US2351720A - Mold for centrifugal casting - Google Patents

Description

June 20, 1944. s, s oo ETAL 2,351,720

MOLD FOR CENTR IFUGAL CASTING Filed Dec. 24, 1941 2 Sheets-Sheet l 5/1540. Srbom;

Rap/ L. A505,

JNVENTOR.

BYJAWWWLN Arm/ways.

June 20, 1944. s. M. STOODY ETAL 2,351,720

MOLD FOR CENTRIFUGAL CASTING Filed Dec. 24, 1941 2 Sheets-Sheet 2 l E 39 2a 37 1 30 Milly/157000);

RALPHLAaos,

IN VEN TOR.

Arm/aways.

Patented June20, 1944 2,351,720 MOLD FOR onNrmF GAL CASTING Shelley M.- Stoody and Ralph L. Abos, Whittier,

CaliL, assignors to Stoody Company, Whittier,

Calii., a corporation of California Application December 24, 1941, Serial No. 424,371

1 Claim.

This invention relates-to a means and method of centrifugally casting.

An object of the invention is to provide a novel mold construction for centrifugally casting metals and like materials which will ensure that the casting produced will be of a fine-grained, homogeneous metal characterized by the absence of dirt or loose particles of mold material and by the absence of oxides or nitrides and by the absence of blow holes;

In the normal method of centrifugally casting metals it has been customary to construct the mold having a plurality of radial passages leading from a central gate to mold cavities. In pouring the molten metal into. the central gate it is subjected to centrifugal action and is drawn outwardly through the' passages to the mold cavities. The initial metal that is poured into the mold is chilled to-some extent on encountering the relatively cold walls or surfaces of the gate and passages. The initial metal is of course subjected to an outward acceleration as it is subjected to the centrifugal action. Any dirt or loose particles of mold material in the passages are of course picke up and thrown outwardly by the accelerating initialmetal. The initial metal also tends to separate into globules or a spray and under normal circumstances as there is air in' the mold this initial metal becomes well oxidized; If the metal is of such a character as to chemically combine with or absorb nitrogen, nitrides may be formed which may be objectionable incertain instances.

In the conventional method of centrifugally casting the radially extending passages lead directly into the mold with the result that dirt, loose particles of mold material, and the oxides or nitrides are all carried into the mold cavity and form a substantial portion or the finished casting. Frequently the radial passages are of considerable volume and the air therein is forced into the mold cavity resulting in blow holes'in the casting unless the mold cavity is adequately vented. The present invention has for its primary ob- I lest the elimination or bypassing of the initial metal that is subjected to centrifugal action so that this metal does not. enter the moldv cavity carrying with it dirt or mold material, the

oxides or nitrides or included air. Only the trailing metal that iollows the initial metal and a which is not subjectedto such a severe chilling that a pressure casting is produced of linerained homogeneously pure metal. I With the foregoing and other objects in view,

which will be made manifest in the following detailed description and specifically pointed out in the appended claim, reference is had to the accompanying drawings for. an illustrative em- I bodiment of the invention, wherein:

' the parts [3 and i4 is indicated at l5. In the" upper part or cope l3 there is a central gate I6 Figure 1 is a top plan view of a mold that may be advantageously employed in performing the method embodying the present invention;

Fig. 2 is a vertical section taken substantially upon the-line 2-2 upon Fig. 1;

Fig. 3 is a vertical section taken substantially upon the line 3-3 upon Fig. 2;

Fig. 4 is a sectional view through an alternative form of mold embodying the present inven-- tion; and

Fig. 5 is a horizontal section taken substantially upon the line 55 upon Fig. 4.

Referring to the accompanying drawings wherein similar reference characters designate similar parts throughout, the mold utilized is usually rotated about a vertical axis and may be rotated, such as by an electric motor l0, having a vertical spindle. H on which is supported a I circular carrier I2. Within the carrier there is positioned the parts formingthe mold, the upper part or cope being indicated at l3 and the lower part or drag at I. These are preferably formed of carbon. The parting line or plane between which leads to the inner ends of a plurality of outwardly or radially extending passages l1 formed in the upper surface of the lower part or drag it. Each passage l'l leads to its respective mold cavity. The mold cavities may be provided by tamping mold material l8 in a cylindrical carbon flask is that is receivable in a vertical bore or aperture in the cope l3 over each radial passage 11. For purposes of illustration the mold cavity illustrated in Fig. 2 extends from approximately the point 20 to the point 2|. Be-

' low the point 2| there is a mold entrance 22 that leads from the passage II to the mold cavity. This entrance it will be noted is disposed some i distance inwardly from the outer end of the passage I1. Above the point 20 there may be one or action is caused to enter the mold cavity. This more vent passages. which may be rotating mold.

