Linear excitation for Coriolis mass flow meters

Abstract

The present invention relates to an excitation device for exciting a vibration, comprising a movable portion configured to move relative to the fixable portion, a connecting portion, wherein the movable portion is connected to the fixable portion via the connecting portion, a piezoelectric element fixedly mounted on the fixable portion, and a connecting element mechanically connecting the piezoelectric element and the movable portion. Furthermore, a Coriolis flowmeter is disclosed, comprising a measuring tube, at least one sensor configured to detect movement of the measuring tube, and an excitation device configured to excite vibration of the measuring tube.

Description

[0001] The present invention relates generally to Coriolis mass flow meters and in particular to the provision of an excitation for Coriolis mass flow meters.

[0002] The present invention is described with a particular focus on the measurement of a mass flow rate in liquid chromatography (LC) and especially high-performance liquid chromatography (HPLC). However, it is understood that the present technology can also be used in the context of other applications under similar conditions, e.g., high pressures and volumetric flow rates in the range of µl / min to ml / min, where precise measurements of the mass flow rate are advantageous.

[0003] Currently, the flow rate of (HP)LC analysis systems, and thus the composition of the mobile phase, can be controlled solely by the operation of the pump, e.g., by the piston movement. This means that the piston movement can be measured during each pump stroke, and the resulting flow rate can be derived based on the piston movement and the volume displaced in the pump chamber. However, this typically places very high demands on the tightness of all components involved. Alternatively, the piston movement may not provide a reliable measure, as fluid can leak out and thus not contribute to the flow rate. This, in turn, can lead to more complex and elaborate pump designs, as well as higher demands on the materials used.

[0004] Furthermore, the compressibility and thermal expansion of the fluid may require compensation, as they can affect the flow rate derived from the displaced volume. Thermal expansion can occur not only due to changes in ambient temperature but also through adiabatic heating during the pumping process. Therefore, deriving the flow rate from the piston displacement volume may require careful calibration with respect to the fluid properties and thus a good understanding of these properties, which can be particularly challenging when solvent gradients are used, i.e., when the composition of the mobile phase varies over time.

[0005] Therefore, it would be desirable to measure the supplied flow rate, which would allow for the correction of any pump deficiencies, for example via appropriate control mechanisms, and a relaxation of the pump's accuracy requirements. However, measuring the flow rate requires the provision of an accurate and cost-effective flow sensor for a corresponding flow range, for example, a flow range from 50 µl / min to 5 ml / min.

[0006] There are three main types of sensors that can be used for flow measurement in HPLC applications: thermal mass flow meters, ultrasonic flow meters, and Coriolis mass flow meters. However, no sensor currently appears to be widely used that can measure with sufficient accuracy within the desired flow and pressure range, e.g., a flow rate of 50 µl / min to 5 ml / min and a pressure range of 5–150 MPa.

[0007] Currently, thermal mass flow meters are primarily used for low-flow HPLC. Each of the different sensor types offers certain advantages and disadvantages. Thermal and ultrasonic mass flow meters, for example, can be dependent on the fluid properties and therefore also require careful calibration. A particular advantage of using a Coriolis mass flow meter is that it provides a linear response to the mass flow through the sensor and is independent of the fluid properties. Furthermore, it can advantageously measure the fluid density independently of the mass flow rate. In other words, a Coriolis mass flow meter is linear, solvent-independent, and can also measure density, which in turn allows for the determination of the volumetric flow rate.

[0008] Unlike current HPLC analysis pumps that control volumetric flow, residence times can be kept stable regardless of ambient temperature if the mass flow rate is kept constant. In other words, measuring the mass flow rate instead of the volumetric flow rate can be advantageous, as this allows for stable residence times independent of ambient temperature, i.e., without having to consider the ambient temperature of the system. Therefore, it can be desirable to have a mass flow rate measurement, which is inherently provided by a Coriolis mass flow meter.

[0009] In a Coriolis mass flow meter, a fluid flow can generally be forced to move non-linearly through at least one pipe, which may have a curved or straight geometry. The at least one pipe is forced to oscillate, and due to its rotational flow, the fluid causes torsion on the at least one pipe by means of the Coriolis force. The torsion can be measured by measuring the displacement of the pipe at at least two locations, one location being upstream and the other downstream of the pipe's center in the flow direction. Preferably, the two locations are arranged symmetrically around the pipe's center in the flow direction. Thus, the torsion can lead to a phase shift between the total oscillation measured at the two locations. Based on the measured torsion, e.g., the measured phase shift, the mass flow rate can be determined.Furthermore, changing the vibration frequency can allow the fluid density to be measured, since the natural frequency of the tube depends on the mass of the tube and the fluid it contains. This enables the measurement of the fluid mass and, based on the known volume of the tube, the fluid density.

[0010] In a Coriolis mass flow meter, it is therefore necessary to excite at least one tube (also called a measuring tube) in some way to set it into vibration. Normally, a small actuator can be attached to the tube for this purpose. However, this may not be possible with small tubes, such as those required for measuring low flow rates, as it would significantly increase the tube's mass. Additional mass, however, can negatively reduce the sensitivity of the Coriolis mass flow meter (or simply mass flow meter).

[0011] Mass flow meters designed to measure small flow rates often employ electromagnetic excitation, as described, for example, in EP 1 719 983 B1. However, since no additional components can be attached directly to the pipe, the pipe itself acts as the electrical conductor. The disadvantage of such mass flow meters is generally their complexity, which can make them expensive, especially for thin pipes.

