US3849277A

US3849277A - Electroplating and conveying apparatus featuring rotation of articles to be plated relative to cathode member

Info

Publication number: US3849277A
Application number: US00369757A
Authority: US
Inventors: A Miyata; A Suzuki; H Okubo; C Tomita
Original assignee: Nippon Kokan Ltd
Current assignee: JFE Engineering Corp
Priority date: 1970-01-30
Filing date: 1973-06-13
Publication date: 1974-11-19
Anticipated expiration: 1991-11-19

Abstract

Apparatus for electroplating a plurality of articles such as bolts, nuts, rivets, machine screws, and the like, in a molten salt bath wherein the articles are located in a spaced relationship on a cathode member in the bath. The articles are in line or face electrical contact with the cathode member and are caused to rotate on the cathode member. Preferably, relative movement is imparted between the cathode member and a holding means for the articles to cause the rotation of the articles relative to the cathode member.

Description

[451 Nov. 19, 1974 ELECTROPLATING AND CONVEYING APPARATUS FEATURING ROTATION OF ARTICLES TO BE PLATED RELATIVE TO CATHODE MEMBER Inventors: Akira Miyata; Hideyo Okubo;

Chikayoshi Tomita; Akio Suzuki, all of Kawasaki, Japan Nippon Kokan Kabushiki Kaisha, Tokyo, Japan Filed: June 13, 1973 Appl. No.: 369,757

Related Application Data Division of Ser. No. 83,714, Oct. 26, 1970, Pat. No. 3,740,323.

Assignee:

Foreign Application Priority Data [56] References Cited UNITED STATES PATENTS 1,079,427 11/1913 Murphy 204/202 1,243,098 10/1917 Potthoff.... 204/202 1,819,603 8/1931 Hughesw; 204/203 I 2,591,042 4/1952 Berman et a1. 204/202 Primary Examiner-John H. Mack Assistant Examiner-W. 1. Solomon Attorney, Agent, or FirmFlynn & Frishauf [57] ABSTRACT Apparatus for electroplating a plurality'of articles such as bolts, nuts, rivets, machine screws, and the like, in a molten salt bath wherein the articles are located in a spaced relationship on a cathode member in the bath. The articles .are in lineor face electrical Jan. 30, 1970 Japan 45-7967 onta t with the cathode member and are caused to rotate on the cathode member. Preferably, relative US- Cl 204/2 movement is imparted between the cathode member 204/225 and a holding means for the articles to cause the rota- Int. Cl 865g {ion of the articles relative to the cathode membep Field of Search 204/25, 202, 203, 204,

2O4/2O5 39 225 11 Claims, 13 Drawing Figures U 1 16 111 6 n e 54 a Q 54 53.

: T. -:EL I 0 T j 59 1 a v 52 [@Ks @56 5O 56 1 57 Q.

PATENIE :aa'v 1 91974 SHEET 2 [IF 4 WOC RELATED INVENTION This is a division of US. Pat. application Ser. No. 83,714, filed Oct. 26, 1970, now US. Pat. No. 3,740,323 issued on June 19, 1973.

FIELD OF INVENTION This application relates to apparatus for electroplating a plurality of articles.

BACKGROUND OF INVENTION Conventionally, a method called the Barrel Plating Method has been very often used for electroplating a number of bolts, nuts, rivets, machine screws and the like. However, there are several disadvantages present in this method. Only a limited number of point-contacts can be obtained between the above-mentioned pieces and between the pieces and the cathode, so that the electric resistance becomes too high to assure uniform cathode current to the whole of the pieces to be coated in a barrel or basket and consequently to obtain asufficient current for electroplating. As the cathode current flows through the point-contacts of high electrical resistance, the remote parts of pieces farther from the cathode becomes anodic, and the electrodeposited metals tend to be dissolved, discolored and nonuniform in such parts of the pieces These phenomena take place on numerous contact points of pieces to be coated caused by the rotations of the barrel, so that many small defects can be scattered over the coating layers provided according to this method. These disadvantages can be especially pronounced in the molten salt electroplating treatment.

The present invention relates to an improved apparatus for electroplating, in a molten salt bath, a plurality of bolts, nuts, rivets, machine screws and the like made of metals such as iron, steel, titanium alloys, etc., and provides good and beautiful smooth coatings on the surfaces of the pieces to be plated.

The present invention was conceivedand developed in light of the above-mentioned background. Therefore, the object of the present invention is to prevent all the pieces to be coated from coming in pointcontact with the cathodesupplying an electroplating current, and to make the pieces in line or face contact directly with the cathode so as to be able to lower the excess current-density in the contacted parts of the piece and to easily supply an electroplating current to the pieces to be coated.

