Nov. 12, 1946. A. B. WELTY 2,410,851 _GRAIIN DEHYDRA'TOR ' Filed March 27, 1944 S Sheets-Sheet 1 Nov. 12, 1946. A. B. WELTY - 2,410,851 GRA'IN DEHYDRATOR Filed March 27, 1944 5 Sheets-Sheet 2 Nm m E 8N Gm mm Am“, mm““MmY l. mgmm E t4, a2 5, w t 5 Patented Nov. 12, .1946 . ' 2,410,851’ . ' UNITED ._ STATES PATENT orrlca ' l : GRAIN nnnvmm'ron Albert B. Welt-y,’ Moline, 111., assignor to Interna tional Harvester Company, a ' corporation ‘of New Jersey. . Application March 27, 1944, Serial No. 528,254 1 China (Cl. 263-19) present invention will become apparent from the following speci?cation and accompanying draw‘ ings, in which: An important object of the present invention _ - Figure 1 is a perspective view of the portabl grain dehydrator of this invention; Figure 2 is an end view of the device as shown _ is to provide .a portable graindryer which may 1 be readily moved to any desired position. Another important object of this invention is in Figure 1; the provision of a corn dryer, wherein a quantity of corn is so treated that the greater percentage ' Figure 3 is a sectional view taken on the line 3—3 of Figure 1; of moisture is removed therefrom.“ Storing of corn without spoilage is a big prob Figure 4 is a sectional view taken on the line 4-4 of Figure 3 ; and Figure 5 is a skeleton perspective view of the - lem to the individual farmer as well as to- those persons.- operating grain elevators. 2'. vOther and further important objects of ‘the This invention relates to a new and improved grain dehydrator and has for one of its principal objects the provision of, novel means for drying‘ quantities of grain preliminary to storage. When the ‘device indicating heat circulation with arrows. corn is picked, the kernels usually contain a high 15 ,“The' reference numeral Ill indicates generally percentage of moisture.’ a chassis or frame upon which is mounted a body - If such corn were im- , mediately shelled from the cobs and- stored in a H. ‘The frame is carriedby wheels I2. ‘The for tight grain bin, spoilage would begin promptly.‘ ' ward end of the frame I0 is equipped with a hitch It has been found by experience that‘if the high l3 which maybe attached to and drawn‘ by a moisture content ‘of this shelled corn‘ were re-‘ 20 tractor or the like. It is obvious that this _grain_ duced to 14% or less, it could'be safely stored dehydrator is portable and maybe moved from in a regular grain bin for an inde?nite period of bin to bin of. an individual farmer, as his needs 7' require. or may be moved to other farms for use. _ time without danger of spoilage. Heretofore, it has been impossible for an individual farmer-45o purchase equipment to dry shelled corn. There fore, rather than shell the corn immediately Howeverywhen the grain dryer is in operation, after it has been picked, the corn would be left » on the cobs and placed in‘ open corn cribs, so that air could‘ circulate through and cause natural drying of the corn. process, however, re-' 30 it is desired to have it remain quite stationary and to this end leg members II are supplied. These legs M’ are of the extension type, and al though they are mounted rigidly at If: on the body I I, they may be extended or retracted by means of~an adjustment l6. ' V quired considerable time, and although there was not much danger of spoilage because the The travel of shelled corn through the grain dryer requires several mechanical devices and a ' kernels were all opened to the atmosphere, losses plurality of'elevator‘s, and to effect an operation did occur. These losses were chie?y caused by rodents or other small animals nesting in the com bins. The danger of fire with the corn in this condition was excessive and also contributed 35 of these units an engine. I‘! is'provided. One of the main functions of the engine is to drive a - fan I8 as shown in Figure 4. As best shownin Figure 1, the internal combustion engine I ‘I im parts rotation to the pulley IS on the crank-shaft '20. It is, ‘of course, understood that power for means for drivingv the'moisture out of corn and 40 the grain dryer operating units may be obtained may therefore safely‘ buy shelled corn which has from other means than an internal combustion a high moisture content. The price of high mois engine such as an electric motor, a, steam engine, ture corn per bushel is much less than the price -_ or the like. A pulleyj2l is mounted on the fan of "dried” corn per' bushel. It is quite advan shaft‘ 22 and is operatively joined‘ to the pulley tageous to corn growers to sell their corn when 45 I! by means of a belt 23. it is dry ‘rather than accept the low price for to the losses. 