US3376210A

US3376210A - Process and apparatus for electroplating annular bodies

Info

Publication number: US3376210A
Application number: US363949A
Authority: US
Inventors: Kiefer Bernhard; Buske Alfred
Original assignee: Karl Schmidt Fa GmbH
Current assignee: Karl Schmidt Fa GmbH; Karl Schmidt Firma GmbH
Priority date: 1963-05-04
Filing date: 1964-04-30
Publication date: 1968-04-02
Anticipated expiration: 1985-04-02
Also published as: GB1056556A; DE1239160B

Description

April 2, 1968 a KIEFER ET AL PROCESS AND APPARATUS FOR ELECTROPLATING ANNULAR BODIES Filed April 30, 1964 ABSTRACT (BF THE DISCLGSURE Electroplating the internal surface of an annular body, such as a bearing, by immersing the bearing in an electrolysis bath, connecting the outer axially extending surface of the bearing as cathode, and passing current through the bath from an anode disposed externally of the annular body. The annular body is held between nonconducting plates disposed at the ends of the annular body and each having an opening coaxial with the annular body.

The subject of the application is an apparatus for the internal electroplating of annular bodies.

It is in the prior art to create an electrodeposit on the internal surface of annular bodies, such as bearing half-shells made of steel and aluminum compound or other bearing metals, in internal anode electroplating apparatus. Thus, half-shells are assembled in pairs to form a circular ring for this purpose, and they are placed in appropriate mountings in the center of which the anode (such as a round rod of nickel, copper or lead) is placed. The objects to be electroplated are connected as the oathode of the apparatus. Like the anode, they draw their current through the suspension arm of the electroplating apparatus or through a cable connection to the current source. It is customary to electroplate one-piece annular bodies, such as bearing sleeves, with an internal anode in a manner similar to that described above. In such operations, however, due to the relatively short distance between anode and cathode, the accuracy which is therefore required in the geometrical positioning of the anode and of the half-shells or annular bodies in relation to one another, is a decided disadvantage. This can be explained briefly by means of an example: if the anode is a mere one millimeter off center in relation to a bushing with a diameter of about 50 mm., the result can be a difference of as much as 5 microns in the thickness of the galvanic plating, which, in the case of an average overall deposit of microns, amounts to Furthermore, the use of an internal anode results in losses of time in connection with the loading of the electroplating apparatus, which cannot conveniently be made automatic in the case of annular bodies.

Lastly, it must be mentioned that disturbances in the electrolytic equilibrium are produced during the electroplating process by the fact that the area ratio of the anode rods in the center of the annular bodies to the cathode area has to be exceedingly unfavorable. Due to the dissolution of the anode during the plating process, continual changes in the anode-to-cathode surface-area ratio occur, which results in additional uncertainty of the electroplating conditions. Also, the removal of anode metal during the electrolysis results in greater danger of the decentering of the anode.

It has, for these reasons, already been attempted to replace the internal anode in electroplating with an external anode in the plating tank. However, the disclosures which have become known in this regard deal exclusively States Patent 0 with plating equipment for half-shells, not with one-piece annular bodies or bearings as in the case of this application. The invention is therefore aimed at the problem of making the use of external anodes possible also in the case of bearing bushes, and half-shells assembled into annular bodies.

According to the invention, an annular body is electroplated by disposing the annular body coaxially with respect to aligned, equal diameter openings in non-conducting side plates positioned one at each end of the body in close-fitting engaging relation therewith. The annular body and the side plates are immersed in an electrolysis bath outfitted with an anode and a cathode connection, and electrical connection is made between the cathode connection and the outer axially extending surface of the body, and passing a current through the bath to electroplate the internal surface. Desirably a rack, specially constructed for use according to the procedure of the invention, is used for holding a plurality of annular bodies. The rack can comprise a vertically elongated chamber defined by end walls, two sidewalls and a bottom, and is open at the top. A plurality of equal diameter openings at equal vertically spaced intervals are provided in each sidewall, and the openings in the two sidewalls are in aligned relation so that there is provided a vertical row of spaced pairs of openings, the openings in each pair being coaxial and the axes of said pairs being vertically aligned. One or more vertical rows of opening pairs can be provided. Exposed surfaces of the end walls and sidewalls, below a level above and adjacent the uppermost pair of openings, are non-conducting. Desirably, to facilitate making electrical connection to the outer axially extending surface of the annular bodies, the bottom is nonconducting except for a portion or portions thereof aligned with the axes of the vertical row or rows of opening pairs. The axis of the lowermost pair of openings in each vertical row can be spaced from the exposed surface of the bottom corresponding thereto, one half the spacing of the axes of each vertical row from each other. Then, in each vertical row of opening pairs, a number of annular bodies equal to the number of opening pairs, and each having an outside diameter equal to the vertical spacing of the openings and of a size to be received in the chamber, can be placed thereon one atop the other with the bottom body in electrical connection with the exposed surface of the bottom and each body in electrical connection with the body next above. One annular body will then be disposed coaxially with respect to the axes of each opening pair in the row. Means are provided for making electrical connection to the exposed portion or portions of the bottom with a cell cathode connection, so that the lowermost annular body or bodies can be connected as cathode, and serve to connect the annular bodies above as cathode. The rack can be suspended in an electrolyte bath and the electroplating effected by passage of a current from an anode provided in said bath, through the bath and to the annular body cathodes.

