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Aug? 2, 19%. W. M. SHWEHQKART ET AL. _ 2am” 1" STOKER Original Filed Aug. 28, 1937 - 5 Sheets-Sheet 1 . _INVENTOR5 BY 4m 1%~ M, BMMZW ' ATTORNEYS ‘ Aug‘, 0, 194. W. M. SCK'iWEECKART Ema; STOKER 01figinal_ Filed Aug. v28, 1937 // I'l Ilka“. '5 sheetswsheet .2 // // WNW INVENTOR’S ATTORNEYS ' ‘ Aug? 2Q, 1%46. @4029 L: W. M. 5CHWEEKART ET AL, STOKER ‘Original Filed vAug. '28, '19s? F/PED 5 Sheets-Sheet 3 6. JUL m/v _ ‘Aug’ 29,. 394% w. M. scE-zwEIcKART ET AL STOKER Origirial Filed Aug. 28, P937 5 Sheets-Sheet.- 4 lI[! I J4'!I lI 'INVENTORS E4 3' W ATTORNEYS v _ Aug. '20, 1946. ’ w; M. SCHWEICKART ETAL _ > 2945,92 STOKER Original‘ Filed ‘Aug. 28,. 1957 5 Sheets-Sheet 5 . 1115 m _ If 22 . ~ 281 - - ., 230 Tam 2a; .2"? A": _ ' °\\ I556, 6 ‘f.’ egg - 1;} _- - g 2/6 . 209 2/7 as» 28' @ j 224 INVENTORS‘ 4454;.“ a E4 1 BY ATTORNEYS . I l Patented Aug. 20, 1.946 2,405,982 UNITED STATES‘ PATENT OFFICE 2,405,982 STOKER William M. Schweickart and Fred G. Julyan, Euclid, Ohio, assignors to Pocahontas Fuel Company Incorporated, New York, N. Y.,a cor poration of Virginia Original application August 28, 1937, Serial No. 161,494, now Patent No. 2,306,189, dated Decem ber 22, 1942. Divided and this application August 8, 1941, Serial No. 405,894 1 6 Claims. (01. 110-45) This invention relates to improvements in auto matic coal burners. A primary feature of this invention is the pro vision of a burner that will burn different types of coking coal efficiently and economically, in small domestic installations as Well as in larger furnaces, and which is adapted to utilize var ious sizes of coal down to slack. 2 der widely varying conditions and economical in operation. Other objects and advantages of the invention will appear from the following description con sidered in connection with the accompanying drawings in which, Fig. 1 is a perspective view of the assembly; Fig. 2 is a longitudinal vertical section through The burner is arranged to provide a novel com bustion zone properly related to the feed so as to the burner; assure e?'icient coking, ignition and combustion of the solid and gaseous components without dan ger of back coking or clinkerformation at points that would interfere with the coal feed and e?i broken away; Fig. 2a is a plan view of the burner with parts Fig. 3 is a detailed side elevation of the grate drive; 4 is a fragmentary view of the coal and cient combustion, arranged moreover to avoid the 15 airFig. feed tubesand air control; back ?ow of gas under appropriate operating con Fig. 5 is a fragmentary side elevation of the ditions. blower and air control viewed from the side of Another object is to provide a burner that will have high combustion efficiency, particularly the assembly which is to the rear as shown in Figs. 1 and 4; when burning bituminous coal. The burner is arranged to produce ‘a relatively thin bed of burn 20v Fig. 6 is a diagram of an electrical control ar rangement schematically applied to the burner ing fuel, and to eliminate di?iculties with clinker assembly installed in a domestic furnace; and formation and ash accumulation which would Fig. 7 is a diagram illustrating the operation of tend to interfere with proper combustion. The ash removal mechanism removes the ashes and 25 the banking control switch shown in Fig. 6. In the speci?c embodiment shown (Fig. 1) the small clinkers rapidly and uniformly without in~ apparatus comprises a drive unit B, a burner unit terference with the ?re bed, conveying them con 0, and an ash discharge unit D. tinuously to an ash discharge. " A coal collector unit, not shown, ispositioned Another purpose is to improve the e?iciency and control of the air supply to the ?re. The 30 in the coal bin and supplies coal to the coal feed tube 22 in which is positioned the coal screw 2|, forced draught is introduced in a zone at the top with the collector unit driven from the coal feed of the retort and outward over the grate, and is screw 2|. A suitable collector unit is shown and provided with an adjustment to meet the condi described in our Patent No. 2,233,085 granted Feb tions of each installation as well as the varying ruary 25, 1941. fusion points and other characteristics of com 35 Where the conveyor tube 22 requires a bend. bustion of different types of coal. Under bank this is preferably made as an angle, for instance,‘ ing conditions provision is made for independ a right angle, through a feed knuckle (not shown) ent regulation of the air drawn by natural provided for conveying the coal around the angle. draught, permitting the efficient and certain The drive unit B includes the motor with its maintenance of a suitable fuel bed. 40 controls, the blower and air supply, the drive for An eincient electrical control system has been the coal feed and ash discharge screws, the grate provided, which may be incorporated in combi rotor drive and gas withdrawal construction. nation with standard proven electrical devices. The drive assembly is mounted on a base 72 In general, the drive unit is controlled from the room thermostat and is protected by safety de 45 provided with a longitudinal cylindrical passage for the coal to which sections of the coal feed tube vices. An important feature of the invention is 22 are connected and through which the last sec the provision of an ef?cient, sensitive and reliable tion of the coal feed screw 2| passes. Supported banking control cooperating with the burner con upon the base 12 is the motor 15 having the rotor struction and the banking air control to assure the maintenance of a minimum ?re by automati 50 11 of the blower 18 secured to one end of its shaft. A housing 80 surrounds the blower air inlet, and cally providing fuel and forced draught accurate air is admitted to the housing by the air inlet ly as needed. tube 82. The other end of the shaft of motor 15 An important object is to provide apparatus is connected to the ash removal shaft 89 through embodying features set forth herein which is sim reduction gearing contained within the casing 86 ple, compact, strong, suitable for installation un 55 and through a sprocket and chaindrive including 2,405,982 3 handle I523 extending outside of the drive unit cover. 