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

Claims

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)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0123] The features and advantages of the present teachings will become apparent from the following description taken in connection with the accompanying drawings.

[0124] FIG. 1 is a schematic of a prior art ITO lens and connections used for defogging goggles and visors.

[0125] FIG. 2 is a schematic of and derivations of Watt density for parallel busbars separated by distance L.

[0126] FIG. 3A is a front view of an exemplary portion of a lens configured implementing a first method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings.

[0127] FIG. 3B is a side view of the exemplary portion of the lens of FIG. 3A implementing the first method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings.

[0128] FIG. 3C is a front view of an exemplary portion of a lens configured implementing a second method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings.

[0129] FIG. 3D is a side view of the exemplary portion of the lens of FIG. 3C implementing the second method of providing intermittent electrical connection with transparent conductive film using clear dielectric printed elements and continuous printed (silk-screened) silver busbars incorporating the present teachings.

[0130] FIG. 4A is a front view schematic of an exemplary derivation of dielectric spacing and electric contact spacing to have uniform heating of the present teachings.

[0131] FIG. 4B is a side view schematic of the exemplary derivation of FIG. 4A of dielectric spacing and electric contact spacing to have uniform heating of the present teachings.

[0132] FIG. 5 is a schematic of and computation of an exemplary dielectric and silver busbar spacing and contact for defogging of a goggle, visor, or other device incorporating the present teachings.

[0133] FIG. 6 is a schematic illustrating exemplary resistance distribution when using tapered busbars for more efficient use of silver and a better viewing area provided by the present teachings.

[0134] FIG. 7A is a schematic of top view of carbon underfloor heaters and busbars.

[0135] FIG. 7B is a side view schematic of the prior art carbon underfloor heaters and busbars shown in FIG. 7A.

[0136] FIG. 8A is a schematic of a front view of an exemplary first type of vacuum formed conductive transparent three-dimensional shapes and busbars for defogging using the present teachings.

[0137] FIG. 8B is a cross-section of the exemplary first type of vacuum formed conductive transparent three-dimensional shapes and busbars of FIG. 8A for defogging using the present teachings.

[0138] FIG. 8C is a schematic of a top cross-sectional view of an exemplary second type of vacuum formed conductive transparent three-dimensional shapes and busbars for defogging using the present method for printing busbars.

[0139] FIG. 9A is a schematic of an exemplary first device and method for providing uniform heating with odd-shaped heaters using an intermittently spaced carbon conductor and uniform busbars using the present teachings.

[0140] FIG. 9B is a schematic of an exemplary second device and method for providing uniform heating with odd shaped heaters using a dielectric and uniform busbars using the present teachings.

[0141] FIG. 9C is a schematic of an exemplary third device and method for providing uniform heating with odd shaped heaters using a variable sheet resistance and uniform busbars using the present teachings.

[0142] FIG. 10 is a schematic of a prior art ITO lens with busbars and connections used for defogging goggles and visors.

[0143] FIG. 11 is a schematic view of an exemplary ITO lens with a scored electrically discontinuous ITO portion using the present teachings.

[0144] FIG. 12 is a schematic view of an exemplary ITO lens using scored ITO in combination with printed clear dielectric to provide electrically isolated cold zone using the present teachings.

[0145] FIG. 13 is a schematic view of an exemplary ITO lens using laser cut or die cut holes in the ITO in combination with printed clear dielectric to provide electrically isolated cold zone using the present teachings.

[0146] FIG. 14 is a perspective schematic view of an exemplary ITO/polycarbonate sandwich using the present teachings.

[0147] FIG. 15 is a perspective schematic view of an exemplary ITO/polycarbonate lens showing a silver/copper wire and silver connecting trace using the present teachings.

[0148] FIG. 16 is a sectional side schematic of an exemplary ITO/polycarbonate lens showing embedded silver/copper wire busbars and a coating of transparent PEDOT conductive polymer on a transparent polycarbonate substrate using the present teachings.

[0149] FIG. 17 is a thermograph of a prior art printed lens such shown in FIG. 10 illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C.

[0150] FIG. 18 is a thermograph of a continuously scored lens such shown in FIG. 12 illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C.; and

[0151] FIG. 19 is a drawing of a top-down view of an exemplary shield with imbedded wire heaters in accordance with the present teachings.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0152] Reference will now be made in detail to the preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to those embodiments. On the contrary, the invention is intended to cover alternatives, modifications, and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Those of ordinary skill in the art would understand that “busbars”, “coatings”, and “sheet resistivity” are terms known in the industry such that these terms would not be limited to the means explicitly disclosed in this specification.

[0153] FIG. 1 shows an existing design of a lens for heated goggles. A uniform coating of conductive material on a polymer film is shown on the lens. Typically, Indium Tin Oxide (ITO) is used as the coating 5. However, other transparent conductive materials can be used as the coating, such as, but not limited to, other transparent conducting oxides (TCO), graphene, carbon nanotubes, and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), to name a few. The lens substrate may be a clear material, such as, but not limited to, polymer, glass, or ceramic, to name a few.

[0154] The coating 5 may have a range of sheet resistivity of 10-60 Ohm/□, and preferably 10-45 Ohm/□, preferably using a 10-12-volt power source. The more conductive the conductive material, the lower the power voltage source needed. For the exemplary embodiments disclosed herein, the coating 5 is applied to the lens substrate using a suitable technique, such as, but not limited to, sputtering, chemical vapor deposition, and sol-gel, to name a few.

