US1840661A - Furnace - Google Patents

Description

Jan. 12, 1932. F. A, FAHRENWALD 1,840,661

FURNACE Original Filed Dec. ll, 1926 Franz: A. 1Jahr-mwen Attorneys Patented Jan. 12, 1932 PATENT OFFICE FRANKA. FAHREN'WALD, 0F CHICAGO, ILLINOIS FURNACE Application led December 11, 1926, Serial No. 154,151. Renewed January 30, 1931. rllhis invention relates to furnaces of the the left hand side of Fig. 1; Fig. 4 is a horitype wherein a plurality of horizontal parallel rolls are mounted in a heated chamber for the purpose of conveying therethrough ,E articles which are to be heated for various purposes, as for rolling or forging operations, metallurgical treatment, enameling, baking, or other industrial purposes. The articles delivered to such furnaces consist of mi rods, sheets, plates, billets, bars, to be heated 30 cooled shafts.

thelnselvesfor containers, boxes, trays, and pallets containing metallic, ceramic, plastic, or even edible substances.

The object of the present invention is the 5 provision of a new and improved construction of roll and support enabling such rolls, to be supported wholly at one side of the furnace, and this, if desired, wholly Without the use of expedients for cooling the rolls. Numerous roll constructions havel heretofore been known and used, having bearings at opposite sides of the heated chamber and outside of the furnace-wall, but certain instances arise wherein it is desirable to locate a furnace either adjacent to a blank wall or to another furnace, which renders it inconvenient or impossible to provide a bearingoutside of one of the furnace walls. Most of these previous constructions have included Water- The present invention includes not only the employment of a cantilever type of roll, but also a roll which is subjected, without cooling. to the full temperature of the furnace, which entails f-urther provisions to inhibit the flow of heat to the bearings and also to support the mechanical strain despite the inevitable weakening of the metal due to its high temperature.

In the drawings accompanying and forming a part of this application I have illustrated a few typical forms in which my inventive idea is embodied. Fig. 1 is a view of two furnaces located side by side and equipped with my improved'rolls; the form varying slightly in the two furnaces; Fig.' 2

. is a horizontal'sectional view on the line 2 2 of the furnace shown at the left hand side of Fig. 1 drawn to much smaller scale; Fig. 3 is an enlarged detail of the bearing shown at zontal sectional view on the line 4-4 of the furnace shown at the right hand side ofFig. 1, drawn to much smaller scale;- Fig. 5 is an enlarged sectional view of the bearing shown at the right hand side of Fig. 1; and Fig. 6 illustrates a modication. v

In these drawings I have shown two furnaces, 1 and 2 located side by side, with a common wall 3 between them, each furnace having a roof 4, and an outside wall 5, formed with apertures 6`for the insertion of the heat producing device, whether it be a gas burner, electric connection, or oil burner or other well known type of device, each wall also having a series of circular openings 7 7 for the reception of the rolls. Outside lof eachY of these apertured walls is located a rigid supporting pier 8, and projecting through each of the apertures 7 is a horizontal, hollow, rotatable roll indicated generally at 10, 10, 10", and having at kits outer end an axial shaft extension 11` 11" journaled in suitable bearings 12 carried by said pier.

In the preferred construction these bearings are carried by the upstanding arms, 13, 13 of brackets rigidly secured to the piers, there being two bearings to each shaft eX- tension and suiiciently spaced apart to hold the roll steady. Between these bearings the shafts are provided with the driving means, vpreferably worm Wheels 15 meshing with a longitudinal worm 16 common to them all, although sprockets 17 and chains 18 can be used, or other known devices.

