US2657031A - Grain drier - Google Patents

Description

OC- 27, 1953 B. ToMLlNsoN ET AL GRAIN DRIER Filed sept,` 4, 1951 Patented Oct. 27, 1953 GRAIN DRIER Ben L. Tomlinson,

E. Carlson,

St. Louis Park, and Donald Litchfield, Minn., assignors to Arid Aire Manufacturing Company,

St. Louis Park,

Minn., a corporation of Minnesota Application September 4, 1951, Serial No. 244,972

This invention relates to dryers and dehydrators for drying grain and other products. More particularly, it relates to grain dryers of the type wherein a source of relatively hot air is utilized to dry the grain during its continuous passage through the dryer.

This invention constitutes improvements over the invention as disclosed and claimed in U. S'. Letters Patent No. 2,490,176, dated December 6, 1949, and entitled Grain Drier, nled by William E. Tomlinson and Ben L. Tomlinson on September 5, 1947. l

Although the invention disclosed and claimed in the patent referred to in the preceding paragraph provides a grain dryer of high operating efciency, we have found that by making certain improvements thereto it is possible to increase the efficiency of the drying unit and practically eliminate fire hazards normally attendant therewith.

It is a general object of our invention to provide a novel and improved grain dryer of simple and improved construction and having increased efficiency, compactability and safety during operation.

A more specific object is to provide an improved grain dryer constructed to distribute the hot air relatively uniformly throughout the length of the drying chamber to accomplish more uniform and effective drying or the grain passing therethrough.

Another object is to provide an improved grain dryer constructed to effectively and continuously remove the dust and dirt which normally collects Within the interior of a grain dryer and thereby substantially reduce the danger of re resulting therefrom.

Another object is to provide an improved grain dryer constructed to prevent substantially allof the hot air, when released within the drying chamber, from rising and passing through only the portions of the conveyor which are immediately adjacent the discharge of such hot air to the neglect of the portions of the conveyor more removed.

Another object is to provide an improved grain dryer constructed to effectively collect along a central area the dust and dirt which Works its way through the grain and the conveyor and to thereafter efliciently remove the same.

6 Claims. (Cl. 263-8) Another object is to provide a grain dryer having inherent means for retaining a substantial portion of the hot air beneath a retaining hood-to release the same at points substantially removed from the discharge area. i Y i Another object is to provide a novel and improved grain dryer having improved structure for accomplishing complete and thorough mixing of the hot air discharged by the burner with cool air prior to its release within the drying chamber of the dryer.

These and other objects and advantages of my invention will be more apparent from the following description made in connection with the accompanying drawings, wherein like reference characters refer to similar parts throughout the several views and in which Fig. l is a perspective view of one embodiment of our invention with portions of the walls broken away to reveal the interior thereof;

Fig. 2 is a vertical sectional view taken longitudinally of the dryer.

Fig. 3 is a transverse vertical sectional view taken along approximately line 3-3 of Fig. 2.

Fig. 4 is a perspective view of the tubular member utilized to effect a more thorough mixing of the hot and cool air adjacent the burner.

One embodiment of our invention may include as shown in Figs. 1-4, an elongated housing indicated generally as and having sidewalls 1, a top wall e, a receiving end SA, and a delivery end 6B. The walls of the housing 6 are insulated to prevent the escape of hot air therefrom and the interior of the housing is divided by a partition 9 into a hot chamber I0 and a cooling chamber ll. The hot chamber I0 has a generally V- shaped bottom I2 while the cooling chamber II has a generally inverted V-shaped bottom I3. The cooling chamber II communicates with the exterior by means of a louvered cooling air intake i4 arranged adjacent the lower portion of the housing and within the opposite side walls thereof as best shown in Fig. 1. Secured to the top wall -8 of the housing within the hot chamber l0 is a drying blower I5 which is driven by a motor I6. Also secured to the top wall 8 of the housing within the cooling chamber I I is a cooling blower I1 driven by a motor I8.

