US3468783A - Electroplating apparatus - Google Patents

Description

Sept. 23, 1969 R. c. AVELLONE ELEGTRQPLA'IING APPARATUS 5 Sheets-Sheet 1 Filed March 8, 1965 ATTORNEYS Sept. 23, 1969 R. c. AVELLONE ELECTROPLATING APPARATUS 5 Sheets-Sheet 2 Filed March 8, 1965 C] INVENTOR Richard C Avellone Fl Illl ATTORNEYS p 23, 1969 R. c. AVELLONE 3,468,783

ELECTROPLATING APPARATUS Filed larch 8, 1965 5 Sheets-Sheet 5 F'- I -1 g Q i l i! l i 'q 1 o INVENTOR Riehard C-AVellone Q ATTORNEYS P 3, 1969 R. c. AVELLONE 3,468,783

ELECTROPLATING APPARATUS Filed March 8, 1965 5 Sheets-Sheet 4 H5 //2 Af/M INVENTQR Richard C Avellone /45 v ATTORNEYS Sept. 23, 1969 R. c. AVELLONE 3,463,783

ELECTROPLATING APPARATUS Filed March 8, 1965 5 Sheets-Sheet 5 INVENTOR Rich ard C. Avellone ATTORNEYS United States Patent 3,468,783 ELECTROPLATING APPARATUS Richard C. Avellone, Mayfield Heights, Ohio, assignor to Republic Steel Corporation, Cleveland, Ohio, 2 corporation of New Jersey Filed Mar. 8, 1965, Ser. No. 437,834 Int. C1. C23]: 5/58, 5/70 US. Cl. 204-207 13 Claims ABSTRACT OF THE DISCLOSURE An electroplating cell for high speed continuous strip plating lines comprises a tray for holding the plating solution having end walls through which the strip passes. A pair of entry and exit dam members cooperate to hold the strip on a pass line as it travels through the tray and in conjunction with the end and side walls of the tray, contain the plating solution at a predetermined level above the pass line. At least one of the exit darn members comprises a resilient wiping strip in uniform contact across the width of the strip which serves to wipe the plating solution from a surface of the strip. A distributor tube submerged in the tray ahead of the wiping strip adjacent the pass line delivers jets of plating solution preferably counterflow to the direction of strip movement to agitate the plating solution which otherwise tends to be dragged out of the cell on the strip surface.

Field of the invention This invention relates generally to the electroplating art, and more specifically to apparatus for electrodepositing a layer of metal such as zinc from a plating bath on a continuously moving base material. It is particularly concerned with new and useful improvements in the construction of the plating cells in a continuous strip plating line and a system for agitating, circulating and purifying the plating bath of each cell so as to obtain a high quality product at maximum production rates.

In the continuous electroplating of strip material, it is usual to move the strip through a series of cells, each comprising a tray containing the plating solution and a number of suitably disposed soluble anodes. Electrical contact to the strip is made at intervals by electric contact rolls which are mounted between the trays, whereby the strip is connected as the cathode in the electroplating circuit. The strip thus receives a metallic deposit as it is progressively moved through the several plating cells.

The thickness of the deposit depends upon the current and the immersion time, and, in a continuous strip plating operation, can be controlled by adjusting the strip speed in relation to the current available for plating and the number of plating cells in the line. Consequently, when producing a deposit of a desired thickness, maximum current and high current densities are required for high line speeds. It is therefore important in a strip plating operation to control the conditions affecting current efliciency.

In order to make full use of the available current and achieve a high rate of production, it is essential to provide effective circulation and agitation of the plating solution in each cell. Maximum solution agitation reduces anode polarizations which restrict current flow. Proper circulation of the solution between the anodes and the cathodic strip is also necessary to assure an adequate supply of the coating metal ions to the strip and thereby improve the plating efficiency, and to prevent deposit burning at the desired high current densities.

Another factor which is important in obtaining high uniform quality of the product at maximum production rates is the control and removal of metal and organic 3,468,783 Patented Sept. 23, 1969 "ice contaminations from the plating bath. Contamination may result from tree growths on the anodes and strip edges, from zinc flakes on the strip surface due to poor adhesion of the deposit, and from damaged equipment such as cell dams, rolls, polishers and the like. Other debris, such as rust, dirt, solid soils and metal chips may drop into the bath from overhead structures or be introduced into the bath on the strip surfaces.

