Method and system for measuring volume and controlling flow

• US 5,533,389 A
• Filed: 09/15/1994
• Issued: 07/09/1996
• Est. Priority Date: 03/04/1986
• Status: Expired due to Term

• Current Assignee: Deka Products Limited Partnership
• Original Assignee: Deka Products Limited Partnership
• Inventors: Seale, Joseph B., Kamen, Dean L., Arnold, Finn, Briggs, Joseph
• Primary Examiner(s): Noland, Thomas P.
• Application Number:
  US08/306,459
• Time in Patent Office: 663 Days
• Field of Search: 73/861.18, 73/149
• US Class Current: 73/149
• CPC Class Codes: A61M 2005/1403 Flushing or purging
• CPC Class Codes: A61M 2205/12 with interchangeable cassettes forming partially or totally the fluid circuit
• CPC Class Codes: A61M 2205/15 Detection of leaks
• CPC Class Codes: A61M 39/22 Valves or arrangement of valves A61M39/02, A61M39/0247, A61M39/16 take precedence; regulating valves in infusion systems A61M5/16881; in devices worn by the patient for the reception of urine, faeces, catamenial or other discharge, or in colostomy devices A61F5/4405
• CPC Class Codes: A61M 39/24 Check- or non-return valves
• CPC Class Codes: A61M 39/26 Valves closing automatically on disconnecting the line and opening on reconnection thereof check valves A61M39/24
• CPC Class Codes: A61M 39/28 Clamping means for squeezing flexible tubes, e.g. roller clamps tube strippers A61M1/83
• CPC Class Codes: A61M 5/162 Needle sets, i.e. connections by puncture between reservoir and tube ; Connections between reservoir and tube in jet-action syringes A61M5/30; connectors for tubes having sealed ends and a needle for piercing them A61M39/14
• CPC Class Codes: A61M 5/16809 by repeated filling and emptying of an intermediate volume pressure infusion using positive displacement pumps A61M5/142
• CPC Class Codes: A61M 5/16813 by controlling the degree of opening of the flow line
• CPC Class Codes: A61M 5/16859 Evaluation of pressure response, e.g. to an applied pulse
• CPC Class Codes: A61M 5/36 with means for eliminating or preventing injection or infusion of air into body dialysis systems, blood oxygenators A61M1/14; haemofiltration equipment A61M1/34; automatic tube cut-off A61M39/281
• CPC Class Codes: A61M 5/365 Air detectors A61M5/1684 takes precedence; in extracorporeal blood circuits A61M1/3626
• CPC Class Codes: F04B 43/043 Micropumps
• CPC Class Codes: F04B 43/14 having plate-like flexible members
• CPC Class Codes: F16K 31/004 actuated by piezoelectric means
• CPC Class Codes: F16K 31/005 Piezoelectric benders
• CPC Class Codes: G01F 1/34 by measuring pressure or differential pressure
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• CPC Class Codes: G01F 17/00 Methods or apparatus for determining the capacity of containers or cavities, or the volume of solid bodies measuring linear dimensions to determine volume G01B
• CPC Class Codes: G01P 13/0066 : by using differences of pressure in the fluid
• CPC Class Codes: G05D 16/0636 : characterised by the loading device of the membrane, e.g. spring
• CPC Class Codes: G05D 16/185 : using membranes within the main valve
• CPC Class Codes: Y10T 137/2541 : With measuring type discharge assistant
• CPC Class Codes: Y10T 137/86027 : Electric
• CPC Class Codes: Y10T 137/87917 : Flow path with serial valves and/or closures
• CPC Class Codes: Y10T 137/87981 : Common actuator

Abstract

A system for controlling the flow of fluid through a line 3. The system may include first and second valves (A, B; and 6, 7) in the line 3 between is located a chamber (52, 82), part of which may be filled with fluid having a variable volume (52), and another part is filled with a measurement gas (V₁), such as air. The chamber may be isolated from the pressure effects in the rest of the line by closing both valves. The valves may also permit fluid to flow into or out of the chamber. The second portion of the chamber has a common boundary with the first part in such a way that the combined volume of the first and second parts is constant. A loudspeaker (22, 33, 571) creates sound waves in the gas in the second part of the chamber, in order to measure the volume of the fluid in the first part, and for directing the operation of the valves and creating subsonic pressure variations to produce the desired flow. The volume measurement is achieved by acoustic volume measurement techniques.

Claims

1. A method, for measuring the flow rate of liquid through a line, comprising the steps of:

isolating in a chamber a section of the line from the pressure effects of liquid in the rest of the line;

associating with the chamber a resonatable mass of known acoustic characteristics so as to form an acoustic resonant system;

generating an electrical signal having a spectrum of frequencies;

converting the electrical signal into an acoustic response in the chamber;

determining, based on the amplitude and phase change of the acoustic response in relation to the electrical signal, whether a frequency in the spectrum causes the resonatable mass to resonate;

determining, based on a resonant frequency, the volume of liquid in the chamber; and

dispensing liquid from the chamber.

2. A method according to claim 1, further including the steps of

providing the chamber with an inlet from the line and an outlet to the line, wherein a first valve is located at the inlet and a second valve means is located at the outlet;

closing the second valve;

opening the first valve, while the second valve is closed, so as to permit liquid to flow from the line into the chamber;

closing the first valve, after liquid has flowed from the line into the chamber, and while the second valve remains closed and while the volume of liquid in the chamber is determined;

opening the second valve, so as to permit liquid to flow from the chamber after the volume has been determined, and

redetermining, after liquid has flowed from the chamber, the volume of liquid in the chamber.

3. A method according to claim 2, further including the step of

continuously determining, as liquid flows from the chamber, the volume of liquid in the chamber.

4. A method according to claim 2, further including the step of

determining, based on-a determined resonant frequency, the presence of a gas-bubble in the liquid.

5. A method according to claim 2, wherein the step of determining a frequency in the spectrum causes the resonatable mass to resonate includes the steps of

determining the phase change of an acoustic response with respect to its corresponding electrical signal;

determining the amplitude of the acoustic response with respect to its corresponding electrical signal;

storing in an array the phase change and amplitude for each frequency;

determining, based on the array, whether a frequency is a resonant frequency of the acoustic resonant system.

6. A method according to claim 1, wherein the step of dispensing liquid from the chamber includes the step of increasing the pressure in the chamber in order to force liquid out of the chamber.

7. A system, for determining the volume of a chamber, comprising:

means for associating with the chamber a resonatable mass of known acoustic characteristics so as to form an acoustic resonant system;

means for generating electrical signals, each having one of a variety of frequencies;

means for converting each of the electrical signals into an acoustic response in the chamber;

means for determining the phase change of the acoustic response with respect to each of the electrical signals;

means for determining the amplitude of the acoustic response with respect to each of the electrical signals;

means for storing in an array the phase change and amplitude for each frequency;

means determining, based on the array, whether a frequency is a resonant frequency of the acoustic resonant system; and

means for determining, based on a resonant frequency, the volume of the chamber.

8. A system according to claim 7 for determining the volume of gas in a container containing gas and liquid, wherein the means for determining the volume of the chamber determines the volume of gas in the container, the system further including means for determining, based on a determined resonant frequency, the presence of a gas-bubble in the liquid.