EP2217388B1 - Screen system with tube-shaped screen and method for operating a screen system with tube-shaped screen - Google Patents

Abstract

The system (3) has a tube or screen frame (31), which is subjected to ultrasound stimulation by an ultrasound converter (13) and a feed pipe sound converter (34). The converter (34) is designed such that amplitude of the stimulation comprises components in a vertical direction to a middle axis of a tube-like screen, and components in a parallel direction to the middle axis of the tube-like screen. The amplitude is transferred to a tube or to the screen frame. The feed pipe sound converter comprises a curved region with a curvature angle of maximum of 90 degrees. An independent claim is also included for a method for operating a screening system.

Description

The invention relates to a screening system according to the preamble of claim 1 and a method for operating a screening system according to the preamble of claim 13.

There are a variety of applications in the industry in which it is desirable to achieve size classification of a material and / or to avoid particle agglomeration or, if it has already occurred, to break it up.

For this purpose, generally known screening machines are used which use screen systems which differ in particular by the design and orientation of the screens used. Conventional vibratory and tumble screening machines use screens which have a screen fabric stretched in a frame and substantially planar, which is oriented substantially perpendicular to the desired direction of flow of the material. Screenings which do not fulfill the classification conditions imposed by the openings in the screen fabric remain behind in the screen; only screenings that fulfill the classification condition can leave the screen.

While these classes of screening machines are well suited for use in applications where the screenings are fed in portions due to the screen arrangement they use, they are poorly suited for use with continuous feed of screenings. In particular, in such cases Zentrifugalsiebmaschinen, which are also known under the name Wirbelstromsiebmaschinen used. Such a screening machine is for example from the DE 30 19 113 C2 known.

In the type of screening machine referred to in this patent application as "Zentrifugalsiebmaschine" the screening system used has a tubular sieve, in the interior of which the screenings are conveyed. The tubular sieve can consist of a tube with sieve openings arranged directly in the wall of the tube, but it can also be stretched by a sieve cloth, which is stretched on a sieve frame, which defines at least the length and the cross-section of a tube the screen fabric forms at least part of the surface of the tubular screen and in particular is not only arranged in one plane. In addition, embodiments are also conceivable in which both a tube with screen openings and an additional screen fabric surrounding this tube are provided.

For the purposes of this patent specification, a tube is an elongate hollow body with an opening passing through it lengthwise and generally of cylindrical cross-section; accordingly, the adjective "tubular" describes an article having the shape of a tube as defined above.

The sieving action of the tubular sieve is achieved by causing a passage of the material to be sieved through the sieve openings and / or the sieve cloth forming the at least part of the tube wall. To ensure that there is a significant material throughput through the screen openings and / or the screen fabric, there are two particularly widespread approaches: One way, which is used in particular at relatively low concentrations of the material to be screened, there is a inside the tubular sieve to provide the material transporting fluid flow which is provided with such a swirling, that a material transport through the screen openings and / or the screen fabric comes.

An alternative possibility, used in particular at high concentrations of the material to be screened, is that inside the tubular screen a so-called "racket system", i. a usually made of metal rotor linkage is provided, which is guided along the wall of the tubular screen and pushes through the screenings through the screen openings and / or the screen fabric and optionally provided radial openings of the frame structure.

Generally, the problem arises in screen systems, even temporary blockage of the screen openings and / or screen fabric, as e.g. By agglomeration of Siebgutteilchen can be done to prevent and ensure the highest possible throughput of screenings through the mesh. In sieve systems, which find use in centrifugal screening machines, this problem is exacerbated mostly because the screenings - for example, by a racket system - in the Sieböfnungen and / or the screen fabric is coated.

For sieve systems with flat sieves, in which the sieve fabric forms a plane spanned in a sieve frame, it is known to reduce the tendency to block the sieve fabric by means of ultrasound excitation. Such a screening system is for example the DE 4418175 refer to. However, a simple transfer of this approach to sieve systems with tubular sieves fails. The desired significant increase in throughput is not achieved.

Starting from this prior art, the problem arises to provide a sieve system for a Zentrifugalsiebmaschine with a tubular sieve and a method for operating a tubular sieve, which leads to an increase in the achievable throughput of Siebgut.

The invention is based on the finding that excitation of a tubular screen by means of ultrasound leads to a significant increase in the throughput of screenings, when the amplitude of the ultrasonic excitation has both a component in the radial direction and a component in the axial direction of the tubular screen.

