Apparatus for single anode brush electroplating

An apparatus for electroplating conductive surfaces, in particular rotatable surfaces. A hand held anode includes a porous surface material such as polypropylene wool, backed by an inert anode mounted on a handle and connected to a source of direct current. A delivery tube through the anode handle allows liquid to be delivered to the surface material. A manually actuatable valve system on the anode handle permits liquids from a selected one of plural supply tubes to be connected to the delivery tube. In operation, the anode is connected to a positive polarity direct current sources, a plating liquid is directed from a supply to the valve system, then to the anode surface material through the delivery tube. Depending on the direct current polarity selected and the liquid selected for delivery to the anode material, the workpiece surface may be cleaned, treated or plated. A series of movable trays are positioned below the workpiece to catch liquid that may drip from the anode surface material. This system permits the rapid and convenient electroplating of selected areas on a workpiece without contamination between different process liquids.

BACKGROUND OF THE INVENTION 
This invention relates in general to electroplating metals on a conductive 
substrate and, more particularly, to an apparatus for brush plating of 
workpieces. 
Forming metal layers on conductive substrates has long been accomplished by 
electroplating. In conventional electroplating, the object to be plated 
(the cathode) and an anode are suspended in an electrolyte that contains 
salts of the metal to be deposited and often other chemicals to assist in 
the electrochemical action. The anode is connected to the positive pole of 
a direct current source, such as a battery, and the object or cathode is 
connected to the negative pole. The anode may be formed from the metal 
being plated or from an inert conductor, such as platinum. Metal from the 
electrolyte is deposited in a uniform coating on the object being plated. 
If the anode is inert, the electrolyte must be regularly replenished with 
the metal being deposited. 
Electroplating is used for many purposes, such as the plating protective, 
hard, metal surfaces on softer metal substrates, the production of jewelry 
by plating precious metals on base metal substrates and the repair of worn 
metal objects, such as bearings and the like, by deposition additional 
metal in worn areas. 
In some cases it is necessary to plate portions of objects that are too 
large to be conveniently placed entirely in a plating bath, or where only 
a small portion of the object is to be plated. Typically, a bearing on a 
long rotating shaft, bearing journals on electric motor shafts and the 
like require repair when worn to the point where excessive play and 
vibration occurs between the shaft and bearing. Often the diameter of the 
shaft has worn to the point that it is 0.0005 to 0.002 inch undersize, so 
that electroplating of a uniform thin, adherent layer of the shaft metal 
around the shaft is necessary. 
Brush plating was developed to permit such localized plating. In its 
simplest form, brush plating can be accomplished with an ordinary paint 
brush, with a small piece of metal adjacent to one side of the bristles to 
act as the anode. The brush anode and the object to be plated are 
connected to a direct current source, the brush is dipped in the 
electrolyte and the brush is moved across the surface to be plated. With 
repeated dipping and brushing, an electroplated layer will be built up on 
the object surface. 
While effective with small areas and limited thickness plating, this prior 
art system of brush plating has a number of problems. Cleaning of the 
object to be plated must be done separately. Electrocleaning, where a 
reverse current and an electrolyte is used to remove a small amount of 
metal from the object surface, is difficult to accomplish and will often 
contaminate the brush. Plating is very slow, with the need to constantly 
dip the brush in the electrolyte. In some cases, a squirt bottle can be 
used to replenish the brush electrolyte. The brush and squirt bottle, if 
used, will tend to drip or splatter electrolyte, especially where a slowly 
rotating shaft surface is to be plated. Some of the plating solutions are 
quite costly, so wasted solution can be a considerable expense. Where 
cleaning solutions and various activator etchant solutions are used to 
obtain improved plating, the process must stop between steps to allow the 
object to be rinsed with water to remove the previous solution and prevent 
contamination. Either different brushes must be used for the different 
solutions or a single brush must be cleaned carefully between solutions. 
While brush plating has applications in some small, light plating, 
applications, these problems prevent brush plating from being effectively 
used in the repair of structural objects where high quality plating to 
uniform thicknesses without contamination on a rapid, production line 
basis is required. 
