Measuring and testing – Volume or rate of flow – Mass flow by imparting angular or transverse momentum to the...
Reexamination Certificate
1998-03-16
2001-05-01
Patel, Harshad (Department: 2855)
Measuring and testing
Volume or rate of flow
Mass flow by imparting angular or transverse momentum to the...
C073S861354
Reexamination Certificate
active
06223605
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a Coriolis-type mass flow sensor with a single measuring tube.
BACKGROUND OF TIE INVENTION
As is well known, mass flow sensors are suitable for measuring the mass flow rate and/or the density of fluids flowing in a conduit in which the mass flow sensor is installed.
Coriolis-type mass flow sensors with at least two measuring tubes can be better made immune to disturbances originating from the conduit, such as vibrations of the conduit or wide pressure variations of the fluid, than Coriolis-type mass flow sensors having only a single measuring tube, which are also more sensitive to other disturbances acting on them, such as impacts on the casing.
These disturbances also include vibration components which are transmitted from the measuring tube vibrating at an instantaneous frequency to the conduit and are reflected from discontinuities in the conduit, thus traveling back to the measuring tube. These vibration components are particularly disturbing because they have the same instantaneous frequency as the measuring tube. Therefore, these disturbances cannot be eliminated by electronic means and are difficult to eliminate by mechanical means.
U.S. Pat. No. 5,307,689 describes two variants of Coriolis-type mass flowmeters whereby an attempt is made to eliminate the above-mentioned conduit-induced disturbances by circuit means, but the components having the same frequency as the vibration of the measuring tube cannot be eliminated. The design of the Coriolis-type mass flow sensor do not show any measures to suppress disturbances.
DE-A 38 24 351 describes a Coriolis-type mass flow sensor in which the rigid connection between two measuring tubes and a casing, which is stiff against vibration, is claimed to keep the above-mentioned external disturbances away from the two measuring tubes. It has turned out, however, that sufficient suppression of external disturbances cannot be achieved in this manner.
U.S. Pat. No. 5,705,754 describes a Coriolis-type mass flow sensor which can be installed in a conduit and which during operation is traversed by a fluid to be measured, comprising:
a casing to be connected with the conduit via a fluid inlet and a fluid outlet;
a support base disposed within the casing,
said support base being connected to the casing via at least one mechanical damping element
which is located on a nodal line of vibration of the support base;
a single measuring tube, traversed by the fluid, which is bent in a plane parallel to a top side of the support base and ends in a fluid inlet and a fluid outlet,
a portion of said measuring tube to be vibrated in a direction perpendicular to said plane being fixed to the support base by a first fixing means provided in the area of a first edge of the support base and by a second fixing means provided in the area of a second edge of the support base, and
a first connecting portion of said measuring tube extending from the first fixing means to the fluid inlet, and a second connecting portion extending from the second fixing means to the fluid outlet;
a vibrator for producing the vibrations; and
a first sensing element mounted near the first fixing means for sensing the vibrations of the tube portion as well as a second sensing element mounted near the second fixing means for sensing the vibrations of the tube portion.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a Coriolis-type mass flow sensor which is made as insusceptible to the aforementioned external disturbances as possible by further mechanical means.
To accomplish this, the invention provides a Coriolis-type mass flow sensor which can be installed in a conduit and which during operation is traversed by a fluid to be measured, comprising:
a casing to be connected with the conduit via a fluid inlet and a fluid outlet;
a rigid support base disposed within the casing,
said support base being connected with the casing via at least one mechanical damping element;
a measuring tube traversed by the fluid and ending in the fluid inlet and the fluid outlet,
a portion of said measuring tube to be vibrated being fixed to the support base by an inlet-side fixing means and an outlet-side fixing means, and
an inlet-side connecting portion of said measuring tube extending from the inlet-side fixing means to the fluid inlet, and an outlet-side connecting portion extending from the outlet-side fixing means to the fluid outlet;
a vibrator arrangement for vibrating the tube portion, said vibrator assembly acting between the casing and the support base;
a first sensing element mounted near the inlet-side fixing means, partly on the tube portion, for sensing the vibrations of the tube portion; and
a second sensing element mounted near the outlet-side fixing means, partly on the tube portion, for sensing the vibrations of the tube portion.
According to a first preferred embodiment of the invention the portion of the measuring tube to be vibrated has the form of the arc of a circle. In addition thereto, each connecting portion of the measuring tube is bent preferably with a smaller radius of curvature as that of the portion of the measuring tube to be vibrated.
According to a second preferred embodiment of the invention the measuring tube has a nominal diameter of less than 10 millimeters, in particular a nominal diameter of about 1 millimeter.
According to a third preferred embodiment of the invention the mass of the support is large compared to the mass of the portion of the measuring tube to be vibrated.
According to a fourth preferred embodiment of the invention a first sensor portion fixed to the portion of the measuring tube to be vibrated and a second sensor portion fixed to the portion of the measuring tube to be vibrated have a small mass compared to that of the portion of the measuring tube to be vibrated.
An essential advantage of the invention is that no component of a vibrator assembly need be fixed to the measuring tube, so that at the point where the measuring tube is excited, the tube have no mass in addition to their own mass. The smaller the nominal bore of the measuring tube, the more apparent this advantage will be. This is particularly important in the case of nominal diameters around 1 millimeter.
A further advantage of the invention is that, according to its problem solution which can be interpreted as an inner vibration compensation, substantially no vibration portions are transferred from the measuring tube vibrating at an momentary frequency to the conduit.
REFERENCES:
patent: 3132512 (1964-05-01), Roth
patent: 4895031 (1990-01-01), Cage
patent: 5307689 (1994-05-01), Nishiyama et al.
patent: 5365794 (1994-11-01), Hussain et al.
patent: 5476013 (1995-12-01), Hussain et al.
patent: 5531126 (1996-07-01), Drahm
patent: 5549009 (1996-08-01), Zaschel
patent: 5705754 (1998-01-01), Keita et al.
patent: 5804742 (1998-09-01), Rademacher-Dubbick
patent: 5854430 (1998-12-01), Drahm et al.
patent: 5969265 (1999-10-01), VanCleve et al.
patent: 3824351 (1990-01-01), None
patent: 0 473 919 (1992-03-01), None
patent: 0 687 893 (1992-07-01), None
patent: 0 770 858 (1996-06-01), None
patent: 1316083 (1962-02-01), None
patent: 2 290 661 (1974-11-01), None
Koudal Ole
Wenger Alfred
Bose McKinney & Evans LLP
Endress + Hauser Flowtec AG
Patel Harshad
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