WO2008040540A1

WO2008040540A1 - Device for the ultrasonic excitement of a screen fabric mounted in a screen frame

Info

Publication number: WO2008040540A1
Application number: PCT/EP2007/008612
Authority: WO
Inventors: Jürgen KISING
Original assignee: Artech Systems Ag
Priority date: 2006-10-05
Filing date: 2007-10-04
Publication date: 2008-04-10
Also published as: DE102006047592B4; DE102006047592C5; DE102006047592A1

Abstract

Disclosed is a device for ultrasonically exciting a screen fabric (1) mounted in a screen frame (3). Said device comprises i) an ultrasonic converter (4), ii) a sound conveying system (7) with a transition piece (5; 5') and/or a feeding conductor of sound (6; 6'), iii) means for introducing the sound into the screen fabric (1), particularly conductors of sound (8). The sound conveying system (7) penetrates the screen frame (3) in a lead-through (12) and is fixedly connected to said screen frame (3).

Description

Device for stimulating a screen fabric enclosed in a sieve frame by means of ultrasound

The invention relates to a device for exciting a mesh enclosed in a sieve frame by means of ultrasound according to the preamble of claim 1.

It is known that through the excitation of the screenings of screening machines by means of ultrasonic waves, the throughput and the quality of the screenings material can be significantly improved. The ultrasonic vibrations reduce the resistance between the screen mesh and the grain, since the static friction is converted into sliding friction by the movement of the wire meshes with ultrasonic frequency and a vibration amplitude in the range of a few μm. This reduces friction and increases throughput. Furthermore, depending on the frequency and amplitude of the vibrating wires of the screen fabric, the grain experiences an acceleration force that breaks up existing powder bridges and prevents the formation of new powder pressures. The loosening of the powder increases its flowability.

To further improve the throughput of the screening machine, it is customary that the screening machine additionally low-frequency vibrations durchfuhrt that lead to high acceleration values of up to 4 g.

There are known several methods to enable a mesh with ^¬ means of ultrasonic vibrations in:

On the one hand there is a tuned to the resonance of this ultrasonic transducer, fitted on the Siebflache sound conductor let directly by means of an ultrasonic converter ^¬ as Re- sonator vibrate, as described in DE 44 18 175 Al. This embodiment proves to be disadvantageous in practice in that, as a result of its arrangement in the powder flow, the converter often causes caking or sticking of the powder due to local heating.

A sometimes used alternative arrangement provides to arrange the ultrasonic converter outside of the powder flow and to stimulate via a feed resonator connected to the vibration maxima of the feed resonator screen frame, as described for example in US 5,386,169. However, especially in the case of large screen surfaces, it is disadvantageous in this excitation that the ultrasonic energy is not distributed sufficiently over the entire screen fabric, so that in particular the center of the screen surface is not vibrated to any appreciable extent.

Therefore, it is also known to provide for excitation of the mesh fabric sound conductor, which can be excited by a Schalltransportssystem that is tuned according to the prior art usually on the ultrasonic converter, consisting of a Zuführschalleiter and possibly arranged between feed sound conductor and ultrasonic converter transition piece.

However, such arrangements lead to problems in connection with the low-frequency vibrations in which the screen frame is displaced by the screening machine. Because of the high accelerations, considerable forces act on the entire system, consisting of converter, transition piece, feed sound conductor and sound conductor, which can lead to damage and even break off of the arrangement, especially in the case of long-term use. While it is possible, a certain Stabilization by means of a mechanical angle, which is attached to the outer wall of the screening machine and the converter is supported to achieve. However, this type of attachment is impractical and it is not always guaranteed that it will be properly implemented in the field.

In addition to the durability problems described above is to be mentioned as a disadvantage of this arrangement that the protruding from the screen frame arrangement hampers its ease of use.

The object of the invention is to provide a generic device for exciting an enclosed in a sieve frame screen fabric by means of ultrasound, on the one hand allows the advantageous arrangement of the ultrasonic converter outside the powder flow and excitation of provided on the screen fabric sound conductors, but on the other hand by the low-frequency vibrations of the screening machine absorbs forces exerted on this arrangement, increases the stability of the system and allows easy handling of the sieve ring.

This object is achieved according to the invention by a device according to the features of patent claim 1.

The invention is based on the finding that an existing from a transition piece and / or a feed sound conductor Schalltransportsystem is passed through the screen frame in a passage and firmly connected thereto. This arrangement leads to the optimal absorption of the considerable forces through the screen frame and thus to a relief of the sound transport structure. Further, in this arrangement, the protrusion of parts from the screen frame can be limited to a single location on the edge of the screen frame, which greatly facilitates the handling of the screen frame. In a particularly advantageous embodiment, the connection of feed sound conductor and screen frame dustproof and / or gas-tight, whereby leakage of the material to be screened in the environment is efficiently avoided.

