US2454961A - Method and apparatus for casting aluminum - Google Patents

Description

Nov. 30, 19. M. F." BOOTH 2 3 METHOD AND APPARATUS EOR CASTING ALUAHNUM Filed June. 7, 1943 5 Sheets-Sheet 1 .Ifql.

INVENTOR MORRIS F. BOOTH ATTORNEY NDV. 3%, 1948. M. F. BOOTH mamop Am) APIARATUS FOR CASTING Awumuu 5 Sheets-Sheet 2 Filed June '7, 1943 HY. Rm MY m l W m m wW m H mm? Nov. 30, 1948. M. F. BOOTH METHOD AND APPARATUS FOR cAs'rme ALUMINUM 5 Shqtg-Sheet 3 Filed June 7, 1943 ,H T m /m ll .WB tO I H b m m M g g W Q Q. NV Y/ til lil' l ll'l I I .2 am 3 a mom. nlmu. Q0;

Nov. 30, 1948. M. F. BOOTH METHOD AND APPARATUS FOR CASTING ALUMINUM 5 Sheets-Sheet 4 Filed am 7, 1943 INVENTOR NORRIS F. BOOTH ATTORNEYS z ll Ill

Nov. 3, 1948. M. F. BOOTH METHOD AND APPARATUS FOR CASTING ALUMINUM Filed June; 7, 1943 5 Sheets-Sheet 5 l A i C &

A. OhEYS Patented Nov. 30, 1948 METHOD AND APPARATUS Foa CASTING ALUMINUM V I I Morris F. Booth, Alden, Mich. Application June I, 1943, Serial No. 489,929

l J This invention relates to casting or molding of metals, and particularly to a process and apparatus for the same wherein high pressure is maintained on the metal in the mold or die during the entire cooling process upon the metal that is cast or molded.

In the art of casting or molding metal, in what is termed the die casting art, it has been the common practiceto melt a body of metal that is to be cast into a mold within-a melting pot and to 2 a processand an apparatus for casting or molding metals in their liquid state under pressure that is constantly maintained on the entire body of unsolidiiied metal within the mold cavity duringthe entire cooling period. Still another object of the invention is to provide a process of molding or casting metals in the liquid state under pressure that is constantly,

- maintained on the unsolidiiied body of metal in force the liquid metal into a suitable mold or die through a gooseneck or spout of many forms under pneumatic or hydraulic pressure. In all of these previous processes and apparatus for moldingor die casting metal, the metal that is cast in the mold completely fills the spout of the die casting machine, the sprues, the runners,v

as well as the mold cavity. The conventional practice has been to cool the molds as quickly as possible by circulating cooling fluid through the same so as to reduce the operating time of each cycle of operation of the machine. Therefore, all parts ofthe mold have been intensely cooled to rapidly chill the metal that is cast into the mold cavity and permit the molds to be quickly opened after the metal has been cast.

While the art of die casting has reached a relatively high stage of perfection, yet articles that are produced by present day commercial die casting or molding methods are substantially limited in size because porosity of themetal is one of the major considerations, and one of the major difilculties of articles that are produced by conventional molding or die casting methods.

It is well-known that the wall thickness of articles produced by conventional die casting or molding purposes must be substantially greater than if the porosity of the metal could be completely eliminated, and that if the density of the metal could be increased during the die casting or molding process, the wall thickness could be considerably reduced.

the mold or die wherein the body of metal in the die is cooled insuch a manner that the body solidifies gradually from the remote portions of the mold. cavity toward the opening through which the mold has been filled so that the metal adjacent the mold opening will be the last portion or the body of metal within th mold cavity to solidify, whereby the pressure that is main-- tained on the metalin the filling opening will be constantly transmitted throughout the body of metal in the die or mold as it is cooling and thereby increase the density of the metal as it is cooling in the mold and substantially elim inate porosity in the cast body of metal.

Another object of the invention is to provide a process of casting or molding metal in a liquid state in such a manner that the metal to be cast is moved into the mold by means of a carrier metal that has a lower melting temperature than the metal that is being cast so that the carrier metal will at least partially'enter the mold or die and thereby constantly maintain pressure upon the metal that is being cast during the cooling period irrespective of the shrinkage of the cast metal during the cooling period because the molten carrier metal can. follow any shrinkage contour developed by the surface of the metal being cast.

It is, therefore. an object of this invention to provide a. process and an apparatus for castingor molding metal under pressure in such a manner that pressure is constantly maintained on the liquid metal in the mold during the entire cooling period so that when a metal shrinks during the cooling period the pressure on the metal that is still in a plastic'or a liquid condition will force it into various parts of the mold to absorb this shrinkage and fill in the mold cavity solidly, whereby the density of the metal cast or molded is greatly increased and the porosity is substantially eliminated.

Another object of the invention is to provide Still another object of the invention is to provide a process of casting metal under pressure in accordance with the foregoing object wherein the cooling of the cast metal is controlled in such a manner that the body of cast metal cools gradually from the portions thereof remote from the filling opening of the mold towardv the filling opening whereby the carrier metal may constantly maintain pressure on the entire body of unsolidified metal during the entire cooling period and cause the unsolidified metal to be continually forced outwardly against the body of solidifled metal until the body of metal being cast has completely solidified.

Another object ofv the invention is to provide a process for casting metals in a liquid state under pressure in accordance with any of the foregoing ,objects wherein a predetermined and selected quantity of metal is cast into a mold cavity.

Another object of the invention is to provide a process of casting or molding metal in a liquid state that is maintained under continuous hydraulic pressure during the entire cooling period wherein a mold "or die'is substantially filled with the metal to be cast or molded and a molten metal having a lower melting temperature than the metal that is being cast fills the remaining portion oi the mold or die and has pressure applied thereon so as toproduce hydraulic pressure upon the metal being cast and wherein the cooling or the cast metal is controlled in such a manner that the body cast metal cools from those por- I tions or the mold that are remote from the filling draulic pressure can be removed from the portion oi! the mold that it fills. or at least substantially so.

Another object of the invention is to provide a process for casting or molding metals in a liquid state under pressure in accordance with any of the foregoing objects wherein hydraulic pressure metal has hydraulic pressure applied thereon for moving the molten metal through a cooling chamber and through an extrusion .die so that the metal is gradually cooled from a liquid to a solid condition over a substantially long passage whereby the metal receiving chamber for molten metal may be intermittently refilled and the hydraulic pressure applied upon the molten metal intermittently without detrimentally efiecting the metal being extruded because of the resiliency of the metal in a portion of the cooling chamber wherein the metal is in what may be termed a slush or spongy state.

Further objects and advantages will become apparent from the drawings and the following description.

In the drawings:

Figure l is a vertical cross sectional view oi an apparatus upon which the principles 01' this invention can be practiced, and showing a diagrammatic hydraulic system for actuating the same. a

Figure 2 is a diagrammatic illustration oi the machine shown in Figure 1 illustrating the first step in the process in casting or molding using the principles of this invention.

is applied upon the metal being cast by -means of a second metal having alower melting temperature than the metal being cast.

Another object 0! the invention is to provide a process for casting metal in accordance with any 01! the foregoing objects wherein the metal being cast is of a different density than the low temperature metal that applies hydraulic pressure upon the cast metal.

