GB2143325A - Apparatus for measuring the value of a fluid variable - Google Patents
Apparatus for measuring the value of a fluid variable Download PDFInfo
- Publication number
- GB2143325A GB2143325A GB08318817A GB8318817A GB2143325A GB 2143325 A GB2143325 A GB 2143325A GB 08318817 A GB08318817 A GB 08318817A GB 8318817 A GB8318817 A GB 8318817A GB 2143325 A GB2143325 A GB 2143325A
- Authority
- GB
- United Kingdom
- Prior art keywords
- tube
- vibratory
- isolator
- holding structure
- vibratory tube
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
- G01L9/0001—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means
- G01L9/0008—Transmitting or indicating the displacement of elastically deformable gauges by electric, electro-mechanical, magnetic or electro-magnetic means using vibrations
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N11/00—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties
- G01N11/10—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material
- G01N11/16—Investigating flow properties of materials, e.g. viscosity, plasticity; Analysing materials by determining flow properties by moving a body within the material by measuring damping effect upon oscillatory body
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/002—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N9/00—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity
- G01N9/002—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis
- G01N2009/006—Investigating density or specific gravity of materials; Analysing materials by determining density or specific gravity using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis vibrating tube, tuning fork
Abstract
Apparatus for measuring the value of a fluid variable e.g. density, pressure or viscosity comprising a vibratory tube (10) through which the fluid is passed and which is mounted in a holding structure (13) for rigid fixing at nodes (11,12) to produce clamped-clamped flexural vibration; driving means (22) arranged in operation to produce resonant vibration of the vibratory tube (10); pick-up means (23) arranged in operation to respond to vibration of the vibratory tube (10); a support (26); and isolator tubes (33,34) which are disposed on opposite sides of and communicate with the vibratory tube (10) and which extend between the support (26) and the holding structure (13) so as to support the holding structure (13) and permit axial extension without compression of the vibratory tube (10), each isolator tube (33,34) being a linerless tube having at least one portion (33a,34a) which does not extend axially of the vibratory tube, and the isolator tubes (33,34) and the vibratory tube (10) having smooth internal surfaces throughout their length. Shock absorbers (40,41) isolate the holding structure (13) from external vibration. The apparatus may be used in food processing plant. <IMAGE>
Description
SPECIFICATION
Apparatus for measuring the value of a fluid variable
This invention concerns an apparatus for measuring the value of a fluid variable such, for example, as the density of a liquid or of a gas. The apparatus of the present invention is, however, also applicable to the measurement of the value of other fluid variables such as viscosity and pressure.
In our British Patent No. 2,039,3698 we have disclosed an apparatus for measuring the value of a fluid variable which comprises a vibratory tube which is rigidly fixed in a holding structure, the holding structure being spaced from a support by way of bellows, e.g. stainless steel bellows, which permit axial extension without compression of the vibratory tube. The internal surface of these bellows, however, is not easy to clean, particularly when glutinous materials lodge in the crevices between convolutions. This is particularly serious if the glutinous materials are constituted by particles of food since such particles can easily get trapped in these crevices between adjacent convolutions which are extremely close to each other.Attempts to clean the internal surface of such a bellows by passing the conventional acid steam mixture through the bellows are unsuccessful and consequently food manufacturers are reluctant to use apparatus comprising such bellows.
It is also known to attempt to overcome this problem by using a rubber or synthetic polymer trim or liner within the bellows, but this produces creep in the instrument calibration and has a limited service life.
It is not possible merely to replace the bellows by a straight tube because any expansion of the straight tube by heat would subject the vibrating tube to compression, and this would affect the accuracy of the apparatus. Moreover, the mass/unit length and stiffness of such a straight tube would be comparable with that of the vibratory tube with the result that the straight tube would form part of the oscillating system and would be liable to couple the support to the oscillating system so as to alter the frequency of vibration and hence alter the calibration.