7 4 edge onto the grate structure through which the the chain QI which engages a sprocket mounted upon the ash removal shaft 89. These connec tions may include a clutch operable from the > The burner unit C hereinafter described in cludes a rotating grate structure which is inter mittently operated by reciprocating shaker rod .' I58. A suitable mechanism is provided for im parting such reciprocating movement at the 10 proper rate. In the form shown best in Fig. l, the sprocket engaged by chain 9! and mounted ashes pass. In the arrangement disclosed the section of the coal feed tube 22 extending from the drive unit base 12 is clamped in the burner body I50 and supplies coal to the throat I5I at the bottom of the ?re pot I52, which preferably ‘is tapered outwardly from throat I5I. The lower portion of pot I52 may consist of a pot wall I53 integral with burner body I55, and a frusto-conical pot liner I54 having a smooth, preferably enameled inner surface, ?tting within wall I53 and resting on a suitable ledge I55 to provide a smooth continuation of the surface of on ash removal shaft 89 is provided with a suit throat'I5L' able cylindrical face cam I II] engaging cam roller A pocket I58 extending beyond throat I5I con I I I rotatably mounted on the upper end offrocker 15 .centric with the axis of coal feed screw 2I has arm I I2 pivoted at its lower end to base I2; H3 is pivoted at one end on rocker arm I i2 ‘with mounted‘ therein a reverse screw I51. One end of this reverse screw is connected to the adjacent section of feed screw H by a connecting shaft I55 and the other end is connected to a terminal shaft its other end engaging ratchet Iii which‘is ro-J . tatably mounted on base 12 and is prevented from backlash by a silent detent cam H5 having an 20 I60 which extends through the bearing I59 at offset pivotal mounting III? on vertical Web II1 the end of pocket I55, the projecting end of shaft of the base 12 arranged so that therunbalanced I55 having a sprocket 239 mounted thereon by weight of cam H5 will maintain its 9am surface in locking engagement with the teeth of ratchet , ‘means of which the terminal shaft I58, reverse screw ‘I51, connecting shaft I58, coal feed screw I I4 to prevent backlash, lug I IE on eamI I5 being positioned to engage the upper face o'f'web H1 when cam II5 is rotated out of engagement‘ with ratchet H4, preventing cam H5 from being acci dentally jarred or otherwise shifted into inopera tive position. _ v Means for regulating the throw of pawl II; and thereby varying the actuation of the rotary grate structure includes an upward extension H9 on pawl I I3 positioned to engage stop lllg I20 adjust ably mounted as by a slot and a locking screw on web I I1 to control the length of the return throw of pawl H3. The lug I25 acts to swing the pawl H3 downward into engaging position with the ratchet H4. Cam roller III is suitably main tained in engagement with cai'n IIB, as by leaf spring I23 bearing against base 12 and rocker arm H2. The intermittent movement of ratchet H4, which in the form shown is actuated twice during each revolution of sprocket engaged by chain 9!, is suitably transmitted to the ash grate, as by eccentric I24 mounted on ratchet H4 and carry ing eccentric strap I25 on connecting rod I26 which may be connectedto shaker rod I59 by a suitable shock absorbing arrangement. For [this] BI and the mechanisms of the coal collector unit (not shown) are driven. To provide for supply of air to the burning fuel, inlet air chamber I6! surrounds the pot wall I53, formed by bottom wall I62 and outer wall I53 and generally open at the top. A suitable upper margin for the pot I52 is provided preferably in separable form and is gen erally referred to as a retort. While the retort may be formed and mounted in various ways, it 35 is advantageous to provide a retort base ring 30 I65 which may perform a number of functions. In the form illustrated ring I56 is held in position by ‘bolts I61 threaded into lugs I64 on outer wall I53 of air chamber IBI, and may have 'a sealed engagement therewith by employing an asbes tos gasket I63. Base ring I65 may likewise form a closure for the junction between pot wall I53 and pot liner I54, the form shown having an annular ridge I10 engaging a seal ring I69 of asbestos or the like located on the suitably bev eled edges of wall ‘I53 in liner I54. The ring I65 is provided with openings I'II (Fig. 2a) to . permit the air from air chamber IGI to pass up 50 wardly to the retort. The retort I12 is removably mounted on the purpose rod I25 may terminate in frame I21 in base ring I65 and forms a continuation of the which the spring cage IE8 is mounted,.including pot I 52, being provided with air outlets or tuyere's end flanges I29 in which shaker rod I89 is slid for furnishing air in the most advantageous zone ably mounted, between which ?anges shock ab sorber spring I35 is set under initial compression 5-5 for e?icient operation. In the form shown the retort I12 is provided with an inner wall I13 and maintained in compressed condition by com forming a continuation of pot I52 and ‘the inner pression collar ISI held in suitable position on rod face of base ring I55, and resting on an asbes IE9 by stop pins I33 projecting from shaker rod tos gasket I14 in a suitable depression in base I09 in position to engage the adjacent ?ange I29 and collar I3l under pressure of spring I35. Col 60 ring IE6. The outer wall I15 slopes outwardly and downwardly to thegrate structure, and rests lar ISI is held against rotation by ‘engagement on an asbestos gasket I16 in a suitable depression with cage I28, and operates through clamp screw in base ring I65. The retort crown I11 provides I32 to hold rod I09 in adjusted position. Cage an integral smooth curve between walls I13 and I28 is preferably mounted removably on frame I21. This shaker rod spring construction will 65 I15, and is ‘preferably relatively narrow to pre vent retention of material thereon. allow the stoker to run even though the grates Suitable tuyére openings I18 extend through are jammed, the rest‘of the mechanism continu the retort I12 at appropriate points. It has been ing to function normally and the placing, of the determined that the most advantageous construc absorber spring I35 under initial compression is tion comprises provision of a series of tuyere important to quiet operation. openings I18 in the upper part of the inner re This rotary grate structure surrounds an inner tort wall I13, preferably sloping slightly down retort of the burner unit C of the type in. which ward-and a smaller number of 'tuyere openings the coal is forced‘upwardly through the bottom I18-extending through the upper part‘ of the outer of the burner retort or pot structureyburning ‘a retort wall I15 at about the same level. The the upper portion thereof and traveling over the 5 2,405,982‘ 6 retort I72 is held in place by means which pref erably permits its ready removal and replace ment, such as hooks I19 which may be cast in tegral with the retort walls I73 and I15, and which engage the lower face of the retort base ring I68 through suitable retort lock Openings, The rotary grate structure located around the ing space normally ?lling with ashes, which form the air seal across the narrow slot between the _ apron margin and ring I8I. ' ' The grate ring I88 is suitably mounted on rotor ring I8I' to permit ready removal without affect ing the rigidity and reliability of the mounting under service conditions. A suitable arrange retort H2 is adapted to receive the burning coal ment is indicated best in Fig. 2a, and includes and ashes which flow outwardly'over'the retort, ‘ beveled wedge lugs I 91 on rotor ring ,I8I engag sifting the ashes into a suitable annular receiver 10 ing beveled wedge lugs I98 on grate ring I88 to in which they are carried around the burner to force