EP0146752B1 - Process and device for the extrusion of plant particles, especially wood particles, mixed with a binder - Google Patents

Abstract

Extrusion of a mixture of vegetable bits with a binder, particularly wood chips with a weather-resistant binder, involves precompressing in a compression chamber of an extrusion press the mixture by a compression stroke transverse to the extrusion axis, the compression stroke being delivered by at least one precompression piston. Prior to the precompression elongated bits of the mixture are acted on by an orienting influence so that the elongated bits are deposited substantially parallel to the extrusion axis. The outer layers of the mixture are compressed with a reduced precompression ratio so that the bits oriented prior to precompression remain fixed in position during the subsequent extrusion stroke. Preferably the elongated bits in the mixture are oriented by free fall of the mixture through a plurality of upright, thin-walled bars of approximately equal height positioned above the compression chamber during filling of the extrusion apparatus by a mechanical hopper moving to and fro over the bars continuously.

Description

The invention relates to methods and devices for the extrusion of vegetable small parts, especially small wooden parts, mixed with in particular weather-resistant binder, in a piston extrusion press in accordance with the features listed in the preamble of the main claim.

These result from DE-AS 12 47 002, with which the aim is to align the individual pressing particles in the extrusion process in a certain direction. For this purpose, the mixture is pre-pressed in a first pressing process by a vertically acting plunger in a vertical press channel with considerable compression and in a second pressing process is pressed by a horizontally acting extrusion piston with only slight further compression. If you understand this teaching, you will find that the small parts located in the area of the outside assume an approximately parallel position to the surface, which is also known long ago from the compression molding process of extrusion plates. In the core area of the strand, however, there is an arbitrary layer of small parts, particularly when thick-walled extruded products are manufactured. Furthermore, the view of the previously known teaching that a considerable compression of the mixture during the pre-pressing process should lead to an increase in the bending strength of the extruded product should not be shared. The more intensive the compression in the pre-pressing process, the less binding the sections pressed against one another during extrusion can experience. Such a product will consequently break relatively easily along the connecting surface of these individual sections and thus will not achieve any useful values in terms of bending strength. In order to avoid this effect, the end face of the known extrusion piston is provided with a concavely recessed curvature, through which the end face of the individual extrusion section is mapped accordingly and a kind of tongue and groove connection of the sections results.

The invention has for its object to develop the known extrusion process in such a way that a considerable increase in the bending strength of the extruded product in the longitudinal direction is achieved with improved connection of the individual extrusion section. In particular, the invention aims to produce high-quality, in particular thick-walled extruded sheets with reduced specific weight and weather-resistant gluing, which can be used, for example, for interior walls of buildings, stables and the like and which have the required strength for this.

The achievement of this task is based on the characterizing features of the main claim.

The invention is based on the knowledge that layers which are clearly distinguishable from one another must be pronounced in the finished extruded product, the longer chips in particular, at least in the outer layers, being intended to have a position which is predominantly oriented parallel to the extrusion direction. It is therefore not only important that the chips lie approximately parallel to the large surface of the strand. The strength is rather increased if this parallel position is directed longitudinally to the extrusion axis.

However, this orientation cannot be achieved simply by pre-pressing the batch, but it is necessary to pre-orient at least the longer small parts of the batch when it is being filled into the press space of the extrusion press. The compression ratio during pre-compression is chosen so that the oriented position of the small parts is fixed and can no longer change significantly during extrusion. A preferred compression ratio is given in claim (2).

The pre-orientation of the small parts is brought about in accordance with the exemplary embodiment of claim (3) during their free fall into the press space during filling. Surprisingly, this is achieved in a very simple manner by filling the batch through narrow shafts which extend longitudinally in the extrusion direction and which are formed by spaced-apart thin-walled and upright webs and which are arranged in a stationary manner.

The principle of this orientation is known per se from DE-OS 29 26 087, although a fleece is to be formed which is required for the compression molding of chipboard. In addition, the webs of different heights must intermesh like a comb and be exposed to vibration.

