US2515194A

US2515194A - Method of and apparatus for sand recovery

Info

Publication number: US2515194A
Application number: US666757A
Authority: US
Inventors: Alfred C Christensen
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-05-02
Filing date: 1946-05-02
Publication date: 1950-07-18
Anticipated expiration: 1967-07-18
Also published as: DE825734C; GB629173A; GB629172A; CH270587A; DE820187C; CH281203A

Description

July 18, 1950 Filed nay 2. 194s N- .NUN

July 18, 1950 A. c. cHRlsrl-:NSEN 2,515,194

METHOD 0F AND APPARATUS FOR SAND RECOVERY Filed May 2, 1946 4 Sheets-Sheet 2 [TH/5.272272 Z/ned dmstemen July 18, 1950 A. c. cHRlsTENsEN 2,515,194

namen or' Arm APPARATUS Fon sm Recon-:Rv

Filed lay 2, 1946 4 Sheets-Sheet 5 July 18, 1950 A. c. cHRlsTENsEN Immon or' Ann APPARATUS Fon smv REcovERY 4 Sheets-Sheet 4 Filed May 2, 1946 Rig;

Patented July ,118, 1950 METHOD OF AND APPARATUS FOR SAND RECOVERY Alfred C.r Christensen, Chicago, Ill., assignor, by mesne assignments, to Herbert S. Simpson,

Evanston, Ill., as trustee Application May 2, 1946, Serial No. 666,757

In establishments using vgranular materials, such as a foundry using mold and core sands, said sands usually consist of silica grains combined with clays, oil or cereal bonding agents tempered with sufficient moisture to develop the strength of the binders and to render the sand moldable. After such sand has been used for making molds, cores and the like, and the sand is subjected to the action of hot molten metal and other treatments in a foundry, the sand becomes spent or inert and is usually coated with unburned bonding material and carbon to such an extent that the sand is no longer fit for further use and must consequently be discarded. Such conditions create a considerable waste and the additional expenditures necessary to purchase new clean sand.

It is, therefore, highly desirable, in foundry practice, to recover the original sand, lby subjecting the spent sand to cleaning treatments to remove both the spent clay bonding and carbonaecous matter from clay bonded sands, and the carbonaceous coatings and foreign matter from oil and cereal bonded sands. The recovery of the sand is accomplished by subjecting the sand to wet scrubbing treatments followed by burning treatments in the case of clay bonded sands, While in the case of oil bonded sands, which do not require a wet cleaning treatment, the spent material may be subjected directly to a burning and plowing treatment followed by final mulling, cooling and dust removal treatments to produce thoroughly cleaned recovered sand, the said grains of which are ready for reconditioning and rebonding to permit the re-use of the cleaned recovered sand.

In the case of clay bonded foundry sands, it has been found that after the bonded sand has been used in foundry practice that the sand grains when observed through a microscope have the appearance of minute potatoes, each grain being covered by spent clay bonding and foreign matter which forms a roughened coating on each of the sand grains. Each of said spent sand grains is also found to have a plurality of scattered indents or eyes which are also filled with spent clay bonding matter and with carbon and the like. Since the clay bonding material is of a refractory nature it cannot be burned off directly, and this invention has therefore been devised to provide an apparatus and a method whereby the spent clay bonded sand is first subjected to a wet scrubbing and mulling treatment for the softening and the removal of the major portion of the clay bonding matter,

after which the scrubbed material is subjected to a high temperature burning treatment, while being plowed, to burn out the carbonaceous material from the eyes of the grain and to cinderize any remaining small portions of clay bonding material which might still be lodged in the eyes of the grains. After undergoing the wet scrubbing and the burning treatments, the material still contains small quantities of dust and fines and it is therefore found necessary to again subject the cleaned material to further mulling and aerating treatments to cool the material, draw off the resulting dust and fines and to recover the material ready for reconditioning and rebonding for further use.

The present invention therefore pertains to a method of and apparatus for more efficiently reclaiming spent and inert material such as bonded foundry sand and the like, by first subjecting the material to preliminary cleaningv steps for breaking up the material and removing metallic particles therefrom, and then subjecting the material to wet mulling and scrubbing treatments, followed by high temperature plowing and mixing treatments in a confined high temperature area, wherein the material is further subjected to burning treatments in the presence of secondary air currents to assist in the cleaning by oxidation as the material is carried through a circular path into the eld of operation of combination air discharging and plowing means to produce a resultant clean sand from which the major portion of the bonding and carbonaceous matters have been removed leaving the sand in a highly cleaned hot state ready to be cooled by further subjecting the material to mixing and mulling treatments in the presence of air currents for the removal of any remaining dust and fines before the material is discharged in a highly clean state ready for reconditioning, re-bonding and re-use.

The invention, therefore, relates to a spent material recovery system and more particularly to a method of and apparatus for recovering spent or inert granular materials, such as foundry sand and the like, to permit the original material grains to be recovered in a highly cleaned state to permit re-use of the same and thereby permit the amount of sand required in foundries and the like to be materially reduced at a great saving in operation and in the amount of new material required.

An object of the invention is to provide an economical way of quickly and efficiently removing spent coatings and foreign matter from used amara:

foundry sand and similar granular materials by subjecting the spent material to successive wet treatments, burning treatments, and cooling and aerating treatments to eillciently clean the material in uninterrupted successive stages, depending upon the type of bonded granular materials which are to be treated for complete recovery and re-use.

It is also an object of this invention to provide an improved method and apparatus for reclaiming inert and spent foundry sand and similar granular materials, which method and apparatus is economical, clean and eifective in reducing the quantity of sand required in a foundry.

