US1286395A - Oscillation-current method and apparatus. - Google Patents

Description

E. F. NORTHRUP. OSCIILLATION CURRENT METHOD AND APPARATUS.

APPLICATION FILED NOV.25. I916. I 1,286,395, Patented Dec. 3, 1918.

2 SHEETS-SHEET 1. FIG. 1 2'76 2 2762.5

A N A N W A N 3 311 uemlioz E. F. NORTHRUP.

OSCILLATION CURRENT METHOD AND APPARATUS. APPLICATION FILED NOV-25, l9l6.

1,286,395. Patented Dec. 3, 1918 2 SHEETS-SHEEN 2.

E] m uem coz the pool as resistor and inducing circumferone illustration in that art, among the vari-' UNITED STA S PATENT OFFICE.

sown; r. 'nonrnnur, or rnmcnron, NE JERSEY, ASSIGNOR To THE AJAX METAL comrm, or PHILADELPHIA, PENNSYLVANIA,- A CORPORATION or PENNSYL- VANIA.

OSCILLATION-CU'BBENT METHOD AND APPARATUS.

' Specification of Letters Patent.

Patented Dec. 3,1918.

Application filed November 25, 1916. Serial No. 133,474.

To all whom it may concern:

Be it known that I, EDWIN F. NORTHRU'P, a citizen of the United States, residing at 30 Wiggins street, Princeton, in the county of Mercer and Stateof New Jersey, have ining through a gap is contrasted with the .forced frequency directly produced by altern'ators.

A further purpose of my invention is to transfer energy from place to lace by electrict currents having natural equency and to transform the energy into' heat at the place of intended use. a

A furthempurpose is to make the resistor, which is to be heated or treated or to be worked while hot the secondary of an inclosing o scillation coil primary or primaries, discharging a condenser or condensers through this primary and a discharge gap to induce currents'of corresponding period within the resistor. I purpose applymg my invention to the electric furnace art, among. others, using the body of ential flow of electric current about it, without the intermediationof a magnetic circuit such as is threaded through the poolor through a connecting tube in existing induction furnaces.

A further urpose is to charge condensers from multip ance coils hav ng a common magnetic path, preferably a common ,core,, protecting the generating. ap sive-current ow and throughthem transferring to another phase or other phases, ener Further urposes will a ar inithe s e'cification and in the claimg iiereof. p

I have referred to illustrate my invention chie y diagrammatically, in view of the broad character of the invention, and have applied it to but one art and to but ous arts and many-forms in which itma be carried out, selecti therefor an art w 'ch is important and a orm which is practical,

frequency of a freely oscillating electric system from a'condenser dischargase currents through inductaratus by them from exceswhich would otherwise be uselessly emp oved.

efiicient and simple, in which my invention has high commercial utility and which at the same timeillustrates the principles of my invention to considerable advantage.

Figures 1 and 2 are diagrammatic views used in discussion of the principles of my invention.

Figs. 3 and 3 are diagrammatic views of connections which may be used in applying my invention;

in Fig. 3.

Figs. .5, and 6 are diagrammatic views showing in a more or less hypothetical way the directions of fiow of induced currents of electricity and of a molten oscillation re sistor when my invention is applied to furnace operation.

Fig. 7 is a diagram used-in discussing the assistance which can be given one phase from the other in-two phase application of my invention.

Figs. 8 and 9 are a vertical elevation through the pool and a top plan view respectively of a structure by which I may apply my invention to induction furnace uses.

Figs. 10 and 11 are diagrammatic views showing application of'my invention to ingot mold and ladle use respectively.

In the drawings similarznumerals indicate like parts.

I My invention applies OSCllltltOlY electriccurrents to the heating of conducting material performing a stirring function also by the same currents when the mass is a molten and in the processes and mechanism by which these principles are utilized in the particularv artfrom which I have taken my illustration.-

Fig. 4 is a-mixed diagrammatic and sec-' tional view of a portion of the circuit shown The broader form or my invention is claimed by me in a co-pending'application, Serial No. 192,049, filed September 19, 1917, for method and apparatus for electric heatin by high frequency currents/ he introduction of inductance into the circuit of a constant speed alternator. transmission line' under forced vibration causes the current'to lag *in phase behind the electro-motive force, and capacity so introduced causes the current to lead in phase. The

preponderance of induction over capacity,

both in the line and in the coils of existing inductionjapparatus applying heat,has reduced the power factor making it prohibionly not required but even injurious.

