Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Title: Material Classifier Having A Scoop Wheel
Field Of The Invention
[0001] The present invention relates to material classifiers, material washers
and dewatering devices, and more particularly to material classifiers having a
scoop wheel.
Background Of The Invention
[0002] Material classifiers are used for many different purposes, including
the separation or classification of solids according to size and/or particle
density.
Many different types of material classifiers are known, including mechanical
and
non-mechanical types.
[0003] According to one type of material classifier, solids to be separated
are
mixed in a suitable liquid such as water, to create a liquid-solid mixture or
pulp.
The mixture is then introduced into a classifier tank. Larger particles settle
to
the bottom of the classifier tank while fine particles remain in suspension in
the
liquid medium (called the overflow). A driven wheel having flights, lifts,
drags,
blades, scoops, scrappers or other means is used to lift solid material which
has
settled on the bottom of the tank and discharge it upon a discharge chute,
conveyor belt or other means for collecting and transporting the settled
material.
The liquid is drawn the classifier or exits as an overflow. Material
classifiers of
this type also provide cleaning of the solid particles.
[0004] A known material classifier of this first type, an example of which can
be seen in U.S. Patent No. 1,107,472, issued Aug. 18, 1914, uses V-shaped
troughs ("buckets") or scrapers spaced around the circumference of a
cylindrical
classifier tank or vessel. The vessel is partially filled with water and
slowly
rotates. Materials lighter than water will float on the water's surface and be
discharged from the vessel via an overflow trough. Heavier materials sink to
the
bottom of the vessel and are scooped-up by the buckets as they rotate. When
the buckets reach a specified height within the vessel, the contents of the
buckets are dumped onto a spout which discharges the material from the vessel.
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[0005] Another known material classifier of this first type, an example of
which can be seen in U.S. Patent No. 2,226,750, issued Dec. 31, 1940, uses a
circular wheel with radially spaced blades. Heavier solids scooped-up by the
blades are pushed to a discharge lip. Lighter solids are kept in suspension
and
exit the classifier at an overflow point such as a weir. The classifier blades
have
a cam mechanism allowing the blades to retract as they move upwards beyond
the discharge lip. On the downward rotation the blades are lowered into the
water edgewise to minimize the liquid surge caused by the blades entering the
water.
[OOOf ] Another type of classifier typically used for classifying sand and
aggregate cleaning use a screw mechanism for moving the sand/aggregate
along the classifier. These designs are commonly referred to as rotary-drum or
screw-conveyor type classifiers, an example of which can be seen in U.S.
Patent
No. 4,151,074, issued Apr. 24, 1979. Screw classifiers can be complex, prone
to
wear, and can be expensive and costly to maintain and set up.
[0007] Another type of classifier uses an elongate classifier tank or trough.
The liquid-solid mixture is introduced at a relatively high flow rate at one
end of
the classifier tank. A number of discharge pipes/outlets are provided near the
bottom of the classifier tank along its length. Larger and heavier particles
settle
closer to the classifier inlet. Smaller and lighter particles remain suspended
longer than heavier/larger particles and travel further from the inlet before
settling. The liquid exits the classifier tank using an overflow or other
device.
By opening the appropriate discharge pipes, solid material having the desired
particle size/density can be withdrawn from the classifier. Typically, the
withdrawn material is subsequently processed by dewatering apparatus, such as
a screw conveyor, to remove the water therefrom.
[0008] A common drawback of existing classifier designs is that good
classifying ability is typically achieved at the expense of capacity and vice
versa.
Typically, a material classifier has either good classifying ability but low
capacity
and a complicated reclaiming system, or high capacity and a relatively simple
reclaiming system but poor classifying ability. Also, material classifiers
with
good classifying ability typically offer a much greater classifying ability
than is
typically required as most fine grade materials have fewer uses.
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[0009] A further drawback of most material classifiers is that they are large
and not easily portable between job sites. Some material classifiers, such as
those at a quarry or aggregate pit, are typically large installations
requiring a
support structure and therefore cannot be transported. Other types of
classifiers, for example screw conveyors and driven wheel apparatus, are
capable of being transported. However, these types of material classifiers
must
typically be loaded onto a truck, for.example using a forklift, lift truck or
crane,
transported to the desired location, and unloaded from the truck. In addition
to
being a source of downtime, loading and unloading of the classifier requires
equipment at both the initial and final destinations to perform the
loading/unloading operation. Further, these types of classifiers may require
some disassembly for transportation and reassembly on arrival.
Summar~i of the Invention
[0010] The present invention provides a material classifier having a scoop
wheel. Example embodiments provide a material classifier which performs the
operations of cleaning, separation, and dewatering, and in some embodiments
provides a material classifier that is easier and less costly to manufacture,
and
which can be relatively easily transported. In some example embodiments, the
scoop wheel rotates at an angle relative to the horizontal. In another example
embodiment, the invention provides a classification system having multiple
scoop wheels arranged in series which, in some embodiments, are driven
independently such that each wheel may be rotated at a separate speed. In yet
another example embodiment, the scoop wheels are offset from the classifying
strea m .
[0011] The present invention, in its various example embodiments, seeks
to provide an improved material classifier that is more cost effective,
reliable,
less prone to wear, requires lower maintenance, has a higher capacity, and/or
is
relatively compact and can be transported relatively easily. Further, in
various
example embodiments, the material classifier of the present invention can be
used to classify sand and other materials, has a lay-out convenient for the
feeding and discharging, can be used in series to increase capacity or
throughput
or gradation of the solid material.
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(0012] According to one example of the present invention, there is
provided a material classifier for classifying a liquid-solid mixture
containing solid
material to be separated, comprising: a tank defining a reservoir for
receiving
the liquid-solid mixture; and a scoop wheel rotatably positioned within the
tank
to rotate about a wheel axis that is tilted relative to a horizontal
reference, the
scoop wheel including a plurality of circumferentially spaced apart scoops for
scooping material from the tank and subsequently discharging the scooped
material from the tank during rotation of the scoop wheel about its wheel
axis.
[0013] According to another example of the present invention, there is
provided a material classifier for classifying a liquid-solid mixture
containing solid
material to be separated, comprising: a tank defining a reservoir for
receiving
the liquid-solid mixture; a drive belt; and a scoop wheel suspended from the
drive belt at least partially within the tank to rotate about a wheel axis,
the
scoop wheel including a plurality of circumferentially spaced apart scoops for
scooping material from the tank and subsequently discharging the scooped
material from the tank during rotation of the scoop wheel.
[0014] According to further example of the present invention, there is
provided a classification system for classifying a liquid-solid mixture having
various grades of solid material therein, comprising: a tank defining a
reservoir
for receiving the liquid-solid mixture; a first scoop wheel rotatably
positioned
within the tank to rotate about a wheel axis, the first scoop wheel including
a
plurality of circumferentially spaced apart scoops for scooping material from
the
tank and subsequently discharging the scooped material from the tank during
rotation of the first scoop wheel about its wheel axis; and a second scoop
wheel
rotatably positioned within the tank to rotate about a wheel axis, the second
scoop wheel including a plurality of circumferentially spaced apart scoops for
scooping material from the tank and subsequently discharging the scooped
material from the tank during rotation of the second scoop wheel about its
wheel
axis.
[0015] According to yet a further example of the present invention, there is
provided a method of classifying material, comprising the steps of:
introducing a
liquid-solid mixture into a tank to a predetermined fill level; rotating a
scoop
wheel about a wheel axis to scoop settled solid material from a bottom of the
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tank, the wheel axis being positioned at an acute angle relative to a vertical
reference; and rotating the scoop wheel further to discharge the scooped
material from the scoop wheel when the scooped material is above an upper
edge of the tank.
