EP1752268A2 - Process and apparatus for obtaining a equal strand density and for curing strands from plant particles - Google Patents

Abstract

In a gap from its compression-side end from about half a strand's crosswise dimension up to about 5-times the dimension of a strand part piece (SPP) (11) created by each pressing stroke or up to a length that the strand covers in a third of a gelling agent's setting time, the strand heats up in water to a temperature of up to about 100[deg] C in a length of between one and four fifths of the SPP. An independent claim is also included for a device for carrying out the method of the present invention.

Description

Method and device for achieving the same high strand density and curing strands of small plant parts.

With DE 10 2005 037 765.3-15 A method has been known with which strands are cured accelerated. In this teaching, water is introduced into the walls of the heating channel, which evaporates in these, penetrates into the strand and this heated. In a subsequent setting zone, the strand is set and cut to length. The process gives very good results in full strands in terms of quality of the strands, especially when pallet blocks are cut from the strands. Its special suitability is to be seen in the high efficiency.

The majority of the pallet blocks, however, is made with a hole.

Users of pallet blocks prefer blocks with a slightly greasy, glossy surface. By contrast, the blocks which have hitherto been produced with steam heating have a surface that is smooth but not shiny or even greasy. The cost of the heating channel are relatively high. In particular, the holes for the water or steam outlet and the steam outlet places to the manufacturer of such devices increased demands and require very expensive production machines.

In the case of the products, disadvantageously, despite a stepped or wedge-shaped widening of the filling and pressing space, also called recipient, a density difference can be established in the strand section produced with each pressing stroke. The density of Euro pallet blocks is standardized at 0.58 to 0.63 kg / dm ³ . The periodic density fluctuations over 10 to 20 press strokes already observed throughout the strand add up to the density differences in each strand section. More accurate measurements of pallet blocks have shown that while the average density is usually within the standard range, a significant portion of the blocks have impermissible differences in density over the length. The reason is that the length of a strand section at a conventional Presshublänge of 650 to 700 mm and a compression of about 1: 4 at a filling of the filling and pressing space of about 95% at about 155 to about 170 mm, the Pallet blocks with standard pallets have a height of 78 mm.

The invention is therefore an object of the invention to provide a method by which full strands and strands can be made with holes that have the desired surface and have the same length equal or approximately equal height over the strand length. Next, the devices should be so executable that they can be manufactured with relatively simple machine tools.

The objects of the invention have been achieved with the characterizing features of claim 1 and claim 12.

• Die Erwärmung innerhalb eines Zeitraumes von weniger als 1 s erfolgen kann.
• Die erforderliche Strecke über die das H₂O in den Strang eindringt, geringer sein kann, als die Länge eines jeden Strangteilstückes.
• Der Strang nach der letzten Dampfaustrittsöffnung, also wenn er seine gewünschte, günstige Abbindetemperatur von bis zu etwa 100°C erreicht hat, seine Querschnittsform nicht mehr verändert.
• Eine Dampfmenge von weniger als etwa 6% des Stranggewichtes, abhängig von der Temperatur der unverdichteten Kleinteile und der gewünschten Strangtemperatur genügt.
• Das, im Strang kondensierte H2O nicht aus dem Strang entfernt werden muss, wenn die abfolgenden Transport- und Stapeleinrichtungen entsprechend ausgelegt sind.
• Je nach Ausstoß der Strangpresse im allgemeinen eine Länge des Abbindekanals von weniger als dem Produkt aus der Geleirzeit des Bindemittels in min x dem Ausstoß der Presse in m/min genügt.
• Kein nennenswerter oder nachteiliger Dampfaustritt in den Füll- und Pressraum erfolgt, wenn die erste Dampfaustrittsstelle von der Hinterfläche des Stranges mehr als etwa dem halben Strangquermaß entfernt ist.

