EP3310566B1 - Screw press device - Google Patents

Description

The invention relates to a screw press device with a first screw press which has a first screw housing, a first screw press rotatably mounted in the first screw housing, a first inlet and a first outlet, at least one second screw press which has a second screw housing, a second screw press which is rotatably mounted in the second screw housing Press screw having a second inlet coupled to the first outlet and a second outlet, and a drive device for driving the first and second press screws.

A screw press device of this type serves to strongly compress pressable and porous material, also referred to as pressed material, that is introduced via the inlet, with the result that liquid present in the material, also referred to as filtrate, is pressed out. In order to expel the liquid from the material, a steadily increasing pressure is required on the affected material. In a continuously working screw press, this process takes place with the help of the press screw due to the pitch of the screw. Since the press screw is usually surrounded by a strainer, which is also known as a so-called strainer basket, the pressed liquid can only flow in one direction towards the colander, i.e. from the inside to the outside. Usually, the extruder screws have a relatively high screw pitch at the inlet to accommodate the material to be extruded. The pitch of the screw generally decreases towards the outlet. As a result, the volume in the screw thread gap or in the conveying threads, which likewise extend in a spiral shape between the spiral-shaped screw webs or spirals, decreases and the compression pressure increases. The material or volume flow is determined by the speed and the screw pitch of the press screw and is also dependent on various influences. The working method of the screw press has the advantage that the material or pressing material is not overheated, so that thermally induced impairments of the material or pressing material cannot occur. The use of two press screws connected in series according to the type mentioned as a two-stage solution offers a better possibility of automation, leads to a more effective degreasing of the product and has a higher throughput while at the same time saving energy and reducing wear.

A screw press device of the type mentioned is generally used in technology. A preferred application is the production of meat meal, where it is important not only to achieve a high degree of comminution, but also a high degree of drying. Another use is the processing of oil-containing plant biomass, in which case the desired starting product is formed at least primarily from the oil pressed out of the biomass.

Such a device is, for example, from DE 196 01 128 A1 is known, which describes a screw press for extracting vegetable oil from oil-containing material, which has at least two identically shaped sub-screw conveyors in terms of the shape of the screw winding to increase the squeezing capacity, which are connected in series with the interposition of an intermediate throttle point on one axis. The two partial screw conveyors are thus seated together on a drive shaft which is set in rotation by a drive device.

The DE 298 20 464 U1 discloses a screw press device for dry or liquid-containing material to be pressed with a single press screw which is rotatably mounted in a screw housing having an inlet and an outlet. Furthermore, pressure means are provided for generating a counter-pressure on the material to be pressed, which resiliently prestress a closure member against the outlet in such a way that it releases a certain outlet cross-section of the outlet depending on the pressure difference between the material to be pressed and the counter-pressure. The pressure means are designed in such a way that the counter-pressure on the material to be pressed can be adjusted.

The DE 20 2007 008 072 U1 discloses a screw press made from individual screw elements of a screw press with a screw housing, an inlet and an outlet, the screw elements being hollow and firmly connected to one another and being driven by an internally arranged drive shaft. Furthermore, a compensator element is arranged on the outlet-side end of the press screw behind the last screw element and in front of fastening parts of the screw elements on the screw shaft and is designed to be resilient.

The DE 299 01 683 U1 describes a screw press for biowaste with a motor-driven screw press, which is enclosed by a tube over a first part of its length and by a sieve over a second part of its length, with a liquid outlet and with a solids outlet, with the press screw being open in the core area tube fixed in the direction of rotation is inserted.

U.S. 2015/076084 A1 discloses a screw press device according to the preamble of claim 1.

As long as the material has sufficient porosity or capillarity, liquid can be squeezed out. However, if the material flow experiences either an increase in speed (overflow) or a decrease in speed (underflow) due to unfavorable circumstances, the liquid discharge is disrupted. In the first case of overflow, the surface of the material is compressed to such an extent that the escape of liquid is severely impeded or even stopped; the friction that occurs and the resulting heat can damage the quality of the material to be pressed or even its Inflammation and thereby also increased wear of components of the screw press device are caused. In the second case of underflow, the liquid drain also dries up because there is now insufficient compression pressure to squeeze out the liquid.

