HK1086881B - Low mass coriolis mass flowmeter having a low mass drive system - Google Patents

Description

Low mass coriolis mass flowmeter having a low mass drive system

Technical Field

The present invention relates to a coriolis mass flowmeter, and more particularly, to a coriolis mass flowmeter having a light weight and a small mass drive system. The invention also relates to a lightweight coriolis mass flowmeter having a small diameter flow tube. The invention further relates to a lightweight small coriolis mass flowmeter suitable for measuring the mass flow of a small mass flow.

Background

Coriolis mass flowmeters of various sizes and capacities can be used to measure material flow and generate information related to the material flow such as mass flow rate, density, etc. Coriolis mass flowmeters typically have one or more straight or irregularly shaped flow tubes that are driven in lateral vibration by an electromagnetic drive. The material flowing through the vibrating flow tube induces coriolis deflections of the flow tube, which deflections are detected by one or more sensors. The output signals generated by the sensors are transmitted to associated measurement electronics to generate flow information of the substance. The total output signal produced by the coriolis deflections and the sensor is proportional to the mass of fluid flowing through the flow tube. The coriolis deflections and the overall output signal generated by the sensor are enhanced when the material filled flow tube has a greater mass than the mass of the associated driver and sensor.

Typical dual-elbow coriolis flowmeters have flow rates in the range of about 100 to 700,000 kilograms per hour and flow tubes with internal diameters in the range of about 0.3 cm to about 11 cm. The desired ratio between the mass of the material filled flow tube and the mass of the driver and sensor is typically in the range of 10 to 1 or higher. Conventional coriolis flowmeters are able to achieve this ratio because the mass filled flow tube has a greater mass than the associated driver and sensor, which have a smaller mass.

Achieving acceptable mass ratios is a problem for lightweight coriolis mass flowmeters that use common magnets and associated fastening mechanisms secured to the vibrating flow tube. Drivers that vibrate a filled metal flow tube are typically magnet/coil combinations, where the magnet is typically fixed to the flow tube and the coil is fixed to a support structure or another flow tube. In the case of lightweight flowmeters, magnet mass is an issue because the smallest size magnet available is limited to about 5 milligrams due to metallurgical factors. Together with the associated hardware to secure the magnets to the flow tube, the total mass is approximately 7 mg. This requires that the mass of the material filled flow tube be at least 70 mg to achieve the desired 10 to 1 mass ratio. When measuring mass flow for small mass flows, it is a problem to have a vibrating flow tube structure filled with material in a coriolis mass flowmeter with a mass below about 70 milligrams.

Disclosure of Invention

The above and other problems are solved by the present invention, which is directed to a small, lightweight, low mass flow coriolis mass flowmeter that is well suited for measuring mass flow and density information for small mass flows. The flow meters of the present invention are small, with a flow rate of about 10 kg/hr or less and a flow tube internal diameter of about 2 mm or less. Such a flow tube may itself be as thin as human hair, for example, and have a corresponding wall thickness.

In the present invention, the flow tube may be made of any suitable material and then coated with a magnetic material. Such magnetic material may be formed by spraying or depositing on the flow tube. The magnetic material may also be integrally formed with the flow tube, or the flow tube itself may be made of a magnetic material. The present invention eliminates the need for separate magnets, avoids the practical problems of excessive mass, and the manufacturing problems of aligning and securing the magnets to the flow tube.

The invention enables the elimination of the magnets of the driver and sensor. Coriolis sensors typically use magnets and coils as phase sensitive sensing components to provide information related to the degree of coriolis deflection in the flow tube. According to the present invention, the magnet for the sensor assembly can be manufactured in the same manner as the driver. Thus, both the driver magnet and the sensor magnet can be manufactured in the manner disclosed herein.

An alternative embodiment of a very lightweight flow tube has a driver of the above construction and a sensor signal generated by optical measurement. A suitable sensor is an optical device with a light emitter and a light collector arranged on both sides of the flow tube. The bending of the flow tube modulates the transmitted beam, which is received and converted into an output signal that represents the vibration of the flow tube, including the coriolis effect.

One of the primary advantages of the coriolis mass flowmeter of the present invention is the use of magnetic coatings or coatings on the flow tubes. Such a coating may be applied by electroplating bath, vapor deposition, plasma deposition, or any other plating system. This has the advantage that a very thin coating can be deposited on the flow tube or be formed integrally with the flow tube. This results in a small distributed mass over a given length of tube, and the coating can then be used with a driver coil to drive the flow tube into proper vibration. The distributed quality of the coating and the low coating quality help to reduce the effect of density variations on the output information produced. The low plating mass also enables the coriolis mass flowmeter to resonate at an acceptable frequency, improving density accuracy.