Still another object of the invention is to provide a process of casting metal in a liquid state in accordance with any of the foregoing objects wherein the metal being cast may be supported upon the lower temperature metal which thereby acts as a carrier metal to move the metal to be I cast into a mold.

-It is another object of the invention to provide a process of casting metals in a liquid state under constant pressure wherein the carrier metal is a heavier metal than the metal to be cast.

It is another object of the invention to provide a process of casting metals in a liquid state under constant pressure wherein the carrier metal is lighter than the metal to be cast.

Another object of the invention is to provide I an apparatus for practicing the'process of this invention wherein the mold is retained in closed position by means of fluid motors and a fluid motor is provided for applying pressure upon the low temperature metal whereby it can apply hydraulic pressure upon the metal being cast.

Another object of the invention is to provide a process for die casting wherein more or less conventional molds can be used but wherein the principles of this invention can be practiced.

Still another object of the invention is to utilize the-principles of this invention in practicing an extrusion process for forming metal articles of substantial length.

Still another object of the invention is to provide an extrusion process wherein molten metal is extruded by means of the application of hydraulic pressure upon'the body oi. molten metal to force the same through an extrusion die.

It is still another object of the invention to provide an extrusion process wherein .molten opening of the cavity.

Figure 5 is a diagrammatic view similar to Figure 4 illustrating the manner in which the final cooling of the cast metal takes place so that hydraulic pressure of the low temperature metal can be constantly maintainedon'the cast metal until it has completely solidified.

Figure 6 is a diagrammatic illustration of the use of the process of this invention, showing a part of the machine in cross section, wherein a metal disc has been placed upon the carrier metal to prevent agitation between the carrier metal and the casting metal when the casting metal is poured upon the carrier metal.

Figure 7 is across sectional view taken along line 'I--'l of Figure 6.

Figure 8 isa diagrammatic view similar to Figure 6 showing the final stages of cooling of the casting metal wherein the carrier metal retains hydraulic pressure on the casting metal.

Figure 9 is a diagrammatic view similar to Figure 6 showing the manner in which a more dense metal can be carried by a light metal for casting or molding purposes.

Figure 10 is a view similar to Figure 8 showing the manner by which the light carrier metal maintains hydraulic pressure on the heavy casting metal during the final stages of cooling of the casting metal.

Figure 11 is a diagrammatic view similar to Figure 6 showing the manner by which chemical reaction, or alloying between the metals can be substantially prevented.

Figure 12 is a diagrammatic view similar to Figure 10 illustrating the final cooling period of the light metal that is forced into the mold by a heavier metal and the manner by which hydraulic pressure can be maintained upon theiight metal during the final cooling period.

Figure 13 is a diagrammatic illustration parw th disclosed in Figure l. Figure 14 is a vertical cross sectional view somewhat diagrammatically illustrating a machine by which the principles of this invention can be practiced in connection with die casting -apparatus. l Figure 15 is a cross sectional view similar to Figure 13 illustrating the manner in which the mold is filled.

Figure 16 is an enlarged cross sectional view of a portion of the mold and nozzle engaged therewith shown in Figure 14 illustrating the location of the liquid level between the casting metal and the carrier metal.

Figure 17 is a cross sectional view of a mold wherein -a plurality of articles are cast simultaneously illustrating the manner in which hydraulic pressure can be maintained upon each of the plurality of articles in a mold during the entire cooling period thereof.

Figure 18 is a cross sectional view ofan apparatus. illustrating somewhat indiagrammatic form, for utilizing the principles of this invention as practiced in an extrusion molding process for extrusion molding metal articles for molten metal. The machine upon which the process of this invention can be practiced consists of a frame ||I having the cored passages ii, l2 and I3 that are machined to receive the cylinders ll, l5 and I5, respectively; The cylinders, l5 and I5 receive rams l1, l8 and i3, respectively, that havethe piston. heads 2|], 2| and 22, respectively, thereon that slidably engage cylinders ll, I5 and I5, re spectively, wherebyto form fluid motors. The end walls of the cylinders ll, l5 and I6 are closed by means of. suitable closure wall members 23, 2|

' and 25, respectively.

The rams I1 and I3 carry mold or die members and 21, each of which has a recess therein whereby to form a mold cavity 23 when the mold members 26 and 21 are in closed position as shown in Figure 1. The rams I1 and i8 thereby provide means for bringing the molds 25 and 21 into closed relationship, the molds being divided along the parting line 23, thus, the hydraulic motors 30 and' 3| are arranged in opposed relationship.

A bed plate 32 is adapted to support the mold or dies 26 which slide upon the upper face 33 thereof cylinder 35 that extends through the bed plate 32.

An electric heating coil 35 is disposed around the toward the filling opening, in a manner and for reasons which will be hereinafter described.

35 in axial alignment therewith. A cylinder bore extends through the cylinders .33 and 35 in A second cylinder 33 extends from the cylinder axial alignment with the mold filling opening 4| that is provided for the mold cavity 28 and is of substantially the same diameter as the cylinder bore 40. and for reasons which will be hereinafter discussed.

.The cylinder bore 40 receivesa piston or a plunger 42' that is provided 'on the end of a ram extending from the cylinder 44 of a hydraulic motor 45.- The ram 4: being provided with a cylinder 35 for maintaining the same at a relatively high temperature whereby to maintain molten metal therein in a molten condition as long as the metal is retained in the cylinder-35, in

a manner and for reasons which will be herein- 7 after described.

The mold members 25 and 21 are provided with cooling passages 31 and 38, respectively, for cooling the body of cast metal contained in the mold cavity 28, these cooling passages 31 and 23 being specifically arranged in the mold members 25 and 21 to cool the body of molten metal within the mold cavity 28 from the outside surface thereof piston head 48 that reciprocates in the cylinder bore 41. A sealing closure wali member 48 is provided for the end of the cylinder 44.

The cylinder 44 is connected to the frame ill of the machine by means of the strain rods 43. four of the strain rods being preferably provided around the cylinder 43. The cylinder 39 contains an electric heating coil 50 that is adapted to maintain the temperature of a metal con.- tained within the cylinder 38 in a molten condition at all times.

The machine It may rest upon a suitable foundation' 5|.

The fluid motors 30. 3| and 45 are preferably of the hydraulic type and a suitable source of fluid under pressure is provided for supplying these motors with operating fluid for reciprocating them in conventional manner. Any suitable type of pumping systemmay be provided for supplying the fluid under pressure, and since such pump systems for supplying fluid under pressure are well-known in the art, and the pumping system forms no part of this invention, no particular type of pumping system will be disclosed or described herein as any of the conventional forms of pumping systems can be used upon the machine of this invention.

In order to control the operation of the hydraulic motors 30 and 3|, a 4-way valve 52 of conventional design is providedhaving a pressure supply conduit 53 that is connected to the pressure side of the pump for delivery of fluid under pressure to the valve 52. Conduits 54 and 55 are connected to opposite ends of the hydraulic motor 3|! for supplying fluid under pressure thereto according to the setting of the 4-way valve 52 by means of the control handle 55. A return line 51 is provided on the 4-way valve 52 for returning fluid to a reservoir from one end of the motor 30 when fluid under pressure is being supplied to the opposite end of the motor 30.