[0155] Conductive silver busbars 4 are applied along the top of the lens and along the bottom of the lens for providing electrical power to the coating 5. The busbars 4 are printed using an ink with a typical resistivity of 0.15 Ohms/□. Note that in this innovative design the lower busbar 4 is discontinuous, therefore requiring multiple electrical connections between the busbar(s) 4 and the power source 6. For example, three electrical connections 1, 2, 3 are shown in the example embodiment of FIG. 1, one to the single top busbar 4, and one each to the two lower busbars 4. Some type of wiring is required from the power source 6 to the busbars 4, using rivets to attach wires. Some designs use a continuous uniform width of busbars 4, that attach to some power source 6 or battery. The busbars 4 can be applied to the lens substrate using a suitable technique, such as, but not limited to, printing, silk-screening, and using an inkjet type of printer, to name a few.

[0156] In the exemplary lens of FIG. 1, power, typically from a battery or other similar power source 6, is applied to the busbars 4. This power is conducted across the uniform coating 5 of conductive material and therefore across the lens, causing the coating 5 to heat up, therefore defogging or de-icing the lens. The power source 6 can be any suitable power source, such as, but not limited to, batteries, solar cells, and from an engine or battery of a snowmobile or other machine, to name a few.

[0157] In a typical prior art goggle or lens, the distance Lx (also referred to as the width herein) between the upper busbar 4 and the lower busbar 4 bar varies depending on the design. For example, as shown in FIG. 1 for a common lens design, the distance L2 is about one-half the distance L1. This can lead to an extremely high temperature in the L2 zone—hot enough at room temperature to be extremely uncomfortable to the touch and produce distortion and wasted energy. This high non-uniform temperature would require a bulky expensive battery adding cost to the product.

[0158] FIG. 2 is a generalized schematic showing the theory behind the heating of a coating 5 using busbars 8, 9, the coating 5 being a uniform conductive material 10 on a lens. In this schematic, the busbars 8, 9 are formed on a lens or other surface having a width W and are separated by some distance L. The resistance R to the applied voltage (V) is

[00010]$R=\rho \frac{L}{W}$

where L is the length between busbars 8 and 9, and ρ is the sheet resistance of the coating 5 in Ohms/□. The power in Watts is I.sup.2R where I is the current amps. As

[00011]$I=\frac{V}{R},$

the power

[00012]$P={\left(\frac{v}{R}\right)}^2\rho =\frac{V^{2}W}{\rho L}.$

The power density is

[00013]$P\rho =\frac{V^{2}W}{\rho L\left(\mathrm{WL}\right)}$

where (WL) is the area so the power density is

[00014]$P\mathrm{\rho }=\frac{V^2}{\rho L^2}$

or Watts/□. Depending on the free convection constant K, it can be said that the ΔT the temperature rise equation is equation (1)

[00015]$\Delta T=K\frac{V^2}{\rho L^2}.$

[0159] Based on the above, it can be seen that in FIG. 1 where L.sub.2 is approximately one-half of L.sub.1, the temperature rise ΔT of the uniform conductive material 10 when power is applied between the busbars 8, 9 and across the uniform conductive material 10 will be four times greater than when L.sub.2 is equal to L.sub.1. This can severely limit the function of the goggles if, for example, it is snowing at −20° C. or lower. The viewing area L.sub.1 preferably has a ΔT=25° C. so as to melt the snow, but if L.sub.2 is approximately one-half of L.sub.1, L.sub.2 would have a ΔT=100° C., which at room temperature could distort or destroy the goggles. A range for ΔT can be from about 10° C. to about 40° C. such that the temperature of the goggles is brought up to an actual temperature sufficient to defog/deice the goggles. More specifically, the ΔT should be sufficient to bring the temperature of the goggles to an actual temperature sufficient to defog/deice the goggles.

[0160] To avoid these problems, the present teachings contemplate providing an intermittent electrical contact with a transparent dielectric material 13 while still providing a continuous busbar 4 as shown in FIGS. 3A and 3B.

[0161] FIG. 3A is a front view and FIG. 3B is a side view of a portion of an exemplary lens implementing a first method of providing intermittent electrical connection with a transparent conductive film 11 using clear dielectric material 13 as printed elements and printed (silk-screened) silver busbars 14 incorporating the present teachings. More specifically, FIGS. 3A and 3B show a continuous clear dielectric material 13 printed on the conductive material 11, which is ITO deposited on some optically clear polymer film 12. A continuous layer of silver conductive busbar 4 is printed with a small segment of busbar 14 extending over the dielectric material 13 and making electrical contact with the ITO. In the example shown in FIGS. 3A and 3B, the base is polymer 12. Completely coating the polymer 12 base is the conductive material 11. Next, the dielectric material 13 is coated over the conductive material 11. As shown, the dielectric material 13 is a continuous strip on the conductive material 11 over the entire width from left to right in FIG. 3A. Next is the silver busbar 14 on top of the dielectric material 13, silver busbar 4 being entirely on top of the dielectric material 13 and not touching the conductive material 11 except for the small segments of busbar 14 touching the conductive material 11 as shown in FIGS. 3A and 3B. The layers of construction of this first method are shown in the side view of FIG. 3B.

