US2155235A - Apparatus and method for the separation of dry materials - Google Patents

Description

4 Sheets-Sheet 1 .5 nww Wm v MN INVENTO RS April 18 1939. D. c. MQRGAN, JR.. ET AL APPARATUS AND METHOD FORTHE SEPARATION OF DRY MATERIALS Filed Feb. 15, 1936 April 18,1939. D. c. MORGAN. JR., ET AL 2,155,235

APPARATUS AND METHOD FOR THE SEPARATION OF DRY MATERIALS Filed Feb. 15, 1936 4 Sheets-Sheet 2 INVENTORS April 18, 1939- D. c. MORGAN. JR.. ET AL 2,155,235

APPARATUS AND METHOD FOR THE SEPARATION OF DRY MATERIALS Filed Feb. 15, 1936 4 Sheets-Sheet 3 J2" e 12 4 F F .5.- 12 8 12 59 M NH!!! INVENTORS April 18, 1939. D. c. MORGAN. JR.. ET AL 2, 55, 3

APPARATUS AND METHOD FOR THE SEPARATION OF DRY MATERIALS Filed Feb. 15, 1936 4 Sheets-Sheet 4 INVENTORS Patented new, 1939 .v AND METHOD FOR THE SEPA- BATION OF DRY MATERIALS Dwight 0. Morgan, Jr., and Thomas Hubbard Morgan, Kittannin g, Pa., assignor, by mesne assignments, to Morgan Concentrating v('Jonipany, Wilmington, Del., a corporation of Delaware Application February 15, 1936, Serial No. 64,078

17 Claims.

This invention relates to'the dry separation of heavier particles from lighter ones, such, for instance, as particles of -metal from sand, and pertains to what is generally known in the art as dry flotation. I

Heretofore apparatus has been-designed to effeet the dry flotation of materials. Apparatus of this generaltype usually comprises a table of some character over which the material to be acted upon is discharged and caused to flow.

The table is usually of a perforate character so that air may be blown up through thematerial as it flows over the table. While apparatus of this general character has been successfully used in some fields as, for instance, in the separation of stone and like materials from coal, we are aware of no apparatuswhich has been successfully developed for the efficient separation of small metal particles from sand. Many attempts have beenmade to extract small particles of gold from dry placer sands, but such apparatus as has been developed is cumbersome to use, is not highly efficient, and results in the removal of only a relatively small percentage of the available gold from the sand. Moreover, such machines as have heretofore been devised for this purpose effect only a partial concentration, leaving a relatively large bulk of material which has to be panned to separate the gold from the concentrate.

According to the present invention, there is provided a concentrating apparatus and method which can be economically used for the so-called dry flotation or dry extraction of metal! particles from the sands in which they are carried, such apparatus and. method functioning with ahighdegree of emciency and resulting in the production of a concentrate in which there is very little sand.' The invention provides a concentrating unit of this nature of such character that it may be conveniently mounted on a motor truck or other easily portable structure and operated from a source of power on the truck.

In the dry concentration of materials, such as the separation of gold from placer sands, we have found that during the process of concentration the entire mass of sand passing through the apparatus must be kept in such a state of agitation that the metal particles therein will gravitate to the bottom. After the metal particles have been precipitated to the bottom, their flow, along with the overlying and surrounding body of sand and gravel, should be in a zone of agitation where there is no possibility of the metallic particles being stirred up from the bottom and mixed with thesurrounding sand and gravel.

In the present invention, there is provided a separating table having means therein forming flutes or riflies. The flutes or riflies, as well as "the entire surface of the bed, are porous to permit the escape of air therethrough from an underlying wind box, whereby air is blown through all of the material passing over the table, and there are no quiescent zones where the particles of heavier materials which have gravitated to the bottom may again be churned up and mixed with the surrounding body of sand and gravel. As

stated later herein, the flutes admit a greater amount of air than do other parts of the'bed,

this being an important feature herein. In theparticular form illustrated this is due to the porous bed being thinner in the flutes or riflles than in other parts, so that, as is later stated, more air 'is admitted through the flutes than through the body of the bed. The invention further contemplates an arrangement wherein the metal particles which are caused to gravitate to the bottom are diverted into a channel having means for trapping the metal or other'particles to be recovered while permitting the larger volume of sand or other material to be discarded to pass on.