According to an exemplary embodiment of the present invention, a magnetic coating with an internal north/south magnetic field is used on the flow tube, which behaves like a magnet. According to another embodiment of the invention, a plating bath is used to deposit soft magnetic material (ferrous or magnetically permeable) on the flow tubes. The ferrous material can only be attracted by the driver coil. Drive systems with a single driver coil using this material are of the "pull only" type, rather than the "push-pull" system of the conventional coriolis mass flowmeter standard. However, opposing driver coils driven by respective half drive waveforms can alternately pull the flow tube in opposite directions according to the drive frequency. According to another embodiment, the flow tube itself may be made of a magnetic material with an internal north/south magnetic field.

The magnetic material coating may be formed continuously over the entire flow tube or only over a certain axial portion, with selective etching to form the final coating pattern. The ferrous material may also be formed by a composite flow tube in which the ferrous material is co-formed on the outside of the flow tube and then selectively etched.

According to one embodiment of the invention, the flow tube is straight and has magnetic material deposited in an axially central portion of the flow tube. Another embodiment is a U-shaped flow tube having left and right tubes and a top center section connecting the two tubes. The central portion of the U-shaped flow tube is deposited with a layer of magnetic material.

The flow meters of both the straight tube embodiment and the U-flow tube embodiment employ optical sensors that detect the coriolis effect of the flow tubes when the flow tubes are vibrated by magnetic coils near the deposited layers of magnetic material. According to another embodiment, the magnetic material layer is composed of a ferrous material, vibrated in a pull-only mode by a single driver coil. Another embodiment of the flow tube has a layer of soft magnetic ferrous material that vibrates in a push-pull mode with a pair of coils disposed on either side of the flow tube. The magnetic material in another embodiment is disposed only in the axially central portion of the flow tube. In another embodiment the flow tube has a magnetic material deposit over the entire axial length of the flow tube. In another embodiment the entire flow tube is made of magnetic material. In another embodiment the magnetic material is applied to the entire axial length of the flow tube.

According to another embodiment, a flow meter includes a pair of U-shaped flow tubes with a magnetic material applied to a top center portion thereof; optical detectors on the left and right side tubes of the flow tube, and a driver magnet disposed between the flow tubes. In another embodiment, a coriolis mass flowmeter includes a pair of linear flow tubes with a magnetic material deposited thereon, and an optical detector and driver coil disposed between the flow tubes. In another embodiment, a pair of linear flow tubes are arranged parallel to each other and vibrated by magnets disposed outside the flow tubes. In another embodiment, a coriolis mass flowmeter includes parallel flow tubes made of a magnetic material, and a driver magnet and a pair of sensor magnets disposed between the parallel flow tubes.

It can be seen that the present invention achieves an advance in the art by providing a coriolis mass flowmeter that is smaller by several orders of magnitude in mass than existing coriolis mass flowmeters made of metal. Although the present invention relates to small coriolis mass flowmeters, the advantages of this solution are equally applicable to larger sensors.

According to one aspect of the present invention, there is provided a coriolis flowmeter comprising:

a flow tube receiving a flow of material;

a driver coil;

measurement electronics applying a drive signal to the driver coil to cause the flow tube to vibrate with the material flow;

the vibration of the flow tube and the material flow generates Coriolis deflection of the flow tube; and

sensor means connected to said flow tube for generating a sense signal representative of coriolis deflection of said flow tube; and

means for applying the sensing signal to measurement electronics to produce an output signal representative of the material flow;

the method is characterized in that:

a magnetic material, wherein at least a portion of the flow tube is comprised of the magnetic material;

the driver coil generates a magnetic field that interacts with the magnetic material to vibrate the material filled flow tube in response to an applied drive signal.

Preferably, the magnetic material is formed by a layer of ferrous material on at least a portion of the outer surface of the flow tube.

Preferably, the magnetic material is present in a range less than the entire axial length of the flow tube.

Preferably, the magnetic material is present over the entire axial length of the flow tube.

Preferably, the magnetic material comprises a ferrous material integrally formed with at least an outer radial portion of the flow tube;

the ferrous material is free of internal magnetic fields.

Preferably, the magnetic material has an extent less than the entire axial length of the flow tube.

Preferably, the magnetic material extends over the entire axial length of the flow tube.

Preferably, the magnetic material comprises a hard magnetic material having an independent magnetic field.

Preferably, the magnetic material comprises an outer layer that extends less than the entire axial length of the flow tube.

Preferably, the magnetic material comprises an outer layer extending the entire axial length of the flow tube.

Preferably, the magnetic material is integrally formed with at least an outer radial portion of the flow tube.

Preferably, the magnetic material has an extent less than the entire axial length of the flow tube.

Preferably, the magnetic material extends over the entire axial length of the flow tube.

Preferably, the flow tube is straight.

Preferably, the flow tube has an irregular shape.

