SUSPENDED LOOPED CONDUIT MASS FLO METER This invention relates to a Coriolis force or Convective inertia force mass flowmeter employing a conduit with a looped midsection of 360 degree loop angle disposed intermediate and supported by an inlet and an outlet section extending from a supporting structure and mechanically tied together at sections adjacent to the looped mid- section, at which tied-together section an electromagnetic vibrator exerts a vibratory force generating a flexural vibration of the conduit in directions perpendicular to a plane parallel to the looped midsection of the conduit. A pair of vibratory motion sensors respectively included in the two opposite halves of the conduit measure the flexural vibration of the conduit at two sections located symmetrically about the center section of the conduit. The mass flow rate of media moving through the conduit is determined as a function of the difference in the flexural vibration between the two opposite halves of the conduit.

Without any exception, all of the existing versions of the Coriolis force or Convective inertia force mass flowmeter employ a straight conduit or a curved conduit with two halves thereof uncoupled from one another and independently supported at the extremities thereof (US-A-4,127,028; 4,187,721; 4,491,025; 4,628,744; 4,660,421; 4,756,198; 4,938,075; etc.), wherein the ambient mechanical vibrations of the structure supporting the flowmeter are transmitted to the two opposite halves of the conduit through the two anchored extremities of the conduit in more or less independent modes and, consequently, introduce undesirable vibrations to the conduit creating noise detrimental to the detection of the Coriolis force or Convective inertia force effect in determining the mass flow rate therefrom, which noise cannot be cancelled out between two electrical signals respectively supplied by two vibratory motion sensors respectively included in the two opposite halves of the conduit due to the lack of common mode in the noise therebetween. The mass flowmeter of the present invention employs a conduit geometry that provides the maximum Coriolis force or Convective inertia force effect created by the mass flow rate of media moving through the conduit as well as the maximum signal-to-noise ratio.

The primary object of the present invention is to provide a mass

flowmeter employing a conduit with a looped midsection of 360 degree loop angle disposed intermediate and supported by an inlet and an outlet section respectively extending from the anchored extremities thereof, wherein the inlet and outlet sections of the conduit are mechanically tied together at sections adjacent to the looped mid- section of the conduit, and an electromagnetic vibrator exerts a vibratory force to the conduit at the tied-together section, which vibratory force generates a primary flexural vibration of the conduit in a symmetric mode about the center section of the conduit, and the mass flow rate of media moving through the conduit is determined as a function of the intensity of a secondary flexural vibration of the conduit of an antisymmetric mode about the center section of the conduit resulting from an interaction between the mass flow of media and the symmetric primary flexural vibration of the conduit. Another object is to provide a mass flowmeter employing a pair of conduits, each of which has the geometry and installation described in the primary object of the present invention, wherein the pair of conduits are in a generally parallel and superimposing arrangement and flexurally vibrated relative to one another. The mass flow rate of media moving through the pair of conduits is determined as a function of the intensity of the antisymmetric secondary relative flexural vibration of the pair of conduits therebetween. A further object is to provide a mass flowmeter including a pair of conduits disposed in a generally parallel and superimposing arrangement, each of which pair of conduits includes a looped mid- section of 360 degree loop angle disposed intermediate and supported by an inlet and an outlet sections of the conduit, wherein the inlet section of the first conduit and the outlet section of the second conduit are mechanically tied together at sections adjacent to the respective looped midsections of the pair of conduits, and the outlet section of the first conduit and the inlet section of the second conduit are also mechanically tied together at sections adjacent to the respective midsections of the pair of conduits. An electromagnetic vibrator exerts a vibratory force to the two conduits at the tied- together sections thereof, that generates a symmetric primary relative flexural vibration between the looped midsections of the pair of conduits. The mass flow rate of the media is determined as a function of the intensity of the antisymmetric secondary relative flexural

vibration between the looped midsections of the pair of conduits. Yet another object is to provide a mass flowmeter employing a pair of conduits disposed in a generally parallel and superimposing arrangement, each of which pair of conduits includes a looped mid- section of an oval or circular shape disposed intermediate and supported by an 'inlet and an outlet section of the conduit, wherein the inlet section of the first conduit and the outlet section of the second conduit are mechanically tied together at sections adjacent to the respective looped midsections of the pair of conduits. An electro- magnetic vibrator exerts a vibratory force to the outlet-side half of the first conduit and the inlet-side half of the second conduit in two opposite directions, that generates a symmetric primary relative flexural vibration between the pair of conduits. The mass flow rate of media is determined as a function of the intensity of the antisymmetric secondary relative flexural vibration between the pair of conduits. These and other objects of the present invention will become clear as the description thereof progresses.

