US2331102A - Sand treating system and method - Google Patents

Description

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BYRON M. BiQD, ALBERT C. QICHAQDSON, lam/4M.

Oct. 5, 1943. B.'M. BIRD SAND TREATING SYSTEM AND METHOD Filed Dec. 4, 1940 SAND TREATING SYSTEM AND METHOD Filed Dec. 4, 1940 3 Sheets-Sheet 2 CLASSlFlER SCIZUBBEE KNOCKOUT f/vl/fA/roes,

BYRON M. BIQD. ALBEQT CLDmHAQDsON.

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3 Sheets-Sheet S B. M. BIRD SAND TREATING SYSTEM AND METHOD Filed Dec. 4, 1940 Oct. 5, 1943.

DYQON M. B121), ALBEQT QElCHAQDSON.

iatented Oct. 5, 1943 SAND TREATING SYSTEM AND METHOD Byron M. Bird, Columbus, Ohio, assignor to The Jeffrey Manufacturing Company, a corporation of Ohio Application December 4,1940, Serial No. 368,524

6 Claims.

This invention relates to apparatus for and a method of treating sand to condition, or recondition, it for use as foundry sand, either in. the making of mold cores or as green moldin sand.

An object of the invention is to provide improved apparatus and an improved method as above outlined.

Another object of the invention is to provide a practical method of and apparatus for treating or reconditioning used core sand, such as oil core sand, so that it can be used again.

Another object of the invention is to provide a method of and apparatus for treating molding sand, either new or used, so that it will be of uniform consistency and thus make uniformly good cores or molds.

Another object of the invention is to provide a method of and apparatus for treating molding sand involving scrubbing or cleaning thereof to remove adhering foreign matter, such as spongy carbon, scale or other foreign matter while the sand is in a bath of water.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings,

Fig. 1 is a plan view of a system comprising my invention which may be employed to carry out the method of my invention;

Fig. 2 is a combination sectional and elevational view of the system taken on the line 22 of Fig. 1 looking in the direction of the arrows;

Fig. 3 is a combination sectional and elevational view of the system of my invention taken on the line 3-3 of Fig. 1 looking in the direction of the arrows;

Fig. 4 is a sectional view taken on the line 44 of Fig. 1 of the drawings looking in the direction of the arrows;

Fig. 5 is a sectional view taken on the line 5-5 of Fig. 1 looking in the direction of the arrows;

Fig. 6 is a plan view showing the upward current classifier which I have used;

Fig. 7 is a sectional elevational view of the classifier of Fig. 6; and

Fig. 8 i a flow diagram of the system and method.

My method and system relates particularly to the treatment of used core sand, such as oil core sand, so that the sand may be substantially free of foreign matter and thereby restored to its original condition or a condition which may be even superior to its original condition. While this is the principal characteristic of my invention,

it is also'to be understood that it may be used to treat'ordinary molding sand which has been used, or it may be used to treat original sand which contains some impurities or foreign mat ter thereby to improve its quality for use. either in the making of sand cores or for use as green molding sand.

With respect to the principal feature of my invention, namely the treating of used core sand so that it may be used again, it may be pointed out that core sand when once used tends o form a coating or outer layer of spongy carbon which is apparently due primarily to the fact that the bonding agent such as oil, molasse or other material tends to carbon under the heat of the casting and this spongy coating or layer of carbon precludes the satisfactory reuse of the sand except that in some cases it has been used in relatively small quantities with new sand. My improved method and the apparatus which I provide has resulted in great saving of used core sand because it has been found that by treating or reconditioning said core sand in accordance with my invention all or substantially all of the original sand is recovered to be used again, and this process of recovery can be carried on indefinitely because the quality of the sand appears to improve rather than degenerate by virtue of the reconditioning or retreating process.

in the accompanying drawings, I have illustrated one form of apparatus which may be employed to carry out my improved method, it being understood of course that numerous modifications of the apparatus may be made.

Referring particularly to Figs. 1 and 2 of the drawings, there is seen at II a knockout grating upon which the used sand, that is core sand or green sand as the case may be or even new sand which is to be treated, is received. In the case of used core sand it will be knocked out of the castings by any well-known means such as a casting vibrator and-fall on the grating Ill. The grating I0 is of a large mesh, for example the openings may be as large as'2" by 4", and thus practically allof the sand, even use core sand, will freely pass through it and any large particles which do not pass through can be easily broken up so that they do pass through.

