US1808000A - Annealing furnace - Google Patents

Description

June 2, 1931- P. A. MEEHAN ANNEALING FURNACE Filed Aug. 23, 1928 INVENTOR JV/'Ef/M/v v/ f4 ORNEY 2 Sheets-Sheet l June 2, 1931. P. A. MEEl-iAN ANNEALING FURNACE Filed Aug. 25, 1928 l 2 Sheets-Sheet 2 ATTORNEY carbon monoxide.

Patented June 2,V 1931 .UNITED STATES PATENT OFFICE PAUL A. MEEHAN, OF CLEVELAND, OHIO, ASSIGNOR, BY MESNE' ASSIGNMENTS, 'lO

SWINDELL-DRESS'LER CORPORATION, OF

PORATION OIE' PENNSYLVANIA PITTSBURGH, PENNSYLVANIA, A COR= ANNEALING FURNACE The present invention relates to kilns andv furnaces in which metallic articles are annealed or subjected to other heat treatment tending to produce undesirable surface oxidation. While certain features of my invention are not restricted to use in connection with any particular ltype of furnace, my invention is especially advantageous when used in annealing metallic. bodies in a tunnel kiln through `which the articles to be heat treated are passedv on cars.

In tunnel kiln annealing operations wherein metallic articles, such as steel sheets used in automobile bodies are passed through the kiln, it is customary lto cover the sheets with a box resting in a sand seal at the bottom of the car. Vhen the cars are passed into the kiln and subjected to the high temperatures therein, the gases within the box are expanded and escape through the sand seal or any other openings. Vhen the material reaches a certain temperature, the carbon in the steel reacts with any iron oxide present to form an atmosphere within the box of almost pure No oxidation. will take place as long as this atmosphere is maintained. After passing the high temperature section the kiln, the gases and articles are cooled and contract. The consequent lowering of the gas pressure within the box permit furnace gases, or if the Ca-r'is drawn outside the kiln, air, to be drawn into the box. With such an atmosphere within the box the sheets on the top of the pile rapidly oxidize while the lower sheets develop undesirable blue or grey edge portions. Sheets used in automobile bodies require asurface finish of the highest degree and surface oxidation must be eliminated. .10.

Oxidation of the sheets or other metallic articles being annealed can be prevented by maintaining the articles in a reducing atmosphere by introducing reducing gases into fthe box during the annealing process and preferably before the articles begin to cool. In annealing operations in a continuous tunnel kiln, in which the articles to be heat treated are passed through the kiln chamber on lkiln cars, practical difficulties arise in continuously supplying reducing gases tov the annealing boxes on the moving cars.

The object of my present invention is to provide an improved method of and apparatus for supplying a fluid, such as reducing gases, to a kiln car in a continuous tunnel kiln. A further object of my invention is to provide an improved construction of a kiln car, especially adapted to receive a fluid from a source of supply supported on the car or connected thereto in any suitable manner.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, and the advantages possessed by it reference should be had to the accompanying drawings and descriptive matter in which l have illustrated and described preferred embodiments of the invention.

Of the drawings: y i

Fig. 1 is a sectional elevation of a tunnel kiln in which a preferred form of my invention is incorporated;

Fig. 2 is an enlarged elevation of a portion of the apparatus shown in Fig. l;

Fig. 3 is a section onthe line 3 3 of Fig. 2;

Fig. 4.- is an enlarged view of a portion of the car showing the gas inlet to the annealing box; j L i Fig. 5 is a sectional elevation of a modified form of my invention; y n

Fig. 6 is an elevation partly in section of a second modification;

Fig. 7 is an elevation third modification;

Fig. 8 is an end elevation of the apparatus shown in Fig. 7 y e Fig. 9 is a side elevation partly broken away and in section of an enlarged modification; and

Fig. 10 is an end elevation illustrated in Fig. 9. A

In the drawings and particularly in Figs. l to 4, I have illustrated a preferred embodiment of my invention in which a tunnel kiln A having the usual refractory side `walls A and crown A2 is provided with a kiln chamber B' extending longitudinally of the kiln.

of the apparatus The lower portion of the kiln chamber is provided with track rails B at its bottom for goods carrying cars or trucks C. The kiln is heated by combustion chambers B2 resting on benches B3 at the sideof the passageway for the body ofthe car C. The combustion chambers B2 through which the burner gases and products of combustion pass lengthwise of the kiln have their heating walls formed with the customary circulating' channels through which a convection current circulation of the kiln atmosphere is set up. The kiln chamber is provided at its-entrance end with an ante-chamber B4 having a door B5 between it and the kiln chamber. At the opposite end of the kiln chamber is an exit chamber B6 also separated from the kiln chamber proper by a door B7. The goods carrying cars are inserted one at a time at the entrance end `of the kiln and the train of cars normally filling the kiln is advanced a cast metal cover plate E extending over and car length each time a caris inserted by a car pusher (not shown) which may be of an suitable or usual type employed for the purpose. Longitudinally extending pits A3 and A4 are provided adjacent the entrance and exit ends respectively, of the kiln, each of the pits being connected to a point externally of the kiln by a lateral tunnel (not shown). Intermediate the pits are one or more cross tunnels A5 extending below the kiln chamber. and providing access at longitudinally spaced points to the underside of thel cars.

