US2258452A - Process of making negatives in metal of solid objects or surfaces - Google Patents

Description

Oct. 7, 1941. H. s. INGHAM ETAL 2,258,452

PROCESS OF MAKING NEGATIVES IN METAL OF SOLID OBJECTS OR SURFACES Filed Jan. 31, 1940 4 Y 42 wi w m ama Y fl B 4 Patented Oct. 7, 1941 PROCESS OF MAKING NEGATIVES IN METAL OF SOLID OBJECTS OR SURFACES Herbert S. Ingham,

New Jersey Jamaica, and Arthur P. Shepard, Forest Hills, Long Island, N. Y., assignbrs to Metallizing Engineering Company, Inc., Long Island City, N. Y., a corporation of Application January 31, 1940, Serial No. 316,583

Claims.

This invention relates to a new and useful process of making negatives in metal of solid objects or surfaces.

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

The application of metal coatings to solid'objects or surfaces by metal spraying is achieved by the use of a metal spray gun, i. e., a device by which metal is fed to a heating zone from which zone metal particles, at least some of which are molten or in a heat plastic condition, are propelled against the object or surface by a blast of air or other gas. Various types of spray guns are commonly used for this-purpose. In order to obtain a substantially coherent coating on the object or surface sprayed, it is essential that the metal particles, as they impinge upon the surface sprayed, enter into a bond with such surface to a sumcient extent to permit the formation of a satisfactory coating thereon. If the bond between the impinging metal particles and the surface sprayed is not sufficient for the formation of a substantially coherent metal coating, the spray metal will not adhere to such surface and is either blown off by the force of the blast from the spray gun or, if it forms flakes upon the surface sprayed, these flakes curl, thus preventing the formation of the desired coating. In such cases it is necessary to provide for the requisite degree of bonding between the impinging metal particles and the surface sprayed by the use of suitable methods. The surface to be sprayed may thus be pre-treated, for instance, by sand blasting, grit blasting, machining, acid etching or the like to render the same rough or porous.

For the procurement of detachable spray metal coatings it is requisite that the spray metal be applied to the surface sprayed in a thickness at least sufficient to yield a substantially self-supporting spray metal shell structure. Spray metal coatings of such thickness, however, have a tendency to peel at the edges, thus resulting in warpage of the spray metal structure and inaccuracy of the negative surfaces obtained. The higher, however, the degree of bonding between the impinging spray metal particles and the surface sprayed, the lower will this tendency to peel manifest itself. Inasmuch as the making of spray metal negatives requires the spraying of coatings that can be separated from the surface sprayed substantially intact, i. e., substantially without injury to the coating, it is necessary that the bond between the spray metal coating and the surface to which it is applied be sufficiently low to permit a severance of that bond without injury to the coating. This requirement, however, necessitates, in many cases, a bond which is insufflciently high to counteract the peeling-of the coating off the edges. I

In the making of negatives or molds and replicas or duplicates in metal of solid objects or surfaces by metal spraying, the object or surface sprayed upon is usually called a matrix, i. e., a substantially accurate negative of the object or surface to be obtained therefrom. If the matrix is itself a negative of a model, a model being an object or surface desired to be reproduced, it constitutes a mold from which replicas or duplicates of such model can be made, whereas if the matrix is itself a positive of a model, it constitutes a so-called master (i. e., either the original of the object or surface desired to be reproduced, or, a substantially accurate replica or duplicate of such object or surface) from which a negative or mold may be made. Such negatives or molds are, for instance, produced for use in the multiple reproduction of articles in various industries and particularly in the plastics, rubber and similar industries.

We have discovered that it is possible to obtain substantially accurate spray metal negatives of a matrix by spraying in a manner which will substantially counter-act the tendency of the spray metal shell to peel off the edges and which will substantially eliminate the necessity for a high degree of bonding between the shell andthe matrix, thus yielding spray metal coatings that may be separated and removed from the matrix sprayed substantially without injury to the coat- In accordance with the present invention, the I object or surface, herein referred to as a matrix, of which a negative is to be formed, is

provided with a base member extending suba substantially coherent spray metal shell, i. e...

a spray metal coating of at least self-supporting thickness, on the matrix and the base member and extending on the base member to the frame If desired, the spraying may be so conducted as to first spray metal, on substantially all sides of the matrix, onto the base member and into the space defined by the matrix, the base member and the frame member at least until a substantially coherent spray metal coat is formed on the base member and extending from the matrix to the frame member and thereafter spraying metal onto the coating thusly obtained and onto the matrix to build up the spray metal shell. It is also possible to first spray the matrix with metal to form a spray metal fiash thereon, i. e., a substantially coherent spray metal coating of relative thinness, whereupon metal is sprayed onto the matrix and auxiliary structures, in accordance with the invention, or first onto the auxiliary structure and thereafter the matrix and such structure as hereinbefore set forth.