the grate ring downwardly into proper po a point of discharge. The various parts are car sition by rotating it relative to rotor ring 'I8I ; ried by a-rotor ring I8I which is rotatably mount stop lugs I99 on- rotor ring I 81 and removable ed on the pot I522. The mounting-of rotor ring locking slugs 288 ?tting between stop lugs I99 and IN on ball bearings is such that the parts may 15 wedges I98 when the grate ring I88 has been be readily assembled, the bearing will be easily turned into proper position. ' ' ‘ accessible and the structure will function smooth . The grate rotor structure is preferably provid ly under the substantial variations in temperature ed with an- ash table 284, receiving ashes which and consequent expansion and contraction of the pass the grate segments I89 and conveying such parts encountered under these conditions, the ball 20 ashes to a point of discharge. A plurality of ash race being formed by cast surfaces. The arrange ment comprises a ball race groove I 82 in the tablesegments 285 forms a continuous annular platform around rotor ring I8I adapted to receive the ashes. Each table segment 285 is provided with an inner ?ange 288 extending inwardly and inner face of the upper part of rotor ring I 8I. An upwardly beveled ?ange I83 on wall I83 and a downwardly beveled ?ange I84 on base ring 25 upwardly, resting on an annular shoulder 281 on I88 are arranged to provide a ball race groove I85 cooperating with groove I82 to retain the balls I88. By the removal of retort base ring rotor ring I8I, the abutting edges of the table segments 285' being preferably in overlapping re lationship to provide continuity and accurate registration. The lower rim 288 of grate ring I88 as the faces of grooves I82 and-I85 are substan 30 bears against ?anges 288 and securely locks the tially at 90° to each other, their spacing permits table segments 285 in ?rm ?xed position when smooth unobstructed travel of the balls under the rotor ring and grate ring wedge lugs are in various conditions of expansion due to changes terlocked as above described. ‘Table segments 285 in temperature. may be accurately located by positioning lugs on The outer margin of the retort base ring I88 35 rotor ring I8I engaging corresponding position is provided with an apron I81 extending out ing recesses in segments 285. wardly and downwardly over the upper edge of An ash trough extends around and below the the rotor ring IIH, apron I87 providing a smooth ash table segments 285, for the direct discharge path of ?ow for ashes around the ball bearing of ashes from the ash table. The ash trough 289 structure and beyond the outer face of rotor ring 40 has an outer wall 2H1, a bottom 2II extending I8I, the adjacent faces of apron E8‘! and rotor beneath and slightly spaced from the table seg ring I8I being suitably shaped to provide a rela ments 285, and an inner ?ange 2I2 extending up tively slight clearance and prevent‘ substantial wardly substantially beyond the lower face of amounts of ashes from reaching the balls I 88, the table segments 285. Segments 285 are preferably opening I89 below said balls permitting any ashes 45 provided with diagonally tangential ribs 2I3 or the like to fall out of the raceway. The an which serve to plow outwardly toward wall 2I9 nular pocket 233 below apron I81 accumulates ashes which fall between ash table 284 and wall ashes and an inner seal of ashes 234 is formed 2I8, preventing the ashes from escaping over at the lower edge of the apron, restricting the ?ange 2I2 while avoiding any engagement be passage of air to' the space above the grate. 50 tween the rotating and ?xed parts. The ashes In the embodiment shown a grate ring I88 is brushed outward by the ribs 2I3 accumulate at utilized, removably mounted on rotor ring I8I the outer edge of the bottom plate 2“ and form and adapted to receive removable grate segments an outer ash seal 28I at the periphery of the I89. These segments are preferably flat integral table 284 so as to restrict the ?ow of air to the I68, the balls ‘I88 will be readily accessible; and castings provided with an inner flange I 98 ex 55 tending into close relationship to retort base ring apron I87. Suitable slots permitting ashes to pass the segments I 89 include the radial slots space above. , The ashes carried around by ash table 284 are vcontinuously discharged by a scraper 2M in cluding an ash plow or vertical plate on the outer I9I, restricted margina1 slots I92 in ?ange I98, wall 2I8 of the ash trough extending into juxta preferably angled inwardly in the direction of 60 position to the ash table 284 and grate ring I88 rotation, and the spaces left between the periph and de?ecting ashes outwardly through a dis ery of each segment I89 and the adjacent parts. charge opening 2I5 in wall 2 I8 into the ash dis Segments I89 are mounted on the grate ring charge pocket 2I8 formed in said wall (Figs. 1 I88 in suitable manner securely held in opera and 6). An ash discharge chamber 2I'I forms tion but permitting ready removal and prefer 65 a downward continuation of pocket 2I6' and ably adapted to construction by casting. In the houses the receiving end of the ash removal screw form shown each grate segment IE9 is provided with two downwardly extending slightly elongated 2I8 mounted on ash removal shaft 89 (Fig. 6). A suitable arrangement ‘is provided for sup annular sockets i93 adapted to receive support porting ash trough 289 and for connecting it to ing studs I94 on the upper margin of grate ring the furnace body. For convenience, trough 209 I88. An integral locking tongue on the advance 70 may be constructed in three segments, supported end of each segment I89 extends'beneath a look at the right of the burner (Figs. 1 and 2) by two ing lug formed on the upper edge of grate ring bracket legs 228 overlying the two junctions of I88. Grate ring I88 may extend to a point higher the segments and removably mounted on the than the lower edge of apron I81, the interven 1‘; burner body I58 to permit convenient mounting 2,405,992. and, disassembly of the ash v‘trough 209. The re maining junction between segments 2l'9 overly ing the coal feed tube 22 is supported by a bracket 22l on the burner body I56, provided with a de tachable clamp 222 overlying the junction and which may be detachably fastened to the bracket 8 unit when the blower :is not in'operation. These functions may all be performed by a single mech anism comprising'a valve flap 2'“ ?xed to pivot spindle 222 located in the upper part of a sec tion of the air control housing 265 in advance of damper 264 and engaging 'valveseat 213, which is preferably inclined in the direction of air flow from the blower. The end of spindle-212 may be The upper margin of the ash trough 209 is con bent downwardly outside of housing 265 to form nected to the furnace ‘body to close the space a pointer 214 serving in conjunction with suitable 15) between the body and the burner unit. This may marks 215 or the like on the outer face of housing be accomplished by providinga closure plate 