AU7778700A

AU7778700A - Sorting device for particles of differing sizes

Info

Publication number: AU7778700A
Application number: AU77787/00A
Authority: AU
Inventors: Hubertus Exner
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-09-20
Filing date: 2000-09-20
Publication date: 2001-04-24
Also published as: CA2401875A1; BR0014127A; EP1214156B1; NO20021371D0; WO2001021512A3; PT1214156E; JP2003509213A; DK1214156T3; DE19945038C1; ES2219402T3; KR20020048412A; PL364812A1; ATE265280T1; MXPA02002442A; NO20021371L; DE50006275D1; WO2001021512A2; EP1214156A2

Abstract

The invention relates to a sorting device for particles (P) of differing sizes, comprising at least two conveying units (1, 2, 3), whereby the particles which are to be sorted are fed upstream to said units. A height gradation (H) of the planes of conveyance is provided between at least two conveyor units that are arranged successively in the direction of conveyance (X), creating a horizontal space or gap therebetween. The products, for example, which have been transported by conveyer units placed upstream, tip over the end of the upstream conveyor unit and fall onto the downstream conveyor unit.

Description

Sorting arrangement for particles of differing sizes The invention relates to a sorting arrangement for particles of differing sizes comprising at least two conveying units to which the particles requiring sorting are fed at an upstream position thereof and wherein there is a gradation in the height of the planes of conveyance between at least two successive conveying units in the direction of conveyance. (0 Such types of conveying units disposed successively in the direction of conveyance and comprising a gradation in the height of the planes of conveyance that are used purely for the conveyance of particles of differing sizes are known. In a plant known from DE 196 17 187 Al for example, bulk materials is are transported by means of conveyor belts which overlap at the point of transition from one conveyor belt to the next so that the bulk material will fall onto the lower lying plane of the downstream conveyor belt for onward transportation. A sorting process is not known from this arrangement. 10 A system for transporting work-pieces on carrier means is proposed in DE 37 29 784 Al. In this case, there are two successive conveyor belts. Here, a complicated mechanism is used for the timing and transportation of the work-pieces such 15 that there will be discrete spacings therebetween. Furthermore, sorting arrangements are known wherein the particles requiring sorting are fed over a gradation in height and the particles are then subjected to an air separation o process whilst they are in free fall. Here however, it is disadvantageous that the particles requiring sorting cannot be divided up in a predictable manner, especially when they are of differing size. 5 For very small particles of a mutually similar order of magnitude, US-PS 5 305 893 proposes that a process of detecting foreign bodies, especially in a stream of tobacco, be effected on a conveyor belt. An air actuated piston is driven out at the end of the conveyor belt in dependence on the result of the detection process so as to eject the foreign bodies together with the adjacent particles from the stream. This arrangement is not suitable for sorting particles of differing sizes. 5 Especially when processing waste paper products, such as those from paper recycling containers for example, there is the problem that small particles of foreign objects, stones, glass splinters, bottle stoppers and the like for example, may be incorporated in this mass of waste paper. However, as the waste 1 paper will be formed into a slurry and dissolved in fluids in the large centrifuges in the paper processing plants for the purposes of removing ink therefrom and converting the waste paper back into usable paper, these foreign constituents such as stones, splinters and other small hard particles can cause IS severe damage, especially if the particles of foreign matter are rubbed against the walls of the centrifuge by the agitator devices. The process of separating out these foreign constituents by Zo means of the known sieve arrangements founders due to the difficulties encountered in transporting the paper over the sieves and the blockages ensuing therefrom. In the case of the air separation devices mentioned hereinabove, 5 there is the problem that, where there are combinations of such materials, cardboard cartons and newspapers etc having a relatively large surface area will behave in an uncontrolled and unpredictable manner in the air stream with the consequence that a reliable process of separation is not possible. Hereby, these 60 problems generally occur when there is a need to separate particles of differing size and the particles are of large surface area for example. A manual sorting process is likewise made more difficult since .5 the aforesaid small foreign bodies such as glass splinters, corks and stones are inclined to be hidden in larger piles of paper, or they adhere thereto and/or are entrained therein.

