USRE3449E - Improvement in apparatus for casting refractory metals - Google Patents

Description

PATENT OFFICE.

MICHAEL SMITH, OF SOKMERVILLE, ASSIG NOR TO lVUGIALLICI COA/[PRESSION CASTING COMPANY, OF BOSTON, MASSACHUSETTS.v

IMPROVEMENT IN APPARATUS FOR CASTING REFRACTORY METALS.

Speeiliealion forming pai-t of Letti-rs lalent No. 70,038, dated October 22, 1867; Reissue No. 3,449, dated May 18, 186').

Improvement in Casting Refractory Metals;

and I do hereby declare the following to be a clear and exact description thereof, reference -being' had to the accompanying drawings, 'which are made part of this specification.

My invention has for its objects the casting of brass, bronze, and others of the refractory metals and metal compositions with a high -.degrec of density and freedom from blowholes; and the greatest of its novelties consists in producing perfect, sharp, and well-defined. fae-similes of the pattern, and relates to that class of devices which for the` above objects employ mechanical pressure on the duid metal during the act of introducing the metal into the molds, and keeping the pressure' on the metal until it is solidified. I-am thus enabledto use molds of great density and of suoli ma terial as could not be used vin the ordinary way of casting and pouring the metal.

In the drawings, Figure 1 is a vertical section of an apparatus embodying my iiivention. Fig. 2 is a partially-seetionalized top view thereof. Fig. 3 is a partially-sectional- J'zed view of my nest or series of molds. Figs. 4 and 5 show modifications and different styles or types adapted to certain kinds of casting. Figs. (i and 7 represent a style of apparatus in which the molds are held in a vertical position, admitting the metal at the lower end of the mold. This stylehas proved in practical use to be best adapted to all kinds of smaller' castings and where itis desirable to cast agreat number at one ope-ration.

Similar letters of reference indicate eorrespending parts of the several figures.

The invention maylbe applied to' one ora' number of molds; but I have selected for illustration a series or nest of moids, AA AL A, Figs.` 1, 3, 6, and 7, formed of baked clay, made in the manner described in the Letters Patent granted J. J. C. Smith, No. 85,340, the 29th of December, 1868, and more particularly, fully, and correctly set filirth in his specification filed with his application for reissue of said patent. I A goed material for the A said molds is potters clay, which, being dried, finely ground, and then moisienei'l sufcicntly for molding, is mixed with sand and placed in a strong` daslc'or casing, together with suitable patterns of inctal'or other niater-ial and of any required shape, the liu-.e ol' which patterns may be prepared'by oiling` and afterward coated .with a clayslush. A, heavy pressure is thcnapplied gradually lo the patterns and clay within the casing, thi, pressure reaching three hundred or four hun'- dred pounds to'the square inch. \\'Iu`n the pressure has been continued for a sufficient time forthe pattern to set and for the surplus water in 'the slush coat-ing to be absorbed by the more dry parts ofthe clay the molds may be taken out and dried and baked ready for use These molds are adapted robe Stacked or piled one above the other and supported on an. iron slab, as rep'resenled in Figs. ll. and 3, or they may be put together 'one al'ter the other, as shown .inl Figs. (j and 7. Ori iices or gates C c, provided in said molds, all ford intheir collective capacity gates or spi-ues for the admission of the molten metal l'iom the injecting apparatus, to be presently described. Said molds and slab B are confined in astrong iron box, D', whose sides may be provided with small suitable ehinks or ori- -lices for the escape of air and gas during the act of casting. An aperture, lil, in the top of the boX'I), (seen in Fig. 1,) oi" at the lower end of boitr D, asin Fig. 7, in continuation of main gate C,` serves to admit the metal there-A to. Set-screws F, tapped through the bot-tom of said box D, Fig. 1,01' through the back side ofthe box 1),"Fig. 7, and bearing against the under side ofthe iron slab I3 or the back side of the iron slab'lS', as shown in Fig. 7, serve to press and hold the molds ii'rmly together and against the iop of box D, Fig. l',

