US2116774A - Mechanical stoker - Google Patents

Description

May 1 0, 1938.

J. H. WALTER MECHANICAL STOKER Filed Nov. 25, 1932 5 Sheets-Sheet 1 man! RN www@ mwN wmw mmm@ mmv mmv www N Tm l. m, o NQQN QN W www h. MQ www@ QQ mi* @QN a o mmw VIL wm LN/wmv, QN mk .3 om NQ w Q wwN @mW/u@ N MQ wm QQN om um bw QN N.n\b

. y Inval/#rsf @fosa/h H May 10, 1938, J. H. WALTER 2,1169774 MECHANICAL sToKER A Filed Nov.. 2S, less 5 sheets-.sheet 2 J. H. WALTER Sheets-Sheet 3 May 10, 1938 MEHANIcAL sToKER Filed N'ov. 25,

@fase/ah H @ad Mavim, 1938. J. H. WALTER 2,116,774

I MECHANICAL sToKER Filed Nov. 25; 1952 '5 Sheets-Sheet 4 PLI May 10,1938.

J. H. WALTER MECHANICAL STOKER FiledNov. 25, 110,32

5 Sheets-$heet 5 Pnienied Mey 1o, 193s MECHANICAL STOKEE Joseph Henry Walter, Springfield, Ohio, assignor,

by mesne assignments to The Steel Products Engineering Company, Springfield, Ohio, a corporation of Ohio Application November 25, 1932, Serial No. 644,247

-1Claim.

The present invention relates to improvements in mechanical stokers.v

021e of the important objects of the invention is to provide a new and improved mechanical s toker of the underfeedtype having a burner retort in which air under pressure is supplied in such a manner that theunburned fuel in the bed is evenly distributed. l WA more specific object is to provide a novel m mechanical'stokermtheeunderfeed type having a burner retort with air andfelipply-ducts-m oning to one side and with air inlet openings relatively small in size and in aggregate area in the side located adjacent the ducts and relativei5 ly large in size andin aggregate area in the side located remotely of the ducts', whereby increased combustion tends to occur in the region of the last mentioned openings to compensate for any excess distribution of fuel otherwise tendingo to occur.

Further objects and advantages vwill become apparent as the description proceeds.

In the accompanying drawings, Figure 1 is a plan view of a stoker embodying the features of the invention.

Fig. 2 is a longitudinal vertical sectional view taken substantially along line` 2-2 of Fig. 1.

Fig. 3'is a longitudinal vertical sectional view taken substantially along line 3-3 of Fig. 1. Fig. 4 is a perspective view of a shear plate forming a closure for the hopper base.

Fig. 5 is a .horizontal sectional view of the transmissionin the stoker drive taken along line 5-5 of Fig. 2.

35 Fig. 6 isle ien end eieveiicnni view of the stoker.

Fig. '7 is a fragmentary horizontal sectional view looking upwardly along line '|--1 of Fig. 9.

Fig. 8 is a fragmentary'detail sectional-view taken substantially along line Hof Fig. 2l.

Fig. 9 is al vertical sectional view ofthe burner retort taken along line 9-9 of Fig. 1.

Fig. 10 is a fragmentary plan view of the retort partiallybroken `away and sectioned along line 445 Io--I'o' ci Fig.

l. Fig. 11 is a. vertical sectional view taken along line il-ii of Iilg. 10.

` Fig.' 12 is n transverse vertical sectional view.