[0162] FIG. 3C is a front view and FIG. 3D is a side view of a portion of an exemplary lens implementing a second method of providing intermittent electrical connection with a transparent conductive film 11 using clear dielectric material 13 as printed elements and printed (silk-screened) silver busbars 4 incorporating the present teachings. More specifically, FIGS. 3C and 3D show an alternate and preferred way of making intermittent contact, as this structure uses less dielectric material 13 and less silver busbar 4, 14 material than, for example, the lens shown in FIGS. 3A and 3B. Here, a transparent dielectric material 13 is printed in busbar segment 14 as so to prevent electrical contact of the continuous printed busbars 4 from making electrical contact with the ITO conductive film 11. The dielectric material 13 is preferably transparent so as to not interfere with the user's vision through the goggles. The dielectric material 13 is shown as discontinuous portions (e.g. squares) on the conductive material 11 so as to not allow contact between the silver busbar 14 and the conductive material 11. Next is the silver busbar 14 on top of the dielectric material 13 squares and also partially on top of the conductive material 11. The small segments 14 shown in FIGS. 3A and 3B touching the conductive material 11 are generally the equivalent of the areas 14 shown in FIG. 3C that is not on top of the dielectric squares 13 and that is touching the conductive material 11. The layers of construction of this lens implementing the second method are shown in the side view of FIG. 3D.

[0163] FIG. 4A is a front view and FIG. 4B is a side view schematic of and derivation of the spacing of the dielectric material 24 and the spacing of the electric contact so as to have uniform heating of the present teachings. The example structure shown in FIGS. 4A and 4B has the same general structure as the structure shown in FIGS. 3C and 3D. FIGS. 4A and 4B show the continuous busbars 25 printed over clear dielectric material 24, connected to a voltage power supply 21, with the busbars having intermittent contact with the conductive material 23 due to the presence of the (squares of the) dielectric material 24. The heating or Watt density

[00016]$\frac{V^2}{\rho L_2^2}\left(\frac{W}{W+M}\right)=P.$

The term

[00017]$\left(\frac{W}{W+M}\right)$

is the percent Watt density from the heated zone W spread over the unheated zone M. It can be said that this average Watt density is equal to the Watt density of the longest and coolest spacing or distance between busbars 25 L.sub.1.sup.2 or

[00018]$\frac{V^2}{\rho L_1^2}$

giving us the equation

[00019]$\frac{V^2}{\rho L_1^2}\left(\frac{W}{W+M}\right)=\frac{V^2}{\rho L_2^2},$

which results in equation (2)

[00020]$M={\left(\frac{L1}{L2}\right)}^{2}W-W$

where M is the non-contacting distance (unheated zone) between contacting zones W (heated zone). For the purposes of equation (2), and as shown in the embodiments of FIG. 1 for a common lens and of FIG. 2 for a generalized lens, busbars 4 extend across at least a portion of the top and bottom edges of the lens in an overall horizontal orientation relative to each other (parallel busbars), and distances Lx in general and L.sub.1 and L.sub.2 in specific extend across the lens between busbars 4 in an overall vertical orientation, with each of distances Lx being parallel to each other in this overall vertical orientation. For busbars 4 not positioned in an overall horizontal position relative to each other (non-parallel busbars), one of ordinary skill in the art would be able to determine the orientation of distances Lx relative to the busbars 4, such as being perpendicular to a center line extending equidistantly between the busbars 4.

[0164] Arbitrary selection of some contacting distance of W and for some given distance of L between busbars 4, 25 can determine the non contacting or dielectric insulated distance. For an example of the contact zone W on the lens shown in FIG. 1, a contact zone W of 0.125″ can be selected. Note the smaller the contact zone the more uniform the Watt density.

[0165] FIG. 5 is a schematic of and computation of exemplary dielectric and silver busbar 4 spacing and contact for defogging of a goggle, visor, or other device or apparatus incorporating the present teachings. In FIG. 5, because the left and right parts of the lens are symmetrical, the spacing of non-contact zone M of the dielectric material is placed in the center with the 0.125″ contacts. The minimum contact length L is 1.5″ and the maximum contact length L.sub.1 is 3″. Hence

[00021]$\left[{\left(\frac{L_1}{L}\right)}^2\left({0.125}^{″}\right)\right]-{0.125}^{″}={0.375}^{″}=M$

(for dielectric space 26). Using the same equation, the spacing for dielectric space 28 can be determined. M=0.156″ for dielectric space 29; M=0.100 for dielectric space 30; M=0.055″ for dielectric space 31; M=0.025″ for dielectric space 32; M=0.025″ for dielectric space 33; M=0.055″ for dielectric space 34; and M=0.100 for dielectric space 35.

[0166] The non-contact spacing of each busbar 4 (upper and lower busbar 4), and therefore the contact spacing of each busbar 4, mirrors one another.

[0167] The contact zone W is 0.125″ and is constant. Also shown in FIG. 5 is where the applied voltage of power source 39 is in contact at connection point 40 and connection point 41, respectively.

[0168] The calculation for the dielectric spacing M was performed in the areas of the lens that would have the hottest zones. A prototype was constructed using the dimensions provided above for M and W, was tested, and the lens was essentially uniformly heated. More specifically, the computing of dielectric spacing M, contact spacing W, and silver busbar 4 spacing for defogging of a goggle, visor, or other device as shown in FIG. 5 is provided below. This is constant for the temperature rise ΔT as a function of Watt density. The average temperature across L is relatively uniform, but can vary. The actual temperature across the surface of the lens is not critical as long as the T over the lens is greater than a T that will defog or deice the optical area of the device.

