US1725144A

US1725144A - Process and apparatus for casting hollow articles

Info

Publication number: US1725144A
Application number: US94713A
Authority: US
Inventors: Kadow August
Original assignee: CHARLES W OWEN; WILBUR OWEN
Current assignee: CHARLES W OWEN; WILBUR OWEN
Priority date: 1926-03-15
Filing date: 1926-03-15
Publication date: 1929-08-20
Anticipated expiration: 1946-08-20

Description

A. KADOW PROCESS AND APPARATUS FOR CASTING HOLLOW ARTICLES Filed March 15, 1926 4 Sheets-Sheet 1 AUGUST KAnow A. KADOW Aug. 20, 1929.

PROCESS AND APPARATUS FOR CASTING HOLLOWARTICLES Filed March 15, 1926 4 Sheets-Sheet 2 gwumdoc AUGUST KADOW @W/m 9 (QM mh 3. ma 2. Mr 2 a A 3 6N.

a m 2 E w on db .2 M Q. Nb 0 Aug. 20, l 929. A. KADOW 1,725,144

PROCESS AND APPARATUS FOR CASTING HOLLOW ARTICLES Filed March 15 1926 4 Sheets-Sheet 3 HES AUGUST KAnow 85 @MQ QWW Quorum;

Aug. 20, 1 929. KADQW 1,725,144

PROCESS AND APPARATUS FOR CASTING HOLLOW ARTICLES Filed March 15 1926 4 Sheets-Sheet 4 N O N ,TfE 1U 3H uc nioz AUGUST KADow Patented Au 20, 1929.

UNITED STATES PATENT OFFICE.

AUGUST KADOW, OF TOLEDO, OHIO, ASSIGNOR OF ONE-HALF IO WILBUR OWEN AND CHARLES W. OWEN, OF TOLEDO, OHIO.

PROCESS AND APPARATUS FOR CASTING HOLLOW ARTICLES.

Application filed March 15, 1926. Serial No. 94,713.

after a shell of solidified metal has formed against the inside of the mold. In order to increase the uniformity of thickness of the walls and the smoothness of the interior of the article, I introduce air into the interior of the mold to displace the liquid metal rapidly and with certainty. When necessary for a smooth job, additional air pressure is applied to the interior of the article after it is emptied of liquid metal.

My apparatus consists of devices suitable for carrying out my method. The details and minor objects ofmy invention will appear as the description proceeds.

In the accompanying drawings forming a part of this specification, Figure 1 is a vertical longitudinal section of one form of my apparatus, parts being. shown in elevation; Fig. 2 is a section on line 22 of Fig. 1; Fig. 3 is a section on the line 33, Fig. 1, showing the-greater part of the apparatus in plan; Fig. 4 is a section of the final blowhead, showing the mouth of the mold in cooperating position; and Figs. 5 to 8 are sec- .tions showing the relation of the mold to the metal during successive stages of the cast ing process. Fig. 9 is a view, partially in section and with parts broken away, show ing a difierent form of mold; Fig,- 10 is an elevation of'the inside of one half of the mold shown in Fig. 9; Fig. 11 is a section .on line 1111 of Fig. 9, and. Fig. 12 is a perspective of the article cast in the mold shown in Figs. 9 to 11. w i

A pedestal 10 has a collar 11 vertically adjustable thereon and rotatable thereabout. A horizontal beam 12 extends from one side of collar 11 and carries a sleeve 13-having a depending pin 14. Mold-supporting arms 15' have hinge lugs 16 mounted on pins 14, and a collar 17, fastened on the lower end of pivot pin 14 by means of a pin 18, retains the lugs onthe pivot. A mold-half 19 is mounted on one end of each of the moldsupporting arms.

A longitudinal frame-member 20 is attached to sleeve 13. One end of frame-member 20 is provided with a handle 21 by means of which its position and movements may be controlled.

A mold-operating handle 22 is mounted upon a vertical pivot pin 23 suitably held in frame-member 20. The rear ends of arms 15 are connected bylinks 24 to a pin 25 which, in turn, is connected by a link-bolt 26 to the front end of handle 22. Bolt 26 is surrounded by a spring 27 which normally presses the bolt forward until nuts 28 on the end of the bolt contact handle 22. Pin 25 has a head 29 moving in a guideway 30 in frame-member 20, so that pin 25, and.

consequently the center of the mold, is held in the central longitudinal line of the framemember.

