US3406950A

US3406950A - Apparatus for conditioning material

Info

Publication number: US3406950A
Application number: US502923A
Authority: US
Inventors: Robert L Mcilvaine
Original assignee: National Engineering Co
Current assignee: National Engineering Co
Priority date: 1965-10-23
Filing date: 1965-10-23
Publication date: 1968-10-22
Anticipated expiration: 1985-10-22
Also published as: DE1508698B1; SE319271B; BR6683605D0; GB1158062A

Description

Oct. 22, 1968 R. L. M ILVAINE APPARATUS FOR CONDITIONING MATERIAL 3 Sheets-Sheet 1 Filed Oct. 25, 1965 rlllll'l'nll I II llll INVENTOR ROBERT L. MclLVAlNE M IQMM , ATTORNEXS Oct. 22, 1968 R. L.. M ILVAINE APPARATUS FOR CONDITIONING MATERIAL 5 Sheets-Sheet 2 Filed Oct. 23, 1965 Wya.

ROBERT L. MOILVAINE M, BY E: z t

ATIORNEYS 1968 R. 1.. MCILVAINE 3,406,950

-APPARATUS FOR CONDITIONING MATERIAL 5 Sheets-Sheet 5 Filed Oct. 23, 1965 60 /a mv ENTOR 4 ROBERT L. MCILVAINE 148 M, kvwm,

ATTORNEYS,

two operations.

United States Patent 01 lice Patented Oct. 22, 1968 3,406,950 APPARATUS FOR CONDITIONING MATERIAL Robert L. Mcllvaine, Winnetlra, Ill., assignor, by mesne assignments, to National Engineering Company, Chicago, Ill., a corporation of Delaware Filed Oct. 23, 1965, Ser. No. 502,923 16 Claims. (Cl. 259151) ABSTRACT OF THE DISCLOSURE Apparatus for conditioning particulate material and the like comprising a mixing chamber, means for supplying material to said chamber and means for discharging material from an opposite portion of said chamber. The chamber includes a floor and a peripheral sidewall sloping upwardly and outwardly therefrom and a mixing head assembly rotatable about an axis upstanding from the chamber floor. The mixing head assembly includes one or more plows supported outwardly of the axis of rotation which traverse a path adjacent the sloping sidewall. An air supply chamber is located beneath the sloping sidewall, and outlet means are formed below the lower edge of the side for directing airflow inwardly from the air supply chamber into the material in said chamber.

The present invention relates to a new and improved apparatus for conditioning material and, more particularly, to a new and improved apparatus for conditioning material, such as molding sand and the like for use in foundry operations.

With the advent of new and automated foundry mold making equipment, it is necessary to supply large quantities of sand having uniform molding properties. In order to achieve the required uniformity in molding characteristics, the sand must be conditioned in an accurately controlled manner wherein the moisture content and temperature are maintained within selected limits. In almost all foundries, the molding sand is used over and over again and is reconditioned after the mold shake-out operation in preparation for reuse in subsequent mold making operations. The sand received from the shake-out operation is hot and relatively dry, and must be cooled and moistened to the desired degree. In addition, lumps in the sand must be broken down and binding materials added so that the sand is finally conitioned to a semiplastic, fluffy state required for molding.

Preferably, conditioning of the sand is accomplished in The sand, as received from the shake-out station, is first cooled to a predetermined temperature, and the moisture content thereof is brought within a predetermined range. The sand is then subjected to intensive mulling and mixing action and the necessary binder is added along with the addition or removal of moisture to obtain the desired semiplastic or fluffy condition. The present invention relates to apparatus for initially conditioning the sand which is then finally delivered to a mulling machine, preferably of the type shown in United States Patents Nos. Re. 25,475 and 2,727,696 for final conditioning prior to use in mold filling operations.

Accordingly, it is a general object of the present invention to provide a new and improved apparatus for conditioning material.

More specifically, it is an object of the present invention to provide a new and improved apparatus for treating material, such as foundry sand and the like, wherein the material is cooled to a predetermined temperature and the moisture content thereof is brought within a selected range.

Another object of the present invention is the provision of a new and improved apparatus for conditioning material as described in the preceding paragraph, wherein continuous mixing and aeration of the material is accomplished during the conditioning treatment.

Another object of the present invention is the provision of a new and improved apparatus for conditioning material as described above, employing multiple stages and operating in a continuous manner rather than a batch system.

Another object of the present invention is the provision of a new and improved apparatus for conditioning material employing a mixing chamber having upwardly and outwardly sloping walls and a rotary plow system whereby the material flows more freely in reaction to the plow forces and is more thoroughly mixed and agitated, yet less power is required to operate the plows.

