US1257649A - Furnace. - Google Patents

Description

F. 'W. STE ERE. I

FURNACE. APPLICATION FILED JULY 3|, 1915-- Pawn Feb. 26, 19118.

2 $HEETS-$HEET lspecification of Itetters llatent.

EPatente Application filed Jfulyflt, lalti. lilo. 12,829.

fb all whom it may concern:

' Be known that l, l nann "W. fireman, a citizen of the United States of America, residing at .lle cit, in the county of Wayne and State o' chigan, have invei ed till coi

i our in an annealii race for brin to a i i i or heat treating me ale, irrcsp ie hind or -W'orh or industry in connechich it is used, that it possess the characteristic Accurate control of temperatures, uniform temperature over the furnace hearth; uniform conditions for all stoclr being t ed on the hearth irrespective of the variety shapes, sizes or materials; the preventing of the hot products of combustion from. contacting the metal during its treatment; coat-in of treatment of stock during the ope; tron of the furnace; fuel economy and inanimum thermal efficiency; minimum loss till i involved in the by cessation in operation; absolute free-- dom from danger of explosion; simplicity of operation With protection to the opera tor; and adaptability tovarious processes production of a great variety of products.

n annealing furnace in accordance with tl invention not only meets the above re quirements but possesses many other ad vantages, all as hereinafter more fully set forth and as Will more clearly appear after consideration of a preferred embodiment of my invention, which is illustrated in the accompanying drawing, tvherein- Figure l is an enlarged transverse vertical section through furnace embodying the invention 2 is a horizontal sectional view taken on or about the line lll-dll of Fig. 1, showing diagrammatically, a: double reversing or four-Way valve, and p a lFig. 3 is a longitudinal sectional vievv of the furnace, on the line llllll-lllll of Fig. 2.

lndescribin my invention by aid of the views above re erred to, I desire to point out that the same are merely intended as illustrative of a furnace Which is now in use, and it do not care to confine my invention to the precise construction and arrangement of parts shown. The following description is tical chambers therefore to be construed as including sub stitute or equivalent constructions and arrangements of parts.

its new erected, the furnace is located upon an inclined foundation it, having a Well at the forward end of the furnace and a pit 3 at the rear end thereof. The furnace, per ac, comprises a meta shell including a bottom plate at, front ii, and a rear Wall 6, said 5 ll Hi a suitable bindin i a refractory structt lln the foundat on nels d, 9, l0 and communion let, iii and 16 through openings in the bottom p e d, and in. said chambers con 'suous to said bottom plate, are if minous supports if for ceramic mater r This material is preferably crushed and sized and the chambers filled with these sparvls or the chambers may be filled with smecially manufactured thin pieces ceramic material of any desired shape to provide suitable regenerating chambers, and these chambers communicate With combustion chambers 19 and Ell-Which are separated by a central division "Wall ere tending upward to and supporting a hearth 22 which, together with the side Walls 23 and an arch supported thereby and span ning the hearth, forms a cl inui'lle or retort having a receiving opening 25 at the forward end of the furnace structure and a dischargc'opening 26 at the rear end thereof. The arch is spaced from the top of the furnace structure to provide a passage 29 Which also spaces the side Walls from the structure and connects the combustion. chambers 19 and 20 into Which the upper ends of the chambers 18, it, 15 and 16 open. llhe flames and hot products of combustion are thus permitted to sweep over and around the muffle, heating it to a bi h temperature Without coming into contact with the material beng treatedtherein, and air and gas to maintain combustion in one combustion chamber may be admitted thereto through the regenerating chambers Which open into its bottom, and the products of combustion from that chamber, after passing around the niullie into the other combustion chamber, may pass out through the two regenerating chambers opening into the bottom thereof.

To assist the feeding or travel of stock through the muffle from its inlet or receivall a till ing end 25 which may be closed by a suitable door or gate 30, to its discharge end 26 which may be closed by a like door, the muflle is constructed at an inclination in the direction of its length, so that the stock placed upon the upper end of the hearth may be easily pushed along the parallel tracks or rails 27 laid thereon .and discharged from the lower end without the necessity for providing means within the mufi'lefor moving the stock or articles along the hearth, the stock being discharged at the lower end by forcing it in at the upper end, thus providing a continuous operation.