Such contaminants affect the bath performance by contributing to anode polarizations, reducing cathode or strip efliciency, and reducing strip and anode current density ranges. They also affect the quality of the product. For example, deposits at high current densities have aboreal, burnt or powdery structures, while deposits produced at medium current density ranges are hard, have poor adhesion, no ductility, and poor continuity and appearance. In addition, when solid contaminants are carried to the processing rolls, they cause defects in the strip surface which have been one of the main reasons for product rejection and scrappage.

It is particularly important to provide an efiicient filtering system in a high speed, high current operation where both sides of the strip are plated because of the desirability of making maximum use of the available current and the fact that any contaminants in the solution have more chance to affect the surface of the strip when it is plated on both sides.

Continuous strip plating operations present the further problem of preventing solution drag-out or loss of the electrolyte due to movement of the strip out of the cells of the plating line. It is customary to provide dams at the exit ends of the cells in an attempt to inhibit solution flow in the direction of strip travel and to prevent loss due to splashing, but the prior arrangements have not been entirely satisfactory, particularly at high line speeds which magnify the problem. Excessive solution flow to the contact rolls contributes to roll plating and to the formation of dried sludges, both of which adversely affect the surfaces of the strip. Moreover, the bath losses which result are costly, since considerable quantities of chemicals are required for make-up additions.

The present invention provides new and improved electroplating apparatus which overcomes the problems discussed above and obtains an eflicient plating line operation in which a continuously moving substrate or base metal strip can be uniformly coated simultaneously on both sides at high line speeds. These advantages are obtained in part by improved solution agitation and circulation of the electrolyte in each plating cells. The new system includes the provision of novel solution distributor tubes. These tubes are preferably mounted near the ends of each cell above and below the strip pass line to provide strip washing, to supply fresh solution to the electrodes in an improved manner, and to create a turbulent circulation of the solution between the anodes and the strip. As discussed above, these conditions are necessary to permit full use of available current and particularly to reduce electrode polarizations and deposit burning at high current densities. With the preferred construction and arrangement, it is therefore possible to obtain thicker coatings on the substrate than has been possible in the past at the same production rates and to obtain coatings of the same thickness as in the past at higher production rates.

Another feature of the invention resides in a new and improved plating cell construction which includes a novel dam arrangement designed to reduce drag out and consequent bath losses. In the preferred embodiment, the cell construction comprises a rubber lined steel tray having slotted ends to permit the passage of the strip. A damming roll is used as the upper portion of each cell end wall and serves to return and hold the strip on a pass line as it travels through the cell. The damming rolls also help to prevent electrical shorting of the strip to the upper anodes. The bottom dams at each end of the cell are preferably in the form of thin squeegees sandwiched between suitable separator plates. These bottom dams or squeegees lie directly below the upper damming rolls and prevent excessive solution flow externally of the cell to the contact rolls. Cell gutters are used across each cell and below the dam assemblies to reduce solution splashing and overflow weirs are located in each corner of the cell. These weirs are constructed to permit usage of full pump capacity so as to obtain proper solution coverage of the upper anodes and to obtain removal of suspended bath contaminants.

The invention further contemplates the provision of a new and improved system for removing bath contaminants and supplying the electrolyte to the plating cells. In the preferred arrangement, a separate pump is used for each plating cell in the line continuously to recircu late plating solution between a reservoir and the cells. These pumps in conjunction with the solution distributor tubes provide the necessary agitation and rapid change of the solution that is required for high speed plating operations. A filter unit also is provided in connection with each cell pump to prevent larger bath debris and contaminants from being recirculated to the strip surfaces and from clogging the solution distributor tubes. The filter units preferably include a removable basket covered with a suitable screen for trapping bath debris. The outlet of each filter unit is connected to the pump intake line and the inlet of each unit is connected to an opening near the base of the reservoir tank. With this arrangement, solution from the reservoir is cleaned prior to its entrance into each pump and plating cell. In addition to the individual cell filter units, large filter presses may be used continuously during operation of the line for removing minute, as well as larger bath contaminants and for removing carbon and zinc dust materials used in bath purification treatments.

All of the foregoing improvements are obtained in an arrangement which minimizes detrimental line stops. In particular, it is possible to replace the cell dams and anodes and to clean the filter units without stopping the stri gther advantages and a fuller understanding of the invention will be had by reference to the following detailed description and the accompanying drawings.

