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CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2014-0021779, filed on Feb. 25, 2014, the disclosure of which is hereby incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a window/door system with a flat track and more particularly, to a window/door system with a flat track having a “         ”-shaped roller support in which the roller support in a cross sectional shape of “         ” having one side being open is used, to provide a nice appearance and to improve air-tightness and water-tightness by reducing the number of grooves shown on a window/door frame when a window/door is opened. 
         [0004]    2. Description of the Related Art 
         [0005]    Generally, a window or door (hereinafter, referred to as a window/door) installed in a building enables people inside to view the outside and has the functions of blocking noise, air and heat flow between the inside and outside. Further, a window/door ventilates polluted indoor air when it is open. A window/door is installed in a window/door frame in a certain size in the form of a sliding or hinged window/door. Following the trend that buildings have been luxurious, many different window/door systems have been developed for use to be easily maintained and managed, to be nice in appearance and to have functionality such as a security function. 
         [0006]    In a conventional window/door system, a window/door frame exposes rail grooves where rails are installed and protrude, to allow a window/door to be opened or closed in a sliding motion. However, when people walk passing the rail grooves formed in the door frame, the rail grooves may be a dangerous obstruction causing them to stumble. Furthermore, since dust or any other foreign materials collect in the rail grooves, it is not easy to clean such dirty rail grooves. Specially, in a case where the window/door system is installed in a veranda, since a draft or rainwater easily comes into through the exposed rail grooves, the flow-tightness (air tightness, soundproof and drainage) is greatly reduced. When typhoon or heavy rain occurs, rainwater may flow inward. 
         [0007]    Technology to solve the aforementioned problems has been presented in Korean Patent Nos. 167124 and 324496. However, since the structures presented in these patents are complicated, it is very difficult to connect and separate the window/door to and from the rail grooves. Further, since no structure to drain rainwater is specially provided, drainage is not good and rainwater flows backward to the inside. Furthermore, since the structure to block a draft is too simple, it is difficult to block drafts. 
         [0008]    The applicant (inventor) of the present invention has repeated the research and development to solve not only the aforementioned problems but also many problems indicated during directly building window/door systems. As a result, the applicant (inventor) obtained Korean Patent Nos. 901994, 1055326 and 1216681 on the technology developed in relation to a rail-covered window/door system wherein a rail covering panel is mounted above rails giving a flat track look. According to this technology, the rails on which a window/door is sliding are not exposed to the outside. Furthermore, while the applicant (inventor) is now directly constructing a window/door system, he continues to develop a window/door system to improve air tightness, water tightness and heat insulation property and to be nice in appearance. The present invention has been also drawn during a series of such research and development. 
       SUMMARY OF THE INVENTION 
       [0009]    Therefore, it is an object of the present invention to solve the above problems and to provide a window/door system with a flat track having “         ”-shaped roller supports in which the roller support is structured to have a cross sectional shape of “         ” having one side being open, thereby providing a nice appearance and improving air tightness and water tightness by reducing the number of grooves exposed between a window/door frame and a rail covering panel when the window/door is opened. 
         [0010]    In accordance with an embodiment of the present invention, there is provided a window/door system with a flat track which comprises; a rail unit stably positioned lengthwise in a window/door frame, the rail unit including a rail panel in a flat shape, rails to allow the window/door to move in the sliding motion on the rail panel, and a rail cover joining channel expending to protrude upward from a top surface of the rail panel; a “         ”-shaped roller support including rollers, a roller mounting section in a lower position under which the rollers are mounted, a window/door connecting section in a upper position, and a connection section connecting one end of the roller mounting section and one end of the window/door connecting section to each other, thereby forming a cross sectional shape of “         ” which is open at one side, wherein a pair of the roller supports is installed such that the open sides of the “         ” shapes face each other and the rollers are stably positioned on the rails of the rail unit; a rail cover having: a rail covering panel and rail cover joining flanges extending to protrude downward under the rail covering panel and to securely fit into the rail cover joining channel of the rail unit, wherein the rail cover is poisoned between in each “         ”-shaped roller support installed to face each other such that the rail covering panel is positioned within each roller mounting section and each window/door connecting section; and a window/door to be securely connected by mounting a lower part of a window/door sash on the window/door connecting section. 
         [0011]    Preferably, a pair of the window/door frames is installed, an insulator is integrally inserted between the pair of the window/door frames, and an insulation cap above the insulator is inserted to fit into the pair of the window/door frames, 
         [0012]    Preferably, each window/door frame comprises: a pair of side parts positioned vertically, a connection part connecting lower ends of the side parts, rail unit connecting protrusions extending to protrude inward from the side parts above the connection part such that both ends of the rail panel of the rail unit are secured, and gasket receiving grooves formed to face each other in inner surfaces of upper ends of the side parts. 
         [0013]    Preferably, the window/door connecting section of the roller support includes a mounting opening where mohair or a gasket is inserted to be mounted, and the top surface of the rail covering panel includes an indent formed at the position where the mohair or the front end of the gasket is in contact. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
           [0015]      FIG. 1  is a side cross-sectional view of a window/door system according to an embodiment of the present invention, which is applied to a double window/door structure; 
           [0016]      FIG. 2  is an exploded view of a lower part of the window/door system of  FIG. 1 ; 
           [0017]      FIG. 3  is a top cross sectional view of the window/door system of  FIG. 1 ; and 
           [0018]      FIG. 4  is a side cross-sectional view of the window/door system according to the embodiment of the present invention, which is applied to a single window/door structure. 
       
