Device for the planar transmission of mechanical vibrations to flowable media

Abstract

The invention relates to a device (10) for transmitting planar mechanical vibrations to flowable media. The device (10) is characterized in that the amplitudes to normal of the planar contact surface points of a resonator (12) are substantially uniform during a resonant vibration and an amplitude vector in the contact surface points of more than 80 percent of a contact surface is substantially parallel to the normal vector of these contact surface points.

Description

[0001] Device for the planar transmission of mechanical vibrations to flowable media

[0002] The invention relates to a device for the planar transmission of mechanical vibrations to flowable media.

[0003] Background of the invention

[0004] A resonator can be excited to resonant vibration at any surface point, multiple surface points, or one or more partial surfaces. A resonator can exhibit multiple resonant frequencies. The resonant frequency of a resonator can be influenced by factors such as the material, geometry, temperature, and contact with a fluid medium.

[0005] The mechanical power transferred from a resonator to a flowable medium via an effective surface depends, among other things, on the properties of the flowable medium, such as temperature, viscosity or pressure, on the size of the effective surface and on the normal amplitude of the effective surface points.

[0006] For some applications, such as pharmacological or biological investigations, e.g., cell lysis, protein extraction, cell homogenization and solubilization, DNA fragmentation, and the like, a largely uniform normal amplitude for at least one active area is desirable. A largely uniform normal amplitude allows for a more uniform power output from the resonator and thus the most homogeneous sample sonication possible.

[0007] Resonators are known which, during resonant oscillation, exhibit a largely uniform normal amplitude in very small segments of the effective surfaces, in which the amplitude vector of the effective surface points is largely parallel to the normal vector of these effective surface points.

[0008] The invention is based on the objective of developing a device with a more uniform transmission of planar mechanical vibrations to flowable media. Description of the invention

[0009] The problem according to the invention is solved by a device for transmitting planar mechanical vibrations to flowable media according to the independent claim. Preferred embodiments are the subject of the respective dependent claims.

[0010] The invention relates to a device for transmitting planar mechanical vibrations to flowable media. The device according to claim 1 is characterized in that the normal amplitudes of the planar contact points of a resonator are largely uniform during a resonant vibration, and an amplitude vector at the contact points of more than 80 percent of a contact area is largely parallel to the normal vector of these contact points. In other words, the device for transmitting planar mechanical vibrations to flowable media comprises a resonator and a vibration generator configured to excite the resonator. The resonator has at least one planar surface (as a contact surface) which is intended to be brought into contact with the flowable media. At least one recess is provided on the side of the resonator opposite the planar surface.During the oscillation of a resonator, it is dynamically compressed or stretched in a variety of ways. In its resting state, the planar surfaces of the effective contact points of a resonator develop a convex or concave profile when displaced. In other words, in the dynamic state, a curvature forms on the otherwise planar surface away from its resting position, corresponding to a non-uniform normal amplitude. Therefore, conventional resonators achieve no homogeneous sonication of the sample, or only to a limited extent. The (introduced) depression thus serves the purpose of at least partially or completely compensating for the curvature formed on the planar surface by the resonant oscillation of the resonator.In other words, a targeted weakening of the resonator material on the opposite side from the (expected) rounding of the resonator's planar surface during vibration counteracts this, thus largely preserving the surface's flatness. In other words, the introduced depression modifies the resonator's vibrational behavior, specifically adapting the resonator's maximum amplitude in that region (locally), such that the normal amplitudes of the resonator's planar contact points are largely uniform during resonant vibration, and an amplitude vector at contact points covering more than 80 percent of the contact area is largely parallel to the normal vector of these contact points.The invention enables the transmission of vibrations with a largely uniform amplitude over at least one large effective area of ​​the resonator surface in contact with the flowable medium. This allows for homogeneous sonication of the sample.

