WO2016110414A1

WO2016110414A1 - Method for producing veneer-layer wood

Info

Publication number: WO2016110414A1
Application number: PCT/EP2015/081113
Authority: WO
Inventors: Ralf Pollmeier
Original assignee: Ralf Pollmeier
Priority date: 2015-01-05
Filing date: 2015-12-23
Publication date: 2016-07-14
Also published as: EP3242781B1; EP3242781A1; DE102015100033A1

Abstract

The invention relates to a method for producing veneer-layer wood, wherein panels (12) of a veneer are examined for flaws and flaw-free panels are glued, stacked in a plurality of layers, and pressed, wherein, for panels that are not flaw-free, at least if the flaws do not exceed a certain size, the locations of the flaws in the stack are calculated and stored and a stacking sequence in which the panels (12) are stacked is determined in accordance with the stored locations of the flaws in a number of layers of the already stacked panels (12).

Description

PROCESS FOR THE PRODUCTION OF FURNIERSCHICHTHOLZ

The invention relates to a method for the production of laminated veneer lumber, in which panels of a veneer are inspected for defects and glue-free panels are glued, stacked in several layers and pressed.

When peeling veneers often arise veneer webs, some of which have significant defects. Typical causes of such defects in the veneer are, for example, knotholes or bumps in the peeled trunk. In veneer lumber, these imperfections can lead to weakening of the material as well as misalignments, that is, the successive veneer shops are not completely glued together due to the imperfection of gaps and therefore do not adhere well to one another.

It is therefore known to cut off defects exceeding a certain size from the peeled veneer sheet, so that the individual sheets into which the veneer sheet is divided are then free of larger defects. However, this procedure results in a significant amount of waste, which can be up to about 30% of the processed veneer material. The object of the invention is therefore to provide a method which allows a production of laminated veneer lumber with less waste.

This object is achieved according to the invention in that for panels which are not free of defects, at least if the defects do not overwrite a specific size, the locations of the defects in the stack are calculated and stored and a stack following is obtained. ge in which the panels are stacked, is determined depending on the stored locations of the defects in a number of layers of the already stacked panels.

In this method, it can be avoided by changing the stacking sequence that multiple defects lie one above the other in the stack formed or are separated from each other only by a few defect-free layers. This can mitigate the harmful effects of flaws so that a higher value can be selected for the size of the flaws that can barely be tolerated so that the blending can be reduced. Also, the workload for the Auskappen the veneers can be significantly reduced in this way, or even eliminate completely.

Advantageous embodiments and further developments of the invention are specified in the subclaims.

If a panel to be next added to the stack has a defect at a location where there is a defect in the next lower panel or in one of the even lower layers in the stack, the panel in question may initially be in a clipboard are stored, and in their place, the next supplied panel is inspected for defects and optionally placed on the Staple. The sheet initially stored in the clipboard can then be added to the stack at a later time if multiple layers of sheets have been piled free of defects at the location where the defect is located. An alternative possibility is that multiple stacks are formed simultaneously and the flawed panel is added to each stack where the condition that no flaws should be superimposed is most likely to be met.

After stacking and stacking, the layered veneers are pressed under heat. At a suitable temperature and humidity The content of the veneers during pressing can lead to a flow process which largely closes the imperfections. According to an expedient development of the invention, therefore, the conditions during pressing are adjusted so that such flow processes are favored. It is particularly advantageous if the laminated veneers are preheated prior to entry into the press, for example by means of microwave radiation.

In the following, embodiments of the invention will be explained in more detail with reference to the drawing.

Show it:

Fig. 1 is a block diagram of a plant for the production of laminated veneer lumber;

Figure 2 is a strand of staggered stacked veneers in plan view.

Fig. 3 is a section along the line III - III in Fig. 2; and

4 shows a flowchart for explaining the essential steps of the method according to the invention.

The plant shown schematically in FIG. 1 for the production of laminated veneer lumber has in sequence the following stations from left to right: a dryer 10, in which panels 12 of a veneer are preferably dried in several stages in a continuous process, one on a conveyor track 14 for the veneer panels arranged defect scanner 16, a Auskappvorrichtung 18, with the larger defects can be capped and possibly the remaining veneer pieces can be reassembled, a gluing station 20, a stacker 22 movably disposed above the conveyor track 14, a preheating station 24, and a press 26.

