US2962780A - Metal casting apparatus - Google Patents

Description

Dec. 6, 1960 L. W. KRUM Filed 00 24, 1957 /5 Fig 1 k I P 3 COPE lit 4 DRAG INVENTOR LESTER W KRUM B JMj 1 A No r n er Unite States Patent METAL CASTING APPARATUS Lester W. Krum, Buffalo, N.Y., assiguor to United States Steel Corporation, a corporation of New Jersey Filed Oct. 24, 1957, Ser. No. 692,091

2 Claims. (Cl. 22-134) This invention relates to the art of metal casting and, more particularly, to an improved method and apparatus for gating metal into a sand mold. In a manner to be described, the improvements contemplate a gating that rises continuously and progressively with the level of the metal being cast in a mold cavity.

In the manufacture of metal castings a mold is prepared, according to the usual and conventional foundry practices commonly employed, by placing a pattern hav ing the identical shape of the desired rough casting, but modified dimensionally to a small degree to compensate for linear shrinkage, into a receiving box called a flask, after which sand is compacted around the pattern by hand or machine. The pattern is then withdrawn from the sand leaving a cavity which is identical to the shape of the pattern. Depending on the required final shape, or whether pockets or holes are a part of the castings design, sand cores may be placed as required in the cavity left upon withdrawal of the pattern. It is generally necessary, in order to withdraw the pattern from the mold thus made, to construct the mold in two or more parts that are thereafter assembled in stacked re ation. The top part or flask is called a cope, the bottom part a drag, and if there are any middle sections they are termed cheeks.

After the mold is made and dried if required, it is closed by setting in the aforementioned cores and placing and securing the relative parts in proper position. Some meta s, because of their shrinkage characteristics also require that feed reservoirs for molten metal over that required to just fill the mold cavity be placed at strategic locations and connected to the mold cavity; this is true to varying degrees of most commercial metals.

The melted metal is introduced into the mold cavity by means of channels called gates. Where the metal is introduced into the top of the mold it is said to be topgated; if at the parting line between the cope and drag, it is said to be parting gated; and if at the bottom of the mold, bottom gated. Unless the mold is very shallow both top and parting gated castings are very apt to be imperfect, because the turbulence of the molten metal introduced in this way plus the velocity and momentum incident to a free fall cuts into the sand of the mold and displaces cores and chaplets used in positioning such cores. Although top gating is theoretically most correct in that it promotes the desired directional freezing from the bottom to the top where the reservoirs or heads are usually placed, because of its mechanical disadvantages it is seldom used for any but small castings; parting gating may be used more often, while bottom gating is relatively standard.

One of the principal obiects of this invention is to provide a means of introducing molten metal into a mold in a manner that will retain the metallurgical advantages of top gating and eliminate its mechanical disadvantages. A further and elated obiect is to provide a gating arrangement which provides an effective gating level that rises progressively with the level of the metal in the mold cavity. These and other objects are accomplished, in a manner to be described by providing a fin-shaped gating or metal feed chamber at one side of a mold cavity with a sprue opening into its bottom for the supply of molten metal thereto, and a narrow elongated and vertically extending opening connecting it with the mold cavity and providing a gate for the delivery of metal therefrom to the mold cavity.

Other objects and advantages of the invention will become apparent from the following description.

The drawings illustrate diagrammatically, as a typical example or a preferred practice, the manner in which the invention is applied to the casting of a cinder pot.

In this showing:

Figure 1 is a diametric and vertical sectional view showing somewhat diagrammatically a mold for casting a cinder pot; and

Figures 2 and 3 are fragmentary sectional views taken substantially along the lines II-II and III--III of Figure l.

The method and apparatus of this invention is especially adapted to the production of heavy castings that have relatively large vertical and small horizontal dimensions in the positions in which they are cast in a mold. Thimble-shaped cinder pots used in the transport of slag from metallurgical furnaces furnish one example of this type of casting for which the principles of this invention are particularly suited. The essential construction and parts of a sand mold for casting a cinder pot of this character are shown diagrammatically in the drawings in Figure 1 of which a cope 1 is shown in its operative position on a drag 2. As in conventional practice, the drag 2 is formed of rammed molding sand in the floor of the foundry and the cope 1 includes a hollow thimbleshaped reinforcing metal shell (not shown) which has a rammed covering of molding sand applied to its outer surface. When the cope 1 is lowered by a crane to its operative position supported on the drag 2 as shown in Figure 1, such parts co-operate to define a mold cavity 3 that conforms to the shape of a cinder pot or other article to be cast therein. The drag 2, in accordance with the principles of this invention, is provided with a fin gate 4 in the form of a narrow and vertically extending compartment through which metal is gated into the mold cavity 3. The casting metal is delivered initially into the compartment 4 through a tile-lined sprue 5 which opens upwardly at 6 through the bottom of the compartment 4.