[0169] Converting Watt density to ΔT, the conversion is measured as K=0.023 W/0° C./in.sup.2. If a 25° C. rise or ΔT for the longest distance L.sub.1=2″ for 45 Ohm/□ ITO is sought, it can be said that

[00022]$\frac{V^2}{\left(2^2\right)\times 45}=\left(25\right).023.$
V=√{square root over ((4)(45)(25).023)}=10.17Volts

The

[0170] [00023]$\mathrm{Watt}\mathrm{density}=\frac{V^2}{{\left(2\right)}^{2}45}=\frac{10.17}{\left(4\right)45}=0.57\mathrm{Watt}/{\mathrm{IN}}^2$

[0171] Through use of intermittent contacts, which can be referred to as the spaces between the dielectric squares where the silver busbar touches the conductive film, and a uniform Watt density and temperature, the heated area (A) can be multiplied to determine the total Watts of 0.57 .sup.Watts/In (A). If this is divided by the voltage, 10.17V, the current can be determined to design the power supply.

[0172] FIG. 6 illustrates the resistance distribution and tapered busbars 4 for more efficient use of silver and a better viewing area provided by the present teachings. More specifically, FIG. 6 represents the placement of busbars 4 and the various resistances R between the busbars 4 across the lens distance L. Once the intermittent connection and equation (2) is found, uniform resistance R across the busbars 4 is present, as shown in FIG. 6. Although R may vary somewhat across the lens, the average R will be the same across the entire width of the lens, with the Watt density being uniform across the lens. From inspection, it can be seen that the maximum current density is at connection points 42 and 44. The current density is at a minimum at endpoints 41 and 45. So, tapered busbars 4 can be used. This minimizes the amount of printed silver, which saves cost, but more importantly allows for a larger viewing area.

[0173] FIG. 7A is a schematic front view of prior art carbon underfloor heater elements 48 and busbars 49, and FIG. 7B is a side view of the prior art device of FIG. 7A. In FIGS. 7A and 7B, drawings of an underfloor heater are shown. Carbon resistive heating elements 48 are printed on a 0.005″ polyester film 51. A silver busbar 49 is printed to provide an uninterrupted electrical connection with the heating elements 48. A continuous metal strip about 0.005″ thick and 0.5″ wide 50 is in contact with the printed silver strip 49 and then adhesively laminated to the coated polyester film 51. In some applications, such as a visor in helmets, large areas are heated using silver busbars 49 as mentioned earlier, and 30% of the energy is lost and a significant part of the viewing area is lost because the busbars 49 are 0.5″ wide. A comparison of the sheet resistivity that was computed from the bulk resistance of various metal and printed silvers is:

For 0.001″ thick copper, ρ=0.8×10.sup.−3 Ohms/□
For 0.001″ aluminum, ρ=1.8×10.sup.−3 Ohms/□
For 0.001″ steel, ρ=5.5×10.sup.−3 Ohms/□
For printed silver, ρ=0.15 Ohms/□

[0174] Clear thin copper is orders of magnitude more conductive than silver. A printed silver busbar only 0.5 mm wide and a copper foil 0.0254 mm thick and 0.5 mm wide bonded together with a conductive adhesive and then laminated with a clear pressure sensitive thin film will be a much more conductive busbar and will also allow for a greater viewing area without Joule heating loss. It will also replace the mechanical contact with a robust secure soldered connection to the voltage source. The difference between the busbar construction in underfloor heaters is the use of much thinner silver/copper busbars, because floor heaters must carry current over meters not centimeters.

[0175] Another significant difference in the floor heater, is that the busbars 49 make uninterrupted contact with conductive carbon heating elements 48 as opposed to the teachings of the present disclosure that describe the use of dielectric insulators to provide intermittent contact. 3M™ sells 0.0014-inch thick copper foil with a conductive adhesive that can be used for the present teachings. Another significant difference is while the floor heater uses continuous strips of metal conductors, due to the design shape the copper foil must be die cut to conform to the lens geometry.

[0176] FIGS. 8A, 8B, and 8C illustrate embodiments of the present disclosure as applied to three-dimensional shapes, such as rounded goggles 53. FIG. 8A is a schematic of a front view and FIG. 8B is a cross-section of a first type of vacuum formed conductive transparent three-dimensional shape 53 and busbars 52 for defogging using the present teachings. FIG. 8C is a schematic of a top cross-sectional view of a second type of vacuum formed conductive transparent three-dimensional shape 53 and busbars 52 for defogging using the present teachings.

[0177] In FIGS. 8A and 8B, a three-dimensional transparent heat formable goggle lens 53 is shown. Transparent films using ITO are impossible to heat form because the ITO is a brittle ceramic. However, Chasm Corporation has developed heat formable transparent conductive films with sheet resistance varying from 10 Ohms/□ to 40 Ohms/□. However, in forming the film, the resistance will vary with the stretched film increasing in resistance. In addition, because of the shape of the surface 53, the distance between busbars 52 will vary giving rise to non uniform heating. To overcome the variable, an intermittent busbar 52 is printed on the flat extended parts of the lens surface 53. The eye of the viewer 55 is shown in FIG. 8B. For example, on the 3D lens shown in FIGS. 8A and 8B, a dielectric may not be necessary towards the middle of the 3D structure, or the spacing of the dielectric may be closer towards the middle and wider towards the sides so that the Watt density across the middle of the 3D lens is the same as across the sides of the lens, as the distance across the 3D shape towards the middle of the lens is greater than the distance across the 3D shape towards the edges of the lens. In FIG. 8C, a fixture 54 (with holes) for holding many lenses is shown to facilitate silk screening silver busbars simultaneously for many lenses and reduced.

