US3693794A

US3693794A - Method and apparatus for separating granular goods

Info

Publication number: US3693794A
Application number: US817127A
Authority: US
Inventors: Hans Oetiker
Original assignee: Buehler AG
Current assignee: Buehler AG
Priority date: 1968-04-17
Filing date: 1969-04-17
Publication date: 1972-09-26
Anticipated expiration: 1989-09-26
Also published as: FR2006345A1; DE1913708A1; ES365656A1; GB1247963A; SE369379B; CS182755B2; CH498664A; JPS5712425B1; AT297626B; JPS5551633B1; ES386492A1; DE1913708B2; BE731593A; DE1913708C3

Abstract

In a method of separating granular goods of different specific gravity, by separating the goods, by a forced air flow therethrough while the goods are on a goods support subjected to a vibration, into a layer of heavier fractions and a layer of lighter fractions, separating the layers and separately discharging the layers, the goods are pre-sorted, in advance of charging thereof onto the support, into a bottom layer, enriched with the heavy fractions, and a superposed layer, free of the heavy fractions. The two layers, while in such superposed relation, are then charged onto the goods support. The apparatus includes a goods feeding device, for pre-sorting of the goods, in the form of a vibrating duct having a gas permeable bottom wall. The duct forms an initial sedimentation path of the heavy fraction of the goods, and the discharge end of the duct is spaced from the outlet for the heavy fraction to form a succeeding sedimentation path of the heavy fraction charged onto the goods support.

Description

[451 Sept. 26, 1972 METHOD AND APPARATUS FOR SEPARATING GRANULAR GOODS [72] inventor: Hans Oetiker, Gallen, Switzerland [73] Assignee: Gebruder Buhler AG, Gallen, Switzerland 22 Filed: April 17,1969 21 Appl.No.: 817,127

[30] Foreign Application Priority Data April 17, 1968 Switzerland ..5678/68 Nov. 17, 1968 Switzerland ..16799/68 [52] US. Cl. ..209/467, 209/490, 209/497 [51] Int. Cl. ..B07b 3/10 [58] Field of Search ..209/3, 424, 426, 442, 456, 209/460, 467, 469, 472, 474, 476, 477, 481, 486, 497, 466, 468

2,852,137 9/1958 Hagopian ..209/139 R 3,045,825 7/1962 Watson ..209/471 FOREIGN PATENTS OR APPLICATIONS 333,622 8/ 1930 Great Britain ..209/467 Primary Examiner-Frank W. Lutter Assistant ExaminerRalph J. Hill Attorney-McGlew and Toren [5 7] ABSTRACT In a method of separating granular goods of different specific gravity, by separating the goods, by a forced air flow th'erethrough while the goods are on a goods support subjected to a vibration, into a layer of heavier fractions and a layer of lighter fractions, separating the layers and separately discharging the layers, the goods are pre-sorted, in advance of charging thereof onto the support, into a bottom layer, enriched with the heavy fractions, and a superposed layer, free of the heavy fractions. The two layers, while in such superposed relation, are then charged onto the goods support. The apparatus includes a goods feeding device, for pre-sorting of the goods, in the form of a vibrating duct having a gas permeable bottom wall. The duct forms an initial sedimentation path of the heavy fraction of the goods, and the discharge end of the duct is spaced from the outlet for the heavy fraction to form a succeeding sedimentation path of the heavy fraction charged onto the goods support.

30 Claims, 6 Drawing Figures PATENTEDSEPz I912 3,693,794

SHEET 2 BF 6 4 TTURME/f PATENTED 8EP26 m2 3 6 93, 7 94 SHEET 6 BF 6 Fig. 6

METHOD AND APPARATUS FOR SEPARATING GRANULAR GOODS BACKGROUND OF THE INVENTION uniformly distributed manner, and thus to mix the lo material in a material-air mixture which flows, in a floating manner, in the direction of descent of the inclined surface. The heavy fractions separate from the light fractions and sink gradually toward the surface. In order to separate these heavy fractions from the superposed light fractions, the surface is vibrated in a direction opposite to the line of descent, so that the heavy fractions are moved in the direction of vibration and separated from the flowing material-air mixture or screen.

The paths along which the separation into light and heavy fractions is effected in the current of goods will hereinafter be called the sedimentation paths. This path depends on the difference between the specific gravities of the light and heavy fractions, on the height of the goods current, on its velocity of flow and on the type of granular goods. In these devices, such as shown in U.S. Pat. Nos. 2,404,414, 2,040,196, 2,427,423, 2,718,306 and 2,928,545, the mixed fractions are charged onto the inclined goods support between a discharge device and the outlets.

