US2865068A - Apparatus for casting metal - Google Patents

Description

Dec. 23, 1958 A. c. DUNN 2,865,068

APPARATUS FOR CASTING METAL Filed Oct. 18, 1954 3 Sheets-Sheet 1 45 4 T h 5 I .l i 48 l I I 22 b 32 4/ 36 44 1 26 20 3 24 g 25 4 19 F/GZ W3 '4 l3 J6 /7 :I: n I I -4 f L; Q IO n:

I l 4 Hp 9-1 ,8; 4 4* 1 4 2 41 W f FIG. 4 28 INVENTOR: ANDREW C. DUNN Dec. 23, 1958 A. c. DUNN 2,865,068

APPARATUS FOR CASTING METAL Filed 001:. 18, 1954 3 Sheets-Sheet 2 INVENTOR. ANDRE W C. DUNN Dec. 23, 1958 AL CKDUNN APPARATUS FOR CASTING METAL 3 Sheets-Sheet 3 Filed Oct. 18. 1954 FIG. /2

FIG/4 FIG /5 INVENTOR. AND/PE W C. DUNN ATT'Y APPARATUS. FOR CASTING METAL Andrew C. Dunn, Chicago, Ill.

Application October 18, 1954, Serial No. 462,701

Claims. (Cl. 22-69) This invention relates to the casting of metals and more particularly to the casting of metals under pressure and under non-oxidizing conditions.

This application is a continuation-in-part ofmy application Serial No. 159,780 filed May 3, 1950, now abandoned, for Method of and Apparatus for Casting Metal.

This invention relates to the production of improved casting, first by degassing of molten metals by percolat-v ing inert or other gasses through the melt and by adsorption and absorption of the impurities before the molten metal is put into the mold.

As the speed of aircraft ha been increased in the last few years, it has become more and more of a need to find a way to produce aircraft castings free from gas, oxides and porosity, thereby providing higher physical properties.

There have been many attempts to meet aircraft requirements but each development and invention hasbeen.

directed toward a single problem in the casting cycle rather than a solution of the cumulative need. This has been like locking one barn door and leaving two others open.

There have been many attempts to degasify the melt in the foundry for sand casting, permanent molds and die castings. This has been done by injecting underneath the surface and near the bottom of the pot, gases. such as chlorine, nitrogen or other substances such as powdered deoxidizers. Battelle Memorial Institute have shown the importance of the uses of these gases and materials for removing impurities from the melt by injecting the gases through the bottom ofthe melting pot which is diflicult and expensive plus the fact that the gas takes the shortest path to the surface and diffuses through only a part of the molten metal in the pot.

Other inventors including F. T. Kitchen in his Patent No. 969,539 of September 6, 1910, have put their minds to the feeding of the molten metal into the moldby applying pressure within an enclosed melting pot but they:

did not develop in their method a workablevalve that would give them continuous production. to overcome this valve problem, Smith Patent 2,181,157 of November 28. 1939, feeds the molten metal into the mold through ribbon-like openings under high pressure. This sprayed the molten metal into the die cavity under the sprayed condition, oxides were formed which froze within the casting, thereby reducing the physical property values. openings Within the mold, the material ofthe mold surrounding these openings becomes heated and time. was required before pressure could be applied to the material within the mold as the heated portions aroundth'e ribbonlike openings do not permit the metal Within to freeze quickly causing advance solidification in parts of the mold before pressure can be applied which means if pressure is put on the molten metal within the mold before the metal filling the ribbon-like openings-is frozen, the pressure will force the molten metal within the mold through these feed openings, the pressure then is lost.

In attempting By forcing the metal through the ribbon-like.

nited States Patent C) 2,8653% Patented Dec. 23, 1%58 ice Another inventor, Gerdien, in Patent 1,514,151 of November 4, 1924, attempted to make ingots by filling the mold by vacuum with a ball valve which was uncontrolled and when in operation, the ball would rise and permit much of the material within the mold to return to the melting pot. This resulted in porosity or a pipe being formed above and below the ball in the center of the ingot as there is a shrinkage of 57% of the metal as it changes from liquid to solid and the side walls and top of the ingot would'be first to freeze. In this invention, the inventor made a one-piece mold instead of a split mold or a mold to carry a core.

