WO2019121005A1

WO2019121005A1 - Fine sieve machine and method for operating a fine sieve machine

Info

Publication number: WO2019121005A1
Application number: PCT/EP2018/083602
Authority: WO
Inventors: Klaus Fennenkötter; Fabian Rölver; Michael Stichling
Original assignee: Haver & Boecker Ohg
Priority date: 2017-12-19
Filing date: 2018-12-05
Publication date: 2019-06-27
Also published as: EP3727709A1; DE102017130595A1

Abstract

The invention relates to a method for operating a fine sieve machine (1) having at least one sieve deck (10) for receiving at least one sieve covering (21) and at least one ultrasonic vibration stimulator (23) for generating ultrasonic vibrations, which are transferred to the sieve covering (21). The method is characterized in that the at least one ultrasonic vibration stimulator (23) is operated in a pulsed manner, wherein the ultrasonic vibration stimulator (23) repeatedly switches between a first operating mode, having a first vibration amplitude, and a second operating mode, having a second vibration amplitude, which is lower compared to the first. The invention further relates to a fine sieve machine (1) having at least one sieve deck (10) for receiving at least one sieve covering (21) and at least one ultrasonic vibration stimulator (23), which is designed to carry out such a method.

Description

Fine screening machine and method for operating a fine screening machine

The invention relates to a Feinsiebmaschine with at least one screen deck for receiving at least one Siebbelags and at least one ultrasonic vibrator for generating vibrations that are transferred to the screen covering. The invention further relates to a method for operating such a fine screening machine.

Fine screening machines are used for separating or classifying screenings with grain sizes in the range of a few tens of micrometers to a few millimeters. In contrast to screening machines with free-swinging screen box screen decks are usually static festste starting in such Feinsiebmaschinen. Used screen coverings are defined at least at two of their edges within the screen deck, for example by being braced in at least one direction Rich within the screen deck by means of a clamping device. Below the screen coverings are usually two or more Schwingungsanre ger, also called vibrator, arranged, for example, have arranged on a vibrating drive beam transverse Erregerleis th. The exciter bars can be excited in different ways to vibrate.

From the document DE 200 08 762 U1, for example, such a sieve machine with an unbalance motor for vibration generation is known. As a special feature, an imbalance mass of the imbalance motor can be changed in this machine so that an amplitude of the vibration excitation can be set to at least two different values. It is thus possible example, cleaning intervals in which the vibration excitation takes place with a deviating from the normal screening amplitude, adjust regularly, in which due to the changed vibration conditions of the Siebbelags stuck grains ("plug grains") are removed.

The document WO 2013/152765 A1 describes a screening machine of the type mentioned in the introduction, in which an ultrasonic vibration generator is coupled to the screen lining in order to excite it at a high frequency between 30 and 38 kHz (kilohertz) to oscillate. In embodiments, excitation with ultrasound is advantageously described in addition to excitation at lower frequencies in the range of 100 Hz (Hertz). The ultra Sound stimulation enhances a self-cleaning effect of the screen covering and reduces adhesion of the screenings to the screen surface.

In practice, so far suggestions of a sieve are used exclusively via Ult ultrasound only for smaller fine screening machines, for example in the field of analysis. For fine screen machines with higher throughput, ultrasound is usually only used as a support for screen cleaning. Through the use of different systems for vibration excitation increases all the more recent design effort and the cost of a Feinsiebmaschi ne.

It is therefore an object of the present invention, a fine screening machine of the type mentioned above, which is also suitable for screening of larger material throughputs to create, in which a screening is done effectively with an ultrasonic excitation of Siebbelags. It is a further object to provide an operating method for such a fine screening machine.

This object is achieved by a fine screening machine or a Betriebsver drive for such Feinsiebmaschine with the characteristics of the respective independent claim. Advantageous embodiments and further developments are the subject of the dependent claims.

In a method according to the invention for operating a Feinsiebma machine of the type mentioned, the at least one ultrasonic vibrator operated pulsed by repeatedly between a ers th operating mode with a first oscillation amplitude and a second mode of operation with a second, compared to the first smaller vibra tion amplitude of at least one Ultrasonic vibrator ge is changed.

