position, where there is no interference from any ofthe electrical equipment. The

doors

56 and 57 may be moved vertically by means of levers 58 having counterweights 59. V

According to one embodiment of the invention the'doors are preferably so placed that the center-line thereof is on aradial line passing midway between adjacent electrodes. By this arrangement the operator can secure a better observation of the arcs and it also provides the greatest uniform possible distance between the arcs andthe door jambs and arches. ,This increases the length of life of the doors and surroundingstructure.

From the foregoing it is believed that the operation of this form of the invention will be apparent. The turntable is moved into a position'where one of the furnaces may be charged while the other chargepreviously inserted in another furnace is being'melted down. As soon as the charge has been suitably melted and refined, there is produced a relative movement between the furnace structure and the electrical equipment. While this relative movement may be secured in a number of different ways, it may conveniently be accomplished by raising the electrodes wlIile, leaving the furnace structure intact and then rotating the turntable to bring the freshly charged furnace into position beneath the electrodes. The electrodes ma then be immediately lowered into the freshl y charged furnace while the refined charge is being removed and the furnace repaired, if necessary, and recharged. There may be times, due to the metal being handled, when it is desirable toretain the molten metal within the furnace for certain periods, thus enabling the furnace to serve also as a ladle. This is true when working, for example, with gray iron. The construction provided by this invention readily adapt-s itself to this operation. It will thus be seen that a single electrical equipment serves a plurality of furnaces. This provides a furnace installation in which the initial cost is materially decreased. At the same time, it permits the electrical equipment to remain substantially continuously in operation at a full load, so that the load factor is substantially constant and of high value. 7

The operating advantages of the furnaie installation constructed in accordance with the present invention become readily ap parent from an inspection of the operating curves shown in Figures 6 and 7. In both of these figures, the ordinates represent the power supplied to the electrical equipment, while the abscissae represent time. InFigure 7 the spaces designated Y measured from the axis of the ordinates represent the time during which electrical energy is supplied to the electrode equipment, while the spaces designated X represent the time during which the electrica equipment is standing idle. This curveis based on a furnace of usual construction in'which the electrical equipment cooperates with but a single furnace.

The curve in Figure 6 represents diagrammatically the operating conditions obtained, with respect to the load factor, in a furnace installation embodying the present invention in which one electrical unit cooperates with a plurality of furnaces, either two or more. The reference letter X represents the time, corresponding to X, during which the electrical equipment is idle or operating at a reduced energy input into the furnace, while the letter Y indicates the time during which the electrode equipment is operating. The spaces Y and Y in the two curves are assumed as being equal as the period required for the melting and refining is relatively fixed. The spaces X, representing only the time required to change the relative position of furnaces to the electrical equipment, however, are considerably smaller than the spaces X, thereby indicating a more nearly continuous operation of. the electrical equipment. Not only does this give a load factor on the electrical equipment which is substantially constant and of high value, but it enables more cycles of operation to take place in a given period than have been heretofore possible. 'In Fi ure 6, there are illustrated diagrammatica ly nine complete cycles, while in Fi ure 7 but six complete cycles are possible uring the same time period.

As power companies are desirous of supplying a nearly uniform amount of power, the cost is to a large extent governed by the load factor. As the load factor obtainable with the present invention is more nearly constant, the cost per kilowatt of electrical energy for a furnace installation in accordance with the present invention is materially less, in some cases as much as 35%,than the corresponding cost for a furnace operating as illustrated in Figure 7.

This arrangement likewise greatly reduces the cost of labor necessary for operating the furnaces as the laborers, when a plurality of furnaces are used with one electrical equip ment, are working substantially continuously, whereas with only one furnace they are working only during that part of the time represented by the spaces X. The electrical equipments now furnished are so completely automatic that they require little or no attention during the time they are in action.

As it is not necessary to move the roofs with respect to the furnaces, heat radiation is minimized and the neutral atmosphere may be maintained therein. The electrode openings through the roof also provide convenient means, as illustrated in Figure 2, for charging the furnaces rapidly with scrap material. This may b accomplished in/one way. by providing a h pper 65 placed on an upper charging level and provided with a chute or pipe 66 adapted to operatively cooperate with the electrode openings in the roof of that furnace which is in charging position. This permits the scrap to enter these electrode openings and thereby insure uniform distribution of the charge within the furnace.

It will also be understood by those skilled in the art that the present invention enables the use of furnace linings in one installation of different metallurgical or physical characteristics. For example, one furnace may be lined with an acid reacting lining while another may be lined with a basic reacting lining. This enables scrap relatively low in sulphur and phosphorus to be treated in the furnace having an acid reacting lining, while relatively impure scrap can be treated in the basic furnace. On the other hand, given one type of scrap, steels of highly refined quality can be made in the basic furnace while second grade steels may be produced in the acid furnace at its lower operating costs. Also, by makin it possible to provide a plurality of di erent linings in one installation, certain metals may be successively subjected, if desired, to treatment under acid, basic or neutral conditions.