In order to obtain a uniform distribution of the mixed fractions on the inclined goods support, the feed is effected in a falling mist extending substantially throughout the entire width of the goods support. All of these devices have the disadvantage that the air cushion, formed on the inclined goods support, is irregular, due to turbulence and different heights of the charge of goods. As a result, the air-goods current and sedimentation of the heavy fractions, that is, their sinking to the goods support, is disturbed, so that separation is inefficient. Another disadvantage is that the heavy fractions, sedimented down to the goods support and which are to slide, under the action of the vibratory movement of the goods support, in a direction opposite to the line of descent and extending to the outlet, must be moved under the above-mentioned falling mist. Due to the turbulence of the air-goods current, occurring in the range of the falling mist, the heavy fractions are again carried along by the air-goods current, which has the same result in that separation is insufficient and inefficient.

Other devices for separating granular goods according to different specific gravity are known, for example, those shown in US. Pat. No. 2,718,307 and British Pat. No. 293,472. These devices also use a vibrating and inclined air-permeable goods support. These devices also include an air feeding arrangement directed beneath the goods and toward the goods for the formation of an air-goods mixture, but the feeding of the mixed fractions takes place in the range of the lowest point and adjacent a lateral boundary of the goods support. The vibratory movement of the goods support likewise is effected in the direction opposite to the line of descent, but separating elements are provided by means of which the separating fractions are directed to the side of the goods support opposite the goods feed, and are there recovered. ln order to attain a satisfactory separating effect, those obtained fractions which are between the lightest and the heaviest fractions are returned, in a cycle, to the goods feed and charged onto the vibrating goods support. This has the result that the capacity of these devices is very low.

SUMMARY OF THE INVENTION This invention relates to the separation of granular goods of different specific gravity and, more particularly, to an improved, simplified and more efficient method and apparatus for effecting such separation.

The invention is directed to a method for separating granular goods of different specific gravity, in which the granular goods are separated in a forced air current while on a support which exerts a vibration on the goods, the goods being separated into a layer of heavy fractions and a layer of light fractions. The goods are then separated and discharged through respective outlets. The invention is further directed to apparatus for separating granular goods in accordance with specific gravity, and including a vibrating and inclined airpermeable goods support, an oppositely directed air feeding device arranged beneath the support, at least one outlet for the heavy fraction arranged at the highest point of the support, a discharge device for the light fraction arranged at the lowest point of the support, and a goods feeding device arranged in between the discharge device and the outlet and opening onto the support.

In accordance with the invention, before the granular goods are charged onto the goods support, the goods are pre-sorted into a bottom layer, enriched with the heavier fractions, and a superposed layer, which is free of the heavy fractions. The superposed layers, without change, are then charged onto the material support. For performing the invention method, the goods feeding device is designed as a vibrating duct with a gas-permeable bottom wall, this duct, up to its discharge end, forming an initial sedimentation path of the heavy fraction of the supplied goods, and the discharge end of duct is spaced from the outlet to form a succeeding sedimentation path of the heavy fraction as charged onto the goods support.

An object of the invention is to provide an improved method of and apparatus for separating granular materials at different specific gravities.

Another object of the invention is to provide such a method and apparatus in which the separation is effected in a simpler, more economical and more efficient manner.

A further object of the invention is to provide such a method and apparatus in which, in advance of charging of the goods onto a material support which is vibrated in a goods-advancing direction, with the goods being subjected to a forced air flow while on the support, the goods are pre-sorted into a bottom layer enriched with the heavier fractions and a superposed layer which is free of the heavy fractions.

Another object of the invention is to provide such a method and apparatus in which the still superposed but separated layers are charged onto the goods support.

A further object of the invention is to provide such a method and apparatus in which a goods feeding device is designed as a vibrating duct having a gas-permeable bottom wall.

A further object of the invention is to provide such a method and apparatus in which this duct forms an initial sedimentation path of the heavy fraction of the material supplied, and in which the discharge end of the duct is spaced from the heavy fraction outlet to form a succeeding sedimentation path of the heavy fraction as charged onto the goods support.

