AU740967B2

AU740967B2 - Device for fractionating and scattering specially fibrous particles

Info

Publication number: AU740967B2
Application number: AU73354/98A
Authority: AU
Inventors: Ove-Walter Cornils; Hans-Joachim Iredi; Ludwig Twick
Original assignee: Kvaerner Panel Systems GmbH Maschinen und Anlagenbau
Current assignee: Kvaerner Panel Systems GmbH Maschinen und Anlagenbau
Priority date: 1997-04-17
Filing date: 1998-04-15
Publication date: 2001-11-15
Anticipated expiration: 2018-04-15
Also published as: NO995045D0; CA2286623A1; DK0975457T3; PL336161A1; ID24634A; WO1998047677A1; BR9808682A; DE59802145D1; CN1256658A; EP0975457B1; EP0975457A1; ATE208692T1; RO119293B1; CN1095737C; NZ500291A; ES2164422T3; AU7335498A; TR199902585T2; NO995045L; RU2177875C2

Description

1A APPARATUS FOR THE FRACTIONATION AND SCATTERING OF PARTICLES, ESPECIALLY FIBROUS PARTICLES The present invention relates to an apparatus for the fractionation of particles, especially fibrous particles, of different sizes, in particular of fibers chips or the like of lignocellulose and/or containing cellulose, comprising a metering hopper containing the non-fractionated particles, a substantially areal screening apparatus inserted after the metering hopper and a supply unit of the metering hopper by which the particles from the metering hopper can be brought onto the surface of the screening apparatus, together with an apparatus for the scattering of the fibrous particles, especially fibrous particles with an admixed binder, in particular wood fibers, wood chips or similar particles.

4 Apparatuses of this kind are known from the German patent specification 17 28 502. In this document a scattering device is :oe described for the manufacture of multilayer chip mats in which ooo• roller rakes are provided at the base of the metering hopper :containing the non-fractionated particles via which the •ge particles are supplied to a thrower type sifting roller arranged after the metering hopper. The particles which impinge on the thrower type sifting roller are fractionated and thrown onto an oscillating screen arranged beneath the thrower type sifting roller. The fractionation thereby takes place in accordance with the principle of throw sifting, so that larger and thus heavier particles fall on one region of the screen which is further removed from the thrower type sifting roller and smaller particles come to lie on the screen closer to the thrower type sifting roller.

-2- Through the movement of the oscillating screen the impinging particles are loosened up further, whereupon they are shed through the oscillating screen onto a conveyor belt arranged beneath the oscillating screen for the production of a mat.

Apparatuses of this kind have several disadvantages. On the one hand it is unavoidable that the screening apparatus used becomes clogged up in the course of time, in particular since the particles falling onto the screening apparatus are normally mixed up with binder. A cleaning of the screening apparatus is relatively time consuming and thus cost-intensive, since the i .operation of the apparatus must be interrupted during the cleaning. On the other hand both the throughput and also the quality of the fractionation is not satisfactory in apparatuses of the initially named kind.

An intention of at least an embodiment of the invention is to so design an apparatus of the initially named kind that on the one hand no clogging of the screening apparatus arises and on the 20 other hand the throughput can be improved with a simultaneous S. improvement of the sifting quality.

According to the present invention there is provided apparatus for the scattering of particles of different sizes, said apparatus comprising a metering hopper containing nonfractionated particles, an apparatus for the fractionation of said particles having a substantially areal screen apparatus inserted after the metering hopper, a supply unit of the metering hopper by which the particles from the metering hopper can be brought onto the surface of the screening apparatus, and a conveyor belt arranged beneath the screening apparatus for the reception of a mat formed of particles which pass through the screening apparatus characterized in that the screening apparatus includes screen zones with different screen openings and in that a transport device is provided in the region of the surface of the screening apparatus having a plurality of -3portioning segments movable along the surface of the screening apparatus within each of which a respective portion of the particles brought by the supply unit onto the surface of the screening apparatus is movable over the surface of the screening apparatus.

In accordance with an embodiment of the invention a metering of particles applied onto the screening apparatus thus takes place in mutually independent part quantities which are transported by the transport device of the invention over the surface of the screening apparatus. Through the movement of the particles along o e the surface of the screening apparatus a clogging up of the screening apparatus is prevented, on the one hand, and, on the other hand, a force acting on the particles is produced which 15 has a component directed perpendicular to the screening apparatus. Through this force the particles are pressed through the screening apparatus so that the through-put of the apparatus is correspondingly increased. Through the metering of the c:o: particles a better fractionation is achieved, because a more eeoc 20 complete through-mixing of the particles is possible within the e relatively small quantities of particles which are respectively located within a portioning segment, whereby a situation is o: •prevented in which small particles located at the top side of the bulk material have no possibility of passing downwards, past the larger particles lying beneath them, to the screening apparatus.

In the bulk material arranged within the portioning segments a rotational and/or turn-over movement of the particles arises through the movement across the screen surface and promotes a mixing of the particles, whereby the sifting quality is increased.

4 In accordance with an advantageous embodiment of the invention at least some of the portioning segments each include a scraping element which contacts the surface of the screening apparatus and is scrapingly guided over the surface of the screening apparatus during the movement of the portioning segments. Through a scraper element which lies under a light pressure on the surface of the screening apparatus, for each or at least some of the portioning segments, the cleaning effect which arises during movement of the portioning segments over the surface of the screening apparatus is further enhanced. At the same time the force component acting on the particles in the direction perpendicular to the screen surface is increased by the scraper elements so that an increase of the throughput is achieved.

