US1923951A - Process and mechanism for separating intermixed divided materials - Google Patents

Description

Aug. 22, 1933. R. PEALE ET AL PROCESS; AND MECHANISM FOR SEPARATING INTERMIXED DIVIDED MATERIALS Filed Dec.

18, 1928 3 Sheets-Sheet. l

@D/EN s Jed/ 2% ATTO y Aug. 22, 1933. R. PEALE ET AL PROCESS AND MECHANISM FOR SEPARATING INTERMIXED DIVIDED MATERIALS Filed Dec. 18, 1928 3 Sheets-Sheet 2 ATTO EY Aug. 22, 1933- R. PEALE ET AL 1,923,951

PROCESS AND MECHANISM FOR SEPARATING INTERMIXED DIVIDED MATERIALS Filed Dec. 18, 1923 3 Sheets-Sheet 3 Patented Au 22, 1933 PATENT oFFicE PROCESS AND REECHANESM FOR SEPARAT- ING INTERMIXEB DEVEDED MATERIALS Richard Peale and Rembrandt Peale, Jr., St. Benedict, Pa.,assigners, by mcsnc assignments, to Peale-Davis Company, Wilmington, Del, a Corporation of Delaware Application December 18, 1928 Serial No. 326,878

9 Claims. (Cl. 209-46? The invention relates to a new and useful process and mechanism for separating intermixed divided materials wherein the parts or particles vary relatively greatly in'size and vary relatively little in specific gravities.

Objects and advantages of the invention will be set forth in part hereinafter and in part will be obvious herefrom, or may be learned by practice with the invention, thesame being realized and attained by means of the instrumentalities and combinations pointed out in the appended claims.

The invention consists in the novel parts, construction, arrangements, combinations and improvements herein shown and described.

The accompanying drawings, referred to here-.

in and constituting a part hereof, illustrate one embodiment of the invention, and together'with the description, serve to explain the principles of the invention.

Of the drawings:- Fig. 1 is a side elevation of a mechanism embodying the invention;

'Fig. 2 is a vertical transverse section on line 2-2 of Fig. 1;

Fig. 3 is a detail section of the shutter valve, taken on line 3-3 of Fig. 2;

V Fig. 4 is afragmentary detail section taken on line 4-4 of Fig. 1, showing a bearing for the shutter valve shaft journalled in the side wall of the main air chamber;

1 Fig. 5 is a top plan, partly diagrammatic, of a double table embodying the invention;

6 and 7 are diagrammatic sections similar to Fig. 2, showing different settings of the shutter valve;

I Fig. 8 is a top plan similar to Fig. 5, with parts broken away, showing a modification of the table provided with sub-areal zoning; and

Fig. 9 is a fragmentary longitudinal vertical section of the deck shown in Fig. 8.

The invention pertains broadly to the separation of intermixed, divided materials, the term divided being used to designate broken, fragmentary, granular, pulverulent or other materials comprising separated parts or pieces of different kinds of material. The invention in its novel features is more particularly directed, however, to effecting automatic separation, to practically the ultimate degree of possible efficiency, of such mixtures of materials wherein the various pieces of the different kinds of materials vary relatively very greatly in size, while varying relatively little in their specific gravities. I

With this purpose in View, the invention is further directed to efiecting, concurrently with the separatitng process, an approximate size classification both, of the mipurities and of the coal, whereby there is attained unusual and practically perfect'efiiciency in cleaning and. separating such widely varying unsized materials. In combination with the concurrent separating and sizing operations effected by theprocess, the invention provides for the subjecting of the intermixed materials to the combined action of various forces, and to a very nice regulation and control in the application of said forces, whereby all the particles comprising the mass of materials to be separated are subjected to exactly the proper combination of forces in exactly the proper relative amounts, whereby the most complete and rapid separation of the materials is 'eifected and maintained.