In its preferred embodiment, the invention further contemplates the provisionof some arrangement whereby the contents of the concentrating cups are protected from unauthorized removal. The invention further provides an arrangement wherein the concentrating table is preferably adjustable to any desired inclination whereby it can be adapted to the particular kind of sand or other material being processed to get the best results. The invention further contemplates an arrangement whereby this adjustable table may be kept constantly in a state of vibration during the processing of the material as the combined action of vibrating and air is essential to the most efiicient removal of the metallic values.

Our invention may be readily understood by reference to the accompanying drawings, in which Figure 1 represents a side elevation of a concentrating unit embodying our invention;

Figure. 2 is a transverse vertical section in'the plane of line IIII of Figure 1;

Figure 3 is a plan view of a porous concentrating table such as is used in the present invention;

Figure 4 is a plan view of the concentrating table with its side flanges removed and without itssupporting frame structure as provided in the machine shown in Figure 1, part of the porous bed of the table being broken away to reveal the underlying structure;

Figure 5 is a fragmentary detail view showing a manner of supporting the porous bed in the frame structure in which it is carried;

Figure 6 is a detail view showing a cushion mounting for. the frame in which the porous table is mounted, and which mounting permits of a limited vibration of the table;

Figure 7 is a plan view of a modified form of a line between the collecting cups; and

Figure 11 is a top plan view of that portion of the machine-shown in Figure 9.

In the drawings, 2 designates a supporting frame structure preferably formed of structural steel and of such proportions that it can be convenientl'y mounted on a motor truck or other mobile structure. Generally, this supporting struc-- ture may have a .base portion 2a, spaced apart front uprights 2b,' and spaced apart rear uprights 2c. Extending along each side of the structure from the topof the uprights 20 to approximately the middle of the uprights 2b are horizontal beams 2d. The front uprights 2b and supporting members 2e provide an elevated support for a hopper 3 having a discharge gate 4 thereon.

Hung from trunnions 5 on the horizontal members 2d is a cradle structure. This cradle structure comprises two depending supports or hangers suspended from the trunnions and designated 6,

. there being one of these supports at each side of the frame. Each of the supports has secured thereto a longitudinally extending channel member 1'. The concentraing table connects the two channels 'I' at opposite sides of the frame and it is resiliently mounted on these two channels 1. The concentrating table unit comprises a hollow base structure 8 having side walls 9 (see Fig. 2)

with outwardly turned flanges l0. Secured to the top of the flanges I are longitudinally extending channel members ll. cured to the side walls 9. near the four corners of the table supporting structure are bracket members l2. The bracket members l2 are each provided with a holel2a therein, the brackets l2 having angular web or gusset plates |2b for giv ing them the necessary strength. The resilient connection between the bracket members I2 and the channel members 'I is provided through a yieldable medium, preferably a live rubber cushion arrangement. One such arrangement is shown in Figure 6. It comprises a bolt member l3 having a cap member H at the top and bottom thereof. There is a cushion of live rubber l confined between the cap I! and th top of the channel 1, and a similar cushion of live rubber l5 between the bottom of the channel I and the lower cap member l4. fI'he boltli passes through the hole 1.2a in the bracket l2.

It will be seen that there are four of the brackets l2, one at each corner of the table supporting structure, and there are four of these cushion units for suspending the table supporting structure from the two channel members I. This manner of suspension for the table supporting structure allows the table supporting structure to be vibrated', but such vibration is cushioned in the live rubber cushions l5 and I! so that the force Welded or otherwise seof the vibration is not transmitted to the chan-- nels 1 or to the structural frame 2.

