US2935927A - Electric melting furnace hood - Google Patents

Description

May 10, 1960 R. c. ORTGIES ELECTRIC MELTING FURNACE HOOD 3 Sheets-Sheet 1 Filed April 16, 1956 INVENTOR. RAYMOND C.ORTG|ES FRONT ATTORNEY May 10, 1960 R. c. ORTGIES ELECTRIC MELTING FURNACE noon 5 Sheets-Sheet 2 Filed April 16. 1956 Fig.7

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ELECTRIC MELTING FURNACE HOOD Filed April 1s, 1.956 3 Sheets-Sheet z INVENTOR. d RAYMOND C.ORTGIES MAW ATTORNEY ELECTRIC MELTING FURNACE HOOD Raymond C. Ortgies, Louisville, Ky., assignor to American Air Filter Company, Inc, Louisville, Ky., a corporation of Delaware Application April 16, 1956, Serial No. 578,370

6 Claims. (Cl. 98-115) The present invention relates to an improved hood for ventilating electric melting furnaces.

In the operation of electric melting furnaces, large quantities of smoke and gases are given off. These must be collected and carried off to avoid contaminating the surrounding atmosphere. This is usually accomplished by enclosing the top of the furnace in a suction hood which communicates through a duct system with a remote dust separator. The conventional hood used is constructed of heavy steel plate and rigidly reinforced throughout to withstand the extreme temperatures to which it is subjected. It is also constructed as an integral unit which makes it very cumbersome and preventsconvenient access to the top of the furnace roof.

With the advent of larger furnaces and the higher temperatures used for obtaining better refining, larger and heavier hoods have been employed. As a result, the difficulties experienced with warping and twisting have been substantially increased. This often varies the annular clearances around the electrodes, where they enter the hood, sometimes causing them to short out against the hood structure. Warping of the hood may also cause it to bind on the furnace structure which makes it diflicult to remove when access to the furnace roof is desired.

The primary object of this invention is the provision of a furnace hood, which, by virtue of its improved construction, accommodates substantial expansion, when subjected toex-trerne temperatures, without warping or twisting in an objectionable manner or to a degree causing serious binding difiiculties.

A more particular object is to provide a furnace hood which will withstand high temperatures without warping or twisting to the extent that the electrodes will short out against the hood structure.

A further object is the provision of a furnace hood of sectionalized construction for ease in handling and access to the furnace roof.

In carrying out my invention, I reduce the 'difiiculties heretofore encountered with a rigidly constructed hood by vertically dividing the hood longitudinally from side to side into at least three (3) sections comprisingtwo (2) side sections and an intervening top section and by connecting each of these sections separately and independently to the centilever beams ofthe furnace so that each section is free to expand and contract independently of the other sections.

the top section with conventional elongated stiifenersbut, instead of making this connection rigid, I make it slidable so that the stiffeners will. restrict the warping of thetop and still accommodate relative-horizontaLmovemeat of the top due toits expansion and contraction at a rate different from that ofthe stitfeners.

rates Patent It will be understood thatthe ,front and rearwall sections, required to complete the Patented May 10, 1960 2 The invention is illustrated in the accompanying drawing wherein: 7

Figure 1 is a plan view of a hood embodying the invention, the outline of the furnace roof being shown in dotted lines;

Figure 2 is a partly broken front elevational view of Figure 1 with the furnace structure outlined in dotted lines; g 7

Figure 3 is a sectional view taken along the line III-III of Figure 1 with the outer limits of the roof ring partly outlined by dotted lines;

Figure 4 is a fragmentary perspective illustrating certain details of the hood structure; Figures 5-7 are sectional views taken along the lines V--V, VI-VI and VII-VII respectively of Figure 1;

Figure 8 is a plan view of a modification of the invention;

Figure 9-is a partly broken front view of the modification of Figure 8; and

Figure 10 is a fragmentary perspective illustrating certain details of the hood structure in the modification of Figs. 8 and 9.

