US2889043A

US2889043A - Apparatus for separating solid materials of different specific gravities by means of a suspension

Info

Publication number: US2889043A
Application number: US574858A
Authority: US
Inventors: Dru Marcel Roger
Original assignee: JARUZA A G SOC
Current assignee: JARUZA A G SOC; JARUZA AG Ste
Priority date: 1955-03-30
Filing date: 1956-03-29
Publication date: 1959-06-02
Anticipated expiration: 1976-06-02

Description

June 2, 1959- V DRU 2,889,043

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 1L INVENTOR MAZCEL 086 ATTORNEY June 2, 1959 DRU APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 2 INVENTOR MA .2651. 02

ATTORNEY June 2, 1959 M R DRL', 2,889,043

APPARATUS FOR SEPARATING SbLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 3 INVENTOR MA 8 CEL DZZ/ BY mmk ATTORNEY June 1 M. R. DRU 2,889,043

APPARATUS FOR SEPARATING SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A SUSPENSION Filed March 29, 1956 4 Sheets-Sheet 4 if BY mfiwh ATTORNEY United States l atent O 2,889,043 APPARATUS FOR SEPARATING SOLID MATE- 'RIALS OF DIFFERENT SPECIFIC GRAVITIES BY MEANS OF A SUSPENSION Marcel Roger Dru, Fontainebleau, France, assignor t Societe Jaruza A.G., Chur, Zurich, Switzerland, a Swiss company Application March 29, 1956, Serial No. 574,858 Claims priority, application France March 30, 1955 2 Claims. (Cl. 209-1725) This invention relates to apparatus for separating solid materials and has more particular reference to apparatus for separating solid materials of different specific gravities by means of a suspension.

One object of the present invention is to provide a novel and improved apparatus for separating solid materials of different specific gravities by means of a suspen sion, as for example, in coal washing installations, for separating slate, sand or other heavy constituents from the coal.

Another object of the present invention is to provide apparatus, as characterized above, including a sedimentation vat into and through which the dense liquid flows so that the float or light weight products pass over the overflow sill or weir of the vat with some of the dense liquid, an inclined casing positioned at one side of the vat with the lower end portion of the casing forming the bottom portion of the vat to receive the sink or heavy settled products, a lifting wheel mounted in the inclined casing for raising the solid material up to an evacuation point, and an inclined chute having its upper receiving end positioned to receive the heavy solids as they are evacuated from the lifting wheel and its lower end positioned to discharge the heavy products gravity flowing therethrough onto a divided draining screen which receives the float products as they pass over the overflow sill of the vat.

Another object of the invention is to provide apparatus, as characterized above, wherein the sedimentation vat is divided into a plurality of separating compartments, each water-tight with respect to the other and adapted to hold dense liquids of diflerent specific gravities, and wherein means are provided for each compartment for evacuating the heavy settle solids therefrom, including an inclined casing positioned at one side of the vat with the lower end portion of the casing forming the bottom portion of its respective compartment to receive the heavy solids settled therein, a lifting wheel mounted in the inclined casing for raising the solid material up to a discharge point, and wherein a plurality of chutes are provided, each positioned to receive the raised solids from one of said compartments, with the chute which receives the raised heavy solids from the compartment adapted to contain the dense liquid of the highest specific gravity positioned to discharge the heavy products passing therethrough onto a separated draining screen which receives the float products from all of the compartments, and with the remaining chutes positioned so that the raised solids from each of the compartments will be discharged into the next compartment which is adapted to hold dense fluid of a higher specific gravity than the compartment from which the heavy products were raised.

Another object of the invention is to provide apparatus, as characterized above, wherein the mechanical parts are so constructed as to minimize the abrasive action of the dense liquids.

A further object of the invention is to provide apparatus for separating solid materials of diflerent densities by means of a suspension, which is simple and inexpensive in construction and eflicient in operation.

