US2274186A - Method of and apparatus for investing patterns under vacuum - Google Patents

Description

c. H. BRA CE 2,274,186

METHOD OF AND APPARATUS FOR INVESTING PATTERNS UNDER VACUUM Feb. 24, 1942.

Filed Dec. 9, 1940 1 3 m I Charles H'.Brace Gamma,

Patented F b. 24,1942

UNITED STATES PATENT OFFICE METHOD OF AND APPARATUS FOR INVEST- ING PATTERNS UNDER VACUUM Charles Harold Brace; Minneapolis, Minn, assignor to General Refineries, Inc., Minneapolis,

Minn., a corporation of Minnesota Application December-9, 1940, Serial No. 369,143

14 Claims. (01. 22-1131) My invention relates to methods of and molding apparatus for investing patterns under vacuum, and has for'an object to provide a method and apparatus whereby the molding can be quickly and efliciently performed.

Another object of the invention resides in pro ducing an apparatus by means of which standard flasks or casting rings may be employed.

A still furtherobject of the invention resides in applying to the upper end of a flask, a flask extension open at its ends and communicating with the interior of the flask and forming an ebullition chamber in which ebullition of the investment occurs during formation of the mold. A feature of the invention resides in providing a coupling. for .detachably connecting the flask extension to the flask. I

Another object of the invention resides in constructing said coupling with two gripping portions adapted to extend about the flask and in constructing said gripping portions of a resilient in subsequently removing the base, coupling and A extension from the flask.

' within. suitable evacuating means.

friction material adapted to hold the flask and extension in properly assembled relation.

Another object of'the invention resides in constructing the coupling with a positioning flange forming seats for engagement with the juxtaposed edges of the flask and flask extension for positioning the'flasks with reference to the coupling and forming a seal between the flask and flask extension. 7

Another object of the invention resides in providing a base for closing the lower end of the flask and supporting the pattern and forming a sprue communicating with the mold cavity.

A still further object of the invention resides in constructing the base with a gripping member formed of flexible resilient material for holding the base attached to the lower endof the flask.

An object of the rinvention resides in the method of investing patterns under vacuum which consists in using an ordinary flask and in placing the pattern within the flask and supportting the. same from the base, in applying aooupling to the upper end of the flask, in inserting a flask extension within said coupling, in placing the mold assembly within a chamber and exhausting the air from within said chamber, and

Fig. 3 is a sectional view of the flask and base of the molding apparatus with the coupling and flask extension removed. r

Fig. 4 is a View similar to Fig. 3 showing the completed mold.

My invention consists of a flask ID to which is attached a base H. A coupling [2 is secured to the upper, end of the flask and'supports a flask extension l3. These various parts will now be described in detail.

In the form of the invention shown, the flask Ill consists of an ordinary casting ring-cylindrical in form which is of proper height and dimensions to receive the pattern and allowfor suffi- 1 cient space to invest the pattern within said flask.

' withstanding the temperature brought about by pouring the molten casting material into the mold. Although I have shown the flask It! as be- "ing cylindrical it can readily be comprehended that the same may be constructed with any suitable form, as for example to fit the particular article desired to be cast in the same. v

The base II is constructed of rubber or some other similar suitable resilient material and is circular in form, being provided at its periphery with an,upwardly extending annular gripping member H adapted to extend about and receive the lower end l8 of the flask III. The rubber from which the base H is constructed is preferably of su ch a nature that the member I! has suflicientfriction to hold the base securely attached to the flask It. At the center of the base II is provided a protuberance H! which extends upwardly into sprue enlargement 2! in which the molten casting material inserted and by which the same is directed in o the mold cavity. This protuberance has at the highest point of thesame formed in it a vertically extending hole 22 which is adapted toreceive and support a sprue pin 23. The wax pattern is indicated at 24 and is mounted upon the sprue pin 23, as clearly shown in Fig. 2.

