Patent ID: 6388452
Filing Date: 2002-05-14
Classification: B41J,B65H,G01B,G03G

Abstract:
A device for capacitively sensing media thickness, comprising:a first support; a second support; and a variable-capacitance capacitor comprising first and second electrodes having a variable gap disposed intermediate between the electrodes, and a dielectric medium disposed in the variable gap, the first electrode is disposed on a portion of the first support, the second electrode is disposed on a portion of the second support, and the dielectric medium is a dielectric selected from the group consisting of a vacuum and a gas, either one of the supports is movable relative to the other support and the supports are configured so that the electrodes are disposed opposite each other in substantially facing relation and are spaced apart by a first distance, and wherein the electrodes are spaced apart by a second distance when the media and either one of supports are urged into contact with one another thereby displacing the supports relative to each other so that the electrodes move from the first distance to the second distance, the media itself is not disposed between the electrodes, and the thickness of the media is derived, irrespective of the dielectric properties of the media, by electronically measuring a capacitance between the electrodes, and the capacitance between the electrodes is determined by the second distance between the electrodes and a dielectric constant of the dielectric medium disposed in the variable gap.