Patent Publication Number: US-9404634-B2

Title: LED light fixture with facilitated lensing alignment and method of manufacture

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of currently pending U.S. application Ser. No. 12/610,077, filed on Oct. 30, 2009. 
    
    
     FIELD OF THE INVENTION 
     This invention relates generally to the field of LED light fixtures and, more particularly, to the field of LED light fixtures for various high-luminance area lighting applications such as roadway lighting, factory lighting, parking lot lighting, commercial building lighting, and the like, and to the manufacture thereof. 
     BACKGROUND OF THE INVENTION 
     In recent years, the use of light-emitting diodes (LEDs) in development of light fixtures for various common lighting purposes has increased, and this trend has accelerated as advances have been made in the field. Indeed, lighting applications which previously had typically been served by fixtures using what are known as high-intensity discharge (HID) lamps are now being served by LED light fixtures. Such lighting applications include, among a good many others, roadway lighting, factory lighting, parking lot lighting, and commercial building lighting. 
     In many of such products, achieving high levels of illumination over large areas with specific light-distribution requirements is particularly important. One example is fixtures for roadway lighting, an application in which the fixtures are generally placed along roadway edges while light distribution is desired along a significant portion of roadway length and, of course, on the roadway itself—generally to the exclusion of significant light off the roadway. And in such situations it is desirable to minimize the use of large complex reflectors and/or varying orientations of multiple light sources to achieve desired illumination patterns. 
     Achieving appropriate light distribution while avoiding or minimizing the use of complex reflectors and/or varying orientations of multiple light sources requires the use of lens systems for that purpose. And, where lens alignment plays a role in lens systems, maximizing their effectiveness requires high precision in lens alignment. 
     At the same time, it must be recognized that what is involved in manufacture of LED light fixtures for roadway illumination and the like is mass, preferably highly efficient, manufacture of light fixtures, rather than manufacture of extremely high-cost precision instruments such as for laboratory usage or the like. More specifically, it is of great importance that the economics of low-cost, high-efficiency manufacture be satisfied, but while still achieving the high-precision lens alignment necessary to maximize performance of high-luminance LED light fixtures for roadway illumination and the like. 
     SUMMARY OF THE INVENTION 
     The present invention is an improved LED light fixture with high-precision lens alignment, and a high-efficiency manufacturing method for such LED light fixture. 
     The method of this invention is a method of assembling an LED light fixture of the sort including (a) a heat-conductive structure having a mounting surface, (b) a circuit board having a plurality of LED arrays spaced thereon with a plurality of primary lenses each over a corresponding one of the LED arrays and (c) a one-piece lensing member having a plurality of secondary lenses each positioned to align with a corresponding one of the primary lenses. The inventive method includes: providing a set of mounting holes through the circuit board and a set of alignment holes in the circuit board; providing a set of mounting holes through the one-piece lensing member and a set of alignment protrusions extending from a circuit-board-adjacent surface of the lensing member; providing first and second sets of fastener-receiving cavities in the heat-conductive structure and open at the mounting surface thereof; mounting the circuit board to the mounting surface by inserting a first set of fasteners through the circuit-board mounting holes into the first set of fastener-receiving cavities; aligning the lensing member with respect to the circuit board by mating engagement of the alignment protrusions with the alignment holes; and installing the lensing member over the circuit board by inserting a second set of fasteners through the lensing-member mounting holes into the second set of fastener-receiving cavities. 
     The lighting apparatus of this invention includes: (1) a plurality of primary lenses each over a corresponding LED array, the LED arrays spaced on a circuit board, the circuit board having a first mating feature; and (2) a one-piece lensing member over the circuit board, the circuit board including a plurality of secondary lenses each spaced over a corresponding one of the primary lenses, the one-piece lensing member having a second mating feature positioned and configured for mating engagement with the first mating feature, the first and second mating features engaged to accurately align the secondary lenses over their corresponding primary lenses. 
     In some embodiments, the second mating feature is a protrusion extending from a circuit-board-adjacent surface of the one-piece lensing member, and the first mating feature is a complementary hole formed in an LED-supporting surface of the circuit board. In such embodiments, the lensing member may have first and second protrusions extending from its circuit-board-adjacent surface, and the circuit board defines (a) a first hole complementary in shape to the first protrusion to fix the position of the lensing member along the circuit board and (b) a second hole receiving the second protrusion to prevent rotation of the lensing member about the first protrusion. The second hole may be elongate along a line extending between the first and second holes to facilitate engagement of the mating features. 
     Certain embodiments of the present invention also include the heat-conductive structure including a mounting surface to which the circuit board and the lensing member are secured. The heat-conductive structure has first and second sets of fastener-receiving cavities open at the mounting surface. The circuit board is mounted to the heat-conductive structure with fasteners extending through mounting holes in the circuit board and into the first set of fastener-receiving cavities. The one-piece lensing member is secured to the heat-conductive structure by fasteners inserted through holes in the one-piece lensing member and into the second set of fastener-receiving cavities. 
     The one-piece lensing member may have a peripheral portion extending beyond the edge of the circuit board. Such peripheral portion preferably encircles the circuit board and engages a gasket providing a weathertight seal around the circuit board. The one-piece lensing member may be of a polymeric material, and compression-limiting inserts are in each of the holes of the one-piece lensing member. 
     Precise alignment of lenses give the full light-distribution benefits that are intended is achieved by this invention, while still allowing highly-efficient assembly. 
     In descriptions of this invention, including in the claims below, the terms “comprising,” “including” and “having” (each in their various forms) and the term “with” are each to be understood as being open-ended, rather than limiting, terms. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded bottom perspective view of an LED light fixture according to the present invention. 
         FIG. 2  is a plan view of a circuit board. 
         FIG. 3  is a plan view of a one-piece lensing member. 
         FIG. 4  is a perspective view of the lensing member of  FIG. 3 . 
         FIG. 5  is a perspective view of the lensing member of  FIG. 3  aligned over the circuit board. 
         FIG. 6  is a plan view of a mounting surface of a heat-conductive structure. 
         FIG. 7  is a perspective view showing the circuit board mounted to the heat-conductive structure. 
         FIG. 8  is a perspective view showing the lensing member aligned over the circuit board mounted to the heat-conductive structure. 
         FIG. 9  is a perspective view showing the lensing member installed to the heat-conductive structure. 
         FIG. 10  is a perspective sectional view across the heat-conductive structure and showing securement of the one-piece lensing member to the heat-conductive structure. 
         FIG. 11  is a perspective sectional view across the heat-conductive structure and showing mounting of the circuit board to the heat-conductive structure. 
     