They construction of roll adopted for any \`given furnace depends upon the size of the furnace, the temperature required, the weight to be supported, the shape and nature of the work, and other considerations which change with each installation. Hence these drawings are intended only to illustrate the principles of myinvention since the details of structure can and do vary very widely. .Thus in a furnace which is intended to operate on large plates, bars, pallets. trays, etc., plain cylindrical rolls may be desirable as shown in Fig.` 1. The material of the rolls depends upon the temperature for which the furnace is designed and the money available, and the 'roll material except that it must be metallic and is generally of some alloy of'chromiumgroup and iron-group metals, some of which exhibit a substantial rigidity of form at temperatures up to 20000 F. The roll shown in Figs. 2 and 3 and at the right hand side of Fig. 1 is formed outside of the wall 5 with an integral, apertured flange tightly bolted to a. companion flange 21, rigid with the shaft 11. Spacers 22, preferably of metal and imperatively of high accuracy and rigidity are interposed between the flanges, and also sometimes a sheet or pad 23 of heat insulating material. The shaft 11 is shown as hollow and as formed with apertures 24 for circulation of air. Ths is not imperative, but is very de- 20 OOsirahle. It is imperative, however, that the roll 10 be hollow to reduce its weight and consequently its strain, as well as to reduce its tendency to heat disruption and while it may not be imperative from this standpoint that the hollow extend entirely through the flange 2O, yet it is practically very convenient to support the core at both ends. Whenthe shaft 11 is also made hollow it becomes important to prevent the movement of hot gases therethrough which is one object ofthe pad 23. The spacers 22 necessarily conduct a certain amount of heat but most high temperature alloys exhibit a rather low degree of heat f conductivity, and the heat dissipating ability of the shaft extension and of the bearings is generally enough to compensate for such conduction without causingl the latter to become sufficiently hot to offer any diiliculties inl operation.

In case a higher temperature is to be empl oyed I prefer the form of roll shown on the right hand side ofv Fig. l, namely, one providing a bulge at its outer end and also preferably, tapering toward its inner end. The

severest conditions to withstand are those existing immediately inside the furnace-wall.

e maximum mechanical strain theoretically occurs adjacent to the hearing, but at this ,point the metal is sufliciently cool to exhibit its full strength, but just inside the furnace ywall the roll partakes of the full furnace temperature and also is required to support the weight of the roll inside thereof. In order to withstand these conditions the roll may be bulged'at this point as shown at 25, but such bulge when employed, is preferably merged directly with a tapered exterior portion 26 leading to the supporting shaft, so as to reduce the total cross section of the metal at this point and thus decrease the conductive transfer of heat. The roll cools very rapidly as it passes through the furnace wall and the stress, though greater in fact, can be sustained with less metal. For this reason it is desirable to form the shaft with a bottlenemesi ,effect due to the high temperatures while at all oints reducing the cross-sectional area avallable for the conduction of heat to the lowest possible amount compatible with the requisite physical strength.

It i's also desirable sometimes to reduce the weight of the roll inside the furnace, and preferably at the free end where the leverage is greatest. .This gives rise to a tapered form of roll as shown in Fig. 6 and the right hand side of Fig. l. This tapering is compensated by the use of disks 30 of uniform external diameter but varying bore mounted at intervals on the rolls, the disks of one roll generally alternating with those on adjacent rolls as shown in Fig. 4, so that plates, sheets, etc., receive a maximum of support. The tapered form of roll, which may either be abruptly bv steps as in Fig. 1, or a uniform cone as in Fig. 6, facilitates construction by requiring only a minimum of external machine work.

Making the roll 10 and shaft 11 separate facilitates the making of the bearings and saves weight of alloy, but at some risk of misalignment. It also enables replacement of a part only of each rotating element in the event of failure for any cause. In some cases it is preferred to make the roll 10b and shaft 1lb in a single casting, in which event the whole is preferably made hollow from end' to end as shown in Fig. 6, ow of hot gases through the same being prevented in some way as by a plug 31, which may be either metallic or cementitious. I have also shown a cement plug in Fig. 5, placed so as not only to`prevent outflow, of hot gas but also'to shield a part of the wall 26 and thus facilitate cooling.

Obviousl vone can use other types of bearings, as in icated in Fig. 6 where 32 denotes a hollow casting with bushings 33 pressed into the ends. In all the forms illustrated an effectual heat-dam isvprovided'which .prevents the i'low of heat to the bearings either by conduction, radiation or convection.

