Abstract:
An LED lamp assembly with a substantial heat sink may be inexpensively constructed using sections of extruded metal as the heat sink. The extruded heat sink sections are trapped in latched sandwich structure assuring good thermal contact between the LED light sources and the extruded heat sink and a metal optic. The inexpensive structure may be rapidly assembled.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to electric lamps and particularly to electric lamps. More particularly the invention is concerned with LED lamps with heat sinks. 
     2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     LED lamps are quickly becoming economical. They however frequently require large heat sinks to increase their lumen efficiency and to preserve their longevity. Heat sinks are expensive to design and to make. Moreover, the radiating fins, pins or other heat conducting elements are frequently fragile, or awkward to position on a lamp exterior. There is then a need to for a simple heat sink structure that is inexpensive to make, and practical to couple to an LED assembly. 
     BRIEF SUMMARY OF THE INVENTION 
     An LED lamp assembly can be economically made with an extruded heat sink. The assembly includes a planar circuit board having a first side and a second side. One or more LEDs are supported on the circuit board to emit light along a path directed away from the first side. A heat sink having a front face is positioned to be adjacent the second side of the circuit board. The heat sink has at least one radiating element extending away from the front face. A back plate has a back wall including an interior wall defining an opening to receive the at least one radiating element, and has at least one latch. An optic is extended through the printed circuit board, the optic having a light receiving face positioned to substantially intersect light emitted from the one or more LEDs. The optic has a portion positioned intermediate the second side of the printed circuit board and the heat sink. A front plate has an inner wall defining a passage and has a latch. The back plate is latched to the front plate, trapping the circuit board and the intermediate portion of the optic in close thermal contact with the front face of the heat sink. Meanwhile, the radiating element extends through the back plate and with the radiating element substantially exposed on the exterior of the lamp assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  shows a front perspective view of a preferred embodiment of an LED Lamp Assembly. 
         FIG. 2  shows a rear perspective view of a preferred embodiment of an LED Lamp Assembly. 
         FIG. 3  shows an exploded front view of a preferred embodiment of an LED Lamp Assembly. 
         FIG. 4  shows an exploded rear view of a preferred embodiment of an LED Lamp Assembly. 
         FIG. 5  shows a perspective view of a reflective optic with the tabs bent. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a front perspective view of a preferred embodiment of an LED Lamp Assembly  10 . The LED lamp assembly  10  is constructed with a circuit board  12 , one or more LEDs  18 , an electrical connector  20 , a heat sink  24 , a back plate  32 , an optic  48 , and a front plate  64 . 
       FIG. 3  shows an exploded front view of a preferred embodiment of an LED Lamp Assembly  10 .  FIG. 4  shows an exploded rear view of a preferred embodiment of an LED Lamp Assembly  10 . The circuit board  12  is a generally planar body with a first side  14  and a second side  16 . Formed in the circuit board is an inner wall  15  enclosing a through passage  17 . The preferred through passage  17  is sized and shaped to snuggly receive an end portion of the optic  48 . The circuit board  12  supports on the first side  14  one or more LEDs  18  that emits light along a path directed away from the first side  14  towards the optic  48 . Supported on the circuit board  12  is electrical circuitry. The electrical circuitry may provide appropriate power and signal conditioning to the supplied electrical power that is then used to operate the LEDs  18 . In the preferred embodiment circuit board  12  electrically connects the LEDs  18  to the electrical connector  20  to receive electrical power to drive the LEDs  18 . The electrical connector  20  is preferably mechanically and electrically coupled to the circuit board  12  and circuitry assembly. In an alternative, the second side of the circuit board  12  may be formed with recesses or protrusions to receive or mate with the tabs of the optic  48 . 
     The heat sink  24  is formed from material with high thermal conductivity, such as a metal, like copper, aluminum, zinc or others. The heat sink  24  has a planar front face  26  that is positioned to be in close thermal contact with the second side  16  of the circuit board  12 . The back side of the heat sink  24  may be formed with one or more ribs or troughs that may couple with corresponding features on the circuit board  12  thereby aligning one with the other. The preferred heat sink  24  a plurality of radiating elements  28  extending perpendicularly away from the planar face  26 . In the preferred embodiment, a plurality of fins  28  extend at 90 degrees to the front face  26 , this enables the exterior back plate to be axially slipped over the radiating fins. Extrusions are inexpensive to make, and redesigning an extruded heat sink to change the fin length, fin width, fin spacing or front side dimensions for differing circuit board, optic, back cover, or exterior limitations can be rapidly accommodated. Extruded heat sinks can be robust. It has also been found that an extruded body has a higher thermal conductivity than has a cast or molded material. For example, extruded aluminum has a thermal conductivity of about 200 W/mK, but a cast aluminum alloy has a thermal conductivity of less than 100 W/mK. Extruding the metal heat sink  24  also greatly reduces the cost of producing the heat sink  24 . The extruded heat sink  24  with a planar front face  26  can be cut along a peripheral line perpendicular to the front face  26 . The easiest cut is straight across the extrusion in two places, leaving a heat sink in the general form of a rectangular block, or polypiped. The extruded heat sink  24  then has a constant cross section taken perpendicular to the direction of extrusion, and has a first perpendicular end and a second perpendicular end. Alternatively the exterior line may be circular, or otherwise thereby forming a cylindrical, oval or other useful shape. In a further alternatively, the front face  26  of the heat sink  24  may be modified with alignment features, such as recesses or protrusions to receive and align printed circuit board  12  or the optic  48  when the group is pressed into contact. 
