HK1222221B - Flow meter - Google Patents

Description

flow meter

This application is a divisional application of a PCT patent application filed on May 9, 2008, which has entered the Chinese national phase (Chinese national application number is 200880129229.8, international application number is PCT/US2008/063262, and the invention name is "Double-tube Coriolis flowmeter with a central fixing plate as a support part for the driver component and the sensor component").

Technical Field

The present invention relates to flow meters and, more particularly, to a Coriolis flow meter having a driver member or pick-off member coupled to a stationary element.

Background Art

It is generally known to use Coriolis effect mass flow meters to measure the mass flow rate and other information of a material flowing through a conduit in the flow meter. Exemplary Coriolis flow meters are disclosed in U.S. Patents 4,109,524, 4,491,025, and Re. 31,450, all to J.E. Smith et al. These flow meters have one or more conduits of straight or curved construction. Each conduit construction in a Coriolis mass flow meter has a set of natural vibration modes that can be of the simple curved, torsional, or coupled type. Each conduit can be driven to resonate in one of these natural modes. Material flows into the flow meter from a connecting line on the inlet side of the flow meter, is directed through the conduit or conduits, and exits the flow meter through the outlet side of the flow meter. The natural vibration modes of the vibrating material-filled system are defined in part by the combined mass of the conduits and the material flowing within the conduits.

When there is no flow through the flow meter, all points along the conduit oscillate due to the applied driver force. The points can oscillate with the same phase or with a small initial fixed phase offset that can be corrected. When material begins to flow through the flow meter, the Coriolis force causes each point along the conduit to have a different phase. For example, the phase at the inlet end of the flow meter lags the driver, while the phase at the outlet leads the driver. Sensors on the conduit(s) generate sinusoidal signals that represent the motion of the conduit(s). The signal outputs from the sensors are processed to determine the phase difference between the sensors. The phase difference between two or more sensors is proportional to the mass flow rate of the material through the conduit(s).

While many sensor arrangements exist, one particularly common driver and sensor arrangement includes a magnet-coil assembly. Typically, in a dual flow tube arrangement, a magnet is affixed to one flow tube and a coil is affixed to the other flow tube and positioned proximate to the magnet. In this arrangement, the drive coil is supplied with an alternating current that causes the flow tube to vibrate. The sensor magnet-coil assembly then generates an induced voltage proportional to the movement of the flow tube. Typically, there is one sensor at the inlet end of the flow tube and another sensor positioned at the outlet end. Thus, each flow tube includes at least a driver component and two sensor components. The operation of a magnet-coil assembly is generally known in the art.

One problem with the above arrangement is connecting the wires to the coils on the moving flow tube. In the past, this problem has been addressed in a number of ways. The first is to use some kind of tape or adhesive to attach the wires to the flow tube. Another approach, particularly in smaller diameter flow meters, is to use a thin, bendable conductor (flexure). Both approaches have disadvantages. The use of tape or adhesive provides an unsatisfactory solution because the tape or adhesive is typically a highly damped material, where the damping changes unpredictably over time and temperature. These changes can cause erroneous flow signals and errors in meter performance. Although flexures have very little damping, they typically have a very unique natural frequency and exciting them at that natural frequency can cause rapid failure. Furthermore, due to their size, they are extremely fragile.

Numerous patents have proposed solutions to the aforementioned problems. For example, U.S. Patent No. 4,756,198 discloses welding a coil mount to the flowmeter housing. The coil is then mounted to the coil mount, with only the magnet attached to the flow tube. A problem with the '198 patent's solution is that the wire hangs freely from the coil. Thus, while this proposed solution offers an improvement in attaching the coil to the flow tube, the same problem of loose wire exists.

Another proposed solution is disclosed in U.S. Patent 5,349,872. The '872 patent discloses removing the coils from the flow tubes and mounting them on two printed circuit boards (PCBs), one positioned above the flow tubes and the other positioned below the flow tubes. While this solution addresses the loose wire issue of the '198 patent, it includes additional components and creates the potential for errors due to inconsistent gaps.

Therefore, it would be desirable to provide a flow meter that does not require the attachment of a coil to the flow tube and that simultaneously uses a minimal number of components.The present invention overcomes these and other problems and achieves an advance in the art.

Summary of the Invention

According to aspects of the present invention, a flow meter including first and second flow tubes comprises:

a fixed plate, wherein at least a portion of the fixed plate is positioned between the first and second flow tubes; and

At least one of a driver member or a sensor member is coupled to the fixed plate.