Consequently, the object of the invention is to provide a sorting arrangement for particles of differing size wherein particles of large surface area can also be separated from small particles of foreign material. This object is achieved by means of a sorting arrangement of the type defined in the preamble of the main claim, wherein provision is made for a horizontal spacing or gap between the successive conveying units. Due to the provision of a horizontal spacing or gap in a chain of successively disposed, gradated conveying units, one obtains, surprisingly, an effective way of sorting particles of differing size, especially those incorporating items of large surface S area, which is not susceptible to jamming. Hereby, the width of the gap is selected such that smaller particles will not reach the downstream conveying unit, but rather, will fall down through the gap. By contrast however, items of greater surface area will bridge the gap. For example, the products that have to been forwarded by means of the upstream conveying unit will tip over at the end of the conveying unit and fall onto the downstream conveying unit. There, they are forwarded by means of the downstream conveying unit. Blockages will thus be excluded by virtue of such an arrangement. P5 Separation by means of such a gap can be effected repeatedly by means of a plurality of conveying units that are arranged in a chain in this manner. Separation of the output material into a plurality of fractions in one throughput process is made possible by means of the close succession of several gap separated sections each having a different horizontal spacing. If the downstream conveying unit of the succession of conveying units operates at a higher speed of conveyance than the upstream conveying unit, the packing density of the particles reaching the downstream conveying unit will be drawn apart whereby smaller particles clamped therebetween will be released.

