U.S. patent application number 11/225933 was filed with the patent office on 2006-01-19 for submicron and nano size particle encapsulation by electrochemical process and apparatus.
This patent application is currently assigned to Surfect Technologies, Inc.. Invention is credited to John W. III Eichman, Thomas P. Griego.
Application Number | 20060011487 11/225933 |
Document ID | / |
Family ID | 35598291 |
Filed Date | 2006-01-19 |
United States Patent
Application |
20060011487 |
Kind Code |
A1 |
Griego; Thomas P. ; et
al. |
January 19, 2006 |
Submicron and nano size particle encapsulation by electrochemical
process and apparatus
Abstract
An apparatus and method for coating or treating powdered
material, particularly ultra-fine powders in the nanometer or
submicron range of mean diameters, by electrolytic processes. A
platen is mounted for rotation upon a fixed shaft, and a rotary
flow-through electrolytic cell is mounted upon a platen for
rotation thereon, the cell's axis of rotation being offset from the
platen's axis of rotation. The cells axis of rotation revolves
around the platen's axis as the platen rotates. The electrolytic
cell accordingly undergoes a planetary rotation, as the cell
revolves around the platen's axis of rotation. The planetary
rotation of the cell allows the powdered material to be collected
by centrifugal force and constantly agitated to promote uniform
electroplating. An electrode array and rolling contact system are
supplied which allow electric potential to be applied only to those
electrodes actually in contact with the powdered material to be
treated.
Inventors: |
Griego; Thomas P.;
(Corrales, NM) ; Eichman; John W. III; (Grants,
NM) |
Correspondence
Address: |
PEACOCK MYERS, P.C.
201 THIRD STREET, N.W.
SUITE 1340
ALBUQUERQUE
NM
87102
US
|
Assignee: |
Surfect Technologies, Inc.
Albuquerque
NM
|
Family ID: |
35598291 |
Appl. No.: |
11/225933 |
Filed: |
September 13, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09872214 |
May 31, 2001 |
6942765 |
|
|
11225933 |
Sep 13, 2005 |
|
|
|
Current U.S.
Class: |
205/143 ;
205/144 |
Current CPC
Class: |
C25D 21/18 20130101;
C25D 5/04 20130101; C25D 7/006 20130101; C25D 17/22 20130101; B22F
1/025 20130101; C25D 21/06 20130101; B22F 2998/00 20130101; B22F
2998/00 20130101; C25D 5/00 20130101 |
Class at
Publication: |
205/143 ;
205/144 |
International
Class: |
C25D 7/00 20060101
C25D007/00; C25D 5/00 20060101 C25D005/00 |
Claims
1. A method for depositing a coating on a substrate powder, the
method comprising the steps of: rotatably mounting a rotary
flow-through electrolytic cell on a platen; loading a substrate
powder comprising a particle size of less than 20 micrometers in
the cell; rotating the cell about a first axis relative to the
platen; rotating the platen about a second axis offset from and
parallel to the first axis, thereby enabling the cell to undergo
planetary revolution; flowing a solution through the cell;
generating sufficient centrifugal force to overcome suspension of
the substrate powder in the solution; and depositing the coating on
at least a portion of the substrate powder.
2. The method of claim 1 wherein the generating step comprises
forcing at least a portion of the substrate powder against the
inner wall of the cell.
3. The method of claim 2 wherein at least a portion of the
substrate powder contacts an electrode strip attached to the inner
wall of the cell.
4. The method of claim 2 wherein most of the substrate powder
collects along a short arcuate segment of the inner wall.
5. The method of claim 4 further comprising the step of tumbling
the substrate powder along the inner wall as the cell rotates.
6. The method of claim 5 wherein the powder contacts one or more
electrode strips arrayed on the inner wall.
7. The method of claim 6 wherein only a subset of electrode strips
is electrically connected to a power supply at any given time.
8. The method of claim 7 further comprising the step of varying
which electrode strips comprise the subset so that most of the
tumbling substrate powder is substantially continually in contact
with at least one charged electrode strip.
9. The method of claim 1 further comprising the step of reversibly
disposing an electrode into the cell.
10. The method of claim 1 further comprising the step of filtering
and recirculating the solution.
11. The method of claim 1 further comprising the step of reversing
the rotation of the cell.
12. The method of claim 11 further comprising the step of auguring
the substrate powder out of the cell.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 09/872,214, entitled "Submicron And Nano Size
Particle Encapsulation By Electrochemical Process And Apparatus",
filed on May 31, 2001, and issuing as U.S. Pat. No. 6,942,765 on
Sep. 13, 2005. The specification and claims thereof are
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention (Technical Field)
[0003] The present invention relates to apparatuses and methods for
electroplating and electrochemically modifying the surface finish
of metal and semiconductor powders, particularly by continuous
centrifugal means for encapsulation, anodizing, electroetching,
electroforming, electrophoretic coating, electrosynthesis, and
electrodeposition on powders without limitation on particle size,
specifically including submicron- or nano-sized particles.
[0004] 2. Background Art
[0005] Note that the following discussion is given for more
complete background of the scientific principles and is not to be
construed as an admission that such concepts are prior art for
patentability determination purposes.
[0006] The technologies for electrochemical enhancement of the
surfaces of the particles in bulk powders has previously been
limited to two main types: chemical copper and electrolytic nickel
auto-catalytic processes; and rotary electroplating devices which
require frequent stopping and starting of the electrolytic cell's
rotation to tumble the powder to achieve uniform dispersion of the
coating upon the particles. A limitation of the previous art using
chemical or auto-catalytic processes is the cost of the chemical
consumption due to the enormous surface areas of powders. Another
limitation of known devices using the rotary techniques is the need
to stop the cell to tumble the powder in order to disperse the
coating and prevent agglomeration of the particles. Known devices
of the latter type known in the art are typified by the disclosure
of U.S. Pat. No. 5,879,520, the teachings of which are hereby
incorporated by reference.
[0007] Previous rotary flow-through devices are capable of
centrifugal clarification of the particles in solution and fixing
them against the cathode ring for electrical contact. A
disadvantage occurs, however, when rotation of the cell must be
stopped to tumble the powder particles to foster even
electrodeposition upon the individual particles. During this "stop
phase," the particles are re-suspended in the electrolyte solution.
