US1810820A - Induction furnace - Google Patents

Description

June 16, 1931. N. R. DAVIS ET AL 1,810,820

INDUQTION FURNACE Filed May 7, 1930 2 Sheets-Sheet 1 Illllllh v9 i 39 x 3 44 Ill 3 INVENTORS NeviIleR-Daw's, Maurice JZMm-ebbamnand JabnH-Ludlow A'TTORNEY Jun' 16, 1931. N. R. DAVIS ET AL 1,810,820

INDUCTI 0N FURNACE Filed May 7. 1930 2 Sheets-Shet 2 INVENTORS Neville R. Davis, Maurice J.Marc]:ban/Ys and Y Jofin E L vdl ow ATTORNEY Patented .luneIG, 1 931 a UNITED 5 STATES PATENT OFFICE NEVILLE RYLAND mm, or SALE, Aim 'xnuarcn minis manennmxs AND JOHN HEYWOOD LunLow, or mancnns'rnn, ENGLAND, assronons 'ro wnsrmonousn ELEc'rmc am) numur'ac'runmo comrnnr, acoarona'rxon or PENNSYLVANIA INDUCTION FURNACE Application filed Kay 7, 1980, Serial No. 450,343, and in Great Britain 1e18,. 1929.

Our invention relates to electric furnaces and more particularly to electric induction furnaces.

An object of our invention is to provide a' frame structure for electric induction furnaces that shall embody a plurality of spaced metal-frame members.

Another object of ourinvention is to provide a skeleton metal frame for an induction furnace that shall be relatively light in wei ht and rigid and that shall be so constructe as to reduce the heating caused by eddy-current losses, therein to a minimum.

In practicing our invention, we provide a skeleton metal frame for surrounding and supporting the crucible and the induction coil of a furnace which shall include a plurality of relatively thin metal members of strip or plate shape, so arranged that no closed metallic circuit is provided for the magnetic flux produced by the energizing coil. The dimensions of such of the metal members as are cut or linked by the magnetic flux,when measured in a direction substantially at right angles to the direction of the magnetic flux, are relatively small and less than that which would cause appreciable heating thereof, having regard to the flux intensity, the frequency and the resistivity of the materialof which such frame members are made. A majority of the joints in the assembled frame structure are of the insulated type and these joints are employed in such manner that, from any earthing point, the electrical cirsuit is of tree-likeform with branches but includes no complete circuit through which magnetic linkage can occur.

In the drawings,

Fi ure 1 is a composite view of an induc tion urnace embodying our invention taken on the line II of Fig. 2, and, p

Fig. 2 is a view, in vertical section, taken on the line 11-11 of Fig. 1.

I The base for the furnace structure includes, more particularly, a plurality of thin metal.

strips 11 which arepreferably made of some non-magnetic steel. The individual strips 11 are spaced apart by thicker strips or bars 12 ofa suitable electric-insulating material, which may be asbestos. A plurality of clampplurality of strips or bars of metal and alternating bars of electric-insulating material.

The bars and strips 11 and 12 rest directly upon a layer 18 of a suitable insulating material, which may be some form of asbestos. The layer 18 of electric-insulating material rests, in turn, on a bottom plate 19 of a suitable metal.

A plurality of bricks or blocks 21 of a suitable refractory electric-insulating material, rest upon a layer of electric-insulating material 22 located on the top of the lamellar base hereinbefore described. The bricks or blocks 21 may be built up to any suitable height and contour to support a crucible 23 which, as shown in the drawings, is tubular in form. The crucible 23 may either be manufactured outside. of the furnace assembly and located therein, or it may be in the form of a lining which is manufactured in situ.

The energizing coil 2 1 for the furnace includes a plurality of turns of a composite conductor which, as shown in the drawings, includes an inner solid current-conducting portion and an'outer-fluid-conducting portion. Any suitable or desired kind of insulation is provided between the adjacent faces of the conductor constituting the energizing coil 24. While no terminal portions are illus trated, it is to be understood that such are provided, the details being omitted for the sake of simplicity and for the reason that they constitute no part of this particular invention.