Preferably, a collar is provided on a component of the sound transport system in the region of the implementation. This allows optimal fastening and support of the sound transport system on the screen frame, so that the forces transmitted by the screen machine are optimally absorbed.

In this case, the collar is preferably arranged on the transition piece, but it can also be located on the feed sound conductor.

Particularly advantageous is the arrangement of the collar adjacent to the inside of the screen frame, as this prevents the penetration of fine Siebgutpartikeln in the implementation from the front.

But it is also possible to attach the collar adjacent to the outside of the screen frame. This facilitates, for example, the assembly.

Welding has proven particularly suitable for fastening the collar to the screen frame. However, it is possible to glue the collar to the screen frame, to pin it or to provide a thread on the collar and a matching mating thread in the interior of the passage through the screen frame, by means of which the collar and the screen frame can be screwed together. As particularly simple and efficient for the production has been found to attach the collar on the sound transport system by shrinking.

A further embodiment has proved to be particularly advantageous in which an insulating sleeve made, for example, of PTFE is slipped over the sound transport system in the region of the bushing, so that there is no direct contact between the sound transport system and the screen frame. In this way, an effective damping of the radial sound can be achieved.

It is advantageous for the connection of the sound transport system to the screen frame if there is a small-area, as far as possible, rigid connection between the feed sound conductor and the screen frame. This can be ensured in several ways: One way to do this is a pin which has at least penetrated the screen frame and the sound transport system penetrating, wherein the pin when an insulating sleeve is provided and this passes. Another possibility is to provide a connection via a fixed to the screen frame and the converter housing of the ultrasonic converter clamp. A third possibility is to use an amplitude reducer welded to the feed sound conductor and to the screen frame, the smaller contact surface of the amplitude reducer facing the feed sound conductor.

The screen frame of the system according to the invention may have any shape per se, preferably are angular or annular configurations. If a tuned transition piece and a tuned sound transport system are provided, the former can be made to modulate the sound amplitude.

At the feed sound conductor sound transducer can be mounted to optimize the entry of the sound energy to the screen fabric, the sound transmitter can be shaped, for example, plate-shaped or square.

A further preferred embodiment provides, in addition to a transition piece to provide a feed sound conductor whose side facing away from the transition piece is shaped like a siphon. This special design ensures that, despite the passage through a possibly narrow executed Siebrahmen a connected to the feed sound conductor sound conductor can be excited from below.

Reference to the following figures, embodiments of the invention will be explained in detail. Show it:

Fig.l: an inventive arrangement with circular

Sound conductor structure and feed sound conductor with siphon-shaped end area.

FIG. 2a shows the arrangement according to the invention from FIG. 1 in an enlarged view while blanking out the sound conductor, screen frame and screen fabric.

FIG. 2b: Arrangement analogous to FIG. 2a in an embodiment variant.

3 shows a SchnittZeichnung an intermediate piece according to the invention with collar. 4a shows an arrangement according to the invention with a circular screen frame in which a plate-shaped sound transmitter is arranged in the center of the screen surface between the sound transport system and the screen surface.

4b: an arrangement according to the invention, with a rectangular screen frame, in which two plate-shaped sound transmitters are arranged between the sound transport system and the screen surface.

FIG. 5 shows a section of the lead-through region in the arrangement shown in FIG. 4b in a sectional perspective along the connecting line AA 'in FIG. 4b.

6 shows an arrangement with an alternative passage through the sieve frame. Fig. 7 is a sectional view with an enlarged view of the connection between the sieve frame and sound conductor in a first embodiment of the invention

8 shows a sectional drawing with an enlarged representation of the connection between screen frame and sound conductor in a second embodiment of the invention

9 shows a sectional drawing with an enlarged representation of the connection between screen frame and sound conductor in a third embodiment of the invention

Unless otherwise stated, the same components in the figures are given the same reference numerals. Fig. 1 shows an embodiment of the device according to the invention for the excitation of the screen fabric 1 by means of ultrasound. An ultrasonic converter 4 arranged outside the screen frame 3 generates an ultrasonic wave, which is introduced into the sound transport structure 7 (FIGS. 2 a, 2 b) on the ultrasonic converter 4. The cylindrically symmetrical illustrated in the drawing adapter 5,5 'passes through the screen frame 3 and has a located outside of the screen frame part 5 and located within the screen frame part 5'. In this case, a collar 8 is provided on the adapted inner piece 5,5 'on the screen inside, which is attached to the screen frame 3. The attachment can be achieved by welding, gluing or riveting or in the presence of suitable threads by screwing. A more detailed illustration of the collar 8 can be seen in FIGS. 2 to 4.