Another object of the invention is to provide a material recovery system for the economical removal by wet and burning treatments of bonding and foreign matter from granular material to recover the material grains in a cleaned bleached state ready for reconditioning and re-use without the necessity of using expensive and extensive auxiliary scrubbing or treating means in the recovery of used sand to permit the same to be re- -used instead of being discarded and replaced by a new sand supply.

Other objects and features of this invention will more fully appear from the following detailed description taken in connection with the disclosures in the accompanying drawings, which illustrate an embodiment of the invention.

In the drawings:

Figure 1 illustrates a top plan view of the machine system constructed and arranged in accordance with the principles of this invention, and capable of expeditiously and economically carrying out the method of recovering spent granular material such as foundry sand and the like.

Figure 2 is a vertical sectional view taken on line II-II of Fig. 1, with parts omitted to more vclearly illustrate the shake out unit, the loading unit, the wet treating unit and the furnace unit of the system.

Figure 3 is a fragmentary vertical sectional viw taken substantially on line III-III of Fig. 1 with parts omitted and with parts shown in section to illustrate portions of the interior of the cooling and transfer units disposed between the furnace unit and the final treating unit of the system.

Figure 4 is a vertical elevational view taken on line IV-IV of Fig. 1 and primarily illustrating the dust collector mechanism connected with the nal material treating unit of the system.

Figure 5 is. an enlarged horizontal sectional view taken on line V-V of Fig. 2 through the furnace unit and illustrating the burner ovens and their association with the air discharging plow groups, disposed within the furnace unit for diversifying the path of travel of the material While being rotated and while being subjected to air currents and llames from opposite directions.

Figure v6 is an enlarged fragmentary vertical sectional view taken on line VI-VI of Fig. 5 and illustrating the mounting and construction of one of the air discharging plow units supported in the furnace material treating area.

Figure 7 is a diagrammatic iiow chart indieating the sequence of processing steps performed in practicing the novel reclamation process of this invention.

As shown in the drawings:

This invention relates to an improved method `or process for the eiiicient recovery of granular materialsV from spent or inert previously used bonded materials such as clay bonded molding sand as well as for the recovery of the silica grains in a clean condition from spent or inert previously used oil or cereal bonded core sand or the like.

The process is adapted to be practiced by means of a connected system of operating units for the efficient 'recovery of the silica grains from spent clay bonded foundry sand which is adapted to be received from a foundry shake out machine and is then adapted to be operated on and treated by batch feeding the material through continuous successive stages, whereby the spent clay or other refractory coating material of the grains, the carbonaceous and other foreign matter as well as the dust and ilnes are adapted to be removed and separated from the material grains in the successive stages of treatments to eventually produce an eiliciently cleaned granular material which is adaptable 'for re-use at a nominal cost. thereby effecting considerable savings in cost as well as savings in the handling, shipping and other work entailed when new sand is used in` stead of recovering and re-using previously used molding and core foundry sands.

The present invention While primarily directed to a method or process of recovering silica grains in a highly cleaned state from spent or inert clay bonded foundry sand or the like,is equally adaptable for the recovery of silica grains from oil and cereal bonded core sand by a selective use of the apparatus units.

The improved method of cleaning and recovering spent or inert granular material such as foundry sand and the like is adapted to be accomplished by means of a machine assembly or system of the type illustrated in Fig. 1 which system includes a material cleaning and magnetic separator unit for screening out lumps and removing metallic refuse and for also withdrawing nes and dust preliminary to delivering the material into a bucket feed unit for batch delivery into a scrubbing unit. The wet scrubbing unit is adapted for softening and removing refractory clay coating matter from the material grains and for forming a paste like batch which is fed through a desilting unit and is then conveyed by a dewatering unit into a furnace'unit in which the material is further subjected to treatments including contemporaneous plowing, aerating and burning treatments as the material is rotated and is forced to move in circuitous paths for effecting further cleaning of the material by oxidation to remove the carbonaceous material and to effect a separation of any remaining refractory matter still adhering to the material grains. While undergoing the plowing, aerating and burning treatment in the furnace unit the material is simultaneously subjected to a suctioning action for the removal of hot gases, dust, fines and the like before the substantially clean, hot material is advanced through a preliminary cooling and transfer unit for delivery into a iinal treating unit wherein the substantially clean material is subjected to mixing and mulling treatment in the presence of air currents whereby the material is cooled while simultaneously being subjected to a suction action whereby any remaining ilnes and clust is removed from the recovered material prior to the discharge of the eiilciently cleaned silica sand grains for storage or for reconditioning for re-use.

As shown in Fig. 1 the various units comprising the system are arranged in compact intercom',

nected relationship and include a screening and magnetic separator unit A, a switch controlled bucket loader unit B, a wet scrubbing unit C. a combination desilting, dewatering and conveyor unit D, a furnace unit E, a combination cooling and transfer unit F, a ilnal mixing, mulling and aerating unit G, and a suction type of collector system H, connected with a plurality of the units for withdrawing ilnes, dust, hot gases and refuse matter therefrom during the material recovery treatments practiced by the machine assembly.

