US2253903A - Mold - Google Patents

Description

Aug.' 26', 1941; F. HAGEMEYER 2,253,905

MOLD

Filed Aug. 2, 1958 2 sheets-*sheet 1 I "N 7@ gi?? I l 77 75 '"I V I Y :l 76" 79 I 'u M 73 @in I I NVE NTo R HEAWFFMEMM ATTo RN EY Aug 26,1941- I H. F. HAGMEYER 2,253,903

M LD I Filed Aug- 2, 19:58

mm I linlr ATTORNEY Patented Aug. 26, 1941 A e UNITED slii'ras a Mou) Henry F. Hagemeyer, Chicago, Iii., assignor to Castings Illinois Patent Corporation, a corporation of A application August z, 193s., serial No. 222,599A

My invention relates to methods and apparatus fon-controlling the temperature of metal which has been poured into a mold in a casting operation and more particularly to such methods and apparatus for expediting the cooling of the poured metal in a controlled manner, whereby the characteristics of the metal in the ,casting may be regulated.

In conventional casting practice cooling of the poured metal is usually uncontrolled, so that, 'as the heat is dissipated, the temperature in diiferent parts of the casting will vary according to the body of such parts. ,By body I mean the relative sizes of the various componentportions of the casting. 'Ihus a part of large body or size will cool more slowly than a 'smaller one.. for all parts oi' the casting are subjected to apy proximately the same temperature differential andv are substantially equally insulated from. the l atmosphere. Such difference in cooling rate occurs. of course, because the larger sectionshave less heat radiating surface in proportion to their volume and heat content 4than have the smaller sections. As the metal in the casting solidifles and cools shrinkage takes place. so that additional metal tends to now toward the solidifying parts from portions of the casting which are still fluid, to compensate for the deficiency caused by such shrinkage. If there are no adjacent fluid sections, as where a liquid pocketor central section is solidifying, sunken. portions on the surface of the casting or internal shrinkage faults may result, which are undesirable.

By the employment of my controlled cooling method the order of solidification of the various portions of the casting may be predetermined to avoid leaving fluid pockets or centers wholly surrounded by set metal, the feeders supplying-the deficiency caused by the `metal shrinkage. Within the term feeder I include the usual gate through which the metal enters the casting cavity, as well as risers, shrink pins, or shrink bobs which may be provided on portions of the casting remote from the gate. Thus there will be no internal shrinkage -in the casting, tendirg to make internal fissures, or sunken portions in the metal surface, for the vshrinkage^deilciency of all solidifying portions will be replaced successively from the next portions to solidify, and the last portions of the castingto solidify `will be filled from reservoirs of molten metal formed byl such feeders outside of the casting proper. 'I'he essence 6f my process lies in controlling the cooling so that the portions of the casting most remote fromthe feeder will solidify rst, and

thereafter portionsprogressively. nearer to the f connection of` a feeder with the casting will remote from the feeder connection as necessary to obtain progressive solidiiication oi the various parts in the sequence above stated.

vAnother type of mechanism m embody a hollow cooling member, the cham r of which contains a cooling medium either at rest or as a liquid owing therethrough. In the latter case the rate of flow through the cooling member may be thermostatically controlled, the flow volume varying `accindfng to the temperature of the cooling fluid.d Also 'the course of the fluid over the castingmay be arranged so that the flow will be toward the feeder connection, that is, from the Darts to be cooled most quickly toward the parts to be cooled at a less rapid rate, the temperature differential between the fluid and the `metal thereby progressively decreasing in the direction of flow. A further variation of cooling rate may be obtained by regulating the ilow quantity o f cooling fluid so that the volume flowing over the portions'of the casting to be cooled most rapidly is greater than \the volume flowing vover other'portion'sof the casting. Such a volume control may be combined with a ilow course toward the feeder connection, if desired, portions of the cooling fluid being tapped oif at inter- 40'vals along the `course to produce the (proper quantity variation.

The principal object of' my invention, therefore, is to obtain a controlled coolingl of a casting-within a mold, so that the portions most remote from the connection of a feeder with the casting will be solidified and cooled first and the `size of the variing proper will in each case be entirely solidiiied,

and cooled as much as possible, .prior to the solidication of a feeder or feeders connected therewith, so that deficiencies of metal in the casting caused by the shrinkage which takes place during such solidification and cooling may be replaced from the still fluid feeders instead of from a surface of the casting, causing a depression therein, or from the interior of the casting, creating internal flaws and fissures.

