US3553846A - Grain dryer - Google Patents

Abstract

A GRAIN DYE IS DISCLOSED IN WHICH THERE ARE OF ANGULARLY-DISPOSED SHELVES, ONE ABOVE THE OTHER, PROVIDING GRAIN BEDS WHICH ARE INCLINED TOWARD COMMON INTERMEDIATE DISCHARGE COLUMNS, THERE BEING A HOT AIR DUCT EXTENDING HORIZONTALLY ALONG THE UPPER EDGE OF EACH SHELF FROM WHICH HOT AIR AT RELATIVELY HIGH TEMPERATURE IS DIRECTED DOWNWARDLY AT HIGH VELOCITY AND PRESSURE, IN CONCURRENT FLOW THROUGH THE BED OF GRAIN SUPPORTED ON THE SHELF, AND THERE BEING COMMON MEANS FOR FEEDING GRAIN TO THE UPPER EDGES OF ALL OF THE SHELVES TO MAINTAIN THE INCLINED BEDS FILLED. METERING MEANS AT THE LOWER EDGE OF EACH SHELF PROVIDES FOR METERING FROM EACH SHELF A PREDETERMINED RATE. THE FEED OF GRAIN INTO THE DRYER IS AUTOMATICALLY CONTROLLED TO MAINTAIN A PREDETERMINED LEVEL. AN OPTIONALLY USABLE COOLER IS ALSO DISCLOSED WHICH MAY BE LOCATED BELOW THE DRYING UNIT AND WHICH IS ADAPTED TO DELIVER COOLING AIR UPWARDLY IN COUNTERFLOW WITH RESPECT TO THE FALLING GRAIN.

Description

Jan. 12, 1971 McKENZ|E ET AL GRAIN DRYER Fild June 25, 1969 5 Sheets-Sheet l |NVENTORS GERALD L. ZACHARIAH BRUCE A. M: KENZIE ROBERT M. PEART RAYMOND R. OHLGREN ATTORNEYS Jan. 12, 1971 B McK N E ET AL 3,553,846

GRAIN DRYER Filed June 25, 1969 5Sheets-Sheet 2 INVENTORS GERALD L. ZACHARIAH BRUCE A. Me KENZIE ROBERT M. PEART RAYMOND FLOHLGREN ATTORNEYS s. A. MCKENZIE ET AL 3,553,846

GRAIN DRYER Jan. 12, 1971 5 Sheets-Sheet 5 Filed Jdne 25, 1969 INVENTORS GERALDL. ZACHARIAH BRUCE A. Mr: KENZIE ROBERT M. PEART RAYMOND R. OHLGREN BY W ATTORNEYS Jan. 12, 1971 McKENZ|E ETAL 3,553,846

GRAIN DRYER I Filed June 25, 1969 5 Sheets-Sheet i INVENTORS GERALD L. ZACHARIAH BRUCE A, MC KENZIE -ROBERT M.PEART RAYMOND R. OHLGRE'N ATTORNEYS Jan. 12, 1971 B. A.

med June 25, 11969 MCKENZIE T T 3,553,846

GRAIN DRYER I 5 Sheets-Sheet INVE NTORS GERALD L. ZACHARIAH BRUCE A. M: KENZIE ROBERT M. PEART RAYMOND R.OHLGREN ATTORNEYS United States Patent 3,553,846 7 GRAIN DRYER Bruce A. McKenzie, Lafayette, and Gerald L. Zachariah and Robert M. Peait, West Lafayette, Ind., and Raymond R. Ohlgren, Pewaukee, Wis., assignors to The Heil Co., Milwaukee, Wis., a corporation of Wisconsin Filed June 25, 1969, Ser. No. 836,387 Int. Cl. F26b 13/10 US. CI. 34-56 18 Claims ABSTRACT OF THE DISCLOSURE A grain dye is disclosed in which there are tiers of angularly-disposed shelves, one above the other, providing grain beds which are inclined toward common intermediate discharge columns, there being a hot air duct extending horizontally along the upper edge of each shelf from which hot air at relatively high temperature is directed downwardly at high velocity and pressure, in concurrent flow through the bed of grain supported on the shelf, and there being common means for feeding grain to the upper edges of all of the shelves to maintain the inclined beds filled. Metering means at the lower edge of each shelf provides for metering from each shelf a predetermined rate. The feed of grain into the dryer is antomatically controlled to maintain a predetermined level. An optionally usable cooler is also disclosed which may be located below the drying unit and which is adapted to deliver cooling air upwardly in counterflow with respect to the falling grain.

