US1645119A - Best available cop - Google Patents

Description

1927' c. STEENSTRUP ELECTRI C FURNACE Filed Dec. 1. 1922 2 Shets-Sheet 1 I m t s B 3 t m 3 u VG A 1T. .6 m. U m 97 m H m a 4 7 Oct. 11; 1927.

(2. STEENSTRUP ELECTRIC FURNACE Filed Dec. 1, 1922 2 Sheets-Sheet 2 Inventor 35 Christian Steenstrup,

b Mag:

His Attorney.

Patented Oct. 11, 1927.

UNITED STATES PATENT OFFICE.

CHRISTIAN STEENSTRUP, F SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC FURNACE.

Application filed December The present invention relates to electric furnaces of the type in which the operations or treatments are carried out in the presence of a selected gas in a closed container which is heated by internal resistors supplied with electric current from a suitable external source.

In the practical application of such furnaces as heretofore constructed much time is lost between operations or treatments. A considerable amount of time is also lost in charging the furnace, sealing the same prior to its operation and unsealing it thereafter and in removing the charge. But the great loss of time is due to the fact that the whole furnace and its contents and especially the fire brick lining must first be heated to operating temperature and then after the working period said furnace and its contents must be cooled before 1 it can be opened. The amount of timeconsumed in these.non-productive operations in a large commercial furnace of this type with which I am familiar is approximately two and one-half times greater than the working period.

The object of my invention is to improve the construction and mode ofoperation of such furnaces to the end that the above-mentioned loss of time is practically eliminated, whereby the output of the furnace for-a given period of time is very greatly increased.

I have discovered that by making the heating portion of the apparatus entirely separated from the cooling that a very great saving is effected not only in time but also in heat energy. By reason of this arrangement I am also able to save the time formerly-consumed in loading and unloading because these operations are carried on simultaneously with the others.

As my invention has particular application to electrically heated closed furnaces in which hydrogen is employed as the selected gas it will be specifically described in that connection. But it is to be understood that the invention is not to be construed as restricted thereto unless such restriction is embodied in the claims.

For a consideration of what I believe to he novel and my invention, attention is directed to the accompanying description and the claims appended thereto.

In the drawing, Fig. 1 illustrates one of my improved furnaces in vertical section;

1, 1922. Serial No. 604,193.

Fig. 2 is a plan view of the same; Fig. 3 is a detail view showing the means for sealing the container; Fig. 4 is a modification of the cooler showing means for circulating the gas therein; Fig. 5 is a plan view of a modified form of turntable; and Fig. 6 is a further modification of the furnace wherein a plurality of heaters and coolers are employed.

In the present embodiment of my invention, I have shown what for convenience may be termed a multiple stage furnace. In the first stage, the charge, work or parts to be operated on or treated are located in a. wellinsulated, suitably heated container in which a supply of selected gas, in this case hydrogen, is constantly maintained. After the heating operation or treatment of the charge has been completed the container is removed and the charge moved to a new position and then enclosed in a cooler in which a' supply of selected gas, inthis case hydrogen, is also maintained. a This cooler' which somewhat resembles the heater or container in external appearances has cooling means toreduce the temperatureof the charge which has reviously been treated. Only a few secon s are required to move the char e from the heater to the cooler and any oiri ation which takes place during the transferperiod will 'be reduced during the 'coolingjoperation because of,the presence of'said gas in'the cooler. In

those cases 'where the cooling operation is' the'limitingfeature in the output of the furnace, additional coolers may be employed in which case the charges may be moved from one toanother. After the temperature of the charge is sufiiciently reduced'the cooler is removed and thecharge moved to aithird position where it is removed fromits supporting platform and another charge mounted thereon preparatory to being moved-into the heater or first mentioned container. The heater and cooler are for simplicity made in the form of cylindrical casings having a top or cover but no bottom. The can advantageously be lifted from the c ar es simultaneously and by the same mechanism. The chargescan be moved from one position to another by any suitable conveyer. One very simple way is to mount the charges on a turntable and when the furnace and cooler are elevated move the same from one position to another by rotating the table.

