Abstract:
A lens particularly suited to elongated grooved lens holders such as heat sinks for light emitting diodes. The lens may have a curved surface which projects light in rectangular beams and a radial flange for engaging grooves of a grooved lens holder. Curvature is that of a flattened or compressed sine wave, with less than one full wave being formed along the lens. In one aspect of the invention, the crest of the wave, which would ordinarily be domed, may be flat. The radial flange has straight sides to enable contiguity when arrayed in abutment as well as for cooperating with the grooves of the lens holder.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date under 35 USC 119(a) of Chinese Patent Application No. 200820203218.7, filed Nov. 11, 2008, the contents of which are incorporated herein by reference. This application is also related to Patent Applications entitled MODULAR LED FLOOD LIGHT and HEAT SINK FOR MODULAR LED FLOOD LIGHT, both of common ownership with the present invention, and filed of even date herewith. 
     FIELD OF THE INVENTION 
     The present invention relates to illumination, and more particularly to lens configuration for lenses intended to be mounted to a heat sink which supports light emitting diodes within a luminaire. 
     BACKGROUND OF THE INVENTION 
     Lights for illuminating large areas such as roads, parking lots, fields, and the like have long been provided. Lighting technology for such lights has progressed from incandescent to specialized high powered types such as sodium vapor and mercury vapor. However, it has become desirable to utilize more efficient light sources, as efficiency relates to units of light output per unit of electrical input. 
     Light emitting diodes (hereinafter LEDs) are among the most efficient types of light sources commercially available today. LEDs enjoy not only relatively high efficiency, but offer long life and relatively uncomplicated construction. LEDs have progressed to the point where white light producing LEDs could be employed in many applications, including overhead or elevated lighting such as that suitable for roads, parking lots, fields, and the like. 
     LEDs require suitable heat sinks to dissipate heat generated by the LEDs. Heat sinks are advantageously fabricated by extruding them from aluminum or an aluminum alloy. It would be desirable to provide lenses for LEDs which are formed to accommodate extruded heat sinks. 
     It would also be desirable to provide lenses which project light in rectangular beams, when the beam is viewed in cross section. This promotes more even lighting than is provided by circular beams. When plural circular beams impinge upon an environmental surface, there are gaps in coverage where between the circular light patches. Alternatively, where circular beams overlap, there are areas where only one beam contributes its light, so that lighting is still uneven. There exists a need for a lens which projects rectangular beams, particularly for lens holders such as heat sinks, and also for serial arrangements of light sources and lenses. 
     SUMMARY OF THE INVENTION 
     The present invention satisfies the above stated needs in a lens intended for use with heat sink mounted LEDs, and advantageously, for overhead or elevated luminaries such as those used to illuminate roads, parking lots, fields, and the like. Despite the various purposes, such lights will be referred to as street lights for brevity. 
     The novel lens is configured to project light as beams which are rectangular in cross section, from a point source such as an LED located proximate the novel lens. To this end, the novel lens may have an undulating exterior or exposed surface, the undulation defining a very shallow sine wave when viewed in side elevation. A half sine wave shaped dome may occupy each square area formed by the novel lens. Where the lens is configured as a non-square rectangle, such as where in plan the lens is viewed as two abutting squares, two half sine wave domes are formed in one orthogonal axis. According to another aspect of the invention, each dome may have a flat uppermost or exposed surface at the center. In one orthogonal axis, the lens is bounded by a partial or truncated dome. 
     The novel lens may be configured to be arranged in rows, with each lens cooperating closely with its neighbors so that no gaps appear between adjacent lenses, as occurs between circles which have been placed in non-overlapping abutment. This comes into play where the lenses are grouped in abutment with each other, such as in a closely spaced line. 
     The novel lens may have lateral flanges for engaging grooves formed in heat sinks or other supporting structure. 
     It is therefore one object of the invention to provide a lens which projects rectangular beams of light from a point light source. 
     Another object of the invention is to provide a lens which cooperates with extruded lens holders such as heat sinks. 
     It is an object of the invention to provide improved elements and arrangements thereof by apparatus for the purposes described which is inexpensive, dependable, and fully effective in accomplishing its intended purposes. 
     These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein: 
         FIG. 1  is a perspective view of a lens according to at least one aspect of the invention. 
         FIG. 2  is a cross sectional view taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a cross sectional view taken along line  3 - 3  of  FIG. 1 . 