Preferably, the entire fixing plate is positioned between the first and second flow tubes.

Preferably, the driver member includes a drive coil, and the flow meter further includes a drive magnet coupled to one of the first or second flow tubes and proximate to the drive coil.

Preferably, the driver member includes a first drive coil coupled to a first side of the fixing plate and further includes a second drive coil coupled to a second side of the fixing plate.

Preferably, the flow meter further comprises a first drive magnet coupled to the first flow tube and proximate to the first drive coil and a second drive magnet coupled to the second flow tube and proximate to the second drive coil.

Preferably, the sensor member includes a sensing coil coupled to the fixed plate and the flow meter further includes a sensing magnet coupled to one of the first or second flow tubes and proximate to the sensing coil.

Preferably, the sensor member includes a first sensing coil coupled to the fixing plate and further includes a second sensing coil coupled to the fixing plate.

Preferably, the flow meter further comprises a first sensing magnet coupled to the first flow tube and proximate to the first sensing coil, and a second sensing magnet coupled to the second flow tube and proximate to the second sensing coil.

Preferably, the flow meter further comprises one or more counterweights coupled to the first and second flow tubes.

Preferably, the flow meter further includes a second fixing plate, wherein one of the first sensing coil or the second sensing coil is coupled to the second fixing plate, and the other of the second sensing coil or the first sensing coil is coupled to the first fixing plate.

Preferably, the fixing plate is connected to the meter electronics.

Preferably, the first and second flow tubes are adapted to vibrate relative to the fixed plate.

According to another aspect of the present invention, a flow meter including first and second flow tubes comprises:

a fixed plate, wherein at least a portion of the fixed plate is positioned between the first and second flow tubes, wherein the first and second flow tubes are adapted to vibrate relative to the fixed plate;

a first sensor comprising a first sensing coil coupled to the fixed plate and a first sensing magnet coupled to the first flow tube and proximate to the first sensing coil;

a second sensor comprising a second sensing coil coupled to the fixed plate and a second sensing magnet coupled to the second flow tube and proximate to the second sensing coil; and

A driver includes a first drive coil coupled to the fixed plate and a first drive magnet coupled to one of the first or second flow tubes and proximate to the first drive coil.

Preferably, the entire fixing plate is positioned between the first and second flow tubes.

Preferably, the first drive coil is coupled to a first side of the fixed plate and the first drive magnet is coupled to the first flow tube, the driver further comprising a second drive coil coupled to a second side of the fixed plate and a second drive magnet coupled to the second flow tube and proximate to the second drive coil.

Preferably, the flow meter further comprises one or more counterweights coupled to the first and second flow tubes.

Preferably, the fixing plate is connected to the meter electronics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 shows a flow meter according to the prior art.

FIG2 shows a flow meter according to an embodiment of the present invention.

FIG. 3 shows a portion of a flow meter together with a fixing element according to an embodiment of the present invention.

FIG. 4 shows a portion of a flow meter together with a fixing element according to another embodiment of the present invention.

DETAILED DESCRIPTION

Figures 1-4 and the following description depict specific examples to teach those skilled in the art how to form and use the best mode of the present invention. To teach the principles of the invention, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate from these examples variations that fall within the scope of the present invention. It will be appreciated by those skilled in the art that the features described below can be combined in various ways to form multiple variations of the present invention. Therefore, the present invention is not limited to the specific examples described below, but is limited only by the claims and their equivalents.

FIG1 shows a Coriolis flowmeter 10 according to the prior art. The Coriolis flowmeter 10 includes an inlet flange 101 and an outlet flange 101′. The Coriolis flowmeter 10 is suitable for connection to a fluid line or the like via the inlet and outlet flanges 101, 101′. When the fluid enters the inlet flange 101, it is diverted into two separate streams by a manifold 102. The fluid is separated and enters one of the flow tubes 103 or 103′. When the process fluid leaves the flow tubes 103, 103′, the manifold 102′ recombines the process fluid before it exits through the outlet manifold 101′. The Coriolis flowmeter 10 also includes a driver 104, which includes a magnet 104A and a coil assembly 104B. Similarly, the Coriolis flowmeter 10 includes a first sensor 105 and a second sensor 106, which include magnets 105A (not shown), 106A and coil assemblies 105B, 106B.

