US2068477A - Furnace - Google Patents

Description

Jan. 19, 1937. .1. c. wooDsoN FURNACE Filed April 17, 1936 4 She ets-Sheet 1 INVENTOR Jan. 19, 1937. J. c. WOODVSON FURNACE Filed April 17, 1936 4 Sheets- Sheet 4 INVENTOR Patented Jan. 19, 1937 PATENT OFFICE FURNACE James 0. Woodson, Cleveland, Ohio, assignor to Lee Wilson, Cleveland, Ohio Application April 17 1936, Serial No. 74,958

11 Claims.

' My invention relates to a furnace and, more particularly, to a furnace of the general type described and claimed in United States Patent to Wilson No. 1,952,402.

My invention comprises an improvement upon the construction disclosed in said patent, particularly as regards the shape and mounting of the heat exchange tubes, and theconstruction of the furnace base. In accordance with the present invention, I provide a furnace of the general type of that shown in the patent with a plu- .rality of one-piece heat exchange tubes bent to a smooth curve substantially throughout their length. This construction eliminates joints in .the heat exchange tube, permits them to be fabricated of welded tubes and makes it possible to install them by inserting one end inwardly through a suitable opening in the side wall of the furnace and outwardlythrough another opening, by moving the tubes therethrough in one direction only.

The above invention also contemplates an improved form of baffle for the heat exchange tubes, to increase the heating efficiency, as disclosed in a copending application Ser. No. 49,078 of Wilson and Corns. I

Another novel feature of the invention is the provision in the furnace base of a layer of refractory units such as brick or block, laid dry,

or without mortar, on a suitable supporting framework. A charge supporting plate is carried above the refractory layer on cross beams embedded therein. This construction avoids warping and distortion of the base which has resulted in previous constructions from the ex posure to the heat of the furnace of metal parts rigidly attached to the frame of the base.

'A- preferred embodiment of the invention is illustrated in the accompanying drawings to which reference is made for a complete understanding thereof. In the drawings:

Figure 1 is a partial transverse sectional view through the cover of a furnace;

Fig. 1A is a vertical section taken through a heat exchange tube isolated from the remainder of the furnace, showing the manner of mounting the baflies therein;

Fig. 1B is a transverse section along the line iB-IB of Fig. 1A;

Fig. 2 is a view of the furnace cover partly in longitudinal section and partly in side elevation;

Fig. 3 is a plan view of the furnace base; Fig. 4 is a partial sectional view taken along the line IV-IV of Fig. 3 with parts shown in elevation;

Fig. 5 is a similar view taken along the line VV of Fig. 3;

Fig. 5A is a longitudinal central section through a curb extending peripherally of the furnace base; I

,Fig. 5B is a transverse sectional view taken along the line 5B5B of Fig. 53; line Eli-5A of Fig. 5B indicates the plan of the section shown in Fig. 5B;

Fig. 6 is a plan view of a refractory layer taken along the line VI-VI of Fig. 4; and

Fig. '7 is a similar view showing the cross beams incorporated in the refractory layer taken along the line VII--VII of Fig. 4.

Referring now in detail to the drawings and,

- for the present, to Figures 1 and 2, particularly, avfurnace cover indicated generally at Iii comprises refractory side walls ii, end walls I2, and a roof l3 assembled within a structural framework l i and a casing l5 of metal plate. The cover is provided with a flange i6 depending on the bottom thereof adapted to enter a sealing channel on a charge supporting base with which heat exchange tubes, as shown in Fig. 1, are bent v to a smooth curve substantially throughout their length, only about the upper quarter of the length departing from the curve and extending along a substantially straight line. While I prefer to give the bent portion of the tubes substantially the curvature of a parabola, the exact degree or shape of curvature is not limited to that shown. The tubes li extend through close fitting openings in an outer refractory member l8 forming part of the side walls of the cover and through larger openings IS in an inner refractory layer 20. The members l8 are free to move up and down as the tubes expand and contract.

Channels 2| extend along the side walls above and below the emerging upper ends of the tubes [1. Each tube is'attached near its upper end to a plate 22 adapted to be secured to the channels 2|. A sealing and insulating layer 23 is formed around the upper end of each tube, behind the plate 22 being preferably cast in plastic form and allowed to set around the'tube adhering permanently thereto.

The lower ends of the tubes il float freely because the blocks l8 through which they extend are slidable in the cover wall. The tubes are rigidly anchored only at their upper ends to the plates 22. This permits expansion or contraction of the tubes on heating and cooling thereof, without injury to the refractory lining or other parts of the structure.