Thus, there is a continuing need for improved brush plating systems 
allowing rapid plating to relatively thick layers on a rapid basis while 
avoiding contamination between different solutions used in the plating 
operation. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of this invention to provide a brush plating 
apparatus overcoming the above-noted problems. Another object is to 
provide a brush plating apparatus capable of plating at a continuous rate 
to relatively thick layers. A further object is to provide an apparatus 
that permits rapid change between solutions used in brush plating without 
contamination between solutions. Yet another object is to provide an 
apparatus that saves excess valuable solutions without contamination. 
Still another object is to provide an apparatus having a brush anode 
capable of covering and plating a considerable area of a rotating object. 
The above objects, and others, are accomplished in accordance with this 
invention by a brush plating system that comprises a hand held anode 
assembly, a system for selectively directing a selected plating liquid to 
the anode and a selective tray arrangement for catching excess plating 
liquids. 
The anode assembly is mounted on a handle and connected to a source of 
direct current. The anode assembly includes an inert conductive anode, 
typically platinum plated niobium, mounted on an anode handle, a porous 
material coverinq the anode and adapted to be brought into physical 
contact with the object to be plated, a delivery tube for delivering a 
plating solution to the porous material and a valve system mounted on the 
anode handle for connecting any one of a plurality of supply tubes to the 
delivery tube. 
A plurality of supply tanks are provided to hold the electrolyte, an 
electrocleaning solution, various activator or etchant solutions and the 
like. A supply tube connects each of the tanks to the valve system on the 
anode handle. Any suitable means, such as pressurized tanks or pumps at 
the tanks, is provided to cause the tank liquids to flow to the valve 
system. 
A support is provide for the object to be plated. Where the object is 
cylindrical and is preferably rotated during plating, provision may be 
made for a low speed motor for rotating the object during plating. 
A tray assembly is provided below the object support to catch overflow or 
other drips from the anode. Different trays may be moved into place to 
catch each solution for use. In some cases, only the electrolyte is of 
sufficient value to require saving in an uncontaminated state. In that 
case, one tray will be positioned to catch electrolyte overflow and a 
second tray will be positioned during all other steps to catch all other 
solutions, which are then disposed of in a proper manner.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring now to FIG. 1, there is seen a base 10 upon which a rotatable 
support 12 is mounted. Support 12 may be any conventional chuck or collet 
capable of holding a generally cylindrical object 14 to be plated. While 
the plating of objects that are surfaces of revolution, while they are 
being rotated, is the preferred application for the apparatus of this 
invention, objects having other shapes could also be plated, if desired. 
A hand-held anode assembly 16 is adapted to be held adjacent to object 14. 
Anode assembly 16 includes a curved backing 18 typically formed from 
plastic, having a conductive anode surface 20 on the inside, mounted on a 
handle 21. While any inert anode may be used, a platinum plated, 
reasonably inert, metal is preferred, such as platinum plated niobium. A 
sheet of porous material 22 is provided over anode 20 and is shaped to 
conform to the exterior of object 14. Any suitable chemically inert, 
electrically insulating, non-absorptive material which is easily rinsed 
clean may be used for porous material 22. Typical materials include fiber 
matts, soft open cell foam and the like. For optimum results, I prefer 
polypropylene wool, of the sort that is available from Liquid Development 
Company, Cleveland, Ohio. 
A conventional direct current power supply 24 is connected through a ground 
cable 26 to rotatable support 12 and object 14 and through a cable 28 
running through handle 21 to anode 20. Depending on the size of the anode 
and object being plated, power supply 24 may provide from 15 volt, 10 amp 
to 25 volt, 500 amp current. Such power supplies are available under the M 
15-20-115-1C and M 500-25-460-3C model numbers from the Liquid Development 
Company. 
The various liquids used during the cleaning and plating operations are 
delivered from a series of conventional tanks 30 through plural tubes 32 
to a valve assembly 34 (described in detail in conjunction with the 
description of FIG. 2) on anode handle 21. Each tube 32 may extend below 
the liquid surface in its respective tank and the air volume above the 
liquid levels in the tanks may be pressurized by an air pump, so that the 
liquids will be supplied to valve assembly 34 under pressure. 
