U.S. patent application number 09/681512 was filed with the patent office on 2001-11-08 for protable device for accurately metering and delivering cohesive bulk solid powders.
Invention is credited to Bell, Timothy Allan, Delfunt, James Todd, Firman, Barton J., Geyen, Darryl W., Hyzny, Michael Thomas, Krieger, Thomas Leroy.
Application Number | 20010038018 09/681512 |
Document ID | / |
Family ID | 27071947 |
Filed Date | 2001-11-08 |
United States Patent
Application |
20010038018 |
Kind Code |
A1 |
Bell, Timothy Allan ; et
al. |
November 8, 2001 |
Protable device for accurately metering and delivering cohesive
bulk solid powders
Abstract
The present invention relates to a portable device for metering
and delivering a desired weight of a cohesive particulate solid
material such as pigmentary titanium dioxide.
Inventors: |
Bell, Timothy Allan;
(Wilmington, DE) ; Delfunt, James Todd; (Waverly,
TN) ; Geyen, Darryl W.; (Plano, TX) ; Hyzny,
Michael Thomas; (Kennett Square, PA) ; Firman, Barton
J.; (Milton, PA) ; Krieger, Thomas Leroy;
(Wilmington, DE) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL DEPARTMENT - PATENTS
1007 MARKET STREET
WILMINGTON
DE
19898
US
|
Family ID: |
27071947 |
Appl. No.: |
09/681512 |
Filed: |
April 19, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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09681512 |
Apr 19, 2001 |
|
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09559104 |
Apr 27, 2000 |
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Current U.S.
Class: |
222/58 ; 222/195;
222/198; 222/608 |
Current CPC
Class: |
G01G 13/16 20130101 |
Class at
Publication: |
222/58 ; 222/608;
222/195; 222/198 |
International
Class: |
B67D 005/08 |
Claims
1. A portable device for delivery and metering of cohesive powders
comprising: (a) a hopper supported on a frame, wherein the hopper
has an opening into which the cohesive powder is charged formed by
vertical walls and a section of generally converging walls
connecting the vertical wall to an opening through which material
is discharged wherein at least the portion of the hopper having
converging walls is lined with a pneumatic fluidizing membrane; (b)
a flow control mechanism; (c) a means of measuring and controlling
the weight of material discharged; (d) a control loop to close the
flow control mechanism when the desired weight has been discharged
from the hopper; and (e) means to render the device portable;
wherein the flow control mechanism is a valve assembly comprising a
piston valve having a cone shaped closure member, a body comprising
a cylinder of which the interior walls are lined with a pneumatic
fluidizing membrane, an automatic means by which the valve is moved
downward and upward between the open and closed positions and is
oscillated at selected amplitudes and frequencies about the opened
position and a ring forming a valve seat wherein the ring has slots
through which a flow of gas is directed.
2. The device of claim 1 wherein the automatic means by which the
valve is moved downwards and upwards or vibrated is a gas pressure
regulated and controlled pneumatic controller.
3. The device of claim 1 wherein the means of measuring the weight
of material discharged comprises load cells positioned between the
hopper and support frame.
4. The device of claim 1 further comprising a discharge chute to
direct the material discharged.
5. The device of claim 4 where the discharge chute is lined at
least on the lower inside surface with a pneumatic fluidizing
membrane.
6. The device of claim 1 further comprising a top-cover placed over
the opening of the hopper wherein the top-cover is formed from a
structural material.
7. The device of claim 1 further comprising a paddle positioned on
the valve closure member and extending into the hopper.
8. The device of claim 1 wherein the means to render the device
portable are wheels or pockets to receive forklift arms.
9. A valve assembly comprising a piston valve having a cone shaped
closure member, a body comprising a cylinder of which the interior
walls are lined with a pneumatic fluidizing membrane, an automatic
means by which the valve is moved downward and upward between the
open and closed positions and is oscillated at selected amplitudes
and frequencies about the opened position and a ring forming a
valve seat wherein the ring has slots through which a flow of gas
is directed.
