DE2414762A1 - Chipboard prodn. appts. - with press formed by endless belts supported by presser rollers and calibrating blocks - Google Patents

Abstract

Chipboard making appts. is provided with cake press composed of a number of vertically spaced cylinders over which are trained endless belts, the runs opposite the cake being provided with heated guide blocks and at least two pairs of the cylinders are provided with a gap setting device which is controlled by a pressure measuring device in the calibrating section. Chipboards of varying thicknesses can be readily produced by the appts.

Description

'Device for the continuous production of an endless plate web of compressed vegetable materials "The invention relates to a device for the continuous production of an endless sheet of pressed vegetable Fabrics, consisting of a double belt press, the two of which are rotating in opposite directions and a straight press gap forming belts on their facing away from the material to be pressed Side are supported by heated pressure bodies and one of the double belt press downstream calibration device, which also has two counter-rotating, endless belts supported by calibration elements and a pressure measuring device to determine the counter pressure of the pressed material passing through the calibration gap.

Numerous proposals for such double belt presses have become known, In most cases, however, an inadequate profitability stood in the way of implementation. A The reason for this is to be seen in the fact that for the technology customary today, the machine expenditure for the required pressing pressures and heating times uneconomical is high.

To avoid this problem a completely new technology would have to be used can be used to reduce pressure or compression work considerably and to shorten the heating time significantly. Before the risk of introducing a new one However, technology is still shying away from the industry, so that to that extent a compromise must be sought.

A very simple proposed solution is the one to be grouted Pulling the mass between steel strips through a gap in fixed sliding blocks (GB-PS 1 055 564). However, this does not allow the required compression work achieve. It has also been proposed to use large-area apron conveyors as press belts walk around polygons and be supported by rolling elements (DK-PS 15 936). The machining accuracy, especially at the joints between the individual plate chain links However, it is a considerable effort. There are also numerous suggestions became known to compress the material to be pressed between flexible belts only by rolling (US-PS 2,853,431, CH-PS 417,940).

However, these suggestions have also proven useless like the thought of running the chip mat through pairs of rollers without any belt cover to leave (DT-PS 1 151 649), because in this process behind each pair of rollers Tear beginning adhesions between the glue points on the chips again.

Only devices that have a large roller have been successfully implemented which is wrapped in tension by a flexible tape (DT-PS 718 341, GB-PS 493 541, US-PS 2,890,484, DT-PS 1,703,637, DT-OS 2,237,464). All These proposed solutions have the disadvantage that the devices only for the production very thin plates are suitable, which correspond to the Roll diameters are flexible. DT-OS 2 237 464 in particular has a disadvantageous one Way: Here a device is disclosed that a pre-compression zone with a straight Has press nip, which is followed by a heated roller with a large diameter is. The pre-heated and pre-compressed material to be pressed in the pre-press zone is heated around the Roll pressed around under tension of an external endless belt, wherein the binder hardens. However, it proves to be technologically inexpedient the molding compound precisely where it is still plastic and flexible, namely at the beginning of the pressing process, to run through a straight press gap, the hardening of the plate string, however, to be made in a curved shape.

The invention is based on the device described above, which can be found in DT-OS 2 058 820. The double belt press this one so far also not yet realized device has a fixed wedge-shaped Plasticizing gap on the heated sliding shoes supporting the press belts is formed.

In the downstream press nip there is an upper and a lower heated one Pressure body provided, which via endlessly rotating rolling elements the rotating steel belt applied. Immediately downstream of the press zone is a calibration zone which is designed in exactly the same way as the press zone and from the same press belts is run through. This system is intended both in the plasticizing gap as well as in the calibration gap to measure the respective counter pressure of the chip mat. Included the counterpressure in the plasticizing gap is intended primarily to regulate the passage width and thus the pre-compression in the plasticizing gap can be used1 during the Counterpressure in the calibration gap, primarily to regulate the amount required for plasticizing Amount of steam and to regulate the speed of the belts and thus the Compaction time. Is to be used in the inlet zone of the calibration gap.

