US2258451A - Process of making negatives in metal of metal surfaces - Google Patents

Description

Patented Oct. 7, 1941 PROCESS OF MAKING NEGATIVES IN METAL OF METAL SURFACES Herbert S. Ingham,

Shepard, Forest Jamaica, and Arthur P. Hills, Long Island, N. Y., as-

signors to Metallizing Engineering Company,

Inc., Long Island New Jersey No Drawing. Application January 31,

City, N.Y., a corporation of Serial No. 316,578

2 Claims. (Cl. 22-190) This invention relates to new and useful improvements in a process of making negatives in metal of metal surfaces.

One object of the invention comprises, inter alia, the making of substantially accurate negatives or molds, and reproductions or replicas in metal of metal surfaces and this and other ob- Jects will be seen from the following description.

In accordance with the process described in a patent to William C. Reid, No. 2,171,599 (September 5, 1939) substantially accurate negatives, molds or replicas in metal of metal surfaces may be made byspraying such metal surface with a metal, which surface is at least at the temperature of incipient adhesion for said object and said applied metal, and below the temperature at which inseparable adhesion occurs,.and continuing the spraying until the surface is covered with applied metal, whereupon the coherent coating so formed is removed from the surface by suitable means, such as quenching. As set forth in the Reid patent, the term "temperature of incipient adhesion designates the lowest temperature at which the sprayed metal shows definite adhesion to the base with the formation of a coherent coating thereon and below which temperature the sprayed metal does not so adhere; the term inseparable adhesion" designates the upper limit of the temperature range within which detachable coatings are formed and connotes that temperature at which inseparable adhesion between the base and applied metal occurs and at which the applied coating cannot be removed intact.

In the formation of detachable metal coatings in accordance with the Reid process the temperature of incipient adhesion for a given spray metal and a given metal surface is sometimes undesirably high as for instance in the spraying of aluminum on a polished cast iron surface (mirror finish) which requires the heating of the base to a temperature of approximately 780 F.

Frequently the object to be sprayed by reason of its particular construction or composition may not be able to stand such high temperatures Without injury. On the other hand even though the particular temperature of incipient adhesion may not be relatively high, the prolonged heating of the base at that temperature may involve injury to the same such as by oxidation.

We have discovered that detachable spray metal coatings'may be obtained on any metal surface, having for a given spray metal a relatively high temperature tained.

without the necessity of heating such surface to that temperature.

In accordance with the present invention the metal surface or base upon which a detachable spray metal coating or shell is to be formed is first provided with a substantially'thin coat of another metal. This coating metal is so selected that the temperature of incipient adhesion for this coating metal and the metal to be sprayed thereon, is lower than the temperature of incipient adhesion for the spray metal and the metal of the base. It is then only necessary for the formation of the first coherent spray metal layer that the metal coated article be sprayed while at the temperature of incipient adhesion for the coating metal and the spray metal.

The coating metal in accordance with our invention may be applied to the base or surface on which a detachable coating is to be made. in any manner well known in the art, such as by electroplating, hot dipping, spraying, flowing molten metal onto a base, or the like. The coating may be also applied by painting the base or surface with a suitable solution of a salt of a metal lower in the electrical series than the metal/of the base or surface, thereby depositing metal from the solution onto the base or surface. Thus, when treating a steel surface with a copper sulphate solution, a satisfactory copper coating is ob- When resorting to spraying for the application of the preliminary metal coating preferably such coating metals should be selected for which the temperature of incipient adhesion to the metal of the base is sufficiently low to permit their application without injury to the base. The coating should be preferably of such relative thinness or at least so evenly and uniformly applied to the surface to be reproduced innegative that it does not interfere with the reproduction of the details thereof. Suitable coating metals for such bases as steel, brass, cast iron, and chromium are, for instance, tin, zinc, cadmium, copper, and tin lead alloy.

Wherever reference is made to the term metal," such term, irrespective of whether used in connection with a coating material or a spraying material or the material of a base, is used in its broadest scope and metals as well as alloys.