The screening and magnetic separator unit A is positioned to permit spent or inert material which is to be treated for the recovery of the silica grains to be delivered manually into the separator unit, or said unit may be positioned Ibeneath a foundry shake out unit to receive material therefrom for treatment. The screening and magnetic separator unit A. is of a selected well known type, comprising a receiving hopper or bin I provided with a vibrating screen 2 which is operable from a driving motor 3. The motor 3 is also connected to drive a conveyor belt 4 fitted with a magnetic head pulley 5 which is adapted after the the screening of the material to separate metallic refuse therefrom for discharge into a receiving box 6 as the screened material is discharged to a delivery chute I for delivery to the bucket loader unit B. The separator unit also lincludes a partial cover or hood 8 for eliminating or withdrawing dust and fines upwardly through fa suction pipe 9 from one side of which an auxiliary suction pipe I0 connects up with the top of the material delivery chute 1.

After the shake out material has been screened and cleared of metallic particles, the material is delivered to the bucket loader unit B which consists of a batch bucket II mounted to permit the same to be alternately raised and lowered by means of cables I2 mounted to be wound and unwound on drums carried by a shaft supported on the upper portion of the loader framework i3. The shaft and drums are operable by means of a motor I4 acting through a feed reducer drive I5.

The operation of the bucket i I is accomplished by means of a reversing switch I6 and a combination start, stop and reverse push button control I'I supported in a convenient position on the loader framework I3. The batch feed bucket II is provided with upper and lower rollers which track in suitable guides within the framework I3 and in auxiliary guide tracks I8 supported on the upper portion of said framework. The auxiliary guide tracks I8 are positioned to serve as guides for the lower bucket rollers when the upper rollers of the bucket reach the closed ends of the main guide tracks, thereby causing the loading bucket at the upper limit of its movement to be upset or reversed to tilt the same and cause discharge of a batch of material into a receiving opening of a wet scrubbing unit C.

The wet scrubbing unit C is of a construction old in the art and substantially similar to the muller shown in the Simpson Patent No. 2,226,023 granted December 24, 1940 and assigned to the assignee of this invention. The unit C consists of a housing or crib I9 supported by means of legs 20 on a foundation 2 I. A cover or hood 22 closes the major portion of the crib I9 and is constructed to t around the material receiving opening of the crib. A suction pipe 23 is connected to the hood 22 and to a pipe 24 ofthe suction system in which the suction pipes 9 and I0 are also connected. The wet scrubbing housing or crib I9 contains -a driven shaft operated by a driving motor 25 through a speed reducing unit 26. The driven shaft projects upwardly into the crib I9 and supports a head. 'Ihe rotatable head carries pivoted brackets on which mullers are rotatably supported. The head also supports arms for carrying plow and scraping blades for mixing and moving the material in the crib and advancing the material into the path of operation of the mullers. The interior of the crib is also equipped with a water distributing funnel and pipes leading therefrom for supplying the required amount of water or moisture to the material being treated in the crib I9.

After the material has been subjected to a suction action in the crib I9 to draw on fines and dust, it is treated to the action of the plows and mullers to wet scour and scrub the material to remove the major portion of the refractory coating therefrom such as clay bonding matter and the like, leaving a wet paste-like batch.

Following the wet scrubbing and mulling treatments in the crib I9, the wet paste-like batch is discharged into a desilting unit 21 which may be of any selected standard construction such as the type disclosed in the pending application of Alfred C. Christensen and James J. Dvorak for a Foundry Sand Reclaiming System and Method filed December 21, 1942, U. S. Serial No. 469,662, now Patent 2,420,392 issued March 13, 1947, and in which a desilting tank is supplied with water and is designed to create a counterflow of water in the tank whereby the fines and silt are drained off anddischarged into a disposal system. The remaining partially cleaned sand batch drops into the lower portion of the desilting tank and into the lower end of a combination dewatering and conveyor unit which coacts with the desilting unit.

The wet scrubbed and desilted batch of material deposited in the bottom of the desilting tank is engaged by a screw conveyor 28 which is belt driven from a driving motor 29 supported on the foundation 2|. The screw conveyor 28 is rotatably mounted in an inclined position in an inclined gutter or trough 30 through which the material is conveyed upwardly and is dewatered preliminary to delivery into a discharge head 3I from which the material is permitted to drop into the furnace unit E for additional cleaning treatments for further refining the sand by contemporaneously subjecting the material to plowing, aerating, burning and suction treatments for the removal of carbonaceous matter by oxidation and for the removal of any remaining portions of refractory material by burning olf of the volatile constituents of the sand and clay mixture.

The furnace unit E comprises a hearth or furnace housing or casing 32 supported on a base 33. The housing 32 is constructed of metal or other suitable material and forms a shell around an insulation lining 34 constructed of any selected type of standard insulating blocks. An inner lining 35 is built within the housing adjacent to the inside of the insulation lining 34, and said inner lining is preferably constructed of a refractory material such as re blocks. The lower end of the furnace housing 32 extends inwardly and is formed with an open collar which projects downwardly into sealing engagement with a bed of insulation material such as foundry sand. The bed of insulation material is carried in a rotatable table which forms the bottom for the furnace housing. The rotatable table is supported on a shaft and is operated from a driving motor 36 through a speed reduction unit mounted in the Y 7 base of the furnace unit. The rotatable table is protected by means of a shield or guard 31 secured to the lower portion of the furnace housing 32.

'I'he top of the furnace housing is provided with an outlet opening which is covered by means of a turret housing or hood 38 which provides outlet chambers or passages whereby flnes, dust, hot gases and other released products of combustion are permitted to escape upwardly from the furnace treating chamber, through the turret hous- `ing and out through a discharge chimney or stack 39 which is supported on the turret housing l38 and leads upwardly to the atmosphere or may be connected with the suction operated collector system of the apparatus.

