US1123966A - Metallurgical furnace. - Google Patents

Description

U. WEDGE.

METALLURGICAL FURNACE. APPLICATION FILED FEB. 14,1913

Patented Jan. 5, 1915.

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U. WEDGE. METALLURGICAL FURNACE. APPLICATION FILED PEB.14.1913

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U. WEDGE.

METALLURGICAL FURNACE.

APPLICATlON YILED PEB.14,1913

Patented Jan.5,1915,

8 BHBETS-SHBET 44 U. WEDGE.

METALLURGICAL FURNACE.

APPLICATION FILED FEB. 14,1913.

Patented Jan. 5, 1915.

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U. WEDGE.

METALLURGICAL FURNACE.

APPLIGATION FILED FEB. 14,1913,

Patented Jan. 5, 1915.

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U. WEDGE.

METALLURGICAL FURNAGE.

APPLICATION FILED FEB.14,1913.

1,,lQ3 966. Patented Ja,n,5,1915.

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U. WEDGE.

METALLURGICAL FURNACE.

APPLICATION FILED FEB.,14,1913

1 123,9fi6 Patented Jan.5,1915;

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METALLURGZCAL FURNACE.

Application filed February 14, 1913.

To all whom it may concern Be it known that 1, linear Wnoen, a citizen of the United States, residing in Ardmore, Pennsylvania, have invented certain Improvements in Metallurgical Furnaces, of which the following is a specification.

My invention relates to furnaces for roasting, oxidizing, reducing, or otherwise treating ores, or other metal bearing compounds, in a pulverized, granular or lumpy state, and hereinafter, for convenience, referred to as ore.

One of the objects of my invention is to so construct a furnace of this type as to provide a maximum hearth area for given dimensions of furnace; a further object is to simplify and cheapen the construction of the furnace; a further object is to provide effective mechanism for rabbling the ore on the furnace hearths and for feeding it from hearth to hearth of a series, and a still further object is to so regulate the How of gases in the furnace, as to utilize to the best advantage, the heat generated therein.

In the accompanying drawings Figui-e l. is a longitudinal vertical section of the furnace on the line aa, Fig. 3; Fig. 2 is a transverse section of the furnace; Fig. 8 is a horizontal section on the line 72-22, Fig. l, with the central portion of the furnace removed; Fig. f is a longitudinal vertical section on the line c-0, Fig. 3; Fig. 5 is a similar section on the line dd, Fig. 3, but showing all of the hearths; Fig. 6 is a transverse vertical section on the line e-e, Fig. 1; Fig. 7 is a transverse vertical section on the line f--f, Fig. 1; Fig. 8 is a longitudinal section, on a larger scale than Fig. 2 of one form of rabble mechanism constructed in accordance with my invention; Fig. 9 is a transverse section of the same on the line g/g, Fig. 8; Fig. 10 is an end view of the mechanism shown in Fig. 8; Fig. 11 is a plan view of part of one of the rabble arms; Fig. 12 is a view, partly in side elevation and partly in section, of certain guiding devices shown in Fig. 2; Fig. 13 is a perspective view illustrating a modified construction of furnace hearth; Fig. l l is a sectional view illustrating a modified plan of supporting the hcarths; Figs. 15 and 16 are sectional views showing modified arrangements of rabble arm supports; Fig. l? is an enlarged section of one of the elements of the furnace, not fully shown in the other views; Fig. 18 is a sectional view illustrat- Specification of Letters Patent.

Patented Jan. 5, acre.

Serial No. 748,389.

ing a modified plan of constructing and reciprocating the rabbles; and Figs. 19 and 20 are sectional views illustrating a special feature of my invention.

The main structure of the furnace comprises side walls 1-1, end walls 22, a roof 3, and a series of transverse partition walls 4C whose continuity is interrupted by longitudinal alleyways 5 which receive the rabble arm carrying and reversing structures hereinafter referred to. These alley" ways divide the furnace into sections and each of these sections is subdivided by the transverse partition walls into a series or row of furnace units:

In the furnace shown in the drawings there are three alleyways, one located centrally of the furnace and the other at each side of the same adjacent to the side walls, thereby dividing the furnace into right and left hand sections, and there are six transverse partition walls in each section, thereby subdividing it into seven furnace units disposed end to end. It should be understood, however, that my invention is not limited to this particular construction, as there may be more or less than three alleyways, and each section of the furnace may have any desired number of transverse partitions at so as to subdivide it into any desired number of furnace units.