Mounted within the interior of the housing to extend longitudinally thereof throughout the major portion of its length and medially disposed relative to the height of the housing is an endless porous conveyor I9. This porous conveyor I 9 is formed of material which will readily permit air to pass therethrough but the openings thereof'are sufficiently small to prevent small grains from Working downwardly therethrough. It has been found that a type of wire mesh belting is best adapted for this type of conveyor. As shown, the conveyor is provided with a rear alignment sprocket 20 and With-a main drive sprocket 2| 'which positively drives the endless conveyor continuously around its mounting. The conveyor is provided with a plurality of apron support rollers 22 to facilitate its movement throughout the length of the housing.

The conveyor is driven by means of a drive chain 23 which is connected with a speed reducer 24 which in turn is driven by al variable speed drive motor 25. Rakes or agitator bars 26 are mounted between the opposite side walls ofmthe housing directly above the conveyor I9 that warm air may readilypasslaterally therebetween 'to rise .upwardly through the 'conveyor I9. A portion of the hot air will be coniined within the confines of the hood and driven longitudinally thereof to be discharged beyond the Wend 'of the hood adjacent the receiving end of will drag along the upper Vsurface of the grain j being dried.

At the receiving end 6a of the housing ll there is provided a wet grain intake spout which empties into the intake hoppe`3l. The intake spout and the hopper act as a conduit for the incoming wet grain and the flow therethrough is controlled by a control gate 32. The control gate 32 may be regulated by an adjustment handle 33. K l A At the delivery end Gb of the housing andat Vthe 'delivery end of the conveyor I9 and slightly therebelow is positioned a hopper 3.4l which extends transversely of the housing. The floor of this hopper 34 is disposed at an angle so that the grain which has been dried` and discharged over the adjacent end of the conveyor will drop into the hopper and slide' to its lowest point Within which a dry grain discharge lscrew conveyor 35 is mounted for rotation on a horizontal axis. This screw conveyor 35 discharges into Ya discharge spout 36 and is driven by a second drive sprocket 31 vwhich is connected as shown to `the variable speed drive motor 25.

Y Mounted fn the Ulower portion 'of the h'using 6 adjacent Vits delivery end v6b is a blast type oil burner indicated generally as 38 which has a discharge 39 which terminates beneath the inverted V-shaped bottom I3A of the Cooling chamber II. The discharge end -3'9 'is surfrounde'd'by a tubular member 40 which tapers throughout its length toward the receiving end of the housing. VThe larger end of the tubular member is disposed so that the discharge 39 oi the burner extends well within the interior oi the 'tubular 'member 4b. The smaller end '4| of 'the tubular member `extends through the partition 9 and into the interior of the hot chamber lll as best shown in Fig. 2.A This tubular member 4o has fa. pal'rjef ports 42 formedtherethrough vand 'disposed directly opposite the discharge 379 of the burner.

These ports cause the interior of the tubular member 40 to communicate terior of that member to therethrough. A supply of cold air is 'available through the screening 43 which is disposed at the neuemr of me housing directly 'below elle discharge of the burner. Thus cool v:air is Spermitted to rise through "this screen and enterthe larger end of the tubular member 40has well as the ports 42 to mix with the extremely hot air discharged at 39 by the burner-38. A n

l Mounted within the interior of thehot chamber I0 and extending longitudinally thereof beneath the conveyor I9 but at a level above the discharge of hot air through Vthe smaller end 4l of the tubular member 4o is a :heed or air distributor 44. As best shown Fig. 3 this `hood is mounted upon a plurality `of upstanding arms 45 which extend upwardly fromthe V-shaped bottom I'2 of the hot chamber l0. This hood 44 Vis preferably of an inverted V-shapewhe'n viewed cross-sectionally., as shown inFig. @Land extends a substantial distance through the length of the hot chamber Il), preier'ably vto a beyond the middle thereof. The sides of the hood A44 are spaced from the side walls `of the housing and from the walls 5 forming the bottom l2 so with the area 'ex- `permit air tc pass the housing;