[0178] The method disclosed for varying the sheet resistance p to obtain uniform heating with nonparallel busbars can be used to provide non uniform heating. A method for obtaining uniform heating is shown in FIGS. 9A, 9B, and 9C is a circular heater. FIG. 9A is a schematic of a first device and method for providing uniform heating with odd shaped heaters and non uniform busbars using the present teachings. FIG. 9B is a schematic of a second device and method for providing uniform heating with odd shaped heaters and non uniform busbars using the present teachings. FIG. 9C is a schematic of a third device and method for providing uniform heating with odd shaped heaters and non uniform busbars using the present teachings.

[0179] In FIG. 9A, areas of a constant sheet resistance are printed on a substrate using uniform conductive material 61. A space 57 is not printed. The spacing between printed segments 61 is determined by equation (2)

[00024]$M={\left(\frac{L1}{L2}\right)}^{2}W-W.$

Here again conductive segment 61 is 0.125″ wide. The busbar 60 is 0.125″ wide, which will give an approximate uniform heating. Again, if contact zone W is made smaller, the heating will get more uniform.

[0180] In FIG. 9B, the formula in equation (2) was again used to provide a dielectric coating to prevent current flow through dielectric coating 59. A uniform constant sheet resistance p is provided for a uniform conductive material 61.

[0181] FIG. 9C illustrates a preferred method of obtaining uniform heating by altering the sheet resistivity. Here the sheet resistivity is altered as shown in equation (3). If the Watt density of the longest path between busbars 60 and the various paths L.sub.2 is set, equation (3) results:

[00025]$\begin{array}{cc}{\rho }_2={\left(\frac{L_1}{L_2}\right)}^2{\rho }_1.& \left(3\right)\end{array}$

This means that for any given distance L.sub.2, the sheet resistivity ρ.sub.2 can be increased so as to obtain uniform heating.

[0182] This can be accomplished by having voids 63 in a portion 62 of the conductive material. If one is printing a resistive uniform conductive material 62 so that as L decreases, there are progressively more voids 63 moving from the center of the shown odd shaped heater towards the outer edge of the shown odd shaped heater. In other words, there are fewer voids 63 and/or the voids 63 are spaced further apart (less dense) towards the center of the shown odd shaped heater (that is, closer to the uniform conductive material 61) and there are more voids 63 and/or the voids are spaced closer together (more dense) towards the edges of the odd shaped heater (that is, further from the uniform conductive material 61). This also is true if the conductive medium is a photo etched metal such as Manganin. If the voids 63 are 50% of the area, the sheet resistivity is 50% greater.

[0183] If the printed conductor has insufficient conductivity, a series of silver conductive dots can be printed over a carbon conductor, for example, to decrease the sheet resistivity in the longest distance L with decreasing silver dots as L.sub.2 gets smaller. One can use a combination of voids 63 in or swiss cheese holes and silver to obtain a wide range of sheet resistivity. Although holes or similar voids 63 are suggested to increase the ρ, the sheet resistivity various geometries such as rectangular voids 63 can be used, but small holes or voids 63 are preferred so as to limit hot spots when the current flows around the voids 63. The size of the voids 63 depends on the printing (e.g., silk screening, rotogravure) resolution.

[0184] As one of ordinary skill in the art would understand, as the sheet resistivity is altered to obtain uniform Watt density, it becomes a very simple matter to design a complex shape heater. The Watt density is multiplied by the area at the heater to obtain the total Watts.

[0185] A method of altering the temperature distribution on transparent ITO conductors is shown below in conjunction with FIGS. 10-16. As disclosed above, the present disclosure provides an equation for uniform sheet resistivity films with non-uniform, non-parallel busbars. The concept, inter alia, is used to prevent excessive heating in ski goggles, visors, etc. using ITO conductive film as shown generally in FIG. 10.

[0186] FIG. 10 shows a schematic of an existing ITO lens with busbars and connections used for defogging goggles and visors. In FIG. 10, L.sub.2 is the shortest distance between printed silver busbars 103, L.sub.1 is the longest distance between busbars 103, and an ITO coating 102 having conductive 30-45 Ω/□. A power source 107 provides electrical power to the system. The greatest heating occurs in the L.sub.1 zone as the watt density (W) is equal to

[00026]$\frac{V^2}{\rho L_2^2}\left(\frac{W}{W+M}\right)=P$

where “V” is the applied voltage, “L” distance between busbars and ρ is the sheet resistivity, typically 30-45 Ohms/□. It has been found even using the concepts disclosed herein using intermittent dielectric insulation that sufficient current will flow to still cause heating in the L.sub.1 or nose area of the goggles. The equations developed assume little or no electrical flow from adjoining conductive areas. However, this is not always the case. To prevent side current flow, a method was devised to prevent current flow from adjoining heated areas. The ITO coating is a transparent brittle ceramic that is an extremely fragile material. By making almost invisible scratches or by using a sharp knife die, the ceramic conductor will be scored and will not have electrical continuity across the scored line. This leaves little or no visible optical change in the lens, and the lens look visibly transparent.

[0187] FIG. 11 shows a schematic view of an ITO lens with a scored electrically discontinuous portion of the ITO coating 102 using the present teachings. In FIG. 11, the lens has a scored electrically discontinuous ITO coating 102 has scored boundaries created by scored lines 105 in ITO coating 102 creating a cold zone 104. The remainder of the lens comprises a printed ITO lens area 106 and the printed silver busbars 103. A power source 107 provides electrical power to the system.