7 Operators of grain elevators employ arti?cial moist com. A heating unit, shown at 24, is provided on the It is, therefore, an important ‘object of this in; ‘. frame III to supply the arti?cial heat needed to drive the moisture from the kernels of grain. vention to provide an arti?cial means for dry ing corn for use by all, that is, the individual 50 The heater 24, shown here, is an voil burner type, and it is obvious that any type of furnace or fa;mer, a group of farmers, or the operator of heater could be employed and still secure the de-‘ a grain elevator. ‘ ' , v I sired dehydration ‘results. A fuel oil tank is A still further important object of this inven shown at 25 for feeding fuel to the oil burner 26. tion is to provide an automatic economically op erating device for drying shelled corn. ‘ 55 A motor 21, preferably driven by electricity from 2,410,851 3 4 , a power-line 28, drives a pump- within the hous Figure 3 is a cross-sectional view of the chamber 42 of the grain'dryer. As the grain discharges from the pipe 31, it forms a central ridge directly beneath the pipe 31 and from there it tapers downwardly as shown by the lines 68. In opera tion, the chamber 42 is entirely ?lled with kernels of corn, and it is the object of this device to heat this column of corn in the ‘chamber 42 and then ing 29. As best shown in Figure-2, supply hopper 3! may be ?lled by any means such as the trough 32 shown here coming from a large receptacle 33. The hop per 3| is substantially V-shaped and is equipped with an auger lying parallel to the vertex. 'The auger (not shown) is‘ adapted to feed the grain discharge it from the bottom thereof, whereupon . to one end of the hopper‘where it communicates with a supply elevator 34. The grain is then lifted 10 it is cooled and then stored. The slope of the up per surfaces of the corn as designated by the lines to the top 35 of the elevator 34, and, as best shown 59 is, substantially parallel with lines drawn in Figure 1, discharges kernels of corn into a hop per-like member 36. A pipe 31 extends longitudi through the heat entrances. The heat entrances, nally of the body II and is attached at one end to as shown at 60, 6|, 62, 63, 64, and 65, are in the the hopper 36 at 38, as shown in Figure 1. 15 upper portions of three plenum chambers 66, 61, and 68. These three plenum chambers are main In the pipe 31 is housed an auger 40 which pro tained with a supply of hot air. The heat en jects within the hopper 36, as shown in Figure 4, trances 60, 6|, and 62 are in a line substantially ‘ and extends the entire length of the pipe 31. The ,parallel with the inclined surface 59 directly auger 40 is equipped with a central shaft 4| which extends beyond the ‘hopper 36 and beyond 20 above, and similarly, the heat entrances 63, 64, and 65 are substantially parallel with the corn surface line directly above them. As the corn the other end of the pipe 31. As the kernels of com are fed to the hopper 36, they are carried by the rotating auger 46 :through‘the pipe 31. ' The holes 319, in the bottom of the pipe, permit the corn to drop through into the chamber 42 within 25 the body ||. The corn will continue to drop through this successive series of holes until suchv time as the column formed therebeneath supplies sufficient back pressure to cause the corn to travel _ to the end of the pipe 31. Any surplus of corn that does reach the end of the pipe will return through the conduit 31* to the supply recep enters the chamber 42, through the openings 39 and the pipe 31,.it is generally cold and rela tively moist. As heat is driven upwardly from the plenum chambers 66, 61, and 68, it causes drying of the com. The height of the column of grain in the chamber 42 is predetermined so that the major portion of the heat is utilized. In other words, by the time the heated air has passed through the column of grain it is’ substantially saturated and approximately at' room tempera ture. The top of the grain drying chamber is open and the air after passing through the column of Referring now to Figure 1, it will be seen that a pulley (not shown) on the fan-shaft 22 35 grain is discharged through the open top.v It is“ obvious that at different levels within the cham drives a belt 44, which in turn drives a pulley 45 ber 42, the corn will be at di?erent temperatures. mounted on a shaft 46. An idler pulley 4.1 is tacle 3|. . _ mounted on the end of a bell-crank 48 which is . As the corn progresses downwardly, it gets hotter and dryer. The parallelism between the upper pivoted at 49 and which has a handle portion 50 swingable on the arcuate member 5|. In the posi 40 surface of the corn and the heat entrances is for the purpose of effecting a-uniformed heating ‘of tion shown, the idler pulley 41 has so tightened the , the corn over the entire width of the dryer. belt 44 that it effects a drive between the fan Grain discharge rolls 68 are positioned ad shaft 22 and the shaft 46. However, if the handle‘ jacent the lower portions of each plenum