Abstract:
A portable light filtering device includes at least two sheets of polarized film material. Each of the at least two sheets are mounted on separate mounting rings that rotate relative to one another such that when the lines of polarization are perpendicular to one another, the amount of light that can pass through is minimized and when the lines of polarization are parallel, the amount of light that can pass through is maximized. The separate mounting rings are held together in a rotational relationship and include a mounting bracket to removeably attach the device to a car window, to the ledge of a car door or to any desired window from which light screening is desired.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     REFERENCE TO MICROFICHE APPENDIX 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the field of light filtering and filtering devices. Specifically, the invention relates to a portable light filtering device that uses multiple sheets of polarized film. 
     2. Background 
     Reducing transmitted light is useful for vehicles, buildings, homes and anywhere else that it may be desired to reduce the amount of light entering a space. Reducing the light passing through glass has been solved in several different ways. 
     Tinted film can be attached directly to the inside of glass. This tends to be permanent and may be too dark which can compromise night vision and if used on vehicle glass in some states, it can result in a police citation. 
     Shades or blinds are practical in homes and buildings but are not very practical in vehicles. 
     Plasma addressed liquid crystal (“PALC”) can be used to assume an opaque state to reduce the transmission of light through glass. For example, see U.S. Pat. Nos. 6,674,419 and 7,245,205. However, the use of PALC requires sophisticated electronic controls and the PALC material alone is exceedingly expensive. 
     Window tinting using polarized film is known. Polarized film has been used in a single layer and in multiple layers to block light or vary the amount of light that is transmitted through glass. 
     When polarized film is used, either in a single layer or in multiple layers; it is incorporated into a complex assembly that becomes an integral part of the window unit. For example, in U.S. Pat. No. 5,940,216 two layers of polarized film are used, with the lines of polarization of each layer being parallel to the other layer. The lines of polarization are shifted relative to the other layer by using a relatively complex motor and cam mechanism. 
     SUMMARY OF THE INVENTION 
     What is needed is a portable light filtering device that can be used on windows. It should be useable to filter sunlight that passes through windows in vehicles and also be useable to filter sunlight in a home or in other desired buildings. It should be externally removable from the glass surface so that it can be easily removed as desired and moved to a different, desired window location. It should also be inexpensive relative to currently existing light filtering devices and it should include multiple mounting options. It should be universally useable by all vehicles. 
     The present invention relates to a light filtering device for windows that satisfies the long felt but unsatisfied need that the present invention solves. The device comprises an inner screen and an outer screen. Each of the screens is comprised of a polarized film material. The inner screen is secured to an inner mounting ring with an inner retaining ring and the outer screen is secured to an outer mounting ring with an outer retaining ring. Each retaining ring may be secured to the mounting rings with machine screws, with an adhesive or with a desired bonding agent. 
     The inner mounting ring has a top inner shoulder on an inner circumference of the inner mounting ring and the outer mounting ring has a bottom inner shoulder on an inner circumference of the outer mounting ring. A coupling ring has a coupling gap on an interior circumference of the coupling ring. The inner mounting ring and the outer mounting ring are in rotatable contact with each other. The top inner shoulder of the inner mounting ring and the bottom inner shoulder of the outer mounting ring are slideably engaged with the coupling gap of the coupling ring whereby each of the coupling rings are slideably engaged and whereby the inner screen and the outer screen can rotate relative to one another. 
     Each of the mounting rings includes a wall on the outer circumference of each mounting ring. The wall of the inner mounting ring slideably engages the wall of the outer mounting ring. A set of splines is positioned along an inner wall of the outer mounting ring and a ratchet tab is positioned on the wall of the inner mounting ring whereby the ratchet tab engages the set of splines to provide a ratcheting action when the outer mounting ring rotates relative to the inner mounting ring. The ratcheting action also provides reliable positioning of the mounting rings and the polarized films relative to one another and prevents uncontrolled rotation thereof. 
     An inner tab is provided on the inner mounting ring and an outer tab is provided on the outer mounting ring whereby the inner mounting ring and the outer mounting ring can be rotated relative to one another and whereby the relative position of each mounting ring can be visually determined. When the two tabs are aligned together, the lines of polarization of the inner and outer screens are perpendicular to one another to restrict or filter the maximum amount of light. The restricted light source that is restricted or filtered is typically sunlight, but any other light source can also be filtered as desired. When the two tabs are separated by a quarter of a turn (90 degrees), the inner and outer screens allow the maximum amount of light. Thus, the user can control the amount of light and see visually the amount of light restricted by the relative positions of the two tabs. 
     An adjustable arm is attached to the light filtering device and a mounting fixture is attached to the adjustable arm, whereby the light filtering device can be mounted to the interior of a car door. The light filtering device can also be moved to any other window inside a building or structure. 
     The portable light filtering device can be mounted to a mounting fixture that comprises a ledge mounting bracket for suspending and mounting the light filtering device to the ledge on the door of a vehicle. The ledge mounting bracket can be bendable to allow for mounting on a variety of ledge shapes. Alternatively, the portable light filtering device can be mounted to a window with suction cup mounting bracket which suspends the light filtering device to the window on the interior of a vehicle. 
     The portable light filtering device for windows can include a plurality of bearing retainers that are positioned between each of the mounting rings; wherein at least one bearing is positioned within each of the bearing retainers whereby each at least one bearing provides for reduced friction between the mounting rings to provide easy rotation of the inner screen and the outer screen relative to one another. 
     Unlike polarized film that is glued to the inside of windows and allows approximately 50% transmittance of light, the instant invention reduces transmittance of light to approximately 0.093%. 
     The instant invention provides many additional surprising and unexpected results including providing protection against:
         visible sunlight;   heat generated by excessive sunlight; and   possible theft by shielding contents from outside view.       