The hydraulic motor 3| has a conduit .58 connected thereto that supplies pressure fluid to the advancing side of the hydraulic motor 3|, this conduit 58 being connected to the conduit 54 that supplied pressure fluid to the advancing side of the hydraulic motor 30. A second conduit 59 connects the opposite end of the hydraulic motor 3|, or the retraction side thereoiZwith the supply conduit 55 that conducts fluid to the retraction side of themotor 30. Thus, it may be'seen that both hydraulic motors 30 and 3| are arranged inparailel circuit relationship for opening and closing the mold members 23 and 31, respectively.

A 4-way valve is connected to a source of aerator to the 4-way valve as for delivery into the supply' conduits 68 and t8 undercontrol of the handle 10. The conduit 68 is connected to the "advancing side of the hydraulic motor 45 while the conduit 65 is connected to the retraction or pushback side of the motor. A return line ll connects the 4-way valve it with a reservoir for delivering fluid thereto from one side of the hydraulic motor 45 when pressure fluid is being supplied to the opposite side of the hydraulic motor.

The process of pressure casting. and the apparatus for practicing the process, is particularly adaptable for casting largemetal objects that have an individual unit weight of 50 lbs. to '75 lbs. or more. While the process of pressure casting of this invention may be used to advantage in pressure casting any size metal article, yet its special advantages are particularly meritorious when quantities of molten metal in units of 50 lbs. to 100 lbs. or more are handled for individual castings, such as cylinder heads of internal combustion engines. One of the particular disadvantages of pressure casting large metal products is the shrinkage of the metal that occursduring the cooling of the metal alter it has beengiorced into a mold under pressure. In the usual form of pressure casting devices, and processes heretofore practiced, the procedure has been to' attempt to follow the usual practice in connection with die casting of small objects wherein a metal was maintained in molten condition and forced through a gooseneck into the mold or die, the excess metal being drained ofl from the dies through the gooseneck after the metal object had cooled in the dies. While this general procedure is satisfactory for small articles wherein the shrinkage of themetal due to cooling is not great enough to cause any defect in the article, yet when large masses of a molten metal are pressure cast by the conventional methods it has not been 7 possible to continuously maintain pressure on the casting metal in the mold during the entire cooling operation because the gates. sprues and runners contain the same metal that is bein pressure cast so that these small cross sections of metal will freeze, or solidify, before the main body of the metal and thereby prevent any pressure which may be maintained on the sprue from being transferred into the main body of the metal cooling in the mold. Thus, when a large mass of metal is cast into a mold there has been no way of compensating for the shrinkage of the metal during the cooling period. This cooling of the metal when dealing with large masses of the the mold will be moved outwardly against the external portions that have cooled or solidified wherebytbie hydraulic pressure that is applied upon the metal within the mold will be continuous throughout the cooling operation.

The practice of the process 0! this invention is particularly disclosed in Figures 2 to 15, inclusive. In the practicing of this process a body of molten. metal 12 is placed in the cylinder bore and is maintained in a molten condition by means of the heating units surrounding the cylinder bore. This molten metal 12 is one that has a lower melting temperature than the metal to be cast. and-preferably has a higher specific gravity than the metal to be cast so that this body of metal 12 may act as a carrier metal for moving a casting metal into the molds. The body of metal 12, of course, rests upon the plunger 12 extending from the hydraulic motor 45 so that when the plunger 42 is moved upwardly the molten body of metal 12 is carried upwardly thereby. In the specific example of this invention the body of molten metal 12 may be lead having a melting temperature or about 621 F. and has a specific gravity of 11.34.

The metal to be cast. as by way of specific example, may be aluminum having a melting temperature of about 1217 F. and a specific gravity of 2.7. In any instance, however, the metal that is to be cast will have a higher melting temperaturethan the carrier metal so that complete solidification of the casting metal can occur within the mold without any solidification of the carrier metal.

The casting metal, having the higher melting I temperature, is poured into the cylinder bore ll upon the surface of the carrier metal 12 in a molten condition. It is. of course, understood that the carrier metal I! may be and preferably is above its melting temperature and is maintained at substantially the casting temperature of the casting metal, which in the case of aluminum shall be about 1217" F., to prevent heat absorptlon from the casting metal by the carrier metal.

The quantity of casting metal to be used will be relatively accurately gauged so that the casting metal will not quite fill the molds, that is the casting metal will not completely fill the filling opening ll of the mold cavity 28. Suificient casting metal is used to completely cast the desired article but in addition to this there is only a slight excess so that there will be a space left .in the mold filling opening when the casting metal has been completely transferred from the cylinder bore 40 into the mold cavity 28. This arrangement is to permit the lowitemperature carrier metal "to rise into the mold filling openlng 4| when the mold cavity 28 has been commetal is extremely vital because the large body pletely filled by the casting metal.

Therefore, as the first step in the process of pressure casting metals, a predetermined quantity of casting metal is placed within the cylinder bore 40 upon the carrier metal 12. This may be done by ladling a predetermined volume of molten casting metal upon the carrier metal as illustrated in Figure 2. It is, of course, understood at this time the molds 28 and 21 are in opened position to permit the casting metal to be poured into the-cylinder bore til. At this point it must be statedthat lead and aluminum. the specific examples used in this instance do not mix, and that'the specific gravity of aluminum is such that it will completely float upon the center 0! lathe body of lead so that the aluminum that is poured into the cylinder bore 40 will ride upon top of the surface of the lead carrier metal.-

After the predetermined quantity of casting metal has been placed in the cylinder bore upon the carrier metal, the molds will be closed by meansof the hydraulic motors 30 and 3|, and

the hydraulic motor 34 will retain the mold members 28 and 21,. upon the bed plate 32 to seal the same against the cylinder 35. The hydraulic motor 65 is then advanced to move the plunger 42 upwardly thereby transferring the casting metal resting upon top of the carrier metal from the cylinder bore t0 into the mold cavity 28, as illustrated in Figure 8.

It will also be noted that, as previously mentioned, the casting metal, shown in light dotted lines, does not quite fill thesnold filling opening M so that the carrier metal, illustrated in heavy dotted lines, will enter the mold filling opening. It is quite apparent that with both casting metal and carrier metal in a molten condition that the pressure applied upon the carrier metal by the plunger M will produce hydraulic pressure upon the casting metal It.

Cooling fiuid can now be circulated through the cooling passages 37 and 38 provided in the mold members 26 and 21 to begin cooling and solidifying the casting metal in a mold cavity 28. As previously mentioned the cooling passages 31 and 38 are arranged'in the mold members 28 and 21 so that the cooling is first effective upon the cast metal in those portions of the mold that are most remote from the filling opening ti thereof. This has been graphically illustrated in Figure 4 by indicating the solidified metal by the cross hatch lines in the upper portion of the'mold cavity 28, which solidified portion of the metal is indicated by the numeral 13a. That portion of the metal indicated in small dots is that which is about ready to solidify and is stated to be in a slush or spongy condition. With the heat being constantly applied upon the cylinder 36 by means of the heating coils 38 and W the carrier metal, or lead, may be maintained in a molten condition. v

From the illustration, shown in Figure 4, it will be apparent that as long as pressure is applied in an upward direction, as indicated by the arrow on the plunger 42 that the carrier metal 12 will constantly apply hydraulic pressure upon the casting metal 13 that is stillin a molten condition within the interior of the mold cavity, thereby producing a dense casting'structure while the casting metal adjacent ,the periphery of the mold begins to cool and solidify. It is, of course, understandable that the more pressure applied upon the plunger 42 the more dense will be the casting metal within the mold cavity 28.