cham50 of the bell-crank 48 were swung in a right ward or counterclockwise direction, viewing the 45 her. One of these rolls is shown in greater de tail in Figure 4. It will be seen that the periph device as in Figure l, the idler pulley 41 would ery of the rolls is provided with intermittent be withdrawn from contact with the belt 44 and so permit rotation of the shaft 22 without re ' pockets 10 so that at no place around the roll is there a continuous icuteout portion, or is there sulting rotation of the shaft 46. Figure 3 shows ‘an enlarged view of the pulley 45 and its shaft 50 a continuous cut-out portion from one end of the roll to the other. The pockets 10 are offset 46. From this view it is seen that a bevel pinion bot'n around and longitudinally of the rolls 69. gear 41’, keyed or otherwise fastened to the end Returning to Figure 3, it will be obvious that the of shaft 46, cooperates with a large bevel gear 48’ which is keyed or otherwise fastened to the auger kernels of corn will ?ll the pockets 10, and upon shaft 4|. From this arrangement of pulleys and 55 rotation of the rolls 63 will permit a discharge of the'kemels at the point 1| at the bottom of gears, ‘it will be understood that the engine |1 the rolls. The size and number of pockets in effects a driving of the fan | 8, the auger 40, in addition to supplying a continuously rotating end the rolls are such that the corn is removed at '43’ of the auger shaft 4|. This rotating end 43' substantially the same rate at which it is fed is best shown in Figures 1, 2, and 4, and in Fig-' .60 ' to the device whereby the hopper is maintained ures 1 and 2 it is evident that a pulley 50' is keyedgi, . substantially ?lled and always presents a uni or otherwise fastened to this rotating shaft form column of grain of the desired altitude. end 49'. . . Partitions 12 are attached to the sides of the sev Several pulleys, namely, 5| ', 52, and 53, are in a eral plenum chambers and, in cooperation with common plane with the pulley 56' and are joined 65 similar partitions 13, provide a trough with an together by means, of a crossed belt 54. The opening in the bottom thereof for feeding di pulley 5|’ is mounted on shaft 55 and directly rectly to the pockets 10 within the rolls 69. Fur drives the grain supply elevator 34. The pulley V ther, the rolls 69 are partially surrounded with 52 is mounted on shaft 56 and imparts a drive to a covering material‘ 14, such as canvas, leather, a grain discharge elevator 51. The pulley 53. is 70 rubber, or possibly synthetic rubbers.) These an idler tightener pulley and is mounted on a covers 14 are in two sections and are fastened directly or indirectly at 15 and 16 to the par The chamber 42 is rectangular in shape and is titions 12 and 13, respectively. The lower ends well insulated from the atmosphere‘by thickly in of the covers 14 areequipped with rods 11 and sulated walls 43 as shown in Figures 3 and 4 75 18 which are yieldably held together by a spring stub-shaft 58. - aeidssi . ‘ 5 . or the like (not shown). The space "H between - the rods ‘ll and ‘i8 is to permit the discharge of kernels. The covers ‘id snugly engage the'an a circular segment and is pivoted on the shaft I00. The vertex "36 of the segment M5 ls.ad-= justably positioned within the slotted bracket 101. The outer arcuate end of the segment Hi5 is'adapted to coincide with the arcuate periph cry of the ratchet wheel i?i. The pawl “it, as nular peripheries of the rolls 69 and so prevent to ‘a great degree the passage of hot air from the chamber 52 to a chamber ‘i9 beneath the plenum chambers. Conversely, cold air in the chamber 19 is prevented from assingr upwardly into the grain column chamber 2,. shown in Figure 2, is thus prevented from con tacting the ratchet teeth and'movement of the ratchet wheel iill is thereby delayed until the At the time the corn kernels are discharged at 10 pawl iM passes beyond the upper limit of the the spaces ‘ii beneath the rolls 89, they are very hot and if stored in that condition would tend to take on considerable surface condensation with the result that the corn would be in no bet ter condition for storing than before dehydration. -_ It is, therefore, necessary to provide means for bringing the temperature of the corn down after it has been heated and dried preliminary to stor ing. The chamber 19 includes a COOlillg means. The corn from all four of the rolls‘ 89 is dropped 20 on to a cross-conveyor 89 which extends sub segment I05. The segment Hi5 maytbe pivoted about its center I50 and ?xed in any desired ' position within the slotted bracket ill‘? to effect any rate of ratchet rotation that-is permissible between thelimits of movement of the pitman 91. A second pawl “18 is resiliently held against the bottom of the ratchet wheel lot by means of a spring "19.. This ratchet