US2833708A - Electroplating apparatus - Google Patents

Description

y 1958 M. B. HAMMOND ET L 2,833,708

ELECTROPLATING APPARATUS Filed May 5, 1955 2 Sheets-Sheet 1 46 |sP 4s 5 INVENTORS.

. Milton 5. Hammond Fl 2 BY Glade B. Bowman THE/R ATTOR/VE Y5 May 6, 1958 M. B. HAMMOND ET AL 2,833,708

ELECTROPLATING APPARATUS 3 Filed May 5, 1955 .2 Sheets-Sheet 2 Milton 5. Hammond F 4 BY Glade B. Bowman THE /R A TTOR/VE Y5 ELECTROPLATING APPARATUS Milton l3. Hammond and Glade B. Bowman, Edgeworth, Pa., assignors to Rockwell Spring and Axle Company, Coraopolis, Pa., a corporation of Pennsylvania Application May 5, 1955, Serial No. 506,338

9 Claims. (Cl. 204-222) This invention relates to a method and apparatus for uniformly electroplating somewhat complex articles of non-uniform curvature and surface, as contrasted with geometrically simpler articles with their uniform and regular surfaces, such as fiatrecording discs, cylinders, and similar articles of revolution or at least articles predominantly annular and/or flat of form.

The invention finds particular application to the plating of automobile bumpers, but is useful, in the broad sense, in other applications not limited to bumpers, for instance, cylinders, discs, or curved shell structures. According to a feature of the invention, the article to be plated, of which a bumper is a good example, is subjected to high physical agitation in a plating bath whereby-the immersed surfaces thereof impinge against the liquid of the bath in a progressively changing direction at which, during'some phase of the operation, the impingement is directly or approximately at right angles to each and every portion of the surface to be plated. The bumper or other article in its progress through the bath describes a path which is conducive to uniform plating, but in which the article is practically continually changing its general relationship to or distance from the plating anodes, or else changing both relationship and distance thereto.

Various features, objects, and advantages will either be specifically pointed out or become apparent when, for a better understanding of the invention, reference is made to the following description taken in conjunction with the accompanying drawings in which:

Figure l is a plan view of an electrolyte tank type article plating apparatus according to the invention presently disclosed;

Figure 2 is a side sectional elevation based on Figure 1' along the section lines II-II so that the showing of Figure 3 is removed;

Figure 3 is a rear elevational view along the lines III-III of Figure 1;

Figure 4 is an end elevational view along the lines IV-IV of Figure l; and

Figure 5 is a visual aid diagrammatically approximatingthe three-dimensional motion of agitation of the articles undergoing plating in the apparatus.

Referring more particularly to the accompanying drawings, in Figures 1-4 an upwardly open plating tank adaptedto contain an electrolyte is shown having front and rear walls and 12,21 rectangularly shaped, horizontally disposed bottom 13 supported at the four corners by means of a set of blocks 15, and a set of opposite end walls 14 and 16, each of which is provided with a transverse outwardly extending flat flange 18 along its upper edge. Adapted to be immersed in the electrolyte within the tank, the level of which is indicated at 21), there are provided a first and a second row of generally cylindrical bagged anodes forming a front plurality of electrodes 22 and a rear plurality of electrodes 24. The electrodes 22, 24, whichwere of nickel in one physically constructed embodiment of the invention,- areeach provided with a hook 26 at their upper ends with which they are 's'us pended from the respective generally parallel opposite legs of a U-shaped anodic bus bar 28. The bus bar 28 is adapted to be appropriately connected, as by means of a heavy woven copper cable 30, to a source of positive electrical potential (not shown). Through the medium or" the electrolyte, the nickel or other'metal from the cylindrically shaped anodes 22, 24 is transferred to the exposed surface of an article to be plated which may be in the form of a steel bumper 32 which is drawn, by die forming or otherwise, into a shell of substantially U- shaped transverse cross section and which is bent at a point along its length so as to be substantially v shaped or U- shaped in over-all appearance between its opposite ends. The bumper 32 is formed with suitable tabs or apertures adjacent the concave side thereof to which any one of three or more vertically spaced apart cross members -34 may be detachably fastened, the cross members being fast to a common hook-carrying hanger 36 which is hooked onto and depends from a horizontally disposed cathode bus bar 33 of rectangular cross section. A set of clamps (not shown) may be provided'to secure the hooked end of the hanger 36 securely to the bus bar 38. A number of these hangers 36 and a plurality of bumpers of a corresponding multiple of that number carried thereby may be secured to depend from the cathode b'us bar 38 in axially spaced positions from the latter. At the opposite ends of the tank outside its end walls 14 and 16, there is provided a pair of vertically disposed and parallel splined shafts 40 having disc- shaped plate 42, 44 at the head or upper end thereof. The head discs 42, 44 are identical to one another and, in the interests of brevity, only the head 44 will be particularly described as follows.

