Note: Descriptions are shown in the official language in which they were submitted.
BlN FOR STORING AND DISCHARGING
FREE FLOWING GRANULAR MATERIAL
Field of the Invention
The invention relates to bulk storage bins with fluid
pressure assisted gravity discharge for material in the bin
after it assumes its angle of repose.
Prior Art
Free flowing granular material, e.g. sugar, sand,
rice, etc. is often stored or contained in silos or bins
having rigid walls and bottoms made of metal or some other
rigid material. A discharge port is generally provided in
the bottom of such a bin or silo, which, when opened,
permits the material in the container to flow out. From
the discharge port, the material may be conveyed away by a
conveying means such as a screw conveyor. IE the bottom of
the silo or bin, extending from the discharge port to the
walls, is flat or horiæontal, not all of the free flowing
granular material will be discharged through the discharge
~ort by gravity. It is a characteristic of free flowing
2~ ~3ran~l1ar material contained in a flat bottomed bin or silo
to stop flowing out the discharge port when the material
remaining in the bin is at an angle of repose. The
material re~aining in the bin after discharge by gravity,
forms an invented partial cone shape inside the silo~ The
face of the of free flowing granular material, extends for
the discharge port in the bottom or wall of the silo upward
at an angle to the wall of the silo or bin.
To ensure the discharge of the entire contents of a
bin, bins have been provided with hopper bottoms~ ~hese
hopper bottoms have inclined sides, extending upward from
the discharge port at an angle towards the bin walls. The
angle at which the hopper botto~n projects from the
discharge port to the bin wall is sufficient to prevent the
material in the bin from resting at an angle of repose and
to direct the entire contents of the bin towards the
discharge port for removal. The shape of the bottom
concentrates the weight of the hopper on a smaller area
than a flat bottomed silo or bin of the same size. In
addition, a bin with a hopper bottom has a higher center of
gravity than the same sized bin with a flat bottom. A
hopper shaped bin is expensive and waste~ul of space.
The general concept of using pneumatically movable
flexible membranes inside a container to move materials in
the container is known. See, e.g~ W. German
Offenlegunschrift 270568~ ~1968). However none of such
prior art has, to applicants knowledge, suggested using a
dual-wall, flexible, cup shaped inflatable bag as the
storage bin with its inner wall moveable by pneumatic
pressure to cause stored materials to flow by gravity from
their angle of repose toward a discharge opening in the
bag.
Summ ~ Invention
The invention may be described in summary as: a bin
for free flowing granular material having a bottom
resting on a support member and a bin structural side wall
extending upward from said bottom and a penumatically
actuable flexible membrane for forcing the free flowing
granular material toward a discharge opening in the bin,
with the improvements comprising; a hollow, inflatable,
~5 flexible, generally cup shaped bag having an inner wall and
an outer wall with a discharging opening therethrough,
means for suspending the top of the bag from the side wall
and attaching the outer wall of the bag to the bottom of
the side wall, means for inflating the hollow flexible bag
after the bin has been partially emptied by gravity to
force remaining material to flow by gravity out the
discharge opening~ and means for deflating the hollow bag
and causing it to assume its original position.
3~:~
Detailed ~escription of the Drawings
Fig. 1 is a sectional elevation view partially
schematic of one embodiment of the storage and discharge
bin of this invention having a center discharge.
Fig. 2 is a fragmentary sectional elevation view of
a portion of the bin around the discharge opening shown
in Fig. 1.
Fig. 3 is a partial sectional elevation view of a
portion aro~nd the bottom outside edge of the bin shown
in Fig~ 1.
Fig. 4 is a detailed sectional elevation view of a
portion of the upper side edge of the bin shown in
Fig. 1.
Fig. 5 is a partial sectional elevation view, also
partially schematic, illustrating another embodiment of
this invention.