wheel prevents rearward or counter-clockwise rotation of the ' ratchet'wheel IUI when the pawl we no longer is engaged with the ratchet teeth. A chain H0 is wrapped around each of the sprockets 95 as well as the sprocket Hi2, an idler sprocket Hi, and stantially across the width of the grain dryer. This conveyer 86 is preferably of the canvas type and extends around end rolls 8i and 82 which the sprocket H2; The sprocket H2 is mounted have centralshafts 83 and M, respectively. Slat‘ 25 on the shaft 84 which is a continuation of the members 85, preferably of wood, run longitudi shaft for the roll 82 of the cross-conveyor 86. nally of the entire grain dryer and transversely From this it will be evident that ‘drive from the pulley 50 through the pawl IN to the ratchet of the conveyor 80 and are attached to the con veyer 89 at regular intervals therearound. The wheel llii imparts rotation to the rolls 89 as well slats 85 are equipped with outwardly extending 30 as the conveyor 80. The idler sprocket iii is nail-like projections 86. These nails extend mounted on a stub shaft H3 and merely per along the entire surface of each .slat, as best . forms the function of maintaining the chain shown in Figure 4. taut. As previously stated, the oil burner throws a ‘ The conveyor Bil is driven in a clockwise di rection, as viewed in Figured, and all grain dis-‘ 35 fuel oil through the tube 30 into a furnace lid charged by the rolls 5t will be carried around the which has a dome-like structure 1 55 within which . end 82 and dropped on a corrugated bottom 87. combustion takes place: The fan id, as shown in This corrugated bottom 81 is best shown in Fig Figure 4, is adapted to take air_ in at H6 and ure 4 and includes peaks 88 and depressions 89. supply it with a high. velocity so that it is pro The nail-like projections 8'6 are adapted to‘ 40 jected downwardly through the opening HT di- 1 project downwardly within the depressions 89, rectly above the dome H5. The air then passes and as the kernels of corn are dropped on to over the furnace dome and down around beneath the chamber 42 as indicated by the arrows. The hot air enters the endsof the plenum chambers the bottom 91 at the point 98, the kernels are carried substantially individually across this cor rugated bottom 81 within the depressions 89. The kernels are discharged at the point 9! closely 66, El, and B8 and escapes upwardly through the screen passageways 8!, 62, 63, 6d, and 65, where adjacent a discharge auger 92 so that the grain ' coming down an inclined surface 93 isfed rear wardly to the point where it joins the grain dis charge elevator 51. ' The rolls $9 have central shaft 96 journaled in upon it continues its upward movement through the column of corn thus performing the dehy drating action.v ~A portion of the air used for the 50 fan intake H6 is not taken directly from the atmosphere but as.best shown in Figure 3 is . the housing ‘which project rearwardly beyond ‘drawn in through an entrance H8 in the bottom the housing ii asshown in the Figure 2 rear of the housing and passes beneath the corru view. Each shaft 95 has a sprocket 95 keyed or gated bottom Bl of the cooling chamber ‘F9. The 55 air thus drawn in is within a chamber Ht be-v otherwise fastened thereto. . It is a requirement of this grain dehydrator tween the bottom plate i20 and the corrugated that the discharge rolls 59 rotate very slowly and partition 81. The kernels of corn are passing to that end a particular drive is employed. The individually along the corrugations within the pulley 50' is equipped with a crank pin 96 to which depressions 89, thus transferring heat from the is attached a pitman at. It will be evident that 60, dehydrated corn to the incoming air. .This per as the pulley 56' rotates, the pitman at will re forms two functions: (1)‘ that of cooling the fin ciprocate vertically. The lower end of the pit ished corn and (2) that of preheating the in- . man is attached at 98 to an arm 99 which is piv- - coming air to be used in the dehydrating process. oted on a shaft 809. A ratchet wheel it! is As best shown in Figure 5, after the incoming mounted on this shaft I88 and carries with it a 65 air has traversed the chamber H9, it enters a sprocket I02 in a common plane with the sprock substantially triangularly shaped chamber i2! ets 95. The arm 99 is equipped with a projec which carries it along the side of the grain dryer 7 tion wt to which is pivoted a pawl wt for engage housing and thence upwardly through the con— ment with the ratchet wheel ilil. As the pit duit E22 where it is drawn into the fan l8 by man 91 is lifted upwardly, the pawl HM engag 70 means of the suction created by the fan. From ing the ratchet teeth causes the ratchet wheel this description, it is seen that the air that ‘is it! to rotate in a clockwise