AU612451B2 - Process and device for separating heavy admixtures from grain - Google Patents

Description

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PCT w OPI DATE 14/06/89 INTERNATIONALE ANME AOJP DATE 20/07/89 INTERNATIONALE ZUSA, APPLN. I D 28104 89 PCT NUMBER PCT/EP88/01079 (51) Internationale Patentklassifikation 4 (11) 1 WO 89/iao 'a 04722 B03B 4/00, B07B 9/02 Al (43) Internationiies Veroffentlichungsdatum: 1. Juni 1989 (01.06.89) (21) Internationales Aktenzeichen: PCT/EP88/01079 (74) Anwlilte: VON SAMSON- HIMMELSTJERNA, R.

usw.; Widenmayerstr. 5, D-8000 Manchen 22 (DE).

(22) Internationales Anmeldedatum: 28. November 1988 (28.11.88) (81) Bcstimmungsstaaten: AU, BR, RUJ, JP, KR, SU, US.

(31) Prioritatsaktenzeichen: 4626/87-6 1110/88-7 Verdffentlicht (32)Priritasdaen: 7. ovemer 987 27.1.87 Aiit internationalem Recherchenhericht.

(32 Pioittsatn:2. vmbr 1987 (24.11.87) Vor A blauf derfiir Andeningen der Anspriiche z-ugelas- 24. drz198 (2.0388) senen Frist. Veridffen licl zing wird iviederholl falls An-f derungen em treffen.

Prioritaitsland: CR (71) Anmnelder (Jir alle Bestimmungsstaaten ausser US):4-f UMUr"JE DO*LE-R-A-e [CR/CR]; e4+924e-15w+ (72) Erfinder; und Erfinder/Anmelder (nur fu~r US) :MUELLER, Roman [CR/CR]; Bilelhofstrasse 22, CH-9244 Niederuzwil

(CR).

(54)Title: PROCESS AND DEVICE FOR SEPARATING HEAVY ADMIXTURES FROM GRAIN (54) Bezeichnung: VERFAHREN UND VORRICHTUNG ZUM AUSLESEN VON SCRWEREN BEIMENGUNGEN AUS KORNGUT (57) Abstract The invention concerns a process and device for separating heavy admixtures from a product stream in particular stones (28) from grain, in which the product stream (20) is fed onto a layering table 3b; 3d) and layered and conveyed in essentially layered form over the inclined, vibrating layering table surface 2 1 1 which is traversed by an air current. The heavy admixtures in direct contact with the layering table 3b; 3c) are conveyed upward over the table, separated and 1 conducted away at the upper end of the table. The product stream (20) is fed by 14 means of a feed channel which opens into the region of the upper end of the table is5 and feeds the corn in a stream of maximum surface -width into the separating zone6 for the corn layers (25, 26) located in said region. (57) ZlisarnmenfassungIL Die Erfindung betrifft emn Verfahren und eine Vorrichtung zumn Auslesen von schweren Beimengungen aus einem Produktstrom insbesondere Steinen 31 (28) aus Korngut, bei welchem der Produktstrom (20) auf einen Schichttisch 3b; 3d) gespiesen und im wesentlichen geschichtet iiber die derart geneigte, luftdurch- T strtimte und schwingende Schichttischfliache geleitet wird, dag die auf dem Schicht- 10/.4 tisch 3b; 3c) direkt aufliegenden schweren Beimengungen tischaufwttrts gef6r- I1.. dert und am h~5her gelegenen Tischende getrennt abgeftihrt werden, wobei die Einspeisung des Produktstromes (20) mit Rilfe eines Speisekanals erfolgt, der in den Bereich des h~her gelegenen Tischendes miindet und das Gut als m6glichst breitfltichigen Strom in die dort befindliche Trennzone der Gutschichten (25, 26) einspeist.

Patent Attorneys B461-82-; 28th November 1988 Process and Device Fjr the Separation of Heavy Admixtures from Grain Material Process for the separation of heavy admixtures, particularly stones, from grain material, whereby the material is fed onto a layer table and is passed in essentially layered form over such an inclined, air-swept and vibrating layer table surface, so that the heavy admixtures, which are in direct contact with the layer table, are transported upwards along the table and are carried away separately at the upper end of the table.

In the past, it has been tried in a number of ways, to divide a grain mixture into heavy and light grain fractions. A central problem hereby is the selection of stones from the grain material. Stones, glass pieces, metal parts and other admixtures, which in size differ significantly from the size of an average grain, are separated by means of sieves. As is well known, the external dimensions of grains of the same type of grain, such as wheat, barley, rye, oats, spelt, but also of other seeds, such as coffee, cacao beans, field beans, seeds, flower kernels etc., lie within a relatively narrow grain size spectrum.

