PRESSURE RESPONSIVE RESISTIVE MATERIAL

• US 3,806,471 A
• Filed: 04/29/1968
• Issued: 04/23/1974
• Est. Priority Date: 04/29/1968
• Status: Expired due to Term

• Current Assignee: Mitchell R
• Original Assignee: Mitchell R
• Inventors: MITCHELL R
• Application Number:
  US04/724,791
• Time in Patent Office: 2,185 Days
• US Class Current: 252/519.31
• 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
• CPC Class Codes: H01B 1/22 the conductive material comprising metals or alloys
• CPC Class Codes: H01C 10/106 on resistive material dispersed in an elastic material H01C10/103 and H01C10/12 take precedence; for electric switches H01H1/029
• CPC Class Codes: H01H 1/029 comprising conducting material dispersed in an elastic support or binding material

Abstract

MATERIALS AND SENSING ELEMENTS HAVING CONTROLLED CHANGES OF RESISTANCE VALUES IN RESPONSE TO PRESSURE ARE PROVIDED BY VOLUMETRICALLY DISPERSING CONDUCTIVE OR PARTIALLY CONDUCTIVE PARTICULATES OF AT LEAST ONE TYPE THROUGHOUT A PREDETERMINED VOLUME. THE PARTICULATE MASS IS FINTIELY BUT MINUTELY COMPRESSIBLE IN AT LEAST ONE DIMENSION, BUT CONFINED IN OTHER DIMENSIONS WITHIN AN ENCOMPASSING STRUCTURE OR BY A BINDER OR MATRIX. THE PARTICLE DISPERSION IS SUCH THAT WITHOUT APPLIED PRESSURE THE ELEMENT, TYPICALLY FORMED IN A RELATIVELY THIN STRATUM, HAS A COMPOSITE RESISTANCE, VALUE DETERMINED BY MULTIPLE CURRENG FLOW PATHS, AND THIS VALUE MAY BE SO HIGH AS TO RENDER THE MATERIAL ESSENTIALY NONCONDUCTIVE. APPLIED OR INCREASED PRESSURE COMPACTS THE PARTICLES SUCH AS TO INCREASE THE NUMBER OF CURRENT FLOW PATHS. INCREASE TO CONTACT AREA BETWEEN PARTICLES AND THEREOFORE THE ARE OF THE CURENT FLOW PATHS, AND ALSO INCREASE INTERNAL STRAINS, WHILE DECREASING THE INTER-PARTICLE CONTACT RESIDENCE AND THE FLOW PATH LENGTHS, ALL THESE FACTORS CONCURRENTLY ACTING TO DECREASE THE RESISTANCE OF THE ELEMENT. THE COMPRESSION AND MOVEMENT ARE VERY LIMITED IN EXTENT, AND THE CURRENT FLOW IS CHANGED IN ESSENTIALLY SOLID STATE FASHION, WITHOUT ARCING OR CROSS-OVER. PARTICULATES, BINDERS AND BUFFERING POWDERS ARE DISCLOSED THAT ARE SUBJECT TO MINIMUM HYSTERESIS EFFECTS AND WEAR. THE RATE OF RESISTANCE CHANGE OF PRESSURE, AND THE RANGE OF RESISTANCE VALUES ARE CONTROLLED AND SELECTED BY VARIATION OF A NUMBER OF FACTORS, INCLUDING THE PROPERTIES AND RATIOS OF THE MATERIALS USED, THE THICKNESS OF THE ELEMENT, THE AREA UNDER COMPRESSION, THE APPLIED VOLTAGE AND THE CONFIGURATION AND SPACING OF COUPLED ELECTRODES.

Claims