Method, equation, design, and construct to provide uniform heating for shaped heaters with improved busbar designs

Abstract

A method, equation, system, and device for electrically heating Indium Tin Oxide (ITO) and other transparent conductive materials having a uniform sheet resistivity for defogging and de-icing in a cold environment. The use of nonparallel busbars for connecting the conductive materials reduces excessive and dangerous hot zones. The mathematical analysis and equations provide a means of precisely providing an intermittent electrical connection so that the Watt density and heating is uniform, allowing much higher temperature for de-icing and defogging and more efficient use of energy. This same concept can be used for three dimensional formed heaters to compensate for non uniform sheet resistivity. Also shown are a means of improved busbar designs and an equation and a means of altering sheet resistivity to produce electric heaters with non parallel busbars of various shapes for uniform heating

1 . A transparent or mirrored heated material of non-uniform width that minimizes the presence of hot spots across a surface of the material comprising:
 a substrate layer defining the shape of the surface;   a conductive film layered over the substrate layer; and   two busbars, where a first busbar is positioned at a top outer edge of the surface and the second busbar is positioned at a bottom outer edge of the surface, wherein a contact between the two busbars and the conductive film is intermittent through the use of a dielectric coating positioned between the busbars and the conductive film, wherein a width of non-contact portions between the conductive film and the busbars as a result of the dielectric coating increases as a function of a decrease in a distance defined by a linear path between the two busbars, and wherein a width of contact portions between the busbars and the conductive film, is constant.   
     
     
         2 . The material as defined in  claim 1 , wherein the conductive film is indium tin oxide. 
     
     
         3 . The material as defined in  claim 1 , wherein the dielectric coating includes a plurality of dielectric spacers that are positioned intermittently between the busbars and the conductive film, and wherein the width of the plurality of dielectric spacers, defining the width of the non-contact portions, increases as a function of a decrease in the distance defined by a linear path between the two busbars. 
     
     
         4 . The material as defined in  claim 1 , wherein the dielectric coating prevents a continuous busbar from contacting the conductive film except where the busbar protrudes past the dielectric coating making contact with the conductive film. 
     
     
         5 . The material as defined in  claim 1 , wherein the busbars are imbedded in the substrate. 
     
     
         6 . The material as defined in  claim 5 , wherein the embedded busbars are coated with a conductive material for improving a contact between the embedded busbars and the conductive film. 
     
     
         7 . Heated goggles comprising a lens composed of the material as defined in  claim 1 . 
     
     
         8 . A helmet comprising a visor composed of the material as defined in  claim 1 . 
     
     
         9 . A transparent or mirrored heated material of non-uniform width that minimizes the presence of hot spots across a surface of the material comprising:
 a substrate layer defining the shape of the surface;   a conductive film layered over the substrate layer; and   two busbars, where a first busbar is positioned at a top outer edge of the surface and the second busbar is positioned at a bottom outer edge of the surface,   wherein sheet resistivity of the conductive film varies as a function of a distance defined by a linear path between the two busbars, wherein the sheet resistivity increases as the distance defined by a linear path between the two busbars decreases in order to improve uniform heating across the surface.   
     
     
         10 . The material as defined in  claim 9 , wherein the sheet resistivity is increased by providing voids or holes in the conductive film, and wherein at least one of the number and density of the voids and holes increases as the distance defined by a linear path between the two busbars decreases. 
     
     
         11 . The material as defined in  claim 9 , wherein the sheet resistivity is decreased by providing conductive dots in the conductive film, and wherein at least one of the number and density of the dots increases as the distance defined by a linear path between the two busbars increases. 
     
     
         12 . Heated goggles comprising a lens composed of the material as defined in of  claim 9 . 
     
     
         13 . A lens configured for uniform heating comprising:
 a substrate layer defining a shape of the lens;   a conductive film applied to the substrate layer;   busbars imbedded in the substrate layer at given intervals across the substrate layer, wherein the imbedded busbars contact the conductive film; and   a coating of a conductive material applied to the busbars to improve contact between the busbars and the conductive film.   
     
     
         14 . The lens as defined in  claim 13 , where the substrate layer comprises a top half and a bottom half, and wherein the busbars are embedded in the substrate layer by being sandwiched between the top half and the bottom half. 
     
     
         15 . The lens as defined in  claim 13 , wherein the busbars are embedded in the substrate layer by passing current through the busbars, causing the busbars to heat and melt the substrate layer, resulting in busbars embedding in the substrate layer. 
     
     
         16 . The lens as defined in  claim 13 , wherein the substrate layer has a non-uniform width, and wherein the busbars follow the shape of the lens. 
     
     
         17 . Goggles comprises the lens as defined in  claim 13 . 
     
     
         18 - 20 . (canceled)