5c wniie ine invention is eiacepiibie of various modications and alternative constructions, I have shown in the drawings and will herein declosed, but intend to cover all modications and alternative constructions falling within the spirit and scope of the invention as expressed in the appended claims'. e

Referring more `particularly to the drawings, 5 the specific stoker selected for illustration of the invention is of the underfeed type, and comprises in general a burner retort I0 opening upwardly and adapted to be suitably located in a combustion chamber (not shown), a vertical hopper Il 10 mounted externally of the combustion chamber and adapted Vto be supplied with the fuel to be burned, a fuel passage preferably in. the form of a cylindrical duct I2 connecting the base of the hopper to the underside of the retort, and power- 15 driven fuel feeding means, preferably in the form of a rotary screw conveyor I3, for advancing the fuel from the hopper through the duct v into the retort as required. Air of combustion under pressure is adapted to be supplied to the retort i0 through a conduit Il from any suitable source, such for example las a power-driven centrifugal blower I5. Ashes and other residual matter of combustion from the retort I0 are adapted to. be removed automatically as quickly 25 as produced by means of a powerdriven ash remover, preferably in the form of a rotary screw conveyor I6 operating in a conveyor duct I1.

While in some aspects of the invention the burner retort i0 (see Figs. 9 to 12) may be pro- 30 vided in any desired form.` preferably it is generally circular in shape, and adapted to be mounted in a combustion chamber ofsimilar shape (not shown in detail, but represented diagrammatically in Fig. 3 by thewall 18). riphery of the retort i 0 is separated from the wall I8 to provide an annular space i9 which constitutes a pit adapted to receive ashes and any other residual products of combustion overflowing from the t'op.

In its preferred form, the retort I0 comprises a hollow generally cylindrical base wall 20 closedv Vat the bottom by a cover plate 2l. An upwardly opening fuel chamber 22 vis Iocatedwithin the wall 20, and has a circular o utlet coaxial with and inv the same plane as the upper edge of` the wall. The fuel chamber 22 converges in size and curves downwardly and laterally and is integral with the inner end of a horizontal sleeve' 23 formed with and opening through oneside of the base wall 2li. The sleeve 23 is formed inwardly from its outer end with a counterbore 24 terl.minatingV in a square annular shoulder 25 inside of the' wan zo, end is adapted snugly :c receive 'the discharge endcf the mervduct 1,2 with the 1st- 5 conveyor I3 terminates in the horizontal inlet of the chamber 22, and in operation causes the entering. fuel as fed to force the bed of fuel 1n the chamber gradually upwardly.

Mounted on the fuel chamber 22 is a tuyre structure, the interior of which constitutes an upward continuation of the fuel chamber 22. The tuyre structure comprises a bottom tuyre ring 26, a plurality of intermediate tuyre rings 21 nested on the bottom ring, and a top tuyre ring 28 resting on the uppermost of the intermediate rings, the rings being of gradually increasing diameter upwardly. Preferably, the rings 26, 21 and 28 are flat in form, with the bottom ring 26 resting squarely on an outer marginal ange 29 on the upper end of the fuel chamber 22, and with each of the other rings 21 and 28 resting respectively upon the ring next below.

A plurality of spaced radial slots 30 defining intervening seating pads 3| are formed in the underside of each of the rings 26, 21 and 28, and preferably each has vertical radial sides and a root surface flared upwardly at both ends so as to define air inlet passages of varying cross-section when the rings are in nested' relation. The slots 30 may be of -any suitable width and spaced in any desired manner. In the present instance,

the slots 30 in each ring are relatively small but equal in width in the half located forwardly or adjacent the duct I2, and relatively large but equal in widthl in the half located rearwardly or remotely of the duct, and are arranged in uniformly angular spaced relation about vthe periphery. I have found that by this difference in size of the vport areas of theslots 30, a superior fuel bed is obtained in that the unburned fuel is evenly distributed, by reason of the fact that the increased combustion at the rear due to the presence of more air compensates for any excess distribution otherwise tending to occur. Preferably, all of the rings 26 to 28 are provided with slots 30 having the same angular spacing, and with the widths of the pads 3| increasing progressively upwardlyv so that the corresponding 1 slots of the respective rings are of equal widths,

and are nested in such a manner that the slots vand pads are located in generally vertical tiers.

