US3627024A - Apparatus for handling and cooling foundry sand - Google Patents

Abstract

Apparatus for handling and cooling foundry sand. No apparatus that uses air or water to cool the sand is used. Instead, conventional equipment including a muller, conveyors, storage tanks, a molding machine, a shakeout machine, a new sand dividing device, and a new sand-metering device, are employed.

Description

United States Patent Inventor Appl. No.

Filed Patented Asnlgnee Joseph S. Schumacher Cincinnati, Ohio July 7, 1969 Dec. 14. I971 lnternatlunul Mlnerals and Chemical Corporation Skokle, Ill.

Continuation-impart of application Ser. No. 714,339, Mar. 19, 1968, now Patent No. 3,461,941, dated Aug. 19, 1969. This application July 7, 1969, Ser. No. 839,259

APPARATUS FOR HANDLING AND COOLING FOUNDRY SAND 8 Claims, 8 Drawing Figs.

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164/5, 164/412 BZZC 5/16, B22d 47/02 [50] Field of Search UNITED STATES PATENTS [56] References Cited 831,595 9/1906 Blundingm, 1,808,366 6/1931 McWanc.... 1,982,824 2,478,461

Al!0rney-W0od, Herron & Evans 12/1934 Miltenberger 8/1949 Connolly FOREIGN PATENTS 1/1928 Great Britain Primary Examiner-Robert D. Baldwin ABSTRACT: Apparatus for handling and cooling foundry sand. No apparatus that uses air or water to cool the sand is used. Instead, conventional equipment including a muller,

conveyors, storage tanks, a molding machine, a shakeout machine, a new sand dividin device, are employed.

g device, and a new sand-metering Patented Dec. 14, 1971 CA5 TING MAYA/VS INVENTOR.

APPARATUS FOR HANDLING AND COOLING FOUNDRY SANlD This invention relates to apparatus for the handling and cooling of foundry sand during the casting of metal into sand molds and more particularly it relates to such apparatus that is especially useful in the process disclosed in my copending application Ser. No. 714,339, filed Mar. 19, 1968, now U.S. Pat. No. 3,461,941, issued Aug. 19, 1969, entitled Method of Handling and Cooling Foundry Sand" of which this application is a continuation-in-part.

In my application Ser. No. 839,339 (1969) entitled Method for Handling and Cooling Foundry Sand," and in my application Ser. No. 866,716 (1969) entitled A Method for Reducing Pollution ln Foundries, related inventions are disclosed. I

in some casting operations metal is cast into previously formed sand molds. After the metal has been cast, the sand mold is broken away from the casting and the sand is reused after it has been cooled and reconstituted by the addition of various types of additives.

Many different types of apparatus for cooling foundry sand prior to its reuse have been used and proposed. In a recent article entitled Survey of Methods to Cool Hot Sand" written by A. .l. Filipovitch, appearing at page 92, Volume 95, No. of the Oct. 1967 issue of Foundry magazine, the author discusses various types of equipment that he found being used in his survey of 211 foundries. All of the various types of equipment described and illustrated in the article depend upon the use of either air or water or a combination of the two to cool the foundry sand.

For years it has been recognized that it would be desirable to cool foundry sand to approximately room temperature before it is reused. If it is not, then serious problems can arise that may adversely affect the molds and the castings. For instance, it is pointed out in the article referred to previously that hot sand is very unstable and its properties frequently change. This adversely affects the quality of the molds and prohibits uniformity of operation. Also, hot sand does not flow very well and tends to pack and agglomerate in the equipment tanks, conveyors, and elevators. Any moisture that is added to cool the sand must be closely controlled or it can cause poor pattern draws resulting in inferior casting quality. Moisture variations must be closely controlled because, even though they may appear to be inconsequential, they can cause radical changes in compressive strength, permeability, and flowability of the sand. Such changes can lead to poor finish, defective castings and increased scrap. If too much moisture is added to cool the sand, the sand tends to agglomerate.