For an understanding of the principles of the invention, reference is made to the following description of typical embodiments thereof as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a longitudinal sectional view through a first embodiment of apparatus in accordance with the invention;

FIG. 2 is a top plan view of the embodiment shown in FIG. 1, with parts being cutaway;

FIG. 3 is a longitudinal sectional view through a second embodiment of apparatus in accordance with DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment of the invention shown in FIGS; 1 and 2, an air-permeable goods support 1 is arranged in the casing 2 and rigidly connected lengthwise with this casing. Support 1 comprises a screen 3 beneath which is arranged, in parallel relation therewith, a perforated plate 4. Perforated plate 4 is formed with circular apertures, whose diameter and spacing is dimensioned in accordance with the required velocity of the air passing through the goods support 1. Baffles 5 are disposed between H screen 3 and plate 4 to form rectangular panels, and these baffles are bonded, along their relatively narrow upper and lower edges, to screen 3 and plate 4, respectively.

The design of goods support 1 is very important for satisfactory operation of the apparatus for separating granular goods, since the action of the air, on the goods to be separated, can be influenced by the suitable selection of the perforations in plate 4 and of the baffles 5 extending between screen 3, which serves'as a porous material support, and perforated plate 4. Toward the range of its highest point, support 1 is tapered and converges into an outlet 6 having associated therewith an elastic tube 11, having a narrow or slit-type outlet, through which the heavy fraction is discharged.

It has been found that the side wall for bounding the separating surface above the goods support, and converging toward the outlet 6, should extend at an angle a, with respect to the transverse axis of the goods support, whose tangent is not less than 1.8 but preferably is between 2 and 3. In this embodiment of the invention, this results in a goods support which is triangular in plan and whose boundaries form, approximately, angles of 30, 60 and with each other. In the range of the lowest point of support 1, the latter is terminated by a rib 7 extending transversely of the line of descent of the support. The height of rib 7 limits the height of the layer of granular goods charged onto the goods support, and this layer drops over rib 7 into a discharge device 8. Device 8 is bounded laterally by the walls of easing 2 and by the rib 7, and is tapered downwardly to a nipple 9 to which is connected an elastic tube 10 which forms a slit-shaped outlet opening at its free end.

Beneath'support 1, casing 2 forms a free chamber 12 which tapers to a nipple 13 which is connected, through a tubular collar 14 and a conduit 15 with a compressed air source 16. Casing 2, to which support 1 is fixedly connected along its outer, edges, is supported on flexible resilient supports 17. A vibrator 18 is arranged on an end face of casing 2, and this vibrator includes a motor 19 having an eccentric weight 20 secured on its driven or output shaft. Toward its upper end, casing 2 is closed by a cover plate 21 which has a sight glass 42 extending at least in the range of outlet 6. Cover plate 21 has a nipple 22 which connects the free space above support 1 and, through a tubular collar 23, with an air exhaust which has not been shown. A laterally extending sleeve 24 is connected with collar 23, and its outer end can be closed by an elastic ring 25. By' virtue of the provision of sleeve 24, which may be termed an arm sleeve, the free space above support 1 is accessible to an operator standing outsidethe apparatus.

The goods feeding device is formedby a duct 26 having a closed front end into'which opens a vertical feed pipe 27. Duct 26 is bounded laterally by a side wall of casing 2 and by a partition 28, the end of partition .28 forming, with the side wall of casing 2, a discharge end or mouth 40 for duct 26. Duct 26, from its head, beneath the discharge end of feed pipe 27, to its mouth 40, forms an initial sedimentation path. Discharge end or mouth 40 of duct 26 is spacedfrom outlet 6 and from discharge device 8, in the direction of movement of goods along support 1, to form a succeeding sedimentation path, so that the-length of support 1,-measured in the direction of its line of descent, is at least double the length of such succeeding sedimentation path. The bottom wall of duct 26 is formed by a part of support 1. Partition 28 has an opening 29 spaced somewhat from mouth 40, and opening 29 opens in a direction transversely of the line of descent of support 1. Opening 29 has a straight bottom edge 30 which is inclined in a direction toward outlet 6.

An air blast nozzle 32, having a nozzle end extending in the direction of descent of support 1 and substantially parallel to the latter, is supplied with air under pressure through a conduit 31 connected to an air source whose pressure is higher than the pressure in casing 2 beneath cover plate 21.

