EP0339497B1 - Method and device for bar extruding or tube extruding - Google Patents

Abstract

The invention relates to a method and a device for bar extruding or tube extruding a mixture of plant particles with binding agents, wherein the mixture is pressed, so as to undergo compression, by a pressing ram from a filling and pressing space into a curing channel. A movably arranged mandrel is mounted in the pressing space and guided through the pressing ram. In this process, the mandrel projects beyond the pressing space into the curing channel. This mandrel is arranged so as to be movable in the direction of the pressing ram independently of the movement of the pressing ram. The pressing ram presses the filled material out of the pressing space into the curing channel, the mandrel being moved simultaneously in such a way that the degree of compression remains constant and a uniform post-compression of the pre-compressed mixture occurs. The mandrel can be heated by a liquid or gaseous medium and a plurality of mandrels of any desired cross-sections and lengths are provided.

Description

The invention relates to a method and an apparatus for extruding or extruding a mixture of small plant parts with binders, the mixture being pressed into a curing channel by a press ram with compression from a filling and pressing chamber.

Through the patents DE-PS 25 35 989, DE-PS 29 32 406 and DE-PS 33 46 469 extrusion presses are known which in the Practice were also carried out as extrusion tube presses with a standing mandrel. Extrusion presses are extrusion presses that produce hollow extrusions using one or more mandrels. Standing mandrels are mandrels that are fixed in the pressing direction and over which the material is pressed in sliding friction.

To shorten the hardening time or increase the pressing speed, these mandrels are provided with electrical resistance heaters as soon as their cross-section permits. The compression is controlled in these extrusion tube presses, as in extrusion presses, by reducing the pressing force of clamping elements on the outer surface of the extrusion in the curing channel. A control with two pressures, a low pressure during pressing, the level of which determines the compression, and a higher pressure during the remaining cycle time, are common. For this purpose, a large number of clamping elements are used in the extrusion hydraulic cylinders, which are supplied with pressure oil by a pump. The necessary many and long lines from the pump to the hydraulic cylinder result in a number of disadvantages:
The system reacts relatively sluggishly at press speeds of more than 0.05 m / s; here must already be switched to the lower stage at the beginning of the press stroke, so that when the final compression of the newly formed strand part has been reached, the lower pressure has actually set on all tensioning elements (DE-PS 29 32 406).
The higher the press speed, the less precise the system works.
Due to the large number of tensioning elements, even the smallest changes in the low pressure cause large changes in the pressing force of the extrusion die and thus in the compression of the weights and the specific weight of the strand. The system works with this inaccurately.
Since the strand the less it sets, the more it springs, the strand is exposed to pulsating pressure surges when compacting the strand part to be newly formed, which disturbs the glue rest during bending; the connection of the parts of the batch deteriorate and lead to cracks in the strand, since tensile stresses also occur at high speeds.
At press speeds of more than approx. 0.9 m / s, uncontrollable press pressure peaks occur, since the strand in its rear end is pressed out faster than it can exit the curing channel at its front end.

The friction between the mandrel and the strand reduces the proportion of the friction between the strand and the walls of the curing channel that is generated by the tensioning elements for controlling the weights. The longer the mandrel is formed, the less controllability of the compression. With longer mandrels, the compaction can only be controlled to a very small extent or not at all. This means that the heating power of heated standing mandrels is very low and the curing time can only be shortened slightly.

From DE-GM 8 56 045 extrusion presses are known in which the parts of the outer layer of the compacted mixture are bent with their surfaces predominantly parallel to the outer skin in that the length of the press cross-section is gradually reduced. Likewise, it is known from DE-PS 17 03 414 to further compact the compacted strand by step-like reduction of the press channel in the outer layer, and thus also to fold the parts of the batch parallel to the outer surfaces of the strand.

EP-A-14 67 52 discloses a method for extruding small vegetable parts, especially small wooden parts, which are mixed with weather-resistant material in particular. This process uses a piston extrusion press with an adjoining, heated curing channel, in which the batch filled in the press chamber is pre-compressed transversely to the extrusion axis before the extrusion stroke. Here, a batch mixed with a proportion of longer chips is subjected to an orientation influence, at least on the longer chips, during the filling into the baling chamber in such a way that the longer chips settle parallel or approximately parallel to the extrusion axis, and that a subsequent compression of the outer one Layers of the batch is made with such a low compression ratio that the oriented chips located in these layers remain fixed in position during the subsequent extrusion stroke.

However, strands manufactured according to these teachings have a low binding strength and cannot be used as components subject to bending stress, such as beam supports, etc. This method also results in a very high degree high weight of the strand, which can hardly be controlled or influenced.

The object of the invention is to propose a solution for the production of strands with extrusion presses, with which the homogeneity and strength of the products is decisively improved by lengthening the glue rest of the strand formed in the curing channel by the setting behavior thus positively changed.

It should be possible to manufacture extruded tube products which can withstand bending, so that they can be used as load-bearing components.
In addition, strands are to be produced from small parts, in particular from small wooden parts with binders, which can be pressed to the greatest possible material-specific compression and strength.