It is an object of the present invention to increase the efficiency of a screw press device of the type mentioned at the outset.

These and possibly other tasks are solved with a screw press device with the features of claim 1.

Accordingly, the first and second press screws can be driven at different speeds, with a special control concept according to the invention, for which purpose a correspondingly suitable speed control device is to be provided. The special control concept according to the invention consists in, for the first case when the pressure in the material or material to be pressed within the first screw housing, essentially adjacent to the first outlet, exceeds a predetermined first threshold value set the second press screw to a speed that is above a first speed value, and for the second case, when the pressure in the material or pressing material within the first press screw housing falls below a predetermined second threshold value, essentially adjacent to the first outlet, the second press screw to a speed set, which is below a second speed value. The invention makes use of the finding that as the speed of the press screw increases, there is less compression of the material or material to be pressed and thus also a lower degree of fragmentation, and with a decreasing speed of the press screw there is greater compression of the material or material to be pressed and thus also a higher degree of fragmentation is achieved. In the first case, this avoids the material or material to be pressed being subjected to compression that is too high for the conditions there, long before the second outlet forming the outlet of the entire screw press device, with the result of increased friction and thus heating and the resulting risk of damage to the quality of the pressing material as well as increased wear of components of the device and clogging of the entire device, and in the second case it is ensured that the material or pressing material does not remain too viscous, but rather has a desired sufficient compression in the course of its path through the screw press device is subjected. The control concept according to the invention therefore ensures that at the second outlet, which also forms the outlet of the entire screw press device, the material or pressed material always exits with a desired compression that is as high as possible, with the result that as much liquid as possible is removed from the material or pressed material could be squeezed out. Accordingly, the solution according to the invention leads to a significant increase in the efficiency of the screw press device without the risk of an increase in wear.

Preferred embodiments and developments of the invention are specified in the dependent claims.

The first threshold should expediently be equal to the second threshold. Likewise, the first speed value should expediently be equal to the second speed value, with the first speed value and the second speed value is equal to the value of the speed of the first press screw.

Thus, in this embodiment, the control concept according to the invention consists in setting the speed of the second press screw to a value greater than the speed of the first press screw for the first case that the pressure in the material within the first press screw housing essentially adjacent to the first outlet exceeds a predetermined threshold value to be raised so that the second press screw runs faster than the first press screw, and in the second case that the pressure in the material within the first press screw housing falls below the predetermined threshold value essentially adjacent to the first outlet, to a value below the speed of the first press screw, so that the second press screw then runs slower than the first press screw.

The screw press device according to the invention is characterized in that the speed control device has a sensor that measures a physical variable that is required by the drive device for driving the first press screw, the speed control device using the physical variable measured by the sensor as a measured variable for the pressure of the material within the first auger housing adjacent to the first outlet and setting the second auger to a speed greater than the speed of the first auger in the event that the physical quantity measured by the sensor exceeds a predetermined first threshold, and in the event that the physical variable measured by the sensor falls below a predetermined second threshold value, is below the speed of the first press screw, the physical variable preferably being a power output or an electrical current.

Preferably, one squeezing screw is driven by a hollow shaft, through which a shaft driving the other squeezing screw extends. Such a measure allows a one-sided arrangement of the drive device, which is provided for the rotary drive of the shafts, so that this embodiment offers spatial advantages. In a further development of this embodiment, the two squeezing screws and the two shafts are arranged coaxially with one another and one squeezing screw sits concentrically on the hollow shaft and the other press screw concentrically on an exposed section of the shaft which is partially surrounded by the hollow shaft. In a further advantageous development of this embodiment, the first squeezing screw is driven by the hollow shaft and the second squeezing screw is driven by the shaft, which is partially surrounded by the hollow shaft. In a further preferred development, the drive device is arranged at that point of the device at which the shaft and the hollow shaft surrounding the shaft are located, each with an end section, and/or adjacent to the first inlet.

