Patent Publication Number: US-2010118496-A1

Title: Heat sink for modular led flood light

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. 200820203227.6, 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 LENS FOR LIGHT EMITTING DIODES MOUNTED ON A HEAT SINK, both of common ownership with the present invention, and both filed of even date herewith. 
     FIELD OF THE INVENTION 
     The present invention relates to illumination, and more particularly to a heat sink which is intended to support a plurality of light emitting diodes. 
     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. 
     Heat sinks for luminaires using LEDs have typically suffered from the characteristic that they are not configured so that they may be extruded or cut to any desired length without sacrificing certain structural features. Notably, structure formed in the end of an extrusion may be lost when the extrusion is cut or is extruded without forming end structures. An example of end structures which may be necessary is tapped holes for receiving fasteners. It would not be feasible to produce an extrusion having a tapped or threaded hole extending the full length of the extrusion. 
     This leads to the situation that many different models must be designed, produced, and stocked, and replacement parts be made available for each model. While this situation offers great versatility in providing varieties of luminaires, such convenience comes at economic cost. 
     A need exists for mass producing heat sinks for luminaires using white LEDs in many light output capacities, so that individual luminaires employing LEDs may be produced in different capacities and configurations using a limited number of different models or designs of heat sinks. As a consequence, it becomes desirable to provide a heat sink for supporting and dissipating heat from LEDs which lends itself to modular construction and efficient fabrication. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above stated need by providing a design for a heat sink which is usable with modular luminaires which utilize LEDs. Firstly, the novel heat sink can be fabricated by extruding a material such as aluminum or its alloys. Secondly, the novel heat sink can be extruded to any desired length and cut to any length while preserving all of its features, especially those of holes for receiving fasteners. 
     The present invention addresses the issue of providing holes for fasteners inserted from the end, or alternatively stated, for fasteners which must be installed into longitudinally oriented fastener holes. This is accomplished by forming generally circular channels at certain points within the heat sink body. By using a relatively soft metal such as aluminum or its alloys, fasteners such as self-tapping screws or simply screws formed from strong materials such as certain steels will be immediately compatible with the extruded heat sink. 
     In another aspect, the heat sink has a centrally located hole, which enables the heat sink to be rotated about its central axis on two fasteners. This enables the heat sink to be angularly adjusted prior to fastening. Such adjustment is possible with certain luminaires such as that which is the subject of one of the above referenced copending applications. 
     The novel heat sink accommodates a narrow elongated array of LEDs, such as a straight row. This enables width of the light generated source to be varied by selecting the number of heat sinks which are to be installed next to one another. 
     In summary, the novel heat sink accommodates variations in both length and width of an array of LEDs in a luminaire. It also enables minor angular adjustment for purposes of modifying projection patterns of light. 
     It is therefore an object of the invention to provide a design for a heat sink which is modular and highly versatile in supporting dimensions and configurations of LED arrays for luminaires. 
     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 top perspective view of a modular luminaire according to at least one aspect of the invention. 
         FIG. 2  is an exploded top perspective view of  FIG. 1 . 
         FIG. 3  is an exploded top perspective detail view of components seen at the center of  FIG. 1 . 
         FIG. 4  is a top perspective detail view of the lowermost component of  FIG. 3 . 
         FIG. 5  is an end detail view of  FIG. 4 , drawn to enlarged scale. 
         FIG. 6  is a diagrammatic representation of possible positions and adjustments to the direction of projection of light from LEDs, according to a further aspect of the invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  of the drawings shows a modular luminaire  10  which uses LEDs  12  (not all of which are individually called out by reference numeral), which may utilize a heat sink  14  according to at least one aspect of the invention. Plural heat sinks  14  are utilized in the modular luminaire  10  for supporting and dissipating heat from the LEDs  12 . 
     The modular luminaire  10  may be of a type in which a plurality of heat sinks  14  are suspended between a proximal end piece  16  and a distal end piece  18  of the modular luminaire  10 . Individual component parts of the modular luminaire  10  are better seen in the exploded view of  FIG. 2 . 
       FIG. 3  shows components of an individual heat sink  14  and parts which are connected thereto to establish a usable modular bloc of LEDs  12 . A plurality of LEDs  12  is mounted on printed circuit boards  28  (not all of which are individually called out by reference numeral) in conventional fashion. The printed circuit boards  28  may be mounted to the heat sink  14  as will be described hereinafter. A lens  30  (not all of which are individually called out by reference numeral) is provided to cover each LED  12 . 
