US2944947A - Electroplating method and apparatus - Google Patents

Description

H. C. LUECHAUER ELECTROPLATING METHOD AND APPARATUS July 12, 1960 :s Shets-Sheet 1 Filed Sept. 5, 1957 k ivk svs INVENTOR.

B -/0//e C. Luechaue/ His Alto/nay I July 12, 1960 H. c. LUECHAUER ELECTROPLATING METHOD AND APPARATUS 3 Sheets-Sheet 3 Filed Sept. 5, 1957 B olle 0. Luec/muer His Afro/nay 2,944,947 QPL T G ME QD ND A PARA W Hqlle C. Luechauer, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich., a corporation of De aware Filed ept. 5, 1951,-Se r. No. 682,127 11 .Claims. (Cl. 204-26) invention relates to electroplating and is particularly'concerned with an apparatus and method. for

the invention to utilize a plating tank having "a trackpassing therethrough which divides the tankinto substantially two compartments wherein the bearings to'be' plated are conveyedon the track'which is longitudinally apertured forlacting as a shield to'provide plating 'of the bearing surfaces.

The electrolyte which leaks out of the tank around the track ingress and egress is continuously replaced whereby the electrolyte level'in the platingtank ismaintained substantially constant' iIn carrying" out the above object, it is a further object of the invention to plate the concavesurfa'c'esof senticylind-rical bearings wherein the'bearings' do'not necessarily require electrical connections in the'pla'ting circuit whereby the movement of the bearings in the continuous plating process is facilitated.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to theaccompanying drawings wherein preferred embodiments of the invention are clearly shown.

In the drawings:

Figure 1 is a sectional view taken through a plating tank including, a track conveyor'therethrough havinga plurality ofbearings thereon.

Figure 2' is a fragmentary view of feeding apparatus shownimFigure-l in another position.

Figure 3' is a fragmentary view showing the feeding apparatus ofFigure 1 instill another position.

Figure?! is a sectional view ofanother type of'plati'n'g tank utilizinga continuous belt conveyor 'ther'ein;

Figure 5 is al sectionalFvie'w taken on line 55 of Fig.1..

:Eigure 6-is a. sectional-z view taken on line 6 -6 of Figure 4;

.Figure 7 is a' fragmentary top view of'a portion of the track shown inFigu'resf4 an'cl 6. V i Figure 8 is a fragmentary view of the top portion of the tank showing another "mean's'fors upplyingf current for electroplating the Semicylindrical' bear' gs p'resent a rather diflicult prpb 1611i ftwd fi i F anna of bea n' s r s he??? These bearingsfare convenj "nany p lated' on the. bearing surfaces withla very thin trolledfelectroplate in-the oirder of frOmQO'QOS to A 1 inch thick,which:plate must 15s uniform :and coe xten ve: is gene ally a; coplate invo atea-me q d nr lea s; of this general nature 1 are, fully W U FP ti -sur e e- B arin B atented July 2, 1966 2 is bonded to a steel backing and wherein the surface of the aluminum is plated with a babbitt.

The plating operations in the past have been carried out in a batch process wherein the bearings are placed boxes, for example, as shown in Patent 2,761,831. These boxes are apertured at the front thereof whereby the bearing surface is partially shielded for providing a uniform thickness of electroplate over the bearing surf c her f,

.In this disclosure, the bearings have a brush contact at the back side thereof which is connected to the negative pole of a current source while the anode is connected to the positive pole of'said source, said anode may be formed from the. metals to be plated or from certain of the metals with the others being added to the electrolyte as is well known. Suitable plating solutions arewell known in the :art and Patent 2,5 86,100 sets forth specifically two such solutions for plating lead-tin and lead tin-copper onto the surface of a bearing such as an aluminum bearing.

In copending application, S.N. 665,503, filed June 13,

11957, and assigned to the assignee of the present invention, another type of plating method is set forth wherein bearings areplated in a box-like structure having shielding means for providing uniform plating on the semiylindrical concave surfaces thereof and wherein a cathode plate is used so that the bearing per se is not directly connected in the circuit, This cathode plate substantially eliminates back plating of the hearing which is highly desirable and likewise eliminates the necessity of direct electrical connections to the bearings.