The drive device preferably has two drive motors, of which one drive motor is designed to drive one squeezing screw and the other drive motor is designed to drive the other squeezing screw. In the previously mentioned embodiment with a hollow shaft and an internal shaft, one drive motor is preferably designed to drive the internal shaft essentially directly, and the other drive motor is designed to essentially drive the hollow shaft.

Alternatively, it is also conceivable, for example, for the drive device to have a drive motor and a gear, in particular a planetary gear, the transmission ratio of which can be changed, the drive motor being designed to drive one press screw essentially directly, and the gear being coupled to the drive motor and is designed to drive the other press screw essentially directly, and the speed control device is designed to control the transmission by changing its transmission ratio.

It is also advantageous to design a drive motor of the drive device in such a way that it essentially drives the internal shaft directly, and to design the transmission in such a way that it essentially drives the hollow shaft directly.

The first squeezing screw housing and the second squeezing screw housing should expediently form a common housing.

In a further preferred embodiment, an expander or extruder is arranged between the first outlet and the second inlet, which expander or extruder has a housing, an extruder screw rotatably mounted in the housing, an inlet coupled to the first outlet and an outlet coupled to the second inlet. Such an extruder causes a slight relaxation of the material or pressed material compressed at the first outlet. The two press screws and the extruder screw are expediently arranged coaxially to one another. Preferably, the barrel of the extruder connects the first press screw barrel to the second press screw barrel. The extruder screw is preferably coupled in a torque-proof manner to the first press screw. Furthermore, the screw pitch of the extruder screw is preferably constant over its length. Finally, the screw pitch of the extruder screw can preferably be smaller than the screw pitch of the extruder screw, which is advantageous for the desired relaxation effect.

In a further preferred embodiment, for at least one of the screw presses, the associated squeezing screw housing forms a cavity that is essentially cylindrical over the entire length of the squeezing screw and the squeezing screw has a steadily monotonically or continuously increasing core diameter and a steadily monotonously or continuously decreasing screw pitch. It is therefore essential in this embodiment that the core diameter increases without any interruption in the working direction and the pitch of the press screw decreases in a corresponding manner without any discontinuity. This solution allows an even higher proportion of liquid to be pressed out of solid material components while at the same time reducing the energy required for the extraction process for the drive device, as a result of which the output of the respective screw press can be increased even further.

Fig. 1

im Wesentlichen im Längsschnitt eine Schneckenpressvorrichtung gemäß einem bevorzugten Ausführungsbeispiel der Erfindung;

Fig. 2

eine ausschnittsweise vergrößerteEinzelheit, die in Fig. 1 durch einen mit "A" gekennzeichneten Kreis markiert ist, im Längsschnitt (Figur 2a) und in perspektivischer Seitenansicht (Figur 2b); und

Fig. 3

eine Anordnung aus zwei Pressschnecken mit dazwischenliegender Extruderschnecke in perspektivischer seitlicher Ansicht (a) sowie im Längsschnitt (b).

A preferred exemplary embodiment of the invention is explained in more detail below with reference to the accompanying drawings. Show it:

1

substantially in longitudinal section a screw press device according to a preferred embodiment of the invention;

2

a partially enlarged detail, which is shown in 1 is marked by a circle marked "A", in longitudinal section ( Figure 2a ) and in perspective side view ( Figure 2b ); and

3

an arrangement of two press screws with an intermediate extruder screw in a perspective side view (a) and in longitudinal section (b).

In the 1 The screw press device shown as a whole comprises a housing 2, within which a first screw press 4 and a second screw press 6 provided downstream of the first screw press 4 are arranged. Due to the use of two screw presses 4, 6 connected in series, the screw press device according to the exemplary embodiment described is a two-stage screw press device. Such a two-stage solution offers a good possibility for automation and leads to a more effective degreasing of the product to be pressed and to a better utilization of the throughput while at the same time saving energy and reducing wear.

The first screw press 4 has a first screw press housing 8, a first press screw 10 rotatably mounted in the first press screw housing 8 with spiral helices or screw webs 10a and conveying passages also extending spirally in between, a first inlet 12 designed as an inlet shaft in the illustrated embodiment, and a first outlet 14 on. The first squeezing screw housing 8 is provided with openings 8a and is usually designed or referred to as a strainer basket.

