Patent Publication Number: US-8109654-B2

Title: LED lamp

Description:
BACKGROUND 
     1. Technical Field 
     The disclosure relates to LED (light emitting diode) lamps for illumination purpose and, more particularly, relates to an improved LED lamp having a large illumination area. 
     2. Description of Related Art 
     An LED lamp is a type of solid-state lighting that utilizes LEDs as a source of illumination. An LED is a device for transferring electricity to light by using a theory that, if a current is made to flow in a forward direction through a junction region comprising two different semiconductors, electrons and holes are coupled at the junction region to generate a light beam. The LED has an advantage that it is resistant to shock, and has an almost eternal lifetime under a specific condition; thus, the LED lamp is intended to be a cost-effective yet high quality replacement for incandescent and fluorescent lamps. 
     Since LED lamps have many advantages, they often act as street, lawn or home lamps for illumination purpose. Known implementations of LED module in an LED lamp make use of a plurality of individual LEDs to generate light that is ample and of satisfactory spatial distribution. The large number of LEDs, however, increase price and power consumption of the module. Considerable heat is also generated, which, if not adequately addressed at additional expense, impacts LED lamp reliability. 
     Further, since the LEDs are generally arranged on a printed circuit board having a flattened face, light emitted from the LEDs is concentrated on a small area confronting the LEDs due to high directivity of the LEDs, which is unsuitable for environments requiring even and broad illumination. Thus, the LEDs mounted on the flattened face of the printed circuit board cannot have a large area of illumination. 
     What is needed, therefore, is an improved LED lamp which can overcome the above problems. 
    
    
     
       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 isometric, assembled view of an LED lamp in accordance with an embodiment of the disclosure. 
         FIG. 2  is an exploded view of the LED lamp of  FIG. 1 . 
         FIG. 3  is an inverted, exploded view of the LED lamp of  FIG. 1 . 
         FIG. 4  is a front view of  FIG. 1 , showing an angular distribution of light generated by the LED lamp. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1 and 2 , a light emitting diode (LED) lamp in accordance with an embodiment of the disclosure is illustrated. The LED lamp comprises a heat sink  10 , an LED module  20  thermally attached to a bottom face of the heat sink  10 , a light-reflecting member  30  disposed on the bottom face of the heat sink  10 , an envelope  40  mounted on the heat sink  10  and correspondingly covering the LED module  20 , a pressing frame  60  securing the envelope  40  to the heat sink  10  and a protecting cage  50  encircling the envelope  40 . 
     Referring to  FIG. 3  also, the heat sink  10  is integrally made of a metal with good heat conductivity such as aluminum, copper or an alloy thereof. The heat sink  10  comprises a circular supporting plate  12 , a cylindrical connecting portion  16  extending perpendicularly and upwardly from a central portion of a top face of the supporting plate  12 , and a plurality of fins  14  extending upwardly from the top face of the supporting plate  12  and arranged around the connecting portion  16 . An annular receiving groove  120  is defined along an outer periphery of a bottom face of the supporting plate  12 . An annular sealing gasket  100  is received in the receiving groove  120  for achieving a hermetical connection between the heat sink  10  and the envelope  40 . A circular protrusion (not labeled) is formed at a central area of the supporting plate  12  and surrounded by the receiving groove  120 . A through hole  124  is defined in a center of the protrusion of the supporting plate  12  for electrical wires (not shown) extending through the heat sink  10  and electrically connecting the LED module  20 . 
     A plurality of protruding ribs  126  protrude outwardly and perpendicularly from an outer circumference of the supporting plate  12 . The protruding ribs  126  are parallel to and equally spaced from each other. The protruding ribs  126  extend along a top-to-bottom direction of the supporting plate  12 , and each has a semicircular cross-section along a horizontal direction. A screw hole  1260  is defined in a central portion of a bottom end of each protruding rib  126 . The fins  14  extend radially relative to the connecting portion  16  on the supporting plate  12 . A passage (not labeled) is defined between every two neighboring fins  14 . An annular groove  160  is defined in a top face of the connecting portion  16 . A sealing ring  200  is received in the annular groove  160  for achieving a hermetical connection between the heat sink  10  and a hollow mounting member  17 . 
