U.S. patent application number 15/741655 was filed with the patent office on 2018-07-12 for vibrating screening feeder and method of use.
The applicant listed for this patent is George D. Dumbaugh. Invention is credited to George D. Dumbaugh.
Application Number | 20180193880 15/741655 |
Document ID | / |
Family ID | 57685503 |
Filed Date | 2018-07-12 |
United States Patent
Application |
20180193880 |
Kind Code |
A1 |
Dumbaugh; George D. |
July 12, 2018 |
VIBRATING SCREENING FEEDER AND METHOD OF USE
Abstract
A vibrating screen feed conveying apparatus for conveying and
separating sticky "moisture laden bulk solids" which are sticky and
wet flowing onto a vibrating screening feeder and into a hopper.
The apparatus includes a bed on which material is conveyed, a
longitudinal counterbalance supported on a plurality of isolation
springs, a plurality of inclined drive springs extending between
the bed and the longitudinal counterbalance, and a plurality of
stabilizers for controlling movement of the drive springs along
their central axes. A plurality of vibratory motors, each having
rotatable eccentric weights are attached to the rear end of the
longitudinal counterbalance. The eccentric weights rotate in phase
with one another to vibrate the bed at a vibration frequency.
Inventors: |
Dumbaugh; George D.;
(Louisville, KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dumbaugh; George D. |
Louisville |
KY |
US |
|
|
Family ID: |
57685503 |
Appl. No.: |
15/741655 |
Filed: |
July 5, 2016 |
PCT Filed: |
July 5, 2016 |
PCT NO: |
PCT/US16/00056 |
371 Date: |
January 3, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62231330 |
Jul 3, 2015 |
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62493460 |
Jul 2, 2016 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B02C 23/08 20130101;
B65G 27/30 20130101; B07B 1/42 20130101; B65G 2201/047 20130101;
B07B 1/28 20130101; B65G 2201/045 20130101; B02C 23/02 20130101;
B07B 1/44 20130101; B07B 1/50 20130101; B65G 27/20 20130101; B65G
27/04 20130101; F23K 1/00 20130101; B07B 2201/04 20130101; B65G
27/32 20130101; B65G 27/26 20130101; F23H 9/04 20130101 |
International
Class: |
B07B 1/44 20060101
B07B001/44; B65G 27/32 20060101 B65G027/32; B65G 27/20 20060101
B65G027/20; B65G 27/04 20060101 B65G027/04; B65G 27/26 20060101
B65G027/26; B65G 27/30 20060101 B65G027/30; B07B 1/42 20060101
B07B001/42; F23K 1/00 20060101 F23K001/00 |
Claims
1. A vibrating screen feeder unit comprising: a generally
rectangular fixed base with a plurality of upward extending support
coil springs, said support coil springs fixedly attach to a top
surface of said fixed base and fixedly attached to a bottom surface
of a generally rectangular intermediate base, said intermediate
base having at least two rows of alternating large and small
triangular abutments extending upward therefrom, said large
triangular abutments having a first side forming about a forty-five
degree angle with a top surface of said fixed base, said first side
of said large triangular abutment having a drive coil spring
extending upward therefrom at about a forty-five degree angle with
a top surface of said fixed base member, said small triangular
abutments having a second side forming about a forty-five degree
angle with a top surface of said fixed base, said second side of
said small triangular abutment having two spaced apart leaf spring
rockers extending upward at about a forty-five degree angle with a
top surface of said fixed base, said first side of said large
abutment facing toward said second side of said small abutment; a
generally rectangular vibrating screen housing having at least two
rows of downward extending trapezoidal abutments on a bottom
surface thereof, said trapezoidal abutments fixedly connected on a
third side to free ends of said upward extending drive coils and on
a fourth side to free ends of said upward extending leaf springs,
said vibrating screen housing having at least one screen, an input
hopper and at least two output apertures formed therein; said
vibrating screen housing having a plurality of single or 3 phase
electrically adjustable alternating current motors mounted at one
end thereof, said motors having output shafts extending from top
and bottom ends with eccentric weights mounted on said shafts in
mechanical time with one another said motors fully electrically
adjustable over the complete range of zero to maximum output; a
vibration drive isolation assembly for vibrating said vibrating
screening unit; said vibration drive isolation assembly including
at least two parallel longitudinal counterbalance beams supported
on a plurality of isolation drive springs distributed across the
width of said vibrating screening unit; at least one vibratory
drive motor installed on said longitudinal counterbalance member;
said vibration drive isolation assembly includes a variable speed
motor controller for adjusting vibration intensity; said variable
speed motor controller being operatively arranged for dynamically
adjusting vibration intensity during a timed cycle; said timed
cycle includes an electrical control enabling a full zero to
maximum output adjustment by means of adding a standard variable
frequency (VFD) combined with adjustable timers so that a vibratory
stroke required screening has an automatic capability of a
momentary "pulsing" to 60 hertz (or higher) for a brief time of
usually 3 to 5 seconds, which generates a "spurt" or "pulse" to the
entire screening body for clearing screen media of a lump or a
particle stuck in a screen opening or to break free accumulated
layers of adhesive and cohesive particles that try to "stick" or
adhere to the surface of a screening media and a passed "unders"
collecting pan therebelow; said input hopper includes a vibratory
motor; and a programmable motor control unit driving said motors
with said weights synchronized with one another and capable of
driving said motors at a selected speed and of periodically
changing said speed for a selected time interval by a selected
amount.
2. A vibrating screen feeder unit consisting of: a generally
rectangular fixed base with a plurality of upward extending support
coil springs, said support coil springs fixedly attach to a top
surface of said fixed base and fixedly attached to a bottom surface
of a generally rectangular intermediate base, said intermediate
base having at least two rows of alternating large and small
triangular abutments extending upward therefrom, said large
triangular abutments having a first side forming about a forty-five
degree angle with a top surface of said fixed base, said first side
of said large triangular abutment having a drive coil spring
extending upward therefrom at about a forty-five degree angle with
a top surface of said fixed base member, said small triangular
abutments having a second side forming about a forty-five degree
angle with a top surface of said fixed base, said second side of
said small triangular abutment having two spaced apart leaf spring
rockers extending upward at about a forty-five degree angle with a
top surface of said fixed base, said first side of said large
abutment facing toward said second side of said small abutment; a
generally rectangular vibrating screen housing having at least two
rows of downward extending trapezoidal abutments on a bottom
surface thereof, said trapezoidal abutments fixedly connected on a
third side to free ends of said upward extending drive coils and on
a fourth side to free ends of said upward extending leaf springs,
said vibrating screen housing having at least one screen, an input
hopper and at least two output apertures formed therein; said
vibrating screen housing having a plurality of single or 3 phase
electrically adjustable alternating current motors mounted at one
end thereof, said motors having output shafts extending from top
and bottom ends with eccentric weights mounted on said shafts in
mechanical time with one another; a vibration drive isolation
assembly for vibrating said vibrating screening unit; said
vibration drive isolation assembly including at least two parallel
longitudinal counterbalance beams supported on a plurality of
isolation drive springs distributed across the width of said
vibrating screening unit; at least one vibratory drive motor
installed on said longitudinal counterbalance member; said
vibration drive isolation assembly includes a variable speed motor
controller for adjusting vibration intensity; said variable speed
motor controller being operatively arranged for dynamically
adjusting vibration intensity during a timed cycle; said timed
cycle includes an electrical control enabling a full zero to
maximum output adjustment by means of adding a standard variable
frequency (VFD) combined with adjustable timers so that a vibratory
stroke required screening has an automatic capability of a
momentary "pulsing" to 60 hertz (or higher) for a brief time of
usually 3 to 5 seconds, which generates a "spurt" or "pulse" to the
entire screening body for clearing screen media of a lump or a
particle stuck in a screen opening or to break free accumulated
layers of adhesive and cohesive particles that try to "stick" or
adhere to the surface of a screening media and a passed "unders"
collecting pan therebelow; said input hopper includes a vibratory
motor; and a programmable motor control unit driving said motors
with said weights synchronized with one another and capable of
driving said motors at a selected speed and of periodically
changing said speed for a selected time interval by a selected
amount.
