Method of making an electrically conductive strain gauge material

• US 5,858,291 A
• Filed: 03/04/1997
• Issued: 01/12/1999
• Est. Priority Date: 03/04/1997
• Status: Expired due to Fees

• Current Assignee: Department of Health and Human Services (State of Victoria)
• Original Assignee: United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration
• Inventors: Pesek, Todd A., Li, Larry C.H., Dawn, Frederic S.
• Primary Examiner(s): ORTIZ, ANGELA Y
• Application Number:
  US08/810,582
• Time in Patent Office: 679 Days
• Field of Search: 264/104, 264/105, 264/125, 264/145, 264/146, 264/148, 264/151, 264/160, 264/163, 252/500, 252/511
• US Class Current: 264/105
• CPC Class Codes: B29C 2791/001 Shaping in several steps
• CPC Class Codes: B29C 2793/009 after shaping
• CPC Class Codes: B29C 43/00 Compression moulding, i.e. applying external pressure to flow the moulding material; Apparatus therefor by liberation of internal stresses B29C61/006
• CPC Class Codes: B29C 70/882 partly or totally electrically conductive, e.g. for EMI shielding conductive floors or floor coverings H05F3/025; EMI shielding in general H05K9/00
• CPC Class Codes: B29C 71/02 Thermal after-treatment B29C71/0063 and B29C71/0072 take precedence
• CPC Class Codes: B29D 28/00 Producing nets or the like, e.g. meshes, latticesby knotting D04G
• CPC Class Codes: B29K 2021/00 Use of unspecified rubbers as moulding material
• CPC Class Codes: B29L 2031/48 Wearing apparel

Abstract

An improved elastomeric electrically conductive strain gauge for use in virtual reality systems is disclosed which involves the flash heating of a doped ethylene vinyl acetate elastomer.

Claims

1. A method for the preparation of an electrically conductive strain gauge material having an electrical resistance which varies with elastic extension and contraction comprising the steps of:

blending an effective amount of conductive particles with a finely divided ethylene vinyl acetate copolymer for a sufficient time to produce uniform mixture of the conductive particles throughout the polymer;

pressing the mixture into a sheet having a thickness of from about 1/32" to about 1/8";

cutting strips of the film and pressing the sheet to a substantially uniform thickness of about 10 mils;

dimensioning the strips for use as strain gauge material; and

flash-heating the strips to a temperature of at least about 600°

F. for a period of at least about three seconds.

2. The method of claim 1 wherein the conductive material is a carbon black.

3. The method of claim 2 wherein the carbon black is present in an amount of from about 20% to about 50% by weight.

4. The method of claim 1 wherein the dimensions of the strips are from about 1/8 to 3/8 inches to about 7/8 to 5 inches long.

5. The method of claim 1 wherein the flash heat was applied for a time of from about 3 to about 20 seconds.

6. The method of claim 5 wherein the temperature of the flush treated material was from about 600°

to about 750°

F.

7. The method of claim 1 which includes the additional step of conditioning the strain gauge material with a sufficient number of stretch cycles to achieve consistency of result.

8. A method for the preparation of an electrically conductive strain gauge material having an electrical resistance which varies with elastic extension and contraction comprising the steps of:

blending an effective amount of conductive particles with a finely divided copolymer for a sufficient time to produce uniform mixture of the conductive particles throughout the polymer;

pressing the mixture into a flexible sheet having a predetermined thickness;

cutting strips of the film and pressing the sheet to a substantially uniform thickness less than the predetermined thickness;

dimensioning the strips for use as strain gauge material; and

flash-heating the strips to a temperature of at least about 600°

F. for a period of at least about three seconds.

9. The method of claim 8 wherein the conductive material is a carbon black.

10. The method of claim 9 wherein the carbon black is present in an amount of from about 20% to about 50% by weight.

11. The method of claim 8 wherein the flash heat is applied for a time of from about 3 to about 20 seconds.

12. The method of claim 10 wherein the temperature of the flush treated material is from about 600°

to about 750°

F.

13. The method of claim 8 which includes the additional step of conditioning the strain gauge material with a sufficient number of stretch cycles to achieve consistency of result.