The v-shepeu bottom ef' me not chamber lo fis provided with an auger type clean-outcon- 'veyol'` 46 which extends longitudinally of the cooling chamber and the housing. This is best shown vin Figs. '2 and 3. This conveyor 46 is rotatably mounted and driven by the clean-out auger drive 41 which is connected to the variable speed drive motor v25 by a pulley 48 and a belt 49. This screw type conveyor discharges at the receiving end of the housing to the exterior of the housing as at 50. l

The controls for the entire unit are mounted adjacent the delivery end of the housing. vThese controls are not considered to be part of the invention but they will be briefly enumerated and identiiied herein yfor the purpose of clarity. In conjunction with the oil burner I0, there is Aprovided a manual -oi'l valve 5I, an oil filter 52, an oil pressure regulator 53, an oil pump 5,4, a solenoid oil valve 55 and an oil burner control motor v56. Also provided is a low limit control 51, a .high limit lcontrol and thermometer 58 and a vaporstat 59. A foot .switch B, an electric control panel BI, an electric eye '62 and a lc'o'n't'rl'll 63 for the electric eye complete the controls.

Operation-s In operation the conveyor `ISI is nrst started. The combustion blower then starts and Opens the solenoid valve which controls the oil feed. This oil feed is connected in series with the valve and the valve is opened only when at full pressure to prevent smoking and/or improper fuel and air mixture. The oil is under pressure approximating l0 pounds and is forced through the spray nozzle of the burner for combustion. Air comes around the nozzle from the rear to provide the oxygen for combustion.

rllhe electric eye, in case the lire of the burner goes out, is electrically connected to cut oi all of the mechanisms within the vburner and to automatically sound a warning horn. The low limit control does the same when the temperature within the chamber above the material being dried reaches a level above 160 `degrees Fahrenheit and the high -limit control does the same if the temperature in the hot air chamber should nreach a level above 260 degrees Fahrenheit.

rIhe grain is fed into the wet grain intake spout -30 Afrom the source of grain to be dried. This grain passes into the hopper 3 I, through the gate 32 and is deposited thereby upon the receiving end Aof the conveyor I9 in `an even stratum. As .the endless conveyor I9 `moves around vits mounting, the stratum of grain .21 passes slowly toward the delivery Yend V6b of the housing at a steady rate. As it .passes through kthe rakes 2.6 the grain is slightly agitated and disturbed to `facilitate the ypassing of the hot air upwardly therethrough. The blower I5 draws the hot air upwardly through the stratum of grain and discharges it by itstangential discharge to the exterior of the housing. Y

y By the time the grain has reached the panel 9 to pass beneath the flap 29 it has been substantially dried but is at a temperature too high for storage. The blower I1, however, draws cool air upwardly through the 'cooling chamber and through the stratum of warm grain to cool the same while it is within the cooling chamber. This cool air, which of course will be warmed by the grain, is discharged to the exterior of the housing. The cooled grain is thereafter discharged i over the end of the conveyor i9 into the hopper 34 and passes downwardly into the dry grain discharge auger 35 which in turn carries the same laterally of the housing and `into the discharge spout 36.

As the grain passes through the hot chamber dust, dirt and other foreign materials, ordinarily found mixed with grain which has not been cleaned, will gradually work downwardly through the stratum of grain and through the porous conv Veyor I9. This downward progression of foreign `substantial fire hazard. `The continuous elimination of this dirt and dust and its discharge to a point exterior of the housing eliminates this fire hazard.

