US2461099A - Metal-casting mold - Google Patents

Description

z/ WQQ Feb. 8, 1949. I Cyl-L WELCH 2,461,099

METAL-CASTING MOLD Filed March' so, 1945 Patented Feb. 8, 1949 UNTTED STATES PATENT OFFICE `Cline H. Welch, Marion, Ohio, assigner Ato The AAlley Cast Steel Company, Marion, Ohio, a corporation of Ohio Application March 30, 1945, Serial No. '585,602

(c1. eef-134) 2 Claims. i

This invention relates to an 'improved mold construction -for the .casting of heated molten materials, particularly those which are subject to certain shrinkages upon cooling.

In its more specific aspects, my vinvention iis concerned with the vcasting of metals Vin molds utilizing one or more head chambers Yinto which the zmolten metal is poured before entering the casting cavityor cavities of the mold under oonditions of gravity flow at atmospheric pressure. Such a system is known in foundry parlance as the blind head system, i

In this system, as customarily practiced, the sand :mold `is formed .generally to provide communicating 'casting and head chambers, the molten imetal vbeing .introduced into a gate opening of the mold and `caused to ow rst into the bottom y'oi the head chamber and, thereafter, through'one-or more .communicating passages into the vcasting chamber or cavity of the mold. In theory, ascooling of the heated metal in thecasting cavity takes place, with accompanying volumetric shrinkage, additional metal, obtained from lthe reservoir present in the head chamber, is 'fed tothe cavity 'tocompensate -for such shrinkage, thereby producing sound castings of desired weight, `form and dimensions.

In actual practice, lli-owever, certain objec* tions or practicable diiculties are presen-t when the blind head method of casting is carried out with conventional molds. The prin-cipal ldiii'iculty is that of maintaining lthev 'reservoir of molten metal in 4the head Vchamber under such conditions that it -will flow or vfeed freely and without-hindranceto the casting cavity-or cavities as thedemand therefor is created.

Toobtain such desirable free and unobstructed low'of the molten metal from the head chamber to the vcasting cavity, under the action of gravity and atmospheric pressure, it `is important Athat the reservoir 4of the highly heated metal in "the headchamber be protected against heat loss and premature solidiicati'on and, further, that the interior of this body of head metalv to be properly vented to the atmosphere in amanne'r precluding the 'development of now-restricting sub-atmospheric pressures inthe shrinkage cavities or pockets formed -therein.

Accordingly, it is "an object lofthe present invention to provide `a practical and economical metal-casting mold, Autilizing the lblind khead principle of operation, and wherein 'an improved venting for the molten metal introduced 'into `the head chamber is provided in 'order to insure proper shrinkage-compensatng flow thereof tothe cas't- V ingcavity.

It is another-object to provide a mold in which atmospheric pressure is maintained on the Afeed portion of themoltenlhead metal-by form-ing the topcof' thehead .chamber with a gate yor metal- 2 pouring opening of reduced -diameter asv compared ywith that of said chamber, so that the metal introduced into the head chamber enters the latter directly through yits top and, vin accordance with the gravitational flow characteristics of molten drietal, expands against the .side walls `:of the head chamber, leaving in approximately the upper central region of the ,head

metal a .pocket or void which is open `to the at` mosphere through the gate opening.

yFior ,a further understanding of theinvention, andadditional objects` and advantages thereof, reference is to .be had to the following :descrip-'- tion and the Vaecon'lpanyin-g drawings, wherein:

fEg. .1-is a vertical sectional view taken through a mold formed in accordance with :the present invention. In this iigure,..there has been shown in vertical section .the headchamber-forming pattern, the separable gate-forming pattern anda core'at the shouldered juncture of the headvchamber with the gate opening.

Fig. 2 is a similar view with the head chamber aridA gate patterns removed, showing the head chamber ylled with molten metal;

Fig, 3 is a fragmentary sectional view, showing the gate opening provided with a modified tubular form of core;

Fig.- 4 aview similar to Fig. 3 and illustrating the appearance yof the gate opening whenthe same is not provided rwith a core;

Fig. 5 "is fa vertical sectional view taken through the Vmetal of the head chamber lfollowing cooling and solidiiication thereof and disclosing a representative appearance of the venting pocket or void formed therein.

Referring more particularly to the drawing, vand especially to Fig. l thereof, the same illustrates a sand mold embodyig a, copev it and a drag 'Il vin which is formed ahead chamber I2, a gate I3, and oneor'more passages it for conducting metal from thehead chamber-to the casting-forming cavity or cavities, not shown, of the mold. The head chamber l2 and the passages M may be formed in the moldby means of a pattern, shown at t5. This pattern is so shaped that, when vre'- moved 7from the mold, the head chamber formed thereby possesses a lower region I6 of greatest diameter which communicates with one or more of the horizontal passages `Ill leading to the cast-V ingcavity or cavities.

