Patent Publication Number: US-9429278-B2

Title: Lighting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a Continuation application of U.S. application Ser. No. 14/016,680 filed Sep. 3, 2013, which is a Continuation application of U.S. application Ser. No. 12/805,796 filed Aug. 19, 2010, which claims priority from Korean Application No. 10-2009-0076953, filed Aug. 19, 2009, No. 10-2010-0030716, filed Apr. 5, 2010, No. 10-2010-0028854, filed Mar. 30, 2010, No. 10-2010-0028855, filed Mar. 30, 2010, No. 10-2010-0028856, filed Mar. 30, 2010, No. 10-2010-0028857, filed Mar. 30, 2010, No. 10-2010-0028858, filed Mar. 30, 2010, No. 10-2010-0028859, filed Mar. 30, 2010, the subject matters of which are incorporated herein by reference 
    
    
     BACKGROUND 
     1. Field 
     Embodiments may relate to a lighting device. 
     2. Background 
     A light emitting diode (LED) is a semiconductor element for converting electric energy into light. As compared with existing light sources such as a fluorescent lamp and an incandescent electric lamp and so on, the LED has advantages of low power consumption, a semi-permanent span of life, a rapid response speed, safety and an environment-friendliness. For this reason, many researches are devoted to substitution of the existing light sources with the LED. The LED is now increasingly used as a light source for lighting devices, for example, various lamps used interiorly and exteriorly, a liquid crystal display device, an electric sign and a street lamp and the like. 
     SUMMARY 
     One embodiment is a lighting device. The lighting device comprises a housing including an upper surface and an inner wall surface; a coupling member coupled to the upper surface of the housing; a reflector disposed between the coupling member and the inner wall surface of the housing; a light source unit coupled to the coupling member and having a light emitting groove in which a light emitting device is disposed, wherein the reflector is disposed over the light emitting groove, wherein the light source unit comprises a projection part disposed around the light emitting groove, and wherein the projection part is provided a prescribed distance from the upper surface, the prescribed distance being greater than or equal to a distance of an end of the housing from the upper surface. 
     Another embodiment is a lighting device. The lighting device comprises a housing; a coupling member disposed in the housing, having a recess, and comprising a first surface and a second surface which are disposed in the recess; and a light source unit comprising a first body and a second body, wherein each of the first surface and the second surface has a first recess and a second recess which is disposed under the first recess, wherein each of the first body and the second body comprises a coupling unit coupled to the coupling member, wherein the coupling unit comprises a projection being inserted into at least one of the first recess and the second recess. 
     Further another embodiment is a lighting device. The lighting device comprises a housing comprising an upper surface, a first side surface, a second side surface facing the first side surface, a third side surface and a fourth side surface facing the third side surface; a coupling member coupled to the upper surface, having a recess, and comprising a first end coupled to the first side surface and a second end coupled to the second side surface; a reflector comprising a first reflector could between the third side surface and the coupling member and a second reflector coupled between the fourth side surface and the coupling member; a light source unit coupled to the coupling member and comprising a first end coupled to the first side surface and a second end coupled to the second side surface, wherein the light source unit comprises a first lighting module emitted lights to the first reflector and a second lighting module emitted lights to the second reflector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Arrangements and embodiments may be described in detail with reference to the following drawings in which like reference numerals refer to like elements and wherein: 
         FIG. 1  is a perspective view of a light device in accordance with an embodiment 1 of the present invention. 
         FIG. 2  is an exploded perspective view of a light device in accordance with the embodiment 1 of the present invention. 
         FIG. 3  is a cross sectional view of a light device in accordance with the embodiment 1 of the present invention. 
         FIG. 4 a    is a cross sectional view of a coupling member shown in  FIG. 3 . 
         FIG. 4 b    is a view showing an enlarged part denoted by “A” of  FIG. 3 . 
         FIG. 4 c    is a view showing a light distribution angle of a light emitting diode mounted in the light emitting recess according to the embodiment 1 of the present invention. 
         FIGS. 5 and 6  are perspective views of a light source unit in accordance with the embodiment 1 of the present invention. 
         FIG. 7  is an exploded perspective view of a light source unit in accordance with the embodiment 1 of the present invention. 
         FIG. 8  is a perspective view of a coupling of a first connection terminal and a second connection terminal of a lighting device in accordance with the embodiment 1 of the present invention. 
         FIGS. 9 a  and 9 b    are plan views of a first connection terminal and a second connection terminal of a lighting device in accordance with the embodiment 1 of the present invention. 
         FIGS. 10 a  and 10 b    show a coupling and separation process of a light source unit and a coupling member in accordance with the embodiment 1 of the present invention. 
         FIGS. 11 a  and 11 b    show how a limit switch in accordance with the embodiment 1 is operated. 
         FIGS. 12 and 13  are cross sectional views showing a light source unit and a coupling member of a lighting device in accordance with a modified embodiment 1. 
         FIG. 14  is a perspective view of a light device in accordance with an embodiment 2 of the present invention. 
         FIG. 15  is an exploded perspective view of the light device in accordance with the embodiment 2 of the present invention. 
         FIG. 16  is a cross sectional view of the light device in accordance with the embodiment 2 of the present invention. 
         FIG. 17 a    is a cross sectional view of a coupling member shown in  FIG. 16 . 
         FIG. 17 b    is a view showing an enlarged part denoted by “A” of  FIG. 16 . 
         FIG. 17 c    is a view showing a light distribution angle of a light emitting diode mounted in the light emitting recess according to the embodiment 2 of the present invention. 
         FIG. 18  is a perspective view of a light source unit in accordance with the embodiment 2 of the present invention. 
         FIG. 19  is an exploded perspective view of the light source unit in accordance with the embodiment 2 of the present invention. 
         FIG. 20  is a perspective view of a coupling of a first connection terminal and a second connection terminal of the lighting device in accordance with the embodiment 2 of the present invention. 
         FIGS. 21 a  and 21 b    are plan views of the first connection terminal and the second connection terminal of the lighting device in accordance with the embodiment 2 of the present invention. 
         FIGS. 22 and 23  show a coupling and separation process of the light source unit and the coupling member in accordance with the embodiment 2 of the present invention. 
         FIGS. 24 a  and 24 b    show how a limit switch in accordance with the embodiment 2 is operated. 
         FIGS. 25 and 26  are cross sectional views showing the lighting device in accordance with a modified embodiment 2. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to accompanying drawings. However, the accompanied drawings are provided only for more easily describing the embodiments. It is easily understood by those skilled in the art that the spirit and scope of the present invention is not limited to the scope of the accompanied drawings. 
     Embodiment 1 
       FIG. 1  is a perspective view of a light device  1  in accordance with an embodiment 1 of the present invention.  FIG. 2  is an exploded perspective view of a light device  1  in accordance with the embodiment 1 of the present invention.  FIG. 3  is a cross sectional view of the light device in accordance with the embodiment 1 of the present invention.  FIG. 4 a    is a cross sectional view of a coupling member shown in  FIG. 3 .  FIG. 4 b    is a view showing an enlarged part denoted by “A” of  FIG. 3 .  FIG. 4 c    is a view showing a light distribution angle θ of a light emitting diode  312  mounted in the light emitting recess (or groove)  316  according to the embodiment 1 of the present invention. In the present disclosure the terms recess and groove are used interchangeably. 
     In  FIGS. 1 to 4   c , a lighting device  1  in accordance with an embodiment 1 of the present invention includes a housing  100 , a coupling member  110 , a reflector  200 , a light source unit  300  and a power supply unit  400 . 
     1. Housing  100  and Coupling Member  110   
     The housing  100  has a shape of a box for accepting the housing  100 , the coupling member  110 , the reflector  200  and the power supply unit  400 . While the shape of the housing  100  as viewed from the outside is quadrangular, the housing  100  can have various shapes without being limited to this. 
     The housing  100  is made of a material capable of efficiently releasing heat. For example, the housing  100  is made of a metallic material such as Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and so on. The housing  100  may be also made of various resin materials. 
     A connecting recess  107  for connecting electrically the power supply unit  400  to an external power supply is formed on a lateral surface and/or an upper surface of the housing  100 . 
     The housing  100  includes an opening  101  such that light radiated from the light source unit  300  is reflected to be emitted by the reflector  200 . 
     Meanwhile, in order to dispose the lighting device  1  on an external support member such as a ceiling or a wall surface, an insertion unit corresponding to a shape of the lighting device  1  is formed in the external support member, and then the lighting device  1  is inserted into and fixed to the insertion unit. Here, a coupling frame  500  is coupled to the lower part of the lateral surface of the housing  100 , so that the lighting device  1  can be securely coupled to the external support member. 
     The coupling member  110  is coupled on an inner upper surface of the housing  100 . The coupling member  110  is coupled to the housing  100  by using various methods. For example, the coupling member  110  is coupled to the housing  100  by means of a coupling screw, an adhesive agent and so on. 
     The coupling member  110  is formed to be extended on an upper surface  102  of the housing  100  in a first direction. For example, the coupling member  110  can be extended from an inner wall surface to the opposite inner wall surface of the housing  100 . 
     The housing  100  and the coupling member  110  are attachable to and removable form the reflector  200 . 
     A second recess  103  is formed on the inner wall surface of the housing  100 . A first side  210  of the reflector  200  is inserted into the second recess  103 . It is possible to form the one second recess  103  or a plurality of the second recesses  103 . 
     A first recess  111  is formed on an outer wall surface of the coupling member  110 . The first recess  111  is formed to be extended in the first direction. A second side  220  of the reflector  200  is inserted into the first recess  111 . 
     The housing  100  and the coupling member  110  can fix and sustain the reflector  200  by inserting the first side  210  of the reflector  200  into the second recess  103  of the housing  100  and by inserting the second side  220  of the reflector  200  into the first recess  111  of the coupling member  110 . 
     In addition, the light source unit  300  is attachable to and removable from the coupling member  110 . 
     An insertion recess  112  is formed in the middle part of the coupling member  110 . A part of the light source unit  300  is inserted into the insertion recess  112 . The insertion recess  112  can be formed to be extended in the first direction. 
     A third recess  113  is formed on an inner wall surface of the insertion recess  112 . A projection  313  of the light source unit  300  is inserted into the third recess  113 . As a result, the light source unit  300  is securely coupled to the coupling member  110  by means of the third recess  113 . The coupling of the light source unit  300  and the coupling member  110  will be described later in more detail. 
     A first connection terminal  120  is formed in the middle part within the insertion recess  112 . When the light source unit  300  is inserted into the insertion recess  112 , the first connection terminal is coupled to and electrically connected to a second connection terminal  330  of the light source unit  300 . When the first connection terminal  120  is connected to the second connection terminal  330 , electric power and/or a driving signal can be transferred to the light source unit  300  through the first connection terminal  120  and the second connection terminal  330 . 
     Based on a design of the light source device  1 , it is possible to form the one first connection terminal  120  or a plurality of the first connection terminals  120 . More detailed descriptions of the first connection terminal  120  and the second connection terminal  330  will be provided later. 
     The coupling member  110  performs a function of directly releasing heat generated from the light source unit  300  or transferring the heat to the housing  100 . 
     It is desirable to form the coupling member  110  by using a material capable of efficiently releasing and/or transferring the heat. For example, the coupling member  110  is made of a metallic material such as Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and so on. 
