EP0086899B1 - Method of and apparatus for the compression moulding of a shaped article, particularly for producing a single or multi-part pallet, a supporting strut or a girder beam profile - Google Patents

Description

The invention relates to a method and a molding press as known from US-A-3632276 for molding a molded body from small plant components mixed with binders according to the preambles of claims 1 and 14, in particular for forming a one-part or multi-part pallet, one Support bar or a load-bearing beam profile.

From DE-A-2 508 493 it is known to extrude entire pallets with feet made of chipboard material which are arranged in one piece thereon, the feet in particular being supposed to be compressed in the web. Such a theoretical teaching, which cannot be used in practice, does not lead to sufficient strength because the small parts are normally oriented transversely to the extrusion direction and thus bring about a very high degree of bending resistance and thus low strength.

It is also known to press a one-piece pallet of wood chips mixed with binders in a die, which has a stationary lower mold and a movable upper mold. The pallet feet are hollow. This pallet, which is in circulation, often shows weak points and breaks on the walls of the pallet feet.

DE-A-3 035 701 teaches to press several pallet feet with joists connecting them into massive pallet foot bars in one form and to design these bars so that they can withstand high bending loads. The aim here is to compress the recessed beams located between the pallet feet more than the other areas of the pallet foot, which actually achieves greater strength and rigidity in relation to bending stress.

EP-A-050 164, which is to be considered as prior art according to Art. 54 (3) for claim 19, shows a support bar made of pressed, small vegetable components mixed with binder, in particular small wooden parts of I-shaped cross section, by upper ones and lower belts and a web is formed, and which has recessed side faces on the web opposite the belts. The I-shaped profile consists of several chipboard panels that are butt-jointed and glued at the joints. As a result, the wood particles in the chipboard lie in an orientation that is favorable for strength, but this gain in strength is negated on the other hand by the glue points.

From US-A-3632276 it is known to produce a box from chip material by different pressing jaws acting on the chip material at different times. The press jaws perform a single-stage stroke and form the press chamber in the end position. The staggered movement of the jaws ultimately only serves to transport partial clippings. A special increase in strength through chip orientation is not associated with this.

The invention has for its object to press moldings of various types, for example one-piece pallet or, in the case of multi-piece pallets, their bars, as well as support bars and beam profiles and the like, from vegetable and small parts mixed with binders in such a way that, compared to the known measures, significantly increased strengths and less sensitivity in handling can be achieved without having to increase their weight.

This object is achieved according to the invention with the characterizing features of claim 1. A molding press which is particularly suitable for carrying out the method is specified in claim 14.

The invention is based on the known finding that the chips in a molded plate are oriented preferably parallel to the surface thereof. However, the thicker such a plate is, the more arbitrarily the chips are in the middle plate area. This phenomenon can be suspected even more if the compact deviates considerably from the plate shape.

Therefore, the invention strives with its characteristic means to enforce a certain chip orientation in all places that are subjected to high loads or are decisive for increasing the strength. With the step-by-step compression of the mixture by means of press molds which can be moved at different times, targeted movements are created in the chip structure, as a result of which the chips are oriented parallel to practically all surfaces.

In addition to the method and a molding press for carrying out the method, the invention also relates to a support bar or a profile according to claims 19 and 23. It is thus possible to produce support bars in one piece, for example in the form of pallet feet or other rigid construction profiles. The increased strength compared to the prior art results from the special chip orientations created in these profiles.

Embodiments of the invention are specified in the subclaims.

• Fig. 1: eine perspektivische Ansicht eines Palettenfuss-Riegels,
• Fig. 2: einen Querschnitt durch eine Formpresse für die Herstellung des Riegels gemäss Fig. 1,
• Fig. 3 bis 5: Querschnitte durch die Formpresse gemäss Fig. 2 in verschiedenen Pressphasen,
• Fig. 6: einen Querschnitt durch eine Formpresse für die Herstellung einstückiger Paletten mit Darstellung eines Vorpressvorganges,
• Fig. 7: einen Querschnitt gemäss Fig. 4 mit Darstellung eines seitlichen Pressvorganges,
• Fig. 8: einen Querschnitt gemäss Fig. 4 und 5 mit Darstellung eines Nachpressvorganges,
• Fig.9: einen Teilquerschnitt entsprechend Fig. 6 in vergrösserter Darstellung,
• Fig. 10: einen Querschnitt durch einen Teilbereich einer gepressten Palette in der Sicht nach den Linien x-x von Fig. 9,
• Fig. 11: einen Querschnitt durch den Palettenfuss eines Palettenfuss-Riegels,
• Fig. 12: eine Draufsicht auf den Palettenfuss- Riegel gemäss Fig. 11,
• Fig. 13: eine Seitenansicht auf einen Tragriegel, entsprechend Fig. 1,
• Fig. 14 und 15: Querschnitte nach den Linien 11-11 und 111-111 durch den Tragriegel gemäss Fig. 1,
• Fig. 16: einen Querschnitt durch eine Pressform zur Herstellung des Tragriegels gemäss Fig. 1,
• Fig. 17: einen Querschnitt durch einen als Träger ausgebildeten Tragriegel und
• Fig. 18 bis 22: Querschnitte durch eine Pressform in verschiedenen Pressstufen zur Herstellung des Tragriegels gemäss Fig. 16.