[0012] Furthermore, approaches based on piezoceramics are known, such as those revealed in the poster "MICRO CORIOLIS MASS FLOW SENSOR DRIVEN BY EXTERNAL PIEZO CERAMIC," presented by Y. Zeng et al. at the 3rd Conference on Microfluidic Handling Systems from October 4th to 6th, 2017 in Enschede, Netherlands (https: / / ris.utwente.nl / ws / portalfiles / portal / 19542377 / coriolis_piezo.pdf). This simple concept has the disadvantage that the excitation is not perfectly symmetrical due to an asymmetry between the piezoelectric element and its mounting. This results in a rotational movement being excited in addition to the desired linear excitation. This rotation introduces a zero-point error in the flow signal, which may not remain stable over time. Consequently, the accuracy of the sensor is limited.

[0013] In light of the above, it is a task to overcome or at least mitigate the shortcomings and disadvantages of the state of the art.

[0014] These tasks are fulfilled by the present invention.

[0015] In one aspect, the present invention relates to an excitation device for generating a vibration, wherein the excitation device comprises a fixable section, a movable section configured to move relative to the fixable section, a connecting section wherein the movable section is connected to the fixable section via the connecting section, a piezoelectric element fixedly mounted on the fixable section, and a connecting element mechanically connecting the piezoelectric element and the movable section. It is understood that the fixable section is generally configured to be attached to another element, e.g., a housing or body of a Coriolis flow meter.In other words, the excitation device comprises a movable section connected via a corresponding connecting section to a fixed section such that the movable section can move relative to the fixed section. The fixed section can generally be configured to be attached to another element, e.g., mounted or mounted. Furthermore, the excitation device comprises a piezoelectric element attached to the fixed section and mechanically connected to the movable section.

[0016] The fixable section can include at least one fastening means, preferably at least one threaded hole. The fastening means can help to attach the fixable section to another element, e.g., to the housing of a corresponding Coriolis flow meter.

[0017] The movable section can be connected to the fixed section via the connecting section in such a way that at least part of the movable section overlaps the fixed section. In other words, at least part of the movable section can be located above the fixed section, for example, such that there is a horizontal overlap between them.

[0018] The excitation device can define a first direction (z), a second direction (x) perpendicular to the first direction, and a third direction (y) perpendicular to both the first and second directions. In such a case, at least part of the movable section can be arranged to overlap the fixed section in the first direction.

[0019] The connecting section can be configured to allow movement of the movable section relative to the fixed section. For example, the connecting section can form a joint between the movable section and the fixed section.

[0020] The connecting section can be configured to provide only one degree of angle or degree of freedom. This means that the connecting section may only be movable in one plane.

[0021] The connecting section can be configured to move only parallel to a plane extending in the first direction (z) and the second direction (x). Additionally or alternatively, the connecting section can be configured to suppress and / or prevent movement of the movable section in the third direction (y).

[0022] The connecting section can include a flexible section. That is, the connecting section can be configured to bend when a corresponding force is applied, preferably via the movable section, thus allowing movement of the movable section relative to the fixed section.

[0023] The connecting section can include a joint. This joint can be, in particular, a solid-state joint. The solid-state joint can be a solid-state hinge. Additionally or alternatively, the solid-state joint can include a bending element. A bending element can be, for example, a bending joint, a bending hinge, or a bending bearing.

[0024] The connecting section can be symmetrical about a connection symmetry plane. The connection symmetry plane extends in the first direction (z) and the second direction (x). Furthermore, the connecting section may only allow movements parallel to the connection symmetry plane.

[0025] In some embodiments, the excitation device can comprise a plurality of connecting sections.

[0026] The piezoelectric element can be configured to exert a force on the movable section via the connecting element. Similarly, the piezoelectric element can be configured to cause movement of the movable section relative to the fixed section via the connecting element.

[0027] The piezoelectric element can comprise a piezoelectric material, for example a piezoelectric crystal or a piezoelectric ceramic.

[0028] The piezoelectric element can be a piezoelectric actuator. In other words, it can generally be a transducer configured to convert electrical energy into mechanical displacement or voltage based on a piezoelectric effect.

[0029] The piezoelectric element can be configured to exert a force in the first direction (z). It is understood that a piezoelectric element configured to exert a force in the first direction (z) may still exert small (undesired) forces in the second and / or third direction. However, it can generally be designed to exert the force in the first direction (z), and forces in additional directions may be undesired byproducts, for example, due to manufacturing limitations.

[0030] The piezoelectric element can be configured to exert a periodic thrust force and / or a periodic tensile force on the movable section via the connecting element in order to cause movement, preferably vibration, of the movable section relative to the fixed section. Thus, the piezoelectric element can be configured to cause a periodic movement of the movable section relative to the fixed section.

[0031] The excitation device can include an insulating element configured to electrically isolate the fixable section from the piezoelectric element. Additionally or alternatively, the excitation device can include an insulating connecting element configured to provide electrical insulation between the piezoelectric element and the connecting element. It is understood that in such embodiments, the connecting element can mechanically connect the piezoelectric element and the movable section via the insulating connecting element. In particular, the connecting element can be attached to the piezoelectric element via the insulating connecting element. The insulating connecting element can, for example, be bonded to the piezoelectric element. Additionally or alternatively, the insulating connecting element can be crimped to the connecting element.In general, the insulating element and / or the insulating connecting element can prevent an unwanted electrical connection between the piezoelectric element and the fixed section and / or the moving section. This can be important because the piezoelectric element may require relatively high voltages.

[0032] The piezoelectric element can be mounted centrally to the fixable section with respect to the third direction. Additionally or alternatively, the piezoelectric element can be mounted on the fixable section such that it is centrally located with respect to the movable section in the third direction (y).