224 265 to indicate the position of ?ap 211. resting on shoulder 225 formed at the upper mar To arrest valve flap 21l at a predetermined gin of outerwa1l'2lo’of theash trough, and ex preferably variable distance from seat 213 we pro tending outwardly to the furnace walls. A suit vide a natural draft regulator spindle 216 thread able'?lling or lagging 226, such as furnace cement ed in housing 255, provided with a laterally ex or the like, maybe employed tofill the spaces tending stop arm 211 within housing 255 posi between plate 224 and thefurnace walls, which tioned for engagement with the face of ?ap 2H are shown as comprising vthe usual water leg 221' and serving as a variable stop for arresting the of a domestic furnace. Plate 224 may be locked downward movement of ?ap 21! at any point be on ‘shoulder 225 by segmental locking plates 228 tween the valve seat 213 and the maximum de ?tting into an annular recess 229 in the upper sired opening of flap 21! by rotation of spindle margin of the outer wall 2“) of the ash trough 216 by means of knob 218, spindle 216 being fric and provided with a longitudinal .rib 230. tionally held in adjusted position as by spring The mechanism for rotating the grate unit washer 219. employs an intermittent drive, imparting a. peri The air control housing 255 is connected to a odic impact to the. rotating structure, as such an suitable air duct 28B running to air inlet cham arrangement serves to break up the fuel mass ber 28! (Fig. 5) in the burner body I55, and merg and. to facilitate the sifting of .the ashes and ing, around the casing for the coal feed passage, small clinkers through the grate. In the con with‘ the air inlet chamber ISI to provide a, gen struction shown the shaker rod ")9 extends be erally tangential air feed adapted to distribute neath the ash trough 2G9 and ispivotally con the air evenly throughout the air chamber l6! 7 nected at its end to the lower'end of 1a feed dog and thence to tuyére openings I18. arm 2“ extending upwardly between the air A suitable arrangement is provided for auto chamber ~|5| and the grate rotor ring l8l and matically removing the ashes from the burner having at its upper end a feed dog 242 projecting unit C and discharging them at an appropriate laterally between the support flange 243 on the point, the construction shown including an ash inner face of rotor ring WI, and rack 244 on said removal conveyor and an elevator for transfer ring overlying ?ange 243. The feed dog 242 is 22l. ‘ i ‘ provided with "a rocking face 245 riding on ?ange 243, and suitable teeth 246 at its forward end adapted to engage rack 244. The arrangement is such that when the shaker rod lilois shifted to the left of ‘Fig. 3 the dog 242 will be rocked on face 245 until teeth 245 engage rack 244, further ring the ashes from the conveyor to a suitable -". discharge point. In the form illustrated the ashes are removed from the ash discharge cham ber 211 by ash removal tube 285 mounted in the burner body l5!) and forming a continuation of chamber 211. Tube 285 extends to an appro priate point and is shown as terminating adjacent movement of the shaker rod I69 serving to ro- ». drive unit B (Fig. 1). At this point a suitable elevator unit D is positioned to receive the ashes. A convenient construction is disclosed, employing an arrangement in which the ash removal tube 285 terminates in an elevator pocket formed in tate ring l8l and the grate parts mounted there on, while ring Hll will be free from dog 242 at the end of such stroke and during the return stroke of shaker rod H39 owing to the disengage ment of teeth 24!; when the dog 242 is rocked in the reverse direction by continued travel of the grate rotor ring l8! under its own momen tum or by the return travel of shaker rod I89. To prevent reverse rotation of the grate ring l8! and associated parts a detent dog 241 is pro vided on detent arm 248 pivotally mounted on stud 249 on the burner body I50 at any con elevator base 288. Ash removal screw 2H3 ter minates at the pocket while the shaft 89 on which the screw is mounted extends through the pocket and a suitable’bearing at the opposite side of the elevator base 268, and thence to the drive mecha nism as already set forth. An elevator tube 29:: is mounted in elevator base 288 extending from the elevator pocket up wardly in any desired direction to permit dis charge at any appropriate point dictated by local conditions, the angle of tube 290 being readily ad justed by clamping base 288 in any desired rotated position about ash removal tube 285 through a venient circumferential point and held yieldably in operative position as by counterweight .1269. Figs. 4,5 and 6 show the air supply and con trol system between the blower ‘18 and the burner unit C. The volume of air from blower 18 is suitably regulated, as by butter?y damper 284 mounted in air control housing 265 on spindle suitable clamping screw. An elevator screw is 266 preferably provided with suitable locking 135 positioned in tube 298 to pick up ashes discharged into the elevator pocket and raise them in tube means, the form illustrated having a lockingdisc 261 mounted on the end of spindle 256 at the rear of housing 265 (Fig. 5) and held iniadiust ed position by locking knob 268 threaded on screw stud 269 extending through'concentric slot 210 andmounted on housing 265. Means are provided for indicating the flow of air from blower 18,’for preventing backflow into the blower system from the burner unit C, and for permitting aregulable-flowof air to the burner 295 to a discharge at the upper end of the tube. A suitable discharge arrangement is provided it at the upper end of elevator tube 29:]. This may comprise a discharge head 3B8 mounted on the upper end of elevator tube 290 and carrying an upper bearing for the elevator shaft. Head 306 is provided with suitable spout discharge means, the illustrated construction employing two dis charge spouts, each of which may be provided 2,405,982 with a flexible tube 3I0 clamped thereto for die recting the ashes to any suitable receptacle, such as ash can 3I I (Fig.1). 7 A suitable arrangement is provided for driving the coal feed screw 2I from shaft 89. In the arrangement indicated shaft 89 extends through a bearing in chamber 2!‘! and a bearing on a bracket on burner body I50, and drives coal feed screw 2| through a sprocket on shaft 89, sprocket chain 240 and sprocket 239 mounted on shaft I60 to which the coal feed screw 2I is connected. 