2,889,043 Patented June 2, 1959 ice Other objects and advantages of the invention will appear in the following specification when considered with the accompanying drawings, wherein:

Fig. 1 is a vertical, transverse section of one embodiment of apparatus constructed in accordance with the present invention;

Fig. 2 is a full elevational view taken on the line 2-2 of Fig. 1, looking in the direction of the arrows;

Fig. 3 is a view similar to that shown in Fig. 1, but showing a modified form of apparatus;

Fig. 4 is a full elevational view taken on the line 4-4 of Fig. 3, looking in the direction of the arrows;

Fig. 5 is a vertical sectional view taken on the line 55 of Fig. 4, showing the construction of the lifting wheel;

Fig. 6 is aview similar to that shown in Fig. 1, but showing another modified form of apparatus;

Fig. 7 is a full elevational view taken on the line 77 of Fig. 6, looking in the direction of the arrows;

Fig. 8 is a vertical sectional view taken on the line 8-8 of Fig. 7, showing the construction of the blades of the lifting wheel;

Fig. 9 is a view similar to that shown in Fig. 1, but showing another modified form of apparatus; and

Fig. 10 is a full elevational view taken on the line 10-10 of Fig. 9, looking in the direction of the arrows.

The present invention is an improvement over that shown and. claimed in my prior Patent No. 2,678,727, granted on May 18, 1954, for Separating Solid Materials by Suspension.

My aforesaid prior patent discloses apparatus for separating solid material of different specific gravities into two classes and comprises a large vat into which dense liquid and the material to be separated are delivered and wherein a liquid level is maintained so that the float or lighter products are evacuated by overflowing with the liquid while the sink or heavier products fall to the bottom, from where they are removed by means of a rotating paddle wheel mounted in an inclined annular casing arranged at one side of the vat. The raised products being evacuated through an opening in the top portion of the annular casing.

The present invention provides improved means for raising the sink or heavy products and provides for these raised products to be discharged onto a divided draining screen positioned to receive the float or lighter products as they pass over the overflow sill of the vat.

The present invention further provides means for separating the material to be treated into more than two classes of diflerent specific gravities by dividing the sedimentation vat into a plurality of separate separating compartments with each compartment water-tight with respect to the other compartments and adapted to contain a dense liquid of a predetermined specific gravity, and with means provided for raising and delivering the sink or heavy products from one compartment to a compartment filled with dense liquid of a higher specific gravity, and with the float products from all of the compartments being delivered onto separate parts of a divided draining screen and with the heavy products from the compartment containing the dense liquid of the highest specific gravity, being discharged onto a separate section of the draining screen which receives the float products from all of the compartments.

Referring now to the drawings, there is illustrated in Figs. 1 and 2, one embodiment of apparatus, constructed in accordance with the present invention. As there shown, the apparatus comprises an elongated generally rectangular sedimentation vat or wash box 10 having an overflow sill or weir 11 on its outlet end and into the opposite end of which are delivered the dense liquid and the solid material to be separated by any suitable usual means (not shown); an inclined open-top casing 12 post 3 tioned at one side of the vat and with its lower end open iug into and forming the'bot't'om'pertion of the vat; an inclined shaft 13 extending up through the bottom wall of the casing in a direction normal, to the plane of inclination .of the casing to the vat; a lifting wheel, indicated generally at 14, mounted on said shaft within said casing; a divided draining screen 15 positioned adjacent the overflow sill of the vat to receive the float products discharged 'thereover onto one side of the screen; and a stationary chute 16 having its upper end positioned to receive the heavy products as they are discharged from the lifting wheel and its lower end positioned to discharge the heavy products passing therethrough onto the other side of the di ided draining screen.

The'sedimentation 'vat 10 is generally similar in construction to the vat shown'inmy. aforesaid patent. It is shown as'an elongated, generally rectangular vat having vertical sidewalls 17, 18 anda-bott'om wall 19 having oppositely inclined portions whichinerge into the bottom end portion of the inclined casing-12; 5 i

The inclined casing'12, whichhous'es thelifting wheel and helps form the bottom portionof the vat, is shown as having a comically shaped bottom "wall'20, through the apex of which the shaft 13 extends, the apex being positioned above the liquid level of the vat, and a side wall 21 extending upwardly from the outer periphery of the bottom wall. A drain nipple 22, provided with a suitable closure member, is shown as being connected to the lower part of the casing 12 to permit the bottom of the vat and the casing to be cleaned out periodically. The lower portion of the bottom wall. of the casing, as indicated at 23, in effect forms a side wall of the vat. The side wall 17 of the vat adjacent the casing acts as a baflie member preventing the flow of the float or lighter products from the vat into the casing.

