EP2089197B1 - Method of pressing pressing-material mats - Google Patents

Description

The invention relates to a method for pressing Pressgutmatten in the course of the production of wood-based panels in a continuous press, wherein the continuous press upper and lower heating plates, inlet side projecting upper and lower inlet plates to form a Einlaufmauls with inlet gap and in press upper part and press base endlessly circulating steel press belts , which are supported with the interposition of rolling rods on the inlet plates and the heating plates, wherein the inlet gap height of the inlet gap and possibly the inlet contour of the inlet plates are set and wherein an upstream in one of the press scattering station produced and optionally pretreated pressed material mat with a certain mat height and a specific Mat density or specific basis weight is introduced into the continuous press and pressed. In this case, there is the possibility that the pressed material mat is pre-compressed in the inlet mouth in a pre-compression zone upstream of the inlet plates up to an inlet gap height h ₀ and then pressed in the region of the inlet plates and finally the heating plates. Einlaufspalthöhe means in the invention, the height of the press nip or the inlet gap in the region of the leading edge of the upper and / or lower inlet plate or in the region of the axis or shaft of the upper and / or lower Einführungsrades for the rolling rods. - Wood-based panels means in the context of the invention, in particular fibreboard, (eg MDF boards), chipboard or OSB boards (Oriented Strand Board). The inlet plates are preferably designed as heatable Einlaufheizplatten. Furthermore, it is preferably highly flexible inlet plates, wherein the upper inlet plate and / or the lower inlet plate for adjusting the inlet contour is acted upon by a plurality of cylinder piston assemblies.

Processes for the production of wood-based panels in continuous presses are known in various embodiments. There is always the need to produce wood-based panels with impeccable quality as economically as possible. For this reason, in a known method or a known press of the type described above, the pressed material mat precompressed already before the inlet plates in a Vorkompressionszone so that the heated inlet plates are then available over their entire plate length for the temperature pressure buildup in the pressed material mats, since excess air is already blown out in the pre-compression zone. The Vorkompressionszone is thereby formed by a range of steel press belts, which are supported on the inlet plates upstream rollers or belt support rollers, which can take over the function of press rollers here (see. DE 102 14 322 A1 ). The extent known measures have proven in principle.

In order to avoid damage to the press during operation, it must be ensured that the compression is kept within the range of possible pre-compression. For this reason, it has been observed in practice that the inlet gap height does not fall below a certain minimum value, this minimum value having been selected taking into account the mat height of the incoming spreading material mat (eg 75% of the mat height).

Also known is a plant for the production of wood-based panels, in which the upper heatable inlet plate is subdivided to form joints in plate sections, so that the inlet contour of the inlet mouth has kinks in the joint areas. The infeed system is preceded by a position measuring system which measures the chip / fiber mat height with a displacement sensor and forwards it to a computer. The measured value is the manipulated variable for the hydraulic actuators for the upper inlet plate sections (cf. DE 43 01 594 A1 ).

The invention has the object of providing a generic method for pressing pressed material mats in a continuous press of the type described above in such a way that you can work in the inlet mouth with high densities without damage or disturbances are to be feared.
To solve this problem, the invention teaches in a generic method for pressing Pressgutmatten in the course of the production of wood-based panels in a continuous press that checks the Einlaufspalthöhe depending on the density and / or the basis weight of the pressed material mat, adjusted and / or regulated. The invention is based on the recognition that it is expedient if the inlet gap height, z. B. in the region of the insertion, not depending on the mat height of the scattered mat, but in dependence on the density or the basis weight of the mat is adjusted. Consequently, a "density-guided" driving style is proposed. Thus, the invention proposes that the described review, adjustment and / or regulation taking into account a predetermined target basis weight occurs. Because in the course of spreading the grit mat is usually entered by the operator at a given Formstraßengeschwindigkeit a target value for the basis weight, the actual basis weight is used to control the spreader or control. The setting according to the invention of the desired setting height h ₀ can then be carried out on the basis of this predetermined setpoint value of the basis weight of the spreading material mat, since this setpoint value is constant as a pure default value at least over a certain period of time. Target weight or target surface weight means in the context of the invention, in particular the so-called "pushed" target surface weight, the addition "pushed" makes it clear that z. B. the belt scale for determining the target basis weight is arranged upstream of the inlet gap with a predetermined distance. It is therefore taken into account in the review or setting the time delay between the time of setting the target weight and the time at which the relevant mats section enters the inlet gap. The setting based on the setpoint has the advantage that it does not have to respond to any weight fluctuation.