The mold-sections have their meeting faces hollowed'out to form a mold cavity 31 and grooved to form vacuum passages 32. Preferably,the molds are ground at 33, between the mold cavity and the vacuum grooves, so as to form a very thin slit through which air passes from the mold cavity tothe vacuum grooves, but which is so narrow that liquid metal does not pass through it.

The mold shown is intended to form a threaded article, and therefore the interior of the mold cavity is threaded at 34. I prefer not to grind away the walls for an air assage at any point where threads occur, as there is likely to be a slight fin of metal left on the article along the line of any such air passage.

A vacuum chest 35 is carried on the frame above the mold. Air is exhausted from the chest through a pipe 36 leading to any means suitable for accomplishing that purpose. The passage between the vacuum grooves in the mold and the vacuum chest is controlled by a valve 37 having a stem 38 and normally closed by a spring 39.

A valve operating bell-crank lever is pivoted to the frame at 40 and has one arm 41 in position to contact stem 38, while its other arm 42 is connected by a link 43 to a lever 44 pivoted at 45 on the frame. A cam 46 on the upper end ofpin 23 isadapted to contact lever 44 and open valve 37 when handle 22 is moved to the position in which it is shown in Figs. 1 and 3.

A 'crucible 47 in suitable relation to pedestal 10,'has molten metal 48 therein. An air nozzle 49 projects above the normal level oft-he metal in the crucible. A valve 50 in the end of the nozzle is normally closed by a weight 51 attached to its stem. Weight 51 operates within an air chest 52 from which the nozzle rises.

= A pipe 53 leads from a suitable air valve 54 to air chest52. Air valve 54 is normally closed by a spring 55, but has a stem 56 extending into the path of a lever 57 pivoted at 58 to a lug 59 connected to the valve casing. handle 60, pivoted at 61 to one of the mold-supporting arms, has a roller 62 in position to be swung against lever 57 to open the valve. Stops 63 and 64 limit the movement of handle 60.

A blow-head 65 is suitably positioned on the crucible support beneath the line of travel of the mold as it is swung about pedestal 10. An air pipe 66, which may be r a branch of the pipe leading to valve 56,

conducts air into an air chamber 67. A sleeve 68 is mounted 'for verticahreciprocation about the air chamber, and is normally ra. :dby. a spring 69.

A valve 70 controls the escape of air from chamber 67 The valve has a stem 71 connected by a spider 72 to sleeve 68, so that the valve is normally seated when sleeve 68 is raised by spring 69. A gasket '73 isprovided on the upper surface of sleeve 68. When the mouth of the mold is rested on the gasket, as shown in Fig. 4, the sleeve and valve are depressed and air enters the mold w from chamber 67 Sleeve 13 is adjustabl positioned on beam 12 by means of collars 4 which are secured in adjusted position by set screws 75. The

' passes through socket-arm 77 which projects beam, in turn, may be secured in adjusted positionby means of a set screw 76 which from collar 11 to receive the end ofbeam 12.

In the operation of the. device, starting with crucible 47 filled with molten metal to a level 78, somewhat above chamber 52, the mold is closed by handle 22, and the 'frame 1s swung about pedestal l0 and then tilted about beam 12 to bring the bottom inlet of it is preferable to open thevacuum valve only after the mold is dipped, so as to avoid a useless draft of air through the mold. The useof one handle which may be moved a certain amount'to close the mold and a further amount to open the vacuum Valve enables the opening of the valve immediately after the mold contacts the metal without any shifting of the operators hand from one handle to another.

When metal rushes in to fill the mold, as shown in Fig. 6, the portion of the metal in contact with the comparatively cool wall of themold immediately solidifies and'forms a metal shell. 79 on the inside of the mold] After the mold is filled, it'is raised and the metal in the interior of the shell runs out.