Each of the tuyrerings28 and 21 is formed with a plurality of peripherally spaced upstanding lugs on the outer edgev which snugly receive and center the tuyre ring next above. In 4the present instance, three. uniformly spaced lugs 32,

' 32 and 33 are provided, with the intermediate lugs 33 of successive rings being located alterf nately at diametrically opposed points. Thabottom ring 28 has two spaced depending lugs 34 extending into notches 36 formed in the flange 29. Formed on each of the rings 21 and 28 between the lugs 32 and diametrically opposite the lug 33, and adapted to interfit with the lug 33 of the ring 26 or 21 immediately vunderneath vso as 'to lock all of the rings against rotation are two closely spaced laterally extending lugs 31.

Mounted on the upper tuyre ringk 28 is a hollow tuyre back 38 having inner and outer walls.

39 and 40. Preferably, the tuyre back 38 is split into two ring sections which arebolted together `.when assembled. The inner wall 39 has a peripheral flange. 4I fitting into an annular groove 42 inthe outer periphery of the ring 28, and iiares sharply, upwardly and outwardly, toward the furnace wall I8. The outer wall extends substantially below the wall 39, and converges uniformly toward its lower end 43 which is cy1iri ter secured tightly against the shoulder. The fuel drical in form. vTwo inner peripheral grooves 44 and 45, defining an annular inner rib 46, are formed in the end 43-of the Wall 40. The groove 44 receives an outer peripheral flange 41 on the upper end of a base ring 48 which is mounted on and bolted to an inwardly extending annular flange 49 on the upper edgeof the base wall 20.

The tuyre structure defines an annular air space 50 for supplying air under pressure through the'inlet passages 30 into the fuel chamber 22. The bottom of the annular space 50 opens between the flanges 29 and 49 into a large plenum chamber 5I defined by the base wall 20. One side of the wall 20 is formed with a tangentially extending duct 52 alongside the sleeve 23, and in communication at its inner end with the plenum chamber 5I. The duct 52 is preferably rectangular in form, and is connected tothe discharge end of the air supply conduit I4.

Ashes and other residual matter of combustion 51 receiving the iletlnd of the4 ash duct I1.

The receiving end of the ash conveyor I 6 extends from the duct I 'I into the trough 53, and the base of the latter conforms generally to the cylindrical contour of the conveyor.

To direct the ashes into the trough 53, an ash ring 58 is mounted on the upper edge of the wall 28 for rotation about the base ring 48. `While the ring 58 hasa fairly close fit with the base ring' 48, it can be turned with very little power since the rest of the retort is stationary, and since in the event of any temperature increase the tolerance is correspondingly 1increased through expansion. The ash ring 58 has an annular iiange 59 along its inner periphery extending upwardly into the groove 45 into overlapping relation with the lower end of the wall 46 of the tuyre Vbaci: 38, and a second annular flange 6I! at its outer periphery depending about the base wall 20 so as-to guard the bearing surfaces against the entry r of ashes or other foreign matter. Formed on the outer periphery of the ring 58. are a plurality 'of uniformly 'spaced radial vanes 6I `for moving ashes lcollecting about the retort III into the trough 63.

'I'he ash ring 58 may be driven vbyany suitable means, and in the present instance is adapted -to be driven continuously in one direction from the ash conveyor I6. Thus, the flange 60 is formed with an internal gear 62 which is constantly in mesh with a pinion 63 fixed on the upper end of a shaft 64. This shaft 64 is journaled in a transmission/casing 65 (see Figs. 11

and l2) bolted to one side of the base wall 28 which togetherwith the bottom tuyre ring `26 is flattened to locate the pinion 63 inside the ash ring 58. Fixed on the'shaftl 64 is a bevel gear 66 which meshes with a. bevel gear 81 integral with a .shaft 68 extending through a bearing sleeve 68 on one end of the easing 65. A packing collar 18 secured to the end of the sleeve 68 prevents the entry of foreign matter along the shaft 68 into the casing 65, and is located in an opening 1I in the rear end wall 55 of the ltrough 5,3. The Shaft 68 has a square end 14 fitting in and having a driving connection with a socket 15 in the end of the ash conveyor I8.

sure relief valve 85C for preventing overloading v with the lubricant or grease.