in actual practice has proved that itis not really necessary 'to inclose. thebox `D in an air-tight chest G. A perfect, sharp, and well defined casting may be .produced if the airtight chest G is dispensed with; but in cases whereit is ot' great importance to have a solid casting free from blow-holes throughoutthe whole body of the casting, it is a great assistance to inelose the box D in the airtight chest G, and by means of the pipe H and a some what large air-suction pump the air is exhausted from the molds and space between the boxes'D and G shortly before or during the act of casting or injecting the metal. Care must bejahen that the joints of the chest G are well closed, and the junction between the injecting-vessel and chest Gare lutednp with wet clay to make all airtight. The perforation E in box D receives a tube or thimble, I, whose central orifice forms the channel of communication for the ilnid'metal between the injecting-vessel and the molds, and is closed with a movable plug or tamp, N. The injecting cylinder or yessel J may be easily slipped orf of the thimble I when the meta-l has become set after the casting operation. The purpose of said thimble is to obviate the diiliculty of detaching the cylinder from a superincumbent head ofmetal, which difficulty would exist in ease of the formation cfa shoulder uponisaid cylinder at the cud or point of discharge into the molds. lf said thinible is made of iron or other metal, it ought to be the cylinder after casting. Continued prae-l tice vhas proved that the best manner of making said thimble is to form or make it by pressing moist clay into a suitable mold, after forming to burn it hard in the manner brick or pottery is burned7 and to use al new ihimble at every` operation of casting` Such mineral .thimbles are strong enough, cheaply made, and easily detached by breaki ngthem in pieces after cast-ing.

Fitting snugly around and extending upward from the thiinblc I isa tube or cylinder, J, as it is shown in Fig. l. In Figs. 7 and -6 the cylinder rests on a platform, and extends horizontally from the ihimblc, To this cylinder is loosely iitted a plunger or piston, K, which is linked at L to a lever, M, by means of which the operator is enabled to lift the plun er clear out 'of the cylinder, so that it may e filled with molten metal, or press the piston downward intothe cylinder and exercise the required pressure on thel metal. The cylinder is made of a capacity fully exceeding-that of the molds, so as io leave a goed head of metal within the cylinder after the molds have been filled by the pressure exercised on the fluid metal. -ltithe style of machine is used as shown in Figs. 6 and ,7, where the cylinder is in a horizont-al position, the same is provided with a funnel for the admission of the metal on the end where the plunger rests.

my apparatus,1 will describe the manner of its use and operation, asnea-r as it may be done Without too great prolixity.

As in all other mechanical operations, continued' practice isa first-class teacher. The rst thing after the apparatus is obtained is to have suitable molds of such nature as to be readily made and of .a material which will take aime and sharp impression of the' pattern, and at the' same time of suieient strength and density to resist the pressure of the metal when injected. The most suitable material for molds forbrass, bronze, and compositions' where only a limited number of castings are wanted of one pattern is fine potters clay of such nat-nre as to resist a somewhat 'high degrec of heat without glazing. A description of the manner inxwhieh such molds aremade is found in the patent of John Jos. Chas. Smith, No. 85,340, dated December 29, 1868, andamorc full and accurate description thereof, as ascertained by actual practice, is contained in a recent application for a reissue of said patent.V For some kinds of casting, es-

pecially in iron and steel, molds of` iron and steel may be used with good success; but it is very essential that such metal molds be s0 arranged that the fluid iron or steel is injected as directly as possible, and without first passing through too long a spaceof gates or sprues before the mold is reached by the metal. The reason why. this should be done is this: -If fluid refractory metals come in direct contact with other metal surfaces, they chill and set more suddenly than those who are not acquainted with this property have any idea. of, even if those surfaces shall have been previously made red-hot. The consequence of this actionl isthat the castingwill show streaks and anuneven surface; but if the moldsare filled directly from the injecting cylinder (avoiding the passing of the fluid metal over a long distance in the gates) and the strong pressure' isbrought to bear on the metal in the 'filled mold linstantaneously before it has had time to form a hard skin or surface, a very good and sharp impression of the mold is thus obtained. Iron and steel molds used in this manner ought to be oxidizcdor rusted on the surface toa certain extent. These rusted or oxidized surfaces are somewhat non-conductive, and serve also to prevent the adhering of the injected metal tothe molds. When the suitable molds are made, they are put in the box D. The iron slab or follower B is made to press and hold the molds firmly together by means of the setscrcws F, tapped through the bottom or rear of the box D, just as the style of thc machine may be, so as to resist the pressure of the injected metal-without parting at the joints. Be it also remarked that the box D must be strong in accordance to its size. When thisis donc, the cylinder or injecting-vessel J is provided on theinsidc with anon-conducting lining, for the purposes hereinafter described.

