Flexible force sensor

• US 4,426,884 A
• Filed: 02/24/1982
• Issued: 01/24/1984
• Est. Priority Date: 02/01/1982
• Status: Expired due to Fees

• Current Assignee: Langer Biomechanics Group Incorporated
• Original Assignee: Langer Biomechanics Group Incorporated
• Inventors: Polchaninoff, Michael
• Primary Examiner(s): Swisher, S. Clement
• Application Number:
  US06/351,961
• Time in Patent Office: 699 Days
• Field of Search: 73/172, 73/862.64, 73/862.68, 338/47, 338/99, 338/114
• US Class Current: 73/172
• CPC Class Codes: A61B 2562/0247 Pressure sensors
• CPC Class Codes: A61B 5/1036 Measuring load distribution, e.g. podologic studies
• CPC Class Codes: A61B 5/1174 using footprinting
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress

Abstract

The flexible force sensor having an electrical conductor releasably attachable to a test site and a plurality of relatively spaced electrical contacts supported for varying contact with the conductor such that when a force is applied to the force sensor, the electrical contacts and electrical conductor move into and out of varying areas of electrical contact to produce electrical resistances therebetween corresponding to the extent of such contact and as a function of the applied force.

Claims

1. A sensor comprising a member of dielectric material defined by inner and outer faces,

electrical contact means on said member with a portion of said contact means substantially aligned with said inner face of said dielectric member, said electrical contact means being substantially non-compressible and of fixed conductivity, and

a flexible conductive member defined by inner and outer faces, the inner one of which is attached to the face of said dielectric member to cover said electrical contact means such that, when a compressive load is applied to the sensor, the load induces an increase in the surface area of contact between facing portions of said conductive member and said contact means to effect a change in the electrical resistance thereacross in proportion to the extent of the applied load and independent of the location over the electrical contact means at which the load is applied.

2. The sensor of claim 1,

electrical lead means electrically coupled to each of said contact means and conductive member to transmit current therefrom.

3. The sensor of claim 1,

said contact means being of curved configuration and being positioned on said dielectric member such that the curved portion thereof is oriented toward and for movement into and out of increased engagement with said conductive member in response to an increase or decrease of the compressive load applied to said sensor.

4. The sensor of claim 3,

wherein there are a plurality of said contact means each being of hemispherical shape,

and electrical leads coupled electrically to each of said plurality of contact means to transmit current therefrom,

said conductive member being movable into and out of increasing or decreasing electrical circuit completing engagement with and across said contact means according to a load applied to said sensor.

5. The sensor of claim 4,

said dielectric and conductive members being of a flexible material.

6. The sensor of claim 5,

releasable adhesive means between said dielectric and conductive members to releasably attach said conductive member to said dielectric member.

7. A force sensor comprising a disposable flexible relatively thin planar electrically conductive member,

a relatively thin flexible permanent member of dielectric material having one face of which is substantially planar and adapted to be detachably affixed to one planar face of said conductive member,

means on said permanent member positioning said electrical contact means and facing one planar face of said disposable conductive member such that the extent of electrical contact between said contact means and conductive member varies in accordance with the extent of a compressive load applied to said sensor to produce a corresponding electrical resistance therebetween,

and means joining said disposable and permanent members together and being releasable to permit their separation and the disposal of said disposable member.

8. The sensor of claim 7,

electrical load means electrically coupled to said electrical contact means and said conductive member to transmit current therefrom.

9. The sensor of claim 7,

said electrical contact means being at least a pair of contact means each being of hemispherical configuration and each being positioned such that the curved portion of each said electrical contact means is directed toward and for varying areas of electrical circuit engagement with said one planar face of said conductive member to transmit varying amounts of current corresponding to that of the applied load.

10. A force comprising a thin flexible permanent electrode having a plurality of spaced electrical contacts supported thereon,

a thin flexible conductive sensor pad defined by two faces,

adhesive means applied to one face of said sensor pad and by which the same is electrically joined to a test site,

adhesive means applied to the other face of said sensor pad to releasably affix the same to said permanent electrode and to define a non-adhesive zone thereon,

said permanent electrode being oriented with respect to said other face of said sensor pad so as to place the electrical contacts in facing opposition to said zone such that when a compressive load is applied across the sensor, the load induces a change in the surface area of contact between facing portions of said zone of said sensor pad and said electrical contacts to correspondingly vary the electrical resistance thereacross.

11. The sensor of claim 10,

said sensor pad being comprised of a conductive silicone rubber,

said adhesive means being on each face of said sensor pad and comprising two stacked adhesive layers each adhered to the other to enable said sensor pad to be adhered to the test site and the other face of said sensor pad to be adhered releasably to said permanent electrode.

12. A pressure transducer comprising a dielectric electrode platform,

electrical contact means on said platform, said contact means being substantially non-compressible and of fixed conductivity,

a flexible conductive member facing said contact means so that the same move into varying extents of engagement in accordance with a pressure applied to the same to effect an electrical resistance that is a function of the pressure applied to the same and independent of the location over the contact means at which the pressure is applied, and

electrical leads connected with said transducer to permit the transmission of said electrical resistance.

13. The transducer of claim 12,

said electrical contact means being curved to present varying areas for engagement with said conductive member according to the applied pressure.

14. The transducer as in claim 13,

said electrical contact means being of hemispherical shape.

15. The transducer of claim 13,

said flexible conductive member being comprised of a carbon impregnated silicone rubber.

16. The transducer of claim 12,

means releasably connecting together said conductive member and dielectric electrode platform to enable their separation and the disposal of said conductive member.

17. A sensor comprising a member of dielectric material defined by inner and outer faces,

electrical contact means on said member with a portion of said contact means substantially aligned with said inner face of said dielectric member,

a flexible conductive member defined by inner and outer faces, the inner one of which is attached to the face of said dielectric member to cover said electrical contact means such that, when a compressive load is applied to the sensor, the load induces an increase in the surface area of contact between facing portions of said conductive member and said contact means to effect a change in the electrical resistance thereacross in proportion to the extent of the applied load, and

releasable adhesive means between said dielectric and conductive members to releasably attach said conductive member to said dielectric member.

18. The sensor of claim 17,

said contact means being of curved configuration and being positioned on said dielectric member such that the curved portion thereof is oriented toward and for movement into and out of increased engagement with said conductive member in response to an increase or decrease of the compressive load applied to said sensor.

19. The sensor of claim 18,

wherein there are a plurality of said contact means, each being of hemispherical shape,

and electrical leads coupled electrically to each of said plurality of contact means to transmit current therefrom,

said conductive member being movable into and out of increasing or decreasing electrical circuit completing engagement with and across said contact means according to a load applied to said sensor.

20. The sensor of claim 19,

said dielectric and conductive members being of a flexible material.

21. A pressure transducer comprising a dielectric electrode platform,

electrical contact means on said platform,

a flexible conductive member facing said contact means so that the same move into varying extents of engagement in accordance with a pressure applied to the same to effect an electrical resistance that is a function of the pressure applied to the same,

electrical leads connected with said transducer to permit the transmission of said electrical resistance, and

means releasably connecting together said conductive member and dielectric electrode platform to enable their separation and the disposal of said conductive member.

22. The transducer of claim 21,

said electrical contact means being curved to present varying areas for engagement with said conductive member according to the applied pressure.

23. The transducer as in claim 22,

said electrical contact means being of hemispherical shape.

24. The transducer of claim 22,

said flexible conductive member being comprised of a carbon impregnated silicone rubber.