In the first mode of operation, the larger first amplitude of the ultrasonic vibrator leads to a jumping movement of the individual grains of the screenings through which the screenings can be moved laterally on the one hand (eg due to a tendency of Siebbelags) and on the other in a high Fre quenz on the screen cover incident. The grains of the screenings have accordingly often the opportunity to pass through a mesh of Siebbelags. The high frequency of ultrasonic vibration generation in the range of several to several tens of kilohertz leads to an effective screening process. In the operation of the ultrasonic vibrator, however, a layer or cloud, in particular a fine fraction of the material to be screened, can be permanently located above the screen lining due to internal shocks during the operation of the ultrasonic oscillator having the large first amplitude. Part of the grains of the screenings thus floats permanently or at least for times that are long compared to a mean residence time of the grains on the screen lining. Accordingly, these grains rarely come in contact with the screen lining and can not pass through it, even if they would have due to their grain size.

The regular operation according to the invention of the at least one ultrasound oscillator having the smaller second amplitude causes the cloud of these grains to settle and, correspondingly, to screen these grains as well. The regular lowering of the amplitude of the ultrasonic excitation thus leads to an even more effective screening process and a higher material passage through the screen lining.

In this case, the second smaller oscillation amplitude can also be zero. The at least one ultrasonic vibration generator is thus switched back and forth between an active operating phase (first operating mode) and a resting phase (second operating mode).

Preferably, in the method, the first and the second operating mode change regularly. More preferably, the at least one ultrasonic vibration exciter is operated for a first time period in the first loading operating mode, which is shorter than a mean residence time of non-sieved Siebgutteilchen on the screen covering. In this way, it is sufficient Siebgutteilchen experienced during their average length of stay on the Siebbelag also the second mode of operation, in which the settling is supported on the Siebbelag. A suitable value for the first period of time depends on various parameters of the screening process, i.a. the properties of the screenings (density, size distribution, etc.). However, it has been shown that in typical fine-mesh processes, a first time duration between 0.1 s (seconds) and 10 s and in particular between 0.5 s and 3 s is advantageous.

A suitable value for the second time period is advantageously chosen to be at least so large that a large part of the "floating" grains of the screenings material can settle. On the other hand, a too long selected second time decreases the material throughput. The optimum value of the second time period is dependent on the parameters of the screening process, with advantageous times between 0.01 s and 5 s and in particular between 0.05 s and 1 s.

By increasing the efficiency and the material throughput in the inventions to the invention process this can be advantageously carried out exclusively with ultrasonic vibration generators. In this way, manufacturing, operating and maintenance costs compared to a Feinsiebmaschi ne, in the ultrasonic vibrator in addition to e.g. Unbalance moto ren used reduced.

Another advantage is that due to the increased efficiency of Siebprozes ses screen coverings can be used, which have a substantially quadrati cal mesh geometry. This applies even if the Siebbe läge strongly inclined to a horizontal orientation who used the. In such a case, sieve coverings are often used with longitudinal meshes according to the prior art, which are longer in the direction of the slope than in the transverse direction. However, these are significantly more expensive than the Siebbe lags with square mesh geometry and regularly lead to a poorer Ansiebequalität, as elongated particles (so-called "fish") can also pass through the Siebbelag.

A fine screening machine according to the invention with at least one screening deck for receiving at least one screen covering and at least one ultrasonic vibration exciter is characterized in that it is set up to carry out such a method. This results in the advantages mentioned in connection with the method.

In an advantageous embodiment of the Feinsiebmaschine are for vibra tion excitation for each Siebbelag two ultrasonic vibration exciter before seen, the spaced apart in the longitudinal direction from each other act on the respective Siebbelag.

Preferably, a transmission of the vibration of the ultrasonic vibration exciter takes place indirectly, for example via a vibration transformer in the form of, for example, a frame with a rectangular basic shape. The screen lining is then tensioned by an externally arranged clamping device and thereby pressed onto the vibration transmitter. Thus, a transfer can take place on a screen lining, which is not firmly connected to a frame, which simplifies the logistics and storage of the screen coverings. In addition, in the case of a Siebbelagswechsels the change time is significantly reduced because the vibration transformer does not have to be glued to the screen lining.

In a further advantageous embodiment of the fine screening machine, the at least one screen covering has an inclination of at least 20 ° (degrees) and preferably at least 30 ° with respect to a horizontal. Preferably, a Siebbelag is used with a substantially square mesh geometry ver.

