Title:
Method of casting articles of intricate design and a product thereof
United States Patent 2118468


Abstract:
The principal object of this invention is facilitate the casting of small metal articles, pa ticularly articles of intricate detail such as jewe ry which frequently are designed with hollow undercut portions and perforations, so that th will have a smooth clean surface faithful in d tail to...



Inventors:
Jungersen, Thoger G.
Application Number:
US74589334A
Publication Date:
05/24/1938
Filing Date:
09/28/1934
Assignee:
Jungersen, Thoger G.
Primary Class:
Other Classes:
29/896.4, 63/15, 164/289
International Classes:
B22D13/06
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Description:

The principal object of this invention is facilitate the casting of small metal articles, pa ticularly articles of intricate detail such as jewe ry which frequently are designed with hollow undercut portions and perforations, so that th will have a smooth clean surface faithful in d tail to the original and free from imperfectior or holes, and to enable such result being acconi plished with the minimum of expense.

A further object of the invention is to enab] the formation of intricate castings which will s closely resemble the original and finished prod uct that the slow and tedious work of patternin and detail cutting required in connection wit] present casting methods is eliminated.

The principal features of the invention ar, hereinafter defined step by step in reference t the accompanying drawing, in which Figure 1 t a sectional view of a flexible mould which is buil in separable sections around a model of th article to be reproduced.

Figure 2 is a sectional view showing the fusible model of the article to be produced invested in the mould in which the article is to be cast. Figure 3 is a diagrammatic sectional elevational view illustrating the manner of centrifugal casting of the fusible model and of the metal.

In carrying this invention into effect the designer of a piece of jewelry or any small article to be cast produces a model of the article in wood, metal or other suitable material, and this may have undercut surfaces, hollows or perforations of any desirable kind. This model is placed upon a base and a flexible mould-forming material such as rubber, is built up around the model, the top surface being arranged to form a parting line along suitable lines of the model.

This bottom section I of the mould is formed with a plurality of dowel or socket holes 2 arranged over the surface thereof closely around the model 3. When the lower mould section is completed the top section 4 is built thereover to encircle the remaining portion of the model and to form projecting teeth 5 to extend into the guide holes in the lower section I.

A suitable gate or pouring recess is formed in the meeting faces of the half sections of the mould.

The mould thus constructed is preferably made of rubber and when the rubber material completely surrounds the model it is suitably vulcanized and caused to flow intimately about the detail structure of the model and thus assumes a permanent shape having a cavity the exact shape and detail of the model embedded therein.

to This mould is then separated arid the model is r- removed and the half sections of the mould are - brought together again and placed in a suitable 's, form of centrifugal casting machine 7.

'y A suitable quantity of a very low temperature - fusing material which may be wax or a metallic s alloy such as Wood's metal is poured into the - gate and the mould is rotated rapidly in the centrifugal casting machine. The wax or metal is e thus forced into the mould and by the centrifugal o action displaces the air within the mould, the - molten material congealing first against the exg posed surfaces of the cavity formed in the h mould and any air which may be trapped in a recess of the mould will be crowded back into the e fluid body under the pressure applied thereto and o the fluid material will advance into the recess as s it crowds the air therefrom and will progressivet ly congeal against the wall of the recess until Sthe extreme limit is reached so that the finest of cavities will be completely filled.

It is essential that the air be expelled from the mould progressively as the molten material flows in so that all interstices whether undercut or otherwise, are completely filled. When this step in the method has been completed the mould is removed from the centrifugal machine and the flexible sections are separated.

The flexible rubber material from which the mould is made permits the moulded wax to be withdrawn without injury to undercut surfaces or delicate parts.

The pattern thus produced is then invested in a material which will form a suitable mould for the metal which it is ultimately desired to form tothat shape. The wax may be dipped in a solution of plaster of Paris or of silica, and it may then have an investment material such as plaster of Paris poured therearound, or it may be invested directly in a more or less fluid mass. This investing material may be dried out in any suitable manner, but is preferably dried in a furnace, but in any event the mould created by the flowing material is subjected to sufficient heat to melt the wax or other material of which the temporary pattern is made' and all traces of this wax are completely removed from the mould.

The mould is then placed in the centrifugal casting machine and the molten metal from which the casting is to be made is poured into this mould and is projected under applied force into the fine recesses preferably by the centrifugal action. Finally, the mould is separated from the casting.