SUMMARY OF THE INVENTION According to the present invention, a molten salt electroplating apparatus includes an electroplating bath, a cathode belt means adapted to receive articles to be plated thereon, a fastener belt means having a plurality of spaced projections, the projections being of speed, means for moving, the fastener belt means through the electroplating bath in the same direction as.

that of the cathode belt means and at a rate-of speed different from the predetermined rate of speed of movement of the cathode belt means, and means for applying direct current to both the cathode belt means and the fastener belt means. The articles to be coated are rotated relative to the cathode belt means and relative to the fastener belt means by the movement of said cathode belt means and fastener belt means at the different rates of speed, to thereby uniformly plate the articles as they are fed through the electroplating bath.

According to another feature of the invention. the bolts, nuts and the like are aligned with equal spaces therebetween and are woven into a kind of plain fabric with a plurality of cathode wires which are drawn through the bath. During movement through the bath, the cathode wires are moved relative to each other to place the pieces in rotation and movement in the plating bath.

According to still another feature of the invention, the apparatus contains, in a plating bath, an anode rod hanging and being freely movable up and down, a cathode belt, a fastener belt supporting and carrying a plurality of pieces to be coated on the cathode belt so that the pieces can be rotated freely and in contact with the cathode belt, driving rollers and guide. rollers for the cathode and fastener belts, and a shoe placed between two sets of the guide rollers. v

Especially in the case of electroplating bolts, it is advantageous to place the bolt shank in line-contact with the cathode. Additionally, to obtain a uniform coating on the whole surface of a bolt shank, it is desirable to rotate the bolt on the cathode by moving the cathode. or by moving both the bolt and the cathode so as to assure a face contact of the whole surface of the bolt shank with the cathode.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 show an electroplating apparatus ac cording to the present invention having a fixed cathode;

FIGS. 3 and 4 show an electroplating apparatus according to the present invention having a movable cathode;

FIGS. S'and v6 show an electroplating apparatus according to the present invention having a belt cathode;

FIGS. 7(a) and 7(b) are an enlarged plan and an oblique perspective of the cathode and fastener belts as shown in FIGS. 5 and 6;

FIGS. 8 and 9 show an electroplating apparatus for nuts and the like according to the present invention;

Example FIGS. 10(a) and 10(b) are plane and side elevations showing the contact of bolts with cathode wires which weave their way between bolts; and

FIG. 11 shows a modified portion of the apparatus of FIGS. 8 and 9.

DETAILED DESCRIPTION OF THE DRAWINGS EXAMPLE 1 1.2 kg of molten salt comprising 60 mol% of anhydrous aluminum chloride, 25 mol% of sodium chloride and 15 mol% of potassium chloride was put in a cylindrical glass receptacle and heated from the exterior so as to maintain the temperature of the salt at C. In

this bath was soaked an electrode holder which supports an aluminium plate as the cathode plate, 1 mm in thickness, 15 mm in width and 80 mm in length, and two aluminium wires as anodes, 3 mm in diameter and 80 mm in length, placed at a height of 80 mm from the cathode plate.

Five flush head screws (of titanium alloy) to be coated for use in aircraft, having a shank 7 mm in diameter and 34 mm in total length, were cleaned, soaked in the plating bath with the shanks of screws mounted on the cathode plate, partitioned from one another by a glass holder and then electroplated on turning the screws on the cathode plate by moving the glass holder back and forth.

The treatment of aluminium electroplating was executed by supplying a DC current of 1 volt and 2 amperes between the cathode and the anode for 30 minutes, and moving the glass holder by 20 mm right and .left at a rate of two reciprocations per minute so as to assure slow rotation of the screws to be coated. As a result, uniform and smooth aluminium coatings of 10 microns in thickness were obtained on the whole surfaces of the screws.

The above example can be carried out by using an apparatus as shown in FIGS. 1 and 2. FIG. 2 is a sectional elevation of the apparatus according to the present invention cut on the line II II in the FIG. 1.

An electroplating tank 10 contains a plating bath 11 in which an aluminium anode rod 12, a cathode plate 13 and a glass holder 14 are submerged. The bolts 15 to be coated are aligned on the cathode plate 13,

spaced and separated by the glass holder 14 from each other, so that the bolt shanks can be in line-contact with the cathode plate. Two guiding rods of glass 16 are also used to prevent the bolts from spilling out of the holder 14. If the glass holder 14 is moved right and left in the directions of the arrows shown in FIG. 1, the bolt shanks can be easily made to be in face-contact with the cathode plate. The cathode plate 13 described in this example in connection with the embodiment shown in FIG. 1 is fixed, but it can be movable, as in Example 2, which is explained below. The moving means 17 may be a motor driven mechanism or the like. Its construction should be apparent to those skilled in the art and is not shown in detail herein for the sake of clarity.