Below the grating I Us a receiving hopper II which catches the sand and directs it to a vibratory feeder 12 which may be of the electromagnetic type such as those known in the art as the Traylor Feeders manufactured by The Jeffrey Manufacturing Company of Columbus, Ohio. The feeder I: when energized will feed 2 thesand to a belt conveyor It by which the sand is conveyed to a delivery chute I4 which feeds a swing hammer crusher l5. The conveyor l2 preferably has a magnetic pulley 16 which attracts any iron which is delivered to chute l4 and causes it to stay on the belt of conveyor 42 until it is scraped off into an iron discharge chute ll which directs'it to a receptacle l8. The swing hammer crusher l5 breaks up the chunks ofmaterial without appreciably reducing the size of any of the sand grains individually thus tending to free each sand grain of other adhering sand grains and thus exposing the entire surface of each grain of sand to be treated as hereinafter described.

Swing hammer crusher l5 discharges onto a belt conveyor I9 which conveys the sand to the boot of an elevating conveyor into which it discharges. The conveyor I9 preferably has a magnetic pulley 2| to catch any iron which is not removed by the magnetic pulley I6 and discharge it by way of chute 22 into receptacle 29. The elevating conveyor 29 discharges the sand into a surge bin 24 which compensates for any variations in the rate of feed of the sand to it to insure continuous operating of the equipment which follows the surge bin.

The surge bin 24 has a hopper-like bottom in which is mounted a screw conveyor 25 which conveys the material into a rotary pebble mill 25 or other scrubbing device. Water is fed to the pebble mill 25 by way of pipe 21 having a control valve 28. As hereinafter pointed out more completely the pebble mill 26 is not used as a mill in the sense that it grinds the sand, but is used as a scrubber to free the sand grains of foreign matter.

In the practice of my invention the sand to be treated is preferably continuously fed to the pebble mill 25 and also continuously fed therefrom. This pebble mill is of the rotating type and its function is to scrub the individual particles of sand toremove the adhering coating of foreign matter, such as spongy carbon, or any scale which may be attached to the sand particles. It is also effective to separate any adhering grains of sand which have not been previously separated by the swing hammer crusher I5. This scrubbing action takes place in a bath of water which is preferably maintained at roughly a 25% solution of water'and a continuous scrubbing action has been found effective particularly in a bath of water to remove all foreign material from the sand grains thereby conditioning them to the most desirable condition possible.

I have found from experiment that where an 011 core sand is being retreated, the pebble mill 25 preferably employs steel punchings as a loose material to scrub the sand. In practice I have .used punchings of the size by 54; which moval of any large particles, this screen being a fairly flne screen. It is particularly effective to remove particles of coke which are placed in sandcoresasiswellknowntothoseskilledin the foundry art, which coke tends to float on the liquid in the pebble mill 26 and is often of considerably larger size than the sand grains and thus is easily removed by the screen 29.

This foreign matter which is removed by the 5 screen 29 is discharged by way of chute 20 into a sludge tank 3! provided with scraper conveyor mechanism 22 for removing the settled sludge a hereinafter described more completely.

The grains of sand as well as the foreign matter such as carbon which has been removed therefrom will pass through the screen cloth of screen 29 where it is received by a hopp r-like structure and directed to an upward current classifler 22, or other type of gravity separator such as a jig of the type well-known in the minins or coal cleaning art. In this installation the upward current classifier is preferred because of its simplicity and cheapness.

The structure of the upward current classifier 20 which I have employed with satisfactory results is shown particularly in Fig. 6 and 7 of the drawings. This classifier comprises a container 24 having three bottom cells 25, and 21 supplied with water from a pipe 29 through individual 25 control valves 29, 40 and 4|. Above the cells 25, 38 and 31 is a perforated plate 42 which slopes downwardly over the cells 25 and 25 but is substantially horizontal above the cell 21. Formed as substantial continuations of the cells 30 25, 36 and 31 and directlyabove each of them respectively are cells or compartments 42, 44 and 45 provided with overflow weirs 45, 41 and 48 over which the liquid flows into receiving compartments 49, 50 and SI respectively.

