US2788554A - Apparatus and method for casting metal in a resin-sand molding - Google Patents

Description

April 16, 1957 Filed April 29, 1953 C PHIPPS C. APPARATUS AND METHOD FOR CASTING METAL IN A RESINSAND MOLDING 2 Sheets-Sheet 1 INVENTOR.

CHARLES C. PHIPPS ATTORNEY Apnl 16, 1957 c. c. PHIPPS 2,788,554

I APPARATUS AND METHOD FOR CASTING METAL IN A RESIN-SAND MOLDING Filed April 29, 1953 2 Sheets-Sheet 2 FIG 6 INVENTOR. CHARLES C. F'-HHPPS BY gdgm ATTORNEY APPARATUS AND METHOD FOR CASTING METAL IN A RESIN-SAND MOLDING Charles C. Phipps, Chattanooga, Tenn., assignor to E. N. Harrison, Chattanooga, Tenn.

Application April 29, 1953, Serial No. 351,811

4 Claims. (Cl. 22-134) This invention relates to resin-sand molding and more particularly to a means and method of providing a metal casting.

Many factors enter into the design and construction of a mold made of sand or of a resin-sand combination in attempting to provide a substantially smooth surface integral casting of substantially uniform structure throughout, formed of metal having few or no impurities. In the green sand practice, it is substantially impossible to form, integrally with the mold, any major obstruction in the path of the molten metal since this molten metal travels at a speed which will cause erosion of these obstructions. Recently, strainers have been used in the molten metal channel to separate the dross and entrained particles from the molten metal. These traps or strainers generally take the form of discs having a plurality of reasonably large apertures or holes, the trap being formed of a high melting material which will not adhere to, be eroded by or dissolved by the molten metal.

In making an ingate for a mold, according to the prior art green sand molding methods, it is desirable to provide a restriction within the ingate so that the solidified metal formed by the sprue and runner may be easily broken from the casting along a line formed by the restriction. In this practice, the casting is thereafter machined to remove the projecting tip which is formed by the metal between the restriction and the casting itself. Because of the ease with which the green sand is eroded by the metal flowing or jetting into the mold, it has been found necessary, according to the prior art, to enlarge the molten metal channel between the restriction and the brake point to thereby reduce the velocity of the molten metal as it enters the casting cavity.

Recently, resinous sand molds have been formed which are substantially rigid bodies, having the sand held together in a porous mass by small amounts of resin, and it is this shell molding practice to which my invention is particularly adapted. I have found that in the shell molding practice, since the sand is held substantially rigid together, the dangers of erosion of the sand by the molten metal is materially reduced. Because of the substantially rigid structure and porous nature of a mold made of a combination of sand and resin, 1 have found that, by providing a plurality of inwardly projecting truncated cones formed integrally with the mold and within the channel through which molten metal passes, a superior casting may be formed Within the casting cavity. I have further found that, using a resinous sand mold, a restriction or break point may be located substantially adjacent the cavity or casting with no deleterious effects to the casting.

Accordingly, it is an object of my invention to provide a means and method of separating air, and foreign matter from molten metal which is poured into a resinuous sand mold, prior to the time that this molten metal enters the casting cavity.

Another object of my invention is to provide a means of introducing metal into a mold cavity of a resinous sand mold at a substantially even temperature, being nited States Patent 6 i 2,788,554 Patented Apr. 16, 1957 ice homogenized or thoroughly commingled, immediately prior to entering the casting cavity.

Another object of my invention is to provide a means 11d method of forming a superior casting of substantially .llfoll'n structure and having a smooth surface which re quires substantially no machining.

Another object of my invention is to provide a trap integrally within a mold, which trap will eliminate entrained air and foreign matter from a stream of molten metal as it passes into the mold.

Other and further objects and advantages of my inven tion will become apparent from the following description when taken in conjunction with the accompanying drawings wherein like characters of reference designate corresponding parts throughout the several views, and wherein:

Fig. 1 is a side elevation of one-half of a mold constructed in accordance with my invention.

Fig. 2 is a side elevation of the other half of the other mold constructed in accordance with my invention.

Fig. 3 is a cross-sectional view of the molds illustrated in Figs. 1 and land joined together in a position to receive molten metal.

Fig. 4 is an enlarged view of a detail showing the ingate of the half of the mold illustrated in Fig. 1.

Fig. 5 is an enlarged view of a detail showing the orifice of a mold constructed in accordance with my invention.

Fig. 6 is a partially broken side elevation of a mold constructed in accordance with my invention, said mold being a variation of the mold illustration in Figs. 1 through 4.

Fig. 7 is a partially broken end view of the mold illus trated in Fig. 6.

Referring now in detail to the embodiments chosen for purpose of illustration, in Fig. 1 there is shown a half mold 10 which is adapted to cooperate with a similar half mold 11 illustrated in Fig. 2, in a well known manner to form a mold cavity. Each half of the mold is formed by sprinkling a sand-resin mixture over an appropriately shaped heated metal surface (not shown) which polymerizes the plastic, thereby forming a somewhat thin shell comprising the mold halves.

