Screening system, eddy-current screening machine, and use of a screening system or of an eddy-current screening machine

Abstract

A screening system (10) comprising at least one first substantially annular screen support (11) and a second substantially annular screen support (12); at least one pressure rod (14), which braces the screen supports (11, 12) with each other in such a manner that a compressive stress is produced between the screen supports (11, 12); at least one substantially cylindrical outer screen surface (13), which is clamped between the screen supports (11, 12); and at least one resonator (15) for the introduction of ultrasonic vibrations directly into the screen surface (13). The resonator (15) may be fastened to the screen surface (13) and essentially runs from the first screen support (11) to the second screen support (12). An eddy-current screening machine is also disclosed.

Claims

1. A screening system, including at least one first substantially annular screen support and a second substantially annular screen support, at least one pressure rod which braces the screen supports together in such a manner that compressive stress is generated between the screen supports, at least one screen surface which is substantially in the form of a lateral cylinder surface and is clamped between the screen supports, at least one resonator for introducing ultrasound vibrations directly into the screen surface, wherein the resonator is fastened on the screen surface and extends substantially from the first screen support to the second screen support.

2. The screening system according to claim 1, wherein the first screen support and the second screen support are formed substantially circular ring-shaped manner and the screen surface is formed substantially in the form of a circular lateral cylinder surface.

3. The screening system according to claim 1, wherein the resonator is held on the first screen support and/or on the second screen support.

4. The screening system according to claim 3, wherein the resonator comprises a first vibration node, on which it is held on the first screen support, and/or a second vibration node, on which it is held on the second screen support.

5. The screening system according to claim 4, wherein the resonator on the first vibration node is held on the first screen support by means of a first decoupling element and/or on the second vibration node is held on the second screen support by means of a second decoupling element.

6. The screening system according to claim 1, wherein at least one screen support comprises a sleeve-shaped portion on which the screen surface is fastened, as well as a collar-shaped portion which protrudes radially outwardly from the sleeve-shaped portion, on which the at least one pressure rod is fastened.

7. The screening system according to claim 1, wherein the screening system includes at least one ultrasound conductor, by means of which the resonator is actuatable by ultrasound vibrations, wherein the at least one ultrasound conductor is guided through a feed-through opening formed in the first screen support into an intermediate region formed between the first screen support and the second screen support.

8. The screening system according to claim 1, wherein the resonator extends substantially in the longitudinal direction from the first screen support to the second screen support.

9. The screening system according to claim 1, wherein the resonator is realized for introducing ultrasound vibrations which comprise substantially only a component in the longitudinal direction.

10. The screening system according to claim 1, wherein the resonator is fastened on the screen surface substantially along an entire length of the resonator.

11. The screening system according to claim 1, wherein the resonator is glued or soldered to the screen surface.

12. The screening system according to claim 1, wherein the resonator is arranged on an outer side of the screen surface and is fastened there to said outer side of the screen surface.

13. The screening system according to claim 1, wherein the screening system includes multiple resonators.

14. The screening system according to claim 13, wherein the multiple resonators are distributed uniformly around a circumference of the screen surface.

15. The screening system according to claim 7, wherein the screening system additionally includes one or multiple ultrasound converters for generating the ultrasound vibrations which are feedable to the at least one ultrasound conductor.

16. The screening system according to claim 1, wherein the screening system includes at least one third substantially annular screen support, at least two screen surfaces which are substantially in the form of a lateral cylinder surface and at least two resonators for introducing ultrasound vibrations into the screen surfaces, wherein a first of the screen surfaces is clamped between the first screen support and the second screen support and a second of the screen surfaces is clamped between the second screen support and the third screen support, at least one first of the resonators is adapted to introduce ultrasound vibrations directly into the first screen surface and at least one second of the resonators is adapted to introduce ultrasound vibrations directly into the second screen surface, the screening system additionally includes a first ultrasound conductor, by means of which the first resonator is actuatable by ultrasound vibrations, as well as a second ultrasound conductor, by means of which the second resonator is actuatable by ultrasound vibrations, the first ultrasound conductor is guided through a feed-through opening formed in the first screen support and the second ultrasound conductor is guided through a first feed-through opening formed in the first screen support and a second feed-through opening formed in the second screen support.