[0188] FIG. 12 shows a schematic view of an exemplary ITO lens also with a scored electrically discontinuous portion of the ITO coating 102 in combination with printed clear dielectric 108 to provide an electrically isolated cold zone 109 using the present teachings. In FIG. 12, the lens has a scored electrically discontinuous ITO coating 102 in combination with printed clear dielectric 108 to provide an electrically isolated cold zone 109, with the printed clear dielectric 108 preventing electrical contact between the ITO coating 102 and the busbars 103. In this embodiment, the cold electrical isolated zone 109, which is on the otherwise heated ITO coating 102/110, is created between the printed silver busbars 103 by way of score lines 127, which create an electrical discontinuity. A power source 107 provides electrical power to the system.

[0189] The knife or die or scored lines 105 are shown in FIG. 11. The cool zone 104 created by the scored lines 105 is electrically isolated from the busbars 103 and is cold. A series of these cool zones 104 may be used to provide intermittent cold areas. By using the equations developed above, relatively even or uniform heating will occur. While a sharp knife edge can be used to score the ITO, a discontinuous or serrated edge also can be used to allow some current flow from “L”. As shown in FIG. 12, it also is possible to print a transparent dielectric 108 insulator between the top and bottom busbars 103 and then score or use a knife die to provide interrupted electrical path from the sides as shown by the score lines 127 in FIG. 12.

[0190] While the electric isolation may be accomplished by die cutting a section out of the ITO coating 102, this is not a practical solution as the lens is mechanically weak and would provide visual discontinuity. By reducing or eliminating the heating in the nose area, as illustrated by the cold electrical isolated zone 109 in FIG. 12, as much as 40% of the energy can be applied to the large viewing area. This will reduce the size and cost of a battery supply, such as power source 107. It also reduces energy loss due to heating the busbars 103 as the resistance is higher and less current is required. Also, for very cold (−° C.) ambient, more voltage and current is required, which would cause extreme heating in the nose area with ΔT temperature rise exceeding 100° C., which at room temperature could damage the lens. Thus, it is preferable to prevent heating in the nose area. Fortunately, the nose area is typically out of the visual area from the eyes.

[0191] FIG. 13 shows a schematic view of an ITO lens using laser cut or die cut holes 113 in the ITO coating 102 in combination with printed clear dielectric to provide an electrically isolated cold zone using the present teachings. In FIG. 13, the lens has an electrically discontinuous ITO coating 102 between the printed silver busbars 103 in the form of the laser cut or die cut holes 113. A power source 107 provides electrical power to the system. As shown in FIG. 13, another method of obtaining relatively uniform heating is to provide such small laser cut or die cut holes 113 in the ITO coating 102 using the equation where the sheet resistivity is changed according to

[00027]$\rho ={\left(\frac{L_1}{L_2}\right)}^2{\rho }_1.$

This can be accomplished by using a laser or knife die to punch the small laser cut or die cut holes 113 in the polyester (or other substrate material) film 126, and then sputtering on a vapor conductive layer such as ITO or other material as shown in FIG. 13 after laminating the film to a polycarbonate substrate. This will create the laser cut or die cut holes 113 in the is ITO coating 102.

[0192] A major concern is the use of these printed silver busbars. The sheet resistivity of printed silver varies between 0.04 f/o and 0.13 Ohm per square. So, the resistance of a silver trace 10″ long and 0.250″ wide would be

[00028]$R=\rho \frac{L}{W}=\text{.1}\frac{10}{25}=4\mathrm{Ohms}.$

A silver wire or copper wire 0.030″ in diameter was measured to be 0.4 Ohms or at least an or of magnitude less. In designs of transparent goggles or visors that are heated electrically, the printed silver traces will take up the visual space and electrical heating loss that would mean less heating and more required energy for battery heated goggles and visors.

[0193] FIG. 14 shows a perspective schematic view of an ITO/polycarbonate sandwich using the present teachings, which will help alleviate the concerns regarding the use of printed silver busbars mentioned above. In FIG. 14, silver or copper wire 115 is placed between a polycarbonate film 118 and the ITO coating 119, so as to form a sandwich. Bakelite® or another equivalent material, blocks are placed on either side of the sandwich and force 116 is applied, thus melting the silver or copper wire conductor into the ITO coating 119/polycarbonate film 118 sandwich. A power source 107 provides electrical power to the system. The wire 115, preferably 0.030″ silver or copper wire, is sandwiched between two rigid thermal insulated plates 117 and in contact with the ITO coating 119/polyester film 118 sandwich. A pressure force 116 is applied on the sandwich. This results in embedding the wire 115 in the polycarbonate film 118. The polycarbonate film 118 will melt into the sandwich when 4 amps of current heats the wire 115 as shown in FIG. 14.

[0194] FIG. 15 shows a perspective schematic view of an ITO/polycarbonate lens showing a silver or copper wire 122 and silver connecting trace 123 using the present teachings. In FIG. 15, a melted wire busbar is used with a thin (0.040″) printed contacting ITO trace, where a transparent polymer substrate 120, an ITO coating 121 on the polymer substrate 120, the silver or copper wire 122, and a printed (0.040″) silver connecting trace 123 is used. The wire 122 protrudes above the surface of the ITO coating 121/polymer substrate 120, which can result in the ITO becoming damaged so it will not conduct electricity. It was found that printing a silver trace 123 1 mm wide≈0.040″ over the wire 122 results in the wire 122 being in electrical contact with the ITO coating 121. This concept of embedded wire busbars provides that the metal (silver or copper) wire 122 is encased and rigidity held by the polymer substrate 120. The coefficient of expansion with temperature of the polymer substrate 120 is three times greater or more than the metal wire 122, but thermal cycling from −5° C. to 70° C. showed the wire 122 was firmly in place. The advantages of using a wire busbar with a slight silver trace 123 are many, including: [0195] 1) the wire can be easily connected or soldered to power supply wires without rivets or clamps when using printed silver busbars which often introduce hot spots at the connection further wasting energy; [0196] 2) less expensive silver is used; [0197] 3) less visual area is obscured; [0198] 4) less energy loss in the more conductive wire busbar; and [0199] 5) longer lengths can be used.