If the particles are of sufficient density, continuing the rotation
of the cell re-clarifies the solution and again fixes the particles
against the electrical contact ring, but the need periodically to
stop and re-start cell rotation prolongs total processing times.
Further, in the case of submicron-sized, low mass powders, the
method of repeatedly stopping and resuming cell rotation is
unacceptable from a practical standpoint, because the material
particles remain in suspension (rather than in contact with the
cathode) for impermissibly, nearly indefinite, lengths of time.
[0008] Also, laboratory experimentation and commercial application
of the known rotary flow- through devices resulted in a
determination that such devices have a powder particle size lower
limit of approximately 20 micrometers for most common metals. These
devices often have limitations related to the substrate powder's
particle density, as well. Because previous rotary flow-through
devices use a sintered membrane to allow the electrolyte to flow
through the cell, a practical particle size limit occurs when the
opening area of the sintered membrane must be smaller than the
particle size. For powders below 50 micrometers mean particle
diameter, the sintered membrane pores must be reduced to 25
micrometers. For powders below 20 micrometers, the sintered
membrane pores must be 10 micrometers. When the sintered membrane
pores are reduced below 10 micrometers, the discharge of
electrolyte through the membrane is significantly impaired, which
in turn depletes the ion species in the electrolyte, dramatically
reducing the performance of the device. Because the distribution of
size of the particles varies, it is possible to have particles
smaller or equal in diameter to the openings in the sintered
membrane, which in turn causes clogging or blinding of the
membrane--further reducing performance. If the solution flow rate
is increased to compensate for the ion depletion, the lightweight
particles will overflow the cell, causing unwanted material loss
and damage to the system.
[0009] Another problem with some previous rotary flow-through
devices, such as the device of the U.S. Pat. No. 5,879,520, is that
they require a complicated level control sensor to prevent the
electrolyte solution from overflowing the top of the cell during
the stop phase. This further limits the efficiency of solution
flow, which also leads to ion depletion.
[0010] Further background in the field of rotary flow-through
elecroforming/electrodeposition devices and methods is supplied by
U.S. Pat. Nos. 5,487,824 and 5,565,079, the disclosures of which
are hereby incorporated by reference.
[0011] Moreover, each time the cell rotation is resumed (after
stopping to tumble the substrate powder), time is required to
clarify the solution and re-fix the particles to the face of the
cathode ring; heavier particles are thrown into renewed contact
with the cathode first, while finer particles require comparatively
more time to move outward under centrifugal force. This results in
heavier particles having preferential electrical contact with the
cathode, resulting in a wide variance in the uniformity of the
thickness distribution. In many cases, ultrafine particles will
receive no electrodeposition at all.
[0012] Another limitation of known rotary flow-through devices is
that the rectifier or power supply must be switched off and on in
sync with the stopping and starting of the rotation of the cell.
Besides causing extended process time during the off cycle, such
intermittent voltage processes risk potential chemical damage to
the substrate powder when no voltage potential is present.
[0013] Another limitation of known rotary flow-through device is
the diameter and overall size of the cell, which had to be
optimized to provide adequate stopping and starting performance. If
the cell diameter is too large, the distance between the electrodes
and the distance of travel of the particles became too great for
efficient processing.
[0014] Another limitation of known rotary flow-through device is
the required stop/start sequence means that the particles are fixed
at the cathode during the on time, increasing the possibility of
undesirably fusing or electroforming substrate components together.
This obligates the high frequency stopping/starting to ameliorate
agglomeration.
[0015] The foremost requirements for commercial electrodeposition
apparatuses are to achieve cathode efficiency (e.g., 60-100 percent
efficiency), prevent fusing or agglomeration of the particles,
achieve high thickness uniformity, not corrode or damage the
substrate powder, perform the electrodeposition in reasonable
process time, and contain all particles in the apparatus with
reasonable material handling methodologies.
SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)
[0016] The invention is a continuous rotary flow-through
electrodeposition system including a rotating platen supporting a
vertical rotating cell on an eccentric axis. The system has a
plurality of nozzles and electrodes alignable concentrically to a
rotating platen. The eccentric rotating cell is actuated by a
planetary gear that allows the cell to orbit around the axis point
of the centered platen and electrode.
[0017] The present invention also features a rotating cell with
sectioned electrical contacts molded into a plastic bowl or vessel,
isolating the electrical contact exposed at the inside of the cell
and extending to the perimeter of the bowl for sequential current
feed from a rotating slip ring device. This innovation promotes
catalytic efficiency by bussing current only to the "outermost"
contacts that are in contact with the powdered materials.
[0018] This invention additionally uses an upper dome to complete
the cell that features a helical inner flange or ramp. During
clockwise rotation of the cell, the upper dome continuously forces
the substrate materials downward to maintain their contact with the
cell cathode contacts. Further, by reversing the cell rotation to
counterclockwise, material can be augered out of the cell to
facilitate unloading the finished powder into the collection drain
basin.
[0019] The cell is provided with a catch basin and a canopy that
catch flow-through electrolyte for return to the solution
reservoir.
[0020] The present invention can also be used with or without a
sintered membrane or laser cut slots to allow solution to
flow-through, since the cell is configured to permit overflow of
process solution from the top port thereof without discharging
therewith the powder material being treated. Further, the present
invention operates with continuous rotation, eliminating the need
to stop and start the cell to tumble parts.
[0021] The present invention has no limitation in diameter of the
cell, allowing for increased loading capacities due to the
continuous operation of the cell and elimination of the stop/start
sequence.
[0022] In the present invention, the particles are continuously
tumbled in contact with the electrical contacts, thereby improving
the dispersion of the coating over the surface of each particle and
eliminating potential fusing or agglomeration of particles.
[0023] A primary object of the processes of the invention is to
provide effective electrolytic microencapsulation of
submicron-sized or "nano scale" particles.
[0024] A primary object of the apparatus of the present invention
is to permit the multi-step electroplating process without physical
transfer of the plating fixture or cumbersome manual exchange of
solutions.
[0025] A primary advantage of the invention is that it can process
submicron-sized materials with high efficiency, with or without a
sintered membrane or slotted dome.
