Measuring drive having ultrasound-mounted shaft, measuring device, method and use

Abstract

Described is a measuring drive for a measuring instrument, in particular a rheometer. The measuring drive has: i) a motor, ii) a shaft, which is coupled to the motor in such a way that the shaft is drivable by the motor, and iii) an ultrasonic device, which is configured to provide ultrasound to the shaft in such a way that at least a part of the shaft is bearable substantially without contact by the ultrasound. Furthermore, the measuring instrument, a method, and a using are described.

Claims

1. A measuring drive for a rheometer, the measuring drive comprising: a motor; a shaft which is coupled to the motor in such a way that the shaft is drivable by the motor, the shaft having a shaft element; and an ultrasonic device, which is configured to provide ultrasound to the shaft in such a way that at least a part of the shaft is bearable substantially without contact by the ultrasound, wherein the ultrasonic device is configured to bear the shaft element substantially without contact both in an axial direction and in a radial direction of the shaft.

2. The measuring drive according to claim 1, wherein the ultrasonic device is configured to emit the ultrasound in such a way that at least a part of the shaft is bearable levitatingly by the ultrasound.

3. The measuring drive according to claim 1, wherein the ultrasonic device is configured as a standing wave effect ultrasonic device and/or a near field effect ultrasonic device.

4. The measuring drive according to claim 1, wherein the motor is a rotational measuring motor, which is configured to rotate the shaft, which is a measuring shaft, in the radial direction.

5. The measuring drive according to claim 1, wherein the motor is a linear measuring motor configured to move the shaft, which is an actuating shaft, in the axial direction.

6. The measuring drive according to claim 1, wherein the ultrasonic device has at least two ultrasonic sources, which are arranged substantially opposingly to each other, and wherein at least a part of the shaft is arranged between the substantially opposing ultrasonic sources.

7. The measuring drive according to claim 3, wherein the ultrasonic source has an ultrasonic emitter and a sonotrode, wherein the sonotrode is arranged in front of the emitter in the sound emission direction.

8. The measuring drive according to claim 1, wherein the shaft element is coupled to the shaft with its main extension direction oriented substantially perpendicular to the axial direction of the shaft, and wherein the ultrasonic device is configured in such a way that the shaft element is bearable substantially without contact by the ultrasound.

9. The measuring drive according to claim 8, wherein the ultrasonic device has at least four ultrasonic sources, wherein, viewed in the axial direction of the shaft, two ultrasonic sources are arranged above and two ultrasonic sources are arranged below the shaft element, and wherein, viewed in the radial direction of the shaft, two ultrasonic sources are arranged substantially opposingly to the other two ultrasonic sources with the shaft in between.

10. The measuring drive according to claim 8, wherein the shaft has at least two shaft elements which are spatially spaced apart from each other and thereby form an interspace, and wherein the ultrasonic device has at least two ultrasonic sources, which are arranged substantially opposingly to each other in such a way that emitted ultrasound at least partially impinges on the interspace, whereby that at least two shaft elements are bearable substantially without contact.

11. The measuring drive according to claim 8, wherein at least one shaft element has substantially a shape, which is selected from the group that consists of a disc, an annular disc, a plate, a truncated cone, a hemisphere, or a truncated pyramid.

12. A rheometer, for determining an information that is indicative of the rheological properties of a sample, the rheometer, comprising: a measuring drive including a motor, a shaft coupled to the motor in such a way that the shaft is drivable by the motor, the shaft having a shaft element, an ultrasonic device configured to provide ultrasound to the shaft in such a way that at least a part of the shaft is bearable substantially without contact by the ultrasound, wherein the ultrasonic device is configured to bear the shaft element substantially without contact both in the axial direction and in the radial direction of the shaft; and a sample carrier for positioning the sample, wherein the shaft is coupleable to the positioned sample.

13. The rheometer according to claim 12, wherein the sample carrier is arranged between the measuring shaft and the actuating shaft.

