US1881714A - Method of electrolytic reproduction - Google Patents

Description

0a. 11, 1932; A. K. LAUKEL rmaon o1 ELECTROLYTIC REPRODUCTION Filed Aug. 8. 1929 ATTORNEY The present invention pertains to the mak- Patented Oct. 11, 1932 ARTHUR K. LAUREL, OF DETROIT, MICHIGAN METHOD OF ELECTROLYTIG'BEPRODUCTION I Application filed August. 8, 1929. Serial No. 384,285.

Although various mean UNITED STATES PATENT orFrca s of metallizing a ing of foundry patterns and core boxes by electrodeposition and particularl to a novel means of metallizing a surface or the electrodeposition of metal thereon, especially in cases where the deposit is to be removed intact. Deposition with a view to removal in this manner may be identified as electroforming as distinguished from electro-plating.

' The principal object of the invention is to provide a satisfactory metallized surface for the production of foundry patterns and core boxes by electrolytic means.

Two general applications of electroforming are contemplated; first, where a duplicate or replica of a given object is to be produced, and second, where a mold or counterpart is to be made froma given object. The first class is in the nature of patterns and the second in the nature of-core boxes, including also 'molds for the shaping of various objects such as rubber products, molded, stone or cement products and imitation wood carvings pressed fromwood pulp composition.

With reference now .to pattern making which is perhaps the most important application of the present process an original pattern in wood or metal is first supplied. A mold of a suitable plastic substance, such as plaster Paris, is poured over the original pattern and allowed to set. It is then dried and rendered resistant to the electrolytic bath, metallized by means disclosed herein, and finally plated until a copper shell of sufficient thickness is ..forme The shell is reinforced by any means such as that disclosed 1 in my co-pending Patent No. 1,792,542 of Feb. 17, 1931, either before or after removal from the mold. 40 Where it is desired to produce an object in the nature of a core box, such as a core box proper or a mold, it is first necessary to provide an object having the configuration of the product to be molded. The object or model is metallized directly, after being ren-- dered resistant to the bath if necessary, plated until the desired thickness of metal is formed, and then separated from the model. Obviously, the deposit may be backed in any de- 59 sired or suitable manner.

surface are known, it has been found to be decidedly diflicult to select one that produces an accurate deposit. It is essential in the interest of an accurate reproduction that the metal shall deposit on all parts of the surface intended to be metallized and shall not readily separate from the metallized surface during-plating. A highly satisfactory means of metallizing the surface, and which constitutes the subject matter of the present invention, consists in applying a solution of a metal to the surface to be plated and'rubbing over the surface a mixture of graphite and a metal dust electropositive to the metal in solution. The accuracy of the reproduction obtained on such a surface is indicated by the fact that metal deposited directly on a wood carving shows the grain of the wood, and this grain is effectively reproduced in wood pulp which is molded by the deposit.

The invention is fully disclosed by way of example in the following (lescri tion and in the accompanying drawing in w ich:

Figure 1 is a plan view of a pattern laid upon a board for the formation of a mold thereover;

Figure 2 is a sectional view showing the mold formed over the pattern;

Figure 3 is a similar section showing the mold removed and metallized;

Figure 4. is a sectional view of an electrolytic'hath showing the mold suspended there- 1n:

Figure 5 is a sectional view of an object metallized directly;

Figure 6 is a sectional view of said object suspended in a bath for the depositing of a mold thereon; and

Figure 7 isa sectional view of the deposit backed up as a mold or die.

Reference to these views will now be had by use of like characters which are employed to designate corresponding parts throughout.

In Figures 1 and 2 is illustrated a pattern 1 which is to be reproduced one or more times. The pattern is laid on a board 2 and surrounded by a wall The exposed surfaces of the board and pattern are oiled, as well as the inner faces of the wall 3, and a I plastic material such as plaster Paris is formed by ,meral 4. a mold which may readily be removed from poured over the pattern to fill the enclosure the wall 3 as ind cated by the nu- When this material sets it forms the contacting members due to the fact that the latter have been oiled.

The mold 4 is now dried and rendered resistant to the electrolytic bath by impregnatty 5 which in with wax, although the body may origina 1y be resistant to the bath or may even be impregnated after metallizing.

The mold is obviously formed with a caviis an impression of the pattern 1.- The surface of the impression is first treated with a solution of a metal such as an organic solution of silver nitrate with sufficient water to permit a reaction with a reducing agent subsequently to be applied.

The organic solvent in this connection is such as to dissolve or penetrate any remaining wax in the surface and permit the solution to reach the bare surfaces. The surface of the impression is now treated with a substance electropositive to the first metal in order to .cause electrolytic precipitation of the first metal. The electropositive substance may be copper dust of about 300 mesh, and in this sprinkling it on the surface of the impression and then brushing off the excess. ,eration is repeated until the surface is seen while the preceding solution is still damp This opto be covered entirely by a metal film, and

three "operations will usually suffice.

used in the solution and as the dust respec tion is such that the The graphite appears to act as a lubricant .or'a vehicle in bringing the metal dust into contact with the first reagent at every point throughout the surfaces, but whatever the action may be, the metallizing is more thorough than if the metal dust alone were used. It

is also to be understood in this connection that other metals than silver and copper maybe tively, so long as their electrochemical rela- I dust displaces the metal of the solution. In Figure 3 the numeral 6 designates the metallized surface.