An inventive solution to this problem is specified in claims 1 and 12. Further developments of the invention are characterized in the associated subclaims.

To ensure good setting conditions with low glue consumption, i.e. to bring about the required glue dormancy, it is proposed to make the static friction between the strand outer wall and the hardening duct inner wall as well as the strand inner wall and mandrel so large that the strand does not settle in the hardening duct and over the mandrel after a compression stroke of the press ram can move back more. Because this would result in the strand compression becoming unnecessarily high, e.g. would no longer allow a nail drive in the finished product strand, it is further proposed to arrange the mandrel no longer rigidly, but axially movable, in order to drag it along in the last part of the press stroke via the sufficiently large static friction on the strand. The strand is therefore only pressed against the sliding friction force on the inner wall of the hardening channel and is thus compressed to a much lesser extent than would be the case if the sliding friction force on the mandrel also had to be overcome.

The resulting strand compression is controlled during the production process of the strands.
This is done by a controlled increase in the forces that oppose the inward movement of the entrained mandrel. The mandrel is braked by the sliding friction on the strand that has already been formed. In addition, a hydraulic drive of the mandrel is switched to a braking position controlled by a valve.
After completion of the press stroke, the press ram is fixed and the mandrel is pulled back hydraulically, whereupon the press ram also returns to its starting position.

The invention thus uses a moving mandrel which is of such a length that the static friction between it and the strand is greater than the compressive force required to compress the batch minus the frictional forces acting on the outer surfaces of the strand.

The term mandrels in press construction refers to mandrels which are guided through the extrusion die, run with the extrusion during extrusion and are withdrawn into their starting position after the press stroke has ended. The moving mandrel is attached to a hydraulic cylinder, which prevents the mandrel from running along with the strand through a pressure relief valve, which acts as a brake, up to an adjustable and very quickly changing pressure. This pressure is selected and set so that the extrusion die can build up the compression pressure. Once the compression pressure has been reached, the new strand section produced by the press stroke is completed and is pressed out along the entire strand by its own length.

The thorn runs along this path with the strand.

Since the static friction between the strand and the boundary walls of the press nozzles and the hardening channel is greater than the sliding friction when the strand starts to move and is pressed out, the oil pressure which is present against the pressure relief valve and brakes the mandrel by adjusting the valve increased so that the pressing force remains the same. This means that the pressing force can be selected, adjusted and with every pressing action is reproducible. The force required to accelerate the strand from its rest position to its squeezing speed is intercepted by adjusting the pressure relief valve so that the pressing force does not change after the final compression has been reached.

The time and the distance that the extrusion die needs to be braked by the pressing speed to its forward end position in the rest position is minimized by increasing the force holding the mandrel. This has the advantage of shortening the pressing time and increasing the output of the press. At the same time, pressure peaks in the cylinder driving the extrusion die are prevented when switching from the pressing movement to the rest position.

When the extrusion die has reached the front end position and the strand has been pressed out by the length of the newly formed strand part, it remains in this position and is preferably secured against being pushed back by the strand by a hydraulic shut-off valve. The mandrel, which has run along with the length of the newly formed strand, is now pulled back into its starting position by overcoming the static friction. The extrusion die then moves back to its original position.

Since the strand on the mandrel is stretched with static friction over its long length according to the invention / this can protrude with appropriate profiles even beyond the end of the hardening channel, it cannot spring in its length in the mandrel region. This allows you to tie in a state of absolute rest and an optimal connection is made the parts of the batch. In the area outside the mandrel, the binder has already set so far that the glue rest of the press file is maintained.

This also gives the very special advantage of the invention in relation to the possible, very high speed of the extrusion die. Since the length of the strand does not spring when pressed, the pressing speed can be up to 15 m / sec. With particularly large, speed-optimized press cylinders, even higher press speeds can be achieved.

Also due to the length of the mandrel, the invention has a further advantage. If the mandrel, which is possible from a certain cross-section, is heated, for example by heat transfer oil, it can transfer a significant part of the thermal energy required to set the binder.

The moisture in the batch and the liquid in the binder, which evaporate from the heat source during curing, serve as the heat transfer medium in the strand. Since the dry batch forms a strong barrier against the passage of heat, the curing becomes disproportionately longer with increasing cross-section of the strand. The heat supply via the mandrel thus represents heating from two sides, and can reduce the curing time of the binder by 30%, even up to 60%, if the strand has the appropriate profile. In contrast to the mandrel, the curing channel, which is very complex, can be manufactured correspondingly shorter. In addition to the lower construction costs, this also results in a significant reduction in the space requirement of the extrusion tube press system.

The object is further achieved according to the invention in that the parts of the batch are transported by a closing slide from below a filling shaft through the filling opening of a filling space and from there fall into the filling space in free fall. After the slide has closed the filling opening of the filling chamber, the batch located in the filling chamber is z. B. 30% compressed.

