USRE22694E - Automatic stoker - Google Patents

Description

Nov. 20, 1945 I. A. WINTER AUTOMATIC S'roK En Original Filed March 31, 1941 3 Sheets-Sheet 1 Fig. 1"

IN VENT OR:

Nov. 20, 1945.

l. A. WINTER AUTOMATIC STOKER 3 Shets-Sheet 2 Original Filed march 31, 1941 A'I'I'ORNEYS.

. Nov. 20, 1945. l. A. WINTER 22,694

' AUTOMATIC STOKER 7 Original Filed March 31, 1941 :s Sheets-Sheet 3 I l l I L INVENTOR:

J/m/ 4.2M may? ATTORNEYS.

Reismed Nov. 20, 1945 Y UNITEDQV'STATES PATENT OFFICE Ireal A. Winter, Birmingham, Ala.

Original No. 2,341,252, am February a, 1944, Serial No. 386,153, March 31, 1941. Application for reissue January 22, 1945, Serial No. 573,960

20 Claims.

This invention relates to automatic stokers for the burning of solid fuel, and particularly to fully automatic stokers and ash removal systems for use in home and apartment house heating plants, and in industrial installations.

Objects of the invention are to provide automatic stokers of novel design, and of novel, combustion characteristics, in which various types of anthracite and bituminous coals may be burned with equal ease andfacility. An object is to provide an automatic stoker in which the fuel and air passages are so related, and the ash is continuously removed in such manner, that the fuel burns with a torchlike flame. An object is to provide an automatic stoker including a rotary hearth, mechanism for feeding crushed coal plying combustion air at regions that result in a fuel bed of substantially constant depth and surrounded by an ash bed that protects the hearth from damage, and devices for agitating the ashes and preventing the formation of a clinker ring. A further object is to provide an automatic stoker of the stated rotary hearth type in which the hearth is retained upon its support by the weight of the hearth and the coal and ash upon the hearth, the hearth being rotated by a rotary v v tions on the planes of lines 9-4 and |l0, respectively, of Fig. 6;

Fig. 11 is an enlarged and fragmentary plan view of the rotating hearth and tllyre;

12 is a sectional view taken'on theplane of line l2-II of Fig. 11;'

Fig. 13 is a fragmentary plan view of another embodiment of the invention that includes an automatic pneumatic ash remover;

Fig. 14 is a fragmentary se'ction,'on an em larged scale, taken on the plane of line ll-H of Fig. 13;

Fig. 15 is a vertical section taken on the plane ofline ll5 ofFig. 14;

Fig. 16 is a fragmentary enlarged section taken on the plane of line Ilil6 of Fig. and

Fig. 17 is a fragmentary section taken on the plane of line l|l| of Fig. 16. I

In the drawings, the reference numeral l identifies a motor that drives the blower 2 and the.

of the tubular member 5. The burner is located in the usual position within the furnace 5, and ashes are removed from the interior of the furnace through an ash tube 1 and deposited in an Fig. 1 is a plan view of a stoker and automatic I v plane of line 55 of Fig. 4;

Fig. 6 is a fragmentar section, on an enlarged scale, taken on the plane of line 0-8 of Fig. 1;

Fig. 7 is a fragmentary horizontal section taken on the plane of line 1-1 of Fig. 8, with parts broken away to show the rotating elements in plan;

Fig. 8 is; fragmentary vertical section through Flgs. 9 and 10 are fragmentary transverse secthe burner, and shows the combustion phases. air flow and other elements of the bm'ningprooess;

ash hopper 8. The volume of air delivered to the burner through the air passage 9 at the bottom of the tubular member 5, see Figs. 3, 6 and 9, is regulated by the. thumbscrew In that controls the air inlet opening ll between the blower manifold and the intake orifice plate I 2. I

The blower shaft is directly driven by the motor shaft but the fuel and ash conveyors are driven at low speed, and intermittently, through a transmisslonincluding sheaves I 3, H on the motor shaft and a countershaft l5, respectively and a V-belt It. The shaft l5 carries an eccentrically mounted roller bearing-l1 that imparts rotation to the fuel feed drive shaft I8 through the ratchet wheel l9, spring-returned pawl 20 and rocker arm 2|. -The eccentricity of the ball bearing I1. is adjustable by known mechanism, not shown, to provide a regulation of the rate of fuel supply.

