US2060136A

US2060136A - Electric furnace

Info

Publication number: US2060136A
Application number: US596980A
Authority: US
Inventors: Company The Colonial Trust; Summey Richard P Weeks
Original assignee: Scovill Inc
Current assignee: Scovill Inc
Priority date: 1932-03-05
Filing date: 1932-03-05
Publication date: 1936-11-10
Anticipated expiration: 1953-11-10

Description

D. L. SUMMEY ELECTRIC FURNACE Original Filed March 5, 1932 11 sheets-sheet i Nov.

10, 1936. p. L. sUMMEY ELECTRIC FURNACE Original Filed March 5, 1932 ll Sheets-Sheet 2 l.lNvEN'roR Jar/a famme] AT oRNEYf Nov. 1o, 1936. D L SUMMEY 2,060,136

ELECTRIC FURNACE Original Filed March 5, 1932 ll Sheets-Sheet 5 A TTORNEYS.

Nov. 1o, 193s. D L. SUMM'Y 2,060,111,6'y

Y ELECTRIC FURNACE 4 Original Filed March 5, 1932 ll Sheets-Sheet 4 ISO Y 3 57 13g '22 127 gfr'' f5@ INVENTOR. .2mb/50mg BY w., man A TTORNEYS.

Nov. 10, 1936.

D. 1 suMMEY ELECTRIC FURNACE original' Filed March 5, 1952 11 sheets-shet 5 T IN1/EN ToR. aw'o/Z. Jam/wey ATTORNEYS..

D. L. suMMEY 2,060,136

ELECTRIC FURNACE Nov 10, 1936.

Original Filed March 5, 1932 1l Sheets-Sheiet 6 ATTORNEYS.

Nov. l0, 1936. D. L. SUMMEY 2,060,136

` ELECTRIC FURNACE l I original Fi1edfmarch 5, 1952 11 sheets-sheet 7 @51 50 203 @7250 W00 t A l 46 fi f 1 000 185 00/ #11001 R700 Q00 W0 f f5 j? V-I/ E. Ww 5 X-X Il' Y I ff NIW 210 Y'Y i 2-2 Suva/44150@ Nov. 10, 1,936'.` D.AYL. suMMEY 2,0605136 I ELECTRIC FURNACE Original Filed March 5., 1932 11 Sheets-Sheet 9 INVENTOR m/(b. fammey.

Mlm/Jan Nvgm, 1936.. D. l.. SUMMEY 2,060,136

` ELECTRIC FURNACE A original Filed March 5, 19:52 11 sheets-shaun Patented Nov. .10, 1936 UNITED STATES PATENT OFFICE ELECTRIC FUBNACE Connecticut Application March 5, 1932, serial No. 596,980 Renewed February 21, 1935 28 Claims.

'Ihis invention relates to electric furnaces, more particularly to electric induction metal melting furnaces, and has for an object the provision of improvements in this art. This application is a divisional in part of my copending application, Serial No. 535,829, filed May 8th, 1931.

This application in certain aspects is also related to my copending applications, Serial Number 605,147, filed April 14, 1932, Serial Number 608,177, filed April 29, 1932 and Serial Number 619,474, filed June 27, 1932 and insofar as patentable subject matter may be disclosed but not claimed in the present application, it is claimed in the copending applications referred to.

The objects and advantages of the invention will be apparent from the'following description and accompanying illustration of an exemplary embodiment of the invention. In the drawings:

Fig. 1 is an elevational view of the furnace, parts being broken away, looking at the pouring end;

Fig. la shows a support detail indicated at a in Figs. l and 4;

Fig. 1c shows a support detail indicated at c in Figs. 1 and 4;

Fig. 1e shows a support detail indicated at e in Figs. 1 and 4;

Fig. 2 is an elevational view, parts being broken away, looking at the right side of Fig. 1;

Fig. 3 is an elevational view, parts being broken away, looking at the charging end;

Fig. 3b shows a support detail indicated at b in Figs. 3 and 4;

Fig. 3d shows a support detail indicated at d in Figs. 3 and 4;

Fig. 3f shows a support detail indicated at f in Figs. 3 and 4;

Fig. 4 is a horizontal section taken principally on line 4-4 of Fig. 1;

Fig. 4a is a diagrammatic plan view;

Fg. 4b is a partial elevation looking at the left end of Fig. 4;

Fig. 4c is a horizontal section taken on the line 4c-4c of Fig. 4b;

Fig. 5 is a vertical longitudinal section taken on line 5-5 of Figs. 1 and 4;

Fig. 6 is a vertical longitudinal section taken on line 6-6 of Figs. 4 and 7;

Fig. 7 is a vertical transverse section taken on line 1-1 of Fig. 6;

Fig. 8 is a top plan View of a channel-transformer unit, parts being shown in section;

Fg. 9 is a horizontal section through the channel-transformer unit taken on line 9 9 of Fig. 11;

(c1. la-zs) Fig. 10 is a vertical section taken on line lill0 of Figs. 9 and 11;

Fig. 11 is a transverse vertical section taken on line ii-ll of Figs. 8, 9, and 13;

Fig. 12 is a transverse vertical section taken on 5 line I2-I2 of Figs. 8 and 9;

Fig. 12a. is av diagrammatic view showing in superposed relation the cross sectional shape of the channel at several points which are indicated on Fig. 9;

Fig. 13 is a fragmentary section taken on line i3-|3 of Fig. 1l;

Fig. 14 is an end elevation of a detached channel-transformer section, certain parts being omitted;

Fig. 15 is a diagrammatic view showing the position of the furnace and metal level at the end of rocking movement in counter-clockwise direction, the view being taken looking at the pouring end of the furnace;

Fig. 16 is a similar view at the end of rocking movement in clockwise direction;

Fig. 17 is a similar view after a normal draught of molten metal has been poured from the right hand spout; 2

Fig.' 18 is a diagrammatic view showing the position of the furnace when it s being emptied;

Fig. 19 is a plan view of certain mechanism employed for oscillating the furnace;

Fig. 20 is a horizontal section through a modi fied channel-transformer unit taken on the line 20-20 of Fig. 21;

Fig. 21 is a vertical section taken on the line 2i2i of Fig. 20; and

Fig. 22 is a transverse vertical section taken on the line 22-22 of Fig. 20.

