HK1162659B - Coriolis flow meter with improved mode separation - Google Patents

Description

Coriolis flowmeter with improved mode separation

Technical Field

The present invention relates to a flow meter, and more particularly, to a method and apparatus for improving the separation between two or more vibration frequencies in a vibrating flow meter.

Background

Flow meters are used to measure mass flow rate, density, and other properties of a flowing substance. The flowable substance may comprise a liquid, a gas, a solid suspended in a liquid or a gas, or any combination thereof. Vibrating conduit sensors, such as Coriolis mass flow meters and vibrating densitometers, typically operate by detecting motion of a vibrating conduit containing a flow material. Properties related to the substance in the conduit, such as mass flow, density, etc., may be determined by processing measurement signals received from a motion transducer associated with the conduit. The vibration modes of a mass-filled vibration system are typically affected by the combined mass, stiffness, and damping characteristics of the containment duct and the mass contained therein.

A typical coriolis mass flowmeter includes one or more conduits that are serially connected in a pipeline or other transport system and convey a substance, such as a fluid, slurry, or the like, in the system. Each conduit can be considered to have a set of natural vibration modes including, for example, simple bending, torsional, radial, transverse, and coupled modes. In a typical coriolis mass flow measurement application, a conduit is excited in one or more vibration modes as a material flows through the conduit, and motion of the conduit is measured at a plurality of locations spaced along the conduit. Typically, the excitation is generated by an actuator that perturbs the conduit in a periodic manner, such as an electromechanical device (e.g., a voice coil type driver, etc.). The mass flow rate may be determined by measuring the time delay or phase difference between the motions at each transducer location. The density of the flow material can be determined from the frequency of the vibrational response of the flow meter. To measure the vibrational response of one or more flow conduits, two transducers of this type (or pick-off sensors) are typically used and are typically provided at positions upstream and downstream of the actuator. The two pickoff sensors are typically connected to the electronics by a cable (e.g., two pairs of individual wires). To obtain flow measurements, electronics receive signals from the two pickoff sensors and process the signals.

In operation, the flow tubes are driven out of phase with one another. The driving force is generated by an electromechanical driver that causes the flow tubes to vibrate out of phase at their natural resonant frequency. For purposes of illustration, the flow tube may be described as being driven in a vertical plane by a driver. These vertical vibrations are relatively large because they are in the first out of phase bending mode of the flow tube and are driven at their natural resonant frequency.

The coriolis effect of a vibrating flow tube with material flow also occurs in the same vertical plane as the drive vibration. The coriolis effect occurs at the drive frequency, but the flow tube deflections are shaped with higher frequency bending modes. Thus, the amplitude of the coriolis effect is much less than the amplitude of the flow tube drive frequency vibration. Even though the amplitude of the coriolis response is relatively small, it is the coriolis response that produces the pickoff output signals that are processed by the meter electronics to produce the desired mass flow rate and other information about the flow material. Many coriolis flow meters are capable of achieving an output error of about 0.15% or less. However, to achieve this accuracy, noise and undesired signals must be minimized.

In operation of a coriolis flow meter, the signals induced in the pickoff sensors include not only the desired relatively small amplitude coriolis response signals, but also undesired signals applied to the processing circuitry and the desired coriolis response signals. These undesired signals impair the ability of the processing circuitry to produce accurate output signals.

The unwanted pick-up signal may be caused by ambient noise from the surrounding environment. The environmental noise may be caused by nearby machines or the like. Ambient noise may also be caused by vibrations in the pipeline to which the coriolis flow meter is connected. Ambient noise can be overcome by properly mounting the flow meter so that it is isolated from external vibrations. Noise from connected pipeline vibrations can be overcome by proper isolation of the flow meter from the pipeline.

Another source of undesired signals is undesired vibrations in the flow meter. These undesirable vibrations are more difficult to overcome but can be minimized by modifying the flow meter configuration, however, these undesirable vibrations generally cannot be eliminated.