The transport apparatus is preferably designed as a scraper belt, in particular an endless scraper belt. In this manner a particular simple and cost-favourable design of the transport apparatus is possible. In this connection the scraper belt is advantageously made permeable for the particles in the direction perpendicular to the surface of the screening apparatus, at least over a part region, so that the particles from the metering bunker can be shed by a supply unit through the scraper band onto the screening apparatus. A complicated design of the supply unit can spared in this manner.

In accordance with a further advantageous embodiment of the invention the scraper belt includes in particular plate-like drivers which are preferably provided at regular intervals on an endless chain- or belt-like carrier element. The carrier element can in this respect in each case be centrally arranged at the drivers. However, the several carrier elements, in particular two chain-like or belt-like carrier elements can be provided which are respectively secured in the region of the lateral outer edges of the drivers. In this manner the stability of a scraper belt formed in accordance with the invention is increased.

The drivers are preferably releasably secured to the carrier element or to the carrier elements and/or of air impermeable design. In this manner it is ensured that, on the one hand, the drivers used are ideally matched to the screening apparatuses that are used and, on the other hand, that worn drivers can be exchanged for new ones.

In accordance with a further advantageous embodiments of the invention the scraper elements are each formed by a section of the drivers. In this manner a particularly cost-favourable design of the apparatus of the invention is possible since no separate components are required for the scraper elements. The drivers are in particular made flexible, at least in their sections which form the scraper elements, and are for example made of hard rubber. In this way an adaptation of the scraper elements to the surface of the screening apparatus is possible so that it is ensured, even with a certainly regularity in the screen surface, that the scraper elements contact the surface of the screening apparatus for the certain pressure over their full width and also over their full range of movement.

In accordance with a further preferred embodiment of the invention the drivers are made abrasion-resistant, at least in their sections which form the scraper elements and have in particular an abrasion-resistant coating, for example a Teflon coating. The sections of the drivers which form the scraper elements can in this arrangement be made both in one piece with the drivers and also made as separate components. If the scraper 6 elements are formed as separate components and they are preferably releasably mounted on the drivers so that they can be exchanged in the case of wear.

In accordance with a further advantageous embodiment of the invention the drivers are made, at least in their sections forming the scraper elements, of water-repellent non-adherent material. In this way a situation is avoided in which the particles with the admixed binder remain stuck to the drivers, whereby the receiving capability of the portioning segments could be restricted.

In accordance with a further preferred embodiment of the invention the screening apparatus include in particular two screening zones with different screen openings. In this way a situation is achieved in which particles of different size are fractionated by the screen zones with the differently sized screen openings. In particular the screen zones are arranged behind one another along the direction of movement of the portioning segments, which can move over the surface of the screening apparatus, with the screen openings of the screen zone or screen zones lying in the direction of movement of the portioning segments preferably being larger than the screen openings of the screen zone or screen zones lying opposite to the direction of movement. In this way a situation is achieved in which, on sweeping over the screen surface, first of all the particles with a smaller diameter pass through the screening apparatus while the next largest particles then pass through the screen following this in the next screen zone. Depending on the number of screen zones and the size of the screen openings the desired fractionation of the particles is thus achieved. The fractionated particles can in this arrangement either be shed into different capture devices for the different particle sizes, or, for 7 example, onto a moving conveyor belt arranged beneath the screening apparatus on which a mat can be produced in this manner having different particle sizes distributed over the thickness.

In accordance with a further advantageous embodiment of the invention the endless scraper belt is guided over two deflection rollers so that a lower belt section extends directly at the surface of the screening apparatus and an upper belt section extends at a certain spacing from the surface of the screening apparatus, in particular in each case substantially parallel to the surface of the screening apparatus. In this manner a particularly compact design of the apparatus of the invention is possible. A receiving apparatus for the reception of separated out particles is preferably provided, at least at one end of the scraper belt, in particular in the region of the deflection rollers. These particles can be foreign bodies which are present in the bulk material, such as for example screws or nails. However, lumps or particles which exceed a maximum permissible size, and which thus cannot pass through even largest screen openings of the screening apparatus, can also be separated out and can be lead away.

In accordance with a further preferred embodiment of the invention an intermediate floor is provided at least regionally between the upper and the lower belt sections, with the ends of the drivers opposite to the sections which form the scraper elements contacting the intermediate floor so that these ends are guided scrapingly over the intermediate floor during the movement of the portioning segments. With this embodiment belt material which is initially brought out of the metering bunker via its supply unit onto the intermediate floor can be brought in a defined manner to a specific position between the deflection rollers.

8 In this arrangement, in accordance with a preferred embodiment, the intermediate floor can extend from the one deflection roller in the direction of movement of the upper belt section to the oppositely disposed other deflection roller, with a region, which is permeable for the particles in the direction perpendicular to the surface of the screening apparatus, being formed between this other deflection roller and the end of the intermediate floor adjacent this other deflection roller. An initial separation of foreign bodies or particles with a size which lies above the size of these screen openings can take place here, especially when this region is formed by further screening apparatuses which can have relatively large screen openings. Only the particles passing through the further screening apparatus fall onto the lower lying screening apparatus over which they are moved away by the means of the transport device.

