Grain drying and storage structure

A unique storage structure is described for drying grain as it is stored without movement of the grain and without forcing heated air through the grain. The storage structure includes a vertical tubular stack extending between the floor and the roof. A plurality of perforated tubes in close proximity to each other extend through the grain at an inclined angle and communicate with the vertical stack. Air from outside the structure flows upwardly through the tubes and out through the stack. A fan may be included at the top of the vertical stack to assist in drawing air upwardly through the tubes and the stack.

FIELD OF THE INVENTION 
This invention relates to grain storage structures. More particularly, this 
invention relates to drying of grain (i.e., reducing moisture content) in 
a storage structure without movement of the grain and without energy 
consumption. 
BACKGROUND OF THE INVENTION 
When grain (particularly corn) is harvested it has a higher moisture 
content than desired or necessary for safe storage. The presence of too 
much moisture will cause the grain to become heated and therefore spoil 
during storage. Accordingly, harvested grain which contains too much 
moisture to permit simple bin storage must be dried (i.e., reduced in 
moisture content) to prevent spoilage. 
The most common and accepted techniques for drying grain have involved 
forcing heated air through the grain to absorb the excess moisture. 
Normally the air is heated by means of propane or natural gas burners, 
although it may also be heated electrically. This, of course, requires a 
very large amount of fuel to heat the volume of air necessary to dry grain 
in large bins. Furthermore, the heated air must be forced through the 
grain thoroughly in order to dry the gain in all parts of the bin. This 
requires the use of one or more large fans of high capacity. Operating 
such fans also consumes much energy. 
A common design for the type of bin utilizing the forced air drying system 
involves the use of a perforated floor through which the heated air is 
forced upwardly. Thus, moisture in the grain near the floor must be driven 
upwardly through grain above it, thereby making the grain wetter as the 
moisture moves upwardly. This creates a moisture front or bank that must 
be driven through all of the grain in the bin. This often limits the rate 
at which the bin may be filled because accumulation of too much moisture 
will cause spoilage of the grain. 
Although various types of bins have been proposed which permit some air 
ventilation, none of these structures are suitable for storage of high 
moisture grain (such as shelled corn). For example, U.S. Pat. No. 
1,817,270 describes a grain bin including a tubular air conducting stack. 
Hinged to the stack at each of two separate vertical positions are four 
arms or auxiliary ventilator members spaced 90.degree. from each other 
around the stack. This bin structure, however, does not provide for entry 
of outside air into the bin nor does it provide sufficient ventilation to 
prevent spoilage of grains with high moisture content. The portable grain 
storage tank described in U.S. Pat. No. 2,357,705 has essentially the same 
disadvantages, although it does allow for air to enter the bottom of the 
stack. A variation of this type of bin structure is described in U.S. Pat. 
No. 1,977,389, but it does not cure the basic deficiencies described 
above. 
Another type of bin structure is described in U.S. Pat. No. 2,645,991 
including a horizontal air duct extending through the bin and a number of 
vertical ducts extending through the bin and a number of vertical ducts 
extending upward from the horizontal duct. Fans at the outer ends of the 
horizontal duct force air into the system. However, there is insufficient 
air movement in the bin structure to enable high moisture grain to be kept 
therein without spoilage. 
Slightly different apparatus is described in U.S. Pat. No. 2,737,878 
including networks of ventilating pipes arranged horizontally at 
predetermined levels within the storage structure. Compressed air is then 
forced through the horizontal tubes. In still another variation, described 
in U.S. Pat. No. 2,126,107, there are intersecting vertical and horizontal 
tubes within the structure. 
Another variation is described in U.S. Pat. No. 3,357,110 in which several 
(e.g., eight) tubes are vertically disposed within a cylindrical bin. The 
bin has an inverted cone bottom. A centrally located elevator lifts grain 
from the bottom of the bin to the top. The grain is then discharged onto a 
cone-shaped upper floor which enables the grain to slide off in all 
directions and downwardly within the bin. This structure, of course, 
requires movement of the grain in the bin. 
