US2281634A - Production of spray metal negatives of models - Google Patents

Description

M. STUSSEL May 5, 1942.

PRODUCTION OF SPRAY METAL NEGATIVES OF MODELS Filed May 29, 1940 INVENTOR. flax fij'ssel ATTORNEY.

Patented May 5, 1942 PRODUCTION OF SPRAY METAL NEGATIVES OF MODELS Max Stiissel, New York, N. Y., assignor to Otto Stosscl, Chicago, Ill.

Application May 29, 1040, Serial No. 337,787

2 Claims.

My invention relates to the production of spray metal negatives of models and particularly the production of molds, dies, patterns, or the like, of the type that are especially useful in the casting or molding of plastics such as synthetic resins, rubber, celluloid or glass and the like.-

At the present, molds for this use are generally produced by cutting the molds from solid metal blocks by means of machining and engraving tools. This method involves considerable time and expense and is not commercially practicable for low-cost production, except when the molds thus made are used in mass production where the cost of the mold'can be distributed over numerous products made therefrom. Even then the length of time necessary to produce a mold is a material drawback.

A few attempts have been made to produce molds for this work by spraying metal upon a model or a positive and thus form a mold or negative. Such attempts were unsuccessful because of distortion and, inaccuracy and the tend ency of the sprayed metal to peel off the model, particularly when spraying with metals having a fusion point above 600 C. This tendency to peel is apparently due touneven thermal stresses produced in the metal when it is sprayed upon the model and is particularly prevalent when the metal is sprayed to a thickness exceeding 0.1 millimeter, or 0.0025 inch. This makes it diflicult to spray an accurate negative or mold having sufficient strength or rigidity for practical use.

It is one of the purposes of my present invention to produce an accurate and usable negative or mold economically and commercially by spraying a model, either the original or a reproduced peeling model, in such a manner as to overcome the I heretofore mentioned difficulties, as well asother defects and limitations. 7

Further objects and advantages will be apparent from the following description taken in connection with the following drawing in which: Fig. 1 is a vertical section illustrating a model structure having inwardly tapering sides and covered with spray metal;

Fig. 2 is a vertical section illustrating a model structure having straight sides and covered with spray metal;

Fig. 3 is a vertical section illustrating a spray points inwardly therefrom, until the model structure is covered with metal to the desired thickmetal covered model structure composed of a model and model base, the latter having inwardly tapering sides;

model and model base, the latter having substantially straight sides;

Fig. 5 is a vertical section illustrating a spray metal covered model structure composed of a model and model base extending beyond the circumference of the model and having substantially straight sides;

Fig. 6 is a vertical section illustrating a spray metal covered model structure composed of a model and model base extending beyond the circumference of the model and having inwardly tapering sides.

Fig. 7 is a vertical section illustrating a spray metal covered model structure composed of a model and model base extending beyond the circumference of the model and having outwardly tapering sides;

Fig. 8 is an enlarged sectional view of a part of the spray metal frame shown in Figs. 1 or 6;

Fig. 9 is an enlarged sectional view of a part of the spray metal frame shown inFigs. 2 or 5;

Fig. 10 is'an enlarged sectional view of a part of the spray metal frame shown in Fig. 3;

Fig. 11 is an, enlarged sectional view of a part of the spray metal frame shown in Fig. 4; and

Fig. 12 is an enlarged sectional view of a part of the spray metal frame shown in Fig. '7.

In accordance with the invention a relatively thin coating of, metal is sprayed onto the surface of a model structure, including the marginal edge thereof; the spraying of the coating is continued over and below the marginal edge to points inwardly therefrom, so as to form a frame of substantially trough-like cross-section substantially around and along the marginal edge. If it is desired toiuse an original article as a model structure, it is of course understood that the surface thereof must be one adapted to be coated with spray metal. Once the first relatively thin coating of spray metal is formed additional metal maybe sprayed on the coating, preferably in the form of a multiple number of additional coatings, each applied -in substantially the same manner, i. e., by spraying metal over the face of the model structure, the marginal edge thereof and below the edge to ness. The spray metal negative formed on the model structure may then be separated from the 'latter in any suitable manner. 'In most cases the separation may be accomplished for instance by suitably severing or removing the underhanging portion or side of the spray metal frame, formed around the marginal edge of the model face of the model structure including the marginal edge and onto the side 4. In this manner the spray metal coating or negative formed on the side 4 will act to tie down the remainder of the spray metal coating on the surface of the model structure thus substantially preventing the peeling thereof. The spray metal is applied by means of a suitable metal spray gun from which finely divided metal particles,'at least some of which are molten or heat softened, are propelled against the surface to be sprayed. After the formation of the first coating as described, additional spray metal 1 may be applied until the model is covered with spray metal to the desired thickness. If the model structure has substantially straight sides as, for instance, the sides 4a illustrated in Fig. 2, it will be necessary for the purpose of tying down the initial relatively thin spray metal coating 6a to extend the same to in back of the model structure. Instead of using a substantially single unit model structure as, for instance, illustrated in connection with Figs. 1 and 2, model structures may be used in which the model or master is attached to a suitable base or auxiliary member as, for instance, illustrated in connection with Figs. 3, 4, 5, 6 and '7. As shown in Fig. 3, the model la is supported by a plate or base 8 secured to the model by suitable means, such as the screws 9. In this case the plate or base 8 has the inwardly tapering side l0. When the initial relatively thin spray metal coating 6b is applied to the model structure it will extend over the marginal edge 4a and inwardly therefrom on the tapered side ID of the base 8. In Fig. 4 there is illus-. trated a model structure composed of the model la suitably secured by means of the screws 9 to a support I l the sides l2 of which form with the sides I3 of the model the marginal edge I4. In