As the cooling and solidifying of the -casting metal proceeds, solidification will be gradually from the outside portions-of the mold cavity 28 toward the filling opening 4! whereby that portion of the casting metal that is within the fillin opening Bi will be the last metal to solidify. As

illustrated in Figure 5, the casting metal 13a has solidified throughout the mold cavity with the exception of that small portion immediately adjacent the mold filling opening 4|. It will, therefore, become apparent hat with the metal solidifying from the outsid extremities of the mold cavity toward the filling opening that the hydraulic pressure applied upon the casting metal by the carrier metal will b continued throughout the entire cooling period.

- The product that is being formed as illusl0 trated in this invention for an internal combustion engine and therefore the casting may contain as much as 50 lbs. to '15 lbs. of casting metal. Such a mass of casting metal has considerable shrinkage. This hrinkage has been. the major problem in connection with the pressure casting of molten metals.

In the application of the process of this invention, however, it will be apparent that since the casting metal cools from th outside periphery of the, mold toward the filling opening thereby always retaining liquid metal toward the center of the casting that will be engaged by the carrier metal, that hydraulic pressurecan be continuousiy applied upon the casting metal as it is solidifying, whereby the natural and normal shrinkage that occurs during the solidifying oi the metal can be compensated for, and the metal in the center of the casting is therefore forced outwardly against the solidified metal c ntinuously until the last portion of the casting metal has solidified. When the last part of the casting metal has solidified there will be a recess in that portion of the casting that is in the filling opening. However, this part of the article will have been designed so that the machining operation will remove this irregularity from the article, and also any alloying that has occurred between the lead and the aluminum will be retained in this portion of the casting that will bemachined from the cast article so that the pure aluminum will have been cast within the article itself.

The plunger 42 is adapted to reciprocate within that portion of the cylinder that is always en-- gaged by the carrier metal, which in this instance is the lead. It is well-known that the high temperature metals such as aluminum, brass, bronzes .and others attack the walls of the chamber into which they are poured so that after a certain period of time the walls become pitted.

Therefore, in order to prevent'the plunger from being damaged by the pitted walls, or to prevent leakage from around the plunger, the quantity of carrier metal in the cylinder will be such that the stroke of the plunger 62 will always be in" the area that has been engaged by the low temperature carrier metal. If for any reason it becomes desirable, th walls of a portion of the cylinder may be recessed to a larger diameter than the plunger so that the plunger could operate within area that would be engaged by the high temperature casting metal. In this latter instance any pitting oi the cylinder Walls would not effect the plunger because there would be a space between the plunger and-the cylinder wall. However, it will be understood that the lower portion of the cylinder will be engaged in a sliding relationship by the plunger and therefore acts as a guide means for the same and to seal the lower end of the cylinder.

, It is a well recognized fact that liquids of different specific gravities can be made to, float upon one another if they are carefully poured upon one another so that even though the liquids will intermix when agitated, that they will stay in layers as long as unagitated. However, as long as there is no agitation liquids of different specific I gravities will form definite layers upon one another. This natural phenomenon has been taken advantage of in the practice of this invention which has already been made apparent by this.

may be a cylinder head 1 usual 11 specific gravity of lead. such examples being magnesium of aspecific gravity 1.74, the brasses and b'onzes having specific gravitics from 1.5 to 8.95. t e cast and gray irons having specific gravities from 7.08 to "1.18, and many others. It is, of course, understood that in all instances the carrier metal must have a vaporization point substantially above the melting temperature of the casting metal. In all of the previous examples the'melting temperatures of metals are below the vaporization int of lead which is about 2960 F. Also, the melt ng temperature of the lead is substantially below the melting temperatures of the other metals. the melting temperature of ma nesium'being about 1208 F.. of the brasses and bronzes from 1625 F. to 2235" F. and the cast and gray irons from 1900 F. to 2200 F. It is. of course, understood that many of the metals, or alloys of the'metals can be used as the carrier metal as long as the specific gravity of the carrier metal is different from the specific gravity of the casting metal and the melting temperature of the carrier metal isv below the melting temperature of the casting metal. This latter feature being important in order to permit the carrier metal to be drained from the mold filling opening after the casting metal has solidified in themold.

In order to reduce the effect of alloying between the carrier metal and the' casting metal, and to prevent agitation at the surface of the carrier metal when the casting metal is poured upon the same and thereby prevent agitation which would tend to produce intermixing and alloying of two metals, there is shown in Figures 6 and 7 a metal disc I! that is positioned in the cylinder 35 and is floated upon the carrier metal 12. The top view of the disc is shown in Figure '7 which illustrates that the disc 15 is a loose fit within the cylinder 30, having the clearance 18 therebetween, whereby the disc ll freely floats upon the carrier metal. The disc 15 is provided with one or more recess portions 'I'l that will permit the carrier metal to move above the illustrated in Figure 8. a p

When the casting metal is poured into the cylinder bore 40 it will thus strike the disc "I! and prevent any agitation between thetwo metals at the surface of the carrier metal. The casting metal may then be transferred into the mold in a manner as heretofore described, and in this latter instance the-disc II will stop at or below the mold filling opening I, asillustrated in Figure 8. The carrier metal 12 may then pass through the recess portions 11 in the disc I! to complete the filling of the filling opening 4| in a manner heretofore described and maintain hydraulic pressure upon the casting metal during the entire cooling period for the same. When the plunger 42 is retracted the carrier metal will, of

course, drop into the cylinder bore ill and the disc 15 will again fioat upon the surface of the carrier metal.

In Figures 9 and there is illustrated a reversal of the process heretofore described, where in the carrier-metal 18 has a lower specific gravity than the casting metal 19. In this instance, a metal disc 80 is placed within the cylinder bore 40 and is a sliding .fit' therewith, and in fact the disc may be slightly flanged in order to improve the engagement between the wall of the disc and the cylinder wall 40. I I

The disc Ill will be placed within the cylinder disc as 12 before the casting metal 18 is pared into the cylinder bore 40.

When the plunger 2 now moves upwardly to transfer the more dense casting metal 19 into the mold cavity 28 formed by the mold members I! and 21, the casting metal. 18 will be carried upwardly by means of the disc 80. In this in The cooling of the casting metal 18 within the mold cavity 28 will proceed as heretofore described so that. as the metal begins to shrink due to solidification there will be need for a movement of the unsolidified casting metal outwardly against the casting metal that has solidified to maintain the pressure upon the entire body of metal in accordance with the practice of the process heretofore described. Since pressure is being applied upon the carrier metal 18 by means of the plunger 42, the disc being a thin material, will bend upwardly when the metal above it solidifies, ormoves outwardly toward the outer periphery of the mold so that the hydraulic pressure applied upon the metal disc at will thus be transferred to the casting metal 18 as illustrated in Figure 10. This bendingof the disc 80 will continue throughout the entire cooling period as long as the casting metal shrinks and it is necessary for the carrier metal 13 to move upwardly into the mold filling opening for constantly maintaining hydraulic pressure upon the casting metal. It will, of course; be understood that the cooling of the casting metal in this last instance is affected in the same way as heretofore described. When the molds are opened the carrier metal 18 will drop' from the mold filling opening leaving the metal disc in the casting which can be machined off of the casting.

