Wind scattering device

Abstract

The invention relates to a wind-based spreading device for spreading material (39) onto a spreading belt conveyor (4), comprising at least: - a wind-based spreading chamber (5) which has an upper spreading material opening (6) through which spreading material (39) is introduced into the wind-based spreading chamber (5), for example from a spreading material bunker (1), and wall and ceiling elements (27, 28); - one or more fans (7) for generating air currents for separating the spreading material (39) in the wind-based spreading chamber (5); - an air supply housing (8) through which the air currents generated by the fans (7) are directed into the wind-based spreading chamber (5); and - an air outlet unit (12) adjoining the air supply housing (8) in the direction of flow, with a plurality of outlet openings (14) arranged in slots and rows; and - a spreading belt conveyor (4) arranged below the wind-based spreading chamber (5), onto which a spreading material mat (38) can be spread.To prevent turbulence caused by air currents from the surroundings into the spreading chamber, it is provided that an ambient air barrier for the wind-blown spreading material chamber is provided at least below the air outlet unit (12) by means of an additional air supply (36).

Description

[0001] The invention relates to a wind-driven spreading device for spreading material onto a spreading belt conveyor, with at least a wind spreading chamber, which has an upper spreading material opening through which spreading material can be introduced into the wind spreading chamber, for example from a spreading material bunker, and wall and ceiling elements, one or more fans for generating air currents for separating the spreading material in the wind spreading chamber, an air supply housing through which the air currents generated by the fans are directed into the wind spreading chamber and an air outlet unit adjoining the air supply housing in the direction of flow with a multitude of outlet openings arranged in slots and rows, as well as a spreading belt conveyor arranged below the wind spreading chamber, onto which a spreading material mat can be spread.

[0002] For such a wind spreading device, DE102015112013A1 is used as the basis as the state of the art. Fig. 3Figure 1 shows an illustration of this known prior art, and the reference numerals used in DE102015112013A1 are retained in the new invention as far as possible for functionally identical components. A wind-based spreading device is generally integrated into a spreading system for the production of spreading mats for the manufacture of engineered wood panels, in particular wood-based panels. Wood-based panels refer specifically to particleboard made from wood chips. However, fiberboard made from wood fibers or annual plants, and sometimes also from synthetic products, is also included. The spreading mats, which are spread onto the spreading belt conveyor, are pressed into wood-based panels, for example, in a press, such as a continuous press or a batch press, using pressure and heat. The quality of the manufactured wood-based panels depends significantly on the quality of the material.The properties of the spreading material mats produced by the wind-based spreading device are crucial. The spreading material is typically adhesive, such as adhesive shavings, which are fed from a spreading material hopper or metering hopper to the wind-based spreading device.

[0003] A spreading system can have several spreading devices or heads, particularly when multi-layered spreading mats consisting of two top layers (e.g., of fine material) and a middle layer (e.g., of coarse material) are to be produced. The individual wind-feed spreading devices are then arranged one after the other along the conveying direction of the conveyor belt, so that first a top layer is spread onto the conveyor belt, then the middle layer onto the first top layer, and then the second top layer onto the middle layer. The wind-feed spreading device according to the invention is particularly well-suited for producing top layers within such a spreading system.The airflow generated in the air spreading chamber separates the chips. Coarser chips fall near the air outlet unit, which can be, for example, an air outlet, while finer chips fall towards the rear of the chamber, i.e., in the area furthest from the air outlet unit. Depending on the orientation of the air spreading device relative to the direction of travel of the conveyor belt, this process creates surface layers with chip sizes that become finer or coarser towards the surface of the mat. One or more chip screens can also be installed in the air spreading chamber to further optimize the separation process.

[0004] In practice, an embodiment of the described type is known in which the air volume flow is adjustable within certain limits. For example, two fans can be provided, arranged side by side, thus supplying air to two different widths of the air outlet unit. Manually adjustable valves can be integrated into the air supply housing to adapt the air distribution to the conditions and thus vary the distribution of the spreading material across the width of the mat. The wind-driven spreading device known from practice has generally proven effective, but it is capable of further development.

