Patent Publication Number: US-2010128474-A1

Title: Led lamp

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to LED (light emitting diode) lamps, and, more particularly, to an LED lamp having an improved lens, whereby light generated by the LED lamp can have a better pattern of distribution. 
     2. Description of Related Art 
     The technology of LEDs has rapidly developed in recent years from indicators to illumination applications. With the features of long-term reliability, environment friendliness and low power consumption, the LED is viewed as a promising alternative for future lighting products. 
     A conventional LED lamp comprises a heat sink, a plurality of LED modules having LEDs attached to an outer surface of the heat sink to dissipate heat generated by the LEDs and a transparent envelope mounted on the heat sink and covering the LED modules therein. The outer surface of the heat sink generally is planar and the LEDs are arranged close to each other. The envelope is used to protect the LEDs from damage. The LED lamp further has a lens for directing light generated by the LEDs to have a desired pattern of distribution, thereby meeting a set lightening requirement. However, the conventional lens cannot enable the light generated by the LEDs to have an optimal pattern of distribution. 
     What is needed, therefore, is an LED lamp which can overcome the disadvantages of the prior art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present embodiments can be better understood with reference to the following 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 embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
         FIG. 1  is an assembled view of an LED lamp in accordance with an embodiment of the present disclosure. 
         FIG. 2  is an exploded view of  FIG. 1 . 
         FIG. 3  is a side view of the LED lamp of  FIG. 2 . 
         FIG. 4  is a luminous intensity curve graph of the LED lamp of  FIG. 1  of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-2 , an LED lamp  100  comprises an elongated printed circuit board  10 , a plurality of LED modules  30  mounted on the printed circuit board  10 , and two lenses  50  mounted on the printed circuit board  10  and covering the LED modules  30 . 
     The LED modules  30  are divided into two spaced, parallel rows along a direction from a front end to a rear end of the printed circuit board  10 . Two adjacent LED modules  30  of each of the rows are spaced from each other. The two lenses  50  cover the two rows of the LED modules  30 , respectively. 
     Referring to  FIG. 3  also, each of the lenses  50  is made of a transparent material such as Polymethyl methacrylate (PMMA) or Polycarbonate (PC). Each of the lenses  50  comprises an arc-shaped body  51  and two elongated mounting portions  53  extending outwardly from lateral ends of the body  51 . Bottom surfaces of the two mounting portions  53  are coplanar and mounted on the printed circuit board  10 . The lens  50  extends over the corresponding row of the LED modules  30  to cover the LED modules  30  therebelow. The body  51  comprises a concave bottom surface  512  and a bulgy top surface  514  located above the bottom surface  512 . The bottom surface  512  and the top surface  514  are respectively constituted by arc-shaped surfaces with different curvatures. The LED modules  30  are covered by and spaced from the bottom surface  512 . Light emitted from the LED modules  30  travels through the bottom surface  512  of the lens  50  into the body  51  and then travels through the top surface  514  into the ambient air. 
     The bottom surface  512  includes a first central surface  512   a  directly over the LED modules  30  and two first lateral surfaces  512   b  respectively adjoining two ends of the first central surface  512   a.  The top surface  514  includes a second central surface  514   a  corresponding to the first central surface  512   a  of the bottom surface  512  and two second lateral surfaces  514   b  respectively adjoining two ends of the second central surface  514   a.  Each of the first central surface  512   a  and the second central surface  514   a  is an arc-shaped surface. The first central surface  512   a  and the second central surface  514   a  have different curvatures. The curvature of the first central surface  512   a  is larger than that of the second central surface  514   a.  The curvature of the second central surface  514   a  is smaller than that of each of the second lateral surfaces  514   b.  The curvature of the first central surface  512   a  is smaller than that of each of the first lateral surfaces  512   b.    
     The two first lateral surfaces  512   b  are corresponding to the two second lateral surfaces  514   b,  respectively. The curvature of each of the two first lateral surfaces  512   b  is larger than that of each of the two second lateral surfaces  514   b.  The two first lateral surfaces  512   b  can have a same curvature or different curvatures. Similarly, the two second lateral surfaces  514   b  can have a same curvature or different curvatures. In the present embodiment, the two first lateral surfaces  512   b  have a same curvature, and the two second lateral surfaces  514   b  have a same curvature. 
     Regarding the light emitted from the LED modules  30 , one portion of the light moves upwardly to enter the body  51  of the lens  50  via the first central surface  512   a,  and spreads outside of the body  51  of the lens  50  from the second central surface  514   a.  That is, on the second central surface  514   a  of the body  51 , a part of the light which corresponds to a central portion of the second central surface  514  is not refracted and directly spreads outside of the body  51 ; another part of the light which corresponds to opposite portions of the second central surface  514  is refracted by the second central surface  514  before it enters the ambient air. The another part of the upwardly moved light is first refracted by opposite portions of the first central surface  514  before it enters the body  51  of the lens  50 . Another portion of the light emitted from the LED modules  30  enters the body  51  from the two first lateral surfaces  512   b  of the bottom surface  512 . Due to the curvatures of the two first lateral surfaces  512   b  being larger than those of the two second lateral surfaces  514   b,  the another portion of the light emitted from the LED modules  30  is refracted twice with different degrees (first by the two first lateral surfaces  512   b  of the bottom surface  512  of the lens  50  and then by the two second lateral surfaces  514   b  of the top surface  514  of the lens  50 ) to radiate from the lens  50 . Thus, a total internal reflection phenomenon occurring at the top surfaces  514  of the lenses  50  can be greatly avoided. The light emitted from the LED modules  30  is oriented toward a plurality of different directions, whereby the LED lamp  100  in accordance with the present disclosure can have a large illumination angle. 
       FIG. 4  shows a luminous intensity curve graph of the LED lamp  100  of the present disclosure. Referring to  FIG. 4 , a curve C shows a luminous intensity curve of the LED lamp  100  along a first direction (i.e. a transverse direction of the LED lamp  100 ), and a curve D shows a luminous intensity curve of the LED lamp  100  along a second direction perpendicular to the first direction. The LED lamp  100  in accordance with the present disclosure can have a light output efficiency of more than  85 %, which is larger than that of the conventional lamp. Therefore, the LED lamp  100  meets the luminous intensity requirement and saves energy at the same time. 
     It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the present disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.