     A part of the coupling member  110  can have an uneven structure  116 . The uneven structure  116  can widen the surface area of the coupling member  110  and improve a heat release effect. 
     2. Reflector  200   
     The reflector  200  includes a first reflector  200   a  and a second reflector  200   b . The first reflector  200   a  and the second reflector  200   b  are attachable to and removable from the housing  100  and the coupling member  110 . 
     For example, as shown in  FIG. 2 , the second reflector  200   b  is coupled to the housing  100  and the coupling member  110  by inserting the second side  220  of the second reflector  200   b  into the first recess  111  of the coupling member  110  and by inserting the first side  210  of the second reflector  200   b  into the second recess  103  of the housing  100 . The second side  220  of the reflector  200  can have a level difference. The first side  210  of the reflector  200  can also have a level difference. At least one insertion end  211  which is inserted into the second recess  103  is formed at the first side  210  of the reflector  200 . A shape of the second recess  103  is formed to correspond to the selection end  211 . 
     The first reflector  200   a  and the second reflector  200   b  have a parabola-shaped surface and are extended in the first direction. Therefore, the first reflector  200   a  and the second reflector  200   b  have a parabolic shape having two parabolic surfaces. Here, the shape of the reflector  200  can be variously changed according to a desired lighting. 
     The reflector  200  is made of a metallic material or a resin material which has a high reflection efficiency. For example, the resin material includes any one of PET, PC and PVC resin. The metallic material includes any one of Ag, alloy including Ag, Al, and alloy including Al. 
     The surface of the reflector  200  is coated with Ag, Al, white photo solder resist (PSR) ink, a diffusion sheet and the like. Otherwise, an oxide film is formed on the surface of the reflector  200  by an anodizing process. 
     Here, the material and color of the reflector  200  are not limited and are variously selected depending on a lighting generated by the lighting device  1 . 
     3. Power Supply Unit  400   
     When the power supply unit  400  is connected to the light source unit  300 , the power supply unit  400  can supply at least one of electric power and a driving signal. 
     As shown in  FIGS. 2 and 3 , the power supply unit  400  is disposed in a space between the parabola-shaped reflector  200  and the inner surface of the housing  100 . That is, due to the parabola shape of the reflector  200 , an empty space is formed between the reflector  200  and a corner inside the housing  100 . As a result, the power supply unit  400  is disposed in the empty space. 
     The power supply unit  400  converts an alternating current (AC) electric power into a direct current (DC) electric power and outputs the direct current (DC) electric power. 
     The power supply unit  400  is electrically connected to the light source unit  300  through a wire or a flexible printed circuit board (FPCB). For example, a wire or a FPCB is extended from the power supply unit  400  and is electrically connected to the first connection terminal  120  through the connecting recess  107  formed in the coupling member  110 . The first connection terminal  120  is electrically connected to the second connection terminal  330 . As a result, the power supply unit  400  is electrically connected to the light source unit  300 . 
     4. Light Source Unit  300   
       FIG. 4 b    is a view showing an enlarged part denoted by “A” of  FIG. 3 .  FIGS. 5 and 6  are perspective views of a light source unit  300  in accordance with an embodiment 1 of the present invention.  FIG. 7  is an exploded perspective view of a light source unit  300  in accordance with an embodiment 1 of the present invention. 
     In  FIGS. 4 to 7 , the light source unit  300  in accordance with an embodiment 1 of the present invention includes a first body  310   a , a second body  310   b , a middle body  320 , a plurality of light emitting diodes (LED)  312  and a coupling cap  350 . The first body, the second body  310   b  and the middle body  320  form a body of the light source unit  300 . The light source unit  300  may be formed to be extended in the first direction, that is, in the direction of length of the reflector  200 . 
     1) First Body  310   a  and Second Body  310   b    
     The lower part of the first body  310   a  is formed to have a first sloping surface. The first sloping surface is formed on the outer wall surface of the first body  310   a . The first sloping surface is formed such that the first sloping surface faces the parabolic surface of the first reflector  200   a . Here, a plurality of the sloping surfaces as well as the first sloping surface can be formed in the first body  310   a.    
     The lower part of the second body  310   b  is also formed to have a second sloping surface. The second sloping surface is formed on the outer wall surface of the second body  310   b . The second sloping surface is formed such that the second sloping surface faces the parabolic surface of the second reflector  200   b . Here, a plurality of the sloping surfaces as well as the second sloping surface can be formed in the second body  310   b.    
     A light emitting recess  316  is formed on the first and the second sloping surfaces respectively. 
     A substrate  311  is provided on the basal surface of the light emitting recess  316 . A plurality of the light emitting diodes  312  may be provided on the substrate  311 . Otherwise, a plurality of electrodes (not shown) are disposed in the light emitting recesses  316  so that a plurality of the electrodes (not shown) is electrically connected to a plurality of the light emitting diodes  312 . An optical structure  318  is formed on a plurality of the light emitting diodes  312 . The optical structure  318  will be described later. 
     The depth and width of the light emitting recess  316  can be variously adjusted according to the light distribution of a plurality of the light emitting diodes  312  disposed inside the light emitting recess  316 . In other words, the lighting device  1  is able to cause the reflector  200  to provide users with light radiated from the light source unit  300  by adjusting the depth and width of the light emitting recess  316  instead of directly providing users with light radiated from the light source unit  300 . As a result, it is possible to provide users with subdued light by reducing glare. 
     A light distribution angle of light emitted from the light emitting recess  316  is from 90° to 110°. The depth and width of the light emitting recess  316  is formed to cause light emitted from the light emitting recess  316  to be incident evenly on the entire area of the reflector  200 . 
     Additionally, the depth and width of the light emitting recess  316  is adjusted such that a part of light radiated from a plurality of the light emitting diodes  312  is radiated to the outside through the opening  101  and the rest of the light is reflected by the reflector  200  and is radiated to the outside through the opening  101 . 
     A plurality of the light emitting diodes  312  are determined, for example, through various combinations of red, green, blue and white light emitting diode which radiate red, green, blue and white light respectively. A plurality of the light emitting diodes  312  can be disposed in the light emitting recess  316  in the form of an array. 
     A plurality of the light emitting diodes  312  are controlled by electric power and/or a driving signal which are provided by the power supply unit  400 , causing a plurality of the light emitting diodes  312  to selectively emit light or to adjust the luminance of light. 
     The optical structure  318  is disposed on a plurality of the light emitting diodes  312 . The optical structure  318  functions to adjust the light distribution and the color sense of light radiated from a plurality of the light emitting diodes  312 , and creates emotional lighting having various luminance and color senses if necessary. 
     The optical structure  318  is coupled to the light source unit  300  by inserting in a sliding way both ends of the optical structure  318  into a fourth recess formed on an inner surface of the light emitting recess  316 . For example, the fourth recess is extended in the first direction and the optical structure  318  is coupled to the light source unit  300  by being inserted into the fourth recess in the first direction. 
     The optical structure  318  includes at least one of a lens, a diffusion sheet and a phosphor luminescent film (PLF). 
     The lens includes various lenses such as a concave lens, a convex lens and a condensing lens and so on according to a design of the lighting device  1 . 
     The diffusion sheet diffuses evenly light radiated from a plurality of the light emitting diodes  312 . 
     The phosphor luminescent film (PLF) includes fluorescent substance. Since the fluorescent substance included in the phosphor luminescent film (PLF) is excited by light radiated from a plurality of the light emitting diodes  312 , the lighting device  1  can produce emotional lighting having various color senses by mixing a first light radiated from a plurality of the light emitting diodes  312  and a second light excited by the fluorescent substance. 
     For example, when a plurality of the light emitting diodes  312  radiate blue light and the phosphor luminescent film (PLF) includes a yellow fluorescent substance excited by blue light, the lighting device  1  radiates white light by mixing the blue light and yellow light. 
     The optical structure  318  is easily coupled to the fourth recess. Accordingly, a lens, a diffusion sheet and a phosphor luminescent film (PLF) can be alternately used as the optical structure  318 . 
     Generally, the light distribution angle of the light emitted from the light emitting diode is about 120°. When the light emitting diode emits the light having such a wide light distribution angle, a part of the emitted light is reflected by the reflector  200  and is emitted to the outside through the opening  101 . However, the rest of the light is directly emitted through the opening  101  to the outside, thereby enabling a user to feel glare. 
     To overcome such a problem, the light emitting recess  316  may be formed to block the light emitted directly from the light emitting diode  312  to the outside of the housing  100 . That is, the light emitting recess  316  includes a projection part  316   b  formed on the basal surface thereof, thereby blocking the light emitted directly from the light emitting diode  312  to the outside of the housing  100 . 
     As a result, due to the projection part  316   b  of the light emitting recess  316 , the light emitted from a plurality of the light emitting diodes  312  is not directly provided to a user and is uniformly incident on the whole area of the reflector  200 . Accordingly, it is possible to provide users with subdued light by reducing glare. 
     Furthermore, it is possible to block the direct light emitted from the light emitting diode  312  to the outside of the housing  100  by adjusting the depth and width of the light emitting recess  316 , the height of the projection part  316   b , the sloping angle of the basal surface  316   a , the height of the housing  100  or the width of the reflector  200  and the like. 
     The sloping plane toward the reflector  200  is formed in the first body  310   a  and the second body  310   b . Therefore, regarding a cross section of the light source unit  300  formed by coupling the first body  310   a , the second body  310   b  and the middle body  320 , the width of the lower part of the light source unit  300  is greater that of the upper part of the light source unit  300 . For example, the cross section of the light source unit  300  can have various shapes such as a fan shape or a polygon shape and the like. 
     The first body  310   a  is formed to have a first coupling unit  315   a . The first coupling unit  315   a  is an upper part of the first body  310   a  and is inserted into the insertion recess  112  of the coupling member  110 . 
     The second body  310   b  is formed to have a second coupling unit  315   b . The second coupling unit  315   b  is an upper part of the second body  310   b  and is inserted into the insertion recess  112  of the coupling member  110 . 
     Due to the first coupling unit  315   a  and the second coupling unit  315   b , the first body  310   a  and the second body  310   b  are higher than the middle body  320 . 
     A projection  313  is formed in the upper ends of the first coupling unit  315   a  and the second coupling unit  315   b  respectively. The projection  313  has a shape in which a part of the upper end of each of the first coupling unit  315   a  and the second coupling unit  315   b  is projected outward. When the first coupling unit  315   a  and the second coupling unit  315   b  of the first body  310   a  and the second body  310   b  are inserted into the insertion recess  112  of the coupling member  110 , the projection  313  is inserted into the third recess  113  formed in the insertion recess  112 . As a result, the light source unit  300  is strongly coupled to the coupling member  110 . 
     2) Middle Body  320   
     The middle body  320  is formed between the first body  310   a  and the second body  310   b . Here, both inner surfaces of the first body  310   a  and the second body  310   b  are opposite to outer surfaces on which the light emitting diode  312  is mounted. A part of a lower surface of the middle body  320  can be exposed between the first body  310   a  and the second body  310   b.    
     The second connection terminal  330  is formed in the middle body  320 . When the light source unit  300  is inserted into and coupled to the coupling member  110 , the second connection terminal  330  is electrically connected to the first connection terminal  120  by being coupled to the first connection terminal  120  formed in the insertion recess  112  of the coupling member  110 . The power supply unit  400  provides electric power and/or a driving signal to the light source unit  300  through the first connection terminal  120  and the second connection terminal  330 . 