     Each heat sink  14  may be said to have a base or platform  35  (see  FIG. 4 ), a proximal end  34 , a distal end  36 , and a length defined therebetween, although designation as proximal or distal in this case is only a semantic convenience. For example, the proximal end  34  may be that engaged and supported at a proximal end of the modular luminaire  10 , while the distal end  36  may be that supported by the distal end of the modular luminaire  10 . 
     The LEDs  12  are located between the proximal end  34  and the distal end  36 , and may for example be ordered in straight rows. Of course, other arrays of LEDs  12  on each heat sink  14  are possible. 
     A heat sink  14  isolated from its associated components, such as the LEDs  12  and printed circuit boards  28  is shown in  FIG. 4 . The heat sink  14  is seen to have a base or platform  35 , lateral cooling fins  46 ,  48  and top cooling fins  50 . 
     As best seen in  FIG. 5 , two short walls  41 ,  43  project upwardly along each side of an upwardly facing surface  68 , which in  FIG. 4  may be the upper surface of the body  35 . The fins  46  may project from the wall  41  (see  FIG. 4 ). The fins  48  may project from the wall  43 . All of the fins  46 ,  48 ,  50  may be parallel to the central axis  58 , seen in  FIG. 4 . 
     Again referring to  FIG. 5 , a gap is defined between every two adjacent fins  46 ,  48 ,  50 . Illustratively, a gap  47  is formed between the fins  50 G and  50 H. Other gaps are also present, but are not called out by reference numeral. Each gap has a width, which refers to the distance between adjacent fins, such as the fins  50 G,  50 H. 
     Gaps are also present between adjacent cooling fins  46 , such as the gap  55 , and between adjacent cooling fins  46 , such as the gap  57 . 
     A floor surface is defined on the body  35  between any two fins, such as the floor surface  49  formed between the fins  50 B,  50 C. The floor surface may be the outer surface of the body  35  between two adjacent fins, such as the fins  50 . 
     A fastener hole  72  may be formed at the central axis  58  of the heat sink  14 , and more particularly, may overlie the central axis  58 . The location of the fastener hole  72  enables angular adjustment of heat sinks  14  and hence of LEDs. This is described hereinafter with reference to  FIG. 6 . 
     Five fastener thread receiving channels  60 ,  62 ,  64 ,  66 ,  72  may be formed in the heat sink  14 . Each one of the fastener thread receiving channels  60 ,  62 ,  64 ,  66 ,  72  may be formed at the floor surface of the body  35  or at the corresponding floor surfaces of the walls  41 ,  43  (see  FIG. 4 ) between two of the fins  46 ,  48 , or  50 . The fastener thread receiving channels  60 ,  62 ,  64 ,  66 ,  72  are generally circular in cross sectional configuration when viewed from the end, as seen in  FIG. 5 , except where the fastener thread receiving channels  60 ,  62 ,  64 ,  66 ,  72  are open to the exterior of the heat sink  14 . The diameter of each one of the fastener thread receiving channels  60 ,  62 ,  64 ,  66 ,  72  may be greater in magnitude than is the width of the gap associated with that fastener thread receiving channel  60 ,  62 ,  64 ,  66 , or  72 . The diameters are taken in a plane which is perpendicular to the central axis  58  of the heat sink. 
       FIG. 5  also shows that the wall  41  may have an inclined inner surface  51 . Similarly, the wall  43  may have an inclined inner surface  53 . When considered in end elevation, as seen in  FIG. 5 , the inclined inner surfaces  51 ,  53  define an acute angle therebetween. The inclined inner surfaces  51 ,  53  enable both a wider angle of light propagation from the LEDs  12  and also enable greater dissipation of heat from the LEDs  12  than would occur if the inner surfaces were perpendicular to the upwardly facing surface  68  (see  FIG. 4 ). 
     It will be seen that the outermost fins  50 A,  50 L are thicker than the other cooling fins  50 B,  50 C,  50 D,  50 E,  50 F,  50 G,  50 H,  501 ,  50 J, and  50 K. 
     The outermost cooling fins  46 A,  48 A of the respective walls  41 ,  43  are generally curved in cross section along their entire length when considered in end elevation. 
     Another feature of the heat sink  14  is grooves  61 ,  63  formed respectively in the walls  41 ,  43 . These grooves may receive flanges formed in lenses, such as the lenses  30 , to assist in securing the lenses in place on the heat sink  14 . 