The invention apparatus operates in a manner which will now be described. Goods support 1, which is mounted on the oscillatable supports 17, is operatively associated with vibrator 18in a manner such that support 1 vibrates substantially parallel to the line of descent, the vibrations acting to advance goods on support 1 upwardly toward outlet 6. Y Compressed air source 16 supplies compressed air through line 15, tu-

bular collar 14, and nipple 13 beneath perforated plate 4. The compressed air flows through the apertures in plate 4 into the panels formed between plate 4 and screen 3 by baffles 5. Baffles 5 insure a uniformly distributed air flow through screen 3 in the volume formed above screen 3 by easing 2, the air leaving this volume through nipple 22 and tubular exhaust collar 23.

The mixed fractions of the granular goods are introduced through feed pipe 27 into duct 26, and float, as an air-goods mixture, on screen 3 toward duct opening 29, with the heavy fractions moving downwardly toward screen 3 due to their higher specific gravity. When the heavy fractions reach screen 3 they receive, through the vibration of support 1, an additional motion component directed oppositely to the descending gradient of support 1, so that the heavy fractions move along duct 26 and beyond the end of partition 28 into the range of outlet 6. The light fractions flow over the lower edge 30 of opening 29 and onto goods support 1.

The special design of the air-permeable goods support 1, formed by screen 3, baffles 5 and perforated plate 4, insures that the amount of air acting on the goods to be separated is within 95 to 125 percent of a value called the critical threshold value. This critical threshold value characterizes the state wherein the material is above air permeable screen 3 as an homogeneous, bubble-free fluidization layer, or airgoods mixture, flowing in the manner of a liquid. This air-goods mixture is uniformly distributed over the support surface. The light fractions flow in the direction of the steepest inclination, in the manner of a liquid, toward rib 7 where they are restrained. If the height of the light fractions floating on support 1 exceeds the height of rib 7, the light fractions flow over the upper edge of rib 7 into discharge device 8 and leave the discharge device 8 through nozzles 10 which transfer the light fractions of the granular goods to a sluice 33 driven by a motor 32.

If heavier fractions of the granular goods are still associated with the light fractions passing through opening 29, these heavier fractions have a further opportunity, until the mixture reaches rib 7, to drop to the screen 3 due to the higher specific gravity. On screen 3, the heavier fractions receive a goods advancing vibrational force directed toward outlet 6, so that they move toward this outlet and through the light fractions in counter flow to the direction of flow of the light fractions. The movement of the heavy fractions, to be separated through the outlet 6, in the range of the converging side wall is influenced greatly by the inclination of the side wall relative to the shortest distance between outlet 6 and the discharge device 8 for the light fractions. The tangent of the angle a of the inclined side wall therefore should be equal to or greater than 1.8.

The heavy fractions sinking in duct 26 below the lower edge 30 of opening 29 pass the end of partition 28 through mouth 40 and onto support 1. If this heavy fraction still contains light fractions of the granular goods, the light fractions spread over support 1 as an air-goods mixture and float in the direction of descent of support 1 toward discharge device 8, while the heavy fractions continue to move toward outlet 6.

In the embodiment of the invention shown in FIGS. 1 and 2, the mixed fractions are pre-sorted initially in duct 26, and into a bottom layer enriched with the heavy fractions and a superposed layer which is free of the heavy fractions. The goods are subsequently charged, as these two superposed layers, onto goods support 1. After the pre-sorted and layered fractions have been transferred to support 1, the layers are separated and discharged through the respective outlets. Any parts of the light fraction which come into the range of outlet 6 are moved, under the action of the air jet issuing from nozzle 32 and directed along the line of descent of support 1 toward discharge device 8, so that passage of the light fractions into outlet 6 is practically impossible.

In the second embodiment of the invention, shown in FIGS. 3 and 4, parts identical with those of the embodiment shown in FIGS. 1 and 2 have been given the same reference number and will not be described further in detail. As best seen more particularly in FIG. 4, the airpermeable goods support 1, in plan, is shaped somewhat differently than in the embodiment of FIGS. 1 and 2. Duct 260 of the goods feeding device is no longer arranged at one side of support 1, but extends symmetrically of the longitudinal axis of the latter. Duct 260 is bounded laterally by

partitions

280 and 281, and is divided into a front region and a rear region which have different bottom inclinations. The rear region, beginning under the discharge end of feed pipe 27, is inclined downwardly toward goods support 1 in order to accelerate discharge of the mixed goods. The front region of duct 260 has a bottom which is coplanar with goods support 1, so that, in this front region, the goods move in a rising manner in a direction opposite to the line of descent of support 1.

