EP0458806B1 - Process and installation for manufacturing particle boards and the like - Google Patents

Abstract

In a double band press for manufacturing particle boards and the like, narrow marginal strips of the dispersed material (33) from which the boards (33) are made are sucked from the edge (32) of the dispersed material as far as stationary ridges (37).

Description

The invention relates to a method of the type corresponding to the preamble of claim 1 and a corresponding system, as are known from DE-PS 23 55 797.

Such a system represents a considerable investment, and operators therefore wish to be able to manufacture not only panel widths corresponding to the nominal working width on such a system, but also, if necessary, panels of a smaller width. For example, the usual panel widths are 210 and 185 cm. Attempts to drive the smaller plate width on the system designed for the larger plate width by setting the width of the bed correspondingly smaller have previously encountered problems because the edges of the forming strips projecting beyond the edge of the bed no longer experienced any counterpressure and were no longer sufficiently pressed against the support structure, from which not only the pressure but also the heat is transferred to the forming belts. As a result, the form strips had no thermal contact with the support structure or the one from the edge DE-PS 23 55 797 known construction transferring the heat from the support structure to the form belts, the entire width of which rolls more so that the temperature of the form belts dropped considerably towards the edge. As a result, the edge areas contracted lengthways and, since the wide central area of the forming tapes was at the working temperature, considerable thermal stresses developed. Such thermal stresses became critical in the area of the deflecting drums, because the thermal stresses were superimposed there with the stresses due to the considerable longitudinal tension of the forming tapes and the stresses due to their deflection due to the stretching of the outer fiber. This resulted in total tensile stresses on the outside of the areas of the forming tapes passed over the deflection drums, which came close to and sometimes exceeded the yield stress, but in any case led to problems in continuous operation, especially since the forming tapes are made of corrosion-resistant steel, which is not able to withstand the permanent bending stresses excessively well .

Similar problems have also occurred with double belt presses before, even if the nominal width was used. The bed does not extend exactly to the edge of the shaped belts, but they protrude a certain amount in the transverse direction over the bed and also over the edge of the rolled-over area. Here too there was a drop in temperature and the resulting tensions.

In the press according to DE-PS 22 43 465 an attempt was made to keep the temperature drop within limits by heating the protruding edges of the forming tapes. However, it has been found that it is necessary to remove the edges of the To heat the forming tapes practically over their entire length, because otherwise the temperature behind a heating point will drop immediately. Heating over the entire length, however, poses considerable structural problems and is generally not an option because of the great expense involved.

Another solution has been found according to DE-PS 28 19 943 in corrugating the protruding edge of the forming tapes, so that there is more material available to a certain extent when the temperature drops towards the edge and not as high longitudinal tensile stresses occur during a thermally induced contraction . This measure is practicable with protruding edges of a few centimeters, but no longer if these edges, in which there is a drop in temperature, are several tens of centimeters.

From DE-OS 37 04 940 a solution to the problem is known, in which in the outside zone of at least one edge of the bed resulting in the plates extending into the vicinity of the edge of the pressing section, an edge bed of binder-free particles is sprinkled onto the lower forming belt and is also pressed. Although excellent results are obtained with this method, the effort for the additional spreading device and the downstream return devices of the scattered binder-free material at the end of the pressing section is considerable.

The invention has for its object to design a generic method and such a system so that a sufficient heat transfer of the form belts at the edge ensuring the same can be achieved on the roller chains with less equipment.

This object is achieved in its procedural aspect by the invention reproduced in claim 1.

The webs that remain between the suctioned-off edge strip sections surprisingly hold the shaped tapes in their area in contact with the roller chains in such a way that sufficient heat transfer is ensured and the bowl-shaped deformation of the shaped tapes, which is caused by the uneven temperature distribution, is within acceptable limits in practice holds. The formation of the form belts in the outer areas also prevents the caking of lubricant on the roller running surfaces there and maintains the lubrication of the rollers.

Another aspect is that the actual spreading width used can be adapted to the plate width used, without the spreading machine having to be adjusted in its working width, which would be very expensive, and without having to saw off wide continuous edge strips of the finished plate.

The effort for a suction device at the edge of the bed is less than that for a spreading device according to DE-OS 37 04 940. Compared to the alternative of simply driving the panel web to its full width and sawing off a correspondingly wide continuous edge strip, there is also one Simplification and savings, because it is much easier to dispose of the not yet hardened chip material than to dispose of a wide edge strip that has already hardened into a plate and is therefore initially to be shredded, and because the extracted and not yet hardened chips can also be returned to the spreading device.

The vacuumed edge strips should be "narrow". What is meant is that with a width of the panel web of approximately 2 m, the edge strip section can be, for example, 2 to 30 cm wide (claim 2). The length of the webs in the longitudinal direction of the web can be about 2 to 20 cm (claim 3), it being recommended that this length is at most as long as the length of the edge strip sections that have been vacuumed off, because otherwise the simplification effect is not sufficiently noticeable.