3. A method of screening aggregate using a vibrating screen unit
including a fixed base unit supporting an intermediate base with
connecting vertical support coil springs, and a vibrating screen
and housing rotatably connected to said intermediate base by drive
coil springs and leaf spring rockers driven by drive motors with
eccentric weights attached to said intermediate base, comprising
the steps of: a) providing said vibrating screen unit comprising: a
generally rectangular fixed base with a plurality of upward
extending support coil springs, said support coil springs fixedly
attach to a top surface of said fixed base and fixedly attached to
a bottom surface of a generally rectangular intermediate base, said
intermediate base having at least two rows of alternating large and
small triangular abutments extending upward therefrom, said large
triangular abutments having a first side forming about a forty-five
degree angle with a top surface of said fixed base, said first side
of said large triangular abutment having a drive coil spring
extending upward therefrom at about a forty-five degree angle with
a top surface of said fixed base member, said small triangular
abutments having a second side forming about a forty-five degree
angle with a top surface of said fixed base, said second side of
said small triangular abutment having two spaced apart leaf spring
rockers extending upward at about a forty-five degree angle with a
top surface of said fixed base, said first side of said large
abutment facing toward said second side of said small abutment; a
generally rectangular vibrating screen housing having at least two
rows of downward extending trapezoidal abutments on a bottom
surface thereof, said trapezoidal abutments fixedly connected on a
third side to free ends of said upward extending drive coils and on
a fourth side to free ends of said upward extending leaf springs,
said vibrating screen housing having at least one screen, an input
hopper and at least two output apertures formed therein; said
vibrating screen housing having a plurality of single or 3 phase
electrically adjustable alternating current motors mounted at one
end thereof, said motors having output shafts extending from top
and bottom ends with eccentric weights mounted on said shafts in
mechanical time with one another said motors fully electrically
adjustable over the complete range of zero to maximum output; a
vibration drive isolation assembly for vibrating said vibrating
screening unit; said vibration drive isolation assembly including
at least two parallel longitudinal counterbalance beams supported
on a plurality of isolation drive springs distributed across the
width of said vibrating screening unit; at least one vibratory
drive motor installed on said longitudinal counterbalance member;
said vibration drive isolation assembly includes a variable speed
motor controller for adjusting vibration intensity; said variable
speed motor controller being operatively arranged for dynamically
adjusting vibration intensity during a timed cycle; said timed
cycle includes an electrical control enabling a full zero to
maximum output adjustment by means of adding a standard variable
frequency (VFD) combined with adjustable timers so that a vibratory
stroke required screening has an automatic capability of a
momentary "pulsing" to 60 hertz (or higher) for a brief time of
usually 3 to 5 seconds, which generates a "spurt" or "pulse" to the
entire screening body for clearing screen media of a lump or a
particle stuck in a screen opening or to break free accumulated
layers of adhesive and cohesive particles that try to "stick" or
adhere to the surface of a screening media and a passed "unders"
collecting pan therebelow; said input hopper includes a vibratory
motor; and a programmable motor control unit driving said motors
with said weights synchronized with one another and capable of
driving said motors at a selected speed and of periodically
changing said speed for a selected time interval by a selected
amount; b) inputting aggregate material to an input hopper at an
input end of said vibrating screen; collecting and using screened
aggregate; c) collecting coarse aggregate; d) reprocessing coarse
aggregate and recycling reprocessed aggregate into said input
hopper; and e) setting programmable drive motor controller for
proper cycling between normal speed and a slightly higher speed for
selected time periods to prevent clogging of vibrating screen.
4. A vibrating screening feeder for feeding biomass and other fuels
comprising: a hopper containing a biomass having particles of
various sizes, said hopper including a down chute; a vibrating
screening unit; said hopper including a outlet interfacing with an
inlet chute of said vibrating screening unit, said inlet chute
including a baffle of 30 to 60 degrees for spreading said biomass
particles across a selected width of a feed plate of said vibrating
screening unit; a vibration drive isolation assembly for vibrating
said vibrating screening unit; said vibration drive isolation
assembly including a longitudinally extending longitudinal
counterbalance member; a plurality of drive springs supported by
said longitudinal counterbalance member with said drive springs
being distributed across at least the width of said vibrating
screening unit; at least one vibratory drive motor installed on
said longitudinal counterbalance member; and a plurality of
isolation springs supporting said longitudinal counterbalance
member.
5. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly includes a variable speed motor
controller for adjusting vibration intensity.
6. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly has a set operating frequency;
and said vibration drive isolation assembly having a linear stroke
for developing a unidirectional conveying action for directionally
vibrating biomass particles to multiple discharge openings located
at a defined discharge end.
7. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly has a defined stroke angle and
includes drive springs that are in alignment with said stroke
angle.
8. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly is positioned under said
vibrating screening unit.
9. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly includes a plurality of drive
springs being distributed across at least the width of said grate
unit.
10. The vibrating screening feeder of claim 4, wherein n said
vibration drive isolation assembly includes a longitudinal
counterbalance member.
11. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly includes a plurality of
isolation springs supporting said longitudinal counterbalance
member.
12. The vibrating screening feeder of claim 4, wherein said
isolations springs and said drive springs are steel coil springs;
said drive springs being stiffer than said isolation springs.
13. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly includes a pair of three phase,
A-C squirrel cage vibratory motors installed on said longitudinal
counterbalance member.
14. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly includes at least one electrical
vibratory drive motor.
15. The vibrating screening feeder of claim 4, wherein said
vibration drive isolation assembly includes a variable speed motor
controller for adjusting vibration intensity.
16. The vibrating screening feeder of claim 4, wherein said
variable speed motor controller being operatively arranged for
dynamically adjusting vibration intensity during a timed cycle.
17. The vibrating screening feeder of claim 16, wherein said timed
cycle includes an electrical control enabling a full zero to
maximum output adjustment by means of adding a standard variable
frequency (VFD) combined with adjustable timers so that a vibratory
stroke required screening has an automatic capability of a
momentary "pulsing" to 60 hertz (or higher) for a brief time of
usually 3 to 5 seconds, which generates a "spurt" or "pulse" to the
entire screening body for clearing screen media of a lump or a
particle stuck in a screen opening or to break free accumulated
layers of adhesive and cohesive particles that try to "stick" or
adhere to the surface of a screening media and a passed "unders"
collecting pan therebelow.
18. The vibrating screening feeder of claim 16, wherein an
electrical control enables a full zero to maximum output adjustment
by means of adding a standard variable frequency (VFD) combined
with adjustable timers so that a vibratory stroke of about 50 Hz
for about 25 seconds has an automatic capability of a momentary
"pulsing" to 60 hertz or higher for a brief time of from 3 to 5
seconds generating a greater vibratory action to the entire
screening body for clearing screen media of a lump or a particle
stuck in a screen opening or to break free accumulated layers of
adhesive and cohesive particles that try to "stick" or adhere to
the surface of a screening media and a passed "unders" collecting
pan therebelow.
19. The vibrating screening feeder of claim 4, wherein said
variable speed motor controller includes a variable voltage motor
controller.
20. The vibrating screening feeder of claim 4, wherein said
variable speed motor controller includes a variable frequency motor
controller.
21. A method of vibrating a conveying apparatus to convey material,
said method including the steps of: providing a bed having an inlet
end and an outlet end on which material is adapted to be conveyed
in a direction; providing a plurality of drive springs, each drive
spring having a first end attached to said bed and a second end
attached to a support, each said drive spring adapted to compress
and extend along a line of stroke; providing a plurality of
stabilizers attached to said bed, each said stabilizer being more
rigid in a direction transverse to said line of stroke than said
stabilizer is rigid in the direction of said line of stroke;
providing a first vibratory motor having a first rotatable
eccentric weight adapted to state about a first axis, a second
vibratory motor having a second rotatable eccentric weight adapted
to rotate about a second axis, a third vibratory motor having a
third rotatable eccentric weight adapted to rotate about a third
axis, and a fourth vibratory motor having a fourth eccentric weight
adapted to rotate about a fourth axis, said first and second axis
being located substantially in a first plane and said third and
fourth axes being located substantially in a second plane, said
second plane being non-coplanar with said first plane said first
and second axes being spaced from said third and fourth axes along
the direction the material is conveyed, said eccentric weights
being free-wheeling with respect to one another, each said
vibratory motor adapted to operate at substantially the same
operating speed and to provide an output force generally
perpendicular to its axis of rotation, said rotatable eccentric
weights adapted to accumulatively synchronize with one another
without being rotationally coupled to one another such that the
combined resulting output force of said first pair of rotatable
eccentric weights is generally parallel to said line of stroke and
the combined resulting output force of said second pair of
rotatable eccentric weights is generally parallel to said line of
stroke; operating said vibratory motors to rotate said eccentric
weights, such that said rotating eccentric weights accumulatively
synchronize and accumulatively add their output forces and their
respective power outputs and thereby vibrate said bed along said
line of stroke at a vibration frequency; and operating each said
vibratory motor at substantially the same selected operating speed
which approaches being equal to, or is less than, the natural
frequency of said drive springs which are vibrating said bed.
22. The method of claim 21 including the step of operating said
pair of vibratory motors located closest to said outlet end of said
bed so as to provide a greater force output than the remainder of
said pairs of vibratory motors.
23. The method of claim 21 including the step of uniformly
adjusting the vibration frequency of said bed by electrically and
simultaneously adjusting the rotational speed of each of said
vibratory motors, while said vibratory motors continue to operate
at substantially the same rotational speed with respect to one
another.
24. The method of claim 21 including the step of adjusting the
operating stroke and frequency of said drive springs and
stabilizers by use of an electrical control connected to each said
vibratory motor for simultaneously changing the rotational speed of
said vibratory motors, while said vibratory motors continue to
operate at substantially the same rotational speed with respect to
one another.
25. The method of claim 21 wherein said first and second rotatable
eccentric weights are rotated in opposite directions relative to
one another, and said third and fourth rotatable eccentric weights
are rotated in opposite directions relative to one another.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims priority from PCT/US2016/000056
filed on Jul. 5, 2016 which claims priority from U.S. Provisional
Application Ser. No. 62/493,460 filed on Jul. 2, 2016 and U.S. Ser.