-7 I r' 2 Anything that is larger than a certain perforation or smaller than a second, finer perforation, can be separated as foreign material quite simply by means of sieving. The difficulty is, to select foreign matter, which is of approximately the same size as the good grain material and to carry it away separately.

In the past, a water bath was used quite often, where all foreign particles, which were heavier than the grain material, sank to the bottom of the water bath. Hereby the gravity effect or the buoyancy force of the water was utilized. A main advantage of this method was considered the simultaneous washing effect of the grain material. Due to the washing water, which was also produced and the micro-bacterial problems connected with it, this solution has for the last couple of years been almost completely replaced by the socalled dry cleaning method.

With the dry cleaning method, essentially similar buoyancy forces similar to those utilized with washing water are produced through vibration and a strong air flow over a table surface. In practice, the generic selection method for stones proposed by the applicant has prevailed more often in the last two decades, at least, where high demands are placed on the degree of selection (see DE-PS 1 913 707). Hereby, preliminary layering along the a prelayering ducts is induced. The heavy admixtures sink to the region nearest to the table. Simultaneously, sliding of the lighter layer, which has some distance to the table surface, takes place in the direction towards the lower end of the table due to the inclination, or towards a corresponding discharge opening for the lighter fractions, respectively.

The heavy admixtures, which lie on the table surface, are transferred towards the elevated end of the table due to the vibrating and feeding movement of the table surface, whereby the stones are separated completely in a final separation zone and carried away through a cnrresponding discharge opening. The main disadvantage of this known solution is the specially required triangular shape of the table, which only permits a limited increase in the material through-put.

'~)iir Kq~ ;1L/z .\44 .i~ S 3 Subsequently, other ideas have been tried, but without any lasting practical success. In the majority of the cases, it was not: possible to achieve the selection quality of the first-mentioned solution. Occasionally, it has been tried to operate with two working tables on top of each other, whereby the upper table often has a sieviring and layering function, as is shown, for example, in DE-OS 25 33 274. With this idea, it is possible only with additional measures, such as special attachments, to achieve an essentially complete, that is, nearly 1000, stone selection.

A grain separator is known from GB-PS 1 536 905, whereby an air flow is generated with the aid of a fan arranged underneath an inclined and perforated chute. The whole separator, together with the housing, which contains the fan, is mounted rigidly and only the reception table can be moved.

Hereby the classic system of recirculating air is disclosed, whereby, however, in practice problems always existed with the pressures in the respective sections of the housing. In particular, the problem of the socalled secondary air could not be eliminated.

Finally, the air-ducting was problematic with the known grain mixture separation processes, in particular the heavy material sorting processes, which is particularly relevant for the mutually undisturbed material and air ducting, including the material and air entry, with the consequence of a limitation of an improvement in the through-put performance, in particular with good selection grade.

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4 It is an objective of the invention, to provide a new process for the selection of heavy admixtures, in particular, a new stone selection process and a new device for the implementation of this process or, respectively, to provide a new dry gravitational selection system, which permits higher through-put.

This task has been solved in a generic process in that the material is fedin as a broad-faced stream into the region of the separation zone of the material layers at the elevated end of the table.

The first practical trial with the new inventive idea was surprising in two respects. Firstly, the dgree of selection was immediately unexpectedly high and secondly, the inventor selected a feed-in point, which, according to all expert opinion, must have been wrong. Still, it led to the desired result. Sofar, based on the idea of a preliminary separation (see DE-PS 1 913 707), a process was postulated, which consisted of two spatially and sequentially separated steps. As a first step, layering was aimed at, whereby the layer closest to the table would contain all heavy admixtures and only as a subsequent step was the preliminary layer, which was guided in a channel, to be transferred undisturbed to the table surface and the stones to the discharge opening for stones. Only in the region of the highest position of the end of the selection table did effective separation and separate elimination of the stones occur. The heavy admixtures should normally be only a small percentage of the grain material, so that, correspondingly, the final separation zone showed the smallest dimension (the point of a triangle), because only a small proportion of the total bulk of the product was carried up to there.

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I I I 5 If now the final separation zone or the inclination of the table was incorrectly adjusted, so that too much grain material entered that region or if the local air flow was chosen unfavourably, then either the stone selection was poor or too much of the good grain was eliminated with the stones. Therefore, the final separation zone was a point, which needed to be monitored specially. It would have been considered as senseless to introduce a large quantity of fresh grain material into the stone separation zone on the table. Any disturbance in that region would have shown up immediately as a deterioration of the functioning of the selection tables.

