Respiration flowmeter

• US 4,425,805 A
• Filed: 10/29/1981
• Issued: 01/17/1984
• Est. Priority Date: 10/31/1980
• Status: Expired due to Term

• Current Assignee: Tokyo Shibaura Denki Kabushiki Kaisha
• Original Assignee: Tokyo Shibaura Denki Kabushiki Kaisha
• Inventors: Ogura, Ichiro, Itoh, Ayao
• Primary Examiner(s): Ruehl, Charles A.
• Assistant Examiner(s): NOLAND, THOMAS
• Application Number:
  US06/316,286
• Time in Patent Office: 810 Days
• Field of Search: 73/861.29, 128/725, 364/510, 364/565
• US Class Current: 73/861.29
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: G01F 1/667 Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters

Abstract

At a pair of recesses formed on an inner wall of a conduit along a line slanted with respect to the flow direction of a respiration gas flowing through the measuring conduit, a pair of ultrasonic transducers are provided with their ultrasonic transmitting and receiving surfaces oppositely facing each other along the above line. A propagating time T1 from the time when one of said ultrasonic transducers is driven to produce ultrasonic wave until the other transducer receives the ultrasonic wave, and a propagating time difference ΔT are measured. A digital processor calculates a flow velocity of the respiration gas using the measured values in accordance with the following equation ##EQU1## where d is a distance between the pair of transducers free from an effect by the flow velocity of the gas; L a distance influenced by the flow velocity of the same; θ an angle of the direction of the respiration flow with respect to a line coupling the pair of transducers; ΔT the propagating time difference; and Ta a value obtained by substituting the propagating time difference ΔT from the double (2 T1) of the ultrasonic propagating time T1.

Claims

1. A respiration flowmeter comprising:

a conduit through which expiration and inspiration flow;

a pair of recesses formed on an inner wall of the conduit along a line slanted with respect to a flow direction of the respiration gas;

a pair of ultrasonic transducers provided in said recesses with their ultrasonic transmitting and receiving surfaces oppositely faced each other along said line;

means simultaneously switching said ultrasonic transducers between a drive mode and a receiving mode;

digital counting means for measuring either of the two propagating times taken for ultrasonic wave radiated from one of said pair of driven transducers to reach the other transducer and a difference between said two propagating times;

means for judging the flow direction of said respiration gas;

means for generating a signal for requesting calculation of a flow velocity of the respiration gas every time said pair of transducers are driven;

means for storing said flow direction, said two propagation times and said propagation time difference in response to said calculation request signal; and

means for calculating and storing a flow rate of said respiration gas on the basis of said stored values.

2. A respiration flowmeter according to claim 1, wherein an electric heater for preventing condensation is provided on the periphery of said conduit and around the ultrasonic transducers.

3. A respiration flowmeter according to claim 1, wherein said switching means include a circuit which supplies a mask pulse for preventing receiving circuits or waveform shapers from receiving signals when drive circuits are driven.

4. A respiration flowmeter according to claim 1, wherein said means for calculating and storing said flow rate of respiration gas include an arithmetic processor for obtaining a flow velocity V by executing the following operation ##EQU10## where d is a distance between said pair of transducers free from an effect by the flow velocity of said gas;

L a distance influenced by the flow velocity of the same;

θ

an angle of the direction of the respiration flow with respect to a line coupling said pair of transducers;

Δ

T the propagating time difference; and

Ta a value obtained by subtracting said propagating time difference Δ

T from the double of the ultrasonic propagating time T1.

5. A respiration flowmeter according to claim 1, wherein said digital counting means for measuring either of two propagating times and propagating time difference are composed of a first clock means generating a first clock, a second clock means generating a second clock, a first clock counting means for measuring the propagating time difference by counting the first clock and a second clock counting means for mesuring the propagating times by counting the second clock, the second clock having a frequency lower than that of the first clock.

6. A respiration flowmeter according to claim 1, wherein an electric heater for preventing condensation is provided on the periphery of said conduit.

7. A respiration flowmeter according to claim 1, wherein an electric heater for preventing condensation is provided around the ultrasonic transducers.