ACCELEROMETER UTILIZING SHEAR RESPONSIVE X-CUT LITHIUM NIOBATE

• US 3,727,084 A
• Filed: 06/29/1970
• Issued: 04/10/1973
• Est. Priority Date: 06/29/1970
• Status: Expired due to Term

• Current Assignee: Endevco Corporation (Illinois Tool Works Inc.)
• Original Assignee: Howard C. Epstein
• Inventors: Epstein, Howard C.
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Budd, Mark O.
• Application Number:
  US05/050,657
• Time in Patent Office: 1,016 Days
• Field of Search: 310/8.2-8.7,9.5,9.6 252/62.9
• US Class Current: 310/329
• CPC Class Codes: G01P 15/0915 of the shear mode type

Abstract

The accelerometer of this invention utilizes a a lithium niobate crystal operated in the shear mode with the shearing planes parallel to a mirror plane and with the axis of the acceleration arranged at an angle of about 32* in the second and fourth quadrants of the Y-Z planes of the crystal. This accelerometer has high efficiency and operates effectively over a wide range of temperatures including high temperatures above 1,000*F.

Claims

2. In an accelerometer as defined in claim 1, an inertia member attached to the other flat surface of said piezoelectric element.

3. In an accelerometer as defined in claim 2, including means defining an axis of acceleration and wherein one of said members has a base provided with a surface attachable to the surface of an accelerating object and in which the Z-axis of said crystal is inclined about 32* with respect to said direction and the Y-axis of said crystal is inclIned about 122* therefrom.

4. In an accelerometer as defined in claim 3, provided with a perforated cover member cooperating with one of said two members for enclosing said crystal.

5. In an accelerometer as defined in claim 2 in which said crystal has a central hole therein, and a bolt extends through said crystal, and said two members are composed of metal, and an insulating washer is mounted between one of said members and said crystal.

6. In an accelerometer as defined in claim 2 in which said crystal has a central hole therein, and a bolt extends through said crystal and said two members, and wherein said bolt and said two members are composed of electrically conductive material, and insulating washers are mounted between said two members and said crystal, said washers being composed of insulating material having a low coefficient of friction.

7. In an accelerometer of the shear type employing force-measuring sensors in which electrical signals are developed across two flat parallel faces of each of at least two piezoelectric elements which are mounted on a force applying member that is adapted to move in a predetermined direction parallel to said faces in response to a force applied to said member and in which means are provided for conducting such electrical signals to a utilization device responsive thereto, said member being attachable to an accelerating object, the improvement wherein said piezoelectric element comprises an X-cut lithium niobate crystal mounted with the X-axis of the crystal perpendicular to said direction, the Z-axis of said crystals being inclined about 32* with respect to said predetermined direction and the Y-axis of said crystal being inclined about 122* to the normal to said surfaces.

8. An accelerometer as defined in claim 7 wherein said crystals have a central hole therein and a bolt extends through said holes in said crystals and said crystals are secured thereby between said two members.

9. An accelerometer defined in claim 8 wherein said two members are composed of metal, and further comprising a first insulating washer mounted between one of said members and one crystal and a second insulating washer mounted between the other member and the other crystal.

10. An accelerometer as defined in claim 6 further comprising a third member and a second crystal, said second crystal being mounted between said third member and said member having a base, said third member and said member having a base being adapted to move relatively to each other in a direction perpendicular to said base in response to an accelerating object secured to said member having a base.

11. An accelerometer as defined in claim 10 in which each of said crystals has a central hole therein and a bolt extends through said crystals, said members being composed of metal.

12. In an accelerometer as defined in claim 7, two inertia members attached respectively to the remaining of said flat surfaces of said piezoelectric elements.