In U.S. Pat. No. 3,913,469 there is described yet another type of grain bin 
structure in which a plurality of vertical dividers separate the bin into 
a plurality of vertically extending grain cells. Each divider is defined 
by a pair of vertical air permeable side walls to provide a vertical air 
space between grain cells. 
None of the structures previously described provide the advantages and 
efficiencies provided by the storage structure of the present invention. 
SUMMARY OF THE PRESENT INVENTION 
In accordance with the present invention there is provided a grain storage 
structure which is adapted to dry stored grain. The structure comprises: 
(a) a floor portion; 
(b) a roof portion; 
(c) upright wall portions disposed between the floor and roof portions; 
(d) at least one vertical tubular stack extending between the floor and 
roof portions; 
(e) a plurality of elongated perforated tubes disposed between the stack 
and the wall portions at an inclined angle of at least about 60.degree.. 
The interior ends of the tubes communicate with the stack, and the spacing 
between adjacent tubes is no greater than about 18 inches. The storage 
structure is adapted to permit air to pass naturally upwardly through the 
perforated tubes into the stack and then through the stack and out of the 
storage structure. 
Because the perforated tubes are inclined upwardly between the walls and 
the stack, air naturally flows from outside the storage structure through 
the tubes to absorb moisture from the grain and then the air passes into 
the stack and upwardly out of the storage structure. In one embodiment a 
small fan may be included in the top of the stack to assist in directing 
the air out through the top. 
The techniques of the invention are applicable to square and rectangular 
storage bins of all sizes as well as circular bins. Normally there are a 
plurality of stacks used in the square or rectangular bins. In such event 
the stacks are aligned in a parallel manner through the center of the 
structure. 
The storage structures of this invention are particularly well suited for 
the storage and drying of high moisture grain directly after harvesting. 
For example, corn typically has a moisture content of about 20 to 30% when 
harvested and cannot be stored in conventional storage structures without 
having the moisture content reduced to about 13 to 15% in order to prevent 
spoilage of the grain. With the use of the storage structures of the 
present invention, grain having high moisture content can be stored safely 
and effectively. Because of the unique design of the storage structure the 
grain is dried during storage without undesirable spoilage. Furthermore, 
the grain is dried in a very economical manner since the techniques of 
this invention do not require the use of fossil fuels or electricity to 
heat air or to force such heated air through the grain as is required by 
conventional techniques. 
The techniques of this invention are applicable to storage structures of 
all sizes. That is, the length, height and diameter of the structure may 
vary so long as the perforated tubes are adapted to extend through the 
grain in the manner described herein.

DETAILED DESCRIPTION OF THE INVENTION 
Thus, in FIGS. 1 and 2 there is shown a storage structure 10 of the 
invention having roof 12, upright wall portions 14, and floor portions 16. 
In this embodiment the floor portions 16 are sloped from wall portions 14 
inwardly and downwardly. Frame members 18 support floor portions 16, as 
shown. 
There are a plurality of tubular stacks 20 disposed vertically between the 
floor and the roof. The stacks 20 are parallel to each other and are 
normally positioned midway between wall portions 14. The diameter of 
stacks 20 may vary. When the storage structure has a width in the range of 
about 14 to 16 feet the diameter of each stack 20 is normally in the range 
of about six to about eight inches. Larger stacks may be used if desired. 
Each stack is hollow and typically has a uniform diameter along its 
length. 
A plurality of elongated perforated tubes 22 are disposed between each 
stack 20 and wall portions 14 at an inclined angle, as shown. Tubes 22 
thus extend through the grain stored in structure 10. The interior ends of 
tubes 22 communicate with stack 20. The outer ends of tubes 22 in this 
embodiment extend to wall portions 14 and are capable of receiving air 
from the outside of structure 10 through appropriately positioned openings 
in the wall portions. Tubes 22 thus carry air from outside structure 10 
through the grain to absorb moisture and then the moisture-laden air 
proceeds into stack 20 where it proceeds upwardly and out of the storage 
structure. Because the floor is sloped in the embodiment shown in FIGS. 1 
and 2 some of the tubes 22 receive outside air through the sloped floor 
16, as shown. 