In the present improved method of casting, I have overcome the diificulty of the prior art by making improvements in what used to be called the different divisions of a casting unit and have built them into a casting cycle which produces castings free from gases, oxides, or porosity, with higher physical properties at normal and high temperatures than heretofore produced. These better results are attained because of the predetermined travel and the automatic closing of the applicants valve which happens before solidification starting in the valve zone, thereby eliminating porosity or the formation of a pipe which is caused by the material within the mold returning to the melting pot; by progressive cooling of the material with the mold; by removing the gases, such as oxygen or nitrogen by percolating a non-oxidizing gas down through the feed pipe openings and rising through the molten metal within the pot, and the absorption of gases from the metal as it is again forced through the many openings of the feed pipe from which it enters and fills the mold.

Numerous objects and advantages will appear from the following description when it is read in conjunction with the accompanying drawings in which:

Figure 1 is a view of a pressure casting apparatus associated with a melting pot of the present invention, certain parts of the mold, the meltingpot and the furnace being shown in section.

Figure 2 is a sectional view of a modified construction, in which the core pressurizing means of Fig. 1 is projected with cooling means;

Figures 3, 4 and 5 show different rotated positions of a valve plug as used in connection with a control valve;

Figure 5a shows a sectional View of a pressure or vacuum feed pipe valve;

Figure 6 is an elevation of one section of a casting mold arranged for bottom filling, and having a control gate with portions in section embodying the present invention;

Figure 7 is a fragmentary sectional view, showing a modification of the structure of Figure 6 wherein the control-gate has a lateral metal sprue connection for side feeding;

Figure 8 is an enlarged detail sectional View of the control-gate structure as taken on line 88 of Figure 6.

Figure 9 is a fragmentary enlarged section of a modified form of the check valve structure of Fig. 1 to control the flow of molten metal from the melting pot to the mold chamber.

Figure 10 is a perspective view of a temperature indicator having a movable pointer for indicating selective points from which the temperature is being read.

Figure 11 is a fragmentary sectional view of the connection of a controlling valve into a single feeding tube;

Figure 12 is a sectional view taken approximately on the line 12-12 of Figure 6 and illustrates a plurality of thermostatic terminals for use in connection with an indicator as shown in Fig. 10 to measure the respective temperatures adjacent a casting as it is being made.

Figure 13 is a sectional view on the line 13--l3of Fig. 1 showing a cross section of the metal delivery tube with straight and spiral openings therethrough.

Figures 14 and 15 show a single cord and a spirally wrapped cord or wire to produce the straight and spiral openings respectively in the delivery tube; and

Figure 16 is a view of the lower end of the delivery tube as shown in Fig. 1.

When metal having a normal amount of included gases which surround the boundaries of the molecules, is subjected to increased temperatures, the gases are the first to expand which lowers the physical properties of the metal more rapidly than normal as the temperature is increased and thereby lowers their working load safety factor.

In this cycle (1), first degassify and purify the metal; (2) then feed feed molten metal into the mold rapidly without turbulence, its surface being protected by an inert gas; (3) apply pressure to the metal within the mold immediately upon the mold being filled; (4) maintain pressure during the cooling cycle, the casting being cooled progressively from the part most remote from the feeding sprues and as solidification takes place remote from the feeding sprue; it thereby eliminates porosity, pin or blow holes; (5) further purifying the molten metal as it is fed to the mold by adding absorption or catalytic elements into the feed tube unit; (6) make cored castings where the core is supplied internally with gas pressure to prevent it from yielding when the molten casting is put under pressure; and (7) make a cored casting, supplying a cooling element to the core, causing the casting first to solidify internally and cool progressively to the outer walls.

The present application is a companion application to my copending mold application, Serial No. 159,113, filed April 29, 1950, and the mold shown therein is that used in the casting operation of the present application.

Referring now more particularly to the drawings, a furnace 10 has a heat insulating lining 11, the furnace is closed by a cover 12 provided with a sealing gasket 13 and the cover is secured in position by fastening means such as bolts 14. At its top, the furnace has a peripheral outside flange 15 which cooperates with the cover 12 and has an inner flange 16 offset inwardly in the furnace and supporting the flange 17 of a melting pot 18 which extends downwardly into the furnace 10 and has a hemispherical bottom as shown. The melting pot has an inclined takeoff connection 19 extending through the cover and sealed at this outer end by a screw cap 2001 thus providing means for the filling of the pot with metal to be processed.

