US1827274A - Electric induction furnace - Google Patents

Description

Oct. 13, 1931. D. wlLLcox 1,827,274

ELECTRIC vvINDUGTION FURNACE Filed Aug. 13, 1928 2 Sheets-Sheet l Oct. 13, 1931. D. wlLLcoX ELECTRIC INDUCTION FURNACE Filed Aug. l5, 1928 2 Sheets-Sheet 2 y Patented Oct. 13, 1931 y UNITED STATES PATENT OFFICE DUDLEY wxnLoOx, or LAWEENOEVILLE, NEWJEESEY, AssrGNon. 'ro aux ELECTRO- '.rHEEiincl conrona'non, or AJA-x rmx, NEW JERSEY, A oOErOEA'rIoN or NEW JERSEY- ELEcrnIc nmucrrON FURNAUE Application led August 13, 1988, Serial No. 299,158, and in Great Britain September 8, 1927.

My invention relates to the cooling of wind seen 1n Figure 9.

ings for electric induction furnaces.

One purpose of my invention is to utilize the conductivity of copper, to carry the heat away from a section so that water-cooling can be eifected by water located in aprotected position.

'A further purpose is to form the currentcarrying part of an inductor of solid material close to the furnace and to locate the A further purpose 1s to attach cooling elements to"a furnace coil at intervals only about the circumference, relying upon these eleiuents to cool by heat conductivity those por- 2d tions of thefcoil lying between.

Further purposes will appear in the speci- {ication and in the claims.

I have preferred to illustrate my invention by a few forms only among the many irr which it may appear, selecting forms which :1re practical, eliicient and reliable and which at the same time well illustrate the principles of my invention.

Figure 1 is a topplan view showing one,

embodiment of my invention.

Figure 2 is a section of Figure 1 taken upon line 2 2.

Figure 3 is a view correspondin to Figure 1 showing the invention applie at inter.

vals about the furnace coil.

Figure 4 is a side elevation ture seen in Figure 3.

vof ther struc- Figure 5 is a section of Figure 3 taken upon line 5 5. A l

Figure 6 is a top plan view of a furnace in which coil supports interfere with the placing of the cooling elements.

Figure 7 is aside elevation of the structure seen in Figure 6.-

Figure 8 is a section upon line 8-8 of Figure 6.

`Figure 9 is a top plan view of a further form.

Figure 9afis a fragmentary top plan view showing a slight modification of Figure 9.

Figure 10 is aside "elevation of the form Figure 11 isa section of Figure 9 taken upon line 11-11.

Figure 12 is a fragmentary section similar to Figure 11, but showing a modilication.

In the drawings similar numerals indicate like parts.

My invention is intended to safeguardl application of water cooling to the coils of electric furnaces and, though applicable most conveniently and to the greatest benefit to inductor coils for furnaces of the so-called coreless type (lacking interthreading of the coils by transformer or crucible lron) is suited also for use with windings of so-called core type furnaces.

By illustrating the coreless type only it is not intended to suggest that the invention is' useful in this type alone.

Existing windings of furnace inductor coils are made of tubing or of solid strips or straps of copper. The tubing is cooled by water passing through the tubing. Onesample of water cooled coils is Ato be seen in Northrup Patent, No. 1,328,336. I

When the inductor is made of solid metal it is necessary to cool the coil by ablastof air or other means to take the place of the water'coolingin the hollow ytubular form.

My invention contemplates cooling an otherwise solid coil by water cooled means llocated outside of the coil where the wate'rcarrying members are protected against flow of molten metal leaking from the furnace. These water cooling members may be attached to the coils, but ordinarily used to be attached at intervals only along the length of the coils. Insteadof direct connection to the coils it is ordinarily suicient to attach the members to the coils at intervals along the coil lengths by heat-conducting tabs.

The points of attachment may be located at different points along the lengths of the coilsor at different points about the circumference or both. In the case of larger coils it is desirable to put several tabs on each turn.

Though the invention is valuable for small furnaces lits paramount value as a safeguard example, which will completely fill the space between the turns instead of the small insulating pieces at intervals about the coil now required with air cooled coils in order to give greater room for penetration of cooling air between the turns.

This makes it possible to carry more turns per axial inch of coil length than previously and to obtain a greater number of ampere turns about a given mass or charge of material to be heated than could otherwise be secured.

The additional safety of the present invention as compared with the usual form of water cooled coil made of conducting tubing through, which a stream of water is passed will be clear `fromthe fact that molten metal leaking through the insulation of a furnace' using a tubular current-carrying inductor coil may melt the inside of one or more of the conducting turns of the coil.- This would not only allow the molten metal to engage the water, but this would take place at a point on the inside of the coil 'where the rev sulting steam or vapor cannot escape, with the possibility of an explosion which would blow molten metal out of the furnace. An interior line of discharge of the water from the coil also throws the water toward the charge increasing the danger. The present invention keeps the cooling liquid well away from the molten metal, discharges the cooling lituid outwardly and utilizes the coil as a shie d and guard against flow of molten metal and water toward each other.

In Figures 1 and 2 the inductor 15 is wound from a copper strip of rectangularcross-section. Every few turns the strip inductor is connected by sheet copper tabs 16 with copper tubing 17 brazed to the tabs. The tubes'are connected together by sections 18 of rubber hose. Inlet and outlet for water supply and discharge are shown at 19 and 20. The surplus heat from the coil is conducted to the' cooling tubes through the tabs and is carried away through the water.

