EP0065582A1 - Particle board press provided with frames spaced from each other - Google Patents

Abstract

In a method for pressing a chip fleece into a chipboard, by a closing process and a pressing process of the press, a chipboard is produced from a chip fleece under the influence of heat, which is characterized by a high surface quality. In a press for the production of chipboard and similar materials, according to the method, a plurality of frames (1) arranged in series and heatable movable press plates (6, 11) are provided, with chip nonwovens being consolidated between the press plates by the action of pressure and temperature to form chipboard . In order to obtain chipboard with a very high thickness, the pressing process is divided into a closing and a pressing process.

Description

The invention relates to a method for pressing a chip fleece into a particle board by a closing process and a pressing process of the press, and a suitable press for carrying out the method.

From DE-OS 25 45 366 a press for exerting a surface pressure has become known. In which several frames arranged one behind the other represent the support structure for a continuous press, and the heatable upper and lower press plates arranged in this support structure are arranged in such a way that their distance continuously decreased to a press nip corresponding to the chipboard thickness, which is controlled over a certain press length by hydraulically operated pistons to a constant thickness. For the production of chipboard, driving means are absolutely necessary in this continuous press, which, as roller chains, loop around the upper and lower heated, movable press plate (DE-PS 22 42 399).

In such presses, it is inevitable that the roller chains leave indentations on the chipboard to be pressed, and it is also a considerable effort to keep the thickness of the press nip constant, since the constant is done by a hydraulic control. Even a design of roller chains, according to DE-AS 25 45 624, could not prevent the indentations in the surface of the chipboard to be pressed, and also could not prevent the effort for hydraulic control in keeping the gap constant.

A discontinuously working hot plate press with self-compensation known from DE-AS 17 o3 296 Renden cylinder piston assemblies, wherein the hot plate press consists of a movable and a fixed press spar, between which one or more pairs of heatable and coolable press plates are arranged, on the long sides of the press spars cylinder piston assemblies receiving press stands are provided, each consisting of two columns and a crosshead connecting them, and which is characterized in that compensation pistons are arranged between the fixed and the movable press spar on the one hand, and the associated press plates on the other hand, which are coordinated with each other on the same hydraulic circuit as the hydraulically effective cross sections so that a load-dependent deflection of the press plates is avoided, was also unable to provide a simple, manageable control of the press plate spacing required to produce a chipboard from a chip fleece with a practically constant thickness due to the hydraulic control of both presses effect plates.

Proceeding from this, the present invention has for its object to provide a pressing method and a press, whereby the guarantee is given that mutually influencing errors are avoided by hydraulic controls of the press plates and a chipboard of constant thickness is produced. This object is achieved in that the closing of the press by moving one press plate against the chip fleece and the final pressing of the chipboard by moving the other press plate against the mechanically fixed and locked press plate. This method avoids the mutual coordination between the hydraulic circuits for the one and the other press plate required in the previous pressing processes. This new pressing process creates a particle board with a very high thickness accuracy and by separating it into a closing process and subsequent mecha Niche fixed locking of the one press plate carrying out this process step against which the other press plate, during the pressing process, the second press step, exactly engages with the interposition of the chip fleece to be pressed.

A press to carry out the process for the production of chipboard and similar materials, with several consecutively arranged frames and heatable movable press plates, with chips between the press plates. Nonwovens are solidified to chipboard by the action of pressure and temperature, characterized in that the heatable a press plate is moved by a small number of hydraulically operated pistons, that a fixable form-fitting support structure can be inserted between the frame and the one heatable press plate, and that the heated other press plate is supported directly on the frame of the press via a plurality of hydraulically actuated pistons and effects the pressing process. With this press according to the invention, a way is shown with which a thickness-accurate chipboard is achieved without the pressure of both press plates being readjusted as a function of the pressures occurring during curing within the chipboard to be cured, and these pressures have to be kept constant over a certain time, which was previously the case can only be achieved with considerable effort and then incomplete or only with defects in the surface by means of impressions.

Only the majority of the hydraulically operated pistons carrying the other press plate are on. to control the same distance against a press plate fixed by means of a support structure.