The lifting wheel 14 is shown as comprising an annular plate 24 having an upstanding flange formed around its outer periphery forming an outer wall 25; a plurality of spokes or arms 26, each attached at its outer end to the bottom of the plate 24 and at its inner end to a hub fixed on the shaft 13 for rotation therewith, and a plurality of curved blades 27 secured to the upper surface of the plate 24 in circumferentially spaced relation; the curvature of the blades being such that the spaces between adjacent blades form baskets opening in a radial direction with respect to the lifting wheel. The shaft 13 is journaled in suitable fixed upper and lower bearings 28 and 28', respectively, and is driven by any suitable means, such as a worm wheel 29 fixed on the lower end of the shaft and driven bya worm 30 on a shaft 31 adapted to be driven by any suitable means (not shown).

The inclination of the casing 12, the downward inclination of the arm 26 of the lifting wheel, and the height of the'upper bearing of the shaft are such that the upper bearing is above the water level of the dense liquid in the tank.

The lifted heavy products are prevented from prematurely sliding out of the baskets by fixed guiding means positioned around the inner periphery of the lifting wheel. The guiding means is shown as being in the form of an interrupted cylinder 32 fixedly held in position adjacent the inner periphery of the lifting wheel, as by means of a plurality of supporting arms 33 connecting the cylinder to the outer side wall 21 of the casing 12. i

The draining screen 15 may be of any usual construction and is shown as comprising an elongated perforated or reticulated bottom wall member 34- having

vertical side walls

35, 36 and having its screening surface divided into two parts by a longitudinally extending vertical wall member 37. The draining screen is mounted adjacent to the discharge end of the vat below the overflow sill or weir in position to receive the outflow liquid and float products onto the left hand side of its divided screening surface, as seen in Fig. 2. i

The chute 16 may be of any suitable usual CQ ISU' JP tion. It is shown as a trough-like structure having a closed bottom 38 and upstanding side walls 39, 40'. The chute has its upper receiving: end fixedly attached to the interrupted ends of the cylinder 32 and with its bottom wall projecting below the annular plate 24 of the lifting wheel, in position to receive the heavy products as they fall from the baskets in the lifting wheel, through the interruption in the cylinder 32, as it rotates. The chute has its lower discharge end positioned to discharge the heavy products gravity flowing therethrough onto the right hand side of the divided surface of the draining screen, as viewed in Fig. 2.

In Figs. 3, 4 and 5, there is illustrated a modified form of the apparatus. In this modification, the vat 10' with its overflow sill or .weir 11,-the inclined casing 12', the shaft 13' with its mounting and drive mechanism, and the divided draining screen 15', are all identical in. construction to the construction of t he corresponding parts. of the modification shown in'Fig's. l and 2. The lifting wheel 14 is shown as comprised of an annular channel member having a bottom wall 41 and inner and outer

cylindrical side walls

42, 43 supported by a plurality of radial arms or spokes 44, each connected at one end to a hub fixed on the shaft 13 and the other end to the bottom wall of the channel member. A plurality of circumferentially spaced blades 45 curve upwardly from the bottom wall of the channel with their outer ends curving inwardly toward the interior of the wheel and ending in discharge spouts 46 positioned above and extending slightly beyond the inner wall 42 of the channel member. The blades 45 divide the channel into a plurality of baskets for receiving the heavy settled products.

In this particular modification the chute 16' is generally similar to the chute 16 shown in Fig. I, but has its upper receiving end positioned to receive the heavy products when they start to slide out of the baskets of the lifting wheel which is a position reached by the baskets after they have passed the highest point in their path of rotation. The upper end portion of the chute may be fixedly supported, as by means of support members 47 connecting the chute to the outer wall 21' of the casing 12. The lower discharge end of the chute 16' is positioned to discharge the heavy products gravity flowing therethrough onto one side of the divided draining screen 15 In Figs. 6, 7 and 8, there is illustrated another modified form of the apparatus. In this modification, the vat 10", the inclined casing 12", the shaft 13" with its mounting and drive mechanism, and the divided draining screen 15", are all identical in construction to the construction of the corresponding parts of the modification shown in Figs. 1 and 2. The lifting wheel 14 is shown as comprising a stationary annular plate or base member 48 having an upstanding flange around its outer periphery forming a cylindrical outer wall 49. The annular base member 48 is fixedly mounted within the inclined casing 12", as by means of a plurality of circumferentially spaced support members 50 connecting the wall 49 of the base member to the wall 21'? of the casing; and a rotatable cylindrical member 51 mounted within the casing 12" and connected for rotation with the shaft 13" by means of a plurality of spokes or arms 52 each connected at one end to the cylindrical memberSl' and at the other end to a hub fixed on the shaft 13"; The

cylindrical member 51 forms a movable wall slightly spaced from the inner periphery of the base member 48 and carries a plurality of circumferentially spaced curved scraper blades 53 extending in scraping position over the upper surface of the base member 48 with the bottom edge of the blades spaced slightly above the upper surface of the base member and with the'outer edges of the blades slightly spaced from the cylindrical wall 49 of the base member.

