U.S. patent number 3,870,627 [Application Number 05/309,896] was granted by the patent office on 1975-03-11 for mechanical screening device for machine-harvested sugar cane.
Invention is credited to John W. Herkes.
United States Patent |
3,870,627 |
Herkes |
March 11, 1975 |
Mechanical screening device for machine-harvested sugar cane
Abstract
A mechanical screening device for loosening extraneous material
from a mat of dirty machine-harvested sugar cane is made up of a
series of heavy toothed rolls of large diameter which are arranged
in parallel spaced relationshio on a rising incline. These toothed
rolls are power-rotated to move the mat up the incline, each
succeeding roll being driven at a speed about 15 percent faster
than the roll next to and below it on the incline thus thinning out
the mat as it travels up the incline. The spaces between the rolls
are sufficiently large that most if not all of the cane stalks as
well as extraneous material passes down between the rolls within
the length of the mechanical screening device. The roll teeth are
large with a straight leading edge having sufficient sweepback to
prevent jamming by rocks but sufficiently steep to strike the mat
decisively and impart a vigorous shaking to the cane.
Inventors: |
Herkes; John W. (Santurce,
PR) |
Family
ID: |
23200127 |
Appl.
No.: |
05/309,896 |
Filed: |
November 27, 1972 |
Current U.S.
Class: |
209/3; 209/146;
209/236; 209/672; 198/784; 209/233; 209/392 |
Current CPC
Class: |
A01D
45/10 (20130101); B07B 1/155 (20130101); A01D
33/08 (20130101) |
Current International
Class: |
A01D
33/00 (20060101); A01D 33/08 (20060101); A01D
45/10 (20060101); A01D 45/00 (20060101); B07B
1/12 (20060101); B07B 1/15 (20060101); B07b
001/14 () |
Field of
Search: |
;209/3,104,106,233,236,235,261,146,393,392 ;198/209,211 ;171/133
;130/276,31 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Lutter; Frank W.
Assistant Examiner: Hill; Ralph J.
Attorney, Agent or Firm: Walter; William B.
Claims
I claim:
1. In a mechanical screening device comprised of a set of spaced
parallel toothed cylindrical horizontal rolls arranged on a slope
and power-rotated to pass material deposited thereon up the slope,
with the teeth on each roll arranged in spaced rows and the rows of
teeth on each roll centered on the space between rows of teeth of
the adjacent rolls, the following:
a. each roller tooth has a substantially straight sweptback leading
edge of about 52.degree.;
b. the rows of teeth are so located as to provide a lateral space
between adjacent teeth of about 6 inches;
c. the roll spacing provides a space of about 12 inches between
adjacent rolls;
d. the mechanical screening device also comprises means to drive
the rolls at tooth tip speed of at least 350 feet per minute with
each roll after the first one to three rolls rotated at a tooth tip
speed which is about 15 percent higher than the next preceding
roll; and
e. the effective length of the mechanical screening device is at
least 21 feet;
whereby as a mat of dirty machine-harvested sugar cane is fed onto
the lower end of the mechanical screening device, sugar cane stalks
will be disentangled, extraneous material will be loosened from the
cane stalks removing large rocks from the mat and all but rocks
will progressively pass through the screening device, being spread
out in length and thus separated farther because of the progressive
increase in speed of the toothed rolls.
2. A screening device as claimed in claim 1 wherein said teeth are
formed in notched rings which are concentric to the rolls and
attached thereto in spaced relationship.
3. A screening device as claimed in claim 1 also comprising a rock
receiver beyond the upper end of the screen.
4. A screening device as claimed in claim 1 also comprising a rock
receiver at the bottom of the screening device.
5. A screening device as claimed in claim 1 wherein in each row of
teeth every other tooth is in the plane of the row, one of the
adjacent teeth in the row is bent so that the tooth tip is on one
side of the row plane and the other tooth adjacent to the tooth in
the row plane is bent so that the tooth tip is on the other side of
the row plane so that each row of teeth acts on a greater width of
material than if all teeth were in the same plane.