Along each side wall of the hollow base member 8 is an angle member Hi. In addition to the member Hi there is a supporting lattice I! (see .4) formed of intersecting structural members; the angles 16 and the lattice ll serving to support a porous bed or table l8. The porous bed or table I8 is preferably comprised of a number of separate blocks cemented together to form a monolith. Live rubber, indicated at iii in Fig. 5, is provided under the porous table where this table rests on the angles It or on the lattice. A similar rubber cushion is provided at 20 around the vertical edges of the table I8. The channel members II which overhang the table l8 have live rubber under them as indicated at 2|. The purpose of so mounting the porous bed on and between the live rubber is that the porous material is of a frangible nature and the live rubber serves to minimize the destructive effect of the vibrating action of the table when the machine is in operation.

In the preferred embodiment of the invention ,the table l8 has a herringbone arrangement of to the centre trough or channel lBa. .Their inclination is toward the lower end of the table.

The supporting member 8 on which the porous bed is carried is not only closed at the sides but is closed at the front and rear, providing in addition to the support for the table, awind box or chamber. In the rear wall of this supporting structure is-azr opening having a flange surrounding it to which a flexible air hose 22 is connected. This air hose 22 leads from the discharge end 23 of a blower 24. The blower 24 is designed to deliver a relatively large volume of air at a relatively low causing the volume of the wind box to diminish serves to maintain a substantially uniform pressure of air escaping through the porous material of the bed over substantially the entire area of the bed. If the wind box were of uniform depth, there would be a tendency for the pressure of the air escaping through the table to be greater adjacent the left hand end of the wind box than the right.

The porous bed I8 is retained in place at the right hand end of the structure as viewed in Figures 1 and 4, by a transversemetal strip 25, the top of which is preferably flush with the top of the porous table. Bolted to the end strip 25, as most clearly shown in Figures 9 and i1, is a runout trough member 26, this trough member being of a depth corresponding substantially to the depth of the groove l8a. in the porous table l8 and being in longitudinal alignment with the said central groove. A port is provided in the end strip 25 to enable the material which passes down the groove l8a to flow into the run-out trough 26. The run-out trough 2B is provided with one and preferably two; holes 21 therein. Under each of these holes 21 is a cylindrical cup 28 and 28', these pressure to the Wind box. It will be. noted from Fig. 1 that the depth of the wind box diminishes toward the right as viewed in this figure, thereby away from the point where the air enters it. This cups preferably being formed of glass and having 7 a relatively thin porous bottom 29. The top of the cup sets in a recess on the under side of the runtically movable supporting plate 30 has an opening under each cup and has a bushing projecting down around each opening, these bushingsbeing designated 3| and 32. The adjustable supporting plate 30 has bushings or sleeves 33 thereon which 'have a sliding fit on pins 34 depending from the under side of the run -out trough. There is a third pin 35 also extending from the bottom of the run-out trough midway between the two pins 34. This third pin 35, best shown in Figure 10, has a nut 36 at its lower end for confining a compression spring 31, which spring bears against the under side of the adjustable plate 30. Slidable on the upper portion of the pin 35 is a cross arm 38. This arm 38 normally rests on the top of the plate 30 and serves to confine the upper end of a flanged bushing 39 in place.

Pivoted onto each side of the run-out trough by bolts 40 are side plates 4| forming part of a bifurcated lever structure 42, this lever structure having an operating handle 43 and a guard plate structure 44. The two sides are each provided with curved cam slots 4 la. Bolts 42a pass through the slots 4la into the cross piece 38 and have a working fit in the slots. 1 The arrangement is such that when the handle 43 is moved upwardly in an are as indicated by the dotted projection line, the member 38, by reason of the curvature of the slots 4 la and the provision of the bolts 420,,

will be forced down against the compression of the spring 31, forcing the supporting plate 38 down. When the supporting plate 30 is forced down in this manner, the two cups 28 and 28 can be lifted off the support 38. As long as the handle 43 is maintained at the upper limit of its movement, the plate 30 will stay down and the cups, after being emptied, can be replaced. The handle 43 is then swung back totheposition shown in Figure 9. When the handle swings back in this manner the cross member 38 is lifted. This allows the spring 31 to exert an upward pressure on the plate 39, whereupon the plate 30 is lifted up, causing the upper edges of the cups 28 and- 28 to be forced into the recesses under the holes 21 provided for the reception thereof.