In detail, the ratio of the length of the vacuumed edge strip sections to that of the webs can be approximately 3: 1 to 15: 1 (claim 4), the length of the vacuumed edge strip sections being in the range of approximately 30 to 100 cm (claim 5).

The apparatus aspect of the invention is the subject of claim 6.

• Fig. 1 ist eine Seitenansicht einer Doppelbandpresse, an der die Erfindung anwendbar ist;
• Fig. 2 ist ein vertikaler Längsschnitt durch die Doppelbandpresse nach der Linie II-II in Fig. 3;
• Fig. 3 ist ein Querschnitt durch die Doppelbandpresse nach der Linie III-III in Fig. 1;
• Fig. 4 ist ein Teilquerschnitt durch den in Fig. 3 mit einer punktierten Umrahmung versehenen Randbereich IV;
• Fig. 5 ist eine Teilansicht von oben auf den Randbereich der Bahn einer Holzfaserplatte in gegenüber Fig. 4 verkleinertem Maßstab.

In the drawing, an embodiment of the invention is shown.

• Fig. 1 is a side view of a double belt press to which the invention is applicable;
• Fig. 2 is a vertical longitudinal section through the double belt press along the line II-II in Fig. 3;
• Fig. 3 is a cross section through the double belt press along the line III-III in Fig. 1;
• FIG. 4 is a partial cross section through the edge region IV provided with a dotted frame in FIG. 3;
• FIG. 5 is a partial top view of the edge region of the web of a wood fiber board on a smaller scale compared to FIG. 4.

In Fig. 1, a double belt press for the production of chipboard, fiberboard and other plate-shaped materials is shown, which consist of particles bound by means of a binder that cures under pressure and heat. It comprises an upper forming belt 1 made of sheet steel of approximately 1 to 1.5 mm in thickness and an equally lower forming belt 2. Between the forming belts 1, 2, a web 4 is compressed from a bed 4 'in a pressing section 3, which is made of a pourable material exists that results in one of the aforementioned materials after pressing.

The upper forming belt 1 runs around rollers or drums 5,6 arranged transversely to the web 4, of which the drum 6 can be pivoted in a fixed stand 7, the drum 5 in a support 8 on the floor about an axis running transversely to the web 4 Stand 9 is mounted. The stand 9 is moved via the hydraulic cylinder 10 and the forming belt 1 is stretched in this way.

Correspondingly, the forming belt 2 runs over drums 11, 12 arranged transversely to the web 4, of which the drum 11 is mounted in a fixed stand 13, the drum 12 in a stand 14 movable on rails is. The stand 14 can be moved in the longitudinal direction of the web by hydraulic cylinders 15 and the forming belt 2 can be tensioned in this way. The form belts are driven by the drums.

The shaping belts 1, 2 run through the device in the sense indicated by the arrows 16, so that the bed 4 ′ applied on the right-hand side according to FIG. 1 by means not shown is drawn into the pressing section 3. The running compressed web 4 is removed in the left region of the forming belt 2 according to FIG. 1 by suitable devices, not shown. In the pressing section 3, an upper support structure 17 is provided in the inner region of the forming belt 1, which cooperates with a lower supporting structure 18 provided in the inner region of the lower forming belt 2. The support structures 17, 18 support the areas of the shaping tapes 1, 2 facing the web 4 against the web and press them flatly against one another with great force.

The support structures 17, 18 each consist of individual supports 19, 20, which are arranged opposite one another above and below the forming belts 1, 2 and the web 4 (FIG. 2). Each pair of supports 19, 20 is clamped by lateral spindles 21 (FIG. 3), so that individual pressure members which are self-contained are formed.

Strong plates 26, 27 are located between the carriers 19, 20 and the shaping bands 1, 2, which transmit the force exerted by the individual carriers 19, 20 evenly to the shaping bands 1, 2 and contain the channels 40 (FIG. 4). in which heating elements are arranged or through which a heating medium is passed.

Roller chains 30 are arranged between the mutually facing sides of the plates 26, 27 and the shaping belts 1, 2, on which the shaping belts 1, 2 roll relative to the plates 26, 27 and which run endlessly in a vertical longitudinal plane around the plates 26, 27. The rollers of the roller chains 30 transmit both the pressure and the heat of the plates 26, 27 to the shaping belts 1, 2 and thus the web 4 that forms.

After a certain point of the roller chains has arrived at the end of the length section 3, the roller chains 30 can either in the actual pressing area, i.e. between the carriers 19, 20 and the plates 26, 27 can be returned, as is indicated in FIG. 2 for the plates 26 and in FIG. 4. This embodiment has the advantage that the roller chains 30 maintain their temperature substantially constant during circulation. However, there is also the possibility of guiding the roller chains 30 around the outside of the support structure, as can be seen in the support structure 18 in FIG. 2 below.

