US2215519A - Hot air furnace - Google Patents

Description

sept 24, 1940 w. s. ANDERSON, JR., Er A1. 2,215,519

HOT AIR FURNACE 3 Sheets-Sheet l Filed Aug. 9, 1957 Sept. 24. 1940- w. s. ANDERSON, JR.. r A1. 2,215,519

HOT AIR FURHACE Filed Aug. 9, 1957 3 sheets-sheet 2 Sept. 24, 1940.

w. s. ANDERSON, JR.. ET AL HOT AIR FURNACE Filed Aug. 9. 1957 3 Sheets-Sheet 3 Patented Sept. 24, 1940 2,215,519 Hor AIR FURNAoE William S. Anderson, Jr., and George I. Staber,

Williamsport, Pa., assignors, by mesne assignments, to Aviation Manufacturing Corporation, a corporation of Delaware Application August 9, 1937 Serial No. 158,104

3 Claims. (01126-107) The invention relates to hot air furnaces.

One object of the invention is to provide a construction of hot air furnaces of the type in which the heater is provided with a magazine for solid fuel at one side and a combustion chamber with an arched roof at the other side, by providing a heater-body which is composed of longitudinal sections and transverse end sections secured together, and connected by expansionjoints.

Another object of the invention is to provide a hot air furnace with cast iron walls around the combustion chamber nre-box, which is adapted to avoid failure in, or grain growth of, the walls when cast of greyviron.

Another object of the invention is to provide a construction of hot air furnace of the magazine feed type which permits the walls of the lire-box and magazine to be formed of grey iron with' the minimum number of sections or plates for economy in manufacture and eicient heating.

Another object of the invention is to provide the walls of the combustion-chamber with radiator-elements or pins whereby the heat will be radiated from the diierent portions of the walls approximately proportionate to the different temperatures produced therein by the fire, to avoid severe iluctuations in the metal walls, which contributes to grain growth or failure.

Another object of the invention is to provide a furnace of this type which is built up of a relatively few numb-er oi cast parts or sections and which are adapted to be sealed at the joints without machining or other expensive labor.

Another object of the invention is to provide an improved radiator for the products Ofcombustion, which is adapted to be thoroughly and readily cleaned out when it becomes coated with soot, to avoid losses in heat transference to theV surrounding air.

Other objects of the invention will .appear from the detailed description.

The invention consists in the several novel features which a-re hereinafter set forth and are more particularly dei-ined by claims at the conclusion hereof.

In the drawings: Fig. 1 is a perspective of a furnace embodying the invention, parts being broken away for illustrative purposes., Fig. 2 is a transverse section on line 2 2 of Fig. 3. Fig. 3 is a side elevation of the heater, the casing being shown in sections. Fig. 4 is afront elevathe heater. Fig. 6 is a section on `line 6-6 of Fig. 2. Fig. 7 is a horizontal section on line 1 1 of Fig. 3. Fig. 8 is a transverse section through the joint at th-e top of the dome vor the apex of the arch over the fire-bed. Fig. 9 is a Section of the sealing-joint between the rear wall and the outer side-Wall of the iuel-magazine,'be inga section on line 9-9 of Fig. 5. Fig. l0 vis a transverse section on line Illl0 of Fig. 3. Fig. 11 is a horizontal section on line I l-Il of Fig. 5'.

The invention is exemplified in a fu'rnace'counprising a heater surrounded byv a sheet metal ca'sing or jacket 2) which is provided with a coldair inlet 2l and a top 23having a hot air outlet 22 for connection to a duct for delivering the hotair to its point or pointsof use.

The heater comprises a magazine a `for coal at one side and adjacent the top of the heaterbody; an inclined grate b of any suitable con# struction; an ash-pit b" below the grate, anda combustion-chamber c with an arched roof at the other side of theV heater and above vthe grat-e, all' extending longitudinally, and ybetween thefront and rear ends, of the heater-body. 'I'hefwa-Ilsfof this heater are preferably cast of greyfiron'and` of plate-like sections which are connected by sealedexpansion-joints and provide a construction which is composed of arelatively small number of parts 0r castings for economy in manufacture and eficiency in operation. The heaterb ody comprises cast longitudinal sections d, e, f, a front end o r transverse section g, and a rear end or transverse section h. The longitudinal sections extend between the end or transverse' sections. The front end-section or plate g is formed of a single casting and fits against the front ends of sections d, e and f. The rear-end section h is formed of a single casting andabuts against the rear ends of sections d, e, Aand f. The joints between the longitudinal sections and bef tween the longitudinal and transverse sectionsare of the expansion-type and provided with'f sealing means to `permit the expansion and con'- traction of the sectionswithout leakage of gases from the heaterto the jacket. "The 'sectiorid comprises a portion d which forms one side-wall of the ash-pit, an inset portion d2 provided with bearings 2i forthe pivots of the grateebars, van upwardly vand inclined portion d3 which forms an inclined wall on which the fuelslides bygravity to the grate b, and a vertical upperportion d4, which forms onevside-Wall ofthe magazine a. The section ehas a lower portion e which forms the other and low side of the ash-.pit with bearings 25 for the grate-bars, and an outwardly and curved portion e3`which forms one 'side-wall PATENT oFFicEgfl stirl sie? l Cil ofthe combustion-chamberc from the grate to the peak of the arched roof. The section f comprises horizontal walls f and f2 which form the top and inner side of the magazine c, respectively, and a curved wall f3 which extends upwardly from the lower end of wall f2 and forms the other side of the arched roof of the combustion chamber. A continuation 26 depending from wall f3 provides an opening between the magazine and the lire-bed to limit the delivery of fuel to the fire.

