Patent Publication Number: US-8985815-B2

Title: Light bulb with upward and downward facing LEDs having heat dissipation

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to lighting technology and more particularly, to a light bulb, which comprises a first circuit board with upward-facing LEDs and a second circuit board with downward-facing LEDs, a metal holder plate set between the first circuit board and the second circuit board to support a light-transmissive shade and a light transmitting lamp shell and to dissipate heat. 
     2. Description of the Related Art 
     Since the invention of a first practical electric light bulb by Thomas Alva Edison (Feb. 11, 1847-Oct. 18, 1931), the use of electric light bulb has more than one hundred years of history. An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light which produces light with a tungsten filament wire heated to a high temperature by an electric current through it, until it glows. A tungsten filament-based electric light bulb throws light in an omnidirectional manner, i.e., in all directions. Thus, it quickly replaces conventional dangerous candles and kerosene lamps. Nowadays, many different omnidirectional brilliant light sources are commercially available. 
     However, tungsten filament-based electric light bulbs consume a large amount of power during operation. It has a low luminous efficacy, i.e., less units of lumens per watt (lm/W). Nowadays, many energy-saving light sources have been created and are intensively used to replace conventional tungsten filament-based electric light bulbs. 
     The most popularly accepted energy-saving light is a compact fluorescent lamp, also called compact fluorescent light and compact fluorescent tube, designed to replace an incandescent lamp. An energy-saving light of this kind uses a tube which is curved or folded to fit into the space of an incandescent bulb, and a compact electronic ballast in the base of the lamp. Under same illumination conditions, an energy-saving light consumes less electric energy than a conventional tungsten filament-based electric light bulb. However, when compared to a T5 fluorescent lamp, a ballast-based energy-saving light consumes much electric energy. 
     Conventional energy-saving lights still has drawbacks. At first, an energy-saving light generates small amount of magnetic waves (4.67 milligauss) and microwaves (3.3 μW/cm 2  per every watt) during operation. Further, an energy-saving light does not allow light intensity adjustment. Further, an energy-saving light contains a small amount of toxic mercury. Delivery of energy-saving lights or disposing of used energy-saving lights must be carefully handled. 
     Further, LED lights draw less energy, which makes them more cost effective to use. Many light fixture manufacturers create LED lights for illumination. LED lights are more rugged and damage-resistant than compact fluorescents and incandescent bulbs; however, they are very heat sensitive. Excessive heat or inappropriate applications dramatically reduce both light output and lifetime of LED lights. Further, LED lights are directional. For illumination application, heat dissipation and light dispersion must be properly designed. 
     A conventional LED light bulb is known comprising a heat sink disposed at the bottom side, a circuit board mounted at the top side of the heat sink, a plurality of light-emitting diodes installed in the circuit board, and a transparent or translucent lamp shell covering the circuit board and the light-emitting diodes. According to this design of LED light bulb, the light-emitting diodes face upward (forward). Due to limited light-emitting angle, a LED light bulb of this design is normally used with a reflector that is mounted around the lamp socket holding the LED light bulb. However, because the light-emitting diodes are directional, the reflector cannot reflect much light rays toward the desired direction. Further, the simple heat sink design cannot effectively and rapidly dissipate waste heat from the light-emitting diodes during the operation of the LED light bulb. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a light bulb, which dissipates waste heat rapidly during operation and has the characteristics of high component positioning stability and enhanced illumination. 
     To achieve this and other objects of the present invention, a light bulb comprises a lamp base unit comprising an electrically insulative hollow column, a base, a metal cylindrical heat sink, a light-transmissive shade and a power supply module, a light source module comprising a metal holder plate, a first circuit board with upward-facing LEDs, a second circuit board with downward-facing LEDs, a first adapter board, a second adapter board, a positioning block and a heat transfer pad, and a light transmitting lamp shell. The metal holder plate of the light source module is kept in close contact with the first circuit board and the second circuit board for quick dissipation of waste heat produced during operation of the LEDs, and works to hold the light-transmissive shade and the lamp shell firmly in place. 
     Further, in addition to the functioning of the metal holder plate to dissipate waste heat from the first circuit board and the second circuit board, the heat transfer pad and the heat sink can also dissipate waste heat from the second circuit board. Further, the metal holder plate comprises a plurality of mounting lugs for securing the light-transmissive shade and the lamp sell firmly in place. The mounting lugs also work as radiation fins to dissipate waste heat during operation of the LEDs. Further, the number of the mounting lugs can be determined subject to the installation quantity of the LEDs. Thus, if the quantity or power watt of the LEDs is increased, the total heat dissipation surface area of the mounting lugs can be relatively increased. 