1 'Where the inlet is of suflicient size ,'ai1 bubbles will enter through the inlet and allow the molten metal to run out when.

the mold is lifted above the. level of. the molten bath; but the outflow is slightly irregular in such a case, and the inrushing air moving in the opposite direction from the out-flowing metal is likely to-spray metal onto the inside of the shell and roughen the interior of the shell. .Air nozzle 49 is used to overcome this d ifiiculty.

Weight 51 holds valve 50 seated while the mold is being filled, thus preventing the entrance of air into the mold through the nozzle. After the mold is filled, valve 54 is opened, admitting air under sufiicient pressure '.to raise valve 50 and weight 51. Air then entersspace 80. As soon as air enters'the upper end of the mold, the molten metal begins to flow out by gravity, and this flow may e hastened to any desired extent by increasing the air pressure. In this way the in-coming air does nothave to bubble through the out-flowing metal, but, as will be readily seen from Fig. 7, the air enters above the metal and drives it out quickly and evenly, so as to leave the shell-with a smooth interior.

When the bulk of the mettl has been driven out, the mold is raised to the position in which it is shown in Fig. 8. Theremay be a small fin 81 extending downward from the mouth of shell 79, but the shell at this stage may be considered a substantially .finished hollow metal article, and may be I removed from the mold immediately, if desired, and the process may be repeated to produce another article.

In order to smooth out any possible blisters or other imperfections in the interior of the cast shell, it is sometimes desirable to introduce air under pressure after the liquid metal has been removed. Blow-head 65 is provided for this purpose, and it will be readily understood that the mold with the article therein may be swung over the blowhead applied thereto in the manner shown in Fig. 4, and air pressure applied to the interior of the article.

With some kinds of metal at certain temperatures and with articles of certain shapes, there is a tendency, when the molten metal is emptied out, for a film thereof to adhere to the under side of a surface of the solidified shell and to gather in drops thereon before solidifying. .It will-be readily seen that this might happen on surface 82 at the top of space 80 shown in Fig. 7. If the mold is tilted to a position like that shown in Fig. 8, this surface is moved out of the horizontal plane so that, if any film adheres thereto in suflicient quantity to flow in any direction over the surface, it will flow evenly towards the lower side and will not gather in drops or seriously roughen the interior of the article. My process, therefore, includes the tilting of the mold so that no interior surface of the shell is horizontal during the emptying step, when this is found nec to avoid the gathering of the metal in roughening drops.

If air is trapped in chamber 52 and pipe 53 under the extreme pressure which allows valve 50 to close, reduction of pressure in the mold below atmospheric allows this air under pressure to raise the valve and enter the mold. If the-nozzle is sufiiciently near the top of the mold, any air passing out of the nozzle may be exhausted before the metal rises above the nozzle, and under such circumstances valve might even be omitted entirely. But ordinarily I prefer to use the valve, and to provide against trapping air under pressure. For this purpose, stem 56 of valve 54 is made hollow, as shown at 83 on Fig. 1, with an inlet hole 84 and an outlet hole 85.. Preferably, outlet hole 85 is in such a position that when valve 54 is closed, as shown in Fig. 1, the hole is above the valve casing and acts as a vent, relieving the pressure in pipe 53 and chamber 52, but when the valve stem is depressed to open valve 54, outlet hole 85 is sealed, and so does not interfere with forcing air under pressure through nozzle 49.

The nozzle must be kept heated in order to avoid solidifying of metal about the nozzle. Conduction of heat from the portion beneath the surface of the molten metal, together with the passage of air heated in pipe 53 and chamber 52, may heat the nozzle sufliciently for this purpose, or additional heating means may be provided, or pipe 53 may be oscillated at one of its joints to immerse the nozzle between molding opera tions.

Of course, the air entering. through pipe 53, chamber 52 and nozzle 49is heated to about the temperature of the bath, and this is an advantage, as it prevents chilling irregularly arranged portions of metal on the interior of the shell and aids in remelting any protruding portions and smoothing the interior of the shell. Ordinarily the air thus heated is hot enough to accomplish the desired results, but, if necessary, additional heating means may be used.

The compressed air used must be free from impurities which will injure the metal withinthe article, and if the metal and the article being produced are of such character that heated pure air has injurious effects, another gas or gases may be selected which will avoid any injury to the hot metal.

