EP0399373B1 - Method and device for the pressing of a flexural rigid girderlike shaped body of vegetable particles - Google Patents

Abstract

The invention relates to methods and devices for the manufacture of girderlike shaped bodies (15) from vegetable particles mixed with binders, in moulding presses. Starting from the knowledge that the core of such shaped bodies (15) is compressed less, the greater the cross-section of the shaped body (15), the invention proposes to form the core region of the shaped body (15) from a particle additional mass which is specifically moved thereto and compressed and which, on compression of the shaped body (15) by cheek plates (2 to 5) surrounding it, acts reactively as a crushing zone (28). In this way, a continuous compression of the shaped body even of large cross- section is achieved, and at the same time a particularly powerful compression of the peripheral regions of the shaped body. The strength and flexural rigidity of such shaped bodies (15) is particularly great, making them suitable even for forming railway sleepers. <IMAGE>

Description

Method and device for pressing a rigid bar-shaped molded body from small plant parts

The invention relates to methods and devices for pressing a rigid bar-shaped molded body from small vegetable parts mixed with binders in a molding press in which mutually movable pairs of press jaws form the filling and pressing space between them and alternately and repeatedly carry out press strokes, after which the pressed molded body is subjected to heat is cured while maintaining the pressure.

Such a method is known from DE-PS 32 27 074. The procedure described therein, to allow the opposing and surrounding the press jaws to act in pairs one after the other and repeatedly on the batch filled in the fill chamber, has proven particularly useful in the production of I-profiles, the webs and legs of which are approximately the same thickness.

However, if you want to press bar-shaped moldings with a much larger cross-section from the vegetable small parts mixed with binder, as would be the case, for example, when pressing railway sleepers, the known technique is not sufficient to effect the pressing of the small parts over the entire cross-section. Even if one repeatedly and intensively acts on the outer surface of the shaped body to be formed with pairs of pressing jaws, the reasonably available pressing pressure is not sufficient to press the small plant parts located in the central area of the shaped body in the required intensity. Instead, a loose microstructure is created in this central area of the molded body firmly, which therefore does not participate in the strength of the entire molded body. There is even a risk of the formation of cavities or similar cavities.

The invention is therefore based on the object of demonstrating a method and a device which is suitable for carrying out the method, with which it is possible to intensively compress small plant parts over the entire cross section of a large-sized bar-shaped shaped body and to avoid the disadvantages described.

Starting from DE-PS 32 27 074, the solution to this problem according to the invention is that before the start of the compression strokes, an additional mass of the small parts is pressed into the part of the mixture filling the filling space intended for the tensile zone region of the molded body, and thereby one against the subsequent compression pressure the press jaw pairs reactively acting compression zone of particularly pre-compressed small parts is created.

With this measure, a core of pre-compressed small plant parts is formed within the filling space, which acts reactively from different directions in relation to the press strokes that take place later. Each individual press stroke of the press jaws leads to a compression of the compacted batch at this pre-compressed central core zone, which in turn further compresses this core zone and increases its reactive effect. The cross-section of the finished pressed body shows how the small parts loosely filled into the filling space are formed in layers and thereby form undulating or curved or even interlocking layers that grip around the pre-compressed small part core like flow lines. In addition, layers can be seen in the edge regions of the molded body which are significantly more densely compacted and which in the edge region of the molded body result in a particularly high resistance.

One can also easily bring two or more additional masses distributed in the sense of the invention to act on the small batch.

With the invention, it has been possible to compact a molded body of large cross section particularly strongly throughout, without any significant design effort, and thus to create the prerequisite for being able to use the molded body for particularly high loads, as is the case, for example, with railway sleepers. However, the invention is not limited to this area of application, but includes all applications of the moldings according to the invention in a wide variety of technical areas.

In one embodiment of the invention, the formation of the precompressed core is brought about in a very simple manner in that the additional mass is pressed from a channel-shaped space which extends the filling space and extends over the entire length of the filling space by means of a press jaw into the mixture filling the filling space. The channel-shaped space is preferably formed by at least one set back press jaw of a row of press jaws, the set back press jaw being moved together with the row of press jaws first and after filling the channel-shaped space. It is also possible to first advance the row of press jaws and then to close the channel-shaped space, both movements also being able to take place simultaneously.

