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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 2007-0096896, filed on Sep. 21, 2007 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     The present invention relates to a metal panel, a manufacturing method thereof and a cooking device using the metal panel, and, more particularly, to the manufacture of an edge portion of the metal panel. 
     2. Description of the Related Art 
     Generally, an oven range is a cooking device with an oven and a range formed as a single body, in which the oven heats cooking ingredients in a sealed cooking chamber and the range directly heats and cooks cooking ingredients disposed on a gas burner or an electric heater. Oven ranges may be largely classified into a gas oven range and an electric oven range according to their heat sources. 
     A conventional oven range includes an oven unit which cooks food accommodated in a cooking chamber by thermal convection; a top burner unit which is disposed at an upper portion of the oven unit to directly heat a container containing food and cook the food; and a drawer unit which is disposed at the lower side of the oven unit to perform a storage function or a simple cooking function. An oven door is disposed at the open front of the cooking chamber to open and close the cooking chamber. The oven door includes a see-through window to allow a user to see food during cooking and a door frame forming a border of the see-through window. 
     In the conventional oven range, however, when the door frame is manufactured using a metal material for general processing, it is difficult to process an edge portion at which a front surface, side surfaces and an upper surface meet each other. 
     That is, when an edge portion is formed using a metal material for general processing, for example, stainless steel, used in the door frame of the conventional oven range or a metal material for seam processing, which has a small thickness equal to or less than about 0.8 mm, there is a problem that the edge portion is torn. Accordingly, in order to prevent the edge portion from being torn, the edge of the metal material is cut and bent to separate upper, lower and side surfaces of the edge. A welding process and a polishing process are performed on the separated upper, lower and side surfaces to from an external appearance of the door frame. 
     However, the door frame of the conventional oven range, which is manufactured such that the upper, lower and side surfaces are separated, has low impact strength and a sharp edge portion. Thus, there is a problem that a consumer may be injured in the opening and closing of the oven door. 
     Further, in the door frame of the oven range which is formed by a manufacturing method wherein the upper, lower and side surfaces are welded and polished, since the welding of the edge is not easy, the welding cost increases. Further, since a surface polishing process should be performed after welding, there is a problem such as a reduction of productivity. 
     The above problems may be generated in various electric and electronic products using a metal plate manufactured to form an edge portion in addition to a cooking device such as an oven range. 
     SUMMARY 
     The present invention has been made in order to solve the above problems. It is an aspect of the invention to provide a metal panel with no sharp edge portion, a manufacturing method thereof and a cooking device using the metal panel. 
     In accordance with an aspect of the invention, there is provided a manufacturing method of a metal panel including: cutting a metal plate to form a cutaway portion at a specified area of a border; bending the border on opposite sides of the cutaway portion; and coupling a bracket to a cutaway groove formed at the border by the bending. 
     The bracket may include a protruding portion corresponding to the cutaway groove and an extending portion extended from the protruding portion, and the bracket may be coupled to the cutaway groove by welding the extending portion to a circumferential side of the cutaway groove. 
     A height of the protruding portion may be formed to be substantially equal to a height of an outer surface of the cutaway groove. 
     The cutaway portion may be formed at a corner of the metal plate. 
     A lower portion of the cutaway portion may be cut to have a specified height higher than a bending line on one side surface of the metal plate, and the lower portion of the cutaway portion adjacent to the bending line on opposite side surfaces may be doubly bent. 
     The corner may be formed at a substantially right angle. 
     In accordance with another aspect of the invention, there is provided a metal panel including: a metal plate which has an edge formed as a single body by bending a border of one side surface and a cutaway groove at a specified area of the border; and a bracket which is coupled to the cutaway groove. 
     A cutaway portion may be formed at one side of the border of the metal plate and the metal plate is bent to form the cutaway groove adjacent to the edge. 
     The bracket may include a protruding portion which is inserted into the cutaway groove and an extending portion which is extended from the protruding portion and welded to a circumferential side of the cutaway groove. 
     An outer surface of the protruding portion may have a height substantially equal to a height of an outer surface around the cutaway groove. 
     The metal plate may be formed of stainless steel. 
     In accordance with yet another aspect of the invention, there is provided an oven range, serving as a cooking device, including a cooking chamber and a door which has a metal panel forming a front surface to open and close the cooking chamber, wherein the metal panel of the door includes a metal plate which has a cutaway groove formed at a specified area of any one surface of opposite side surfaces in which an edge is formed by bending, and a bracket which is coupled to the cutaway groove. 