The hot air which is discharged by the burner 33 is at such a high temperature that cool air is mixed therewith prior to its release beneath the conveyor for drying purposes to prevent injury to the grain. This is accomplished through the use of the tubular member 40 which permits cool air to enter its larger end in surrounding relation to the discharge 39 of the burner. -The arrows in Fig. 2 indicate the direction of flow of such cool air. We have found, however, that it is important that means be provided for uniformly mixing this cool air with the hot air discharged by the burner. have tapered the tubular member 40 to facilitate the mixing of the warm and hot air. In addition we have found it to be advantageous to provide a pair of ports 42 positioned as shown so that additional cool air will be drawn therethrough to mix with the hot air discharged from the burner at 39. The introduction of cool air from this lateral point of vantage and having a cross-directional movement induces or creates a vorticity within the interior of the tubular member 4i) which substantially increases the mixing action of the warm and cool air. Thus by the time the hot air has reached the discharge 4| of the tubular member 4G, it has been thoroughly mixed so as to have an even temperature throughout its mass.

The hot air discharged by the tubular mem'ber 40 is released at a point beneath the hood 44 as best shown in Fig. 2. This hot air of course tends to rise immediately upon its release. We have found however that if such rising action is permitted uninhibited, uneven drying may result within the stratum of grain at its passes along with the conveyor.` In other Words, we have found that a greater eiiiciency may be obtained by distributing the discharge of hot air over a major portion of the hot chamber lil so that the hot air will be released more uniformly throughout the various points of the hot chamber. The inverted V-shaped hood 44 permits a substantial To accomplish this, we

` portion of this hot air to move laterally and upwardly between its sides and the bottom l2 to dry the grain immediately thereabove. At the same time, a substantial portion of the hot air remains within the conne of the hood and is driven longitudinally of the housing and of the hood to be released adjacent the end of the hood which is adjacent the receiving end of the housing. Thus it can be readily seen that a relatively uniform distribution of the hot air is provided so that the grain deposited upon the conveyor will be dried substantially equally as rapidly adjacent the receiving end as it will adjacent the partition 9. We have found that such a hood produces a substantially uniform distribution of the hot air within the hot chamber I0 and effects a substantially more uniform drying action.

It should be noted also that by mounting the blowers l5 tnd l1 Within the confines of the housing we have substantially increased the compactability-of the unit. Thus it can be seen that we have provided an improved grain drying unit constructed to effectively and continuously remove the dust and dirt which normally collects Within such a unit and which normally constitutes a serious iire hazard thereto. At the same time we have provided structure which substantially increases the eiciency of the unit as a result of accomplishing improved mixing of the hot and cold air and uniform distribution of the mixed air throughout the interior of the hot chamber.

It will, of course, be understood that various changes may be made in the form, `details,.ar rangement and proportions of the various parts twithout departing from the scope of our invenion.

What We hereby claim is:

l. A continuous grain dryer having in combination a housing having `a delivery end and a receiving end and a top and a bottom, an endless porous conveyor extending substantially horizontally throughout the major portion of the length of said housing and medially disposed relative to the height thereof, conduit means in the receiving end of said housing adapted when connected to a source of grain to be dried to deliver continuously a stratum of such grain upon the receiving end of said conveyor, means for delivering dry grain from the delivery end of said housing to a point exterior thereof, a blast type burner mounted Within said housing adjacent its delivery end and having a hot air discharge, a transverse partition dividing the interior of said housing into a larger hot chamber extending from a point inwardly of said burner to the receiving endof said housing and a cooling chamber extending from said partition to the delivery end of said housing, said cooling chamber communicating with the exterior at points below said conveyor, said partition having an aperture in the central portion thereof for accommodating said conveyor and the stratum of grain carried thereby, hot air conduit means receiving from the discharge of said burner and discharging hot air into said hot chamber of said housing `below said conveyor `and directed longitudinally and centrally of said nemesi ily distribute the warm iair more uniformly the delivery 'portion Aof lsaid conveyor 'and icirciulated-.in said cooling-chamber.