[0005] German patent DE 198 35 419 A1 discloses a wind-based spreading device in which several vertically arranged perforated plates are integrated into the air supply housing, which functions as a diffuser. Air is supplied to the spreading chamber via the last perforated plate in the direction of airflow. There, the particles introduced from above are sorted by size according to their trajectories by the airflow and fall onto the spreading belt conveyor. For the purposes of this invention, this last perforated plate is also considered a series of outlet openings. Dust particles are removed via discharge rollers or suction devices in DE 198 35 419 A1.

[0006] Above the spreading belt conveyor and well below the upper spreading material opening and below the air outlet units, prior art devices are provided that can divert coarse material, such as glue lumps, which is to be separated, and distribute only permissible chip sizes onto the spreading belt conveyor. DE102015112013A1 already uses a distribution roller screen and a coarse material discharge with a discharge screw for this purpose.

[0007] There are currently three main problems with the known wind dispersal systems.

[0008] First of all, one wants to prevent wood dust from settling on the wall or ceiling elements and then falling uncontrollably onto the conveyor belt.

[0009] Furthermore, the aim is to improve the removal of coarse material and lumps of glue that should not be spread along with the other materials and to minimize their influence on the spreading process.

[0010] Finally, there is an effort to prevent turbulence caused by air currents or negative pressure acting on the surface of the scattered mat.

[0011] The object of this invention is to create a wind scattering device of the type described above, with which the problems described are minimized and, in particular, turbulence due to air currents from the environment into the scattering chamber is prevented.

[0012] To solve this problem, the invention teaches that an ambient air barrier for the wind grit chamber is provided at least below the air outlet unit by means of an additional air supply.

[0013] An additional seal for the grit chamber can be achieved by creating a controlled airflow that prevents the ingress of outside air. This additional air supply is directed across the entire width of the grit, between the grit and the air outlet unit, towards the extraction point. The airflow is laminar and does not create turbulence on the mat surface, but has the advantage of sealing off the grit chamber below the air outlet unit from incoming or outgoing air.

[0014] Preferably, for this additional air supply, a portion of the air volume flow from the air outlet unit can be diverted by means of an air distribution element.

[0015] This eliminates the need for an additional fan. Furthermore, it is preferable if the volume flow of the additional air supply is adjustable.

[0016] It is advantageous if a pre-distribution of the spreading material and a coarse material discharge are arranged between the upper spreading material opening and the air outlet unit.

[0017] Previously, such distribution elements, for example rollers, and coarse material discharges, such as discharge screws for glue lumps, were located below the air outlet unit. The new arrangement eliminates obstructions within the air spreading chamber and allows for more targeted airflow. Simultaneously, the separation properties of the pre-distribution rollers / screen are utilized not only to filter out glue lumps but also to ensure a more even distribution of the spreading material through the numerous spreading slots at the top. Furthermore, the large number of spreading slots ensures that the spreading material is already separated and can be further improved by the airflow from the air outlet unit.

[0018] Advantageously, the pre-distribution is provided by a preferably horizontally arranged set of distribution rollers. Furthermore, it is preferred that the slot width between the distribution rollers is individually adjustable and that the slot width tends to increase in the direction of coarse material discharge.

[0019] The rotation of the distribution rollers allows the material thrown onto them to be either directed into the nozzle air stream or larger material particles to be transported closer to the coarse material discharge, which may be formed by a discharge screw. Particles up to a certain size are still thrown into the nozzle jet, while particles that are too large are removed in the coarse material discharge before they can interfere with the nozzle air discharge.

[0020] The distribution rollers can be constructed like similarly arranged spreading rollers in spreading systems without air classification, consisting of many discs and / or with spikes.