14. The rheometer according to claim 12, further comprising: a measuring unit for measuring the indicative information on the shaft.

15. The rheometer according to claim 12, further comprising: a hermetically lockable cell, wherein at least a part of the ultrasonic device, at least a part of the shaft, and the sample carrier are arranged in the hermetically lockable cell; and a pressure container for charging the hermetically lockable cell with a pressure profile.

16. A method for determining an information that is indicative of the rheological properties of a sample by a rheometer, which has a motor and a shaft coupled to the motor, the shaft having a shaft element, the method, comprising: providing the sample and coupling the shaft to the sample; driving the shaft by the motor so that indicative information is transferred to the movement characteristic of the shaft; emitting ultrasound by an ultrasonic device to the shaft in such a way that at least a part of the shaft is beared substantially without contact by the ultrasound; emitting ultrasound by the ultrasonic device in such a way that the shaft element is beared substantially without contact in the axial direction and in the radial direction of the shaft; and detecting the movement characteristics of the shaft to determine the information indicative of the rheological properties of the sample.

17. The method according to claim 16, further comprising: wherein the shaft element, which is coupled to the shaft with the main extension direction oriented substantially perpendicular to the axial direction of the shaft.

18. The method according to claim 16, wherein detecting includes providing a capacitive measuring unit, for measuring the indicative information on the shaft or shaft element.

19. The method according to claim 16, further comprising: inserting at least a part of the rheometer, and the sample, into a hermetically locked cell; wherein the hermetically locked cell is at least partially filled with a gas, which has a higher density than air.

20. The method according to claim 19, further comprising: providing a pressure container for charging the hermetically locked cell with a pressure profile.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, exemplary embodiment examples of the present invention are described in detail with reference to the following drawings.

(2) FIG. 1 shows a measuring device having a measuring drive according to an exemplary embodiment example of the invention.

(3) FIG. 2 shows a measuring device having a pressure cell according to an exemplary embodiment example of the invention.

(4) FIG. 3, FIG. 4, FIG. 5, FIG. 6 and FIG. 7 show exemplary embodiments of a shaft and the ultrasonic device of the invention.

(5) FIG. 8 shows a measuring device having a multiple drive according to an exemplary embodiment example of the invention.

DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS

(6) Identical or similar components in different figures are provided with the same reference numerals.

(7) Before exemplary embodiment examples of the invention are described with reference to the figures, some general aspects of the invention will be explained.

(8) According to an exemplary embodiment example, the bearing (or supporting) of the measuring drive in a rheometer via an ultrasonic bearing provide the following advantages over conventional air bearings: i) no “flowing” gas (e.g. compressed air) necessary, ii) cheaper because no air treatment is necessary, iii) mobile and independent of availability of compressed air, iv) applicable in a completely closed environment (e.g. pressure chamber), v) simpler design (no porous materials necessary), vi) more robust due to higher air gaps, vii) lower energy consumption in comparison to compressed air. Compared to conventional ball bearings, there may be the advantages of lower residual friction and better adjustability (constant-angle residual friction curves).

(9) According to an exemplary embodiment example, the bearing of the measuring drive in a rheometer via an ultrasonic bearing may provide the following further advantages: i) alternative bearing forms for easier manufacturability (e.g. double-spherical, double-conical), (ii) combinable with the capacitive normal force measurement, (iii) combinable with the known drive technology, (iv) scalable (normal force and transverse force stiffness), (v) load capacity can be increased to alternative gases (e.g. argon), (vi) possible improvement of the bearing properties by exploiting and combining the standing wave effect and the near field effect.