It should be understood that with molten metal in the pot 18, it is necessary to provide heating means for maintaining the metal in a molten condition. While no heating means is shown, it will be obvious that the furnace 10 may contain electrical heating means disposed beneath and around the pot, or some other heating means may be employed.

Depending within the pot 18 is a metal delivery tube 27 which has an upper reduced portion 26 extending adjustably through the cover 12 and held at any desired elevation in the pot 18 by threaded glands and 24 surrounding the reduced portion and secured in the cover. At the upper end of the tube is a hemispherical portion 23. Extending longitudinally through the tube 27 are a plurality of small bores 20 and also a number of spiral bores 21 outside of the small bores. These bores feed into a common chamber 22 and extend from a common chamber 79 at the bottom filled with coarsely ground carbon or other materials 80 which will act to absorb or filter out coarser impurities. At the bottom of this chamber is a perforated plate 78 threaded into the end of the tube 27 to close the chamber and to retain the filter material 80 in the chamber.

The feed delivery tube is preferably constructed of carbon, lamp black and other catalysts or absorbing materials which have a catalystic action in drawing out and absorbing gases from the metal. When the metal is forced through a large portion of the length of the multitude of small tubes, the pure metals run freely, and foreign materials are pushed to the walls of the small tubes where they are adsorbed or absorbed.

The gases are first adsorbed and then penetrate into the carbon materials of the feed tube by capillary action. In some cases, the porous matter 80 above the plate 78 may be dispensed with and the capillary tubes within the delivery tube 27 may be increased in length.

When it is desired to further strengthen the cast metals, boron, tungsten and other metals may be added to the material in the delivery tube in coarsely ground particles, parts of which will project into the many passages where they will be consumed by the metal as alloying agents or will act as catalysts. There are many other metals or materials that may be used for this purpose which are known to men skilled in the art and which may be developed by trial.

To produce the passageways in the delivery tube, they may be drilled or bored in the delivery tube, or single wires or fibers 82 as shown in Fig. 14 or spirally wound wires or fibers 83 and 84 as shown in Fig. 15 may be placed in the mold when the delivery tube 27 is being cast. When this tube is scintered, the wires will melt and flow out and the fibers will be shrunk forming additional carbon leaving the openings 20 and 21 for the passage of molten material therethrough. The spirally wound fiber of Fig. 15 provides an additional surface within the passages for more adsorption or catalytic action. The passages may also be formed by other materials such as the material to be treated or other metals which will melt before the melting of the carbon or alloys of which the delivery tube is composed.

The upper hemispherical end 23 of the delivery tube engages the hemispherical sprue 32 formed of the two halves 33 and 34 as shown in section in Fig. 8. Any conventional structure may be employed for opening and closing the die, but as shown, die part 33 is fixed whereas die part 34 is movable on guides 35 and 36 when actuated through a control rod 37. A source of high pressure gas (preferably a gas inert with respect to hot molten metal), is supplied through a pipe 38 to supply lines 39 and 40 controlled by valves 41 and 42 respectively. The pipe line 39 leads to a metal collecting cavity 56 which may also be a large portion of the castings, to which it may apply high pressure, whereas the pipe line 40 leads to the interior bore 22 of the tube 27 through a pipe 43, and also to a mold cavity through a take-off pipe connection 44, both pipes controlled through a four-way control valve 30. This four-way valve 30 permits pressure to be admitted to the mold cavity 45 through the pipe 44 and/ or to the ante-chamber at the top of the bore 22 through the pipe line 43.

As represented in Figs. 3, 4 and 5, this valve has a connection 29 to the atmosphere and two valve passages 28 and 27 in the valve itself. The valve may be turned as shown in Fig. 3 to admit pressure by passage 27 from the pipe 40 through the valve and pipe 43 to the antechamber at the top of the tube 27; it may be turned as shown in Fig. 4 connecting the passage 28 to admit atmospheric pressure from the atmospheric inlet 29 to the pipe 43 as shown in Fig. 4; and it may be turned to connect the pipes 40 and 44 by the passage 28 as shown in Fig. 5.