Referring to the drawings, 5 indicates a foundation made of concrete or other suitable material. Mounted thereon is a bed plate 6 above which is supported on ball bearings 6 a rotating head or table 7 which turns about the central vertical column 8 as an axis. 9 and 10 indicate other columns which support the ends of the overhead bridge beam 11, the latter being V-shaped in plan as shown in Fig. 2. The vertical column also acts as a support for the middle portion of the bridge. Mounted on the bridge are two hydraulic cylinders 12 and 13 each containin" a piston 14, shown in dotted lines. To tile lower end of each piston rod is secured a clevis 15 which in turn is pivotally connected to the part to be raised and lowered. Water under pressure is simultaneously supplied to the cylinders by the pipes 16 under the control of a suitable valve so that the heater and cooler may be raised and lowered together.

The heater is indicated at 17 and comprises a metal cylinder 18 having closed sides and top and an open bottom which is arran ed to be seated by its own weight on the p iate19 that is carried by the turntable. This plate forms a part of the loadingplatform. Inside the cylinder is a thick lining 20 of fire brick'or other heat resisting material andabove it is ahead 21 of similar material but made in the form of a relativel large: disk or slab. The lining is held etwe'ena'ringj'22 which is welded to the container and the cover of the heater. If desired,,'holding bolts 23, Fig. 2, may also be 'prdvided. L0catedjin thebottom of the chamberjl s firmed and comprising a part of the loading platform is a. bed of sand or equiyal ent; l 2 1 upon which the is 'suppqgted 11 1311]. suitable way.

. .ch'ar' e v s i ma nt slia e' s'nppe in devices 25 are'jor ay providedfso as tolocate the eharge -welrup-ihside the chamber and also to separate the parts'o'f said charge one frointh'e other." By locating the charge or work in the manner shown the possibility of trapping air; as the container descends and thereby forming eitheran explosive mixture or' oxidjzing'thesurfacesof the charge is avoided. The charge; is indicated at 26, and in the present illustration takes the form of turbine elements the parts of which are to beunited by the fusion of metal, copper beingthe materialused for the purpose. However, it will be understood that the charge may be of a different character, and that instead of being fused may be otherwise treated. For example, the charge may be steel sheets or partially completed dieformed parts which it is desired to anneal.

Surrounding the work is any suitable form of heating element or resistor 30. As shown, it comprises one or more units made generally in the form of a helix and supported by the lining of the container by being partially embedded therein. The particular type of heating element is not material to the present invention. The circuit of the heating element is established through flexible conductors or cables 31, Fig. 2, which extend through the wall of the container. In order to permit the heater to be raised and lowered an I-bcam is provided at the top which is connected to the bottom ring 22 by long rods 32. At the center the beam is connected to the clcvis. I prefer to pivotally connect the piston rod to the beam so that in lowering the heater it may be freely directed by guides thereon en gaging the vertical columns and thus moved into exact register with the fixed labyrinth packing on the loading platform. When the hydraulic pressure under the elevating pistons is relcascd the heater rests by its own weighton the base. and if by any chance an explosion should occur the heater will more upwardly by a slight amount and thus act as a safety valve.

Hydrogen is continually supplied to the heater by the pipe 33 which is connected to the source of supply by a flexible pipe, not only while it is down over the charge but also when in its elevated position. The fact that hydrogen is lighter than air causes it to rise in the heater and hence very little will escape around the bottom thereof when the heater is elevated. 34=indicates a pipe of relatively small diameter through which a small amount of the gas may be permitted to escape and be burned at the end thereof. Since gas can only escape through the pipe when the heater is filled it follows that the flame at the end of the pipe forms a visual indicator. at all times of the amount of gas within the heater.

The pressure of the gas in the heater is slightly above atmosphere and hence there a tendency for it to escape around the bottom of the heater during the operating period. To prevent this, or at least to limit it to a: negligible amount, a special packing is'provided. This may be made in a variety of ways but I have found the one shown to give satisfactory results. Referring to Fig.3, 22 indicates the metal ring on the container which is supported by the platform plate 19. there being an annular spacing block'36 between, which sustains the weight of the heater. In the ring and plate are turned concentric grooves, cach of which contains a cylindrical packing member 37. These members are so spaced or disposed as to form a laby rinth. In the annular spaces between the members is a filling material to further rcstrict the escape of gas. Sand may he used for this purpose but the most satisfactory material which I have found is composed of fine shot-like particles 38 of cast iron. such as are used in sand blasting castings. The size of the shot has been largely exaggerated in the figure for the purpose of illustrati n. 1

(Vhen the heater is lowered to its operating position it will be noted that the parts of the packing carried by it extend between the parts carried by the loading platform and thus it will be seen that the sealing of the two parts of the heater is automatically establi hed, a feature which is of very great value in an apparatus of this character.