4, the plates 26, 27 are made up of a heating and support plate 43 and a return plate 44 separate therefrom with return grooves 42 for the roller chains 30. It is a partial cross section through an edge region located above the web 4 according to FIG. 2.

The plates 43 have the heating channels 40, which are connected to one another at the ends via pipe elbows 45 to form a closed conduit, and smooth running surfaces 41, which form the common rolling surfaces for the roller chains 30 arranged next to one another, which can be seen in FIG. 4.

During the forward movement of the shaping belts 1, 2, the roller chains 30 roll between them and the facing running surfaces 41 of the plates 43. Adjacent roller chains 30 lie directly opposite one another with their outer end faces.

What is essential to the chain arrangement is the fact that two adjacent roller chains 30 can be moved forward independently of one another. The entirety of the support elements of the shaping belts 1, 2 forms a field which is divided into individual strands in the longitudinal direction, which can shift relative to one another in the longitudinal direction when subjected to corresponding stress. It is therefore not possible for any constraining forces arising from the different entrainment of the form belts to form within the roller chain arrangement.

When driving on the double belt press shown with the full working width 34, the right edge 31 of the bed and the plate web 4 according to FIG. 4 lies approximately at the level of the right edge of the roller chains 30. However, it is now desirable to use a narrower one on the same press To produce a plate web whose right edge 32 according to FIG. 4 is located inside the rolling area of the roller chains 30.

A bed 33 of wood shavings or other suitable particles is then applied in the usual way, the width of which corresponds to the nominal working width 34 and is characterized by the position of the edge 31 in FIG. 4. These wood chips or other particles are provided with binders, which is to be indicated in the drop area 39 in FIG. 2 by the dotted lines.

On the two edges of the bed 33, a suction device 50 is arranged in front of the inlet between the forming belts 1, 2, by means of the edge strips 38 (see FIG. 5) of the bed 33 which can be sucked off intermittently by corresponding actuation of the valve 51, so that the Bulk 33 is "notched" at the edge. The length of the vacuumed edge strip sections 38 is denoted by 36 in FIG. 5 and its width from the edge 31 corresponding to the maximum working width to the edge 32 which represents the actual limitation of the respective working width. Webs 37 remain between the vacuumed edge sections 38, in which the bed 33 up to the full working width 34, ie 4 and 5 stops up to the edge 31. The length of the webs 37 in the longitudinal direction of the web 4 is designated 46. In the region of the width 35 of the webs 37, the shaped strips 1, 2 are supported in the manner shown in FIG. 4 and pressed against the roller chains 30, 30. In the area of the edge strip sections 38, which extend in the longitudinal direction of the web 4 between the webs 37, there is no chip material and there is no support. However, it has been shown that the interrupted support in the toothed edge of the web 4 enables sufficient heat transfer in the edge zone.

Claims (6)

1. A process for the continuous preparation of chipboard panels and similar panel materials consisting of particles bonded by a heat and pressure cured binder in a twin belt press in which the binder-treated particles are sprinkled on a horizontal run of a bottom forming belt as a loose fill and heat and pressure cured in a pressing zone between the top and bottom metal forming belts, which co-rotate in the feed direction of the press, to form a stock or web for the future panels, the working pressure and the forming heat in the pressing zone being transferred from the support structures of the press to the forming belts and therefrom to the loose fill, characterised in that a narrow edge strip of the loose fill (33) which will subsequently form the web (4) of panel material is removed by suction on at least one edge of the loose fill (33) except for residual ribs (37).
2. A process according to claim 1, characterised in that the width (35) of the edge strip parts (38) thus removed is approximately from 2 to 30 cm.
3. A process according to claim 1 or 2, characterised in that the length (39) of the ribs (37) lengthwise of the web (4) is from approximately 2 to 20 cm.
4. A process according to claim 3, characterised in that the ratio of the length (36) of the removed edge strip parts (38) to the length (39) of the ribs (37) is approximately from 3 : 1 to 15 : 1.
5. A process according to any of claims 1 to 4, characterised in that the length (36) of the removed edge strip parts (38) is approximately from 30 cm to 100 cm.
6. An apparatus for the continuous preparation of chipboard panels and similar panel materials consisting of particles bonded by a heat and pressure cured binder, the apparatus comprising a twin belt press having two metal forming belts which are disposed one above another in a pressing zone and which bear on a support structure, a material which is in the pressing zone being adapted to be pressed together between the rollers in association with pressure and heat, the apparatus comprising sprinkling means adapted to sprinkle the binder-treated particles on a horizontal run of the bottom belt to form a loose fill, characterised in that an intermittently operating suction device (50, 51) is disposed on at least one edge of the loose fill (33) and is adapted to remove by suction narrow edge strip parts (38) of the loose fill (33).

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