BACKGROUND OF THE INVENTION Field of the invention The present invention is particularly adapted for the drying of corn, but is suitable for use in the drying of other grains or granular materials.

Description of the prior art In the most commonly used grain dryers the grain is permitted to descend by gravity in a column, flowing downwardly over and on both sides of horizontally-disposed hot air ducts, or else hot air is directed in cross flow through the colmun. One such an arrangement is described in Randoplh Pat. No. 1,239,216 where the entire stack is filled with vertical and horizontal rows of air ducts, each of which is surrounded by the grain. In other types of constructions the air ducts of the general type disclosed in the Randolph patent are inverted Vs in cross section and open on the underside. Another type of dryer which is common in the prior art makes use of oppositely-directed downwardly-inclined shelves in a zig-zag arrangement, one shelf discharging from above into an oppositely-directed shelf below. In all of these prior devices, if the drying air is at too high a temperature, there will be damage to the grain. Therefore, in these prior devices, relatively low temperature air is used (about 230 F.) and the grain is subjected to the drying air for a relatively long period of time. Thus the installations must belarge 3,553,846 Patented Jan. 12, 1971 ice SUMMARY OF THE INVENTION The present invention provides, in-a grain dryer, at least one tier of inclined shelves providing spacing for inclined beds which are kept filled with grain introducedfrom above. There is means at the lower end of each shelf for metering grain from the bed at a predetermined rate and there is a horizontally-disposed air duct at the upper end of each shelf over which the entering grain moves, each air duct being equipped to discharge air in concurrent flow at high velocity and pressure through each bed of grain, in a manner providing for fast and uniform drying without damage to the grain. The feed of grain into the dryer is automatically controlled to maintain a predetermined level. In addition, there is optional means, preferably located below the drying unit, which is capable of directing cooling air upwardly through the falling grain in counter flow.

One of the objects of the invention is to provide for eificient drying of grain by the use of high velocity, high pressure air at a relatively high temperature.

A further object of the invention is to provide a grain dryer by which more grain can be handled over the same flow space than dryers heretofore proposed.

A further object of the invention is to provide a grain dryer in which all particles of the grain are subjected to substantially the same amount of heat for substantially the same lengthof time.

A further object of the invention is to provide a grain dryer which is relatively simple in design and construction, reliable in operation, relatively small in size for its capacity, and otherwise well adapted for the purposes described.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings, in which the same reference numerals designate the same or similar parts in all of the views:

FIG. 1 is a front elevational view of the improved grain dryer, parts of the casing being broken away to show the interior;

FIG. 2 is an end view thereof with the lower portion of the casing broken away;

FIG. 3 is a vertical sectional view through the dryer portion of the device'taken approximately on the line 33 of FIG. 1; a

FIG. 4 is a vertical sectional view taken approximately on the line 44 of FIG. 1;

FIG. 5 is a view looking at the top of one of the hot air ducts taken approximately on the line 5-5 of FIG. 3, parts being broken away and shown in section;

FIG. 6 is a horizontal sectional view through the lower portion of the device showing the blowers and air ducts in plan view;

FIG. 7 is a vertical sectional view through the cooling unit; I

FIG. 8 is a sectional view taken on the line 8-8 of FIG. 7;

for the motors which operate the feed augers;

FIG. is a diagrammatic view of the emergency level control;

FIG. 11 is a diagrammatic view illustrating the drive for the grain metering wheels; and

FIG. 12 is a diagrammatic view showing the control circuit for those metering wheels which control the discharge from the cooler.