A shear pin 22 couples the hubof the ratchet wheel I! to the stub shaft "to prevent damage A lubricated roller bearing 25 is mounted on the sheave guard at tosupport the stub shaft II, the

dirt by a felt packing 26.

A casting. or plate member 21 is mounted on the lower front portion of the fuel hopper 3 to form a housing for the sprockets 2a, 29 and chain to,

see Figs. 4 and 5, that drive the ash conveyor shaft 3| from the stub shaft l8. The roller bearinner end of the bearing being protected from hearth 4| and the ash scraper ring 46 are retained in place on the burner solely by their weight. Supporting wheels 52' are secured to the ring 45 between certain of the radiallyprojecting 32 in the housing member 21, and the bracket fuel hopper through the housing plate 21, and a felt packing 3G seals the shaft to ,prevent the escape of fuel at this point.

The upper passage of the tubular member 5 comprises the fuel feed tube 38 that is turned upwardly, at its inner end, to open into and to support the stationary conical retort 39, that flares outwardly to terminate in a slightly concaved annular flange 40. The. burner ring or rotating hearth 4| is located immediately above the flange 40 and a large number of tuyere oriflces "are provided between these members to admit combustion air to the retort and hearth from the annular air chamber 43 at the upper end of the air supply passage 5. The tuyere orifices are preferably formed in the base of the rotatin hearth by deep notches between the lugs 44 that have lower faces conforming to the curvature of the flange 4| and spaced from the flange by a small clearance of, for example, about.

inch. The cross-sectional area of each tuyre is substantially constant, and the air velocity ing fins 53, the wheels being mountedon inclined shafts 54 for supporting the hearth and ash scraper ring upon the housing member 55.

' The double-coned wheels 52 roll along the inner edge of the annular flange 55' that projects radially from the housingmember 55 at a point slightly below its upper edge. The upper part of the member 55 thus forms a cylindrical guide for centering the rotatable assembly to maintain a small clearance 56 between the ash scraper ring '45 and the housing member 55. This clearance is essential as the resulting flow of air from the annular chamber 45 sweeps across the supporting flange 55' to remove ashes from the wheel track and to provide preheated secondary airfor rapid and efficient combustion of gases above the fuel bed. Additional preheated secondary air is supplied through the annular orifice 59 between the upper edge of the ash scraper ring 46 and through the tuyre is therefore practically constant, but the circumferential length and the axial height of the tuyere vary progressively along the radial length of the tuyre to provide a long and shallow inlet opening at the outer edge of the hearth 4| and a short and deep outlet opening at the inner edge of the hearth.

As shown in Figs. 6, 7, 11 and 12, the side walls of each tuyere orifice are plane surfaces,

and the top and upper walls are conical surfaces of diflerent slope comprising, respectively, the flange 40 and the upper surfaces of the hearth 4| between the lugs 44. The inner ends of the tuyere orifices are approximately square with an aggregate circumferential length of about 180;

and a relatively large number of orifices are used to distribute the air eilioiently around the burner and to direct the jets into the fuel bed.

Any ash or small clinkers that may collect in the tuyere orifices 42 and on the retort flange ened and scraped back into the retort by a plowinc tionv of the lugs 44 or are blown back by the air blast.

The hearth 4| is rigidly secured by screws 45 to the ash scraper ring 46 that is intermittently rotated by the attached tooth ring 41 and drive pins 48 on a collar 49 on the end of the ash conveyor screw 5|, Figs. 6, 7. and 9. The collar 49 is lubricated by a spring loaded graphite stick 50 carried by the casing. The pitch of the pins 48 is somewhat greater than that of the teeth of the ring 41 and the centerlineof the ash screw 5| and collar 49 is offset from the axis of the toothed ring '41, thus limiting the engagement of the drive pins 48 with the teeth 41 to a horizontal approach to and a downward movement along the vertical flanks of the teeth. This the hearth 4|. l

A rake 63 is hinged upon the open topped ash hopper 64 that is secured to the housing 55 of the burner and supports the inner end of the ash removal tube 1, Figs. 1, 2 and 6. The rake 63 is a tapered metal plate with its smaller end or point resting upon the edge of the rotating hearth 4| to agitate the'ash bed and prevent the formation of the large annular clinker ring that is characteristic of some prior rotating hearth burners. The hinged mounting of the rake permits easy removal of the hearth and ash scraper ring, and also permits the rake to ride over any unburned embers that may be present in the ash. thus serving to expose the embers to the surrounding air to facilitate complete combustion. The tapered construction of the rake protects it from destruction as the largeradiating surface outside of the fuel bed dissipates heat more rapidly than it is absorbed by the small inner end that is exposed to the ash and fuel bed.