Preferably, the flow tube is U-shaped.

Preferably, the sensor means comprises first and second optical sensors, each optical sensor comprising a light emitter and a light receiver for converting received light into an electrical signal.

Preferably, the driver coil vibrates the flow tube in a pull-only mode, and when energized, the flow tube material is magnetically attracted to the driver coil, and when de-energized, the inherent elasticity of the flow tube returns the flow tube to a rest state.

Preferably, the driver coil constitutes a first driver coil;

the coriolis flow meter further comprises a second driver coil;

the first and second driver coils are disposed on either side of the flow tube;

the measurement electronics apply opposing sinusoidal currents to the first and second driver coils, generating a periodically varying magnetic field that causes the flow tube to periodically vibrate in a push-pull mode between the first and second driver coils.

Preferably, the mass flow rate of the material flow is less than 10,000 g/h.

Preferably, the flow tube has an inner diameter of less than 2 mm.

Preferably, the flow tube has an inner diameter of less than 2 mm and the mass flow rate of the material flow is less than 10,000 g/hr.

Preferably, the mass flow rate of the material flow is less than 10 g/h.

Preferably, the flow tube has an inner diameter of less than 0.2 mm.

Preferably, the flow tube has an internal diameter of less than 0.2 mm and the mass flow rate of the material flow is less than 10 g/h.

Preferably, the flow tube has an inner diameter of less than 0.9 mm.

Preferably, the flow tube has an inner diameter of less than 0.9 mm and a mass flow rate of less than 10,000 g/hr.

Preferably, the flow tube comprises a single flow tube.

Preferably, the flow tubes include a first flow tube and a second flow tube parallel to the first flow tube;

the driver coil is disposed between the first and second flowtubes and vibrates the first and second flowtubes in anti-phase.

Preferably, the first and second flow tubes are U-shaped having left and right tubes, respectively, connected by a top central portion;

the sensor means includes first and second optical sensors proximate the flow tube for generating a sensing signal representative of the coriolis deflection of the flow tube.

Preferably, the driver coil is disposed near an axially intermediate portion of the top central portion.

Preferably, the magnetic material comprises a hard magnetic material having an internal magnetic field;

the magnetic material extends along the axial length of the flow tube so that the magnetic field of the material is applied to the sensor;

the sensor is responsive to the magnetic field of the magnetic material and the coriolis deflections of the U-shaped flow tube to generate a sensing signal representative of the coriolis deflections.

Preferably, the sensor means comprises first and second optical sensors proximate the flow tube for generating an output signal representative of the coriolis deflection of the flow tube.

Preferably, the flow tube is made of stainless steel.

Preferably, the flow tube is made of a hard magnetic material having an internal north/south magnetic field;

the sensor device is a magnetic transducer;

the magnetic material extends axially over a flow tube proximate the driver coil and the magnetic transducer; and

vibration of the mass filled flow tube generates a magnetic field in the magnetic transducer that represents coriolis deflections.

Preferably, the flow tube comprises a double linear flow tube;

the driver coil is disposed between the flow tubes for vibrating the dual flow tubes in anti-phase.

Preferably, the flow tubes comprise parallel double linear flow tubes;

the coriolis flow meter further includes a pair of driver coils disposed outside of the flow tube for vibrating the dual flow tube in anti-phase.

Preferably, the sensor is an optical sensor.

Preferably, the sensor is a magnetic transducer.

Preferably, said driver coil is adapted to vibrate said flow tube in anti-phase in a push-pull mode;

the sensor arrangement includes a magnetic transducer to interact with the magnetic field of the vibrating flow tube to produce a sensing signal.

Preferably, the flow tube comprises a pair of linear flow tubes;

the driver coil is disposed between the flow tubes proximate the axially central portion of the flow tubes to vibrate the flow tubes laterally in anti-phase;

the sensor means is arranged between the flow tubes on both sides of the driver coil.

Preferably, the flow tube comprises a pair of U-shaped flow tubes;

the driver coil is disposed between the flow tubes proximate a top axially central portion of the flow tubes;

the transducer is disposed between the flow tubes on either side of the driver coil.

Drawings

The above and other advantages and features of the invention will be better understood by reading the following detailed description with reference to the drawings, in which:

FIG. 1 shows details of an exemplary embodiment of a line flow pipe;

FIG. 2 shows a detail of an exemplary U-shaped flow tube;

figures 3 and 4 show details of a coriolis mass flowmeter in which the linear flow tube of figure 1 is disposed;

figures 5 and 6 show details of a coriolis mass flowmeter in which the U-shaped flow tube of figure 2 is disposed;

FIG. 7 shows a detail of the light emitting diode and photodetector of the sensor of FIGS. 3-6;

FIG. 8 shows the flow tube of FIG. 1 and a "pull only" type driver coil;

FIG. 9 shows the flow tube of FIG. 1 and a "push-pull" type driver;

FIGS. 10-13 illustrate an alternative embodiment of a linear flow tube;

FIG. 14 shows a double U-shaped flow tube embodiment of the invention; and

fig. 15-17 illustrate an embodiment of a dual linear flow tube of the present invention.

