Accelerometer assembly

• US 3,884,085 A
• Filed: 04/05/1972
• Issued: 05/20/1975
• Est. Priority Date: 04/05/1972
• Status: Expired due to Term

• Current Assignee: Transicoil, Inc. (Transdigm Group Incorporated)
• Original Assignee: Benjamin F. Gerding, Paul Beckman, Prabhat Kumar Jain
• Inventors: Beckman, Paul, Gerding, Benjamin F., Jain, Prabhat Kumar
• Primary Examiner(s): Gill, James J.
• Application Number:
  US05/241,318
• Time in Patent Office: 1,140 Days
• Field of Search: 73/516,517,70.2,71,71.2,71.4,88.5R,141A,497 338/2,5,3
• US Class Current: 73/514.33
• CPC Class Codes: G01P 15/122 by metal resistance strain gauges, e.g. wire resistance strain gauges

Abstract

An accelerometer assembly for determining acceleration forces in a predetermined direction and which is adapted for use in a high temperature environment. The assembly includes a ceramic beam positioned internal to a hermetically sealed chamber. The ceramic beam is cantilever mounted on one end and is partially insertable within an elastic stop assembly at an opposing end. A predetermined weight is rigidly secured to the beam to act as a strain amplifier. Acceleration forces cause displacement of the weight and ceramic beam unit which in turn provides known strain in the ceramic beam. Strain gauges bonded to the ceramic beam are connected to an externally located Wheatstone Bridge which provides a read out of the acceleration forces experienced by the accelerometer assembly.

Claims

1. Cantilever restraining means rigidly secured to a first end of said longitudinally extended ceramic beam, said cantilever restraining means including a frame member fastened to an internal wall of said housing, said ceramic beam being rigidly fastened to said frame member on said first end for maintaining said longItudinally extended beam in spaced relation to said internal wall to said housing;

and,

2. The accelerometer assembly as recited in claim 1 wherein said cushin assembly includes:

a. a first screen mesh contiguous said forward wall of said base frame;

b. a high temperature fabric interfacing with said first screen mesh on a first face of said fabric; and

, c. a second screen mesh interfacing with said high temperature fabric on a second face thereof, said second face of said fabric opposing said first face.

3. The accelerometer assembly as recited in claim 2 wherein said high temperature fabric is composed of zirconium oxide.

4. The accelerometer assembly as recited in claim 3 wherein said screen mesh is composed of stainless steel, said mesh having a size approximating 400.

5. The accelerometer assembly as recited in claim 1 wherein said recess formed within said forward wall includes sidewalls having a longitudinal taper, said recess having a maximum cross-sectional area at a most forward portion of said forward wall.

6. The accelerometer assembly as recited in claim 5 wherein said longitudinal taper of said recess sidewalls forms an angle approximating 2.5* with respect to said longitudinal direction.

7. The accelerometer assembly as recited in claim 1 wherein said longitudinally extended ceramic beam includes means for amplifying bending moment stresses in said beam when said beam is movably actuated in said predetermined direction.

8. The accelerometer assembly as recited in claim 7 wherein said stress amplifying means includes a weight, said weight rigidly secured to said ceramic beam at a predetermined location in said longitudinal direction.

9. The accelerometer assembly as recited in claim 8 wherein said weight has a mass substantially greater then the mass of said ceramic beam and said predetermined location of said weight is between said first and second ends of said beam and at least far enough from said second end so that said weight does not contact said stop means.

10. The accelerometer assembly as recited in claim 9 wherein said weight is composed of a tungsten alloy.

11. The accelerometer assembly as recited in claim 1 wherein said ceramic beam is composed of a monocrystalline structure.

12. The accelerometer assembly as recited in claim 1 wherein said acceleration measurement means includes a plurality of strain gauges bonded to said ceramic beam, said strain gauges electrically connected to an external device for measuring strains produced in said gauges by said movement of said beam.

13. The accelerometer assembly as recited in claim 12 wherein said acceleration measurement means includes a first pair of strain gauges bonded to an upper surface of said ceramic beam and a second pair of strain gauges bonded to a lower surface of said ceramic beam.

14. The accelerometer assembly as recited in claim 13 wherein said strain gauges are composed of platinum wire.

15. The accelerator assembly as recited in claim 14 wherein said strain gauge wires are bonded to said ceramic beam by a ceramic base bonding cement, saId strain gauge wires for contacting said beam continuously throughout a predetermined portion of said strain gauge wires.

16. The accelerometer assembly as recited in claim 1 wherein said housing hermetically seals said internal chamber from said high temperature environment.

17. The accelerometer assembly as recited in claim 16 wherein said housing is constructed of stainless steel.

18. A high temperature accelerometer assembly for use in environments having extensive temperature excursions, comprising:

a. a hollow housing defining a hermetically sealed internal chamber;

b. a monocrystalline ceramic beam member longitudinally extended within said internal chamber, said beam member being cantilever mounted on a first end thereof to a frame secured to an inner wall of said chamber;

c. a weight secured to said beam at a predetermined point in said longitudinal extension of said beam;

d. means for flexibly partially constraining a second end of said beam, said second end of said beam longitudinally opposing said first end of said beam; and

, e. a plurality of strain gauges bonded to said ceramic beam for measuring the strain in said beam when said beam is displaced in a predetermined direction.

19. The high temperature accelerometer assembly as recited in claim 18 wherein said flexible constraining means includes a base frame rigidly secured to said housing said base frame having a tapered recess diverging away from said inner wall and toward said beam formed within the inner wall facing said second end of said beam for partial insertion of said monocrystalline ceramic beam.

20. The high temperature accelerometer assembly s recited in claim 19 wherein said flexible constraining means includes resilient beam impact means contiguous with said forward wall and said tapered recess formed therein and securely fastened to said base frame, said ceramic beam for contacting said flexible constraining means when said ceramic beam is displaced in said predetermined direction.

21. The high temperature accelerometer assembly as recited in claim 20 wherein said flexible constraining means includes a high temperature cloth positionally fixed between opposing layers of screen mesh.

22. An accelerometer assembly for measuring acceleration forces in a predetermined direction adapted for use in a high temperature environment, comprising:

a. a housing defining an internal chamber;

b. a longitudinally extended monocrystalline ceramic beam within said chamber, said beam rigidly secured at one longitudinal end thereof to said chamber and partially constrained on the opposing longitudinal end thereof, said beam being moveable in said predetermined direction responsive to said acceleration forces applied to said housing;

c. means for respectively rigidly securing and partially constraining said monocrystalline ceramic beam on opposing longitudinal ends thereof within said internal chamber of said housing; and

, d. elastic displacement measurement means rigidly secured to said monocrystalline ceramic beam for measuring said beam elastic displacement when said beam is moveably actuated in said predetermined direction.