     The hollow mounting member  17  is correspondingly disposed on a top side of the connecting portion  16  of the heat sink  10  and cooperates with the connecting portion  16  to define a receiving chamber  172  for accommodating a driving module (not shown) therein. A safety connector  18  is further provided to the mounting member  17  for allowing the electrical wires to extend therethrough into the receiving chamber  172 . The mounting member  17  is in a can shape and comprises a circular top wall  174  and a cylindrical sidewall  176  extending perpendicularly and downwardly from an outer periphery of the top wall  174  and an annular flange  178  extending horizontally and outwardly from a bottom end of the sidewall  176 . The sidewall  176  has a diameter slightly smaller than that of the connecting portion  16  of the heat sink  10 . The flange  178  of the mounting member  17  is fixed to the connecting portion  16 , and the sealing ring  200  is compressed between the flange  178  and the connecting portion  16  for achieving a waterproof sealing performance of the LED lamp. A mounting hole  170  is defined in one side of the sidewall  176  of the mounting member  17  for threadedly engaging the safety connector  18  thereinto. 
     The safety connector  18  is tubular and defines a central hole  180  corresponding to the mounting hole  170  for extension of the electrical wires. A cutout  182  is defined in one side of the safety connector  18  for receiving a pressing piece  184  therein. The cutout  182  communicates with the central hole  180  for exposing a portion of the electrical wires received in the safety connector  18 . The pressing piece  184  is arced, and defines two fixing holes (not labeled) at two opposite ends thereof. The pressing piece  184  is connected to the safety connector  18  via bolts (not shown) extending through the fixing holes thereof and screwing into the safety connector  18 . The pressing piece  184  tightly secures the electric wires against an inner face of the safety connector  18 , whereby the electrical wires are reliably held in the central hole  180  via the pressing piece  184 . 
     Referring to  FIG. 2  again, a fixing bracket  300  is disposed on the top wall  174  of the mounting member  17 . The fixing bracket  300  is an elongated and bended sheet, and comprises a upright U-shaped fixing portion (not labeled) which is fixed on the top wall  174  and two arms (not labeled) extending outwardly and horizontally from two opposite sides of the fixing portion. In use, the LED lamp can be fixed to walls or ceilings via the fixing bracket  300 . 
     The LED module  20  comprises a circular printed circuit board  22  and a plurality of LEDs  24  mounted on the printed circuit board  22 . The printed circuit board  22  is thermally attached on the bottom face of the supporting plate  12  of the heat sink  10 , and the LEDs  24  are arranged evenly on the printed circuit board  22 . The LEDs  24  comprise a plurality of first LEDs  242  located at a central region of the printed circuit board  22 , and a plurality of second LEDs  244  located near an edge region of the printed circuit board  22 . That is to say, the second LEDs  244  surround the first LEDs  242 . It is understood that the printed circuit board  22  is a base which can support the LEDs  24  and electrically connect the LEDs  24  to a power supply. The first LEDs  242  are used to illuminate a main working space facing the LEDs  24  on the printed circuit board  22 , and the second LEDs  244  are used to additionally illuminate an area outside of the main working space. The LEDs  24  are arranged in a number of imaginary concentric circles. 
     The light-reflecting member  30  is located between the second LEDs  244  and the first LEDs  242 . The light-reflecting member  30  is concentric to the imaginary concentric circles defined by the LEDs  24 . The light-reflecting member  30  comprises a planar and annular seat  32  and a cylindrical reflecting portion  34  extending downwardly and outwardly from an outer circumference of the seat  32 . A diameter of the reflecting portion  34  increases gradually along a direction downwardly away from the seat  32 . An inner surface of the reflecting portion  34  faces the first LEDs  242  and an outer surface of the reflecting portion  34  faces the second LEDs  244 . The inner surface of the reflecting portion  34  is configured to guide the light generated by the first LEDs  242 , and the outer surface of the reflecting portion  34  is configured to guide the light generated by the second LEDs  244 . A plurality of concave portions  36  are recessed inwardly from the outer surface of the reflecting portion  34 , whereby the reflecting portion  34  has a waved shape. The concave portions  36  are spaced from each other, and each of the concave portions  36  is located corresponding to one second LED  244 . The seat  32  defines a plurality of thread holes (not labeled), for a plurality of screws (not shown) extending therethrough and threadedly engaging into the printed circuit board  22  to thereby secure the light-reflecting member  30  on the printed circuit board  22 . 
     The concave portions  36  of the light-reflecting member  30  each has a concave outer reflecting surface  362  facing the second LED  244  and a convex inner reflecting surface  364  facing the first LED  242 . The outer reflecting surface  362  of each concave portion  36  correspondingly faces one second LED  244  and partially surrounds the second LED  244 . The outer reflecting surface  362  and the inner reflecting surface  364  each can be a paraboloid surface, a spherical surface, an aspheric surface or an ellipsoid surface, and functions to reflect and adjust the distribution of luminous intensity of the light generated by the first LEDs  242  and the second LEDs  244 , respectively. In detail, the outer reflecting surfaces  362  are for converging a part of the light emitted from the second LEDs  244  into light beams which leave the LED lamp with large light-emergent angles, to thereby illuminate an area away from the main working space; the inner reflecting surfaces  364  are for diverging a part of the light emitting from outmost first LEDs  242  towards the main working space, to illuminate the main working space with an even intensity. 