The second screw press 6 has a second screw press housing 16, a second press screw 18 rotatably mounted in the second press screw housing 16 with spiral helices or screw webs 18a and itself conveyor passages also extending in a spiral shape in between, a second inlet 20 and a second outlet 22 . Like the first squeezing screw housing 8, the second squeezing screw housing 16 is also perforated or provided with openings 16a and is usually also designed or referred to as a strainer basket. The press screw housings 8, 16 designed as strainer baskets are usually composed of two half-shells or several shell-shaped sections; This is advantageous, on the one hand, in order to allow easy access to the press screw, for example for maintenance purposes, and, on the other hand, as a simple way of adjusting the permeability of the press screw housing, which is designed as a strainer basket, by replacing the press screw housing with a press screw housing with a different degree of perforation or a different number of To create openings and / or openings with a different diameter.

As the figures 1 and 2 can also be seen, in the illustrated embodiment, an expander 24, also referred to as an extruder, is provided between the two screw presses 4, 6, which has an expander housing 26, an expander screw 28 rotatably mounted in the housing with spiral coils or screw webs 28a and also spirally extending in between Conveyor passages 28b, an inlet 30 coupled to the first outlet 14 and an outlet 32 coupled to the second inlet 20. In contrast to the two press screw housings 8, 16, the wall of the expander housing 26 has no perforations or openings, but is closed. How in particular 2 can be seen, through the wall of the expander housing 26 pins 26a, which are designed as threaded bolts in the illustrated embodiment, are inserted through the wall of the expander housing 26 and protrude far into the conveyor passages 28b, which are delimited by the spiral-shaped screw webs 28a and also extend spirally. Therefore, the extruder or expander used in the illustrated embodiment is also referred to as a pin extruder or expander. So that the spiral-shaped screw flights 28a do not collide with the pins 26a, the screw flights 28a are provided with interruptions at the appropriate points, which allow the pins 26a to pass through and in Figure 2b not marked, but clearly recognizable. By designing the pin extruder 24 with the pins 26a, which are arranged in pin levels, such as Figures 2a and b can be seen, and pass through the interruptions in the screw webs 28a, there is a particularly good conveying effect. The splitting of the extrudate stream at each interruption in the screw flights 28a into a part that passes through the interruptions in the screw flights 28a in a substantially axial direction and a part that enters the spiral-shaped conveyor passages 28b following in the flow direction creates a achieves a particularly good mixing effect.

How 2 also in connection with 1 can be seen, the first press screw housing 8 and the second press screw housing 16 and the intermediate expander housing 26 form a common housing and thus enclose a common continuous space in which the two press screws 10, 18 and the intermediate expander screw 28 are arranged. The two squeezing screw housings 8, 16 and the expander housing 26 each have a cylindrical shape, with the two squeezing screw housings 8, 16 having essentially the same outer diameter and also essentially the same inner diameter in the illustrated embodiment, while the outer diameter of the expander housing 26 is smaller, but its Inner diameter approximately the inner diameter of the press screw housing 8, 16 corresponds. In contrast, the inside diameter of the expander screw 28, i.e. the diameter of its cylindrical base body without taking into account the radial extent of the screw webs 28a, at the inlet 30 of the expander housing 26 is smaller than the inside diameter of the first press screw 10 at the first outlet 14 and larger than the inside diameter of the second Press screw 18 at the second inlet 20, wherein the inside diameter of the expander screw 28 remains constant over its entire length.

How in particular 3 combined with 1 can be seen, the second squeezing screw 18 sits on an exposed portion of an inner shaft 34, which is otherwise surrounded by an outer hollow shaft 36, on which the first squeezing screw 10 and the expander screw 26 sit. The inner shaft 34 and the outer hollow shaft 36 are rotatably mounted coaxially to one another about a common axis of rotation R, but can of course be driven independently of one another. Since the first press worm 10 and the expander worm 26 are mounted on the hollow shaft 36 and are thus connected to it in a rotationally fixed manner, they are set in rotation by the latter together at the same speed. In contrast, the inner shaft 34 ensures that, independently of the outer hollow shaft 36 and thus the first press screw 10 and the expander screw 26, the second press screw 18 is set in rotation, since it is mounted on the inner shaft 34 and is non-rotatably connected to it.

