Abstract:
A high capacity grain aeration apparatus ( 10 ) is provided which includes opposed, upright, tubular, ported inlet and outlet ducts ( 24,26 ) positioned within a grain bin ( 12 ) and having inlet and outlet fans ( 28, 30 ) adjacent the upper ends of the ducts ( 24, 26 ). The ducts ( 24, 26 ) preferably present smooth, uncorrugated walls ( 40, 44 ). In use, aeration air is directed through the inlet duct ( 24 ) and then transversely through the ports ( 42 ) to the interior ( 20 ) of grain bin ( 12 ). Such air flows transversely through the grain within bin ( 12 ) and is pulled upwardly through outlet duct ( 26 ) by means of outlet fan ( 30 ). Additional aeration air enters through vents ( 50 ) or the grain inlet port ( 47 ) and enters the outlet duct ports ( 46 ) by passing through the grain.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation-in-part of application Ser. No. 09/211,244 filed Dec. 14, 1998. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of grain aeration. More particularly, the invention is concerned with an apparatus for grain aeration to effect cooling, conditioning (e.g., partial drying) or fumigating grain stored in upright bins. In preferred forms, the invention provides grain aeration apparatus including upright, opposed, tubular perforate air inlet and outlets ducts within a grain bin with a fan assembly for forcing air through the inlet duct, transversely through the stored grain within the bin, and then upwardly through the outlet duct. 
     2. Description of the Prior Art 
     The standard grain aeration systems either push or pull air through the height of the grain using a fan located at the base of the grain bin, the top of the grain bin or a combination of fans on both top and bottom of the grain bin. Because the air must traverse the entire height of the grain mass, resistance to airflow is great, and large fans that consume large amounts of electrical power must be used to achieve acceptably large airflow. An alternative apparatus places two semi-circular, perforated, corrugated, metal ducts vertically on the sides of the bin to move air through grain stored in the bin horizontally instead of vertically. However, installation of the semi-circular ducts on the walls is costly and the weight of the grain causes damage to the corrugated ducts as grain is withdrawn from the silo. A hole, near the bottom of the grain bin is still required for the installation of the aeration fan and/or duct. 
     A 1985 publication by K. F. Loo entitled  Silo Storage in Malaysia,  Proceedings of International Seminar held at Kuala Lampur, Malaysia, Oct. 9-11 (1985) describes a grain aeration system comprising perforated air inlet and outlet ducts with axial fans coupled to the ducts. However, this reference makes use of identically sized (10 hp) fans. 
     Another reference  Aeration of Grain in Commercial Storages  published by the U.S. Department of Agriculture discloses an aeration system with opposed perforate ducts, that makes use of only a single exhaust fan. 
     SUMMARY OF THE INVENTION 
     The present invention solves the problems mentioned above and provides a distinct advance in the state of the art. In particular, the apparatus for aeration of grain hereof is efficient and economical to install, operate and maintain. 
     The preferred grain aeration apparatus of the present invention is operated in combination with a grain bin. The grain aeration apparatus includes inlet and outlet ducts positioned adjacent the inside face of the grain bin wall and extending along at least a portion of the height thereof. The duct walls are preferably smooth and un-corrugated, with ports distributed along a portion of their length. An inlet fan is attached to the inlet duct&#39;s upper end. The inlet fan forces aeration air through the inlet duct, out the inlet ports and into grain stored in the bin. An outlet fan is attached to the upper end of the outlet duct. The outlet fan pulls air from the outlet duct and thereby pulls aeration air from grain stored in the bin through the outlet ports. The outlet fan is relatively larger than the inlet fan in terms of air-moving capacity in order to move more air than is supplied by the inlet fan. Thus air is pulled from the grain surface in a separate airpath than the duct-to-duct flow, in order to cool or condition the grain above the level of the perforations. 