(0016] According to yet another example of the present invention, there is
provided a material classifier for classifying aggregate material, comprising:
a
support frame; a tank mounted to the support frame for receiving a mixture of
aggregate material and fluid, the tank having a sidewall with a slanting,
upward
facing surface; a scoop wheel having a plurality of radially extending scoops
for
scooping aggregate material from the tank, the scoop wheel being located
adjacent the upward facing surface and having a plate substantially parallel
to
and facing the upward facing surface; a suspension drive system for driving
the
scoop wheel, the suspension drive system including a pair of spaced apart belt
guides secured to the support frame and an endless belt passing through the
guides, the scoop wheel being suspended from the belt between the guides for
rotation in a direction substantially parallel to the upward facing surface;
and a
pressurized fluid source for applying pressurized fluid to the plate of the
scoop
wheel to bias the wheel away from the upward facing surface; the scoop wheel
and sidewall being arranged such that in use the scoops discharge aggregate
material scoped from the tank over an edge of the sidewall.
[0017] Other aspects and features of the present invention will become
apparent to those ordinarily skilled in the art upon review of the following
description of specific embodiments of the invention in conjunction with the
accompanying figures.
Brief Description of the Drawings
[0018] Reference will now be made to the accompanying drawings which
show, by way of example, embodiments of the present invention, and in which:
[0019] FIG. 1 is a side view of a material classifier constructed according to
one embodiment of the present invention with a cut-away portion showing a
scoop wheel;
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[0020] FIG. 2 is a top view of the material classifier of FIG. 1;
[0021] FIG. 3 is a perspective view of the material classifier of FIG. 1;
[0022] FIG. 4 is an end view of the material classifier of FIG. 1;
[0023] FIG. 5 is a perspective view of the scoop wheel of the material
classifier of FIG. 1;
[0024] FIG. 6 is an schematic diagram of the material classifier of FIG. 1
associated with a conveyor belt for transport of discharged solid material;
[0025] FIG. 7 is a side view of a second embodiment of a material classifier
constructed according to the present invention;
[0026] FIG. 8 is a perspective view of an alternate embodiment of a scoop
wheel for a material classifier implemented according to the present
invention;
[0027] FIG. 9A is a sectional end view of the material classifier of FIG. 1
showing the water line in the tank during operation;
[0028] FIG. 9B is a sectional end view of a material classifier having the
scoop wheel of FIG. 8 showing the water line in the tank during operation;
[0029] FIG. 10 is a sectional end view of another embodiment of a material
classifier constructed according to the present invention;
[0030] FIG. 11 is a sectional view of the scoop wheel of FIG. 10 taken along
the line 11--li;
[0031] FIG. 12 is a schematic diagram of a classification system constructed
according to the present invention having three scoop wheels and a suspended
drive system;
[0032] FIG. 13 is a partial end view of a scoop wheel having a U-shaped
guide circumferentially attached thereto;
[0033] FIG. 14 is a partial end view of a scoop wheel having a L-shaped
guide circumferentially attached thereto;
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[0034] FIG. 15 is a side view of a further embodiment of a material classifier
constructed according to the present invention;
[0035] FIG. 16 is a sectional view of the scoop wheel of FIG. 15 taken along
the line 16--16; and
[0036] FIG. 17 is an enlarged view of a section of the scoop wheel of FIG. 16
indicated by the reference 17;
[0037] FIG. 18 is a schematic diagram of a material classifier according to
one embodiment of the present invention;
[0038] FIG. 19 is an exploded view of the scoop wheel of the material
classifier of FIG. i5 showing the inner and outer plates mounted to the inner
hub;
[0039] FIG. 20 is an exploded view of the scoop wheel of a material classifier
similar to that shown in FIG. 19 except that a single plate is mounted to the
inner hub;
[0040] FIG. 21 is a perspective view of the scoop wheel of the material
classifier of FIG. 15;
[0041] FIG. 22A is a side view of a material classifier having a diverter for
scooped material attached to its discharge chute; and
[0042] FIG. 22B is an end view of a material classifier having a diverter for
scooped material attached to its discharge chute.
[0043] Similar references are used in different figures to denote similar
components.
Detailed Description of the Embodiments
[0044] Reference is first made to FIG. 1 to 4, which show a system 12 for
classifying a liquid-solid mixture implemented according to the present
invention. The system 12 comprises material classifiers 14, indicated
individually by references 14a, 14b and 14c, a support frame 16, wheels 18,
hitch 20, and a mixing box 22. The material classifiers 14 are coupled in
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succession to form a series of three classifier stages beginning with the
first
material classifier 14a. In other embodiments, greater or fewer stages may be
used. A single material classifier 14 may be used, if desired.
[0045] Each material classifier 14 comprises a tank or hopper 30, and an
angularly mounted scoop wheel 32 having a plurality of radially extending,
curved scoops or lifts 34. The wheels 32 and their corresponding scoops 34
scoop settled material out of the tanks 30 and deposit it on discharge ramps
or
chutes 36. Each discharge chute 36 directs the scooped material onto a
corresponding conveyor belt 37 (FIG. 6). The conveyor belt 37 which transports
the material elsewhere, for example, to a discharge pile (not shown) for open
storage. In other embodiments, the discharge chutes 36 may direct the
scooped material to a common conveyor belt. Other transport means may be
used to transport the material from the discharge chutes 36. Each of the
wheels 32 is driven by an independently controllable drive mechanism 38. For
example, in one embodiment each wheel drive mechanism 38 is a hydrostatic
drive. An electric motor 39 powers three hydraulic pumps, each pump driving
an independent hydrostatic drive. In other embodiments, alternative drive
mechanisms are used, such as independent electric motors for each wheel, for
example. In an example embodiment, the rate of rotation of the wheels 32 is
different for each stage, with the wheel 32 in the first stage having a higher
rpm
than the wheel 32 in the second stage, which in turn has a higher rpm than the
wheel in the third stage. Generally, slower rotation results in less agitation
and
allows lighter material to settle on the bottom of the tank 30 so that it can
be
collected by the scoops 34. However, slow rates of rotation reduce the rate at
which settled material is collected from the tanks. Thus, process requirements
are considered when selecting the appropriate rates of rotation for the wheels
32.
[0046] Referring now to FIG. 6 and 9A, the tanks 30 will be described in
more detail. The tanks 30 each have a bottom wall 55 and side wall 54
adjacent to the respective wheel 32. The side wall 54 includes a guard plate
53
in an upper portion of thereof. A discharge area or opening 51 is defined in
the
upper portion of the side wall 54 adjacent the guard plate 53. The discharge
chutes 36 are attached to an outer surface of the side wall 54 each of the
tanks
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30 at an upper edge 33 of the side wall 54 in communication with the discharge
opening 51. A drain 61 is provided in a lower portion of each side wall 54 for
draining the respective tanks 30 during shutdown.
[0047] The angle of the side wall 54 corresponds to an angle T° at
which the
wheel 32 is mounted relative to a vertical reference "V", thus ensuring that
substantially all of the solid material scooped up by the wheels 32 remains on
the scoops 34 until the scoops 34 reach their respective discharge chutes 36.
Alternatively, the tilt or angle of the side wall 54 can be defined in terms
of
horizontal reference. In such cases, the side wall 54 is positioned at an
angle 8
relative to a horizontal reference such as, for example, the base of the
support
frame 16.
[0048] When the scoops 34 reach the discharge chute 36, the scooped
material carried by the scoops 34 falls down the chute 36 and onto the
corresponding conveyor belt 37. The tanks 30 may also include an overflow
weir or gate 40 between them. In some embodiments, the gates 40 define an
opening allowing water and suspended material to pass through to the next
stage in the classifier system. In other embodiments, there are no gates and
the tanks 30 open into each other.
