US1750884A - Apparatus for heating - Google Patents

Description

arch E8, i930. E. M. FREELAND m AL M759@ APPARATUS Fo HEATING Filed May 51, 1927l 2 Sheets-Sheet l March H8, M330. E. M. FREELAND ET m. L@

APPARATUS FOR HEATING Filed May 51. 1927 2 shams-sheet .2

Mams?,

Patented Mar. 18, 1930 l UNITED. STATES "PATENT OFFICE EDWARD M. FREELANCE), OF STEIBIEINVILLE,` OHIO, AND FRANK MCGOUGH, OF FOLLAINS- BEE, WES'I1 VIRGINIA, ASSIGNORSv` TO FOLLNSBEE BROTHERS COMPANY, OF PITTS- BURGH, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA APPARATUS Fon `:HEATING Application filed May 31,

Ufor the handling of metal sheets and plates, it

being understood thatthe constructional features of the furnace are' such as to adapt it to other uses, and the manner of heating is such as to render it desirable not only for heating for reworking, but for the heat treating ofA any desired obj ect.

lrVith heat treating surfaces 0f the character referred to, it isdesirable not only to provide a construction capable of operating efficiently from the standpoint of fuel consumption, but also of creating temperature conditions, such that a sheet is subjected onv y all of its sides' and throughout substantially the entire area thereof to substantially uniform temperature conditionsat some time prior to its discharge from the furnace. It is further important to provide a furnace structure such that the articles being heated or heat treated are maintained out of contact with surfaces or supports having` such tem-1 perature characteristics as to mar the surfaces of the articles in contact therewith, or to prevent the obtaining of the desired temperature conditions. It is one of the objects of the present invention to provide a furnace of the general'charater referred to and capable of eiiicient operation both from the standpoint Iof fuel consumption and from the standpoint of the temperature conditions created and maintainedv therein.

With continuous furnaces, 1t has been customary to provide conveying mechanism i effective for supporting and conveyingthe sheets through the heat-treating zone. It has frequently been found that such mechanism under the conditionsy heretofore avail- 1927. serial im. 195,241.2;A

able has resulted ,in the pitting of the sheets at the points. of contact between the sheets and the mechanism. We have found that this pitting of the sheets is due to a large extent and almost entirely by reason of the temperature differential between the sheets and such mechanism. r

lVe have further found that in the handling of relatively large sheets, the sheets themselves constitute, in effect, a partition between the source of heat and the mechanism effective in such manner that, during the major portion of the time the furnace is in operation, the mechanism is subjected to A temperature produced largely, if not entirely, by radiation from the lower sides of the sheets. Not only is such radiation insufcient to raise the temperature of the mecha` nism to a-temperature equal to that of the main body of the sheets themselves, but it tends to lower the temperature of the sheets on one side in direct proportion l to the amount of heat radiated, whereby it has been extremely difcult, ifrnot impossible, to obtain a .uniform temperature throughout the same. This temperature differential while substantially negligible with relatively thin sheets by reason of the heat convection characteristics thereof, as well as the intermittent and varied points of contact where the construction of the mechanism is such as to provide a contact of this character, becomes increasingly moremarked as the thickness of the sheets is increased. The actual difference in temperature is also dependent upon the character of the mechanism and its mass, as compared to the mass of the sheets. This is particularly true where the mechanism is of ated downwardly from the sheets to the conveying mechanism, but it is also radiated downwardly to at least certain portions of the bottom of the furnace. In usuali furnace structures, thebottom is of considerable mass and consequently lcapable of absorbing a very substantial amount of heat without being able to effect any return to the sheet of an equivalent amount of heat. The result has been that a temperature differential has existcombustion gases.` f

vbeen found that the time of treatment may,

however, be reduced by the use of heating ases in direct contact with material, and t at the cost of producing the desired temperature conditions therein may likewise be e reduced where provision ,is made for direct Contact. It is also well known that direct contact provides a more desirable atmos-K phere from the standpoint of non-oxidation than does a furnace of the muiie type.

