US1795842A - Induction furnace - Google Patents

Description

March 10, 1931. N. R. DAVIS INDUCTION FURNACE Filed Jan.

w w. m l l n n I l NvENTOP, /VeU/Ze E. Edi/5.

Patented Mar. `I0, 1931 UNITED STATES .PATENT OFFEE NEVILLE BYLAND DAVIS, OF SALE, ENGLAND, AVSSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFAUTURING COMPANY, A CORPORATION 0F PENNSYLVANA INDUCTION FURNACE Application filed January '8, 1930, Serial No. 419,436, and in Great Britain January 5, 1921 ?n My invention relates to electrici furnaces and more particularly to electric-induction furnaces.

It is one of the main objects of my invention to provide a novel means for, and a method of, drying out the lining of an electric-induction furnace.

Another object of my invention is to provide a means permitting of initially drying out the lining of a furnace which shall be available for protective purposes during subsequent operation of the furnace.

In practicing my invention, I provide a suitable furnace structure including an energizing or induction coil, a Crucible located therewithin, electric-insulatin material separating the coil fromv the cruci le, and a starlike cage or basket .immediately surrounding the Crucible.`

In the single sheet of drawings,

Figure 1 is a View, in vertical. section, through an inductionfur11ace assembly embodying my invention,

Fig. 2 is a bottom plan view of the parm ticular element embodying my invention, illustrated as located alone9 and Fig. 3 is a fragmentary View,I on an enlarged scale, of the star-like cage element.

Referring more particularly to Fig 1 of the drawings, I have illustrated a suitable outside casing 11 which, is shown as consistin of metal but which may or may not be utilized. An energizing foil, designated by 12, corn`1 prises a plurality of turns of a suitable eurrent-con ucting wire or bar, shown as being substantially rectangular in lateral section, although the energizing coil forms no par tieular part of my present invention.

The space Within the casing'12 is shown as being partially filled by aV suitable electricinsulating granular material 13 which may be Zircon sand.. A crucible 1d, which may be of any suitable material, in accordance with the materials which are to be melted therein, is located within the Casin 11 and is sup ported by the granular e ectric-insulating material 18..

A pouring spout 16 is provided at the upper edge of the Crucible 14, and suitable means, not specifically illustrated in the "drawings,

. stantially as shown in Fig. 3 of fact that the casing,the energizing coil and the Crucible proper may be of any suitable or desired kind and do not constitute specific parts or elements of my present invention..

A star-like metallic cage or basket 17 is providedvvhich is located outside of, and in direct operative engagement with, thel crucible 14. The cage or basket 1.7" is preferably made of a non-magnetic steel and comprises an upper open ring or annular member 18 to which are connected a plurality of downwardly extending strips 19. The strips 19 are suitably riveted against the outer surface of the ,strip 18, as by a plurality of rivets 20, and it is one of the important elements of my invention to provide a plurality of relatively deep recesses 21 extending upwardly from the bottom edge of the strip 18, sub the drawings. A substantially flat openannulus also of metal, is provided at the bottom of the bentin strips 1.9, the strips-beine' riveted. to the.

annulus 22 by a plurality or rivets 23, as is shown more particularly in Fig. 2 of the drawings. Another important 'element of my invention is that each of the strips 18 at that portion thereof, immediate-sl f adjaecnt to the outer peripheral edge of t e member 22, are reduced in width, as shown at 245iin Fig. 2 of' the drawings.

The cross section of each of the-bars 19 should be such that R is the resistivity in electro-magnetic units ofthe material used. in the bars, and. l? is equal to 2n times the frequency This eneures that the eddy' current losses in the strips or bars 19 shall be belcuT a p redeter= mined value, so that the bara shall not be excessively heated during normal operationl of the furnace.

The sand 13 is rammed between the inductor coil and the cage or basket, as well as between the inductor coil and the casing. The relatively narrow spaces between the bars i9 may be packed with ganister or other suitable material to prevent the escape of sand, in case the Crucible is removed for replacement. The inside of the cage or basket may be coated with asuitable lining material, such as'silica sand or magnesite, with or without a suitable binder, such as tar.

The cage 17 may be grounded, either to the casing ll. it the same is of metal, or directly to a ground, the casing 11 being grounded as shown at 26 in Fig. l of the drawing, ii oi metal. l t Upon the initial application of electric energy to the inductor coil, heat is developed in the cage or basket by inductive efect, and the amount of energy translated into heat is made'such that the lagging or lining materials are properly dried out. lWhen the proper amount oi drying out has been effected, the restricted portions of the member 18 and of the individual bars 19 will be melted, because of the general heating up of the furnace, or the amount of energy provided at the terminals of the coil 12 may be increased lto malte sure that proper melting oi all of the restricted portions is eected. When the cage is thus opened, further generation of heat in the .individual bars is reduced 'to a very small amount.

It may be pointed out that the initial melting oi metal in the crucible, particularly if it is of a metal or an alloy inelting at a relatively high temperature, will eiect sintering oi the lining to form a hard or coherent Afurnace lining which may be easily broken out and replaced if and when injured or worn out during the operation oi the 'iurnace. The restrictedportions of the cage or basket may be provided in any part or parts thereof, and it is obvious that the separated elements oi the cage or basket *will act as a Screen in the case of escape of molten metal through the wall of the crucible. v

Various modilications may be made in the device embodying my invention without departing from the spirit and scope thereof and I desire therefore, that only such limitations shall be placed thereon as are imposed by the prior Aart or are set forth in' appended claims.

.l claim as my invention:

l.n ln an electricdnduction iurnace having a refractory lining and an energizing4 coil, the method oit drying the lining which comprises locating in the lining, during its construction, a distributed metallic cage within the coils and energizing the coil to effect heating of the metallic cage by induction, whereby to eilect drying ofthe liningu agencia 2. ln an electricdnduction furnace having a refractory lining and an energizing coil, the method of drying the lining which comprises locating a star-like distributed metallic cage in the lining during its construction, energizing the coil to a predetermined degreeto effect heating oi the metallic cage by induction to eiiect drying of the lining and continuing said induction heating oi the cage and the lining until the electric continuity oi the metallic cage is interrupted at a plurality of places.

3. In an electric-induction furnace having a refractory lining and an energizing coil, the method oi drying the lining which comprises locating a star-like distributed metallic cage in the lining during its construction, said metallic cage comprising a plurality oi strips including a connecting portion of reduced area of cross section, energizing the coil to effect heating of the metallic cage by induction to e'ect drying of the lining andcontinuing the induction heating of the cage and of the lining until the electric continuity of the cage is interrupted by the melting ofthe connecting portion of reduced area oi cross section.

ln testimony whereof, I have hereunto subscribed my name this twenty third day oiglecember, i929,

NEWLLE RYLAND DAVIS.

Images