[0011] Furthermore, the embodiments described in paragraphs a) to m) below are preferred, particularly in any combination of two or more of these embodiments: a) The resonant oscillation preferably lies in the range of 15 kilohertz to 60 kilohertz. In other words, the resonator is configured to oscillate resonantly in the range of 15 kilohertz to 60 kilohertz. b) The resonator is preferably largely cylindrical. In other words, the resonator is preferably largely cylindrical. c) The resonator is preferably largely rotationally symmetrical. The maximum diameter of the resonator is preferably between 40 millimeters and 500 millimeters, preferably at least 80 and / or at most 300 millimeters, and particularly preferably at least 120 millimeters and / or at most 200 millimeters. d) The resonant oscillation preferably propagates radially. The resonant frequency is preferably determined by the diameter.In other words, the resonator is configured so that the resonant oscillation propagates radially and its frequency is determined by the diameter. In other words, the resonator is preferably designed as a radial oscillator. In a radial oscillator, the height (or length) of the resonator is preferably less than or equal to the diameter of the resonator. e) The diameter is preferably λ / 2 or a multiple thereof. In other words, the resonator is preferably designed such that its diameter corresponds to half a resonance wavelength or a multiple thereof. f) The length of the largely cylindrical resonator is preferably less than λ / 2. In other words, the length of the largely cylindrical resonator is preferably half a resonance wavelength or less. g) The planar effective surface is preferably located on an end face of the largely cylindrical resonator.An end face preferably refers to a cross-sectional area representing the largest cross-section of a body. The planar working surface is preferably located in a recess of the end face of the largely cylindrical resonator. In other words, the planar working surface is preferably surrounded by a projecting rim. The rim can serve as a collecting or reservoir for the flowable medium. Alternatively, the planar working surface is preferably located on a raised area of ​​the end face of the largely cylindrical resonator. In this case, the lateral surface of the raised area and / or the area of ​​the end face not encompassed by the raised area can serve as a locking surface for a fastening material, a seal, an attachment, and the like, for example, to couple a sample container to the locking surface in order to place the sample holder above or directly onto the planar surface.h) Compared to the planar effective surface of the largely cylindrical resonator, the surface preferably has a surface geometry that enables the requirements of claim 1 to be met at the planar effective surface. The surface geometry essentially comprises at least one recess designed to at least partially or completely compensate for a curvature formed on the planar surface by the resonant vibration of the resonator. The at least one recess is preferably arranged at the height of the zenith of the expected curvature. Preferably, the recess is tapered, for example, conical. The tapered or conical shape of the recess helps to compensate for the expected curvature more uniformly. Alternatively or additionally, a plurality of recesses are provided, which preferably differ in depth (corresponding to the depth of the curvature).In the simplest case, the recess is preferably designed as a bore. i) The maximum amplitude along the planar effective surface points of a resonator is preferably between 0.1 and 100 micrometers, preferably at least 10 micrometers and / or at most 75 micrometers, and particularly preferably at least 20 micrometers and / or at most 50 micrometers. j) The resonator preferably consists of a single piece. In other words, the resonator is formed in one piece or integrally. One-piece resonators are particularly inexpensive to manufacture, and the resonance behavior is particularly easy to predict. In this respect, a particularly simple calculation of the recess's positioning can be achieved. k) The resonator preferably consists of a metallic material. Alternatively, the resonator can consist of a non-metallic material.l) The planar effective area of ​​the resonator is preferably 10 to 2000 square centimeters, more preferably 100 to 500 square centimeters. m) The power transmitted by the resonator to a flowable medium via the effective area by means of resonant mechanical vibrations is preferably 1 to 20,000 watts or up to 10,000 watts, more preferably 100 to 6,000 watts. In other words, the resonator is configured such that the power transmitted to a flowable medium via the effective area by means of resonant mechanical vibrations is 1 to 20,000 watts or up to 10,000 watts, more preferably 100 to 6,000 watts. n) The resonator is preferably mechanically connected to a vibration exciter. In other words, the resonator is preferably connected to the vibration exciter by frictional, positive, and / or material bonding, particularly preferably via a screw connection.In preferred embodiments, a coupling opening, for example a screw thread, is provided in the recess for mechanical connection to the vibration exciter. This results in a particularly compact device, and the coupling opening or screw thread is at least partially utilized for forming the recess. o) The resonator is preferably mechanically connected to an electromechanical vibration exciter, which converts electrical vibrations into mechanical vibrations piezoelectrically or magnetostrictively. In other words, the electromechanical vibration exciter is configured to convert electrical vibrations into mechanical vibrations piezoelectrically or magnetostrictively. p) The resonator is preferably mechanically connected to another resonator. In other words, a resonator consisting of at least two parts is used. The second resonator preferably includes a similar recess.q) More than 80 percent of the planar active area preferably has a normal amplitude in a range of -20 percent to +20 percent around the mean value. Particularly preferably, more than 85 percent of the active area has a normal amplitude in a range of -15 percent to +15 percent around the mean value. The resonator is preferably configured such that more than 80 percent of the active area has a normal amplitude in a range of -20 percent to +20 percent around the mean value, and preferably more than 85 percent of the active area has a normal amplitude in a range of -15 percent to +15 percent around the mean value. r) The amplitude vector of the active area points of more than 70 percent of the planar active area is preferably largely parallel to the normal vector of these active area points. More preferably, the amplitude vector of the active area points of more than 80 percent of the planar active area is largely parallel to the normal vector of these active area points.Preferably, the amplitude vector of the points on the effective surface is largely parallel to the normal vector of these points on more than 90 percent of the planar effective surface. s) At least one vibration-free and / or low-vibration surface point is preferably located opposite the planar effective surface. t) At least one seal / support, in particular a seal and / or a support, is preferably located opposite the planar effective surface. u) At least one media inlet and / or a media outlet is preferably located extending from the planar effective surface. v) At least one media inlet and / or a media outlet is preferably located extending from the planar effective surface through the resonator. w) At least one partial diameter reduction and / or a partial diameter expansion is preferably located on the diameter of the resonator.

