US1444584A - Electric fttbnace having besistob dome - Google Patents

Description

G. H. CLAMER ET AL.

ELECTRIC FURNACE HAVING RESISTOR DOME. I FILED NOV. 20, 1920. a S'HEETSSHEET.I-

Feb. 6, 1923. 1,444,584.

Fgl.

Feb, '5 1923. 1,444,584.

G. H.CLA|\/1ER ET AL.

ELECTRIC FURNACE HAVING RESlSTOR DOME.

FILED 1:0 /.20,1920. u SHEETS-SHEET a.

Feb. 6, 1923. 1,444,584.- (5. H. CLAMER ET AL.

ELECTRIC FURNACE HAVING RESISTOR DOME.

FILED NOV. 20, I920 8 SHEETS-SHEET 4.

Feb. 6, 1923. 1,444,584. 6. H. CLAMER ET AL.

ELECTRIC'FURNACE HAVING RESISTOR DOME.

FILED NOV. 20. 1920. z: SHEETS-SHEET a 1;]. H CLAMER H AL.

kLECTRIC FURNACE HAVING RESISTOR DOM 8 SHEETS SHEET u,

FILED NOV. 20,1920.

Feb. 6, 1923.

G. H. CLAMER ET AL.

ELECTRIC FURNACE HAVING RESISTOR DOME 8 SHEET SHEET 7.

FILED NOV- 20, 1920.

In I!! Feb. 6, 1928. 1,444,584. (3. H. CLAMER ET AL.

ELECTRIC FURNACE HAVING RESISTOR DOME F1LEDNOV.20, 20. SHEETS SHELT a -{Z'grli Patented Feb. 6, 1923. y

UNITED, STATES PATENT orrlca.

G'UILLIAI H. CLAIRE, OI ATLANTIC CITY, AND JAMES R. WYATT, O! CAIDRN, NEW JERSEY, ASSIGNORS TO THE AJAX METAL COIPANY, OI" YHILADELPHIA, PINN- SYLVANIA, A CORPORATION 01 PENNSYLVANIA.

ELECTRIC FURNACE HAVING RESISTOR DOME.

Application filed November T 0 all whomz't, may concern Be it known that we, GUIL'LIAM H. CLAMER and JAMES R. WYA'rr, citizens of the United States, residing at Atlantic City and Camden, in the counties of Atlantic'and Camden and State of New Jersey, have invented a certain new and useful Electric Furnace Having Resistor Domes, of which the following is a specification.

Our invention relates to furnaces of a type which are capable of rotation or oscillation in use and of tilting transversely to the axis for pouring, if desired, and utilizes both the reflected and radiated heat from the upper furnace walls upon the surface of the metal and subsequent direct contact of the pool with these,upper walls as the furnace is rotated or oscillated.

-'The purpose of our invention is to provide for generation of the heat within the furnace wall over the charge by reason of theresistance offered by said Wall to the passa e of electric current therethrough.

A Eurther purpose is to equalize the current and heat generation as nearly as possible throughout the entire wall.

A further purpose is to pass the electric current circumferentially about the wall in a single series passage or in oppositely di-' rected parallel paths as preferred.

' A further purpose is to apply electrical current to a radiating upper wall of a furnace by induction and to rotate or oscillate the furnace to rest the molten metal upon this heated wall without necessity for interrupting the inductive transfer of current.

A further pur ose is to combine a ty e of fluid-resistor ind liction furnace with a heatradiating domed roof, heated .by the induced current.

Further urposes will-appear in the specification and in the claims.

Our invention relates to the processes involved as well as to the structures suggested as among themeans by which these processes can be carried out.

We have preferred to illustrate our invention by a few forms only among the many by which it may be carried out, selecting forms by reason of their simplicity, efliciency and practicability, and because at the same time they well illustrate the principlesof our invention.

an, 1920. Serial No. 453,420.

Figure 1 is a side elevationof one form of our nvention.

Figure 2 is a broken end elevation of the furnace. I

Figure 3 is a vertical central section upon l1ne 33 in Figure 1.

Figure 4 is a section upon line 44 of F1 re 3.

igure 4 is a similar section of a form corresponding nearly to Figure 4.

Figure 5, is a section corres ondin to Flgure 1 but showing a second orm of our invention.