     Yet further, the device also provides privacy for passengers. It provides a safety benefit for vehicle drivers by reducing glare caused by sunlight. Further still, it protects the interior of vehicle from the harmful effects of ultra violet degradation from the sun light. 
     Other than the polarized screens, the components that are included for the inventive device may be constructed of polymers or of metallic materials or of any other desired materials. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of the inventive light filtering device shown mounted to the inside of a car with a ledge mount. 
         FIG. 2  shows the inventive light filtering device including section line  4 - 4 . 
         FIG. 3  is an assembly drawing of the inventive light filtering device. 
         FIG. 4  shows the section view of the inventive light filtering device taken from line  4 - 4  of  FIG. 2 . 
         FIG. 5  shows the inventive light filtering device with the outer polarized screen and inner polarized screen aligned to allow the maximum amount of light to pass through. 
         FIG. 6  shows the inventive light filtering device with the outer polarized screen and inner polarized screen oriented to allow the minimum amount of light to pass through. 
         FIG. 7  shows the inventive light filtering device mounted to the inside of a car with a surface mount. 
         FIG. 8  shows the inventive light filtering device mounted to the inside of a car with a window mount. 
         FIG. 9  shows the inventive light filtering device including section line  10 - 10 . 
         FIG. 10  shows the section view of the inventive light filtering device taken from line  10 - 10  of  FIG. 9 . 
         FIG. 11  shows the inventive light filtering device including a uniform retaining ring. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     For ease of understanding the invention in relation to the detailed description, the following parts list is provided: 
     
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 Part 
                   
               
               
                   
                 Number 
                 Description 
               
               
                   
                   
               
             
             
               
                   
                 D 
                 sunscreen device 
               
               
                   
                 L 
                 door ledge 
               
               
                   
                 20a 
                 inner retaining ring 
               
               
                   
                 20b 
                 outer retaining ring 
               
               
                   
                 21a 
                 inner uniform retaining ring 
               
               
                   
                 21b 
                 outer uniform retaining ring 
               
               
                   
                 22 
                 machine screw 
               
               
                   
                 22a 
                 securing hole 
               
               
                   
                 22b 
                 threaded hole 
               
               
                   
                 24a 
                 inner polarized screen 
               
               
                   
                 24b 
                 outer polarized screen 
               
               
                   
                 26 
                 inner mounting ring 
               
               
                   
                 26a 
                 inner mounting ring wall 
               
               
                   
                 27 
                 lower inner surface of outer mounting ring 
               
               
                   
                 28 
                 outer mounting ring 
               
               
                   
                 28a 
                 outer mounting ring wall 
               
               
                   
                 30 
                 coupling ring 
               
               
                   
                 31a 
                 inner coupling lip 
               
               
                   
                 31b 
                 outer coupling lip 
               
               
                   
                 32 
                 coupling gap 
               
               
                   
                 34 
                 ratchet tab 
               
               
                   
                 34a 
                 ratchet tab retainer 
               
               
                   
                 42 
                 ratcheting teeth 
               
               
                   
                 44 
                 first inner shoulder 
               
               
                   
                 46 
                 second inner shoulder 
               
               
                   
                 52 
                 flexible arm 
               
               
                   
                 54 
                 ledge mounting bracket 
               
               
                   
                 62 
                 surface mounting bracket 
               
               
                   