Since some of the liquids will be consumed during use, in particular the 
plating electrolyte, a constant flow of each liquid is desirable during 
application of that liquid. Excess liquid will run down and drip into a 
selected one of plural trays 36 movable to positions below anode assembly 
16. Each tray 36 is slidable from a stacked storage location below 
rotatable support 12 to a position below anode assembly 16. In many cases, 
only two trays 36 will be needed, one to catch the high value plating 
electrolyte and one to catch all of the lower value cleaning and 
activation liquids for disposal. A drain line 38 may be provided on the 
cleaning solution tray. Of course, additional trays may be provided in a 
stack with cooperating slides so that different trays can be moved into 
position to catch different process liquids as desired. 
A schematic representation of the control box including valve assembly 34 
for the various liquids entering through tubes 32 is provided in FIG. 2. 
Valve assembly 34 is mounted on anode handle 21. Valves 35 selectively 
connect any one of supply tubes 32 to delivery tube 40 that directs the 
selected liquid to porous material 22 for application to object 14. 
Preferably, water rinse valve 37 has a larger and more apparent push 
button, since the water rinse will be used more often. A conventional 
three-position electric switch 42 may be provided with valve assembly 34 
to reverse polarity of the direct current applied to anode 20 between the 
electroclean and plating operations. The switch has three positions; 
"off", "positive" and "negative". In that case, cable 28 will include two 
separate wires carrying both positive and negative polarity to switch 42. 
Switch 42 may also, if desired, be directly mounted on power supply 24. 
Valves 35 are preferably conventional solenoid valves using self cleaning 
mechanical plastic valves components and no metal in contact with the 
liquids. Suitable valves include 1/8 in. minivalves available from Hardie 
Irrigation Co. under the I7024N24V designation. Valve 37, for greater 
flow, may be a polyvinyl chloride ball valve available from McMaster Carr 
under the 4506K17 designation. 
A typical sequence of operation of this apparatus is as follows. The object 
14 to be plated is put in the rotatable support 12. Ground cable 26 is 
connected to support 12 and anode cable 28 is connected to anode 20 
through handle 21 and switch 42 (if used). Rotation of the object is 
begun. A catch tray 36 is positioned below the area to be plated. 
The valve to the electrocleaning solution is turned on with the power 
supply switch 42 providing negative polarity to anode 20. Any suitable 
electrocleaning solutions may be used. A typical simple electrocleaning 
solution for steel comprises about 8 ounces of sodium hydroxide and about 
2 ounces of laundry soap chips per gallon of water. Suitable cleaning 
solutions are available from the Liquid Development Company (LDC) under 
the LDC Electroclean designation. 
When sufficient cleaning has been accomplished, the cleaning solution valve 
is closed and the rinse water valve is turned on for a time sufficient to 
flush the cleaning solution from the anode porous material 22. Current of 
negative polarity is provided to the anode switch 42 and the valve to the 
first activator supply is turned on. This activator typically contains 
water, sodium chloride and hydrochloric acid. A suitable activator is LDC 
Activator #2. When the color of the surface of object 14 is uniformly dark 
grey, the activator valve is turned off and the rinse water valve is 
turned on to rinse porous material 22. 
The valve for the second activator solution is then turned on. The second 
activator solution typically contains water, sodium hydrochloride and 
citric acid. A suitable second activator is LDC Activator #3. When the 
surface of object 14 is uniformly light grey, the activator valve is 
closed and the rinse water valve is opened for a period sufficient to 
rinse porous material 22. In many cases all of these solutions and rinse 
water will be caught in a single tray 36 for disposal. If desired, 
selected ones of stacked trays 36 may be moved into place to catch each 
solution separately. 
The power supply 24 is adjusted for the selected plating parameters. A 
second catch tray 36 is moved into position below the plating area. The 
valve to the plating solution is then turned on and positive current is 
supplied to the anode. Any suitable plating solution, such as LDC Nickel 
High Build, may be used. After the desired plating is accomplished, often 
judged by recording amp hours during plating, the plating solution valve 
is turned off, the power supply is turned off, the rinse valve is turned 
on for a sufficient time to rinse porous material 22 and object 14 and the 
object is removed from the assembly. 
Additional valves and supply tanks are provided beyond those used in this 
exemplary description of typical operation of the apparatus for the cases 
where plating of more than one metal may be desired, or other treating 
steps may be used. 
Other applications, variations and ramifications of this invention will 
occur to those skilled in the art upon reading this disclosure. Those are 
intended to be included within the scope of this invention, as defined in 
the appended claims.