     On the middle body  320 , a spring  340  is disposed between the first body  310   a  and the second body  310   b . For example, as shown in  FIG. 4 b   , the spring  340  can have a ‘ ’-shape and can be disposed contacting with the upper surface and the lateral surfaces of the first body  310   a  and the second body  310   b . In more detail, the spring  340  is disposed contacting with the inner surfaces of the first coupling unit  315   a  and the second coupling unit  315   b.    
     The spring  340  provides an elastic force to the first body  310   a  and the second body  310   b , coupling securely the light source unit  300  to the insertion recess  112  of the coupling member  110 . The spring  340  provides the first body  310   a  and the second body  310   b  with an elastic force widening a space between the first body  310   a  and the second body  310   b . That is, the spring  340  is disposed between the first body  310   a  and the second body  310   b  and performs a function of pushing outward the first body  310   a  and the second body  310   b . Accordingly, when the light source unit  300  is inserted into the coupling member  110 , the projections  313  formed in the upper ends of the first body  310   a  and the second body  310   b  are strongly coupled to the insertion recess  112  of the coupling member  110  by the force from the spring  340 . 
     A sensor  321  is included in the lower part of the middle body  320 . For example, the sensor  321  is exposed between the first body  310   a  and the second body  310   b  and senses various data such as an image, a voice, a pressure, a temperature and an electric wave and the like. 
     The lighting device  1  includes the sensor  321 , thereby providing a user with various functions including light. The various data sensed by the sensor  321  is connected with the operation of a plurality of the light emitting diodes  312  and is used for driving the lighting device  1  suitably for an environment. For example, luminances and color senses of a plurality of the light emitting diodes  312  are adjusted by the data sensed by the sensor  321 . 
     The sensor  321  includes at least one of a camera, a photo sensor, a pressure sensor, a temperature sensor, a burglarproof sensor, an electric wave sensor and the like. 
     A limit switch  323  is provided on both sides of the middle body  320 . The limit switch  323  is in an on-state or in an off-state as the first body  310   a  and the second body  310   b  move toward the middle body  320 . The limit switch is hereby configured in such a manner as to connect or disconnect the electric power supplied to a plurality of the light emitting diodes  312 . The detailed description of the limit switch  323  will be described later. 
     Heat generated from a plurality of the light emitting diodes  312  is radiated by the body of the light source unit  300  or is transferred to the coupling member  110  and radiated. Thus, it is desirable to form the first body  310   a , the second body  310   b  and middle body  320  with a material capable of efficiently radiating heat. For example, the first body  310   a , the second body  310   b  and middle body  320  can be formed of a metallic material such as Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and so on. Additionally, a part of the light source unit  300  has an uneven structure capable of efficiently radiating heat. 
     When the light source unit  300  is inserted into the insertion recess  112  of the coupling member  110 , there is an empty space between the light source unit  300  and the insertion recess  112 . Therefore, heat generated from the light source unit  300  can be effectively released through the empty space. Additionally, a part of the light source unit  300  has an uneven structure capable of efficiently radiating heat. 
     When the light source unit  300  is inserted into the insertion recess  112  of the coupling member  110 , there is a contact area between the inner surface of the insertion recess  112  and both the first coupling unit  315   a  and the second coupling unit  315   a . As such, one surfaces of the first coupling unit  315   a  and the second coupling unit  315   b  contact with the inner surface of the insertion recess  112 , thereby forming a thermal conductivity route from the light source unit  300  to the coupling member  110 . In this case, the wider the contact surface is, the more increased a radiant heat effect is. But, the heights of the first body  310   a  and the second body  310   b  are increased. Consequently, the height of the housing  100  should be increased. Therefore, it is necessary to consider a relation between the contact area and the height of the housing  100  in order that the lighting device  1  obtains an optimized radiant heat effect. 
     In addition, in order to improve the heat radiating effect, it is preferable that the first body  310   a  and the second body  310   b  are made of a metallic material having a high thermal conductivity, such as Al and the like. Since electrical components are mounted in the middle body  320 , it is required that heat should not be transferred to the middle body  320 . Accordingly, the middle body  320  may be made of a material having low thermal conductivity, for example, plastic, in order to prevent heat generated from the first and the second bodies  310   a  and  310   b  from being transferred to the middle body  320 . 
     3) Coupling Cap  350   
     The first body  310   a , the second body  310   b  and middle body  320  are coupled to each other by coupling a coupling cap  350  to one ends thereof. Here, the first body  310   a , the second body  310   b  and middle body  320  are coupled such that they can rotate. 
     As shown in  FIG. 7 , a first recess  361   a  is formed on one side in the middle of the first body  310   a . A second recess  361   b  is formed on one side in the middle of the second body  310   b . A third recess  361   c  is formed in the middle of the middle body  320 . One side of each of the first recess  361   a  and the second recess  361   b  is opened to the outside of the light source unit  300 . 
     A fourth recess  361   d  is formed on the other side of the lower part the first body  310   a . A fifth recess  361   e  is formed on the other side of the lower part of the first body  310   b . The sixth recess  361   f  is formed in the lower part of the middle body  320 . 
     The coupling cap  350  includes a first deterrent protrusion  351   a , a second deterrent protrusion  351   b , an upper part fixing protrusion  351   c , a first axis protrusion  351   d , a second axis protrusion  351   e  and a lower part fixing protrusion  351   f.    
     The first body  310   a , the second body  310   b  and the middle body  320  are coupled to each other by inserting the first deterrent protrusion  351   a  into the first recess  361   a , inserting the second deterrent protrusion  351   b  into the second recess  361   b , inserting the upper part fixing protrusion  351   c  into the third recess  361   c , inserting the first axis protrusion  351   d  into the fourth recess  361   d , inserting the second axis protrusion  351   e  into the fifth recess  361   e , and inserting the lower part fixing protrusion  351   f  into the third recess  361   f.    
     The coupling cap  350  is fixed to the middle body  320  by inserting the upper part fixing protrusion  351   c  and the lower part fixing protrusion  351   f  into the third recess  361   c  and the sixth recess  361   f  respectively. 
     The spring  340  retains a force pushing outward the first body  310   a  and the second body  310   b . When the force causes a space between the first body  310   a  and the second body  310   b  to be widened to a certain extent, the space between the first body  310   a  and the second body  310   b  is not widened anymore because the first body  310   a  and the second body  310   b  are fixed by the first deterrent protrusion  351   a  and the second deterrent protrusion  351   b  respectively. In this case, a maximum angle between the first body  310   a  and the second body  310   b  is formed by the first deterrent protrusion  351   a  and the second deterrent protrusion  351   b.    
     The first axis protrusion  351   d  is inserted into the fourth recess  361   d  and functions as an axis of rotation of the first body  310   a . The second axis protrusion  351   e  is inserted into the fifth recess  361   e  and functions as an axis of rotation of the second body  310   b . As a result, the first body  310   a  and the second body  310   b  can rotate about the first axis protrusion  351   d  and the second axis protrusion  351   e  respectively. Since one side of each of the first recess  361   a  and the second recess  361   b  is opened to the outside, the first recess  361   a  and the second recess  361   b  are separated from the first deterrent protrusion  351   a  and the second deterrent protrusion  351   b  respectively, during the rotations of the first body  310   a  and the second body  310   b . The first axis protrusion  351   d  and the second axis protrusion  351   e  formed in the lower part of the coupling cap  350  are closely adjacent in order to function as axes of rotation. 
     Meanwhile, since the first body  310   a  and the second body  310   b  are formed to have the first sloping surface and the second sloping surface facing the reflector  200 , with the viewpoint of a section of the light source unit  300  formed by the coupling of the first body  310   a , the second body  310   b  and the middle body  320 , the width of the lower part of the light source unit  300  is greater that of the upper part of the light source unit  300 . For example, the light source unit  300  can have a fan-shaped section or a polygon-shaped section. The light source unit  300  can have various sections without being limited to this. 
     4) First Connection Terminal  120  and Second Connection Terminal  330   
     A first connection terminal  120  is provided in the middle part of the insertion grove  112  of the coupling member  110 . A second connection terminal  330  is provided on the middle body  320  of the light source unit  300 . The second connection terminal  330  is coupled to and electrically connected to the first connection terminal  120 . Based on a design of the light source device  1 , it is possible to form at least one or more the first connection terminals  120  and at least one or more the second connection terminals  330 . 
     The first and the second connection terminals  120  and  330  may be electrically connected to each other by inserting the light source unit  300  into the insertion recess  112 . 
     The first and the second connection terminals  120  and  330  is able to transfer electric power and/or a driving signal which are provided by the power supply unit  400  to the plurality of the light emitting diodes  312  and/or the sensor  321 . 
       FIG. 8  is a perspective view of a coupling of a first connection terminal  120  and a second connection terminal  330  of a lighting device  1  in accordance with an embodiment 1 of the present invention.  FIGS. 9 a  and 9 b    are plan views of a first connection terminal  120  and a second connection terminal  330  of a lighting device  1  in accordance with an embodiment 1 of the present invention. 
     The first connection terminal  120  includes a first female block  121   a  and a second female block  121   b  and without being limited to this, the first connection terminal  120  can include at least one pair of the female blocks. 
     For example, the first female block  121   a  includes a pair of a first terminal  123   a  and a second terminal  123   b  and another pair of a third terminal  123   c  and a fourth terminal  123   d . The second female block  121   b  includes a pair of a fifth terminal  123   e  and a sixth terminal  123   f  and another pair of a seventh terminal  123   g  and an eighth terminal  123   h.    
     The first female block  121   a  and the second female block  121   b  are symmetrical to each other. That is, the first to the fourth terminals  123   a  to  123   d  and the fifth to the eighth terminals  123   e  to  123   h  are symmetrical with respect to a line between the first female block  121   a  and the second female block  121   b.    
     The second connection terminal  330  includes a first male block  331   a  and a second male block  331   b  and without being limited to this, the first connection terminal  120  can include at least one pair of the male blocks. 
     For example, the first male block  331   a  includes a pair of a first socket  333   a  and a second socket  333   b  and another pair of a third socket  333   c  and a fourth socket  333   d . The second male block  331   b  includes a pair of a fifth socket  333   e  and a sixth socket  333   f  and another pair of a seventh socket  333   g  and an eighth socket  333   h.    
     The first male block  331   a  and the second male block  331   b  are symmetrical to each other. That is, the first to the fourth sockets  333   a  to  333   d  and the fifth to the eighth sockets  333   e  to  333   h  are symmetrical with respect to a line between the first male block  331   a  and the second male block  331   b.    
     A polarity of the first female block  121   a  and a polarity of the second female block  121   b  may be symmetrical to each other. 
     The polarities of the first and the second terminals  123   a  and  123   b  are symmetrical to the polarities of the seventh and the eighth terminals  123   g  and  123   h . For example, if the polarities of the first and the second terminals  123   a  and  123   b  are ‘+’ and ‘−’ respectively, the polarities of the seventh and the eighth terminals  123   g  and  123   h  are ‘−’ and ‘+’ respectively. If the polarities of the first and the second terminals  123   a  and  123   b  are ‘−’ and ‘+’ respectively, the polarities of the seventh and the eighth terminals  123   g  and  123   h  are ‘+’ and ‘−’ respectively. 
