US2112333A - Method of producing molding sand addition agents - Google Patents

Description

March 29, 1938. A, REW 2,112,333

METHOD OF PRODUCING MOLDING SAND ADDITION AGENTS Filed May 12, 1956 a co fie Lira??? Fj r mary an grade -ude B y cal 1 ,2 Group] [asst/Yer v Z4 5 5 F a d pm gj OuiZcE Z a 9 7 x. 0 6' 30K Palvcrnzcr .ZO .31 L lz ll Healer I 18 J6 B I Hi l Z 8 23 32 1 I 33 .12 Jbaizaqz/li' 719(1) Patented Mar. 29, 1938 UNITED STATES PATENT OFFICE Joshua A. Crew, Zanesville, Ohio, assignor to The Ayers Mineral Company, Zanesvllle, Ohio, a

corporation of Ohio Application May 12, 1936, Serial No. 79,307

2 Claims. (CI. 22-21?) This invention relates to the production of ground pulverulent materials of the type which are mixed with sand for use in the formation of molds for the production of metallic castings.

5 In foundry practice, the use of sand alone as the facing material for direct contact with molten metal, or in the'formation of mold cores is open to considerable objection, since the sand tends to adhere to the surfaces of a casting, frequently does not provide for clean and complete separation of the casting from the sand of a mold, is often so closely packed as to be impermeable to the passage of steam therethrough developed by the heat of the casting, and, in the formation of cores, the sand is frequently compacted to such a degree that a casting upon cooling and contracting within a mold forms cracks and other types of imperfections.

To improve this situation, modern foundry practice now quite widely employs as molding material a mixture composed primarily of sand, clay and a finely divided organic material such as coal dust. In order to render such a mixture effective, it is necessary to thoroughly and intimately commingle the same so that the several ingredients will be uniformly distributed throughout any given part of the mixed materials and foundries experience. considerable difficulty, without the use of costly equipment, in the matter of effecting the uniform distribution of these materials in the desired state of physical admixture.

It is, therefore, an outstanding object of the present invention to provide an improved method and means for thoroughly grinding, drying and uniformly mixing such foundry sand addition agents so that when the same are delivered to foundries, they are well prepared for ready and convenient admixture with molding sand and without the use on the part of the foundry of special mixing apparatus or facilities.

For a further understanding of the invention, reference is to be hadto the following description and the accompanying drawing, wherein:

Fig. 1 is a diagrammatic view in side elevation of the mixing and drying apparatus utilized by the present invention;

Fig. 2 is an enlarged vertical sectional view phalt, graphite, charcoal, cereal binders, cereal cokes, sawdust, synthetic hydrocarbons, cellulosic plastics and other solid carbonaceous or carboniferous materials. Secondly, mixed with any one or more of the above materials for use as 5 binding agents in molding sand are one or more of the following ingredients selected from the group comprising fire clay, plastic clay, talc, bentonite, volcanic ash, diatomaceous earths, molasses; cereal binders,- milk products, or other 10 equivalent organic or inorganic substances, the effect of which is to maintain or increase the bond or cohesion between the grains of molding or core sand.

In order to prepare these materials for ready 15 use in foundries, the present invention of an improved method and apparatus simultaneously pulverizes, dries and intimately and uniformly mixes the same in desired relative proportions so that when delivered to a foundry, they will be 2 instantly available, without further preparation, for admixture with molding sand and without special or costly facilities at the foundry site.

In accordance with the present invention, the carbonaceous material selected from group 1, 25 above mentioned, or the equivalents thereof, and known in the metallurgical industry as peeling" agents, together with the binding agent or agents, selected from the group defined in group 2, supra, are simultaneously introduced by means of feed 30 passages or the like, indicated at 5, into the feed entrance 6 of a roller mill 1, or other suitable type of pulverizer. In the diagrammatic illustration of the mill disclosed, the same comprises a vertically and axially situated, power driven, ro- 35 tatable shaft 8, carrying at its upper end a cross yoke 9 from the outer ends of which depend supports Ill carrying at their lower ends rollers H, the latter being normally disposed in engagement with a stationary annular bull ring I2. 40

Depending from the yoke 9 is a sleeve i 3 which carries at its lower end a plow M, which agitates f the solid materials introduced into the mill and causes their elevation into crushing contact withthe bull ring I! and the revolving rollers ll. 45

which require further subdivision, the classifier returning such heavier particles to the bottom of the mill for further reduction.