Referring more particularly to the drawings, the numetal designates an inlet passageway for grain. Any suitable means may be employed for feeding grain into the dryer. In the illustrated example the grain is directed onto the ends of augers 21 and 22. The auger 21 operates in an auger housing 23 which is located over the plenum chamber only, there being no auger housing for the rest of the length of the auger, and the auger 22 in a similar auger housing 24. Grain is thus directed in two directions by the augers and is discharged from the open bottomed augers into the dryer sections 25, one on each side, to flow by gravity down the oppositely-inclined walls 26 (see FIG. 3) of an interior casing 27 having a top dividing ridge 28.

Each auger may be driven through an endless drive belt or chain 82 (see FIGS. 1 and 4) driven by an electric motor 83. When the grain on the right hand side of FIG. 1 is filled to a proper level this is sensed by the level detector 84 which automatically opens a switch 85 to the electric motor 83 for the particular side, stopping the motor and auger (see FIG. 9). A similar action takes place on the other side where the detector 86 causes opening of a switch 87 to the other electric motor 83 to stop the operation of the auger on this side. When the level of the grain drops below the detectors 84 and 86 the augers will again automatically operate to replenish the grain.

As an extra precaution there may be emergency indictator fingers 88 and 89 on the two sides, as shown in FIG. 1. Referring now to FIG. 10, should the grain level fall below the emergency detector fingers 88 or 89, said fingers will be released as shown in the full line position of FIG. 10, causing closing of a microswitch 90 and operation of a horn 91 or other signal which will warn the operator that the level controls 84 and 86 have not been operating properly, and that the level has fallen to a dangerous point.

The lower edges of the inclined walls 26 are connected as at 30 to the upper edges of walls 29 which diverge outwardly from the upper end of the discharge column 49. Spaced below each of the inclined walls 29 is a tier of inclined shelves 31 for supporting beds of grain to be dried. Inasmuch as the construction on the two sides of the plenum chamber is the same, only one will be described. At the upper edge of each shelf 31 is a hot air duct 32. Each hot air duct is constructed as shown in FIG. 5 to provide a downwardly-inclined top wall 33, a back wall 34, and a bottom wall 35. As one way of providing for efiicient discharge of this air, within each duct is an angularly-extending partition 36, one end of which meets the back wall 34 at one end of the air duct, and the other end of which meets the forward edge of the top wall 33 at the other end of the duct. Another angular partition 37 extending at the same angle as the partition 36 has one end starting midway of the width of the air duct as at 38 at the inlet end of the duct, and has its other end terminating midway of the length of the duct adjacent the forward portion thereof, as at 39. With this arrangement, part of the air introduced into the inlet end 40 will flow through a passageway 41 located between the partitions 36 and 37, and the remainder will flow through a passageway 42 located in front of the partition 37'. The passageway 42 is in open communication with a bed of grain supported on one of the inclined shelves 31 and filling the space between said shelf and the wall thereabove. The passageway 41 is in communication throughout the latter half of its length with the bed of grain. With this arrangement the air entering each duct at the end 40 is well distributed so that it is discharged from all portions of the length of each duct. Other means of providing even air distribution may be employed. There is preferably insulation 43 over and under the passageway 41 and insulation 44 over and under the passageway 42. Thus grain entering a column and initially supported on top of a hot air duct will not be scorched. The lowermost hot air duct on each side is connected by a deflector sheet 45 with the adjacent wall so that no grain can pass downwardly below the lowermost shelf.

In the drying of com the preferred angle for the shelf is 51 from the horizontal. The angle, however, may be anywhere between the lowest angle which will produce a flow of the grain, about 40, and 60. In a typical corn installation each shelf 31 may be 8 feet long and the spacing W (FIG. 3) between ach pair of shelves may be as much as 15 inches. The mean depth D (FIG. 3) of each bed of grain is 3 feet. The ratio W/D may be anywhere between 1/1.5 to 1/8. Each hot air duct 32 is approximately 8 inches wide and 8 feet long, and the clearance between the top wall 33 of each duct and the angular wall thereabove is approximately 4 inches and as small as possible without impeding the flow of grain. It is preferred to have the ratio A/ W anywhere between 1/2 to 9/ 10, where A is the height of a duct as shown in FIG. 3. For corn a ratio of 2/ 3 is very satisfactory. It is to be noted that each hot air duct has a dead air space 46 providing insulation for the back wall 34. Thus any grain in contact with the back wall 34 will not become scorched. The angle of the shelves provides for gravity feed toward the metering wheels 48 but prevents too dense compacting of the bed of grain on each shelf. If the column of grain were vertical it would be packed so densely that an objectionably high air pressure might be required to move air through it.