Several exemplary embodiments of the invention are shown schematically in the drawing. Show it:

• 1 is a perspective view of a pallet foot latch,
• 2: a cross section through a molding press for the production of the bar according to FIG. 1,
• 3 to 5: cross sections through the molding press according to FIG. 2 in different pressing phases,
• 6: a cross section through a molding press for the production of one-piece pallets, showing a pre-pressing process,
• 7: a cross section according to FIG. 4 with a lateral pressing process,
• 8: a cross section according to FIGS. 4 and 5, showing a repressing process,
• 9: a partial cross section corresponding to FIG. 6 in an enlarged view,
• 10: a cross section through a partial area of a pressed pallet in the view along lines xx of FIG. 9,
• 11: a cross section through the pallet foot of a pallet foot bolt,
• 12: a top view of the pallet foot latch according to FIG. 11,
• 13: a side view of a support bar, corresponding to FIG. 1,
• 14 and 15: cross sections along lines 11-11 and 111-111 through the support bar according to FIG. 1,
• 16: a cross section through a press mold for producing the support bar according to FIG. 1,
• 17: a cross section through a support bar designed as a carrier and
• 18 to 22: cross sections through a press mold in different pressing stages for the production of the support bar according to FIG. 16.

In a first exemplary embodiment, a pallet foot latch that can be produced according to the invention is shown in FIG. 1 and the tool useful for its formation is shown in FIGS. 2 to 5. In principle, the pallet foot latch 1 has an elongated cuboid shape, the top (roof surface 16) of which is flat and the underside of which is formed by pallet feet 2 and indentations 5 located therebetween, the transition of which should have a strong curvature 6. The lower surfaces of the pallet feet 2 are parallel to the roof surface 16. The beam 3 remaining in the area of the indentations 5 must have such a strength that the latch 1 resists considerable loads, in particular bending stresses. In order to increase the strength, impressions 4 are pressed into the side walls of the bolt 1, which are indicated by dash-dotted lines in FIG. 1.

It is possible to produce the bar shown in FIG. 1 with different collections of fine and coarse small parts.

2 shows a cross section of a molding press, such as corresponds to the section 11-11 in FIG. 1 of the bolt 1, if one imagines a shape enveloping the bolt 1.

Thereafter, the molding press shown in FIG. 2 is first formed by guides 7 of a fixed type, between which molds 10, 11, 12, 13 are movably guided. The press mold 13 (cf. FIG. 3) is moved back into a raised position (not shown) in the illustration in FIG. 2 in order to make room for a filler shaft 8 through which the chip mixture mixed with binder can get into the press chamber 9. All the molds 10, 11, 12 shown are in a set-back initial position. It is assumed that a dosed amount of the mixture, which is adapted to the volume of the pallet bar 1 to be produced, is filled into the pressing chamber 9. After completion of the filling process, which is carried out in the usual way, the mold 13 is moved into the position shown in Fig. 3 in a first embodiment of the invention. At the same time, the opposing mold 10 can be advanced into the position shown in FIG. 3. In contrast, the lateral molds 11, 12 remain in the position shown in FIG. 2 in this exemplary embodiment. The consequence of this first pre-pressing process is that a part of the small parts adjusts itself parallel to the pressing molds 10, 13. As shown in FIG. 3, the bottom surface 17 and the roof surface 16 of the bolt 1 are formed by these molds 10, 13. The material pre-compacted during this movement of the molds 10, 13 can deviate somewhat in the direction of the other molds 11, 12 set back according to FIG. 2 and still assume an indefinite orientation there.

If, in the course of a second section of the pre-pressing process, these lateral molds 11, 12 are moved into the position shown in FIG. 3, while the molds 10, 13 remain in their pre-press position, then the small parts are oriented in layers parallel to the pressing surfaces of the lateral ones Press molds 11, 12.

