US2169544A - Method and apparatus for separating material into constituents of different specific gravity - Google Patents

Description

Aug. 15, 1939. G A, WSSAC 2,169,544

METHOD AND APPARATUS FOR SEPARATING MATERIAL INTO CONSTITUENTS OF DIFFERENT SPECIFIC GRAVITY Filed MaICh 16 1936 Patented Aug. 15, 1939 UNITED STATES PATENT orifice METHOD AND APPARATUS FOR SEPARAT- ING MATERIAL INTO CONSTITUENTS OF DIFFERENT SPECIFIC GRAVITY This invention relates to a method of separating material into constituents of different specific gravities and to an apparatus, i. e. a jig, for carrying out such method.

Different methods and apparatus for effecting the separation of material into constituents of different specific gravities by means of pulsating currents of water, have been suggested and used, and my invention, which has been developed more particularly in connection with the separation of coal from its impurities, is an improvement on such methods and apparatus.

The jig, according to the invention, includes a screen across which material to be separated is adapted to pass, the screen being supported in a hutch lled with water and associated with an air pressure and Vacuum tank which are adapted to be periodically brought into communication with it by means of rotating valves, the pressure tank being provided also with a bye-pass through which a substantially continuous current of water may, when desired, be allowed to flow into the hutch.

One of the great difficulties in prior methods and apparatus using pulsating currents of water has been the large volume of water necessary to obtain suiciently active surges and a reasonable output. According to the present invention this diiculty is entirely overcome by particularly shaping the hutch and tanks and using certain guiding plates therein and employing extremely sensitive variable speed drives for the rotating valves so that in each case a speed may be obtained at which the pressure tank and hutch act as resonators, with the result that the pulsations of the air and water are greatly amplified by the effect of resonance. In this way the most efficient surges with the minimum amount of power are obtained.

Another great diiculty in prior methods and apparatus has been to produce the form of surge exactly adapted to each particular problem of separation. Depending on the sizes and specic gravities of the particles to be separated, the most eiicient surge may have a slow or a sharp rise, a short or a long top and a sharp or a slow fall, which latter may even acquire a negative value in the form of a suction. Thus, an undesirable shape of surge is a straight line in the rise or fall, as it means a constant speed period of motion during which the sizes that can be separated are limited by the law of equivalence. A desirable shape of surge is a parabolic curve, which means accelerated motions and separation by specific gravities alone independently of sizes. Again with a surge having too sharp a rise small particles of refuse can be washed over before they can be drawn down on the fall of the surge; while with a surge having too sharp and brief a fall or a suction at the end of the fall, small particles of refuse may be drawn down through the screen into the bottom of the hutch. The apparatus of the present invention, however, provides the necessary means and enables the necessary adjustments of such means to permit the production of surges of the desired form for any given case.v

When the proper and correct stratication of the products to be separated has been achieved, another great difculty in prior methods and apparatus has been to withdraw the separated constituents correctly and consistently. The constancy of the degree oi separationis generally achieved by regulating the removal of one of the constituents, the refuse in the case of coals, through a refuse extractor or evacuator, the remaining or clean constituent being washed over the Weir of the jig.

According to my invention, the regulation of the removal of the refuse is achieved by combining a float control dependent on the specific gravity of part of the bed of material to be separated, with a float control dependent on the resistance of this part of the bed caused by the accumulation of material.

The shape and eiciency of the surges caused in the hutch by its periodic communication with the pressure or vacuum tanks are controlled by (l) driving the rotating Valves at exactly the speed capable of giving the ei'ects of resonance,

this speed being ldetermined by observation in each case; (2) the setting of the valve controlling the bye-pass from the pressure tank to the hutch; (3) the regulation of the resistance or of the assistance presented to the surges in the hutch by a plate freely hung in the path of movement of the water passing between either of the tanks and the screen, this regulation being effected by adjusting the angular relation to the plate of an arm connected with it and by adjusting the position of a weight on this arm; (4) the relative angular settings of the rotating valves from the pressure and vacuum tanks; (5) the opening of the valves on feed or drain pipes from the pressure and vacuum tanks.

The means for maintaining constant the degree of separation of the material comprise a float in the bed of material which is formed on the screen, this oat controlling the operation of a switch in the circuit of a motor driving an evacuatoi` for ejecting the heavier constituent of the material y The evacuator is situated at the lower operation of the evacuator is regulated by the specific gravity ofthe heavier constituent. rI-'his control is supplemented by a further control of the amount of a ilushing current of water for the heavier constituent, this control being effected by valves connected to a float whose movement is responsive to the resistance offered by the material on the Vscreen to the upward passage of water therethrough and thus to the accumulation of material on the bed.