The present invention may be described with a greater clarity and specificity by referring to the following figures : Figure 1 illustrates a perspective view of an embodiment of the mass flowmeter of the present invention and operating principles thereof. Figure 2 illustrates a perspective view of another embodiment of the mass flowmeter of the present invention. Figure 3 illustrates an alternative arrangement of the inlet and outlet of the mass flowmeter, that converts an embodiment of the mass flowmeter with dual conduits bifurcating the media flow therethrough into another embodiment employing dual conduits recirculating the media flow without bifurcating. Figure 4 illustrates a perspective view of a further embodiment of the mass flowmeter of the present invention. Figure 5 illustrates a perspective view of yet another embodiment of the mass flowmeter of the present invention. Figure 6 illustrates a perspective view of yet a further embodiment of the mass flowmeter of the present invention. Figure 7 illustrates a perspective view of still another embodiment of the mass flowmeter of the present invention.

Figure 8 illustrates a perspective view of still a further embodiment of the mass flowmeter of the present invention. Figure 9 illustrates a perspective view of additional embodiment of the mass flowmeter of the present invention.

In Figure 1 'there is illustrated a perspective view of an embodiment of the mass flowmeter constructed in accordance with the principles of the present invention, which embodiment comprises two conduits 1 and 2 having substantially identical constructions. Each of which two conduits includes a looped midsection 3 of the loop angle generally equal to 360 degrees disposed intermediate and supported by an inlet section 4 and an outlet section 5 respectively extending from the extremities 6 and 7 thereof anchored to a supporting structure 8. The two looped midsections 3 and 9 of the two conduits 1 and 2 are respectively disposed substantially on two planes intersecting one another at a small angle along a line of intersection 10 wherein the two looped midsections 3 and 9 cross one another at the midsections thereof, and the inlet and outlet sections of the two conduits 1 and 2 are disposed substantially parallel to the line of intersection 10. The inlet section 4 of the conduit 1 and the outlet section 11 disposed on one side of the line of intersection 10 are tied together by a clip 12 at sections adjacent to the looped midsections 3 and 9 of the two conduits 1 and 2, while the outlet section 5 of the conduit 1 and the inlet section 13 of the conduit 2 disposed on the other side of the line of intersection 10 are tied together by a clip 14 at sections adjacent to the looped midsections 3 and 9 of the two conduits 1 and 2. An electromagnetic vibrator 15 with an action and reaction elements respectively anchored to the clips 12 and 14 exerts a vibratory force that generates a relative torsional vibration between the looped midsections 3 and 9 of the two conduits 1 and 2 about an axis substantially coinciding with the line of intersection 10. A pair of motion sensors 16 and 17, which may be operating on the principles of induction on a magnetic coil or piezo electric generation, respectively included in two opposite halves of the combination of the looped midsections 3 and 10 of the two conduits 1 and 2 respectively measure relative vibratory motion between the two looped midsections 3 and 9 of the two conduits 1 and 2 at the two opposite halves of the combination thereof.

The electromagnetic vibrator 15 energized by an alternating or .pulsed current power supply 18 creates a relative torsional vibration between the looped midsections 3 and 9 of the two conduits 1 and 2 about the torsion axis 10, which relative torsional vibration produces a symmetric primary relative flexural vibration between the looped sections 3 and 9 υf the two conduits 1 and 2 about the midsection of the combination thereof. A dynamic interaction between the mass flow of media moving through the two conduits 1 and 2, and the symmetric primary relative torsional vibration created by the electromagnetic vibrator 15 produces an antisymmetric secondary relative torsional vibration about the midsection of the combination of the curved midsections 3 and 9 of the two conduits 1 and 2. The amplitude ratio of the antisymmetric secondary relative torsional vibration to the symmetric primary relative torsional vibration is proportional to the mass flow rate of media moving through the conduits 1 and 2. Of course, the symmetric primary relative torsional vibration can be obtained from an additive combination of the two alternating electrical signals respectively supplied by the two motion sensors 16 and 17, while the antisymmetric secondary relative torsional vibration can be obtained from a differential combination of the two electrical signals. Therefore, the mass flow rate can be determined as a function of the amplitude ratio of a differential combination to an additive combination of the two alternating electrical signals respectively supplied by the two motion sensors 16 and 17. The mass flow rate can also be determined as a function of phase angle difference between the two alternating electrical signals respectively supplied by the two motion sensors 16 and 17. Alternatively, the mass flow rate can be determined as a function of ratio of one value of the first alternating electrical signal measured at an instance when value of the second alternating electrical signal vanishes to another value of the first alternating electrical signal measured at another instant when value of the second alternating electrical signal reaches its peak value. wherein the first and second alternating electrical signals are respectively supplied by the two motion sensors 16 and 17. A data processor 19 determines the mass flow rate 19 from two alternating electrical signals V, and V ₂ respectively supplied by the two motion sensors 16 and 17 by using an empirically determined relationship in accordance with one of the three methods mentioned

