Measuring and testing – Volume or rate of flow – Tank type
Patent
1993-12-08
1996-01-16
Chilcot, Jr., Richard E.
Measuring and testing
Volume or rate of flow
Tank type
G01F 338
Patent
active
054838304
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method and a apparatus for measuring a liquid flow.
In the laboratory field and, in particular, in the medical field there is a need to be able to measure small volume flows of liquids in a very accurate manner. Certain problems occur more particularly in the clinical field.
The liquids to be measured are on occasions chemical-aggressive body fluids, which are inter alia mixed with solids, e.g. protein. For the measurement of such fluids, a simple measuring apparatus construction is necessary, offering minimum attack surfaces to the impurities. This simple construction is also opposed by the high hygienic requirements of a clinical department.
A number of different principles are known for the determination of the volume of a liquid flow, particularly in the case of urine meters.
A method and an apparatus according to the invention of the above-mentioned type are known from U.S. Pat. No. 4,619,273.
The method and apparatus known therefrom are primarily designed for determining the discharge speed of a urine-discharging patient and for determining also the quantificated amount of the discharged liquid by means of a subsequent siphon arrangement.
This method and the apparatus are therefore designed for the spontaneous discharge of a relatively large volume of a liquid. As a result of this high flow rate, air is sucked in relative to the through-flowing liquid via the aerating duct, which is annularly arranged around the filling duct and is in connection with its surroundings, whereby air bubbles are produced for separating individual liquid volumes from each other. In case this apparatus was used for determining the volume of very small discharged volumes, as those that occur in the case of patients which have been provided with a bladder catheter, a liquid discharge of a kind of a dripping film would occur in the lower rounding of the siphon discharge area, which is positioned in a horizontal plane with the upper rounding of the inlet area, when this horizontal level is reached, as a result of the geometrical design of the siphon arrangement. This, however, does not allow a defined determination of the outflowing volume and by no means the forming of equally-sized measuring volumes.
Thus, it is the object of this reference to disclose that the apparatus described is suitable for measuring high liquid flows and that only here the measuring method functions. Due to the effect of a liquid stopper in the discharge tube, the corresponding amount of liquid is sucked out of the siphon.
In the case of a slow liquid flow, this stopper would dissolve, dripping along the walls of the siphon, so that the suction effect and consequently also the function of the measurement determination would be lost.
Further, a measuring apparatus is known in U.S. Pat. Nos. 4,683,748 and 4,589,280) which is designed for receiving a larger measurement volume of discharged urine. From the corresponding measuring chamber, a pressure duct passes upwards from the base and is terminated by a transducer detecting the analog values of the pressure rise. These analog values can then be converted by means of an electronic evaluating circuit into the measuring chamber filling level and, therefore, into the measurement volume.
In order to avoid a undesired retention of the discharged urine and so as to exclude any contamination, said measuring apparatus also has an overflow in the manner of a siphon, whose intake duct starts well above the lowest level of the measuring chamber. The function of this known siphon arrangement can therefore be looked upon as a purely overflow function, which as a result of a partial emptying of the measuring chamber brings about a corresponding pressure difference for the transducer.
In said measuring apparatus the complicated construction of the electronic evaluating device is problematical and the analog determination of the indirect parameter of the pressure can give rise to significant errors. In addition, sediments which are washed out with the urine are deposited in the measuring chamb
REFERENCES:
patent: 2069677 (1937-02-01), Ollagnon
patent: 3919455 (1975-11-01), Sigdell et al.
patent: 4589280 (1986-05-01), Carter
patent: 4619273 (1986-10-01), Iosif
patent: 4683748 (1987-08-01), Carter
Dietz Xaver
Kothmeier Georg
Chilcot Jr. Richard E.
Durango holding GmbH
Patel Harshad
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