In experiments with a heating of the strand to a favorable setting temperature of up to 100 ° C, it has surprisingly been found that:

• The heating can take place within a period of less than 1 s.
• The required distance over which H ₂ O enters the strand may be less than the length of each strand section.
• The strand after the last steam outlet opening, that is, when it has reached its desired, favorable setting temperature of up to about 100 ° C, its cross-sectional shape no longer changed.
• An amount of steam of less than about 6% of the weight of the rope, depending on the temperature of the uncompressed small parts and the desired strand temperature, is sufficient.
• The condensed H2O in the strand does not have to be removed from the strand when the subsequent transport and stacking devices are designed accordingly.
• Depending on the output of the extruder in general, a length of the Abbindekanals of less than the product of the gel time of the binder in min x the ejection of the press in m / min is sufficient.
• No appreciable or detrimental escape of steam into the fill and compaction space occurs when the first exit of steam from the back face of the strand is more than about half the strand traverse.

Completely surprisingly, and in contrast to all previous assumptions, it was found in further experiments that the differences in density over the length of each strand section are completely or almost completely eliminated when the introduction of steam commences as close as possible to the press end strand end. So from a range of about half the strand cross-dimension to a distance up to about the length of up to about 5 strand sections or the length that travels the strand in up to about 1/3 of the setting time. The cause was found to be that the strand is indeed stable in cross-section, but since, after the steam injection, it exerts only a lower pressure against the boundary walls and the leg parts lie in the strand transversely to the pressing direction, a certain densification takes place in the strand part region with a lower density. if the binder is not or only partially gelled.

The invention therefore builds a press as follows:
The filling and pressing space is preferably carried out with easy-to-manufacture parallel walls. At most, to reduce the friction of the forming strand section during the press ram stroke, the invention provides a lower than usual, wedge-shaped or stepped extension to the first steam entry point or to the pressing nozzle in a degree of up to about 1.5% of the strand transverse dimension. The known first section of the curing channel, usually about 1.5 to 1.7 m in length, is replaced by a very short rigid zone heating zone. Their length is approximately equal to or about six times greater than the length of the strand section formed with each pressing stroke. In this heating zone, the heating of the strand is carried out by steam. For full strands without a hole, the steam is introduced from the outer walls of the heating zone in the strand. The heating zone is heated by an electrical resistance heater or by hot water or heat transfer oil. The H ₂ O can be fed into the walls of the heating zone both as steam, with sufficient heating, as well as water, wherein the steam is formed only in the walls. The advantage of the latter embodiment of the invention is that no steam boiler has to be operated with the known high operating costs and safety requirements.
Advantageously, the invention combines the heating zone with the filling and pressing space and indeed in its closed area, following the inlet opening. In contrast to extrusion presses, eg for metals, it is not possible to speak of a press nozzle when extruding wood chips, since a nozzle always means a constriction. Here, however, the pressing channel is executed with the same or slightly widening profile. The closed area of the filling and pressing space is usually according to DE 29 32 406 performs and has a length of about 300 to 400mm. He is usually provided with a cooling, which had no practical but only a patent-legal cause. The inventive length of the closed part of the filling and pressing space has a degree of The approximately simple to about six times the strand length. It is preferably carried out with parallel inner walls. Of advantage, however, may be a very small wedge-shaped extension of up to about ½%. The closed part is heated more intensively than usual. Its temperature can be up to about 240 ° C, instead of the previous about 160 ° C. The heating can be done both by thermal oil which circulates in turbulent flow through holes, as well as by an electrical resistance heater. Due to the higher temperature and / or. The intense heat input through the turbulent flow of the thermal oil results in the desired greasy surface. Another advantage of the heating of the closed part of the filling and pressing space is that virtually no or only a little wear occurs. The binder contains grease or paraffin, which, as soon as the surface of the strand is heated, emerges from it, reduces friction and virtually forms a protective layer against wear, which is constantly renewed. It may be structurally quite advantageous to divide the closed part of the filling and pressing space transversely to the pressing direction or to manufacture in two sections.

The steam input is introduced compared to the previous teachings in a much shorter distance, which is at best just short of the length of the strand formed with each pressing stroke strand section. As a particularly favorable measure, a length of about 1/5 to about 9/10 of the Strangteilstücklänge has proven. The closed part of the filling and pressing space is generally carried out with parallel boundary walls. However, a wedge-shaped extension of up to about ½% of the strand transverse dimension may be advantageous, in particular in the processing of waste wood chips. The steam entry into the strand can be done both continuously and intermittently, during the strand standstill in the press cycle.