Only because the inventor has dissociated himself from all previous concepts and the presumably deduced unalterable natural laws, be it that preliminary separation is at all required, and that this requires time and distance for the separation of the heavy admixtures or that the product is introduced over a wider region of the table, with the intention that each stone gets the best possible chance for separation, could he freely and uninhibited realize the new idea, which, in particular, consists in that the material feed-in occurs as a broadest possible material stream and that this is introduced directly into the region of the separation zone at the upper end of the table.

The layer table should wor'k as a good layering table, if it transports the lower lying heavy admixtures upwards on the table. This way, if the material is introduced at the elevated end of the table, most of the heavy admixtures remain in the region of the separation zone.

T- I---1 6 Should they be dragged downwards for a short distance, then they will migrate back into the final separation zone with much greater certainty than with all known solutions sofar. It is now only a question of neat construction of the final separation zone, the correct adjustment of the quantity of air and the inclination of the table, to achieve optimal functioning. The invention establishes particularly favourable preconditions for an easy practical optimization, because due to the creation of a broad-faced material stream, the final separation occurs at maximum possible width, that is, without unnecessary layer thickness.

The new invention permits quite a number of further, particularly advantageous forms of construction. Thus, it is preferred that a uniform layer flow (heavy towards the upper end of the table, light towards the lower end of the table) is generated, with reversal of direction of flow in the region of the elevated end of the layer table and that the product flow is fed-in in the immediate vicinity of the reversal of the direction of flow.

The reversal of direction of flow for the light parts is generated in the known manner, whereby an upwardly extended table piece is also swept with air, so that the lighter parts become separated from the table surface.

Simultaneously, the product layer, with the exception of the stones, is prevented from migrating further towards the top of the table through an air flow directed onto the separation zone and downwards along the table, which almost acts like a kind of blast or air ram device (see fig. 2).

In a further, particularly preferred form of construction, the material is fed initially into a first, upper layer table and at least a first part of Ithe heavy goods fraction, which cosi3sts of a mixture of heavier grain material and stones and flows towards the upper end of the table, is directed onto the upper end of the table in such a way that the heavy goods fraction is fed from there in broad form to the upper end region of the table surface of a second layer table underneath it, which is swept by the same air.

A -7 This measure permits the transfer about half of the through-put quantity, which now contains almost 100% of all heavy admixtures, to the lower table as a heavy layer. The actual separation of the heaviest admixtures to be separated occurs on the lower table. This way, the material through-put can be doubled in a single ievice with the same quantity of air, without the slightest impairment with respect to the separation quality.

In a further preferred form of implementation of the process according to the invention, the material on the upper layer table is fed upwards with a smaller feed component than on the lower layer table and a second part of the heavy goods fraction is fed from the upper layer table onto the region of the lower end and/or the centre of the lower layer table.

The advantage of this is that the stone selection occurs in two sequentially and spatially separated steps.

It is particularly preferred, if the product flow is fed in over a guide panel arranged at a distance above the table surface. Hereby, the product flow can be directed advantageously over the whole width of the layer table.

Further, it is poposed that the product flow is fed-in in the flow direction of the lighter grain layer (26) against the flow direction of the heavy grain layer).

I I -8 In a particularly preferred form of implementation of the process according to the invention, an airflow (reverse blast flow) is blown onto the separation zone in the direction of the reversal of the flow of the heavy grain material, which migrates towards the upper end of the table for the purpose of separation of the heaviest admixtures (stones) from the grain material.

The advantage of this is that a transfer of the light parts or grains upwards on the table together with the heaviest admixtures is prevented.

In another advantageous implementation of the process, the reverse blast flow is directed between the guide panel and the layer table. This allows to direct the air flow in a simple manner. by means of which the separation of the heavy particles from the light particles of the material is possible.

In a further preferred form of implementation of the process, simultaneous vibrations are induced into at least one of the layer tables, together with the cowling for the recirculating air flow attached to it, with separate channels for supply and exhaust air.

The advantage of this is that the whole system has a self-cleaning effect.

Due to the shaking movement, any adhering dust particles are continuously shaken off. Time-consuming cleaning operation can therefore be dispensed V with. This ensures that flow paths are not changed in their cross-sectional area through adhering particles, so that steady flow conditions can be guaranteed at all times.

Because the individual elements are arranged within the cowling, and the cowling can covibrate, the material is shaken continuously during the supply of the material onto the material table.

9 Because the table, as well as the material distribution elements, are shaken simultaneously, the veil-type broad-faced spreading of the material onto the layer table is obtained, which is essential for the separation process. Also, another advantage of this common construction of the elements essential for the separation process within the cowling is, that the disadvantageous sealing problems, as in the state-of-the-art, can be avoided.

In a further paiticularly preferred form of construction. the cowling, together with the layer table, forms a box supported in such a way as to be capable if being set into vibration and that the box, including the layer table, is set into simultaneous vibration.