[0033] The connecting element may comprise a rod. In some cases, the connecting element may be a rod. The rod may have a diameter of at most 1 mm, preferably at most 0.5 mm, more preferably at most 0.3 mm.

[0034] In general, the connecting element can be configured to transfer a thrust force provided by the piezoelectric element to the moving section.

[0035] In some embodiments, the connecting element may be a wire. Generally, the connecting element may be configured to transmit a tensile force provided by the piezoelectric element to the moving section. It is understood that in some embodiments, the connecting element may be configured to transmit both a shear and tensile force, for example, embodiments in which the connecting element comprises a rod.

[0036] The connecting element can be attached to the moving section by crimping or riveting.

[0037] In general, the connecting element can extend along the first direction (z). In some embodiments, the connecting element can have a length in the first direction (z) in the range of 5-50 mm, preferably 5-20 mm, more preferably 8-15 mm.

[0038] In some embodiments, the connecting element can be attached centrally to the movable section with respect to the third direction (y).

[0039] The movable section can be configured to accommodate a measuring tube. In some embodiments, the excitation device can include the measuring tube. The measuring tube can be attached to the movable section at two mounting points. The two mounting points can be located further away from the connecting section in the second direction (x) than the point where the connecting element is attached to the movable section. Additionally or alternatively, the two mounting points can be arranged at equal distances in the second direction (x) with respect to the connecting section.

[0040] The measuring tube can be arranged in a loop between the two mounting points. The loop can be positioned between the fixed section and the movable section in a first direction (z). The loop can be symmetrical about a loop symmetry plane. Furthermore, the loop symmetry plane can extend in the first direction (z) and the second direction (x). The loop symmetry plane can be identical to the connection symmetry plane. That is, the loop is symmetrical about the connection symmetry plane.

[0041] The excitation device can be configured to excite only one eigenmode of the measuring tube. The eigenmode can be symmetrical about the loop's plane of symmetry. In some embodiments, the eigenmode can only include movement in the first direction (z).

[0042] The measuring tube can be attached by crimping, riveting, soldering, or welding. This advantageously ensures a secure fixation of the measuring tube to the movable section.

[0043] The length of the measuring tube between the two mounting points can be in the range of 50–500 mm, preferably 100–200 mm, more preferably 120–180 mm. Additionally or alternatively, the measuring tube can have a diameter in the range of 0.2–1.0 mm, preferably 0.3–0.6 mm, more preferably 0.3–0.4 mm.

[0044] The measuring tube can be configured for a mass flow rate of at least 0-2 g / min, preferably 0-5 g / min, more preferably 0-10 g / min. Additionally or alternatively, the measuring tube can be configured to carry fluids at pressures of at least 0-30 MPa, preferably 0-100 MPa, more preferably 0-200 MPa. Additionally or alternatively, the excitation device can be configured to cause the movable section and / or the measuring tube attached thereto to oscillate at a frequency in the range of 50-500 Hz, preferably 80-200 Hz, more preferably 100-150 Hz.

[0045] The movable section can be symmetrical about a plane of symmetry of the movable section. The plane of symmetry of the movable section can extend in the first direction (z) and the second direction (x). Additionally or alternatively, the plane of symmetry of the movable section can be identical to the connecting plane of symmetry.

[0046] Similarly, the fixed section can be symmetrical about a plane of symmetry of the fixed section. The plane of symmetry of the fixed section can extend in the first direction (z) and the second direction (x). Additionally or alternatively, the plane of symmetry of the fixed section can be identical to the plane of symmetry of the connection.

[0047] In general, the excitation device can be symmetrical about a device symmetry plane. The device symmetry plane can extend in the first direction (z) and the second direction (x).

[0048] The movable section can be configured such that inertial forces acting on the piezoelectric element are reduced and preferably prevented. That is, the movable section can be dimensioned and arranged to at least reduce the respective inertial forces. For example, the movable section can be configured to also act as a counterweight by extending horizontally in two opposite directions along the connecting section. In general, this can allow the center of mass of the movable section to be shifted close to an axis of rotation of the connecting section. In particular, the movable section can be configured such that its center of mass lies in the first direction (z) of the connecting section.Overall, this can advantageously reduce inertial forces, as the moving section acts on the piezoelectric element, which can reduce mechanical stresses and thus potential damage to the piezoelectric element.

[0049] In another aspect, the present invention relates to a Coriolis flow meter comprising a measuring tube, at least one sensor configured to detect movement of the measuring tube, and an excitation device as described above, configured to excite vibration of the measuring tube.

[0050] The excitation device can include the measuring tube. The Coriolis flow meter can preferably include two sensors. The at least one sensor can generally be an optical sensor.

[0051] The Coriolis flow meter can be configured to measure mass flow rates at least in the range of 0-2 g / min, preferably at least in the range of 0-5 g / min, and more preferably at least in the range of 0-10 g / min. The Coriolis flow meter can also be configured to measure mass flow rates at fluid pressures at least in the range of 0-30 MPa, preferably at least in the range of 0-100 MPa, and more preferably at least in the range of 0-200 MPa.

[0052] In yet another aspect, the present invention relates to the use of the excitation device or the Coriolis flow meter described herein for measuring a mass flow rate. The mass flow rate can be in the range of 0-2 g / min, preferably at least in the range of 0-5 g / min, more preferably at least in the range of 0-10 g / min. Additionally or alternatively, the mass flow rate can be measured at fluid pressures in the range of 0-30 MPa, preferably in the range of 0-100 MPa, more preferably in the range of 0-200 MPa.