In accordance with a further preferred embodiment of the invention two scraper belts arranged behind one another in the longitudinal direction are provided, with the scraper belts in particular being arranged with mirror symmetry relative to one another. A distribution device, in particular in the form of a pendulum distributor, is advantageously provided in this embodiment after the supply unit of the metering hopper, by means of which the particles which are lead by the supply unit from the metering hopper can be supplied, in particular alternately supplied, to the two scraper belts. Through this design it is possible, starting from one metering hopper, to distribute particles onto two different scraper belts. It is possible, especially when the two scraper belts can be driven in opposite directions, so that the two upper belt sections move away from one another, and when an intermediate floor is provided in the already described manner between the upper and the lower belt sections, for the particles brought by the distribution apparatus onto the respective intermediate floors to be transported to the outwardly disposed ends of the scraper belts in opposite directions and to be respectively brought there onto the screening apparatuses arranged beneath the scraper belts. It is possible, with corresponding dimensioning of the screen openings of the screening apparatuses, in particular when the size of the screen openings increases in the direction of movement of the lower belt sections, for a symmetrical mat with a lower fine cover layer and an upper fine cover layer which include a coarse middle layer between them to be formed on a moving conveyor belt arranged beneath the screening apparatuses.

Instead of a distribution apparatus two metering hoppers can for example also be provided by which the two scraper belts are fed with particles.

The screening apparatus and/or the further screening apparatus is preferably formed in all embodiments as an oscillating screen or as a vibrating shaking screen. In this connection the bulk material dispensed onto the screening apparatus is further loosened up whereby fine particles and subsequently medium-sized particles disposed remote from the screen more rapidly reach the screen openings and pass through them.

In accordance with a further preferred embodiment of the invention the oscillating screen is movable to and fro via a crank drive. In this connection the maximum stroke of the oscillating screen advantageously amounts to between ca. 10 cm and 1 m, preferably to between ca. 30 cm and 70 cm and in particular to ca. 50 cm.

Through the movement of the oscillating screen, which can be adjustable in its frequency, the chips lying on the screens are made more uniform and are sifted out fraction-wise in accordance with the screen openings.

The drivers can scrape over the surface of the screens during this or can be moved relative to it at a small spacing.

Since both the drivers and also the oscillating screen are simultaneously in motion and, as a result of the changing direction of movement of the oscillating screen, a co-movement and then an opposite movement is produced, particles arranged in the portioning segments are repeatedly stacked up and turned at the front and rear sides of the drivers.

Especially when, in accordance with a preferred embodiment, the maximum speed of movement of the oscillating screen in the transport direction is greater than the transport speed of the portioning segments, the particles collect at the sides of the drivers disposed opposite the transport device when the drivers and the oscillating screen are moved in the same direction. In this manner the particles are thrust against the rear sides of the drivers and turned.

If the oscillating screen moves opposite to the transport direction of the portioning segments, and thus opposite to the direction of movement of the drivers, then the particles are turned over at the front-sides of the drivers.

Through this repeated turning over a uniform distribution of the particles is achieved within the portioning segments which enables the smaller particles to migrate rapidly through the total quantity of the particles arranged within a portioning segment in the direction of the screen surfaces and to fall through the screen openings.

In addition the self-cleaning effect of the screens is increased by the simultaneous but different speeds of movement and directions of the oscillating screen and the drivers. Since the lower edges of the drivers scrape on the surface of the oscillating screen, or are arranged at a small spacing from the latter, particles which are stuck in the screen openings are broken as they are swept over by the drivers or they are pressed through the screen openings. A clogging of the screen is thereby precluded.

In accordance with a further advantageous embodiment of the invention the portioning segments are made so that they are at least regionally closed at the sides. In this way a situation is achieved in which an emergence of particles and particle dust sideways out of the portioning segments is avoided, so that the environment of the apparatus is kept practically dust-free.

Sealing elements, especially lobe-like sealing elements are advantageously provided in the lateral regions of the portioning segments and are in particular secured to the lateral end faces of the drivers. Through the lobelike sealing elements a simple sealing of the portioning segments is possible, and it is also made possible to retrospectively equip existing apparatuses with the sealing elements in a simple manner.

In accordance with a further preferred embodiment two respective sealing elements following one another in the transport direction overlap at least regionally, whereby in each case a seal extending through the whole width of a portioning segment is produced. Through this overlapping design account is taken of the fact that in designing the transport apparatus as an endless scraper belt the drivers have a greater spacing relative to one another at their radially outwardly disposed edges than between the radially inwardly disposed edges when moving around the deflection rollers. Since a fixed seal of the lateral regions of the portioning segments is not possible in this case the seal can be advantageously achieved by overlapping sealing elements. Fundamentally it is also possible to make the sealing elements for example flexible, with it being possible to achieve the flexibility on the one hand by specific material characteristics and on the other hand for example by a type of accordion fold.

In accordance with a further preferred embodiment a middle sealing element, especially a middle sealing element formed as a side-wall, is arranged between the upper and the lower belt sections laterally outside of the portioning segments. In this arrangement the central sealing element preferably seals off laterally substantially the whole region between the upper and the lower belt sections. Through the middle sealing element the region between the upper and the lower belt sections is sealed off relative to the environment so that the freedom of the environment from dust is further improved by the middle sealing element.