The flask extension l3 has been shown in the drawings as a duplicate of theflask Ill. This flask extension is cylindrical in form, being open at its ends, as designated at 25, and forms. an

/ebullition chamber 26 communicating with the interior of the flask II) when superimposing the same. This flask extension is formed with sharpened edges 21 which serve the same purpose as the sharpened edges l4 of the flask II). It can readily be comprehended, however, that the flask extension I3 can be constructed of any desired shape and size, although with my invention an' extra flask which is always available in the casting room may be used to form this extension. Inasmuch as the flask extension l3 is'n'ot sub- :Iected to temperatures above room temperature, the same may be constructed of any desired material;

The flask extension I3 is held attached to the flask M by means of the coupling l2. This coupling is constructed of any suitable flexible material having suflicient friction to hold the parts in place and if desired may be constructed of rubber or the same material as the base ll.

The said coupling comprises a positioning flange 28 which is adapted to be disposed between the juxtaposed sharpened edges 21 and I4 of the'flask extension'l3 and the flask ill and forms a seal between these two parts preventing leakage of investment from between the same. The coupling 12 has an annular grip issuing upwardly from the positioning flange v23 of the same material as said flange, which grip is adapted to enparatus' is prevented. After the parts have been circle the lower end 3| of the flask extension I3 to hold the same rigidly attached thereto. Coupling 12 has another similar annular grip 32 issuing downwardly from flange 28 which is adapted to encircle the upper portion 33 of the flask ID to hold the said coupling securely attached to the flask. The positioning flange 28, in addition to forming a seal between the ends of the flask and flask extension, also serves to v position the coupling with relation to the ends of the flask and flask extention so that the two' ends thereof project similar distances into the coupling. By means of this construction the coupling .is rigidly secured to the two parts with the parts in proper relation to one another. The internal diameter of the flange 28 is substantially equal to the internal diameter of the flask I I and also that of the flask extension l3 which may be the same as thatof said flask. In this manner the inner surfaces of the flask extension I! and the flask Ill lie substantially in continuation of one another.

In the use of my invention I employ evacuating apparatus which consists of a table 34 supported upon feet 35. Thistable has a smooth top 33 and has connected to it an air outlet 32 which in turn is connected to a hose or tube 38 leading to a suitable vacuum pump or any suitable evacuating chamber. The said apparatus further includes a bell jar 39, having a cylindrical wall 4l, a=top 42 and a knob 43 secured to said top. The lower 'edge 44' of the wall 4l is ground to form an air-tight seal between said bell jar and the table 34 so that, when the said bell .iar is placed upon the table in a manner to enclose the air outlet 3'5, an evacuating chamber 45 is provided. g

The method of using the invention is as follows: The sprue pin 23 is first inserted into the hole 22 in .the base I! and the wax pattern attached to the same in any suitable manner. The said sprue pin is of such length and dimensions as to, support the pattern in spaced relation to the walls of the flask l0 when the same is applied to the base. Flask Ii! is next placed over the pattern and the lowermost end 18 thereof. inserted into the annular grip ll of the base. until the sharpened edge Id of said flask engages the upper surface of the base I i. when so applying the flask to the base the grip ll hugs the lower end it of the flask and holds the base rigidly attached to the flask." The coupling 12 is next applied to the upper end 33 of the flask It by forcing the grip 32 over the end of the same and moving the said coupling downwardly. This procedure continues until the sharpened edge l4 of the flask 10 engages the underside of the flange 2B. The flask extension I3 is now applied to the upper end of the coupling l2 by inserting the lower end 3! thereof into the annular grip 29' until the sharpened edge 2'! of said flask extension engages the upper surtace of the flang 28. By pressing downwardly upon the assembled. structure-both the sharpened edge 14 and the sharpened edge 21 are caused to form a seat against the flange 28 whereby leakage of investment out of the molding apassembled, as designated. a sufficient quantity of investment in plastic form is inserted into the flask l0 through the open end of the flask extension l3. An amount suflicient to fill the flask Ill may be employed or a lesser amount may be used if less investment is required to completely invest the pattern within the same. The molding apparatus is then set upon the table 34 and the bell jar 39 placed over the same and caused to rest upon the said table to bring the ground edge 44 thereof in contact with the surface 36 of said table. The chamber 45 within the bell jar 39 is then evacuated through the .air outlet 31 and the tube 38. Such evacuation produces ebullition within the ebullition chamber 36 whereby all of the air trapped in the investment is withdrawn therefrom. The chamber 45 is preferably subjected to vacuum during a period continuing throughout the ebullition within chamber 26. Thereupon the vacuum is cut off and the bell Jar'39 removed to give access to the molding apparatus. During ebullition the investment bubbles up into the ebullition chamber 26, and upon termination of ebullition settles back into the flask ID to completely invest. the pattern.-- In Fig. 2 the investment is shown as reaching up to the top of the flask l0 and is indicated by the reference numeral 46. At this stage the flask extension l3, the coupling l2 and the base II are all removed from the flask Ill. The relation of the parts with the flask extension and coupling removed is shown inFig. 3. Thereafter the sprue pin 23 is withdrawn from the investment. Upon applying heat to the mold comprising the flask In, the investment 46 and the pattern 24. the

