Grain bins for storing various types of grain commonly include aeration systems to enhance drying of the grain within the bin. One type of aeration system comprises a perforated floor in the bin through which air is forced. Such aeration systems dry grain from the bottom up, which often leaves the grain in the center and top of the bin damp. Another type of aeration system is one or more horizontal tubes extending through the bin with holes in the tubes to provide drying air.
Another aeration system utilizes a centrally located vertical aeration tube extending upwardly from the bottom of the bin, with holes in the cylindrical tube wall to provide drying air to the grain in the bin. Such vertical tube aeration systems are typically used in grain bins having a sloped hopper bottom with a central discharge opening with a gate moveable between open and closed positions. One type of vertical tube aeration system known as the Grain Guard Rocket has a hollow center core to increase the amount of available air flow into the grain and to reduce the obstructive nature of the unit by allowing grain to flow downwardly through the hollow center during unloading of the bin. A significant problem with vertical aeration units is structural failure during unloading of the storage bin. When hopper bottom grain bins are unloaded, the downward movement of the grain exerts high forces on all surfaces which contact the grain. Thus, an aeration unit within the grain bin must be able to resist these forces under a variety of conditions, or be subject to structural failure.
There are two types of bulk grain material flow during unloading of hopper bottom bins, either funnel flow or mass flow. In funnel flow, the grain material forms a reverse cone as it is unloading and tends to draw from the center of the bin with the particulate material falling away from the side walls of the bin, rather than sliding down the side walls. In mass flow, the grain tends to unload without forming a reverse cone in the center, and the material moves downward in the bin in a mass form that creates much greater drag on the side walls of the in. The controlling factor to determine mass flow versus funnel flow is the slope of the bottom cone of the hopper bin. With grain, funnel flow normally occurs with hopper slopes of 45° or less, while mass flow occurs with hopper slopes of 50° or more. The actual angle at which the flow changes from funnel to mass is affected by the type of stored commodity and the rate of unload.
The “Rocket” vertical aeration systems sold by Edwards Grain Guard of Alberta Canada, normally perform well when installed in a hopper bin that stores common grain commodities, such as cereal grains, and the bin unloads with funnel flow. However, the failure rate is high when vertical units are installed in a steep cone hopper bin where mass flow is present. The structural failure arises, since the inside and outside walls of the hollow vertical tube do not have sufficient strength to resist the vertical forces that are created from the boundary layer drag during unloading. While the light gauge sheet metal used in conventional vertical aeration systems may survive the vertical forces as long as the unit remains absolutely vertical, these units are also subject to relatively high horizontal and bending forces during unloading. The physical weight of the grain against the walls of the vertical tube can create deformations that destroy the vertical alignment of the light gauge walls, and significantly reduce the load carrying capacity of the tube. Then, the walls are crushed and the structure fails.
Another problem with vertical bin aeration systems is the inability to retrofit such systems into existing bins. Typically, the sheet metal walls which form the cylindrical tube are factory assembled using rivets and self-drilled sheet metal screws, which are not reasonably feasible to field assembly within a bin. Therefore, the vertical aeration system must be installed at the time of original manufacture or assembly of the grain bin.
Accordingly, a primary objective of the present invention is the provision of an improved vertical aeration system for use in a hopper bottom grain bin.
Another objective of the present invention is the provision of an improved grain bin vertical aeration system having a pyramid frame to withstand the unloading forces of grain from the bin.
A further objective of the present invention is the provision of an improved grain bin vertical aeration system having concave walls which are subject to tensile forces, rather than compression forces, during unloading of grain from the bin.
Yet another objective of the present invention is the provision of an improved vertical aeration system for bottom hopper grain bins which will withstand vertical and horizontal unloading forces.
Still another objective of the present invention is the provision of an improved vertical aeration system for grain bins which can be mounted in bottom hoppers having varying angles of slope.
Another objective of the present invention is the provision of an improved vertical aeration system for grain bins which can be retrofit into existing grain bins.
The improved aeration system of the present invention is intended for use in a grain bin having a sloped hopper bottom. The system includes a pyramid frame including legs with lower ends attachable to the hopper bottom. Base plates are pivotally mounted to the lower end of each leg so that the frame can be secured to hopper bottoms having different slopes. A cap covers the upper ends of the legs. Concave perforated walls are attached to the legs. Braces extend between the legs to provide structural support for the concave walls. An air duct extends upwardly and centrally through the bottom of the frame to supply air to the interior of the frame for flow outwardly through the wall perforations. The unit may be three sided or four sided.
The present invention is directed towards an improved vertical aeration system 20 having a pyramid frame 22 and concave walls 24.
The walls 24 are preferably made from sheet metal material. The walls 24 are perforated to allow air to flow outwardly through the walls. The perforations may be formed in the walls 24 in a conventional manner. The perforations may be punched holes 40 or elongated slots 42 (
The aeration systems 20, 20A can be preassembled and installed in a bin 10 during construction of the bin. Alternatively, the components of the aeration systems 20, 20A can be retrofit into existing bins through conventional openings in the bin.
An air duct 50 has a lower end connected to a conventional grain bin fan 52. The upper end 54 of the duct 50 is connected to a collar 56 centrally mounted between the braces 36 in the frame 22, so as to supply air from the fan 52 to the interior of the aeration system 20, 20A. By entering the frame 24 at a central lower position, air is supplied evenly through all the walls 24 to enhance drying of grain in the bin 10.
In use, the concave walls 24 of the aeration systems 20, 20A are subjected to tensile force during unloading of grain from the bin 10, and thus will not be crushed as in prior art tubular aeration systems having cylindrical walls which are subject to compressive forces during unloading. The concave, curved surface of the walls 24 will withstand the substantial loads induced by the stored commodity, including both horizontal and vertical forces. The internal braces 36, 38 provide additional structural support for the concave walls 24. The tapered or pyramidal shape of the frame 22 minimizes the volume within the bin 10 that is displaced when the aeration systems 20, 20A are installed, and also minimizes the horizontal footprint on the bottom hopper 16 of the bin 10, thereby reducing the drag and resulting vertical forces acting on the systems 20, 20A during unloading.
The height of the aeration systems 20, 20A may vary. For example, typical heights may range between 4-10 feet, to accommodate bins having various capacities. The holes or openings 40 in the walls 24 are formed in such a way so as to minimize or prevent clogging by the grain the bin 10. The thickness of the walls 24 may vary, depending upon the bin capacity. The top cap 48 provides a small surface area so as to minimize the vertical load on the aeration systems 20, 20A.
The introduction of air through the large diameter duct 50 in a straight upward line to the bottom center of the frames 22 minimizes back pressure and delivers the maximum volume of air to the aeration systems 20, 20A. The open interior of the systems 20, 20A also allows air to be evenly distributed to the perforations 40, 42 in the walls, from bottom to top, and thereby provide more uniform drying of grain in the bin 10.
The invention has been shown and described above with the preferred embodiments, and it is understood that many modifications, substitutions, and additions may be made which are within the intended spirit and scope of the invention. From the foregoing, it can be seen that the present invention accomplishes at least all of its stated objectives.