With the steam injection from the outer walls can of course also produce strands with a hole. However, it has been shown that a steam input from the outer walls of the mandrel brings significant advantages in terms of mandrel friction. Since in this type of steam introduction, the friction of the strand on the mandrel is considerably lower than with a steam input from the outer boundary walls ago. Since the already mentioned densification eliminates density differences in the strand section, it is advantageously no longer necessary to use a follower mandrel. Its advantages are achieved without the considerable design effort by a fixed mandrel with steam outlet openings in the aforementioned range. The H ₂ O may be supplied to the mandrel as water if it has sufficient heating, or as steam in an external steam boiler.

The pressing die moving over the mandrel does not run completely evenly, but transmits certain shocks during compression of the strand and in the transition from static friction to gel friction as the strand starts to move. Surprisingly, these shocks cause, in particular when the mandrel is provided with a sliding layer, e.g. Nanocoated, no limescale deposits on the drill holes. A heated mandrel can therefore be operated with tap water and no distilled water is required, which simplifies the operation of the device and reduces product costs.

Also surprisingly, it has been found that expensive structures made of narrowest slits unnecessary for steam escape. It suffice for the steam outlet a variety of small holes in a diameter range of about 1 to about 4 mm. Blockages are surprisingly not observed in the designated steam outlet area.

When using recycled waste wood chips with a dust content, however, it has proved to be advantageous to use fewer steam outlet points, but to cover them by sintered metal disks, sintered metal rectangles or Sintermetallovale. The average hole diameter in the sintered metal covers may be about 5 μm to about 100 μm. The material can be sintered bronze or stainless steel. When the steam of thorns is introduced into the strand, the invention uses sintered metal rings, preferably of stainless steel, or manufactures the mandrel head from which the vapor exits from sintered metal, with metal guide rings, To prevent abrasion and a front seal, so that no steam enters the spike hole. Advantageously, the saw-side end of the sintered metal head can be made so thick that the steam diffuses completely through the lateral surface.

In prior art presses, a ram head is mounted on the ram piston rod. The press piston rod is hollow drilled and moves into the filling and pressing space. The mandrel protrudes through the bore of the pressing piston rod. Since the mandrel is heated in the invention by the flowing steam, it gives off its heat to a considerable extent on the pressing cylinder. This leads to an energy loss and reduces the life of the cylinder seals. The energy must be dissipated by the hydraulic oil.

The invention, on the other hand, uses a standard profile tube as a press die, for example. gem. DIN EN 10210 on which it assembles the press die head. The ram is guided by a suitable linear guide, and driven by a hydraulic cylinder. The mandrel protrudes through the ram and is located at a suitable location, e.g. attached to the press frame. It is of no particular disadvantage when the ram is heated by the mandrel. Due to the dimensions, however, it is possible in a simple manner to isolate the press ram against the mandrel for energy saving. The mandrel is formed in an advantageous embodiment so that it is adjustable in its position in the press or strand in the pressing direction, e.g. through a screw thread.

The invention makes the mandrel longitudinally adjustable in order to be able to vary the region of the steam outlet in the pressing direction. The optimum position of the rearmost steam outlet opening is in a range between approximately half the strand transverse dimension and approximately six times the length of a strand section. It is determined by experiment, since they depend on strand and dome cross section and the state of wear of the filling and pressing chamber. The optimum position can change during the operation of the press and is corrected later. In it, the punch needs the least force to compact the strand to the desired value.

The length of the steam outlet region from the mandrel is about 1/5 to about 9/10 of the length of a strand section.

Holes with holes are generally heated by vapor injection from the mandrel to a setting temperature of up to about 100 ° C. In high-performance presses, however, it is advantageous to heat the strand both from the walls of the filling and pressing chamber ago as well as simultaneously from the mandrel, since these presses have a very short cycle and strand downtime.

The introduction of steam can be carried out both continuously and discontinuously, and in an equally advantageous manner, with interruptions in the press cycle. In a discontinuous steam injection, the control of the amount of steam over time, with a continuous on the vapor pressure and / or a flow rate control.