Means is provided for breaking olf clinkers at the edge of the retort I0 without spilling unburned coal into the ash pit I8. This means comprises two sweep arms 16 which are mounted in diametrically opposedV relation on the ash ring 58 for rotary movement therewith, and which extend upwardly almost to the edge of the tuyre back 38 and then rearwardly relatively to the direction of rotation and'upwardiy at a slight angie to above the retort l0. While two sweep arms 16 are shown, it will be understood that only one may be used if desired. 'Ihe arms 10 thus act to` break off the clinkers bylifting them, thereby returning unburned coal into the re pot instead of cascading same into the ash pit I9.

The fuel hopper (see Figs. 1 to 3) comprises a base 11 having a vertical rear wall 18, an inclined forward wall 19, and.oppositely inclined side walls 00 and 8| dening an upwardly opening generally V-shaped trough 82. Two depending brackets 03 and 84, on opposite ends of the base 11, rest on a foundation 85 to support the hopper Vil andlits attachments. The front bracket t3 is integral with and extends forwardly of the front wall 19, and is formed with an elongated cylindrical bearing 88 in alignment with the apex of the trough 02. An external horizontal sleeve t1 formed on the rear wall 'll and towhich the fuel. duct l2 is connected defines an outlet opening 88 also in alignmentl with the trough 02. The fuel conveyor i8 extends along the hopper trough 02 through the outlet opening t0 into thev duct l2, and the apex of the trough conforms generally to the cylindrical contour o the conveyor vane. The' forward end ofthe conveyor il extends into and is guided and supported in the bearing 80.

To secure the hopper base 11 in rigid assembly with the retortlll, the fuel duct l2 extends at its inlet end into a counterbcre I9 against a peripheral end shoulder 90 in the sleeve 01, and is clamped between the shoulders 25 and 90 by means ofthree peripherally spaced tie rods 0| engaging with ears 02 on the ends of the sleeves tt and el.

To afford convenient and ready access'to the interior of the hopper base 11 where the conveyor it enters the outlet opening 88, an opening $3 is formed' partlyin the top of the sleeve 81 and partly in the wall 18 at the juncture. That part of the opening 93 in the wall 18 may he viewed as an enlargement of thel outlet .opening 8l. An angular plate` 08 is removably secured against the wall 10 and the top of the sleeve 81 toA close the opening 93, and preferably vhas, an inward projection 95 to preserve the cylindrical contour of the outlet opening 88 and to denne an upper shearing edge coasting with the vane of the conveyor i3. It will-be evident that'any obstructions coming between the shearing edge and the conveyor vane and tending to stall the conveyor Y can quickly be removed through the opening Il v without emptying the hopper. l

The superstructure of the hopper |I an outwardly inclined front wall II. a vertical rear wall 81 extending substantially above the ange interiits with i power, such as an electric motor front wall, and vertical sides 98 and 89 with upper inclined edges. While the hopper walls may be joined in any suitable manner, preferably, the front and rear walls 98 and 91 have vertical side flanges |00 overlying the side walls 98 and 8l, and the latter have side flanges |0| in the upper portion of their rear edges engaging the inside of the rear wail. The top of the hopper con- 'stitutes the supply opening |02, and is inclined, with one edge lower as at the front wall 88, for the convenience of the attendant in throwing in the fuel.

