Abstract:
A rotatable grain tower mounted on a stationary base. The base includes an opening for the removal of grain from a grain plenum in the tower. As the tower is rotated, a metering device adjacent the opening meters the rate of grain exiting the plenum. The rotating tower alleviates uneven drying due to sun, wind and other conditions to more evenly dry grain in the plenum. A cleaning device may be positioned adjacent the tower to clean the plenum as the tower rotates, thereby eliminating catwalks and other expensive equipment and devices used for cleaning stationary towers.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 61/420,948 filed Dec. 8, 2010, the disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to grain dryers in general and more particularly to tower or vertical grain dryers. 
       BACKGROUND OF THE INVENTION 
       [0003]    In many instances, agricultural grain products must be stored for an extended period of time prior to being used. However, prior to storage, it is necessary to dry the grain to a condition in which it is less subject to molding or other deterioration. Accordingly, it has become known to remove moisture from grain by passing the grain through a grain dryer prior to storage. 
         [0004]    Tower grain dryers are well known. Generally, they comprise a vertical tower having a cylindrical shape with an annular grain plenum. The outer wall of the plenum is generally cylindrical. An inner cylindrical wall coaxial with the outer wall is spaced inwardly from the outer wall. Generally, the inner cylindrical wall has a diameter of about two feet less than the outer wall, resulting in an annular plenum between the walls having a thickness of about 12 inches. The plenum provides a vertical grain path between the two walls. The walls are constructed from perforated stainless steel screens to be porous such that heated air from within the plenum may be forced through the walls and through the grain in the plenum. 
         [0005]    A typical annular plenum is divided into a series of vertical columns by dividers which are circumferentially spaced one to two feet apart in the plenum. Grain loaded in the top of the tower descends under force of gravity thought the vertical columns in the plenum. 
         [0006]    As heated air moves through the grain, moisture is removed. Dried grain is continuously discharged from the lower end of the plenum. Additional grain to be dried is loaded into the upper end of the drying path. 
         [0007]    To control the amount of moisture removed from the grain, it is necessary to precisely control the flow rate of the grain through the grain columns of the plenum. Grain in the grain columns exposed to heated air for an extended period of time may become too dry. Grain that passes quickly through the grain columns may retain an undesirable amount of moisture. 
         [0008]    Heated air is supplied to the grain by means of one or more burner/blower assemblies. Heated air is forced from within the radially inner wall of the plenum through the plenum&#39;s porous or perforated inner wall, through the grain in the drying paths, and finally through the porous outer plenum wall, carrying away moisture from the grain. 
         [0009]    Expensive and elaborate sweep systems have been developed to remove grain from drying towers. Sweep systems are located at the bottom of the plenum and remove grain from the bottom of the grain columns when dried to a desired moisture content. As is well known, sensors in the grain tower determine the moisture content of the grain and signal the grain removal system, typically a sweep system, to remove certain amounts of grain from the bottom of the vertical columns. However, for various reasons, grain descending through the various columns does not dry at the same rate, with some grain being over dried and some grain being under dried. 
         [0010]    Currently available grain dryers can be inefficient for several reasons. The primary source of inefficiency is imprecise drying due to uneven drying among the various vertical grain paths. This can result from various factors, such as wind and sun affecting some vertical grain columns more than others. Sweep systems at the bottom of a typical grain dryer sweep grain generally evenly from the adjacent columns even though grain in adjacent columns may have different moisture content. 
         [0011]    Another possible source of inefficiency is that the perforated plenum walls or screens often clog from the grain or grain shells, etc. To maintain dryer efficiency, it is necessary to clean the screens periodically. Typically this is done manually. Large grain towers typically have catwalks vertically spaced approximately every 10 feet for this purpose. Catwalks add capital cost to the dryers, and manual cleaning adds operating or maintenance costs. Frequent cleaning of the plenum is necessary for maximum efficiency. Unfortunately, because of the high cost of cleaning, grain towers are not always operated at maximum efficiency. 