The setting channel following in the pressing direction essentially has the task of maintaining the glue residue during the gelling process of the binder and of cushioning interfering influences of the traveling saw. Next, the strand density is determined by him in a known manner. During strand standstill, one of its angles or subshells is tensioned by e.g. Hydraulic cylinder, pressed with less force against the strand than during the movement of the strand. The lower force determines the strand density and is either adjusted by a pressure relief valve or the setting is computer determined. The strand density is measured by a measuring device before or after the saw and a computer determines the lower force. Equally advantageously, it is possible to dispense with a high and a low pressure and to work with an adjustable pressure.

The setting range can be kept shorter in length than previously known. For a press capacity of approx. 60,000 pieces of pallet blocks of 78 mm height per 24 hours, a length of approx. 3 meters is generally sufficient. For high performance presses of 120,000 or more blocks per 24h, a length of 6 meters or more is chosen.

If the H ₂ O condensed in the strand after steam injection is left stranded, the setting channel has only one tempering task. He therefore no longer supplies the strand with heat, but essentially keeps it at its attained temperature. Since the presses work in full time, so are turned off only for maintenance and repair purposes, can be dispensed with a heating. It is only a very good insulation necessary to keep the heat losses as low as possible. In order to be able to open the movable angle or the movable part shell in case of failure, the invention for weight relief on train acting gas springs before.
After the Abbindekanal the strand is sufficiently dimensionally stable and can be cut to length by a saw.

If the strand condensed in it H ₂ O are completely or partially withdrawn, so a relatively dry strand are generated, this accomplishes the invention of a much simpler and more advantageous manner than in the prior art applications. It heats the strand by supplying heat in the heating area and / or the subsequent setting zone, which is then heated, to the extent that the strand at least a portion of the heat of vaporization of the condensed water is supplied. The strand temperature does not increase beyond the ambient evaporation temperature of water. The entire area from the filling and pressing space to the saw is sealed according to the invention and in a known manner. The pressure-tight connection from Abbindekanal to follower saw is made for example by a telescoping tube or a bellows. The suction of the saw works with a suction, which works with a negative pressure of approx. 08 to 0.9 bar. This vacuum is sufficient to allow the condensed H ₂ O to evaporate. It is in contrast to prior art teaches no vacuum device required. Of course, the invention provides just as advantageous a separate suction with a conventional negative pressure of about 08, to about 0.9 bar before. Likewise, a vacuum device is conceivable and advantageous.

In tests with a press constructed according to the invention, it has surprisingly been found that the required specific pressing pressure on the batch of about 55 kgf / cm ² in presses according to DE 29 32 406 reduced to about 35 kp / cm ² . Furthermore, it is easily possible with this device to process processed waste wood, which was not possible with the aforementioned systems.

• Fig. 1. einen Längsschnitt durch eine Strangpressanlage.
• Fig. 2. einen Querschnitt auf der Linie I-I gem. Fig. 1.
• Fig. 3. einen Querschnitt auf der Linie I-I gem. Fig. 1.
• Fig. 4. einen Querschnitt auf der Linie II-II gem. Fig. 1.
• Fig. 5. einen Längsschnitt durch eine Strangpressanlage.
• Fig. 6. eine Teilansicht eines Domes
• Fig. 7. eine Teilansicht eines Domes
• Fig. 8. eine Ansicht eines Dornkopfes
• Fig. 9.

The invention will now be described by way of example without limitation of the general inventive concept by means of embodiments with reference to the drawings, wherein the remainder of the disclosure of all unspecified in the text details of the invention is expressly noted.
Show it:

• Fig. 1. a longitudinal section through an extrusion press.
• Fig. 2. A cross section on the line II gem. Fig. 1.
• Fig. 3. a cross section on the line II gem. Fig. 1.
• Fig. 4. a cross section on the line II-II gem. Fig. 1.
• Fig. 5 . a longitudinal section through an extrusion press.
• Fig. 6. A partial view of a dome
• Fig. 7 is a partial view of a dome
• Fig. 8 is a view of a mandrel head
• Fig. 9.