The ash conveyor screw 5| is connected to the ash screw shaft 3| by a coupling 65 and shear pin 66. An agitating arm 51 is secured to the ash screw within the discharge T 68 from which the outlet branch 69 slopes upwardly to deliver the ashes to the ash can 8. The agitating arm 51 prevents the ash from packing tightly in the end of the discharge T, and stirs and aerates'the ash to maintain the condition of semi-fluidity that is essential to a free flow of the ash. The blade of the ash screw 5| does not extend to the agitating arm 51 but terminates at about the center line of theoutlet branch 59, thus leavin a small space in which. the ash is relatively at rest. The agitating arm and the exposed end of 'the screw move the ash up the outlet branch by a pumping action at each rotation of the ash screw and, since the displacement of the ash screw is about three times the volume of ash being removed, the zone of non-agitation forms a storage pocket that prevents a constant rinding of the ash between the rotating parts and 'the wall of the discharge T. The crosssectional area of the discharge branch 59 increases towards the discharge end to prevent the ash from packing, the increase being equivalent to that of a conical tube of from 2 to 5 total included angle. The cross-section of the outlet branch preferably varies progressively from a square inner end, Fig. 6, to the cylindrical outer and upon which the thin conical shield 10 isfixed. The ash can l has a circular opening H which nts over the conical shield I. and, under a slight pressure, deforms the conical Shield to form a tight seal between the ash can and the ash conveyor system. The ashes are transported sembling plastic flow, and the upward inclination of the discharge branch 69 provides a body of ashes that forms a seal to prevent the escape of pressure air, and entrained flne ash, from the interior of the furnace.

The phases and elements of combustion for' the burner are illustrated in Fig. 8. The body of fuel A is forced upward into the conical retort 38 by the feed screw 23, and is ignited in the region B by air blasts a that are directed inwardly through the tuyre orifices 42, The fuel bed is agitated by the intermittent rotation of the hearth ll, through the toothed wheel 47 and pins ll, and the air readily penetrates to the interstices of the burning fuel and eflects rapid and efficient combustion. A portion of the air and gas which has been preheated in the annular combustion region B is forced inwardly to supplement radiant heat from region B in preheating the fuel in the interior zone C. thereby driving oil the gas and volatile matter to form a cone D above the fuel bed. The

remainder of the primary air from the tuyere serves to complete the combustion of the outwardly mushrooming degasifled fuel from the region C, while secondary air preheated by cooling contact with the outer surface of the bumer,

namely, the retort 39 including its flange ll, ash scraper ring 46 including its fins 53, flange 55', and hearth ll, issues from the annular orifice 58 and the clearance II, as indicated by arrows b. c.-

respectively, to effect the complete combustion of the gases of cone D in the torchlike flame E. These secondary air streams flow along the rotating hearth and ash scraper ring to protect them against overheating and warping.

The bed F of ashes and embers which overlies the outer flange of the rotating hearth ll acts as an insulation for the hearth and also serves to maintain a fuel bed of 'suflicient depth to force the air blasts a into the incoming body of fuel A to preheat it, and to prevent the upwardly moving air streams from blowing the fuel from the burner at the combustion region B.

The depth of the burnin region B is thus governed by the slope of the outer flange of the hearth II, and this slope may be selected in by the screw as a slowly moving mass, re- 1 I .by preheated to efl'ect a, quick and efllcient combustion of the gases that rise above the fuel bed.