As shown in Fig. 2, the classifier includes an internal cone l5 which extends downwardly within the walls of the classifier casing and has its upper portion provided with openings l6 govferned by adjustable vanes or shutters H. The reduced material is drawn upwardly into the classifier, passing exteriorly over the cone I5 and thence into the interior of said cone by way of the opening l6 whereby through centrifugal action, the undesired heavier particles fall to the bottom of said cone and through a trip release are returned to the mill. The lighter particles,

together with the carrier fluid, pass outwardly of the classifier through a conduit I8. This conduit leads to the suction side of a motor driven fan l9 which, when in operation, tends to produce a negative pressure within the reduction mill and the classifier. The discharge side of the fan I9 is connected by means of a conduit 20 with a centrifugal separator 21 of the so-called cyclone type. The separator 2| serves to effect separate discharge of the reduced finely divided particles from the carrier gas, the said finely divided particles being expelled from the bottom of the separator as indicated by the outlet 22,

while the carrier gas or fluid is removed from the top of the separator by way of the conduit 23. This conduit is provided with a bleeder outlet 24 for the escape of excess carrier fluid and any steam developed, as hereinafter described, in the reduction mill or pulverizer. The conduit 23 is provided beyond the outlet 24 with an adjustable damper 25, whereby suflicient back pressure may be developed in the region of the outlet 24 to provide for the controlled escape of fluid therefrom and yet to maintain the desired balance of the carrier fluid within the system.

To secure the drying, or at least partial dehy dration, of the materials introduced into the mill or pulverizer, use is made of a heater 26 of any suitable type. The outlet flue 21 of the heater extends to a fan 28 driven by a motor 29, and leading from the discharge side of the fan 28 is a pipe 30, damper controlled as at 3|, to provide for the introduction of a heated gaseous fluid into the return conduit 23. The conduit 23 terminates in a manifold 32, which surrounds the lower portion of the mill or pulverizer and is disposed in communication with fluid inlet openings 33 formed in the lower walls thereof. By this construction,-a continuous circulation of the carrier fluid takes place wherein the finely ground particles' of solid material introduced into the mill or pulverizer are heated and dehydrated under temperatures of the order of 300 F. and automatically discharged, when in the required state to the pulverizing zone, heating thereof being effected by the inclusion of the heater 26. Excess gas and steam are drawn 03 through the outlet 24 and the system maintained in a continuously operating balanced state,

By the employment of this system of production, the pulverized molding agents are reduced to the required state of subdivision to render their use eflective and efficient in metal casting operations. The materials when discharged from the outlet 22 in the bottom of the separator 2| are in a dry, uniformly mixed and prepared state and are preferably introduced into suitable containers, such as large sacks, bags or drums and transported for subsequent foundry use in such containers.

When removed from the containers, the materials may be readily mixed with molding sand available at the foundry and either fresh or previously used sand may be admixed therewith. Preferably, the addition agents are incorporated in the sand of a mold forming the mold pockets or cavities to produce facing layers with which the molten material comes into direct contact when a mold is poured. The use of such a facing material prevents or minimizes imperfections in the cast metal and moreover enables a casting to be cleanly removed from a mold with a minimum of adhesion material. The preparation of these addition agents by the present invention is so thorough that no additional treatment is required at the foundry, other than to mix the said agents in desired proportions with the molding sand. This may be conveniently effected without the use of special or costly equipment.

When coal is employed in molding sand for use as a peeling agent, the normal tendency thereof is to weaken the bonding strength of the bonding material in the sand to the extent that the same soon has to be replenished or the sand discarded. In accordance with the present inven-.

tion, however, the combined addition agents employed serve to counteract this weakening effect through incorporating a binding agent with the peeling agent so that the strengthening influence of the former balances or counteracts the weakening influence of the latter.

What is claimed is:

1. The method of producing addition materials for molding sands used in metal casting operations comprising simultaneously introducing a solid carbonaceous material and a binding agent having the property of increasing the bond or cohesion between sand grains into a pulverizing zone, reducing said materials in said pulverizing zone to a fine state of subdivision, removing the materials from said pulverizing zone following the desired subdivision thereof by passing a heated carrier gas through said zone, and finally separating the carrier fluid from the pulverized material.

2. The method of producing a molding sand. addition agent comprising the steps of simultaneouslypulverizing and mixing coal and clay in a mechanical pulverizer in the presence of a carrier gas heated to a temperature of the order of JOSHUA A. CREW.

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