Most vibratory flow meters have various modal shapes that result from driving the flow meter at the flow meter resonant frequency. Typical flow meters can have vibration modes characterized by their shape, as follows:

in-phase bending (IPB)

In-phase transverse (IPL)

Out-of-phase bending (Drive)

Out-of-phase transverse (OPL)

Out of phase bending is generally the desired drive mode, while the others are generally undesired modes. The modes mentioned above are inherent in most vibratory flow meters, including coriolis flow meters. The frequency of these modes generally varies with the density of the flowing substance. When the modes change frequency, interactions between adjacent modes may occur that cause the flow meter to become unstable and produce erroneous output data. As described above, the desired mode for producing the desired output signal of the flow meter is an out of phase bending drive mode. It is this mode that generates coriolis forces. The resulting coriolis response is detected by the pickoff sensors, which generate signals that provide flow meter output information.

In-phase lateral and out-of-phase lateral vibrations can create problems when processing signals received by the pickup sensors that are indicative of coriolis forces. The transverse mode vibrations are typically off the drive plane. The transverse mode vibration is generally substantially perpendicular to the drive mode vibration. The transverse plane is substantially perpendicular to the applied oscillation.

One way to minimize the adverse effects of two different transverse frequencies is to increase the difference between the drive mode frequency and the undesired transverse frequency. If these undesired lateral mode signals have too large an amplitude and/or are close to the frequency of the coriolis response signal, the electronic processing circuitry may not be able to process the coriolis signal to produce output information with the desired accuracy.

As can be appreciated from the foregoing, minimizing the adverse effects on the signal caused by the undesired mode of vibration is a problem in the design and operation of a coriolis flow meter, and therefore the processing of the coriolis response signal is not compromised by the output accuracy of the output signal of the flow meter.

Many prior art methods attempt to increase the difference between the drive mode frequency and the transverse mode frequency. One such method is set forth in U.S. patent 6,314,820 assigned to the applicant of the present invention. The' 820 patent contains a lateral mode stabilization device that slides over the entire flow tube and includes inwardly extending extensions to stiffen the lateral portion of the flow tube to increase the lateral vibration frequency. A stabilizer is held using a stabilizer bar. While the method disclosed in the' 820 patent provides desirable results, the method requires an excessive number of components in addition to the balance bar. In addition, although the lateral mode stabilization devices can be implemented in curved flow tube designs, they are more suitable for straight tube designs.

Another prior art method is disclosed in us patent 5,115,683, which uses a bracket with one end attached to the flow tube near the driver and the other end attached to the base. The support is flexible to allow motion of the flow tube due to coriolis reactions but to limit the ability of the flow tube to move laterally. Furthermore, the' 683 patent requires an excessive number of vulnerable components.

Another prior art method is disclosed in us patent 6,354,154 assigned to the applicant of the present invention which uses a balance bar with side ribs which dampen undesirable lateral vibrations and thereby increase the frequency of the lateral vibrations. Us patent 6,598,489 uses a similar concept to the' 154 patent but designs the shape of the ribs to increase the resonant frequency of the drive mode relative to the transverse mode. A limitation of the '154 and' 489 patents is the need for a stabilizer bar. This approach has limited applicability since the balance bar is not typically implemented in a dual flow tube flow meter.

Another prior art approach is disclosed in us patent 7,275,449 and us 4,781,069, both of which disclose the use of plates or brackets that connect two flow tubes together in a manner that increases the transverse mode frequency to separate the transverse mode from the drive mode. A problem with this approach is that the drive mode can also be adversely affected since the plate connects two independent flow tubes together. This is especially true in low flow rate applications.

Accordingly, there is a need in the art for a flow meter design that is capable of separating at least two vibration modes. There is also a need to separate at least two vibration modes without requiring excessive components. The present invention addresses these and other problems and advances in the art.

Disclosure of Invention

According to one aspect of the invention, there is provided a flow meter comprising one or more flow tubes and a driver adapted to vibrate the one or more flow tubes at a drive frequency, the flow tubes comprising:

a gusset coupled to and extending along the flow tube such that a frequency difference between the drive frequency and at least the second vibration frequency is increased.

Preferably, the gusset extends along a portion of the flow tube.

Preferably, the gusset extends along substantially the entire flow tube.

Preferably, the gusset joins two or more portions of the flow tube together.

Preferably, the at least second vibration frequency comprises a transverse vibration mode.

Preferably, the gusset is coupled to the flow tube such that a portion of the flow tube is increased in stiffness.

Preferably, the gusset is adapted to increase the frequency of the lateral vibration mode.

Preferably, the gusset is formed as an integral part of the flow tube.