A fine screening machine according to the invention can be constructed as a single or multi-deck screening machine. Within a sieve decks, sieve units arranged one behind the other can be present, each of which comprises a sieve bed with at least one ultrasonic vibration exciter. In this case, at least two of the screen coverings of a screen deck can be inclined to different degrees in order, on the one hand, to achieve the best possible material transport and, on the other hand, the best possible separation of the various fractions.

The invention will be explained in more detail below with reference to exemplary embodiments with the aid of figures. The figures show:

Fig. 1 is a schematic isometric view of a multi-deck fine screening machine;

Fig. 2 is a schematic isometric view of a single-deck fining machine; and

3 shows a schematic longitudinal section through a screen lining with ultrasonic vibrators.

Fig. 1 shows a fine screening machine 1 in an isometric schematic representation in a first embodiment. The same reference numerals in this as in all subsequent figures identify the same or equivalent elements.

The fine screening machine 1 comprises in the illustrated embodiment, three superimposed screen decks 10. The number of three screen decks 10 is exemplary. In alternative embodiments of the fine screening machine 1, the Number of screening decks 10 also be less than or greater than three. In addition, an operating method in accordance with the invention can also be used in a single-deck flattening machine (see FIG. 2).

The screen decks 10 are inclined with respect to a horizontal orientation, arranged here by way of example at an angle of about 45 degrees. It is an inlet chute 2 to the task of screenings on the top screen deck 10 is provided. A release of the screened or classified Siebguts via delivery shafts 3 to the side or down. The upper screen deck 10 is covered by a cover 4 to minimize the ingress of contaminants into the screenings. The fine screening machine 1 is mounted on the lower screen deck mounting feet 5 on a frame, not shown here.

In Fig. 2 is reproduced as a further example of a Feinsiebmaschine 1 Eindeck- Feinsiebmaschine. In its basic structure corresponds to in Fig.

2 shown Feinsiebmaschine 1 of the first embodiment.

In the case of the fine screening machine 1 shown in FIG. 2, the screening deck 10 has side parts 11, between which three screening units 20 are used by way of example. The screening units 20 are arranged in the longitudinal direction of the screen deck 10 hinerei nander, so that a Siebgutstrom from the inlet chute 2 com mend the screening units 20 successively in Fig. 2 from top right to bottom left through. The inclination of the screening units 20 varies, wherein the first in the direction of the screenings Siebeinheit 20 has a steeper orientation than the second and this in turn has a steeper orientation than the third screening unit 20. Apart from the orientation, the screening units 20 each have a same structure. It is noted that the number of three screen units 20 in the screen deck 10 here is purely exemplary. An in accordance with the operation method can be implemented even with a single screen unit with a screen covering.

In the side panels 11 of the screen deck 10 20 associated access openings are introduced on each side of the respective you leg. The edges of the access openings are provided with a circumferential profile seal. Each of the access openings is closed by a flap 12.

In the embodiment of FIG. 2, the cover 4, which covers the screen deck 10 upwards, in several parts, so that each screen unit 20 with a eige cover NEN 4 can be covered. Of the covers 4 is shown in the Example, only the first screen unit 20 assigned mounted. In the other two screening units 20, the cover 4 is removed in order to represent the structure of the screening units 20 can.

Each of the screening units 20 has a screen covering 21 which extends over the entire surface over the screen unit 20. This is shown in FIG. 2 only for the lower of the screening units 20. In the middle of the screening units 20, the screen covering 21 is omitted in order to be able to depict the components arranged below the screen lining 21.

Below the Siebbelags 21 excitation transformer 22 are provided, vorlie ing two excitation transformer 22 for each Siebbelag 21, which in this exemplary embodiment are designed as a frame with a rectangular basic shape. Corners of the frame are preferably rounded.

Each of the excitation transformers 22 is coupled to an ultrasonic vibrator 23. From this generated vibrations in the ultrasonic range between a few and a few tens of kilohertz are transmitted to the excitation transformer 22 and from there to the Siebbelag 21. The selected number of two excitation transmitters 22 and correspondingly two ultrasonic vibrators 23 per screen covering 21 can be varied in alternative designs of the fine screening machine. Any number of ultrasonic vibrators 23 per excitation transformer 22 is possible. It can be one or more excitation transformer 22 per Siebbe lay 21 are used. The number of selected excitation transformer 22 and ultrasonic vibrators 23 is dependent on the total be required sound power transmitted to the screen covering and the screenings who should, as well as the size of Siebbelags 21. Furthermore, a pos as homogeneous distribution of sound energies should the surface of Siebbelags 21 take place. Areas with too little sound excitation can lead to unwanted material accumulation.