Means are provided for adjusting the width of the horizontal spacing so as to enable the sorting arrangement to be rapidly reset for differing materials and/or some other fractional distribution. Since the height gradation also has an effect 5 upon the result of the separating process, it is preferable if means are likewise provided for adjusting said height gradation. An alternative embodiment of the gap-separated arrangement is provided by arranging at least one drum, which is driven in rotary manner in the direction of conveyance and has an axis of rotation that is substantially perpendicular to the direction of conveyance and substantially parallel to the planes of conveyance, within the gradation and the gap between two successive conveying units in the direction of conveyance whereby a simple method of adjusting the width of the gap is attainable especially if the rotational axis of the drum is adjustable, substantially horizontally, in the direction of conveyance. The two conveying units bordering the gap do not then need to be provided with adjusting means so that they can o be fixed in place in an economical manner. By virtue of the aforesaid adjusting means in accordance with claim 3, 4 and/or 6, differing materials, such as, for example, paper, wood, metal, cardboard, synthetic materials etc can be .5 sorted or separated without the need for time-intensive and costly reequipping processes. Changing of sieves or the like, or modifications to the arrangement when altering the separating section are not required. The gap-separated section in accordance with the invention can be adjusted to provide the desired fractional separation in a continuous manner. If conveying units in the form of conveyor belts are used, then one obtains a particularly smooth running arrangement which produces little noise. In the event that vibratory conveyors 15 are used, then the material requiring separation will be loosened during the advancing process. By virtue of providing that end of the conveyor belt that is directed towards a spacing-gap with a guide roller having a diameter which is smaller than or equal to the dimensions of the particles requiring sorting, there is a very sharp deflection of the conveyor belt at the gap-separated section so that the process of tipping the particles lying on the plane of 5 conveyance occurs spontaneously under the effects of gravity as soon as the centre of gravity of the particle is no longer lying on the plane of conveyance, this process being substantially unaffected by the curvature of the deflection of the conveyor belt. Similar reasoning applies to the impingement of the 10 particles requiring sorting on the downstream plane of conveyance. In essence, the particle will ensure bridging of the gap if its surface area exceeds a certain dimension. Due to the sharp deflection, there will be scarcely any merely fortuitous onward conveyance of a particle which falls off the 15 deflected conveyor belt at the point of curvature onto the upstream end of the second conveyor belt. For the purposes of catching the small particles which have been sorted out by falling through the gap, a collecting container is aO arranged below the horizontal spacing. As an alternative thereto, a further conveying unit, a conveyor belt or a vibratory conveyor for example, is arranged at this point for conveying away the small, sorted particles. The small, sorted particles can then be subjected to further processing, and also 25 to a further separating process for example. If an air separation device is provided below the horizontal spacing or downstream of the further conveying unit, the sorted fraction of smaller particles can be separated still more. When O using the sorting arrangement for sorting wastepaper, small paper particles would fall through the horizontal gap together with the small, unwanted foreign bodies such as glass splinters, corks, stones, etc and these would be reliably separated out by means of the air separation device due to the differing 5 individual weights thereof. In contrast to paper or items of cardboard having a large surface area, small paper particles or paper chips will behave in a predictable manner in a wind screening device and good results for the separating process can thereby be achieved. The separated fraction of small paper particles (chips) is preferably then supplied to the paper processing plant. By virtue of providing a device for turning the larger particles in the advancing stream of material, small particles lying on or between particles of large surface area will be isolated and reliably separated therefrom in the next gap-separated section. Hereby, it is preferred that the material be turned by means of a stepped arrangement. 10 Particles of differing size can be separated in a highly efficient manner by means of the sorting device in accordance with the invention. In particular, particles of large surface area can be separated from small foreign particles. A 115 considerable reduction in the expenditure on manual separating processes can be obtained in the course of recycling processes such as the recycling of wastepaper for example. In addition, damage to the plants used for the processing of the 2o wastepaper will be prevented. Practical tests have already shown that the sorting arrangement in accordance with the invention is also usable for a multiplicity of other conglomerations and materials and mixtures P5 thereof in addition to the above mentioned usage. Thus, for example, materials such as wood, glass, synthetic materials, metal and the products manufactured therefrom can also be processed. kO An arrangement consisting of a plurality of successive conveying units separated from one another by spacings opens up still further possibilities. Hereby, such sorting arrangements can even be constructed by using conveyor belts of two different types. .5 The invention will be explained in detail hereinafter by means of four embodiments taken in conjunction with the accompanying drawings. Therein Fig. 1 shows a sorting arrangement incorporating conveyor belts, in the form of a schematic spatial view, Fig. 2 a second embodiment of the sorting arrangement incorporating a vibratory conveyor for feeding the material requiring sorting, in the form of a schematic spatial view, Fig. 3 a schematic spatial view of a sorting arrangement 7 incorporating two gap-separated sections and Fig. 4 a further embodiment of the sorting arrangement including an additional drum in the gap region, in the form of a schematic spatial view. 5 A sorting arrangement incorporating three conveyor belts 1, 2, 5 is illustrated in Fig. 1 in the form of a schematic spatial view. The first conveyor belt 1 in the conveyor stream comprises a conveyor belt guide roller 12 of small diameter at ZO the downstream end thereof so that a sharp deflecting edge is produced at this end 11. A second conveyor belt 2 is arranged thereafter in the direction of conveyance X, this second belt being gradated in height by 5 the amount H relative to the plane of conveyance 13 of the first conveyor belt 1. The upstream end 21 of the conveyor belt 2 likewise comprises a guide roller 22 of small diameter so as to produce a curvature of the conveyor belt which is as sharp as possible at this point. In addition to the gradation in height Q H of the two successive planes of conveyance 13, 23 of the two conveyor belts 1, 2, there is provided, in accordance with the invention, a horizontal spacing A between the downstream end 11 of the first conveyor belt 1 and the upstream end 21 of the conveyor belt 2. A further conveying unit 5 for removing the particles that have fallen through the gap is provided below the transition point between the conveyor belt 1 and the conveyor belt 2, i.e. below the horizontal spacing or gap A. The conveying unit 5 is constructed in the form of a conveyor belt and has a direction of conveyance Y which is aligned substantially perpendicularly to the direction of conveyance X. The conveyor belt 5 can be selectively driven for rotation in both directions. The manner of functioning of the arrangement will be described hereinafter. The particles P requiring sorting are fed to the conveyor belt 1 and are located on the plane of conveyance 13 as illustrated in Fig. 1. At the downstream end 11 of the first K) conveyor belt 1, the particles P tip over the relatively sharp edge of the guide roller and fall directly onto the plane of conveyance 23 at the upstream end 21 of the second conveyor belt 2 in dependence on the ratio of their size relative to the height gradation H and the horizontal spacing A, or, they fall through the horizontal spacing (gap) A onto the further conveyor belt 5. The particles P 2 of greater surface area thereby bridge the gap, whereas the smaller sized particles Pi fall through the gap onto the conveyor belt 5. 30 The stream of particles P requiring sorting is thereby separated into a further stream of particles P 2 which continues to be advanced and consists of particles of greater surface area, and into a stream of particles P 1 of smaller size. In order to bring the results of the separation into line with the use of 25 different materials and/or some other wanted separating section, at least one of the two successively disposed conveyor belts 1, 2 is preferably adjustable in height and in the direction of conveyance X. It is thereby possible to adjust the height gradation H and the horizontal gap spacing A in a continuous O manner. Thus, for example, the plant used for the separation of the wastepaper can be modified for the purposes of separating items of synthetic materials whereby films, plastic bags or even bubble packaging materials can be separated from empty yoghurt containers and small plastic items etc. As an alternative to the arrangement of Fig. 1, Fig. 2 depicts an embodiment of the invention incorporating a vibratory conveyor 1' which forms the conveying unit to which the particles P requiring sorting are supplied. In the case of the vibratory conveyor 1', the downstream edge 11' thereof is arranged at an appropriate height gradation H above the plane of conveyance 23, in correspondence with the downstream end 11 of the conveyor belt 1 in the embodiment of Fig. 1, and it has a S horizontal spacing A relative to the upstream end 21 of the conveyor belt 2. The other components in this arrangement correspond to those in the previously mentioned embodiment and bear the same 0 references. The manner of operation likewise corresponds to the aforesaid example. A schematic spatial view of a sorting arrangement comprising two gap-separated sections is illustrated in Fig. 3. A third conveyor belt 3 is arranged between the upstream conveyor belt 1 and the downstream conveyor belt 2 in correspondence with the embodiment of Fig. 1. Guide rollers 32 of small diameter are arranged at both ends 30, 31 thereby forming a conveyor belt having "two knife edges". The process of driving this conveyor a belt is effected by a central drive means 34. A height gradation H 1 is formed between the plane of conveyance 13 of the first conveyor belt 1 and the plane of conveyance 33 of the central conveyor belt 3. Furthermore, there is provided 15 a horizontal spacing A 1 between the downstream end 11 of the conveyor belt 1 and the upstream end 30 of the central conveyor belt 3. A further height gradation H 2 is formed between the plane of conveyance 33 of the central conveyor belt 3 and the plane of conveyance 23 of the conveyor belt 2, and a horizontal 0 spacing A 2 is also formed between the downstream end 31 and the upstream end 21. The particles P requiring sorting, which are supplied via the conveyor belt 1, fall from the plane of conveyance 13 onto the ,5 spaced and height gradated plane of conveyance 33 of the conveyor belt 3 whereby the small sized particles P 1 will fall through the gap A 1 into a schematically illustrated collecting container 63. The fraction of particles of larger surface area that are conveyed onwards on the conveyor belt 3 now reach the next gap-separated section whereby here, only the particles P3 of large surface area will reach the plane of conveyance 23 of the conveyor belt 2. The particles P 2 of average size fall through the gap A 2 into a collecting container 62 arranged 5 therebelow. The continually advancing particles P 3 of large surface area reach a collecting container 61 via the conveyor belt 2. As an alternative to the collecting containers 61, 62, 63, conveying units could also be provided for removing the separated fractions, for the purposes of further processing for t example. In an arrangement of this type, the horizontal spacing and the height gradation increase in the direction of conveyance X from gap-separated section to gap-separated section. In the is exemplary embodiment illustrated, Al < A 2 and Hi < H2. The embodiment of Fig. 3 can be constructed from two identical, but anti-symmetrically arranged conveyor belts, which then form the conveyor belt 1 and the conveyor belt 2. These two conveyor 2 belts then each comprise a guide roller of small diameter at just one end, somewhat in the sense of a roller edge. The central conveyor belt 3 is of a different type and comprises small diameter guide rollers 32 at both ends. Several conveyor 25 belts of this type could also be arranged successively between the conveyor belt 1 and the conveyor belt 2, thereby forming respective gap-separated sections each having height gradations. Due to the fact that, basically, only two different types of such conveyor belts and their corresponding additional 30 components (motor, transmission, guide rollers etc) are needed, a multiplicity of differing sorting arrangements for different fields of application can be obtained, and this, with proportionally low manufacturing costs. 15 The drive motor used for driving the conveyor belts can also be equipped with integrated or external frequency converters. It thereby becomes possible to regulate the speed of the belt whilst simultaneously observing the stream of material and the separating effect that is being produced, for example, so as to take account of external effects, for example, because the products are showing some other form of separating characteristics due to damp weather conditions or different temperatures. The height gradations and the spacing between the individual conveyor belts, i.e. the gap-separated sections, can be adjusted in a flexible manner, preferably by means of an adjusting unit. This can also involve the angle of inclination of the conveyor 0 belt. Tests have already indicated that only a small number of adjustments is required in the course of operation so that these adjustments could be effected manually on each occasion. Belt widths of approximately 1000 mm to 2000 mm have proved to is be satisfactory for the width of the conveyor belts, although other widths are possible. In dependence on the field of application, the width of the belt should be at least 200 mm wider than the material feed point; a particularly effective form of lateral guidance for the stream of material is thereby WO possible. The axial spacing of the conveyor belts and hence the length thereof lies in the general order of magnitude of 12,000 mm, however other sizes could be provided as required. The radii of the guide rollers having roller edges of relatively small diameter may be between 5 and 12 mm for example. There is practically no blocking or clogging of the spacings ;O between the conveyor belts. The sorting arrangements are also virtually unaffected by possible operating errors which cannot in practice lead to malfunctioning of the plant, but merely affect the precision with which the materials are separated. Values in the order of magnitude of approximately 80 mm have ts proved satisfactory for the height gradation between each two conveyor belts. The spacing between each two conveyor belts in the horizontal direction can be varied between 0 and 500 mm in dependence on the material being sorted.

