US3706650A

US3706650A - Contour activating device

Info

Publication number: US3706650A
Application number: US128240A
Authority: US
Inventors: Steve Eisner
Original assignee: Norton Co
Current assignee: Saint Gobain Abrasives Inc
Priority date: 1971-03-26
Filing date: 1971-03-26
Publication date: 1972-12-19
Anticipated expiration: 1989-12-19

Abstract

A rotatable activating device for contacting and activating a contoured surface during the electrodeposition thereon of a metal coating. The device has an outer surface composed of a nonconductive, porous, compressible, fluid-entrapping and circulating, fixed hard particle-supporting media contoured to complement the contours of the surface to be activated and an internal complete or partial core of a conductive material.

Description

Umted States Patent Eisner 1 Dec. 19, 1972 I54] CONTOUR ACTIVATING DEVICE FOREIGN PATENTS OR APPLICATIONS [72] In Steve Eisner, Schenectady, N 18,643 1899 Great Britain ..204/DIG. 10 [73] ssig e z Norton Company, Troy, N Y. 493,108 9/l938 Great Britain ..204/DIG. 10 [22] Filed: March 26, 1971 Primary Examiner-John H. Mack I Assistant ExaminerRegan J. Fay [2]] Appl- N05 1281240 Attorney-Hugh E. Smith and Herbert L. Gatewood [52] 11.5. C1 ..204/217, 204/224 R, 204/271, [57] ABSTRACT 204/DIG. l0 A rotatable activating device for contacting and ac [51] Int. Cl. ...B23p l/00 tivating a contoured rf ring he elec rodeposi- [58] Field of search....;...204/217,D10. 10, 224, 271 tion thereon of a metal coating- The device has an outer surface composed of a non-conductive, porous, [56] References Cited compressible f'luid-entrapping and circulating, fixed' hard particle-supporting media contoured to comple- UNITED STATES PATENTS ment the contours of the surface to be activated and an internal complete or partial core of a conductive 3,619,401 11/1971 Eisner ..204/D1Gv 10 materiaL 3.6l6,289 lO/l97l Ellis ..2()4/2l7 i 1,214,271 1/1917 Bugbee ..204/D[G. 10 5 Claims, 9 Drawing Figures SHEET 1 BF 2 PATENTEDME 19 mm Inventor Steve Eisner W wk UNIT" 7 u A r /H mmk His Afforney.

sum 2 or 2 PATENTED DEC 19 1912 II 11/ I CONTOUR ACTIVATING DEVICE RELATED APPLICATIONS This application represents a specific embodiment of the porous-activating media disclosed and/or claimed in one or more of my copending U.S. Applications Ser. No. 34,500 filed May 4, 1970, now U.S. Pat. No. 3,619,384; Ser. No. 863,509, filed Oct. 3, 1969, now U.S. Pat. No. 3,619,389; and Ser. No. 863,499, filed Oct. 3,1969, now U.S. Pat. No. 3,619,401.

FIELD OF THE INVENTION The present product, although resembling an abrav sive product, is specifically designed to provide essentially no stock removal in use. This seemingly contradictory statement stems from a process discovery as described and claimed in the aforementionedapplication, Ser. No. 34,500 of Steve Eisner, filed May 4, 1970, now U.S. Pat. No. 3,619,384. As related therein, the use of products of the general type to which that of the present invention belongs to lightly and repetitively contact a surface (an electrodeposit surface in the cited application) results in an activation of the surface making possible speeds of electrodeposition far above those indicated as achievable by the prior art. In particular, the present device relates to that portion of the electrodeposition field wherein the surface to receive the deposit may be other than flat and smooth and hence a problem of obtaining uniform current density exists.