The thickness of the solidified shell depends upon the character of the metal being cast, the temperature of the bath, the temperature of the mold and the character of its surface where it contacts the molten metal, and the length of time the molten metal remains in the mold. If the product is too thin, the bath or the mold or both may be cooled or the molten metal may be retained in the mold for a longer time. If the product is too thick, the molten metal may be discharged more quickly, the temperature of the bath or the mold or both may be raised or the interior of the mold may be coated with a non-conducting material.

The molten metal remains in contact with the lower part of the mold longer than with the upper part, and so the upper part needs to be cooler in order to obtain an even thickness in the walls of the product. Normally, the greater heating of the mold by contact with the bath and longer retention of the molten metal within it results in proper difference in temperature between the bottom and top'of the mold to secure substantially even thickness in the walls of the product. Where conditions warrant, any desired portion of the mold may be artificially cooled or separately heated either to produce desired uniformity in the product or increase'or decrease the thickness of the prodnet at desired points. Where desired, a portion only of the mold may be coated with non-conductingmaterial to reduce the thickness of the wall in the corresponding portion of the product. 5

It will be understood thatEhe metal, passing the lower end of the mold as the mold solidified against the mold wall would be thinner at thebottom. However, the metal contacts the lower end of the mold first, and

the liquid metal is in contact with the inside.

of the shell atthe lower end of themold last. This normally counterbalances the .heating tendency mentloned, and resultsm a shell of substantially even thickness. However, the discharge of themetal could be so hastened as to result in a shell thinner at the lower end of the mold; or the discharge could be sufficiently slow to allow a thicker shell to .form at the bottom, and it is possible to even stop the discharge for a time at any desired pointin order to increase the thickness of the wall-below that point.

In Figs. 9 to 11 there is shown a modified device suitable for forming a head such as shown in Fig. 12. )In this device there is shown a mold 19 supported and operated in substantially the same way as mold'19, except for features described below.

The two halves of the mold are constructed somewhat differently, mold half 86 being modified merely by having its cavity shaped to conform to the back of the desired head,v

including the back of the ears, while half 87 is shaped to form the fronthalf of the head, and is provided with means for introducing air into the mold through theearforming cavities.

Carried on the mold frame there is a valve casing 88 into which air is introduced through pipe 89, leading from any suitable source of air under pressure. Flow of air through the valve casing is controlled by a valve 90 normally closed by a spring 91.

The valve has a stem 92 projecting 1n the path of member 93 of an operating handle 94, by which the valve may be opened when desired. I

A pipe 95 having a flexible portion 96 leads from valvecasing 88 to mold half 87.

Mold half 87 is provided with projections 97 adapted to form the hollows in the'ears.

The construction for the two ears is the by a spring 101.

Air from pipe 95 enters a passage 102 in the mold half, and a branch 103 leads from passage 102 to the passage around each valve stem 98. A screw 104 closes the outer end of branch passage 103, and this screw may be used, if desired, to adjust the size of the opening into the branch passage.

Preferably, the end of valve stem 98 is provided with'a tip 105 of graphite or similar material, which is refractory and a poor conductor of heat, and a washer 106 similar material is applied to the end of pro- ,jection 97. r

In the operation of this device, the mold is operated and the metal is introduced into the mold in the same Way as described above in connection with mold 19. During this time valve 90 remains closed.

When it is time to discharge the metal from the interior of the casting, valve 90 is opened, and compressed air, passing through pipe 95 and

passageways

102 and 103, presses pistons 100 outward and so opens the inlet passages at valve seats v99. The air then enters the hollow casting and expels the molten .metal therefrom without the necessity for the passage of gas through the molten metal.

sage into the interior of the casting, but if the tip and washer are omitted, ressure sufiicient to puncture the shell can he used, as the shell will be thinner over such a projection than elsewhere, even if of the same material. v

The article produced in this mold is a hollow head 107, such as shown in Fig. 12, having a hole 108 in each ear, thr ,ugh which the metal-expelling air enters. other hollow articles, having morethan one opening into the interior, may be constructed in a similar manner by molds of such design that metal may be introduced and expelled through on opening and expelling gas may be introduced through one or more of the other openings. This is a simple and efficient way of introducing the gas, where the casting has more than one opening. Gas

introduced in this manner may be heated to some extent, if desired, but not as conveniently as Where the gas is introduced through the molten metal, as described in connection with the referred form.

