Abstract:
An LED lamp includes a lamp holder, a heat sink, a plurality of LED modules, a cover, an envelope and a sealing cushion. The lamp holder has a connecting portion at a bottom thereof adapted for engaging with a lamp socket to fix the LED lamp in position. The heat sink is disposed on the lamp holder. The LED modules are attached to a circumference of the heat sink. The cover is coupled to a top of the heat sink. The envelope encloses the heat sink and the LED modules therein and has a lower end engaging with the lamp holder and an upper end engaging with the cover. The sealing cushion is provided between at least one of the combinations of the lamp holder and the envelope, and of the cover and the envelope to prevent an entry of foreign matter.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an LED lamp, and more particularly to an improved LED lamp having a sealed structure to prevent an entry of mist, dust, rainwater and other foreign matter into the LED lamp. 
   2. Description of Related Art 
   An LED lamp is a type of solid-state lighting that utilizes light-emitting diodes (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. 
   When the LED lamp is used in the outdoors for illumination, mist, dust, rainwater or other foreign matter is prone to creep into the LED lamp, which may cause electric leakage or short circuit of the LED lamp, or a contamination of the LEDs used in the LED lamp. 
   What is needed, therefore, is an improved LED lamp which has a simple and novel structure, whereby the LED lamp is suitable to mass-manufacture and has an improved waterproof configuration for preventing rainwater, dust, etc. from creeping into the LED lamp. 
   SUMMARY OF THE INVENTION 
   An LED lamp includes a lamp holder, a heat sink, a plurality of LED modules, a cover, an envelope and a sealing cushion. The lamp holder has a connecting portion at a bottom thereof adapted for engaging with supporting rod to fix the LED lamp in position. The heat sink is disposed on the lamp holder. The LED modules are attached to a circumference of the heat sink. The cover is coupled to a top of the heat sink and thermally connects therewith so heat of the heat sink can be dissipated to surrounding air of the LED lamp through the cover. The envelope encloses the heat sink and the LED modules therein and has a lower end engaging with the lamp holder and an upper end engaging with the cover. The sealing cushion is provided in at least one of the combinations of the lamp holder and the envelope, and of the cover and the envelope to prevent an entry of foreign matter into the LED lamp. 
   Other advantages and novel features will become more apparent from the following detailed description of preferred embodiments when taken in conjunction with the accompanying drawings, in which: 

   
     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 a preferred embodiment of the present invention; 
       FIG. 2  is an exploded view of  FIG. 1 ; 
       FIG. 3  is an inverted view of  FIG. 2 ; 
       FIG. 4  shows a lamp holder of the LED lamp of  FIG. 2 ; and 
       FIG. 5  shows a heat sink of the LED lamp of  FIG. 2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIGS. 1-3 , an LED lamp in accordance with a preferred embodiment is illustrated. The LED lamp comprises a lamp holder  10 , a heat sink  20  mounted on the lamp holder  10 , a plurality of LED modules  30  attached to the heat sink  20 , a cover  40  covered on a top of the heat sink  20 , and an envelope  50  located between the lamp holder  10  and the cover  40  and enclosing the heat sink  20  and the LED modules  30  therein. Three connecting shafts  200  are mounted around the envelope  50  and stand between the lamp holder  10  and the cover  40 . The LED lamp is further provided with a first annular cushion  100  sandwiched between the envelope  50  and the lamp holder  10 , and a second annular cushion  102  sandwiched between the envelope  50  and the cover  40  to prevent an entry of foreign matter such as mist, dust and rainwater from entering the LED lamp to cause the LED lamp to have an electric leakage or short circuit or to cause the LED modules  30  to be contaminated. 
   As expressly shown in  FIG. 4 , the lamp holder  10  comprises a discal base  12  and a connecting portion  14  extends downwardly from a central portion of a bottom of the base  12  for securing the LED lamp onto a supporting structure (not shown) such as a supporting rod. The base  12  has a bowl-shaped receiving chamber  120  downwardly recessing from a central portion thereof, for receiving a driving circuit module  300  therein. A through bore  121  is defined in a centre of a bottom of the receiving chamber  120  for an extension of lead wires into the LED lamp. The base  10  has an annular inner flange  122  extending upwardly from the top thereof and surrounding the receiving chamber  120  and an annular outer flange  124  concentric with the inner flange  122  and protruding upwardly from a top thereof. The inner flange  122  is preferred to have a height larger than that of the outer flange  124 . The inner and outer flanges  122 ,  124  are spaced from each other, thereby defining a first groove  126  therebetween for receiving a bottom end of the envelope  50 . Three cutouts  1240  are equidistantly defined in the outer flange  122  for facilitating an outflow of rainwater accidentally infiltrated into the first groove  126 . Three first securing holes  128  are evenly defined in the base  12  and surround the outer flange  124 , for respectively receiving three lower ends of the connecting shafts  200 . 
