Abstract:
An interior lens is provided for a light bar mountable onto the roof of a vehicle. The interior lens has a plurality of fluted lenses or lens segments forming a ribbon shaped to receive illumination prior to exiting the light bar outer dome. The fluted lenses extend vertically parallel to each other and are each shaped to increase the horizontal viewing angle of light from the light bar. The ribbon of fluted lenses may continuously extend within the light bar around the optical assembly to improve performance of light projected from different sides of the light bar, thereby providing an improved optical assembly for a light bar.

Description:
Priority is claimed to U.S. Provisional Patent Application No. 61/707,941, filed Sep. 29, 2012, which is herein incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an interior lens for a light bar, and particularly to an interior lens for a light bar composed of vertically disposed fluted lenses or lens segments for dispersing incident light (e.g., by diffusing and/or refracting) produced by light sources of the light bar. Such interior lens may be transparent, of a color, or have portions of different colors, so as to provide desired colors of light from the light bar. 
     BACKGROUND OF THE INVENTION 
     Light bars are mounted on the roof of vehicles, such as police, fire, or other emergency vehicles to provide warning lights. It is important that such warning light which may flash, rotate, or patterns are viewable over a wide angle. Such light bars are available from Star Headlight and Lantern Company of Avon, New York. When light sources, such as LEDs, are used in light bars, it is important that light from such light sources spread light outward from the light bar. Typically in light bars, such as prior art light bar  1  of  FIG. 1 , to use a parabolic reflector  2  behind LEDs  3  provided in banks. In this example, four parabolic reflectors  2   a ,  2   b ,  2   c , and  2   d  are shown each reflecting LED light incident thereto.  FIG. 2  shows the parabolic reflectors  2  apart from light bar  1 . The parabolic reflectors  2  and LEDs  3  form the optical assembly of light bar  1 . The parabolic reflectors  2  are mounted on a base  4  and collect and reflect light from their respective LEDs  3  that would otherwise not be emitted in the desired outward direction towards the light bar dome  5 . Although useful, the reflected light in light bar  1  is limited in its viewing angle, and then illumination from the light bar may not have desired dispersion characteristics, such as in terms of uniformity or viewing angles of individual LED&#39;s.  FIG. 3  shows the use of two optical assemblies of parabolic reflectors  2  and LEDs  3  along the left and right of a prior art light bar  1   a , which like light bar  1  is mountable onto the roof of a vehicle. 
     Although lenses for controlling dispersion characteristics have been used in vehicle lamps, such as described in U.S. Pat. No. 5,373,430, such have not been used heretofore on light bars between illumination light sources and the outer light bar dome. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to improve dispersion characteristics in light bars by the addition of an interior fluted lens providing wider viewing angles of the individual LEDs than if such interior lens were not present between the light bar&#39;s optical assembly and exterior dome. 
     Briefly described, the present invention embodies an optical element providing an interior lens for a light bar. The body of the optical element has a plurality of fluted lenses (or lens segments) forming a ribbon shaped to receive illumination prior to exiting an outer dome of the light bar. The fluted lenses are shaped to increase the viewing angle of light from the light bar. 
     Preferably the interior lens is located between the dome and parabolic reflectors located behind light sources, such parabolic reflectors reflect light received from the light sources (such as LEDs). The illumination from the light sources, and their reflected light from parabolic reflectors, is projected to the dome, via the interior lens, and out the sides of the light bar. The light sources and parabolic reflectors form the internal optical assembly of the light bar. The ribbon of fluted lenses may continuously extend within the light bar around the optical assembly to improve viewing angle performance of the light bar, thereby providing an improved optical assembly for a light bar. 
     The fluted lenses or lens segments may extend along a first dimension (or vertically) parallel to each other and are each shaped to disperse (e.g., increase the viewing angle) of incident illumination in a second dimension (or horizontally). 
     The interior lens may releasably attach by clipping onto the reflectors. Also, the interior lens may be transparent, of a color, or have portions of different colors, so as to provide the desired color of light from the light bar. 