If, on the other hand, electric energy be stored in a condenser and the latter be then allowed to discharge itself through a closed circuit, the electricity oscillates back and forth like a pendulum until the energy stored in the condenser is finally dissipated in electric radiation and in heat. The inductance in such a circuit does not affect the total energy transformed, only the natural frequency, the time within which the vibrations will cease, the damping factor and the number of vibrations. In this it is comparable with the mass of a ball swinging at the free end of a spring whose opposite end is fixed. There is no dissipation of energy in this mass and its increase merely alters the natural period of the vibration, the time within which the spring comes to rest and the, number of vibrations of the spring.

' If the capacity and inductance be large,

the fraction of energy dissipated in radiation is negligibly small. The movement of electricityin the circuit constitutes a natural, unforced or free vibration having a period Since T-should be less the. the period of the alternating current supp y and in pracas tice is therefore limited, the product of LXC must be keptwithin limits. This can very readily be kept within required limits for any total values of capacity and induc It might benoted thatthe currents in the oscillation resistor correspond to those in the oscillation coilin period and follow the fluctuations of the oscillatory currents even though they be not themselves of free vibra ,tion.

The only points or places in such a free e cillation circuit where heat is dissipated are where there is 'ohmic' resistance or where there is an inductively coupled circuit hav' ing ohmic resistance, such as. a solid, liquid 01 plastic body of conductin material, or

container or holder therefor ormin asecondary to such a free oscillation pr1mary.

ltf follows that conductors which lead from the condenser to the oscillation coil at the place where it is required to convert be well understood from this figure.

L, and L washes the energy stored in the condenser intoheat may be quite long and may have considerable inductance without wasting energy objec-v tionably in heat during this transmission, provided these conductors have small ohmic resistance. Practically, as well as theoretically, therefore, energy stored in a condenser can be transmitted a considerable distance from the location of the condensers with low heat losses, and there converted almost ,wholly into heat. This conversion may not denser'and the voltage applied in charging it. The power is then determined by the number of times the condenser is charged to this voltage and discharged per unit of time.

The inductance of the circuit, the resistivity of the metal constituting the secondary coupled circuit or resistor and the closeness of the coupling have no efiect upon the power generated and, theoretically, no

efiect upon the power delivered to the metal.-

-Where the available voltage is sufficient to charge the condenser directly from it, no transformer is required between the supply and-the condenser and I have shown s ch' a construction in Fig. 1. The theory wig single phase alternating current circuit vis shown having-sides A, N. The condenser to be charged is shown at C, the oscillation coil, through which the'condenser discharges at O, the inductance of the two sides of the circuit at L and L and L L and a discharge gap at G. These inductances are intended to represent the entire inductance of each sideof the circuit and are-divided for convenience in the later discussion.

-Tlie energy stored at each charge is 1/2 CVK When the discharge gap G breaks down, the energy will surge in the oscillation circuit until 1t is all dissipated in radiation andheat, for low frequencies chiefly in heat.

The means .of dissipation are as follows:

1-Dielect'ric loss in condenser. 2- I+ R loss; in discharge gap G} 3 -I R loss in line, where R is theomm reslstance of the line possessinginductance 4"TI2R, loss where R is the ohmic resis tance or its equivalent of that portion of of energy utilized in radio telegraphy and is quite negligible for low frequencies.

' 6Losses 1n the transformer D which feeds the oscillatory circuit.

It is indifferent whether R is a resistance located in the oscillatorycircuit or whether it is a resistancein an inductively coupled circuit, 2'. e., in the oscillation resistor, or the sum of these. And because the secondary circuit constitutes buta single turn within the mass and the inducing circuit has several turns, the magnitude of the current in the. oscillation resistor is correspondingly great.

In speaking of the mass I desire to make clear that, though in some uses of my invention the oscillation coil may operate upon a thick mass, the shape may vary widely according to the application intended and may be, for example, a mereshell of cylindrical or other shape, solid, in paste form, molten or normally liquid.

It will be noted that the oscillation coil 0 inthe illustration forms a part of two circuits. It is part of the secondary alternating circuit for charging of the condenser and also constitutes an oscillation primary .in the discharging circuit for the oscillation resistor as a secondary.

