U.S. patent number 3,872,361 [Application Number 05/407,436] was granted by the patent office on 1975-03-18 for electrodynamic apparatus for controlling flow of particulate material.
Invention is credited to Senichi Masuda.
United States Patent |
3,872,361 |
Masuda |
* March 18, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
ELECTRODYNAMIC APPARATUS FOR CONTROLLING FLOW OF PARTICULATE
MATERIAL
Abstract
Flow of particulate material along a defined path is controlled
electrodynamically by means of elongated electrodes curved
concentrically to the path, as axially spaced rings or interwound
spirals. Each electrode is axially spaced from its neighbors by a
distance about equal to its diameter and is connected with one
terminal of a multi-phase alternating high voltage source. Adjacent
electrodes along the path are connected with different terminals in
a regular sequence, producing a wave-like non-uniform electric
field that repels electrically charged particles axially inwardly
and tends to propel them along the path.
Inventors: |
Masuda; Senichi (Nishigahara,
Kita-ku, Tokyo, JA) |
[*] Notice: |
The portion of the term of this patent
subsequent to December 11, 1990 has been disclaimed. |
Family
ID: |
27003442 |
Appl.
No.: |
05/407,436 |
Filed: |
October 18, 1973 |
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
366655 |
Jun 4, 1973 |
|
|
|
|
151789 |
Jun 10, 1971 |
|
|
|
|
237822 |
Mar 24, 1972 |
3806763 |
|
|
|
Current U.S.
Class: |
361/233;
118/621 |
Current CPC
Class: |
H02N
11/006 (20130101); B05B 5/1683 (20130101); B05B
5/088 (20130101); B23K 9/324 (20130101) |
Current International
Class: |
B05B
5/08 (20060101); B05B 5/00 (20060101); B05B
5/16 (20060101); H02N 11/00 (20060101); B23K
9/32 (20060101); Hb5 () |
Field of
Search: |
;317/3,262R,262E
;118/620,621 ;417/48,49 ;308/10 ;239/3 ;117/93.4,93.44 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miller; J. D.
Assistant Examiner: Moose, Jr.; Harry E.
Parent Case Text
This application is a continuation-in-part of each of the
applicant's copending applications Ser. No. 366,655, filed June 4,
1973 as a continuation of Ser. No. 151,789, filed June 10, 1971;
and Ser. No. 237,822, filed Mar. 24, 1972 now Pat. No. 3806763; and
inasmuch as the present application contains only subject matter
disclosed in those applications, this application constitutes a
consolidation of portions of those applications. There is being
filed in connection with this application a terminal disclaimer
which effects expiration of the patent issuing hereon concurrently
with expiration of the patent issuing on applicant's copending
allowed application, Ser. No. 226,750, filed Feb. 16, 1972 now Pat.
No. 3,778678.
Claims
1. Apparatus for controlling the movement of powder-like
particulate material along an elongated path which is defined by
surface areas of solid material that surround a longitudinal
centerline of said path, and for confining the particulate material
to a zone near said centerline and against substantial lateral
dispersal therefrom into contact with said surface areas, said
apparatus comprising:
A. a plurality of elongated electrodes, each curved along its
length to be substantially concentric to said centerline, said
electrodes being spaced from one another along said path by
substantially uniform distances, and adjacent electrodes along said
path being curved to radii about said centerline that differ no
more than slightly; and
B. means for connecting each of the electrodes with only one of the
several terminals of a polyphase alternating high voltage source,
and with each of said electrodes connected to a different one of
said terminals than the electrodes that are longitudinally adjacent
to it along said path, so that a constantly varying electric field
is produced by each pair of the electrodes that are so adjacent
whereby particles are urged toward said centerline, and so that the
several electrodes cooperate to produce a net electric field of
wave-like character that urges the particles in one
2. The apparatus of claim 1 wherein each of the electrodes is
substantially
3. The apparatus of claim 2 wherein the number of said annular
electrodes is larger than the number of different terminals at said
alternating voltage source, and wherein said means for connecting
electrodes with said terminals provides for connection of a
plurality of electrodes with each
4. The apparatus of claim 1 wherein each of said electrodes is in
the form of a spiral extending a substantial distance along said
path, and wherein the number of such spiral electrodes is equal to
the number of different terminals at the alternating voltage
source.