[0053] The following refers to embodiments of the excitation device. These embodiments are abbreviated by the letter "D" followed by a number. Whenever this document refers to "device embodiments," these embodiments are meant. D1. Excitation device for exciting an oscillation, comprising a fixable section; a movable section configured to move relative to the fixed section; a connecting section, wherein the movable section is connected to the fixable section via the connecting section; a piezoelectric element that is permanently mounted on the fixable section; and a connecting element that mechanically connects the piezo element and the moving section. D2. Excitation device according to the preceding device embodiment, wherein the fixable section comprises at least one fastening means, preferably at least one threaded bore. D3. Excitation device according to one of the preceding device embodiments, wherein the movable section is connected to the fixable section via the connecting section in such a way that at least a part of the movable section overlaps with the fixable section. D4. Excitation device according to one of the preceding device embodiments, wherein the excitation device defines a first direction (z), a second direction (x) perpendicular to the first direction, and a third direction (y) perpendicular to both the first and second directions. D5. Excitation device according to one of the preceding device embodiments, wherein the connecting section is configured to allow movement of the movable section relative to the fixable section. D6. Excitation device according to one of the preceding device embodiments, wherein the connecting section forms a joint between the movable section and the fixable section. D7. Excitation device according to one of the preceding device embodiments, wherein the connecting section is configured to provide only one degree of angle or degree of freedom.

[0054] This means that the connecting section may only be movable in one plane. D8. Excitation device according to one of the preceding device embodiments with the features of embodiment D4, wherein the connecting section is configured to be movable only parallel to a plane extending in the first direction (z) and the second direction (x). D9. Excitation device according to one of the preceding device embodiments with the features of embodiment D4, wherein the connecting section is configured to suppress and / or prevent movement of the movable section in the third direction (y). D10. Excitation device according to one of the preceding device embodiments, wherein the connecting section comprises a bendable section.

[0055] This means that the connecting section can be configured to bend when a corresponding force is applied, preferably via the movable section, thus enabling movement of the movable section relative to the fixed section. D11. Excitation device according to one of the preceding device embodiments, wherein the connecting section comprises a joint. D12. Excitation device according to the preceding device embodiment, wherein the joint is a solid body joint. D13. Excitation device according to the preceding device embodiment, wherein the solid joint is a solid hinge. D14. Excitation device according to one of the two preceding device embodiments, wherein the solid joint comprises a bending element.

[0056] A bending element can be, for example, a bending joint, a bending hinge, or a bending bearing. D15. Excitation device according to one of the preceding device embodiments, wherein the connecting section is symmetrical to a connecting symmetry plane. D16. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the connection symmetry plane extends in the first direction (z) and the second direction (x). D17. Excitation device according to one of the two preceding device embodiments, wherein the connecting section only allows movements parallel to the plane of symmetry of the connection. D18. Excitation device according to one of the preceding device embodiments, wherein the excitation device comprises a plurality of connecting sections. D19. Excitation device according to one of the preceding device embodiments, wherein the piezo element is configured to exert a force on the movable section via the connecting element. D20. Excitation device according to one of the preceding device embodiments, wherein the piezo element is configured to cause movement of the movable section relative to the fixable section via the connecting element. D21. Excitation device according to one of the preceding device embodiments, wherein the piezoelectric element comprises a piezoelectric material. D22. Excitation device according to one of the preceding device embodiments, wherein the piezo element is a piezoelectric actuator. D23. Excitation device according to one of the preceding device embodiments, wherein the piezo element is configured to exert a force in the first direction (z). D24. Excitation device according to one of the preceding device embodiments, wherein the piezo element is configured to exert a periodic thrust force and / or a periodic tensile force on the movable section via the connecting element in order to cause a movement, preferably vibration, of the movable section in relation to the fixable section. D25. Excitation device according to one of the preceding device embodiments with the features of embodiment D4, wherein the piezo element is mounted centrally to the fixable section with respect to the third direction (y). D26. Excitation device according to one of the preceding device embodiments with the features of embodiment D4, wherein the piezo element is mounted on the fixable section such that it is arranged centrally in the third direction (y) with respect to the movable section. D27. Excitation device according to one of the preceding device embodiments, wherein the excitation device comprises an insulating element configured to electrically isolate the fixable section from the piezoelectric element. D28. Excitation device according to one of the preceding device embodiments, wherein the excitation device comprises an insulating connecting element configured to provide electrical insulation between the piezoelectric element and the connecting element. It is understood that in such embodiments, the connecting element can mechanically connect the piezoelectric element and the moving section via the insulating connecting element. In particular, the connecting element can be attached to the piezoelectric element via the insulating connecting element. D29. Excitation device according to the preceding device embodiment, wherein the insulating connecting element is bonded to the piezoelectric element. D30. Excitation device according to one of the two preceding device embodiments, wherein the insulating connecting element is crimped to the connecting element. D31. Excitation device according to one of the preceding device embodiments, wherein the connecting element comprises a rod. D32. Excitation device according to the preceding device embodiment, wherein the rod has a diameter of at most 1 mm, preferably at most 0.5 mm, more preferably at most 0.3 mm. D33. Excitation device according to one of the preceding device embodiments, wherein the connecting element is configured to transmit a thrust force provided by the piezoelectric element to the movable section. D34. Excitation device according to one of the device embodiments D1 to D30, wherein the connecting element is a wire. D35. Excitation device according to one of the preceding device embodiments, wherein the connecting element is configured to transmit a tensile force provided by the piezoelectric element to the movable section. D36. Excitation device according to one of the preceding device embodiments, wherein the connecting element is attached to the movable section by crimping or riveting. D37. Excitation device according to one of the preceding device embodiments having the features of embodiment D4, wherein the connecting element extends along the first direction (z). D38. Excitation device according to one of the preceding device embodiments with the features of embodiment D4, wherein the connecting element has a length in the first direction (z) in the range of 5-50 mm, preferably 5-20 mm, more preferably 8-15 mm. D39. Excitation device according to one of the preceding device embodiments with the features of embodiment D4, wherein the connecting element is attached centrally to the movable section with respect to the third direction (y). D40. Excitation device according to one of the preceding device embodiments, wherein the movable section is configured to receive a measuring tube. D41. Excitation device according to one of the preceding device embodiments, wherein the excitation device comprises the measuring tube. D42. Excitation device according to the preceding device embodiment, wherein the measuring tube is attached to the movable section at two attachment points. D43. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the two attachment points in the second direction (x) are located further away from the connecting section than the point at which the connecting element is attached to the movable section. D44. Excitation device according to one of the two preceding device embodiments with the features of embodiment D4, wherein the two attachment points are each arranged at the same distance in the second direction (x) with respect to the connecting section. D45. Excitation device according to one of the 3 preceding device embodiments, wherein the measuring tube is arranged in a loop between the two mounting points. D46. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the loop is arranged between the fixable section and the movable section in a first direction (z). D47. Excitation device according to the 2 preceding device embodiments, wherein the loop is symmetrical to a loop symmetry plane. D48. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the loop symmetry plane extends in the first direction (z) and the second direction (x). D49. Excitation device according to one of the two preceding device embodiments and having the features of D15, wherein the loop symmetry plane is identical to the connection symmetry plane.