         [0012]    What is needed is a grain tower which more efficiently dries grain and which can be less expensively manufactured and maintained. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is a rotatable grain tower mounted on a stationary base. The base includes an opening for the removal of grain from the grain plenum. As the tower is rotated, a metering device adjacent the opening meters the rate of grain exiting the plenum. The rotating tower alleviates uneven drying due to sun, wind and other conditions to more evenly dry grain in the plenum. A cleaning device may be positioned adjacent the tower to clean the plenum as the tower rotates, thereby eliminating catwalks and other expensive equipment and devices used for cleaning stationary towers. 
         [0014]    Various other aspects of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is a partially cut away view of a conventional prior art tower grain dryer. 
           [0016]      FIG. 2  is a cross-sectional view of the bottom portion of a grain dryer of the present invention. 
           [0017]      FIG. 3  is a cross sectional top view of the grain dryer of  FIG. 2  taken along line  3 - 3  of  FIG. 2 . 
           [0018]      FIG. 4  is a cross-sectional view of the grain dryer of  FIG. 2  taken along line  4 - 4  of  FIG. 3 . 
           [0019]      FIG. 5  is a schematic view of the grain dryer of  FIG. 2  including a cleaning device. 
           [0020]      FIG. 6  is a schematic view of the grain dryer of  FIG. 2  including an alternative cleaning device. 
           [0021]      FIG. 7  is a cross-sectional view of a bottom portion of an alternative embodiment of the grain dryer of the present invention. 
           [0022]      FIG. 8  is a top plan view of a component of the alternative embodiment of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0023]      FIG. 1  shows a conventional vertical grain dryer  10 . The dryer includes a vertical grain drying tower  12  which, for example, may be fifty feet or more in height. The tower has a base  13  of suitable structural steel members mounted in a suitable foundation (not shown). The grain dryer includes a plenum  30  defined by a generally cylindrical porous inner plenum wall  32 . An outer cylindrical wall  34  of porous construction surrounds plenum wall  32  and is coaxially spaced outwardly therefrom so as to define a vertical, annular grain drying path. Radial spacing between porous walls is generally 11-13 inches and is typically about 12 inches. Grain is supplied to grain drying path by means of a grain inlet  14  at the top of tower. 
         [0024]    A heater/blower assembly  50  is provided within the grain dryer. The assembly  50  draws ambient air through closable windows  51  and through the grain path in the lower portions of the tower. The assembly  50  heats air within the tower and discharges the heated air under pressure through the plenum  30 . In this manner, the air discharged from the heater/blower  50  is distributed substantially uniformly within the plenum. Heated air is forced to flow through the porous plenum wall  32 , through the grain in grain drying path, and through the porous outer plenum wall  34 , thereby drying the grain in the grain path and carrying moisture from the grain to the atmosphere. 
         [0025]    The heater/blower  50  may be located outside the tower in close proximity thereto, with heated air from the heater/blower ducted into the tower Typically, fuel and electricity for the heater/blower assembly  50  is supplied by electrical and gas fuel supply lines  19 . Operation of the heater/blower assembly and overall operation of tower dryer is controlled by a computer control housed in a control panel  21 . Typical prior art tower dryers have multiple catwalks  24  to facilitate cleaning of the tower. 
         [0026]      FIG. 2  shows a grain tower of the present invention. The upper portion of the grain tower of the present invention is substantially the same as the prior art tower  10 . A base  22  is formed by a series of circumferentially spaced supports  23 , such as steel beams or posts which may be anchored in a concrete pad (not shown). The base includes an annular outer plate  60  rigidly affixed to the support posts  23 . The top surface  60   a  of the outer plate  60  under the plenum  30  is coated with a low friction coating such as Teflon, nylon or a high density plastic coating so that grain may easily be dragged along the plate when the tower is rotated as will be described herein. The outer plate includes a grain discharge opening  64 . 
