US 2835007 A
Description (OCR text may contain errors)
May 20, 1958 w. F. HOEFER 2,835,007
SCREEN FOR MOLDING FLASKS Filed March 12, 1954 1' I i T I l i /2 I I I I l I I a 3 I 1 /7 l I /4 i I I, a /a i I I lo I E I O /"6 /6' I I 4 f I I 1 INVENTOR. WM. ff/QEFEA flame AM fli'iy.
United States Patent l 2,835,007 SCREEN FOR MOLDING FLASKS William F. Hoefer, Pasadena, Calif.
Application March 12, .1954, SerialNo. 415,929 2 Claims. cl. 22-134) This invention'rela'tes tothe art of molding, or casting metals.
In casting most metals the present practice is to use a flask composed of a drag and a cope rammed with sand to provide the molding cavity or cavities in the drag. Through the rammed flask of thecope a pouring well or reservoir is usually formed, the lower end of which extends into the sand in the upper portion of the drag. From the lower portion of this pouring duct, a gate or gates lead off to molding cavities in the drag.
In the lower portion of the reservoir it is the best practice to place a screen of disc form which is provided with a considerable number of perforations, and in pouring the molten metal it is best to pour the metal into the reservoir so that its level in the reservoir is maintained at a high point. By doing this any slag in the molten metal floats up from the lower portion of the reservoir and substantially none of it passes into the casting. This practice insures castings of good quality.
It has been attempted to employ perforated discs or strainer cores as they are commony called, for the purpose mentioned, many composed of ceramic material, but some of these ceramic discs have been known to explode in use, due probably to the effect of the high heat on water crystallization in the disc. Other materials have also been used for this purpose, but without marked success.
The object of the present invention is to provide a more satisfactory type of disc to be employed as a screen in a mold, than those heretofore available, and which will be quite inexpensive to produce.
Another object of the invention is to employ a disc having a composition which particularly adapts it for resisting the high temperature.
Another object of the invention was to discover a material which is admirably adapted by its chemical composition and physical structure to function satisfactorily as a screen in a mold duct leading into a mold cavity.
Further objects of the invention will be evident from a careful reading of the specifiation and a study of the accompanying drawing.
The invention consists in the novel parts and combinations of parts to be described hereinafter, all of which contribute to produce an efiicient screen for molding flasks.
A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.
In the drawing:
Figure 1 is a plan of screen in the form of a disc embodying my invention.
Figure 2 is a vertical section through the side walls of a pouring well or reservoir of a mold which is shown in Figure 3, with the screen shown in elevation.
Figure 3 is a side elevation and partial section of the flask and illustrating a pouring well or main gate for the mold and also showing the screen of my invention in 2,835,007. Patented May 20, 1958 2, position, located on the dividing plane between the drag and the cope.
Referring particularly to Figures 1 and 3, the invention includes a novel screen 1, which is illustrated here as of plate-form, for example, a disc of circular for-m, provided with a plurality of perforations 2 preferably spaced uniformly throughout the area of the disc. This disc may, if desired, be manufactured of a plurality of thin 'shims or laminae 3 composed of a material having the characteristics of silicate of aluminum.
In Figure 3 I illustrate the preferred manner of employing this screen in' a common form of molding flask, comprising a drag 4 ofcommon form, and'a cope 5 supported upon it. These two parts comprise the complete mold, each having a wooden frame 6 of suflicient .depth to contain the mold cavity, or cavities in. which the castings are to be molded.
In many instances there will be a plurality of molds such as the mold cavity 7 shown in Figure 3, in which the" cavity is formed to produce a pot having the form of a common flower pot, involving the use of a tapered cores. This mold cavity'may be formed in the usual manner, the core 8 being provided with a round projection 9 to form a drain opening at the bottom of the pot.
Such small objects are usually molded in a gang mold having individual gates 10 through which the molten metal passes from the lower end of a main gate or reservoir 11, that passes down from the upper face of the molding sand 12 that has been rammed around a pattern having the usual cylindrical form to produce a circular duct through the cope when it is withdrawn. Such a pattern would usually have a conial head at its upper end to produce a large mouth 13 to catch the molten metal when pouring the casting.
Before ramming the sand in the drag to the point which will be the level of the upper end of the core 8, the sand should be rammed around a core-print or pattern to form a short duct 14 on the central axis of the mold, as it must align with the main gate or reservoir 11 that receives the molten metal.
In the practice of the invention, before placing the cope n position over the drag (which has been inverted) I lay one of the screens 3 on the upper face 15 of the rammed sand 16 of the drag, after which the cope is put into position to register with the drag and complete the flask.
As the density of the sand in both cope and drag is the same, the screen will impress itself equally into the sand touching its upper and lower faces which will increase the sand density above and below all around the edge of the disc.
In doing this it is preferable that the disc 3 be not forced down into the sand of the drag, because I wish to have the sand portion at 17 that immediately overlies the edge of the disc to be finally in compression. This enables it to resist any scouring action of the molten metal when it is poured into the reservoir or main gate 11 when commencing the molding operation; but of course, as soon as the reservoir or main gate has been filled with the molten metal up to a high level which may approximate the level of the dotted line 18, the hydrostatic pressure at the bottom of the reservoir will assist in compacting the sand in the annular vicinity of the point 17.
This is advantageous because it prevents the molten metal from passing down around the superficial edge surface 19 of the disc 3 where it could find its way into any crevices between the laminae 20 of which the disc is composed.
In Figure l the circular pitch line 20 indicates approximately the location of the face of the main duct 11 would be with relation to the edge of the disc. The distance that the disc should project past the face of the Well of the reservoir 11 should depend somewhat upon the material that is being molded and possibly to some extent upon its melting point." So, it is preferable that the outer pitch circle on which the perforation centers are located, should not be too close to the edge of the disc. Then they will not be too near to the face of the reservoir wall.
In accordance with my invention I may manufacture the screens from thin sheets of silicate of aluminum or other refractory material in which case it is preferable to press the shims forcibly together and then coat their edges completely with a suitable binder. But natural mica lends itself admirably to my purpose as it can be split on its planes of cleavage to any desired thickness for the disc.
Many other embodiments of this invention may be resorted to without departing from the spirit of the invention.
I claim and desire to secure by Letters Patent:
1. A flask having a drag and a cope rammed with sand and having a pouring reservoir extending down through the cope and into the drag, in combination with a perforated screen of plate form and composed of laminations of mica, said screen having an area considerably greater than the area of the horizontal cross section of the reservoir, and having its edge buried in the sand beyond the face of the pouring reservoir wall, so that References Cited in the file of this patent UNITED STATES PATENTS 900,970 Washburn Oct. 13, 1908 1,030,066 Erlandson June 18, 1912 1,049,877 Lange Jan. 7, 1913 1,100,831 Kline June 23, 1914 2,014,224 Campbell Sept. 10, 1935 2,431,879 Mebs Dec. 2, 1947 FOREIGN PATENTS Great Britain Oct. 8, 1925 OTHER REFERENCES Gates and Risers for Castings, 3rd ed., 1949, by Pat Dwyer, published by The Penton Publishing Co., pages 314, 315, 349, and 350.