The present device is designed for use in a process in which the current density is high compared with that of conventional processes and in which the surface of the deposit is repetitively contacted at extremely short time intervals by what is termed herein as dynamically hard particles. By this term is meant that the combination of the hardness of the particles, the contact pressure of the particles on the surface of the electrodeposit and the speed at which such particles are moving relative to the electrodeposit surface is such as to produce an action on such surface sufficient to mechanically activate'? the surface. Activating the surface of the electrodeposit as the term is used herein'requires the generation of new surface defect sites through mechanically distorting the crystal lattice of the metal deposited. It is believed that the mechanism is rather complex and consists of several actions taking place essentially simultaneously. First, there is the new surface defect site generation resulting from distortion of the crystal lattice structure as mentioned above. This provides growth sites for many more asperities than would be the case absent this mechanical distortion. Additionally, any dominant asperities already formed are cut off or bent over and crushed by the dynamically hard particle contact. These two actions result in substantial elimination of the current robbing which takes place at the asperities formed in normal plating and is believed to be one of the major contributing factors to the ability to maintain high current densities for substantial periods of time while maintaining acceptable deposits with this process. Further, the action of the activating medium is believed to result in the removal or substantial diminution of the stagnant polarization layer overlying the electrodeposit surface and to maintain a high concentration of metal ions adjacent such surface due to the pumping action of the activating medium which carries a supply of fresh electrolyte across the electrodeposit surface at a high flow rate.

The device utilized in this process consists of a surface disturbing or activating medium having the characteristics of providing a plurality of small, dynamically hard, relatively inflexible, non-conductive particles held in substantially fixed, spaced relationship to one another and generally vertical to the surface receiving the deposit by a preferably porous, compressible, fluid-entrapping and circulating matrix or supporting member. Further, relative motion is provided during the deposition operation between the surface receiving the deposit and the activating medium.

7 In addition, sufficient pressure is applied to said activating medium in a direction normal to the electrodeposit surface to causemechanical distortion of the crystal lattice structure of the metal deposited thereon. The spacing of the particles and the speed of relative movement is such that the deposited metal surface above any given point on the cathode surface is contacted or influenced by a particle at extremely short time intervals, e.g. intervals in the range of 6.1 X 10- to 3.8 X 10' seconds. Fresh electrolyte is supplied to the zones of activated metal deposit at a high rate through entrapment by the porous, fluid-entrapping and circulating activating medium.

Where the surface to be plated (the cathode surface) is not flat and smooth, i.e., has convex and concave contours, the problem becomes complicated due to variations in current density resulting from uneven distances from a fixed anode system. The device of the present invention is directed primarily to this type of surface plating. Another problem encountered is that seldom can one single device he contoured to fit all of the contours of a complex workpiece. This requires the use of multiple devices according to the present invention in order to cover the entire surface of the workpiece and imposes the additional problem of covering adjacent areas with plate from different operations without leaving parting lines or lines of demarcation between the plates laid down at different times or by different devices.

DESCRIPTION OF THE PRIOR ART Abrasive products have historically been so constructed as to maximize the cut or abrading potential of the specific construction concerned. In the present instance the opposite is true. Spaced particles are essential, but they must be so positioned in the product as to provide a minimum of abrasion in use. The closest type of product to that described herein, we believe, has been the brush or cloth used in so-called brushplating. This, however, does not contain the spaced particles required in the present structure.

SUMMARY The device of the present invention is a rotatable formed wheel or drum having an outer surface of a porous, compressible, non-conductive hard particlesupporting media which is capable of entrapping and circulating fluid with which it comes into contact. The distance from the axis of the drum to the outermost portion of such surface may be uniform throughout the drum length or it may vary over such length. The device will be tailored for the particular surface upon which it is to be used and will be formed into a complementary profile of such surface.

l060ll 0285 lnwardly spaced from the outer surface is an inert, conductive anode means. The anode means may underliethe entire outer surface or it may underlie only a portion thereofFurther, the anode means may be a unitary member or it may be made up of a plurality of members, e.g. discs.

Electrical contact between the anode means and from the anode means to ground is achieved through the shaft which extends along the axis of rotation of the device.

DRAWINGS FIG. 1 is a perspective view of one form of the device of the present invention.

FIG. 2 is a sectional view of the device of FIG. 1 along the line A-A.

FIG. 3 is a partial plan view of a modification of the device of thepresent invention.

FIG. 4 is a sectional plan view of still another type of device according to this invention.

FIG. 5 illustrates in a cross-sectional view the anode arrangement for overlap plating.