Another object of the present invention is the provision of a new and improved apparatus for conditioning material employing novel means for feeding and cooling the material flowing into the apparatus.

Another object of the present invention is the provision of a new and improved apparatus for conditioning material wherein clearances are provided between the moving plows and the mixing chamber walls, thereby greatly reducing wear yet still providing thorough mixing action.

Yet another object of the present invention is the provision of a new and improved apparatus for conditioning material employing multiple stages wherein excess moisture is added to the material for evaporative cooling in an initial stage, and continuous agitation and aeration are employed in the following stage for further cooling of the material.

Still another object of the present invention is the provision of a new and improved apparatus for conditioning material including a mixing chamber adapted to continuously receive material at one end and discharge the material at the other end after thorough conditioning of the material as it is moved through the chamber to discharge.

Briefly, the foregoing and other objects and advantages of the present invention are accomplished by the provision of a new and improved apparatus for conditioning material comprising a mixing chamber having a floor and an outwardly and upwardly sloping sidewall. A mixing head assembly is mounted for rotation in said chamber about an axis upstanding from said floor, and the head assembly includes one or more mixing plows outwardly of the axis movable in a path overlying the sloping wall of the chamber. An air supply chamber is provided beneath the sloping wall of the mixing chamber for supplying air to the material through outlets positioned be tween the floor and the lower edge of the sloping wall. As the mixing plows move around the chamber toward the sloping sidewall, material is moved upwardly and outwardly along the wall in advance of the plow and then slides downwardly and inwardly after the plow has passed. The inwardly and downwardly moving material moves directly in front of the air chamber outlets, and the material is thoroughly aerated as it returns to the floor of the mixing chamber.

Another aspect of the invention comprises the material feeding apparatus which is associated with a mixing head assembly and includes an annular distributing member concentric with the axis of rotation of the head assembly for feeding a thin annular stream of material into the mixing chamber. The material in the annular stream is moistened by water supplied from an annular manifold positioned to direct a water spray thereon. The moistened material is cooled by evaporative cooling as the material is agitated by the mixing plows and subjected to the cooling air supplied from the air chamber outlets. The hot, moisture-laden air is carried out of the mixing chamber by an exhaust system and the material is further conditioned in a second stage by another rotating mixing head assembly similar to the first before eventual discharge from the mixing chamber.

For a better understanding of the invention, reference should be had to the following detailed description taken in conjunction with the drawings, in which:

FIG. 1 is a horizontal sectional view of a new and improved material conditioning apparatus constructed in accordance with the present invention taken substantially along line 1-1 of FIG. 2;

FIG. 2 is a vertical sectional view along line 2-2 of FIG. 1;

FIG. 3 is a transverse sectional view of the apparatus of FIG. 1 taken substantially along line 3-3 of FIG. 4; and

FIG. 4 is a top plan view of the apparatus of FIG. 1 with portions in section taken substantially along line 44 of FIG. 2.

Referring now to the drawings, therein is illustrated a mixer constructed in accordance with the present invention. The mixer 10 is adapted to receive a continuous flow of material, such as foundry sand, and condition the sand by mixing, cooling, and aeration in preparation for a final stage or conditioning process performed in another machine, preferably a muller of the type disclosed in the aforementioned United States patents.

The mixer 10 includes a mixing chamber 12 having a pair of spaced-apart, rotary, mixing

head assemblies

14 and 16 mounted for rotation therein. Material to be conditioned by the mixer is introduced into the chamber 12 adjacent the mixing head assembly 14 through a material feeding system 18 and is conditioned by the mixing head assembly 14 until picked up by the mixing head assembly 16. The mixing head assembly 16 further mixes the material and, eventually, the material passes out of the mixing chamber through a discharge gate assembly 20. The material is cooled and aerated as it is mixed in the chamber 12, and cooling air is supplied through an inlet air duct 22 for distribution through a manifold system and discharged into the material. The chamber 12 is enclosed by a hood structure 24 and moisture-laden, heated air is continuously removed from the chamber through an exhaust system 26. In addition to the cooling action of the air supplied from the duct 22, the temperature of the material in the mixing chamber is also lowered by evaporative cooling and the water required for the evaporative cooling is supplied by a water supply system 28 adjacent the material feeding system 18.

