US2420962A

US2420962A - Industrial furnace

Info

Publication number: US2420962A
Application number: US501526A
Authority: US
Inventors: Fred H Loftus
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-09-08
Filing date: 1943-09-08
Publication date: 1947-05-20
Anticipated expiration: 1964-05-20

Description

May Z0, 947. F, H I OFTUS 2,420,962

INDUSTRIAL FURNACE Filed sept. 8, 1945 2 sheets-sheet 1 JNVENTOR. Hm). Lorus Patented May 20, 1947 Unire sa amsn Tgs emessi* otros 13 Claims.

My invention relates to industrial furnaces, and is particularly directed to certain new and useful improvements in furnaces for heating elongate blanks or work pieces of aluminum, preparatory to a forging or rolling operation. The invention will be described as it has been developed for such particular eld of service, with the understanding that within the terms of the appended claims various other fields are within the contemplation of the invention.

In the accompanying drawings Fig. I is a fragf mentary view of a furnace installation in which the invention has in exemplary way been embodied, and Fig. II is a View of the installation in transverse vertical section. Fig. I appears partly in plan and partly in horizontal section on the plane I-I of Fig. II, while Fig. II, drawn to larger scale, shows the furnace in vertical transverse section, on the plan II-II of Fig. I.

Referring to the drawings, the furnace installation in which the invention is herein illustrated comprises a pit furnace having

side walls

2, 2, end wall 3, 3, and a floor 4 constructed of refractory masonry, externally sheathedin steel plate 5 and reinforced and tied by means of steel buckstays 6 that are anchored at their lower ends to a concrete foundation 1. The pit 8 is closed from above by means of a cover 9 adapted to swing on an axis IIJ between open and closed positions, and in closed position the cover cooperates with a pit-encompassing seal I I, to provide a substantially air-tight chamber in which the material to be heated or heat treated i-s enclosed. The cover is power operated, but the means to this end, as well as the specific details of the cover-sealing structure, are not an immediate concern of my present invention, and for this reason will not be described in detail.

Inlet ports I2 are provided in opposite walls of the furnaces for introducing hot gases or burning columns of fuel into the chamber or pit 8, and it will be noted that such inlet ports are located adjacent to the top or cover of the chamber. In this case the inlet ports I 2 are provided in the

opposite side walls

2, 2; the ports are spaced apart longitudinally of such side walls, as appears in Fig. I; and the fuel is preferably, though not necessarily, burned at a point remote from the ports, rather than being admitted immediately to the furnace chamber by mean-s of burners located in the ports.

More particularly, the fuel is burned in a combustion chamber I3 removed from the furnace structure proper, and the hot products of combustion are propelled by means of a fan 22 (driven by an electric motor 23) through a passage 24 into a flue I4 equipped with a damper I5. The ue I4 is the inlet flue of the furnace. It comprises a tunnel flue that extends longitudinally beneath the chamber or pit 8 of the furnace, and from such tunnel flue passageways I6 lead through the furnace hearth and side walls to the inlet ports severally. The passageways I6 are provided with dampers Ilia which afford control of the hot gases flowing into the furnace chamber. The hot products of combustion delivered into the furnace chamber, at uniformly distributed points longitudinally thereof, sweep over and between the pieces of work to be heated- 'in this case bars B of aluminum--and nd escape in outgo ports I1.

The outgo ports I'I are formed in the iloor 4 of the furnace chamber, and are spaced apart on the longitudinal center-line thereof. An 'outlet tunnel flue I 9 extends longitudinally beneath the furnace chamber, and to this flue the outgo ports deliver the exhaust gases by way of passageways E8. The tunnel flue I9 extends from the furnace to a point adjacent to the remotely situated combustion chamber I3, and a duct 20 affords communication between ue I9 and the ycombustion chamber. A burner 2I is arranged to direct ud `fuel and air into the combustion chamber, and

under the propulsion offan 22, a continuous circulation of hot gases is established .and maintained. The hot gases generated by the combustion of fuel are delivered into the tunnel flue I4, whence they stream to and through the passageways I6 and ports I2 into the furnace chamber containing the work to be heated.