direction as viewed inthe device of Figure 2. The effective move used to directly contact the corn is free from con tamination with any exhaust gases inasmuch as merit of the pawl we may be curtailed by the ' the furnace H4; is sealed from the chamber I28 member Edd. This member “it is in the form of 75 surrounding the furnace. , 2,410,851 7 storage bin. The exhaust gases formed after combustion of The testing for moisture may be g the oil within the furnace II4 pass upwardly done inseveral ways. The subject grain dryer through the dome II5 into the conduit I24, then downwardly into the cylindrical conduit I25 is adapted to employ a mechanical means to test for moisture content and to that end a pulley I40 is fastened to the shaft 56 and by means of a belt “I acts to cause rotation of the pulley I42 which operates a grain testing device (not shown). An idler pulley I43 maintains tension 'which causes the hot exhaust gases to progress circularly and upwardly in the manner indicated by the arrows. It will be obvious that the gases are required to travel through one-half of the cylindrical conduit I25 where it progresses up wardly into a second section I25 of the cylin in the belt MI. The details of the moisture test ing device, indicated at I44 and driven by the pulley I42, is shown in greater detail in my co-' pending application having Serial No. 528,255 and filed March 27, 1944. drical conduit, whereupon it proceeds back around another half revolution and then-up t0 the third and top section I21 of the cylindrical conduit. This is shown in great detail in Figures 4 and 5; This circulation of exhaust gases con Numerous details of construction may be va 15 ried throughout a. wide range without departing from the principles disclosed herein. The sub-, tributes greatly to the heating of the chamber ject device has been described as a corn dryer I23, thus utilizing more of the combustion heat when in fact it may be used successfully for dry produced by the oil burner 24 or by any type of ing other smaller grains with but slight changes fuel or furnace that may be employed. The exhaust gases continue travel upwardly'as ‘at I28 20 in the structures. The intention therefore is only to limit the in into a second set of heat transfer conduits which vention within the scope of the appended claims. surrounds the fan I8. This also contributes high What is claimed is: operating e?iciency by the utilization of all heat 1. In a grain dehydrator, a grain chamber, available. The exhaust gases enter the vertical means for moving grain from the top to the bot column I29 and pass through numerous tubes tom of said chamber,‘ a heating compartment, a I30 where they congregate in a second vertical furnace within said compartment, 9. fan for blow column i3I and are discharged into a horizontal ing air downwardly over said furnace and up tubular memberv I32. This tubular member I32 through the grain chamber, and means for utiliz is positioned directly beneath the feed pipe 37 ing exhaust gases from the furnace to preheat and is buried within the column of corn in the the incoming air, said nieans comprising coils chamber 42. Here again the exhaust gases are of enclosed conduits positioned around said fan. utilized to their maximum capacities and con 2. A grain dryer comprising a grain chamber, tribute greatly in preheating the columnof corn a grain feed device at the top of said grain cham in the chamber 62. The tubular member I32 is superposed by an outer tubular member I33. The 35 ber, a grain discharge device at the bottom of said chamber, a heating compartment adjacent end of the member I33 is secured to the end wall said grain chamber, a sealed furnace within said of the grain dryer at I34. As exhaust gases cool, heating compartment, a discharge conduit for they tend to condense, and it is therefore neces exhaust furnace gases, said discharge conduit sary to provide a drain for such condensation. taking a circuitous‘ path around said heating The bottom of the tubular member I33 is U compartment, and fan means for blowing air shaped as shown at I35. This lower U-shaped downwardly through said heating compartment portion of the tube-I33 tapers downwardly to and up through the, grain chamber, a continua ward the rear of the grain drying machine, and tion of said discharge conduit circling the fan at its end communicates with a drain pipe lat} means. ' which projects through the insulated wall lit. 3. A grain dryer comprising a grain chamber, The tube I32 terminates at a point short of the a grain feed device at the top of said grain end wall, thus permitting the flue gases to come chamber, a grain discharge device at the bottom out into the outer tubular member I33 where of said chamber, a heating compartment adja upon they are caused to return by contact with cent said grain