In the effort to transmit. the energy stored in, potential form in the condenser to the conducting material heated with maximum efiiciency, it is indifierent, within wide limits, what maybe the natural frequency of the oscillatory circuit. The eificiencv which wel'wish toget is where p is power dissipated and held as heat in the oscillation resistor and P the powersupplied at' the primary terminals of the Hush rmer. f

To obtain high efliciency the following losses must be small .ends of the oscillation coil 0, measured at e in Fig.- 1 can be kept comparatively low. This will facilitate insulation between the coil and its secondary.

With each surge of the oscillatory current through the coil circuit, there will be a tendency of the supply current to short circuit'through the ionized air acros the dis- 1,Dielectric loss. '(Low frequency of os-- sired to charge the condenser, the circuit will more usually be as indicated in Fig. 2, where the supply circuit A, N, is transformed at D and the condenser is charged from the; secondary transformer connections a, 1. While the short circuiting of the supply, (here taking place in the secondary) across the discharge gap, can still bacontrolled by primary inductance, or by special provisions for blowing or vacuum at the discharge, it is more desirable to control it by inductance in that portion of the circuit between the discharge gap and the transformer secondary, indicated diagrammatically at Z, 2,. The discussion of Fig. is then applicable to this form also with the change in symbols from A, N, to a, n, and L L to Z 1,. In Figs. 1 and 2 the oscillati on coil may be placed in the discharge pable of easiest clear explanation.

Because transformers will be required usually to .ste p-up the voltage from that available to the much higher voltage under which my invention becomes most eflicient, I have shown transformers here, the system beingpracticable wherever two phase current may be obtained. The transformers can be omitted where the commercial current is of suitable voltage. 0

.The two phase primary circuit has sides A' andB and neutral N and supplies transformers I) and E. The secondary of transformer D is connected with one side each of discharge gap G and condenser Q by conductors a, a and a and with the other side of the discharge gap and condenser by conductors, n, n, 72. n and n. Likewise the secondary of transformer E is connected with the two sides of discharge gap G and condenser C by conductors b,'? ,.b and n, a 11. 'n and n3.

The windings L and L, respectlvely of a reactance. coil L are placed in series with the discharge gaps G and G, andtheir connections n, n and n, n; and the oscillation coil 0 may be placed in the charging circuit in the common connections n n therefor, or coils may be placed in the discharge gap connections a, b, where distant location of the coils makes this desirable.

There are condenser charging expedients, at present well known, which do not require stated.

alternating currents. Since they are in the nature of makeshifts or ubstitutes and, so far as they are successful, are electrical equivalents of the alternating current charging source, I desire to be understood as in cluding them within my claims where the latter include alternating current and these substitutes can be used in the combinations Fig. 3* shows other connections suitable -to use with a local charging circuit includ ing the condenser or condensers and the indu'ction coilor coils and an oscillation coil or coils, thedischarge gap beingpermissibly placed at any point in the discharge circuit.

,If no transformer be neededlt'o vary the voltage of the alternating supply circuit, the sides A, B would beconnected directly to conductors a and b and the neutral to n and n In the use of multiphase supply it will be noted that the'discharge from different c0ndensers will occur at different times, since they are charged by currents of difierent phase.

In any condenser operation, if short cir- .cuiting of an alternating current, condenser charging circuit through the condenser discharge gap or gaps be prevented by the in troduction of inductances in this supply (whether transformers be used or not) there is a considerable advantage in the use of multiphase currents since they make it possibleito use a common core for the inductance co1ls in thedifferent phases, returning to the other phase orphases energy which would otherwise be spent uselessly in the discharge gap, if the useful transfer of energy from phase to phase were not provided.

' This transfer of energy from phase to phase-between inductances in multiphase circuits can be used with greatadvantage not only in the arts inwhich an oscillation coil is used to apply heat to an oscillation re- 'sistor, which forms part of my invention claimed herein, but both the-process and apparatus are also applicable to other arts,

where the heating effect, is not of importance, such, for example, as in the arts of wireless telegraphv and telephony, and this subject matter is intended to be'cl'aimed by me as-broadlynew.