     The cutaway groove may be positioned adjacent to the edge formed by bending. 
     The bracket may include a protruding portion which is inserted into the cutaway groove and an extending portion which is extended from the protruding portion and welded to a circumferential side of the cutaway groove. 
     An outer surface of the protruding portion may have a height substantially equal to a height of an outer surface around the cutaway groove. 
     As described above, in the metal panel, the manufacturing method thereof and the cooking device using the metal panel according to the present invention, the bracket is coupled to the cutaway groove of the edge side. Accordingly, since welding and polishing processes of the edge can be emitted, it is possible to simplify the manufacturing process and reduce the manufacturing cost. Further, there is an effect of protecting a consumer from accidents by removing a cut surface of a sharp edge portion. 
     Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects and advantages of the exemplary embodiments of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, of which: 
         FIG. 1  illustrates a perspective view of a cooking device according to an embodiment of the present invention; 
         FIG. 2  illustrates a side cross-sectional view of the cooking device according to the embodiment of the present invention; and 
         FIGS. 3 to 6  are diagrams for explaining a manufacturing method of a metal panel included in the cooking device according to the embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference will now be made in detail to exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       FIG. 1  illustrates a perspective view showing an external appearance of a cooking device according to the present invention.  FIG. 2  illustrates a side cross-sectional view showing a configuration of the cooking device according to the present invention. 
     As shown in  FIG. 1 , the cooking device according to the present invention includes an oven unit  10  which heats and cooks food in a sealed state; an oven door  20  which opens and closes the oven unit  10 ; a top burner unit  30  disposed at the upper side of the oven unit  10  to cook food while supporting a container containing the food; a drawer unit  40  disposed at the lower side of the oven unit  10  to perform a storage function or a simple cooking function; and a controller  50  disposed at the rear of the top burner unit  30  to control an operation of the cooking device. 
     Electrical burners  31  are installed on the top burner unit  30  to heat food disposed thereon. The controller  50  includes a display  51  to display an operation state of the cooking device and a series of operation knobs  52  to control an operation of an oven range. The drawer unit  40  is provided in a drawer shape. The drawer unit  40  may include an additional heater (not shown) installed therein to warm cooked food or perform simple cooking. 
     The oven unit  10  cooks food by thermal convection. As shown in  FIG. 2 , the oven unit  10  includes a cooking chamber  60  defined by an upper plate  11 , a bottom plate  12 , both side plates (not shown) and a rear plate  13 . 
     A fan cover  14  is coupled to the outside of the rear plate  13 , and a convection fan  15  is provided between the fan cover  14  and the rear plate  13  to circulate air in the cooking chamber  60 . An electric heater  16  is installed at an outer periphery of the convection fan  15  and a fan motor  17  is installed at the rear of the fan cover  14  to operate the convection fan  15 . 
     A number of suction holes  13   a  are formed at a central portion of the rear plate  13  facing the convection fan  15  to suck air in the cooking chamber  60 , and a number of discharge holes  13   b  are formed at a periphery of the rear plate  13  to supply heat into the cooking chamber. 
     The oven door  20  is disposed to be vertically rotatable at the front of the cooking chamber  60  of the cooking device according to the present invention to open and close the oven unit  10 . The oven door  20  includes a first metal panel  70  and a second metal panel  80  which form a front external appearance and a rear external appearance, respectively. Openings  71  and  81  are formed at central portions of the first metal panel  70  and the second metal panel  80 , respectively. See-through windows  72  and  82  are installed at the openings  71  and  81 , respectively, such that a user can observe the inside of the cooking chamber  60  through the oven door  20 . 
     The see-through windows  72  and  82  include a rear see-through window  82  installed at the second metal panel  80  and a front see-through window  72  installed at the first metal panel  70 . The rear see-through window  82  is formed of a pair of heat reflective glasses capable of preventing heat leakage by reflecting heat generated in the cooking chamber  60  into the cooking chamber  60  again. The front see-through window  72  is formed of heat resistant tempered glass so as not to be easily deformed by heat transferred from the cooking chamber  60 . 