         [0027]    The tower  12  includes inner and outer plenum walls  32 ,  34  defining a grain plenum  30 . The plenum walls are rigidly affixed to an inner annular plate  70  as will be described herein. The inner plate  70  is mounted for rotation on the outer plate  60  by a swing bearing  72  which can be sourced from Timken, PSL, etc. The bearing may be a tapered roller bearing, but a tapered bearing is generally not required for a tower of typical height because the bearing does not need to carry significant lateral forces. The only significant lateral force is the force of wind on the tower. Seals  62  attached to either the outer plate  60  or the plenum walls  32 ,  34  are used to seal the bottom of the plenum to the outer plate as the tower rotates relative to the outer plate. 
         [0028]    A louver system  86  is rigidly mounted on the inner plate  70  with bolts  88 . Alternatively, the louver system may be mounted for rotation on the inner plate  70  with bearings. A conduit  36  is provided through the louver system to supply electrical power and fuel to the heater/blower. The louver system  80  eliminates the need for the air doors  51  ( FIG. 1 ) of prior art towers. 
         [0029]    An electric motor  52  is operationally connected to the tower though a drive train  76 . A gear  74  engages gear teeth on the inner plate  70  to slowly rotate the inner plate, causing the tower to rotate. 
         [0030]    Referring to  FIG. 3 , the grain path is divided into vertical grain channels by vertically extending pairs of channels  54  (only three shown in  FIG. 3 ) having inner and outer flanges  54   a,    54   b  secured to the inner and outer plenum walls  32 ,  34 , respectively, by welding, bolting, etc. Depending on the diameter of the tower  12 , the grain path may be divided into about 12-20 of such grain channels (only two shown in  FIG. 3 ). 
         [0031]    Referring to  FIGS. 3 and 4 , the tower is mounted to the inner plate  70  by means of supports  56 . The supports are rigidly connected to the inner plate  70  by bolts, welding or the like. The supports are rigidly connected to the inner and outer plenum walls through channels  54  by welding, bolting or the like. 
         [0032]    Referring again to  FIG. 1 , a metering device  80  is attached to the underside of the outer plate  60  underneath the grain discharge outlet  64 . Dried grain from the metering device can be transported to storage through conduit  82 . Preferably the metering device is an airlock metering roll which can be used not only to meter the rate of grain discharge, but also to form part of an airtight system to pneumatically transport the dried grain to storage through conduit  82 . 
         [0033]    In operation, grain fed through the top of the tower  14  moves vertically downwardly under gravitation force through the plenum  30 . The tower is rotated by motor  52  at the rate of about one to two (1-2) rpm around a central vertical axis of rotation. Tower rotation alleviates hot spots in the grain caused by uneven exposure of one side of the tower to sun, wind, rain and other elements. Sensors in the grain tower determine the moisture content of the grain and automatically allow the optimum amount of grain to be removed from each vertical column as it passes over the grain discharge opening  64 . This system better accommodates uneven grain moisture in adjacent columns than widely used sweep systems. Better metering stops over drying, thereby adding efficiency and increasing capacity tower dryers. 
         [0034]      FIG. 5  shows a cleaning system for use with the rotatable tower. A cleaning device  92  having a nozzle  94  is movably mounted on a cleaning tower  90  such as a pole or truss adjacent the tower. The cleaning device may include a pressurized fluid ejection devices such as blowers and power washers to clean the outer plenum wall  34  with pressurized air or water or other fluids. In addition, the cleaning device  92  may include retractable brushes  96  which may selectively engage the outer plenum wall  34 . 
         [0035]    Cleaning device  92  may be raised and lowered along the tower  90  using any typical method, such as a ball screw actuator  98 . Cleaning device  92  can be positioned at various vertical positions in discreet timed steps, or the device  92  can be vertically moved continuously as the tower turns, either automatically or manually. The outer plenum wall  34  can thereby be cleaned while the tower slowly rotates. The rotatable tower allows the elimination of expensive catwalks used for this and other purposes. 