Fig. 6 is a partial detailed elevation view of a
portion of the embodiment shown in Fig. 5~
Fig~ 7 is a schematic side elevation view of another
embo~liment oE this invention and its controls;
Fig. 8 is a detail elevation view of a top cover of
the bir~; ,
Fig. 9 is a detail sectional view of the means for
attachment of the bag to the bin walls;
Fig. 10 is an elevation view looking along line 10-10
of Fig. 7;
Fig. 11 is a detail sectional elevation of the
discharge area of th~ bin;
Fig. 12 is a partial sectional elevation of another
embodiment of the invention;
Fig. 13 is a view taken along line 13-13 of Fig. 12;
Fig. 14 is a partial sectional elevation of another
embodiment of the invention;
Figs. 15A 15F are a series of schematic views showing
the sequence of conditions and actions in unloading the
bin.
Fig. 16 is a schematic side elevation of another
embodiment of the side unloading bin of this invention.
Figs. 17A-17D are a series of schematic views showing
the sequence of conditions and actions in unloading the bin
of ~ig. 16.
Figs. 18A-18F are a series of schematic views showing
the sequence of conditions and actions in deflating the
flexible cup shaped bag~
Fig. 1~ is a schematic view of a safety pressure
relief system for the bag.
Detailed Description of the Preferred Embodiments
~ s shown in Fig. 1 a storage bin 10 for storing and
discharging free-flowing granular material is provided
with an inflatable, double-walled, flexible cup-shaped bag
12 having an inner wall 14 and outer wall 16. The bag 12
provides a bottom 18 and side walls 20 of a flexible bin
for storing free-flowing granular materials which may be
discharged through a discharge opening 22.
The bin rests on a 100r ~4 having an opening 26 to
accommodate discharge of the materials Erom the bin. A
discharge conduit 30 with any suitable type gate or valv~
valve means 3~ may be utilized to control the discharge o~
material from the bin.
To discharge the free flowing granular material
from a bin constructed in accordance with this invention
the gate 32 of the discharge opening 26 must be opened.
The contents of the bin may then flow out the opening to be
carried away by a conveying means, such as a screw
conveyor (not shown), or to be discharged into a moveable
container for transport to a different area. The free
flowing granular material will continue to flow out oE the
bin through the discharge port by gravity until the angle
of repose for the particular material in the bin is
reached, or nearly reached. At the angle of repose, the
inner face R of the free flowing material assumes an
.2
inverted cone shape with its apex at the discharge opening
and discharge of the material by gravity stops.
To overcome the angle of repose and complete the
discharge operation, air under low pressure is forced into
the bag 12 between the inner and the outer walls~ The bag
12 begins to inflate at the top of the bin and bulge
inwardly towards the center of the bin. This inflation
forces the free flowing granular material nearest the top
of the inverted cone to cascade down towards the discharge
opening by gravity. The pneumatic pressure within the cup
shaped bag needs to be relatively low, e.g. about 1/4 to 1
psi, sufficient to overcome the limited resistance caused
by the small quantity of granular free flowing material
at the top of the inverted cone.
As air continues to inflate the bag, the inner wall 14
extends further towards the center of the storage area
until full inflation is achieved and substantially the
entire contents of the bin are discharged through the
discharge opening.
The flexible cup-shaped bag 12 is anchored adjacent
the discharge opening to a stationary member such as the
~loor opening 26 or conduit 30. In the embodiment
illustrated in Fig. 2 it is anchored to the conduit 30 b~-
means of a flat annulus 34 and a flange 36 forced together
by a nut and bolt 38 to sandwich the ends of the inner and
outer bag walls 14 and 16 adjacent the discharge opening
22. To assist in the anchoring a rope 40 may be secured to
the end of the inner wall 14 by an extra loop of material
and a heat seal 42 provided, as illustrated in Fig. 2.
The outer edge of the bottom portion and lower side
wall of the cup-shaped bag 12, and particularly the outer
wall 16, are anchored to the floor 24 as shown in detail in
Fig. 3. Also, the inner wall 14 may be o~ such size as to
require an additional portion of the inner wall to be
cemented or heat-sealed to the bottom portion as shown at
heat seal 44. The outer wall 16 is looped around a rope 46
and doubled back and heat-sealed at 48. A stud 50
extending from floor 24 has a nut 51 screwed down against a
flange 54 of a corrugated side wall 52 sandwiching the
vottom edge of outer wall member 16 between the flange 54
and the floor 24.