A parallel curing channel adjoins the filling chamber with an inclined surface running in the pressing direction, which runs from a larger radius into a smaller radius, which cross-section is therefore smaller than the front of the filling chamber. In this hardening channel, the partially compressed mixture is pressed by the extrusion die in such a way that the degree of partial compression is maintained until the extrusion die reaches the end of the filling space. There is a compression oriented parallel to the outer surfaces, through which a higher compressed outer layer is formed when the final compression is achieved. This results in strands with a much higher strength and resilience. Due to the excellent bending, torsional, tensile and compressive strengths as well as the elasticity, the products are consolidated in such a way that they can be used as load-bearing components.

Apart from the acceleration and the braking acceleration, the extrusion die moves with an adjustable but preferably constant speed from its rear to its front end position. In the starting position of each press cycle, the end of the strand that has already been pressed is below the front surface of the Sliding gate at the same height as the end of the filling chamber.

Until the batch has reached the desired part of the final compression through the process, the mandrel is held in its rear setting by an adjustable force acting against the pressing direction. When the desired part of the final compression has been reached, the holding force of the mandrel acting against the pressing direction - until the end face of the extrusion die reaches the end of the filling chamber - is regulated in its direction and size in such a way that the compression is not increased, even though the extruded strand is squeezed. So there remains the distance between the end face of the extrusion die and the end of the previously pressed strand over the distance the extrusion die from the point at which the desired degree of compression is reached to the point at which the end faces of the extrusion die the leading edge of the closing slide, the same size.

If the force required for the desired partial compression is greater than the friction between the strand and the curing channel, then the force must be directed against the pressing direction. If it is smaller, it must be directed in the pressing direction and the pushing out of the strand is supported by the mandrel.

Since the static friction is greater than the sliding friction, the mandrel holding force must be changed accordingly along the way. Likewise, the kinetic energy for accelerating the strand at rest to the speed of the extrusion die is changed by changing the size of the mandrel holding force Transfer extrusion stamp that the desired degree of partial compression does not change.

The total pressing force is a transporting force, which is composed of the pressing force of the extrusion die, the frictional force of the strand that has already been pressed, the part of the strand that is in the compression and the mandrel holding force. If the end face of the extrusion die moves from the filling chamber into the curing channel, the total compression force, realized in an ideally short way, is increased, so that the final compression of the extruded part to be compressed is established. This is done by changing the sizes and possibly the direction of the mandrel holding force. While the extrusion die continues to move towards its detection in the curing channel, preferably at a constant speed, the speed of the mandrel running or pressing along with the strand is reduced so that the static friction between the mandrel and the pressed strand is just retained. As a result, the distance between the end face of the extrusion die and the end of the extruded strand is reduced to such an extent that the final compression of the extruded part is obtained.

The new part of the strand to be pressed is thus completed and the extrusion die and the mandrel move back into their position at the beginning of the pressing space in such a way that the mandrel pulls the strand back with the static friction between the mandrel and the strand against the pressing direction and pulls the extrusion die until the Face of the extrusion die and the end of the strand at the end of the filling space. At this point, the backward movement of the extrusion die is stopped, but the mandrel is overcome by overcoming the Stiction between the mandrel and the strand moved into its rear end position and thus into its starting position. The extrusion die then also moves back to its rear end position and to its starting position.

The desired partial compression and the precisely adjustable final compression can be controlled both by the pressure forces of the extrusion die and the mandrel as well as by time / travel relations of the press die and mandrel.

• Das hergestellte Profil kann in beliebiger Länge gefertigt werden und ist nicht an die Längendimension der Presse gebunden.
• Die Strangrohrpresse arbeitet mit einer relativ geringen Druckkraft von etwa 35 bis 80 kp/cm² auf die Stirnfläche des Stranges, wogegen Formpressen die weiche spezifische Kraft auf den gesamten Umfang erzeugen und während der gesamten Aushärtezeit aufrechterhalten werden müssen.
• Die Herstellkosten einer Strangrohrpresse betragen weniger als die Kosten einer Formpresse.
• Die Produktkosten je cm³ verpreßten Gemenge sind sehr viel geringer als bei Formpressen.

These extrusion tube presses according to the invention have a number of advantages:

• The manufactured profile can be made in any length and is not tied to the length dimension of the press.
• The extrusion tube press works with a relatively low compressive force of about 35 to 80 kp / cm² on the end face of the strand, whereas molding presses generate the soft specific force over the entire circumference and must be maintained during the entire curing time.
• The manufacturing costs of an extrusion tube press are less than the costs of a molding press.
• The product costs per cm³ of compressed mixture are much lower than for molding presses.

Compared to natural wood, there is the advantage of avoiding material waste with the same high or greater bending strength. Likewise, no cracks form in the course of use compared to timber, the profile does not twist and does not shrink or swell significantly, so its dimensions are essential more constant. The manufacturing costs are significantly lower than for natural wood.

The invention is further based on the knowledge that the strength of pressed small parts, in particular small wooden parts with binders, in contrast to naturally grown wood, is greatest when they are compressed to such an extent that they deform plastically and permanently and close to one another pressed mixture, but their fiber structure is preserved and they do not flow. The mandrel is to be moved in such a way that its end is at the beginning of the hardening zone. The desired final compaction is then achieved by enlarging the mandrel that does not move in the longitudinal direction in this operation. The cross-sectional enlargement takes place in the length of the strand section to be formed with the press stroke. The mandrel part adjoining it in the strand has the same cross section and is somewhat smaller than the mandrel part which has been enlarged in cross section. After the final compaction, the mandrel cross-section of the expandable mandrel part is reduced to such an extent that the mandrel can be pulled out of the strand and brought into its end position without subsequent compression of the strand part produced with the press stroke.