Although, therefore, the present invention is primarily directed to any novel integer or step, or combination of integers or steps, as herein described and/or as shown in the accompanying drawings, nevertheless, according to one particular aspect of the present invention to which, however, the invention is in no way restricted, there is provided apparatus for measuring the value of a fluid variable comprising a vibratory tube through which the fluid may be passed and which is mounted in a holding structure; driving means arranged in operation to produce a vibration of the vibratory tube; pick-up means arranged in operation to respond to vibration of the vibratory tube; a support; and isolator tubes which are disposed on opposite sides of and communicate with the vibratory tube and which extend between the support and the holding structure so as to support the holding structure and permit axial extension without compression of the vibratory tube, each isolator tube being a linerless tube having at least one portion which does not extend axially of the vibratory tube, and the isolator tubes and the vibratory tube having smooth internal surfaces throughout their length.
Each isolator tube is preferably directly connected to the vibratory tube. Moreover, each isolator tube is preferably a metal tube having a smooth external surface throughout its length.
Preferably at least part of each isolator tube is non-linear. Preferably also at least part of each isolator tube extends substantially perpendicular to the axis of the vibratory tube.
At least part of each isolator tube may be substantially circular. Thus each isolator tube may be helically coiled throughout at least part of its length.
Alternatively, each isolator tube may extend from the surface of the support to an end of the vibratory tube which is remote from said surface. In this case, each isolator tube is preferably bent both adjacent said surface and adjacent said end.
In one particular embodiment of the present invention, each isolator tube has a figure-of-eight portion.
The vibratory tube may be rigidly fixed at its nodes in the holding structure for clamped-clamped flexural vibration.
The driving means and the pick-up means may be rigidly carried by the holding structure.
The stiffness of the holding structure may be at least 40% greater than that of the vibratory tube.
The invention is illustrated, merely by way of example, in the accompanying drawings, in which:
Figure 1 is a diagrammatic cross-sectional view of one embodiment of an apparatus according to the present invention for measuring the value of a fluid variable, and
Figures 2 and 3 are diagrammatic views illustrating modifications of portions of the structure shown in Figure 1.
In Figure 1 there is shown a first embodiment of an apparatus according to the present invention for measuring the value of the density of a fluid. The apparatus of Figure 1 comprises a long, slender vibratory tube 10 which may be made of a magnetisable material, or of a non-magnetic material such as glass or stainless steel. Although the vibratory tube 10 would normally be cylindrical, this is not essential since the vibratory tube could, if desired, be of smooth non-circular cross-section, while its centreline is not necessarily linear. However, the vibratory tube 10 has a smooth internal surface throughout its length.
The vibratory tube 10 is rigidly fixed at nodes 11, 12 thereof to a holding structure 13 whose stiffness is at least 40% greater than that of the vibratory tube 10. Thus the stiffness of the holding structure 13 is preferably at least twice, and may be 10 times or more, that of the vibratory tube 10. This construction ensures that when, as described below, the vibratory tube 10 is set into vibration, it will vibrate in the clamped-clamped flexural mode of vibration.
The holding structure 13 comprises spaced apart frame members 14, 15 each of which is rigidly secured to the vibratory tube 10 at a respective node thereof. The frame members 14, are rigidly interconnected by a plurality, e.g. two, tubular interconnecting members 16 each of which may consist if desired of one, two or more stiffening bars.
The interconnector members 16 may either be rigidly secured to or may be integral with the frame members 14,15. The stiffness of each of the interconnector members 16 is at least twice, and may be ten times or more, that of the vibratory tube 10.
The holding structure 13 also comprises arms 20, 21 which extend from respective interconnector members 16 and which respectively carry a driving coil 22 and a pick-up coil 23. The driving coil 22 and the pick-up coil 23 form part of a feedback oscillator (not shown) that maintains the vibratory tube 10 vibrating at its natural frequency. Although, for the sake of clarity, the driving coil 22 and pick-up coil 23 are shown as being well spaced from the vibratory tube 10, in practice the space therebetween is maintained as small as possible.Energisation of the driving coil 22 (by means not shown) causes the vibratory tube 10 to vibrate in the clamped-clamped flexural mode of vibration as indicated by the dotted line 24, such vibration being produced either by the direct magnetic effect on the vibratory tube 10, if the latter is made of a magnetisable material, or, by the magnetic effect on a magnetisable member carried by the vibratory tube 10, as described below.