[0026] Another advantage of the present apparatus is that it has
virtually no limitation on solution flow rate; thus, the
electrolytes ion species can remain at optimum levels during the
high mass transfer that is required for the high surface area
powdered substrate.
[0027] A primary advantage of the process of the invention is that
a wide range of useful particles and materials can be made thereby
including, but not limited to:
[0028] inert micron scale isotope particles for blood trace;
[0029] critical stoichiometry alloy composition powders;
[0030] reduced cost noble metal catalytic powders;
[0031] alloy powders for powder metal forming;
[0032] electrophoretic coated iron for soft magnetic powder;
[0033] battery and fuel cell negative electrode powders;
[0034] micro-ball grid array spheres;
[0035] microencapsulation of radioactive fuel rods; and
[0036] electrosynthesis of ceramic oxides.
[0037] Other objects, advantages and novel features, and further
scope of applicability of the present invention will be set forth
in part in the detailed description to follow, taken in conjunction
with the accompanying drawings, and in part will become apparent to
those skilled in the art upon examination of the following, or may
be learned by practice of the invention. The objects and advantages
of the invention may be realized and attained by means of the
instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0038] The accompanying drawings, which are incorporated into and
form a part of the specification, illustrate several embodiments of
the present invention and, together with the description, serve to
explain the principles of the invention. The drawings are only for
the purpose of illustrating a preferred embodiment of the invention
and are not to be construed as limiting the invention. In the
drawings:
[0039] FIG. 1 is a side sectional view of the overall apparatus
according a preferred embodiment of the present invention;
[0040] FIG. 2 is an enlarged side sectional view of a portion of
the apparatus depicted in FIG. 1;
[0041] FIG. 3 is a plan view of a preferred embodiment of the
apparatus of the invention, with directional arrows showing
counterclockwise rotation of the platen and clockwise planetary
rotation of the cell bowl assembly;
[0042] FIG. 4 is a side view of the principal components of the
apparatus of the present invention, showing the anode and feed
nozzle assemblies in the raised position, withdrawn from the
electrolytic cell bowl assembly;
[0043] FIG. 5 is a plan view of the platen component of the
apparatus of the invention, showing the planetary gear and the
electrical cable running from the axis of the drive gear to the
wire wheel contact;
[0044] FIG. 6 is a plan view of the interior of the bowl component
of the bowl assembly with the dome removed;
[0045] FIG. 7 is a side sectional view of the bowl component
depicted in FIG. 6, taken along section line 7-7 seen in FIG.
6;
[0046] FIG. 8 is a side view of the platen and gear components of
the apparatus of the invention;
[0047] FIG. 9 is a plan view of the platen component of the
apparatus of the invention;
[0048] FIG. 10 is a side sectional view of the platen component
depicted in FIG. 9, taken along section line 10-10 seen in FIG.
9;
[0049] FIG. 11 is a perspective view from above of the platen
component of the apparatus of the invention;
[0050] FIG. 12 is a side view of the principal components of the
apparatus of the present invention, showing the anode and feed
nozzle assemblies in a lowered operational position within the
electrolytic cell bowl assembly;
[0051] FIG. 13 is a perspective view from above of the dome
assembly of the apparatus of the invention, showing the helical
auger flange within the dome;
[0052] FIG. 14 is a plan view of the dome assembly depicted in FIG.
13;
[0053] FIG. 15 is a side view of the dome assembly depicted in FIG.
13;
[0054] FIG. 16 is a perspective view from above of the overall
apparatus according to a preferred embodiment of the invention, but
without the containment canopy in place;
[0055] FIG. 17 is a side view of a single cathode contact strip
according to the apparatus of the invention, a plurality of such
strips being incorporated into the apparatus;
[0056] FIG. 18 is a plan view of the cell bowl assembly of the
apparatus of the invention, showing with directional arrows that
the cell when working rotates clockwise about its axis, and when
being unloaded rotates counterclockwise; and
[0057] FIG. 19 is a side sectional view of the bowl assembly seen
in FIG. 18, taken along section line 19-19 in FIG. 18.
DESCRIPTION OF THE PREFERRED EMBODIMENTS (BEST MODES FOR CARRYING
OUT THE INVENTION)
[0058] The present invention offers major improvements to
apparatuses and methods in electrolytic cell technologies for
microencapsulating or coating powdered materials. The apparatus of
the invention incorporates some of the desirable aspects of devices
and processes known in the art, such as multiple return drains and
multiple selectable feed nozzles, while yet overcoming various
disadvantages manifested in previous efforts.
[0059] The present invention capitalizes upon the fundamental
concept of harnessing centrifugal force to compact bulk materials,
particularly submicron- or nano- sized powders, in solution
(preferably aqueous) against an electrolytic cathode contact.
Throughout this disclosure and in the claims, "substrate material"
or "substrate powder" refers to the bulk materials to be treated,
and specifically includes but is not limited to super-fine
conductive and semi-conductive powders having mean particle
diameters in the nanometer or submicron range.
[0060] The central component of the apparatus is the cell, which
features an upper dome mounted upon a bowl. The substrate material
is loaded through a top opening in the cell, and the plating cell
is rotated at sufficiently high rpm to centrifugally cast the
substrate material against the cathode contact at the outer
perimeter of the cell. Electroplating solution is then introduced
at the top opening, and flows through the cell, eventually exiting
through an osmosis filter disposed between the dome and the top
edge of the bowl, or alternatively by overflowing at the top
opening of the cell. A key advantage of the present invention is
that the cell containing the electroplating solution and the
substrate material undergoes planetary rotation, that is, a
compound rotary motion wherein the cell rotates about its own axis
while simultaneously revolving around a fixed axis offset from the
axis of the cell. This planetary rotation of the cell eliminates
the counter-productive requirement, common in known devices, that
electroplating be accomplished with a cycle of periodic stopping
and starting, and/or counter rotation with sequential switching of
the DC power supply to the cell. Known devices employ these
inefficient stop-start and sequential switching methodologies to
circulate the particle position for even coverage and prevention of
agglomeration/bridging of the substrate material. Thus, in marked
contrast with prior devices, the planetary rotation of the cell of
the present invention results in the efficient constant movement
and controlled agitation of the substrate material in contact with
the cathode, with constant rotation of the cell.