=It will be `noted vthat the' passages Ill have their lower walls disposed in -a horizontal yplagne somewhat above the concave bottom wall I8 of the head chamber, yfor a purpose to be hereinafter explained. Above the enlarged lower region 16, the headchamber issomewhat reduced in diameter to provide an upper region vI9 and communicating with the top of the region I9 vis the-centrallydisposedlower-end of the gateopen'- ing 1'3, -Which `is substantially smaller in "diameterv than the region I9, forming an annular shoulder shown at 2G. Y

In the. preferred form of my invention, as illustrated in Figs. 1 and 2, the top of the pattern l5 is formed with a central boss 2l and a surrounding circular groove 22. upwardly from the center of the boss 2| is arpin 23, .the latter being received within a socket provided in the lower end of a gate stick or pattern 24, the pin 23 serving to center the gate stick during the formation of the sand body of the mold. The boss or projection 2l of the pattern I 5 serves to support the gate stick above a ring-like core 25, so that the latter will not be injured when the gate stick is tapped preparatory to removing the same from the mold. The outer annular surfaces of the core 25 are downwardly tapered, as at 26, in order to hold the core in proper position in the mold after removal of the pattern I5. The bottom of the coreis positioned in the groove 22 of the pattern in order to hold and support the same in proper position while the mold is being rammed.

In the modication shown in Figure 3, the ringlike core of Fig. l has been shown as replaced by a tubular or sleeve-type core 2?, which is of a height to extend throughout the major portion of the total length of the gate. Both cores, however, serve to maintain the shoulder 2S at the juncture of the gate opening with the head chamber. However, as in Fig. 4, the use of the core may be omitted when the sand body of the mold possesses a composition admitting of the absence of a core.

Following the removal of the pattern I5 and the gate stick 24, the mold is poured by introducing the molten metal directly into the head chamber through the gate passage in its top. The metal so introduced first fills the sump or basin formed in the bottom of the chamber I2, thereafter overiiowing its upper edges and traveling through the passage or passages I4 leading to the casting cavities of the mold. The provision of this sump or basin provides for a smooth uniform travel of the molten metal intoV the casting cavities by minimizing flow turbulence and thereby also reducing the washing of sand by the action of the iiowing metal from the walls of the metal passages of the mold. As the molten metal enters and lls the head chamber, the same expands into engagement with the side surfaces of the upper region I'S, leaving, as shown in Fig. 5, a pocket or void 2S in the upper region of the blind head Sli, which is in communication with the atmosphere through the gas permeable core and sand structure of the mold and, also, the gate I3.

As explained above, the fault of the ordinary blind head arises primarily from the early solidification of the molten metal in the areas immediately adjoining the wall surfaces of the head chamber, with resultant exclusion of atmospheric pressure from the still molten metal in the interior of the head. By pouring the molten metal directly into the top of a head chamber possessing a greater diameter than the pouring gate, the vent pocket or void 29 is created so that atmospheric pressure continues to be applied to the molten interior of the blind head for a suiiicient period of time to effect the required feeding of the molten metal to the casting cavities to compensate for cooling shrinkages. Fig. 5 discloses representatively the appearance of the pocket or void following solidification of the head metal, It will be observed that this pocket Extending Y in the drawing, are possible.

i or void extends well down into the body of the metal, indicating the withdrawal or atmospheric displacement of the molten metal within the interior of the head following initialsolidification ofthe head metal on the surfaces of the head chamber of the mold.

By introducing the molten metal directly into the top of the head chamber, the metal remains in a owable liquid state for a longer period of time than can be obtained with prior molds, since heat losses are minimized through less exposure of the metal to the atmosphere. Again, due to the gate entering the top of the head chamber, smaller volumes of metal are required for a given operation, since the long gates of the prior art are omitted. Further, the highly heated metal at its maximum temperature enters the head chamber directly, increasing the temperature of that region so that proper feeding thereof to the casting cavity is insured, since the metal remains in its highly fluid state for a longer period of time than other molds of which I am aware. In castings employing multiple blind heads, it will be understood that metals are introduced directly vinto one of the chambers for such heads and in the other chamber or chambers, the openings in the top thereof may serve as vents, rather than as gates.

In practicingV my invention, it is important to form the mold so as to maintain the corner or shoulder, indicated at 20 and formed at the juno tion of the gate i3 and the bed chamber I9. This is done preferably through the use of the core 25, although other arrangements, as shown By maintaining this corner or shoulder, I take advantage of the natural pouring characteristics of molten metal which, through expansion into contact with the side walls of the chamber I9, causes such delayed cooling and shrinkage of the hot metal that atmospheric pressures are maintained on its molten interior or free-flowing constituents to assure the complete filling of the mold cavities and the production of sound castings.

I claim:

1. A metal casting mold of cope and drag sections having a sand body including a blind head cavity with passage means to communicate with a casting cavity, a pouring gate, said blind head cavity having said pouring gate disposed at the top thereof and in direct communication therewith and forming with said blind head cavity an upward extension of smaller volume than said blind head cavity, said blind head cavity having an upper region and a lower region, said upper region providing substantially perpendicular surfaces vforming an expansion zone for metal introduced into the blind head cavity, the lower region having a greater diameter than the upper region, and the upper region having a greater diameter than the passage of the pouring gate, a core located at the juncture of the pouring gate passage and the blind head cavity and defining an annular shoulder, the lower region or the blind head cavity having a bottom dening a sump.

2. A metal casting mold of cope and drag sections having a sand body including a blind head cavity with passage means to communicate with a casting cavity, a pouring gate, said blind head cavity having said pouring gate disposed at the top thereof and in direct communication therewith and forming with said blind head cavity an upward extension of smaller volume than said blind head cavity, said blind head cavity having an upper region and a lower region, said upper region forming an expansion zone for metal introduced into the blind head cavity, the lower region having a greater diameter than the upper region and the upper region having a greater diameter than the passage of the pouring gate, and a core located at the juncture of the pouring gate passage and the blind head cavity and depending downwardly into said cavity and denng an annular shoulder.

CLINE H. WELCH.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number 15 Number Germany Aug. 31, 1922

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