Alternatively, the vibratory tube 10 may be excited mechanically (e.g. by piezo-electric or magnetostrictive means), acoustically (e.g. by the emission of a sound wave from a loudspeaker), or electrostatically.
The vibrations of the vibratory tube 10, which are affected by the density of the fluid passing through the latter, are sensed by the pick-up coil 23 from which signals are sent to a meter 25 which indicates that the density of the fluid or which controls a process in dependence upon the value of such density.
The holding structure 13, and the vibratory tube 10 which is clamped within the latter, are mounted within a support 26 having wall members 27, 28, 29, 30. Opposite ends of the vibratory tube 10 communicate with and are respectively directly connected to linerless isolatortubes 33, to tubes 35, 36 respectively which pass through the wall members 28,30 respectively of the support 26. Each of the isolatortubes 33, 34is a metallic tube having smooth external and internal surfaces throughout its length.
Each of the isolator tubes 33,34 extends between the support 26 and the holding structure 13 and has therebetween at least one non-linear portion (e.g.
two such portions, as shown in Figure 1) which do not extend axially of the vibratory tube 10.
Optionally, shock absorbers 40 are interposed between the wall member 27 of the support 26 and the frame members 14,15 ofthe holding structure 13, while shock absorbers 41 are interposed between the frame members 14,15 ofthe holding structure 13 and the wall member 29 of the support 26. The provision of the isolator tubes 33,34 and of the shock absorbers 40, 41 isolates the holding structure 13 from the support 26 in such a way as substantially to prevent transmission of vibration therebetween.
The shock absorbers 40,41, however, need not be provided if the isolator tubes 33,34 are strong enough to support the vibratory tube 10 and holding structure 13.
Thus, as will be appreciated, both the vibratory tube 10 and the holding structure 13 are connected to the support 26 by way of respective isolator means constituted by the isolator tubes 33,34 and shock absorbers 40, 41 respectively, the latter being disposed at right angles to the vibratory tube 10. The isolator tubes 33, 34 permit axial extension without compression of the vibratory tube 10, this being desirable since axial compression will increase the apparent density when the pressure of the fluid rises. Such axial extension without compression is possible because each of the isolator tubes 33,34 has a helically coiled portion 33a, 34a respectively the flow through which follows a substantially circular path.Each helically coiled portion 33a, 34a is shown as having two coils, but it may for example have six coils or any other convenient number.
Moreover, the helically coiled portions 33a, 34a extend substantially perpendicular to the axis of the vibratory tube 10. This increases the lateral compliance and the mass/unit length of the coupling provided by each isolator tube 33,34 between the vibratorytube 10 and the support 26, thus allowing the said coupling to act as a low pass filter which considerably alters the transmission of vibration therethrough.
The construction shown in Figure 1 has substantial advantages. Since the vibratory tube 10 vibrates in the clamped-clamped flexural mode of vibration, the viscosity of the fluid passing through the vibratory tube 10 has very little damping effect on the vibration thereof. Moreover, the vibratory tube 10 may be constituted by a tube whose internal surface is smooth but whose cross-sectional shape is not of importance and which therefore does not require any precision machining, nor matching with a similar tube, balancing weight, counter lever or the like.
Furthermore, the vibratory tube 10 can be made of materials such as stainless steel, glass, or ceramics, which normally cannot be employed in a density meter. In fact, the apparatus of the present invention can be made of dissimilar materials and yet can achieve an automatic temperature correction without the use of special materials such as that marketed undertheTrade Mark "Ni-Span-C".
The holding structure 13 constitutes a stiff structure which defines the nodes of the clampedclamped flexural mode of vibration, and the use of the holding structure 13, which is very simple to manufacture, thus avoids the need to use complicated constructions to balance the reactions at the nodes. Since the holding structure 13 is substantially stiffer than the vibratory tube 10, only very small amplitude vibration will be transferred from the vibratory tube 10 to the holding structure 13.
In the construction shown in Figure 1, moreover, both the driving coil 22 and the pick up coil 23 are mounted on the arms 20, 21 respectively of the holding structure 13 and are thus mounted on the same stiff structure as holds the vibratory tube 10.