[0200] FIG. 16 shows a sectional side schematic of an ITO/polycarbonate lens showing embedded silver/copper wire busbars 124 and a coating of transparent PEDOT conductive polymer 125 on a transparent polycarbonate substrate 126 using the present teachings. While the method of heating the wire 124 electrically and melting it into the substrate 126 works well, other means such as using hot rollers and pressure or hot platens also may be used. The heated platens or rollers may cause distortion in the plastic substrate 126. While a round wire 124 is shown, rectangular extruded wires with more conductive cross sections may also be used. In the embodiment shown in FIG. 16, experiments were performed using a coating 125 of Oracon® 1CP 1050 across two embedded wires 124 in the polycarbonate substrate 126. The Oracon® 1CP 1050 is a conductive transparent polymer 125 Ohms/□/Mill or PEDOT from AGFA Corp. The material, when dried is conductive with a slight blue tint and allows 90% or more light transmittance. The material is in order of magnitude less costly when compared with ITO. When current or voltage is applied between the wires 124, heating occurred. The ΔT versus light transmission and coating thickness can be optimized.

[0201] FIGS. 17-18 are thermographs of lenses illustrating the teachings of the present disclosure. Standard (unscored) lenses (prior art) are shown in the thermograph of FIG. 17 and scored lenses are shown in the thermograph of FIG. 18. The thermographs were taken on lenses tested at both 10-volt input at an ambient temperature of 22° C. The dielectric coating, in this case ITO, was tested unscored, discontinuously scored, and continuously scored to show the impact of scoring on temperature distribution across the lenses.

[0202] FIG. 17 is a thermograph of a standard printed lens such shown in FIG. 10 illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C. As can be seen, at a central nose portion of the lens, the temperature of the lens is 80.0° C.

[0203] FIG. 18 is a thermograph of a continuously scored lens such shown in FIG. 12 illustrating an electrically isolated cold zone created using a 10-volt input at an ambient temperature of 22° C. As can be seen, at a central nose portion of the lens, the temperature of the lens is 53.4° C.

[0204] The testing of the unscored, discontinuously scored, and continuously scored lenses shows that at a 10-volt input, discontinuous scoring of the dielectric coating creates a drop in the temperature of the lens relative to the unscored lens, creating a cold zone, while continuous scoring of the dielectric coating maintains this drop in the temperature of the lens relative to the unscored lens, maintaining but not affecting to any great degree the temperature of the cold zone relative to the discontinuously scored lens. This leads one to understand that with a 10-volt input, either discontinuous scoring or continuous scoring of the dielectric coating would be necessary to create the cold zone proximal to the goggle-wearer's nose for better comfort.

[0205] The discontinuity or discontinuities formed in the dielectric coating also can be formed by laser ablation. The concept of laser ablation is to use a high-power laser such as a CO.sub.2 laser or a pulse laser to heat the surface of the dielectric coating on the polyester substrate so that the polyester substrate surface will be very hot and cause ablation or a hot vapor that will cause an electrical disconnect or discontinuity in the dielectric coating. A photoetch thin 0.001″-0.002″ reflective copper mask can be fabricated with 0.001″, or 0.002″ wide traces in contact with the lens that will allow the laser energy to impinge on the dielectric coating/polyester substrate surface in the etched area causing sublimation or ablation. The thin lines can be etched on the reflective foil in a pattern that would electrically isolate selective zones (around the nose, for example) so no electrical heating will occur when a voltage is applied to the busbars. An advantage of the laser ablation concept is that very thin lines of material can be ablated leaving very little optical change. While a mask is suggested, a programmed laser beam 0.001″ wide may be programmed to impinge on the surface to form a continuous area of electrical discontinuity that will not be heated. A high-power water jet also may be used to score the dielectric coating.

[0206] In some examples, the conductive coating can be added only to portions of the busbar where heating is required. For instance, the conducting coating can be added to the portions of the busbars that are located on the portions of the lens vis-A-vis the eyes (and not the nose).

[0207] In some examples, when the lens has a non-uniform width (width defined as the distance from the top of the lens to the bottom of the lens, such as L2 or L1), the busbars may follow the shape of the lens (follow the curvature of the lens).

[0208] The lens can be used as a shield (such as a windshield) for certain vehicles as snowmobiles, all-terrain vehicles such as gators and side-by-side vehicles, four-by-fours, caterpillars, snowcats, motorcycles, scooters, etc. The lens may also be used for goggles, helmets (as the vizor), etc.

[0209] Heated Shield Using Embedded Heater Wires:

[0210] In some embodiments, as shown in FIG. 19, a shield 200, such as a windshield found on a side-by-side vehicles), may include embedded heater wires 215 (e.g. copper or silver) positioned at given intervals through the shield 200 for, e.g., defogging and/or de-icing. The wire heaters 215 are connected to busbars 210 positioned at opposite ends of the lens (e.g. soldered thereto through the use of tin or led), the busbars 210 connected to a power source 220. The busbars 210 are normal to the embedded wire heaters. The wire heaters 215 may be curved if the shield 200 is curved (i.e. an uneven width).

