US2309700A - Annealing furnace - Google Patents

Description

Feb. 2, 1943.

E. l. HUFF ANNEALING FURNACE Filed Dec. 1, 1941 3 Sheets-Sheet l INVENTOR ATTORN EYS Feb. 2, 1943. HUFF' 2,309,700

ANNEALING FURNACE '7 Filed Dec. 1, 1941' 3 Sheets-Sheet 2 2 III] lk-ll ll,

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INVIENTOR ATTORNEYS Patented Feb. 2, 1943 ANNEALING FURNACE Edward 1. Hail, Nutley, N. J., assignor to Huff Equipment Company, a corporation of Pennsylvania Application December 1, 1941, Serial No. 421,150

5 Claims.

This invention relates to annealing furnaces of muflie type, fired by flame, in which the muflie chamber is of annular form in horizontal section, and adapted by shape to the annealing of such articles as coiled steel strip and coiled wire. Furnaces so characterized are shown and described in Letters Patent granted on my application, No. 2,146,432, February 7, 1939, and. No. 2,250,868, July 29, 1941; and also in a pending application, filed by me November 25, 1941; Serial No. 420,393.

In the furnaces of the patents named, the flame enters the furnace chamber at the base and through the walls of the hood, and flows upwardly over the outer wall of the annular mufile and, passing over the top, descends through the central columnar space defined by the inner wall of the muffle. According to my present invention, as also in the application named, the flame enters the furnace chamber at the bottom of the columnar space defined by the inner wall of the mufiie, and flows thence upwardly, over the top of the mufile and downwardly over the outer wall of the mufile to exit at the base of the hood.

This new arrangement is not a mere reversal in organization, for in consequence of reversal new utility is realized; and, furthermore, in consequence of such reversal, it has been possible to make particular structural changes, with the effect that the annealing operation is improved and rendered more efiicient.

In the accompanying drawings Fig. I is a view in vertical and axial section of an annealing furnace in which my invention is embodied; Fig. II is a fragmentary view to larger scale of a portion of the furnace as seen in Fig. 1; Figs. III and IV are views in horizontal section, on the planes indicated, respectively, at III-III and IVIV, Fig. I; Fig. V is a fragmentary view (on reduced scale) in horizontal section, on the plane indicated at VV, Fig. II; and Fig. VI is a fragmentary view showing in vertical and axial section the lower portion of a furnace in which are embodied specific structural features, other than those of Figs. I-V.

Referring, first, to the furnace as shown in Figs. I-V, it is, as has been said, an annealing furnace of mufile type, in which the mulile is of annular shape. Upon a suitable floor plate I is placed a hearth block 2; the hearth block carries the base plate 3 of the muflle; and upon this base plate the muiile 4 is removably borne. The hood 5 is removably borne by the floor plate I,

' 9 and III by air under pressure.

and when in place the hood at its base immediately surrounds the hearth block 2.

The hearth block 2 of refractory material is centrally perforate; the orifice is circular and is of substantially equal diameter with the columnar space defined by the inner wall of the muflle. In the central perforation of the hearth block 2 is set the burner block 6 of a burner I. The burner block too is formed of refractory material. The burner may be adapted to burn any suitable fuel-gas, oil, or finely divided coal. As here shown, it is an oil burner, fed through a pipe 8 by oil under pressure, and through pipes Through the burner block 6 the burner projects flame upwardly from below into the columnar space defined'by the inner wall of the mulfle which columnar space is part of the furnace chamber beneath hood 5.