[0049] Referring now to FIG. 5, one embodiment of a wheel 32 will be
described in more detail. Each wheel 32 comprises scoops or lifts 34, an inner
hub 44, spokes 46, drive shaft 48, and an outer hub 50. As shown in FIG. 5,
the
inner hub 44 may comprise a substantially cylindrical wall or ring from which
the
scoops extend, at least some of the scoops having a width greater than that of
the cylindrical wall. However in other embodiments the inner hub 44 may
comprise two or more spaced apart concentric rings inset from respective end
edges of the scoops 34. As shown in FIG. 5, the outer hub 50 comprises
concentric support bars 52, however other configuration of the outer hub 50
are
also possible. The drive shaft 48 of each wheel 32 is coupled to its
corresponding drive mechanism 38 (FIG. 1-4). To facilitate discharging of
material from the scoops 34, the wheels 32 are angularly mounted to have at
least a downwardly oriented side within the corresponding material classifier
14
at an angle T° relative to the vertical V (referred to as the tilt
angle). Thus, the
axis of rotation of each wheel 32 is oriented at an angle T° from the
horizontal H.
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In various embodiments, the tilt angle is selected based on the classifying
application that the system 12 is used for. For example in one embodiment, the
tilt angle is equal to or less than 50 degrees from the vertical. In another
example embodiment, the tilt angle is substantially 32 degrees from the
vertical.
However, such angles are merely examples and the tilt angle can vary in
various
embodiments to achieve desired results for the material being classified.
[0050] The scoops 34 each include an outer scoop edge 35 which engages
settled material on the bottom of the tanks 30. The scoops 34 are oriented
such
that the curvature of the scoops 34 opens in the direction of movement of the
wheels 32, thus allowing the scoops 34 to scoop material settled on the bottom
of the tanks 30. Different shapes of the scoops 34 are possible. In one
example embodiment, the scoops 34 are detachable to assist in transportation
of
the system 12 by lowering its overall height. In such embodiments, the scoops
34 are attached to the inner hub 44 using bolts or other suitable removable
fasteners. In other example embodiments, the support bars 52 of the outer hub
50 are divided into sections with a plurality of scoops 34 attached to each
section. These sections may then be attached and detached to the inner hub 44
as required, allowing for easier transportation and repair of the system 12.
In
an example embodiment, the inner hub 44 is narrower than the scoops 34 such
that the inner hub 44 is spaced apart from the side wall 54 allowing water to
flow ofF inner edge portions 42 of the scoops 34 that extend beyond the inner
hub 44 during rotation of the wheel 32.
[0051] As shown in FIG. 9A, in one example embodiment, the bottom wall
55 is perpendicular to the side wall 54, such that the bottom wall 55 is
substantially parallel to the outer scoop edge 35 of the scoops 34, and so
that
settled aggregate material collects in the portion of the tank 30 where the
wheel
32 is located. As the wheel 32 rotates upwards with full scoops 34, the scoops
34 rise out of the water with material trapped in the scoops 34 and supported
by
the side wall 54. As the scoops emerge from the water, water trapped by the
scoops 34 flows off and back into the tank 30. As the scoops 34 rotate
further,
the scooped material undergoes dewatering whereby entrained water is drained
from the scooped material. The dewatering continues until the scoops 34 reach
the top of the tank 30 and are discharged.
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[0052] Referring now to FIG. 1 and 6, the discharge of solid material
collected by the system 12 will be described. In the shown embodiment, the
discharge chutes 36 of each stage are associated with a corresponding conveyor
belt 37 however a single conveyor belt may also be used. The discharge chutes
36 are downwardly oriented towards the conveyor belts 37 to facilitate
discharging. Vertical guides 58 may be provided on one or both sides of the
discharge chutes 36 direct and channel scooped material toward the lower end
of the chutes 36 and onto the corresponding conveyor belts 37. In other
embodiments, the discharge chutes 36 may direct scooped material to a single
conveyor belt. In some applications, a single conveyor may be used having
separate channels for material from each of the classifier stages. In other
embodiments, a single conveyor belt may be used for all of the scoop wheels.
The use of a common conveyor belt allows scoop material to be recombined to
form a mixed aggregate having a particle size/density distribution within
product
tolerances. For example, in some applications the amount of scooped material
from each classifier stage can be selected so that when recombined, the final
product has a desired amount of material in each particle size/density range.
Using this approach, cleaned and dewatered aggregate having desired
characteristics for different applications can be produced.
[0053] As shown in FIG. 22A and 22B, a portion of the material collected by
a scoop wheel may be scalped or removed. In the shown embodiment, the
discharge chute 36 includes a diverter 270. The diverter 270 comprises a
hollow
conduit or tube communicating with an opening 271 in the discharge chute 36 at
one end. Flexible tubing 272 may be attached at the other end of the diverter
270. A portion of the scooped material discharged onto the chute 36 falls
through the diverter 270 and the tubing 272. The tubing 272 discharges the
diverter material onto a conveyor belt 274 for transportation elsewhere, for
example, to a separate discharge pile. The trajectory of material avoiding or
bypassing the diverter 270 and entering the conveyor belts 37 for collection
as
part of the final product is represented by the reference "d". The use of a
diverter 270 allows the required amount of scooped material collected at a
scoop
wheel 32 to be obtained by removing or diverting any excess portion in order
to
meet the specifications of the final product. In other embodiments, a
pivotally
mount bar or arm may be used rather than a diverter tube. In such cases, the
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bar may be pivotally mounted to pivot about its centre. The pivotally mounted
bar may be, for example, a finger gate. Adjustment of the position of the bar
changes the portion of scooped material which is diverted from the main
portion
of the discharge chute 36 which discharges onto the conveyor belt 37 as part
of
the final product to increase or decrease the amount of diverted material.
[0054] Referring now to FIG. 1 to 4, the operation of an example
embodiment of the system 12 will be described in more detail. The direction of
movement of the wheels 32 is indicated by reference 56. In this embodiment,
the wheels 32 of each classifier 14 rotate in the direction of the mixing box
22.
Aggregate material is transported by a conveyor belt (not shown) or other
transport means into the mixing box 22. The aggregate material may be pre-
screened to remove particles that are larger than the application tolerance
such
as rocks. Water is continuously fed into the mixing box 22 through an inlet
pipe
(not shown). The water and aggregate material forms a liquid-solid mixture or
pulp that passes through the mixing box 22. The liquid-solid mixture is fed
into
the tank of the first classifier 14a. A gate 40 provides an opening between
the
tank 30 of the first classifier 14a and the tank 30 of the second classifier
14b
which allows water and suspended material to flow from the first stage to the
second stage. Similarly, a gate 40 provides an opening between the tank 30 of
the second classifier 14b and the tank 30 of the third classifier 14c which
allows
water and suspended material to flow from the second stage to the third stage.
A gate 40 may also be provided at a discharge end of the tank 30 of the final
stage 14c. In other embodiments, an outlet chamber 59 (FIG. 2) is located
opposite the mixing box or feed tank 22. Liquid from the third tank overflows
a
lip or weir in the end wall of the tank and flow into the outlet chamber 59.
An
opening in the outlet chamber 59 is connected to a flexible hose or tubing
which
flows out to a tailings pond (not shown).
(0055] The gates 40 include a control mechanism that allows the gate
opening to be enlarged or contracted by raising or lowering the gates 40.
Controlling the size of the gate openings allows the flow rate of water and
suspended solids between classifier stages to be controlled, and consequently
the water level in each of the tanks 30. In one example embodiment, water
flow through the system 12 is regulated such that the water level drops from
the
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first stage to the second stage, and then from the second stage to third
stage.
In other embodiments, the water level may increase from the first stage to the
last stage. Other means for controlling the flow through the system 12 may be
used in addition to, or in place of, the gates 40. In some embodiments, the
water level in the tanks 30 is also controlled by pumping some of the water
from
one or more later stages back into earlier stages. The flow of water between
the tanks 30 may also be affected by the level of the classification system
12.
