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Title:
A COUNTER PRESSURE SYSTEM FOR A SCREW PRESS WITH AUTOMATICALLY ADJUSTED COUNTER PRESSURE AND A SCREW PRESS COMPRISING SUCH A COUNTER PRESSURE SYSTEM
Document Type and Number:
WIPO Patent Application WO/2018/033192
Kind Code:
A1
Abstract:
A counter pressure system (6) for a screw press (1) for compaction of materials, such as for instance reusable waste products, is disclosed, which counter pressure comprises at least one moveable pressure jaw (8), the position of which determines the size of an opening through the counter pressure system through which the compacted material passes, wherein the counter pressure system is arranged so that the size of the opening and, thereby, the counter pressure exerted by the counter pressure system onto the material passing through it is automatically adjusted depending on the forward pressure exerted onto the material entering the counter pressure system by a press screw (7) of the screw press, of which the counter pressure system forms part, the adjustment being either a passive adjustment directly and mechanically depending on the pressure exerted by the press screw or an active adjustment based on a measurement of the same pressure.

Inventors:
ROSSEN BECH, Søren (Kløvertoften 20, 7100 Vejle, 7100, DK)
Application Number:
DK2017/050265
Publication Date:
February 22, 2018
Filing Date:
August 16, 2017
Export Citation:
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Assignee:
RUNI A/S (Industriparken 8, 6880 Tarm, 6880, DK)
International Classes:
B30B9/18; B30B9/30
Domestic Patent References:
WO2007057293A12007-05-24
Foreign References:
US4709628A1987-12-01
US5012731A1991-05-07
GB1170315A1969-11-12
FR1275477A1961-11-10
Attorney, Agent or Firm:
CARLSEN, Bjarne (Patender ApS, Birk Centerpark 40, 7400 Herning, 7400, DK)
Download PDF:
Claims:
Claims

1 , A counter pressure system (6) for a screw press (1) for compaction of materials, such as for instance reusable waste products, which counter pressure comprises at least one moveable pressure jaw (8), the position of which determines the size of an opening through the counter pressure system through which the compacted material passes, wherein the counter pressure system is arranged so that the size of the opening and, thereby, the counter pressure exerted by the counter pressure system onto the material passing through it is automatically adjusted depending on the forward pressure exerted onto the material entering the counter pressure system by a press screw (7) of a screw press, of which the counter pressure system forms part, and wherein the counter pressure adjustment is either a passive adjustment directly and mechanically depending on the forward pressure exerted by the press screw or an active adjustment based on a measurement of the forward pressure exerted by the press screw. 2. The counter pressure system according to claim 1, wherein the counter pressure system is arranged so that, when the forward pressure exerted by the press screw (7) exceeds a certain predefined level, the counter pressure system moves away from the remaining parts of the screw press in the axial direction of the press screw, and the position of the at least one pressure jaw changes in a direction increasing the size of the opening through the counter pressure system, whereby the counter pressure exerted by the at least one pressure jaw and thereby also the forward pressure exerted by the press screw is reduced and the counter pressure system moves back towards the remaining parts of the screw press again. 3 , The counter pressure sy tem according to claim 2, wherein the position of the counter pressure system relatively to the remaining parts of the screw press is mechanically controlled at least partly by means of one or more springs (11) with spring bolts (12) fixed at one end to the remaining parts of the screw press, which springs and spring bolts are arranged so that, when the counter pressure system is in its position closest to the remaining parts of the screw press, the springs are in their most expanded position defining the predefined pressure level above which the counter pressure system moves away from the remaining parts of the screw press and, the position of the counter pressure system furthest away from the remaining parts of the screw press being defined by a mechanical stop.