Application of this inductance coil energy transfer between phases to the remain- (her of my invention herein will be clear from Fig. 3, where the two reactance coils L L are-wrapped about a common core L As a result, when the voltage in phase A, I ig. 7), rises to'some such point as p, charging. the condenser G',-the'inductive action. of the coil L upon the coil. L to some extent affects thevoltage, (or the phase of the voltage) being impressed by phase B,

through coil L upon condenser C The gap G now breaks-down and the secondary at D-is put on short circuit through the gap G. The rush of current which tends to follow, magnetizes the core, and the energy represented by this magnetization is in 'part transformed to the coil L hastening or retarding, (according to the relative directions of the windings on the core) the rises of voltage being impressed upon condenser C The same action takes place when condenser C is being charged and when gap G breaks transformers D and E, confining them to the i;

circuit shown in the lower part of the figure through the oscillation coil and discharge gap.

In operation, the multiphase electro-motive forces are impressed upon the primaries of the two transformers D and E and the condensers. C and C are charged through reactance coils L and L and with the particular connections shown, also through oscillation coil 0, until their capacity is reafihed with the discharge gap adjustment use As each discharge gap breaks down the oscillatory currents .will surge through the oscillation coil 0, acting as a primary and will induce oppositely directed current flow I in the resistor W, formin the oscillation secondary, the current flow 1n the oscillation secondary being in substantially parallel planes or strata to that in the inducing oscillation coil.

The successive chargings of the condenserswill alternate, as will .also their discharges,

at irregular intervals dependent upon the capacities of the condensers, the applied voltage, theseparation of the discharge gap and possibly other variables, a rapid series of heating impulses which also have a stirring vact1on. proportlonate to the energy input ends at G and G are provided with nozzles G, and (it capable of operation with either yacuum or air pressure, to red ce thearcmg, and the bar Gr carrying contacts G, and Gr is adjustable as by screw G operating in a support G I have illustrated my invention'by application to an electric induction furnace, and will describe its use in connection with the particular furnace shown in Figs. 8 and 9, to which the principles are well adapted, but which is described by way of illustration and not limitation.

I-would expressly point out that though there is patentable novelty in the a plica- 'tion of'the broad invention to'the rnace art, and to the particular furnace illustrated, electric furnace operation is one only of'various uses ofthe broader invention.

Successful furnace operation requires rapid transfer of heat betweenthe metal most actively heated and the remainder of the metal. This must be by conduction or by circulation or both. In existing gas and coke furnaces, conduction and Joule effect within the pool are relied upon and have proved fairly satisfactory. In the various electric induction furnaces heating the metal in channels connected with the pool, the opportunity for conduction is poor and circulation by pinch effect, motor effect or Joule effect is largely relied upon to obtain and maintain substantial uniformity of temperature- Moreover, in most at leastv of these channel induction furnaces, the more highl heatedmetal must be removed from the c annel to the pool rather quickly to avoid overheating within the channel. This is particularly true with such metals, as

brass, as contain easily vaporizable contents,

. whose vaporization will vary the cross section of or break the (secondary) channel c rcuit and also causea change of proport1on of content. The narrow range of temperature available in such a metal maybe.

seen from the fact that brasses melt at 940 C. and zinc, begins'to vaporize from brass at 1090 o;

For furnace operation my invention possesses the advantage of inducing closed currents of electricity in the furnace or crucible pool, as distinguished from utilizing a channel or other outlying path. The oscillation coil may conveniently surround the. pool and lie in any desirable plane or series of parallel planes inducing current'flow in the pool in planes parallel to its own. It is most convenient to place it horizontal with the crucible furnace shown.

The freedom from channels and other outlying containe s of molten metal makes my furnace'more nearly comparable with existing gasor coke-heated crucibleffup naces and the position of the induced cur rent path within the metal still further helps in unifying the temperature of'the pool.