The supply of fresh fuel forces ashes outwardly from therim of the ash bed F, and this flow is facilitated by the slight shaking action resulting from the step-byestep movement of the rotary hearth II and by the scraping actionof rake Bl that prevents the formation of a clinker ring; The ash falls upon the radial flange 55' of the housing I5, and is swept along the flange and into the ash hopper '84 by the fin -Bl of the ash scraper ring 46. The removal of uh is essential to. stable burner operati and the illustrated construction has a number of structural features or operating characteristic that are of major importance. It is essential that the clearance 58 between the radial flange 55' and the or only a small part, of the screw extends beneath theflns l3. Insuflicient clearance at this point might allow clinkers to lamb between the screw II and the fins II, thereby lifting the hearth 4| to disengage the toothed wheel 41 from the drive pins 48 and thus preventing further rotation.

accordance with the weight and burning characteristics of the fuel. The illustrated slope of about 35 degrees is appropriate for various grades of lignite, bituminous and anthracite coal but a greater slope may afford more eflicient opera- I tion when burning coke orsawdust.

The described process of burning the fuel results in a high burner eillciency, both with respect to the quantity of fuel which may be burned in a given time and with respect to the-heat value received per unit of fuel. Further, since combustion within the burner is confined to the small annular region B and producing a flame which, both in appearance and the rapidity with which it build up from quiescence, resembles that produced by an oil burner, overheating of the parts is prevented as is attested by the fact that after a short period of quiescence during whiclrburning recedes into the retort, the ashes can be scraped away and the burner lifted out using only a gloved hand. The protection of the bumer parts from destructively high temperatures A relatively large quantity of ash will accumulate within the burner during quiescent operation and, when the burneris again operated at full capacity, the rate of ash discharge from the burner may exceed the capacity of the ash screw II for a short interval. The excess quantity of ashes is temporarilystored upon the flange ll of the housing 55, between the fins 53, and is eventually removed through the ash' hopper 84 when the ash screw catches up with the rate of ash discharge.

In an alternative embodiment of the invention, as shown in Figs. 13 to 1'1, inclusive, the ashes are removed by a pneumatic system.- In general, the burner and associated mechanisms may be substantially as previously described and like parts are therefore designated by corresponding reference numerals but will not be describedindetail.

The drive pins 48 for the rotary hearth are carried by a shaft 5| that is alined with and coupled to the shaft II. The shaft 5| extends through the ash hopper I2 and carries crusher wheels 13 forbreaking up clinkers before they enter the outlet section 14 of the ash hopper.

The ashes and finely ground clinkers that collect in the section II are sucked away and blown surrounding said retort and minimum; but as a further precaution against the escape of finely divided ash and gas, the vent pipe to is carried to the intake orifice on the blower 2, thus providing a closed circulation system which aids in removing ashes to the ash can 15 by reducing the back pressure on the ejector Ii.

The ash can I5, which for convenience of illustration has been shown adiacent to-the stoker,

can be located .anywhere that may be desired, such as in the alley, in which case the 'vent 80 would be unnecessary. This feature would be highly desirable in large installations, since the ash could be readily removed to a large storage space without the necessity for local handling of large quantities of ash.

. Wherea in the foregoing specification there has been described the specific embodiments of 1. An underfeed stoker comprising a stationary upwardly flaring conical retort member, a rotatable annular hearth member supported above and concentric with said retort, means for 'forcing fuel upwardly through said retort and hearth member, a pressure air chamber surrounding said retort, said annular hearth member having tuyre passages in the underside thereoffor discharging air from. said pressure air chamber radially into the fuel bed and having a conical upper surface sloping outwardly and upwardly from the upper end of said stationary retort for I supporting an annular fuel and ash bed of sufficient depth to confine the flow of air entering through said tuyeres to the central portion of the fuel bed within the hearth and retort, and means for rotating the hearth member.

2. An underfeed stoker as claimed in claim 1, in combination with a horizontally hinged rake mounted laterally of the hearth and having the tip thereof resting upon the upper edge of the rotatable hearth, thereby to prevent the formation of a clinker ring about the combustion zone.

3. An underfeed stoker comprising an upwardly flaring conical retort member terminating at its upper end in an outwardly flaring annular flange a rotatable hearth member disposed above said annular flange, means for forcing fuel upwardly through said members, a pressure air chamber surrounding said retort. and tuyere'orifices comprising recesses 1n the under surface of said hearth member facing the annular flange of said retort, wherein each tllyre orifice is of areaconstant cross-sectional substantially .force. The air vent II is placed at the center of the can where the suspended ash is at a her in which said orifice-defining recesse are formed, each adjacent pair of recesses being spaced apart at said wall by an intervening wall of substantially thesame circumferential length as one of said recesses.