In operation, a drive signal is sent by meter electronics 20 to drive coil 104B via lead 110. The drive signal causes flow tubes 103, 103' to vibrate about bending axes W, W', respectively. Axes W, W' are partially defined using a plurality of struts 120-123 that limit the active area of flow meter 10. The vibrating flow tubes 103, 103' generate a voltage in sensors 105, 106, which is sent to meter electronics 20 via leads 111 and 111'. Based on the signals sent by sensors 105, 106, meter electronics 20 generates mass flow information, along with other information such as material density. Temperature measurement devices, such as multiple RTDs (not shown), can also provide temperature measurements. Meter electronics 20 can send this information to downstream processes via lead 26.

As can be seen in FIG1 , leads 110, 111, and 111′ connecting coil assemblies 104B, 105B, and 106B to meter electronics 20 are attached to flow tube 103′ using adhesive 130. Adhesive 130 can adversely affect the performance of the Coriolis flow meter by introducing additional damping and making the sensor unstable. Furthermore, if flow meter 10 is exposed to fluctuating temperatures, the adhesive may begin to flake off, requiring additional maintenance.

FIG2 illustrates a flow meter 30 according to an embodiment of the present invention. According to one embodiment, the flow meter 30 comprises a Coriolis flow meter. However, it should be understood that the flow meter 30 may comprise other types of flow meters, such as a vibrating densitometer. Thus, the scope of the present invention should not be limited to Coriolis flow meters.

Flow meter 30 is similar to prior art flow meter 10; the difference is the presence of a mounting plate. The mounting plate can comprise a variety of materials and configurations. According to one embodiment of the present invention, the mounting plate comprises a printed circuit board (PCB) 250. However, it should be understood that the mounting plate can comprise other materials or combinations of materials, and the present invention should not be limited to the use of a PCB. However, although the mounting plate will be considered a PCB for simplicity of the following description, it should be understood that the present invention is not limited thereto.

According to an embodiment of the present invention, at least a portion of the PCB 250 is positioned between the two flow tubes 103, 103'. According to another embodiment, the entire PCB 250 is positioned between the two flow tubes 103, 103'. The PCB 250 can be secured to a structure external to the flow meter 30, or alternatively, in some embodiments, the PCB 250 is secured to a flow meter housing (not shown). According to another embodiment of the present invention, the PCB 250 is secured to one or more of the struts 120-123. The specific method used to secure the PCB 250 is not critical to the present invention; however, in most embodiments, the PCB 250 remains substantially stationary relative to the flow tubes 103, 103'. However, it should be understood that in some embodiments, minor vibrations of the PCB 250 can be accommodated and compensated for during the calibration procedure.

According to the embodiment shown in FIG. 2 , a driver component is coupled to PCB 250. The driver component described herein includes a drive coil, such as drive coil 104B, or a drive magnet, such as drive magnet 104A. It should also be understood that the wires connecting coil 104B to meter electronics 20 may be coupled to PCB 250. According to another embodiment of the present invention, a sensor component is coupled to PCB 250. The sensor component described herein includes a sensing coil or a sensing magnet. It should also be understood that the wires connecting the sensor to meter electronics 20 may be coupled to PCB 250. The driver and sensor components may be coupled to PCB 250 using known bonding or fastening techniques. According to an embodiment of the present invention, magnets 104A, 105A, and 106A are coupled to PCB 250. According to another embodiment of the present invention, all coils 104B, 105B, and 106B of the driver 104 and sensors 105 and 106 are coupled to a PCB 250, with the magnets 104A, 105A, and 106A attached to the flow tubes 103 and 103′. Advantageously, both the flow tubes 103 and 103′ of the flow meter 30 are lighter than the flow tubes 103 and 103′ of the flow meter 10. Furthermore, the PCB 250 eliminates the need to secure the leads 110, 111, and 111′ to the flow tubes 103 and 103′. Thus, the aforementioned issues regarding attaching wires to the flow tubes 103 and 103′ can be reduced or, in some embodiments, eliminated. According to another embodiment, only the sensing coils 105B and 106B are coupled to the PCB 250, while the drive coil 104B is connected to the flow tubes 103 and 103′ according to prior art methods. In this embodiment, the PCB 250 may include an aperture through which the driver 104 fits, with the sensing coils 105B, 106B integrated into the PCB 250. Alternatively, the PCB 250 may be positioned below the driver 104.

According to an embodiment of the present invention, leads 100 directly connect PCB 250 to meter electronics 20. According to an embodiment of the present invention, each individual lead 100 can be routed through the interior of PCB 250, thereby eliminating exposure of the wires. Alternatively, multiple PCBs 250 can be implemented, and individual leads 100 can be routed between two PCBs. In another alternative, leads 100 can be bonded or fastened to the exterior of PCB 250.