Though theoretically the induced currents the heat conductivity and other character'- istics of the material being heated, the quanwithin the pool are distributed over a large. part of the body of the pool inv closed conducting lines, skin effect causes the curcurrent, with the result that this current flow within the oscillation resistor, can be made great enou h to develop useful pinch contraction of t e current-carrying metal, giving I commercially practical stirring, which is articularly'useful with the circumferential heating of the pool by te current in it or in the crucible walls. or all practical purposes pinch effect has prevlously been regarded as confined to passages of small cross section used in connection with pools. A

The stirring movement lsdue to combined pinch and Joule effects and is quite noticeable I in the molten pool when the oscillation cur-' rent is passed through the surrounding coil. Its direction, however, cannot be 'so accurately determined from observation. It probably takes places within radial planes through the coil axis, with greatest concentration'at about the middle of the coil height and an inward and upward direction there, about as indicated in Fig. 6. The center of thepool lifts'above its normal level, which would confirm this.

Since the metal ofthe pool is heated along the outside throughout the whole of its vertical height, the oscillation coil stirring effectually mixes the metal. The concenof the top of the pool obtained by this circulation, at the point where fresh charge is put in, tends also to equalize the temperature reducing the temperature difference as the charge is melted.

I .have shown how effective stirring may be obtained. The question of its need is dependent so much upon the speed of heating or melting required, the heat losses planned,

tity of fluid being handled, the shape of the pool, the range of difference in temperature permitted by the intended use and other where 1 but a very small energy input per 180 tration of relatively hot metal at the center factors determined, by the character of involume .is required, for the temperature results sought,lthere will be little orno oscillation stirring: On 'the other hand, an induction furnace, melting metals and planned to secure maximum output will utilize a large induced current density and will need and obtain corresponding stirring benefit. Obviously additional stirring can be employed if special circumstances require it, to at this is neither necessary nor desirable under normal circumstances.

Though the stirring-effect is secondary in my view to the heating effect of the oscillation current, and may be omitted or disre- 1:5 garded, as shown, in some applications of my invention, it is not for that reason unimportant, as the stirring may be proportionedto the need by varying the, current density, enabling the designer to so'proportionthe oscillation current and volume or shape of the pool of the crucible or furnace as that the conduction, Joule effect and oscillation stirring will maintain sub stantially uniform 'temperatuie conditions throughout the body of the furnace, and I purpose claiming this oscillation stirring broadly as applicable not only to induction furnaces, but to the stirring ofany molten or otherwise liquid electrically conducting 80 mass. r

In the furnace illustrated in Figs. 8 and 9, I have shown a crucible furnace having the crucible fixed atthe time of use and with bottom outlet, because the simplicity, re-

liability, economy in labor and operation and low cost of this form make it the most desirable and because notwithstanding the ideal character of this furnace, induction heating has not been previously applied to it successfully. 1 The crucible 10 is removable for cleaning and replacement and may be removed for pouring by lifting mechanism engaging.

with the crucible and already known in the furnace art. This is suggested sufiiciently for present purpose by holes 11. I prefer to give the crucible a bottom outlet "12 for pouring purposes placing it off-center in insulated from the crucible.

order to giveas muchroom as possible. for

charging. The crucible is formed of any suitable refractory, which may be an electrical conductor oranon-conductor as suits the needs of the installation or.the preference of the engineer. It is most desirably of sufficient mechanical strength to permit themetal to be chilled init without breakage. The tapering of the sides of the 1nterior crucible wall reduces the danger of breakage. Where the crucible is itself. a conductor, the lines of induced current How will of course-take place largely. if not exclusively in the walls bf the crucible and the heating of the pool will be by conduction from these crucible walls.

v The cover and plug-operating mechanism The bath or pool content may be a conductor or non-conductor of electricity, normally liquid, or ofv paste consistency or fused, as barium chlorid,-and may be under treatment itself or be used in treating other materials as in tempering, for example).

The outlet 12 is closed by a refactory plug 13, of any suitable materiahsuch as carbon, which I insert. through the cover 11 and the body W of the pool. The outlet and plug are placed off-center so as to give room for charging through any opening in the cover, closed by a gap 15. The plug can be withdrawn for pouring purposes, and I show one means for this. The wheel 16 operates a sleeve 17 which turns within a bracket support 18 secured to the cover. Relative vertical movement is prevented by set screw 19 and annular sleeve groove 20. Lost motion istaken up by spring 21. The interior of the sleeve is threaded to'engage with a screw 22 which is formed at its lower end as a socket at 23 to receive the upper end of the plug 13, the cpupling being completed by a pin 24. The screw is kept from rotation by engagement of a non-circular part of the socket with thewalls of a 001: respondingly shaped hole in the cover, as at 25.

can thus be lifted without disturbing the plug and the crucible can be removed with nearly the same freedom as if intended to be lifted for pouring, known in the furnace art.