[0012] The portion of the resonator's surface that is in contact with ambient air, coolant, compressed gas, protective gas, or inert gas is not considered part of the effective area. In other words, the effective area refers to the surface of the resonator that is in contact with the fluid medium into which the planar mechanical vibrations are to be introduced. This contact can be direct, or alternatively, a protective film or similar material can be placed between the planar effective area of ​​the resonator and the fluid medium.

[0013] Definitions and terms

[0014] Flowable media (medium, media) include, for example, fluids, gases, liquids, melts, plasma, supercritical or supercritical gases, liquid metals, dispersions, emulsions, cell suspensions, pastes, paints, polymers, resins, and nanomaterials, or mixtures thereof. Flowable media can have different viscosities from 0 centipoise to 30,000,000,000 centipoise, preferably from 0.1 centipoise to 1,000,000 centipoise, e.g., 200 centipoise.

[0015] A resonator point is an element of the resonator. The resonator is the set of all resonator points. A surface point (resonator surface point) is a point located on the surface of the resonator that bounds it. The resonator surface is the set of all resonator surface points. The resonator surface can range from 0 square centimeters to 100,000 square centimeters, preferably from 10 square centimeters to 5,000 square centimeters, e.g., 1,000 square centimeters.

[0016] The effective area is the portion of the resonator's surface that is in contact with one or more flowable media. The effective area can range from 0 square centimeters to 95,000 square centimeters, preferably from 10 square centimeters to 4,500 square centimeters, e.g., 950 square centimeters.

[0017] The effective surface point is a point located on the part of the resonator's surface that is in contact with a flowable medium.

[0018] Active power is the power transferred from the resonator to a flowable medium via resonant mechanical vibrations across its effective surface. The active power can range from over 1 watt, preferably 10 watts, up to 24,000 watts, e.g., 4,000 watts.

[0019] Vibrations are mechanical oscillations with an operating frequency of 0.1 kilohertz to 100 kilohertz, preferably 15 kilohertz to 60 kilohertz, e.g., 20 kilohertz. During the vibration, resonator points move regularly around a rest position.

[0020] The resting position (equilibrium position) is the position of all resonator points in the absence of vibrations.

[0021] Vibration displacement (displacement) indicates the instantaneous distance of a resonator point from its equilibrium position. The vibration displacement for each surface point can be described by a combination of the displacements along the X, Y, and Z axes.

[0022] Amplitude is the magnitude of the greatest possible distance of a resonator point from its rest position during the movement made by that resonator point during the deflection.

[0023] The location of a resonator point is determined by its position vector (e.g., Cartesian coordinates). ten) is given. The amplitude vector of a resonator point is obtained by subtracting the position vector of the resonator point at rest from the position vector of the resonator point at the time of greatest possible distance from its rest position.

