Patent Publication Number: US-2012025708-A1

Title: Light emitting diode bulb using thermal conductor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2010-0073218, filed on Jul. 29, 2010 and Korean Patent Application No. 10-2010-0101486, filed Oct. 18, 2010, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference in their entireties. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates generally to an LED bulb using a thermal conductor and, more particularly, to an LED bulb using a thermal conductor, in which a housing is formed using a thermal conductor, and a heat dissipating plate is integrated with the housing by conducting insert injection molding, so that the LED bulb is capable of easily dissipating heat that is generated by an LED element. 
     2. Background Art 
     Recently, lighting apparatuses that use a light emitting diode (hereinafter, referred to as an LED) to substitute for a fluorescent light have been subject to active development. The LED is advantageous in that the efficiency with which power is converted into light is excellent, the efficiency of light per unit power is high, its life span is long, power consumption is low, and high luminous intensity is obtained. Such LEDs have been used for a variety of purposes. 
     LED lights are advantageous because the processing speed is high and power consumption is low, whereas LED lights are disadvantageous because the light emitting part comprises a semiconductor element, so that it is more vulnerable to heat than are incandescent bulbs or fluorescent lights. That is, since LED lights are constructed so that a plurality of LED elements is mounted on an LED module, the amount of heat that is generated is large. 
     A conventional LED bulb mainly includes a light transmitting cover, a housing, a bottom case into which an inverter is inserted, and a socket. The conventional LED bulb connects the inverter connected to the socket with an LED module having an LED element thereon via wires so as to supply power to the LED element. Especially, when the LED bulb is produced, the socket, the bottom case, the housing, and the light transmitting cover must be integrally fastened to and assembled with each other. However, an increase in the number of assembling processes unnecessarily consumes assembling labor, managing labor, and material costs. 
     Especially, the conventional LED bulb is problematic in that the surface area of the housing is relatively small, and an additional heat dissipating structure is not provided, so that it is difficult to effectively dissipate heat emitted from the LED element. Hence, it is impossible to supply a predetermined or more of electric current to the LED element, so that a relatively large number of LED modules are required to use the LED element as a lighting apparatus. 
     Further, in the case of applying a cooling method to the LED bulb, there is a limitation in dissipating heat which is generated when the LED element is driven. In order to overcome the problem, the size of a heat dissipating member may be increased. This causes the size, weight, and cost of a product to increase, so that it is difficult to satisfy consumers. 
     DISCLOSURE OF THE INVENTION 
     Technical Problem 
     Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide an LED bulb using a thermal conductor, which is constructed so that a heat dissipating plate is integrated with a housing by insert injection molding. 
     Another object of the present invention is to provide an LED bulb using a thermal conductor, which does not require a bottom case into which an inverter is inserted, by using a connector fastened to the inverter. 
     A further object of the present invention is to provide an LED bulb using a thermal conductor, which is constructed so that a plurality of heat dissipating protrusions protrudes from an outer circumferential surface of a housing that is formed using a thermal conductor, thus increasing the surface area of the housing, therefore effectively dissipating the heat generated by an LED element. 
     Yet another object of the present invention is to provide an LED bulb using a thermal conductor, in which a housing and a light transmitting cover are constructed to be fastened to each other in a rotary locking manner, thus allowing the housing and the light transmitting cover to be fastened to each other in a simple manner. 
     Technical Solution 