The invention is further described in reference to the accompanying drawings, wherein:

FIG. 1 is a side 'elevation view of a rack according to the invention;

FIG. 2 is an end elevation of the rack shown in FIG.

FIG. 3 is a cross-section of the rack shown in FIG. 1, taken along line 3-3 in FIG. 1;

FIG. 4 is a cross-section taken on line 44 in FIG. 3; and FIG. 5 is a schematic representation of an electrolysis bath wherein a rack according to the invention is used.

In the various views of the drawings, like reference characters refer to corresponding parts.

Referring to the drawings, the rack l is formed by sidewalls 2 which can be of plastic, end walls 5, and bottom wall 511. The rack has an open top 5b, by way of which annular bodies can be placed between the sidewalls. The rack is divided into a plurality of compartments 2 by the partitions 3 and end pieces 3a, and a row of vertically spaced openings 8 is provided for each compartment. As is described in more detail above, these openings are of equal diameter and are equally spaced, and the openings in the two sidewalls are arranged to provide opening pairs in which the openings of each pair are coaxial.

As can be best seen in FIG. 3, the sidewalls 5 are made up of the metal strip 11 and rubber covering 12, and are fixedly secured to the end pieces 3a by bolting 13. The bolting 13 can be suitably covered by insulating material, or, can be by utilization of a non-conducting material. The construction of the bottom is best seen in FIG, 4. The bottom is formed of the metal strip 11a and the rubber covering 12a. Portions 15 of the bottom metal strip are uncovered so that electrical connection can be made at these portions. Desirably, the metal strip 11a of the bottom is integral with the metal strip 11 of the sidewall, whereby electrical connection to the exposed portions 15 of the bottom, and the providing of a rigid frame for the rack is facilitated. The bottom is also provided with weep holes 16 which facilitate suitable drainage.

At the upper portion of the rack, the sidewalls 5 connect with a cross-piece 17 to which a suspending means 9 is connected. The sidewalls are rubber covered to the upper end thereof, and the cross-piece 17 is also rubber covered, and, further, includes a metallic core (not shown) in electrical connection with the metal strip of the sidewalls. The suspending means 9 includes a metallic core in electrical connection with the metallic core of the crosspiece 17, and the lower portion 18 thereof is rubber covered, while the upper portion 19 thereof is uncovered to expose the metal to facilitate making electrical connection. Thus, a circuit is provided from the upper portion 19 of the suspending arm to the exposed portions 15 of the bottom, the circuit being through the suspending arm, the cross-piece 17, the sidewalls 5, and the bottom 5a.

The spacing of the axis of each of the lowermost open.- ings 8, from the exposed portion 15 of the bottom 5a, is equal to the outside diameter of the annular bodies to be electroplated, and the axis to axis spacing of the openings in each vertical row is equal to the outside diameter of the annular bodies to be electroplated. Further, the spacing of the sidewalls 2 from each other is such that the annular bodies when disposed with their axes parallel to the axes of the openings, can be received between the sidewalls in close-fitting engaging relation therewith.

In operation, the compartments 2 are filled with annular bodies, and in each compartment the lowermost annular body is in electrical connection with the exposed portion 15 of the bottom, which corresponds to the compartment in question, The annular bodies are disposed one atop the other, so that the outer surface of the bodies is in electrical connection, each annular body being in electrical engagement with the annular body or bodies above and/ or below it. The rack can then be suspended from a holder 18 (FIG. 5), which serves as a cathode connection and is connected to a source of negative voltage. The rack, immersed in the electrolyte bath 19 contained in the tank 20, also has immersed therein the anodes 21, which are connected to the source of positive voltage. Electroplating can then be performed in the usual manner.