     Further, the first adapter board and the second adapter board are respectively electrically connected to the first circuit board and the second circuit board by spot welding, and the first adapter board and the second adapter board are electrically connected together by means of the electric connector. By means of inserting the electric connector into a respective connector hole at the first circuit board, the metal holder plate and the second circuit board and then bonding the electric connector to the second circuit board and then bonding the first adapter board to the upright contact pins of the electric connector, the electric connection is done. 
     Further, the upper part of the outer perimeter of the heat sink is tapered for reflecting the light emitted by the downward-facing LEDs of the second circuit board, enhancing lateral and rear side illumination that passes through the light-transmissive shade. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of a light bulb in accordance with the present invention. 
         FIG. 2  is an exploded view of the light bulb in accordance with the present invention. 
         FIG. 3  is similar to  FIG. 2  when viewed from another angle. 
         FIG. 4  is a sectional view of the light bulb in accordance with the present invention. 
         FIG. 5  is an enlarged view of a part of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1-5 , a light bulb in accordance with the present invention is shown. The light bulb comprises a lamp base unit  1 , a light source module  2 , and a lamp shell  3 . 
     The lamp base unit  1  comprises an electrically insulative hollow column  11 , which comprises an externally threaded coupling neck  111  disposed at the bottom side thereof and a plurality of hooks  112  equiangularly disposed at the opposing top side thereof, a base  12 , which is configured like the base of a conventional incandescent bulb having a ring contact and a tip contact for connecting the positive and negative terminals of a power source and, which comprises an inner thread  121  located on the inner perimeter thereof and threaded onto the externally threaded coupling neck  111  of the electrically insulative hollow column  11  and an outer thread  122  located on the outer perimeter thereof for threading into an external lamp socket (not shown), a metal cylindrical heat sink  13 , which surrounds the electrically insulative hollow column  11  and which comprises an annular step  131  extending around the outer perimeter thereof, a plurality of longitudinal female studs  132  formed integral with and equiangularly spaced around the outer perimeter, a screw hole  1321  located on the top side of each longitudinal female stud  132  and a plurality of locating notches  133  equiangularly disposed at the top side thereof in a staggered manner relative to the longitudinal female studs  132  and respectively forced into engagement with the hooks  112  of the electrically insulative hollow column  11 , a light-transmissive shade  14 , which surrounds an upper part of the metal cylindrical heat sink  13  and which comprises a tapered bottom part  141  fitting the outer perimeter of the metal cylindrical heat sink  13  and supported on the annular step  131  of the metal cylindrical heat sink  13 , a plurality of mating notches  1411  equiangularly disposed at the inner perimeter of the tapered bottom part  141  and adapted to accommodate the longitudinal female studs  132  of the metal cylindrical heat sink  13  and a plurality of retaining grooves  142  equiangularly spaced around the outer perimeter at the top side, and a power supply module  15  mounted inside the electrically insulative hollow column  11  and electrically connected to the ring contact and tip contact of the base  12 . 
     The light source module  2  comprises a metal holder plate  21 , a first circuit board  22 , a second circuit board  23 , a first adapter board  24 , a second adapter board  25 , a positioning block  26 , and a heat transfer pad  27 . The metal holder plate  21  is arranged at the top side of the electrically insulative hollow column  11  and light-transmissive shade  14  of the lamp base unit  1 , comprising a plurality of retaining lugs  211  and retaining holes  212  alternatively arranged around the border area thereof. The respective bottom ends of the retaining lugs  211  of the metal holder plate  21  are respectively forced into engagement with the retaining grooves  142  of the light-transmissive shade  14 . The first circuit board  22  is mounted at the top side of the metal holder plate  21 , comprising a plurality of LEDs (light-emitting diodes)  221  disposed at the top wall thereof and electrically connected to the power supply module  15 . Further, screws  222  are mounted at the first circuit board  22  and driven into the screw holes  1321  to affix the first circuit board  22 , the metal holder plate  21 , the second circuit board  23  and the heat transfer pad  27  to the lamp base unit  1 . The second circuit board  23  is mounted at the bottom side of the metal holder plate  21  and supported on the head sink  13 , comprising a plurality of LEDs (light-emitting diodes)  231  disposed at the bottom wall thereof and electrically connected to the power supply module  15  and an electric connector  232  