US1875346A

US1875346A - Mold or matrix for plating

Info

Publication number: US1875346A
Authority: US
Publication date: 1932-09-06
Anticipated expiration: 1949-09-06

Description

Sept. 6, 1932. LAUKEL 1,875,346

' MOLD OR MATRIX FOR PLATING Filed May 13, 1926 gwmntoz 172%02" Zak! Patented Sept. 6, 1932 UNITED STATES ARTHUR K. LAUKEL, OF DETROIT, MICHIGAN MOLD B MATRIX FOB PLATING Application filed Kay 18,

This invention relates to the production or preparation of molds, matrices or molded bodies, for electrodeposition, such for example as in the making of electrodeposited met- '5' al patterns according to Patent No. 1,570,634 granted to me on the 26th day of January,

One of the outstanding features of an electrodeposited pattern is that it may be 0 made in true duplication of another pattern, there being no shrinkage in the electrodeposited pattern to be provided for and no necessity for machining and finishing as in ordinary molded metal patterns to prolduce precise dimensions or fineness of finish,

but to insure such true duplication of a pattern it is necessarythat the impression in the mold shall be a true counterpart of the pattern to be duplicated. It will be obvious that if a mold be made with such true impression and thereafter the impression coated with a medium of any appreciable thicliness to produce a conductive surface so that it may be plated, such medium would alter the dimensions or contour of the impres sion to a degree depending upon the thickness thereof and a resultmg electrodeposited pattern would suffer distortion to such extent.

The plating of molds having deep relief, such as in the production of electrodeposited patterns, involves peculiar roblems or conditions requiring more particular consideration than ordinary electroplating processes such for instance as the production of electrotypes wherein pulverized graphite is often used .to produce a conductive surface, and other electroplating processes well known to those conversant with the art wherein powdered metal suspended in lacquer is often used toprovide a conducting surface, and it is found that in plating molds having deep relief in which the molds are often suspended for long periods in the electrolyte before a complete flashing or initial plating in the deeper recesses, and in which accuracy is to be maintained as hereinbefore stated, that such methods of providing a conductive surface are not suitable. Pow- 0 ders, such as graphite, do not always adimmediately surrounding the pattern. After 1928. Serial 1T0. 108,715.

here sufficiently to the surface of the mold, are diflicult to apply to intricate and extensive surfaces in a manner ensuring an even coat, are diflicult to apply to deep depressions such as often occur in molds for mechanical patterns; and lacquer may be de ficient in conducting quality due to separation of metallic grains by the vehicle or surface insulation of the grains by such vehicle as well as altering the contour of the mold due to the thickness of the coating of lacquer as before stated.

It is also desirable that the conductive coating on the mold be porous, which is not always the case with lacquers, and that the deposit shall tend to adhere to the coatin in contradistinction to the effect secured Where graphite is used.

' Further objects subsidiary to or resulting from the aforesaid objects or from the construction or operation of the invention as it may be carried into effect will become apparent as the said invention is hereinafter further disclosed. a

In carrying the said invention into effect I may arrange a pattern to be duplicated on a suitable board or plate upon which is placed a frame surrounding the pattern to determine the size of the mold to be made. I then coat this patternrwith a mixture of copper dust plaster of Paris and water having the consistency of a heavy paint. Care is taken to make this coating thorough and also to spread the coating on the surface of the plate this coating has set sufliciently to prevent its being inadvertently erased from the surface of the pattern the frame may be filled with plastic material such as plaster of Paris which will adhere to the aforesaid coating so that the two will become to all intents and purposes integral. The resultant mold being removed from the pattern when it has set sufiiciently to warrant such removal. The impression of the pattern in the resulting mold and the immediately surrounding surface of the mold then have a surface in which is imbedded copper dust, and I treat this surface with silver nitrate which produces a silver surface of a conductive nature suitable for subsequent plating operations. To prevent deleterious action of the electrolyte on the material from which the mold is formed, I impregnate the mold with wax in any suitable manner such as by immersing for a sufficient length of time in a hot bath of wax, after which the surface of the impression and the surface of the mold contiguous thereto are cleaned of wax by means of a suitable solvent such as ether. The silvering may be effected before or after the waxing operation or both before and after the waxing operation, and silver nitrate may be used in combination with the wax solvent in order to effect this silvering when the wax is removed. If, as on large molds the wax leaves a clean surface due to its absorption by the material of the mold, such cleaning is not necessary.