Referring now, more in detail, to the mixing chamber 12, it includes a floor or bedplate 30 supported on a framework 32 formed of side channel members 34 (FIG. 3), end channel members 36 (FIG. 2), and a plurality of cross beams 38 (FIG. 2). The framework 32 is preferably fabricated by welding, and is supported from the floor or other surface by a plurality of legs 40. Around the periphery of the floor 30, the mixing chamber is provided with a short, vertically upstanding sidewall 42. The sidewall 42 extends upwardly above the floor 30 for a short distance (FIGS. 2 and 3) and is continuous around the peripheral edge of the floor 30 except in the region occupied by the discharge gate assembly 20.

It can be seen from FIG. 1 that the mixing chamber floor 30 is generally rectangular in shape, with chamfered corners. Accordingly, the upstanding sidewall 42 comprises a pair of relatively short end sections 42a at 0ptaken substantially posite ends of the chamber, a long sidewall section 42b on the side opposite the discharge gate assembly 20, a shorter two-piece sidewall section 420 on the same side as the discharge gate assembly, and four corner or chamfering sections 42d.

The mixng chamber 12 also includes an upwardly and outwardly sloping main sidewall 44 comprising a plurality of planar sections. The sloping sidewall 44 is much greater in vertical dimension than the wall 42 and is continuous around the periphery of the mixing chamber 12 except in the region of the discharge gate assembly 20. The sidewall 44 extends upwardly from the top edge of the sidewall 42 and slopes outwardly at approximately a 60 angle to the horizontal. Preferably, the sidewall is constructed from flat, planar sections of steel plate and comprises opposite end sections 44a,

side sections

44b and 44c, and chamfered corner sections 44d, corresponding to adjacent sections of the lower sidewall 42. Because the sidewalls of the mixing chamber are constructed of these flat planar sections rather than a continuous rolled or curved wall, fabrication costs are reduced considerably. Sharp pockets or corners are eliminated by the chamfered corner sections 44d, and unclesirable collections or deposits of material are reduced or eliminated even though planar wall sections, rather than curved walls, are utilized. Preferably, the sections are joined to one another by welding, and the lower peripheral edge of the wall 44 is welded to the upper edge of the short wall 42.

The main sidewall section 440 and lower sidewall section 420 are discontinuous in the area occupied by the discharge gate assembly 20. The gate assembly includes a pair of upstanding end walls 46, an outer sidewall 48, and a top wall or cover which form a discharge enclosure. The

sidewall sections

42c and 440 are split into two pieces and each piece abuts against one of the end walls 46 of the discharge enclosure and, preferably, is joined thereto by welding.

The sidewall 44 forms the upper wall of an air supply chamber or manifold 52 which extends around the perimeter of the mixing chamber 12 except for the region occupied by the discharge gate assembly 20. The manifold 52 includes a bottom wall 54 and a vertical, outer sidewall 56 which is formed in

planar sections

56a, 56b, 56c, and 56d corresponding to the sections of the adjacent sidewall 44 of the mixing chamber. Preferably, the sidewall 56 and mixing chamber sidewall 44 are joined together at their upper edges by welding, and the lower edge of the sidewall 56 is likewise welded to the outer edge of the bottom wall 54. The inner edge of the bottom wall 54 is joined to the lower edge of the lower vertical sidewall 42 of the mixing chamber 12 and thus the air manifold 52 is somewhat trapezoidal in cross section, as illustrated in FIGS. 2 and 3.

Cooling air is supplied to the manifold 52 from the inlet air duct 22 which is joined to the sidewall 56b. Air entering the manifold through the duct 22 flows in opposite directions around the perimeter of the mixing chamber until reaching the end walls 46 of the discharge gate assembly 20, as indicated by the arrows in FIGS. 1 and 4. Cooling air is directed inwardly into the bed of material on the floor 30 through a plurality of narrow, horizontally extending slots or outlets 58 provided in the lower sidewall 42 of the mixing chamber. The slots 58 are formed along the upper edge of the wall 42 just below the lower edge of the sloping wall 44 and are relatively narrow in vertical dimension and long in horizontal width so that the air flowing from the manifold 52 into the mixing chamber is accelerated into fiat, thin, high velocity streams. The sloping wall 44 serves to direct the airflow in a downward direction as it moves through the outlet slots 58 and, accordingly, the airstreams penetrate I the material in the mixing chamber with a considerable downward velocity component.