As will present-ly appear in greater detail, the billets or bars B of aluminum that constitute the furnace charge are positioned in a cradle 25 of skeleton construction, and the individual bar-s are supported in spaced relation. The hot gases streaming into the top of the furnace chamber passl downward through the spaces between the bars B of the charge and enter the outgo ports Il, whence they iiow through Athe outgo flue I9 and return to the combustion chamber I3. The hot gases owing through the furnace chamber yield large quantities of heat to the 'furnace charge, and upon returning to the combustion chamber I3 the heat thus yielded by the ga-ses is restored by the burning fuel. In this way, the residual heat Ain the gases leaving the work-heating chamber 8 of the furnace is conserved, and the thermal efficiency of the installation maintained at maximum value. A quantity ofy gas is bled from the continuously circulating stream,

and such quantity is equal to the quantity of hot gases generated by the combustion of fuel injected by the burner 2l. A vent 25 including a valve 2l is provided at the cool end of the combustion chamber, the end into which the gases returning from the furnace enter the combustion chamber, and this vent provides for the bleeding away of the excess gas. The adjustment of the valves I5 and 28 in the flues I4 and I9, respectively, together with the adjustment of the bleeder valve 2l, and the regulation of the speed of the fan and the rate of combustion within the chamber I3, affords the desired control of the circulating hot gases, and ofthe heatingeffect of the furnace. The adjustment of the dampers I 6a, that individually control the flow of the hot gases to the inlet ports I2, provides for the regulation of the heating effect longitudinally of the furnace chamber. Uniform heating conditions ythroughout the extent of the furnace chamber are lobtained.

Having described furnace structure per se, at-` 'tention will 'now be directed to the improved support for the work to be heated. A problem in `the heating of a batch of articles, such as the bars B, lhas been to provide a uniform flow of the 'hot gases over the surfaces of all of the articles; that is, a now of gases that Will afford uniform heating effect throughout all of the furnace charge. The cradle 25 affords a solution `of this problem.

A As already mentioned the rcradle 25 is of skeleton "construction, More particularly, lthe 'cradle is formed lof a plurality of W shaped frame members '(Fig. II) to which the reference numeral 25 is immediately applied. These frame members arelspaced apart to provide an elongate cradle for the bars to be supported, and are integrated by -means of sections 29 of I-beams extending in parallelism 'between the successive rmembers l2li and being Welded thereto at the bottomsof the two Vs ofthe W. The members 25 are vfurther united and reinforced by means of 'longitudinal tie-rods 3i) extending Ybetween the side arms of said vW-shaped framefmembers, as may cbe understood upon comparing Figs. I and QII. The bodies or'limbs of the `W -shaped members 2 5 areof I-shape Vin cross section, and are provided-at Ithe upper ends of the limbs with eyes 31, whereby the 'cradle maybe engaged by a crane vand 'lifted with its load of Work pieces B into "and from the furnace chamber. The cradle Vstructurels formed of cast iron or steel, a material of adequate strength under the effect of the heat to which the aluminum bars B are sub- 'jected 'In-this case, the bars B are of a length `that approximately equals the length of the Yfurnace chamber, Aand the bar-supporting cradle is of commensurate length. In Fig. I the bars and the cradle are shown fragmentarily, in orderthat the larrangement ofthe outgo ports Il inthe floor cradle, together With the spaced arrangement of the billets or bars B supported therein, provides for an uniformly distributed flow of the hot gases through the group of supported bars. The spaces between the bars serve in effect as lues through which the hot gases, delivered by the ports I2, stream on their way to the outgo ports I'I. The W-like arrangement of the group of bars is instrumental in establishing a uniform pressure drop through all of the devious paths of flow of the -hot gases, whereby substantially the same quantity of hot gases flows through each of the paths, with the consequence that the heating ef- -fect Yis uniformly distributed to all of the bars in the cradle.