     The present invention further embodies a light bar having a base, an optical assembly disposed upon the base providing illumination towards different sides of the light bar, a dome covering the base to contain the optical assembly therein, and an interior lens having a plurality of fluted lens segments shaped to increase the viewing angle of illumination received from the optical assembly prior to exiting different sides of the light bar via the dome. 
     The interior lens when located in a light bar forms part of the optical assembly of the light bar. As such, an optical assembly for a light bar may be provided by the present invention having an optical element having fluted lenses, one or more light sources providing illumination, at least one parabolic reflector which reflects light received from the light sources towards the optical element, and the lenses of the optical element being shaped to increase viewing angle of received illumination from the light sources and the parabolic reflector. 
     The term light bar may refer to any light bar mountable onto the roof of a vehicle having an optical assembly which projects light outward from the side(s) of the light bar. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing objects, features and advantages of the invention will become more apparent from a reading of the following description in connection with the accompanying drawings, in which: 
         FIG. 1  is an example of a light bar of the prior art without the interior lens of the present invention; 
         FIG. 2  is an example of the parabolic reflectors of the optical assembly of the prior art light bar of  FIG. 1 ; 
         FIG. 3  is another example of a light bar of the prior art having two optical assemblies without the interior lens of the present invention; 
         FIG. 4  is a perspective view of the interior lens in accordance with the present invention having a plurality of vertical fluted lens segments; 
         FIG. 5  is a cross-sectional view taken horizontally through part of the interior lens of  FIG. 4 ; 
         FIG. 6  is a perspective view of the interior lens of  FIG. 4  mounted onto the optical assembly of a light bar; 
         FIG. 7  is a top view of the interior lens and optical assembly of  FIG. 6 ; 
         FIG. 8  is view of one of the sides of the interior lens of  FIG. 4 ; 
         FIG. 9  is a partial perspective view of the interior lens of  FIG. 6 ; 
         FIG. 10  is a perspective view of one of the two halves of the interior lens of  FIG. 4 ; 
         FIG. 11  is an example of a light bar with the interior lens of  FIG. 4 ; and 
         FIG. 12  is an example of another light bar having two of the interior lens of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 4 to 12 , a lens (or optical element)  10  of the present invention is shown having a body  11  composed of multiple parallel lenses, referred to herein as flutes or lens segments  11   a , that form a ribbon extending along two elongated sides  9   a ,  9   b  and curved ends  9   c ,  9   d . The shape of lens  10  is in accordance with the extent of the reflectors  2  when lens  10  is positioned over such reflectors, as discussed later below. Each lens segment  11   a  extends vertically from the top and bottom of lens  10 . The lens  10  is made of molded plastic formed by left and right mirrored halves  13   a  and  13   b  (e.g., a single half  13   a  is shown in  FIG. 10 ) which align with each other along their respective edge  22  (see  FIG. 9 ) when properly positioned in a light bar. 
     Alternatively, lens halves  13   a  and  13   b  may be joined, such as by adhesive, to each other along their edges  22 , when lens  10  is manufactured. In a further alternative, lens  10  may be a unitary plastic structure when molded. 
       FIG. 5  shows a detailed partial cross-sectional view of lens  10  of  FIG. 4 . Lens segments  11   a  provide light diffusing humps  17  along the interior surface of lens  10 . Such cross-section of each hump  17  being the same at it extends vertically, and between each adjacent hump  17  is a valley  15 . Each lens segment  11   a  has a smooth outer surface  18  continuous with its adjacent lens segments  11   a  with a curved (or convex) inner surface  19 . The radius of curvature of curved surface  19  may be, for example, 3/16 inches, but other radius values may be used which provides the desired horizontal diffusion (by refraction) of light produced by LEDs incident the surface of hump  17 . Alternatively, lens segments  11   a  may have humps  17  along their outer surfaces  18  with inner surfaces  19  being smooth to obtain a similar effect of diffusion of light. 