Stokers are installed under widely varying condltions. In some instances, it might be extremely inconvenient to charge fuel into the hopper from the frontend of the stoker. One of the ieatures'of the invention therefore resides in so constructing the hopper that in lassembling the upper porton with the base 11, the top opening |02 and particularly the lower edge thereof may be orientated to best adapt it to the 'installation for which the stoker is intended.

illus, the top of the hopper base 11 is square in shape so that the upper portion of the hopper may be orientated thereon as desired in any one of four different positions. The upper edge of the base 11 is formed on all sides with a marginal external flange |03.- Each of the upper walls 98 to 88 of the hopper is formed along its lower edge with an inwardly facing gi'oove |04 adapted to receiveV the contiguous section of the flange Preferably, the groove l|04 is defined by striking the lower marginal portion of each wall irst outwardly, then downwardly and then inwardly. In assembling the hopper il, three of the upper walls, namely the walls 01, 88 and 88, are joined together into an integral structure, and are then positioned on the base 11 by sliding the4 grooves |04 of the two extreme walls Q8 and 99 longitudinally onto two spaced sections of the flange |03 until the intermediate section of the the groove of the intermediate wall 01. Then, the remaining wall, namely the wall 96, is secured to the-walls 88 and @9, with its groove |05 receiving the remaining section of the flange |08. The hopper top may thus be lo- 'cated in any one of four different positions. In the position shown, the lowest wall 96 constitutes a straight continuation of the inclined base Iwall 19. A

vThe fuel and ash conveyors i8 and lo areadapted to be driven from a common source of |05, through a transmission mechanism |06. In its preferred form, the mechanism |08 comprises a closed casing .|01havng a removable rear .cover sccticn |00. As a means of support, the cover section |08 is provided externally with a generally circular flange |09 which constitutes a clutch housing, and which is removably mounted at its outer peripheral margin on the supporting bracket 83 coaxially with the fuel conveyor I0 and bearing 86. A mounting plate ||0 is interposed between the ilange |09 and the bracket 03, and the parts are securely bolted together.

The mounting plate ||0 extends substantially above the casing |01, and constitutes a primary support for themotor |05. Thus, the motor |0|i is mounted directly on a horizontal supporting base plate of which one end is pivotally secured to the plate H0, and the-other end is connected through a depending adjusting screw ||2 with an ear ||3 on the top of the casing |01. A cover ||I for the motor |05 is mounted on the plate H0. VIt will be evident that through anguu lar adjustment of the plate III, the motor |05 can be located accurately in position to place the driving surfaces and interchangeably related to one or the other of the sets of aligned grooves to provide two selective speeds. An outlet or driven shaft I 2| (See Fig. 5) extends below and transversely of' the inlet shaft ||5 through the casing |01. Of the shaft I2I, the rear end is rotatably journaled in a bearing |22 in the rear cover section |06, and extends to the exterior for -operative connection with the fuel conveyor I3, and the front end is journaled in a bearing`|23 in the front wall of the casing |01. 'I'he front end of the shaft I2I normally is enclosed in acap |24 removably secured to the Vfront of the casing |01, and engages an end thrust bearing |25 disposed against the front wall of the cap. Upon removal of the cap |24, a hand tool (not shown) may be applied to a squared section |26 of the exposed end of the shaft I 2| to turn it and the fuel conveyor I3 manually as may be necessitated on occasion.

A second outlet or driven shaft |21 parallel to the shaft I2I extends through the casing |01. Of the shaft |21, the rear end is journaled in a bearing |28 in the cover section |08, and extends to the exterior .thereof for operative connection with the ash conveyor I6, andthe front end extends through and has a driving connection with a sleeve I29journaled 'in a bearing |30 in the front wall of the casing |01. "The rear end of the outlet shaft |21 is formed with a transverse bore |3I, and extends into a socket |32 in one end of an extension shaft |33, wherein it is secured for a driving connection by means of a pin |34 extending loosely through the bore. Similarly, the other end of the extension shaft |33 has a transverse bore I 35, and extends into. a socket |36 in the forward end of the shaft lof the ash conveyor I6 to which it is operatively connected by means of a pin |31 extending loosely through the bore. The front end of the shaft |21 and sleeve |29 assembly also extends to the exterior of the casing |01, but normally is enclosed by a removable cap |30.