'In the practical application of is intended to include my invention,

, for example, a polished steel surface carrying a of incipient adhesion,

given design, to be reproduced in negative, .is first coated in the usual electro-plating bath with a thin coating of copper of about .002 inch thickness in the well known manner. The thusly coated article is then heated to a temperature of 750 F. and while at that temperature, steelis sprayed onto the copper coating by means of a conventional spray gun preferablyof the wire feeding type, and the spraying is continued at substantially that temperature until a substantially coherent coating is formed. Once an adherent substantially coherent coating is obtained, it is not necessary to further maintain the temperature and the sprayed steel shell may then be backed by continuing the spraying of the steel with either the same steel or another metal or alloy as desired. As soon as the spray metal shell or coating is sufficiently strong it may be removed from the base by suitable thermo or mechanical means as, for instance, by quenching. If the steel surface had been directly sprayed with the steel the temperature necessary for incipient adhesion would have been approximately 950 F., while with the aid of the intermediary thin copper coating a heating to but 750 F. sufices for the production of the detachable sprayed steel coating. The detached coating or negative obtained carries a substantially accurate negative reproduction of the surface design of the original surface or base to which it was applied.

It is often of advantage to apply the coating metal to the base in a molten condition. Resort to such practice will permit the metal spraying for the formation of the detachable spray metal shell on the intermediary coating without the necessity of heating temperature required for incipient adhesion to the spray metal, for, in this case the coating metal applied in molten form will, after its solidrange of temperatures between inseparable and incipient adhesion and within which detachable coatings may be formed.

Where a given object of which a negative is to be made is suificiently bulky, it may not always be necessary to heat the entire object to the temperature of incipient adhesion and it may sufilce to heat any particular surface to be sprayed to that temperature.

The method in accordance with our invention may beapplied to the making of molds for the manufacture of smooth moldable articles, such as articles of rubber, plaster, artificial resins, and molds for use in casting metals. In this case we take in the first instance a metal master or pattern having substantially the dimensions of the article to be reproduced, from which any number of molds may be obtained by the application of our process, 1. e., by coating said master or pattern with a suitable coating metal of the aforerecited characteristics, spraying metal against the coated master or pattern to form a coherent detachable metal coating, and thereafterdetaching and removing the coating so formed. The mold so obtained is an accurate negative of said master or pattern and its surface will bear substantially the same degree of smoothness and finish as the original.

Alternatively, the method in accordance with our invention may be used for the production of replicas or duplicates of an original article or a model thereof. In this case a metal mold of the the coating metal to the ification and while cooling pass through the ally referred to as article itself is first prepared in any suitable manner, the mold surface thereafter, as recited in the foregoing, coated with the desired coating metal and the coated mold is thereupon sprayed with a metal until a structure of the desired thickness is formed which is finally detached and removed from the mold.

The metal spray application to the surface sprayed is carried out in accordance with well known practices and should be continued until a coating of satisfactory thickness covering the surface has been formed, which coating is usua shell. This shell may be further backed up at least to an extent sufficient to be capable of separation from the surface sprayed, as a self-supporting structure, by either spraying with metal, or in any other suitable manner, such as by casting a backing onto the shell.

The foregoing specific description is for purposes of illustration and not of limitation and it is therefore our intention that the invention be limited only by the appended claims or their equivalents wherein we have endeavored to claim broadly all inherent novelty.

We claim:

1. In the process of making a metal negative of a smooth metal surface with metal, while said surface is at a temperature of incipient adhesion for said spray metal, and removing the coherent spray metal coating formed, the improvement which comprises first applying to said surface prior to said spraying, a substantially thin coat of a first metal and thereafter spraying said coated surface with a, second metal, while said coated surface is at a temperature of at least incipient adhesion for said second metal and below the temperature at which inseparable adhesion occurs, at least until the surface sprayed is covered with spray metal, said first metal being so selected that the temperature of incipient adhesion of the therewith coated surface to said second metal is lower than the temperature of incipient adhesion of said uncoated surface to said second metal.

2. Inthe process of making a metal negative,

of a smooth metal surface by spraying such surface with metal, while said surface is at a temperature of incipient adhesion for said spray metal, and removing the coherent spray metal coating formed, the improvement which comprises first applying to such surface, prior to said spraying, a substantially thin coat of a first metal in substantially molten condition and, after the substantial solidification of said first metal, spraying said coated surface with a second metal, while said coated surface is still hot and at a temperature of at least incipient adhesion for said second metal and below the temperature at which inseparable adhesion occurs, at least until the surface sprayed is covered with spray metal, said first metal being so selected that the temperature of incipient adhesion of the therewith coated surface to said second metal is lower than the temperature of incipient adhesion of said uncoated surface to said second metal.

HERBERT S. INCiI-IAM. ARTHUR P. SHEPARD.