4. The counter pressure system according to claim 2, wherein the position of the counter pressure system relatively to the remaining parts of the screw press is controlled at least partly by means of one or more hydraulic cylinders connected to a hydraulic accumulator in such a way that the hydraulic cylinders and the hydraulic accumulator together work as a hydraulic spring, the predefined pressure level above which the counter pressure system moves away from the remaining parts of the screw press being defined by an air pressure within the hydraulic accumulator when the counter pressure system is in its position closest to the remaining parts of the screw press,

5. The counter pressure system according to any of claims 2-4, wherein the counter pressure system is supported by a support tower (9), the position relatively to the remaining parts of the screw press is fixed, and wherein the pressure jaw is rotatabiy connected to the remaining parts of the counter pressure system at one end and rotatabiy connected to a guide bar (10) at the other end, and the guide bar is also rotatabiy connected to the support tower in such a way that, when the counter pressure system moves relatively to the support tower in a direction away from the remaining parts of the screw press, the guide bar forces the position of the pressure jaw to change in a direction increasing the size of the opening through the counter pressure system, and when the counter pressure system moves relatively to the support tower in a direction towards the remaining parts of the screw press, the guide bar forces the position of the pressure jaw to change in a direction narrowing the opening through the counter pressure system.

6. The counter pressure system according to claim 5, wherein the length of the guide bar is made variable, for instance through insertion of a spring load or a controlled actuator between its two connection points. 7. The counter pressure system according to claim 4, wherein the position of the at least one pressure jaw is controlled by one or more hydraulic jaw cylinders arranged between the one or more hydraulic cylinders controlling the position of the counter pressure system relatively to the remaining parts of the screw and the hydraulic accumulator in such a way that, when the counter pressure system moves away from the remaining parts of the screw press, hydraulic oil moves between the one or more hydraulic cylinders controlling the position of the counter pressure system and the one or more hydraulic jaw cylinders causing the position of the pressure jaw to change in a direction increasing the size of the opening through the counter pressure system, and when the counter pressure system moves towards the remaining parts of the screw press, hydraulic oil moves between the one or more hydraulic cylinders controlling the position of the counter pressure system and the one or more hydraulic jaw cylinders in the opposite direction causing the position of the pressure jaw to change in a direction narrowing the opening through the counter pressure system.

8. The counter pressure system according to claim 1, further comprising one or more pressure sensors arranged to measure the pressure exerted onto the material entering the counter pressure system by the press screw and to send signals representative of the magnitude of the exerted pressure to one or more power sources, such as hydraulic cylinders, pneumatic cylinders or electric actuators, which power sources are arranged to control the position of the at least one pressure jaw depending on the received signals in accordance with predefined dependencies between the measured exerted pressures and the position of the at least one pressure jaws,

9, A screw press (1) for compaction of materials, such as for instance reusable waste products, which screw press comprises a counter pressure system (6) according to any of the preceding claims.

Description:
A COUNTER PRESSURE SYSTEM FOR A SCREW PRESS WITH AUTOMATICALLY ADJUSTED COUNTER PRESSURE AND A SCREW PRESS COMPRISING SUCH A COUNTER PRESSURE

SYSTEM The present invention relates to a counter pressure system for a screw press for compaction of solid materials, such as for instance reusable waste products, and to a screw press comprising such a counter pressure system.

Background of the invention

In order to obtain the desired compacting of solid materials in a screw press, some kind of resistance or friction creating means is needed to create a counter pressure working against the pressure applied by the screw onto the material to be compacted. One well-known way of obtaining such a counter pressure consists in the use of counter pressure systems with channel structures comprising one or more adjustable pressure jaws, the positionfs) of which determine(s) the internal cross-sectional area of the narrowest part of the channel structure and, thereby, the opening of the passageway through which the compacted material must pass. In this way, the created counter pressure can be regulated by adjusting the positionfs) of the one or more pressure jaws.

In order to ensure an appropriate and uni form compacting of the material passing through the screw press, it is important to keep the forward pressure exerted by the press screw relatively constant or at least within certain limits. It is known to use spring-loaded pressure jaws so that the counter pressure is reduced if the forward pressure exerted onto the pressure jaws by the compacted material exceeds a certain predefined level. However, such adjustment systems are inaccurate and insufficient, because the regulation of the counter pressure is not depending on the pressure exerted by the press screw onto the material but on the pressure exerted by the material on the pressure jaw after passage of the counter pressure system. Brief description of the invention

It is an object of the present invention to provide a counter pressure system and a screw press, which overcome the above-mentioned disadvantages related to counter pressure systems and screw presses known in the art.