         FIG. 4  is a perspective view of a lens according to another aspect of the invention. 
         FIG. 5  is a cross sectional view taken along line  5 - 5  of  FIG. 4 . 
         FIG. 6  is a cross sectional view taken along line  6 - 6  of  FIG. 4 . 
         FIG. 7  is a bottom perspective view that would apply to both  FIGS. 1 and 4 . 
         FIG. 8  is a diagrammatic representation illustrating light projection from the lens of  FIG. 1  or that of  FIG. 4 . 
         FIG. 9  is a diagrammatic representation illustrating light projection from a plurality of lenses which may be those of  FIG. 1  or those of  FIG. 4 . 
         FIG. 10  is an exploded perspective view of a heat sink assembly with which the lens of  FIG. 1  or that of  FIG. 4  may cooperate. 
         FIG. 11  is a perspective detail view of a heat sink shown in  FIG. 10 . 
         FIG. 12  is an end view of the heat sink of  FIG. 11 , shown proximate the lens of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  of the drawings shows a lens  10  for projecting light in beams which are rectangular when viewed in cross section, using a point light source (described hereinafter). The lens  10  may comprise a body  12  having a length  14 , a width  16 , and depth or thickness in a third orthogonal direction. The body  12  has a curved top surface  18  extending along the length  14  and width  16  of the body  12 . Also, referring to  FIG. 2 , the curved top surface  18  may have configuration of a truncated flattened sine wave when viewed in cross section from a first direction and of a complementing truncated flattened sine wave when viewed in cross section from a perpendicular second direction. As employed herein, the term “flattened sine wave” refers to the graphic effect on the resultant wave of compression of the vertical axis (along the direction of the thickness, as depicted in  FIG. 2 ) relative to the horizontal axis (along the direction of the length  14  or of the width  16 ). The first direction may be that parallel to the length  14 , with the second direction being that which is parallel to the width  16 , for example. 
     Curvature in the two directions results the curved top surface  18  having a central domed portion  20  (best seen in  FIG. 2 ), which central domed portion  20  has a flat facet  22  at the center thereof. Flattening of the flat facet  22  should not be confused with flattening or compression of the sine wave which is employed herein to characterize curvature of the top surface  18 . 
     In a true sine wave or even a sine wave wherein the vertical axis is compressed, the top of the wave would be curved. Therefore, for the lens  10 , the term “sine wave” is provided as a semantic convenience in conveying the overall effect seen in side view, apart from the flat facet  22 , and should not be literally construed. 
     The body  12  may comprise a radial flange  24  extending outwardly therefrom in the direction of the length  14  and also in the length of the width  16 . Of course, the radial flange  24  may extend outwardly in only one direction, if desired for a particular application. 
       FIG. 2  shows the lens  10  and the sine wave curvature of the top surface  18  in the length direction. The wave is seen to be declining from the leftmost point as depicted in  FIG. 2  towards the right to form a first trough  26 . The central domed portion  20  rises to the right of the trough  26 . The wave again declines to the right of the central domed portion  20  to define a second trough  28 . The first trough  26  terminates at the radial flange  24  at an inclined surface  30 . Similarly, the second trough  28  terminates at the radial flange  24  at a corresponding but generally mirror image inclined surface  32 . The lowest points of the troughs  26  and  28  are located below the upper surface  38  of the radial flange  24 . 
     It should be noted at this point that orientational terms such as upper, lower, uppermost, right, left, and others refer to the drawing as viewed by an observer. It will be understood that these orientational terms do not connote that any particular orientation of the invention assume criticality in defining the invention. Therefore, orientational terms must be understood to provide semantic basis for purposes of description, and do not limit the invention or its component parts in any particular way. 
     Curvature from the inclined surface  30  to the inclined surface  32  represents the entirety of the sine wave which is present on the lens  10  in that there is only one iteration of the sine wave formed on the body  12  in each of the directions of the length  14  and of the width  16 . 
       FIG. 3  shows sine wave curvature of the top surface  18  in the width direction. In this direction, curvature forms opposed slopes  34 ,  36  which at their lowest points are below the upper surface  38  of the radial flange  24 . Another way of saying that portions of the sine wave in both of the orthogonal directions are below the upper surface  38  is to say that curvature of the curved top surface  18  extends in the direction of thickness below the radial flange  24 . Similarly, it may be said that part of the curved top surface  18  extends above the radial flange in the direction of thickness. 