Each screening unit 20 also has a receiving and tensioning device, with which the screen lining 21 is fastened and tensioned within the screening unit 20. This receiving and tensioning device is not marked separately in FIG.

FIG. 3 shows a longitudinal section through the screen lining 21 of a screening unit 20. In this figure, it can be seen that the screen lining 21 is located between an ner receiving strip 24, with which it is connected to the fluid, and a clamping conductor 25, in which it is hooked, is stretched in the longitudinal direction. Recording strip 24 and clamping bar 25 are part of the aforementioned receiving and tensioning device. In the example shown, a screen lining 21 is used with anmon ended recording bar 24 in the fine screening machine 1. However, in this example, the screen lining 21 is not mounted on a separate frame, but maintains its shape and stability through the tensioning process. Before given to the screen deck 10, for example, mounted on the side panels 1 1 you arranged treatment strips that easily overlap the screen cover 21 in the edge area to prevent screenings laterally next to the screen cover 21 can go down through the screen level. Said sealing strip can be in two parts and also clamp the screen lining in sections or over its entire length.

Below the Siebbelages 21, the two are already arranged from the in conjunction with Fig. 2 said excitation transformer 22. These are positioned so that the screen lining 21 presses after the distortion on the excitation transmitter 22, so that a good mechanical contact between the excitation transformer 22 and the screen lining 21 is established, which was to effec tive ultrasonic transmission from the excitation transformers 22 on the Siebbe 21 leads.

Each exciter transformer 22 is coupled to an ultrasonic vibrator 23. The ultrasonic vibrator 23 may be a piezoelectric transducer or an electromagnetically operating transducer.

Each of the ultrasonic vibrator 23 is connected to a Ultraschallgenera tor 31, which provides the necessary for operating the ultrasonic vibrator 23 electrical signal. In an alternative embodiment, it is possible to operate both ultrasonic vibration generators 23 with the aid of only one common generator 31. Only purely by way of example and schematically are the generators 31 below the ultrasonic exciter 23 arranged. In general, they are outside the fine screening machine 1 in a corresponding control arrangement for the Feinsiebma machine. 1

In an operating method according to the application for a fine screening machine, for example for the fine screen method described in connection with FIGS. Machine 1, the at least one ultrasonic vibrator 23 is not operated continuously, but pulsed.

In the arrangement shown in Fig. 3 this is achieved by a generator 31 superordinate control device 30, which outputs a corresponding pulse signal for pulsed operation of the generators 31. The Steuereinrich device 30 may be formed as shown externally or internally in the Ultraschallgenerato Ren 31.

Due to the pulsed operation of the ultrasonic generators 31, the ultrasonic vibrator 23 are ben for a certain first period of time, which may be in the range of a few tenths of seconds to a few seconds Be. This is followed by a pause for a second period of time, which may be in the range of a few hundredths of a second to a few seconds. The second time period is also referred to below as the pause time. The operating modes - active operation and pause - alternate regularly and repeatedly.

The active operation of the ultrasonic vibrator 23 leads to a vibrational and / or hopping movement of the individual grains of the material to be screened by the Siebgut moves on the one hand laterally and on the other impinges at a high frequency on the Siebbelag 21 and correspondingly often has the opportunity to pass through a mesh of Siebbelags 21. The high fre quency of vibration excitation leads to an effective screening process.

In active operation of the ultrasonic vibrator 23, however, a layer or cloud, in particular a very fine fraction of Siebgu tes form, which is due to internal shocks during the turn-on of the ultrasonic generator 23 approximately permanently over the screen lining 21 be. Due to the floating state of the grains of the screenings they do not or rarely come into contact with the screen lining and can not pass through this accordingly, even if they would have due to their grain size.