FIG. 6 illustrates in cross section another form of the present device. I

FIG. 7 is a schematic view showing a device of the present invention as applied to a complex contour surface.

FIG. 7-A shows another portion of the surface shown in FIG. 7 being plated so as to overlap the portion plated in FIG. 7.

FIG. 8 illustrates the use of a device according to the present invention using a flood of electrolyte instead of an immersed system.

DESCRIPTION OF PREFERRED EMBODIMENTS The device of the present invention provides for the controlled application under pressure, both normal to and parallel with the electrodeposit surface, of a supporting, preferably porous and compressible, non-conductive, fluid-entrapping and circulating matrix which supports on its surface in closely-spaced, fixed'relationship a plurality of small, relatively inflexible non-conductive particles. These particles are so positioned in and on the matrix as to contact the deposit forming on 'As described above, the electrodeposit surface is activated by multiplying many times the number of nucleation sites on such surface and generating a controlled growth of a tremendous number of very short asperities which are repetitively restricted in vertical growth throughout the deposition cycle. The metal deposit reflects this action since photomicrographs of the cross sections of such deposits illustrate a structure in which the growth axis of the crystals appears substantially parallel to the substrate rather than showing the normal columnar vertical orientation of conventional electrodeposits.

This technique has been found to increase the limiting currentdensity many times beyond that possible with other methods, resulting in much more rapid metal deposition than is possible with such other methods and has further been found to produce a hard, dense, smooth metal deposit. These results are achieved even through there may be minor metal removal from .the' deposit on the cathode surface, cutting down slightly the total thickness of such deposit. This metal removal is minimized by control of the pressure applied to the activating medium but in order to insure adequate activation of the surface it is necessary to apply sufficient pressure to produce a light scratch patternin the metal deposit. Thus the dynamic hardness of the particles may be substantially greater than the actual hardness, e.g. a resin particle may produce a scratch in a much harder nickel deposit. This scratch pattern may be visible to the naked eye but, in any case, will be seen under a magnification of 10,000 power or less. While the scratches may be produced by metal removal, preferably the dynamic hardness is so controlled that a displacement of metal atoms on the surface rather than actual removal is the basis for the scratch formation.

By using small, relatively inflexible, non-conductive particles as the activating tool, no spot on the deposit surface is covered for any appreciable length of time by the activating particle. Further, since the activating particles are fixed to the supporting matrix, there is no danger of a particle being occluded as a crack-initiating impurity in the electrodeposit. These particles are generally randomly distributed over at least the external surface of the matrix and are preferably spaced in fixed relation to one another over very short spans, e.g. 1.25 X 10" inches to 5.65. X 20' inches. If desired, accurate and non-random distribution-of the particles on the supporting matrix can be resorted to although this is generally an unnecessary complication. By the term particle as is used herein is meant not only completely separate and discrete three-dimensional bodies, but also larger bodies with a plurality of points, tips, projections or the like thereon as for instance a relatively hard resinous coating on a fiber wherein the coating contains multiple irregular spaced projections and is generally uneven in nature. The particles, as described herein, contact or at least influence essentially all of the surface of the electrodeposit and are believed to knock down or cut off as they form most of the dominant asperities on such surface. The particles themselves may vary widely in size from I X 10" inches to 1.25 X 10" inches (average diameter) for example, but should generally be in the size range of from 9 X 10" inches to 2 X 10" inches for best results. The particles can generally be defined as hard, i.e., having a Knoop hardness in excess of 10.0, but the degree of hardness per se is not critical except that control should be exercised not to use a product which is too abrasive for the particular metal being deposited. The degree of pressure applied must also be considered with respect to the hardness of the particles and generally with the softer range of particles more pressure normal to the cathode surface is required than with the harder range of particles.

l060ll 0286 As indicated above, the controlling factor is the dynamic hardness of the particles, i.e., the apparent hardness resulting from a combination of the actual Knoop hardness, the pressure applied and the speed with which the particles are moved across the electrodeposit. A visible indication that the dynamic hardness is sufficiently high is the presence in the deposit of the scratches visible under 10,000X magnification.