The present. invention has for one of its objects the provision of a furnaceof suchf construction that where utilized for the heat treating of sheets, successive sheets may be rapidly subjected'to the desired temperaturel conditions in such manner that pitting thereof is obviatedf Another objectl of the invention is to provide a method suitable for the treatment of sheets and of such nature that`not only is the time of 'treatment reduced, lbutv lalso that `the cost.l is considerably decreasedbothv by the more effective conservation-of heat and the more effective utilization of the heat of the Still another object ofthe presentinvention is to provide a method and apparatus for theheat-ing for reworking or for theV heat treating ofmetal articles, bodies or shapes,

` -such that they are subjectedto progressively" higher temperatures from the inlet of the` furnace to the outlet thereof,"whereby the relatively cold entering bodies become effective lfor absorbing the maximum amount of heat from the waste gases charge thereof.

Inl the accompanying drawings, we have shown for purposes of illustration only, certain preferred embodiments ofthe present invention, it being understood that the drawings do not define the limitssthereof, as changes in the construction and operation Y, may be made without departing either from btheispirit of the present .invention or the scope of our broader claims.`

In the drawingsz f Figure 1 is a longitudinal vertical section, partly in elevation and partly broken away, through one form of furnace constructed .in

' j accordance with the present invention;

Figure 2 is a transverse sectional View on 1 Figure 3 -is a view similar to Figure '1, illustrating a slightly-modified embodiment of the present invention. 5 l In accordance with the present invention,

there maybe provided a furnace having any prior to the disi have heretofore prevented the maintaining vention, we may tion and manner of supporting the same, the present invention being adaptable for' use with furnaces of diderent characteristics in -this respect. As illustrated herein, the furdesired constructional characteristics with relspect to the general arrangement, construcnace, is-a suitable run out table 6. The dis-lVv charge opening may be controlled in any desired manner, but for purposes v which are hereinafter more fully setp'forth we have found that desirable results may be obtained by the u`se of an adjustable closure 5.

For effecting movement of thev material through the furnace, there may be provided conveying mechanism 7 of` any desired contrated as ,comprising a series of water cooled -transversely extendingA shafts 8 each pro struction, such mechanism being herein illusprovision of beveled gears .1() thereon cooperating with suitable dmriving mechanism.'

For heating the furnace there .may be provided any desired number and arrangement of burners 11 cooperating with the furnace chamber in such manner as to produce a re` gion of highest temperature adjacent the closure 5. The combustion gases are permitted to come into direct contact with the material supported by the conveying mecha nism insuch manner as to directly envelop the same. Where, however, sheets are being conveyed, it has been found that such sheets of`conditions effective for the desired temperature both in the conveying mechanism and throughout the entire area of the sheets. As previously pointed out we have found that this is due'in large measure tothe tendency of the sheets to radiate heat downwardly without the provision of any means'for restorin or renewing the-heat thus lost. In A accor ance with one feature of the present inprovide` `the floor of thel furnace `with a series of lues 12 extending longitudinally thereof. At one endthe flues are adapted to receiveheating gasesidirectly from the furnace chamber as willfbe clearly a parent from Figure 1 of the drawings w 111e at the opposite end they discharge into a stack flue 13 leading to the stack 14. tiWhile the iues may be of any desiredV construction, we have found that the most advantageous results are obtained by the provision of a liue structure such that a temperature condition the conveying mechanism and in the furnace floor, substantially equal to the temperature in the main portion of the furnace chamber,

may bedmaintained. To this end, the iues are conveniently constructed of material having a high heat transfer coefficient and* preferably of relatively light mass at least at that portion representing the division between the furnace chamber and the line.

With a construction of the generall character'referred to, sheets admitted to the furnace through the charging opening and passed therethrough are subjected to progressively increasing temperatures. Adjacent the charging end of the furnace, the relatively cold sheets are effective for absorbing the maximum amount of heat from the waste gases, whereby heat conservation is effected. As the sheets approach the discharge end of the furnace, they are brought into a temperature zone of substantially uniform characteristics throughout. The heat radiated upwardly to the conveying mechanism and to the sheets by the ues 12 maintains that portion of the conveying mechanism which comes into contact with the sheets at a temperature substantially equal to the temperature in the sheets themselves.' This temperature equilibri'um between the sheets and the conveying mechanism obviates the objectionable pitting which has heretofore resulted. f