.An additional object of my. novel method is not only to control theL cooling of acastingso that the parts thereof will -be solidified in a desired sequenceLbut also to control the r-ate at which the various parts are cooledin order to obtain desired grain structure and physical characteristics in the cast metal.

It is also desired to accomplish the aforementioned objects' by mechanism of simple though effective design, which may be readily adapted to y carry out my cooling `method on castings of al wide variety of shapes and sizes.

Specifically it is an object to provide appropriate `cooling fins, specially proportioned molds, or supplementary artificial coolingA mechanism,

A or a combination of these features, most suited lto -the proper cooling of a particular casting in the manner desired. i y

More specific objects, inherent in the examples of mechanism shown in the drawings, will be understood from the following description thereof. The drawings illustrate the application of my method to, and the use of apparatus in carry-` v bledl mold and associated mechanism, illustrated cooling apparatus combining a plurality of exwill not have internal shrink faults or surface depressions even when cast without special cooling control, because the metal will naturally solidify from the end farther from the gate, which is poured first. The same natural proper directional sol-ldification will occur unassisted where the casting tapers from the size of the gate outward. the solidification progressing from the end v most remote from the gate toward the connection of the gate with the cavity, and the gate will be the last to become solid, so that deficiencies caused by the metal shrinkage in the casting may l be replaced from the gate. Few castingsare of these types, however, and where the gate or other feeder Ais of smaller cross section than the portion of the casting to which it is joined, as is usually the case, the metal in the feeder tends to solidify before the metal in the casting, thus cutting o nection will be caused to solidify first@ Thereafter, parts progressively nearer the feeder connections will in turn solidify and this order of solidiflcation will be preserved regardless of the castings shape, or variation in body, that is., either thickness or width or both, of the severall portions of the casting.

In cooling anaircooied airplane engine cylin-vl der head casting,lsuch as shown in Figs. 1 and 2, iinsuid cooling mechanism, and a shell mold may all be employed. In this instance the fins,

instead of beingadded especially to carry out pedients employed separately in the previous iigures.

Fig. 2 is a transverse sectional view taken along line I-i of Fig. i.

In the casting of metal the general practice heretofore has been to provide a sprue, a runner, and risers if necessary, positioned and dimensioned only to obtain complete filling of the mold cavity. There' has been no effort to proportion the runner or riser to have a definite relationship to -the size or shape of the casting to be produced for the purpose of maintaining such feeder fluid until the casting is completely solidified. Despite the insulating quality of the -moldmaterial therefore, the feeders and their I ing therefrom toward the centerof 'the casting,

If these defects are to be avoided, the metal in -the feeder or feeders and their connections with the casting must remain liquid until all the metal of the casting proper has solidified, so

that the feeders may actas reservoirs to make up for the 4shrinkage deficiency in the casting. A bar' casting of thesame size as ythe gate ent, unless a very thick mold wall is employed to minimize the heat radiating eii'ect of the hns.

`S, since the cross section of the casting increases fairly uniformly to the connection of the sprues therewith. The only diiiiculty might be in the, tendency of the sprues S to solidify prior to complete solidii'ication of the heavy casting, in which case internal shrinkage or a sunken the rocker boxes might result.

In this particular type of casting, however, the fins are required as a vital, integral part of the finished casting. l The provision of fins on the exterior of this casting without additional artificial cooling mechanism not only tends to set up strains caused by the unequal cooling resurface on suiting from the greater heat radiation surface afforded by the fins, but also tends to cool more ausm -I 1 ance the cooling action of the exterior una if trolled cooling sequence. While in the application of my cooling method to some castings the heat may be removed in a controlled manner almost entirely from one side only thereof because of the thinness of the metal, this procedure will not operate satisfactorily upon a thick walled casting such as the cylinder head shownv in Fig. 1. The reentrant portion of the skirt Il would not solidify until after solidiilcation of the finned rocker boxes 'H had cut olf. passage therethrough for fluid metal from the sprue B to the skirt 1l, to compensate for metal shrinkagel therein. A sunken surface within the skirt and dome would result. It is therefore necessary t provide articial cooling mechanism both for'the interior and for the exterior surfaces of the skirt 10, so that Vit will be solidified completely before the axial parts of the rocker boxes 'Il solidify.