The anchoring arrangement shown in Figs. 2 and 3
assists in preventing the flexible wall bag from tilting
due to large forces of the stored material if it shifts
due to loading or unloading. Additionallyt wall 52,
which may conveniently be corrugated material such as
used for grain bins, Earm buildings or the like, provides
some lateral load support for the outer flexible wall 16.
The wall 52 extends upwardly as shown in Fig. 1 and
surrounds the outside of the flexible cup-shaped bag 12.
There is provided an opening 54 into the space
between the walls 14 and 16 near the top of the side
walls o the bag for inflating the bag 12. There is also
an exhaùst opening 58 near the bottom of the side walls
between the walls of the bag as c;hown in Fig. 1.
As shown in Fig. 4 r the corrugated side wall 52 has
a top flange 60. A suitable means for provlding slack at
the upper portion of the side walls to assist in the
dischar~e includes a slack loop 62 in the upper end of wall
1~ which is held up by means of a heat-sealed or cementea
loop 64 of fabric material, an O-ring 66 and a coil spring
68 hooked to the O-ring and to a support 70. A hcop 72 is
secured to the side wall 52 by a nut and bolt 74 to provide
support from the side wall for the outer flexible wall 16.
A rope 76 and heat seal arrangement similar to that
previously described is also provided as shown in Fig. 4.
An extension of the outer flexible wall 16x may extend
upwardly over flange 60 and be sandwiched between flange 60
and spring support 70 and secured by nut and bolt 77.
As shown in Fig. 1, material may be placed into the
storage bin via an inlet chute 78 which may be supported
from building structure, not shown, and connected to
tension cables 80 extending to the spring support 70. A
fabric roof 82 of a material similar to that from which the
flexible walls of the flexible wall bag are made is
provided to cover the top of the bin. The roof has a
one-way vent 84 which will allow air to escape rom the bin
when the bin is being filled, but will not allow dust or
particulate material from the granular free-flowing
material to escape.
The slack provided by slack loop 62 assists in the
inflation of the bag to discharge the flexible
free-flowing material from its angle of repose R in
Fig. 1. After material is discharged down to the angle
of repose R, fluid under pressure such as air is blown
into inlet 56 which initially inflates the flexible loop
64 providing a good start for the flexible wall assisted
discharge of the material.
Another and alternative embodiment for providing
slack in the inner side wall at the top of the material
a~ter discharge to the angle of repose and to assist in the
discharge is shown in Figs. 5 and 6, where in the same
reference numbers indicate the same parts as previously
described. Figs. 5 and 6 show, however, a separate
lnflatable annulus or tire 86 with a separate inflation
openin~ 88. The tire may be inflated to create a bulge or
slack in the inner side wall 14 as shown in Fig. 5. The
side wall 14 is secùred to the corrùgated wall 52 by means
25 of hoop 72 and nut and bolt 74 as shown in Fig. 6.
A center discharge side-unloading bin which does not
re~uire a hole in the bottom of the supporting floor can be
accomplished by providing a false, or raised, floor to
create a discharge well at least in the discharge area of
the center of the bin and an elcngated, closed casing
conveyor extending from this raised discharge well to the
side of the bin.
The slack above the angle of repose near the top of
the flexible side walls of the cup-shaped bag eliminates
undue stress at that point during the initial inflation
period. The corrugated wall back-up support allows the use
of a lighter-weight fabric material and prevents puncturing
~8~
o~ the Elexible bags. The anchoring to the floor at the
outer corners of the outer wall prevents tipping or tilting
and is conveniently accomplished by securing this wall
under a flange of the corrugated wall.
Embodiments of the invention in side unloading form
are shown in Figs~ 7-18. Referring to Fig. 7, a bin 10' of
this invention is especially suitable and adapted for bulk
storage and handling (discharging) free flowing granular
material. The bin is supported on a floor or other support
12' having suitable strength to bear the load of the
material in the bin. The bin is constructed with side
walls 14' which are preferably light weiyht corrugated
metal of the type commonly used for farm grain bins,
buildings and the like. The side walls 14' have formed
therethrough a discharge opening 16' in the lower portion
thereof.