Example 2" The treatment of molten salt aluminium-electroplating was applied to hexagon-headed bolts of high tension steel having a shank 9 mm in diameter and 54 mm in total length. The composition of the molten salt and the temperature of electroplating in use were the same as in Example I.

This time, the treatment of electroplating bolts was effected by placing the bolts in fixed position on the cathode plate so that the bolt shank can be in linecontact with the cathode plate, and moving the cathode plate with the holder kept at rest so as to assure rotation of the bolts. The anode was a pure aluminium rod and the cathode plate was an aluminium plate. The holder can be made of Teflon (polytetraflu' oroethylene), glass, porcelain or other heat and corrosion resisting electrically insulating materials.

Twenty hexagon-headed bolts of steel and of the above-mentioned dimensions were put in this apparatus, and electroplated for 30 minutes at 1 volt and 5 amperes of current on moving the cathode plate by about mm to the right and left at a low velocity of 3 reciprocations per minute. As a result, uniform, smooth, white and beautiful aluminium coatings of about 8 microns in thickness were obtained on the whole surfaces of bolts.

This example can be carried out by an apparatus as shown in FIGS. 3 and 4. FIG. 4 is a sectional elevation of the apparatus cut on the line III III in FIG. 3. In FIGS. 3 and 4, elements corresponding to those shown in FIGS. 1 and 2 are referred to with the same reference numerals. I

In FIGS. 3 and 4, a plurality of bolts 15 to be coated are placed in alignment one by one between a plurality of equally spaced bolt holders 31 which are fixed to horizontally extending member B. Members 31, B com prise holder 17 which is spaced from cathode plate 30. The bolts are rotated by an according to the movement of the movable cathode plate 30 which is moved in the directions of the arrows in FIG. 3. A space A is provided between holder 17 and cathode plate 30 to allow for horizontal movement of cathode plate 30.

Example 3 In the case of electroplating a number of bolts and the like continuously, the bolts to be coated are placed bridging over the two parallel belt holders running at the same speed, and these belts are passed through the plating bath. lnthe plating bath, the bolts with their shanks in line-contact with the cathode plate are electroplated on turning on the cathode plate (that is, in face-contact with it) according to the movement of the belt holders, and carried out of the bath one by one by the belt holders after treatment for the desired period of time.

An apparatus for thus electroplating bolts and the like continuously is shown in FIG. 5. FIG. 6 is a sectional elevation of the apparatus cut on the line VI VI in FIG. 5. FIG. 7(a) is a partial plan of the belts and FIG. 7(b) is an oblique perspective of the parts of the belts. In these Figures, an electroplating tank or vessel contains an electroplating bath 51 and an anode rod 52 which can be adjusted to be placed at an appropriate position in the tank or vessel 50. A cathode belt 53 to be in contact with the pieces to be coated and a fastener belt 54 moving on the cathode belt 53 are passed through the plating bath, driven and guided by two sets of driving rollers 55 and two sets of guide rollers 56. A shoe 57 is placed between the two sets of guide rollers 56. The driving rollers 55, the guide rollers 56 and the shoe 57 are mounted on and between two porcelain plates 58in the bath 51, as shown in FIG. 6. The porcelain plates 58 are supported by-supporting structures 59 (FIG. 5). The fastener belt 54 is located over the cathode belt 53 as shown in FIGS. 7(a) and 7(b). The fastener belt 54 is in the overall sectional form of a channel with side extensions, for example, and has a plurality of slits defined by members 61 wide enough for the bolts 60 to be able to turn freely and to be spaced from each other in the longitudinal direction of the belt. The bolts 60 are inserted between adjacent ones of the slit forming members or projections 61, in contact with a surface of the cathode belt 53 which is engaged with the fastener belt 54 in the tank 50. This causes the bolts 60 to turn mechanically as the fastener belt 54 moves on the shoe 57 in the plating bath 51, and be made in line-contact with the cathode belt 53so as to provide uniform coatings on the whole surfaces of bolts.'ln this case, of course, the cathode belt 53 is movable with a different velocity than that of the fastener belt 54 and the velocity thereof is freely regulatable. Sets of bolt holders 62 are fixed erectly upon the surface ofthe fastener belt 54 in correspondence with the width of slits so as to prevent the bolts 60 from slipping out of the cathode belt.

