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US 4,070,544 AGranted
Electrographic apparatus and method of producing an electrode surface therefor
AssigneeQuest Automation Limited
InventorMartin Roy Lambden
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AssigneeQuest Automation Limited
InventorMartin Roy Lambden
Estimating the term…
Electrographic apparatus, that is apparatus for obtaining electrical signals related to the movement of a point, such as a pen or stylus, over a pressure sensitive surface, and a method of producing an electrode surface for such apparatus. The pressure sensitive surface is formed by the upper surface of a taut flexible membrane. Two generally parallel electrode surfaces are formed by electrically conductive coatings on the lower surface of the flexible membrane and on an upper surface of a backing member so that pressure applied to the pressure sensitive surface locally interconnects the electrode surfaces. In use, voltages are applied orthogonally to the respective electrode surfaces so that the potentials developed at points on the surfaces correspond to the X and Y coordinates of those points. The method of forming such an electrode surface comprises the steps of forming the coating so as to have a region of high resistivity traversed by parallel lines of low resistivity, the lines being interconnected by film resistor tracks, and selectively removing portions of the film material of the resistor tracks to provide uniform potential gradients between adjacent pairs of the lines when a voltage is applied to the electrode surface. The membrane is substantially uniformly tensioned by springs, and the upper surface of the backing member is concave so that the force required to be applied to the membrane to cause the membrane to contact the upper surface of the backing member is substantially independent of the location at which the force is applied.
A method of producing an electrode surface for electrographic apparatus, comprising the steps of forming on an insulating surface an electrically conducting coating comprising a series of elongated, separate strips of low surface resistivity interconnected by areas of high surface resistivity, providing connection means electrically connected with said coating so that the potential gradient developed in said coating in response to voltage supplied to said connection means is substantially orthogonal to the direction of elongation of said strips, and adjusting the total resistances between respective adjacent pairs of said low surface resistivity strips so as to substantially equalize the mean potential gradients which are developed across respective ones of said high surface resistivity areas in response to such voltage supplied to said connection means.
Electrode surface means for electrographic apparatus, said electrode surface means comprising an insulating support member, an electrically conductive coating on a surface of said support member comprising a series of elongated separate strips of low surface resistivity material interconnected by areas of high surface resistivity material connection means electrically connected with said coating so that the potential gradient developed in said coating in response to voltage supplied to said connection means is orthogonal to the direction of elongation of said strips, and means for adjusting the total resistance between respective adjacent pairs of said strips.
Electrographic apparatus comprising an electrically insulating backing member formed with a first surface, a first electrically conductive coating on said first surface, a taut membrane of electrically insulating flexible material including a working area disposed in a plane adjacent said first surface and presenting thereto a second surface, a second electrically conductive coating on said second surface and electrically isolated from said first coating, at least one of said first and second coatings comprising a series of elongated, separate parallel strips of low surface resistivity material interconnected by areas of high surface resistivity material, connection means for connecting a voltage to said at least one of said first and second coatings in a direction substantially orthogonal to the direction of elongation of said strips, and means for adjusting the total resistances between respective adjacent pairs of said strips of said at least one of said coatings.
Dependencies are inferred from the claim text.