In an apparatus of this character there is a slight leakage of hydrogen from the heater when in its operating position and more when it is lifted and the seal at the packing broken. To prevent this from escaping unnoticed and possibly forming an explosive mixture, a ring burner 39 is provided to which iliuminating gas is continually supplied. The burner has a relatively large number of orifices 40 on its under side through which the illuminating escapes and is burned at the point of exit. As a re sult of this any hydrogen which escapes is instantly burned and hence all danger of explosion is avoided. The burning of the selected gas at this point forms a visual indicator to show whether the supply of gas is being properly maintained. \Vhen the heat er is in its elevated position during the transfer period, that portion of the gas at its bottom, due to the admixture with air, burns with a bright red flame, the amountthus consumed being continually supplied from the source. V

In an apparatus of this character it is necessary to ascertain the conditions inside of the furnace, that is to say, itis necessary to determine the proper temperature so that resistors may be put into or cut out of service or' the current varied or both to maintain the proper temperature. The simplest way to accomplish this is to provide one or more valve tubes, such as 41 for example, each having a sight glass. These tubes preferably enter the furnace at different levels and atdifferentpoints in the circumference so that the average conditions may be'observed.

Referring now to the cooler, which has been generally designated by the reference numeral 45brie.fly, this comprises a double wall container 46 which is closed at the top and open at the bottom. Between the walls of the container is a space 47 which is con-' tinualiy supplied with cooling water as for example from a service main. Cool water is admitted at the bottom by the pipe 48, Fig. 2, and the heated water escapes at the top through the outlet 49 which is connected to a suitable drain. Both the inlet and the outlet are connected by flexible pipes so as not to interfere with the movements of the container.

The means for fastening the parts of the cooler together and the packing means are similar to those described in connection with the heater and hence a detail description is unnecessary. Hydrogen is continuously supplied to the cooler during the cooling operation by the pipe 50 and a small amount'may be permitted to escape from the outlet 51 where it is burned and forms a visual indi cator. The cooler is also provided with an annular burner around the packing of the character previously described, and for the same purpose.

The loading platform comprises the plate 19, ring 36, sand body 24 and its holder and also the lower part of the packing element, all of which were described in connection with the heater.

The operation of the apparatus is as foilows: assuming for the purpose of the dezcription that the heater has been heated to working temperature and that it has been properly loaded, the work, whatever may be its character, is permitted toremain therein until the operation or treatment is completed. If, by way of illustration the work comprises the parts of .a turbine which are to be brazed with copper .the temperature is adjusted to the proper amount-sand maintained until the copper melts and runs into all of the joints between theLpartsWhiGh are to be united, the supply of hydrogen being continuously maintained. V

YVhile the, heateris performing its work, the attendant removes the.finished work and places a new charge composedof partswhich are to be fused or otherwiSetreated-mn the loading platform. 2 After the-heating operation is completed as determined. by the sight tubes or other indicatingrmeans, water under pressure is. admitted to the cylinder-s12 by the pipes 16.;--:This"causes thfe' pistonsi in the 5 cylinders iito-isimultaneously raise; the beaten;- and the cooler... -When1ijraised .-,sufficiently to clear. the ;charges the attendant causes theturn-tablei to-berotated. so as to bring the new charge;directly,into=-register with the heater and that ..wh'ich,;has';.been brazed or otherwise ,treatedfdirectl-y into're r ister withthe :cooler; The'=tabl e; n1ay be rotated by power on bythehand lever 55, Fig. 2. This leveris pi-votallymttached to,- the. table at 56*and has associatediavith it a table locking device comprising.assliding locking bolt 57 one end of which enters" oneof. the peripheral notches-58 onethe table. yConnected to the bolt by a pin-.and-slot connection is a lever 59,-.the outer-end of which has a cam 60 which is acted uponby a-pin 61 carried by the lever. lVhenthe attendant applies pressure to the lever to turn the table the lever first swings on the pivot 56 and in so doing causes the cam 60 and pin 61 to withdraw the locking bolt and thereafter strikes the stop 62, after which the table can be rotated to the new po ition and the locking bolt permitted to enter another notch 120 from the first. .The next step is to lower the heater and cooler to their operative positions; after which the operations as above recited are repeated.