The pot 18 is also provided with a gas supply pipe 46 under the control of a valve 47 for supplying gas under low pressure to the pot for metal ejection when the mold is to be filled under low pressure. This valve may be turned as shown in Fig. 5a to exhaust or relieve the pressure from within the melting pot.

The gate for the mold is closed by a check valve comprising a ball 48 (Fig. 6) in a chamber 49 having a seat 50 closed by the ball. The seat 50 is a reduced extremity of a rod 50A which extends through the mold part with the seat projecting within the chamber 49 so that the seat remains in place when the mold parts are separated and a ball 48 embedded in and is removed with a casting. A rod 51 extends across the top of the chamber for confining the ball within the chamber 49 formed between the seat 50 and the rod 51. The gate for the moldis closed by the ball 48 which permits the flow of metal into the mold when under pressure, but prevents retrograde movement when the pressure within the pot is relieved. When the mold has been filled and the metal solidified therein, the ball 48 will be embedded in the metal in the sprue and will be removed therewith when the sprue, gate and casting are removed from the mold. The rod 51 is an- 'chored in the mold part 34 and the casting is slipped or'f from it when the casting is removed from the mold.

Before each successive filling of the mold, a new ball 48 will be placed on its seat and this provides a convenient and inexpensive means for controlling the one-way flow of molten metal into the mold.

While the check valve has been illustrated as c-ompris ing a seat and a ball, this form of the invention resides in the use of a valve having a removable portion which becomes embedded in the cast material and .is replaced before each casting operation. Various types of check valves may be used in this manner and also another common form has been illustrated in Fig. 9.

The arrangement of Fig. 2. as hereinafter described is similar to that of Fig. 1 except that one end of a coolant line 60 is connected to the interior of the cavity 45 for internal cooling of the casting.

Referring now to Fig. 6, one of the mold sections of Fig. 1 is illustrated, it being understood that the other mold section is similar thereto. Although the mold sections may take various forms of construction, it is desired to illustrate the present invention with the section made bythe'method of my copending application referred to above. The 'mold comprises solid blocks of sintered powderedmaterial having a plurality of cavities shaped in the faces thereof. At the opposite side of the center of the blocks are article forming cavities 52 connected by the branches of the gate cavity which lead from the sprue 32 The dome-shaped cavity of the sprue 32 fits thetop of the tube 27 as shown in Fig. 1 so that metal may enter from the pot 18 through the valve 48 and then up through the gate branches into the article cavities as well as into a reservoir cavity 56 to provide a supply of molten metal for the purposes described hereinafter. Extending from the reservoir into the outer wall of the mold, a half cylindrical cavity is provided for receiving a plunger 57 extending through the top of the mold.

If it is desired to provide a hollow casting, a core 58 is disposed in the article cavity as shown in Fig. 6. If this core is made of porous material, a feed pipe 59 has its end embedded in the core and suitable pasages are provided to enable fluid under pressure in the pipe 59 to fiow into the pores of the core and build up and sustain pressure in the core. The pressure in the core enables it to withstand compacting pressure of the metal in the mold. After the mold has been filled and the metal has been solidified, this sustaining pressure is relieved and the casting is allowed to contractas in normal casting operations. Pipes 69 leading into and from the cores provide a circulating passage within the core when it is desired either to cool or to heat the core byfluid passing through the pipes.

As illustrated in Fig. 6, the mold may be made of sintered powder of different heat conductivity, the powder forming the walls of the article cavities opposite that of the gate may be of high conductivity such as copper while the powder forming the walls of the gate is of low conductivity such as iron or clay. Extending from the article cavities to the outer walls of the mold are vents 61 of the usual ribbon-like form to permit the escape of air or gas when the mold is being filled. The cavity 56 receives molten metal in excess of that necessary to fill the cavities forthe articles 52 and charged into the mold through the sprue 32 and gate controlledby the balli48. The plunger 57 is provided for the mechanical application of pressure to the molten metal which has been charged into the mold cavities. The gate valve provides an eflicient and inexpensive and readily replaceable check-valve which seats by gravity and prevents the back-flow of molten metal. from the mold into the ante-chamber and into the tube 27 or its equivalent when the actuating pressure is removed andwhen pressure is applied to the metal in the reservoir 56 throughthe plunger 57. The upward travel of the ball is limited by the cross pin 51.