10. A portable device for delivery and metering of cohesive powders
comprising: (a) a hopper supported on a frame, wherein the hopper
has an opening into which the cohesive powder is charged formed by
vertical walls and a section of generally converging walls
connecting the vertical wall to an opening through which material
is discharged wherein at least the portion of the hopper having
converging walls is lined with a pneumatic fluidizing membrane; (b)
a flow control mechanism; (c) a means of measuring and controlling
the weight of material discharged; (d) a control loop to close the
flow control mechanism when the desired weight has been discharged
from the hopper; and (e) means to render the device portable;
wherein the flow control mechanism is a valve assembly comprising a
piston valve having a cone shaped closure member, a body comprising
a cylinder of which the interior walls are lined with a pneumatic
fluidizing membrane, an automatic means by which the valve is moved
downward and upward between the open and closed positions and a
ring forming a valve seat wherein the ring has slots through which
a flow of gas is directed.
11. A valve assembly comprising a piston valve having a cone shaped
closure member, a body comprising a cylinder of which the interior
walls are lined with a pneumatic fluidizing membrane, an automatic
means by which the valve is moved downward and upward between the
open and closed positions and a ring forming a valve seat wherein
the ring has slots through which a flow of gas is directed.
Description
BACKGROUND OF INVENTION
[0001] The present invention relates to a portable device (a bin
system) for metering and delivering a desired weight of a cohesive
particulate solid material such as pigmentary titanium dioxide.
[0002] Solid, powder materials are generally delivered to an
industrial user as large bulk volumes such as hopper cars or truck,
as shipments of large single bags containing a ton or metric ton of
material, or as pallets of individual bags, each weighing 50 pounds
or more.
[0003] Often times in an industrial process, the manufacturer may
need to add a small amount of solid powder to make or top off a
batch of product. The weight needed may be too small to be
conveniently delivered from a large bulk storage device or an
amount that is not a convenient multiple of a small package of
material, for example, a 50-pound bag.
[0004] Although prior art describes various schemes or devices for
small bulk delivery of powders, no system has provided the accuracy
or complete discharge of cohesive powders necessary to industrial
processes.
[0005] U.S. Pat. No. 3,820,697 teaches a valve system for
controlling the flow of fluids or easy-to-flow granules from a
storage hopper. This valve system appears to be prone to possible
jamming or leakage and contamination of the powder by the fluids
actuating the valve.
[0006] U.S. Pat. No. 4,691,843 teaches a valve assembly which may
be used on fixed or portable storage bins to discharge bulk solid
materials, but this system has proved inadequate in the delivery of
cohesive powders such as titanium dioxide as reported in the
article by Bell and Grygo, Applications of Solid Flow Testing to
Portable Bin Systems, published in the Proceedings of the Second
Israel Conference for Conveying and Handling Particulate Solids,
Jerusalem, May, 1997, pages 10.8 to 10.13.
[0007] Other patents relate to solids delivery systems are U.S.
Pat. Nos. 4,378,897; 4,337,880; European Patent Application 0 1 97
342; U.S. Pat. No. 5,145,009 and European Patent EP 0 678 736 B1,
but none of these teach or suggest a delivery or metering system
for cohesive powders.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention is a portable device (bin system) for
delivery and metering of bulk cohesive powders comprising:(a) a
hopper supported on a frame, wherein the hopper has an opening into
which the bulk powder is charged formed by vertical walls and a
section of generally converging walls connecting the vertical wall
to an opening through which material is discharged wherein at least
the portion of the hopper having converging walls is lined with a
pneumatic fluidizing membrane; (b) a flow control mechanism; (c) a
means of measuring and controlling the weight of material
discharged;(d) a control loop to close the flow control mechanism
when the desired weight has been discharged from the hopper; and(e)
means to render the device portable; wherein the flow control
mechanism is a valve assembly comprising a piston valve having a
cone shaped closure member, a body comprising a cylinder of which
the interior walls are lined with a pneumatic fluidizing membrane,
an automatic means by which the valve is moved downward and upward
between the open and closed positions and is optionally oscillated
at selected amplitudes and frequencies about the opened position
and a ring forming a valve seat wherein the ring has slots through
which a flow of gas is directed.
