US2314486A - Apparatus for cooling sand mullers - Google Patents

Description

Filed Sept. 14, 1942 5 K 3 g N E N Vs. Q m

Patented Mar. 23, 1943 UNITED STATES PATENT 'OFFlCE APPARATUS FOR COOLING SAND MULLERS James J. Dvorak, Chicago, 111., assignor to Herbert S. Simpson, Evanston, Ill.

Application September 14, 1942, Serial No. 458,302

3 Claims.

This invention relates to an apparatus for cooling sand mullers.

With the advent of the present war and the tremendous increase in the production of foundry castings, it becomes necessary to speed up the reconditioning of molding sands so that the same may be re-used with as little delay as is possible. As a consequence, the molding sands are delivered from the molds while in a still hot condition to the conditioning or mulling apparatus, thereby making it desirable for the subsequent treatment to take into consideration the fact that the sand is in a hot condition.

Specifically, this invention pertains to. the treatment or conditioning of molding sand and other granular material such as is used in foundries and like establishments and has to deal more particularly, during the'reconditioning or mulling of hot molding sand, with the reducing of the temperature present by an air exhaust apparatus rather than by an air pressure apparatus. The difllculty with the so-called pressure cooling arrangement resides in the fact that the pressure blower acts not only to blow particles of sand being treated out of the machine and into the bearings and working parts of the machine, but furthermore causes sand to cake on the walls of the treating chamber and in the pipes leading therefrom. Y

An object, therefore, of this invention is to provide an improved apparatus for reconditioning hot molding sands.

More specifically, this invention contemplates mulling and mixing hot molding sand to recondition the same in a confined area and at the same time exhausting air from the confined area and particularly from above the sand being mulled, whereby to cause effective cooling of the sand and the removal of hot gases and steam from the confined area without passing the air through the sand.

In accordance with the general features of this invention, there is provided an improved and simplified apparatus for treating or conditioning hot molding sand including the mulling and mixing of the sand with bonding and moistening materials, and cooling the mixture while being treated, by drawing air by suction into a confined area in which the sand being treated is disposed to cool the sand in such a way as to obviate caking of the sand and other deleterious effects such as exist when positive air blasts are employed.

In accordance with other features of this invention, there is provided an improved and simplified apparatus for treating or conditioning molding sand which involves mulling and mixing the sand and applying liquid thereto in predetermined proportions and, during the mulling and mixing operations, causing cooling of the mixture by Pulling or drawing atmospheric air into a confined area in which the sand is disposed but not through the sand being mulled.

A further feature of the invention relates to the provision of a foundry sand mulling and mixing machine including a closed crib or container containing power operated plowing and mixing mechanisms and liquid supply means, with said crib arranged for atmospheric air intake by means of a regulatable suction or exhaust mechanism connected with the crib for drawing atmospheric air into and through the crib to cool the sand mixture while it is being conditioned prior to discharge from the crib in a moldable condition for foundry use but without passing the air through the sand.

An additional and further feature of the invention relates to the drawing of air by suction from a point adjacent the bottom of a sand mulling chamber upwardly over the mass or body of sand being mulled and then out of the chamber, whereby the air is not caused to pass through the sand but is, in reality, deflected upwardly by the body of sand along with any steam or hot gases generated during the mulling and conditioning operation. A

Other objects and features of this invention will more fully appear from the following detailed description taken in connection with the accompanying drawing, which illustrates several embodiments thereof, and in which:

Figure 1 is a somewhat diagrammatic side elevation of a structure embracing the invention, which elevation is partly broken away and which also includes some parts shown in section; and

Figure 2 is a fragmentary, sectional view corresponding to the left-hand portion of the mulling chamber shown in Figure 1 illustrating a modified construction for introducing air in the chamber under the impelling action of a suction fan.

As shown on the drawing:

It should be noted at this time that the muller per se of the apparatus illustrated does not constitute a part of the present invention since it is of a construction old in the art. This invention, as noted before, is particularly concerned with the apparatus for treating with air the sand or other materials being conditioned and in such a manner that this air treatment properly cooperates with the mulling operation.