The compartment 4, more particularly, is defined by a vertically extending end wall 7 spaced from one side of the mold cavity 3, side walls 8 and 9, and horizontal top and bottom walls 10 and 11. A vertically extending and narrow opening 12 defined by side edges 13 and 14 provides a communicating connection between the compartment 4 and the mold cavity 3. The sprue connection 6 opens through the bottom wall 11 into the compartment 4 adjacent its end wall 7 and at a point that is remotely located with respect to and spaced from the lower end of the gating opening 12. The sidewalls 8 and 9 are spaced apart at this point a distance that is not substantially greater than the diameter of the sprue tiles, which is about 4 inches for a casting of this character, in order that the metal entering through the sprue opening 6 will have an unrestricted flow upwardly into the compartment 4. The compartment side walls 8 and 9 are planar as shown in the drawings and preferably converge in a direction toward the gating opening 12 and thus act somewhat to restrict the size of the opening 12 and thereby the flow of metal from the compartment 4 into the cavity 3. Generally stated, the side edges 13 and 14 are spaced apart a distance such that the horizontal dimension of the opening 12 therebetwccn at any given level is somewhat less than the horizontal dimension of the cavity 3 in a direction away from the opening 12. The side edges 13 and 14 further have a diverging relation in an upward direction so that the restriction to the flow of metalthrough the opening 12 decreases at vertically increasing levels.

In operation a casting is formed in the mold cavity 3 by teeming metal from a ladle through a refractory pouring gate 15 into the sprue 5. The metal flowing through the sprue 5 is led upwardly through the opening 6 into the compartment 4 and flows by gravity therefrom into the mold cavity 3. During the initial stage of the casting operation, the metal flows from the compartment 4 over the outer edge of the bottom wall 11 which thus defines the lowest effective level of the gating opening 12. However, metal accumulates in the compartment 4; as the level of the metal in the cavity 3 rises above the bottom wall 11, and this operates to raise the effective level of the gating opening 12. In explanation of this action, it will be appreciated that the metal flowing through the sprue opening 6 will tend to continue its upward vertical movement through the metal already in the compartment 4; however, as it reaches the surface of the metal in the compartment 4, it will flow by gravity outwardly over such surface through the gating opening 12 and into the mold cavity 3. As the pouring operation continues, the surface of the metal in the compartment 4 and thereby efiective level of the gating opening 12 will thus progress upwardly with the level of the metal in the cavity 3.

From the foregoing it will be apparent that the arrangement of the compartment 4 between the sprue 5 and mold cavity 3 provides a gate that rises progressively with the level of the metal in the mold cavity 3. Attention is further directed to the fact that this arrangement is effective in confining to the gating compartment 4 turbulence that results from metal flowing upwardly through another body of molten metal as in conventional bottom gating practices. In addition, the action of the gating compartment 4 serves to place the hotter metal at the top of the mold cavity and thus provides the theoretically correct directional freezing from the bottom to the top of the casting, but this is accomplished without the mechanical disadvantages of conventional top gating.

While a preferred practice of the invention as applied to the casting of a cinder pot has been shown and described, it will be understood that the principles of the invention as thus disclosed are applicable to the casting of other articles and that modifications and adaptations of such practice for this and other purposes may be made without departing from the scope of the following claims.

I claim:

1. A casting apparatus comprising a mold having a cavity in which metal is to be cast, a feed chamber arranged along one side of said cavity, a narrow elongated and vertically extending gating opening providing a communicating connection between said chamber and cavity, said opening having laterally spaced and vertically extending edges, said chamber having planar sidewalls diverging outwardly from the said vertical edges of said opening, and a sprue opening into the bottom of said chamber at a point remotely located with respect to the lower end of said opening, said sidewalls being spaced apart at the widest dimension of said chamber a distance not substantially greater than the diameter of said sprue, said vertical edges of said gating opening diverging relative to each other in an upward direction.

2. An apparatus as defined in claim 1 characterized further by the said vertical edges of said opening being spaced apart at any selected vertical level a distance less than the horizontal dimension of said cavity at such level in a direction away from said opening.

References Cited in the file of this patent UNITED STATES PATENTS 1,104,037 Custer July 21, 1914 1,296,594 Norton Mar. 4, 1919 1,589,730 Williams June 22, 1926 2,466,235 Hawk Apr. 5, 1949

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