US1219466A - Method of manufacturing metal articles by deposit. - Google Patents

Description

H. C. KIRK, JR. & G. H. DUMLER. METHOD OF MANUFACTURING METAL ARTICLES BY DEPOSIT. APPLICATION FILED JUNE 3.1915.

1,21 9,466. Patented Mar. 20, 1917.

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H. c. KIRK, JR- & e. H. DUMLER.

METHOD OF MANUFACTURING METAL ARTICLES BY DEPOSIT.

APPLICATION FILED JUNE 3,1915.

1,219,466. Patented Mar. 20, 1917.

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HENRY C. KIRK, JR, OF ROLAND PARK, AND GEORGE H. DUMLER, 0F BALTIMORE, MARYLAND.

METHOD OF MANUFACTURING METAL ARTICLES BY DEPOSIT.

Specification of Letters Patent.

Patented Mar. 2%, 1917.

Application filed June 3, 1915. Serial No. 31,816.

To all whom it may concern:

Be it known that we, HENRY C. KIRK, J r., and GEORGE H. DUMLER, citizens of the United States of America, the former residing at Roland Park, Baltimore county, Maryland, and the latter in the city of Baltimore, State of Maryland, have invented certain new and useful Improvements in Methods of Manufacturing Metal Articles by Deposit, of which the following is a Specification.

Various methods of coating the baser metals with silver deposited from solution are extremely old and the art of silver-plating is in such general use that it is familiar in a greater orless degree to almost everybody.

The present invention is similar to the silver-plating art in, and only in that it is dependent upon the deposit of silver or other precious metals from solution. While the art of silver-plating is, as we have stated,- highly developed and generally known, the art of manufacturing solid silver articles by deposit of silver from solution has never in the past been so developed as to make it possible to get commercial results in the manufacture of hollow ware and particularly in the manufacture of under-cut forms or designs, meaning patterns which, to use a foundry term, will not draw.

In addition to the difiiculty encountered in making ware of under-cut design, it has in the past been'found impossible to make hollow ware of anything approaching uniform thickness by deposit.

With these points in view, the applicants have developed a process or method ofmanufacturing silver or othermetallic ware, either hollow or solid, of under-cut and other patterns by deposit of the metal from solution, and in so doing, have overcome the various important difiiculties encountered in the previous attempts to accomplish this result.

In the practice of the method which is the subject .of this invention, the applicants first make a flexible or elastic mold of the pattern, provided it has under-cut portions; otherwise, it is possible to use a mold which is inelastic. After the formation of the first mold, the pattern is withdrawn and the imprint thickly coated or filled with mater'a to form a positive of the pattern. For

this purpose, wax or other suitable material may be used. 'T he flexible mold is then removed from the wax positive and the lat ter is given a thin coating of finely divided material possessing a considerable degree of electrical conductivity. The positive thus coated is placed in a copper, or zinc, or equivalent solution and coated with baser metal, which for convenience we will here ina'fter designate as copper, forming a negative, the imprinted surface of which is like that of the original elastic mold. When the copper isof sufficient thickness, it is taken out of the solution and cleaned in any convenient manner as by heating, brushing and wiping. Next, the copper negative is placed in a silver bath, or solution containing any metal of which the final product is to be made, the term silver being used for convenience to denote any equivalent, and given a thick coating of silver on the imprinted surface, the other parts being covered with a stopping-off coating to prevent the deposit of silver. In order that the deposit and therefore the finished article may be of uniform thickness, we prefer to use a plating bath, and particularly an anode, of peculiar arrangement and construction, and while the arrangement of the plating bath and the anode forms a feature of some of the combination claims in this application, it is a separate and independent invention which-is the subject of another application Serial No. 31817 of even date herewith.

When a suiiiciently thick deposit has been formed on the 00 per cathode, which is a negative of the original pattern, the formation of the finished article according to this invention is complete, but it is necessary to remove the copper cathode to which the deposited metal adheres. To do this, the silver article thus produced, together with the copper mold is made the plus pole or anode in a weak acid cell or bath and in a short time the copper is removed from the silver and deposited on'the cathode which leaves a finished silver article, which so far as the molded surface in concerned, is an exact duplicate of the pattern, and in addition to this, when made according to the preferred method, using all the steps disclosed herein,

much more dense than any pure silver now particularly the preferred arrangement of v the plating bath and anode, the deposit is known-to the trade and the thickness of the sandths of an inch.

In the drawing which forms a part of this application Figure 1 shows a silver-plating bath containing a copper mold or cathode and a silver anode arranged according to the preferred form of this feature of the invention;

Fig. 2 shows in cross-section an elastic mold containing a pattern;

Fig. 3 is a cross-sectional view showing the elastic mold after the pattern has been withdrawn and wax or other suitable material substituted therefor;

' Fig. 4 shows a wax positive wired, coated with carbon and placed in a copper bath to receive a copper deposit to form the copper cathode shown in Fig. 1; the receptacle for the solution being in section and the other parts in elevation; and

Fig. 5 shows a copper mold with a silver deposit constitutingtlie silver article manufactured; the combined mold and silver deposit being placed in an acid solution and connected to the plus pole for the dissolution of the copper, the side of the container being broken away to show the contents.