[0057] This means that the loop is symmetrical about the plane of symmetry of the connection. D50. Excitation device according to one of the 9 preceding device embodiments, wherein the excitation device is configured to excite only one eigenmode of the measuring tube. D51. Excitation device according to the preceding device embodiment and with the features of D47, wherein the eigenmode is symmetrical to the loop symmetry plane. D52. Excitation device according to one of the 2 preceding device embodiments with the features of embodiment D4, wherein the eigenmode comprises only a movement in the first direction (z). D53. Excitation device according to one of the 12 preceding device embodiments, wherein the measuring tube is attached by crimping, riveting, soldering or welding. D54. Excitation device according to one of the 13 preceding device embodiments, wherein the length of the measuring tube between the two mounting points is in the range of 50-500 mm, preferably 100-200 mm, more preferably 120-180 mm. D55. Excitation device according to one of the 14 preceding device embodiments, wherein the measuring tube has a diameter in the range of 0.2-1.0 mm, preferably 0.3-0.6 mm, more preferably 0.3-0.4 mm. D56. Excitation device according to one of the 15 preceding device embodiments, wherein the measuring tube is configured for a mass flow rate of at least 0-2 g / min, preferably 0-5 g / min, more preferably 0-10 g / min. D57. Excitation device according to one of the 16 preceding device embodiments, wherein the measuring tube is configured to guide fluids with pressures of at least 0-30 MPa, preferably 0-100 MPa, more preferably 0-200 MPa. D58. Excitation device according to one of the preceding device embodiments, wherein the excitation device is configured to cause the movable section and / or the measuring tube attached thereto to vibrate at a vibration frequency in the range of 50-500 Hz, preferably 80-200 Hz, more preferably 100-150 Hz. D59. Excitation device according to one of the preceding device embodiments, wherein the movable section is symmetrical to a plane of symmetry of the movable section. D60. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the plane of symmetry of the movable section extends in the first direction (z) and the second direction (x). D61. Excitation device according to one of the two preceding device embodiments and having the features of D15, wherein the plane of symmetry of the movable section is identical to the plane of symmetry of the connection. D62. Excitation device according to one of the preceding device embodiments, wherein the fixable section is symmetrical to a plane of symmetry of the fixable section. D63. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the plane of symmetry of the fixable section extends in the first direction (z) and the second direction (x). D64. Excitation device according to one of the two preceding device embodiments and having the features of D15, wherein the plane of symmetry of the fixable section is identical to the plane of connection symmetry. D65. Excitation device according to one of the preceding device embodiments, wherein the excitation device is symmetrical about a device symmetry plane. D66. Excitation device according to the preceding device embodiment with the features of embodiment D4, wherein the device symmetry plane extends in the first direction (z) and the second direction (x). D67. Excitation device according to one of the preceding device embodiments, wherein the movable section is configured such that inertial forces acting on the piezoelectric element due to the movable section are reduced and preferably avoided. D68. Excitation device according to one of the preceding device embodiments and having the features of D4, wherein the movable section is configured such that a center of mass of the movable section is located in the first direction (z) of the connecting section.

[0058] The following refers to embodiments of the Coriolis flow meter. These embodiments are abbreviated by the letter "F" followed by a number. Whenever this document refers to "flow meter embodiments," these embodiments are meant. F1. Coriolis flow meter, including a measuring tube; at least one sensor configured to detect movement of the measuring tube; and an excitation device according to one of the preceding device embodiments, configured to excite a vibration of the measuring tube. F2. Coriolis flow meter according to the preceding flow meter embodiment, wherein the excitation device comprises the measuring tube. F3. Coriolis flow meter according to one of the preceding flow meter embodiments, wherein the Coriolis flow meter comprises 2 sensors. F4. Coriolis flow meter according to one of the preceding flow meter embodiments, wherein the at least one sensor is an optical sensor. F5. Coriolis flow meter according to one of the preceding flow meter embodiments, wherein the Coriolis flow meter is configured to measure mass flow rates at least in the range of 0-2 g / min, preferably at least in the range of 0-5 g / min, more preferably at least in the range of 0-10 g / min. F6. Coriolis flow meter according to one of the preceding flow meter embodiments, wherein the Coriolis flow meter is configured to measure mass flow rates at fluid pressures of at least in the range of 0-30 MPa, preferably at least in the range of 0-100 MPa, more preferably at least in the range of 0-200 MPa.