One kind of intermixed divided materials which the invention isespecially capacitated to successfully separate, is a mixture of c0al,"bony and rock, with the other impurities usually present in the coal, as it comes from the mine, that is, run of the mine coal, except that the large lumps, say from seven inches up are crushed,

although this crushing is not necessary even up to pieces ten inches in size. Usually, however, it is simpler to remove a few large chunks of coal and rock than to run them over separating tables. The rock and other impurities are separated from the run of mine coal by the present invention entirely automatically, on a single cleaning table, and without previous sizing of the materials, except as to said crushing; or removing the very largest lumps, the practically perfect separation being eifecteddown through the finest dust of the intermixed materials.

The conditions of the inventive problem solved by the invention are of the greatestfpractical difficulty due to the wide range of variations in the sizes of the pieces or particles of the intermixed materials, and concurrently therewith the relatively small diiferences in the specific gravities of the materials, and due further, frequently, to a very high percentage of impurities in the finer part of the mixture. Separating work of this kind, withthese factors present, requires practically an entirely different process and mechanism or apparatus from the separation of materials which are very finely pulverized and which vary very widely in their specific gravities on the one hand, or which, on the other hand, are very carefully and extensively sized prior to the separating process. This is especially true in the separation of coal, particularly bituminous coal, different lots or runs of which may vary greatly in their characteristics, especially as to the ratio of coarse particles to fines, the amount of impurities in the .fines or in the larger'sizes, the friability of the particles, and in the frictional qualities of the coal and impurities.

The terms lighter and heavier as used hereinafter will be understood as applying to the specific gravities of the various intermixed, divided materials and not to the difference in mass of particular pieces of various sizes.

According to previous commercial practice in separating or cleaning intermixed materials varying relatively greatly ins'izes of the pieces or the particles, while varying very little in the specific gravities of the materials, and especially in the cleaning of coal, it has been necessary to very closely size the coal by preliminary screening before attempting the automatic'separation of the intermixed coal, bony, rock and other impurities. This previous commercial practice has necessitated the employment of a large number of screening or sizing devices-and likewise a corresponding number of small tables for separately cleaning' the thus sized or classified coal, one table being necessary for each of the sized classifications of the coal created by the screening devices. It has been quite usual to employ six or eight screens and the same number of small cleaning tables to clean run-of-mine coal, of sizes, say from three inches down, while efficient cleaning of the larger sizes has been impossible of accomplishment by such tables.

The present invention as preferably practiced comprises feeding the unsized runof-the-rriine coal onto an air-pervious table or deck at a regulable rate, so as to maintain substantially uniformly upon the table a bed of the materials of appreciable thickness, usually several inches in thickness. This bed is progressed forwardly and simultaneously undergoes gradual separation into horizontally-disposed strata, the superior one of clean coal, and the inferior one of the impurities, by reason of the longitudinal reciprocation of the bed and forcing upwardly through the bed lifting air currents. The coal, as the lighter materiabis fioated in a superior stratum and the impurities, as the heavier material, comes to rest upon the table, and are thence impelled forwardly by friction and inertia to discharge along a predeterminedpath.

For most rapidly and efficiently effecting the horizontal stratification of the bed of materials so as to properly accommodate the various sized particles, the lifting air currents forced through the bed are preferably of a wave-like or pulsatlng nature, the intensity of the air force being con tinuously modified between upper and lower pressure limits, whereby a series of recurrent waves of air is passed upwardly through the bed. By virtue of this continuous and recurrent modification of the air forces, each particle in the bed of materials is, at some time during the modulations of an air wave, subjected to exactly the proper stratifying conditions. On the other hand, the maximum intensity or upper limit of the air waves is never so great as to disturb the stratification already established in the bed or to remix the separating materials. Usually the rapidity of Stratification is greatly promoted by the use of air waves as distinguished from a steady blast.

