Measuring and testing – Liquid level or depth gauge
Reexamination Certificate
1999-05-28
2001-11-27
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
C073S149000
Reexamination Certificate
active
06321597
ABSTRACT:
TECHNICAL FIELD
The present invention relates to systems and methods for measuring the volume of liquid in a chamber.
SUMMARY OF THE INVENTION
The invention includes methods for measuring the volume of a liquid in a subject chamber, such as the mixing chamber in a system for mixing and delivering drugs, for example. In a preferred method, a volume of a control gas in communication with the subject chamber is isolated, such that the total volume of the control gas and the liquid is held constant, and the initial pressure of the control gas is measured. Then, a known (i.e., measured or measurable) volume of liquid—referred to herein as a reference volume—is moved into or out of the subject chamber. In a preferred method, the reference volume is exchanged between the subject chamber and a measurement chamber, such as a delivery chamber, where the reference volume is measured. The final pressure of the control gas is also measured after the reference volume has been removed from or added to the chamber and while the volume of control gas remains otherwise isolated. The volume of liquid in the chamber may then be measured based on (a) the initial pressure, (b) the final pressure, (c) the reference volume and (d) the volume of gas in the subject chamber when the subject chamber is empty of liquid.
A system for measuring the volume of a liquid in the subject chamber, according to a preferred embodiment of the invention, includes an isolatable volume of a control gas in communication with the subject chamber such that the total volume of the subject-chamber control gas and the liquid in the subject chamber may be held constant; a port through which liquid may flow into and out of the subject chamber; and a transfer system that causes the reference volume of the liquid to flow through the port. The system also includes a controller, which controls the transfer system. The controller also receives data from a pressure sensor in communication with the isolatable volume and from a delta-volume system that measures the reference volume. The controller also calculates the volume of liquid in the subject chamber based on the pressure data, the reference volume and the volume of gas in the subject chamber when the subject chamber is empty of liquid.
In a preferred embodiment, the transfer system causes the reference volume of the liquid to flow between the subject chamber and a measurement chamber, and the delta-volume system includes means for measuring the change in volume of a control gas in the measurement chamber when the reference volume flows through the port. Preferably, this means for measuring the change in volume of the control gas includes an acoustic volume-measurement system, which applies vibrations to the control gas in the measurement chamber and measures the response of the control gas to the applied vibrations. Preferably, the acoustic volume-measurement system calculates the reference volume based on a resonant frequency of the control gas in the second chamber.
The transfer system preferably includes one or more pressure adjusters for adjusting the pressure of a control gas. In a preferred embodiment, the pressure adjuster includes means for adding or removing a control gas, to or from the subject chamber and/or the measurement chamber. The pressure adjuster preferably includes positive- and negative-pressure reservoirs, which urge control gas into or out of the chambers.
A preferred embodiment of a system, incorporating the present invention, for mixing and delivering medical liquids to a patient includes a solvent-supply port; a solute-supply port; an outlet; a measurement (or delivery) chamber; a mixing chamber; a valve system which controls flow among the solvent-supply port, the solute-supply port, the outlet, the measurement chamber and the mixing chamber; an isolatable volume of a control gas in communication with the mixing chamber such that the total volume of the control gas and the liquid in the mixing chamber may be held constant; a pressure sensor in communication with the isolatable volume; a pressure adjuster which urges fluid into or out of the mixing chamber; a delta-volume system which measures changes in volume of liquid in the measurement chamber; and a controller, which (i) controls the valve system and the pressure adjuster so as to cause a reference volume of liquid to flow between the mixing chamber and the measurement chamber, (ii) receives pressure data from the pressure sensor before and after the reference volume of liquid has flown between the mixing chamber and the measurement chamber, (iii) receives volume data from the delta-volume system, and (iv) calculates the volume of liquid in the mixing chamber based on (a) the pressure data, (b) the reference volume and (c) the volume of gas in the mixing-chamber when the mixing chamber is empty of liquid.
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SU 1 670 418 A (Uralsky NII Trubnoj Promy) Aug. 15, 1991 Abstract.
Demers Jason A.
Mandro Marc A.
Bromberg & Sunstein LLP
DEKA Products Limited Partnership
Williams Hezron
Wilson Katina
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