It has been shown that the orientation of the small parts in this after-and-after pre-pressing described according to the invention is considerably more favorable than in the closer measure, in which all the molds are simultaneously moved into the final pressing position.

The pre-pressed bolt 19 shown in FIG. 1 is still oversized compared to the final shape of the bolt 1. It is now shown that at least the lateral molds 11, 12 are made in several parts. An inner mold part 15 is arranged to be movable relative to one another between two outer mold parts 14. Each compression molding 14, 15 is assigned its own lifting drive (not shown). On the way from the position according to FIG. 2 to that according to FIG. 3, all the mold parts 14, 15 have been moved forward at the same time. In the further course, however, the internal mold parts 15 are moved forward from the position according to FIG. 3 into that according to FIG. 4. These molds 15 can have the shape of the impression 4 shown in FIG. 1. It is therefore essential that this movement of the compression mold parts 15 brings about a strong and final compression of the side regions of the bolt 1. Of course, the edges of the molded part 15 are rounded. In the basic position, this has the result that open fillets 20 (see FIG. 3) are formed which are filled by the pre-pressed material and therefore form protruding ridges. However, these burrs are removed when the inner mold parts 15 are advanced to the position shown in FIG. 4.

It is now conceivable that the molds 11, 12 can also be divided along the bar 1 (that is to say one behind the other parallel to the plane of the drawing). For example, it is conceivable that the pallet feet 2 and the beams 3 above the indentations 5 (see FIG. 1) are each assigned a press (not shown) molded parts are adapted, which are expediently adjacent to each other in the longitudinal direction.

If it has been said in advance that a separate lifting drive is assigned to each molding part, this does not exclude that molding parts which are moved in the same direction but are separated from one another are connected to a pressing cylinder or similar lifting element via bridge-like structures.

In Fig. 5 it is now shown that while maintaining the position of the mold parts 15, a kind of compression by the molds 10, 13 is carried out. The movement of these molds 10, 13 then leads to the final shaping of the latch 1. It can be imagined that the swarf or small parts located in the vicinity of the roundings 23 of the mold parts 15 experience a kind of displacement process as a result of this upsetting process. They had already been brought into a position approximately parallel to their press surfaces by the movement of the press mold parts 15 according to FIG. 4. The upsetting according to FIG. 5 now requires an enveloping compression of the material in the region of the curved transitions. 5 also leads to a considerable stiffening of the entire bolt 1.

What has been disclosed in the drawing with regard to the lateral compression molds 11, 12 can now also be used in the. use lower mold 10. In the example of FIGS. 2 to 5, it was left open whether this mold 10 follows the lower contour of the bolt 1. But you can also imagine this mold 10 divided along the bar 1, in that one part is assigned to the pallet feet 2 and the other parts to the indentations 5 of the bar 1. In the pre-pressing according to FIGS. 2 and 3, the surfaces assigned to the pressing chamber 9 can still lie in one plane. In an intermediate phase, not shown in the drawing, which is expediently between those of FIGS. 3 and 4, the mold parts forming the indentations 5 can then be moved by themselves against the upper mold 13, which remains stationary, in order to profile the pallet feet 2 with respect to the indentations 5 to form. However, it is also conceivable to work with a uniform lower die 10, which is adapted to the contour of the bolt 1, in accordance with FIG. 3.

A second exemplary embodiment of the method according to the invention is shown schematically in FIGS. 6 to 8, which relates to the production of one-piece pallets, but can also be applied to the production of pallet foot bars according to FIG. 1.

The pallet 24 should have a plurality of spaced-apart pallet feet 2 which are connected to one another by beams 3. In the example according to FIG. 6, a mold 25 acts over the entire surface from top to bottom of the mixture of small plant parts, in particular wood chips and binding agent, which is formed, and compresses this against the lower molds 26, 27, which initially remain stationary Molds 26 are moved while the other lower molds 27 are still stationary. The pallet pressed raw in this way is still oversized.

7, the molds 25 to 27 are now slightly ventilated. There is no need to travel any distance; it is sufficient if only the pressing force is reduced or eliminated. In this released state of the raw pallet 24, the lateral molds 28 are now set in motion against one another, which in the example act only on the outer side surfaces of the pallet 24. It may be advisable to keep the lower molds 27 in their original position so that they have to absorb part of the lateral deformation pressure.

While the side molds 28 remain in their press position while maintaining the pressure, the other molds 25, 26 and 27 are moved against each other to form the desired pallet size, as shown in FIG. 8, whereby the pallet 24 is compressed again so that it has the required high load capacity and maintains rigidity.

It goes without saying that similar to the lateral molds 28 shown in FIG. 6 act on the side surfaces of the pallet 24, which are parallel to the plane of the drawing.