Due to the compression characteristic of the small parts to be compressed, the mandrel only has to be slightly enlarged will. According to this enlargement, the final compaction and the specific weight, which can be selected, adjusted and adjusted to the yield point of the material, result from the lowest compaction required to introduce the pre-compacted batch into the curing channel or to move the small parts parallel to the pressing direction is reproducible with every stroke.

The particular advantage of the three-stage compression, pre-compression by press ram, further compression by press ram and mandrel with previous folding of the small parts, the outer layer transverse to the pressing direction and final compression by enlarging the cross-section lies in the ideal matting of the small parts with an oriented outer layer, which gives the best possible fastening and elasticity.

Since the thickness of the oriented outer layer is determined by the reduction of the filling and pressing space onto the hardening channel, it is of course possible to carry out the compression in two stages without having to turn over the parts of the outer layer. Here, the batch is pre-compressed by the ram and then finally compressed and pressed out by widening the cross-section. Likewise, the invention teaches to bring the batch to be pre-compacted by the press ram into the curing channel by moving the press ram and mandrel, and subsequently to finally compress it by widening the cross-section of the mandrel. This can be particularly advantageous if the product to be produced is subjected to more pressure than bending strength.

The degree of enlargement of the mandrel does not of course have to be the same size in relation to its profile. Much more teaches the invention to adjust the cross-sectional enlargement of the wall thickness and the type of loading of the strand and thus to produce the same or, if this is advantageous, a different compression at each point of the strand cross-section. Furthermore, the invention is not limited to one mandrel, but also provides two or more mandrels, which may have the same or different cross sections, according to the profile of the strand.

The mandrels can be enlarged in different ways and the enlargement can take place not only simultaneously, but also at different times. This makes it possible to use particularly thin-walled profiles stiffened with ribs, e.g. Manufacture windows or door profiles that have high impact, bending and pressure resistance, do not warp or warp and, unlike plastic profiles, are insensitive to temperature. In addition, the workpiece is produced more cost-effectively and consists of a naturally renewable material, the processing of which is largely free of environmental problems.

The mandrel can be enlarged by one or more tension or compression parts. The part of the mandrel that lies in the cavity of the strand part produced with the press stroke and is not moved in the longitudinal direction during the final compression with the entire mandrel is pressed against the walls of the cavity by longitudinal movement of the tension or compression parts and thus compresses the strand section to the final dimension. If necessary, the parts are moved such that the friction is reduced and the mandrel is pulled out of the strand and moved to its starting position without re-compressing the strand part. In the case of designs with multiple spikes, the invention provides that the spikes are common to be pulled out individually or in groups with or without movement of the tension or compression parts in the mandrels in order to avoid recompaction.

Likewise, the cross-sections of the mandrels are not enlarged at the same time or individually or in groups with corresponding extruded profiles. This is necessary with these extruded profiles so that the mandrel centers of gravity maintain their position in the extruded cross section. It has proven to be particularly advantageous and economical since, since there are no mechanical friction losses and the final compression can take place very quickly, the cross section of the mandrel can be made elastic in the region that can be expanded in cross section. The cross-sectional expansion is carried out, for example, by pressurizing with a liquid medium. In the depressurized state, the cross section corresponds to the mandrel part adjoining on the press ram side. The cross section is expanded by the pressure of the medium in such a way that the strand section reaches its final compression. If necessary, the pressure of the medium is reduced to such an extent that the mandrel can be pulled out of the strand without re-compressing the strand part produced with the press stroke.

It is also provided to provide the elastic mandrel part with, for example, a metallic protective layer which protects it against the penetration of parts of the batch and, if necessary, reduces the friction against the strand. According to the invention, the mandrel parts which cannot be expanded in cross section are connected to one another by a tensile or compressive element. The jacket, which can be expanded by pressure, can be secured in the pressing direction by supporting elements. Of course, the mandrels can be heated. This can be done with a liquid Medium or by an electrical resistance heater.

Another idea of the invention is to design the mandrels with curved surfaces on the outside. This is advantageous with regard to the compression, the controllability of the extrusion tube press, the swelling behavior of the part of the strand that has not yet or not yet been adequately set, and the mobility of the strand in the curing channel. The less the strand has set through its binder, the more it swells. This swelling is prevented by the walls of the curing channel to the outside. However, if the swelling force becomes too great, the strand sticks in the curing channel and can no longer be pressed out. The mandrel could also jam if the expandable cross-section were not reduced by a necessary amount after the final compression. When the cross section of the mandrel is reduced, the compacted mixture tries to swell inwards, that is, into the cavity formed by the mandrel and to reduce the cross section of the cavity. When the mandrel is designed according to the invention, the boundary layer to the cavity behaves more or less like a vault. It is further compressed by the swelling and forms an increasing resistance to a reduction in cross-section until the swelling and compression forces are in equilibrium. The degree of reduction is very small due to the compression characteristic of the material. In practice, a deterioration of the surface is not or hardly detectable.