    
    
       [0019]      
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 [Description of numbers for constituents in drawings] 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 10: window/door frame 
                   
               
               
                   
                 13: rail unit connecting protrusion 
               
               
                   
                 14: gasket receiving groove 
                 15: gasket 
               
               
                   
                 16: insulator 
                 17: insulation cap 
               
               
                   
                 20: rail unit 
                 21: rail panel 
               
               
                   
                 22: window/door weight support 
                 23: rail 
               
               
                   
                 24: rail cover joining channel 
               
               
                   
                 30: roller support 
                 31: roller 
               
               
                   
                 32: roller mounting section 
               
               
                   
                 33: window/door connecting section 
               
               
                   
                 34: guide protrusion 
                 35: gasket supporting 
               
               
                   
                   
                 protrusion 
               
               
                   
                 38: mohair 
               
               
                   
                 40: rail cover 
                 41: rail covering panel 
               
               
                   
                 42: rail cover joining flange 
               
               
                   
                 50: window/door 
                 51: window/door sash 
               
               
                   
                 52: glass 
               
               
                   
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0020]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which the preferred embodiments of the invention are shown so that those of ordinary skill in the art can easily carry out the present invention. 
         [0021]    The greatest technical characteristic of a window/door system with a fiat track according to the present invention is that a roller support is manufactured to have a cross sectional shape of “         ”. According to the present invention, the appearance is nice and the air tightness and water tightness are improved by decreasing the number of grooves (gaskets) exposed to be shown between a window/door frame and a rail covering panel to one (1) per window/door when the window/door is opened. 
         [0022]    In this application of the present invention, the “flat track” means a rail covering structure in that rails on which the window/door slides are not shown in the window/door system since the rails are covered by the rail covering panel. According to this structure, the rails are never shown to the outside and only the top surface of the rail covering panel in a flat shape is shown when the window/door is open. 
         [0023]    The window/door system according to the present invention has a basic constitution comprising: a window/door frame  10  fixedly installed in a building; a rail unit  20  fixedly connected to an inside of the window/door frame  10 ; a roller support  30  stably held and slid on the rail unit  20 ; a rail cover  40  connected to the rail unit  20  and secured in position to cover a rail; and a window/door  50  secured on the rail cover  40  and the roller support  30 . 
         [0024]    The window/door frame  10  is fixedly installed in the building. The window/door frame  10  to be vertically positioned includes a pair of side parts  11  forming both side walls, and a connection part  12  connecting lower ends of the side parts  11  to each other. A cross section of the window/door frame  10  has a rectangular shape which is open upward. Gasket receiving grooves  14  are formed to face each other in the inner surfaces of the upper ends of the side parts  11 . Rail unit connecting protrusions  13  each extend to protrude inward from the side parts  11  lengthwise, above the connection part  12 , so that both ends of a rail panel  21  of the rail unit  20  are connected to the rail unit connecting protrusions  13 , respectively. 