Leading from the front of the wind box to a position beneath the cup 28 is a pipe 45 having a hand valve 46 therein. The pipe between the valve 46 and coupling 4'! below the cup, which coupling is secured to bushing 32, is flexible, preferably being a hose. Leading from the front of the wind box at the opposite side of the run-out trough is a similar air pipe 48 having a hand valve 49 therein and having a terminal portion '58 which is secured to the bushing 3| projecting -below the cup 28'. This arrangement provides for air to be blown through the porous bottom of either or both cups selectively, the terminal arrangement between the ends .of the pipes and the bushings 3| and 32 on the plate 38 providing for the necessary vertical movement of the plate 30 when it is necessary to remove a re-concentrating cup.

Secured to the front strip 25 above the runout trough is a sheet metal guard plate 5| which extends over the run-out trough a slight distance above the top thereof. The outer end of this guard member 5| projects under the part 44 of the bifurcated lever arrangement. The arrangement is 'such that when the lever is in the position shown in Figure 9, it is not possible for an unauthorized person to remove either of the reconcentrating cups or the contents thereof, the first cup .being covered by the guard member 5| and the second cup being covered in part by the outer end of the guard member 5| and in part by the part 44 of the bifurcated lever. Provision is made forlocking the lever in place. prises the provision of a registering hole in portion 43a with a similar hole in a lug 26a at the end of the run-out trough. The hasp of a padlock A passes through these registering holes and serves to-normally lock the reconcentrating arrange.- ment on the run-out trough from being opened or tampered with, except by an authorized person.

Secured to the two supporting frame members 2d are bearings for a transverse power shaft 56 for vibrating the bed of the machine. This shaft, the axis of which is parallel to the axis of the trunnions 5, is shown as having a pulley 51 at its outer end, but it will be understood that in place of a pulley at 5! a'sprocket gear or other gear drive can be positioned anywhere along this shaft. The pulley or other driving means on the shaft 56 is adapted to be coupled to a source of power as, for instance, a source of power driven from the motor vehicle on which the whole unit is mounted. Mounted on the side channels ll, above the concentrating table are bearings 58 for a shaft 59. The shaft 59 where it extends across the bed of the machine, is enclosed in a cylindrical casing or dust shield 60. The shaft 59 is provided at one end with pulleys 6| which are driven through belts 62 from pulleys 63 on the shaft 56. The shaft 59 carries at each end thereof unbalanced weights, such as the unbalanced discs 65. By reason of the size of the pulleys, the

' shaft 59 is operated at a much higher speed than the shaft 56. The effect of the unbalanced discs or weight 65 on the shaft 59' is to cause the whole concentrating table unit to vibrate, the magni-' ude of vibration being controlled by the eccentricity or degree of unbalance of the weights 65 and bythe degree of resilience of the cushions l5, l5'. The vibration is of relatively high frequency by reason of the high speed of rotation of the shaft 59 under normal conditions of operation. The table, by reason of this arrangement, is

caused to vibrate very rapidly during the operation of the machine, but the degree of movement or amplitude of vibration is relatively slight, it being a vibration as distinguished from any appreciable bodily movement of the table.

The shaft 56 is also provided with a pulley which drives a belt 66 to operate the blower 24.

By reason of the fact that the table is suspended from the trunnions 5 and the axis of rotation of This comthe shaft 59 coincides with the axis of the trun- I from one of the channel members I. The other hub member 68 engages a similar'link member 69' supported on th base of the structure. By turning the hand wheel in one direction or the other, the inclination "of the table can be adjusted, the

truimions 5 being the pivoting point for the structure The upper or left hand end of the table is at all times positioned directly under the discharge, gate 4 of the hopper 3. In the operation of the machine, the hopper 3 is loaded with the ore-bearing sand or other material to be processed. The drive shaft 56 is set into operation, causing air to be blown into the wind box beneath the porous table. The air valves to both reconcentrating cups are opened. When the machine has reached its operating .speed, the gate 4 is opened to the desired extent.