Similar combinations may be made by using neutral linings, or linings consisting of rammed-in carbon for reduction processes in the melting and refining of gray iron.

It will be apparent that the furnaces may be operated by supplying a constant voltage during both the melting and refining periods, or by the use of two voltages as indicated by the curves in Figures 6 and 7 and as now deemed advisable in this art for certain purposes. In accordance with the well known Olnns law, the power input may be varied by holding a constant voltage and reducing the current by lengthening the are, or a constant current may be maintained and the voltage reduced by shortening the arc. Either method may be used with my invention.

The present invention also enables substantially continuous operation irrespective of repairs required. This is true for the reason that with a plurality of furnaces and one electrical equipment it is never necessary to completely shut down, as at least one furnace may always be maintained in condition for use. p

In the inodification illustrated in Figure 8, there are shown three

furnaces

60, 61 and 62 carried by a turntable 1. The turntable, the tilting mechanism and the other operating parts may be the same as heretofore described. With this form of installation two electrical units are preferably utilized, one embodying electrodes 63, while the other embodies electrodes 64. Both of these units may be of identical construction similar to that already described, or may be of different constructions as will be more fully pointed out hereinafter.

As the furnaces are located on the turntable at substantially 120 from each other, it will be apparent that each 120 of rotation of the turntable in the direction indicated by the arrow in Figure 8 will be effective for bringinga freshly charged furnace into eo operative engagement with the electrodes 63, and to move the furnace which was previously in cooperative engagement with these electrodes into position where the electrodes 64 may be lowered thereinto. This construction makes it possible to partially melt with the electrical equipment at one station and compfete the melting by the electrical equipment at the other station, or tomelt down the charge" at one station and refine thecharge at another station.

Whereit is desired to utilize a lower power input during the final melting operation, or during the refining period, the present form of apparatus is highly desirable. This is due to the fact that the electrical equipment embodying the electrode 63 may be designed put and the voltage change with respect to a given charge is varied are definitely determined by the process itself. This is a decided advantage over constructions in which a single electrical equipment has supplied a single furnace, thereby necessitating voltage changing means adding to the cost and complication of the equipment, occupying additional space and requiring skill and attention from the melter to know when to make the voltage change.

After the tapping operation it is usually necessary to fettle' and otherwise prepare the tapped furnace for recharging. This operation, as well as those of melting down and refining the charges in the other two furnaces, areso regulated as to consume substantially equal times. This enables the two electrical units to remain in substantially continuousoperation at substantially full load, whereby the load factor is substantial- 1y constant and of highvalue. The respective periods required for the different operations being performed by electrical energy on the metal at different stations may easily be regulated by changing the effective or operating KVA capacity at any one station with respect to the other. This may he definitely determined, and the apparatus initially designed accordingly.

It will be apparent that the present invention embodies advantageous features both of operation due to the substantially constant load factor, low operating cost,high efliciency and flexibility as to furnace construction; and va-lso with respect to the construction enabling efficient furnace design insuring long life.

Further advantages arise with. special re gard to'that form of the invention shown in Figure 8 by reason of the ease of operation with difl'erent power inputs.

I claim:

1. The method of operating electrical furnaces which consists in melting downthe charge in, one furnace and refining a similar charge in another furnace in substantially the same length of time, and maintaining at. all times a predeterminedatmosphere in said furnaces, substantially as described.

2. The method of operating electrical furnaces which consists in simultaneously subjecting two furnaces to the action of electrical units onevto melt down the charge therein and the other to refine a similar charge previously melted down by the first named unit, substantially as described.

3. In the method of operating electric furnaces, the steps consisting in simultaneously subjecting two furnaces to the action of electrical units. one to melt down the charge therein and the other to refine a similar change previously melted down by the first named unit, and proportioning the electrical energy supplied to the two furnaces to complete the melting and refining operations n nearly the same time interval, substantially as described.

4. The method of operating electrical furnaces which consists in melting down the clung-e in one furna e \rhile refining the charge in another furmu-e. nnn'ing said furnaces. maintaining a predetermined atmosphere there u. and repeating the above operation while tapping and recharging the furnace hose charge was first etined. substantially as described.

5. in the method of operating electrical furnaces, the steps consisting of supplying electrical energy for treating a charge in one furnace while discharging a treated charge from another furnace at a discharge stat on, and bodily moving the set of furnaces to bring them successively to the discharge station after electrical treatment, substantially as described.