In a variant of the invention, the aforementioned ventilation of the molds 25, 26, 27 can also take place simultaneously with the pressing of the lateral molds 28. It is also feasible to move the molds 26, 27 simultaneously with the mold 25 (FIG. 6).

The molds 25 to 28 (not shown) are stepped, corrugated or the like profiled in their pressing surface, depending on which shape the pallet 24 is to receive. In the drawing, for the sake of simplicity, the thickness of the pallet plate is not shown, which is less than the height of the beams 3, which can run like a frame. As a result, the molds 27 are stiff, unless a separate mold or even a die plate that remains stationary is used for pressing the lower surface of the pallet plate. The lower molds 26 are preferably used exclusively for pressing and recompressing the pallet feet 2.

In a third exemplary embodiment according to FIGS. 9 and 10, a partial cutout for pressing a pallet foot 1, 2 shows the consequence of the stepwise and time-shifted pressing according to the invention. This is because the upper die 25 covers a considerably greater distance than the lower die 26, for example in a ratio of 10: 1, during the pressing operation according to FIG. At the end of this first press movement, the molds 25, 26 assume a position according to the dashed lines 29 and 30. Lines 31 and 32 indicate the positions of the molds 25, 26 at the end of the entire pressing process. Move along the long compression path of the mold 25 to line 29 the chips in the batch are not arbitrary, but they are apparently oriented due to the various frictional flows. The areas of the batch that are close to the mold walls 33 are likely to be subject to greater friction than the more central areas. In any case, at the end of the entire pressing process, the chips assume a positional orientation according to FIG. 10, according to which the layers 34 adjacent to the pressing surfaces of the pressing molds have a chip orientation which runs predominantly parallel to these surfaces and is known from the surface pressing of chipboard. The middle regions 35, on the other hand, have a curved chip orientation, which — viewed in the pressing direction 36 of the press mold 25 — runs concavely. Such a curved structure contributes significantly to the increase in strength. It is increased by the fact that side compression and post-compression take place at different times. If you want to create a reverse curvature, the pallet must be pressed in a position turned by 180 °.

If hollow pallet feet 2 are to be produced, then the time-shifted, gradual pressing is also recommended, but it is understandable that it is no longer possible to achieve clear arch structures. The lateral pressing according to FIG. 7 can then form ribs, depressions and the like in the walls of the pallet feet, which can also run parallel to the axis of the pallet foot and contribute significantly to stiffening the walls. It goes without saying that the pressed pallets or pallet foot bars are hardened in the mold by applying heat in the pressed state.

In the fourth exemplary embodiment according to FIGS. 11 and 12, finally, a partial region of a pallet foot bolt 1 is shown, the pallet foot 2 of which has a nose-like projection 37, the surface of which is flush with that of the bolt 1 and which has a tapered downward configuration. The associated pallet board 38 rests on this extension 37 and, after being nailed to the extension 37, acts as an anti-tilt device for the bolt 1. Such nose-like approaches can also have bare pallet blocks, which can be produced by the method according to the invention, but which can also be produced by die or even by extrusion.

It has proven to be expedient if the nose-like projections 37 are located at the locations of the pallet feet that face the central region of the pallet, which can be seen in FIG. 12 by the position of the pallet boards 56.

For the representation of the fifth exemplary embodiment, FIG. 13 uses a spatial shape which corresponds to that of FIG. 1. It is a support bar 38, as it is designed in cross-section I-shaped according to Figures 14 and 15. As a result, upper and lower belts 39 and the web 40 are formed, the web 40 being only slightly smaller in its thickness in relation to the belt width. The representation of FIG. 13 is significantly reduced compared to that of FIG. 15. FIGS. 14 and 15 show, for example, the cross sections according to their natural size, but these pictures are only to be seen as exemplary embodiments.

As already stated, web formation 40 occurs in that the side surfaces 42 of web 40 are set back with respect to the belts 39 while maintaining a peripheral edge 41. This movement back is brought about by a pressing process with compression of the material in the web 40.

It is clearly shown in FIGS. 14 and 15 that a parallel structure 43 is formed in the belt region 39 and a distinct convex structure 44 of the pressed small parts is formed in the web region 40. The direction of loading is shown at 45. In this case, the convex structure 44 should be provided with respect to this loading direction 45, that is to say in the opposite direction. However, if the compacts were pressed in the position shown in FIGS. 14 and 15, this would result in a concave structure in the web area. The invention therefore teaches that the support bars 38 are produced in a position rotated by 180 ° with respect to the use position. However, this does not preclude the provision of concave curvatures in the load position of the support bolts 38 if special circumstances make this appear useful.

