Abstract:
The invention discloses a three dimensional LED arrangement and heat management method using a heat transfer or conduction pipe to enable rapid heat transfer from a three dimensional cluster of LEDs to a heatsink with or without active cooling, the light emitted from the three dimensional cluster not being obstructed by a heat sink arrangement such that the light beam profile generated by the light appears similar to that generated by traditional incandescent bulbs.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application, Ser. No. 61/207,751, filed on Feb. 17, 2009, the disclosure of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates to the field of LED lighting and, more particularly, to concentrated LED lighting devices that transfer heat quickly to a separate heat sink with or without active cooling to dissipate the heat away from the concentrated LED light source. 
       BACKGROUND OF THE INVENTION 
       [0003]    Light emitting diodes (LEDs) are considered an efficient light source to replace incandescent, compact fluorescent lights (CFLs) and other more conventional light sources to save electrical energy. LEDs use significantly less than the energy required by incandescent lights to produce comparable amounts of light. The energy savings ranges from 40 to 80% depending on the design of light bulbs. In addition, LEDs contain no environmental harming elements, such as mercury that is commonly used in CFLs. Light bulbs using LEDs as the light source for replacing traditional incandescent bulbs, CFLs and other conventional sources are required to produce the same as or better quantities and qualities of light. The quantity of the light depends on light output, which can be increased with increasing LED efficiency, number or size, as well as electronic driver efficiency. The quality of the light is related to factors affecting the color rendering index and the light beam profile. Since most packaged LED devices do not emit light omni-directionally, a challenge exists when designing replacement bulbs using packaged LEDs that do emit light omni-directionally. On the other hand, LEDs emitting in one direction can be easily adopted for down lighting as is done with MR16 lights with heat management systems and an electronic driver. However, in order to radiate light spatially using LEDs—i.e., in a non-unidirectional or omni-directional fashion similar to that provided using incandescent bulbs—a special three-dimensional positioning arrangement for multiple LEDs is generally required. Various embodiments of spatial, radial or otherwise non-unidirectional lighting using LEDs have been described in the prior art, with examples being found in: U.S. Pat. No. 6,634,770 (Cao); U.S. Pat. No. 6,634, 771 (Cao); U.S. Pat. No. 6,465,961 (Cao); U.S. Pat. No. 6,719,446 (Cao) issued Apr. 13, 2004. Various further examples can be found in co-owned and pending U.S. patent applications, having Ser. Nos.: 11/397,323; 11/444,166 and 11/938,131. The above mentioned prior art provides solutions that create light beam profiles similar to those produced by incandescent light bulbs. The disclosures of the foregoing issued patents and applications are incorporated herein by reference. The invention described below advances the prior art devices through inventive means of advantageously transferring heat energy away from the LED lighting device to a separate heat sink to dissipate the heat away from the LED light source. The invention thus helps to improve heat management and light beam profiles in LED-based lighting. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention discloses a 3 dimensional LED arrangement and heat management method using a heat transfer pipe to enable the heat transferred quickly from a 3 dimensional cluster of LEDs to a heatsink with/without active cooling. The light emitted from the 3 dimensional cluster is not obstructed by any heat sink arrangement so that the light beam profile can be similar to traditional incandescent bulbs. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1  provides a perspective view of one embodiment of an LED lighting device according to the present invention; 
           [0006]      FIG. 2  provides a cross sectional view of the LED lighting device illustrated in  FIG. 1 ; 
           [0007]      FIG. 3  provides a cross sectional view of one embodiment of a heat pipe as used in the present invention; 
           [0008]      FIG. 4  provides a cross section view of a second embodiment of an LED lighting device according to the present invention; 
           [0009]      FIG. 5  provides a perspective view of a yet further embodiment of an LED lighting device according to the present invention; 
           [0010]      FIG. 6  provides a cross sectional view of the LED lighting device illustrated in  FIG. 5 ; and 
           [0011]      FIG. 7  provides a cross sectional view of yet another embodiment of an LED lighting device according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    Referring to  FIGS. 1 and 2 , an embodiment of the present invention is illustrated depicting an LED lighting device  100  having a plurality of panels  102  and LEDs  103  mounted to the panels  102  and advantageously arranged about a central axis for space lighting—i.e., lighting in a non-unidirectional fashion similar to that provided using incandescent bulbs. Illumination from the lighting device  100  is provided by the plurality of LEDs  103 . A glass or plastic bulb (or transparent housing)  106  encases the LEDs and the various components that incorporate the assembled lighting device  100  and is sized such that the bulb  106  appears like a traditional light bulb. If desired, the bulb can be frosted, colored or transparent, which further permits the lighting device  100  to appear as a traditional light source. 