         [0036]      FIG. 6  shows an alternative cleaning tower  190  which includes a series of fixed nozzles  192  vertically spaced throughout the entire length of the tower  90 . A fluid pressure system  194  provides pressurized fluid through the nozzles  192 , which may selectively discharge pressurized air or fluid over the entire vertical length of the plenum. Retractable brushes (not shown) may also be positioned along the entire length of the tower  190  in addition to or in place of the pressurized fluid system. With this arrangement, cleaning tower  190  can be used to clean the entire plenum with one revolution of the tower  10 . Of course, several revolutions of the tower may be necessary for a more thorough cleaning. 
         [0037]    It will be readily understood that the cleaning systems described above will be less costly to install than catwalks necessary in currently used towers, and less costly to use than manual cleaning procedures currently used. Because of the reduced cost and automated use, a tower plenum can be cleaned more frequently, even continuously if desired, to maintain maximum efficiency. 
         [0038]      FIGS. 7  shows an alternative embodiment in which the tower  12  is rigidly mounted on an annular grain drag  100 . The grain drag  100  has an annular inner wall  102  and annular outer wall  104  which are rigidly connected by a series of drag plates  106  which are welded to the walls. The drag plates  106  extend into a grain pan as will be described. The tower screens  32 ,  34  are mounted on top of the annular walls  102 ,  104 , respectively, for rotation therewith. Although not essential, the number of drag plates  106  is the same as the number of vertical tower channels  54 , and the drag plates are aligned with the vertical channels  54 . Annular seals  108  may be used at the interface of the grain drag and tower screens to assure a sealed connection. 
         [0039]    An annular grain pan  200  is positioned under the grain drag  100 . The grain pan has inner  202  and outer  204  annular walls generally vertically aligned with the grain drag walls  102 ,  104 , respectively. Annular seals  208  allow rotation of the grain drag  100  relative to the grain pan  200 . Annular grain pan bottom wall  206  is coated with a smooth plastic or comparable surface to allow easy dragging of grain. The pan bottom  206  includes one or more grain discharge openings  210 . If the grain pan has more than one discharge opening  210 , it is preferred that they are equally circumferentially spaced around the grain bottom  206 . 
         [0040]    The drag plates  106  are dimensioned to closely fit within the grain pan  200 . It is possible to coat the inside surfaces of the grain pan walls  202 ,  204  with a smooth plastic or comparable coating to facilitate grain movement and any contacting of these surfaces by the drag plates  106 . Alternately, the edges of the drag plates  106  may be similarly coated. 
         [0041]    Outer grain pan wall  204  may include removable sections for accessing the inside surface of the grain pan  200 . For example, a section could be removed and a brush could be inserted to clean the grain pan surface as it is pushed around the grain pan by the drag plates  106 . The removable sections may also be used to access the grain pan for replacement of a plastic or other low friction surface coating on the inside surface of the grain pan. 
         [0042]    Grain pan  200  is rigidly attached to a radially inwardly extending annular support plate  260  by welding. Support plate  260  is rigidly supported by posts or pillars  123 . Support posts or pillars  124  positioned radially outwardly of the grain pan  200  may be used instead of or in addition to supports  123 . In either case, the supports rigidly support the grain pan  200  in a stationary position. 
         [0043]    Grain drag  100  is rigidly attached to an annular grain drag support plate  170  by welding. The grain drag  100  is supported on a bearing  172  through the support plate  170 . Bearing  172  is in turn supported for rotation on grain pan support plate  260 . As in the prior embodiments, a motor  52  connected by a drive train  76  operates a set of gears  74  to rotate the grain drag  100 . 
         [0044]    A metering device  80  is connected to the grain pan  200  below each grain discharge opening  210 . As the tower and grain drag  100  rotate, drag plates  106  carry grain over openings  210 . Metering devices  80 , controlled by computers being fed with input from the sensors, remove the appropriate amount of grain. 
         [0045]    Referring to  FIG. 7 , the shape of the grain discharge openings  210  can be fine tuned. For example, the openings can be round or square, but preferably are generally quadrilateral shaped, having curved radially inner and outer boundaries and radially extending circumferential boundaries to more closely pattern the volume of the plenum above the openings across its radial width. 
         [0046]    The principle and mode of operation of this invention have been explained and illustrated in its preferred embodiments. However, this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope as defined by the appended claims.