However, the invention also encompasses those method variants in which the inlet gap height is checked, set and / or regulated as a function of the actually set basis weight actually set. For this purpose, the invention proposes that the weight per unit area of the mat is (continuously) measured continuously in front of the inlet mouth and the inlet gap height is then regulated (continuously) as a function of these measured values. Immediately before the inlet mouth means within the scope of the invention, an area in front of the inlet mouth, which no further processing of the mat and in particular no further compression follows, before it then enters the inlet mouth of the press.
Consequently, the invention proposes a "density-guided mode of operation", ie the inlet gap height, or its permissible minimum value, is no longer checked (exclusively) taking into account the mat height of the incoming press material mat and adjusted, if necessary, but a setting takes place taking into account the setpoint values. or actual basis weight. The invention is based on the recognition that the pressing process can be carried out very effectively if a strong compression already takes place in the inlet mouth and possibly even in the region of a pre-compression zone in front of the inlet plates. Now, for example, grit mats with Pressed relatively low density, it can be done within the scope of the invention, a relatively strong precompression, which would have been previously inhibited in only one evaluation of the mat height. A perfect adaptation of the inlet gap height to the properties of the pressed material mat can always be carried out, with the invention as a whole starting from the knowledge that a more exact adaptation of the inlet gap height becomes possible taking into account the weight per unit area. If, on the other hand, press material mats having a relatively high density and low mat height are pressed, which have been pretreated, for example, in a strong (separate) pre-press, then there is the possibility within the scope of the invention that the inlet gap height be chosen such that a further pre-compression in the pre-compression zone is completely dispensed with. Consequently, the method according to the invention functions independently of whether working with non-pre-pressed or only slightly pre-pressed mats or with strongly pre-pressed pressed material mats.
In the context of the invention, there is the first possibility that "only" a check takes place, whether the set inlet height is allowed taking into account the determined basis weight or not. In this case, the continuous press in a conventional manner be preceded by a controllable Fehlschüttungseinrichtung. According to the invention, this defective filling device is controlled with dependence on the basis weight and / or the inlet gap height. Such a misfire device usually consists of a misfed hopper arranged below the mat transport and an adjustable strip section arranged above it, so that the grit mat produced is dropped into the hopper with the hopper open and is fed to the press only in the case of the "closed" hopper. If the spreading operation is started, then within the scope of the invention there is the possibility that the defective filling device will not be closed until the set inlet gap height is within the given value Way corresponding to the basis weight. According to a preferred development is not only a simple check, but a control of the inlet gap height, ie the inlet gap height is adjusted taking into account the (determined) basis weight, possibly several times or virtually continuously or at predetermined time intervals or continuously. Finally, there is also the possibility that a "real" regulation of the inlet gap height is effected as a function of the weight per unit area. For this purpose, it is expedient that the inlet gap height is determined with a suitable measuring device and fed into the control process.
According to a further proposal of the invention, it is then provided that the inlet gap height is set or regulated at a desired or actual basis weight with the proviso that the nominal density ρ _{0 of} the mat in the area of the inlet gap does not exceed a maximum predetermined limit value ρ _max exceeds.