Rigid with the inlet shaft |I5 is a worm |39 which meshes with a worm wheel |40 keyed to an elongated sleeve |4| rotatable on the outlet shaft I2I. A gear, |42 also keyed to the sleeve I4I meshes with a gear |43 keyed tothe sleeve |29, thus completing the drive connection from the inlet shaft I|5 to the outlet shaft |21. The gearlng just described affords two substantial speed reductions. Preferably the outlet shaft |21 also constitutes a countershaft in the drive for the outlet shaft I2I. To this end. aysmall gear I 44 keyed to the shaft |21 meshes with a, relatively larger gear' |45 keyed to the shaft I2I. An anti` friction bearing |46 is interposed between. the .cover section |06 and the .gear |44 to take the end thrust ofthe shaft I 21'.

To provide means for connecting the shaft I2I to the fuel conveyor I3, a clutch sleeve |41 in the housing |09 is non-rotatably splined for axial movement on the rear end of the shaft I2I, and is formed with a peripheral groove I 48-and with two diametrically opposed clutch dogs or elements |49 on its rear face. A coupling |50 having a square end |5| in driving engagement in a socket |52 on the forward end of thefuel conveyor I3, is provided on its forward end with two diametreally opposed clutch dogs or elements |53 adapted to coact with the elements |49. 'Ihe side faces of the coacting elements |49 and |53 are undercut as shown so that the rotative force will tend to hold the elements tightly in engagement when in use. It will be evident that upon engagement of the clutch elements |49 and I 53, the drive connection from the inlet shaft I I5 to the outlet shaft I 2| will be completed.l

The means for actuating the clutch sleeve |41 comprises a yoke |54 xed to a vertical rock' shaft |55 rotatably mounted in spaced lugs |56 in the housing |09, and operatively engaging in the groove |40. A hand lever |51 is pivotally secured to the upper end of theshaft |55, and is adapted to rock the shaft selectively to engage or disengage the clutch elements |49 and I 53. The free end of the lever |51 is adapted to be pivotally lowered to one side or the other of a lug |58 on a horizontal plate |59 integral with the cover section |08 so as to lock the clutch sleeve |41 in either position of adjustment.

By reason of the gear reduction between the outlet shaft |21 and the shaft I2I, the ash conveyor I6 is always driven at a greater speed than the coal conveyor I3. Hence, the immediate and complete removal of ashes Without any likelihood of clogging and regardless of the rate of fuel supply is assured. Upon opening the clutch |49, |53 in the drive for the fuel conveyor I3, the ash conveyor I6 and the' blower I5 still can be driven to complete combustion of the fuel in the retortv I0 even though the supply of additional fuel is discontinued.

Preferably, the drive connection between the sleeve |29 and the shaft |21 is automatically separable upon the'application of an excessive force. In the present instance, this connection is shown as a shear pin |60. Since both conveyors I3 and I6 are driven from the shaft |21, it will be evident that the single shear pin |60 serves to protect the gear transmission mechanism |06 and also the motor |05 in the event that either or. both of the fuel and ash conveyors become obstructed.

The blower I6, which constitutes the source of air under pressure for supporting combustion, is not disclosed in detail since per se it forms no part of .the invention, and generally comprises a housing |62 -which is mounted on a bracket |63 bolted to one end of the transmission casing |01, a rotor |64 driven directly from the shaft of the motor |05, and a damper I 65 adjustable to vary the supply of air. A suitable blower is shown in the patent to May No. 1,834,959. A suitable guard |66 for the drives from the motor |05 to the transmission |06 and the rotor |64 is mounted on one side of the housing |62. The air conduit I4 (see Fig. 1) opens tangentially from the lower portion of the housing |62. Preferably. the conduit I4 is substantially straight, rectangular in cross-section, and in the same horizontal plane as the fuel and ash ducts I2 and I1. A clean-out cover |61 may be provided in one side of the conduit I4,