Figure 6 is a section of Figure 5 upon line 6-6 thereof.

Figure 6 is a similar section correspondin nearly to Figure 6.

Figure 1 but showing a third form of our invention.

Figure 8 is a side elevation, artly broken away, of the structure seen in igure 7.

Figure 9 is a section upon line 9-9 of Fi re 10.-

igure 10 is a side elevation of the structure seen in Figure 9.

Figure 11 is a section 'line 1111 of Figure 12.

Figure .12 is a side elevation, partly broken away showing the structure seen in Figure 1 Figures 13 and 14 are a side elevation and an end elevation, res ctively, showing one way in which any 0 our furnaces may be tilted for end pouring.

In the drawings similar numerals indicate like parts.

Electric furnaces having a refractory lining'which is heated by the electric arc and in which the furnace is oscillated or rotated to bring the charge in contact with the portion of the lining which has previously constituted the dome and which has been so heated, are well known. A conducting lining heated by current applied at the ends or by Jablochkofi candles at the periphery is also old. It is our purpose to utilize the exposed portion of the furnace lining or a belt thereof above the char as a conductor of electricity, preferably o the second class and to induce an electric current in it or directly conduct such a current to it at points about its circumference so that the 1 I entire ora very large part of the heat of the furnace is represented by the CPR developed within this conducting lining;

As will be recognized, this requ res that the conductor of t e second class shall have a very high-fusingpoint andthat it shall "have either a relatively small cross section when cold but which improves greatly in conductivity. as the'temp'eratiire rises, and which we call a ,conductor off the second class. Two examples of suchconductors are found in carborundum and gr aph1te. I

Throughout all the forms of our nvention it he intention is to pass thecurrent\of electricity circumferentia-lly about the walls, or belts or bends therein, either in a single path, (with the belts in multiple where more than one belt is used) in series, (by lnduction or by electrodes) or in multiple paths dividing about opposite sides of the furnace. Likewise in all of ourforzms the resistor lining or'beltabove the pool adds to the heat of the metal during the main melting or heating operation by radiation and reflection from or upon it but in the preferred manner of use the furnace is oscillated so that the metal flows over the heated wall or belt which had previously been above 'it, with or without separate heating as by an induction resistor c annel. At the same time that the metal of the pool is being heated by the new portion of the lining or wall over which it then fiOWSythIS portion of the lining or. Wall is cooled somewhat by the metal of the pool and excessive heating is avoided.

In all our forms we provide for the rotation or oscillation of the furnace in its entirety and for-the heating of the furnace by heating the lining, including and in most cases particularly, the dome or belt, by which we mean to include all of the conductlng furnace wall above the pool of molten metal.

We prefer not to have the ends/lined with conducting material. v

In the forms shown in Figures 16 we have applied the current by induction from an alternating currenttransformer threading the circuit, while in the remaining fig ures the current is applied directly to the conductive lining.

Describing the forms shown by way of illustration and not by way of limitation In Figures 1%, the cylindrical furnace is enclosed within a metal supporting casing or shell 16 which is circumferentially interrupted and insulated as at 17 to break up vflow of current circumferentially about this shell. The shell covers not only the outer cylindrical surface but may also enclose the ends at 18 nearly to the center, providing for a passage way Within which the central leg 19 of transformer 20 passes. This opening is lar e enough for the winding 21 of the transformer and the winding is protected by a heat insulating and electrically insulating tube 22 for which the material known as electrobestos is suggested as suitable. Airv spacing is rovided at 23 about the transformer win 'ng and the transto pointing out the indepen ence of the invention with respect to such features. Either of these could be applied. .to any of the forms. Their character can obviously also be greatly varied. Where the filling and pouring take place from the side, as seen in the earlier views, the shell 16 may be interrupted at any suitable point to provide an opening closed by a plug 25 which may be held in place by astrap 26. With end pouring, the shell may be rotated freely without re erence, to the pouring opening while with side filling and ouring, the difficulty of properly sealing t e opening will'ordinarily make it more desirable to oscillate the shell as distinguished from rotating it. Continuing the description particularly of Figures 1 and 2, but including matter applicable also to other figures, the shell is lined with a heat insulating and electric insulating material 27 next to the shell, for which SilOCel is suggested as suitable, and within this insulator is placed the lining 28 which is intended to receive and hold the charge.