At the lower end of each shelf is a closure plate 47 which terminates short of the lower edge of each shelf 31. Each plate is perforated by holes of a size to release air but not grain. This leaves space within which a rotary metering paddle wheel 48 may be accommodated. Between the tiers on the two sides of FIG. 3 is a vertical discharge space 49 open at the lower end as at 50. The metering Wheels 48 may all be driven by a variable speed D.C. electric motor 92 (see FIG. 11) which through an endless chain drive 93 drives the sprockets of the metering valves 48 in the directions indicated in FIG. 11 to discharge grain into the central column 49. Heated air under pressure is forced through the ambient temperature grain supported on the tiers 31 into the central chamber 49,

i as will be hereinafter described. Due to the inclines of the tiers 31 the grain flows by gravity through the inclined drying chambers at a rate determined by the rotational speed of the metering paddle wheels 48.

Between the two sides of the dryer, i.e. the side fed by the auger 23, and the side fed by the auger 24, is a plenum area 51 which is illustrated in FIG. 4, the construction on the two sides of the plenum being the same. Extending upwardly within the plenum area are vertical plenum ducts 52 through which hot air is delivered, as will be hereinafter pointed out. Each duct 52 communicates with openings 53 in each of the walls of the plenum area, each opening 53 being in registration with the intake end 40 of one of the hot air ducts 32.

THE COOLER The cooler is designated generally by the numeral 54 (see FIGS. 2 and 7), and may fit below each dryer section, each cooler comprising two sections, one below the portion of the dryer fed by the auger 23 and the other below the portion of the dryer fed by the auger 24. If desired, the cooler may be omitted and the grain cooled by any conventional means. Grain discharged through the opening 50 of FIG. 3 of each dryer section is divided by inclined walls 55 of a suction duct 56 which extends lengthwise of each cooler section. The inclined walls 55 are spaced a short distance below wall portions 55 to provide passageways 116 therebetween, of limited height, through which the grain slowly descends, the grain maintaining said passageways substantially sealed against the inflow of exhaust air from the dryer section into the cooling section below. Below the duct 56 are open-bottomed cooling air passageways 57. Grain descendingfrom the sides .55 of the duct 56 is distributed to fall on top of the air cooling ducts 57 and on top of the downwardly-inclined baflles 58. Below. the central air duct 57 is an inverted V-shaped guide 59 having inclined walls 60. Grain from these walls is intercepted by inclined baffles 61 and the grain is ultimately discharged through spaces 62 and 63 onto an endless discharge conveyor 64, which, conveyor extends the entire length of the dryer of FIG. 1 and conveys the dried grain to a point of discharge, as is clear from FIG. 1.

The discharge from the spaces 62 and 63 iscontrolled may be located in the passageways 62 and 63 or in any other location, and which are driven byan electric motor 96. The motor on each side for driving the discharge wheels 62 and 63' is under the control of a level detector 97 positioned in the feed chute above each cooling section, as shown in FIGS. 7 and 12. The motor causes the discharge wheels 62' and 63 to discharge grain'when the level L reaches the level of the detector 97, as shown in FIG. 7. When this level drops below this height the motor 96 is automatically shut .olf to stop the operation of the rotary discharge wheels 62' and 63 and allow the level of grain to build up to the required point. When the level reaches the proper point the detector again startsthe motor 96 to again cause grain to be discharged. In case the detector 97 fails to operate, there is a safety device 100 well below the air lock passageway. If the level of grain falls below this point a horn or other signal sounds. This safety device is arranged to operate the same as is illustrated in FIG. 10. Above the normal level L is another safety device 101. If the level gets to this point the device 101 will also act vtosound a signal or .turn on a light to prevent too high a level of grain. These level detectors may be of any known commercially available [ype I Cooling air is adapted to enter holes 65 in the bottom of each cooling unit, and air also enters holes 66 com municating with ends of the air cooling ducts 57. In addition, there are open-bottomed cooling ducts 67 which extend through each cooling section at right angles to the duct 66. These ducts 67 connect with openings 69 in the lower portion of the air duct' 56.