During the period that the heater is raised from its platform to permit the charge to be transferred air has access to the bottom end of the heater chamber with the result that a combustible mixture is formed but at said end only, and which burns freely. To prevent the burning area from progrelsively working upwardly into the chamber as the hydrogen is consumed, the supply of hydrogen admitted thereto is so adjusted, or regulated, as to compensate for the amount consumed and therefore. to keep the burning area at approximately the level of the lower end of the heater or container. The purpose of this is to prevent the formation of an explosive mixture of hydrogen and air in the container eitherbefore or after it is seated and also to prevent oxidation of the charge due to the presence of oxygen when the container is closed or seated. If air were permitted to enter the cooler and mix with the hydrogen therein in proper proportions to form an explosive mixture. the introduction of the highly heated charge from the heater would ignite the mixture and might result in an explosion. To prevent this, hydrogen is constantly admitted to the cooler when in an elevated position and in sufiicient amount to maintain may either increase the effectiveness of the cooler or provide an additional cooler or both. In Fig. 4 is illustrated a cooler of the general character heretofore described but in addition a cooling coil 65 is provided which is wound in the form of an open helix and water is circulated therethrough from end toend. The inlet and outlet pipes are connected to the source of water supply and the drain respectively. In addition to this a circulating fan 66 may be provided to circulate the selected gas within the cooler so as to increase the effective cooling action. The fan may be driven by an electric motor 7 through pulleys and a quarter turn belt. In such an arrangement it is preferable to provide a directing and guiding means such as 68 which comprises a cylindrical sheet metal arrangement having an opening 69 to receive the hot gas and direct it to the center of the fan and a cylindrical guiding member to direct the discharged gas downward chiefly between the coil and the inner wall of the cooler.

Another way to increase the cooling effects is to provide an additional cooler such as shown in Fig. 5. In this figure l7 represents the heater, 45 and 45 coolers similar to those illustrated in Fig. 1, and '24 the sand bed on the platform at the loading and unloading station. \Vith this arrangement the cooling period is twice as long as the heating period.

In Fig. 6 I have shown a further modification of the invention in which the heating is accomplished by steps, an arrangement which is necessary in the treatment of some kinds of steel and desirable in others. In other words, it is undesirable to take some kinds of metals, such as high speed steel used in the manufacture of tools and cutters at room temperature and suddenly subject them to the maximum or operating temperature. In such cases I provide a number of heaters and operate them at different temperatures whichcan readily be done by regulating theainount of electric current passing through the resistors or heating elements. In this figure, 7 indicates the turntable asbeforeand mounted thereon are as many charge-supporting platforms as there are-.heatersand;-c0olers plus one which is used as aloadingplatform. .F or example, but not as' a limitation, heater 1? may be continuously maintained at a temperature of 400 C.. heater 17 at 600 C. and heater 17 at 1000" C. In such an arrangement the cooling may also be accomplished in steps by providing different cooling means in each .cooler 45, 45 and 45 designed to produce different eifects, or all of the coolers may be designed to operate at the same temperature. The difference in cooling effects may beobtained by changing the amount of circulating water flowing through the cooling coil or coils, or theefi'ective surface of the-latter may be different for the different coolers as will readily be appreciated. The means for raising and lowering the heaters and coolers and for rotating the turntable may advantageously be of the same character as that previously described, suitable modifications being made to take care of the increased number of units. In operation the charges will be successively moved from one position to the other as before.

The apparatus is particularly Well adapt ed for annealing sheet iron or steel either in the form of sheets or in the form of partially completed articles. As is well known with many articles made by a succession of drawing operations it is necessary to anneal between certain operations. This is commonly done by placing the parts to be annealed in containers and putting the containers in furnaces, first covering the parts with sand or other material so as to exclude the air as fully as possible. Obviously, this procedure is relatively slow and even when the great est care is exercised the parts are never very bright when removed and often have some scale thereon which is of course. highly objectionable when the parts are to be subs ion .o f metals w i th copper it is necessary t'o .ratl iei uickly lower the .temperature of thevir orkgr poi ntaboiit 100 below it in or er to prevent .-3