Detailed Description

FIG. 1 illustrates

Fig. 1 shows a detail of a linear flow tube 101 comprising a hollow tube 102, the axial part of which is surrounded by magnetic elements 103 of hard or soft ferromagnetic material. The hollow tube 102 has a left end 104L and a right end 104R. The magnetic elements 103 may be a coating on the surface of the linear tube 102. The coating was very thin, approximately 0.0013 cm thick. The plated elements 103 can extend along the entire axial length of the flow tube 102, as shown in fig. 11; or may be centered on an axially intermediate portion of the flow tube 102 as shown in fig. 1 and 10. In an exemplary embodiment, the element 103 may be a magnetic coating that behaves like a magnet. Such materials may be deposited by a plasma deposition system. The use of such materials enables the element 103 to behave like a magnet with a north or south magnetic field. This in turn allows the flow tube 101 to be vibrated in a "push-pull" mode with a single driver coil.

According to a second exemplary embodiment, the element 103 may be constructed of a soft ferromagnetic material that does not have a north/south magnetic field by itself, but may work in conjunction with a single coil, only attracting the element 103 to the coil. This type of drive system is called a "pull only" system because its driver coils can only attract the ferrous material 103. Regardless of the direction of current flow through the coil, the ferrous material 103 is attracted to the energized coil. In use, energizing the associated driver coil draws the ferrous element to the coil and the flow tube 101 vibrates. When the current through the driver coil ceases, the inherent elasticity of the flow tube 101 is used to bend the flow tube back to its rest state. A flow tube and associated coil of this type is shown in fig. 8.

Alternatively, the flow tube 101 may be operated using two driver coils, as shown in FIG. 9, with coils D1 and D2 alternately energized to vibrate the flow tube 102 and its element 103.

FIG. 2 illustrates

Fig. 2 shows a U-shaped flow tube 201 similar to flow tube 101. The U-shaped flow tube 201 comprises a tube member 202 having a left side 202L and a right side 202R with a magnetic element 203 attached to the top center portion 202C of the tube 202. U-shaped tube 202 has a left lower end 204L and a right lower end 204R. In use, flow tube 202 is vibrated by magnetic interaction between magnetic elements 203 and associated driver coils, as shown in fig. 5 and 6.

FIGS. 3 and 4 illustrate

Fig. 3 and 4 illustrate a coriolis mass flowmeter 300 using a flow tube 101. Coriolis mass flowmeter 300 includes a flow tube assembly 101 that includes a flow tube 102, a magnetic material 103, a driver coil D, a left pickoff LPO, a right pickoff RPO, a left flange or process connection 105, and a right flange or process connection 106. Coriolis mass flowmeter 300 further includes measurement electronics 321 having leads 306 and 307 controllably energized to driver coil D to vibrate flow tube 101 in a pull-only mode, wherein current through energized coil D deflects flow tube 101 toward the driver coil, and when current through driver coil D ceases, the inherent elasticity of flow tube 101 causes flow tube 101 to return to its quiescent state.

The flow of material to be processed is conveyed from a source of material, not shown, to the process junction 105. The material flow then flows right through the flow tube 102 to the process connection 106 and exits the coriolis mass flowmeter. The vibration of the flow tube 102 and material flow generated by the driver coil D induces coriolis deflections of the flow tube 102. The deflection is detected by the sensors LPO and RPO and converted into an electrical signal. The electrical signals are applied to measurement electronics 321 via leads 304, 305, 308, and 309, and measurement electronics 321 processes the signals and generates information related to the flow of the substance. Information is applied to application circuitry, not shown, via output conductor 322. In order to minimize the complexity of the drawing, only the measurement electronics 321 are shown in fig. 3.

Driver coil D causes flow tube 102 to vibrate in a "pull only" mode when intermittently energized by leads 306 and 307, wherein energized coil D intermittently attracts tube 102. The flow tube 102 returns to its quiescent state by its inherent elasticity whenever the current through the coil D ceases. The driver coil D vibrates the flow tube up and down as shown in fig. 4. The tube 102 in fig. 3 vibrates in and out with respect to the plane of the paper. The sensors LPO and RPO are preferably optical sensors comprising a light emitting diode 701 and a photodetector 702, as shown in fig. 7. The flow tube 102 is vibrated by the driver coil D. In so doing, the flow tube 102 blocks and alters the light beam 703 emitted from the light emitting diode 701 toward the photodetector 702. Photodetector 702 converts the received lightwave waveform into an output signal that is transmitted to measurement electronics 321 via conductors 304, 305, 308, and 309.