A further embodiment of the invention comprising two conveyor belts 1, 2 is illustrated in Fig. 4. In contrast to the exemplary embodiment illustrated in Fig. 1, the separating gap in accordance with the invention is formed between the 5 downstream end 11 of the first conveyor belt 1 and a drum 4 which is provided with an appropriate height gradation and a horizontal gap. The second conveyor belt for transporting away the particles of larger surface area P 2 is located below the drum 4. A vibratory conveyor 5' is provided below the gap for 0 the purposes of carrying away the sorted particles having a smaller order of magnitude P 1 . The peripheral surface of the drum 4 is driven such that it rotates in the direction of conveyance X, whereby the rotational 1 axis 41 is mounted 42 [sic] in an adjusting arrangement 42 such as to be displaceable horizontally substantially in the direction of conveyance X. Due to the adjusting arrangement 42 for the rotatably driven drum 4, the spacing gap can be varied in trouble free manner so that the results of the sorting 2o process can be affected thereby, or, the arrangement can be adapted to the different types of material that require sorting without the conveyor belts themselves having to comprise complex adjusting means. is Additional compensation for the output materials and the separation thereof into different categories can be obtained by using a different, and especially increasing, speed of the belts. The turning stages contribute to this separating and loosening effect, possibly without changing the direction of the >0 stream of material. The roller edges of small diameter contribute to the process of separation in accordance with the different sizes of the grains. Separating processes can be effected by varying the width of the 5 gap in accordance with the size of their outer contours. In addition materials of differing stiffness can be separated. This is assisted by adjusting the slope or the inclination of the conveyor belts.