The matrix used to support the activating particles is preferably electrolyte-permeable, having a through porosity in the order of at least 6.5 Sheffield units (as measured by a Sheffield porosimeter using a 2% inch ring). Preferably, this matrix is also at least somewhat compressible and deformable so that it can be conformed to irregular surfaced cathodes and'associated deposits where necessary.

In the device of the present invention, the porous, particle-supporting media described above is formed into a wheel or drum. This may take several forms as is more fully described below, but in each instance, at least the outer surface of the drum is formed of this type of media. In some instances the outer surface may be provided in the form of a sheath surrounding or superposed over a central core. In other instances the outer surface may be formed by discs of the porous media positioned around and extending outwardly from the shaft upon which the device is rotated in use.

Underlying the outer surface over at least aportion of the length of the drum is an inert, conductive anode material. The distance from the outer portion of this anode material to the outer surface of the overlying porous, particle-supporting media is preferably substantially the same at all points along the length of the drum in those portions where the anode material is present.

The anode material used in the device of this invention is preferably lead. This is easy to form, inert to most electrolytes which are desirable for use and has the desired conductivity. Preferably the electrolyte to be used with this device is of the sulfate type. This causes a minimum problem with respect to corrosion and fumes and is less toxic than most other systems. The porous media may be of the non-woven variety, described in the aforementioned copending applications, and may be needle-punched for increased strength if desired. So long as the porosity and resistance to the chemical action of the electrolyte is met, any non-woven media may be used for the support. Woven materials may also be used if desired and any of a variety of weaves, sateen, leno, square, etc., can be utilized. The principle function of the supporting media is to provide a cushioned or resilient support for the hard particles with the secondary function of entrapping and circulating or pumping fresh electrolyte into the plating zone. As illustrated below, brush materials can be utilized with the hard particles anchored on or in the bristles.

Referring now to the drawings, FIGS. 1 and 2 illustrate one type of device embodying the present invention. A drum having a concave portion 11 is provided with an outer sheath of a non-conductive, porous particle-supporting media 12 having a plurality of spaced particles 13 affixed thereto. Internal of the outer sheath 12 is a corresponding layer of inert anode material 14. The anode material 14 is supported from a centrally-disposed hollow hub member 15 by a plurality of support members 16. I-Iub member 15 is adapted to slip over and fasten rotatably to a drive shaft 17 which is connected to the positive pole of a DC. source as shown at 18. Keys 19 are used to connect shaft 17 to hub 15 and electrical conductivity is maintained from the shaft 17 through hub 15 and support members 16 to the anode layer 14.

FIG. 3 illustrates another type of device embodying the present invention. Here a plurality of discs 20 of the porous non-conductive particle-supporting media are provided affixed to a rotatable shaft 21. Again, a plurality of spaced particles 22 are affixed to at least the surfaces of the discs 20. Interleaved between discs 20 on shaft 21 are a plurality of inert anode discs 23, likewise mounted for rotation on shaft 21. For purposes of illustration, the discs 23 are shown as providing definite demarcation areas between the outer ends of discs 20. In actual construction, the discs 20 are usually sufficiently uneven and compressibly resilient that the outer ends of discs 20 will form a substantially unbroken surface and anode discs23 will be completely hidden. Again, shaft 21 is designed to be electrically grounded and to in turn ground the anode discs 23.

FIG. 4 illustrates the use of bristles 40 having spaced 7 hard particles 41 affixed to the outer ends thereof. Here, as in FIG. 3, a plurality of inert anode discs 42 are provided, mounted for rotation on shaft 43 which acts also to electrically connect the anode discs 42 to the positive pole of a DC. source. Bristles 40 are shown as mounted at their inner ends in resin blocks 44 affixed to shaft 43. As illustrated, the anode discs 42 and bristles 40 vary in length to provide a contour surface for the device. It will be noted here, as in FIGS. l-3, that the distance'between the outer surface of the particle-supporting media 40 and outer ends of the anode discs 42 remains substantially the same over the entire length of the device regardless of the variation in distance between such outerv surface-and the shaft 43. As mentioned in connection with FIG. 3, the particlesupporting media tends to hide the presence of the anode discs and the characteristic is illustrated in this drawing.