According to another aspect of the invention, there is provided a flow meter comprising one or more flow tubes and a driver adapted to vibrate the one or more flow tubes at a drive frequency, the flow tubes comprising:

a gusset coupled to and extending along the flow tube such that a portion of the flow tube is increased in stiffness.

Preferably, the gusset extends along a portion of the flow tube.

Preferably, the gusset extends along substantially the entire flow tube.

Preferably, the gusset joins two or more portions of the flow tube together.

Preferably, the gusset is adapted to increase the frequency discrimination between two or more vibration modes.

Preferably, the gusset is adapted to increase the difference between the frequency of the driving vibration and the frequency of the lateral vibration.

Preferably, the gusset is adapted to increase the frequency of the lateral vibrations.

Preferably, the gusset comprises an integral part of the flow tube.

According to an aspect of the invention, there is provided a method of increasing the discrimination between two or more vibration frequencies of a vibrating flow meter, the vibrating flow meter including one or more flow tubes and a driver arranged to vibrate the one or more flow tubes in a drive plane at a drive frequency, the method comprising the steps of:

a gusset is coupled to the flow tube such that a difference between two or more vibration frequencies is increased.

Preferably, the step of coupling the gusset to the flow tube comprises extending the gusset along a portion of the flow tube.

Preferably, the step of coupling the gusset to the flow tube comprises extending the gusset along substantially the entire length of the flow tube.

Preferably, the step of coupling the gusset to the flow tube comprises coupling two or more portions of the flow tube together.

Preferably, the two or more vibration frequencies include a drive frequency and a lateral vibration frequency.

Preferably, the step of coupling the gusset to the flow tube comprises coupling the gusset to two or more portions of the flow tube such that the frequency of the lateral vibration mode is increased.

Preferably, the step of coupling the gusset to the flow tube comprises coupling the gusset to two or more portions of the flow tube such that a portion of the flow tube is increased in stiffness.

Drawings

Fig. 1 shows a prior art flow meter.

FIG. 2 shows a flow meter including gussets coupled to outer bends of a flow tube, according to an embodiment of the invention.

FIG. 3 shows a flow meter including gussets coupled to an inner bend of a flow tube, according to another embodiment of the invention.

FIG. 4 shows a flow meter according to another embodiment of the invention including gussets coupled to an outer bend and an inner bend of a flow tube.

FIG. 5 shows a flow meter according to another embodiment of the invention comprising individual gussets joining three straight sections of flow tube.

FIG. 6 illustrates a flow meter including gussets coupled across an outer bend of a flow tube, according to another embodiment of the invention.

FIG. 7 shows a flow meter including gussets coupled to straight and curved portions of a flow tube, according to an embodiment of the invention.

FIG. 8 illustrates a straight tube flow meter including gussets coupled to the flow tube, according to an embodiment of the present invention.

Detailed Description

Fig. 1-8 and the following description present specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, certain conventional aspects have been simplified or omitted. Those skilled in the art will envision modifications to these examples that would fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Accordingly, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.

Fig. 1 shows a flow meter 10 according to the prior art. The flow meter 10 may comprise, for example, a coriolis flow meter. The flowmeter 10 includes an inlet flange 101 and an outlet flange 101'. The flow meter 10 is adapted to be connected to a fluid line by an inlet flange 101 and an outlet flange 101'. As fluid flows into inlet flange 101, manifold 102 diverts the fluid to form two separate sub-streams. The fluid separates and flows into one of the flow tubes 103 or 103'. As the process fluid exits the flow tubes 103, 103 ', the manifold 102 ' rejoins the process fluid before the process fluid exits via the outlet manifold 101 '. Flowmeter 10 further includes a driver 104, driver 104 including a magnet 104A and a coil assembly 104B. Similarly, flowmeter 10 includes a first pickoff sensor 105 and a second pickoff sensor 106 having magnets 105A (not shown), 106A and coil assemblies 105B, 106B.

The flow tubes 103, 103' may be generally divided into the following tube sections. However, it is contemplated that the tube sections are shown for ease of understanding only, as the flow tubes 103, 103' are typically formed as a single continuous piece. Furthermore, the pipe sections relate to U-shaped flow pipes as shown in the figures. However, it should be understood that the present invention is equally applicable to straight flow pipes (see fig. 8). Additionally, although the flow meter is shown as a dual flow tube flow meter, it should be understood that the present invention is equally applicable to a single flow tube flow meter. Therefore, the invention should not be limited to the embodiments shown in the drawings, and those skilled in the art will recognize that various modifications will fall within the scope of the claims.