The present invention is specifically directed to ap par'a'tiis and a plating method which is continuous in its operation so that any number ofbearings may be fed to and removed from the apparatusprogressively when they are properly plated and wherein the apparatus operates throughout the day and thus eliminates the necessity of loadingthe plating boxes and placing them in plating tanks, etc, as se't forth in the prior art as explained herein. This enables the user to elfect tremendous savings] in the operation.

Referring specifically to Figure 1, one form of the invention is shown wherein a plating tank 20 is provided havingentrance and exit apertures 22 and 24 in the endwalls26 'and 28 thereof respectively. The specific shapje'of the apertures is shown in Figure 5. The plating tank 20 is maintained Within a second tank 30 which is disclosed atent 2,i8,6,()99;wherein an aluminum layer 7 larger and which acts as a means for collecting electrolyte which leaks out of the tank 20 as will be described hereinafter. Passing through the tank 20 and fixedly fastened therein is a track 32 which, like the tanks 20 and 30; is formed from nonconducting material or is rubber plated as is well known in the art so that it is not attacked or affected by the electrolyte. The track 32*as shown in Figure 5 divides the tank 20 into two longitudinally extending compartments, namely, an upper compartment 34 and a lower compartment 36. The track is longitudinally apertured at 38 preferably with a continuous slot or a plurality of interrupted slots as shown hereinafter so that, when a bearing 4t) is set thereon in inverted position, the concave surface thereof faces the aperture 38. The aperture 38 is dimensioned so as to provide a shield 'for the bearingto effect a uniform plating on the surface thereof as is Well known in the art. The track 32'has longitudinally extending ridges 42 and 44 thereon which fixedly position the bearings 40 transversely of the track-but'which permitthe bearings to be moved longitudinally thereof. 1

in practice, assho'wn inFi'gure 1, aplurality of bearings 4d aresupplied to the track from a feed device 50 which includes" a verticle magazine 52 having a cam operatedstop 54therein which stop is synchronized 3 v with a cam operated pushing device 56. The timing of thepushing device 56 is calculated in accordance with the length of the plating tank so that bearings passing through the tank are immersed in the electrolyte a sufli- "cient length of time to accumulate the desired amount of electroplate at their concave surfaces. Each time the pushing device 56 moves to a position as shown in Figure 2, one bearing begins to pass out of the tank and another bearing begins to pass in. At the end of the stroke as shown in Figure 3, the release stop 54 is retracted to permit another bearing to fall into position on top' of the pushing device which, as it is retracted to the position shown in Figure 1, permits the bearing to fall onto the track while the stop 54 is again effective in the magazine. Thus, the feed device 50 progressively feeds bearings to the track, passes them through the tank and ejects them from the tank at the opposite end thereof when the concave surfaces thereof are plated.

In the lower compartment 36 of the tank, there are positioned a plurality of transversely disposed rods 60 which span the tank and act as a bed for anode plates 61 which are plates of the metal to be plated such as lead-tin alloy, for example. These plates are slipped into the tank and onto the bed racks as they are needed and carry current from one to another through contact. In the upper compartment 34, there is positioned .a longitudinaly. extending metallic plate 62 which extends throughout the length of the compartment directly above the bearings. This plate acts as the cathode as set forth in the aforementioned copending. application S.N. 665,503. The plate 62 may be steel, copper, etc., as determined by the'electrolyte used. Since the track 32 divides the tank into tow compartments wherein there is no free flow within the electrolyte from one compartment to the other, there is little or no back plating of the bearings and substantially all of the electroplate deposits on the concave surfaces thereof.