It has been found that a significant proportion of the swelling forces are eliminated by the counteracting resistance of the cross-sectional reduction, and thus the remaining swelling force on the outer surfaces of the strand is so small that the controllability of the compression and the extrusion tube press is retained and the specific weight is precisely adjustable, selectable and reproducible with each press stroke.

Fig. 1

einen Längsschnitt durch eine Strangpreßvorrichtung in den Linien II-II-II-II der Figur 2

Fig. 2

einen Querschnitt in der Linie I-I der Figur 1

Fig. 3

eine Einzelheit innerhalb des Kreises III in Figur 1

Fig. 4

einen schematischen Längsschnitt durch eine Strangrohrpreßvorrichtung nach der Linie I-I gemäß Figur 5

Fig. 5

einen Querschnitt nach der Linie II-II gemäß Figur 4

Fig. 6

einen Längsschnitt durch eine Strangrohrpreßvorrichtung, in der das Gemenge vorverdichtet ist

Fig. 7

einen Längsschnitt durch eine Strangpreßvorrichtung, in der das Gemenge weiterverdichtet ist,

Fig. 8

einen Längsschnitt durch einen Strangrohrpreßvorrichtung, in der das Gemenge endgültig verdichtet ist

Fig. 9

einen Längsschnitt durch einen Dorn

Fig. 10

einen Querschnitt durch einen Dorn auf der Linie I-I gemäß Fig. 9

Fig. 11

einen Querschnitt durch einen Dorn

Fig. 12

ein Strangprofil

Fig. 13

ein Strangprofil

Fig. 14

ein Strangprofil

Die Figur 1 zeigt einen versetzten Längsschnitt durch eine Strangpreßvorrichtung 1. Aus dem Einlaufschacht einer Befüllvorrichtung 2 für Strangpressen wird das Gemenge durch den Schließschieber 3 über Füll- und Preßraum 4 transportiert, in den es im freien Fall fällt. Danach wird der Füll- und Preßraum 4 durch den Schließschieber 3 verschlossen und das Gemenge durch den Preßstempel 5 bei stehendem Dorn 6 auf eine gewünschte Vorverdichtung, z.B. 30 %, verdichtet. Durch die gemeinsame Bewegung von Dorn 6 und Preßstempel 5 wird das vorverdichtete Strangteilstück in den Aushärtekanal 7 geführt und der sich im Aushärtekanal 7 befindliche Strang entsprechend weit ausgepreßt. Solange, bis der Preßstempel 5 das vordere Ende des Füll- und Preßraumes 7 erreicht, wird der Dorn 6 in der Weise bewegt, daß der Abstand zwischen dem hinteren Ende des Stranges 10, das dabei in der Höhe des hinteren Ende 12 des Aushärtekanals 7 liegt, und der Stirnfläche 11 des Preßstempels 5 gleich bleibt.The details of the invention are shown systematically and by way of example in the drawings, in which:

Fig. 1

2 shows a longitudinal section through an extrusion device in lines II-II-II-II of FIG. 2

Fig. 2

2 shows a cross section in line II of FIG. 1

Fig. 3

a detail within the circle III in Figure 1

Fig. 4

5 shows a schematic longitudinal section through an extrusion tube pressing device according to line II according to FIG. 5

Fig. 5

a cross section along the line II-II of Figure 4

Fig. 6

a longitudinal section through an extruder tube, in which the batch is pre-compressed

Fig. 7

2 shows a longitudinal section through an extrusion device in which the batch is further compressed,

Fig. 8

a longitudinal section through an extruder tube, in which the batch is finally compressed

Fig. 9

a longitudinal section through a mandrel

Fig. 10

a cross section through a mandrel on the line II of FIG .. 9

Fig. 11

a cross section through a mandrel

Fig. 12

an extruded profile

Fig. 13

an extruded profile

Fig. 14

an extruded profile

FIG. 1 shows an offset longitudinal section through an extrusion device 1. From the inlet shaft of a filling device 2 for extrusion presses, the batch is transported through the closing slide 3 over the filling and pressing chamber 4, into which it falls in free fall. Then the filling and pressing chamber 4 is closed by the closing slide 3 and the batch is compressed by the press ram 5 with the mandrel 6 to a desired pre-compression, for example 30%. Due to the joint movement of mandrel 6 and press ram 5, the pre-compacted strand section is guided into the hardening duct 7 and the strand located in the hardening duct 7 is pressed out correspondingly far. Until the ram 5 reaches the front end of the filling and pressing space 7, the mandrel 6 is moved in such a way that the distance between the rear end of the strand 10, which is at the height of the rear end 12 of the curing channel 7 , and the end face 11 of the ram 5 remains the same.

From the front end 9 of the filling and pressing chamber 4, the cross section over the circumferential inclined surfaces 13 with the radius 14 is reduced to the cross-sectional dimension of the hardening duct 7. When this reduction is passed through the pre-compressed mixture, the parts on the outer layer are folded parallel to the outer surfaces . The parts of the batch are not kinked or kinked due to the degree of pre-compaction, but retain their strength.