In my aforementioned patent application a novel method of cooling foundry sand that does not depend upon the use of either air or water to cool foundry sand is disclosed. Briefly described, the process consists of cooling the hot used sand by adding to it cool sand. The way to calculate the amount of cool sand that should be used is described hereinafter.

An important objective of this invention is to provide apparatus for cooling foundry sand to approximately room temperature without the need for using expensive and complicated cooling equipment. Another objective of my invention is to provide to provide apparatus for cooling foundry sand which does not use air or water as the cooling medium. A still further objective of my invention is to provide apparatus for handling and cooling foundry sand wherein the composition of the foundry sand can be easily controlled and the compositional variations can be minimized.

ln the casting of metals into sand molds, the amount of sand used to form a mold is usually expressed as a function of the amount of metal to be poured into it. This relationship is called the sand to metal ratio. For example, sufficient sand is frequently used for the mold to give a sand to metal ratio of from 3 to l to to 1. While these ratios are frequently used, others are oftentimes used too. A common ratio used is a ratio of about 6 to l. That is, a mold is formed which consists of 6 pounds ofsand for each pound ofmetal to be cast.

Foundry sand is, of course, not sand alone but contains additional constituents such as clays and/or carbons and/or other additives and/or temper water. Carbons in common use are powdered coal, coal tar, pitch, asphalt, graphite and coke. Other additives can be added such as celluloses, cereal binders, etc. After one or more molding operations, new sand, clays and/or carbons can be added to the used sand to replace the portion of the original sand which has been made unuseable. Temper water is also frequently added. The following is a typical table which shows the amount of additives which usually must be added after the batch of sand has been used. This table is for ferrous metals other than steel. Other data for nonferrous metals, steel and ductile metals is known to those in the foundry industry.

Table l SUGGESTED ADDlTlVE REQUIREMENTS PER MULLER LOAD OF 2,000 POUNDS As it can be seen from this table, it requires about 34.8 pounds of new clay and additives plus pounds of new sand to reconstitute the molding sand for reuse at a sand to metal ratio of 3 to 1. However, at a ratio of 20 to 1 it requires only 5.2 pounds of new clay and additives, plus 15 pounds of new sand to reconstitute it at this ratio.

1 have discovered that if one desires to operate a sand system at a normal sand to metal ratio of about 4 to l to 6 to 1 that conventional cooling methods can be eliminated if a batch of foundry sand is mixed so as to provide a 20 to 1 ratio, the molds are made, for example, on a 4 to l to 6 to 1 ratio, and if immediately after the molds are used and broken up, the remaining unused cool portion of the mixed sand is mixed with the hot used sand. By mixing the unused sand with the used sand, the temperature of the combination of sand is lowered so that a portion of the batch can be reused immediately after it has been remulled and any desired additives and/or temper water added without further cooling. No other cooling step is needed. Moreover, sand used in this manner is easy to reconstitute because the amount of additives lost per molding cycle expressed as a percent of the total batch is very small. It can be seen, therefore, that my invention provides a novel method of cooling foundry sand while at the same time it provides a method of controlling the composition of the foundry sand and for minimizing variations in composition.

1 have found that it is generally desirable to cool the used sand as close to ambient temperature as possible after the molds are shaken out and prior to the mulling and reconstituting of the sand. While ambient temperature is preferred, sand at a temperature of F. can be used. However, it is desirable to cool the sand to below l20 F. to obtain the best mixing results. Most clays are difficult to wet and plasticize when the temperature is over 120 F. If sands are prepared at I20 F. then drying out will rapidly occur due to evaporation till ambient temperature is reached. Moisture losses change the properties of the molding sand. A consistent molding media is desired for best results. Therefore, 1 have found that the most efficient mixing is achieved when the sand is at ambient temperature. The amount of sand which must be added after shakeout in order to obtain a mixture of used and unused sand at a particular temperature is, of course, dependent upon the temperature of and the amounts of the used and unused sands. l have found that the approximate amount of unused sand which must be added can be calculated in the following way.