     The light-reflecting member  30  can be made of plastic or metallic material. According to practical requirement, the inner and outer surface of the reflecting portion  34 , especially the outer and inner surfaces  362 ,  364  of the concave portions  36 , can be particularly treated to optimize light reflection of the light-reflecting member  30 . For example, the surfaces can be treated to be diffused, reflective surfaces by spraying or coating white reflecting material thereon, or highly reflective surfaces by plating a metallic coating thereon. 
     The envelope  40  is integrally formed of a transparent or half-transparent material such as glass, resin or plastic. The envelope  40  comprises a bowl-shaped main body  41  defining an opening (not labeled) at a top end thereof and an engaging flange  42  extending outwardly and horizontally from a periphery of the top end of the main body  41 . The engaging flange  42  has a size corresponding to the receiving groove  120  of the supporting plate  12 . When the envelope  40  is connected to the heat sink  10 , the engaging flange  42  is fitly accommodated in the receiving groove  120 , and the sealing gasket  100  is sandwiched between the engaging flange  42  and the supporting plate  12  for achieving a waterproof sealing performance of the LED lamp. 
     The pressing frame  60  is annular and has a plurality of spaced protruding tabs  64  extending radially and outwardly from an outer periphery thereof. The pressing frame  60  has a diameter substantially equal to that of the engaging flange  42  of the envelope  40 . The protruding tabs  64  are evenly distributed along a circumference of the pressing frame  60 . Each of the protruding tabs  64  is substantially semicircular shaped, and defines a securing hole  640  at a center thereof. The securing holes  640  of the protruding tabs  64  are aligned with the screw holes  1260  of the protruding ribs  126 , respectively. Fasteners (not shown) are brought to extend through the securing holes  640  and the screw holes  1260  to secure the heat sink  10  with the pressing frame  60 . A plurality of spaced protruding blocks (not labeled) protrude inwardly from an inner periphery of the pressing frame  60 . Each of the protruding blocks defines a blind securing hole  620  therein. 
     The protecting cage  50  has a shape corresponding to that of the envelope  40 , and has a size slightly larger than the envelope  40 . The protecting cage  50  comprises a plurality of wires (not labeled) interlaced with each other. The protecting cage  50  is configured as a bowl-shaped mesh having a plurality of openings between the wires. A pressing flange  52  extends horizontally and outwardly from a top end of the protecting cage  50 . A plurality of apertures (not labeled) are defined along a circumference of the pressing flange  52 . The apertures are aligned with the securing holes  620  of the pressing frame  60 , respectively. Fasteners (not shown) are extended through the apertures and the securing holes  620  to secure the pressing frame  60  with the protecting cage  50 . 
     In assembly, the LED module  20  is mounted on the bottom face of the supporting plate  12 ; the light-reflecting member  30  is fixed to a bottom face of the printed circuit board  22  with the LEDs  24 ; the engaging flange  42  of the envelope  40  is hermetically received in the receiving groove  120  of the heat sink  10  to receive the LED module  20  and the light-reflecting member  30  therein; the pressing frame  60  is disposed on the envelope  40  and fixed to the heat sink  10  to press the envelope  40  against the heat sink  10 , wherein the protruding tabs  64  of the pressing frame  60  horizontally protrude outside of the engaging flange  42  and located just above the protruding ribs  126 , respectively; the protecting cage  50  surrounds an outer periphery of the envelope  40  with the pressing flange  52  thereof securely fixed to the pressing frame  60 . 
     The above-described LED lamp can be applied in various occasions to meet large-area illumination requirements thereof. For example, the LED lamp could be secured to a ceiling via the fixing bracket  300 , as shown in  FIG. 4 . Referring to  FIG. 4 , the LED lamp has three illumination regions including a main working region A just below the LED lamp, a periphery working area B/C surrounding the region A and beneath a plane of the printed circuit board  22 , and a subordinate working area D above the plane of the printed circuit board  22 . In operation, the light generated by the first LEDs  242  directly illuminates the main working area A. The light directly emitted by the second LEDs  244  and the light of the second LEDs  244  reflected by the reflecting portion  34  illuminates the periphery working area B and C. A part of light reflected by the reflecting portion  34  from the second LEDs  244  escapes to the subordinate working area D. Thus, the light emitted by the LED lamp has an emergent angle over 180 degrees. 
     It is to be understood, however, that even though numerous characteristics and advantages of the disclosure have been set forth in the foregoing description, together with details of the structure and function of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.