The manner in whichthe lining of the cylinder is performed is this: Take som-e fine tireprool' clay or kaolin free from sand or grit, and thoroughly blend the same with about one-half of good plumbago; then mix with water,- so as to form a paste. The cylinder is heated to about 200 Fahrenheit, and with a brush the aforesaid paste is applied on the inside of the cylinder to a uniform thickness of about one-eighth of an inch, the heatof the iron cylinder drying the paste -as applied. This done, the cylinder is heated more to evaporate all moisture from the lining, and is ready for further operation. If the style of machine is used, as showirin Fig. 7, the piston l( is fastened during the operation of coating, and coated also on the surface coming in contact with the fluid metal. This lining of Une cylinder serves several useful purposes. It serves to pack the space or joint between the cylinder and piston and prevents the intrusion of the metal between the two, 'which intrusion would certainly and rapidly clog these parts and stop the operation, as the heat of the fluid metal will at once expand the cylinder more than the piston and admit the metal between the joint. It slipuld be explained that the plunger or piston K fits the cylinder, and is therefore larger than the internal diameter of the lining, and that at every operation the cylinder must be relined or recoated, as such lining` is detached from the cylinder .l and pushed in adva'nce ofthe piston K at every forward movement of the latter, the effect of which is to close the joint and prevent the intrusion of the metal between the piston and side of the cylinder, as above stated. No matter how high the pressure is on the fluid metal not a drop can leak out. The'detached lining will pack the joint so lmuch the more closely. The importance of this detachable lining can scarcely be overestimated, since it forms by its non-conducting property the onlyl practicable means for preventing the chilling or rapid setting andalso the adhering of the molten metal, which would arrest the forward motion of the piston and preclude any successful operation. Those acquainted with the nature of refractory metals know how rapidly they chill and set if they come in contact with other metal surfaces, even if said surface is made red-hot, and it requires several minutes time to lill the cylinder and perform the operation of injecting. This lining serves also to prevent the direct contact of the iluid metal with the surface of the cylinder, which would soon spoil the cylinder by the excessive heat of a mass of molten metal, even it' the other aforesaid advantages were notof such great importance. Then the lining and drying ofthe cylinder are performed, I take the thimble I, close its oriiice with a plug or tamp, N, (made also of burned clay,) in such a manner that the plug will yield or move at a pressuie of about sinr or eight pounds to the square inch. \Vhcn this is done, the thimble is 'used to close the open end of the cylinder, resting l on a shoulder or offset on the inside near the end of' cylinder.v The other end of the thimble is set in the perforation H on top of box D, so that the main orifice or gate in the molds forms the continuation of the orifice plugged up in the thimble. This done, the cylin-deris fastened to the box D by means of screws or otherwise, and is readyto receive the molten metal. The metal is poured in, if the machine is of the style represented in Figs. 1, 2, and 3, at theppen end or top, and if of the type as seen in Figs. 6 and 7, at the funnel connected with the cylinder. As soon as the cylinder is lled, pressure is at once applied on the fluid metal, and is continued until the molds are filled and the metal is well set. to sixty'pou-nds to the square inch, and sometimes inore, is to be applied to the metal; but experience and a little practice will soon show how much pressure is required for certain l kinds of casting.

The office of the plug 0 1 tamp N in the thimblc I is to prevent the gradlalpassage of the metal from the cylinder-into the molds. l If pressure .is applied on the 1netal,the p lug'willv yield and pass along in the main gate, giving the metal free passageinto the molds. When the casting isperformed andthe metal is set, the cylinder is readily detached Aby breaking the metal in the gate at the junction of the thimble and the molds. This ought .to be done right after the casting is done and before the gate has acquired -its full strength by cooling olf. The remaining head of metal in' the cylinder is easily removed a'fter cooling. 4I have selected to illustrate my inventionthe preferred style or type thereof; but I do not propose to restrict myself th creto so longasthe same results are obtained lby meanssubstantially equivalent. For an example, the pressure of steam or condensed air may be applied to act ou the piston, or even the direct pressure ofthe steam or condensed air may be used to exercise direct pressure on the fluid metal, if the cylinder is in a vertical position and the end of the cylinder closed, although practical experience vhas proved to me that the mechanical pressure is the'most reliable and least complicated.