In the drawings:

FIGURE 1 is a schematic top plan view of a portion of a plating line embodying the apparatus comprising the present invention;

FIGURE 2 is a side elevational view taken on the line 22 of FIG. 1 showing one cell of the illustrated plating line;

FIGURE 3 is an end elevational view of the plating cell taken on the line 3-3 of FIG. 2;

FIGURE 4 is an enlarged side elevational view, partially in cross-section, of a portion of the plating cell;

FIGURE 5 is an enlarged end elevational view, partially in cross-section, of a portion of the plating cell;

FIGURE 6 is a fragmentary top plan view of a portion of the cell assembly;

FIGURE 7 is a vertical cross-sectional view taken on the line 77 of FIG. 6;

FIGURE 8 is a vertical cross-sectional view taken on the line 88 of FIG. 6;

FIGURE 9 is a fragmentary top plan view of another portion of the apparatus;

FIGURE 10 is a cross-sectional view taken on the line 1010 of FIG. 9;

FIGURE 11 is a view taken on the line 11--11 of FIG. 10;

FIGURE 12 is a view diagrammatically illustrating the preferred filtering and solution circulating system for cells of the plating line;

FIGURE 13 is a fragmentary top plan view of a portion of the filtering and circulating system; and

FIGURE 14 is a side elevational view, partially in cross-section, of the structure shown in FIG. 13.

The invention is hereinafter specifically described in connection with the formation of a zinc coating on both sides of a ferrous metal strip. However, it is to be understood that the improvements which are provided can be used in electrodepositing other metals on various conductive materials, including tubes, wires and the like. It will also be understood that the invention is not limited to the plating of both sides of the base material simultaneously, although it has particular utility in such an operation.

Referring now to the drawings, and to FIG. 1 in particular, the illustrated strip plating line embodying the present invention is indicated generally by reference numeral 15. The plating line 15 is comprised of a desired number of individual plating cells designated by the letters AF. Roll assemblies 16 which are preferably positioned between each pair of adjacent cells of the plating line are used to move the strip 17. As shown in FIGS. 2, 3 and 4, each of the assemblies 16 includes a contact roll 18 by which electric current is supplied to the strip 17 and a cooperating back-up roll 19. The rolls 18, 19 may be suitably mounted in a roll stand 20 for adjustment toward and away from each other as is well understood in the art and the contact roll driven by a motor 21.

The cells AF are shown mounted above a plating solution reservoir tank 24. This tank may be of a sufiicient size to hold the total volume of plating solution required for all of the cells. It is also possible to use a multiple number of reservoir tanks, if desired. As described in greater detail below, each of the plating cells A-F is connected to the reservoir 24 so that the solution is individually pumped through each cell and is filtered to remove solution contaminants.

Referring now more particularly to FIGS. 2-8, the preferred construction of each of the plating cells A-F is shown to comprise a tray 25 having side walls 26, 27, a bottom wall 28 which slopes downwardly from the side wall 26 to the opposite side wall 27, and end walls 29. As is conventional, the tray 25 has a rubber coating 30 on its inner surfaces. The tray 25 is mounted within a structural framework comprised of vertical members 31 and horizontal top members 32.

Each of the opposite end walls 29 is slotted to provide entrance and exit openings for the strip 17 so that it can be moved through the tray 25. In the preferred embodi ment of the invention, each of the slotted end walls 29 is comprised of a lower dam in the form of a squeegee 35 and an upper dam in the form of a roll 36. The squeegee 35 and the roll 36 at each end of the tray cooperate to establish a pass line (see particularly FIG. 4) along which the strip 17 is moved through the cell. The bottom dams 35 also prevent excessive flow of the plating solution externally of the cell to the reservoir 24 and the roll assemblies 16.

As shown most clearly in FIG. 7, the squeegee 35 is an assembly comprised of three adjacent strips 37 that are held between separator plates 38. The strips 37 are preferably formed of a non-corrosive, flexible material, such as polyurethane or the like. The strips 37 and the intermediate separator plates 38 are secured between a rubber coated clamp bar 49' and a rubber coated dam support bracket 41 by means of studs 42. The studs 42 are secured to the clamp bar along its length and extend through the assembly of the strips and separator plates. Nuts 43 are threaded on the outer ends of the studs against the outside of the dam support bracket 41. The squeegee assemblies are each secured to an end of the cell by a bumper 44 which comprises a steel plate and a rubber coating 45 between the plate and the clamp bar 40. The bumper 44 is secured to a portion of the tray 25 by accessible bolts (not shown). With this arrangement in which the nuts 43 and the bolts for the bumper 44 are on the outside of the tray the dam or squeegee 35 can be easily removed for repair or replacement without stopping the strip 17.