All of which is more particularly described and ascertained hereinafter, by way of example, having reference to the accompanying drawing, wherein Figure 1 indicates in plan a pattern mounted upon a board upon wh ch a frame is arranged, the said pattern being shown as partly coated withthe composition used in producing the conducting surface of the mold to be made;

Figure 2 is a vertical section of the same illustrating the complete coating applied;

Figure 3 is a similar view to Figure 2, illustrating the frame subsequently filled with plastic material;

Figure 4 illustrates in section a completed mold, and

Figure 5 is a face view of the same.

Similar characters of reference indicate similar parts in the several figures of the drawing.

1 indicates a pattern board upon which is mounted a pattern 2 intended to be reproduced by electrodeposition, and 3 is a frame arranged on the board around the pattern to form a box-like structure, in which the mold may be prepared. It is presumed that the surface of the pattern and pattern board are of such nature that the materials used in the manufacture of the mold will not adhere thereto, otherwise such surfaces may be oiled or treated in any material suitable to pre- Vent such adherence.

The first step in producing the mold is to prepare a mixture of plaster of Paris or similar suitable material and copper with sufiicient water to provide a heavy paint-like composition, and for this purpose I have found that these ingredients may be in the proportions of 112 grammes of copper dust, 168 grammes of plaster of Paris, and about 200 c. c. of water. In order to get the best'results in such composition the copper should be of that nature which has a tendency to be wetted by water, and I prefer to use dust of a fineness which will pass through three hundred mesh screen. I

y the pattern board as indicated by the'reference numeral 5, taking care that all the corners and depressions in the pattern are effectively filled. After this coating has set lsufiiciently that it will not be broken or eroded from the pattern when other material is poured into the frame, I,fi1l the frame with plastic material such as plaster of Paris 6, to form the body of the mold. This material in setting adheres to and becomes practically integral with the coating already applied to the pattern so that the mold so formed is characterized by the impression 7 of the pattern having a surface layer densely filled with small particles of copper, the same being true of the surface of the mold immediately surrounding said impression.

These copper particles are not in such close association, however, that they will form a good conducting surface, and in orderto secure such good conducting surface I treat the exposed copper particles with a solution containing a metal electro negative to the copper such as a solution of silver nitrate, whereupon the said surface is silvered and the effect of such silvering is to produce a practically continuous silver surface which is an excellent conductor and eminently suitable for the purposes.

The copper is embedded in the surface mixture, and since at least a part of this copper is comprised in the conductive coating, it may be said that this coating is partially embedded or anchored in the surface. The particles of metal which are deposited in the subsequent process of electro-plating adhere firmly to the conductive coating. The firm adherence of the conductive coating to the plaster and of the deposited metal to the coating constitutes such a great resistance to lifting by gas bubbles resulting from the action of the electrolyte on the plaster of Paris, that this gas pressure, acting by bubbles, is insuflicient to lift the coating or the deposited metal from the plaster. Consequently the deposit remains undistorted by gas bubbles, and such gas escapes by minute division of the bubbles and penetration of these divisions through the deposit which is porous in its early stages.

Plaster of Paris in the form in which it is most convenientlv secured contains about one percent of calcium carbonate which the acid in an electrolyte, such as copper sulphate electrolyte, will ordinarily attack and decompose with the evolution of carbon dioxide,.and in the making of patterns by electrodeposition the evolution of such gas is objectionable as it is liable to accumulate under the deposited metal and thereby distort it. Moreover, unprotected plaster of Paris would be quickly disintegrated by the action of such anelectrolyte, so that it is necessary that the mold be suitably treated to enable it to resist the deleterious action of the electrolyte.

This protection of the mold against the action of the electrolyte may be accomplished by impregnating the mold withv wax, and the resulting coating of wax may be afterwards removed from the surface of the impression in the mold and the immediately surrounding surface of the face of the mold by means of a solvent such as ether if the wax hasnot been absorbed by the mold to such an extent as to render this unnecessary.

Th silvering process already referred to may be carried out either before or after the waxing process, or both before and after the waxing process, as it may be repeated as often as desired to secure an effective silvering of the surface, and, if thought necessary or desirable the silver nitrate may be in solution with the alcohol and ether so that the removal of the wax surface and the silvering may be effected to all intents and purposes in one operation.