[0061] The overall and general configuration of a preferred
embodiment of the constant rotary flow-through plating apparatus
according to the invention is illustrated in FIGS. 1-3 and 15.
Principal components of the invention include a rotationally fixed
shaft 20, upon which a platen 30 is rotatably disposed, the shaft
20 and platen 30 both being disposed concentrically with and above
a rotatable drain basin 24. Bearings 107 may provide for smooth
rotatable disposition of the platen upon the shaft 20. The shaft 20
effectively acts as a foundation for many of the other components
of the apparatus, and platen 30 rotates about its vertical axis A,
which is coaxial with the fixed shaft 20. A constant flow-through
bowl assembly 36 is rotatably mounted upon the platen 30 so as to
be rotatable about its vertical axis B and with respect to the
platen; as shown in the figures, the bowl assembly 36 is mounted
eccentrically upon the platen 30, i.e., the bowl's axis of rotation
B is offset from the platen's axis of rotation A. Bowl bearings 109
smooth and ease the rotation of the cell bowl assembly 36. A
plurality of radially arranged cathode contact strips 44 are
uniformly spaced within the bowl assembly in a manner to be
described further. An anode assembly 50 is mounted upon a movable
boom according to known construction, so that the anode assembly is
controllably movable between a use position immersed in solution
within the bowl assembly 36 and a retracted position exterior
thereof. The upper circumferential rim or edge of the basin 24 is
in sealed, but removable, contact with the lower circumferential
rim of a closed overarching, e.g. generally hemispherical, canopy
38, so that the combination of the shaft 20, basin 24 and canopy 38
substantially surround and enclose the platen 30 and bowl assembly
36.
[0062] In this disclosure, reference is made to an "anode" assembly
and to "cathode" contact strips. It is immediately understood by
one of skill in the art that the electrochemical roles of the
electrodes in an electrolytic cell may be reversed according to the
type of electrolysis to be performed. Thus, in every cell there is
a primary electrode and an opposing electrode, and which of the
pair functions as the anode and which serves as the cathode may be
selectively determined by the operator to perform the desired
electrolytic process within the cell. Thus, while the electrode 50
movable upon an overhead boom in this disclosure is denoted as an
"anode," it may actually serve as an electrode in various
alternative embodiments or processes without departing from the
scope of the invention. Likewise, the "cathode" contact strips 44
may in alternative applications function as anodic strips. Further,
the anode 50 may be either soluble or insoluble according to know
principles in the art, depending upon the specific electrolytic
process to be performed.
[0063] The placement of the anode 50 upon an adjustable boom
permits the anode or anode assembly to be controllably disposed
into the cell for immersion into the electrolyte, and then
controllably withdrawn to a position exterior of the cell. Thus,
the anode 50 is positionable outside the bowl assembly 36 so as not
to be within the cell during, for example, post- or
non-electrolytic processing steps, such as rinsing. Further, a
multi-anode assembly may be provided, wherein one type of anode may
be withdrawn, and another controllably disposed in its stead, to
perform a series of process steps in the cell using different anode
types.
[0064] A specialized dome 40 is mounted upon and above the bowl
assembly 36, with an annular osmosis filter 42 disposed between and
in sealed contact with the lower circumferential rim of the dome 40
and the rim of the bowl assembly 36. The bowl assembly 36 and dome
40, together with the anode assembly 50, collectively are the
principal elements of the electrolytic cell of the invention. The
drain port 26 of the basin 24 is locatable above the inlet of a
solution reservoir 80, which may be any one of a plurality of
solution reservoirs disposed radially about the exterior of the
drain basin 24. Solution from within the reservoir 80 may be pumped
into the bowl assembly 36, via one or more feed nozzles 83, by
means of a suitable pump 81 and re-circulation conduit 84.
[0065] The flow of working solution through the apparatus of the
invention during any given treatment cycle is described with
reference to FIG. 1. At the outset of operation, with the substrate
material previously disposed inside the bowl assembly 36, the
re-circulation conduit 84 is connected with the discharge port 85
of a selected solution reservoir 80 containing the first solution
or liquid of interest (e.g. a pre-rinse, perhaps de-ionized water).
Solution is then pumped by the pump 81, via the discharge port 85,
from the reservoir 80 through a filter and then the re-circulation
conduit 84 to the feed nozzles 83 and into the bowl assembly 36,
until the desired solution level in the bowl assembly is attained.
An advantage, therefore, is the re-circulation of filtered
treatment solution, improving process efficiency without demanding
fluid restocking with new, unused solution. The driving mechanisms
of the apparatus are actuated to rotate the platen 30 and the bowl
assembly 36, and the centrifugal force from the bowl assembly's
rotation casts the substrate material against an arcuate segment of
the inside wall of the bowl assembly in a manner to be further
described. The working solution likewise is urged toward the inside
wall of the bowl assembly 36 (where the intended electrolytic
processes occur), and tends to flow under centripetal force up to
the point of maximum cell diameter, i.e. the annular juncture of
the bowl assembly 36 with the dome 40. An annular osmosis filter 42
is situated at the juncture between the rim of the dome 40 and the
rim of the bowl assembly 36. The solution then is forced through
the osmosis filter 42, and is free to flow by gravity down the
exterior bowl skirt 73 and/or the inside surface of the canopy 38
to be collected in the bottom of the drainage basin 24. Recovered
solution may then be released through the drain port 26 for return
to the solution reservoir 80 for re-use or reclamation, as
desired.
[0066] Specific reference is made to FIGS. 1 and 2. The platen 30
is mounted, as with thrust bearings 107 or the like, for rotation
upon the upper end of the fixed shaft 20. The hub 62 (or some other
suitable portion) of the platen 30 is engageable, as by a pinion
gear or the like, with a drive shaft 34 which is operably connected
to a drive motor 32. Drive motor 32 turns the drive shaft 34, which
when engaged with the platen 30 imparts rotary force to the platen,
causing it to rotate about the axis A (FIG. 12) defined by the
shaft 20.
[0067] Attention is invited to FIGS. 8-11 for additional detail of
the platen 30 according to a preferred embodiment of the invention.
FIG. 10, in particular, shows how the second axis of rotation B is
offset from the first axis of rotation A pertaining to the platen.
