Electronically controlled flow meter and flow control system

• US 4,315,523 A
• Filed: 03/06/1980
• Issued: 02/16/1982
• Est. Priority Date: 03/06/1980
• Status: Expired due to Term

• Current Assignee: Medical Flow Systems Ltd.
• Original Assignee: Medical Flow Systems Ltd.
• Inventors: Boyle, Timothy J., Mahawili, Imad
• Primary Examiner(s): Cohan, Alan
• Application Number:
  US06/127,918
• Time in Patent Office: 712 Days
• Field of Search: 137/486, 137/487.5, 73/269, 73/270, 73/271
• US Class Current: 137/486
• CPC Class Codes: G01F 11/08 of the diaphragm or bellows type
• CPC Class Codes: G01F 3/20 having flexible movable walls, e.g. diaphragms, bellows
• CPC Class Codes: Y10T 137/7759 Responsive to change in rate of fluid flow
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

A novel, low-friction, low-inertia flexible diaphragm containing a magnet formed as an integral part of the diaphragm is mounted in a chamber (preferably cylindrical). The chamber comprises part of the flow meter in a flow control system. One or more sensing devices are mounted on the walls of the chamber to sense the instantaneous position of the diaphragm. A novel electronic control circuit processes the data from the one or more sensing devices to provide measures of the flow rate during the displacement of the diaphragm along the cylinder. Signals are generated by the electronic control circuitry for switching a pair of three-way valves (one valve comprising the input valve and the other valve comprising the output valve) such that during one-half of a cycle the intput valve transfers fluid into the cylinder on one side of the diaphragm and, during the other half of the cycle, transfers fluid into the cylinder on the other side of the diaphragm. The output valve is switched synchronously with the input valve to transmit fluid from the other side or one side of the diaphragm to the output valve.

The electronic control system includes means for amplifying the output signals from the one or more sensing devices ("sensors") to provide one or more signals representing the position of the diaphragm as a function of time, means for converting the output signals from these amplifiers to digital form, and computation means for operating on the digitized output signals from the sensing devices to provide control signals for controlling a second input valve thereby to control the flow rate of the fluid being metered to within a desired range.

Claims

1. Structure comprising:

a chamber containing a first and a second opening through which fluid can pass;

a flexible diaphragm located in said chamber so as to divide said chamber into two portions, a first chamber accessed through said first opening and a second portion being accessed through said second opening;

a magnet attached to said flexible diaphragm;

means for directing fluid whose flow is being measured through said first opening into said first chamber while withdrawing the fluid whose flow is being measured through said second opening from said second chamber and, into response to a control signal, reversing the chambers in which the fluid is inserted and from which the fluid is withdrawn, the movement of fluid into one chamber and out of the other chamber causing said flexible diaphragm to move into the chamber from which the fluid is being withdrawn;

means for continuously producing an output signal representative of the position of said magnet;

means for converting said output signal to a sequence of digital signals;

means for processing said sequence of digital signals to produce a second signal representative of the flow rate of said fluid into and out of said chamber;

means for comparing said flow rate to a reference flow rate to produce a control signal representative of the difference between said measured flow rate and said reference flow rate; and

means, responsive to said control signal, for changing the flow rate of said fluid.

2. Structure comprising:

a chamber containing a first and a second opening through which fluid can pass;

a flexible diaphragm located in said chamber so as to divide said chamber into two subchambers, a first subchamber which is accessed through said first opening and a second subchamber which is accessed through said second opening;

a magnet attached to said flexible diaphragm, said magnet being formed as an integral part of, and being completely enclosed by, the material of said flexible diaphragm;

means for directing fluid whose flow is being measured through said first opening into said first subchamber while withdrawing the fluid whose flow is being measured through said second opening from said second subchamber and, in response to a control signal, reversing the subchambers into which the fluid is inserted and from which the fluid is withdrawn, the movement of fluid into one subchamber and out of the other subchamber causing said flexible diaphragm to move into the subchamber from which the fluid is being withdrawn;

means for producing an output signal representative of the position of said magnet;

means for converting said output signal to a sequence of digital signals;

means for processing said sequence of digital signals to produce a second signal representative of the flow rate of said fluid into and out of said chamber;

means for comparing said flow rate to a reference flow rate to produce a control signal representative of the difference between said measured flow rate and said reference flow rate; and

means, responsive to said control signal, for changing the flow rate of said fluid.