According to the embodiment, however, it is possible to dispense with a height measurement, so that the inlet gap height is then adjusted or regulated only as a function of the desired or actual basis weight (in kg / m ² ). The invention is based on the recognition that in the area of the inlet gap a certain maximum density must not be exceeded. From the quotient of the weight per unit area on the one hand and the inlet gap height on the other hand, the density of the mat produced in the area of the inlet gap is obtained directly. In other words, the inlet gap height results from the quotient of the one hand (nominal) basis weight and on the other hand the maximum mat density ρ _max . This can be a real one Density measurement of the mat before entering the press be waived. In operation, therefore, the infeed gap height is automatically set at a certain target basis weight in consideration of the maximum denomination density input to a controller. If the nominal basis weight is changed, then an automatic adjustment of the inlet gap height takes place.
The invention proposes that in the course of the production of OSB boards, the maximum permissible mat density in the region of the inlet gap 100 to 200 kg / m ³ , preferably 150 to 200 kg / m ³ , z. B. is about 160 kg / m ³ . Consequently, a desired value for the mat density in the region of the inlet gap is predetermined, and then the inlet gap height is set taking into account the respective weight per unit area (eg desired basis weight).
In the course of the production of MDF boards, the maximum mat density in the area of the inlet gap is z. B. 100 to 200 kg / m ³ , preferably 150 to 200 kg / m ³ , z. B. 190 kg / m ^3.
In the course of the production of chipboard, the maximum mat density in the region of the inlet gap is preferably 200 to 350 kg / m ³ , z. B. 250 to 300 kg / m ³ . An article not according to the invention is an apparatus for pressing pressed material mats during the production of wood-based panels in a continuous press. This device comprises a continuous press with press base and press top, in the press base and press top endlessly circulating steel press belts and with an inlet mouth, wherein in the press base and the press upper part each have a heatable pressure plate or hot plate is arranged and on the heating plates inlet side projecting heatable inlet plates under education connect the inlet mouth and the steel press belts are supported on the press plates and inlet plates with the interposition of rolling rods. In the inlet mouth, the inlet plates may possibly be preceded by a precompression zone, in which the mat is optionally precompressible to the inlet gap height. Furthermore, a device for adjusting the inlet contour of the inlet mouth and the inlet gap height is provided. In such a device, it is provided that the continuous press is preceded by at least one mat measuring device for determining the density and / or the basis weight of the spreading material mat. In addition, an inlet gap measuring device may be provided for determining the height of the inlet gap. The mat measuring device can be composed of a surface weight measuring device (eg belt scale) on the one hand and a height measuring device (eg one or more laser measuring devices) on the other hand, the density being determined from basis weight and height. If the mat measuring device only serves to determine the weight per unit area, then a belt scale is sufficient without further height measuring devices.
According to a particularly preferred embodiment, a control / regulating device is further provided, which is connected to the mat measuring device and / or with the inlet gap measuring device and with the device for adjusting the inlet gap height and optionally the device for adjusting the inlet contour.

Fig. 1

eine Vorrichtung zur Herstellung von Holzwerkstoffplatten mit einer kontinuierlichen Presse,

Fig. 2

einen Ausschnitt aus der Vorrichtung nach Fig. 1 und

Fig. 3

eine abgewandelte Ausführungsform des Gegenstandes nach Fig. 1.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment. Show it

Fig. 1

a device for producing wood-based panels with a continuous press,

Fig. 2

a section of the device according to Fig. 1 and

Fig. 3

a modified embodiment of the article according to Fig. 1 ,

In Fig. 1 is a detail of a device for pressing Pressgutmatten shown to wood-based panels. The core of such a system is a continuous press 1. This has in its basic structure a press base 2 and a press top 3, in the press base and press top endlessly circulating steel press belts 4, 5 and an inlet mouth 6, wherein in the press base 2 and in the press upper part 3 each one heated pressing plate or heating plate 7, 8 is arranged and to the heating plates 7, 8 on the inlet side projecting heatable inlet plates 9, 10 to form the inlet mouth 6. The steel press belts 4, 5 are supported on the press plates 7, 8 and inlet plates 9, 10 with the interposition of rolling rods 11. In the area of the inlet mouth 6, the rolling rods 11 are guided over rolling rod insertion wheels 12, 13. Furthermore, a device 14 for adjusting the inlet mouth or for adjusting the inlet gap height h _{0 is} provided. In addition, a device 15 for adjusting the inlet contour of the inlet mouth 6 and for adjusting the inlet contour of the inlet plates 9, 10 is provided. This device 15 for adjusting the inlet contour has a plurality of predetermined distribution to the inlet plates connected cylinder piston assemblies 16, which are preferably designed as double-acting differential piston arrangements, with both tensile forces and compressive forces can be transferred to the highly flexible inlet plates 9, 10.