    
    
     DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS 
       FIGS. 1-9  illustrate LED light fixture  10  according to the present invention and a high-efficiency manufacturing method for such LED light fixture  10  which gives high-precision lens alignment. 
       FIG. 1-5  best illustrates that LED light fixture  10  includes a heat-conductive structure  20 , a circuit board  30  and a one-piece lensing member  40 . Heat-conductive structure  20  has a mounting surface  23  best seen in  FIGS. 1 and 6 .  FIGS. 1, 2 and 5  best illustrate circuit board  30  which has a plurality of LED arrays  31  spaced thereon with a plurality of primary lenses  32  each over a corresponding one of LED arrays  31 .  FIGS. 3-5  best show one-piece lensing member  40  having a plurality of secondary lenses  41  each positioned to align with a corresponding one of primary lenses  32 . 
     In the inventive method, a set of mounting holes  33  is provided through circuit board  30  and a set of alignment holes  34  is provided in the circuit board  30 , as best seen in  FIG. 2 . A set of mounting holes  42  (best seen in  FIG. 3 ) is also provided through one-piece lensing member  40 . A set of alignment protrusions  43  (best seen in  FIGS. 3 and 4 ) is also provided, protrusions  43  extend from a circuit-board-adjacent surface  44  of lensing member  40 . In heat-conductive structure  20 , first and second sets of fastener-receiving cavities  21  and  22 . 
     As seen in  FIG. 1 , cavities  21  and  22  are open at mounting surface  23  of heat-conductive structure  20 .  FIGS. 1, 7 and 11  show that circuit board  30  is mounted to mounting surface  23  by inserting a first set of fasteners  11  through circuit-board mounting holes  33  into first set of fastener-receiving cavities  21 .  FIG. 5  illustrates alignment of lensing member  40  with respect to circuit board  30  by mating engagement of alignment protrusions  43  with alignment holes  34  such that secondary lenses  41  are accurately aligned over their corresponding primary lenses  32 .  FIGS. 1 and 10  show that lensing member  40  is installed over circuit board  30  by inserting a second set of fasteners  12  through lensing-member mounting holes  42  into second set of fastener-receiving cavities  22 . 
     It is best seen in  FIGS. 3-5  that lensing member  40  has first and second protrusions  431  and  432  extending from its circuit-board-adjacent surface  44 .  FIG. 2  shows that circuit board  30  defines first and second alignment holes  341  and  342 . First hole  341  is complementary in shape to first protrusion  431  to fix the position of lensing member  40  along circuit board  30 . And, as seen in  FIG. 5 , second hole  342  receives second protrusion  432  to prevent rotation of lensing member  40  about first protrusion  431 .  FIG. 2  further shows second hole  342  elongate along a line  35  extending between first and second holes  341  and  342 . This facilitates engagement of mating features in the form of alignment holes  34  and protrusions  43 . 
       FIGS. 1, 5, 10 and 11  show that one-piece lensing member  40  has a peripheral portion  45  extending beyond edge  36  of circuit board  30 . Peripheral portion  45  encircles circuit board  30  and engages a gasket  13  which provides a weathertight seal around circuit board  30 . Since one-piece lensing member  40  may be of a polymeric material, compression-limiting inserts  46  in such embodiments are used in each of mounting holes  42  of one-piece lensing member  40 . 
     While the principles of the invention have been shown and described in connection with specific embodiments, it is to be understood that such embodiments are by way of example and are not limiting.