Center-mount capacitive sensor with overload protection

• US 6,718,827 B1
• Filed: 11/15/2002
• Issued: 04/13/2004
• Est. Priority Date: 11/15/2002
• Status: Active Grant

• Current Assignee: Setra Systems Incorporated (Fortive Corp.)
• Original Assignee: Setra Systems Incorporated (Fortive Corp.)
• Inventors: Foley, Thomas, Lee, Shih-Ying, Pinto, Gino A.
• Primary Examiner(s): OEN, WILLIAM L
• Application Number:
  US10/298,102
• Time in Patent Office: 515 Days
• Field of Search: 737/18, 737/24, 737/09, 361/281.3
• US Class Current: 73/718
• CPC Class Codes: G01L 19/0618 Overload protection
• CPC Class Codes: G01L 9/0072 using variations in capacitance

Abstract

A capacitive sensor includes an elastic member extending about a central axis, having a central region, a peripheral region, a first side, and a second side. An overpressure stop member has an inner surface and an outer surface. The inner surface of the overpressure stop member has a contour adapted to limit deflection of the elastic member caused by a differential pressure between the two regions across the elastic member. The outer surface of the overpressure stop member has an first electrically conductive region. A second plate is spaced apart from the outer surface of the overpressure stop member, and being connected to the central region of the elastic member by a post, wherein the post transfers deformation of the elastic member caused by differential pressure across the elastic member to movement of the second plate along the central axis. The second plate has a second electrically conductive region opposite the first electrically conductive region, wherein the first electrically conductive region and the second electrically conductive region form a capacitor.

Claims

1. A capacitive sensor comprising:

A. an elastic member disposed about a central axis of said sensor, said elastic member having a central region, a peripheral region, a first side, and a second side;

B. a support member supporting the peripheral region of said elastic member;

C. an overpressure stop member rigidly coupled to said support member, said overpressure stop member extending over said elastic member except for an aperture region, and having an inner surface and outer surface, said inner surface facing said elastic member;

D. a first plate rigidly coupled to said support member and extending over said elastic member except for an aperture region, and having a first surface including a first electrically conductive region thereon;

E. a post affixed to and extending from said second side of said elastic member along said central axis, said post passing through said aperture regions; and

F. a second plate extending from said post transverse to said central axis, said second plate having a second electrically conductive region opposite said first electrically conductive region of said first surface of said first plate, wherein said opposite electrically conductive regions are electrically insulated from each other.

2. A capacitive sensor according to claim 1 further comprising a boss extending from said central region of said elastic member along said central axis.

3. A sensor according to claim 1, wherein said overpressure stop member and said first plate form an integral structure wherein said outer surface of said overpressure stop member and said first surface of said first plate are coincident.

4. A sensor according to claim 1, wherein said capacitive sensor further comprises an electrically conductive path being provided from a first electrode, via said post, said elastic member, said overpressure stop member, and said first plate, to said first electrically conductive region, a second electrode being connected to said second electrically conductive region, said first and second electrodes being used to indicate the changes in capacitance caused by relative motion of said first and second electrically conductive regions due to pressure differential induced motion of said elastic member.

5. A sensor according to claim 1, wherein said inner surface of said overpressure stop member has a contour adapted to limit deflection of said central region of said elastic member caused by a differential pressure across said elastic member.

6. A capacitive sensor according to claim 1, wherein said inner surface of said overpressure stop member defines a support contour which substantially conforms to a configuration defined by said elastic member when said elastic member deflected to a predetermined extent.

7. A sensor according to claim 1, wherein said pressure differential derives from a pressure being in contact with said first side of said elastic member and a constant, controlled environment being in contact with said second side of said elastic member.

8. A capacitive sensor according to claim 1, wherein said elastic member is an elastic diaphragm.

9. A capacitive sensor according to claim 1, wherein said elastic member is an elastic plate.

10. A capacitive sensor according to claim 1, wherein said elastic member is an elastic beam.

11. A capacitive sensor according to claim 1, wherein said elastic member is made from a material selected from a group of steel, stainless steel, ceramic and glass.

12. A capacitive sensor according to claim 1, wherein said overpressure stop member is made of a substantially rigid material.

13. A capacitive sensor according to claim 1, wherein said elastic member is substantially flat.

14. A capacitive sensor according to claim 1, wherein said elastic member is dome-shaped.

15. A capacitive sensor according to claim 1, wherein said inner surface of said overpressure stop member is substantially planar.

16. A capacitive sensor according to claim 1, wherein said inner surface of said overpressure stop member is concave.

17. A capacitive sensor according to claim 16, wherein said inner surface of said overpressure stop member is contoured such that said inner surface of said overpressure stop member fully and uniformly supports said elastic member when said elastic member deflected to a predetermined extent.