In the manufacture of silver and other metallic ware bydeposit in accordance with the method of our invention, the first step consists in the preparation of an elastic mold using a pattern of the thing to be produced. The mold may be made of gelatinous substance which can be poured over the pattern and has the ability to set and form a clear and correct impression of the pattern sufficiently elastic to permit the pattern, even though, it bears an elaborate under-cut design, to be withdrawn from the mold without lnjuring the imprint. Such a mold, indicated in Fig. 2 of'the drawings,v and bearing reference character 1, may be made of glue or other gelatinous substance or from any of the-various gums or other material capable of solidifying to form an elastic imprint from a pattern after the manner described.

The mold 1 is placed within a receptacle 2 containing the pattern 3. When the mold has taken a suflicient set, the bottom 4 of the receptacle 2 is removed, and the pattern is withdrawn, care being taken'not to injure the imprint. Next the mold 1 is preferably inverted as shown in Fig. 3, and the imprint is filledwith orgiven a thick coating of melted wax 5 or similar material capable of setting in the elastic mold and 'formin a positive of the pattern, having a consi erable degree of rigidity. Next, the Wax positive 6 is separated from the mold in any suitable manner, as by dissolution of the-- mold in waterv or by withdrawing the wax positive in the same manner in which the pattern was withdrawn. The imprinted portion of v the positive is then coated with finely divided graphite or similarly conductive material and wiredas shown in Fig. 4, the wires being connected at 7 to a source of electricity. The wax positive thus coated and wired is placed as the cathode in a rather weak .acid solution of copper and a copper anode 8 is used. The graphite acts as a conductor distributing the current over the imprinted surface of the wax positive and the copper is deposited on this surface after the manner of the similar step in the elect'ro-typing process. The copper negative thus formed and the wax positive are then removed from the solution and the wax is stripped from the copper by heating and brushing or other convenient means, leaving a clean copper negative of the original pattern, indicated by reference character 9 on t the drawing, Fig. 5. The copper negative,

face which does not form part of the imprint, coated with a stopping-off solution, as varnish or the like, is then placedin an electro-plating bath in which it forms the cathode, the anode being of silver or.

other metal of which the final product is to be formed, the same metal, which will be termed silver for the purposes of this description, being also in solution in the bath. By a contlnued deposit of silver on the copper negative, a silver positive duplicate of the original pattern is formed and it only remains to separate the copper negative from the silver positive to complete the product. This is done by inserting the combined copper mold and silver positive, shown in Fig. 5, the positive at 10 and the mold at 9, in'a weak acid solution connecting the combined silver positive and copper negative to the positive pole of a source of electricity, and using a copper negative pole or cathode. The passage of a current under these circumstances serves to dissolve the copper mold and deposit the copper on the cathode 11, where it is left in condition to be used in the further conduct of the same process.

An important difliculty previously encountered in attempts to make hollow articles by electrolytic deposit of metal from solution has been that incident to the appar ent impossibility of securing a deposit of anything like uniform thickness. In the P overcome by the use of the cell or bath shown in Fig. 1 and the anode disclosed in that figure. found that the rate at which the metal is deposited varies directly with the density of the solution, which is greatest at the bottomof the tank and decreases toward the top.- The rate of deposit also' varies inversely with the distance of the anodefrom the cathode. Attempts have been made to By experiment, it has been 7 85 havlng 1ts external surface or all of its surovercome the difficulty incident to the production of a deposit of varying thickness on diderent parts of the cathode by making the anode of a shape somewhat similar to the cathode and hanging the two in the tank with their adjacent surfaces parallel, but owing to the difference in depth of the different parts of the anode and the cathode on which the silver is being deposited, there is a considerable variation in density of the silver solution and hence, in the ease with which the metal is deposited, as between the top and bottom of the article. This, where the two are hung in parallel positions, gives a much thicker deposit at the bottom so that the object in view is defeated.

By repeated experiments, the applicants have found that advantage of the varying density of the silver solution can be taken by placing the cathode in horizontal position near the bottom of the bath and placing the anode at the top. But it is found that with the heaviest solution that can be obtained, the deposit of silver is slow, and further, it is roughened and disfigured by particles of oxid and other dirt which descend from the anode and lodge on the cathode. To ,meet these difi'iculties, a new anode, shownat 12 in Fig. 1, has been devised. This consists of a jar or receptacle 13 having a porous bottom preferably formed of unfilled textile fabric Or the like, 14. This is bound to the edges of the bottom by suitable means, as a band 15 covered with tape 16. In the bottom of the receptacle, resting on the textile fabric, there is a thick layer of particles of silver 17, known as shot silver, which forms the actual metallic anode and in these, the positive wire 18 is dipped or buried, the wire above the shot silver being covered with a stopping-01f solution to prevent it from being eaten ofl by the liquid. In order to facilitate the plating operation by keeping up a continuous circulation of the silver solvent which carries the metal to the cathode, the receptacle 13 is pierced by a series of openings 19 spaced a short distance above the bottom of the receptacle and above the shot silver 17.

