Note: Descriptions are shown in the official language in which they were submitted.
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AERATED STORAGE BIN FOR CROP MATERIALS
FIELD OF THE INVENTION
This invention relates to an aerated storage bin for crop materials and
to a method for manufacturing the bin.
BACKGROUND
Conventionally a storage bin for crop materials comprises a cylindrical
bin wall which is generally but not always mounted upon a cast concrete pad
which
is circular in plan view so that the bin wall is arranged adjacent to the edge
of the
concrete pad with the bin wall and the crop materials supported on the
concrete
pad.
The proper storage of crop materials within a bin of this type requires
careful management of the temperature and moisture content of the crop
materials
to prevent spoilage.
In climatic conditions where the air temperature surrounding the bin
can fall to temperatures below freezing, the wide ambient air temperature
variations
necessitate the use of aeration systems in the storage bin and this is
particularly
necessary for large storage bins (100 cubic meters or larger). Large bins have
a
larger diameter and therefore provide more opportunity for the development of
convection currents of the air within the interstices between the crop
materials. In
particular, warming of the crop materials adjacent the side walls of the bin
can
generate a rising air flow at the bin wall and a falling air flow in the
cooler crop
material at the center of the bin. This air flow can generate moisture
migration
reducing the moisture content in the area adjacent the wall and increasing the
moisture content in the area at the bottom of the center of the bin. This
moisture
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migration, unless carefully controlled and managed can cause significant crop
spoilage.
In view of this natural process, aeration systems have become more
common in bins installed in recent years, particularly the larger size bins
which have
become more popular.
The general purpose of an aeration system is to produce the lowest
practical temperature and the least temperature variation within the stored
grain.
The amount of air required to change the temperature of the grain will produce
very
little change in moisture content. Aeration is not a grain drying system and
should
not be considered as such. Under ideal weather conditions some drying occurs
during aeration but the low air flows used are not sufficient for reliable
safe storage
of grain that is more than 1 per cent above "dry", unless grain temperatures
are near
or below 0° C. The air flow rates for aeration are normally 1 or 2
liters of air per
second per cubic meter of grain. The necessary rates for drying grain are
significantly higher than this.
An aeration system can comprise a full false floor mounted above the
base pad or a partial pit formed within the concrete pad of the bin with a
duct
extending from the pit to a fan outside the bin which draws ambient air and
pumps
the air through the duct into the pit. The pit is covered by a perforated
floor structure
generally in the form of a plurality of parallel planks laid over the pit with
perforations
in the planks providing means for passage of air to enter the crop. The pit
arrangement offers the advantages of more volume in the bin for crop storage
and a
lower manufacturing cost for the floor..
Conventional pit shapes are shown in a book entitled GRAIN
AERATION AND UNHEATED AIR DRYING by Manitoba Agriculture Agtex 732-1
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Revised October 1987. The simplest form of pit is simply a single elongate
duct
along a diameter of the concrete pad with that duct extending outwardly to the
fan
beyond the bin wall. A further arrangement uses a second duct or channel
across a
diameter 90° to the first. A further alternate arrangement is Y-shaped
in which the
pit is formed as two ducts converging to an apex at the duct communicating to
the
fan. These shapes are generally somewhat unsatisfactory in that it is desired
to
maximize the amount of floor area taken up by the pit. Another common shape
which has been adopted is that of the square pit which is located within the
area of
the pad. However all of these arrangements have some disadvantages in that the
concrete tends to crack at the corners of the ducts or pit. Furthermore it is
very
difficult to effect leveling of the concrete floor in and around the pit and
to form the
ninety degree corners of the pit. Uneven leveling of the pit base can lead to
failures
in the perforated floor due to highly concentrated loads.
SUMMARY
It is one object of the present invention, therefore, to provide an
improved aeration bin of this general type.
According to a first aspect of the invention, therefore, there is provided
an aerated storage bin for crop materials comprising:
a cylindrical bin wall;
a concrete base pad cast on a supporting ground surface;
the base pad defining a horizontal upper surface on which the bin wall
sits so as to be supported thereby, with the bin wall arranged around an outer
edge
of the base pad;
the base pad being arranged for supporting the crop material stored
within the bin wall and on top of the base pad;
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a pit formed in the base pad so as to be recessed from the horizontal
upper surface of the base pad;
a perforated floor covering the pit for supporting the crop material while
allowing passage of aeration air through the perforated floor into the crop
material;
and a duct connected to the pit for communicating aeration air from a
fan to the pit for passage through the floor;
the pit being shaped to define in plan view a smoothly curved outer
periphery such that a portion of the horizontal surface of the base pad
between the
outer periphery of the pit and the bin wall is substantially ring-shaped.