10 by a thermal element located suitably for prompt and sensitive reaction to changes in the tem perature of the ?re. There are extreme differ ences in such temperature between periods of maximum operation and the low ?re bed which it is desirable to maintain under banking con ditions when the effort is simply to maintain a minimum heating as in domestic installations in spring and fall. Electrical control apparatus regulating the operation of motor ‘I5 in connection with the While ‘various proportions and designs may be house thermostat system may have appropriate employed in the different parts of the apparatus parts thereof mounted as shown in control hous disclosed herein, the proportions are of impor ing I33 (Fig. 1) carried by a bracket on drive tance in various parts, and particularly in the 15 casing 86. It has been found advantageous to burner structure, the size and proportions of the locate the thermally responsive element of the pot, retort, grate segments, ash slots in the spac banking control apparatus in the combustion ing thereof, having been determined after sub chamber 34 I at a distance from the ?re su?icient stantial experiment as adapted to most e?icient to permit the employment of a sensitive thermal operation with coking bituminous coal; and the device which will operate accurately with slight drawings herein are drawn to scale to show the changes in temperature. For instance, such de proper dimensional relationships between the vice may be located upon or at the furnace door various parts. . mounted in suitable position .to be directly affect A suitable electrical control arrangement is ed by both radiation and convection from the illustrated in Fig. 6, and may be of the type in ?re, without being in?uenced by various factors which the motor ‘I5 is operated at full speed at affecting temperature at other points in the fur- . suitable intervals, though the invention is not nace. Speci?cally, it has been found that the necessarily restricted to a control of this type. absorption and radiation of heat by portions of Motor 15 is connected to the line 320 by motor the furnace such as the water legs 22'! and 342, the variations in draught due to dampers and stack openings such as those shown at’ 343, and other variations in draught and temperature con itions seriously affect a sensitive thermal con trol unit located in the furnace at points other than the combustion chamber 3“. In the form shown the thermal element com overheating of the motor. prises a bimetal coil 335 arranged to extend The motor circuit 32I includes the upper con through a suitable opening in the furnace door tacts 326 of duplex relay 32'! whose coil 328 is in line 323 passing through the secondary of 40 or other part of the furnace into position in the combustion chamber 34! where there will be no the low voltage transformer 339 whose primary is obstructions between thermal coil 345 and the ?re connected across the main line 325. The main in retort I12. . secondary lead 329 carries the protective and The thermal coil 3ll5is connected at its rear control devices in the heat generating apparatus, which in the present instance is illustrated by a ;. end to rotary switch rod 351. Switch arm 358 is centrally mounted on the end of rod 351 domestic hot water furnace 33I. Invthe form and is provided at its lower end with a clip illustrated the line 329 carries a high point out carrying the mercury type bank switch 353. The out switch 332 operative to break the circuit when mercury type out switch 35I is carried by av clip the heating medium has reached a predetermined which is preferably mounted on arm 353 by temperature or pressure, and this line 329 also means permitting the angular adjustment of carries the banking control switch unit 333 here switch 36I relative to switch 360. inafter described. Line 3223 continues to the lower Under certain circumstances, and particularly contact 334 of a room thermostat 335 of the when burning certain types of coal, gases may be type which includes a bimetal strip 335 operative when the room drops below the desired tem 55 forced back through the coal feed tube 22, and an arrangement is provided for preventing the es perature to close contacts 333 initially and after cape of such gases. Such an arrangementmay a further temperature drop to close the con include a trap in which the gases will collect, and nected upper contacts 331, thermostats of this means for conducting the gases from the trap type being well known. The contacts 334 and 33? are connected ill to a suitable discharge. In the preferred arrange ment the gases- are conveyed to the burner. through strip 333 and holding circuit line 338 Owing to the relatively low velocity of such gases with the lover contacts of relay 32? which it has been found that under certain conditions connect with the main circuit 323. The upper there is a tendency for ?ne solid particles to room thermostat contacts 337 are connected accumulate in the return pipe and eventually to through shunt circuit line 343 with the line 329 I clog the pipe. The preferred form therefore at relay 327. includes means for preventing such accumulation The banking control switch unit 333 is pro of dust and the like, and for returning the gases vided with two switches, a bank switch arranged to the burner or elsewhere by positive means, to start motor ‘I5 when additional fuel and air such as a suitable supply of air, which may be are required during banking periods, stopping taken from the blower system. motor 15 automatically after a suitable period; An arrangement of this type is embodied in and an out switch arranged to stop motor ‘I5 the preferred form illustrated herein, and is automatically if its operation under control of shown best in Fig. 4. It includes afresh air con the bank switch does not result in a suitable nection I35 with the outlet of blower ‘I8 con— pickup of the ?re. These switches are operated circuit 32I in which suitable motor protective de vices are located, such as the overload cutout 322 and the thermal type cutout 323 which may in clude a heating coil 324 and a bimetal strip 325 adjacent thereto. The thermal cutout 323 may be mounted directly on the motor so that it may be affected rapidly by all conditions which cause :1 nected by air pipe I36 and return bend I 37 with' 2,405,982 11 12 for only a short distance from the burner, an jet nozzle I38 extending through a wall of the arrangement which not only reduces to a mini gas pocket I39 formed in the upper face of the mum the power necessary for feeding at this coal feed passage 13 in base 12. The fresh air most exacting point, but which also is desirable connection I35 thus utilizes a higher pressure since a full feed tube 22 for a short distance from the blower than can be found anywhere be from the burner is serviceable in forcing the gases yond the damper control. A gas return pipe hi0 to travel upwardly through the burner and not extends through the other side of pocket 139 in back through tube 22. alinement with nozzle I38 and spaced therefrom In burner retorts of the prior art di?iculties by 'a distance suitable for obtaining an injector have been encountered because of the tendency 10 effect under the conditions of air pressure and of the coal under certain conditions to burn down dimensions employed in the arrangement. The in the pot toward the feed screw, resulting in the gas return pipe M0 is connected to the burner formation of coke and clinkers which obstruct unit C at the ash discharge pocket 216. Gas the feed and burning of the coal and may result pocket I39 is sealed by a removable cover Ml. While the apparatus is adapted for use with 15 in breakage or stoppage of the mechanism. The travel of the coal upwardly in the pot may like various types of coal it has been particularly de wise be obstructed by the formation of clinkers signed to solve certain special problems encoun and the like which adhere to the pot walls, and tered in the burning of bituminous coal, which by mechanical obstructions provided by the wall has special characteristics affecting its collec surfaces.’ In the present construction a retort 20’ tion‘, transportation and combustion. is provided in which the zone of active combus tion is restricted to the upper portion, and which extends downwardly for a suf?cient distance be low the lowest point of air supply so that the conditions. There is also secured a careful bal 25 fire will not reach the region where formation of clinkers, coke and the like will interfere with ~ancing between the rate of coal feed, the rate of the feed mechanism. Any clinker formation de air supply and the combustion characteristics of veloping will ‘be prevented from adhering to the the coal, both as to the time required to burn to pot by the smooth liner I54 but will be forced up ash and the volatilization of combustible gases. ward and broken up by the incoming coal. 30 The latter problem is especially important in the Under full draught conditions the relation be burning of" bituminous coal, and involves like tween the coal feed and the rate of combustion wise the formation of coke, which heretofore has is such that the burning fuel over?ows gradually been a source of serious di?iculty and obstruction across the retort I72 and over grate segments due to the tendency of’the coal to coke back into I89, and may reach the Walls of the furnace. the feed zone, interfering with the operation of The relatively slight projection of the retort I12 the feed mechanism and frequently causing com~ above segments I89 facilitates the lateral flow, plete stoppage ofv the machine. The design also and is particularly advantageous in bituminous contemplates the effect of oil which is frequently coal combustion in which the incandescent coke used for dust prevention. is more or less ?uent, the arrangement permit The rotating element I51 provided at the side ting the formation of a relatively wide thin ?re of the throat opposite to the discharge end of which produces maximum efficiency, rather than the coal feed tube serves to prevent the coal from a high ?re above the retort. The rate of com forming a packed mass at this point, and thereby bustion will naturally increase with the spread increasing notably the facility with which it may be forced upwardly by the horizontal pressure of 45 ing of the ?re until it will equal the rate of coal feed when the fire has reached its maximum area the feed screw. In one sense it may be said that at the walls of the furnace. The inner tuyere this auxiliary screw increases the relative fluidity openings I18 assure full combustion of gases or ?owing qualities of coal at this point. In the which pass upwardly from the coking zone and preferred form the rotating element is in the form of a' reverse screw exerting a counterbal 50 provide an adequate supply of air for full com bustion, the outer tuyére openings in wall I75 ancing horizontal pressure on the coal discharged assisting if necessary in the combustion of the by the feed screw while likewise preventing the portion of the fire outside of the retort H2. The formation of a solidly packed mass of coal, the spreading of the fire is facilitated by the unu result being that the coal will travel upward as gradually as may be desired without exerting any 55 sual power of the upward thrust of the coal, which likewise serves to scour away any clinkers pressure whatever on the surfaces opposite the which may tend to form on and adhere to the coal feed tube discharge. The reverse screw may surface of the pot structure or retort I72. be arranged to impel coal continuously away from When the drive unit is cut off and the ?re op the feed screw bearing, which may therefore be of any desired type. The elimination of the 60 erates under banking conditions, the portion of the burning coal beyond retort H2 will gradually tendency to pack the fuel in throat l5! further burn up, and if banking conditions are main more permits the maintenance ofv fuel feed in tained for a sufficient period, the fire area will tube 221 at substantially less than the full ca gradually contract toward retort I72. Eventu pacity of the tube as already indicated, since sub stantial. back pressure on the fuel at the burner 65 ally the ?re may contract to a zone in the upper part of retort H2 limited in depth by the dis owing to the resistance caused by forcing the tance that air will penetrate from tuyére open fuel'upward under previous conditions causes the ings H8. This arrangement, limiting the bank coal to back up along the feed screw; and even tuyere to a zone at the top of the pot substan if.’ feeding at less than coal tube capacity is at tempted, substanti'al‘back‘ pressure at the ‘burner 70 tially spaced from the feed Worm 2 l , eliminates the possibility of coking back under banked condi and the resultant accumulation of coal in the tions, a serious difficulty with prior arrangements. tube "will'm'ake it impossible to operate the feed Atthe same time a small zone of de?nitely burn tube- zlipartially ‘?lled ’ at any point within asub ing fuel is maintained so that when the drive stantial' distance of the burner. With the con ‘struction illustratedhowever the feed tube is?lled 75 unit is again started and the coal feed is re The burner unit C is particularly designed to provide thoroughly efficient combustion both un der active operating conditions during coal feed and operation of the blower, and under banking 2,405,982 13 - 14 sumed, there will be no difficulty about kindling moval mechanism abruptly after motor. ‘I5 is up promptly the green coal that is more or less to speed, exerting a sudden impulse that may be valuable in dislodging a slight obstruction. The apparatus is likewise arranged so that the motor ‘I5 will be stalled before breakage of any of the abruptly forced upwardly in the pot I52. When operating under banking conditions air is drawn through the tuyere openings I18 by the ordinary stack draught in a manner similar to drive parts, allowing the electrical system to the operation of hand-?red coal furnaces. This throw out the motor circuit and take care of emer is made possible by the action of stop arm 21‘! gency conditions without damage to any part which holds valve flap ZI'I open to the proper of the machine. extent, thereby permitting the maintenance of 10 The blower structure has been carefully ar a minimum bed of burning material without risk ranged to give rapid and accurate control of an ing the extinguishing of such bed by insu?icient adequate supply of air at all times without the air, sudden in?ux of fuel or the burning out of usual excessive intake noise. . accessible fuel by excessive draught. The general operation of the electrical control The arrangement likewise is adapted to mini 15 system will be understood from the speci?c de mize the tendency to form coke in the lower por scription. Assuming that the building is at or tion of the pot where it might interfere with above the desired temperature for which the room screw 2| through the depth of the pot, the air thermostat 335 is set, the motor 15 will be out cooled walls and the double-wall construction. of operation, since contacts 334 and 331 of ther If however coke should form in throat I5I, it 20 mostat 335 will be open and relay 327 will con would not wedge between the screw and the end sequently be de-energized, opening the motor cir of the feed passage, as in prior arrangements, cuit at the upper contacts 326. When the ther but would tend to be broken up by the rotary mal element 336 contracts due to reduction in action of the feed screw 2| and reverse screw room temperature thermostat contacts 334 will I51. 