     As shown in  FIGS. 6, 7, 8, and 9 , lens  10  is positioned over the optical assembly of the parabolic reflectors  2  and LEDs  3  shown in  FIG. 1  to provide an improved optical assembly  14 . Each of the lens halves  13   a  and  13   b  has three clips  21  which latch or clip onto the top edge of that portion of reflector  2  adjacent thereto when properly positioned in the light bar, thereby securing or retaining the lens  10  to reflector  2  and thus providing optical assembly  14 . For example, clips  21  may be provided by one or more flanges, tabs, or other features which releasably attach lens  10  to reflector  2 . 
     Fluted lens segments  11   a  are disposed in front of the parabolic reflectors  2 . The interior of lens  10  is sized according to the height, width and length of reflectors  2  so that the bottom of lens  10  lies upon the surface of base  4 , as shown in  FIG. 11 . Two spacers  20  may extend from frame  12  of the lens  10  to the circuit board  6  upon which the LED&#39;s  3  are mounted thereto in different banks with respect to their associated reflectors  2 . The lens  10  thus extends continuously in a ribbon of parallel fluted lens segments  11   a  within dome  5  adjacent the front of reflectors  2 .  FIGS. 7 and 8  show top and elevation views of assembly  14 . Base  4  lies horizontal with respect to the vertically fluted lens segments  11   a  (see  FIGS. 11 and 12 ). 
     An example of a complete light bar  23  with interior lens  10  in assembly  14  is shown in  FIG. 11 , and also in  FIG. 12  on a longer light bar  23   a  with two lenses  10  with left and right assemblies  14 . In these examples, interior lenses  10  have been added to the light bars  1  and  1   a  of  FIGS. 1 and 3 , respectively, to provide light bar  23  and  23   a , respectively. 
     In operation, the fluted lens segments  11   a  of lens  10  diffuse the light either emitted directly from LEDs  3 , or via reflection by parabolic reflector  2 , by refraction over a wide angle. Further, the fluted lens segments  11   a  assist in blending or mixing light side by side from different LEDs  3  thereby hindering viewer perception of the LED&#39;s as point light sources. 
     Lens  10  and its use in optical assembly  14  can provide the following advantageous features in light bars: 
     I. The vertical fluted lenses or lens segments  11   a  provide horizontal dispersion of light, allowing wider viewing angles of the individual LED&#39;s  3  than if lens  10  where not present. 
     II. The vertical fluted lenses of lens segments  11   a  provide for a larger more uniform lights source image size, whereas without lens  10 , the individual LED&#39;s  3  can be seen more as hot spots. 
     III. The lens  10  snaps onto the existing light source reflector assemblies. This makes it quick and easy to install for manual assemblers inside light bar  23  and  23   a  in house (e.g., during manufacture of light bars), a quick add-on for distributors, and a quick upgrade add-on for end users. 
     IV. The lens  10  has two separate halves  13   a  and  13   b , such that when it is desired to have different color light from different halves of assembly  14 , each half may be composed of different color plastic so as to provide a filter of desired color of light from the light bar from LED illumination when incident such lens halves. This avoids the additional expense of providing different color LEDs in each half of the prior art assembly shown in  FIG. 1 . Further, the color of light from each half may be modified by merely replacing one half of one color with one of another color, without the expense of replacing LEDs and their associated circuitry with different color LEDs. Lens  10  can be molded in colors, and two of the same, or two lens halves  13   a  and  13   b  of different colors can be quickly and easily added inside the bar  23   a  to achieve numerous two-color light sources quickly and economically. 
     Although the lens  10  is shown for use in an optical assembly  14  for exterior roof mountable light bar, it may also be sized for use in other light bars such as mini-light bars or lower profile light bars than shown in  FIGS. 11 and 12 . Further, lens  10  may be provided in light bars different from that shown in the figures. 
     From the foregoing description, it will be apparent that there has been provided a lens which may be added to an existing light bar to provide improve light dispersion from light sources. Variations and modifications in the herein described interior lens, light bar with such lens, and its optical assembly within a light bar, within the scope of the invention will undoubtedly suggest themselves to those skilled in the art.