From EP-A 0 065 660 it is known to press railway sleepers from small plant parts mixed with binding agents, particularly by the area on which the rails of the tracks come to rest condensed. At these points, according to the teaching of this document, either plate-shaped parts are inserted into the surface of the threshold or a cluster of small parts, which has been formed on the bearing surfaces of the rails, is pressed together with the mixture filled into a mold, resulting in a superficial strip-shaped compression results.

It may be true that this strip-like compression of the support surface for the rail leads to the fact that the pressure of locomotives and carriages on the rail does not lead to the rail being pressed into the threshold. However, it was obviously overlooked that the overall strength of the threshold produced in this way is far too low because it is not possible to produce a high-strength and rigid body from small plant parts by compressing the small part mass in a mold only in one direction.

The invention differs from this in principle in that the additional mass introduced according to the invention into the core area of the filling space is intended to oppose the pressing forces acting from different directions, so that the small parts located between the pressing jaws and the pre-compressed zone experience a compression which the previously described streamlined structure of layers. In this way it is achieved to produce a shaped body of large cross section with particularly high strength.

In the context of the invention, it has proven particularly useful if the mixture of small parts to be pressed is mixed with a proportion of long chips and introduced into the filling space in such a way that the long chips are oriented parallel to the longitudinal direction of the shaped body. Such long chips are prepared in a suitable manner for the pressing process according to the invention. It has been proven to be long chips in the Size of about 150 mm in length, 5 - 8 mm in width and 0.4 - 0.8 mm in thickness, but the invention is not limited to these dimensions but is only intended to provide an indication of the direction in which the long chips are formed should.

From DE-PS 33 46 469 it is known how to bring pin chips (these are long chips of smaller dimensions) oriented in the longitudinal direction into a filling space, in order to then carry out a pre-pressing and then to extrude the pre-pressed object. Although extrusion is not an option in the invention, it is possible to use the previously known measures for orienting the long chips. For the disclosure of the invention, reference is therefore expressly made to the teaching of the aforementioned publication.

Process claims 6 - 8 teach that shaped bodies of particularly large cross-section can best be obtained by pre-pressing in a first press and final pressing of the shaped body in a subsequent second press. It is important here to push the shaped body formed in the first press together with shaped sheets which act against the side walls of the shaped body out of the first molding press and to insert them into the second molding press.

From DE-OS 33 07 557 it is known to push the finished molded body together with its enveloping pressing jaws out of the press and, while maintaining the pressing pressure, to bring it into a hardening zone, where the mixture sets under the action of heat. The teaching shown in this document for guiding the press jaws can be used without further ado in the invention, in which, however, the press jaws remain in the molding press and the molded body is merely pushed off with the molding plates.

Claims 9 to 14 finally disclose a suitable device which allows the inventive methodology to be carried out.

• Fig. 1: einen Querschnitt durch einen von Preßbacken umgebenen Füllraum, nachdem eine seitliche Querpressung vorgenommen worden ist,
• Fig. 2: einen Querschnitt gem. Fig. 2 mit Darstellung einer vorverdichteten Stauchzone aufgrund einer zweistufigen Vertikalpressung,
• Fig. 3: eine schematische Schrägansicht eines vorgepreßten Formkörpers mit seitlichen Formblechen beim Übergang von einer Formpresse in die andere,
• Fig. 4 bis 7: Querschnitte durch die Preßeinrichtung einer zweiten Formpresse in verschiedenen Preßstellungen,
• Fig. 8: einen Querschnitt durch einen gepreßten Formkörper und
• Fig. 9: eine Alternativdarstellung zu Fig. 1

These and other details of the invention emerge from the drawing. In it, the invention is shown schematically and for example. Show it:

• 1 shows a cross section through a filling space surrounded by press jaws after a lateral transverse pressing has been carried out,
• 2: a cross section acc. 2 shows a pre-compressed compression zone due to a two-stage vertical pressing,
• 3: a schematic oblique view of a pre-pressed molded body with lateral molded sheets during the transition from one molding press to the other,
• 4 to 7: cross sections through the pressing device of a second molding press in different pressing positions,
• 8: a cross section through a pressed molded body and
• 9: an alternative representation to FIG. 1

In the example in FIG. 1, the cross section of a first molding press is shown, in which a filling space (1) is filled with a mixture of small plant parts and binders. Depending on the intended use, wood chips or parts made from other vegetable fibers, such as straw and the like, can be used as small parts. If moldings from Particularly high strength and large cross-section, such as railway sleepers, are to be produced, it is recommended to use long chips, which are filled into the filling chamber (1) in an oriented position. Care should be taken to ensure that the long chips extend in the longitudinal direction of the shaped body.

