US1452246A - Art of and apparatus for casting metals - Google Patents

Description

Apr. 1 1,' 1923.

V 1,452,246 S. P. MARSHALL ART OF AND APPARATUS FOR. CASTING METALS Filed Dec. :50 1922 2 Sheets-Sheet 1 Apr. 17, 1923.

S. P. MARSHALL ART OF 1W1) APPARATUS FOR CASTING METALS Filed Dec 30 1922 2 Sheets-Sheet 2 QZZW 6am,

attozneq v undue li Patented Apr. 17, 1923.

UNITED STATES PATENT OFFICE.

STANMORE'P. MARSHALL, WASHINGTON, DISTRICT OF COLUDI IBIA, ASSIGNOR TO H. B. BYRD MANUFACTURING COMPANY, INCORPORATED, OF WASHINGTON, DIS- TRICT OF COLUMBIA, A CORPORATION OF VIRGINIA ART OF AND APPABATUE FOR CASTING METALS.

Application filed December 30, 1922. Serial No. $09,781.

T o'all Whom it may concern:

Be it known that 1, STANMonu P. MARSHALL, a citizen of the United States, residing in the city of Vashington and District of Colum- 6 bia, have invented certainnew and useful Improvements in the Art of and Apparatus for Casting Metals, .of which the following is a specification.

My invention relates to the art of casting 10 metals, such as gold and alloys thereof, and

to improved casting apparatus of th'c'pneumatic pressure and vacuum type, and in whicht e metal'is-fused in a separate crucible shave the flask or mold, so as to avoid ating of the flask and its investment.

\Vhile iny method and apparatus are capable of general utility in producing erfect castingls of any. suitable material, is ey are particu arly'concerned with the production of dental; castings, for use as inlays for filling cavities or as bridges or plates forsupplorting artificial teeth.

emain objects'underlying this inven tion are the provision ofimproved means and methods of operation over those disclosedin my copending application Serial No. 509593, filed Oct. 22,1921, of which this application is a continuation in part and by which dlelicate castings may be perfectly formed even in a comparatively cold mold, and any chilling before the molten metal reaches every part of such a mold avoided, and which is also adapted to avoid the disas in the usual practice, in which the investment material is often cracked or disin tegratedi A further. object 0t my invention is to' provide meaiis and a method by which relatively large tastings may be produced more quickly than is possible with other methods and dental machines.

A further object of the invention isthe production of a compact and simple apparatus in which the casting is effected in the minimum of time and therefore at the least expense, and which does not require special skill in operation.

, A further object of the invention is the provision of simple means whereby both the vacuum pressure and the casting pressure containers may be simultaneously or, if desired, separately, filled with compressed air,

tortion resulting from casting in a hot mold."

and wherein a vacuum-producing device, of the e ector type, 1s operated by the compressed air.

Another object of my invention is to dispense with the use of pump rods andhand levers, as in ray-former machines, and the substitution. of valves and :1 spring flywheel for releasing the pneumatic pressure device required to force the molten metal into the mold, while preventing leakage of corrliylirezised air past said metal and into said mo A. still further object is the substitution of simpler means, such as the provision of separable but normally closed slits in the base of an integral crucible, and which are openable to discharge the crucible contents by air pressure alone,'for the lever means and divided crucible illustrated in my copending application' In my present structure, finally, the asbestos lined guide funnel provided in the crucible containing receptacle of my former casting machine is eliminated by the provision of a guiding hopper that does not require a lining and is not a separate element,

'but is integrally formed with the receptacle at its base.

Other features of my invention. will he set forth hereinafter and pointed out in the claims.

With the above and such other objects in view and realized advantages, as will be apparent 'from the description,my invention resides in thejnovel methods and in the novel construction, combination and arrangement of parts, as 'hereinafter described and claimed, taken in connection with the ac companying drawings, in which Fig-Q1 representsa perspective view of the assembled casting apparatus, with the compression valve stem and cover in raised position.

Fig. 2 is an enlarged vertical central sectional view; taken through the piston latch, of the compression valve stem, spring fly wheel, and its connecting parts, and showing the upper portion of the supporting bracket and ejector control valve stemin elevation.

Fig. 3 is an enlargedvertical central sectional viewthrough the ejector andparts connected therewithand of a portion'of the base plate and of the ejector control valve stem, and also showing thev ower portion of one of the compression tanks and the supporting bracket in elcvat-ion.