Referring now to FIGS. 6, 7 and 8, the air which enters the openings 66 of FIG. 7 flows out of the bottoms of the ducts 57 and rises, entering the bottoms of the ducts 67. An exhaust fan 75 having an outlet opening 76 and driven by a suitable motor 77 is connected through ducts 78 and 79 with the opening 70 to create a suction within the suction duct 56, which suction causes the cooling air to move upwardly through the descending grain.

Referring now to FIG. 6, atmospheric air from the blowers 71 passes through ducts 72 into the lower ends of the vertical ducts 73. This air flows upwarly past and through burners 74 located in the lower end of the ducts 52 in the plenum area 51. Here the air is heated to a relatively high temperature, higher than is usually considered permissible in grain drying applications. After being heated by the burners the heated air enters the ducts 52 to flow upwardly therein and enter the openings 53 of FIG. 4 leading to the tiered'hot air ducts 32.

SUMMARY OF OPERATION In operation, the grain entering the hopper at the top is distributed by the augers 21 and 22 in both directions and is caused to fall on top of the inclined walls 26 so that part is directed in one direction and part in the opposite direction on each side of the plenum. Grain is fed in until the inclined columns are completely filled, as well as the side spaces 80 of FIG. 3, and there will also be a head of grain resting on the inclined walls 26 up to the level of detectors 84. The blowers 71 are delivering atmospheric air past the burners 74 and this air is heated to a relatively high temperature, between 300 F. and 600 F. The blowers 71 deliver the air at high velocity and at a pressure equal to 10-20 inches of water pressure. This air travels upwardly in the hot air passageways 52 and enters the end openings 53 leading to the hot air ducts 32. In each hot air duct 32 the air is divided, part flowing in the passageway 41 and part flowing in the passageway 42. The air is then delivered in a down direction, as indicated by the arrows in FIG. 3, at high velocity and pressure through the inclined columns of grain. In moving the air through the columns of grain it takes substantial pressure, which pressure, as before stated, is equal to 10-20 inches of water pressure.

At the same time the metering wheels 48 are being rotated at a relatively slow rate, the hot air flowing in the same direction as the grain. However, it may take 15 minutes to an hour for the grain to travel the length of the inclines 31, depending upon the speed of the discharge meters 48, whereas the hot air is moving at high velocity, taking less than a second .to travel through the entire depth of the beds of grain. This air can be at a relatively high temperature, depending upon the requirements of the particular products, and may be as high as 600 F. It is usually between 300600 F. The discharged drying air flows upwardly in the central chambers 49 and then out of the top outlet 81 through communicating opening 81' (FIG. 4).

The temperature of the air emerging from the inclined shelves through the perforated closure plates 47 is sensed by the temperature-responsive device 94. Since the temperature and pressure of the entering air are controlled to fixed values, the quantity of moisture removed from the grain is a function of the length of time the grain takes to pass through the dryer. The warm air, entering at 53, gives up heat to the grain, warming the grain and cooling the air. As the grain warms, it gives up moisture, further cooling the air by evaporative cooling. The temperature-sensing device 94 is immersed in the air which emerges from the drying shelves 31. Thus, under running conditions, if the exit air is cooler than the temperature which has been set on the temperature-sensing device, the grain is moving through the dryer too rapidly, and the grain metering wheels 48 should be slowed. Conversely, if the air is too warm, the grain flow rate should be increased. As an alternative, a known type of temperaturesensing device may be located in the exiting grain as at 194 (FIG. 7). Thus under running conditions if the grain at this region is cooler than the temperature which has been set on the temperature-sensing device, the grain is moving through the dryer too rapidly and the grain metering wheels 48 should be slowed. As another alternative, the sensing device, instead of being responsive to temperature, can be any well known type which is responsive to the moisture of the exiting grain as at 294 (FIG. 7). In this situation, if the exiting grain is too moist, then the grain is moving through the dryer too rapidly and the grain metering wheels 48 should be slowed.