The bin is optionally provided with a suitable top 18'
which may be either metal or cloth and preferably has vent
means therein tnot shown) to allow venting of air from the
bin when it is being filled while preventing loss of dirt
size particulate material. A suitable loading chute 20'
may be supported from the upper floor 22', for example.
However, any suitable known mean~ can be used for p~lttiny
material to be stored into the bin.
The bin side walls 14' have flanges at both ends
including flange 24' around the upper periphery of the side
wall anc( flange 26' at the bottom edge of the side wall~
Within the bin there is an inflatable generally cup-shaped
bag 28' having an inner wall 30' and an outer wall 32'. A
portion of the outer wall 32' may be held beneath the lower
flange 26' of the side wall 14' and an upper extension of
inner bag wall 30' may be supported over the top of bin
side wall flange 24'. The bottom flange 26' is bolted or
othwerwise securely attached to the floor by conventional
securing means, see Fig. 3.
There is provided through the outer wall 12' of the
bag and wall 14' of the bin an inflation opening 34' and a
1 2
deflation opening 36'. Although the inflation opening is
shown near the top of the cup shaped bag, it can be at any
other suitable location.
The top of the double walled bag 28' is slanted and
the top of the two bag walls are clamped together by a
clamp 38'. This clamp spirals around the bin from a high
portion near the top of the bin opposite the discharge
opening 16' to a lower portion above the discharge opening,
see Fig. 7.
The clamp 38' is shown in detail in Fig. 9 and
includes a pair of metal straps 40' sandwiching the ends of
the inner and outer wall 30' and 32' and the end of inner
wall extension 42' therebetween. The assembly is clamped
together and clamped to the bin side wall 14' in numerous
locations by a nut and bolt means 44'. The ends of the
flexible material bags may have rope 46' around them for
securing in the clamp.
The inner and outer bag wal;Ls 30' and 32' may in some
instances be glued together so that they may not inflate in
2~ a generally triangularly shaped area 48' extendiny above
and outwardly ~rom the discharge opening 16', see Fig. 10.
This prevents the walls from separating upon inflation of
the bag. However, such adherence was not necessary in '~
handling sugar, and its use is optional. Both walls of the
?.5 bag 28' are sealed around the discharge opening by a plate
50' abuttin~ a~ainst a backup plate 51'.
A discharge shroud 52' shown in detail in Fig. 11
extends outwardly from the bin discharge opening a distance
sufficient so that the material in the bin can flow into
a discharge conveyor by gravity. The discharge shroud 52'
includes side walls 54', a top wall 56' and a bottom wall
58'. A transparent hatch 60' having a handle 62' is hinged
at 64' for closing the top of the discharge shroud and
providing access to material therein~ At the bottom of the
shroud 52' there is a screen 66' for screening the material
and a gate valve 68 which may be operated by handle 70'.
Below the discharge shroud and particularly below the gate
~i59~Ji~
valve 68' there is a screw type conveyor 72' in a conveyor
ho~sing 74' for conveying away material discharged.
Beca~Jse the discharge opening 16' is above the level of the
floor 12' a built up floor segment 7S' is provided.
For inflation and deflation of the bag there is pro-
vided a blower 76', see Fig. 7, having an outlet line 78'
with valves 80' and 82' controlling whether the outp~t of
the blGwer is directed to inflating the inflatable bag 28'
through line 86' or venting to atmosphere. Alternatively
the blower could just be turned on when air pressure is
required. Line 86' is provided with a check valve 88' to
prevent collapsing of the bag during an emptying cycle or
if the blower stops. There is a further line 87' con-
nected to deflation opening 36' leading back to the inlet
of the blower 76' and controlled by valves 90' and 92'. A
control box 84' is provided with suitable controls for con-
trolling valves 80', 82', 90' and 92'. The control box can
also be used to directly control the switching on and o~f
of the blower thus eliminating some o~ the automatically
2a controlled valving~ Manually controlled valves would then
be used to select either inflation or deElation.