Preferably the pit is circular in plan.
Preferably the pit has a depth at least equal to the thickness of the
concrete such that the pit is formed through the concrete to a supporting
surface
which can be the ground or a preferred recessed cast concrete pad.
Preferably the duct is formed in the base pad and extends from the pit
through the base pad to an outside edge of the base pad for connection to the
fan.
Preferably the floor is substantially co-planar with the upper surface of
the base pad.
Preferably the floor comprises a plurality of planks.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate an exemplary
embodiment of the present invention:
Figure 1 is a plan view of a grain bin according to the present invention
with the roof removed.
Figure 2 is a cross-sectional view along the lines 2-2 of Figure 1.
Figure 3 is a cross-sectional view along the lines 3-3 of Figure 1.
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Figure 4 is a cross-sectional view similar to that of figure 2 showing the
formation of the cast concrete pad.
DETAILED DESCRIPTION
The crop storage bin illustrated in the figures comprises a cylindrical
bin wall 10 and a concrete pad 11. The details of the bin wall are not shown
since
these are well known to ones skilled in the art and various arrangements and
designs of bin wall together with the connection of the bin wall to the edge
of the
concrete pad can be used in accordance with design requirements. In one
arrangement, shown schematically in the drawing, the bin wall is attached to a
lower
angle 12 which extends inwardly and downwardly with the flange being bolted to
the
concrete pad by bolts 13 cast in the pad.
The concrete pad 11 is cast on a supporting ground surface 15 after
suitable leveling of the ground surface and removal of the top layer of the
ground
surface where required. The concrete pad is reinforced by suitable reinforcing
(not
shown) in conventional manner.
An aeration system for the bin comprises a fan 17 which is mounted
outside the bin and connects to a fabricated duct 18 which extends to the edge
of
the concrete pad.
In the concrete pad is formed a pit 20 and a duct 21 extending from
the pit to the fabricated duct 18. The fabricated duct 18 is bolted to the
concrete
pad at the duct 21 so as to direct air from the fabricated duct into the duct
21 for
communication to the pit.
As shown in Figure 1, the pit is shaped with a curved or circular
peripheral edge 22 at the upper surface 23 of the concrete pad. This defines
between the peripheral edge 22 and the outer edge 16 of the pad an annulus or
ring
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shape of the concrete pad which is of substantially constant width between the
edge
22 and the edge 16.
The duct 21 is relatively narrow in comparison with the diameter of the
pit, having a width sufficient only to define an air flow channel of
sufficient area to
accommodate the required air flow from the fan 17. The pit and the duct are
formed
by omitting the concrete in the area of the pit and the duct so that the
concrete is
cast mainly in the form of the ring surrounding the pit. The pit can be
recessed from
the ground surface as required to increase the depth of the pit. In most cases
the
pit will include a layer of concrete 30 which is relatively thin at the base
of the pit so
that the depth of the pit is determined by the difference in depth between the
upper
surface 23 of the concrete and the upper surface of the concrete layer 30 at
the
base of the pit. The layer 30 provides a support for the vertical loads
communicated
to the layer from the floor over the pit.
In one arrangement (not shown), around the edge of the pit the
concrete is recessed to form a shelf which has a depth from the upper surface
23
sufficient to accommodate a series of floor planks 25. The width of the shelf
is
sufficient to accommodate and support ends of the planks and in practice the
depth
will be of the order of 1 inch and the width of the shelf of the order of 3
inches. In the
arrangement as illustrated, the planks 25 are supported by a plurality of
cross-
supports 26 extending from the underside of the planks to the concrete support
layer 30.
The pit is covered by the planks 25 which are arranged side by side
across the pit. In order to provide the necessary circular shape to cover the
pit, the
planks are of differing lengths. The planks are perforated so as to allow the
passage of air from the fan 17 and the duct 21 into the pit and through the
flooring.
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The planks are well known and of complex interlocking cross section which is
not
described herein.
In an alternative arrangement (not shown), the pit is not exactly circular
but has a smoothly curved outer periphery so it could be slightly elliptical
or it could
have side portions which are straightened, provided there are no sharp corners
or
apexes in the outer periphery of the shape of the pit.