The base plate 3 is formed of metal-ordinarily, of cast-iron. It is essentially annular (since it forms part of the annular muflie) and consists of a horizontally extending web II, radially arranged flanges 33 that extend from the nether face of web II, co-axially arranged cylindrical flanges I2, I3, I4, and I5 that extend from the upper face of web II, and radially arranged flanges I6 that extend from the upper face of web II and between the cylindrical flanges I3 and I4. The radial flanges 33 immediately engage the upper face of the hearth block and, with the block below and the web II above, define passageways 25 beneath the muflie, whose utility will presently be indicated. The pairs of cylindrical flanges I2, I3 and I6, I5 form with the web II troughs into which in the assembly the inner and outer rims at the lower end of the movable muflle 4 extend and within which the muiiie is sealed by the familiar sand seal. The radial flanges I6 afford support for an annular plate II which is the stool-plate upon which the furnace charge rests.

The muffle is formed of heatconducting material, ordinarily of steel; it is, as has been said, of annular form and includes inner andouter substantially cylindrical side walls II, 42 that companion flange l3, and the flange IS in turn rises higher than the flanges I4 and ii, that the application of the muilie to the base plate may be facilitated.

The hood is formed essentially of refractory material it is of a general form and arrangement already well known to the art. It is provided externally wth rings l8 that engage stationary posts I! rising from the floor plate, and by such engagement the hood is guided when being applied and removed. Within the hood walls flues 20 are formed. Ports 2| open to these flues from within and near the base of the hood. At their upper ends these flues are freely open. They may vent to the open air, as here they are shown to do; or, manifestly, they may be brought into communication with a stack or other draftinducing apparatus.

Through the floor plate and base block tubes 22, 23 may extend, for the circulation within the closed muflle of any desired gas (non-oxidizing, reducing, etc.) and tube 24 also may be similarly arranged, for the introduction of a thermo-couple or other instrument for determining conditions within the mums.

Operation is conducted in familiar manner. When hood and mufile have been removed the charge of material to be annealed is stacked upon the stool plate IT. The muflle 4 and the hood 5 are then successively brought to position. At the beginning, or as operation progresses, such gas as may be desired for protection or for reaction is caused to circulate through pipes 22, 23 and through the muflie chamber. The burner I is lighted, or being already lit, is adjusted to afford a flame of desired size and character. The flame streams in the course indicated by arrows in Fig. I, upward through the columnar space formed by the inner wall of the muille, over the top, and down over the outer wall of the muille, to the exit ports 2 I. have been completed and large quantities of heat generated by combustion will have been absorbed by the muille walls. The products of combustion will escape through the flues 20 in the hood.

The passageways 25 formed by and between the flanges 33 that extend from the nether surface of the base plate H afford a by-pass, through which a portion of the stream of spent gases will return to mingle with the stream of burning gases that springs from the burner.

The heating operation properly controlled (as. may be, with the aid of a thermo-couple) is performed in accordance with a known temperature gradient; cooling may be accelerated by shutting oi the fuel and causing air at suitable temperature to enter through the burner block and circulate through the furnace chamber; and when a proper degree of temperature has been reached the furnace may be opened and the annealed charge removed from it.

'The advantages of the structure as described, in which the stream of flame is upward through the columnar space within the ring-shaped muffle and downward over the exterior surface, over the usual arrangement, in which the flow of flame is upward over the exterior and downward through the central columnar space, are these: (1) The structure of the hood is not complicated, and its manipulation in service is not embarrassed by the presence of burners in that portion of the structure. (2) There is more perfect dis tribution of heat circumferentially of the mufile than is possible in case oil burners be arranged oircumferentlally and at intervals at the base of In this course combustion willconsequence of flow of spent gas from the base of the hood adjacent the ports 2| inward through passageways 25 to the stream of burning gases that springs from burner block 6, an equilibrium of pressure is established throughout the course of stream flow, with the consequence and eflect that localized concentration of heat is avoided, heat absorption by the muflle walls is more evenly distributed and brought to maximum total value, and the life of the structure is prolonged.