The filling space (1) is encased by the press jaws (2,3,4,5). The lateral press jaws (2, 3) and the press jaws (4, 5) movable in the vertical direction form pairs of press jaws, the movement of which is controlled in such a way that the pairs of press jaws act successively and repeatedly on the mass filled into the filling space (1), which will be described later becomes.

In the exemplary embodiment, the lower press jaw (5) consists of a series of individual press jaws (6, 7) arranged next to one another, of which the middle press jaw (6) is set back and thus forms a channel-shaped space (12), which adjoins the filling space (1) the place where the material is located on small parts that are intended for the formation of the tensile zone area of the molded body. In the example in FIG. 2, the contour of a cross-section of the bar can be seen, in which the area of the draft zone is in the lower zone of the filling space (1).

In Fig. 1 it is assumed that the filling space (1) is filled in any suitable manner, it being possible to imagine that the upper press jaw (4) is removed during the filling process. After the filling process has been completed, the upper press jaw (4) is moved back into its starting position. There is then a first pressing stroke of the lateral pressing jaws (2, 3) along the arrows (10), the pressing stroke of the lateral pressing jaws (2, 3) being transferred to the batch located in the filling chamber (1) via shaped plates (8). The shaped sheets (8) extend over the entire length of the filling space (1) and have the Embodiment on a bend (9), which is intended to form a lateral upper oblique surface in the molded body (15) to be formed. This is important, for example, if railway sleepers are to be manufactured. Depending on the cross section of the molded body (15), the profiling of the molded sheet (8) will be designed appropriately.

1 corresponds to the position of the shaped sheets (8) after the end of the first press stroke along the arrows (10).

This is followed by the steps according to FIG. 2, which are essential for the invention, in that the middle pressing jaw part (6) carries out a pre-pressing stroke along the arrow (11) and thus the additional quantity of the small plant parts located in the channel-shaped space (12) into the already filled filling space (1 ) pushes in, creating a compression zone (28) of compacted small parts. In the embodiment of FIG. 2, this compression zone (28) is located in the lower region of the filling space (1), because it is assumed that the tensile zone of the molded body is to be formed there.

If the intended use of the molded body to be formed requires a highly stressed tensile zone elsewhere, it would be advisable to relocate the compression zone (28) accordingly. It is crucial that the compression zone (28) should be located in the core area of the filling space (1) where the greatest stress on the molded body is to be expected. The pressed position of the molded body does not always correspond to the position of use. Therefore, Fig. 1 represents only one of several possibilities. For the same reason, several such compression zones can be created by appropriate press jaw design.

The essential purpose of the compression zone (28) formed is to create a resistance force in the core area of the molded body (15) to be formed, which has a reactive effect on the pressing force of the pressing jaws (2 to 5). If the compression zone (28) had not been formed, the pressing force of the pressing jaws (2 to 5) would not be sufficient to press the central region of the molded body to be formed in the required intensity.

The pre-pressing stroke along the arrow (11) leads to the fact that a flush pressing surface (14) then forms on the end face of the pressing jaw parts (6, 7). From now on, the pressing jaw parts (6,7) are moved together like a single pressing jaw.

However, it is also possible first to advance the row of pressing jaws (6, 7) and only then to close the channel-shaped space (12) by additional movement of the pressing jaw (6). Both movements can also take place simultaneously.

In the example of FIG. 2, the position of the press jaws (6, 7) after the press stroke is shown along the arrows (13). The side pressing jaws (2, 3) have maintained their position under pressure with their shaped sheets (8), whereas the upper and lower pressing jaws (4, 5) have been moved against one another.

These movements according to FIGS. 1 and 2 take place in a first molding press (18). 2, the work in the first molding press (18) is complete. The compact is then pushed together with the two shaped sheets (8) in the longitudinal direction from the first molding press (18), as is symbolically indicated in FIG. 3 by the arrow (17). The shaped sheets (8) slide along the lateral pressing jaws (2, 3), which is why a low-friction guidance should be ensured. Corresponding proposals are the prior art mentioned at the beginning removable.

The exemplary embodiments in FIGS. 4 to 7 now show various pressing sections in a second molding press (19), into which the molding of the molding (15) together with the molding plates (8) has been pushed off.