In order to smoothly accelerate the cooling air to reach a maximum velocity as it passes through the outlet slots 58 into the mixing chamber, the manifold 52 is provided with an interior bafile 60 which is continuous around the periphery of the mixing chamber except for the area occupied by the discharge gate assembly 20. The inner edge of the bafile 60 is joined to the wall 42 at a level even with the lower edge of the outlet slots 58, and the baffle slopes upwardly and outwardly away from the wall 42, as shown in FIGS. 2 and 3. The baflle is formed by a plurality of

planar sections

60a, 60b, 60c, and 60d corresponding to the adjacent sections of the wall 42, and the outer edges of the baflie sections are supported by a vertical partition 62 which is also formed of

sections

62a, 62b, 62c, and 62d corresponding thereto.

Adjacent facing sections of the mixing chamber sidewall 44 and the baflie 60 form convergent nozzle sections in whichthe cooling air from the manifold 52 is smoothly accelerated and directed inwardly and downwardly through the outlet slots 58 into the material bed on the mixing chamber floor 30. Because of the high velocity of the air flowing through the slots 58, plugging or clogging of the slots with material presents no problems and, should the air supply to the manifold 52 be interrupted, the upward slope of the bafiie 60 prevents any appreciable amount of material from flowing outwardly through the slots into the manifold.

The mixing

head assemblies

14 and 16 are supported from the mixer floor 30 and are rotatable about upstanding, spaced-apart, vertical axes 14a and 16a, respectively. Preferably, the mixing head assemblies are identical, and each includes an upstanding cylindrical casing 64 having an annular base flange 64a which is seated within an opening 30a in the mixing floor 30. A heavy supporting ring 66 is provided beneath each of the openings 30a in the mixer floor, and the rings 66 have a recessed shoulder therein for receiving the flanges 60a so that the upper surfaces thereof are flush with the upper surface of the floor 30. Each supporting ring 66 provides support for a gear reducer 68 secured to the underside thereof, and the gear reducers are driven from a common drive shaft 70 coupled to the input shaft of the reducer by coupling assemblies 72.

The shaft 70 is supported from the underside of the framework 32 by a pair of bearings 74, each carried on a depending channel-shaped support bracket 76, as illustrated in FIG. 2. The shaft 70 is driven by a motor 78 or other prime mover through a belt drive assembly 80. Each gear reducer 68 includes an upstanding output shaft (not shown) which is coupled to a drive shaft 82 of its respective head assembly. The drive shafts 82 are supported for rotation within the cylindrical turret casings 64 and project upwardly therefrom. Each of the mixing head assemblies includes a crosshead 84 mounted on the projecting upper end of its drive shaft 82. The crosshead 84 of each mixing head assembly supports two pairs of oppositely outwardly extending

arms

86a, 86b, 88a, and 88b, respectively. The

arms

86a and 86b of each crosshead extend generally normal to the

arms

88a and 88b thereof and the crossheads of the mixing

head assemblies

14 and 16 are arranged on their respective support shafts 82 so that the arms of one crosshead will move in selected synchronous relation between the arms of the other, as will be described in detail hereinafter.

The arms 88a provide support for lower plow members 90 which are positioned with their lower edges below the slots 58 in the mixer sidewall 42. The plow members 90 traverse a circular path about the axes 14a and 16a of their respective mixing head assemblies, as indicated by the circles 92 and 94 in FIG. 1. The circles 92 and 94 are slightly smaller in diameter than the distance or space between the

opposite sidewalls

42b and 42c of the mixing chamber providing ample clearance between the plow member 90 and the sidewalls. The circles 92 and 94 representing the outer limit of the circular paths traversed by the plow members 90 extend closely adjacent to the

wall section

42a and 42d; however, ample clearance is provided.

The arms 88b of the mixing head assembly include plow members 96 similar to the plow members 90 and diametrically opposite thereto. The plow members 96 traverse the circular paths represented by the circles 92 and 94 in FIG. 1. The plow members 96 are positioned upwardly above air supply slots 58 in the sidewall 42 and aid in mixing the upper level of material in the mixing chamber.

The arms 86a of the mixing head assemblies provide support for large plows or skimmer plates 98. Each skimmer plate 98 includes a sloping outer edge 98a parallel to, but spaced from, the planar sections of the outwardly sloping mixer sidewall 44 (FIG. 3). The skimmer plates or plows 98 are disposed to traverse a central or middle section around the mixing chamber approximately halfway up a sloping sidewall 44. The edges 9811 move toward and away from the wall sections and are in closest proximity to the flat sections in areas Where the sections are almost tangent to the circular path traversed by the plows. The material in the mixing chamber in advance of the moving skimmer plates is moved upwardly and outwardly on the sloping sidewall 44 and, after the skimmer plate has passed, the material then slides downwardly and inwardly returning to the bed of material on mixer floor 30.