     In order to accomplish the above objects, the present invention provides an LED bulb using a thermal conductor, including an LED module having a PCB on which at least one LED element is mounted, a housing having a plurality of heat dissipating protrusions which protrude from an outer circumferential surface thereof, and made of a thermal conductor, with a thread being formed on a predetermined portion of the housing, a light transmitting cover having a thread by which the cover can be fastened to the thread which is formed on the predetermined portion of the housing, in a threaded manner, an inverter supplying a direct current to the LED module, a heat dissipating plate provided between the LED module and the housing to dissipate heat generated by the LED element, and a socket fastened to the housing. 
     Further, the heat dissipating plate may be integrated with the housing by insert injection when the housing is formed. 
     The heat dissipating plate may further include a heat dissipating part which is provided on a lower portion of the heat dissipating plate that faces the housing, and has at least one of a wavy shape and an uneven shape. 
     Further, the heat dissipating plate may be made of a material having heat conductivity. 
     The LED bulb may further include a connector coupled to the inverter by a one-touch-type coupling manner. 
     Further, the plurality of heat dissipating protrusions may be radially arranged on the outer circumferential surface of the housing in such a way as to protrude in a direction perpendicular to an axial direction of the housing. 
     Further, each of the heat dissipating protrusions may be tapered such that an area thereof increases in a direction from a lower portion to an upper portion of the housing. 
     Further, the inverter may be connected to the socket via an electrode wire, and may convert an alternating current, input from an outside through the socket, into a direct current and then supply the direct current to the LED module. 
     Furthermore, the housing may be formed using a thermal conductive resin including thermal conductive plastics. 
     Advantageous Effects 
     Therefore, the present invention provides an LED bulb using a thermal conductor, which is constructed so that a heat dissipating plate is integrated with a housing by insert injection molding, thus allowing heat generated by an LED element to be easily dissipated. 
     Further, the present invention provides an LED bulb using a thermal conductor, which does not require a bottom case into which an inverter is inserted, by using a connector fastened to the inverter, thus reducing the number of the assembling processes of the LED bulb, the assembling and managing labor, and material costs. 
     Furthermore, the present invention provides an LED bulb using a thermal conductor, which is constructed so that a plurality of heat dissipating protrusions protrudes from an outer circumferential surface of a housing that is formed using a thermal conductor, thus increasing the surface area of the housing, therefore effectively dissipating the heat generated by an LED element, and the housing is formed using a light thermal conductor, thus reducing the weight of the LED bulb. 
     Further, the present invention provides an LED bulb using a thermal conductor, in which a housing and a light transmitting cover are constructed to be fastened to each other in a rotary locking manner, thus allowing the housing and the light transmitting cover to be fastened to each other in a simple manner. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, features and advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view showing an LED bulb using a thermal conductor according to an embodiment of the present invention; 
         FIG. 2  is a front view showing the LED bulb using the thermal conductor according to the embodiment of the present invention; 
         FIG. 3  is a sectional view showing the LED bulb using the thermal conductor according to the embodiment of the present invention; 
         FIG. 4  is an enlarged view illustrating a heat dissipating plate of  FIG. 3 ; 
         FIG. 5  is an enlarged view illustrating another embodiment of the heat dissipating plate of  FIG. 3 ; 
         FIG. 6  is an enlarged view illustrating a further embodiment of the heat dissipating plate of  FIG. 3 ; 
         FIG. 7  is an enlarged view illustrating a connector and inverter fastening structure of  FIG. 3 ; and 
         FIG. 8  is an exploded perspective view showing the LED bulb using the thermal conductor according to the embodiment of the present invention. 
     
