SK286200B6 - Extruder for vegetal particles mixed with a binding agent - Google Patents

Abstract

Extruder (1) for vegetal particles mixed with a binding agent, in particular for the production of pallet blocks from pieces of wood, in which strand (2) is intermittently pushed by an extruder ram (3) of the extruder (1) through a container (4) and a hardening channel (6). The walls (8) of the hardening channel (6) in a first portion (5) being arranged in such a way that they can yield and thereby reduce friction as the extruder ram (3) advances. For the extrusion of particles of relatively high moisture, for example 8% to 14% absolutely dry, a radial pressing station with intermittently controllable lifting drives (11) for the movable walls (8) is provided in this first portion (5) or in a following portion (5 ) for the purpose of calibrating the strand.

Description

Technical field

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plant extruder mixed with a binder, in particular for producing pallet blocks of wood particles, wherein the extrudate is moved through the plunger of the extruder in the bar and curing channel. as biased and thus reducing friction.

BACKGROUND OF THE INVENTION

These are known from A 32 15 693, in which it is disclosed to support at least one wall of a curing channel which is capable of deflection against the roasting effect in order to prevent jamming of the pressed particles. However, the known embodiment does not have an overpressure calibration container and does not include the theory of how wet chips can be extruded without the risk of jamming.

WO 99/48659 describes a typical construction of a conventional extruder, according to which a fixed part of the curing channel, which is referred to in the technical terminology as a preheating passage, is first fed to the pressing space. This fixed part should make it difficult or prevent the axial deflection of the still unheated overpressure during the return stroke of the extruder piston. In principle, however, the overpressure is calibrated in this fixed part.

As far as the extrusion of wood particles is concerned, in practice, dried wood material from 2% to 3% and at least the residual moisture has been used in practice. In order to achieve this state of drying, substantial investments are needed in the basic means, which, for reasons of economy, assume that a correspondingly large consumption of dried chip material for extrusion is available.

However, the residual moisture is raised considerably by the addition of a water-containing adhesive, resulting in a final product with about 7% to 9% moisture.

If wood particles are to be made of pallet blocks, this low wood moisture is not required. In conjunction with pallets, the wood has a moisture content of about 18% after production, while naturally the pallet stack, which has less moisture, retains water. In later use of pallets, moisture contents are set between 14% and 30% depending on the conditions under which the pallets are stored.

Therefore, it is questionable to press the pallet blocks with very low wood moisture, which is actually not necessary at all, since the moisture content is significantly higher in the pallet assembly and later use.

Thus, it would offer the possibility of pressing wood particles of higher humidity to produce pallet blocks, which, however, could not be successfully accomplished with known devices.

In fact, the higher humidity chips cause a rapid increase in the feed resistance in the extrusion press, which leads to a failure of the press during low strokes of the extruder piston. The blasting material exhibits different elastoplastic behavior with higher humidity. While the dry chip is practically incapable of flow (the so-called non-rising mixture) and thus only transfers a slight fraction of the pressure of the main piston to the channel wall, the material reacts increasingly plastic with increasing humidity. With the same feed resistance, the material is compacted more and the pressure on the side walls of the container increases. This means that a greater stroke force is needed in the next stroke to overcome the higher friction against the walls and this overpressure is compacted more than the previous, which again increases the wall pressure and friction. This process is intensified and leads to jamming of the press during few strokes.

It is known from DE-A-25 35 989 and from DE-A-32 05 866 to support the walls of the hardening channel on the motors of the lifting mechanism. In the case of DE-A-25 35 989, this is carried out in order to vary the friction force acting on the extrusion without changing the path of the hardening wall. In the case of DE A 32 05 866, the motors of the lifting mechanism cause a change in the path of the movable walls of the curing channel so that different product dimensions can be made on the same device.

In either of these cases, the overprint to calibrate does not compress a radially varying shape.

However, this does not take into account the extrusion of wood particles with higher humidity, nor is it possible to calibrate the extrusion properly.

SUMMARY OF THE INVENTION

The object of the present invention is therefore to provide an extruder with which plant particles, in particular wood waste, can be extruded with higher moisture contents, so that investment in expensive chip-drying equipment becomes unnecessary. The aim is to process wood material in the range of 8% to 14% wood moisture. This wood moisture is common in the production of glued wood products and wood waste from gluing plants is available in sufficient quantities.

SUMMARY OF THE INVENTION The present invention is directed to a plant extruder mixed with a binder, in particular to produce pallet blocks of wood particles, in which the extruder moves the plunger in the bar and the curing channel, the walls of the curing channel in the first section being displaceably extruder and thus reduce friction. According to the invention, a radial pressing station with stroke-actuable stroke-actuating stroke drives is provided for the extrusion of particles with a humidity in the range of 8% to 14% atro in this first section or in the following section for calibrating the overpressure.