LIST OF REFERENCE NUMBERS

1

Solid strand

2

extruder

3

press die

4

Front end position of the press ram

5

inlet shaft

6

Filling and pressing space.

7

Closed part of the filling and pressing room

8th

heating zone

9

Holes for thermal oil

10

steam holes

11

String section

12

Measurement of the length of a strand section

13

Inlet area of the filling and pressing space

14

Dimension up to the area of the first steam outlet

15

Steam outlet opening

16

boundary walls

17

Strangquermaß

18

Range of the steam outlet

19

Measure of the length of the steam outlet

20

Press side strand end

21

Measure between the strand end and the first steam outlet

22

Dimension of the closed part of the filling and pressing space

23

Height of the last steam outlet

24

Revolving saw

25

Abbindekanal

26

setting zone

27

Dimension of the setting zone

28

force transmitter

29

Moving angles or subshells the binding channel

30

Measuring device for strand density

31

feed

32

drilling

33

Steam outlet opening

34

Dimension of the steam outlet

35

Sintered metal element

36

Fixed angle of the binding channel

37

axis

38

gas spring

39

Hole in the strand

40

mandrel

41

Line for H ₂ O

42

heater

43

linear guide

44

screw thread

45

mother

46

Front part of the closed part of the filling and pressing chamber

47

Rear part of the closed part of the filling and pressing room

48

Outer edge layer of the strand

49

bellow

50

suction

51

Separate suction

52

Front surface of the dome

53

Turning in the mandrel

54

Drill holes in the mandrel

55

Sintered metal rings

56

mandrel head

57

metal rings

58

drilling

59

lateral surface

1 shows a longitudinal section through an extrusion press for the production of full strands 1. In the extrusion press 2 , the press die 3 is in its front end position 4.
The mixture passes in the embodiment of an inlet shaft 5 in the filling and pressing chamber 6 and is compressed by the ram 3 and in the closed part 7, this also represents the heating zone 8 , the filling and pressing chamber 6 transported. It is heated in the embodiment by thermal oil, which flows in turbulent flow through the holes 9 , intensive and with high heat output to a higher temperature than usual, of up to about 240 ° C. As a result of this intensive heating, the strand 1 acquires the greasy surface desired by the users. Strand 1 is heated to its setting temperature of up to about 100 ° C, essentially by H ₂ O. The H ₂ O penetrates from the steam holes 10 in the strand 1. It can be supplied to the closed part of the filling and pressing chamber 7 as water and is evaporated in this in, or as a steam from a boiler.
With each pressing stroke a strand section 11 is produced with the length in the measure 12 and connected to the generated in the forward stroke. The inlet region 13 of the filling and pressing chamber 6 or the region in the dimension 14 to the first steam outlet opening 15 is preferably formed with parallel boundary walls 16. To reduce the friction, however, it may be advantageous to wedge it in the pressing direction or step by step by up to about 1.5%. The closed part 7 of the filling press room 6 is also generally carried out with parallel boundary walls 16 . In particular, in the processing of waste wood, it may be advantageous to wedge in the region of the closed part 7 of the filling and pressing chamber 6 also wedge-shaped or stepped. The degree of extension can be up to ½% of the strand cross dimension 17th For a stepped extension, the number of stages may be up to about 4. The extension can also be advantageously carried out only in the region of the steam outlet 18 in the dimension 19 and the subsequent area with parallel boundary walls 16 are performed.
The heating of the strand happens almost abruptly and essentially by the release of the heat of condensation of the penetrated vapor to him. The H ₂ O is introduced in a length of dimension 19 of about 1/5 to about 9/10 the length of a strand section 11 in the measure 12 in the strand. The invention aims to ensure that a strand section in each case about the length of a strand section is brought to its setting temperature of up to about 100 ° C. The fact that the distance between the press side strand end 20 in dimension 21 is about half to about five times the length of a strand section 11 in the measure 12 are the compression of a strand section have occurred in the subsequent strokes of the press ram 3 eliminated and the extrusion line generated with strands their length completely or approximately completely the same density.
The length in the dimension 22 of the closed part 7 of the filling and pressing space or the heating zones is between about simple and six times the length of a strand section 11 in dimension 12th
At the level of the last steam outlet 23 , the strand has reached its setting temperature of up to about 100 ° C. Subsequently, the actual setting process of the binder begins. In order to maintain the Leimruhe and avoid disturbing influences of the traveling saw 24 on the setting strand 1 , the invention provides a Abbindekanal 25 before. The setting zone 26 can be kept shorter in length than previously known. For a press capacity of approx. 60,000 pieces of pallet blocks of 78 mm height per 24 hours, a length of approx. 3 meters in dimension 27 is generally sufficient. For high-performance presses of 120,000 or more blocks per 24 hours, a length of 6 meters in dimension 27 or more is selected. The binding channel 25 regulates via the force generator 28, the strand density. During the strand standstill, the movable angle 29 or the movable part shell is pressed by the force transmitter 28, for example hydraulic cylinder, with a lower force against the strand than during the movement of the strand. The lower force determines the strand density and is either adjusted by a pressure relief valve or the setting is computer determined. The strand density is measured by a measuring device 30 before or after the saw and a computer determines the lower force. Equally advantageously, it is possible to dispense with a high and a low pressure and to work with an adjustable pressure.