[0009] The preferred automatic means by which the valve is moved
downwards and upwards and optionally vibrated is a gas pressure
regulated and controlled pneumatic controller.
[0010] The preferred means for metering the weight of material
discharged are load cells positioned between the hopper and support
frame.
[0011] To provide convenient delivery to a specific location, the
device of the present invention may further comprise a discharge
chute positioned below the flow control mechanism to direct the
material discharged. With very cohesive powders, it is preferred
that the discharge chute be lined at least on the lower inside
surface with a pneumatic fluidizing membrane.
[0012] To reduce dusting, the device of the present invention may
be fitted with a top-cover placed over the opening of the hopper
wherein the top-cover is formed from a structural material or from
fabric. Additionally, the device may be fitted with a paddle
positioned on the valve closure member and extending into the
hopper to aid in breaking up lumps of the powder.
[0013] The device of the present invention includes as a part of
the device a means to render the device portable such as wheels or
pockets to receive forklift arms.
[0014] The present invention also includes a method for adding a
predetermined amount of a cohesive powder to an in-process product
batch comprising discharging the cohesive particulate solid
material from a bulk storage device into equipment processing the
product batch wherein the bulk storage device comprises: (a) a
hopper supported on a frame, wherein the hopper has an opening into
which the bulk powder is charged formed by vertical walls and a
section of generally converging walls connecting the vertical wall
to an opening through which material is discharged wherein at least
the portion of the hopper having converging walls is lined with a
pneumatic fluidizing membrane; (b) a flow control mechanism; (c) a
means of measuring and controlling the weight of material
discharged; (d) a control loop to close the flow control mechanism
when the desired weight has been discharged from the hopper; and
(e) means to render the device portable; wherein the flow control
mechanism is a valve assembly comprising a piston valve having a
cone shaped closure member, a body comprising a cylinder of which
the interior walls are lined with a pneumatic fluidizing membrane,
an automatic means by which the valve is moved downward and upward
between the open and closed positions and is optionally oscillated
at selected amplitudes and frequencies about the opened position
and a ring forming a valve seat wherein the ring has slots through
which a flow of gas is directed.
[0015] The present invention also includes a valve assembly
comprising a piston valve having a cone shaped closure member, a
body comprising a cylinder of which the interior walls are lined
with a pneumatic fluidizing membrane, an automatic means by which
the valve is moved downward and upward between the open and closed
positions and is optionally oscillated at selected amplitudes and
frequencies about the opened position and a ring forming a valve
seat wherein the ring has slots through which a flow of gas is
directed.
BRIEF DESCRIPTION OF DRAWINGS
[0016] FIG. 1 shows cut away view of a portable bin system
according to the present invention.
[0017] FIG. 2 shows a flow control valve according the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention provides a portable device for
accurately metering, and delivering, at a controllable rate, a
predetermined weight of a cohesive powder.
[0019] As used herein, the terms moved upwards and downwards in
reference to the control valve of the present invention includes
the rapid movement such as vibration or oscillation.
[0020] Particles with an average size less than about 0.15 mm are
frequently difficult to handle in large volume and are generally
referred to as powders. Examples of powders include pigments,
powdered carbon black, white wheat flour and confectioner's sugar.
Most powders are cohesive and will not flow readily through small
hopper outlets and valves.
[0021] The minimum size of outlet necessary for reliable gravity
discharge of cohesive powders from a hopper having converging walls
will frequently exceed 150 mm. Valves used to control the flow of
cohesive powders must usually be as large as the required outlet
size (150 mm or more). Such valves, when open, may deliver powders
at high rates, but smaller valves (or partially open large valves)
will not deliver any powder at all. High discharge rates from large
diameter valves are not easy to control since it is not possible to
open and close the large valves fast enough to provide precision
metering.
[0022] In addition to the issue of valve size, many cohesive
powders exhibit high friction against the walls of the hopper,
causing a flow pattern (known as funnel flow) in which the powder
preferentially flows down the center of the hopper to the outlet.