Description
This invention relates to apparatus for controlling the movement of
particulate material along a defined path while confining the
material to a zone near the centerline of that path; and the
invention is more particularly concerned with apparatus whereby
such control of the movement of powder-like material is effected
substantially without permitting contact between the material and a
solid surface and while the material is maintained in a loose and
uncompacted state, that is, with its particles not adhering or
cohering to one another.
The general object of the present invention is to provide apparatus
by which powder-like particulate material can either be transported
along a defined elongated path or stopped or otherwise controlled
in its movement along such a path, at the same time that such
material is confined to a zone near the centerline of the path and
against lateral dispersion into contact with surface areas of solid
material which are substantially concentric with that
centerline.
Thus one of the specific objects of the invention, achieved in
certain embodiments of it, is to provide means for causing coloring
powder or other particulate material to move along a substantially
horizontally disposed tube at a controlled rate, from a source of
the material near one end of the tube to a destination zone or
point of application near the other end of the tube, with the
material uncompacted and loose in the tube and more or less
levitated to be substantially out of contact with the tube
surfaces.
Another specific object of the invention, realized in other
embodiments thereof, is to provide apparatus by which a stream of
particulate material, dropping from a source thereof under the
influence of gravity, can be caused to flow intermittently, with
flow being controlledly started and stopped as desired, so that a
valve-like operation can be obtained although the apparatus
includes no valve element or its equivalent, and with the material
being at all times more or less levitated in a loose, cloud-like
condition so that free and steady flow of the material is obtained
at times when discharge is desired.
It will be apparent that the apparatus of the present invention is
useful, in general, for transporting a variety of kinds of
particulate material and metering or feeding such material out of a
source or supply thereof, and that the apparatus is thus generally
useful for such varied purposes as powder spray painting and
coating, printing and decorating various articles, classifying
particles as to size, and otherwise guiding and controlling the
flow of powder and particulate materials.
In general the objects of the invention are achieved with apparatus
comprising elongated concentrically curved electrodes that are so
connected with the terminals of a multi-phase alternating voltage
source as to produce a constantly changing electric field that has
a wave-like variation along the axis about which the electrodes are
curved, which field tends to repel charged particles in a manner
that confines them to a zone near the axis of the electrodes as
well as tending to impart to them a net motion in one direction
along that axis.
With these observations and objectives in mind, the manner in which
the invention achieves its purpose will be appreciated from the
following description and the accompanying drawings, which
exemplifying the invention, it being understood that changes may be
made in the specific apparatus disclosed herein without departing
from the essentials of the invention set forth in the appended
claims.
The accompanying drawings illustrate several complete examples of
embodiments of the invention constructed according to the best
modes so far devised for the practical application of the
principles thereof, and in which:
FIG. 1 is a more or less diagrammatic view, partly in longitudinal
section and partly in side elevation, illustrating apparatus which
embodies the present invention and which enables particulate
material to be controlledly propelled along a defined generally
horizontal path in a substantially steady stream;
FIG. 2 is another somewhat diagrammatic view, partly in side
elevation and partly in section, illustrating a modified form of
the general type of apparatus illustrated in FIG. 1, particularly
intended for use in electrostatic powder coating and decorating
applications; and
FIG. 3 is a generally diagrammatic illustration of another
embodiment of the invention comprising apparatus by which a gravity
produced flow of particulate material downwardly from a source
thereof to a delivery zone can be controlled.
Referring now more particularly to the accompanying drawings, the
numeral 26 designates generally a cylindrical tube of dielectric
material that defines an elongated generally horizontal path along
which powder-like particulate material can be caused to flow in a
substantially steady stream. The tube has a partial closure 27 at
its rear end that leaves an opening 50 through which the lower end
portion of a supply duct 48 projects obliquely downwardly and
forwardly for delivery of particulate material into the rear end
portion of the tube. It will be understood that the supply duct
communicates at its upper end with a source (not shown) of
particulate material and that it conducts such material into the
tube 26 by gravity.