Between the chambers 13, 14, 15 and 16 are passages 31 of less depth than the regenerating chambers and having the forward ends thereof in communication with the atmosphere through openings 32 in the.

chambers 13, 14, 15 and 16, thus precluding any leakage from one chamber to another which would result in heat loss and less efficiency in operation. The metallic walls of the air Ppassages are cooled by the passage of air t rough the chambers, thus preventing the breaking down of the metallic plates forming the air tight jacket for the walls.

The pipe 34 is in communication with a double reversing valve 38 located within the pit 3 and constructed upon the principle of an ordinary four-way cock. This vali e has been diagrammatically illustrated in Fig. 2 ashaving connected thereto a gas supply pipe 39, gas outlet pipes 40, 41, 42 and 43 communicating with the lower ends of the channels 8, 9, 10 and 11 respectively, and an exhaust pipe 44 for products of combustion. This exhaust pipe extends upwardly through the bottom 45 of and discharges into asclosed tower 46 which is in communication with the discharge opening 26 of the muflie or retort. In the tower 46 is a conventional form of endless conveyer 47 adapted to receive the articles or stock from'the mufile and carrythe same upward in the tower where they are cooled during their travel, in the comparatively cool products of combustion discharged from the furnace, thus tending to prevent oxidization.

I As shown in Fig. 2, the valve 38 is so adusted that gas passing through the valve from the supply pipe 39 entersthe channel 10 and passes upwardly through the regeneratmg chamber. 15 into the combustion chamber 19. In this chamber, the gas comingles with a supply of air drawn through the passages 31, pipe 34, valve, the pipe 43, and channel 11 into the regenerating chamber 16. The admixture in the combustion chamber 19 is ignited and the flames and hot products of combustion sweep over and around the mufile or retort 28 and pass from the other combustion chamber downwardly through the- regenerating chambers 13 and 14 where a large portion of their heat is absorbed by the spawls, and through thechannels 8 and 9, pipes 40 and 41, through the valve, and are discharged in a comparatively cool state into the tower through the exhaust pipe 44.

This action is continued for a predetermined period of, say thirty minutes and thenthe valve 38 is operated to reverse the flow, causing the gas to pass into the regenerating chamber 14 and the air into the regenerating chamber 13 from which they enter and mix in the combustion chamber 20 and are ignited by the heat, their products of combustion then sweeping under and over the muffle or retort 28, passing downwardly through the regenerating chambers 15 and 16 which have been cooled by the ingoing gas and air during the previous cycle of operation and giving off their heat to the spawls therein, and then discharging through the channels 10 and 11, valve 38, and exhaust pipe 44 into the tower in a cooled state In this operation, it is to be notedthat the air and gas passing through the regenerating chambers 13 and 14 are preheated by the absorbed heat held in the material contained in the chambers and that the products of combustion are cooled by passing through the regenerating chambers 15 and 16 containing material which was cooled by air and gaspassed through the chambers during the previous cycle of operation. The heat of the products of combustion is thus stored for use in heating the ingoing air and gas and the products of combustion leave the furnace in a comparatively cool state, thus eflecting a great saving in fuel and making the cooled exhaust available for cooling the stock after it leaves the muffle, thus tending to prevent the oxidization which might otherwise take place if cooled in the open air.

In the present well known types of furnace the material is loaded onto the hearth from a doorway at the front ofthe furnace, the door closed, the material brought up to heat, the stock withdrawn through the same doorway, and then the stock quenched or air cooled according to the process involved. From the very nature of such furnace constructions, the heating process is intermittent, resulting in a large heat loss, expenditure of time, energy and the space required for the operation.

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neonate fin the other hand, where the stock'is fed through the furnace, passing in at one end stock. The inclination of the hearth is also an important feature in certain manufacturing plants where it is desirable to have an extended hearth to give the desired capacity or to increase the length of travel through the furnace and a corresponding increase in the length of time which the stock will be subjected to the heat. The action of gravity is thus employed to assist in feeding the stock through the muffle, obviating the neces sity for mechanical feeding means within the muflie to move the-stock along the hearth.