The present invention relates to a counter pressure system for a screw press for compaction of materials, such as for instance reusable waste products, which counter pressure comprises at least one moveable pressure jaw, the position of which determines the size of an opening through the counter pressure system through which the compacted material passes, wherein the counter pressure system is arranged so that the size of the opening and, thereby, the counter pressure exerted by the counter pressure system onto the material passing through it is automatically adjusted depending on the forward pressure exerted onto the material entering the counter pressure system by a press screw of a screw press, of which the counter pressure system forms part, and wherein the counter pressure adjustment is either a passive adjustment directly and mechanically depending on the forward pressure exerted by the press screw or an active adjustment based on a measurement of the forward pressure exerted by the press screw.

Counter pressure systems with counter pressure adjustment configured as in the present invention are advantageous, because the regulation of the counter pressure depends directly on the forward pressure exerted by the press screw onto the material to be compacted.

In an embodiment of the invention, the counter pressure system is arranged so that, when the forward pressure exerted by the press screw exceeds a certain predefined level, the counter pressure system moves away from the remaining parts of the screw press in the axial direction of the press screw, and the position of the at least one pressure jaw changes in a direction increasing the size of the opening through the counter pressure system, whereby the counter pressure exerted by the at least one pressure jaw and thereby also the forward pressure exerted by the press screw is reduced and the counter pressure system moves back towards the remaining parts of the screw press again.

In an embodiment of the invention, the position of the counter pressure system relatively to the remaining parts of the screw press is mechanically controlled at least partly by means of one or more springs with spring bolts fixed at one end to the remaining parts of the screw press, which springs and spring bolts are arranged so that, when the counter pressure system is in its position closest to the remaining parts of the screw press, the springs are in their most expanded position defining the predefined pressure level above which the counter pressure system moves away from the remaining parts of the screw press and, the position of the counter pressure system furthest away from the remaining parts of the screw press being defined by a mechanical stop.

The use of mechanical springs is relatively simple and reliable and it requires no electronic control and almost no maintenance. In an embodiment of the invention, the position of the counter pressure system relatively to the remaining parts of the screw press is controlled at least partly by means of one or more hydraulic cylinders connected to a hydraulic accumulator in such a way that the hydraulic cylinders and the hydraulic accumulator together work as a hydraulic spring, the predefined pressure level above which the counter pressure system moves away from the remaining parts of the screw press being defined by an air pressure within the hydraulic accumulator when the counter pressure system is in its position closest to the remaining parts of the screw press.

Also the use of hydraulic springs is relatively simple and reliable and it requires no electronic control and almost no maintenance. In an embodiment of the invention, the counter pressure system is supported by a support tower, the position relatively to the remaining parts of the screw press is fixed, and wherein the pressure jaw is rotatably connected to the remaining parts of the counter pressure system at one end and rotatably connected to a guide bar at the other end, and the guide bar is also rotatably connected to the support tower in such a way that, when the counter pressure system moves relatively to the support tower in a direction away from the remaining parts of the screw press, the guide bar forces the position of the pressure jaw to change in a direction increasing the size of the opening through the counter pressure system, and when the counter pressure system moves relatively to the support tower in a direction towards the remaining parts of the screw press, the guide bar forces the position of the pressure jaw to change in a direction narrowing the opening through the counter pressure system.

Such a relatively simple mechanical coupling between the movement of the counter pressure system relatively to the remaining parts of the screw press and the movement of the pressure jaw within the counter pressure system ensures a reliable and lasting function with small maintenance requirements.

In an embodiment of the invention, the length of the guide bar is made variable, for instance through insertion of a spring load or a controlled actuator between its two connection points.

This is advantageous, for instance if the compacted material constitutes a significant resistance against the inward movement of the pressure jaw, which would otherwise prevent the movement of the counter pressure system towards the remaining parts of the screw press.

