Abstract:
An exemplary LED lamp includes a housing having an opening, a printed circuit board, at least one LED, a light reflective element, at least one light-shielding sheet and a lamp cover. The printed circuit board is positioned on a bottom of the housing. The LED is electrically connected with the printed circuit board. The light reflective element defines at least one through hole, the LED passing through the corresponding through hole. The at least one light-shielding sheet corresponds to the at least one LED respectively. Each light-shielding sheet comprises a bottom reflective plate and a pair of opposite sidewalls extending from two opposite ends of the bottom reflective plate. A plurality of light holes is defined at ends of the bottom reflective plate adjacent to the two opposite sidewalls. The lamp cover is fixed on the opening of the housing. The LED lamp assembly has a uniform luminance.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is related to two copending U.S. patent applications, application Ser. No. 11/766,106 filed on Jun. 21, 2007, entitled “LED LAMP ASSEMBLY”, application Ser. No. 11/773,979, filed on Jul. 6, 2007, entitled “LED LAMP ASSEMBLY”. In the copending applications, the inventor is Shao-Han Chang. All of the copending applications have the same assignee as the present application. The disclosures of the above identified application are incorporated herein by reference. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a lamp assembly, and particularly to a light emitting diode lamp assembly employed in a direct type backlight module of a liquid crystal display. 
   2. Discussion of the Related Art 
   Typically, light emitting diodes (LEDs) are preferred over other types of light sources because LEDs exhibits low energy consumption, long service life, and other advantages. Therefore, LEDs are widely used as light sources. 
     FIG. 1  illustrates a typical LED lamp assembly  10  using LEDs as a light source. The LED lamp assembly  10  includes a housing  11 , a printed circuit board  12 , a plurality of side-lighting type LEDs  13 , a light reflective module  14 , a plurality of circular reflective layers  15  and a lamp cover  16 . The housing  11  is an elongated, hollow structure having an opening  112 . The LEDs  13  are arranged apart and electrically connected to the printed circuit board  12 . The printed circuit board  12  with the LEDs  13  is disposed on a bottom surface of the housing  11 . The light reflective module  14  includes a rectangular bottom reflective plate  144  and four connecting sidewalls  142  extending from a periphery of the bottom reflective plate  144 . The bottom reflective plate  144  defines a plurality of through holes  146 , configured for allowing the light-emitting portions of the LEDs  13  to pass through. The light reflective module  14  can be correspondingly mounted into the housing  11  via the opening  112 . The circular reflective layers  15  are positioned at the tops of the LEDs  13  respectively. The lamp cover  16  is fixed on the opening  112  of the housing  11 . Light from the light-emitted portions of the LEDs  13  is substantially reflected at the sidewalls  142  and the bottom reflective plate  144 , finally outputted from the lamp cover  16 . With the help of the light reflective module  14 , an efficiency of utilization of light energy of the LED lamp assembly  10  is increased. 
   Nevertheless, the brightness above the LEDs  13  of the LED lamp assembly  10  is decreased due to the light reflection off the circular reflective layers  15 , and a plurality of dark areas between the two adjacent LEDs  13  still occur. Accordingly a uniform brightness of the LED lamp assembly  10  is low. 
   What is needed, therefore, is an LED lamp assembly that overcomes the above mentioned disadvantages. 
   SUMMARY 
   An LED lamp assembly according to a preferred embodiment includes a housing having an opening, a printed circuit board, at least one LED, a light reflective element, at least one light-shielding sheet and a lamp cover. The printed circuit board is positioned on a bottom of the housing. The LED is electrically connected with the printed circuit board. The light reflective element defines at least one through hole, the LED passing through the corresponding through hole. The at least one light-shielding sheet corresponds to the at least one LED respectively. Each light-shielding sheet comprises a bottom reflective plate and a pair of opposite sidewalls extending from two opposite ends of the bottom reflective plate. A plurality of light holes is defined at ends of the bottom reflective plate adjacent to the two opposite sidewalls. The lamp cover is fixed on the opening of the housing. In addition, the light reflective element in the LED lamp assembly can be replaced by a high reflective layer formed on a top surface of the printed circuit board or a high reflective plate positioned on a top surface of the printed circuit board. 
   Other advantages and novel features will become more apparent from the following detailed description of various embodiments, when taken in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present LED lamp assembly. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views, and all the views are schematic. 
       FIG. 1  is an exploded, isometric view of a conventional LED lamp assembly. 
       FIG. 2  is an exploded, isometric view of an LED lamp assembly according to a first preferred embodiment of the present invention. 
       FIG. 3  is a top plan view of the LED lamp assembly without a lamp cover. 
       FIG. 4  is a side, enlarged, partial, cross-sectional view of the LED lamp assembly of  FIG. 3 , taken along line IV-IV thereof. 