ainsan d gj It is to be especially noted that the heater iscalvvayskeptat ,worl:ing temperature and thejcooler at cooling temperature and hence the rate of production can be very greatly increased over those furnaces which have to ,beheated and cooled between two successive complgteoperations .In a large single stage furnace pf-.tl e latter character with which I am familiar the complete cycle of operat ion requires approximately 41 hours, di v id ed as, fo1lows: heating 12 hours, cooling hours. With large iurnaces such as are in common. use for an- .nealingslieetironthe complete cycle from start to finish requires 7Q hours It may be anillust-ration but; not asalimitation of rnyjnv'entionyihat once the furnace is heated togvorki ng temperature it takes only about one and one half hours to do the work andwhile this is done the cooling of the finished gharfge andthe loading of the platforin are also completed.

,In certain lines.of.worlr, notably the fuom operatingtem erature to a fui'ther alloyage r, other undesired action. Ifhis-was aidiflicult-thing todo with the old 'ofi fiiriiac es where the temperature of the whole mass of the furnace lining as well .as that of the work had to bereduced togather. Moreoyer, the loss of heat because of th s operatlon was very greatand as abovenoted very seriously handicapped the outplut With the cooler arranged as described the cooli'ng'operation takes place rapidly andparticularly from the highest temperatures. which is exactly the thing which is required to do the best work.

Because of the constantly heated furnace element and a separate cooler the product will be more nearly uniform. Furthermore, the rate of cooling can be varied at will by merely regulating the amount of circulating water admitted to the cooler.

I have described the furnace clement, cooler and loading platform as being mounted on a turntable SC as to move simultaneously but it is evident that each of these devices may be separate in itself and other means employed to move them about. li'here it be desired to cool the work more slowly as for annealing sheet steel the water circulation in the cooler may be omitted in which case a greater number of coolers is preferably provided, and arranged to be moved to a point distant from the furnace element so as not to interfere with its operations.

The invention has been described in connection with apparatus in which the furnace element and the cooler are raised and lowcred with respect to the charge but it is evident that instead of this the charges can be lowered while the other parts remain fixed, the real point to be considered being that of introducing and removing the ..charge without disturbing it, and in the s hortest possible time so tha the efi'ects of the.' air thereon are reduced to a minimum.

As will be noted the parts .conipris'in the charge are mounted one above the o the i' on suitable supports. This vertical arrim gement in combination with the heaterand cooler which are raised and lmid'fioin above is particularly desirable becaiise the heated charge can theii bemovedwithout inury to the componentpzirts 'yvhichiare softened by the heat. ,1, :f

Ashefore stated, it is important tii a void The only opportunity ljfor. such a, mixture to form is when the container is awayiirom its seat either during the raising or lowering operation. As previously described 'the container is kept filled with hydrogen and since 9 hydrogen is lighter than air itItnds to rise. Vihen the container is ofi it's'seat tlieadmixture of gas and air takes place onlyjatithe bottom end of its chamber and burns a bright red flame. To keep the burning 1 area at the bottom of the container the supply of gas admitted is properly regulated.

As the container is gradually lowered to core: the charge which rises above the platform, the charge displaces a certain amount 1 of gas which may cause a slight change'of level of the burning aiea. ,Such air as is contained in and around the charge progressively mixes with the gas as thecontainer descends and the mixture is burned so that when the container finally reaches its seat all of the air has been consumed. By this arrangement the presence ofan appreciable body of air in the lower orrelatively fixed parts is avoided.

In accordance with the provisions of the patent. statutes, I have described the principle of my invention, together with theapparatus which I now consider to represent the best embodiment thereof but I desireto 2 have it understood that the apparatus is only illustrative and that the invention can be carried out by other means.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In a furnace, the combination of a heater comprising a container which is closed except at the bottom, means which form a closure and also a seat for the container, a device for moving the heater and the means with respect to each other to permit the introduction and removal of the charge, and means for maintaining a supply of selected gas in the container in both its closed and open positions.

2. In a multi-stage furnace, the combination of a heater and a cooler, both comprising containers which are closed except at the bottom, charge-supporting means which also form closures and seats for the open ends of the containers, devices for simultaneously moving the heater and cooler with respect to their seats to permit the introduction and removal of the charges, and means for continuously supplying the heater and cooler with selected gas in both their closed and open positions.