A further, particularly advantageous idea for construction can be seen in titat the material in-feed occurs as a broad.st possible stream in the region of the separation zone of the material layers at the elevated end of the table, that the air is extracted in the upper central part of the cowling and supplied in a broad form in the region of the lower end of the layer table. The advantage of this is that the air supply charges the entire width of the table from underneath right from the beginning. It is also possible, to achieve an air flow in the box, which almost does not generate the undesirable vortex formation.

Due to the compact, elegant form of construction and the transfer of the required vibration 'to all construction parts, it is now suddenly possible in a simple manner, with the individual functions separated, to fasten the cowling in such a way that it seals.

In a further preferred form of implementation of the process, the recirculating air is cleaned of dust particles in the region above the central air extraction and in the lower supply region. Thus, cleaning of the flowing air can advantageously occur at a point in time, where undesirable vortex formation due to the cleaning elements does not yet have disruptive influence on the air stream charging the table.

S 10 In a further, preferred idea for implementation, the material is passed over a trough-shaped pit (stone and material sink) on the upper layer table, whereby the heavy goods fraction, which enters the pit, is transferred through bottom openings in the pit and subsequently through a chute, which is inclined in the opposite direction to that of the upper layer table, onto the central region of the lower layer table, and, conversely, where the light goods fraction, which overflows the trough-shaped pit of the upper layer table in flow direction, is channeled towards a discharge opening for light material. In this manner, the heavy layer can advantageously sink continuously and completely into the stone sink and can be discharged directly downwards. This results in a high degree of selection for the heaviest admixtures and, in addition, clean separation can be achieved with only minimal additional expenditure.

In a further, particularly preferred, form of construction, a covibrating suction hood, as well as a stationary platform arranged above it, is attached to the layer table, whereby the material is fed through an entry opening in the stationary platform, then channeled via flexible sleeves into the distributor box of a feeder duct, which covibrates with the suction hood and then, from the distributor box, is poured cascade-like onto a guide panel, whereby a uniform drop flow over the entire width of the layer table is generated.

Further, the invention concerns a device for the separation and sorting of heavy admixtures from a product flow, in particular, of stones from grain j material with a feeder duct for the feed-in of the product flow onto an Sair-swept, inclined layer table, which can be set into vibrations, with one I component of the vibrating feeder into the direction of the elevated end of the table.

j 11 The task mentioned previously within the framework of the process is solved with a generic device in such a way that the feeder duct enters in the region of the elevated end of the table.

Surprisingly good were the first test results with the new device, since with similar degree of selection and similar air consumption, the material through-put could be increased by sometimes more than 50%, without extensive constructional expenditure being necessary for the new device.

In a preferred form of construction of the device according to the invention, the feeder duct enters over the whole width of the layer table. This has the advantage that broad-faced and generous charging with the material to be seperated is possible.

In a particularly preferred form of construction, the entry of the feeder duct shows a guide panel arranged at a distance above the layer table. The advantage of this guide panel is, to distribute the material to be charged uniformly across the layer table and also, at the same time, with its underside, serve as a baffle for the air flows.

In another preferred form of construction, the feeder duct shows a distributor box, as well as the guide panel, which form a cascade for the feed product flow for the generation of a uniform drop flow over the entire width of the layer table.

In a particularly preferred form of construction, the guide panel shows an overflow edge and bottom openings in the region of the down-stream end, in such a way that the main bulk of the material flows onto the layer table as a broad-faced material stream and that the heavy admixtures are removed through the bottom openings.

I I 12 This overflow edge achieves a particular broadness of the product stream, because, after the trough has been filled in full width, a uniform stream, which is fed from the trough, trickles down onto the layer table underneath.

In a preferred form of construction, a final separation zone for sortingout of the stones is arranged between the guide panel and the table surface of the layer table.

A further break-through with respect to a larger through-put performance could only be achieved, when two jointly vibrating layer tables were arranged directly on top of each other and were swept by the same air.

It is preferred, if the lower layer table has a larger feeder component in the upwards direction than the upper layer table and that hereby its surface is rougher than that of the upper layer table. Hereby, the upper layer table serves in an advantageous manner as a pre-layer table. It is equally advantageous, if the upper layer table shows at its elevated end at least one discharge opening, which serves as a feeder duct for the lower layer table. Thus, the smallest heavy goods fraction can be fed directly onto the elevated end of the lower table.

It is of particular preference, if the feeder duct for the lower layer table extends over the entire width of the upper layer table, in order to generate uniform material distribution on the lower layer table.

It is advantageous, if the two layer tables are arranged with each other in such a way that the upper layer table feeds well onto the upper table end of the lower layer table. This makes it possible that almost the entire portion of the material to be separated is fed into that point on the lower table, where the unexpectedly good separation is possible.