electrically connected to the metal holder plate  21 . The electric connector  232  comprises a plurality of upright contact pins  2321 . Further, screws  233  are mounted at the second circuit board  23  and driven through the metal holder plate  21  into the first circuit board  22  to affix the first circuit board  22 , the metal holder plate  21  and the second circuit board  23  together. The first adapter board  24  and the second adapter board  25  are respectively mounted at the top side of the first circuit board  22  and the bottom side of the second circuit board  23  and electrically connected to the upright contact pins  2321  of the electric connector  232  of the second circuit board  23 . Further, the first adapter board  24  electrically connects the first circuit board  22  to the power supply module  15 . The positioning block  26  is mounted at the bottom side of the second adapter board  25  and partially press-fitted into the top open side of the electrically insulative hollow column  11 , comprising an upright post  261  disposed at the top center thereof, a plurality of ribs  2611  spaced around the periphery of the upright post  261 , and a plurality of positioning notches  262  equiangularly spaced around the border of the top side thereof and respectively forced into engagement with the hooks  112  of the electrically insulative hollow column  11 . The heat transfer pad  27  is an annular pad sandwiched between the second circuit board  23  and the metal cylindrical heat sink  13 . Further, through holes  28  are respectively formed on the metal holder plate  21 , the first circuit board  22 , the second circuit board  23  and the heat transfer pad  27  for the passing of the screws  222 ;  233 . Further, center openings  4  and notches  41  are respectively formed on the metal holder plate  21 , the first circuit board  22 , the second circuit board  23  and the second adapter board  25  for the passing of the upright post  261  and ribs  2611  of the positioning block  26 . Further, connector holes  5  are respectively formed on the metal holder plate  21 , the first circuit board  22  and the second circuit board  23  for accommodating the electric connector  232 . 
     The lamp shell  3  is mounted at the top side of the metal holder plate  21 , comprising a plurality of retaining grooves  31  equiangularly spaced around the periphery thereof and respectively forced into engagement with the respective top ends of the retaining lugs  211  of the metal holder plate  21 , and a plurality of bottom hooks  32  extended from the bottom side thereof and arranged at equiangular intervals and respectively hooked in the retaining holes  212  of the metal holder plate  21 . 
     The metal holder plate  21  of the light source module  2  is made of a metal material having excellent thermal conductivity, for example, aluminum or aluminum magnesium alloy. The LEDs  221  of the first circuit board  22  are facing upward and the LEDs  231  of the second circuit board  23  are facing down. Thus, the light source module  2  provides a wide range of illumination. Further, the first circuit board  22  and the second circuit board  23  are respectively kept in close contact with the opposing top and bottom walls of the metal holder plate  21  for quick dissipation of waste heat during operation of the LEDs  221 ;  231 . Further, subject to engagement between the retaining lugs  211  of the metal holder plate  21  and the retaining grooves  31 ;  142  of the lamp shell  3  and light-transmissive shade  14 , the lamp shell  3  and the light-transmissive shade  14  are firmly secured together to show a view of a bulb shape. 
     Further, the light-transmissive shade  14  and the lamp shell  3  can be selected from a group of transparent or translucent materials. Further, the light-transmissive shade  14  and the lamp shell  3  can be separately made, and then fastened together. Alternatively, the light-transmissive shade  14  and the lamp shell  3  can be made in one piece. 
     Further, the light bulb not only uses the metal holder plate  21  to dissipate waste heat from the first circuit board  22  and the second circuit board  23 , but also has the heat transfer pad  27  be sandwiched between the heat sink  13  and the second circuit board  23  to transfer waste heat from the second circuit board  23  to the heat sink  13  for quick dissipation. Thus, waste heat can be quickly dissipated from the light source module  2  during operation of the LEDs  221 ;  231  to keep the LEDs  221 ;  231  under an optimal working environment, thereby prolonging the lifespan of the light bulb. 
     Further, the number of the retaining lugs  211  of the metal holder plate  21  can be 2, 3, 4 or 5, subject to the installation amount of the LEDs  221 ;  231  and the overall power watt level of the light bulb. Further, the amount and locations of the retaining grooves  31 ;  142  of the lamp shell  3  and light-transmissive shade  14  are determined subject to the amount and locations of the retaining lugs  211  of the metal holder plate  21 . Thus, the retaining lugs  211  of the metal holder plate  21  also work as radiation fins to dissipate waste heat being received by the metal holder plate  21  from the LEDs  221 ;  231  of the first and second circuit boards  22 ;  23 . 