FIG. 5 illustrates an anode to outer surface configuration which is used to minimize problems where overlapping plate is to be deposited. As will be more clearly shown in FIGS. 7 and 7-A, it is frequently necessary, in order to cover all the contours of a'multi-contoured article, to utilize two or more formed devices according to the present invention. The best way to accomplish this is to ensure that the edges of the deposit laid down beyond or immediately adjacent the end of an activating device, such as those illustrated herein, are not burnt. By keeping the current density at the ends of the activator low enough to prevent any burnt electrodeposit growth at such ends, a tapered plate is deposited under the activator. When the next device overlaps to apply plate to the next section of the workpiece, the plate goes down without leaving any noticeable line of demarcation. This current density gradient is obtained by spacing the anode from the ends of the device as is illustrated in FIG. 5. Here, in contrast to the alternate anode disc-porous media disc construction of FIG. 3, a unit is shown with a single anode disc 50 mounted on shaft 51 which again is connected to the l060ll 0287 positive pole of a D.C. source. Multiple porous media discs 52 carrying spaced particles 53 are mounted on each side of anode disc 50 as shown. The current density at the outer ends 54 of the last discs 52 will be low enough to prevent burning and to prevent overlap of the plate deposited. 1

FIG. 6 illustrates a cross section of another device somewhat similar to that of FIG. 1 in that a sheath or covering 60 of porous particle-supporting media is provided having a plurality of spaced particles 61 thereon. In this instance, the anode 62 forms a shell inside the cover 60 and is adapted to fasten at one end to a drive shaft 63 by means of bushing 64. Shaft 63 is electrically connected to the positive pole of a D.C. source.

FIGS. 7 and 7-A illustrate the application of a device of the present invention to a complex shape and further illustrate the overlap plating mentioned above. Here a plating bath 70 is provided in a suitable tank 71. Mounted within the plating bath 70 is a contoured workpiece 72 which is to be plated. As shown, this is supported by

members

73 and 74 in a fixed relationship to tank 71. Workpiece '72 is electrically connected, as schematically shown at 75, to'act as a cathode in the bath 70 and, in order to prevent immersion plating, has previously been given a strike or thin, conventionally-electrodeposited metal film. This use of a strike is required when the contoured part is to be plated immersed as shown in FIGS. 7 and 7-A. In FIG. 7, a formed wheel 76 mounted on drive shaft 77 which is connected to the positive pole of a D.C. source is shown. As in the previous illustrations, the outer surface of wheel 76 is composed of a porous media supporting spaced particles thereon. Wheel 76 contacts a portion of one end only of workpiece 72 as shown. The anodic center of wheel 76 is illustrated in dashed lines at 78. As the wheel 76 rotates under the drive of shaft 77 from a suitable driving source such as an electric motor (not shown) the surface of workpiece 72 in contact with wheel 76 receives an electrodeposit at a high rate of speed. Due to the configuration of the anode 78, that portion of the workpiece 72 designated as X. in the drawing will receive a plate which thins out as the outer edge of the wheel is reached. In FIG. 7-A, the same workpiece 72 is now being plated over an adjacent section by wheel 80. Here the anode center 81 tapers slightly, as illustrated, to keep a current density gradient going from a minimum at the wheel end 82 to a maximum just beyond the portion X" of workpiece 72. Wheel 80 is rotated by shaft 83 which is also mounted for lateral oscillation as shown by the arrows. The plate which is now deposited on portion X complements the plate deposited thereon in the illustration of FIG. 7 and gives a uniform structure of equal thickness to that elsewhere deposited

underthe activating wheels

76 and 80. I

FIG. 8 illustrates another manner of using the devices of the present invention in a plating operation. Here a formed wheel 90, again consisting of the type of construction previously described, is rotated by ground shaft 91 against a portion of the surface of a cathodic workpiece 92. Here, however, workpiece 92 is not immersed in a plating bath but the electrolyte 93 is supplied by

high pressure jets

94 and 95 directly into the interface between wheel 90 and workpiece 92. Excess electrolyte 93 is collected in the bottom 96 of a suitable container 97 and recirculated as at 98 for re-use. In this type of system, a preliminary strike on the workpiece 92 is not required although it may be used if desired.