Fig. 2. shows a cross section on the line II gem. Fig. 1. The closed part 7 of the filling and pressing chamber 6 is heated in the embodiment by thermal oil circulating through holes 9 in turbulent flow. From the supply line 31 H ₂ O passes in the form of water that evaporates in the holes 32 , or steam through the steam outlet openings 33 in the strand 1. The size of the steam outlet openings may be in the dimension 34 to about 4 mm without clogging by abrasion were determined from the strand 1 . The number of steam outlet openings 33 depends on the cross section of the strand 1 and is chosen so that the most uniform possible penetration takes place with steam.

Fig. 3. shows a cross section on the line II gem. In the exemplary embodiment, the steam is introduced from the bores 32 via the connecting bores 35 through sintered metal elements 35 into the strand 1. The mean hole diameter in the sintered metal elements 35 can be between 5 .mu.m and 100 .mu.m. The material of the sintering elements 35 may be sintered bronze or stainless steel or a wear resistant material. The advantage of these sintered elements 35 is that even in the processing of waste wood, no blockages are to be expected. Next there is a completely uniform distribution of the steam in the strand 1 and it can be observed even with larger cross sections no water seepage. The sintered metal elements 35 may be formed as discs or rectangles or feather keys similar to DIN 6885 or in other advantageous Forman.

Fig. 4. a cross section on the line II-II gem. Figs. 1 and treats the Abbindekanal 25. He may in contrast to prior channel devices are very simple, as it has in the embodiment does not have heating. The strand 1 is tempered in his area only, that is, he must maintain its temperature reached in about to bind quickly. The movable angle 29 and the fixed angle 36 are bent from a stronger sheet. A seal is not required. The heating angle is pivoted about the axis 37 in case of disturbances. As weight compensation, the invention selects train-operated gas springs 38.