The first curved portion 151, 151 ' connects the first straight portion 150, 150 ' with the second straight portion 152, 152 '. The second curved portion 153, 153 ' connects the second straight portion 152, 152 ' and the third straight portion 154, 154 '. The third curved portion 155, 155 ' connects the third straight portion 154, 154 ' and the fourth straight portion 156, 156 '. The fourth curved portion 157, 157 ' connects the fourth straight portion 156, 156 ' with the fifth straight portion 158, 158 '. It is contemplated that other configurations are known in the art, and thus the present invention should not be limited to requiring all of the above. Furthermore, the present invention may be practiced with flow tubes having more than the tube sections listed above.

In operation, a drive signal is sent to drive coil 104B via lead 110 by meter electronics 20. The drive signal causes the flow tubes 103, 103' to vibrate in the drive plane. The drive plane is defined by flow tubes 103, 103 'that oscillate about bending axis W, W', respectively. The axis W, W' is defined in part by a plurality of struts 120 and 123 that bound the effective area of the flow meter 10. Vibrating flow tubes 103, 103 'induce a voltage in pickoff sensors 105, 106, which is sent to meter electronics 20 via leads 111 and 111'. The meter electronics 20 generates mass flow information and other information, such as material density, based on the signals sent by the pickoff sensors 105, 106. Temperature measurement devices (not shown) such as RTDs may also perform temperature measurements. The meter electronics 20 can send this information to a downstream processor via lead 26.

The relatively unstable flow tubes 103, 103' of the prior art flowmeter 10 are disturbed by noise generated by transverse mode vibrations. The transverse mode vibrations are typically close to the drive mode vibrations and thus cause excessive disturbances in the signals received from the pickup sensors 105A, 105B and 106A, 106B.

Fig. 2 shows a flow meter 20 according to an embodiment of the invention. For simplicity, some components of flow meter 20, such as support rod 120 and 123, are omitted. However, it should be understood that these components are included in most cases. Although flow meter 20 is shown as a coriolis mass flow meter, it should be understood that the present invention is equally readily applicable to other vibratory flow meters that lack the mass flow measurement capability of a coriolis mass flow meter. Thus, the present invention is not limited to coriolis mass flowmeters, but may include other vibratory flowmeters, such as vibrating densitometers.

In addition to the components included in the prior art flow meter 10, the flow meter 20 according to embodiments of the present invention includes one or more gussets 260. One or more gussets 260 may be coupled to the flow tubes 103, 103'. One or more gussets 260 may extend along the flow tube 103, 103'. One or more gussets 260 may extend along a portion of the flow tube 103, 103', or alternatively, the gussets 260 may extend along substantially the entire flow tube. For clarity, the following discussion describes gusset 260 coupled to first flow tube 103 only; however, it is contemplated that in many embodiments, both flow tubes 103 and 103' may include one or more gussets 260.

According to an embodiment of the invention, the flow meter 20 includes one or more gussets 260 coupled to the flow tube 103 and extending along the flow tube 103. For example, one or more gussets 260 may be coupled to a portion of the flow tube 103 and extend along a portion of the flow tube 103. In the embodiment shown in fig. 2, the gussets 260 are coupled to and extend along portions of the flow tube 103. According to an embodiment of the invention, one or more gussets 260 join two or more straight portions of the flow tube together. According to an embodiment of the invention, one or more gussets 260 are coupled to the flow tube 103 such that a portion of the flow tube 103 is increased in stiffness. According to embodiments of the present invention, one or more gussets 260 may be coupled to the flow tube 103 such that the frequency discrimination between two or more vibration modes is increased. According to an embodiment of the present invention, the two or more vibration modes may include a driving mode and a lateral mode. However, it should be understood that the gussets 260 may be coupled to the flow tube 103 such that other vibration modes are separated. Thus, the present invention should not be limited to separating the vibration frequencies of the drive mode and the transverse mode. It is envisioned that, unlike prior art solutions, gussets 260 of the present invention may be coupled to flow tube 103, and not to other components of flow meter 20. Thus, the present invention can advantageously simplify flowmeter construction and separate frequencies between two or more vibration modes.

