Abstract:
An exemplary LED lamp includes a housing, a printed circuit board, at least one LED, a light reflective module and a lamp cover. The printed circuit board is positioned on a bottom of the housing. The LED electrically connects with the printed circuit board. The light reflective module includes at least one light-shielding sheet and a bottom reflective plate disposed between the printed circuit board and the light-shielding sheet. The bottom reflective plate defines at least one through hole. The LED passes through the at least one through hole correspondingly. Each light-shielding sheet defines a plurality of light holes and covers the LED correspondingly. The lamp cover is fixed on the opening of the housing. The LED lamp has a uniformity brightness.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a lamp assembly, and more particularly to a light emitting diode lamp assemblies employed in a direct type backlight module of a liquid crystal display. 
   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. 
   Typically,  FIG. 1  illustrates a 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 the 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 top of each LED  13  respectively. The lamp cover  16  is fixed on the opening  112  of the housing  11 . Light rays from the LEDs  13  are substantially reflected at the sidewalls  142 , the bottom reflective plate  144 , and finally output 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  10  is increased. 
   Nevertheless, the brightness above the LEDs  13  of the LED lamp assembly  10  is decreased due to the light reflection off of the circular reflective layers  15 , and a plurality of dark areas between 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 which have a uniform brightness. 
   SUMMARY 
   An LED lamp assembly according to a preferred embodiment includes a housing, a printed circuit board, at least one LED, a light reflective module and a lamp cover. The housing has an opening. The printed circuit board is positioned on a bottom of the housing. The at least one LED is electrically connect with the printed circuit board. The light reflective module includes at least one light-shielding sheet and a bottom reflective plate disposed between the printed circuit board and the light-shielding sheet. The bottom reflective plate defines at least one through hole. The at least one LED passes through the at least one through hole correspondingly. The at least one light-shielding sheet defines a plurality of light holes and covers the at least one LED correspondingly. The light-shielding sheet and the bottom reflective plate cooperatively define a light-mixing space. The lamp cover is fixed on the opening of the housing. 
   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. 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, partly, 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 an LED lamp assembly according to a second preferred embodiment of the present invention. 
       FIGS. 7 through 11  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 4 , 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 module  24 , and a lamp cover  26 . The housing  21  is an elongated, hollow structure defining a receiving opening  212 . The LEDs  23  are separately arranged and electrically connected to the printed circuit board  22 . The printed circuit board  22  with the LEDs  23  is disposed in the receiving opening  212  on a bottom surface of the housing  21 . 
   The light reflective module  24  can be mounted into the opening  212  of the housing  21 . The light reflective module  24  includes a rectangular bottom reflective plate  244  and four connecting sidewalls  242  extending vertically from a periphery of the bottom reflective plate  244 . Inner surfaces of the sidewalls  242  and bottom surface of the bottom reflective plate  244  are high reflective surfaces, and the sidewalls  242  and the bottom reflective plate  244  are made of a combination of metal materials and/or plastic materials. The bottom reflective plate  244  defines a plurality of through holes  246  corresponding to the LEDs  23  on the printed circuit board  22 . The bottom reflective plate  244  is supported by base portion of each of the LEDs  23 . Side light-emitting portions of the LEDs  23  pass through the through holes  246  correspondingly. The light reflective module  24  further includes a plurality of light-shielding sheets  245 . Each LED  23  is covered by one of the light-shielding sheets  245  correspondingly. Each light-shielding sheet  245  extends at midsections from two opposing sidewalls. In the preferred embodiment, the opposing sidewalls receiving the two ends of the light-shielding sheet  245  are the two longest sidewalls of the four connecting sidewalls  242 . A plurality of light holes  247  are defined at ends of each light-shielding sheet  245  adjacent to the two opposite sidewalls  242 . The lamp cover  26  seals the opening  212  of the housing  21 . The lamp cover  26  can be either a transparent plate or a light diffusion plate. 
   In this embodiment, the light holes  247  have same shapes and sizes, and are formed in a matrix manner close to the edges of the light-shielding sheet  245 . A diameter of each of the through holes  246  is shorter than a nearest distance between adjacent light holes at two edges of the light-shielding sheet  245 . In alternative embodiments, the bottom reflective plate  244  can be positioned on the printed circuit board  22  and the LEDs  23  substantially protrude through the through holes  246  entirely. In addition, the sidewalls  242  of the light reflective module  24  and sidewalls (not labeled) of the housing  21  correspondingly define a plurality of latching elements (not labeled), thus the light reflective module  24  and the housing  21  can be assembled together securely. 
   Referring to  FIG. 5 , the light-shielding sheets  245  and the bottom reflective plate  244  cooperatively define a light-mixing space  28 . Light from the side light-emitting portions of the LEDs  23  are reflected many times between the light-shielding sheets  245  and the bottom reflective plate  244  of the light mixing space  28  before substantially exiting at an area between the two adjacent light-shielding sheets  245 . 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  245 . Furthermore, some of the light projects to the lamp cover  26  via the light holes  247  of the light-shielding sheets  245 . Since the light holes  247  are formed on the two sides of each of the light-shielding sheets  245  adjacent to the two sidewalls of the housing  21 , a light brightness adjacent to the two sidewalls of the LED lamp assembly  20  is increased. Thus, a uniformity of light output from the LED lamp assembly  20  is increased. 
