PIEZOELECTRIC PRESSURE TRANSDUCER

• US 3,801,838 A
• Filed: 05/19/1972
• Issued: 04/02/1974
• Est. Priority Date: 05/19/1972
• Status: Expired due to Term

• Current Assignee: Walter P. Kistler
• Original Assignee: Walter P. Kistler
• Inventors: Kistler, Walter P.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Budd, Mark O.
• Application Number:
  US05/255,191
• Time in Patent Office: 683 Days
• Field of Search: 310/8.7,8.3,9.1,8.8
• US Class Current: 310/338
• CPC Class Codes: G01L 23/10 by pressure-sensitive members of the piezoelectric type
• CPC Class Codes: G01L 9/008 using piezoelectric devices piezoelectric resonators G01L9/0022; surface acoustic waves G01L9/0025

Abstract

A piezoelectric pressure transducer particularly adapted for measuring fluid pressure up to and above ballistics levels of the order of 75,000 pounds per square inch with an accurate, linear response over a wide pressure range. The piezoelectric sensing element is housed in a cylindrical sleeve which is threaded into a wall of the chamber within which the pressure to be measured is developed. An end wall extending across the end of the sleeve is exposed to the pressure and deflects, compressing the piezoelectric element to generate an electric signal representing the pressure. A supporting wall for the end wall is located between the sensing element and the housing sleeve. Two flexure zones are formed in the end wall, one between the piezoelectric element and the supporting wall and the other between the wall and the sleeve. The supporting wall is connected with the end wall through a third flexure zone. The compliance of the supporting wall is less than the compliance of the piezoelectric element but greater than the compliance of the housing sleeve. Deformation of the housing sleeve, as by pressure on the mounting threads, is accommodated by the flexure areas and error creating stress on the piezoelectric element is minimized.

Claims

1. A ballistic type piezoelectric fluid pressure transducer, comprising:

a piezoelectric sensing element;

a mounting sleeve surrounding said element and having a surface supporting said sensing element;

an end wall secured across the end of said sleeve for exposure to a pressure to be measured, the central portion of the end wall transmitting pressure to said piezoelectric sensing element, the sensing element being held under compression between the supporting surface and end wall; and

means supporting said end wall, between said central portion and said sleeve.

2. The piezoelectric pressure transducer of claim 1 in which said supporting means is spaced from both said piezoelectric sensing element and said sleeve.

3. The piezoelectric pressure transducer of claim 1 in which the compliance of said supporting means to deformation by pressure applied to the end wall is less than the compliance of said piezoelectric sensing element and greater than the compliance of said sleeve.

4. The piezoelectric pressure transducer of claim 1 in which a flexure area is provided in said end wall between said piezoelectric sensing element and said support means.

5. The piezoelectric pressure transducer of claim 1 in which a flexure area is provided in said end wall between the mounting sleeve and said support means.

6. The piezoelectric pressure transducer of claim 1 in which a flexure area is provided between said support means and said end wall.

7. The piezoelectric pressure transducer of claim 1 having a first flexure area in said end wall between said piezoelectric element and said support means and a second flexure area in said end wall between said mounting sleeve and said support means.

8. The piezoelectric pressure transducer of claim 7 having a third flexure area between said support means and said end wall.

9. The piezoelectric pressure transducer of claim 8 in which the compliance of said supporting means to deformation by pressure applied to the end wall is less than the compliance of said piezoelectric sensing element and greaTer than the compliance of said sleeve.

10. The piezoelectric pressure transducer of claim 1 wherein said piezoelectric sensing element is circular, said mounting sleeve is cylindrical and has an internal shoulder means therein facing the end of the sleeve, and said support means is a cylindrical wall resting on said shoulder means.

11. The piezoelectric transducer of claim 10 with an end piece secured to said support means wall providing said supporting surface for said piezoelectric sensing element which is between said end wall and said end piece, with the cylindrical support wall stressed longitudinally to maintain the piezoelectric sensing element under compression.

12. THe piezoelectric transducer of claim 1 wherein the mounting sleeve has open front and rear ends, and including a cup with a wall forming said supporting means and the closed end forming a part of said end wall, said piezoelectric sensing element being located in said cup, an end piece secured to the open rear end of said cup, a carrier secured to said end piece and threaded into the rear end of said mounting sleeve, and a weld securing the cup wall to the front end of the mounting sleeve.

13. The piezoelectric transducer of claim 12 having an inturned flange at the front end of said mounting sleeve and secured to the periphery of said cup, said flange forming with the closed end of the cup the end wall of the transducer.

14. The piezoelectric transducer of claim 12 in which a rearwardly facing inwardly extending shoulder is located inside said mounting sleeve, said cup having forwardly facing outwardly extending shoulder which engages the shoulder inside the mounting sleeve.

15. The piezoelectric transducer of claim 1 wherein the mounting sleeve has an open front end, and including a cup with a wall forming said supporting means and the closed end forming a part of said end wall, said piezoelectric sensing element being located in said cup, an end piece secured to the open rear end of said cup, a forwardly facing, inwardly extending shoulder in said mounting sleeve, a retainer extending longitudinally forwardly through said sleeve engaging with said end piece to hold said cup against said shoulder, and a weld securing the cup wall to the front end of said mounting sleeve.

16. The piezoelectric transducer of claim 15 having an outturned flange at the closed end of the cup secured to the open end of said mounting sleeve, said flange and closed end forming the end wall of said transducer.

17. The piezoelectric transducer of claim 1 with an annular sealing ring on said mounting sleeve, outside said end wall.