Patent Publication Number: US-2012038260-A1

Title: Lamp envelope and led lamp using the same

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to lamps, and more particularly to a lamp having an envelope which improves heat dissipating efficiency of the lamp. 
     2. Description of Related Art 
     Usually, a lens is integrally formed with an LED (light emitting diode) package used as a light source of an LED lamp. However, the lens is directly located on the LED package and encapsulates the LED package thereby decreasing heat dissipating efficiency of the LED package and shortening a lifespan of the LED package. 
     What is needed therefore is a lamp having an envelope which can overcome the above limitations. 
    
    
     
       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 views. 
         FIG. 1  is an isometric, assembled view of an LED lamp in accordance with an embodiment of the present disclosure. 
         FIG. 2  is an isometric, exploded view of the LED lamp in  FIG. 1 . 
         FIG. 3  is an enlarged, cross-sectional view of a part of the LED lamp in  FIG. 1 . 
         FIG. 4  is an enlarged, cross-sectional view of a part of a LED lamp in accordance with another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS. 1-2 , an LED lamp in accordance with an embodiment of the present disclosure comprises a lamp holder  10 , a heat sink  13  connected to the lamp holder  10 , a driving circuit  12  accommodated in the heat sink  13 , a light source  14  mounted on the heat sink  13 , and a lamp envelope  15  mounted on the heat sink  13  and covering the light source  14 . 
     The lamp holder  10  comprises a securing portion  112  and an electrical connector  114 . The electrical connector  114  is secured to an end of the securing portion  112 , and is configured for connecting to a power source (not shown) which can supply power to the LED lamp. The securing portion  112  is configured for securely connecting with the heat sink  13  to accommodate the driving circuit  12  in the lamp holder  10  and the heat sink  13 . The electrical connector  114  is configured to be inserted into a standard socket for a conventional incandescent bulb or compact fluorescent lamp which is electrically connected with the power source, whereby the LED lamp in accordance with the present disclosure can replace the conventional incandescent bulb or compact fluorescent lamp. 
     The driving circuit  12  is disposed in the heat sink  13  and the lamp holder  10 , and is electrically connected to the electrical connector  114  and the light source  14 . The driving circuit  12  is configured for providing driving voltage for the light source  14 . 
     Also referring to  FIG. 3 , the heat sink  13  includes a base  132 , a number of fins  134 , and a hollow post  136 . The base  132  comprises a top surface facing away from the lamp holder  10  and a bottom surface opposite to the top surface. The light source  14  is directly mounted on the top surface of the base  132 . The base  132  is made of thermally conductive and electrically insulating material, such as ceramics. The ceramics can be selected from a group consisting of alumina ceramics, aluminum nitride, and so on. The base  132  defines a ring-shaped assembling groove  1321  surrounding the light source  14  on the top surface of the base  132 . The assembling groove  1321  is used for assembling the lamp envelope  15  on the base  132 . The base  132  further defines at least one though hole  1322  running through the top and bottom surfaces. The though hole  1322  is provided for an extension of a wire therethrough, wherein the wire is used for the electrical connection between the light source  14  and the driving circuit  12 . 
     The fins  134  and the hollow post  136  are formed on the bottom surface of the base  132 . The fins  134  are arranged surrounding the hollow post  136 , and each of the fins  134  is connected to an outer surface of the hollow post  136 . In the present embodiment, the fins  134  and the hollow post  136  are integrally formed with the base  132 . The fins  134 , the hollow post  136 , and the base  132  can be made of a same material. An end of the hollow post  136  away from the base  132  is fixed to an end of the securing portion  112  away from the electrical connector  114 . The driving circuit  12  has a large portion received in the hollow post  136 ; thus, the structure of the LED lamp can be compact and the volume of the LED lamp can be small. 