In addition to the described arrangement of the group `of bars to be heated, another important feature Vis to be noted. The sections 29 of I-beam, that interconnect the frame members 25 of the cradle, form, When the cradle is in position of service yupon lthe :hearth of the fur-nace, parallel ycurtain Walls that extend longitudinally of and on opposite sides of the line o'foutg-o ports 1'1. These curtain `walls prevent Aa short-circuit flow of the hot gases beneath the charge of bars 1B to the outgo ports. See the arrows in Fig. 1'I that indicate the flow of the gases.

'Still another feature merits particular consideration. lt wiil be observed that the central portions of each W-shaped frame member l25, that is, the portions that form the linverted V ofthe W, support the work in such position that Va longitudinally extending flue is provided above the outgo ports Il. That Iis to say, the inverted V portions of the W-shaped frame members `25 are centered with `res-peet to the lline of outgo ports, and form with the :bod-ies of the supported 4bars B a flue into which the -gases streaming through nthe spaces between the bars-passontheir way into the outgo ports I1. The pro-vision of such flue, particularly in conjunction with the curtain walls "2S, contributes to the realization of thedesireddistribution ofgaseous novi/through the body ofthe furnace charge.

It-will be understood that various modifications Vof Vthe structure described may be adopted 'with- `tending from said vflue to said `ports, a rsecond tunnel flue ext-ending parallel tothe rst tunnel flue under the furnace chamber `and `communicating Withan outlet forwaste gases, outgo ports opening 'from the lsa-id'c'hamber at spaced-apart points, and passageways forwas-te gases leading from said foutgo ports to said second tunnel flue.

2. A furnace including a Work-containing chamber, a tunnel 7flue extending-under the Ifurnace chamber, nfiea-ns forsuppl-yinghot gases to `such flue, inlet portsopeningth'rough the opposite side walls of the chamber at spaced-'apart points in the longitudinal extent-of such walls,

-passageways extending from said flue 'to said ports, a second tunnel flue extending parallel to the rst tuunel flue under the furnace "chamber and communicating with an outlet for waste gases, outgo vports opening in the floor of the Vfurnace vchamber 'at Vspacedapart points `in 'the horizontal extent thereof Iand passageways for waste gases' extending from said outgo ports to said second tunnel flue.

3. A furnace including a work-containing chamber, a tunnel flue extending under the furnace chamber, means for supplying hot gases to such flue, inlet ports opening through the opposite side walls of the furnace chamber at spaced-apart p-oints in the longitudinal extent of such wall and adjacent to the top of said furnace chamber, passageways extending downward in the furnace structure and establishing communication between said ports and said tunnel iiue, a second tunnel flue extending parallel to the first tunnel flue under the furnace chamber and communicating with an outlet for waste gases, outgo ports opening through said floor at spaced-apart points in a longitudinal extent thereof, and passageways for waste gases leading from said outgo ports to said second tunnel flue.

4. Apit furnace including a work-containing pit, a tunnel flue extending under the pit, means for supplying hot gases to said flue, inlet ports opening through the opposite side walls of the pit, said inlet ports being located adjacent to the top of the pit and being spaced apart in the longitudinal extent of said side Walls, a second tunnel flue extending under said pit, outgo ports opening through the floor of said pit below said ports and at spaced-apart points in the horizontal extent thereof, and passageways for Waste gases leading from said outgo ports to said second tunnel flue.

5. A pit furnace including a work-containing pit, a tunnel flue extending under the pit, means for supplying hot gases to said flue, inlet ports opening through the opposite side walls of the pit, said inlet ports being located adjacent to the top of the pit and being spaced apart in the longitudinal extent of said side walls, a second tunnel flue extending under said pit, outgo ports opening through the floor of said pit below said ports and at spaced-apart points inthe horizontal extent thereof, and passageways for waste gases leading from said outgo ports to said second tunnel flue, means in said pit for supporting a plurality of pieces of work in spaced-apart relation athwart the paths of flow of hot gases streaming from said inlet ports to said outgo ports.