1 This lining 28 (which may be one or more belts if desired) is preferably of some material which is a conductor, though not a good conductor of electricity when heated but which is a non-conductor of electricity when cold, known in this art as a conductor of electricityv of the second class. For this purpose carborundum or graphite is suggested, either one of which is sufliciently refractory and sufficiently poor aconductor of heat at all times, to be raised to a high temperature by the electric current. in it, while offering enough resistance so that a high power factor may be maintained.

- Alternating electric current may be supplied to the transformer in any suitable way, which we have not considered necessary to illustrate.

In order that the furnace may be rotated, I

former, the entire furnace is supported within an outer drum made up of two flanged parts 29, 29 insulated from each other. Brackets 30 space the drum from the shell sufficiently to give fullair circulation between, and at the same time rigidly support the shell. Tracks 31 are provided upon this drum and bear upon grooved rollers 32.

In operation the molten metal forms a pool 33 in the bottom of the furnace and additions to the charge are put in through the opening 34 closed by plug 25. The current induced by the transformer passes through the conducting lining alone above the bath, and the combined bath' (if it be electrically conducting) and lining below its level. Since the resistance of an electrically conducting bath will b( quite low, the heat generation will take place almost wholly in the conductive lining or belt above it, raising the lining or belt to incandescence and heating the bath at first chiefly by radiation. However, turning the furnace in either direction brings a section of highly heated conductor-lining beneath the pool and exposes the section upon which the pool has rested. This newly-exposed section then becomes heated by the induced current and the action continues as before.

As the furnace is rotated or oscillated, it will be noted that new portions of the lining are lifted above the pool to progressively and automatically receive major concentration of current.

In Figure 4 a plurality of belts of conducting material 28 are substituted for the lining of conducting materiahas may be done in any of my forms in order to reduce the cross section and improve this power factor.

In the form shown in Figures 5 and 6 we have combined the advantage of a molten inductor furnace with the structure previously described. We have enlarged the furnace chamber at one side so that the shell 16, refractory lining 27' andsecondary conductor 28 conform to the enlargement and provide an axially extending trough 35. Within this trough the protective tube 22 for transformer leg 19 defines a resistor channel 36 for molten metal between the tube and the shell, completely surrounding the shell and communicating with the pool as best seen in Figure 5.

In this furnace the extra weight of the lateral extension is compensated by a lobe 37 upon the opposite side of the furnace and the entire construction is mounted to provide a track and wheel support of the same character as that seen in Figure 3.

In the position shown in Figure 5, a complete secondary path is formed through the bath and the greater part of the secondary current will short circuit above into and across the metal of the pool. Some part will flow through the conductive (dome) lining or belt, and the proportion of current through each may be predetermined to make this useful or negligible in this position as desired. However, if the furnace be oscillated until the molten metal has left any part of the channel 36, substantially all of the current flow will take place through the conductive lining forming the dome. In this changed position of the furnace the current passing through the pool itself would be equivalent to that merely which passes through the pool in theform shown in F i ure 3.

he resistor channel may extend in an axial direction the full length of the furnace, as in Figures 5 and 6, or a part of this length only, as may be desired.

This form in Figures 5 and 6 is, therefore, capable of use in either way, to operate as in the first form, or to operate as an induction furnace of the molten resistor chan* nel type. It may also be designed to use the resistor channel at all times, taking advantage of the heat-radiating capability of the dome.

In this latter use the furnace offers special advantage in the case of materials which are poor conductors of electricity or nonconductors, in which case the current passes through the conductor 28 chiefly if not entirely, heating it to a high degree. About the channel this heat conductor comes in contact with so thin a layer of the molten content as to heat it more rapidly than it heats the pool and the heat transfer takes place through Joule circulation, or a combination of pinch and Joule circulation.

In Figure 6 the channel width is reduced in width as at 36 and the band at the top is correspondingly narrower than the dome of Figure 6 to reduce the cross section and improve the power factor.