FIGS. 5 and 6 illustrate

Fig. 5 and 6 show a front view and a perspective view, respectively, of a coriolis mass flowmeter 500 using the flow tube 201 of fig. 2. The legs 202L and 202R of the U-shaped flow tube 202 are secured to the shunt tubes 503. the shunt tubes 503 receive the flow of material through the process connection 501. a portion of the received material flows through the left tube 202L, the center section 202C, and the right tube 202R, where the flow of material is received by the output ends of the shunt tubes 503 and delivered to the right process connection 502. The driver coils D vibrate the flow tube 202C in a "pull only" mode, similar to the mode of the coriolis mass flowmeter 300 described with reference to fig. 3 and 4. The vibration of the flow tube 202 and the material flow induces coriolis deflections of the flow tube 202 that are detected by the pickoffs LPO and RPO and applied to measurement electronics 321 by the leads 304, 305, 308, and 309, and the measurement electronics 321 processes the signals and generates information related to the material flow. The output information is transmitted over conductor 322 to application circuitry not shown.

The coriolis mass flow meter of fig. 5 and 6 has been produced and found to be capable of achieving a 10 to 1 ratio of the mass of the filled material flow tube to the mass of the driver and sensor. In such an embodiment, the flow tube has an inner diameter of 0.2 mm and a flow rate of 10 g/hr. In another embodiment, the flow tube has an inner diameter of 0.9 mm and a flow rate of 10,000 g/hr.

FIGS. 8 and 9 illustrate

The flow tube 102 operates in a "pull only" vibration mode with an associated single driver coil D, as shown in fig. 8. In this mode, current through driver coil D draws flow tube 102 away from its natural rest position. The flow tube 102 can return to the rest position by its inherent resiliency when power is lost. Alternatively, the flow tube 102 can be vibrated in a "push-pull" mode using a pair of driver coils D1 and D2, as shown in FIG. 9. In this mode, current through coil D1 deflects element 103 and flow tube 102 upward. When current through driver coil D1 ceases, current through driver coil D2 deflects element 103 and flow tube 102 downward. This alternating energization and de-energization of the driver coils D1 and D2 produces an alternating magnetic field that causes the flow tube 102 to vibrate laterally as shown in fig. 9.

The embodiment of fig. 8 is applicable where the inherent elasticity of the flow tube 102 structure is sufficient to restore the flow tube 102 to its rest state when the driver coil D is not energized. The "push-pull" embodiment of the type of embodiment of fig. 9 may be used in applications where the flow tube 102 is required to oscillate back and forth under a magnetic field in a direction perpendicular to the longitudinal path of the flow tube. The U-shaped flow tube 202 may similarly operate in either "pull only" or "push-pull" mode. The leads 306A and 307A in fig. 9 are connected to measurement electronics 321.

FIGS. 10-13 illustrate

Fig. 10-13 illustrate alternative different configurations of flow tubes 101 and 202. Fig. 10 shows a flow tube in which the magnetic material is integrally formed with the axial center portion 1002 of the flow tube 1000. End portions 1001 and 1003 do not include magnetic material. The embodiment of fig. 11 differs from that of fig. 10 in that the entire flow tube 1100 is dark, indicating that the magnetic material is integrally formed over the entire length of the flow tube. The magnetic material of flow tube 1100 in fig. 11 can be soft or hard magnetic. Furthermore, flow tube 1100 can be made entirely of a material such as steel or 400 stainless steel which itself has an internal north/south magnetic field. Fig. 12 shows an embodiment in which the magnetic material is applied as a thin film to the surface of the flow tube. In fig. 12, magnetic material 1202 is applied to the central portion 1202 of the flow tube, while end portions 1201 and 1203 do not have magnetic material. The embodiment of fig. 13 differs from that of fig. 12 in that the magnetic material 1301 is applied to the surface of the flow tube 1300 over its entire length. The magnetic material of the flow tubes of fig. 10-13 can be either soft or hard magnetic.

Fig. 10-13 illustrate an alternative embodiment of the linear flow tube 101 of fig. 1. The U-shaped flow tube 203 may accordingly have a similar embodiment wherein the magnetic material may be integrally formed with the entire flow tube or a portion of the flow tube. Alternatively, the magnetic material may be deposited over the entire length or a portion of the length of the U-shaped flow tube 203 of FIG. 2. Alternatively, the U-shaped flow tube in FIG. 2 may be made of a material such as steel or 400 stainless steel which itself has an internal north/south magnetic field.

The term "magnetic material" as used herein applies to "soft" ferrous materials that do not have a north/south magnetic field by themselves, as well as to hard magnetic materials that have a permanent north/south magnetic field.