6. A pit furnace including a work-containing pit, a tunnel iiue extending under the pit, means for supplying hot gases to said iiue, inlet ports opening through the opposite side walls of the pit, said inlet ports being located adjacent to the top of the pit and being spaced apart in the longitudinal extent of said side walls, a second tunnel iiue extending under said pit,outgo ports opening through floor of said pit at spaced-apart points in the horizontal extent thereof, and passageways for waste gases leading from said outgo ports to said second tunnel flue, means in said pit for supporting a`plurality of pieces of work in spaced-apart relation athwart the paths of flow of hot gasesstreaming from said inlet ports to said outgo ports, said last means comprising a cradle of skeleton construction and of W shape in cross section. A

7. A pit furnace including` a work-containing pit, atunnel iiue extending under the pit, means for supplying hot gases to said ue, inlet ports opening through the opposite side walls of the pit, said inlet ports being located adjacent to the top of the pit and being spaced apart in the longitudinal extent of said side walls, a second tunnel iiue extending under said pit and comgases into said chamber, an outgo p-ort opening through the iloor of said chamber for leading waste gases therefrom, anda cradle of skeleton construction for the support of a plurality of pieces of work in said chamber, said cradle being of W-shape in cross section, with the inverted V of the W positioned over said outgo port.

9. A furnace including a work-containing chamber, inlet ports for introducing hot gases through the opposite side walls of said chamber at spaced-apart points in the longitudinal extent thereof, outgoports opening through the floor .of

the chamber at spaced-apart points in the extent of the center-line thereof, and a cradle of skeleton construction and W shape in cross section for supporting a plurality of pieces of work in said chamber, said cradle being arranged with the inverted V of the W centered 'with respect to said center-line.

10. A furnace includingV a work-containing chamber, inlet ports for introducing hot gases through the opposite side walls of said chamber at spaced-apart points in the longitudinal extent thereof, outgo ports opening through the fico-r of the chamber at spaced-apart points on the center-line thereof, and a cradle of skeleton construction for supporting a multiplicity of pieces of work in spaced-apart relation in said chamber, said cradle being formed of material of higher resistance to heat than the pieces of work contained therein, said cradle being formed to provide in conjunction with the supported pieces of work a flue above the outgo ports in the fio-or of said pit.

11. A furnace including ,a work-containing chamber, inlet and outlet flues extending under the furnace chamber, a plurality of inlet ports opening thro-ugh a wall of the furnace chamber at spaced-apart points in the extent thereof, passageways extending from said inlet flue to said inlet ports, a combustion chamber connected to deliver hot products of combustion into the inlet flue, a plurality of outgo ports opening from the furnace chamber, passageways c-onnecting said outgo ports to said outlet ilue, a passage from said outlet flue to said combustion chamber, means for supplying fuel to said combustion chamber, means for propelling pro-ducts of combustion from said combustion chamber through said inlet ue to said inlet ports and into the furnace chamber, from said furnace chamber through said outgo ports into said outlet ue, and from the outlet flue back into said combustion chamber, and means for bleeding spent gases from such circulating stream of gases.

12. `A furnace including a work-containing chamber having a line of outgo ports opening through the floor of the chamber for the escape of exhaust gases, means for supplying work-conditioning gases to said chamber, a work-support of skeleton construction for supporting a plurality of pieces of work in said chamber, said work-support including portions which, with the 7 work-support in service position Within the furnace chamber, form baffles that extend longitudinally of and on opposite sides of said line of outgo ports, to provide within the loaded work-support, the effect of a iue extending along said line of outgo ports.

13. A furnace including a furnace chamber, means including inlet ports for introducing hot gases to said chamber, outgo ports for leading gases away from the chamber, and means for supporting a group of elongate articles spaced apart and extending horizontally across the lines of flow of the hot gases streaming from said iniet ports to said outgo ports, said means being constructed to support said spaced-apart articles, with the cross-sectional extent of the group decreased toward the bottom of the group, whereby CES CITED The following references are of record in the le of this patent:

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