Fig. 5. shows a longitudinal section through an extrusion press. The embodiment deals with the extrusion of strands with a hole. The hole 39 is created by the mandrel 40 . The steam flows from the line 41 through the hollow mandrel 40 and penetrates via the steam outlet openings 33 in the strand 1. If the mandrel is heated, for example by a thermal oil or electric resistance heating, the H ₂ O can be introduced as water in mandrel 40 . It is brought by the heater 42 in a vaporous state of aggregation and penetrates as steam from the steam outlet holes in the strand 1 a.
The H ₂ O is introduced in a length of dimension 19 of about 1/5 to about 9/10 the length of a strand section 11 in the measure 12 in the strand. The invention aims to ensure that a strand section in each case about the length of a strand section is brought to its setting temperature of up to about 100 ° C. The fact that the distance between the press-side strand end 20 in dimension 21 is about half to about five times the length of a strand section 11 in the measure 12 will be that when compacting a strand section have occurred in the subsequent strokes of the press ram 3 eliminated and the extruder produces strands with over their length completely or approximately completely the same density.
The press ram 3 is guided by the linear guide 43 and driven by a linear drive, usually a hydraulic cylinder. The mandrel 40 protrudes through the press die 3. It can be isolated against the hot mandrel 40 . The mandrel 40 is, in the exemplary embodiment by a screw thread 44 and nuts 45 longitudinally adjustable to adjust the ideal position of the region of the steam outlet 18 in the closed part 7 of the filling and pressing chamber 6 . In the embodiment, only the front part 46 of the closed part 7 of the filling and pressing chamber 6 is heated. The rear part 47 remains unheated and can be optionally cooled. When the H ₂ O penetrates the strand and condenses, it precipitates as water in the area of the rear part 47 in the outer edge layer 48 of the strand 1 . As a result, the invention produces a particularly smooth and higher-density edge layer when the water evaporates on reaching the front part 46 again .
In the exemplary embodiment, the Abbindekanal 25 is heated and the strand is to be completely or partially withdrawn the condensed water in it.
In this case, the strand is supplied at least a portion of the heat of vaporization of the condensed water. The strand temperature does not increase beyond the ambient evaporation temperature of water. The entire area from the filling and pressing chamber 6 to the revolving saw 24 is sealed in a known manner. The pressure-tight connection from the Abbindekanal 25 to the follower saw 24 is made for example by a telescoping tube or a bellows 49 . The suction of the saw works with a suction 50, which operates at a negative pressure of usually about 08 to 0.9 bar. This vacuum is sufficient to allow the condensed H ₂ O to evaporate. It is in contrast to prior art teaches no vacuum device required. Of course, the invention provides just as advantageous a separate suction 51 in the Abbindekanal 25 with a negative pressure of about 08, to about 0.9 bar before. Likewise, a vacuum device is conceivable and advantageous.

Fig. 6 shows a partial view of a mandrel. In the embodiment, the front surface 52 of the mandrel 40 is closed. It is hollow and on its peripheral surface, the steam outlet openings 33 are introduced as holes. The distance between the holes to each other can be between 10 and 50 mm, their diameter can be up to about 4 mm.

Fig. 7 shows a partial view of a mandrel. In the embodiment, the front surface 52 of the mandrel 40 is closed. It is hollow and on its peripheral surface recess 53 and holes 54 are introduced. DeH ₂ O diffuses through the sintered metal rings 55 into the strand. This embodiment of the invention ensures a particularly uniform heating of the strand and also prevents the processing of waste wood, blockages.

8 shows a view of a dome head 56 made of sintered metal. Unless a wear-resistant material is used, the invention proposes as wear protection, the metal rings 57 , which may be nitrided. The mean hole size of the sintered metal may be about 5μ to about 100μ. The bore 58 is held so short that the H ₂ O does not exit from the front surface 52 but from the peripheral surface 59 .

Claims (27)

