US3890839A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Apparatus for measuring a fluid flow rate
Assignee: Instituttet for Produktudvikling PS
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Filing: 1973-07-20
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Granted: 1975-06-24
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Expires: 1993-07-20
Abstract
Abstract An apparatus for measuring the flow rate of fluid comprises a DC unit coupled in parallel with an AC unit. The DC unit is a positive displacement screw rotor machine driven by a motor, the rotational speed of which is controlled by a signal derived from the AC unit, which unit comprises a cylinder and a piston axially movable therein. The position or velocity of the piston determines the output signal of the AC unit, which thus is representative of the AC component of the fluid flow, while the instantaneous rotational speed of the rotor of the DC unit is representative of the DC flow component. A filter may be included in the line which transmits the control signal from the AC unit to the drive motor in order to filter out frequencies above a predetermined value from the control signal.
Inventors
- 👤 Erik Trostmann
- 👤 Jens Andreas Toft Fensvig
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 17:52
CPC Classifications
G; G01; G01F; G01F3/00; G01F3/02; G01F3/04; G01F3/06; G01F3/10; G01F1/00
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
222 words
An apparatus for measuring a fluid flow rate, said apparatus comprising: a. a positive displacement screw rotor device having a stator with a fluid inlet and a fluid outlet, a displacer screw rotor rotatably supported in said stator, and a variable speed drive motor for said rotor; b. a cylinder made of an electrically insulating material connected between said fluid inlet and said fluid outlet in parallel with said positive displacement screw rotor device; c. a piston-like body at least the surface of which is made of an electrically conductive material, said piston-like body being freely movable within said cylinder in the longitudinal direction thereof substantially without viscous friction between said piston-like body and the internal wall of said cylinder; d. two capacitor plates which are insulated from one another and from said piston-like body, said capacitor plates extending in the longitudinal direction of said cylinder substantially diametrically opposite each other with a distance between them which decreases from one end of said cylinder towards the opposite end thereof; e. a converter for supplying an electric output signal dependent upon the capacitance of the capacitor formed by said capacitor plates and said piston-like body; f. means responsive to said output signal for controlling the rotational speed of said screw rotor; and g. means for indicating the rotational speed of said screw rotor.
Claim 2
Independent Claim
222 words
An apparatus for measuring a fluid flow rate, said apparatus comprising: a. a positive displacement screw rotor device having a stator with a fluid inlet and a fluid outlet, a displacer screw rotor rotatably supported in said stator, and a variable speed drive motor for said rotor; b. a cylinder made of an electrically insulating material connected between said fluid inlet and said fluid outlet in parallel with said positive displacement screw rotor device; c. a piston-like body at least the surface of which is made of an electrically conductive material, said piston-like body being freely movable within said cylinder in the longitudinal direction thereof substantially without viscous friction between said piston-like body and the internal wall of said cylinder; d. two capacitor plates which are insulated from one another and from said piston-like body, said capacitor plates extending in the longitudinal direction of said cylinder substantially diametrically opposite each other with a distance between them which decreases from one end of said cylinder towards the opposite end thereof; e. a converter for supplying an electric output signal dependent upon the capacitance of the capacitor formed by said capacitor plates and said piston-like body; f. means responsive to said output signal for controlling the rotational speed of said screw rotor; and g. means for indicating the rotational speed of said screw rotor.
Claim 3
Dependent Claim
36 words
Apparatus as recited in claim 1 wherein said piston-like body is formed so as to contact said cylinder in a sealing fashion substantially only along a circumferentially extending line intermediate the ends of said piston-like body.
Claim 4
Dependent Claim
22 words
Apparatus as recited in claim 2 wherein said piston-like body is a ball movable with a close radial fit in said cylinder.
Claim 5
Dependent Claim
23 words
Apparatus as recited in claim 1 wherein the density of said piston-like body is substantially the same as the density of the fluid.
Claim 6
Dependent Claim
35 words
Apparatus as recited in claim 1, wherein the wall-thickness of said cylinder decreases from one end thereof towards the opposite end thereof and said capacitor plates are mounted on the outer surface of said cylinder.