3. In a multi-stage furnace, the combination of a heater, a cooler, both of which are closed except at the bottom, means for maintaining a supply of selected gas in the heater and cooler both in their open and closed positions, and means for transferring the charge from the heater to the cooler.

4. In a multi-stage furnace, the combination of a normally closed heater a normally closed cooler, means for maintaining a supply of selected gas in the heater and cooler both in their open and closed positions,

' means for circulating a cooling fluid through the cooler, means for opening and closing the heater and cooler, and means for transferringthe charge from one to theother when said parts are open. i

5. In a multi-stage furnace,'the.combiiiation of a heater comprising an 'op'en-ended container which encloses the charge and an end closure therefor, a cooler comprising an open-ended container and an end closure therefor, means for maintaining supplies of selected gas in the heater and cooler both in their open and closed positions, means for circulating a cooling fluid through the cooler, means for separating the partsof the heater and cooler to expose the charge, and means for transferring the charge from the heater to the cooler when the parts thereof are separated.

6. In a multi-stage furnace, the combination of a heater and a cooler both of which comprise containers each having an open lower end, charge-containing platforms on which the containers are normally seated, means for maintaining a supply of selected gas in the heater and cooler both in their open and closed positions, and rotary means for supporting and for simultaneously moving the platforms about a vertical axis when the heater and cooler are separated therefrom.

7. In a multi-stage furnace, the combination of a heater and a cooler both of which comprise containers each being closed at the top and sides and open at the bottom, chargecontaining platforms on which the containers I:

are normally seated to prevent the free escape of gas, means for maintaining a supply of selected gas in the heater and cooler both in the open and closed positions, means for separating the heater and cooler from their respective platforms by a vertical movement, and a turntable on which the platforms are mounted for rotating them with respect to the heater and cooler when the latter have uncovered their respective charges.

8. In a furnace, the combination of a retary platform means, a heater and a cooler which are closed except at their bottom ends and are seated by their own weights on the platform means to prevent the free escape of was, means for moving the heater, cooler an platform means with respect to each other to enclose or uncover the charges in the heater and cooler, conduits -for supplying selected gas to the heater and cooler, and means for burning the gas which escapes from the bottom ends of the heater and cooler.

9. In a furnace, the combination of movable platform means, a heater and a cooler which are closed except at their bottom ends and are seated'by their own weights on the platform means to prevent the free escape of gas and the' admission of air, means for maintaining a supply of selected gas within ,the heater and cooler,'means for movin the heater, cooler-and; platform means wit respect to each'T-othertto' enclose or uncover the charges in the heaterand cooler.

10. In a furnace, the combination of a heater'comprising an open-ended container, a closure on which the container is seated thereby closing said outer end and which also supports the charge,means for maintaining a supply of selected gas within the container, and a packin for restricting the escape of gas between the open end of the container and the closure.

11. In a furnace, the combination of a heater comprising an open-ended container, a closure on which the container is seated and which also supports the charge, means for maintaining a supply of selected gas within the container, and a labyrinth pa clring for preventing the escape of gas between the open end of the container and the closure which comprises annular interspaced members carried by the container and closure respectively.

12. In a multi-stage furnace, the combination of heating and cooling containers having open lower ends, conduits for supplying the container With selected gas both in the open and closed positions, platforms on which the containers are seated, an additional platform for loading and unloading purposes, means for raising and lowering the containers with respect to the platform, a turntable which carries said platforms, and means for turning the table when the containers are in their raised positions.

13. In a furnace, the combination of a heater comprising an open-ended container, a closing means for the container, means for maintaining a supply of selected gas within the-container, a packing for restricting the escape of gas at the joint between said end at the container and the closing means, and a burner located in proximity to the packing which ignites the escaping gas.

14. In a furnace of the character described, the combination of a container which is closed except at one end and is provided with a lining of heat-resisting inaterial,. an electric resistor located inside of .the container, a closing'means for the open end of the container, the two parts :bemg

separable to permit the int-roductionandle- -moval' of the charge, means for maintaining a supply of selected gas within the container at all times, and a burner adjacent the joint between the container and-closing means to ignite any gas escaping through. said joint.