Three insulated elongated electrodes 62, 63, 64 are curved along
their lengths to the form of concentric spirals that surround the
tube 26 and closely embrace its outer periphery. Each of the spiral
electrodes extends along the full length of the tube and has a
uniform axial pitch along its length. The three electrodes are
spaced apart by small but uniform axial and circumferential
distances, as more fully described below.
The three electrodes 62, 63, 64 are respectively connected with the
terminals U, V, W of a three-phase a.c. voltage source. Attention
is directed to the fact that each electrode is connected with only
one of the voltage source terminals, and that the connections to
the several electrodes are such that the alternating voltage
applied to each of them is 120.degree. out of phase with that
applied to its adjacent electrodes.
As a result of this connection of the electrodes to an a.c. voltage
source, a constantly varying nonuniform electric field is generated
by the several electrodes. Such a field is nonuniform and varying
in the sense that its intensity varies from point to point within
it at any given instant, and, at any given point within it, varies
from one instant to another during the voltage cycle. As a result,
a small electrically charged particle in that field is subjected to
repulsive forces that set it into oscillatory motion along curved
paths. As more fully explained in the applicant's above mentioned
copending application Ser. No. 366,655 (continuation of Ser. No.
151,789), with proper connections of the electrodes to a
multi-phase alternating voltage source, the intensity of the field
thus produced changes in a wave-like fashion, so that the
oscillations of a charged particle in that field will tend to be
unequal, that is, the particle will always tend to move farther in
one direction of its oscillation than in the other, and will thus
tend to have a net motion in one direction or another transversely
to the several electrodes producing the field.
The values required for satisfactory operation with charged powder
particles having diameters on the order of one to 100 microns are
approximately as follows:
The electrodes should be of fairly uniform diameter; their diameter
should be not more than about 5 cm., and for particles of less than
30 microns the electrode diameters should be less than 1 cm.; and
the spacing between adjacent electrodes should be about equal to
the diameter of an electrode.
Preferably the peak voltage of the applied alternating voltage
should be high, but should be just low enough to insure that no
sparking or arcing takes place between electrodes. Coating the
electrodes with a suitable insulation (e.g., teflon or epoxy resin)
is desirable because it tends to raise the applied voltage at which
arc-over occurs.
The frequency of the alternating voltage should be on the order of
10 to 120 Hz. For particles of less than 30 micron diameter the
frequency is preferably below 120 Hz; for particles of less than 10
micron diameter the frequency is preferably below 60 Hz; for
particles of less than three microns the frequency is preferably
below 30 Hz.
It will now be apparent that powdered material that is delivered
into the rear of the tube 26 from the duct 48 tends to fall down
onto the inner bottom surface of the tube. But owing to the
constantly changing electric field which exists there, the
particles pick up an electric charge and are repulsively acted upon
by the electric field in the manner explained above. Such repulsion
confines the particles to a zone near the axis of the tube, owing
to the fact that the particles are urged away from the spiral
electrodes that surround the tube; and because the repulsively
produced oscillations of the particles are unequal, as explained
above, the particles also have a net motion along the axis of the
tube. If the connections of the several electrodes to the several
terminals of the alternating voltage source are in the correct
sequence, the direction of such net motion of the particles will be
forwardly, and the particulate material will move to the front end
of the tube in a stream and at a controlled rate of flow that
depends upon the parameters of the electrodes and the a.c. applied
to them. While so moving, the stream of particulate material will
be more or less levitated in being confined to a zone near the tube
axis and repelled away from contact with the inner surface of the
tube.
FIG. 2 illustrates apparatus generally like that shown in FIG. 1,
but in a form which particularly adapts it to applying to a solid
article 101 a coating of particulate material obtained from a
source 120 thereof. The apparatus illustrated in FIG. 2 is thus in
the nature of an electric field pump that can be utilized for
electrostatic painting, coating, dyeing, pile planting and similar
processes. In this case a tube 26' of electrical insulating
material that defines a path along which the particulate material
is to be controlledly transported can be a flexible one, and the
elongated electrodes 62, 63, 64 that spiral all along the exterior
surface of the tube are secured to it by a flexible insulating
cover or coating that not only insulates them from one another but
substantially fixes them in relation to the tube and one another
while constraining them to flex with the tube. The dimensions and
spacing of the electrodes are as described above.