While have described my invention in connection with the formation of metal articles and, for convenience, use the term metal in the claims, it will be readily understood that my invention is applicable to substances other than those commonly classified as metals, where the physical characteristics of the substances are such that the features of the inv ntion are applicable thereto for the purposes described.

It will be understood that different shapes of articles may be produced by my apparatus and process, and that many changes, not specifically enumerated, may be made within the scope of the appended claims which define my invention.

What I claimis:

1. A method of forming hollow metal articles, which consists in filling a mold with molten metal, allowing'the metal in contact Obviously,

mold, and introducing-gas under pressure and forcing the liquid metal out of the interior of the shell.

3. A method of forming hollow metal arti cles, which consists in filling a mold with molten metal through an inlet in its under side, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing gas through the inlet into the interior of the shell so that it first contacts the molten metal at a point above the inlet, and emptying molten metal from the shell. 4. A method of forming hollow metal articles, which consists in filling a mold with molten metal through an inlet in its under side, allowin the metal in contact with the moldto solidify and form a hollow shell, and introducing gas under pressure through the inlet and forcing out the liquid metal from the shell. a

5. A method of forming hollow metal articles, which consists in filling a mold with molten metal through an inlet in its under side, allowing the metal in contact with the mold to solidify and form a hollow shell,'and introducing gas under pressure into the shell at a point above the inletand displacing the molten metal within the shell.

6. 'Amethod of forming hollow metal articles, which consists in filling a mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing heated gas under pressure into the interior of the shell and forcing molten metal out. of the shell.

7: A method of forming hollow metal articles which consists in filling a mold with molten metal through an inlet in its bottom, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing gas through a pipe surrounded by molten metal into the interior of the shell allluh displacing the molten metal from the s e r V 8. A method of forming hollow metal articles, which consists in filling a mold with molten metal through an inlet in its under side, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing heated air under pressure into the shell at a point above/the inlet and forcing the moltenmetal from/the interior of the shell.

9.' A method of forming .hollow metal articles, which consists in filling a mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing gas heated to substantially the temperature of the molten metal into the shell and emptying molten metal from the shell.

10. A inethod of forming a hollow metal article having a single opening, which consists in filling a mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell complete except where the metal enters, and introducing into the interior of the shell a gas so that it first contacts the molten metal at a point within the shell and emptying molten metal from the shell.

.11. A method of forming molten metal articles, which} consists in filling a mold with molten metal,.}allowin the metal in contact with the mold to solidify and forma hollow shell, and introducing into the interior of the shell a gas heated to approximately the temperature of the molten metal and which does not re-act injuriously with the molten metal and emptying the shell of molten metal.

12. A method of forming hollow metal articles, which consists in filling a mold with molten metal through an inlet in its under side, allowing the metal in contact with the mold to solidify and form a hollow shell, and

introducing into the shell at a, point above its inlet a heated gas under pressure which does not re-act injuriously with-the molten metal and driving the molten metal out of the shelL- I 13. A method of forming hollow metal articles, which consists in exhausting the air from a mold, filling the mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing into the interior of the shell a gas under. pressure and forcing molten metal from the shell.

143A method of forming hollow metal articles, which consists in exhausting the air from a mold, filling the mold with molten metal through an inlet in its under side, allowing the metal in contact with" the mold to solidify and form a hollow shell, and introducing 'gas into the shell so that it first contacts the molten metal at a point above .the inlet and emptying molten metal from the shell.

15. A method of forming hollow metal articles, which consists in exhausting the air from a mold, filling the. mold with molten metal through an inlet in its under side, allowin the metal in contact with the mold to solidify and form a hollow shell, and introducing gas under pressure into the shell at a point above the inlet and forcing molten .metal out of the shell.