FIG. 13 also shows the typical shape that is required if the support bar 38 is to be used as a pallet foot. Accordingly, there are three projecting foot parts 52 with recessed web parts 53 located between them, which are connected to one another via a grooved transition 54.

16 shows a modified method with the aid of which it is possible to achieve the structures 43, 44 according to FIGS. 14 and 15. A cavity 46 is formed by stationary guides 51 and press rams 47 to 50 displaceable therein, into which the material mixed with binders, in particular small vegetable parts made of wood and the like, is filled arbitrarily. The press rams 49, 50 together with the vertical guide walls 51 form a shaft which is closed at the bottom in the exemplary embodiment by a press ram 48. Instead of this press stamp 48, a stationary shaft wall can also be provided. In the basic position, the pressing surfaces of the pressing punches 49, 50 are aligned with the vertical guide surfaces 51. Fixed shaft walls (not shown) are provided on the end face. If a support bar 38 is to be produced in accordance with the shape according to FIG. 13, the press ram 47 has a press surface configuration which forces the shape of the foot parts 52 and web parts 53. The press die 48, however, is flat in its pressing surface.

First, the press ram 47 is pressed down in the direction of the arrow. If a press stamp 48 is provided, this can be moved in opposite directions, but this is not initially necessary. As a result, the mixture located in the cavity 46, which has been introduced in a metered amount, is compressed over the high edge. It is obvious that the small parts along the surfaces of the press punches 49, 50 are subject to a higher friction than in the core of the compact. After the press stroke of the press rams 47, 48, their press pressure is loosened or released, but the press rams 47, 48 remain in their position. This is followed by a transverse compression of the mixture by the press rams 49, 50. The shape of these is designed such that the side surfaces 42 are thereby imaged. The material displaced by the movement of the press rams 49, 50 compresses the core area of the support bar 38 and, since the material cannot move beyond the press surfaces of the press rams 47, 48, leads to the structure 43, 44 shown in FIGS. 14 and 15. At the end of the movement of the press rams 49, 50, these are locked or their pressing pressure is maintained, whereupon the press rams 47, 48 are moved against each other again, which leads to the high compression of the structure 43 in the belt area 39 (cf. FIGS. 14 and 15) .

In this final stamping position, the compact is cured by applying heat. It may be advisable to release the press rams 47 to 50 and the guides 51 from the drive units for the press rams 47 to 50 without giving up the press position. Such an aggregate can then be placed in a curing channel or oven and the next pressing process can be carried out with corresponding other tools.

In the context of a sixth exemplary embodiment, the support bar 1 shown in FIG. 17 has a clear I cross-section, as can be used for the production of beams that are stable, in particular rigid. In this cross-section too, a structure 43 of the small parts that extends parallel to the belts 39 is clearly pronounced. However, the arched structure, as can be seen in FIGS. 14 and 15, is missing in the web 40. Instead, the outer layers of the web 40 are characterized in a considerably thick structure 43, which also extends parallel to the web side surface 42. In the transition regions from the web 40 into the belts 39, curved structures 55 are formed, which roughly follow the outer contour of the support bar 38.

The structures are similar for other cross sections, for example U, Z or L profiles. These structures result from method steps as are given in FIGS. 18 to 22 in the context of an exemplary embodiment.

In this case too, the filling space of a press mold is formed by press punches 47, 48, 49, 50 and guide walls 51. The mixture of small plant parts, in particular wood chips and binding agents, poured loosely into this mold is first pre-compressed by the press ram 47. A compact with a rectangular cross section is formed. The press stamp covers the path shown in FIG. 18 up to the dashed position. In this position, the pressure acting on the ram 47 is released.

In the next method step according to FIG. 19, the two lateral press punches 49, 50 are moved against one another, and in fact in a partial area of their entire stroke, the other press punches 47, 48 being allowed to dodge. The web 40 (FIG. 17) is preformed. After this press stroke has ended, however, the lateral press punches 49, 50 remain locked or their press pressure is maintained.

20 is now moved a further distance forward, which can be seen from the comparison with FIG. 19. Subsequently, the pressing pressure of this pressing die 47 is released again, and the lateral pressing dies 49, 50 are moved into their press end position according to FIG. 21 and held there in a locked position, which in turn can be done by maintaining the pressing pressure.