This is an important feature because it ensures that the whole system is balanced. Thus in accordance with Newton's Third Law, the driving force on the vibratory tube 10 has equal and opposite reactions on the driving means comprising the driving coil 22.
Consequently, the reactions at the nodes 11, 12 are therefore balanced. Thus the construction shown in
Figure 1 permits the use of a single vibratory tube which is balanced in a particularly simple and therefore inexpensive way.
The provision of the isolator tubes 33, 34 serves to isolate the vibratory tube 10 from any pipe-work carrying the fluid to be tested to and from the structure shown in Figure 1, and thus prevents energy transmission therebetween. The vibratory tube 10 is also, in effect, isolated from the support 29 by the shock absorbers 40,41 which act as antishock mountings so that plant vibrations will not affect its performance as a density meter.
In the construction shown in Figure 1, the vibrating tube 10 is a straight tube. However, the vibratory tube 10 may be U-shaped or may have the shape of the vibratory tube 10 of either Figure 2 or Figure 3 of
British Patent Specification No. 2,039,369B.
In Figures 2 and 3 there are shown portions of an apparatus which is generaily similar to that of Figure 1, and which for this reason will not be described in detail, like reference numerals indicating like parts.
In the Figure 2 construction, however, each isolator tube, instead of being provided with a helically coiled portion 33a, 34a, is provided with a "Figure of 8" portion 42 which comprises intercommunicating coils 43, 44. As indicated by the arrows, the flow passes from a linear portion 45 of the isolator tube into the coil 43 so as to flow counter-clockwise therein, passes to the coil 44 so as to flow clockwise therein, and then passes to a linear portion 46. The linear portions 45,46 extend axially of the vibratory tube 10, but the coils 43,44 (except for small portions thereof) do not so extend. Moreover, there are also small portions of the coils 43,44 which extend substantially perpendicular to the axis of the vibratory tube 10.
In the Figure 3 construction isolator tubes 50,51 are employed. The isolator tube 50 extends from the internal surface 52 of the wall member 28 of the support 26 to an end of the vibratory tube 10 which is remote from the surface 52. Similarly, the isolator tube 51 extends from the internal surface 53 of the wall member 30 of the support 26 to an end of the vibratory tube 10 which is remote from the surface 53. The isolatortube 50 has bends 54,55 therein adjacent the surface 52 and the end of the vibratory tube 10 remote therefrom respectively. Similarly, the isolator tube 51 has bends 56,57 therein adjacent the surface 53 and the end of the vibratory tube 10 remote therefrom respectively. Consequently, the isolator tubes 50, 51, except at the portions thereof adjacent the vibratory tube 10, do not extend axially of the vibratory tube 10, while the bends 54-57 form non-linear portions, parts of which extend substantially perpendicular to the axis of the vibratory tube 10.
The axes of the portions of the isolator tubes 50,51 immediately adjacent to the support 26 may be at an angle a, e.g. of 10 , to the axis of the vibratory tube 10. Similarly, in the Figure 1 construction, the axes of the portions of the isolator tubes 33, 34 immediately adjacent to the support 26 may be at an angle of up to 10" to the axis of the vibratory tube 10, thus allowing for production tolerances in the bending of the isolator tubes.
Claims (15)
1. Apparatus for measuring the value of a fluid variable comprising a vibratory tube through which the fluid may be passed and which is mounted in a holding structure; driving means arranged in operation to produce vibration of the vibratory tube; pick-up means arranged in operation to respond to vibration of the vibratory tube; a support; and isolator tubes which are disposed on opposite sides of and communicate with the vibratory tube and which extend between the support and the holding structure so as to support the holding structure and permit axial extension without compression of the vibratory tube, each isolatoitube being a linerless tube having at least one portion which does not extend axially of the vibratory tube, and the isolator tubes and the vibratory tube having smooth internal surfaces throughout their length.
2. Apparatus as claimed in claim 1 in which each isolator tube is directly connected to the vibratory tube.
3. Apparatus as claimed in claim 1 or 2 in which each isolator tube is a metal tube having a smooth external surface throughout its length.