Each of the goods carrying cars or trucks C comprises a refractory body portion-D consisting of massive blocks of refractory material D supported on a metallic frame C on the lower side of whicha plurality of pairs of wheels forming the car running gear C2 is suitably mounted. Each of the trucks has a protecting the upper sides of the refractory blocks D. The cover plate is preferably divided into two sections E and E2 in overlapping relation and each of which is formed on its upper side with a. rib E3 extending longitudinally of the car and adjacent the outer edge of the cover plate. A trough shaped roove or channel E4 with inclined sides is formed in the upper side of each rib E3. A plurality of roll-er elements, such as cast iron or steel balls F, are mounted in each of the channels and form a support for a metal work support or tray G which extends over the top of the composite car. The tray is formed on its underside with a pair of downwardlf.v projecting longitudinal ribs G, each of which has a channel G2 in which the tops of the balls F are received.

The metal plates or other material to be annealed are piled on the tray and are ordinarily covered by a removable metallic cover H which as shown is formed of heavy metal plates riveted together. The cover is in the form of a box with a closed top and open bottom. Hooks H are provided on the sides of the box H to permit engagement by a suitable hoisting mechanism (not shown) for lowering the box on to and lifting it ofl the tray. The top of each box H is provided at points adjacent the ends with openings H2 closed by removable plugs H3. A sand seal H4 surrounds each plug to prevent the escape of the gases from theinterior of the box when the plug is in position.l The plugs can be removed to permit-air within the box to be swept out before the box is passed into the kiln and also to permit the escape of reducing gases after the car passes out of the kiln chamber. A sand seal H5 is also provided for sealing thelower edges of the box as shown in Fig. 2. In my improved form of carfone ofthe center balls has its lower portion F shaped to fit the inclined sides of the groove E4 and shoulders F2 resting on the upper surfaces of the' cover plate ribs as shownin Figs. 3 and 4. The ball is welded to the rib and provided with a vertical passage F3 therethrough connected at its lower end to an aligned vertical passage D2 in the subjacent refractory block D. vA pipe D2 is positioned in thevpassages D2 and F3 and extends upwardly to the center portion of the ball. A Afluid nozzle F4 is mounted in a vertical recess F5 formed in the ball and connected to and in alignment with the passage F3. The nozzle projectsl u wardly into an enlarged vertical passage formed in the tray G and rib G. A groove G4 extends transversely of the tray beneath the pack of sheets to ensure a proper distribution of the reducing gases. Longitudinal grooves may also be vprovided if desirable. lVith this construction any fluid passing upwardly through the pipe D3 ,will pass into the space enclosed by the box H. A fluid tight connection between the :ball andthe rib G is provided by a tray F6 mounted on the upperA portion of the ball.` The space between the tray and lower side of the rib is-illed with lireclay, which is supported on the tray. The kiln car construction heretofore described is disclosed and claimed in my divisional application, Serial No. 475,161, filed August 14, 1930.

j Various means may be provided for supplying a -reducing "gas such as natural gas, cokeoven gas or producer gas to the cars. In the construction illustrated in Figs. 1 to 4 a pipe J is supported beneath the metallic car frame C and extends longitudinally thereof. This pipe is connected to the vertical pipe D3 bya lateral pipe J in which a control valve J2 is mounted. The pipe J is' provided adjacent its ends with cut off valves J 3 and J4. A T fitting J 5 to which an inlet valve JQ and hose connection J 7 is attached is positioned in the pipe J. The pipe is also provided with a hose connection J 8 at one of its ends beyond the corresponding cut-olf lil valve by which it is connected tQ the main pipe J of the following car. l

The pit A3 adjacent the entrance @11d 0f the kiln preferably extends two car lengths longitudinally of the kilnand is provided with a supply pipe K connected to asource of reducing gas. The control valve K for the supply pipe is provided with a double outlet to which two lengths of hose, l and 2 are con. nected. Each hose has sufficient length to permit it to be connected to the hose connec? tion J -7 on any of the cars mounted on the tracks above and accessible from the pit A3.