Referring to the drawing, the outline of the furnace 1 with pouring spout 2, charging receptacle 3, andelectrodes 4 is shown in outline form in Figure 2with the furnace hood assembly in operative position and substantially enclosing the roof ring 5 of the roof, the top of which roof and ring are shown in outline formin Figures 1 and 2. Cantilever arms 6, 6' which are pivotally supported at some remote point to the rear of the furnace, extend horizontally over the furnace roof and are used for lifting the furnace roof and hood assembly as a unit to a' position sufiiciently above the furnace to vclearit and then swinging that unit aside. The connect tions between the cantilever arms and the roof form no part of this invention and are not shown.

The cantilever arms, 6, 6, are also utilized in the present invention to support the furnace hood assembly. This assembly comprises: a top section in the 'forniof a heavy, fiat steel plate 7 which extends horizontally over and covers a major portion of the furnace roof; "a rear end section 8 which substantially encloses the portion. of the top of the furnace roof at the rear end of top plate 7; a front end section 9 which substantially encloses the frontend portion of the furnace roof; fa side section 10 which substantially encloses that portion of the top of the furnace roof lying on the outer side of (left) cantilever arm 6; and a side section ll'which substantially encloses that portion of the top of the are nace roof lying on the outer side of (right) cantilever arm 6'. The top hood section 7 cooperates with cantilever arms 6, 6, the various other (front, rear and side) sections of the hood and the furnace roof to provide a substantially closedhood chamber over the furnace roof. Gases which escape from the furnace during refining operations are collected in this hood chamber and, by means of an exhausting dust separator (not shown), are drawn off from the furnace hood chamber through (right)s i de section 11, plenum 14 and duct 15. With the particular type of furnace shown in Figure 2, which includes a pouring spout 2 and a charging r'eceptacle, 3, it is desirable that' gases, given offal: such times as these components are used, be captured and drawn into the furnace hood chamber. To facilitate this, front end section 9 is provided with a canopy "12 which extends outwardly from the front 'end section 9 and has an open bottom and front which functions as a suction inlet during charging operations. Side section 10 also has a pouring spout canopy 13' which extends outwardly over the pouring spout 2. To assist in compelling the gases given off in the pouring operation to flow into "the inlet of canopy 13, the space on each side of the spout 2,

.of plates 17, 17.

between the spout and the canopy, is bafiied by welding a plate 16 to the furnace. Both canopies 12 and 13 are preferably provided with a damper therein (not shown) which may be closed, during non-charging and non-pouring intervals, to prevent the admission of excessive amounts of air to the hood. Since these canopies form no part of the present invention they will not be further described.

The top plate extends across the roof space between cantilevers from adjacent the bottom of one cantilever to the other. It is supported from cantilever arms 6, 6' by plates 17, 17' which are welded or by other suitable means fastened to the bottom surface of arms 6, 6'. These plates 17, 17 have a portion which extends inwardly from arms 6, 6 and underlaps portions of the top plate 7. At those points where plates 17, 17 are fastened to arms 6, 6', rectangularly shaped cut-outs are provided in the top plate 7 so that triangularly shaped and vertically positioned gussets 18, 18' may be fastened to the inner side surface of arms 6, 6' and the upper surface These gussets serve not only to strengthen plates 17, 17 but also prevent any substantial lateral movement of top plate 7 towards the direction of either end section.

The central part of top plate 7, is provided with a somewhat triangular opening 32 through which the electrodes 4 pass into the furnace. Hinged electrode doors 19 are provided on top of the top plate 7, one on each side of the opening 32, to close off the opening except for a small annular clearance around each of the electrodes. T-bars, which extend across the closed-off portion of the opening, support the electrode doors in their closed position. At the four corners of top plate 7, additional cut-outs 27 leave openings between the arms 6, 6' and the edges of top plate 7. These openings are sized in accordance with the quantity of air which is to be exhausted from the furnace hood chamber, and function as the main inlets for this air.

