INTRUDER DETECTION SYSTEM EMBODYING A BIMORPH TRANSDUCER

• US 3,868,667 A
• Filed: 04/06/1972
• Issued: 02/25/1975
• Est. Priority Date: 04/06/1972
• Status: Expired due to Term

• Current Assignee: Romans Skujins Jr
• Original Assignee: Romans Skujins Jr
• Inventors: Skujins, Romans Jr.
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): Nowicki, Joseph E.
• Application Number:
  US05/241,646
• Time in Patent Office: 1,055 Days
• Field of Search: 340/38,258,261,272,409 310/9.7,9.8,8.6,8.5,9.6 137/81 73/47R,47PR,DIG.4
• US Class Current: 340/544
• CPC Class Codes: G08B 13/20 Actuation by change of fluid pressure
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

The disclosed invention is an intruder detection system wherein the piezoelectric transducer responsive to two distinctive pressure signals comprises a hydrostatically balanced, two terminal bimorph assembly.

Claims

1. A system for detecting penetration of a restricted area by an intruder comprising:

first and second substantially identical fluid-filled elongated tubular chambers adapted for ground burial, said elongated chambers adapted to generate representative internal pressures in response to external pressures of the variety produced by movement of intruders in the vicinity of said elongated chambers when buried;

piezoelectric transducer means having first and second pressure sensitive inputs and a single electrical signal output, said piezoelectric transducer means being a planar dual crystal element bimorph structure wherein said first and second pressure sensitive inputs incorporate substantially identical planar crystal elements adapted for like flexure action, said bimorph structure adapted to produce an output signal potential when one crystal expands and the other contracts in response to an instantaneous pressure differential at said first and second pressure sensitive inputs;

said first and second tubular chambers mechanically and hydraulically connected to said first and second pressure sensitive inputs such that the full surface area of one side of each respective planar crystal element is subject to said representative internal pressures within its respective tubular chamber;

an indicator means electrically connected to said electrical signal output of said piezoelectric transducer means and adapted to produce an indication in response to said instantaneous pressure differential.

2. A system as defined in claim 1 wherein said electrical signal output of said transducer means is a two terminal output and the electrical signal is measured thereacross, and wherein said dual crystal bimorph structure comprises first and second planar crystal elements cemented in fact to face relation with a first flexible metallic surface therebetween electrically connected to one terminal of said electrical signal output, plus second and third flexible metallic surfaces afixed to the outward facing planar surfaces of said bimorph structure and electrically connected in parallel to the second terminal of said electrical signal output, each of said outward facing planar surfaces of said bimorph structure disposed in relation to a respective elongated sensor to react to fluid pressure deviations therein.

3. A system as defined in claim 2 wherein said flexible metallic surfaces have a thickness substantially less than the thickness of said planar crystal elements such that the flexural characteristics of said dual crystal bimorph structure are essentially determined by the flexural characteristics of said planar crystal elements.

4. A system as defined in claim 3 wherein each of said flexible metallic surfaces and said planar crystal elements have a circular disc configuration.

5. A system as defined in claim 4 wherein each of said flexible metallic surfaces and said planar crystal elements has substantially the same size circular disc configuration and said metallic surfaces and said crystal elements are disposed and alligned in a substantially symmetrical sandwich arrangement.

6. A system as defined in claim 5 wherein said circular disc configuration is a circle.