[0024] A normal vector is a vector that is orthogonal (i.e., perpendicular) to a straight line, curve, plane, (curved) surface, or a higher-dimensional generalization of such an object. The normal vector of a curved surface at a point is the normal vector of the tangent plane at that point. For determining the normal vector, curvatures, dents, profiles, indentations, bumps, grooves, and pores resulting from the surface roughness (ra < 200 pm) are to be neglected or smoothed out.

[0025] The normal vector of a surface point is the normal vector of the resonator surface at that surface point.

[0026] The normal vector of a point on the active surface is the normal vector of the resonator surface at that point on the active surface.

[0027] The normal amplitude of a surface point is the magnitude of the greatest possible distance of this surface point along the normal vector of this surface point on the motion performed by this surface point during the deflection.

[0028] The normal amplitude of a point on the surface is the magnitude of the greatest possible distance of this point on the surface along the normal vector of this point on the surface on the motion performed by this point on the surface during the deflection.

[0029] Two lines or vectors are largely parallel if they have a small angle to each other, preferably an angle of 0 to 20 degrees, e.g. less than 12 degrees.

[0030] Values ​​are considered largely uniform if they are closely clustered. Values ​​are preferably considered largely uniform if more than 80 percent of them lie within a range of -20 percent to +20 percent around the mean. For example, values ​​are also considered largely uniform if more than 85 percent of them lie within a range of -15 percent to +15 percent around the mean.

[0031] A resonator can be any mechanical structure. A resonator can be, among other things, rod-, ring-, bell-, plate-, beam-, cuboid-, cylinder-, spherical-, cube-, conical-, hollow-cylindrical-, polygonal-, or plate-shaped, rotationally symmetrical or non-rotationally symmetrical, preferably rod-, cylinder-, or beam-shaped and rotationally symmetrical, e.g., cylindrical and rotationally symmetrical about the longitudinal axis of the cylindrical shape. The material of a resonator can be any, preferably solid or liquid, e.g., solid. Materials for a solid resonator can be, for example, metals, non-metals, crystals, plant products such as wood, ceramics, glass, polymers, or composite materials, preferably metals, e.g., titanium alloys. A resonator can consist of one part or of several connected sub-components, preferably of one or two parts, e.g., a single part.

[0032] The invention is explained below in exemplary embodiments with reference to the accompanying drawings.

[0033] Figures 1 to 7 show exemplary embodiments. They show:

[0034] Fig. 1 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a first embodiment in a radial excitation configuration.

[0035] Fig. 2 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a second embodiment in a longitudinal excitation configuration.

[0036] Fig. 3 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a third embodiment in a radial excitation configuration.

[0037] Fig. 4 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a fourth embodiment in a longitudinal excitation configuration.

[0038] Fig. 5 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a fifth embodiment in a longitudinal excitation configuration.

[0039] Fig. 6 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a sixth embodiment in a longitudinal excitation configuration.

[0040] Fig. 7 shows a schematic representation of a device with a resonator having a planar working surface and a vibration exciter according to a seventh embodiment in a longitudinal excitation configuration.

[0041] Figure 1 shows a schematic representation of a device 10 with a resonator 12 having a planar working surface 16 and a vibration exciter 14 according to a first embodiment in a radial excitation configuration. The device 10 is configured to transmit planar mechanical vibrations to flowable media. The vibration exciter 14 is coupled to the resonator 12 and configured to excite the resonator 12 to vibrate according to its resonant frequency. For example, the vibration exciter 14 is configured to generate the vibrations along its longitudinal direction, i.e., in the vertical direction from the plane of Figure 1. The planar working surface 16 of the resonator 12 is designed to be brought into contact with the flowable media.The resonator 12 is specifically designed to convert the movements generated by the vibration exciter 14 into planar mechanical vibrations, i.e., along the horizontal direction from the plane of Figure 1, and to transmit them to the flowable medium contacting the planar working surface 16. Preferably, cavitation is induced in the flowable medium. The vibration exciter 14 is arranged orthogonally with respect to the normal vector of the planar working surface 16.

[0042] On the side of the resonator 12 opposite the planar effective surface 16, at least one recess 18 is provided. The illustrated embodiments show two recesses 18 by way of example, but this is not the only possible representation. Rather, exactly one recess 18 or any number of recesses 18 can be provided on the side of the resonator 12 opposite the planar effective surface 16. During oscillation, the resonator 12 is dynamically compressed or stretched in various ways. In the state of displacement, the surfaces of the effective points of the resonator 12, which are planar in their rest position, form a convex or concave profile. In other words, in the dynamic state, a curvature forms in the otherwise planar surface, corresponding to a non-uniform normal amplitude.Therefore, conventional resonators achieve no homogeneous sample sonication or only homogeneous sample sonication to a certain degree.