A screen system according to the invention therefore has a tube which has at least one section (12) with screen openings arranged directly in the wall of the tube and / or a screen mesh which defines a screen frame which defines at least the length and the cross section of a tube , is stretched, so that the screen fabric forms at least part of the wall of the tubular screen, and at least one ultrasonic converter and at least one arranged between ultrasonic converter and the screen frame inlet conductor, wherein the tube or the screen frame by means of the ultrasonic converter and the lead scarf conductor of an ultrasonic excitation can be suspended and wherein the lead acoustic conductor (s) is / are configured so that the amplitude of the ultrasonic excitation transmitted to the tube or screen frame has a component in the direction perpendicular to a central axis of the tubular screen and a component parallel to the Mi has the axis of the tubular sieve. By providing such longitudinal and transverse components of the oscillation amplitude, on the one hand, the propagation of the ultrasound over the entire tubular sieve is ensured and on the other hand at each location a component of the vibration amplitude is provided which causes an intensive, throughput-promoting interaction between screenings and screen openings and / or screen mesh.

In a preferred embodiment, when ultrasonic excitation, both components of the amplitude of the ultrasonic excitation at a single point of contact between the feed line conductor and pipe or screen frame are transmitted. This allows a particularly cost-effective design with only one ultrasonic converter and only one feed line conductor.

This can be achieved, in particular, if the one feed line sound conductor has at least one curved area. Advantageously, the angle of curvature of the curved region is above 0 degrees and at most at 90 degrees, with a bend angle of 90 degrees being most suitable for most applications.

The use of a feed line conductor with a diameter of 12 mm has proven to be particularly advantageous.

A particularly robust and interference-resistant embodiment of the screen system is obtained by providing fixed connections between the feed line conductor and the surface of the tube or surface of the screen frame. This can be done in particular by screwing or welding.

Furthermore, the provision of a fixed connection between the feed line conductor and the ultrasonic converter has proven to be conducive to the robustness and interference resistance of the screening system.

Here, in particular, the screwing is suitable to produce such a solid connection.

If one wishes to obtain a sieve system in which a particularly high vibrational energy can be introduced into the sieve fabric, this can be achieved by providing more than one ultrasound converter and more than one feeder sound conductor.

Moreover, if more than one lead acoustic conductor is present and the tube or screen frame is ultrasonically excitable via the lead acoustic conductors, then the presence of a component in a direction perpendicular to a central axis of the tubular screen and a component in a direction parallel to the central axis of the tubular screen may also occur Siebs are achieved in that the direction of the amplitude of the ultrasonic excitation, which is transmitted through different feed line conductors on the pipe or the screen frame, is different. This embodiment of the invention has proven to be particularly useful when a particularly targeted adjustment of the size of the two components of the amplitude of the ultrasonic excitation is necessary.

For the operation of such a screen system, it is also useful to arrange the existing ultrasonic converter outside the Siebgutstromes, since these can cause material changes in the screenings on the one hand and on the other dirty and can be damaged in Siebgutstrom. This goal can be realized if the screen system has a housing which prevents leakage of screenings into the environment and all existing ultrasonic converters are arranged outside the housing.

The tubular screen systems described herein are particularly suitable for use in centrifugal screening machines.

In the method according to the invention for operating a sieve system with a tubular sieve, a pipe with sieve openings, which are arranged directly in the wall of the tube and / or a screen fabric, which strained on a screen frame, which defines at least the length and the cross section of a tube is such that the screen fabric forms at least part of the surface of the tubular screen, the pipe with the screen openings or the screen frame are excited with an ultrasonic excitation having an amplitude which is a component in the direction perpendicular to a central axis of the tubular screen and a component in a direction parallel to the central axis of the tubular screen. The presence of these two amplitude components ensures that, on the one hand, a propagation of the vibrations caused by the ultrasonic excitation takes place over the entire tubular sieve, while at the same time good conditions for increasing the efficiency of the sieving process are ensured at each point of the sieve.

The process can be carried out with particularly low material expenditure if the amplitude which a component has in the direction perpendicular to a central axis of the tubular sieve and a component in a direction parallel to the central axis of the tubular sieve is produced by exactly one feed line sound conductor.