     Additionally, the polarities of the third and the fourth terminals  123   c  and  123   d  are symmetrical to the polarities of the fifth and the sixth terminals  123   e  and  123   f . For example, if the polarities of the third and the fourth terminals  123   c  and  123   d  are ‘+’ and ‘−’ respectively, the polarities of the fifth and the sixth terminals  123   e  and  123   f  are ‘−’ and ‘+’ respectively. If the polarities of the third and the fourth terminals  123   c  and  123   d  are ‘−’ and ‘+’ respectively, the polarities of the fifth and the sixth terminals  123   e  and  123   f  are ‘+’ and ‘−’ respectively. 
     The polarities of the first to the eighth sockets  333   a  to  333   h  can be various formed depending on the polarities of the first to the eighth terminals  123   a  to  123   h.    
     When the light source unit  300  is coupled to the coupling member  110  in the first direction, the first connection terminal  120  is electrically and physically connected to the second connection terminal  330  by inserting the first and the second terminals  123   a  and  123   b  into the first and the second sockets  333   a  and  333   b , inserting the third and the fourth terminals  123   c  and  123   d  into the third and the fourth sockets  333   c  and  333   d , inserting the fifth and the sixth terminals  123   e  and  123   f  into the fifth and the sixth sockets  333   e  and  333   f , inserting the seventh and the eighth terminals  123   g  and  123   h  into the seventh and the eighth sockets  333   g  and  333   h.    
     In addition, when the light source unit  300  is coupled to the coupling member  110  in a second direction (that is, a reverse direction to the first direction), the first connection terminal  120  is electrically and physically connected to the second connection terminal  330  by inserting the first and the second terminals  123   a  and  123   b  into the seventh and the eighth sockets  333   g  and  333   h , inserting the third and the fourth terminals  123   c  and  123   d  into the fifth and the sixth sockets  333   e  and  333   f , inserting the fifth and the sixth terminals  123   e  and  123   f  into the third and the fourth sockets  333   c  and  333   d , inserting the seventh and the eighth terminals  123   g  and  123   h  into the first and the second sockets  333   a  and  333   b.    
     As such, since the structures and polarities of the first connection terminal  120  and the second connection terminal  330  are symmetrical to each other, it is possible to connect the light source unit  300  to the coupling member  110  irrespective of the coupling direction. Accordingly, the lighting device  1  according to the embodiment 1 makes it easier to couple the light source unit  300  to the coupling member  110 , enhancing a convenience for use thereof. 
     In the meantime, when the light source unit  300  is coupled to the coupling member  110 , the first, second, seventh and eighth terminals  123   a ,  123   b ,  123   g  and  123   h  are used as connectors for transferring electric power. The third, fourth, fifth and sixth terminals  123   c ,  123   d ,  123   e  and  123   f  are used or not used as connectors for transferring a driving signal. 
     On the contrary, the third, fourth, fifth and sixth terminals  123   c ,  123   d ,  123   e  and  123   f  can be used as connectors for transferring electric power. The first, second, seventh and eighth terminals  123   a ,  123   b ,  123   g  and  123   h  can be used or not used as connectors for transferring a driving signal. 
     5. Coupling and Separation of Light Source Unit  300  and Coupling Member  110 , and Operation of Limit Switch 
       FIGS. 10 a  and 10 b    show a coupling and separation process of a light source unit  300  and a coupling member  110  in accordance with an embodiment 1 of the present invention. 
     1) Coupling Process 
     First, as shown in  FIG. 10 a   , in the light source unit  300 , an angle between the first body  310   a  and the second body  310   b  is reduced by applying a first force F to the first body  310   a  and the second body  310   b  which are coupled such that they can rotate about the lower part of the light source unit  300 . Here, the direction of the first force F is reverse to the direction of the elastic force applied by the spring  340 . When the lower parts of the first and the second coupling units  315   a  and  315   b  are pressed by applying the first force F, a space between the first and the second coupling units  315   a  and  315   b  is reduced, so that an angle between the first body  310   a  and the second body  310   b  is reduced. 
     If the first force F is not applied, a space between the first body  310   a  and the second body  310   b  is widened by the elastic force applied by the spring  340 , so that it is difficult to insert the light source unit  300  into the insertion recess  112  of the coupling member  110 . 
     As mentioned above, as a space between the first and the second coupling units  315   a  and  315   b  is reduced, the first and the second bodies  310   a  and  310   b  approach close to or come in contact with both sides of the middle body  320 . Here, a limit switch  323  detects the motions of the first and the second bodies  310   a  and  310   b  and becomes in an off-state, and then disconnects the electric power supplied to the light emitting diode  312 . 
     In general, a lighting device such as a fluorescent lamp can be replaced while the lighting device is connected to a power supply. However, when a lighting device using the light emitting diode  312  is connected to a power supply and is replaced, the light emitting diode  312  may be damaged. To overcome such a problem, through the use of the limit switch  323 , the lighting device according to the embodiment 1 recognizes an operation in which the first and the second bodies  310   a  and  310   b  move toward the middle body  320  as an operation of replacing the light source. As a result, during the operation of replacing the light source, it is possible to disconnect the electric power supplied to the light emitting diode  312 . 
     As shown in  FIG. 10 b   , as the first force F is applied to the first and the second bodies  310   a  and  310   b , the light source unit  300  is inserted into the insertion recess  112  of the coupling member  110 . Here, if the first force F is not applied, a space between the first and the second bodies  310   a  and  310   b  is widened again, so that the projection  313  is inserted into the third recess  113  formed on the inner surface of the insertion recess  112 . As a result, the light source unit  300  can be coupled to the coupling member  110 . 
     When the light source unit  300  is inserted into the coupling member  110 , the spring  340  disposed between the first body  310   a  and the second body  310   b  pushes the first body  310   a  and the second body  310   b , causing the projections  313  to be more securely coupled to the third recess  113 . 
     The spring  340  gives continuously a uniform pressure to a contact surface formed by causing the first coupling unit  315   a  and the second coupling unit  315   b  to be contact with the insertion recess  112 . Therefore, heat generated from the light source unit  300  can be more efficiently transferred through the contact surface mentioned above. 
     As described above, when the light source unit  300  is thoroughly coupled to the coupling member  110 , the space between the first and the second bodies  310   a  and  310   b  is widened again by the elastic force from the spring  340 . The limit switch  323  hereby recognizes that the operation of replacing the light source is completed and becomes in an off-state, and then connects again the electric power supplied to the light emitting diode  312 . 
     2) Separation Process 
     When the light source unit  300  is required to repair, the light source unit  300  can be separated from the coupling member  110 . 
     In separating the light source unit  300  from the coupling member  110 , after the angle between the first body  310   a  and the second body  310   b  is reduced by applying the first force F to the first body  310   a  and the second body  310   b , the light source unit  300  is separated from the coupling member  110 . 
     6. An Example of Limit Switch 
       FIG. 11 a    shows how a mechanical limit switch according to an embodiment 1 is operated.  FIG. 11 b    shows how a sensor type limit switch according to an embodiment 1 is operated. 
     The limit switch according to the embodiment 1 is able to employ a mechanical limit switch or a sensor type limit switch. 
     1) Mechanical Limit Switch 
     When the first force F is applied to the first and the second bodies  310   a  and  310   b , the first and the second bodies  310   a  and  310   b  rotate in the direction of the middle body  320 , so that the inner surfaces of the first and the second bodies  310   a  and  310   b  approach close to both sides of the middle body  320  respectively. When the first and the second bodies  310   a  and  310   b  approach close to both sides of the middle body  320  to a certain extent respectively, the limit switch  323  contacts with the first and the second bodies  310   a  and  310   b . Here, the limit switch  323  disposed on both sides of the middle body  320  is pressed through the use of button by the first and the second bodies  310   a  and  310   b  and becomes in an off-state. In this case, the limit switch  323  is capable of electrically separating the second connection terminal  330  from the light emitting diode  312 . 
     Next, after the light source unit  300  is completely coupled to the coupling member  110 , a distance between the first body  310   a  and the second body  310   b  is increased. As a result, the limit switch  323  becomes in an on-state, so that the second connection terminal  330  may be electrically connected again to the light emitting diode  312 . 
     2) Sensor Type Switch 
     When the first force F is applied to the first and the second bodies  310   a  and  310   b , the first and the second bodies  310   a  and  310   b  rotate in the direction of the middle body  320 , so that the inner surfaces of the first and the second bodies  310   a  and  310   b  approach close to both sides of the middle body  320  respectively. Here, the limit switch  323  disposed on both sides of the middle body  320  detects the motions of the first and the second bodies  310   a  and  310   b.    
     There are two kinds of the aforementioned detecting method. One is a method using the intensity of pressure applied by the first and the second bodies  310   a  and  310   b  and the other is a method using a magnetic field intensity measured from the first and the second bodies  310   a  and  310   b.    
     The limit switch  323  using the intensity of pressure may include a pressure sensor. Such a limit switch  323  measures the intensity of pressure applied by the first and the second bodies  310   a  and  310   b . If the measured intensity of pressure is greater than a predetermined intensity of pressure, the limit switch  323  becomes in an off-state. Here, the limit switch  323  recognizes that the light source is replaced and may generate a control signal for disconnecting the electric power supplied to the light source  300 . 
     Subsequently, when the first connection terminal  120  is connected to the second connection terminal  330 , the control signal generated by the limit switch  323 , as shown in  FIG. 11 b   , may be output to the power supply unit  400  through the first connection terminal  120  and the second connection terminal  330 . As a result, the power supply unit  400  is hereby able to disconnect the electric power output based on the control signal. 
     After the light source  300  is completely coupled to the coupling member  110 , as the first force F is decreased, a distance between the limit switch  323  and both the first and the second bodies  310   a  and  310   b  is increased. Since the first and the second bodies  310   a  and  310   b  are further from the limit switch  323 , the intensity of pressure applied by the first and the second bodies  310   a  and  310   b  becomes lower than a predetermined intensity of pressure. In this case, the limit switch  323  becomes in an on-state, the control signal is not output. In such a case, the second connection terminal  330  may be electrically connected again to the light emitting diode  312 . 
     The limit switch  323  using the magnetic field intensity may include a magnetic sensor. The limit switch  323  using the magnetic field intensity has the same electrical operation method as that of the limit switch  323  using the pressure sensor. However, in case of the limit switch  323  using the magnetic sensor, a magnet is provided on the inner surfaces of the first and the second bodies  310   a  and  310   b . The position of the magnet corresponds to the position of the magnetic sensor. Accordingly, it is possible to measure the magnetic field intensity according to a distance between the middle body  320  and the first and the second bodies  310   a  and  310   b.    
     The limit switch  323  using the magnetic sensor is able to recognize the existence, approach and location of an object through a non contact method. The limit switch  323  using the non contact method may be produced by using various proximity sensors as well as the aforementioned magnetic sensor. 
     Meanwhile, the middle body  320  may include a separate power supply for starting and operating the limit switch  323 . 
     According to the embodiment 1, when the light source unit  300  is required to be disposed or replaced for maintenance, it is possible to safely attach or remove the light source unit  300  by using the limit switch  323  even though the lighting device is in a live status. 
     Modified Embodiment 
       FIGS. 12 and 13  are cross sectional views of a light source unit  300  and a coupling member  110  of a lighting device in accordance with a modified embodiment of the present invention. In description of the lighting device  1  according to a modified embodiment, repetitive descriptions thereof will be omitted. 