The bottom of duct 260 in the rear region has the same design as support 1, and comprises a perforated plate 44 which is fixedly connected with a screen 30 by baffles 50. The length of duct 260 is selected so that a first separation between the light fractions and the heavy fractions is effected in the duct along an initial sedimentation path, as in the embodiment of FIGS. 1 and 2.

Partitions

280 and 281 have, at their free ends, a stepped recess corresponding to the opening 29 of the embodiment of FIGS. 1 and 2, so that limiting

edges

300 and 301, respectively, are formed. The goods, which have already been freed of the heavy fractions in duct 260, can pass over these edges onto goods support 1, while any mixed fractions, as well as the heavy fractions leave duct 260 only in the range of mouth 40 and then pass onto goods support 1.

FIGS. 5 and 6 illustrate a third embodiment of the invention, in which it is possible to obtain a greater separating effect than in the embodiments shown in FIGS. 1 through 4. The air-permeable goods support I is again positioned in casing 2 and fixedly connected with the latter longitudinally. Support 1 comprises screen 3, perforated plate 4 and baffles 5, which are firmly bonded to each other so as to form a unit. The side walls of support 1 can both converge toward the range of the highest point thereof, and lead to the outlets 6 and 60 through which the heavy fraction is discharged. The two side walls of easing 2 have the same angle of inclination a, and the tangent of the angle a again is equal to or greater than 1.8.

Support 1 is bounded, at its lowest point, by rib 7 over which the light fraction flows into discharge device 8. Discharge device 8 has nipples 9 to each of which is connected an elastic tube 10 through which the light fraction is discharged into a sluice 33 of a pneumatic conveyor system. Chamber 12, beneath support 1, is connected to compressed air' source 16 through nipple 13, tubular collar 14 and conduit 15. Casing 2 is mounted on the oscillatable resilient supports 17.

Vibrator 18 is secured on casing 2 and includes a motor 19 and an eccentric weight 20 driven by the motor. Casing 2 is closed, at its upper end, by cover plate 21 formed with a nipple 22 to which there is connected the tubular collar 23 leading to an air exhaust.

The material feeding device comprises a duct 260 into which a vertical feed pipe 27 discharges, and duct 260, as best seen in FIG. 6, extends symmetrically with respect to the plane of symmetry of support 1. This duct is bounded laterally by

partitions

280 and 281, and its bottom is inclined toward support 1. The bottom of duct 260has the same construction assupport 1, and comprises a perforated plate 44, which is firmly bonded with screen '30through the medium of baffles 50. The length of duct 260 is selected so that an initial separation between the heavy fractions and a large part of the light fractions is effected in the duct along an initial sedimentation path. Mouth 40 of duct 260 is spaced from outlets 6 and 60, and from discharge device 8, in the direction of the line of descent of support 1, to form a succeeding sedimentation path. The length of support 1, measured in the direction of its line of descent, is thus at least double the length of such succeeding sedimentation path.

A wedge 34 is secured on screen 3 and, as best seen in FIG. 6, is arranged symmetrically relative to the plane of symmetry of support 1 and has its pointed or tapered edge extending into the range of mouth 40 of feeding device 260. In the ranges of the intersections of the flanks of wedge 34 with the converging side walls of easing 2, there are arranged respective outlets 6 and 60 through which the heavy fraction of the goods is discharged. Due to the flanks of wedge 34, the goods issuing from duct 260 are positively deflected laterally and distributed uniformly over goods support 1. The greater uniformity in the distribution of the goods on support 1 results in an increased separating effect of the apparatus.

, In a further embodiment of the invention, which has not been illustrated as it is believed that it will be readily understandable to one skilled in the art, duct 26 or 26d of the goods feeding device is completely separated from goods support 1 and provided with a separate vibrating drive. In this case, the duct extends transversely of the line of descent of goods support 1 and dischargescentrally onto the support 1. The limiting edges or 300 can be directed toward discharge device 8, while the

duct

26 or 260, for the mixed and heavy fractions, has a discharge mouth directed transversely to the line of descent of support 1, or toward the outlet 6.

In each of the above-described embodiments, the compressed air source can be eliminated by exhausting air above goods support 1 while providing a free opening to atmosphere beneath perforated plate 4.