The head 44 is rotatably and axially fast to its coin panion shaft {it and adapted to rotate concentrically ther with about a common axis 46. At an eccentric location in the head 44 relative to the axis 46, a pivot .pin 48 is provided having an upper end threadably received in a rectangular block of metal 50 and having its lower end depending through an opening in the head 44 and secured thereto as by means of a cotter pin 52. The metal block 50 has a rectangularly shaped through bore therein, Figure 4, which is complemental to and receives the rectan gularly cross-sectioned cathode bus bar 38 therewithin and has a thumbscrew 54 for holding the bus bar 38 axially fast to the metal block 50.

At the end portion of the bus bar 38 adjacent the metal= lic block 50, a woven flexible copper wire cable 56 is secured, as by means of a set of screws 58, to the bus bar in electrically conducting relationship for receiving cathodic current therefrom and transmitting it to a source of electrical power to which the anode cable 30 is connected. I,

In one physically constructed embodiment of the invention, the electrical pressure or potential difference maintained between the bus bars 28 and 38 was approximately 9 /2 volts D. C. The end of the cathode bus bar 38 opposite to the portion to which the cable 56 is eonnected is similarly supported and connected to the head 42. The parallel splined shafts 40 have their respective mid-portions received in and passed through a complementally splined hub portion of a set of driven or output sprockets 60 and 62. In the interests of brevity, only the sprocket 60 will be hereinafter described.- The sprocket 60 is supported between a pair of vertically spaced apart plates 64 secured, as by means of a bracket and a set of fasteners as at 66, to one ofthe two opposite end flanges at the upper ends of the opposite end walls 14 and 16 of the plating tank. The s'plined connection between the sprocket 60, having teeth receivable in a drive chain, and the shaft 40 therethrough is such that the shaft isrotatably fast but axially slid-able with relation. to .the sprocket 60.. The sprocket 60 is prevented from axial travelby means, of the spaced apart plate 64, but the shaft 40 has freedom of motion in two directions, notably axially and rotatably about its axis 46. Another sprocket of somewhat smaller diameter than the sprockets 60and 62, isprovided at 68which serves as a drive sprocket in a manner hereinafter described and five similarly small idlersprockets are provided at the four corner positions of the tank at 70 and at 72 on the opposite or front side of the tank from the drive sprocket 68.

Drive transmitting means as follows is provided for coordinating the motion of the shafts 40 as they rotate about their separate axes. A link chain 74 is trained over the respective drivesprocket 68, driven sprockets 60 and 62, and idler sprockets 70 and 72, and at all times exactly coordinates the movement of the heads 42, 44 and the opposite ends of the cathode bus bar 38 such that the attitude of the bus bar is always parallel to the front and rear walls and 12 of the rectangularly shaped electroplating tank. This feature of parallelism accounts for one of several reasons why the cable 56 onthe bus bar has no tendency to wind up and kink and twist in the present apparatus.

The lower end portion of each of the shafts 40 includes auction of smooth circumference as at 76 which at its lower extremity rigidly carries a transversely disposed circular thrust disk 80 received within a shallow cupshaped recess formed in the head of a reciprocating cylindrical piston 82 of metal, preferably brass. An interposed ball thrust bearing 84 is received on the floor of the cup-shaped recess and supports the disk 80 and the shaft 40 so as to permit relative rotation between 'the shaft 40 and the piston 82, at the same time holding the shaft 40 and the reciprocating piston 82 in an accurately spaced apart relationship for coordinated axial motion as the piston lifts the shaft on its upward stroke and the shaft thereupon follows the piston under gravity as the piston returns on its downward stroke of reciprocation. The cylindrical or cup-shaped recess in the head of the piston 82 contains a suitable quantity of lubricant so as to lubricate the antifriction thrust bearing in which the thrust disk 80 on the extremity of the shaft is journaled. A pin passing through the opposite sides of a generally flat milled portion adjacent the base of the piston 82 pivotally carries a pair of short depending links 86 which at their swinging lower ends are formed with a pair of registering apertures receiving therewithin another pin 88. The lower pin 88 extends transversely through a bore formed in one end of a rectangularly cross-sectioned walking beam or lever 92. The end wall 16 of the plating tank carries a hollow cylindrical bearing or guide 90 secured thereto by means of a suitable bracket and receiving and guiding therewithin the reciprocating piston 82 which is preferably kept coated with grease. At its mid-portion between the opposite ends, the beam 92 is pivoted at 94 to the end wall 16 of the plating tank for rocking movement about the pivot 94 as a center. At its opposite end the walking beam 92 is provided with an elongated pin receiving slot 96. The stationaryposition of the pivot 94 prevents the rectangularly crosssectioned beam 92 from moving out of its own plane, and accordingly, the pin and link connection 88, 86 at one end of the beam satisfactorily prevents the shaft receiving piston 82 from rotating with theshaft 40.