No. 62/231,330 filed on Jul. 3, 2015 all of which are incorporated
by reference herein in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to the field of industrial
vibrating screens for separating small elements from large
elements, such as in the case of coal or stone.
BACKGROUND OF THE INVENTION
[0003] In the handling of particulate bulk material, there are
numerous ways for conveying such material and feeding it over an
open end of the conveyor to a desired point of delivery. This
invention is concerned with a conveyor or feeder vibrated as a free
mass, i.e., the trough or conveyor is suitably isolated from the
ground so that it may be vibrated in response to an oscillating
force, as distinguished from a mass which is positively connected
to the exciting force, as, for example, by driving the conveyor
through an arm rigidly connected to a fixed stroke eccentric
drive.
[0004] Vibrating screens are in use in numerous industrial
situations where the necessary separation of dust and fine
particles of a given product is necessary. For example, electrical
utility companies burn coal, which must be delivered to the boilers
in almost powdered form and screening of the coal aggregate is
necessary in very great volumes.
[0005] Conventional mechanical means operate by varying the
frequency or the stroke of the feeder. An exception to mechanical
means for adjusting rates of feed is in the case of an
electromagnetic drive for a feeder, in which case the frequency or
the voltage of the applied pulsating current applied to the
electromagnetic drive is varied. However, in this type of device
the vibrations per minute used are generally above 1800 cycles per
minute and have relatively short strokes with the result that such
feeders are limited to bulk materials of the more free-flowing type
as distinguished from those which are characterized as damp or
viscous.
[0006] Mechanical means such as either a variable rate spring
device which may include an air bag interposed in the drive with
the pressure in the air bag being adjustable to effect the change
of spring rate, or some form of mechanical adjustment of the drive
motors angularity or position relative to the pan. There have been
many attempts, in vibratory feeders, to utilize some form of
adjustable feed rate control using electrical phenomena, but to
date none of these have been successful for a number of reasons.
The electromagnetic type vibrators have high energy losses and are
restricted to essentially high frequency and short stroke
combinations. Low frequency, long stroke devices have been
conceived that utilize adjustable frequency A.C. drives,
multi-speed, and/or multi-winding A.C. motors, or adjustable
voltage D.C. drives. have met with success because of high initial
cost, and the cost of maintenance due to brush wear, commutator
problems and the like.
[0007] Induced conveying improves material handling in applications
where different kinds of solid fuels are used to produce heat in a
boiler with a vibrating stoker grate that burns it. The vibratory
feeders and screens induce the fuel's movement instead of forcing
it. This avoids squeezing and bunching the fuel. The Particles
remain loose which facilitates more efficient burning. Some power
plant boilers are fired by fuels such as coal meeting a demanding
specification wherein the fuel met the designation of "steam coal"
having a particle size, density, and moisture content specified for
efficient combustion.
[0008] When fuel is scarce because of shortages uncleaned ROM coal
and the waste coals such as culm, gob, silt, or high moisture "wet"
coal are burned, especially in countries having economic
difficulties. The biomass fuels of bagasse, wood waste such as
bark, chips, shavings, and sawdust fuel is used to fire boilers.
Refuse derived fuels (RDF) which is shredded municipal waster and
whole or shredded rubber tries can also be sources of fuel. Density
and moisture content are difficult to control. The induced vertical
flow and induced conveyance flow provided by vibrating feeders,
screens, and conveyors are used because these fuels are usually
obstinate to flow from storage.
[0009] Generally, a vibrating screen is fixedly mounted in a screen
housing with supporting frame work. The screen housing is then
supported above a fixed base by springs or rotatable arms. The
screen housing is caused to vibrate by some sort of drive which
shakes the housing. Some drives are fixed to the base and connected
by a crank journal to the vibrating screen housing. The prior art
illustration shown in FIG. 1 shows a fixed base member 102, a motor
and a crank journal driving a vibrating screen housing 108 which is
movable relative to the fixed base 102 about rotating arms 104 with
damper springs 20. Other drives consist of a motor fixed to the
vibrating screen housing driving eccentric weights which then cause
the screen housing to vibrate. These units have inherent
disadvantages such as difficulty of changing or repairing motor
drives and large energy consumption.
[0010] In the vibratory industry, vibratory conveying apparatus
such as vibrating feeders, vibrating conveyors, vibrating screens,
vibrating heat transferring fluidized beds, attrition mills, and
the like, were all powered by a well-known and popular driving
method called the "Single Input" or "Brute Force" type of drive. A
single pair of rotating eccentric weights is the sole source of the
input power in this kind of drive. Being installed directly across
from one another, a single pair of eccentric weights rotating in
opposite directions vibrate the vibratory conveying apparatus with
a linear or "back and forth", straight line motion. As the load
carrying capability of the conveying apparatus increased over the
years, the weight of the rotating eccentric weights also
necessarily increased in size, and the horsepower demand of the
electric motor utilized to rotate the eccentric weights increased
accordingly.
[0011] When more input power is needed to move heavier loads along
the length of the conveying trough, more rotating eccentric weight
force and horsepower are needed. Consequently, the rotatable
eccentric weights become larger and heavier and have a greater
force output. Likewise, the electrical windings in the vibratory
motor increase in size to produce more horsepower. This increase in
eccentric weight force output and the respective vibratory motor
horsepower has approached the point that the vibratory motors are
presently as large as practical to manufacture or to utilize on a
vibratory conveying type of apparatus.
[0012] Electric motor applications attempt to match motor torque
operating characteristics with load torque characteristics.
Conventional electric motor applications teach that an AC. squirrel
cage motor is not to be used for adjustable speed drive, because
the load torque requirements are such that when an attempt is made
to substantially alter speed through change in voltage, the motor
is overloaded and will burn out, except in the case when the motor
drives a fan or a pump which is used in moving a fluid, wherein the
load torque requirements are consistent with the thermal capability
of a squirrel cage motor.
[0013] In the present invention it is possible to use an A.C.
squirrel cage motor and adjust the voltage thereon to vary the feed
rate of the vibratory system is because the vibratory system is of
the free mass, natural frequency type, that is, the motor exciter
drive is a part of a natural frequency vibratory system and the
vibratory system is isolated from ground, as distinguished from a
vibratory system which is driven positively from a fixed stroke
rotary eccentric member as best described by Applicant prior U.S.
Pat. No. 3,251,457 for a Method and Apparatus for Driving Vibratory
Devices which issued in 9165 and is incorporated by reference
herein in its entirety.
[0014] As the system operates below natural frequency, the mass
inertia vector is diminished, the spring effect is diminished, the
damping losses are diminished, and the applied force is subdivided
into a horizontal and vertical component, with the horizontal
component matching the damping losses, and the vertical component
acting in opposition to the spring effect. This in itself creates a
mechanical impedance on the motor resulting in the stroke of the
feeder being diminished, and explains why the current drawn by the
motor, which is proportional to the damping losses, diminishes as
one moves below natural frequency. Therefore, an AC. squirrel cage
motor may be used effectively to change the speed of the motor and
a natural frequency resulting in a free mass vibratory system.
[0015] Watts, volts, amperes, and stroke characteristics vary
exponentially in relation to speed, and that a small change in
speed causes a marked change in feed rate, current, and watts,
which explains why the feed rate can be changed in this manner
without burning up the motor. The load torque characteristics of
the motor are being matched with the load torque demands of the
vibratory mass system.
[0016] It is the objective of this invention to operate as near the
peak of the curve as is possible for maximum feed and normal load
conditions. As a practical matter, the spring rates are chosen for
no load condition so as to have the system operate so that when the
vibrating screening feeder is carrying a normal load. As voltage is
reduced on the motor to move from maximum feed rate to a lesser
feed rate, the frequency and` stroke are both being reduced until a
zero feed rate is approached.
[0017] Although it is contemplated that a fixed rate spring would
be used `for tuning the vibratory mass to the frequency of the
oscillatory drive, it is possible that a variable rate spring might
in some instances be used to approximate the natural frequency of
the system and then adjust the rate of such spring until the
frequency of the vibratory mass system. After that, the control of
frequency and stroke would be accomplished in the manner previously
described by dropping the voltage on the AC. squirrel cage
motor.
[0018] An autotransformer has shown in prior art FIG. 19 provides a
way to adjust the voltage on the AC motor. Other ways in which the
voltage may be regulated is, for example, by the use of solid state
type control including a gating transistor.
[0019] Another common problem with vibrating screens occurs when
screens become jammed or clogged with aggregate material. This
clogging slows or stops throughput causing costly shutdown for
screen cleaning and unclogging. The instant invention includes a
pulsing solution to dislodge contaminants from the screens.