       FIG. 5  is a side, enlarged, cross-sectional view of the LED lamp assembly of  FIG. 3 , taken along line V-V thereof. 
       FIG. 6  is a side, cross-sectional view of the LED lamp assembly according to a second preferred embodiment of the present invention. 
       FIG. 7  is an exploded, isometric view of an LED lamp assembly according to a third preferred embodiment of the present invention. 
       FIG. 8  is a side, enlarged, cross-sectional view of the LED lamp assembly of  FIG. 7 . 
       FIGS. 9 through 13  are top plan views of distributions of light holes defined in light-shielding sheets of the LED lamp assembly of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   References will now be made to the drawings to describe preferred embodiments of the present LED lamp assembly, in detail. 
   Referring to  FIGS. 2 through 5 , an LED lamp assembly  20  in accordance with a first preferred embodiment of the present invention is shown. The LED assembly  20  includes a housing  21 , a printed circuit board  22 , a plurality of side-emitting type LEDs  23 , a light reflective element  24 , a plurality of light-shielding sheets  25 , and a lamp cover  26 . The housing  21  is an elongated, hollow structure including four sidewalls  214 . The sidewalls  214  cooperatively defines a receiving opening  212 . The LEDs  23  are separately arranged and electrically connected to the printed circuit board  22 . The printed circuit board  22  including the LEDs  23  is disposed in the receiving opening  212  on a bottom surface of the housing  21 . 
   Referring to  FIG. 5 , each LED  23  includes a base portion  231 , a semiconductor chip  233  fixed on the base portion  231 , and an optical lens  235 . The optical lens  235  is bonded or snap-fitted onto the base portion  231  sealing the semiconductor chip  233  within. A width of the base portion  231  is larger than that of the optical lens  235 . 
   Also referring to  FIGS. 2 through 4 , the light reflective element  24  includes a base  241  and four sidewalls  242  extending from a periphery of the base  241 . The base  241  and the sidewalls  242  cooperatively define a cavity  243 . The base  241  defines a plurality of through holes  244  for allowing the optical lenses  235  of the LEDs  23  to pass through the corresponding through holes  244 . The base portions  231  of the LEDs  23  support the light reflective element  24 . 
   Each light-shielding sheet  25  includes a bottom reflective plate  251  and a pair of opposite sidewalls  252  extending from two opposite ends of the bottom reflective plate  251 . A plurality of light holes  257  are defined at ends of the bottom reflective plate  251  adjacent to the two opposite sidewalls  252 . In this embodiment, the light holes  257  are of the same shapes and sizes, and are formed in a matrix manner at the ends of the light-shielding sheet  25 . Each light-shielding sheet  25  is disposed in the cavity  243  of the light reflective element  24  and the two opposite sidewalls  252  of each light-shielding sheet  25  are connected to the sidewalls  242  of the light reflective element  24  respectively. Each LED  23  is covered by the corresponding light-shielding sheet  25 . Generally, the light-shielding sheet  25  is integrally manufactured by stamping a raw metal sheet. Surfaces of the bottom reflective plate  251  and the sidewalls  252  are high reflective surfaces; the bottom reflective plate  251  and the sidewalls  252  are made of a combination of metal materials and/or plastic materials. 
   The lamp cover  26  is fixed on the opening  212  of the housing  21 . The lamp cover  26  can be either a transparent plate or a light diffusion plate. The sidewalls  242  of the light reflective element  24  and the sidewalls  214  of the housing  21  may, correspondingly, further define a plurality of latching elements (not shown), thus the light reflective element  24  and the housing  21  can be assembled together securely. 
   Also referring to  FIG. 5 , in assembled, the light-shielding sheets  25 , and the light reflective element  24  cooperatively define a light-mixing space  28 . Light from the optical lens  235  of the LEDs  23  is reflected many times between the bottom reflective plate  251  of the light-shielding sheets  25  and the base  241  of the light reflective element  24  before substantially exiting at an area between the two adjacent light-shielding sheets  25 . As a result, a light brightness above the gaps of the LED lamp assembly  20  is increased. In addition, a light brightness above the LEDs  23  of the LED lamp assembly  20  is decreased due to the light reflection of the light-shielding sheets  25 . Furthermore, some of the light projects to the lamp cover  26  via the light holes  257  of the light-shielding sheets  25 . Since the light holes  257  are formed on the two sides of each of the light-shielding sheets  25  adjacent to the sidewalls  214  of the housing  21 , a light brightness of the two side portions of the LED lamp assembly  20  is increased. Thus, a uniformity of light output from the LED lamp assembly  20  is increased. 