17. The screening system according to claim 16, wherein the first ultrasound conductor is connected or connectable to a first ultrasound converter and the second ultrasound conductor is connected or connectable to a second ultrasound converter, wherein the first ultrasound conductor and the second ultrasound conductor are connected or connectable to one and the same generator.

18. The screening system according to claim 16, wherein the second ultrasound conductor and the second resonator are offset in the circumferential direction in relation to the first ultrasound conductor and the first resonator with reference to a central axis of the screening system by an angle within the range of between 90 and 270.

Description

(1) The invention is explained in detail below by way of exemplary embodiments and several drawings, in which

(2) FIG. 1: shows a first perspective view of a first screening system according to the invention, but without a screen surface;

(3) FIG. 2: shows a second perspective view of the screening system according to FIG. 1 with a screen surface;

(4) FIG. 3a: shows a detail of a side view of part of a first screen support of the screening system and of a first decoupling element according to FIGS. 1 and 2;

(5) FIG. 3b: shows a detail of a side view of part of a second screen support of the screening system and of a second decoupling element according to FIGS. 1 to 3a;

(6) FIG. 4a: shows a detail of a top view of part of the first screen support and of the first decoupling element according to FIGS. 1 to 3b;

(7) FIG. 4b: shows a detail of a top view of part of the second screen support and of the second decoupling element according to FIGS. 1 to 4a;

(8) FIG. 5a: shows a perspective view of a second screening system according to the invention;

(9) FIG. 5b: shows a perspective sectional view of the second screening system according to the invention;

(10) FIG. 6: shows a side sectional view through the second screening system according to the invention according to FIGS. 5a and 5b;

(11) FIG. 7: shows an outlined side view of a third elongated screening system according to the invention with three screen supports, two screen surfaces, two resonators and two ultrasound conductors;

(12) FIG. 8: shows a photo of a detail of a fourth screening system according to the invention with anti-rotation safeguard;

(13) FIG. 9a: shows a perspective view of a detail of a fifth screening system according to the invention, but without anti-rotation safeguard;

(14) FIG. 9b: shows a perspective view of the anti-rotation safeguard of the fifth screening system according to the invention;

(15) FIG. 9c: shows a perspective view of a detail of the fifth screening system according to the invention with anti-rotation safeguard according to FIG. 9b;

(16) FIG. 10a: shows a perspective view of a sixth screening system according to the invention with a groove and an O-ring seal;

(17) FIG. 10b: shows a side view of the sixth screening system according to the invention according to FIG. 10a;

(18) FIG. 10c: shows a top view of the sixth screening system according to the invention according to FIGS. 10a and 10b;

(19) FIG. 10d: shows an enlarged view of the detail A from FIG. 10b;

(20) FIG. 11a: shows a side sectional view of a screen support of the sixth screening system according to the invention;

(21) FIG. 11b: shows an enlarged view of the detail X from FIG. 11a.

(22) The screening system 10 shown in FIG. 1 includes a first annular screen support 11 and a second circular ring-shaped screen support 12, both of which are designed identically to one another. In other embodiments not shown here, however, it is also conceivable for the two screen supports 11, 12 not to be designed identically to one another. A screen surface 13, which is in the form of a circular lateral cylinder surface and extends in a longitudinal direction L, can be clamped between the screen supports 11, 12; said screen surface 13, however, is better illustrated firstly in FIG. 2. Each of the two screen supports 11, 12 comprises in each case a sleeve-shaped portion 16 or 17 as well as a collar-shaped portion 18 or 19 which protrudes radially outward from the sleeve-shaped portion 16 or 17.

(23) For fastening the screen surface 13 on the outer side of the sleeve-shaped portions 16, 17 and tensioning the screen surface 13 axially, a respective clamping ring 27, 28 is provided on both screen supports 11, 12, of which only the clamping ring 28 arranged on the second screen support 12 is visible here. The sleeve-shaped portions 16, 17 additionally have in each case four recesses 29 or 30, which are distributed uniformly in the circumferential direction and extend in the direction of the respectively other screen support 11, 12, that is to say also in the longitudinal direction L.