     Referring to  FIGS. 12 and 13 , a plurality of the third recesses  113   a ,  113   b  and  113   c  are formed on the inner surface of the insertion recess  112  of the coupling member  110  of the lighting device  1 . While the three third recesses  113   a ,  113   b  and  113   c  are shown, there is no limit to the number of the third recesses. 
     The light source unit  300  is inserted into and coupled to the insertion recess  112 . Here, the projection  313  of the upper part of the light source unit  300  is inserted into one of a plurality of the third recesses  113   a ,  113   b  and  113   c , so that the light source unit  300  is strongly coupled to the coupling member  110 . 
     As shown in  FIG. 12 , depths of a plurality of the third recesses  113   a ,  113   b  and  113   c  are different from each other, it is possible to diversely adjust the light distribution of the lighting device  1  in accordance with one of a plurality of the third recesses  113   a ,  113   b  and  113   c  into which the projection  313  of the light source unit  300  is inserted. 
     As shown in  FIG. 13 , the insertion recess  112  has a sloping inner surface. When a plurality of the third recesses  113   a ,  113   b  and  113   c  are formed on the sloping inner surface of the insertion recess  112 , an angle between the first body  310   a  and the second body  310   b  of the light source unit  300  varies in accordance with one of a plurality of the third recesses  113   a ,  113   b  and  113   c  into which the projection  313  of the light source unit  300  is inserted. Therefore, it is possible to diversely adjust the light distribution of the lighting device  1 . 
     As described above, it is possible to diversely adjust the light distribution of the lighting device  1  by forming a plurality of the third recesses  113   a ,  113   b  and  113   c  on the inner surface of the insertion recess  112 . As a result, even though a width or curvature of the reflector  200  changes, it is possible to provide an efficient lighting without changing the light source unit  300 . 
     Embodiment 2 
       FIG. 14  is a perspective view of a light device in accordance with an embodiment 2 of the present invention.  FIG. 15  is an exploded perspective view of the light device in accordance with the embodiment 2 of the present invention.  FIG. 16  is a cross sectional view of the light device in accordance with the embodiment 2 of the present invention.  FIG. 17 a    is a cross sectional view of a coupling member shown in  FIG. 16 .  FIG. 17 b    is a view showing an enlarged part denoted by “A” of  FIG. 16 .  FIG. 17 c    is a view showing a light distribution angle of a light emitting diode mounted in the light emitting recess according to the embodiment 2 of the present invention. 
     In  FIGS. 14 to 17   c , a lighting device in accordance with an embodiment 2 of the present invention includes a housing  100 , a coupling member  110 , a reflector  200 , a light source unit  300  and a power supply unit  400 . 
     1. Housing  100  and Coupling Member  110   
     The housing  100  has a shape of a box for accepting the housing  100 , the coupling member  110 , the reflector  200  and the power supply unit  400 . While the shape of the housing  100  as viewed from the outside is quadrangular, the housing  100  can have various shapes without being limited to this. 
     The housing  100  is made of a material capable of efficiently releasing heat. For example, the housing  100  is made of a metallic material such as Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and so on. 
     A connecting recess  107  for connecting electrically the power supply unit  400  to an external power supply is formed on a lateral surface and/or an upper surface of the housing  100 . 
     The housing  100  includes an opening  101  such that light radiated from the light source unit  300  is reflected to be emitted by the reflector  200 . 
     Meanwhile, in order to dispose the lighting device on an external support member such as a ceiling or a wall surface, an insertion unit corresponding to a shape of the lighting device is formed in the external support member, and then the lighting device is inserted into and fixed to the insertion unit. Here, a coupling frame  500  is coupled to the lower part of the lateral surface of the housing  100 , so that the lighting device can be securely coupled to the external support member. 
     The coupling member  110  is coupled on an inner upper surface of the housing  100 . The coupling member  110  is coupled to the housing  100  by using various methods. For example, the coupling member  110  is coupled to the housing  100  by means of a coupling screw, an adhesive agent and so on. 
     The coupling member  110  is formed to be extended on an upper surface  102  of the housing  100  in a first direction. For example, the coupling member  110  can be extended from an inner wall surface to the opposite inner wall surface of the housing  100 . 
     The housing  100  and the coupling member  110  are attachable to and removable form the reflector  200 . 
     A second recess  103  is formed on the inner wall surface of the housing  100 . A first side  210  of the reflector  200  is inserted into the second recess  103 . It is possible to form the one second recess  103  or a plurality of the second recesses  103 . 
     A first recess  111  is formed on an outer wall surface of the coupling member  110 . The first recess  111  is formed to be extended in the first direction. A second side  220  of the reflector  200  is inserted into the first recess  111 . 
     The housing  100  and the coupling member  110  can fix and sustain the reflector  200  by inserting the first side  210  of the reflector  200  into the second recess  103  of the housing  100  and by inserting the second side  220  of the reflector  200  into the first recess  111  of the coupling member  110 . 
     A first insertion recess  112  is formed in the middle part of the coupling member  110 . A part of the light source unit  300  is inserted into the first insertion recess  112 . The first insertion recess  112  can be formed to be extended in the first direction. 
     A plurality of third recesses  113  are formed on an inner wall surface of the first insertion recess  112 . A projection  313  of the light source unit  300  is inserted into the third recess  113 . As a result, the light source unit  300  is securely coupled to the coupling member  110  by means of the third recess  113 . The coupling of the light source unit  300  and the coupling member  110  will be described later in more detail. 
     A first connection terminal  120  is formed in the middle part within the first insertion recess  112 . When the light source unit  300  is inserted into the first insertion recess  112 , the first connection terminal  120  is coupled to and electrically connected to a second connection terminal  336  of the light source unit  300 . When the first connection terminal  120  is connected to the second connection terminal  336 , electric power and/or a driving signal can be transferred to the light source unit  300  through the first connection terminal  120  and the second connection terminal  336 . 
     Based on a design of the light source device, it is possible to form the one first connection terminal  120  or a plurality of the first connection terminals  120 . More detailed descriptions of the first connection terminal  120  and the second connection terminal  336  will be provided later. 
     The coupling member  110  performs a function of directly releasing heat generated from the light source unit  300  or transferring the heat to the housing  100 . 
     It is desirable to form the coupling member  100  by using a material capable of efficiently releasing and/or transferring the heat. For example, the coupling member  110  is made of a metallic material such as Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and so on. 
     A part of the coupling member  110  can have an uneven structure  116 . The uneven structure  116  can widen the surface area of the coupling member  110  and improve a heat release effect. 
     2. Reflector  200   
     The reflector  200  includes a first reflector  200   a  and a second reflector  200   b . The first reflector  200   a  and the second reflector  200   b  are attachable to and removable from the housing  100  and the coupling member  110 . 
     For example, as shown in  FIG. 15 , the second reflector  200   b  is coupled to the housing  100  and the coupling member  110  by inserting the second side  220  of the second reflector  200   b  into the first recess  111  of the coupling member  110  and by inserting the first side  210  of the second reflector  200   b  into the second recess  103  of the housing  100 . The second side  220  of the reflector  200  can have a level difference. The first side  210  of the reflector  200  can also have a level difference. At least one insertion end  211  which is inserted into the second recess  103  is formed at the first side  210  of the reflector  200 . A shape of the second recess  103  is formed to correspond to the selection end  211 . 
     The first reflector  200   a  and the second reflector  200   b  have a parabola-shaped surface and are extended in the first direction. Therefore, the first reflector  200   a  and the second reflector  200   b  have a parabolic shape having two parabolic surfaces. Here, the shape of the reflector  200  can be variously changed according to a desired lighting. 
     The reflector  200  is made of a metallic material or a resin material which has a high reflection efficiency. For example, the resin material includes any one of PET, PC and PVC resin. The metallic material includes any one of Ag, alloy including Ag, Al, and alloy including Al. 
     The surface of the reflector  200  is coated with Ag, Al, white photo solder resist (PSR) ink, a diffusion sheet and the like. Otherwise, an oxide film is formed on the surface of the reflector  200  by an anodizing process. 
     Here, the material and color of the reflector  200  are not limited and are variously selected depending on a lighting generated by the lighting device. 
     3. Power Supply Unit  400   
     When the power supply unit  400  is connected to the light source unit  300 , the power supply unit  400  can supply at least one of electric power and a driving signal. 
     As shown in  FIGS. 15 and 16 , the power supply unit  400  is disposed in a space between the parabola-shaped reflector  200  and the inner surface of the housing  100 . That is, due to the parabola shape of the reflector  200 , an empty space is formed between the reflector  200  and a corner inside the housing  100 . As a result, the power supply unit  400  is disposed in the empty space. 
     The power supply unit  400  converts an alternating current (AC) electric power into a direct current (DC) electric power and outputs the direct current (DC) electric power. 
     The power supply unit  400  is electrically connected to the light source unit  300  through a wire or a flexible printed circuit board (FPCB). For example, a wire or a FPCB is extended from the power supply unit  400  and is electrically connected to the first connection terminal  120  through the connecting recess  107  formed in the coupling member  110 . The first connection terminal  120  is electrically connected to the second connection terminal  336 . As a result, the power supply unit  400  is electrically connected to the light source unit  300 . 
     4. Light Source Unit  300   
       FIG. 17 a    is a cross sectional view of a coupling member shown in  FIG. 16 .  FIG. 17 b    is a view showing an enlarged part denoted by “A” of  FIG. 16 .  FIG. 17 c    is a view showing a light distribution angle of a light emitting diode mounted in the light emitting recess according to the embodiment 2 of the present invention.  FIG. 18  is a perspective view of the light source unit  300  in accordance with the embodiment 2 of the present invention.  FIG. 19  is an exploded perspective view of the light source unit  300  in accordance with the embodiment 2 of the present invention. 
     Referring to  FIGS. 17 a    to  19 , the light source unit  300  according to the embodiment 2 of the present invention includes a first body  310 , a second body  320 , a middle body  330 , a first main light emitting diode module  304 , a second main light emitting diode module  306 , an auxiliary light emitting diode module  308  and a spring  340 . The body of the light source unit  300  includes the first body  310 , the second body  320  and the middle body  330 . The light source unit  300  may be extended in the first direction, that is, in the direction of length of the reflector  200 . 
     Hereinafter, the structure of the light source unit  300  will be described in more detailed. 
     1) First Body  310   
     A first coupling unit  310   a  is formed in the upper part of the first body  310 . The first coupling unit  310   a  constitutes the upper part of the first body  310  and is inserted into the first insertion recess  112  of the coupling member  110 . 
     A first projection  310   c  is formed in the upper end of the first coupling unit  310   a . The first projection  310   c  has a shape in which a part of the upper end of the first coupling unit  310   a  is projected outward. 
     A first light emitting recess  312  is formed on one side of the lower part of the first body  310 . The basal surface of the first light emitting recess  312  is formed to have a first sloping surface  310   b . The first sloping surface  310   b  is formed to face the parabolic surface of the first reflector  200   a . Here, a plurality of the sloping surfaces as well as the first sloping surface  310   b  may be formed in the first body  310 . 
     The first main light emitting diode module  304  is disposed in the first light emitting recess  312 . The first main light emitting diode module  304  includes a first substrate  313 , a plurality of main light emitting diodes  314  and a first optical structure  315 . 