The body of the platen 30 is fashioned from stainless steel or
other suitable durable material, and preferably is circular in plan
profile (FIG. 9). The platen 30 features a generally disk-shaped
upper portion 60 having an integral, downwardly depending, hollow
cylindrical inner hub 62 defining shaft recess 63 therein. A
narrowed portion of the shaft recess 63 penetrates the upper
portion 60 and is manifested as an access tunnel 67 opening to the
top surface of the upper portion. An integral annular outer flange
65 depends downward from the perimeter of the upper portion 60. A
circular recess in the top surface of the platen 30 defines a bowl
boss seat 66 in the upper portion 60.
[0068] The bowl assembly 36 is situated upon the platen 30 for
rotation thereupon. Reference is made to FIGS. 5, 6, and 16, which
provide further detail of the bowl assembly 36. The bowl assembly
36 includes a rigid, durable bowl 70 in the shape of a truncated
cone, having a generally disk-shaped planar floor 71 integrally
molded with a frustum-shaped wall 72. Depending downward and
radially outward from the wall 72, and preferably integrally molded
therewith, is a bowl skirt 73. The entire bowl 70, including the
floor 71 and skirt 73, preferably is molded from a suitable inert
material, preferably a plastic such as a thermoplastic, or
alternatively may be of copolymers, fiberglass or fiber composite.
A generally cylindrical centrally located mounting boss 74,
preferably integrally molded with the floor 71, depends downward
from the bottom surface of the bowl 70. Mounting boss 74
facilitates the rotatable disposition of the bowl 70 upon the
platen 20, as the boss 74 is receivable in the bowl boss seat 66 in
the upper portion 60 of the platen.
[0069] Continued reference is made to FIGS. 5 and 6, illustrating
that the bowl 70 defines in the interior surface of the wall 72
thereof a plurality of radially arranged contact channels 76, 76',
76''. As best seen in the top view of FIG. 6, the contact channels
76, 76', 76'' are disposed in a uniformly spaced, spoke-like array.
Contact channels 76, 76', 76'' are sized to receive
correspondingly-sized cathode contact strips 44, 44', 44''. In the
preferred embodiment, the cathode contact strips 44, 44', 44'' may
be integrally molded into the bowl 70 at the time the bowl itself
is molded. FIG. 6 shows the cathode contact strips 44, 44', 44'' in
their radial array; thirty-two uniformly spaced cathode strips are
depicted in the plan view of FIG. 6, although for the sake of
clarity only three strips 44, 44', 44'' are explicitly labeled in
the drawing.
[0070] FIG. 17 offers a side view of a single cathode strip 44
fashioned from a durable electrically conductive material, such as
titanium. Alternative material possibilities include stainless
steel, or copper, depending on the particular process. Description
of one strip 44 with reference to FIG. 17 serves to describe each
in the plurality. The cathode strip 44 has a wall leg 45 and a
floor leg 48. The wall leg 45 is inlaid into, or preferably
integrally molded into, a corresponding contact channel 76 in the
wall 72 of the bowl 70. The wall leg 45 preferably but optionally
may be provided with concave indents or apertures 46, 46' to
promote molded bonding with the material of the bowl wall 72 when
integrally molded therewith, as suggested by FIG. 7. When the
cathode strip 44 is properly disposed in a contact channel 76, the
inside face 47 of the wall leg 45 remains exposed to the contents
of the bowl 70 (i.e. the electrolytic solution and the substrate
material), while the remaining surfaces of the strip 44 are in
insulative contact with the material of the bowl. As indicated in
FIG. 7, the floor leg 48 of each cathode strip 44 is mostly
embedded in the floor 71 of the bowl 70; the floor separates the
floor leg from the contents of the bowl. However, as best seen in
FIG. 7, a contact portion 49 of the floor leg 48, near its
intersection with the wall leg 45, remains exposed on the exterior
of the bowl, on the underside of the floor 71 near its perimeter.
This contact portion 49 permits an electrical potential to be
applied sequentially to individual cathode strips 44, 44', 44''
(via a wire wheel contact 92, FIGS. 5 and 8) in a manner to be
further described. It is seen therefore, that each cathode strip is
everywhere insulated against electrical contact, except at the
inside face 47 where electrical contact may be had with the
contents of the bowl 70, and at the contact portion 49.
[0071] FIGS. 13-15 depict the particular features of the open dome
40 according to a preferred embodiment of the invention. The
elements of the dome 40 are crafted from any suitable chemically
resistant material or materials, and may be comprised of plastic,
fiberglass, or combinations of these or other materials. The dome
rim flange 99 is for attaching the dome to the upper rim of the
drainage basin 24. Dome 40 has a frustum-shaped wall 101 that
converges upwardly to terminate in an annular top rim 102 which
defines the broad top opening or port 103. A key feature of the
dome 40 is a helical auger flange 100 disposed upon the inside
surface of the wall 101. The auger flange 100, from its lower end
104 situated at about the same vertical level as the rim flange 99,
spirals upward (progressing clockwise as seen in FIG. 14) to its
upper end 105 at about the same level as the top rim 102. The helix
of the auger flange 100 preferably spirals through approximately
180 to 190 angular degrees, as suggested in the figures. The auger
flange 100 is used especially to extricate from the electrolytic
cell the treated substrate at the completion of the treatment
process.
[0072] FIG. 19 is a side sectional view of the assembled
electrolytic cell of the preferred embodiment of the invention. The
bowl 70 includes the radially arranged cathode strips 44, 44', 44''
within the bowl wall 72. The dome 40 is removably mounted
concentrically upon the bowl 70 by temporarily securing the rim
flange 99 of the dome to the upper rim 77 of the bowl wall 72, as
by bolts or the like, but with the annular osmosis filter 42
sandwiched there-between. The cell is rotatably coupled to the
platen 30 by situating the mounting boss 74 in the bowl boss seat
66 in the upper portion 60 of the platen, as seen in FIGS. 1 and 2.
The boss 74 rotates in the seat 66, the contact there-between
featuring bearings and/or lubrication to reduce friction. The
engagement of the boss 74 in the seat 66 maintains the bowl 70, and
thus the complete electrolytic cell, at all times concentric with
the circular seat.