In an embodiment of the invention, the position of the at least one pressure jaw is controlled by one or more hydraulic jaw cylinders arranged between the one or more hydraulic cylinders controlling the position of the counter pressure system relatively to the remaining parts of the screw and the hydraulic accumulator in such a way that, when the counter pressure system moves away from the remaining parts of the screw press, hydraulic oil moves between the one or more hydraulic cylinders controlling the position of the counter pressure system and the one or more hydraulic jaw cylinders causing the position of the pressure jaw to change in a direction increasing the size of the opening through the counter pressure system, and when the counter pressure system moves towards the remaining parts of the screw press, hydraulic oil moves between the one or more hydraulic cylinders controlling the position of the counter pressure system and the one or more hydraulic jaw cylinders in the opposite direction causing the position of the pressure jaw to change in a direction narrowing the opening through the counter pressure system.

This embodiment combines the well-known and reliable use of hydraulic cylinders for controlling the position of pressure jaws with the above-described use of hydrauli c springs for controlling the position of the counter pressure system relatively to the remaining parts of the screw press.

In an embodiment of the invention, the counter pressure system further comprises one or more pressure sensors arranged to measure the pressure exerted onto the material entering the counter pressure system by the press screw and to send signals representative of the magnitude of the exerted pressure to one or more power sources, such as hydraulic cylinders, pneumatic cylinders or electric actuators, which power sources are arranged to control the position of the at least one pressure jaw depending on the received signals in accordance with predefined dependencies between the measured exerted pressures and the position of the at least one pressure jaws.

This embodiment requires electronic control but reduces the number of moving parts, because the counter pressure system is stationary relatively to the remaining parts of the screw press. In an aspect of the invention, it relates to a screw press for compaction of materials, such as for instance reusable waste products, comprising a counter pressure system as described above.

In the following a few exemplar}' embodiments of the invention are described in further detail with reference to the figures, of which

Fig. 1 is a partly cross-sectional view of a screw press according to an

embodiment of the invention,

Fig. 2 is a perspective view of a counter pressure system for a screw press according to an embodiment of the invention,

Fig. 3a is a cross-sectional view of the counter pressure system shown in Fig. 2 in a fully contracted position, and

Fig. 3b is a cross-sectional view of the same counter pressure system in a fully expanded position.

Detailed description of the invention

Fig. 1 is a partly cross-sectional view of a screw press 1 according to an embodiment of the invention. In the illustrated embodiment, the material to be compacted is filled into a hopper 3, from which it passes through a conical connection part 5 into a counter pressure system 6 before leaving the screw press I in compacted form. In other embodiments, the connection part between the hopper 3 and the counter pressure system 6 may not be conical. An auger 4 within the hopper 3 and a press screw 7 within the conical connection part 5 extending partly into the counter pressure system 6 is mounted on a common shaft for being rotated by an electric motor 2. The auger 4 moves the material to be compacted from the hopper 3 to the conical connection part 5 and the press screw 7 presses the material through the conical connection part 5 and further into the counter pressure system 6, in which a moveable pressure jaw 8 is used to vary the opening of the passage through the counter pressure system 6 and, thereby, the counter pressure exerted onto the material and the degree to which the material is compacted.

Fig. 2 is a perspective view of a counter pressure system 6 for a screw press 1 according to an embodiment of the invention. In this embodiment, the counter pressure system 6 is supported by a support tower 9, the position of which is fixed relatively to the remaining parts of the screw press 1 (not shown in this figure), whereas the counter pressure system 6 is moveable relatively to the remaining parts of the screw press 1.

Two spri ng bolts 12 are fixed at one end to the remai ning parts of the screw press 1 (typically to a conical connection part 5 as illustrated in Fig. 1). The counter pressure system 6 can slide along the spring bolts 12 depending on the forward pressure exerted by the press screw 7 shown in Fig. 1 onto the material being compacted and, thereby, onto the counter pressure system 6.

