US2319596A - Method of separating electrodeposited layers - Google Patents

Description

May 18, 1943 A, w, GRANT, 2,319,596

METHODOF SEPARATING ELECTRODEPOSITED LAYERS Filed April 3, 1940 INVENTOR. 4/? 7 901? 144 6/?4/1 7' Ma-W ATTORNEY deposited iron from the original pattern.

Patented May 18, 1943 UNITED STATES PATENT OFFICE METHOD OF SEPARATIN G ELECTRO- DEPOSITED LAYERS Arthur W. Grant, Detroit, Micln, assignor to United States Rubber Company, New York, N. Y., a corporation of New Jersey Application April 3, 1940, Serial No. 327,604

2 Claims. This invention relates to electroforming of metals, and, in particular, it relates to the electrodeposition of iron upon a metal or metal coated pattern. More" particularly, the invention relates to the treatment of a pattern prior to electrodeposition, in a manner to provide proper separation of the deposited metal upon completion of the operation.

In many cases in the electrodeposition of iron, it is desirable that minute details be reproduced from the original pattern. This requires high fidelity in the reproduction operation and in the method used to provide separation of the electro- In accordance with my invention, I propose to cover an original metal or metal coated pattern with a layer of copper which layer may be formed thereon by electrodeposition. Over this layer a thin layer of silver is deposited. Thereafter the iron is electrodeposited upon the surface of the silver. In separating the iron from the pattern, the point of separation lies between the silver and copper deposits. In some cases the use of a layer of silver iodide as a separating medium has been practiced, but such material is not applicable to an iron plating solution as the ferrous ion reduces the silver salt to metallic silver and destroys the film. The invention, therefore, contemplates the use of a layer of metallic silver.

Among the objects of my invention are: to provide separating means between a metal or metal coated pattern and an electrodeposited body of iron which may be easily parted'while maintaining minute details and surface finish; to provide a separation layer which will prevent any of the electrolyte from flowing between the surfacesdefining the plane of separation; and, to 'provide a separation layer which may remain on the finished electrodeposited body of iron. These and other objects and advantages will appear more fully in the following detailed description to be considered in connection with the accompanying drawing, in which:

Fig. 1 is a perspective view illustrating an original pattern;

Fig. 2 is a perspective view of the-original pattern illustrating a layer of copper deposited thereon;

Fig. 3 is a perspective view of the original pattern with the layer of copper and a layer of silver deposited thereon;

Fig. 4 is a perspective view of the original pattern, the separation layers, and an electrodeposited body of iron formed against the surface of the deposited layer of silver; and,

Fig. 5 is a perspective view of the original pattern and the deposited iron illustrating the plane of separation between the bodies.

Where the original pattern in an electroforming operation is composed of a material which in itself is not an electrical conductor, various types of conducting paints may be coated on the surface so as to render the pattern capable of receiving an electrod'epositing body of metal. In such cases the conducting paint itself serves as a means to facilitate separation of the deposited metal from the original pattern. A distinguished from this practice, the present invention refers to the use of a pattern which, in itself, supports a conducting surface.

As an example of the practice of my invention,

Fig. 1 illustrates an original metallic pattern or metal coated pattern I which may be of any desired shape consistent with the practicability of providing an electrodeposited bodyof iron therefrom. Such a pattern may represent an original engraved article containing intricate designs. The surface of the pattern from which the electrodeposited body of iron is to be formed is cleaned and a thin layer of copper 2, as shown in Fig. 2, is deposited thereon. This layer of copper should be relatively thin, and it is essential that the copper be electrodeposited thereon, as distinguished from a deposit formed by immersion of 1 the metal pattern in a bath of copper salts. A thin layer of copper is required so that minute details on the pattern will not be substantially varied. Also, application of the copper by elec trodeposition is esential to obtain the proper degree of adhesion between the metal pattern and the deposited copper.

Directly against the copper surface is provided a layer of metallic silver 3, as shown in Fig. 3. This layer of silver is deposited in an immersion operation, that is by displacement, as distinguished from electrodeposition. A typical solution for they silver bath is a solution containing five ounces of silver cyanide per gallon of water.

A silver deposit may be formed by either immersbe electroformed against the layer of metallic silver. During this operation a sufficient degree of adhesion between the copper layer and the silver layer is formed to prevent any of the electrolyte from seeping in between the separation layers. This is an essential requirement, as the presence of any electrolyte between the separation layers will destroy the detail formed in the electrodeposition operation.

Fig. 5 illustrates the method of separating the deposited body of iron from the original metallic pattern. As these-portions are separated the copper layer 2 remains adhered to the metallic pattern I, and the silver layer 3 adheres to the electrodeposited body of iron I. The fact that the metallic silver is not electrolytically deposited on the copper provides that desired degree of adhesion which permits the layers to be subsequently separated. While some form of electronic action takes place in the immersion deposit of the silver, it is to be understood that reference to electrodepositing as disti uished from immersion deposition is intended to signify that extraneous electrical energy is required in the electrodeposition operation, whereas no source of outside electrical energy is utilized in the immersion process.

The layer of silver 3 which remains in adhesion with the electrodeposited body of iron may be retained on the electrodeposited iron as an integral part thereof. As the layer of silver 3 is firmly bonded to the deposited iron, it provides a bright finish on the transferred portion of the deposited iron and also protects the surface from oxidation.

While I have shown a preferred method of practicing the invention, it is to be understood that it may be otherwise practiced, as indicated by the scope of the appended claims.

' an iron matrix which consists in electro-plating the mold surface of the matrix with copper, coating the copper with a thin layer of silver deposited by displacement, electro-depositing a thick layer of iron on the silver and separating the electro-deposited iron with the silver layer from the copper surface.

' ARTHUR W. GRANT.

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