In the form shown in Figures 7 and 8, the current is applied directly from the source of supply (which may be alternating or direct current) to the lining 28 by means of leads 38, 38' and conductors 39, and, entering the lining, divides and flows in multiple through opposite sides of the lining from the one conductor to the other. In the illustration the points of application of the current are shown as at the top and bottom, in the normal position of the furnace, so as to heat both sides of the conducting wall as, nearly equally as possible, above the pool. However, as the furnace turns, wherever the conductors are located, there will be times when the current does not divide uniformly and when one part of the dome or belt is consequently more'highly heated than another. The conductors 39 may be placed at any point or points along the length of the cylinder desired.

The operation of this form is quite similar to that of the first form with the difference. however, that the current at all times passes through the two opposite parts of the conductive lining in multiple.

In the form shown in Figures 9 and 10, the current is applied to the lining or belt by form offurnace and electrical connections therefor are shown as in Figures 9 and 10 with a single commutator only, however,

means of a number of conductors 39 of \instead of the two commutators of the latter copper or any othersuitable material, here shown as'connect-ing at their inner ends with the lining 28 and as united to and sustained by commutator bars 40 at their outer ends. These commutator bars are engaged by brushes 41 mounted in supports 42, 42' and spring pressed at 43 for the purpose and with the elfect of leading the current in at approximately the same points, relatively to the metal pool at all times, providing a sufficient number of commutators to secure any closeness of approximation to this which may be desired. The brushes are here applied at the top and bottom so as to divide the current nearly equally about the walls of the dome.

Two sets of brushes are shown. one at each end. suiting to the use of'two hase current in separate belts, if desired. int c same manner that the three belts of Figure 4* adapt it to use with three phase current applied to the separate belts. if desired, through the use of three sets of contact brushes. similar in their connection to Figures 9 and 10, connecting with the three belts. instead of using the transformer seen in Figure 4. At the same time it is recognized that these forms having a plurality of belts, instead of a dome, are well suited to connection of the currentby brushes from a direct current of single phase current and with the several belts connected in multiple.

The operation of this form is substantially the same as that in the form shown in Figures 7 and 8, but secures amore uniform division of current about the walls above the pool.

In the form shown in the Figures 11 and 12 the conductive lining 28 or belt is not continuous about the circumference but is interrupted at the top by insulation 44 and the edges are connected to terminals 39 fed from leads 38. The same opportunity for use of a plurality of belts in multiple or with multiphase supply exists herein, and, indeed, in all of my forms.

In this form the electric current is fed directly through the entire circumferential exfigures. These figures are given to show an adaptation of one of our forms of the furnace to end filling and pouring, with recognition by us-of he fact that any form of our invention mi ht be applied in this manner or in various other ways to secure end filling and pouring.

Our furnace of whatever .form. in regard to the remainder of the structurein this case corresponding generally to Figures 9 and 10-may be provided with an end filling opening typified at 4:5 and with an end pouring spout 46 which may be so placed as to allow complete rotation of the furnaces when desired with bodily tilting for pouring purposes.

The construction which we have shown for accomplishing this comprises a platform at? upon which the entire furnace and track 31 are mounted, and the rollers 32 with their supporting structure. The platform is shown as comp-rising side rails 47, supported about bearings 48 in brackets 49, the axis of the bearings being preferably in line with the end of the pouring spout; so as to maintain the position of the pouring spout as the platform and furnace carried thereby are swung about the bearings 48. The platform is counterbalanced through chains 50 and counterweights 51.

We have not believed it to be necessary to complicate the figures .by showing positive means for rotating the cylindrical furnace body about its axis-such means being common, for example in circular racksand pinions. The end of the platform may be lifted for pouring by chain 52 engaging sprockets 53 upon shaft 54 which carries sprocket 55.

In order to avoid complication of the tilting by possible rotation of the furnaces about their own axes, we clamp the furnaces tightly before tilting, as by brake-bands or straps 56 which may be held fixedly at either end. or may be tightened at both ends. as shown. In the tightening. the ends of the bands are secured about off-center pins 57 operated by handles 58 which are shown in tightened positions in Figure 14 to hold the furnace tightly whiletilting takes place.

\Ve recognize that. the lining itself comprises a belt of greater axial extent only than the narrow belts shown in Fgures 1 and 6 and we. therefore. use the expression lining or belt in the claims for the pur-- pose of indicating a belt which may be either narrow, forming a lining for a part only of the interior (usually cylindrical) surface, or may have sufficient axial extent to form the entire cylindrical surface with which the pool may come in contact, i, e., forming a complete dome.