     The lamp envelope  15  is made of transparent or translucent plastic. The lamp envelope  15  is located on and connected with the base  132  wherein the lamp envelope  15  and the base  132  corporately define a receiving room  16 . The lamp envelope  15  includes a connecting portion  152  connected to the base  132  of the heat sink  13 , and a covering portion  154  connected to the connecting portion  152 . The connecting portion  152  and the covering portion  154  are formed by plastic injection molding. The connecting portion  152  has a disk-shaped configuration with a central hole  151  and has a joint ring  1523  surrounding the central hole  151 . A plurality of ears  1524  extend horizontally and outwardly from a bottom end of the joint ring  1523 . The joint ring  1523  and the ears  1524  are disposed in the assembling groove  1321  of the heat sink  13  and can be secured to the base  132  by screws or clips. In this embodiment, the joint ring  1523  has an annular shape. The number of the ears  1524  is four, and the ears  1524  are evenly and symmetrically distributed at the bottom end of the joint ring  1523 . A first positioning structure  1521  is formed on a top of the connecting portion  152 . The first positioning structure  1521  is an annular protrusion protruding upwardly from the top of the connecting portion  152 . 
     The covering portion  154  is hemisphere-shaped. The covering portion  154  includes a light incident surface  1542  and a light output surface  1543  opposite to the light incident surface  1542 . The light incident surface  1542  is located at an inner side of the covering portion  154  and faces the heat sink  13 . The light incident surface  1542  forms a plurality of lenses  17  therein. The plurality of lenses  17  are spaced from each other, and a protrusion is formed between two adjacent lens  17 . The light output surface  1543  is smooth and located at an outer side of the lamp envelope  15 . A second positioning structure  1541  is formed on a bottom of the covering portion  154  for matching with the first positioning structure  1521  of the connecting portion  152 . The second positioning structure  1541  is an annular recess for fitly receiving the first positioning structure  1521  therein. The first and second positioning structures  1521 ,  1541  are engaged with each other to secure the connecting portion  152  and the covering portion  154  together. It is noted that, the first and second positioning structures  1521 ,  1541  can also be combined by a process of ultrasonic welding. The strength of the combined connecting portion  152  and the covering portion  154  by ultrasonic welding is substantially equivalent to that of an integral envelope. Compared with the envelope made by the process of blow molding, the connecting portion  152  and the covering portion  154  of the lamp envelope  15  made by the process of plastic injection molding have a high yield. In addition, since the lamp envelope  15  of the present disclosure is divided into two separate parts, namely, the connecting portion  152  and the covering portion  154 , the connecting portion  152  can be joined with a covering portion  154  with a different shape than the shown to form a desired lamp envelope  15  having a different configuration. Hence, varieties of envelopes  50  with the same connecting portion  152  can be provided, and the inventory cost of the lamp envelope  15  can be decreased. 
     The light source  14  is directly mounted on the top surface of the base  132  and received in the receiving room  16 . The light source  14  faces the light incident surface  1542 . The light source  14  is electrically connected to a circuit (not shown) formed on the top surface of the base  132 . Preferably, the circuit is formed on the top surface by plating. 
     In the present embodiment, the light source  14  includes five LED packages. It is understood that the number of the LED packages is not limited to the present embodiment. 
     In operation, light rays generated by the light source  14  enter into the lamp envelope  15  via the light incident surface  1542 , and then travel out of the lamp envelope  15  via the light output surface  1543 . The plurality of lenses  17  formed on the light incident surface  1542  of the lamp envelope  15  collect the incident light rays on the light incident surface  1542  of the lamp envelope  15 . Moreover, the plurality of lens  17  are spaced from the LED packages whereby heat generated by the LED packages can be directly dissipated into an outer atmosphere and heat dissipating efficiency can be improved. The plurality of lens  17  can be integrally formed with the plastic injection molding, or formed by a machining after the plastic injection molding, such as hot embossing or sandblasting. 
       FIG. 4  shows an LED lamp according to an alternative embodiment. The difference lies in the lamp envelope  25 . In this alternative embodiment, a light incident surface  2542  of the lamp envelope  25  is smooth, and a plurality of lenses  27  are formed on a light output surface  2543  of the lamp envelope  25 . 
     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 disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.