Tubes 22 may be metal or plastic cylindrical pipes, for example, which have 
a plurality of small openings or apertures therein which are smaller than 
the kernels of grain stored in the structure. The apertures enable air to 
pass therethrough. The diameter of tubes 22 may vary, e.g., 0.75-2 inches. 
A preferred diameter, however, is in the range of about 0.75 to about 1 
inch. The cross-sectional configuration of tube 22 may vary, e.g., it may 
be circular, oval, square, triangular, etc. so long as it has a bore 
therethrough which permits air to pass through it from one end to the 
other. 
Preferably tubes 22 are parallel to each other and are spaced no more than 
about 18 inches apart. More preferably they are spaced no more than about 
16 inches apart. If it is desired to store grain in the structure which 
has a very high moisture content (e.g., 30%), it is preferred that tubes 
22 be spaced about 12 inches apart so that the total air carrying capacity 
of the tube system is increased even further. 
The tubes are inclined from the walls to the central stack so that air 
flows upwardly through the tubes to the stack. The tubes are inclined at 
an angle of 60.degree. or greater (e.g., 70.degree.) to facilitate upward 
movement of the air. 
Moist grain in the structure has a tendency to become warm and as it does 
this the air tends to flow naturally upwardly through the tubes 22 and 
stack 20. The greater the degree of warming of the grain the greater the 
amount of air flow through the structure. The grain is cooled and dried by 
this air flow. Accordingly, grain spoilage is avoided. 
High moisture grain (e.g., shelled corn) can be kept in good condition so 
long as the temperature of the grain is kept below about 60.degree. F. The 
storage structures of this invention are capable of maintaining the moist 
grain below an unsafe temperature by circulation of outside air through 
the grain as described herein. Of course, as with prior techniques, the 
grain is screened before being placed in the storage structure in order to 
remove dirt, trash, etc. 
At the top of each stack 20 is a conventional rotatable vent cap 24. The 
cap prevents rain, etc. from entering stack 20. 
In a preferred embodiment, a small fan may be included near the top of each 
stack. The fan may be electrically powered or it may be operably connected 
to the rotatable vent cap 24 in such a manner that wind will power the 
fan. The purpose of a fan is to assist in directing and drawing moist air 
upwardly through the stack and out of the storage structure. This will 
tend to increase the rate of air flow through tubes 22 when the grain 
contains a high amount of moisture, for example. 
In a more preferred embodiment temperature sensors may be operably 
connected to each fan in such a manner that they will activate the fan 
associated with each particular stack in any area where the grain has 
become heated to an undesirable temperature (e.g., 70.degree. F.). In this 
manner only the fans at the top of those stacks near the heated grain are 
activated to increase the air flow in the area where it is needed. 
The size of the fans is typically small (e.g., six inches) and they may be 
each powered with a small electric motor (e.g., less than 0.25 
horsepower). 
The storage structure may be emptied, for example, by means of conveyer 19 
extending the length of the structure. A plurality of removable plates in 
the lowermost portion of the storage structure may be removed as needed in 
order to enable the stored grain to flow onto the conveyer. 
The rectangular storage structures are normally about 14 to 16 feet in 
width and up to about 60 feet long in order to permit transport of the 
structures along roads and highways. Several of the structures may be 
positioned in end-to-end fashion, if desired, at the intended storage 
site. 