(10) According to an exemplary embodiment example, an ultrasonic bearing may be in use in a multi(plural)drive rheometer (air bearings were previously in use). At least two, preferably four, ultrasonic sources may be arranged on the shaft of a linear motor, which in combination with flat cantilevers hold the measuring shaft (linear feed, deflection either limited linear or in oscillation). For this purpose, the ultrasonic emitters with corresponding horns may be mounted opposite to each other in the air gap. Gap geometry may be optimized here so that the stiffness may be sufficient for the rheometer. The load-bearing capacity may be reinforced by gases of higher density, or by the combination of lift and push modes for the bearing. On the bottom side, the bearing may be operated in the push mode, thus the counter-movement to gravity may be amplified. On the top side, the bearing may be operated in the lift mode in an attracting manner. Thereby, the centering in the rotation bearing may be improved.

(11) According to an exemplary embodiment example, the acting torque may be a central parameter for the rheological measurements. The torque may be either determinable from the angle of rotation in the case of a motor axis with a spring-loaded arrangement (e.g.: Brookfield type viscometer), or it may be measured by the motor current consumption for a certain speed (depending on the motor type, the torque M may be proportional to current I or I.sup.2). The normal force or axial deflection may play a central role in dynamic mechanical analysis with linear deflections, but also in the rotational test procedure when the rotary movement may cause additional axial forces (for example Weissenberg effect).

(12) FIG. 1 shows a rheometer 101 for determining an information that may be indicative of the rheological properties (e.g. the viscosity) of a sample 150 (in the present case a liquid). The measuring device 101 may have a measuring drive 100 having a motor 110, a shaft 120, and an ultrasonic device 130. The shaft 120 may be coupled to the motor 110 in such a way that the shaft 120 may be drivable by means of the motor 110. Thus, the motor 110 may be a rotary motor and may put the shaft 120, which may be a measuring shaft, in rotation. The ultrasonic device 130 may be arranged in the axial direction A of the shaft 120 and may provide ultrasound in such a way that a part of the shaft 120 may be beared without contact by the ultrasound 135.

(13) The rheometer 101 may have a sample carrier 155 onto which the sample liquid 150 may be applied. Herein, the shaft 120 may be coupled to a measuring element 156, configured as a measuring cone, which element may cover the sample 150. Now, when the shaft 120 may rotate, the rheological properties, in particular the viscosity, of the sample liquid 150 may affect the movement characteristics, in particular the torque and/or the angle of rotation and/or the normal force N, of the rotating shaft 120. For capturing these measurands and/or information that may be indicative of the rheological properties of the sample fluid 150. For torque measurement, the prevailing torque may be determined from the current consumption of the measuring motor, and for capturing the normal force N, the rheometer 101 may have a measuring unit 161. In the present case, this may concern a capacitive measuring unit 161, which may carry out a measurement of the normal force N in a known manner via capacitors. The determined data may be forwarded to a control unit 160. The control unit 160 may further be configured to control and/or to regulate the motor 110. In order to advantageously carry out the measurement, the shaft 120 may have a shaft element 125 in the form of a disc, the main extension direction of which, may be arranged perpendicularly in the axial direction A of the shaft 120 on the latter.

(14) In the embodiment example shown, the shaft element 125 in particular may be the part of the shaft 120, which may be beared without contact by the ultrasonic device 130. In this case, the ultrasonic device may be configured to provide and/or emit ultrasound 135 in such a way that the shaft element 125 (and thus also at least partially the shaft 120) may be beared levitatingly, in particular frictionless levitatingly, by the ultrasound. The ultrasonic device 130 may have four ultrasonic sources 131a, 131b, 131c, 131d, wherein, viewed in the axial direction A of the shaft 120, two ultrasonic sources 131a, 131b may be arranged above and two ultrasonic sources 131c, 131d may be arranged below the shaft element 125. Furthermore, viewed in the radial direction R of the shaft 120, two ultrasonic sources 131a, 131c may be arranged substantially opposite to the other two ultrasonic sources 131b, 131d, with the shaft 120 between them. In this preferred embodiment, the ultrasonic device 130 may be configured to bear the shaft member 125 without contact both in the axial direction A as well as in the radial direction R of the shaft 120. The air gap may be filled with a gas having a higher density than air (e.g. argon) in order to achieve a higher rigidity.