The process of separating out lighter materials can be assisted by means of air-blasting strips located between the belts, i.e. in the region of the gap. 5 The gapped belts themselves can be constructed in a very compact and space-saving manner. They themselves can be fabricated in any arbitrary manner and they are put together in dependence on the requirements. Maintenance is simple and each area thereof is readily accessible. Parts or individual belts can easily be to replaced in the event of wear.

List of references 1 conveying unit, conveyor belt 11 downstream end 12 guide roller 13 plane of conveyance 1' vibratory conveyor 11' downstream edge 2 conveying unit, conveyor belt 21 upstream end 22 guide roller 23 plane of conveyance 3 conveying unit, conveyor belt 30 upstream end 31 downstream end 32 guide roller 33 plane of conveyance 34 central drive means 4 drum 41 rotational axis 42 adjusting device 5 further conveying unit, conveyor belt 5' vibratory conveyor 6 collecting container 61 collecting container 62 collecting container A spacing, gap Ai spacing, gap

A

2 spacing, gap H height gradation

H

1 height gradation

H

2 height gradation P particles

P

1 particles

P

2 particles

P

3 particles X direction of conveyance Y direction of conveyance

Claims

1. A sorting arrangement for particles (P) of differing sizes comprising at least two conveying units (1, 2, 3) to which 5 the particles (P) requiring sorting are fed at an upstream position thereof and wherein there is a gradation (H) in the height of the planes of conveyance between at least two successive conveying units in the direction of conveyance (X), characterised in that there is provided a horizontal spacing or gap (A) between the successive conveying units (1, 2, 3).