     In preferred forms, the inlet and outlet duct are formed from synthetic resin pipe. The duct walls are imperforate for a distance of 1.5 to 1.9 bin diameters below the top of the grain bin, after which the ports consist of between 6 and 8% of the remaining duct surface area. Each pipe section is approximately 20 feet long, and requires only two attachment brackets per section. The preferred outlet fan is relatively larger than the inlet fan and both fans are positioned on top of the grain bin. Furthermore, it is preferred that the outlet duct be positioned in proximity to the area within the grain bin where the grain height is the greatest. This is done in order to keep air from “short-circuiting” within the bin. 
     In alternate embodiments, the aeration system of the invention includes level sensor(s) located within the grain bin and operable to determine the level of grain therein, and particularly whether or not the level of grain in the bin is above the level of the duct ports. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial, perspective view with portions of the bin wall removed to illustrate the internal construction of the preferred grain aeration apparatus in accordance with the present invention; and 
     FIG. 2 is a schematic vertical sectional view of the preferred grain aeration apparatus, illustrating the position of the grain inlet relative to the outlet duct in order to prevent short circuiting of air. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The drawing figures illustrate the preferred grain aeration apparatus  10  in combination with grain bin  12  in accordance with the present invention. Referring initially to FIG. 1, grain bin  12  includes top  14 , bottom  16  and bin wall  18  therebetween defining bin interior  20 . Bin wall  18  presents inside face  22 . 
     Grain aeration apparatus  10  includes tubular inlet duct  24 , tubular outlet duct  26 , inlet fan  28 , outlet fan  30 , low sensor  32  and high sensor  34 . The inlet fan  28  is connected to upper end  36  of inlet duct  24  and outlet fan  30  is connected to upper end  38  of outlet duct  26 . Air propelled into the bin by the inlet fan  28  passes down the inlet duct  24  and into the grain through the inlet ports  42 . This air passes through the grain and enters the outlet duct  26  through the ports  46 , providing a duct-to-duct airflow. 
     As shown in FIG. 1, inlet duct  24  preferably presents a smooth, uncorrugated duct wall  40  with structure defining a plurality of inlet ports  42  along at least a portion of the height thereof. Outlet duct  26  also preferably presents a smooth, uncorrugated duct wall  44  with structure defining a plurality of outlet ports  46  along at least a portion of the height thereof. Outlet duct  26  is positioned opposite inlet duct  24  and close to a grain entry port  47  to ensure maximum length of the airflow path from the grain surface to outlet ports  46 , thus preventing short circuiting. In particular, and referring to FIG. 2, it will be observed that the maximum height H of the grain within the bin  12  is closely adjacent to outlet duct  26 . In this fashion, the outlet duct  26  is also close to the maximum height of the grain on the bin wall (Hw). Cooling air seeks the shortest path through the grain within the bin  12 . Therefore, placement of the outlet duct  26  relative to the inlet  47  as shown ensures that a cooling air current traverses the body of grain rather than passing along the upper surface of the grain from the inlet duct to the outlet duct. 
     Both ducts  24 ,  26  are electrically grounded to eliminate static charge build up. Ports  42 ,  46  are positioned along duct walls  40 ,  44  starting at a point from about 1.5 to 1.9 diameters of grain bin  12  below the grain height Hw, during normal operation of the apparatus  10 . Also, ports  42 ,  46  present an open area of between about 6% and 8% of the total surface area of the perforated portions of the inlet and outlet ducts  24 ,  26 , respectively. 