In Fig. 7, the same elements as shown and described with respect to.Fig. 6 are included except that thesprue 32 is arranged for side filling.

For the purposes of clarification, the detailed operation of the apparatus shown in Fig. 1 is as follows: With the mold part 34 in the position shown, and the ball 48 on its seat, metal such as aluminum will be supplied to the pot 18 through the connection 19'and the closure 20 placed in closed position. This metal will flow around the delivery tube 27 and upwardly into the bores 20 and 21 until it finds a level in the bores substantially equal to that of the level of the metal in the pot 18.

Gas under low pressure is now supplied through the pipe 46 which will force the molten metal upwardly through the delivery tube 27 into the ante-chamber 22 and unseating the ball 48,'passing into the gate and from thence into thearticle cavities 52 and to the reservoir 56. When the article cavities and reservoir are filled, high pressure will be applied from supply line 39 to the reservoir cavity 56 and if applicable to the cores 45 through pipe connection 44 by manipulation of valves 42 and 30," the valve 30 being positioned at this time as shown in Fig. 5, the pipe 43 being closed to pressure from the valve 30 at this time.

Immediately upon application of pressure, the entire amount of metal within the mold including that in the article cavities, the reservoir and the gate will be subjected to high pressure and the mold check valve 48 will immediately seat against the low pressure in the tube 27. The closing of the valve serves to trap the pressure in the mold allowing the pressure applied to the article cavities to build up.

It is noted that the sizable stream of molten metal under pressure at the top of the pot 18 flows without turbulence through the bores 20 and 21 of the tube 27 into the gate, and thence to the article cavities. Con-V tamination from the oxidizing influence of air in the mold is prevented and this feature constitutes an improvement over prior art when fed ribbons of metal, or utilize an atomizing efiect and the corresponding turbulence of a pressure spray. The reservoir 56 presents a ready supply of molten metal under pressure for feeding into the article cavities as the metal in the cavities solidifies and shrinks. The metal fed from the reservoir progressively fills the spaces caused by shrinkage.

When starting the unit, the metal is fed into the mold, the mold is filled by using the delivery tube 27 and re filling the mold a number of times and each time remov ing imperfect starting castings, in a well known manner, to bring the mold up to the proper working temperature. As soon as the mold is filled, the valve 36 for controlling a source of inert refining gas under pressure is opened as shown in Fig. 3 to inject the refining gas into the delivery tubes. The gas forces the molten metal back into the pot. The valve may be leftopen for a predetermined length of time until the proper amount or gas is applied for returning the metal to the pot and refining it by removing the gases and other impurities. The inert refining gas is forced to the bottom of the pot where it mushrooms outwardly and then rises, purging the impurities away from the mouth of the feeding tubes.

When an inert refining gas is forced downwardly through the passages 20 and 21, a portion of the im purities, such as gas and oxides, are Washed out with it leaving the tubes filled with inert gas and some impurities, solid or gases adhering to the tube walls. When the molten metal again enters the tubes, the refining gas is forced upward ahead of the metal into the mold and out through the mold vents, as hereafter explained. This gas fills the mold and purges the air from the mold leaving the complete mold cavity full of refining gas at low and controlled pressure. As the gas is purged out of the mold by the incoming molten metal, the walls remain coated with inert gas held thereon by adhesion, and preventing the molten metal from oxygen Or other gas absorption.

The pressure behind the molten metal fills the mold and forces the refining gas out through the vents, the refining gas always covering and protecting the molten metal.

A special feature of this invention is that after each casting injection valve 47 is opened to let the pressure out of the pot, and then, refining gas is purged through the tubes 20 and 21 of the delivery tube 27 forcing-the metal downwardly into the pot, mushrooming or spreading the refining gas at the bottom of the pot at the same time refining the metal. The gas follows down through the metal and rises all around the delivery tube 27, thereby refining the molten metal in the pot for the next injection. This cycle goes on, the metal to be cast becomes cleaner and more refined.

