Note: Descriptions are shown in the official language in which they were submitted.
RAIN LIFTING AMD DISCHARGE APPARATUS
ACK~ROUND OF THE IN~ENTION
For many years, it has been necessary to lift
~rain an~ discharge it into various kinds of
S receptacles, such as storage bins, silos, hoppers and
the like. This has been done by belts to which have
bePn attached metal buckets for carrying the grain~ ~he
belts have run at high speed over a pair of vertically
spaced pulleys. The buckets on the belt dip into a
reservoir of grain, which is usually continuously
replenished, and travel generally vertically upwardly.
At the top of the run of the belt, the belt travels over
the top or head pulley and returns downwardly thereby
throwing the grain ~rom the buckets into a collection
~zone or chute from which the grain is discharged through
a-spout into a desired receptacle.
Of major importance in the design of grain
lifting and discharge apparatus is the ability to
maintain a high volume throughput of material. Often,
the apparatus is required to maintain a flow rate of as
much as 60, ono bushels per hour. In order to achieve
such efficient operation, the buckets, which have
generally been of metal fabrication, are made to travel
at high speed. ~owever, the high speed causes excessive
dusting, grain damage and substantial wear and tear of
the apparatus. Heretofore, a high volume throughput
could not be obtained by the use of larger volume
buckets ~ravelling at a lower speed. This is ~ecau.se
commercially available belts are not presently capable
of withs~anding the stresses created by the increased
weight of larger metal buckets. Lower bucket speed is
desirable since it reduces wear and tear on the
apparatus and permits plug ~low, thereby reducing damage
to the grain.
Accordingly, it is a main object of this
~6~
invention to provide improved apparatus which can handle
substantial volumes of grain with less dusting, reduced
grain damage, and minimum wear and tear to the apparatus.
According to the present invention there is
provided an apparatus for conveying, lifting and discharging
grain by plug flow, with reduced dusting, spraying, damage
to grain and wear, the apparatus being adapted to run at low
belt speeds while maintaining high volume throughpuk.
The apparatus has a belt driven at speed S, a head pulley
having an effective diameter of D' inches and a tail pulley
with the belt being trained around the pulleys. A plurality
of buckets is mounted transversely of the direction of
travel of the belt, the buckets having a lip projecting
P inches from the belt, the buckets transporting the grain
at the speed, and discharging the grain b~ plug flow as
the buckets travel over the head pulley thereby minimizing
dusting, spraying and grain damage. I'he speed S has a
value from about .95 x ~ feet per second to about
69~5D' ~ ' + 2P
1.05 x ~D' + ~p feet per second. Driving means is provided
for moving the belt at speed S.
More specifically the invention comprises a
generally vertically travelling belt which may extend upwardly
more than 200 feet. The belt travels between the lower or
tail pulley located in the region of a grain reservoir or
boot and the upper or head pulley located adjacent a discharge
chute. The belt and pulleys are generally enclosed within
a housing. Attached to the belt at spaced intervals are
.~
-- 2 --
68~1
the buckets which may be lightweight urethane. The
buckets project outwardly a predetermined dis-tance
from the belt to the bucket lip. The diameter of the
head pulley, the speed of the belt, and the outward
projection of the bucket lip from the belt are all
correlated to achieve plug flow of grain from the buckets
thereby minimizing grain damage and dus-ting. A high
volume throughput can be maintained at much lower belt
speeds with resulting minimization of wear and tear on
the apparatus. The use of urethane buckets in the
apparatus combines strength and durability with light
weight so that the various features of the invention
can be enjoyed. More particularly, the urethane buckets
permit each bucket to
.
- 2a -
carry large volumes of yrain so that a high volume
throughput can be achieved in combination with plug flow
of the grain.
It will be understood that various equivalents
5 may he provided once the parameters of this invention
are perceived and these variations can be extrapolated
from the data provided in this Specification~ .
Plug flow and efficient operation has been
achieved in commercial operations at a belt speed of
about 450 feet per minute which i8 about one-half the
bel~ speed heretofore used in lifting grain. The belt
travels over a head pulley having a diameter of about 60
inches. The buckets are attached to the belt on 14 inch
centers by means of bolts~ The buckets are fabricated
from urethane, weigh about 30 pounds each, and project
outwardly from the bel~ to the bucket lip abou~ 1~
inches. Each bucket i5 about 29 inches wide and 13
i~ches deep, and has capaci~y of about 1.5 bushels (3100
cubic inches).