Each furnace unit has a series of superposed hearths, each extending in width from an end wall to the first partition wall or from one partition wall to another, as shown in Fig. 1, each iearth being somewhat less in length than the distance between two alleyways and said hearths being disposed, as shown in Fig. 2, so as to provide a vertical passage first at one end of one hearth of the series and then at the opposite end of the next hearth of said series, whereby material may be fed from each hearth to the hearth below and after being deposited upon one hearth must travel throughout the length of said hearth before dropping onto the hearth below.

In the present instance there are, in each furnace unit, ten hearths lettered 92 s0 :0 m etc., beginning at the top, and each of the hearths m to m is hollow, being built up of horizontal tiles 6 and vertical side tiles 7, as shown in Fig. 1, each hearth above or below it being separated from the adjacent hearths by means of vertical side tiles 8, as also shown in Fig. 1, or, in place of this construction, the hearths may consist of tiles 6 with the desired fines or passages formed therein, as shown in Fig. 13, and either the tiles 6 or the hollow tiles 6" may rest upon separating tiles at the sides of the hearths, or upon shoulders or flanges 7 and 8 formed on the partition walls l, as shown in Fig. 1%, the construction in either case being light and strong and being such as to facilitate the rapid construction of the furnace.

Both the outer walls and the partition Walls of the furnace may be constructed of concrete and the hearths, owing to their limited span, can be constructed without the necessity of an arch formation and can, consequently, be disposed as closely to one another as is compatible with the introduction and operation of a rabble carrying arm between them. A much greater number of hearths can thus be provided in a given height of furnace than is possible where the arch formation of the hearth is necessary, as in circular furnaces or rectangular furnaces having hearths of relatively wide span, since in such furnaces all of the space required for the spring of the arch is practically wasted.

The arch formation of a hearth, moreover,

greatly increases the trouble and expense of building the hearth as compared with one constructed in the manner which I have shown and described.

The furnace which I have shown in the drawing is one of the muffle type, the products of combustion whereby the heating of the furnace is effected beingsupplied to the hollow hearths and having no access to the ore which is being treated on said hearths. The hearths of each furnace unit of a row are in communication with the corresponding hearths of the other furnace units of said row through apertures 9 in the partition walls 4, as shown in Figs. 1, 2 and 3, thus providing passages extending through the corresponding hearths of each furnace unit from one end of the furnace to the other, as shown in Figs. 1, 3 and 5.

Any desired means may be provided for supplying heated products of combustion to the hollow hearths, oil burners 10 being pre ferred, which burners, in the present instance, supply ignited oil or oil vapor to seven of the hearths, burners located at one end of the furnace supplying the hearths 00 1: :0 and a9, and burners located at the opposite end of the furnace supplying the hearths 00*, as and 718, as shown in Fig. 1. The hollow hearths 0: :0 at, 00 communicate, at that end of the furnace opposite to the burners with vertical fiues 11 (Figs. 3, 5 and 7) which communicate at the top with one end of the row of hollow hearths a," (Fig. 5) the latter communicating at the other end with a discharge stack 12 (see Fi 1). In like manner the hollow hearths m a? and 00 communicate with vertical flues 13 (Figs. 3, 5 and 6) whose upper ends are in communication, through the row of hollow hearths 2, with a stack 14, as shown in Fig. 1. The lowermost hearth 03 consists of metal plates or tiles with openings therethrough so as to permit of discharge of the ore therefrom into a storage bin 15, one of these being located at the bottom of each of the furnace units and being provided with any suitable means for the delivery of the ore therefrom either continuously or at intervals.

Flues 16 in the end walls are crossed by the oil burners 10, said iiues communicating at the bottom with the space below the hearths 02 and at the top, by means of branch iiues 17 (Figs. 6 and 7) with the chambers above the top hearths :0 so that relatively cool gases derived from the bottom of the furnace may enter the lines 16, and becoming highly heated in said flues by reason of their contact with the hot casings of the oil burners 10, will be caused to rise and in their highly heated state will be discharged into an upper chamber or chambers of the furnace.