155In a-furnace-of the character described, the combination of a container :which is closedexcept at one end and is provided with alining of heat-resisting material, an electric resistor located inside of members carried by: the container and closing means-respectively and arranged tore- .st-rictaleakage through the joint between the two, and a burner. which'surrounds the packing and is adjacent thereto for igniting any gas escaping through the packin '1 16. In a mnlti-stage furnace, the combination of separate containers," each of which is closed except at the bottom, one of said containers serving as a heater and another as a cooler, means for sup dying a selected gas to the containers, a c arge-containing platform on which each container is seated, an additional platform for loading and unloading purposes, means located above the containers for simultaneously raising them above the charge on the platform, and means for movinga charge from the heater into the cooler and then from the cooler to a place where it can be unloaded.

17. In a furnace, the combination of a cooler comprising a container which is closed except at the bottom, a loading platform for closing the bottom, means for-circulating a cooling medium through the cooler, means for maintaining a supply of selected gas in the cooler, and a packing to restrict the escape of gas through the joint between the container and platform.

18. In a furnace, the combination of a cooler comprising a container which is closed except at one end, a means for closing said end, means for artificially cooling the walls of the cooler, means for maintaining a body of selected gas in the container, a. fan located in the container for circulating the gas, and means for driving the fan.

19. In a. multi-stage furnace, the combination of an open-ended heater, an open-ended cooler, charge supporting platforms which also form closures for the heater and cooler, means for raising and lowering the heater and cooler with respect to their seats on the platforms, means for continuously suppl 'ing the heater and cooler wit-h h'drogen both when on their seats and w en elevated, means for transferring the heater charge to the cooler and a new charge to the heater when said heater and cooler are elevated, and packing means for preventing leakage of the .gas when the heater and cooler are seated 20. In a furnaee, the combination of a container in which a bodyflo'f selected gas is maintained, saidlcontainef being closed except 'at'one end, a .inea'ns for closing said end, a labyrinth packing, one member of ,which is. carried by the container'pand the other bv said me'ahs,. aiid a liner located between the parts of one of the packing niembeis into whichfthecorresponding parts of the other'packing rhember extend when the container is closed. 7 i .121) In ,a' furnace, the combination of a containerwhichis'closed excep t-at one end and; is' arranged'to reeeivea selected gas under, pressu're,' aflmeans for'closin'g said end, the 'eoiitaiher 'and means being relatively .n'l ovable permit the introduction of a charge',,j a, packing' comprising concentric fimembersai ranged 'tof o'rm a labyrinth, one element of which is associated with the container and the other with the closing means, said packingautomatically opening and closingasthe container and means are separated and re-united.

In a furnace, the combination of a container which is closed except at the bottom, means for supplying selected gas to the container both in the open and closed positions, resistor means within the container, a seat for the container, means for moving the container and seat vertically with respect to each other and the seat angularly to permit the introduction and removal of the charge, and conductors for continuously supplying current to the resistor means both when the container is on its seat and when separated therefrom.

23. In a furnace, the combination of a seat, a container which is closed except at the bottom and which rests by its own weight on the seat, resistor means within the container, means for moving the seat and container with respect to each other to permit the introduction and iemoval of the charge, and conductors and a conduit which supply electric current to the resistor means and a selected gas to the container respectively both when the container is on its seat and when separated therefrom.

24.-In a furnace, the combination of a heater which is constantly maintained at the desired high temperature, a cooler, a water cooling means for the cooler to maintain it at the'desired low temperature, means for uncovering the charges in the heater and cooler-{means for moving the hot charge from the heater -into the cooler and the cooled charge'from' the cooler to a point outsidethereof, conduits for maintaining supplies of'selected gas in the heater and cooler at'all 'times-and means at the-boti'tomof'thheaterand cooler to prevent escape-of gas ,when'in'their closed ositions. 25. InwYfur'nace, thecombination of a heater wliich' is constantly maintained at the desiiedhigh temperature, a cooler, a water cooling means for the cooler to mamtain it a'tthe desired low temperature, means for uncovering th'e'eharges in the heater and cooler, meansf'fonmoving the hot charge from thheater into the cooler and the cooled eharg'efrom'the' cooler to a point outside thereof; and 'means for supplying selected gas to both the heater and cooler 7 when the charges are covered and uncovered.

26. In a multi-stage furnace, the combination of a, plurality of normally closed heaters which operate' at different temperatures, conduits for supplying a selected gas to the several heaters, cooling means, conduits for circulating-cooling fluid through the cooling means, charge-supporting means, and carrier means for movin the charges from one heater to another an thereafter to the cooling means.