A change of speed of grain flow has almost no affect on the temperature of the exit air for a period of time say 10 to 20 minutes, so it is desirable to wait for approximately this time interval to determine if the change made was correct, insufficient, or too much. If the change in flow rate was insuflicient, additional change in the same direction should be made. If the correction was too much, the rate should be changed in the opposite direction.

The grain which is metered out by the metering wheels 48 falls downwardly in the space 49, out of the opening 50 of FIG. 3, and onto the inclined walls 55 of FIG. 7, where it is divided, descending down on top of the cooling ducts 57, baflles 58, 60 and 61., and eventually onto the discharge belt 64. This action is under the control of the rotary discharge valves 62 and 63'. As the grain descends, cooling air which enters the spaces 65 of FIG. 7 and also the ends of the air ducts 66 is sucked out of the lower ends of the ducts 66 and caused to rise through the descending grain in countercurrent. The cooling air is then drawn into the bottoms of the ducts 67, into the openings 69, and out of the exhaust openings 70. This, of course, is accomplished by the action of the exhaust fan 75 which is connected by the ducts 78 and 79 with the end opening 70 of the suction duct 56. The grain in the area between level L of FIG. 7 and the lower portion of the ducts 67 is free from the effect of either hot air currents or cooling air. This area may, therefore, be termed a tempering area where the moisture in the kernels has a chance to reach a state of equilibrium. This allows the grain, as it descends into the region where it is acted upon by the cooling air, to release some additional moisture to the cooling air, which release serves to speed up the cooling process by aiding in the evaporative cooling efi'ect. Due to this tempering area and to the counterflow cooling, there is an absence of undesriable stresscracked kernels.

With the improved dryer, higher temperatures are possible for the drying air because the hot air is only in contact with the grain in the inclined beds for a short period of time, as the air is moving at high velocity and at high pressure. Heretofore dryers have been cumbersomely large so that lower temperature air could be used to contact the grain, such as corn, at a longer period of time, and it has heretofore been customary to have the heated air at a temperatude of about 230 F. maximum.

By having the tiers of angular drying shelves it is possible to use a smaller installation while still permitting the use of relatively high air temperatures for a relatively short period of time. Prior art grain dryers have been cumbersomely large so that lower temperature air could be used to contact the corn for a suificient length of time to accomplish drying.

With the arrangement of the present invention, the air discharged from the ducts 32 passes uniformly through the entire body of grain on each shelf to accomplish uniform drying, with all particles being subjected to substantially the same amount of heat for substantially the same length of time. Thus, there is high drying efficiency. With the present invention all of the drying air is exhausted at one place, through the exhaust duct 81. Thus, pollution control need be carried on at this point only.

While it is desirable to employ the cooler in the arrangement illustrated and heretofore described, the drying apparatus is useful with or without the cooling adjunct. There are users who may prefer to cool the dry product through other methods of their own selection. The present invention, therefore, contemplates the use of the dryer either with or without the cooling arrangement shown and described. In addition, the principles of the invention may be employed with only one tier of shelves 31 instead of the four tiers illustrated, two on each side. Also, any multiple of tiers may be used.

What we claim is:

1. A dryer comprising a tier of spaced inclined shelves, each shelf having an upper portion and a lower portion, a heating duct of less height than the space between shelves extending along the upper portion of each shelf and having air .openings positioned to direct air downwardly along the inclined shelf, means for maintaining the space between each pair of shelves and over the heating duct filled with a bed of grain, means at the lower end of each bed for controlling the metering of grain from the bed, there being air discharge openings at said lower end for the discharge of drying air from each bed, and means for delivering heated air to the heating ducts at high velocity and at sufficient pressure to cause the air to travel rapidly through the inclined beds of grain to dry the latter while grain is being metered slowly from each bed.

