US1582294A - Method of preparing molds for dental castings - Google Patents

Description

April. 27 1926. 1 582291 F. C. MONTUORI METHOD OF PREPARING MOLIIDS FOR DENTAL CASTINGS original Filed July 30. 1924 gwuentou VWM Patented Apr. 27, 1926.

UNITED STATES 1,582,294 PATENT OFFICE.

FELIX C. MONTUORI, OF WASHINGTON, DISTRICT OF COLUMBIA.

METHOD OF PREPARING MOLDS FOR DENTAL CASTINGS.

Original application filed July 30, 1924, Serial No. 729,186. Divided and this application filed April 21,

To all whom it may concern:

Be it known that I, FELIX C. MoNTUonI, a citizen of the United States, residing at- W'ashington', in the District of Columbia, have invented certain new-and useful Improvements in Methods of Preparing Molds for Dental Castings, of which the following is a specification.

My invention relates to a method of preparing molds for dental castings, and has for its object to properly regulate the elimination of the wax pattern and prepare the mold for casting without accident, such as the cracking of the mold from excessive or too rapidly applied heat, or the bursting of it from rapidly generated internal vapor or gaseous pressures; and to make the preparation of the molds rapid, certain as to result, convenient and economical of time and labor.

In the preparation of a flask for dental castings to make it ready for the casting of a metal object, such as metallic dental filling, the usual procedure is to form a wax pattern exactly similar in size. and shape to the desired casting, and then support this pattern on a wire, and properly arrange these parts in the middle part of the flask,- and then pour or place into the flask around the pattern and its supporting wire, a suitable mold material or investment, such as silica and plaster or other investing refractory material or compound.

It is now necessary to have this investing material set and dried, and the pattern entirely removed so as to leave a mold suitable for the reception of the casting. At a suitable time, after the investment is set, the wire is removed to leave a sprue leading from the exterior of the flask to the mold cavity.

My improvement comes into operation for the purpose of so drying out the investment and melting and dissipating into vapor or gas the wax pattern.

This last step has usually been performed.

by the aid of gas flames turned up more. or

less high or by other available sources of heat such as electric ovens or mufiles, and much difliculty has been experienced from applying too much heat to the flask initially, and trouble has been involved in from time to time increasing the heat as the drying of theflask and removal of the pattern proceeded. The ap'plication'of too much heat at the beginning has resulted in the cracking Serial No. 24,760.

.ofthe investment from uneven drying or the bursting of it from suddenly created inthe mold of investment material as de-' scribed, an electric heater or heating conductor adapted to have the investment material molded directly within it, the electric conductor being suitably insulated from the investment material, then a suitable electric current is applied through said conductor to gradually and evenly dry out the investment and dissipate the pattern in the desired manner, and so as to leave the mold, in its interior parts, entirely free from cracks or imperfections. The usual incandescent lighting current is suitable for this purpose when passed through the conductor within which the mold has been prepared.

\Vith such objects in view, as well as other advantages which may be incident to the use of the improvements, the invention consists in the steps of procedure and combinations thereof hereinafter set forth and claimed, with the understanding that variations may be made in proportions and arrangement without departing from the nature and scope of the invention. v

In order to make the invention more clearly understood there are shown in the'accompanying drawings means for carrying the same into practicaleftect, without limitingthe improvement, in its useful applications, to the particular constructions which, for the purpose of explanation, have been made the subject of illustration.

In said drawings: v

Fig. 1 is a vertical sectional view of a flask for dental castings suitable for use in carrying out my invention.

Fig. 2 is a vertical section of the same after the mold has been prepared for heating.

Fig. 3 is a plan view showing the flaskconductor attached in an electric heating circuit. i

Fig. 4 is a vertical section showing the mold completed and empty, and the investment dried, ready for the casting o eration.

Referring to the drawing, A indicates a flask which comprises interior and exterior walls 1 and 2 which are somewhat spaced apart from each other.

On the exterior surface of the wall 1 is preferably applied a sheet of mica 3, and exterior to this mica is arranged an electric heating element 4, such as the coils of a resistance wire, this wire being of round or flattened cross-section. At the outer side of the unit 4 is arranged another sheet of mica 5 extending all around the outer side of said inner coil. At the outer side of this second layer of mica is arranged a second electricheating unit or coil 6, which may be connected with the coil 4 either in series or parallel. The two ends a, b, of this two-part coil 4, 6, are led out through the outer wall 2 of the flask by means of porcelain or other refractory insulating bushings 7 and have terminals suitable to be applied tocorresponding terminals of an electric circuit or source of suitable electric tension or power.

The spaces between said layers of mica and the exterior wall 2 of the flask are solidly filled with a highly refractory and insulating material 10, such as porcelain or a composition forming a kind of artificial stone or equivalent heat and water resisting and electric insulating compound or material, eompositions for this purpose being well known and available.

The lower edge of the inner wall 1 preferably terminates in a flange 8 which is more material to be poured or placed within the I flask and at the same time within the area defined by the heating element 4, 6 in the mold forming operation. This material or investment may be silica and plaster or other suitable refractory material or compound 11,

in which may be formed the mold cavity 12 by means of the pattern 13 supported by the wire 14 on a suitable base 14', the wire forming the sprue 15, all as above described. The wire 14 may be removed before the application of the electric current and the heating of the flask, or it may be left in place during such operation, as may be found most convenient and desirable.

After the use of the flask as above set forth and the completion of the casting operation the material 11 may be broken or washed out of the same, for the repeated using of the flask for different castings in the usual manner.

In Fig. 3 is shown a stand 16 for electrical terminals 17 with which the terminals a and b may be brought into contact for the passage of the electric current through the electrical conducting and resistance or rheostat coils 4 and 6.

After the flask has been completed for the production of a particular casting I do or may proceed with the casting process as set forth in my Patent No. 1,490,625, granted April 15, 1924.

This application is a required division of my application Serial No. 729,186, filed July 30, 1924, in which is claimed my improved apparatus, and I do not herein claim said apparatus.

What is claimed is: The method of preparing molds for dental castings which consists in pouring the investment material around a fusible pattern and a spruc former" placed within a surrounding electric heating element electrically insulated from the said investment material, and then passing an electric current through said heating element, thereby fusing and dissipating the pattern, thus preparing the mold cavity and also gradually drying the investment material for the casting operation.

In testimony whereof I aflix my signature.

FELIX C. MONTUQRI.

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