(3. The method of operating electrical furnaces whichconsists in placing electrodes into a plurality of furnaces to melt down the char e in one While refining the charge in anot ier, moving said furnaces to bring the melted charge to a refining station and the refined charge to a tapping and recharging station and a newly charged furnace to the melting station, substantially as described.

7. So timing the operations recited in claim 6 as to complete them substantially simultaneously, substantially as described.

8. In furnace operating means the combination of a turntable, a plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said furnaces through openings in the roof thereof and means for supporting said electrodes independently of the furnaces, substantially as described.

9. In furnace operating means the combination of a turntable, a plu ality of furnaces mounted on said turntable, an electrical unit con'iprising electrodes adaptedto enter said furnaces through openings in the roof therei-if. means for supporting said electrodes independently of the furnaces, and one tilting means for all the furnaces, substantially as described.

10. In furnace operating means the combination of a turntable, a plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said furnaces through openings in the roof thereof, means for supporting said electrodes independently of the furnaces, and

means for locking the turntable in positioning charges in a plurality of furnace chamwhile the electrodes are in a furnace. substantially as described.

11. In furnace operating means the combination of a turntable, a plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said furnaces through openings in the roof thereof. means for supporting said electrodes independently of the furnaces, one tilting means for all the furnaces and means for locking the turntable in position while the electrodes are in a furnace, substantially as described.

112. In furnace operating means the combination of a turntable, a'plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said fu naces through openings in the roof thereof, means for supporting said electrodes independently of the furnaces, one tilting means for all the furnaces, and means rendering the tilting means inoperative While the turntable is unlocked, substantially as described.

13. In furnace operating means the combination of a turntable, a plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said furnaces through openings in the roof thereof, means for-supporting said electrodes independently of the, furnaces, means for locking the turntable, an electric motor for tilting said furnaces and means holding the circuit of said motor open While said locking means are ineffective, substantially as described.

14. In furnace operating means the combination of a turntable, a plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said furnaces through openings in the roof thereof, means for sup orting said electrodes independently of t e furnaces, an electric motor for tilting said furnaces and means for locking the turntable and holding the circuit of said motor closed While the electrodes are in a furnace, substantially as described.

15. In furnace operating means the combination of a turntable. a plurality of furnaces mounted on said turntable, an electrical unit comprising electrodes adapted to enter said furnaces through openings in the roof thereof, means for supporting said electrodes independently of the furnaces, means for locking the turntable and means for locking said locking means while a furnace is tilted, substantially as described.

16. In the method of operating electrical furnaces, the steps consisting in supplying electrical energy to a plurality of different electrical units, maintaining the electrical energy supplied to one of said units at a different value from the other, and subjectill) hers successively to said units, substantially as described.

17. In the method of operating electrical furnaces, the steps consisting in melting a charge in one furnace by means of electrodes operating at a suitable voltage as delivered by a transformer, simultaneously refining a charge which has been previously melted by said electrodes, said refining taking place in a secondfurnace by means of a second set of electrodes operating at a substantially different voltage, and simultaneously removing from a third furnace a charge previously melted and refined under said two sets of electrodes, substantially as described.

18. In the method of operating electrical furnaces. the steps consisting in supplying electrical energy to refine the charge in one furnace while discharging the treated charge from another furnace at a discharge station and bodily moving the set of furnaces to bring them successively to the discharge station after electric treatment, substantially as described.

19. In the method of operating an electrical furnace, the step consisting in performing a series of metallurgical operations in said furnace at diflerent positions while maintaining a neutral atmosphere within said furnace, substantially as described.

7 20. An electrical furnace, electrodes therefor, a source of electrical power, secondary cables connected to said electrodes of suflicient length to just reach from said source of power to the electrodes when the furnace is in operative position, and means for tilting said furnace without destroying the operative connections between said source of power and said secondary cables, substan tially as described.

21. In the method of operating electrical furnaces, the step consisting in melting down a charge in one furnace, and simultaneously refining a similar charge in another furnace while maintaining a neutral atmosphere within the furnaces, substantially as described.

The combination with an electric furnace, of water cooling means therefor, means for moving the furnace to different stations. and a source of water supply so located that itmaintains a fixed relative position to the furnace during the movement thereof, substantially as described.

23. The combination with an electric furnace, of water cooling means therefor, means for moving the furnace to different stations. and a source of water supply equidistantly spaced from all of the stations to which the furnace is moved, substantially as described.

24. In the method of operating electrical furnaces, the steps consisting in supplying electrical energy to melt the charge in one furnace while discharging the treated charge from another furnace at a discharge station and bodily moving the set of furnaces to bring them successively to the discharge station after electric treatment, substantially as described. I

In testimony whereof I have hereunto set my hand.

FRANK W. BROOKE.