     Inlet and outlet ducts  24 ,  26 , as illustrated in FIG. 1, are preferably formed of synthetic resin material (PVC) pipe with a 16″ diameter. Ducts  24 ,  26  are assembled in 20′ long sections of PVC pipe and are coupled with inside face  22 . PVC pipe is preferred for low cost, light weight and easy assembly. 
     Inlet fan  28  and outlet fan  30  are preferably positioned on top  14  of grain bin  12  and are conventionally connected to the upper ends of respective ducts  24 ,  26 . Outlet fan  30  is larger than inlet fan  28 . Specifically, outlet fan  30  is sized between 3 and 5 horsepower and inlet fan  28  is sized between 0.75 and 1 horsepower to provide optimum cooling and conditioning airflow. Outlet fan  30  pulls outlet air from outlet duct  26  and thereby pulls aeration air from grain stored within bin interior  20  by way of outlet ports  46 . Vents  50  and fill port  47  supply aeration air to the volume of grain above ports  42 ,  46 . This aeration air flows in through vents  50  and fill port  47 , down through that volume of grain above ports  42 ,  46  and into outlet ports  46 . This cools and conditions the topmost portion of the grain stored in grain bin  12  by a surface-to-duct airflow. Because fans  28 ,  30  are respectively attached to upper ends  36 , 38  above grain bin top  14 , there is no need for an opening in bin wall  18 . This reduces construction costs and eliminates the need to weaken bin  12  structure by cutting an opening at base  48  of bin wall  18  where grain pressures are greatest. 
     Low grain level sensor  32  is positioned adjacent bin wall  18  and placed such that it senses when grain levels cover ports  42 ,  46 . High grain level sensor  34  is positioned adjacent bin wall  18  and placed such that it can determine when grain bin  12  is full. Vents  50 , defined in the grain bin top  14 , are shiftably covered by schematically depicted vent closer  51  shiftably operable between open and closed positions. Fill port  47  described previously is the opening through which grain enters the bin  12 . Fill port  47  is equipped with a fill port closer  51   a,  which is shiftably operable between open and closed positions. Sensors  32 ,  34  are conventionally connected with the vent and fill port closers, and the motor controls for inlet and outlet fans  28 ,  30 . 
     As shown in FIG. 1, the sensors  32 ,  34  are coupled with a conventional microprocessor controller  52 , which is also coupled with vent and fill port closers  51 ,  5 l a  and the motor controls for inlet and outlet fans  28 ,  30 . 
     In operation, if low sensor  32  does not detect grain covering ports  42 ,  46 , then the low sensor signals controller  52  and the fans  28 ,  30  are turned off. This prevents short circuiting of aeration air through empty interior space of bin  20 . 
     If the low sensor  32  detects grain covering ports  42 ,  46 , but high sensor  34  does not detect grain, then fans  28 ,  30  are enabled by a signal from controller  52 . Also, controller  52  signals vent closer  51  and fill port closer  51   a  to shift to the closed position. This results in all of the aeration air passing through the inlet duct  24 . That is, inlet fan  28  operates to force aeration air through inlet duct  24  and out through inlet ports  42  into grain located in bin interior  20 . Outlet fan  30  operates to pull outlet air from outlet duct  26  and thereby pull aeration air from grain stored within bin interior  20  by way of outlet ports  46 . In this way, all of this aeration air follows a course through grain stored in said bin  12  generally transverse relative to the height thereof. 
     If high grain level sensor  34  detects a sufficient grain level, then controller  52  signals vent closer  51  and fill port closer  51   a  to shift to the open position and aeration air enters bin interior  20  from vents  50 , grain fill port  47  and inlet duct  24 . 
     Table 1 clearly demonstrates the airflow and ratios of surface-to-duct vs. duct-to-duct airflow rates of the present invention used with wheat or grain sorghum. Likewise, Table 2 demonstrates the airflow and ratios of surface-to-duct vs. duct-to-duct airflow rates of the present invention used with corn or soybeans. 
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Estimated airflow and ratios of surface-to-duct vs. duct-to-duct airflow rates 
               