Infeed gap height h ₀ in the context of the invention means either the inlet gap height in the region of the front edge of the upper and / or lower inlet plate 9, 10 or (preferably) the inlet gap height in the region of the axes A of the upper and / or lower insertion gears 12, 13 for the rolling rods 11 In practice, these two points are very close together.

In the figures, it is further indicated that the inlet plates 9, 10 may be preceded by a Vorkompressionszone V in the inlet mouth 6, in which the Pressgutmatte M is precompressed from its Ausgangsmattenhöhe h _M to the extent of the inlet gap height h ₀ . This Vorkompressionszone V is formed in the embodiment of a range of steel press belts 4, 5, which are supported in the region of the inlet mouth 6 of rollers or belt support rollers 17. Part of a plant for the production of wood-based panels is usually one or more scattering stations for the production of the grit mat. Such a spreading material mat can then be pretreated, for. B. be precompressed in a pre-press. These components are not shown in the figures.

According to Fig. 1 and 2 is now the continuous press 1 a mat measuring device 18 for determining the basis weight F _{M of} the spreading material mat M upstream. Basis weight F _{M of} the spreading material M here means the basis weight of the material to be spread immediately before entering the continuous press 1, ie the basis weight of a scattered and optionally in a (not shown) pre-press pre-pressed grit mat. In the exemplary embodiment, the measuring device 18 is designed as a belt scale. Furthermore, in the figures, a control or regulating device 19 is indicated, which on the one hand with the described measuring devices 18 and on the other hand with the device 14 for adjusting the inlet gap height h ₀ and optionally with the device 15 for Setting the inlet contour of the inlet mouth is connected. This control / regulating device can be designed as a computer.

Incidentally, the device usually has a faulty means, not shown, which has a below the strip running Fehlschüttungspichter or the like, which can be opened to drop the mat and closed for transport of the mat in the direction of the press. Then there is the possibility that this controllable defective bulk means is also connected to the control and / or regulating device 19.
With the help of the belt scale 18 can be, for. B. at first open Fehlschüttungseinrichtung determine the basis weight F _{M of} the spreading material in the course of startup of the system. It is now possible to adjust the inlet gap height h ₀ taking into account this determined basis weight such that the density ρ _{0 of} the mat in the inlet gap a certain limit of z. B. does not exceed 150 kg / m ^3. In the sense of a relatively simple check can thus be ensured that the misfire device is not closed until basis weight F _M on the one hand and inlet gap height h _{0 are} on the other hand in a reasonable ratio. In the context of the invention, however, the inlet gap height h ₀ is preferably adjusted continuously or quasi-continuously as a function of the determined density ρ _M or the determined basis weight F _M. If the inlet gap height h _{0 is} detected metrologically, a real control process can be performed.
It is always ensured that the infeed gap heights are optimally adapted to the determined mat thicknesses, so that the system can be operated under perfect conditions without the risk of damaging the system.

A modified embodiment of a device is to be based on Fig. 3 be explained. This shows schematically a plant for the production of thin wood-based panels, z. B. thin MDF boards or thin chipboard. The scattering station is not shown. After the scattering station, a first height measurement H ₁ and a measurement of the weight per unit area can be made with the belt scale 18. This belt scale 18 is now not arranged directly in front of the press inlet, but following the scattering station. This belt weigher primarily serves to control or regulate the scattering station. This is followed by a first prepress V ₁ , which compresses the mat to a height h ₂ . Subsequently, a further pre-pressing takes place in the area of the pre-press V ₂ on a mat height h ₃ . Immediately before the entry into the continuous press 1, a determination of the height of the mat h _M can take place with the aid of a height measuring device 20. The mat height h ₀ in the region of the inlet gap is also indicated. As already explained, the inlet gap height h ₀ can take place taking into account the setpoint specification for the mat weight F _soll and taking into account a predetermined maximum value ρ _max for the nominal density ρ _{0 of} the mat in the region of the inlet gap. This maximum value is stored in the controller 19 as value X, so that the inlet gap height h _{0 is set} as the quotient of F _soll on the one hand and X on the other hand. The different plant conditions can be accommodated by depositing different values X. If then during operation a specific desired basis weight is adjusted or the desired basis weight is changed, an automatic adjustment of the height h ₀ is then carried out, so that a perfect operation is always guaranteed. The controller 19 is in Fig. 3 not shown.