(15) FIG. 2 shows a measuring device 201 according to a further exemplary embodiment example of the invention. The measuring device 201 may additionally have a hermetically (in particular fluid-tight) lockable cell 220, which may concern a pressure cell. A part of the ultrasonic device 130, a part of the shaft 120b, and the sample carrier 155 together with the sample 150 may be arranged in the pressure cell 220. The measuring device 201 may have a pressure container 210 for applying a pressure profile to the pressure cell 220 via a valve 211. For example, the pressure cell 220 may be pressurized by a hydraulic system or similar means.

(16) A second part of the sensing shaft 120b may have magnets 230b at the upper end, which may couple with magnets 230a of a first part of the sensing shaft 120a of the motor 110. The measuring motor 110 may rotate the first part of the shaft 120a with the permanent magnets 230a, and these magnets may couple with the magnets 230b on the second part of the shaft 120a in the closed pressure cell 220. It may be possible with this embodiment to provide a fluid-tight form with ultrasonic bearing.

(17) FIG. 3 shows an exemplary embodiment example of the shaft 120 and two shaft elements 125a, 125b. The two shaft elements 125a, 125b may be arranged on the shaft 120 and may be spaced apart from each other so that an interspace 126 may be formed between the two shaft elements 125a, 125b on the shaft 120. The ultrasonic device 130 may have two ultrasonic sources 131a, 131b, which may be arranged opposite to each other. Each ultrasonic source 131a, 131b may have an emitter 132a, 132b and a sonotrode 133a, 133b, wherein the sonotrodes 133a, 133b may each be directed towards the region of the shaft 120, at which the interspace 126 may be located. The sonotrodes 133a, 133b may be arranged in front of the emitters 132a, 132b in the direction of sound emission. The ultrasound 135 that may be emitted by both ultrasonic sources 131a, 131b may impinge on the interspace 126 from opposite directions, whereby the two shaft elements 125a, 125b may be beared without contact. In the example shown, both shaft elements 125a, 125b may be formed as hemispheres, wherein the interspace 126 may be formed between the rounded surfaces.

(18) FIG. 4 shows an exemplary embodiment example of the shaft 120 and a shaft element 125. The shaft element 125 may be oriented with its main extension direction perpendicular to the axial direction A of the shaft 120 and may be coupled to the same. The ultrasonic device 130 may be arranged in such a way that the shaft element 125 may be beared without contact both in the axial direction A and in the radial direction R of the shaft 120 by the emitted ultrasound 135. For this purpose, the ultrasonic device 130 may have four ultrasonic sources 131a-d. Viewed in the axial direction A of the shaft 120, two ultrasound sources 131a, 131b each may be arranged above and two ultrasound sources 131c, 131d each may be arranged below the shaft element 125. Furthermore, viewed in the radial direction R of the shaft 120, two ultrasonic sources 131a, 131c each may be arranged opposite to each of the two other ultrasonic sources 131b, 131d, with the shaft 120 between them.

(19) FIG. 5 shows an exemplary embodiment example of the shaft 120 and the ultrasonic device 130. The shaft 120 may be a measuring shaft or an actuating shaft and two ultrasonic sources 131a, 131b may be arranged opposite to each other with the shaft 120 in between. In a preferred embodiment example, four ultrasonic sources 131a-d (not shown) may be arranged around the shaft 120, each opposite to each other. The shaft 120 may be formed round (e.g. rod-shaped), but also rectangular. By the emitted ultrasound 135 from the ultrasonic sources 131a, 131b, the shaft 120 may be beared particularly efficiently in a specific position.