6. A mechanical screening device as claimed in claim 1 in which the
diameter of each roller is about 30 inches and the tooth tip
diameter is about 48 inches.
7. A method of preparing a mat of tangled dirty machineharvested
sugar cane for cleaning before extracting sugar comprising:
a. feeding the mat of tangled sugar cane off the end of a conveyor
at a maximum mat thickness of about 12 inches onto the lower end of
a mechanical screening device comprised of a set of spaced parallel
horizontal toothed rolls with the teeth on each roll arranged in
rows and the rows of teeth on each roll centered on the space
between rows of teeth of the adjacent rolls through which material
may pass;
b. rotating the rolls, to pass material thereon up a slope, at a
tooth tip speed of about 380 feet per minute on the first one to
three rolls, rotating each succeeding roll at a speed approximately
15 percent higher, thus disentangling the cane stalks and pulling
the portion of the stalks at the bottom of the mat and advancing
the stalks at a higher speed than those stalks not contacting the
teeth;
c. the tooth rolls progressively raking the bottom of the mat,
pulling individual stalks loose whereby cane stalks are spread out
into a thinner mat of separated stalks and fed through between the
rolls together with soil, sand, small rocks, and leaves from the
cane stalks as the mat passes over the rolls; and
d. any rocks mixed in with the cane are thus struck loose from the
cane and onto the top of the material to roll back down the slope
of the mechanical screening device into a rock receiver or driven
by the tooth rolls up into a rock receiver beyond the last roll.
Description
BACKGROUND OF THE INVENTION
Due to the rising cost of labor and transportation throughout the
years sugar companies in many parts of the world have had to
discontinue hand harvesting of cane in favor of harvesting by
machine. In hand harvesting the canes are manually cut at ground
level, the leaves and tops removed, and a bundle of clean cane thus
manually carried to a receiving station consisting of a cart,
flume, railcar or truck.
Because canes are tough they are not broken open except at the ends
in hand cutting, are only dirty at points where the stalk may lie
on the ground during its growth, or where stacked prior to
bundling, and contains no rocks because of hand bundling. Hand cut
cane is ideal for processing into sugar juices of acceptable purity
and clarity because of its cleanliness.
Because hand cut cane need not be washed and because it is not
broken open except at each end, very little juice is lost even if
transported to the factory in flumes.
On the other hand, machine harvested cane in some methods of
growing, and certain types of harvesting contains heavy amounts of
dirt, leaves, sand, and rock which become so intermingled with the
cane that much effort is required to prevent it from being carried
into the sugar extraction process.
Sugar growing and harvesting varies considerably from region to
region. In Australia varieties of sugar cane have been selected and
put into production, a principle characteristic of which is that it
grows erect. Although this type of growth is not uniform throughout
Australia, in fields of erect cane no cane is on the ground and the
stalks in each row present a vertical wall. Machines developed to
harvest erect Australian cane merely cut the cane off at ground
level, draw it back into conveyors in such a manner that the cane
is not bent or broken, and is not allowed to touch the ground
again.
While erect Australian cane, and sugar cane in many other areas of
the world is grown as a one year crop, usually on relatively level
ground, in Hawaii a very lush growth of cane selected primarily for
a high yield of sugar is grown as a two or three year crop. In its
growth this lush cane becomes in this period an intertwined mass of
canes which have grown up bent at all angles and lying on the
ground. In contrast to a one year crop of about 40 tons of material
to be harvested from each acre this lush two to three year crop
amounts to an average of about 150 tons per acre at a density of
approximately 13 pounds per cubic feet when piled.
Whereas a man can freely walk between rows spaced on 4'6" centers
in Australian cane at harvest time an experienced machine operator
in Hawaii sitting above the cane tops on his harvesting machine can
only speculate on the location of rows of cane similarly
spaced.
Ground conditions in which this cane is grown in Hawaii and
harvested includes steep hills, deep, soft, wet soil, soil mixed
with rock, rock with little evidence of soil, dry dusty soil and
dry dusty soil mixed with rock.