Such flow patterns lead to flow obstructions known as ratholing, in
which the powder drains from the center of the hopper but remains
in a cohesive mass near the walls. When viewed from above, such a
condition resembles a vertical tunnel through the powder. When such
flow patterns exist, much of the hopper contents may remain in
place. Even a relatively large outlet at the bottom of the hopper
may not cause the powder to fall away from the walls.
[0023] The behavior of particle systems interacting with a gas
stream is often described using a criterion developed by Geldart
(Powder Technol. 7, 285-292, 1973). In Geldart's criterion,
particle assemblages are described by their mean diameter and
particle density. Geldart characterizes four categories, identified
as A, B, C and D. The larger, denser particles, such as grains of
rice, dry sand and table salt (average size larger than 0.150 mm),
fall into Geldart's categories B and D. Such materials can be
easily delivered and metered by a variety of means. Smaller,
lighter particles will fall into categories C and A. Particle
systems with mean particle diameters less than approximately 0.020
mm generally are considered to be category C (or Cohesive),
regardless of their density. Essentially all pigments fall into
this category. Particle systems with mean diameters between 0.020
mm and 0.150 mm may be category C or category A (Aeratable)
depending on their density and other factors influencing
interparticle forces and interactions with gas streams. Particle
systems that are aeratable can sometimes be fluidized with a
counter-current gas flow, and can be delivered and metered in a
fluid-like state. However, the gas flow rates required for
fluidization can be significant, leading to dusting problems with
both the hopper and downstream equipment. In addition only a small
proportion of powders of industrial interest are actually
aeratable.
[0024] Many powders used in industry, particularly pigment
particles, are Type C particles (1) requiring large valve and
discharge openings, (2) displaying high discharge rates, if they
will discharge at all and (3) being characterized by high wall
friction and ratholing.
[0025] The present invention may be used to deliver and meter both
aeratable and cohesive powders as defined by Geldart. The term
cohesive powders as used herein means particles characterized as
Geldart Type A and C particles.
[0026] Prior art metering and delivery systems required the
addition of noisy or heavy vibrators or mechanical stirrers to
force the powder toward the outlet. Such vibrators and stirrers
make accurate weight delivery impossible.
[0027] The inventors in the present invention wanted to provide a
device that would accurately meter and deliver cohesive powders
such as titanium dioxide pigment powder without the disruption in
material flow that characterizes such strongly cohesive powders.
They also wanted a device that would be compact enough to be easily
portable so that it could be moved from one location to another in
a manufacturing plant. To be fully functional, the inventors wanted
a device that required only a minimum amount of auxiliary services
such as electric and air service, two services commonly available
at manufacturing locations.
[0028] The present invention combines a hopper having vertical
walls and a conical shaped lower section and a pneumatic membrane
with a support frame adapted to be portable, a novel valve system,
a weight monitoring system and a control loop. This combination,
referred to herein as the bin system of the present invention,
results in a portable device that may be designed to be compact,
contain one metric ton of material which can be metered and
delivered with an accuracy of about .+-.5 pounds for a system
containing one metric ton. This device may be fully self-contained
requiring only air and electrical services. Electrical service may
be provided by a variety of means including a battery that could be
mounted on the bin system. The size and weight of this particular
design (the hopper, one metric ton in capacity, may be from about
50 to 70 inches high having a cone angle of from about 30 to 45
degrees) can be easily moved from location to location, even when
fully loaded, by a 4000 pound capacity fork lift or other equipment
commonly available at manufacturing locations.
[0029] FIG. 1 shows a portable bin system according to the present
invention with a hopper 1 and a removable top cover 2. The
pneumatic fluidizing membrane serves as a lining in selected parts
of the bin. The preferred placement of the pneumatic fluidizing
membrane is in the regions of the bin as indicated by short dashed
lines in FIG. 1. At 4a, the membrane lines the conical portion of
the hopper, and at 4b, the membrane lines the lower surface of the
discharge chute 6. The pneumatic fluidizing membrane provides a
means to promote powder flow along the walls toward the outlet for
complete emptying of the hopper without the use of vibrators or
stirrers. This is of particular importance for finely divided
pigment powders.