An estimation of the temperature of the sand at shakeout can be made if it is assumed that all the heat evolved from the hot metal is transferred to the sand. The temperature of the metal in an average pouring for iron is about 2,600 F. The heat evolved can be calculated from the following formula H=cp (2-60) where cp mean specific heat of pure iron at 2,600 F., t shakeout temperature, and 60 standard ambient temperature. No heat of solidification has been included because of the different metals which might be used. The following table shows the heat evolved at the indicated shakeout temperature when the pouring temperature is 2,600" F.

These results can be plotted on a graph so that the intermediate values can be easily obtained.

Knowing the heat evolved from the metal and assuming that all of this heat is transferred to the sand then the temperature of the said at various shakeout temperatures can be calculated. The formula that should be used is H=Cp sand weight per pound of iron .1 (1-60) where H is the heat evolved from the iron, Cp is the heat for SiO, for r60, and t sand temperature at shakeout. The following tables show the temperature of the sand at various metal shakeout temperatures.

Table III 20 to 1 Sand to Metal Ratio Casting shakeout Temp. Sand Temperature 2,000 F. I20 F. L600" F. l40 F. l,200 F. l60 F. 800' F. 180' F. 400 F. 200 F.

Table iv 10 to 1 Sand to Metal Ratio Casting Shulteout Temp. Sand Temperature 2,000 F. Hi F. 1,600 F. 220 F. L200 F. 260 F. H00 F. 300 F. 400 F. 340 F.

Table V 4 to 1 Sand to Metal Ratio Casting shakeout Temp. Snnd Temperature 1.200 F. $40 F. 800' F 630' F.

Again it was assumed that the pouring temperature of the metal was 2,600 F. The above temperatures can be plotted so that intermediate temperatures can be determined quickly. The above-calculated sand temperatures assume that there is no moisture in the sand. However, in practice there is usually between 3 percent to 5 percent of water in the sand. The evaporation of this moisture will cool the sand still further. For example, at a 10 to l sand to metal ratio the sand, at shakeout temperatures, will be cooled about 53 F. for each 1 percent of moisture evaporated. In most foundries the shakeout temperature is between l,000 F. and 1,300 F. Therefore, in order to have sand at not more than l20 F. as it goes into the muller, the sand to metal ratio at this point must be between to to l and 20 to l. A 10 to l mixture will provide this temperature because about 3 percent of moisture has been evaporated.

The amount of sand actually used to form the mold can be any ratio but common values are a sand to metal ratio of 4 to l to about 6 to 1.

My invention may best be understood in connection with the drawings in which:

FIG. 1 is a diagrammatic view showing the system that l have invented;

FIG. 2 is a plan view ofa divider plow;

HQ 3 is a plan view of a divider hopper;

FIG. 3A is a side view of a divider hopper;

FIG. 4 is a side view ofa rotary divider;

FIG. 4A is a section taken along the lines 4A-4A of FIG. 4;

FIG. Sis a plan view ofseveral mixing plows; and

FIG. 6 is a diagrammatic view ofa sand metering device.