FIG. 14 illustrates

Figure 14 illustrates a coriolis mass flowmeter 1400 having dual U-shaped flowtubes embodying the present invention. Coriolis mass flowmeter 1400 in fig. 14 is similar to the coriolis mass flowmeter of fig. 6 having a single U-shaped flow tube, except that it has a pair of U-shaped flow tubes 1402-1 and 1402-2. The driver coil D is arranged between the two flow tubes. The magnetic material on the axially intermediate portion of the flow tube top member is denoted by 1403-1 and 1403-2. Such magnetic material may be soft or hard magnetic. If soft magnetic, the driver coil D, when energized, attracts the flow tubes causing them to vibrate in anti-phase, and when the current ceases, the flow tubes return to their normal rest position due to their inherent elasticity. The driver coil D is able to vibrate the two flow tubes in anti-phase bi-directionally if the magnetic material is a hard magnetic material with an internal north/south magnetic field. The sensors LPO and RPO are composed of a light emitter and a photodetector. Operating in a well known manner, produces an output signal indicative of the vibration of both flow tubes. The output signal is modulated by the amount of light received by the photodetector according to the location of the flow tube vibration. The output conductors 304, 305, 308, 309, 306 and 307 extending to the measurement electronics 321 are denoted in the same way as in fig. 6. The effect of this includes controlling the driver coil D so that the two flow tubes can vibrate at a resonant frequency with the material flow. Its function also includes applying the sensor output signal to the measurement electronics 321, enabling it to generate information about the substance flow, and applying the information via a lead 322 to an application circuit, not shown. The shunt 503 operates in the same manner as described with respect to fig. 6. The left tube of the U-shaped flow tube is indicated by 1402L1 and 1402L 2. The right tube is denoted by 1402R1 and 1402R 2. The top elements of the flow tubes are designated 1402C1 and 1402C 2.

FIGS. 15 and 16 illustrate

Fig. 15 and 16 show coriolis mass flowmeters 1500 and 1600 having dual linear flow tubes. The embodiment of fig. 15 utilizes a single driver coil D disposed between two flow tubes to vibrate the flow tubes in anti-phase. When flow tube elements 1503-1 and 1503-2 are comprised of soft magnetic material, driver coil D can vibrate the flow tubes in anti-phase by a pull-only mode. In this mode, the flow tube is attracted to the driver coil D only when energized. When the current ceases, the flow tube returns to a quiescent state due to its inherent elasticity. When the magnetic material is a hard magnetic material with an internal north/south magnetic field, the driver coil D can vibrate the flow tube in a "push-pull" mode. The pickoffs LPO on and LPO off and pickoffs RPO on and RPO off may be of the optical type as described in fig. 14 to produce pickoff signals indicative of the location of the flow tube vibrations. The sensing signal is transmitted to the measurement electronics 321 in the same manner as in fig. 14.

The embodiment of fig. 15 and 16 includes a left input shunt 1505 that receives substance flow through its opening 1508. The embodiment of fig. 15 and 16 also includes an output shunt 1506 attached to the right side of the flow tube through which material can exit the coriolis mass flowmeter at its output 1509.

The embodiment of fig. 16 is similar to the embodiment of fig. 15, except that it has a pair of driver coils D1 and D2. Driver coils D1 and D2 vibrate the two flow tubes in anti-phase under the control of measurement electronics 321. If the magnetic material is soft magnetic, the "pull only" mode is used. If the magnetic material is hard magnetic, a "push-pull" mode is used.

FIG. 17 illustrates

Figure 17 shows a coriolis mass flowmeter having dual linear flow tubes made of magnetic steel with its own internal north/south magnetic field. This type of steel may be 400 stainless steel or ordinary steel which itself has an internal magnetic field. By using such materials, no internal or external separate magnetic coating or magnetic material is required. But the internal magnetic field of a flow tube made of such steel can be utilized. As shown in fig. 17, the measurement electronics 321 controls a single driver coil D to vibrate the two flow tubes 1703-1 and 1703-2 in anti-phase. The magnetic sensors LPO and RPO detect the vibrational position of the two flow tubes and transmit signals representative of the vibrational conditions of the flow tubes, including the coriolis deflections produced by the vibrating flow tubes and the material flow, to measurement electronics 321. The advantage of the coriolis mass flowmeter of fig. 17 is that it is not necessary to deposit an external magnetic coating or to provide a special manufacturing process for the magnetic material to the flow tubes because the flow tubes are made of a material that has its own magnetic field. For the mass flow meters having U-shaped flow tubes shown in fig. 5, 6 and 14, the flow tubes can also be made of magnetic steel instead of using hard or soft magnetic coatings. As shown in fig. 17, a double hairpin tube embodiment uses a driver coil to vibrate the flow tube in a "push-pull" mode and a magnetic transducer as a sensor to sense deflections of the flow tube, including coriolis deflections produced by material flow.