If the classification system is not level, the water level in each of tanks
will be
affected by the level of the system.
[0056] Although aspects of the present invention can be used for sorting a
number of different types of material, for example various types of aggregate
and reclaimed solids from sewage or wastewater treatment operations,
hereinafter the use of the system 12 as a sand classifier will be described.
[0057] In the first stage 14a of the classification system, the speed of the
wheel 32 is selected so that a desired grade or amount of settled solids are
collected in the first stage 14a. In some embodiments, the rotation of the
wheel 32 contributes to agitation of the water in the tank 30 of the first
classifier
14a such that sand particles that are generally less than a predefined mass
are
kept suspended, whereas particles that are generally heavier than the
predefined mass sink to the bottom of the tank 30 where they are scooped up by
the scoops 34. As the wheel 32 rotates, upward moving scoops 34 emerge
from the water. As the scoops 34 emerge, water captured by the scoops 34 is
drained off and returned to the tank 30. Some suspended particles are carried
back with the water into the tank 30. As the wheel 32 rotates further, the
entrained water is drained away from the scooped materials until the scoops 34
reach the discharge opening 51. Once at the discharge opening, the scooped
material carried by the scoops 34 slides off and down the discharge chute 36
to
a collection device such as a conveyor belt 37 (FIG. 7). Lighter particles
that
remain suspended in the water of the first stage then travel through the gate
40
and into the tank 30 of the second stage.
[0058] In the second stage 14b, similar to the first stage, the wheel 32 turns
at a speed such that a desired amount or grade of settled solids are collected
in
the second stage 14b. In some embodiments; the rotation of the wheel 32
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contributes to agitation of the water in the tank 30 of the second classifier
14b
such that particles that are generally below a certain mass are suspended in
the
water in the tank 30, while particles that are generally heavier than that
mass
sink to the bottom of the tank 30 where they are scooped up by the scoops 34
of
wheel 32 of the second stage. As in the first stage, when the scoops 34
emerge from the water as the wheel 32 rotates, water captured by the scoops
34 is initially drained off and returned to the tank 30. As the wheel 32
rotates
further, the entrained water is drained away from the scooped materials until
the
scoops 34 reach the discharge opening 51. Once at the discharge opening, the
scooped material carried by the scoops 34 slides off and down the discharge
chute 36 to the conveyor belt 37. Lighter particles that remain suspended in
the water of the second stage then travel through the next gate 40 and into
the
tank 30 of the third stage.
[0059] In the third stage 14c, very fine particles or silt is removed. The
wheel 32 of the third classifier 14c moves at a speed slow enough that at
least
some of the silt particles can settle on the bottom of the tank 30, where they
are
scooped up by the scoops 34 of the wheel 32 and deposited on the discharge
chute 36 of the third stage. Water leaves the third stage by the final gate 40
(FIG. 9A) and is sent to a tailings pond (not shown). This water contains
residual suspended solids that did not settle on the bottom of the tank 30 of
the
third stage. The rate of rotation of the wheel 32 in the third stage 14c is
selected so that a predetermined percentage of silt particles are removed. In
one embodiment, the speed of the wheel 32 is selected to obtain 20 percent
recovery of silt particles. Recovery of silt particles reduces the need for
and
cost associated of recovering silt from the tailings pond.
[0060] In other embodiments, finer particles are removed from the third
classifier stage while most silt particles, for example particles having a
particular
diameter of less than 400 pm, remain in suspension. The silt particles exit
the
classifier system as overflow and are sent to tailings pond.
[006i] It will thus be appreciated that in this example embodiment, sand
passing through the system 12 is cleaned, classified into different sizes, and
at
least partially dewatered. The range of sizes extracted at each stage
depending
upon a number of variables including, for example, the rate at which the
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aggregate material and water is fed into the system 12, the agitation
occurring
in the mixing box 22, the distance from the mixing box 22, the rates at which
the wheels 32 rotate, the size and number of scoops 34 on the wheels 32, and
the location and size of the gate openings between stages.
[0062] A programmable logic controller (PLC) or other suitable controller
may be used to improve process control in relation to the rate which the
aggregate material is fed to system 12, the rate that water is fed to system
12,
the rate of rotation of the wheels 32, and possibly the size of the gate
openings
between the stages.
[0063] Variations of the system 12 will now be described. In one
embodiment, the wheel 32 in the first stage rotates between 8 and 12 rpm, the
wheel 32 in the second stage rotates between 4 and 6 rpm, and the wheel 32 in
the third stage rotates at less than 4 rpm. Such speeds are provided merely as
non-limiting examples and other speeds for the wheels 32 are possible with
desired wheel speed depending upon, among other things, wheel size, tank size,
the number and size of scoops, the tilt angle and the material being
classified.
Further, the speed at which each of the wheels 32 rotates is a selectable
parameter and need not decrease between successive stages as in the present
embodiment. In some embodiments, each wheel 32 rotates at the same speed.
[0064] Wheel speed, wheel size, the number of scoops, scoop size, shape
and spacing, title angle, tank size, gate size and opening, among other
things,
are parameters that can vary in different embodiments of the invention, and
can
vary between the classifier stages in some embodiments, in order to achieve
desired results for the material being classified. For example, in some
embodiments, the wheel 32 in the third stage has narrower scoops 34 than the
wheels 32 in the first and second stages. Shorter scoops 34 may be used in the
third stage because the volume of aggregate material removed in this stage is
smaller compared to the first and second stages where the bulk of the material
is removed.
[0065] Generally, the wheel speed is set to rotate as quickly as possible, but
slow enough to allow at least some dewatering to occur. If the wheel speed is
set too high, too much water will be retained by the scooped material and, in
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some cases, water trapped by the scoops 34 may not drain off and will be
scooped out of the tanks 30 with the discharged material. The number of
scoops 34 per wheel is set such that the wheel 32 is filled, however the
scoops
34 cannot be packed so tightly that the operation or one scoop 34 interferes
with
the operation of the adjacent scoops 34. The length of the scoops 34 is
typically set to achieve a certain tons per hour capacity. Wheel diameter is
typically as large as possible to increase capacity, but small enough for the
system 12 to be transported (for example in a freight container), and small
enough to be manageably setup by the end user.
[0066] In the embodiment shown in FIG. 1 to 4, the system 12 is supported
by the common frame 16 which has wheels 18 at one end thereof, and a hitch
20 at the opposite end thereof so that the classifier can be easily moved, for
example, by towing the system 12 using a freight truck. In one non-limiting
example embodiment, the system 12 is sized to be easily transported in a
standard freight container (for example, a container having approximate
interior
dimensions of 7'-6" x 39'-6"). In such cases, the system can be transported as
a normal legal load without special load constraints. In other embodiments,
the
system has a stationary configuration and is not readily portable. In yet
other
embodiments, the classifiers 14 are separate units that do not share a common
frame.
[OOf7] Reference is now made to FIG. 7, which shows a further example
embodiment of a system 60 for classifying a liquid-solid mixture implemented
according to the present invention. The system 60 is similar to the system 12,
except that the orientation of the wheels 32 is different. The system 60
comprises three material classifiers indicated individually by references 62,
64
and 66. The first and second classifiers 62 and 64 rotate in the direction of
the
hitch 20 i.e. in a downstream direction, whereas the third classifier 66
rotates in
the opposite direction towards the mixing box 22 i.e, in a upstream direction.
The direction of movement of the wheels 32 is indicated individually by
references 72, 74, and 76 (FIG. 7). As with the system 12, the scoops 34 are
curved in the direction of movement of the wheels 32 to scoop the material
settled on the bottom of the tanks 30. In yet other embodiments, the first and
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second classifiers rotate towards the mixing box 22 and the third classifier
rotates away from the mixing box 22.