The belts are effectively made of strong materials which can be corrosion resistant to the bath and which do not adversely effect the electroplating process. For

example, in case of a molten salt aluminium electroplating process, materials such as thin aluminium plate, thin steel plate, Teflon (polytetrafluoroethylene), Teflon (polytetrafluoroethylene) strengthened with glass cloth, etc., can be suitable for the belts. The bolt holder can be made of glass, Teflon (polytetrafluoroethylene) or wires coated with Teflon (polytetrafluoroethylene). The bolt holders 62 can be fixed erectly on the surface of the fastener belt 54 by any type of means which is suitable for the belts.

In a typical example, a molten salt composed of 60 mol% of anhydrous aluminium chloride, 25 mol% of sodium chloride and mol% of potassium chloride was put in the electroplating tank as shown in FIG. 5 and maintained at 160C.

The belts as shown in FIGS. 7(a) and 7(b) were made ofa composition of aluminium plates (0.5 mm in thickness) and glass rods (3 mm in diameter). Flush head steel screws 60 to be coated (having shanks of 7 mm in diameter and 34 mm in total length) were inserted between the cathode belt and the fastener belt with a 12 mm spacing between the screws, and electroplated at a belt speed of 45 mm per minute, with a plating voltage of 3.5 V and a current of 60 A. As a result, about four counter-sunk screws with smooth and uniform aluminium coatings of 9 microns in thickness were obtained continuously each minute.

Example 4 In the following description, the process of electroplating a plurality of nuts is detailed. This example can be carried out by an apparatus as shown in FIGS. 8, 9 and 11. The nuts 70 to be coated were hexagon nuts of steel, about 8 mm in diameter. It is desirable in the case of nuts to provide sufficient coatings both on the outside surface and on the tapped inside surface of each nut. In order to obtain such coatings, the nuts 70 may be rotatable between small protrusions 71 provided on the surface ofthe cathode plate 72, and some auxiliary anodes 74 (for example, aluminium wires of 3 mm in diameter) may be inserted into the tapped holes 73 of the nuts 70 to cause rotation of the nuts and to be utilized for electroplating the threaded holes 73 themselves. Rotation of the nuts is caused by sidewise reciprocal motion of the auxiliary anodes 74 in the direction of the arrows in FIG. 8. As shown in FIG. 11 auxiliary anodes 74 of aluminium wire, 3 mm in diameter, may be covered with Teflon (polytetrafloroethylene) tubes 75 (6 mm in outside diameter and 5 mm in inside diameter) having a number of pores 81 (2 mm in diameter),

to thereby prevent the anodes from being in direct contact with the nuts 70, but not to prevent the anode current from passing through the anodes. The auxiliary anodes 74 covered with Teflon (polytetrafluoroethylene) tubes 75 are passed through a plurality of nuts 70 and a plurality of glass spacers 76 alternately aligned (FIG. 9). An anode 77 is used to electroplate the outside surfaces of nuts 70.

In using such an apparatus and the molten salt electroplating bath of the same composition as used in Example eight hexagon steel nuts (4 X 2 lines), 8 mm in diameter, were subjected to a aluminium electroplating treatment. After 30 minutes of operation with 2.5 2.7 A. of current to electroplate the outside surfaces of the nuts'and 0.8 A of current to electroplate the inside threaded surfaces of the nuts, aluminium coatings of excellent appearance and about 9 microns in thickness could be obtained on the outside and inside surfaces of the nuts.

Example 5 An example of an embodiment according to the present invention using cathode wires (for example, flat aluminium wires) instead of the cathode plate so as to electroplate a plurality of bolts is detailed in the following description with reference to FIGS. 10(a) and 10(b). Before putting the bolts in the plating bath, the

bolts 81 are woven into a kind of plain fabric with a plurality of cathode wires 80, as shown in FIGS. 10(a) and 10(b). The plain fabric of bolts and cathode wires is moved in an electroplating bath by means of rollers and the like. In this case, if a plurality of cathode wires are moved in the alternately opposed directions as shown by the arrows in FIG. 10(a), the bolts 81 can turn according to the movements of the cathode wires 80, so as to provide uniform and smooth coatings on the.

whole surfaces of bolts.

1n the examples described hereinbefore and in the accompanying drawings, all the bolts and the like are shown aligned on the cathode with heads in the same direction, but the present invention need not, of course, be limited to this arrangement.