Formed within the turret housing 38 is a material receiving chute or hopper 40 the lower end of which projects downwardly into the upper portion of the treating chamber of the furnace housing. The lower end of the hopper 40 is adapted to be closed by means of a feed control gate or valve 4| attached on the lower end of an operating rod the upper end of which is pivotally connected to a manually operable operating lever 42 fulcrumed intermediate its ends on the top of the turret housing 38.

When the material control gate 4| is opened `the batch of partially cleaned dewatered material in the hopper 40 is discharged downwardly into the furnace operating chamber and is deposited upon the insulation bed of the rotatable table. so that when the table is rotated the material to `be treated is carried through a substantially circular path in the field of operation of a combination plow and air supply unit disposed within the treating chamber of the furnace.

The combination air'supply and plow unit is disposed diametrically within the furnace treating chamber, and said mechanism comprises an air distributing and plow supporting pipe 43 the ends of which project through the furnace lining walls and the outer furnace housing or casing. One projecting end of the pipe 43 is closed by means of a cap while the other projecting end of said pipe is rigidly connected to a secondary air supply pipe 44. The pipe 44 is also connected with an air pump 45 which is operated by means of a motor 4G.

The air supply pipe 43 serves the double purpose of supplying air from the .blower or pump 45 and at the same time acts as a support for a plurality of plow or rake mechanisms. The plow mechanisms are provided in two groups or banks disposed within the furnace chamber and are mounted on the pipe 43 on opposite sides of the center of the burner chamber and on diagonally opening 63 which communicates with the lower end of the plow shaft 41. and said opening 53 has two oppositely directed discharge slots 54 leading therefrom for directing air currents from the pipe 43 through the plow shaft 41 and the opening 53 in the plow head, and then outwardly and downwardly adjacent opposite sides of the plow blade 52 for the purpose of cooling the plow blade and for the further purpose of supplying a secondary source of air to the material while being treated in the combustion and plowing chamber of the furnace.

The upper end of each of the plow shafts 41 projects ellrough the upper bushing and has the upper end thereof exposed to receive the collar 55 of a plow operating lever 56 pinned or otherwise rigidly secured to the plow shaft. The upper end of the plow shaft 41 is thus closed by means of its operating lever 56. Four of the plow units form a stationarygroup and are connected by means of a connecting bar 51. Bolts 58 connect the plow levers in the stationary group of plows to the bar 51.

The second group of plows are adjustable and are connected by means of bolts 58 to a shiftable connecting bar 59. Connected to the middle portion of the shiftable connecting bar 59 is a downwardly bent end of a plow operating rod 60 which projects outwardly through the furnace wall. The outer end of the plow adjusting rod 60 is provided with a handle 6| having rigidly secured adjacent one side thereof a locking plate 62.

The locking plate 62 projects downwardly-so that opposite sides of the pipe 43 as shown in Fig. 5.

lower rows of diametrically opposite openings.

Each of the plow devices comprises a hollow plow shaft 41 having a plurality of air apertures or openings 48 provided therein and in communication with the interior of the pipe 43 as illustrated in Fig. 6. Each plow shaft 41 projects diametrically through the pipe 43 and through suitable bushings engaged in the pipe openings. Pinned or otherwise rigidly secured to the lower projecting end of each of the plow shafts 41 is a plow holder which is longitudinally grooved and is provided with a bottom slot 50. Slidably en gaged in each of the groover plow holders 49 is the head 5| of a plow blade or rake plate 52. Each of the plow heads 5| is provided with an the lower edge thereof is adapted to be removably engaged between the -teeth of a locking rack 63 for the purpose of holding the adjustable plows in a set position of adjustment with respect to the stationary plows.

The two groups or gangs of plows are arranged so that one group is stationary while the other group is adapted to vbe adjusted with respect to the stationary set, so that material carried by the rotatable furnace table is passed toward the center of the furnace by one group of plows while the other group acts to direct or divert the material outwardly toward the periphery of the table thereby causing the material while being rotated to be moved through a circuitous path. The cushion of silica sand, which lls the recess in th'e table serves as an insulator as well as a seal between the bottom flange of the stationary furnace housing and the revolving bottom or table for the housing. Y

The material out of which the air supply and plow mechanisms is constructed, is of a heat resisting composition to resist the high temperatures to which the parts are subjected within the furnace housing. The air which is discharged from the pipe 43 through the discharge slots 54 of each plow plate is directed against opposite sides of each plow plate and serves as a means for cooling the same. The secondary supply of air coming from the plow bladesalso serves as an aid to thorough combustion of the carbonaceous and foreign material coatings on the sand grains which are being treated in the furnace.

The hearth or furnace is equipped with two ovens 64 which are supported on the furnace housing and are arranged in substantially parallel relation and project in opposite directions from opposite sides of the plow mechanism as clearly illustrated in Fig. 5. The ovens communicate with the interior of the furnace treating chamber an'd are provided with an insulation lining 65. The inner end of each of the oven chambers 66 opens into the furnace 'chamberJ while the outer..end of each of said ovens has disposed therein a re brick sleeve 61 constructed of a refractory material and shaped to receive a flame throwing nozzle 68 which forms a part of a standard .oil burner unit 69 such as the Hauck oil burner. Each of the oil burners is equipped with an oil supply pipe connected with a suitable sourcey of oil supply, and with a primary air supply pipe 1| to provide a. primary supply of air for mixing with the oil to provide the necessary fuel whereby heating flames are adapted to' be directed through each oven into. the "mixing and burning chamber of the furnace to produce the high temperatures necessary for burning oil` the oil and othercarbonaceous bonding materials and foreign matter from the sand grains while the batch of material is being thoroughly plowed and aerated from the secondary source of air supply delivered by the plow mechanisms.