A portion of the fixed outer wall 49 of the base mem-' ber 48 is cut away to provide an opening 54 through which the heavy products lifted by the blades 53 are discharged when the heavy products have reached a position where they start to slide out of the baskets formed by the space between adjacent blades, which position is a position reached by the baskets after they have passed the highest point in their path of rotation.

The upper receiving end of a chute 16'' having a bottom wall 55 and

upstanding side walls

56, 57, is fixedly connected to the ends of the side edges of the opening 54 in the wall 49 of the annular base member 43 so that the heavy products will be received in the chute as they slide outwardly through the opening 54 in the wall 49. The chute 16 then curves downwardly and across the front of the inclined casing 12 with its lower discharge end positioned to discharge the heavy products gravity flowing therethrough onto the divided draining screen 15".

In Figs. 9 and 10, there is illustrated still another modification of the apparatus. In this particular modification, the apparatus is shown as comprising an elongated generally rectangular sedimentation tank or vat 58 divided into separate inner and outer elongated wash boxes or separating compartments 59 and 60, respectively, which are water-tight with respect to each other; a pair of inclined casings 61, 62 positioned at one side of the vat in vertically spaced superposed relation with the upper casing 61 having its lower end opening into and forming the bottom portion of the inner compartment 59 and with the lower casing 62 having its lower end opening into and forming the bottom portion of the outer compartment 60; an inclined rotatable shaft 63 extending up through the bottom walls of both casings in a direction normal to the planes of inclination of the casings to the vat; lifting Wheels 64, 65 mounted within the upper and lower casings 61, 62, respectively, are connected to the shaft 63 for rotation therewith; a divided draining screen 66 positioned adjacent the overflow sills of the two compartments 59, 60 to receive the float products discharged thereover onto separate sections of the screen; a stationary chute 67 having its upper end positioned to receive the heavy products as they are discharged from the lifting wheel 65 and its lower end positioned to discharge the heavy products gravity flowing therethrough into the receiving end of the inner compartment 59; and a second stationary chute 68 having its upper end positioned to receive the heavy products as they are discharged from the lifting wheel 64, and its lower end positioned to discharge the heavy products gravity flowing therethrough onto one section of the divided draining screen 66.

The inner separating compartment 59 is shown as having

vertical side walls

69, 70 and a bottom wall 71 having oppositely inclined portions which merge into the bottom end portion of the inclined casing 61.

The inclined casing 61, which houses the lifting wheel 64 and helps form the bottom portion of the inner compartment 59, is shown as having a conically shaped bottom wall 72, through the apex of which the shaft 63 extends, the apex being positioned above the liquid level of the compartment, and a side wall 73 extending upwardly from the outer periphery of the bottom wall. The lower portion of the bottom wall of the casing, as indicated at 74, in effect forms the inner side wall of the compartment. The side wall 69 of the inner compartment acts as a bafie member preventing the flow of the float or lighter products from the compartment 59 into the casing 61.

The outer separating compartment 60 is shown as having a vertical outer side wall 75, a vertical inner side wall formed by the vertical side walls 70 of the inner compartment 59, and a bottom wall 76 having oppositely inclined portions which merge into the bottom end portion of the inclined casing 62.

The inclined casing 62, which houses the lifting wheel 65 and helps to form the bottom portion of the outer compartment 60, is shown as having a conically shaped bottom wall 77, through the apex of which the shaft 63 extends, the apex being positioned above the liquid level of the compartment, and a side wall 78 extending upwardly from the outer periphery of the bottom wall. The space between the lower portions of the two

casings

61, 62, in effect forms a compartment communicating with the outer compartment 60 and the dense liquid from compartment 60 fills this space up to the same liquid level as exists in compartment 60.