This is the basic shortcoming of the previous presses, which consists in the fact that by arching both press plates, an exact measurement of the distance between the two differently arching and tracking plates in the central area of the plates is not possible (normal plate presses generally have press plate dimensions of 2.5 m width and 8 m length). By introducing the form-fitting support structure between the frames and the upper heatable press plate or between the spar carrying the press plate and the frame, a considerable increase in the section modulus of this press area is achieved, so that a practically flat counter bearing for the chipboard to be finished is obtained; a noticeable reduction in the amount of press oil required is also achieved.

In an embodiment of the press according to the invention, it is proposed that the support structure consist of a plurality of honeycombs with plane-parallel end faces. As a result, while maintaining the high section modulus, a lightweight construction of the press is achieved which, when using this form-fitting support structure for the upper heatable press plate, brings practically no additional load, so that the upper heatable press plate can also be made thin without the risk of sagging. In addition to the honeycomb structure, the following known, height-adjustable support structure components can also be used as a positive support structure, which fixes and fixes the upper press plate, namely wedges, step wedges, threaded spindles, racks. If the group of honeycombs, wedges and step wedges each have flat, parallel end faces as contact surfaces, to the press frame and to the spar or to the top of the press plate, then these support structures are each form-fitting with the frame and the Spar or the press plate connected. When using threaded spindles or toothed racks between the frame and the spar or press plate, the small number of hydraulically actuated pistons makes the certain distance manufactured between the frame and the press plate and then fixed and locked this distance by moving the threaded spindles in nuts or the toothed racks on pinions.

In yet another embodiment of the press according to the invention it is proposed that the height of the form-fitting support structure can be varied depending on the lifting height of the majority of the hydraulically actuated pistons resulting from the desired chipboard thickness. This ensures that even in the production of chipboard or similar boards from different types of wood, different types of chip and different board thickness for the closing process of the press, no complex control of the small number of pistons causing the closing process is required, but only by replacing the support structures in the case of the honeycomb structure against another support structure which represents a greater or lesser fixed interlocking distance, or by changing the height of the same support structure in the case: wedges, step wedges, threaded spindle, rack.

The invention thus proposes a method for pressing a particle board fleece into particle board, in which a discontinuously operating press can be used in a lightweight construction, preferably as a one-day press. In addition, the control for the plurality of hydraulic pistons is considerably simplified by the use of known displacement measuring devices which are arranged in or next to the pistons and which can measure the distance between the upper fixed heatable press plate and the lower heatable press plate without reaction; a not insignificant saving in the amount of press oil to be kept is achieved.

If the press according to the invention is simultaneously used as a pre-press for pre-pressing chip nonwovens, the press pistons holding the upper heatable press plate become first extended to its maximum stroke intended for this case. The upper heatable press plate then lies on the chip fleece with a certain pre-pressure. After inserting the form-fitting support structure between the aligned frames and the top of the upper spar or the upper press plate, in a honeycomb structure the chip fleece is pre-pressed with practically the same pressure and at the same time a stable, flat support surface is created for the subsequent pre-pressing process, which is carried out solely by the several pistons . According to the length of the press, several frames are arranged one behind the other, the frames being aligned with one another.

The following percentage distribution was found to be particularly suitable: 5% small number of hydraulically operated pistons, 95% majority of hydraulically operated pistons. Likewise, with a 16 mm thick pre-pressed chipboard made of softwood, the ratio of the lifting height between the plurality of hydraulically operated pistons and the small number of hydraulically operated pistons was 1: 2. It is understandable that the lifting height between the majority and the small number of hydraulically actuated plungers varies depending on the type of Helz, type of chip, and plate thickness.

• Figur 1: ein Gestell aus einem geschlossenen Rahmen für eine erfindungsgemäße Presse,
• Figur 2: ein Gestell ausgebildet als Säulenpresse für eine erfindungsgemäße Presse.

The subject matter of the invention is explained in more detail in the following drawing, in which:

• FIG. 1: a frame made of a closed frame for a press according to the invention,
• Figure 2: a frame designed as a column press for a press according to the invention.

