US2656593A - Cooling castings over sizing forms - Google Patents

Description

Oct. 27, 1953 J. C.'HE|NTZ 2,656,593

coounc CASTINGS OVER srzmc FORMS Filed Sept. 21, 1951 JNVBVTOR.

JAMES C. HE/NTZ ATTORNEY Patented Oct. 27, 1953 UNITED STATES PATENT OFFICE 2,656,593 COOLING CASTINGS OVER SIZING FORMS James C. Heintz, Lakewood, Ohio; The Cleveland Trust Company, executor of the said James C.

Heintz, deceased Application September 21, 1951, Serial No. 247,729

cast tire matrix, especially an aluminum matrix.

It relates more generally to the production of castings from magnesium, brass, and other metals and alloys.

The mold in which the metal is cast is made partly of metal and the balance may be plaster of Paris.

The metal portion of the mold, which will be referred to herein as the chill element (or the chill ring of a matrix mold) will be made of a metal which has a higher melting point than the metal which is being cast, 50 that it will not be affected by it. Generally cast iron will be most suitable. The chill element will ordinarily be relatively thin so that it can expand and contract readily and so that it will not store up heat which will prevent its frequent reuse. Thus, a chill element or chill ring which can be reused at intervals of a half hour or an hour will be found more efficient than elements which must stand twenty-four hours or longer after using in order to cool down to a temperature at which they may be reused.

In the manufacture of tire matrices, I prefer to form the intricate tread and sidewall design in a plaster of Paris form with a flexible pad which can be made of rubber or a vinyl composition, or any flexible setting plastic. The material known as Perma-Flex cold molding compound, sold by the Perma-Flex Mold Company of Columbus, Ohio, has proved very satisfactory. The flexible forming pad is formed from any suitable pattern such as a pattern carved from hard plaster, and the plastic is brought into contact with this pattern surface and set in any usual manner, as by being poured into a cavity formed next to the surface just prior to setting. The use of flexible forming pads is not new in the art and the pad may be made in any known or novel manner.

The chill ring for molding a tire matrix forms the outer surfaces of the matrix which contact the shell of the tire mold. Its cooling action on the cast metal is advantageously dampened or retarded by coating its inner surface with a heatinsulating composition, e. g., a granular earthen material such as china clay or the like. All

3 Claims. (Cl. 29-148) metal surfaces exposed to contact with th molten metal are advantageously insulated in this manner. By retarding the solidification of the molten metal in this manner, the metalwhich is still molten feeds in against the plaster surface to make up for shrinkage. The molten metal is first fed on the plaster of Paris surface. .As the molding cavity fills with the molten metal the area of contact with the "dampened" or insulated chill increases. There isllittle dis turbance of the metal-in contact with the plaster of Paris because the direction of flow is toward the surface of the chill. plaster of Paris surface'and collect on the surface adjacent the chill before solidification.

This application is a contmuation-in-part of nection with the drawing which is an elevation,

partly broken away, of a finished tire matrix, inverted, and with the sizing ring in place.

The drawing illustrates the use of a sizing ring with a tire matrix. If plaster of Paris forms are used in the assembly of the mold, it is necessary that they be correctly positioned in orderto have an annular mold cavity. By correctly locating the forms and removing any excess plaster, as may be required, the surface of the tread of the matrix may be made circular with a variation of less than a ten thousandth of an inch." .This is accomplished without any machining or other finishingof the matrix. The method of doing this and apparatus therefor are claimed in application Serial No. 379,949, filed September 14, 1953. In assembling the mold six segmental plaster of Paris forms may be used to .form the inner wall of the annular mold cavity. The chill ring is lowered over these and forms the outer wall and top of the cavity. Suitable means is provided for supplying the molten aluminum or other metal to the cavity.

Various aluminum alloys are available for casting such objects as tire matrices. An alloy of 95 per cent aluminum and 5 per cent silicon has been used satisfactorily, but others may be used as satisfactorily.

Bubbles rise from the The aluminum is melted and poured at about 1250 F. (Its melting point is about 1100 F.) This is a higher temperature than would be permissible if the mold were formed entirely of plaster of Paris. Using molds composed entirely 5 of plaster of Paris the metal cools slowly, and the gas generated forms a porous product. Using a chill em nt p r n the metal 1 9S $i at a higher temperature and cools rapidly, and sets .in a non-porous condition.

The metal may be poured simultaneously into opposite sides of the mold cavity from twp difle r: ent ladles. Eventually, as thecavity is filled, the whole under surface of the ring gjs QQQ: tacted by the molten metalland heated by The metal rapidly dissipates the heat and chills the metal.

The chill ring is relatively expensive and it is desirable to reuse it several times each ,day. Therefore, after the aluminum has set, the chill are s li d i em h east ma riz axed ethe tandin ae c en time to .99. H ,reus

=Zrh rlaster Pa farm re hen Qmt matrix and wi -thau en an ai remov isu hasitha wh c jm adher -the sin q nthe ,e oev s .i -th t ed- 52 15 is r 9 be p e th ntra t n whieh'aqee a? es 90. 2 asb enem lete I9 ont eetiona i ip-t e. fthemat iix. izing ,5 M55 or i-pthiffi mlll r P. .1 e ttsd :i he e ge em the matri a 'il stre in t e drawin {lhe i a i' x n ra t a st i and a th ilt ma re ee 9 tli has een :maehincd .tw .i l e s n l .ihame a .ne i t n ietee na and li l maue -tliant e en ii be r gs ri r re mplq ed am th eas ieet are al.-

wit e hl r ed .pastpbie t .w iqh bl re rdles f th g yne.qhmql in ,yal e nip mederfect in every detail and need little or no trimming or other machining. Any machining that is required may be done before or after the matrices are heated to prevent growth.

Although the invention has been described more particularly in connection with the production of tire matrices, especially from alumialloys, it is t be understood that it relates o the produ tion pf othe lbl ifq t f fi i eral the chill ring, or chill element employed will ime ,made of cast iron or other ferrous metal, and the gg e ta ls are to be cast will be metals with a melting point not over 1000 C.

1, mgthgd forming a metal casting with an opening in ,it, which comprises casting the metal in a mold, removing the cast metal from the mold while still hot and shrinkable, putting 3, ,cool sizing form smaller than the opening in the opening inthe casting, said sizing form ,eggactly .fitting the opening when the castove still ijet riiiibef i it ih as dirilnsidns, Se inel t. mf

ing" mm in 'the casting at'abdut its'lafg am r he a m-, e smallcool and shrink "areufiawms firm/whereby casting-is prevented iro mbecoming missh tneiiediia wi ii Lshrinking ti ring I then separating,

AAME EQ References Cited in the file gi thispatent

Images