[0043] However, the (introduced) depression(s) 18 consequently serve the purpose of at least partially or completely compensating for a curvature formed on the planar effective surface 16 by the resonant vibration of the resonator 12. In other words, a targeted weakening of the material of the resonator 12 on the opposite side of the (expected) curvature of the planar effective surface 16 of the resonator 12 in the vibrational state counteracts this curvature in order to largely maintain the flatness of the planar effective surface 16.In other words, the vibration behavior of the resonator 12 is changed by the at least one introduced depression 18, in particular the maximum amplitude of the resonator 12 in the area (locally) is adapted such that the normal amplitudes of the planar effective surface points of a resonator are largely uniform in a resonant vibration and an amplitude vector in the effective surface points of more than 80 percent of an effective surface is largely parallel to the normal vector of these effective surface points.

[0044] Figure 1 further shows that the side of the resonator 12 opposite the planar effective surface 16 is coupled to, and in particular rests on, a seal 20 and / or a support. The seal 20 serves to prevent the transmission of mechanical vibrations. A housing is preferably coupled to the seal 20 or support.

[0045] Figure 2 shows a schematic representation of the device 10 shown in Figure 1 in a second embodiment with a longitudinal excitation configuration. Recurring features are identified by the same reference numerals. In the following, a repetitive description of the recurring features is omitted, and only the differences are described in more detail. In contrast to the device 10 shown in Figure 1, the vibration exciter 14 is arranged parallel to the normal vector of the planar working surface 16. This offers the advantage that the vibration exciter 14 can be integrated into the housing to obtain a compact device 10.

[0046] Figure 3 shows a schematic representation of a further development of the device 10 shown in Figure 1 according to a third embodiment in a radial excitation configuration. In this embodiment, the resonator 12 includes a recess 22 in its end face in which the planar active surface 16 is arranged. In other words, the planar active surface 16 is preferably surrounded by a projecting rim. The rim can serve as a collecting or reservoir for the flowable medium. A sample holder, such as a microtiter plate, can be inserted into the recess 22 and thus onto the planar active surface 16.

[0047] Figure 4 shows a schematic representation of the device 10 shown in Figure 3 in a fourth embodiment in a longitudinal excitation configuration. This embodiment essentially corresponds to the embodiment shown in Figure 2 in combination with the recess 22 introduced in Figure 3 in the end face of the resonator 12.

[0048] Figure 5 shows a schematic representation of a further development of the device 10 shown in Figure 4 according to a fifth embodiment in a longitudinal excitation configuration. In contrast to Figure 4, the device 10 is shown rotated by 90 degrees to illustrate that a flowable medium introduced into the recess 22 remains in the recess 22 (due to gravity). In this embodiment, the device 10 comprises a media inlet 24 for introducing the flowable medium and a media outlet 26 for drawing off or draining the flowable medium. The media inlet 24 and the media outlet 26 are each shown as lines, one end of each of which opens into the recess 22.

[0049] Figure 6 shows a schematic representation of an alternative further development of the device 10 shown in Figure 4 according to a sixth embodiment in a longitudinal excitation configuration. In contrast to the embodiment shown in Figure 5, the media supply line 24 and the media discharge line 26 run through the resonator 12. This allows for a particularly compact device.

[0050] Figure 7 shows a schematic representation of a further development of the device 10 shown in Figure 3 according to a seventh embodiment in a longitudinal excitation configuration. Compared to the embodiment shown in Figure 3, the device 10 is also shown rotated by 90 degrees, and the resonator 12 comprises a partial diameter reduction 28 in at least one side wall that is orthogonal to the planar effective surface 16. The partial diameter reduction 28 preferably extends completely around the radial side wall of the resonator 12. The partial diameter reduction 28 partially or completely compensates for a curvature in the radial side wall caused by the vibration of the resonator 12. The mode of operation is analogous to the recess 18 in the side of the resonator 12 opposite the planar effective surface 16.This reduces the lateral space requirement of the device 10 (in the horizontal direction of the image plane of Figure 7).

