US1870958A - Apparatus for metal plating - Google Patents

Description

Aug. 9, 1932. K. c. MONROE APPARATUS FOR METAL PLATI-NG Filed March 29, 1929 Patented Aug. .9, 1932 UNITED STATES PATENT OFFICE KENNETH C. MONROE, F BRIDGEPORT, CONNECTICUT, ASSIGNOR TO BRIDGEPORT BRASS COMPANY, OF BBIDGEPORT, CONNECTICUT APPARATUS FOR METAL PLATIN G Application filed March 29, 1929. Serial No. 350,994.

This invention relates to apparatus for metal plating, and more particularly for the electro-deposition of such metals as chromium or the like, from the solutions of their salts or acids.

The electrodeposition of chromium, for example, has been carried on for some time from chromic acid baths, and while it has been determined that a satisfactory and lasting deposit may be formed in this manner, it has likewise been determined that satisfactory results are more frequently obtained when careful control is exercised in the composition of the solution, the temperature of the bath and the voltage between the anode and the cathode. I contemplate bythis invention, a method and apparatus whereby a more exact control may be exercised over the current voltage within the solution or between the anode and cathode.

It will be appreciated that when chromium or other metal plating is carried on commercially relatively large tanks are used to contain the solution. In the usual form where the current enters the bus bars, or the current carrying members suspended over the tank, at one end of the tank, the amount of metal in the circuit is considerably varied depending upon the position in the tank ofthe articles to be plated. The same is true even if the current enters the bars at one end of the tank and leavesat the other end, if the cross section of these bars is not properly determined. It will, of course, be obvious that if there is more metal in the circuit at some times than at others, there 'will be a greater voltage drop within the line, and hence a smaller voltage drop within the solution or between the anode and cathode, even though the voltage of the supply of current is maintained at a constant value.

By the present invention, I contemplate so arranging the anode and cathode bars that regardless of the point in the tank at which the articles are suspended, there will be the Another object of the invention is the provision of an apparatus for metal plating, such that the voltage drop between the racks upon which the work is hung may be kept constant.

To these and other ends, the invention consists in the novel features and combinations of parts to be hereinafter described and claimed.

In the accompanying drawing:

Fig. 1 is a top plan view, partly in diagrammatic form, of an apparatus for the electrodeposition of metal;

Fig. 2 is an end view of the electroplating tank and the leads from the source of current;

Fig. 3 is a sectional view through the tank on line 33 of Fig. 1.

To illustrate a preferred embodiment of my invention, I have shown in a diagrammatic way, a direct current generator at 10, having lead wires 11 and 12, carrying the current to the anode and cathode bars 13 and 14. A voltage regulator 15 is placed across the service lines 11 and 12, and is preferably connected thereto as near as possible to the tank itself, so as to maintain, as nearly as possible, a constant voltage passing to the bus- bars 13 and 14 across the tank.

As shown in the drawing, I employ three of the anode bars 13 and two of the cathode bars 14, although this number may, of course, be varied as conditions may require. Each of these bars is connected with the proper service line 11 or 12, by means of relatively thin wide conductors 16, which pass around the anode and the cathode bars 13 and 14, and after rising perpendicularly to the proper height are carried horizontally as at 17 to have their ends embrace relatively heavy conductors 18, which in turn are oined fiatwise together to comprise the leads 11 and 12. These thin wide conducting strips 16 and 17 are sufiiciently flexible to permit the shifting of the anode and cathode bars towork 21 to be plated, and likewise, to make good contact with the racks which carry the anodes 22. These bars are preferably of copper although any good conducting metal may be used, and I prefer to use lead for the anodes 22.. It will also be noted that the risers 16 are connected to the anode bars adj acent one end of the tank, and to the cathode bars adjacent the opposite end of the tank.