The final result is that an article is cast which is the exact replica of the original model. It em will be readily understood that once the original fac flexible mould is made any desirable number of 2 the patterns of fusible material may be produced int to be invested in metal-receiving material to form mo moulds and any desirable number of metal cast- in ing moulds may thus be produced from the same ar model. All will be equally accurate and as the int final mould is a complete investment of the wax mc or other fusible pattern, there will be a min- th imum of irregularities to be removed. fop The ultimate result is that metal castings of pl rings, brooches and many pieces of jewelry which fu are frequently very fine and intricate may be th 16 produced at the very minimum of cost. For ex- in ample, with known processes of casting rings, it w] may take an expert jewelry worker several hours de to finish a ring to a certain standard after casting, tr while with the present process, only fifteen to in thirty minutes may be required to finish a ring P1 to the same standard. These figures are for or- n dinary rings, such as "Exhibit A on file herein. c With finer work in platinum, from twelve to fifteen dollars' worth of labor may be expended cl in making a ring by hand by known methods, o while as little as ten minutes would cover the time ti of casting the same ring by the present process, n and the time necessary for finishing it might cost r as little as one dollar, or about one-twelfth of the r cost of finishing the ring by known methods.

The process of the present invention will produce c rings on a quantity basis without the necessity of making dies,-a huge saving in itself, since a good set of dies costs from $100 to perhaps $1000. As compared with this excessive investment which the use of dies requires, the present process makes rings and other articles of jewelry at a total cost of from $2 to $3.50 for the first mould.

Thus a manufacturer employing this process may effect large savings in capital investment in dies and in precious metals (since a large number of rings etc., must be made at the same time from a die in order to justify the expense of a die, while only a few rings need be made from a mould made in accordance with this invention to pay for the cost of the mould several times over). Hence it is clear that the process of the present invention may effect savings up to 90% in the cost of production, especially if the production is for orders of less than 1000.

It will be understood.that this process is particularly applicable to the casting of precious metals, but it will also be understood that various other metals may be handled in the same way and particularly, base metals of tin and similar alloys.

What I claim as my invention is:1. A method of casting articles of jewelry of intricate design consisting in first producing a model of the article to be. cast, then forming about said model a primary mould of a plastic material which will retain a lasting shape through subsequent treatment, then removing the model from 6the primary mould, then by centrifugal action forcing into the primary mould molten wax or other material of a low fusing point that will not injure the primary mould to form a pattern, and ploying the patterns so made for the manu;ture of casting moulds.

1. A method of casting articles of jewelry of ricate design consisting in, first making a del of the article desired to be cast, then forma primary mould in separable sections thereound of plastic material capable of assuming imate contact with the intricate designs of the del and adapted to retain the assumed shape, en removing the model, then by centrifugal rce projecting into the mould cavity and cometely filling same a molten material of a low sing point which will not injure the mould, en removing the fusible pattern so cast, then vesting said pattern in a refractory material hich will assume all the contours of its intricate *sign to form a secondary mould, then heat eating said investment removing the low fus.g pattern therefrom, then by centrifugal force ojecting molten metal into the heat treated lould, and finally removing said mould from the ast article.

3. A method of casting articles of jewelry as 1aimed in claim 1 in which the plastic material f which the primary mould is formed is treated o retain its assumed shape and after such treatLent remains flexible and is flexed in the act of emoving the model to withdraw the mould mateial from the intricacies of the model.

4. A method of casting articles of jewelry as laimed in claim 2 in which the pattern formed y projecting the pattern material into the prinary mould under applied force and thereby provided with a surface free from imperfections s invested with a fluid coating of a finely ground refractory material, said refractory material being built up to a thickness sufficient to withstand the stresses to be applied by forcing molten metal thereinto to form the article to be produced. 5. A method of casting an article of jewelry or a part thereof of a design intricate to the extent of having one or more small projections or depressions, comprising first producing a model of the article to be cast, then forming about said model a primary mould, then removing the model from the primary mould, then introducing into the mould by force sufficient to deposit the material into the depression or depressions of the primary mould molten wax or other material of low fusing point that will not injure the primary mould to form a pattern, and employing the patterns so niade for the manufacture of a casting mould.

6. An article of jewelry or a part thereof of a design intricate to the extent of having one or more small projections or depressions made by a process comprising first producing a model of the article to be cast, then forming about said model a primary mould, then removing the model from the primary mould, then introducing into the mould by force sufficient to deposit the material into the depression or depressions of the primary mould, molten wax or other material of low fusing point that will not injure the primary mould to form a pattern, and employing the pattern so made for the manufacture of a casting mould.

THOGER G. JUNGERSEN.