     The first substrate  313  is disposed on the basal surface of the first light emitting recess  312  along the first sloping surface  310   b.    
     The plurality of the main light emitting diodes  314  are disposed on the first substrate  313  along the first sloping surface  310   b  and are electrically connected to the first substrate  313 . Otherwise, a plurality of electrodes (not shown) are disposed on the first sloping surface  310   b , and then the plurality of the main light emitting diodes  314  are electrically connected to the plurality of electrodes (not shown) respectively. Such a plurality of the main light emitting diodes  314  may be arranged within the first light emitting recess  312  in the form of an array. 
     The plurality of the main light emitting diodes  314  are determined, for example, through various combinations of red, green, blue and white light emitting diode which radiate red, green, blue and white light respectively. 
     The plurality of the main light emitting diodes  314  are controlled by electric power and/or a driving signal which are provided by the power supply unit  400 , causing the plurality of the main light emitting diodes  314  to selectively emit light or to adjust the luminance of light. 
     The first optical structure  315  is disposed on the plurality of the main light emitting diodes  314 . The first optical structure  315  functions to adjust the light distribution and the color sense of light radiated from the plurality of the main light emitting diodes  314 , and creates emotional lighting having various luminance and color senses if necessary. 
     The first optical structure  315  is coupled to the inside of the first light emitting recess  312  by inserting in a sliding way both ends of the first optical structure  315  into a fourth recess  312   a  formed on an inner surface of the first light emitting recess  312 . More specifically, the fourth recess  312   a  is extended in the first direction and the first optical structure  315  is coupled to the inside of the first light emitting recess  312  by being inserted into the fourth recess  312   a  in the first direction. 
     The first optical structure  315  includes at least one of a lens, a diffusion sheet and a phosphor luminescent film (PLF). 
     The lens includes various lenses such as a concave lens, a convex lens and a condensing lens and so on according to a design of the lighting device. 
     The diffusion sheet diffuses evenly light radiated from the plurality of the main light emitting diodes  314 . 
     The phosphor luminescent film (PLF) includes fluorescent substance. Since the fluorescent substance included in the phosphor luminescent film (PLF) is excited by light radiated from the plurality of the main light emitting diodes  314 , the lighting device can produce emotional lighting having various color senses by mixing a first light radiated from the plurality of the main light emitting diodes  314  and a second light excited by the fluorescent substance. For example, when the plurality of the main light emitting diodes  314  radiate blue light and the phosphor luminescent film (PLF) includes a yellow fluorescent substance excited by blue light, the lighting device radiates white light by mixing the blue light and yellow light. 
     The first optical structure  315  is easily coupled to the first light emitting recess  312  through the fourth recess  312   a . Accordingly, a lens, a diffusion sheet and a phosphor luminescent film (PLF) can be alternately used as the first optical structure  315 . 
     The depth and width of the first light emitting recess  312  can be variously adjusted according to the light distribution of the plurality of the main light emitting diodes  314  disposed within the first light emitting recess  312 . In other words, the lighting device is able to cause the reflector  200  to provide users with light radiated from the light source unit  300  by adjusting the depth and width of the first light emitting recess  312  instead of directly providing users with light radiated from the light source unit  300 . As a result, it is possible to provide users with subdued light by reducing glare. 
     A light distribution angle of light emitted from the first light emitting recess  312  is from 90° to 110°. The depth and width of the first light emitting recess  312  is formed to cause light emitted from the first light emitting recess  312  to be incident evenly on the entire area of the reflector  200 . 
     Additionally, the depth and width of the first light emitting recess  312  is adjusted such that a part of light radiated from the plurality of the main light emitting diodes  314  is radiated to the outside through the opening  101  and the rest of the light is reflected by the reflector  200  and is radiated to the outside through the opening  101 . 
     A first hinge  311  may be formed on the other side of the lower part of the first body  310 . The first hinge  311  has a shape protruding outward. Also, the first hinge  311  may be extended in the first direction. 
     2) Second Body  320   
     A second coupling unit  320   a  is formed in the upper part of the second body  320 . The second coupling unit  320   a  constitutes the upper part of the second body  320  and is inserted into the first insertion recess  112  of the coupling member  110 . 
     A second projection  320   c  is formed in the upper end of the second coupling unit  320   a . The second projection  320   c  has a shape in which a part of the upper end of the second coupling unit  320   a  is projected outward. 
     A second light emitting recess  322  is formed on one side of the lower part of the second body  320 . The basal surface of the second light emitting recess  322  is formed to have a second sloping surface  320   b . The second sloping surface  320   b  is formed to face the parabolic surface of the second reflector  200   b . Here, a plurality of the sloping surfaces as well as the second sloping surface  320   b  may be formed in the second body  320 . 
     The second main light emitting diode module  306  is disposed in the second light emitting recess  322 . The second main light emitting diode module  304  includes a first substrate  323 , a plurality of main light emitting diodes  324  and a first optical structure  325 . 
     The first substrate  323  is disposed on the basal surface of the second light emitting recess  322  along the second sloping surface  320   b.    
     The plurality of the main light emitting diodes  324  are disposed on the first substrate  323  along the second sloping surface  320   b  and are electrically connected to the first substrate  323 . Otherwise, a plurality of electrodes (not shown) are disposed on the second sloping surface  320   b , and then the plurality of the main light emitting diodes  324  are electrically connected to the plurality of electrodes (not shown) respectively. Such a plurality of the main light emitting diodes  324  may be arranged within the second light emitting recess  322  in the form of an array. 
     The plurality of the main light emitting diodes  324  are determined, for example, through various combinations of red, green, blue and white light emitting diode which radiate red, green, blue and white light respectively. 
     The plurality of the main light emitting diodes  324  are controlled by electric power and/or a driving signal which are provided by the power supply unit  400 , causing the plurality of the main light emitting diodes  324  to selectively emit light or to adjust the luminance of light. 
     The first optical structure  325  is disposed on the plurality of the main light emitting diodes  324 . The first optical structure  325  functions to adjust the light distribution and the color sense of light radiated from the plurality of the main light emitting diodes  324 , and creates emotional lighting having various luminance and color senses if necessary. 
     The first optical structure  325  is coupled to the inside of the second light emitting recess  322  by inserting in a sliding way both ends of the first optical structure  325  into a fourth recess  322   a  formed on an inner surface of the second light emitting recess  322 . More specifically, the fourth recess  322   a  is extended in the first direction and the first optical structure  325  is coupled to the inside of the second light emitting recess  322  by being inserted into the fourth recess  322   a  in the first direction. 
     The first optical structure  325  includes at least one of a lens, a diffusion sheet and a phosphor luminescent film (PLF). 
     The lens includes various lenses such as a concave lens, a convex lens and a condensing lens and so on according to a design of the lighting device. 
     The diffusion sheet diffuses evenly light radiated from the plurality of the main light emitting diodes  324 . 
     The phosphor luminescent film (PLF) includes fluorescent substance. Since the fluorescent substance included in the phosphor luminescent film (PLF) is excited by light radiated from the plurality of the main light emitting diodes  324 , the lighting device can produce emotional lighting having various color senses by mixing a first light radiated from the plurality of the main light emitting diodes  324  and a second light excited by the fluorescent substance. For example, when the plurality of the main light emitting diodes  324  radiate blue light and the phosphor luminescent film (PLF) includes a yellow fluorescent substance excited by blue light, the lighting device radiates white light by mixing the blue light and yellow light. 
     The first optical structure  325  is easily coupled to the second light emitting recess  322  through the fourth recess  322   a . Accordingly, a lens, a diffusion sheet and a phosphor luminescent film (PLF) can be alternately used as the first optical structure  325 . 
     The depth and width of the second light emitting recess  322  can be variously adjusted according to the light distribution of the plurality of the main light emitting diodes  324  disposed within the second light emitting recess  322 . In other words, the lighting device is able to cause the reflector  200  to provide users with light radiated from the light source unit  300  by adjusting the depth and width of the second light emitting recess  322  instead of directly providing users with light radiated from the light source unit  300 . As a result, it is possible to provide users with subdued light by reducing glare. 
     A light distribution angle of light emitted from the second light emitting recess  322  is from 90° to 110°. The depth and width of the second light emitting recess  322  is formed to cause light emitted from the second light emitting recess  322  to be incident evenly on the entire area of the reflector  200 . 
     Additionally, the depth and width of the second light emitting recess  322  is adjusted such that a part of light radiated from the plurality of the main light emitting diodes  324  is radiated to the outside through the opening  101  and the rest of the light is reflected by the reflector  200  and is radiated to the outside through the opening  101 . 
     A second hinge  321  may be formed on the other side of the lower part of the second body  320 . The second hinge  321  has a shape protruding outward. Also, the second hinge  321  may be extended in the first direction. 
     As described above, the first body  310  and the second body  320  have the same structure and configuration. 
     Also, the first body  310  and the second body  320  may be manufactured in such a manner as to have a constant cross section in the first direction by means of an extrusion molding method. 
     Also, the first body  310  and the second body  320  may be formed of metallic material such as Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and the like so as to release heat generated from the plurality of the main light emitting diodes  314  and  324 . 
     Generally, the light distribution angle of the light emitted from the light emitting diode is about 120°. When the light emitting diode emits the light having such a wide light distribution angle, a part of the emitted light is reflected by the reflector  200  and is emitted to the outside through the opening  101 . However, the rest of the light is directly emitted through the opening  101  to the outside, thereby enabling a user to feel glare. 
     To overcome such a problem, the first and the second light emitting recesses  312  and  322  may be formed to block the light emitted directly from the light emitting diodes  314  and  324  to the outside of the housing  100 . That is, the first and the second light emitting recesses  312  and  322  includes a projection part  316   b  formed on the basal surface thereof, thereby blocking the light emitted directly from the light emitting diodes  314  and  324  to the outside of the housing  100 . 
     As a result, due to the projection part  316   b  of the light emitting recess  316 , the light emitted from a plurality of the light emitting diodes  314  and  324  is not directly provided to a user and is uniformly incident on the whole area of the reflector  200 . Accordingly, it is possible to provide users with subdued light by reducing glare. 
     Furthermore, it is possible to block the direct light emitted from the light emitting diodes  314  and  324  to the outside of the housing  100  by adjusting the depth and width of the first and the second light emitting recesses  312  and  322 , the height of the projection part  316   b , the sloping angle of the basal surface  316   a , the height of the housing  100  or the width of the reflector  200  and the like. 
     The sloping plane toward the reflector  200  is formed in the first body  310  and the second body  320 . Therefore, regarding a cross section of the light source unit  300  formed by coupling the first body  310 , the second body  320  and the middle body  330 , the width of the lower part of the light source unit  300  is greater that of the upper part of the light source unit  300 . For example, the cross section of the light source unit  300  can have various shapes such as a fan shape or a polygon shape and the like. 
     3) Middle Body  330   
     A second insertion recess  331  is formed on both sides of the lower part  330   a  of the middle body  330 . The second insertion recess  331  is extended in the first direction. Here, the first hinge  311  of the first body  310  and the second hinge  321  of the second body  320  are inserted into the second insertion recess  331 . For example, the first hinge  311  and the second hinge  321  may be inserted into the second insertion recess  331  respectively in a sliding way. The first body  310  and the second body  320  are hereby coupled to both sides of the middle body  330  in an attachable and removable manner. Also, the first body  310  and the second body  320  may be coupled to rotate about the first hinge  311  and the second hinge  321  respectively. 
