Measuring and testing – Volume or rate of flow – Mass flow by imparting angular or transverse momentum to the...
Patent
1989-01-24
1990-06-19
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Mass flow by imparting angular or transverse momentum to the...
G01F 184
Patent
active
049341952
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to coriolis mass flowmeters that can advantageously be used industrially.
DESCRIPTION OF THE PRIOR ART
A coriolis force is defined as a velocity dependent force that apparently arises when the motion of object is reckoned with respect to a rotating coordinate system and mass flowmeters involving this principle are known and commercially available.
OUTLINE OF THE INVENTION
An object of the present invention is to provide a tube structure carrying the fluid to be measured arranged in such a way that the forces arising in the operation of the meter enable the structure to have reduced stiffness and consequently reduced risk of fatigue failure and economy in the power required to operate the meter.
According to the present invention a coriolis mass flowmeter comprising substantially parallel tubes for fluid of which the mass flow is to be measured when passing in the same direction therethrough; first means for adapting said tubes at one end thereof jointly to receive said fluid to pass therethrough; second means for adapting said tubes at the other end thereof jointly to deliver said fluid after passing therethrough, each said tube being formed between its ends with a loop from which two arms, constituting portions of said tube, extend respectively to said first and second means, means remote from said loops holding said arms fixed in the flowmeter, characterized in that each loop lies substantially wholly in a flat plane and means are provided for vibrating said loops respectively in the areas of the planes thereof while said planes remain substantially fixed and with equal frequency in opposite phases whereby coriolis forces are experienced by said arms, said arms being flexible between said loops and said first and second means and said vibrations being such as to exert vibratory torques on said loops in their respective planes, the torques having a phase-shift dependent on the mass of said fluid when passing through said tubes and sensing means responsive to said phase-shift for providing a measurement signal corresponding to the mass flow of said fluid through said tubes.
DESCRIPTION OF THE DRAWINGS
In order that the invention may be clearly understood and readily carried into effect, coriolis mass flowmeters in accordance therewith will now be described, by way of example, with reference to the accompanying drawings, in which:
FIG. 1 is a plan of a mechanical assembly in a coriolis mass flowmeter;
FIGS. 2a, 2b are side and end elevations of the assembly of FIG. 1;
FIGS. 3a, 3b and 3c show very diagrammatically plan, side and end elevations of a modification of the arrangement shown in FIGS. 1 and 2;
FIG. 4 is a block diagram showing an electronic circuit for use with the assemblies of FIGS. 1 to 3c.
FIGS. 5, 6 and 7 are explanatory diagrams;
FIG. 8 is a diagram showing a modification of the assembly of FIGS. 1, 2a, 2b; and
FIG. 9 is a diagram showing a further modification of the assembly of FIGS. 1, 2a, 2b.
FIGS. 1, 2a, 2b show a tube configuration comprising two identical lengths 1, 2 of tube having a circular cross-section throughout. Inlet ends of these tubes merge at 3 to receive the fluid whose mass flow is to be measured. At their opposite ends the tubes merge at 4 for the discharge of the fluid.
The central portion of each tube is folded back on itself to form a rectangular loop 5, 6 with rounded corners. The tubes 1, 2 are parallel and the similar loops 5, 6 are juxtaposed as shown in FIG. 1 with arms A and B projecting in opposite directions therefrom. The ends of the tubes 1, 2 are rigidly mounted in frame members 7, 8 upstream and downstream of the loops 5, 6 so that when the loops are vibrated as described below, the tubes are vibrated at their resonant frequency in the planes of the loops.
The vibration of the loops 5, 6 is in opposite phase so that one moves up as the other moves down. This is effected by electromagnets 9, 10 allocated respectively to the loops and designed to provide sufficient amplitude of oscillation to vibrate th
REFERENCES:
patent: 4491025 (1985-01-01), Smith et al.
patent: 4660421 (1987-04-01), Dahlin et al.
"Measuring Mass Flow Using Vibrating Tubes", in Engineering Materials & Design, V29 (85), Mar., #3, p. 25.
"atp-Marktanalyse Durchflussmesstechnik", in Automatisierungstechnische Praxis atp., 4/86, pp. 169-178.
Goldstein Herbert
The Foxboro Company
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