A particularly well controllable size distribution of the two components of the vibration amplitude is achieved when the amplitude, which is a component in the direction perpendicular to a Central axis of the tubular screen and a component in the direction parallel to the central axis of the tubular screen, is produced by more than one feed line conductor.

It has been shown that a further significant increase in the throughput can be achieved by not working at a fixed excitation frequency, but the frequency of the ultrasonic excitation is varied. This is done by appropriate control of the ultrasonic converter with a control unit. The range in which the frequency is varied is advantageously between 32 kHz and 38 kHz. Particularly good results can be achieved if the frequency modulation is sweeped, i. done by a continuous frequency variation.

Fig.1:

ein Siebsystem mit einem rohrförmigen Sieb gemäß einer ersten Ausführungsform der Erfindung

Fig.2:

ein Siebsystem mit einem rohrförmigen Sieb gemäß einer zweiten Ausführungsform der Erfindung

Fig.3:

ein Siebsystem mit einem rohrförmigen Sieb gemäß einer dritten Ausführungsform der Erfindung

Specific embodiments of the invention will be discussed in detail with reference to the following figures. It shows:

Fig.1:

a screen system with a tubular sieve according to a first embodiment of the invention

Figure 2:

a screen system with a tubular sieve according to a second embodiment of the invention

Figure 3:

a screen system with a tubular sieve according to a third embodiment of the invention

Identical components are, unless otherwise indicated, provided with identical reference numerals in all figures.

FIG. 1 shows a screen system 1 with a tubular sieve 10, which in the illustrated embodiment, the shape of a hollow cylinder Has. The tubular sieve 10 consists of a tube 11 having two annular end portions 111, 112, between which a cylindrical portion 113 is disposed. In the cylindrical region 113 are a plurality of brightly illustrated areas 114, in which the tube 11 has numerous small screen openings that are not drawn individually because of their small size for reasons of clarity. In addition, the tube 11 in the cylindrical portion 113 has a plurality of reinforcing ribs 12, which are drawn dark to distinguish them from the areas with screen openings.

Furthermore, the screen system 1, two ultrasonic converters 13 and two feed line conductor 14. The use of two feed scarf ladders 14 and two ultrasonic converters 13 in this embodiment serves, in particular, to increase the vibrational energy transmitted to the tube 11. It has the central axis A-A.

The tube 11 is mechanically connected via the feed line conductors 14 with the ultrasonic converters 13. The lead scarf ladder 14 are curved. As indicated by the arrows in FIG. 1 is indicated by the ultrasonic converter 13, an ultrasonic vibration with a vibration amplitude, which is directed parallel to the central axis AA, fed into the feed line conductor 14. The curvature of the feed line conductor 14 causes the oscillation amplitude receives an additional, perpendicular to the central axis AA component. The exact division of the components is determined by the geometric configuration of the feed line conductors 14, in particular by their curvature.

At contact points 115, the ultrasonic vibration is transmitted to the tube 11. The vibration caused thereby spreads via the pipe 11. In particular, the longitudinal component of the amplitude of the ultrasound excitation promotes propagation of the ultrasound over the entire length of the tubular sieve, while the transverse component particularly increases the efficiency of the sieving process at any given location of the tube 11.

FIG. 2 shows a screening system 2 with a tubular sieve 10, which has the shape of a hollow cylinder in the illustrated embodiment. The tubular sieve 10 consists of a tube 11 having two annular end portions 111, 112, between which a cylindrical portion 113 is disposed. In the cylindrical region 113 are a plurality of brightly illustrated areas 114, in which the tube 11 has numerous small screen openings that are not drawn individually because of their small size for reasons of clarity. In addition, the tube 11 in the cylindrical portion 113 has a plurality of reinforcing ribs 12, which are drawn dark to distinguish them from the areas with screen openings.

Next you can see four ultrasonic converter 13 and four feed line conductors 24, which belong to the screening system 2. The use of four feed scarf ladders 24 and four ultrasonic converters 13 in this embodiment serves, in particular, to increase the vibration energy transmitted to the tube 11. The sieve system has the central axis AA. The tubular sieve is surrounded by a housing 15, through which the feed line conductors 14 are guided. The ultrasonic converters 13 are outside the housing and thus outside the area in which a contact with screenings would be possible arranged.