Although the embodiment of FIG2 shows a single PCB 250, it should be understood that according to some embodiments, more than one PCB 250 is positioned between the flow tubes 103, 103'. According to one embodiment, each coil 104B, 105B, and 106B is mounted on a separate PCB. Therefore, the present invention should not be limited to a single PCB 250.

By positioning PCB 250 between flow tubes 103, 103', the need to secure leads 100 connecting driver 104 and sensors 105, 106 to meter electronics 20 can be reduced. In embodiments where all coils 104B, 105B, and 106B are coupled to PCB 250, the need to secure leads 100 to flow tubes 103, 103' can be eliminated. Advantageously, leads 100 do not affect the damping or natural frequency of flow tubes 103, 103'. Consequently, flow meter 30 provides a more stable and efficient vibrating flow meter than the prior art. Furthermore, flow meter 30 does not include the added weight of straps and wires that could unbalance the sensor, thereby impacting sensor performance. Furthermore, the use of PCB 250 in flow meter 30 eliminates the aforementioned issues associated with the use of flexures.

FIG3 shows a top view of a flow meter 30 according to an embodiment of the present invention. FIG3 does not show the entire flow meter 30, but rather shows a portion of the flow tubes 103, 103' along with the PCB 250. As can be seen, according to an embodiment of the present invention, at least a portion of the PCB 250 is positioned between the flow tubes 103, 103'. According to another embodiment of the present invention, the entire PCB 250 is positioned between the flow tubes 103, 103'.

The embodiment shown in FIG3 differs from the embodiment shown in FIG2 in one important respect; the embodiment shown in FIG3 includes only one magnet 105A at the inlet end of driver 104 and only one magnet 106A at the outlet end of driver 104. Thus, first sensor 105 is coupled to only one flow tube 103 or 103'. Similarly, second sensor 106 is coupled to only one flow tube 103, 103'. Thus, flow tube 103' has first sensor 105 and flow tube 103 has second sensor 106. According to one embodiment of the present invention, flow meter 30 measures the phase difference between the inlet end of flow tube 103' and the outlet end of flow tube 103.

Although the embodiment shown in FIG. 3 shows the first sensing magnet 105A positioned on the flow tube 103′ and the second sensing magnet 106A positioned on the flow tube 103′, it should be understood that in other embodiments, the magnets 105A and 106A may be interchanged. The precise positioning is not critical to the present invention. However, according to an embodiment of the present invention, the first sensing magnet 105A and the second sensing magnet 106A are positioned on different flow tubes 103 and 103′.

FIG4 shows a top view of a portion of the flow meter 30 according to an embodiment of the present invention. The embodiment shown in FIG4 is similar to the embodiment shown in FIG3 , except for the counterweight 415. As described above, according to an embodiment of the present invention, the flow meter 30 includes only one sensor 105 at the inlet end of the driver 104 and only one sensor 106 at the outlet end of the driver 104. Because only a single sensing magnet is included on each flow tube 103, 103′, the flow tubes 103, 103′ may be unbalanced.

According to an embodiment of the present invention, a balancing weight 415 is provided to compensate for the unbalanced flow tubes 103, 103'. According to one embodiment, the balancing weight 415 is positioned on the flow tubes 103, 103' at a position that is approximately the same as the position where the magnets would be positioned according to the prior art. According to another embodiment of the present invention, the balancing weight 415 is placed at a position that is different from the position where the magnets would be positioned according to the prior art. In some embodiments, the balancing weight 415 may be positioned outside the flow tubes 103, 103', rather than inside as shown in Figure 4. In still other embodiments, the balancing weight 415 may be positioned approximately around the entire outer diameter of the flow tubes 103, 103', for example, as a sleeve. According to an embodiment of the present invention, the balancing weight 415 and the magnets 105A, 106A have approximately the same weight. However, the weight of the balancing weight 415 may have a different weight than the magnets 105A, 106A.

A counterweight 415 is provided to balance the flow tube 103, 103' by offsetting the weight added to the flow tube 103, 103' by the magnets 105A and 106A. Thus, even if the flow tube 103, 103' includes only one sensing magnet 105A, 106A, the flow tube 103, 103' will still be balanced.

The present invention provides a flow meter 30 that does not require lead wires 100 to be attached to the exterior of the flow tubes 103, 103'. Furthermore, the present invention provides a flow meter 30 that includes only a single sensor attached to each of the flow tubes 103, 103'. It should be understood that the inventive principles disclosed above are applicable not only to Coriolis flow meters, but also to other flow meters that require the use of wires extending from the sensor.