this instance the spray metal coating 60 is applied to the model structure in substantially the same manner as described in connection with Fig. 2, i. e., by applying the spray metal to the surface of the model structure including the marginal edge I 4 and extending the coating 60 to points on the back of the model structure, i. e., to the back of the plate or base H. In Figs. 5 and 6 substantially the same procedure is followed in the application of the initial relatively thin spray metal coatings 6d and 6e respectively as was described in connection with Figs. 1, 2, 3 and 4. The spray metal coating (id, as illustrated in Fig. 5, is applied to the surface of the model structure including the marginal edge l5 and to in back of the base 16; the marginal edge l5 in this case is formed on the base I6 which is attached, by means of screws 9, to the model do. In Fig. 6, the model structure there shown is composed of the model M and the'plate or base 20 secured to the model by means of screws or the like 9. The plate or base 20 has the marginal edge 2| and the inwardly tapering side 22.

The initial spray metal coating 62 applied to the model structure in the manner hereinbefore described in connection with the preceding examples extends over the surface ofthe mode structure including the marginal edge 2| and the inwardly tapering side 22. Instead of inwardly, or partly inwardly, tapering sides, as illustrated in connection with Figs. 1, 3 and 6, the model structure may have outwardly tapering sides as, for instance, illustrated in Fig. 7 in which the plate or base 23, attached to the model 4a by means of screws or the like 9, possesses outwardly tapering sides 24 and the marginal edge 25. The initial spray metal coating 6] applied to the model structure, in the hereinabove prescribed manner, extends over the surface of the model structure including the side 24 and around the marginal edge 25 to inback of the plate 23.

Once the first spray metal coating is formed on a model structure, additional spray metal such as the spray metal I referred to in the figures may be applied until the model is covered with spray metal to the desired thickness. It is preferred to spray at least the major portion of such additional spray metal onto the initial coating in the form of a multiple number of additional spray metal coatings in substantially the same manner as the "initial coating was applied. In order to separate the model or model structure from the spray metal negative, the

underhanging side of the spray metal frame, as, for instance, identified ,in the examples illustrated in Figs. 8 to 12 by the numerals a 30b, 30c, 30d and 30a respectively, is suitably severed or removed from the remainder of the spray metal frame, whereupon the spray metal negative may be separated fromthe model. If desired, the surface of the model structure to be sprayed may be suitably treated, such as by sandblasting, gritblasting, acid etching or the like to roughen the same and thus facilitate or enhance the adhesion of the spray metal. Once a spray metal shell of suitable thickness is obtained the same may be backed up by spraying or casting.

It will be understood from the foregoing that the first relatively thin spray metal coating, and preferably also subsequent coatings or amounts of spray metal, are applied to the model structure in a manner such that a frame of substantially trough-like cross-section is formed around and along the marginal edge of the model structure. This is, for instance, further exemplified in Figs. 8, 9, 10, 11 and 12 in which cross-sections of part of the spray metal frames obtained on the various model structures are shown. The part of the spray metal frame section shown in Fig. 8 is that of a spray metal frame obtained on the model structure illustrated in Fig. 1 or on the model structure illustrated in Fig. 6, whereas the part of the frame section shown in Fig. 9

is that of a spray metal frame obtained on the model structure shown in Fig. 2 or on the model,

structure shown in Fig. 6; Figs. 10, 11 and 12 show parts of spray metal frame sections of corresponding spray metal frames obtained on the model structures shown in Figs. 3, 4 and 7 respectively. It will be observed that in each case '2, 3, 4 and 5, the marginal edge of the model structure is defined by a substantially straight surface. The term marginal edge as used herein in connection with a model structure is therefore intended to designate that edge which is defined by the contours of maximum dimensions of the model structure in a direction substantially transverse to the direction of draw, 1. e., transverse to the direction of removal of the spray metal negative from the model or model structure, and irrespective of whether such edge constitutes a corner, or, a spherical configuration, or, a side or other surface.

It will be apparent to those skilled in the art that minor variations and deviations from the foregoing processes as described may be indulged in without departing from the spirit and scope of this invention, as defined in the appended claims.

I claim:

1. Method of preventing warping in the manufacture of a spray metal negative of a model adapted to be coated with spray metal, which comprises applying to such model, including the marginal edge thereof a relatively thin coherent coat of spray metal, at least part of said coat being so bonded as to be strippable from said model, continuing the spraying of said coat over and below said edge to points inwardly therefrom so as to form a spray metal frame of substancoat of spray metal, at least part of said coat being so bonded as to be-strippable from said model, continuing the spraying of said coat over and below said edge to points inwardly therefrom so as to form a spray metal frame of substantially trough-shaped cross-section, substantially along and around said edge, spraying additional metal onto said coat until the model is covered with metal to the desiredthickness,

opening said spray metal frame to permit draw-v ing of the spray metal shell formed overlying said model, drawing said spray metal shell and recovering a substantially accurate nonwarped spray metal negative of said model.

. MAX s'rossaL.

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