The ore is supplied to each of the uppermost hearths w of each furnace unit from a hopper 19 which extends along the top of the furnace and is provided with any suitable means for delivering ore therefrom either continuously or intermittently. When a furnace of the muffle type is not desired the hearths need not be hollow, and, in furnaces other than those of the muffle type, air, either hot or cold, or heated products of combustion, may be permitted to come in contact with the ore on the hearths of the furnace, depending upon the character of treatment to which said ore is to be sub jected.

In the term hollow hearth I include any construction in which a chamber for the flow of the products of combustion inter venes between an ore receiving hearth above it and the roof of a treating chambe below it.

I have not shown any stack for the escape of the gases evolved from the heated ore preferring to permit highly heated gases to accumulate in the top of the furnace for action upon the incoming supply of cold ore. TV hen the gases are to be subsequently utilized, however, or air or other combustion maintaining gas is introduced in such vol.- ume as to necessitate escape of some of the evolved gases, such escape may be effected at the bottoms of the fines 16, as for instance by special flues communicating with the outwardly extending lateral branches shown in Fig. l at the lower ends of said fines 16.

Operating in connection with each oblong hearth of each of the furnace units is a rabble carrying arm, one of such arms being shown in the uppermost treating chamber of each of the sections of the furnace in Fig. The rabble mechanism is constructed as hereinafter described so that when moved crosswise of the hearth, or in the direction of its lesser dimension, it will cause the ore lying upon said hearth to move lengthwise of the hearth or in the direction of the greater dimension of the latter, the rabbles being also constructed so that whether the rabble carrying arm is moved forwardly or backwardly the rabbles will impart movement in one and the same direction to the ore lying upon the hearth. By reason of this construction each rabble arm has to move over its hearth only for a short distance, in other words, the full length of the furnace is subdivided into a series of relatively short units which short units determine the length of travel of the rabble arms, consequently I am enabled to provide simple and efiective mechanism for accomplishing such movements of the rabble arms and thus overcome a serious objection to ordinary rectangular furnaces in which the hearths extend from end to end of the furnace and necessitate a corresponding length of travel of the rabble arms and cumbersome, expensive and impracticable means for effecting such long movements.

In my improved furnace all of the rabble arms of each section of the furnace are mounted upon a pair of supporting structures located in the alleys 5 which flank said section of the furnace, each rabble arm being carried at one end by one of said supporting structures and at the opposite end by another one of the same.

In the furnace shown in the drawing it is contemplated to move the rabble arms of one section of the furnace in one direction while the rabble arms of the other section of the furnace are being moved in the opposite direction and this necessitates the use of two rabble arm supporting structures in the central alleyway. If all of the rabble arms moved in the same direction at the same time, however, a single supporting structure in the central alleyway might carry the inner ends of both sets of arms, as shown for instance in Fig. 15, and if the rabble arms are supported at one end only a single alleyway for each section of the furnace will suflice, as in Fig. 15 or by interposing rabble arm reversing devices such as hereinafter described between the rabble arm supporting structures in the central alleyway that alleyway would suflice for both sections of the furnace, as shown in Fig. 16.

The rabble arm supporting structures are mounted 'upon wheeled trucks running on rails at the bottoms of the alleyways, as shown in Figs. 2 and L, and the upper end of each of the supporting structures is steadied and guided by means of guide wheels and rails as hereinafter set forth, or in some other suitable manner, whereby the supporting structure will be maintained in its proper vertical position during the short reciprocating movements which are imparted to it in order to carry the rabble arms over the hearths of the series or row of furnace units comprising each section of the furnace.

Each of the rabble arm supporting structures has at the bottom a hollow tube or girder 20 which is in communication with a series of vertical pipes 21, the latter being in communication with a horizontal top pipe 22 and with a series of intervening horizontal pipes 23 one for each horizontal row of hearths in a furnace section. Preferably, each of the structures is built up of short sections and coupling members so as to facilitate communication between. the vertical and horizontal pipes but this is not essential, as any other method of construction providing for such communication may be adopted.

