CAPACITIVE WEIGHING MAT

• US 3,875,481 A
• Filed: 10/10/1973
• Issued: 04/01/1975
• Est. Priority Date: 10/10/1973
• Status: Expired due to Term

• Current Assignee: Uniroyal Chemical Company Inc (Lanxess AG)
• Original Assignee: Henry F. Miller, Jonathan Mishory
• Inventors: Miller, Henry F., Mishory, Jonathan
• Primary Examiner(s): Goldberg, E. A.
• Application Number:
  US05/405,216
• Time in Patent Office: 538 Days
• Field of Search: 317/246,249R,261 177/210 73/141A
• US Class Current: 361/283.1
• CPC Class Codes: G01G 3/00 Weighing apparatus characterised by the use of elastically-deformable members, e.g. spring balances
• CPC Class Codes: G01G 7/06 by electrostatic action

Abstract

A weighing mat adapted to be loaded by a range of forces which preferably includes three elastomeric, conductive layers. The outer conductive layers are separated from the central conductive layer by two dielectric, elastomeric layers having ribs of trapezoidal cross section to form a capacitance which varies with compressive loading. The mat provides linear changes of capacitance with changes of compressive load, has increased load capacity, and has improved resistance to shear forces.

Claims

1. A weighing mat adapted to be loaded by a range of forces to be measured comprising:

at least two electrically conductive layers separated by a deformable dielectric layer, said deformable dielectric layer comprising projections individually having a cross-sectional shape having a first base near a first conductive layer and a second base near a second conductive layer, said first base being wider than the distance between said first and second bases and said projections individually having a substantially trapezoidal cross-sectional shape.

2. A weighing mat in accordance with claim 1 in which said second base is no wider than said first base and is no less than one-tenth as wide as said first base.

3. A weighing mat in accordance with claim 1 in which the distance between adjacent projections is no greater than the width of said first base.

4. A weighing mat in accordance with claim 1 in which said dielectric layer includes a web integral with said projections and in which the thickness of said web is no greater than one-half the distance between said first and second bases.

5. A weighing mat in accordance with claim 1 in which said conductive and dielectric layers comprise elastomeric materials.

6. A weighing mat in accordance with claim 1 which includes three electrically conductive layers comprising two outer layers and a central layer and which includes two deformable dielectric layers comprising projections of similar cross-sectional shape, with individual ones of said dielectric layers positioned between said outer conductive layers and said central conductive layer and separating said outer conductive layers from said central conductive layer.

7. A weighing mat adapted to be loaded by a range of forces to be measured comprising:

at least two electrically conductive layers separated by a deformable dielectric layer, said deformable dielectric layer comprising projections individually having a cross-sectional shape having a first base near a first conductive layer and a second base near a second conductive layer, said first base being wider than the distance between said first and second bases and the cross-sectional shapes of said projections individually having curvilinear sides between said first and second bases.

8. A weighing mat in accordance with claim 7 in which said projections are elongated ribs.

9. A weighing mat in accordance with claim 1 in which said projections individually have a substantially frusto- conical shape.

10. A weighing mat in accordance with claim 9 in which the spacings between adjacent projections in perpendicular directions is no greater than the width of said first base.

11. A weighing mat in accordance with claim 1 in which said projections individually Have a substantially frusto-pyramidal shape.

12. A mat in accordance with claim 11 in which the spacings between adjacent projections in perpendicular directions is no greater than the width of said first base.

13. A weighing mat in accordance with claim 1 in which said conductive layers comprise elastic material and said dielectric layers comprise elastomeric material.

14. A weighing mat adapted to be loaded by a range of forces to be measured comprising:

at least two electrically conductive layers separated by a deformable dielectric layer, said deformable dielectric layer comprising elongated ribs individually having a cross-sectional shape having a first base near a first conductive layer and a second base near a second conductive layer, said first base being wider than the distance between said first and second bases and said elongated ribs individually having a substantially trapezoidal cross-sectional shape.

15. A weighing mat in accordance with claim 14 in which said second base is no wider than said first base and is no less than one-tenth as wide as said first base.

16. A weighing mat in accordance with claim 14 in which the distance between adjacent ribs is no greater than the width of said first base.

17. A weighing mat in accordance with claim 14 in which said dielectric layer includes a web integral with said ribs and in which the thickness of said web is no greater than one-half the distance between said first and second bases.

18. A weighing mat in accordance with claim 14 in which said conductive and dielectric layers comprise elastomeric materials.

19. A weighing mat in accordance with claim 14 which includes three electrically conductive layers comprising two outer layers and a central layer and which includes two deformable dielectric layers comprising elongated ribs of similar cross-sectional shape, with individual ones of said dielectric layers positioned between said outer conductive layers and said central conductive layer and separating said outer conductive layers from said central conductive layer.

20. A mat in accordance with claim 19 in which said ribs of one dielectric layer are substantially parallel to each other and said ribs of the other dielectric layer are substantially parallel to each other and said dielectric layers are so positioned with respect to each other than said ribs of said one dielectric layer are substantially normal to said ribs of said other dielectric layer.

21. A weighing mat adapted to be loaded by a range of forces to be measured comprising:

three electrically conductive layers comprising elastomeric material and comprising the two outer layers and a central layer;

two dielectric layers comprising elastomeric material and comprising spaced elongated ribs of similar substantially trapezoidal cross-sectional shape with individual ones of said dielectric layers positioned between said outer conductive layers and said central conductive layer and separating said outer conductive layers from said central conductive layer, said cross-sectional shape of said ribs having a first rib base near one of said one of conductive layers and a second rib base near another of said conductive layers, said first rib base being wider than the distance between said first and second rib bases, said second rib base being no wider than said first rib base and no less than one-tenth as wide as said first rib base, the distance between adjacent ribs of each dielectric layer being no greater than the width of said first rib base.

22. A weighing mat in accordance with claim 21 in which each of said dielectric layers includes a weeb integral with said ribs of each dielectric layer and in which the thickness of each web is no greater than one-half the distance between said first and second rib bases.

23. A weighing mat in accordance with claim 14 in which said ribs are disposed symmetrically and obliquely with respect to the outer perimeter of said mat.

24. A weighing mat in accordance with claim 10 in which said spacings between adjacent projections in perpendicular directions are the same.

25. A weighing mat in accordance with claim 10 in which said spacings between adjacent projections in perpendicular directions are different.

26. A weighing mat in accordance with claim 12 in which said spacings between adjacent projections in perpendicular directions are the same.

27. A weighing mat in accordance with claim 12 in which said spacings between adjacent projections in perpendicular directions are different.