The tube 11 is mechanically connected via the feed line conductors 14 with the ultrasonic converters 13. The lead scarf ladder 24 are in the FIG. 2 executed with two curvature areas. As based on the FIG. 1 has already been explained, is fed by the ultrasonic converter 13, an ultrasonic vibration with a vibration amplitude, which is directed parallel to the central axis AA, in the feed line conductor 24. The curvature of the feed line conductor 24 causes oscillation amplitude receives an additional, perpendicular to the central axis AA component. The exact division of the components is determined by the geometric configuration of the feed line conductors 24, in particular by their curvature. In the embodiment of FIG. 2 Therefore, in particular, there is a different division of the components of the amplitude of the ultrasonic excitation than in the embodiment of FIG. 1 in that the geometric configuration of the feed line conductors 24 is different from that of the feed line conductors 14 in FIG FIG. 1 , In addition to the angles of curvature, radii of curvature and cross section of the feed line conductors 14 and 24 also play a decisive role in the achieved size distribution of the two components of the amplitude of the ultrasound excitation.

At contact points 115, the ultrasonic vibration is transmitted to the tube 11. The vibration of the tube 11 caused thereby spreads across the tube 11. In this case, the longitudinal component of the amplitude of the ultrasound excitation in particular promotes a propagation of the ultrasound over the entire length of the tubular sieve, while the transverse component particularly increases the efficiency of the screening process.

FIG. 3 shows a screening system 3 with a tubular sieve 30. The sieve 30 consists of a sieve cloth 32, and a sieve frame 31. The sieve frame consists of four annular sections 311, 312, 313, 314, which define the cross section of a pipe or hollow cylinder via two also belonging to the frame connecting strips 316, 317, through which the length of the tube is given, are connected to each other. By the components of the screen frame length and cross section of the tube are given in this way. The screen cloth 32 is stretched on the screen frame such that the screen cloth 32 forms at least part of the surface of the tubular screen 30. In particular, the screen cloth 32 is not arranged in one plane only. It would also be possible to use fewer or more annular sections 311, 312, 313, 314 and / or fewer or more connecting strips 316, 317 as long as at least two annular sections 311, 312, 313, 314 and at least one connecting strip 316, 317 are present ,

Next shows FIG. 3 two ultrasonic converters 13 and two feed line conductors 34, which in FIG. 3 each have two areas of curvature. The feed line conductors are connected to the screen frame 31 at contact points 315. During operation of the screening system 3, an ultrasound vibration with an oscillation amplitude, which is directed parallel to the central axis AA of the tubular screen 30, is fed into the supply sound conductors 34 by the ultrasonic converters 13. The curvature of the supply line conductors 34 causes oscillation amplitude receives an additional, perpendicular to the central axis AA component. At contact points 315, the ultrasonic vibration is transmitted to the screen frame 31. The result Vibration of the screen frame 31 caused at the contact points 315 propagates over the entire screen frame 31 and at the same time leads to ultrasound excitation of the screen fabric 32. In this case, the longitudinal component of the amplitude of the ultrasound excitation particularly propagates the ultrasound over the entire length of the tubular screen 30 promoted, while the transverse component, the efficiency of the screening process and the throughput through the screen fabrics 32 particularly increases.

LIST OF REFERENCE NUMBERS

1

Sieve system (first embodiment)

2

Sieve system (second embodiment)

3

Sieve system (third embodiment)

10

tubular sieve

11

pipe

12

Pipe section with sieve openings

13

ultrasonic converter

14

Supply sound conductor

15

casing

24

Supply sound conductor

30

tubular sieve

31

screen frame

32

mesh

34

Supply sound conductor

111

end

112

end

113

Cylindrical area

114

reinforcement ring

115

contact point

311

annular section of the screen frame

312

annular section of the screen frame

313

annular section of the screen frame

314

annular section of the screen frame

315

contact point

316

connecting strip

317

connecting strip

Claims (18)

