Patent Publication Number: US-2011050103-A1

Title: Led lamp having heat-dissipating device

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to cooling devices applied to illuminators, and more particularly, to an LED lamp having a heat-dissipating device. 
     2. Description of the Related Art 
     In the field of solid-state lighting (SSL), a light-emitting diode (LED) includes the advantages of small size, long working time, no mercury, and low energy consumption. As the brightness of the LED keeps enhanced, the lighting apparatuses based on the LED have been available in commerce and are expected to replace the conventional tungsten, halogen, and fluorescent lamps for saving energy and reducing carbon dioxide. However, because the photoelectric conversion efficiency of the LED is limited, while a high-power LED is working, a great amount of heat will be generated. If such heat cannot be effectively dissipated, it will bring serious negative effect on the photoelectric property of the LED and then thermally damage the LED. 
     In light of the problem mentioned above, there was an improved lighting apparatus having a heat-dissipating plate, an LED mounted to a bottom side of the heat-dissipating plate, and a plurality of fins mounted to a top side or a lateral side of the heat-dissipating plate. The heat generated by the LED can be conducted through the heat-dissipating plate to the fins and the air passing by the fins can take the heat away, thus resulting in thermal dissipation. However, the effect of such thermal dissipation is not satisfactory because the airflow resistance between the fins is large. Besides, while the fins absorb the heat, they fail to dissipate the same and even worse to dissipate the heat of the LED. Such circumstances often happen on LED lamps mounted outdoors. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide an LED lamp, whose thermal dissipation is based on preferable natural convection. 
     The secondary objective of the present invention is to provide an LED lamp, which still keeps thermal dissipation while external heat is transferred thereto. 
     The foregoing objectives of the present invention are attained by the LED lamp composed of a columnar heat-dissipating member having at least one air passage axially running through its inside; a cooling fan mounted to the heat-dissipating member and to a top end of the air passage; at least one LED disposed on a surface of the heat-dissipating member; and a controller electrically connected with the cooling fan and the LED for enabling the cooling fan to drive the airflow to flow upward and for driving the LED to light up. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a first preferred embodiment of the present invention. 
         FIG. 2  is a sectional view of the first preferred embodiment of the present invention. 
         FIG. 3  is a sectional view of a part of the first preferred embodiment of the present invention. 
         FIG. 4  is a system block diagram of the first preferred embodiment of the present invention. 
         FIG. 5  is another system block diagram of the first preferred embodiment of the present invention. 
         FIG. 6  is similar to  FIG. 2 , illustrating that the air flows through the air passage to exhaust the heat from the heat-dissipating member. 
         FIG. 7  is similar to  FIG. 6 , illustrating that the cooling fan functions to reinforce the upward flow of the airflow to enhance the thermal dissipation of the heat-dissipating member. 
         FIG. 8  is a sectional view of a second preferred embodiment of the present invention. 
         FIG. 9  is a sectional view of a second preferred embodiment of the present invention at work. 
         FIG. 10  is a sectional view of a third preferred embodiment of the present invention. 
         FIG. 11  is a sectional view of a part of a third preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1-5 , an LED lamp constructed according to a first preferred embodiment of the present invention is composed of a heat-dissipating member  11 , a cooling fan  12 , a plurality of LEDs  13 , and a controller  14 . The heat-dissipating member is columnar, including a plurality of air passages  111  axially running through an inside thereof. The cooling fan  12  is mounted to the heat-dissipating member  11  and to top ends of the air passages  111 . When the cooling fan  12  is driven, the airflow goes upward. The LEDs  13  are disposed on a surface of the heat-dissipating member  11  axially along the heat-dissipating member  11 . The controller  14  is electrically connected with the cooling fan  12  and the LEDs  13  for enabling the cooling fan  12  to drive airflow to flow upward and for driving the LEDs to light up. 
     In this embodiment, the controller  14  includes a temperature sensor  141  and a control circuit  142 . The temperature sensor  141  can detect the temperature of the heat-dissipating member  11 . The control circuit  142  is electrically connected with the cooling fan  12 , the temperature sensor  141 , and the LEDs  13  for receiving signals of temperature from the temperature sensor  141 . When the temperature of the heat-dissipating member  11  goes beyond a predetermined one, the control circuit  142  can activate the cooling fan  12  to drive the airflow to flow upward and enable the LEDs  13  to light up. 
     Referring to  FIG. 5 , the controller  14  can alternatively be a delay circuit  143  electrically connected with the cooling fan  12  and the LEDs  13  for controllably activating the cooling fan  12  after the LEDs  13  light up for a predetermined duration, like five or ten minutes, and for controllably enabling the LEDs  13  to light up. 
     Referring to  FIGS. 4 and 5 , the LED lamp can further include a constant-current device  16  electrically connected with the control circuit  142  or the delay circuit  143  for providing constant current in such a way that the working time of relevant electronic components can be elongated. 