    
    
     MODE FOR INVENTION 
     Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. The terminology or words used in the description and the claims of the present invention should not be interpreted as being limited merely to common or dictionary meanings. On the contrary, they should be interpreted based on the meanings and concepts of the invention in keeping with the scope of the invention on the basis of the principle that the inventor(s) can appropriately define the terms in order to most clearly describe the invention. 
     Therefore, it is to be understood by those skilled in the art that the form of the invention herein shown and described is to be taken as a preferred embodiment of the present invention and does not cover all spirits of the present invention and that all changes which fall within the meets and bounds of the claims, or the equivalence of such meets and bounds are intended to be embraced by the claims. 
       FIG. 1  is a perspective view showing an LED bulb using a thermal conductor according to an embodiment of the present invention.  FIG. 2  is a front view showing the LED bulb using the thermal conductor according to the embodiment of the present invention.  FIG. 3  is a sectional view showing the LED bulb using the thermal conductor according to the embodiment of the present invention.  FIG. 4  is an enlarged view illustrating a heat dissipating plate of  FIG. 3 .  FIG. 5  is an enlarged view illustrating another embodiment of the heat dissipating plate of  FIG. 3 .  FIG. 6  is an enlarged view illustrating a further embodiment of the heat dissipating plate of  FIG. 3 .  FIG. 7  is an enlarged view illustrating a connector and inverter fastening structure of  FIG. 3 .  FIG. 8  is an exploded perspective view showing the LED bulb using the thermal conductor according to the embodiment of the present invention. 
     Referring to  FIGS. 1 to 8 , an LED bulb  100  using a thermal conductor of the present invention includes a light transmitting cover  10 , a housing  20 , and a socket  30 . 
     The hemispherical light transmitting cover  10  and the housing  20  are fastened to each other in a rotary locking manner, namely, a threaded manner. To this end, threads  10   a  and  20   b  are formed, respectively, on predetermined portions of the light transmitting cover  10  and the housing  20  so that they are fastened to each other in a threaded manner. Thus, the light transmitting cover  10  and the housing  20  can be simply fastened to each other. 
     According to this embodiment, the light transmitting cover  10  has a hemispherical shape, but is not limited to the hemispherical shape. As long as only the area of the light transmitting cover  10  having the thread  10   a  to be fastened to the housing  20  has a circular shape, the light transmitting cover  10  may have any shape. 
     An LED module  50  is adhered to the housing  20  in such a way as to face the light transmitting cover  10 , and includes a PCB on which a plurality of LED elements  40  is mounted. 
     The housing  20  includes a plurality of heat dissipating protrusions  20   a  which protrude from the outer circumferential surface of the housing  20 . The heat dissipating protrusions  20   a  protrude from the outer circumferential surface of the housing  20  in a direction perpendicular to an axial direction, and are radially arranged. Here, the heat dissipating protrusions  20   a  may protrude integrally from the outer circumferential surface of the housing  20 . 
     Further, each heat dissipating protrusion  20   a  is tapered such that its area increases in a direction from a lower portion to an upper portion of the housing  20 . In detail, the heat dissipating protrusion  20   a  is shaped such that its area is gradually increased in a direction from the lower portion of the housing  20 , that is, a position adjacent to the socket  30 , through a position adjacent to the middle portion of the housing  20 , to the upper portion of the housing  20 , that is, a position adjacent to the LED module  50 . 
     The LED bulb  100  includes the plurality of heat dissipating protrusions  20   a  on the housing  20 , thus enlarging the surface area of the housing  20 . Especially, since the area of each heat dissipating protrusion  20   a  is increased towards a surface of the housing  20  to which the LED module  50  is adhered, namely, towards the upper portion of the housing  20 , heat generated from the LED elements  40  can be dissipated as quickly as possible. 
     A step, which corresponds to the extent to which the heat dissipating protrusions  20   a  protrude, is formed on the housing  20 . The housing  20  itself is made of a thermal conductor resin such as a plastic, thus reducing the weight of the LED bulb  100 , and lowering the temperature of heat generated by the housing  20 . 
     When the housing  20  is formed by injection molding after inserting a plate made of a thermal conductive material, such as aluminum, a heat dissipating plate  55  is integrated with the housing  20  in such a way as to be in contact with a surface of the housing  20 . 
     Further, the LED module  50  makes contact with a PCB on which the plurality of LED elements  40  is mounted and is furthermore assembled with the heat dissipating plate  55  which is formed in the housing  20  by insert injection. 
     Insert injection is a method of integrating different kinds or colors of plastics with each other or integrating plastics with parts (metal, electric wires, magnets, etc.) other than the plastics in a mold. This method provides a molded product having characteristics which are difficult to be achieved exclusively by the use of plastics. 
     The molded product is shown in  FIGS. 4 to 6 . The heat dissipating plate  55  formed in the housing  20  by insert injection includes a heat dissipating part  60 , and the housing  20  has a fastening hole  60   a  so that the heat dissipating part  60  is inserted into the fastening hole  60   a.    
     If the heat dissipating part  60  is formed as shown in  FIG. 4 , heat dissipating parts  60  may be located, respectively, at positions where the heat dissipating plate  55  is trisected, and besides, fastening holes  60   a  may be preferably formed to correspond to the heat dissipating parts  60 . 
     Further, if the heat dissipating part  60  has a wavy shape as shown in  FIG. 5 , the housing  20  facing the heat dissipating part  60  also has a wavy shape to correspond to the wavy heat dissipating part formed on the heat dissipating plate  55 , so that the heat dissipating part  60  may be fastened to the housing  20 . 
     Furthermore, if the heat dissipating part  60  has an uneven shape as shown in  FIG. 6 , the housing  20  facing the heat dissipating part  60  also has an uneven shape that corresponds to the uneven shape of the heat dissipating part  60  formed on the heat dissipating plate  55 , so that the heat dissipating part  60  may be fastened to the housing  20 . 
     When the heat dissipating plate  55  is formed as shown in  FIG. 5  or  6 , the surface area of the heat dissipating part  60  is enlarged, thus allowing heat generated by the LED elements  40  to be more effectively dissipated. 
     The following table 1 shows the results of performing experiments on the LED bulb  100  according to the present invention. Here, the LED bulb described as an “aluminum housing” means an LED bulb that does not have the heat dissipating plate which is manufactured by insert injection molding. Meanwhile, the LED bulb described as a “heat dissipating plate (1 mm)” means an LED bulb having a heat dissipating plate which is manufactured by insert injection molding and has the thickness of 1 mm. 
     