(24) Four pressure rods 14, which are distributed uniformly in the circumferential direction and extend along the longitudinal direction L from the first screen support 11 to the second screen support 12, are fastened on the collar-shaped portions 18, 19. In this case, the pressure rods 14 are fastened on the first screen support 11 as a result of welding or screw connection and are connected to the second screen support 12 by means of a clamping device which is as described above. In this way, the pressure rods 14 brace the screen supports 11, 12 together in such a manner that compressive stress is generated between the screen supports 11, 12.

(25) Two hollow-profile-shaped resonators 15 which have a rectangular cross section, are diametrally opposed and consequently uniformly distributed in the circumferential direction, additionally extend along the longitudinal direction L from the first screen support 11 to the second screen support 12. The resonators 15 can consist, for example, of chrome steel or plastics material.

(26) The resonators 15 comprise in each case a first and a second vibration node. At the first vibration node, the resonators 15 are held on the first screen support 11 by means of a respective first decoupling element 22, and at the second vibration node they are held on the second screen support 12 by means of a respective second decoupling element 23. The ends of the resonators 15 are received in the recesses 29, 30 of the sleeve-shaped portion 16, 17.

(27) Four feed-through openings 24, which are distributed uniformly in the circumferential direction, are formed in the collar-shaped portion 18 of the first screen support 11. An ultrasound conductor 25 extends in each case through two oppositely situated feed-through openings of said feed-through openings 24 into an intermediate region 26 of the screening system 10 formed between the first screen support 11 and the second screen support 12. The ultrasound conductors 25 are guided through the feed-through openings 24 without contact such that no ultrasound vibrations are transmitted directly on the first screen support 11. They extend parallel to the longitudinal direction L of the screening system 10 and comprise a circular cross section.

(28) The screening system 10 can additionally include one or multiple ultrasound converters, not shown here, for generating the ultrasound vibrations which are feedable to the ultrasound conductors 25 and then to the resonators 15. The at least one ultrasound converter can be connected to the ultrasound conductors 25, for example, by a screw connection.

(29) FIG. 2 shows the entire screening system 10 with screen surface 13. The screen surface 13 is realized as a screen fabric and is produced as one entity of sections which all run parallel to the longitudinal direction L. In the longitudinal direction L, the screen surface 13 can comprise a length of within the range of between 100 mm and 1000 mm and a diameter of within the range of between 100 mm and 500 mm. It is fastened on the outer side of the sleeve-shaped portion 17, not shown here, of the second screen support 12 by means of the clamping ring 28. In addition, the screen surface 13 can also be bonded on the outer side of the sleeve-shaped portion 17. Other types of fastening of the screen surface 13, not shown here, are however also conceivable.

(30) The resonators 15 are fastened on the outer side of the screen surface 13 along their entire length as a result of bonding. Ultrasound vibrations can be introduced into the screen surface 13 by means of the two resonators 15. On account of the elongated realization of the resonators 15, they enable the generation of ultrasound vibrations which comprise substantially only a component in the longitudinal direction L of the screening system. The fastening of the resonators 15 along their entire length allows sound to be introduced into the screen surface 13 in a particularly effective manner.

(31) FIG. 3a shows a detailed side view for fastening the pressure rods 14 and the resonators 15 on the first screen support 11. As already mentioned, the ultrasound conductor 25 is guided through the feed-through opening 24 formed in the collar-shaped portion 18 without contact. The ultrasound conductor 25 is connected to the end face of the resonator 15 in order to be able to transmit ultrasound vibrations to said resonator. In a first vibration node, the resonator 15 is held on the collar-shaped portion 18 by means of the first decoupling element 22. The first decoupling element 22 is fixedly connected to the collar-shaped portion 18, for example by means of a weld connection. FIG. 4a shows a top view of substantially the same cutout. All in all, as a result of said design, ultrasound vibrations can only be transmitted to the resonator 15, not however also to the first screen support 11. No ultrasound vibration of the first screen support 11 is generated that is not necessary for the actual purpose of screening.

(32) The fastening on the second screen support 12 is developed in a different manner, as is produced from the views of details in FIGS. 3b and 4b. Here, namely, the second decoupling element 23 is not fixedly connected to the sleeve-shaped portion 19. Instead of which, a clamping device is present. Said clamping device includes a clamping element 31 which is provided with an external thread and is fixedly connected to the second decoupling element 23. A bore 20 is provided in the sleeve-shaped portion 19 of the second screen support 12. As a result of interaction between the external thread and the bore 20 and two clamping nuts, not shown here, the clamping element 31 and consequently also the resonator 15 can be fastened and braced on the sleeve-shaped portion 19 of the second screen support 12. In a similar manner, the pressure rod 14 can be fastened and braced in a bore 21 by means of a clamping device, not shown here in any detail. FIG. 4b shows a top view of the substantially identical cutout.