         [0013]    The panels  102 , in one embodiment, are mounted to a multi-faceted frame  124 . A heat conduction pipe  105  extends substantially along the central axis referred to above and includes a proximal end  120  and a distal end  122 . Generally speaking, the heat conduction pipe refers to any structure or material capable of conducting heat from high to low temperature. The frame  124  is secured to the proximal end  120  of the heat conduction pipe  105 . The frame  124  has an upper  126  and lower  128  surface with holes  132  extending through the surfaces for mounting the frame  124  to a rod-like  130  portion of the heat conduction pipe  105 . The frame  124  can be secured to the heat conduction pipe  105  using a tight friction-fit or a heat conductive paste between the outer surface of the pipe  105  and the inner surface of the holes  132  or using suitable adhesives or fasteners. 
         [0014]    Further, the frame  124  can be solid or hollow, depending on the heat load or weight requirements. For a relatively lightweight lighting device, for example, the frame  124  is advantageously constructed from metal sheet stock—e.g., aluminum or any other heat conducting material—and constructed using fold lines positioned on the sheet stock to yield the desired three-dimensional multifaceted shape or design. On the other hand, for a relatively heavier lighting device, the frame can be constructed using a slug of metal or any other heat conducting material, the slug being cast or machined or otherwise molded into the desired multifaceted shape or design. Embodiments employing the hollow design may include heat conducting means—e.g., rods or fins—connecting the frame  124  to the heat conducting pipe  105  for enhanced transfer of heat from the frame to the pipe. The facets of the frame  124  can be vertical or angel positively or negatively, depending upon the desired light beam profile of the lighting device  100  and the emitting patterns of the component LEDs. 
         [0015]    As further indicated in  FIGS. 1 and 2 , the plurality of panels  102  and LEDs  103  are secured to one or more of the faces of the multi-faceted frame  124 . In one embodiment, pairs of screws  134  secure corresponding panels  102  to each face of the frame  124 . The light emitting portion of each LED  103  extends through a hole in the panel  102  while the backside of the LED is attached to either the panel  102  or the face of the frame or both using a heat conductive paste  144 . In one embodiment, the LEDs  103  are wired in series by connecting corresponding positive and negative leads from each LED  103  using wires  104 . The LEDs can also be connected using combinations of serial and parallel circuitry depending on the components used and the requirements of the electronic driver. A pair of power conducting wires  140 ,  142  supply power to the LEDs  103  from an electronic driver  145 . The electronic driver  145  is used to convert AC input to DC output that is generally required to drive LED circuitry, electrically isolate various components of the device from one another and to control operation of the LEDs—e.g., control dimming. The electronic driver  145  is positioned inside a standard Edison base  111  of the lighting device  100  and connected to the Edison base which generally receives AC power through conducting leads  246 ,  247 . However, if the LEDs on the frame  124  can be driven directly by AC power, then the electronic driver  145  is not required in the embodiment. The threaded base portion generally comprises the components and sizes associated with a standard Edison screw base—e.g., size E27, and ranging from E5 to E40; while threaded base portions are generally preferred for connection with an external supply of power, other means of connection—e.g., pins or prongs—are considered within the scope of the invention. Surface mounted LEDs are generally preferred for the foregoing embodiment, and those skilled in the art will appreciate that while the above description refers to wiring the LEDs in series, the LEDs are also readily wired in parallel or using combinations of series and parallel circuitry. 