2. A sorting arrangement in accordance with Claim 1, characterised in that the downstream conveying unit (2, 3) of the successive conveying units (1, 2, 3) has a higher conveying speed than the upstream conveying unit (1, 2). O

3. A sorting arrangement in accordance with Claim 1 or 2, characterised in that means are provided for adjusting the width of the horizontal spacing (A).

4. A sorting arrangement in accordance with Claim 1, 2 or 3, characterised in that means are provided for adjusting the height (H) of the gradation.

) 5. A sorting arrangement in accordance with Claim 1, 2, 3 or 4, characterised in that at least one drum (4), which is driven in rotary manner in the direction of conveyance and has an axis of rotation (41) that is substantially perpendicular to the direction of conveyance (X) and substantially parallel to the planes of conveyance (13, 23), is arranged within the gradation and the gap between two conveying units (1, 2, 3) that succeed one another in the direction of conveyance (X).

6. A sorting arrangement in accordance with Claim 5, characterised in that the axis of rotation (41) of the drum is adjustable substantially horizontally in the direction of conveyance.

7. A sorting arrangement in accordance with any of the preceding Claims, characterised in that the conveying units are conveyor belts (1, 2, 3) and/or vibratory conveyors (1').

8. A sorting arrangement in accordance with Claim 7, characterised in that an end (11, 21, 30, 31) of the conveyor belt (1, 2, 3) directed towards a spacing gap has a guide roller (12, 22, 32) having a diameter which is smaller than or equal to the dimensions of the particles (P1, P2) requiring sorting.

9. A sorting arrangement in accordance with any of the preceding Claims, characterised in that a further conveying unit (5, 5') or a collecting container (61, 62) is arranged below the horizontal spacing. 5

10. A sorting arrangement in accordance with Claim 9, characterised in that an air separation device is provided below the horizontal spacing or downstream of the further conveying unit (5, 5'). o

11. A sorting arrangement in accordance with any of the preceding Claims, characterised in that a device is provided for turning the larger particles in the advancing stream of material.