The bottom girder or flue 20 has at one end a pipe :24 passing through a suitable stufling box in one of the end walls of the furnace and at the opposite end a pipe 25 passing through a similar stu'liing box in the brickwork 26 with which that end of the alleyway is filled, such brickwork construction being used in order that it may readily be taken down so as to open that end of the alleyway when it is desired to remove the rabble supporting structure for inspection or repairs, the rabble arms having first been detached therefroi'n. Said arms can be removed through openings 27 provided for that purpose in the side walls of the furnace, as shown in Fig. 4.

Introduction of air or gas (hereinafter termed air to the pipes of the rabble arm supporting structure and circulation of the air through said pipes may be effected in any desirable way. In the present instance the inlet pipe 2% has a suitably packed telescopic connection with a conduit 30 (Fig. 17) to which air under pressure may be supplied in any suitable way and the top horizontal pipe 22 of each rabble arm supporting structure is perforated as shown in Fig. 12 whereby the "air may be discharged therefrom into the treating chambers of the top hearths a of each section of the furnace, the air being heated in its passage through the pipes of the rabble arm supporting structure and serving also to prevent the overheating or burning of the latter.

As the casing of the furnace is closed or substantially closed against the escape of gas therefrom, circulation of the gases throughout the interior of the furnace is de pendent upon variation in the temperature of said gases. As before stated, in a furnace of this type the tendency of the hot gas is to accumulate in the uppermost treating chamber of the furnace but as it there comes into contact with the incoming cold ore its temperature is reduced and it descends into a chamber below, being replaced by hot gas from said chamber or from the fines 16 or alleyways 5.

In a general way, like circulation of the gases takes place in each of the successive treating chambers of the furnace, the hotter gases rising from the chamber and the cooler gases descending to the chamber below and said cooler gases being drawn from the bottom of the furnace by the fines 16, being caused to ascend in the latter by reason of the rise in temperature imparted to them by the burners 10, and being finally discharged from the upper ends of said flues 16 into the uppermost treating chambers of the furnace, which also receive heated air from the rabble-carrying structures in quantity sufiicient to maintain combustion in said upper chambers of the furnace.

The circulation of the gases as above described is not incompatible withthe escape of a limited volume of the gases from the furnace, hence my description of the furnace casing as being substantially closed against the escape of the gases. Escape of gases from the alleyways 5 may be prevented by providing said alleyways with suitable caps or covers, as shown for instance at 5 in Fig. 12.

Many different forms of rabble mechanism may be employed for effecting movement of the material over the hearth both on. the forward and on the backward movement of the rabble arm. One means which I have found to be effective for the purpose is illus trated in Figs. 8, 9, 10 and 11, on reference to which it will be observed that the rabble arm 33 is rotatably mounted at each end in a bracket secured to one of the horizontal pipes 23 of one of the supporting structures. The rabble arm 33 has sides and inclined in respect to one another, and each carrying projecting rabble blades 35 or 36, the blades 35 being pitched in a direction the reverse of the blades 36 and the sides 35 and 36 bearing such angular relation to one another that when the blades 35 are in the lowered position so that they will. engage the ore lying upon the hearth the other blades 36 will be lifted to such position that they will be free from engagement with said ore, and vice-versa. (See Fig. 9.)

At one end of each rabble arm is a pinion 3S meshing with a rack 39 secured to one of the pipes 23 of a structure similar to that which supports the rabble arms, said structure comprising a base flue 20 carrying upright pipes 21- which are connected by the horizontal pipes 23 the two structures being disposed alongside of each other in each of the outer alleyways 5.

At one end of the furnace are a pair of beams or girders 40 which are intended to be reciprocated by any suitable mechanism so that one will move toward the end of the furnace as the other is moving away from the same, it being preferable to cause the rabble arm supporting structures to move continuously but at a low rate of speed. Each of the beams 40 is secured to the pipe 24 of the base flue 20 of the rabble arm reversing structure of its respective section of the furnace and plays between a pair of buffers L1 carried by the pipes 24 of the rabble arm carrying structures of said section of the furnace, said buffers being spaced apart to an extent somewhat greater than the width of the beam 4:0 in order to provide a slight amount of lostmotion of the beam between them. By reason of this construction each rabble arm when at the limit of its movement in one direction across the hearth will be reversed before starting on its back ward movement, the reversal being effected while the beam 40 is traveling between the buffers ii on the pipes 2%.