16. A method of forming hollow metal articles, which consists in filling a mold with molten metal through an inlet in its under side, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing into the interior of the shell gas heated to approximately the temarticles, which consists in positioning a'mold so that its inlet is on its under side, dipp ing the inlet into a bath of moltenmetal, ex-

hausting the air from the mold and fillingthe mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, and introducing gas into the shell and emptying molten metal from the shell back into the bath,

18. A method of forming hollow metal articles, which consists in positioning a mold with its inlet on its under side, dipping the inlet in a bath of molten metal, exhausti the air from the'mold and filling the mdl with molten metal, allowin the metal in contact with the mold to solidify and form a hollow shell, and introducing compressed gas into the interior of the shell at a point above the inlet and forcing molten metal out of the shell;

19. A method of forming hollow metal articles, which consists in filling a mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, introducing gas into the interior of the shell and emptying molten metal from,

the shell, and governin the thickness of the shell by the rapidity o cooling of the metal in contact therewith. v

20. A method of forming hollow metal articles, which consists in filling a mold with molten metal, allowin the metal in contact w1th the mold to solidify and form a hollow shell, introducing gas into the interior of the shell-and emptying molten metal from the i shell, and regulating the temperature" of the mold to govern the thickness of the shell.

21. A method of forming hollow metal articles, which consists in filling a mold with molten metal; allowin the metal in contact with the mold to solidlfy and form a hollow shell, introducing gas into thejinterior of the shell and emptying molten metal from shell, introducin the shell, and regulating the temperature of the molten metal to govern the thickness of the shell.

A method of forming hollow metal artlcles, which consists in filling a mold with moltenmetal, allowin the'metal in contact with the mold to solid fy and 'form a hollow gas into the interior of theshell and emptying molten metal from the shell, and regulating the temperature of the introduced gas'to govern the thick articles, which consists in filling a mold with molten metal through an inlet, allowin the metal in contact withthe mold -to"sol1dify metal from the shell.

and form a hollow shell, introducing gas under pressure into the interior of the shell with its inlet downward, dipping the inlet into molten metal, exhausting the air from thekinterior of the mold and filling the mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, introducing gas under pressure into the interior of the shell above the inlet, and forcing the molten metal out of the shell and regulating the pressure of the gas to govern the relative thickness of the shell adjacent the inlet.

25. The method of forming hollow metal articles, which consists in positioning a mold with its inlet downward, dipping the inlet into a bath of molten metal, exhauaing the air from the mold and filling the mold with molten metal, allowing the metal in contact with the mold to solidify and form a hollow shell, introducing gas into the interior of the shelland emptying out molten metal from w the shell while holding the mold in such aposition-that all its interior surfaces are at an angle to the horizontal.

'26. The method of forminghollow metal articles, which consists in positioning a mold with its inletdownward, dipping the inlet into a bath of molten metal, exhaustingthe air from the mold and filling the mold with molten metal, allowing the metal -in;'contact-- with the mold to solidify and-form a hollow shell, introducing gas throughv the bath-into the interior of the shell and emptying molten 27. The methodof forming hollowmetal articles, which consists in positioning a-mold with its inlet downward,' dipping fthe inlet intoa bath of molten metal,-iexhaustin g. the air'iroin the mold and fillingthe'n lold. with molten metal, allowing the'm'etalin contact with the mold to solidifyjand form a hollow shell, introducing gas throughthe bath into the interior of the shell and emptying molten metal from the shell while holding the mold in. sucha position that all of its interior surfaces are at an angle to the horizontal.

, 28. A method of forming hollow metal articles, which consists-in filling a mold with molten metal, allowing the metal incontact with the mold to solidify and form a hollow shell, introducing gas into the interior of the shell and emptying molten metal from the shell and thereafter introducing gas under pressure into the shell within the mold.

29. The method of forming hollow metal articles, which consists in posltioning a mold with its inlet downward, dipping the inlet into a bath of molten metal, exhausting the air from the mold and filling it with molten metal, allowing the metal in contact with the -mold to solidify and form a hollow shell.

into a bath of molten metal, exhausting the air from the moldand filling it with molten metal, allowing the metal in contact with the .mold to solidify and form a hollow shell,

introducing gas through the bath into the interior of the shell and emptyingmolten metal from the shell, and thereafter subjecting the interior of the shell to gas under pressure.