SUMMARY OF THE INVENTION
[0020] A continuous, steady flow of the supply of the incoming bulk
solid such as coal, ore, wood waste, or the like is required as
feed material for optimal control and screening performance of the
feeding and screening system. It is recommended that the vibrating
screening feeder be installed under the outlet of a storage bin or
silo or surge bin. The outlet of the steady feed source must be
interfaced with the vibrating screening feeder inlet chute that
connects to the feed bin. The chute typically includes a baffle of
30 to 60 degrees and preferably about 45 degrees to help convert
the vertical feed flow into the inlet to a horizontal or near
horizontal flow and spread across the full width of the vibrating
screen feeder feed plate. The screen media is usually woven wire of
perforated plate with longitudinal side clamps, flap plastic
squares or any standard screen media. Three screening decks are
typically used in the apparatus; however, it is contemplated that
additional decks may be added. The passed "unders" (under sized
particles) collecting pan is disposed beneath the screening plates
and extends the full width and length of the screen for collecting
and conveying all of the passed "unders" to an outlet located near
to the end of the screen. The collecting pan includes an outlet for
discharging the "passed unders" located near the end of the screens
and can be full width or converging. The means for powering the
vibrating screening feeder is accomplished by motorized an AC motor
rotating unbalanced eccentric weights combined with sub-resonant
tuned steel coil drive springs which are attached to the end of a
longitudinal counterbalanced support base which is a longitudinal
structure which can be cut into sections that are bolted together
if necessary. The instant invention concentrates and nests the
steel drive coils in selected positions or locations connecting the
screening unit to the longitudinal counterbalance support base.
[0021] A novel feature of the instant invention is based on the
electrical control enabling a full zero to maximum output
adjustment by means of adding a standard variable frequency (VFD)
combined with adjustable timers so that a vibratory stroke required
screening has an automatic capability of a momentary "pulsing" to
60 hertz (or higher) for a brief time of usually 3 to 5 seconds,
which generates a ver vigorous vibratory action "spurt" or "pulse"
to the entire screening body similar to a dog shaking off water.
The pulsing action is usually automatically repeated to keep the
screen media clear of "pegging" or being blinded by lumps or
particles) stuck in the openings) or to break free accumulated
layers of adhesive and cohesive particles that try to "stick" or
adhere to the surface of the screening media and the passed
"unders" collecting pan below it.
[0022] Another novel feature of the present invention is the
feedback control operation of the vibrating screening feed based
upon the throughput capacity of the equipment it is feeding. For
instance, if feeding a rock crusher, a standard 4 to 20 ma direct
current (D.C.). signal can be used to automatically control the
vibrating screening feeder's variable frequency (VFD) control of
the screening feeder. The closed loop of the control circuit
monitors the amps drawn by the rock crusher to control the feed
rate of the vibrating screening feeder by increasing or decreasing
the output of the fed from the vibrating screening feeder. Thus,
the amps pulled by the equipment being fed will control the rate of
feed. The variation form zero to maximum TPH output and the
repeated "pulsing" of making the motor with eccentric weights to go
faster and then return to a slower, steady speed is accomplished
with the 3 phase alternating current (A.C.) squirrel cage
motor.
[0023] Another feature facilitating processing of sticky feed
material is a cross bar with water spray nozzles which can
optionally be used when adhesive and cohesive bulk solids are being
screened to clean the sticking particles to the screening surface
of the collecting pan underneath.
[0024] Use of stainless steel or other alloys which tend to resist
sticky residues are also useful to eliminate sticky residue and
agglomerates. Coatings such as TEFLON may also be used to treat the
surface of equipment to resist sticky residue.
[0025] The vibrating screening feeder is dust tight having a bolted
top cover with quick opening view ports add to the screen body.
Enclosed vertical chutes are added to the discharge end. Flexible
connections also seal the inlet and the outlets.
[0026] In accordance with features of the invention, the vibration
drive isolation assembly includes a longitudinally extending
longitudinal counterbalance member. A plurality of drive springs
are supported by the longitudinal counterbalance member. The drive
springs are distributed across the width and the length of the
enclosed screening unit. At least one vibratory motor or mechanism
is installed on the proximate end of the longitudinal
counterbalance member. A plurality of isolation springs support the
longitudinal counterbalance member.
[0027] Induced conveying is accomplished by imparting a proper
stroke at the needed frequency to move the load. The result is a
conveying motion that is induced instead of being forced. It can be
a very gentle type of movement or when necessary, a very sharp,
reacting type of vibration which can be produced by using an
appropriate stroke angle. A helical or elliptical stroke pattern
will convey the material in a circular path resulting in a backspin
on the particle. A linear stroke is the most efficient one to use
for unidirectional movement which moves the material in a straight
line. The vibratory action does most of the work. When vibrated,
the inner particle friction of the moved material is reduced.
[0028] A particle can be vibrated and conveyed over a hard surface
by means of a series of repetitive "hops". Each "hop" is a cycle.
The distance hopped is directly related to the unit's stroke length
and the angle at which it is applied. The "hops" per unit of time
is the operating frequency which is usually expressed in "cycles
per minute" or (CPM).
[0029] An alternative vibratory motor embodiment suitable as a
drive means for the vibratory screening feeder utilizes a double
extended shaft with eccentric weights installed on both ends of the
shaft and are cumulatively considered as a single rotatable
eccentric weight. Vibratory motors equipped with shaft mounted
eccentric weights will be emphasized herein, but other jack shaft
driven combinations can also be used such as vee-belts and the
like. In either instance, the pair of rotatable eccentric weights
are installed on and become an integral part of the conveying
assembly.
[0030] It is an object of this invention to provide a vibrating
screen for separating of at least two particle sizes of aggregate
in a continuous flow process.
[0031] It is an object of this invention to provide a vibrating
screen for separating of at least two particle sizes of aggregate
in a continuous flow process which has a low horsepower to tonnage
throughput ratio as compared to other separation processes.
[0032] It is an object of this invention to provide a vibrating
screen which includes a periodic cleaning and unclogging of the
screens wherein the speed of the drive motors is periodically and
briefly changed by a nominal amount for a short time to dislodge
blockages.
[0033] It is an object of this invention to provide a vibrating
screen which provides motors located in an easy to maintain
location at one end of the vibrating screen unit.
[0034] It is an object of the present invention to provide an
electrically controlled, a vibratory drive powered by electric
motors or high frequency electromagnets that are combined with
steel coil springs that are sub-resonant tuned (enabling drive
springs to drive harder under loaded conditions), to provide a
vibrating screen for unidirectional material movement whereby the
vibratory drive is the prime mover of the material (induced
conveying) as opposed to conventional vibratory feeds which depend
upon the force of gravity (induced vertical flow) as the prime
mover of the material.
[0035] It is an object of the present invention to convey and
screen material in response to applied vibratory action via a free
force vibratory input combined with subresonant tuned springs to
reduce interparticle friction and stratify the material into layers
by particle size.
[0036] It is an object of the present invention to utilize the
principle of resonance or natural frequency and to subresonant tune
the drive springs to produce more under load whereby the machines'
operating frequency is always kept below or under the resonant
point of all the drive springs.
[0037] It is an object of the present invention to provide a
vibratory feeder and screen apparatus whereby the dynamic
acceleration is the same in both directions of the back and forth
movement of its vibratory motion versus a reciprocating motion that
moves forward slowly and then accelerates rapidly on its return
stroke.
[0038] It is an object of the present invention to provide a
vibratory feeder capable of screening wet bulk solids that are
adhesive and cohesive.
[0039] It is an object of the present invention to provide a
vibrating feeder and vibrating screen assembly which can tolerate
variation in moisture content.
[0040] It is an object of the present invention to incorporate a
drive system for a vibratory feeder and conveyor powered by one or
more electric motors with input power provided by eccentric weights
rotated by each motor, a linear stroke pattern, a wide range of
operating frequencies, electrically adjustable output with zero to
maximum output by variable voltage, with the stroke and frequency
simultaneously changed, subresonant operational tuning,
longitudinal counterbalanced vibratory force isolation, and capable
of smooth repetitive starts and stops.
[0041] It is an object of the present invention to provide a drive
system having three primary components comprising a steel coil
drive spring that produces the portion of the load that opposes the
vibratory motion, a plurality of flat bar stabilizers guide the
motion, and the motor produces the remaining portion of the load
that resists it.
[0042] It is an object of the present invention to provide an
energy efficient drive system for the vibrating feeder and screen
apparatus.
[0043] It is an object of the present invention to provide a
screening deck for: cleaning unit pieces by removing clinging
particles such as adhered sand or trimming edges; for washing by
mounting rows of liquid sprays directly over the screen medium, a
bulk solid or a unit piece so the liquid spray such as water, oil,
surfactant, defactant, or other washing action; sizing to separate
flakes and sizes; scalping to remove oversize particles; removing
undersize particles; grading; deliquifying; desliming by washing
the clinging fines from freshly crushed lumpy materials; rinsing;
dewatering; and draining.
[0044] It is an object of the present invention to include an
underside pan fo recollecting all the "passed" unders.
[0045] It is an object of the present invention to utilize
conveying surfaces dynamically counterbalanced and isolated with
isolation springs to reduce motor power consumption by 50 to 70
percent compared to conventional motors achieving the same
performance.
[0046] It is an object of the present invention to utilize multiple
small low HP motors with synchronized rotating eccentric weights in
place of larger higher HP motors.
[0047] It is an object of the present invention to provide a
"dust-tight" vibrating screen design.