By providing the two burner and oven units for the furnace, the combustion flames are directed into the interior of the furnace tangentially from opposite directions so that a whirling action of the flames is created to act on the material while itis being plowed and rotated to thoroughly clean the material grains by the plowing and oxidation treatments in the presence of the secondary air currents discharged by the plows. Since the oil burning units are of a standard construction and type, the details of the burners have been omitted.

For the purpose of observing the mechanisms in the interior of the hearth orV furnace and for the further purpose of hand loading the furnace, one side of the furnace housing is provided with an observation opening which is closed by means of hingedly supported inspection door 12 operable bymeans of a handle 13.

Formed in one side of the furnace housing is a discharge door opening adapted to be closed by a pivotaly supported discharge door 14 provided with an operating handle 15. When the door 14 is opened the cleaned dry material is discharged from the furnace treating chamber into a receiving chute 18 from which the `material is discharged into the lower receiving mouth 11 forming part of the combination cooling and transfer unit F. y

The combination cooling and transfer unit F comprises a housing or cabinet 18 having the material receiving mouth 11 formed in the lower portion thereof as illustrated in Fig. 3. The housing 18 contains an endless bucket type conveyor 19, trained around sprocket wheels mounted within the housing 18, and is adapted to be operated by means of a driving motor 80 on the shaft of which the lower sprocket gear of the bucket conveyorA mechanism is supported. A shield or baille 8| is mounted within the housing 18 in an inclined positionand extends downwardl`ly beneath the bucket conveyor to form a trough for the reception of the material from the furnace chute 16, so that When the bucket conveyor is set in operation the material is scooped up in small quantities by the buckets and is gradually carried upwardly in the housing 18 permitting the material to be partially cooled 01T. To assist in the cooling of the material, the housing 18 is also equipped with one or more apertured water spray pipes which sprinkle or spray water into the conveyor housing 18. The water sprays coming into contact with 'the hot quantities of the conveyed material are vaporized and thereby act to draw off heat from the material as the air and vapor currents are suctioned through the housing 18. The housing 18 is also provided with a downwardly inclined apertured guide plate or table 83 which extends upwardly to a point near` the top of the bucket conveyor to receive the material in small quantities as it is discharged from the buckets at the upper end of the bucket conveyor. The material discharged from the conveyor buckets drops` upon the apertured plate or/table and spreads out as it passes downwardly into a discharge hopper 94 for delivery into the final treating unit G as shown in Fig. 3. The air and vapor currents suctioned through the cooling unit housing 18, are drawn through the apertures in the plate or table 83 and through the discharging material to further cool the material before it enters the final treating unit G of the system.

Connected to an upper corner ,of the conveyor housing 18 is one end of a suction pipe 85, the other end of which connects up with a main suction pipe 86 to one arm of which the suction pipe 24 is connected. The suction pipe 86 forms a part of the collector system and has one end thereof connected to a dust collector 81 from the upper end of which a pipe 88 connects up with a fan 89 from which an exhaust pipe 90 discharges the gases and air while the dust, fines and other refuse materials are deposited in the dust collector 81 and are permitted to beA discharged from the lower end thereof.

The discharge hopper 84, forming a part of the housing 18, permits the substantially cooled and cleaned material, traveling through the cooling unit F, to be discharged into the top of the suction cover or hood 9|,of the final treatment unit G of the system.

The suction cover or hood 9| of the unit G is connected by means of a suction pipe 92 with one arm of the main exhaust pipe 86. The cover or hood 9| is supported on a housing or crib 93 which is supported by means of legs 94 on a, foundation 95. 'I'he final treatment unit G contains rotatable Scrapers, plows and mullers similar to those contained in the crib I 9 of the treating unit C. Both of said treating units C and G are known to the trade as Simpson intensive mixers and are similar to the foundry mixer and muller disclosed in the Simpson Patent No. 2,226,023 dated December 24, 1940, previously referred to herein.

The nal cooling and treatment unit G is adapted to receive the substantially cool material from the unit F, permitting the material to drop into the crib 93 to be subjected to mixing and mulling action as well as to aerating treatments to subject the material to final cleaning operations whereby any resultant dust and fines still remaining in the material is suctioned off through the pipe 92 leaving the silica sand grains in a, completely cooled and cleaned recovered state ready for discharge from the crib 93 into a truck or car 96 which operates on tracks 91 for delivering the material to a receiving station for storage. If desired, the highly cleaned silica sand grains may be delivered to a reconditioning ystation where the cleaned material may be subjected to reconditioning operations, and tempered and rebonded for further use in the making of foundry molds, cores and the like.

The apparatus or machine assembly whereby into another. The system permits a series of batch treatments to be conducted simultaneously in the various units in which .the respective batches may be subjected to the successive manually timed treatments of the improved material recovery method or process.

'I'he improved method or process consists of batch treating the material to be reclaimed, such as,previously used foundry sand or spent granular materials which is usually obtained from old foundry molds, cores and the like. Theffoundry molds and cores are iirst crushed in the ordinary type of crusher and shake out mechanisms, from which the material to be treated is delivered to the screening and magnetic separator unit A, where the. material is received in the screening bin I. The lumps are screened oif and the nner material shakes through the screen member onto a conveyor belt and passes over a magnetic pulley which serves to remove the metallic particles from the material and allows the screened material to be discharged into the receiving bucket Il of the bucket loader unit B.

