US4559831A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method and device for flow measurement of small liquid volumes
Assignee: Siemens AG
•
Filing: 1984-09-06
•
Granted: 1985-12-24
•
Expires: 2004-09-06
Abstract
Abstract The invention relates to a method and a device for flow measurements of small liquid volumes through a thin tube. The measurement of small liquid volumes on the order of e.g. 1-500 μl/h is important, especially for medication dispensers. Gas bubbles are fed into the tube, the diameter of the gas bubbles being essentially the same size as the inside diameter of the tube. The liquid flow pushes the gas bubble forward. The flow time of the gas bubble is determined at pre-set measuring points which are located at a predetermined distance from each other along the tube. A control signal may be emitted according to the flow time and may be used to control the flow rate. The method and the device are suitable for electrically conductive liquids, in which variations in the electrical resistance is determined in the direction of the flow when the bubbles enter the measuring section.
Inventors
- 👤 Karl Prestele
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 15:46
CPC Classifications
A; A61; A61M; A61M5/00; A61M5/14; A61M5/168; A61M5/16886; G; G01; G01F; G01F1/00; G01F1/56; G01F1/64; G01F1/704; G01F1/708
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
158 words
A method for measuring small liquid flow volumes passing through a tube-like conduit in which a gas bubble is introduced, the longitudinal flow time of the bubble being measured between two points on the conduit which are separated from each other by a predetermined distance, the diameter of the bubble being approximately equal to the inside diameter of the conduit and the flow rate being determinable from the flow time, comprising the steps of: measuring the electrical resistance between the two points on the conduit; characterizing the resistance as a one of two categories which include a relatively low resistance corresponding to an absence of a gas bubble between the two points and a relatively high resistance corresponding to a presence of a gas bubble between the two points; starting a timing period upon measuring a relatively high resistance between the two points; and stopping the timing period upon measuring a relatively low resistance between the two points.
Claim 2
Independent Claim
158 words
A method for measuring small liquid flow volumes passing through a tube-like conduit in which a gas bubble is introduced, the longitudinal flow time of the bubble being measured between two points on the conduit which are separated from each other by a predetermined distance, the diameter of the bubble being approximately equal to the inside diameter of the conduit and the flow rate being determinable from the flow time, comprising the steps of: measuring the electrical resistance between the two points on the conduit; characterizing the resistance as a one of two categories which include a relatively low resistance corresponding to an absence of a gas bubble between the two points and a relatively high resistance corresponding to a presence of a gas bubble between the two points; starting a timing period upon measuring a relatively high resistance between the two points; and stopping the timing period upon measuring a relatively low resistance between the two points.
Claim 3
Dependent Claim
29 words
The method of claim 1, further comprising the steps of checking the conduit to detect gas bubbles which interfere with liquid flow, and repeating flow measurement upon such detection.
Claim 4
Dependent Claim
36 words
The method of claim 2, wherein ongoing measurement of flow time is cut off upon such detection and a moment of such detection is used as a new beginning for a new measurement of flow time.
Claim 5
Dependent Claim
30 words
The method of claim 1, further comprising the steps of deriving a control signal from the measured flow time, and using the control signal to regulate the liquid flow rate.
Claim 6
Dependent Claim
104 words
A flow measurement device of the type having a conduit through which a liquid flows, means for repeatedly feeding a gas bubble into the conduit and a means for timing the passage of the gas bubble between two points along the conduit which are separated from each other by a predetermined distance, comprising: first and second electrodes, each located at a corresponding one of the two points along the conduit; means for measuring electrical resistance between the first and second electrodes; and means for activating and deactivating said timing means in accordance with changes in electrical resistance measured between the first and second electrodes.
Claim 7
Dependent Claim
104 words
A flow measurement device of the type having a conduit through which a liquid flows, means for repeatedly feeding a gas bubble into the conduit and a means for timing the passage of the gas bubble between two points along the conduit which are separated from each other by a predetermined distance, comprising: first and second electrodes, each located at a corresponding one of the two points along the conduit; means for measuring electrical resistance between the first and second electrodes; and means for activating and deactivating said timing means in accordance with changes in electrical resistance measured between the first and second electrodes.
Claim 8
Dependent Claim
21 words
The device of claim 5, wherein said means for measuring resistance distinguishes only between a conductive state and a non-conductive state.
Claim 9
Dependent Claim
23 words
The device of claim 5 wherein said means for repeatedly feeding gas bubbles contains an electrolytic device which generates gas bubbles by electrolysis.
Claim 10
Dependent Claim
40 words
The device of claim 5, wherein the conduit is set in an electrically conductive housing, wherein a discharge opening of the conduit is outside the housing in an electrically conductive environment; and wherein the housing is one of said electrodes.
Claim 11
Dependent Claim
16 words
The device of claim 5, further comprising means for detecting interfering gas bubbles in the conduit.
Claim 12
Dependent Claim
42 words
The device of claim 9, wherein said means for detecting interfering gas bubbles comprises means for the measurement of resistance and two electrodes spaced apart from each other along the conduit and being connected to said means for the measurement of resistance.
Claim 13
Dependent Claim
20 words
The device of claim 9, wherein said means for detecting interfering gas bubbles includes means for emitting an alarm signal.
Claim 14
Dependent Claim
20 words
The device of claim 5, wherein said means for timing is connected to regulate the flow rate of the liquid.
Claim 15
Dependent Claim
26 words
The device of claim 5, wherein said means for repeatedly feeding gas bubbles is an electrolytic decomposition device which contains an electrolyte located outside the conduit.
Claim 16
Dependent Claim
26 words
The device of claim 13, wherein the electrolyte surrounds a gas-permeable part of the conduit, whereby gas which is generated during electrolysis may enter the liquid.
References Cited (Backward Citations)
US1616481A
Cited
DE861610C
Cited
US2683986A
Cited
US3500366A
Cited
US3621715A
Cited
US3739636A
Cited
DE2218459A1
Cited
FR2135304A1
Cited
US3898637A
Cited
DE2752328A1
Cited
GB2083612A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-12-23 | 1989-06-24 | 1989-12-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-12-23 | 1993-06-24 | 1993-12-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-12-23 | 1997-06-24 | 1997-12-24 | $7700.00 | Window Closed / Lapsed |