Claim 7
Dependent Claim
100 words
Apparatus as recited in claim 5 and further comprising: a. an outer protective tube surroundinG said cylinder and forming therewith an annular chamber; b. sealing means for closing that end of the annular chamber between said outer protective tube and said cylinder at which the wall-thickness of said cylinder is at its maximum; and c. means for connecting the interior of the annular chamber between said outer protective tube and said cylinder with the interior of said cylinder, said means being located at the end of the annular chamber at which the wall-thickness of said cylinder is at its minimum.
Claim 8
Dependent Claim
60 words
Apparatus as recited in claim 1 and further comprising: a. an outer protective tube surrounding said cylinder and forming therewith an annular chamber; b. sealing means for closing one end of the annular chamber between said outer protective tube and said cylinder; and c. means for connecting the other end of the annular chamber with the interior of said cylinder.
Claim 9
Dependent Claim
34 words
Apparatus as recited in claim 1 and further comprising a compression spring located axially outside each end of said cylinder and coaxially therewith for preventing said piston-like body from moving out of said cylinder.
Claim 10
Independent Claim
162 words
An apparatus for measuring a fluid flow rate, said apparatus comprising: a. a positive displacement screw rotor device having a stator with a fluid inlet and a fluid outlet, a displacer screw rotor rotatably supported in said stator, and a variable speed drive motor for said rotor; b. a cylinder connected between said fluid inlet and said fluid outlet in parallel with said positive displacement screw rotor device; c. a piston-like body freely movable within said cylinder in the longitudinal direction thereof substantially without viscous friction between said piston-like body and the internal wall of said cylinder; d. measuring means for measuring a parameter related to the movement of said piston-like body within said cylinder; e. means for indicating the instantaneous linear speed of said piston-like body within said cylinder; f. means responsive to an output signal of said measuring means for controlling the rotational speed of said screw rotor; and g. means for indicating the rotational speed of said screw rotor.
Claim 11
Independent Claim
162 words
An apparatus for measuring a fluid flow rate, said apparatus comprising: a. a positive displacement screw rotor device having a stator with a fluid inlet and a fluid outlet, a displacer screw rotor rotatably supported in said stator, and a variable speed drive motor for said rotor; b. a cylinder connected between said fluid inlet and said fluid outlet in parallel with said positive displacement screw rotor device; c. a piston-like body freely movable within said cylinder in the longitudinal direction thereof substantially without viscous friction between said piston-like body and the internal wall of said cylinder; d. measuring means for measuring a parameter related to the movement of said piston-like body within said cylinder; e. means for indicating the instantaneous linear speed of said piston-like body within said cylinder; f. means responsive to an output signal of said measuring means for controlling the rotational speed of said screw rotor; and g. means for indicating the rotational speed of said screw rotor.
Claim 12
Dependent Claim
28 words
Apparatus as recited in claim 9 wherein the parameter measured by the element recited in subparagraph (d) is the longitudinal position of said piston-like body in said cylinder.
Claim 13
Dependent Claim
36 words
Apparatus as recited in claim 9 wherein said piston-like body is formed so as to contact said cylinder in a sealing fashion substantially only along a circumferentially extending line intermediate the ends of said piston-like body.
Claim 14
Dependent Claim
22 words
Apparatus as recited in claim 11 wherein said piston-like body is a ball movable with a close radial fit in said cylinder.
Claim 15
Dependent Claim
23 words
Apparatus as recited in claim 9 wherein the density of said piston-like body is substantially the same as the density of the fluid.
Claim 16
Dependent Claim
34 words
Apparatus as recited in claim 9 and further comprising a compression spring located axially outside each end of said cylinder and coaxially therewith for preventing said piston-like body from moving out of said cylinder.
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) | 1978-06-23 | 1978-12-23 | 1979-06-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-06-23 | 1982-12-23 | 1983-06-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-06-23 | 1986-12-23 | 1987-06-24 | $7700.00 | Window Closed / Lapsed |