The bucket loader unit is switch controlled to permit the material to be delivered in batches into Y the wet scrubbing unit C from which the dust and nes are suctioned off, through a suctioning mechanism, while the spent granular material is subjected to mixing, plowing and mulling actions. When the material is of a clay bonded type, the material grains-are wetted with approximately of water to effect thorough mixing, plowing and mulling treatments whereby the granular coatings are 'softened and liberated from each of the sand grains.

After the wet scouring and scrubbing treatments the scrubbed material grains together with the removed bonding matter is discharged into the desilting attachment adjacent the wet scrubber unit. The desilting treatment is supplied by` the action of water designed to create a countery flow of the water in the desilting unit whereby the E wherein the material is consigned to a con-` fined area, where the material is rotated and advanced and simultaneously subjected to plowing treatments in the presence of tangentially directed flames creating a whirling flame area contemporaneously with the directing of auxiliary ain currents into the agitated mass of material lto establish a more complete combustion and burning away of foreign and carbonaceous materials from the sand grains to further complete,

the cleaning thereof. The treatment of the material in the confined area, of the furnace unit involves not only the carrying of the material` through to a circular path but also includes the subjecting of the material while so traveling to plowing actions for diversifying the path of travel of the material, while beingrotated, to cause said material to be moved inwardly toward the center of the area during a part of its travel and subsequently causing the material to move outwardi ly from the center of the area toward the periphery thereof. The material is thus thoroughly agitated and plowed while being simultaneously subjected to the whirling iiame actions and to the auxiliary air currents whereby the oxygen.

supplied to the material being treated is augmented to eiect a. substantially complete burning away of the carbonaceous matter las well as the' cinderization and loosening of any particles of refractory coating material which may still be adhering to the sand grains when they are delivered to the furnace unit. While the material is being subjected to the burning and aerating treatments within the coniined furnace area, the

material is dried and any resultant dust and fines are suctioned therefrom leaving the substantially cleaned material in a hot condition ready for discharge into the cooling and transfer unit F of the system. Y

The next step in the process is the transfer of the hot clean material into the enclosed area wherein the hot material is conveyed in small quantities, is water sprayed with the result that the heat vaporizes the ilne water sprays and draws the heat from the material to cool the same. The conveyed materialv which is partly cooled while being elevated by the conveyor is next discharged over an aerating field whereon the material is spread out in small quantities and is further subjected to the cooling action oi' the vapor and air currents which pass through the discharging material and to the action of the upper water sprays which are also vaporized by the remaining heat in the material which is thereby cooled. The air and vapor currents are suctioned out through the suction pipe and carry off any released lines and hot gases resulting from the cooling treatment.

The substantially cooled and cleaned material, from the unit F, is next transferred into the iinal treatment unit G where the material is subjected to mixing, plowing and mulling actions in a conned area from which any remaining nes and dust released by the nal treatments are suctioned off while the highly cleaned material is undergoing the final mixing, plowing and mulling treatments leaving the silica sand grains inan eiliciently cleaned substantially bleached or white recovered state ready for discharge into a receiving container for delivery for storage, or for delivery to an area wherein the highly cleaned material is retempered, reconditioned and rebonded to t the same for re-use in the making of foundry molds, cores and the like.

While the method and process hereinbefore described was directed primarily to the cleaning and recovery of spent clay bonded foundry sand and the like, which necessitates the subjecting of the material to the wet scrubbing treatments before being delivered to the furnace unit for the plowing, burning and auxiliary air treatments, it is to be understood that the furnace unit may also be used for the direct recovery of spent materials,

such as oil bonded sands, which do not require thewet cleaning treatments. Oil bonded materials.

to be treated may be delivered from a shake out unit into the screening unit A, and then to the bucket loader unit B from which the material may be directly delivered into the top of the furnace unit E. The oil bonded material which has been freed of lumps, metallic particles. dust and fines is delivered into the furnace unit where the material is carried through a rotary path in a confined area and is subjected to plowing treatments, whereby the path of movement of the material while being rotated is alternately diverted toward the center of the area and then outwardly away from the center of the area in the presence of whirling flame actions and in the presence of auxiliary air currents, to cause foreign and carbonaceous matter to be thoroughly burned and removed from the material grains by oxidation leaving a substantially cleaned hot material ready to be delivered for conveyance through the cooling unit F, and subsequently through the final treatment unit G from which the cleaned material may be removed for retempering, rebonding and re-use. If desired, the cleaned materials while undergoing the final cleaning treatments in the unit G may be mixed with retempering and rebonding agents; within the treating area of the unit G, to properly retemper and recondition the material so that when it is delivered into the transfer truck 96 it may be delivered directly to the molding or core making departments of a foundry to again be formed into molds, cores and the like.

It is understood that the machine assembly or system herein described, and the method or process adapted to be practiced therewith, may be employed for the purpose of reclaiming spent or inert clay bonded foundry sands, as well as oil or cereal bonded sands. The various steps or stages in the recovery of spent granular materials by means of the machine assembly herein described, may be separately and independently timed, by an attendant, by a manual operation of the various controls of the units of the system, thereby permitting a treated batch of material to be discharged from one of the units before a new batch is admitted from another unit or from the batch supply units of the system.

