US1364124A - Method of removing patterns from molds - Google Patents

Description

UNITED STATES PATENT OFFICE.

VICTOR LOUGHEED, OF SAN FRANCISCO, CALIFORNIA, ASSIGNOR T0 ENTERPRISE FOUNDRY COMPANY, OF SAN FRANCIS'GQ, CALIFORNIA, A CORPORATION OF CALIFORNIA.

METHOD OF REMOVING PATTERNS FROM MOLDS.

No Drawing.

T 0 all to ham it may camera Be it known that I, VICTOR LOUGHEED, a citizen of the United States, residing at San Francisco, in the county of San Francisco and State of California, have invented a new and useful Method of Removing Patterns from Molds; and I do hereby declare that the following is a full, clear, and exact description of my invention, such as will enable others skilled in the art to which it appertains to make and use the same.

It has been the practice in making fine and accurate castings, for instance, dental inlays and the like, to form the mold by setting a suitable mold-forming material as an integral non-parted unit around a pattern of wax or similar material, which is easily melted, reduced, or dissipated. But in this practice certain practical difiiculties are encountered, particularly in the problem of removing the material of the pattern completely at a reasonable cost, and without impairment of the mold surface. The mold is generally made of some refractory material, usually with plaster-of-Paris (calcium sulfate) as a binder, and the pattern made of wax, molded by any suitable method and has the mold material poured in and set around it.

According to one method, the pattern is removed from the mold by subjecting the mold to sufficient heat to cause the wax to melt and become absorbed by the mold material, subsequent to which the mold is subjected to a temperature sufiiciently higher to cause the absorbed wax to volatilize and burn, until it no longer gives off any gas. It has been definitely determined, in this procedure, that the use of waxes which are most completely volatile affords the best results, because any non-volatile residue burns ultimately to a carbonaceous ash, which is very objectionable in that it obstructs the pores of the mold material and thus interferes with venting through the pores of the mold material.

Another practice that has been proposed, and which i the better practice when the nature of the mold material will admit, is to immerse the entire mold in hot water, at or near the boiling point, so that as the material of the wax pattern reaches its melting point, which is in all cases below the boiling point of water, it is prevented, by the Specification of Letters Patent.

Patented Jan. 4, 1921.

Application filed August 18, 1919. Serial No. 318,207.

presence of the water, from being absorbed by the mold, and consequently can be caused to float out through the opening to the mold cavity. But this practice has not heretofore been available with mold materials which are in common use, and which best serve the purpose from other standpoints, for the reason that at least some of the components of such mold material are soluble in water to such an extent that in additipn to its desired effect, the water has the undesired effect of dissolving away enough of the mold material to impair materially the accuracy of the mold cavity, and, consequently, of the ultimate casting.

The object of my invention is to avoid this last-named difliculty, and I attain this object by rendering the pattern fusing bath inert with respect to the material of the mold, this being preferably done by using, instead of pure water, water which, even at the maximum temperature at which it is employed, already contains in solution such proportion (preferably up to saturation) of the soluble material or materials in the mold as will incapacitate the bath to dissolve any material part of such substances from the mold.

As an example, if a mold material be used which is composed of a finely divided refractory material with calcium sulfate as a binder, it is simply necessary to supply, to the pattern-melting bath of water, a sufficient quantity of ground gypsum to saturate the bath (say by maintaining an excess or precipitate therein) whereupon the bath may be safely heated even to the boiling point without endangering the mold surfaces.

By my improved method, the cheaper and more satisfactory mold materials are made available; the pattern material may be collected on the water and conserved; accuracy of mold surface is insured; and, as a result, a process which has heretofore found its principal uses in the fine arts and the sciences is rendered economically available for commercial production of machine parts.

I claim:

1. The improvement in the art of removing from a molded mold the patterns of fusible material about which the mold is formed, which consists in subjecting the mold to a pattern fusing-bath containing a substance which renders the bath inert with respect to the material of the mold.

2. The improvement in the art of Waterfusing the pattern from a mold embodying in its structure a material soluble in water, which consists in first saturating the water of the bath at the required temperature With a supplyof such soluble material, and then subjecting the mold to the bath.

3; The improvement in the art of removing water fusible patterns from molds composed of porous material with a Water soluble binder-material, which consists in first supplying to a bath-of water a quantity of 15 the binder material at least suflicient to saturate the Water at the pattern-fusing temperature, and then subjecting the mold to such bath.

4. The improvement in the art of casting, which consists in forming a pattern from a material fusible in hot water, forming around said pattern a mold of refractory material having a Water soluble binder, preparing a bath of hot Water saturated with the material of the binder, and subjecting the mold with its contained pattern to the heat of the bath.

Signed at Chicago, Illinois, this 25th day VICTOR LOUGHEED.

. of July, 1919.