Fig. 4 is a vertical central sectional view on a larger scale, of the assembled flask, funnel, asbestos crucible and cover with some of the connectin parts broken off, and showing a ball or p ug of molten gold in position above the sprue channel in section, and its previous position on the asbestos crucible in dotted lines.

Fig. 5 shows a vertical detail view of the latch bushing and a portion of the coiled spring secured to it.

Fig. 6 is a top plan view of the asbestos crucible, showing the normally 7 closed crossed slits in its center, and

Fi T is a top plan view on smaller scale, of the tank valves, their connections with the flask not showing the parts of the pressure and casting devices above the latter, including a somewhat tanks and the pressure gage and the hose connecting 5" which may be the casting device with the tanks.

\ei'erring now to the drawings and particularly to Figures 1, 2 and T, 1 represents a metal base plate integrally supporting the bracket 2 and carrying all of -the operating mechanism, and which is usually secured by screws to a wooden base for handy transportation of the assembled; casting machine or to any other convenient support. Pressure tanks 3 and 4 are secured preferably by means of straps 5 or fastened by means of screws (3 or bolts 6, or in any other suit- I able manner to the bracket 2.

On tank 3'is a valve casing 7 preferably provided with a nipple 8 adapted to take a hose leading to a pressure pump r pressure line not shown, and containing a 3- way valve 9, provided with a handle 10 and bored across horizontally, and vertically from said passage way downwardly so as to lead into said tank 3. Valve 9, by means of a passageway 11 communicates with a support 12, carrying the-pres sure-registering gage 13 and with a passageway leading thereto and which support, by means of passageway 14, communicates with an end piece 15 on the tank 4 and leading thereinto. Preferably the valve casingi', support 12 and end piece 15 and their interconnections are formed integrally in one casting to which the tanks 3 and 4 are then secured, but, of course, they may be formed separately and secured to the tanks in any well-known way. In case it be desired to. fill either of the containers separately, instead f simultaneously, it is obviously only necessary to provide a bypassin the 3-way valve casing 7.

Means. such as nipple 16, which maybe provided on tank 4, as shown in Fig. 7, or on the support 12, as is preferred, operatively connects tank 4; with a' flexible hose 17,

stand but Hose 17 is fitted to the nipple 18 of a sleeve 19, which is provided at its upper portion with a valve chamber 2O in which the valve disk 21 may have up and downward play, and is threaded below on the inside for screwing over the threaded end of the hollow compression shaft 22.

Shaft 22 is provided with large square screw-threads for the greater portion of its length for up and down movement'in a bushing 23 and at its lower smooth end fixedly carries a notched guide plate 24, whose notch straddles the front rib 25 of the bracket 2, and serves to prevent shaft 22 from turning as it is moved up and down.

Bushing 23, shown in detail in Figs. 2 and 5, is threaded internally at its upper portion with large square threads for re-- cciving shaft 22, but for the remainder of its length is slightly larger in internal diameter than the external diameter of the said shaft. Externally. said bushing is threaded at its upper end, is then enlarged in diameter to provide a shoulder to which a flat coiled spring 26 is fixed by means of screw 27, and is then again increased in diameter to near its lower flanged end 28, excepting for the provision of a horizontal circular groove 29 near its top, and a concave portion provided with teeth 30 below said groove. The bushing 23 is rotatablv.held mounted in the upper circularly bored-out arm 31 of the bracket 2 by means of a pin 32.

To the front of the arm 31 is screwed a horizontal spring casing 33, which is slotted to provide play for the vertical rod handle 34 secured to a bolt or piston latch 35. wh ch is held in the said casing forwardly projected against one of the grooves between two of the teeth 3 by the tension of the spr ng 36 which bears against the end of said casing.

The horizontal flat spring 26 carries a vertical pin 37, which fits in a socket provided in the top of the bracket 2 and there ralitv of downwardly directed passageways 414 leading from a chamber located int c narrower upper portion or neck of the said crucible and which freely communicates with the hollow shaft 22.

A. spring 45 is interposed between the upper edge of the neck of the crucible and an inner shoulder and tends to hod the said crucible cover slightly extended, leaving a circular gatp between its shoulder and the ower and 0 said shaft, but permittin said cover to move upwardl closing saic l ap, against the tension of said spring, w en the cover strikes or rests upon the crucible to be described later.

The base'plate 1 is bored to receive the reduced and threaded lower end of an upright flask support 47 which isheld in place by the nut 48, and which flash support is made flaring at the top and furnished with a raised -rim 49 to provide a flat circular recess or table 50 adapted to receive the base of a flask.