Supporting means for the coil include a plurality of stanchions 26, here shown as elongated plates which are relatively thin in a peripheral direction and which extend longitudinally and radially of'the crucible 23. a Each of a plurality of vertically extending bars 27 of suitable electric-insulating material has a groove or recess in one face thereof i which is adapted to receive the edge of a recessed portion 28 of the inner edge of a corres onding stanchion 26. Relatively small locks 29 and 30 of electric-insulating material areprovided adjacent to the top and the bottom turns, respectively, of the energizing coil, and the weight of the coil is supported directly by the members 30, which, in turn, are supported on ledges at the bottoms of the recesses 28 in the members 26.

An annular member 31, which is here shown as bein of substantially channel shape in lateral section, rests upon the plate 22 of electric-insulating material. member 31 is provided with at least one gap therein, indicated at the left-hand side of Fig. 2 of the drawings, in order that it may provide no closed electric circuit for the flux generated by coil 24. An annular member 32 of electric-insulating material is located on the member 31, andthe bottom edgesof the respective stanchions 26 rest directly upon it.

In addition to the inner set of stanchions 26, we provide an outer set of stanchions 33, also made of relatively thin metal in a direction peripherally of the furnace. Anglebar members 34 may be bolted to the bottom portions of the respective radially aligned pairs of stanchions 26 and 33, and similar angle bar members 36 are located at the upper endsof the pairs of stanchions; By refermembers including angle-bar members 38 at the bottom plate, sheets 39 intermediate their ends and angle-bar members 41 at the top thereof. Referringto Fig.1 of the drawings, it will be noted that insulated bolts 42 are utilized and that a small metal washer 43 is located between one of the plates 39 and the stanchion 33, while a washer 44 of electricinsulating material is located between the other plate 39 and the other face of stanchion 33 to prevent a closed electric circuit at this point. t I

In order to secure the skeleton-frame structure hereinbefore described tightly on the base, we provide a plurality of electricallyinsulated bolts 46, only one of which is shown in Fig. 2 of the drawings, for the sake of simplicity, these bolts extending through the angle-bar members 38. It will be understood that the details may be varied within wide limits, in accordance with the size and weight of the entire furnace structure.

The annular The top portion of the furnace includes a framework consisting of a plurality of peripherally spaced metal members 51 which may be either of T-shape or of angle-bar shape in lateral section. These members have their lower ends connected, by plates 52 of T- section, to atop plate 53 which is of annular shape and which has its inner edge resting upon the electric-insulating member 29. The

I ring 53 is split, as shown at the right hand side of Fig. 2. Insulated bolts 54 are provided to effect the clamping connection between the members 52 and the plate 53, small plates- 56 of electric-insulating material being provided to prevent direct electrical engagement between the metal members.

A split flat ring 57 is provided at the top of the furnace structure, and the upper ends of members 51 are bolted thereto by bolts 58.

We provide a plurality of top rings 59, of

refractory material, which may be cemented together and, in addition, be held by bolts or rivets 61.

The members 59 are, in general, of annular shape, but, at one portion thereof, they are of somewhat different shape to provide a pouring-spout structure 62, a metal member 63 having a plurality of lateral ribs thereon, being provided to better support the refractory material constituting the s out 62.

As a furnace of this type is usual y tilted to empty the molten material from the crucible,-we provide a pair of trunnions 63 and 64 which may be suitably secured against two diametrically opposed plates 39 to cooperate with any suitilble supporting and tilting means to effect tilting of the furnace structure when and as required. It may be noted that an annular member 66, of electric- 1nsulating material, is located between the plate 53 and the upper ends of the stanchions 26 and 33.

It may be here noted that, in the past a furnace structure of this general type has included an outer tubular metal casing withm which was located the lining or crucible and the energizing coil, with such granular electric-insulating material as would with stand the high temperatures utilized in the melting of metals. In contradistinction to this, the furnace structure embodying our invention is constituted by a skeleton-frame structure, not only as to the base, but also as to the supporting means for the energizing coil, and also in regard to such additional frame elements as may be necessary in order to permit of properly handling the furnace when in use in melting metals and alloys.

It may be noted alsothat our improved frame structure provides no closed metallic circuits which are threaded by either useful or stray flux, so that no closed circuits are provided which might result in excessive heating of the metal members.

It is to be further noted that the frame members are so located that the faces of the. frame members of substantially late shape extend in such directionsas to substantially parallel to the general direction of the flux generated bythe energizing coil, and. that these plates are relatively t m, so that the losses caused by eddy currents in the individual plate members will be relatively small.