The inclination of the table is set to the desired angle. The rapid vibration of the material together with the blowing of countless small streams oi air through it over the entire surface of the bed makes the mass 1 similar to a liquid, any heavier body sinking to the bottom and li hter bodies floating to the top. The materialin this state fiows just like a'stream of liquid down the table to its lower discharge end, the depth being substantially even over the entire table. The particles of greatest specific gravity quickly sink to the bottom and as they move down over the surface of the table they fall into the various herringbone grooves I 8b. The inclination of the grooves plus the inclination of the table causes these particles, with the vibration of the table and the current of air coming up through the bottom of the grooves to move toward the central discharge channel l8a on the table. As more air enters the grooves than the surface of the table proper, the material is not only fed along, but the larger amount of air greatly aids in separating metal particles and retaining them in the grooves or rimes. By the time the sand reaches the lower Here the sand is being agitated by vibration andend of the table, the metal particles therein practically all become trapped in the system of grooves. or riflles provided'in the table. The sand will flo out over the lower edgeof the table.

If desired, a conveyor may be located under the discharge end of'the table for carrying the sarld away to a dump heap or other point of disposal. The metal particles to be recovered along with the overlying and surrounding body of sand pass down the central groove I8a. into the run-out trough 26. The run-out trough 26 is a rigid structure. nd the vibration of the table is, .of course, communicated to the run-out trough. As the sand with the metalparticles flows down the runout trough 26, it'passes over the first hole 21.

also by air coming up through the bottom of the first ,collectingcupa The metal particles quickly gravitate to the bottom of .the cup, displacing any sand that may have preceded the metal particles into the cup. As the cup gradually fills up with metal particles, the sand is displaced and continues down along' the run-out trough over the,

second collecting cup. Should the first collect ingcup be full of metal particles or for some reasonshould any metal particles escape the first cup, they willbe collected in the second cup,

- provided that at such time the valve 49 for blowrug .air into the second cup is open. Once the machine is put into operation, ore-bearingsand is continuously fed to the hopper 3 and the material continuously flows over the porous table,

the metal particles gradually accumulating in the first receiving cup 28. Sand'fiowing down the run-out'trough and passing both cups eventually flows out the end.o1' the run-out trough onto the waste sand being discharged from the end of the table, When it is observed that the first cup 28 is full of metal particles, the machine is preferably stoppedand'the cup 28 removed and emptied. If desired, the machine may be run until both cups are full, or, when the first cup 28 is removed, the second cup which may have a few gold particles but principally full of sand, can be moved up to the position of the first cup. The first cup, after being emptied, is then put in the position previously occupied by the second cup, and this cycle of interchangin screen (not shown) may be located below the discharge of. the hopper 4, any conventional type of screening apparatus being satisfactory for this purpose. The operator of the machine can readily determine the rate at which the material should be fed to thetable and the inclination of the table. He can also control the volume of air supplied to each of the reconcentrating cups. By reason of the fact that the material is evenly diffused across the width of the table, all of the material is aerated to substantially the same degree, whereas if the material were supplied to the table in such manner that it was deeper along one portion of the table than another, such deeper portion would be less effectively aerated and air pressure would be lost on the less heavily covered areas of thetable.

The table shown in Figure 3 wherein the grooves are provided in the porous material, con-' stitutes a highly effective form of table. The herringbone arrangement of grooves in eifect provides riiiles or flutes. At thesame time, the thickness of porous material at the bottom of these flutes is less than the thickness of the porous bed between the grooves. This is a desirable feature, because the air permeates to a greater degree through these areas of lesser thickness. This-is oifset by the fact that there is a greater depth of overlying sand because of the deeper sand directly over the grooves, there is more air supplied at these points; Instead, however, of providing a plurality of riiiies asillustrated in Figure 3, an arrangement such as that shown in Figures 7 and 8 may also be used, In

these figures, the porous bed of the 'machine is designated I0. It is supported over a wind box structure 8a similar to that previously described.