In FIG. 6 there is illustrated an alternative embodiment in which the outer 
ends of perforated tubes 22 do not extend through the wall. In this 
embodiment the outer ends of tubes 22 communicate with a vertical conduit 
26 adjacent to the wall 14. Conduit 26 is adapted to permit outside air to 
enter (normally through an opening in wall 14), and the air is then able 
to pass into each of the tubes 22. The advantage of this embodiment is 
that it is not necessary to provide an opening in wall 14 for each tube 
22. Rather, since the outer ends of tubes 22 communicate with vertical 
conduit 26, it is only necessary to provide an opening to conduit 26 from 
the outside. This reduces the number of openings required in wall 14 and 
accordingly facilitates installation of the system in existing storage 
structures (which may be of the rectangular type, the circular type, or 
any other configuration). Furthermore, the integrity of the wall 14 is 
less affected by this embodiment. Such a conduit 26 is associated with 
each set of tubes 22, of course. 
Vertical conduits 26 may be of various sizes and cross-sectional shapes. 
For example, they may be cylindrical or they may be rectangular, oval, 
etc. in cross-section. The diameter may also vary. Typically a diameter in 
the range of about 2 to about 4 inches is adequate for most common size 
storage structures. 
In another embodiment of the invention the outer ends of tubes 22 may be 
provided with caps or covers so that air passage into the tubes may be 
discontinued when the grain in the storage structure has been dried to the 
desired extent. For example, shelled corn need not be dried below about 
13% moisture content. In the embodiment shown in FIG. 6, the cap or cover 
may instead be provided at the outside opening to each conduit 26. 
In FIGS. 7 and 9 there is illustrated one type of closure means 50 which is 
in the form of an elongated strip having a plurality of spaced apertures 
52 therealong which register with the ends of the perforated tubes 22 
extending through the wall 14 of the structure. The strip may be held 
against the wall 14 by means of clips 54. When the apertures 52 register 
with the ends of tubes 22 air may pass through the tubes. When the strip 
is moved vertically (illustrated in FIG. 7 as 50A), air is prevented from 
entering the tubes 22. 
In FIG. 8 there is illustrated a closure means which is useful in 
connection with the type of storage structure shown in FIG. 6. Adapter 60 
is fastened to the end of the outlet on vertical conduit 26. A sliding 
door 62 may be moved downwardly to close off the opening into conduit 26 
when it is desired to stop further air flow into conduit 26. 
In FIG. 5 there is shown a cross-sectional view of another embodiment of 
perforated tube 23 which is useful in the present invention. In this 
embodiment the perforations or apertures 28 through tube 23 are not 
present on the underside of the tube. Accordingly, when moisture condenses 
inside tube 23 the water will run down the tube (because of the solid 
underside) and exit the storage structure through the wall where the tube 
communicates with the outside. This prevents the condensed moisture from 
draining into the grain. 
In FIGS. 3 and 4 there is shown another embodiment of storage structure 30 
of the invention having roof 32 and wall 34. There is a central vertical 
tubular stack 36 disposed between the roof and the floor. A plurality of 
inclined tubes 38 extend between the wall 34 and stack 36. Tubes 38 are 
inclined at an angle of at least 60.degree. or more. The spacing between 
tubes 38 is similar to that described above in connection with the 
embodiment of FIG. 1. Air enters the storage structure through the ends of 
tubes 28. Air may also enter the structure through the floor, as shown by 
the arrows. 
Central stack 36 is generally cylindrical and normally has a diameter of 
about 30 inches when the diameter of the storage structure is about 50 
feet. The top of the stack may be provided with a rotatable vent cap 40. 
Near the top (normally powered by an electric motor which is less than 
about 2 horsepower). If desired, temperature sensors may be operatively 
associated with the fan so that it is activated when grain in any area 
becomes too warm. 
In another embodiment the fan may be adapted to be driven by the force of 
the wind acting upon rotatable vent cap 40. The embodiment of FIG. 6 may 
also be utilized in order to reduce the number of required openings in 
wall 34. This is important, for example, when adapting the techniques of 
the present invention to existing structures. 
The storage structures of this type may be emptied by means of conventional 
augers, etc., if desired. They may be filled through appropriate openings 
in the roof of the structures. 
Other variants are possible without departing from the scope of the present 
invention.