PRESSURE TRANSDUCERS AND METHOD OF PHYSIOLOGICAL PRESSURE TRANSDUCERS

• US 3,724,274 A
• Filed: 02/11/1971
• Issued: 04/03/1973
• Est. Priority Date: 02/11/1971
• Status: Expired due to Term

• Current Assignee: Huntley D. Millar
• Original Assignee: Huntley D. Millar
• Inventors: Millar, Huntley D.
• Primary Examiner(s): Prince, Louis R.
• Assistant Examiner(s): Shoon, Frederick
• Application Number:
  US05/114,610
• Time in Patent Office: 782 Days
• Field of Search: 338/4 73/398AR 128/2.5D,2.5E
• US Class Current: 73/726
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 2562/0261 Strain gauges
• CPC Class Codes: A61B 5/0215 by means inserted into the body catheters A61M25/00
• CPC Class Codes: G01L 9/0052 of piezoresistive elements circuits therefor G01L9/06

Abstract

A unique pressure transducer is disclosed which has particular application in making physiological measurements such as intraarterial or intra-venous blood pressure measurements. The transducer employs the principle of a cantilever beam which is exposed directly to the source of pressure. The pressure applied to the cantilever beam causes flexure which is measured by a strain gauge, or other means for measuring its deformation, and a related electrical signal is produced.

Claims

1. A pressure transducer comprising:

a housing defining an opening;

a diaphragm formed by an elongated member mounted in the opening in the housing;

the elongated member being free to flex in response to fluid pressure applied to the surface of the elongated member;

means for measuring deformation of the elongated member;

a pair of electrodes in electrical connection with the means for measuring deformation of the elongated member; and

an elastic material sealing the gap between the housing and the elongated member to create a seal for the diaphragm, the housing being adapted for a source of reference fluid pressure to be applied on one side of the diaphragm against the elongated member, the housing being further adapted for a source of fluid pressure to be measured to be applied against the elongated member on the other side of the diaphragm.

2. A pressure transducer as defined in claim 1 wHerein:

one end of the elongated member is rigidly affixed to the housing and the other end of the elongated member is free to flex in response to applied fluid pressure.

3. A pressure transducer as defined in claim 1 wherein the elongated member comprises a rectangular beam mounted as a cantilever.

4. A pressure transducer as defined in claim 1 wherein:

the elongated member includes a transverse notch; and

the means for measuring deformation comprises a strain-sensitive element affixed to the elongated member bridging the notch.

5. A pressure transducer as defined in claim 1 wherein:

the means for measuring the elongated member comprises a first element secured to one major surface of the elongated element and a second element secured to the opposite position on an opposite major surface of the elongated member.

6. A pressure transducer as defined in claim 1 further comprising a temperature compensating element affixed to the elongated member.

7. A physiological pressure transducer comprising:

a catheter tip including a tubular wall having a tip end and a shank end, a section of the tubular wall being removed;

a diaphragm formed by an elongated member mounted in the catheter tip below the section of the tubular wall which is removed and being free to flex in response to fluid pressure applied to the surface of the elongated member;

means in the catheter tip for measuring the deformation of the elongated member;

an elastic material sealing the gap between the catheter tip and the elongated member to create a seal for the diaphragm;

a flexible cable secured to the shank end of the catheter tip, the flexible cable providing a fluid passage from a source of reference pressure to one side of the diaphragm within the catheter tip; and

a pair of conductors within the flexible cable, the conductors being electrically insulated from each other and being in electrical connection with the means for measuring the deformation of the elongated member.

8. A physiological pressure transducer as defined in claim 7 wherein:

one end of the elongated member is rigidly affixed to the shank of the catheter tip and the other end of the elongated member is free to flex in response to fluid pressure applied to the elongated member.

9. A physiological pressure transducer as defined in claim 7 wherein the elongated member comprises a rectangular beam.

10. A physiological pressure transducer as defined in claim 7 wherein:

the elongated member includes a transverse notch; and

the means for measuring deformation of the elongated member comprises a strain-sensitive element affixed to the elongated member bridging the notch.

11. A physiological pressure transducer as defined in claim 7 wherein the section of the tubular wall being removed from the catheter tip extends to and includes the tip end.

12. A physiological pressure transducer as defined in claim 7 further comprising a temperature compensating element affixed to the elongated member.

13. A physiological pressure transducer as defined in claim 7 wherein the means for measuring deformation of the elongated member comprises:

a first element secured to one major surface of the elongated element and a second element secured to the opposite position on an opposite major surface of the elongated member.

14. An implantable blood pressure transducer comprising:

a catheter tip of dimensions permitting receipt in an artery, the catheter tip including a hollow tube closed at one end to form the tip end and a flattened side, an opening being formed in the hollow tube in the flattened side;

a rectangular beam being mounted in the opening on the flattened side, one end of the beam being affixed to the hollow tube at the end opposite the tip end, the other end of the beam being free to flex in response to fluid pressure, the beam having a transverse notch spaced from the end of the beam which is free to flex;

a strain gage aFfixed on the inward side of the beam bridging the notch;

an elastic material sealing the gap between the beam in the hollow tube to create a sealed compartment inside the catheter tip;

a flexible cable secured to the hollow tube opposite the tip end, the flexible cable providing an air passageway from the sealed compartment in the catheter tip to the ambient atmosphere;

a pair of electrical conductors within the flexible cable, the conductors being electrically insulated from each other and being respectively in electrical connection with points on the strain gage on opposite sides of the notch.

15. An implantable blood pressure transducer as defined in claim 14 further comprising a temperature compensating strain gage affixed on the inward side of the beam.

16. A pressure transducer comprising:

a conduit adapted to carry a fluid, the conduit having an opening in the wall structure thereof;

an elongated member mounted in the opening in the wall structure of the conduit, one end of the elongated member being rigidly affixed to the conduit, the other end of the elongated member being free to flex in response to the pressure difference between the inside and the outside of the conduit;

means for measuring the deformation of the elongated member;

electrodes in electrical connection with the means for measuring deformation; and

an elastic material sealing the gap between the housing and the elongated member to create a pressure bulkhead.

17. A pressure transducer as defined in claim 16 wherein the elongated member comprises a rectangular beam.

18. A pressure transducer as defined in claim 16 wherein the elongated member includes a transverse notch and wherein the means for measuring deformation of the elongated member comprises a strain-sensitive element affixed to the elongated member bridging the notch.

19. A pressure transducer as defined in claim 16 further comprising a temperature compensating element affixed to the elongated member.

20. A differential pressure transducer comprising:

a pressure housing having two compartments separated by a bulkhead, the pressure housing having fittings for connecting a first and second source of fluid pressure to be measured, the bulkhead having a passageway extending from one compartment to the other;

a diaphragm formed by an elongated member mounted in the passageway in the bulkhead and one end being rigidly affixed to the bulkhead, the other end of the elongated member being free to flex in response to the composite of fluid pressures applied against the surfaces of the elongated member from the respective compartments;

means for measuring the deformation of the elongated member;

a pair of electrodes in electrical connection with the means for measuring deformation of the elongated member; and

an elastic material sealing the gap between the elongated member and the walls of the passageway in the bulkhead to create a seal for the diaphragm.

21. A pressure transducer as defined in claim 20 wherein:

the elongated member comprises a rectangular beam.

22. A pressure transducer as defined in claim 20 wherein:

the elongated member includes a transverse notch; and

the means for measuring deformation comprises a strain-sensitive element affixed to the elongated member bridging the notch.

23. A pressure transducer as defined in claim 20 further comprising a temperature compensating element affixed to the elongated member.