The incorporating of the copper dust in the coating at the surfaces of the mold 'to be plated also reduces the percentage of carbonate content in such coating, incidently reducing the tendency of the electrolyte to evolve gas on the surface to be plated. There is always liable to be a certain amount of such gas produced, however, where plaster of Paris is used, and it is a feature of the describedmethod of producing a conducting surface that such surface is more or less porous and allows such gas to freely escape during the flashing, or early stages of plating, as distinguished from the trapping of such gases which would result were such surface coated with a substantially non-porous lacquer, and thus the raising or distorting of the flashing which might otherwise occur'during the early stages of the plating operation, is avoided.

Furthermore, theiilvering process doesnot reduce the dimensions ofthe im ression of the pattern as it would be reduce by the application of a coating of lacquer or other conducting film of appreciable thickness to the surface of the impression so that the true form of the pattern to be duplicated is fullymaintained.

Such conductive surface will not wash off in the electrolyte, and there also is the peculiarity that deposited metal tends to adhere closely thereto instead of to detach itself therefrom as is the case where graphite is used. This adherence also tends to prevent the deposited film from leavin the mold under influence of gas from the mo (1.

It will be realized that although copper dust is described as being utilized in the coating applied to the pattern in the manufacture of the mold other materials may be effectively used, and that other .mediums may be'employed for producing the final conductive surface, for instance, zinc dust may be used and theconductive surface attained by treating with a cadmium salt solution or platinum solution, tin dust may-be used and treated with a, solution of silver or copper, or

lead dust may be used and treated with a solution of silver, mercury or copper, and so forth.

The ingredient incorporated in the coat ing for the production of the conducting surface need not necessarily be a metal. For instance, cadmium oxide and ,cadmium suboxide may-be mixed with plaster of Paris and subsequently treated with a solution of nitrate of silver to produce a metallic silver surface or silver chloride may be mixed with plaster of Paris andsubsequently treated with potassium iodide to produce a conducting surface of silver iodide and such variations may be made through the chemical range of ingredients suitable for the production of a conducting surface in the manner related.

The nature ofthe metal forming-the conducting surface must of course be suited to the electrolyte in which the mold is to be plated;

It will be also understood that although plaster of Paris is referred to herein as being very convenient and practical material for use in the manufacture of molds in accordance with this invention, other moldable materials, as for example wax, having characteristics lending themselves to manipulation in the manner described and use in a plating bath, may be utilized.

It will be further understood that although the invention has been described more especially in connection with molds for use in the making of electrodeposited metal patterns of a mechanical nature, the incorporating of a material adapted to enter into the eventual production of a conductive surface on an article to be plated in. the. material forming the surface of the article to be plated is capable of a very wide range of application. Thus ornamental or other objects to be plated may have their entire surface coating prepared in the manner described or in fact the entire object to be plated may be made of a plastic material with which is admixed copper dust or such ingredient, the article being afterwards treated with the re quired solution to secure the conducting surface inthe manner hereinbefore explained. Therefore it is to be understood that expressions such as surface coating used herein and in the claims are not intended to indicate that the coating referred to shall be necessarily restricted to the surfacelayer of the article as the article to be plated may be completely formed of the composition hearing the copper dust or such ingredient, in which case of course the surface of the article would still have the properties and be of the nature ascribed thereto.

Still further it should be noted that the second stage in the process of treating the article may consist in the actual plating thereof instead of a treatment of the surface of the article in the manner described prior to such plating. For instance, the article to be plated may have copper dust incorporated in its surface and be then plated in a silver bath, in which case the initial effect would he a flashing similar to that secured by the previously described treatment with the solution of the silver salt, the only difference being that the plating is continued until a required thickness of deposit such as may be called for in the finished article is secured.

The invention also is not limited to treatment by a metallic salt in order to secure a conductive coating, as the surface of the article may have incorporated therein any suitable substance which is adapted to enter into a reaction with any other agent, which may as a result of such reaction, form a conductive coating on the article in the manner required. Thus silver or copper dust may be incorporated in the surface of the article which may then be subjected to the action of a gas such as hydrogen sulphide, thereby resulting in the formation on the surface of the article of copper or silver sulphide as the case may be, which is of a conductive nature. Then again, silver may be incorporated in the A surface of the article and treated with a solution of iodine in an organic solvent such as carbon disulphide, thereby forming a coating on the surface of the article of silver iodide which is also of a conductive nature.