Machines generally used for production harvesting of the Hawaiian
cane are heavy push rakes mounted on the front of a heavy
track-laying tractor which literally bulldoze the cane across the
ground into mounds 6 to 12 feet in height, and in so doing pick up
a great quantity of wet or dry soil, rocks, and leaves. This
foreign material becomes attached and almost hopelessly entangled
in the intertwined and interwoven stalks of cane, which average 12
feet in length.
Other types of harvesting, V-cutting and grab harvesting similarly
result in much soil, rock, and leaves being intermixed with the
harvested cane. Where adaptations of the machines used to harvest
erect one year cane are used in Hawaii, using gathering devices to
pick up recumbent cane, much less soil and rock as picked up.
However, even this cane when harvested accumulates soil and leaves
which must be removed before final processing. The cane left behind
by each of these methods is swept up by much lighter tractors and
rakes.
This final ground clearing operation of machine harvesting is
responsible for the addition of a great proportion of dirt, sand,
leaves, and rocks to the product. In many wet, rocky, or hilly
areas trucks and trailers which will haul the cane to the factory
cannot be operated off the road infield. Field cranes with heavy
cane grabs are used to load hauling units from large piles on the
ground, handling up to two tons of material at a time. Oftentimes
such operations are repeated several times for the same material
and each time more dirt is accumulated, canes are bent and broken
open, and cane, rocks, leaves and dirt become more interwoven.
This cane is hauled in large semi-trailers of a unique design in
which the 15 to 30 tons of material is suspended in a chain net. To
unload the trailer one side of the net is raised so that the
material is raised therein and rolled over the opposite side of a
temporary storage area. This process can further entangle the cane
and foreign material and break open stalks in highly stressed
areas. A mill yard grab is next used to load the material, about 5
tons at a grab load, onto the factory conveyors.
This entire harvesting and hauling process has long been recognized
as a brute force method of getting the cane from field growing
conditions to harvested cane on factory conveyors and one which
thoroughly entangles, dirties, and breaks open the cane. Any soil,
sand, rocks and/or leaves remaining in the cane when fed into sugar
extraction processes not only increases the cost of processing, but
as the sugar juices are released from the cane stalk cells, the
foreign material becomes saturated thereby and methods used to
separate sugar juices from foreign material result in sugar losses
into the discarded foreign material. These losses of sugar are
extensive. In addition, repairs to factory equipment and time lost
when the factory is not operating because of emergency repairs due
to rocks is expensive.
A method commonly used to clean machine harvested cane as described
above has been to pass the cane being conveyed into the factory
through strong streams of water thus washing mud and dust away.
Disadvantages of this so called "wet cleaning" process are the cost
of the water and settling basins required to meet water pollution
standards and the loss of sugar washed off the broken mangled
cane.
For several years then, many attempts have been made to substitute
for the wet cleaning processes a waterless or dry cleaning process
using air blasts, peg tooth drums, and pocketed conveyors as shown
in U.S. Pat. No. 3,384,233 to Bolles.
Although somewhat successful, these dry cleaners have yet to take
the place of wet cleaners in any but experimental use in production
sugar factories.
A major step in the cleaning of cane, whether by dry cleaning or
wet cleaning processes is the separation of foreign materials from
the cane by releasing them from the stalk surface and disentangling
rocks, etc. from the blanket of material being conveyed into the
sugar extraction processes.
Machinery designed for this purpose for other food products has
included the shaker rolls used for cleaning of sugar beets as in
Rienk's U.S. Pat. No. 1,899,292, and Armer U.S. Pat. No. 2,997,086
and in the cane sugar industry "sunflower" rolls and "stooling"
drums. In each case the function of the device is to shake the
foreign material free of the sugar beet or sugar cane.
FIGS. 4, 5, 6, and 7 of the Armer patent are illustrative of the
theory of accelerating or tossing about of the sugar beet to shake
loose the soil adhering thereto, while at the same time allowing
the extraneous material to drop through the shaker rolls. Silver
shows another variation in his leaf catcher for beet dumps, U.S.