In some embodiments, gussets 260 may separate the transverse mode frequency from the drive mode frequency by increasing the transverse mode frequency. According to an embodiment of the present invention, the lateral mode frequency of the flow tube 103 is increased by increasing the stiffness of the flow tube 103 in the lateral direction using the gussets 260. This stiffness enhances the transverse mode vibration without substantially affecting the drive mode frequency. By providing the gussets 260 at the bends 151, 157 of the flow tube 103, the flow tube stiffness in the lateral plane is more affected than the stiffness in the drive plane.

While the transverse mode stiffness of the flow tube 103 can be increased by increasing the thickness of the flow tube 103, such an increase in thickness may also increase the stiffness in the drive plane. Thus, such an increase in thickness of the flow tube 103 does not produce a significant increase in mode separation. Furthermore, it is undesirable to increase the flow tube thickness because more energy is required to vibrate the flow tube to effect the measurement.

Gusset 260 may be joined using methods known in the art including, but not limited to, brazing, welding, bonding, and the like. Although the gusset 260 is shown as being brazed to the flow tube 103 using the brazing material 261, it should be understood that the particular method used to join the gusset 260 to the flow tube 103 is not critical to the purpose of the present invention and, therefore, should not limit the scope of the present invention. Further, it should be understood that the gusset 260 may be formed as an integral part of the flow tube 103, 103'. For example, it is known to form flow meters from plastic using molding techniques, such as disclosed in U.S. patents 6,450,042 and 6,904,667. Thus, the gusset can be formed at the same time as the flow tube is molded.

Preferably, gusset 260 is formed of a substantially rigid material such that gusset 260 contributes to the stiffness increasing effect on flow tube 103. Thus, according to an embodiment of the present invention, the gussets 260 are formed of a material having a stiffness at least the same as the stiffness of the flow tube material. It should be understood that the gussets 260 need not be formed of the same material as the flow tubes 103, but gussets having a stiffness less than that of the flow tubes 103, 103' may not provide as much frequency discrimination between vibration modes. Accordingly, it is contemplated that the desired mode separation may be controlled to some extent based on the selection of the particular material for the gusset 260. Further, vibration mode separation can be controlled by adjusting the size of the gusset 260.

According to an embodiment of the invention, the flow meter 260 comprises gussets 260 coupled to the first and second straight portions 150, 152 of the flow tube 103. According to an embodiment of the invention, the gusset 260 joins the first straight portion 150 and the second straight portion 152. In addition, the embodiment shown in fig. 2 includes a second gusset 260 that joins the fourth straight portion 156 and the fifth straight portion 158 of the flow tube 103. It is anticipated that the gussets 260 shown in fig. 2 all produce the same effect, i.e., stiffening the flow tube 103 in the lateral direction without significantly inhibiting motion in the drive plane. Thus, gussets 260 may increase the transverse mode frequency without significantly adversely affecting the drive mode frequency. Thereby, the difference between the transverse mode frequency and the drive mode frequency is greatly increased. It is contemplated that gussets 260 may affect drive mode frequency; however, the transverse mode frequency is affected to a greater extent. Additionally, gussets 260 shown in FIG. 2 are shown coupled to the outer flexures 151, 157. This can increase the stiffness of the flow tube 103 and thus increase the frequency of the transverse mode vibrations. However, as described below, gussets 260 may extend across the bend without being coupled to the bend.

Fig. 3 shows a flow meter 20 according to another embodiment of the invention. The embodiment shown in fig. 3 includes gussets 260 similar to gussets 260 shown in fig. 2 except for the location of gussets 260. The gussets 260 of fig. 3 are coupled to the inner bends 153, 155 of the flow tube 103, rather than to the outer bends 151, 157 as shown in fig. 2. The gusset 260 shown in fig. 2 is coupled to the second straight portion 152, the second bent portion 153, and the third straight portion 154 of the flow tube 103. In addition, the second gusset 260 is coupled to the third straight portion 154, the third bent portion 155, and the fourth straight portion 155 of the flow tube 103. Thus, the first gusset plate 260 shown in fig. 3 couples the second straight portion 152 with the third straight portion 154, and the second gusset plate 260 couples the third straight portion 154 with the fourth straight portion 156. Since gusset 260 shown in fig. 3 extends across bends 153, 155, gusset 160 is able to substantially increase the lateral mode frequency, thereby distinguishing the lateral mode frequency from the drive mode frequency.