The forward end of the table, however, instead 'the point where the two lips 12 come together there is provided a run-out trough 13. This runouttrough may be provided with reconcentrating 2 cups as heretofore described, With this arrangement, the forward edge of the porous table 10 is supported on an angle bar 14 as shown in Figure 8, and this angle bar is provided with nu-v merous perforations 14a. The lower 'edge of the porous strip I2 is supported above the angle bar of'being square, is provided with converging for- H, leaving an air space 15. By reason of this arrangement, air will not only flow through the porous bed 10, but will also flow up through the porous edge or riffle 12. This arrangement, therefore, provides a form of porous riflle similar to that provided by the herring bone grooves of th structure shown in Figures 3 and 4.

In use, where a table having this modified form is employed, the material to be processed is discharged onto the left hand end of the table as viewed in Figure 7. The table is supported in the manner of the table heretofore described, being inclined downwardly toward the pointed end. As the material moves down the table, the table is vibrated and air is blown up through it, causing the precipitation of the heavier particles to the bottom of the mass. The heavier particles gravitate down the table with the overlying and surrounding mass of sand. When the sand encounters the porous bead or rifle 12 at the discharge end of the table, it will flow over the edge and be discharged. The metal particles, however, will be caught against the bottom of the bead or porous strip 12 and be carried down to the run-out trough 13. By reason of the fact that the bead I2 is porous, air will be forced into the sand to keep the heavier particles from being lifted up and churned around by the great overlying mass of sand. We have found that if than $5 of one ounce per 2000 pounds of sand.

It is contemplated that the unit shown in the accompanying drawings, being of a width suitable for mounting on an automobile truck, will process the sandat a rate nearly a ton a minute. It will therefore be seen that with this volume of sand passing over the table in a short unit of time, the rifles or other means for trapping the sand must be such that the particles of gold or other metal particles to be recovered, once they come against the base of a rifle, will not be swept along by the continuously flowing stream of sand. It is for this reason that the porous rifle arrangement of the present invention is an important factor inthe efliciency of the machine.

The porous 'bed of the machine may be formed ofvarious commercially available materials of a generally porous character permeable to the flow of air thereth'rough.' Typical materials are bonded silicon carbide grains, natural pumice, mineral filters, and substances of like nature which are porous or permeable to the flow of air or gas, and are less resistant to air flow through the flutes than through other parts of the porous bed. By the word air in our broader claims, we intend to include any gaseous medium which is the equivalent of air under the conditions of this system. I

While we have illustrated and described in detail certain specific embodiments of our invention, it will be understood that the drawings are merely for the purpose of illustration and that the invention may be otherwise embodied and that various modifications and changes may be made therein.

We claim:

l. A dry concentrating apparatus of the class described, comprising a porous table, and means for forcing air upwardly through said table, the table having flute or rifle portions arranged to contain a greater depth of thematerial fed than other table portions and cooperating with the air The content of gold in ordinary feed to supply a larger amount of air upwardly through the flute or rifle portions.

2. A table for use in dry concentrating-machines, comprising a slab-like member of porous material having open flutes formed therein and means for forcing air upwardly through said table, the flutes and air-forcing means being arranged to supply larger amounts of air to the flutes wherein the feeding material is deeper than upon other table portions.

3. In a dry concentrating apparatus, a permeable bed portion' having a concentrating flute more permeable than another part of the bed, said flute being arranged to contain thicker or deeper portions of the material feeding over the bed, means for forcinga gaseous medium upwardly through the bed and flute.

4. In a dry concentrating apparatus, a permeable bed portion having a concentrating flute more permeable than another part of the bed, said flute being arranged to contain thicker or deeper portions of the material feeding over the bed, means forforcing a gaseous medium upwardly through the bed and flute, and means for vibrating or jarring the bed and flute.