Heavy stiffener members such as rails 20 are arranged on the top surface of top plate 7 and may be rigidly fastened thereto. Preferably, they are welded to the top at one point along their length. At spaced intervals along the remainder of the rails lengths, inverted L- shaped clips 21 (Figures 1 and 6) are positioned with the end of one leg of each clip welded to the top plate 7 and the foot thereof extending over a part of the flange of the rail and holding the flange against the top plate 7. On other areas of the top plate 7 additional stiffener members in the form of bars 22 (Figure 7) with saddle clips 23 are used. The saddle clips have their outwardly extending flanges rigidly fastened to top plate 7 and the bars 22 are thus free to move in relation to the clips and top plate. These bars 22 may also be welded to the top plate 7 at some point along their length preferably remote from the clips. Thus it may be seen that with the present invention the top plate 7 may expand and contract freely while the stiffener members 20 and 22, which are not subject to the intense heat, restrain any tendency of the plate to warp, twist or sag. It is also to be noted from Figure 1 that the distance between the inner side surfaces of arms 6, 6' is slightly greater than the corresponding sidewise dimension of top plate 7. This permits expansion of the top plate between the arms without any resultant binding therebetween.

To provide a support for the front end section 9 of the hood, a cross channel-shaped member 24, with its flanges directed rearwardly, is positioned to extend across the space between the upper corners of the free ends of the cantilever arms and is rigidly welded thereto. The bight of this cross channel member 24 carries a 2 member 25 which, in cross section, extends horizontally rearward into engagement with the bight of cross member 24, thence downwardly beyond the bottom of the bight to the level of the bottoms of the cantilevers and thence rearwardly to the underside of the top plate 7.

The upwardly facing surface of the uppermost flange of 2 member 25 carries a series of upright pins 26 integrally secured to it. These pins serve as a means for detachably holding the front end section 9 in its operative position and are therefore positioned to correspond with the position of the pinholes in the top surface of the front end section 9. The lower horizontal flange of 1 member 25, in underlapping the front edge of top plate 7, helps to support the top plate and, at the same time, effects a closure of the hood chamber along the front edge of the top plate.

Rear end section 8, which does not have the extra weight of a canopy, may and preferably is supported directly from the rear end of the top plate 7. Accordingly, the rear edge of the top plate is turned upwardly at 33 and then flanged rearwardly and this rearward flange is provided with a series of upright pins 26 corresponding to pinholes in the rear end section 8.

The side sections 10 and 11 preferably are detachably fastened in operative position by means of pins 26. Accordingly, angles 28, 28, each carrying a row of upright pins 26, are fastened along the outer sides of cantilever arms 6, 6 respectively. Naturally, the side sections are provided with appropriate pinholes.

The space between the furnace roof ring 5 and the lower end of the outer wall of each of the two end sections and of the two side sections should be closed. Accordingly, the lower end of the outer wall of each section is turned inwardly to provide a bottom closure 29 extending across the adjacent space.

The front corners of the hood chamber, between opposite ends of the front end section 9 and adjacent ends of the side sections 10 and 11, are closed by providing the opposite ends of section 9 with wings extending underneath cantilevers 6, 6' and by providing side sections 10 and 11 with wings such as the wings 10a on section 10, which also extend underneath the cantilever arms and terminate near the vertical edge of wings 9a. These wings 9a and 10a are spaced, below the bottom of the cantilevers, a distance sufficient to enable the sections to be raised enough to clear the pins 26.

The rear corners of the hood chamber are closed by interposing, between opposite ends of the rear end section 8 and the adjacent wing of the side sections, such as the wing 10a of side section 19, members 30 and 31, each of which closes off the bottom and the sides of the intervening space but leaves, along the inner side of the adjacent cantilever, a top opening which constitutes a part of the inlet opening 27. The members 30, 31 are most conveniently secured to the bottom side of the cantilevers. It will be apparent that any of the individual perimetric sections may be simply and quickly removed from the remainder of the furnace hood assembly by lifting any of the individual sections a sufficient distance to clear pins 26 and then swing the section away from the remainder of the hood assembly. In this embodiment the top and rear sections could be removed together but normally it will be desirable to remove the rear section first.