In the event that a different head pulley
diameter is used or that the bucket: extension from the
belt is changed, the belt speed should be adjusted to
achieve ~he desired grain flow. ~he point is that the
belt speed, the projection of the bucket from the belt
~o.the bucket lip and the pulley diameter are
functionally related to provide plug flow. The use of
urethane buckets permits the handliny of increased
volumes per bucket and thereby makes possible the
advantages of the invention.
Belts are commercially available in 60 inch
widths so that two buckets can be attached to the belt
in two rows~ The buckets in the respective rows are
s~aggered to achieve balance in operating. However,
this additiorlal row oE buckets is not a special feature
of this in~ention.
-
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a side elevational view of the
grain lifting and discharge apparatus of the invention
with portions broken away to show parts contained within
the housing.
~ IGURE 2 is a view taken along line A-A in
Figure 1 showing the buckets on the belt.
FIGURE 3 is a side view of the internal portion
of the top section of the grain lifting and discharge
apparatus of the invention showing the buckets
travelling over the head pulley and the grain being
discharged in the plug flow conditivn.
FIGURE 4 is also a side view of an internal
portion of the top section of a grain lifting and
discharge apparatus, similar to Figure 3, but having an
old~ small bucket design and showing the grain being
discharged in a rapid non-plug flow condition.
FIGURE 5 is a perspective view o~ a large
urethane bu~ket.
FIGURE 6 is a graph of belt speed as a function
of effective head pulley diameter for the generation of
plug flow from buckets having a 16 inch projection.
DESCRIPTION OF THE PREF RRED EMBODIMENT
Now referring to the drawings, there is
illustrated a commercial embodiment of the invention.
The apparatus c com~rises a casing 11, made generally of
12-~uage steel, which is generally rectangular in cross
section. At the bottom of the casing 11 is provided a
boot 13 which serves as a grain reservoir. Grain is
continuously fed into the boot by a feed spout 15. At
the top of the casing 11 there is provided a discharge
chute 17 which terminates in a discharge spout 19. The
~asing 11 is ~bout ~20 feet in height and is provided
throughout its vertical extent with access panels and
doors (not shown) for repair and maintenance purposes.
Journaled at the bottom of the casing 11 is a
bottom or tail pulley 21 and at the top of the casing 11
there is journaled a top or head pulley 23, which is
located above the discharge chute 17. A bel~ 2~, which
is commercially available, is trained around the pulleys
21 and 23. The belt 25 is driven in a conventional
manner by a 500 horsepower motox (not shown). In the
illustrated embodiment~ the belt 25 i5 60 inches wide
and is driven at a speed of about 450 feet per minute.
The diameter of the tail pulley 21 is not
particularly critical to the operation of the apparatus
o~ the invention but in the apparatus shown in the
drawings, is 42 inches in diameter. The diameter of the
head pulley shown in the drawings is ~0 inches in
15 diameter. As before indicated, the diameter of the head
pulley 23 is important in relation to belt speed and the
projection of the bucket lip from t:he belt surface.
Attached to the belt 25 are a series of
transversely mounted buckets 27 for picking up grain in
the boot 13, transporting the grain to the top of the
casing 11, and discharging the grain to the discharge
chute 17. In Figure 5, the configLlration of the bucke~s
27 i5 shown. The buckets 27 are relatively light in
weight, being fabricated from urethane, and weigh about
30 pounds eachO The rear wall 28 of each bucket 27 is
bolted to the belt 25. The buckets 27 are located on 14
inch centers. The buckets 27 are 29 inches wide and the
front wall 30 extends outwardly and is 16 inches from
the belt surface at its lip 31 which is an important
30 dimension for purposes of this invention. Gussets 42
provide the buckets 27 with strength and rigidity. The
buckets are 13 inches in depth.
The buckets 27 are dimensioned to provide a
grain capacity of 1.5 bushels (3100 cubic inches) and
35 front walls 30 of the buck~ts 27 are angled with respect
to the rear wall 28 to facilitate loading and emp~ying .