The conditioning machine comprises foundation or supporting block I having supported and secured on the top thereof supporting legs 2, on which the bottom or base 3 of a container or crib 4 is supported. Supported on the top of the container or crib 4 is a hood or cylindrical shell 5 having a removable closure top 6. Mounted on the bottom of the crib base3 is a driving motor I which is coupled with suitable driving gears disposed within a gear housing 8 also supported on the bottom of the crib base 3. Projecting upwardly into the crib 4 is a turret 9 within which a vertical driving shaft is journaled to receive a drive from the gear mechanisms within the gear housing 8. Supported on the upper projecting end of the vertical driving shaft is a spider or rotatable head In in which a stub shaft I I is Journaled. Supported on one end of the shaft II is a pivoted arm or bracket, on the free end of which a solid wheel or muller I2 is rotatably supported. Several of the mullers, as is well known, may be used if desired. With the rotation of the vertical driving shaft and the spider Ill supported thereon, the muller I2 is caused to travel around within the crib 4 to track over a body or sand S disposed on the inner surface of the crib base or bottom 3. As is understood in the muller art. when material or sand is disposed within the crib on the bottom 3, the muller l2 will rise and fall as the periphery thereof travels over the material which is being treated.

Supported on the rotatable spider or head I!) and projecting radially from one side thereof is a bracket or arm l3 having a downwardly extend ing arm or support l4, on the lower end of which a plow or deflector I5 is secured to travel over the inner surface of the crib bottom 3 and over the lower portion of the inner wall of the crib 4.

Supported on an extension I1 on the rotatable spider or head [0 is the pipe union 3 having liquid supply pipes or tubes l9 projecting outwardly anddownwardly therefrom. Engaged on the lower end of the liquid supply pipes or tubes l9 are spray heads or nozzles 20. The pipe union I8 is connected with a suitable coupling 2| to which a liquid supply pipe 34 is connected. The pipe 34 projects upwardly through a suitable opening in the closed top 6 of the crib. By means of the sprinkler system just described, the liquid spray nozzles are adapted to move through a circular path and spread a liquid such as water or the like into the crib 4 over the sand and other materials which are to be mulled and mixed within the crib 4.

In the conditioning of foundry sand, for example, the sand which is deposited in the crib 4 may be previously used, cleaned, reclaimed sand which is usually hot or the sand deposited in the crib usually becomes hot from the mulling and mixing treatments to which it is subjected within the crib. If other materials, such as the ingredients necessary for the production of a battery pas or the like, are being treated in the crib 4, there is usually suflicient chemical reaction taking place to cause heating of the materials aided by the treatment of the material by the mulling and mixing devices within the crib.

Due to the heating of the materials being treated within the crib, as well as the hot gases and steam emanating from the same, it is therefore desirable to provide a means for cooling the contents of the crib during the mulling and mixing treatment of the sand or during the mixing of pastes such as battery pastes or the like. To obviate the tendency of the materials to cake on the walls of the crib and hood of the machine and to obviate the clogging up of the operating mechanisms within the crib and hood which usually results when air is forced under pressure through the materials, the crib 4 is provided at one side with an opening 22 above the materials or sand S and over which the upper end of an atmospheric air intake tube or duct 23 is engaged. The tube or duct 23 is directed downwardly adjacent one side of the exterior of the crib and has the lower end thereof open to the atmosphere.

Associated with the inlet opening 22 is an in clined baffle secured to the crib for directing the incoming air stream, as shown by the arrows, downwardly toward the top of the mass S.

Connected to an upper side of the machine opposite from the side on which the air intake duct or tube 23 is engaged and covering an outlet opening in the, shell or hood 5 is a damper hood or box 24. Mounted in the damper hood or box 24 are one or more control blades or damper plates 25 which are supported on a vertical shaft 26, on the upper end of which a control bar or wheel 21 is engaged for turning the damper plates 25 into selwted positions of adjustment for regulating the suction or exhaust of the cooling air from the mulling and mixing chamber of the machine. Connected with the damper hood or box 24 is an exhaust flue 28 which connects up with a high volume exhauster or suction fan 29, which is provided with a discharge flue or pipe 30. The exhauster or suction fan 29 is driven by means of a belt 3| operated by a driving motor 32 which, together with theexhauster or suction fan, is mounted on a suitable platform or support 33.