Fig. 4 shows a flow meter 20 according to another embodiment of the invention. According to the embodiment shown in fig. 4, the flow meter 20 includes gussets 260 coupled across each bend 151, 153, 155, 157 in the flow tube 103. By providing gussets 260 at each bend 151, 153, 155, 157, stiffness can be maximized in the lateral direction, thereby increasing the lateral mode frequency to a greater extent than the embodiments shown in fig. 2 or 3. Thus, the embodiment shown in fig. 4 is capable of a greater distinction between the transverse mode frequency and the drive mode frequency than the embodiments described above.

Fig. 5 shows a flow meter 20 according to another embodiment of the invention. The flow meter 20 of fig. 5 has a single gusset 260 that extends substantially completely across the third portion 154 of the flow tube 103, thereby coupling the second portion 152 with the fourth portion 156. Gusset 260 shown in FIG. 5 substantially eliminates the need for two gussets as shown in the previous embodiments.

Fig. 6 shows a flow meter 20 according to another embodiment of the invention. According to the embodiment shown in fig. 6, gussets 260 join the two portions of flow tubes 103, 103' together without joining to bends 151, 157. Thus, the gusset 260 is only end-coupled to the flow tube 103. This configuration leaves a gap 670 near the bends 151, 157. However, since the two straight portions of the flow tube 103 are joined together, the stiffness of the flow tube 103 in the transverse plane is increased. Thereby, the transverse mode frequency is substantially increased without substantially affecting the drive mode frequency. The two vibration modes are clearly distinguished so that the noise caused by the transverse mode frequency is reduced. Although gussets 260 extending across the bends are only shown as extending across the outer bends 151, 157, it should be understood that similar configurations may be applied to gussets extending across the inner bends 153, 155.

Fig. 7 shows a flow meter 20 according to another embodiment of the invention. According to the embodiment shown in fig. 7, the gusset 260 is only coupled to a portion of the single straight portion and the curved portion. For example, a first gusset 260 is shown coupled to the first curved portion 151 and the second straight portion 152. However, the first gusset 260 is shown as not being coupled to the first straight portion 150. Similarly, the second gusset 260 is shown as being coupled to the fourth straight portion 156 and the fourth bend 157. However, the second gusset 260 is not joined to the fifth flat portion 158. In certain embodiments, the gussets having smaller dimensions may achieve sufficient stiffness increase such that the frequencies between the two vibration modes are sufficiently separated. Thus, it should be understood that although the gusset 260 is still coupled to the two portions of the flow tube, the two portions need not be two straight portions to achieve sufficient frequency discrimination.

Fig. 8 shows a flow meter 20 according to another embodiment of the invention. In the embodiment shown in fig. 8, flow meter 20 comprises a straight flow tube configuration. As shown in fig. 8, flow meter 20 includes a straight flow tube 103, a meter housing 801, a balance bar 802, and gussets 260. According to the illustrated embodiment, driver 104 may be coupled to flow tube 103 and balance bar 802. The pickoff sensors 105, 106 are able to detect the resulting vibrations as described above. Although not shown, it is contemplated that the driver 104 and pickoff sensors 105, 106 can be coupled to the meter electronics, as described above.

According to the embodiment shown in fig. 8, the gusset 260 may be coupled to the flow tube 103 and extend along the flow tube 103. In the illustrated embodiment, the flow meter 20 includes four separate gussets 260, each gusset 260 extending along a portion of the flow tube 103. The gusset 260 may be sized and positioned to increase the frequency discrimination between two or more vibration modes, as described above. According to another embodiment of the invention, the flow meter 20 may include a single gusset 260 extending along substantially the entire flow tube 103. In some embodiments, multiple vibration sensors including driver 104 and pickoff sensors 105, 106 may be coupled to gusset 260 rather than directly to flow tube 103.

The invention as described above provides a flow meter with improved mode separation. In some embodiments, the two modes that are separated include a drive mode and a transverse mode. According to this embodiment, the transverse mode frequency is increased relative to the drive mode frequency by providing one or more gussets 260. The one or more gussets 260 stiffen the flow tube 103 in the transverse plane, thereby increasing the transverse mode frequency.

The above detailed description of embodiments is not intended to be exhaustive or to limit all embodiments contemplated by the inventors to the scope of the invention. Indeed, those skilled in the art will recognize that certain elements of the above-described embodiments may be combined or removed in different ways to create additional embodiments, which fall within the scope and teachings of the invention. It will be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to form additional embodiments within the scope and teachings of the invention.