In this second molding press (19), the lateral pressing jaws (2 ', 3') with the molding plates (8) resting thereon are moved towards one another in the direction of the arrows (20) in the course of a further pressing stroke. It is important to ensure that the upper and lower edges of the shaped plates (8) do not yet reach the plane of action of the upper and lower press jaws (4 ', 5'). 4 is followed by a vertical press gear according to FIG. 5, after which the upper and lower press jaws (4 ', 5') are moved against one another along the arrows (21). So that these press jaws (4 ', 5') almost reach their final press end position.

This process is followed by a further transverse pressing process according to FIG. 6, in which the shaped plates (8) are moved forward into their final press end position. So that the gap between the mold plates (8) and the upper and lower press jaws (4 ', 5') is compensated. This transverse movement takes place along the arrows (22).

In Fig. 7 the absolute press end position is shown, in which the upper and lower press jaws (4 ', 5') have been moved along the arrows (23) against each other. It can be seen that the pressing surface of the upper pressing jaw (4 ') now coincides with the upper bend in the bend (9) of the shaped sheets (8) and thus a shaped body (15) according to FIG. 8 is formed, in which the bevel ( 16) is an impression of the shaped sheets (8). These shaped sheets (8) have also formed the side walls (27) of the shaped body (15).

The symbolically drawn compression zone (28) is shown in the middle section (24) of the molded body (15), which generates reaction forces according to the arrows (29) when a pressure is exerted on the outer surfaces of the molded body (15) via the press jaws (2 to 5) or (2'to 5 ') acts. The small parts in compression then slide off from this compression zone (28) insofar as they do not remain directly compressed thereon, which leads to an arcuate deformation structure according to lines 30 in the molded body (15). At the same time, a particularly strongly compressed edge area (34) is formed on the molded body (15). The edge areas (35) are even more particularly pronounced. From this it can be explained that a molded body (15) produced according to the invention is very resistant, particularly in the edge areas which are normally at risk.

The embodiment of FIG. 9 finally shows a machine arrangement as an alternative to FIG. 1, in which the filling space (1) is filled independently of the position of the upper press jaw (4). For this purpose, the machine is divided, after which the press jaw (4) is arranged in one machine part (31) and the other press jaws (2, 3, 5) with the shaped plates (8) in another machine part (32). If you move the machine parts (21, 32) relatively to each other, the filling chamber (1) can be filled regardless of the position of the upper press jaw (4).

In an alternative, the lower press jaw (5) can also be left in the position shown in FIG. 1, so that only the lateral press jaws (2, 3) with the shaped plates (8) can be moved to below the filling opening (36). This movement can be caused by appropriate stroke design of the drives for the lateral pressure plates (2, 3).

PARTS LIST

1

Filling and press room

1'

Filling and press room

2nd

lateral press jaws

2 ′

lateral press jaw

3rd

lateral press jaw

3 ′

lateral press jaw

4th

upper press jaw

4 ′

upper press jaw

5

lower press jaw

5 ′

lower press jaw

6

middle press jaw part

7

side press jaw part

8th

Shaped sheet

9

Bend

10th

first press stroke

11

Prepress stroke

12

channel-shaped space

13

third press stroke

14

flush press surface

15

Molded body

16

bevel

17th

Direction of removal

18th

first molding press

19th

second molding press

20th

fourth press stroke

21

fifth press stroke

22

sixth press stroke

23

seventh press stroke

24th

middle section

25th

Train zone area

26

adjacent section

27th

Side wall

28

Upsetting zone

29

Reaction force

30th

Deformation structure

31

Machine part

32

Machine part

34

Edge area

35

Corner area

36

Filling opening

Claims (14)