In Figure 1, a frame 1 is shown from a frame press, which consists of a plurality of frames arranged one behind the other. Upper pistons 2, 3 are fastened to fastening points 4, 5 of the frame 1. It is entirely sufficient for moving a heatable upper press plate 6 if an upper piston pair 2, 3 is not arranged on each frame 1. It has proven to be particularly advantageous if an upper piston pair 2, 3 is arranged on every fifth frame. The frames 1 are on an inside 7 on one. Support structure 8 can be applied, aligned over the entire length of the frame press and also over its width, for example by planing. In contrast to this, there are a plurality of hydraulically actuable pistons 9 on each surface of the frame 1 arranged one behind the other, delimiting the cutout of the frame press, the bearing surface 10 of which on the frame 1, in each frame 1 in itself flat, but not aligned with the must be another framework. A heatable lower press plate 11 lies directly on the majority of the hydraulically actuated pistons 9.

The pressing process is first carried out via an oil reservoir _. 12, press oil via lines 13, 14 to the upper pistons 2, 3, which represent the small number of hydraulically actuated pistons. This moves the heated upper press. enplatte 6, in a position shown in dashed lines with its underside 15. As shown in Figure 1, a certain pre-compression of a chip fleece 16 to be pressed is already achieved. Subsequently, the support structure 8, in the exemplary embodiment the honeycomb structure between the inside 7 and the top 17, of the spar 18 carrying the heatable upper press plate 6 is inserted and, by retracting the upper pistons 2, 3, the support structure 8 and the flat underside 15 of the heatable are locked and fixed upper press plate 6 reached. This position of the underside 15 is now used as the zero position for the subsequent finishing maintain pressure. In the simplest case, it is sufficient if a path measuring device 20 is arranged on each side of the press plate top 19, the lower heatable press plate 11, which during the pressing process the distance between the top 17, the heatable lower press plate 11 and the bottom 15 of the heated upper press plate 6, constantly monitored. In accordance with the information coming from the displacement measuring devices 20, a high-pressure hydraulic system 21, which is connected to the plurality of hydraulically actuable pistons 9 via lines 22, is acted on such that, depending on the desired pressure profile, a parallel position of the lower heatable press plate 11 to the upper heatable press plate 6, is complied with. In FIG. 2, a column press is shown from a press that consists of several column presses arranged one behind the other, in which the components that are the same as FIG. 1 are given the same numbering. An upper yoke 31, held in the simplest configuration by two columns 30, carries the spar 18 and the upper heatable press plate 6 via the upper pistons 2, 3. Extending from the zero position 32, a support structure 8 is inserted between the upper fixed yoke 31 and the spar 18 and the final pressing process of the lower plurality of hydraulically operated pistons 9 - of which approximately 500 are available with a press plate size of 2500 - 8000 millimeters, against the underside 15 of the locked heatable upper press plate.

For the final pressing, a high-pressure hydraulic system 20 is also connected to the plurality of hydraulically actuated pistons 9 via lines 21.

Claims (4)

1. A method for pressing a chip fleece to a chipboard by a closing process and a pressing process of the press, characterized in that the closing of the press by moving the one press plate against the chip fleece and that the pressing of the chipboard by moving the other press plate against the mechanically fixed locked a press plate happens. 2. Press for performing the method according to claim 1 for the production of chipboard and similar materials with a plurality of consecutively arranged frames and heatable movable press plates, chip fleeces being solidified between the press plates by the action of pressure and temperature to form chipboard, characterized in that the heatable one Press plate (6) is moved by a small number of hydraulically operated pistons (2, 3) such that a fixable form-fitting support structure (8) can be inserted between the frame (1) and the one heatable press plate (6), and that the heatable, re other press plate (11) is supported via a plurality of hydraulically operated pistons (9) directly on the frame of the press and effects the pressing process. 3. Press according to claim 2, characterized in that the positively 'fixable support structure (8) consists of a plurality of honeycombs provided with plane-parallel end faces. 4. Press according to one or more of the preceding claims, characterized in that the height of the form-fitting support structure (8) depending on the resulting from the desired chipboard thickness Lifting height of the majority of the hydraulically operated pistons (9) can be varied.

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