Drive transmitting means as ,follows is provided for coordinating motion of the shafts 40 axially in unison. A piece offline shafting 98 is journaled in a pair of spaced apart sleevebearings 100 for rotation along its axis 102 and the bearings 100 are secured to the lower surface portion of the rear wall 12 of the plating tank. At its opposite extremities, the line shafting 98 has a pair of disks 104 rotatably and axially fast thereto and each of which carries a pin 106 disposed eccentrically to the outer face thereof and passing through the elongated slot 96 in the adjacent walking beam 92. The pins 106 are axially aligned at all times 'with one another and each has a retaining collar 108 preventing its withdrawal from the slot 96 in which the pin is received. Rotation of the line shafting 98 about its axis 102 causes coordinated motion of the end discs 104 and the mutually aligned eccentric pins 106 which results in imparting an oscillating movement to the walking beams 92 and a reciprocatory movement of substantially simple harmonic motion to the shafts 40 in unison along their axes 46. Upon rotation of the discs 104, the walking beams will oscillate between thefull line position and the dotted line position 92a, Figure 4, with a resulting amount of vertical travel at the shaft end as indicated at 110, Figure 4. In addition to the vertical travel of a magnitude corresponding to the dimension 110, the shafts 40 are capable of successive and continued rotation through their full 360 degrees of are as determined by the position of thecompanion driven or output pulleys 60, 62. The coordination in phase between the shafts 40 as they reciprocate upwardly and downwardly together results in the fact that the attitude of the bus bar 38 is always such that it is parallel to the horizontal bottom 13 of the tank. This feaure of parallelism accounts for another of several reasons why the cable 56 on the bar 38 has no tendency to wind up or knot during sustained operation of the present apparatus.

Separate power means are provided for driving the shaft rotating chain 74 and for driving the line shafting 98. An illustrative example of one of the power means is a reversible electric motor 112 which is connected by means of a combined fluid coupling and reduction spur gear component 114 to the drive pulley 68 for the chain 74. The reversible motor 112 is of well-known electrically double wound rotor construction whose respective windings are selectively connectable at will to a power source as at 116 as by means of a double throw switch 118. Thedouble throw switch 118 is movable from a neutral position in which neither rotor winding is energized into opposite positions for energizing one or the other windings of the rotor so as to drive the drive sprocket 68 in one direction or the other as desired.

Illustrative of the other power means is an electric motor 120 which is mechanically connected through a reduction gear box 122 to the line shafting 98 at the mid as follows.

portion of the latter. The motor is arranged to be electrically connected to a source of electrical power 124 through a single throw manual switch 126 which is operator operable. The direction of rotation of the motor 120 is a matter of design choice, and is not selectable by the operator inasmuch as the line shafting 98 imparts the same simple reciprocatory motion to the end shafts 40 regardless of which way the line shfting 98 is rotated.

The following is given as an example of the cyclical frequency of oscillation of the shafts 40 axially and in a direction about their axes 46:

' Cycles per minute Axial frequency of cycle 5-60 Rotative frequency of cycling 5-60 Normal axial frequency 30 Normal rotative frequency 36 Operation of the high agitation plating apparatus under control of the manual switches 118, 126 is accomplished timers,'not shown, the double throw switch 118 is maintained in one operating position for a period of from a few seconds to several minutes and then maintained in the opposite operating position for a similar period with the result of circulating the bumpers 32 in circular paths in sequentially opposite directions. Simultaneously therewith, the single throw switch 126 may be controlled by means of an electrical timer, not shown, so as to close and compound the circular motion with the substantially simple harmonic motionof reciprocation of the shafts and heads 40, 42,'and 44 which imparts a three-dimensional motion tothe bumpers 32 being plated. In cer- By means of manual control or electrical 'tain instances of plating particular articles, an-automatic cycling operation has been used to advantage wherein the single throw switch 126 is held closed for-twenty seconds and held open for twenty seconds, with the result that the plated articles are alternately subjected to three-dimensional motion and two-dimensional motion, even though the reversibility of the chain '74 in the latter sense actually provides for opposite directions of rotation in the single plane providing the two directions of motion. The interspersing of periods of the three-dimensional motion described, among the two-dimensional motion periods, has been found to be particularly effective in the bumper plating field in which the intricate surface of the bumper, due to the varying radii of curvature of its developed exterior, is otherwise 'di ffic'ult to plate uniformly.