A respective middle sealing element is preferably provided at both sides outside of the portioning segments, so that dust emergence in the environment is prevented on both sides of the apparatus.

The middle sealing element is preferably sealingly connected to the sealing elements which terminate the portioning segments of the side and stands in scraping and sealing contact with the latter, in particular with moved sealing elements. In this manner the total lateral region is sealed off by a substantially continuous unitary sealing unit consisting of the middle sealing elements and the sealing elements which terminate the portioning segments at the side, so that the side environment of the apparatus of the invention is practically dust-free.

In order to prevent emergence of dust upwardly out of the apparatus an upper sealing element formed especially as a wall section is provided, in accordance with a further advantageous embodiment, above the upper belt section.

In accordance with a further advantageous embodiment of the invention a transport device is provided above the portioning segments with which the particles which emerge from the metering hopper can be transported to a predetermined region above the screening apparatus. The transport device can in particular be formed in this arrangement as a preferably endless transport belt.

The transport apparatus can in this arrangement be additionally provided, or provided in place of the already described intermediate floor since the function of transporting the particles emerging from the metering hopper to a predetermined region above the screening apparatus can be satisfied both by the transport device and also by the intermediate floor in conjunction with the upper belt section moved over the intermediate floor.

Thus, all the advantages and combinations of features described with respect to the embodiment with an intermediate floor can also be possible and hereby claimed in an apparatus with a transport device, especially a transport device formed as an endless transport belt. By the way of example it is possible, via the transport device, to bring the particles dispensed from the metering hopper onto the transport device in the region of the one deflection roller to the oppositely disposed other deflection roller and their to dispense them through the scraper belt onto the surface of the screening apparatus.

-14- In accordance with a further advantageous embodiment of the invention the fractionating apparatus is made displaceable relative to the conveyor belt in the longitudinal direction in an apparatus in accordance with the invention for the scattering of particles. In this way, in particular when a cyclically operating press is disposed after it for the pressing of the mat, the next mat can already be scattered by movement of the fractionating apparatus relative to the conveyor belt so that, after pressing has been completed, the next mat is already fully scattered and can be supplied directly to the cyclically operating press.

*5 S" Furthermore, in accordance with an embodiment of the invention

S.

S 15 for middle layer roller scattering heads to be provided for the scattering of a middle layer of a mat in addition to one or more fractionating apparatuses in accordance with the invention, o ~which are used for the scattering of one or more covering ":-layers.

S Further embodiments of the invention are set forth in the ego *e subordinate claims.

The invention will be explained in more detail in the following with reference to the embodiments and to the drawings in which are shown: Fig. 1 a schematic side-view of an apparatus formed in accordance with the invention for the fractionation of fibrous particles, such as for example wood fibers, woods chips or like particles with at least one admixed binder, Fig. 2 a detailed view of the apparatus shown in Fig. i, Fig. 3 an apparatus formed in accordance with the invention for the formation of a symmetrical mat, Fig. 4 a further embodiment of the invention, Fig. 5 a partly sectioned perspective illustration of a further embodiment of the invention and Fig. 6 a further embodiment of the invention.

Fig. 1 shows a metering hopper 1 in which three back scraping rakes 2 are arranged. The bulk material consisting of differently sized particles 3, for example of fibrous chips and binder is supplied to the metering hopper 1 from above, as is indicated by the arrow 4.

A floor belt 6 running over two deflection rollers 5 is arranged at the lower side of the metering hopper 1 and forms a supply unit 8 together with a carry out roller 7.

The particles 3 fed into the metering hopper 1 fall onto the floor belt 6 and are evened out there by the back scraping rakes 2 in the arrow directions shown and are conveyed along an arrow 9 in the direction of the carry out roller 7.

An endless scraper belt 10 guided over two deflection rollers 9, 9' is arranged beneath the carry out roller 7 and can be moved by rotation of the deflection rollers 9, 9' in accordance with the arrows 11. The scraper belt 11 includes an upper belt section 12 and a lower belt section 13, with the lower belt section 13 being movable on a rotation of the deflection rollers 9, 9' in the direction of an arrow 14.

The scraper belt 10 consists of a belt-like carrier element 15 on which plate-like drivers 16 standing substantially perpendicular to the belt-like carrier element 15 are secured at regular intervals. Portioning segments 17 are formed between the drivers 16 and are made permeable in the direction perpendicular to the belt-like carrier element A screening apparatus 19 formed as an oscillating screen 18 is so arranged beneath the scraper belt 10 that the lower edges of the drivers 16 of the lower belt section 13 contact the oscillating screen 18 and, with a movement of the lower belt section 13 along the arrow 14, scrape with a specific pressure over the surface of the oscillating screen 18. The oscillating screen can be moved to and fro via non-illustrated means in accordance with a double arrow 20 and include two screen zones 21, 22 with different screen openings 23, 24, with the screen openings 24 formed in the screen zone 22 being larger than the screen openings 23 formed in the screen zone 21. The s&reen zones 21, 22 can in this arrangement be formed for example as mesh screens, round-hole screens, elongate hole screens or as any other known screen types as desired.