Pat. No. 1,895,268, in which beets, leaves and dirt cascade over an
inclined toothed open belt moving in a direction opposed to that of
the falling material onto a second inclined toothed open belt
moving in the same direction as the beets.
Although it would be of assistance to the sugar cane industry to
utilize the teachings of the prior art in the cleaning of sugar
beets for the cleaning of sugar cane, such is not possible because
of the great difference in the physical nature of the two products.
Sugar cane stalks range in diameter at their base to about 13/4
inches tapering to leaves at the end of the stalk which may be up
to 15 feet in length. Sugar cane stalks in Hawaiian culture are
seldom straight. Sugar cane stalks are strong, tough, and if not
burned prior to harvest, have much leaf growth. If burned, the
stalks will have less or possibly no leaves but will be more bent
from the heat. Cane stalks can hairpin around moving parts of cane
machinery, bunch up, and jam at the machinery unless especially
designed to reduce or eliminate jamming.
As stated above, some sugar factories have either "sunflower" or
"stooling" drums to assist in the cleaning process. In each case
the drums are power-driven rolls, driven in the direction of travel
of the material, and having spaced concentric plates attached
thereto. The spaced plates of the "sunflower" drums have large
gently rounded teeth in the form of a sine curve while the spaced
plates of the "stooling" drums have large sharp teeth, the leading
edges of which are radial. Because of the gentle form of the
"sunflower" drum teeth very little loosening of extraneous material
occurs as the dirty cane travels over them. The sharp teeth of the
"stooling" drums are more aggressive and more effective in their
cleaning. However, because of the radial leading edge, cane is
damaged and rolls are jammed with rocks, stools, and cane to break
drive components and thus requiring frequent shutdown of the entire
plant for repair.
A common practice in sugar factories to remove large rocks from
machine harvested sugar cane is to pass it through a trough of
water called a rock gap. Sugar losses into this water are expensive
and therefore an undesirable cost for removing rocks.
BRIEF SUMMARY OF THE INVENTION
This invention is a mechanical screening device having a series of
large, toothed, power-driven rollers in parallel spaced
relationship on a steep incline. The toothed rollers are driven at
a high speed in a direction as to propel material to be screened up
the incline as it is also progressively passed down between the
rollers. The roller teeth have an angle of sweepback sufficient to
allow material stuck thereby to not jam against adjacent rollers
and yet sufficiently erect to aggressively strike and raise the
material being propelled by the rollers. The preferred sweepback
angle is about 52.degree. from radial.
The primary object of this invention is to break up a mat of
machine-harvested sugar cane passing over and through it, thinning
the mat and loosening extraneous adhered and intermingled material
from the cane stalk so that other devices and apparatus can
separate the extraneous material from the sugar cane thus cleaning
the sugar cane.
Another object of this invention is to remove large rocks from the
mat of cane without the use of water.
Another object of this invention is when used with other apparatus
to clean mechanically harvested sugar cane using as little water as
possible while functioning in a reliable manner without much damage
to or breaking of sugar cane stalks.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings FIG. 1 is a schematic side elevation of one version
of my mechanical screening device.
FIG. 2 is a schematic side elevation of another version of my
device.
FIG. 3 is an enlarged plan view of a portion (three toothed rolls)
of my device in a plane parallel to the inclined plane of my
device.
FIG. 4 is an enlarged end view of two adjacent rolls in my device
to illustrate the intermeshing of the notched rings or teeth.
FIG. 5 is an enlarged side view of another version of notched ring
for use in my device.
FIG. 6 is a schematic side elevation of a version of my device in
which a few rolls each on a series of inclines provide a sawtooth
arrangement.