It should be clearly understood that the invention is not limited to the preferred embodiments described but that other modifications and variations may be made within the scope and spirit of the principles of the invention. The term "soft magnetic material" or "ferrous material" should be understood to mean a material that is attracted by a magnetic field but does not have an internal north/south magnetic field by itself.

Either "soft" or "hard" material can be applied as a coating, film or skin to the already formed flow tube, or can be combined with the flow tube at the time of manufacture to form an integral structure as soft or hard material used in its manufacture.

The terms "fluid" and "liquid stream" as used herein should be understood to include fluids, such as liquids, and the like, as well as any flowing material, such as plasma, gas, and the like. Moreover, while the disclosed invention is particularly applicable to small coriolis mass flowmeters having small flow tubes and small flow volumes, it should be recognized that the principles of the invention are also highly advantageous and applicable to flowmeters of any size and made of any material.

Claims (42)

1. A coriolis flow meter comprising:

a flow tube (102) receiving a flow of matter;

a driver coil;

measurement electronics (321) for applying a drive signal to the driver coil (D) to vibrate the flow tube with the material flow;

the vibration of the flow tube and material flow causes coriolis deflections of the flow tube; and

sensor means (LPO, RPO) connected to said flow tube for generating a pickoff signal representative of said coriolis deflection of said flow tube; and

means (304, 305, 308, 309) for communicating the sensing signal to the measurement electronics, generating an output signal representative of the flow of substance,

the method is characterized in that:

a magnetic material (103), wherein at least a portion of the flow tube is comprised of the magnetic material;

the driver coil is responsive to the drive signal to generate a magnetic field that interacts with the magnetic material to vibrate the filled flow tube.

2. The coriolis flow meter of claim 1 characterized in that said magnetic material comprises a layer of ferrous material (103, 203) on at least a portion of an outer surface of said flow tube.

3. The coriolis flow meter of claim 2 characterized in that said magnetic material (103, 203) has an extent less than the entire axial length of said flow tube.

4. The coriolis flow meter of claim 2 characterized in that said magnetic material (1101) spans the entire axial length of said flow tube.

5. The coriolis flow meter of claim 1 characterized in that said magnetic material comprises a ferrous material (1101) integrally formed with at least an outer radial portion of said flow tube; the ferrous material is free of internal magnetic fields.

6. The coriolis flow meter of claim 5 characterized in that said magnetic material (1002) has an extent less than the entire axial length of said flow tube.

7. The coriolis flow meter of claim 5 characterized in that said magnetic material (1101) spans the entire axial length of said flow tube.

8. The coriolis flow meter of claim 1 characterized in that said magnetic material (103, 203) comprises a hard magnetic material having an independent magnetic field.

9. The coriolis flow meter of claim 8 characterized in that said magnetic material comprises an outer layer that spans less than the entire axial length of said flow tube.

10. The coriolis flow meter of claim 8 characterized in that said magnetic material (1301) comprises an outer layer over the entire axial length of said flow tube.

11. The coriolis flow meter of claim 8 characterized in that said magnetic material (1101) is integrally formed with at least an outer radial portion of said flow tube.

12. The coriolis flow meter of claim 8 characterized in that said magnetic material (1002, 1202) has an extent less than the entire axial length of said flow tube.

13. The coriolis flow meter of claim 11 characterized in that said magnetic material (1101, 1301) is disposed over the entire axial length of said flow tube.

14. The coriolis flow meter of claim 1 characterized in that said flow tube (102) is straight.

15. The coriolis flow meter of claim 1 characterized in that said flow tube (202) has an irregular shape.

16. The coriolis flow meter of claim 1 characterized in that said flow tube (202) is U-shaped.

17. The coriolis flow meter of claim 1 characterized in that said sensor means comprises first and second optical sensors (700), each of said optical sensors comprising an optical transmitter and an optical receiver for converting received light into an electrical signal.

18. The coriolis flow meter of claim 1 characterized in that said driver coil (D) vibrates said flow tube in a pull-only mode, said flow tube material being magnetically attracted to said driver coil when energized and the inherent elasticity of said flow tube returning said flow tube to a rest state when de-energized.

19. The coriolis flow meter of claim 1 characterized in that said driver coil constitutes a first driver coil (D1);

the coriolis flow meter further includes a second driver coil (D2);

the first driver coil and the second driver coil are disposed on either side of the flow tube;

the measurement electronics apply opposing sinusoidal currents to the first driver coil and the second driver coil to generate a periodically varying magnetic field that causes the flow tube to periodically vibrate in a push-pull mode between the first driver coil and the second driver coil.

20. The coriolis flow meter of claim 1 characterized in that said mass flow rate of said material flow is less than 10,000 grams per hour.