   It is to be understood that, by selecting the size and shape of the light holes  247 , or distribution of the light holes  247 , a uniformity of the light brightness above the light-shielding sheets  245  of the LED lamp assembly  20  is adjustable. It should be noted that, not only can the light reflective module  24  be integrally manufactured by punching a metal sheet, it can also be manufactured by assembling a plurality of parts, such as the housing  21 , the bottom reflective plate  244 , the four sidewalls  242  of the light reflective module  24 , and the light-shielding sheet  245 . 
   A method for assembling the light reflective module  24  includes the following steps. Firstly, a metal sheet is punched for manufacturing the bottom reflective plate  244  connecting with four sidewalls  242 . Secondly, the bottom reflective plate  244  connecting with four sidewalls  242  is punched to define a plurality of through holes  246  in the bottom reflective plate  244 . Thirdly, the bottom reflective plate  244  and the four sidewalls  242  of the light reflective module  24  are mounted into the housing  21 . Each of the light-shielding sheets  245  further includes two flanges (not labeled) at the two opposite ends correspondingly. Finally, two flanges of the light-shielding sheets  245  are respectively riveted or welded to correspondingly connect with the two opposite sidewalls  242  of the light reflective module  24 . 
   Referring to  FIG. 6 , an LED lamp  30  in accordance with a second preferred embodiment of the present invention is shown. The LED lamp  30  includes a housing  31 , a printed circuit board  32 , a plurality of side-emitting LEDs  33 , a light reflective module  34 , and a lamp cover  36 . The LED lamp  30  is similar in principle to the LED lamp assembly  20  of the first embodiment, except that the light reflective module  34  is different from the light reflective module  24 . The light reflective module  34  includes a frame  343 , a bottom reflective plate  344  and a plurality of light-shielding sheets  345 . The frame  343  and the reflective plate  344  are separate. The bottom reflective plate  344  defines a plurality of through holes (not labeled). The bottom reflective plate  344  is positioned on the printed circuit board  32 . The LEDs  33  pass through the through holes  346  correspondingly. The frame  343  includes four connecting sidewalls (not labeled). The frame  343  is correspondingly assembled into the housing  31 , each connecting sidewall being in contact with inner surfaces of the sidewalls of the housing  31 . The sidewalls of the frame  343  are adjacent to or in contact with the reflective plate  344 . The frame  343  and the reflective plate  344  cooperatively define a light-mixing unit  38 . 
   Light rays from the side light-emitting portions of the LEDs  33  are reflected many times between the light-shielding sheets  345  and the bottom reflective plate  344  of the light mixing space  38 , and finally many or most of the light rays escape from gaps between the two adjacent light-shielding sheets  345 . This results in that a light brightness above the gaps of the LED lamp  30  is increased. In addition, a light brightness above the LEDs  33  of the LED lamp  30  is decreased due to the light reflection of the light-shielding sheets  345 . Furthermore, some of the light rays transmit to the lamp cover  36  via the light holes  347  of the light-shielding sheets  345 . Because the light holes  347  are distributed at the two sides of each of the light-shielding sheets  345  adjacent to the two sidewalls of the housing  31 , a light brightness adjacent to the two sidewalls of the LED lamp  30  is increased. Therefore, a uniformity of light output from the LED lamp  30  is increased. 
   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 , each light-shielding sheet  245 ,  345  of the LED lamps assembly  20 ,  30  may have the same distributions as shown in  FIGS. 7 through 11 . 
   Referring to  FIG. 7 , a distribution of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is circular. A shape and an area of each of the light holes are same. The light-shielding sheet defines a middle point. The light holes are arranged apart along a plurality of imaginary circles that have a same center. The center of the imaginary circle is also a middle point of the light-shielding sheet. 
   Referring to  FIG. 8 , a distribution design 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. The light-shielding sheet defines a middle point. The light holes are arranged apart along a plurality of imaginary circles that have a same center. The center of the imaginary circles is also a middle 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. 9 , a distribution design 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. At each edge of the light-shielding sheet, the three light holes are equidistant from each other. Length of the three light holes is same. 
   Referring to  FIG. 10 , a distribution design 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. At each edge of the light-shielding sheet, the three light holes are equidistant from each other. Lengths of the three light holes are different from each other, lengths of the light holes progressively increases along a direction away from a middle portion of the light-shielding sheet. 
   Referring to  FIG. 11 , a distribution design of the light holes of a light-shielding sheet is described below. A shape of each of the light holes is an annular opening that. The three light holes of one side of the light-shielding sheet are equidistant from each other. The annular light holes have a same center that is a middle portion of the light-shielding sheet. 
   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.