[0068] Reference is now made to FIG. 8 and 9B, which show another
embodiment of a material classifier 80 according to the present invention. The
material classifier 80 is similar to the material classifier 14, with the
exception
that the shape of the scoops attached to the scoop wheels is different. Each
material classifier 80 comprises a tank or hopper 30 having a side wall 54,
and
an angularly mounted wheel 82 having a plurality of radially extending, curved
scoops or lifts 84. Each scoop 84 has an outer scoop edge 85 which engages
settled material on the bottom of the tanks 30. As before, the wheels 82 and
their corresponding scoops 84 serve the dual purpose of agitating the contents
of each of the tanks 30, and scooping material out of the tanks 30 and
depositing it on discharge ramps or chutes 36.
(0069] Similar to the scoops 34 of the system 12, the scoops 84 are curved
in the direction of movement of the wheels 82 to scoop the material settled on
the bottom of the tanks 30. However, the scoops 84 are tapered away from the
side wall 54 such that the outer scoop edge 85 is substantially parallel to
the
surface of the water in the tank 30. In this manner, the taper of each scoop
84
corresponds to the tilt angle at which the wheels 82 are mounted within the
tanks 30. Tapering of the scoops 84 provides improved ejection of the water
carried by the scoops 84 when they emerge from the water during the discharge
operation.
[0070] Referring now to FIG. 9A and 9B, the tapering of the scoops 84 will
be explained in more detail. FIG. 9A illustrates a wheel 32 of a material
classifier 14 with a liquid-solid mixture such as sand and water received
therein.
The water line in the tank 30 is indicated by reference 86. For convenience,
only one scoop 34 is shown. Similarly, FIG. 9B illustrates a wheel 82 of the
material classifier 80 with a liquid-solid mixture such as sand and water
received
therein. The water line in the tank 30 is indicated by reference 86.
[0071] Referring now to FIG. 9A, it will be appreciated that as the wheel 32
emerges from the water at the water line 86, the entire outer scoop edge 35 of
the scoop 34 does not emerge from the water at one time, rather an upper
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portion 88 of the scoop 34 emerges first. Referring now to FIG. 9B, it will be
appreciated that tapering allows the entire outer scoop edge 85 of the scoop
84
to emerge from the water at one time, thus allowing captured water to be
ejected evenly from the scoops 84 from both sides thereof.
[0072] Other variations of the material classifier are also possible. Instead
of using separate tanks for each wheel 32, a single large tank could be used
to
house all the wheels 32. Minor adjustments to the classifier may be required
in
the single tank configuration, for example, partitions or baffles may be
needed
to provide some separation between the classifier stages. In this embodiment,
lighter particles held in suspension are allowed to flow to the far end of the
tank
nearest the last wheel 32. In other embodiments, more or few classifier stages
are used, for example, in one example embodiment only two classifier stages
are
used with the overflow from the second stage containing very fine particles or
silt, which is sent to a tailings pond. In still other example embodiments,
only a
single classifier stage and wheel is used. In another example embodiment,
multiple classifier stages are used, with the wheels 32 operating at different
speeds, but the tilt angle is substantially 0° from the vertical V, the
wheels being
serially offset to allow for material discharge. For example, three vertically
oriented material classifiers may be used in series.
[0073] It will be appreciated by one of skill in the art that in some
embodiments of the present invention, the wheels 32 are offset to one side
from
the flow of the classifying stream, i.e. the flow of the liquid-solid mixture,
through the system 12 such that in each tank, the classifying stream can flow
from the inlet at the mixing box to the outlet at the opposite end of the
classification system past the offset scoop wheels. Offsetting of the wheels
32
can partially or completely isolate or separate the wheels 32 from the
classifying
stream, depending on the specific embodiment. In such cases, rotation of the
wheels 32 contributes very little, if at all, to the agitation of the
classifying
stream, and the distance from the mixing box 22 becomes one of the dominant
factors which affect the settling rate and size of settled particles in a
particular
stage when other variables remain constant. In these embodiments, the
classification system may include a longitudinally extending partition
defining an
inlet channel for receiving the liquid-solid mixture to further isolate the
scoop
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wheels 32 from the classifying stream. The longitudinal partition may be
disposed opposite the scoop wheels, and may be aligned with the side wall 54
and/or the inner side of the scoop wheels 32. In some embodiments, the
longitudinal partition extends substantially parallel to the side wall 54. In
some
applications, the liquid solid-mixture may be introduced into the inlet
channel at
high flow rate. In such applications, the inlet channel is relatively
turbulent
while the liquid-solid mixture surrounding the scoop wheels is relatively calm
facilitate settling.
(0074] Referring now to FIG. 10 and 11, another embodiment of a
classification system 100 for classifying a liquid-solid mixture according to
the
present invention will be described. The system 100 is similar in operation
and
function to the previously described systems 12 and 60, except that the system
100 uses a suspended drive system to rotate the scoop wheel rather than a
drive system implemented using a drive shaft as used in the systems 12 and 60.
The system 100 includes one or more material classifiers 102 for classifying a
liquid-solid mixture containing solid material to be separated. The material
classifier 102 includes a tank 104 having a side wall 106 and bottom wall 108
defining a reservoir for receiving the liquid-solid mixture. The side wall 106
is
positioned at an angle 8 relative to a horizontal reference (e.g. base of the
support frame 16). A wheel 110 is suspended at least partially within the tank
104 to rotate about a wheel axis perpendicular to the side wall 106. In some
example embodiments, the angle 8 of the side wall 106 relative to the
horizontal
reference is greater than 30 degrees and less than 90 degrees. In other
embodiments, the angle ~ of the side wall 106 relative to the horizontal
reference is greater than 40 degrees and less than 70 degrees, and in some
embodiments, the angle A of the side wall 106 relative to the horizontal
reference is greater than 50 degrees and less than 60 degrees. In one example
embodiment, the angle 8 of the side wall 106 relative to the horizontal
reference
is approximately 56 degrees. The above examples are merely illustrative and
other angles may be employed in different embodiments.
[0075] The wheel 110 includes an inner hub 112 and a plurality of spaced
apart scoops 114 extending radially from the inner hub 112 for scooping solid
material which has settled on the bottom wall 108 and subsequently discharging
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the scooped solid material from the tank 104 during rotation of the wheel 110
about its' wheel axis. The inner hub 112 may comprise a substantially
cylindrical wall or ring from which the scoops extend, at least some of the
scoops
having a width greater than that of the cylindrical wall. However, in other
embodiments the inner hub 112 may comprise two or more spaced apart
concentric rings inset from respective end edges of the scoops 114. The wheel
110 is suspended in the tank 104 and driven by a drive belt 118. The wheel
110 may also includes a circumferential guide or track 116 for cooperating
with
the drive belt 118 for rotating the scoop wheel 110 about its wheel axis, the
guide 116 being provided around an outer circumference of the scoop wheel
110. As will be appreciated by one of skill in the art, the wheel 110 is not
rigidly mounted. The suspension of the wheel 110 from the drive belt 118
permits the wheel axis to float about a plane substantially perpendicular to
the
wheel axis, for example, the wheel 110 may float about the side wall 106.
[0076] As shown in FIG. 10 and 13, in one example embodiment the guide
116 has a U-shaped cross-section for receiving the drive belt 118. The guide
116 may, in some embodiments, have a L-shaped cross-section (FIG. 14) and
be formed from angle iron. In the present embodiment, the guide 116 provides
a smooth track for the drive belt 118 to ride on, however teeth for engaging
the
drive belt 118 may also be provided if desired. The guide 116 may be used in
addition to, or in place of, an outer hub 50 comprising concentric support
bars
52 described earlier. In one example embodiment, the guide 116 comprises a
flat rail mounted around the outer circumference of the wheel 110 with a pair
of
spaced apart concentric bars attached to the outer surface of the flat rail.