The advantage tobe gained by the useof a muffle having a stock receiving opening at one end and a discharge opening at the oppositeend, is that the stock may be fed in at one end and taken out at the other with a continuing movement of the stockthrough the muffle and it is possible to control with accuracy the treatment temperature of the stock. if it is desired to maintain a temperature of seventeen hundred and fifty degrees Fahrenheit in the retort and a certain tonnage is to be hourly delivered from the furnace, the temperature is maintained, after the gas and air have been adjusted, by

' varying the rate of passage of the stock through the furnace. If the temperature tends to drop, the feeding of stock is slowed up. if the temperature tends to rise the feeding of stock is speeded up. it has been i found by a test extending over several weeks,

that by a combination of these two methods of controlling the temperature, the temperature of the material on the furnace hearth is maintained within a variation of ten degrees,

and this has been accomplished with ordinary labor and without the use of mechani cal feed Within the mutiie, which feeding means may be dispensed with as the action of gravity is utilized to assist in the movement-of the stock along the hearth which is inclined for the purpose.

- Uniform conditions for all stock on the hearth at any one time is also important and this condition is attained by passing the stock with a continuing movement over the entire length of the hearth; that is, one piece after another is fed into the furnace at one end so that the stock is not piled up but is at the same depth on all parts of the hearth and passes out of the opposite end in the same manner, whereby all stock is subjected to the same heat conditions.

it is generally agreed by inetallurgists that the closed muffle is the ideal furnace forheat treating operations for the reason that such a furnace prevents the hot products of combustion from coming into contact with the metal. If the products of combustion carry an excess of oxygen, scaling results from such contact and it is also claimed that the. steel tends to absorb impurities. The principal point urged against the muffle furnace so far, has been the high cost of fuel; This objection, however, has been eliminated in my furnace by. using the regenerating chambers 13, 14c, 15 and 16, which absorb and hold the heat that ordinarily passes out with the products of combustion untiltaken up,

upon reversal of flow, by the ingoing air and gas and returned to the muffle, asset forth in the operation of the furnace.

ft. cheap method of burning coal isto first convert it into producer gas, and this gas is the cheapest known fuel which is suitable to furnace worlr. lit has the advantage of being very dilute and large volumes bfioome necessary to produce the required heat. The products of combustion are therefore large in volume as compared with oil or a higher calorific power fuel, which makes local heating impossible. This difficulty from local heating is very serious in oil fired furnaces as it is very disastrous to brick work and necessitates frequent rep airs. By my process of heat treating, the life of the brickwork or body of the furnace is indefinitely prolonged. I

lit is sometimes urged that gas furnaces are dangerous because of inexperienced operators attempting to light them. This feature has been eliminated in connection with my furnace from the fact-that after the furnace is once placed in operation, there is no occasion to relight it, unless shut down for a considerable period of time, as the regenerating chambers and. the body of the furnace hold sufficient heat to ignite the com bustible fuel when it is turned on.

By the method of burning gas involved in my furnace the products of combustion leave the furnace at a very low temperature and they are therefore available for cooling the stock as it leaves the hearth. The tower at simply constitutes a receptacle into which the stock is delivered and cooled by the'cool products of combustion before being discharged into the atmosphere. ft is well known that oxidizing and scaling result from cooling stock in the open air, and if have found that this difficulty is largely eliminated by subjecting to the cooling action of the products of combustion which have had their initial heat removed and returned to the furnace hearth by the regenerating chambers.

Considering the regenerators, T obtain a distinct advantage by eliminating the ordithe stock nary brick checkered work built up of the which is capable of absorbing and giving off heat very rapidly. In my furnace, the ceramic material may be in very thin sections disposed so that at no one place will there be a great thickness of'material which that after the gas and air is closed off for v a period of thirty-eight hours, the drop in temperature is so small that the furnacecan again be placed in operation after a few minutes heating. This is due largely to the construction of the furnace whereby a thorough heat insulation is secured. It is therefore apparent that there is practically no stand by loss aslong as the furnace is used...-each day, and that it is only necessary to manually ignite the combustible fuel when the furnace is first put in operation.