In combination with the wave-like modulations of the lifting air force, the air forces in the different parts of the bed may preferably,

an upwardly projecting,

although not necessarily, be further regulated by providing zones of varying air-perviosity at different parts of the air-pervious deck, these zones being preferably arranged along the deck in gradated relation both forwardly and later ally of the deck. Hence there is provided a constant air-controlling factor for each zone, super imposed upon the continuously changing air waves forced through the deck.

In addition to the regulations of the lifting air forces hereinbefore mentioned, in certain cases and with certain types of coals or other materials, a further regulation of the air forces may be employed. According to the invention, stratification and separation of the materials in the bed may be greatly expedited and perfected by subjecting different areas of the bed to air waves having different upper and lower pressure limits. That is, certain areas of the bed, and preferably those in which the primary stratification of the coarser impurities takes place, are subjected to recurrent lifting air waves whose pressure intensities vary between a maximum and an intermediate limit. Other areas of the bed, and preferably those wherein the stratification of the finerparticles is accomplished and perfected, are subjected to air waves which vary between an intermediate and a maximum pressure limit. The extents of the different areas so treated and the pressure limits may be varied as necessary or desired.

A further refinement of the air control which may be optionally employed in certain cases and with certain kinds of coals consists in further selectively regulating the amount of air supplied to diiferent parts of the bed of materials in various sub-zones or sub-areas within the respective areas or zones of different air-perviosity; this selective regulation in the various sub-zones being susceptible of exceedingly nice gradation through a very wide range. 7

Hence, the lifting air currents which pass through the bed may be subjected to a combination of different controlling and regulating fac- V tors which cooperate to provide exactly the proper stratifying and separating forces at each point in the bed of materials. Furthermore, the regulating features described in combination with other regulating features provided'by the invention, can be used to so modify or tune the separating condi in the bell of materials to provide a practically perfect separating action for coals having any given co aination of characteristics and for coals presenting exceedingly difficult problems of separation.

It will be understood that the foregoing general description and the following detailed description as well are exemplary and explanatory of the invention but are not restrictive thereof.

Referring now in detail to the embodiment of the invention illustrated by way of example in the accompanying drawings, anair pcrvious table 10 is shown consisting preferably of two halves or parts, which be of similar construction but in reverse position. The deck 10 is provided with bed-retaining wall 11 across the rear end thereof, and with upwardlyprojecting, bed- retaining walls 12 and 13 extending along either exterior side of the table from the rear wall 11 preferably to the front ends of the table. The discharge edge for the lighter superior stratified material is preferably in the form of a transversely inclined spillage edge 14, extending from the forward outer edge of one side of each table, or each half of the table backwardly and inwardly for a relatively large proportion of the length of the table. If desired, also, there may be a central, upwardly-projecting, longitudi' nally-extending partition 15, from the rear wall 11 to the innermost point of the spillage or de-' livery edges 14 for the lighter. superior stratified material. 1

The two halves of the table may both be in-' clined transversely upwardly and outwardly, and this degree of inclination maybe varied. In certain cases it may even be desirable to incline the halves of the table downwardly and outwardly. It will be understood that either half of the table could be used as a single table if desired, in so far as concerns many features of the invention.

The pervious table deck 10 is supported upon a suitable frame structure, consisting of longitudinally and transversely-disposed channel- beams 19 and 20, and this structure, with certain other portions later to be described, are longitudinally reciprocated through a short path to impel the.

bed of materials lengthwise of the table. With this in view, the frame structure 19, 20 is pivotally mounted upon the upper ends of a plurality of arms 21, the lower ends of the arms in turn being pivotally mounted upon the side members 27 of the stationary structure of the air chamber. The arms are preferably inclined upwardly and backwardly when the table is at the rear end of its stroke, so that the path of reciprocation of the table is upward and forward and downward and backward. The fixed portion of the stationary air chamber 29 is attached to the frame 27, and is clearly shown in Figs. 1 and 2, and need not be described in detail. It ispreferably decreased cross-sectionally gradually forwardly of the table to more effectively control the air pressure lengthwise of the table. A suitable air-impervious flexible connection 30 connects the reciprocable table with the stationary air chamber. The embodied means for supplying the air current comprises a rotary fan 35, which is equipped with some suitable form of air current regulating means such as a slide 36 applied to the intake opening of the fan. The fan connects by a con-' duit 37 with the air chamber 29. Thereby the intensity of the air current supplied to the entire table can be primarily controlled.