[0059] The following refers to various forms of use. These forms are abbreviated with the letter "U" followed by a number. Whenever this document refers to "forms of use," these forms are meant. U1. Use of the excitation device according to one of the preceding device embodiments or the Coriolis flow meter according to one of the preceding flow meter embodiments for measuring a mass flow rate. U2. Use according to the preceding embodiment, wherein the mass flow rate is in the range of 0-2 g / min, preferably at least in the range of 0-5 g / min, more preferably at least in the range of 0-10 g / min. U3. Use according to one of the preceding embodiments of use, wherein the mass flow rate is measured at fluid pressures in the range of 0-30 MPa, preferably in the range of 0-100 MPa, more preferably in the range of 0-200 MPa.

[0060] Embodiments of the present invention will now be described with reference to the accompanying drawing. These embodiments are intended only to illustrate, but not to limit, the present invention.

[0061] Fig. Figure 1 represents an embodiment of an excitation device.

[0062] In general, embodiments of the present invention relate to an excitation device for exciting a vibration. An exemplary embodiment of such an excitation device is shown in Fig. Figure 1 shows the excitation device. The excitation device 1 generally comprises a fixable section 11 and a movable section 12 configured to move relative to the fixed section 11. It is understood that the fixable section 11 can generally be configured to be attached to another element, such as a body or housing of a corresponding Coriolis flow meter, during operation of the excitation device. The fixable section 11 can, for example, include fastening means 111, such as at least one threaded bore 111.

[0063] Furthermore, the excitation device 1 has a connecting section 13, and the movable section 12 is connected to the lockable section 11 via the connecting section 13. The connecting section 13 can generally be configured to allow movement of the movable section 12 relative to the lockable section 11. Thus, the connecting section 13 can provide a joint between the lockable section 11 and the movable section 12.

[0064] The movable section 12 can be connected to the fixable section 11 via the connecting section 13, such that the movable section 12 and the fixable section 11 overlap at least partially. In particular, the movable section 12 and the fixable section 11 can overlap perpendicular to the z-direction, i.e., they can have a common base.

[0065] Preferably, the connecting section 13 can provide only one angular degree of freedom. In other words, it may only be movable in one plane. This advantageously reduces and / or suppresses undesired angular movements of the movable section 12 relative to the fixed section 11. In particular, it can be movable in or parallel to a plane extending in the first direction (y-direction) and a second direction (x-direction), the second direction (x-direction) being perpendicular to the first direction. In other words, the connecting section 13 can preferably be movable only parallel to the xz-plane. Thus, it can reduce and / or suppress movement in a third direction (y-direction) that is perpendicular to the first direction (z-direction) and the second direction (x-direction).

[0066] The connecting section 13 can be a bendable section 13. That is, the connecting section 13 can be configured to bend when a corresponding force is applied, preferably via the movable section 12. This allows the movable section 12 to move relative to the fixed section 11 when a corresponding force is applied. Preferably, the connecting section 13 can be a joint, and more preferably a solid joint, e.g., a solid hinge, or a bending element, e.g., a bending joint, a bending hinge, or a bending bearing.

[0067] The connecting section 13 can be symmetrical about a connecting symmetry plane. In the Fig. In the embodiment shown in Figure 1, the connecting section is, for example, symmetrical about the plane of connection symmetry, which extends in the first direction (z-direction) and the second direction (x-direction), i.e., parallel to the xz-plane. Preferably, the connecting section 13 only allows movements parallel to the plane of connection symmetry, thereby limiting the movement of the connecting section 13 to only one angular degree of freedom.

[0068] The movable section 12 can be similarly symmetrical about a plane of symmetry of the movable section. Preferably, the plane of symmetry of the movable section can also extend in the first direction (z-direction) and the second direction (x-direction). More preferably, the plane of symmetry of the movable section can be identical to the connecting plane of symmetry.

[0069] Furthermore, the fixable section 11 can be similarly symmetrical about a plane of symmetry of the fixable section. Preferably, the plane of symmetry of the fixable section can also extend in the first direction (z-direction) and the second direction (x-direction). Even more preferably, the plane of symmetry of the fixable section can be identical to the plane of symmetry of the connection.

[0070] In a preferred embodiment, the excitation device 1 can be symmetrical about a device symmetry plane. Here too, the device symmetry plane can extend in the first direction (z-direction) and the second direction (x-direction). Thus, in such a case, the connection symmetry plane, the symmetry plane of the movable section, the symmetry plane of the fixable section, and the device symmetry plane can be identical, i.e., coincident.

[0071] Furthermore, the excitation device 1 comprises a piezoelectric element 14 and a connecting element 15. The piezoelectric element 14 is fixedly mounted on the fixable section 11, and the connecting element 15 mechanically connects the piezoelectric element 14 to the movable section 12. Thus, the piezoelectric element 14 can generally enable movement of the movable section via the connecting element 15.

[0072] The piezoelectric element 14 can be mounted centrally on the fixable section 11 with respect to the third direction (y-direction). In the case of a symmetrical fixable section 11, the piezoelectric element 14 can therefore also be symmetrical with respect to the plane of symmetry of the fixable section. Preferably, the piezoelectric element 14 can be mounted on the fixable section 11 such that it is arranged centrally with respect to the movable section 12 in the third direction (y-direction). In other words, the piezoelectric element 14 can be mounted on the fixable section such that its projection onto the movable section in the first direction (z-direction) is arranged centrally with respect to the third direction (y-direction). Similarly, the connecting element 15 can preferably be attached centrally with respect to the third direction (y-direction) to the movable section 12.This advantageously avoids the effect of a torque on the moving section in the second direction (x-direction).