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13 Particularly preferred is, if at least one of the layer tables is part of a box designed for recirculating air operation, which jointly vibrates with it.

The advantage of this is that not only the layer table but simultaneously also the box connect to it, are shaken at the same time. The self-cleaning effect can be achieved that any adhering dust particles are shaken off during the operation of the line.

At the same time it is possible to design 'the whole system within the box without the usual sealing problems, because the system according to the invention is sealed to the outside, so that the air inside can be controlled with pin-point accuracy.

If the system within the box were not sealed against the outside air, secondary air would penetrate and the whole air management system would be disturbed. Also, it is possible, and of advantage, to introduce air broadly in the lower region of the material table over the total area of the lower table surface. Altogether, an optimal product in-feed with the possibility of broad-faced spreading with simultaneously optimal air supply, without mutual disturbance of product in-feed and air supply, can now be achieved.

In a further advantageous form of construction of the device, the material in-feed is part of the box. The advantage of this is that the material infeed vibrates together with the box and that, due to the vibration movement, the material is already loosened up before it is deposited on the vibrating table and thus forms a socalled veil. This veil ensures a broadfaced distribution on the table. Additionally, apart from simultaneous cleaning due to the shaking movement, joint cleaning of the material infeed can also be expected.

0i 14 In a further preferred form of construction, the inside of the box is equipped with: an air extraction space and a supply duct for recirculating air separate from it, which enters in the region of the lower end of at least one of tle layer tables. This makes it possible to design the air extraction space, as well as the supply duct for the recirculating air dimensionally generous, so that no sharp reductions cause unwanted vortices or other undesirable flow effects. The total air flow can be directed through the tables without interference within the box and, in particular, can pass through uniformly in full width at the width of the underside of the lower table.

In a further preferred form of construction of the device according to the invention, the top side of the box is equipped with: a material entry opening on one end, an air extraction at about the centre and an air return duct at the opposite end for the recirculating air duct. This makes it possible, to extract the circulating air, which has passed through each respective layer table, centrally, at good flow conditions, without the expectation of any disturbance of the flow characteristics through in-fed material. It is still possible with lateral material in-feed, to direct the in-fed material to the centre of the layer table to be charged.

SSimultaneously, it is possible with this preferred form of construction, to extract the air comfortably in the centre. Therefore, sufficient space remains for the supply duct for the recirculating air, because the socalled run-outs for the material can be made relatively narrow, without interfering with the material flow. Thus, the air supply in the lower part of the layer table can be broad from the beginning, that is, it charges the entire width of the table from uLmderneath.

T- Y~ ~C -i- 15 In a further, particularly preferred form of construction, the box is supported in a frame capable of vibrating, which in its upper region shows a stationary header, whereby the header is connected to a recirculating air separator via the air extraction connector and to the box via flexible sleeves. With this compact and elegant form of construction, sealing problems can only occur at the three connectors at the top surface of the box, which are connected through flexible sleeves with the stationary part of the non-vibrating frame, which is the head. The seals can be made particularly reliable, because flexible sleeves can be used, which have been well tried for a long time. The reliability due to the seals leads finally to a flow distribution within the box, which is free from interference.

In a preferred form of construction, the recirculating air separator is connected to a suction fan and a dust extraction duct. In this manner, the interfering part of fine husks and dust may be removed from the air flow.

Further, it is of advantage, to connect the duct for the recirculating air with the aspiration connector for the fine-dust filter. Dust accumulation in the whole device can thereby be avoided advantageously and reliability and hygiene can be increased. Due to the operation with recirculating air, only a small part of the total air quantity has to be passed through the fine dust filters.

In a further preferred form of construction, the upper table surface shows in its lower region a trough-like pit (stone or material sink) with drop passages in the bottom of the trough for the additional separation of the product stream into a heavy and light fraction.

ftrJ(I 16 Additionally, the invention permits a high degree of stone selection, that is, selection of all foreign heavy parts, which may still be present in the sifted grain material. Also, advantageously little air is used and the process and the device are simple and, in particular, are not very sensitive to through-put variations.

In the following, a few embodiments of the invention are explained with further details. It is shown in: Fig, 1 the simplest form of a small table selector for stones, Fig. 2 the product in-feed onto the layer table, Fig. 3 the same solution principle as in fig. 1, but with two table surfaces, in particular, for large product through-put, Fig. 4 a solution according to fig. 1, but with a recirculating air duct, Fig. 5 a solution according to fig. 3, but with a recirculating air duct, Fig. 6 fig. 5 with recirculating air separator, Fig. 7 is a solution similar to fig. 3 with the additional formation of two heavy fractions apart from the stone selection, Fig. 8 a variation of construction to that of fig. 7, Fig. 9 shows a stone sink on -the layer table surface, Fig. 10 shows the device as in figs. 3, 7 and 8 with the duct for the recirculating air fed through the box.