Claims (13)

1. Method of pressing pressing-material mats during the production of wood-based boards in a continuous press (1)
   wherein the continuous press (1) comprises upper and lower heating plates (7, 8), upper and lower inlet plates (9, 10) projecting at the inlet side and forming an inlet opening (6) with an inlet gap, as well as in the upper part (2) of the press and the lower part (2) of the press continuous circulating steel pressing bands (4, 5) which with the intermediate arrangement of roller bar (11) are supported on the inlet plates (9, 10) and the heating plates (7, 8),
   wherein the height (h₀) of the inlet gap is adjusted,
   and wherein a pressing-material mat (M) produced in a forming station upstream of the press (1) is introduced into the continuous press (1) and pressed,
   wherein observing a nominal weight per unit area (F_nominal) the pressing-material mat (M) is produced with an actual weight per unit area (F_actual), characterised in that

   the actual weight per unit area (F_actual) is measured continuously before the inlet opening and in the inlet gap height (h₀) is set or adjusted as a function of these measured values,
   or

   in that the inlet gap height (h₀) is set or controlled with the proviso that the inlet gap height (h₀) is determined from the nominal weight per unit area (F_nominal) on the one hand and the maximum permissible mat density (p_max) on the other hand in the area of the inlet gap.
2. Method according to claim 1 wherein the inlet gap height (h₀) is the height of the pressing gap in the area of the front edge of the upper and/or the lower inlet plate (9, 10) or in the area of the axle (A) or shaft of the upper and/or lower introduction wheel (12, 13) for the roller bars (11).
3. Method according to claim 1 or 2 wherein in the inlet opening (6) the pressing-material mat (M) is precompressed to the inlet gap height (h₀) in a precompression zone (V) upstream of the inlet plates (9, 10) .
4. Method according to any one of claims 1 to 3 characterised in that the actual weight per unit area (F_actual) of the pressing-material mat (M) is measured before the inlet opening (6).
5. Method according to any one of claims 1 to 4, wherein a controllable incorrect filling device is arranged before the continuous press, characterised in that the incorrect filling device is controlled as a function of the weight per unit area (F_actual or F_nominal) and/or the inlet gap height (h₀).
6. Method according to any one of claims 1 to 5 characterised in that the maximum permissible mat density (p_max) in the area of the inlet gap during the production of orientated strand board is 100 to 200 kg/m³.
7. Method according to claim 6 characterised in that the maximum permissible mat density (p_max) in the area of the inlet gap during the production of orientated strand board is 150 to 200 kg/m³.
8. Method according to any one of claims 1 to 5 characterised in that the maximum permissible mat density (p_max) in the area of the inlet gap during the production of MDF board is 100 to 200 kg/m³.
9. Method according to claim 8 characterised in that the maximum permissible mat density (p_max) in the area of the inlet gap during the production of MDF board is 150 to 200 kg/m³.
10. Method according to any one of claims 1 to 5 characterised in that the maximum permissible mat density (p_max) in the area of the inlet gap during the production of chipboard board is around 200 to 350 kg/m³.
11. Method according to claim 10 characterised in that the maximum permissible mat density (p_max) in the area of the inlet gap during the production of chipboard is around 250 to 300 kg/m³.
12. Method according to any one of claims 1 to 11 characterised in that the inlet contour of the upper and/or lower inlet plate (9, 10) is set and/or regulated as a function of the weight per unit area of the mat.
13. Method according to any one of claims 1 to 12 characterised in that the inlet gap height and/or the inlet contour is/are set and/or regulated as function of the board's density (P_p) or the board's weight per unit area (F_p) and/or the height (h_p) of the finished wood-based board.

Images