Referring to the drawings and especially Figs. 1 and 2, two spaced hearths A and B are shown mounted on opposite ends of a rocking fr ame F supported upon a base cradle generally designated by the letter D.

As best shown in the lower portion of Figs. 1 and 2, the cradle D comprises a base plate 20 surmounted near the four corners thereof by two pairs of chairs 2| forming bearing supports for

shafts

22, 23, 24, 25, at least one of which (25, as shown) may be a live shaft adapted to cause oscillation of the frame F. The shafts are each provided with a flanged roller 26 supporting parallel spaced arcuate rocker rails 2l of the rocking frame F.

The shafts 22 and 25 are mounted in fixed bearings while the shafts 23 and 24, as best shown at the lower right hand corner of Fig. 1, are mounted upon levers 3| which are pivoted intermediate their ends by journals 32 upon the chairs 2 i. The ends of the levers 3| opposite the shaftsupporting ends are pressed downward by strong springs R3 adjustable by bolts 34 to press the rollers 26 iirmly upward against the rocker rails 21 thereby causing them to take a portion of the load.

The power driven shafts 25 Vare equipped with pinions 35 rigidly secured thereon beyond the rollers 26. The pinions are in mesh with arcuate racks 36 which are rigidly attached to the rocking frame F adjacent the arcuate rocker rails 21. The two shafts 25 may be connected (see Fig. 2) by a flexible coupling 31; and one ofthe shaftsthat one shown on the right or charging side in Fig. Z--may be connected by a similar flexible coupling 38 to a drive shaft 39 forming a part of the furnace oscillating mechanism later to be described. The frame F thus supported is adapted to have a controllable oscillatory movement about a definite horizontal axis indicated in the central portion of Figs. 1 and 2 by the letter Z.

The hearths A and B are generally cylindrical in cross section, as may be observed in Fig. 7, and each comprises an outer metallicshell 4| and suitable refractory interior lining which, as shown in Figs. 4, 6, and 7, includes a rammed refractory material 40 in the lower portion of the hearth, and at the upper portion of the hearth includes an outer layer of insulating material 43, an intermediate layer of rammed asbestoscontaining material 44 and an inner layer of firebrick 45, the latter llining being shown in conventional section lines in all views except Fig. 2 where it is more particularly delineated.

The shell 4|, as shown in Figs. 2, 4, and 6, comprises semi-cylindrical lower end castings 4Ia, 4 ib, semi-cylindrical upper end castings 4|c, lid, and semi-cylindrical lower and upper steel `girth plates 4|e and 4|f, one of which 4|e is secured to and embraced within the edges of the lower end castings 4|a, 4|b, as shown at the bottom of Fig. 6, and the other 4 if is secured to and embraced within angle-bar straps 42 carried by the upper end castings 4| c, 4|d, as shown at the top of Fig. 6 and in Fig'. 2. The end castings and girth plates meet their mating parts at approximately the horizontal central plane of the hearths, as shown in Fig. 7, and may be secured together by bolts or other appropriate devices acting upon flanges supplied on the mating parts.

As shown in the diagrammatic Figures 15 and i6, each of the hearths A and B is adapted to hold a pool of moltenmetal, these spaced pools being joined at several places (see Fig. 4) along the bottom by generally horizontal bodies of molten metal enclosed in refractory lined channels L, M, N, which in turn are enclosed by tubular metal casings. The casings comprise flanged tubular extensions 46 attached to the shells of the hearths, and central flanged tubular sections 5|, hereinafter termed channel-transformer units, removably secured to the extensions 46 by bolts or set screws 54 passing through mating

external anges

41, 52 on the hearth extensions 48 and the units 5| respectively. Desirably the flanges are separated by insulation 55 and the bolts are separated from the flanges by suitable insulating sleeves and washers (not shown).

Since the tubular casings enclosing the channels L, M, N (Fig. 4) which join the hearths A vand B and the hearths themselves-are subject to expansion and contraction under varying degrees of temperature, means are herein provided for permitting movement of this assembly relative to the supporting frame F. As shown near the mid-height of Fig. l. the rocking frame F is formed with ledges 61 upon which the hearths are supported through lugs 6| secured to the sides of the hearths in any suitable manner. Insulating plates 62 and overlying metal plates 63 are preferably interposed between the -adjacent faces of the frame ledges 51 and the hearth lugs 6| the insulating plates 62 serving to prevent electrical grounding to the frame F and the plates 63 serving to take the sliding movement between parts wherever present to prevent injury to the insulating plates. If desired, the hearths, the channel transformer units and other parts of the furnace may be directly grounded in any suitable manner.

As shown in Fig. 4, each of the hearths A and B is supported upon the rocker frame F at four points, the hearth A at the points a, b, c, d and the hearth B at the points c, d, e, f the supporting structures of the hearth B at the points c and d being the reverse duplicates of those for the hearth A at the points c and d. f

The supporting structure at the point f for hearth B is best shown at the left of Fig. 3 and in Fig. 3f. Here the metal plate 63 is shown to have a circular boss 63a fitting within a larger socket formed in the supporting ledge 61, the insulating plate 62 being correspondingly cupped to fit the boss and separate it from the socket walls. Bolts 64 insulated by suitable sleeves and washers secure the plate 63 upon the ledge 51. A V-edged key 68 engages mating under-cut grooves formed in the plate 63 and in the hearth lug 6| respectively to prevent their separation, the key being retained by set screws 69. A second key 10 fits within mating grooves also formed in the plate 63 and the lug 6| and at right angles to the grooves for the V-edged key 68 to prevent endwise sliding movement, i. e. across the frame F, between the parts. In effect, the hearth B is rigidly fixed at the corner f and expansive movement of the furnace in any direction will originate at this fixed point. At every other point of Support relative movement of appropriate character is provided between supported and supporting parts.