' When foundry sand is to be conditioned within the machine crib 4, the cover 6 is removed and fresh sand or hot, reclaimed, clean sand S is deposited within the crib together with the required quantity of bonding agents, such as clay, cereal binders, pitch, cement, oil, etc., which are then tempered with suflicient water to develop the strength of the binders so that, when the mixture is thoroughly mulled and mixed, it will be rendered' in a moldable condition ready to be delivered to a foundry in a properly cooled state ready to be used in the making of molds, cores, and the like. The arrows designate the path of the air stream flowing through the machine and show that such air does not pass through the relatively compact mass of sand S being mulled.

In addition to using the described apparatus or machine for conditioning foundry sand, the machine may be used for accomplishing an improved apparatus for the making of a paste such as a battery paste for the making of battery plates. The practice followed for the proper formation and cooling of a battery paste comprises depositing finely divided material such as lead oxide in the crib 4 and then adding, in

predetermined proportions, suitable quantities I of liquid such as sulphuric acid, and then mulling and mixing the ingredients by means of the muller l2 and the plows l2 and IS. The reaction between the sulphuric acid and the lead oxide produces heat during the mixing treatment which, by the use of the high volume exhauster or suction fan 29, causes atmospheric air to be continuously drawn into the mixing chamber through the intake tube or duct 23 to pass over the ingredients being mulled and mixed to withdraw the heat of reaction out through the damper hood 24 to be discharged in controlled quantities for regulating the cooling temperature of the paste being prepared in the machine.

In the mulling and mixing of the materials 8 on the bottom 3 of the apparatus, these mate- I rials are maintained in a relatively solid mass so as to enable an efiicient rubbing and intermixing of the materials during the course of the mulling and agitating operation. It has been found that better results are secured in so handling such materials rather than throwing them into a suspended state or condition.

Consistent with this desirable end in the mullingoperation, there is provided in accordance with the features of this invention, as is now evident from the foregoing detailed description, an air circulatory system which circulates a body or a stream of air sufilcient in volume to carry away heated gases and steam generated during the mulling operation, as well as to cool by conduction rather than by aeration the relatively solid and compact mass of materials S being mulled at the bottom of the machine. Such a cooling treatment has been found to be very desirous since it precludes the entrapment of substantial quantities of said particles in the flowing stream of air such as would cause caking and clogging and also such as would deleteriously affect the moving parts of the air circulatory apparatus. Thus, contrary to previous practices, I expressly provide a cooling arrangement which is enabled to cool the sand or materials by direct conduction rather than by forced aeration of the sand and which permits of a sweeping across of the entire upper side of the mass of said with a sufilcient volume of air to cool agitated mass of materials. Particularly good results have been secured with the arrangement shown in Figure 1, wherein theair inlet is 'adjacent the bottom 3 of the mulling chamber but enters the chamber slightly above the mass of materials or sand S.

In Figure 2, I have illustrated a modification of the invention which differs from that shown in Figure 1 only in that the air inlet, instead of being at the bottom of the chamber, comprises a downwardly extending pipe 23',,which passes through the hood 6' of the mulling machine. The lower end of this pipe defines an inlet opening 22' to which air is drawn into the mulling chamber above the relatively compact mass of sand S. With this exception, the form of the invention shown in Figure 2 operates in substantially the same manner as that previously described.

In an actual installation made embodying the present invention for treating hot molding sands, the following observations were made.

' The cooling hood 5 was constructed with a plenum chamber in the top to distribute the air evenly to the duct permitting a volume 01 air at high velocity to be delivered into the mixer at a point near the bottom at an average vequite rapidly the I locity of 1000 F. P. M. around the entire periphery of the hood.

The theory of sand cooling by the use of this hood is based on the principles of thermodynamics whereby water is added to the sand to absorb the heat. This water in contact with the hot sand vaporizes and circulated air is used as a carrier to absorb and remove the water vapor. It will be understood that the warmer the air circulated the quicker the sand cooling for absorption of the vapors. It should be further will be effected because, of the increased capacity understood that there is a point where further addition of water would not be beneficial. After this point is reached, the remaining temperature drop is caused by the air stream passing over the agitated sand.