2. A dryer as claimed in claim 1 in which the means for deliverying the heated air to the heating ducts includes a common plenum chamber communicating with the ends of the heating ducts.

3. A dryer as claimed in claim 1 in which there are two sets of spaced inclined tiers of shelves, the tiers of one set being inclined toward the tiers of the other set, and in which there is a common discharge space between the two sets of tiers through which grain metered from the beds falls and from the upper ends of which the drying air is exhausted.

4. A dryer as claimed in claim 3 in which there is means for delivering grain to both tiers to maintain the grain beds filled.

5. A dryer as claimed in claim 1 in which there is means including an auger for feeding grain toward the beds to keep them filled, in which there is a motor for driving the auger, and in which there is means for automatically shutting oif the motor when the grain is above a predetermined level and for starting the auger motor when the grain is below said level.

6. A dryer as claimed in claim 1 in which there is a level detector normally maintained in inoperative position by grain when the level of the latter is above said detector, and in which there is means controlled by said detector for operating a signal when the level of the grain is below the detector.

7. A dryer as claimed in claim 1 in which the means at the lower end of such grain bed isa rotary metering wheel, in which there is a variable speed motor for driving all of the rotary metering wheels.

8. A dryer as claimed in claim 1 in which there is a cooler below the dryer, and in which there is means providing for restricted flow of grain discharged from the dryer into the cooler, said restricted flow means serving as a seal against the entrance of drying air into the cooler.

S. A dryer as claimed in claim 1 in which there is a cooler, means for directing dried grain from the dryer into the cooler, rotary metering wheels for discharging dried and cooled grain from the cooler, and means responsive to the level of grain in the cooler for controlling the operation of said rotary metering wheels.

10. A dryer as claimed in claim 1 in which there is drive mechanism for driving the metering means at a selected speed, the inclined shelves being at such an angle that the grain flows by gravity from each bed at a rate determined by the speed of the metering means.

11. A dryer as claimed in claim 10 in which the metering means comprises a metering paddle wheel for each bed and in which the rate of discharge is determined by the rotational speed of said wheels.

12. A dryer as claimed in claim 1 in which there is a cooler below the dryer, means for directing dried grain from the dryer to the cooler, means for discharging dried and cooled grain from the cooler, and means for causing cooling air to flow in counter current to the descending grain in the cooler.

13. A dryer as claimed in claim 1 in which there is a cooler below the dryer, means for directing dried grain from the dryer to the cooler, means for discharging dried and cooled grain from the cooler, means for causing cooling air to flow from the lower portion of the cooler upwardly in counter current to the descending grain in the cooler, and means for discharging said cooling air at a location short of the top of the cooler whereby there is a tempering area thereabove in which the grain in free of the effects of both cooling air and drying air.

14. A dryer as claimed in claim 1 in which the angle of the shelves is between 40 and 60 degrees from the horizontal.

15. A dryer as claimed in claim 1 in which the ratio between the distance between shelves and the mean depth of each bed of grain is in the range between 1/l.5 and l/ 8.

16. A dryer as claimed in claim 1 in which the ratio between the height of the hot air duct and the distance between shelves is in the range between 1/2 and 9/10.

17. A dryer as claimed in claim 1 in which the ratio between the distance between shelves and the mean depth of each bed of grain is in the range between 1/ 1.5 and 1/8, and in which the ratio between the height of the hot air duct and the distance between shelves is in the range between 1/ 2 and 9/ 10.

18. A dryer as claimed in claim 1 in which the angle of the shelves is between 40 and 60 degrees from the horizontal, in which the ratio between the distance be tween shelves and the mean depth of each bed of grain is in the range between 1/ 1.5 and 1/8, and in which the ratio between the height of the hot air duct and the dis- References Cited UNITED STATES PATENTS 2,060,581 11/1936 Laessig 3465UX 2,759,274 8/1956 Jonsson 3 4-65X 3,274,701 9/1966 Niemitz 34168X 10 CARROLL B. DORITY, JR., Primary Examiner US. Cl. XJR. 34-65, 67, 168 3

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