The use of a circular or curved pit has advantages that the floor area
covered by the pit can be maximized. In some cases, therefore, the amount of
floor
area of the pit can be increased from the conventional square pit of the order
of 35
to 44 per cent up to as much as 60 to 75 per cent of the floor area. This
increase in
floor area defined by the pit increases the air flow through the crop
materials so as
to provide an increased ability to manage the humidity and temperature of the
crop
material.
A further advantage of the annular shape of the concrete pad as
defined between the outer edge 16 and the peripheral edge 22 is that it is
simpler to
obtain a leveling of the cast concrete pad as it is formed between the
shuttering
defining the outside edges and the inside edges of the annular shape.
Turning now to Figure 4, the method of manufacturing the concrete
pad 11 including the pit floor layer 30 is shown.
This includes providing an inner form 40, which may be used in
combination with an outer form 41. Each form comprises a series of panels of
corrugated steel which are arranged end to end with the ends of two panels 40A
and
40B arranged to overlap as indicated at 42 and connected together by bolts 43.
The
panels 40A, 40B etc. thus form a cylindrical wall defining the inner form 40
for
defining the inner edge of the layer 11 and thus the outer periphery of the
pit at the
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edge 22 of the pit. The panels are supported relative to the ground surface 15
by a
plurality of vertical retaining pins 44 which are driven into the ground at a
right angle
upper end 45. Each panel 40A, 40B has a plurality of brackets or loops 46 on
the
outside surface for receiving a respective one of the pins 44 engaged through
the
brackets. The height of the form 40 on the pins can then be adjusted so as to
provide an accurate level of the upper edge of the panels so that the circular
upper
edge of the panels lies in a common horizontal plane.
At the upper edge may be attached a right angle flange 47 having a
vertical flange portion 48 and a horizontal flange portion 49 projecting
inwardly
across the top edge of the panels so as to define a band lying in a horizontal
plane.
This provides one preferred method for attaching flashing pieces on 70 (in
Figure 2)
used to span any gaps between the planking and the top surface of the concrete
pad 11.
The outer form 41 comprises a similar plurality of panels which are
bolted together as previously described to form a similar cylindrical wall
coaxial with
the form 40. The panels are similarly attached to vertical locating pins 49,
50 driven
into the ground in a ring surrounding the pins 44. Brackets 51 hold the panels
on
the pins as previously described again allowing the height of the top edge of
the
panels to be adjusted to lie in a common horizontal plane. A plurality of
supporting
bolts 52 are arranged at spaced positions around the form with an inner right
angle
end 53 for engaging into the cast concrete and an outer threaded end 54
projecting
through the form 41.
With the two forms in place, concrete is poured to form the layer 30
inside the inner form and concrete is poured to form the pad 11 between the
inner
form and the outer form.
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With the concrete so poured, the concrete can be accurately leveled
using a first screeding bar 60 mounted on a central swivel pin 61 and a second
screeding bar 62 mounted on a second central swivel pin 63.
In view of the fact that the forms 40 and 41 are both cylindrical,
rotation of the screeding bars 60 and 62 about the centre of the bin causes
the outer
end of the respective screeding bar to sweep around the inside surface of the
respective form.
Thus the layer 30 is leveled accurately simply by sweeping the
screeding bar 60 around the pin 61 so that the concrete is leveled and swept
out to
the form 40 to accurately engage the form 40 at the bottom end of the form 40
and
to provide a proper laying of a consistent pad which is thus resistant to
deformation
and cracking.
The pad 11 between the inner and outer forms can be leveled by
sweeping the screeding bar 62 across the top of the flange 47 and this again
accurately and consistently forms the layer of concrete to form the pad 11.
There is
thus no necessity to manually move concrete into corners or to push the
concrete
toward the forms since the leveling action will automatically provide a
consistent and
effective layer properly leveled to the accurate height of the flange 47.
With the concrete in place and set, the forms may be left in position as
structural elements of the concrete pad for receiving the components of the
floor
and the bin.
Thus the outer form 41 acts as a support structure for the bin wall as
previously described. In addition the flange 47 as best shown in Figures 2 and
3
provides an attachment for a flashing 70 which overlies the horizontal flange
portion
49 and the edges of the planks adjacent the flange portion 49 so as to cover
the
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irregular space therebetween defined by the difference between the rectangular
planks and the circular inner edge of the horizontal flange portion 49. The
annular
planar horizontal flashing 70 is screwed to the flange portion 49 and to the
adjacent
portion of the adjacent planks by self drilling screws 71.
While one embodiment of the present invention has been described in
the foregoing, it is to be understood that other embodiments are possible
within the
scope of the invention. The invention is to be considered limited solely by
the scope
of the appended claims.