[0048] It is an object of the present invention to provide an
unidirectional induced conveying apparatus can be non-balanced and
fixed to the earth or dynamically counterbalanced with isolator
springs to support it.
[0049] It is another object of the present invention to provide an
extremely simple and practical way to adjust frequency and stroke,
in the drive for vibrating devices combined with mechanical
impedances which are purposely built into the vibrating mass
system.
[0050] A further objective of the invention is to provide an
electric drive for vibratory equipment which lends itself to
simplified remote control for changing the frequency and the stroke
of the vibratory equipment.
[0051] A still further object of the invention is to make use of an
A.C. squirrel cage induction motor which is well known to have
rugged performance characteristics, low maintenance costs and low
initial costs as compared to other electrical motors which are
capable of adjustable speeds.
[0052] Other objects, features, and advantages of the invention
will be apparent with the following detailed description taken in
conjunction with the accompanying drawings showing a preferred
embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0053] A better understanding of the present invention will be had
upon reference to the following description in conjunction with the
accompanying drawings in which like numerals refer to like parts
throughout the views wherein:
[0054] FIG. 1 is a side view of a prior art vibrating conveyor
showing a fixed base member, a motor and a crank journal driving a
vibrating screen housing which is movable relative to the fixed
base about rotating arms with damper springs;
[0055] FIG. 2 is a side elevational view of the vibrating screening
feeder unit illustrating natural frequency vibrating screening
feeder in which the exciter motor is suspended from the vibratory
mass system and acts in parallel with the drive springs which are
selected to give the system natural frequency characteristics;
[0056] FIG. 3 is a view of a section of the vibrating screening
feeder showing the screening unit connecting to drive springs
mounted on brackets supported by the longitudinal counterbalance
support base;
[0057] FIG. 4 is an end view of the vibrating screening feeder
showing the screening unit connecting to a plurality of drive
springs mounted in a row across the width of the screening unit and
longitudinal counterbalance support base which is supported by a
plurality of horizontal coil steel isolation springs supporting the
longitudinal counterbalance support base on a base and showing a
plurality of motors mounting on the rear end of the longitudinal
counterbalance support base;
[0058] FIG. 5 is a perspective view of the vibrating screening
feeder unit of the present invention showing the screening unit
side walls and pan having brackets connecting to a plurality of
drive springs mounted in a row across the width of the screening
unit and longitudinal counterbalance support base;
[0059] FIG. 6 is an elevated perspective view of the vibrating
screening feeder unit showing the discharge chutes extending from
the rear end of the present invention;
[0060] FIG. 7 shows that when the drive springs 20 are expanded,
the rocker springs 24 are flexed upward.
[0061] FIG. 8 shows that when the drive springs are compressed, the
rocker springs 24 are flexed downward.
[0062] FIG. 9 shows a vibratory motor with rotatable eccentric
weights;
[0063] FIG. 10 shows the vibratory motor of FIG. 9 including extra
weights added to the shaft;
[0064] FIG. 11 is an end view of a vibrating screening feeder unit
showing the storage bin positioned above the vibrating screening
feeder and connecting the bin outlet to the feeder inlet
interfacing chute;
[0065] FIG. 12 is a side view of the vibratory screening feeder
showing a chute connecting the bin to the feeder inlet and the
screening unit supported by the longitudinal counterbalance on
drive springs and the longitudinal counterbalance supported on the
base with steel coil isolation springs;
[0066] FIG. 13 is an end view of the vibrating screening feeder
showing the motors attaching to the rear end of the longitudinal
counterbalance, a row of isolation springs supporting the screening
unit above the longitudinal counterbalance and the drive springs on
the outside of the row extending across the screening unit
supported by the longitudinal counterbalance;
[0067] FIG. 14 is an elevated side view of the vibratory screening
feeder showing a chute connecting the bin to the feeder inlet and
the screening unit supported by the longitudinal counterbalance on
drive springs and the longitudinal counterbalance supported on the
base with steel coil isolation springs wherein the longitudinal
counterbalance is angled downward at a 15 degree angle with respect
to the base;
[0068] FIG. 15 is an elevated side view of the vibratory screening
feeder of FIG. 16 showing a chute connecting the bin to the feeder
inlet and the screening unit supported by the longitudinal
counterbalance on drive springs and the longitudinal counterbalance
supported on the base with steel coil isolation springs wherein the
longitudinal counterbalance is angled downward at a 15 degree angle
with respect to the base and showing the optional water spray bars
and discharge connection to a crusher;
[0069] FIG. 16 is an end view showing the connection of the
vibrating screening feeder to the crusher and the discharge
chute;
[0070] FIG. 17 is a side elevational view of prior art showing the
drive of this invention applied to a natural frequency vibratory
feeder where the springs are in series with the motor drive.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0071] As shown in the FIGS. 1-17, a vibrating screening feeder
system 1 includes a vibratory storage bin 8 feeding a vibrating
screening feeder unit 10 feeding and crusher 70 for oversized
material. The intermediate storage bin 8 is positioned above the
vibrating screening feeder 10 connecting the bin outlet 102 to the
feeder inlet interfacing chute 104. The size of the bin 8 is
determined by the throughput to maintain a maximum feed rate to the
vibratory screening feeder 10 and ensure an appropriate amount of
storage to enable it to continuously operate at its rated TPH (ton
per hour) capacity. The bin's outlet 102 is positioned close to the
feeder inlet 103 separated by the feed plate 105. Preferably the
bin 8 is a vibratory bin or hopper having the capability to shake
accumulations or bridging particles from the sidewalls to effect a
smooth flow of feed to the vibratory screening conveyor 10. The
following U.S. patents are incorporated by reference herein are
some of the vibratory hoppers which may be useful for utilization
with the present invention:
U.S. Pat. No. 3,261,592; U.S. Pat. No. 3,257,040; U.S. Pat. No.
5,046,643; U.S. Pat. No. 4,960,229; U.S. Pat. No. 3,735,963; U.S.
Pat. No. 4,744,893; U.S. Pat. No. 4,899,669; and U.S. Pat. No.
4,844,289.
[0072] As shown in FIGS. 2, and 11-11, a chute 104 or stove pipe
can be used to connect the bin to the feeder inlet 104. On
"start-up" the top section or cover is temporally removed to permit
the adjustment of the "mat depth" flowing into the vibrating
screening feeder 10. When adjusted properly, full width spreading
is obtained and the cover 56 is reinstalled over the unit. Also
shown are the horizontal coil steel isolation support springs 22
which are nested in sets and mounted to support members 23
extending across the width of the conveyor. The isolation springs
22 rest on a base, floor or other immobile support surface. A
alternate motor 58 is shown mounted to the longitudinal
counterbalance 26.
[0073] FIG. 13 is an end view of the vibrating screening feeder
showing the motors attaching to the rear end of the longitudinal
counterbalance, a row of isolation springs 22 supporting the
screening unit above the longitudinal counterbalance and the drive
springs 20 on the outside of the row extending across the screening
unit supported by the longitudinal counterbalance. The vibrating
screening feeder 10 shown includes 200 drive springs 20 are
arranged in sets of two rows each extending across the width of the
conveyor attaching to the conveyor bed frame or integral body/frame
support members 18 supported at a 45 degree angle by brackets 19
mounted on the top of the longitudinal counterbalance support base
26. Each drive spring or coil is equivalent to 1/2 HP. Thus, 200
drive springs provide the equivalent of 100 HP of driving force to
the vibrating screening feeder 10.
[0074] As shown in FIG. 14, the vibratory screening feeder shows a
chute connecting the bin to the feeder inlet and the screening unit
supported by the longitudinal counterbalance on drive springs and
the longitudinal counterbalance supported on the base with steel
coil isolation springs wherein the longitudinal counterbalance is
angled downward at a 15 degree angle with respect to the base.
[0075] FIG. 15 is an elevated side view of the vibratory screening
feeder of FIG. 14 showing a chute 104 connecting the bin 8 to the
feeder inlet and the screening unit 10 supported by the
longitudinal counterbalance on drive springs 20 and the
longitudinal counterbalance supported on the base with steel coil
isolation springs 22 wherein the longitudinal counterbalance is
angled downward at a 15 degree angle with respect to the base and
showing the optional 450 gallon per minute (GPM) water spray bars
52 and valve 54 and discharge connection 44 to a crusher 70 for
minus 7 millimeter material. FIG. 16 is an end view showing the
connection of the vibrating screening feeder to the crusher 70 and
the discharge chute 44.
[0076] The vibrating screening feeder 10 consists or comprises a
trough or pan defined by a bottom floor 11, side walls 12 and 13,
and a rear end wall 14, with the forward end wall 15 including
chutes 40, 42, and 44 in fluid engagement with downstream
processing equipment. The processed feed material is delivered to a
desired conveyor or process equipment point at some selected rate
of speed. The vibrating screening unit 10 is mounted on support
members 18 which are carried at selected points at the front and
rear portions of the a vibrating screening feeder 10r mounted
beneath the trough, bed, or pan 11.