As an example of the metals that can be used in this latter instance, aluminum having a specific gravity of 2.7 with a melting temperature of 1217" F. can be used as the carrier metal while some of the brasses and bronzes having specific gravities of 7.5 to 8.95 with melting temperatures of l625 F. to 2235 F. can be used as the casting metal. It is, of course, understood that in this latter instance that the cylinder within which the plunger operates will be constructed from a material that will not be readily attacked by the high temperature metals, such cylinder being constructed from a silica iron or the like, or may have a quartz liner in the same.

Many of the metals have a great affinity for one another and alloying proceeds very easily when they are in a molten condition. This is particularly true with the aflinity of the brasses and bronzes for tin and zinc so that under these circumstances it may be desirable to prevent any direct contact of the metals with one another at the time the casting metal is poured into the cylinder. This condition is true whether the casting metal is a light or a heavy metal and whether the carrier for the casting metal is more dense or less dense than the casting metal. The arrangement just previously described would be satisfactory to prevent such alloying between the metals, but is illustrated in Figures 11 and 12. A flat'thin disc 8i positioned within the cylinder bore 40 may be sufllcient to prevent the alloyin of the metals. The disc 8| will bend to conform to the shape of the casting as it shrinks which is illustrated in Figure 12, and as particularly described with regard to the disc 80 illustrated in Figure 10.

bore 40 upon the surface of the carrier metal 1'8 76 I In Figure 13 there is illustrated a slightly modifled arrangement for practicing'the process of casting metal under pressure and for constantly maintaining hydraulic pressure on the casting metal as it is cooling within a mold. The general arrangement of the machine may be substantially, as heretofore described with regard to Figure 1 wherein the mold members-92 and 83 are suported upon a bed plate 84 and are moved toward one another by means of the rams i1 and I8 that extend from the hydraulic motors 90 and 9!. The mold members 82 and engage one an-' other along the parting line 85. The ram l9 carries a platen 86 that engages the molds 92 and B3 to close the mold cavity 91 and to retain the molds against the bed plate 9t so as to 'seal the mold 92 against the upper end of the cylinder 98 that has a cylinder bore 89 .for receivinfga body of material 90 that has a melting temperature that is below the melting temperature of the casting metal that is placed within the 'mold cavity 81.

In this arrangement the mold cavity 91 has the filling opening 9i extending through the top walls of the mold members 82 and, 93 so that the mold extremity of the mold cavity 91 toward the filling opening 9i in the same manner as heretofore described with regard to the operation of the machine, as illustrated in Figure 1.

A fluid passage 9t extends upwardly through the mold member 92 and connects with the cylinder bore 99. The passage 99 has a horizontal portion 96 that is provided with a downwardly slanting wall 96 so that any liquid in the passages 99 and 95 will return to the cylinder bore 99 when the plunger 92 is in its downward position.

Cooling passage 91 may be provided in the platen 96 above the filling opening M for reasons which will hereinafter become apparent.

When producing a casting -in the apparatus just described with regard to Figure 13, the molds 82 and '83 will first be closed by operating the hydraulic motors and 9!. A predetermined quantity of casting metal will then be introduced into the'mold cavity 91 to fill the same to the approximate level indicated by the liquid level 99.

The platen 86 will then be brought down upon the mold members 82 and 83' thereby closing the mold filling opening 9|, the hydraulic motor 38 being operated for this purpose.

The metal within the cylinder bore 99 will have a lower melting temperature than the casting metal that has been introduced into the mold cavity 81, this metal being retained in a molten condition at all times by means of the electric heating coil 99 that is provided in the wall of the cylinder 89. Also, the body of metal 90 will be a lighter metal than the casting metal that has been poured into the mold cavity 81. As a specific example, the pressure metal'99 may be zinc having a melting temperature of about 786 F. and a specific gravity of 7.4 while the casting metal may be one of the brasses or bronzes having a melting temperature of 1625 F. to 2235 F. and with specific gravities of 7.5 to 8.95. It will, therefore, be seen that, when the zinc is transferred through the passages 94 and 95 into the space I09 above the casting metal in the mold cavity 81 that it will float thereon due to the 14- difference in these specific gravities of the metals.

Since the molds 92 and 99 are now closed and the platen 88 has been brought into engagement therewith, the hydraulic motor 45 may advance the plunger 42 to transfer the molten pressure metal 99 through the passa es 94 and 95 into the space Hill in the mold cavity 91 whereby hydraulic pressure will be applied upon the surface 99 of the casting metal. As previously described, the cooling of the casting metal in the mold cavity 81 will proceed from the outer extremities of the mold toward the filling opening, so that the filling opening will be the last portion of the casting metal to solidify. Since the pressure metal 99 has a lower melting temperature than the casting metal it will remain fluid throughout the entire cooling period and maintainhydraulic pressure ,upon the surface of the casting metal irrespectiye of the contour that is finally developed in the surface of the casting as a result of the shrinkage of the casting metal during the cooling process.

After sumcient time has elapsed to permit com- Itzwlll be noted that at this time there will be a small amount of pressure metal that will have remained in the space I90 that will be entrapped in the cavity i'fli produced in the surface of the casting as a result of the shrinking of the casting metal during the cooling process. Therefore, at this time cooling fluid can be circulated through the passages 91 provided in the platen at so as to solidify the pressure metal that has been entrapped in the recess illl before the casting is removed from the mold whereby to prevent spilling of any hot metal when the molds are opened. 1 As previously described the portion of the casting that containsthe recess is machined from the casting so that any pressure metal that might remain in this recess will not appear in the finished article.

It will, of course, 'be necessary to make up periodically for the loss of the pressure metal in the cylinder 98, but small pieces of metal can be periodically introduced into the cylinder 88 to make up for this loss. of pressure metal.

In the case where the casting metal in the mold cavity 91, illustrated in Figure 13, is a metal having a specific gravity less than the specific gravity of the pressure metal, then before the pressure metal is introduced upon the surface of the casting metaha thin metal disc may be in-' serted in the mold filling opening 9i that closely fits the wall thereof and rests upon the surface of the casting metal. In this instance, the metal disc will bend and conform to the shape of the recess H as the casting metal shrinks during the cooling process so that hydraulic pressure can be continuously maintained upon the casting metal during the cooling process in the same man ner'as heretofore described with regard to the functioning of the metal discs and Bi, illustrated in Figures 9 to 12, inclusive.

In all of the illustrations thus far described it will be noted that the mold filling opening is relatively large so that the quantity of casting metal retained in this mold filling opening is relatively large and therefore will retain a large quantity oi heat'during the cooling operation,

- I particularly so since the cooling passages in the mold members have been arranged so that they will not extract e. large quantity oi heat from the area the mold filling opening until aiter the main body of the casting has solidified whereby the casting metal in the mold filling opening will be maintained in a fluid condition unlil the last part oi the cooling cycle. It is, oi course, within the purview oi this invention that a plurality of cooling passages could be provided around the mold cavity and cooling fiuid be passed thereby hydraulic pressure can be constantly maintained on the casting metal because the pressure metal will be at a lower-melting temperature than the casting metal and will always be in a fiuid condition while it is within the mold filling opening and even though the casting metal has completely solidified. It is. of course, understood that at no time will the temperature in the mold be below the melting temperature of the pressure metal except as illustrated in Figure 13 aiter the casting metal has completely solidiv However, the applicant's invention is not confined strictly to a mold having a mold filling opening o! a large diameter, but rather the process oi this invention is applicable to any mold or die having a small sprue with connecting runners to one or more casting articles, I! in the practice oi this invention the quantity oi casting metal that is introduced'into the mold is controlled to the extent that the casting metal will completely fill the mold cavity or cavities in which the articles are to be produced but will not fill the sprue and runners. The low temperature pressure metal will be introduced into the sprue and runners so that hydraulic pressure developed within the main cylinder containing the main body of pressure metal will be transmitted constantly through the sprue and runners to the casting metal in the various parts of the mold. 4

This arrangement has been particularly illustrated in connection with the die casting apparatus shown in Figures 14 and 1'7, inclusive.

