US1532090A - Induction furnace - Google Patents

Description

March 31. 1925. v 1,532,090

M. UNGER INDUCTION FURNACE File e 16, 1921 3 Sheets-Sheet Fg. l. u

Inventor: Magms Unger,

His Attorney.

` March SL 1.925.

153239@ M. UNGER INDUCTION FURNACE Filed Feb. 16, 1921 3 Sheets-Sheet 3 Inventor: magnus Unger,

HIS Attorney.

Ptented 31, 1925;

UNITED STATES PATENT OFFICE.

MAGNUS UNGEB, OF

PITTSFIELD, MASSACHUSETTS, ASSIGNOB. TO GENEBAL ELECTBIG COMPANY, A CORPORATION OF NEW YORK.

nmucron FUENACE.

Application med rebruar 16, 1921. Serial na. 44s,ss.

To all whom z't may concem: a

Be it known that I, MAGNUS UN GER, a citizen of the United States, residng at Pittsfield, county of Berkshire, State of 6 Massachusetts, have invented certain new and useful Improvem'ents in Inducton Furnaces, of which the following is a specification. v The present invention -relates to induc-i tion furnaces, and comprises a furnace par- `ticularly adapted for melting highly conductive noh ferrous metals, such, for exview taken on the line 4-4, Eig. 1; Fig. 5 is a vertical section (part broken away) of the furnace shown in Fig. 1 and 4 taken on lines 4--5, Fi 1 at right angles to the plane of Fig. 1; ig. 6 is a perspective view of a furnace embodying my invention; Figs. 7 and 8 are vertical sections taken in planes at right angles to each other of a modificaample, as brass, copper, aluminum and the like.` It is one of the objects of my invention to provide a furnace n which the power factor will be high, and in which the permissible power input will be greater than in furnaces now' in'use.

Heretofore induction furnaces having a pool of molten charge communicatng at the bottom with a vertically disposed channel or loop in which current is induced, have been constructcd with a channel of substantially constant shape or circumference.

In such a furnace the power input is limited by the magnetic field breaking the current carrying molten conductor at the upper end of the channel where the hydrostatic force of the molten column is less than at the bottom of the loop.

Ihave provided a furnace in which the shape of the Channels is varied to equalize the danger of circuit interruption. In ac-v cordance with one of the features of my invention, I have provided a furnace in which the channel is constructed with a substantially uniform cmss-sectional area, but

shaped to transfer the power input limitation to the lowermost part of the loop where 0 the compressive efi'ect of 'the magnetic field,

or pinch force, is counteracted to the-maximum degree by the hydrostatic head of metal. The novel features of my invention will be set forth with greater particularity in the appended claims. V

In the accompanyin drawing, Figs 1, 2, 3 and 9 are vertica sectional views of different forms of induction furnaces embodying my invention; Figs. 13 1 Q 2, 2, 2 3 3", are sectional views* of diflerent channels; Fig. 4 is a "horizontal sectional tion; Fig. 9 is a vertical section of a modification in which the respective channel arms are oriented at right angles, and Fig. 10 is a horizontal section of a furnace having a plurality of Channels.

A furnace embodying my invention, as shown in` Figs. 1 to 3, inclusive, comprises in the main a housing or crucible 9 consisting' of refractory material, which constitutes the main part of the furnace body, and is adapted to contain a charge to be heated. In my improved furnace the charge is contained both in a main chamber 10, ada'pted to contain a considerable body 'or pool of molten'charge 8, and also in a looped chan- 'nel 11 communicating with the chamber 10 at two places, preferably at the bottom. This channel 11, which preferably extends vertically downwards in the working position of the furnace, is interlinked with a magnetic core 12 carrying a primary winding 13. The transformer core 12 preferably,

but not necessarily, is of the shell type. The

primary winding 13 is mo-unted on the central leg of the core which passes through the channel loop 11, and the core and primary winding preferably are concentric with the channel.

. shown).