(33) Even during assembly, the decoupling elements 22, 23 protect the resonator 15, which is already fastened on the screen surface 13, against rotation, which could impair or destroy the fastening. In this way, it is possible in this exemplary embodiment to dispense with an anti-rotation safeguard shown in FIG. 8.

(34) The screening system 10 shown in FIGS. 1 to 4b can be used in an eddy-current screening machine, for example for control-screening, separating, loosening, recovering or fractionating screening material. For this purpose, the eddy-current screening machine can include a rotor which is arranged in an interior surrounded by the screen surface 13. By means of such a rotor, screening material situated in the interior can be excited to form an eddy current, as a result of which fine material can be conveyed outwardly through the screen surface 13, whilst coarse material can be conveyed to a coarse material outlet arranged on the end of the screen surface.

(35) The second screening system 10 according to the invention shown in FIGS. 5a and 5b also includes a first annular screen support 11 and a second circular ring-shaped screen support 12, both of which are designed in a substantially mirrored manner with respect to one another. A screen surface 13, which is in the form of a circular lateral cylinder surface and extends in a longitudinal direction L, is clamped between the screen supports 11, 12. The first screen support 11 comprises a sleeve-shaped portion 16 which can only be seen in FIG. 5b and a collar-shaped portion 18 which protrudes radially outwardly from the sleeve-shaped portion 16. In an analogous manner, the second screen support 12 comprises a sleeve-shaped portion 17 and a collar-shaped portion 19 which protrudes radially outwardly from the sleeve-shaped portion 17.

(36) In the case of this embodiment also, a respective clamping ring is provided for fastening the screen surface 13 on the outer side of the sleeve-shaped portions on both screen supports 11, 12. In contrast to the first exemplary embodiment according to FIGS. 1 to 4b, the sleeve-shaped portions here, however, do not include any recesses which extend in the direction of the respectively other screen support.

(37) Three pressure rods 14, which are distributed uniformly in the circumferential direction and extend along the longitudinal direction L from the first screen support 11 to the second screen support 12, are fastened on the collar-shaped portions 18, 19, only two of which, however, can be seen. The pressure rods 14 are fastened on the screen supports 11, 12 by means of clamping nuts 40.

(38) In addition, a resonator 15, which can consist, for example, of chrome steel or plastics material, extends along the longitudinal direction L from the first screen support 11 substantially to the second screen support 12. Said resonator 15 comprises a first bar-shaped portion 32 with a first end 33 and a second end 34 and a second bar-shaped portion 35 with a first end 36 and a second end 37. Only the first bar-shaped portion 32, but not also the second bar-shaped portion 35, is fastened on the outer side of the screen surface 13 by means of bonding. The first ends 33, 36 of the first bar-shaped portion 32 and of the second bar-shaped portion 35 are connected together by means of a first U-shaped portion 38, and the second ends 34, 37 of the first bar-shaped portion 32 and of the second bar-shaped portion 35 are connected together by means of a second U-shaped portion 39. The two bar-shaped portions 32, 35, the two U-shaped portions 38, 39 and a central axis M of the screening system 10 extend in a common radial plane.

(39) As can be seen from the side sectional view in FIG. 6, a feed-through opening 24, through which an ultrasound conductor 25 with a circular cross section extends into an intermediate region 26 of the screening system 10 formed between the first screen support 11 and the second screen support 12, is formed in the collar-shaped portion 18 of the first screen support 11. The ultrasound conductor 25 is held on the collar-shaped portion 18 by means of a fastening tube 45. On an axial end facing away from the first screen support 11 (not shown on the right in FIG. 6), the ultrasound conductor 25 is fastened on an ultrasound converter, not shown, by means of an indicated thread. Sleeves 46 between fastening tube 45 and ultrasound conductor 25 prevent screening material from escaping. On an axial end facing the first screen support 11 (on the left in FIG. 6), the fastening tube 45 is connected to the collar-shaped portion 18 by means of an intermediate piece 47. The intermediate piece 47 includes radial continuations, not visible in FIG. 6, with openings, through which screws can be screwed into the collar-shaped portion 18. In this way, the ultrasound conductor 25 is mounted so as to slide in the axial direction inside the fastening tube 45 and the sleeves 46.