In connection with the controls, there i9 a material
ir~dicator 94' of a commercially available type (e.g. Z-tr~n
level switch made by Dexelbrook Engineering) which indi-
cates when there is material flowing over it in the bin.This material indicator is positioned just adjacent the
discharge in an area just outside the normal boundary of
the material emptied to its angle o~ repose, and is con-
nected electrically to the control box 84', or to directly
control the blower.
A perforated vacuum hose 96' is positioned between the
walls o~ the bag 28' at the outside periphery o~ the bottom
to assure that the bag assumes its original position during
deflation~
In operation, the bin 10' of Fig. 7 is initially
~illed with the bulk material to be stored, e.g. sugar,
rice, corn, powders, grains, etc. This material should be
free Elowing material and of a type which can be handled
within the bin. Fig. 15A shows the bin loaded with
material. When it is desired to discharge material from
the bin, gate 68' is opened by virtue of pulling on handle
70' and the material flows out of the bin and o~t of the
discharge opening until such time as it approximates its
angle of repose and uncovers the sensor of bin material
indicator 94'. At this time the material is in the condi-
tion of Fig. 15B. When it senses no material the bin level
indicator 9~' gives a signal to the control box 84' to
start inflating the bag by relatively low pressure from the
blower 76'. The top of the bag 28' starts inflating by the
inner wall 30' bulging inwardly as shown in Fig. 15C. The
material continues to flow and the bag wall 30' continues
to expand as shown in Figs. 15D and 15E. During discharge
when the material covers the indicator 94' the inflation
stops, the check valve 88' holds the low pressure, and the
material discharges by gravity until it again uncovers the
indicator. This cycle is repeated during the discharge.
Near the end of the emptying cycle the inner wall 30' of
the bag 28' has raised off the bottom and lifted the small
amount o~ material remaining into the discharge opening,
see Fig. 9F, - ;~
For deflating the bag and causing it to assume its
original positionJ vacuum applied through perforated vacuum
hose 96' draws the bottom of the inner bag wall into the
bottom corners of the bin. Inflated torroidal tube 97' is
provided to assure that enough slack exists so that the
walls of bag 28' are not unduly strained when the bag is
again loaded with bulk materials.
If at any time during the discharge there was a
problem it could be inspected through transparent hatch 60'
and if access is required at the point of discharge the
hatch can be openedO Other transparent viewing areas can
be provided in the bin wall~
As a safety measure and to prevent overpressure on the
bag wall and consequent damage to the bag duriny the
12
discharge cycle a pressure relief means is included in the
blower system. Overpressure could occur if there were a
malfunction of the probe and/or blower, a blockage of
material near the probe causing it to misread material
flow, or a malfunction of the shut off switch over the bin
is completely emptied. An accurate, simple and inexpensive
pressure relief means for the very low pressures involved
(1/4 to 1 psi or about 6 to 28" water gauge) is shown in
Fiy. lg. A manometer 110 is connected to blower outlet 78'
via line 112, of the same diameter and having a check valve
114 therein. A vented collection connector 116 surrounds
the outer leg of t:he manometerO The system illustrated
provides a pressure relief at 22 inches of water because at
an~ higher pressure the water will be blown out of the
manometer into the canister. The check valve prevents
vacuum from sucking the water into line 78'. The manometer
can be easily refilled with water after a pressure relieE
blow out.
Figs. 12, 13 and 14 show alternative embodiments in
which, for various reasons, it is desirable to have the
discharge opening 16' several feet above the level of the
floor. In the Fig. 12 and 13 embodiments a false floor 90'
which may be installed on top of a honeycomb support 100'
is positioned to raise the level of the bottom of the bin
until a point just below the discharge opening 16'~
Fig. 14 represents another approach to the problem in
which the floor is a tapered false floor 102' tapering
upwardly from a point at the floor opposite the discharge
opening to a point above the floor and just below the
discharge opening.
The advantage of both the Fig. 12 and Fig. 14
embodiments is in having the discharge opening above the
level of the floor but not requiring the bag 28' to lift
relatively heavy weight of material being discharged any
significant distance.