The cathode thus'prep'ared is then immersed in an electrolytic tank 7 containing a "solution of the metal to be deposited. An

acid copper sulphate bath has been found to yield a very satisfactory deposit. The metal may be deposited directly out of the solution or from an anode 8l of the metal to be deposited, suspended in the bath. Obviously the cathode and anode are connected respectively to the negative and positive sides of the circuit.

A shell 9 of deposited metal forms within the cavity 5 on the metallized surface 6 and constitutes an accurate dimensional reproduction of the original pattern '1. This shell may then be filled with a suitable material and mounted on a plate so that it may be used as a pattern.

Where a mold is to be deposited, a model.

the configuration of the produce of such a mold is first provided. The model may be, for example, a wood carving 10 which is mounted on a board 11 for convenience in handling, plays no part in the present invention. If the model is not already resistant to the bath it is rendered resistant by preferably soaking in wax at to C. for one half to one hour. The excess wax is wiped off the surface on which deposition is to take place and these surfaces are next metallized to form a conductive film 12 in the manner already described.

The model is then immersed in the bath 13 preferably after being mounted on another board 14 to the lower edge of which is attached a weight 15 for the purpose of holding the board in a vertical position. This bath is similar to that described in connection with Figure 4. The passage of current through the bath forms a deposit 16, the interior of which reproduces all the detail of the plated surface of the model 10. The

or sample having deposit, after reaching a suflicient thickness,

is separated from the model, and after being properly backed and supported as by means of metal 17 cast over the deposit, may be used as a mold for forming-objects of'the same configuration as the mo inner surface of the deposit is a highly accurate reproduction, in converse form, of the surface which has been metallized. In the case of depositing upon wood carvings, for example, it has been found that the deposit shows even the .grain of the wood, which inturn is reproduced in the material molded in the deposit.

The deposit 16 is in the nature of a core box and illustrates the method of forming a core box wherein the molding surfaces consist of deposited metal. In such case the model 10 would be a body having the configuration of the core to be made in the core box. The deposit would naturally be backed and supported for core box use, as shown herein or as disclosed, for example, in my erg-pending Patent No. 1,7 92,542 of Feb. 17, 1 31.

As a modification of the manner of metallizing, I may first treat the object with a solvent for the wax or other material on the surface of the body, thus bearing the surface forthe application of the conductive coating. The surface is then thoroughly although the board del 10. The T rubbed with the copper-graphite mixture and finally treated with silver nitrate in a solvent adapted to wet the surface, or in other words, dissolve the remaining surface impregnant not taken up by the first solvent.

In either method, however, it will be seen that the surface is first bared preparatory to receiving the conductive coating formed by the reaction of copper with silver nitrate. In this sense, the solvent of the silver nitrate may be described as surface-penetrating.

Although the invention has been developed with the principal object of making patterns and'core boxes by electrolytic reproduction, it is also useful in the direct reproduction of other objects by depositing upon a mold of such an object and in the formation of molds for various objects by depositing directly upon such objects.

What I claim is I 1. The method of metallizing an object consisting in baring the surface of the object, applying thereto a solution of a metal, and brushing. while the solution persists, with a mixture of graphite and a metallic dust electropositive to the first named metal.

2. The method of metallizing an object consisting in applying thereto a surface-penetrating solution of a metal, and brushing, While the solution persists, with a mixture of graphite and a metallic dust electropositive to the first named metal.

3. The method of metallizing an object consisting in applying thereto a surface-pence trating solution of a metal, and brushing, while the solution persists, with a mixture of thirty per cent to seventy per cent graphite and seventy per cent to thirty per cent of a metallic dust electropositive to the first named metal. 7

4. The method of metallizing an object consisting in impregnating the same with wax, wiping ofl the excess wax from the surface to be metallized, applying to said surface a wax dissolving and slightly aqueous solution of a metal, and brushing, while the solution persists, with a mixture of graphite and a metallic dust electropositive to the first n amed meta 5. The method of metallizing an object consisting in baring the surface of the object, applying thereto a slightly aqueous solution of silver nitrate, and brushing, while the solution persists, with a mixture of graphite and a metallic dust electropositive to silver.

6. The method of metallizing an object consisting in applying thereto a surface-penetrating and slightly aqueous solution of a reducible silver salt, and brushing, while the solution persists, with a mixture of graphite and copper dust.

' 7. The method of metallizing an object consisting in impregnating the same with Wax, wiping off theexcess wax from the surface to be metallized, applying to said surface a wax-dissolving and slightly aqueous solution

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