Abstract:
In a lighting apparatus using microwave, a lighting apparatus using microwave including a resonator excluding microwave and transmitting a fight, a waveguide placed at an internal domain of the resonator and transmitting the microwave, a microwave generating means installed at the side of the resonator and oscillating microwave into the waveguide, and a bulb placed at the center of the resonator and emitting light by generating a plasma by the microwave transmitted through the waveguide is capable of miniaturizing a lighting system and at the same time improving a lighting efficiency.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lighting apparatus using microwaves and in particular to a lighting apparatus using microwaves which is capable of emitting lights by applying microwaves an electrodeless bulb. 
     2. Description of the Conventional Art 
     A lighting apparatus using microwaves emits visible rays or ultraviolet rays by applying microwaves to an electrodeless bulb, it has longer life span and better lighting effectiveness than a general incandescent lamp or a fluorescent lamp. 
     FIG. 1 is a longitudinal sectional view illustrating an internal structure of a lighting apparatus using microwaves. 
     A lighting apparatus using microwaves includes a magnetron  1 , a waveguide  3  transmitting microwaves from the magnetron  1  to a bulb  5 , the bulb  5  emitting light from the plasma generated from the enclosed materials which are excited by the microwave energy transmitted through the waveguide  3 , and a resonator  10  placed in front of the waveguide  3  and the bulb  5 , excluding the microwaves and transmitting the light emitted from the bulb  5 . 
     Particularly, the resonator  10  has a cylindrical shape and has a metal mesh structure in order to exclude microwaves while transmitting the light emitted from the bulb  5 . 
     The lighting apparatus using microwaves further includes a high voltage generator  7  for boosting the voltage of an alternating current and supplying it to the magnetron  1 , a cooling unit  9  for refrigerating the magnetron  1  and the high voltage generator  7 , a reflector  11  intensively reflecting the light emitted from the bulb  5 , and a control unit (not shown) controlling various elements including the high voltage generator  7  and the cooling unit  9 . 
     In the lighting apparatus using microwaves, when an operating signal is inputted from the control unit to the high voltage generator  7 , the high voltage generator  7  boost the voltage of the AC power and supplies the boosted AC power to the magnetron  1 . 
     The magnetron  1  oscillates due to the high voltage supplied from the high voltage generator  7  and generates microwaves having a very high frequency, the generated microwaves are emitted into the resonator  10  through the waveguide  3 , materials enclosed inside the bulb  5  are discharged, accordingly light having an inherent emission spectrum is generated. 
     The light generated from the bulb  5  is reflected by a mirror  12  and the reflector  11  and lights up a space. 
     However, in the lighting apparatus using microwaves in accordance with the background art, because the resonator  10  is constructed with a cylindrical metal mesh, most of the light emitted from the bulb  5  transmits through the metal mesh, and part of the light is reflected on the metal mesh and scattered all over the place inside the resonator  10 , accordingly there is a limitation in maximizing a lighting efficiency. 
     In more detail, because the resonator  10  has the cylindrical shape, a focus of the light reflected onto the metal mesh is not fixed and the light is reflected intricately and scattered all over the place, accordingly the lighting efficiency is lowered due to the loss of the light. 
     In addition, because the resonator  10  projects lengthwise from the front of the waveguide  3 , and a large size reflector  11  is required to surround the resonator  10 , it is difficult to minimize the size of the lighting system. 
     SUMMARY OF THE INVENTION 
     In order to solve the above-mentioned problems, it is an object of the present invention to provide a lighting apparatus using microwaves which is capable of improving a lighting efficiency and miniaturizing a lighting system by minimizing a loss of light emitted from a bulb by installing a waveguide inside a resonator and installing a bulb at the center of the resonator. 
     In order to achieve the object of the present invention, a lighting apparatus using microwaves includes a resonator transmitting a light but preventing the escape of microwaves, a waveguide placed at an internal domain of the resonator and transmuting the microwaves, a microwave generating means installed at the side of the resonator and transmitting microwaves into the waveguide, and a bulb placed at the center of the resonator and emitting light resulting from a plasma which is excited by the microwaves transmitted through the waveguide. 
     Herein, the resonator has a spherical shape, and the waveguide is installed within a radial sector of the resonator. 
     The waveguide has a conical shape, the vertex of the waveguide is placed at the center of the resonator, the cover portion of the waveguide is formed as a curved surface having a shape the same as the spherical shape of the resonator and Is placed so as to correspond to an external extended portion of the resonator. 
     The lighting apparatus using microwaves having the microwave generating means further includes a high voltage generator and a casing covering a cooling unit, and the casing is combined and fixed to the cover portion of the waveguide at the external extended portion of the resonator. 
     The bulb is placed at the center of the resonator, and the microwave generating means is fixed to the waveguide at the external extended portion of the resonator. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
     FIG. 1 is a longitudinal sectional view illustrating a lighting apparatus using microwaves in accordance with the background art. 
     FIG. 2 is a longitudinal sectional view illustrating a lighting apparatus using microwaves in accordance with the present invention; 
     FIG. 3 is a plan view illustrating the lighting apparatus of FIG. 2 taken along the line of A—A; and 
     FIGS. 4A,  4 B, and  4 C are plan views of other embodiments illustrating shapes of waveguide in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, a lighting apparatus using microwaves in accordance with the present invention will be described with reference to the accompanying drawings. 