In one embodiment of the invention, however, webs of the same height are used, which are arranged on both sides of the press space at a greater distance from one another than in the prior art.

Another important idea of an embodiment of the invention is to press the batch accumulated in the baling chamber from both sides. Because of the arrangement of the aforementioned webs, the pre-press punches must therefore penetrate through the shafts present between the webs. At the same time, however, the press stroke of this pre-punch is limited by the height of the webs. Therefore, only a limited pre-compression of the outer layers is brought about by each pre-compression die, the compression ratio of which is considerably lower than that of DE-AS 12 47 002.

However, this also creates the prerequisite for connecting the individual extrusion sections to one another extremely firmly, without the precompression proving to be a hindrance.

The method according to the invention can both can be used with vertical as well as horizontal piston extrusion presses. An oblique pressing direction can also be carried out. However, since horizontal extrusion is preferable, only one is assumed below, without the invention being restricted thereto.

In claim 9, an apparatus for performing the method according to claim 1 is defined.

In the subclaims (14 and 15) preferred embodiments in the sense of independent inventions are listed, the technical success of which follows from the drawing and the description. It is surprising here that the longitudinal orientation of the small parts can be varied to some extent. For example, it is possible to place the small parts in the outer layers, preferably lengthways, but more or less matted in the core area. However, it is also possible to produce the desired longitudinal orientation of the small parts over the entire thickness of the extruded product, at least to a considerable extent.

This is particularly important when the extruded product is intended to have longitudinal channels as defined in claim (14). It was surprisingly found that when the method according to the invention is used, the wall area encompassing the channels is compacted in a shell-like manner and that a longitudinal orientation of the small parts can nevertheless be determined between the channels. Surprisingly, the closer the channels are adjacent, the more likely this phenomenon occurs, although a minimum distance must be maintained because the press space is completely filled. The channels are optimally spaced if they are equal to or slightly larger than the radius of the channels.

In addition, the invention teaches with claims (11) and (12) to move the upper pre-press along the webs covering the filling opening for the pressing chamber so that the pressing chamber is released for the filling process. Experience has shown that part of the batch accumulates in free fall on the upper end faces of the webs. It is therefore expedient to provide a squeegee which is movable lengthwise or transversely to the webs and which scrapes the batch and helps to bring the small parts into the desired orientation.

• Fig. (1): eine perspektivische Teilansicht eines mehreren Schichten aufweisenden Strangpreßerzeugnisses,
• Fig. (2): eine Teilansicht gem. Fig. (1) bei einem mit durchlaufenden Kanälen versehenen Strangpreßerzeugnis,
• Fig. (3): eine Teilansicht des Strangpreßerzeugnisses gem. Fig. (2) entlang einer Schnittebene 111-111,
• Fig. (4): einen Querschnitt durch den Preßraum einer Kolbenstrangpresse (senkrecht zur Strangpreßrichtung gesehen),
• Fig. (5): einen Querschnitt gem. Fig. (4) mit Darstellung von Vorpreßstempeln in ihrer Pre- ßendlage,
• Fig. (6): einen schematischen Längsschnitt durch die Kolbenstrangpresse,
• Fig. (7): einen Teillängsschnitt durch eine Beschickungsanordnung mit einer Rakel,
• Fig. (8): einen Querschnitt durch ein mit Kanälen versehenes Strangpreßerzeugnis mit Bemessungsangabe und
• Fig. (9 und 10): perspektivische Teilansichten eines Strangpreßkolbens in zwei Ausführungsvarianten.

Further details of embodiments of the invention emerge from the subclaims, the drawing and the description. In the drawing, embodiments of the invention are shown schematically and for example. Show it:

• 1 is a partial perspective view of an extruded product having multiple layers,
• Fig. (2): a partial view acc. (1) in an extruded product provided with continuous channels,
• Fig. (3): a partial view of the extrusion according to. (2) along a sectional plane 111-111,
• Fig. (4): a cross section through the press chamber of a piston extrusion press (seen perpendicular to the extrusion direction),
• Fig. (5): a cross section acc. Fig. (4) showing pre-press rams in their press end position,
• 6 shows a schematic longitudinal section through the piston extrusion press,
• (7): a partial longitudinal section through a loading arrangement with a doctor blade,
• Fig. (8): a cross section through an extruded product provided with channels with designation and
• (9 and 10): perspective partial views of an extrusion piston in two design variants.