   Referring to  FIG. 6 , an LED lamp assembly  30  in accordance with a second preferred embodiment of the present invention is shown. The LED assembly  30  includes a housing  31 , a printed circuit board  32 , a plurality of side-emitting type LEDs  33 , a light reflective element  34 , a plurality of light-shielding sheets  35 , and a lamp cover  36 . The LED lamp assembly  30  is similar in principle to the LED lamp assembly  20  of the first preferred embodiment except that the light reflective element  34  is different from the light reflective element  24 . The light reflective element  34  includes a base  341  and a plurality of sidewalls  342  separate from the base  341 . The base  341  defines a plurality of through holes (not labeled) for allowing the base portion  331  of the LEDs  33  to pass through the corresponding through holes. The base  341  is in contact with the printed circuit board  32 . The plurality of sidewalls  343  is fixed to corresponding sidewalls (not labeled) of the housing  31 . The light-shielding sheets  35 , and the light reflective element  34  cooperatively define a light-mixing space  38 . 
   Since the base  341  is disposed on the printed circuit board  32 , the light-mixing space  38  is larger than the light-mixing space  28  of the first preferred embodiment. Light from the LEDs  33  can mix more fully in the light-mixing space  38  when compared with the light-mixing space  28 . Therefore, the uniformity of light output from the LED lamp assembly  30  is better than the uniformity of light output from the LED lamp assembly  20 . 
   Referring to  FIGS. 7 and 8 , an LED lamp assembly  40  in accordance with a third preferred embodiment of the present invention is shown. The LED assembly  40  is similar in principle to the LED assembly  20  of the first preferred embodiment, however a high reflective layer  421  is formed on a top surface of the printed circuit board  42  instead of the light reflective element  24  of the LED assembly  20 . 
   The light-shielding sheets  45 , the housing  41 , and the high reflective layer  421  formed on the top surface of the printed circuit board  42  cooperatively define a light-mixing space  48 . Light from LEDs  43  is reflected many times between the high reflective layer  421  and the bottom reflective plate  451  of the light-shielding sheet  45  before substantially exiting at an area between the two adjacent light-shielding sheets  45 . As a result, a light brightness above the gaps of the LED lamp assembly  40  is increased. In addition, a light brightness above the LEDs  43  of the LED lamp assembly  40  is decreased due to the light reflection of the light-shielding sheets  45 . Furthermore, some of the light projects to the lamp cover  46  via the light holes  457  of the light-shielding sheets  45 . Since the light holes  457  are formed on each of the light-shielding sheets  45  adjacent to the sidewalls  414  of the housing  41 , a light brightness of the two side portions of the LED lamp assembly  40  is increased. Thus, a uniformity of light output from the LED lamp assembly  40  is increased. 
   It should be noted that, the high reflective layer  421  formed on the top surface of the printed circuit board  42  can be replaced by a high reflective plate, in order to form a light-mixing space between the high reflective plate and the bottom reflective plate  451  of the light-shielding sheet  45 . 
   It is to be understood that, by selecting the size and shape of the light holes  257 , or distribution of the light holes  257 , a uniformity of the light brightness above the light-shielding sheets  25  of the LED lamp assembly  20  is adjustable. In an alternative embodiment, in order to obtain a good optical performance such as uniformity of light output from the LED lamps assembly  20 ,  30 , 40 , each light-shielding sheet  25 ,  35 , 45 , of the LED lamps assembly  20 ,  30 , 40 , may have the same distributions as shown in  FIGS. 9 through 13 . 
   Referring to  FIG. 9 , a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is circular. The shape and the area of each of the light holes are the same. A mid-point is defined in the light-shielding sheet. The light holes are arranged apart along a plurality of imaginary circles and the center of a row of light holes intersects with the perimeter of an imaginary circle. The imaginary circles have a same center collinear with the mid-point of the light-shielding sheet. 
   Referring to  FIG. 10 , a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is circular, but have a different radius. A mid-point is defined in the light-shielding sheet. The light holes are arranged apart along a plurality of imaginary circles and the center of a row of light holes intersects with the perimeter of an imaginary circle. The imaginary circles have a same center collinear with the mid-point of the light-shielding sheet. The radius of the light holes increase along a direction away from the center of the imaginary circles. 
   Referring to  FIG. 11 , a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an elongated opening parallel to the sidewalls of the housing of the LED lamp assembly. At each end of the light-shielding sheet, the three light holes are separated to each other uniformly. Length of the three light holes is the same. 
   Referring to  FIG. 12 , a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an elongated opening parallel to the sidewalls of the housing of the LED lamp assembly. At each end of the light-shielding sheet, the three light holes are separated to each other uniformly. Lengths of the three light holes progressively increase along a direction away from a middle portion of the light-shielding sheet. 
   Referring to  FIG. 13 , a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an annular opening. At each end of the light-shielding sheet, the three light holes are separated to each other uniformly. The annular light holes have a same center that is a mid point of the light-shielding sheet. 
   Finally, while various embodiments have been described and illustrated, the invention is not to be construed as being limited thereto. Various modifications can be made to the embodiments by those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.