5. In a dry concentrating apparatus, a permeable bed having flutes arranged to allow lengthwise travel of dry material, said flutes being arranged to contain deeper portions of the material heated and being more permeable than other parts of the bed, and means for forcing air upwardly through the flutes and bed.

6. In a dry concentrating apparatus, a permeable bed having 'a flute of greater permeability and arranged to be below a greater depth 01' flowing material than other bed portions, connections arranged to force air upwardly through the bed and flute, and a reconcentrating apparatus to which the bed feeds. I

'7. In a dry concentrating apparatus, a bed which has parts permeable to a gaseous medium, said bed having a plurality of flutes arranged to underlay greater depths of flowing material than other portions of the bed and being of greater permeability to the gaseous medium, the flute system being arranged to feed the dry material forwardly, means for vibrating or jarring the bed, means for forcing air through the bed portion and flute system, and a re-concentrator to which the material is fed from'said concentrating table. g

8. In dry concentrating apparatus, a stratifying table having pervious portions at ageneral level and pervious groove portions into which the concentrates sink, and means for feeding a gaseous fluid upwardly through the table and groove portions, the groove portions and gaseous feed being arranged to supply greater amounts of .air through the groove portions than through other table portions.

9..In dry concentrating apparatus, an inclined stratifying table having pervious portions at a general level and pervious groove portions into which the concentrates sink, and means for feeding a gaseous fluid upwardly through the table and groove portions, the groove portions and gaseous feed being arranged to supply greater amounts of air through the groove portions than through other table portions.

10. In dry concentrating apparatus, a stratif ing table having pervious portions at a general level and pervious groove portions into which the concentrates sink, and controllable means for feeding a gaseous fluid upwardly through the table and groove portions, the groove portions and gaseous feed being arranged to supply greater amounts of air through the groove portions than through other table portions.

11. In the dry concentration of material having heavier and lighter particles, the steps contrates to sink into permeable grooves of the table beneath lighter portions of the material, and feeding a gaseous fluid in greater amount upwardly through the grooves and in lesser amount through other table portions.

13. In the dry concentration of material having heavier and lighter particles, the steps consisting of feeding the material over a permeable stratifying table causing the concentrates to sink into permeable grooves of the table beneath lighter portions of the material, and feeding a gaseous fluid in greater amount upwardly through the grooves and in lesser amount through other table portions, and vibrating the table.

14. A dry concentrating apparatus of the class described comprising a pervious table, means for vibrating the table, and means for forcing a gaseous medium upwardly through said table, the

table having flute or riille portions arranged to contain a greater depth of the material fed than other table portions and cooperating with the gaseous feed to supply a larger amount of said gaseous medium upwardly through the flute or riille portions.

15. A dry concentrating apparatus of the class described comprising a pervious table inclined from a receiving end portion downwardly toward a discharging end portion, means for vibrating the table, and means for forcing a gaseous medium upwardly through said table, the table having flute or riflie portions arranged to contain a greater depth of the material fed than other table portions and cooperating with the gaseous feed to supply a larger amount of said gaseous medium upwardly through the flute or riflie portions.

16. In the method of dry concentration of the heavier particles in a dry mixture, the steps consisting of feeding the mixture forwardly over a pervious table having a flute or riflie portion arranged transverse to the forward movement of the mixture and'containing a greater depth of the mixture than other table portions, agitating the mixture, forcing air upwardly through the table and causing a greater feed of air through the flute or riflle portion than through othertable portions.

1'7. A dry concentrating apparatus-of the class described comprising a porous table, means for forcing air upwardly through said table, said table having flute or riille portions therein below a plane representing a surface level of said table,

said flute or riflie portions being arranged to contain a greater depth of material fed than, other table portions, said air means cooperating with said table and said portions thereof to supply air through the upper and lower table portions, with a larger amount of air upwardly through said flute portions than through other portions of the table.

DWIGHT C. MORGAN, JR.-

T. HUBBARD MORGAN.

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