US2466235A - Slot-gate foundry mold - Google Patents

Description

April 5, 1949.

' R. c. HAWK ET AL 6, 35 SLOT-GATE FOUNDRY MOLD Filed June 13, 1946 ATTORNEYS Patented Apr. 5, 1949 2,466,235 SLOT-GATE FOUNDRY MOLD Ralph C. Hawk, Bay Count Bay City, Mich., assignor Company, Midland, Mi

Delaware y, and John G. Mezofl, s to The Dow Chemical ch., a corporation of Application June 13, 1946, Serial No. 676,380 1 Claim. (Cl. 22134) This invention relates to improvements in bottom-pour slot-gate molds and in foundry procedures for casting metal in such molds.

In making castings of many types, it is desirthe slot-gate horizontally into the cavity, thus entering on top of earlier poured metal. In this and hottest metal should always be at the highest point in the mold, so that upward freezing will be assured.

In practice, slot-gate molds of types heretofore known have been only partially effective in operating in the desired manner. In most instances, the metal being poured, instead of first flowing in the Well to the prevailin metal level and thence into the cavity, tends to cut through the slot below the metal level and stream upward within the casting cavity, upsettin the thermal balance.

such resistance.

With these considerations in mind, it is the principal object ofthe present invention to provide an improved slot-gate mold construction which in actuality achieves in large measure the desirable flow path for the metal being poured which has been intended in prior slot-gate molds. Another object is to provide a mold which is particularly adapted to the founding of magnesium-base alloys and permits pouring sound heavy castings with in general less rigging than has been required heretofore. An additional object is to provide an improved procedure for filling slot-gate molds.

These objects are realized in the invention by positive means associated with the inlet well of the mold for insuring that the effective level at which the metal being poured passes through the slot-gate into the casting cavity is neither materially above nor below the level of the metal already in the cavity. These means may include a restricted orifice for controlling the entry of metal into the well, and a perforated baflle for controlling the movement of metal from the well into the casting cavity.

As is known, the metal being introduced into the well of a bottom-pour slot-gate mold should preferably enter at the bottom center as a stream flowing vertically upward and having a crosssectional area small relative to that of the well. In this way, whatever jet action the stream may possess tends to convey the entering metal within the well to the prevailing metal level with minimum side-flow through submerged parts of the slot-gate. In the invention, this desirable flow is insured by providing at the bottom center of the Well a restricted inlet orifice connecting the well with the sprue and runner through which the metal is poured, the orifice havin an area small in comparison to that of the well, i. e.-

having a diameter which is a minor fraction of that of the well. In addition to furnishing a stream of the requisite small area, the orifice also acts as a choke to maintain the rate of flow relatively constant, eliminating the need for extreme care in the pouring.

In the slot-gate molds of the invention, it is also desirable to place a screen or other multiplyperforated baifie in the well and covering the entrance to the slot-gate. A major purpose of such a screen is to stabilize the flow of metal from the well into the casting cavity. By momentarily retarding the metal and requiring to pass through a large number of small openings, the screen effectively reduces eddying and vortical motion in the stream, permitting quiet flow into the casting cavity. The screen may also function as' somethin of a guide, impeding sidewise flow through the slot-gate below the prevailing metal level in the mold. While simple sheet screens or multiply-perforated plates may be employed, preferred construction calls for a tubular screen centered in the well and extending its full depth, the screen havin a cross-sectional area which materially exceeds that of the inlet orifice, e. g. having a diameter which is a major fraction of that of the well.

In the founding of readily-oxidizable metals, such as magnesium-base alloys, the screen performs the additional function of skimming unavoidable oxide inclusions from the metal as it advantage that, since the metal level is constantly rising during pouring, a fresh screen surface is continually presented to the metal. A further advantage of the screen according to the invention is that possible plugging by the oxide filtered out takes place from the bottom of the well upward, and this plugging assists in restraining fiow of entering metal into the casting cavity at levels below that prevailing in the well.

Some further advantage may be realized, according to the invention, by placing a guide wire such as a strand of steel wool in the well of a bottom-pour slot-gate mold to smooth out the flow of metal. 1

While the bottom inlet orifice, screen, and guide wire as described are individually helpful in establishing the desirable flow path of metal entering a slot-gate mold, molds including combinations of these elements are especially effective. A particularly desirable construction, which illustrates a preferred embodiment of the invention, is shown in the accompanying drawing, in which Fig. 1 is a fragmentary vertical section of a bottom-pour slot-gate mold, taken along the line l-l of Fig. 2, and

Fig. 2 is a horizontal section of the mold, along the line 2.--?. of Fig. 1.

The mold shown in the drawing is a conventional two-part mold of rammed foundry sand 3 defining a casting cavity 4. An open-top vertical well 5 is formed in the mold adjacent to the casting cavity and extending the full depth thereof, with a slot-gate 6 connecting the well with the cavity. The mold is filled through a pouring cup I and sprue 8 from which a runner 9 leads to a point beneath the well 5. Inset in the mold at the bottom of the well is an orifice core Ill provided with a vertical opening H connecting the bottom center of the well with the runner, the diameter of the opening being a minor fraction of that of the well and being materially less than that of the sprue. Centered in the well 5 is a tubular screen 12 made of sheet iron having a very large number of closely-spaced small perforations, or of woven wire fabric, and rolled and crimped into a tube of diameter more than half that of the well. The screen is steadied at its upper end by a rammed-sand ring 13 resting on the top of the mold. A strand of steel wool 14 is centered axially in the well, being tucked under the screen at the bottom.

In using the mold of Figs. 1 and 2, the molten metal to be cast is poured into the cup I at a rate sufiicient to keep it nearly full. The metal flows through the sprue 8, runner 9 and the inlet H as a stream of constant rate and rises inside the screen l2. On reaching the level of metal in the mold, the stream spreads out horizontally without turbulence and flows gently through the slot-gates opening from screen I2 and slot-gate B into the casting cavity 4. While the invention has been described with reference to an inlet well having a single slotgate, it is equally possible to have two or more a single well and leading to the same or different casting cavities. It will also be appreciated that the principles of this invention are applicable in plaster and in permanentemold casting as in sand-casting.

The foregoing description is illustrative rather than strictly limitative, there being many possible variations of the construction described within the scope of the following claim.

Attention is directed to our co-pending application Serial No. 676,379, filed June 13, 1946, in which there is claimed a top-inlet slot-gate foundry mold assembly embodying some of the same principles as the present invention.

What is claimed is:

A foundry mold having a casting cavity, a vertical inlet well adjacent to the cavity, a slot-gate connecting the cavity with the well, a sprue in communication with the well through a central bottom inlet in the well having a diameter which a minor fraction of that of the well, a tubular screen having a diameter which is a major fraction of that of the well centered in the well and extending the full height thereof, and a strand of steel wool centered axially within the screen and extending the full height thereof.

RALPH C. HAWK. JOHN G. MEZOFF.

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

UNITED STATES PATENTS OTHER REFERENCES A Manual of Foundry Practice (2nd edition, reprinted 1941), Laing and Rolfe, page 300, Figure 162.

Non-ferrous Foundry Practice (3rd edition,

1M3) Laing and Rolfe, page 168.

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