When the forward pressure exerted by the press screw 7 exceeds a certain limit determined by the preload of the two springs 11 mounted around the spring bolts 12, the counter pressure system 6 moves in a direction away from the remaining parts of the screw press I . The position furthest away from the remaining parts of the screw- press 1 is reached when the counter pressure system 6 reaches a mechanical stop (not shown). In the illustrated embodiment, the springs 1 1 are coil springs, but in principle any type of springs 1 1 may be used. A guide bar 10 is rotatably connected at one end to the fixed support tower 9 and at the other end to one end of the pressure jaw 8. The other end of the pressure jaw 8 is rotatably connected to the remaining parts of the counter pressure system 6. Figs. 3a and 3b are cross-sectional views of the same counter pressure system 6 illustrating schematically the function thereof.

In Fig, 3a, the counter pressure system 6 is in a fully contracted position, i .e. in the position closest possible to the conical connection part 5 of the screw press 1. The compression of the springs 12 in this position determines the pressure level above which the counter pressure system 6 will start moving away from the conical connection part 5. In this position, the pressure jaw 8 is in the position narrowing the opening of the passage through the counter pressure system 6 as much as possible, thereby exerting maximum counter pressure onto the material passing through the counter pressure system 6.

In Fig, 3b, on the other hand, the counter pressure system 6 is in a fully expanded position, i.e. the position furthest away from the conical connection part 5 of the screw press 1. This position i s reached when the counter pressure system 6 reaches a mechanical stop (not shown). The axial motion of the counter pressure system 6 relatively to the remaining parts of the screw press 1 including the support tower 9 has caused the guide bar 10 to rotate into a more horizontal position thereby lifting the pressure jaw 8 and increasing the size of the opening of the passage through the counter pressure system 6.

The increased size of the opening reduces the counter pressure exerted onto the material passing through the counter pressure system 6 and, thereby, the pressure exerted by the press screw 7 onto the material for pushing it through. This, in turn, causes the counter pressure system 6 to move back towards the remaining parts of the screw press 1, thereby causing the pressure jaw 8 to rotate and narrow the opening through the counter pressure system 6. Thus an increase of the forward pressure exerted by the press screw 7 immediately results in a reduction of the counter pressures exerted by the counter pressure system 6 and vice versa, and a direct and reliable regulation of the pressure exerted by the press screw 7 is obtained.

In other embodim ent of the invention (not illustrated), the springs 1 1 and spring bolts 12 may be replaced by on ore more hydraulic cylinders, which are pushed in or out when the counter pressure system 6 moves relatively to the remaining parts of the screw press 1 . The displaced hydraulic oil is conducted in hoses to an air-filled hydraulic accumulator, the air pressure within which determined the pressure level above which the counter pressure system 6 starts to move. In yet other embodiments, one or more hydraulic jaw cylinders are arranged between the hydraulic cylinders controlling the position of the counter pressure system 6 and the hydraulic accumulator in a so-called master-slave configuration so that a movement of the counter pressure system 6 causes hydraulic oil to be displaced between the hydraulic cylinders so that this motion is directly connected to a movement of the pressure jaw 8. In this case, one hydraulic port of a hydraulic jaw cylinder is connected to a hydraulic port of a hydraulic cylinder controlling the position of the counter pressure system, whereas the other hydraulic port of the hydraulic jaw cylinder is connected to the hydraulic accumulator, which ensures a hydraulic spring function for both the hydraulic jaw cylinders and the hydraulic cylinders controlling the position of the counter pressure system 6.

Other embodiment of the invention (not illustrated) include electronic control of one or more power sources, for instance in the form of hydraulic cylinders, pneumatic cylinders or electric actuators, regulating the position of the one or more pressure jaws 8, on the basis of electric signals representing the forward pressure exerted by the press screw 1 onto the material to be compacted. This pressure may, for instance, be measured by one or more pressure sensors arranged between the counter pressure system 6 and the remaining parts of the screw press 1. List of reference numbers

1. Screw press

2. Electric motor

3 , Hopper

4. Auger

5. Conical connection part

6. Counter pressure system

7. Press screw

8, Pressure jaw

9. Support tower for counter pressure system

10. Guide bar for pressure jaw

1 1. Spring

12. Spring bolt