From the various examples which have been given, it will be understood that the material incorporated in the surface of the article may in some cases be metallic and in others non-metallic, and the reagent used may be of a metallic or non-metallic nature according to the chemical requirements necessary to obtain the result desired, and the essence of the invention therefore lies in the incorporation in the surface of the article to be plated of a substance lending itself to treatment by a suitable reagent which will as a result of such reaction, form a conductive surface on the article. Consequently, although the reagent may be characterized by its containing a metal electro-negative to the material incorporated in the surface of the article, this need not always be the case, as generally speaking the reagent may be said to be reducible by the incorporated material in the surface of the article whether this be the result of electrolytic or of chemical action.

This invention may be developed within the scope of the following claims without departing from the essential features of the said invention, and it is desired that the specification and drawing be read as merely illustrative and not in a limiting sense, except as necessitated by the prior art.

What I claim is 1. The method of preparing a molded counterpart of a model for electroplating which consists in applying to the model a coating of plastic material having incorporated therein a substance which when treated with the salt of a metal reducible by it will result in a conductive coating of such metal being formed on the surface treated, subsequently backing said coating with a body of plastic material adapted to adhere to said coating, removing the resulting mold after setting from the model, and treating the exposed surface of the coating with such metallic salt.

2. The method of preparing an article for electroplating which consists in making a body of the article of a mixture of plaster of Paris and metallic dust, and treating the surface of the article with the salt of a metal electro-negative to said metalic dust.v

3. The method of preparing an article for electroplating, which consists in making a body of plaster of Paris containing carbonate, reducing the percentage of carbonate content in the surface of the article by incorporating in the plaster of Paris a substance of lower carbonate content than plaster of Paris and which when treated with the salt of a metal reducible by it will result in a conductive coating of such metal formed on the surface treated, and treating the surface of the article with such salt.

4. The method of preparing an article for electroplating, in order to reproduce an object by electro-deposition, consisting in applying to said object a plaster of Paris mixture of such low carbonate content as to evolve a negligible quantity of carbon dioxide when immersed in an acid bath, backing said material for reinforcement, separating the article thus formed from said object, and rendering the impressed surface of said material conductive.

5. The method of preparing a cathode for reproduction of an article by electro-deposi tion, wherein the cathode-carrying body consists mainly of a material containing carbonate, said method consisting'in applying over said article a substance of lower carbonate content than said material, backing said substance with said body material, and rendering the impressed or molded surface of said substance conductive.

6. The method of preparing a cathode for reproducing an object by electro-deposition, consisting in selecting two substances capable of reacting with each other to form a conductor, mixing one of said substances with a material adapted to set without substantial shrinkage,applying said mixture in substantial thickness over said object, backing said1 mixture with another material adapted to adhere firmly to said mixture, removing the whole, after setting, from said object, and treating the impressed surface of said mixture with the other selected substance.

7. The method of preparing a cathode for reproducing an objectby electro-deposition, consisting in selecting two substances capable of reacting with each other to form a conductor, mixing one of said substances with a material adapted to set without substantial shrinkage and adapted to become porous to carbon dioxide when set, applying said mixture in substantial thickness over said object, backing said mixture with another material adapted to adhere firmly to said mixture, removing the whole, after setting, from said object, and treating the impressed surface of said mixture with the other selected substance.

8. The method of reproducing a surface by electro-deposition consisting in applying to said surface a plastic mixture containing a reagent incorporated therein, reinforcing said material, removing said material and reinforcement, from said surface after hardening, intact from said surface, treating the impressed surface thereof with a reagent capable of reacting with the first reagent to form an electrically conductive surface, depositing metal electrolytically on said conductive surface, and separating the deposit from said conductive surface.

9. The method of reproducing a surface by electro-deposition consisting in applying to said surface a plastic mixture containing a reagent incorporated therein, said mixture bein' adapted to set without substantial shrin age, reinforcing said material, re moving said material and reinforcement from said surface after hardening, intact from said surface, treating the impressed surface thereof with a reagent capableiof reacting with the first reagent to form an electrically conductive surface, depositing metal electrolytically on said conductive surface, and separating the deposit from said conductive surface.

10. The method of reproducing a surface by electro-deposition consisting in applying .to said surface a plastic mixture containing a reagent incorporated therein, said material being adapted to set without substantial shrinkage and being porous when set,

chemically united with said particles.

In testimony whereof I aflix my signature.

' ARTHUR K. LAUKEL.

reinforcing said material, removing said material and reinforcement, after hardening, intact from said surface, treating the impressed surface thereof with a reagent caable of reacting with the first reagent to orm an electrically conductive surface, de-