US874877A - Method of casting. - Google Patents

Description

No. 874,877. PATENTBD DBc.z4,r19o7. E. G. UNDBRwooD.

METHOD 0F GASTING.

APPLICATION FILED JAN. 26. 1904.

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ES' f@ 7 7 Mr I MIII I Y Lsnw/xyiQ/ t k" awe?? Y x MAZ I? znoe'mto'r HERBERT GEORGE UNDERwooD, or srAMroEn, coNNEc'rIoUr.

rre'rnon oF CASTING.

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Specieation of Letters Patent.

Patented Dec. 24, 1907.

Application led January 26. 1904i. Serial No. 190.669.

To all whom it may concern:

Be it known that I, HERBERT GEORGE f .f UNnERwooD, a citizen of the United States,

`and a resident of Stamford, county of Fair- .field,i'St ate of Connecticut, have invented certain new and useful Improvements in Methods of Casting, of which the following is a description, reference being had to the acvso made therefrom weak and brittle.

companying drawing, in which the figure is a lon itudinal section of a casting apparatus suc as may be used for the carrying out of my method and such as is more fully described and claimed in an application for patent filed on the same date as this. V 4 Whilel for clearness I illustrate my method b reference to adrawing of a particular form of casting apparatus, it will be understood that I may use any other construction capable of carrying out my method.

Heretofore the operation of casting 'as ordinarily practiced where the metal flows merely y gravity or is poured into ordinary molds,

has lbeen attended withr'a number of disadvantages. In order to get the metal to flow freel it must be raised to a degree of heat muc above the freezing point. This--particularly with alloys-tends to drive off some A of the most important elements or constituents in the form of gas, a'nd further tends to .kill the molten metal, and render a cating t is therefore detrimental to perfect casting that the metal in the melting pot should be raised lto a temperature above the 'fusing point. Again, where the molten metal is takenfrom a rnace into a ladle, and the ladle moved to a distant part of the casting room, it is necessary in order Athat the metal may retain enough heat to flow freely from the ladle, that it be very highly heated at first and such heating as above stated takes .away from the strength' of the casting. Furthermore the loss of important constituents of the metal through over heating not only renders the resultant casting weak but such over heated 'metal continues to give forth gas even in the mold itself, and such gas unless it escapes through the vents ofthe mold causes bubbles andblow holes in the casting. Also underthe common gravity system of casting and even under pressure system, there is always more or less air confined in the mold itself and unable to escape, which' prevents the metal completely and sharply filling the mold' in all its angles and contours. When the metal is forced into the mold as by a plunger, though the'resultant casting is muc betterthan under the ordinary gravity method, yet

great care must be taken 1n lacing the vents, as the whirling inrush of t 'e metal into the mold tends to close the vents before the gases and inclosed air can escape. Again, plungers Aor other mechanical devices moving 1n the molten metal to force it into the mold, tend to chill the metal and to become clog ed, or if the metal be raised to a very high egree of heat such as is necessary in alloys containing a large percentage of aluminium, to the casting of which my process is intended particularly to be applied, such moving parts become melted before the metal is in condition for casting. It is necessary then in order to make a perfect castingv at a highftemperature,

that the air be exhausted from'the mold on all sides and that the forcing of the intensely heated metal into the mold be done by some means not mechanical. l

vMy method of casting does away with' these disadvantages and a casting made in accordance therewith is much denser and more homogeneous in mass and much sharper and cleaner in surface than ordinary castings.

Broadly my invention has for its main feature the exhausting of the air from the mold and forcing the metal into said mold at the same time by compressed air, and in carrying out my method I can use such an a paratus as illustrated -in the drawing ufhere A indicates 'a melting furnace heated by ordinary means such as air and gas inlet B.

Supported in the furnace is the melting pot C having a forwardly. projecting nozzle or mouth D and outlet port E which coincides with the inlet in the face plate of a mold containing chamber F which Ais supported on tracks G, H so as to move across the face of the nozzle E and thus bring the outlet and inlet ports into or out of coincidence with each other and thereby close or open the outlet E. As far as the main feature` of mymethod goes however it is only necessary that there be a connection between the melting pot and' the mold.