       FIG. 3  also shows that the body  18  extends beyond the radial flange  24  in the direction thickness on both of two opposed sides of the radial flange  24 . Notably, the body  12  further comprises a base portion  40  which extends below the radial flange  24 . This base portion may comprise a flat bottom surface  42 . A corresponding flat bottom surface (not shown) may be provided in the absence of the extending base portion  40 . 
       FIG. 4  shows a lens  110  which differs from the lens  10  in that the former does not have the flat facet  22 . Rather, a central domed portion  120 , which corresponds to the central domed portion  20  of the lens  10 , is truly domed as it displays curvature continuously therealong, despite compression of the vertical axis of curvature. In other ways, the lens  110  may be the structural counterpart of the lens  10 , the former having a body  112  having a length  114 , a width  116 , and depth or thickness in a third orthogonal direction. The body  112  has a curved top surface  118  extending along the length  114  and width  116  of the body  112 , a central domed portion  120 , a radial flange  124  extending outwardly from the body  112 , a first trough  126 , a second trough  128 , inclined surfaces  130  and  132 , and a base portion  140  which may comprise a flat bottom surface  142 . The components of lens  110 , with the exception of the central domed portion  120 , may be structurally identical to those of their similarly named counterparts of the lens  10 . These components are shown in  FIGS. 4-6 . 
     The flat facet  22  of the lens  10 , which flat facet  22  is absent in the lens  110 , modifies the pattern of light projection from that of the lens  110 . 
       FIG. 7  shows a perspective view of a possible appearance of the bottoms of both lenses  10  and  110 . It is seen that the body  12  (or the body  112 ) has a generally rectangular perimetric boundary  46  ( 146 ) having rounded corners  48  ( 148 ). 
       FIG. 8  shows a characteristic of both lenses  10  and  110 . Notably, both lenses  10 ,  110  are configured to project light in a beam  44  (or, for lens  110 , a beam  144 ) which is rectangular in cross section. This is shown diagrammatically in  FIG. 8 , it being understood that due to the presence of the flat facet  22  in the lens  10  but not in the lens  110 , the actual projected beams  44 ,  144  will differ somewhat. 
       FIG. 9  illustrates an optical effect which can be obtained using the lens  10  or the lens  110 . Plural lenses  10  or  110  may be focused to project rectangular patches of light  50 A,  50 B,  50 C,  50 D,  50 E,  50 F which abut one another. It will be appreciated that because the rectangular patches  50 A,  50 B,  50 C,  50 D,  50 E,  50 F provide abutting straight lines where they abut, there are no gaps in illumination, or alternatively, doubly covered areas beside singly covered areas. By contrast, it would be impossible to achieve this effect with circular beams (not shown), as are frequently provided by luminaries generally, or by light beams (not shown) that have curved if not circular outer boundaries. Thus the novel lenses  10 ,  110  may contribute to even illumination of environmental surfaces. 
       FIG. 10  shows a heat sink assembly comprising a heat sink  2 , a plurality of LEDs  4  which are mounted on printed circuit boards  6 , and a plurality of lenses  10  ( 110 ) which may be mounted to the heat sink assembly  2 . It will be seen in  FIG. 10  that with the LEDs  4  mounted in a straight row, the lenses  10 ,  110  should be similarly arrayed in abutment. Because of the straight lines of the rectangular perimetric boundary  46  ( 146 ) (see  FIG. 7 ), a compact formation of the lenses  10  ( 110 ) ensues, with no gaps visible between adjacent lenses  10  ( 110 ). The straight sides of the perimetric boundary  46  ( 146 ) also assure cooperation with grooves  9  of the heat sink  2  in which the lenses  10  ( 110 ) are received and supported. These grooves  9  are more clearly seen in  FIG. 11 .  FIG. 12  still better shows cooperation of the grooves  9  and the lens  110  as the radial flange  124  fits to the grooves  9 . Of course, the lens  10  would cooperate equally given that the only difference between the lens  10  and the lens  110  is the flat facet  22 , which does not come into play as to insertion of a lens  10  or  110  within the heat sink  2 . 
     The present invention is susceptible to modifications and variations which may be introduced thereto without departing from the inventive concepts. For example, although the inventive lenses  10 ,  110  have been indicated as being of glass, it would be possible to fabricate them from a suitable synthetic resin, such as acrylic plastic among others. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is to be understood that the present invention is not to be limited to the disclosed arrangements, but is intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible.