US2800318A - Slot furnace - Google Patents

Description

July 23, 1957 G. E. MARKLEY SLOT FURNACE Filed Sept. 11, 1955 5 Sheets-Sheet 1 FIG 2 FIG I INVENTOR. GEORGE EMARKLEY BY July 1957 E. MARKLEY 2,800,318

SLOT FURNACE Filed Sept. 11, 1955 3 Sheets-Sheet 2 INVENTOR.

GEORGE E. MARKLEY July 23, 1957 G. E. MARKLEY SLOT FURNACE 3 Sheets-Sheet 5 Filed Sept. 11, 1955 FIG 7 FIG ll INVENTQR. GEORGE E. MARKLEY W This invention relates to industrial furnaces of the class comprising a slot in the wall of the furnace through which work pieces in the form of bars etc. may be projected into the furnace chamber to be heated preparatory to forging, bending or otherwise working them.

Known furnaces of this class have objectionable features; among which are that flame and heat from the burning fuel in the furnace chamber flows back out of the slot; and the attendant worker who must stand close to the slot to serve the furnace, is exposed to the heat thereof; and this besides being a safety hazard, reduces the efficiency of his operations.

Another objection is that such furnace as is well known, are thermally ineflicient because of incomplete combustion of the fuel; and because the work being heated is not exposed to the heat produced by the fuel in a manner to efl iciently absorb the heat. I

Other objections to present slot furnaces are known.

It is among the objects of this invention to provide a slot furnace in which the objections referred to above among others are obviated.

Other objects are:

To provide generally an improved construction of slot furnaces;

To provide generally an improved construction of slot furnace firing burners;

To provide a slot furnace having an improved mode of operation;

To provide a slot furnace having improved means to prevent flame and hot products of combustion in the furnace chamber from being ejected back out of the slot;

To provide a slot furnace having improved means to increase absorption of heat in the furnace chamber by articles being heated therein;

To provide a metal heating furnace provided with a burner that fires fuel into the furnace chamber in a thin sheet of flame substantially the full width of the furnace chamber;

To provide a metal furnace provided with means to cause flame and hot products of combustion in the furnace chamber to rotate cyclically within the chamber and repeatedly over the work to be heated.

With these objects in view, and others which will occur to those skilled in the art to which the invention appertains, the invention as set forth in the appended claims has been made. p

The embodiment of the invention in a furnace construction chosen to illustrate and describe the same herein, comprises, in general, the following.

The fuel, preferably gas, is supplied into the furnace chamber from a gas manifold at controlled pressure, by a nozzle of improved form projecting into the slot.

The work pieces are projected through the slot and into the furnace chamber under the nozzle and lie on a floor, or hearth of the chamber.

A combustible gas and air mixture is supplied to the burner at high pressure and the burning fuel leaves the burner nozzle at highvelocit'y.

-. States Patent The burning fuel impinges on and flows over the work in contact therewith at high velocity, and thereby continuously wipes off therefrom the heat insulating film that tends to form thereon, whereby heat is efliciently absorbed by the work.

The interior wall surface of the chamber is formed so as to cause the high velocity flame and products of combustion to flow over the work to the rear of the furnace chamber and then successively upwardly and for- Wardly and downwardly and again rearwardly over the work and so on, cyclically, in a revolving stream of flow; and the fuel is thereby brought into high velocity contact with the work, repeatedly, whereby more of the heat units of the fuel are absorbed by the work.

The roof of the chamber is provided with outlets through which burnt fuel escapes as the stream cyclically revolves; and, as observed in operation, very little flame is ever seen to emerge from the outlets, indicating that the combustion is complete; and also indicating that the burnt fuel or products of combustion are largely on the outside of the revolving stream and the burning hottest part is on the inside where its heat can be most readily absorbed by the work.

The high velocity of the fuel entering the furnace at the lower part of the chamber and at the level of the slot, and the revolution of the flame and products of combustion in the chamber, prevents the development of back pressure at the slot so that no flame or hot prodnets of combustion emerge back out of the slot.

The burner and manifold are constructed so that the linear direction of the fuel at nozzle velocity may be readily adjusted to be horizontal or at a selected downward angle toward the work, in accordance with the thickness of the work, and to attain optimum operating conditions.

The nozzle projects the flame into the furnace chamber in the form of a thin sheet of flame, the sheet of flame being as wide transversely of the chamber as the chamber itself, whereby a layer of work as wide as the chamber will be uniformly heated, and all parts of the flame and products of combustion will be uniformly propelled around the chamber between its side walls in the cyclical revolution thereof referred to.

An embodiment of the invention is fully described in the following description taken in connection with the accompanying drawing in which:

Fig. 1 is a front elevational view of a furnace embodying the invention;

Fig. 2 is a top plan view of the furnace of Fig. 1;

Fig. 3 is a fragmentary side elevational view of the furnace of Fig. 1;

Fig. 4 is a sectional view taken from the plane 44 of Fig. 1;

Fig. 5 is a sectional view from the plane 55 of Fig. 4;

Fig. 6 is a fragmentary sectional view from the staggered plane 66 of Fig. 4 showing in plan view a fuel manifold and burner construction of the furnace of the other figures;

Fig. 7 is a view of the said manifold and burner taken in the direction of the arrow 7 of Fig. 6;

Fig. 8 is a sectional view of the burner and manifold taken from the plane 8-8 of Fig. 6 and to enlarged scale;

Fig. 9 is an end view of the burner taken in the direction of the arrow 9 of Fig. 8;

Fig. 10 is a fragmentary view showing the manifold and burner of Fig. 4 in a different adjusted position; and

Fig. 11 is a longitudinal sectional view of a coupling which I may employ.

Referring to the drawing there is shown, at 10-40, legs supporting a furnace proper 11. The furnace 11 comprises, a bottom wall 12, a rear wall 13, a top wall and all but the top wall 14 being generally enclosed in a steel sheet metal jacket 17.

A furnace chamber 18 is thus provided within the said walls.

The walls are constructed from refractory material, preferably blocks or bricks as shown. 7

The interior surface of the bottom wall 12constitutes a chamber floor or hearth 19 preferably horizontal;,,and

a portion ofthis wall may be made, of refractory conglomerate 20 as shown, to facilitate renewal.

The interior surfaces 21-21 of the side walls 16 of the chamber may be flat, vertical and parallel as shown.

a The interior surface 22 of the rear wall 13 continues from the floor 19, and is inwardly concave, for example, part-cylindrical, and curves rearwardly, upwardly and forwardly, and merges with the inner surface 23, of the top wall 14.

The inner surface 23 of the top wall is'downwardly concave at relatively large radius, and extends forwardly to and merges with the inner surface 24 of the front wall, the latter being in general inwardly concave and of form corresponding to that of the horizontally opposite portion of the rear wall surface 22 but being interrupted by a furnace slot 25 which opens through it.

The inner wall surface 24 terminates downwardly at a horizontal top wall surface 26 of the slot; the slot being forwardly open and inwardly communicating with the chamber.

The slot surface 26 is spaced upwardly from a horizontal bottom slot surface 27, the latter being preferably a continuation of the chamber floor 19.

The horizontally opposite end surfaces 28-28 of the slot 25 are preferably continuations of the chamber side' .wall surfaces 21-21.

The top wall 14 of the furnace chamber is provided with a selected number of openings or flues therethrough 29-29, of restricted size and number preferably provided by making the top wall of refractory bricks or blocksas referred to and by removing or omitting selected bricks; and the top wall may be a self-supporting masonry arch as shown but supports of heat resisting metal alloy may be provided.

As referred to, the work to be heated in the furnace may be in the form of bars projected at one end into the chamber 18 through the slot 25, and resting on the chamber floor 19 with the outer ends projecting out of the slot, and in some cases it may be desired to help support the outer ends by an apron, and one such apron is illustrated at 30 in the form of an angle section steel bar 30 extending along the front of the furnace.

A slag hole 31 is provided extending downwardly through the bottom wall 12, and open at thechamber floor 19, and normally plugged at its top opening by a plug of refractory clay or the like, whereby slag accumulating on the chamber floor may be drained off periodically by removing the plug, and then renewing it;

Or the hole 31 may be left open, or filled with pieces of stone jammed therein with openings therebetween.

As shown at 32 the front wall 15 may be extended upwardly above the level of the top wall 14 to serve as a heat barrier between the operator standing at the front of the furnace and the products of combustion emerging from the flues 29-29 in the operation of the furnace to be described.

The top wall of the slot is supported on a heat resisting casting 52 of Z section as shown one flange being bolted as shown to the front of the furnace and the web 54 of the Z being generally horizontal and supporting the slot top wall, the inner flange depending and serving a purpose to be described.

An important part of the invention is a fuel manifold and burner which will now be described.

A gas manifold 33 in the form of a length of pipe 34 extends horizontally across and adjacent to the front of .-the furnace; and is supported by a number, preferably two, of hangers comprising rings 35 telescoped over it; the rings having long studs 36 welded thereto, extending upwardly therefrom and passing through holes in a horizontal flange 37 of an angle section bar 38 mounted on the front of the furnace.

The studs 36 are threaded, and nuts 39 thereon at opposite sides of the flange, provide means for adjustably raising and lowering the ends of the manifold to position it and for locking it in adjusted position.

The manifold 33 is closed at one end, by a closure plate 48 welded thereon, and preferably of the same outside diameter as the manifold to facilitate telescoping it into the rings; and the other end is threaded for connection by standard pipe connections, to a pipe 41; which comes from a fuel supply system and apparatus, not shown in detail but indicated at 42.

This apparatus 42 may be of known commercial form and is therefore indicated diagrammatically, and comprises an automatic gas. and air mixer which proportions the air and gas in a combustible ratio, at all pressures of the air, and the air pressure may be set to a high value, so that a combustible fuel mixture is supplied to.the pipe 41 and manifold 34 at high pressure.

The manifold may be rotated in the hanger rings, suitable clearance being provided therefor, for a purpose to be described; and the threaded end may concurrently turn in the threads of the pipe connections; or a sealed rotary connection may be provided thereat to be referred to.

At any rotated position of the manifold it may be fixed thereat by set screws 35A in the rings.

, A burner nozzle shown generally at 43 projects from the side of the manifold 33 into the slot 25; and laterally the nozzle 43 extends substantially to the end surfaces 28-28 of the slot 25, and is therefore as wide as the furnace chamber between the inside surfaces of its side walls.

The nozzle 43, as best shown in Figs. 6 to 9, is generally in the form of a fiat tube, open at both ends, and may for convenience be made from rectangular plates 44-45 spaced apart and parallel, and with strips 46-47 welded to their opposite side edges.

One open end of the burner nozzle is inserted into a perforation 48 in the wall of the manifold, and secured to the manifold in sealed relation to the entire periphery of the perforation by welding, as indicated at 49-49.

Preferably, the burner nozzle 43 extends generally tangentially from near the underside of the manifold 33 as shown in Fig. 8.

The interior of the tube of the nozzle is divided up into a plurality of parallel longitudinal passages by which gas leaving the manifold and entering the nozzle is guided rectilinearly and evenly distributed laterally, through the nozzle and is discharged into the furnace chamber in that condition; and when ignited projects a thin sheet of flame into the chamber, the full width of the nozzle and the full width of the distance between the inner surfaces of the side walls.

As a convenient means for providing such passages, a sheet of metal is bent into corrugations and telescoped into the nozzle tube, substantially fitting it.

In Figs. 8 and 9, the corrugations are shown at 50-50 and the passages provided thereby, at 51-51.

The manifold may be adjustably rotated within the hanger rings 35-35 as described, to determine the direction of the sheet of gas flame from the nozzle. In Fig. 4 it is shown in an extreme horizontal position, and to aid in adjusting it to this position the depending flange of the aforesaid Z-bar 52 is disposed to serve as a stop engaged by the upper side of the nozzle.

The nozzle, however, if desired, may in some cases be inclined to the horizontal by adjustably rotating the manifold; one such position being shown in Fig. 10.

The aforesaid rotary seal connection referred to, for the supply-connected end of the manifold, when such is wanted, may be variously constructed. One form is assume nipple 57 and the inner wall surface of the sleeve 56 seals upon it. 7

The structure thus provides for sealed rotary and also longitudinal movement of the manifold to adjust its position, as will be understood.

The operation of the furnace followsi Gas regulated to a constant reselected high pressure at the apparatus 42 is supplied therefrom to the inanifold 33, and is projected therefrom out of the nozzle 43, into the furnace chamber at high velocity, and When ignited, and due to the form and construction of the nozzle, flame from the nozzle is projected into thechar'nher in a thin sheet of flame, extending across substantially the full width of the furnace, between the inner surfaces of its sidewalls. I

7 Work pieces to be heated, are laid on the horizontal floor 19 of the furnace chamber, and the high velocity flame is directed, (by positional adjustment of the no'zzle if necessary) to sweep over or brush the work, to continuously remove the usual heat insulating film that tends to form thereon, insuring efficient heat absorption by the work. p

The interior wall surface at the rear, top and front of the chamber have an inwardly concave form described above, that causes the flame, after passing rearwardly over the work initially, to be directed to flow in a revolving stream within the chamber, which recycles the heat of the flame andhot products of combustion, repeatedly over the work.

The edges of the thin flame are parallel to and are guided rectilinearly rearwardly by the inner surfaces of the side walls.

The cycling flow is initially over the chamber floor 19, then upwardly over the rear wall surface 22', and forw'ardly over the top wall surface 23, and downwardly over the front wall surface 24, and again rearwardly over the floor 19.

Heat units not absorbed by the work during the initial passage of the flame thereover, are absorbed by successive passages thereover due to the said cyclical revolution.

A few outlets or vents for burnt fuel are provided in the top wall of the chamber, the outlets being of restricted size and number, so that the revolution of the stream is not interrupted thereby.

The repeated cyclical revolution of the stream insures complete combustion, and insures absorption of most of the heat by the work; resulting in the maximum of thermal efficiency.

Some back pressure is developed in the chamber, but it does not cause any part of the flame and heat to reverse and flow back out of the slot, being counteracted by the velocity of the fuel and air entering the slot; and this counteraction is rendered more effective than otherwise by reason of the fact that the incoming gas impinges on the revolving stream at a point where the stream is flowing downwardly, namely, over the front wall surface 24 and over the slot and at right angles to the incoming gas. The pressure in the chamber is relieved to aid this counteraction by providing a suitable restricted number of vents in the top wall 23 of the chamber by omitting or removing a corresponding number of bricks.

An operator standing near the furnace front to serve it, is therefore not subjected to heat of the flame or hot products of combustion.

The slot extends transversely substantially the full width of the chamber and the nozzle and sheet form flame are as wide as the distance between the inner side walls so that work covering the entire width of the chamber will be uniformly heated and the maximum production capacity of the furnace made available.

It is one of the outstanding improvements of the above described slot furnace, that burnin fuel may be injected into the furnace chamber at a high rate and velocity, at the slot, without flame of hot products of combustion coming back out of the slot.

This has been explained above; but may be further explained as follows, by analogy to a bucket type water turbine'. When the turbine wheel is at rest, the nozzle jet of water impinging on a bucket tangentially of the wheel, is stopped and reversed by the shape of the bucket and flows back away from the bucket, generally toward the nozzle and the reversal produces the force reaction that turns the wheel. When the wheel is rapidly rotating, the buckets yield under the impulsion of the jet and move in its direction and there is little reversal of the jet, the reversal decreasing as the speed of rotation increases.

In the furnace, if the jet of fuel were an expanded conical thick jet, as is commonly the case and if it were simply fired into the center of the chamber filled at the time with burnt and burning gas and having no movement in the direction of the J jet, the jet would impinge upon it as upon an obstruction and be caused to How back out of the slot; but according to this invention the jet impinges on the gaseous contents of the chambers at a point where the contents have been given rapid revolving movement by the jet in the direction of the jet, namely at the outer periphery of the revolving gaseous contents; and the incoming jet, being in the form of a thin sheet, and directed upon the lower portion of the revolving contents, the jet flow is not obstructed by the contents and none of the contents is caused to flow back out of the slot by the force of the jet. 7

The invention is not limited in all respects to the exact details illustrated and described. Changes and modifications may be made therein as will occur to those skilled in the art; and the invention comprehends all such changes and modifications that come within the scope of the appended claims.

I claim:

1. An industrial furnace comprising a walled furnace chamber having a floor wall, a :front wall, a rear Wall and horizontally spaced side walls; a horizontally elongated slot through the front wall extending substantially to both side walls through which work to be heated may be projected into the chamber and laid on the floor wall; a gas fuel burner comprising a nozzle projecting into the slot and as wide horizontally as the slot; the nozzle formed with a plurality of parallel ducts therethrough in a horizontal series, and the ducts extending forwardly and rearwardly, and at their forward ends opening into the chamber; gas supply means supplying combustible gas to the rearward ends of all of the ducts at predetermined pressure to cause gas to flow out of the forward ends of the ducts into the chamber at predetermined velocity; the open ends of the ducts being disposed in a horizontal series substantially coextensive with the Width of the nozzle and substantially in a horizontal line and sufficiently close to each other so that when the combustible fuel is ignited, flames from all of the ducts merge into a single flame at the open ends of the ducts, and the single flame is projected from the nozzle into the chamber and over the fl-oor wal-l toward the rear wall in the form of a vertically thin planar sheet of flame as wide as the distance between the side walls; the side walls confining the flame against lateral expansion.