Although, as indicated above, a variety of structures embodying the present invention are available, the method of formation of the devices of this invention is common to all up to apoint. In all instances it is desirable to first prepare a line drawing of the contour surface to-be plated. This can conveniently be-done either from a drawing of the part to be plated if one is available, or directly from the part using a contour or profile gage. This is an assemblage of flat plates, usually aluminum, and quite commonly of about one-sixteenth inch thickness per plate. The plurality of plates is slideably mounted on one or more rods so that the vertical distance of any one plate can be altered with respect to that of any other plate. Suitable clamping means are provided in these conventional devices to hold the plates in any desired relationship. The assembly of plates is applied to the contour to be plated and the gage is adjusted so that the contour is defined by the edges of the plates. The plates are then clamped in this position and a line is drawn on a sheet of paper connecting each edge of the plates thus giving a reproduction of the contour on the paper. A second line parallel to this contour line is then drawn at a short distance from the first line. This distance, which will be the distance between the outside edge of the anode and the outside surface of the porous particle-supporting media in the finished drum, can be varied within quite wide limits, i.e., from about one-sixteenth inch or less to as much 4 inch or more. Generally it is desired to maintain this distance as short as possible in order to minimize the IR drop between the anode and the contoured workpiece cathode. The minimum distance is set by the distance at which short circuiting becomes a problem and this will be controlled somewhat by the type of porous surface media used in terms of its compressibility and wearability. Also, the amount of movement permitted by the work-mounting fixture and the drive spindle of the device must be considered. The

preferred distance between the anode and the outer.

surface of the porous media ranges from one-sixteenth to 1 inch although, as indicated above, greater and lesser spacings are operable. Oncethese two lines are established, they can be used to lay out the design for the drum or wheel. A base line is drawn to represent the axis of rotation and lines are drawn normal to such base line at each end of the portion of the contour it is desired to reproduce in wheel form. This then represents a plan view of one half of the wheel to be formed. If spaced discs are to be used, the width of the discs and the anode spacers is determined and then lines are drawn to represent these. The distance from the base line to the nearest contour line is the radius of the anodes while the distance to the farther of the contour line from the base line isthe radius of the porous media discs. If a sheath-type wheel is to be made, the anode can be formed using the contour drawing for measurement of proper dimensions. For the disc-type structure, a center hole is provided in each disc dependent upon the size of shaft upon which they are to be mounted.

As a simple example of this type of device, a formed wheel was made up of alternate lead anode discs and porous non-woven material discs. The anode discs were one-sixteenth inch thick while the porous non-woven was approximately one-fourth inch thick. A profile was made of a contour consisting of the arc of a 1% inch circle. The chord of the arc was 1% inch. Using a profile gage, this contour was transferred to a sheet of paper and the measurements from an arbitrarily drawn base line gave the following dimensions for the porous discs (reading from left to right as the discs were to be assembled:

Disc

1. 1% to 1% inch(l% inch) 2. 1% to 1-7/16 inch (1-7/16 inch) 3. 1% to 1-% inch (1% inch) 4. 1% to 1-7/16 inch 1-7/16 inch) Rather than to exactly match the contour, the longer radius was used in each instance as indicated in the parenthesis. The anode discs which go between each of the porous discs were then measured from the diagram with A being the anode disc between discs 1 and 2 above, etc.: 7

Anode Disc A l-1/16-l% inch (1% inch) B 1-3/16-1% inch (1%1 inch) C 1% -1% inch (1% inch) D l-3/16 inch-1% inch 1% inch) Again, the longer radius for each disc was used as indicated in the parenthesis. Two additional lead discs, treated with stop-off lacquer (conventional plating technique) of 1 inch radius were used outside discs 1- and 5. The discs were then assembled on a inch diameter steel shaft having threaded ends and a nut was threaded up against each outside lead disc to hold the assembly in position. The make-up of the wheel, using the numerical designations above was:

1 inch lead disc-lA-2-B3-C4D -5-l inch lead disc The formed wheel was then mounted in a drill chuck affixed to an electric motor and rotated at a speed of 250-300 RPM. The contour part was immersed in a room temperature, brightener-free zinc pyrophosphate plating bath and connected to a source of negative potential. The wheel was then rotated against the contour surface for one minute and plate was deposited at a current density of 1,200 amps/ftF. A uniform bright zinc plate plate was deposited in the area under the wheel. 1n the adjacent areas of the contour outside that covered by the wheel, the deposit was dull and burnt.