The crucible rests upon a heat insulating block26 supported by a base 27 for both of which alberene stone is well suited. The block and base rest upon stone-legs 28 and are cut away, as at 29 and 30, below the discharge opening 12, to allow free flow of- :metal through the block and base to any, -mold, not shown.

The removability of the crucible from the body of the furnace,'whether required for pouring or not, requires that the furnace coil O shall beseparately mechanically supported, and that itshall be particularly well I have indicated the support and insulation as com- 116 [prising cylinders '31 and 32, for. which alberene and quartz, respectively are well suited. Oscillation coil 0 is preferably formed of edge-wound copper strip, nickel plated to prevent oxidation and is mounted me upon or about the outer cylinder. Its windings are spaced and insulated by an asabestos cord 33. I

Both ofthe cylinders are set within a recess or recesses shown at 34. in the block- 26, and may be made removable from the base for convenience. k The cylinders and coils are placed within an outer insulating cylindrical casing 35 from whlch they, are preferably spaced, as

at 36, to rovidefor a surrounding insulation 37, w ich I have illustrated as sea-sand and which may be loosely poured in place after the parts have been seated.

The cover 14 fits down into the outer casing as at 38, far enough to prevent it from side movement, and the intended position to bring its plug opening in line with the outlet in the crucible is fixed by a pin 39 or other keying means.

' Outside current connection is best made from below, on account of the high currents intended to be passed-through the oscillation coil 0 and I have provided for this conveniently by holes 40, 41 within which conductor rods 42,43 are inserted,

the connections with the two ends of coil being shown as formed by ins 44, threaded into holes in the rods an connected with the coil ends by conductors 45and nuts 46. For convenient access. to drill the holes 44 through which the pins pass; I have rovidedholes 4:4 in the outer casing, which atter are subsequently plugged. The lower ends of the conductor-rods are protected by tubing, preferably quartz, shown at 47,

48. The tubing is surrounded by a.

grounded casing 49 in each case. v

Because :of the high voltage utilized by the furnace-and to avoid possibility of injury therefrom, I have ounded all of the metal..pai'ts,rincluding t e yoke or bracke't at the top, and lifting mechanism for the plug rod and have surrounded the furnace ounded cage, comprising, as shown, top an bottom rings 50, 51 and connecting bars 52, to an one of which themetal arts and grounded casing may be connected The process and apparatus abovegenerallydescribed when applied to heating and stirring molten metal in a furnace, as will be seen from the mechanism illustrated, secure results closely approximating the perfect furnace.

It will-be evidentfthat the theory of op-' eration, process and referred structures used as lllustrations erein, will suggest many and various forms in which my inventlon may be utilized by the public to heat or heat and stir. liquids or molten metal, or for welding or forging purposes at temperatures lower than the melting point or barely reaching the melting point and without stirring; and thatthe application of the same or allied structures or processes to any sucli uses will embody my invention,

whether additional inventive skill be re-' quired or not.

It is further evident that my invention has general utility in the transfer of power for'various purposes utilizing the discharge from a condenser for the accomplishment of work at a considerableidistance.

The metal can be chilled in the furnace without breakage, develops no. cracks on "intermediate withdrawal of the crucible.

torily met before.

' mouth to prevent melting and can be melted in place from the solid state.

The furnace is easy to fill and empt the molten metal can be drawn off from below the level of the metal, and there need be no movable parts except the stopper plug and the mechanism by which it is moved.

There is a marked economy in the labor required.

he inductive electric heating isclean and uses no electrodes. My application of it produces no disruptive internal pressure orces and the path of the current in the molten metal cannot be interrupted. The metal cannot be subjected to contamination from gasesand so large a mass of metal is in contact with the portion most rapidly heated that conduction greatly assists the circulation in preventing any considerable difference in temperature of different parts 85 of the 001, minimizing the importance of circulatlon. There is no danger of vaporization of constituents having a low vaporization point, unless substantially the entire mass is overheated.

The types of the furnace otherwise best suited to carry out my invention facilitates heat insulation, sothat substantially all of the heat generated remains in.the metal.