The
support rails are spaced apart so that the drive belt 118 is at least
partially
received within the guide 116. A drive 120 is provided for driving the drive
belt
118 to rotate the wheel 110 within the tank 104. The drive 120 engages and
drives the drive belt 118 so as to rotate the wheel 110 about its wheel axis.
Discharge chutes 36 for each wheel 110 collect the discharged solid material
and
direct it onto a corresponding conveyor belt (not shown) where it will be
transported elsewhere, for example to a discharge pile for open storage.
[0077] The drive belt 118 may be a drive chain, cable, web, belt, twisted
cable or similar means. In some embodiments, the drive belt 118 includes a
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drive chain and the drive 120 comprises a driven sprocket wheel 121a and a
passive sprocket wheel 121b. The driven sprocket 121a may be driven by a
motor 117. The driven sprocket wheel 121a and passive sprocket wheel l2ib
are laterally offset from one another at a distance greater than the outer
diameter of the wheel 110 and located higher than the wheel axis so as to
allow
the wheel 110 to be suspended between them. The passive sprocket 121b does
not drive the drive chain, but allows the chain to pass over it as it is
pulled by
the driven sprocket 121a. In other embodiments where the drive belt is a cable
or belt, the drive may comprise a driven wheel or roller and a passive (guide)
roller, e.g. pulley, for passively allowing the drive cable or belt to pass
over it.
[0078] The side wall 106 includes a lower portion 122 opposite the wheel
110 for impeding scooped solid material from discharging from the scoops 114
while rotating inside the tank 104, and an upper portion 124 over which the
scoops 114 discharge the scooped solid material. The upper portion 124
i ncludes a guard plate 53 and defines a discharge area or opening 51 adjacent
to
the guard plate 53. The discharge chutes are attached to an outer surface of
the side wall 106 each of the tank 104 at an upper edge 33 of the side wall
106
i n communication with the discharge opening 51. The scoops 114 discharge the
scooped solid material when rotated higher than the discharge opening 51. In
the shown embodiment, the bottom wall 103 is substantially perpendicular to
the side wall 106. As shown in FIG. 10, the classifier may also include a
longitudinally extending partition 144 defining an inlet channel 146 for
receiving
the liquid-solid mixture and to assist in isolating the scoop wheels 110 from
the
classifying stream. The longitudinal partition 144 may be disposed opposite
the
scoop wheels 110, and may be aligned with the side wall 106 and/or the inner
side of the scoop wheel 110s. In some embodiments, the longitudinal partition
144 extends substantially parallel to the side wall 106. The longitudinal
partition 144 does not extend to the bottom of the classification system
allowing
the liquid-solid mixture to enter and fill the tanks 104 by passing underneath
it.
The longitudinal partition 144 may also define openings along its length to
allow
the liquid-solid mixture to pass therethrough. In some embodiments, the
system uses a central tank rather than separate tanks for each scoop wheel.
In these embodiments, lateral partitions or baffles (not shown) may be located
between the scoop wheels. In some applications, the liquid solid-mixture may
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be introduced into the inlet channel at high flow rate. In such applications,
the
inlet channel is relatively turbulent while the liquid-solid mixture
surrounding the
scoop wheels is relatively calm facilitate settling.
(0079] As shown in FIG. 11, the material classifier 102 in an example
embodiment includes a plurality of spaced apart rollers 126 rotatably mounted
at
one end thereof to the inner hub 112 of the wheel 110 and extending radially
inward therefrom. The rollers 126 extend radially inward from the inner hub
112
and are positioned for rolling on the side wall 106 during rotation of the
wheel
110 about its wheel axis. Each roller 126 has a roller surface 128 for rolling
on
the side wall 106. The roller surface 128 may be made of a material having a
low frictional resistance. In some embodiments, the rollers 126 are urethane
bearing rollers. The rollers 126 are mounted so as to maintain a first
operating
distance between the wheel 110 and the side wall 106. In some embodiments,
the first operating distance may be, for example, approximately ~/4 inch,
however
other distances are used in other embodiments. The side wall 106 is
substantially planar and includes a central bearing portion having a bearing
surface upon which the rollers 126 are positioned for rolling. The rollers 126
and
bearing surface 130 reduce the friction associated with the rotation of the
wheel
110.
(0080] The wheel 110 is suspended from the drive 120 so as to maintain a
second operating distance between the wheel 110 and the bottom wall 108
which may be, for example, only approximately 1 inch. Suspension of the wheel
110 from the drive 120 allows the wheel 110 to float relative to the side wall
106
as the wheel 110 is rotated about its wheel axis thereby reducing the
opportunity for obstructing material to become jammed between the wheel 110
and side wall 106. The first operating distance created by the rollers 126
being
disposed against the bearing surface 130 ensures that the wheel 110 does not
ride directly on the side wall 106 as it rotates, thereby reducing the
friction that
would otherwise occur. The rollers 126 and bearing surface 130 also reduce the
frictional resistance and work required to rotate the wheel 110 about its
wheel
axis.
(0081] FIG. 12 shows a classification system having three material classifiers
102, indicated individually by references 102a, 102b, and 102c. The three
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material classifiers 102 are located between a driven sprocket 121a at one end
and a passive sprocket 121b at the other end. A passive sprocket 140 is
disposed between the first material classifier 102a and second material
classifiers 102b. A passive sprocket 142 is disposed between the second
material classifier 102b and third material classifiers 102c. Although the
driven
sprocket 121a and a passive sprocket 121b are disposed above the material
classifiers 102, the passive sprockets 140 and 142 need not be disposed above
the classifiers 102. In the shown embodiment, a single driven sprocket 121a is
used to drive a plurality of scoop wheels 110 with passive sprockets 140, 142
or
other guide means interposed therebetween. In other embodiments, each
material classifier 102 may have its own drive belt 118 and drive 120. In such
cases, each wheel 110 is independently controllable and can be independently
driven.
[0082] Process parameters and operating conditions similar to those
described above in relation to the systems 12 and 60, for example the
direction
and rates of rotation of the scoop wheels, may also be applied to the system
100. In some applications, suspension of the scoop wheel 110 can provide
improved performance, for example, with trouble material that is prone to
clumping. Suspending the wheel 110 within the tank 104 rather than fixing the
wheel may reduce the chance of material binding or becoming caught between
the scoops 114 and the side wall 106 because the wheel 110 can float over any
obstructions on the side wall 106 as it rotates. Further, because the wheel
110
is not rigidly mounted, the wheel axis is permitted to float about a plane
substantially perpendicular to the wheel axis, for example on the side wall
106.
The use of a drive belt 118 may also reduce the work required to rotate the
wheel 110 by creating a larger reduction ratio as compared to using a drive
shaft. Thus, the wheel 110 is relatively easy to drive and apply torque to and
allows a smaller drive motor to be used. In some embodiments, a reduction
ratio of 7:1 may be utilized.
[0083] The system 100 may be coupled to a PLC or other suitable controller
as described above with reference to the systems 12 and 60. Typically, a
pressure load cell or strain gauge (not shown) measures the load applied to
the
wheel 110 and transmits this information to the PLC. The PLC then adjusts the
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rate of rotation of the wheel 110 so as to increase to the rate of rotation as
the
load increases and decease the rate of rotation as the load decreases. In this
way, improved classification and dewatering of the solid material may be
achieved. Other factors may also be monitored and controlled by the PLC to
improve control of the classification process.