The size of the openings 8 is preferably slightly greater than the inside diameter of the annular bodies. The spacing of thesidewalls 2 with respect to the axial length of the annular bodies can be so that a slight positive clearance is provided between the bodies and the sidewalls, to facilitate placement and removal of the annular bodies 4. The sidewalls 2 can be constructed of any suitable nonconducting plastic material. The rack of the invention is particularly well suited for the plating of the internal surface of bushings.

While the invention has been described with respect to particular embodiments thereof, these embodiments are merely representative, and do not serve to define the limits of the invention.

What is claimed is:

1. A rack for holding annular bodies for electroplat ing the inner surface thereof comprising:

(a) a vertically elongated chamber defined by end walls, two sidewalls, and a bottom, and having an open top, a plurality of equal diameter openings at equal vertically spaced intervals in each of said sidewalls, the openings in the two sidewalls being aligned providing a vertical row of spaced pairs of openings, the openings in each pair being coaxial and the axes of said pairs being vertically aligned,

(b) substantially all of the exposed surfaces of said chamber below a level above and adjacent the uppermost pair of openings being non-conducting,

(c) means for suspending said rack in an electroplating bath, and means for making electrical connection to the external surface of annular bodies disposed within said chamber,

(d) the axis of the lowermost pair of openings being spaced from the bottom onehalf the spacing of said axes from each other.

whereby a number of annular bodies equal to the number of pairs of openings and each having an outside diameter equal to the vertical spacing of said openings and of a size to be received in said chamber, can be placed therein one atop the other with each annular body in electrical connection with the annular body next below, with one annular body coaxially disposed with. respect to the axis of each opening pair.

2. A rack for holding annular bodies for electroplating the inner surface thereof comprising:

(a) a vertically elongated chamber defined by end walls, two sidewalls and a bottom, and being open at the top, a plurality of equal diameter openings at equal vertically spaced intervals in each sidewall, the openings in the two sidewalls being aligned providing a vertical row of spaced pairs of openings, the openings in each pair being coaxial and the axes of said pairs being vertically aligned,

(b) exposed surfaces of the end walls and sidewalls being non-conducting below a level above and adjacent the uppermost pair of openings, and a portion of the inner surface of the bottom wall including the portion thereof aligned with the axes of said openings being conducting,

(c) the axis of the lowermost pair of openings being spaced from said exposed surface of the bottom onehalf the spacing of said axes from each other,

(d) means for suspending said rack in an electroplating bath,

(e) means for making electrical connection to said exposed surface of the bottom,

whereby a number of annular bodies equal to the number of pairs of openings and each having an outside diam eter equal to the vertical spacing of said openings and of a size to be received in said chamber, disposed therein one atop the other, with the bottom body in electrical connection with said exposed surface of the bottom and each body in electrical connection with the body next above, 7 with one annular body coaxially disposed with respect to the axis of each opening pair.

3. A rack according to claim 2, said chamber comprising a plurality of vertical rows of spaced pairs of openings, as aforesaid, there being a conducting portion of said bottom wall for each vertical row of opening pairs, the conducting portion for each pair being aligned with the axes of its opening pairs.

4. A rack according to claim 2, the sidewalls being of plastic, the end walls and bottom being formed of metal covered by insulating material, the metal of the bottom being exposed to provide said conducting portion, a suspension arm being connected to the upper portion of said sidewalls, the suspension arm including conducting material, said conducting material being in electrical connection with the metal of the end walls, said means for making electrical connection to said exposed surface including the metal of the end walls and the conducting material of the suspension arm.

5. A rack according to claim 4, the conducting material of the suspension arm being metal, the lower portion of the suspension arm being covered with insulating material, and the upper portion of the suspension arm being exposed to provide the conducting material of the suspension arm for electrical connection thereto.

6. The method of electroplating the internal surface of an annular body which comprises disposing said body coaxially with respect to aligned equal diameter openings in non-conducting side plates positioned one at each end of the body in close fitting engaging relation therewith,

said body and side plates being immersed in an electrolysis bath outfitted with an anode disposed externally of the annular body and cathode connection, electrically conmeeting the outer axially extending surface of the body to the cathode connection, and passing a current through the bath to electroplate said internal surface.

References Cited UNITED STATES PATENTS 258,214 5/1882 Brinckmann 204-297 1,010,638 12/1911 Kitchen 204-297 1,517,631 12/1924 Jones 204-287 HOWARD S. WILLIAMS, Primary Examiner. JOHN H. MACK, Examiner. D. R. JORDAN, Assistant Examiner.