The mold halves 10 and 11 are respectively provided with complementary concavities 12, 12', half channels 13, 13', pockets 14, 14' and horizontally disposed troughs 15, 15 which when the two halves are joined, form the sprue cup, the sprue, the reservoir and the runner. In the embodiment illustrated in Figs. 1 through 5, the sprue, formed by half channels 13, 13' is vertically disposed and communicates with the reservoir formed by pockets 14-, 14' which in turn communicate with the horizontally disposed runner formed by troughs 15, 15. Between the reservoir and the runner, is a substantially rectangular shaped orifice, illustrated by numeral 16 in Fig. 5, and being formed by downwardly projecting walls 17, 17' in mold halves 1t) and 11 respectively. It is to be noted that the reservoir and the runner have their bottom portions disposed in substantially the same horizontal plane and that the lower portion of the orifice 16 is on that plane. It is therefore apparent that when molten metal is poured into the sprue cup and passes down the sprue into the reservoir, only the metal at the bottom-most portion of the reservoir will then pass into the runner.

Located above the runner is the casting cavity, illus trated by numeral 18 in Fig. 3, and being formed by cavity shells 19, 19* of mold halves 10 and 11 respectively. It should be remembered that the sprue cup is higher than the casting cavity so that molten metal may flow by gravity into casting cavity 18, providing maximum pressure to the molten metal at the reservoir and runner.

According to my invention, between the upper portion of the runner and the lower portion of the casting cava?) ity 18 is an ingate 20 which comprises ingate walls 21, 21' located respectively in mold halves and 11. From an examination of Figs. 1, 2 and 4, it will be seen that ingate walls 21,21 are substantially the same width and each are provided with curvilinear ends, defining with walls 21, 21, the ingate 21). Thus, it will be apparent the the length of ingate gradually decreases and then gradually increases while the width thereof diminishes as the ingate approaches casting cavity 13. It will also be seen that the break line formed at 22 by the ingate 2t. and the casting cavity 18, thereby providing a separation point between the finished casting and the metal within the ingate which substantially corresponds to the shape of the finished casting.

According to my invention, a trap comprising a plurality of baflles or teeth-like projections are provided as obstacles in the path of the molten metal prior to the time it enters casting cavity 18. Preferably these baffles or projections are provided along the walls 21, 21 of ingate 20 as shown in the drawings, even though they may be formed at any place along the path of the molten metal, such as in the runner, without departing from the scope of my invention. These teeth comprise a plurality of gas absorbent aggregates formed as upstanding truncated cones which are made integrally with the mold halves and of the same resinous sand which forms the mold.

As seen most clearly in Fig. 4, the cones of this illustrated embodiment are formed in staggered rows along wall 21, the primary cones being denoted by numeral 23, the secondary cones by numeral 23, the tertiary cone by numeral 23" and the other cones by numeral 23". It will be seen that primary cones 23 are evenly spaced adjacent trough 15 and that each successive row of cones is of successively smaller size and are positioned between the cones of the preceding row to form therewith, points of an isosceles triangle. The last row of cones is arranged adjacent the cavity shell 19 and is positioned in a row adjacent break line 22. Cones 24 which project from wall 21' are formed in substantially identical manner as cones 23, 23, 23"; however, in the preferable embodiment of my invention the cones 24, in each row, are arranged to intersect the cones in its complementary row on wall 21. In some instances it may be found advisable to provide cones which project from opposite wall so that the truncated portion of the cones are contiguous and abut each other.

It may or may not be found advisable to provide a riser such as vent riser 25, however, this is a matter of choice with each foundryman and depends to some extent on the thickness of the mold.

Now it may be seen that in forming a casting, the mold halves 10 and 11 are joined as illustrated in Fig. 3, and the molten metal is then poured into the sprue cup where it passes down the sprue into the reservoir. As the molten metal passes down the sprue and sprue cup, it may pick up certain impurities from concavities 12, 12, half channels 13, 13' and pockets 14, 14'. Some of these impurities float to the top of the molten metal which is carbonaceous appearing material and other impurities may be burned out by the molten metal; however, still other impurities pass through the orifice 16 and into the runner with the molten metal, the orifice serving to allow only the metal under greatest pressure, and with the least amount of gases, to enter the runner. The molten metal then fills the runner, passes around the maze of cones 23, 23, 23", 23" and 24, and into the casting cavity 18, filling it to form the casting, the molten metal standing in the sprue and sprue cup when the casting cavity 18 is filled.

By the molten metal passing around the maze of cones, the air and gases are removed therefrom, the porous nature of the resin-sand of which they are formed providing ample surface for absorbing gases and vapors entrapped or entrained in the molten metal. Also, these cones serve as a pre-mixer which homogenizes or thoroughly mixes the molten metal immediately prior to its entering the casting cavity 18; in this way any alloying additives introduce-d in the ladle are evenly dispensed throughout the metal.