[0073] Reference is made to FIGS. 1, 2, 4, and 8. Coaxially
connected to the top of the shaft 20, and fixed against rotation
with respect thereto, is a toothed drive gear 52. Drive gear 52 is
fixedly connected to the shaft 20 the access tunnel 67 at the
center of the upper portion 60 of the platen 30, but the drive gear
is situated at a level somewhat above top surface of the platen, as
indicated by the figures. Because the drive gear 52 is fixed
against rotation, the platen 30 rotates around the drive gear 52 as
well as the shaft 20 when the motor 32 is actuated to drive the
platen 30.
[0074] Combined reference is made to FIGS. 1 and 2. Attached to the
underside of the bowl assembly 36, for example by being secured
circumferentially around the mounting boss 74, is a toothed
planetary gear 54. The planetary gear 54 is in geared engagement
with the drive gear 52, with both the gears arranged about parallel
to, and disposed just above, the top surface of the upper portion
of the platen 30, as best seen in FIG. 2. Preferably, the planetary
gear 54 is removably attachable to the bottom of the bowl assembly
36, so that a variety of different planetary gears may be
selectively employed to vary the gear ratio between the drive gear
52 and the planetary gear. Accordingly, if it is desired to rotate
the electrolytic cell (around its own axis) at a high rpm, a gear
ratio of, for example, 3:1 (planetary to drive) may be selected and
a planetary gear of appropriate size selected for temporary but
secure attachment to the bowl assembly 36. In many instances, the
gear ratio may be 1:1, so that the bowl's rate of rotation is
generally equal to its rate of revolution about the first axis A
defined by the shaft 20. The bowl 70, being rotatable on the platen
30, likewise is the planetary gear 54 rotatable in relation to the
platen.
[0075] Continuing reference to FIGS. 1, 4, 8, and 12, and also
inviting attention to FIG. 2, it is seen that the afore-described
gear train results in a planetary rotation of the electrolytic cell
when the platen is rotated upon the shaft 20. When the drive motor
32 is actuated and engaged with the platen (e.g. at the inner hub
62), the platen 30 rotates about its central axis, defined by the
shaft 20. As the platen rotates, it carries with it the bowl
assembly 36, which is situated upon the platen some distance from
the platen's axis of rotation (e.g. the central vertical axis of
the bowl assembly is disposed approximately one-third of the radius
of the platen from the axis of the platen). Thus, the bowl assembly
36 revolves around the axis of the platen 30. As the bowl assembly
36 revolves, the engagement of the rotatable planetary gear 54 with
the fixed drive gear 52 results in the rotation of the planetary
gear about its axis. As the planetary gear 54 is compelled to
rotate, so too is the bowl assembly 36. Consequently, as the platen
30 rotates about its first, fixed vertical axis, the second
vertical axis of the bowl assembly 36 revolves around the platen's
axis, the two axes at all times parallel. Concurrently, as the
engagement of the fixed drive gear 52 with the rotatable planetary
gear 54 compels rotary motion in the planetary gear, the bowl
assembly 36 of the electrolytic cell rotates about its axis, since
the planetary gear 54 is attached to the bowl's mounting boss 74.
The rotation of the bowl assembly 36 thus truly is planetary in
relation to the shaft 20.
[0076] Reference is made to FIGS. 1, 3, 4, 12, and 16. The
apparatus is configured so that, throughout the practice of the
invention, the imaginary vertical line defining the first axis A
passes through the bowl assembly 36, i.e., a greater or lesser
portion of the bowl assembly "overlaps" the fixed axis A. Thus, as
the axis B of the bowl assembly orbits the fixed axis A, an
ever-changing portion of the bowl 70 always overlies the shaft
recess 63. Importantly, during operation of the apparatus the anode
assembly 50 is situated near, preferably exactly at, the central
vertical axis A of the apparatus. Both the platen 30 and the bowl
assembly 36 rotate around the anode 50, but it is seen that as the
bowl assembly 36 rotates the distance separating the anode 50 from
the bowl wall 72 is constantly changing. Nevertheless, the anode 50
remains within the interior of the single bowl 70 to permit the
electrolytic treatment to proceed at the substrate material. With
the unmoving anode 50 at the central axis A, the substrate material
undergoes treatment at the cathode strips 44, yet the flow-through
circulation of the electrolyte is ongoing.
[0077] A key advantage of the present invention thus is presented.
The electrolytic cell (mainly including the bowl assembly 36)
containing the electroplating solution and the substrate material
undergoes planetary rotation, that is, a compound rotary motion,
wherein the cell rotates about its own axis B while simultaneously
revolving around a fixed axis A offset from the axis of the cell.
As the cell orbits around the central axis A of the apparatus, the
substrate material is cast by centrifugal force against the
"outermost" portion of the interior of the bowl 70. As suggested by
FIGS. 3 and 6, at any given time during the operation of the
invention some point P on the interior face of the wall 72 of the
bowl 70 is at a maximum distance from the axis of the rotating
platen 30. This outermost point P, being farthest from the platen's
axis of rotation, has the highest absolute linear speed.
Consequently, the centrifugal force due to rotation of the platen
30 impels the substrate material within the bowl 70 to collect
along a short arcuate segment of the wall 72 in the immediate
vicinity of the outermost point P. An advantage of the invention
therefore is that the substrate material M to be treated tends to
collect at a comparatively short segment of the perimeter of the
bowl 70, rather than around the entire circumference of the bowl,
as in prior art devices.
[0078] A further advantage of the invention is that while the
substrate material M collects at a certain surface within the bowl
70, it nevertheless is in a constant state of agitation. Deliberate
agitation of the substrate material fosters uniform
electrodeposition upon the individual powder particles. Wherein
prior art devices typically repeatedly interrupt and re-start cell
rotation to tumble the substrate material, the agitation in the
present invention is constant as a result of the continuous
rotation of the bowl assembly 36. As seen in FIG. 3 and 6, the
rotation of the platen 30 maintains the substrate material against
the segment of the bowl adjacent to the outermost point P. However,
because the bowl assembly 36 is also constantly rotating about its
own axis, the segment of the bowl wall 72 that is at a maximum
distance from the platen's rotational axis also is constantly
changing. As a result, the substrate material tumbles along the
inside wall of the bowl assembly 36, in the vicinity of point P,
while the wall of the bowl moves continuously "beneath" it.