Flask support 47 is provided with a vertical central bore 51 extending from the to to near 'its base and with two aligned horizontal passageways at or near its center, of which one, 52, is of smaller diameter and flares inwardly, while the other 53 islarger in diameter and threaded to receive a threaded nipple 54 projecting into said bore 51 and constituting therewith an ejector for enhausting the air or vapor content of said bore 51 when compressed air or any other suitable medium under pressure is forced through said nipple 54 and across bore 51 into the flaring inward end of the passageway 52 and out into the external atmosphere.

'lhe threaded end portion of nippie54. projecting outside said flask support is screwed into a vertical valve casing 55, which is bored vertically to receive the ejector control valve stem 56 carrying a conical valve disk 57, which is normally heid upwardly'against its seat by a compression spring 58 resting upon the threaded plug 59, and thereby closes communication between passageways 60 and 61 leading from the air outlet pipe 62 and tank 3 into the nipple 54.

The upper end of the ejector control valve stem 56 pro ects through an opening in the guide plate 24 and is provided below the latter with a stop collar 63, fixedly but adjustably secured by a set screw 64.

()f the several kinds of flasks which are employed in, connection with the aforedescribed casting machine, Figs; 1 and 4 illustrate two types in common use, namely, a flaring large-size flask 65, shown in Fig. 1 and employed when making large dental castings, such as dentures and the like, and a small cylindrical flask 66, shown in Fig. 4, for making small castings, such as individual gold teeth. In all cases the upper openings or mouths of said flasks are preferably all made of the same uniform diameter, so

rovided on the shaft 22.

as to adapt them for receiving the same size of receptacle or funnel 67, of brass or other suitable material whose flange is fitted upon the faced to of the flask walls. Said funnel is inwardly'curved and provided at its bottom with a downwardly tapering central hopper 68, for receiving the molten casting metal and of suflicient size and taper to guide the same into and completely pin up the sprue channel 69 leading to the mol cavity 70, formed in the investment 71, which is apl'astic composition usually comprising plaster of Paris and silica.

Over said funnel and with its rim resting on the funnel flange is placed metal receiving means, such as the receptacle or crucible 72, preferably of asbestos or other heatresistant material, shown in Figs. 4 and 6, and of less curvature than the said funnel, so that it is separated from the latter by an arr space 73, and having cross-shaped slits 74 at its lowest portion, which are normally closed but are adapted to be forced open bv air pressure from aboveto admit of passage through them of the old .or other metal, shown as 75 in dotted lines in Fig. 4, which is melted in said crucible by means of an acetylene blowpipe or. similar means not-" shown.

t In practising my invention, and in particular in dental casting, I usually proceed as -follows:

I first connect up the casting apparatus with a suitable source of air or gas pressure, such as an ordinary hand pump, and open the 3-way valve mounted incasing 7 by means of the handlelO, that is, I place said handle in the position shown in full lines in Fig. 7, whereby communication is established between the source of pressure and both tanks 3 and 4, and force air into them. When gage 1'3 registers the pressure desired say 40 lbs. per square inch, then the sai 3-way valve is closed by turning handle 10 to the position shown in Fig. 1 and in dotted lines in Fig. 7, whereby the supply line from the above source of pressure and also air pressure between the two tanks 3 and 4 is cut oft.

I now place the properly prepared flask, such as shown in Fig. 4, and enclosing the mold cavity and with the funnel 67 in position, on the table 50 of the flask support 47, and put the asbestos crucible 72 on said funnel. The metallic alloy or other materialto he used in making the casting, designated by the reference numeral 7 5 in Fig. 4, is now placed in the crucible, and fused therein, by suitable means, such as a portable blowpipe.

When the alloy has been thoroughly melted, the piston latch 35 is released by pulling it backward against its spring, whereupon the threaded shaft 22, carrying the crucible cover, and impelled y spring 26, moves downwardly. As shaft 22 proceeds down its guide plate 24 strikes the stop collar 63 mounted on the ejector control valve stem 56 and opens the ejector valve 57. thereby creating a vacuum as far as is possible with the means employed. to wit, a partial vacuum in the flask investiture and mold cavity, just prior to the sealing of the cruc,i-

ble cover on its seat provided on the brass funnel and with the interposed gasket pro vided by the rim of the asbestos crucible. Air pressure from tank 3. released by valve 21. now forces the molten metal through the slits of the crucible into the sprue channel and into the mold cavity. This is efl'ected. it should be noted. by the threaded shaft 22 still continuing its .lownward course for a. short distance. after the crucible cover is impeded from further movement. the play provided between the shoulder on said crucible cover and the bottom of the threaded shaft serving to raise valve 21 off its seat and bring spring pressure from element 45 to bear on said cover and hold it tightly in place on the crucible and the bottom of receptacle UT tightly against the top of said flask.