The pool requires but little melted metal to operate well and can be started with turnings or even with more solid chunks of metal. The entire charge can be emptied and a new charge started ,with or without Commercial charging frequencies can be used and the furnace 1s capable of highly advantageous use .on olyphase circuits, avoiding unbalancing of such circuits.

The primary voltage from the generator can be used where high voltages are. available, avoiding. step-up or step-down transformers. V

l The ower'factor may be maintained substantially at unity and the efliciency markedly increases with the size ofthe furnace.

It is particularly suited for melting precious metals where the requirements are most exacting and have not been satisfac-' Closely allied to furnace uses are those in which material in'a path or pool, whether electrically conducting or nonconducting is to be maintained hot or heated, but in which no melting or ore reduction ,,(such as might be performed in the furnace illustrated) is required, and I have shown two diagrammatic illustrations of such uses in Figs. 10; and 11 In Fig. 10 an ingot mold I is provided with an -roscillating' heating coil Ofifor the the metalyhot at the piping which has so seriouslyinterfered withthe use of theentire ingot in steel'work ,Here the heating purpose of keeping is intended to be local only andthe stirring function may be negligible. p

In Fig. 11 a pouring ladle K is shown with a heating'coil O for the purpose of keeping the metal in the ladle hot during the desirable settling after filling the ladle and before pouring from it. Some slight stirring would be helpful here.

It will be evident that the several uses suggested are but a few of the large number to which the broad principles of my in-. vention are applicable. The transfer of energy to the distance by oscillatory currents, the trading of energy between phases of a 'multi-phase current and. the. induced heating effects from oscillatory discharge are separately useful-.indifi'erent as well as in many of the same arts. The heat-treatment of metal alone includes not only-the furnace treatment of ore and metal, but tempering, annealing, forging, solderlng, etc.

.In treating liquids I believe that I am the I first, moreover to usefully employ pinch from currents induced in a .pool or bathitself, as distinguished from channel discharge into or through the pool or bath.

I recognize that, with the disclosures a com enser charged t erefrom and adapted to be discharged, a transformer primary in the discharge circuit from said condenser and a heating coil secondary in inductive relation thereto.

QaAn induction heating system comprising a primary alternating sourceof current,

a transformer'connected therewith, a, condenser charged from the secondary of said transformer, a heating oscillation primary in the. discharge circuit of said condenser and in inductive relation'to the resistor to be heated, and aninductance-coil in the secondary circuit protecting aga nst conphasefan inductance coil in series with each 1 denser discharge.

In apparatus utilizing oscillatory currents, a multiphase current source, con densers-. charged therefrom, "one for each phase-of the charging current, thecoils hav- -mg inductive .relation to each other, and

connections for discharging the condensers fife." Iniheating" .mechanism,.; an oscillation heating'eoii mductiye relation to the maenalgto be heated, a 'mu'lti-phase current.

mechanism com-' prism an alternatin current transformer,

neeaaee source, condensers charged therefrom, inductance coils in series w th the charging current, one in each phase and in inductlve relation to eachrother, and a discharge gap 10- cated. between the inductance COIlS and ductive windings in series with the charg-v mg circuit, one 1n each phase and having a common magnetic core and discharge gaps between the windings and condensers for discharging the condensers through the oscillation coil.

6. In a heating system; an; oscillation heating coil in inductive relation to the material to be heated, a multi-phase current I source, condensers connected with the 0scillation coil, discharge gaps for discharging .the condensers through the coil and connections between the current source and the circuit including the coil,condensers and discharge gaps foi charging the condensers, said connections having inductive windings about a commoiT core adapted to trade energy from one circuit of said connections to another. \V 7. In a heating system, oscillation heating coil provision in inductive relation to the material to-be heated, two condensers and two discharge gaps forming discharge circuits through the oscillation coil provision, two charging circuits, one for each condenser and passing through windings upon a common core providing inductance and adapted to trade energy anda multi-phase current source for said charging circuits.