According to the invention, the thickness of the outer layer is determined by the degree of reduction. So with the same total compression or total weights, strands with different Strength are generated. For components subject to bending loads, e.g. B. load-bearing beam profiles, one will choose a higher flexural strength with lower overall compression and weights, for components subject to pressure, e.g. B. pallet blocks, correspondingly a higher total compression with higher compressive strength.

This folding in the partially compressed state, in addition to the higher compression of the outer layer of the strand during the final compression, results in the high bending and bending strength of the strand according to the invention.

As soon as the press ram 5 passes over the rear end 9 of the curing channel 7 - moving into its predetermined front end position - the mandrel 6 is moved in such a way that the desired final degree of compaction is obtained. The strand section produced with the press stroke is thus completed. Due to the static friction between mandrel 6 and strand 8, the strand and the press ram 5 are withdrawn by the mandrel 6 to such an extent that the end face 11 of the press ram 5 and the end 10 of the strand 8 are located at the rear end 12 of the curing channel 7. In this position, the press ram 5 stops and when the static friction is overcome, the mandrel 6 is pulled out of the strand 8 and moved into its starting position. Thereafter, the press ram 5 moves to its starting position and ends the press operation.

Of course, the invention is not limited to the use of the mandrel. Rather, any number of mandrels can be used, which can protrude through the filling and pressing space 4 into the curing channel 7 at any point.

If several spikes are used, the static friction between the spikes and the strand can become so large that a subsequent compaction takes place when the spikes are pulled out of the strand. In cases in which no post-compaction is to take place, the invention provides for the mandrels not to be pulled out of the strand at the same time, but rather individually or only a certain number of mandrels. The invention further teaches that the mandrels for increasing or reducing the friction are designed to be conical or wedge-shaped in length or parts of the length. If the cross section of the thorn (s) is changed, this can also be done along non-straight lines.

In the embodiment shown in FIG. 4, a pallet block profile with two cavities is created. Two press cylinders 19, 19 'with their piston rods 20, 20' are attached to the crossmember 15 of the filling and pressing space 16 with the press nozzle 17 to which the curing channel 18 is connected. The extrusion die 21 is connected to the press cylinders 19, 19 'via the cylinder cross member 22. During the press stroke, the extruded tube punch 21, driven by the press cylinders 19, compresses the mixture in the filling and pressing space 16 and presses it by the length of the extruded part produced with the press stroke with the strand 23 already produced in the previous strokes into the curing channel 18. The extrusion die 21 runs over the mandrels 24, 24 ', which are movably guided in the pressing direction by means of a mandrel traverse 25 with the mandrel holding cylinder 26.

If the extrusion die 21 has pressed the mixture in the filling and pressing space 16 to its final compression, the mandrels 24, 24 'run in the pressing direction. The level of compression is determined by the pressure in the mandrel holding cylinder 26 determined, which is precisely selectable, adjustable and reproducible with every cycle by a pressure relief valve attached to the cylinder or connected with lines. When the extrusion die 21 reaches its front end position, it stops and is secured against being pushed back by the strand 23 with a hydraulic shut-off valve which is connected to the press cylinders 19, 19 '. The mandrels 24, 24 ', which have run along with the length of the newly formed strand part, are pulled back into their starting position by the mandrel holding cylinder 26. The extrusion die 21 then moves back to its starting position.

In Figure 5, the profile of the strand 23 is shown, which is formed by the boundary walls 27 and the closing slide 28 and the mandrels 24, 24 '. The closing slide 28 is moved back and forth by a stroke transmitter 29 and, with its passage opening 30, enables the batch to fall from the filling shaft 31 into the filling and pressing space 16 in free fall.

In the exemplary embodiment in FIG. 6, a longitudinal section through an extruded tube pressing device, the mixture 32 in the filling and pressing space 33 is pre-compressed by the pressing ram 34, the filling and pressing space 33 being closed by the closing slide 35.

The mandrel part 36, which can be expanded in cross section, is not expanded and has the cross section of the mandrel part 37 adjoining the press ram. The strand 39 is located in the hardening channel 38 and therein the non-expandable mandrel part 40 on the hardening channel side.

During the pre-compression, the mandrel 41 is in its initial position. The amount of precompression can be determined via the path or the pressing force of the press ram 34.

The next compression process is shown in FIG. By moving the ram 34 and mandrel 41, the batch was further compacted and moved to its final length by moving the small parts of its outer skin over the reduction 42 between the filling and pressing space 33 and the curing channel 38, so that at the end of this step the end 43 of the strand part 44 is at the beginning 45 of the curing channel 38. The expanded mandrel part 36 is in the non-expanded state and is located in the strand part 44.

In FIG. 8, the strand part 44 produced with the press stroke has been completed and has extended the strand by its length. The final compression takes place by widening the cross section of the mandrel part 36. In order to allow the mandrel 41 to be pulled out into its end position without re-compressing the strand section 44 produced with the press stroke, the cross section of the mandrel part 36 was expanded to a larger cross section than that of the mandrel part 40 located in the strand 39 This cross-sectional expansion was reduced to at least the cross section of the mandrel part 40 after the final compression before the mandrel 41 was pulled out.