In the following a specific embodiment of our invention is set forth by way of example but not by way of limitation and the invention will be more fully understood from the following description read in conjunction with the drawing in which Fig. 1 is a cross section through an article to be reproduced;

Fig. 2 is a top view of a structure showing a frame member and a base supported matrix in the form of a master of the article shown in Fig. 1;

Fig. 3 shows a cross section through a matrix in the form of a master of the article shown in Fig. 1 with a frame member on its base member and having a coating of applied spray metal;

Fig. 4 illustrates a cross section through the finished negative;

Fig. 5 is a cross section through a finished negative in the form of a mold having a base member as a flash shearing ring; and

Fig. 6 is a cross section through a finished negative in the form of a mold having a single unit base member and frame member as a fiash shearing ring,

In the drawing l designates the article to be reproduced. A matrix 2 in the form of a substantially accurate master or duplicate of the article I and having preferably a base portion 3 is provided with a spray metal coating 4 applied in the manner well known in the metal spraying art to produce a separable mold shell by means of a gas blast type spray gun schematically indicated at 5. The spray metal coating 4 fills the space between the matrix 2 and a frame member 6 in the form of a ring surrounding the matrix and resting on the base member 3 and preferably secured thereto by such means as screws Ill. After separation of the spray metal shell from the matrix the former may be suitably machined to represent the finished negative or mold 1 shown in Fig. 4 possessing the' ring 6 adjacent the base of the mold body.

' The material of the matrix may be any suitable metallic or non-metallic material provided the same lends itself to be suitably separated from the spray metal coating thereto applied in accordance with well known practices. We prefer, however, to use a metal matrix.

Instead of using, as for instance'illustrated in Fig. 3, a matrix having a suitable base member,

'as a substantially integral part thereof, it is possible and sometimes of advantage to construct the matrix without such base member and to separately provide the matrix with any suitable object or surface adapted to be sprayed upon with metal. Irrespective, however, of whether the base member constitutes an integral part of the matrix or not, the same should be so fitted on the matrix that it extends substantially on all sides from the matrix adjacent the surface thereof. In most cases it will suffice to select as the base member a suitable plate or the like surface to which the matrix as well as the frame member are fitted. This is particularly true where the matrix constitutes a male structure. In many cases where the matrix is essentially a female structure good results are obtained by inserting the matrix into a correspondingly cut-out portion of a suitable plate, to an extent sufiioient to bring the outer rim of the surface of the matrix as closely as possible in alignment with the plate used as a base member.

The particular spraying technique for the building up of the spray metal shell in accordance with our invention onto and over the surface of the matrix depends to some extent upon the particular type of matrix used. If the matrix is substantially a male structure the metal spraying will ordinarily proceed by building from the base member upward onto and around the structure, whereas if the matrix is substantially a female structure the formation of the spray metal shell is accomplished by building up the spray metal from the base member into the cavity or cavities of the structure and thus onto and over the matrix.

The base member, instead of being either a constituent part of the matrix or of being an individual separate structure, may form a constituent part of the frame member to be suitably fitted to the matrix substantially as a single base member-frame member unit. It is understood that it is also possible to arrange the base member as well as the frame member and matrix as a substantially single unitary structure. The base member may be removed from the spray metal shell or left thereon, as desired. When retaining the base member on the spray metal shell, as for instance, when desiring to use the same as a fiash shearing member in a spray metal mold structure, it is of advantage to select a ring-like base member of high tensile and transverse loading strength such as a steel ring or the like. Such flash shearing base member is for instance illustrated in Fig. 5 in which the flash shearing, ring like base member I5 is carried by the spray metal shell IS.

The material of the frame member may be any suitable metallic or non-metallic material. We prefer to use, however, a suitable metallic ring as the frame member. The metal of the ring may be the same metal in solid form as the metal used for the preparation of the spray metal shell or may even consist of spray metal. The frame member need not necessarily surround the matrix on all sides; it suffices in most cases if the frame member but partially surrounds the same. The frame member need not necessarily be one continuous member and may comprise a multiplenumber of individual members and irrespective of whether the same are joined together or closely spaced around the matrix. Though we prefer as a matter of convenience an arrangement whereby the frame member rests upon or is fitted to the base member, this is not absolutely essential and the frame member may be arranged or supported in any other manner, provided the base member substantially extends at least to the frame member with at least a portion of the frame member extending above the surface of the base member to be sprayed.