The arrangement of roller body chains between the steel belt and the pressure horn reduces the stress on the steel belts considerably, but is more than relatively large length of the press and calibration gap relatively expensive. The regulation of the passage width, the amount of steam introduced and the draft speed requires a lot of effort and ultimately does not prove to be useful. sense regulation of the passage width of one formed between rigid sliding blocks Press gap is inappropriate because the sliding friction does not change at will because the strength limit of the steel strip can be reached quickly, or the static friction between the drive roller and the steel belt for the passage is no longer sufficient. The change in the throughput speed is special disadvantageous, since all devices used for mat forming, in particular the spreader for a continuous work process at a constant speed are designed.

The invention is based on the object of the device explained above to be improved in such a way that it can also be used to produce thicker panel strips, which have a high thickness accuracy, with the machine effort in comparison to other known proposals should be kept low.

This object is achieved according to the invention in that the pressure body the double belt press in a manner known per se from several, each in pairs opposed pressure rollers exist, between which the belts with constant, adjustable pressure supporting, heated sliding shoes are provided, at least two pairs of pressure rollers a device for adjusting their press nip distance have, which are acted upon by the pressure measuring device of the calibration zone.

The adjustment of the press gap distance can be done via mechanical devices, e.g. with the help of servomotors or the like, or it results by changing the pressure.

An essential feature of the invention is the fact that the sliding friction between the press belts and the sliding shoes that support them is not changed. You will on one for the tensile strength of the tape and its Static friction set on the drive rollers permissible value, which is basically should be as high as possible in order to avoid any springback of the pressed material.

Another essential advantage of the invention arises from the Thickness control. The back pressure is used as a controlled variable in a fixed gap between relatively large areas removed.

If there is no longer any counter pressure at this point, the runway is too high been compacted, or by drying out in the final phase of the pressing process shrunk too much. If the counterpressure in the calibration gap is too high, the plate will Spring back elastically by an uncontrollable amount. However, if one puts an empirical determined nominal dimension as gap distance in the calibration gap, which is a small can be less than the nominal thickness of the plate, a is obtained as a controlled variable relatively low back pressure and thus achieved with the relatively complicated Material the greatest possible control accuracy.

Control devices for controlling the thickness of continuously manufactured Wood-based panels have become known through DT-Gm 7 209 285 and 7 315 138. Here, behind the press or behind another processing machine, the thickness is measured the plate path is scanned by rollers that operate on a hydraulic piston with large Surface act that with another hydraulic piston with a very small cross-section connected and with minimal changes the scanning roller causes large deflections on the small piston, which in turn control pulses for trigger the preceding units. However, these suggestions are just as impractical like the regulation with the help of a rigid press gap adjusted to a precise fixed dimension (DT-OS 1 291 506). Wood-based materials have both plastic and elastic properties, which are still superimposed by swelling and shrinking as a result of changes in humidity of the highly hygroscopic material With a partially elastic WerEtOff can an exact thickness control can never be achieved by roller scanning.

In an expedient embodiment of the invention, the endless Belts of the double belt press in a manner known per se at the same time as the belts the calibration device, whose calibration elements consist of at least two, on fixed There are pairs of calibrating rollers adjustable between the gap, of which at least one is heated, and between which there is also an adjustable gap distance heated pair of calibration sliding shoes is arranged, which is connected to the pressure measuring device is provided.

The rollers of the last roller pair seen in the direction of passage can each be mounted on a rocker arm and at the same time as drive and tensioning rollers be designed for the endless belts. These drive rollers are unheated and can be coated with a heat-resistant rubber coating or another suitable friction lining be coated. The tensioning of the steel belts is carried out by the drive rollers exerted drive torque. By relocating the belt tension to the drive rollers the front infeed rollers can be designed as adjustable pressure rollers.

The ratio of the press nip distances of the individual pressure roller pairs can be permanently adjustable and remain constant even during regulation.

The endless belts of the double belt press can be used in front of the actual rectilinear pressing zone in a manner known per se form a pre-pressing zone in which the material to be pressed is successively guided around two heated rollers that the conveying direction of the goods is changed twice by around 1800 each time. It is there advantageous if at least at the transition between pre-press zone and straight press zone an adjustable counter-curvature roller is provided. This can be done again a slight counter-curvature of the pressed material, which is already beginning to harden carry out. Appear in the fully cured sheet after leaving of the calibration gap still curvature tendencies, the counter-curvature roller can accordingly be adjusted. Two or more such counter-curvature rollers can also be used are provided.

In a modified embodiment, the endless belts be designed as fabric belts, which are in the prepress zone from the outside by smooth, endless steel belts are covered. Such fabric tapes are known in principle (see e.g. DT-OS 2 205 575).