FIG. 9 shows a longitudinal section through a mandrel 41. The cross-sectionally expandable mandrel part 36 is expanded to the cross-section of the hardening channel-side mandrel part 40 or somewhat larger and between it and the press-die side mandrel part 37 kept such that it is not or not significantly longitudinally movable. The expansion took place via the pull wedge 46. In the non-expanded state, the cross section of the mandrel part 37 corresponds to that of the mandrel part 36. The expandable mandrel part 36 can be made of a plastic material or, if it is not plastic, can be made with expansion slots.

A cross section on the line I-I according to FIG. 9 is shown in FIG. For the example, a round mandrel was selected, which is heated by an electrical resistance heater 47. The current is supplied through the bore 48. The elastic, but not or almost incompressible mandrel part 36 is provided with a protective layer 49, for example metallic, which prevents the penetration of parts of the mixture and reduces the friction.

FIG. 11 shows a longitudinal section through a mandrel 41, in which the mandrel part 36 is widened under pressure, with a liquid medium in the cavity 57. Here, the applied protective layer 49, which reduces the friction and prevents the penetration of parts of the batch, is designed to be longitudinally stable and prevents the hose-like element 50 from laying excessively over the possibly rounded corners 52, 52 'when pressure is applied. The protective layer 49 is also longitudinally stable in such a way that it can overcome the frictional forces of the strand 39 when the mandrel 41 is pulled out.

Of course, the invention is not limited to the named ways of expanding the mandrel part 36 but teaches that the advantages of the invention can also be achieved with other types of cross-sectional expansion.

Figure 12 shows the cross section of a profile that can be used for example as a wall element in house construction. The lightweight construction with a large spacing of the outer surface 53 with oriented chips is advantageous here. The cross-sectional expansion was carried out here from line 54 to strand wall 55.

Figure 13 shows a support profile, for example for prefabricated houses. The final compression is also carried out here by expanding the mandrels from lines 54 to the inner walls 55 of the strand. In the exemplary embodiment, only the two outer surfaces 53 are oriented.

For example, FIG. 14 shows a window or door profile in which all outer surfaces are oriented. The final compaction was carried out by expanding the mandrel from lines 54 to strand walls 55.

In the profiles of FIG. 13 and FIG. 14, the inner walls of the strand are formed with inner surfaces corrugated in the strand in order to support the swelling pressure.

Claims (23)

1. Method of bar or tube extrusion of a mixture of vegetable particles with binding agents, wherein the mixture is pressed and thereby compacted by a ram (5) from a charging and compaction compartment (4) into a setting passage (7), wherein both the static friction between the outside wall of the strand and the inside wall of said setting passage and also between the inside wall of the strand and a mandrel (6) is utilized for holding the last part of the strand so produced in said setting passage (7),
   characterized in that

   (a) independently of said ram (5, 34), during the movement and standstill of said ram, as a function of the controllable degree of compaction of said mixture, a mandrel (6, 24, 41) axially mobile in the extruding direction is moved in the extruding direction of said ram or in opposition to this direction of movement, and that, at least during the last part of the compaction stroke, said mandrel is entrained into said setting passage (7, 18, 38) through the static friction on said strand (8, 23, 39), which is then sufficiently great, with a controlled deceleration taking place, and that during the compaction stroke until the final compaction degree has been achieved by an adjustable force which may be varied during the compaction stroke, said mandrel forming the cavity of said strand is retained in its rear end position, which causes the standstill of the strand due to static friction;

   (b) said mixture is compacted in said charging and compaction compartment (4, 16) by the movement of said ram (5, 34), and that upon achievement of the desired compaction degree said mandrel (6, 24, 41) is moved in such a way that the desired degree of final compaction will be achieved and the strand already compacted will be expelled from said setting passage (7, 18, 38);

   (c) following the extruding operation, said mandrel (6, 24, 41), and along with it the extruded strand (8, 23, 39) as well as said ram (5, 34), are retracted, as a result of static friction between said mandrel and the strand, until the face side (11) of said ram and hence the end of the strand reach said charging and compaction compartment (4, 16, 33); that thereupon said ram is stopped and said mandrel is retracted into its initial position, whereupon said ram is equally returned into its initial position so as to release said charging and compaction compartment for a further charging operation, with the force retaining said mandrel upon achievement of the final degree of compaction being so varied that despite the change of friction between said strand and the walls of said extruder orifice (17) of said setting passage, on account of the conversion of static friction into sliding friction, the pressing force of said ram remains approximately the same;