The table is preferably variably upwardly and forwardly inclinable, the front end in most cases being slightly higher than the rear end, although this slope may be reversed if required. In the embodied form, the table is provided at either side near the rear thereof with pivot bearings 40, and

"a pluralityof screw posts 41 are arranged as supports along and beneath the stationary side frames 27 of the air chamber. A suitable power driven feeding mechanism 44 is provided for feeding a regulable amount of material to the rear end of the table.

The embodied means for reciprocating the table comprises a link 45, connected at its forward end to the rear reach of the frame 19, 20, and connected at its rear end to an eccentric 46 fixed on a shaft 47, which shaft is journalled in suitable bearings and mounted upon a suitable support, 48..

The shaft 47 is driven in any suitable manner, by'a belt and pulley 49.

Cooperating with the reciprocating" means 'is a suitable spring buffer mechanism, which preferably is always under tension and designed so that the degree of tension doesnot vary greatly during the short path of reciprocation of the table. As embodied a plurality of rods 50 extend forwardly from the front end of the table and are reciprocable in apertures in a fixed support 51.. On the opposite side of the support50 helicalsprings 52 encircle the rods, and'are provided with tension-adjusting nuts 53.

In the embodied form of table, separating partitions are provided which act both during the separating process, and later to impel the settled heavier material by friction and inertia to the desired place of delivery. As embodied, these separating partitions 55 are inclined forwardly and outwardly, for the purpose of directing the heavier material which has settled upon the deck by the shortest andquickest route to the side edge of the bed to be discharged therefrom at a median point in the length of the bed. By'

edge 14, which is much greater in length than the width of the table. Furthermore, the heavier material which has settled upon the deck, is impelled by friction and inertia quickly and shortly to the side of the table and is discharged practically immediately upon reaching said side edge. This avoids the inconvenience and disadvantage of accumulation of a large, wide and thick bed of this heavy impure material, with the consequent unnecessary work of reciprocating it for a relatively long period of time, and with the attendant disadvantage of a crowded or congested movementof the lighter materials on the table and the remixing to some degree of the heavier and lighter materials.

As stated, the heavier material is discharged from the bed practically immediately upon its reaching the side edge thereof, apertures being provided along the side walls 12 and 13 for permitting egress of the separated impurities. The discharge of the heavier materials through these apertures may be very closely regulated by the provision of discharge devices 60, which may be the same or similar to those shown in the copending application Ser. No. 200,080, of Kenneth Davis, and need not be described in detail, as the specific structure thereof'constitutes no part of the present invention; The headers for supplying air currents to the discharge devices are indicated by 61 and 62, and the flexible connections therefrom by 63, the headers receiving the air through the bed at different times and at diifer- 'ent areas thereof.

means, the invention provides a gradated zon- Among these air-regulating ing of the perviosity of the air-pervious surface of the deck, different areal zones thereof being preferablycovered with perforated metal sheets having different percentages of perviosity. It

will be understood, however, that the zoning of the deckmay be effected by other means, that described being exemplary but not restrictive of the "invention. 7

So far as concerns most features of the invention, the zoning of the air currents, that is, the variation in air-perviosity of the deck, may be variously arranged. As shown, the air current area or zone of greatest perviosity is at the rear of the table, the intensity decreasing forwardly as indicated by the letters A to D. The arrangement shown is usually preferable and the one most generally employed. However, there may be situations where the zoning may be the reverse of that shown, that is, with the air perviosity increasing forwardly along the table. With the zoning shown, it will be understood that the forwardly-moving bed of materials on the table progresses through gradated zones of a continuously decreasing air force while the transversely moving heavier materials, generally speaking, also progress laterally outwardly into areas of decreasing air-perviosity.