In the drawing are three exemplary embodiments the invention shown schematically in side view. They show: FIG. 1 a double belt press, which is combined with a calibration device; Fig. 2 one with Double belt press equipped with fabric belts, which is followed by a calibration device and FIG. 3 shows a double belt press according to FIG. 1, but with an upstream one Pre-press zone.

The double belt press according to FIG. 1 has a straight pressing zone 1, which is formed between two counter-rotating steel belts 2, the on its side facing away from the pressed material 3 by three opposing pairs in each case heated pressure rollers 4 are supported. Downstream of these are two pairs of calibrating rollers 5. The rollers 6 of the last roller pair seen in the direction of passage are on each a rocker 7 and also serve as drive and tension rollers for the endless belts 2.

Heated sliding shoes 8 are provided between the pressure rollers 4, which support the belts 2 with a constant, adjustable pressure.

Between the two pairs of calibrating rollers 5 there is also one fixed gap distance adjustable heated calibration sliding shoe pair 9 arranged, which is provided with a pressure measuring device not shown, e.g. Pressure cans or the like can exist. This pressure measuring device is applied Not shown devices for adjusting the nip distance between the pressure rollers 4. These adjusting devices can e.g.

consist of servomotors that have a spindle drive or the like the respective overhead pressure rollers 4 adjusted in the vertical.

The calibration gap is thus of the calibration roller pairs 5 and the calibration sliding shoe pair 9 g formed and expediently based on an empirically determined Dimension, e.g. 2% below the nominal thickness of the panels to be produced. One too empirically 2nd counter pressure of the molding compound, e.g. 0.2 kp / cm is set as a controlled variable and controls when it is over or undercut Value is the gap between the pressure roller pairs 4. The specific pressure on the sliding shoes 8 preferably remains constant at the minimum 2 possible value, e.g. 2 kp / cm2, to prevent the pressed material 3 from springing back too much.

The pressure rollers 4, the sliding shoes 8 and 9 and at least one pair of calibrating rollers 5 are heated and at the same time serve to heat the pressed material 3. The drive and tension rollers 6 are unheated and with a heat-resistant rubber coating or the like

coated.

A press of this type is relatively uncomplicated and achieved a large heating surface, so that even with conventional technology it is economical Throughput speeds can be achieved. That is through the individual Regulation of the individual pressure rollers 4 resulting gradual closing program with very high line pressures for the gradual compression of the pressed material 3 with intervening low specific pressures to prevent the spring back of the pressed material to extremely low thickness tolerances. The scheme is a result of the great Area scanning within the calibration zone very precisely, so that the otherwise usual Grinding losses in the panels produced can largely be avoided.

In the system according to FIG. 2, the double belt press is a separate one Calibration device 10 connected downstream. The entire system includes starting from the left a tension roller 11 for a lower wire cloth belt 12, a spreader 13 for Forming a mat, a downstream one Scale 14 for checking the weight per unit area and a tension roller 15 for the upper wire mesh belt 12. Within the two endless circumferential wire mesh belts 12, a surface moistening 16 is provided in each case, which can consist of a longitudinally slotted tube with a wick wiper. It This is followed by unheated tensioning and draw-in rollers 17 for steel strips 18, which alternate heated heating plate sliding shoes 19 and pressure roller pairs 20 are arranged downstream. That penultimate pair of rollers 21 is used to drive and deflect the steel belts 18 and is just as unheated as the last pair of rollers 22, which is used to drive and deflect the Wire mesh belts 12 are used. There then follow cooling plate sliding shoes 23, which with low grind the specific pressure over the sheet and through surface cooling, Condensation and surface moistening plasticize the grain of the screen Resulting material to be pressed.

The downstream calibration device 10 has unheated calibration plates 24, the previously softened sieve graining via endlessly revolving rolling element chains 25 press smooth and with rolling friction the counterpressure of the plate web on the calibration plates 24 transferred. This back pressure is measured using load cells and used as a control variable entered for the pressure roller pairs 20 in a controller, not shown. In this a counterpressure corresponding to an undersize is set as the nominal value. at of this device are the endless belts through the endless rolling element chains 25, which can consist of precision round steel rods between guide chains are attached.