27. In a multi-stage furnace, the combination of a plurality of normally closed heaters which operate at different temperatures. conduits forsupplying selected gas to the several heaters both during their closed and open positions, a plurality of coolers, conduits for circulating cooling fluid through the coolers, charge-supporting means, a carrier which is common to the charge-supporting means, and means for moving the carrier to bring the several charges into successive register with the heaters and coolers.

28. In a multi-stage furnace, the combination of a plurality of normally closed heateis which operate at different temperatures, conduits for supplying selected gas to the heaters both during their closed and open positions, a plurality of coolers, conduits for circulating a cooling fluid through the coolers, means for raising and lowering the heaters and coolers, charge-supporting platforms for the heaters and coolers, a carrier for the platforms, and means for moving the carrier when the heaters and coolers are elevated to progressively more the charges from one to another.

29. In a furnace, the combination of a platform upon which the charge is placed. the said charge rising above the piane of the platform, a container that is closed ex cept at the bottom end and is arranged when seated by its own weight on the platform to completely cover the charge, means for impartingrelativc axial and angular movements to the platform and container when it is desired to expose and remove the charge, and means for maintaining a supply of selected gas in the container both in its closed and open positions.

30. In a-- furnace, the combination of a platform upon which the charge is placed, the said charge rising above the plane of the platform, a container that is closed except at the bottom end and is arranged when seated by its own weight to completely cover the charge, means for raising and lowering the container to respectively expose and cover the charge, means for moving the charge out of legister with the container when the latter-is in its raised position,'and means for maintaining a supply of selected gas in the container at all times.

31. In a furnace, the combination of a container which is closed except at its bottom end and which completely encloses the charge andits platform, a platform for the charge, a support therefor, conduit means for supplying a selected gas to the container both during its raised and operating positions, a packing means for the bottom end of the container, one portion of which is carried by the container and the other by the support, an overhead structure, and means carried by the structure for raising and lowering the container, said containeropening the packing on its upward movement and closing it on itsdownu-ard movement.

In a furnace, the combination of a container the chamber of which is closed except at the bottom, a support, a charge-supporting means mounted on the support which rises vertically therefrom and extends up ward into the chamber, conduit means for maintaining a supply of selected gas in the chamber, packing elements. each comprising concentric rings, located below the upper surface of the clnirge-supporting means to prevent the tree escape of gas or the admission of air, one of said elements being aisociated with the container and the other with the support, means for separating the container and support by relative axial movement, and means for guiding the movements of the container and one of the pack ing elements.

33. In a furnace, the combination of a container having a heat-insulated chamber which is closed except at one end, a resistor located in the chamber for heating it, a closure for the open end of the container, packing means carried by the container and closure respectively for preventing the free escape of gas from the chamber, a restricted outlet located near the open end of the chamber and through which a limited amount of gas is permitted to escape and be burned to serve as an indicator, means for maintaining such an amount of selected gas in the chamber that a small amount will escape through the outlet, and means for separating the container and closure to permit the introduction and withdrawal of the charge.

34. An apparatus of the character described, including a stationary pedestal adapted to receive material to be annealed, a removable hood provided with electric re sistance elements adapted to be placed over the material and pedestal, and means for raising and lowering the hood.

35. An apparatus of the character described, including a stationary pedestal adapted to receive material to be annealed, a removable hood provided with electric resistance elements adapted to be placed over the material and pedestal, means for maintaining an inert gas within the hood, and means for raising and lowering the hood.

36. An apparatus of the character described, including a stationary pedestal adapted to receive material to be annealed, a removable hood provided with electric resistance elements adapted to be placed over the material and pedestal, and means for circulating an inert gas around the hood.

37. An apparatus of the character described including a pedestal adapted to receive material to be annealed, a removable hood having electric resistance means fixed therein and adapted to be placed over the material and pedestal, and means located above the hood to raise and lower it with respect to the pedestal.

38. An apparatus of the character described including a pedestal to receive material to be annealed, a removable hood having electric resistance elements fixed therein and adapted to be placed over the material and pedestal, and means to provide for a circulation of gas around the material.

In witness whereof, I have hereunto set my hand this 29th day of November, 1922.

CHRISTIAN STEENSTRUP.

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