ELECTRICAL WEIGHING APPARATUS USING CAPACITIVE FLEXIBLE MAT

• US 3,565,195 A
• Filed: 04/16/1969
• Issued: 02/23/1971
• Est. Priority Date: 04/16/1969
• Status: Expired due to Term

• Current Assignee: Nippon Dyne-A-Mat Corp.
• Original Assignee: Marvin Miller, Robert P. Miller, Stephen P. Bailey
• Inventors: Miller, Robert P., Miller, Marvin, Bailey, Stephen P.
• Application Number:
  US04/816,692
• Time in Patent Office: 678 Days
• US Class Current: 177/210.00R
• CPC Class Codes: G01G 7/06 by electrostatic action

Abstract

Weighing apparatus is disclosed comprising electronic circuitry and a weighing mat adapted to be loaded by a force to be measured. The mat is composed of layers of electrically conductive elastomeric material separated by strips of dielectric elastomeric material to form an electrical capacitor whose capacitance varies linearly with the application of a load to the mat. The particular arrangement of the dielectric strips in the preferred embodiment serves to extend the effective linear range of capacitive variation of the mat. Electronic circuitry is also provided to measure the variation of capacitance of the mat when the mat is loaded and to give an indication corresponding to the magnitude of the load.

Claims

1. Weighing apparatus comprising a weighing mat adapted to be loaded by a range of forces to be measured, said mat comprising at least two electrically conductive strata separated by a deformable dielectric layer having an essentially linear deformation characteristic when the mat is loaded by said range of forces, whereby the electrical capacity of the weighing mat varies in accordance with the magnitude of the load applied to said mat.

2. Weighing apparatus according to claim 1, further comprising means connected to said strata for measuring the electrical capacitance of said mat.

3. Weighing apparatus according to claim 1, further comprising means connected to said strata for measuring the change of electrical capacitance of the mat upon the application of a load to said mat.

4. Weighing apparatus comprising a weighing mat adapted to be loaded by a force to be measured, said mat comprising:

a. a first electrically conductive stratum;

b. a second electrically conductive stratum formed of a deformable elastomeric material;

c. a plurality of first dielectric elastomeric elements arranged in spaced relationship with each other and separating said first and second strata;

d. a third electrically conductive stratum; and

e. a plurality of second dielectric elastomeric elements arranged in spaced relationship with each other and separating said second and third strata.

5. Weighing apparatus according to claim 4, wherein said first dielectric elastomeric elements comprise a first plurality of elastomeric strips arranged in spaced parallel relationship with each other, and said second dielectric elastomeric elements comprise a second plurality of elastomeric strips arranged in spaced parallel relationship with each other and in nonparallel relationship with said first plurality of elastomeric strips.

6. Weighing apparatus according to claim 4, further comprising means for electrically connecting said first and third strata, and circuit means connected to said first and second strata for measuring the electrical capacitance of the mat.

7. Weighing apparatus according to claim 4, further comprising means for electrically connecting said first and third strata, and circuit means connected to said first and second strata for measuring the change in electrical capacitance of the mat upon the application of a load to said mat.

8. Weighing apparatus according to claim 6, wherein said circuit means comprises constant current means for charging said mat to a predetermined voltage and timer means for measuring the time required to charge said mat to said voltage.

9. Weighing apparatus according to claim 7, wherein said circuit means comprises constant current means for charging said mat to a predetermined voltage, a timer means for measuring the time required to charge said mat to said voltage, and comparator means for comparing the times required to charge the mat to said voltage under two different loading conditions.

10. Weighing apparatus according to claim 9, further comprising automatic means for periodically connecting said constant current means to said mat, and switching means for periodically discharging said first and second strata when said constant current means is not connected to them.

11. Weighing apparatus according to claim 4, wherein said first and third strata are formed of a deformable, elastomeric material.