     Meanwhile, a door handle  21  is installed at a front upper portion of the first metal panel  70  such that the user can grasp the door handle  21  in the opening and closing of the oven door  20 . A thermal insulator  83  is disposed at the border of the rear see-through window  82  to prevent heat inside the cooking chamber  60  from being transferred into an outer space through the oven door  20 . 
     Further, an outlet port  73   a  is formed at an upper portion of a front surface  73  of the first metal panel  70  to discharge hot air in a separation space between the front see-through window  72  and the rear see-through window  82  to an outer space. An inlet port  74   a  is formed on a bottom surface  74  of the first metal panel  70  to introduce exterior air between the front see-through window  72  and the rear see-through window  82 . 
     Thus, the air heated in the separation space between the front see-through window  72  and the rear see-through window  82  rises to be discharged to the outside through the outlet port  73   a  formed at the upper portion of the front surface  73  of the first metal panel  70 . In this case, exterior air is introduced into the separation space with a decreased pressure through the inlet port  74   a  formed the bottom surface  74  of the first metal panel  70 . That is, the air between the front see-through window  72  and the rear see-through window  82  is convection circulated to prevent an increase in the temperature of the front surface of the oven door  20 . 
     The first metal panel  70  is formed of a metal material such as stainless steel having high hardness by press processing. In order to form a shape desired to be finally formed, as shown in  FIG. 3 , a metal plate  90  is cut in a developed shape, and the border thereof is bent to form upper and lower surfaces  76  and  74  and side surfaces  75  as shown in  FIG. 4 . 
     In this case, the first metal panel  70  may be formed of another type of a metal material with a hardness comparable to stainless steel. Further, the first metal panel  70  may be formed of a metal material for seam processing, which causes the edge to be torn in press processing due to a small thickness (equal to or less than about 0.8 mm). 
     As shown in  FIGS. 5 and 6 , edges  77  at which the upper surface  76  and the side surfaces  75  of the first metal panel  70  meet each other are bent so as not to be sharp and cutaway grooves  78  is formed on the upper surface  76  adjacent to the edges  77 . The cutaway grooves  78  are formed in the bending of the metal plate  90  according to the shape of cutaway portions  91  formed as in  FIG. 3  in the cutting of the metal plate  90  to prevent the edges  77  from being torn in the bending of the metal plate  90 . The cutaway grooves  78  may be formed in various shapes and sizes according to the shape of the cutaway portions  91 . 
     Further, brackets  100  are inserted and coupled to the cutaway grooves  78  to cover the cutaway grooves  78 . In this case, the brackets  100  are formed in a shape and a size corresponding to the cutaway grooves  78 . The brackets  100  are fixed and coupled to the cutaway grooves  78 , thereby preventing sharp cut surfaces of the cutaway portions  91  from being exposed to the outside. 
     Next, a method of manufacturing the first metal panel disposed on the front surface of the oven door of the cooking device according to the present invention will be described in detail. 
     In general, the first metal panel is manufactured using a thin metal plate for general processing, which is made of stainless steel or the like and has poor ductility to reduce the manufacturing cost. The edge is cut and the border is bent to prevent an edge portion from being torn in the processing of stainless steel. In this case, a gap is formed at the edge due to a cutaway portion. The gap is filled by welding and the sharp edge is polished by a polishing process to complete the manufacture of the first metal panel. 
     However, the manufacturing method is complicated and causes a problem such as an increase in the manufacturing cost. Accordingly, the embodiment of the present invention provides a relatively simple manufacturing method of the first metal panel capable of reducing the manufacturing cost. 
       FIGS. 3 to 6  are diagrams explaining a manufacturing method of a metal panel included in the cooking device according to the embodiment of the present invention. 
     First, the metal plate  90  is cut in a desired shape as in  FIG. 3 , that is, a developed shape of a metal panel desired to be finally formed. In this case, the outlet port  73   a  and the opening  71  are formed on the front surface of the metal plate  90  at the same time. The metal plate  90  may be formed of various metal plate materials such as stainless steel (SUS), electro-galvanized steel (SECC), hot-dipped galvanized steel (SGCC) or the like. 
     A general press method may be used as a cutting method, but it is preferable to use an N.C.T. machine to maintain accurate dimensions and realize the automation. 