At the entrance and exit 22 and 24 respectively of the track, two plug members 66 and 68 respectively are placed which are attached to the tank wall and pass up wardly through the slot 38 and which more or less conform to the concave surfaces of the bearings. It is understood that these plug members are of insuflicient size to bind on the bearings but are sufiicient to reduce the free flow of electrolyte outwardly of the tank. However, it is apparent that considerable electrolyte does flow out of these openings 22 and 24 which electrolyte is caught in the outer tank 30. Pump means 70 in the outer tank 30 operate to replenish electrolyte in the plating tank 20. The pump means 70 are adjusted so as to maintain the levelof electrolyte in the tank 20 constant regardless of the amount of leakage around the track. In this manner, bearings are progressively supplied and removed from the track and pass through the plating tank and are plated at the concave surfaces thereof. Anode metal is added when needed and electrolyte is also replenished for strength and quantity when needed as is well known in the art. The cathode plate 62 does not accumulate much plate thereon since there is little or no free flow past the track. Whenever the cathode plate does accumulate sufficient plate thereon to warrant removal, it is replaced and stripped and subsequently reused. 1

It is understood that other types of feeding devices may be used andthat deviations in design may be made without departing from the spirit of my invention, for example, the plugs 66 and 68 are not necessary if the pump means. 70 hassufiicient capacity to maintain the level of electrolyte in tank20 above the cathode 62. Similarly, ifit is desired to have direct electrical contact to the bearings instead of using a cathode plate 62 out of physical contact with the bearings, it can be accomplished as shown in Figure 8 by providing a cathode formed from a plurality of chains '63 or rollers, etc., attached to a cathode plate 65, which drag over the upper surfaces of the bearings to provide a low friction contact as the bearings are moved through the electrolyte which chains are connected to the negative source of current and supply current directly to the bearings. In this instance, there will be more back plating but since the electroplating being deposited is critical and very thin, the back plating is generally not too objectionable in certain instances although, generally, the use of apparatus as shown in Figure 1 is more desirable.

Figure 4 shows another type of apparatus similar to the apparatus shown in Figure 1. In this embodiment, a plating tank is used which has a continuous elastomeric track 102 passing therethrough that is carried by a pair of plastic, or rubber-covered rollers 104 and 106. Supporting rollers 108 are positioned where needed to maintain the track substantially level. The track 102 is apertured in the form of a slot or as an interrupted slot such as a pluralityof aligned diamonds, '(see Figure 7), circular holes, etc., as shown in Patent 2,761,831, which apertures are spacedso as to be aligned with the bearings 40 as they are fed to the track through a cam operated feeding device 110 which functions in a somewhat similar mauner to the device 50 previously described. In this instance, however, a double escapement is used which is operated by cams 111 and 113 that are synchronized with the movement of the track 102 so that bearings fall onto the track in timed relation to longitudinal movement of the track. The track is rotated by means of a suitable drive 112 connected to a motor 114. In this instance, plugs 116 and 118 are supplied for the openings at the ends of the tank which plugs are held on elongated supports 120 and 122, respectively, attached to the outer tank 30. All other phases of the operation arethe same as that described in connection with Figure 1 including the pump 70, the cathode 62 and anodes 61. Similarly, the cathode 62 may be replaced by contacts as previously described. 7

It is apparent that the present invention provides a means whereby continuous plating operations may be carriedout on a plurality of semicylindrical bearings by merely feeding the bearingsto the plating tank whereby the bearings pass through the tank in a predetermined period of time and are ejected therefrom in plated condition. It is manifest that this operation greatly reduces the cost and complexity of the plating operations heretofore used on semicylindrical bearings wherein a batch process was used that required many manual operations such as loading of the boxes, positioning the boxes and removal of the boxes from the plating tank.

It is also to be understood that the bearings entering the feeding device 50 or 110 may be supplied thereto continuously from a cleaning vat or other previous operation. Similarly, as the bearings leave the plating operation, they may either fall into a bin or may be transferred to another conveyor whereupon they pass through washing operations, etc., as is well known in the art. In fact, all steps in conventional electroplating operations, other than the actual electroplating step, have heretofore been feasible in continuous operation but, until the prescathode and their connections, must be electrically nonconductive. These parts may'be made from plastic or rubber-like material or they maybe made from metal coextensively covered with plastic or rubber, or similar nonconductive material as is well known in the art.