Another feature in the regulation of the air forces comprises continuously modifying the intensity of the entire current of air supplied to the air chamber to produce a series of recurrent waves of lifting air force whose intensities vary between upper and lower limits. This recurrent modulation of the air intensity may be employed either with the deck zoning hereinbefore-described, or, in other cases, may be employed independently of the areal zoning, the latterbeing dispensed with and the wave-like modifying of the air currents being performed on an air current passing through a deck of uniform perviosity, the question of whether or not the two features will be combined or the pulsating current be used alone being largely determined by the characteristics of the material to be separated.

The present preferred means for effecting the wave-like or pulsating air current comprises a rotary shutter or butterfly valve 70, mounted within the main air chamber 29 on a transverselydisposed shaft 71, which is journalled in the side walls of the chamber 29, the walls being preferably provided with hubs or bosses 72 for receiving and supporting the ends of the shaft. The rotary shutter 70 may be operated in any manner desired, as by means of a drivim sprocket 75 keyed to shaft '71 and driven in any suitable manner as by chain 76 from a sprocket 77 on shaft 47. The shutter may be driven or controlled by any known or suitable variable-speed device if desired, to produce the wave-like air action through the bed; or the shutter 76 may be stationary, in horizontal position, thereby permitting a continuous or nonpulsating lifting air current action through the bed. It will usually be found most eiiicient to time the rotation of the controlling shutter with the reciprocatory movement of the table, by cffecting av half-rotation of the shutter for each complete reciprocatory movement of the table. With many kinds of materials to be separated, the wave-like air blast willbe timed so that the shutter will begin to open and. go to full open or horizontal position on the forward stroke of the table, and will then go to the closed position, at the half-revolution on the backward or return stroke of the table. This will prevent any backward sucking on the return stroke of the table,

and will secure the full separating effect of the pulsating air blast.

Means are provided by the invention for subjecting different areas of the table surface to air waves having different intensity limits, whereby one area of the table may be receiving waves of air force which vary in intensity between a major and an intermediate pressure limit, while another area receives waves varyingbetween intermedi-. ate and minor pressure limits. In the arrangement shown in Figs. 1 and 2, the area of the bed to the rear'of the shutter valve '70 is subjected to air pressure waves whose limits of intensity vary between a maximum of pressure equivalent to the entire air force delivered by the fan and localizedby the damming effect of the shutter which closes the entire cross-sectional area of the air-chamber, except for some possible slight leakage around the edges; and whose lower limit of pressure intensity occurs when theshutter is in the horizontal or full-open position, at which time the rear area of the bed is subjected to the normal portion of air pressure which it would receive if the air-chamber were unobstructed by the shutter valve. The forward area of the bed, on the other hand, receives airwaves varying in pressure between the normal or intermediate pressure produced when the valve is in its horizontal full-open position and the minimum pressure created when the Valve is in the closed or vertical position. In the latter position, the forward area of'the bed receives a minimum of zero, or atmospheric, pressure. It will further be noted that the pressure wavesin the rear and forward areas of the bed are diametrioally out phase, the maximum intensity in the rear area occurring when the air is entirely shut off inthe forward area, while the normalorfull open shutter produces the minimum limit in the rear area and the maximum limit in the forward area. A screen 78 of canvas or the like may be hung above the top of the shutter to provide an air seal between the shutter and the bottom of the decks.