1. Process for pressing a flexion-resistant girder-like shaped body (15) comprising vegetable particles mixed with binders, in a moulding press (18, 19) in which mutually movable pressing pairs (2 to 7) form between them the filling and pressing chamber (1) and perform pressing strokes alternately and repeatedly, after which the pressed shaped body (15) is hardened under the effect of heat while maintaining the pressing pressure, characterized in that before the start of the pressing strokes at least one additional quantity of the particles is pressed into the part of the mixture filling the chamber (1) which is intended for the drawing zone region (25) of the shaped body (15) to be formed, and thus at least one packed zone (28) of particularly pre-compressed particles which is particularly reactive to the subsequent pressing pressure of the pressing jaw pairs is produced.
2. Process according to Claim 1, characterized in that the additional quantity is pressed by means of a pressing jaw (6) into the mixture filling the filling chamber (1) from at least one channel-shaped chamber (12) which extends the filling chamber (1) and reaches over the entire length of the filling chamber (1).
3. Process according to Claim 1 or 2, characterized in that the channel-shaped chamber (12) is formed by at least one set-back pressing jaw (6) of a row of pressing jaws (6, 7), the set-back pressing jaw (6) first being moved by itself and, on reaching a position flush with the adjacent pressing jaws (7), being moved further together therewith (6, 7).
4. Process according to Claim 1 or 2, characterized in that the channel-shaped chamber (12) is only completed by a set-back pressing jaw (6) once the adjacent pressing jaws (7) have reached their pressing end position.
5. Process according to Claim 1 or one of the subsequent claims, characterized in that the mixture of particles to be pressed is mixed with a portion of long chips and is brought into the filling chamber such that the long chips are oriented parallel to the longitudinal direction of the shaped body (15).
6. Process for pressing a flexion-resistant girder-like shaped body (15) from vegetable particles mixed with binders, in a moulding press (18, 19) in which mutually movable pressing pairs (2 to 7) form between them the filling and pressing chamber (1) and perform pressing strokes alternately and repeatedly, after which the pressed shaped body (15) is hardened under the effect of heat while maintaining the pressing pressure, characterized in that the shaped body (15) is compressed at its two side walls (27) with the aid of moulding plates (8) which, together with the pre-compressed shaped body (15), are pushed along its longitudinal axis out of a first moulding press (18) and, while maintaining a pressing pressure, are introduced into a second moulding press (19) for performing the further pressing stages.
7. Process according to Claim 6, characterized in that, in the first pre-pressing stage, first the lateral pressing jaw pairs (2, 3) and then the upper and lower pressing jaw pairs (4, 5) are moved, the pressing jaws (5) associated with the bottom boom of the shaped body (15) producing a greater compression in the central region (24) than in the marginal region.
8. Process according to Claim 1 or one of the subsequent claims, characterized in that, in the second moulding press (19), first the lateral (2′, 3′) and then the upper (4′) and lower (5′) pressing jaws are moved in pairs, alternately and repeatedly, and in that the pressing procedure is concluded by after-pressing (23) the top boom and bottom boom surfaces of the shaped body (15).
9. Apparatus for carrying out the process according to Claim 1 or one of the subsequent claims, comprising a moulding press (18, 19) having mutually movable pressing jaw pairs (2, 3, 4, 5) forming between them the filling and pressing chamber (1) and having a control for the staggered advancing of the individual pressing jaw pairs (2, 3 and 4, 5), characterized in that the pressing jaw (5) associated with the bottom boom of the shaped body (15) is divided, with at least one central pressing jaw (6), during filling with the material for pressing, adopting a set-back position with respect to the other pressing jaw parts (7) associated with the marginal regions of the bottom boom, and this central pressing jaw (6) having a pressing stroke which is greater by the amount of offset and is performed predominantly in two steps.
10. Apparatus for carrying out the process according to Claim 3, characterized in that complementary moulding plates (8) are arranged in front of the pressing surfaces of the lateral pressing jaw pairs (2, 3).
11. Apparatus according to Claim 10, characterized in that the moulding plates (18) have an upper marginal region (9) which is angled off in the direction of the pressing chamber (1).
12. Apparatus according to Claim 10 or 11, characterized in that the moulding plates (8) are guided against their pressing jaws (2, 3) along the longitudinal axis of the shaped body (15).
13. Apparatus according to Claim 9 or the subsequent claims, characterized in that two moulding presses (18, 19) are arranged one behind the other in the direction of the longitudinal axis of the shaped body (15), and in that a push drive (17) acting on the end face of the shaped body is provided and transfers the pre-pressed shaped body (15), together with the moulding plates (8), out of the first moulding press (18) into the second moulding press (19) in which the stepwise final pressing takes place.
14. Apparatus according to Claim 9 or one of the subsequent claims, characterized in that a machine part (31) having the upper and in some cases also the lower pressing jaw (4) and a machine part (32) having the other pressing jaws (2, 3, 5) are constructed to be relatively movable transversely with respect to one another such that the filling chamber (1) is accessible for filling without being hampered by the upper pressing jaw (4).

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