The regular interruption of the active operation of the ultrasonic vibrator 23 according to the invention causes the cloud of these grains to settle and, correspondingly, to screen these particles as well. The regular shutdown (or even operation with low rer amplitude) of the ultrasonic vibrator 23 thus leads to a even more effective screening process and a higher material passage through the screen lining 21st

The turn-on and turn-off of the ultrasonic vibrator 23 should be selected depending on the screenings and also depending on the particle size distribution in the screenings so that within the times that Siebgut moves on average in the range of Siebbelags 21, at least one but preferably several break times from Siebgut be experienced. The pause time itself should be chosen so long that the material is allowed to settle due to poor strength. In practical operation, both on and off times in the range of a few 100 ms to a few seconds have been found to be particularly advantageous.

The increased screening throughput by the method according to the application allows advantageous even with Feinsiebmaschinen to use the Siebbeläge 21 at a relatively high inclination of 10, ° 20 ° or more and allows the United use of Siebbelägen 21 with a square mesh geometry. In order to be able to achieve sufficiently high sieve flow rates without the pulse method according to the application, linings with long stitches have hitherto been used in particular in fine screening machines with strongly inclined screen coverings. In these, the dimension of the stitches in the longitudinal direction is greater than in the transverse direction. However, these screen coverings are compared to the screen coverings with square Ma rule dimensions comparatively expensive and have a lower stand time.

LIST OF REFERENCES

1 fine screen machine

2 intake chute

3 discharge shaft

4 cover

5 mounting foot

10 sieve deck

1 1 side panel

12 access door

20 sieve unit

21 Screening

22 excitation transformers

23 ultrasonic vibrators

24 recording bar

25 clamping bar

30 control device

31 ultrasonic generator

Claims

claims

A method of operating a fine screening machine (1) having at least one screen deck (10) for receiving at least one screen pad (21) and at least one ultrasonic vibration pickup (23) for generating ultrasonic vibrations transmitted to the screen pad (21) be, characterized in that

the at least one ultrasonic vibration exciter (23) is operated pulsed ben, the ultrasonic vibration exciter (23) repeatedly between a first operating mode with a first Schwingungsamplitu de and a second operating mode with a second, compared to the first smaller amplitude of oscillation changes.

2. The method of claim 1, wherein the second smaller vibration amplitude is zero.

3. The method of claim 1 or 2, wherein the first and the second operating mode Be regularly alternate.

4. The method according to any one of claims 1 to 3, wherein the at least ei ne ultrasonic vibration exciter (23) is operated for a first period of time in the first operating mode, which is shorter than an average residence time of not sieved Siebgutteilchen on the Siebbelag.

5. The method of claim 4, wherein the first time period is between 0.1 s and 10 s and preferably between 0.5 s and 3 s.

6. The method according to any one of claims 1 to 5, wherein the at least ei ne ultrasonic vibration exciter (23) is operated for a second period of time in the second operating mode, which is between 0.01 s and 5 s and preferably between 0.05 s and 1 s is.

7. The method according to any one of claims 1 to 6, wherein the Siebbelag (21) is excited only by ultrasound.

8. The method according to any one of claims 1 to 6, wherein the Siebbelag (21) has a substantially square mesh geometry.

9. fine screening machine (1) having at least one screen deck (10) for receiving at least one Siebbelags (21) and at least one ultrasonic vibration exciter (23), characterized in that

the fine screening machine (1) is set up to carry out a method according to one of the preceding claims.

10. Fine screening machine (1) according to claim 9, wherein the vibration excitation for each Siebbelag (21) two ultrasonic vibration exciter (23) see pre-spaced from each other in the longitudinal direction of the respective Siebbelag (21) act.

1 1. Fine screening machine (1) according to claim 9 or 10, wherein the at least one screen covering (21) has an inclination of at least 10 ° and preferably at least 30 ° with respect to a Florizontalen.

12. fine screening machine (1) according to one of claims 9 to 1 1, wherein the at least one screen covering (21) has a substantially square Ma rule geometry.

13. Fine screening machine (1) according to one of claims 9 to 12, comprising at least two longitudinally within a screen deck (10) hinerei nander arranged sieve units (20) each comprising a Siebbelag (21) with at least one ultrasonic vibration exciter (23) ,

14 fine screening machine (1) according to claim 13, wherein at least two of the Siebbeläge (21) of a screen deck (10) are inclined to different degrees.