4. Apparatus as claimed in any preceding claim in which at least part of each isolator tube is non-linear.
5. Apparatus as claimed in any preceding claim in which at least part of each isolator tube extends substantially perpendicular to the axis of the vibratory tube.
6. Apparatus as claimed in any preceding claim in which at least part of each isolator tube is substantially circular.
7. Apparatus as claimed in any preceding claim in which each isolator tube is helically coiled throughout at least a part of its length.
8. Apparatus as claimed in any of claims 1-5 in which each isolator tube extends from a surface of the support to an end of the vibratory tube which is remote from said surface.
9. Apparatus as claimed in claim 8 in which each isolator tube is bent both adjacent said surface and adjacent said end.
10. Apparatus as claimed in any of claims 1-6 in which each isolator tube has a Figure-of-8 portion.
11. Apparatus as claimed in any preceding claim in which the vibratory tube is rigidly fixed at its nodes in the holding structure for clamped-clamped flexural vibration.
12. Apparatus as claimed in any preceding claim in which the driving means and the pick-up means are rigidly carried by the holding structure.
13. Apparatus as claimed in any preceding claim in which the stiffness of the holding structure is at least 40% greater than that of the vibratory tube.
14. Apparatus for measuring the value of a fluid variable substantially as herein before described with reference to and as shown in any of Figure 1-3 of the accompanying drawings.
15. Any novel integer or step, or combination of integers or steps, hereinbefore described and/or shown in the accompanying drawings, irrespective of whether the present claim is within the scope of, or relates to the same or a different invention from that of, the preceding claims.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08318817A GB2143325B (en) | 1983-07-12 | 1983-07-12 | Apparatus for measuring the value of a fluid variable |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB08318817A GB2143325B (en) | 1983-07-12 | 1983-07-12 | Apparatus for measuring the value of a fluid variable |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8318817D0 GB8318817D0 (en) | 1983-08-10 |
| GB2143325A true GB2143325A (en) | 1985-02-06 |
| GB2143325B GB2143325B (en) | 1986-10-01 |
Family
ID=10545595
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08318817A Expired GB2143325B (en) | 1983-07-12 | 1983-07-12 | Apparatus for measuring the value of a fluid variable |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2143325B (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2187286A (en) * | 1986-02-24 | 1987-09-03 | Hatschek Rudolf | Fluid density measuring apparatus |
| GB2321105A (en) * | 1997-01-10 | 1998-07-15 | Rolls Royce Plc | Remote detection of fluid properties uses magnetostrictive transducer |
| US6286361B1 (en) | 1998-01-05 | 2001-09-11 | Rolls-Royce Plc | Method and apparatus for remotely detecting pressure, force, temperature, density, vibration, viscosity and speed of sound in a fluid |
| EP4092402A4 (en) * | 2021-04-08 | 2023-08-02 | Zhejiang University | Device and method for rapidly detecting blood viscosity based on ultrasonic guided waves of micro-fine metal pipe |
-
1983
- 1983-07-12 GB GB08318817A patent/GB2143325B/en not_active Expired
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2187286A (en) * | 1986-02-24 | 1987-09-03 | Hatschek Rudolf | Fluid density measuring apparatus |
| GB2187286B (en) * | 1986-02-24 | 1990-01-04 | Hatschek Rudolf | Fluid density measuring apparatus |
| GB2321105A (en) * | 1997-01-10 | 1998-07-15 | Rolls Royce Plc | Remote detection of fluid properties uses magnetostrictive transducer |
| GB2321105B (en) * | 1997-01-10 | 2001-02-28 | Rolls Royce Plc | A method and apparatus for remotely detecting pressure,force,temperature,density,vibration,viscosity and speed of sound in a fluid |
| US6286361B1 (en) | 1998-01-05 | 2001-09-11 | Rolls-Royce Plc | Method and apparatus for remotely detecting pressure, force, temperature, density, vibration, viscosity and speed of sound in a fluid |
| EP4092402A4 (en) * | 2021-04-08 | 2023-08-02 | Zhejiang University | Device and method for rapidly detecting blood viscosity based on ultrasonic guided waves of micro-fine metal pipe |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2143325B (en) | 1986-10-01 |
| GB8318817D0 (en) | 1983-08-10 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19950712 |