         [0016]    Still referring to  FIGS. 1 and 2 , the distal end  122  of the heat conduction pipe  105  extends into a heat sink  108 . The heat sink  108  is illustrated having fins  110  for dissipation of heat, although rods or other configurations of heat dissipations means may be used. The fins  110  extend from a heat conducting slug  112  that conducts heat away from the distal end of the heat conduction tube  105  and to the fins  110 . In one embodiment, a fan assembly  114  is positioned below the heat sink  108  and directs a flow of cooling air past the fins  110  of the heat sink  108 . The bulb  106  may be completely sealed, as illustrated in  FIG. 2 . In such case, the flow of cooling air is directed through the fins  110  and about the outer surface of the bulb  106 . Alternatively, the bulb  106  may include an opening adjacent the fins  110 , in which case the flow of cooling air is directed past the fins  110  and into the interior of the bulb  106 . Referring to embodiments where a fan  114  is used, a storage space  116  is incorporated into the lighting device  100 , typically above the threaded base portion  111  and the below the heat sink  108 . 
         [0017]    Referring to  FIG. 3 , in one embodiment, a heat conduction pipe  150  for use with the present invention includes a sealed cylindrical tube  152 , a wicking structure  154 , a working fluid within the wicking structure  152  and a hollow space  156  interior to the wicking structure  154 . Application of heat at a proximal end  170  of the heat conduction pipe  150  causes the working fluid at that point to evaporate to the gaseous state, picking up the latent heat of vaporization. The gas, which then has a higher pressure, travels along the hollow space  156  toward the cooler distal end  172  where it condenses back to the liquid state, releasing the latent heat of vaporization to the distal end  172  of the heat conduction pipe  150 . The condensed working fluid then travels back along the wicking structure  152  toward the proximal end  170  and repeats the process. 
         [0018]    In an alternative embodiment the heat conducting pipe may include an interior section housing an interior solid material having a melting point below that of the material used to construct the heat pipe. In such case, the latent heat of melting of the interior material may be used to store a portion of the heat generated by the LEDs as the interior material changes phase from a solid to a liquid: In one embodiment, for example, the heat conduction pipe is constructed of aluminum or copper and houses an interior material comprising tin or lead, both of which exhibit melting points substantially below that of both copper and aluminum. Gallium may also be used as a suitable metal for the interior material. A still further alternative is to substitute a solid rod, constructed using materials having good heat conduction properties, e.g. aluminum or copper, for the more conventional heat conduction pipes described above. 
         [0019]    In one embodiment, the heat conduction pipe is a cylindrical rod between about two (2) and about three (3) inches in length and between about one-quarter (¼) and about three-quarters (¾) inch in diameter and constructed of copper; the heat sink  108 , including the heat slug  112 , is between about one-half (½) and about one (1) inch in diameter and between about one-quarter (¼) and about one (1) inch in thickness and constructed of aluminum; and the frame is a six-sided hexagon-shaped hollow frame constructed of aluminum sheet, having an average diameter between about one-half (½) and about one (1) inch, a length between about one-quarter (¼) and about one (1) inch and a sheet thickness of between about one thirty-second ( 1/32) and about one quarter (¼) inch. The shape of the bulb  106  approximates the shape of a standard 100 W incandescent bulb having a standard E27 Edison screw base. 