FIG. 2 a shows an enlarged view of the arrangement according to the invention from FIG. 1, with blanking of sound conductor 2, screen frame 3 and screen fabric 1. In this illustration, in particular the collar 8 and the exact configuration of the feed sound conductor 6 can be seen more clearly. It is clear that the collar 8 is formed on a sleeve 9 in the embodiment shown here. This can be pushed onto the transition piece 5, 5 'together with the integrally formed collar 8 and then fixed by shrinking, gluing, welding or the like.

In the embodiment according to FIG. 2 a, a feed sound conductor 6 designed in a siphon shape in the end region is provided on the end of the adapted transition piece located in the screen interior, which is shown here in an embodiment with a square cross section. The siphon-shaped shaping allows the excitation of a sound conductor 2 from below through the in him merging feed sound conductor 6, wherein still up to the U-shaped bend at the bottom of the "siphon", the device is located substantially in the plane of the screen frame 3, which allows easy handling of the frame.

The variant shown in FIG. 2b with a linear feed sound conductor 6 'permits a further improved handling, since the entire arrangement lies in the plane of the sieve frame 3.

The collar 8 is advantageously arranged in the interior of the screen frame 3 in the attached state, as this tightness of the bushing 12 is ensured against the ingress of fine Siebgut- powders. But it is also conceivable to arrange it from the outside on the screen frame 3. The attachment of the collar 8 on the screen frame 3 is advantageously carried out by welding, but it is also possible to impart a thread on the collar, which can be screwed into a cut into the bushing (12) of the screen frame 3 counter thread, or the collar 8 with the screen frame 3 to gluing, riveting or pinning.

Further possible details of the arrangement according to the invention are shown in the sectional drawing of the transition piece 5, 5 'according to FIG. Here, the collar 8 emerges particularly clearly. It can also be seen that the transition piece 5, 5 'is made up of two axial sections of different diameters. In addition, a guide ring 11 is shown in FIG. 3, which enables the accurately fitting insertion of the transition piece 5, 5 'into the passage 12 of the sieve frame 3.

Figures 4a and 4b show further embodiments of the device according to the invention. For example, you can rightfully provide square or annular screen frame 3. Furthermore, these figures show systems according to the invention in which instead of a sound conductor 8 one or more dish-shaped sound transmitters 10 are excited. As a result, a good introduction of the sound energy and an improved distribution of the sound energy over the screen mesh 3 can be achieved.

Figure 5 shows details of the attachment of the transition piece 5, 5 'on the screen frame 3 based on a section through the embodiment shown in Figure 4b along the line AA', the figure is limited to a left partial section of the screen frame 3. On the ultrasonic converter 4, the transition piece follows with the first axial section 5 outside of the screen frame 3 and the second axial section 5 'within the screen frame 3. The passage through the screen frame 3 takes place in the passage 12. In the embodiment shown here, the collar 8 is integral with one Sleeve 8 is formed, which is pushed onto the transition piece 5,5 'and there z. B. is fixed by welding.

An alternative attachment of the transition piece 5, 5 'on the screen frame 3, Fig. 6. Here, the seal is not achieved by the welded collar 8, but by an insulating sleeve 13, which closes the gap between the transition piece 5' and nenlochflache the screen frame 3 , Advantage of this solution is that the radial vibration is damped to the frame.

To accommodate the acceleration forces a hole 14 is drilled with a diameter of 4 mm and pinned. Acoustically, this solution has the advantage that over the small contact surface of the pin to the screen frame 3 only very little sound energy is transferred to the screen frame 3, even if the pin is positioned at the maximum motion.

As described in detail above, it is thus possible to provide a device for exciting a screened fabric 3 enclosed in a screen frame 3 by means of ultrasound, which allows the advantageous arrangement of the ultrasonic converter 4 outside the powder flow and the excitation of sound filters 8 provided on the screen fabric 1 , At the same time it is able to absorb the forces exerted by the low-frequency vibrations of the screening machine on this arrangement forces to increase the stability of the system and to allow easy handling. This is achieved in a simple manner by passing a sound transport system 7 through the screen frame 3, wherein the sound transport system has a collar 8 which is attached to the screen frame 3 or alternatively by means of insulating sleeve 13 and pinning.

Figure 7 shows in cross-section an enlarged view of the connection between the sieve frame and sound conductor in a first embodiment of the invention. A sound transport system 7 passes through a screen frame 3. In the field of implementation, the sound transport system 7 is surrounded radially by an insulating sleeve 13, which in turn is radially embedded in a sleeve 9 made of metal, which in turn is followed radially a screen frame 3. The attachment is made by a pin 15, which passes through the screen frame, the sleeve 9, the insulating sleeve 13 and the sound transport system 7.