     Referring to  FIG. 6 , while the LED lamp is working, the control circuit  142  or the delay circuit  143  makes the electric current of the constant-current device  16  be electrically connected with the LEDs  13  to enable illumination of the LEDs  13 . The LEDs  13  generate heat while lighting up and then the heat is conducted to the heat-dissipating member  11 . Because the heat-dissipating member  11  includes the air passages  111 , the air located in the air passages  111  flows upward due to the heat conducted to the heat-dissipating member  11 . In the meantime, the air located below the air passages  111  flows upward to generate natural convection and then the heat can be taken outside. Thus, the heat-dissipating member  11  can thermally dissipate the LEDs  13 . The air can pass through the air passages  111  to be taken outside because the flow resistance in the air passages  111  is lower than that of the conventional fins. Thus, the efficiency of the thermal dissipation of the present invention is higher than that of the prior art. 
     Referring to  FIG. 7 , the LEDs  13  keeps illumination and then transfer the heat to the heat-dissipating member  11 , or the heat-dissipating member  11  is heated externally, such that the temperature of the heat-dissipating member  11  keeps rising. Under the circumstances, the LED lamp  11  of the first embodiment can come up with the following two manners of thermal dissipation. 
     First, the temperature sensor  141  keeps detecting the temperature of the heat-dissipating member  11  and transmitting the signals of temperature to the control circuit  142 . When the temperature of the heat-dissipating member  11  is higher than a predetermined one, the control circuit  142  makes the constant-current device  16  be electrically connected with the cooling fan  12  to drive the cooling fan  12  to amplify the upward flowage of the airflow in such a way that the efficiency of thermal dissipation of the heat-dissipating member  11  is enhanced. Besides, the control circuit  142  keeps electric connection between the constant-current device  16  and the cooling fan  12  until the control circuit  142  deactivates the electric connection between the constant-current device  16  and the LEDs  13 . 
     Second, while the delay circuit  143  is electrically connected with the constant-current device  16  and the LEDs  13 , it starts to keep time. When a predetermined time point is reached, the cooling fan  12  is activated to reinforce the thermal dissipation of the heat-dissipating member  11  until the delay circuit  142  deactivates the electric connection between the constant-current device  16  and the LEDs  13 . 
     In light of the above two manners, while the heat-dissipating member  11  keeps absorbing the heat to heighten the temperature thereof, the cooling fan  12  can keep running to intensify the upward flowage of the air to further enhance the thermal dissipation of the heat-dissipating member  11 . Compared with the prior art, when external heat is transferred to the LEDs  13 , the present invention can still keep thermal dissipation. 
     Referring to  FIG. 8 , an LED lamp constructed according to a second preferred embodiment of the present invention is similar to and different from that of the first embodiment as recited below. 
     The LED lamp further includes a lamp holder  21  and a lamp cover  22 . The lamp holder  21  at a bottom side thereof is fixed to the cooling fan  12 , having a plurality of louvers  211  and a thermal passage  212 . The louvers  211  are formed on a top side of the lamp holder  21  for heat to exhaust therethrough. The thermal passage  212  is in communication with the louvers  211 . The lamp cover  22  is covered on the LEDs  13  and fixed to the lamp holder  21 , having a plurality of pores  221  running therethrough, for preventing an external object from colliding with the LEDs  13  and for generating visual effect of diffusion of the rays emitted by the LEDs  13 . The pores  221  are for the air to pass therethrough into the lamp cover  22 . 
     Referring to  FIG. 9 , an LED lamp constructed according to a second preferred embodiment of the present invention is similar to that of the first embodiment, having the following difference. The air passes through the pores  221  into the lamp cover  22  and then the heat of the heat-dissipating member  11  is transferred to the air while passing through the air passages  111 , such that the air becomes hot. Next, the hot air passes by the cooling fan  12  and through the thermal passages  212  and then exhausts outside through the louvers  211 . Therefore, the heat-dissipating member  11  thermally dissipates the LEDs  13 . 
     Referring to  FIGS. 10 and 11 , an LED lamp constructed according to a third preferred embodiment of the present invention is similar to that of the second embodiment, having the following difference. There is only one air passage  111  and the heat-dissipating member  11  is taped-shaped to have its upper side be larger than its lower side in diameter. In this way, the light of the LEDs  13  can emitted downward to enhance the brightness of the LED lamp. The operation of the third embodiment is identical to that of the second embodiment, so no more recitation in this regard is necessary. 
     In conclusion, the present invention includes the following advantages.
         1. It makes good use of the air for passing through the air passages  111  to enable more efficient thermal dissipation.   2. The cooling fan  12  is activated to drive the airflow upward to further enhance the thermal dissipation of the heat-dissipating member  11 , such that the heat-dissipating member  11  still keeps thermal dissipation while the external heat is transferred to the LEDs.       

     Although the present invention has been described with respect to specific preferred embodiments thereof, it is no way limited to the details of the illustrated structures but changes and modifications may be made within the scope of the appended claims.