Again, the electrodes are connectable with the terminals U, V, W of
a three-phase alternating voltage source, but in this case a switch
40 that provides for such connection is so arranged that it can be
thrown to an alternative closed position at which the sequence of
connections of the electrodes to the terminals is the reverse of
that in the illustrated switch-closed position. By reason of such
alternative closed positions of the switch 40, the direction of
wave-like variation of the electric field with time can be
reversed, which is to say that, depending upon the position of the
switch, particles can be caused to move either forwardly or
rearwardly through the tube 26'.
At its rear end the tube has an upwardly curved end portion or
elbow 138, and on this elbow portion are arranged electrodes 141,
142, 143 . . . that extend generally parallel to the tube axis and
are spaced from one another at intervals circumferentially around
the tube. These axially extending electrodes are connected, in a
regular sequence around the tube, with the terminals U, V, W of the
alternating voltage source, and they serve to produce a field that
repels charged particles from the wall of the elbow portion of the
tube, tending to confine them to a zone near the longitudinal
centerline of the elbow as they move through it by gravity.
In this case it is not desired to have the particles contact the
tube wall to pick up the electrical charge that they need for
repulsion by the electric fields in the tube, and therefore a
charge must be impressed upon them before they enter the tube.
Apparatus for imparting such a charge to the particles (e.g., known
corona discharge apparatus) is designated by 120. Upon leaving the
charging apparatus, the particles 121 are introduced into an
electric field hopper 78 of the type illustrated in FIG. 3 and
described hereinafter, from which they are controlledly permitted
to fall into the open upper end of the elbow 138.
As shown, the a.c. voltage source comprises step-up transformer
means 29 that has the neutral side of its secondary connected with
a.d.c. voltage source 102. The voltage of the d.c. voltage source
is preferably adjustably variable, as denoted by the oblique arrow
through the symbol for it. Since the d.c. voltage source is
grounded to the workpiece 101 that is to be coated with particulate
material, as well as being connected to the spiral electrodes 62,
63, 64 as just described, there is a d.c. potential difference
between the workpiece 101 and the electrodes, hence also a
potential difference between the workpiece and the particles; and
by reason of this potential difference the particles tend to be
attracted to the workpiece, across the space between it and the
front end of the tube.
The hopper illustrated in FIG. 3 provides for control of the
gravity flow of particulate material from a source or inlet located
above the hopper to a point or zone of use below it. In this case
charged particles 121 are introduced into the top of the hopper
from an outlet at the bottom of an upright inlet duct 77. Near the
level of the lower end of the duct 77 and concentric with it is a
disc 54 of dielectric material or electric insulating material that
supports a plurality of elongated electrodes 56, 57, 56' 57' 56".
These electrodes are bent along their lengths to an annular shape,
and they are secured to the underside of the insulating disc 54, by
means of screws 55, in concentric electrodes so differ in diameter
from one another that each is radially spaced from its neighbors by
a distance substantially equal to its diameter. These several
electrodes are so connected with two of the terminals U and W of a
three phase alternating current source that each is connected with
only one of said terminals, which terminal is other than the one
that both of its radially adjacent electrodes are connected to.
Hence there is a single-phase alternating voltage field beneath the
disc 54.
As brought out in more detail in the above mentioned copending
application Ser. No. 366,655, the effect of a single-phase
alternating field upon charged particles is to set them into an
oscillation along curved paths, which oscillation carries them
substantially equal distances in both directions of their
oscillatory motion so that they have no net motion as a result of
the electric field itself. However, the single-phase alternating
electric field does serve to repel the particles from the
electrodes, forcing them downwardly out of the inlet duct 77 and
into the body portion of the hopper, and preventing them from
settling on the disc 54 and the several electrodes that it
carries.
The hopper itself is defined by annular electrodes 59, 60, 59' . .
. 60" and 65, 66, 67 . . . 74. These are generally similar to the
above described annular electrodes that are secured to the disc 54,
and, like them, they are concentric to the upright axis of the
hopper. But the electrodes 58-60" and 65-74 are vertically spaced
from one another, although, again, the vertical distance between
each electrode and those adjacent to it is equal to its diameter.