Finally, the two press rams 47, 48 are moved towards one another in their final press position according to FIG. 22, as a result of which the compact receives its final shape and the structure of the small parts according to FIG. 17.

example

17 has in its final form a width and height of 90 mm each with a web thickness of 30 mm. The height of the filling space according to FIG. 18 is 350 mm. The press ram 47 first compresses the filled batch by 150 mm (FIGS. 18 and 19). The lateral press rams 49, 50 move into the precompressed batch by ^{2/3 of} their total stroke (FIG. 19). The press stamp 47 now covers a further distance of 90 mm (FIG. 20). The lateral press rams 49, 50 are moved into their final press position (FIG. 21), the total stroke of a press ram 49, 50 being approximately 30 mm. Both press rams 47, 48 are then brought into their final press position. (Fig. 22).

It is entirely possible to move the lower punch 48 in a different way and with a greater stroke.

• Die Querschnittsgestaltung des Tragriegels und die Strukturausbildung der pflanzlichen Kleinteile, im Querschnitt gesehen, stehen in einer funktionellen Beziehung zueinander. Es wäre z.B. nicht möglich, die erfindungsgemässe Struktur der Kleinteile mit vorbekannten Verfahren zur Herstellung von Spanplatten zu erhalten, also beispielsweise einen Pressstempel in eine passend ausgebildete, kastenartige Form einzupressen. In diesem Falle würden nämlich die pflanzlichen Kleinteile sich etwa parallel zur Pressplattenfläche bzw. zur parallel gegenüberliegenden Formfläche orientieren, und zwar im Oberflächenbereich. Im inneren Bereich des so hergestellten Presslings wird wegen der rapiden Abnahme des Drucks eine mehr oder weniger willkürliche Strukturierung der Kleinteile stattfinden. Unter gar keinen Umständen entsteht dadurch aber eine konvexe oder konkave Struktur, wie sie mit einem Teil der Erfindung gelehrt wird.

These two last exemplary embodiments are based on the following consideration:

• The cross-sectional design of the transom and the structure of the small plant parts, seen in cross-section, are in a functional relationship to each other. For example, it would not be possible to obtain the structure of the small parts according to the invention using previously known methods for the production of chipboard, that is to say, for example, to press a press stamp into a suitably designed, box-like shape. In this case, namely, the small plant parts would orient themselves approximately parallel to the press plate surface or to the parallel opposing mold surface, specifically in the surface area rich. Due to the rapid decrease in pressure, a more or less arbitrary structuring of the small parts will take place in the inner area of the compact thus produced. Under no circumstances does this create a convex or concave structure as taught by part of the invention.

If, on the other hand, a support bar has an I-shape in cross-section according to the teaching of the invention, the web area being dimensioned much thicker than in other I-profiles, then the structure of the small parts according to the invention can be achieved by having the small parts filled into a mold first presses in one direction along the longer axis and only then, while loosening or even removing the pressing pressure, carries out the lateral shaping by pressing, which creates the I-type profile. If the support bar is compressed again over the longer axis after the shaping thus formed, a particularly intensive convex or concave structure is formed in the web area of the support bar. The pellet is then cured under the influence of heat while maintaining the all-round pressure.

It is important that the pressing process is rotated by 180 ° compared to the position in which the support bolt is to be loaded. It has been shown that in the pressing process described, the arched formation of the structure always arises only in one direction, namely in the pressing direction in which the upper press die moves, especially when it has a much longer stroke than the press die opposite it executes. If the support bar pressed and hardened in this way is turned through 180 °, the convex structure appears as a kind of inner vault in the area of the web, which is the reason why the support bars according to the invention are able to absorb extremely high loads and show better values than these can be reached with comparable objects made from natural wood.

It could be clearly established that the load-bearing capacity of a support bar produced according to the invention is greater, the more pronounced the convex structure in the web area and the parallel structure of the small parts in the belt area is present. It is assumed that the structure formation depends on the dimension of the crossbeam cross-section and on the different frictional forces among the small plant parts depending on their position. If, for example, a support bar with a rectangular cross-section is pressed upright in a shaft-like shape, it can be expected that the friction of the small plant parts to be pressed, in particular wood shavings, will be greatest on the shaft wall and lowest in the central area of the web. As a result, a somewhat loose structure is still present in the core of the compact, although there is already a tendency that the chips or small parts in this central region are neither oriented arbitrarily nor parallel to the pressing plane, but rather rather obliquely. If a pressing deformation is now exerted on the compact from the side walls of the shaft, so that it changes from the originally rectangular shape into the I-cross-sectional shape, then a specific compression is generated in the core area of the compact, which leads to the very clearly recognizable convex Structure formation leads. The material originally present in the side wall area of the compact is shifted inward by the pressing process, which leads to the compression of the previously relatively loose structure and at the same time to the structure formation mentioned. Finally, if the compact is compacted again via the raw edge, but the lateral pressure is maintained, the support bar according to the invention is particularly high-strength.