In order to rotate the two shafts 34, 36, two drive motors 38, 40 are provided. In the exemplary embodiment described, an electric motor is used as the drive motor. How 1 can be seen, in the illustrated embodiment, the two drive motors 38, 40 form a common structural unit, which is arranged adjacent to the first inlet 12 at the upstream end of the housing 2. How 1 combined with 3 can also be seen, the outer hollow shaft 36 is driven by the first drive motor 38 and the inner shaft 34 by the second drive motor 40. Alternatively, it is also conceivable, instead of the second drive motor, to use a gear which is coupled to the first drive motor 38 and is preferably designed as a planetary gear. The two shafts 34, 36 are one in Figure 3a indicated axis of rotation R rotatably mounted in bearings, which are not marked in detail in the drawings; in principle, the drive motors 38, 40 can also serve as one of these bearings.

How 1 Furthermore, as can be seen, the assembly consisting of the two screw presses 4, 6 and the expander 24 is arranged inside the housing 2 on supports 42, which in turn are seated on a horizontal support element 44. A compartment 46 is formed within the housing 2 below the assembly mentioned above, in which a filtrate emptying screw 48 is rotatably mounted above the bottom 2a of the housing 2, the pitch of its spiral helices or screw webs being in the opposite direction towards the centre, where the housing 2 with a filtrate outlet 50 is provided. How 1 further recognize leaves, a second compartment 52 is formed in the downstream end of the housing 2, in the lower portion of which a paddle wheel 54 is rotatably mounted, which is also referred to as a so-called. Reed crusher.

The screw press device described serves to strongly compress pressable and porous material, also referred to as pressed material, which is entered via the first inlet 12, with the result that liquid present in the material, also referred to as filtrate, is pressed out and the material in a dry , compressed state from the second outlet 22 is discharged. Thus, the first inlet 12 of the first screw press 4 also forms the inlet for the entire screw press device and the second outlet 22 of the second screw press 6 forms the outlet for the entire screw press device for dispensing the then compressed material or material to be pressed. In order to expel the liquid from the material, a steadily increasing pressure is required on the affected material. For this purpose, the two screw presses 4, 6 connected in series are provided in the illustrated embodiment, in which this process takes place with the aid of the continuously operating press screws 10, 18 due to the screw pitch. Since the squeezing screws 10, 18 are surrounded by the respective squeezing screw housing 8, 16, which is provided with openings or perforations or is designed as a strainer or sieve body, the liquid that is pressed out can only flow in one direction towards the squeezing screw housings 8, 16, i.e. from inside out, flow. As the figures 1 and 3 reveal that the first press screw 8 at the first inlet 12 of the first screw press 4 and the second press screw 18 at the second inlet 20 of the second screw press 6 and thus at its upstream beginning each have a relatively high screw pitch. In contrast, the screw pitch of the first press screw 10 decreases towards the first outlet 14 of the first screw press 4 and the screw pitch of the second press screw 18 towards the second outlet 22 of the second screw press 6 . As a result, the volume in the screw flight gap decreases and the compression pressure increases.

While the first screw press 4 takes over the primary pressing process, the downstream second screw press 6 carries out post-processing instead of. The expander 24 connected between the two screw presses 4, 6 causes the material exiting at the first outlet 14 to relax, as a result of which the material to be pressed is broken up and thus remains porous. Accordingly, the expander 24 acts as a kind of buffer. For this purpose, the cavity delimited by the inner wall of the first press screw housing 8 increases at the transition from the first outlet 14 to the inlet 30 of the expander 24, which already leads to a first relaxation of the material to be pressed when it enters the expander 24. How in particular 3 can be seen, the screw pitch of the expander screw 28, which is non-rotatably coupled to the first press screw 10, is constant over its length and is less than the screw pitch of the two press screws 10, 18.