In this apparatus there is provided a metal pot I05 that contains a body of molten castin metal I00, the pot being heated by means of an electric heating coil I01. Suitable heat insulating walls I08 are provided around the metal pot I00.

A cylinder I00 extends into the metal pot I05 and has a cylinder bore IIO to receive a plunger III that is operated by means of a hydraulic motor in any conventional manner. The upper end of the cylinder I00 has a filling opening in which there is placed a rotary valve H3 that is adapted to close the opening III for purposes of operation to be hereinafter described. The cyllnder I09 is also provided with a spout H4 that into the spout H4.

The cylinder I00 has a cylinder bore II8 that is adapted to receive a body oi metal II9 that melts at a lower temperature than the casting metal I00 so that the heating coil I01, which also surrounds the cylinder I00 will retain the pressure metal Ill in-a molten condition at all times.

'Ihe'spout H4 is provided with a nose I20 that engages a socket I2I in a mold member I22 in more or lessconventional manner that is now common practice in the die casting machine art. The nozzle I20 has an opening I28 that communicates with a tapered sprue I24 provided in the mold member I22, 'the taper on the sprue I20 having its apex toward the nozzle opening I23.

A second mold member I2! is associated with the mold member I22 and each has a recess therein, or a plurality of recesses, forming one or more mold cavities I28. The mold members I20 and I22 are provided with cooling passages I21 and I20. respectively, that are arranged around the mold cavity I20 in such a manner that the casting metal that is transferred into the mold cavity I28 is cooled from the outer periphery oi the mold cavity toward the sprue I24 so that the casting metal in the sprue will be the last oi the casting metal to completely solidify. This is in accordance with the practice-previously described in connection with the general description of the process whereby it is possible to constantly maintain hydraulic pressure on the body at casting metal as it cools and thus iollows any shrinkage oi the metal. 1

In the operation oi the apparatus illustrated in Figures 14 and 15, the valves IIB and H3 are first placed In position as illustrated in Figure 14, the plunger III being in toll-retracted position as shown therein. The casting metal having a lower specific gravity than the pressure metal, may then enter the cylinder bore 8 through the valve H3 and the passage I I2 so that the casting metal will float upon the pressure metal I I8. Since the valve IIIi now has the solid portion I28 thereoi across the passage II 4, the cylinder bore IIO will receive a predetermined quantity of casting metal. The exact quantity of casting metal filled into the cylinder bore at each filling operation can be readily controlled either by means oi the liquid level oi the pressure metal H8 or by means oi the position oi'the plunger I II to increase or decrease the volume of the space above the level of the pressure metal H9.

When the upper portion oi the cylinder bore II! has completely filled with casting metal, the valve II3 will be closed and the valve IIB will be opened, as illustrated in Figure 15. The plunger III will then be advanced into the cylinder bore II! thereby causing the pressure metal M9 to raisethe casting metal through the passage IN and through the sprue I24 into the mold-cavity mold cavity I20 and may partially enter the sprue I24 to a level indicated .by the liquid line I80. The low temperature pressure metal will fill the remaining portion of the sprue I24 and will extend back into the cylinder bore 8 through the passage 4..

Since the cooling oi the casting in the mold cavity I28 proceeds from the outer periphery of the casting toward the sprue I24 it will be apparcut that portion of the casting metal adjacent the sprue I24 will be the last 01 the casting metal to solidify so that with the pressure metal I23 constantly applying pressure upon the casting I7 metal that the pressure will be transmitted to the casting metal as it is solidiiying and thuslncrease the density of the casting metal and prevent any porosity due to shrinkage of the casting metal. As soon as sufllcient time has elapsed to permit complete solidification oi' the casting metal, including that small portion in the sprue, the plunger III will be retracted to permit the pressure metal to drop back into the cylinder bore 8. The mold lower melting temperature permits complete solidification of the casting metal without critically controlling the temperature reduction of the casting metal, as would be required if a single metal I was used in the process and the general cooling arrangement disclosed herein was attempted. It would be exceedingly diflicult to have the same metal in the nozzle passage I23 and in the sprue I24 and so accurately control the cooling of the casting in the mold cavity I26 that only that metal in the casting and down to the liquid level I30 would solidify and the remainder of the metal in the sprue I24 would remain in a liquid condition. With a substantial temperature diiferential between'the casting metal and the pressure metal, the cooling of the casting metal can be controlled in a manner heretofore described to complete solidification without any solidification of the pressure metal, so that the hydraulic pressure produced by the pressure metal will be retained on the casting metal throughout the cooling process.

As a further illustration of the use of this process of casting metal under pressure for producing a plurality of individual casting, the mold illustrated in Figure 17 is constructed with a plurality of individual casting cavities I3I that are connected to a sprue I32 by means of runners I33. In this instance cooling passages I34 may be provided only in the upper die member I35, the lower die member I36 containing the sprue and runners I32 and I33. In practicing the process of this invention to produce individually cast articles as illustrated in Figure 1'7, the quantity of casting metal is predetermined in accordance with the practice heretofore described so that the quantity of casting metal that is carried into the molds by the pressure metal is sumcient to fill the individual casting cavities I3I, but there will be only a slight excess. In fact, the pressure metal-will fill the sprue I32 and substantially fill the runners I33 to the liquid level I3'I.

Since the cooling passages I34 are only'in the upper mold member I35 it will be quite apparent that the castings I3I will cool from the top side down and that therefore the casting'metal in the lower portion of the mold cavities I 3| will be the last to solidif so that the liquid pressure metal in the runners I33 will constantly maintain hydraulic pressure upon the castingv metal as it solidifies and therefore increase the density of the same and follow the shrinkage of the metal to maintain constant density throughout the entire casting.

The bottom wall I38 of the runners I33 is tapered downwardly toward the sprue I32 so that when the plunger III is retracted the pressure 18 metal in the runners and the sprue I33 and I32 will drop into the cylinder bore I I8.

As a further examplification of the process this invention. Figure 18 illustrates an apparatus wherein the process is used for extrusion extending from a double-acting hydraulic motor I43 for reciprocating thesame within the cylinder bore I4I.

oured to the cylinder I40 by means of strain rods or bolts I44.

I A suitable pressure actuated system is provided for the double-acting hydraulic motor I43.

and may consist of a pum I45that may be of any conventional type such as a constant pressure variable delivery pump of any of the well-known constructions. The pump I45 is, of course,.driven by a suitable power source. The pump I45 receives pressure fluid from a reservoir I46through a conduit I41 and delivers the same under pressure to a conduit I48 that supplies a 4-way valve I49 that is regulated by means of a control handle I50 for delivering fluid under pressure to the supply lines I5I and I52 that are connected to opposite ends of the hydraulic motor I43 for supplying fluid under pressure thereto in .the well-known and conventional man'- ner to produce reciprocation of the plunger I42. The 4-way valve I49 is provided with a return conduit I53 that is connected to the reservoir I46 for returning pressure fluid to the reservoir from either of the conduits I5I and I52 according to the setting of the 4-way valve, this circuit being a conventional hydraulic control circuit.

The cylinder I40 is provided with an inlet chamber I54 that is connected to asupply reservoir I55 by means of a connecting conduit I56. A swinging check valve I57 is provided in the inlet chamber I54 to close the conduit I56 when pressure is created in the chamber I54, the check valve I51 opening only in a rightward or counterclockwise direction. A discharge chamber I58 is provided on the cylinder I40 and is disposed on the opposite side thereof from the inlet chamber I54, the discharge chamber I58 being connected to a die'or forming chamber I59 in any suitable manner. A heat insulating material I60 is disposed between the discharge chamber I58 and the die or forming chamber I59. The cylinder I40, the inlet chamber I54 and the discharge chamber I58 are heated by means of an electric coil I6I that is adapted to maintain the body of metal within the chambers in a molten condition at all times. These chambers are enclosed by a suitable heat insulating'material I62.

The reservoir I55 that contains a quantity of metal in molten condition is heated by means of an electric heating coil I63 and has heat insulating material I64 surrounding the same to prevent heat loss therefrom.

The reservoir I55 is provided with a cover I65 secured thereto in any suitable manner and has a filling opening I66 through which molten metal can be passed into the chamber or reservoir I55, the opening I66 being closed by a cover member I61. A conduit I68 extends through the cover member I65 for conducting an inert gas into the chamber to prevent oxidation of. the molten metal in the chamber, a check valve I69 providing means for the escape of air or asmall quantity of inert gas if it is desiredto circulate The hydraulic motor I43 is sethe conduit I56 can be closed'from the body of molten metal in the reservoir I55 when desired.

7 A lever I14 is pivoted to the ring I12 by means of a pin I15 that can be swung into engagement with the top cover I65 to hold the valve I10 I02 oi the pressure metal I01 approaches the betin an upward position as illustrated'in Figure 18.

A vent valve I16 is provided in the top of the cylinder I40 tovent air that may be entrapped therein when the machine is first started or to permit venting of gases that may accumulate in the top of the cylinder during the operation of the machine. The vent valve I16 is closed by means of a spring I11 that retains the same closed at all times except when pressure is applied upon the top side of the valve to force the same downwardly for venting purposes.

The extrusion die or forming chamber I59 is provided with cooling passages I18 extendin throughout the length thereof having fiuid supply connections I10. The extrusion 'dieor forming chamber I59 may be of any suitable length for cooling and solidifying the molten metal as it passes through the chamber I59. The extrusion opening I80 may be of any desired cross section to produce the desired article in any well known fashion,

In the operation of the machine in Figure 18 a body of molten metal Ii8I is placed in the lower end of the cylinder, I40 and is maintained in a molten condition at all times by means of the heating coil I I. This body of molten metal has a lower melting temperature than the metal that is to be extruded and also has a greater density than the metal to "be extruded so that it will always remain in the bottom of the cylinder I40. As an example, this pressure metal IOI may be lead having a melting temperature of 621 F. and a specific gravity of 11.34. The metal to be extruded is initially placed in'the reservoir I55 and brought to a molten condition therein. Subsequently, the valve I will be opened to permit the molten metal to flow throughthe conduit I56, the check valve I51 and into the chambers I54, I58 and the cylinder bore I4I, whereby the metal to be extruded will float upon the surface of the pressure metal I8I. The metal to be extruded is one that has a higher melting temperature than the pressure metal and has a low specific gravity so that it will always float upon the pressure metal. As an example, the metal to be extruded may be aluminum having a melting temperature of 1217 F. with a specific gravity of 2.7 or may be one of the cast or gray irons having a melting temperature of 1900" F. to 2200" F. with specific gravities 'of 7.03 to 7.13.

As soon as the molten metal to be extruded enters and fills the cylinder bore MI and the discharge chamber I58, the hydraulic motor I43 will be operated to advance the plunger I42 into the cylinder bore I4I thereby producing hydraulic pressure upon the extruding metal by means of the pressure metal I8l. The check valve I51 closes so that the molten extrusion metal is forced outwardly through the extrusion opening I80. In its passage through the extrusion chamber I59 and the extrusion opening I80, the metal is gradually cooled from its molten condition through successive stages of a, slush, semlsolidity and a solid material so that when it passes from the extrusion opening I80 the metal will be in a substantially solid condition. The plunger I42 is permitted to stroke upwardly until the surface level extrusion chamber tom level of the inlet and discharge chambers I54 and I58. The hydraulic motor I43 is then reversed to drop the plunger I42 and permit the pressure metal to fall back into the cylinder bore I4I, whereupon molten extrusion metal from the reservoir I55 will pass through the conduit I56 and open the check valve I5'l to pass into the chamber I54 and again fill the chamber I54 and the cylinder bore I4I with a fresh charge of molten extrusion metal. The hydraulic motor I43 can then make another strokeof operation.

Due to the fact thatthe body of metal in the I59 is gradually passing through a stage from a molten metal to a solid metal throughout a substantial length of the chamber I59, the intermittent operation of the machine, while stopping the actual extrusionof the solid metal from the end of the extrusion opening I80, will have no detrimental effect on the continuous extrusion of the metal because each charge can knit thoroughlywith a previous charge because of the gradual change that occurs in the condition of the metal through the extrusion chamber, it being remembered that molten metal in each instance is being supplied into the extrusion chamber to knit with molten metal that is already there. a

By the use of the process heretofore described, the pressure metal I8I may maintain hydraulic pressure on the metal that is being extruded as long as there is any movement of the metal in the extrusion chamber so that the density of the metal in the extruded member will be substantially constant. It will alsobe. apparent that since the metal is gradually cooling as it passes through the extrusion chamber, and the metal most remote from the filling opening from the discharge chamber is that which is solidified, that hydraulic pressure will be continuously maintained on that body of the metal that is in the process of solidification so that during the solidiflcation of the metal, pressure is retained thereon to increase the density of the metal and absorb any shrinkage that occurs due to the solidification. This, of course, is in accordance with the general process heretofore 'describedwherein hydraulic pressure is continually maintained on the body of casting metal while it is in process of cooling and solidification.

In describing the process there has been incorporated herein several examples of metals that can be used in practicing the process, but it is to be understood that the process is not limited to the specific examples set forth but that other metals and other alloy of metals can be used in the practice of the process. Also, while in the general description of the process it has been stated that the metals are to be of different specific gravity, yet it is entirely within the purview of this invention that the metals may be of practically the same specific gravity and with their temperatures substantially divergent, for if the metals are of substantially the same specific gravity they may be separated by a quiescent working of the molten metals to prevent substantially any agitation therebetween whereby to keep them separated or the disc means may be used to prevent their intermixing. The temperature differentials between the metals should be sufficient to permit the functioning of the process without critical control.

While the process disclosed and described herein and the apparatus constitutes the preferred forms of the invention, yet, it is to be understood that the process as well as the apparatus can be varied without going beyond the generaliscope of the spirit of the invention, and that all such modifications of the invention that fall within the scope of the appended claims are intended to be included herein.