[0079] Further understanding of this function is had with reference
to FIG. 3. It is seen that the platen 30 rotates counterclockwise
around first axis A. Because the bowl assembly 36 orbits axis A,
the centrifugal force resulting from that revolution forces the
substrate material against the wall of the bowl assembly in the
vicinity of the outermost point P. However, because the bowl
assembly 36 is itself undergoing rotation about axis B, point P is
not a point fixed at one physical location on bowl wall 72; rather,
P designates a figurative point that is stationary in space (i.e. a
point on the perimeter of the bowl at a maximum distance from axis
A) in relation to which the wall of the bowl moves. The substrate
material tends to collect at point P, but as the bowl wall moves
with respect to point P, the substrate material is caused to
tumble. The constant tumbling of the material promotes a uniform
electrodeposition upon the individual particles of the substrate
material.
[0080] Because the segment of the bowl assembly 36 against which
the substrate material collects is predictable and defined, the
apparatus advantageously limits to that segment the application of
the working electrical potential. The electrical potential required
to perform the electrolytic processing of the substrate material M
is applied via the anode assembly 50 and the cathode strips 44,
44', 44''.
[0081] The mode of applying the working electrical potential to the
substrate--a distinct advantage of the invention--is explained with
combined reference to FIGS. 2-8, especially FIGS. 5-7. Electricity
at the user-selected and appropriate voltage and amperage is
supplied from the mercury slip ring 87 to the electrical cable 90
via the access tunnel 67 in the platen 20. Current flows through
the cable 90 to the wire wheel contact 92 which is mounted to
rotate in a vertical plane upon the axle 93, which in turn is
secured to extend from the top of the platen 20. The transmission
cable 90 preferably is attached to the upper surface of the platen,
as seen in FIG. 5. The cable 90 runs generally radially outward
from the access tunnel through the axis of the drive gear 52, and
is routed to avoid the planetary gear 54 en route to the wire wheel
contact 92. Electrical potential is applied serially to the cathode
strips 44, 44'', 44'' by the wheel contact 92.
[0082] As previously mentioned, as the bowl assembly 36 rotates,
the substrate material is constantly tumbling or rolling along the
inside of wall 72. The general location of the substrate remains
unchanged in radial relation to the platen's axis of rotation A due
to the centrifugal force of the bowl assembly's revolution around
first axis A. The substrate tumbles along the wall 72 due to the
rotation of the cell bowl assembly 36 around its own axis B,
meaning that the wall 72 has a constantly changing radial relation
to the first axis A, and thus is always in motion with respect to
the substrate material itself.
[0083] Combined reference is made to FIGS. 5 and 6. The bowl's axis
of rotation B is depicted in FIGS. 5 and 6; in FIG. 5 the bowl's
axis of rotation B appears central to the planetary gear 54 which
is coaxial with the cell bowl 70. FIG. 5 also illustrates that the
bowl's axis of rotation B is at all times between the wheel contact
92 and the platen's axis of rotation (at the central axis tunnel 67
in FIG. 5). The bowl's axis of rotation B is fixed with respect to
the platen 20, the axis' position being at the center of the bowl
boss recess 66, as indicated in FIG. 9. The wire wheel contact axle
93 also has a fixed location upon the platen 20. Accordingly, the
axle 93, the bowl's axis of rotation B, and the platen's axis of
rotation A are always collinear along a radius of the platen, also
as best seen in FIG. 9.
[0084] Because the wire wheel contact 92 is radially collinear with
the bowl's axis of rotation B, the wheel contact 92 is at all times
situated below the portion of the bowl 70 that is radially
outermost from the platen's axis of rotation A. Thus, even thought
the bowl 70 is constantly rotating around its own axis B (and thus
the portion of the bowl that is maximally distanced from the first
axis of rotation A is constantly changing), the wheel contact 92
ever remains below that outermost bowl portion in the vicinity of
point P. Significantly, the mass of substrate to be treated also
remains in the vicinity of the outermost point P, so that the wheel
contact 92 and the tumbling substrate are always in radial
alignment with respect to the bowl's axis B.
[0085] The constant radial alignment of the tumbling substrate with
the wheel contact 92 allows the application of the working voltage
to be coordinated with the position of the substrate. As the bowl
assembly 36 rotates about the second axis B, the radially arrayed
cathode strips 44, 44', 44'' consecutively contact the wire wheel
contact 92, which is in rolling contact with the underside of the
rotating bowl 70. As the wheel contact 92 turns, the cathode strips
44, 44', 44'' come into physical and electrical contact, e.g. one
at a time, with the wheel contact 92, permitting a voltage to be
applied momentarily to the contacting one of the strips. It will be
immediately understood by persons skilled in the art that strips
44, 44', 44'' need not make electrical contact with the wheel 92
one at a time; alternatively, the contact strips may be
interconnected electrically so as to function in groups (e.g., two
to five strips per group). In such alternative embodiments, all the
strips in a designated group or cluster are electrically active
when any one of them is in electrical contact with the wheel 92.
Such alternative embodiments may promote better application of
current to some types of treated substrate materials. The temporary
and abbreviated electrical connection between each strip 44 or 44''
is provided by the rolling contact of the wheel contact 92 with the
exposed contact portion 49 on each cathode strip.
[0086] At the instant a given one of the cathode strips 44, 44',
44'' is in contact with the wheel contact 92, that strip (i.e.
strip 44'' in FIG. 6) is radially aligned with the outermost point
P about which the tumbling substrate is collected. So long as some
portion of the collected substrate is in electrical contact with
the strip 44'' that is also in contact with the substrate, the
substrate undergoes electrolytic processing by the electrical
current at that strip. As the bowl assembly 36 continues to rotate
(e.g. clockwise in FIG. 6), the one cathode strip 44'' moves out
from beneath the collected substrate and out of contact with the
wheel contact 92, and the next adjacent cathode strip (e.g. strip
64 in FIG. 6) moves into contact with (the relatively stationary)
substrate and the wheel contact 92, and assumes the role of
cathodic electrode. The process is repeated as the bowl assembly
rotates, with each of the plurality of cathode strips acting as the
working electrode one time per bowl rotation. Advantageously,
therefore, electrical potential need be and is applied to only one
cathode strip, or interconnected group of cathode strips, at a
time, and due to centrifugal collection the substrate material is
constantly in contact with the charged electrode strip. The
efficiency of the apparatus is marked; among other benefits of the
invention is that the only charged cathode strips are the one or
more that are in contact with the wheel contact 92 at a given time.