     Further, the power supply module  15  has its bottom terminal electrically connected to the base  12  by electric wires, and its top terminal electrically connected to the first adapter board  24  by electric wires. The first adapter board  24  and the second adapter board  25  are respectively electrically bonded to the first circuit board  22  and the second circuit board  23  by spot welding. The first adapter board  24  and the second adapter board  25  are electrically connected by means of the electric connector  232 . If electric wires are used to electrically connect the first circuit board  22 , the second circuit board  23 , the first adapter board  24  and the second adapter board  25 , the welding procedure will be complicated, and an accommodate space must be provided for accommodating the electric wires. Using the electric connector  232  to electrically connect the first circuit board  22 , the second circuit board  23 , the first adapter board  24  and the second adapter board  25  simply needs to make the connector holes  5  on the metal holder plate  21 , the first circuit board  22  and the second circuit board  23  for accommodating the electric connector  232 , simplifying the installation procedure. 
     Instead of the aforesaid arrangement to electrically connect the electric wires at the top terminal of the power supply module  15  to the first adapter board  24 , the electric wires at the top terminal of the power supply module  15  can be electrically connected to the second adapter board  25  to provide power supply to the second adapter board  25 , enabling the second adapter board  25  to transmit power supply to the second circuit board  23  and the first circuit board  22 . 
     Further, the upper part of the outer perimeter of the heat sink  13  above the elevation of the annular step  131  can be tapered to reflect the light emitted by the downward-facing LEDs  231  of the second circuit boards  23 , enhancing lateral and rear side illumination. Further, the outer perimeter of the heat sink  13  can be covered with a reflecting coating, enhancing reflection. Further, a lamp socket for light bulb may be equipped with a reflector for reflecting backward and lateral light toward the front side. Subject to the arrangement of the downward-facing LEDs  231  of the second circuit boards  23  and the light reflection function of the head sink  13 , the light bulb of the present invention enhances lateral and backward illumination for reflection by the reflector at the lamp socket toward the front side, enhancing the brightness. 
     In actual application, the light bulb of the present invention has the features and advantages as follows:
     1. The metal holder plate  21  of the light source module  2  is kept in close contact with the first circuit board  22  and the second circuit board  23  for quick dissipation of waste heat produced during operation of the LEDs  221 ;  231 , and works to hold the light-transmissive shade  14  and the lamp sell  3  firmly in place.   2. In addition to the functioning of the metal holder plate  21  to dissipate waste heat from the first circuit board  22  and the second circuit board  23 , the heat transfer pad  27  and the heat sink  13  can also dissipate waste heat from the second circuit board  22 ; the mounting lugs  211  of the metal holder plate  21  also work as radiation fins to dissipate waste heat during operation of the LEDs  221 ;  231 ; the number of the mounting lugs  211  can be determined subject to the installation quantity of the LEDs  221 ;  231 , and thus if the quantity or power watt of the LEDs  221 ;  231  is increased, the total heat dissipation surface area of the mounting lugs  211  can be relatively increased.   3. The first adapter board  24  and the second adapter board  25  are respectively electrically connected to the first circuit board  22  and the second circuit board  23  by spot welding, and the first adapter board  24  and the second adapter board  25  are electrically connected together by means of the electric connector  232 ; by means of inserting the electric connector  232  into the connector holes  5  and bonding it to the second circuit board  2  and then bonding the first adapter board  24  to the upright contact pins  2321  of the electric connector  232 , the electric connection is done.   4. The upper part of the outer perimeter of the heat sink  13  above the elevation of the annular step  131  is tapered for reflecting the light emitted by the downward-facing LEDs  231  of the second circuit board  23 , enhancing lateral and rear side illumination that passes through the light-transmissive shade  14 .   

     In conclusion, the light bulb of the present invention comprises a lamp base unit, which comprises a base connectable to a lamp socket, an electrically insulative hollow column fastened to the base, a heat sink surrounding the electrically insulative hollow column, a light-transmissive shade surrounding the upper part of the metal cylindrical heat sink and a power supply module mounted in the electrically insulative hollow column and electrically connected to the base, a light source module consisting of a metal holder plate, a first circuit board with upward-facing LEDs, a second circuit board with downward-facing LEDs, a first adapter board, a second adapter board, a positioning block and a heat transfer pad and supported on the heat sink in the light-transmissive shade, and a lamp shell fastened to the metal holder plate and capped on the light-transmissive shade. During operation of the upward-facing and downward-facing LEDs, waste heat can be quickly dissipated into the outside open air through the mounting lugs of the metal holder plate, the heat transfer pad and the heat sink. 
     Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.