I may also in some instances employ such modifications as are shown in Figs. 4 and 5, and inv which corresponding parts are indicated by'the same letters of reference.v Said styles may be more adapted for heavy castings. In such machines the plug may be dispensed with but this is not advisable. This style is a more simplified form, involving few parts in its construction, more calculated for a single piece of casting at one operation.

, In the apparatus shown in Fig. 6 and 7 in horizontal and vertical sections, and where corresponding parts are also indicated by the same letters of reference as in Figs. 1, 2, and 3, the differences are the introduction of a sliding rod, N, for temporarily .closing comj munication between the cylinder J and molds A, and the abandonment of the air-tight chest A pressure from thirty (Sr.` This sliding rod may be used as a substitute for the plug N, its functionbeing the samethat is to say, to retard the gradual passage of the metal into the molds until pressure is applied. When pressure is applied to the metal in thecylindeigt-he rod N will be forced back by the metal, so as to open communication between the cylinder and the molds. The extent of motion ofthe rod N may be regulated by means of an adjustable collar, l), which arrests therod by coming in contact with au abutment, T; but experience obtained by continued practice has proved to me that the'clay plug or camp is the most reliable and least complicated of the two.

In Vorder. to lhave the utility of my appara-' i tus fully appreciated, Ishall give a few words of explanation. Practical founders know` that if a mold could be used ont of a material more dense than sand-as sand loama lnore perfeet and sharp mold could be made, and there would not-be so great liability of the sharp lines of the mold beingv washed by the inflowing metal; but they are also aware that if a mold is made too dense by ramming and stamping or by the use of dense material the gases generated and the air in the molds will not be ejected by the mere pressureobtained by the weight ofthe metal itsel t'. The consequence is that'the metal is blown out ofthe mold and the casting is useless; but by the application of my casting'apparatus I am enabled to use molds of great density and of material taking a very tine and sharp impression of t-he patterns by great pressure applied to the material formed into molds. By providing sepa-- rate injecting-vessels for the reception of the molten metal previous to its introduction into the mold, and having e a high pressure to bear on the fluid metalinthe very act ot' its rapidly filling of the mold, the elimination of the gases generated and the air in the mold is compelled to take place through very tine pores and small orifices made at the joints ot'- the molds, and as the pressure is kept on the metal until it is well set or solid, such a thing as blowing will never orfvery seldoln take place; but the metal is compelled to lill every cavity of the mold, producing a perfect, sharply defined, and smooth surface.

In cases 'where it is of great importance to because the metal enters the mol d' at the bottom and rises up. i

Novelty is not claimed in the special means employed for applying power to the piston or follower. It is immaterial whether thisisdone by a lever or screw or by the pressure of 'air or steam. These various means andmodes of operation are referred to not as involving dis tinct invention, but as mechanical' equivalents of each other, in order that those parts of the invention which are new may be used to the best advantage under varying circumstances.

Having thus described my invention, what I e-laim as new, and desire iosecure by Letters Patent, is

1. The provision of and. combination with one or a series of molds for casting meta-1, of a separate injecting vessel or cylinder, Jtsaid cylinder being provided with apistonorplunger, K, and au internal non-conducting lining made of clay and plumbago or other non-couducting material equivalent thereto, said lining to be detached and used in themanner and for the purpose described.

2. The provision on said cylinder-J of a temporarily-closable but self-opening communication with the molds, asv and for the purpose set forth.

3. The combination ot' the mold-box D, detachable thimble I, injeetingvessel J, and plunger K, all constructed,arranged, and operating in the manner and for the purposes explained.

4. The arrangement of aseries of moldshaving consecutive orifices or gates, a slab or follower, B, and set-screw F, and inclosed in a box,=D, 'as and for the purpose set forth.

5. The subjects of clause last recited when inclosed in au air-tight chest, G, having connections with an air-exhaust, for the purpose specified.

MICHAEL SMITH, ME'lAliLlC COMPRESSION CASTING C0. By J. J. CH. SMITH, President. Witnesses:

JOHN STEPP,

havev'ery solid casting the application of the air-tight chest G, provided with au air-ex-l F. H. KrNGsBURY.

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