25 ?rst be closed; and continued reduction in tem The rotary ash collecting unit is arranged to perature will thereafter close contacts 331, com remove accumulations of ashes with a minimum ' pleting the circuit between the line 329 and the disturbance of the ?re bed. This operation is shunt line 340, closing relay 327 and starting facilitated by the smooth-surfaced grate seg motor ‘l5. At the same time the contact 333 of ments I89 and the intermittent shaking action 30 relay 321 will be closed; and as thermostat con imparted thereto. The formation of the de tacts 337 open when the room becomes warmer, scribed type of ?re bed likewise facilitates the motor ‘I5 will continue to operate since the sec scouring of ?ne clinkers from the retort I12 and ondary circuit through line 329 will be completed their discharge on to segments I83, which may be by the holding circuit line 338 until the room is provided with slots suf?ciently large to receive '. warm enough to open thermostat contacts 335, whereupon relay 32? is de-energized and motor the small clinkers as formed and to maintain a clean ?re even under conditions which operate ‘F5 will stop. A sudden excessive load on motor the burner at infrequent intervals. The ashes ‘Iii-will open cutout 322, while heating of motor are effectively sealed in the ash receptacle and 15 for any reason will operate thermal cutout 323, readily discharged ‘from the burner in a manner affording full protection to the motor. If the already indicated. temperature of the heating medium should reach Any gas which is formed will normally be gen a point beyond which it is dangerous to continue, erated so high in the pot I52 that it will tend the high point cutout 332 will operate to break to flow upwardly and to be burned; but in case the, main secondary circuit line 329, open relay gas is forced back through coal feed tube 22 it 321 and stop motor ‘I5. It is noted that as soon will be positively returned to the ash pocket ZIB as the heating medium returns below the danger by the action of jet nozzle I38, and will pass up; point said circuit will be closed and the motor ' wardly to combustion past the grate segments again started, assuming of course that the room I89. This arrangement will also provide a slight thermostat 335 is in appropriate position with air feed outside of the retort I12 which will be 50 the contacts 334 and 331 closed. operative to some extent when the blower ‘I8 is The banking control unit 333 is arranged for not running, since the natural flue draught of operation at times when the room thermostat the furnace will exert a certain suction effect on 335 is open; and such operation may be readily the gas return pipe I40. This arrangement also understood from Fig. 6. The thermal coil 345 prevents any tendency for dust to collect in the will naturally expand and contract in accordance gas return line.- It may be noted that when the with the heat given o? by the ?re, thereby ro valve ?ap 2l'I is allowed to fall upon its seat it tating switch rod 35‘! and the switch structure provides positive means for preventing gases mounted thereon. The coil 345 is constructed and from the combustion zone from returning arranged so that the bank switch 360 will be ap through the blower structure, if conditions should propriately» positioned with the mercury out of arise that demand such an arrangement. contact with the terminals when the temperature The operation of the arrangement for convey in the chamber 3!“ is above a predetermined ing the ashes to a suitable point of discharge minimum banking temperature. /As the tem will be apparent from the detailed description. perature in said chamber approaches such bank The construction is such that the ashes may be ing temperature rod 35'! is rotated by thermo discharged at any desired point, and are kept stat 345 to turn the arm-carrying switches 36!) completely housed in conveniently located con and MI and swing switch 350 downwardly‘until veying tubes. the mercury ?ows to the contacts of both switches The drive, operated by a single motor and com when such banking minimum temperature is pactly arranged, is constructed so that the blower reached'thereby closing an auxiliary circuit in may be operated without the coal feed, which cluding conductor I26, switch 332, switch con may at times permit operation by hand ?ring in tacts 36%, 36L conductors 312, 340, coil 328 of re cold Weather pending repairs to the coal feed lay 321 and conductor 329. The resultant closing mechanism. The clutch islikewise arranged to of switch 360 completes a circuit through the permit throwing in the coal feed and ash re- - banking shunt line 372 with the shunt circuit 340 2,405,982 16 1-5 ditions the natural draft draws air through the partly open valve ?ap 21! and damper 264 into the spaces around the retort and through tuyere openings I18 together with some slight leakage from the ?re will rotate the switch rod 351 in from the coal tube through pipe 143 and open the ‘opposite direction until the bank switch 363 ing 2E6 into the space below the grate. There is turned oil by the flow of mercury from its ter may also be some seepage of air through the minals at the maximum banking temperature, ash seals for the rotor ring I81 and ash table thereby opening relay 321 and stopping motor 204. In this way the air supplied below the 315. It is noted that this operation is independ ent of the thermostat 335, and is effective only :10 grates is negligible in amount, substantially the entire supply being through the tuyere openings when said thermostat is not closed. of the retort both under running and banking The arrangement consequently serves to main conditions. tain a minimum banking ?re independently of This is a division of our application Serial No. the house temperature control without interfer ing with the operation of such control and ef 15 161,494, ?led August 28, 1937, now Patent No. 2,306,189 of December 22, 1942, fective when such control is not active. It per We claim: mits