DETAILED DESCRIPTION OF THE INVENTION
The screening device 1 as shown in FIGS. 1 and 2 is so located that
harvested sugar cane 3 is deposited near the left end of it by
conveyor 4. The rolls 2 and driving arrangements 5 are supported on
a framework 6 so that the rolls are an angle of inclination of
between 20.degree. and 35.degree. from the horizontal. Where the
harvested cane 3 to be processed has been chopped into short
lengths before being deposited on the shaker and rock removal
apparatus 1 the angle would be about 20.degree. as in FIG. 1. If
the cane 2 has not been chopped and therefore mostly consisting of
long stalks it can be elevated on the shaker device 1 at a steeper
angle without excessive fall back and thus would be at an angle up
to 32.degree. as in FIG. 2. This steeper angle will assist in rock
removal and also allow for more rolls or a decreased length and
thus demand less factory area.
All rolls 2 are driven in the direction of travel of the cane 3 to
the right and therefore clockwise as shown in FIGS. 1 and 2.
If the blanket of cane 3 is fed onto the shaker rolls 2 from the
preceding conveyor 4 at a blanket velocity of 20 to 40 feet per
minute, which would be normal and preferable, the first roll 2 or
two would be driven at about 30 RPM or a peripheral speed such that
the tips of the roller teeth 7 will be traveling at approximately
377 feet per minute or about ten to twenty times the blanket speed.
Succeeding rolls 2 are then driven each at a speed of approximately
15 percent higher progressively so that the ninth roll will be
rotating at a top speed of 1,155 feet per minute.
One way of increasing roller speed progressively is that shown here
in FIG. 3 where the second roll 2 is chain driven by the first roll
2 with a 15 tooth driving sprocket 10 on the first roll and a 13
tooth driven sprocket 11 on the second roll.
In the arrangement illustrated here three 30 horse-power motors 12
are used to drive the entire assembly of shaker rolls 2.
The construction of the rolls 2 is as illustrated in FIGS. 3 and 4
simple and rugged with a series of 48 inch diameter notched rings
13 made of 3/4 inch steel plate welded coaxially to the outside of
a 30 inch schedule 30 pipe 14 which has a wall thickness of
five-eighths inches with the notched rings 13 spaced at 12 inches
on center. Tooth tips of the notched rings are thus 9 inches above
the roll surface. The ring spacing from the roll ends will differ
by 6 inches in alternate rolls 2 so that when assembled the rings
13 intermesh leaving a generous 111/4 inches opening between rings
13 on each roll 2 with the rings 13 on the next roll centered on
this space.
The 30 inch pipe 14 making up the cylindrical portion of the roll 2
is about as long as the width of the screening device strengthened
by 3 .times. 3 .times. 3/8 inch steel angles 15 welded to its
inside surface and provided with 7 inch diameter solid steel stub
axles 16 at each end. These axles 16 are suitably supported in
bearings 17 attached to the frame 6.
The ruggedness of this design attests to the heavy shock loads from
rock, and the resistance of the tough sugar cane to the shaking and
driving action.
The detail design of the teeth formed in the notched ring 13 is a
principal element of my invention and highly responsible for the
success of my sugar cane shaking and rock removal apparatus.
The leading edge 18 of each tooth is straight with a sweepback
angle 19 of approximately 52.degree. as shown. If the leading edge
18 were to be much steeper, as for instance as an extreme, the
radial leading edge of the stooling drums as used in some sugar
factories, rocks, the stool or root and base section of the sugar
cane plant which is occasionally pulled out and mixed in with
harvest cane, or heavy accumulations of cane stalks will be caught
between the tooth of one roll and the teeth and cylindrical section
of the next roll and jammed with such force as to break the driving
chains, or other part of the system thus stopping the entire
process feeding cane into the extraction process. The angle of
sweepback 19 then of the tooth leading edge 18 must be great enough
to prevent jamming by camming the material free and yet steep
enough to vigorously move the cane 3 for effective loosening of
extraneous material and to effectively move rocks.
I have found that a preferred sweepback angle if 52.degree..
The tooth leading edge 18 in my shaker roll is not rounded at its
terminal end 21. The tooth at its end 21 is about 2 inches long for
adequate strength, and the trailing edge 22 is radial and straight.
The space between teeth 7 is 2 inches on notched ring at the base
and 10 inches at the tip.