Method for extruding small vegetable parts, in particular small pieces of wood, in which the small parts are fed to the filling and pressing space of the extruder, precompressed in compaction with a precompression and compacted by a ram and the strand is transported, characterized in that the strand is in a range at a distance from its press-side end of about half the strand transverse dimension (17) to about five times the amount of strand section produced with each pressing stroke (11) or up to a length of the strand in 1/3 of the setting time of the gelling, in one Length of about 1/5 to about 4/5 of the length of the strand section (11) produced with each press stroke is heated substantially by H ₂ O to a temperature of up to about 100 ° C. A method according to claim 1, characterized in that the H ₂ O from the walls of the closed part (7) of the filling and pressing space (6) is introduced into the strand. A method according to claim 1, characterized in that the H ₂ O from the mandrel (40) is introduced into the strand. Claim according to claim 1, characterized in that the H ₂ O from the walls of the closed part (7) of the filling and pressing chamber (6) and from the mandrel (40) is introduced into the strand. Method according to one of claims 1, 2 or 4, characterized in that the walls of the heating zone (8) are maintained at a temperature of up to 240 ° C. A method according to claim 5, characterized in that in the walls of the heating zone (8) water is introduced, which evaporates in them and penetrates into the strand (1). A method according to claim 5, characterized in that steam is introduced into the walls of the heating zone (8) and from these penetrates into the strand (1). A method according to claim 3, characterized in that the mandrel (40) is heated and water is supplied to it, which evaporates in it and penetrates from steam outlet openings (15) in its peripheral surface in the strand (1). A method according to claim 1, characterized in that the strand is supplied by supplying heat in the heating zone (8) and / or the subsequent setting zone (26) at least a portion of the heat of evaporation of the condensed water, the area from the filling and pressing space (6) is sealed to the saw (24) and by the negative pressure of Sägeabsaugung (50) in the strand (1) condensed H ₂ O completely or partially evaporated and the steam through the hole in the strand (39) is withdrawn, whereby the strand (1) is dried. Method according to one of claims 1 to 8, characterized in that the strand (1) is supplied by supplying heat in the heating zone (8) and / or the subsequent setting zone (26) at least a portion of the heat of evaporation of the condensed water, the range of filling and pressing space (6) is sealed to the saw (24) and in the strand (1) condensed H ₂ O thereby completely or partially evaporated that in the region of the setting zone (26) a separate suction (51) with a negative pressure of about 0 , 8 to about 0.9 bar, whereby the strand (1) is dried. Method according to one of claims 1 to 8, characterized in that the strand (1) is supplied by supplying heat in the heating zone (8) and / or the subsequent setting zone (26) at least a portion of the heat of evaporation of the condensed water, the range of filling and pressing space (6) is sealed to the saw (24) and in the strand (1) condensed H ₂ O thereby completely or partially evaporated that in the region of the setting zone (26) a vacuum device is connected, whereby the strand (1) is dried , Apparatus for carrying out the method according to claim 1, characterized in that in the boundary walls (16) of the closed part (7) of the filling and pressing chamber (6) steam outlet openings (15) are introduced, where H ₂ O penetrates into the strand. Apparatus according to claim 12, characterized in that the measure (14) to the first steam outlet opening (15) in the pressing direction a distance to the press side strand end (20) from approximately half strand transverse dimension (17) to about five times the length of a strand section (11) or up to a length which the strand travels in 1/3 of the setting time of the gelling agent is. Apparatus according to claim 13, characterized in that the region of the steam outlet (18) has a length (19) of about 1/5 to about 9/10 of the length of a strand section (11). Apparatus according to claim 14, characterized in that the mandrel (40) has steam outlet openings (15), wherein the measure (14) to the first steam outlet opening (15) in the pressing direction a distance to the press side strand end (20) of approximately half strand transverse dimension (17). Up to about five times the length of a strand section (11) or up to a length of the strand travels in 1/3 of the setting time of the gelling agent is. Apparatus according to claim 15, characterized in that the mandrel (40) can be moved in the pressing direction. Device according to one of claims 12 to 16, characterized in that the H2O passes through / from sintered metal elements (35) and / or by sintered metal rings (55) in the strand (1). Apparatus according to claim 12, characterized in that the mandrel head (46) is made of sintered metal and the bore (58) is designed only so deep that the H ₂ O does not get into the hole (39) in the strand (1). Apparatus according to claim 12, characterized in that the Abbindekanal (25) is unheated. Apparatus according to claim 12, characterized in that the Abbindekanal (25) is heated. Apparatus according to claim 12, characterized in that the area from the filling and pressing space (6) to the saw (24) is sealed. Device according to claim 12, characterized in that the pressing ram (3) is guided by a linear guide (43) and driven by a linear drive. Device according to claim 15, characterized in that the mandrel is unheated. Apparatus according to claim 15, characterized in that the mandrel is heated and the supplied water is evaporated in it. Apparatus according to claim 12, characterized in that the filling and pressing space (6) in the measure (21) up to the first steam outlet opening with parallel boundary walls (16) or by up to about 1.5% the Strangquermaßes (17) wedge or stepped designed to widen in the pressing direction. Apparatus according to claim 12, characterized in that the closed parts (7) of the filling and pressing space with parallel boundary walls (16) or by up to about ½% of the strand transverse dimension (17) is wedge-shaped or stepwise widening in the pressing direction. Apparatus according to claim 12, characterized in that the filling and pressing space (6) is transversely divided.

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