in the preceding paragraphs. In order to accurately measure the mass flow rate, the conduits 1 and 2 must be vibrated at the natural frequency of the combination thereof. The data processor 19 may also determine the value of the natural frequency f and supplies the information thereon to the vibrator power supply 18 whereby the electromagnetic 'vibrator 15 is energized by an alternating electric current with a frequency coinciding with the natural frequency f of the vibration. It is well known that the natural frequency f is proportional to the square root of the ratio of the structural stiffness of the conduits 1 and 2 to the combined mass of the conduits 1 and 2 and the media moving therethrough and, consequently, the density of media can be determined from the natural frequency f by using another data processor 20. The looped midsections 3 and 9 of the two conduits 1 and 2 may be left untied as shown in the particular illustrative embodiment, or they may be mechanically tied to one another at the midsections thereof including the line of intersection 10. In Figure 2 there is illustrated a perspective view of another embodiment of the mass flowmeter, which embodiment is a modified version of the mass flowmeter shown in Figure 1. In this embodiment, the looped midsection 21 and 22 respectively included in the two conduits 23 and 24 extend from the inlet and outlet sections of the conduits 23 and 24 towards the anchored extremities thereeof and pass through a space between the two clamped combinations of the inlet and outlet sections, which arrangement is in contrast to the looped midsections 3 and 9 of the two conduits extending from the inlet and outlet sections away from the anchored extremities thereof as shown in Figure 1. The mass flowmeter shown in Figure 2 operates on the same principles as those described in conjunction with Figure 1. In Figure 3 there is illustrated an arrangement of the inlet and outlet sections of the conduit, that can be used to modify a mass flowmeter employing dual conduits bifurcating the flow through the flowmeter to another mass flowmeter with dual conduits recirculating the flow without bifurcating. For example, the mass flowmeter shown in Figure 1 employing the two conduits 1 and 2 bifurcating the flow can be modified to a nonbifurcating recirculating mass flowmeter by disconnecting the inlet section 4 of the conduit 1 from the intake

manifold and disconnecting the outlet section 5 of the second conduit 2 from the discharge manifold, and then connecting the inlet section 4 and the outlet section 5 to one another by a U-shaped conduit section 25. This conversion can be applied to any embodiments of the mass flowmeter shown in Figures 1, 2 and 4-9. In Figure 4 ^* there is illustrated a perspective view of a further embodiment of the mass flowmeter of the present invention, which embodiment comprises two conduits 26 and 27 having substantially identical constructions and disposed in a substantially parallel and superimposing arrangement. Each of the two conduits 26 and 27 includes a coplanar looped midsection 28 of a loop angle generally equal to 360 degrees disposed intermediate and supported by an inlet section 29 and an outlet section 30 respectively extending from the extremities thereof anchored to a supporting structure and a spacer 31, wherein the inlet and outlet sections of each of the two conduits 26 and 27 are tied together by a clip 32 at sections adjacent to the looped midsection 28. An electromagnetic vibrator 33 with an action and reaction elements respectively anchored to the two clips respectively tying together the inlet and outlet sections belonging to the two conduits 26 and 27 exerts a vibratory force that generates a relative flexural vibration between the two conduits 26 and 27 in directions perpendicular to a plane parallel to the looped midsections of the two conduits 26 and 27. A pair of relative motion sensors 34 and 35 respectively included in the two opposite halves of the combination of the looped midsections of the two conduits 26 and 27 respectively measure relative flexural vibration between the two conduits 26 and 27 at two symmetrically opposite sections about the midsection of the combination including the axis of symmetry 36. The symmetric primary relative flexural vibration between the conduits 26 and 27 generated by the electromagnetic vibrator 33 interacts with the mass flow of media moving through the two conduits 26 and 27, and generates an antisymmetric secondary relative flexural vibration. The mass flow rate of media can be determined by one of three methods described in conjunction with Figure 1. The looped midsections of the two conduits 26 and 27 may be left untied as shown in the particular illustrative embodiment, or they may be tied to one another at the midsections thereof including the axis of symmetry 36 as shown in Figure 5. In an alternative design, one of the two motion sensors 34