Means are provided for varying the pressure limits to which the different areas of the bed are subjected. For instance, in some cases it may be desirable to subject the forward area of the bed to pressure waves whose minimum intensity is above atmospheric pressure and in such cases it may also be desirable to subject the rear area of the bed to a blast whose upper limit of intensity is less than the. producible maximum, whereby the pressures throughout the bed as a whole are more uniform. As embodied, the shutter valve '70 is preferably formed so as to be variable in extent, whereby the effective diameter of rotation of the valve may be varied within desired limits. In Figs. 2 and 3 the shutter 71) is shown composed of two fixed blades 80 and 81 extending from a winged sleeve 82 mounted to rotate on shaft 71. The blades 80 and 81 are adapted to support extensible wing members 83 and 84 at their respective outer ends, said wings 83 and 84 being attached to the blades 80 and 81 respectively by bolts 85 engaging with slots 86 in the wings, whereby the effective diameter of the shutter may be lengthened or shortened as desired. 1 1

As will be clear from Figs. 6 and '7, the diameter of the shutter may be reduced to occupy only three fourths or other fraction of the cross section of the air chamber. This may be done as shown in Fig. 6, by spacing'the wings 83 and 8% equally from the central shaft, or, as shown in Fig. 7 by moving one of the wings to provide the whole area of clearance. In either case, it will be understood that the rotating shutter never entirely closes off the'supply of air from the fan 35 to the forward portion of the bed. Therefore, the maximum limit of pressure in the rear area (that area to the rear of the shutter shaft) is maintained lower by the escape of air around which escapes around the shutter.

In accordance with one feature of the invention, the differential pressure areas createdby the position of the shutter valve relative to the bed may be varied so as to vary the area subjected to the pressure waves of higher or lower limits. As embodied, the side walls 29 of the air chamber are provided with a plurality of apertures 90 and shaft bearing hubs 72 for the reception of the shaft '71, whereby the shaft and shutter may be moved to any one of the various positions shown to thereby vary the relative extents of the differential pressure areas of the bed. It will be understood that the invention is-not limited to the number of shutter positions indicated, but that the shutter may be placedat any position desired, its position usually being determined by preliminary tests and fixed for a given run of coal. It will be noted that bearing apertures 91 are provided in the walls of the'air conduit at the rear end of the table, whereby the entire bed of materials may be subjected to air waves of the same pressure limits and in the same phase. The bearing apertures are provided with removable caps 92 for preventingescape of air when the current action with a very great degree of eXactness and through a very wide range of variation in the amount of air supplied, in a plurality of subzones or sub-areas of each of the various zones or areas of a given air-perviosity.

In the embodied form of said means girder plates 111 are supported at their-ends by the vibratable or reciprocable frame 19, 20, an'd extend preferably transversely forwardly and outwardly at the same angle with the separating partitions.

These plates also conveniently support the deck supporting beams 110 by means of brackets 109. These" girder platesconstitute some of the side walls of a plurality of relatively small or localized air chambers beneath each of the various zones of differing air current intensity. Other chamberdefining plates or walls 117 cooperate with the plates 111, and these'are preferably disposed longitudinally of the table, although this may be varied as desired. Plates 117 also serve conveniently to support the deck supporting beams 11%. There are formed by the deck 10 and the plates 111 and 117 a plurality of chambers 118 beneath each zone area of the air-pervious deck. Re ferring to the means for selectively regulating the air current intensity in each of the chambers 118, each chamber is provided with a floor 119, each of these floors being provided with a plurality of apertures 120, and these apertures having a rea place of discharge.

air intensity in each of these sub-areas in con nection with the general zonal arrangement of the air currents. This feature of the invention, however, could be used independently of the generalgradated zoning of the table if desired.

In the operation of the hereinbefore-described mechanism, the table may be regarded as having thereon a bed of the intermixed materials, such as run of the mine coal undergoing separation. The table is reciprocated through a short path, preferably with a slow rising forward motion and a quick descending rearward motion, the lifting air currents being forced upwardly through all parts of the bed with intensities dependent upon the degree of air-perviosity of the bed and the setting or regulation of the other air intensity controlling devices. The lifting air current at the rear end of the table separates and loosens the particles or pieces of material, and the coalor other lighter material is buoyed or lifted'upwardly into a superior horizontally-disposed stratum and the rock and other impurities settle upon the table, and thereafter are forwarded by friction and inertia to The stratifying and separating operation continues in like manner forwardly along the table as the bed progresses from the rear toward the front.