In the following, reference is made to figs. 1 and 2. Fig. 1 shows a basic type for a new stone selector 1, whereby the fresh grain material is fed through an inlet opening 2 onto a layer table 3 and from there is discharged as cleaned grain material through outlet opening 4. A closed hood is arranged above the layer table 3, which shows a suction opening 6.

l 17 The hood 5, together with the layer table 3, forms a vibration unit 7, which, with the aid of a vibration generator 8, can be set into vibration with a vibration component into the direction of the upper end of the layer table 3. The upper end of the layer table 3 is formed as a final separation zone by means of guide panel 19. The whole vibration unit 7 is supported through spring elements 9 on a frame 10, which is firmly connected to the floor. Also connected to the frame 10 is the non-vibrating header 12, to which the inlet 2, as well as the air extraction line 13 is attached. Further, an air quantity regulating flap 14 is installed in the air extraction line for the adjustment of the aspired air through the whole stone selector 1. The connection of the vibrating parts, or the vibrating unit 7 with the header 12, respectively, occurs through flexible sleeves which are arranged after the inlet 2.

Seen in plan view, the layer table 3 shows a preferably at least approximate rectangular shape. At the side of the elevated end of the layer table, the layer table 3 may be withdrawn for the purpose of maintenance work. The product transfer point extends over the full width of the table.

The width is designated with in fig. 2, the layer thickness with The formation of a broad-faced material stream 20, also called material I veil, for the purpose of material in-feed, occurs in two steps. As part of the vibrating hood 5, the fresh grain material is fed into a distributor box 17. The vibration enhances the uniform, broad distribution of the grain material in the distributor box 17, which, in order -to reinforce the effect, is widened cascade-like towards the bottom. A baffle plate 18 provided on -the distributor box 17 serves the same purpose, so that the grain material is fed onto the guide panel 19, which extends over the whole width of the table, already as a broad-faced product stream and then as a uniform, wide product stream 20 onto layer table 3.

1 1 c 18 The broad-faced spread of the product stream 20 is further supported in that the free end of the guide panel 19 has an overflow edge 16, thus, it is formed in a trough-like manner. For the purpose of preliminary separation of heavy material from light material, the trough-shaped guide panel 19 may also show bottom openings for the passage of the heavier admixtures.

The broad, uniform spread of the product stream on the layer table 3 is made particularly clear in fig. 2. The same figure shows the layering, which has been exaggerated deliberately. Layer table 3 shows a rough mesh grating 21 as a product support and is constructed in the known form of sandwich construction, whereby the mesh grating forms the top side, which is carried by sheet metal strips 34 in honeycomb-fashion, which at the bottom are held together through a finely perforated sheet metal 22.

Cleaning bodies 24 are arranged in the individual fields 23 between the sheet metal strips 34, which keep the mesh grating 21, as well as the perforated sheet metal 22, clean. Important is also, that the perforated sheet metal 22 has an air resistance, which is much higher than the air resistance of the mesh grating 21, ie., in the order of magnitude of 1:10.

With this measure, the air distribution can be held approximately constant independent of the layer thickness on the mesh grating 21 over the whole surface area of the layer table 3.

The layering of the material itself consists essentially of three different layers, whereby the lower, heavy layer 25, which contains the heavy admixtures, is conveyed upwards on the table through the mechanical throwing movement of the vibration. A light layer 26, which has been freed of heavy admixtures, is held, not only in the loosened state, but also in suspension at a distance above the mesh grating 21 through ta"getted air flow. Since 'the layer table 3 is slightly inclined, and the upper light layer 26 does not receive a direct feeder impulse in the upwards direction of the table, but is still under vibration, it flows towards the lower part of the table.

h c c- -19- Moreover, the inclination of the layer table 3 can be set with an adjustment device 35. A third layer 27 consists of the actual heavy admixtures, mostly only individual particles, individual foreign bodies, stones 28 etc.

Good, heavy grains 29 and light particles, such as half grains, husk parts are represented in their approximately corre'ponding shape. The heavy material with the stones 28 sinks straight onto the vibrating table surface 7 and, due to the vibration and the rough table surface formed by the mesh i grating 21, moves upwards on the table.

It is now important for the described function, that the air flow is guided correctly, The whole layer table surface is swept uniformly from bottom to top with a suction air flow, whereby the flow direction is made clear through arrows 31. This air flow 31 sets the grain material into a highly fluidized state. Since only the heaviest parts, that is, the stones 28, should be separated onto the elevated end of the table and transferred frothere into a stone lock 45, a corresponding reverse blast flow 33 is formed, which prevents light particles or grains from being transported upwards along with the heaviest admixtures. The reverse blast flow is formed preferably underneath the guide panel 19. If the guide panel 19 is firmly attached to the wall of the hood, then the air directed into the slot between guide panel and layer table can only escape in the direction 33.