     There can be a plurality of embodiments of a lighting apparatus using microwaves in accordance with the present invention, hereinafter the most preferable embodiment will be described. 
     FIG. 2 is a longitudinal sectional view illustrating a lighting apparatus using microwaves in accordance with the present invention, and FIG. 3 is a plan view illustrating the lighting apparatus of FIG. 2 taken along the line of A—A. 
     As shown in FIG. 2, lighting apparatus using microwaves in accordance with the present invention includes a resonator  50  having a metal mesh structure and an opened lower portion, a waveguide  60  inserted into the opened portion of the resonator  50 , placed at the internal area  53  of the resonator  50  having a spherical structure and transmitting microwaves, and a casing  70  combined to the bottom portion  62  of the resonator  50  (see also FIG. 3) and the waveguide  60 . 
     A plurality of outwardly extended flange portions  51 ,  61 ,  66 ,  71  are respectively formed at the resonator  50 , waveguide  60  and casing  70  and adhered tightly by bolts  90  as shown in FIGS. 2 and 3. 
     The resonator  50  has a metal mesh structure constructed with a certain size of hole except at the flange portion  51  so as to exclude microwaves and transmit light, and the bulb  80  (also see FIG.  3 ), emitting light resulting from a plasma which is excited by the microwaves transmitted through the waveguide  60 , is placed at the center of the sphere shaped resonator  50 . 
     The waveguide  60  has a conical shape having an opened bottom portion  62  and is constructed with a body portion  63  placed inside the resonator  50  and a cover portion  65  formed as a curved surface same as the spherical shape of be resonator  50  and combined to the bottom portion  62  of the body portion  63 . 
     At least one outlet  63   a  is formed at the inclined plane of the body portion  63  in order to transmit the microwaves transmitted from the magnetron  73  into an internal area  53  of resonator  50 . 
     Particularly, a hollow concave portion  84  of a hemisphere shape is formed in order to make a place for the bulb  80  at the vertex of the waveguide  60 . 
     A reflecting mirror  85  is installed between the bulb  80  and the concave portion  64  in order to reflect light emitted from the bulb  80 . 
     Herein, a reflecting layer coated with materials having reflecting elements can be formed at the external surface of the concave portion  64  of the waveguide  60 . 
     A rotation shaft  77  penetrating the waveguide  60  is connected to the bulb  80 , and a bulb motor  78  rotating the bulb  80  is connected to the end portion of the rotation shaft  77  is installed at the bottom surface of the waveguide  60 . 
     The magnetron  73  is installed at the bottom surface  65  of the waveguide  60  inside the casing  70  and oscillates microwaves inside the waveguide  60 . 
     A high voltage generator  74  boosting AC current and supplying the boosted AC current to the magnetron  73  is installed at the internal side of the casing  70 , and a refrigerating fan  75  and a motor for the refrigerating fan  76  are installed at the lower portion of the casing  70  in order to refrigerate the magnetron  73  and the high voltage generator  74 . 
     As depicted in FIG. 3, four slots  63   a ′ (first slots) with lengths formed in the radius direction and four slots  63   a ″ (second slots) with lengths formed in the circumferential direction are arranged with a certain distance which is the same as in FIG.  2 . Other elements shown in FIG. 3 include resonators  50 , waveguide  60 , body portion  63 , reflecting mirror  85 , and bolts  90 . 
     FIGS. 4A,  4 B and  4 C are plan views of other embodiments illustrating shapes of waveguide in accordance with the present invention. 
     As depicted in FIG. 4A, in another embodiment of the present invention, three slots  63   a ′ with lengths formed in the radius direction are spaced apart by 120° at the outlet of the waveguide  60 . 
     As depicted in FIG. 4B, in still another embodiment of the present invention, two slots  63   a ′ with lengths formed in the radius direction and one slot  63   a ″ with a length formed in the circumference direction are spaced apart by 120° at the outlet of the waveguide  60 . 
     As depicted in FIG. 4C, in yet still another embodiment of the present invention, three slots  63   a ′ with lengths formed in the radius direction and one slot  63   a ″ with a length formed in the circumference direction are spaced apart by 120° at the outlet of the waveguide  60 . 
     The operation of the lighting apparatus using microwaves in accordance with the present invention will be described. 
     When the magnetron  73  oscillates microwaves, the microwaves are transmitted into the waveguide  60  and are radiated inside the resonator through each outlet. 
     Herein, the microwaves emitted inside the resonator  50  perform a resonance motion inside the resonator  50 , and generate a plasma and an inherent spectrum by exciting the materials enclosed inside the bulb  80   
     Most of light generated in the bulb  80  and reflected onto the reflecting mirror  85  is emitted in the front through the hole of the resonator  50 , part of the light reflected onto the metal mesh of the resonator  50  is concentrated on the center C of the resonator  50  as shown in FIG. 2, namely the bulb  80  placed at the focus of the sphere, and is reflected in the front through the reflecting mirror  85 , accordingly loss of the light can be reduced. 
     The lighting apparatus using microwaves in accordance with the present invention is capable of improving a lighting efficiency and miniaturizing a lighting system by minimizing loss of light emitted from a bulb by placing the bulb at the center of a resonator having a spherical shape and installing a waveguide inside the resonator. 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.