Variable transparency window
This is a continuation of application Ser. No. 954,346, filed Oct. 25, 1978. 
    
    
     BACKGROUND OF THE INVENTION 
     It is known in the art to which this invention pertains to provide a variable density window comprising a pair of overlying light-polarizing elements wherein one of the light-polarizing elements is fixedly positioned and the other element is rotatable with respect thereto. Generally representing the prior art is U.S. Pat. No. 2,311,840 issued Feb. 23, 1943 in the name of Edwin H. Land. In the Land patent, hand-operated crank means are provided to drive the rotatable light-polarizing element. However, in such references as U.S. Pat. No. 3,521,300 dated July 21, 1970, a drive roller controlled by electrically energized motor means is also suggested in order to effect rotation of the movable light-polarizing element. 
     It has been observed that when using only a pair of polarizing elements, one stationary and the other rotatable, although almost complete extinction of the light transmitted by the variable density window is effected when the principal axes of polarization of the elements are at right angles to each other, it is still possible for an observer situated on one side of the window to see an object disposed on the other side, especially if viewing of the object is effected at an angle to the parallel planes of the polarizing elements. Such inconveniences and shortcomings of the prior art are completely eliminated by the structure of this invention utilizing a pair of spaced-apart stationary polarizing elements having their principal axes of polarization aligned, and placing the rotatable polarizing element between the stationary elements and spaced therefrom. 
     SUMMARY OF THE PRESENT INVENTION 
     The instant invention is directed to a polarizing window assembly which features a plurality of polarizing window elements, a pair of these elements being axially spaced from one another, with their principal axes of polarization mutually aligned, and fixedly secured to suitable supporting structure, which may be an aircraft cabin wall, a van body wall, or the like. There is also provided a spaced apart third polarizing window element which is located intermediate and therefore in relatively closer proximity to the first and second elements, but still substantially relatively far therefrom, and which is mounted for rotation with respect thereto. By provision of three elements constructed and arranged in the manner to be more fully disclosed hereinafter, much more accurate control is achieved in the amount of light transmitted by the polarizing window assembly and complete opacity is achieved when the rotatable polarizing window is rotated such that its principal axis of polarization is disposed at a right angle to the aligned principal axes of polarization of the stationary polarizing windows. 
     The third and rotatable element may be manually or motor driven, and when motor means are utilized, the third element is secured to a partially toothed or geared ring member actuated for rotation through a limited arc by means of a relatively simple mechanism which includes gear means cooperating with the motor means, a plurality of limit switches and associated cam means, and a three-position electric switch means. By so proceeding, there is achieved a better light control, the entire assembly has a minimum number of parts and can be quickly installed in any window opening, and versatility of use is accomplished by having the rotatable light-polarizing element actuated either manually or electrically. 
     The invention also achieves improved passenger comfort, psychological well-being, and convenience, as well as relieving maintenance conditions by elimination of shades, drapes, curtains and the like. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the light polarizing window assembly of this invention; 
     FIG. 2 is a fragmentary vertical sectional view taken substantially along the line 2--2 of FIG. 1; 
     FIG. 3 is a side elevational view of the assembly of FIG. 1; 
     FIG. 4 is an end view to more fully illustrate certain portions of the assembly of this invention; and 
     FIGS. 5 and 6 are schematic views useful in explaining the operation of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the drawings, there is shown a variable transparency window assembly generally designated by the legend A and which comprises a plurality of polarizing window elements, a first element being indicated in the drawings by the numeral 10. a second polarizing element at 12, and a third and intermediate polarizing element generally designated by the numeral 14. 
     Referring now also to FIGS. 2 and 4, the first polarizing element 10 is constructed to include an outer window frame member 16 shaped to include an upstanding wall section 16a and a downwardly directed wall section 16b connected by a lateral wall section 16c. Constructed in a similar manner there is provided in the polarizing window 12 an inner window frame member 18 having an upstanding wall section 18a, a downwardly directed wall section 18b and a lateral connecting wall section 18c. It may further be seen from FIG. 2 that the outer window frame members 16 and 18 further include downwardly dependent leg sections 16d and 18d, respectively. 
     The first polarizing element 10 incorporates therein an outer glass or plastic pane 20 to which is adhesively or otherwise secured an outer light polarizing pane 22. The assembly thus formed is held in position by elastomeric seal or gasket means 24 which wedges the outer pane structure against the dependent frame wall section 16d. The pane members 20 and 22 can be of any desired shape, and, as shown, are substantially rectangular. In any event, seal member 24 extends entirely around the periphery or circumference of the pane members 20 and 22 to effect cushioning and to prevent the ingress of undesired elements. 