All the other strips, having no substrate pressed against them at
the time, remain uncharged.
[0087] The operation and method of the invention are apparent to
one of ordinary skill in the art having reference to the foregoing.
The complete apparatus of the invention, in position for use, is
depicted in FIG. 16. The substrate material to be treated is
deposited in the cell bowl 70, along with the desired volume of
electrolytic solution. The drive motor 32 and shaft 34 are
actuated, causing the platen to rotate counterclockwise about the
fixed first axis (see large directional arrow in FIG. 3), and the
engagement of the drive and planetary gears resulting in
counterclockwise rotation of the bowl assembly 36 around the second
axis (as indicated by the small directional arrow in FIG. 3). The
pump 81 is engaged to pump electrolyte into the cell. The cell bowl
assembly 36 orbits around the first axis, the resulting centrifugal
force causing the substrate to collect along a radially outermost
(in relation to the first axis) segment of the inside wall of the
bowl assembly. The rotation of the bowl assembly 36 agitates and
tumbles the substrate, while the substrate comes into successive
brief contact with each one of the cathode strips 44, 44', 44'' to
permit the electrolytic circuit (including the anode assembly 50)
to effectively remain constantly closed. Electrolytic solution is
urged by the rotation of the bowl assembly to flow toward the
annular osmosis filter 42 (or suitable alternative discharge means)
pass therethrough and pour into the basin 24 for collection.
[0088] During the working stage of the process, the auger flange
100 screws about the second axis B of the cell in a manner that
urges the cell contents downward into the cell for continued
processing, as suggested by the smaller directional label W in FIG.
18.
[0089] Advantageously, processing continues without the need to
stop and start the cell to agitate the substrate. Processing may be
staged using different chemicals feed nozzles 83 and solution
reservoirs 80 according to known methods and devices.
[0090] At the conclusion of the complete processing, the discharge
of processing or rinsing liquids into the interior of the cell via
the nozzle assembly 83 is discontinued, and the vast bulk of the
liquid in the cell interior is spun out through the filter 42 by
centrifugal force, leaving the substrate comparatively dry. The
directions of rotation of the platen 20 and the bowl assembly may
then be reversed to empty the substrate from the bowl assembly. The
reversal of the direction of bowl rotation, as indicated by the
large directional arrow U in FIG. 18, causes the auger flange 100
to auger the substrate out of the bowl 70 for discharge up and out
the dome port 103 for collection. Of course, the spiral of the
flange 100 can be configured oppositely from that illustrated
herein, in which case the direction of rotation of the platen 30
need merely also be reversed to perform the corresponding unloading
or downward pushing functions described.
[0091] The inventive apparatus has manifold uses. For example, the
following materials constitute but a partial list of the powders,
micron scale to sub-micron scale, that may be processed in the
invention to satisfy particularized needs: [0092] Inert micron
scale isotope particles for blood marker [0093] Critical or fixed
stoichiometry alloy composition powders for powder metal forming
and solder paste applications [0094] Filament platinum-coated
nickel catalytic submicron powders [0095] Microsphere grid array
microencapsulation of crushed radioactive fuel rods [0096]
Electrosynthesis of ceramic oxides [0097] Compactible surface alloy
for refractory metal powder forming [0098] Corrosion protection for
nanoscale powders [0099] Insulating and dielectric coatings for
soft magnetic powders [0100] Electrophorectic/electrophrenic
polymer coatings on metallic powders [0101] Noble metal
encapsulated base metal powders [0102] Capacitive dielectric oxide
coatings on tantalum powders [0103] Ordnance powders [0104] Armor
piercing cores [0105] Metal encapsulated reactive ignition powders
[0106] Metal encapsulated organic materials for implantable
pharmaceutical delivery systems [0107] Metal encapsulated
photocopier toner materials [0108] Anodized aluminum fines for
automotive and industrial paint systems [0109] Metal encapsulated
in conductive metal encapsulated particles for arc welding
electrode [0110] Metal coated diamond and refractory metal powders
for cutting tool inserts [0111] Metal-coated graphite particles and
fibers [0112] Composite metal foils [0113] Multilayer metal alloy
powders [0114] Metallic flake electro-deposited alloys for pigments
and printing ink [0115] Metallic electro-deposited alloys for
brazing and soldering powders [0116] Metal matrix composites [0117]
Powder metal superconductor material [0118] Inert submicron
magnetic particles marker material for nondestructive testing
[0119] Nickel encapsulated metal hydride battery powders [0120]
Insulating metal powders [0121] Enhanced compaction surface
elements [0122] Electropolished metal powders [0123] Low fusing
temperature metal coatings over metal powders for rapid prototyping
using stereo laser systems [0124] Anodic coatings of submicron
metallic powders [0125] Low noble weight silver termination paste
for multilayer chip capacitors [0126] Low noble weight micron scale
nickel/platinum electrode inks for multilayer chip capacitors
[0127] Dielectric coatings on metallic powders for electronic
component inks [0128] Gold-plated stainless-steel powders for
medical and dental implantable components [0129] Compactable
permanent magnetic powder [0130] Frangible bullets [0131] Thermal
management particles for screenable inks [0132] Solid rocket fuels
[0133] Metallic powder coating pigments [0134] Colloidal chemical
catalysts [0135] Critical stoichiometry sintered sputtering targets
[0136] Metal encapsulated mesoscale radioactive powder for waste
remediation [0137] Nickel coated iron powder for magnetic recording
media [0138] Multilayer electrodeposited composition powders for
pyrotechnics and explosives [0139] Zinc encapsulated copper powder
for batteries.
[0140] Although the invention has been described in detail with
particular reference to these preferred embodiments, other
embodiments can achieve the same results. Variations and
modifications of the present invention will be obvious to those
skilled in the art and it is intended to cover in the appended
claims all such modifications and equivalents. The entire
disclosures of all patents and publications cited above are hereby
incorporated by reference.
* * * * *