US4173143A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fluid flow measuring apparatus
Assignee: Ricardo PLC
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Filing: 1978-08-10
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Granted: 1979-11-06
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Expires: 1998-08-10
Abstract
Abstract A fluid flow meter, for example for measuring the velocity of an air flow, comprises a flow duct having a transverse vortex-shedding bar, the ultrasonic or other detector means for sensing the shedding of Karman vortices from the bar as the fluid flow passes the bar, and for converting the alternating output signal of the detector means into a signal of square-wave form of operating a digital counter, and one or more additional cross-members extending across the flow duct downstream of the flow section where the vortex-sensing means operates, the additional cross-member extending transversely to the vortex-shedding bar and being of cylindrical or aerofoil cross-section, or of rectangular or other cross-section having a flat upstream face parallel to the bar. The provision of the additional cross-member is found to improve the regularity of the vortex-shedding from the bar and hence the accuracy of the meter reading.
Inventors
- 👤 Roy Venton-Walters
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 23:43
CPC Classifications
G; G01; G01P; G01P5/00; G01P5/01
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
158 words
A fluid flow meter which comprises a flow duct through whose interior a fluid flow whose velocity to be measured can be passed, and a vortex-shedding bar positioned in the duct to extend across its interior transversely to the direction of fluid flow therein, means for sensing the passage of Karman vortices shed from the bar across a flow section close to the bar in the downstream direction said means producing an alternating output signal, and means for deriving from the output signal a modified output signal of square wave form suitable for operating a digital counter, wherein the improvement comprises at least one additional cross-member positioned in the duct to extend across its interior close to and down-stream of the said flow-section where the vortex-sensing means operates, the additional cross-member extending transversely to the vortex-shedding bar and having sufficient width, in the direction transverse to the flow direction, to cause the divergent parting of the fluid flow.
Claim 2
Dependent Claim
158 words
A fluid flow meter which comprises a flow duct through whose interior a fluid flow whose velocity to be measured can be passed, and a vortex-shedding bar positioned in the duct to extend across its interior transversely to the direction of fluid flow therein, means for sensing the passage of Karman vortices shed from the bar across a flow section close to the bar in the downstream direction said means producing an alternating output signal, and means for deriving from the output signal a modified output signal of square wave form suitable for operating a digital counter, wherein the improvement comprises at least one additional cross-member positioned in the duct to extend across its interior close to and down-stream of the said flow-section where the vortex-sensing means operates, the additional cross-member extending transversely to the vortex-shedding bar and having sufficient width, in the direction transverse to the flow direction, to cause the divergent parting of the fluid flow.
Claim 3
Dependent Claim
33 words
A fluid flow meter as claimed in claim 1 in which the additional cross-member is symmetrical in cross-section about an axis parallel to the direction of fluid flow past it in the duct.
Claim 4
Dependent Claim
22 words
A fluid flow meter as claimed in claim 2, in which the upstream surface of the additional cross-member is of part-cylindrical form.
Claim 5
Dependent Claim
25 words
A fluid flow meter as claimed in claim 3 in which the additional cross-member is of aerofoil cross-section tapering in section on its downstream side.
Claim 6
Dependent Claim
18 words
A fluid flow meter as claimed in claim 3 in which the additional cross-member is of cylindrical shape.
Claim 7
Dependent Claim
31 words
A fluid flow meter as claimed in claim 2 in which the upstream face of the additional cross-member is flat, with its width parallel to the length of the vortex-shedding bar.
Claim 8
Dependent Claim
20 words
A fluid flow meter as claimed in claim 6 in which the additional cross-member is of rectangular or triangular cross-section.
Claim 9
Dependent Claim
32 words
A fluid flow meter as claimed in claim 6 in which the additional cross-member is of T-shaped cross-section, arranged with the cross-bar of the T upstream of the leg of the T.
Claim 10
Dependent Claim
32 words
A fluid flow meter as claimed in claim 6 in which the additional cross-member is of channel section, arranged with the base of the channel upstream of the sides of the channel.
Claim 11
Dependent Claim
26 words
A fluid flow meter as claimed in claim 1, in which the additional cross-member is straight and extends lengthwise at right angles to the vortex-shedding bar.
Claim 12
Dependent Claim
31 words
A fluid flow meter as claimed in claim 1, in which the additional cross-member is straight and is inclined obliquely to the vortex-shedding bar at an angle in excess of 45°.
Claim 13
Dependent Claim
23 words
A fluid flow meter as claimed in claim 1 having at least two of the said additional cross-members arranged in parallel side-by-side relationship.
Claim 14
Dependent Claim
22 words
A fluid flow meter as claimed in claim 1 having at least two of the said additional cross-members which intersect one another.
Claim 15
Dependent Claim
54 words
A fluid flow meter as claimed in claim 1, in which the means for sensing the passage of Karman vortices comprises an ultrasonic generator arranged to project a beam of ultrasonic sound waves across the duct immediately downstream of the vortex-shedding bar and transversely thereto, and a transducer arranged to receive the ultrasonic beam.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1982-11-05 | 1983-05-07 | 1983-11-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1986-11-05 | 1987-05-07 | 1987-11-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1990-11-05 | 1991-05-07 | 1991-11-06 | $7700.00 | Window Closed / Lapsed |