While all of the functions of the cones are not completely understood by me, the slag impurities seem to adhere to the cones and are separated thereby while other extraneous and suspended insolubles tend to be caught in the maze of cones and thus never enter the casting cavity.

The cones serve an additional purpose in that they reduce the initial inlet speed of the molten metal entering the casting cavity and yet provide, in combination with the converging ingate Walls 21, 21' a pressure and velocity suificient to quickly fill the casting cavity.

It should also be noted that, because of the erosion resistant nature of the resin-sand mixture forming the mold, the overall velocity of the molten metal entering the casting cavity is increased with respect to the prior art green sand practice. This increased overall velocity as the molten metal passes around the cones and into the casting cavity tends to provide suflicient turbulence to maintain a more uniform temperature throughout the molten metal as it enters casting cavity 18.

An examination of Fig. 3 will indicate that the casting is poured in a substantially vertical position which thereby reduces to a minimum the top surface area of the molten metal entering the casting cavity 18. Pouring a casting in this manner presents a minimum molten metal surface exposed to oxidation by the gases within casting cavity 18 and provides the maximum back pres sure opposing the entrance of molten metal and thus reducing the danger of the molten metal trapping gases due to its turbulence.

In Figs. 6 and 7, is illustrated an alternate arrangement of my invention which comprises mold halves 26 and 27 formed of resin-sand. In this embodiment, the mold is disposed horizontally while the sprue cup 28 and sprue 2% are disposed vertically. The casting cavity 30, ingate 31, and cones 32 are formed in substantially identical manner as the previous embodiment; however, the orifice 33 between runner 34 and reservoir 35 is provided a restricted channel between the lower portions thereof, for the purposes described above. In this alternate arrangement, it is apparent that the sprue cup 28 and sprue '29 may be formed separately from the molding and does not necessarily have to be formed of resinsand. In fact, the sprue cup 28 and sprue 29 may consist of any material found suitable for the purpose.

Generally speaking, the alternate embodiment shown in Figs. 6 and 7 in most instances presents a greater molten metal surface to oxidation by gases within the mold and provides less back pressure; therefore, it should be utilized when the configurationof the casting does not lend itself well to vertical casting.

My trap may conceivably be also used with other than resin-sand molds, i. e. various combinations of sand and binders, or molding mixtures entering into formation of preformed mold facings, or rigid mold facings similar to present resin-sand shell molds. Also, the trap may be formed independently and inserted into the mold, and the projecting teeth may have various shapes and arrangements.

It will be apparent to those skilled in the art that many variations may be made in the embodiments chosen for purpose of illustration without departing from the scope of my invention as defined by the appended claims.

I claim:

1. A process of casting molten metal in a resinoussand mold having a casting cavity for receiving and forming said metal, the steps of directing said molten metal in said mold through a predetermined downward path, then passing said molten metal horizontally within said resinous-sand mold, directing said molten metal upwardly while diminishing the cross-sectional area of said molten metal, absorbing the gases from said molten metal by interposing in the path of said molten metal a plurality of protrusions formed of resinous-sand, said protrusions being in staggered relationship, and then introducing said molten metal into said cavity.

2. A process of casting molten metal in a mold having a casting cavity for receiving and forming said metal comprising directing said molten metal into said mold along a predetermined path, absorbing the gases from said molten metal as the same moves along said predetermined path by sucessively contacting said molten metal with a plurality of gas-absorbing resinous sand protrusions arranged along said path, and thereafter introducing said molten metal into said casting cavity.

3. Apparatus for casting metal comprising a resinoussand mold provided With a casting cavity and a channel communicating with said casting cavity through which molten metal is fed to said cavity, part of said channel forming an ingate adjacent said cavity, and a plurality of resinous-sand gas absorbing teeth projecting from said mold into said ingate, said teeth being in a position to be contacted by said molten metal in its travel through said ingate.

4. A mold for casting metal comprising mold halves formed of resinous sand, said mold halves defining a casting cavity and a passage through which molten metal may be introduced into such molds, said mold halves being provided with opposed walls which define an ingate communicating with said passage and said casting cavity, said opposed walls tapering toward each other as they approach said casting cavity, and a plurality of resinous-sand teeth projecting from each of said Walls into said ingate, said teeth being generally cone-shaped with the bases of said teeth mounted on said Walls, said teeth being arranged in a plurality of rows across said Walls, the teeth in one row across said walls being staggered with respect to the teeth in the other of said plurality of rows.

References Cited in the file of this patent UNITED STATES PATENTS 277,131 Harrison May 8, 1883 508,884 James Nov. 14, 1893 772,720 Ladwig Oct. 18, 1904 1,385,201 Chapple July 19, 1921 1,817,012 Merle Aug. 4, 1931 2,654,925 Ensign et al Oct. 13, 1953 FOREIGN PATENTS 579,469 Great Britain Aug. 6, 1946 590,733 Great Britain July 28, 1947 956,146 France July 18, 1949

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