How 3 can also be seen, in the illustrated embodiment, the two press screws 10, 18 are designed essentially the same in terms of their dimensions and their screw pitch. Furthermore, you can 3 see that in the illustrated embodiment, both press screws 10, 18 have a steadily monotonically or continuously increasing core diameter of their cylindrical body and a steadily monotonously or continuously decreasing screw pitch, while according to figure 1 the two squeezing screw housings 8, 16 define a cylindrical cavity extending over the entire length of the associated squeezing screw 10 or 18, respectively. Thus, in the illustrated embodiment, the core diameter of the cylindrical base body of the press screws 10, 18 increases without any interruption in the working direction, which is defined from left to right in the figures, and the pitch of the press screws 10, 16 decreases in a corresponding manner without any discontinuity. whereby the width, defined in the axial direction, of the conveying passages, which also extend spirally between the spiral-shaped screw webs 10a and 18a, respectively, decreases accordingly.

The expelled from the material and through the openings 8a, 16a of the press screw housing 8, 16 emerging liquid passes through the first compartment 46 due to gravity down and collects on or above the bottom 2a, where it then by the action of Filtrate discharge screw 48 is driven to the filtrate outlet 50. The finally compressed material, on the other hand, exits the second outlet 22 of the second screw press 6 and enters the second compartment 52, where it falls down due to the influence of gravity and is conveyed with the help of the impeller 54 through an outlet not shown in the drawings also referred to as the so-called reed exit.

The material or volumetric flow is determined by the speed and the screw pitch of the press screws 10, 18 and is also dependent on other different influences. As long as the material has sufficient porosity or capillarity, liquid can be squeezed out. However, if the material flow experiences either an increase in speed (overflow) or a decrease in speed (underflow) due to unfavorable circumstances, the liquid discharge is disrupted. In the first case of overflow, the surface of the material is compressed to such an extent that the escape of liquid is severely impeded or even stopped; the friction that occurs and the resulting heat can damage the quality of the material to be pressed or even cause it to ignite, and this can result in increased wear of the components of the screw press device. In the second case of underflow, the liquid drain also dries up because there is now insufficient compression pressure to squeeze out the liquid.

In order to avoid these disadvantageous effects, the two press screws 10, 18 can be driven selectively at different speeds by the drive motors 38, 40 and a speed control device 60 is also provided to which the drive motors 38, 40 are connected. If a gearbox is used instead of the second drive motor 40, this must be designed in such a way that its transmission ratio can be changed, namely by the speed control device 60. Furthermore, the speed control device 60 is designed in such a way that, via a sensor 62, it receives the data from the first drive motor 38 measures the power consumption required for driving the first press screw 10 or a correspondingly required electrical current. The measured variable obtained in this way is then used by the speed control device 60 to determine the pressure of the material within the first press screw housing 8 adjacent to the first outlet 14 evaluated accordingly. The control concept of the speed control device 60 now consists of controlling the drive motors 38, 40 or at least the second drive motor 40 in such a way that the speed of the second press screw 18 for the first case when the pressure in the material within the first press screw housing 8 adjacent to the first outlet 14 exceeds a predetermined threshold value, is increased to a value greater than the rotational speed of the first press screw 10, so that the second press screw 18 runs faster than the first press screw 10, and for the second case when the pressure in the material inside the first press screw housing 8 is substantially falls below the predetermined threshold value adjacent to the first outlet 14, is lowered to a value below the rotational speed of the first press screw 10, so that the second press screw 18 then runs more slowly than the first press screw 10.