A receiving apparatus 25 formed as a conveyor belt is arranged beneath the end of the oscillating screen 18 adjacent the deflection roller with the transport direction of the receiving apparatus extending perpendicular to the plane of the drawing.

A conveyor belt 26 is provided beneath the screening apparatus 19 and extends along its conveying direction indicated by an arrow 30 parallel to the direction of movement of the lower belt section 13 illustrated by the arrow 14.

The particles 3 led away by the carry out roller 7 from the metering hopper 1 fall through the portioning segments 17 of the upper belt section 12 of the scraper belt 10 until they land on the surface of the oscillating screen 18. Through the movement of the scraper belt 10 a metering of the continuous particle inflow is achieved on the surface of the oscillating screen 18 into individual particle portions which are arranged within the portioning segments 17, with the individual portions being moved by the drivers 16 over the surface of the oscillating screen 18 in the direction of the arrow 14.

On sweeping over the first screen zone 21, those particles 3' having dimensions smaller than the size of the screen openings 23 pass through the screen openings 23 formed in the oscillating screen 18 and fall onto the lower lying conveyor belt 26. In contrast those particles 3" having dimensions larger than the size of the screen openings 23 are shifted by the drivers 16 over the suiface of the oscillating screen 18 until they reach the second screen zone 22. On being swept over the screen zone 22 those particles 3" having dimensions smaller than the size of the screen openings 24 pass through the oscillating screen 18 and fall onto the lower lying conveyor belt 26. Particles which are larger than the screen openings 24, such as for an example excessively large fiber particles, lumps or foreign bodies fall onto the receiving apparatus 25 and are transported away by the latter after leaving the screen zone 22.

The particles 3" which pass through the oscillating screen 18 form a mat 27 on the conveyor belt 26, with the small particles 3' passing through the oscillating screen 18 in the region of the first screen zone 21 impinging first of all onto the conveyor belt 26 and thus forming a lower layer 28 of the mat 27. The large particles 3" which pass through the oscillating screen in the region of the second screen zone 22 fall onto the lower layer 28 formed by the small particles 3' and form an upper layer 29.

The mat 27 formed in this manner can be transported on the conveyor belt 26 in the direction of the arrow 30 to a non-illustrated pressing device and pressed in this device in known manner to form a board. In the context of the invention it is also possible and advantageous to arrange a further apparatus of this kind after the apparatus of Fig. 1 in mirrorimage like manner such that additional large particles 3" pass onto the mat 27 and onto them smaller particles, whereby one obtains a symmetrically build-up mat which can be pressed to a shaped article. An apparatus of this kind is described further below with reference to Fig. 3.

In accordance with the detailed view shown in Fig. 2 formations 31 are formed on the drivers 16 by which the drivers 16 are releasably secured to the belt-like carrier element The drivers 16 are flexibly designed so that the lower section 32 of the drivers 16, which scrape over the surface of the oscillating screen 18 during a movement of the lower belt section 13 along the arrow 14, adopt the curved shape shown in Fig. 2. As a result of the curved shape of the lower sections 32 of the drivers 16 a force directed in the direction of an arrow 33 act on the particles 3 arranged within the portioning segment 17 formed between the drivers 16 and has a component perpendicular to the surface of the oscillating screen 18. As a result of this force the particles 3 arranged within the portioning segments 17 are pressed in the direction of the oscillating screen 18, whereby the through-put through the oscillating screen 18 is increased. Furthermore, through the pushing movement of the drivers 16, a turn-over movement indicated by arrows 34 arises in the portions of the particles 3 arranged within the portioning segments 17, so that small particles disposed remote from the screen are conveyed as a result of this turn-over movement in the direction towards the surface of the oscillating screen 18 and can pass through the oscillating screen 18 through the screen openings 23.

Furthermore it is evident from Fig. 2 that clogging of the oscillating screen 18 is prevented by the drivers 16 which scrapingly sweep over the surface of the oscillating screen 18 so that a complicated cleaning of the oscillated screen 18 is not required.

In the embodiment shown in Fig. 3 in which elements identical to the apparatus of Fig. 1 are provided with the reference numerals used in Fig.

1, two scraper belts 34, 36 arranged in series in the longitudinal direction and each followed by a screening apparatus 39, 40 formed as an oscillating screen 37, 38 are provided instead of one scraper belt with a screening apparatus provided after it.

The scraper belts 35, 36 are designed substantially identically to the scraper belt 10 described in connection with Fig. 1 and are driven in opposite directions via the deflection rollers 9, 9' as is indicated by arrows 41 to 44.

The scraper belt 35 includes an upper belt section 45 and a lower belt section 46, with an intermediate floor 47 extending over the full width of the scraper belt 35 being arranged at the lower side of the upper belt section 45. The intermediate floor 47 is so positioned in this arrangement that the inwardly disposed edges of the drivers 16 contact the upper side of the intermediate floor 47 and are scrapingly guided over the intermediate floor 47 on a rotation of the scraper belt The intermediate floor 47 extends from the inwardly disposed deflection roller 9 up to shortly before the outwardly disposed deflection roller 9', with a region 49, which is permeable for the particles 3 in the direction perpendicular to the oscillating screen 37 being formed between the end 48 of the intermediate floor 47 and the outwardly disposed deflection roller 9'.