The arms 86b of the mixing head assembly support skimmer plates or plows 100, similar to the plows 98, but positioned lower in the chamber slightly above the lower edge of the sidewall 44, as indicated in FIGS. 2 and 3. Each skimmer plate 100 includes an upwardly and outwardly sloping edge 100a positioned to move in close proximity with the sloping walls 44 of the mixing chamber at points where the wall sections approach a tangential relation with circular paths of the skimmer plates. As the skimmer plates 100- move around the chamber, material in advance thereof is forced upwardly and outwardly along the sloping sidewall 44, and, after passage, the material then flows inwardly and downwardly on the sidewall and returns to the bed of material on the mixer floor 30. The

skimmer plates

98 and 100* of the mixing head assembly 16 traverse a path indicated generally by the circle 102 (FIG. 1), and it should be noted that the path 102 extends outwardly of the lower wall 42 of the mixing chamber. The

skimmer plates

98 and 100 of the mixing head assembly 14 traverse the circular path indicated by the circle 104 (FIG. 1), and the path 104 also extends outwardly of the sidewall 42. The circles 92 and 94 overlap one another near the center of the mixing chamber 12, forming a common area A which is traversed by the plow members and 96 of both mixing

head assemblies

14 and 16. The

circles

102 and 104 likewise overlap near the center of the mixing chamber in an area somewhat larger than the area A, designated by the letter B. Accordingly, the outer skimmer plates 98 and of both mixing head assemblies traverse a common area in the mixing chamber, indicated by the letter B.

In addition to the plow members 90 and 96 and skimmer plates 98 and 100', each of the mixing

head assemblies

14 and 16 includes a curved inner plow member 106 positioned to extend out-wardly toward the walls of the mixing chamber. The plow members 106 continually move the material outwardly from the areas around casings 64 toward the outer plow members as the mixing head assemblies are rotated.

As indicated in FIG. 1, the mixing

head assemblies

14 and 16 rotate in opposite directions; for example, the mixing head 14 rotates in a clockwise direction about its axis and the mixing head 16 rotates in a counterclockwise direction. The mixing head assemblies are synchronized with one another so that a plow member or skimmer plate of one head assembly will pass over the areas A and B on the mixer floor in selected spaced intervals behind or ahead of a plow member or skimmer plate of the other head assembly. Accordingly, as material is fed into the mixing chamber 12, it is moved around the chamber in a clockwise direction by the plow members 90 and 96 and skimmer plates 98 and 100' of the mixing head assembly 14 in a first or initial stage of conditioning. During this stage, the material is thoroughly mixed by the plows and skimmer plates and is aerated as it passes in front of the air supply slots 58 in the sidewall 42. The material is moved by the head assembly 14 into the common areas A and B traversed by both mixing head assemblies. It is picked up by the plow members 90 and 96 and

skimmer plates

98 and 100 of the second mixing head assembly 16. The mixing head assembly 16 moves the material in a generally counterclockwise direction and again the material is thoroughly mixed and agitated by the plow members and skimmer plates of the mixing head assembly 16 and is aerated as it passes in front of the air slots 58 in the wall 42. The mixing head assembly 16 moves material centrifugally outward into the discharge gate assembly 20 for delivery to the next conditioning stage in a mulling machine. Not all of the material adjacent to the head assembly 16 is discharged immediately, and this material is back blended into the areas A and B where it is again picked up by the mixing head assembly 14. The inner plows 106 serve to continually move the bed of material outwardly from around the support casings 64 of the mixing head assemblies into the areas where thorough mixing is accomplished by the faster moving plow members and skimmer plates.

Referring now, more specifically, to the material feeding system 18, it includes a feed hopper 108 having inwardly tapered, converging sidewalls, and a narrow cylindrical throat section 110 at the bottom thereof. The throat section 110 extends through an opening in a top wall 24a of the hood structure 24 and the opening is axially aligned with the axis of rotation 14a of the mixing head assembly 14. Material placed in the hopper 108 gravitates downwardly through the feed throat section 110 onto a circular distribution or feed plate 112 which is supported from the mixing head assembly 14 by several supporting members 114. The distribution plate 112 is concentrically aligned with the axis 14a and rotates with the mixing head assembly 14. A distributing cone 116 is mounted on the distribution plate to direct the material flowing downwardly through the feed throat 110 outwardly towards the peripheral edge of the distribution plate and, as the material flows onto the feed plate, it is centrifuged outwardly toward the peripheral edge. In order to control the fiow rate of material onto the distribution plate from the feed throat 110, a movable, cylindrical delivery chute 118 is engaged on the lower end of the feed throat. The delivery chute 118 is movable in a vertical direction toward and away from the distribution plate 112, and movement of the chute is controlled and adjusted by a plurality of adjusting bolts 120 which extend downwardly through the top wall 24:: of the hood structure and threadedly engage outwardly extending ears 118a formed at the upper end of the delivery chute. To increase the flow rate of material into the mixing chamber, the bolts 120 are adjusted to raise the delivery chute 118 away from the feed plate 112 and, conversely, when it is desired to decrease the flow rate of material into the chamber, the bolts are adjusted to lower the delivery chute. The material reaching the outer peripheral edge of the feed plate 112 falls downwardly towards the floor 30 of the mixing chamber in a thin cylindrical stream or curtain of flowing material represented by the arrows 122 (FIG. 2). The diameter of the feed plate 112 is considerably larger than the diameter of the feed throat section 110 and, accordingly, the curtain of flowing material is relatively thin.