[0030] The pneumatic membrane does not fluidize the mass of the
bulk material, but serves to loosen the bulk material and reduce
its attraction to, or friction against, the walls of the hopper.
For strongly cohesive powders such as titanium dioxide, the
pneumatic membrane may be used to line the control valve body (the
hatched region indicated by 4c of FIG. 2) and at least one internal
surface of a delivery chute or slide (6 of FIG. 1).
[0031] Other features of the preferred embodiment of the present
invention shown in FIG. 1 are load cells at 7, pockets for forklift
arms at 8 and a flexible connection for the chute at 9.
[0032] As used herein, the term pneumatic fluidizing membrane means
a porous surface through which air or some other suitable gas is
fed. The membrane contains a multitude of small holes, less than
0.030 mm in diameter, spaced closely together. The pathway by which
the gas passes through the membrane is tortuous, resulting in a
measurable resistance to the flow of gas. Membranes can be formed
from cloth felt, polymers, sintered metal, or metal laminates. Such
membranes are available from Young Industries of Muncy, Pa.
[0033] Pneumatic membranes may be selected to meet requirements of
specified powders. For example, membranes with larger holes or less
tortuous gas flow paths may not be effective with many forms of
powders. The gas flow rate through the membrane does not have to be
sufficient to fluidize the entire hopper contents. Gas flow rates
may be adjusted for the powder that is to be metered and delivered
by the bin system.
[0034] A flow control mechanism as used herein means a device to
start and stop the flow of the powder from the hopper into a
delivery chute or slide. In FIG. 1 , the placement of the flow
control mechanism is indicated at 3. A flow control mechanism of
the present invention is illustrated in FIG. 2.
[0035] Material may be discharged directly from the hopper without
using a chute or slide by placing the bin system so that the hopper
discharge opening is over the opening of a receiving device such as
a tank, vessel, feed device, or kettle.
[0036] The preferred flow control mechanism is a valve as described
below.
[0037] A means for measuring and controlling weight of the material
discharged as used herein is a means to monitor the weight of the
hopper and the powder to be delivered as the powder is discharged.
The weight delivered is determined by difference. Load cells are
the preferred means for measuring and controlling the weight of
material discharged. Such load cells are shown as 7 of FIG. 1. When
load cells are used, the hopper is positioned over the load cells.
Load cells are preferred because their position under the hopper
results in a compact bin system. The hopper of the present
invention could also be suspended from a support frame, and the
means of measuring and controlling weight of the material
discharged could be positioned above the hopper.
[0038] The essential features for a mechanism that monitors the
weight of the hopper plus the powder load are 1) the mechanism
monitor the weight continuously or at intervals that are for
practical purposes continuous, and 2) the mechanism can be coupled
with, or have incorporated into it, a controller. The controller
(shown at 5 in FIG. 1) is an interface between the bin system
operator, the flow control mechanism or control valve, and air
service. Using the controller, the bin system operator may enter a
set point or a desired weight of powder to be delivered and
initiate the discharge. The controller may automatically stop the
discharge when the desired weight of powder has been delivered.
Although the bin system may be operated automatically or manually,
automatic operation is recommended for accurate and precise powder
delivery.
[0039] The controller, coupled with air service, the means of
monitoring the weight of the hopper and powder load, and the flow
control mechanism make up the control loop.
[0040] The controller may also control the flow of air to various
portions of the pneumatic fluidizing membrane located in the bin
system as well as operate the control valve or a flow control
mechanism. Locations of various air service ports on the bin system
is not critical. The assembly of air valves regulating the air flow
to the pneumatic membranes located through the bin system may be
operated independently by the controller to achieve desired
accuracy in the delivery of the powder. The control loop may
contain numerous solenoids that open and close various air valves
providing air to the flow control mechanism or the pneumatic
membrane. The control loop receives input signals from the weight
monitoring mechanism to start or stop the discharge of the powder
by opening or closing the flow control mechanism. Components of
such a control loop are well known in the art.