In the same manner the scraper belt 36 has upper and lower belt sections 51 with an intermediate floor 52 which is contacted by the inwardly disposed edges of the drivers 16 being provided at the lower side of the upper belt section 50 and with these edges being scrapingly guided over the intermediate floor 52 during a rotation of the scraper belt 36.

A pendulum distributor 53 is arranged in the region between the carry out roller 7 and the scraper belts 35, 36 and has two pendulum flaps 56 which can be swung along an arrow 54 about axes 55 as well as a wedgelike separating element 57 with two oblique surfaces 59, 60 the tip 53 of which is directed into the center between the axes Scattered material conveyed out of the metering hopper 1 by the carry out roller 7 is alternately directed by the same sense pivoting of the pendulum flaps 56 onto the respective oblique surfaces 59 and 60 of the wedge-like separating element 57, from which the particles 3 of the scattered material are respectively guided to the scraper belts 35 and 36 respectively.

The particles 3 fall onto the intermediate floors 47 and 52 respectively, with portions of the scattered material containing a certain quantity of 21 particles 3 being formed inside the portioning segments 17 each formed between two adjacent drivers 16. These portions are conveyed by the drivers 16 moving over the intermediate floors 47, 52 in the direction of the outwardly disposed deflection rollers 9' where they fall, after passing the ends 48, 61 of the intermediate floors 47, 52, downwardly through the open regions 49, 62 in the direction of the oscillating screens 37, 38.

The particles 3 falling onto the surface of the oscillating screens 37, 38 are fractionated in accordance with their size, as was already described in connection with Fig. 1, with a symmetrical mat 27 with two outer layers 63, 64 containing small particles 3' and an inner layer 65 containing large particles 3" being formed on the conveyor belt 26 in the embodiment of Fig. 3 as a result of the symmetrical layout with two mirror-image scraper belts 35, 36.

Particles which are too large are respectively deposited at the inwardly disposed deflection rollers 9 onto a receiving apparatus 25 and are transported away by the latter.

In the embodiment shown in Fig. 4, in which elements formed identically to Figs. 1 and 3 are again designated with the same reference numerals as in Figs. 1 and 3, an intermediate floor 66 is arranged beneath the upper belt section 50 with a further screening apparatus 68 adjoining its end 67 and with the inwardly disposed edges of the drivers 16 being scrapingly guided on a rotation of the scraper belt 36 both over the surface of the intermediate floor 66 and also over the surface of the further screening apparatus 68.

A screening apparatus 69 is arranged beneath the lower belt section 51 with the outwardly disposed edges of the drivers 16 being scrapingly guided on rotation of the scraper belt 36 over its surface.

The further screening apparatus 68 has screen openings 70 and the screening apparatus 69 has screen openings 71, with the screen openings being made larger than the screen openings 71.

Three receiving apparatuses 72, 73 and 74 are provided beneath the scraper belt 36, with the receiving apparatus 72 being located over the length and width of the screening apparatus 69, the receiving apparatus 73 being located in the region beneath the deflection roller 9' and the receiving apparatus 74 being located in the region beneath the deflection roller 9.

If particles 3 are dispensed in accordance with the arrow 4 onto the surface of the intermediate floor 66 and then the particles 3 are guided portion-wise through the drivers 16 of the scraper belt 36 over the surface of the intermediate floor 66 up to its end 67 and thus subsequently over the surface of the screening apparatus 68. Since the screen openings 70 of the screening apparatus 68 are relatively large essentially all particles 3 fall through the screen openings 70 onto the surface of the screening apparatus 69. Only particles which exceed a permissible maximum size defined by the size of the screen opening 70 are led up to the deflection roller 9' via the surface of the screening apparatus 68, where they subsequently fall into the receiving apparatus 73 and are further processed or separated out.

The particles 3 which impinge on the surface of the screening apparatus 69 are guided by the drivers 16 in individual portions over the surface of the screening apparatus 69 with particles 3' having dimensions smaller than the size of the screen openings 71 passing through these and being caught by the receiving apparatus 72.

Particles 3" of which the dimensions lie beneath the size of the screen openings 70 but above the size of the screen openings 71 are conveyed beyond the end of the screening apparatus 69 and drop into the receiving apparatus 74.

A separation of particles of different size is thus possible through the described apparatus. In this connection, instead of one screening apparatus 69, two or more screening apparatuses connected in series with differently sized screen openings can also be provided and in this case a separate receiving apparatus for catching the particles corresponding to the respective screen opening is present beneath each of these screening apparatuses.

In the embodiment shown in Fig. 5 elements already described with reference to Fig. 1 to 4 are provided with the same reference numerals.

As can be seen from Fig. 5 plate-like elements 80 are provided at the end faces of the drivers 16 and are connected via the formations 31 to the beltlike carrier element 15 formed as a link chain. The sealing elements have a substantially rectangular shape and a size such that in each case the ends of two adjacently disposed sealing elements 80 overlap when the associated drivers 16 are guided over the screening apparatus 19.

In the region of the deflection rollers 9, 9' the radially outwardly disposed edges of two adjacent sealing elements 80 move away from one another so that a V-shaped gap 81 arises between two adjacent sealing elements.

In order to enable a problem-free overlap of the sealing elements 80 the respective oppositely disposed overlapping zones 82, 83 of the sealing element 80 are arranged laterally offset relative to one another so that the overlapping zone 82 is offset to the outside and the overlapping zone 83 is offset to the inside, whereby the best possible friction-less overlapping of these end regions 82, 83 with the corresponding end regions 82, 83 of the adjacent sealing elements 80 is made possible.

The portioning segments 17 are substantially fully sealed off by the sealing elements 80 in both the upper and lower belt sections 12, 13 so that an emergence of particles or dust arranged in the portioning segments 17 is reliably prevented.

In the region between the upper and the lower belt section 12, 13 a middle sealing element 84 formed as a side-wall is provided, of which only the respective end regions 84' and 84" are shown in Fig. 5, as a result of the illustrated part-section. The middle sealing element 84 is in scraping contact at its upper and lower edges 85, 86 with the radially inwardly disposed edges of the sealing elements 80, so that a seal against emerging particles or dust takes place over the entire side surface of the scraper belt Thus it is ensured that the belt-like carrier element 15, for example formed as a link chain, and also the deflection rollers provided with teeth, as well as the further outwardly disposed elements of the apparatus, remain substantially dust-free.

An upper sealing plate 87 which is only partly shown in Fig. 5 is arranged above the upper belt section 12 and also prevents an escape of dust upwardly.

The screening apparatus 19 consists in the embodiment shown in Fig. 5 of five screen zones 75 to 79, each with differently sized screen openings, with the size of the screen openings increasing from the screen zone 75 to the screen zone 79. Depending on the application a different number of different screen zones can be provided in order to thereby control the structure and the quality of the mat produced with the apparatus.

The movement of the screening apparatus 19 formed as an oscillating screen 18 in accordance with the double arrow 20 is produced, in the illustrated embodiment, by a crank drive 88 the speed of rotation of which is preferably adjustable. The crank drive 88 comprises a crank rod 89 the end 90 of which is connected via a joint 91 to a roller guide 92.

The roller guide 92 includes a spatially fixedly arranged rail 93 provided with running rollers on which a roller block 94 is displaceably mounted.

The roller block 94 is connected to the screening apparatus 19 so that with a displacement of the roller block 94 along the rail 93 via the crank drive 88 the oscillating screen 19 is likewise shifted.

By means of the crank drive 88 a very easily moving and controlled to and fro movement of the screening apparatus is produced.

The link chain 15 can for example also be formed as a roller chain or as another suitable belt-like carrier element. In just the same way the sealing elements 80 can have a different form, so long as it is ensured that the -0 portioning segments 17 are substantially sealed off sidewise by the sealing elements 88, in particular when the drivers 16 sweep over the screening apparatus 19.

Fig. 6 shows an apparatus formed in accordance with the invention which corresponds substantially to the apparatus shown in Fig. 3. Instead of the intermediate floors 47, 52 shown in Fig. 3 two endless transport belts 96 are provided onto which the particles 3 conveyed out of the metering hopper 1 are brought via the pendulum distributor 53. The transport belts 96 are driven in the direction of the arrows 97, 98 so that the particles 3 lying on the transport belts 95, 96 are transported in the direction of the open regions 49, 62 and fall through the latter in the direction of the oscillating screen 37, 38.

Thus the same functionality can be achieved through the transport belts 95, 96 as through the intermediate floors 47, 52 shown in Fig. 3.

Advantageous in this respect is the fact that the friction present when using the intermediate floors 47, 52, between the lower edges of the drivers 16 and the intermediate floors 47, 52, and the wear associated therewith is avoided. The transport belts 95, 96 can be used in all embodiments instead of the intermediate floors so that an apparatus in accordance with Fig. 4 can also for example be built-up in a corresponding manner with transport belts.

In all described apparatuses a sifting of known kind, such as for.example a wind sifting, can be fundamentally effected in addition to the described screen sifting in order to further increase the quality of sifting. This can be achieved in that one wind sifting apparatus is arranged in each case between the described screening apparatuses and the conveyor belt lying beneath them.

