Method and apparatus for ultrasonic detection of inclusions in a flowing fluid

• US 3,921,622 A
• Filed: 02/26/1974
• Issued: 11/25/1975
• Est. Priority Date: 02/27/1973
• Status: Expired due to Term

• Current Assignee: Edward Michael Cole
• Original Assignee: Edward Michael Cole
• Inventors: Cole, Edward Michael
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/445,870
• Time in Patent Office: 637 Days
• Field of Search: 128/2V,2.5F,2.5Z 73/67.5,61R,19,29
• US Class Current: 600/437
• CPC Class Codes: A61M 1/3626 Gas bubble detectors
• CPC Class Codes: G01N 2291/02433 Gases in liquids, e.g. bubbles, foams
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/0421 Longitudinal waves
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves

Abstract

Inclusions in a flowing fluid, such as bubbles in a flow of blood, are detected by transmitting a continuous ultrasonic signal normally across the flow and detecting changes in the amplitude of the received ultrasonic signal, these changes being caused by changes in the acoustic impedance of the fluid due to inclusions.

Claims

1. Apparatus for detecting inclusions in a fluid flowing within a flexible tube of substantially circular cross-section and not forming part of said apparatus, said inclusions being of different acoustic impedance from said fluid, said apparatus comprising:

an ultrasonic detector head having defined therein an aperture of substantially rectangular cross-section, said aperture being dimensioned to receive said tube and to deform said tube to adopt a substantially rectangular cross-section;

a pair of flexible elongate supports mounted to respective ones of a pair of opposite surfaces of said aperture, said supports being mounted parallel to and oPposite one another and each extending substantially entirely across said surface to which it is mounted, and each support being above said surface to which it is mounted, whereby, when said tube is received in and deformed by said aperture, each of said supports is urged against substantially the whole of a respective one of a pair of opposite sides of said substantially rectangular crosssection of said tube;

an ultrasonic transmitter mounted to said ultrasonic detector head and operatively coupled to one of said supports to transmit an ultrasonic signal, via said one support and the wall of the tube, into and across said fluid flowing within the tube, said signal being transmitted through the flow in the form of a planar beam substantially transverse to the direction of flow and traversing substantially the whole of the crosssection of the flow;

means for energizing said transmitter to cause it to continuously transmit said signal;

an ultrasonic receiver mounted in said ultrasonic detector head and operatively coupled to the other of said supports to receive said signal; and

means coupled to said receiver to detect a change in amplitude of the signal received by the receiver caused by an inclusion passing through said planar beam.

2. Apparatus according to claim 1 wherein said ultrasonic transmitter and said ultrasonic receiver comprise respective ultrasonic transducers each including a transducer element.

3. Apparatus according to claim 2 wherein said transducer elements are piezoelectric crystals.

4. Apparatus according to claim 2 wherein said transducer elements are magnetostrictive devices.

5. Apparatus according to claim 2 wherein said means for energizing said ultrasonic transmitter comprises oscillator means connected to energize said transmitter with a continuous wave electric signal.

6. Apparatus according to claim 5 wherein said electric signal has a frequency in the range 25 to 400 kilohertz.

7. Apparatus according to claim 5 wherein said electric signal has a frequency of 65 kilohertz.

8. Apparatus according to claim 1 wherein said head is a generally C-shaped body formed of resilient material and said aperture is the central aperture within said body.

9. Apparatus according to claim 1 wherein said ultrasonic detector head comprises a metallic body comprising two parts movable with respect to one another to allow said tube to be received thereby, said aperture being elongate and respectively defined by a pair of mating surfaces of said two parts.

10. Apparatus according to claim 1 wherein said supports are of a plastic material.

11. A method of detecting inclusions in a fluid flowing within a flexible tube of substantially circular cross-section, said inclusions being of different acoustic impedance from said fluid, said method comprising the steps of:

deforming at least part of said tube so that it adopts a substantially rectangular cross-section;

positioning a pair of flexible elongate supports so that they are parallel to and opposite one another and so that they are each urged against a respective one of a pair of opposite sides of said substantially rectangular cross-section of said tube;

energizing an ultrasonic transmitter operatively coupled to one of said supports to transmit an ultrasonic signal, via said one support and the wall of the tube, into and across said fluid flowing within the tube, said signal being transmitted through the flow in the form of a planar beam substantially transverse to the direction of flow and traversing substantially the whole of the cross-section of the flow; and

detecting a change of the signal received by an ultrasonic receiver operatively coupled to the other of said supports caused by an inclusion passing through said planar beam.

12. A method according to claim 11 wherein the flowing fluid is blood and the inclusions are bubbles.