21. The coriolis flow meter of claim 1 characterized in that said flow tube has an inner diameter of less than 2 millimeters.

22. The coriolis flow meter of claim 1 characterized in that said flow tube has an inner diameter of less than 2 millimeters and said mass flow rate of said material flow is less than 10,000 grams per hour.

23. The coriolis flow meter of claim 1 characterized in that said mass flow rate of said material flow is less than 10 grams per hour.

24. The coriolis flow meter of claim 1 characterized in that said flow tube has an inner diameter of less than 0.2 millimeters.

25. The coriolis flow meter of claim 1 characterized in that said flow tube has an inner diameter of less than 0.2 millimeters and said mass flow rate of said material flow is less than 10 grams per hour.

26. The coriolis flow meter of claim 1 characterized in that said flow tube has an inner diameter of less than 0.9 millimeters.

27. The coriolis flow meter of claim 1 characterized in that said flow tube has an inner diameter of less than 0.9 millimeters and said mass flow rate of said material flow is less than 10,000 grams per hour.

28. The coriolis flow meter of claim 1 characterized in that said flow tube comprises a single flow tube (102, 202).

29. The coriolis flow meter of claim 1 characterized in that said flow tube comprises a first flow tube (1402C1) and a second flow tube (1402C2) parallel to said first flow tube;

the driver coil is disposed between the first flow tube and the second flow tube to vibrate the first flow tube and the second flow tube in anti-phase.

30. The coriolis flow meter of claim 29 characterized in that said first flow tube and said second flow tube are U-shaped having a left tube and a right tube, respectively, connected by a top intermediate tube;

the sensor apparatus includes first and second optical sensors proximate the flow tube for generating a pickoff signal representative of the coriolis deflection of the flow tube.

31. The coriolis flow meter of claim 30 characterized in that said driver coils (D) are disposed proximate an axially intermediate portion (1403-1, 1403-2) of said top intermediate tube.

32. The coriolis flow meter of claim 29 characterized in that said magnetic material comprises a hard magnetic material having an internal magnetic field;

the magnetic material extends along the axial length of the flow tube, whereby the magnetic field of the material is applied to the transducer (LPO, RPO);

the pickoffs (LPO, RPO) are responsive to the magnetic field of the magnetic material and the Coriolis deflection of the U-shaped flow tube to generate pickoff signals representative of the Coriolis deflection.

33. The coriolis flow meter of claim 29 characterized in that said sensor means comprises first and second optical sensors (700) proximate said flow tube for producing output signals representative of said coriolis deflections of said flow tube.

34. The coriolis flow meter of claim 1 characterized in that said flow tube is made of stainless steel.

35. The coriolis flow meter of claim 1 characterized in that,

the flow tube is made of a hard magnetic material with an internal north/south magnetic field;

the sensor devices (LPO, RPO) are magnetic transducers;

the magnetic material extends axially over the flow tube proximate the driver coil and the magnetic transducer; and

the vibration of the mass filled flow tube generates a magnetic field at the magnetic transducer representative of the coriolis deflection.

36. The coriolis flow meter of claim 1 characterized in that said flow tubes are comprised of dual linear flow tubes (1511, 1512);

the driver coil (D) is disposed between the flow tubes and is used to vibrate the dual flow tubes in anti-phase.

37. The coriolis flow meter of claim 1 characterized in that said flow tubes comprise parallel double straight flow tubes;

the coriolis flow meter further includes a pair of driver coils (D1, D2) disposed outside the flow tube for vibrating the dual flow tube in anti-phase.

38. The coriolis flow meter of claim 37 characterized in that said sensor is an optical sensor.

39. The coriolis flow meter of claim 37 characterized in that said sensor is a magnetic transducer.

40. The coriolis flow meter of claim 1 characterized in that:

the driver coil (D) is used to vibrate the flow tube (1703-1, 1703-2) in anti-phase in a push-pull mode;

the sensor arrangement includes a magnetic transducer to interact with the magnetic field of the vibrating flow tube to produce a sense signal.

41. The coriolis flow meter of claim 1 characterized in that:

the flow tubes comprise a pair of linear flow tubes (1502-1, 1502-2);

the driver coil (D) is disposed between the flow tubes, near an axially central portion of the flow tubes, for vibrating the flow tubes laterally in anti-phase;

the sensor means (LPO, RPO) are arranged between the flow tubes on both sides of the driver coil.

42. The coriolis flow meter of claim 39 characterized in that,

the flow tube comprises a pair of U-shaped flow tubes (1401C1, 1401C 2);

the driver coil (D) is disposed between the flow tubes near a top axially central portion of the flow tubes;

the transducers (LPO, RPO) are arranged between the flow tubes on both sides of the driver coil.