5. In an underfeed stoker, a stationary upwardly, flaring retort, a rotatable hearth above said retort having an outwardly and upwardly flaring ash supporting flange, and a horizontally hinged rake supported laterally of said hearth whereby it can be raised or lowered over the fuel bed and having an active end thereof adapted to extend into a bed of fuel or ash on said flange, said rake being tapered'to provide a large heatradiating surface from the hearth to cool the small active end of the rake that contacts 7 the bed. I

retort, a housing member surrounding said retort having a 'radialflange adjacent the upper end thereof, a rotatable assembly comprisin anv annular hearth member of less circumference than said flange disposed above and concentric with said retort and an ash scraper ring secured to said hearth member and having radial fins extending over said flange on said housing member, wheels mounted on said rotatable assembly and bearing-on said flange to support said assembly thereon, an ash hopper adjacent said housing member positioned to receive ash falling on said flange over the edge of said hearth and swept from said flange by said fins, means for removing ash from said hopper, means for forcing fuel upwardly through said retort and hearth, means for forcing air into saidhousing and re forrotating said assembly comtort and m a s prising said hearth and ash scraper ring.

'1. In an underieed stoker, the invention as claimed in claim 6, wherein said wheels support said assembly above said'flange to provide an 'opening through which air flows to blow ashes from said flange, thereby cleaning the track upon which said wheels rotate.

8. An underfeed stoker comprising a ary upwardly flaring retort member, a rotatable annular hearth member supported above and concentric with said retort member, means for forcing fuel upwardly through said members, a pressure air chamber surrounding said retort, one of the aforesaid members having tuyere passages provided therein for discharging air from said pressure air chamber into the upwardly moving fuel bed, said hearth member having an upwardly flaring upper surface extending upwardly from through the length thereof, and is of less'height at its air entrance end than at its air discharge end. a

4. An underfeed stoker comprising an upwardly flaring conical retort member atits u per end in anoutwardly flaring annular flange, a rotatable hearth member annular flange, means forforcing fuel upwardly through said members, a pressure air chamber multiplicity of tuyere orifices comprising recesses in the under surface of said hearth member facing the annular flange of said retort, said multiplicity of tuyere orifices having an a gr gate circumferential length of approflmately 180 at the interior wall of the memdisposed above 'said the level of the tuyere passages for supporting an annular fuel and ash bed of suflicient depth to provide for combustion taking place between the level of the tuyere passages and the top of said hearth member and confine the flow of air entering through said tuyre passages to the central portion of the fuel bed within the hearth and retort members, and means for rotating the hearth member. I

9. .An underfeed stoker as claimed in claim 8, in combination with a horizontally hinged rake mounted laterally, of the hearth whereby it can be raised or lowered over the fuel bed and having the tip thereof located adjacent the upper edge of the hearth and adapted to extend into a bed of fuel or ash on said hearth, whereby to prevent the formation of a clinker ring about the comwardly flaring retort member, a rotatable hearth member over said retort member, means station 7 forforcingfuelupwardly'thronghsaid gate circumferential length 180' at the interior members,

apilvccsureairchambersaidretortv member. and tuyere provided in one of theaforeaaidmembersforairfrom said pressure air chamber into the upwardly movdimensionatitsairentranceendthanatitsair dischargeend.

11. An underfeed stoker comprising wardlyflaringretort'munbenarotatablehearth memberdispoeedoversaidretortmember,means MUD.

for forcing fuelupwardly through said members,

and a pressure air chamber surrounding said retort,oneoftheaforcsaidmembershavlng tuyere 1 providedthereinincircumferentiallyspacedrelationi'orairfrom said pressure air chamber into. the upwardly movlngfuelbemsaidhavinganaggreofapproximately wallofthememberinwhich providedcachadjacentpair passages eingspaccd said are of togetherdeflningapartition separating the fuel bed from the air chamber, said partition containing a, plurality or tuyere forairfromtheairchambel'intothefuelbed,thenirchamberwallbeing spaced ashortdistanoefrom the hearth member toprovideaeforairtoflowfromtheair chamber upwardlyalongtheoutersm'faceof the hearth to supply preheated secondary air for the flame and also cool said hearth, the annular hearth member having an upwardly flaring upper surface for supportin "an annular fuel bed, and means for rotating the hearth relative to the retort member.