pattern is melted a d flows out of the mold to able size and shape. Withdrawal of the sprue pin from the mold provides the sprue 49 and the sprue enlargement 2| being formed by the protuberance 19 of base H. The mold ascompleted is shown/in Fig. 4 and is ready to receive the molten casting material.

Theadvantages of my invention are apparent.

By evacuation, the air within the investment is completely withdrawn so that airbubbles are prevented from forming at the surface of the mold cavity whereby extremely smooth and perf ect castings result. By the use of the base with ,the flexible annular grip the lower end of the 1 mold is readily and easily closed. By means of the flask extension standard flasks such as are readily found in the casting room may be employed without alteration. The coupling used serves to,connect the flask extension to the flask which functions only during the ebullition of the I investment and which may 'be easily removed after setting of the investment to permit of continuing with the elimination of the wax from the mold cavity and the casting of the molten casting material. The flange formed in the coupling serves to position the juxtaposed ends of the flask and flask extension within the coupling so that each part extends the required distapce into the couplingand in addition forms a seal between two ends of the flask and flask extension preventing leakage of the investment out of the flask. Due'to the fact that the flask extension-is of the same dimensions a the flask the inner surface thereof lies in continuation of the inner surface of the flask whereby the investment in the ebullitionfchamber readily returns into the flask upon cessation of ebullition and with a minimum danger of adhering to the walls of the flask extension. By employing a bell jar for forming an evacuation chamber the upper end of the flask extension'may be left open to permit of pouring the investment into the flask through the open end thereof, thus greatly simplifying the method of investing the pattern.

With my improved method the teps are exceedingly simple and practical and result in considerable economy in time and in addition produce castings of smooth surface andwithcut flaws.

Changes in the specific form of my invention, as herein disclosed, may be made within the scope of what is claimed without departing from the spirit of my invention.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

l. Molding apparatus for investing patterns .under vacuum comprising a flask open at its ends, and adapted to receive a quantity of inand forming an ebullitionchamber communicating with said flask, and a coupling having a part forming a seat for engagement with the edges of said flask and flask extension to form a seal therebetween.

3. Molding apparatu for investing patterns under vacuum comprising a flask open' at its ends, a base attached to said flask and closing the lower end thereof, means for supporting the pattern and forming a sprue leading to the mold cavity, a flask extension superimposing said flask and forming an ebullition chamber communicating with said flask, a coupling having two flexible frictiomgrip for engagement with the juxtaposed ends of said flask and flask extension for connecting them together, and positioning means within the coupling for engagement with .the edges of said flask and flask extension for procuring proper engagement of the grips with said flask and flask extension.

4. Molding apparatus for investing patterns under vacuum comprising a flask open at its ends, a base attached to said flask and closing resilient material and holding said parts in proper relation, and positioning means within .the coupling for engagement with the edges of said flask and flask extension for procuring proper engagement of the grips with said flask and flask extension.

5. Molding apparatus for investing patterns. 'under vacuum comprising a flask open at its ends, a base on which said flask is adapted to rest for closing the lower end thereof, an annular grip formed on said base and constructed of flexible resilient material for embracing the lower end of said flask upon the exterior thereof and holding the base attached thereto, and means carried by the base for supporting the pattern and forming a sprue leading to the mold cavity.