In order to aid in cooling the material during its first stage of conditioning, water is introduced into the material as it feeds into the mixing chamber from the water supply system 28. The supply system 28 includes an inlet line 124 having a control valve 126 therein for regulating the water flow. The line 124 is connected to a circular pipe or manifold 188 arranged in concentric relation with the axis 14a of the mixing head assembly 14. The ring manifold 128 is concentric with the axis 14a and is formed with a plurality of spaced orifices 128a therein for directing high velocity streams of water inwardly towards the thin cylindrical curtain of material feeding downwardly from the feed plate 112. As the high velocity streams of water from the manifold orifices 128a (represented by arrows 123 in FIGS. 2 and 3) strike this curtain of hot sand particles, large quantities of steam are formed and the sand particles are rapidly cooled by evaporative cooling as the water changes into steam. The steam formed in the vicinity of the mixing head assembly 14 is immediately removed from the mixing chamber 12 through an outlet opening 130 in the adjacent end wall 24b of the hood assembly 24. An exhaust duct 132 is connected to the opening 130 and a suitable fan (not shown) is provided to aid in moving the steam out through the duct 132 as rapidly as the steam forms.

Because the steam formed by cooling of the material is rapidly removed from the mixing chamber, there is little opportunity for the cooled sand particles to pick up moisture from the steam condensing thereon. The material is thoroughly mixed and aerated by the mixing head assembly 14 and the airstreams passing through the adjacent outlets 58 in the mixer sidewall 42. by the time the material reaches areas A and B and is picked up by the mixing head assembly 16 for the next stage of conditioning, its temperature has been reduced considerably under the entry temperature, and it has been thoroughly mixed, agitated, and aerated.

In the next stage, the material is cooled to a lower temperature while being mixed, agitated, and aerated by the mixing head assembly 16 and the air flowing into the material through the adjacent slots 58 in the sidewall 42. No additional moisture is added for cooling in the second stage of conditioning but evaporative cooling continues at a rate somewhat less than that in the first stage. Because the material has been cooled to a considerable extent by the time it reaches the second stage, there is less steam formed and the air leaving the second stage is somewhat drier and lower in temperature. The air entering the chamber through the slots 58 for cooling in the second stage is removed from the chamber through the exhaust assembly 26. The assembly 26 includes a plenam chamber 134 mounted on the top wall 24a of the hood assembly and an exhaust duct 136 is connected to the plenum chamber to carry out the air. Suitable (not shown) fan means are provided to exhaust the air out through the duct 136. It should be noted that two separate exhaust ducts 132 and 136 are utilized for removing hot air and moisture from the mixing chamber. The exhaust duct 132 is connected directly to the opening 130 in the hood end wall 24b and functions to rapidly carry out most of the steam and vapor laden hot air formed in the first conditioning stage adjacent the feeding system 18, water supply system 28, and mixing head assembly 14. By providing for the immediate removal of the large quantities of steam formed in the first stage of conditioning, the evaporative cooling is extremenly efiicient and there is little cooling loss effected by the steam being reabsorbed in the sand as it moves into the next stage.

Hot air and moisture from the second stage of conditioning is removed from the mixing chamber through the exhaust duct 136 adjacent the head assembly 16. It has been found that by removing the air and moisture from the mixing chamber 12 in two separate paths, one for each stage, cooling etficiency is greatly improved over that wherein a single duct is utilized and the air from two stages is mixed therein.

The following calculations show how the necessary amounts of water and air to cool sand from 200 F. to F. are determined.

From handbook: B.t.u. per lb. Specific heat of sand .19 Specific heat of air .24 Specific heat of water 1.0 Latent heat of water (970 evaporation plus 30 sensible) 1000.