15. An underfeed stoker comprising a, stationary upwardly flaring retort member, a. rotatable annular hearth member supported above and concentric with said retort, means for forcing fuel upwardly through said retort and hearth members to form a fuel bed, a pressure air chamber surrounding said retort, said hearth member and retort member together defining a partition partition containing a plurality of tuyre es for discharging air from the air chamber into the fuel bed, the annular hearth member having an upwardly flaring upper surface for supporting an annular fuel and ash bed,means for rotating the hearth relative to the retort member, the pressure chamber wall havin an annular flange whose plane the axis of hearth rotation,'hearth supporting means movably engaging the flange, means providing a passage communicating with the air chamber for directing a stream of air outwardly over. the flange to remove ashes from the track of the hearth supporting means, and means for rotating the hearth relative to the retort.

16. An underfeed stoker comprisin a stationary upwardly flaring retort member, a rotatable annular hearth member supported above and concentric with said retort, means for forcing fuel upwardly through said retort and hearth members to form a fuel bed, a pressure air cham- .ber surroundin said retort, said hearth member and retort member together defining a; partition separating the fuel bed from the air chamber, said partition containing a plurality of tuyere es for discharging ber into :the fuel bed, the annular hearth member flnsturningwith having an upwardly flaring upper surface for supporting an annular fuel and ash bed, means for rotating the hearth relative to the retort member, the pressure chamber wall having an annular flange whose plane is. perpendicular to the axis of hearth rotation, hearth supporting means movably engaging the flange, means proa e communicating with the air chamber for directing a stream of air outwardly over the flange to remove ashes from the track ofthe hearth supporting means, means for rotating the hearth relative to the retort, an ash receiving hopper positioned beneath the flange in position to receive ashes therefrom, scraper the hearth and positioned adjacent theupper surface of the flange to transfer ashes to the ash hopper, and means for removing ashes from the hopper.

17. An underfeed stoker comprising a stationary upwardly flaring retort member, a rotatable passages for discharging air from the air cham her into the fuel bed, the annular hearth member having an upwardly flaring upper surface for supporting an annular fuel and ash bed, means for rotating the hearth relative to the retort member, the pressure chamber wall having any annular flange whose plane is perpendicular to the axisof hearth rotation, hearth supporting means movably engaging the flange, means proriding a passage communicating with the air chamber for directing a stream of air outwardly the air chamber,

is perpendicular to air from the air chamovertheflangetore no've-ashestrom the'track. of. the hearth means iorrotatingthehearth relativetothe reeeivinghopperbeneaththeflange ashes to' the ash hopper, means for removing ashes trmnthe hopper, and arake having one endpivotedtotheashhopper wall andthe other end thereof disposed adjacent the upper edge of the hearth, forming meansfor preventing the formationotaelinkerringabouttheeombustion zone. a

18. an underi'eed striker comprising'a stationary upwardly flaring retortmember, an annular hearth member supported for rotation above the retort,ahoutanaxiseoncentricwiththelatter, means for rotating the hearth'reiative to the retort, means for forcing fuel upwardly through 'saidretortandhesnh'toformaruelbeiapressure air chamber surroimdingthe retort, one or the aforesaid retort and hearth members conjacenttheuppersurfsoeoftheflangqtotranster throughwhichairmay,

flowi'romthepressureairchamberintothetuel bed. the hearth having an upwardly flaring upper surface for supporting an annular fuel and ash bed of suflicient 'depthto confine the flow of air m t ugh the tuyere passages to the een-. trai portion of the fuel bed within the retort and hearth, a flange positioned beneath the rotating hearth member in position to receive ashes discharged from the latter, an ash receiving hopper positioned underneath the flange, and means connected with the hearth for transferring ashes from the flange to the ash hopper.

V 19. In an under-feed stoker, the invention as claimed in claim 12, wherein an annular air orifice is provided between said hearth and said ash scraper ring to direct a cooling stream of air along the lower surface of said hearth.

20. In an underfeed stoker, the invention as claimed in claim 12, wherein said housing member extends abovesaid flange to provide a cy1in-" drical guide arranged to be engaged by the hearth supporting means to center said'hearth relative to said retort.

IREAL A. WINTER.-

Images