[0077] The drive springs 20 are preferably selected with K factors,
that is, spring rates which are appropriately related to the
frequency of the motor drive, the mass of the motor drive
component, and the total mass of the driven vibratory system, so
that under normal synchronous speed of the drive motor, the springs
20 will be at or near natural frequency with the system. For ideal
operation, the vibratory system with its exciter drive is designed
to operate at, as close to, the natural frequency of the system as
illustrated by the stroke-frequency curve of FIG. 7 of U.S. Pat.
No. 4,015,705 wherein the natural frequency is at the peak of the
curve.
[0078] It will be understood that the drive springs 20 are also
designed so that lateral forces transverse to the longitudinal axis
of the vibrating screening feeder 10 are absorbed by the lateral
deflections of the springs 20. Of course, if desired dual motors
having the same characteristics as the motor 30, except for being
each one-half the horsepower of the single motor, may be used in
place of the single motor 30, in which case they are driven in
opposite directions and have their motor housings rigidly joined
together in a manner well known in the art so as to cause the
rotating weights to phase together and cancel out the lateral
forces while producing a resultant linear stroke.
[0079] A motor 30 for vibrating the vibrating screening feeder 10
at a selected frequency and stroke for moving particulate material
on the pan 11 toward the feeding forward end 15 of the feeder. The
motor drive in the present invention is capable of adjusting the
rate of feed by varying the frequency and the stroke of the
vibratory system.
[0080] An unexpected surprising and unique relationship exists
between the characteristics of the vibratory system and the driving
motor, whereby it is possible to vary not only the frequency, but
also to simultaneously vary the stroke of a natural frequency
vibrating feeder or similar vibratory system merely by changing the
voltage on the A.C. motor 30. An A.C. squirrel cage motor has
always been thought of as essentially a constant speed motor
(except, of course, a multi speed or multi-winding A.C. motor) one
which could not have its speed effectively varied by voltage
control. The variable load requirements of a free mass, natural
frequency, vibratory system in relation to speed are similar to
those of a fan or a fluid pump and that it is possible to use
variations in the voltage applied to the A.C. squirrel cage motor
as an effective means for controlling the feeding rate of this type
of vibratory system, and that, surprisingly, this can be
accomplished without motor overload.
[0081] The ability to control feeder rate merely by voltage control
lends itself to the remote control of systems of this type, and is
far more convenient than attempting to adjust or vary the rate of
the force-transmitting spring units interposed between the motor 30
and the vibrating screening feeder 10.
[0082] The motor drive 30 comprises a single alternating current
squirrel cage induction motor which is supported on the rear end of
the longitudinal counterbalance 26 from a motor mount bracket
rigidly secured thereto. The motor has a squirrel cage rotor, and
is thereby characterized as one which does not have brushes. For
convenience the type of A.C. motor will hereinafter be referred to
simply, as an A.C. squirrel cage motor, and is to be distinguished
from a variable speed A.C. motor having multiple windings or
multipoles for speed control.
[0083] As shown best in FIGS. 9-10, at each end of the shaft 33 of
the motor 30 an eccentric weight 52 is mounted, and usually these
weights are fixed to the shaft in parallel relationship, although
in some instances, it may be desirable to vary their angular
relative positions to achieve adjustment of the effective eccentric
mass operating on the vibratory system, or adjusting weights 54 may
be added to or subtracted from the eccentric weights, as required.
Shrouds cover the ends of the motor to protect personnel from the
revolving eccentric masses.
[0084] The motor 30 is supported on the longitudinal counterbalance
in such a manner that the exciting oscillatory force supplied by
the eccentrically weighted motors is applied to the vibratory
conveyor screening unit 9 along a fixed angle of attack. This angle
of attack is ordinarily on the order of from 20 to 40 degrees, and
it will be seen that as an oscillating force is applied to the
vibrating screen 9 along this axis, the particulate on the
vibrating screen 9 is caused to move toward the open end of the
vibrating screen 9 by what might be termed a hopping action. As the
frequency of the oscillating force is reduced and/or as the stroke
is reduced, the rate of feed is correspondingly reduced and it is
desirable to have this rate of feed variable between zero, or
substantially zero, and the maximum rate of feed.
[0085] It is an accepted fact in the natural frequency vibrating
system field (as for example in the type of feeder shown in
Klemencik U.S. Pat. No. 2,725,984) that one can normally determine
whether the system is operating in natural frequency by checking
the current draw on the motor, because, when the system is
operating at true natural frequency, the current draw is at a
minimum. Conversely, to the extent that a system of this type is
not operating at natural frequency, the power requirements go up,
and this is reflected in increased current draw, regardless of
whether one is operating above or below the point of natural
frequency. Contrary to conventional teachings, when the present
invention is operating in natural frequency, the current drawn by
the motor is at its maximum, and, as the frequency (i.e. speed) of
the motor is changed by dropping the voltage, the current
decreases. As one moves below natural frequency with the system the
current going through the motor drops rather than rises, as might
normally be expected. It is possible to effectively vary the feed
rate of a vibratory conveying or feeding system from-substantially
zero to its maximum feed rate, merely by adjusting the voltage of
an A.C. squirrel cage motor. This of course can conveniently be
done with an auto transformer, such as shown in FIG. 17.
[0086] The vibrating screening feeder is adapted to be driven by a
plurality of accumulatively phased pairs of free-wheeling rotatable
eccentric weights. The accumulative force output produced by the
rotating eccentric weights will be a unified amount equal to the
sum of all the multiple pairs of eccentric weights. The respective
power outputs of the motors turning these eccentric weights will
also accumulatively add. This wanted "phasing" of multiple pairs of
rotating eccentric weights will only occur when used in conjunction
with properly stabilized, sub-resonant tuned, stiff drive
springs.
[0087] The accumulative phasing of a plurality of pairs of rotating
eccentric weights is applicable to vibratory conveyors of the
non-balanced type, which must be rigidly fixed to their support
structure. It is also applicable to vibratory conveying machines
that are dynamically counterbalanced and provided with isolation
springs. The longitudinal counterbalance can be one single
longitudinal assembly, or the longitudinal counterbalance can be
sectionalized in a plurality of sections as shown in Dumbaugh U.S.
Pat. No. 4,149,627. It is important to note the vibrating screen 9
must employ the sub-resonant tuned springs kind of vibratory drive
configuration that is properly stabilized for this wanted multiple
phasing of a plurality of pairs of rotatable eccentric weights to
occur.
[0088] The multiple pairs of rotatable eccentric weights are
installed on and become an integral part of the conveying trough
assembly of the conveying apparatus when the vibratory conveying
apparatus is the "non-balanced" type. This means its longitudinal
counterbalance frame is rigidly "fixed" to a robust stationary
foundation. Conversely, when the vibratory conveyor is "dynamically
counterbalanced", the pair of rotatable eccentric weights can be
installed on either the conveying trough or on a counterbalancing
member. When the conveying apparatus is longitudinal
counterbalanced, the pair of rotatable eccentric weights are almost
always installed on the counterbalancing member.
Method of Use:
[0089] A continuous, steady flow of the supply of the incoming bulk
solid such as coal, ore, wood waste, or the like is required as
feed material for optimal control and screening performance of the
feeding and screening system. It is recommended that the vibrating
screening feeder 10 be installed under the outlet of a storage bin
or silo or surge bin 8. The outlet 105 of the steady feed source
must be interfaced with the vibrating screening feeder inlet chute
104 that connects to the feed bin 8. The chute typically includes a
baffle of 30 to 60 degrees and preferably about 45 degrees to help
convert the vertical feed flow into the inlet to a horizontal or
near horizontal flow and spread across the full width of the
vibrating screen feeder feed plate 17.
[0090] The screen media 53 is usually woven wire or a perforated
plate with longitudinal side clamps, flap plastic squares or any
standard screen media. Three screening decks, a (top deck 50, a
middle deck 55, and a bottom deck 58), and a bottom trough or pan
11 are typically used in the vibrating screening feeder 10;
however, it is contemplated that additional decks may be added. The
passed "unders" (under sized particles) collecting pan 11 is
disposed beneath the screening plates and extends the full width
and length of the screen for collecting and conveying all of the
passed "unders" to an outlet located near to the end of the screen.
The collecting pan 11 includes an outlet 44 for discharging the
"passed unders" located near the end of the screens and can be full
width or converging. The means for powering the vibrating screening
feeder is accomplished by motorized an AC motor rotating unbalanced
eccentric weights combined with sub-resonant tuned steel coil drive
springs which are attached to the end of a counterbalanced support
base which is a longitudinal structure which can be cut into
sections that are bolted together if necessary. The instant
invention concentrates and nests the steel drive coils 20 in rows
at selected positions or locations connecting the screening unit to
the longitudinal counterbalance support base 26.
[0091] The electrical control enables a full zero to maximum output
adjustment by means of adding a standard variable frequency (VFD)
combined with adjustable timers so that a vibratory stroke of about
2 Gees for the require screening (50 Hz at for about 25 seconds)
has an automatic capability of a momentary "pulsing" to (60 hertz
(or higher) for a brief time of usually 3 to 5 seconds), which
generates a ver vigorous vibratory action "spurt" or "pulse" to the
entire screening body similar to a dog shaking off water. The novel
pulsing action is usually automatically repeated to keep the screen
media clear of "pegging" or being blinded by lumps or particles)
stuck in the openings) or to break free accumulated layers of
adhesive and cohesive particles that try to "stick" or adhere to
the surface of the screening media and the passed "unders"
collecting pan 11 below it.
