EP0109456A1 - Method of and apparatus for equalizing the density distribution in an artificial-wood panel - Google Patents

Abstract

In a method for equalizing the density distribution in synthetic wood panels made from glued bulk material and in a device for producing synthetic wood panels according to the method, with a floor conveyor bunker (1) with discharge, the discharge width of which is the same as the spreading width (s) for the synthetic wood panels to be produced, and that Bottom belt bunkers (1) downstream devices for bringing down the discharged bulk material (6) as fleece (8) on a forming belt (9), for the purpose of eliminating the density errors present in the bulk material when it is discharged from the floor belt bunker (1), the density errors across the width the outlet opening is detected and accordingly eliminated; if necessary, a density profile for a finished synthetic wood panel is also specified when the bulk material (6) is discharged from a floor conveyor bunker (1).

Description

The invention relates to a method for equalizing the density distribution in synthetic wood panels made from glued bulk material and a device for carrying out the method for producing synthetic wood panels with a floor conveyor bunker with discharge, the discharge width of which is the same as the spreading width for synthetic wood panels to be produced and devices downstream of the floor conveyor bunker for bringing down the discharged Bulk goods as an endless fleece on a forming belt.

In the manufacture of synthetic wood panels, there is great economic interest in the production of nonwovens that are spread as evenly as possible, because only in this way the properties of the finished synthetic wood panels, such as. B. their density, the bending strength or the transverse tensile strength can be the same at all points of the end product and unnecessary additions to the bulk material to be processed for glue and energy can be avoided. From DE-PS 22 14 900, which relates to a scattering device to compensate for different basis weights in the transverse direction of chip or fiber fleeces or the like for the production of chipboard, fiberboard and the like, a device has become known in which a metering conveyor belt is used to to be able to drop it there from bulk material for a nonwoven to be built up on a mold base. In order to compensate for different weights per unit area in the transverse direction of chip or fiber fleeces, it is provided there that the metering conveyor belt is infinitely variable and differently adjustable in height in the transverse direction below the stripping roller. Such additional devices are not suitable, that is to say in the area where a bulk material veil is formed, different basis weights in the transverse direction of chip or fiber nonwovens, ie to uncover and remove synthetic wood panels. It is also not possible to determine the different density in the transverse direction on the metering conveyor belt.

From DE-PS 25 57 352 a continuous process for the continuous scattering of a fleece from wood chips and / or fibers, which consists of several layers scattered separately from one another and whose basis weight is regulated to a predetermined desired value, is known, in which the weight of the finished scattered nonwoven is measured and displayed, and corresponding electrical measurement signals regulate the scattering of at least one layer of nonwoven to a predetermined target value of the finished scattered nonwoven. However, this also does not make it possible to even out the density distribution across the fleece. A basis weight scale (cf.wood as raw and material 40 (1982) page 385) has also become known, in which the basis weight distribution in the scattered chip fleece is determined by means of radiometric methods and traversing devices along and across the production direction.

Proceeding from this, the present invention is based on the object of proposing a method and a device for carrying out the method, detecting and eliminating density errors present in the bulk material as soon as it is discharged from a floor conveyor bunker and, if necessary, a density profile for to specify a finished synthetic wood panel when the bulk material is discharged from a belt conveyor. This object is achieved with the characterizing features of method claim 1.). By measuring the weight distribution over the discharge cross section and comparing it with a predetermined target density distribution of the finished synthetic wood panel, a separation command that is generally different across the cross section is generated.

An inventive embodiment of this method is protected with the characterizing features of claim 2.). For the production of equally heavy synthetic wood panels, which at the same time have a predetermined target density distribution, a control command is derived from a comparison between the existing basis weight of the synthetic wood fleece and the target density distribution, which contains the target weight of the finished synthetic wood panel, with which the discharge of the bulk material can be influenced becomes.

The characterizing features of claim 3.), With which a device for the production of synthetic wood panels is placed under protection, show, as by inventive arrangement of a measuring surface above a guiding surface, which is arranged between the bunker outlet and the further depositing devices for the bulk material, information about the instantaneous density distribution over the molded cross-section to be obtained, which, in conjunction with a density distribution specified for the finished synthetic sheet, determine a value which, as a control value, a separating device extending over the entire bulk width is too much for the decrease in the resulting density difference in individual areas over the cross-section scattered bulk material affected.

In the embodiment of the measuring surface, it is proposed in the characterizing features of claim 4.) how a better approximation to the density profile over the outlet width of the bulk material is achieved by dissolving the measuring surface in individual plates provided with strain gauges, and that in an inventive manner by adapting the individual Tongues of the downstream separating device, this resulting density profile can be made more uniform if, for example, a density profile across the width of this plate is required in the finished synthetic wood panel, which has a constant profile Has density value.