Because the bucket 27 has a depth of 13 inches, there is
a space of about 1 inch between the bottom of one bucket
~7 and the top of the following bucket. In the
apparatus, as shown in Fig. ~, ~here are two rows of
buckets 27 on the belt 25, thereby doubling the capacity
Qf the apparatus. The buckets 27 in each row are
staggered to provide balance to the belt.
I~ is also important that the buckets 27 be
10 made of a lightweight material that has the ability to
withstand wear during operation. One such material is
urethane. Urethane buckets provide a unique combi~ation
of features for this invention by allowing high volume
throughput at a belt speed slow enough to provide plug
lS flow.
In operation, the boot 13 is continuously fed
wi h grain to provide a reservoir of grain. The buckets
27 attached to the belt 25, enter the grain reservoir
and scoop up the grain as they move upwardly from the
tail pulley 210 The buckets 27 travel upwardly and over
the head pulley 23 causing the grain to be thrown from
the buckets 27 into the chute 17 and out of the spout
19. As the grain is discharged from the buckets 27, it
leaves under plug flow ~onditions (Fig. 3).
The plug flow condition of the grain flow, as
it is discharged from the buckets 27, is obtained by
correlating the belt speed, head pulley diameter and the
pxojection of the bucket lip 31 from the belt 25
surface. Buckets 27 loaded with grain 33 are shown
travelling upward toward the head pulley 23 on the
right-hand portion of the belt 25 in Fig. 3. By
correlating the above-mentioned parameters/ as the
bucket travels over the head pulley 23, the radial
acceleration on a kernel of grain located at the lip 31
of the bucket 27 is balanced with the acceleration due
to gravityO Ideally ~hen, the kernel of grain should
remain motionless with respect to the bucket 27 until
the orientation of the loaded bucket 27 has changed at
least 90. Some minor movement may, however, actually
occur prior to this time primarily due to the angled
relationship between the front 30 and rear 28 walls of
the buckets 27. In any event, as the bucket 27
continues its path over the head pulley 23, the angled
front wall 30 produces an outward resultant force from
the centrifugal force acting on the grain~ The grain is
then gently dischargedt en masse as a "plug" 35 into the
discharge chute ~7 (not shown in Fig. 3).
Plug flow should be compared with grain
discharge from conventional metal buckets 27' that have
generally been of smal~er dimensions and operated with
higher belt speeds to obtain comparable grain throughput
(Fig~ 4). The buckets 27~ travelling over the head
pulley at high speed ~end to "spray" the grain 33 in the
area of the discharge chute 17 (not shown in Fig. 4).
Thus, the grain kernels collide with one another and the
casing 11 causing damage to the grain and increasin~
dusting.
To correlate belt speed, head pulley diameter
and bucket dimensions for obtaining pluq flow the
following calculations are made. The radial
acceleration (A) on a kernel of grain is given by the
expression:
A= V~
where V = the tangential velocity of a kernel of grain
in feet per second as the bucket passes over the head
pulley; and
where R = the radial distance of a kernel of grain from
the head pulley center in feet.
~6818~
In plug flow the radîal acceleration A is e~ual
to the acceleration of gravity so
~2
or R = g = 32.17 ft./sec.
V = ~ R
A kernel of grain located at the lip 31 of the
bucket 27 (the furthest point from ~he head pulley
center) under goes the greatest radial acceleration. In
order to prevent the "spraying" of grain the radial
acceleration on a kernel of grain at this location is
balanced with that due to gravity. R is then a function
of the head pulley diameter, D (measured in inches), and
the projection of the bucket 27 from the surface of the
~elt 25 to the bucket lip 31, desîgnated as P ~measured
- in inches). In grain lifting and discharge apparatus
the belt 2S is often times up to one inch thick and the
head pulley 23 may be provided with lagging (not shown)
up to about an inch thick to help prevent ~elt
slippage. These two factors can substan~ially e~fect
the radial distance R so that the t:erm effective head
pulley diameter, D', as used herein is meant to include
the effect o~ belt thickness as well as lagging on R.