In the accompanying drawing:

Figure 1 is a somewhat'diagrammatic cross-section of the apparatus. Y

VFigure 2 is a face view oiY a cam used in connection therewith, and f Figure 3 is a cross-section on the line 3--3 of Figure 2.

f The` main body of the apparatus is composed of a round bottomed shell I divided by a wall 2 into a hutch 3 and pressure tank 4 and having alongside the pressure tank a vacuum tank 5. From the pressure tankrll runs a pipe 6 having therein a valve I and connected either to the pressure side of a pump or to a certain constant head of water. From the vacuum tank likewise leads a pipe 8 having therein a valve 9 and connected to the suction side of a pump or to a draft tube. The openings from the hutch to pressure and vacuum tanks 4 and 5 are adapted to be closed by butterfly valves I and Il respectively, which may be rotated by belts or chains I3 and I4 from variable speed drives operated from a suitable source of power such as a motor I2. When the valve II is closed, a partial vacuum is formed in the tank 5 owing to the fact that Vwater is constantly flowing therefrom through the pipe 8. When the valve is opened, water is drawn into the tank 5 fro-m the hutch. The valves I0 and I I may be adjusted on their shafts to change their angular setting with respect-to one another so that, instead of one being closed during Ythe whole time ,the other is open,fas shown in the drawings, one may open somewhat before Vthe other closes. If, for example, thevalve II opened somewhat before the valve I8 closed, the top of the surge would be flattened and the fall of the surge would be sharpened. "If, on the other hand, Ythe valve I0 opened before the valve II closed, the rise of the surge would be smoothed.

In some cases, in order to produce a particular shape of surge in the hutch, it may be desirable of the screen 22.

Freely swung from the bottom of the wall 2 is a plate I9 extending entirely across the apparatus for aiding inthe control of the shape of the surges in the hutch. To the rotatable shaft sup- ;porting this plate is adjustably fixed an arm 28 and on the arm a weight 2| is adjustable. The amount'of resistance which the plate will present to a surge in the hutch and the point in the rise lor fall of the surge at which such resistance will occurmay thus be controlled by adjusting the angular` settingY of the arm 20 and the setting of therweight 2l on the latter. Across the hutch 3 is fixed a screenl 22,V below which a plate 23 articulated on wall 2 gives the proper lateral com- Y ponent to the surge, to aid feeding of material across the screen. The delivery opening of a suitable hopper or chute for the material to beseparated is situated above the screen at the side nearest the pressure tank 4. Y

Connected with the hutch throughV an opening 24 in the left hand wall 25 thereof is a pressure Vtor 28 for this constituent, which is driven through a suitable drive 29 from a variable speed motor 30. An adjustable sludge valve 62, connected to the elevator 2l or to a sludge tank, isV

positioned in the bottom of the hutch, for the extraction of small particles of the heavier constituent drawn down through theV screen 2lV by suction. Y

Leading from the chamber 26 is a pipe 3| through which water may flow o-ut from the chamber, the opening of this pipe being controlled by valves 32a and 32h connected to a stem 33 having mounted thereon a float 34. It is to be noted that the valves 32a and 32h are thoroughly compensated so that a minimum offorce to move them is required. The former is subjected to a downward and the latter to an upward pressure, and the latter is slightly smaller than the former to take care of the difference in hydrostatic pressure owing to the different vertical elevations. Y

Just abovethe screen 22 and near the opening 24 isa float 35 mounted Oria rod 36 connected to an arm 31 of a bell crank lever pivoted at 38 and the other arm 39 of which is pivotally connected at 40 to a rodV 4I suitably supported by rollers. At the right hand end of this rod are .adjustable stops 42 and 43, one of which upon suiicient movement of therrod in a horizontal direction lis `adapted .to engage Va circular'projection 44 of a cylinder 45 to which is fixed a cam 46. rI'he. cylinder'45 ispslidable along but rotate-s with a shaft 4I suitably driven, as for example through a drive 48, from the motor I2. The left hand face vof theV cam is formed with an indented track as shown in Figures 2 and 3 whilev at the right hand side its circumference is: continuous.