     The back plate  32  is designed to provide pressure against the heat sink  24  in the direction of the circuit board  12 . The back plate  32  has a back wall  34  including one or more first interior walls  36  defining one or more openings  38 . The openings  38  are sized and shaped to receive respectively one or more radiating elements  28 . The respective radiating element or elements  28  may then be interdigitated with respective openings  38  formed in the back plate  32 , and extend through the back plate  32  to the exterior for exposure on the exterior of the lamp assembly  10 . Formed on the back plate  32  are a side wall that has at least one latch  42 , and a second wall  44  defining at least in part an opening  46  to receive the electrical connector  20 , thereby forming a socket portion  46 .  FIG. 2  shows a rear perspective view of a preferred embodiment of an LED Lamp Assembly. 
       FIG. 5  shows a perspective view of a reflective optic  48  with the tabs  55  bent. The optic  48  is preferably mechanically coupled to the printed circuit board  12 . The preferred optic  48  has a light reflecting surface, and a light receiving face  50  substantially spanning, and intersecting the light path. The optic  50  is mechanically inserted in the hole formed in the circuit board and coupled to the circuit board  12 ; the optic  48  is a metal body of revolution having a side wall  52  with at least a portion of the side wall  52  being reflective. The preferred optic  48  is a stamped metal sheet in the form of a trumpet, the outer surface of which is reflective, and shaped to reflect light perpendicular to the lamp axis, so the light may be further intercepted by a forward directing reflector. The preferred optic  48  has a thermal contact  54  pressed against either the printed circuit board  12  or the heat sink  24 . The preferred optic  48  is made of metal, and has a thermal contact  54  trapped under mechanical pressure pressed between the printed circuit board  12  and the heat sink  24 . In one embodiment, the rear facing end of the optic  48  is formed with one or more tabs  55 . Preferably the tabs  55  are equally distributed around the rear facing end of the trumpet shaped optic. Once the optic  48  is inserted into the hole formed in the circuit board, the tabs  55  may be bent outwardly at 90 degrees, to trap the optic  48  in the circuit board hole. In the preferred embodiment the cone portion of the optic is small enough in diameter to pass through a passage formed in the front plate  64 , but large enough in diameter to span the axial projection of the one or more LEDS to substantially intercept the light emitted by the one or more LEDS. 
     The front plate  64  has a planar face  66 , an inner wall  68  defining a passage  70  sufficiently large and otherwise shaped to fit over the optic  48 , and sufficiently spaced away from the LEDs  18  to not interfere with the light emitted by the LEDs  18  in the direction of the reflective surface of the optic  48 . The front plate  64  is further formed with at least one latch portion  72  to couple with a corresponding latch portion formed on the back plate  32 . For example, the front plate  64  may be formed as an annulus with one or more peripheral latch tabs  72 . The inner side of the front plate  64  may be formed with nubs or stand offs  74  sized and positioned to mate with areas of the circuit board  12 , so that the front plate  64  may mate with and press against the circuit board  12 . 
     The LED lamp assembly is assembled by positioning the heat sink  24  in the back plate  32 . The optic  48  is inserted through the hole in the circuit board  12  and the tabs  55  are bent radially away from the axis to trap the optic  48  in the circuit board  12 . The second side of the circuit board  12  may be placed against the flat face of the heat sink  24 . It is understood that the electrical integrity of the printed circuit board  12  should be preserved, so an interfacing layer of a thermally conductive, but electrically insulating layer such as a lacquer, silicone, or similar thin layer of material may be interposed. The electrical connectors  20  are aligned and positioned in the socket portion  46 . The bent tabs  55  are then trapped between the front face  26  of the heat sink  24  and the second side  16  of the circuit board  12 . The front plate  64  is passed over the forward end of the optic  48 , and aligned to latch with the back plate latches  42 . The front plate  64  or the standoffs (numbs)  74  of the front plate  64 , as the case may be, press against the circuit board  12 , pressing the circuit board  12 , and captured tabs  55  in close thermal contact with the heat sink  24 . The latches  72  of the front plate  64  couple with the latches  42  of the back plate  32  retaining the assembly in tight contact. 
     While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention defined by the appended claims.