     The cutaway portions  91  are formed at the edge side of the cut metal plate  90  to prevent the metal plate from being torn in the bending. The cutaway portions  91  are formed in a specified shape such that the cutaway grooves  78  are formed on the upper surface  76  of the first metal panel  70  after the bending of the metal plate  90 . In this case, the cutaway portions may be formed such that the cutaway grooves are formed on the side surfaces of the metal panel. 
     Next, a border portion of the cut metal plate  90  is bent as in  FIG. 4  using a molding machine. 
     The molding machine is formed in an approximately rectangular shape corresponding to the front surface  73  of the metal plate  90 . The cut metal plate  90  is disposed on the molding machine and press processed, thereby bending each side of the border of the metal plate  90  at a right angle to form the upper and lower surfaces  76  and  74  and the side surfaces  75 . 
     The molding machine and a press machine used in this case may be easily configured by those skilled in the art according to the size and shape of the metal panel to bend the border side of the metal plate  90 . The material of the molding machine may vary according to the material of the metal plate. 
     When the border is bent, the cutaway portions  91  formed at the edge side in the cutting process form the cutaway grooves  78  by bending as shown in  FIG. 4 . 
     In this case, lower portions  91   a  of the cutaway portions  91  are cut to have a specified height higher than a bending line L on one side surface of the metal plate  90 . Accordingly, when the metal plate  90  is bent, the lower portions  91   a  of the cutaway portions  91  adjacent to the bending line L on the opposite side surfaces are doubly bent. 
     Then, as shown in  FIG. 6 , the brackets  100  are inserted into the cutaway grooves  78  adjacent to the edges  77 , which are formed by the cutaway portions  91 , and coupled thereto by welding to complete the manufacture of the first metal panel  70 . In this case, spot welding may be performed in the welding. Preferably, the brackets  100  are inserted and coupled to the cutaway grooves  78  by projection welding to prevent traces of welding from being formed on an external appearance of the first metal panel  70 . 
     In this case, as shown in  FIG. 5 , the brackets  100  have a shape corresponding to the cutaway grooves  78  and are inserted into the cutaway grooves  78 . The brackets  100  include protruding portions  101  having a height approximately equal to a thickness of the metal plate  90  and extending portions  102  which are formed around the protruding portions  101  and are extended therefrom such that the brackets  100  can be inserted into the cutaway grooves  78 . 
     Accordingly, the protruding portions  101  of the brackets  100  are inserted into the cutaway grooves  78  of the upper surface  76  of the first metal panel  70 , and the projection welding is performed on the extending portions  102  and the upper surface  76 , whereby the brackets are coupled to the upper surface of the first metal panel. In this case, the protruding portions  101  of the brackets  100  are not protruded from the upper surface  76  of the first metal panel  70  and outer surfaces of the protruding portions  101  of the brackets  100  have a height approximately equal to a height of the upper surface  76  on the circumferential side of the cutaway grooves  78  of the first metal panel  70 , thereby improving an external appearance. 
     The manufacturing method may be used in the manufacture of a metal panel formed on a front surface of the drawer unit in addition to the first metal panel. Accordingly, an upper edge of the drawer unit may also have the same shape as that of the first metal panel. 
     The oven door is configured using the first metal panel manufactured as described above, thereby forming the edge having a different shape from the edge of a conventional oven door to improve an external appearance. Further, since the welding process and the polishing process of the edge can be emitted, it is possible to simplify the manufacturing process and reduce the manufacturing cost. 
     Further, there is an effect of protecting a consumer from accidents by removing the cut surface of the sharp edge portion. 
     In the above-described manufacturing method of a metal panel, a metal plate for general processing, which is made of a relatively inexpensive material with hardness, is manufactured into a case, a metal panel or the like, and brackets are coupled to cutaway grooves of bent edges, thereby removing a sharp edge portion. 
     Thus, when the metal panel produced by the manufacturing method of a metal panel according to the present invention is applied to a panel and a case of electric and electronic products having an external appearance capable of being contacted with the consumer, there is an effect of reducing the manufacturing cost. 
     Although embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.

Summary:
A metal panel, a manufacturing method thereof and a cooking device using the metal panel capable of improving an external appearance of edges, enhancing efficiency of a manufacturing process and reducing the manufacturing cost. The manufacturing method of a metal panel includes cutting a metal plate to form a cutaway portion at a specified area of a border, bending the border on opposite sides of the cutaway portion, and coupling a bracket to a cutaway groove formed at the border by the bending.