[0021] It is also advantageous if at least one wall or ceiling element is formed by a belt circulating around deflection devices and if a deflection device of the belt is adjacent to a dust extraction duct.

[0022] This ensures the easy removal of dust that has settled on the belt section forming the wall or ceiling area of ​​the air-spraying chamber. Otherwise, especially on fixed wall and ceiling elements, this dust could fall as coarse clumps onto the spraying belt conveyor. The belt sections forming the wall or ceiling areas should converge towards the extraction duct, thus helping to convey the settled dust into the extraction duct. A deflection roller, for example, is a cost-effective solution for this purpose. At least one of these rollers has a motor drive to ensure the smooth rotation of the belt forming the wall or ceiling area.

[0023] This design is particularly effective if at least a first and a second wall or ceiling element are formed by a first and second belt circulating around deflection devices, and if a deflection device of the first belt and a deflection device of the second belt are adjacent in such a way that an extraction channel for dust is formed between them.

[0024] This means that only one extraction channel is needed to collect the deposits, for example, on a wall and a ceiling element.

[0025] It is advantageous that a cleaning device for at least one belt is provided in the extraction channel.

[0026] This allows the dust to be actively removed from one or both belts simultaneously and vacuumed up immediately afterwards.

[0027] Preferably, the cleaning device comprises a rotating brush whose bristle spacing provides clearance for the passage of dust from the wind scattering chamber.

[0028] Such a rotating brush is easy to install and replace when worn. The cost is minimal. In a convenient arrangement between two deflection devices, the brush can clean both belts and direct the dust or glue particles into the extraction duct.

[0029] Preferably, the cleaning device also forms an airflow barrier.

[0030] This prevents excessively high air currents from the wind scattering chamber into the extraction duct, so that no disturbing turbulence can occur on the mat surface.

[0031] It is advantageous that at least one belt is guided parallel to the surface of the spreading mat or to the spreading belt conveyor over a section.

[0032] A small gap between a parallel belt and the mat surface or the spreading belt conveyor creates a type of labyrinth seal, preventing increased air inflow or outflow into the aeration chamber. This avoids unwanted turbulence of the spreading material on the mat surface. Such a section extends over a length of 0.2 to 1.0 m, depending on environmental conditions. The length of the parallel section can be calculated using virtual methods or determined experimentally. The invention thus ensures that stray air can no longer penetrate the aeration chamber over the already spread material. This prevents turbulence of the spreading material, which can render a plate unusable, and allows for higher air velocity extraction, which in turn has a positive effect on chip separation.

[0033] A particular advantage is the provision of a height adjustment device for the section of a belt parallel to the mat surface.

[0034] Since the desired thickness varies in the production of wood-based panels, and therefore also the height of the mat to be pressed, the gap can be adjusted as needed using the height adjustment device. This ensures the gap always maintains the desired minimum height, ranging from 1 mm to 20 mm. It is also possible to place the parallel section onto the mat, creating a complete seal to the area outside the air-spraying chamber. In this case, the belt is driven by a motor synchronized with the speed of the spraying belt conveyor.

[0035] Preferably, the return section of the belt used for the ceiling element can be used as a conveyor belt for the spreading material in the spreading material bunker located above the wind spreading chamber.

[0036] The band forming the ceiling element can thus easily take on a second task and transport the material within the grit bunker up to the upper grit opening.

[0037] The invention will now be explained in more detail with reference to a drawing that illustrates only one embodiment. The drawing shows: Fig. 1 shows a spreading system with a wind-driven spreading device according to the invention in a simplified side view, Fig. 2 shows a section of such a spreading system in a simplified side view, Fig. 3 shows a spreading system according to the prior art of DE102015112013A1. Identical components as in the embodiment according to the invention have the same reference numerals.

[0038] In Fig. 1A spreading material system for the production of spreading material mats for the manufacture of wood-based panels, in particular particleboard, is shown. This spreading material system has a spreading material hopper 1, which is designed as a metering hopper and discharges the spreading material 39, e.g., via return stripping rollers or metering rollers 2a, 2b, to a wind spreading device 3. The wind spreading device 3 spreads the spreading material onto the spreading belt conveyor 4, on which a spreading material mat forms. This mat is then pressed in a press under pressure and heat to form a wood-based panel, e.g., particleboard. Such a spreading material system typically has several wind spreading devices for producing multiple layers of a spreading material mat, e.g., surface layers and a middle layer. Fig. 1Only one area with a wind-spreading device 3 for generating a top layer of relatively fine shavings is shown as an example. This wind-spreading device 3 has a wind-spreading chamber 5, which has an upper spreading material opening 6 through which the spreading material enters the wind-spreading chamber 5 from the spreading material hopper 1. The wind-spreading device 3 also has several fans 7 for generating airflows to separate the spreading material in the wind-spreading chamber. An air supply housing 8 is arranged between the fans 7 and the wind-spreading chamber 5, through which the airflows generated by the fans 7 are directed into the wind-spreading chamber 5. The airflows in the wind-spreading chamber 5 separate the shavings, with coarser shavings falling into the area of ​​the wind-spreading chamber 5 facing the air supply housing 8 (e.g., the outer layer).B for the inner top layer) and finer chips fall into the rear area of ​​the wind scattering chamber 5, facing away from the air supply housing 8 (e.g., for the outer top layer). Two example flight paths for chips in . Fig. 1The flight path is shown. Trajectory A represents the smaller and lighter particles, while trajectory B represents the heavier particles. Additionally, screens 9 (chip screens) can be arranged in the air scattering chamber 5 in a generally known manner. These screens are positioned transversely to the flow direction and are equipped with vibrators to ensure optimal chip distribution and precise granulometric separation. In contrast to the prior art according to DE102015112013A1, a distribution roller screen 10 with a discharge screw 11 is provided above the flight path for the discharge of coarse material. Alternatively, a vibrating screen can be used instead of the distribution roller screen. For example, lumps of glue can be retained by the distribution roller screen 10 or a corresponding vibrating screen, which can then be removed by the discharge screw 11.The spreading material is also distributed better than before via the distribution roller screen 10 into the airflow of the air outlet unit 12, which can be, for example, an air outlet unit.

[0039] The air outlet unit 12 connects to the air supply housing 8 in the direction of flow, thus forming the transition between the air supply housing 8 and the wind scattering chamber 5. The airflows therefore exit the air supply housing at its end, pass through the air outlet unit 12, and from there enter the wind scattering chamber 5.

[0040] This air outlet unit 12 has a nozzle chamber 13 with a plurality of outlet openings 14 arranged in columns and rows.

[0041] Furthermore, the air outlet unit 12 has a register unit 16 located downstream of the nozzle chamber 13 in the direction of flow. This register unit has several register strips 17 arranged side by side, each corresponding to a column and having several openings 18 distributed along its height, which are corresponding to the outlet openings 14. These register strips 17 are height-adjustable to allow for variable outlet cross-sections of the air outlet unit 12. This means that the airflows do not always exit through the full outlet cross-section of the outlet openings, but rather – depending on the setting of the register strips 17 –

[0042] Basically, it is within the scope of the invention to provide not only two levels, but three or more levels of register strips, so that a very variable adjustment of the flow conditions becomes possible.

[0043] The register strips 17 are arranged on a common carrier 19, which is equipped with corresponding adjustment means 20. The adjustment is carried out manually, e.g. during commissioning, e.g. via screws, spindles or the like, but can also be equipped with adjustable drives.

[0044] Furthermore, in the Figure 2 It can be seen that the air outlet unit 12 has a plurality of outlet pipes 21, which are assigned to the individual outlet openings 14, the outlet pipes 21 being arranged downstream of the register unit 16 in the direction of flow. The air enters the wind scattering chamber 5 from these outlet pipes 21.

[0045] Furthermore, in Figure 1It is evident that the fans 7 generate vertically oriented airflows. In the exemplary embodiment, the fans 7 are designed as axial fans. The air supply housing 8, in the exemplary embodiment, is designed as a deflecting housing. It has a vertical housing section and a horizontal housing section, with a corresponding deflecting section in between. Consequently, in the deflecting section, the airflows are deflected by 90° from the vertical to the horizontal.

[0046] The flow conditions can be further optimized by using guide vanes 25 and diffuser plates. Guide vanes 25 are arranged in the vertical housing sections, each assigned to one of the individual fans 7. These vanes are oriented approximately parallel to the flow direction and, consequently, in the exemplary embodiment, are oriented vertically. Guide vanes 25 can also be provided at the nozzle outlet.

[0047] As usual, an extraction channel 15 for excessively small dust particles is arranged on the side of the wind scattering chamber 5 opposite the air outlet unit 12.

[0048] In contrast to the solid walls of the wind scattering chamber 5 of the prior art, in the embodiment according to the invention, Figure 1 A first belt 29, rotating over deflection rollers 32, forms a first wall or ceiling element 27, and a second rotating belt 30 forms a second wall or ceiling element 28. The belts 29 and 30 can be made of metal or plastic, for example, and extend across the entire width of the wind scattering chamber. Naturally, the wall or ceiling elements can also consist of several rotating belts arranged side by side or one behind the other.

[0049] In the embodiment according to the invention, the extraction channel 15 is integrated between a deflection roller of the first circulating belt 29 and a deflection roller of the second circulating belt 30. This has the advantage that, with the correct direction of rotation of the belts 29 and 30, the chips and dust particles adhering to the first wall or ceiling element 27 and the second wall or ceiling element 28 are transported directly to the extraction channel. There, they are extracted and, if necessary, recycled. A cleaning device in the form of a brush 33 arranged in the extraction channel is also helpful. The brush can clean both belts 29 and 30. Its bristle spacing is designed so that the extraction of dust from the wind-spreading chamber 5 remains easily possible. The brush also acts as a barrier to prevent strong air currents that could potentially lead to undesirable turbulence in the area of ​​the spreading mat.

[0050] Two further measures have been taken for the same purpose of preventing unwanted air currents.

[0051] First, the first circulating belt 29 runs parallel to the spreading belt conveyor 4 or the spreading mat 38 at a short distance. This creates a labyrinth seal against ambient air. To adapt to the height of the spreading mat 38, a height adjustment device, indicated only by arrows 35, is provided. Two deflection rollers 32 pivot upwards or downwards around a radius center point to keep the belt taut.

[0052] Secondly, an ambient air barrier for the wind-dispersed grit chamber is provided at least below the air outlet unit by means of an additional air supply 36. The supply air volume is diverted from the wind-dispersed air and is adjustable via a slide valve 40. The supply air flows towards the extraction point and essentially acts as a seal against outside air. The uniform laminar flow prevents turbulence on the grit mat surface.

[0053] In another aspect, the circumferential second belt 30 forming the ceiling element 28 is used in the return as a conveyor belt 34 for spreading material 39 in the dosing bunker 1. Reference symbol list

[0054] 1 grit bunker 2a scraper rollers 2b Metering roller 3 Wind scattering device 4 Spreader conveyor 5 Wind scatter chamber 6 Upper grit opening 7 Fans 8 air supply housing 9 Sieves (chip sieves) 10 Distribution roller screen, pre-distribution 11 discharge screw, coarse material discharge 12 Air outlet unit 13 Nozzle chamber 14 Outlet openings 15 extraction duct 16 Register unit 17 Register strip 18 Openings 19 carrier 20 Adjustment device 21 Outlet pipes 22 Vertical housing section 23 Deflection section 24 Horizontal housing section 25 Guide plate 26 diffuser plate 27 First wall or ceiling element 28 Second wall or ceiling element 29 First circumferential band 30 Second circumferential band 31 Parallel section of the band 32 Deflection device, deflection roller 33 Cleaning device, brush 34 Conveyor belt, return run of the ceiling belt 35 Height adjustment device 36 Additional air supply 37 Air distribution element 38 grit mat 39 grit 40 Slider A Flight path of lighter chips B Flight path of heavier chips

Claims

1. An air classifier for the spreading of spreading material (39) onto a spreading material conveyor (4), with at least - one air classifier chamber (5), which comprises an upper spreading material opening (6), via which spreading material (39) can be brought into the air classifier chamber (5), and wall and ceiling elements (27, 28), - one or more fans (7) for producing air flows for the separation of the spreading material (39) in the air classifier chamber (5), - an air supply housing (8) through which the air flows produced by the fans (7) is directed into the air classifier chamber (5) and - an air outlet unit (12) adjoining the air supply housing (8) in the flow direction with a plurality of outlet openings (14), arranged in columns and rows as well as - a spreading material conveyor (4) arranged below the air classifier chamber (5) onto which a spreading material at (38) is spreadable, characterised in that an ambient air barrier is provided for the air classifier chamber, at least under the air outlet unit (12), by way of an additional air supply (36).

2. The air classifier according to claim 1, characterised in that for this additional air supply (36), a part of the air volumetric flow can be branched off from the air outlet unit (12) by means of an air distribution element (37).

3. The air classifier according to claim 1 or 2, characterised in that the volumetric flow of the additional air supply (36) is adjustable.

4. The air classifier according to any one of claims 1 to 3, characterised in that a pre-distributor (10) of the spreading material (39) and a coarse material discharge (11) are arranged between the upper spreading material opening (6) and the air outlet unit (12),5. The air classifier according to claim 4, characterised in that the pre-distributor (10) is formed by a horizontally arrange distribution roller screen.

6. The air classifier according to claim 5, characterised in that the slit width between the distribution rollers is individually adjustable.

7. The air classifier according to claim 5 or 6, characterised in that the slit width increases, at least tendentially, in the direction of the coarse material discharge (11).

8. The air classifier according to any one of claims 1 to 7, characterised in that at least one wall or ceiling element (27, 28) is formed by a belt (29, 30) circulating about deflection devices (32) and in that one deflection device (32) of the belt (29, 30) is adjacent to an extraction channel (15) for dust.

9. The air classifier according to claim 8, characterised in that at least one first wall or ceiling element (27) is formed by a first belt (29) circulating about deflection devices (32) and a second wall or ceiling element (28) by a second belt (30) circulating about deflection devices (32) and in that one deflection device of the first belt and one deflection device of the second belt are adjacent to each other in such a way that an extraction channel (15) for dust is formed between them.

10. The air classifier according to claim 8 or 9, characterised in that in the extraction channel (15) a cleaning device (33) for at least one belt (29, 30) is provided.

11. The air classifier according to claim 10, characterised in that the cleaning device (33) comprises a rotating brush, the bristle spacing of which ensures clearance for the passage of dust from the air classifier chamber (5).

12. The air classifier according to any one of claims 10 to 11, characterised in that the cleaning device (33) also forms an air flow barrier.

13. The air classifier according to claim 8 to 12, characterised in that over one section (31) at least one belt (29, 30) is guided in parallel to the surface of the spreading material mat (38) or to the spreading conveyor belt (4).

14. The air classifier according to claim 13, characterised in that for the section (31) of a belt parallel to the surface of the spreading material mat (38), a height adjustment device (35) is provided.

15. The air classifier according to any one of claims 8 to 14, characterised in that the return run of the belt (30) used for a ceiling element, is usable as a conveyor belt (34) for the spreading material (39) in the spreading material hopper (1) arranged above the air classifier chamber (5).

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