Fig. (1) of the drawing shows a partial perspective of an extruded product (1), which can have a considerable thickness, for example (8, 5) cm, and is preferably used as a screed, inner wall of a building, load-bearing plate and the like. The invention does not preclude the production of thin-walled extrusions according to the method described later.

The product (1) produced along the extrusion axis (5) has a typical layer formation which is to be produced during extrusion. The upper cover layer (2) and the lower cover layer (3) should be pre-compressed with respect to the core layer (4). It is essential that at least in these cover layers (2, 3) especially the longer small parts have a chip orientation (6) oriented parallel or almost parallel to the extrusion axis (5).

It is assumed that a mixture of small plant parts, in particular small wooden parts, is to be extruded with a binder, the small parts also having a substantial proportion of elongated chips. However, it is not intended to use special mixtures for the formation of layers (2, 3, 4). The binder should be weatherproof.

In Fig. (2) a variant of the extruded product (1) is shown, which have longitudinally running and mutually parallel channels (7). The layer (8) forming the channel wall in turn has a higher compression than the core layer (4). If, according to FIG. (3), a section is taken along the plane 111-111 in FIG. (2) through the extruded product (1), then the aim is also in this sectional plane to have an orientation (6) oriented parallel to the extruding axis (5) to achieve longer chips or small parts.

(1) to (3) represent possible products of the method according to the invention described below.

According to the embodiment of FIG. (4-6), it is assumed that a press chamber (10) of the press ram contour (12) of the usual extrusion piston is circumscribed. This extrusion piston (20), which is shown in more detail in FIGS. (9 and 10), has an in particular rectangular cross section designed in accordance with the extrusion product (1) of FIGS. (1) and (2). It is guided between the press room walls (11) perpendicular to the plane of the drawing in Fig. (4). A plurality of webs (13), which are at a certain distance, for example (8) mm, from one another, are relatively thin-walled and are fixed vertically upright on the top and bottom of the press ram contour (12). Because they are wearing parts, the use of a steel band suitable for the formation of saw blades is recommended. Between the upper webs (13) there is free access for the batch located in the loading arrangement (14), which is intended to get into the baling chamber (10) in free fall. In the shafts (18) between the lower webs (13) protrude prong-like strips of a lower pre-compression ram (16) which is guided to move back and forth along the arrow (22) in the exemplary embodiment in the vertical direction. The free end faces of these strip-shaped approaches form strip-shaped pressing surfaces (40). The webs (13) engage with play in the matching column (17) of the lower pre-press ram (16).

The webs (13) have the function of aligning the small parts of the mixture in the charging arrangement (14) during free fall, so that, as shown in FIGS. (1) and (2), they predominantly have a parallel chip orientation ( 6) to the extrusion axis (5). This chip orientation (6) is favored in that the loading arrangement (14) - as shown later in FIG. (6) - is moved back and forth along the webs (13) with its outlet opening (15). The lower edge of the loading arrangement (14) can be arranged at a distance from the upper edge of the upper webs (13). In this case it is to be expected that a small part of the batch will settle on the upper edge of the webs (13) to form a bridge. In order to safely and evenly distribute these accumulations in the press chamber (10), it is recommended according to FIG. (7) to arrange at least one doctor blade (27) on the oscillating feed arrangement (14), which also contributes to the small parts due to its movement to be oriented along the extrusion axis (5).