3. Structure as in claim 2 including:

means for sensing the approach of said magnet to one or the other ends of said chamber and for switching the flow of fluid into said chamber from said first subchamber to said second subchamber and for switching the flow of fluid from said chamber from said second subchamber to said first portion.

4. Structure as in claim 3 including reference means representing the relationship between the position of said magnet and the volumetric displacement of said diaphragm, thereby to enable the determination of the volumetric displacement of said diaphragm from the output signal from said means for producing.

5. Structure as in claim 4 including:

means for varying the position at which the motion of said flexible diaphragm is reversed by determining the flow rate of said fluid and selecting a reversal point to maximize the sensitivity of the output signal from said means for producing as a function of the displacement of said flexible diaphragm.

6. Structure as in claim 4 including:

means for reversing the direction of motion of said flexible diaphragm in response to the expiration of a predetermined time.

7. Structure as in claim 2 wherein said chamber is cylindrical.

11. Structure as in claim 2 wherein said means for producing comprises means for continuously producing an output signal representative of the instantaneous position of said magnet, thereby to enable a measure of the instantaneous flow rate of the fluid entering said chamber to be obtained during the trave of said diaphragm from any one position to any other position in said chamber.

8. Structure which comprises

a chamber containing two openings therein;

a flexible diaphragm containing as a part thereof a magnet, said diaphragm separating said chamber into a first and a second portion and sealing said first portion from said second portion so as to prevent leakage of fluid from said first portion to said second portion or vice versa;

means for continuously producing an output signal representative of the position of said diaphragm;

means for selectively controlling the flow into said first portion and out of said second portion and for reversing the flow as desired so that the fluid flows into the second portion and from the first portion;

means for processing the output signal from said means for producing including

switching path means for selectively accessing the output signal from said means for producing

conversion means for converting said output signal from said means for producing to a first digital signal;

buffer means for storing said first digital signal from said conversion means;

means for inputting to said system a second digital signal representing a desired fluid flow rate;

means for storing said second digital signal representing said desired fluid flow rate;

processing means for operating on said first and second digital signals to produce an estimate of the flow rate of fluid into and out of said chamber;

means for storing a signal representative of the flow rate calculated by said processing means; and

driver circuit means periodically actuated by said output signal from said processing means to move a control valve either open or closed in response to the output signal stored in said means for storing.

9. Structure as in claim 8 including

means for storing the output signal from said processing means representing the calculated flow rate;

and

means for displaying the calculated fluid flow rate.

10. The method of measuring a fluid flow rate using a chamber containing a first opening and a second opening through which fluid can pass with a flexible diaphragm located in said chamber so as to divide said chamber into two subchambers, a first subchamber which is accessed through said first opening and a second subchamber which is accessed through said second opening, and a magnet attached to said flexible diaphragm, comprising:

directing the fluid whose flow is being measured through said first opening into said first subchamber while withdrawing the fluid whose flow is being measured through said second opening from said second subchamber and, in response to a control signal, reversing the subchambers in which the fluid is inserted and from which the fluid is withdrawn, the movement of fluid into one subchamber and out of the other subchamber causing said flexible diaphragm to move into the subchamber from which the fluid is being withdrawn;

producing a continuous output signal representative of the position of said magnet;

converting said output signal to a sequence of digital signals;

processing said sequence of digital signals to produce a second signal representative of the flow rate of said fluid into and out of said chamber;

comparing said flow rate to a reference flow rate to produce a control signal representative of the difference between said measured flow rate and said reference flow rate; and

changing the flow rate of said fluid in response to said control signal.