18. A capacitive sensor according to claim 1, wherein said outer surface of said overpressure stop member is substantially planar.

19. A sensor according to claim 1, wherein said capacitive sensor further comprises an electrode assembly including a first electrode electrically coupled to said first electrically coupled region, and a second electrode electrically coupled to said second electrically conductive region.

20. A capacitive sensor comprising:

A. an elastic member extending about a central axis, said elastic member having a central region, a peripheral region, a first side, and a second side;

B. a support member supporting the peripheral region of said elastic member;

C. an overpressure stop member coupled to said peripheral region of said elastic member, said overpressure stop member having an inner surface and an outer surface, said inner surface of said overpressure stop member facing said second side of said elastic member and being spaced apart from said central region of said elastic member by a predetermined distance;

D. a first plate coupled to said support member, said first plate having a first surface comprising a first electrically conductive region thereon; and

E. a second plate spaced apart from and being substantially parallel to said first plate, said second plate being connected to said central region of said elastic member by a post, wherein said post transfers deformation of said central region of said elastic member caused by differential pressure across said elastic member to movement of said second plate along said central axis, said second plate having a second electrically conductive region opposite said first electrically conductive region, wherein said first electrically conductive region and said second electrically conductive region form a capacitor.

21. A capacitive sensor according to claim 20 further comprising an electrode assembly being electrically connected to said first electrically conductive region and said second electrically conductive region, said electrode assembly being adapted for indicating pressure differential derived from a pressure being in contact with said first side of said elastic member and a constant, controlled environment pressure being in contact with said second side of said elastic member.

22. A capacitive sensor according to claim 20, wherein said post is connected to a central point of said elastic member and is adapted for transferring the deformation of said central point to the movement of said second plate.

23. A capacitive sensor according to claim 20 further comprising an electrically conductive path extending from said post to said first electrically conductive region, said electrically conductive path being insulated from said second electrically conductive region.

24. A capacitive sensor according to claim 20, wherein said overpressure stop member and said first plate form an integral structure wherein said outer surface of said overpressure stop member and said first surface of said first plate are coincident.

25. A capacitive sensor according to claim 24, wherein said overpressure stop member defines an aperture region disposed about said central axis, and wherein said post passing through said aperture region, said post having a first end connected to the central region of said elastic member and a second end connected to said second plate, said post being adapted for transferring the deformation of said central region to the movement of said second plate.

26. A capacitive sensor according to claim 20, wherein said first plate is mounted to said outer surface of said overpressure stop member.

27. A capacitive sensor according to claim 26, wherein said first plate and said overpressure stop member define an aperture region disposed about said central axis, and wherein said post passing through said aperture region, said post having a first end connected to the central region of said elastic member and a second end connected to said second plate, said post being adapted for transferring the deformation of said central region to the movement of said second plate.

28. A capacitive sensor according to claim 20, wherein said elastic member is an elastic diaphragm.

29. A capacitive sensor according to claim 20, wherein said elastic member is an elastic plate.

30. A capacitive sensor according to claim 20, wherein said elastic member is an elastic beam.

31. A capacitive sensor according to claim 20, wherein said elastic member is made from a material selected from a group of steel, stainless steel, ceramic and glass.

32. A capacitive sensor according to claim 20, wherein said overpressure stop member is made of a substantially rigid material.

33. A capacitive sensor according to claim 20, wherein said elastic member is substantially flat.

34. A capacitive sensor according to claim 20, wherein said elastic member is dome-shaped.

35. A capacitive sensor according to claim 20, wherein said inner surface of said overpressure stop member is substantially planar.

36. A capacitive sensor according to claim 20, wherein said inner surface of said overpressure stop member is concave.

37. A capacitive sensor according to claim 36, wherein said inner surface of said overpressure stop member is contoured such that said inner surface of said overpressure stop member fully and uniformly supports said central region when said central region deflected to a predetermined extent.

38. A capacitive sensor according to claim 20 further comprising a boss extending from said central region along said central axis.

39. A sensor according to claim 20, wherein said inner surface of said overpressure stop member has a contour adapted to limit deflection of said central region of said elastic member caused by a differential pressure across said elastic member.

40. A capacitive sensor according to claim 20, wherein said inner surface of said overpressure stop member defines a support contour which substantially conforms to a configuration defined by said elastic member when said elastic member deflected to a predetermined extent.

41. A sensor according to claim 20, wherein said pressure differential derives from a pressure being in contact with said first side of said elastic member and a constant, controlled environment being in contact with said second side of said elastic member.