For many types of decorative plate, the exacting procedure outlined above is not required. It will usually be used in forming a wheel or drum using a cover sheath over a shaped anode but may often be dispensed with in the case of the ganged disc construction. For example, using the same contoured workpiece described above, a porous wheel was made up using the same non-woven, particle-supporting media as was used in the above example. Here the discs were all 4 inches in diameter and were roughly trimmed on the outside surface of the desired curvature. Five non-woven discs, each about one-fourth inch thick were assembled on a inch diameter steel shaft alternating with l/l6 inch thick lead washers. In this instance, no attempt was made to match the contour of the washers with the outer surface contour and all six of the lead discs were 2% inch in diameter. The outer lead discs were again treated with stop-off lacquer. Used in the same manner as the previously-formed assembly, an acceptable plate from the standpoint of appearance was produced on the curved work surface.

A further example showing the overlap capability of this type of device was run utilizing a flat, highly polished sheet of copper as the substrate to be plated. This type of surface was used since an overlap line could more readily be seen on such surface than on a contoured surface.

Here the wheel was made up of two sections of porous non-woven, each 1% inch thick and 4 inch in diameter. The anode was a single one-sixteenth inch thick disc, 2% inch in diameter, positioned on a inch shaft between the two porous disc sections. Mounted as above and rotated at 250-300 RPM on the substrate immersed in the pyrophosphate zinc bath, plate was deposited at amps/ft. for 1 minute. The area under the wheel was a bright zinc plate which visibly tapered in thickness towards the ends of the wheel. The wheel was then moved so that it overlapped by one-half inch the first plated section and the run repeated. The resulting deposit showed no overlap lines. The same experiment was repeated with a Watts nickel bath and under the same conditions as above, no overlap line was detectable. in all instances described above, the porous non-woven was of the type illustrated in U.S. Pat. No. 3,020,139 to J. C. Mueller and the spaced non-conductive particles bonded thereon were flint grains of about 220 grit size.

As illustrated immediately above, it is necessary where the rotative device of the present invention covers only a portion of the contoured surface to be plated to provide a variation in current density over the surface under the device. Where the single device covers the entire surface to be plated, this necessity does not exist and the current density is preferably maintained substantially uniform over the entire surface, i.e., the anode will conform to the contour in the outer surface of the rotative device and will be maintained at substantially equal distances from such outer surface over the entire length of therotative device. Where a second device is to be used to apply additional plate adjacent to an area covered by a first device, it is then necessary to so dispose the interior anode within each device as to provide a current density gradient at the ends of the rotative device, or at least at the end of each where the overlap is to occur. This is generally done by increasing the distance from the anode to the workpiece at such ends. Preferably the distance is such that the porous particle-carrying media covers all of the plate deposited with such plate tapering down from the relatively uniform thickness common to the central portion of the area covered by the device to zero thickness at the ends of the device. This is not always practical and the controlling factor is that any plate which does extend beyond the edge of the rotative device must be unburnt. If this criteria is met, the plate will inherently taper and will provide a smooth juncture with such plate laid down by the adjacent rotative device as to minimize any apparent parting or demarcation line between the adjacent plating zones. Determination of the arrangement of the internal anode to accomplish this is essentially empirical since a wide variety of variables enter into the plate deposition. As a guide to accomplish this arrangement, a conventional Hull cell may be used. This is filled with the porous particle-supporting media to be used and with the plating solution to be used. The cell is run at the current density to be used in the actual plating and the run is continued for the time period which will be employed for the obtaining of the desired thickness of deposit. The distance along the line perpendicular to the anode from the anode to the edge of the burnt area of deposit on the cell plate gives an approximation of the correct distance of the edge of the anode in the rotative device from the end of the rotative device. This is a guide only, and the correct distance will be found empirically as stated above for each particular device. Oscillation of the rotative device may be employed in some instances to help brake up any sharp line of demarcation between adjacent plate areas.