     An auxiliary light emitting diode module  308  is disposed on the basal surface of the lower part  330   a  of the middle body  330 . More specifically, a third light emitting recess  332  is formed on the basal surface of the lower part of the middle body  330 , and the auxiliary light emitting diode module  308  is disposed within the third light emitting recess  332 . The auxiliary light emitting diode module  308  includes a second substrate  333 , a plurality of auxiliary light emitting diodes  334  and a second optical structure  335 . 
     The second substrate  333  is disposed on the inner upper surface of the third light emitting recess  332 . 
     The plurality of the auxiliary light emitting diodes  334  are disposed on the second substrate  333  and are electrically connected to the second substrate  333 . Otherwise, a plurality of electrodes (not shown) are disposed on the inner upper surface of the third light emitting recess  332 , and then the plurality of the auxiliary light emitting diodes  334  are electrically connected to the plurality of electrodes (not shown) respectively. 
     The second optical structure  335  is coupled to the inside of the third light emitting recess  332  by inserting in a sliding way both ends of the third optical structure  335  into a fifth recess  332   a  formed on the inner surface of the third light emitting recess  332 . More specifically, the fifth recess  332   a  is extended in the first direction and the second optical structure  335  is coupled to the inside of the third light emitting recess  332  by being inserted into the fifth recess  332   a  in the first direction. 
     The plurality of the auxiliary light emitting diodes  334  are controlled by electric power and/or a driving signal which are provided by the power supply unit  400 , causing the plurality of the auxiliary light emitting diodes  334  to selectively emit light or to adjust the luminance of light. For example, the auxiliary light emitting diode  334  is used in producing more illuminations, a subdued lighting condition and a display apparatus and the like. 
     The second optical structure  335  is disposed on the plurality of the auxiliary light emitting diodes  334 . The second optical structure  335  functions to adjust the light distribution and the color sense of light radiated from the plurality of the auxiliary light emitting diodes  334 , and creates emotional lighting having various luminance and color senses if necessary. 
     The second optical structure  335  includes at least one of a lens, a diffusion sheet and a phosphor luminescent film (PLF). 
     The lens includes various lenses such as a concave lens, a convex lens and a condensing lens and so on according to a design of the lighting device. 
     The diffusion sheet diffuses evenly light radiated from the plurality of the main light emitting diodes  314 . 
     The phosphor luminescent film (PLF) includes fluorescent substance. Since the fluorescent substance included in the phosphor luminescent film (PLF) is excited by light radiated from the plurality of the main light emitting diodes  314 , the lighting device can produce emotional lighting having various color senses by mixing a first light radiated from the plurality of the main light emitting diodes  314  and a second light excited by the fluorescent substance. For example, when the plurality of the main light emitting diodes  314  radiate blue light and the phosphor luminescent film (PLF) includes a yellow fluorescent substance excited by blue light, the lighting device radiates white light by mixing the blue light and yellow light. 
     The second optical structure  335  is easily coupled to the third light emitting recess  332  through the fifth recess  332   a . Accordingly, a lens, a diffusion sheet and a phosphor luminescent film (PLF) can be alternately used as the first optical structure  315 . 
     The middle body  330  according to the embodiment 2 may be manufactured in such a manner as to have a constant cross section in the first direction and to have a symmetrical structure by means of an extrusion molding method. 
     As described above, when the first body  310 , the second body  320  and the middle body  330  are coupled to each other, the outer surfaces of the first hinge  311  and the second hinge  321  are in contact with the inner surface of the second insertion recess  331 , so that a heat release path can be created between the first body  310 , the second body  320  and the middle body  330 . 
     Therefore, in order to improve the heat radiating effect, the lower part  330   a  of the middle body  330  is made of a metallic material having high thermal conductivity, for example, Al, Sn, Ni, Ag, Cu, Ti, Mo, W, Au and Pt and the like. Since electrical components are mounted in the upper part  330   b  of the middle body  330 , it is to be desired that heat is not transferred to the upper part  330   b  of the middle body  330 . Therefore, the upper part of the middle body  330  is made of a material having low thermal conductivity, for example, plastic material and the like such that it is possible to prevent the heat generated by the first body  310 , the second body  320  and the lower part of the middle body  330  from being transferred. 
     Further, the heat generated from the main light emitting diodes  314  and  324  and the auxiliary light emitting diode  334  is released by the body of the light source unit  300  or is transferred to the coupling member  110 , and then is released. That is, when the light source unit  300  is inserted into the first insertion recess  112  of the coupling member  110 , the first coupling unit  310   a  and the second coupling unit  320   a  have a contact area with the first insertion recess  112 . As such, one sides of the first coupling unit  310   a  and the second coupling unit  320   a  contact with the inner surface of the first insertion recess  112 , a thermal conductivity route from the light source unit  300  to the coupling member  110  can be formed. Here, the larger the contact area is, the higher the heat radiating effect is. However, the heights of the first body  310  and the second body  320  are increased, so that the height of the housing  100  is required to be increased. Accordingly, in order for the lighting device to have optimal heat radiating effect, it is necessary to consider the relationship between the contact area and the height of the housing  100 . A part of the body of the light source unit  300  has an uneven structure, thereby effectively releasing the heat. 
     Meanwhile, the coupling unit  110  of the housing  100  includes the first insertion recess  112  of which the inner wall surface is extended by the length of the light source unit  300  (that is, extended in the first direction). The light source includes a light source safe holder contacting directly with a light source and having the light source seated therein, and includes the first coupling unit  310   a  and the second coupling unit  320   a  which come in surface contact with the inner wall surface of the first insertion recess  112  formed in the coupling unit  110 . Here, the light source safe holder signifies the light emitting recess in which the light emitting diodes are disposed and signifies the lower part of the light source unit  300  in which the light emitting recess is formed. 
     When the lighting device is operated, heat generated from the light source safe holder is released to the coupling unit  110  through the first coupling unit  310   a  and the second coupling unit  320   a . In this case, the first coupling unit  310   a  and the second coupling unit  320   a  come in surface contact with the inner wall surface of the first insertion recess  112 , so that the heat generated from the light source safe holder can be transferred to the coupling unit  110 . Here, since the inner wall surface of the first insertion recess  112  is extended by the length of the light source unit  300  (that is, extended in the first direction), a maximum contact area of the first coupling unit  310   a  and the second coupling unit  320   a  is obtained. As a result, it is possible to improve the heat radiating effect of the lighting device. 
     Meanwhile, the lower parts of the first body  310  and the second body  320  are manufactured to have sloping surfaces toward the reflector  200 . Therefore, regarding a cross section of the light source unit  300  formed by coupling the first body  310 , the second body  320  and the middle body  330 , the width of the lower part of the light source unit  300  is greater that of the upper part of the light source unit  300 . For example, the cross section of the light source unit  300  has a fan shape or a polygon shape and the like. However, the cross section of the light source unit  300  can have various shapes without being limited to the shapes mentioned above. 
     4) Spring  340   
     A spring  340  is disposed in the upper part or in the middle part of the middle body  330 . For example, as shown in  FIG. 17 b   , the spring  340  can have a ‘ ’-shape and can be disposed between the lower part  330   a  and the upper part  330   b  of the middle body  330 . When the first body  310  and the second body  320  are coupled to each other on both sides of the middle body  330 , the spring  340  is disposed contacting with the inner surfaces of the first body  310  and the second body  320 . 
     The spring  340  provides the first body  310  and the second body  320  with an elastic force widening a space between the first body  310  and the second body  320 . That is, the spring  340  is disposed between the first body  310  and the second body  320  and performs a function of pushing outward the first body  310  and the second body  320 . Accordingly, when the light source unit  300  is inserted into the coupling member  110 , the projections formed in the upper ends of the first body  310  and the second body  320  are strongly coupled to the first insertion recess  112  of the coupling member  110  by the force from the spring  340 . 
     5) First Connection Terminal  120  and Second Connection Terminal  336   
       FIG. 20  is a perspective view of a coupling of a first connection terminal  120  and a second connection terminal  336  of the lighting device in accordance with the embodiment 2 of the present invention. 
     Referring to  FIG. 20 , the first connection terminal  120  is formed in the first insertion recess  112  of the coupling member  110 . The second connection terminal  336  coupled to the first connection terminal  120  is formed on the middle body  330  of the light source unit  300 . 
     The first and the second connection terminals  120  and  336  are coupled to each other by inserting the light source unit  300  into the first insertion recess  112 . 
     The first connection terminal  120  includes a first female block  121   a  and a second female block  121   b  and without being limited to this, the first connection terminal  120  can include at least one pair of the female blocks. For example, the first female block  121   a  includes a pair of a first terminal  123   a  and a second terminal  123   b  and another pair of a third terminal  123   c  and a fourth terminal  123   d . The second female block  121   b  includes a pair of a fifth terminal  123   e  and a sixth terminal  123   f  and another pair of a seventh terminal  123   g  and an eighth terminal  123   h.    
     The first female block  121   a  and the second female block  121   b  are symmetrical to each other. That is, the first to the fourth terminals  123   a  to  123   d  and the fifth to the eighth terminals  123   e  to  123   h  are symmetrical with respect to a line between the first female block  121   a  and the second female block  121   b.    
     The second connection terminal  336  includes a first male block  336   a  and a second male block  336   b  and without being limited to this, the first connection terminal  120  can include at least one pair of the male blocks. 
     For example, the first male block  336   a  includes a pair of a first socket  336   a  and a second socket  336   b  and another pair of a third socket  337   c  and a fourth socket  337   d . The second male block  336   b  includes a pair of a fifth socket  337   e  and a sixth socket  337   f  and another pair of a seventh socket  337   g  and an eighth socket  337   h.    
     The first male block  336   a  and the second male block  336   b  are symmetrical to each other. That is, the first to the fourth sockets  3373   a  to  337   d  and the fifth to the eighth sockets  337   e  to  337   h  are symmetrical with respect to a line between the first male block  336   a  and the second male block  336   b.    
     A polarity of the first female block  121   a  and a polarity of the second female block  121   b  may be symmetrical to each other. 
     The polarities of the first and the second terminals  123   a  and  123   b  are symmetrical to the polarities of the seventh and the eighth terminals  123   g  and  123   h . For example, if the polarities of the first and the second terminals  123   a  and  123   b  are ‘+’ and ‘−’ respectively, the polarities of the seventh and the eighth terminals  123   g  and  123   h  are ‘−’ and ‘+’ respectively. If the polarities of the first and the second terminals  123   a  and  123   b  are ‘−’ and ‘+’ respectively, the polarities of the seventh and the eighth terminals  123   g  and  123   h  are ‘+’ and ‘−’ respectively. 
     Additionally, the polarities of the third and the fourth terminals  123   c  and  123   d  are symmetrical to the polarities of the fifth and the sixth terminals  123   e  and  123   f . For example, if the polarities of the third and the fourth terminals  123   c  and  123   d  are ‘+’ and ‘−’ respectively, the polarities of the fifth and the sixth terminals  123   e  and  123   f  are ‘−’ and ‘+’ respectively. If the polarities of the third and the fourth terminals  123   c  and  123   d  are ‘−’ and ‘+’ respectively, the polarities of the fifth and the sixth terminals  123   e  and  123   f  are ‘+’ and ‘−’ respectively. 