[0084] Referring now to FIG. 15 to 19, and 21 another embodiment of a
system 200 for classifying a liquid-solid mixture according to the present
invention will be described. The system 200 has a suspended drive system
similar to the previously described system 100. The system 200 includes one or
more material classifiers 202 for classifying a liquid-solid mixture
containing
solid material to be separated. The material classifier 202 includes a tank
204
having a side wall 206 and bottom wall 208 defining a reservoir for receiving
the
liquid-solid mixture. The side wall 206 is positioned at an angle 8 relative
to a
horizontal reference (e.g. base of the support frame 16). A wheel 210 is
suspended at least partially within the tank 204 to rotate about a wheel axis
perpendicular to the side wall 206. In some example embodiments, the angle 8
of the side wall 206 relative to the horizontal reference is greater than 30
degrees and less than 90 degrees. In other embodiments, the angle 8 of the
side wall 206 relative to the horizontal reference is greater than 40 degrees
and
less than 70 degrees, and in some embodiments, the angle 8 of the side wall
206 relative to the horizontal reference is greater than 50 degrees and less
than
60 degrees. In one example embodiment, the angle 8 of the side wall 206
relative to the horizontal reference is approximately 56 degrees. The above
examples are merely illustrative and other angles may be employed in different
embodiments.
[0085] The wheel 210 includes an inner hub 212 and a plurality of spaced
apart scoops 214 extending radially from the inner hub 212 for scooping solid
material which has settled on the bottom wall 20~ and subsequently discharging
the scooped solid material from the tank 204 during rotation of the wheel 210
about its wheel axis. As shown in FIG. 15-17, 19 and 21, the inner hub 212
may comprise two or more spaced apart concentric rings 213 inset from
respective end edges of the scoops 214. However, in other embodiments the
inner hub 212 may comprise a substantially cylindrical wall or ring from which
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the scoops extend, at least some of the scoops having a width greater than
that
of the cylindrical wall. The wheel 210 is suspended in the tank 204 and driven
by a drive belt 218. The suspension of the wheel 210 from the drive belt 218
permits the wheel axis to float about a plane substantially perpendicular to
the
wheel axis, for example, the wheel 210 may float about the side wall 206. The
wheel 210 may also includes a circumferential guide or track 216 for
cooperating
with the drive belt 218 for rotating the scoop wheel 210 about its wheel axis.
The guide 216 is provided around an outer circumference of the scoop wheel
210. The guide 216 may be similar to the guide 116 described earlier.
(0086] The drive belt 218 is at least partially received within the guide 216.
A drive 220 is provided for driving the belt 218 to rotate the wheel 210
within
the tank 204. The drive 220 engages and drives the drive belt 218 so as to
rotate the wheel 210 about its wheel axis. Discharge chutes (not shown) for
each wheel 210 collect the discharged solid material and direct it onto a
corresponding conveyor belt (not shown) where it will be transported
elsewhere,
for example to a discharge pile for open storage. The drive belt 218 and drive
220 may be similar to the drive belt 118 and drive 120 described earlier.
[0087] The wheel 210 is suspended from the drive belt 218 so as to
maintain an operating distance between the wheel 210 and the bottom wall 208.
Suspension of the wheel 210 from the drive allows the wheel 210 to float
relative to the side wall 206 as the wheel 210 is rotated about its wheel axis
thereby reducing the opportunity for obstructing material to become jammed
between the wheel 210 and side wall 206.
[0088] The side wall 206 includes a lower portion 222 opposite the wheel
210 for impeding scooped solid material from discharging from the scoops 214
while rotating inside the tank 204, and an upper portion 224 over which the
scoops 214 discharge the scooped solid material. The upper portion 224 defines
a discharge area or opening 51 through which scooped solid material is
discharged. The upper portion 224 may also include a guard plate 53 which
impedes scooped solid material from discharging from the scoops 214 before
reaching the discharge opening 51 on the upper portion of the scoop rotation.
The discharge chutes are attached to an outer surface of the side wall 206
each
of the tanks 204 at an upper edge 33 of the side wall 206 in communication
with
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the discharge opening 51. The scoops 214 discharge the scooped solid material
when rotated higher than the discharge opening 51. In the shown embodiment,
the bottom wall 208 is substantially perpendicular to the side wall 106. As
shown in FIG. 16 and 18, the material classifier 202 may also include a
longitudinally extending partition 244 defining an inlet channel 246 for
receiving
the liquid-solid mixture and to assist in isolating the scoop wheels 210 from
the
classifying stream. The longitudinal partition 244 may be disposed opposite
the
scoop wheel 210, and may be aligned with the side wall 206 and/or the inner
side of the scoop wheel 210. In some embodiments, the longitudinal partition
244 extends substantially parallel to the side wall 206. The longitudinal
partition 244 does not extend to the bottom of the classification system
allowing
the liquid-solid mixture to enter and fill the tanks 204 by passing underneath
it.
The longitudinal partition 244 may also define openings along its length to
allow
the liquid-solid mixture to pass therethrough. As shown in FIG. 18, the
classification system 200 may include an elongate central tank 201 rather than
separate tanks for each scoop wheel 210. In these embodiments, lateral
partitions or baffles 248 may be located between the scoop wheels. The lateral
partitions 248 extend partially across the central tank 201 and define the
tanks
204 of the respective scoop wheels. The lateral partitions 248 are spaced
apart
to define the tanks 204 in a series extending from a mixing box 22 at one end
to
an outlet at an opposite side thereof. The outlet may be located within a
outlet
chamber located opposite the mixing box 22. In some embodiments, liquid
from the tank 201 overflows a lip or weir in the end wall of the tank and flow
into the outlet chamber. An opening in the outlet chamber is connected to a
flexible hose or tubing which flows out to a tailings pond (not shown).
[0089] As shown in FIG. 18, the scoop wheels 210 are offset from the inlet
channel 246 at least partially isolating the scoop wheels 210 from the
classifying
stream. In such applications, the distance from the mixing box 22 becomes one
of the dominant factors which affect the settling rate of the solid material.
In
some applications, the liquid solid-mixture to be separated may be introduced
into the inlet channel 246 at high flow rate. In such applications, the inlet
channel is relatively turbulent while the liquid-solid mixture surrounding the
scoop wheels is relatively calm facilitate settling.
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[0090] As will be appreciated by one of skill in the art, the particular
characteristics of the starting aggregate fed into the mixing box 22 may vary.
As a result, determination of the process parameters that are required to
obtain
the necessary separation at each stage typically requires adjustment between
different batches of material to be separated. Adjustment of the wheel speed
allows the operator to affect the particle size/density or grade of material
collected at each scoop wheel 210. For new batches of material to be
classified, the operator may collect a sample of the material discharged by
the
scoop wheels 210. The sample then undergoes testing to determine the particle
size distribution using sieve trays other suitable testing methodology. Based
the
particle size distribution, the wheel speed of one or more of the scoop wheels
210 may be increased or decreased to affect the particle size/density or grade
of
material collected. The material collected using the new operating parameters
may then be tested. Using an iterative process, the process parameters
required to obtain the desired particle size/density or grade of material at
each
wheel may be determined for a particle aggregate feed.
[0091] As shown in FIG. 15 and 16, the side wall 206 may include a housing
251 which defines a reservoir 250. The housing 251 is received within the
inner
hub 212 of the wheel 210. In the shown embodiment, the housing 251
comprises a generally cylindrical housing which is attached to inner surface
of
the side wall 206, however other shapes may also be used. In other
embodiments, the housing 251 may be formed by a recess in the side wall 206.
An inlet pipe 252 is coupled to the reservoir 250 through an opening 254 in
the
side wall 206. In the shown embodiment, the inlet pipe 252 and the reservoir
250 are generally inline (coaxial) with the wheel axis. The inlet pipe 252 is
connected to a water source, such as a water pump (not shown), which feeds
water into the reservoir 250. A pair of plates is disposed opposite the inlet
pipe
252 forming an end of the reservoir 250. The plates include an inner plate 262
and an outer plate 264. The inner plate 262 defines a plurality of openings or
holes which allow water from the reservoir 250 to exit therethrough. The inner
plate 262 may also include hollow conduits or nozzles 266 attached to the
inner
side thereof in communication with the openings in the inner plate 262. In
other embodiments, the inner plate 262 has openings but does not include
nozzles. Further, the size and shape of the openings may vary across the inner
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plate 262. In some embodiments, the inlet pipe 252 has a diameter of 1-2" and
feeds a reservoir 250 having a diameter of 14". In some example embodiments,
the inner plate 262 may be positioned approximately 12" from the side wall 206
defining a depth of the reservoir 250 and the nozzles 266 may be ~/2" in
diameter.