A burner 24 is mounted in the lower end of each of the tubes II. A spark gap lighter 25 is mounted adjacent the end of each burner. The lighter 25 is connected to the secondary winding of a. transformer indicated at 26. The construction and system of connections of the spark gap lighters are described more fully and claimed in the copending application of James C. Woodson, Serial No. 58,705, filed January 11, 1936 for Electrical ignition system and method for furnaces.

A string of baflies Ila secured together by pins I'lb is suspended in each tube I! by a hook IIc. As explained in copending application Ser. No. 49,078, these baflles increase the heating efflciency of the tubes and cause the greater part of the combustion to take place in the lower portion of the tube.

Fuel is supplied to the burners 20 from a manifold 21 connected to a supply line 28 through a main valve 29. Branch connections 39 including control valves 3| extend downwardly from the manifold 21 to Venturi passages 32, each of which supplies a fuel-air.mix-

ture to a pair of burners 24 through flexible connections 33, the air being induced into the Venturi passages by the flow of fuel therethrough.

The manifold 2i, the connections 30, valves 3! and passages s2 as well as the transformers 26, are enclosed within a compartment 34 formed by channels 35 extending along the side walls of the furnace and a covering panel 35. Holes 3'! in the panel 336 admit atmospheric air to the induction ports of the Venturi passages.

The connections 35 are similarly enclosed behind a panel 38 and between channels 35. The enclosure for the connections 33 is gas tight and thus forms a seal preventing leakage of the gaseous atmosphere usually maintained within a furnace cover.

It will be apparent that upon the delivery of a fuel-air mixture to the burners '24 and the application of sufllcient voltage to the spark gaps 25, the mixture issuing from the burners will become ignited. Combustion of the fuel takes place as the mixture advances through the tubes ii. The latter are thereby heated to a high temperature and radiate heat to a charge of material enclosed by the cover and resting on the base to be described in greater detail later. After complete combustion, the gases are discharged to the atmosphere through the upper open ends of the tubes I'I.

Referring now more particularly to Figs. 3 through 7 for a detailed description of the base, the latter, indicated generally at 45, includes a frame composed of longitudinal beams 46 connected by transverse beams 41. A bottom plate 48 overlies the frame and has an upstanding peripheral wall 49. A similar wall 50 is spaced inwardly of the wall 49, the two together providing a sealing channel extending around the edge of the base.

A row of blocks 5| of a relatively strong, yet lightweight material such as haydite" extends around the base within the wall 50, the latter being reinforced by gussets 52. Within the row of blocks 5| is a curb 55 composed of refractory blocks disposed side by side. The curb 53 is provided at intervals with bumper plates 54,

aoeacw to protect the curb against injury by the lower edge of the furnace cover shown in Figures 1 and 2, as the latter is lowered into a position such that it rests'on the cover supporting shoulder formed by the row of blocks 5|.

As shown in Figs. 5A and 5B, the bumper plates 54 have integral'ribs 540,. As the curb is constructed the ribs of the bumpers are inserted between notched out portions of adjacent curb blocks and secured in position by pins 54b. The inner ends of the bumpers overhang the outer flange 59 of the inner sealing channel as shown at 540. This construction locks the bumpers to the curb and prevents inward warping of the outer flange of the sealing channel.

Within the curb 53, a row of refractory blocks 55 extends around the base. The space within the row of blocks 55 is filled with hollow tile indicated generally at 56.

On top of the tile 56, a relatively thin block of refractory material 51 is disposed. Similar material is placed under the curb 53 and the blocks 55. A sealing pan 58 rests on the block 51 and the blocks 55 and has spaced walls 59 upstanding thereon forming an inner sealing channel. The surface of the sealing pan 59 within the inner wall 59 is covered by a layer of fire brick 60. The refractorylayer 60 has longitudinal and transverse expansion joints 6i embedded in the several courses thereof.

Cross beams 62 rest on the refractory layer 60. The spaces between adjacent beams are filled with refractory bricks 63. The bricks indicated at 60 and 63 are laid dry and are held in position by the inner wall 59 of the inner sealing channel. Straps 64 extend between the ends of adjacent cross-beams and are secured thereto, to hold the bricks 63 between the cross-beams.

A charge supporting plate 65 rests on the cross-beams. When a charge of material such as sheets, to be annealed, is placed on the plate 65, the load is carried by the cross-beams and the brick therebetween, to the refractory layer 66, the hollow tile 56 and thence to the frame of the base comprising the beams 46 and 41 which rest on any suitable foundation.

Inlet pipes 66 extend inwardly of the ends of the base and upwardly through the refractory layers thereof, for supplying a gaseous atmosphere of any desired character to the space within the cover. A thermocouple pipe 61 similarly extends inwardly from the sides of the base.