As soon as the press chamber (10) is filled, an upper pre-press die (19) is brought into a position between the upper webs (13) by a longitudinal displacement parallel to the extrusion press axis (5), which is approximately that of the lower pre-press die shown in Fig. (4) (16) corresponds. In this position, the mixture is pre-pressed in an approximately vertical direction (in the case of horizontal piston extrusion presses) with the aid of the pre-compression punches (16, 19). The strip-like approaches of the pre-press punches (16, 19) penetrate the shafts (18) between the webs (13) and reach their end position shown in FIG. (5), with the contour (12) of the extrusion piston shown in FIG. (4) matches. In this way, the outer layers (2, 3) (see Figs. (1) and (2)) are pre-compressed, but should only reach such an extent that the extrusion stroke to be carried out afterwards achieves a secure connection of the individual extrusion sections to one another should let. For example, pre-compression in a ratio of 1: 2 has proven to be expedient. The consequence of this pre-compression is that the already longitudinally oriented small parts are fixed in their position and remain in this position during the extrusion stroke.

In the schematic representation of FIG. (6), a vertical longitudinal section through the press arrangement is shown. The extrusion piston (20) is driven to reciprocate in the horizontal direction in accordance with the arrow (21). An extrusion technology according to DE-PS 29 32 406 is preferably used. The movement distance of the extrusion piston (20) is symbolized by the webs (13) arranged above and below, the position of the lower pre-compression ram (16) with its stroke direction (22) being made clear. At the press chamber (10) in the direction of the extrusion axis (5) is followed by a curing channel (25), which is preferably designed according to the teaching of DE-PS 25 35 989 and DE-PS 27 14 256. Above the upper webs (13), the loading arrangement (14) can be moved back and forth in the direction of the arrow (26). In the exemplary embodiment, this loading arrangement (14) is arranged on a carriage (24) which also carries the upper press ram (19). This press ram (19) dips a certain distance into the shafts (18) between the upper webs (13) (cf. Fig. 4) and also has the function of accumulating during the reciprocating movement of the carriage (24) of the batch introduced into the baling chamber (10) to have a balancing effect. As soon as the baling chamber (10) is filled with the batch, the carriage (24) comes into a position in which the upper pre-compression die (19) comes to lie congruently over the lower pre-compression die (16). Stroke generators (23) are arranged on the slide (24) and move the upper pre-compression die (19) into the end position shown in FIG. (5) in the direction of the arrows (22).

The two prepress rams (16, 19) remain in their position shown in Fig. (5) when the extrusion stroke of the extrusion piston (20) is subsequently carried out.

It is in the hand to achieve different effects with the device shown in FIGS. (4) to (6). If it is important to produce a predominantly longitudinal chip orientation (6) in the entire cross section of the extruded product (1) according to FIGS. (1) and (2), then it is advisable to move the reciprocating movement of the loading arrangement (14) along the arrow (26) to be maintained continuously until the baling chamber (10) is filled. However, if you value it, just to equip the cover layers (2, 3) with such a preferred longitudinal orientation (6) and to bring the mixture in the core layer (4) to a greater or lesser degree of felting without a clear chip orientation being recognizable, then it is recommended that the back and forth movement to be carried out only during the filling of the shafts (18) (FIG. 4) between the webs (13), whereas the filling of the press space to form the core layer (4) can be carried out during a greatly slowed feed movement of the loading arrangement (14). In this case, the small parts of the falling mixture are more or less left to their own devices.

In the course of these considerations, a variant lends itself to being able to achieve the similar effect. For example, the loading arrangement (14) can be designed in such a way that it covers the entire filling area of the pressing space (10). It is then conceivable to set the webs (13) in vibrations along their longitudinal direction, which could have a low amplitude but a high frequency. This measure also makes it possible to achieve a longitudinal orientation (6) parallel to the extrusion axis (5) of the small parts without the dynamic flow effect of the movable loading arrangement (14) shown in FIG. (6) being used. Such a movement is possible in that the webs (13) are connected on one end face to a vibration-generating arrangement, for example a vibrating magnet. It would serve the same goal if the webs (13) remained stationary, whereas the loading arrangement (14) was set in vibration along the extrusion axis (5).

It should also be pointed out that the strip-like approaches of the pre-compression punches (16, 19) do not lead to partial pre-compression of the mixture, although they have gaps (17). Experience has shown that the pre-pressure propagates along the strip-shaped pressing surface (40). On the finished extrusion, there are only stripe-shaped shades on the surface, but there are no disadvantages in terms of strength. If you do not want to laminate the extruded product (1), for example with veneers, a slight sanding of the surface is sufficient to remove these shades.