(0092] The outer plate 264 is fixed to inner hub 212 of the wheel 210. As
shown in FIG. 15 to 17, 19 and 21, in the shown embodiment the outer plate
264 is attached to the concentric rings 213 of the inner hub 212. The outer
plate 264 includes a circumferential guide ring 268 extending inwardly towards
the side wall 206 when the wheel is suspended within the tank 204. The
diameter of the guide ring 268 is larger than the diameter of the inner plate
262
providing some clearance thereabout. When not in operation and when no
water is flowing from the inlet pipe 252, the outer plate 264 is positioned
against
and partially supported by the inner plate 262. As a result of the contact
between the inner plate 262 and outer plate 264, solid material being
classified,
such as sand, typically cannot enter the reservoir 250. As shown in FIG. 19, a
cross-member 269 fixes the outer plate 264 to the outer of the concentric
rings
213 of the inner hub 212. A sufficient clearance is provided between the guide
ring 268 and the inner plate 262 to allow the wheel 210 to float thereabout
during its rotation about its wheel axis.
[0093] In some embodiments, the inner plate 262 defines 6 evenly
distributed openings. The number, size and distribution of the openings in the
inner plate 262 may vary depending on the water pressure that is to be applied
against the wheel 210 and the distribution required to create the water
cushion
and balance the wheel 210. In some applications, the water distributed by the
inner plate 262 should balance the wheel to facilitate its rotation.
[0094] During operation, water from the inlet pipe 252 fills the reservoir
250. As the water pressure within the reservoir 250 increases, water is
discharged through the nozzles 266 and ultimately through the openings in the
inner plate 262. Water discharged through the openings in the inner plate 262
presses against the outer plate 264, pushing the wheel 210 away from the side
wall 206 and creating a small buffer or space between the wheel 210 and the
side wall 206. The space created between the wheel 210 and the side wall 206
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fills with water from the reservoir 250 creating a water cushion as the wheel
210
rotates about its wheel axis. This water cushion allows the wheel 210 to be
rotated without riding directly on the side wall 206, thereby reducing the
friction
that would otherwise occur. Without being bound by theory, the discharge of
water through the inner plate 262 may, in some applications, provide a water
cushion or hydroplaning effect providing lubrication between the inner plate
262
and outer plate 264 thereby reducing wear.
[0095] Because of the clearance between the inner plate 262 and the guide
ring 268 on the outer plate 264, the wheel 210 is able to float about the
inner
plate 262 within the confines of the guide ring 268. In some applications, a
benefit of this clearance may be that the wheel 210 may be suspended and
rotating about its wheel axis without tight tolerances, thereby simplifying
the
construction of the material classifier 202 and making it less costly to
manufacture. A further advantage, in some applications, may be that the risk
of
stalling the material classifier 202 is reduced because tight tolerances are
not
used, for example, at the principle moving parts such as the points of
rotation.
The use of tight tolerances may increase the risk of stalling because the sand
or
other solid material being classified may cause clogging or binding. Stalling
may, in some applications, require the classifier tank to be dug out manually
by
an operator.
[0096] An alternative embodiment of the present invention shown in FIG. 20
in which the inner plate 262 is eliminated and a single plate 26 similar to
the
outer plate 264 is positioned adjacent to the opening 254 for receiving water
under pressure from the water source in the side wall such that the scoop
wheel
can rotate thereabout when it is rotated about its wheel axis. In this
embodiment, the plate 265 does not include a guide ring 268 as did the outer
plate 264. The cross-member 269 is used in this embodiment to secure the
plate 265 to the inner of the concentric rings 213 of the inner hub 212. The
wheel 210 is allowed to float about the plate 265 during its rotation about
its
wheel axis. Without a guide ring 268, the freedom of movement of the wheel
210 may be more than that the previously described embodiment shown in FIG.
15 to 19. During operation, a water cushion is created between the outer plate
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264 and the side wall 206 by the water from the inlet pipe 252 press against
the
plate 265.
[0097] According to another example embodiment, there is provided a
material classifier for classifying a liquid-solid mixture containing solid
material
to be separated, comprising: a tank defining a reservoir for receiving the
liquid-
solid mixture; a drive belt; and a scoop wheel suspended from the drive belt
at
least partially within the tank to rotate about a wheel axis, the scoop wheel
including a plurality of circumferentially spaced apart scoops for scooping
material from the tank and subsequently discharging the scooped material from
the tank during rotation of the scoop wheel.
[0098] According to a further example embodiment, there is provided a
material classifier for classifying aggregate material, comprising: a support
frame; a tank mounted to the support frame for receiving a mixture of
aggregate material and fluid, the tank having a sidewall with a slanting,
upward
facing surface; a scoop wheel having a plurality of radially extending scoops
for
scooping aggregate material from the tank, the scoop wheel being located
adjacent the upward facing surface and having a plate substantially parallel
to
and facing the upward facing surface; a suspension drive system for driving
the
scoop wheel, the suspension drive system including a pair of spaced apart belt
guides secured to the support frame and an endless belt passing through the
guides, the scoop wheel being suspended from the belt between the guides for
rotation in a direction substantially parallel to the upward facing surface;
and a
pressurized fluid source for applying pressurized fluid to the plate of the
scoop
wheel to bias the wheel away from the upward facing surface; the scoop wheel
and sidewall being arranged such that in use the scoops discharge aggregate
material scoped from the tank over an edge of the sidewall.
[0099] In some embodiments, the scoop wheels are arranged in series.
[0100] In some embodiments, the scoop wheels may be independently
controllable permitting the scoop wheels to be rotated at separate speeds and
in
separate directions.
[0101] In some embodiments, the classification system may comprise an
inlet at a first end of the tank for feeding the liquid-solid mixture into the
inlet
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channel, and an outlet at an opposite second end of the tank for receiving
overflow from the tank.
[Oi02] In some embodiments, the classification system comprise angularly
mounted discharge chutes attached to an outer surface of the tank opposite
each of the scoop wheels, the discharge chutes being attached at an upper edge
of the tank.
[0103] In another aspect of the present invention, there is a provided a
method of classifying material. According to one example embodiment, there is
provided a method of classifying material, comprising the steps of:
introducing a
liquid-solid mixture into a tank to a predetermined fill level; rotating a
scoop
wheel about a wheel axis to scoop settled solid material from a bottom of the
tank, the wheel axis being positioned at an acute angle relative to a vertical
reference; and rotating the scoop wheel further to discharge the scooped
material from the scoop wheel when the scooped material is above an upper
edge of the tank.
[0104] In some embodiments, the scoop wheel is rotated at angle of
greater than 30 degrees and less than 90 degrees relative to the vertical
reference.
[0105] In some embodiments, the scoop wheel is rotated at angle of
greater than 40 degrees and less than 70 degrees relative to the vertical
reference.
[0106] In some embodiments, the scoop wheel is rotated at angle of
greater than 50 degrees and less than 60 degrees relative to the vertical
reference.
[0107] The present invention may be embodied in other specific forms
without departing from the spirit or essential characteristics thereof.
Certain
adaptations and modifications of the invention will be obvious to those
skilled in
the art. Therefore, the presently discussed embodiments are considered to be
illustrative and not restrictive, the scope of the invention being indicated
by the
appended claims rather than the foregoing description, and all changes which
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come within the meaning and range of equivalency of the claims are therefore
intended to be embraced therein.
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