The delivery tube 27 may be of any suitable length; it may be insulated or heated to any desired temperature, and a portion may be above or outside of the melting pot. It may be straight as shown, coiled within the pot or a portion extended on the outside of the pot. The refining gas may be recovered, refined, and rinsed when desired, or it may be flushed out. With this cycling, as described, the resulting castings will be clean and dense, and thereby have higher physical properties than other currently made castings at both normal or high temperatures and they will have a higher marketing value.

These castings may be used where high physical properties are needed, as in aircraft, as pre-form shapes as used in my Forging Method Patent No. 2,494,935 of January 17, 1950, as slabs or ingots for rolling or prefabrication, or as castings to be machined.

This method and operation is of particular advantage when the mold is constructed of conducting material affording differential cooling of the cast parts. With this type of mold, the high conducting portion of the mold surrounding the article opposite the feed gates, and graduating to the low conducting portion of the mold surrounding the cavity adjacent the gate thereby promote progressive solidification of the castings. The metal under high pressure solidifies in a thin layer against the cavity wall, any tendency to separate from the wall being prevented by the high pressure supply of molten metal. An inner thin layer is solidified against the first layer, and thus, layer by layer the solidification takes place, each layer being forced to the shape of the article cavity until the metal in the cavity is entirely solidified. This layer by layer solidification is by way of illustration only, as distinct layers are not presented. However, this serves to emphasize the progressive solidification from the far side of the article cavity to the side adjacent the gate. This increases the density of the casting and forces it to h ld to the dimensions of the article cavities. When castings with high physical properties are not necessary, supply line 39, pressure on the cavity 56 or by plunger 57 need not be used.

After a casting operation has been completed and the metal in the mold has solidified and cooled to a predetermined temperature, the pressures are removed, the mold is opened and the castings and the metal of the gate and sprue including the ball 48 are removed. Another ball is inserted, the mold halves are closed and the apparatus is ready for another casting operation. The rod 51 and the interior mold parts are coated by spraying or washing with a lubricant or parting material to prevent them from adhering to the cast material, as commonly done in casting production.

Immediately after the application of high pressure through the supply line 39, or by plunger 57, the upper portion of the melting pot is subjected to atmospheric pressure by turning the valve 47 to atmosphere as represented by the position in Fig. 5a at the same time the valve 30 is opened to line pressure as shown in Fig. 3 or open to atmosphere, Fig. 4, whereupon the metal sinks in the tube 27 to the level of the metal in the pot. This prevents freezing or solidification of the metal in the upper portion of the tube 27 adjacent to the sprue 33 and therefore continuous subsequent casting operations are possible. It is clear that by turning the valve 30 to the atmosphere and opening the valve 47 to atmosphere (Fig. 5a), the vacuum caused by the column of molten metal in tube 27 is broken, thereby allowing the metal in the tube to sink to the level of the molten metal in the pot. When refining gas is used as shown in Fig. 3, the molten metal that fills tube 27 is forced out the bottom opening of tube 27 back into the pot.

The admission of pressure through the pipe 44 into the core of the casting prevents the collapse of core when it is subject to the pressure of the molten metal which in turn, is subject to the pressure in the supply line 39 or plunger rod 57. It may be desirable to cool the core at about the time pressure is applied by the plunger 57, to provide progressive solidification of the metal in the cavity. In this operation, the conductivity of the mold is so designed as to promote progressive solidification around the core line. The core 45 may be cooled by fluid applied through the coolant line 53.

To make a tight flexible joint between the tube 27 and the cover 12 of the pot, an expansible Sylphon sleeve as shown in Fig. 11 may be attached at its lower end to a ring 61 secured to the top of the cover surrounding the tube 27 by fastening bolts 62. The top of the Sylphon is secured to the tube 27 by a split clamping ring 63. The valve 30 may be connected through the Sylphon to the central bore 27 of the tube by the pipe 43 which has a plug 64 at its end with minute holes therein so that the molten metal does not enter the pipe 43 nor clog it when the metal fills tube 27.

