Patent Publication Number: US-8979312-B2

Title: Light emitting diode bulb

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to illumination devices, and more particularly to a light emitting diode (LED) bulb, wherein the LED bulb has an improved light distribution by disposing LED modules on different faces of a polyhedron-shaped mounting base which have different orientations. 
     DESCRIPTION OF RELATED ART 
     LEDs are solid state light emitting devices formed of semiconductors, which are more stable and reliable than other conventional light sources such as incandescent bulbs. Thus, LEDs are being widely used in various fields such as numeral/character displaying elements, signal lights, light sources for lighting and display devices. 
     A traditional LED bulb includes a holder, a substrate located at one end of the holder and a plurality of LEDs mounted on a planar mounting face of the substrate. However, a light emitting angle of the traditional LED bulb is less than 120 degrees and a light intensity distribution of the traditional LED bulb is mostly concentrated at a center axis while becomes gradually weaker towards a periphery of the traditional LED bulb. 
     That is to say, when the plurality of LEDs are arranged on a same plane, it will result in an uneven light intensity distribution. Therefore, such an LED bulb is difficult to satisfy the requirements of uniform light distribution. 
     What is needed therefore is an LED bulb which can overcome the above mentioned 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 a cross sectional view of an LED (light emitting diode) bulb in accordance with a first exemplary embodiment of the present disclosure. 
         FIG. 2  is a cross sectional view of an LED (light emitting diode) bulb in accordance with a second exemplary embodiment of the present disclosure. 
         FIG. 3  is a cross sectional view of an LED (light emitting diode) bulb in accordance with a third exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a light emitting diode (LED) bulb  100  in accordance with a first exemplary embodiment of the present disclosure includes a connecting body  10 , a lamp cap  20  located at a first end  104  of the connecting body  10 , a mounting base  31  located at a second end  105  of the connecting body  10 , at least two LED modules  32  mounted on the mounting base  31  and a lamp cover  40  connected to the connecting body  10  to cover the mounting base  31  and the LED modules  32 . 
     The connecting body  10  is a hollow tube and provided with a passage  101  communicating with the two opposite ends, i.e., the first end  104  and the second end  105 . The first end  104  of the connecting body  10  is an opened end which is sealed by the lamp cap  20 . The second end  105  of the connecting body  10  is also an opened end which is sealed by the mounting base  31 . In the present embodiment, the second end  105  of the connecting body  10  has a size larger than that of the first end  104  of the connecting body  10 . The passage  101  has a diameter gradually increasing from the first end  104  to the second end  105 . 
     The LED bulb  100  further includes a driving circuit module  102  received in the passage  110  of the connecting body  10 . The driving circuit module  102  electrically connects the LED modules  32  and the lamp cap  20 . The driving circuit module  102  is configured for supplying the electrical power to the LED modules  32 . 
     A ring-shaped groove  103  is defined in the connecting body  10 . The ring-shaped groove  103  is adjacent to a joint of the mounting base  10  and the second end  105  of the connecting body  10 . The lamp cover  40  is fixed in the ring-shaped groove  103  of the connecting body  10 . 
     The lamp cap  20  is electrically connected to an external power supply (not shown). In the present embodiment, the lamp cap  20  can be a B22 (bayonet 22 mm) male base. In another embodiment, the lamp cap  20  can be an E27 (Edison 27 mm) male screw base. As an alternative, screw threads could be formed on an outer circumference of the lamp cap  20  for securing the LED bulb  100  in a socket. 
     The mounting base  31  is made of a material with high heat dissipation efficiency (high heat conductivity), such as aluminum. The mounting base  31  is a polyhedron. The mounting base  31  has a top face  311  and at least three surrounding walls  312  connected to the top face  311 . The top face  311  orients toward a direction different from that of each of the at least three surrounding walls  312 . 
     In the present embodiment, the mounting base  31  is a frustum of a pyramid. The mounting base  31  includes four surrounding walls  312  connected end-to-end. The mounting base  31  includes a bottom face  313  spaced from and parallel to the top face  311  of the mounting base  31 . The mounting base  31  is connected with the connecting body  10  via the bottom face  313  thereof. The bottom face  313  of the connecting body  10  has a same size as that of the second end  105  of the connecting body  10 . An angle β is formed between each surrounding wall  312  and the top face  311  of the mounting base  31 . In the present embodiment, the angle β is an obtuse angle between 100 degrees and 140 degrees. In this embodiment, the angles β between the surrounding walls  312  and the top face  311  are identical to each other. Each of the surrounding walls  312  orients toward a direction different from that of each of the remaining surrounding walls  312 . 