In Figures 3, 4 and 5the tabs and water- 'cooled tubes connected. with the inductor water directly through the blocksand the pass 18 and-nipples 22. These passages with their Walls in the blocks are viewed as in effect tubes but the larger masses of these block tabs, their larger number and more general distribution and the better Contact ofthe water with the tabs from the standpoint of heat conduction makes this form avery much beter cooling system than that in Figures 1 an 2.

In each of these forms shown in Figures 1-5 each turn of the inductor forms a single .strip of copper.

In Figures 6 to 12, however, each inductor turn comprises a plurality of strips 15 electrically in parallel, greatly increasing the conductivity of the turn. In all of these ligures heat insulation within the coil is shown at 23, electrical insulation between the coil and the heat insulation is shown at 24 and insulation between the conductors of each turn to reduce eddy currents and between the turns is seen at 25. In Figures 6, 7 and 8 non-metallic coil supports are shown at 26.

Figures 9, 10 and 11 correspond in all of these parts with Figures 6, 7 and 8 except for the fact that laminated magnetic return circuits for the ma etic flux of the coil are shown at 27 instea of the coil supports 26.

The water cooling of Figure 6 1s secured b attened copper tubing 28 flat-wound a ut the turns and brazed or soldered to the turns between the supports or at any other suitable interval as at 29 and outwardly extended to pass about the non-metallic supports between these points as at 30.

In Figure 9a where the laminated return circuits are spaced enough f rom the coil to permit the water-cooling tube to continue along the outside of the strips the tubing 28 is in continuous contact with the solid stri comprising the electrically conducting coll.

Connectlons with inlet and outlet tubing 19 and 20 are made through nipples 31 en,- gaging with the tubing for example, at a point where it is not attened.

In addition to the difference of Figures 9, 10 and `11 from 6, 7 and 8, in that magnetic return laminated material is shown at 27 instead of the coil supports, these latter figures differ also from Figures 6, 7 and 8 in that the flattened Vhollow conductors 28 are not continuousabout the coil but are interrupted by the insertion of connecting tubing 1-8 to provide for transitionv about the laminated magnetic return circuit.

In both of the forms shown in Figures 6 to 11 the same hollow watercooling conductor is connected to cool a number of conductors in parallel, making up a complete turn of the inductor and engaging the contour of these conductors at intervalsor following the contour with such continuity about the ages are connected in seriesvby rubber tubing/ circumference as may be required to cool the inductor eectively. l i

In all of the forms the liquid conduit is on the outside where it is `protected from flow of molten metal not only by the turns of the inductor itself but by any electrical insulation or other filling which may be desired, permitting com lete sealing of the melt from the water-carrylng, tube by a wall formed by the current-carry'g part of the inductor and the insulation wit 1n it and between its conductors. d

The selection of the form of cooling and the number of places aboutthe circumference of the coil at which the cooling is applied depend. ofcourse upon the needs of t e individual installatlons. My illustrations for l this reason have been suggested merely as ways in which my invention may be carried out so as to place the cooling tubing on the outside where leakage of water from it will least affect the charge and furnace and where the tubing is best protected from flow `of -metal from the charge. The cooling system is not confined so as possibly to result in a serious explosion if it be voverheated.

For large furnaces of the high frequency induction t pe holdin for example, ve tons of stee it wouldgbe desirable to have 4the furnacelcoil made of a plurality of layers of edgewise wound copper strips of straps a proximately as shown in Figures 8 and 11. ery thin insulating material, such as mica, should be used between the individual turns to prevent setting up of eddy currents and it is desirable to'have the copper .or other conductor as close as possible to the furnace 1. In a cooling system for furnace coils, an inductor and water-cooled tabs at intervals onthe outside of the inductor adapted to cool the inductor and protected from. the furnace charge bythe body of the inductor.

2. In un electric furnace an inductor coil of edge-wound materialtabs connected with the ind uctor at intervals and extending outwardly. from the inductor and water-cooled connections with the tabs for cooling the inductor through the tabs.

3. In an electric furnace, an inductor coil, water-cooled connections outside of the coil at intervals and Vtubing between the connections to supply the water cooling progresslvely about the inductor length.

4. In an electric furnace, a vertical inductor coil, magnetic materiali-spaced at intervals about the inductor to form a magnetic return path, water-cooled tubing thermally connected with the inductor. to cool it at intervals between the ma etic circuit parts, and connections about t e magnetic clrcuit to su ply water to the tubing.

5. n' an electric furnace, an inductor and water-cooled device for cooling the inductor, thermally connected with the inductor at intervals about the inductor length and se arated from the inductor, and connections etween the devices to supply waterto them.

6. In'- an electric furnace, a` solid metal primary winding, soli'd metal tabs connected to the primary at intervals along the length of the primary and water-cooled tubing in heat-transfering connection with the tabs.

DUDLEY WILLCOX.

charge. Not all of the conductors of a turn need be in thermal contact with the cooling element. In Figure 12 alternate layers o the strap conductors extend further away from the furnace charge than the layers ofA conductors between them, so that they cooling water is still further removed from the hot metal for the sake of safety. In such a construction good heat-conducting .contact is desirable between the intervening those engaging the tube.

The use of a water cooled tube continuous ly enga the outer e of the coil, as s own in 1 re 9a, woul be more efectiva nd less like y to give trouble than the other orms.

In view of my invention and disclosure variations andmodiiications to meet individual whim or particular need will doubtless become'evident to others skilled in the art, to obtain part or all of .the'benets of my invention without oop v the structure shown,and I, therefore, c aimall such in so far as theyfall within the reasonable spirit and scope of m invention. 1

Having thus descri my invention, what I claim as new and desire to obtain by Letters Patent 1s: l p

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