Due in a large measure to the differential air action on the different areas of the bed, whereby the rear portion of the bed is subjected to the largest amount of air of the maximum intensity, the largest pieces of rock or other heavier material settle immediately upon the table at or very near the place of feeding on of the material and are thereby separated from the mass of material, and are thenceforth-progressed immediately to discharge by joint action of friction and inertia. The wave-like action of the air forces greatly enhances the rapidity 'and thoroughness of this stratification. The remaining portion of the mass flows freely forwardly along the table, the' upper part consisting of already stratified and separated coal, and the lower part consisting of material yet intermixed, but rapidly undergoing the process of complete separation. As the material so moves forward, the smaller and smaller pieces of the heavier material progressively settle lower in the stratum, and,as they move into progressively decreasing areas of lifting air force, at one point or another finally sink behind the separating partitions andare immediately impelled to discharge at the sideedge of the bed, while the overhead stratum of progressively purifying coal moves freely and directly forwardly to discharge over the front spillage edges 14. It will thus be seen that concurrently with the separating action there occurs an automatic classification of the refuse according to sizes, the greater portion of the large sizes of refuse being discharged through the rear discharge boxes, and the refuse in the forward boxes progressively decreasing in size as indicated.

In accordance with certain features of the invention, there is also efiected a concurrent process of both cleaning and. sizing the unsized coal, or

equivalent lighter upper stratum of material. During the separating operation, and concurrently with the Stratification; separation and cleaning of the impurities out of the coal, the coal is classified as to size positionally transversely of the table. That is, as the bed of materials progresses gradually forwardly along the table, undergoing stratification and separation, in the upper stratum of clean coal the larger pieces gradually workto the outer side edge of the-table, and then travel forwardly to discharge at the forward end of the table. The pieces of coal of next largest dimension gradually work to a position in the upper stratum of .coal just within the aforesaid largest pieces, and travel forwardly in the bed to dischargeat the forwardend of the table, and so on across/the table, the size of the coal in the upper, clean stratum decreasing transversely and gradually toward thelower side edge of the table and of the bed. Thus, the upper stratum of coal is discharged in pure or clean condition at the sforward end of the table, and also in classified condition :as to size.

The invention in its broader aspects is not :limited tothe specific mechanisms shown and described but departures may be made therefrom within the scope of the accompanying claims without departing from the principles of the invention and Without sacrificing its chief advan- ,tages.

What we claim is:- p -l. Ifhe process of. separating intermixed divided smaterials varying relatively greatly-in size, but varying relatively little in their specific gravities, .Whiohcomprises maintaining a bed of the materials [of substantial thickness in continuous progression -.over an ;air-pervious table, forcing lifting air currents upwardly through the bedto progressively stratify the materials in su-stan- -.tially horizontal superposed strata, whereby -a lighter :material forms a distant superior stratum and .aheavier-material' settles to the table surface, eontinuouslyand recurrently modifying the force aQf lthe air-currents supplied to the be in wave like impulses =between upper and lower limits, said 'upper and lower-limits being diiirerent indifferent areas ,of the bed, i and varying the relative-extents of said different areas 1? or materials having differ- ,ent characteristics.

. :2. 'lllheprocessefseparating intermixed divided materials varying relatively greatly in .size; but varying'relatively little in their specific gravities,

which-comprises maintaining a bed of the ma terials of substantial thickness in continuous progression over an -air-pervious table, forcing :liftingair currents upwardly through the bed to progressively stratif yithe materials in substantialil-yihorizontalsuperposed-strata, whereby a lighter material forms :a flota-nt superior stratum and -.a heavier material-settles to the table surface, continuously and recurrently modifying the force of the .air currentssuppl-ied to the .bedin wave-like impulses, subjecting one area of the bed to impulses between an upper and an intermediate limit and subjecting another area'of the bed to impulses between an intermediate and a lower limit, 'and progressing the superior stratum of lighter material and the heavier material todifferent places of discharge.