Claims

Claims 1. Device (10) for transmitting planar mechanical vibrations to flowable media, characterized in that the normal amplitudes of the effective surface points of the largely or completely planar effective surface (16) of a resonator (12) are largely uniform during a resonant vibration and an amplitude vector in the effective surface points of more than 80 percent of an effective surface is largely parallel to the normal vector of these effective surface points.

2. Device (10) according to claim 1, wherein the resonant oscillation is in the range of 15 kilohertz to 60 kilohertz.

3. Device (10) according to one of the preceding claims, wherein the resonator (12) is largely cylindrical.

4. Device (10) according to one of the preceding claims, wherein the resonator (12) is largely rotationally symmetric.

5. Device (10) according to claim 4, wherein the maximum diameter of the resonator (12) is between 40 millimeters and 500 millimeters.

6. Device (10) according to one of the preceding claims, wherein the resonator (12) is arranged to cause the resonant oscillation to propagate radially and its frequency is determined via the diameter.

7. Device (10) according to any of the preceding claims, wherein the diameter corresponds to half a resonance wavelength or a multiple thereof.

8. Device (10) according to one of the preceding claims, wherein the length of the largely cylindrical resonator (12) is less than or equal to half a resonance wavelength.

9. Device (10) according to one of the preceding claims, wherein the largely or completely planar effective surface is located on an end face of the largely cylindrical resonator (12).

10. Device (10) according to one of the preceding claims, in which, in relation to the largely or completely planar effective surface (16) of the largely cylindrical resonator (12), the surface contains a surface geometry comprising a recess (18) which is configured to at least partially or completely compensate for a rounding formed on the planar surface by the resonant vibration of the resonator (12).

11. Device (10) according to one of the preceding claims, wherein the maximum of the amplitudes along the effective surface points of a resonator (12) is between 1 and 100 micrometers.

12. Device (10) according to one of the preceding claims, wherein the resonator (12) consists of a single part.

13. Device (10) according to one of the preceding claims, in which at least one vibration-free and / or low-vibration surface point is located opposite the planar effective surface (16).

14. Device (10) according to one of the preceding claims, in which at least one seal (20) and / or a support is located opposite the planar working surface (16).

15. Device (10) according to one of the preceding claims, in which at least one media supply (24) and / or one media discharge (26) extends from the planar working surface (16).

16. Device (10) according to one of the preceding claims, in which at least one media supply (24) and / or one media discharge (26) extends from the planar working surface (16) through the resonator (12).

17. Device (10) according to one of the preceding claims, wherein the diameter of the resonator (12) has at least a partial diameter reduction (28) and / or a partial diameter expansion.

18. Device (10) according to one of the preceding claims, wherein the resonator (12) is made of a metallic material.

19. Device (10) according to one of the preceding claims, wherein the effective area of ​​the resonator (12) is 10 square centimeters to 2000 square centimeters.

20. Device (10) according to one of the preceding claims, wherein the resonator (12) is configured such that the power transmitted via the effective surface to a flowable medium by means of resonant mechanical vibrations is 1 watt to 10000 watts.

21. Device (10) according to one of the preceding claims, wherein the resonator (12) is mechanically connected to a vibration exciter (14).

22. Device (10) according to one of the preceding claims, wherein the resonator (12) is mechanically connected to an electromechanical vibration exciter (14) which is configured to convert electrical vibrations into mechanical vibrations piezoelectrically or magnetostrictively.

23. Device (10) according to one of the preceding claims, wherein the resonator (12) is mechanically connected to another resonator (12).

24. Device (10) according to one of the preceding claims, wherein the Resona- tor (12) is configured such that more than 80 percent of the effective area has a normal amplitude in a range of -20 percent to +20 percent around the mean value, preferably more than 85 percent of the effective area has a normal amplitude in a range of -15 percent to +15 percent around the mean value.

25. Device (10) according to one of the preceding claims, wherein the amplitude vector of the effective surface points of more than 90 percent of the effective surface is largely parallel to the normal vector of these effective surface points.

26. Device (10) according to claim 9, wherein the planar working surface is located in a recess (22) of the end face of the largely cylindrical resonator (12).

27. Device (10) according to claim 9, wherein the planar effective surface is located on a raised area of ​​the end face of the largely cylindrical resonator (12).

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