and 35 may be relocated to the midsection including the axis of symmetry 36 and a dummy motion sensor installed at the off-center position originally occupied by the now relocated motion sensor in order to maintain the symmetric conduits mass distribution, wherein the mass flow rate can be determined as a function of phase angle difference between two alternating electrical signals respectively supplied by the two motion sensors, or as a function of ratio of two values of the first alternating electrical signal supplied by a first motion sensor located off-center respectively measured at two instances when the value of the second alternating electrical signal supplied by the second motion sensor located at the center vanishes and reaches the peak value, respectively. In Figure 5 there is illustrated a perspective view of yet another embodiment of the mass flowmeter of the present invention, which embodiment is a modified version of the mass flowmeter shown in Figure 4. This embodiment results when the straight inlet and outlet sections of the conduits 26 and 27 shown in Figure 4 are bent at sections adjacent to the electromagnetic vibrator in such a way that the combination of the inlet sections 37 and the combination of the outlet sections 38 respectively extend from the respective anchored extremities thereof towards one another. The embodiment shown in Figure 5 operates on the same principles and methods which are described in conjunction with Figure 4. In an alternative design, the two motion sensors 39 and 40 may be respectively relocated to a section 41 in the combination of the inlet sections and a section 42 in the combination of the outlet sections. In another alternative design, the tying plate 43 tying the looped midsection of the two conduits at the center sections thereof may be omitted. In such an alternative design, one of the two motion sensors 39 and 40 may be relocated to the center section of the combination of the looped midsection of the two conduits. In Figure 6 there is illustrated a perspective view of yet a further embodiment of the mass flowmeter of the present invention, which embodiment is another modified version of the mass flowmeter shown in Figure 4. The looped midsections 44 and 45 of the two conduits 46 and 47 extends from respective combinations of the inlet and outlet sections towards the anchored extremities thereof and pass through a space between the two combinations of the inlet and

outlet sections. The alternative designs described in conjunction with Figure 4 can be applied to the embodiment shown in Figure 6. In Figure 7 there is illustrated a perspective view of still another embodiment of the mass flowmeter of the present invention, which embodiment is a modified version of the mass flowmeter shown in Figure 6 that results when the same modification as that which changed the embodiment shown in Figure 4 to the embodiment shown in Figure 5 is applied to the mass flowmeter shown in Figure 6. The alternative designs described in conjunction with Figure 5 can be applied to the embodiment shown in Figure 7. It should be mentioned that the spacer plates 47 and 49 separating the two conduits 50 and 51 at the extremities thereof may be isolated as shown in the particular illustrative embodiments shown in Figures 4-7 or may form a part of the supporting structure as shown in Figures 1 and 2, which are interchangeable in their roles. It should be understood that the embodiments shown in Figures 4-7 can be modified to a version of the mass flowmeter comprising a single conduit by eliminating one of the two conduits, and anchoring the accessory elements to a supporting frame now playing a role structurally equivalent to the now omitted conduit. In Figure 8 there is illustratd a perspective view of still a further embodiment of the mass flowmeter of the present invention, which embodiment results in when the Λ-shaped midportions of the two conduits included in the embodiment shown in Figure 5 is replaced by a new pair of looped midsections 52 and 53 of 360 degree oval or circular shape. The inlet and outlet sections of each of the two conduits 54 and 55 are tangential to the looped midsection of the respective conduit. All of the design alternatives described in conjunction with Figure 5 are applicable to the embodiment ^" shown in Figure 8. It should be understood that the embodiments shown in Figures 4-8 can be modified to a version of the mass flowmeter comprising a single conduit by eliminating one of the two conduits, and securing the accessory elements initially anchored to the now omitted conduit to a supporting structure now playing a role sutucturally equivalent to the now omitted conduit. Each of the two conduits included in the mass flowmeters shown in Figures 4-8 has two opposite halves tied together at junctions where the two ends of the looped midsection of the conduit are respectively connected to the