,3. Theprocess of separatingintermixed divided materials varying relatively greatly in size, but relatively little in their specific gravities, which comprises maintaining a bed of the materials of substantial thickness in continuous progression :over an air-pervieus table, forcing liftingair cur rents upwardly through the bed to progressively stratify the materials in substantially horizontal superposed strata, whereby a lighter material forms .a flotant superior stratum and a heavier material settles to the table surface, continuously'and recurrentlymoditying the force of the air currents supplied to the 'bed in wave-like :impulses, subjecting-a rear portion of the bed to impulses between :an {upper and an intermediate pressure limit, and subjecting a forward portion ref ithe lied to irrrnulses between an intermediate and a lower'limit, and progressing the superior stratum of lighter material and the heavier -rnaterial to different places of discharge.

a. A mechanism for separating intermixed, di-

vided materials varying relatively very greatly -'E in size and varying relatively little in their specific gravities, which comprises an air-perv? ous table, feeding means adapted to maintain a bed of materials on the table undergoing separation, means for reciprocating the table, means for forcing lifting air currents upwardly through the bed of materials, whereby a lighter material 'stratifies as a fiotant superior stratum and a heavier material settles to the table surface, means for continuously and recurrently modify- :ing'the iorceof the air currents supplied to the bedbetween upperand lower pressure limits, said limits being difierent at different areas of the bed, and means for varying the extent of said different areas, means for directing the settled heavier material transversely over the table by friction and inertia as soon 'as it settled, and means for discharging the superior lighter material. a

.5. mechanism'for separating intermixed, divided materials including in --combination an 'air-pervious table, efeeding means adapted'to .maintain a bed of materials on the table undergoing separation, means for supplying air under pressure to an air chamberbeneath the-table, and means located within the' air c'hambermedianly of the ends of the table for modifying the pressure of the air supplied to produce a continuous series of recurrent wave-like impulses in the air supplied to the bed of materials whereby different areas of the bed are subjected to impulses of different force.

6. A mechanism for separating intermixed, divided materials including .in combination "an -air-pervious table, feeding means adapted to maintain a bed of materials on the tableundergoing separation, means for supplying-air under pressure to an air chamber beneath the table, and means located medianly of'the ends of the .table for modifying the pressure of-the air supplied to produce a continuous series oi recurrent wave-like impulses in the air supplied to the bed of materials whereby different areas of thefibed are subjected to impulses of difier- .ent force and means for varying the position or said pressure-modifying means to change the pressures at different areas of the bed.

'i. A processfor separating intermixed divided materials varying relatively greatly in size but relatively little in their specific gravities which comprises maintaining a bed of the material'sof substantial thickness in progression over a-v-i- .brating air-pervious table, forcing lifting and loosening air currents through the moving bed to size and varying relatively little in their specific gravities, which comprises an air-pervione table, feeding means adapted to maintain a bed of materials on the table undergoing. separation, means for reciprocating the table, means g are including an air-chamber beneath the table Ior forcing lifting air currents upwardly through the bed of materials, whereby a ligh er material stratifies as a flotant superior stratum and a heavier material settles to the table surface, means for continuously and recurrently modifying the force of the air currents supplied to the bed between upper and lower pressure limits, comprising a rotatable shutter valve mounted across the air-chamber intermediate the ends of the table.

9. A mechanism for separating intermixed, divided materials varying relatively very greatly in size and varying relatively little in their specific gravities, which comprises an air-pervious table, feeding means adapted to maintain a bed of materials on the table undergoing separation, means forreciprocating the table, means

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