(40) The fastening tube 45 protects, also during assembly, the resonator 15, which is already fastened on the screen surface 13, against rotation, which could impair or destroy the fastening. In this way, it is possible in this exemplary embodiment also to dispense with an anti-rotation safeguard shown in FIG. 8.

(41) By means of the ultrasound conductor 25, the first U-shaped portion 38 and consequently the first ends 33, 36 of the bar-shaped portions 32, 25 are actuatable by ultrasound vibrations. Bending vibrations, above all, can be introduced into the screen surface 13 by the resonator 15, in a radial direction with reference to the central axis M of the screening system 10. The transformation of a longitudinal vibration of an ultrasound conductor into a bending vibration, in this case, is performed by the first U-shaped portion 38. Naturally, in addition to the bending vibrations, proportions of other modes of vibration such as, for example, longitudinal vibrations, can also be present. The advantage of such a resonator 15, furthermore, is that the ultrasound can be introduced into the first bar-shaped portion 32 not only at the first end 33, but also at the second end 34 of the first bar-shaped portion 32 by means of the second bar-shaped portion 35 and the second U-shaped portion 39. A vibration that is more uniform over the length of the bar is generated in the first bar-shaped portion 32 in this way.

(42) The vibration amplitudes are particularly small on the first end 33 and on the second end 34 of the first bar-shaped portion 32. This results in the resonator 15 being fastened in a more reliable manner on the screen surface 13 as the bonded connection becomes detached less easily. In addition, the resonator 15 is adjustable to the frequency that excites it in a particular simple manner, for example, by adjusting the length of a slot 42 formed between the first bar-shaped portion 32 and the second U-shaped portion 32.

(43) FIG. 7 shows a third screening system 10 according to the invention which is realized as an elongated screening system. Said screening system includes a first substantially annular screen support 11, a second substantially annular screen support 12 and a third substantially annular screen support 51, the central axes M of which coincide and which are arranged in an equidistant manner. In addition, the screening system includes two pressure rods 14, only one of which can be seen here. Said pressure rods 14 brace the screen supports 11, 12, 51 together in such a manner that compressive stress is generated between the screen supports 11, 12, 51. The pressure rods 14 can extend from the first screen support 11 through the second screen support 12 to the third screen support 51. As an alternative to this, it is also conceivable for first pressure rods 14 to extend only from the first screen support 1 to the second screen support 12 and for second pressure rods 14 to extend only from the second screen support 12 to the third screen support 51. The pressure rods 14 can be fastened on the screen supports 11, 12, 51, for example, as shown in FIGS. 1 to 6.

(44) The screening system 10 additionally includes a first screen surface 13 which is substantially in the form of a lateral cylinder surface and is clamped between the first screen support 11 and the second screen support 12, as well as a second screen surface 52 which is substantially in the form of a lateral cylinder surface and is clamped between the second screen support 12 and the third screen support 51. The clamping of the screen surfaces 13, 52 is effected as in the previously described exemplary embodiments. In addition, the screening system 10 includes a first resonator 15 for introducing ultrasound vibrations directly into the first screen surface 13 and a second resonator 53 for introducing ultrasound vibrations directly into the second screen surface 52. The first resonator 15 is actuatable by ultrasound vibrations by means of a first ultrasound conductor 25 and the second resonator 53 are actuatable by with ultrasound vibrations by means of a second ultrasound conductor 54.

(45) The first ultrasound conductor 25 is guided through a feed-through opening 24 formed in the first screen support 11 into a first intermediate region 26 formed between the first screen support 11 and the second screen support 12. The second ultrasound conductor 54 is guided through a first feed-through opening 55 formed in the first screen support 11 and through a second feed-through opening 56 formed in the second screen support 12 into a second intermediate region 66 formed between the second screen support 12 and the third screen support 51. The second ultrasound conductor 54 and the second resonator 53 are offset by 180 in the circumferential direction with reference to the central axis M of the screening system 10 in relation to the first ultrasound conductor 25 and the first resonator 15, and are therefore diametrally opposed to one another. In this way, the ultrasound conductors 25, 54 have particularly little influence on one another. The ultrasound conductors 25, 54, similarly to as shown in FIGS. 1 to 6, can be held on the screen supports 11, 12, 51 by means of decoupling elements or fastening tubes which are not shown here. As an alternative to this or in addition to it, anti-rotation safeguard can also be provided, as shown in FIG. 8 and described below.