     In like manner, the polarizing element 12 incorporates therein an inner glass or plastic pane 26 to which is secured an inner light polarizing pane 28, the two panes being held between the window frame member leg portions 18b and 18d by elastomeric seal means 30. As with the outer polarizing window element 10, the inner polarizing element 12 may be circular or rectangular or of any other desired shape. 
     A significant aspect of the instant invention is, as was earlier noted, the provision of a third polarizing element 14 in combination with two other polarizing elements 10 and 12 and in which the third element is disposed between the two other elements in axially spaced relationship with respect thereto at a substantial distance from the two other elements, as best shown at FIGS. 1, 2 and 4. The third polarizing element 14 comprises a glass or plastic polarizing plate 32 which is preferably circular in shape and has secured along its circumference a ring member 34 toothed or geared as at 34a, FIG. 1, along an arc extending over at least 90° of the circumference of the ring member. A plurality of generally U-shaped guide and bearing means 36 are provided for the ring member 34, and as is best seen in FIG. 2, the outwardly directed tab means 36a and 36b are attached to the outer frame members 16 and inner frame members 18 by fastening means 38. 
     The guide means 36 is further shaped to include a roof portion 36c which connects with the tab portions 36a and 36b through leg portions 36d and 36e. The leg portions 36d and 36e on the guide means are suitably apertured to receive opposite ends of a ring guide roller 40 having a central reduced diameter portion 40a. Fastening means 40 serve to attach the ring guide roller 42 to the upstanding leg portions 36d and 36e of the guide means 36. For protective reasons a generally U-shaped plastic or metal cover 44 seats upon the guide means 36 and is attached thereto by a screw means or the like 46, shown in the drawing only in FIG. 2. 
     In order to effect rotative movement of the central polarizing window element 14 with respect to the polarizing elements 10 and 12, there is provided electric motor means 48 secured by bracket means 50 to a fixed structure forming a part of the aircraft cabin or related stationary environment or, as shown in the drawing at 50a to the roof portion 36c of adjacent guide means 36. The motor means 48 mounts a stub shaft 52 having a toothed or geared head portion 52a which meshes with the geared portion 34a on the ring member 34. 
     The motor means mounting bracket 50 may also have suitably affixed thereto limit switches 54, shown in FIGS. 1 and 3, and 56, shown in FIG. 3 only, each of which is equipped with contact portions 54a and 56a which through cam followers 57 and 53 intermittently contact limit switch actuating cams 58 and 60, respectively, engageable with the ring member 34 forming a part of the third polarizing element 14 to control the extent of radial movement thereof. 
     Connecting the limit switch 54 to the motor 48 is a lead 62 and a lead 64 also runs from the limit switch 56 to the same motor 48. A pair of leads 66 and 68 connect the limit switches 54 and 56, respectively, to toggle switch means 70. This particular switch is a three-position switch having on-off-on stops to control the direction and extent of rotary movement of the third polarizing element 14. 
     The operation of the variable transparency window assembly of this invention is believed to be manifest from the foregoing description of the structural details thereof. A person desirous of controlling the extent of light transparency through the window assembly A need only actuate the toggle switch 70 to the appropriate &#34;on&#34; position which controls the motor means 48 to rotate the central polarizing element 14 through a total arc of 90° from full transparency of the window assembly A to complete opacity, or in a reverse direction. Any intermediate position is obtained by releasing the toggle switch 70 to the &#34;off&#34; position. In other words, at one extent of the arc there is achieved maximum transparency, FIG. 5, when the principal axes of polarization of all three polarizing elements 10, 12 and 14 are aligned and at the other end of the arc minimum transparency is achieved, FIG. 6, when the principal axis of polarization of the rotatable polarizing element 14 is disposed at a right angle to the principal axes of polarization of the stationary polarizing elements 10 and 12. At other intermediate locations on the arc, by control of the toggle switch 70 and associated mechanisms, varying degrees of transparency can be readily obtained. 
     The toothed sector 34a of the ring member 34 extends over an arc of more than 90°, for example, it extends over an arc of 110°. This arrangement provides a tolerance of ±10° at both ends of the 90° arc of rotation of the rotatable element 14 which permits to calibrate the limits of that arc by adjustably presetting the position of the cams 58 and 60 on the ring member 34 and/or the positions of the limit switches 54 and 56. 
     The material which provides a polarizing function for the elements 22, 28 and 32 is of course well known to the art and is available under the trademark &#34;Polaroid&#34;. A more specific description of this material is contained in U.S. Pat. No. 2,311,840, previously referred to, and also in subsequently published literature. 
     It is believed apparent from the foregoing that various changes and modifications may be made in the structures disclosed without departing from the spirit of the invention or the scope of the subjoined claims.