While a selected machine assembly or system of units has been illustrated and described for practicing the improved method or process of recovering spent or inert bonded foundry sands and other similar materials, it is to be understood that the machine assembly is one exemplication of the principles involved, and the right is accordingly reserved to make such changes in the1 construction and in the arrangement and combinations of the units and the parts of the sytem as will widen the field of utility and increase the adaptability of the system without departing from the principles of this invention. 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:

l. In a method of treating clay bonded granular material such as foundry sand, the steps of mulling and agitating the material and wetting the same in a given area to soften and remove the major portion of the clay coatings from the material grains, then transferring the partially cleaned material and removed clay coating matter while still in a partially wet state into a succeeding desilting area to remove the coating matter and silt, and then contemporaneously subjecting the resultant material in a confinedarea to movement in a circular path and subjecting the material to a plowing treatment in the presence of air currents and changing the course of travel of the material while simultaneously subjecting the same to the further action of swirling flames directed into the material to remove carbonaceous matter by oxidation and any remaining clay bonding matter by driving off the volatile constituents from the clay and sand mixture.

2. In a method of treating clay bonded granular material such as foundry sand, the steps of wet mulling the material in a given area to soften and remove spent refractory coating matter therefrom, then transferring the material and the removed matter through a desilting operation to divest the material of the removed bonding matter and silt, then transferring the resultant material into a second conned area and simultaneously subjecting the material while being carried in a circular path to plowing actions in the presence of air currents and to the actions of oppositely projected flames acting to augment one another to create a swirling flame action directed into the material to remove carbonaceous matter by oxidation and any remaining clay bonding matter by driving off the volatile constituents from the clay and sand mixture, and simultaneously suctioning the resultant hot gases, fines and dust from the cleaned material grains as they are progressively laid bare by the applied treatments.

3. In a method of treating clay bonded granular material such as foundry sand, the steps of wet mulling the material in a given area to soften and remove spent refractory coating matter therefrom, then transferring the material and the removed matter through a desilting operation to divest the material of the removed bonding matter and silt, then transferring the resultant material into a second confined area and simultaneously subjecting the material while being carried in a circular path to plowing actions in the presence of air currents and to the actions of oppositely projected flames acting to augment one another to create a swirling flame action directed into the material to remove carbonaecous matter by oxidation and any remain ing clay bonding matter by driving off the volatile constituents of the sand and clay mixture, and simultaneously suctioning the resultant hot gases, fines and dust from the cleaned material grains as they are progressively laid bare by the applied treatments, then conducting the hot cleaned material grains through a cooling and aerating path, and finally subjecting the'material grains in a confined area to plowing, mixing and mulling actions in the presence of air currents to cool the cleaned material grains and withdraw the final resultant dust and fines therefrom.

4. The method or process of recovering spent bonded foundry sand and the like for re-use, said method including subjecting a series of batches of material in continuous sequences, each batch to a different treatment as the series of batches are advanced at timed intervals, subjecting sand broken from used molds to screening and magnetic treatments to clear the material of 'lumps and metallic particles, batch delivering the material and subjecting the same to wet scrubbing and scouring actions in a confined area as the material is being mixed and mulled to soften and remove the bonding matter from the material grains to form a paste, treating the paste to a desilting operation and hydraulically removing organic and foreign matter from the resultant batch, conducting the remainder of the batch through a dewatering area, depositing the dewatered batch into a confined area and rotating the material and subjecting the same to different angular plowing treatments in the presc-nce of swirling flames and auxiliary air currents to further clean the batch by oxidation, transferring the hot cleaned granular material through an enclosed cooling area and subjecting the material to the action of sprinkling and air currents and to further suctioning action to further withdraw dust and fines from the cooling material, and finally delivering the cooled recleaned and substantially recovered ready forl re-use.

5. The combination wet and dry method of recovering used inert foundry sands and the like for re-use comprising the steps of advancing the material in batch quantities through a continuous sequence of timed operations comprising sub- Jecting the material to cleaning and magnetic treatments to remove lumps and metallic particles therefrom, batch delivering'jthe screened material and subjecting the batch to wet scouring and mulling treatments to soften and remove coating matter from the material grains leaving a paste-like batch, subjecting the paste-like batch to a desilting treatment and removing organie and foreign matter therefrom, then subjecting the resultant batch to a dewatering treatment, next delivering the dewatered batch of material into a confined area and carrying the batch through a circular path and continuously subjecting the batch to diierent angular mulling treatments while contemporaneously subjecting the agitated mulled batch to the action of swirling flames and secondary air currents to burn off foreign and carbonaceous matter by oxidation leaving a resultant cleaned hot batch of granular material, delivering the clean hot batch of granular material into av confined cooling area and gradually conveying and spreading small quantities of the material and subjecting the material to moisture sprays and air currents and drawing off resultant dust and fines while the material is being cooled and advanced into a nal treating area, and finally plowing and mulling the cooled batch of material in the final area and withdrawing final dust and fines therefrom prior to the discharge of the cooled cleaned granular batch of recovered material for re-use.

6. A foundry sand recovery method-consisting of simultaneously advancing batches of material in manually timed sequences through a series of successive stages, said sequence of operations including wet mulling and desilting a batch of screened material, dewatering and transferring the partially treated batch into a confined area and advancing the batch through a circular course and intermittently subjecting the granular material to different angularplowing actions and simultaneously subjecting, the batch to the action of flames and to the application of auxiliary air currents to further clean the batch by burning of lcarbonaceous bonding materials and removing nes and hot gases therefrom.