The system that l have found especially useful for practicing the method disclosed in my aforesaid patent application is diagrammatically illustrated in H0. 1. Referring to HO. 1 there is shown a sand hopper 1 for receiving and storing sand. Hopper 1 may be of any conventional type. Hopper l is not necessary for the successful operation of my system and may be eliminated from my system. Connected to the hopper l by any suitable conveyor device is a muller 2. While the muller 2 may be of any conventional type commonly used in the foundry industry, I have found that an especially useful muller is a muller of the continuous type shown in U.S. Pat. No. 3,408,052. A continuous muller is one in which sand is fed continuously into and through the muller. The mulling mechanism may be enclosed in a steel shell and and may consist of several rotatable wheel and plow units. In operation the incoming sand is picked up by the rotating plows and placed in orbit around the periphery of the shell where it is mulled by high-speed rotating muller wheels. Stainless steel baffles in the muller insure that sand does not bypass any of the muller wheels. After the sand is mulled and any desired additives added, it is deposited upon a conveyor belt 3, of any conventional design. The sand moves along the conveyor until it reaches divider plow 4. At this point a major portion of the sand is diverted into a hopper 5. This hopper may be of any conventional design. The minor portion of the sand that is not diverted into the hopper 5 continues along the conveyor 3 until it reaches the molding machine 6, the purpose of which is to form molds from the sand received from the conveyor 3. This molding machine 6 may be of any conventional design. After molten metal is cast into the sand molds, the molds and castings are conveyed to a shakeout machine 7 at which point the castings are separated from the sand molds and the molds broken. The shakeout machine 7 may be of any conventional type. When the sand leaves the shakeout apparatus 7, it will in most instances be very hot, some of it probably approaching a temperature of l,000 F. The hot sand from the shakeout machine 7 is deposited on conveyor 3 which leads back to the hopper I. At a point between the shakeout station 7 and the hopper l the cool sand that has been diverted from conveyor 3 and stored in hopper 5 is discharged in a way more fully described later. The hot sand and cool sand are mixed as they are conveyed along the conveyor 8. Depending upon the amount of cool sand that is mixed with the hot sand the temperature of the resultant mixture may be reduced to approximately room temperature by the time the mixture reaches the hopper 1. It is desirable to mix the cool sand with the hot sand as soon as possible after the castings are removed from the hot sand. By doing so dust which normally tends to pollute the foundrys atmosphere may be greatly reduced.

The apparatus for dividing the sand as it exits the muller is one of the more important aspects of my invention. One such type of apparatus, that I have chosen to call an adjustable divider plow 4, is shown in detail in FIG. 2. This adjustable divider plow 4 consists of a divider plow blade 1155, an adjusting screw 16, and an adjusting screw crank handle 17. The divider plow blade is pivotally secured adjacent one side of the conveyor at its end 18 by any conventional means so that the end B9 of the divider plow 15 that is not pivotally secured may be moved from one side of the conveyor 3 to the other side 21. By moving end 19 of the divider plow 15 from side 20 of the conveyor toward the other side 21, an increasing amount of sand on the conveyor 3 may be diverted into the hopper 5. One end of the adjusting screw 16 is secured to the free end of the divider plow blade 15. The screw is threaded through a bracket 14 mounted adjacent the side 20 of the conveyor 3, and is suitably journaled to the free end 19 of the plow. The divider plow end 19 is caused to move across the conveyor 3 by turning the crank handle 17 which in turn causes the adjusting screw 16 to move across the conveyor 3 carrying with it the end 19 of the divider plow to which it is secured.

Referringnow to FIG. 3 there is shown another apparatus for dividing sand as it passes along a conveyor belt. Sand from the muller 2 is discharged into hopper 22. Hopper 22 may be of any conventional design so long as it has at least two discharge outlets for permitting sand to pass through the hopper. The hopper 22 that is shown in FIGS. 3 and 3A has two gates 23 in the bottom thereof. These gates 23 are vertically adjustable in height so that varying amounts of sand can be discharged through the openings 24 they form. Two conveyor belts 25 and 26 receive the sand that is discharged through the gates 23. One of the conveyor belts is connected to the hopper 5 and the other is connected to the molding machine 6, The amount of sand that passes through the hopper to the molding machine 6 can be controlled either by varying the speed of the conveyors 25 and 26 or by varying the amount of sand that passes through the openings 24 onto the conveyors 25 and 26.

