Capacitor and pressure transducer

• US 5,168,419 A
• Filed: 07/16/1991
• Issued: 12/01/1992
• Est. Priority Date: 07/16/1991
• Status: Expired due to Fees

• Current Assignee: Panex Corporation
• Original Assignee: Panex Corporation
• Inventors: Delatorre, Leroy C.
• Primary Examiner(s): GRIFFIN, DONALD
• Application Number:
  US07/730,694
• Time in Patent Office: 504 Days
• Field of Search: 73/718, 73/724, 73/733, 73/735, 361/283
• US Class Current: 361/283.2
• CPC Class Codes: G01L 9/003 using variations in capacitance

Abstract

A dual capacitor device for utilizing dependent capacitances for measurement purposes where an upper capacitor base member and a lower capacitance base member are arranged with parallel capacitor surfaces in horizontal planes and where the parallel capacitor surfaces are located on opposite sides relative to a vertical axis to define first and second capacitors. The lower capacitor base member has a centrally located section connected to an outer section of the lower capacitor base member by a torsion beam and the centrally located section is attached to the upper capacitor base member by a vertical arm member. The torsion beam means has a displacement axis normal to the central axis so that angular displacement of the torsion beam and the centrally located section about the displacement axis produces a capacitance change in the first and second capacitors. A force moment applied to the centrally located section by a spirally wound bourdon tube in response to pressure develops a low force on the torsion beam which is less than the micro yield point of the torsion beam material and develops a micro dimensional angular displacement of the centrally located section and a capacitance change as a function of the force to measure high pressures with small deflections of the capacitor. The structure is arranged to compensate for changing temperature.

Claims

1. A dual capacitor device for utilizing dependent capacitances for measurement purposes comprising:

an upper capacitor base member and a lower capacitance base member arranged with parallel capacitor surfaces in horizontal planes where said parallel capacitor surfaces are located on opposite sides relative to a vertical central axis and said capacitance surfaces define first and second capacitors;

said lower capacitor base member having a centrally located section connected to an outer section of said lower capacitor base member by torsion beam means, said centrally located section being attached to said upper capacitor base member by a vertical arm member;

said torsion beam means having a displacement axis normal to said central axis so that angular displacement of said torsion beam means and said centrally located section about said displacement axis produces a capacitance change in said first and second capacitors;

force means coupled to said centrally located section for producing a torsion force on said torsion beam means for developing angular displacement of said centrally located section and a capacitance change as a function of said torsion force.

2. The capacitor device as set forth in claim 1 wherein the torsion beam means has a rectangular cross section with long and short dimensions relative to first vertical plane orientations which are parallel to said central axis and wherein said long dimensions are parallel to said central axis,

said force means including a moment arm member extending along said central axis where said moment arm member extends below said lower capacitor base member and where said torsion force is applied to said moment arm at a location below said lower capacitor base member.

3. The capacitor device as set forth in claim 2 wherein said lower capacitor base member has a first vertically walled slot means which define a central portion coupled to said moment arm and which define said torsion beam means where said torsion beam means connect to an outer base portion of said lower capacitor base member.

4. The capacitor device as set forth in claim 3 wherein said lower capacitor base member has a second vertically walled slot means which define transverse torsion beam means where said transverse torsion beam means are in said outer base portion of said lower capacitor base member and are located in a plane transverse to said first vertical plane.

5. The capacitor device as set forth in claim 3 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics and wherein the force means is a bourdon tube arranged for developing a torsion force which does not exceed the micro yield point of the torsion beam means.

6. The capacitor device as set forth in claim 5 and further including a force connector member in said force means where said force connector member is coupled between said bourdon tube and said moment arm, said force connector member having rectangular cross sections in transverse horizontal plane orientations to said first vertical plane orientations with long dimensions normal to the short dimensions of the torsion beam means.

7. The capacitor device as set forth in claim 1 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics and wherein the force means is a bourdon tube arranged for developing a torsion force which does not exceed the micro yield point of the torsion beam means.

8. The capacitor device as set forth in claim 7 wherein said force means includes a moment arm member extending to a location below said lower capacitor base member,

said bourdon tube having a closed end and an open end which are aligned along a common axis with the central portion of said bourdon tube and with the central portion of the bourdon tube arranged in a spiral about a bourdon tube coil axis which is offset laterally from and parallel to said common axis, said common axis being aligned with said central axis and said closed end being coupled to said moment arm so that the bourdon tube develops a force in a direction normal to said common axis.

9. The capacitor device as set forth in claim 8 and further including a force connector member in said force means where said force connector member is coupled between said bourdon tube and said moment arm, said force connector member having rectangular cross sections in transverse horizontal plane orientations to said first vertical plane orientations with long dimensions normal to the short dimensions of the torsion beam means.

10. The capacitor device as set forth in claim 9 wherein the torsion beam means has a rectangular cross section with long and short dimensions relative to first vertical plane orientations which are parallel to said central axis and wherein said long dimensions are parallel to said central axis,

said force means including a moment arm member extending along said central axis where said moment arm member extends below said lower capacitor base member and where said torsion force is applied to said moment arm at a location below said lower capacitor base member.

11. The capacitor device as set forth in claim 10 wherein said lower capacitor base member has a first vertically walled slot means which define a central portion coupled to said moment arm and which define said torsion beam means where said torsion beam means connect to an outer base portion of said lower capacitor base member.

12. The capacitor device as set forth in claim 11 wherein said lower capacitor base member has a second vertically walled slot means which define transverse torsion beam means where said transverse torsion beam means are in said outer base portion of said lower capacitor base member and are located in a plane transverse to said first vertical plane.