A gutter 50 is provided across each cell end directly below the lower dam assembly 35 in order to reduce solution splashing and to return to the reservoir the solution that passes between the squeegee and the upper dam roll 36. The gutter 50 is in the form of a metal trough which is secured to the cell ends and is coated on its inside surface with rubber 51. The bottom wall 52 of the gutter slopes from one end to the opposite end which is provided with a downspout 52 that communicates with the reservoir 24. The downspout 52 is also formed of rubber coated metal.

The upper dam roll 36 comprises a metal shell 56 having a soft rubber-like coating 57 formed of polyurethane resin or the like. The metal shell 56 is provided at its ends with roll necks 58. Each of the roll necks 58 is bearinged in pillow blocks 59. These pillow blocks 59 are secured to the vertical framework members 30 for limited vertical adjustment to accommodate roll wear. As shown most clearly in FIGS. 4, 5 and 6, the pillow blocks 59 are each mounted by a bracket 60 that includes adjusting blocks 61 above and below the pillow blocks. The adjusting blocks 61 are tapped to receive vertical adjustment screws 62 which are provided with jam nuts 63. The adjusting screws 62 extend into engagement with the pillow blocks which are secured to the bracket plate 60 by means of cap screws 64. These cap screws 64 are engaged through slots formed in the pillow blocks (FIG. 5) so that the cap screws can be loosened and the pillow block and roll assembly adjusted up and down by means of the adjustment screws 62. The pillow block and bearing assemblies are preferably shielded within bearing covers 65 which are also secured to the vertical frame members 30. As is the case with the lower dam 35, it will be apparent that the roll 36 can be conveniently removed from the cell when necessary.

A pair of slingers 70 in the form of rubber disks are mounted on the roll necks 58 between each pillow block and bearing assembly 59 and the ends of the metal shell or cylinder 56. These slingers 70 spin off the film of solution which tends to run along the roll necks into the bearing assemblies. As shown in FIGS. 6 and 8, the slingers 70 on each roll neck are mounted in a housing 71 and are separated by a housing partition 72. Each housing 71 communicates with a rubber coated overflow weir 73. The solution which tends to creep outward of the roll necks 58 is spun 01f by the slingers 70 into the housing 71 and runs down into the overflow weir 73 which communicates with the reservoir 24. The overflow weirs 73 are preferably located at each corner of the tray 25 and have upper open ends 74. Thus arranged, the overflow weirs establish a solution height which is above the pass line of the strip 77 and the anodes mounted in the tray.

In the preferred embodiment of this invention, two banks of zinc anodes are mounted above and below the pass line of the strip 17 in the cells for plating the strip with zinc on both sides in a continuous operation. The top bank of anodes are adjusted up and down from the strip surface and are contained in a conductor bar assembly rack or framework to permit the removal and/or replacement of the top anodes in one operation. The lower anodes are mounted on conductor bars and means are provided for raising and loweirng the anodes from the strip surface.

Referring particularly to FIGS. 4 and 5, there is shown two pairs of upper conductor bars 80 which carry anodes 81. The anodes 81 are suitably spaced across the width of the tray 25 above the pass line of the strip and are preferably supported on the bars 80 by hanger arms 82. Suitable hold-down structure (not shown) may be provided to assure good contact between the hanger arms 82 and the conductor bars. Each pair of the conductor bars is mounted in a separate framework or rack. The rack comprises two arms 85 that project upwardly at each side of the tray 25 and are connected by members 86. The

bars extend transversely of the tray and are secured between the lower ends of the arms 85. The upper ends of members are engaged over anode bed supports 87. Suitable jacks or the like, which are diagrammatically illustrated at 88, may be provided between the bed supports 87 and the structural members 32 for positioning the anodes 81 relative to the upper surface of the strip 17.

The lower anodes are supported on two pairs of lower conductor bars 96. Each pair of the bars 96 also forms part of a removable rack that includes arms 97. These arms 97 are engaged over lower anode supports 98. Jack mechanisms 99 similar to the upper jacks 88 may be disposed below the supports 98 for positioning the anodes 95.