As shown in Fig. 6, the furnace is provided with an external casing 14: and is mounted upon trunnions 15. A suitable tilti ing mechanism may be provided, for example. the gearing 16 and hand wheel 17. The furnace is provided with a pouring spout 18 and a suitable charging door (not A hole in the furnace roof having a cover 19 is sometimes provided to observe the chare and give access to the furnace interior ut for Simplicity this cover has not been shownnin Figs. 1, 2, 3 and 9.

When a current is flow-ing in any conductor, the magntic field which is set up exerts a compressive action on the conductor, known as the pinch force which in a liquid conductor may be great enugh to break the continuity of the ercuit. When the conductor has a minimum circumference, this pinch force is most concentrated and hence with a given current its eflect is greatest in a circular conductor and becomes reduced in the same degree that the conductor departs from the circular form. In furnaces embodying my invention, I have provided for a ci'culation of the molten charge by varyin the pinching eect of the secondary field by reason of an inequality of 'circumference of the channels containing the charge. The channels may or may not be of uniform cross-sectional area, but in either case the relative dimensions and orientation .of the Channels are so varied throughout their length as to vary or reduce the pinch force in a desired manner. shape and cross-section of the channel throughout its length will depend upon the characteristics desired in the furnace. In some cases it may be important to get a maximum resistance whereas in other cases all other considerations should be sacrificed to et good circulation.

the modification illustrated by Fig. 1, the cross-section of the channel 11 is substantially square at the bottom, as indicated in Fg. 1 at 20. Other compact shapes may be used. The channel section becomes elongated at its upper portion in a direction arallel to the axis of the primary winding. he section of the channel adjacent its junetion with the chamber 10 is indicated in Fig. 1 at 21, the gradual widening of the channel in a vertical direction parallel to its axis being shown in Fig. l The cross-sectional area of the channel is uniform throughout. The pinch force is a maximum at the bottom where the section is of lesser circumference than at the Vertical portions. At this lowermost point the opposing hydrostatic pressure of the molten charge also is a maximum. As the hydrostatic pressure decreases in an upward direction, the pinch force correspondingly decreases due to the change of shape so that the two forces will be substantially equally counterbalanced throughout. In this way more power may be applied to the furnace than would be the case were the channel of uniform circumference throughout.

In the modification illustrated in F gs. 3, 3 and 3, the channel section likewise is square at the bottom (see 20 Fig. 3 and becomes elongated in-an upward direction, (see 22, Fig. 3 but in this case the longer axis is oriented at right angles to the winding axis of the channel loop, as best shown in Fig. 3. In a direction parallel to the -axis the channel becomes narrower as shown in Fig. 3, the cross-s -tional area remaining substantially'the r-me. The construc-' tion shown in Figs. 3 3 and 3 will give The particular` mss-,090

charge occurs. This circulation may be increased f desred by placng a yoke or core 25 of magnetic material (Conveniently, iron) near the bottom of the channel, as shown in Figs. .7 and 8.

When it is desired to get unidirectional flow of metal in the loop, I prefer to make one arm of the loop of different cross sectional shape than the-other arm. For example, as illustrated in Fig. 2, and the adjoining detail views, the bottom of the loop is rectangular or fiat, as shown at 26 and 26'. The left arm of the loop has a square section at the upper part, as shown at 27, which flattens out toward the bottom in a direction parallel to the axis of the loop. The right arm of the loop is of constant rectangular section, a section of the upper part being shown at 28. pinch force occurs in the square part of the loop. As it is easier for the metal to be ejected directly into the pool than through the length of the loop, a unidirectional flow is set up, the metal entering the looped channel from the pool at the right hand arm, and leaving the channel at the left hand arm. In addition to the unidi'rectionalflow, there will be superimposed thereon some incidental local crculation. For example,`where the channel enters the pool, metal will be ejected and run back but there will be more metal ejected at one channel outlet than at the other outlet, hence a unidirectional flow results.

In Fig. 9 I have shown a modification of my invention in which the geometric construction of the channel results in a greater repulsive force in one arm than in the other, thereby causing uni'directional flow. The

In the form of furnace of Fin The maximum channel is constructed to equalize the danger of circuit interruption due to pinch etfe'ct.

