US 3007861 A
Description (OCR text may contain errors)
Nov. 7, 1961 J, B, WW1-ERS 3,007,861
PILOT ELECTROPLATING CELL Filed April 6, 1959 l l /4 PA/EVJ 3,007,361 Patented Nov. 7, 1961 3,007,861 PEUT ELECTRPLATING CELL John B. Winters, Westlake, Ghia, assigner to linear, Inc., Cleveland, Ohio, a corporation of @his Filed Apr. 6, 1959, Ser. No. $04,368 8 Claims. (Cl. 204-195) This invention relates generally to the electroplating art and is particularly concerned with a new pilot electroplating apparatus for use in studying the electrochemical behavior of electrolytic systems, more particularly the operating characteristics of electroplating baths.
An important object of this invention is to provide laboratory apparatus in which can be duplicated on a small scale the conditions which will be encountered in operating a commercial electroplating installation. Several attempts have been made heretofore to devise such an apparatus, but none of these attempts has been entirely satisfactory so far as l am aware.
The successful commercial reduction of modern electroplating installations demands accurate control of all factors affecting the quality of the electrodeposit. Moreover, all such factors must be recognized and the effects of variations of such factors must be known in order properly to control them and thus produce uniformity in the resulting product. In addition, it is often quite desirable to be able to produce in the laboratory the various factors and variations therein so as to study on a small scale the effects of changes in those Various factors which may be found to yield improved results; and so that these things should be determined before such changes are adopted in production equipment. When it is realized that modern commercial electroplating installations involve baths containing several thousand gallons of solution and are depended upon to turn out thousands of uniformly plated pieces, it is readily seen that accurate control and knowledge of all of the Variables is essential and that no changes should be risked unless it is known before hand what the results of those changes will be. The factors generally recognized as being of paramount importance n operating commercial electroplating baths are bath composition, bath temperature and average current density. Of equal importance are such mechanical factors as relative movement of bath and Work being plated, which is obtained by various means such as bath agitation, bath circulation, cathode movement and air agitation. All of these factors may profoundly affect the physical characteristics of the electro-deposited metal. Moreover, they are related interdependently to the bath composition, temperature and current density factors. In controlling the operation of commercial plating installations it is highly desirable to be able to `determine what elect the mechanical factors mentioned above will produce when changes are made in the bath composition, bath temperature and average current density.
By the present invention I have provided new apparatus with which to determine the effects of variations of the various foregoing factors and thereby to determine the exact conditions to be created and maintained in a commercial size plating installation.
ln the accompanying drawings which form a part of this specification,
FlG. l is a perspective view of one form of apparatus embodying the present invention;
FIG. 2 is a fragmentary vertical sectional View taken on line 2 2 of FIG. l with parts added;
FIG. 3 is a fragmentary vertical sectional view taken on line 3-3 of FIG. l, with parts added;
FIG. 4 is a fragmentary View of a modied form of apparatus embodying the present invention; and
FIG. 5 is a fragmentary side elevational View of the cathode moving mechanism.
FIG. l shows apparatus embodying the present invention except that the heating element and thermostat have been omitted for the sake of clarity, these parts being shown in FIGS. 2 and 3. The apparatus of FlG. 1 comprises a base l on which is supported a tank 2 which is preferably rectangular in shape as shown and which is also preferably made from suitable transparent and electrical insulating material, for example, lucite. The bottom of the tank which is indicated at 3 is much thicker than the side walls and is provided near one end, with a recess S which is suitably proportioned as to length, Width and depth to accommodate a heating element 6 and a thermostat 7. As is better shown in FIG. 2, one end wall of tank 2 is provided with a hole in which a tube lll fits with fluid tight contact. The heating element 6 extends through, and is supported by, tube lll and a flexible sleeve 11 surrounds the tube 10 and the heating element 6 and is held in liquid tight contact with these two parts by resilient rings 12. It Will be understood that tube l0 may be formed integrally with tank 2 if desired. The parts 10, 11 and f12 form a liquid tight joint with element 6.
