Accelerometer

• US 5,572,081 A
• Filed: 02/24/1995
• Issued: 11/05/1996
• Est. Priority Date: 10/09/1992
• Status: Expired due to Term

• Current Assignee: A/S Bruel & Kjaer
• Original Assignee: A/S Bruel & KJAE Butted R
• Inventors: Starck, Lars
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US08/387,851
• Time in Patent Office: 620 Days
• Field of Search: 310/338, 310/339, 310/333, 310/329
• US Class Current: 310/329
• CPC Class Codes: G01P 15/0915 of the shear mode type

Abstract

An accelerometer of the shear type comprises a base (1) with uprights (2) supporting one or more seismic masses (3) by way of one or more piezoelectric elements (4). According to the invention, the seismic mass(es) (3) and the piezoelectric elements (4) are arranged between the uprights (2). The seismic masses (3) and the piezoelectric elements are clamped between the uprights (2) by means of a clamping ring (5). The resulting resonance frequency is very high, and the accelerometer is less sensitive to temperature transients, magnetic fields and easier to produce than the known accelerometers.

Claims

1. An accelerometer comprising a base with at least two uprights supporting at least one seismic mass and at least one piezoelectric element, and a securing means for securing said seismic masses and said piezoelectric elements to an inner side of each of said uprights.

2. An accelerometer as claimed in claim 1, wherein said inner sides are positioned substantially parallel to each other.

3. An accelerometer as claimed in claim 1, wherein said at least one seismic mass has a rectangular cross-sectional shape.

4. An accelerometer as claimed in claim 1, wherein said inner sides are positioned at an angle with respect to each other, said angle being from about 1°

to about 3°

.

5. An accelerometer as claimed in claim 1, wherein said at least two uprights are formed integral with the base.

6. An accelerometer as claimed in claim 1, wherein each of said piezoelectric elements has a polarization direction which is parallel to and/or perpendicular to the uprights.

7. An accelerometer as claimed in claim 1 wherein said at least one piezoelectric element and said at least one seismic mass are retained between said inner sides of said uprights by said securing means which exerts a pressure on an outer side of each of said uprights, said pressure being directed towards the inner side of each of said uprights.

8. An accelerometer as claimed in claim 7, wherein said securing means is a clamping ring which surrounds said uprights.

9. An accelerometer as claimed in claim 8, wherein said clamping ring completely covers said uprights.

10. An accelerometer as claimed in claim 7, wherein said securing means comprises a bolt extending through the uprights, the piezoelectric elements and the seismic masses, said bolt having a thread upon which a nut having a thread is screwed to produce said pressure.

11. An accelerometer as claimed in claim 1, wherein the piezoelectric element and the seismic mass are retained between the uprights by means of glue.

12. An accelerometer as claimed in claim 1, wherein said uprights extend downward from a cover plate and said base has an upward extending cylindrical housing serving as a clamping ring and a cover for said downward extending uprights, said piezoelectric elements and said seismic masses being arranged between said uprights.

13. An accelerometer as claimed in claim 1, wherein one of said seismic masses is positioned along a vertical axis of said accelerometer, said one of said seismic masses having an inner cylindrical wall provided along said vertical axis for inserting a mounting bolt therethrough.

14. An accelerometer as claimed in claim 1, wherein one of said seismic masses has a top plate formed integral thereto.

15. An accelerometer as claimed in claim 1, wherein said at least one seismic mass has a cross-sectional shape formed as a circle with parallel cut segments.

16. An accelerometer as claimed in claim 10, wherein said bolt is screwed into a thread in one of said uprights.

17. An accelerometer as claimed in claim 1, wherein one of said seismic masses has a top plate secured thereto.