2. A continuous :grain dryer having ,in combination a lhousing 4'having a delivery :end and a `.receiving 'end and a top .and a bottom, fan 'endless porous conveyor extending substantially horizontally throughout the maj or po'rtio'n of the :length `offsaid housing 'and mediall'y disposed -rel- :ative `to `the .height thereof, :conduit means in v'the receiving end of said housing adapted when fconncted toa source `o'f :grain rto'be "dried to deliver A'continuously a .stratum of such grain upon the .receiving fend :'of said conveyor, means for Adeliv -er-ing'dry grain from the delivery fend fof fsaid lhousing to a point :exterior thereof,`a blast y-type burner mounted Within said housing adjacent .rits-delivery endandhavn'g a hot air discharge, a transverse partition dividing the 'interior fof vsaid housing vinto "a larger `not chamber extending from apoint inwardiy of fsa-id lburner -tothe -receiving end of said housing .and a cooling cha-'mber extending fromsaidpartition to the :delivery end of said housing, fsaid cooling chamber `comt.

m-unicating with the exterior :fat Ipoints l below l'said conveyor, saidpartitionhavingan,apertureinthe central portion thereof for accommodating fsaid conveyor and the stratum V'of 'grain carri'e'dfthereyby .hot .fai-r conduit "means receiving from 'the dis` 1 :charge of -sayi'd v:burner .and'ischargingfhotair into -said hot chamberzof said housing below l@said conveyor rand fdirected Sl'ongitu'din'aiiy and .'centrally of :said housing toward the receiving fend `thereof, 'a cleaneout fconveyor .mounted in `the V-lovver yportion l,of said housing lbeiow :said endless porous `v.conveyor and 'extending longitudinally thereof in position to receive l-vvhatever dust fand -d-iigt may pass through said ,porous 'conveyorand fall downwardly and to `discharge rtsthnsly iac- Y quired vload exterior-ly Iof said housing, rand `an Aex-pelle-r-type blower mounted ,in the upper jportion. Aof said .housing Vabovesa-id :conveyor :and V.having ,an intakeand a discharge communicating @with `:the finterior Aand the exterior foi said .housf,

respectively whereby hot air .and products fof .combustion will Ybefd'raWn-eand circulated upward- .,ly through said porous lconveyor and the stratum .of grain l:therein and then discharged from the -dryer and whereby l,cool Vair vv-illuloe` drawn :and circulated upwardly through the'delivery portion of said `conveyor and circulated :sa-id fcooling chamber.

. 3. A continuous Ygrain dryer vhaving in com- `lbination :a -housing lhaving Va .delivery en'dzan'd a receiving end and a 'top and Limperforate V-shaped bottom, an' endles's .porous :conveyor :ex- 'tendin-gvsubstantially .horizontally thronghotthe :major portion of :the length :of said .fhousinga'nd media-lly disposed relative to the height ther-eef, conduitmeans in the receiving end of fsa-id .hous- .ing adapted when connected :to fassoiirceV o'f i'grain Ato be driedwto-deliver continuously 1.a stratumfof such .grain upon the receiving end `of-.'said1c'on .veyon means for delivering :dry grain from the @8 delivery fend fof `=said housing to a point exterior thereof, :a blast type burner-mounted `withirrsaid housing adjacent its delivery-fend and 'fh-airing a .not "air discharge, 'a `transverse partition dividing the interior of said :housing into a larger vhot chamber extending from :a :point inwardly of said burner tto the receiving end .o`f said `housing and "a cooling 'chamber extending'from said partition to the delivery end of I'said housing, said cooling :chamber 'communicating with the `exterior -at points below said conveyor, said partition :having Aan apertine inthecentral portion thereo for accommodating said conveyor and the stratumcof grain carried thereby het air conduit 'meai:ls.r'e iceivn'g :from the discharge yof :said burner :and `idisclrarging .not .lair .into said vfloot chamber -Aof'zisaiid housing below said conveyor and' directed .longi- `tudinally fand centrally yof said housing toward fthe 'receiving fend thereof, a `clean-'out conveyor extending `fl'ongitudfi'nally of said 'housing' land A.mounted 'in the .lower .portion thereof' below fsaiid endless porous conveyor and at 'the apex zofsaid 'Veshaped bottom position to receive whatever dust, dirt and other foreign' materials Which/'may pass through lsaidpclirous conveyor :andfall l.dovvnlwardly-and to discharge its ithusly acquired load rexteriorly of -said housing, and an expelientype blower mounted in 'the 'upper portion of said housing above fsaid vconveyoralid .havingan intake and a dischargecommunicating*with ther-'interior and the 'exterior Vof said housing respectively whereby hot air and products of combustion will be drawn and :circulated upwardly 'through said porous oonveyorand thefstratumrof .grain 'thereon 'and :then discharged frornfthe dryer 'and whereby foo'ol air will be drawn -land circulated upwardly through the delivery .portionfof 'said-conveyor and circulated 'inrsaid cooling chamber. f