In order to observe the temperatures present at various parts of the mold, a plurality of thermocouple terminals 65, 66 and 67 are variously disposed in one of the mold sections 34 as shown in Fig. 12 with respect to the cavity 56 and at different points along an article forming cavity 52 and these thermocouples are connected to a pyrometer 68 as shown in Fig. 10 at the points marked 1, 2 and 3 thereof respectively. Different contacts are made with either of the points 1, 2 and 3 in the pyrometer as indicated by a rotatably movable pointer 70 so that the pyrometer reading for any one of the locations of the thermocouple terminals can be obtained and observed on a scale 69 of the pyrometer. This will enable an operator to observe what is taking place at the various points within the mold at any desired time, thereby enabling one to obtain the best results in mold cooling in order to produce uniform castings.

In Fig. 9, a conical valve 71 is shown seated on a corresponding valve seat 72 instead of the ball valve 48. A chamber 73 is provided in a sprue 33B over the top of the valve allowing it to rise therein when molten metal rises in the bores 22 ahead of the delivery tube 27. To limit the upward raising movement of the valve 71, the valve has a depending stem 74 in which is a longitudinal slot 75 engaged by a cross pin 76 which limits the rising movement of the valve from its seat. This valve would have the same operation as the ball valve but is not removed with the casting or feed sprue. The sprue and casting are removed from the mold as previously set forth without the value.

The present invention produces castings with smooth 9, surfacesand sharp-definition at thecorners and edges, and castings held to close dimensional tolerances. The physical properties are more, satisfactory, and consequently; represent a great advance over the products made by the die casting or sandcasting processes of the prior art. The single feature of supplying a sizable steady stream of molten metal to the article cavity which prevents the internal structure of the metal from coming in contact with the air produces a more homogeneous internal structure in the cast article. This is particularly significant when highly oxidizable metals such as aluminum are cast, as the turbulence accompanying feed in the prior methods tends to separate the metal intoparticles which are oxidized and are frozen in the casting when it cools.

The refining method here described removes many impurities. The most injurious are the gases such as hydrogen, oxygen and other included gases which are removed by inert gas delivered to the molten material downwardly through the delivery tube 27 and then rising through the molten material."

The method of supplying refining gases under the surface of the molten metal has been used before this, but supplying it into the delivery tube at the top thereof and through the tubes to the bottom of the melting pot where the gas mushrooms and spreads throughout the entire melt which can be refined after the making of each casting, is believed to be new.

It is also considered novel to use refining material surrounding the delivery tubes which adsorbs and absorbs impurities between each casting operation as herein described.

In this method, preferably the material being cast is not only refined by the inert gases, but the feed pipe is made by a refining or catalytic agent that further refines the metal as it progresses on its way to the mold. The metal remaining within the delivery tube at the time the mold is filled is again refined as it is returned to the furnace.

When refining gases are injected beneath the molten material, the gas expands into bubbles which form partial vacuums into which foreign matters are drawn and they are carried to the top of the melt where they unite with the flux at the surface of the melt and are removed from time to time when the removable cover is ofi for refill.

The small openings of the delivery tube also act as filters for the included substances such as oxides and other foreign matters such as iron are acted upon by the catalyst of the feed pipe and are converted to iron oxide which is trapped.

When the delivery tube is saturated with impurities such as .solids filtered out, it may be bored to renew the feed tubes, and when saturated with gases, it may be rehabilitated by heating it to the temperature that will drive the gases out of the material of the feed pipe.

While the technique set forth above has been described specifically as applied to the casting of metals, it is to be understood that the invention is also applicable to the casting of other materials such as plastics, ceramics and the like. Accordingly the above description is to be read and interpreted broadly, and not limited to the casting of metals.

It will be understood that only a few of the modifications of this invention have been illustrated, and that various changes and modifications will be possible within the scope of the appended claims, without departing from the spirit and scope of the invention.

Having thus described the invention, what is claimed is:

1. A casting mold comprising a plurality of mold sections having an inlet associated therewith and a check valve in said inlet, to permit flow of liquid into said mold under pressure but to prevent reverse flow, said valve including a controlling member and a fixed seat forming a part of said inlet and a removable portion which becomes embedded in the molded material when 10 themold is filled, the division of 'saidmold into a plurality of sections passes through and divides saidinlet, exposing said 'removableportion for removal with the molded material.

2. A casting mold comprising a plurality of sections forming a vented cavity, a sprue for said mold, check valve means having a controlled movable part carried by molten metal in said sprue for permitting only one-way flow of molten material through said sprue, an oversupply of molten material in communication with said cavity, and pressure applying means associated with said supply for applying pressure to the molten material in said cavity, to thereby subject the casting to high densifying pressure while it is cooling.