Front end-section g is provided with an integral forward extension 2l which extends through the front-wall of the jacket 20 and is provided with a door 28 for access to the ash-pit; an integral forward extension 29 which passes through the front wall of jacket 20 and is provided with a door 30 for access to the fire-bed and combustion-chamber c; a forward extension 3| which passes through the front wall of the jacket 20 and is provided with a door 32 for charging the magazine with fuel; and an integral upwardly extending duct 33 which forms a smoke-flue leading from the upper front corner of the combustionchamber to a raditor lc for the combustion pro ducts.

The longitudinal and transverse sections are held` together by a series of longitudinal rods which are adapted to hold the sections g and h into abutting relation with the ends of the sections d, e, and f. The series of rods comprises: a pair of rods 35, which extend loosely through lugs 36 which are integral with front-section y, lugs 37 which are integral with section e, and lugs 38 which are integral with section h; a rod 40 at the magazine side of the heater which extends through similar lugs on sections g, d and h; a rod 44 which extends loosely through lugs 45 on section f, lug l5a on section y, and a lug 45' on section h; and a rod 4l which extends through section g, lugs 46 in the magazine a and integral with section f, and is screwed into section h. Each of the rods 35, and 44 is provided with nuts at its ends `and rod 4l is provided with a nut at its front end. A spring 48 `is interposed between each of the lugs 31 on the rear-end section h and a nut on each of said rods 35, 40 and 44 to yielding force the longitudinal and transverse sections into abutting relation and to permit expansion and contraction thereof. A spring 48 is applied to the front end of rod 4I for the same purpose. Vertical ribs e5 are formed on the outer side of section e. Flanges d6 are formed on the ends of section d and have edges which conform to the adjacent edges of the sections g and h.

This construction exemplifies a hot air furnace of the magazine-type which is built up of longi- `mitting expansion or contraction thereof. kis accomplished by a strip of very thin metal-foil,

tudinal and transverse or end-sections which are held together in abutting relation by tie rods and springs, so as to permit expansion and contraction of the section. 'I'he sections are held together without placing any load on the sealing e. g., .0020" aluminum-foil which is lapped around or over the walls of the joint and has its margins cemented by means of a fire-resistant cement, such as putty or furnace cement, to the This walls of the joint. The seal between sections e, f, at the apex of the arched roof of the combustion-chamber c is illustrated in Fig. 8. The arched walls e3 and f3 of sections e and f, respectively, rest on lugs 50 on the transverse sections. A strip of aluminum-foil 5l is lapped around the overlapping portions of said walls and has its margins sealed at 52 to walls e3, f3, respectively. The seal between the longitudinal sections and the transverse sections is illustrated in Fig. 9. A strip of aluminum-foil 54 lapped around the outer face and edge of the transverse end-wall and a bead 53 on the outer side of the longitudinal section has its margins bonded at 55 to said walls by cementitious material 55. The seal between sections d and f is illustrated in Fig. 10 and comprises a strip of aluminum-foil 56 which laps the outer faces of said sections and has its margins cemented, as at 51, to said walls, respectively. In practice, it has been found that a flexible strip, such as aluminum-foil, which has its margins cemented respectively to the joined walls, and is somewhat crinkled or loose between its margins, will form an elective seal for the joints which permits expansion and contraction of the sections responsively to thermal changes.

In the operation of the heater, different portions of the walls around the combustion-chamber, rebed and magazine are subjected to different temperatures. When the differential in temperature is high, due to constant fluctuation, growth fatigue of the grey iron in some portions of the walls results. The invention includes means for reducing and approximately equalizing the temperature of the different portions of the walls of the combustion-chamber to prevent growth fatigue.

It is important to prevent excessive localized temperatures in the different portions of the walls and to keep them below 950 F. This temperature reduction and equalization is accomplished by providing heat-radiating pins or elements 68 which are integrally formed with and on the outside of the walls of the combustionchamber and in making them so they will have different heat-radiating or heat-transferring capacities in the different portions of the Walls, approximately proportionate to the different temperatures therein. These different capacities may be attained by having longer elements 68 in the zone of greatest temperature and shorter elements in the zone of lesser temperatures or by variation in the number of or in the distribution of the elements to provide the proportionate capacities desired.