The joint d for hearth B and the joints d and b for hearth A which are aligned along one of the rockers of the frame F with joint Bf need to provide only for expansion in one direction, i. e., along the rocker. Accordingly, the joint d for hearth B is constructed as shown in Figs. 3 and 3d, the same construction serving for joint d of hearth A, which, as stated, is a reverse duplicate of that for hearth B. Here the plate 63 is insulated from and secured to the ledge 51 in the same manner as for joint Bf'but is provided upon its upper surface with a rib disposed in a groove of the lug 6| for permitting expansion along the length of the rocker-i. e. toward the right, Fig. 3. The parts are restrained from vertical separation by a shoe 1| mounted upon and insulated from a cross-rocker channel beam 12. The beam is attached to an upstanding pedestal 13 of the rocker by suitably insulated bolts 14, the shoe being slidable upon the upper surface of the lug 6|.

The joint at b for hearth A is shown in Figs. 3 and 3b to comprise a plate 63 mounted upon the ledge 51 as in joint Bf. The plate at joint b, however, has only the V-edged key 68 and in this instance the key is aligned with the rocker instead of across it, and is secured to the plate 63 by set screws 69, so as to provide for expansive x v amm sliding movement'mifdimaun but to' prevent sliding movementacrcsstherockerandalsoto.

prevent vertical separation of parts. h

Thejoint ate for hearth B,showninFlgs. i and leisseentobeidenticalin all respectswith the joint at Bf except that in the joint Be the key 10 is omitted to permit sliding movement transversely of the rocker.

Joint c forhearthB (and this applies equally to joint c for hearth A) must provide for sliding along two coordinates. As shown in Figs. i and 1c it has a thinner plate ,than'the joints previouslyconsidered but the plate is secured to and insulated from the rocker ledge I1 just as before. The upper-f. surface of the plate I is grooved transversely of -the rocker to accommodate the lower rib of` an auxiliary plate Il. The plate Il on its upper sln'face is provided with a rib disposed at right angles to the rib onits lower surface and this upper rib slidably nts in a groove in the hearth lug Il. A shoe 1| mounted as that for joint Bd prevents vertical separation of parts.

Joint a for hearth A must also provide for sliding along two coordinates and, as shown in Figs. 1 and 1a, has like joints Bc and Ac a thin grooved plate 63 provided upon its upper surface transversely of the rocker with an undercut groove for the mating rib of an auxiliary plate B6. 'I'he latter upon its upper surface is supplied with an undercut groove facing a similar groove in the lug 6| for the reception of a V-edged key 68. The key may be retained in the plate 65 by set screws 69 or equivalent devices.

The hearth and channel assembly, i. e., the furnace proper, as thus mounted is ilxed adjacent and vbehind the pouring spout but free to expand in all directions in a horizontal plane from the fixed joint Bf. Nevertheless, the assembly is rmly retained upon the rocking frame F regardless of the oscillating movements.

Resilient abutment means are provided at the I end of the rocker frame remote from the point of xed attachment between the furnace assembly and frame. 'Such means will permit expansion of the furnace assembly in that direction but will strongly resist the same and will partly support the lower hearth when the furnace is tilted to the extreme position for emptying shown in Flg. 18. This will reduce thev strain which would other- Wise b imposed upon the channel-transformer units and their connecting flanges.

The abutments comprise, (Figs. 4, 4b, 4c) heavy springs 15 disposed between the hearth A and an abutment 11. The abutment 11 is attached to the frame F by adjustable bolts 80. The springs 15 aremounted upon plungers 16 guided in the abutment 11, the ends of the springs opposite those engaged with the abutment 11 being engaged with a spring plate 18 connected to a longitudinal rib 19 fast on the side of the shell 4| ofthe hearth A. The plungers 1i and spring plate 18 areinsulated from the rib 19 by sheet insulation 8|.

In removing a channel-transformer unit the metal is first drained from the furnace as shown in Fig. 18. Then the furnace is returned to the horizontal position and one end of all units is suspended. The flange bolts for that end are removed. 'Ihe bolts l0 are loosened to take tension off the springs 15. The hearths are next forced apart vby any appropriate means. 'I'he other end of the unit which it is desired to remove is suspended and its flange are removed. 'I'he unit is then pushed away from its hearth flange and lowered to the floor.

Means are herein provided for imparting to the furnace its required movements, whether for rocking to circulate metal through the channels (Figs. 15, 16), for tilting to pour metal in the normal operation of the furnace (Fig. 17) or for 'tilting to the extreme angle for emptying the furnace (Fig. 18).

As previously explained in connection with Fig. 2, the drive shaft 39 is connected to the shafts 25 which carry the driving pinions 3l. Referring to Fig. 19, the shaft 39 is mounted in fixed bearings 85 and is driven from a jack shaft .I mounted in fixed bearings I1 through a gear I8 on shaft 39 and a pinion I! on the jack shaft. The jack shaft 86 in turn is driven by the low speed shaft 92 of a reduction gear train housed in a gear casing $3 through a gear Il on the jack shaft and a pinion 95 on the low speed shaft.

On the high speed side ofthe gear train housed in the casing 93 there are two drive shafts 91 and 98, the one 91 being directly connected with the shaft of a tilting motor T through a flexible coupling 99 and the other `9| being connected `with the shaft of a rocking motor R through means including av magnetic clutch I", a second gear train housed in a gear casing IDI, a shaft |02, and a exible coupling |03.