     An extension of the top face  311  of the mounting base  31  interests with the lamp cover  40  at a point L. A tangent line Y of the lamp cover  40  through the point L and the extension of the top face  311  form an included angle α which is less than 60 degrees. Furthermore, a center of the lamp cover  40  is located above the top face  311  of the mounting base  31 . 
     The LED module  32  includes a substrate  321  and at least two LEDs  322  mounted on the substrate  321 . In this embodiment, the LEDs  322  can be mounted on the substrate  321  via surface mounted technology. The mounting base  31  defines an inner passage (not shown) communicating with the passage  101  of the connecting body  10 . Electrical wires (not shown) pass through the inner passage of the mounting base  31  and the passage  101  of the connecting body  10  to electrically connect the LED modules  32  and the driving circuit module  102 . 
     The lamp cover  40  is made of transparent or translucent material such as glass, polycarbonate, for transmission of the light emitted from the LED module  32  therethrough. In the present embodiment, a lower portion of the lamp cover  40  is brought to clamp into the ring-groove  103  of the connecting body  10 . The lamp cover  40  encloses the LED modules  32  therein. In another embodiment, the lamp cover  40  could be secured to the connecting body  10  via screwing means, ultrasonic welding or the like. 
     In the present embodiment, the LED modules  32  are mounted on the top face  311  and the surrounding walls  312  of the mounting base  31 . The angle β between each surrounding wall  312  and the top face  311  is an obtuse angle in the range of 100-140 degrees. The LED module  32  on the top face  311  emits light in a direction different from the direction of the light beam emitted from the LED module  32  on each of the surrounding walls  312 . The LED module  32  on each of the surrounding walls  312  emits light in a direction different from directions of the LED modules  32  on the remaining surrounding walls  312 . 
     Therefore, the LED modules  32  emit light in all directions into the space around the LED bulb  100 , including light toward the backside of the LED bulb  100  which is the light emitted from the LED modules  32  on the surrounding walls  312  and refracted backwardly by the lamp cover  40 . Thus, the LED bulb  100  with omnidirectional light distribution similar to an incandescent bulb is obtained. 
     In addition, the geometric relationship that the angle α between tangent line Y of the lamp cover  40  through the point L and the extension of the top face  311  is less than 60 degrees and the center of the lamp cover  40  is located above the top face  311  of the mounting base  31 , helps a portion of the light emitted from the LED module  32  mounted on the top face  311  of the mounting base  31  to be refracted by the lamp cover  40  toward the backside of the LED bulb  100 . 
     Referring to  FIG. 2 , a light emitting diode (LED) bulb  100   a  in accordance with a second exemplary embodiment of the present disclosure includes a connecting body  10   a , a lamp cap  20   a  located at a first end  104   a  of the connecting body  10   a , a mounting base  31   a  located at a second end  105   a  of the connecting body  10   a , at least three LED modules  32   a  mounted on the mounting base  31   a , a lamp cover  40   a  connected to the connecting body  10   a  and a lens  50  coupled to and covering the LED module  32  mounted on the top face  311  of the mounting base  31 . 
     The lens  50  includes a concave light incident face  51 , a convex light exiting face  52  opposite to the light incident face  51 , and a connecting face  53  interconnecting the light incident face  51  and the light exiting face  52 . The light exiting face  52  includes a first curved surface  502  and a second curved surface  504  connected with the first curved surface  502 . 
     An inner periphery of the first curved surface  502  intersects with an inner periphery of the second curved surface  504  in a straight line p (the straight line p is illustrated in a dot shown in  FIG. 2 ). The first curved surface  502  is symmetric with the second curved surface  504  with respect to a plane Z that contains the straight line p and is perpendicular to the top face  311   a  of the mounting base  31   a . A distance between the light incident face  51  and the light exiting face  52  increases from the straight line p toward side faces  501 ,  503  of the lens  50  along a lateral direction. The light incident face  51  has a central axis of symmetry, and the central axis of the light incident face  51  lies in the plane Z. 
     Referring to  FIG. 3 , different from the LED bulb  100   a  shown in  FIG. 2 , a light incident face  51  of the lens  50  of an LED bulb  100   b  in accordance with a third exemplary embodiment of the present disclosure includes a first light incident face  511  and a second light incident face  512  spaced from the first light incident face  511 . 
     The first incident face  511  has a central axis M of symmetry, and the central axis M of the first incident face  511  deviates from the plane Z. The second face  512  has a central axis N of symmetry, and the central axis N of the second incident face  512  deviates from the plane Z. The central axis M of symmetry and the central axis N of symmetry are located on opposite sides of the plane Z, respectively. 
     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.