' Since the air of combustion from the blower Il is supplied to the retort I0 under pressure,

it is possible in the event of a poor draft that the pressure in the combustion chamber may build up very substantially `and tend to force obnoxious gases through the re pot 22, the fuel duct I2 and the fuel hopper into the atmosphere. The pressure may also tend to force such gases outwardly through the ash duct |1. To obviate this serious difficulty, particularly where there is a poor or inadequate furnace stack (not shown), air pressure is maintained in the Vfuel and ash ducts I2 and |1, by connesting same through by-passes with the air supply, sufliciently high to resist the internal furnace pressure. In the case of the fuel duct |2, the by-pass comprises an opening |88 formed Y in the top of the sleeve 28 inside the wall 28.

A slot |88 is formed in the top of the discharge end of the fuel duct I2 in communication with the opening |88 so asyto connect the interior of .the duct with the plenum chamber 8|. The slot |88 is inclined inwardly toward the nre pot-22 soasto directthejet of airtowardthclatter to build up kinetic as well as static resistance to the furnace pressure. -The by-pass-for` the ash remover comprises a by-pass line |18 communicatingat one end with the plenum cham;

ber 8|, and connected at the other end to the 'ash duct |1. In the preferred form, the discharge end of the line |18 is connected to a e |1| formed in a bracket |12 secured to the ash lduct |1. A slot |18 formed in the duct I1 at an angleinwardly and toward the fire pot 22 communicates with the inner end of the passage |1| to complete the connection.

The ash duct I1 is connected at its discharge end to ash receiving means comprising one or more receptacles.4 Preferably, two receptacles |14 and |18, arranged in series, with the second adapted to receive the overflow from the rst, are

provided, and constitute in eilect a continuation other end wall |18 is connected to the ash duct I1 by means of a flanged ring |8l. Preferably,

the ring |8| is formed with a counterbore |82 receiving the end of the duct |1 so that the duct is held in place by the endwise lock applied by the tie rods 9|. As an additional means of support, the duct |1 may be strapped to the fuel duct `5 end walls |19 and |18 ofthe receptacles is a short 10 duct |85 which is formed on one side of a bracket |86 secured to the hopper base 11. The ash conveyor I8 extends from the duct |1 through the first receptacle |14 and the duct |88 into the second receptacle |18 where the screw vane ter- 15 minates. `The shaft extension `|88 extends through the forward wall |18 of the receptacle for connection to the conveyor I8 as described. A cap |81 on the wall-|18-about the shaft |88 and filled with mineral-wool serves to prevent the 20 escape of ashes. y

'I'he outer sides of both ash receptacles are open to receive removable ash cans |88 and |88 l of similar shape. It will be evident that `when the ash can |88 becomes illed, the ashes ,therein 25 form a passage above the conveyor |8 through which additional ashesare carried into the second receptacle ns. Upon removing the asn san m to empty same, the second ash can |88 which may. be partially filled can be substituted there- -fore in the receptacle |18..

If desired, each ash receptacle may have a hinged cover |88 secured to the outer edge of the top -wall |11-to facilitate removal or insertion of the ash can.

I claim as my invention:

In a-s|;oker ,inv combinationl a ilrepot, a base wall dening a .plenum chamber about said tire -.pot, a fuel supply duct opening through one side of' said wall to said me pot. an air supply duct `40 opening to the same side of said plenum chamber. a nest of tuyre rings mounted on said p ot, said tuyre rings defining a plurality of peripherally spaced air ports in communication with said in the. side of said rings adjacent said ducts being smaller in eilective area. than the ports Vin the vother side of said rings.

JosEPH HENRY WALTER.

chamber and opening to said re potthe ports

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