The lifting wheel 64, which is rotatably mounted within the upper inclined casing 61, is shown as comprising an annular plate 79 having an upstanding flange formed around its outer periphery forming an outer wall 80; a plurality of spokes or arms 81 connecting the annular plate 79 to a hub fixed on the shafts 63 for rotation therewith; and a plurality of curved blades 82 secured on the upper surface of the plate 79 in circumferentially spaced relation, the curvature of the blades being such that the space between adjacent blades forms a basket opening inwardly in a radial direction with respect to the lifting wheel.

The heavy products lifted by the wheel 64 are prevented from prematurely sliding out of the baskets by fixed guiding means positioned around the inner periphery of the wheel. The guiding means is shown as being in the form of an interrupted cylinder 83 fixedly held in position adjacent the inner periphery of the lifting wheel as by means of a plurality of supporting arms 84 connecting the cylinder to the outer side wall 73 of the upper casing 61.

The chute 63 which carries the heavy products raised by the lifting wheel 64 and deposits them on the divided draining screen 66, is shown as a trough-like structure having a closed bottom wall 85 and upstanding side walls 86, 87. The chute has its upper receiving end fixedly attached to the interrupted ends of the cylinder 33 and with its bottom wall projecting below the annular plate 79 of the lifting wheel in position to receive the heavy products as they fall from the baskets on the lifting wheel through the interruption in the cylinder 83. The chute has its lower discharge end positioned to dis charge the heavy products gravity flowing thereflhrough onto one side of the divided draining screen 66.

The lifting wheel 65, which is rotatably mounted within the lower inclined casing 62, is shown as comprising an annular plate 88 having an upstanding flange formed around its outer periphery forming an outer wall 89; a plurality of spokes or arms 90 connecting the annular plate 38 to a hub fixed on the shaft 63 for rotation therewith; and a plurality of curved blades 91 secured on the upper surface of the plate 88 in circumferentially spaced relation, the curvature of the blades being such that the space between adjacent blades forms a basket opening inwardly in a radial direction with respect to the lifting wheel.

The heavy products lifted by the wheel 65 are prevented from prematurely sliding out of the baskets by fixed guiding means positioned around the inner periphery of the wheel. The guiding means is shown as being formed by an upper cylindrical portion 92 of the side wall 73 of the upper inclined casing 61. This upper cylindrical portion 92 merges into the bottom wall member 71 of the inner separating compartment 59 and has an interruption formed therein in its upper portion forming an opening 93 through which the heavy products lifted by the wheel are discharged onto the chute 67.

The chute 67, which receives the heavy products raised by the lifting wheel 65 and deposits them into the receiving end of the separating compartment 59, is shown as a trough-like structure having a closed bottom wall 94 and upstanding side walls 95, 96. The chute has its upper receiving end fixedly attached to the end of the opening 93 formed in the cylindrical portion 92 of the side wall 73 of the upper inclined casing 61 and with its bottom wall projecting below the annular plate 88 of the lifting wheel, inposition to receive the heavy prod ucts as they fall from the baskets in the lifting Wheel through the opening 93. The chute has its lower discharge end positioned to discharge the heavy products gravity flowing therethrough into the receiving end of the separating compartment 59.

The shaft 63 is journaled in suitable fixed upper and lower bearings 97, 98, respectively, and is driven by any suitable means, such as shown in Fig. 1, for driving the corresponding shaft 13.

The draining screen 66 is similar in construction to the draining screen shown in the modification illustrated in Fig. 2, and is divided into three sectons by longitudinally extending

upstanding wall members

100, 101, 102, and 103, one for receiving the float products as they are discharged over the overflow sill 104- of the separating compartment 60, one for receiving the float products as they are discharged over the overflow sill 105 of the separating compartment 59, and one for receiving the heavy products discharged by the chute 68.

The blades of the lifting wheel 64 are so curved that the lifted products slide inwardly toward the center of the wheel before reaching the highest point in the path of rotation of the wheel and the blades of the lifting wheel 65 are so curved that the lifted products slide inwardly toward the center of the wheel after passing over the highest point in the path of rotation of the wheel. Also, the dense liquid lifted by the baskets in each wheel will drain back into the compartment from which it was lifted through the space between the guiding means for retaining the heavy products in the baskets and the inner periphery of the wheel, thus preventing any mixing of the dense liquid in the two separating compartments.