By this embodiment according to the invention, blocking of the overpressure is avoided and calibration of the overpressure is achieved.

In contrast to the state of the art, an embodiment of the invention simultaneously achieves the compression of wood particles of higher humidity without the risk of blocking the extruder as well as proper calibration of the extrusion.

A preferred embodiment of the invention consists in that the pressing pressure of the walls (8 ') in the radial pressing station is measured to achieve the final dimension of the extrusion.

A further advantageous embodiment of the invention consists in that a work station is provided for supplying saturated steam to the surface of the extruded outer sheath of the extruded extrusion, in which a sealing means, in particular press jaws, is arranged to prevent leakage along the extruded surface.

Yet another preferred embodiment of the invention is that the saturated steam feed station is integrated into the radial press station.

Yet another preferred embodiment of the invention is that the saturated steam feed station is arranged in the region of the heating passages of the curing channel.

In other words, the movable side walls of the radial press station are suspended on hydraulic cylinders which can again be connected to the pressure reservoir. In the inlet stroke, the pressure is reduced to a certain level and maintained by the pressure reservoirs. In this way, the walls of the radial pressing station rest with constant force on the extrudate produced. The higher pressure on the wall of the product is reduced to a predetermined level by deflecting the wall. The pressure reservoir acts as a pneumatic spring and the return force remains approximately the same. When the main piston is lifted back, the overpressure is in a quiet state. Now, the container is retracted and the hydraulic pressure is increased to such an extent that the portion of the extrusion located in the radial pressing station is pressed to a preset dimension that is smaller than said dimension. Before the next stroke, the pressure level decreases again and the tank is connected.

It now cushions the material overprint to the specified size. In this way, the elastic tendency of the extrusion material is absorbed. The pressing force of the side walls can be measured such that the elastic cushioning of the extrudate material leads to the desired friction and there is no dimensional change in the following movable heating corridors.

In another aspect of the invention, there is provided a station for supplying saturated steam to the outer surface of the molded extrusion housing in which a sealing means, in particular a pressing jaw, is arranged to prevent steam escape along the surface of the extrusion. Such a workstation was proposed by earlier PCT / EPOO / 06872. However, its use is not intended for pressing chips of higher humidity. By the present invention, on the other hand, the introduction of saturated steam onto an overpressure, which is also preferably carried out in such a process, causes intense overheating of the overpressure, with the result that the binder solidification takes place by impact and curing of the overpressure proceeds faster than hitherto.

In one variation of the invention, it is provided that the saturated steam feed station is integrated into a radial press station. In both stations, for the same reason, the same functional elements are present which exert a pressure radially from the outside of a still untreated or only an over-cured extrusion and thus cause slight formation. It is therefore expedient to use the device necessary for controlling the friction ratios according to the invention also for supplying steam. Said radial press station is a suitable heat transfer medium, however, the heat and the surface pressure required to produce the final outer contour is sufficient to ensure that the press jaws are sealed against leakage of process steam.

The extruder constructed in this way is particularly short and requires only a shortened length of the heating passage that keeps the material clamped until the adhesive reaction is so complete that the inherent stresses of the material of the pressurized product no longer result in a combined radial press / steam supply line. shape changes. It is common to all the described embodiments that, in the area of energy supply and temperature increase, the side walls either ventilate in such areas or have sufficient interspaces to prevent the said vapor pressure from forming in the structure. In conjunction with a heating corridor, which is shortened compared to conventional extruders, the friction ratios of the walls are exactly controllable.

Alternatively, however, the saturated steam feed station may also be provided in the region of the heating passage of the curing channel, in which the temperature increase in the peripheral region of the extrusion is carried out in a conventional manner.

BRIEF DESCRIPTION OF THE DRAWINGS

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail with reference to the drawings, in which: FIG. 1 is a vertical cross-sectional view of an extruder with flexible walls of a first section of a curing channel downstream of the container and a subsequent radial press station; FIG. 2 shows a vertical section through the variant according to FIG. 1 with a radial pressing station integrated in the first section, FIG. 3 is a vertical sectional view of the extruder of FIG. 2 with an additional saturated steam feed station; and FIG. 4 shows a vertical section through the extruder of FIG. 2 with an integrated workstation for feeding saturated steam in a radial press station.