The theory of the operation is as follows: The portion of the solution which contains the most silver is of course the heaviest so that as the uncharged or lightly charged solution comes in contact with the shot silver and dissolves its quota, it becomes heavier and passes downward toward the bottom of the tank, and, incidentally, towardthe cathode, where it displaces the lighter or weaker solution which in turn has the greater ability to dissolve or take up metallic silver. The lighter solution rises and is drawn in through the openings 19 filling the place of that which has become saturated and passed downward through the fabric. This light solution then comes in contact with the shot silver and dissolves it, becoming heavy and passing downward toward the cathode. lhen, as the silver is being withdrawn from the solution at the cathode and deposited thereon, a continuous circulation is kept up, for the light solution formed at the cathode is forced up, being replaced by the heavy solution atthe anode, and is in turn drawn through the holes 19 and brought in contact with the shot silver where it takes up metal, becomesheavy and passes downward.

Owing to the fact that the heaviest solution lies at the bottom and the density, and therefore the silver content, decreases from the bottom toward the top, and incidentally, from the bottom toward the anode, there would be an apparent tendency to deposit a layer of silver which would be thickest at the bottom of the article being plated. However, this tendency seems to be overcome by the counter-tendency to plate fastest at the point where the distance between the cathode and the anode is the least. Thus we have a tendency, due to the varying weight of the solution, to deposit heaviest at the bottom and lightest at the top, and a tendency, due to the electrical resistance and varying extent of the intervening liquid, to deposit heaviest at the top and lightest at the bottom, and, in the arrangement of the apparatus shown in Fig. 1,-these two tendencies are so utilized that they counteract one another, and as a result, produce a substantially uniform deposit, which is of a density and hardness greater than that of any pure silver heretofore known and at least equal in hardness to sterling, which contains a percentage of baser metal to give suflicient hardness.

l/Vhile we refer in the specification and in the claims to the use of an elastic mold which may be made of glue, to the production of a positive of wax-like material, to the manufacture of a solid silver article and to the use of a copper negative on which the silver is deposited, it is to be understood that these terms are merely used for convenience in description and that while the invention has particular reference to the manufacture of solid silver articles, it is within the scope of the invention to use the same general method in the manufacture of solid articles of precious metals other than silver, and that while it may be shown that various chemical baths may be substituted for those used by us and that other metals may be substituted for copper and other materials for Wax, these obvious variations are within the scope of the claims of this application and specific mention of all the possible means for practising the method of our invention is omitted merely in the interest of clearness and brevity and be,

cause these details and variations will be obvious to the skilled Workman having this description at hand.

We have thus described specifically and in detail a method embodying the features of our invention in its preferred form in order that the nature of the invention may be fully understood; ,however, the specific terms herein are used descriptively rather.

than in their limiting sense and the scope of the invention is defined in the claims:

1. The method of manufacturing solid silver articles by'deposit which consists in making a pattern, making a flexible, elastic mold from the pattern, removing the pattern from the mold, making a positive from the I'lOld by coating the print with waxlike 1 iaterial and removing the mold, using the,positive as the cathode in a copper bath whereby a coating of copper is deposited on the positive forming a copper negative, coating the surface of the copper negative, exclusive of the imprint, with a stoppingotf compound, using the copper negative as the cathode in a silver solution having. a silver anode, and placing the copper and silver deposit in a weak acid solution and connecting it as the anode whereby the copper is dissolved and deposited on the oathode.

2. The method of manufacturing solid silver articles by deposit which consists 'in making an undercut pattern forming a flexible mold about the pattern, removing the pattern from the mold, making a positive from the mold, placing the positive in an making a chased pattern, making an elastic mold from the pattern, makingv a positive from the mold, making a metallic negative from the positive, depositing silver on the negative and dissolving the metallic negative.

4. The method of manufacturing solid silver articles by deposit which consists in making a pattern having an irregular surface, making a' mold from the pattern, making a positive from the mold, coating the positrve with electrically conducting material, making a metallic negative by deposit from the positive by electrolytic deposit, depositing silver on the negative and dissolving the metallic negative.

Signed by us at Baltimore, Maryland, this 27th day of April, 1915.

HENRY C. KIRK, JR. GEORGE H. DIUMLEB.

Witnesses EDWARD L. BAsH, H. A. VVALDKOENIG.

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