For example, the section e which forms one side of the combustion chamber is provided with long pins 68 which are gradually reduced in length, from the approximate point where the heat is greatest toward the ash pit where the heat is less and gradually reduced in length above the point ofgreatest heat, and again increased in length toward the apex of the combustion chamber where the temperature is high.

Pins 69 are also provided on the wall f3 which forms the other side of the arched roof of the combustion-chamber, to reduce its temperature correspondingly to the other side. The inclined wall d3 of section d on which the coal slides from the magazine to the re-bed is provided with integral pins 'l0 to dissipate heat from the coal suiiiciently to prevent the coal in the throat from releasing gases which will form coke and to retard the flow of heat from the fire-box to the coal in the magazine. The side and top Cil walls of the magazine are not provided with heat-radiating elements, so that their temperatures will not be reduced. The heat will be radiated from the hottest portions of the walls more rapidly than from the cooler portions and, if the temperature diierential is kept between 800 and 980 F., crystalization will be avoided. This 'feature also results in a more even and constant distribution of the heat from the heater, as contradistinguished from the complete shutting down and ring of the furnace in relatively short cycles.

The radiator 7c comprises a pair of parallel longitudinal and horizontal tubular ducts 12, 13 with semi-circular front and rear connecting ends 74, 15. The rear ends of these branches terminate in an outlet 'I6 which is adapted to be connected to the smokestack or iiue for carrying off spent products of combustion. The front end of the radiator is provided with a pair of clean-out ducts 11, respectively, aligned with the longitudinal ducts 12. Each duct 11 is closed by a removable cover 18. Heat transference through the walls and the eiiiciency of the radiator are reduced as soot accumulates on its inside. The clean-out ducts 'E8 extend through the iront-Wall of the casing 20. A clean-out duct for, and at the front of, each longitudinal branch of the radiator makes it possible to easily and thoroughly clean both branches of the radiator and remove the soot, by a suitable tool.

'Ihe invention exemplies a hot air furnace of the magazine-type; in which the Walls of the heater are formed of longitudinal sections and transverse or front and rear end-sections with sealed expansion-joints between the sections so they can be made of cast-iron and manufactured economically; in which means is provided for dierentially radiating heat from the different portions of the Walls of the heater proportionately to their exposure to heat to keep the ternperatures of the differente portions approximately uniform and prevent grain growth or cracking of the grey iron; in which the radiator, through which the products of combustion pass to the stack, is constructed of elongated branches and provided with means for facilitating its cleaning so that it will not be permitted to become partially lled with soot which reduces its eiciency; and which is efficient in operation.

The invention is not to be understood as restricted to the details set forth, since these may be modified within the scope of the appended claims, without departing from the spirit and scope of the invention.

Having thus described the invention, what we claim as new and desire to secure by Letters Patent is:

1. In a hot air furnace, the combination of a heater body comprising a longitudinally extending inclined grate at one side of the body, a longitudinally extending combined combustion chamber and fire-box disposed over the inclined grate, and a longitudinally extending fuel magazine at the upper side of the inclined grate for automatically delivering fuel to the grate, a casing surrounding, spaced from, and forming a hot air jacket around the top and sides of the combustion chamber and the magazine, the roof, one side wall, the roof and the end-walls of the combined combustion chamber and lire-box and the lower part of one side-wall of the magazine being provided with heat radiating elements having different heat transfer capacities approximately proportionate to the diierent temperatures generated respectively therein to maintain uniform temperature in said walls.

2. In a hot air furnace, the combination of a heater body comprising a longitudinally extending inclined grate at one side of the body, a longitudinally extending combined combustion chamber and nre-box disposed over the inclined grate, and a longitudinally extending fuel magazine at the upper side of the inclined grate for automatically delivering fuel to the grate, a casing surrounding, spaced from, and forming a hot air jacket around the top and sides of the combustion chamber and the magazine, the roof, one side and both end-walls of the combustion chamber, and the lower part of one side-wall and the end-walls of the magazine being provided with heat radiating elements having different heat transfer capacities approximately proportionate to the different temperatures generated respectively therein to maintain uniform heat in said walls.

3. In a hot air furnace, the combination of an inclined grate, a hot air jacket, a heater body within said jacket and having at one side a longitudinally extending magazine with an inclined side leading to the grate for feeding fuel to the grate and at its other side a longitudinally extending combustion chamber with an arched roof, the body comprising metal longitudinal sides and top sections and transverse end sections forming the walls of the magazine and the combustion chamber, the walls of the combustion chamber being provided with heat-radiating elements, the inclined side of the magazine leading to the grate being provided with heat-radiating elements.

WILLIAM S. ANDERSON, JR. GEORGE I. STABER.

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