Figure 8 shows in cross-section an enlarged view of the connection between the sieve frame and sound conductor in a second embodiment of the invention. A sound transport system 7 passes through a screen frame 3. In the field of implementation is the sound transport system 7 radially surrounded by an insulating sleeve 13 which has at both ends in the longitudinal direction in each case a collar 8 which is fixed to the Schalltransprot system 7. Between the collar 8, a sleeve 9 is embedded in metal, which is welded to a screen frame 3. In the example shown in Figure 8, the metal sleeve 9 rests on a part of the collar and is not in direct contact with the sound transport system 7; but it could also be in direct contact.

Figure 9 shows in cross-section an enlarged view of the connection between the sieve frame and sound conductor in a first embodiment of the invention. A sound transport system 7 passes through a screen frame 3, to which an amplitude reducer 16 is welded. The small contact surface of the amplitude reducer 16 is welded to the sound transport system 7 and establishes a firm connection between the screen frame 3 and the sound transport system 7. Despite the connection between screen frame 3 and sound transport system 7 is ensured by this arrangement of the amplitude reducer 16 that only small vibration amplitudes are introduced into the screen frame 3 by the vibration of the sound transport system 7.

Reference s list of signs

1 screen mesh

2 sound conductors

3 sieve frames

4 ultrasonic converters

5 transition piece, section outside the screen frame

5 'transition piece, section inside the screen frame

6 supply sound conductor ("siphon")

6 'feed sound conductor

7 sound transport system

8 collar

9 sleeve

10 sound transformers

11 guide ring

12 implementation

13 insulating sleeve

14 hole, hole

15 pen

16 Ampiitudenreduzierer

Claims

claims

1. Device for exciting a sieve frame (3) surrounded by ultrasound, with - an ultrasonic converter (4), a sound transport system (7) with a transition piece (5,5 ') and / or a feed sound conductor ( 6, 6 '),

Means for initiating the sound in the screen cloth (1), in particular sound conductors (8) and / or Schallübertragern (10) characterized in that the sound transport system (7) in a passage (12) passed through the screen frame (3) and fixedly connected thereto is.

2. Device according to claim 1, characterized in that the connection between bushing (12) and sieve frame (3) is dust and / or gas-tight.

3. A device according to claim 1, characterized in that a collar (8) is provided on a component of the sound transport system (7) in the region of the passage (12).

4. A device according to claim 3, wherein a collar (8) is attached to the transition piece (5, 5 ') or to the feed sound conductor (6).

5. Device according to claim 3 or 4, characterized in that the collar (8) rests against the inside of the screen frame (3).

6. A device according to claim 3 or 4, wherein a

Collar (8) on the outside of the screen frame (3) is present,

7. A device according to any one of claims 3 to 6, wherein a collar (8) is welded, glued or pinned to the screen frame (3).

8. Device according to one of claims 3 to 6, characterized in that the collar (8) on the screen frame (3) facing side has a thread and that the passage (12) has a corresponding mating thread for screwing the collar (8) with the Screen frame (3).

9. The device according to one of claims 3 to 6, characterized in that the collar (8) on the sound transport system (7) is fixed by shrinking.

10.Vorrichtung according to any one of claims 3 to 9, d a d u r c h e c e n e c e s in that the collar (8) at a node of a upon excitation with the ultrasonic converter (4) forming standing ultrasonic wave in the sound transport system (7).

11.Vorrichtung according to claim 1, characterized in that the Sound transport system (7) in the region of the passage (12) through the screen frame (3) by an insulating sleeve (13) is surrounded such that there is no direct contact between the sound transport system (7) and the screen frame (3).

12. Device according to claim 11, characterized in that the insulating tube (13) consists of plastic, in particular of PTFE.

13. Device according to claim 1, characterized in that for connecting the sound transport system (7) to the Siebrah- men (3) a pin (15) is provided which at least the sieve frame (3) and the sound transport system (7) is penetrated penetrating.

14. The device according to claim 1, characterized in that the connection between feed sound conductor (6, 6 ') and screen frame (3) by a on the screen frame (3) and the converter housing of the ultrasonic converter (4) fixed clamp is made.

15. The device according to claim 1, characterized in that the connection between the feed sound conductor (6, 6 ') and the screen frame (3) by a Zuführschalleiter (6, 6') and on the screen frame (3) welded Amplitudenredu- zierer (16) is prepared ,

16. Device according to one of the preceding claims, characterized in that the sieve frame (3) is square or circular.

17. A device according to one of the preceding claims, wherein a transition piece (5, 5 ') is designed to modulate the amplitude of oscillation.

18. Device according to one of the preceding claims, characterized in that one or more sound transmitters (10) are attached to the feed sound conductor (6; 6 ').

19. Device according to claim 18, wherein a

Sound transformers (10) are plate-shaped or square.

20. Device according to one of the preceding claims, characterized in that the end section of the delivery sound conductor is configured in a siphon shape (6) or linearly (6 ').