A graphic curve showing rate of heat loss levels out very rapldly as the temperature drops and approaches ambient conditions around the medium to be cooled. Therefore, it is advantageous to divide the cooling operation into two stages, for example, a first stage of 200 to 150 and a second Stage of 150 to 120. In the following calculations the heat loss obtained from increasing the air temperature from ambient to discharge level is ignored. Ambient air condition is assumed to be 80 F. dry bulb, 72 wet bulb or 80% RH.

First stage 200 to 150:

2,000# sand X 50 X .19 B.t.u.: 19,000 B.t.u. heat to loss 19,000 B.t.u.=19# water required for evaporation. 1,000 B.t.u.

Each pound of air entering cooler at 80 F.-72 W.B. 80% RH contains .017# moisture. Each pound of air leaving cooler at 140 F.128 W.B. 70% RH contains .105# moisture. Moisture evaporated per pound dry air=.088#.

19# water=201# air required to evaporate water. .088# I .201# air=2,700 cubic feet of air required. .075#

Second stage 150 to 120:

2,000# sand X 30 X .19 B.t.u.=l1,400 B.t.u. heat to lose 11,400 B.t.u.=11.4# water required for evaporation. 1,000 B.t.u.

Each pound of air entering cooler at 80 --72 WB 80% RH contains .017# moisture. Each pound of air leaving cooler at 110 -l W.B. 70% RH contains .044 moisture. Moisture evaporated per pound dry air=.027#.

It is apparent from these calculations that cooling in the higher ranges requires much less air. Actually, at over 180 the vapor pressure is so high that little more than a stack vent would be required. However, the supersaturated air leaving the mixer cools and the moisture condenses on duct work and mixer walls. It is for this reason calculations are based on suflicient air to provide dry ducts at all temperatures. To take advantage of this, the mixer 10 is provided with two separate exhaust ducts 132 and 136. The duct 132 carries out the hot steamy vapors generated when the hot sand is wet down in the first stage and the duct 136 handles the much lower temperature and drier air from the second stage. If a single exhaust only was provided, theoretically nearly twice the colume of air would be required. The two stage cooling thus afforded is a tremendous advantage.

As the mixing head assembly 16 rotates, a portion of the material in the second Stage is continuously being moved by the plow members 90, 96 and

skimmer plates

98 and 100 outwardly into the discharge gate assembly 20 between the sidewalls 46 thereof. The gate assembly 20 includes a floor or gate 140 mounted for pivotal movement on an axle 142 extending underneath the gate along the inner edge thereof and protruding through the sidewalls 46. The protruding ends 142a of the axle are connected to lever arms 144 which in turn are connected to adjustable spring biasing assemblies 146. The biasing spring assemblies are adjustable for biasing the floor gate to provide the desired discharge rate from the mixer. The gate assembly 20 is similar in operating principle to that disclosed in the copending US. patent application Ser. No. 356,708, filed Apr. 2, 1960, now Patent No. 3,231,146, and provides a continuous material seal between the gate and the

walls

46 and 48 as the material is discharged. The gate assembly is sealed at the upper end by a fixed top wall 148 to prevent air leakage from the discharge gate assembly into the mixing chamber. Material moves outwardly on the gate 140 causes the outer edge of the gate to move downwardly against the biasing force of the spring assemblies 146, and the amount of downward movement of gate edge determines the flow rate of material from the mixing chamber. As the gate pivots downwardly to a greater degree, the outer edge thereof moves away from the wall 48 and increases the discharge rate while the converse is true if the gate edge moves upwardly to reduce the clearance between the wall and gate.

While there has been illustrated and described a single embodiment of the present invention, it will be apparent that various changes and modifications thereof will occur to those skilled in the art. It is intended in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. Apparatus for conditioning material comprising a mixing chamber, material supply means for feeding said material into said chamber adjacent one portion thereof, water supply means for introducing moisture into the material as it is fed into said chamber, means for dis charging said material from an opposite portion of said chamber, a pair of mixing head assemblies in said chamber, said assemblies rotatable about spaced-apart upstanding axes and each assembly including one or more plows outwardly of its respective axis of rotation, said mixing chamber including an upwardly and outwardly sloping sidewall having a lower edge, an air supply chamber beneath said sloping wall portion having an outlet opening below said lower edge for directing air inwardly into the material in said chamber, and exhaust means for exhausting air and moisture from said chamber.

2. The apparatus of claim 1 wherein said material supply means includes a circular distribution member concentric with the axis of rotation of one of said head assemblies for feeding a thin annular stream of material downwardly into said chamber.