In the features of claim 5) a further inventive embodiment of the measuring surface is protected, in which the measuring surface itself is designed according to the invention as a narrow plate which can be moved back and forth across the entire bulk width in front of the guide surface. An embodiment of this movable narrow plate is that the arrangement for transverse movement of the plate also extends outside the dumping width, so that the entire device for maintenance and adjustment work can be removed from the dumping area without interrupting the pouring process .

The characterizing features of claim 6) provide a device for carrying out the method under protection, in which, in addition to compensating for the density profile, which would lead to a slightly lighter finished synthetic wood panel, this slight change in the weight of the finished synthetic wood panel compared to the predetermined synthetic wood panel by increasing the discharge of bulk material by increasing the belt speed.

The characterizing features of claim 7) protect the inventive use of a scraper belt which simultaneously serves as a discharge element, as a separating element and as a return transport element for the proportion of incorrectly discharged bulk material. Instead of the scraper belt, in which the scraper webs are arranged on circumferential chains or toothed belts or belt straps, the outlet cross section of the floor belt hopper can also be provided with spiked rollers arranged one above the other, which extend over the entire width of the discharge cross section. In this case, according to the invention, the discharge spiked roller closest to the floor conveyor then takes over the function of separation of the excess material and the return transport of it to the floor conveyor bunker in connection with a trough conveyor, which is designed as a spiral vibratory conveyor or screw conveyor.

In the claims 8.) to 12.) inventive embodiments for the attachment of the measuring surface as a narrow plate are protected, in which the guarantee is given that contamination of the movable parts for receiving the movable narrow plate are excluded and also Care is taken to ensure that the bulk material itself does not hinder the measuring surface in its measuring activity, for example by pinching the bulk material between the guiding surface and the measuring surface when moving the measuring surface across the guiding surface.

According to the invention, a pole-changing motor which is acted upon by control commands or a direct current motor can be used to change the belt speed.

In the following drawing, the subject of the invention is explained in more detail using exemplary embodiments.

• Fig. 1 zur Erläuterung des Verfahrens eine Schemaskizze der gesamten Anlage
• Fig. 2 die Anordnung einer verfahrbaren Meßfläche
• Fig. 3a eine Ausgestaltung eines Kratzerförderers
• Fig. 3b eine Ausgestaltung einer Verstellmöglichkeit einer Zunge in einer Abscheideeinrichtung
• Fig. 3c eine sich über die gesamte Austragsbreite erstreckende Meßfläche aus einzelnen Platten
• Fig. 3d Gewichtsverteilung über die Streubreite

They show:

• Fig. 1 to explain the method, a schematic diagram of the entire system
• Fig. 2 shows the arrangement of a movable measuring surface
• 3a shows an embodiment of a scraper conveyor
• 3b shows an embodiment of an adjustment Possibility of a tongue in a separator
• Fig. 3c a measuring surface extending over the entire discharge width from individual plates
• Fig. 3d weight distribution over the spread

In the figures, the same components are designated with the same reference numerals.

In a plant for the production of synthetic wood panels, for example chipboard, glued chips for the production of a particle board according to the vertical arrow 3 are fed to a floor conveyor bunker 1 via a feed 2 which rotates in the direction of the arrow. Instead of the scraper belt shown, other entry processes such as plate belts can be used. A scraper belt 4 covers the outlet cross section of the floor belt hopper. The scraper belt 4 rotates in the direction of the arrow and, in cooperation with a revolving floor belt 5, which closes the floor belt bunker downwards and whose speed can be adjusted, takes off a quantity of bulk material 6 that can be preselected for the production of chipboard from the front side. This removed bulk material is fed to a scattering unit 7 and then brought down by this scattering unit 7 as a fleece 8 onto a forming belt 9. When the fleece 8 is transported further on the forming belt 9, which is preferably covered with documents 10, which close together without gaps, the respective fleece weight is determined by a scale 11, whether as the total weight including the underlay or as a pure net nonwoven weight by subtracting the weight of the underlay .

Instead of the spreader unit 7 shown, a further spreader unit may be present in mirror image to the one shown while maintaining a floor conveyor bunker, or there may be two floor conveyor bunkers which feed the spreader units arranged in mirror image arrangement. Instead of the scattering units shown, which operate by means of the throwing principle, it is also possible to use scattering units which, by means of a blower, bring about a spreading good for the production of a nonwoven. Here, too, fan outlet openings arranged in mirror image can be used with a high throughput of fleece to be scattered, as is known, and combinations between scattering units based on the throwing principle and scattering units based on the wind scattering principle, as known, can also be used.