         [0025]    In the case of a double window/door structure, as shown in  FIG. 1 , one pair of the window/door frames  10  is installed inside and the other pair of the window/door frames  10  is installed outside. An insulator  16  is integrally inserted between each pair of the window/door frames  10  lengthwise. An insulation cap  17  is inserted to be secured on the insulator  16  between the window/door frames  10 , so that the insulator  16  is not exposed upward. 
         [0026]    The rail unit  20  is stably positioned lengthwise and fixedly secured inside the window/door frame  10 . The rail unit  20  comprises: the rail panel  21  in a flat shape, rails  23  positioned on the rail panel  21  to allow the window/door  50  to slide, and a rail cover joining channel  24  extending to protrude upward from the rail panel  21  to be connected to rail cover joining flanges  42  of the rail cover  40 . The rail unit  20  further comprises a pair of window/door weight supports  22  to safely support the weight of the window/door  50  to be mounted on and to be connected to the rail unit  20 . The window/door weight supports  22  extend downward from the under surface of the rail panel  21  lengthwise and are spaced apart from each other at a proper distance. It is desirable that the window/door weight supports  22  are supported on the connection part  12  of the window/door frame  10 . 
         [0027]    The rails  23  are positioned lengthwise an either side of the rail cover joining channel  24 . It is preferable that one pair of the rails  23  is positioned at one side of the rail cover joining channel  24  and the other pair of the rails  23  is positioned at the other side of the rail cover joining channel  24  in consideration of safety. The cross section of the rail cover joining channel  24  has an “H” shape. The opposite inner surfaces of the rail cover joining channel  24  include notches, respectively. Protrusions formed on the outer surfaces of the rail cover joining flanges  42  of the rail cover  40  are fit into the notches of the rail cover joining channel  24  by a one-touch manner (see  FIG. 2 ). 
         [0028]    The roller support  30  comprises: a window/door connecting section  33 , a roller mounting section  32 ; and a connection section (not indicated by a drawing reference number) connecting one end of the window/door connecting section  33  and one end of the roller mounting section  32  to each other. Accordingly, the window/door connecting section  33 , the roller mounting section  32  and the connection section between the window/door connecting section  33  and the roller mounting section  32  forms a cross sectional shape of “         ” which is open at one side, In the roller support  30 , rollers  31  are mounted, at equal intervals, under the roller mounting section  32 . A pair of the roller supports  30  is mounted in one window/door frame  10  such that the open sides of the “         ” shapes face each other and the rollers  31  are stably positioned on the rails  23  of the rail unit  20 . The rollers  31  may be mounted in one (1) row (single roller) under the roller mounting section  32  but it is desirable that the rollers  31  are mounted in two (2) rows (a plurality of rollers) in consideration of safety. 
         [0029]    The roller support  30  includes a gasket supporting protrusion  35  extending outward from an outer surface of the connection section positioned between the window/door connecting section  33  and the roller mounting section  32 . A gasket  15  has an upper end being bent in the form of “         ” The gaskets  15  are connected in the gasket receiving grooves  14  formed in the inner surfaces of the upper ends of the side parts  11  of the window/door frame  10 . When the window/door system is assembled, the bent end of the gasket  15  is positioned on the gasket supporting protrusion  35  to be locked with each other. Accordingly, the end of the gasket  15  is prevented from slipping into the gap between the side part  11  and the roller support  30 , thereby improving the seal, air tightness and water tightness between the side parts  11  of the window/door frame  10  and the roller support  30 . 