                 72 
                 mounting arm 
               
               
                   
                 74 
                 suction cup 
               
               
                   
                 75 
                 bearing retainer 
               
               
                   
                 80a 
                 upper bearing 
               
               
                   
                 80b 
                 lower bearing 
               
               
                   
                 82a 
                 inner tab 
               
               
                   
                 82b 
                 outer tab 
               
               
                   
                 S1 
                 inlet sunlight 
               
               
                   
                 S2 
                 maximum outlet sunlight 
               
               
                   
                 S3 
                 minimum outlet sunlight 
               
               
                   
                   
               
             
          
         
       
     
       FIG. 1  shows an embodiment of the portable light filtering device D as used in a vehicle using the ledge mounting bracket  54  which is attached to a window ledge L of a car door. A flexible arm  52  connects the mounting bracket  54  to the outer retaining ring  20   b , but may also be connected to the inner retaining ring  20   a . The flexible arm  52  allows the light filtering device D to be adjusted to the desired position relative to the window and relative to the direction of incoming sunlight. The mounting bracket  54  can be shaped to conform to the shape of the ledge L of the car door. It can also be constructed of a bendable material to more accurately conform to the shape of the car door ledge. The mounting bracket  54  can also include a hook and loop fastener material to attach it to the ledge L of the car door. 
       FIG. 7  shows the light filtering device D secured to the inside of a car door by inserting the assembled inner retaining ring  20   a  and outer retaining ring  20   b  into the surface mounting bracket  62 . This provides a fixed position for the screen device D on the inside of the car door and car window. The surface mounting bracket  62  may be permanently affixed to a desired position on the interior surface of a car door or it can be releasably attached using a hook and loop type fastener. 
       FIG. 8  shows the light filtering device D secured to a car window with a suction cup  74  that is attached to the window. The suction cup  74  is connected to a mounting arm  72 , which may be rigid or flexible so that the light filtering device D can be positioned as desired relative to the window and relative to the direction of incoming sunlight. Flexible mounting arm  72  and rigid mounting arm  52  are interchangeable and may be mounted on the outer mounting ring  20   b  or to the inner mounting ring  20   a , permanently or with removable fasteners. 
     Refer now to  FIG. 3 , which shows an assembly drawing of the light filtering device D. An inner retaining ring  20   a  secures an inner polarized screen  24   a  to an inner mounting ring  26  with a plurality of machine screws  22 . The machine screws  22  are inserted through the securing holes  22   a  and engage each threaded hole  22   b . An outer retaining ring  20   b  secures an outer polarized screen  24   b  to an outer mounting ring  28  with a plurality of machine screws  22 . The machine screws  22  are inserted through the securing holes  22   a  and engage each threaded hole  22   b  in the lower inner surface  27  of the outer mounting ring  28 . 
     Refer to both  FIGS. 3 and 4  to see the inner mounting ring  26  which has a first inner shoulder  44  about the inner circumference of the inner mounting ring  26  and the outer mounting ring  28  has a second inner shoulder  46  about the inner circumference of the outer mounting ring  28 . A coupling ring  30  includes a coupling gap  32  that is at least as wide as the width of the first inner shoulder  44  and the second inner shoulder  46  when the first inner shoulder  44  and the second inner shoulder  46  are positioned together. The coupling ring  30  is typically constructed of a resilient material, such as a resilient polymer, that allows the coupling ring  30 , the inner coupling lip  31   a  and the outer coupling lip  31   b  to flex so that the coupling lips  31   a ,  31   b  can be positioned to capture the first inner shoulder  44  and the second inner shoulder  46  within the coupling gap  32 . The coupling gap  32  is sufficiently wide that the first inner shoulder  44  and second inner shoulder  46  are free to slide relative to one another but they are maintained in an assembled configuration. 
     The inner mounting ring  26  has a wall  26   a  about the outer perimeter of the inner mounting ring  26 . The outer mounting ring  28  has a wall  28   a  about the perimeter of the outer mounting ring  28 . The outer edge of the wall  26   a  slideably engages with the outer edge of the wall  28   a , while the outer surface of the first inner shoulder  44  slideably engages with the outer surface of the second inner shoulder  46 , as best seen in  FIG. 4 . 