By placing the regenerating chamber directly under the hearth, uniformity of temperature throughout its area is secured, and minimum loss of heat by a radiation through the furnace Walls is secured, and the absorbed heat of the regenerators is imparted to the hearth. Like pyrometer readings have been obtained at various points along the hearth, and this accurate control of the temperature has been obtained by regulating the quantity of air and gas admitted to "the furnace by the valve, and also by regulating the-feeding of stock into the furnace, as heretofore set forth.

The construction and arrangement of regenerating chambers in a furnace will be found tobe applicable to furnaces for making gray iron castings, furnaces for use in the glass industry, and in fact to most all furnaces where fuel economy and speed of operation are desired, and while in the drawings is shown a furnace especially adapted for annealingpurposes, the same construction, with slight modifications, is applicable to forge work, drop forging operations, and almost an indefinite number of other heating and heat treating opera tions used in modern industries.

What I claim is 1. A mufiie having a stock receiving opening at one end thereof and a discharge opening at its opposite end, a receptacle in communication with the discharge opening of said muflie adapted to receive stock therefrom, and means for heating said muflle by products of combustion and for discharging the products of combustion into said receptacle after having given off their heat to the mufiie to prevent oxidization of stock received therein from the muffle,

2. A mufile having a stock receiving opening and a discharge opening, a receptacle in communication with the discharge opening of said muflie to receive stock therefrom, means for directing products of combustion to said muffle to heat the same and for conducting said products of combustion to said receptacle, and means in the path of flow of the products of combustion for removing heat from saidproducts of combustion after the same have passed and heated said mufile and before they enter said receptacle.

3. In a furnace, the combination of a muffle, a combustion chamber adjacent said mufiie, regenerating chambers in communication with said combustion chamber to supply fuel thereto and conduct products of combustion therefrom, means for reversing the flow of fuel and products of combustion through said regenerating chambers, means between said regenerating chambers adapted to supply air thereto to mix with the fuel and form a combustible mixture, and a receptacle to receive products of combustion from said chambers and arranged to receive the discharge material from the muffle.

4. In a furnace, a muffle, connected combustion chambers adjacent said muflie, a pair of regenerating chambers in communication with each combustion chamber, means for alternately supplying air and fuel to each pair of chambers to reverse the flow, each pair being adapted to alternately receive and conduct away the products of combustion from the combustion chamber with which it is in direct communication, and means for receiving the cooled products of combustion from said chambers and arranged to receive material from the mufile to be cooled by the cool products of combustion.

5. In a furnace, a mufiie adapted to be heated by products of combustion and adapted to receive stock at one end thereof'and discharge stock at the opposite end, sets of chambers adapted to be alternately used for supplying products of combustion and fuel, said chambers being disposed whereby each set is adapted for alternate use as an inlet for fuel and an exhaust for the products of combustion, and a receptacle to receive stock from the muffieconnected with said chambers to receive the cooled products of combustion therefrom.

6. In a furnace, a mufiie, a combustion chamber adjacent the muflie for heating the same, regenerating chambers in communication with said combustion chambers to supply fuel and air thereto and to conduct products of combustion away from said combustion chamber, means for, reversing the flow of fuel and air and products of combustion through said regeneration chambers, air passages adjacent said regenerating chambers in communication therewith and controlled by said reversing means, and a chambers adapted to be receptacle to receive stock from the mue and the exhaust products of combustion from 4 the said regenerating chambers.

Zn. In a furnace, a mufiie adapted to receive stock at one end thereof and discharge stock at the opposite end, acombustion' chamber adjacent said mufie, sets of regenerating alternately usedfor supplying fuel to said combustion chamber and exhausting products of combustion therefrom, air passages between said regencrating chambers, a tower adapted to cornrnunicate with said regenerating chambers to receive exhaust products of combustion therefrom and adapted'to" receive stock from said muifie, and avalve common to all of said chambers and passages for controlling the direction 0t flow of fuel and products of combustion therethrough.

In testimony whereof I atfiz t-my signature in presence of two witnesses.

. rennin w. STE ERIE).

Witnesses:

ANNA M. Donn, LEWIS 1E. Fmnnnns.

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