[0092] A novel feature of the present invention is the control of
the vibrating screening feed by the equipment it is feeding. For
instance, if feeding a rock crusher 70, a standard 4 to 20 ma D.C.
signal automatically controls the vibrating screening feeder's
variable frequency (VFD) control of the vibrating screening feeder
10. The closed loop of the control circuit comprises or consists of
monitoring the amps drawn by the rock crusher to control the feed
rate of the vibrating screening feeder by increasing or decreasing
the output of the fed from the vibrating screen. Thus, the amps
pulled by the equipment being fed will control the rate of feed.
The variation form zero to maximum TPH output and the repeated
"pulsing" of making the motor with eccentric weights to go faster
and then return to a slower, steady speed is accomplished with the
3 phase A.C. squirrel cage motor.
[0093] More particularly, there is provided a vibrating screen unit
9 comprising, consisting of, or consisting essentially of a
generally rectangular frame 88 supported by a fixed base defining a
longitudinal counterbalance 26 by a plurality of upward extending
isolation support coil springs 22 fixedly attaching to a top
surface of the longitudinal counterbalance 26 and fixedly attached
to a bottom surface of the generally rectangular frame 8. The
intermediate frame 8 has triangular shaped support members 18
defining alternating large and small triangular abutments extending
upward therefrom. The large triangular abutments have a first side
forming about a forty-five degree angle with a top surface of the
longitudinal counterbalance 26. The first side of the large
triangular abutment 18 have a drive coil spring 20 extending upward
therefrom at about a forty-five degree angle with a top surface of
the longitudinal counterbalance 26. The small triangular abutment
has two spaced apart leaf spring rockers 24 extending upward at
about a forty-five degree angle with the top surface of the
longitudinal counterbalance 26. The first side of the large
abutment faces toward the second side of the small abutment. A
generally rectangular vibrating screen housing 79 has at least two
rows of downward extending trapezoidal abutments on a bottom
surface thereof. The trapezoidal abutments fixedly connect on a
third side to free ends of the upward extending drive coils 20 and
on a fourth side to free ends of the upward extending leaf springs.
The vibrating screen housing 79 has at least one screen and
preferably a plurality of screens extending the width and length of
the frame 8, an input hopper 88 and at least two output apertures
formed therein. The longitudinal counterbalance support base 26 has
a plurality of motors 30 mounted at a rear end thereof. The motors
have output shafts extending from top and bottom ends with
eccentric weights mounted on the shafts in mechanical time with one
another. A programmable motor control unit is capable of driving
the motors with the weights synchronized with one another and
capable of driving the motors at a selected speed and of
periodically changing the speed for a selected time interval by a
selected amount.
[0094] The present application provides a vibrating screen for
separating different sizes of aggregate in a continuous flow
process wherein aggregate flows into a hopper, down onto one end of
a vibrating screen, and is transported over the screen by vibration
of the screen. Fine and medium sized portions of the aggregate fall
through the first screen to a second screen. Only fine portions
fall through the second screen. Thus the aggregate is separated
into three grades of material. The vibrating screen is rotatably
connected to a moveable intermediate base member by a plurality of
leaf springs fixedly connected at about a forty-five degree angle
between the longitudinal counterbalance 26 and the vibrating screen
frame unit 9 and a plurality of coil springs called `drive springs`
20 which are connected at 45 degrees with the leaf springs between
the longitudinal counterbalance and the vibrating screen. The
longitudinal counterbalance in turn is supported above a fixed base
member by vertical coil springs 22. The longitudinal counterbalance
includes a number of electric motors 30 which have eccentric
weights connected directly to the shafts. When the motors are
running the spinning eccentric weights cause the vibrating
screening frame 10 to vibrate at a frequency consistent with the
speed of the motors. The speed of the motors can be varied to give
a different vibrating frequency.
[0095] The mostly horizontal left and right motion of the
intermediate base member therefore causes a left to right and an up
and down motion of the vibrating screen housing 79. It can also be
seen that, primarily, the `drive springs` 20, and to a smaller
degree, both the leaf springs 24 and the drive springs 20, store
and release energy every cycle of movement. This system of springs
establishes a harmonic system which tries to maintain a frequency
of movement of the system. This storing and releasing of energy
allows for a more efficient system with fewer and smaller drive
motors for a given throughput of aggregate.
[0096] The motors 30 are variable speed and run at one selected
speed most of the time. Periodically, however, the speed is changed
by a selected amount for a selected period of time and then
returned to normal. This change in speed dislodges jams or clogs
that occasionally occur in the process, due to density and particle
variance, moisture, and so forth. The vibrating screen of the
present invention gives superior performance where moist aggregate
is an issue.
[0097] A programmable motor controller easily accomplishes this
periodic cycle of motor speed change. A user can easily change the
cleaning cycle time and amount of speed change, as desired.
[0098] The preferred embodiment includes an input hopper with a
vibratory motor 31 to vibrate the provide consistent feed rate of
aggregate onto the vibrating screens. Another preferred embodiment
has a hopper without a separate vibratory drive motor and wherein
the gap between the bottom of the hopper is adjusted manually to
give an ideal flow of aggregate over the input end of the vibrating
screen. This hopper is preferably fitted with a device which
strikes the side of the hopper periodically or whenever a bridging
or clogging of aggregate is detected.
[0099] It is anticipated that a feed box may be used between the
hopper and the vibratory screen comprising a short length conveying
trough utilized at the inlet end of the conveyor where the incoming
bulk solid needs to be stratified to avoid abrasive wear from
impacting and the unnecessary blinding of the screen medium on its
upstream extremity. The feed to the screening unit needs to be
uniform and with a reasonable spread across its width.
[0100] Referring now to the drawings, the vibration drive isolation
system or assembly is arranged to minimize vibration to exterior
plant equipment. Vibration drive isolation system includes a
longitudinal counterbalance member 26, a plurality of drive springs
20 supported by longitudinal counterbalance member 26 and a
plurality of isolation springs 22 supporting the longitudinal
counterbalance member 26. A structural steel base 4 supports the
isolation springs 22. The vibration unit has a variable speed motor
control capable for adjusting the vibration intensity.
[0101] Both the time between oscillations and the intensity of the
oscillation can be controlled with an easy control panel adjustment
of controller. They require no mechanical adjustment of
eccentrics.
[0102] The electric motors 30 of the vibratory drive assembly are
attached to the dynamic counter-balance 261 and positioned at the
rear or under the combination of the steel coil drive springs 20
and multiple flat bar type of stabilizers. The assembly is
supported from the longitudinal counter-balance 26 by the
appropriately spaced isolating springs 22 mounted in compression
and appropriately spaced along its length. The vibratory motors
with shaft mounted eccentric weights 30 are either installed on
each side of the counter-balance 180 as shown in FIG. 7, or
combined together, and placed at the rear of the
counter-balance.
[0103] The steel coil type drive springs 20 are distributed across
the width and along the length of the underside of the screen unit
9. The drive springs 20 are combined with flat bar type stabilizers
24 to assure a uniform stroking action. The flat bar type
stabilizers 24 are used to guide the movement of the stiff drive
springs 20.
[0104] The drive springs 20 are sub-resonant tuned to cause them to
inherently work harder under load, where sub means under and
Resonant means natural frequency. Therefore, "Sub-resonant" means
the maximum running speed of the vibratory motors 30 is always
under the natural frequency of the combined drive springs. For
example, if the top motor speed is 570 RPM, which in this instance
is the same as CPM, then the natural frequency of all the drive
springs 182 would be, for example, 620 CPM. While 570 CPM is
preferred, other frequencies such as 720 CPM, 900 CPM or 1200 CPM,
might be useful for various applications.
[0105] The axial centerline of the steel coil drive springs 20 is
provided in line with the wanted stroke angle, but the axial
centerline of the stabilizer 24 is perpendicular to the stroke
angle. By utilizing paralleled counter-balance or structural beams
26 as a longitudinal configuration, the enclosed vibrating
screening feeder 10 is dynamically counter-balanced. The structural
Natural Frequency of the counter-balance assembly will be at least
1.4 times the maximum speed of the motors, but preferably will
exceed it. In this instance, the RPM of the motor 30 is the same as
the vibrating CPM of the enclosed vibrating screening feeder
10.
[0106] Relatively soft steel coil type isolation springs 22 are
used to support the longitudinal counter-balance 26 which in turn
supports the enclosed vibrating screening unit 9 above it.
Preferable needed input power is proved by three phase, A-C
squirrel cage vibratory motors 30. Electrical adjustment of
conveying speed is provided by the controller implements either as
a variable voltage or an adjustable frequency type of electrical
control. The conveying speed of the ash over the vibrating
screening feeder 10 can be electrically adjusted.
[0107] In operation, the vibratory motor(s) 30 are energized and
the shaft mounted eccentric weights are accelerated to full speed.