Assuming that the kiln is filled with'cars to its capacity andthe hose 1 is connected to the hose connection J 7 on the last car, the pipe J of which has its cut-oil valve J 3 closed. The hose l ,Will then be in the position shown in Fig. l and the hose 2 will be disconnected. As the cars are pushed forward one car length and a new ca r introduced into the kiln chamber, the hose l travels forward with the car to which it has been attached into the position occupied by the hose 2 in Fig. l. The hose connection between the last car, to which the hose l is connected, and the new car will then be connected and the rear cut off valve J 3 on the last car opened while the rear cut off valve of the new car remains closed. The hose 2 will then be connected to the hose connection J 7 of the new car and the inlet valve J 6 to that car opened. When this has been done the train is receiving a supply of reducing gases not only from the hose l but also from the hose 2. Ihe hose l thenv being in the forward end of the pit is disconnected and brought back into position to be connected to the inlet hose of the next car to be inserted in the chamber. In this way a continuous supply of reducing gases is delivered to the cars and annealing boxes.

As each car reaches the pit at the exit end of the kiln chamber, the front cutod valve J* on the car passingover the pit is closed and as the rear end of the Acar passes over the pit the rear cut off valve is closed simultaneously with the front valve of the next car. The hose connection J 8 between the two ca rs is then disconnected and the iirst car vpassed into the exit chamber where another source of reducing gas is coupled to the hose connection J7 to continue the supply of gases 7 to the annealing boX.

Vith the reducing gas supply connections shown and operating as described the annealing boxes may be supplied with reducing gases throughout the passage of the cars through the kiln chamber or only from a` point intermediate the ends of the chamber. This point is preferably adjacent the high temperature section .0f the kiln. A cross tunnel A5 is provided at this point to permit access to the inlet valve J 6 on each car. Vith this mode of operation a continuous supply of reducing gases passes through theV pipes J and hose connections J8 but nene 0f the .reducing gases pass inte the annealing boxes H. until the cars reach thev high teniperature Section f the kiln at which. POIlt an operator in the cross tunnel A opens the inlet valve J 6 on each carand permit the reducing gases t@ Pass upwardly into the corresponding annealing bOX.-

In the construction illustrated the underside of the car and the operators in the pits are protected from they high temperature chamber atmosphere by plates G3 mounted on the sides of the car frame and extending downwardly into a trough C* lilled with sand.

In the modification illustrated in Fig. 5 a dierent form of apparatus'for supplying a reducing atmosphere continuously to the annealing boxes is illustrated. In this construction a tank L filled with a highly compressed gas or volatile vliquid such as gasolene, is connected to the underside of the metallic platform C. The tank has a valved connection L to the vertical pipe D3. In this modification the fluid nozzle F4 is arranged with a relatively small'orifice through which the fluid can slowly leak.

When a volatile liquid is used in the tank the rate of evaporation increases as the car reaches thev higher temperature sectionsof the kiln and the rate of evaporation is a maximum in the cooling section of the `kiln since the lower portion of the car is at its highest temperature at that point` due to the heat soaking down through the car frame.

l/Vhen compressed gas is used the supplyv tanks may be replenished at longitudinally spaced points along the kiln by means ofy cross tunnels such as shown in Fig. Al.

In some instances it is desirable Vto provide a tunnel extending throughoutv the greater portion of the kiln chamber where access is necessary to the undersideV of the cars throughout that portion of the kiln. Such a construction is illustrated in Fig. 6 wherein cross tunnels M are connected to the longitudinal tunnel Mv beneath the kiln chamber lli) to permit access thereto at longitudinally i spaced points.

Another arrangement for supplying reducing gases to the car train is shown in Figs. and 8,'wherein a continuous metallic hose N mounted on sheaves N at each end of the tunnel O which extends substantially the length .of the kiln chamber. The hose N is provided with connectors N2 at intervals of one car length which are connected to supply conduits N-3 onthe individual cars.' In this arrangement the source of sup-ply of reducing gases is connected to the Amoving hose by a. pair of connectors in the manner described in connection with the forward pitof Fig. l'. As each car ispassed into the kiln chamber, it is connected to the metallichose and at the same time the source of supply s connect'- itil) is provided with a pairof tracks Q and Q at its bottom. Small cars-R carrying tanks R of compressed gas are arranged to move on the track Q.V The track Q is a return track for the cars carrying empty tanks. In this arrangement as each kiln car is inserted, it isvconnected by a suitable hose connection S to one of the cars R on the track Q, which moves through the kiln along with the kiln car. As the kiln reaches the exit end of the kiln the tank car R is detached and returned on the track Q to the entrance end of the kiln where the tank is refilled.

lIn some installations, it may be desirable to combine several of the gas supply systems shown. For example, it may be desirable to' install a tank car supply system such as illustrated in Figs. 9 and 10 at the exit end of the kiln shown in Fig. l so that during the interval when the car is detached from the` supply. r

rlhe Vapparatus and method described is primarily designed for the production of steel sheets having the highest degree of finish.