8. .In an .alternatin current heating s stem, oscillation coil he rality of condenser and discharge gap c1rcuits adapted to discharge therethrou'gh, separate charging circuits for said condensers having windings in series therewith upon a common magnetic core and multi phase current supply for the charging circults. v In an induction heating system, a primary source of electric current, a transformer connected therewith, a rea'ctance coil connected in series with the transformersecondary, a condenser charged from the secondary, a discharge gap across the charg- -ing circuit between the condenser and recontainer thereinadapted to hold material 1n lflfllld form and free oscillation current supp y for said coilating means, a'p u- 1 11. In a heatin device 'a source of electric current, a con enser c arged therefrom, a discharge ap for the condenser and an oscillation 0011 through which the condenser is adapted to discharge in inductive relation to electrically-conducting material to be heated. g

12. In a heating device, a source of electric current, a condenser charged therefrom, an oscillation coil adapted to surround a liquid pool and connected 'inth'e chargin circuit and a dischar e gap across the con enser on the far side 0 the coil therefrom.

13. In a'heating and stirrin device, a container having a draining out et, a heating and stirring oscillation coil. thereabout, and free-oscillation current supply for said 001 14. In a heating and stirring device, a container for an electrically conducting pool and having a bottom outlet, a plug for said outlet extending downthrough the pool and induction means setting u closed current paths in said pool for heating the pool and stirrin it.

15. n a heating device, atwo-phase current supply, two condensers, one charged from each phase of the supply, two reactance coils, one in series with each phase of the charging circuits, the'two coils having a common core, a container for a pool, an oscillatlon 0011 in series with each phase of the char 'ng circuits and surrounding the 001 an break-down discharge means for t e condensers, discharging in each phase throu the oscillation coil.

16. n a'heatin device, an induction coil, a crucible inserti le into and withdrawable from the coil and an oscillation current supply for the terminals of the coil.

17. In aheating device, a crucible having a draining outlet and direct induction means for causing closed lines of electric current flow within the content to heat it.

18. In aheating device, acrucible having a draining outlet, a plug for closing. said outlet, (passing through the body of the pool, a con for charging said condenser and means for discharging the condenser through the con-' ductor.

19. In a heating device, .a furnace adapted to contain a pool a d to remain fixed during use, in comblnation with a coil surrounding the furnace and free oscillation current supuctor surrounding the crucible, a condenser connected with said conductor, means 21. In a' heating device, an oscillation coil, insulation therefor, a crucible within the coil and having an off-center draining outlet and free oscillation current supply for the ter- 'minals of said coil.

22. In a heating device, a removable crucible having a draining outlet, a furnace casing from which said crucible is removable, a coil winding in-said furnace casing in proximity to the crucible and connections for transmitting primary current through said coil to induce secondary current flow in the crucible.

23. In a heating device, a crucible having generally cylindrical outer. contour and bottom outlet and adapted to contain a pool, a casing within which the crucible is removably supported and a cylindrical coil winding within the casing close to-the opening for the pool.

24. In a heating device, a crucible, in combination with .an edge-wound coil conductor surrounding the crucible. j 25. In a heating device, a hollow coil support, an edge-wound oscillation coil there about and a crucible removably supported within said support.

26. In a heating device, a base, a refractory annular insulation removable therefrom,'a coil winding upon said insulation, an 95' about, the container to induce current flow in the container as a seconcary.

29. The process of charging and discharging condensers which consists in charging the condensers in parallel through moss in inductive relation to each other and in discharging the condensers through dis charge spark gaps located between the reactances and the condensers.

30. The process of charging and discharg into electriecurrent having natural, as distinguished from forced frequency, in transmitting itto a distance in this condition by conductors and in transforming it at the point of use for heating urposes;

32. The method of uti izing electric potential energy at a distance which. consists in storing the energy in condensers, in dis-' charging the condensers through conductors extending to a distant point and through a conducting coil-located at that point and in inductively coupling the coil and the work at the oint of use for heating purposes.

33. he method of utilizing at a distance electric ener stored in a condenser which consists in c arging a condenser through a: local circuit at one point. in dischargingit memes through conductors extending to e distance point and in there utilizingthe oscillatory discharge fromsaid condensers.

34. The we utilizing at e distance. electric potential ener stored in .a con denser which consists mcharg the com denser through a local circuit including an inductance coiland in' discharging fiiecondenser through a difierent circuit excluding the inductance coil and extending to a distant point, and there passing the'dis charge throu h 'e-transformercoil and mi lizing the in uction from-sffllidmoilfor a production of heat within a meteriel adapt ed to heated EDWIN NOEL-H23;

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