Mounted on a rod49 moving in a guide 50 is a roller 5I and pivotally connected to the rod 49 is a rocker arm 52 centrally `pivoted at 53 and pivoted as' at 54 at its other end to a rod 55 moving in guides 56 and continually urged upwards by a spring 51. The rocker arm 52 has mounted on it a mercuroid tube switchr52a controlling the circuit 52b feeding the motor 30. J

The operation of the-device is as follows:

The material to be separated is allowed to feed from-the hopper or chute to the screen 22. 'I'he opening of the valves 'I and 9 and the bye-pass Vvalve I'I,.th'el speed of rotation of the butterfly valves I (land I I, their angular setting with respect to one another and consequently the relation of their times of openingy and closing, the angular setting of the elliptical sprocket I5 with respect to the valve I8, the angular setting of the arm 28 with respect lto the plate I9 and the posivtion of the weight 2I on the arm 28 Vare all adjusted to give in the hutch 3 surges of the required form and frequency which, as will be understood, vary according to the material being treated and the degree of separation required. Owing'to the water surges in the hutch, the float 35 will oscillate about a position of rest which is a function of the apparent specific gravity of the medium in which it is. When the medium is water alone, the position of rest will be such as to bring the bottom of the float very close to, if not resting on, the screen 22. In this position of the float the rod 4| will be sufficiently far to the right of the position in which it is shown in the drawing not only to bring the stop 43 into contact with the circular projection 44 but to hold the cylinder and the cam 46 so far to the right on the shaft 47 that the roller 5| will be resting on the cylinder l5 and the rocker arm 52 will consequently have the opposite angularity to that shown, the mercury in the tube 52a being thus at the left hand end of the latter so that the circuit 521) for the motor 36 is b-roken and the. evacuator 28 will not be rotating.

In these circumstances a bed of material will be formed on the screen 22, the portion of which nearest the wall 25 will be stratified. As the specic gravity of the bed increases, the float 35, which is normally entirely submerged in the bed, will rise and when the predetermined thickness and consequent specic gravity of the bed has been reached, the rise of the float will be such as to draw the arm 4| and consequently the cam 43 sufficiently to the left to cause the roller 5l to enter the indented cam track 58 of the cam. Owing to the anti-clockwise rotation of this cam, as shown by the arrow in Figure 2, the roller 5| will, through its contact with the wall 59 of the track 58, be forced up onto the outer circumference of the cam. As soon as the roller does reach the outer circumference of the cam, the latter will be free to move under the pull of the stop 42 on the rod 4| slightly further to the right so that the roller will ride on its continuous circumference. The rise of the roller 5| will force the rod 49 upward and the rod 55 downward against the action of the spring 5`| so that the mercuroid tube switch 52a will be brought into the position shown in Figure 1 of the drawing and the circuit feeding the motor will be established. As soon as this happens the evacuator 24 will begin rotation to evacuate refuse into the chamber 25. Even when the roller 5| is not riding on the continuous circumference of the cam 46, the lip 30 on the latter will prevent the roller from having any greater drop than that to the point 6|, which is insuiiicient to open the switch 52a.

The speed of the motor 3i) has been previously so adjusted as to drive the evacuator at the best average speed to keep the thickness of the bed constant. So long as the thickness and consequently the apparent specic gravity of the bed remains constant the average position of the float 35 will remain the same, i. e. it will oscillate about a position of rest such that neither the stop 42 nor the stop 43 will touch the projection 44, the stops being set apart a distance corresponding to the maximum amplitude of oscillation of the float.

If, for any reason, the thickness of the bed alters, the controls actuated by the floats 34 and 35 will operate to bring it back to normal. If the bed gets thinner, there will be a decrease in its specic gravity as a result of which the oat 35 will drop, pushing the rod 4| to the right and, through consequent contact of the stop 43 with the projection 44, moving the cam 46 to the right so that the roller 5| will, under the action of the spring 57, drop off it onto the cylinder 45. As the circuit feeding the motor 30 will thusl be broken the evacuator 28 will stopand the bed will be able to build up to its normal thickness.

In the above case, the action of the control described will be supplemented by the action of the controls operated by the oat 34. The pressure in chamber 25 is directly proportional to the resistance of the bed on the screen 22 to the upward passage of water through it, and the position of the float 34 and of the valves 32a and 32h attached to its stern 33 depends entirely upon the pressure prevailing in the chamber 25. Therefore, the amount by which the valvesY 32a and 32h are opened and, consequently, the amount of the current through the opening 24 and out through the pipe 3 Ytending to carry refuse with it will be proportional to the resistance of the bed. When the bed gets thinner this resistance will decrease, the float 34 will assume a lower position and the flushing current will be decreased or even shut off entirely. If the thickness of the bed increases above normal, the float 34 will rise, thus opening the valves 32a and 32h wider and causing an increase in the ushing current. Even though the refuse evacuator 28 is turning at a constant speed, this increase in the flushing current causes a quicker and better llling of the troughs of the star evacuator, with the result that the thickness of the bed will be reduced to normal.