As previously stated, I employ in the form of my invention shown in the drawing, three anode bars and two cathode bars. It will be apparent that if these bars were allof the same size and the work were suspended adjacent one end of the tank, for instance adjacent the left-hand'end, as shown in Fig. 1, a relatively great length of the anode bars would be employed in the circuit and a relatively short length of the cathode bars, while the reverse would be true if the work were suspended at the other end of the tank. As there are a greater number of vanode-bars this would result in there being more metal employed in the circuit when a greater length of the anode bars are used (provided, of course, that the bars were of the same size in cross section), and, therefore, the voltage drop between the anode and cathode in one case would be less than in the other.

To overcome this variation and to provide for a constant voltage between the anodes and cathodes, regardless of where the Work is hung, 1 so determine the cross sectional size of the anode and cathode bars that the sum of the cross sectional area of the anodes will be equal to the sum of the cross sectional area of the cathodes. For instance, in the present case where three anode and two cathode bars are employed, the cross section of each anode bar is two-thirds thecross section of a cath-.

ode bar. By having one more anode bar than cathode bars I am able to have an anode bar on each side of each cathode bar, and thus secure more uniform results and more 'even distribution of the chemical action which takes place.

While I do not wish to be limited to exact dimensions, for the purpose of fully illustrating my invention I have obtained very satisfactory results from using anode bars of rectangular shape in cross section and one and one-half inches wide and two inches thick, and using cathode bars one and onehalf inches wide and three inches thick. I may also carry out this principle through the rest of the circuit by employing for the risers 16, and horizontal portions 17, which lead from the anode bars, copper strips six inches wide and one-quarter inch in thickness, while therisers 16 and horizontal extensions 17 leading from the cathode bars may be six inches wide and three-eighths inch thick. In like manner, the conductors 18 from the anode bars may be-six inches wide and onehalf inch in thickness, while the members 18 sults in the electrodeposition of metals, such i as chromium, for example, it will be apparent that improved results will be obtained by the use of my improved method and apparatus;

While I have shown and described a pre- -ferred embodiment of my invention, it is to be understood that the same is not to be limited to the exact details shown and described, but is capable of modification and variation within the spirit of the invention and within the scope of the appended claims.

What I claim is:

1. Apparatus for the electrodeposition of metal from solution, comprising a source of current, a container for the solution, anode and cathode bars supported adjacent the container which in-turn support the anodes and the work, means to conduct current from the source to said bars, the cross sectional area of the anode bars being substantially equalto that oi the cathode bars, and the ends of said anode bars connected to the source of current belng remote from the ends of the cathode bars connected to the source of current, the number of anode bars being unequal to thatof the cathode bars, and said bars being alternately placed.

2. Apparatus for the electrodepositiom of metal from solution, comprising a container for the solution, anode and cathode bars supported above the container with a cathode bar between each two adjacent anode bars, a source of current, conductors leading from said source to one end of the anode bars, conductors leading from said source tothe re mote ends of the cathode bars, said bars being disposed in overlapping relation, the number of anode bars being greater than that of the cathode bars and the aggregate conductivity of the anode bars being equal to that of the cathode bars.

3. Apparatus for the electrodeposition of metal from solution, comprising a series of anode bars and a series of an unequal number of cathode bars arranged in overlapping relation with a cathode bar between each two adjacent anode bars, a source of current connected to the adjacent ends of the anode bars and connected to the ends of the cathode bars remote from the anode connection, and'the aggregate cross-sectional area of the anode bars being substantially equal to the aggregate cross sectional area of the cathode bars.

' tainer, and connections from said members I 4; Apparatus for 'electrodeposition of metal from solution, comprising a container for the solution, anode and cathode bars supported in, parallel relation above the container, a source of current, connections from said source of current to the anode and cathode bars, said connections including leads from the source of current and relatively wide, thin, flexible conducting strips connected to the anode and cathode. bars and extending upwardly to said leads whereby the positions of the anode and cathode-bars may be laterally adjusted relatively to the container by flexing said conducting stri s.

5. Apparatus for -electrodliposition of metal from solution, comprising a container for the solution, an anode circuit comprising anode members supported adjacent the conto a source of current, a cathode circuit comprising cathode members adjacent the con tainer, and connections from said members to the source of current, said connections being at one end of the anode bars and at the opposite end of the cathode bars, said anode connections having a conductivity equal to that-

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