In addition, it has surprisingly been found that the aforementioned vault structure can be changed in the web area of the support bar if the compact is subjected to a repetition of the successive vertical and lateral pressing. This measure has made it possible to produce support bars with cross-sectional profiles that are more similar to those of rolled metal profiles. Above all, there is a web that is considerably slimmer in thickness than can be achieved in the previously mentioned variant of the invention.

A measure according to claim 13 is expedient for the pressing, because the lifting or loosening of the pressure acting on the vertical press ram has the consequence that no tear-off in the microstructure can take place during the lateral pressing. Strangely enough, however, the lateral press rams can remain under pressure in their intermediate and final press positions if the vertical press rams carry out the pressing operations assigned to them.

The result of this pressing process is the alignment of the small parts in a position that is predominantly parallel to the assigned pressing surface, namely in a relatively thick layer. At the transition of the web into the belts, there is a curved course of the chip orientation, seen in cross section.

parts list

• 1 pallet foot latch
• 2 pallet feet
• 3 beam
• 4 embossing
• 5 indentation
• 6 curvature
• 7 leadership
• 8 feed chute
• 9 press room
• 10 mold (bottom)
• 11 mold (side)
• 12 mold (side)
• 13 mold (roof)
• 14 outer molded part
• 15 inner molded part
• 16 roof area
• 17 floor area
• 18 side surface
• 19 pre-pressed bars
• 20 fillet
• 21 laterally compressed and embossed pallet feet
• 22 Pallet base compacted at the top and bottom
• 23 rounding
• 24 pallet
• 25 mold
• 26 mold
• 27 mold
• 28 mold
• 29 dashed line
• 30 dashed line
• 31 dashed line
• 32 dashed line
• 33 mold wall
• 34 layer
• 35 middle area
• 36 pressing direction
• 37 nose-like approach
• 38 support bolts
• 39 strap
• 40 bridge
• 41 margin
• 42 side surface
• 43 parallel structure
• 44 convex structure
• 45 Direction of loading
• 46 cavity
• 47 stamps
• 48 stamps
• 49 stamps
• 50 stamps
• 51 leadership
• 52 foot section
• 53 bridge part
• 54 grooved transition
• 55 curved structure
• 56 pallet boards

Priority allocation

Claims (23)

1. Method of compression moulding a shaped article (1) from vegetable particles mixed with binding agents, more particularly for producing a single or multi-part pallet, which on its underside comprises projecting pallet feet and, between the feet, girders, which are set back and which have rounded transitions, or for producing pallet feet (2), supporting struts (38) or profiles having a suitable cross section for use as a rigid beam, the shaped article being compressed between pressing moulds (10 to 13), which may be displaced staggered in time with respect to one another, and following the moulding process being hardened by the effect of heat, characterised in that the shaped article (1) is compressed in stages, the basic shape of the shaped article (1) firstly being formed oversized by means of the pressing moulds (13, 10) forming the top and underside of the shaped article between the lateral pressing moulds (11, 12), which remain stationary for the time being, then impressions (4) are formed in the lateral faces by means of the lateral pressing moulds (11, 12), and finally the top and underside (16, 17) of the shaped article (1) are subsequently compressed to the specified size of the shaped article (1) by maintaining the moulding pressure of the lateral pressing moulds (11, 12).

2. Method according to claim 1, characterised in that the pressing moulds (13, 10) forming the top and underside of the shaped article (1) are displaced staggered in time with respect to one another, by the basic shape of the shaped article (1) being firstly formed by the upper pressing mould (13), and then the lower pressing mould (10) being displaced opposite thereto before the lateral pressing moulds (11, 12) are actuated.

3. Method according to claim 2, characterised in that the upper pressing mould (13) has a considerably longer stroke than the lower pressing mould, for example in the ratio 10:1.

4. Method according to any one of claims 1 to 3, characterised in that, for producing pallet feet struts, the lateral impressions (4) are formed on opposite sides of the projecting pallet feet (2) and the girders (3) connecting the said feet.

5. Method according to any one of claims 1 to 3, characterised in that, for producing one-piece pallets, the lateral impressions are only formed on the outsides of the pallet feet and girders belonging to the pallet.

6. Method according to any one of claims 4 or 5, characterised in that the edges of the lateral impressions (4) are formed such that they lie parallel to the edges of the pallet feet (2) and the girders (3).

7. Method according to claim 5, characterised in that the lateral impressions (4) on the pallet feet of one-piece pallets, which may also be hollow, are formed such that they extend longitudinally relative to the direction of loading.