   As shown in  FIG. 5 , the heat sink  20  is integrally made of a metal with a good heat conductivity, such as aluminum, copper or an alloy thereof. The heat sink  20  has an elongated cylinder  22  with a through hole (not labeled) defined therein. The heat sink  20  has a plurality of conducting arms  24  evenly extending outwardly from a circumferential surface of the cylinder  22 . The conducting arms  24  are identical and centrosymmetric to each other relative to an axis of the cylinder  22 . The conducting arms  24  have a number which is consistent with that of the LED modules  30  in the preferred embodiment, and can be different in different embodiments. In this embodiment, the numbers of the conducting arms  24  and the LED modules  30  are both six. A plural pairs of first fins  26  are formed on two opposite lateral sides of each of the conducting arms  24 . Each pair of the first fins  26  extend outwardly and perpendicularly from two lateral sides of a corresponding conducting arm  24  and are symmetrical to each other relative to the corresponding conducting arm  24 . The first fins  26  at a lateral side of each of the conducting arms  24  increase in length outwardly from the cylinder  22  to a distal end of the corresponding conducting arm  24 . Each of the conducting arms  24  has a distal end terminating at an inside face of an outmost first fin  26  thereof. An outside face (not labeled) of each outmost first fin  26  is flat and used for thermally contacting with one of the LED modules  30 , when the LED module  30  is mounted on the outside face. Three elongated ridges  23  extend inwardly from an interior surface of the cylinder  22  of the heat sink  20  and are evenly distributed at the cylinder  22 . Each of the ridges  23  therein defines a vertical mounting orifice  230 . 
   Referring to  FIGS. 2 and 3  again, the LED modules  30  are respectively attached to the outer faces of the fins  26  of the heat sink  20 , and each comprises an elongated printed circuit board  32  with a size corresponding to that of the outmost first fin  26  of the heat sink  20  and a plurality of LED components  34  which are mounted on the printed circuit board  32  and arranged in a line along a length of the printed circuit board  32 . 
   The cover  40  is secured on the top of the heat sink  20  and comprises a circular plate  42  and a plurality of second fins  44  arranged on the plate  42 . Corresponding to the mounting orifices  230  in the ridges  23  of the heat sink  20 , three through orifices  430  are defined in the plate  42 . Three screws  46  are brought to extend through the through orifices  430  to engage into the mounting orifices  230  to thereby fix the cover  40  to the top of the heat sink  20 . An annular inner protrusion  422  and an annular outer protrusion  424  concentric with the inner protrusion  422  extend downwardly from a bottom surface of the plate  42 . The inner protrusion  422  and the outer protrusion  424  are spaced from each other, thereby defining a second groove  426  therebetween. The second groove  426  is in alignment with the first groove  126  of the lamp holder  10  and engagingly receives an upper end of the envelope  50 . The second fins  44  are parallel to each other and extend perpendicularly from a top surface of the plate  42 . A plurality of spaced channels (not labeled) is defined in the second fins  44  for facilitating airflow taking heat away from the second fins  44  into ambient air. Corresponding to the first securing holes  128  in the base  12  of the lamp holder  10 , three second securing holes  428  are defined in the plate  42  for receiving upper ends of the connecting shafts  200 . 
   The envelope  50  has a tubular shape with a through hole (not labeled) defined therein. A diameter of the envelope  50  decreases gradually from a middle toward two opposite ends of the envelope  50 . The two opposite ends of the envelope  50  each have a shape substantially similar to that of a corresponding one of the first and second grooves  126 ,  426 . The envelope  50  is made of a transparent or semitransparent material such as glass, plastic, etc., for allowing the light emitted by the LED module  30  traveling therethrough to illuminate a surrounding environment. 
   The first and second cushions  100 ,  102  respectively have configurations which are similar to those of the first and second grooves  126 ,  426 , respectively. The first and second cushions  100 ,  102  are received fitly in the first and second grooves  126 ,  426 , respectively. The first and second cushions  100 ,  102  respectively define recesses (not labeled) at top and bottom surfaces thereof facing the lower and upper ends of the envelope  50 , respectively. The lower and upper ends of the envelope  50  are interferingly fixed into the recesses of the first and second cushions  100 ,  102 . 
   Each of the connecting shafts  200  has a shape of an elongated post and forms screw thread on two opposite ends thereof for respectively engaging with two nuts  202 . 
   In assembly, the driving circuit module  300  is placed in the receiving chamber  120  of the lamp holder  10 . The heat sink  20  has a lower end snugly received in the receiving chamber  120  of the lamp holder  10  and enclosing the driving circuit module  300  therein. The LED modules  30  are respectively attached to the outer faces of the first fins  26  of the heat sink  20  in a thermal conductive relationship. The envelope  50  encloses the heat sink  20  assembled with the LED modules  30 . The cover  40  then is coupled onto the heat sink  20  and the envelope  50 . The first and second cushions  100 ,  102  are respectively received in the first and second grooves  126 ,  426 . The first cushion  100  is sandwiched between the envelope  50  and the lamp holder  10 ; the second cushion  102  is sandwiched between the envelope  50  and the cover  40 . Two opposite ends of each of the connecting shafts  200  respectively extend through the first and second securing holes  128 , 428  and respectively engage with two nuts  202  to securely connect the lamp holder  10  and the cover  40 . 
   In operation, heat generated by the LED modules  30  is conducted to the heat sink  20  and then reaches the cover  40  via the heat sink  20 . The heat is finally dissipated into ambient through the second fins  44  of the cover  40 . The first and second cushions  100 ,  102  are respectively in the first groove  126  of the lamp holder  10  and the second groove  426  of the cover  40 . The upper and lower ends of the envelope  50  tightly engaged into the recesses of the first and second cushions  100 ,  102 , thereby enhancing waterproof function of the LED lamp. Furthermore, by locking the nuts  202  with the connecting shafts  200  as tightly as possible, wherein the nuts  202  are respectively located above the cover  40  and below the lamp holder  10 , the lamp holder  10  and the cover  40  can be forced to move toward each other, thereby further reinforcing the hermetic connection between the envelope  50  and the cover  40  and between the envelope  50  and the lamp holder  10 . 
   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 invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.