Flexible force sensor

• US 4,503,705 A
• Filed: 03/14/1983
• Issued: 03/12/1985
• Est. Priority Date: 02/24/1982
• 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:
  US06/475,085
• Time in Patent Office: 729 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: 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 and/or paths of electrical contact to produce electrical resistances therebetween corresponding to the extent of such areas and/or paths and as a function of the applied force.

Claims

1. For use with a sensor comprising a body having spaced electrodes, a conduction sensor pad comprising a sheet of flexible conductive material having upper and lower faces and shaped to be received on said sensor body and to span the space between said electrodes, said lower face of said sheet being adapted to be secured to said sensor body and having adhesive portions to engage said body, said adhesive portions being spaced from one another at a location corresponding to the space between said electrodes, said upper face of said sheet having an adhesive portion adapted to be secured to a test site on the person of an individual.

2. The sensor pad of claim 1, in which said adhesive portions respectively comprise double-sided adhesive tapes.

3. The sensor pad of claim 2, in which at least one of said adhesive portions comprises two superposed layers of double-sided adhesive tape.

4. The sensor pad of claim 1, in which said sheet is formed of carbon-impregnated silicone rubber.

5. The sensor pad of claim 1, in which said sheet is formed of an insulative rubber having a conductive coating operatively disposed on the lower face thereof intermediate said adhesive portions.

6. The sensor pad of claim 5, in which said insulative rubber is neoprene and said conductive coating is a conductive acrylic.

7. The sensor pad of claim 1, in which said sheet comprises a thin flexible plastic film having a coating of conductive ink disposed on the lower face thereof intermediate said adhesive portions.

8. The sensor pad of claim 7 wherein said plastic film is formed of an insulative polyester.

9. The sensor pad of claim 1 in which said sheet is a laminate comprising a thin flexible plastic layer defining the upper face of said sheet, a thin flexible conductive layer defining the lower face of said sheet intermediate said adhesive portions, and a thin flexible compressible elastomeric layer disposed intermediate said plastic layer and said conductive layer.

10. The sensor pad of claim 9, in which said adhesive portions respectively comprise double-sided adhesive tapes.

11. The sensor pad of claim 10, in which at least one of said adhesive portions comprises two superposed layers of double-sided adhesive tape.

12. A sensor comprising a member of dielectric material defined by inner and outer faces;

at least one spaced pair of electrical contact means on said inner face of said dielectric member;

electrical lead means electrically coupled to each of said pair of contact means; and

a flexible conductive member operatively connected to said dielectric member and having an inner face overlying the inner face of said dielectric member to cover said contact means;

said sensor being characterized by said pair of contact means defining therebetween a geometric dielectric pattern;

said conductive member having an electrical resistivity different from that of said contact means and being adapted for movement into and out of increased engagement with said contact means on opposite sides of said pattern in response to a variation in the compressive load applied to said sensor; and

said pair of contact means being configured and dimensioned such that, when a compressive load is applied to said sensor, the load induces a variation in the mean length of the travel path of current between said contact means of said pair through said conductive member.

16. The product of any of claims 12-15 wherein said conductive member has a different electrical resistivity than said contact means;

and said pair of contact means is configured and dimensioned such that, when a compressive load is applied to said sensor, the load induces an increase in the surface area of contact between facing portions of said conductive member and said contact means, thereby to effect a variation in the mean length of the travel path of current between said contact members of said pair through said conductive member and so change the electrical resistance across said contact means in proportion to the extent of the applied load.

17. The product of claim 16 wherein said conductive member has a greater electrical resistivity than said contact means, and the variation in the mean travel path of the current is a decrease.

18. The product of any of claims 12-14 wherein said geometric dielectric pattern has a periphery sloping towards the centerline of said pair of contact means as the periphery approaches the ends of the centerline.

19. The product of any of claims 12, 13 and 15 wherein said geometric dielectric pattern is configured as a diamond.

20. The product of any of claims 12-15, wherein said conductive member is comprised of an insulative rubber and has on its inner face an electrically conductive coating.

21. The product of claim 20, wherein said flexible conductive member comprises an acrylic coated neoprene.

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

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

at least one spaced pair of electrical contact means on said one face of said dielectric member;

electric lead means electrically coupled to each of said pair of contact means;

means on said dielectric member for positioning said contact means facing said one planar face of said 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 conductive and dielectric members together and being releasable to permit their separation and the disposal of said conductive member;

said sensor being characterized by each said pair of contact means defining therebetween a geometric dielectric pattern and being covered by said one planar face of said conductive member, and said conductive member being adapted for movement into and out of increased engagement with said contact means on opposite sides of said pattern in response to variations in the extent of a compressive force applied to said sensor to produce a corresponding electrical load across said electrical lead means.

14. A force sensor comprising a thin, flexible permanent electrode having at least one spaced pair of electrical contact means supported thereon;

a thin, flexible conductive sensor pad having a flexible conductive member defined by two faces;

adhesive means disposed on one face of said sensor pad to electrically join same to a test site; and

adhesive means disposed on 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 said contact means in facing opposition to said non-adhesive 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 non-adhesive zone and said contact means to correspondingly vary the electrical resistance thereacross;

said sensor being characterized by said contact means having a different electrical resistivity than said non-adhesive zone, each said pair of contact means defining therebetween a dielectric pattern in the shape of a diamond, and said non-adhesive zone being adapted for movement into and out of increased engagement with said contact means on opposite sides of said pattern in response to an increase or decrease of the compressive force applied to said sensor, such that, when the compressive load on said sensor is changed, the load also induces a change in the mean length of the travel path of current between said contact means of said pair through said non-adhesive zone.

15. A pressure transducer comprising a dielectric electrode platform;

at least one spaced pair of 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 an inverse function of the pressure applied to the same;

electrical leads connected with said transducer to permit the transmission of said electrical resistance, said electric lead means being electrically coupled to each of said contact means of said pair;

said transducer being characterized by each said pair of contact means defining therebetween a geometric dielectric pattern having a periphery sloping towards the centerline of said pair of contact members as the periphery approaches the ends of the centerline, and said conductive member being adapted for movement into and out of increased engagement with said contact means on opposite sides of said pattern in response to an increase or decrease of the compressive force applied to said sensor, such that, when a compressive load is applied to said transducer, the load also induces a variation in the mean length of the travel path of current between said contact members of said pair through said conductive member and so change the electrical resistance across said contact means in proportion to the extent of the applied load.