Thus, ahead of the final separation zone, the material, with the exception of the stones 28, is prevented from migrating further up by the air flow.

The stones 28 may continue their movement towards the elevated end of the table, 'YrIV7 Y i oevr teiciaio ftelye al anb e ih najsc I- 20 In practice, this reverse blast flow 33 causes a flow front, or flow front reversal 32, respectively, to be clearly established. At the point of the reversal of direction of flow 32, the grain material 29, which is freed of stones 28 is lifted from the table surface by the strong air flow 31, 33 and flows now freely downwards along the table, together with all other light material in the upper separated light layer 26. The lightest fraction is carried out straight at the outlet 4; a medium grain fraction can possibly make several circular migration movements up and down the table, which is particularly applicable to boundary grains.

In figs. 1 and 2, the product stream 20 is fed directly into the zone of the flow reversal 32. The flow reversal 32 is caused by three forces, namely the mechanical feeder effect upwards along the table, fluidic flow of the upper layer 26 downwards along the table, as well as the reverse blast flow 33.

The constructional main difference bel <en fig. 3 and fig. 1 is, that fig.

3 shows that two layer tables are used, one layer table 3a and a lower layer table 3b. Fundamentally, both layer tables 3a and 3b are of the same construction, such as shown in fig. 2. In principle, the reverse blast flow 33 is missing in the upper layer table 3a, so that not only the heaviest admixtures, but the whole heavy layer 25 is moved upwards on the table and drops through a discharge channel 40 over a baffle 41 onto the guide panel 19. From the guide plate 19 onwards, the functioning of the layer table 3b is identical to that of the layer table 3 of fig. 1 or 2, respectively, In order -to prevent the freshly entered product stream 20 from the distributor box 17 being mixed directly with the heavy layer 25, a baffle plate 42 is arranged at the uppermost point between the distributor box 17 and the layer table 3a.

I i 21 The off-flowing product stream is released through a product lock 43 directly into a discharge channel 44 of the lower layer table 3b. The two material streams of the two layer tables 3a and 3h, which have been freed of the heaviest admixtures, are combined again at outlet 4. All heaviest admixtures, such as stones 28, etc., are separated first, together with the heavy layer 25. The actual separation and the diposal of the stones 28 through the stone lock 45, takes place on the lower layer table 3b. The stone selection takes place in two sequentially and spatially separated steps. Initially, a concentrate is formed with all heavy material, for example, 30% to 60 00 of the whole material through-put on the upper layer table 3a and only from the reduced material through-put are the stone and other heaviest admixtures be sorted and discharged separately.

With regard to product guidance, fig. 4 is identical with fig. 1 and fig. corresponds to fig. 3. The solution proposal in fig. 4 and fig. 5 contains, however, a hermetically sealed box 50, which is divided by the layer table(s) into an upper extraction room 51 and a lower suction room 52. On the side at the lower end of the layer table(s), a duct for recirculating air 53 is placed, which is connected to an air return duct 55 by means of a flexible hose 54 and a air return connector 55'. An air flow restrictor 56 is arranged in the air return duct 55. In fig. 4 and fig. 5, the box itself is supported on a fixed frame 10 through spring elements 9. On the top side of the box 50, a material inlet connector which connects to the material inlet 2, is arranged on one end, an air extraction connector 13', which connects to the air extraction line 13, is arranged approximately in the centre and an air return connector 55', which connects to the air return line 55, is arranged on the opposite end.

i: .i i i 22 The previously mentioned connectors 13', 55' are connected, on one hand, to the non-vibrating header 12 through flexible sleeves 15, 54 and on the other hand, to the box 50, in order to take part in the movement. In the double machine in fig. 5, two outlets 4 are arranged as tubular product ducts 57 on each side (perpendicularly to the plane of the drawing), so that the remaining space between the two product ducts 57 remains available for the recirculating air duct 53. For better identification, box 50 is surrounded with a dashed line in figs. 4 and In fig. 6, as a supplement to figs. 4 and 5, a recirculating air separator with suction fan 61, as well as motor drive 62, is additionally shown.

Hereby, the air extraction connector 13 leads directly into the recirculating air separator 60, whereby the significant or, respectively, the interfering part of fine husks and dust is extracted from the air flow through the dust extraction line 64.