rlhe two controls supplement and complete each other and regulate most efficiently the separation of thematerial in all cases. As is well known, a density float such as 35 is safer and more sensitive with pieces of small size, while a pressure iioat such as 34 is safer and more sensitive with pieces of large size. The action of float 34 operating compensated, direct actingvalvesis quick and sensitive and the action of float 35 is also most sensitive, since roller bearings can be used at all points of rotation and a very small displacement of the average oscillating position of the float and, consequently, a very small displacement of cam 45 is sufcient to catch the roller 5| or to let it drop. The power required from the float 35 is thus only that necessary for this small displacement, as the rotation of the cam is effected from an auxiliary source of power.

This application is a continuation in part of my co-pending application Serial No. 716,707, filed March 21, 1934.

I claim:

1. A jig comprising a hutch, a screen over the hutch, a pressure tank, means for continuously forcing `water into said tank, a vacuum tank, means for continuously withdrawing water from said vacuum tank, an opening below said screen from said hutch to each of said tanks, means for periodically and substantially alternately closing said openings to cause surges of water in said hutch, and a swingable plate freely hung in the hutch in the path of movement of any water passing back and forth between the screen and the openings from the hutch to the pressure and vacuum tanks and on an axis of pivotal move.- ment transverse to the path of the water, said plate being adapted evenly to distribute the flow of water over the screen during one surge thereof and to swing back to permit the free movement of water during the return surge thereof.

2. A jig according to claim 1 comprising means for variably adjusting the inertia of the swingable plate to modify the form of the surges.

3. A jig comprising a hutch, a screen over the hutch, a pressure tank, means vfor continuously forcing Water into said tank, a vacuum tank,

means' for continuously withdrawing water from said vacuum tank, an opening below said screen from said hutch to eachrof said tanks, means for periodically and substantially alternately closing said openings to cause surges of water in said hutch, and a plate pivoted on the wall of the .hutch below the screen on an axis of pivotal movement transverse tothe path" of the water and `in the path of the upward surges of water to give a lateral component to said surges. Y

- 4. A jig lcomprising a round bottomed shell, a pressure .tank with a closed top and an open ftopped hutch formed in said shell side by side, a

downwardly directedopening from the tank to the hutch vsubstantially above the bottom of the shell, a Valve in saidropening, plates extending outwar'dly'anddownwardly from two opposite iwalls of the tank, a connection toa source Yof 'water under pressure in'one of said walls below the pointY of juncture of the plate with the wall, said plate thus directing incoming water downwardly in the tank, and together with the other `plate tending to reduce eddies inthe tank, a

ating member, a iioat in the material above the screen and responsive to the specic gravity of said material, a rod connected to the float having stops thereon, a constantly revolving cam adapted to be moved axially by one of the stops upon any change in the average position of the oat, and being adapted upon such movement to engage or disengage the switch operating member to control the motor of the evacuator.

6. A jig'comprising a hutch, a screen overth'e vhutch means for causing surges of water throughV the screen, means for passing material to beseparated across the screen, a water pressure chamber connected with the hutch, means in the pressure chamber for removing material from the screen,

a water discharge opening in the pressure cham- Y. ber, a valve normally closing the water discharge opening, a oat connected to the Valve responsive to an increase in the water pressure in theV pressure chamber to permit Water to ow therefrom, said ilow of water from the pressure chamber being adapted to create a ow of water substan-V tially across the screen to .assist in the removal of the material.

7. A jig, as denedin claim 6, in whichv th discharge valve comprises a pair of Valves mounted one above the'other'on a stem connected to the iioat, the lower Valve being smaller than the upper one. to compensate for the Vdifference in hydrostatic 4pressure owing to their different vertical positions.

8. A jig comprising a hutch, a screen over the f hutch, means for causing surges of water through said screen, means for passing material to be separated across said screen, a separate discharge chamber communicating with the hutch through an opening atV the discharge end of the screen, a rotary evacuating valve in said opening for removing material from the screen,

' means including a oat for actuating the rotary valve, a flushing Valve in'said separate chamber controlling the only outlet thereof, and means including a oat for actuating the ilushing valve for selectively creating a ow of water substantially across the screen to assist in the evacuation of the material.

GSTAVE ANDRE VIssAc.

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