[0211] In these embodiments, as the heating is achieved through the heater wires 215, the substrate layer (e.g. polycarbonate layer) 212 does not require a conductive layer (e.g. ITO layer).

[0212] In some examples, when adding the wire heaters 215 to the substrate layer 212 of the shield 200, the wire heaters 215 may be embedded simultaneously in the substrate layer 212, e.g., by passing a current through the wire heaters 215, causing the wire heaters to heat up and melt the substrate layer 212, resulting in the embedding. In some embodiments, the wire heaters 215 may be imbedded in the substrate layer 212 through injection-molding.

[0213] In some examples, when the shield 200 has a non-uniform width (width defined as the distance from the top of the lens to the bottom of the lens, such as L2 or L1), the wire heaters 215 may follow the shape of the shield (follow the curvature of the shield).

[0214] The wire heaters 215 are positioned at spaced intervals across the shield and can be positioned lengthwise.

[0215] However, if closer spacing is required, the diameter of the wire heaters may be smaller as explained herein. It is of note that simply bonding the wires to the substrate using a transparent adhesive film may result in air gaps or air bubbles that may interfere with transparency and optical clarity, and reduce bonding between busbar and the substrate.

[0216] In some embodiments, to facilitate the soldering of the busbars and to improve visibility due to the colour of tin, the copper wire may be tinned or coated with silver.

[0217] The shield can be used as a windshield for certain vehicles as snowmobiles, all-terrain vehicles such as gators and side-by-side vehicles, four-by-fours, motorcycles, caterpillars, snowcats, boats, aircrafts, etc.

[0218] The present disclosure provides a simple way to design and construct complex shaped heaters for any shape. Many existing heaters use complex long lines of continuous conductive material which results in bends in the shape. Each shape requires a new design and current path. These twists and turns result in nonuniform heating and hot spots. Obviously, this concept greatly improves the design and uniformity.

[0219] As one of ordinary skill in the art would understand, it can be said that as the Watt density is constant, the area of the heater can be multiplied by the Watt density to get the total wattage and hence the current so the power supply can be determined.

[0220] The various embodiments are provided by way of example and are not intended to limit the scope of the disclosure. The described embodiments comprise different features, not all of which are required in all embodiments of the disclosure. Some embodiments of the present disclosure utilize only some of the features or possible combinations of the features.

[0221] Variations of embodiments of the present disclosure that are described, and embodiments of the present disclosure comprising different combinations of features as noted in the described embodiments, will occur to persons with ordinary skill in the art. It will be appreciated by persons with ordinary skill in the art that the present disclosure is not limited by what has been particularly shown and described herein above. Rather the scope of the invention is defined by the appended claims.

[0222] In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, it is the express intention of the applicant not to invoke 35 USC § 112(f) for any limitations of any of the claims herein, except for those in which the claim expressly uses the words “means for” together with an associated function.

[0223] Therefore, although selected aspects have been illustrated and described in detail, it will be understood that various substitutions and alterations may be made therein without departing from the spirit and scope of the present invention, as defined by the following claims.

LIST OF REFERENCE NUMBERS

[0224] 1 Electrical connection [0225] 2 Electrical connection [0226] 3 Electrical connection [0227] 4 Busbar [0228] 5 Coating [0229] 6 Power supply [0230] 7 Power supply [0231] 8 Busbar [0232] 9 Busbar [0233] 10 Uniform conductive material [0234] 11 Uniform conductive material [0235] 12 Polymer film [0236] 13 Dielectric material [0237] 14 Busbar segment [0238] 21 Power supply [0239] 23 Uniform conductive material [0240] 24 Dielectric material [0241] 25 Busbar [0242] 26 Dielectric space [0243] 27 Polymer film [0244] 28 Dielectric space [0245] 29 Dielectric space [0246] 30 Dielectric space [0247] 31 Dielectric space [0248] 32 Dielectric space [0249] 33 Dielectric space [0250] 34 Dielectric space [0251] 35 Dielectric space [0252] 39 Power supply [0253] 40 Connection Point [0254] 41 Connection Point [0255] 42 Connection Point [0256] 43 Connection Point [0257] 44 Connection Point [0258] 45 Connection Point [0259] 48 Heating elements [0260] 49 Busbar [0261] 50 Metal strip [0262] 51 Polyester film [0263] 52 Busbar [0264] 53 Surface/shape [0265] 54 Fixture [0266] 55 Viewer [0267] 56 Uniform conductive material [0268] 57 Space [0269] 58 Space [0270] 59 Dielectric coating [0271] 60 Busbar [0272] 61 Uniform conductive material [0273] 62 Uniform conductive material [0274] 63 Voids [0275] Lx Length between busbars [0276] M Unheated or non-contact zone [0277] V Power supply [0278] W Heated or contact zone [0279] 102 Coating [0280] 103 Busbar [0281] 104 Cold zone [0282] 105 Scored lines [0283] 106 Lens area [0284] 107 Power source [0285] 108 Dielectric [0286] 109 Cold zone [0287] 110 Coating [0288] 113 Holes [0289] 115 Wire [0290] 116 Force [0291] 117 Insulated plate [0292] 118 Film [0293] 119 Coating [0294] 120 Substrate [0295] 121 Coating [0296] 122 Wire [0297] 123 Trace [0298] 124 Wire [0299] 125 Polymer [0300] 126 Substrate [0301] 127 Scored lines