     The lateral cooling fins  46  may project in a direction represented by the arrow  52 . The lateral cooling fins  48  may project in a direction represented by the arrow  54 . The bottom cooling fins  50  may project in a direction represented by the arrow  56 . The directions of the arrows  52 ,  54 ,  56  may be arranged such that each direction is perpendicular to an adjacent direction. Alternatively stated, a right angle A may exist between any two adjacent ones of the directions indicated by the arrows  52 ,  54 ,  56 . 
     However, it is not necessary that perpendicularity be present. It is desired that the cooling fins  46 ,  48 ,  50  face in three substantially different directions outwardly away from the central axis  58 . 
     As employed herein, orientational terms such as top and bottom will be understood to refer to the orientations depicted in the referenced drawing figures. 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. This also holds true as to designation of the fins  50  as being at the bottom of their associated heat sink  14 . The location of the fins  50  may change due because a modular luminaire such as the luminaire  10  may be mounted in any orientation. 
     It will be seen that all of the fins are longitudinally oriented in that they are parallel to the central longitudinal axis  58  of the heat sink  14 . Also formed in the heat sink  14  may be a plurality of fastener thread receiving channels  60 ,  62 ,  64 ,  66 , which extend along the length of their associated heat sink  14 . Screws  42  (see  FIG. 3 ) which may be self-tapping screws, or which may otherwise be sufficiently robust as to thread to the fastener thread receiving channels  60 ,  62 ,  64 ,  66  may be employed without the necessity of drilling and tapping screw holes. It will be appreciated that all of the features of the heat sink  14  which may be seen in end elevation, such as the fins  46 ,  48 ,  50  and also the fastener thread receiving channels  60 ,  62 ,  64 ,  66 , may be advantageously and inexpensively formed for example by an extrusion process, although other fabrication methods such as casting or injection molding could be employed if desired. 
     It will also be seen in  FIG. 6  that the overall perimetric boundary of the heat sink  14  may approximate the configuration of a rectangle. This may be achieved by coordinating the outermost extent of the fins  46 ,  48 , and  50 , and the uppermost surfaces of the walls  41  and  43 . 
     It will also be seen that the thicknesses of the body  35  and of the walls  41  and  43  may be relatively constant along more than half of their respective widths. As depicted in  FIG. 5 , the widths of the walls  41  and  43  extend vertically, with the respective thicknesses being shown in a horizontal plane. Similarly, the width of the body  35  extends in a horizontal plane in  FIG. 5 , with the thickness being shown in a vertical plane. 
       FIG. 4  also shows a mounting surface  68  for mounting the printed circuit boards  28  and fastener holes  70  which may be drilled into the heat sink  14  after extrusion, for receiving fasteners to secure the printed circuit boards  28  to the heat sink  14 . 
     Referring to  FIG. 6 , five representative heat sinks  14 A,  14 B,  14 C,  14 D,  14 E are shown. These heat sinks  14 A,  14 B,  14 C,  14 D,  14 E may be structural and functional counterparts to the heat sinks  14  described priorly, for example. The heat sinks  14 A,  14 B,  14 C,  14 D,  14 E are angularly adjustable about their respective central longitudinal axes  58 A,  58 B,  58 C,  58 D,  58 E. Representative angular adjustment of the heat sinks  14 A,  14 B,  14 D,  14 E is depicted, showing one position in solid lines and an alternative position in broken lines. Considering the heat sink  14 A as an example, the directions of the center line of light propagation is indicated by the arrows B and C. The center heat sink  14 C could be angularly adjusted if the resulting asymmetry of light projection were deemed not objectionable. 
     It is an important characteristic of the heat sink  14  that the body  35 , the first wall  41 , the second wall  43 , and the fastener thread receiving channels  60 ,  62 ,  64 ,  66 , and  72  individually and collectively display invariable cross section continuously along the entire length of the heat sink  14 . This characteristic enables heat sinks  14  to be extruded to any desired length, or to be cut to any desired length, without losing structure for receiving fasteners which are may be driven into the fastener thread receiving channels  60 ,  62 ,  64 ,  66 , and  72 . This greatly enhances modularity of the heat sink  14  as well as versatility in accommodating luminaires of different dimensions and capacities. 
     The present invention is susceptible to modifications and variations which may be introduced thereto without departing from the inventive concepts. For example, although the invention has been described with respect to individual LEDs, it would be possible to provide LEDs in pluralities or clusters (not shown), with each cluster being treated as described priorly with regard to individual LEDs. The flat mounting surface  68  easily accommodates different LED arrays. Also, LEDs need not be arrayed in perfect linear rows as illustrated, provided that a plurality of LEDs is provided along the length of each heat sink, such as the heat sink  14 . 
     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.