In the casting operation itself the excess of molten metal forced through the slits in the bottom of the crucible completely plugs up the charging cavity above the sprue way and thus prevents compressed air from escaping past the metal and also prevents the union of the compressed and the exhausted air in the mold cavity and in vestiture during the casting. The provision of means to effect this in my casting apparatus constitutes what I consider a very important advance over prior constructions of dental casting apparatus. in which the advantage accruing from the use of both pressure and a vacuum in casting. over either alone. has never. it is believed. been demonstrated.

Positive pressure obtained from tank 4 is maintained upon the metal head in hopper 6B. which commuricates by the neck in the si'irue-way G9 with the casting itself. until the latter has cooled sulliciently to admit of lifting of the crucible cover and removal of the flask and its contained casting. while the pressure in tank 3, acting through the ejector system represented by elements 62. (it). 57. 61. M and 5?. draws air and water vapor from the base of the flask. through bore 51. until it has been reduced to normal atmospheric pressure. Then. by turning the spring wheel 38 by hand in the direction to wind up spring 26. the threaded shaft 22 is raised and with it the crucible cover. to an) desired height. say to the elevated position shown in Fig. l. where it is held. until in leased. by the latch bolt 35. This completes the cycle of the working of the machine. which is now ready for another casting operation.

What I claim as new is:

1. In the art of casting by machines in which two pressure containers are employed, the steps of filling said containers simultaneously from a single source of pressure, then cutting off the pressure between said containers, then fusing the material to be molded in temporary retaining means so arated by an air gap from means for mol lug said material. then producing a vacuum in said molding means by an ejector device operated by pressure derived from one of said containers. and finally forcing said material through said temporary retaining means by fluid pressure derived from the other of said containers into said molding means.

2. In the art of casting by machines in which two pressure containers are employed,

the steps of filling said containers simultaneously from a single source of pressure, then cutting off the pressure between said containers. then fusing the metal to be molded in a normally n'ietal-retaining means for the temporary holding of said metal without undue heating of the metalmolding-means then exhausting air from said metal-molding means by an ejector de- .ice operated by pressure derived from one of said containers. and finally forcing the molten metal through said temporary metalretaining means by fluid pressure derived from the-other of said containers into said molding means while maintaining a vacuum therein.

3. In the art of casting metal by machines in which two pressure containers are employed, the steps of first. filling said containers simultaneously from a single source of pressure. then cutting ofl' the pressure between said containers. then fusing the metal to be molded in a normally-closed valvular crucible located above a flask but separated therefrom excepting at its rim, then exhausting air from said flask by an ejector device opt'liltt'd by pressure derived from one of said containers. and finally forcing the molten metal through the valve of said crucible by air pressure derived from the other of said containers into said flask. while maintaining a vacuum in said right crucible-carrying flask. controllable means for supplying, the said pressure medium from one of said containers to said with the other of said containers for ex h-austing the lower end of said flask through said support and means connected with said controllable means for starting said exhausting action before said pressure medium is admitted to said crucible.

7. In a casting apparatus the combination of a pair of interconnected pressure tanks with means for admitting a pressure medium to and cutting 011' its flow between said tanks, a support provided with passage ways therethrough and adapted to hold an upright crucible-carrying flask, controllable means for supplying the said pressure medium from one 0 said tanks to said crucible, ejector means communicating with the other of said tanks for exhausting the lower end of said flask through the passage-ways of said support, and means for controllinq the start of operation of the last means refativeltv to that of the said controllable means.

81 n a casting machine the combination of a pair of interconnected pressure tanks with means for admitting a pressure medium to and cutting off its flow between said tanks, 8. support provided with passageways therethrough and adapted to old an upri ht flask open at its ends and tightly fitte with a closable crucible on its upper and, controllable means for suppl ing said pressure medium from one of said tanks to said crucible when it contains molten material and is closed, and ejector means for prcviousl drawing air and vapor from the lower en of said flask through its support .and started in operation by said first con trollable means.