Claims (16)

1. Screw press device having

   a first screw press (4), which has a first press screw housing (8), a first press screw (10) that is rotatably mounted in the first press screw housing (8), a first inlet (12) and a first outlet (14), at least one second screw press (6), which has a second press screw housing (16), a second press screw (18) that is rotatably mounted in the second press screw housing (16), a second inlet (20) that is coupled to the first outlet (12) and a second outlet (22),

   and a drive device (38, 40) for the rotational drive of the first and second press screws (10, 18), which is designed to drive the first and second press screws (10, 18), optionally at different rotational speeds, characterised in that the screw press device has a rotational speed control device (60),

   which has a sensor (62),

   which measures a physical quantity that is required by the drive device (38, 40) for driving the first press screw (10),

   wherein the physical quantity is a power or an electrical current, and

   the rotational speed control device (60) uses the physical quantity measured by the sensor (62) as a measure of the pressure of the material inside the first press screw housing (8) adjacent to the first outlet (14) and sets the second press screw (18) to a rotational speed at which, in the case that the physical quantity measured by the sensor (62) exceeds a predetermined threshold value above the rotational speed of the first press screw (10), and in the case that the physical quantity measured by the sensor (62) falls below the predetermined threshold value below the rotational speed of the first press screw (10), the second press screw (18) then runs slower than the first press screw (10).
2. Device according to claim 1, wherein the one press screw (10) is driven by a hollow shaft (36), through which a shaft (34) driving the other press screw (18) extends.
3. Device according to claim 2, wherein the two press screws (10, 18) and the two shafts (34, 36) are arranged coaxially with each other and one press screw (10) sits concentrically on the hollow shaft (36) and the other press screw (18) sits concentrically on an exposed section of the shaft (34) partially surrounded by the hollow shaft (36).
4. Device according to claim 2 or 3, wherein the first press screw (10) is driven by the hollow shaft (36) and the second press screw (18) is driven by the shaft (34) that is partially surrounded by the hollow shaft (36).
5. Device according to at least one of claims 2 to 4, wherein the drive device (38, 40) is arranged at that position of the device at which the end sections of both the shaft (34) and the hollow shaft (36) surrounding the shaft (34) are respectively located, and/or is arranged adjacent to the first inlet.
6. Device according to at least one of the preceding claims, wherein the drive device has two drive motors (38), (40), of which one drive motor (38) is designed to drive one press screw (10), and the other drive motor (40) is designed to drive the other press screw (18).
7. Device according to at least one of claims 2 to 5 as well as according to claim 6, wherein one drive motor (38) is designed to drive the internal shaft (34) essentially directly, and the other drive motor (40) is designed to drive the hollow shaft (36) essentially directly.
8. Device according to at least one of claims 1 to 5, wherein the drive device has a drive motor and a gear, in particular a planetary gear, the transmission ratio of which is adjustable, wherein the drive motor is designed to drive one press screw (10) essentially directly, and the gear is coupled with the drive motor and is designed to drive the other press screw (18) essentially directly, and the rotational speed control device is designed to control the gear by changing its transmission ratio,
9. Device according to claim 8 as well as at least one of claims 2 to 5, wherein the drive motor is designed to drive the internal shaft (34) essentially directly, and the gear is designed to drive the hollow shaft essentially directly.
10. Device according to at least one of the preceding claims, wherein the first press screw housing (10) and the second press screw housing (18) form a common housing.
11. Device according to at least one of the preceding claims, wherein an extruder (24) is arranged between the first outlet (14) and the second inlet (20), which extruder (24) has an extruder housing (26), an extruder screw (28) rotatably mounted in the extruder housing (26), an inlet (30) coupled to the first outlet (14), and an outlet (32) coupled to the second inlet (20).
12. Device according to claim 11, wherein the two press screws (10, 18) and the extruder screw (28) are arranged coaxially to each other.
13. Device according to claim 11 or 12, wherein the extruder housing (26) connects the first press screw housing (8) with the second press screw housing (16).
14. Device according to at least one of claims 11 to 13, wherein the extruder screw (28) is coupled non-rotatably with the first press screw (10).
15. Device according to at least one of claims 11 to 14, wherein the screw pitch of the extruder screw (28) is constant across its length and/or is smaller than the screw pitch of the press screws (10, 18).
16. Device according to at least one of the preceding claims, wherein the press screw housing (8, 16) forms a hollow space that is essentially cylindrical across the whole length of the press screw (10, 18) for at least one of the screw presses (4, 6) and the press screw (10, 18) has a consistently monotonically or continuously increasing core diameter and a consistently monotonically or continuously decreasing screw pitch.

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