\Ve recognize that our invention may appeal in various other forms than those shown, depending upon the needs of individual installations and the training or even the whim of the designer and in the light of our disclosure and we intend to include herein all such forms and variations as fall within the fair spirit and scope of our invention.

Having thus described our invention, what we claim as new and desire to secure by Letters Patent is 1. An inductive electric furnace, comprising a chamber having an annular electrical conductor with which the pool is adapted to engage at the bottom and which is adapted to overlie the pool at the top in the form of a dome, and a transformer therefor having one leg passing through the electrical conductor.

2. An electric furnace having an electrically-conductive dome or belt above the pool through which the operative electric furnace current passes and whose conductor resist ance as connected as distinguished from resistance due to spacing of the parts, in conjunction with the pool develops the effective heat of the furnace from the (PR- energy expended therein.

3. An induction furnace having an electrically-conductive dome above the pool and included in the secondary transformer circuit.

4. In an electric furnace adapted to contain a pool of molten metal, a casing, means for turning the casing about a longitudinal axis, a refractory insulation protecting the casing, a conductor of the second class forming lining or belt within the insulation and means for passing electric current circiunferentially through the conducting lining or belt and generating the entire heat of the furnace by the (PR conversion within the lining or belt and the pool of current into heat,

In an electric furnace adapted to hold a pool, a casing having a longitudinal axis, mounting for turning the casing about the longitudinal axis, a. refractory within and protecting the casing, a conductor of the second class forming a lining or belt within the refractory and adapted to come in contact with the pool, and a transformer having one leg passing through the conductive lining or belt and adapted to induce current circumferentially in it.

6, in an electric furnace, a metallic casing interrupted to prevent flow of electric current thereabout and having a longitudinal approximately horizontal axis, mounting to support and guide the casing so that it may be turned about the axis, a refractory within and protecting the casing, a substantially cylindrical conductive lining or belt on the pool side of the refractory, comprising a conductor of the second class and means for passing electric current in series from the top to the bottom through the conductive lining or belt. 7. In an electric furnace, a metallic casing having a longitudinal axis, mounting to support and guide the casing so that it may be turned about the longitudinal axis, a refractory within and protecting the casing, a substantially cylindrical conductive lining or belt on the pool side of the refractory, comprising a conductor of the second class and a transformer having one leg passing through approximately the axis of the conductive lining or belt. 8. In an electric furnace, a metallic casing having a longitudinal axis, mounting to support and guide the casing so that it may be turned about the longitudinal axis, a refractory for the casing, a substantially cylindrical conductive lining or belt on the pool side of the refractory, comprising a conductor of the second class and a transformer having one leg passing through aproximately the axis of the conductive linmg or belt and adapted to rotate with it. 9. In an electric furnace, a metallic casmg having refractory insulation therein and an electrically conductive lining or belt within the insulation intended to lie partly above and partly beneath the pool level, in combination with a transformer therefor having a leg extending through the conductive lining above the intended level of the pool.

10. An induction furnace, comprising an annular electrically-conductive band, a support therefor, mounting to permit turning of the band and support and a transformer within the band adapted to pass current throu h it.

11. nan induction furnace, a closed conductor adapted to form both a hearth and a dome therefor, a support for the conductor, mounting permitting turning of the conductor to vary the portion effective as a hearth and transformer means for passing electric current through the conductor.

12. In an electric furnace, a metallic casing, having refractory insulation therein and a conductive resistor within the insulation extending both above and below the intended pool level and separated axially into several parts by insulation, in combination with means for passing current thrlough the separated resistor'parts in multip e.

13. The method of operating furnaces by electricity which consists in providing a recircumferentially to heat the resistor above the pool level.

14. The method of operating an electric furnace which consists in providing a resistor for the electric current in the form of a lining or belt above the pool and extending beneath the pool, in passing current by induction through said resistor ciroiimferentially to heat the lining or 'belt to a greater extent than the portion below the pool and in turning the resistor to pour the pool over a new section of the resistor at one side While exposing a new section thereof at the other side of the pool and while maintaining inductive passage of electricity through theresistor.

G'UILLIAM H. CLAMER. JAMES R. WYATT.

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