The operation of the various modifications of the apparatus, as illustrated in Figs. 1 to 8, inclusive, is believed apparent. The vat is filled with a dense liquid or suspension, such for example, as a mixture of fine sand and water, up to a desired liquid level. The raw materials to be treated fall into the front end of the vat. products or light fractions are discharged over the overflow sill or weir with the overflow of dense liquid and fall onto the draining screen. The sin products or heavy fractions fall into the bottom of the series of baskets of the lifting wheel and are lifted by the wheel, as it rotates, and, at an elevated point in the path of rotation, slide on the curved blades and the bottom of the wheel into the chute mounted to receive them, and are discharged by the chute onto one side of the draining screen near the light fractions discharged thereon.

In the apparatus shown in Figs. 9 and 10, considering the case of coal washing, the operation takes place as follows:

The raw coal (consisting of coal, middlings and shales) falls into the outer compartment 60 where a first separation is effected.

The treated coal, referred to as washed coal, passes above the weir 104 with some overflow of dense liquid and is discharged upon the outer section of the draining screen 66. The mixture of middlings and shales falls to the bottom, into the rotating series of baskets formed by the blades 91 of the lifting wheel 65. They drain during lifting and, after passing beyond the highest point in the path of rotation of the wheel, fall into the chute 67 which conveys them to the inner compartment 59 containing dense liquid of a higher specific gravity than that in the compartment 60.

In this wash box compartment 59, the mixture of middlings and shales is separated as follows:

The middlings float, are driven by the liquid flow and leave the apparatus above the weir 105, with the overflow of liquid; they are discharged onto the central section of the partitioned draining screen 66.

The shales sink in the series of baskets formed by the blades 82 of the lifting wheel 64, are lifted, and, before 8 reaching the highest point in the path of rotation, slide into the chute 68, which discharges them outside the apparatus onto the inner section of the draining screen 66.

As will be seen from the above description, the raw mixture entering the apparatus is separated into three fractions by two separating gravities. These fractions travel automatically and are finally discharged in parallel directions and in the same area, opposite the entrance opening of the raw mixture.

Obviously, the invention is not restricted to the particular embodiment thereof herein shown and described, but is capable of various modifications within the scope of the appended claims.

What is claimed is:

1. In an apparatus for separating solid materials having different specific gravities, comprising an elongated sedimentation vat for holding a body of dense liquid, said vat having an overflow sill along one end over which the light fraction is discharged with overflow dense liquid; a draining screen positioned below the overflow sill, said draining screen being divided into a plurality of separate longitudinally extending sections with one section positioned to receive the light fractions discharged with the overflow dense liquid; an inclined open top casing positioned at one side of said vat with its lower end opening into and forming the bottom portion of the vat to receive the heavy settled fraction, the side wall of the vat adjacent the casing acting as a baflle member preventing the flow of the light fraction from the vat into the casing; a shaft extending upwardly through the bottom of said casing in a direction normal to the plane of inclination of said casing to said vat; a lifting wheel including an annular plate having an upstanding flange around its outer periphery forming an outer wall mounted in said casing and fixedly connected to said shaft for rotation therewith by a series of supporting arms, said lifting wheel carrying a plurality of circumferentially spaced blades positioned adjacent its outer periphery with the spaces between the blades forming baskets in which the heavy fractions are received when they sink into the bottom of the vat and are lifted by the baskets as'the wheel rotates, said blades being' baskets at an elevated point in the path of rotation of the baskets and extending downwardly across the open top of said inclined casing with its lower discharge end positioned adjacent to and at a height substantially equal to that of said overflow sill to discharge the heavy fractions gravity flowing therethrough onto another section of said draining screen adjacent the light fractions discharged thereon; and means for rotating said shaft and said wheel for raising said heavy fractions up from the bottom of the vat.

2. Apparatus as set forth in claim 1, including an interrupted cylindrical member fixedly mounted within said casing with its outer surface slightly spaced from the inner periphery of said annular plate to prevent the lifted heavy fractions from prematurely sliding out of said baskets and wherein the upper receiving end 'of said chute is connected to the end of the interruption in said cylinder so that the heavy fractions will slide through the opening formed by the interruption into said chute.

References Cited in the file of this patent UNITED STATES PATENTS 2,678,727 Dru May 18, 1954 2,690,261 Maust Sept. 28, 1954 2,753,998 Hardinge July 10, 1956