9. In a casting machine the combination of a pair of interconnected tanks with means for admitting a pressure medium to and cutting oil its flow between said tanks, a sup port provided with passageways forming an ejector therethroug an adapted to hold an u ri ht flask open at its ends and tightly fltte with a closable crucible on its upper and, movable means including a valve for sup lying said pressure medium from one of as cl tanks to said crucible when it contains molten material and is closed, spring means for actuating said movable means, locking means for restraining the operation of said for exhausting the lower end of said flask.

through the ejector in-said support, and means for controlling the operation of said last namedvalve actuatcd'by said movable means.

10. In a casting machine the combination of a supporting base having an upright angular bracket arm, a pair of closed tanks for compressed air secured to said base. a threeway valve for controlling the supply of and means for leading compressed air to and from said tanks mounted thereon, a nipp e on said means, aflexible hose secured to said nipple communicating with one of said tanks and fastened to a sleeve containing a normally-closed disk valve, an outwardly threaded hollow shaft threaded to said sleeve and containing the stem of said valve, an inwardly threaded-bushing rotatably mounted in said bracket arm and carrying said shaft for reciprocating motion, a spring wheel for moving said shaft fixed on said bushing, a latch for locking said bushing against movement mounted on said bracket arm, a crucible coyer slidably and resiliently mounted on the lower end of said shaft and carrying the end of said valve stem but permitting its upward movement to open -said disk valve, when the movement of said cover is arrested, a straddle plate secured to said shaft and guided by said bracket arm to prevent rotation of said shaft but adapted, when said shaft moves downward, to strike a stop collar, a centrally bored flask support secured to said base and provided with an ejector communicating with the sec end of said tanks. a valve casing containing a normally closed disk valve interposed between said support and the last-named tank, a stem upwardly extended from said valve and. an adjustablv mounted stop-collar on said stem adapted to open said valve to admit compressed air to said ejector when moved downward by said plate on said shaft.

11. In a compression and vacuum casting machine, a vertically reciprocatable cover carried by a hollow shaft adapted to supply air pressure for casting, a temporary retaining means for fused metal adapted to be closed by said cover .when said shaft reaches the end of its downward motion, and fixed but normally closed slits provided in said temporary metal-retaining means adapted to be opened to release its contents of fused metal and operated by air pressure supplied by said first-named means after it has reached its lowest position. r

12. In a compression and vacuum casting machine provided with a rcciprocatable cover. a crucible of refractory material adapted to enact with said cover to form an enclosure for tem )orarily retaining molten metal, said crucibe having a convex body and a flat rim and slits provided in said body which are normally closed to the passage of molten metal but are adapted to be opened when iluid pressure. admitted through said cover. is exerted upon their upper surface.

13. In a compression and vacuum casting machine provided with a reciprocataldo cover, fused metal-receiving means adapted to form a covered enclosure with said cover, and a conical tunnel for supporting said metalweceiving means by its rim and pro vidcd at its base with a charging hopper, and adapted to lit tightl upon a molding flask and its investiture and to hold a head of fused metal above and therewith plug a. sprne provided in said invcstiture against the ingress of air.

14. In an apparatus for casting articles ol metal the combination with a flask adapted to enclose a mold of porous material and having an upper and lower opening," of a receptacle above the upper opening of the flask and in communication therewith. a crucible within the receptacle above the up per opening of the flask and at such distance from it as to leave a substantial air space between the crucible and the flask. means for creating a. partial vacuum within the llask, and means permitting fluid pressure to discharge the contents of said cru ible into said flask.

15. In an apparatus for casting articles of metal the combination with a llaslt a lapted to enclose a mold of porous material and having an upper and a lower opening. of a normally open receptacle above the upper opening ol the flash and in clnnmunication therewith, a crucible within the receptacle above the upper opening of the llask and at such distance from it as to leave a substnntial air space between the crucible and the flask. means for creating a partial vacuum in the flask. means for closing the receptacle and for forcing air under pressure into it. and means permitting air pressure to dis charge the contents of \Illil crucible into the upper opening of mid ilash.

l6. In an iI])ll-;ll'1i for casting ailiclcs of metal the combination with a tlask adape ed to enclose a mold ol' porous material and having an upper and a lower opening. of a re eptacle above the upper opening ol the flask and in conunuuicalion therewith. a. crucible within the re i aclc above the upper opening of the and at such dis-- tance from it a to a ill-wan ed air space between the cro phniel tilt lLhl-i'.

means lor creating a partial \ill'lllll t in the flask. means permitting laid pressure to discharge the cunlcntcl will tiiii'll lt" into said flask. and menu cawiw by the their for guiding the conlruis o: the crucil h into the sprue channel oi th mold therein.