12. A sorting arrangement in accordance with Claim 11, characterised in that the device used for the turning process is a stepped arrangement. Amended pages 1 to 3a Sorting arrangement for particles of differing sizes The invention relates to a sorting arrangement for particles of differing sizes comprising at least two conveying units to which 5 the particles requiring sorting are fed at an upstream position thereof and wherein there is a gradation in the height of the planes of conveyance between at least two successive conveying units in the direction of conveyance. Such types of conveying units disposed successively in the direction of conveyance and comprising a gradation in the height of the planes of conveyance that are used purely for the conveyance of particles of differing sizes are known. In a plant known from DE 196 17 187 Al for example, bulk materials S are transported by means of conveyor belts which overlap at the point of transition from one conveyor belt to the next so that the bulk material will fall onto the lower lying plane of the downstream conveyor belt for onward transportation. A sorting process is not known from this arrangement. A system for transporting work-pieces on carrier means is proposed in DE 37 29 784 Al. In this case, there are two successive conveyor belts. Here, a complicated mechanism is used for the timing and the transportation of the work-pieces such that there will be discrete spacings therebetween. In order to sort similarly shaped but differently sized objects according to their size, such as fish for example, FR-PS 974980 proposes that a plurality of successively disposed transportation belts be mutually spaced so that those fish that are too small will fall through the respective spaces. Furthermore, sorting arrangements are known wherein the particles requiring sorting are fed over a gradation in height and the particles are then subjected to an air separation process whilst they are in free fall. Here however, it is disadvantageous that the particles requiring sorting cannot be divided up in a predictable manner, especially when they are of differing size. For very small particles of a mutually similar order of magnitude, US-PS 5 305 893 proposes that a process of detecting foreign bodies, especially in a stream of tobacco, be effected on a conveyor belt. An air actuated piston is driven out at the end of the conveyor belt in dependence on the result of the detection process so as to eject the foreign bodies together 10 with the adjacent particles from the stream. This arrangement is not suitable for sorting particles of differing sizes. Especially when processing waste paper products, such as those from paper recycling containers for example, there is the problem that small particles of foreign objects, stones, glass splinters, bottle stoppers and the like for example, may be incorporated in this mass of waste paper. However, as the waste paper will be formed into a slurry and dissolved in fluids in the large centrifuges in the paper processing plants for the kW purposes of removing ink therefrom and converting the waste paper back into usable paper, these foreign constituents such as stones, splinters and other small hard particles can cause severe damage, especially if the particles of foreign matter are rubbed against the walls of the centrifuge by the agitator L5 devices. The process of separating out these foreign constituents by means of the known sieve arrangements founders due to the difficulties encountered in transporting the paper over the 50O sieves and the blockages ensuing therefrom. Consequently, sieve-like arrangements such as that disclosed in US-PS 4 627 541 are not intended for sorting processes of this type. In that document, many successively disposed rotatable 5 drums are operated with respective mutual spacings so as to sort agricultural products (potatoes perhaps) in dependence on their sizes whereby those potatoes that are too small will fall down between the drums. In a proposal made in US-PS 3 799 336, similar, long objects are moved over a vibrating table having sieve-like recesses therein for the purposes of sorting out objects of a certain length. This conception of a sieve is also not intended for use with 5 paper. In the case of the air separation devices mentioned hereinabove, there is the problem that, where there are combinations of such materials, cardboard cartons and newspapers etc having a 0 relatively large surface area will behave in an uncontrolled and unpredictable manner in the air stream with the consequence that a reliable process of separation is not possible. Hereby, these problems generally occur when there is a need to separate particles of differing size and the particles are of large 5 surface area for example. A manual sorting process is likewise made more difficult since the aforesaid small foreign bodies such as glass splinters, corks and stones are inclined to be hidden in larger piles of IC paper, or they adhere thereto and/or are entrained therein. Consequently, the object of the invention is to provide a sorting arrangement for particles of differing size wherein particles of large surface area can also be separated from small )G particles of foreign material. This object is achieved by means of a sorting arrangement for particles of differing sizes comprising at least two conveying units to which the particles requiring sorting are fed at an O upstream position thereof, wherein there is a gradation in the height of the planes of conveyance between at least two successive conveying units in the direction of conveyance, wherein a horizontal spacing or gap is provided between the successive conveying units and wherein at least one of the two .5 successive conveying units is a conveyor belt. Due to the provision of a horizontal spacing or gap in a chain of successively disposed, gradated conveying units, one obtains, surprisingly, an effective way of sorting particles of differing size, especially those incorporating items of large surface area, which is not susceptible to jamming. Hereby, the width of the gap is selected such that smaller particles will not reach the downstream conveying unit, but rather, will fall down 5 through the gap. By contrast however, items of greater surface area will bridge the gap. For example, the products that have been forwarded by means of the upstream conveying unit will tip over at the end of the conveying unit and fall onto the downstream conveying unit. There, they are forwarded by means o of the downstream conveying unit. Blockages will thus be excluded by virtue of such an arrangement. Separation by means of such a gap can be effected repeatedly by means of a plurality of conveying units that are arranged in a chain in this manner. Separation of the output material into a plurality of fractions in one throughput process is made possible by means of the close succession of several gap separated sections each having a different horizontal spacing. tO If the downstream conveying unit of the succession of conveying units operates at a higher speed of conveyance than the upstream conveying unit, the packing density of the particles reaching the downstream conveying unit will be drawn apart whereby smaller particles clamped therebetween will be released. 05 Means are provided for adjusting the width of the horizontal spacing so as to enable the sorting arrangement to be rapidly reset for differing materials and/or some other fractional distribution. Since the height gradation also has an effect 10 upon the result of the separating process, it is preferable if means are likewise provided for adjusting said height gradation. Continued on page 4 of the original description