What is claimed is:

1. In a method of separating granular goods of different specific gravity, wherein the granular goods are separated, by a forced air flow therethrough while the goods are on a goods support subjected to a vibration, into a layer of heavier fractions and a layer of lighter fractions, the layers are separated, and the layers are separately discharged: the improvement comprising the steps of, in advance of charging the granular goods onto the support, pre-sorting the goods into a bottom layer, enriched with the heavy fractions, and a superposed layer, free of the heavy fractions; subsequently flowing the layered pre-sorted material onto the support as a continuous current, with at least the layer enriched with heavy fractions having a laminar flow; on the support, separating the two layers to flow along the support in substantially opposite respective directions; and separately discharging each layer.

2. In a method of separating granular goods of dif-,

ferent specific gravity, the improvement claimed in claim 1, including the step of conducting the continuous current along a laterally confined path which is coplanar with the goods support.

3. In a method of separating granular goods of different specific gravity, the improvement claimed in claim 1, including subjecting at least one of the fractions to substantially a reversal in flow direction when charged onto the goods support.

4. In a method of separating granular goods of different specific gravity, wherein the granular goods are separated, by a forced air flow therethrough while the goods are on a goods support subjected to a vibration, into a layer of heavier fractions and a layer of lighter fractions, the layers are separated, and the layers are separately discharged: the improvement comprising the steps of, in advance of charging the granular goods onto the support, pre-sorting the goods into a bottom layer, enriched with the heavy fractions, and a superposed layer, free of the heavy fractions; maintaining such superposed relation while subsequently charging the two layers onto the goods support; the layered presorted material being flowed onto the support as a continuous current, with at least the layer enriched with heavy fractions having a laminar flow; conducting the continuous current along a laterally confined path which is coplanar with the goods support; and laterally discharging at least a part of the superposed layer, free of the heavy fractions, from the path onto the goods support in advance of the discharge end of the path.

5. In apparatusfor separating granular goods of different specific gravity, and of the type including an inclined gas-permeable goods support, means directing a gas current upwardly through the support, an outlet for the heavy fractions at one end of the support, a discharge device for the light fractions at the other end of the support, the support having a gradient which descends from the outlet to the discharge device and being vibrated in a direction opposite to the descending gradient, and a goods feeding device discharging onto thegoods support: the improvement comprising, in combination, a vibrating duct, having a gas-permeable bottom and a discharge mouth, included in said feeding device; means directing a gas current upwardly through said gas-permeable bottom; said duct forming an initial sedimentation path of the heavy fraction of the fed goods, and along which path the goods are pre-sorted into a bottom layer, rich with the heavy fractions, and a superposed layer, free of the heavy fractions; said duct mouth discharging the goods onto said goods support intermediate the upper and lower ends of said goods support; the portion of said goods upport between said duct discharge mouth and said outlet forming a succeeding sedimentation path for the heavy fraction of the goods charged onto said goods support; said duct mouth being coplanar with said goods support.

6. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which the discharge direction of the duct mouth is opposite to the direction of the descending gradient extending from said outlet to said discharge device.

7. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which the discharge direction of said ductmouth extends at an angle of not more than 90 to the direction of the descending gradient from said outlet to said discharge device.

- 8. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said duct has at least one side wall separating the duct from the good support; said one 7 side wall being formed with an overflow opening whose lower edge is spaced above the goods support, said overflow opening discharging toward the goods support.

9. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said duct forms part of said gaspermeable goods support and is bounded by side walls on said support.

10. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said gas-permeable bottom of said duct has a gradient rising toward said outlet at least in a front region adjacent said duct mouth.

11. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 10, in which said gas-permeable bottom of said duct has a descending gradient between the goods receiving end of said duct and said front region.

12. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said duct mouth is spaced from said discharge device by at least the length of said succeeding sedimentation path. I

13. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, including a casing enclosing said goods support and said vibrating duct; said means directing gas upwardly through said support opening into said casing beneath said support; a hood closing said casing above said goods support; and gas exhaust means opening through said hood.

14. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 13, in which said goods support with said duct is fixedly connected with said casing along its peripheral edges.

15. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 14, in which said goods feeding device extends along one side of said goods support and substantially parallel to the gradient of said goods support; said casing having side walls; one side wall of said duct being formed by a side wall of said casing, and the other side wall of said duct being formed by a partition.

16. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 14, in which said duct is covered by said hood.

17. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 13, in which the exhaust opening through said hood comprises a tubular collar; a sleeve connected to said collar and communicating therewith, said sleeve extending laterally from said collar; and means selectively operable to close said sleeve.

18. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 13, in which said hood includes a transparent portion at least in the range of said outlet.

19. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, including a blast nozzle in the range of said outlet and directing a gas blast in the direction of the descending gradient of said goods support and substantially parallel to said goods support.

20. In apparatus for separating granularv goods of different specific gravity, the improvement claimed in claim 5, in which said goods support comprises a screen; and a perforated plate beneath said screen and extending in spaced parallel relation thereto and controlling the gas velocity through said goods support.

21. In apparatus for separating granular goods of different specific gravity, the improvement claimed inclaim 20, including baffles extending between said screen and said perforated plate and bonded to each thereof, said baffles sub-dividing the surface of said screen into panels.

22. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said goods support has side walls converging from said discharge device toward said outlet; said duct extending intermediate said side walls parallel to the longitudinal center line of said goods support; and a wedge on said goods support between said duct and said outlet, the tapered end of said wedge facing said duct mouth.

23. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 22, in which said goods support has a plane of symmetry; said duct and said wedge being positioned symmetrically with respect to the plane of symmetry of said goods support.

241 In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 23, including respective outlets each in the range of the intersection of a respective wedge flank with a respective side wall of said goods support.

25. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 22, in which each of said converging side walls forms, with a normal to the longitudinal center line of said goods support, an angle whose tangent is at least equal to 1.8, both angles being equal to each other.

26. In apparatus for separating granular goods of different specific gravity, the improvement claimed in 1 1 claim 22, in which the included angle of the flanks of said wedge is equal to twice the angle of inclination of each side wall of said goods support.

27. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said goods support has lateral boundries extending from said discharge device toward said outlet, said lateral boundaries forming, with the normal to thelongitudinal center line of said support, an angle whose tangent is at least equal to 1.8.

28. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 27, in which the tangent of said angle is between 2 and 3.

29. In apparatus for separating granular goods of different specific gravity, and of the type including an inclined gas-permeable goods support, means directing a gas current upwardly through, the support, an outlet for the heavy fractions at one end of the support, a discharge device for the light fractions at the other end of the support, the support having a gradient which descendsafrom the outlet to the discharge device and being vibrated in 'a direction opposite to the descending gradient, and a goods feeding device discharging onto the goods support: the improvement comprising, in combination, a vibrating duct, having a gas-permeable bottom and a discharge mouth, included in said feeding device; means directing a gas current upwardly through said gas-permeable bottom; said duct forming an initial sedimentation path of the heavy fraction of the fed goods, and along which path the goods are pre-sorted into a bottom layer, enriched with the heavy fractions,

and a superposed layer, free of the heavy fractions; said duct mouth discharging the goods onto said goods support intermediate the upper and lower ends of said goods support in the form of said two layers maintained in such superposed relation; the portion of said goods support between said duct discharge mouth and said outlet forming a succeeding sedimentation path for the heavy fraction of the goods charged onto said goods support; said duct mouth being coplanar with said goods support; a casing enclosing said goods support and said vibrating duct; said means directing gas upwardly through said support opening into said casing beneath said support; a hood closing said casing above said goods support; and gas exhaust means opening through said hood; said goods support with said duct being fixedly connected with said casing along its peripheral edges; said goods feeding device extending along one side of said goods support and substantially parallel to the gradient of said goods support; said cas- 7 ing having side walls; one side wall of said duct being formed by a side wall of said casing, and the other side wall of said duct being formed by a partition; said partition extending to said duct mouth, and being formed with an overflow port between said duct mouth and said discharge device.

30. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim' 29, in which said over flow port has a bottom rectilinear edge inclined downwardly, in a direction toward said outlet, relative to said goods support.

Claims

2. In a method of separating granular goods of different specific gravity, the improvement claimed in claim 1, including the step of conducting the continuous current along a laterally confined path which is coplanar with the goods support.

4. In a method of separating granular goods of different specific gravity, wherein the granular goods are separated, by a forced air flow therethrough while the goods are on a goods support subjected to a vibration, into a layer of heavier fractions and a layer of lighter fractions, the layers are separated, and the layers are separately discharged: the improvement comprising the steps of, in advance of charging the granular goods onto the support, pre-sorting the goods into a bottom layer, enriched with the heavy fractions, and a superposed layer, free of the heavy fractions; maintaining such superposed relation while subsequently charging the two layers onto the goods support; the layered pre-sorted material being flowed onto the support as a continuous current, with at least the layer enriched with heavy fractions having a laminar flow; conducting the continuous current along a laterally confined path which is coplanar with the goods support; and laterally discharging at least a part of the superposed layer, free of the heavy fractions, from the path onto the goods support in advance of the discharge end of the path.