Having thus fully described my invention what I claim as new and desire to secure by Letters Patent is:

1. A process of pressure casting molten metal that includes, introducing a molten metal into a mold until the casting cavity in the mold is full and the molten metal stands partially in the filling opening for the mold, introducing a second molten metal having a lower melting temperature than the first metal into the unfilled portion of the filling opening or the mold, and applying pressure upon the second metal to condense the first metal thereby and retain pressure thereon throughout the entire cooling period oi the first metal.

2. The process of molding metal under pressure that includes, filling a mold cavity with a molten metal until the level of the molten metal reaches into the filling opening of the mold cavity, introducing a second molten metal under pressure maintained at a lower melting temperature than the first metal into the mold filling opening for applying pressure upon the first metal, cooling the first metal from the outer opening thereof whereby the most liquid metal will always be toward the filling opening, and maintaining pressure upon the first metal by means of the second metal until the first metal has completely solidified.

3. The process of pressure casting molten metal in a mold cavity that includes, filling a mold cavity with suflicient molten metal whereby to produce a complete casting but wherein the molten metal will not completely fill the. mold cavity filling opening, introducing a second molten metal under pressure into the mold to completely fill the mold filling opening whereby to apply hydraulic pressure upon the first molten metal in the mold cavity, said second molten metal having a lower melting temperature than the first molten metal whereby it retains its molten condition at all times during the casting process, and withdrawing heat from the molten metal within the mold cavity in such a manner that the solidification of the metal within the cavity proceeds toward the mold filling opening whereby hydraulic pressure is constantly'maintained on the metal in the cavity when solidifying within the mold.

4. The process of pressure casting metal that consists of, retaining a body of metal in molten condition within a cylinder, introducing a casting metal having a higher melting temperature than the first metal upon the body of the first metal and which is supported thereby, applying pressure upon a relatively large portion of the first body of molten metal to produce movement thereof and transfer the casting metal into a mold together with a small portion of the first metal that enters the filling opening of the mold. maintaining pressure upon the first metal whereby to produce hydraulic pressure thereby that is constantly maintained on the body of the molten metal in the mold as solidifying and until completely solidified.

5. The process of pressure casting metal that includes, maintaining a body of molten metal within a chamber, placing a second body of molten metal having a higher melting temperaperiphery of the mold cavity toward the filling pressure upon a relatively large portion ofthe first metal to transfer the second metal from the chamber into a mold cavity together with a small portion of the first metal that remains in the filling opening for the mold cavity, abstracting heat from the second metal within the cavity in such a manner as to solidify the second metal from the outer extremities of the mold cavity toward the filling opening, and maintaining pressure on the first metal'during the solidification of the second metal whereby to maintain hydraulic pressure upon the second metal in the mold cavity as it solidifies.

6. The process of die casting which consists of, providing a body of molten metal within a chamber within which pressure is adapted to be produced, introducing a, second body of molten metal into the chamber having a higher melting temperature than the first metal for flotation upon the first metal, applying pressure upon a relatively large portion of the firstmetal to transfer the second metal from the chamber into a mold together with a quantity of the first metal that remains in the sprue of the mold, and withdrawing heat from the metal within the mold in such a manner that solidification progresses toward the sprue whereby pressure maintained upon the first metal will be constantly transmitted to the metal in the mold as it solidifies.

7. The process of simultaneously pressure casting a plurality of cast articles from molten metal that includes, providing a body of molten metal within a chamber, introducing a predetermined quantity of casting metal into the chamber for 'flotation upon. the first metal and having a higher melting temperature than the first metal, said predetermined quantity of casting metal being sufficient to fill the mold cavities to produce the plurality of articles and only a slight excess, and applying pressure upon the first metal to transfer the casting metal into the individual mold cavities for simultaneously producing a plurality of cast articles, said first metal entering the sprue and runners of the mold whereby to maintain pressure on the cast articles constantly while the casting metal is solidifying.

8. An apparatus for die casting that includes, a metal pot for holding a supply of molten die casting metal, means forming a chamber having a portion thereof disposed within the metal pot, an inlet passage in said chamber forming means through which molten metal from said pot can pass into said chamber, valve means for opening and closing said passage means, a discharge spout extending from said chamber, valve means in said discharge spout for opening and closing the same, a body of molten metal within the lower portion of said chamber having a lower melting temperature than said casting metal which is floated thereupon upon opening of said inlet valve, and

plunger means reciprocable in said chamber for applying pressure upon said low temperature metal to transfer casting metal from said chamber through said spout into a mold adapted to be associated therewith and carry said low temperature metal into said spout to fill the same when casting said casting metal within a mold cavity.-

9. An apparatus for die casting that includes, a metal pot for holding a supply of molten die casting metal, means forming a chamber having a portion thereof disposed within the metal pot,

an inlet passage in said chamber iorming means through which molten metal from said pot can pass into said chamber, valve means for opening and closing said passage means, a discharge spout extending fromsaid chamber, valve means in said discharge spout for opening and closing the same, a body oi'molten metal within the lower portion of said chamber having a lower melting temperature than said casting metal which is floated thereupon upon opening of said inlet valve, a mold positioned in operative association with said spout having a mold cavity therein provided with a sprue to receive molten metal from said spout, plunger means reciprocable in said chamber to apply pressure upon said low temperature metal and transfer said casting metal into'said mold cavity and dispose said low temperature metal in said spout and in a portion of said sprue to thereby maintain pressure on the metal in said cavity, and means for withdrawing heat from said mold in such a manner that the casting metal therein solidifies from the outer extremities of the mold cavity toward the sprue. 10. An apparatus for die casting that includes, a metal pot for holding a supply of molten die casting metal, means forming a chamber having a portion thereof disposed within the metal pot, an inlet passage in said chamber forming means through which molten metal from said pot can pass into said chamber, valve means for opening,

and closing said passage means, a discharge spout extending from said chamber, valve means in said discharge spout for opening and closing the same, a body of molten metal within the'lower portion of said chamber having a lower melting temperature than said casting metal which is V 24 perature metal and transfer said casting metal into said'mold cavities and dispose said low temperature metal in said spout and in said sprue and a portion of said runners to thereby maintain pressure on the metal in said cavities, and means for withdrawing heat from said mold in such a manner that the casting metal therein solidifies from the outer extremities of the mold cavities toward the sprue.

11. The process of simultaneously pressure casting a plurality of east articles from molten metal that includes, introducing a predetermined quantity of casting metal into a mold to fill the several cavities therein with only a slight excess, introducing a second molten metal having a lower melting temperature into the sprue and runners oi the mold through which the first metal was introduced, applying pressure upon the second metal to produce hydraulic pressure upon the first metal, withdrawing heat from the first metal in such a manner that it solidifies toward the level between the metals whereby the second metal continuously maintains hydraulic pressure on the first metal while it is solidifying.

MORRIS F. BOOTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 755,722 Stroh Mar. 29, 1904 1,219,358 Stewart Mar. 13, 1917 1,486,751 Hult' Mar. 11, 1924 1,912,981 Hoy June 6, 1933 1,971,652 Haessler Aug. 28, 1934 2,143,323 Ko'rsmo Jan. 10, 1939 2,339,265 Held Jan. 18, 1944 FOREIGN PATENTS Number Country Date 204,743 Great Britain Oct. 8, 1923

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