It me, be noted also that a suflicient number of irect electrical and mechanical con- 'nections between the respective plate members constituting the frame are provided, so that all of the plates are grounded at a convenient int which may be either one or both of this trunnions 63 or.64 which, in turn, may eitherbe grounded through the supporting structure (not shown in the drawings) or may be especially grounded 1f such precaution is deemed necessary.

Our improved furnace structure, therefore, provides a relatively light-weight skeleton frame for a furnace crucible and coil which will be eas to ventilate to reduce the temperature o the furnace, and which will still be relatively rigid and electrically safe for the operating rsonnel.

Various mo fications may be made in the device embodying our invention without departing from the s irit and scope thereof, and we desire, there ore, that only such hmi tations shall be placed thereon as are imposed by the prior art or are set forth in the ap nded clalms.

e claim as our invention:

1. In an induction cible, and an energizing coil surrounding it, means for supportlng said coil including annular top and bottom members, a plurality of relatively thin metal members extending radially and longitudinall between the top and bottom members, eac of said thin metal members having a recess in its inner edge, and electric-insulating material in said recesses for supporting the energizing coil.

2. In an induction furnace includln a crucible and an energizing coil surrounding it, means for sup orting said coil including annular to and ottom members, a pluralit of relative y thin radial stanchions extending between the top and bottom members, each of said stanchions having a recess in itsinner edge extending to the tog thereof, electricinsulating material in sai recesses for bolding the energizingcoil tightly in the rece and below the top member. t

3. In an induction furnace including a crucible and an ener 'zing coil therefor, supporting means for t e coil and the crucible includln substantially annular member of refractory material for supporting the crucible, an. annular bottom member restin on said laminated base, a plurality of ra ially-extending thin-metal stanchions supported by said botfurnace having a crua base of lamellar construction,a

, and means for mechanically tom member, each stanchion having a recess in its inner edge, electric insulating material in said recess for supportingthe coilaml pressing it radially inward, and an upper annular member secured to the tops of said stanchions and operatively engaging a portion of the electric-insulating material to prevent upward movement of said coil. M a

4.. In an induction furnace includin a crucible and an energizing coil there or, means for supporting the coil including a plurality of peripherally spaced inwardlyrecessed thin-metal members, electric-insulating material in said recess for ing the coil to hold it in proper operative osition, interrupted annular members ad: 1acent to the top and the bottom of the thinmetal members, and means securing the res ective ends of the thin-metal members to t e top and the bottom members.

5. In an induction furnace including a crucible and an energizing coil therefor, a skeleton metal' frame for the furnace including a base comprisingalternate stri s of insulation and of thin metal, interrupte top and bottom rings of metal, radially and longitudinally extending thin-metal plates extending between the to and bottom rings and surrounding the crucible and the energized coil, and electric-insulating means for supporting the crucible on the base and the energizing coil on certain of said thin-metal plates.

6. In an induction furnace having a crucible and an energizing coil, therefor, a frame structure for the furnace including a lurality of thin-metal plate members, the

aces of the plate members extending in such directions as to be substantially arallel to the general direction of the stray ux generated by the energizing coil, and electric-insulating c a mping members for securlng the respective plate members together to frame having a plurality o cuits therein.

7. In an induction furnace having a crucible and an energizing coil therefor, a frame structure for supporting the crucible and the coil and including a laminated-metal base, a skeleton metal frame on said base and surrounding the crucible, the base and the provide a skeleton open electric cirskeleton metal frame including thin metal members the respective faces of which extend in such directions as to be substantially parallel to the general direction of the stray flux from. said energizing 'coil to reduce eddycurrent losses therein.

p In an induction furnace having a crucible and an energizing coil, a frame structure tiltably supporting the coil and crucible and including a plurality of peripherally s aced inner and outer stanchions, means or insulatedly supporting the coil from the inner stanchions, trunnions supported from certain of the outer stanchions,

connecting the directly engaginner end outer stanchions together both radially and peripherally thereof to provide open electric circuits for the strays-flux from said coil while effecting an electric connecb tionof all of said stanchions to one of said trunnions.

In testimony whereof, we have hereunto subscribed our names this 23rd day of April, 1930. Y

w NEVILLE RYLAND DAVIS.

MAURICE JAMES MARCHBANKS.

JOHN I-IEYWOOD LUDLOW;

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