5. In apparatus for separating granular goods of different specific gravity, and of the type including an inclined gas-permeable goods support, means directing a gas current upwardly through the support, an outlet for the heavy fractions at one end of the support, a discharge device for the light fractions At the other end of the support, the support having a gradient which descends from the outlet to the discharge device and being vibrated in a direction opposite to the descending gradient, and a goods feeding device discharging onto the goods support: the improvement comprising, in combination, a vibrating duct, having a gas-permeable bottom and a discharge mouth, included in said feeding device; means directing a gas current upwardly through said gas-permeable bottom; said duct forming an initial sedimentation path of the heavy fraction of the fed goods, and along which path the goods are pre-sorted into a bottom layer, rich with the heavy fractions, and a superposed layer, free of the heavy fractions; said duct mouth discharging the goods onto said goods support intermediate the upper and lower ends of said goods support; the portion of said goods upport between said duct discharge mouth and said outlet forming a succeeding sedimentation path for the heavy fraction of the goods charged onto said goods support; said duct mouth being coplanar with said goods support.

7. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which the discharge direction of said duct mouth extends at an angle of not more than 90* to the direction of the descending gradient from said outlet to said discharge device.

8. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said duct has at least one side wall separating the duct from the good support; said one side wall being formed with an overflow opening whose lower edge is spaced above the goods support, said overflow opening discharging toward the goods support.

9. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said duct forms part of said gas-permeable goods support and is bounded by side walls on said support.

12. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said duct mouth is spaced from said discharge device by at least the length of said succeeding sedimentation path.

20. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said goods support comprises a screen; and a perforated plate beneath said screen and extending in spaced parallel relation thereto and controlling the gas velocity through said goods support.

21. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 20, including baffles extending between said screen and said perforated plate and bonded to each thereof, said baffles sub-dividing the surface of said screen into panels.

24. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 23, including respective outlets each in the range of the intersection of a respective wedge flank with a respective side wall of said goods support.

26. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 22, in which the included angle of the flanks of said wedge is equal to twice the angle of inclination of each side wall of said goods support.

27. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 5, in which said goods support has lateral boundries extending from said discharge device toward said outlet, said lateral boundaries forming, with the normal to the longitudinal center line of said support, an angle whose tangent is at least equal to 1.8.

29. In apparatus for separating granular goods of different specific gravity, and of the type including an inclined gas-permeable goods support, means directing a gas current upwardly through the support, an ouTlet for the heavy fractions at one end of the support, a discharge device for the light fractions at the other end of the support, the support having a gradient which descends from the outlet to the discharge device and being vibrated in a direction opposite to the descending gradient, and a goods feeding device discharging onto the goods support: the improvement comprising, in combination, a vibrating duct, having a gas-permeable bottom and a discharge mouth, included in said feeding device; means directing a gas current upwardly through said gas-permeable bottom; said duct forming an initial sedimentation path of the heavy fraction of the fed goods, and along which path the goods are pre-sorted into a bottom layer, enriched with the heavy fractions, and a superposed layer, free of the heavy fractions; said duct mouth discharging the goods onto said goods support intermediate the upper and lower ends of said goods support in the form of said two layers maintained in such superposed relation; the portion of said goods support between said duct discharge mouth and said outlet forming a succeeding sedimentation path for the heavy fraction of the goods charged onto said goods support; said duct mouth being coplanar with said goods support; a casing enclosing said goods support and said vibrating duct; said means directing gas upwardly through said support opening into said casing beneath said support; a hood closing said casing above said goods support; and gas exhaust means opening through said hood; said goods support with said duct being fixedly connected with said casing along its peripheral edges; said goods feeding device extending along one side of said goods support and substantially parallel to the gradient of said goods support; said casing having side walls; one side wall of said duct being formed by a side wall of said casing, and the other side wall of said duct being formed by a partition; said partition extending to said duct mouth, and being formed with an overflow port between said duct mouth and said discharge device.

30. In apparatus for separating granular goods of different specific gravity, the improvement claimed in claim 29, in which said over flow port has a bottom rectilinear edge inclined downwardly, in a direction toward said outlet, relative to said goods support.