1. A screen system (1, 2, 3) with a tubular screen (10, 30), which has a tube (11) which comprises at least one portion (12) with screen openings which are arranged directly in the wall of the tube (11), and/ or which has a screen frame (31) which defines at least the length and the cross-section of a tube, and a screen cloth (32) which is stretched on the screen frame (31), so that the screen cloth (32) forms at least part of the wall of the tubular screen (10, 30), characterized in that the screening system (1, 2, 3) has at least one ultrasonic converter (13) and at least one feed line sound conductor (14, 24, 34) arranged between the ultrasonic converter (13) and the tube (11) or the screen frame (31), wherein the tube (11) or the screen frame (31) is capable of being subjected to an ultrasonic excitation by means of the ultrasonic converter (13) and the feed line sound conductor (14, 24, 34), and wherein the feed line sound conductor or the feed line sound conductors (14, 24, 34) is or are designed in a such way that the amplitude of the ultrasonic excitation transmitted to the tube (11) or to the screen frame (31) has a component in the vertical direction to a centre axis (A-A) of the tubular screen (10, 30) and a component in the parallel direction to the centre axis (A-A) of the tubular screen (10, 30).
2. A screen system (1, 2, 3) according to claim 1, characterized in that in the case of the ultrasonic excitation the amplitude of the ultrasonic excitation at a contact point (115, 315) to the tube (11) or to the screen frame (31) has a component in the vertical direction to the centre axis (A-A) of the tubular screen (10, 30) and a component in the parallel direction to the centre axis (A-A) of the tubular screen (10, 30).
3. A screen system (1, 2, 3) according to claim 2, characterized in that at least one feed line sound conductor (14, 24, 34) has at least one curved region.
4. A screen system (1, 2, 3) according to claim 3, characterized in that the curved region has an angle of curvature which is greater than 0 degrees and is a maximum of 90 degrees.
5. A screen system (1, 2, 3) according to claim 4, characterized in that the angle of curvature is 90 degrees.
6. A screen system (1, 2, 3) according to a preceding claim, characterized in that the at least one feed line sound conductor (14, 24, 34) has a diameter of 12 mm.
7. A screen system (1, 2, 3) according to a preceding claim, characterized in that at least one feed line sound conductor (14, 24, 34) is screwed or welded to the surface of the tube (11) or the screen frame (31).
8. A screen system (1, 2, 3) according to a preceding claim, characterized in that at least one ultrasonic converter (13) is screwed to at least one feed line sound conductor (14, 24, 34).
9. A screen system (1, 2, 3) according to a preceding claim, characterized in that more than one ultrasonic converter (13) and more than one feed line sound conductor (14, 24, 34) are present.
10. A screen system (1, 2) according to claim 1, characterized in that more than one feed line sound conductor (14, 24, 34) is present, and the tube (11) or the screen frame (31) is capable of being regulated with ultrasound by way of the feed line sound conductor (14, 24, 34), wherein the direction of the amplitude of the ultrasonic excitation through different feed line sound conductors (14, 24, 34) is different.
11. A screen system (1, 2, 3) according to a preceding claim, characterized in that the screen system (1, 2, 3) has a housing (15) which presents the escape of screening material into the environment, and all the ultrasonic converters (13) present are arranged outside the housing (15).
12. A centrifugal screening machine for a screen system (1, 2, 3) according to a preceding claim.
13. A method of operating a screen system (1, 2, 3) with a tubular screen (10, 30), which has a tube (11) which comprises at least one portion (12) with screen openings which are arranged directly in the wall of the tube, and/or which has a screen frame (31) and a screen cloth (32), in which the tube (11) or the screen frame (31) is excited to perform oscillations by means of ultrasound, characterized in that the tube (11) or the screen frame (31) is excited with an ultrasonic excitation, the amplitude of which has a component in the vertical direction to a centre axis (A-A) of the tubular screen (10, 30) and a component in the parallel direction to the centre axis (A-A) of the tubular screen (10, 30).
14. A method according to claim 13, characterized in that the amplitude which has a component in the vertical direction to a centre axis (A-A) of the tubular screen (10, 30) and a component in the parallel direction to the centre axis (A-A) of the tubular screen (10, 30) is produced by precisely one feed line sound conductor (14, 24, 34).
15. A method according to claim 13, characterized in that the amplitude which has a component in the vertical direction to a centre axis (A-A) of the tubular screen (10, 30) and a component in the parallel direction to the centre axis (A-A) of the tubular screen (10, 30) is produced by more than one feed line sound conductor (14, 24, 34).
16. A method according to a preceding claim, characterized in that the frequency of the ultrasonic excitation is varied.
17. A method according to claim 16, characterized in that the frequency of the ultrasonic excitation is varied continuously in a range of between 32 kHz and 38 kHz.
18. Use of a method according to any one of claims 13 to 17 for the operation of a centrifugal screening machine.

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