       
         
           
               
               
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                   
                   
                 Average 
                   
                 Maximum 
               
               
                   
                   
                 External 
                 Temperature of 
                   
                 Temperature 
               
               
                   
                 Heat 
                 Average 
                 Heat 
                 Maximum 
                 of Heat 
               
               
                   
                 Conductivity 
                 Temperature 
                 Dissipating 
                 Temperature 
                 Dissipating 
               
               
                   
                 (W/m-K) 
                 of Housing 
                 Plate Surface 
                 of Housing 
                 Plate 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 Aluminum 
                 8.1 
                 45.4(° C.) 
                 — 
                 45.6(° C.) 
                 — 
               
               
                 Housing 
               
               
                 Heat 
                 8.1 
                 54.9(° C.) 
                 61.7(° C.) 
                 61.7(° C.) 
                 61.9(° C.) 
               
               
                 Dissipat- 
               
               
                 ing Plate 
               
               
                 (1 mm) 
               
               
                   
               
            
           
         
       
     
     As seen in table 1, the conventional LED bulb having the aluminum housing has a heat conductivity of 8.1 when the external average temperature of the housing and the maximum temperature of the housing are 45.4° C. and 45.6° C., respectively. 
     In contrast, the LED bulb  100  of the present invention which includes the heat dissipating plate  55  of 1 mm has heat conductivity equal to that of the conventional. LED bulb when the external average temperature of the housing  20  is 54.9° C., the maximum temperature of the housing  20  is 61.7° C., the average temperature of the surface of the heat dissipating plate  55  is 61.7° C., and the maximum temperature of the heat dissipating plate  55  is 61.9° C. 
     Thus, when comparing the LED bulb  100  having the housing  20  made of plastic and the heat dissipating plate  55  manufactured by insert injection with the conventional LED bulb, it can be seen that heat generated by the LED elements  40  is efficiently dissipated by the latter. 
     Further, there is a space in the housing  20  so that the inverter  70  can be inserted into the housing  20 . The inverter  70  inserted into the housing  20  is coupled to the connector  45 . The inverter  70  is a device that converts alternating current into direct current. The inverter  70  converts an alternating current, input from the socket  30  through electrode wires  70   a , into a direct current, and supplies the direct current through the connector  45  to the LED module  50 . 
     Here, the connector  45  and the inverter  70  are constructed to be coupled to each other in a one-touch-type coupling manner. Thus, after the connector  45  is placed to face the inverter  70 , pressure acts on ends of the connector  45  and the inverter  70 , so that the connector  45  is coupled to the inverter  70 . Since the connector  45  passes through the LED module  50  and is fitted over the inverter  70 , direct current can be supplied to the LED module  50 . This is shown in  FIG. 7 . 
     As such, the present invention provides the LED bulb  100  which does not need the bottom case into which the inverter  70  is inserted, thus saving on resources including assembling processes, the labor used to assemble and manage, and material costs. Further, the connector  45  and the inverter  70  are coupled in a one-touch-type coupling manner, so that the connector  45  can be more easily coupled to the inverter  70 . 
     According to the present invention, each heat dissipating protrusion  20   a  has a tapered shape, but is not limited to the tapered shape. That is, the heat dissipating protrusion  20   a  may have the shape of a streamlined wedge or a right-angled triangular wedge. As such, the shape of the heat dissipating protrusion  20   a  may be freely changed depending on the shape of the housing  200 . 
     Further, according to the present invention, the heat dissipating protrusion  20   a  protrudes integrally from the outer circumferential surface of the housing  20 , but is not limited to the shape. That is, after a plurality of heat dissipating protrusions  20   a  is separately manufactured, the heat dissipating protrusions  20   a  may be adhered to the outer circumferential surface of the housing  20 . 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.