13. The capacitor device as set forth in claim 1 and including support means attached to said outer base portion of said lower capacitor member adjacent to said torsion beam means.

14. The capacitor device as set forth in claim 13 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics and wherein the force means includes a bourdon tube arranged for developing a torsion force which does not exceed the micro yield point of the torsion beam means and said bourdon tube is attached to said support means.

15. The capacitor device as set forth in claim 14 wherein said force means includes a moment arm member extending to a location below said lower capacitor base member,

said bourdon tube having a closed end and an open end which are aligned along a common axis with the central portion of said bourdon tube with the central portion of the bourdon tube arranged in a spiral about a bourdon tube coil axis which is offset laterally from and parallel to said common axis, said common axis being aligned with said central axis and said closed end being coupled to said moment arm so that the bourdon tube develops a force in a direction normal to said common axis.

16. The capacitor device as set forth in claim 15 and further including a force connector member in said force means where said force connector member is coupled between said bourdon tube and said moment arm, said force connector member having rectangular cross sections in transverse horizontal plane orientations to said first vertical plane orientations with long dimensions normal to the short dimensions of the torsion beam means.

17. The capacitor device as set forth in claim 16 wherein said lower capacitor base member has a first vertically walled slot means which define a central portion coupled to said moment arm and which define said torsion beam means where said torsion beam means connect to an outer base portion of said lower capacitor base member.

18. The capacitor device as set forth in claim 17 wherein said support means includes arcuate wall segments diametrically arranged and attached to said outer base portion.

19. The capacitor device as set forth in claim 18 wherein said support means further includes diametrically arranged rod members connected by a horizontal plate member to said wall segments where said rod members are disposed in a vertical plane orientation which is transverse to a vertical plane orientation for said wall segments.

20. The capacitor device as set forth in claim 19 wherein the support means have a material construction providing an effective thermal co-efficient of expansion which is substantially equal to the effective thermal co-efficient of expansion for the material construction of the upper base member, torsion beam means and force means.

21. The capacitor device as set forth in claim 1 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics with a macro yield point above the working stress levels in said torsion beam means.

22. The capacitor device as set forth in claim 1 wherein the torsion beam means are constructed from a material having good elastic characteristics with a micro yield point above the working stress levels of the torsion beam means.

23. The capacitor device as set forth in claim 1 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics in the stress range of the torsion mean means.

24. The capacitor device as set forth in claim 1 wherein the force means is a bourdon tube arranged for developing a torsion force which does not exceed the micro yield point of the torsion beam means.

25. The capacitor device as set forth in claim 1 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics and wherein the force means is a bellows arranged for developing a torsion force which does not exceed the micro yield point of the torsion beam means.

26. The capacitor device as set forth in claim 1 wherein the torsion beam means are constructed from a high strength metal material having good elastic characteristics and wherein the force means is a bellows arranged for developing a torsion force which does not exceed the macro yield point of the torsion beam means.

27. A method of measuring capacitance in a dual capacitor device utilizing dependent capacitances for measurement purposes and wherein the capacitor device has an upper capacitor base member and a lower capacitance base member arranged with parallel capacitor surfaces in horizontal planes where said parallel capacitor surfaces are located on opposite sides relative to a vertical central axis and said capacitance surfaces define first and second capacitors having first and second capacitance gaps comprising the steps of:

torquing said upper capacitor base member about a horizontal displacement axis located in a torsion beam means disposed normal to said central axis and in a horizontal plane in said lower base member by applying a moment force about said displacement axis so that angular displacement of said upper base member about said displacement axis produces a dependent change in said capacitance gaps of said first and second capacitors; and

maintaining the force and the force moment below the yield point of the torsion beam means to minimize permanent distortion in said torsion beam means.

28. A method of measuring capacitance in a dual capacitor device as set forth in claim 27 wherein the force and the force moment are maintained below the macro yield point of the torsion beam means.

29. A method of measuring capacitance in a dual capacitor device as set forth in claim 27 wherein the force and the force moment are maintained below the micro yield point of the torsion beam means.

30. A method of measuring capacitance in a dual capacitor device utilizing dependent capacitances for measurement purposes and wherein the capacitor device has an upper capacitor base member and a lower capacitance base member arranged with parallel capacitor surfaces in horizontal planes where said parallel capacitor surfaces are located on opposite sides relative to a vertical central axis and said capacitance surfaces define first and second capacitors having first and second capacitance gaps and wherein the lower capacitance base member has torsion beam means disposed along a horizontal displacement axis with the torsion beam means coupled to a vertical moment arm on the upper capacitor base member comprising the steps of:

torquing said upper capacitor base member about said horizontal displacement axis located in a torsion beam means by applying a force to said moment arm for developing a moment force about said displacement axis and develop an angular displacement of said upper base member about said displacement axis for producing a dependent change in said capacitance gaps of said first and second capacitors., and

maintaining the force below the yield point of the torsion beam means to minimize permanent distortion in said torsion beam means.

31. A method of measuring capacitance in a dual capacitor device utilizing dependent capacitances for measurement purposes as set forth in claim 30 and further including developing said force with a spirally wound bourdon tube arranged to develop a force on the moment arm in a direction normal to displacement axis.

32. A method of measuring capacitance in a dual capacitor device as set forth in claim 31 wherein the force and the force moment are maintained below the macro yield point of the torsion beam means.

33. A method of measuring capacitance in a dual capacitor device as set forth in claim 31 wherein the force and the force moment are maintained below the micro yield point of the torsion beam means.