               
                 in a cross-flow aeration system used with WHEAT or GRAIN SORGHUM 
               
             
          
           
               
                 Exhaust 
                 Inlet 
                 Bin 
                 Bin 
                 Total Airflow 
                 Surface-to-Duct 
                 Duct-to-Duct Airflow 
               
               
                 Fan HP 
                 Fan HP 
                 Diameter 
                 Height 
                 (cfm/bu) 
                 Airflow (% of total) 
                 (% of total) 
               
               
                   
               
             
          
           
               
                 3 
                 0.75 
                 20 
                 80 
                 0.09 
                 55 
                 45 
               
               
                 3 
                 0.75 
                 20 
                 100 
                 0.07 
                 55 
                 45 
               
               
                 3 
                 0.75 
                 20 
                 120 
                 0.06 
                 56 
                 44 
               
               
                 3 
                 1 
                 20 
                 80 
                 0.09 
                 40 
                 60 
               
               
                 3 
                 1 
                 20 
                 100 
                 0.07 
                 40 
                 60 
               
               
                 3 
                 1 
                 20 
                 120 
                 0.06 
                 41 
                 59 
               
               
                 5 
                 1 
                 20 
                 80 
                 0.14 
                 64 
                 36 
               
               
                 5 
                 1 
                 20 
                 100 
                 0.11 
                 64 
                 36 
               
               
                 5 
                 1 
                 20 
                 120 
                 0.1 
                 64 
                 36 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Estimated airflow and ratios of surface-to-duct vs. duct-to-duct airflow rates 
               
               
                 in an cross-flow aeration system used with CORN or SOYBEANS 
               
             
          
           
               
                 Exhaust 
                 Inlet 
                 Bin 
                 Bin 
                 Total Airflow 
                 Surface-to-Duct Airflow 
                 Duct-to-Duct Airflow 
               
               
                 Fan HP 
                 Fan HP 
                 Diameter 
                 Height 
                 (cfm/bu) 
                 (% of total) 
                 (% of total) 
               
               
                   
               
             
          
           
               
                 3 
                 0.75 
                 20 
                 80 
                 0.14 
                 53 
                 47 
               
               
                 3 
                 0.75 
                 20 
                 100 
                 0.11 
                 52 
                 48 
               
               
                 3 
                 0.75 
                 20 
                 120 
                 0.09 
                 52 
                 48 
               
               
                 3 
                 1 
                 20 
                 80 
                 0.14 
                 39 
                 61 
               
               
                 3 
                 1 
                 20 
                 100 
                 0.11 
                 39 
                 61 
               
               
                 3 
                 1 
                 20 
                 120 
                 0.09 
                 38 
                 62 
               
               
                 5 
                 1 
                 20 
                 80 
                 0.18 
                 54 
                 46 
               
               
                 5 
                 1 
                 20 
                 100 
                 0.14 
                 53 
                 47 
               
               
                 5 
                 1 
                 20 
                 120 
                 0.11 
                 53 
                 47 
               
               
                   
               
             
          
         
       
     
     As it will be appreciated, aeration apparatus  10  can be installed as an original aeration system on a newly built grain bin or installed as a kit on a preexisting grain bin. The kit would normally include all parts of the aeration apparatus  10 , and would allow any pre-existing vents or fans to be incorporated into the aeration apparatus  10 . For a grain bin 120′ tall, for example, the kit would include 4 nonperforated 20′ sections of 16″ diameter PVC ducts, 8 perforated 20′ sections of 16″ diameter PVC ducts, two mounting brackets per section, inlet fan  28  and outlet fan  30 . 
     Those skilled in the art will now appreciate the benefits of the present invention. For example, the low friction coefficient of smooth, uncorrugated ducts  24 ,  26 , decreases the damage caused by the removal of grain from a bin with corrugated metal ducts. Another benefit is smaller fans may be used to cool and condition the grain because aeration air travels transversely across bin  12  as opposed to the entire height of bin  12 . Smaller fans are less expensive to purchase and operate. Also, because fans  28 , 30  are attached to ducts  24 ,  26  above top  14 , no opening has to be made in bin wall  18 . This reduces construction costs and eliminates the need to weaken the bin structure by cutting an opening in the base of the wall where grain pressures are the greatest. 
     Those skilled in the art will also appreciate that the present invention encompasses many variations in the preferred embodiments described herein. For example, inlet and outlet ducts  24 , 26  could be made from other materials with low friction coefficients such as ceramics, aluminum or other synthetic resin materials. Also, the preferred embodiment is made of 16″ ducts, but other sizes could be used. As another example, either one or both of fans  28 ,  30  could be positioned on the side of grain bin  12 . The size and location of ports  42 ,  46  could be varied. Additionally vent  50  could be defined in bin wall  18  or there could be a plurality of vents  50 . Further, a recirculating fumigant system could be connected with the aeration system to treat grain more efficiently and more thoroughly. 
     Having thus described the preferred embodiments of the present invention, the following is claimed as new and desired to be secured by Letters Patent: