The invention relates to the field of manufacturing of wood-based panels, primarily particleboards or fiberboards. More particularly, the invention relates to an improved dosing hopper and an improved forming station for use in the manufacturing of particleboards or fiberboards, in particular high, medium and low density fiberboards HDF, MDF and LDF. The invention further relates to a method for filling particles into a dosing hopper.

In the production of particleboards or fiberboards, there are used predominately flowable or free-flowing particles of differing sizes containing lignocellulose and/or cellulose, such as fibers, chips and the like. After having being provided with binder agents, these particles are discharged out of a dosing or metering hopper and delivered to a spreading head as a spreading apparatus, by means of a forming station. Through the spreading head, the particles, chips or fibers are spread to form a fleece or mat onto a continuously running forming belt, and are then formed to a finished panel in a subsequent pressing station, as is known for example from documents US 4,948,322 and US 6,695,605.

A very similar design is also used in a known forming station for medium density fiberboard„Forming Station MDF" manufactured Dieffenbacher Maschinen- und Anlagenbau GmbH in Eppingen, Germany, which forming station will be described in more detail with reference to Fig. 1 .

As shown in Fig. 1 , wooden particles, such as chips or fibers provided with a binder agent, are transported to a first cyclone 10, an outlet of which is connected to a first inlet 21 of an X-shaped mixing and distributing device 20. Inside the mixing and distributing device 20, there is arranged a flap 25 for switching the particle stream direction. The flap 25 can be actuated by an actuator 26 such as to be positioned in a first position, in which the particle stream entering through the first inlet 21 is guided to a first outlet 23 of the mixing and distributing device 20, and a second position, in which the particle stream entering through the first inlet 21 is guided to a second outlet 24 of the mixing and distributing device 20.

When the flap 25 is positioned in the first position, the particle stream is guided to exit the mixing and distributing device 20 through the first outlet 23 and falls onto a belt conveyor 30 also referred to as reject band for the particle stream to be transported to a dump collecting bin 35. This may for example be necessary in case of activation of a spark extinguishing system. This position may be used also for example when shutting down the forming station, respectively the entire manufacturing plant, e.g. in case of preparation for maintenance. The forming station and the entire manufacturing plant can thus be emptied from particles by dumping the particles still held in the cyclones 10, 12 into the dump collecting bin 35.

In normal operation, however, the flap 25 is positioned in the second position so that the particle stream is guided to exit the mixing and distributing device 20 through the second outlet 24, into a double-flap distributing unit 40 and through this distributing unit 40 into an inlet opening 51 of a dosing hopper 50.

Fig. 2 shows the double-flap distributing unit 40 in more detail. As shown in Fig. 2, the double-flap distributing unit 40 comprises two adjustable flaps 41 , 42, which are actuated by an actuator 45 such as to adjustably divert the position of the particle stream in a sideward direction, i.e. a direction perpendicular to the lengthwise direction of the dosing hopper 50. In this way, by actuating the adjustable flaps 41 , 42 as needed, the double-flap distributing unit 40 can effectively widen the width of the particle stream so as to cover essentially the entire width of the dosing hopper 50, respectively of the inlet opening 51 and thus ensure a substantially uniform filling of the dosing hopper 50 in the widthwise direction.

With reference again to Fig. 1 , the particle stream exiting the double-flap distributing unit 40 passes through the inlet opening 51 of the dosing hopper and impinges onto a plate element, also referred to as impinging table 52 that is arranged beneath the inlet opening 52 inside the dosing hopper 50. By providing the table 52, the particles passing through the inlet opening 51 at relatively high velocity impinge on the table 52 and in this way substantially loose their kinetic energy, so that it is prevented that the entering particle stream impinges directly onto the particles already held in the dosing hopper 50.

In the dosing hopper 50, there is also provided a striper device 53, which extends over substantially the entire width of the dosing hopper 50. The striper device 53 comprises striper elements 54, such as e.g. bars, paddles, rakes or the like, that are interlinked by e.g. chains 55 or steel cables that are guided around two drive rollers 56. The drive rollers 56 are rotatably driven in continuous fashion such as to move the striper elements 54 as indicated by the arrows. Moreover, the striper elements 54 of the striper device 53 pass above the table 52 in the direction toward the discharging end of the dosing hopper 50, and pass beneath the table 52 in the direction toward the rear end of the dosing hopper 50. As a consequence, particles that are deposited on and accumulate on the table 52 are moved in the direction of the discharge end of the dosing hopper 50, until the particles are moved beyond the extent of the table 52 in the longitudinal direction of the hopper 50, at which point the particles under influence of gravity drop down into be interior space of the dosing hopper 50 where the particles are temporarily held. When a sufficient amount of particles have accumulated on top of a floor belt 57, the particles reach up to the height of the striper device 53. By means of the striper device 53, new particle material that is fed into the dosing hopper 50 is hence striped and moved towards the back of the dosing hopper 50. The upper layer of the accumulated particle material is thus evened out, and it can be prevented that patches having a higher density, so-called pockets, occur within the stored particles, or that the upper particle layer exhibits irregularities transversely and longitudinally to the longitudinal axis of the dosing hopper 50. Particles are continuously discharged out of the dosing hopper 50 with the aid of a floor belt 57 and discharge rollers 58. In this context, the dosing hopper 50 has a width corresponding to at least the maximum board resp. panel width that is to be produced. The discharged particles are then transported through an outlet 59 to a spreading head 60, in order to then be spread onto a forming belt 70. Spreading rolls of a certain width are arranged in the spreading head, whereby these spreading rolls distribute the particles, chip or fibers to a fleece or mat 80 of a certain width onto the forming belt 70.

The fleece or mat 80 is then trimmed in height by means of a scalper roller 90, and the scalped off, and the excess particle material is recovered and transported to a second cyclone 12, which discharges the recovered particle material into the second inlet 22 of the mixing and distributing device 20. Within the mixing and distributing device 20, the stream of recovered particles is mixed with the stream of new particles discharged from the first cyclone 10 into the first opening 21 . The respective streams of new and recovered particles are thus effectively mixed within the distributing device 20 and are fed jointly into the dosing hopper 50, as described above.

This type of forming station offers the advantage of allowing to form high quality, and in particular highly uniform fleeces or mats at high levels of productivity. However, there is the drawback that because of the need to arrange the cyclones well above the dosing hopper, and the need for voluminous devices for handling the particle streams, in particular for mixing, routing or diverting the particle streams that need to be arranged in between the dosing hopper and the cyclones, this type of forming station typically requires large and voluminous, and hence costly, steel frame installations for carrying the various components. Moreover, the numerous components also require

considerable and costly maintenance.

It is therefore an object of the present invention to propose a dosing hopper and a forming station and a method for filling a dosing hopper having lower installation, operating and/or maintenance costs.

In a first solution, there is provided a dosing hopper for use in the production of boards of wood-based material, comprising: a plurality of inlet openings arranged on an upper side of the dosing hopper and respectively adapted to receive a stream of

lignocellulose and/or cellulose containing particles, the plurality of inlet openings comprising at least two inlet openings, each inlet opening being spaced from an adjacent inlet opening in a lengthwise direction of the dosing hopper; an impinging surface arranged inside and at an upper portion of the dosing hopper, wherein impinging surface is positioned beneath the plurality of inlet openings and spans at least over the cumulative length of the plurality of inlet openings so that the particles of each particle stream entering through the plurality of inlet openings impinge on the impinging surface; and conveying means adapted for moving the particles of the plurality of particle streams having impinged on the impinging surface in a direction towards a discharging end of the dosing hopper to then drop into a space for storing the particles in the dosing hopper.

In another aspect, there is provided a forming station for use in the production of boards of wood-based material, comprising the dosing hopper; and a plurality of cyclones arranged above the dosing hopper, the plurality of cyclones comprising at least two cyclones, wherein each cyclone is connected to a respective one of the inlets of the dosing hopper. Preferably, the impinging surface may be constituted by a table, and the conveying means may be constituted by a striper device comprising a plurality of striper elements adapted to be driven to move in a continuous movement, the movement encircling the table. Alternatively, the conveying means may be constituted by a belt conveyor device, wherein the belt of the belt conveyor device constitutes the impinging surface.

According to the aspects, the different particle streams are fed separately to the dosing hopper and are mixed inside the dosing hopper due to the action of the conveying means, in particular the action of the striper elements striping over the table, onto which the different particle streams impinge. It is therefore no longer necessary to provide separate means for joining and mixing the particle streams upstream of the dosing hopper, which allows positioning the cyclones at a lower height almost directly above the dosing hopper. In this way, the overall height of a forming station may be reduced by up to 15 m. Accordingly, the forming station can be constructed with less components and also less height, leading to a large reduction in masses that have to be carried and supported by steel frames, which in turn enables to also reduce the masses of the steel frames. This can result in a substantial reduction of tons of steel necessary to construct a forming station, leading to savings in installation time and costs. Moreover, by reducing the number of system components, it is also possible to avoid the installation, operating and (planned and unplanned) maintenance costs that would otherwise be associated with the (now omitted or simplified) system

components. By feeding the different particle streams separately into the separate inlet openings of the dosing hopper, and by mixing the different particle streams by means of the action of the striper device striping over the table, respectively and alternatively by the action of the conveyor belt moving the particles, it is also made possible to individually adjust (statically or dynamically, e.g. by means of diverting flaps) the distribution of the individual particle streams in the widthwise direction of the dosing hopper, thus enabling an additional degree of freedom for controlling and optimizing the overall straying distribution. In a preferred embodiment, the conveying means are further adapted to be operated in a dumping mode, in which the particles of the plurality of particle streams having impinged on the impinging surface are moved in the direction towards the rear end of the dosing hopper for the purpose of being dumped in a dump collecting bin. It is further preferred that the conveying means and the impinging surface both extend through the rear end opening to an outside of the dosing hopper, and the conveying means are preferably adapted to, in the dumping mode, move the particles of the plurality of particle streams having impinged on the impinging surface through the rear end opening and outside of the dosing hopper for being dumped. Alternatively, the dosing hopper may further comprise a moveable rear end that may be pivoted between a closed position and an open position, wherein in the open position of the rear end the conveying means may be operated in the dumping mode for dumping the particles of the plurality of particle streams having impinged on the impinging surface into a dump collecting bin. In this way, it is possible to obviate the need for a separate reject band. Preferably, each cyclone of the plurality of cyclones is connected to the respective corresponding inlet of the dosing hopper via a respective distributing unit. The distributing units may comprise at least one double-flap distributing unit and/or may comprise at least one distributing chute. Using double-flap distributing units allows for a greater level of control that may be exerted upon how the flow of particles of the corresponding particle stream should be distributed over the width of the dosing hopper. Conversely, using simple chutes has the advantage of a simpler and cheaper design, reducing cost and maintenance efforts required. Depending on the specific application's requirements, it is possible to choose separately with respect to each inlet opening, resp. with respect to each cyclone, whether it is more advantageous to utilize a double-flap distributing unit or a chute.

Preferably, the at least one distributing chute comprises at least one inclined portion, wherein an inclination of the inclined portion towards a vertical axis is preferably between 5 and 30 degrees, and preferably between 10 and 20 degrees. Angling the chutes, respectively providing inclined walls and portions in the chutes, has the effect that the particle stream is made more narrow in the longitudinal direction of the dosing hopper, which has shown positive effects with regard to further improving the quality of mixing the different particle streams.

In a preferred aspect, the at least one distributing chute comprises a viewing window or viewing opening allowing to inspect the impinging surface. It is thus possible for an operator to verify the operating status of the dosing hopper.

In another preferred aspect, the plurality of cyclones comprises at least two cyclones for newly prepared particle matter, and at least one cyclone for recovered particle matter, wherein the at least one cyclone for recovered particle matter is connected to an inlet opening located between the inlet openings to which the at least two cyclones for newly prepared particle matter are respectively connected. The fraction of recovered particle matter is thus mixed in between the fractions of newly prepared particle matter, resulting in more uniform mixing of the fractions.

Preferably, the forming station further comprises a spreading head for receiving the particles from the outlet of the discharge hopper and spreading the particles to a fleece or mat.

In a yet further aspect, there is provided a method for filling lignocellulose and/or cellulose containing particles into a dosing hopper of a forming station for the production of panels or boards of wood-based material, the method comprising:

providing, by a plurality of cyclones, a plurality of particle streams, supplying each of the plurality of particle streams directly and separately into a respective one of a plurality of inlet openings of the dosing hopper such as to impinge on an impinging surface, the plurality of inlet openings being arranged on an upper side of the dosing hopper, the plurality of inlet openings comprising at least two inlet openings, each inlet opening being spaced from an adjacent inlet opening in a lengthwise direction of the dosing hopper, the impinging surface being arranged inside and at an upper portion of the dosing hopper, the impinging surface being positioned beneath the plurality of inlet openings and spanning at least over the cumulative length of the plurality of inlet openings so that the particles of each particle stream entering through the plurality of inlet openings impinge on the impinging surface; and mixing the plurality of particle streams inside the dosing hopper by moving, with a conveying means, the particles of the plurality of particle streams having impinged on the impinging surface in a direction towards a discharging end of the dosing hopper to then drop into a space for storing the particles in the dosing hopper.

Preferably, the method further comprises operating the dosing hopper in a dumping mode, wherein the particles of the plurality of particle streams having impinged on the impinging surface are moved, by means of the conveying means, in the direction towards the rear end of the dosing hopper for the purpose of being dumped in a dump collecting bin.

The dosing hopper may preferably be a dosing hopper as described above.

Additionally or alternatively, the forming station may preferably be a forming station as described above.

Moreover, amongst the plurality of particle streams that are supplied by the plurality of cyclones, at least one particle stream may be a particle stream of newly prepared particle matter, and/or at least one particle stream may be a particle stream of returned particle matter, in particular particle matter that is returned from a scalper unit.

In a further preferred embodiment, the method further comprises broadening resp. fanning out one particle stream in a widthwise direction of the dosing hopper by means of a distributing unit that is arranged between the corresponding cyclone supplying the particle stream and the inlet opening that is receiving the stream. More preferably, more than one, and in particular all of the particle streams may be broadened resp. fanned out in this way by means of a corresponding plurality of distributing units. The invention will be described in more detail in the below with reference to the figures:

Fig. 1 shows schematically a forming station of the state of the art;

Fig. 2 shows the distributing unit of FIG. 1 ;

Fig. 3 shows schematically a forming station according to a preferred

embodiment;

Fig. 4 shows schematically a dosing hopper according to a further preferred

embodiment; and

Fig. 5 shows schematically a distributing chute according to an embodiment.

A forming station according to a preferred embodiment will now be described with reference to Fig. 3. As shown in Fig. 3, the forming station according to the embodiment comprises a dosing hopper 100. Different from the dosing hopper 50 of Fig. 1 , the dosing hopper 100 of this embodiment comprises not only one, but a plurality of inlet openings, exemplarily shown as four inlet openings 101 , 102, 103, and 104, which each may serve to introduce a respective particle stream into the dosing hopper 100. Preferably, each of the inlet openings 101 , 102, 103, 104 spans over substantially the entire width of the dosing hopper 100 and the inlet openings 101 , 102, 103, 104 are arranged at a distance from each other in the longitudinal direction of the dosing hopper 100.

Preferably, the inlets 101 , 102, 103, and 104 are arranged in the first half of the length of the dosing hopper 100. Moreover, the forming station comprises a plurality of cyclones, for example four cyclones 1 1 1 , 1 12, 1 13 and 1 14, as shown in Fig. 3, for receiving newly prepared particle material (in Fig. 3 e.g. cyclones 1 1 1 and 1 13) and for receiving recovered particle material (in Fig. 3 e.g. cyclones 1 12 and 1 14) that has been recovered and returned from the scalper unit (not shown in Fig. 3), and/or may be recovered and returned from air grading or lateral trimming operations performed downstream of the dosing hopper 100, and/or particle material that has been otherwise rejected and removed from the mat or fleece 80 (not shown in Fig. 3).

In the embodiment of Fig. 3, the respective particle streams discharged from the plurality of cyclones 1 1 1 , 1 12, 1 13, 1 14 are fed directly into the plurality of inlet openings 101 , 102, 103 and 104 by means of distributing units 121 , 122, 123, 124, which respectively serve the purpose of widening the particle streams in the widthwise direction of the dosing hopper 100 so that, at the inlet openings 101 , 102, 103, and 104, the particle streams have respectively been widened to extend over substantially the entire width of the inlet openings 101 , 102, 103, 104, resp. the entire width of the dosing hopper 100.

The distributing units 121 , 122, 123, 124 may be realized e.g. as double-flap distributing units, such as e.g. the double-flap distributing unit 40 shown in Fig. 1 .

Alternatively, some or all of the distributing units 121 , 122, 123, 124 may be realized as chutes, such as the distributing chute 130 (see Fig. 5), which may be equipped with metal plates arranged to effect a desired distribution of a particle stream. Chutes may be used for example for particle streams of recovered material, as the relative amount of recovered material will typically be only a small part of the total particle material flow into the dosing hopper 100, and/or may be used also for particle streams of newly prepared particles in case that the maximum width of the boards resp. panels that are to be produced are less than 8 feet in width, preferably less than 6 feet in width, as in this case it will be typically possible also with a chute to achieve a sufficiently uniform particle flow density over the extent of the inlet opening in the widthwise direction of the dosing hopper 100.

Thus, in the forming station of the embodiment, there is not performed a mixing and joining of the different, plural particle streams upstream of the dosing hopper, and accordingly, it is not necessary to provide separate devices for mixing and joining particle streams, such as e.g. the mixing and distributing device 20 shown in Fig. 1 . Instead, in the embodiment of Fig. 3, the plural particle streams are fed into the dosing hopper 100 separately through the respective inlet openings 101 , 102, 103, 104, and impinge on the table 105 at different locations corresponding to the different locations of the respective inlet openings 101 , 102, 103, 104. The different fractions of particle material that have fallen onto the table 105 are then mixed together due to the action of the striper device 106. For example, recovered particle material stemming from the cyclone 1 14 and having fallen onto the table 105 at the location beneath the inlet opening 104 is moved by the striper elements of the striper device 106 in the direction towards the discharging end of the dosing hopper 100 and in this course will be moved at a location on the table 105 that is beneath the inlet opening 103. At this position, the recovered particle material stemming from the cyclone 1 14 is mixed with newly prepared particle material that stems from cyclone 1 13 and falls through the inlet opening 103. The resulting mixture of newly prepared particle material and recovered particle material is then moved by the striper elements to a location beneath the next inlet opening 102, where it is mixed with recovered particle material stemming from cyclone 1 12, and that resulting mixture is then moved to a location beneath the next inlet opening 101 , where it is mixed with newly prepared particle material from cyclone 1 1 1 and thereafter is moved to the frontward end of the table 105 to then fall into the particle storage area inside the dosing hopper 100.

As further shown in Fig. 3, the dosing hopper 100 also comprises a floor belt 107 and discharge rollers 109 for continuously discharging particles out of the dosing hopper 100, whereby the discharged particles then may be transported through an outlet 1 10 to a spreading head 60 (not shown in Fig. 3) for forming a fleece or mat 80 on a forming belt 70 (not shown in Fig. 3). The formed fleece or mat 80 then may be trimmed in height by means of a scalper roller 90 (not shown in Fig. 3), and the excess particle material may be recovered and transported to the cyclones 1 12, 1 14.

The dosing hopper 100 according to this embodiment therefore allows different particle streams, and in particular also particle streams of different material fractions, to be supplied separately to the dosing hopper 100, and to perform a mixing and blending of these different particle streams and particle fractions within the dosing hopper 100.

Supplying the different particle streams (in particular also of different particle fractions) separately to the dosing hopper 100, and performing mixing and blending inside the dosing hopper 100, also offers the additional advantage that the different particle streams (of same or different particle fractions) may be adjusted separately, e.g. with regard to where, in the widthwise direction of the dosing hopper 100, one wants to have a larger or smaller particle flow density. This has the advantage of offering more control and optimization possibilities for further tuning and optimizing the quality and properties of the boards or panels that are to be manufactured. In the dosing hopper 100 of the forming station of the embodiment, the striper device 106 also is capable of moving not only in one direction only, but the moving direction may be reversed, as indicated by the double arrows. Also, the length of the striper device 106 as well as the table 105 is extended such that striper device 106 and table 105 both extend through an opening 108 in the rear end of the dosing hopper 100. Accordingly, particle material, that has fallen through the inlet openings 101 , 102, 103, 104 and onto the table 105 may be removed, by appropriately controlling the operating direction of the striper device 106, out of the dosing hopper 100 and e.g. dumped into a dump collecting bin 35. With such an arrangement, it is also no longer necessary to provide a separate reject band 30, as shown e.g. in Fig. 1 .

Accordingly, the forming station of the embodiment allows to significantly reduce the number of separate devices and units that otherwise would be necessary (cf. Fig. 1 ), and also allows to lower the position of the cyclones 1 1 1 , 1 12, 1 13, 1 14 as compared to what would have been required in the state of the art, resulting in significant material reductions for steel frames etc.

Although a preferred embodiment has been described in detail in the above, the present disclosure is not limited to the above embodiment.

For example, although in the above embodiment, the dosing hopper 100 has been described as comprising a table 105 and a striper device 106, the skilled person will understand that the same or similar effects may be achieved also with a belt conveyor device, wherein the belt conveyor device operates as conveying means for the particles that have fallen through the inlet openings 101 , 102, 103, 104 and thus achieves the same effect as the striper device 106, and wherein the belt of the conveyor belt device acts as a surface onto which the particles impinge upon, thus achieving the same effect as the table 105. Moreover, although the above description describes embodiments where the striper device 106 is operable in two directions, the present disclosure is not limited in this regard. For example, it is also possible to have the striper device 106 operating only in one direction, and thus not supporting a dumping mode. In this case, unwanted particle material may be removed from the dosing hopper 100 by known methods, such as by running the dosing hopper 100 empty through normal discharging operation through the spreading head 60 and/or by opening e.g. a door in the rear end of the dosing hopper 100 and removing unwanted particle material directly from the inside of the dosing hopper 100.

Also, although Fig. 3 shows an embodiment wherein the striper device 106 and the table 105 extend through an opening 108 at the rear end of the dosing hopper 100, the skilled person will understand that such is not necessary for implementing a dumping operation as described. For example, as shown in Fig. 4, it is also conceivable to equip the dosing hopper 100 with a moveable rear end 1 15, for example a rear end 1 15 that swings around a pivot axis, allowing to open the dosing hopper 100 at its rear side when a dumping operation should be performed.

It is also possible to provide a dosing hopper having only a single inlet opening, such as e.g. the dosing hopper 50 of Fig. 1 , with a striper device operable in two directions and thus supporting a dumping mode such as explained with regard to the above described striper device 106, and in this way obviating e.g. the need for a separate belt conveyor such as the reject band 30 of Fig. 1 .

List of reference numerals P 1564 WO

10, 12 cyclone

20 mixing and distributing device

21 first inlet

22 second inlet

23 first outlet

24 second outlet

25 flap for switching particle stream direction

26 actuator

30 belt conveyor

35 bin

40 distributing unit

41 , 42 flap

45 actuator

50 dosing hopper

51 inlet opening

52 table

53 striper device

54 striper elements

55 chain

56 drive roller

57 floor belt

58 discharge rollers

59 outlet

60 spreading head

70 forming belt

80 fleece or mat

90 scalper roller

100 dosing hopper

101 , 102, 103 104 inlet openings

105 table

106 striper device

107 floor belt 108 opening

109 discharge rollers

110 outlet

111, 112, 113114 cyclone

115 rear end

121, 122, 123, 124 distributing units

130 distributing chute