In the dryer 10, the veneers are dried to an average mean humidity of 4 to 8%, whereby the setpoint value of the residual moisture can be maintained with an accuracy of +/- 0.5 percentage points. The dried panels 12 are then - optionally after storage in a storage, not shown - isolated and transported in succession on the conveyor track 14. In doing so, they pass under the defect scanner 16, which extends over the entire width of the conveyor track, and thus is able to take a complete picture of the veneer sheet. A connected electronic control unit 28 contains image processing software with which the defects can be located and optionally classified according to their size and shape. For each panel 12, the location coordinates of the defects found in the plane of the conveyor track 14 and preferably also data on the shape and extent of the defects are stored. In the example shown, it is also decided in the control unit 28 whether the extent of a defect is so great that it can no longer be tolerated. In that case, the defect in question is cut off with the aid of the extraction device 18. Optionally, the inspection for defects and the Auskappen faulty veneer panels can also be done before the caching. The sorting out of the faulty veneer sheets and the cutting off are then preferably carried out in a separate work station, in which the pieces remaining after the cutting out are reassembled and stored again into new, useful, sheets until they are fed back into the regular process.

In the gluing station 20, the panels 12 are glued and, with the aid of the stacker 22, they are then staggered to form together a stack 30 in the form of a continuous strand of veneer. In practice, the stack 30 may for example consist of twelve veneer layers, although in the simplified drawing tion in Fig. 1, only five layers are shown. In the longitudinal direction of the strand, the individual panels are each offset by about 150 mm from each other. The stacker 22 is movable along the stack 30 and, under control of the control unit 28, picks up a glued panel from the gluing station 20 and sets it down at the next free location of the stack 30. In the situation shown in Fig. 1, a panel is being deposited in the uppermost layer of the stack. The next panel would then placed on the drawing in the left end of the strand directly on the conveyor track 14 so that it rests against the existing trailing edge 32 of the strand. The next panels would then be incrementally applied from left to right progressively until the topmost tier is reached and a new cycle begins.

The control unit 28 stores not only the locations of the defects within the panels, but also the location in which the panel in question is stored in the stack 30. Thus, the control unit 28 is also able to calculate the location coordinates of the defects in an absolute coordinate system attached to the stack 30. As a result, the control unit 28 may also determine whether two defects located in different layers of the stack 30 overlap each other.

If it is determined prior to depositing a panel 12 that such overlap of imperfections would occur, the panel in question will not initially be added to the stack 30, but deposited in a clipboard 34, and in its place will become the next stack added from Beleimungsstation 20 coming panel.

If, after the creation of further panels, a situation arises in which the panel deposited in the clipboard 34 could be added without causing a pinhole overlap, this panel is picked up from the clipboard 34 and added to the stack. In this way it can be achieved that never two defects lie directly above each other. In addition, it can also be achieved that overlapping defects either do not occur at all or are separated from one another by a certain minimum number of defect-free veneer layers. In the preheating station 24, the sheets 12 stacked to the stack 30 are preheated to a temperature of about 80 ° C., for example by means of microwave radiation. Thereafter, the stack 30 is pressed in the press 26 in a continuous process between press plates, which in turn have a temperature of about 140 to 220 ° C. The veneer sheets are pressed into a (endless) laminated veneer lumber panel. The heat applied from the outside also heats the veneer layers in the core of the board to a temperature of 105 ° C or more at which the glue (eg a phenolic resin) hardens.

When pressing the heated veneer sheets, a flow occurs that largely closes the defects in the veneer sheets. This effect is mainly made possible by the fact that due to the above-described change in the stacking sequence either no overlaps between defects or these defects are at least separated by a sufficient number of veneer layers, so that even in the area of the defects sufficient pressure can be applied, so that larger imperfections close and the board is completely glued to the adjacent panels. In this way, it is possible to produce a high-quality veneer plywood board free of weak points even if there are defects with a size of, for example, 8 cm or more in the individual veneer panels.

In Fig. 2, an end portion of the stack 30 is shown on an enlarged scale in plan view. At the right end you look at two panels 12a, which are in the uppermost layer of the stack. To the left of this one can see the end portion of a panel 12b projecting in the second highest position due to the offset between the panels, and subsequently a panel 12c, which is also in the second highest position and has a defect 36. On the left you can see in the end sections of three others Plates 12d in the lowermost layers of the stack. One of them has a further defect 38.

Another panel 12e is shown separately in Fig. 2, in the longitudinal position in which it should actually be added next to the stack 30, namely so that it rests on the two panels 12b and 12c and on impact at the last Plate 12a is present. However, the panel 12e also has a flaw 40, and the control unit 28 recognizes that the flaws 36 and 40 would overlap each other if the panel 12e were dropped as planned. In this situation, therefore, the control unit 28 changes the stacking sequence so that the panel 12e is first stored in the clipboard 34 and replaced with another panel.