A suitable source of DC current, for example, two rectifiers (not shown), is provided for each cell. The positive lead from one rectifier is connected to the top anode conductor bars 80 and the positive lead of the other rectifier is connected to the bottom anode conductor bars 96. The negative leads of the rectifiers are connected to the contact rolls 18 for each cell.

As generally described above, an important feature of this invention resides in the provision of a pair of novel solution distributor tubes (FIGS. 4 and 7) which are mounted above and below the pass line of the strip 17 adjacent each cell end wall 29. The tubes 110 are preferably formed of a non-corrosive material, such as polyvinyl chloride or the like, and extend across the width of the tray 25 below the bath level established by the weirs 73. In FIGS. 9, 10 and 11, the construction of each tube is shown to include a closed end 111 and an opposite open end having a flange 112. The flanged end portion of each tube extends within a rubber coated sleeve 113 which projects externally of the side wall 26 of the tray 25. The tube flange 112 is secured between a flange 114 on the outboard end of the sleeve 113 and a flange 115 of a pipe 116. The pipes 116 for each pair of tubes form part of a cell header connection 118. In the preferred construction, the flanges 112, 114 and 115 are secured together by bolts 119 that project through circumferentially spaced bolt holes 120 in the flange 112. The tubes 110 can be rotatably adjusted about their axes for a purpose to be described by selectively locating the bolts 119 in the proper bolt holes 120.

The solution distributor tubes 110 are also formed with slotted openings which are spaced along the lengths of the tubes. In use, the tubes are oriented as shown in FIG. 7 to spray the plating solution from the openings 125 in jet stream patterns that converge on the strip pass line toward the center of the cell. The jet streams fan across the full width of the strip 17 to provide improved strip washing and an adequate supply of electrolyte to the electrode surfaces. The arrangement also obtains optimum solution turbulence around the anodes as is necessary to permit the use of high current densities and reduce anode polarizations. With the preferred construction, it is possible to change the angle of the solution spray by rotatably adjusting the tubes about their axes in the manner described above.

If desired, a vertical plate 128 (FIG. 4) may be pro vided above and below the pass line of the strip 17 near the center of the tray 25. These plates 128 serve as baflles for the solution sprayed from the tubes 110 and further increase the turbulence of the bath. The plates also function as guards to prevent electrical shorts between the strip 17 and the anodes.

Reference is now made to FIG. 12 which illustrates the preferred solution pumping and circulation system contemplated by this invention. As thereshown, the main solution reservoir 24 is connected to one or more conventional filter presses suitable for removing minute as well as larger bath contaminants and for removing carbon and zinc dust materials used in bath purification treatments. The solution in the reservoir 24 is continu- 7 ously circulated through the filter press or presses 135 by a pump 136.

The preferred circulation system also includes a separate pump 140 and a filter unit 141 for each cell which prevents larger bath debris and contaminants from being recirculated to the strip surfaces and from clogging the solution distributor tubes 110. Each cell pump 140 has its intake side connected to the reservoir 24 and its discharge side connected to the cell headers 118 by pipes 142 and 143 (also see FIGS. 2 and 3). The filter unit 141 for each cell is connected to the intake side of the pump 140 by a pipe 145 and to the base of the tank 24 by a pipe 144. Suitable valves 146 may be provided in the pipes 143 and 145.

Referring to FIGS. 13 and 14, the preferred construction of each filter unit 141 is shown to include a housing 151. The housing 151 is normally closed by a removable plate 152. Within the housing 151 there is mounted a removable filter basket 153. The basket 153 in its preferred form comprises a wire frame 156 which supports a filter screen 157. The basket may be disposed on either an upright or an inverted position. However, for convenience, the basket is upright and the screen 157 is located on the inside of the frame 156 so that the pressure flow of the solution forces the screen against the frame. In this manner, the contaminants in the solution are trapped in the basket 153 as the solution is pumped through the filter unit from the reservoir 24. The basket can be periodically removed from the housing 151 for cleaning or replacement.

The operation of the apparatus comprising this invention will be largely apparent from the foregoing description. In summary, the several plating trays are filled with the electrolyte to a level above the upper anodes 81 and the solution distributor tubes 110, the level being established by the weirs 73. The upper and lower banks of anodes are suitably positioned in the trays and electric connections are made to contcat rolls 18 and the conductor bars 80, 95. Actuation of the power driven roll assemblies 16 serves to move the strip 17 through the cells, whereby the strip is simultaneously plated on both sides.