As it has been above-described, the apparatus according to the present invention permits, in the molten salt electroplating process, the surfaces of pieces to be coated to come in line or face-contact with the cathode so that the cathode current can be supplied sufficiently to the pieces to be coated and that the whole surface of the pieces to be coated can be provided with uniform and beautiful coatings. Therefore, the apparatus according to the'present invention is suitable for electroplating pieces that require high precision (for example, screws and the like for aircraft), and is very advantageous in industry, because the present invention can assure an effective electroplating treatment of a number of bolts, nuts, rivets, machine screws and thelike continuously. The present apparatus is also suitable for electroplating a multitude of types of articles other than bolts, nuts, etc.

The present invention can. of course, be applied also to conventional electroplating treatments instead of to the conventional Barrel Plating Process.

Various modifications and alterations canbe made to the illustrated embodiments within the spirit of the present invention as defined in the appended claims.

We claim:

I. A molten salt electroplating apparatus comprising:

a vessel adapted to contain molten salt electroplating bath;

cathode belt means adapted to receive articles to be plated thereon; Y

a fastener belt means adjacent said cathode belt means and having a plurality of spaced projections thereon, said projections extending above said cathode belt and being adapted to receive the articles to be plated therebetween and to maintain the articles'on the cathode belt means in a predetermined spaced apart relationship with said articles in electrical contact with said cathode belt means;

means for moving said cathode belt means through said electroplating bath at a first rate of speed;

means for moving said fastener belt means through said electroplating bath in the same direction as that of said cathode belt means and a second rate of speed different from said first rate of speed of movement of said cathode belt means so that the articles to be coated are rotated relative to said cathode belt means and relative to said fastener belt means by said movement of said cathode belt means and said fastener belt means through said electroplating bath at said different rates of speed, to thereby uniformly plate said articles as they are fed through said electroplating bath; and

means for applying direct current to both the cathode belt means and said fastener belt means.

2. Apparatus according to claim 1 wherein said fastener belt is engaged with said cathode belt, said belts being relatively movable with respect to each other.

3. Apparatus according to claim 1 wherein said cathode belt means is below said fastener belt means'in said electroplating bath.

4. Apparatus according to claim 3 wherein said projections of said fastener belt means extend above the upper surface of said cathode belt means.

5. Apparatus according to claim 3 wherein said fastener belt means has a longitudinal recess therein, and said cathode belt is received in said recess.

6. Apparatus according to claim 1 comprising an anode member in said electroplating bath, said anode member being movable in an up and down direction relative to said electroplating bath.

7. Apparatus according to claim 5 wherein said anode member is an anode rod.

8. Apparatus according to claim 1 wherein said projections of said fastener belt means includes first projections maintaining said articles in said spaced apart relationship on said cathode belt means and second projections to retain the article in position in the transverse direction of said fastener and cathode belt means.

9. Apparatus according to claim 8 wherein said second projections are located between first projections in the longitudinal direction of said fastener belt means.

belt means with said shoe means for guiding and sup porting said cathode belt means.

Claims

1. A molten salt electroplating apparatus comprising: a vessel adapted to contain molten salt electroplating bath; cathode belt means adapted to receive articles to be plated thereon; a fastener belt means adjacent said cathode belt means and having a plurality of spaced projections thereon, said projections extending above said cathode belt and being adapted to receive the articles to be plated therebetween and to maintain the articles on the cathode belt means in a predetermined spaced apart relationship with said articles in electrical contact with said cathode belt means; means for moving said cathode belt means through said electroplating bath at a first rate of speed; means for moving said fastener belt means through said electroplating bath in the same direction as that of said cathode belt means and a second rate of speed different from said first rate of speed of movement of said cathode belt means so that the articles to be coated are rotated relative to said cathode belt means and relative to said fastener belt means by said movement of said cathode belt means and said fastener belt means through said electroplating bath at said different rates of speed, to thereby uniformly plate said articles as they are fed through said electroplating bath; and means for applying direct current to both the cathode belt means and said fastener belt means.

3. Apparatus according to claim 1 wherein said cathode belt means is below said fastener belt means in said electroplating bath.

7. Apparatus according to claim 5 wherein said anode member is an anode rod.

10. Apparatus according to claim 1 comprising shoe means below said fastener belt means and said cathode belt means for supporting said fastener and cathode belt means during movement thereof through said electroplating bath.

11. ApparatUs according to claim 10 wherein said cathode belt means is below said fastener means and comprising means for slidably engaging said cathode belt means with said shoe means for guiding and supporting said cathode belt means.