         [0020]    Referring now to  FIG. 4 , another embodiment of the present invention is illustrated. An LED lighting device  200  includes a plurality of LED chips  203  that are mounted to a multi-faceted frame  224  and advantageously arranged about a central axis for space lighting. Illumination from the lighting device  200  is provided by the plurality of LED chips  203 . This lighting configuration is similar to that discussed above regarding  FIGS. 1 and 2 , with the exception that the lighting in the current embodiment is provided by LED chips mounted on the multi-faceted lead frame  224 , rather than surface mounted LEDs. Various exemplar chips suitable for use with the present invention are disclosed in U.S. Pat. No. 6,719,446 (Cao), the disclosures of which were previously incorporated by reference. As illustrated in the figure, the LED chips  203  are mounted directly to the multi-faceted frame  224 . Suitable adhesives, such as epoxy, may be used to mount each chip to the frame  224 . A glass or plastic bulb  206  encases the LED chips and frame  224  and, as detailed below, the various components that incorporate the assembled lighting device  200 . 
         [0021]    If desired, an optional layer of phosphor  250  encases one or more of the LED chips  203 . The layer of phosphor is advantageous in that it, for example, in one embodiment, produces a white light or the appearance of a white light—e.g., by using an ultraviolet LED chip to stimulate a white-emitting phosphor or by using a blue LED chip to stimulate a yellow-emitting phosphor, the yellow light stimulating the red and green receptors of the eye, with the resulting mix of red, green and blue providing the appearance of white light. In one embodiment, white light or the appearance thereof is produced through use of a plurality of 450-470 nm blue gallium nitride LED chips covered by a layer of yellowish phosphor of cerium doped yttrium aluminum garnet crystals. 
         [0022]    The LED chips are electrically connected within the lighting device  200 , in one embodiment, by connecting a negative terminal of each chip to the frame  224  using a first wire  210  and by connecting a positive terminal of each chip to an electrically conducting cap  212  using a second wire  214 . The electrically conducting cap  212  is positioned atop the frame  224  and electrically insulated therefrom by an insulation layer  216 , which can be constructed using epoxy, AlO or any other material having electrically insulating properties. A pair of electrical conducting wires  240 ,  242  supply power to the LED chips  203  from a standard threaded base portion  211  of the bulb device  200 . The pair of power supply wires  240 ,  242  extend, respectively, from corresponding contacts at the base portion  211  to the electronic driver  245  inside. Similar to that described above, the electronic driver  245  is used to covert AC input to DC output that is generally required to drive LED circuitry, electrically isolate various components of the device from one another and control operation of the LEDs—e.g., control dimming. The electronic driver  245  is positioned inside a standard Edison base  211  of the lighting device  200  and connected to the Edison base which generally receives AC power through conducting leads  246 ,  247 . However, if the LEDs on the frame  224  can be driven directly by AC power, then the electronic driver  245  is not required in the embodiment. In this sense, the LED chips  203  are wired in parallel. As discussed in reference to the previous embodiment, however, series-wired counterparts to that disclosed in this embodiment are readily apparent to those skilled in the art and are considered within the scope of the present invention. If desired, an epoxy cap  208  is used to cover the frame  224 , first and second wires  210 ,  214 , LED chips  203  and phosphor layer  250 , among other components of the lighting device. The epoxy cap  208  acts as an optical lens and also as a protection layer for the various identified components. 
         [0023]    Still referring to  FIG. 4 , a heat conduction pipe  205  extends substantially along a central axis of the lighting device  200  and includes a proximal end  220  and a distal end  222 . The frame  224  is secured to the proximal end  220  of the heat conduction pipe  205  in a manner similar to that described above with the previous embodiments. Likewise, the distal end  222  of the heat conduction pipe  205  extends into a heat sink  208  that is constructed and positioned similar to that described above with the previous embodiments. The various embodiments of the heat conducting pipe and heat sink discussed above, including the means of cooling the same, apply equally to the embodiments just described with reference to  FIGS. 1 and 2 . 