By reference to Fig. 6 of the drawings it will also be seen that the cell or compartment 43 has an extension 52 which first receives the mixture of water, sand grains and foreign matter which passes through the screen 29. The function of 40 the upward current classifier 22 is of course to effect a separation of the pure sand grains from the foreign matter. In operation the mixture from the screen 29 flows into the extension 52 and into cell or compartment 43. The upwardly flowing current which flows through pipe 24, valve 29 and bottom cell 35 and thence upwardly through cell or compartment 42 has a relatively low velocity; and so it is effective to classify the sand and foreign matter so that the heavy sand grains will move downwardl against the upwardly flowing water while the spongy carbon and other foreign matter, whichhas a much lower specific gravity than sand. together with any very fine material, and slime will flow over the weir 45 and into the receiving compartment 49 from where it flows by pipe 52 (see Fig. 1) to the sludge sett i g tank 2 i It is thus evident that all foreign matter, slime and carbon, will be removed by the upward current classifier in compartment 42 and delivered to the sludge tank 2| where it will settle to the bottom and be removed by the scraper conveyor 22 up the inclined wall thereof as clearly illustrated at 54 in Fig. 3 of the drawings. As above mentioned, the sand grains which are the desired size, that is, all of them except the very fine ones, due to their high specific gravity will accumulate on the plate 42 since they move downwardly in the cell 42, and since they are maintained in a continuous agitation b the water flowing upwardly through the plate 42 they will slide downwardly along said plate 42. The valve 40 is so adjusted that the upwardly flowing current flows at a higher rate therethrough than 75 through the cell 25, and consequently the water through cell 44 flows at a higher rate than that through cell 43. This is effective to carry over the smaller particles of sand and in one typical installation the sand from 120 mesh to 70 mesh is carried over in this compartment flowing over the weir 4'! to receiving compartment 50. The larger sand grains continue to move downward to.a position above cell 31 through which the water flows upwardly at a still higher rate than that through cells-35 and 35, and consequently the sand is preferably carried off through compartment or cell 45 over weir 45 into receiving compartment 5|. In other words, the two compartments 44 and 45 are primarily for obtaining two different size ranges of sand grains, and in many installations this separation will not be necessary 7 or even desirable in which case a two-compartment upward current classifier will be used, the

first compartment to remove the very fine sand which is not fed for reuse, the slimes, the carbon and any other foreign matter, the cleaned sand all being removed in the second compartment. If a jig isused, the sand of course will form on the bottom stratum, and all other material such as the fines, slime, carbon and foreign matter will be discharged over the weir as the low gravity material and will be conveyed to the sludge tank.

In the system disclosed I have shown apparatus for separating the reconditioned sand into two size ranges which are subsequently separably dewatered and dried. This separation and separate drying is not at all essential to my system or method in its broader aspects, but under certain conditions may be desirable in case two different size ranges of sand are desired.

Referring particularly to Fig. lot the drawings it will be seen that the sand and water delivered to receiving compartment 55 flow by way of pipe 55 to an elevating dewatering scraper conveyor 55, and the sand and water delivered to receiving compartment 5! flow by way of pipe 51 to an elevating dewatering scraper conveyor '58. The water which accumulates in the bottom of the conveyors 55 and 55 is recirculated by a pump 59 being delivered to the system and used by the upward current classifier 33 and/or the pebble mill 25. r 7

Referring to Fig. 2 of the drawings, it will be seen that each of the elevating scraping conveyors 55 and 55 ha an upwardly inclined portion which insures complete dewatering-of the sand, that is, the removal of all free flowing water, and this sand is then delivered to chutes 55 and 5| from conveyors 55 and 58, respectively, by which it is directed to rotary dryers 52 and 53, respectively. These rotary dryers 52'-and 53 are of-well-known construction and briefly described comprise rotary cylinders which slope slightly downwardly from the receiving end at the rear to the discharge end at the front, the interior walls of which are provided with projections which lift the material to be dried, which in this case is wet sand, and let it fall through a heated atmosphere provided by a gas burner, that associated with the dryer 52 being indicated at 54, which extends into the front end thereof and shoots a flame of burning gas into the dryer.

An exhaust gas fan means 55 is shown associated with the dryer 52, there being similar exhaust gas fan means associated with the dryer 53 to remove the exhaust gas which collects moisture delivered from the'sand in the process of drying the sand and delivers it outside the building which contains the equipment.

As illustrated particularly in Fig. 5 of the drawings, at its forward end the dryer 52 has a'discharge chute 55 which delivers the dried sand onto a collecting belt conveyor 51. Dryer 53 also discharges onto the belt conveyor 51 or, if desired, it may discharge onto another belt. In the first instance there will be a mixing of the sands delivered by the dryers 52 and 53 if they are operating simultaneously, while in the second instance such a mixing will not take place. It is of course possible to operate alternately the dryers 52 and 53 andthus maintain their productionsseparate by discharging from only one of them at a time onto the single belt 51.

As best illustrated in Fig. 4 of the drawings, the belt 51 delivers the dried into the boot of an elevating conveyor 58 which elevates it and delivers it to a distributing belting v conveyor 59 by which it may be distributed to any one of three hoppers 10, ll and l2. s The bin into which the sand on distributing conveyor 59 discharges may be governed by controllable discharge plates 13 and 14. The green sand ready for reuse is thus stored in the bins 10, H and i2, and it may be separated according to size into one or more of said bins if desired. From any of the bins 15, ii and 12 the reconditioned sand may be obtained for use by way of discharge hopper and chute mechanism, one of which -is illustrated at 15 associated with the bin 10 in Fig. 3 of the drawings.