DETAILED DESCRIPTION OF THE INVENTION

In the example of FIG. 1 schematically shows an extruder 1 in which the piston 3 of the extruder 1 is movable in a horizontal direction back and forth. This piston 3 of the extruder 1 forms an extrusion 2 which is compressed by the container 4 and the curing channel 6. The container 4 consists of rigid walls with an opening angle 7 extending in the direction of extrusion. This opening angle 7 can be greater than in conventional devices when it comes to pressing the extrudates 2 from plant particles, in particular wood, with high humidity.

The first section 5 of the curing channel 6 is arranged in connection with the container 4, which generally consists of rigid walls in conventional extrusion presses 1 and is referred to as a preheating passage. If plant particles of higher humidity are pressed, such a solid preheating corridor would lead to blocking of the extruder

Therefore, the invention proposes to make the walls 8 of this first section 5 of the hardening channel 6 capable of buckling, i. j. deflectable, which can be carried out, for example, by elastically supported deflectable walls 8.

In connection with the first section 5 with its deflecting walls 8 there is a radial pressing station 5 ', the walls of which by means of stroke drives 11, e.g. of the lift motors press against the overpressure 2 during the return stroke of the piston 3 of the extruder 1 in order to calibrate the overpressure 2. In the embodiment of FIG. 2, the radial press station 5 'is integrated in the first section 5 of the curing channel 6. In an exemplary embodiment, the lateral deflecting walls 8' of the radial press station 5 'according to the invention are suspended by hydraulic cylinders which can be connected to the pressure reservoir 9 again. the pressure is lowered to a certain level and maintained by the pressure reservoirs 9. Thus, the deflecting walls 8 ' of the radial pressing station engage with a constant force on the produced overpressure 2.

In this case, a radial pressing station 5 'with deflecting walls 8' is formed which replaces the preheating corridor available with known devices.

This yaw, respectively. the deflection movement of the deflection walls 8 'does not yet cause a clear contour of the outer surfaces of the extrusion 2. For this reason, the deflection walls 8' can be pushed by the lift drives 11 onto the extrusion 2 during the return stroke of the extruder piston 1. the stations 5 'thus exert pressure on the area of the overpressure 2 which is located between the deflecting walls 8'. This pressure adjustment of the lateral deflecting walls 8 'takes place in such a way during the return stroke of the piston 3 of the extruder 1. In this way, the outer contour of the extruder 1 is precisely determined.

In connection with the radial press station 5 ', a curing channel 6, which is conventionally equipped with heating pipes 15, extends to cause the extrusion 2 to cure and dry. The formation of such a curing channel 6 is known and therefore does not need to be illustrated in detail.

In the example of FIG. 3 shows how the blank 2 can overheat by feeding saturated steam and can therefore solidify more quickly. Starting from the embodiment of FIG. 2, a work station 10 for supplying saturated steam is provided in connection with a plurality of heating passages of the curing channel 6 by means of steam supply bores 14. In order to prevent saturated steam from escaping along the surface of the overpressure 2, the work station 10 has pressing jaws 13 which are pressed against the overpressure 2 by means of stroke drives 11.

A braking and cooling area 16 is provided in connection with the steam supply work station 10 to prevent uncontrolled expansion of the still uncured extrudate 2.

However, as shown in FIG. 4, combine the functions of the radial press station 5 'and the steam supply work station 10. This embodiment complements the radial pressing station 5 'with steam dispensing and supply units. The pressing of the pressing jaws 13 leads to a contractive forming of the extrusion 2 in order to thereby produce the final outer dimensions of the extrusion 2. It is essential that this formation is used to prevent the supplied steam from escaping along the extrusion 2.

Claims (5)

1. An extruder for plant particles mixed with a binder, in particular for producing pallet blocks of wood particles, wherein the extrusion (2) of the extruder piston (3) is moved in such containers (4) and the curing channel (6), the walls ( 8) the curing channel (6) in the first section (5) are arranged during the displacement of the piston (3) of the extruder (1) as deflectable and reducing friction, characterized in that for extrusion of particles with a humidity ranging from 8% to 14 The% atro is provided in this first section (5) or in the following section for calibrating the overpressure (2) with a radial pressing station (5 ') with stroke actuators (11) controllable in such deflection walls (8'). Extrusion die according to claim 1, characterized in that the pressing pressure of the deflection walls (8 ') in the radial pressing station (5') is measured to achieve the final dimension of the extrusion (2). The extruder according to claim 1 or 2, characterized in that a work station (10) is provided for supplying saturated steam to the outer shell surface of the extruded press (2), in which sealing means, in particular press jaws (13) are arranged, to prevent steam escape along the surface of the extrusion (2). The extruder according to claim 3, characterized in that the saturated steam feed station (10) is integrated into the radial press station (5 '). The extruder according to claim 3, characterized in that the saturated steam supply station (10) is arranged in the region of the heating passages of the curing channel (6).