7. A foundry sand recovery system comprising in combination a screening and magnetic separator unit, a switch controlled bucket loader unit for receiving and batch feeding the material. a we t scrubbing and mulling unit to receivea batch from the loader unit and form a sandpaste of the batch, a desilting unit for receiving the paste batch and including means for desilting the paste by removing organic and'foreign matter therefrom leaving a wet batch, a transfer unit for advancing the wet batch and dewatering the same, a furnace unit for receiving the dewatered batch, said furnace including a rotatable table and stationary and adjustable groups of plow units, a burner unit having oppositely disposed nozzles projecting tangentially into the furnace unit from opposite directions for directing flames into the furnacefunit, means for delivering air currents through the plow groups intol the furnace unit, means for drawing off resultant hot gases and flnes from the material being treated ing unit for conveying the material therethrough,

- an apertured'material receiving plate in the cooling unit, means for ldrawing air currents through the cooling unit and through said plate, means in the cooling unit for sprinkling the air currents therein to assist in the cooling operation of the material being conveyed through the cooling unit, and a nal mixing and mulling unit for receiving the cooled material and including means for suctioning remaining dust and fines therefrom to condition the treated material for re-use.

8. In a foundry sand recovery system comprising a batch loader unit, a screening and magnetic separator unit for screening material for delivery to the loader unit, a wet mulling and scouring unit for receiving material from the loader unit to wet treat the received material and form a paste batch therefrom, means for receiving the paste batch and subjecting the same to a desilting treatment to remove the organic and foreign matter from the wet scrubbed sand, a dewatering conveyor for receiving the wet scrubbed sand to further advance the same through the system, a plowing and burning unit for receiving the dewatered batch of material, said plowing and burning unit including flame ejecting burners and air delivery means to create a burning olf of the foreign matter and carbonaceous material from the material grains, a cooling housing positioned to receive hot clean material from the plowing and burner unit, a conveyor in saidhousing for advancing the material therethrough, an apertured receiving plate in said housing, means for directing water sprays and air currents through the receiving plate and through the material discharged thereon by the conveyor mechanism to cool the cleaned material, a mixing and mulling unit for receiving the cooled material to give the material a final mixing and mulling treatment, means for aerating the material in the mixing and mulling unit, and means for withdrawing remaining dust and fines from the mixing and mulling unit to complete the cleaning of the material batch to condition the same for re-use.

9. A foundry sand recovery system including in combination a mixing and mulling unit for wet scrubbing and scouring a batch of material, a iurnace unit including stationary air discharging plows, llame ejecting burners and a rotatable bottom for carrying a batch of material to be treated through the field of action of the plows and into the burning area produced by the burners, a final mixing and mulling unit including aerating and suctioning means, and a plurality of transfer units connecting the treating units to provide a system wherein consecutive batches of material are adapted to be intermittently fed through consecutive stages of the system to eifect a substantially complete removal of bonding and carbonaceous coating materials from the material grains to recover the material grains in a, cleaned state ready for re-use.

10. A used foundry sand recovery system in cluding in combination a material screening unit including means for removing metallic particles, dust and fines from the material as it is screened, a batch loading unit receiving material froml the 17 screening unit, a wet mulling unit positioned to receive a batch of screen material from the load.

ing unit, a desilting unit for receiving the wet scrubbed batch of material from the wet scrubbing unit, a combination plowing, aerating and burning unit having a batch control feeding mechanism supported thereon, a conveyor screw type dewaterlng unit connecting the desilting unit with the batch control feed mechanism of the furnace v unit, a suction type of mixing and mulling unit for completing the final stages of recovering the sand grains, and a conveyor type cooling unit connecting the furnace unit with the suction type mixing and mulling unit, said cooling unit including an apertured material delivery support, means for suctioning air currents through the cooling unit and through the apertured support to cool the material passing thereover. and means for water sprinkling the hot material conveyed through the cooking unit to cool the material by the vaporization of the water by the heat withl 18 terial by oxidation, a combination desilting and dewatering unit connecting the wet mulling unit with the batch control feed mechanism ofthe furnace unit, an air suction type of mixing and mulling unit for completing the nal cleaning operation on the batch of material, and a cooling unit connecting the furnace unit with the mixing and mulling unit, said cooling unit comprising an enclosed chamber, a conveyor mounted in the cham ber for receiving material from the furnace and moving it through the chamber, means for spraying water on the material passing through the chamber, and an apertured support through which vapor and air currents are conducted through the material to cool the same while passing through the cooling unit and over said support into the mixing and mulling unit.

ALFRED C. CHRISTENSEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,552,694 Groebe Sept. 8, 1925 2,309,036 Beardsley Jan. 19, i943 2,314,486 Dvorak Mar. 23, 1943 2,331,102 Bird Oct. 5, 1943 2,412,057 Nichols v Dec. 3, 1946 2,420,392 Christensen May 13. 1947

Claims

6. A FOUNDRY SAND RECOVERY METHOD CONSISTING OF SIMULTANEOUSLY ADVANCING BATCHES OF MATERIAL IN MANUALLY TIMED SEQUENCES THROUGH A SERIES OF SUCCESSIVE STAGES, SAID SEQUENCE OF OPERATIONS INCLUDING WET MULLING AND DESILTING A BATCH OF SCREENED MATERIAL, DEWATERING AND TRANSFERRING THE PARTIALLY TREATED BATCH INTO A CONFINED AREA AND ADVANCING THE BATCH THROUGH A CIRCULAR COURSE AND INTERMITTENTLY SUBJECTING THE GRANULAR MATERIAL TO DIFFERENT ANGULAR PLOWING ACTIONS AND SIMULTANEOUSLY SUBJECTING THE BATCH TO THE ACTION OF FLAMES AND TO THE APPLICATION OF AUXILIARY AIR CURRENTS TO FURTHER CLEAN THE BATCH BY BURNING OF CARBONACEOUS BONDING MATERIALS AND REMOVING FINES AND HOT GASES THEREFROM.