I claim:

1. A rotatable activating device having a complementary contoured outer surface adapted to be placed in contacting relationship with a contoured metallic work surface to be electroplated, said outer surface comprising a layer of a porous, flexible, compressible, non-conductive fluid-entrapping and circulating material having a plurality of spaced hard non-conductive particles secured in fixed relationship on at least the outer surfaceof such material; and an inert anode material so disposed and arranged within said outer surface of said rotatable activating device as to provide a substantially uniform current density at the surface of at least the central portion of said contoured work surface when said rotatable device is in contact with said.

made cathodic with respect to said inert anode.

2. A rotatable activating device as in claim 1 wherein said inert anode material comprises an inner shell of lesser diameter at any given point than that of said outer surface at the same point and is spaced substantially equi-distant from said outer surface over substantially the entire length of said rotativedevice.

3. A rotatable activating device as in claim 1 wherein said outer surface is provided by a plurality of discs of such porous, flexible, compressible, non-conductive fluid-entrapping and circulating material mounted concentrically on a supporting shaft with the outer peripheral portions of such discs in engagement one with the other.

4. A rotatable activating device as in claim 3 wherein said inert anode material is provided in the form of discs concentrically mounted on said shaft between adjacent discs of said fluid-entrapping and circulating material, said discs of anode material having a lesser diameter than said discs of fluid-entrapping and circulating material.

5. A rotatable activating device as in claim 1 wherein said inert anode material is so disposed and arranged that when said work surface is made cathodic with respect to said inert anode material, the current density at the surface of the contoured workpiece has a gradient at at least one end of said rotative device from said uniform current density down to a current density which is less than that which will produce a burnt electrodeposit on that surface of such work iec e immediately ad acent and free from contact wit said end of said rotative device.

* UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,706,650 Dated December 19, 1972 Inventors Steve Eisner It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Col. 4 line 38, change "5.65 x 20' to read -5.65 x 1o- Col. 8, line after the word "much" insert -as-.

Col. 9 line 26, change (1-1/4- 1. inch)" to read 1-1 4 inch)-.

Col. 1]., line 18, change the word "brake" to -break-.

Signed and sealed this 26th day of March 19m.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 60376-P69 U.5. GOVERNMENT PR INTING OFFICE I969 0-366-334 Disclaimer 3,706,650.-Steve E 21mm", Schenectady, NY. CONTOUR ACTIVATING DE- VICE. Patent dated Dec. 19, 1972. Disclaimer filed May 26, 1972, by the assignee, N 07t07L Company. Hereby disclaims the portion of the term of the patent subsequent to Nov. 9, 1988.

[Ofiioz'al Gazette September 11 1.973.]

Claims

1. A rotatable activating device having a complementary contoured outer surface adapted to be placed in contacting relationship with a contoured metallic work surface to be electroplated, said outer surface comprising a layer of a porous, flexible, compressible, non-conductive fluid-entrapping and circulating material having a plurality of spaced hard nonconductive particles secured in fixed relationship on at least the outer surface of such material; and an inert anode material so disposed and arranged within said outer surface of said rotatable activating device as to provide a substantially uniform current density at the surface of at least the central portion of said contoured work surface when said rotatable device is in contact with said contoured work surface and when said work surface is made cathodic with respect to said inert anode.

2. A rotatable activating device as in claim 1 wherein said inert anode material comprises an inner shell of lesser diameter at any given point than that of said outer surface at the same point and is spaced substantially equi-distant from said outer surface over substantially the entire length of said rotative device.

5. A rotatable activating device as in claim 1 wherein said inert anode material is so disposed and arranged that when said work surface is made cathodic with respect to said inert anode material, the current density at the surface of the contoured workpiece has a gradient at at least one end of said rotative device from said uniform current density down to a current density which is less than that which will produce a burnt electrodeposit on that surface of such workpiece immediately adjacent and free from contact with said end of said rotative device.