11'. In an apparatus l'oi' eisting articles of metal the combination with a flask adapted to enclose a mold of porous material and having an upper and a lower opening, of a receptacle above the upper opening of the flask and in communication therewith, a crucible within the receptacle above the upper opening of the flask and at such distance from it as to leave a substantial air space between the crucible and the flask, means for (mating a partial vacuum in the flask. means permitting air pressure to discharge the contents of said crucible. into the upper opening of said flask and a tunnel carried by the flask for guiding the contents of the crucible into the spruc channel of the mold enclosed therein, thereby preventing the air pressure from escaping past the metal in he mold.

18. In an apparatus for casting articles of metal the combination with a flask adapted to'euclose a mold of porous material and having an upper opening and a lower opening, of a receptacle above the upper opcning of the llask and in communication therewith, a crucible within the receptacle above the upper opening of the flask and at such distance therefrom as to leave a substantial air space between it and the flask, means for holding the bottom of said receptacle tightly againstthe top of said flask air exhausting means adapted to be placed in communication with the lower opening of the flask, means permitting air pressure to discharge the contents of said crucible into the upper opening of said flask, and means for connecting the exhausting means with the.

flask to create a partial vacuum therein and then discharging the. contents of the crucible.

19. In an apparatus for casting articles of metal the combination with a flask adapt ed to enclose a mold of porous material and having an upper opening and a lower opening} of a normally open receptacle above the upper opening of the flask and in communication therewith. a crucible within the receptacle above the upper opening of the liash and at such distance therefrom as to leave a substantial air space between it and the llask. means for closing said receptacle and holding the bottom of said receptacle tightly against the top of said flask, air exhausting means adapted to be placed in comnninic: tion with the lower opening of the iia k. air pressure means adapted to be. placed in communi 'ation with the receptacle, and means permitting air pressure to dis charge the contents of said crucible into the upper opening of said flask.

2t In an apparatus for casting articles oi metal :he combination with a flask adapted to enclose a mold of porous material and having an upper opening and a lower open ing. of a normally open receptacle above the upper opening of the flask and in communication therewith. a crucible within the re- 1,4aame ceptacle above the upper opening of the flask and at such distance therefrom as to leave a substantial air space between it and the flask, means for closing said receptacle and holding the bottom of the receptacle tightly against the top of said flask, air exbans-ting means adapted to be placed in communiration with the lower opening of the flask. air pressure means adapted to be placed in communication with the receptacle,

means permitting air pressure to discharge the contents of said crucible into the upper opcnin; of said flask, and means for first connecting the exhausting}, means with the flask to create a partial vacuum therein and then simultaneously closing the receptacle, turning on the air pressure and discharging the contents of the crucible.

21. In an apparatus for casting articles of metal the combination with a flask adapted to enclose a mold of porous material and having an upper opening and a lower opening, of a normally open receptacle above the i upper opening of the flask and in communication therewith, a crucible within the receptacle above the upper opening of the flask and at such distance therefrom as to leave a substantial air space between it and the flask, means for Closing said receptacle and holding the bottom of said receptacle tightly against the top of said flask air exhausting means adapted to be placed in communication with the lower opening of the flask, air pressure means adapted to be placed in communication with the receptacle, means for discharging the contents of the crucibleinto the upper opening of the flask, operating means and means operated thereby for first connecting the exhausting, means withthe flask to create a partial vacuum therein and then simultaneously closing the receptacle, turning on the air pressure and discharging the contents of said crucible.

STANMORE P. MARSHALL.

Certificate of Correction.

It is hereby certified that Letters Patent No. 1,452.24-6, granted April 17, 1923, I

upon the application of Stanmore P. Marshall, of Washington, District of (Jolumhia, for an improvement in The Art of and Apparatus for Casting Metals, were erroneously issued to H. B. Byrd Mannfacturm Companx, Incorporated, of \Vashington. Distrivt of Columbia, a Corporation 0 Virginia, as assignee of the entire interest in said invention, whereas said Letters Patent should have issued to the inventor, said Marshall, and H. B. Byrd Manufacturing Company, hwurpomfml, said corporation hein assignee of one-half interest only in said inrentimnas shown by the records 0? assignments in this ofiice; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 29th day of May, A'. D., 1923. I

[sun] KARL F ENNING;

Acting Omission of Patents.

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