Force transducer

• US 4,739,211 A
• Filed: 01/16/1987
• Issued: 04/19/1988
• Est. Priority Date: 09/28/1983
• Status: Expired due to Fees

• Current Assignee: Elf Atochem North America, Inc. (Totalenergies Se)
• Original Assignee: John S. Strachan
• Inventors: Strachan, John S.
• Primary Examiner(s): BUDD, MARK OSBORNE
• Application Number:
  US07/003,982
• Time in Patent Office: 459 Days
• Field of Search: 310/321, 310/323, 310/316, 310/317, 310/319, 310/331, 310/332, 310/338, 310/339, 310/800
• US Class Current: 310/321
• CPC Class Codes: G01L 1/162 using piezoelectric resonators
• CPC Class Codes: Y10S 310/80 Piezoelectric polymers, e.g. PVDF

Abstract

A force transducer device adapted to function in a system having electrical means to cause the device to oscillate at its natural resonant frequency and means to monitor said frequency, the device having an intermediate resilient member being capable of mechanically oscillating at a natural resonant frequency, at least two piezoelectric transducers mounted on said resilient member and means for connecting the transducer sheets into said system, is disclosed herein.

Claims

1. A load cell comprising an electrical amplifier, a force transducer including a resilient member capable of oscillating at a natural resonant frequency and, when operative, having at least one curved major surface, at least two piezoelectric resin sheet transducers mounted on one or more surfaces of said resilient member, said amplifier having its output attached to at least one of said transducers to thereby oscillate said resilient member and its input attached to at least one other of said transducers to thereby receive electrical frequency signals from such transducer, and means to monitor changes in electrical frequency connected to the load cell circuit.

2. The load cell of claim 1 wherein at least one of said transducers comprises a piezoelectric resin sheet mounted on said curved major surface, an electroconductive layer contacting at least the outer surface of said resin sheet, and an electrical lead attached to said layer.

3. The load cell of claim 2 wherein said transducers all comprise piezoelectric resin sheets, an electroconductive layer contacting at least the outer surface of each of said resin sheets, and an electrical lead attached to said layer.

4. The load cell of claim 3 wherein the amplifier output is attached to the outer surface of one of the transducers and the amplifier input is attached to the outer surface of the outer transducer.

5. The load cell of claim 3 wherein said piezoelectric resin sheet is vinylidene fluoride homopolymer or a copolymer of at least 65 mole percent vinylidene fluoride and at least one other copolymerizable monomer.

6. The load cell of claim 1 wherein said resilient member is a tube.

7. The load cell of claim 6 wherein means are provided to supply a fluid for passage into said tube.

8. The load cell of claim 2 wherein said resilient member is a tube and said transducers are mounted on the outer surface of said tube.

9. The load cell of claim 8 wherein means are provided to supply a fluid for passage into said tube.

10. The load cell of claim 9 wherein said piezoelectric resin sheet is vinylidene fluoride homopolymer or a copolymer of at least 65 mol percent vinylidene fluoride and at least one other copolymerizable monomer.

11. The load cell of claim 10 wherein said copolymerizable monomer is selected from the group consisting of trifluoroethylene, tetrafluoroethylene, vinyl fluoride and mixtures thereof.

12. A force transducer comprising a resilient member capable of oscillating at a natural resonant frequency and, when operative, having at least one curved major surface, at least two piezoelectric resin sheets each continguous with at least one surface of said resilient member, and an electroconductive layer contacting at least the outer surface of each said resin sheets whereby an electric current applied to at least one of said electroconductive layers will cause said resilient member to mechanically oscillate and the oscillating resilient member will cause at least one other electroconductive layer to transmit an electrical current corresponding to said mechanical oscillation.

13. The transducer of claim 12 wherein said piezoelectric resin sheets are films of vinylidene fluoride homopolymer or copolymer of at least 65 mole percent vinylidene fluoride and at least one other copolymerizable monomer.

14. The transducer of claim 13 wherein at least one of said piezoelectric sheets is in contact with the curved surface of said resilient member.

15. The transducer of claim 14 wherein at least one piezoelectric resin sheet is in contact with a surface opposite said curved surface.

16. The transducer of claim 14 wherein said resilient member has opposite major curved surfaces in parallel.

17. The transducer of claim 16 wherein at least two of said piezoelectric resin sheets are continguous with the same surface of said resilient member.

18. The transducer of claim 16 wherein at least one of said piezoelectric resin sheets is continguous with one of said surfaces and another of said piezoelectric resin sheets is continguous with the opposite surface.

19. The transducer of claim 16 wherein said electroconductive layers are vapor deposited metal coatings.

20. The transducer of claim 16 wherein said resilient member is a material selected from the group consisting of steel, hard rubber, synthetic plastic, silicon and glass.

21. The transducer of claim 16 wherein said resilient member consists of laminated slabs each having different rates of thermal expansion.

22. The transducer of claim 16 wherein said sheets are films of a copolymer of at least 65 mole percent vinylidene fluoride and a monomer selected from the group consisting of trifluoroethylene, tetrafluoroethylene, vinyl fluoride and mixtures thereof.

23. The transducer of claim 16 wherein said resilient member is a ring or pipe.

24. A force transducer comprising a resilient member capable of oscillating at a natural resonant frequency and, when operative, having at least one curved major surface, a piezoelectric resin sheet continguous with at least one surface of said resilient member, and at least two separate electroconductive layers contacting a surface of said resin sheet whereby an electric current applied to at least one of said electroconductive layers will cause said resilient member to mechanically oscillate and the oscillating resilient member will cause at least one other electroconductive layer to transmit an electrical current corresponding to said mechanical oscillation.

25. The transducer of claim 24 wherein said piezoelectric resin sheet is a film of vinylidene fluoride homopolymer or copolymer of at least 65 mole percent vinylidene fluoride and at least one other copolymerizable monomer.

26. The transducer of claim 25 wherein said other copolymerizable monomer is selected from the group consisting of trifluoroethylene, tetrafluoroethylene, vinyl fluoride and mixtures thereof.

27. The transducer of claim 25 wherein said resilient member has opposite major curved surfaces in parallel.

28. The transducer of claim 24 wherein said electroconductive layers are vapor deposited metal coatings.

29. The transducer of claim 27 wherein said resilient member is a ring or pipe.

30. The transducer of claim 27 wherein said resilient member is a material selected from the group consisting of steel, hard rubber, synthetic plastic, silicon and glass.