A measuring surface 12 is arranged between the floor belt bunker and the spreading unit 7, which is explained in more detail in connection with FIGS. 2 and 3c. This measuring surface indicates the weight distribution of the pouring stream 13 in accordance with the bulk flow 13 conducted over it across the width of the spread s (cf. FIG. 3d). These values are fed to a controller 14, to which a setpoint 15, which contains the total weight of the finished chipboard with a uniform density distribution, is simultaneously fed. From the different weight information of the bulk flow 13, which is a measure of the different density distribution in the particle board, compared to the constant information from the target value 15, a control variable that changes over the scattering range is obtained and is fed to an actuator 16. This actuator is pressurized now _tongues' of a separation device 18 in such a way 17 that the individual tongues protrude 17 through the spread width more or less corresponding to the distribution (see. Fig. 3d) in the bulk stream 13. As a result, chips accumulate on the individual tongues, which are stripped off by the tongues 17 with the aid of the scraper belt 4 and over the returning run of the scraper belt 4 can be fed back to the feeder 2 of the floor belt bunker 1. It has proven to be advantageous if a guide plate 19 is provided over the total spreading width in the region of the deflection of the scratch 4.

If the actual weight of the fleece 8 having the same density distribution is now also fed to the controller 14 via the scale 11 and there is now a difference between this actual weight and the target weight 15, a control gear 21 with a control command becomes via a further output 20 of the controller 14 acted on, so that a larger bulk flow 13 is discharged from the bottom conveyor bunker 1 by changing the speed of the bottom conveyor 5.

If, instead of the scraper belt 4, a row of scraper rollers arranged one above the other is used, the last scraper roller also has a guide plate 19 as a partial sheathing, to which a trough conveyor (not shown) is connected for returning the material to be returned to the belt bunker 1. The trough conveyor can be provided with a screw or can be designed as a vibratory conveyor. The arrangement of a guide plate 19 thus prevents return material from falling back into the bulk flow 13.

The measuring surface shown in Fig. 2 has a narrow plate 22 which is arranged on a lever 23. The lever 23 is supported on the one hand on a cross spring joint 24 and on the other hand is supported on a support rod 26 via a force measuring device 25. The support rod 26 is mounted in a transverse guide 27 which extends over the entire spread.

A threaded nut 28 is also fixedly arranged on the support rod 26, as a result of which the narrow plate 22 can be moved transversely to the bulk width in cooperation with a threaded rod 29.

A housing 30, which contains the narrow plate 22 and the suspension parts of the narrow plate 22, carries a guide surface 31 in front of which the narrow plate 22 is moved at a distance a. The distance a is selected according to the invention such that when the narrow plate 22 is moved, no part of the bulk flow can get stuck between the guide surface 31 and the narrow plate 22, so that there is no fear of the narrow plate failing. The narrow plate still ends within the guide surface 31, so that the scattering unit 7 cannot be influenced by a non-uniform inflow of the bulk flow 13. Also, since the region b in which instantaneously the narrow plate 22 is located, even as far ends above the end of the guide surface, that even _this' partial bulk flow 13 can recombine with the remaining bulk stream 13 and evenly from the end edge 32 of the guide surface 31 flows to the scattering unit 7.

The housing 30 also carries a baffle plate 33 which, together with the guide surface 31, forms a slot along which the narrow plate 22 can be moved.

As already shown in FIG. 1, according to the control commands of the controller 14, tongues 17 protrude into the stray current 13. In order to remove too much poured material as described in FIG. 1 and to feed it back to the belt conveyor bunker 1 together with the scraper 4 or with a scraper roller.

3a shows tongues 17 standing in the bulk stream 13 and a baffle 19 within the angle scraper 34, which absorb the material picked up by the tongues 17 by moving along the inside of the baffle 19 and, due to its angular configuration, does not drain back into the floor belt bunker.

The configuration of the adjustment shown in FIG. 3b a tongue 17 shows the tongue 17 in a roller bearing 35. The tongue 17 has at its rear end 36 a threaded bore 37 which cooperates with a threaded pin 38. The setscrew 38 is mounted in a guide 39 and is adjusted by an adjustment drive 40, in the simplest case as a drill chuck, on its threaded head 41 by turning the adjustment drive 40 to the right or left for its region of the pouring stream 13 into or out of the pouring stream .

Corresponding to the dissolution of the entire bulk width into a plurality of such tongues 17, which are all arranged next to one another, the guide 39 can be supported as a cross-member extending to the left and right of the bulk width over the entire bulk width. In this case, the adjustment drive 40 moves from tongue 17 to tongue 17 transversely to the stray current 13 and adjusts each individual tongue according to the information received from the controller.