8. Method according to claim 7, characterised in that ribs or grooves are formed with the impressions.

9. Method according to claim 7 or 8, characterised in that ribs or grooves are formed with varying heights and/or widths.

10. Method according to any one of claims 1 to 3, characterised in that for producing the supporting struts (38) or profiles, the particles mixed with binding agent are poured into a cavity formed between press rams (47, 48, 49, 50), the press rams (47, 48) associated with the flange faces are firstly caused to act upon the mixture, followed by the press rams (49, 50) associated with the lateral crosspiece faces (42) in each case by a partial amount, there is subsequently an extensive compression of the mixture in the same sequence, and finally a final compression by means of the press rams (47, 48) acting upon the flange (39), the hardening of the pressed article subsequently being effected by the effect of heat whilst maintaining the overall moulding pressure.

11. Method according to claim 10, characterised in that the press rams (47, 48) acting upon the flange faces (38) compress the mixture in a first moulding stage by approximately 60%, in a subsequent moulding stage by approximately 35%, and in a final stage by approximately 5% of the overall pressure stroke.

12. Method according to claim 10, characterised in that the press rams (49, 50) acting upon the lateral crosspiece faces (42) compress the mixture in the first moulding stage by approximately ²/₃ and in the subsequent moulding stage by approximately '/₃ of the overall pressure stroke.

13. Method according to claim 1 or any one of the subsequent claims, characterised in that the press rams (47, 48) acting on the flange faces (39) are released of moulding pressure following their respective pressure stroke before the press rams (49, 50) acting on the lateral crosspiece faces (42) carry out their pressure stroke.

14. A moulding press for carrying out the method according to claim 1, the moulding cavity (9) for forming shaped articles (1) being surrounded by a plurality of pressing moulds (10, 11, 12, 13), which are guided so as to be displaceable with respect to one another, and which are provided with stroke drives, which are controlled so as to be staggered in time, characterised in that the lateral pressing moulds (11, 12) comprise rounded (23) end faces and, in the end position of their stroke, project with the said end faces into the moulding cavity (9).

15. A moulding press according to claim 14, characterised in that the lateral pressing moulds (11, 12) are formed in each case by an inner and an outer pressing mould part (14, 15) which engage in one another and which are connected to separate drives producing strokes of differing lengths.

16. A moulding press according to claim 14, characterised in that the pressing moulds (26, 27) directed towards the undersides of the shaped article (1), more particularly the pallet feet and girders, are formed separately according to the contour of the said undersides and are connected to drives producing strokes of differing lengths.

17. A moulding press according to claim 14, characterised in that the pressing mould directed towards the undersides of the one-piece pallet or the pallet foot strut is formed in one piece.

18. A moulding press according to any one of claims 14, 16 or 17, characterised in that the stroke of the pressing mould (25) forming the top of the shaped article (1), more particularly the pallet or the pallet foot strut, is considerably greater than the stroke of the pressing mould (26) forming the underside, for example by a ratio of 10:1.

19. Supporting strut (38) made from compressed vegetable particles, more particularly wood particles, mixed with a binding agent, which supporting strut (38) is formed I-shaped in cross section by means of upper and lower flanges (39) and a crosspiece (40), and which, on the crosspiece, comprises lateral faces (42), which are slightly set back with respect to the flanges (39), the supporting strut (38) being moulded in one piece and the structure of the particles in both flange regions (39) being predominantly parallel (43) to the flange face, in relation to the direction of loading (45) and when viewed in cross section, and predominantly convex (44) or concave in the region of the crosspiece.

20. Supporting strut according to claim 19, characterised in that the thickness of the crosspiece corresponds to approximately 80 to 90% of the width of the flange.

21. Supporting strut according to claim 19 or 20, characterised in that, at its end face, the crosspiece (40) extends into a rim (41) corresponding to the width of the flange (39).

22. Supporting strut according to claim 19 or any one of the subsequent claims, characterised in that it is formed as a pallet foot (2) with three projecting foot parts (52) and, between the said foot parts, crosspieces (53) which are set back and provided with a recessed transition (54).

23. A profile made from compressed vegetable particles, more particularly wood particles, mixed with a binding agent, having a cross section suitable for use as a rigid beam, for example in the shape of an I, U, Z, L or the like, characterised in that the profile is compressed in one piece and the structure of the particles in the flange regions (39) is predominantly parallel (43) to the flange face and in the region of the crosspiece (40), at least in the outer layers thereof, is predominantly parallel (43) to the outsides (42) of the crosspiece.

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