(20) FIG. 6 shows a top view of the embodiment example described above for FIG. 5, wherein four ultrasonic sources 131a-d may be arranged around the shaft 120. In this example, the ultrasonic sources 131a-d each may have a horn 134 between the emitter 132 and the sonotrode 133.

(21) FIG. 7 shows an exemplary embodiment example of the shaft 120 and the ultrasonic device 130, wherein the ultrasonic device 130 may be configured as a casing (or envelope) of the shaft 120. Herein, the ultrasonic sources may be mounted within the casing, or the inner side of the casing may serve as an ultrasonic source.

(22) FIG. 8 shows an exemplary embodiment example of a measuring device 800, which may have a measuring shaft 120 and an actuating shaft 121. Such a multi-drive system may use a combination of a linear motor 111, which may drive the actuating shaft 121, and a rotary motor 110, which may drive the measuring shaft 120. Herein, a common control unit 160 may control and/or regulate both the rotary motor 110 and the linear motor 111. In addition, the control unit 160 may monitor (or readjust) the rotation speed or the torque, and may be connected to an angle encoder 166 and a torque detector 165 for this purpose. A sample carrier 155, into which the sample fluid 150 may be introduced, may be arranged between a measuring element 156 at the lower end of the measuring shaft 120 and a measuring element 157 at the upper end of the actuating shaft 121. Both the measuring shaft 120 and the actuating shaft 121 may have a coupling 128. At the level of the measuring device, the rotary motor 110 may be provided in a first carrier 170 and the linear motor 111 may be provided in a second carrier 171 of the measuring device. The carriers 170, 171 may be attached to a stand 180 and the first carrier 170 may be adjusted in height relative to the second carrier 171 via an actuating part 181 and an actuating spindle 182 by an actuating motor 183. The interplay of the rotating measuring shaft 120 and the linearly movable actuating shaft 121 may enable particularly accurate (rheological) measurements.

(23) The measuring shaft 120 may have the shaft element 120 already described above in the form of a disc. Four ultrasonic sources 131a-d may be arranged with respect to the sides of the shaft 120 and the shaft element 125 in such a way that the shaft element 125 may be beared in the axial direction A and in the radial direction R of the shaft 120 without contact by ultrasonic levitation (see in this respect the description of FIG. 4 above). Two (preferably four) ultrasonic devices 130 may be arranged around the actuating shaft 121 in a similar manner as shown in the FIGS. 5 to 7. The emitted ultrasound 135 may ensure that the deflection of the actuating shaft 121 may be limited and the stability may be increased.

(24) Supplementarily, it is to be noted that “having” (or “comprising”) does not exclude other elements or steps, and that “a” or “an” does not exclude a plurality. It is further be noted that features or steps, which have been described with reference to any of the above embodiments, may also be used in combination with other features or steps of other embodiment examples described above.

REFERENCE NUMERALS

(25) 100, 800 measuring drive

(26) 101, 201 measuring device, rheometer

(27) 110 motor, rotary motor

(28) 111 linear motor

(29) 120 shaft, measuring shaft

(30) 120a first shaft section

(31) 120b second shaft section

(32) 121 actuating shaft

(33) 125 shaft element

(34) 125a first shaft element

(35) 125b second shaft element

(36) 126 interspace

(37) 128 coupling

(38) 130 ultrasonic device

(39) 131a-d ultrasonic source

(40) 132a,b emitter

(41) 133a,b sonotrode

(42) 134 horn

(43) 135 ultrasound

(44) 150 sample

(45) 155 sample carrier

(46) 156 measuring element

(47) 157 further measuring element

(48) 160 control unit

(49) 161 capacitive measuring unit

(50) 165 torque detector

(51) 166 angular encoder

(52) 170 first carrier

(53) 171 second carrier

(54) 180 stand

(55) 181 actuating part

(56) 182 actuating spindle

(57) 183 actuating motor

(58) 210 pressure container

(59) 211 pressure valve

(60) 220 pressure cell

(61) 230a,b magnets