2. An industrial furnace comprising a walled furnace chamber having a floor wall, a front wall, a rear wall and horizontally spaced side walls; a horizontally elongated slot through the front wall extending substantially to both side walls; a gas manifold supported at the front of the furnace, connected to gas supply means supplying combustible gas thereto at predetermined pressure; a nozzle projecting through the slot into the chamber and as wide horizontally as the slot; the nozzle formed with a plurality of ducts therethrough open at one end into the chamber and at their other ends communicating with the manifold and supplied with gas by themanifold atsaid pressure to cause gas to flow at predetermined velocity through the ducts into the chamber; the open endsof the ducts being disposed in a horizontal series substantially coextensive with the width of the nozzle and substantially in a horizontal line and sufliciently close to each other so that when the fuel is ignited flames from all of the ducts merge into a single flame at the open ends of the ducts and the single flame is projected from the nozzle into the chamber and over the floor wall toward the rear wall in the form of a vertically thin planar sheet of flame as wide as the distance between the side walls; the side walls confining the flame against lateral expansion.

3. The furnace construction described in claim 2 andin which, the manifold and nozzle are spaced above the lower side of the slot providing a free open space therebetween for the projection of articles therethrough to be laid on the floor wall to be heated. a

4. The construction described in claim 2 and inwhich the manifold is in the form of a pipe and the nozzle is connected to the manifold and the manifold is supported by means providing for adjustable rotation on its axis, to adjust the direction of the sheet of flame with respect to the floor wall.

5. An industrial furnace as described in claim 1 and in which the ducts are positioned to direct the flame to impinge upon and sweep rearwardly over work supported on the floor wall to be heated, and the chamber comprises also a top wall having an upwardly curved surface, and the rear wall comprises a lower surface portion extending upwardly rearwardly from the floor wall at an inclination thereto, and comprises an upper surface portion merging into the curved surface of the top wall, and the curved surface of the top wall continues into a forward-1y curved surface of the front wall, so that the flame and products of combustion are caused to flow rearwardly over the floor wall and from the rear of the floor wall upwardly over the lower surface portion of the rear wall and successively over the upper surface portion of the rear wall and over the curved surfaces of the top wall and front wall and again over the floor wall, repeatedly, with a revolving movement.

6. The construction described in claim 5 and in which the top wall has a plurality of flue vents therethrough to relieve pressure in the chambersufliciently to prevent flame and combustion products from flowing backward out of 'the slot."

7. An industrial furnace, a walled chamberhaving as described in claim 1 and in which the ducts are positioned to direct the flame toimpinge upon and sweep rearwardly over work supported on the floor wall to be. heated, and the chamber comprises also a top wall having an upwardly curved surface, and 'the rearwall comprises a lower sur- "a forwardly curved surface of the front wall, so that ,the

flame and products of combustion are caused to flow rearwardly over the floor wall and from the rear of the floor w'all upwardly over the lower surface portion of the rear Wall and successively over the. upper surface portion of the rear wall and over'thecurved surfaces of the top wall and front wall and again rearwardly over the floor wall, in repeated cycles; and in which the downward flow over the front wall surface in the cycle passes the inner termination of the slot; and the velocity of flow of gas inwardly at the slot is predetermined by predetermining the said gas pressure, and vprevents said downward flow over the inner termination .of the .slot from flowing outwardly through the slot; and "in which a chamber wall has restricted outlets therethrough to relieve pressure accumulating in the chamber.

References Cited in the file of this patent UNITED STATES PATENTS 419,407 Bullard Jan. 14, 1890 1,205,436 Crone Nov. 21, 1916 1,363,188 Muckle Dec. 21, 1920 4,550,902 Hansen Aug. 25, 1925 1,605,089 "Bickel et a1. Nov. 2, 1926 1,615,087 Kidder Jan. 18,1927 1,617,609 Smith Feb. 15, 1927 2,177,225 =Ohlsson Oct. 24, 1939 2,511,676 Morton June 13, 1950

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