The formula used in adapting this heat transfer principle to a muller is as follows:

The specific heat of the sand, or .2, multiplied by the weight of the batch, multiplied by the temperature differential desired between the incoming and outgoing sand, equals the number of B. t. u.s to be removed. Since it requires 1100 B. t. u.s to evaporate a pound of water at atmospheric temperature, the total B. t. u.s divided by the constant 1100 gives the pounds of water to be evaporated for cooling. (To this water which will be vaporized, additional water must be added for the desired finished moisture content of the sand.)

Nextly, the total number of grains of water to be evaporated is determined by multiplying the pounds of water by 7,000, which is the number of grains per pound of water. The number of pounds of air which will be necessary to absorb and remove the evaporated water can then .be determined by dividing the total grains of water by 250, which is the number of grains of water that 1 pound of air will absorb at F. and average humidity.

The number of cubic feet of air required to absorb the desired amount of water may then be determined by multiplying the number of pounds of air by 14.10, which represents the number of cubic feet per pound of air at 100 F.

Knowing the number of cubic feet of air required, it is then possible to determine the cubic feet of air per minute which will be required to effect the desired cooling. Then the cubic feet of air required is divided by the mixing time in S -=.2 or specific heat of sand W =Weight of sand batch T-1=Temperature of sand entering mixer T-2=Temperature of sand leaving mixer A =1100 B. t. u.s or heat units required to evaporate 1 pound of water B =Pounds of water required for desired cooling 0 .=7000, or number of grains per pound of water D =Total number of grains of water to be evaporated E =250, or grains of moisture absorbed per pound of air at 100 F. I F =Pounds of air required to remove D G =14.10, or cubic feet of air per pound at 100 F. H =Total cubic feet of air required for desired cooling J =Mixing time in number of minutes K =Cubic feet of air required per minute To find B- SX W'X(T1X.T2/1100) :3 To find D- B C'=D To find F- D/E=F 'To find -H FXG=H T0 find K--.

HIJ=K It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention, and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. In an apparatus for mulling and agitating material such as hot molding sand used in foundries and which apparatus includesa mulling chamber adapted to have disposed on the bottom thereof a relatively compact mass of material to be mulled, air inlet means for the chamber disposed above and directly over the top level of the mass of material being mulled, and suction means connected to the chamber for continuously drawing a stream of air in said inlet over the top of the material whereby to withdraw heat by conduction from the material as well as to withdraw from the mulling chamber heated gases and steam without such air passing through the material.

2. In an apparatus for mulling and agitating material such as hot molding sand used in foundries and which apparatus includes a mulling chamber adapted to have disposed on the bottom thereof a relatively compact mass of material to be mulled, air inlet means for the chamber disposed above the top level of the mass of material being mulled, and suction means connected to the chamber for continuously drawing a stream of air in said inlet over "the top of the material whereby to withdraw heat by conduction from the material as well as to withdraw from the mulling chamber heated gases and steam without such air passing through the material, said air inlet comprising a lateral oflset conduit ad- Jacent the bottom of the mulling chamber and communicating'with the interior of the chamber in a plane directly above the top of the material being mulled.

3. In an apparatus for mulling and agitating material such as hot molding sand used in foundries and which apparatus includes a mulling chamber adapted to have disposed on the bottom thereof a relatively compact mass of material to be mulled, air inlet means for the chamber disposed above the top level of the mass of material being mulled, and suction means connected to the chamber for continuously drawing a stream of air in said inlet over the top of the material whereby to withdraw heat by conduction from the material as well as to withdraw from the mulling chamber heated gases and steam without such air passing through the material, said air inlet comprising a lateral oifset conduit adjacent the bottom of the mulling chamber and communicating with the interior of the chamber in a plane above the top of the material being mulled, said suction means being connected to the mulling chamber on a side opposite to that of the inlet and adjacent' the top of the mulling chamber.

JAMES J. DVORAK.

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