In the construction just described, the refractory layers 60 and 63 constitute a chargesupporting pier, the metal parts of which, viz., the beams 62 and the plate 65, are relatively free as regards the remainder of the metallic structure of the base such as the frame composed of beams 46 and 41. As a result, the expansion or contraction of the metal parts exposed to the furnace heat does not cause distortion or warping of the base. The bricks of which the refractory layers are formed are free to move individually and thus provide a further safeguard against warping. The sealing pan 58 prevents the escape of the furnace atmosphere through the refractory bricks which are not absolutely impervious thereto and during cooling prevents atmospheric air and moisture from passing through the refractory into the space under the inner cover. The infiltration of moisture or atmospheric .air carrying moisture through the refractory interferes with securing the desired bright annealing. By the use of the sealing plate which extends continuously under hinted at.

over the charge into position with its lower edge penetrating the sealing material disposed in the channel. The inner wall of the channel also maintains the bricks of refractory layer 60 in position.

The advantages of the heat exchange tube shown in Figs. 1 and 2 have already been They include a reduction in cost as compared with earlier types of heat exchange tubes employing elbows which required welding in the cover and careful bricking up around them. The curved tube and the manner of suspending it described herein greatly facilitates changing or renewing tubes so that this operation can be performed without shutting down the furnace any material length of time. The

free floating lower end eliminates the setting up of any stresses as a result of expansion or-contraction of the tubes.

Although I have described and illustrated herein but one preferred form of construction of a furnace cover and base, it will be obvious that changes in the construction shown may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A base for a cover type furnace comprising a structural frame, a bottom plate overlying the frame, a pier composed of a plurality of layers of refractory units built up on said plate, a sealing pan between certain of said layers, sealing channels extending peripherally of said pan and plate, and a curb between said channels.

2. The combination with a base for cooperation' with a cover type furnace, of a peripheral curb upstanding from said base, and bumpers spaced along said curb having portions extending thereinto and secured thereto.

3. The combination with a base for cooperation with a cover type furnace, of a peripheral curb upstanding from said base, a sealing channel inside of said curb comprising inner and outer flanges, and bumpers spaced along the curb, the inner ends of the bumpers overhanging the outer flange of said channel.

4. A base for a cover type furnace comprising a frame, a refractory hearth built up on said frame. a sealing pan on the hearth comprising a metallic plate and a channel formed around the outside of said plate and 'being contiguous with the plate, the edge of the plate forming the bottom of the channel, a refractory pier on said pan inside the channel, and a refractory curb on the hearth adjacent to and around the exterior of the channel serving to protect said channel and restrain the pan against lateral movement.

5. A furnace comprising a hearth and a cover having side walls and a roof, a burner tube having a gradually curved intermediate portion merging directly into upper and lower terminal portions, the burner tube having the curved intermediate portion inside the furnace and having the end portions passing through a side wall of the furnace at an obtuse angle to each other, the tube being disposed in a vertical plane and having a burner at the lower terminal portion thereof, the lower terminal portion being inclined inwardly and upwardly.

6. A furnace comprising a hearth and a covering having side walls and a roof, means for heating material disposed in the furnace comprising a plurality of tubes disposed in a vertical plane, the tubes having a curved intermediate portion inside the furnace, which intermediate portion merges directly into upper and lower terminal portions, the terminal portions of the tube passing through the side walls of the furnace at an obtuse angle to each other, the tubes being provided at their lower ends with a burner, the intermediate portion and the lower terminal portion of the tubes describing a parabola.

'7. The furnace defined by claim 6 characterized by said tube being suspended at its upper terminal portion, the lower end of the tube being free-floating.

8; A base for a cover type furnace, comprising a structural frame, a bottom plate overlying the frame, a pier composed of layers of refractory material built up on said plate, a charge supporting plate resting on the upper layer, a sealingpan in said pier, the edges of said pan, projecting outwardly of the edges of the layers thereabove, and means including arefractory curb extending around the pier but spaced therefrom to provide a sealing channel along said pan edges.

9. A base-for a cover type furnace comprising a frame, a refractory hearth built up on said frame, a sealing panon the hearth having a refractory pier thereon, the pan projecting beyond the pier, a sealing channel extending around the edge of said pan, and means including a refractory curb extending around the outer edge of the pan and spaced from said pier, forming the outer wall of said channel.

10. The base defined by claim 9 characterized by a second sealing channel extending about the periphery of the base. said refractory curb being between the two channels adjacent to and around the exterior of the first channel and providing a protection therefor.

11. A base for a cover type furnace comprising a frame, a refractory hearth built up on said frame, a sealing pan on the hearth, a charge-supporting pier on the pan. said pan comprising a metallic plate, and means including a refractory curb along the edges of the plate and spaced from said pier, defining a channel around the outside of said plate, the edges of said plate extending beyond the inner wall of the channel sufficiently to form a barrier against infiltration of air through the hearth.

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