4. .YA fco'ntinuou's grain "'dry'er having in co'nbinati'on sa housing having a delivery Iend and a receiving end anda-Stop and a f'generaily v-snaped bottom when viewed cross-"sectionally, vane'ncl'ess poro'us conveyor extending substantially horizon- 'tallythroufghou't' the major por-tion v'of the flength 4of 'said :housing `and rmedialiy disposed relative .Kto l'the yheight thereof., conduit means inthe receivfin'g vend "'of said iho'usingiadapted lwhen connected to a source for grain Yto deliver .continuously a stratum* 'of such grain upon the -receivingiendof :said conveyor, means `for delivering 'gra-in 'from the delivery end .of said housing r`to ya .point VIe'l'rte'rior thereof, a blast .type `burner mounted lwithin said-fnousingfadjacexrt its delivery end2end having a hot -air discharge, a transverse partition .dividing :the interior of s'aid'fhousing into :lailrger -hotlcha'inber 'extending from a point inwardly #of :saidbur-ner to the'frece'ivihg'end 'of said housing .and a S-coolin-g fchamb'er extending fromzsai'dpartition to the fde'livery end of 1said housing, said fcoolinfg chamber communicating V'with the fexterior at points below said conveyor, said partition having ian aperture in the eer'itral portion :thereof 'for :accommodating 1Said ,conveyor andthe 'stratum of grain 'carried thereby, ho't fair fcon'duit :means rec'zeiving from the Adischarge of said burner and discharging hot Pair into said hot fchamberfofisiid housing fbelow 'said .conveyor Iand Sdirectedwlongiftudmally and centrally of said housing :toward :the receiving lfend thereof, atpowere'drivn aug-er- 'itype clean-out 'conveyor extending longitudinally of said housing and `mounte'dforrotation"about its Alongi'tuclinal axis `vvithin the :apex 'o'f said V'sh'a'ped 'bottoni and .discharging fexteriorly'f'of 'saidhousin'g Vwhereby dust, .'dirt and-'other foieign materials which pass'through said porous 'con- E@ veyor and fall downwardly to constitute fire hazards may be continuously and effectively elimi nated and thereby prevented from accumulating Within said housing, and an expeller-type blower mounted in the upper portion of said housing above said conveyor and having an intake and a discharge communicating with the interior and the exterior' of said housing respectively whereby hot air and products of combustion will be drawn and circulated upwardly through said poro-us conveyor and the stratum of grain thereon and then discharged from the dryer and whereby cool air will be drawn and circulated upwardly through the delivery portion of said conveyor and circulate within said cooling chamber.