The detailed description of the above embodiments is not an exhaustive description of all embodiments contemplated by the inventors to be within the scope of the present invention. Indeed, those skilled in the art will recognize that certain elements of the above-described embodiments may be variously combined or eliminated to form additional embodiments, and such additional embodiments are within the scope and teachings of the present invention. It will also be apparent to those skilled 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 present invention.

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

Claims (11)

1. A flow meter (30) comprising first and second flow tubes (103, 103'), comprising: A printed circuit board (250), wherein at least a portion of the printed circuit board (250) is positioned between the first and second flow tubes (103, 103'), wherein the first and second flow tubes (103, 103') are adapted to vibrate relative to the printed circuit board (250); A driver component, which is connected to the printed circuit board (250); The first sensor (105) includes a first sensing coil (105B) connected to the printed circuit board (250) and a single first sensing magnet (105A) connected to the first flow tube (103) and close to the first sensing coil (105B). The second sensor (106) includes a second sensing coil (106B) connected to the printed circuit board (250) and a single second sensing magnet (106A) connected to the second flow tube (103') and close to the second sensing coil (106B). Leads (100) are connected to the printed circuit board (250) and pass through the printed circuit board (250) to communicate electronically with the first sensor (105), the second sensor (106) and the driver component; One or more counterweights (415) are connected to the first and second flow tubes (103, 103'). 2. The flow meter (30) according to claim 1, wherein the entire printed circuit board (250) is positioned between the first and second flow tubes (103, 103'). 3. The flow meter (30) according to claim 1, wherein the driver component includes a drive coil (104B) and the flow meter (30) further includes a drive magnet (104A) connected to one of the first or second flow tubes (103, 103') and close to the drive coil (104B). 4. The flow meter (30) according to claim 1, wherein the driver component includes a first drive coil (104B) coupled to a first side of the printed circuit board (250) and a second drive coil (104B) coupled to a second side of the printed circuit board (250). 5. The flow meter (30) according to claim 4, characterized in that it further comprises a first driving magnet (104A) connected to the first flow tube (103) and close to the first driving coil (104B) and a second driving magnet (104A) connected to the second flow tube (103') and close to the second driving coil (104B). 6. The flow meter (30) according to claim 1, characterized in that it further comprises a second printed circuit board, wherein one of the first sensing coil (105B) or the second sensing coil (106B) is connected to the second printed circuit board, and the other of the second sensing coil (106B) or the first sensing coil (105B) is connected to the printed circuit board (250). 7. The flow meter (30) according to claim 1, wherein the printed circuit board (250) is connected to the metering electronics (20). 8. A flow meter (30) including first and second flow tubes (103, 103'), comprising: A mounting plate including a printed circuit board (250), wherein at least a portion of the printed circuit board (250) is positioned between the first and second flow tubes (103, 103'), wherein the first and second flow tubes (103, 103') are adapted to vibrate relative to the printed circuit board (250); The first sensor (105) includes a first sensing coil (105B) connected to the printed circuit board (250) and a single first sensing magnet (105A) connected to the first flow tube (103) and close to the first sensing coil (105B). The second sensor (106) includes a second sensing coil (106B) connected to the printed circuit board (250) and a single second sensing magnet (106A) connected to the second flow tube (103') and close to the second sensing coil (106B). A driver (104) comprising a first drive coil (104B) coupled to the printed circuit board (250) and a first drive magnet (104A) coupled to one of the first or second flow tubes (103, 103') and proximate to the first drive coil (104B); and Leads (100) are connected to the printed circuit board (250) and pass through the printed circuit board (250) to communicate electronically with the first sensor (105), the second sensor (106) and the driver (104); One or more counterweights (415) are connected to the first and second flow tubes (103, 103'). 9. The flow meter (30) according to claim 8, characterized in that the entire fixing plate is positioned between the first and second flow tubes (103, 103'). 10. The flow meter (30) according to claim 8, characterized in that the first drive coil (104B) is connected to a first side of the fixed plate, the first drive magnet (104A) is connected to the first flow tube (103), and the driver (104) further includes a second drive coil (104B) connected to a second side of the fixed plate and a second drive magnet (104A) connected to the second flow tube (103') and close to the second drive coil (104B). 11. The flow meter (30) according to claim 8, wherein the fixing plate is connected to the metering electronic device (20).