By the utilization of an adjustable closure 5 for the discharge opening, in combination with the adjustable closure-3 for the charging opening it will be apparent that the pressure conditions within Mthe furnace chamber may be varied at will. By restricting the iiow through these openings, a relatively higher pressure resulting in the passage of a greater proportion of the gases through the flues will be established, while by adjusting the closures in such manner that a relatively freer flow of gases directly Jfrom the chamber is permitted,

' a proportionately smaller flow through/the flues may be obtained. The adjustable closures in addition to regulating the pressure within the furnace and the flow of combustion products through the flues, likewise determine the character of the atmosphere within the furnace and the frequency (if complete renewal of such atmosphere.

The construction also'lends itself admirably to conveyin mechanism of the water cooled type, there y enabling the use of material of a relatively vinexpensive nature in contrast to the more expensive materialsrequired wherewater cooling is not employed. In other words, the utilization of lues having the characteristics referred to, results in the creation of a temperature condition immein the furnace. Consequently, they are effective for maintaining a temperature `in the portions of the conveying mechanism which contact with the sheets, which is substantially equal to and preferably as high as or higher than the temperature of the sheets themselves. This temperature conditionwhile of relatively minor importance adjacent the charging end of the furnace, is of utmost importance in the zone or zones of higher temperature in the furnace, in which zones uniformity of temperature throughout the material being heated for reworking or heat treated is both desirable and essential.

In Figure 3, thereis illustrated a slightly modified embodiment of our invention, in

which we have indicated lues 12 so disposed.

as to lie closely adjacent the under side of the material M being treated and between the vsupporting parts of the conveying mechanism 7. Inthis position, they are directly effective o'n the'supporting portions of the conveying mechanism and on the lower surfaces of the material whereby radiation or convection of heat from such material to the conveying mechanism or to the bottom of the furnace,

isaprevented.

It will be apparent toy those skilled in the art that the present invention involves an operation either in connection with the heating forkreworking or the heat treating ofimaterial whichy represents afundamental advance in the art. Such advance is obtained by reason of the creation of temperature zones such that uniform temperature conditions throughout an entire body of material are obtainable in the zone or zones of higher temperature within the furnace, such conditions i being obtained with the use of a conveying tmechanism the supporting portions of which are kept at all times at a temperature such that pitting of the surfaces with which they come into Contact is obviated. Our invention, therefore, is limited only to the construction of a furnace such that the desired temperature conditions at a predetermined zone or zones may be obtained and maintained irrespective of the constructional features provided for effecting the same. More particularly our invention is predicated on therealization ofthe cause of pitting in material sueh as sheets and in the maintaining of temperature conditions such that pitting is prevented, together with the obtaining of uniform temperature conditions ,throughout the material itself. j

The term heating as hereinafter utilized in the claims is used in its generic sense as definitive of an operation having for its purposs.either a heat treating or a heating for for supplying products of combustionrto said fichamber, and indirect heating means inter.

mediate the supporting plane of said conveying means andthe main "furnace bottoni receiving and conveying such products of combustionvand serving to heat said conveying means and prevent radiation of heat .downwardly from material thereon.

2. vIn aheating furnace having a heating chamber, conveying means therein, burners for supplying productsof combustion to said chamber, and indirect heating means intermediate the supporting plane of said conveying means and the main furnace bottom, said indirect heating means lcomprising a pluf rality of flues adaptedV to receive and convey such productsl of combustion from said cham-y ber and serving to heat said conveying means our hands.

and prevent radiation of heat downwardly from material thereon.

, 3. In a heating furnace having a heating chamber, conveying means therein, burners for supplyin products of combustion to said chamber, an mediate the supporting plane ofsaid conveying means and the main furnace bottom receiving its heating medium fromA said cham- 'ber' adjacent the discharge end thereof receiving and conveying such products of comf bustion and serving to heat said conveying means and prevent radiation of heat .down-l wardly from material thereon.

In testimony whereof we have hereunto set EDWARD M. FREELAND. FRANK MCGOUGH.

mdirect heating means inter- A

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