Another and an alternative elaboration of structure, rendered possible by the reorganization of the furnace and the arrangement of the burner at the centre with stream flow upward through the centre of the muille and downward over the outside, is illustrated in Fig. VI. In this case the passageways 25 are not provided. Instead, the floor plate IN is provided with central and peripheral troughs 26 and 21 adapted to contain proper quantities of sealing liquid. Both troughs extend downward below the level of the floor plate; the walls of the inner trough 26 rise above the level of the floor plate and between the burner block I06 and the hearth block I02; these two blocks in this case being spaced apart sufficiently to allow such an intrusion of the trough. The walls of trough 21 are arranged wholly below the level of the floor plate. The muflle is so adapted that, when in place, it is borne by the floor plate and yet its outer and its inner lower rims extend free within the two troughs 26 and 21. To accomplish this the inner wall of the muflle near its lower end is provided with a flange 28, by which it rests on the rim of trough 26 with its own rim extending free within the trough 26, while the outer wall of the muille near the lower rim is spread outward in a flange-like plate 29 which in the assembly rests immediately upon the floor plate NH, and at the outer edge of this outward spreading flange-like plate 29 the muille wall is continued in a downward prolongation 36 that extends free within trough 21. The hood when applied rests immediately upon the flange 29 of the muille, which flange in turn rests immediately upon the floor plate It. The two troughs 26 and 21, arranged as they are beyond and beneath the substantially continuous horizontal wall of refractory material afforded by the burner block [06, the base block I02, and the hood 5, are remote from the region of intense heat. With such arrangement the seals for both the inner and the outer rims of the mufile may be liquid seals, and in consequence the isolation of the material under treatment within the muille may be rendered more perfect. More complete protection of the liquid seals from access of heat may be afforded by cooling the floor plate by means of streams of liquid circulating in conduits 3| arranged beneath and conveniently formed upon its lower face.

I claim as my invention:

1. In an annealing furnace of muiiie type and having a muil'ie of annular shape, such furnace including a base, a muifle, and a hood, the muifle and the hood being severally applicable to and removable from the base and when applied forming between themselves a furnace chamber, the invention herein described which consists in means for introducing flame to the furnace chamber at the base of the columnar space defined by the inner wall of the annular mufile,

and flues for the products of combustion opening from the furnace chamber through the hood and at the base thereof.

2. The structure defined in claim 1, having the additional provision of a pressure-equalizing passageway leading from the outer basal portion of the furnace chamber to the inner basal portion thereof.

3. The structure defined in claim 1, having the additional provision that the base is provided with inner and outer concentric sealing troughs in which the inner and outer lower rims of the mufile are borne, and pressure-equalizing passageways arranged beneath said sealing troughs and leading radially inward from the outer basal portion of the furnace chamber to the inner basal portion thereof.

4. The structure of claim 1, the base including a floor plate with inner and outer concentrically arranged troughs for sealing liquid extending below the level of the floor plate and opening upwardly through the floor plate, the muflle at its lower end being adapted, when applied, to rest upon the floor plate, the muflle being provided with rims that, when the muflle is applied, enter the said troughs, and, so entering, are adapted to be submerged in liquid contained therein.

5. In an annealing furnace of muflle type and having a muflie of annular shape closed above and at its lower end terminating in inner and outer concentric rims, the combination with a floor, a hearth block of refractory material and of annular shape borne by the floor, a burner block of refractory material centrally arranged within the hearth block, a trough adapted to contain sealing liquid formed in the floor, opening between hearth block and burner block, and extending below the floor level, a second trough adapted to contain sealing liquid formed in the floor at an interval beyond the outer edge of the hearth block and extending below the floor level, the muflie provided adjacent its lower inner and outer rims with supporting flanges, which flanges when the muflie is applied bear upon the floor and support the muflle with its rims in sealing positions within the troughs, a hood of refractory material adapted to rest by its rim upon the floor-engaging flange of the outer rim of the muflle. and a burner adapted to deliver a flame through the burner block, the burner block, the hearth block, and the hood forming at the floor a substantially continuous wall of refractory, protecting the bodies of liquid in the said troughs from access in injurious quantity of heat from EDWARD I.

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