In the operation of the mechanism comprising my invention with the consequent carrying out of the method of my invention, the sand to be treated or retreated, be it used core sand, used foundry sand or new sand, any one of which may have foreign matter therein, is first received by the grating [0 which of course keeps large particles, such as castings, core flasks and the like in their proper place, from which the sand is conveyed to the swing hammer crusher l5, the metal being removed at least in part before the sand to be treated is delivered to said swing hammer crusher. Said crusher I5 is effective to break up the sand into individual grains, at least to a large extent. From the crusher IS the sand is conveyed to surge bin 24, any iron passing through the crusher being removed by the magnetic pulley In the surge bin 24 the sand to be treated which may be called the impure sand is fed to the scrubbing device which in this case is a pebble mill 25 to which suificient water is fed to form a bath for the sand, an approximately 25 solution of water having been found desirable.

Within the pebble mill 25 a thoroughscouring action is performed upon the individual sand grains, and if any sand grains tend to adhere to each other they will be separated during the process of this scouring action. The scouring or scrubbing action will remove any adhering particles of carbon or foreign matter from the sand grains thus conditioning them for future separation. This mixture of material, that is, water and sand and foreign matter, will have a very high specific gravity. A light material, such as coke particles which are present because of the fact a sand grains, coke particles or other large particles of foreign matter and small particles of carbon, scale or other foreign matter. The larger partiand reconditioned sand.

cles will be removed by the screen 2! and delivered to'the sludge tank II while the small particles with the water pass through said screen II and into the upward current classifier 33. This classifier will act as was described in detail above, first to separate the slimes, fine sand, carbon and other foreign matter, and deliver it to the ludge tank II. The pure sand is thereafter delivered into two sizes in the system and method disclosed, whereas in other systems and methods within my invention it will be delivered only as a single size of clean sand, for subsequent drying and storing. In the system and method disclosed one size range of sand, for example 70 mesh to 120 mesh, is delivered to the dewatering conveyor 56 and another size range of sand, for example, '70 mesh plus to dewatering conveyor 58. The dewatering conveyors i6 and 58 are effective to reduce the water content of the clean sand appreciably, for example, to approximately 20%, and this dewatered but wet sand is delivered by chutes 60, 6| to dryers 62, it where it is dried to a completely satisfactory state of dryness and delivered to the conveyor 61 which then delivers it to the elevating conveyor 68, thence to distributing conveyor 69 and other storage bins 10, II and 12, or any one of them as desired. If desired, each of the dryers 62, it may have a belt conveyor comparable to the single conveyor 61 and a separate elevating conveyor comparable to the elevating conveyor 88 which may deliver it into a separate storage bin instead of the three storage bins I0, H and 12.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I therefore wish not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

1. The method of treating used foundry sand, comprising scrubbing the sand in a liquid bath to separate pure sand from foreign matter, screening the wet sand and foreign matter in remove foreign matter of large size, treating the screenings by an upward flow of water to produce products of usable sand and foreign matter, directing the separated products along different paths, and drying the usable sand.

2. The method of treating sand, comprising scrubbing the sand in a liquid bath to separate pure sand from foreign matter, screening the wet sand and foreign matter to remove foreign matter of large size, treating the screenings by an upward current of water to produce products of usable sand and foreign matter, and directing the separated products along different paths.

3. The method of treating used foundry sand, comprising scrubbing the sand in a liquid bath to separate pure sand from carbonized binder foreign matte treating the sand and foreign matter by an upward current of water to produce products of usable sand and foreign matter, and directing the separated products along diiferent paths.

4. Apparatus for cleaning used foundry sand comprising means for crushing large particles formed by adhering sand grains, scrubbing means comprising a rotary pebble mill having loose scrubbing material therein for removing adhering foreign matter from the sand grains, means for supply g water to said scrubbing means, means for conveying the used sand from said crushing means to said scrubbing means, means fed by said scrubbing means for separating the sand grains from the foreign matter, means for drying the cleaned sand, and means for storing said cleaned sand.

5. Apparatus for cleaning used foundry sand including a rotary scrubber having loose particles therein to aid the scrubbing action on the said grains during rotation of said scrubber, means for supplying water to said scrubber, a screen positioned to receive material from said scrubber and remove large particles of foreign matter, and an upward current gravity separator adapted to separate the clean sand from the foreign matter.

matter, and a gravity separator adapted to separate the clean sand from the foreign matter.

BYRQN M. BIRD.

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