In cooling the cylinder head according to my method I prefer to lemploy metal formera Il which are'insertediwithin the reentrant portion of the skirt 1 and may be spaced therefrom as shown in Fig. 1. This intervening space is filled with an annulus of mold material gradually in- .creasing in thickness from the edge of the skirt arranged in the vertical direction. their formation would be diillcult.- I prefer, therefore. to use a core incorporating metal cooling formera as described. Since the cast metal contracts in cooling, the cavity likewise will become smaller. and to prevent fracturing the vcasting by resisting such contrastive stress. the formera Il encircling the cavity are yieldably Four such'formers may conveniently be employed, as shown in Fig. 2. Between the adjacent edges and ends of these formers should be placed some crushable substance, such as mold material which toward the central portion of the dome. Because the plurality o'f fins provides so much-heat radiating surface it may be necessary to use additional means for expediting the removal of heat from the inner surface. such as cooling fluid flowing through passages llfin the formera. The' direction of iiow should be as indicated by,the arrows in Fig. lrthe fluidy flowing i'lrst past the skirt llil and being warmed asitilows toward the sprue or feeder connection. the warmest uid being discharged from the formera near their upper ends through pipes 14, which may all unite in a may be of th'e gypsum base type. capable of yielding under the stress created by the Icontracting cylinder head skirt. No appreciable resistance to the contraction of the cast metal will therefore b offered, so that no strains will be developed in the casting as would be the case if the core were of rigid construction. The members 12. supported on plate I'L may slide substantially unrestrainedly away from the mold supporting plate under thepressure of the shrinking cast metal. Pivoted levers 1l, suspended from a mold form base plate 1l, may ,be provided, which engage the bases of the formera 12, for use in drawing them from the casting cavity after the metal has solidified. Such withdrawalmay be made at any temperature desired after solidification to allow further cooling to take' place more slowly without using the artificial cooling means of the core,

or the cooling may bedelayed bypassing hot v fluid through the passages 1l. Within the circle of for'mers a thin wall of mold material may be employed to support their backs. as shown, if

necessary to enable the core-to withstand the force of the inrushing'metal without deformat I tion.

header I5 discharging into an outlet conduit Il 40 where gypsum base molds of sumcient porosity having therein a thermostatic valve The operation of this complete mechanism will -eiiect proper directional cooling, because the combined action of the skirt fins on the outside with the fluid and metal cooling means on the inside will cause rapidv solidiflcation ofthe skirt from its edge toward its base. 'I'he uns on and between the rocker boxes il will hasten their solidlnca-A tion, but this will not be complete prior to the l entire soudincauon or the skirt and dome poralthough completely surrounded by solidified portions, such iluid pockets causing shrinkage faults upon solidication, the solidincation .of the4 entirecasting will be progressive from the edge of the skirt 10 upward to the bases of the rocker boxes and thence to their upper ends. All the solidi-.- ncation in the casting will take place while the sprues S lare still inthe fluid state lo that they will serve as reservoirs from which metal may be supplied throughout the entire solidiiicationfof the casting, to compensate for the deficiency of metal in the casting cavity caused by the shrink. 'age of the solidiiying metal.

As has been stated, the iins which expedite cooling vof the exterior wall of the casting are formed as part of the finished While temporary uns might be provided in the reentrant portion of-the cylinder head skirt to bal- This process may be used in either sand or plaster molding operations. but it is most useful to allow the pouring gases to seep through the mold body are used. Every riser added for a shrinkage reservoir requires additional pattern expense,.an excessive amount of casting metal,

and necessitates additional machining in the nnishing operation. With my process applied to a porous gysum molding operation, ordinarily the only exterior reservoir of molten metal will be the'gate, runner and sprue arrangement which is a necessary provision in every case. If for an intricate casting an additional feeder is foundto be necessary when my directional cooling process is employed, several more feeders would be necessary if my process were not used, one for each part or the casting where animated molten pocket would occur in natural cooling. Hence considerable expense is eliminated, as well as a better product obtained. by the use of my procf ess, and castings can be made where it is employed which could `not be produced without flaws if such process were not used.

As my invention, I claim:

In a moldhaving therein a cavity for casting an internal combustion engine cylinder head; the

combination of a centrally pertured base plate supporting the mold, a plurality of rigid metal members projecting upward through the base plate aperture in laterally spaced relation. mold material covering/said members to form areentrant wall for the casting cavityl and further mold material interposed between adjacent members, means supporting said members from said base plate for individual lateral movement with respect thereto toward the center of its aper- 4 :,asspcs ture under pressure of the cast metal shrinking sages therethrough, an individual cooling liquid during cooling, a lever for each of said mem'bers supply conduit connected to each ot said mem pivoted upon said base plate and engaging the bers, a common discharge manifold for said lower end o! its member for withdrawing it at members and thermostatic means controlling the will from the mold through the aperture in said 5 discharge of cooling iiuid from said manifold. base plate, said rigid metal members having pas- A HENRY F. HAGEMEYER.

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