3. A casting mold comprising a plurality of sections forming a cavity, a core in said cavity, check valve means having a controlled movable part carried by molten metal for regulating the supply of moltenmetalto said cavity, pressure supply means for applying densifying pressure tothe'molten metal in the cavity, and pressure supply means for applying substantially equal pressure to the interior of said core.

4. Pressure casing apparatus comprising a pot of molten metal, a mold including article cavities and a surplus material section, and a gate connecting said cavities and section, said gate including a controlled check valve admitting metal to said mold but automatically closing said valve, a delivery tube depending in said pot and connecting said pot with said mold, means for applying pressure to said pot to deliver metal from said pot to said mold through said check valve, and means for subjecting the metal in said section to high pressure through the connecting gate to subject the metal in said article cavities to said high pressure.

5. The apparatus as specified in claim 2, wherein said movable part is adapted to close said valve, the movable part remaining within the casting, and a seat through which the metal moves in filling the mold.

6. The apparatus as described in claim 4, wherein the metal forming the article cavity of the mold is of relatively high heat conductivity in the region of the cavity opposite the feed gate entrance thereto decreasing gradually to the feed gate side thereof.

7. A mold comprising an article cavity and a gate comprising an entrance in and into said mold, an entrance to said article cavity, a reservoir connected to said gate intermediate said entrances, means for applying pressure to the metal in said reservoir, and a check valve having a fixed seat and a controlled movable part at said entrance to said mold.

8. A mold as described in claim 7 wherein said mold is formed in sections for ready removal of the cast article and said check valve includes a controlled movable valve portion and a fixed seat in said sectional construction for holding the movable valve portion as part of the solidified casting.

9. The mold of claim 7 including a check valve with a fixed bar for limiting the movement of said movable part in said mold entrance and means for subjecting the material in said mold to high pressure, said check valve preventing the metal leaving said mold under the influence of said pressure being applied immediately upon filling the mold.

10. A casting mold comprising a mold having an article forming cavity and an entrance conduit and gate for receiving molten material into the mold and conducting it to the article cavity at the side thereof, a reservoir for excess metal within said mold and communicating with said gate, an automatic check valve at said entrance, and means for admitting a pressure force to said reservoir, said mold being formed of powdered materials of progressively different heat conductivity to conduct the heat from said cavity in a predetermined order to provide for progressive solidification of the cast metal in that order.

11. In a casting apparatus, a supply receptacle, a casting mold, small purifying tubes for delivering molten material from the receptacle to the mold, and means for applying an inert gas through the tubes and to return the molten material into the container, and to percolate the gas through the material in the container to further purify the material.

12. In a casting apparatus, in accordance with claim 11, the tube being composed of catalytic adsorbent and absorbent materials which constitute a purifying agent for the said gas.

13. In a casting apparatus in accordance with claim 11, the tube being composed of an alloy of catalytic material which acts upon the molten material which passes through the tube.

14. In a casting apparatus in accordance with claim 11, the tube comprising a plurality of passages therethrough for the passage of gases and molten materials in both directions.

15. In a casting apparatus in accordance with claim 11,

an expandable connection between the receptacle and the tube.

References Cited in the file of this patent UNITED STATES PATENTS 721,381 McAdams Feb. 24, 1903 969,539 Kitchen Sept. 6, 1910 1,019,965 Kelly Mar. 12, 1912 1,150,318 Wetherill Aug. 17, 1915 1,214,904 Doehler Feb. 6, 1917 1,514,151 Gerdien Nov. 4, 1924 1,717,608 KadoW June 18, 1929 1,895,245 Geisler Jan. 24, 1933 1,996,335 Jones et al. Apr. 2, 1935 2,040,165 Baldwin Mar. 12, 1936 2,181,157 Smith Nov. 28, 1939 2,268,981 Ericson Jan. 6, 1942 2,281,867 Anthony May 5, 1942 2,479,364 Jocelyn Aug. 16, 1949 2,495,276 Milton Jan. 24, 1950 2,522,046

Knowlton et a1 Sept. 12, 1950

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