The rocking of the furnace to circulate the metal may be quite slow relative to its tilting movement for pouring. Also the angle of movement may be quite small. So the motor R may be of relatively small power. But the tilting of the furnace for pouring must be quite rapid and requires a greater angle lof movement so the motor T must be of relatively greater power. The use of two motors of different operating characteristius has been found to give more satisfactory results than could be obtained by the use of a single lmotor with the concomitant change-speed gearing entailed.

In operation, the magnetic clutch |00 is automatically engaged whenever the tilting motor T 'the movement of the furnace and such vmeans will be adjustable to vary the points of stoppage and reversal as desired. Referring especially to Figs. 6 and '7, each of the hearths A, B is provided at one end with a restricted charging opening formed with a raised breast I0, parallel sides I and an arched top H2. The breast is suiiiciently high to retain a' pool of molten metal of considerable depth in a basin thus formed Within the hearth. The hearth casing at this end forms a frame comprising a sill ||3 and parallel vertical sides (Fig. 4) having interior guide flanges IM and exterior flanges |I for retaining a vertically slidable door IIB over the aperture. The door when closed serves to seal the hearth gastight or suiliciently so vfor all practical purposes. Referring to Figs. 3 and 4, clamp bolts I1 threaded into the door retaining anges i I5 are provided for clamping the doors closely overY their openings.

As shown in Figs. 4 and 6, the door I i6 comprises an enclosing metal rim |20 anged interiorly to retain a refractory lining such as fire brick or fire clay |2| and a front plate |22 Exieri 'riy therim izo may be provided with side ribs |2 cooperating with the flanges ||5 of the frame to retain, the door'closely over the opening and in proper alignment at all times.

Suitable meansare provided herein for actuating the doors ||6. Referring to Figs. 2, `3, and 5, each hearth is surmounted at the end adjacent the door by spaced columns |30 attached to the hearth casing at their lower ends in any approved manner and held upright by inclined braces |3| attached to gusset plates |32 carried by the upper ends ofethe columns. At their lower ends the braces are attached to the casing of the lhearth by suitable angle plates |33.

The columns |30 are provided adjacent their upper ends with bearings |35 rotatably supporting a transverse shaft |36 having rigidly secured thereupon a pair of end pulleys |31, a pair of intermediate pulleys |36 and a power pulley |39. To the intermediate pulleys |36 (Fig. 2) there are attached, at a point |36a on their periphery, cables or chains |40 which are wound upon the pulleys and pass over the front side of the pulleys downwardly to points of attachment |4| with the door ||6 which they support. l

To the end pulleys |31 (Fig. 5) there are attached, as at a point |31a on their peripheries,

When the furnace is to be charged the de- I sired door is opened by admitting pressure fluid to the upper end of the cylinder |56 for that door, whereupon the piston rod |55 is moved4 inward carrying with it the movable pulley |53. One endof the cable |52 which passes over the pulley |53 is thereby pulled downand, this end being attached to the periphery of the power pulley |39 of the pulley shaft |36, causes left hand rotation of that shaft (as viewed in Fig. 2). Since the door supporting cables |40 which pass over the intermediate pulleys |36 are wound in the same direction as the power cable |52 is wound over the power pulley |39, the door is raised by left hand rotation of shaft |36. When .pressure isrelieved from the cylinder the door returns to closed position. u

Means are provided for drawing oil.' molten metal from the furnace. Such means (Figs. 1, 2, and 4) are provided at the end of the 'hearth or hearths opposite the charging doors. The

furnace is adapted and intended to be used for the production of metal of extremely high quality, especially with respect to its freedom from oxygen and oxides. For example.` it may be used for producing oxygen-free copper. For auch usefthere is provided a structural housing or enclosure to exclude atmospheric air from the molten metal between the place where it becomes molten and the place where it becomes.

is enclosed by a hood |61 belonging to another` unit of the plant. There is relative movement between the spout |66^of hearth B and the hood |61 so a bearing plate |10 which is sealed about the spout |66 is resillently pressed against the end ct the hood |61 to accommodate the movement and keep the space closed olf.

The. throat to the spout |66 slopes upward and a baille |13 extends downward to isolate the metal in the spout from that in the furnace.

'I'his not only prevents the passage of gases 111115.25

also prevents escape of the material which covers the metal pool in the furnace. Since the metal in the spout becomes isolated from the main body of metal in the furnace it may tend to solidify to some extent by cooling. The spout is not conveniently accessible because of the enclosing hood, so if incrustations of metal are formed in the spout it is difficult to remove them. It is, therefore, desirable to heat the metal as it flows through the spout. For this purpose resistors |14 are mounted in a space above the spout.Y They are supplied with current through resilient electrodes |15. The resistors are composed of a non-metallic material such as silicon-carbide and are subject to injury by splashing'metal. Oxygen-free copper is especially likely to splash and attack them. To prevent'this a thin sheet |16 of earthen material such, for example, as alundum is placed between the` resistors and the stream of metal. The45 heat is transmitted through the plate to the metal.

Means are provided for automatically or manually controlling the supply of current to the resistor heaters |15 as well as to the large lx1- duction heaters for the channels by thermoelectric devices acting in response to the heat produced by the heating units. Automatic regulators of this character are disclosed in my copending application, Serial Number 535,829.5 5

vided to form a. loop around the middle legs ofl the transformer cores. The central one of these units (Figs. 4 and 5) is disposed between the rocker rails 21 of the frame while the two outer units are located outside the rockers.

All of the channels may, if desired, terminate (Fig. 4) within the hearths in a shallow longitudinal trough |11 formed in the bottom of the hearth basin. 'I'hls provides that the ends of the channels will be connected by a body of `moltenmetale'venthomhthleremaybeonlya.