Thus, while specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize. The teachings provided herein are applicable to other flow meters and not just the embodiments described above and shown in the drawings. Accordingly, the scope of the invention should be determined from the following claims.

Claims (23)

1. A flow meter (20) including one or more flow tubes (103) and a driver (104A, 104B) adapted to vibrate the flow tubes (103) at a drive frequency, comprising:

one or more gussets (260), ones of the one or more gussets (260) coupled to a single flow tube (103) of the one or more flow tubes (103) and extending along the single flow tube (103) such that a frequency difference between the drive frequency and at least a second vibration frequency is increased.

2. The flow meter (20) of claim 1, wherein the gusset (260) of the one or more gussets (260) extends along a portion of the flow tube (103).

3. The flow meter (20) of claim 1, wherein the gusset (260) of the one or more gussets (260) extends along substantially the entire flow tube (103).

4. The flow meter (20) of claim 1, wherein the gusset (260) of the one or more gussets (260) joins two or more portions of the flow tube (103) together.

5. The flow meter (20) of claim 1, wherein the at least second vibration frequency comprises a frequency of a lateral vibration mode.

6. The flow meter (20) of claim 5, wherein the gusset (260) of the one or more gussets (260) is adapted to increase a frequency of a lateral vibration mode.

7. The flow meter (20) of claim 1, wherein the gusset (260) of the one or more gussets (260) is coupled to the flow tube (103) such that a portion of the flow tube (103) is increased in stiffness.

8. The flow meter (20) of claim 1, wherein the gusset (260) of the one or more gussets (260) is formed as an integral part of the flow tube (103).

9. A flow meter (20) comprising one or more flow tubes (103) and a driver (104A, 104B) adapted to vibrate the flow tubes (103) at a drive frequency, comprising:

one or more gussets (260), a gusset (260) of the one or more gussets (260) coupled to a single flow tube (103) of the one or more flow tubes (103) and extending along the single flow tube (103) such that a portion of the flow tube (103) is increased in stiffness.

10. The flow meter (20) of claim 9, wherein the gusset (260) of the one or more gussets (260) extends along a portion of the flow tube (103).

11. The flow meter (20) of claim 9, wherein the gusset (260) of the one or more gussets (260) extends along substantially the entire flow tube (103).

12. The flow meter (20) of claim 9, wherein the gusset (260) of the one or more gussets (260) joins two or more portions of the flow tube (103) together.

13. The flow meter (20) of claim 9, wherein the gusset (260) of the one or more gussets (260) is adapted to increase a frequency discrimination between two or more vibration modes.

14. The flow meter (20) of claim 9, wherein the gusset (260) of the one or more gussets (260) is adapted to increase a difference between a frequency of the driving vibration and a frequency of lateral vibration.

15. The flow meter (20) of claim 14, wherein the gusset (260) of the one or more gussets (260) is adapted to increase the frequency of the lateral vibration.

16. The flow meter (20) of claim 9, wherein the gusset (260) of the one or more gussets (260) is formed as an integral part of the flow tube (103).

17. A method of increasing the discrimination between two or more vibration frequencies of a vibratory flow meter, the vibratory flow meter including one or more flow tubes and a driver arranged to vibrate the one or more flow tubes in a drive plane at a drive frequency, the method comprising the steps of:

the gusset is coupled to a single flow tube of the one or more flow tubes such that a difference between two or more vibration frequencies is increased.

18. The method of claim 17, wherein the step of coupling the gusset to the flow tube comprises extending the gusset along a portion of the flow tube.

19. The method of claim 17, wherein the step of coupling the gusset to the flow tube comprises extending the gusset along substantially an entire length of the flow tube.

20. The method of claim 17, wherein the step of coupling the gusset to the flow tube comprises coupling two or more portions of the flow tube together.

21. The method of claim 17, wherein the two or more vibration frequencies comprise a drive frequency and a lateral vibration frequency.

22. The method of claim 21, wherein the step of coupling the gusset to the flow tube comprises coupling the gusset to two or more portions of the flow tube such that the frequency of the lateral vibration mode is increased.

23. The method of claim 17, wherein the step of coupling the gusset to the flow tube comprises coupling the gusset to two or more portions of the flow tube such that a portion of the flow tube is increased in stiffness.