The positioning of the solution distributor tubes 110 and the manner of spraying the solution on the strip 17 maintains maximum circulation and agitation of the electrolyte between the strip and the anodes. Consequently, it is possible to employ high current densities and obtain a high line speed. In the preferred embodiment, the plating current supply and the line speed are synchronized and can be raised or lowered simultaneously for control of the deposit thickness.

During operation of the line, the solution is continuously circulated through the large filter presses to remove the minute as well as larger bath contaminants. At the same time, the individual filter units for each cell serve to remove the large bath contaminants and prevent such debris and contaminants from being recirculated to the strip surfaces and from clogging the solution distributor tubes 110. With the illustrated circulation arrangement, the solution from the reservoir 24 is effectively cleaned prior to its entrance into the pumps 149 and the plating cell trays 25.

When it is necessary to remove the cell dams for replacement or repair, the solution level in the individual cells can be lowered below the pass line of the strip 17 by turning off the pump 140 which is connected to the cell. The Squeegees and/ or the rolls 36 can then be easily disconnected by means of the accessible, externally located bolts and nuts Without stopping the strip. It is also possible to remove the dams without lowering the solution level, the solution simply being allowed to run into the gutters 50. The upper and lower banks of anodes can be easily removed by lifting the supporting racks with a crane or the like.

Many modifications and variations of the invention will be apparent to those skilled in the art in view of the foregoing detailed description. Therefore, it is to be understood that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically shown and described.

What is claimed is:

1. An electroplating cell comprising:

(a) a tray for containing a plating solution through which stock is passed,

(b) said tray including two pairs of dam members each being electrically non-conductive with respect to the plating solution and stock,

(0) said dam members cooperating to hold stock on a pass line as it travels through said tray,

(d) one of said dam members in each pair being formed by a roll having a non-conductive surface rotatably engageable with one side of the stock and the other of said dam members being formed by a resilient element having a non-conductive surface continuously engageable with the opposite side of the stock for stripping the plating solution therefrom;

(e) a pair of contact rolls each making electrical contact with the stock beyond opposite ends of the tray so that the stock is subjected to a plating potential as it travels through the tray independently of said dam members.

2. An electroplating cell comprising:

(a) a tray containing a plating solution through which stock is passed,

(b) said tray including slotted wall portions,

(c) each of said wall portions being formed by first and second dams, each dam being electrically non-conductive with respect to the plating solution and stock,

(d) one of said dams being a roll having a non-conductive surface rotatably engageable with one side of the stock and the other of said dams being formed by a resilient element having a non-conductive surface continuously engageable with the opposite side of the stock for stripping the plating solution therefrom,

(e) said dams cooperating to establish a pass line along which stock is moved through said tray,

(f) means for establishing a solution level in said tray above said pass line,

(g) means mounting said dams so that they can be released and removed without stopping the stock, said mounting means being located in accessible positions externally of said tray, and

(h) a pair of contact rolls each making electrical contact with the stock beyond opposite ends of the tray so that the stock is subjected to a plating potential as it travels through the tray independently of said dams.

3. The cell as claimed in claim 2 wherein the other of said dams in each pair comprises a squeegee mounted below said roll.

4. An electroplating cell comprising:

(a) a tray,

(b) said tray including opposed wall openings for permitting stock to be moved through said cell, and first and second dam members on opposite sides of each opening,

(c) one of said dam members being formed by an assembly of squeegee elements continuously engageable with one side of the stock for stripping the plating solution therefrom,

(d) the other of said darn members being formed by a roll,

(e) said dam members cooperating to define a pass line along which stock can be moved through said cell, (f) solution distributor tubes disposed on opposite sides of the pass line adjacent each opposed wall opening,

(g) each of said tubes including openings spaced along its length, said tubes being oriented to spray solution from said openings in jets converging on the pass line toward the center of said cell,

(h) means mounting each of said tubes for movement about its longitudinal axis so that the spray angle can be selectively adjusted,

(i) anode means mounted in said tray on opposite sides of the pass line, and

(j) overflow means mounted in said tray to establish a solution height above the pass line, said tubes and said anodes.

5. A plating cell as claimed in claim 4 wherein said anode means on each side of the pass line comprises a plurality of conductor bars, a plurality of anodes connected to said conductor bars, and a removable rack in which said bars are mounted.