The chamber F contains the.moldI held in place thereby by` any suitable means asa bridge-clamp J. The mold may be provided with'venting openings i though this is not necessary in a mold made in sections. 'The chamber F has a cover K held in place by any appropriate fasteningr device, such as the bridge clamp L and om the chamber runs a pipe M which communicates by means of a valve m either with the air or with an exhaust pipe O which is connected to any air exhausting apparatus. By means of this pipe air may be exhausted from the chamber and from the contained mold. The extension of this pipe is shown in dotted lines 8. v The top of the melting pot C is closed and provided with any suitable cover P heldin place thereon, and entering into said melting pot above the surface of the metal therein is an air pipe R opening to the outside air-or attached to a compressing apparatus or some source of compressed air, wherebythe said air will force the metal in the pot into the mold when the port E is opene'd.

The application of my method is as follows. After the metal is brought to a proper temperature in a melting pot, the air is exhausted in' the mold-containing chamber. The said chamber is then moved until its inlet and the mold inlet co-incide with the outlet from the meltin pot and the metal having no impediment efore it, and forced by pressure ofthe compressedair behind it, is sucked and forced in, completely and entirely filling the mold in its smallest part orv sharpest angle, and this with a lluidity of metal far less than ordinarily necessary.

It is absolutely requisite when a sand mold is used that it be contained in a vacuum chamber, as by no other means can complete exhaustion of the air be accomplished, as, if the air be exhausted from one point only and not over the entire surface of the mold, the porosity of the mold admits air as fast as it is exhausted, thus preventing the formation of a complete vacuum. In addition to this' necessity of complete exhaustion there is also a great advantage in castin in a sand mold surrounded by a vacuum c amber, as thereby the inilowing metal is drawn to all parts of the mold equally. j

I have-found that it is not necessary to do more than charge the melting pot once with compressed air as the gases given off by the molten metal will keep up suiiicient degree of compression when the surface of the metal is lowered. This is of advantage in. that continued oxidation by the admission of fresh air is obviated.

By using compressed air as a means of forcing the metal into the mold, I get a uniform pressure over the whole surface of the metal and also I do away with any mechaniral parts moving in the metal and liable to c og ratus of the drawing merely by way ofillustration, and do not wish tolhav'e my method m any way limited in its application either As before stated I show the casting appa-V as to the material to be cast, or theappara-'I tus used--the essential feature of my invention being capable of being applied in a variety of ways and to casting from lad-les, or dippers as well as directly from a melting pot. 'N either do I wish to be limited to any special degree of temperature or fluidity in the metaltby the term molten as the degree necessary to make a casting depends upon varying conditions.

Having described claim is 1. A method of casting which consists in compressing the air above the surface of an inclosed massl of molten metal, and maintaining said pressure therein without forcing additional' air therein exhausting the air from my invention what I the interior of a mold, and opening connection between said mold and the metal Whereby the molten metal will be forced and drawn into the mold by both pressure and exhaustion, substantially as described.

4 2. A method of'casting which consists in compressing the air above the surface of an inclosed mass of molten metal, and maintaining said air under pressure therein Withsealing a metal pot or other receptacle containing metal from outside air, charginlT the space above the metal with a compressed gas and cutting off the supply of gas until the melted metal has been forced from the melting pot, thus preventingcontinu'ed oxidation of the metal in the pot.

4. A method of casting which consists in sealing a melting pot or other receptacle con# taining molten metal from outside air, charging the space above the molten metal with compressed air, and cutting off the supply of compressed air until all the metal has been forced from the melting pot, thus preventing continued oxidation of the metal 1n the pot, substantially as described.

5. A method of casting which consists in sealing from out-side air a melting pot or other receptacle containing metal to be 'melted and cast, charging the space above from said melting pot into the mold.`

6. A method of casting which consists in sealing a melting pot or other receptacle containing molten metal from outside air, charg` ing the space above the'molten metal with compressed air. and cutting off the supply of the molten metal Will be ioreed and drawn compressed air until the metal has been from the melting pot into `the exhausted forced from the melting pot, thus preventing mold. continued oxidation of the metal in the pot,

5 exhausting air from the mold and bringing Witnesses:

the exhausted mold into communication W. H. RUBY, with the bottom of the melting pot whereby F. B. WRIGHT.

HERBERT GEORGE UNDERWOOD.

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