[0073] By connecting the movable section 12 to the fixable section 11 via the connecting section 13 and providing a mechanical connection between the piezoelectric element 14 and the movable section 12, movement of the movable section 12 relative to the fixable section 11 can be effected by the piezoelectric element 14, which is attached to the fixable section 11. Furthermore, the connecting section 13 can restrict movement of the movable section 12 by preferably providing only one angular degree of freedom for the movement, which can advantageously make it possible to reduce and / or suppress undesired angular movements of the movable section 12 that could otherwise be caused at the piezoelectric element 14.

[0074] The piezoelectric element 14 can comprise a piezoelectric material such as a piezoelectric single crystal, a piezoelectric ceramic, and / or a piezoelectric thin film. The piezoelectric element 14 can therefore also be referred to as a piezoelectric element 14. In particular, the piezoelectric element 14 can be a piezoelectric actuator. More generally, the piezoelectric element 14 can be configured to provide mechanical movement based on an applied electrical voltage, utilizing the inverse piezoelectric effect. Specifically, the piezoelectric element can be configured to provide a periodic push or pull force, which enables a corresponding oscillation of the movable section 12 relative to the fixed section 11 to be effected via the connecting element 15.The piezoelectric element 14 can preferably be configured to provide a force acting in the first direction (z-direction).

[0075] The piezoelectric element 14 can be electrically isolated from the fixable section 11 by suitable electrical insulation, for example, an insulating element 16. This prevents the electrical voltage applied to the piezoelectric element 14 from flowing to the fixable section 11. The excitation device 1 can further comprise an insulating connecting element 17, which provides electrical insulation between the piezoelectric element 14 and the connecting element 15. The insulating connecting element 17 can, for example, be crimped to the connecting element 15 and / or bonded to the piezoelectric element 14.

[0076] The connecting element 15 can, for example, be a thin rod. The connecting element 15 can be attached to the movable section 12, for example, by crimping or riveting, thus forming a positive-locking and force-locking connection. In general, the connecting element 15 can be flexible but must simultaneously be sufficiently rigid to prevent buckling due to axial compressive stress; that is, the critical Euler load must not be exceeded. For example, the connecting element can be a stainless steel rod, e.g., with a diameter of 0.3 mm and a length of 10 mm. This advantageously compensates for angular errors if the piezoelectric element 14 does not move precisely in the z-direction.Thus, the connecting element 15 can enable the piezoelectric element 14 to push the movable section 12 away from the piezoelectric element 14 and therefore from the fixable section 11, thereby causing a corresponding movement of the latter. Alternatively, the piezoelectric element 14 can pull the movable section towards the piezoelectric element 14 and thus towards the fixable section. In such a case, the connecting element 15 could, for example, be a wire.

[0077] In general, the movable section 12 can be configured to accommodate a measuring tube 18. In some embodiments, the excitation device can include the measuring tube 18. In particular, the measuring tube 18 can be attached to the movable section at two mounting points. The measuring tube 18 can be symmetrical about the plane of symmetry of the connecting section 13. That is, the measuring tube 18 can be arranged in a symmetrical loop between the two mounting points.

[0078] The two fastening points can preferably be located further away from the connecting section 13 in the second direction (x-direction) than the point where the connecting element 15 is attached to the movable section 12. The fastening points can thus be located, for example, at an end of the movable section opposite a connection between the movable section 12 and the connecting section 13, with the connecting element 15 attached to the movable section 12 in between. This advantageously allows the greatest displacement of the movable section 12 to be located near the fastening points.

[0079] The present invention thus advantageously enables the controlled induction of vibration of the movable section, and consequently of the measuring tube 18, by means of the piezoelectric element. In particular, the present invention makes it possible to excite only one eigenmode of the measuring tube that is symmetrical to the xz-plane. The excitation of other eigenmodes with a lateral vibration direction can be advantageously suppressed. Compared to direct excitation with a piezoelectric actuator, higher measurement accuracy is achieved.

[0080] The length of the measuring tube 18 between the two mounting points can be in the range of 50-500 mm, preferably 100-200 mm. This means that the flow path length between each of the two mounting points can be within the specified range.

[0081] In other words, the excitation device 1 comprises a fixable section 11 and a movable section 12, which are connected to each other via a connecting section 13, for example, a solid-state joint. A piezoelectric element, preferably a piezoelectric actuator 14, is attached to the fixable section. Optionally, electrical insulation 16 can be provided between the fixable section 11 and the piezoelectric element 14. A connecting element 15, for example, a thin rod 15, is attached to both the piezoelectric element 14 and the movable section. An insulating connecting element 17, i.e., another electrically insulating body 17, can be located between the connecting element 15 and the piezoelectric element 14. The insulating connecting element 17 can be attached to the connecting element 15, for example, by crimping and / or to the piezoelectric element 14 by gluing.This means that the connecting element 15 can be attached to the piezoelectric element 14 via the insulating connecting element 17. The connecting element 15 can be attached to the movable section 12, for example, by crimping or riveting. The measuring tube 18, which is to be excited to vibration, can be attached to the movable section 12, for example, by crimping, riveting, soldering, or welding.

[0082] The connecting section 13 can comprise multiple loops, but it can also consist of a single thin wall. It can be configured to allow only movements parallel to the plane of symmetry (xz) of the connecting section 13. In the connecting area of ​​the measuring tube 18, this can predominantly involve movement in the z-direction in the example. In particular, rotation about the x-axis can be prevented by the connecting section.