3. The apparatus of claim 1 wherein said mixing head assemblies are rotated in synchronism in opposite directions and the plow of one assembly traverses an area in said chamber traversed by the plow of the other assembly.

4. The apparatus of claim 1 wherein said mixing chamber includes a floor positioned beneath the lower edge of said sloping sidewall, each of said mixing head assemblies including a first plow having a portion extending below said lower edge and traversing a path adjacent said floor and a second plow disposed to traverse a path overlying said sloping wall whereby material is moved upwardly and outwardly on said wall in advance of said second plow and may slide inwardly and downwardly toward said floor after passage of said plow.

5. Apparatus for conditioning material comprising a mixing chamber having a floor and a peripheral sidewall, and a mixing head assembly rotatable about an axis upstanding from said floor and including one or more mixing plows outwardly of said axis traversing a path adjacent said sidewall, said sidewall including at least one planar section sloping upwardly and outwardly of said axis, said path overlying a portion of said planar section.

6. The apparatus of claim 5 including an air supply chamber beneath said sidewall, said supply chamber in 1 1' eluding outlet means beneath said sloping planar section for discharging air into the material in said chamber.

7. Apparatus for conditioning material comprising a mixing chamber having a floor and a peripheral sidewall, a mixing head assembly rotatable about an axis upstanding from said floor and including one or more mixing plows outwardly of said axis traversing a path adjacent said sidewall, said sidewall including at least one planar section sloping upwardly and outwardly of said axis and having a lower edge spaced upwardly of said floor, an air supply chamber beneath said planar section having outlet means between said floor and the lower edge of said planar section for directing air into the material in said chamber. 1

8. The apparatus as defined in claim 7 wherein said outlet means includes converging nozzle means having one wall formed by said planar section and a lower converging wall, said walls forming a narrow opening for said air below said lower edge of said planar section.

9. The apparatus as defined in claim 7 wherein said mixing head assembly includes a pair of mixing plows, one of said plows traversing a circular path having a portion overlying a portion of said sloping planar section, the other of said plows traversing a path inwardly of said outlet means and below said lower edge of said planar section.

10. Apparatus for conditioning material comprising a mixing chamber, a mixing head assembly in said chamber, said head assembly rotatable about an upstanding axis and including one or more plows outwardly of said axis for mixing said material, material feeding means including a rotating circular distribution member concentrically of said axis for directing a thin annular stream of material into said chamber, water supply means including an annular manifold concentric of said axis for directing water into the annular stream of material flowing from said distribution member, said material feeding means including a material delivery chute concentric with the axis of said mixing head assembly and having an open lower end, and means for adjusting the clearance between the lower end of said chute and said distribution member for regulating the flow rate of material into said mixing chamber.

11. The apparatus of claim 10 wherein said distribution member is mounted on the mixing head assembly and said manifold is concentrically outward of said member,

12 said manifold including a pluralityof outlets therein for directing water inwardly toward said annular stream of material.

12. The apparatus of claim 10 wherein said material feeding means includes a conically shaped member cen tered on said distribution member and having an apex extending upwardly toward said delivery chute.

13. Apparatus for conditioning material comprising a mixing chamber, material supply means for feeding said material into said chamber adjacent one portion thereof, water supply means for introducing moisture into the material as it is fed into said chamber, means for discharging said material from an opposite portion of said chamber, a pair of mixing head assemblies in said chamber, said assemblies rotatable about spaced-apart upstanding axes and each assembly including one or more plows outwardly of its respective axis of rotation, said mixing chamber including an upwardly and outwardly sloping sidewall having a lower edge, an air supply chamber beneath said sloping wall portion having an outlet opening below said lower edge for directing air inwardly into the material in said chamber, and exhaust means for exhausting air and moisture from said chamber, said exhaust means including a pair of separate exhaust ducts and a hood means enclosing said chamber.

14. The apparatus of claim 13 wherein one of said exhaust ducts is connected to said hood means adjacent said one portion of said chamber to remove hot steam and vapors therefrom generated when water is introduced into said material, and wherein said other exhaust duct is connected to said hood means adjacent said other portion of said chamber.

15. The apparatus of claim 5 wherein said sidewall comprises a plurality of planar sections sloping upwardly and outwardly of said axis forming a continuous wall around said mixing head. I

16. The apparatus of claim 15 wherein each of said planar sections includes a midportion parallel with a tangent to the paths traversed by the plows of said mixing head. 1

ROBERT W. JENKINS, Primary Examiner.