6. A tray for an electroplating cell having side and bottom walls and comprising:

(a) a pair of dam members defining entry and exit openings at opposite ends of the tray through which the strip travels and cooperating with said side walls to contain a plating solution above the strip pass line,

(b) at least one of said dam members in each pair comprising a resilient wiping strip essentially normal to the plane of the strip and having one edge extending transversely in uniform wiping contact with the surface of the strip being free to bend in the direction of strip movement, and,

(c) means for mounting said wiping strip.

7. A tray according to claim 6 in which the means for mounting the wiping strip comprises:

(a) a bracket removably securable to the tray having studs projecting outwardly so as to be accessible from the outside of said tray, and

(b) a clamp bar received on said studs holding the lower portion of said wiping strip between said bracket and clamp bar.

8. A tray according to claim 6 in which each said darn member comprises:

(a) a roll journaled at each end in the side walls of the tray having a non-conductive surface in rolling contact with the upper surface of the strip, and

(b) said resilient wiping strip extending upwardly into Wiping contact with the lower surface of said strip opposite the roll.

9. A tray according to claim 8 comprising:

(a) a pair of aligned pillow block members for receiving the opposite ends of each roll projecting through the side walls of the tray,

(b) mounting means for each pillow block member including adjusting screws accessible from the outside of said tray for adjusting the vertical position of each with respect to the strip pass line, and

(c) sealing means at each end of the rolls for inhibiting the escape of solution into the pillow block members.

10. A tray according to claim 6 having an overflow weir in each corner formed by a partial enclosure extending vertically from the bottom wall of the tray defining a vertical channel, the upper end of said enclosure extending above the pass line of the strip and establishing the solution level in the tray and the lower end opening through the bottom wall.

11. An electroplating line apparatus having a series of cells through which continuous strip material is passed, each cell comprising:

(a) a tray for maintaining a plating solution above the pass line of the strip while moving through the tray,

(b) said tray including side and bottom walls, the side walls extending vertically to a height substantially above the pass line and including overflow weir means for establishing the proper height of plating solution above the pass line, said height being sufficient to allow the solution to rise throughout the tray substantially above the pass line before overflowing through said overflow wier means,

(c) a pair of dam members at each end of the tray for damming the plating solution in cooperation with the side walls to a height at least equal to the height established by said overflow wier means,

(d) one of said dam members in each pair being formed by a roll and being rotatably mounted so as to roll in tangentially continuous contact with the strip traveling through the tray, each said roll being electrically non-conductive with respect to the strip and plating solution,

(e) the other dam member in each pair of dam members extending transversely across the tray opposite the roll dam member and having a resilient, nonconductive surface continuously engageable with the surface of the strip opposite the roll dam member for stripping the plating solution therefrom,

(f) said electroplating line apparatus including anode and cathode means associated with each cell, the anode means being immersed in the plating solution in each cell adjacent the strip pass line and the cathode means comprising,

(g) a pair of contact rolls each making electrical contact with the strip beyond opposite ends of the cell so that the strip is subjected to a plating potential as it travels through the cell independently of said dam members whereby cathode roll plating is minimized.

12. An electroplating line apparatus according to claim 11 wherein the other dam member positioned at the strip exit end of the cell is formed by a resilient wiper element having a wiping edge engageable with the strip which is free to bend in the direction of strip movement and said cathode roll beyond the strip exit end of the cell is engageable with the strip on the same side of the strip as said resilient wiper element.

13. An electroplating line apparatus according to claim 11 wherein each cell comprises:

(a) a forced circulation system including a pump for delivering plating solution to the tray and return circuit means for recirculating the plating solution to the pump, and

(b) jet means in the tray submerged in the plating solution adjacent the pass line for directing streams of plating solution against the strip.

References Cited UNITED STATES PATENTS 1,242,695 10/1917 Hood 20428 XR 1,484,653 2/1924 Kirschner 204238 XR 1,483,722 2/1924 Eustis 204237 XR 1,768,358 6/1930 Harrison 204206 XR 2,307,928 l/l943 Hogaboom 204206 XR 2,392,687 l/1946 Nachtman 204206 2,490,055 12/ 1949 Hoff 204237 1m 2,569,578 10/1951 Rieger 204-206 JOHN H. MACK, Primary Examiner W. B. VANSISE, Assistant Examiner U.S. Cl. X.R.

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