'6. Molding apparatus for investing patterns under vacuum comprising a flask open at its vestment sufficient to invest the pattern; a base H attached to said flask and closing the lower end thereof, means carried by the base for supporting the pattern and forming a sprue leading to the mold cavi y a flask extension su erimposing said flask and open at its ends, said flask extension forming an ebullition chamber communicating with said flask, and having a capacity suflicient to receive a portion of the contents of the flask during ebullition, and a coupling connecting said extension to said flask. 2. Molding apparatus for investing patterns under vacuum comprising a fla'sk open at its ends, a base attached to said flask-and closing the lower end thereof, means for supporting the pattern and forming a sprue leading to the mold cavity", a flask extension superimposing said flask ends, a base on which said flask is adapted to rest for closing the lower id thereof, an annular grip formed on said base and constructed of flexible resilient material for embracing the lower end of said flask and holding the base attached thereto, means for supporting the pattern and forming a sprue leading to the mold cavity, a flexible coupling having two annular friction grips for engagement with the juxtaposed ends of said flask and flask extension, said friction, grips being constructed of flexible resilient material and connecting said parts, and positioning means within thecoupling for engagement with the edges of said flask and flask extension for holding said flask and flask extension in proper relation with respect to one another andto said grips.

'7. Molding apparatus for investing patterns.

flask and forming an ebullit ion chamber conimunicating with said first. named flask, and a coupling encircling said flasks upon the exterior thereof and connecting said flasks together in a manner to produce substantial continuity between the surfaces of said flasks. d

8. Molding apparatus for investing patterns under vacuum comprising a casting ring open at its ends, a base attached to said casting ring and closing the lower end thereof, means for supporting the pattern and forming a sprue leadrings properly mounted in said coupling and suitably positioned relative to one another.

9. Molding apparatus for investing patterns under vacuum comprising a casting ring open at its ends, a base attached to said casting ring and closing the lower end thereof, means for supporting the pattern and forming a sprue leading t o the mold cavity, a second casting ring of the same diameter .as said first named casting ring and open at its ends, said second named casting ring superimposing said first named casting ring and forming an ebullition chamber communicating with said first named casting ring, and an annular coupling encircling the juxtaposed ends 01 said casting-rings and having a positioning flange intermediate its ends adapted to engage the edges of said casting rings for holdingthe casting rings properly mounted in said coupling and suitably positioned relative to one another, the internal diameter of said flange beextension, in placing the entire mold assembly into a chamber, in exhausting the air from the chamber for a period continuing during ebullition o! the. investment within said flask extension and in removing said flask, extension coupling and base from said flask.

11. The method of investing patterns under vacuum which consists in attaching a base to a casting ring open at its ends in a manner to close'the lower end thereof, in supporting the pattern within the casting ring, in applying an annular coupling to the exterior of said casting ring at the upper end thereof, in inserting the lower end of a second casting ring into said coupling in a manner to form an ebullition chamber communicating with the interior of said first named casting ring in placing the entire mold assembly'intc a chamber, in exhausting the air from the chamber for a period continuing during ebullition of the investment within said ebullition chamber and in removing said second ingsubstantially equal to the internal diameter of said casting rings to make the inner surfaces of said casting rings lie substantially in continuity relative to one another.

10. The method oi investing patterns under vacuum which consists in attaching a base to the lowerend of a flask in a manner to close the same, in supporting the pattern from the named casting ring, coupling and base from said first named coupling ring. T

12, Molding apparatus for investing patterns under vacuum comprising a flask open at its ends, a base attached to said flask and closing the lower end thereof, means carried by the base for supporting the pattern and forming a sprue leading to the mold cavity, a second flask open at its end and superimposing said first named flask and forming an ebullition chamber communicating with said first named flask, and means havinga chamber under vacuum communicating with the upper end of the second flask.

13. Molding apparatus for investing'patterns under vacuum'comprising a flask open at its ends, a'base attached to said flask and closing the lower end thereof, meanscarried by the base for supporting the pattern and forming a sprue leading to the mold cavity, a flask extension superimposing said flask and means having a chamber under vacuum communicating with'the upper end oi said flask extension.

14. Molding apparatus for investingv patterns under vacuum comprising a flask open at its ends, a base on which said flask isadapted to rest for closing the lower end theroef, an annular base, in applying a flaskextension open at its ends to the upper'end of the flask by means of a coupling in a manner to'communicate with the interior of the flask, in pouring into the flask through the open end of the flask extension sufflcient investment to invest the pattern and less than the combined volume of the flash and flash flange formed on said base and constructed of flexible resilient material, said flange embracing the lower end of the flask upon the exterior thereof and means carried by the base for supporting the pattern and forming a sprue leading to the mold cavity.

CHARLES HAROLD BRACE.

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