While the embodiments ofthe present invention as herein disclosed constitute preferred forms, it is -to be 4* a 1:3 is-c a mesi as fo lows:

1.1.. Inv aumethod for co tin o s y e p a in the Q IQ W JIfi QQS. o a plurality of semicylindrical'bearings, the s eps compr sin providi a pl l n taining anelectrolyte, providing a longitudinally apertured conveyor track within said tank for longitudinally i id ng h t nk nta We gm a meats dina e a i d ic e r n s 9 sa 1; 9 .11% e bearin bu n n thertmdbri lswtr aperture lhQh' L99 cave surfaces facing the aperture and act as a barrier toward free passage of electrolyte from one compartment to another through said aperture, positioning an anode in the lower compartment of said tank beneath said track and insubstantially parallel relation thereto, positioning a conductive plate in the upper compartment above said bearings and in substantially parallel relation to said anode, electrically connecting the anode and the plate to opposite poles of a current source, progressively moving the bearings along said track and between the anode and the plate while maintaining the aperture bridged by said bearings, and maintaining the electrolyte at a level suificient to cover said plate at all times.

2. In a method for continuously electroplating the concave surfaces of a plurality of semicylindrical bearings, the steps comprising; providing a plating tank containing an electrolyte, dividing said tank into two longitudinally extending superimposed compartments by providing a longitudinally apertured conveyor track within said tank, feeding semicylindrical bearings to said track so that the bearings abut one another and bridge the aperture with their concave surfaces facing the aperture and act as a barrier toward free passage of electrolyte from one compartment to the other compartment through said aperture, positioning an anode in the lower compartment of said tank beneath said track and in substantially parallel relation thereto, positioning a conductive plate in the upper compartment abovesaid bearings and in substantially parallel relation to said anode, electrically connecting the anode and the plate to opposite poles of a current source, progressively moving the bearings along said track while maintaining the aperture bridged by said bearings, and pumping sufficient electrolyte into said tank to maintain the electrolyte level substantially constant and sufficient to cover said plate at all times.

3. In a method for continuously electroplating semicylindrical bearings at the concave surfaces thereof wherein a tank is provided for the electrolyte which includes a divider track therethrough. for dividing the tank into two superimposed compartments, said track including a longitudinal aperture therein and having a cathode and an anode disposed in opposed relation on opposite sides of the track with the cathode being positioned above the track, the steps comprising; progressively feeding semicylindrical bearings to the track in abutting relation so that the concave surfaces of the bearings face the aperture and bridge the aperture and prevent free passage of electrolyte from one compartment to the other, electrically connecting the cathode and anode to opposite poles of a current source, continuously plating the concave surfaces of bearings with the tank progressively moving bearings along said track and out of said tank, and continuously supplying sufficient electrolyte to the tank to maintain the level of electrolyte therein above the said cathode.

4. In a method for continuously electroplating semicylindrical bearings at the concave surfaces thereof wherein a tank is provided for the electrolyte which includes a divider track therethrough for dividing the tank into two superimposed compartments, said track including a longitudinal aperture therein and having an anode disposed beneath the track, the steps comprising; progressively feeding inverted semicylindrical bearings to the track in abutting relation so that the concave surfaces of the bearings bridge the aperture and face the aperture and prevent free passage of electrolyte from one compartment to the other establishing, an electrical circuit including the bearings. and the anode forelectrodepositing anode metal on the concavesu'rfacesof the bearings, re plenishing electrolyte in the tank for maintaining a level thereof sufiicient to immerse completely the bearings during the platin re igd and a re ve re o bearings from the track at the end opposite to the end at which the bearings are fed to the track.

5a lh tmeflt d shined. in shim 4 wherein th l n ea htu gt stem a a rlished .by pump e ectro y into the tank from a reservoir surrounding the tank and having a level of electrolyte therein considerably below the normal level of electrolyte in the tank.

6. Apparatus for continuously electroplating semicylindrical bearings, comprising in combination; a first tank adapted to hold electrolyte and including apertures at opposite ends thereof, a longitudinally extending apertured track connecting said apertures at opposite ends of the tank and dividing the tank into two superimposed compartments, said track being adapted to receive bearings in abutting relation for bridging said apertured track, a second tank surrounding the first tank and adapted to receive electrolyte which leaks out of the first tank through said apertures, pump means associated with the second tank and adapted to pump electrolyte rom the second .tank into the first tank for maintaining the level of the electrolyte in the first tank at a predetermined level, and a feeding device adapted to feed bearings progressively to said track.