         [0024]    Referring now to  FIGS. 5 and 6 , a still further embodiment of the present invention is disclosed. An LED lighting device  300  has a plurality of panels  302  and LEDs  303  mounted to the panels  302  and advantageously arranged about a central axis for space lighting. Illumination from the lighting device  300  is provided by the plurality of LEDs  303 . A glass or plastic bulb  306  encases the LEDs and, as detailed below, the various components that incorporate the assembled lighting device  300 . The panels  302 , in one embodiment, are mounted to a multi-faceted frame  324 , which can be constructed as described with respect to the embodiments referred to above. More particularly, the shape of the frame  324  in this embodiment approximates a sphere, such that vectors pointing outwardly normal from each face sweep in both longitudinal and latitudinal directions with respect to the sphere approximated by the frame, thereby producing a higher degree of omni-directional special lighting—i.e., a closer approximation to light emanating outward in a spherical direction, with the greater the number of faces in the longitudinal and latitudinal directions, the better the approximation. 
         [0025]    A heat conduction pipe  305  extends substantially along a central axis of the lighting device  300  and includes a proximal end  320  and a distal end  322 . The frame  324  is secured to the proximal end  320  of the heat conduction pipe  305  in a manner similar to that described above with the previous embodiments. Likewise, the distal end  322  of the heat conduction pipe  305  extends into a heat sink  308  that is constructed and positioned similar to that described above with the previous embodiments. The various embodiments of the heat conducting pipe and heat sink discussed above, including the means of cooling the same, apply equally to the embodiments described above. Further, it is noted that the various embodiments concerning the use of surface mounted LEDs and LED chips, including the manner of wiring in series or parallel, the optional use of phosphors or epoxy coverings and the optional use of a cooling fan, may be used with or incorporated into the embodiments depicted in  FIGS. 5 and 6 . 
         [0026]    Referring now to  FIG. 7 , a still further embodiment of the present invention is illustrated and disclosed. An LED lighting device  400  includes a first heat sink in the form of a disk-shaped frame  424  and a plurality of LEDs  403  mounted to the frame  424  and advantageously arranged about the frame for directional space lighting. Illumination from the lighting device  400  is provided by the plurality of LEDs  403 . In one embodiment, the LEDs  403  are wired in series using connecting wires  404 . A pair of electrical conducting wires  440 ,  442  supply power to the series-wired LEDs  403  from a standard threaded base portion  411  of the lighting device  400 . An electronic driver inside the base  411  provides power to the LEDs. The frame  424  can be constructed as described with respect to the frame elements of the embodiments referred to above—i.e., the frame can be solid or hollow. In an alternative embodiment, the frame  424  includes a first or upper surface  451  and a second or lower surface  452  and a plurality of heat dissipating fins  453  disposed between the two surfaces. 
         [0027]    A heat conduction pipe  405  extends substantially along a central axis of the lighting device  400  and includes a proximal end  420  and a distal end  422 . The frame  424  is secured to the proximal end  420  of the heat conduction pipe  405  in a manner similar to that described above with the previous embodiments. Likewise, the distal end  422  of the heat conduction pipe  405  extends into a heat sink  408  that is constructed and positioned similar to that described above with the previous embodiments. The various embodiments of the heat conducting pipe and heat sink discussed above, including the means of cooling the same, apply equally to the embodiments described above. Further, it is noted that the various embodiments concerning the use of surface mounted LEDs and LED chips, including the manner of wiring in series or parallel, the optional use of phosphors or epoxy coverings and the optional use of a cooling fan, may all be used with or incorporated into the embodiments depicted in  FIG. 7 . 
         [0028]    The LED devices or LED chips used to construct the lighting devices described above may emit single or multiple colors or white color. The bulbs or encapsulating cover can also be frosted or clear or coated with phosphor to convert the light from LED to different colors as required. While certain embodiments and details have been included herein and in the attached invention disclosure for purposes of illustrating the invention, it will be apparent to those skilled in the art that various changes in the methods and apparatuses disclosed herein may be made without departing from the scope of the invention, which is defined in the appended claims.