Fig. 16 shows another and presently preferred embodi~
ment. The parts illustrated in Fig. 16 which are
3~
substantially the same as those in Fig. 7 bear the same
reference numerals. Fig. 16 for example has the same
dou~le walled slanted top cup shaped bag 28' clamped to the
walls by annular clamp 38'. Additionally, the embodiment
of Fig. 16 shows in more detail the inflatable tube 97'
with an inflation opening 99' therefor. This inflatable
tube or collar extends around the periphery of the bin
below the clamp 38'. By inflating tube 97' slack is
provided for the inner wall 30' of bag 28'. Thus, this
slack is needed when loading the bag with heavy material
which causes the bag to conform to the corrugations of the
outer wall 14'. By allowing such strain to be absorbed by
the air in the inflatable tube 97' s~rain is removed to a
large extent from the clamp 38' and walls of the bag.
Additionally, inflatable tubes 102' and 104' may be
placed at levels above the clamp 38' and provided with
suitable inflation openings 103' and 105' for further
assisting in the discharge of the materials if the top end
of the inflatable bag does not reach the top side of the
bin opposite the discharge opening.
In the Fig. 16 embodiment a screw conveyor 106'
extends radially from the bin at an angle to the floor to
provide discharge at a suitable level to equipment, furt~Jer
storage, etc. I'his conveyor is beneath a built up false
floor 108' also extending at an angle across the segment of
the floor. A discharge opening 16' in the floor above the
conveyor is closed by a hand operated slide gate 110'~ The
indicator probe 94' is positioned above the discharge
opening 16' and a access opening 112' is provided to allow
inspection of the discharge area and access thereto.
In operation of this embodiment reference is had to
Figs. 17A-D consecutively. As shown in Fig. 17A the bul~
material M will flow by gravity at the discharge when the
gate llO' is removed and the conveyor 106' is operative.
To assist in discharge above the line of clamp 38' tube
102' is inflated, see FigO 17Ct and later tube 104' may be
inflated as in Fig. 17D.
14
In all embodiments the inner wall of the inflatable
bag is self cleaning. This is believed to be due to its
periodic flexing and the fact that the material always
flows by gravity without being lifted or forced by the bag
under high pressure.
Figs. 18A-~` illustrate the use of the perforated
vacuum tube or hose 96' and the inflatable bag during the
deflation and reloading of the bin. As seen in Fig. 18A
deflation is starting and vacuum is applied to perforated
vacu~lm hose 96' and at the same time inflatable tube 97' is
inflated to bulge it, see Fig. l~B. Therea~ter the bag
gradually assumes its original position fitting snugly into
the corners of the cylindrical bin as shown in Figs. 18C, D
and E. However, the inner wall will be bulged out to
provide slack when loading the bin as shown in Fig. 18E.
Fig. 18F shows how this slack is provided and such is
useful in allowing the inner wall to conEorm to the
corrugations in bin wall 14' and otherwise stretch as
needed to fill voids when refilling the inner bag with the
bulk material to be stored. The inflatable collar 97' may
be inflated by the same power source that provides the
vacuum to per~orated vacuum hose g6'~
In the center discharge embodiment te.g. Fig. 1), the
sensing probe to control the inflation can be in a separate
hopper between the bin discharge and a conveyor. As shown
in Fig. 1 the discharge conduit 30 leads to a hopper 130
and is controlled by valve means 32 (which can also be a
slide valve positioned at the discharge opening 22). The
hopper feeds to a conveyor 132 for carrying the material
away. A probe 134 is similar in construction, function and
operation to probe 94' in the side unloading embodiment.
As can be seen the invention disclosed provides a
unique pneumatically assisted handling and discharge means
for granular free flowing material in which the bin for
storing the material is simple and inexpensively
constructed, it has uniform weight distribution over a
supporting floor and can automatically assist in
v~
discharging material beyond the angle of repose by
automatically inflating the supporting double walled bag.
~s compared with conventional bulk storage and hoppers the
present invention presents dramatic differences in size of
the silos required, shipping weight, erection time
equipment and costs, floor loading, maintenance and cost.