         [0030]    When the window/door system with the flat track is assembled, the grooves where the gaskets  15  are positioned are exposed lengthwise between the side parts  11  of the window/door frame  10  and the ends of the roller supports  30 . In the present invention, since the roller supports  30  in the “         ” shape are used, only two (2) lines of the grooves which are formed at both ends lengthwise are shown per window/door frame  10 , thereby providing a nice appearance and improving the water tightness and air tightness. However, in a case where a “□”-shaped roller support is used, the grooves in two (2) lines are shown along the both ends of each roller support and therefore, a total of four (4) lines of the grooves are shown per window/door frame  10 . In this case, the appearance is not good and the water tightness and air tightness are lowered since the number of the grooves is increased, 
         [0031]    The rail cover  40  comprises: a rail covering panel  41  in a flat shape; and a pair of rail cover joining flanges  42  extending downward from the rail covering panel  41 . The rail cover joining flanges  42  are stably connected with the rail cover joining channel  24  of the rail unit  20  so that the rail cover  40  is secured to cover the rails  23  not to be shown upward. The rail covering panel  41  is positioned between and in each roller supports  30  which are installed such that the opening sides of the roller supports  30  face each other. That is, the rail covering panel  41  is positioned within the window/door connecting sections  33  and the roller mounting sections  32  (see  FIG. 1 ). 
         [0032]    The window/door connecting section  33  of the roller support  30  includes mounting openings where mohair  33  or gaskets are inserted to be mounted. On the rail covering panel  41 , indents  41   a  are formed at the places where the mohair  36  or the front ends of the gaskets are in contact. When the window/door system is assembled, the mohair  36  or the front ends of the gaskets are inserted into the indents  41   a , thereby filling the gap between the under surface of the window/door connecting section  33  of the roller support  30  and the top surface of the rail covering panel  41  and therefore improving the seal, air tightness and water tightness. Mohair or gaskets may be mounted in one roper support  30  in one (1) or two (2) rows. When these are mounted in two (2) rows, the mohair (or gaskets) may be mounted in all of the two (2) rows or the mohair may be mounted in one (1) row and the gaskets may be mounted in the other one (1) row. 
         [0033]    The window/door  50  is fixedly connected by mounting a lower section of a window/door sash  51  on the window/door connecting section  33  of the roller support  30 . Drawing reference number  52  not described indicates glass. 
         [0034]    Guide protrusions  34  protrude and extend upward and obliquely at both ends of the window/door connecting section  33  of the roller support  30 , to guide a location of connecting the window/door sash  51 . Since the guide protrusions  34  are formed, the window/door  50  can be easily mounted and assembled at the correct location. 
         [0035]      FIG. 4  shows the window/door system with the flat track according to the present invention is used in a single window/door structure. The window/door system with the flat track used in the single window/door structure is identical with that used in the double window/door structure as shown in  FIG. 1 , except for only the insulator  16  and the insulation cap  17  installed between the window/door frames  10 . 
         [0036]    In the window/door system with the flat track as characterized above, since the cross section shape of the roller support is “         ” which is opened at one side, only one (1) groove is exposed lengthwise between the window/door frame and the rail covering panel per window/door when the window/door is opened. Therefore, the appearance is nice in comparison with the conventional window/door system with the flat track where two ( 2 ) grooves are exposed per window/door. Further, since the number of the grooves to be exposed decreases, the air tightness and water tightness are improved. Additionally, since the number of the grooves to be exposed is reduced, the number of the gaskets to be inserted into the grooves is reduced, the material costs required in manufacturing and the management and maintenance costs can be reduced. 
         [0037]    The invention has been described using preferred exemplary embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Summary:
There is provided a window/door system with a flat track having “         ”-shaped roller supports to provide a nice appearance and to improve air tightness and water tightness by reducing the number of grooves exposed on a window/door frame when a window/door is opened, by using the roller supports in a cross sectional shape of “