The rabble arm carrying structures and the rabble reversing structures each have at the top a pair of rollers 42 and d8, the rollers a2 running in contact with side rails let and the rollers 43 running in contact with an interposed rail 45, as shown in Figs. 2 and 12. By this means the upper ends of said structures are properly guided in a straight course while at the same time being rigidly held in a proper upright position.

By separating the interior of the furnace, by means of the alleyways, into a plurality of furnace sections, the length of the furnace hearths in each section can be limited so as to accord with the length to which a rabble arm or shaft can be carried without the necessity of so strengthening or bracing the same that it cannot'be introduced into the limited vertical space intervening between successive hearths, the latter being one of the features of my invention constituting an improvement over furnaces having more widely separated hearths of the arched type.

Although it is preferable in carrying out my invention to provide each furnace unit with a series of superposed and communicating hearths, the reciprocating rabble-carrying structure having a row of rabble arms corresponding to the row of furnace units may be used even if each of said furnace units has only a single hearth, or the row of rabble arms may correspond to the superposed hearths of a single furnace unit, and the use in connection with a rabble arm of two sets of reversely pitched rabbles with means for maintaining one set out of operation when the rabble arm is moving in one direction and the other set out of operation when the rabble arm is moving in the opposite direction, or means for reversing the relation of the rabbles at the end of each reciprocating movement may be employed even in a single hearth furnace.

The rabble arm carrier may also be reciprocated crosswise of the alley instead of lengthwise of the same, if desired, so as to move. the rabble blades lengthwise instead of crosswise of the hearths of the furnace units, especially when the rabble arm has a series of sets of transverse rabble blades located relatively close to one another and pivoted, as shown in Fig. 18, so as to push the ore ahead of them when the arm is moving in one direction, and slide over it when said arm is moving in the opposite direction, as in such case the extent of reciprocation of the rabble arm carrier need not much exceed the distance apart of the sets of transverse rabbles. it will also be apparent, that although I have shown my invention as applied to a furnace of rectangular shape, many of the features of my invention can be adopted in furnaces other than those of the rectangular type.

in conducting some metallurgical operations the hot Zone of the furnace is some distance below the top and in order to prevent overheating of this hot Zone such as might cause sintering of the ore I provide for the cooling of one or more of the hearths below the top and I can also, if desired, utilize the air thus heated for increasing the temperature of the treating chambers at and near the top of the furnace. In Fig. 19 for instance T have shown a construction in which one of the end walls of the furnace has in it a vertical flue 46 which may, at its lower end, receive air either from inside or outside of the furnace, this air passing through any desired number of the hollow hearths into a vertical flue at in a partition wall 4, which flue serves to convey it to one or more of the upper chambers of the furnace, or, as shown in Fig. 20, a number of the hollow hearths may be connected by a line 48 so that the air will circulate in one direction through one hollow hearth and back again through the next hollow hearth and until the desired number of hearths have been cooled, a fine 49 serving finally to convey the air to the chamber or chambers of the furnace in which it is to be discharged. If the use of the heated air in the upper chamber or chambers of the furnace is not desired the same may be permitted to escape directly to the atmosphere. The construction shown in Figs. 19 and 20 applies to a non-muflie furnace or to a furnace which is only partially muffle.

I claim:

1. A. furnace having outer walls, and hearths forming a row of furnace units disposed end to end, rabble arms for the hearths ,of said row of furnace units, a structure extending alongside of the row of furnace units and'carrying the rabble arms of the row, and means for reciprocating said rabble arm carrier.

2. A furnace having outer walls and hearths disposed to form a row of furnace units, each comprising a series of superposed hearths, rabble arms for the hearths of each unit of the row, a structure carrying the rabble arms of said row of furnace units, and means for reciprocating said rabble arm carrier.

3. The combination, in a furnace, of outer walls, a plurality of furnace sections separated by an alleyway and each comprising a row of furnace units disposed end to end, rabble arms for the hearths of said row of furnace units, and a rabble arm carrier mounted in the alleyway so as to be reciprocable therein.

4-. The combination, in a furnace, of outer walls, a plurality of furnace sections separated by an alleyway, each furnace section comprising a row of furnace units disposed end to end and each unit having a series of superposed hearths, rabble arms for the hearths of each unit, and a rabble arm supaortinn' structure movabl 7 mounted in the lleywey so as to be reciprocable therein.