The radial distance7 R, is put in terms of effectiYe
head pulley diameter, D', and bucket projection, P, as
. ~ollows:
R =' 1 '[Dl + P] -- '('D'' -~' '2P)
12 2 24
Similarly, ~ is put in terms of D', P, and belt speed, S
~measured in ft.~min.), as follows~ -
60 [~~~
Therefore: 6S0 x ~ 8 -
69,5D'
S = _.
or r~
~ D~ ~ 2P
R~ferring now to Fig. 69 it can be seen tbat
the solid line represents belt speed, S, plotted as a
function of efective head pulley diameter~ D', for the
generation of plug flow from buckets having a 16 inch
projection, P. The two broken lines drawn on both sides
; . of the above mentioned solid line represent a
permissible plus or minus five percent deviation in belt
~peed for a given ef~ective head pulley diameter.
Experimentation has shown that a plus or minus five
percent deviation in belt speed from that predicted by
~he derived :Eormula will still produce plug flow
conditions. Accordingly, experimental examples A .
through D have been plotted in Fig. 6 and are explained
lS below.
In examples A and B plug f.low was obtained
through the proper correlation of belt speed and
effective head pu7ley diameter for a 16 inch bucket
projection~ In Example A, a grain lifting and discharge
apparatus was fitted with a 60 inch diameter head pulley
and a belt thickness of 3/8 inch thus yeilding an
ef~ective head pulley diameter of S0.75 inches. The
aparatus was operated at a belt speed of 430 feet per
minute and produced plug flow. In Example B, apparatus
~S having a 60 inch diameter head pulley, a belt thickness
of 3/4 inch and one inch lagging was operated at a belt
speed of 450 ~eet per minute. The effective head pulley
diameter~ D', in Example B was 63-1/2 inchesO Grain
discharge from the buckets in Example B was also in the
plug flow condition.
In Examples C and D9 apparatus having a 60 inch
8.~
--10--
diameter head pulley, a belt thickness of 3/8 inch and
no lagging failed to produce plug flow because of
improper belt speed. In Example C, ~he apparatus was
operated at a belt speed of 400 feet per minute. This
proved to be too low and the grai~ spilled out before
the buckets 27 reached the discharge chute 17 resulting
in a condition known as "back-legging". In Example D,
the apparatus was operated at a belt speed of 480 feet
per minute which resulted in excessive spraying and
throwing of the grain.
On the basis of Examples A through D, it was
determined that a deviation in belt speed (for a given
effective head pulley diameter and bucket projectio~) of
about plus or minus five percent from that predicted by
the derived formula will still produce plug flow of the
grain upon discharge fxom the buckets.
To further illustrate the predictability of
plug flow by the correlation of belt speed, bucket
projection and effective head pulley diameter a grain
lifting and discharge apparatus was fitted with a 42
inch diameter head pulley, a 3/8 inch thick belt, and
buckets projecting 14 inches from ~he belt surface to
the bucket lip. Plug flow of the grairl was observed,
through the use of high speed photography, at a belt
~peed of 340 feet per minute. This compares very
favorably with that predicted by the derived formula,
about 353 feet-per minute. The belt speed at which plug
flow was observed was within about 3.7 percent of that
predicted~
As was previously mentioned, the use of
urethane buckets permits the combination of high volume
grain throughput and plug ~low in the grain lifting and
discharge apparatus. Apparatus having a 60 inch
diameter head pulley and two rcws of ~he 1.5 bushel
capacity urethane buckets shown in Fig. 5 spaced on 14
~8~
= 11-
inch centers, operated at a belt speed of about 425 to
465 feet per minute has a throughput capacity of about
57,000 to 61,800 bushels per hour. Similarly, apparatus
having bucket dimensions and spacing ~s described above
and a 72 inch diameter head pulley, operated at a belt
speed of about 475 to 525 feet per minute has a
throughput capacity of about 63,000 ~o about 69,600
bushels per hours. These high volume throughputs are
obtained in combination with the reduced dusting and
grain damage attributable to plug flow.
It should be understood that although certain
preferred embodiments of the present inven~ion have been
illustrated and described, various modifications,
alternatives and equivalents thereof will beco~e
apparent to those skilled in the art and, accardingly,
the scope o~ the present invention sho~ld be defined
only by the appended claims and equivalents thereof.
Various features of the invention are set forth
in the following claims.