31. The method of forming hollow metal articles, which consists in positioning a mold with its inlet downward, dipping the inlet into a bath of molten metal, exhausting the air from the mold and filling it with molten metal, allowing the metal in contact withthe mold to solidif and form a hollow shell, introducing gas 1; rough the bath into the interior of the shell and emptying molten metal from the shell while holding the mold in such a position that all ofits interior surfaces are at an angle to the horizontal, and thereafter subjecting the interior of the shell to gas under pressure.

32. Apparatus for forming hollow metal articles comprising a mold, means to fill the mold with molten metal, and means to in troduce gas under pressure into the interior of the mold to drive out unsolidified portions of the molten metal. Y

Apparatus for forming hollow metal articles comprising a mold, means for filling the mold with molten metal, means for introducing gas into the mold to .displace therefrom unsolidified molten metal, and means for subjecting the interior of a hollow shell thus formed within the mold to gas under pressure.

34. Apparatus for forming hollow metal articles comprising a mold, means to position the mold with its inlet downward, means to till the mold with molten metal through its inlet, and a pipe in position to introduce gas through the central portion of the inlet into the interior of the mold cavity to displace the molten metal therefrom.

35. Apparatus for forming hollow metal articles comprising a mold, means to position the mold with its inlet downward, means to fill the mold with molten metal through its inlet, and a gas pipe passing through the inlet and opening into the interior of the mold cavity at a point near the top of the mold cavity.

36. Apparatus for forming hollow metal articles comprising a mold, a receptacle adapted to contain a bath of molten metal adapted to contain a bath of molten metal,

means to move the mold into positionwith its inlet dipped into a bath within said ceptacle, and a gas pipe extending through said receptacle and through the inlet of the mold when the mold is so positioned.

r 37 Apparatus for forming h ollow metal articles comprising a mold, a receptacle 7 means to move the mold into position with its inlet dipped into a bath within said receptacle, a gas pipe extending through said receptacle and through the inlet of the mold when the mold is so positioned, means to exhaust air from the interior of the mold, and means to introduce gas through said gas pipe into the interior of the mold.

38. Apparatus for formin articles comprising :1 mol a receptacle adapted to contain a bath of molten metal,

hollow metal means to move the mold into position with its inlet dipped into a bathwithin said receptacle, a gas pipe extending through said receptacle and through the inlet of the mold when the mold is so positioned, means to exhaust air from the interior of the mold, means to introduce gas through said gas pipe into the interior of the mold, and a valve in the end of the gas pipe within the mold.

39. Apparatus for forming hollow metal articles comprising a mold, anreceptacle adapted to contain a bath of molten metal, means to position the mold with its inlet in a bath within the receptacle, a gas pipe extending through the bath intothe mold when so positioned, means to exhaust air from the mold, a valve for admitting compressed gas into said pipe, a valve in the end of said pipe within the mold, and relief articles comprising a mol a; receptacle adapted to containa molten metal bath,

means for moving the moldin a fixed path from a position with its inlet dipped in a bath of molten metal within the receptacle to a discharge position, and a blow-head adjacent the path of the inlet of the mold between said two positions. k

41. Apparatus for formin *hollow metal articles comprising a mol a receptacle adapted to contain a bath of molten metal, means to move a mold from a position with its inlet dipped in the bath to a discharge position, means to exhaust air from the interior of the mold, means to introduce gas into the interiorof the mold to displace molten metal therefrom, and a blow-head adjacent the path of the mold inlet between said two positions.

42. Apparatus for forming metal articles comprising a mold, a receptacle adapted to contain a bath of molten metal, means to move'themold between a-position with its inlet dipped in a bath of molten metal in the receptacle and a discharge position, a handle adapted to open andclose the mold, a vacuum valve for themold and operative connections between said handle and valve.

43. Apparatus for forming metal articles comprising a mold, a receptacle adapted to contain a bath of molten metal, means to move the moldrbetween a position with its inlet dipped in a bath of molten metal in the receptacle and a discharge position, a

handle adapted to open and close the mold, a vacuum valve for the mold and operative connections between said handle and valve,

said operativeconnections being constructed to operate b additional movement of said AUGUST KADOW.