inlet and outlet sections of the conduit. As a consequence, the two separate noise vibrations respectively transmitted through the inlet and outlet sections of the conduit becomes integrated at the tied-together section of the conduit and the noise vibrations transmitted to the looped midsection of the conduit become symmetric about the center ^* section thereof. Therefore, the noise generated by the undesirable ambient structural vibration can be readily cancelled out between the two signals respectively supplied by the two motion sensors disposed symmetrically about the center section of the looped midsection of the conduit in extracting the antisymmetric secondary flexural vibration as a measure of the mass flow rate. For the above-mentioned reason, a single conduit version of the mass flowmeter shown in Figures 4-8 can be effectively operated without being swamped by noise. In Figure 9 there is illustrated a perspective view of an additional embodiment of the mass flowmeter of the present invention, which embodiment comprises two conduits 56 and 57 disposed in a substantially parallel and superimposing arrangement. Each of the two conduits 56 and 57 includes an inlet section 58 and an outlet section 59 parallel to one another and tangential to the looped midsection 60 of 360 degree oval or circular shape. The inlet section 58 of the conduit 56 and the outlet section 61 of the conduit 57 are tied together by a clip 62 at sections located on a plane dividing the combination of the two conduits 56 and 57 into two equal opposite halves. An electromagnetic vibrator 63 secured to the clip 62 exerts a vibratory force on the outlet section 59 of the conduit 56 and the inlet section 64 of the conduit 57 in two opposite directions and, consequently, generates a relative flexural vibration between the looped midsections 60 and 65 of the two conduits 56 and 57. A pair of relative motion sensors 66 and 67 disposed symmetrically about the center section of the combination of the two conduits 56 and 57 respectively measure the relative flexural vibration between the two conduits at two opposite halves of the combination thereof. The design alternatives described in conjunction with Figure 5 such as the relocation of the motion sensors 66 and/or 67 and the ommission of the tying plate 68 are also applicable to the embodiment shown in Figure 9. The mass flow rate of media is determined by one of the same methods as those described in conjunction with Figures 1 and 4.

It should be understood that the torsional or flexural vibration of the conduit or conduits included in the mass flowmeters of the present invention may be induced by continuously exerting electro- magnetic vibratory forces to the conduits, wherein it is desirable that the electromagnetic vibratory force has a frequency substantially equal to the nat'ural frequency of vibration of the conduit or conduits, or the ringing vibration of the conduit or conduits may be induced by intermittently exerting a mechanical impulse delivered by the electro- magnetic vibrator, wherein the ringing vibration of the conduit automatically occurs at the natural frequency. The best Coriolis force or Convective inertia force mass flowmeter is the one that includes a looped conduit suspended in a free-floating arrangement free of any external structural restrains or transmission of external vibrations, which looped conduit will precess like a spinning top under the influence of the Coriolis force or Convective inertia force of mass flow therethrough when it is subjected to a pivotal vibration, and the degree of precession will be a measure of the mass flow rate. Unfortunately, it is impossible to set up such a suspended loop or ring of the conduit. The structural arrangement of the conduit or conduits taught by the present invention is the next best thing to the magically suspended floating conduit of a ring shape. One of the most noble features in the present invention is the clamped connection between the inlet and outlet sections of the conduit at sections adjacent to the looped midsection of 360 degrees loop angle and the locating of the electromagnetic vibrator at the clamped section of the conduit, which combination provide maximum signal-to- noise ratio as the two separate noise vibrations traveling through the inlet and outlet sections of the conduit become integrated at the clamped sections thereof and attain a symmetric distribution about the center section of the looped midsection of the conduit when the noise vibration travels to the looped midsection, wherein the noise of symmetric distribution is cancelled between the two alternating electrical signals respectively supplied by the two motion sensors symmetrically located about the center section of the looped mid- section of the conduit in the process of extracting the antisymmetric component of the conduit vibration representing the mass flow rate by forming a differential combination of the two alternating electrical signals or by using other algorithms providing the same end result.

It should be also understood that further alternative designs of the embodiments of the mass flowmeters shown in Figures 4-9 can be readily obtained by omitting the tying plate mechanically tying the looped midsections of the two conduits together at sections thereof located on the center plane of the combination of the two conduits if the tying plate such as the elements 43 and 68 respectively shown in Figures 5 and 9 is employed, and then relocating the electromagnetic vibrator from the existing location defined by the tied-together section of the combination of the inlet and outlet sections of the two conduits to a new location defined by the center plane that divides the combination of the looped midsections of the two conduits into two equal opposite halves, which modification is an obvious one in view that all of the existing versions of the mass flowmeter have the electromagnetic vibrator disposed at the middle section of the conduit or conduits. Therefore, such modified versions of the embodiments of the mass flowmeter of the present invention shown in Figures 5-9 must be regarded as falling within the scope of the present invention as defined by the claims which follow.