- s anc-"1 it is een um the lining materiau at' quantityofmetalinthehearth. It also Provides that ends of the channels will not be' stopped up when a heavy charge oi solid metal is introduced. even though it settles to the pool of molten metal. The narrow trough prevents the yunmelted metal from the ends of the channels. In Figs.

the bottom of the hearth is built up from within the circular outline of the hearth chamber on either side of the longitudinal vertical plane to form the trough. Interseeting the trough |11,

'totheouterendsilowerendinrig 18) of the` transverse gutters |13 in the hearth basin which is the lowest point when the furnace is tilted.

'Ihe opening normally kept completely filled with fire' clay or similar material which may be punchedoutwhentheopening is to be used.- In order tov permitthe plug to be removed quickly-and this is necessary since it must be removed while the furnace is tilted to the opposite side and before the metal has had time to freezeit is formed of a thin` inner layer of refractory material such as aluminum brick or a rammed sand and a soft outer layer such as crushed insulating brick. A metal cap. lli covers the outer end of the opening.

As explained above, special precautions are taken to keep the molten metal of the furnace out of contact with an oxidizing atmosphere. Air is excluded from the furnace by having the charging doors iit closely and keeping them closed except when it is necessary to open them for charging, as well as by keeping al1 other openings closed against the entry of atmospheric air. Additional means are provided for keeping a treating and/or protecting atmosphere in at least one of the hearths if desired. As shown in Fig-2, hearth B at the top is 'provided with a plurality. of nippled openings Il! for the injection of the desired gas, for example, carbon monoxide, nitro- 'genorsuchotherneutralordie-oxidizing gasas may be appropriate to give the desired treatment or protection to Athe molten metal. Also a deoxidizing or protecting covering such as carbon maybemaintainedowerthebathofmetal in one or bothof the heart-lu. Carbon is preferred because it leaves no objectionable residue in the metal.

charged exclusively. the furnace merely reilning .it

Means are herein provided for starting the furnace when molten metal is not available for this purpose. This may be accomplished by tilting the furnace far over on one side and melting metal by the cil burners in the lower hearth. The hot gases pass through the transformer channels and heat them as in preheating. After the metal has been thoroughly melted the furnace is turned back to normal position to cause the metal to flow into the connecting channels and.

through them into the other hearth. The current.

is now supplied to the primary coils of the transformers to keep the metal in the channels molten. After starting the oil burners will be removed and the suction openings closed up as by plugging them.

Means are provided for withdrawing hot gases from the suction conduits |84a, |8|b and from about the charging doors. If cathodes are charged the latter are not needed but may be needed if scrap metal is charged because the latter may contain grease and other combustible material. As shown in Figure 5 a. conduit |83 is connected by a turning joint with a conduit |84 I fixed to the ends of the cross channel beams 12.

The center of movement is in the axis of oscillation Z of the furnace. The conduit |84 is connected with the branch conduits |84a, I Blib and with other branch conduits I8Ic, |84d leading to Aopen hoods at the charging door openings for the hearths A and B respectively y(Fig. 3).

'I'here are, as previously mentioned and as shown in Figs. 4 and 5, three channel-transformer units, one for each phase of a threephase alternating current supply circuit. Further. each channel-transformer unit comprises a plurality of distinct transformer elements arranged along the length of the channel. In the present embodiment there are four such elements,

each including a primary winding 220 and a core tion of their origin is not thought to bc in keeping with the purposes of the present description but a few of the advantages may well be briefly noted. The provision of a number of transformer elements distributed over some length of the molten metal secondary channel instead of a single large element provides easier cooling of the transformer elements; permits closer association of primary and secondary conductors; allows some of the elements to be shut oi in case itis not desired to melt actively but merely to maintain the molten state or to prevent freezing in the channels; permits 'the design of a more rigid and substantial casing in which; for example, the parts housing the separated secondary channels may be braced together between each element; renders the handling of the elements easier; and makes the replacement of disabled elements less expensive.

Besides being attached by flanges at their ends the channel-transformer units are further supported, as seen in Fig. 5, by eye bolts |85 supported in whole or in part by longitudinal beams I attached (Fig. 4) beneath the cross-rocker beams u mentioned stove: Themas m su -1 port the channel-transformer units through apertured lugs Informed integral with the lat-t ter. This suspension permits free horizontal expansive movement of `the furnace proper from the corner Bf as an origin point, the bolts either swinging about their supports if the 'expansive beneath-the header ISI 4simply air to spreadeis movement is along the rochers or slight. fly if the movement is across;` the rockers. 1,

The transformer elements may' be cooled by air. A conduit I! (Fig. 5)- receiving asupply of air from any suitable source,l is connected byfa turning joint with"a horizontal header lli supe ported across the top of the rockerframe l". 'nie center of movement is in the. of oscillation Z of the furnace.` Branch conduits |02 opening |02 disposed above each of the channel-transformer units. The spreaders'are providedwith discharge openings |94 for airupon the cores and primary coils Vof the heating units.

Referring to Fig. 5. apronsV4 I0! at the ends of the furnace protect the channel-transformer nunits from injury by moving machines, by mae terial falling from cranes, and the like. 'Iheae aprons are secured to the ends ofthe rocker beams -12 and their castings may-comprise -portions of the conduits.