5. The combination, in a furnace, of outer walls, a plurality of furnace sections, each having an alleyway alongside of the same and each comprising a row of furnace units disposed end to end, a rabble arm for each furnace unit of the row in each section, and a plurality of rabble arm carriers, each mounted in one of the alleyways so as to bereciprocable therein, and each carrying a rabble arm of each furnace unit of the section with which it cooperates.

6. The combination, in a furnace, of outer walls, a plurality of furnace sections, each having an alleyway alongside of it and each comprising a row of furnace units disposed end to end and each with a series of superposed hearths, rabble arms for the hearths of each unit of the row, and rabble arm carriers, each mounted in one of the alleyways so as to be reciprocable therein and each carrying rabble arms for hearths of the units of the row in that section with which said carrier cooperates.

7. The combination, in a furnace, of outer walls, a plurality of furnace sections, each having an alleyway on each side of it and each comprising a row of furnace units, rabble arms for the furnace units of each section, and rabble arm carriers mounted in said alleyways so as to be reciprocable therein, whereby each rabble can be supported at each end upon a rabble arm carrier.

8. The combination, in a furnace, of outer walls, a series of furnace sections each having an alleyway on each side of it and each comprising a row of furnace units, each with a series of superposed hearths, rabble arms, one for each hearth of each furnace unit, and rabble arm carriers mounted in said alleyways so as to be reciprocable therein, whereby each rabble arm can be supported at each end upon a rabble arm carrier. I

9. A furnace structure having outer walls and partition walls forming a row of furnace units, each. having hearths composed of tile structures bridging the spaces between adjoining pa tition walls or between a partition wall and an outer wall of the furnace, and vertical supporting tiles independent of the main walls at each side of a hearth, whereby said hearths are separated from one another,

10. A furnace structure comprising outer walls, a row of furnace units inclosed there by said units being disposed end to end and each having a hollow hearth, walls interposed between the units of the row and apertured, to provide for communication between the hollow hearths of the row, and means for causing flow of products of combustion through the hollow hearths of the row.

11. A furnace having an outer casing sub stantially closed at the top but having treating chambers connected from top to bottom of the furnace whereby the hot gases in the upper portion of the furnace, when cooled by contact with incoming fresh ore, are caused to descend, a flue for conveying these cooled gases again to the upper portion of the furnace, and means for heating said gases during their upward flow through said flue.

12. The combination, in a furnace, of outer walls one of which has a chamber therein, aseries of superposed hollow hearths, and means for supplying products of combustion to said hearths, said means crossing the chamber in the wall of the furnace but not communicating with said chamber.

13. The combination, in a furnace, of a series of superposed hearths, each with treating chamber above the same, said chambers being in communication with one another, an outer casing substantially closed at the top against the escape of gases from the treating chamber, a flue serving to convey from the lower to the upper portion of the furnace the gases which have descended through the treating chambers, means for heating said gases in their passage through said flue, and means for discharging gases from the lower portion of said flue.

14. The combination, in a furnace, of a series of superposed hearths, each with treating chamber above the same, saidtreating chambers being in communication with one another, an outer casing substantially closed at the top against the escape of gases therefrom, a flue serving to convey from the lower portion of the furnace to the upper portion of the same the gases which have descended through the treating chambers, means for discharging gases from the lower portion of said flue, and means for supplying products of combustion for heating the furnace, said means crossing said flue so as to heat the gases contained therein and cause them to rise.

15. The combination, in a furnace, of superposed hearths, each with treating chamber above the same, said chambers being in communication with one another, means for moving the ore over the hearths and causing it to pass from hearth to hearth of the series, an outer casing substantially closed at the top against the escape of gases therefrom, a flue providing for the passage from the lower portion of the furnace to the upper portion of the same of gases which have descended in the treating chambers, means for heating the gases in said flue and causing them to rise therein, and means for discharging gases from the lower portion of said flue.

16. The combination, in a furnace, of a series of superposed hearths, each with treating chamber above the same, said hearths being in communication with one another,

an outer casing substantially closed at the top against the escape of gases therefrom, means for supplying air to the gases in the upper portion of the furnace, and a flue which serves for the escape of gases from the lower portion of the furnace.