Conductive flow is impeded in Figs. 1, 2, 3 and- 5 by restricting the cross-sectional area of metal available for such conduction and also by the fact thathigh-temperature resistant alloys customarily exhibit a rather high resistance to heat conduction; and in Figure 6' by the restriction of cross-section due to the bottle-neck shape. Radiation along a tubular member of small bore is of comparatively little importance, and the transfer of heat therealong by the outflow of furnace gases which are often maintained at a slight superatmospheric pressure is most easily prevented by plugging or obstructing the interior at some point along its length. The same result would obviously be produced by making i supported.

the hollow roll without any opening communicating with the furnace interior, or by using a solid shaft at 1l as heretofore suggested- Accordingly I intend the word "means in1 my claims to include any feature whether of construction, design, or addition as shall prevent any harmful heat-flow along the roll. namely such a rate of heat-How as shall exceed the normal dissipating rate of the exposed portions at a practical bearing temperature. d

l have not shown any provision for closing the gap between each roll and its aperture. This is often left open, since the vpressure gradient is either zero or very low. It will be understood that many changes can be made within the scope of my invention.

Having thus described my invention what I claim is:

l. The combination with a furnace having a side wall provided with apertures, of a series of hollow. horizontal, metal rolls projecting into said furnace, one in each aperture, said rolls being made of high-temperature-resistant alloy, the thickness of the walls of the hollow portions being everywhere substantially the same, hollowfshaft extensions coaxial with said rolls at their outer endsf bea rings for said shaft extensions, and means preventing the flow of fluid from the interior to the exterior of said furnace through said rolls, the inner ends of said rolls being un- The combination with a furnace having a side wall provided with apertures, of a series of hollow, horizontal, metal rolls projectin into said furnace, one in each aperture. sha y extensions coaxial with said rolls at their outer ends, means for preventing flow of fluidsthrough said rolls between the interior andexterior of said furnace in either direction, and bearings for said shaft extensions, the inner ends of said rolls being free and at least that portion of each roll which is exposed inside the furnace chamber being made of high-temperature-resistant alloy.

3. The combination with a furnace having a side wall provided with apertures, of a series of hollow, horizontal, metal rolls projecting into said furnace. one in each aperture, hollow shaft extensions coaxial with `said rolls at their ends, lneans for preventing gas flow between the interior and exterior of said furnace by way of'said shaft extensions, and cantilever bearings for said shaft extensions located outside of said furnace Walls.

at least that portion of each roll which is exposed inside the furnace chamber being of lii,gh-temperature-resistant alloy. i

4l The combination with a furnace having a side wall provided with apertures, of a series of horizontal hollow metal rolls projecting into said furnace, one in each aper-` ture, shaft extensions coaxial with said terior and exterior of said furnace by way of the interiors of said rolls, at least that portion of each roll which is exposed inside the furnace wall being of high-temperature-resistant alloy and the cross sectional area of said rolls being smaller, at the bearing por\ tion than within the furnace.

5. The combination with a furnace having a side wall provided with apertures, of a series of hollow, horizontal, metal rolls projecting into said furnace, one at each aper- Y ture, each of said rolls having a larger external diameter inside the furnace than outside the same, an axial shaft extension rigid with said roll outside said wall, the walls of said roll having substantiallyr equal thickness at all points, means for preventing movement of heated gases through said roll from the furnace interior through said wall, and cantilever bearings for each of said shaft extensions, the opposite ends of said rolls being free.

6. A roll for furnaces consisting of a metal body which is symmetrical about a longitudinal axis and is formed at one end only with a portion of bottle-neck shape where it traverses the furnace wall, said body being hollow and made of high temperature' resistant alloy and having walls of substantially uniform thickness at all points inside the furnace chamber, an axial shaft extension carried by the smaller end of such bottle-neck portion, and spaced external bearing 'portions formed on said shaft extension.

7. A cantileverrollforfurnacescomprising a hollow metal body having at one end a hollow axial shaft' extension, and at the other end an axial opening, and means for preventing gas convection between the interior and exterior of said furnace through said shaft extension, said Vshaft extension being alone provided with bearing surfaces.