(46) The first ultrasound conductor 25 is connected to a first ultrasound converter 57 and the second ultrasound conductor 54 is connected to a second ultrasound converter 58. The first ultrasound converter 57 and the second ultrasound converter 58 are connected to one and the same generator 59. As an alternative to this, it is naturally also conceivable for both ultrasound conductors 25, 54 to be connected to one and the same ultrasound converter.

(47) A particularly space-saving arrangement for the elongated screening system 10 is produced in said embodiment as, amongst other things, the ultrasound conductors 25, 54 can be guided through at the same axial position (with reference to a longitudinal direction of the screening system 10).

(48) FIG. 8 shows a photo of a detail of a fourth screening system 10 according to the invention. This is also a screening system 10 with two substantially annular screen supports (only a first screen surface 11 of which can be seen here), a screen surface 13 in the form of a lateral cylinder surface and a resonator 15 which is realized similarly to the resonator 15 shown in FIGS. 5a to 6 and is fastened directly on the screen surface 13. The screening system 10 includes an ultrasound conductor 25, by means of which the resonator 15 is actuatable by ultrasound vibrations. The ultrasound conductor 25 comprises a rectangular cross section and is guided through a feed-through opening 24 which is formed in a collar-shaped portion 18 of the first screen support 11.

(49) The screening system 10 additionally includes an anti-rotation safeguard 60. Said anti-rotation safeguard comprises a plate 62 which is held at a distance from the feed-through opening 24 by means of two spacer elements 63, in the direction away from the first screen support 11 and toward the screen surface 13. Radial continuations 65, which are fastened on the collar-shaped portion 18 of the first screen support 11 by means of screws 64, are integrally formed on the spacer elements 63. The plate 62 comprises an anti-rotation protection opening 61, which is realized as an elongated hole, through which the ultrasound conductor 25 is also guided.

(50) As a result of realizing the anti-rotation protection opening 61 as an elongated hole and as a result of the rectangular cross sectional form of the ultrasound conductor 25 and as a result of suitable dimensioning, the anti-rotation protection opening 61 only allows rotation of the ultrasound conductor 25 about its longitudinal axis within a predetermined angular range. For example, the angular range can be 10 such that the anti-rotation protection opening 61 permits a rotation of the ultrasound conductor 25 around a central angular position in both directions of rotation by a maximum of 5. In this way, the fastening of the resonator 15 on the screen surface 13 can be protected when a holding structure, holding the ultrasound conductor 25, for example a fastening tube 45 shown in FIG. 6, is fastened on the screen support 13. Sealing means, not shown here, which can prevent the screening material passing though the feed-through opening 24, can be introduced between the plate 62 with the anti-rotation protection opening 61 formed therein and the screen support 11.

(51) As the fifth exemplary embodiment, FIGS. 9a to 9c show a slightly modified variant of the screening system shown in FIG. 8. FIG. 9a shows the screening system 10 without the anti-rotation safeguard 60 which is shown in detail in FIG. 9b. This screening system 10 also includes two substantially annular screen supports (only one first screen support 11 of which can be seen here), a screen surface 13 which is in the form of a lateral cylinder surface and a resonator 15 which is realized in a similar manner to the resonator 15 shown in FIGS. 5a to 6 and is fastened directly on the screen surface 13. The resonator 15 is actuatable by ultrasound vibrations by means of an ultrasound conductor 25.

(52) The ultrasound conductor 25 comprises a first portion 69 with a circular cross section which faces an ultrasound converter, and a second portion 70 with a rectangular cross section which faces the resonator 15. The first portion 69 is guided through a feed-through opening 24 which is formed in a collar-shaped portion 18 of the first screen support 11.