17. The combination, in a furnace, of a series of superposed hearths, each with treating chamber above the same, said chambers being in communication with one another, an outer casing substantially closed at the top against the escape of gases therefrom, a flue providing for the passage from the lower portion of the furnace to the upper portion of the same of gases which have descended in the treating chambers of the furnace, means for heating the gases in said flue and causing them to rise therein, means for discharging gases from the lower portion of said flue, and means for supplying air to the gases in the upper portion of the furnace.

18. The combination, in a furnace, of a series of superposed hearths, each with treating chamber above the same, said chambers being in communication with one another, an outer casing substantially closed at the top against the escape of gases therefrom, means for supplying air to the gases in the upper portion of the furnace, means for preheating said air, and means providing for the escape of gases from the lower por tion of the furnace.

19. The combination, in a furnace, of a series of superposed hearths, each with treating chamber above the same, said chambers being in communication with one another, an outer casing substantially closed at the top against the escape of gases therefrom, a flue through which may pass, from the lower to the upper portion of the furnace, gases which have descended in the treating chambers, means for heating the gases in said flue, and causing them to rise therein, means for supplying air to the gases in the upper portion of the furnace, means for preheating said air, and means providing for the escape of gases from the lower portion of said flue.

20. The combination, in a furnace, of an outer structure, a row of furnace units therein, a rabbling arm for each of said units, and a movable supporting structure for said rabbling arms mounted so as to reciprocate across the ends of the furnace units of the row and having the rabble arms projecting therefrom in a direction at a right angle to the direction of reciprocation, said supporting structure being composed of connected tubular members disposed in angular relation to one another, and providing for a flow of cooling fluid through said members.

21. The combination, in a furnace, of a hearth, a rabbling device having two sets of rabbles one pitched in a direction the reverse of the other, means for reciprocating said rabbling device back and forth over the hearth, and means whereby one set of rabbles is rendered operative during movement of the device in one direction and the other set is rendered operative during the movement of the device in the opposite direction whereby the material will be fed in the same direction over the hearth during both movements of the rabble.

The combination, in a furnace, of a hearth, a rabbling device projecting over said hearth and comprising a rocking arm having angular-1y disposed sides each with projecting rabbles, those of one side being pitched in one direction and those of the other side in the opposite direction, means for reciprocating said rabbling device back and forth over the hearth, and means for rocking said arm at each end of the reciprocation of the same whereby the material will be fed in the same direction over the hearth during both movements of the rabble.

23. The combination, in a furnace, of a series of superposed hearths each with treating chamber above the same, said chambers being in communication with one another, and an outer casing substantially closed at the top against the escape of gases therefrom and containing an alleyway which is in communication with each of the superposed chambers of the series, said casing containing a flue which provides for the escape of gases from the bottom of the furnace.

2a. The combination, in a furnace, of a series of superposed hearths each with treating chamber above the same, said chambers being in communication with one another, an outer casing substantially closed at the top against the escape of gases therefrom and containing a fine for conveying gas from the lower to the upper portion of the furnace, and an alleyway in communication with all of the superposed series of chambers, means for heating the gases in their passage through said flue, and means providing for the escape of gases from the lower portion of the furnace through said flue.

25. The combination, in a furnace, of a plurality of hearths each having a rabble arm, a reciprocating carrier upon which each of said rabble arms is mounted so as to rock, rack and pinion mechanism for rocking the arms, and a reciprocating carrier for said racks.

26. The combination, in a furnace, of a plurality of hearths, a rabble arm for each hearth, a carrier for said rabble arms, rabble arm reversing devices, a carrier therefor, and means for reciprocating said carriers so that one will have a lead on the other.

27. The combination, in a furnace, of a plurality of hearths, a rabble arm for each hearth, a carrier for said rabble arms, reversing devices for said arms, a carrier for said reversing devices, and a reciprocated member having a direct connection with said reversing device carrier and a lost motion connection with said rabble arm carrier.

In testimony whereof, I have signed my name to this specification, in the presence of two subscribing witnesses.

UTLEY WEDGE.

lVitnesses KATE A. BEADLE, HAMILTON D. TURNER.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents.

Washington, I). C."

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