[0041] The unique aspects of the present invention result from the
combination of a control loop with the pneumatic membrane and the
flow control mechanism. This combination accurately discharges and
delivers cohesive powders such as titanium dioxide pigment within
.+-.5 pounds or less for a system containing one metric ton.
[0042] Means to render the device portable as used herein includes
fork lift arm pockets (8 of FIG. 1), preferably located on the
support frame, wheels, skids and suspension systems to support the
bin system so that it can be moved along an overhead track.
[0043] Air service means the use of air or an inert gas to activate
the pneumatic membrane and for use in the flow control mechanism.
The term air as used herein includes air other inert gases suitable
for use in the operation of the present invention.
[0044] FIG. 2 shows a preferred flow control mechanism of the
present invention. The placement of the control mechanism in the
bin system is indicated at 3 in FIG. 1.
[0045] In FIG. 2, the flow control mechanism is a valve assembly
having a cone shaped closure member 10 and a valve body 11, of
which a portion is lined with pneumatic membrane 4c and a stem 12.
If desired the valve body may have a service door, 17.
[0046] For precise metering of the powder, the valve is opened and
closed automatically from a signal generated by the controller. The
cone moves down to the open position and powder flows downward
through the annular space. Powder may be directly discharged from
the opening at the base of the valve body, or discharged through a
delivery chute or slide (6 of FIG. 1) joined to the system at the
base of the flow control mechanism. In this way the flow of the
powder may be directed to a specific delivery point. The cone
shaped closure member, when closed, is seated against a ring 13
that forms the valve seat. This ring is slotted at 14, shown in
FIG. 2 as a beveled edge that forms a gap through which air flows
when the valve is in the open position. Air service is provided
through port 15; when the valve is opened, the gap at 14 forms an
air lance. This flow of air or lance keeps the region at the top of
the valve body between the valve seat and the valve cone 10 from
becoming clogged with a build-up of the cohesive powder.
[0047] For strongly cohesive powders such as an untreated titanium
dioxide pigment, for example a plastics grade product, a paddle or
lump breaker 16 may be fixed atop of and attached to the cone
shaped closure member. In addition to moving to an opened or closed
position, the valve stem with the cone shaped closure member may be
automatically oscillated about the open position without closing
the valve. The oscillations of the valve stem up and down move the
paddle or lump breaker up and down to break up lumps of powder for
a smooth, fluid-like flow into and through the valve body. The
oscillations may be made at selected amplitudes and frequencies
about the opened position and may be selected to optimize the flow
of a particular powder.
[0048] The preferred automatic means by which the valve is moved
downwards and upwards and optionally vibrated is a gas pressure
regulated and controlled by pneumatic controller. Such pneumatic
controllers comprise air valves and solenoids.
[0049] A delivery chute or slide may be used to direct the
discharge. When such a chute or slide is used with a strongly
cohesive powder all interior surfaces of the chute or slide may be
lined with the pneumatic membrane. It is recommended that at least
the bottom or lower surface of the chute is lined with the
pneumatic membrane.
[0050] Typically the bin system of the present invention shown in
FIG. 1 would function as follows. The hopper could be filled from a
bulk storage or by dumping metric ton or so-called big bags of
material into the hopper. An operator would move the bin system to
the desired location in the plant for discharging the desired
weight of powder. The bin system may be positioned directly over
the receiving vessel so that the discharged powder falls from the
base of the valve body into the vessel, or the bin may be fitted
with a discharge chute or slide to direct the flow of the powder
discharged to a desired location.
[0051] Once the bin system is positioned and connected to electric
and air services, the operator can enter the desired discharge
weight into the controller and initiate the discharge operation
either directly or via a remote device that is hard wired to or
communicates with the controller. The powder is automatically
discharged from the hopper until the weight desired is delivered
and the controller automatically closes the flow control valve.
[0052] The bin system may have a top cover to prevent dusting and
to protect the contents of the hopper. To promote discharge, the
cover may be vented, the hopper may be vented or the cover may be
formed from a fabric. Vents may be connected to a dust collection
system or other equipment to collect or recycle the powder. The bin
provides a fluid-like and continuous flow for even strongly
cohesive powders.
* * * * *