In most cases, where recirculating air is used, air cleaning is of advantage, because dust acuun:;,lation in the whole plant can be effectively avoided and reliability and hygiene can be increased. The recirculating air operation has the significant advantage that only a minimal amount of air, for example, 10% of the recirculating quantity of air, must be directed through fine (lust filters. The aspiration connection 65 is provided for this. The recirculating air separator 60 can, together with the fan, be mounted directly on the room ceiling 66.

Fig. 7 shows a basic difference to fig. 3, whereby in fig. 7 only a small part of the material through-put is transferred from the upper layer table 3c at the highest point through a series of large holes 71 across the width of the entire table, downwards to the uppermost zone of the flow reversal of the lower layer table 3d.

-i Y F- I- -C-YII_ 23 The main bulk of the heavy material is directed in the region of the lower end of the table, over a chute 72, to approximately the centre of the lower layer table 3d, again, across the entire width of the table. Several test series have shown that with this solution, still the main part of the stones is transferred through the holes 71 directly onto the lower layer table 3d. With the solutions according to fig. 7 and 8, it is important that the upper layer table has only a less rough surface than the lower layer table 3d, as is shown in fig. 9, whereby the upper layer table 3c consists of perforated sheet metal and the lower layer table 3d is made from mesh grating.

A particularly interesting original thought is now shown in figs. 8 and 9.

This is the use of a stone sink 80 in the region of the upper layer table 3c. The functioning is as follows: The stone sink 80 consists of a troughlike pit 81, which extends over the entire width of the layer table 3c.

Similar to fig. 2, two different layers are formed in figs. 8 and 9 as well, that is, one heavy layer 25 and the light layer 26, which r-s been freed of heavy admixtures.

Becase the surface of the upper layer table 13 shows only slight roughness, no actual upwards flow occurs; at least the whole of the heavy layer cannot be be moved upwards. It is more likely that the heavy layer moves downward along the table at a greatly reduced rate, as is indicated by the single arrow 82. In contrast, the light layer 26 moves down the table with high velocity (double arrow 83). Upon reaching the region of the pit, the heavy layer sinks of necessity into the stone sink 80. The stone sink 80 shows a number of passage openings 84 at the bottom, through which part of the material, together with the stones, is discharged continuously onto the chute 72 underneath it, or, respectively, the lower layer table 3d.

24 With correct tuning of the number of effective passage openings 84 in relation to the mass flow of the heavy layer, the light and heavy layers can be separated in such a way that the heavy layer 25 is constantly sinking completely into the stone sink 80 and carried away directly downwards. This results in two great advantages: 1. A high degree of selection for the heaviest admixtures (stones, etc.) is achieved 2. With minimal additional expenditure, the additional separation of the heaviest admixtures into a clean heavy fraction (good grain) and the rest into a light material fraction (husks, undersize and broken grains) can be achieved.

This makes it possible to carry out the separation of the various basic fractions (stones, etc., heavy, light) in a single device and with very high quality.

Finally, fig. 10 shows a device, which works along the same principles as the devices according to figs. 3, 7 and 8. For this reason, a repetition of the description of the same structural components is superfluous. The device according to fig. 10 distinguishes itself from the previously mentioned devices merely in that a recirculating air duct 53 is arranged separately in the box 50, so that the influence by it on the flow characteristics of the air in the box 50 can be avoided.

Claims (1)

1. 7- C-L- 25 THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS: i. Device for the separation and sorting of heavy admixtures from a product flow, in particular, of stones from grain material with a feeder duct for the feed-in of the product flow onto an air-swept, inclined layer table, which can be set into vibrations, with one component of the vibrating feeder into the direction of the elevated end of the table, the feeder duct enters in the region of the elevated end and over the entire width of the layer table whereby the feeder duct shows a guide panel arranged at a distance above the layer table, characterized in that two jointly vibrating layer tables are arranged directly on top of the other and are swept by the same air, the two layer tables are arranged with each *other in such a way that the upper layer table feeds the material onto the lower layer table, a second feeder duct for the lower layer table extends over the entire width of the upper layer table. 2. Device according to claim i, characterized in that the layer tables are part of a box, which jointly vibrates *see with it. S 3. Device according to claim 2, characterized in that the material feeder is part of the box. 4. Device according to claim 2, characterized in that the feeder duct shows a distributor box, as well as the ji guide panel, which form a cascade for the feed product flow for the generation of a uniform drop flow over the entire width of the layer table. Device according to claim 4, characterized in that the guide panel shows an overflow edge and bottom openings in the region of the down-stream end, in such a way that the main bulk of the material flows onto the layer table "a! i c ii 4 I I I 26 as a broad-faced material stream and' that the heavy admixtures are removed through the bottom openings. DATED this 2~8 day of March 1991 BUEHLER AG Patent Attorneys for the Applicant: F.B. RICE CO. 0 0000 *000 0 @00 S @00000 0 @0 S 0 50 SO 47S