Referring now to FIGS. 4 and 4A there is shown therein another apparatus for dividing sand as it passes along a conveyor belt, As the sand exits the muller 2 it is discharged into a rotary hopper or tank 27. The sand passes through the rotary hopper 27 through openings, not shown, and is discharged upon a rotating disc 28. The disc is rotated by means of shaft 29 that is operably connected to a power source such as an electric motor, not shown. Fixed plows 30 and 31, that may be secured to the bottom of the rotary hopper 11, divert sand from the rotating disc 28 as it rotates onto two conveyors, not shown. One conveyor transports sand to the molding machine 6 and the other conveyor transports sand to the hopper 5. The length of the plows 30 and 3] extending over the rotating disc 28 determines how much sand is diverted onto the conveyor belts. Plow 31 shown in FIG. 4A diverts more sand onto the conveyor than does plow 30.

After the cool sand is diverted into the hopper 5 it must be discharged by some means onto the conveyor 8. An ordinary metal chute, not shown, could be used. However, it is desirable to provide a device that will regulate the amount of sand discharged according to the amount that is being conveyed along the conveyor 8. Such a metering device is shown in FIG. 6. The metering device shown in FIG. 6 includes a wheel 32 that is pivotally connected to a wheel arm 33. Wheel arm 33 is attached to a conventional electric switch 34 which in turn is operably connected to solenoid 35. Solenoid 35 when activated causes a valve 36 to move gate 37 on hopper 5. When the gate 37 is opened, sand is discharged from hopper 5 onto conveyor 8. It may be useful in some instances to include in such a device means that vary the amount of sand discharged from the hopper 5 according to the height of the sand of the conveyor 8.

In some instances it may be desirable to take steps to mix the cool sand deposited on conveyor 8 with the hot sand. A device for accomplishing this is shown in FIG. 5. The device consists of a plurality of mixing plows 38 which extend at acute angles above the conveyor 8 so that as the sand passes by the plows it is diverted first from one side to the belt and then to the other. Accompanying this diversion is a mixing of the sand. Also, a conventional aerator could be used at this point for this purpose. Such a device is shown and described at page 94 of the aforesaid Foundry" magazine.

If desired, the hopper 5 may be entirely eliminated and the sand from conveyor 3 may be deposited directly onto the conveyor 3.

The sand-handling capacities of some of the equipment in my system will, of course, be greater than other pieces of equipment. For instance, referring to FIG. l, the portion of the conveyor 3 between the divider plow 4 and the muller 2 must convey more sand than the remaining portion of the conveyor 3. If desired then, to reduce the cost of the system, conveyor 3 can consist of two conveyors, one having a greater capacity than the other. Also, the conveyor 8 can be divided into two conveyors in the same manner since the part of the conveyor from the shakeout machine 7 to the point of the cool sand addition handles less sand than the portion of the conveyor 8 which conveys sand from the cool sand addition point to the hopper 1. It may also be necessary in some installations to increase the number of mullers 2 and/or the muller output over what is conventionally employed.

Having thus described my invention, I claim:

l. A foundry system for mulling, handling, molding and cooling foundry sand while substantially reducing foundry pollution, comprising in combination;

a sand muller for mulling said foundry sand,

forming and casting means for forming said foundry sand into molds and casting metal into said molds,

shakeout means for separating said castings and said molds,

means for dividing sand into a minor and major portion after it has been mulled in said muller,

first sand conveyor means for conveying sand from said muller to said divider means,

second sand conveyor means for conveying said minor portion of sand from said divider means to said forming and casting means,

third conveyor means for conveying said sand molds and castings from said forming and casting means to said shakeout machine,

fourth conveyor means for conveying said sand from said shakeout means to said muller, and

fifth sand conveyor means for conveying and depositing said major portion of sand from said sand divider means onto said fourth conveyor means, said fifth conveyor means disposed so as to deposit-said major portion of sand substantially adjacent said shakeout means onto said fourth conveyor means.

2. The foundry system of claim I wherein said means for dividing sand into a major and minor portion includes;

a conveyor belt connected to said muller, and

a divider plow moveable across said conveyor belt.