8. A cantilever roll for furnaces comprising a hollow metal body having its exterior at the portion which traverses the furnace wall reduced gradually in diameter from within outwardly, said roll comprising means to prevent gas flow therethrough, thev Wallthickness of said roll being everywhere substantially the same, said roll having bearing portions at one end only and these confined to the portion of reduced diameter.

9. A metal roll for furnaces, tapered throughout the portion' inside the furnace andvhaving spaced seats thereon, in combination' with a series of circular metal disks of equal -external and unequal internal diam-` hollow throughout the portion inside the furnace and having a substantially uniform wall-thickness t throughout the hollow portion, and an axial shaft extension projecting from the outer end thereof, said shaft extension being smaller than the roll and formed with bearing provisions.

11. A metal roll for furnaces, having an axial shaft extension at one end only, a rapidly flaring hollow portion adjacent to said shaft extension, and a hollow portion beyond v such flaring portion, and means for preventing gas flow through said roll.

12. The combination with a furnace having a sidewall provided with apertures, of a series of horizontal metal rolls projecting into said furnace, one in each aperture, each roll comprising a hollow body-portion inside the furnace and an axial shaft-portion outside the furnace, the body-portions at least of said rolls being made of high-temperatureresistant alloy and of larger diameter than the shaft portions, a pair of cantilever bearings'for each of said shaft-extensions located outside of said furnace wall whereby said rolls arersupported and means preventing the abstraction of heat from said furnace by fluid How through said roll.

13. The combination with a furnace having a side wall provided with apertures, of a series of horizontal rolls projecting into said furnace, one in each aperture, each roll having a coaxial shaft-extension at one end only, at least the body of said roll being hollow and made of a high-temperature-resistant alloy, cantilever bearings for said shaft extension, and means for preventing abstraction of heat from said furnace by heat flow alongA said roll.

14. A roll for furnaces comprising a hol` low body ofhigh temperature resistant alloy having walls of substantially equal thickness at all points, and a shaft-extension separate from said body and secured to an end thereof,

said shaft-extension'having an enlarged portion by which the body is supported and a portion of smaller diameter coaxial with said bodyand formed with longitudinally spaced bearing portions.

15. The combination with a roll body of high temperature resistant alloy, said body being hollow vand having an unimpeded central bore, of a support therefor comprising a shaft extension having a portion of smaller diameter than said body coaxial with said body and having axially spaced bearing p0rtions, said shaft extension having an enlarged portion at the end adjacent to said body and operatively secured thereto, and a supporting device for said shaft extension havingl spaced tions.

16. The combination with :a furnacehav ing an apertured side wall, of rolls journaled outside of said wall and projecting through journal boXes for said bearing porsaid openings into the furnace chamber, each roll comprising a .hollow body portion of high-temperature resistant alloy, and a separate shaft-extension rigidly secured thereto, said shaft-extension having at the end next to said body an enlarged portion by which said body is supported and also having a portion of reduced diameter formed with axially spaced bearing portions, and a supporting device located outside of said wall and provided with spaced journal boxes for said bearings respectively.

17. A metallurgical furnace of the rollhearth type-having a side Wall formed with horizontally spaced apertures, horizontal rolls traversing said apertures, each roll comprising a hollow body portion of hightemperature-resistant alloy having la shaft extension separate therefrom and operatively secured thereto, said shaft extension comprising an enlarged circular head adjacent to said wall and a reduced portionprojecting outwardly from said wall provided with bearing portions at axially spaced points, and two bearings for each of said shaft-extensions located one beyond the other at unequal distances outside of said wall.

18. A metallurgical furnace of the rollhearth type having a side wall formed with horizontally spaced apertures, ahoizontal roll traversing each aperture, and cantilever bearings for said rolls in line with said apertures, each of said bearings comprising horizontally spaced journal boxes located one beyond the other at unequal distances from said Wall, shaft extensions journalled in said bearings and having enlargements adjacent to said Wall, and a hollow body carried by the enlarged end of each shaft extension` at least the body-portion ofv each roll consisting of high temperature resistant alloy and the diameter of such body portion being greater than that of the corresponding bearings.

In testimony whereof Ihereunto alix my signature.

'FRANK A. FAHRENWALD.

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