5. A continuous grain dryer having in combination a housing having a delivery end and a receiving end and a top and a bottom and side walls, an endless porous conveyor extending substantially horizontally throughout the major portion of the length of said housing and medially disposed relative to the height thereof, conduit means in the receiving end of said housing adapted when connected to a source of grain to be dried to deliver continuously a stratum of such grain upon the receiving end of said conveyor, means for delivering dry grain from the delivery end of said housing to a point exterior thereof, a blast type burner mounted within said housing adjacent its delivery end and having a hot air discharge, a transverse partition dividing the interior of said housing into a larger hot chamber extending from a point inwardly of said burner to the receiving end of said housing and a cooling chamber extending from said partition to the delivery end of said housing, said cooling chamber communicating with the exterior at points below said conveyor, said partition having an aperture in the central portion thereof for accommodating said conveyor and the stratum of grain carried thereby hot air conduit means receiving from the discharge of said burner and discharging hot air into said hot chamber of said housing below said conveyor and directed longitudinally and centrally of said housing toward the receiving end thereof, an elongated hood member mounted below said conveyor at a level above the discharge of said hot air conduit means and extending from a point adjacent the point of discharge of said hot air conduit means longi tudinally of and in spaced relation to the side walls of said housing toward the receiving end thereof to effectively distribute the warm air more uniformly throughout said hot chamber than would otherwise take place, said hood member having side portions extending at a lower level than its medial portion when viewed crosssectionally, and an expeller-type blower mounted in the upper portion of said housing above said conveyor and having an intake and a discharge communicating with the interior and the exterior of said housing respectively whereby hot air and products of combustion will be drawn and circulated upwardly through said porous conveyor and the stratum of grain thereon and then discharged from the dryer and whereby cool air will be drawn and circulated upwardly through the delivery portion of said conveyor and circulated in said cooling chamber.

6. A continuous grain dryer having in combination a housing having a delivery end and a receiving end and a top and bottom, an endless porous conveyor extending substantially horizontally throughout the major portion of the length of said housing and medially disposed relative to aesmsi the height thereof, conduit means in the receiving end of said housing adapted when connected to a source of grain to be dried to deliver continuously a stratum of such grain upon the re ceiving end of said conveyor, means for delivering dry grain from the delivery end of said housing to a point exterior thereof, a blast type burner mounted within said housing adjacent its delivery end and having a hot air discharge, a transverse partition dividing the interior of said housing into a larger hot chamber extending from a point inwardly of said burner to the receiving end of said housing and a cooling chamber extending from said partition to the delivery end of said housing, said cooling chamber communicating with the exterior at points below said conveyor, said partition having an aperture in the central portion thereof for accommodating said conveyor and the stratum of grain carried thereby, hot air conduit means receiving from the discharge of said burner and discharging hot air into said hot chamber of said housing below said conveyor and directed longitudinally and centrally of said housing toward the receiving end thereof, said hot air conduit means comprising a tubular element having a receiving end surrounding the discharge of said burner in spaced relation and a discharge end extending into said hot chamber, said tubular element being tapered inwardly throughout its length away from its receiving end whereby increased mixing of the hot air discharged by said burner and the cold air drawn into said element around the discharge of said burner may be accomplished prior to its discharge into said hot chamber, and an expellertype blower mounted in the upper portion of said housing above said conveyor and having an intake and a discharge communicating with the interior and the exterior of said housing respectively whereby hot air and products of combustion will be drawn and circulated upwardly through said porous conveyor and the stratum of grain thereon and then discharged from the dryer and whereby cool air will be drawn and circulated upwardly through the delivery portion of said conveyor and circulated in said cooling chamber, said tubular element having at least one port formed in its walls opposite the discharge of said burner to provide increased communication between the interiorof said element and the exterior and to therebyinduce increased mixing of the hot air with the cool air drawn into said tubular element from.

its exterior as a result of the vorticity set up within the interior of said tubular element by the flow of cool air through said port into said. element.

BEN L. TOMLINSON. DONALD E. CARLSON.

References Cited in the le 0f this patent UNITED STATES PATENTS Number Name Date 889,560 Thull June 2, 1908 2,369,706 Altamore Feb. 20, 1945 2,406,822 Fox Sept. 3, 1946y 2,490,176 Tomlinson et al Dec. 6, 1949 2,518,021 Keay Aug. 8, 1950 2,553,029 Bailey May 15, 1951 FOREIGN PATENTS Number Country Date 905,242 France Nov. 28. 1945

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