In Figure 5, the diagrammatic two-dimensional path of motion represented will be an aid to the visualization of the actual three-dimensional path of motion described by the bumpers during a portion of .the operation of the preceding paragraph. Figure represents the path of article motion viewed from the position of the anodes 22 of Figure 2, it being observed that the bumpers do not rotate as they bodily orbit nor do they revolve about a rotational axis in any sense, but retain their original position of orientation in a horizontal plane in much the same manner as the cathode bus bar 38, which, as already noted, -maintains its relation of parallelism to "the front, bottom, and rear Walls of the plating tank even though it is being oscillated with a compound motion. Through the flatter portions of the path of the bumper as indicated at 128 and 130, the bumper is moving transversely of the anodes 22, whereas in the more curved portions 132, 134 of the path of travel, the bumper is moving respectively toward and from one row of electrodes 22 and from and toward the other row of electrodes 24. Simultaneously, the vector of motion of the bumpers in the more curved portions 132, 134 has a pronounced component lengthwise of the depending electrodes. Inasmuch as any motion of reciprocation is subject to a dwell phase and to a maximum velocity phase in each cycle, the transverse movement of the bumpers along the path portions 128 and 130 is relatively free of up and down travel of the bumpers, whereas the motion of approach and separation of the bumpers at 132, 134 relative to the anodes is accompanied by a rather pronounced up and down component of motion thereof. In view of the constant angular rotation of the heads 42, 44 compared to their constantly varying velocity of axial travel and in view of the fact that the cyclic frequency of reciprocation is slightly at variance with, and preferably slower than, the rotative frequency, it will readily be appreciated that the opposed convex surfaces to be plated on the bumpers 32 undergo such widely varying directions of motion with respect to the fluid against which they impinge that at one time or another each portion of the surface to be plated is impinging directly at right angles against the electrolyte fluid. The resulting coating of electroplated nickel has been observed to attain a very desirable uniformity of.

thickness about the article to be plated and the results have been found very satisfactory in practice.

While we have described certain presently preferred embodiments of our invention, it is to be understood that it may be otherwise embodied within the scope of the following claims.

We claim:

1. Apparatus for electroplating a three-dimensional article having convex surfaces comprising a tank for fluid in which the article is to be immersed, a member thereon adapted to suspend the article in the fluid and having means for conducting current therefrom, rows of elongated electrodes defining an unobstructed open space in the tank, spaced apart means for moving the member and the suspended article through a curved path oscillating so as to weave between the electrode rows to continually reverse direction with respect thereto and to the length of the tank to constantly change the di'stancebee: tween the article andthe electrodes, saidmemberhaving opposite end structures disposed one over each of said means, connections supporting each end structure with a rotating fit upon the means at that end for motion in a path closing on itself, and thrust delivery means, for applying thrust to shiftably operate said spaced apart means for moving the member and the suspendedarti'cle in reciprocatory motion in a direction perpendicular to the plane of rotation aforesaid, said means constituting the sole means of support of said member. I I

2. In apparatus for electroplating an article, having convex surfaces, a cathode member adapted to suspend the article and having means for conducting current there from, rows of elongated electrodes anod'ically cooperating therewith and defining an unobstructed open 'spa'ce'for receiving the article therebetween, spaced apart reversible means for moving the member and the-suspended article in either of two directions through a curved path oscillating to and fro in the tank and continuously weaving-between the electrode rows so as to cyclically vary the motion and constantly change the distance between the article and the electrodes, said member having opposite end structures disposed one over each of said means, connections supporting each end structure with a rotating fit upon the means at that end for motion in a path closing on itself, and thrust delivery means for applying thrust to shiftably operate said spaced apart means for moving the member and the suspended article in substantially simple harmonic motion in a direction perpendicular to the plane of rotation aforesaid, said means constituting the sole means of support of said member.

3. In a means for electroplating three-dimensional drawn articles, a bar member from which the articles are adapted to be suspended, disc means, said bar member having at least one end structure disposed over said disc means, a connection comprising crank pin means supporting said one end structure with a rotating fit upon said disc means at that end for swinging motion in a path closing on itself, operator controlled means whereby the disc means is rotated in either direction, and separate operator controlled means for raising and lowering the disc means independently of the control of the disc rotating means, said means constituting the sole means of support for said bar member.