If you want to produce extruded products (1) according to Fig. (2), it is not indifferent what distance the channels (7) have from each other. In the case of known extruded products, the distance between the channels (7) is at least 1.5 times the radius of the channels (7). In contrast, the invention proposes to reduce this distance. In Fig. (8) it is shown that the distance corresponds approximately to half the diameter D of the channel (7). The optimum of the distance should be slightly above this design theory, but significantly below the previously known design. Experiments have shown that, on the one hand, the dimensioning shown in FIG. (8) enables an optimal formation of the compression layer (8) (see FIG. 2), which is arched around the individual channels (7). On the other hand, it is achieved that when the press space (10) is filled appropriately, the core webs (34) located between the channels (7) have a considerable proportion of small parts (6) aligned parallel to the extrusion axis (5), as shown in FIG. (3) emerges.

However, the closer the channels (7) are adjacent, the more difficult it is to fill the baling area below the bars forming the channels (7) in the free fall of the small parts. In order to avoid this disadvantage, the lower pre-press ram (16) with the lower webs (13) and with the housing guiding these parts is moved back and forth transversely to the extrusion axis (5) during filling, as a result of which a distribution of the area in the lower press area is accumulated Batch is brought about (Fig. 4).

Finally, FIGS. (9) and (10) show schematic, perspective partial views of an extrusion piston (20). From DE-AS 12 47 002 it is known to concave the end face of the extrusion piston. Instead, Fig. (9) teaches a convex design by a protruding end profile (35) and two slightly recessed intermediate profiles (36) that merge continuously. In contrast to the previously known teaching, however, the edge areas between the alignment lines (37, 38) are provided with undulating deviations (39), which has the advantage that the teeth of the extruded sections to be connected to one another are more intensive without the chip orientation (6) being significantly increased influence.

In the embodiment of Fig. (10), a concave curvature (41) of the end face of the extrusion piston (20) is shown, which merges into sawtooth-like profiles (42) along the piston edges, which are very rounded.

In both cases, it is advisable to cool the extrusion piston in order to prevent the batch parts in contact with the extrusion piston from pre-setting.

The end profiles of the extrusion die can be designed as strip profiles and screwed onto the actual die bodies. It has proven to be advantageous if the above screw heads are used because their impression in the molding compound promotes the interlocking of the extruded sections pressed against one another.

parts list

• 1 extruded product (e.g. plate)
• 2 top cover layer
• 3 lower cover layer
• 4 core layer
• 5 extrusion axis
• 6 chip orientation
• 7 channel
• 8 compaction layer
• 9 parting plane
• 10 press room
• 11 press room wall
• 12 stamping contour
• 13 bridge
• 14 loading arrangement
• 15 outlet opening
• 16 lower prepress stamp
• 17 gap
• 18 shaft
• 19 upper pre-stamp
• 20 extrusion pistons
• 21 stroke direction of the extrusion piston
• 22 Direction of stroke of the pre-press punches
• 23 stroke generators
• 24 sledges
• 25 curing channel
• 26 Direction of stroke of the loading arrangement
• 27 squeegees
• 28 Bridge extension
• 29 open frame on one side
• 30 stroke direction
• 31 swivel bar
• 32 swivel axis
• 33 batches
• 34 core bridge
• 35 forehead profiling
• 36 Intermediate profiling
• 37 Escape Line
• 38 escape line
• 39 wavy deviation
• 40 strip-shaped pressing surface
• 41 concave curvature
• 42 sawtooth-like profiling

Claims (17)

1. Process for the extrusion of plant particles, especially wood particles, mixed with a binder, particularly a weather-resistant binder, in a piston-type extruder having an adjacent heatable curing channel (25), in which the mixture is pre- compressed before the extrusion stroke transversely to the axis (5) of extrusion, characterized in that a mixture to which a quantity of relatively long chips, for example pin-shaped chips, has been added is exposed during feeding into the extrusion chamber (10) to an orientation influence acting at least on the relatively long chips in such a manner that the relatively long chips settle parallel or approximately parallel to the axis (5) of extrusion, and in that then the outer layers of the mixture are precompressed at a compression ratio which is so low that the oriented chips in these layers (2, 3) remain fixed in position during the subsequent extrusion stroke.

