Switchable electrochromic devices for use in aircraft transparency windows

#The present invention relates to switchable electrochromic devices for use in windows for aircraft. More particularly, the present invention is directed to aircraft transparency windows which are anti-fogging and which have variable light transmittance.

#The transmission of unwanted sound/vibrations through an aircraft transparency and into the aircraft, in particular the aircraft cabin, is undesirable and can cause discomfort to the cabin's occupants. Efforts have been made to reduce the transmission of sound/vibrations through aircraft transparencies. Such efforts have been generally directed to transparencies having several panes (e.g. four or more panes) maintained in spaced-apart relationship within a spacer-frame assembly, which spacer frame assembly is affixed to a corresponding opening in the body of the aircraft. The spaced panes provide a plurality of airspaces therebetween, which, among other things, reduce or eliminate the transmission of external sound/vibrations through the transparency into the cabin. Such transparencies may further include an electroconductive layer that can be heated upon application of electrical current thereto, thus providing an anti-fog characteristic to the aircraft window assembly.

#Electrochromic devices have been proposed for a number of uses, such as architectural windows and automotive windows and mirrors. Such electrochromic devices typically include a sealed chamber defined by two pieces of glass that are separated by a gap or space that contains an electrochromic medium. The glass substrates typically include transparent conductive layers coated on facing surfaces of the glass and are in contact with the electrochromic medium. The conductive layers on both glass substrates are connected to electronic circuitry that is effective to electrically energize the electrochromic medium and change the color of the medium. For example, when the electrochromic medium is energized, it may darken and begin to absorb light.

#The foregoing summary, as well as the following detailed description of embodiments of the invention, will be better understood when read in conjunction with the appended drawings. In the drawings:

#FIG. 1 is a perspective view of a multiple-glazed electrochromic aircraft window assembly incorporating features of present invention, with portions removed for clarity.

#FIG. 2 is a cross-sectional view of the aircraft window assembly of FIG. 1 taken along line 2-2 of FIG. 1.

#The present invention is directed to an aircraft window assembly incorporating electrochromic principles. In one nonlimiting embodiment of the present invention, the aircraft window assembly includes a first pane assembly and a second pane assembly spaced from the first pane assembly, providing a space or chamber therebetween. The second pane assembly is a fog preventing assembly and includes a first transparent substrate coated on one side with a first transparent electrically conductive coating capable of being heated to prevent fogging of the assembly. The second pane assembly is also an electrochromic assembly, and includes a second transparent substrate spaced from the first substrate to define a chamber therebetween, with an electrochromic medium contained in the chamber.

#The first substrate of the second pane assembly forms a first pane of the electrochromic cell, and includes a second transparent electrically conductive coating on a surface thereof. The second substrate includes a third transparent electrically conductive coating on a surface thereof, with the second conductive coating and the third conductive coating facing each other within the electrochromic cell. Application of an electrical current to the first conductive coating heats the first conductive coating and the chamber between the pane assemblies to prevent fog in the window assembly. Application of an electrical current to the second and third conductive coatings impresses an electrical potential between the second and third coatings and through the electrochromic medium, which in turn causes the electrochromic medium to change color, thereby causing light transmittance of the window assembly to change or vary, e.g. reduce the light transmittance. As used herein, the terms “light transmittance” and “luminous transmittance” mean the measure of the total amount of visible light transmitted through a transparency or window assembly. The luminous transmittance data provided in this specification is measured for CIE standard illuminant A and indicted as LTA.

#For the purposes of this specification, unless otherwise indicated, all numbers expressing quantities such as dimensions, thicknesses, luminous transmittance and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.