' My invention is as applicable for producing what are known as blue sheets by passing steam in the vsame mannerlinto the annealing boxes while the cars are in the cooling section of the kiln. Y

VhileL in accordance with the provisions of thestatutes, 'I have illustrated and described the best forms of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes maybe made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims and that in some cases certain features of my invention may be used to `advantage without a corresponding use of other features. Y

Having now described my invention what I claim as new and desire to secure iby Letters Patent, is I 1. A continuous tunnel kiln having a goods passageway therein normally closed at its ends and through which kiln cars carrying goods to be heat treated in an inclosed car chamberare passedmeans for moving a plurality of cars simultaneously through said passageway, .a fixed source of fluid within the entrance end of the kiln and below said cars A and means for maintaining a continuous supplyY of fluid from said source to said car chambers while said cars are moving through said passageway. i

2. A continuous tunnel kiln having a goods passageway vtherein through which kiln carscarrying goods to be heat treated are passed, apit below said passageway and adjacent the entrance end of the kiln, a container on said cars arranged to receive a fluid, a fluid supply insaidpit,means for passing fluid from said supply to said container, and a second pit at a longitudinally spaced point along said passageway and from which said fluid supply is disconnected from said container.

3. A continuous tunnel kiln having a goods passageway therein normally closed at its ends and through which kiln cars carrying goods to be'heat treated in an enclosed car chamber and passed, means for moving a plurality; of cars simultaneously through said passageway, a pit opening to said passageway adjacent the entrance end of the kiln, and means for continuously supplying a fluid to said car chambers while in said passageway comprising a fluid supply in said pit and means for connecting said supply to saidV car chambers.

U 4. The method of maintaining metallic articles Yin a fluid atmosphere during heat treatment thereof in a continuous tunnel kiln which comprises enclosing 'said articles in a substantially air tight receptacle, connecting v said enclosed space withafsource of fluid at the entrance end of said kiln, and disconnecting said'space from the source and closing said space to the atmosphere at the exit end of the kiln.

' .5. rllhe method of supplying fluid toa train of kiln lcars I'which comprises supplying fluid from a source of fluid to said train, moving said train in a tunnel kiln a predetermined distancev and inserting an additional car at one end of said train, and connecting said last mentioned car to saidsource of fluid and maintaining a continuous supply of fluid to adtrain during its movements through said r1 n. Y

6. The method of supplying fluid to a series of goods enclosing containers mounted on a 'train of kiln cars passing through a tunnel kiln which comprises maintaining a continuous supply of fluid to all of said cars, supplying said fluid to each container when said container reaches a predetermined point in said kiln, and disconnecting each container from said supply and closing said container to the atmosphere when it reaches a second predetermined point in said kiln.

7. The method of continuously supplying a fluid to a train of tunnel kiln cars in a tunnel kiln, in which the cars are moved intermittently by the insertion of an additional car at predetermined intervals, which comprises connecting the fluid conduit lines of the individual cars, supplying fluid to the 13o last car of the train when said train is in a predetermined position, inserting an additional car in said kiln, connecting the fluid conduit of the new car to that of the last car of the train, connecting the conduit of the additional car to said source of fluid supply while maintaining the iirst connection to said supply, and disconnecting said first connection when said last car reaches a predetermined position.

8. A continuous tunnel kiln having a goods passageway extending longitudinally thereof, a plurality of kiln cars in said passage- Way carrying metallic articles to be heat treated, a box on each car enclosing said articles, and means for continuously supplying a fluid to the interior of said boxes while in said passageway, said means comprising a pipe extending longitudinally of each of said Y cars, a cut-ofil valve at each end of said pipe, a conduit connecting said pipe to the interior of said box, flexible conduit means connecting the adjacent pipe ends of adjacent cars, a source of fluid adjacent the entrance end of the kiln, and a flexible conduit connecting the longitudinal pipe of a car adjacent said source to said source.

9. A continuous tunnel kiln adapted for annealing metallic articles and having a goods passageway extending longitudinally thereof, a plurality of kiln cars in said pas'- sageway carrying metallic articles to be annealed, an annealing box on each car enclosing said articles, and means for continuously supplying a fluid gas to the interior of said annealing boxes while in said passage- Way, said means comprising a pipe extending longitudinally of each of said cars, a cut-oil' valve at each end of said pipe, a conduit con- 40 necting said pipe to the interior of said box,

a control valve in said conduit, flexible conduit means connecting the adjacent pipe ends of adjacent cars, a source of fluid adjacent the entrance end of the kiln, and a exible conduit continuously connecting the longitudinal pipe of a car adjacent said source to said source.

Signed at Cleveland, in the county of Cuya hoga and State of Ohio, this 20th day or' August, A. D. 1928.

j PAUL A. MEEHAN.

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