In casting metal in accordance with the present invention the molten metal 'is poured into the central gate -l6 through which it flows down- A suitable cover 24 stationary largely encloses the s be in the passages l1.

tionable oxides or nitrides are thus to the ends of the passages 11 beyond the enatrances 22 of the mold cavities. metal that follows the wardly to the inner ends of the radiating passages It is there subjected to centrifugal action. The initial metal that first enters the passages I1 is of course subjected to centrifugal action first and accelerates outwardly through the passages I! under the ing mold. This initial metal picks up and carries with it any dirt or loose material that may It frequently divides or separates into a spray and is thrown outwardly to the extreme end of the passages with considerable force. The initial metal is of course usually chilled to a considerable extent by the cold mold. All dirt or chilled metal and objeccarried out The trailing initial metal is not subjected to as great a chilling action by the mold due to the fact that the initial metal has already heated it and is not subject to oxidation or nitrlding to the same extent as the initial metal. It piles up behind the initial metal and under the continued centrifugal force develops a considerable pressure with the result that the trailing metal is forced upwardly through the entrance 22 into the mold cavity. Air that is present in the mold cavityis of course expelled through the vent 23. In this way only trailing metal which is free of dirt, free of oxides, and free of air is caused to enter the mold cavity resulting in a fine-grained, clean homogeneous casting. When the metal has cooled the parts of the mold are thentaken apart or broken open and the casting recovered. The casting is usually broken off at the entrance 22. The metal that remains in the passages ll may be either regarded as waste or "may be .melted a second time in which case the dirt and oxides present in the initial metal at the outer ends of the passages I! usually can be removed from the remelt as slag. In this way it is possible to secure what are in effect pressure castings with- -out having the casting include chilled dirty or posed relationship two cast iron blocks -oxided metal.

In the preferred form of construction the mold cavity is arranged vertically above the radial passages II which rotate in a, horizontal plane. However, these mold cavities may be arranged below the passages II it necessary or desirable. The centrifugal force in Figs. 4 and 5, wherein the centrifugal molding apparatus comprises a suitable carrier 30 rotated as by a motor 3|. The carrier supports in super- 32 and 33 which are separatedfrom each other by a carbon plate 3 in which the radiating. passages 35 are formed.- The opposed faces of the cast influence of the rotati developed in the metal will ordinarily throw itout in a horizontal direction iron blocks may be flat and straight. The blocks .have apertures therethrough indicated at 36 that receive carbon flasks 31 in which carbonaceous molding material 38 has been rammed up about a pattern to form the mold cavity 39. As will be noted the entrances 40 to the mold cavities communicate with the radial passages 35 inwardly of the outer ends of the radial passages. A central gate 4| is formed in the upper block. This form of construction is preferable where the size and shape of the casting to be produced is such as to enable a large number of castings to be cast during a single operation. -By arrangtion that it ,flows directly across trailing metal enters the mold cavity,

'casting metals it ing the molds above and below their respective radial passages 35, each radial passage will supply the metal to both molds. However, as the radial passages extend outwardly beyond the entrances 40 they form at their outer ends recesses or cavities which receive the initial metal that is apt to be chilled, dirty, and badly oxidized. In this form of construction as before, only the and as the trailing metal is relatively clean, a solid, fine-grained, homogeneous casting can be produced.' The initial metal that flows outwardly through the radial passages does not flow by gravity into the lower mold cavities but is usually thrown out with suflicient force and accelera the lower mold entrances into the outer ends of the radial passages which serve to bypass it from entering the mold cavities. Ordinarily the metal cast will not eat into or burn or dissolve the-faces of the cast iron blocks at the top and bottom of the passages. However, should this occur the blocks can be easily machined or planed off so as to cause the parts of the casting apparatus to properly fit together against opposite sides of the carbon plate.

While we have referred herein to centrifugally will be appreciated that the invention is in no way restricted thereto but' may be advantageously employed for casting other substances which will harden when poured into a mold. The present inventionlends itself to the making of fine small precision castings requiring very little if any machine work. The presentapplication may be regarded as a continuation in part of an application contemporaneously filed herewith entitled Method of making precision castings, Serial No. 424-,3'70,

- filed December 24, 1941.

SHELLEY M. STOODY. RALPH L; ABQS.

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