A rod l5, preferably composed of the same material as that of the tank 2, extends through an end wall of the tank and is positioned near the upper end of recess S. This rod makes a fluid tight connection with the walls of the opening through which it extends. Rod l5 has an axially extending recess i6 into which the -thermostat 7 extends.
It will be noted from FIGS. 2 and 3 that there is a space in recess 5 around rod l5 and heater 6 and that liquid heated in the bottom of the lower part of recess 5 may how up into tank 2 and be replaced by cooler liquid.
The terminals of the heating element may be connected to a source of current (not shown) and the terminals of the thermostat may bev connected to apparatus which is enclosed in housing 2t? and which serves to control the flow of current to the heater automatically to maintain a predetermined temperature of the electroplating liquid in tank 2. In FIG. l, 2l indicates a manually adjusted means which will set the current controller so that the heater will maintain the temperature desired. 22 indicates a light bulb which shows whether the heating current is on or oil.
The tank is provided with a tube 25' which extends through a side wall near the bottom wall 3 and a flexible hose 26 such as shown in FIG. l has its open end clamped to the tank near its upper end. This hose may have two functions. It may serve as a means for lowering the liquid level in the tank and even for substantially emptying the tank or it may serve to conduct compressed air into the tank to agitate the electrolyte.
An anode 3% is shown as being supported by the end wall of the tank 2. adjacent to the housing 20. 'I'his anode may vary in length as desired and of course may consist of any metal which is to be electrodeposited.
At the opposite end of the tank the cathode which o is to be plated is indicated at 35. This cathode is clamped against a bar 36 which is preferably composed of the material constituting the tank, for example, Lucite. The cathode 35 is held in contact with the bar 36 by a spring 37 which is a good conductor and which is connected to a source ott current by a screw 38 which also secures the clamp 37 to bar 36. Conductor 37 is insulated from the liquid in the tank by being partially coated or wrapped with some material such as lacquer or tape which is impervious to the electroplating liquid, but the conductor is in metal-to-metal contact with the cathode 35. A hole 39 extends through cathode for a purpose presently to appear.
Means is provided for varying the position of t-he cathode in the tank. As shown, this means comprises two plates 40 and 41 preferably composed of the same material as that of the tank and these two plates are spaced apart far enough to have a good sliding contact with the inner and outer walls of the end of the tank and are held in that position by spacers 42 interposed between plates 40 and 41 and 36 by screw 38 and a nut on the outer end thereof.
A motor 50 mounted on the base 1 and, as is better shown in FIG. 5, has a disc 51 attached to one end of its rotor and this disc carries an eccentrically mounted pin 52 which engages with a block 53 attached to the lower end of plate 40. When motor Sti is energized, pin 52 will raise the assemblage of plates 40, 41 and 36 vertically and then will allow them to move down vertically, the end wall of the tank guiding the assemblage in both directions.
It will be noted that cathode 3S is bent to simulate a wide variety of cathode shapes which may be encountered in commercial electroplating. It includes a straight vertical section at the top, a straight horizontal section at the bottom, a straight section inclined a a small angle to the vertical near the bottom, and upper and lower surfaces inclined at acute angles to the vertical with radii of different curvatures interposed between these adjacent portions, and the hole 39 in a vertical section.
It will be understood that the cathode 35 may be given any form and shape desired so as to study the ef- -fects of various operating conditions. For example, with the cathode 35, as illustrated, the eiects of the throwing and covering powers of the bath and the nature of the plating on the various flat and angular surfaces of curves may be studied as well as plating in and around holes and with electrolytes of a wide variety of compositions, temperatures and current densities, with and without mechanical or air agitation or heating. By changing only one variable at a time, the interdependence of the various variables may be determined and each variable may be selected which will tgive the best results in combination with the other variables.
in FIG. 4 is shown a slightly modified form of the invention. In this case the tank 2 lacks the thick bottom and recess 5 of the tank of FIG. 1, the heaters 6 and thermostat 7 are positioned side by side and are mounted in the tank by means of liquid tight joints in much the same way as has been described in connection with heater 6 and thermostat 7 of FIGS. 1 to 3.