One of the three channeltransformer units 5i nr shown in detail in the enlarged views' to 13 inclusive. The enclosing casing of the unit, by reference to Figs..8 andf'b-12, is seen tocomprlse two major side-and-bottom-formlng `smells 200 of non-magnetic metal such as bronze ntting together at their ends along the meetingedgesof the flanges 52 (previously described) and at their vbottoms along vertical nanges (similar to nanges 201 for the top'shells to be described presently) which extend for a short distance back from the end llanges. The bottom shells are spaced apart intermediate their ends to receive the transformer primaries and cores. Insulating plates 2M' and insulation for the clamping" bolts 208 electrically separate the two shells along their joints. Mating covers 202 close the top-of the easing..l These covers are securedto the shells' 200 .along their outer edges by cap bolts 204. They fit together at their ends (forming a part o! the nanges 52) and at their tops alongvertical flanges 201 whichv extend for a short distance back from the end flanges. They are secured together by bolts 200 passing throughftheanges 201 thereon. Insulating plates 203 and insulation for the joining4 bolts electrically separate the two parts of the cover. 'Ihe covers are spaced apart intermediate their ends like the bottom shells for the recep7 tion of the central-legs ofthe transformer cores and the primaries. 4

At several points (Fig. 8) along their spaced intermediate portions. the bottoms of the shells 200 and the covers 202 curve inward toward the central vertical plane, and.` atthese convergent points (Fig. 11) they areprovided with transy gooogiss Again reverting to Fig.. 8. the casing between` the spacersl2l0 widens in oval shape for the accommodation of the oval-shaped primary coils 220 and the central legs 222 of the closed E' shaped transformer cores 22| which t within the primary coils. y

lnteriorly the enclosing casing comprises (Figs. 9, 10. '11, 12) curved shell plates 225 of non-- magnetic metal iltting along their upper andlower edges within notches 220`forxned inthe covers 202 and in the bottoml the shells 200. Over the inner faces of these curved shell plates protecting sheets 221 of high melting wint metal.

for example, non-magnetic steel, are secured to prevent molten metal ever reaching the transformer coils in case, the lining and other parts of the casing should be melted.'

retaining 'strips 23o nem the sneu Y plates 225 and the protecting sheets 221 in position around the transformer openings. The

ends of the protecting sheets 221 are held be-j tween the plates 225 and the ,spacers 2i0. as seen in Fig. 9, and are fastened to the spacers by bolts 23| provided with heads which"are countersunk into the sheets 221.

At each end opening of the channel-transformer unit the sheets 221 are electrically separated by plate insulation 232 and are held t0- gether by insulated'bolts 230.

In Fig. 11 terminals 235 for attachment of electrical conductors are shown. These terminals are insulated from the casing and are at#- tached theretov by bolts 236 which are also insulated. The connections between the terminals v and the transformer primaries are not shown.

The casing as thus constructed provides a divided enclosure for the secondary channels LI l and L2, or MI,y M2 or NI, N2) and a converging enclosure at each end for the common channel L. It is also seen that the two halves of the casing are electrically insulated from each other so that no appreciable eddy currents may be set up in them.` The entire enclosing casing, as stated.

is of nonmagnetic material. The channels for metal, if not rammed up of continuous materiaLgmay be formed (Fig. 9) byv refractory branch conduit blocks 240 and junction conduit blocks 2li. The blocks are held at their joints by alternate side lugs 2&2 and edge lugs 242 on opposite ends of the blocks. The

joints may be cemented by any suitable plastic substance to make the channels uid tight.

The refractory blocks may'be enclosed in a rammed bed of re clay, asbestos cement, or other heat resistant insulating material as indicated by the numeral 245. 'I'he latter may be at least partially enclosed by a second layer of heat resistant insulating material 246. In someV of the views. such as Figs. 9, 10, and 14 the rammed material is omitted in order to show the other parts more clearly. v

The channels, as shown in Figs. 9 and 12a. are

rectangular along their straight secondary portions, the greatest diameter'being vertical, then become vertically elliptical as they approach the junction points, and then in the single channels vbecome somewhat elliptical horizontally. `The `secondary channels, though varying in shape remain of uniform cross sectional area throughout their length. The elliptical shape toward the junctions reduces radiation of heat from the molten metal. Ihe area of the single end channels is considerably greater than the combined cross-sectional areas of the twov secondary chanf.

acconto I l nels. This promotes smooth dow of metal from the secondary heating loop to the hearths. Here it may be particularly noted that all of the heating takes'place in the secondary loops and none inthe single channels. The electrical heating circuit-therefore does not depend upon the maintenance of metal in the hearths or in the channels leading thereto and the seccndaries are so located that they willalways remain fllled in all normal operations of the furnace. There are.

also other advantages in the selected construction.

The junction block, as shown in'Flgs. 9 and l0, may project from the end of the enclosing casing to form a joint with a mating conduit block in the tubular extension I6 of the hearth, the projection, however, being only slight-for example, half the thcknessof the joint insulationso as to offer no obstruction to the insertion or removal of the channel-transformer unit. The end joints are not illustrated in deta'il since their formation may be fully understood by reference to the above described construction.

A channel transformer unit constructed as described above is easy to assemble. 'I'he channel linings and surrounding rammed insulation-may, for example, be placed in the assembled side and bottom shells 200 before the covers 202 are put on. This not only facilitates thorough packing of the lining but permits ready inspection to insure that the work is well done. Inasmuch as leakage of molten metal usually necessitates the stoppage of an electric furnace for replacement of the lining it will be understood that the thorough packing of the channels is a matter of extreme importance. i

Not only is the unit designed for convenient assembly whereby ready inspection may assure a good channel lining butthe metallic structure of the unit is designed to furnish the maximum support to the lining. This permits the use of a thin lining which places the primary coils at a minimum distance from the molten metal secondary yet furnishes ample .protection for the primary coils.

Further, the high melting point sheets221 placed immediately around the primary coils will prevent molten metal reaching the coils even inv case the curved shell plates 225 should be melted by molten metal escaping through ilssures in the channel lining. Here it is to be noted that the sheets 221 are bolted directly to the spacers 2I|i and the spacers are positioned inside the sheets where the danger of being melted is small.