The several vertically spaced electrodes can be supported by means
of a pair of diametrically opposite upright pillars or standards 63
of insulating material that also serve to support the disc 54.
Conducting arms 61, secured in an obvious manner by screw threaded
elements 62, extend through the standards 63 and provide for
connection of the vertically spaced apart electrodes with the a.c.
voltage source terminals.
Note that the electrodes 59-60" that define the upper portion of
the hopper are of substantially equal diameters; whereas each of
the electrodes 65-71 in the medical portion of the hopper has a
slightly smaller diameter than the one above it; while the
electrodes 71-74 that define the lowermost part of the hopper are
again of uniform diameter and smaller in diameter than those above
them. Thus the hopper as a whole that is defined by the several
vertically space apart electrodes is more or less
funnel-shaped.
The electrodes 59-60" that define the large diameter upper portion
of the hopper are connected with the terminals U and W of the
three-phase voltage source, each with only one terminal, which
terminal is different from the one that its adjacent electrodes are
connected to. Hence electrodes 59-60" repel the charged particles
toward the hopper axis and tend to levitate them in the upper
portion of the hopper, where they form a clould-like accumulation
79.
Since the individual particles of this accumulation 79 have like
charges, they repel one another. Furthermore, the constantly
changing intensity of the electric field at any point in the
interior of the hopper tends to maintain the particles in a state
of agitation while repelling them radially. Hence the particulate
material of the accumulation 79 will neither compact into a
cohesive mass nor settle on the solid surfaces of the hopper.
Of course gravity also acts upon the particles, and under its
influence they tend to move downwardly in the hopper.
The electrodes 69-74 that define the lower outlet portion of the
hopper are so connectable with all three terminals U, V, W of the
voltage source as to provide a constantly varying potential
difference between every pair of adjacent ones of those electrodes,
and, as explained above, this variation in potential difference
produces a wave-like moving field that tends to repel the particles
either upwardly or downwardly, depending upon the sequence of
connection of the several terminals with the terminals U, V, W as
established by the two-position switch 40.
It will now be apparent that with the switch 40 in one of its
closed positions, the moving field produced by the electrodes 69-74
propels particles downwardly out of the hopper, in effect drawing
them down out of the cloud-like accumulation and causing them to be
discharged in a controlled stream, at a rate dependent upon the
parameters of the electrodes and the charging voltage source. A
workpiece 101 located beneath the outlet of the hopper can thus be
smoothly and evenly coated with the particulate material by moving
it steadily in a direction transverse to the hopper axis, as
indicated by the arrow to the left of the workpiece. Preferably the
workpiece and the lowermost electrode 74 are respectively connected
with the opposite terminals of a.d.c. voltage source that is also
connected with the a.c. terminal U to which said electrode is
connected, to provide for electrostatic attraction of particles to
the workpiece.
To terminate discharge of particles from the bottom of the hopper,
the switch 40 is thrown to its other closed position. The
constantly changing field now produced by the electrodes 69-74 has
a repulsive effect upon the particles that tends to impart to them
a net upward motion, which is to say that said electric field
overcomes the force of gravity upon the particles and confines them
to the interior of the hopper, where they remain in a cloud-like
accumulation as described above. The switch 40 thus provides for
control of the flow of particulate material with a sort of valving
action, although, as contrasted with a conventional valve, the
particles are maintained out of contact with solid surfaces while
they remain in the hopper and, by being kept in a state of
agitation and mutual repulsion, they are substantially prevented
from cohering to one another so that compaction of the material is
prevented and controlled discharge can be resumed as soon as the
switch 40 is thrown over to its material discharging position.
Since the principles of this invention can be applied to
controlling the flow of particulate material either in
supplementing or overcoming the force of gravity upon the
particles, it will be obvious from a consideration of the last
described embodiment of the invention that it is also possible to
use apparatus according to the invention for either supplementing
or overcoming the viscous force which a flowing gas imposes upon
particulate material carried in it.
Those skilled in the art will appreciate that the invention can be
embodied in forms other than as herein disclosed for purposes of
illustration.
The invention is defined by the following claims:
* * * * *