The above described apparatus has many advantages. The rectangular tank may be made large enough to hold a sizable quantity of electrolyte, enough to make the results of the tests quite reliable. The transparent walls of the tank make possible visual observation from various directions of what is taking place in the tank. Any suitable transparent material may replace the Lucite to make the tank, for example, any thermoplastic resin which is transparent, insulating and capable of withstanding the service conditions to which the tank will be subjected.
The location of the heater within the tank insures uniform heating of the liquid without undue heating of the tank walls. The location of the thermostat adjacent to 4 the heater means close control of the temperature of the electrolyte.
While two specifically described modifications of apparatus embodying the present invention have been shown, it is to be understood that many obvious variations of the several parts of these devices may be made without departing from the present invention or the intended scope of the appended claims. Furthermore, while only agitation of the plating liquid by means of air conducted into the tank through hose 26 has been described, it will be understood that any suitable mechanical agitator may be used, if desired, including stirrers, paddles and the like to simulate operating conditions in a commercial installation.
Having thus described this invention in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains to make and use the same, and having set forth the best mode contemplated of carrying out this invention, I state that the subject matter which I regard as being my invention is particularly pointed out and distinctly claimed in what is claimed, it being understood that equivalents or modifications of, or substitutions for, parts of the above specifically described embodiment of the invention may be made without departing from the scope of the invention as set forth in what is claimed.
What is claimed is:
l. A pilot electroplating apparatus, for use in determining suitable operating conditions for a commercial electroplating system, comprising a tank to contain an electrolyte and having a bottom wall and upright walls, an anode supported in iixed position by, and adjacent to, one of said upright walls, a cathode in the tank adjacent to the opposite upright wall, and means for supporting said cathode, said means including vertically movable inner and outer plates connected together near their upper ends and slidably engageable with the inner and outer surfaces of the said opposite upright wall and connected to said cathode, and means for reciprocating said plates vertically.
2. The combination of elements set forth in claim 1 in which a rotatable member is fixed in position outside of the tank and is engageable with the said outer plate to control the vertical position of said plates.
3. The combination of elements set forth in claim 1 in which a rotatable member is disposed outside of the tank and is engageable with said outer plate to move said plate vertically.
4. The combination of elements set forth in claim 1 in which a motor is tixed in position outside of said tank, and -a cam member is attached to the rotor of the motor and is engageable with said outer plate to move said plates vertically.
5. The combination of elements set forth in claim 1 in which the bottom wall of the tank is provided with a recess and a heater is positioned in the lower part of said recess and thermostatic means is disposed above the heater in said recess.
6. The combination of elements set forth in claim 1 in which the bottom wall of the tank is provided with a recess and a passage extending from the recess to the outside of the tank a tube having liquid-sealing engagement in said recess, a heater extending through said tube and into said recess, and means for sealing against escape of liquid between said tube and said heater, said means comprising a flexible sleeve surrounding said tube and said heater, and O-rings surrounding the iiexible tube and pressing against said tube and said heater with fluid sealing pressure.
7. The combination of elements set forth in clalm 1 in which the bottom wall of the tank is provided with a recess and thermostatic means is disposed in a rod positioned in the upper part of said recess.
8. The combination of elements set forth in claim 1 in which the tank is provided with a tube leading through 5 one of the upright walls of the tank and a hose connected to the tube and suiciently long to extend to above the surface of liquid in the tank.
References Cited in the le of this patent UNITED STATES PATENTS 6 Todd Sept. 28, 1926 Holland Mar. 16, 1937 Armstrong et a1 Jan. 31, 1939 Hull Mar. 7, 1939 Irish Sept. 20, 1949 Rines May 8, 1956 Guillette May 22, 1956 Gilmont Nov. 17, 1959