chamber, a sealed furnace within the end wall 43 and pass the length of the tube said heating compartment, a discharge conduit I33, whereupon they are discharged by means of for exhaust furnace gases, said discharge con an exhaust fan at I31. ‘ duit taking a circuitous path around said heat Heat created by the oil burning unit 213 is ing compartment. fan means for blowing air utilized. The in-take air is preheated. The heat downwardly through said heating compartment ed air which emerges, from the column of grain and up'through the grain chamber, a continua from the chamber 42 is substantially room tem tion of said discharge conduit circling the fan per‘ature, and the combustion gases pass through means, and a conduit extending longitudinally numerous heat transfer devices so that the entire through the grain chamber near the top thereof, grain dehydrator circulation has attained its said conduit joining with the discharge conduit maximum ef?ciency. for exhaust furnace ‘gases whereby complete uti The grain discharge elevator 51 connects with . two discharge spouts I38 and I33. A valve (not shown) can be operated to cause discharging of corn to either of these spouts‘lll or I39. The spout I33, however, discharges into the bin as’ which is the supply for the corn to begin its travel through the grain dehydrator. At inter lization of furnace heat is accomplished. 4. In a grain dryer, 9. grain chamber, means for maintaining said grain chamber constantly ?lled, said means comprising a means for feeding grain at the top of said chamber and means for removing grain from the bottom of the chamber, said last named means comprising an endless vals in the operation of this grain dehydrator, belt conveyer beneath said grain chamber adapted the moisture content of the discharged kernels is carrythe grain to its discharge end, a corru tested and, if the content is above some predeter 70 to gated partition beneath and projecting beyond mined percentage, then- the grain is diverted to the discharge end of said conveyer and adapted the spout I38 where it is again dried. If, how to receive the grain from the conveyer, projec ever, the moisture content is low enough to have tions on said belt conveyer on its under side good storing qualities, then the grain is dis charged through the spout I39 to some desired 75 adapted to run through said corrugations whereby 2,%10,851 the grain deposited on the corrugated partition is carried in the opposite direction by said pro jections through said corrugations, a bottomvb'e neath and spaced apart from said corrugated partition, and means for drawing air through .10 space between the corrugated shelf and the bottom for preheating air for the air circulating means and simultaneously cooling the grain in its dis charge over the corrugated shelf. 6. A grain dryer comprising a grain chamber, the space between the corrugated partition and means for feeding grain to the top of said cham the bottom for preheating the air preliminary ber and means for removing grain from the bot to its circulation through the grain chamber, and tom of said chamber, a furnace adjacent said simultaneously cooling the grain in its travel grain chamber, a discharge conduit for furnace through the corrugations. 10 combustion gases extending longitudinally of said 5. In a grain dryer, a grain chamber, means grain chamber immediately beneath the top for feeding grain at the top of said chamber thereof, a superposed return conduit for said and means for discharging grain from the bottom longitudinally extending discharge conduit, and of the chamber, an endless band conveyer be means for exhausting the combustion gases. neath said grain chamber discharge means, said 15 '7. A grain dryer comprising a grain chamber, endless band conveyer adapted to carry the grain means for feeding grain to the top of said cham to one side of the grain chamber, a corrugated bar and means for removing grain irom the bot shelf spaced beneath said conveyer and adapted to receive grain from said endless band conveyer, a grain chamber, a’ discharge conduit for furnace tomof said chamber, a furnace adjacent said on the return of the endless band on its under 20 combustion gases extending longitudinally of said side, projectionson said endless band conveyer adapted to run through said corrugations whereby the grain is carried in the opposite direction by said projections over said corrugations, air-circu lating means for said grain chamber, a bottom 26 beneath and spaced apart from said corrugated shelf, and means for drawing air through the grain chamber immediately beneath the top thereof, a superposed return conduit for said longitudinally extending discharge conduit, means for exhausting the combustion gases, and‘ a con densate drain for said superposed return conduit. - ALBERT B. WELTY.