(53) A plate 62 of the anti-rotation safeguard 60, which is shown in detail in FIG. 9b, comprises an anti-rotation protection opening 61, through which the second portion 70 of the ultrasound conductor 25 is guided (see FIG. 9c in this respect). The anti-rotation protection opening 61 is open on one side, inwardly in the radial direction with reference to a central axis of the screening system. More precisely, the anti-rotation protection opening 61 includes a circle-segment-shaped portion 67 which merges into a slot 68 which widens inwardly in the radial direction, at the end of which the anti-rotation protection opening 61 is open.

(54) For assembly, the anti-rotation safeguard 60 can be displaced inwardly in the radial direction above the ultrasound conductor 25, which penetrates in part into the annular portion 67 through the slot 68, and then is fixed by means of screws 64. The screws 64 are realized as hexagon socket screws in FIG. 9c. In the end position, which is achieved as a result, there is no contact between the ultrasound conductor 25 and the plate 62.

(55) As a result of said realization in FIGS. 9a to 9c also, the anti-rotation protection opening 61 allows rotation of the ultrasound conductor 25 about its longitudinal axis only within a predetermined angular range. Said rotatability is made possible, among other things, as a result of the slot 68 being widened inwardly in the radial direction.

(56) FIGS. 10a to 10d show a sixth exemplary embodiment according to the invention of a screening system 10 with a first circular ring-shaped screen support 11 and a second circular ring-shaped screen support 12, both of which are designed in a substantially mirrored manner with respect to one another. Pressure rods 14 brace the screen supports 11, 12 together in such a manner that compressive stress is generated between the screen supports 11, 12. A screen surface 13 which is in the form of a circular lateral cylinder surface and extends in a longitudinal direction L is clamped between the screen supports 11, 12 by means of two hose clips 76. The first screen support 11 comprises a sleeve-shaped portion 16 and a collar-shaped portion 18 which protrudes radially outwardly from the sleeve-shaped portion. In an analogous manner, the second screen support 12 comprises a sleeve-shaped portion which cannot be seen here and a collar-shaped portion 19 which protrudes radially outwardly from the sleeve-shaped portion.

(57) A resonator 15, which is designed identically to that shown in FIGS. 5a to 6, extends along the longitudinal direction L from the first screen support 11 substantially to the second screen support 12. The resonator 15 is excited by means of an ultrasound converter 77 and an ultrasound conductor 25 to form ultrasound vibrations. The ultrasound converter 77 is held on the collar-shaped portion 18 of the first screen support 11 by means of a plate-shaped converter holder 79 and two spacers 78. The ultrasound conductor 25 is guided through a feed-through opening 24. An anti-rotation safeguard as shown in FIGS. 8 to 9c can also be provided here as an option.

(58) FIG. 10d shows the detail A from FIG. 10b in an enlarged manner. On an axial end 74 facing the second screen support 12, the sleeve-shaped portion 16 of the first screen support 11 comprises a groove 71 on its radial outer side 73. A sealing ring realized as an O-ring seal 72 is inserted in said groove 71. The O-ring seal 72 protrudes slightly outwardly in the radial direction above the groove 71 (which is not shown in the figures to simplify the drawing). The screen surface 13 is clamped in the radial direction by means of said O-ring seal 72. An axial end of the screen surface 13 is held by means of a hose clip 76 on an axial end 75 of the sleeve-shaped portion 16 facing away from the second screen support 12.

(59) FIGS. 11a and 11b show the first screen support 11 again in a separate and enlarged manner, FIG. 11b showing the detail X from FIG. 11a. A sleeve-shaped continuation 80 extends from the sleeve-shaped portion 16 in the direction of the second screen support 12. It is thinner than the sleeve-shaped portion 16 in the radial direction, but runs flush with the sleeve-shaped portion 16 on the radial inner side 82. A thickening 81 extends radially outwardly from the end of the sleeve-shaped continuation 80. The groove 71 is formed by an end face 83 of the sleeve-shaped portion 16, by the sleeve-shaped continuation 80 and by the thickening 81. In this case, the thickening 81 has a radial extent which is smaller than the radial extent of the end face 83. This makes it easier to introduce the O-ring seal 72 into the groove 71. As the screen surface 13 is clamped away from the thickening 83 in the axial direction by means of the hose clip 76, the O-ring seal 72 is prevented from slipping out of the groove 71.