Claims

2. Apparatus in accordance with claim 1, characterized in that at least some of the portioning segments each include a scraping element which contacts the surface of the screening apparatus and is scrapingly guided over the surface of the screening apparatus during the movement of the portioning segments.
3. Apparatus in accordance with claim 1, characterized in that the transport device is formed as an endless scraper belt.
4. Apparatus in accordance with claim 3, characterized in that the scraper belt is made permeable to the particles -28- at least over a partial region in a direction perpendicular to the surface of the screening apparatus. Apparatus in accordance with claim 3, characterized in that the scraper belt includes plate-like drivers which are provided at regular intervals on one or more endless chain- or belt-like carrier elements.
6. Apparatus in accordance with claim 5, characterized in that the drivers are releasably secured to the carrier element or to the carrier element and/or are made o e impermeable to air.
7. Apparatus in accordance with claim 5, characterized in S 15 that the drivers are arranged substantially perpendicular to the surface of the screening apparatus.
8. Apparatus in accordance with claim 5, characterized in :that the scraper elements are each formed by a section of oooo S: 20 the drivers. 9999 9e Apparatus in accordance with claim 5, characterized in that the drivers are made flexible in their sections forming the scraper elements. Apparatus in accordance with claim 5, characterized in that the drivers are made abrasion-resistant, in particular in their sections forming the scraper elements and in particular have an abrasion-resistant coating.
11. Apparatus in accordance with claim 5, characterized in that the drivers are made of a water repellent non- adherent material in their sections forming the scraper elements. -29-
12. Apparatus in accordance with claim i, characterized in that the screening apparatus includes two screen zones, with different screen openings.
13. Apparatus in accordance with claim 12, characterized in that the screen zones are arranged behind one another along the direction of movement of the portioning segments movable over the surface screening elements.
14. Apparatus in accordance with claim 13, characterized in that the screen openings of the screen zone or screen zones lying in the direction of movement of the portioning segments are larger than the screen openings of the screen zone or screen zones lying opposite to the direction of movement. 000 Apparatus in accordance with claim 3, characterized in that the endless scraper belt is guided over two e: deflection rollers so that a lower belt section extends oeeo S.20 directly on the surface of the screening apparatus and an upper belt section extends at a specific spacing from the ooo surface of the screening apparatus, in each case osubstantially parallel to the surface of the screening apparatus.
16. Apparatus in accordance with claim 3, characterized in that a receiving apparatus for the reception of separated out particles is provided at least at one end of the scraper belt in the region of the deflection rollers.
17. Apparatus in accordance with claim i, characterized in that at least one catcher device for the particles sifted through the screening apparatus is provided beneath the screening apparatus.
18. Apparatus in accordance with claim 15, characterized in that an intermediate floor is provided at least regionally between the upper and lower belt sections and in that the ends of the drivers opposite to the sections forming the scraper elements contact the intermediate floor so that they are guided on movement of the portioning segments scrapingly over the intermediate floor.
19. Apparatus in accordance with claim 18, characterized in that the intermediate floor extends from the one o deflection roller in the direction of movement of the *upper belt section to the other, oppositely disposed .9 9* S.deflection roller and in that a region is formed between 15 this other deflection roller and the end of the intermediate floor adjacent this other deflection roller and is permeable for the particles in a direction perpendicular to the surface of the screening apparatus. oo• 20 20. Apparatus in accordance with claim 19, characterized in that the region is formed as a further screening ree apparatus.
21. Apparatus in accordance with claim 3, characterized in that two scraper belts in particular scraper belts formed with mirror image symmetry are disposed lying behind one another in the longitudinal direction.
22. Apparatus in accordance with claim 21, characterized in that a distribution apparatus in the form of a pendulum distributor, is connected after the supply unit with which the particles led out from the metering hopper by the supply unit can be alternately supplied to the two scraper belts. -31-
23. Apparatus in accordance with claim 1, characterized in that the screening apparatus and/or the further screening apparatus is formed as an oscillating screen or as a vibrating shaking screen.
24. Apparatus in accordance with claim 23, characterized in that the oscillating screen can be moved to and fro via a crank drive.
25. Apparatus in accordance with claim 23, characterized in that the maximum stroke of the oscillating screen amount to between approximately 10 cm and 1 m.
26. Apparatus in accordance with claim 23, characterized in that the oscillating screen is shifted along a roller guide.
27. Apparatus in accordance with claim 23, characterized in oo o that the maximum speed of movement of the oscillating ooe• 20 screen in the transport direction is greater than the speed of transport of the portioning segments. oo
28. Apparatus in accordance with claim 21, characterized in .9 S"that the two scraper belts are driven in opposite directions, with the two upper belt sections being movable away from one another.
29. Apparatus in accordance with claim 1, characterized in that the portioning segments are made at least regionally closed at the side. Apparatus in accordance with claim 1, characterized in that lobe-like sealing elements are provided in the side regions of the portioning segments. -32-
31. Apparatus in accordance with claim 30, characterized in that the sealing elements are secured to the lateral end faces of the drivers.
32. Apparatus in accordance with claim 30, characterized in that in each case two sealing elements which follow one another in the transport direction overlap at least regionally whereby in each case a seal is produced which extends over the full width of a portioning segment.
33. Apparatus in accordance with claim 15, characterized in ooee that a middle sealing element, formed as a side wall, is arranged between the upper and lower belt sections 00 00 0 0C S" laterally outside of the portioning segments. 00 00
34. Apparatus in accordance with claim 33, characterized in that substantially the entire region between the upper and the lower belt section is laterally sealed by the middle sealing element. so** *o 35. Apparatus in accordance with claim 33, characterized in that respective middle sealing elements are provided at both sides outside of the portioning segments.
36. Apparatus in accordance with one of the claims 33, characterized in the middle sealing element is sealingly connected to the sealing elements which laterally close off the portioning segments and stands in sealing and scraping contact with moved sealing elements.
37. Apparatus in accordance with claim 15, characterized in that an upper sealing element formed as a wall section is provided above the upper belt section.
38. Apparatus in accordance with claim i, characterized in that a transport device is provided above the portioning -33- segments with which the particles which emerge from the metering hopper are transportable to a predetermined region above the screening apparatus.
39. Apparatus in accordance with claim 38, characterized in that the transport apparatus is formed as an endless transport belt. Apparatus in accordance with claim 39, characterized in that the fractionating apparatus is made movable in the longitudinal direction relative to the conveyor belt. 0000 r
41. Apparatus in accordance with claim 1, characterized in that middle layer roller scattering heads are provided 15 for the scattering of the middle layer of the mat in Sq addition to one or more fractionating apparatuses for the scattering of one or more covering layers. So
42. Apparatus substantially as herein described with 20 reference to the accompanying drawings. o c