4. In combination, a bar member from which articles to be electroplated are adapted to be suspended, a pair of spaced apart discs disposed one below each end structure of the bar member, connections including crank pin means supporting each end structure With a rotating fit on the disc at that end for swinging motion in a path closing on itself, operator controlled means whereby the discs are rotated in the same one sense together or in the opposite sense together, and separate operator controlled means for raising and lowering the pair of discs simultaneously but independently of the control of the disc rotating means, said means constituting the sole means of support for said bar member.

5. In means for electroplating articles, a cathode bar from which the articles are to be h ng, a plurality of horizontally spaced apart heads by which spaced portions of the bar are individually eccentrically mounted and supported, a vertical rotatable support shaft connected to each head in driving relationship thereto for imparting eccentric motion of oscillation to the cathode bar,*and means for moving the shafts in unison axially and in a direction about their axes.

6. In means for electroplating articles, a bus bar from which the articles are to be hung, horizontally spaced apart discs by which the opposite ends of the bus bar are supported and eccentrically mounted, a vertical rotatable support shaft connected to each disc in driving relation ship thereto for imparting eccentric oscillation to the bus bar, means having an eccentric rocking action for moving each of the shafts axially in unison with the other shaft,

, 7 and separate ghavingta splined connection to each shaft-for rotating it about its own axis in synchronism with the other shaft. A p r 7.-Mechanism for high agitation electroplating of articles comprising a plurality of upstanding splined sup port shafts disposed in parallelism to one another, a like number of coplanar heads supported thereby and each ticles comprising a plurality of splined vertical shafts,

Il -like number of.cop lanar plates fast'thereto and each hayinganupstandingeccentrically located pin in the face thereofiacathodelbus means pivotally carriedby the pins in common, drivesprocket means splined to the shafts, 20

eccentricallyt driven walking beam means connected to said; shafts for shifting them axially, a common chain coordinating the drive sprocket means for rotating the shafts in unisonQand means including common line shafting and eccentric means connected to the walking beam means forshifting, the shafts axially in unison.

9 For use with a plating tank provided with horizontal bar means and suspension members hanging therefrom downwardly into the tank for supporting articles with curving surfaces to be plated, electrical cable means secured to the bar means for conducting plating current, support means connected to the bar means for simultaneously producing motion having a vertical component, a horizontal component in the plane of the vertical component, and a horizontal component in a plane perpendicular to the vertical component and to the first said horizontal component, all in a curving path closing on itself in a manner to prevent kinking of the cable means,

said support means comprising eccentrically mounted means supporting thebar means at opposite ends and mounted for vertical movement and for rotation in horizontal planes, and power means for driving the eccentrics both ways. I

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. APPARATUS FOR ELECTROPLATING A THREE-DIMENSIONAL ARTICLE HAVING CONVEX SURFACES COMPRISING A TANK FOR FLUID IN WHICH THE ARTICLE IS TO BE IMMERSED, A MEMBER THEREON ADAPTED TO SUSPEND THE ARTICLE IN THE FLUID AND HAVING MEANS FOR CONDUCTING CURRENT THEREFROM, ROWS OF ELONGATED ELECTRODES DEFINING AN UNOBSTRUCTED OPEN SPACE IN THE TANK, SPACED APART MEANS FOR MOVING THE MEMBER AND THE SUSPENDED ARTICLE THROUGH A CURVED PATH OSCILLATING SO AS TO WEAVE BETWEEN THE ELECTRODE ROWS TO CONTINUALLY REVERSE DIRECTION WITH RESPECT THERETO AND TO THE LENGTH OF THE TANK OF CONSTANTLY CHANGE THE DISTANCE BETWEEN THE ARTICLE AND THE ELECTRODES, SAID MEMBER HAVING OPPOSITE END STRUCTURES DISPOSED ONE OVER EACH OF SAID MEANS, CONNECTIONS SUPPORTING EACH END STRUCTURE WITH A ROTATING FIT UPON THE MEANS AT THAT END FOR MOTION IN A PATH CLOSING ON ITSELF, AND THRUST DELIVERY MEANS FOR APPLYING THRUST TO SHIFTABLY OPERATE SAID SPACED APART MEANS FOR MOVING THE MEMBER AND THE SUSPENDED ARTICLE IN RECIPROCATORY MOTION IN A DIRECTION PERPENDICULAR TO THE PLANE OF ROTATION AFORESAID, SAID MEANS CONSTITUTING THE SOLE MEANS OF SUPPORT OF SAID MEMBER.

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