   (d) said strand is clamped onto said mandrel by the static friction in such a way that the strand does not resiliently yield and that said binding agent may set in a condition of special rest.
2. Method according to Claim 1,
   characterized in that said ram (5, 34) urges said mixture with an appropriate movement of said mandrel (6, 24, 41) from said charging and compaction compartment (4, 16, 33) into said setting passage (7, 18, 38), while the degree of compaction is maintained, until the ram reaches the end of said charging and compaction compartment, and that subsequently said ram is pressed into said setting passage until it has reached a specified position, and that during this compaction step in said setting passage said mandrel is so entrained that the degree of compaction remains constant and that a uniform subsequent compaction of the pre-compacted mixture will occur.
3. Method according to Claim 1 or 2,
   characterized in that the particles contained on the outside surfaces of the mixture pre-compacted in said charging and compaction compartment (4, 16, 33) are bent during their passage into said setting passage (7, 18, 38) on account of the fact that said setting passage presents a smaller cross-sectional area.
4. Method according to Claim 3,
   characterized in that the particles at the outside surfaces of said pre-compacted mixture are bent in such a way that, as a function of the degree of pre-compaction, the parties in the pre-compacted mixture will not be bent off and retain their strength.
5. Method according to Claim 3 or 4,
   characterized in that those particles of the mixture, which are bent to extend in parallel to the outside surfaces, constitute an outside layer presenting a higher degree of compaction, and that the strength and load-bearing capacity of the strand are improved.
6. Method according to any of Claims 1 to 5,
   characterized in that the thickness of said more strongly compacted outside layer is defined by the measure of reduction (13, 14) between the end of said charging and compaction compartment (9) and the beginning of said setting passage (12).
7. Method according to any of Claims 1 to 6,
   characterized in that said mandrel (6, 24, 41) is heatable and, as a result of its length, transfers a substantial proportion of the setting energy into said strand (8, 23, 39).
8. Method according to any of Claims 1 to 7,
   characterized in that said pre-compacted and further compacted mixture is subject to additional compaction by way of an enlargement of the cross-section of said mandrel (41), so that the mixture reaches its final, selectable, adjustable density or specific weight, respectively, which can be reproduced for each stroke.
9. Method according to Claim 8,
   characterized in that the mixture is pre-compacted by the movement of said extruding ram (34), arrives in said charging and compaction compartment (38) in the condition so compacted under the action of said extruding ram and said mandrel (41), and is subjected to a continued pre-compacton there under the movement of said extruding ram and said mandrel until it has reached its final length and until its final degree of compaction is achieved by an enlargement of the cross-section off said mandrel.
10. Method according to Claim 8 or 9,
    characterized in that the degree of compaction is selectable, adjustable and reproducible for each compaction stroke by an enlargement of the cross-section of said mandrel (41), from the minimum compaction possible, which is required to bend the particles in the outside layer of the mixture into an orientation parallel to the extruding direction, up to the yield point of the material.
11. Method according to any of Claims 1 to 10,
    characterized in that a heated liquid or gaseous medium flows through the employed mandrel (41).
12. Devise for carrying through the method according to Claims 1 to 11, comprising a ram (5), a charging and compaction compartment (4), a setting passage (7) and a mandrel (6), as well as the necessary mechanisms for driving said ram,
    characterized in that an axially mobile mandrel (6, 24, 41), equipped with driving means, is passed through said charging and compaction compartment (4, 16, 33) by said ram (5, 34) and projects beyond said charging and compaction compartment into said setting passage (7, 18, 38), with said mandrel being designed to have such a length that the static friction between the mandrel and the strand (8, 23, 39) exceeds the extruding force reduced by the frictional forces acting upon the outside surfaces of said strand, and that provisions are made for a variable expansion of the cross-section of said mandrel (41).
13. Device according to Claim 12,
    characterized in that several mandrels (6, 24, 41) are provided which present each an optional cross-section and length.
14. Device according to Claim 12 or 13,
    characterized in that said mandrel(s) (6, 24, 41) may be designed to be variable over their length or parts of their length in a wed-shaped or conical form, and/or in such a way that their cross-sections are variable along non-linear lines.
15. Device according to any of Claims 12 to 14,
    characterized in that said mandrel (6, 24, 41) is adapted to be variable in its length, so as to increase or reduce the friction between the mandrel and the strand (8, 23, 39), in such a way that the profile varies along non-straight outside contours.
16. Device according to any of Claims 12 to 15,
    characterized in that two or more mandrels form cavities having a specific profile.
17. Device according to any Claims 12 to 16,
    characterized in that said mandrel (41) is expanded in that part of its length which is located within the strand segment (44) formed by said compaction compartment (33).
18. Device according to Claim 12 or 17,
    characterized in that the expansion of the cross-section of said mandrel (41) is achieved by means of longitudinally mobile traction wedges (46).
19. Device according to Claim 18,
    characterized in that the cross-section of said expandable mandrel segment (36) is resilient in terms of pressure.
20. Device according to Claim 19,
    characterized in that the cross-section of said mandrel (41) may be expanded by means of the pressure of a liquid or gaseous medium.
21. Device according to Claim 19 or 20,
    characterized in that said pressure-resilient mandrel segment (36) is provided with a protective layer (49) which prevents the penetration of particles in the mixture.
22. Device according to any of Claims 12 to 21,
    characterized in that said mandrels are produced to have an oval shape for supporting said strand against the swelling pressure.
23. Device according to any of Claims 12 to 22,
    characterized in that said mandrels are provided with convex outside surfaces for supporting the swelling pressure.

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