The frame member in accordance with the invention may be removed from the spray metal shell or the same may be left thereon, as desired. The removal of the frame member may be accomplished either incident to the separation of the spray metal shell from the matrix, or, alternatively, as a separate independent step prior or subsequent to such separation. In some cases it is of advantage to retain the, frame member as a part of the spray metal shell. This is particularly true in the case of molds where a metal ring-like frame member is used. We then find it of advantage to select a metal ring possessing a certain elasticity combined with high tensile strength, such as a steel ring or the like. Such ring will impart to the finished mold a high degree of tensile and transverse loading strength. The same is preferably so constructed as to form a substantially single unit with the base member; and a constituent part of the mold shell posi- Depending upon the material of. the matrix and the material of the structural elements composing the auxiliary structure in accordance with the invention, the separation of the'spray metal tioned and capable to act as a flash shearing member or ring in the molding operation of the article to be reproduced. Such base memberframe member unit is for instance illustrated in Fig. 6 in which this unit, as a flash shearing ring I I, is carried by the spray metal shell I2.

The surface of the matrix or of the base member or of the frame member may be suitably treated if desired to secure a satisfactory bonding with the impinging spray metal particles. Thus, for instance, if such surface consists of a substantially smooth material, the same may be lightly sand or grit blasted and thereafter sprayed.

If the frame member or base member are desired to be obtained as a constituent part of the finished mold shell it is of advantage to suitably treat the same to improve the bonding with the spray metal so that they may become as much as possible anchored to the spray metal mold shell. This may be accomplishd by heavy sand blasting, grit blasting, or the like or by otherwise heavily roughening, dove-tailing or keying the surface of the frame member or base member or both, as the case may be, which is to be contacted by the spray metaL If the particular surface already presents a heavily porous or rough aspect such pre-treatment may not materially increase its spray metal bond and would not be necessary in such case.

The spraying of the matrix and of the auxiliary structure within our invention, i. e., the base member and frame member either separately or as a unit, may be carried out in accordance with wen known practices and should be continued at least until a spray metal shell is formed on the matrix of a thickness sufficient to be capable of separation therefrom as a substantially selfsupporting structure. This shell may be further backed up, if desired, by either spraying with metal, or in any other suitable manner, such as by casting a backing thereon.

shell therefrom may be effected in numerous ways. Thus, for instance, where the matrix or the elements in question comprise a metallic material, the detachable spray metal shell may be for exampl formed thereon and removed therefrom in accordance with the process set forth in the U. S. patent to Wm. 0. Reid, No. 2,171,599. If the matrix or these elements comprise a nonmetallic material, the separation from the spray metal shell may be accomplished in most cases by suitable stripping therefrom.

All of the structural elements composing the auxiliary device in accordance with our invention should be preferably secured to each other and in substantially fixed relation to the matrix by such suitable means as screws, bolts or the like.

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 in which we have endeavored to claim broadly all inherent novelty.

We claim:

1. Process of making negatives in metal of a matrix by metal spraying which comprises providing a matrix with a base member extending substantially from the surface of said matrix adjacent all sides thereof, at least partly surrounding said matrix in spaced relation thereto with a frame member, said frame member being positioned to substantially define with said matrix and said base member a space, spraying metal onto said matrix, said base member, and into said space at least until a spray metal shell of substantially self-supporting thickness is formed on said matrix and said base member substantially extending on said base member from said matrix to said frame member, tied down by the corner formed by said frame member and base member, and removing at least that part of said shell covering said matrix substantially intact from said matrix.

2. Process in accordance with claim 1 in which said matrix is surrounded by said frame member on substantially all sides thereof.

3. Process of making negatives in metal of a matrix by metal spraying which comprises providing a matrix with a base member extending substantially from the surface of said matrix adjacent all sides thereof, surrounding said matrix in spaced relation thereto with a'frame member, said frame member being positioned to substantially define with said matrix and said base member a space, providing said matrix with a flash of spray metal, thereafter spraying metal onto said matrix, said base member, and into said space at least until a spray metal shell of substantially self-supporting thickness is formed on said matrix and said base member substantially extending on said base member from said matrix to said frame member, tied down by the corner formed by said frame member and base member, and removing at least that part of said shell covering said matrix substantially intact from said matrix.

4,. Process of making negatives in metal of a matrix by metal spraying which comprises providing a matrix with a base member extending substantially from the surface of said matrix adjacent all sides thereof, surrounding said matrix in spaced relation thereto with a frame member,

said frame member being positioned to substantially define with said matrix and said base member a space, spraying metal onto said base member and into said space at least until a substantially coherent spray metal coat is formed on said base member and extending from the matrix to the frame member, and tied down by the corner formed by said frame member and base member, thereafter spraying metal onto said coat and said spray metal shell on said matrix and said base member substantially extending on said base member from said matrix to said frame member, and removing at least that part of said shell covering said matrix substantially intact from said matrix.

5. Process according to claim 4 in which said matrix prior to spraying metal onto said base member and into said space is first provided with a flash of spray metal thereon.

' HERBERT S. INGHAM. ARTHUR P. SHEPARD.

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