A modified channel-transformer unit is illus trated inFigs. 2Q to 22. This modified unit is identical in all respects with the unit already described in most of its parts so these parts are here designated by the same reference numerals as they are in the preceding figures except that a prime is added. Thus there are found the bottom shells 200' covers 202', their securing cap boltsznl', etc. Y

'I'he channel lining vmaterial 215' is disposed directly about the channels and the preformed refractory blocks are not employed. The refractory lining material may, for example, be rammed up about shaped cores which are later melted, burned or removed in some other appropriate manner. Preferably a form is used which will burnl out completely and leave no obstruction in the channels. For example, a built up hollow laminated wooden core may be wrapped with sheet celluloid until the channel shape is produced. Later resistance ribbons are threaded and secondary close together.

through the form and heated by current to lgnite the form. The channel shape is the same as that for the nrst form. 'This is of such a nature that it permits a. full view of the straight sections of the secondary channels by holding a mirror at the end of the straight section, placing a light at the remote end of the channel and sighting through the other end of the channel.

Another departure of the modified channeltransformer unit from the one described is found in the interior shell plates i225'. The heat which is generated in the'molten metal secondary in the channels is very intense. The

primary coils according to the present invention` have been placed very close to the hot molten secondaries for higher emciency. -The tendency is for the primary coils to become overheated so air cooling means have been provided for the primary and the adjacent parts of the channel enclosing shell. The cooling air may convey away considerable heat, which is an operating loss, but the loss from this cause is overbalanced by the benets gained by having the primary Further, a safer and more permanent construction of the entire unit is realized.

It may occur, however, thatsmooth-surfaced shell platesv may not radiate heat fast enough, even when air is forced past them, to keep from buckling, melting or permitting excessive heating of the primary coils. The plates 225' are therefore modified by providing vertical fins 225a thereon. Air entering above the unit may ilow down along and between the ns giving the best possible cooling eifect. Preferably the ns are machined on the plates rather than cast thereon so as to give aclean active surface upon which the cooling air may impinge. Manganese bronze metal is thought to be best for making the plates because it is strong and has good radiating qualities,- i. e., high conductivity of heat.

The upper and lower retaining strips 230 are not used with the ribbed plates for these plates are rigid and strong enough to take the fastening bolts directly.

The ribs of the `two opposite end plates are considerably wider than the ribs of the side plates.

is greatest.

Directly between the primaries and molten metal secondaries the plates 225 are recessed on their outer sides and in these recesses are secured strips 225b of non-magnetic steel having a high melting point. Small bolts (not shown) may constitute the means for securing the steel strips to the bronze plates. If -a crack develops in the channel lining it is most likely to develop in a line between the channel and the primary, in which case escaping metal would first comeV into contact with the high melting point steel strips and be checked, thus protecting the bronze cooling plates and the primaries.

As best shown in Figs. 10 and 14,'lifting lugs 25| are formed on the casings of the channeltransformer units and to these lugs lifting links 25| are secured by eye bolts 252. For convenient lifting of the units (Figs. l, 2, 3, and 5) a superstructure comprising vertical columns 255 resting on the frame F and top beams 256 may be provided for mounting block and tackle, power boists or other like apparatus. The super-structure may be braced by cross bars 251 and angle .braces 25|. The units are lo'wered from their attached positions down between the rockers and 7i This gives greater radiation near the ljunction of the branch channels where the heat newunits are raised into position in the same' way.

The operation of the furnace will vary according to the kind of metal which is treated and the function which this furnace is designed to have in the entire plant. In any case, however, it will be rocked from side to side by the rocking motor to circulate metalthrough the secondary heatingfchannels. There it is heated inductively and when-'it reaches the hearthslwill melt fresh charges of solid metal placed therein. Inasmuch as mechanical circulation is employed no reliance need be placed upon electrical effects for producing circulation.

Metal may be charged at either or both doors and while the doors are usually kept closed, particularly if a treating gas is maintained in the hearths, there is no harm in having them opened from time to time if a carbon covering is maintained upon the pools of metal in the hearths. The doors may be sealed by the devices herein providedv for'that purpose when they are kept closed long enough to warrant it. When metal isV to be poured the rocking motor is stopped and the tilting motor is started. Normally the furnace will be tilted to pour metal through the hood-enclosed spout of hearth B. When the furnace is to be shut down or when a channeltransformer unit is to be removed the -furnace is tilted far enough toward the hearth A to drain all the metal through the opening |80 as previously explained. Some of the pouring hood parts may be removed to permit of this movement. After the furnace is restarted it is again put under the ,influence of the rocking motor.

From the above description it will be apparent that the improved electric furnace in its design and operation has many practical advantages. It will produce metal in a highly purifiedstate;

40 is easy to operate; may without any material change in design be built either in small or very large sizes, the one illustrated having a holding capacity of thirty tons of copper. It has heretofore been considered impossible to operate large induction furnaces for non-ferrous-metals but the present furnace has produced hundreds of tons of copper at a single'run and at times at the rate of five tons per hour. The copper produced was also of a superior quality heretomerciai methods. It also provides a very strong and efficient transformer heating arrangement; permits convenient and effective relining of the channels of the units; and in numerous other respects constitutes a distinct advance in the art. The invention, however, is not limited to the exact embodiment described but may have various other embodiments within the scope of the subjoined claims.

I claim:

l. Inail electric furnace in combination, a tilt-- 75 nxed Joint.

fore thought impossible of production by com' 2. In an electric furnace, in combination, a tilting frame, a furnace assembly mounted on said frame, and means to retain said assembly upon and insulate it from said frame while permitting free expansive movement thereon, said means comprising a plurality of joints each including an insulating plate and a metal plate for bination, a supporting frame, two spaced hearths mounted on said frame, a plurality of channeltransformer units attached to and supported by said hearths, said hearths each being supported upon said frame in four spaced joints, one of saidV joints forming a fixed anchor for the hearth at that point, one of the jointspermitting sliding movement transversely of the frame in a vcoordinate through said fixed joint, three of said joints permitting sliding movement longitudinally of the frame in a coordinate through said fixed joint, three of said joints permitting sliding movement either transversely or longitudinally of said frame, and all of said joints preventing ver,- tical separation ofthe hearths from the. frame.