In a preferred arrangement 30 inch diameter rolls are spaced at
about 42 inches on center to leave a gap between rolls of 12 inches
and a clearance between tooth tips on one roll and the adjacent
roll of 3 inches. In some arrangements the roll spacing is not
uniform throughout the length of my screening device and can have
rolls closer for a smaller gap at one section and wider for a wider
gap at another to control the type, size, and rate of flow of
material passing between rolls at each section. Since the notched
rings 13 are 12 inches on center on each roll 2 and alternately
spaced on adjacent rolls 2 this leaves a clear space of 51/4 inches
by 11 to 13 inches. This facilitates the passage of extraneous
material and cane stalks down through these spaces between
rolls.
In an alternate form of my invention the roller teeth 7 are bent as
illustrated in FIG. 5. In this form, tooth 7C will be bent to the
left, adjacent tooth 7D will be straight and the next tooth 7E will
be bent to the right and so on. The purpose of this alternate form
is to more effectively engage the short length of stalk in chopped
cane and is a simple expedient obviating the need for closer
spacing of notched rings 13. Preferably my device would consist of
9 to 15 rolls but as few as six or more than 15 could be used.
Design limitations might require use of a series of short elements
of a few rolls each in a sawtooth like arrangement.
MODE OF OPERATION OF INVENTION
sand and operation of my mechanical screening device 1 a heavy
tangled mat of machine harvested sugar cane stalks, leaves and tops
with adhering soil and sand entangled rocks and stools is deposited
on the receiving end of the device 1 by a preceding conveyor 4 or
chute. Preferably the preceding conveyor 4 has thinned the blanket
down to a uniform height no greater than 12 inches and its velocity
as it leaves this conveyor 4 from 20 to 40 feet per minute.
Since the material will drop onto my mechanical screening device 1
much, if not all, of its forward velocity will have been lost. Also
as the material falls off the preceding conveyor 4 the blanket
opens up. Thus as it drops onto the first rolls 2 the tooth action
is very effective in engaging and shaking the material.
My device 1 moves the material, to the right as seen in FIGS. 1 and
2 and simultaneously elevates it at a blanket speed of about 40 to
60 feet per minute. Great and vigorous action occurs within the
blanket of material as it moves across and through my screening
device 1 because rather than merely being carried or dragged by the
conventional conveyor it is constantly struck by the teeth 7 of the
notched rings 13. The action of the teeth 7 with sweptback leading
edge 18 is not only to raise and let drop the pile locally, at a
speed of six times per second to 18 times per second but to pull
individual cane stalks through the pile so that rubbing action
between stalks performs a self cleaning function. The spring of the
cane stalks increases this action.
As the blanket of material moves up and across my screening device
1 individual cane stalks are constantly falling through the spaces
between rollers 2 along with loosened soil and extraneous material.
Large rocks released from the tangled cane stalks are either kicked
up into a rock receiving conveyor or chute 23 in the apparatus with
a low angle of inclination as shown in FIG. 1 or tumble down into a
rock receiving chute or conveyor 24 on the apparatus having a steep
angle of inclination as shown in FIG. 2. Actually it might be found
desirable to have a rock receiver at each end of my screening
device 1 as shown in FIG. 1.
All of the cane stalks fall through between the shaker rolls 2 so
that none are kicked into the rock receiver 23 at the upper
end.
Because the shaker rolls 2 are made with 30 inch diameter pipe 14
cane stalks will not wrap around the rolls 2 but are fed freely
over and between them. This eliminates jamming of cane stalks along
with the action of the sweptback teeth 7 which will not cause the
cane stalks to wrap around the teeth 7 in the shape of a
hairpin.
The overall action of my screening device 1 is (a) to take a heavy
dense 12 inch thick mat of entangled dirty cane, rocks and leaves,
(b) disentangle the cane, (c) loosen soil, dust, sand and leaves
from the cane, (d) remove large rocks, and (e) spread out all this
remaining material by increasing its speed so that subsequent
apparatus can separate the cane stalks from the loose extraneous
material.
* * * * *