The force output of the rotating eccentric weights excites or
induces all the stiff steel coil drive springs 20 and flat bar
stabilizers 24 to vibrate back and forth in a straight line. The
speed (RPM) of the vibratory motors 30 is the same as the vibrating
frequency (CPM) of the drive springs 20. This happens even though
the natural frequency of the drive springs 20 is above the motor
speed. Consequently, the enclosed vibrating screening feeder 10
vibrates at a prescribed amount of linear stroke at the wanted
angle, which is usually 45 degrees. As an equal reaction to the
vibratory movement of feeder 10, the counter-balance member 26
inherently moves in an opposite direction. Thus, the opposing
dynamic forces cancel one another. The counter-balance 26 freely
moves or floats on top the soft isolation springs 22 supporting
it.
[0108] A resulting directional, straight line stroke on the
enclosed unit induces the particles to unidirectional move forward
simultaneously over the screens and pan. This particle movement is
the result of a series of hops or pitches and catches by the
applied vibration. Normally, the particles first settles on screen.
Then, it is gradually moved forward by repetitive on and off cycles
of applied vibration. For example, the particles are moved 3 feet
every 6 minutes. Alternatively, the particle movement over the
screen surfaces could be electrically adjusted via adjustment of
motor operation by controller to provide, for example, a conveying
speed of 0.5 FPM. The particles conveyed on the screens discharges
into vertical chutes. The particle sifting that fall through any
openings in the screens drop onto the bottom conveying pan 11. When
the vibratory conveying action is applied, these particles move
forward. Eventually, these particles fall down through outlets
located near the discharge end of the screening unit 9.
[0109] The vibrating screening feeder 10 includes a plurality of
vibratory motors 30 placed relatively close together on the rear or
back section 14 of the longitudinal counterbalance 26. In one
embodiment, a total of six vibratory motors are disposed
transversely across from one another with respect to the
longitudinal width of the vibrating screening feeder 10. Each
vibratory motor includes a rotatable eccentric weight. Since the
rotating eccentric weights are located on the top and bottom of
each motor, a total of twelve individual eccentric weights would be
involved, but all of the eccentric weights on a single motor are
considered herein to be a single eccentric weight. The eccentric
weight attached to one of the vibratory motors in a pair of
vibratory motors is substantially equal in size to the eccentric
weight attached to the other vibratory motor in the pair of
vibratory motors. Each motor is rated 45-60 HP, which would make a
total of 270-300 HP provided by the six vibratory motors although
other sizes of motors can be used. While electric motors are
preferred, air motors or hydraulic motors can also be used.
[0110] Each vibratory motor preferably has the substantially same
size eccentric weight attached thereto, such that each vibratory
motor and eccentric weight produce substantially the same force
output during operation.
[0111] All six motors synchronize and provide an accumulatively
phased force output equal to the sum of the individual force
outputs of all of the eccentric weights. The proper phasing of the
eccentric weights happens if each pair of motors is started
separately, or in any combination, or all started at the same time.
These motors would still try to "phase" even if the rotation was
different when these six motors are working in conjunction with
sub-resonant tuned steel coil drive springs that have flat bar type
stabilizers to guide their stroke line.
[0112] The goal is to make the load carrying vibrating screening
feeder 10 to vibrate at a prescribed stroke of, for example,
one-half inch at a frequency of 570 cycles per minute (CPM), which
is the same as the rotational speed of the motors at 570
revolutions per minute (RPM). In other words, the operating
frequency of the conveying apparatus 10 in CPM is the same as the
RPM of the motors.
[0113] After being energized at the same time all six the motors
accelerate the rotatable eccentric weights installed on the top and
bottom shaft extension of the motors. While the weights are
accelerating, a slight "shimmy" or shudder-like movement may be
present. After all six motors have reached full speed, the stroke
on the conveying trough assembly begins to grow steadily from, for
example, from one-eighth inch to the desired maximum of one-half
inch in about twenty seconds. Thus, the three pairs of motor
combinations require about ten to twenty seconds after being
energized to accelerate the eccentric weights and to properly
"phase" or to accumulatively synchronize the outputs of the
eccentric weights.
[0114] All of the rotating eccentric weights may have exactly the
same force output. If any of these motors is de-energized, then the
resulting stroke on the vibrating screening feeder will decrease
from its maximum amount.
[0115] The "phased" or synchronized eccentric weights on the
vibratory motors excite or prompt the steel coil drive springs 20
to move back and forth, or compress and extend, in a straight line
of stroke. That "line" is guided by the flat bar type stabilizers
24 installed at 90 degrees or perpendicular to the axial centerline
of the steel coil drive springs 20. The vibratory screening unit 9
positioned on top of the drive spring brackets vibrates back and
forth in reaction to the movement of the longitudinal
counterbalance 26 below. This is in keeping with Newton's Law of an
"equal and opposite reaction". Stabilization of the drive springs
20 must be relatively rigid in a direction transverse to the line
of stroke and relatively weak in the direction of stroke. For
example, the flat bar stabilizer 24 may be five inches wide across
its transverse width and only one-eighth inch thick in the
direction of the stroke. If the drive springs 20 are not rigidly
stabilized in a direction transverse to the line of stroke, then
the rotating eccentric weights may not synchronize. The stabilizers
24 may be formed in other configurations than as flat bars so long
as the stabilizer is relatively rigid in a direction transverse to
the line of stroke and relatively weak in the direction of stroke.
The vibratory motors are tilted or inclined from horizontal to
agree with the stroke line and the installed inclined angle of the
drive springs 20.
[0116] The entire apparatus vibrates very smoothly and quietly when
all six motors are up to their full speed. The amount of vibratory
stroke remains constant or steady. A given amount of bulk solid,
such as foundry sand, in the vibrating screening feeder installed
above the longitudinal counterbalance 26 can be conveyed forward at
a steady speed of, for example, approximately forty feet per minute
(FPM).
[0117] In another embodiment, the stiff steel coil drive springs 20
have a combined natural frequency that is always above the maximum
speed of the motors being utilized. "Sub" means "under" and
"resonant" means "natural frequency". Therefore, "sub-resonant"
means to maintain the top running speed of the motor (for example,
600 RPM or CPM) to always be under the "natural frequency" of all
the steel coil drive springs 20 (for example, 650 CPM) when the
vibratory conveyor 10 is in the "no load" state or empty condition.
When a load is applied to the vibrating screening feeder the
"natural frequency" of all the installed drive springs 20 will
inherently reduce in response to the added weight of the load (for
example, to 625 CPM). Because the natural frequency of the drive
springs 20 has decreased (from 650 to 625 CPM), and moved closer to
the motor speed (600 RPM or CPM), the entire drive configuration
works harder. The more the natural frequency of the drive springs
decreases because of additional load being added to the vibrating
screening feeder, the more close the natural frequency of all the
drive springs 20 comes to the running speed of the motors. Thus,
the drive configuration works even harder. This is the advantage of
"sub-resonant" tuning.
[0118] Consequently, the stiff steel coil drive springs 20 in
combination with the six motors inherently drive harder when load
is applied to the vibrating screening feeder 10. Therefore, the use
of "sub-resonant" tuning takes advantage of the principal of
"natural frequency". However, it should be noted this kind of drive
configuration does not normally operate in "natural frequency".
[0119] The objective is to make the respective force outputs of the
eccentric weights to "pull" the screens of the vibrating screening
feeder 10 in tension from the discharge end as compared to
"pushing" the inertial mass in compression from the inlet end. The
same relationship is wanted from the total number of drive springs
20 installed that help to make the apparatus vibrate. This is the
reason the collective forces from both the rotating eccentric
weights and the drive springs should place the overall length of
the vibratory apparatus in tension as compared to being in
compression. More simply stated, the vibratory apparatus is
dynamically being "pulled" instead of being "pushed".
[0120] When an electrical means for adjusting the operating stroke
and frequency of the vibratory machine is wanted, it is preferred
to be large enough to control the total combination of paired
motors installed on the vibratory apparatus. To ensure each of
those individual controllers are responding to the same electrical
pilot signal (usually 4 to 20 ma D.C.) to ensure each of the motors
is rotating at the same speed throughout the range of adjustment.
This maybe accomplished by use of a common electrical potentiometer
on either the variable voltage or the frequency inverter type of
electrical controls. The simultaneous adjustment of the operating
stroke and frequency by means of a variable voltage electrical
control as outlined in U.S. Pat. Nos. 3,251,457 and 4,015,705 can
be successfully utilized. As a substitute for the variable voltage
control, a frequency inverter can also be utilized.
[0121] Since these motors are combined with sub-resonant tuned
drive springs 20 that are properly stabilized by stabilizers 24,
the plurality of motors requires less work output to align with the
movement of the stiff drive springs 20 than it would be to try to
be "out of step" or not phased or accumulatively synchronized with
all the sub-resonant tuned drive springs 20.
[0122] The foregoing detailed description is given primarily for
clearness of understanding and no unnecessary limitations are to be
understood therefrom, for modification will become obvious to those
skilled in the art upon reading this disclosure and may be made
without departing from the spirit of the invention and scope of the
appended claims. Accordingly, this invention is not intended to be
limited by the specific exemplification presented herein above.
Rather, what is intended to be covered is within the spirit and
scope of the appended claims.
* * * * *