5. In an electric furnace in combination, a supporting frame, a hearth rigidly secured thereto in at least one point, a second hearth mounted on said frame so as to be freely slidable rectilineally from and toward said first hearth, channel casings rigidly connecting -both of said hearths, said casings serving to attach said hearths positively together and to take part of the strain imposed by the weight of the second hearth when it is disposed below the rst hearth, Said casings being freely movable in response to any movements of the hearths, said furnace being tiltable toward said second hearth, and resilient means urging said hearths toward each other.

6. In an electric furnace in combination, a supporting frame, a hearth rigidly secured thereto in at least one point, a second -hearth slidably mounted on said frame so as to move rectilineal- 1y from and toward the first hearth, and channel casings rigidly connecting both of said hearths, said casings serving to attach said hearths positively together and to take part of the strain imposed by the Weight of the second hearth when it is disposed below the first hearth, said casings being freely movable in response to any movements of the hearths.

7. In an electric furnace, in combination, a flattened loval secondary channel loop for molten metal, a refractory lining for said loop, a metal casing for said channel providing openings within the loop for a plurality of transformer elements,

and rigid metal spacers bracing said casing beof oval transformer elements, and rigid metal spacersbracing said casing between. the openings.

9. A channel transformer casing for `an electric induction furnace comprising a bottom-andside shell having a central bottom opening therein, a cover having a. corresponding opening therein, a plurality of curved plates secured between 4said bottom and cover anditogether with the supporting said furnace for oscillation, said furnace having a plurality of pouring openings, one of said openings extending into said furnace at the lowest point whenthe furnace is tilted toward .the opening for completely draining the metal, saidv draining opening being plugged during normal operation of the furnace, the plug comprising a thin refractory interior section and a thick soft easily removable exterior section.

1l. In a molten metal electric furnace in com- 5 bination, a pair of spaced. horizontally cylindrical hearths connected by metal channels mounted for oscillation to cause the metal level to vary in said hearths, a pouring spout in the head of one of said hearths, said spofut being tapered upwardly, and a baille extending downwardly toward said spout sufficiently Eto seal the outer end of the spout at the surface of the metal in all normal movements of the furnace.

-12. An electric induction furnace comprising casing walls forming a channel for molten metal, the channel being intermediately divided to form an elongated `loop-shaped secondary channel, and a plurality of cooperating transformer elements each including a core leg and a primary coil disposed between the spaced sides of the secondary channel and along the length thereof. 1

13. An electric induction furnace comprising a channel for holding a body of molten metal joiningbodies of metal at each end, said channel being divided intermediate its length to -form an elongated loop-shaped secondary channel, the sides of said secondary channel being substantially parallel throughout the greater part of their length, and a plurality of transformer elements spaced along and between the sides of the secondary channel.

14. In an`electric induction furnace, in combination, basins for holding pools of molten metal, and a plurality of channels joining said 'basins for carrying bodies of metal connecting the pools, each of said channels comprising a loopshaped .portion forming a transformer secondary, and means for heating metal in the loop portions of said channels.

15. A channel transformer casing for an electric induction furnace comprising an elongated metal shell enclosing an elliptical shaped channel loop and having an opening between the sides of the elliptical shaped channel for the reception of a heating transformer primary, and shell plates forming a wall about said opening, said plates being provided with cooling ribs and the plates,

near the ends of the loop having deeper ribs than the plates on the side. '1

16. A- channel transformer unit for an induction electricfurnace, comprising lining forming an elliptical shaped secondary loop channel and end channels extending therefrom,A said loopH channels varying in shape from vertically deep rectangular at the center to thick elliptical at the ends.

17. Apparatus as set forth in claim 16 in which said end channels are each of more than the combined areas of the loop channels.

18. Apparatus as set forth in claim 16 in which said end channels are each of horizontally extended elliptical shape and of greater area than the combined areas of the loop channels.

19. A channel transformer casing for an electric induction furnace comprising a metal shell forming the outside of the channel casing and providing an intermediate opening for a primary coil, bronze shell plates forming a wall about saidl opening, and thin non-magnetic steel bands secured upon said bronze plates at the region of the channel location.V

, 20. A channel transformer casing for an electric induction furnace comprising a metal shell i forming the outside of the channel casing and providing an intermediate opening for a primary coil, shell plates provided with cooling fins forming a wall about said opening and a belt formed of strips of a high melting point metal disposed Von the cooling plates to protect them from metal escaping from the channel. v

21. A channel transformer casing as set forth in claim-20 in which said strips are recessed into the channel facing side of the cooling plates.

22. In an electric furnace, in combination, a supporting frame, a hearth assembly comprising two spaced hearths rigidly connected by a channel casing resting upon said frame, one of said hearths being rigidly attached to the frame in at least one point and the other hearth being slidable away from and towards the iirst hearth,

and resilient means opposing theV sliding movement of said second hearth away from the first the first hearth, the connection between said hearths and frame being established by a plurality of sets of insulating plates and metallic retaining devices, and said resilient means including a spring acting upon abutments on the second hearth and on the frame, there being an insulating plate and metal plate separating the hearth and frame at one end'of the spring, whereby movement and insulation between the hearth and v frame are provided without direct wear on the insulation.

24. In an electrical furnace, in combination,

. two spaced chambers adapted to contain pools of molten metal, a substantially horizontal secondary channel connecting said chambers, said channel includingI an intermediate elliptical loopshaped portion which constitutes the complete path of the secondary circuit and single-duct end portions connecting the ends of the elliptical portion with the chambers, and electric induction heating means for said channel disposed within.