highly accurate and e?icient regulation of 1. A stoker combustion system comprising in banking conditions, since it may be constructed combination with a retort expanding and open for any desired range of banking temperatures, and the temperatures at which it operates may 20 ing upward, of means forming a combustion chamber above said retort adapted to be sub be readily adjusted by shifting arm 358. Further jected to subatmospheric pressure by virtue of more, it is located at a point where it is affected the ?ue draft thereby effecting a natural draft promptly and directly by very small changes in of air into said chamber, means forming the bot the banked ?re, and is sensitive to slight varia tom of said chamber and sealing it against en tions in temperature. and‘through the out switch 3B|_ with the main secondary line 329, energizing relay 321 and start ing motor 15._ The resulting increase in heat Out switch 36! is arranged and connected to trance of air through the area around said retort stop motor 15 if the ?re temperature should not including a stationary annular ash member and rise after the motor has been turned on by a grate structure movable around a central axis and comprising an annular upper grate sur switch 36!]. If the temperature in combustion chamber 34! drops to a predetermined extent be 30 rounding the upper portion of said retort and a lower aSh table overlying said member, said over low the minimum banking temperature, switch lying table cooperating with the overlaid part of rod 351 will continue to rotate and tilt banking said member to form an air seal, means for sup switch 36l until at a predetermined temperature the mercury will ?ow away from the contacts of switch 36l, breaking the circuit between bank plying coal to said retort and forcing it upward ly therethrough, and means for supplying air under pressure to the upper portion of the coal switch 360 and line 329 and opening relay 321. column in said retort, said means comprising a This arrangement is utilized to provide man ual regulation of the coal feed and forced draught during starting of the ?re. This is accomplished by pressing the button 3'“, closing contacts 368 and 363, short-circuiting the out switch 361 and blower operable to supply air above atmospheric pressure and an air supply ori?ce for passing air 40 to said upper portion of said coal column under starting motor 15, which runs as long as button 37! is pressed. If the ?re ignites properly the heat will promptly affect thermal element 345, which may be so sensitive that even very slight heat from the ?re will be sufficient to close out switch 36l and permit release of button 31!. In igniting, bituminous coal ?res this period is ex tremely short, and may be two minutes or less, since the unit 333 preferably operates at very low -~. temperatures and thereby reduces to an absolute minimum the amount of coal burnt during non heating bank periods. The operation of control unit 333 cooperates with the setting of the main air damper 264, .~ which controls the forced draught, and the set ting of valve ?ap 2'“, which controls the nat ural draught; since it is possible by employing a sensitive control directly responsive to changes in a very low ?re, with an air regulating means especially suited for the maintenance of the ?re steadily at such low point, combined with a predetermined conditions of banking aircontrol when said blower is inoperative and the combus tion chamber is under pressure below atmos pheric. 2. A stoker combustion system as set forth in claim 1 in which the retort and the grate struc ture have cooperating parts for trapping an ac cumulation of ashes and thereby forming an in ner air seal. 3. A stoker combustion system as set forth in claim 1 in which the stationary ash member is annularly spaced from the outer surface of the retort so as to leave an air space therebe tween. 4. Stoker apparatus as set forth in claim 1 having an ash removing conveyor and means cooperating with the air sealing means to form a substantially air tight enclosure beneath the grate for receiving the ashes sifting through the grate and conveying such ashes to and discharg ing them into the ash removing conveyor and for substantially preventing the passage of air from the furnace room to the furnace combustion forced draught regulation which appropriately zone by way of the furnace ash pit and the grate, builds up such small ?re properly in a brief time, to provide a novel and highly ef?oient banking 65 thereby providing ash collection and removal while preserving the action of the banking air arrangement. control when the blower is not in operation. The air supply for the ?re is intended to come 5. Stoker apparatus as set forth in claim 1 mainly from the tuyere openings of the retort having ash collecting and removing means in ring 115, and this supply serves in addition to cluding an annular ash receiver positioned under maintain a proper cooling of the retort. Under the grate and rotatably supported upon the re running conditions substantially all of the air tort, an ash removal conveyor and means for from the fan passes through the air spaces rotating the ash receiver to transfer the ashes around the retort tending to cool it and prevent thereon to the entrance end of the ash removal overheating and improper coking and clogging conveyor, with the air sealing means of the bank of the rising column of coal. Under banking con 17 2,405,982 ing air control including means forming an in ner ash air seal between the ash receiver and the retort, an annular closure means closing the 18 fecting a natural draft of air thereinto, means forming the bottom of said chamber compris ing an annular grate below the top level of said retort and having an inner edge overlapping said central structure and forming an ash seal therewith against the entrance of air to the com bustion space, an ash ring carrying said grate and providing a lower ash seal substantially shutting space between the furnace Walls and the grate and having an extension projecting downward below the grate, and means forming an outer ash air seal between the closure extension and the ash receiver, both such ash air seals substantially limiting the leakage of air from the furnace room to the furnace combustion zone by way of the 10 off the air flow to the space below said grate ' around said ash ring, means for supply coal to clearances around the ash receiver incident to said retort and forcing it upward therethrough, supporting the ash receiver for rotation. an air conduit for supplying air to the upper 6. A stoker combustion system comprising in ‘ portion of the coal column in said retort under combination with a central structure having a retort expanding and opening upward, of means 15 said natural draft and a blower adapted to force forming a combustion chamber above said re tort adapted to be subjected to subatmospheric pressure by virtue of the ?ue draft thereby ef air through said conduit at pressure above at mosphere. WILLIAM M. SCHWEICKART. FRED G. JULYAN.