2. Process according to Claim 1, characterized in that the mixture is pre-compressed at a compression ratio of approximately 1:1.5 to 1:2.5, preferably 1:2.

3. Process according to Claim 1, characterized in that the particles are oriented with the aid of upright thin-walled webs (13) extending in the free fall region of the mixture parallel to the axis (5) of extrusion with mutual spacing.

4. Process according to Claim 3, characterized in that accumulations of the mixture forming on the webs (13) are scraped off (27) into the region of the shafts (18) between the webs (13).

5. Process according to Claim 1 or one of the following characterized in that the mixture is introduced into the extrusion chamber (10) during a to and fro motion along the axis (5) of extrusion, performed by the charging arrangement (14) having an exit opening (15).

6. Process according to Claim 1 or one of the following, characterized in that the mixture in the extrusion chamber (10) is pre-compressed through the shafts (18) between the stationary webs (13).

7. Process according to Claim 1 or one of the following, characterized in that the pre-compressed mixture is extruded over a length of at least 200 mm, preferably 400 to 600 mm, and the friction of at least part of the curing channel (25) acting on the extruded part is reduced or removed during the advance by extrusion.

8. Process according to Claim 1 or one of the following, characterized in that the extrusion piston (20) is cooled.

9. Apparatus for the extrusion of plant particles, especially wood particles, mixed with a binder, particularly a weather-resistant binder, comprising a piston-type extruder with a heatable curing channel (25) adjacent to the extrusion chamber (10) determined by the piston stroke and with arrangements (14, 16, 17) for charging the extrusion chamber and for pre-pressing the mixture in the extrusion chamber (10) transversely to the axis (5) of extrusion, characterized in that there is arranged on the upper feed side and on the opposite side of the extrusion chamber (10) a plurality of upright thin-walled webs (13) parallel to the axis (5) of extrusion and spaced from one another, between which matching sections of two pre-pressing dies (16, 19) guided transversely to the axis (5) of extrusion are movable as far as a plane corresponding to the contour (12) of the extrusion piston (20).

10. Apparatus according to Claim 9, characterized in that the individual pre-pressing die (16, 19) is in the shape of a comb-type structure which has a gap (17) extending parallel to the axis of extrusion between teeth having strip-shaped pressing surfaces (40), for receiving the webs (13).

11. Apparatus according to Claim 9 or 10, characterized in that the pre-pressing die (19) associated with the feed opening of the extrusion chamber (10) is guided movably along the webs (13) from a position releasing the feed opening to a position covering this opening.

12. Apparatus according to Claim 9 or the following, characterized in that a movable scraper (17) acting on the mixture (33) accumulating on the webs (13) is provided.

13. Apparatus according to Claim 9 or one of the following, characterized in that the charging arrangement (14) covers the entire feed region of the extrusion chamber (10) and either the webs (13) or the charging apparatus (14) may be made to oscillate along the web extensions.

14. Apparatus according to Claim 9 or one of the following, characterized in that to form channels in the extruded product, rods are provided which pass through the extrusion chamber and the extrusion piston parallel to the axis of extrusion, and in that the spacing between the rods corresponding approximately to the radius of the rods.

15. Apparatus according to Claim 9 or one of the following, characterized in that the central end face region of the extrusion piston (20) has a concave or convex profile (35,41), and in that the edge region (36) of the extrusion piston (20) either side of the curved profile (35, 41) is shaped in the manner of teeth (42) transversely to the axis (5) of extrusion.

16. Apparatus according to Claim 9 or one of the following, characterized in that the pre-pressing die (16) opposite the feed opening (15) is guided in a manner movable to and fro transversely to the axis (5) of extrusion with the webs (13) associated with it and its guide.

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