7. Apparatus for continuously electroplating semicylindrical bearings, comprising in combination; a first tank adapted to hold electrolyte and including apertures at opposite ends thereof, a longitudinally extending apertured track connecting said apertures at opposite ends of said tank and dividing the tank into two superimposed compartments, said track being adapted to receive bearings in abutting relation for bridging said aperture, a second tank surrounding the first tank and adapted to receive electrolyte which leaks out of the first tank through said apertures, pump means associated with the second tank and adapted to pump electrolyte from the second tank into the first tank for maintaining the level of the electrolyte in the first tank at a predetermined level, means for moving the track through said first tank continuously and a feeding device for progressively feeding hearings to the track at one end thereof which bearings are progressively removed from the track at the other end thereof.

8. Apparatus for electroplating a plurality of semicylindrical bearings simultaneously, comprising in combination; a tank adapted to hold electrolyte and including a pair of opposed apertures in the end walls thereof, a track passing through said tank and connecting said apertures at opposite ends of said tank, said track being longitudinally slotted and of a dimension suflicient to substantially divide the tank into two superimposed compartments, means for holding anode metal in the lower compartment, a cathode plate mounted in the upper compartment above said track and extending substantially parallel thereto, a second tank surrounding the first tank and adapted to receive electrolyte leaks out of said apertures and around said bearings, means associated with the first and second tanks for replenishing electrolyte in the first tank from electrolyte in the second tank, and means for progressively feeding bearings to said track at one end thereof whereby the bearings are moved along the track through the electrolyte and between the electrodes and are electroplated during their passage through the tank.

9. The apparatus claimed in claim 8 including plug means within the apertures and dimensioned so as to be noninterfering with respect to said bearings, said plug means reducing the leakage of electrolyte through said apertures.

10. The apparatus claimed in claim 8 wherein the track is an endless conveyor belt which moves through said first and second tanks.

7. '11. The apparatus claimed in claim 8 wherein the track is a' stationary track and wherein the bearings are progressively moved therealong by action of the feeding means.

References Cited in the file of this patent UNITEDSTATES PATENTS Thomas et a1 Sept. 27, 1955 "Martin et a1. May 8, 1956 Luecharler. Sept. '4, 1956 Jackso Sept. 11, 1956 FOREIGN PATENTS Great Britain Sept. 16, 1948 Great Aug. 21, 1946 Germany May 8, 1936

Claims (1)

1. IN A METHOD FOR CONTINUOUSLY ELECTROPLATING THE CONCAVE SURFACES OF A PLURALITY OF SEMICYLINDRICAL BEARINGS, THE STEPS COMPRISING, PROVIDING A PLATING TANK CONTAINING AN ELECTROLYTE, PROVIDING A LONGITUDINALLY APERTURED CONCEYOR TRACK WITHIN SAID TANK FOR LONGITUDINALLY DIVIDING THE TANK INTO TWO COMPARTMENTS, FEEDING SEMICYLINDRICAL BEARINGS TO SAID TRACK SO THAT THE BEARINGS ABUT ONE ANOTHER AND BRIDGE THE APERTURE WITH THEIR CONCAVE SURFACES FACING THE APERTURE AND ACT AS A BARRIER TOWARD FREE PASSAGE OF ELECTROLYTE FROM ONE COMPARTMENT TO ANOTHER THROUGH SAID APERTURE, POSITIONING AN ANODE IN THE LOWER COMPARTMENT OF SAID TANK BENEATH SAID TRACK AND IN SUBSTANTIALLY PARALLEL RELATION THERETO, POSITIONING A CONDUCTIVE PLATE IN THE UPPER COMPARTMENT ABOVE SAID BEARINGS AND IN SUBSTANTIALLY PARALLEL RELATION TO SAID ANODE, ELECTRICALLY CONNECTING THE ANODE AND THE PLATE TO OPPOSITE POLES OF A CURENT SOURCE, PROGRESSIVELY MOVING THE BEARINGS ALONG SAID TRACK AND BETWEEN THE ANODE AND THE PLATE WHILE MAINTAINING THE APERATURE BRIDGED BY SAID BEARINGS, AND MAINTAINING THE ELECTROLYTE AT A LEVEL SUFFCIENT TO COVER SAID PLATE AT ALL TIMES.

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