     The polarities of the first to the eighth sockets  337   a  to  337   h  can be various formed depending on the polarities of the first to the eighth terminals  123   a  to  123   h.    
     When the light source unit  300  is coupled to the coupling member  110  in the first direction, the first connection terminal  120  is electrically and physically connected to the second connection terminal  336  by inserting the first and the second terminals  123   a  and  123   b  into the first and the second sockets  337   a  and  337   b , inserting the third and the fourth terminals  123   c  and  123   d  into the third and the fourth sockets  337   c  and  337   d , inserting the fifth and the sixth terminals  123   e  and  123   f  into the fifth and the sixth sockets  337   e  and  337   f , inserting the seventh and the eighth terminals  123   g  and  123   h  into the seventh and the eighth sockets  337   g  and  337   h.    
     In addition, when the light source unit  300  is coupled to the coupling member  110  in a second direction (that is, a reverse direction to the first direction), the first connection terminal  120  is electrically and physically connected to the second connection terminal  336  by inserting the first and the second terminals  123   a  and  123   b  into the seventh and the eighth sockets  337   g  and  337   h , inserting the third and the fourth terminals  123   c  and  123   d  into the fifth and the sixth sockets  337   e  and  337   f , inserting the fifth and the sixth terminals  123   e  and  123   f  into the third and the fourth sockets  337   c  and  337   d , inserting the seventh and the eighth terminals  123   g  and  123   h  into the first and the second sockets  337   a  and  337   b.    
     As such, since the structures and polarities of the first connection terminal  120  and the second connection terminal  336  are symmetrical to each other, it is possible to connect the light source unit  300  to the coupling member  110  irrespective of the coupling direction. Accordingly, the lighting device according to the embodiment 2 makes it easier to couple the light source unit  300  to the coupling member  110 , enhancing a convenience for use thereof. 
     In the meantime, when the light source unit  300  is coupled to the coupling member  110 , the first, second, seventh and eighth terminals  123   a ,  123   b ,  123   g  and  123   h  are used as connectors for transferring electric power. The third, fourth, fifth and sixth terminals  123   c ,  123   d ,  123   e  and  123   f  are used or not used as connectors for transferring a driving signal. 
     On the contrary, the third, fourth, fifth and sixth terminals  123   c ,  123   d ,  123   e  and  123   f  can be used as connectors for transferring electric power. The first, second, seventh and eighth terminals  123   a ,  123   b ,  123   g  and  123   h  can be used or not used as connectors for transferring a driving signal. 
     6) Limit Switch  337   
     A limit switch  337  is provided on both sides of the middle body  330 . The limit switch  337  is in an on-state or in an off-state as the first body  310  and the second body  320  move toward the middle body  330 . The limit switch is hereby configured in such a manner as to connect or disconnect the electric power supplied to the light emitting diode module. The detailed description of the limit switch  337  will be described later. 
     5. Coupling and Separation of Light Source Unit  300  and Coupling Member  110   
       FIGS. 22 and 23  show a coupling and separation process of a light source unit  300  and a coupling member  110  in accordance with an embodiment 2 of the present invention. 
     1) Coupling Process 
     First, as shown in  FIG. 22 , an angle between the first body  310  and the second body  320  is reduced by applying a first force F to the first body  310  and the second body  320  of the light source unit  300 . Here, the direction of the first force F is reverse to the direction of the elastic force applied by the spring  340 . When the lower parts of the first and the second coupling units  310   a  and  320   a  are pressed by applying the first force F, a space between the first and the second coupling units  310   a  and  320   a  is reduced, so that an angle between the first body  310  and the second body  320  is reduced. 
     If the first force F is not applied, a space between the first body  310  and the second body  320  is widened by the elastic force applied by the spring  340 , so that it is difficult to insert the light source unit  300  into the first insertion recess  112  of the coupling member  110 . 
     Next, as the first force F is applied to the first and the second bodies  310  and  320 , the light source unit  300  is inserted into the first insertion recess  112  of the coupling member  110 . 
     As shown in  FIG. 23 , if the first force F is not applied, a space between the first and the second bodies  310  and  320  is widened again, so that the projection is inserted into the third recess  113  formed on the inner surface of the first insertion recess  112 . As a result, the light source unit  300  can be coupled to the coupling member  110 . 
     When the light source unit  300  is inserted into the coupling member  110 , the spring  340  disposed between the first body  310  and the second body  320  pushes the first body  310  and the second body  320 , causing the projections to be more securely coupled to the third recess  113 . 
     The spring  340  gives continuously a uniform pressure to a contact surface formed by causing the first coupling unit  310   a  and the second coupling unit  320   a  to be contact with the first insertion recess  112 . Therefore, heat generated from the light source unit  300  can be more efficiently transferred through the contact surface mentioned above. 
     2) Separation Process 
     When the light source unit  300  is required to repair, the light source unit  300  can be separated from the coupling member  110 . 
     In separating the light source unit  300  from the coupling member  110 , after the angle between the first body  310  and the second body  320  is reduced by applying the first force F to the first body  310  and the second body  320 , the light source unit  300  is separated from the coupling member  110 . 
     6. An Example of Limit Switch 
       FIG. 24 a    shows how a mechanical limit switch according to an embodiment 2 is operated.  FIG. 24 b    shows how a sensor type limit switch according to an embodiment 2 is operated. 
     The limit switch according to the embodiment 2 is able to employ a mechanical limit switch or a sensor type limit switch. 
     1) Mechanical Limit Switch 
     When the first force F is applied to the first and the second bodies  310  and  320 , the first and the second bodies  310  and  320  rotate in the direction of the middle body  330 , so that the inner surfaces of the first and the second bodies  310  and  320  approach close to both sides of the middle body  330  respectively. When the first and the second bodies  310  and  320  approach close to both sides of the middle body  330  to a certain extent respectively, the limit switch  337  contacts with the first and the second bodies  310  and  320 . Here, the limit switch  337  disposed on both sides of the middle body  330  is pressed through the use of button by the first and the second bodies  310  and  320  and becomes in an off-state. In this case, the limit switch  337  is capable of electrically separating the second connection terminal  336  from the light emitting diode module. 
     Next, after the light source unit  300  is completely coupled to the coupling member  110 , a distance between the first body  310  and the second body  320  is increased. As a result, the limit switch  337  becomes in an on-state, so that the second connection terminal  336  may be electrically connected again to the light emitting diode module. 
     2) Sensor Type Switch 
     When the first force F is applied to the first and the second bodies  310  and  320 , the first and the second bodies  310  and  320  rotate in the direction of the middle body  330 , so that the inner surfaces of the first and the second bodies  310  and  320  approach close to both sides of the middle body  330  respectively. Here, the limit switch  337  disposed on both sides of the middle body  330  detects the motions of the first and the second bodies  310  and  320 . 
     There are two kinds of the aforementioned detecting method. One is a method using the intensity of pressure applied by the first and the second bodies  310  and  320  and the other is a method using a magnetic field intensity measured from the first and the second bodies  310  and  320 . 
     The limit switch  337  using the intensity of pressure may include a pressure sensor. Such a limit switch  337  measures the intensity of pressure applied by the first and the second bodies  310  and  320 . If the measured intensity of pressure is greater than a predetermined intensity of pressure, the limit switch  337  becomes in an off-state. Here, the limit switch  337  recognizes that the light source is replaced and may generate a control signal for disconnecting the electric power supplied to the light source  300 . 
     Subsequently, when the first connection terminal  120  is connected to the second connection terminal  336 , the control signal generated by the limit switch  337 , as shown in  FIG. 141 b   , may be output to the power supply unit  400  through the first connection terminal  120  and the second connection terminal  336 . As a result, the power supply unit  400  is hereby able to disconnect the electric power output based on the control signal. 
     After the light source  300  is completely coupled to the coupling member  110 , as the first force F is decreased, a distance between the limit switch  337  and both the first and the second bodies  310  and  320  is increased. Since the first and the second bodies  310  and  320  are further from the limit switch  337 , the intensity of pressure applied by the first and the second bodies  310  and  320  becomes lower than a predetermined intensity of pressure. In this case, the limit switch  337  becomes in an on-state, the control signal is not output. In such a case, the second connection terminal  336  may be electrically connected again to the light emitting diode module. 
     The limit switch  337  using the magnetic field intensity may include a magnetic sensor. The limit switch  337  using the magnetic field intensity has the same electrical operation method as that of the limit switch  337  using the pressure sensor. However, in case of the limit switch  337  using the magnetic sensor, a magnet is provided on the inner surfaces of the first and the second bodies  310  and  320 . The position of the magnet corresponds to the position of the magnetic sensor. Accordingly, it is possible to measure the magnetic field intensity according to a distance between the middle body  330  and the first and the second bodies  310  and  320 . 
     The limit switch  337  using the magnetic sensor is able to recognize the existence, approach and location of an object through a non contact method. The limit switch  337  using the non contact method may be produced by using various proximity sensors as well as the aforementioned magnetic sensor. 
     Meanwhile, the middle body  330  may include a separate power supply for starting and operating the limit switch  337 . 
     According to the embodiment 2, when the light source unit  300  is required to be disposed or replaced for maintenance, it is possible to safely attach or remove the light source unit  300  by using the limit switch  337  even though the lighting device is in a live status. 
     Modified Embodiment 
       FIGS. 25 and 26  are cross sectional views of a light source unit  300  and a coupling member  110  of a lighting device in accordance with a modified embodiment of the present invention. In description of the lighting device according to a modified embodiment, repetitive descriptions thereof will be omitted. 
     Referring to  FIGS. 25 and 26 , the plurality of the third recesses  113   a ,  113   b  and  113   c  are formed on the inner surface of the first insertion recess  112  of the coupling member  110  of the lighting device. While the three third recesses  113   a ,  113   b  and  113   c  are shown, there is no limit to the number of the third recesses. 
     The light source unit  300  is inserted into and coupled to the first insertion recess  112 . Here, the projection of the upper part of the light source unit  300  is inserted into one of the plurality of the third recesses  113   a ,  113   b  and  113   c , so that the light source unit  300  is strongly coupled to the coupling member  110 . 
     As shown in  FIG. 25 , depths of the plurality of the third recesses  113   a ,  113   b  and  113   c  are different from each other, it is possible to diversely adjust the light distribution of the lighting device in accordance with one of the plurality of the third recesses  113   a ,  113   b  and  113   c  into which the projection of the light source unit  300  is inserted. 
     As shown in  FIG. 26 , the first insertion recess  112  has a sloping inner surface. When a plurality of the third recesses  113   a ,  113   b  and  113   c  are formed on the sloping inner surface of the first insertion recess  112 , an angle between the first body  310  and the second body  320  of the light source unit  300  varies in accordance with one of a plurality of the third recesses  113   a ,  113   b  and  113   c  into which the projection of the light source unit  300  is inserted. Therefore, it is possible to diversely adjust the light distribution of the lighting device. 
     As described above, it is possible to diversely adjust the light distribution of the lighting device by forming a plurality of the third recesses  113   a ,  113   b  and  113   c  on the inner surface of the first insertion recess  112 . As a result, even though a width or curvature of the reflector  200  changes, it is possible to provide an efficient lighting without changing the light source unit  300 . 
     As described above, it will be appreciated by those skilled in the art that the present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. 
     The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the foregoing embodiments is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.