In the sectional view in Fig. 3 further flaws 42, 44 and 46 can be seen. The defect 44 overlaps with the defect 36, but is separated therefrom by two defect-free veneer layers. The flaws 46 also form a pair of overlapping flaws between which there are several flawless plies.

The stacking sequence is always selected by the control unit 28 so that there is always a certain minimum number n of (in this place) veneer layers between two overlapping defects, where the number n may also depend on the size of the defects in question.

In a particularly advantageous embodiment, by suitably changing the stacking sequence, the control unit 28 also ensures that the defects or at least the larger imperfections are preferably located in the middle layers of the strand 30. As the strand is pressed between the heated press plates of the press 26, the heat gradually spreads from the upper and lower layers to the middle layers. In the middle layers, therefore, more time remains within which the material can flow and close the flaws before the phenolic resin cures and prevents further flow. In a modified embodiment, the plant for the production of laminated veneer lumber boards downstream of the defect scanner 16 or at the latest downstream of the gluing station 20 forks into two or more parallel production lines, in each of which a strand-like stack 30 is formed from veneer panels. These parallel production lines are operated by a common stacker 22 or possibly also by several stackers. If there were an overlap of imperfections, then, in addition to the option to place the panel concerned in the clipboard 34, there is also the option of placing this panel on another stack in one of the other production lines.

The decision processes that take place in the control unit 28 in this embodiment are shown in FIG. 4 in a flow chart. In step S1, a panel 12 is scanned by the defect scanner 16 and it is checked whether this panel has a defect. If this is not the case, the tablet is placed in step S2 on the stack provided for them (stack 1). Otherwise, it is decided in step S3 on the basis of the size of the defect, whether this defect is still tolerable or must be capped in step S4. If it is tolerable, then in step S5 the position that would occupy this defect in the stack (stack 1) is calculated.

In step S6 it is checked on the basis of the calculated position of the defect whether there is already another defect in the last n-layers of the stack 1 which would overlap with the defect in the new sheet to be added. If this is not the case, a branch is made to step S2, and the board is added to the stack 1 as planned.

Otherwise, in step S7 it is calculated which position the defect of the newly added sheet would occupy in another stack (stack 2) in a parallel production line. In step S8 it is then checked whether there is also a defect in this stack in the last n-layers which would overlap with the new defect. If there are no overlapping defects in the stack 2, the panel will be in step S9 stored on the stack 2. Otherwise, it is stored in the clipboard 34 in step S10.

For the panel arriving at the defect scanner 16 next, the procedure described above is repeated, but preferably the roles of the stacks 1 and 2 are exchanged to ensure that normally (no defects) both production lines are operated evenly.

Claims

A process for the production of laminated veneer lumber, in which panels (12) of a veneer are inspected for imperfections and glue-free panels are glued, stacked and pressed in multiple layers, characterized in that for panels which are not free of defects, at least if the defects do not exceed a certain size, the locations of the defects in the stack (30) are calculated and stored, and a stacking sequence in which the panels are stacked is determined depending on the locations of the defects in a number of layers of the already stacked panels.

A method according to claim 1, wherein for a panel having a defect which does not exceed the predetermined size, it is checked whether it would overlap with a defect of one of the already stacked panels in said number of plies, and if so is, the stacking sequence is changed.

3. Method according to claim 2, wherein the change of the stacking sequence consists in the fact that the board is temporarily stored in a clipboard (34) and inserted into the stacking sequence at a later time.

A method according to claim 3, wherein the change of the stacking sequence consists of inserting the panel into a stacking sequence for another stack.

5. The method according to any one of the preceding claims, wherein the number of layers, which are taken into account in the determination of the stacking sequence, is dependent on the size of the defect.

A method as claimed in any one of the preceding claims, wherein the stack (30) formed from the panels (12) is in the form of an endless strand in which the panels in successive layers are offset in the longitudinal direction of the strand against each other.

A method according to any one of the preceding claims, wherein the stack (30) is pressed under heat and the stacking sequence is determined so that the panels with defects or at least the panels with defects having a certain minimum size, preferably in the inner layers of the stack (30) are stored.

A method according to any one of the preceding claims, wherein the stack (30) is pressed under heat in a press (26) and the panels (12) are preheated prior to entering the press (26).