[0083] The connecting element 15 can be a rod that is so thin as to be as flexible as possible, yet still stiff enough to prevent buckling under axial compressive stress. This allows angular errors to be compensated for if the piezoelectric element 14 does not move exactly in the z-direction.

[0084] The movable section 12 can extend over the connecting section 13 to form a counterweight. Preferably, the counterweight is designed such that the center of mass of the movable section 12 is located very close to the axis of rotation of the connecting section 13. This has the advantage that, during high accelerations during transport of the device, virtually no inertial forces act on the piezoelectric element 14, and mechanical stresses that could damage the piezoelectric element can be avoided.

[0085] It is understood that the foregoing serves only as an exemplary embodiment of the present invention and that the movable section 12, the fixable section 11 and / or the connecting section 13 may, for example, have different shapes, as shown in Fig. Figure 1 is shown. Additionally or alternatively, in some embodiments the excitation device 1 can, for example, comprise a plurality of connecting sections 13.

[0086] Thus, the present invention can generally advantageously enable the direction of movement of the piezoelectric element 14 to be decoupled from the direction of movement, for example, the vibration, of the measuring tube 18 in such a way that small angular errors are compensated and the movement occurs predominantly (preferably exclusively) in a desired direction. This can be achieved by transmitting the excitation via a connecting element, for example, a flexible rod, to a movable section 12, the direction of movement of which is restricted by a connecting section 13.

[0087] In this process, a connecting section, preferably a solid-state joint, is used, which may only allow movement in the desired direction and prevents unwanted rotational movement. For excitation, a piezoelectric element 14, for example a piezoelectric actuator, is connected to the connecting section via a connecting element 15, for example a thin rod, which can compensate for small angular errors. Thus, the requirements for the piezoelectric element 14 can be reduced, and a cost-effective piezoelectric (bending) element can be used for excitation.

[0088] Thus, the present invention can enable cost-effective vibration excitation of the measuring tube in a Coriolis mass flow meter with very high measuring accuracy at low flow rates (measuring range from approximately 1 mg / min to approximately 10 g / min).

[0089] Whenever a relative term such as "approximately", "essentially", or "about" is used in this patent specification, this term should also be interpreted as including the exact term. That is to say, for example, "essentially exactly" should also be interpreted as including "(exactly) exactly".

[0090] Whenever steps are mentioned in the preceding or attached claims, it should be noted that the order in which the steps are listed in this text may be arbitrary. That is to say, unless otherwise specified or clear to a person skilled in the art, the order in which the steps are listed may be random. Thus, if this document states, for example, that a method comprises steps (A) and (B), this does not necessarily mean that step (A) precedes step (B), but it is also possible that step (A) is carried out (at least partially) simultaneously with step (B), or that step (B) precedes step (A). Moreover, if it is stated that one step (X) precedes another step (Z), this does not imply that no step takes place between (X) and (Z).This means that step (X), which precedes step (Z), includes the situation where step (X) is executed directly before step (Z), but also the situation where (X) is executed before one or more steps (Y1), ..., followed by step (Z). Similar considerations apply when expressions like "after" or "before" are used.

[0091] While a preferred embodiment has been described in the preceding explanations with reference to the accompanying drawing, those skilled in the art will understand that this embodiment has been provided for illustrative purposes only and should in no way be construed as limiting the scope of protection of this invention as defined by the claims. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 1 719 983 B1

[0011] Cited non-patent literature

[0000] MICRO CORIOLIS MASS FLOW SENSOR DRIVEN BY EXTERNAL PIEZO CERAMIC" are disclosed, which was presented at the 3rd Conference on Microfluidic Handling Systems from October 4 to 6, 2017

[0012] Y. Zeng et al. were presented (https: / / ris.utwente.nl / ws / portalfiles / portal / 19542377 / coriolis_piezo.pdf)

[0012]

Claims

[1] Excitation device for exciting an oscillation, comprising a fixable section (11); a movable section (12) configured to move relative to the fixed section (11); a connecting section (13), wherein the movable section (12) is connected to the fixable section (11) via the connecting section (13); a piezo element (14) that is fixedly mounted on the fixable section (11); and a connecting element (15) that mechanically connects the piezo element (14) and the movable section (12). [2] Excitation device according to the preceding claim, wherein the connecting section (13) is configured to allow movement of the movable section (12) in relation to the fixable section (11). [3] Excitation device according to one of the preceding claims, wherein the connecting section (13) is configured to provide only one degree of angle or degree of freedom. [4] Excitation device according to one of the preceding claims, wherein the connecting section comprises a joint. [5] Excitation device according to one of the preceding claims, wherein the piezo element (14) is configured to effect a movement of the movable section (12) relative to the fixable section (11) via the connecting element (15). [6] Excitation device according to one of the preceding claims, wherein the excitation device comprises a measuring tube (18) and wherein the measuring tube (18) is attached to the movable section at two attachment points. [7] Excitation device according to the preceding claim, wherein the excitation device is configured to excite only one eigenmode of the measuring tube. [8] Excitation device according to one of the two preceding claims, wherein the measuring tube is configured for a mass flow rate of at least 0-2 g / min, preferably 0-5 g / min, more preferably 0-10 g / min. [9] Excitation device according to one of the 3 preceding claims, wherein the measuring tube is configured to guide fluids with pressures of at least 0-30 MPa, preferably 0-100 MPa, more preferably 0-200 MPa. [10] Coriolis flow meter comprising a measuring tube; at least one sensor configured to detect movement of the measuring tube; and an excitation device according to any one of claims 1 to 9, which is configured to excite a vibration of the measuring tube.

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