Apparatus for electroplating the interior of an elongated pipe

[57] ABSTRACT

Herein described is an apparatus and a method for plating a uniform thickness of material upon a substrate. The disclosed apparatus and method is particularly adapted for electroplating the inside diameter of a hollow member. A travelling compartment is included with is adapted to traverse the inside of the member to be plated. The compartment has an inlet and an outlet port. A source of electroplating solution includes a first conduit coupled between the source to the inlet port and a second conduit coupled between the source and the outlet port. Means are included for circulating the electroplating solution into the travelling compartment through the first and second conduit. An anode disposed within the compartment is coupled to a source of electrical energy.

Claim, 5 Drawing Figures

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PATENTED JUN 2 7 1972

3,673,073

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ATTORNEY.

3,673,073

APPARATUS FOR ELECTROPLATING THE INTERIOR OF AN ELONGATED PIPE

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to plating apparatus and methods and more particularly, to a novel and improved apparatus and method for the electroplating of the inside of a hollow member such as a tube or pipe, particularly adapted for electroplating long lengths of pipes or tubing which were heretofore difficult, if not impossible, to plate.

2. Discussion of the Prior Art

Prior art methods of plating a substrate with a material has been done by the electroplating method which includes an anode disposed in a solution along with the substrate to be plated. The methods of electroplating are well known to those skilled in the art, and in essence, they are preformed by an electrical energy being transmitted between the anode and the substrate to cause electron flow between the anode and the substrate which deposits electrons from the anode onto the substrate in a uniform manner.

to couple the sealing members together. A source of electrical energy is coupled to the anode. An inlet port is included in at least one of the sealing members and communicates with the compartment. An outlet port is also coupled to one of the seal5 ing members and communicates within the compartment. A source of electrical plating solution is provided and is coupled between the inlet and outlet ports of the compartment by mean of conduits.

In one embodiment shown, means are included before the ^ϋ travelling compartment to wash the inside of the hollow member just prior to the arrival of the travelling compartment. In the embodiment shown, at least one spray nozzle is disposed on one side of the sealing members, and a source of । g washing solution is coupled thereto by a conduit means.

An advantage of the apparatus and process is that a smaller length anode is used which requires less current, and thus less heat is generated. Further, the anode is exactly centered in the pipe substrate for providing uniform thickness of plated 20 material thereon.

DESCRIPTION OF THE DRAWINGS

A problem arises when a steel tube, for example, is to be plated on the inside thereof. For example, should a length of pipe or tubing be required to be plated in a uniform thickness 25 throughout the interior of the pipe, prior art methods include inserting an anode of the same length into the pipe. Next, the anode has to be centered in the tube so as to obtain the same distance between the entire inside surface of the tube and the anode. This is necessary to plate uniform deposits on the inside of the tube. This is only possible if short lengths of tubes are used. If extremely long lengths of tubes are used, the cost of the anode to be used for the plating is sometimes prohibitive, especially on the use of precision anodes such as platinized titanium, which is recommended for nickel plating. Further, difficulties arise in controlling the gas evolution in the temperatures of the solution and the pH when narrow tubing is plated over long lengths. Each of the paramaters above mentioned affects plating uniformity and quality.

Another problem in the prior art plating apparatus and methods is that current densities of the anode decrease rapidly down the tube from each end. Anode current carrying capacity is usually limited because of the diameter and length of the anode in relation to cathode surface area. When the current carrying capacity of the anode is exceeded, the resistance becomes greater, thus generating excess heat. For example, a 1-inch diameter tube, 31.6 inches long, (using ½ inch copper anode the same length with current carrying capacity of 200 amp) plated or etched at 100 amp current density per square foot would require approximately 825 amperes. This being four times the current capacity of the anode, most of the current will dissipate as heat in the pitting solution.

Thus, a need has arisen for a plating process and apparatus which can uniformly plate the inside of a tubular or hollow member at a low cost yet one which can deposit a uniform thickness within the interior of the substrate to be plated. Further, the need for a plating process and apparatus has arisen which does not require long lengthy anodes, so that current requirement can be kept low in order to keep the heat therefrom low.

SUMMARY OF THE INVENTION

Briefly described, the present invention comprises an apparatus and a process for electroplating the inside diameter of 65 a hollow elongated member. The apparatus includes a pair of sealing members which define a compartment therebetween which is adapted to move within the confines of said hollow member. The shape of the sealing members is substantially constructed to mate with the shape of the inside of the hollow 70 member. For example, should the hollow member be a tubular member such as a pipe, then the sealing members would also be round to match that diameter.