     A plurality of splines form ratcheting teeth  42  along the inner surface of the outer mounting ring wall  28   a . A ratchet tab  34  is positioned on the inner surface of the inner mounting ring wall  26   a . The ratchet tab  34  is constructed of a resilient material and is secured to the inside wall of the inner mounting ring wall  26   a  with a ratchet tab retainer  34   a . The ratchet tab  34  engages the ratcheting teeth  42  thereby creating a ratcheting effect and clicking sound as the inner mounting ring  26  and outer mounting ring  28  rotate relative to one another. This helps to provide secure rotational effect and prevents the inner and outer mounting rings  26 ,  28  from rotating uncontrollably. The ratcheting teeth  42  could also be positioned along the lower inner surface  27  of the outer mounting ring  28  wherein the ratcheting tab  34  engages the ratcheting teeth  42  as the inner mounting ring  26  and outer mounting ring  28  rotate relative to one another. 
     A tab  82   a  is positioned on the inner retaining ring  20   a  and a tab  82   b  is positioned on the outer retaining ring  20   b . Tabs  82   a  and  82   b  provide a means for rotating the inner retaining ring  20   a  and outer retaining ring  20   b  relative to one another. Because the inner polarized screen  24   a  is attached to the inner mounting ring  26  with the inner retaining ring  20   a  and the outer polarized screen  24   b  is attached to the outer mounting ring  28  with the outer retaining ring  20   b , moving tab  82   a  relative to tab  82   b  rotates the inner polarized screen  24   a  relative to the outer polarized screen  24   b . The relative positions of the tabs  82   a  and  82   b  provides a visual reference to indicate whether the inner and outer screens  24   a ,  24   b  are allowing a maximum or a minimum amount of light through the inner and outer screens  24   a ,  24   b . Instead of tabs  82   a ,  82   b , the outer edges of the retaining rings  20   a ,  20   b  can be serrated and indicia or other representing indicators can be placed on the surface of each edge to indicate the relative position of the retaining rings  20   a ,  20   b  and therefore the relative positions of the screens  24   a ,  24   b.    
     Refer now to  FIGS. 5 and 6 . In  FIG. 5  the lines of polarization of the inner polarized screen  24   a  are oriented in the same direction as the lines of polarization of the outer polarized screen  24   b . When the lines of polarization are oriented in the same direction on each of the polarized screens  24   a ,  24   b , the amount of light entering S 1  is not restricted so the amount of light existing S 2  is the same amount as the amount of light entering S 1 . In  FIG. 6  the lines of polarization of the inner polarized screen  24   a  are oriented perpendicularly to the lines of polarization of the outer polarized screen  24   b . When the lines of polarization on each of the polarized screens  24   a ,  24   b  are oriented perpendicularly, the amount of light entering S 1  is restricted so the amount of light existing S 3  is significantly reduces from the amount of light entering S 1 . The amount of light existing S 3  can be as little as 0.093% of the amount of light entering S 1 . 
     An inner tab  82   a  is shown on the top of the inner retaining ring  20   a  and an outer tab  82   b  is shown on the outer retaining ring  20   b . The tabs  82   a ,  82   b  are used to rotate the inner and outer polarized screens  24   a ,  24   b  relative to one another to reduce or allow the desired amount of light to pass through the polarized screens  24   a ,  24   b . When the tabs  82   a ,  82   b  are rotated relative to one another, the ratchet tab  34  engages the ratcheting teeth  42  to provide a controlled rotational movement and also provides a clicking sound as the inner and outer retaining rings  20   a ,  20   b  are rotated relative to one another (Best seen in  FIGS. 3 and 4 ). 
       FIG. 10  illustrates an alternative embodiment wherein an upper bearing  80   a  and a lower bearing  80   b  are captured within a bearing retainer  72  (shown in section in  FIG. 9 ). The upper bearing  80   a  is in rolling contact with the inner surface of the inner mounting ring  26  and the lower bearing  80   b  is in rolling contact with the inner surface of the outer mounting ring  28 . As the upper and lower mounting rings  26 ,  28  rotate relative to one another, the upper and lower bearings  80   a ,  80   b  reduce friction between the upper and lower mounting rings  26 ,  28  to provide an extremely smooth rotational movement. Lubrication of the bearings may be provided to reduce friction even further. 
       FIG. 11  illustrates an alternative embodiment wherein an inner uniform retaining ring  21   a  is secured to the inner mounting ring  26  with an adhesive or other bonding agent. The uniform retaining ring  21   a  sandwiches and secures the inner polarized screen  24   a  to the inner mounting ring  26 . An outer uniform retaining ring  21   b  can also similarly be used to secure the outer polarized screen  24   b  to the outer mounting ring  28 . 
     The inventor has contemplated using the invention to filter any light source for which it would be advantageous to reduce or filter the amount of transmitted light. 
     The invention is not limited to the embodiments identified above and variations may fall within the scope of the invention as claimed below.