As-in the case of the furnace illustrated by' Losaoeo winding axis, Conseqentl the repulsive force is greater in the leftand arm than in the right-hand arm. Downward flow of metal from the chamber 10 ocgurs through the arm 31 and upward fiow into the chamber through the arm 30.

In Fig. 1071 hav hown in horizontal section a furnace having a plurality of channels 32, 33 and 34 having a common' connection 35 at the bottom. Both arms of each of the channels 32, 34 are oricntcd with the longer dimension at right angles to the axis of the primary 13 but the longer dimension of both arms of the channel 33 is arallel to the axis of primary 13. As a consequence of the unequal repulsive force, downward flow of molten charge occurs from the pool (not shown) through the arms of the channel 33 and an upward flow into the pool through the channel arms 32, 34. The cross-sectional area of the channels of the modifications illustratcd by Figs. 9 and 10 is substantially equal. r

I have described and claimed an induction furnace having a plurality of channels 'interlinked with the same magnetic field in my copending application Serial No. %5,514 filed February 16', 1921.

What I clam as new and desire to secure by Letters Patent of the United States, is,--

1. An electric induction furnace comprising a core of magnetic material, a primary winding and refractory walls constituting a furnace chamber adaptcd to contain .a Pool and a looped channel communicating at the ends thereof with said chamber, said channel having a substantially uniform crosssectional area throughout but being shaped counter-balance substantially equally throughout the pinch force of the magnetic field upon a liquid charge when carrying current by the hydrostatic pressure of said charge. v

2. An electric induction furnace comprising a core of magnetic material, a primary winding therefor' and refractory walls forming a furnace chamber and a looped channel interlinked with said core, said channel having a substantially uniform cross-section area, but one section of said channel difiering in shape with respect to another section of said channel.

3. An electric induction urnace compris ing a core ofmagnetic material, refractory walls forming a furnace chamber adapted y to contain a molten charge or pool and a channel of substantially uniform cross-sectional area communcatng with said chamber below the surface of said pool, said channel normally extending downwarly during the operation of said furnace, and beingshaped to reduce the pinch force in the upper part of the channel arms where the hydrostatic pressure of the charge is less than at the bottom.

a substantially uniform cross-sectional area but unsymmetrical sha e, the upright. part of at least one arm o said channel bein flattened in a plane extending through sai "loop at right angles to the axis thereof and the lowermost part of said channel being substantially square.

5. An electric induction furnace comprising a magnetic core, refractor walls forming'a furnace chamber adapte to contain a molten charge, and a looped vertical channel of substantially uniform cross sectional area communicating with the chamber at the bottom thereof, the cross section of that part of said channel in which the hydrostatic pressure of molten charge is greatest having the least perimeter. 6. An electric induction furnace comprismg a magnetic core, refractory walls forming a chamber' for the charge and a looped channel having a uniform ?cross sectional area, but non-uniform cross sectional. shape communicating with the chamber at the bot=- tom thereof, the cross section of the lowermost 'part of said channel having the least permeter.

7. An electric induction furnace comprising a magnetic core, a winding thereon, and a refractory furnace body constitting a furnace chamber and a looped channel interlinked with said core, said channel com-` charge within said channel and chamber,

the arms of said channel being shaped to produce a materially greater repulsive force upon said charge in one arm than inthe other arm, thereby causing unidirectional 1 circulation of char e throu h said channel 9. An electric inuction ace comprising refractory walls providing a reservoir and a looped channel of uniform cross sec tional area having legs of elongated crosssection disposed with the longer axes at right angles to each other', and means for inducing an electric current in a charge in said channel.

10. 'An electric induction furnace comprising 9, magnetc core, a primary wnding leg of said channel nearer to the center of thereon, a refractory furnace body provdsaid primary winding than the other leg.

ing a reservoir, a looped open channel of In Wtness whereof, I have hereunto set unfo-m cross-sectonal area interlinked my hand this fourteenth day of February, With said core and communcating With said 1921.

reservoir,- the legs of said channel being difierently shaped to bring the center of one MAGNUS UNGER.

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