3. The foundry system of claim 1 wherein said means for dividing sand into a major and minor portion includes;

a sand hopper;

said first conveyor means adapted for conveying sand from said muller into said sand hopper,

said sand hopper having a plurality of openings in the bottom thereof for releasing sand therethrough onto said second and fifth sand conveying means, and

means for regulating the amount of sand released through said openings.

4. The foundry system of claim 1 wherein said means for dividing sand into a major and minor portion includes;

a sand hopper;

said first conveyor means adapted for conveying sand from said muller into said sand hopper,

said sand hopper having a plurality of openings in the bottom thereof for releasing sand therethrough onto said second and fifth sand conveying means, and

means for varying the speed of said second and fifth sand conveying means.

5. The system of claim 1 wherein said means for dividing sand into a major and minor portion includes;

a sand hopper,

said first conveyor means adapted for conveying sand from said sand muller into said hopper,

said hopper having at least one opening in the bottom thereof and a plurality of plows secured to said bottom, and

a rotating disc with divider plows positioned below the opening in said hopper.

6. The system of claim 1 wherein said first and fourth conveyor means have a sand handling capacity of at least 3 times greater than the sand handling capacity of said second conveyor means.

7. The system of claim 1 wherein said fourth conveyor means includes means for mixing together said minor and major portions of sand.

8. The system of claim 1 wherein sand storage means are connected with said fifth conveyor means.

Claims (8)

1. A foundry system for mulling, handling, molding and cooling foundry sand while substantially reducing foundry pollution, comprising in combination; a sand muller for mulling said foundry sand, forming and casting means for forming said foundry sand into molds and casting metal into said molds, shakeout means for separating said castings and said molds, means for dividing sand into a minor and major portion after it has been mulled in said muller, first sand conveyor means for conveying sand from said muller to said divider means, second sand conveyor means for conveying said minor portion of sand from said divider means to said forming and casting means, third conveyor means for conveying said sand molds and castings from said forming and casting means to said shakeout machine, fourth conveyor means for conveying said sand from said shakeout means to said muller, and fifth sand conveyor means for conveying and depositing said major portion of sand from said sand divider means onto said fourth conveyor means, said fifth conveyor means disposed so as to deposit said major portion of sand substantially adjacent said shakeout means onto said fourth conveyor means.

2. The foundry system of claim 1 wherein said means for dividing sand into a major and minor portion includes; a conveyor belt connected to said muller, and a divider plow moveable across said conveyor belt.

3. The foundry system of claim 1 wherein said means for dividing sand into a major and minor portion includes; a sand hopper; said first conveyor means adapted for conveying sand from said muller into said sand hopper, said sand hopper having a plurality of openings in the bottom thereof for releasing sand therethrough onto said second and fifth sand conveying means, and means for regulating the amount of sand released through said openings.

4. The foundry system of claim 1 wherein said means for dividing sand into a major and minor portion includes; a sand hopper, said first conveyor means adapted for conveying sand from said muller into said sand hopper, said sand hopper having a plurality of openings in the bottom thereof for releasing sand therethrough onto said second and fifth sand conveying means, and means for varying the speed of said second and fifth sand conveying means.

5. The system of claim 1 wherein said means for dividing sand into a major and minor portion includes; a sand hopper, said first conveyor means adapted for conveying sand from said sand muller into said hopper, said hopper having at least one opening in the bottom thereof and a plurality of plows secured to said bottom, and a rotating disc with divider plows positioned below the opening in said hopper.

6. The system of claim 1 wherein said first and fourth conveyor means have a sand handling capacity of at least 3 times greater than the sand handling capacity of said second conveyor means.

7. The system of claim 1 wherein said fourth conveyor means includes means for mixing together said minor and major portions of sand.

8. The system of claim 1 wherein sand storage means are connected with said fifth conveyor means.

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