Side section 11 not only acts as part of the enclosing chamber, but also provides an open passageway from the chamber to plenum 14. Section 11 and plenum 14 are not joined together and thus when the furnace roof and hood are raised by arms 6, 6' and swung aside, plenum 14 remains in its mounted position on furnace 1.

Figures 8, 9 and 10 illustrate a modification wherein the top plate 7 is operatively positioned above the cantilever arms 6, 6'. The front and rear margins of the top plate are extended forwardly and rearwardly respectively to form the top of the front and rear sections and then turned downwardly to form the perimetric walls of such sections. These walls may be provided with wings to assist in closing the corners of the hood chamber, but the wings should allow the hood to be raised enough to clear the angles 35 whichare referred to later. The

side edges of the top plate 7 are rigidly attached to elongate box members 34, 34. These box members rest on the upper surfaces of the cantilever arms 6, 6' and are unattached thereto so as to provide for either lateral or longitudinal expansion of the top plate. Top plate restraining means, in the form of angles 35, are provided at the ends of members 34, 43', said angles being rigidly fastened to the top surface of the cantilever arms and spaced slightly away from the end corners of the box members. The spacing of these angles from the end corners of the box members is determined in accordance with the anticipated expansion of the top plate.

In the present modification, the side sections 10 and 11 may be detachably secured as before. The bottom space of the hood chamber between the perimetric sections and the roof ring may be closed as before. If desired the side edges of the bottom closures on the top (including front and rear) sections may be spaced slightly inward from the inner side surfaces of cantilever arms 6, 6' to provide for simple removal of the top plate 7 and its associated end sections. The front corner wings may be fastened to the cantilevers rather than to the front section. I

In other respects, the modification is similar to the previously described embodiment of this invention with slight changes in constructions such as fastening the securing pins 26 for the side sections on the top surface of cantilever arms 6, 6 rather than on angles attached to the side of the cantilever arms, and such as rearranging the, position of the stiffener members 20 and 22 to provide increased stiffening of the top plate 7 around the triangular opening 32.

Having described my invention, I claim:

'1. A hood for the top. of a furnace of the type hav: ing a pair of laterally spaced beams extending horizontally forward over its top, comprising: hood forming means extending over the top of the furnace and cooperating with the roof thereof to enclose a chamber therebetween, said hood forming means having a front-to-rear extending central assembly covering an area bounded generally on the sides by said laterally spaced beams, said central assembly being composed of a top section forming a top wall, and end sections forming the perimetric front and rear end walls of said hood, said hood forming means further having, on the outer side of each beam, a side section forming the perimetric side walls; interengaging support means integrated with and shared by said central assembly and said beams detachably mounting said central assembly on said beams; and interengaging means integrated with and shared by said side sections and by said beams detachably mounting each of said side sections to the adjacent beam.

2. The hood of claim 1 wherein: said top section of said central assembly includes a top plate loosely mounted on said support means for substantially unrestrained horizontal expansion and contraction.

3. The hood of claim 2 including: means for reinforcing said top plate against warping and twisting com- 1 prising a stiffener member and means holding the stiffener member in firm frictional contact with the plate while allowing relative movement therebetween to accommodate dilferential expansion and contraction.

4. The hood of claim 3 wherein: the holding means ineludes means rigidly secured to the plate and held thereby in firm frictional engagement with said stifiener member. 7

5. The hood of claim 1 wherein: at least one of said end sections is separable from said top section.

6. The hood of claim 1 including: means providing perimetric walls forming an upwardly open air inlet opening between one end of a side section and the adjacent end of an end section.

References Cited in the file of this patent

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