An elongated anode is disposed between the sealing members and centered along the center axis thereof and is adapted 75

These and other features and advantages will become more apparent to those skilled in the art when taken into consideration with the following detailed description, wherein like reference numerals indicate like and corresponding parts throughout the several views and wherein:

FIG. 1 is a section view of the travelling compartment in accordance with one embodiment of the present invention;

FIG. 2 is a section view taken along the lines 2—2 of FIG. 3;

FIG. 3 is a section view taken along the lines 3—3 of FIG. 1;

FIG. 4 is a section view taken along the lines 4—4 of FIG. 1; and

FIG. 5 is an enlarged section view of the spray nozzle portion illustrated in FIG. 1.

DESCRIPTION OF ONE PREFERRED EMBODIMENT

Turning now to FIG. 1 there is shown one preferred embodiment of the invention which illustrates a substrate 10, shown in this particular instance as a tubular pipe. It should be understood, though, that the substrate 10 need not be a pipe or any other specific shape but is shown here as a matter of convenience as being tubular.

A pair of sealing members 14 and 16 are shown in this embodiment as discs and have a diameter which matches the diameter of the inside of the pipe 10. An anode 18 is coupled between the discs 14 and 16 and forms a travelling compartment 20. The anode 18 is coupled to the disc 16 by the bolt 22 being threaded onto the anode 18 in a suitable manner. An insulated sleeve 24 is positioned between the disc 16 and the anode 18 to electrically isolate them from one another. The other end of anode 18 is coupled to the disc 14 in a suitable manner and is isolated therefrom by the insulated sleeve 26.

As is shown in FIGS. 1 and 4, a pair of ports 28 and 30 are provided through the disc 16 and communicate into the compartment 20. A hose or conduit 34 is coupled into the port 28 and a hose or conduit 36 is coupled into the port 30. The other end of hose 34 is coupled into a tank 38 and the hose 36 is coupled into the tank 38 through a pump 40. The length of both hoses 34 and 36 is sufficient to enable them to reach from the tank 38 down the entire length of the pipe being plated.

The tank 38 contains the electroplating solution which is pumped by the pump 40 through the inlet port 30 into the compartment 20 and back through hose 34 into the tank 38.

The sealing member 14, as shown in FIG. 3, includes a plurality of spray nozzles 44 thereon evenly disposed around the center axis of the anode 18 but on the outside of the compartment 20. A hose 46 leads into the spray nozzles 44 and has one end coupled to a source of solution which is used to wash the inside of the diameter before the arrival of the travelling compartment 20. The washing method is used to prevent passivation or oxidation. Also coupled through the pipe 46 is a lead

3,673,073 wire 48 electrically insulated from the fluid within the hose 46. The lead 48 is coupled in a suitable manner to a source of electrical energy 50 which is used to energize the anode 18. The other end of the source of electrical energy 50 is coupled directly to the wire 48. While the lead wire 48 to anode 18 is shown as being disposed inside of hose 46, it may just as well be positioned on the outside in any suitable manner.

End seal 52 on sealing member 14 and end seal 54 on sealing member 16 are used to isolate the compartment 20 from the pipe 10 yet allow freedom of movement of the compartment 20.

In operation the compartment 20 is moved along the inside of the pipe 10 in a suitable manner, and if desired, it may be rotated therein to assure the even plating of a uniform thickness onto the inside diameter of the plate 10. It may be desired to rotate the pipe instead of the compartment 10 and thus eliminate the need for universal joints in the various hose and wire connections.

Plating solution from tank 38 is pumped through the hose 36 by means of the pump 40 into the compartment, circulated therethrough, and back through the hose 34 into the solution tank if desired. The compartment is moved by mechanical means through the pipe 10 while plating current is being applied from the source of electrical energy 50 to the anode 18. The inside diameter of the pipe surface external to the compartment is continually washed by the fluid source through the pipe 46 into the nozzles 44 with a suitable solution which prevents the passivation or oxidation of the inside diameter of the pipe.

If specific interest is in nickel plating, for example, the bore of an elongated small diameter pipe or tubing may be plated in the described manner. This method, however, can be used in plating either the ID or OD surfaces of pipes or tubing fabricated from ferrous or nonferrous alloys with many metals such as chromium, silver, zinc, cadmium, etc. The concept can also be used to plate curved as well as straight pipes if the length of the compartment is kept at a minimum length.