The measuring surface 12 shown in FIG. 3c consists of a plurality of plates 42, the individual widths b1 to b of which are selected according to the requirements. If, for example, measurements in the finished particle board have determined that the greatest density fluctuations occur at the edge of this plate, it will be advisable to provide small widths b there. The individual plates 42 are provided with strain gauges 43 and thus enable the measurement of the respective weight distribution over a certain partial width of the entire bulk width. This results in the weight distribution image shown in FIG. 3d over the scattering width s without a narrow plate having to be moved over the guide surface 31.

In the simplest form, the tongues 17 are formed in their width corresponding to the plates 42, so that a direct to there is a relationship between the measured instantaneous distribution and the quantity to be purchased.

Claims (12)

1. A method for comparing the density distribution in glued bulk material (6) made of synthetic wood panels, characterized in that, depending on the weight distribution of the bulk material (6) discharged from a supply (1) measured over a discharge cross section, a separation command for those present in corresponding partial cross sections a predetermined target density distribution deviating weight quantities of the bulk material (6) is formed for their separation. 2. The method according to claim 1), characterized in that depending on a comparison between the actual basis weight of the synthetic wood fleece and the target density distribution in the synthetic wood panel and its target weight, the discharge (4) of the bulk material (6) is influenced. 3. Apparatus for carrying out the method according to claim 1.) For the production of synthetic wood panels with a floor conveyor bunker (1) with discharge (4), the discharge width of which is the same as the spread for the synthetic wood panels to be produced and the equipment downstream of the floor conveyor bunker for bringing down the discharged bulk material ( 6) as an endless fleece (8) on a forming belt (9), characterized in that the bulk stream (13) emerging from the floor belt bunker (1) is fed to a guide surface (31) covering the entire spreading width, that at a parallel distance to the guide surface ( 31) and in front of this a measuring surface (12 or 22 or 42) is provided that the current partial cross-sections taking into account the current partial cross-sections starting from the measuring surface (12) are fed to a controller (14) after conversion into electrical signals , in addition a setpoint (15) for the weight of the finished synthetic wood panel at the same Density distribution is supplied, that the resulting control signal is fed to an actuator (16) arranged at the output of the controller (14), and that individual tongues (17) of a separating device covering the entire spreading width (s) and consisting of several mutually adjustable tongues (17) are adjusted will. 4. Apparatus according to claim 3), characterized in that the measuring surface (12) consists of a plurality of plates (42) arranged next to one another, each plate being provided with a strain gauge arrangement (43). 5. The device according to claim 3), characterized in that a narrow plate (22) over the entire spread (s) is movable. 6. The device according to one or more of the preceding claims for performing the method according to claim 1.) and / or 2.), characterized in that from a in the forming belt (9) arranged scales (11) information about the current weight of the synthetic wood fleece the controller (14) that in the controller (14) a comparison is made between the predetermined weight (15) of the synthetic wood panel in the target density distribution and the synthetic wood fleece having the target density distribution, that this control signal sends a control gear (21) to change the speed of the Floor belt (5) in the floor belt bunker (1) is fed. 7. The device according to one or more of the preceding claims, characterized in that the outlet cross section of the floor conveyor bunker is covered by a scraper belt (4), the leading run of which is arranged to be drivable in the discharge direction, that the length of the individual scraper web (34) covers the entire discharge width ( s) of the floor conveyor bunker (1) and that the scraper webs (34) Remove in the returning run of the scraper belt as a driver of the glued bulk material separated from the bulk flow (13) by the separating device and return it to the floor belt bunker (1). 8. The device according to one or more of the preceding claims, characterized in that the narrow plate (22) is arranged on a via a cross spring joint (24) at one end of the lever (23) that the other end of the lever (23) is supported by a force measuring device (25) on a support rod (26) which is mounted in a transverse guide (27) and is secured against rotation. 9. Apparatus according to claim 8), characterized in that a threaded nut (28) is fixedly arranged on the support rod (26) and that a cooperating with this over the entire spread (s) extending rotatable threaded rod (29) is provided. 10. The device according to one or more of the preceding claims, characterized in that a housing carrying the transverse guide and support brackets for the threaded rod (30) has a baffle plate (33) extending over the entire width (s) that the housing (30) the guide surface (31) carries and that the baffle plate (33) and the guide surface (31), parallel to one another, overlap and are arranged at a distance from one another. 11. The device according to one or more of the preceding claims, characterized in that the measuring surface (12 or 22 or 42) arranged at a predetermined distance (a) in front of the guide surface (31) in the bulk flow direction at a predetermined distance (b) the end edge (32) of the guide surface (31) ends. 12. The device according to one or more of the preceding claims, characterized in that each tongue (17) is adjusted in the separating device via an adjustment drive (40) which can be moved over the bulk width (s) in accordance with the corresponding control signal.

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