Measuring and testing – Volume or rate of flow – Mass flow by imparting angular or transverse momentum to the...
Patent
1989-07-13
1990-07-03
Goldstein, Herbert
Measuring and testing
Volume or rate of flow
Mass flow by imparting angular or transverse momentum to the...
73198, 604246, G01F 100
Patent
active
049380729
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention concerns a flow measurement device.
BACKGROUND OF THE INVENTION
There is a frequent need to check on infusion devices as used for a variety of treatments for infusing fluids into medical patients. There are a vast number of infusion devices with the different types giving different rates of flow; the total range needed is from 1 milliliter per hour to 1 liter per hour and in special cases even values outside this range may be called for. One way of measuring flow rates is to have the infusion device pump a liquid into a container or tube and to measure the time difference for the liquid to pass between two sensors; knowing the volume between the two sensors and the time difference, it is easy to calculate the flow rate. However the infusion devices do not have a uniform flow rate due to sanction effects and it is difficult to calculate flow rates over a wide range of flow rates accurately without changing the tube or container. The present invention aims at providing a measuring device with a wide range of measurement without requiring containers or tubes to be replaced to cope with different flow rates.
SUMMARY OF THE PRESENT INVENTION
The present invention provides a flow measurement device having a tube or other container for receiving a flow of a liquid, a plurality of sensors associated with the container to sense when the liquid reaches a level in the container corresponding to each sensor, and a timing device deriving a time difference between sensing of two levels, characterised in that there are more than two sensers and in that logic means associated with the timing device checks whether the time difference exceeds a predetermined minimum and if so calculates the flow rate from that time difference but if not inhibits that calculation and arranges for a time difference derived from a subsequent senser to be used in calculating flow rate.
By having a smaller container than usual, a quicker indication of flow rate can be given at the expense of the indication applying to an instantaneous flow rate (which due to stiction in the infusion device can be erratic). The measuring device can however repeat the measurements rapidly and the logic means derive an averaged measurement so the operator gets an initial quick indication and shortly afterwards an averaged reading getting progressively more reliable. At the same time the device can be smaller and more portable.
The sensors are conveniently optical sensors preferably operating in the infra-red region of the spectrum. The tube or container can be arranged to have increasing cross-sections as by stepping and/or tapering so as to reduce the size of the container.
The measuring device according to the present invention can be used to check on a wide range of types of infusion devices providing infusion rates of 1 to 1000 milliliters per hour and possibly even rates outside those figures without any need for changing the tube or container which changing might introduce calibration errors and might introduce an error due to leakage or the introduction of air bubbles at remakeable seals.
The measuring device can be used to measure the effect of back pressure by using a suitable pressure regulator on the outlet of the device. It is possible to arrange the device with a closed liquid system so the entire system can be pressurised with that system being connected by a drain connection to a sump.
BRIEF DESCRIPTION OF THE DRAWING
The drawing is a schematic section of a flow measuring device according to the present invention.
DESCRIPTION OF AN EXEMPLARY EMBODIMENT
The flow measuring device illustrated comprises a valve 1 having an inlet connection 3 and an exhaust or drain connection 4. Upstanding from the valve, there is a transparent or translucent tube 5 along the side of which in staggered relationship there is a succession of sensors 6, 7, 8 and 9, the spacings between which increase progressively say in a geometric ratio of three to one. Each sensor comprises a light emitting diode 10 and a photo-se
REFERENCES:
patent: 3605741 (1971-09-01), Spencer
patent: 3930411 (1976-01-01), Beeker et al.
patent: 4409844 (1983-10-01), Schweiso
patent: 4458539 (1984-07-01), Bilstad
Brown Malcolm C.
Hammond Paul E.
Goldstein Herbert
Masar Limited
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