Die.Spann- and draw-in rollers 17 cause only a slight pre-compression. The downstream heating plate sliding shoes 19 are heated up to 0 to 300 C and provide for an intense burst of steam. The main compaction of the mat is done by the first pair of pressure rollers 20. The specific pressure runs in strong pressure peaks between the adjustable pressure roller pairs, which alone do the compression work. The compression takes place exclusively with rolling friction. The whole The pressing distance is about 8 m. A 9 mm thick plate could be fed at about 8 m / min be driven. A three-shift daily production can be achieved with such a system of around 120 cubic meters. Let by avoiding grinding losses save approx. 10% of the manufacturing costs. In addition, the fall out of the Grinding dust separation resulting environmental problems away.

The system according to FIG. 3 consists of one of those shown in FIG Press-like pressing device, which is preceded by a pre-pressing zone. These consists essentially of two heating drums 26, 27 and three deflection and pressure rollers 28.29.30.

An upper fabric belt 31 is around the deflection and pressure roller 28, on the outside around the heating drum 26, then on the inside around the heating drum 27 and finally on the outside Via a counter-curving roller 32 through the press zone 1 and finally around a deflection drum 33 led. The upper steel belt 2 runs from the deflection u.

Pressure roller 29 on the outside of the heating drum 26 and then on the inside onto the heating drum 27 and finally via the first pressure roller 4 back to the deflection and pressure roller 29. The lower steel belt 2 runs over a tension roller 34 on the inside on the heating drum 26, then on the outside of the heating drum 27 and over the Deflection and pressure roller 30 back to tension roller 34. The lower fabric belt 31 overflows the tension roller 34 on the inside on the heating drum 26 after it has previously been removed from the spreader 13 is covered with the chip mat to be pressed and then runs over the outside Heating drum 27 and from there via the deflection and pressure roller 30, the counter-curvature roller 32 through the pressing zone 1 and the lower deflection drum 33 back.

The chips are directly on the returned strand between the tension roller 34 and heating drum 26 sprinkled. When changing the direction of the curvature between the heating drums 26 and 27 inevitably occurring thrust forces are by a Sliding movement between the steel belts 2 and the fabric belts 31 balanced, therefore do not have any effect on the stored pressed material 3.

Claims (7)

Patent claims: rn 0 Device for the continuous production of an endless plate web from pressed vegetable materials, consisting of a double belt press, whose two belts rotating in opposite directions and forming a straight press gap are supported on their side facing away from the pressed material by heated pressure bodies and a calibration device downstream of the double belt press, which also two counter-rotating endless belts supported by calibration elements and a pressure measuring device for determining the counter pressure of the one passing through the calibration gap Has pressed material, d a d u r c h g e -k e n n n z e i c h n e t that the pressure body the double belt press in a manner known per se from several, each in pairs opposed pressure rollers (4; 20) exist, between which the belts (2; 18) supporting, heated sliding shoes (8; 19) are provided, at least two Pressure roller pairs have a device for adjusting their press nip spacing, which are acted upon by the pressure measuring device of the calibration zone. 2. Apparatus according to claim 1, characterized in that the endless The belts (2) of the double belt press are also the belts of the calibration device (5,9), whose calibration elements consist of at least two, fixed gap spacing adjustable pairs of calibrating rollers (5), of which at least one is heated is, and between them a heated one that can also be set to a fixed gap distance Calibrating sliding shoe pair (97 is arranged, which is provided with the pressure measuring device is. 3. Apparatus according to claim 2, characterized in that the rollers (6) of the last pair of rollers, seen in the direction of passage, on one rocker each (7) stored and at the same time as drive and tension rollers for the endless belts (2) are formed. 4. Apparatus according to claim 1, 2 or 3, characterized in that that the ratio of the press nip distances of the individual pressure roller pairs (4; 20) is permanently adjustable. 5. Device according to one of the preceding claims, characterized in that that the endless belts (2) of the double belt press before the actual straight one Press zone (1) form a pre-press zone in a manner known per se, in which the Good (3) is guided one after the other around two heated rollers (26, 27) that the conveying direction of the good is changed twice by 0 about 180 each time. 6. Apparatus according to claim 5, characterized in that the transition between the pre-press zone and the straight press zone (1) at least one adjustable counter-curvature roller (32) is provided. 7. Apparatus according to claim 5 or 6, characterized in that the endless belts are designed as fabric belts (31) in the pre-pressing zone are covered from the outside by smooth, endless steel strips (2).