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FIELD OF THE INVENTION AND PRIOR ART 
     In the following description, since the door system is identical to the window system, the description of the invention of the window system will be applied to the description of the door system. 
     In the present invention, a sliding window and door system includes a rectangular window frame having upper, lower, left and right members. The rectangular window frame is mounted on a wall, and a rectangular window having upper, lower, left and right members is mounted on the rectangular window frame, thereby preventing dust, water, noise, and heat from coming into the interior of the room. 
     A conventional window and door system will be described hereinafter with reference to the drawings. 
     FIG. 1 shows a front view of a conventional window and door system, and a sectional view taken along line A—A will be illustrated in FIG.  2 . 
     FIG. 2 is a sectional view taken along line A—A of FIG. 1, illustrating a conventional window and door system. 
     The conventional window and door system comprises a lower member  1  on which exposed rails  11  are formed and lower members  2  which are opened and closed while being guided by the rails  11  and mohairmohair members  22 . Rollers  21  are disposed on the rails  11 . 
     PROBLEM TO BE SOLVED BY THE INVENTION 
     In the above described window and door system, since the door or window is opened and closed along the exposed rails, a water drain portion should be formed on the rails. This limits the improvement of airtightness, watertightness, and thermal insulation, deteriorating the energy efficiency. 
     In addition, although it is easy to assemble and disassemble the door or window from the frame because of a simple insertion of the door or window into the frame, there may be a possibility that the window and door can be removed from the frame by a strong wind or when it is opened and closed. Accordingly, when it is used for a multistory building, the removal of the window or door can cause an accident. 
     Since it is not easy to remove dust gathered between the rails and traces of water, the air can be contaminated by the dust when opening and closing the window. When the drain hole formed on the rail is blocked, the water can infiltrate into the interior. 
     The lower member formed in the prominence and depression manner also deteriorates the aesthetic aspect. 
     Therefore, the present invention has been made in an effort to solve the above described problems. It is an object of the present invention to provide a window and door system that can improve airtightness, watertightness, thermal isolation, aesthetic aspect and prevent the window (door) from detaching by providing a flattened rail structure. 
     To achieve the above object, a railless window and door system of the present invention is characterized in that a flat surface member is formed on a window (or door) frame lower member to provide a flat structure, a guide device is provided on the window (or door) frame lower member and window (or door) lower members to provided a railless structure, and since the window (or door) lower members are opened and closed by being guided by the guide devices, the window (or door) lower members are not inadvertently separated from the window frame lower member even when the rollers are operated on the flat surface member. 
     In addition, a railless window and door system of the present invention is further characterized in that to provide a railless structure, guide devices  131  include guide grooves  132  formed on a window (or door) lower member  130  and guide rollers mounted on lower extension portions extended from lower portions  143  of a window (or door) lower members  140   a  and  140   b,  and since the window (or door) lower members  140   a  and  140   b  are opened and closed while being guided by the guide devices  131 , the window (or door) lower members  140   a  and  140   b  are not inadvertently separated from the window (or door) frame lower member  130  even when rollers are driven on the railless surface members. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic view of a conventional window and door system viewed from an outside of a room; 
     FIG. 2 is a sectional view taken along line A—A of FIG. 1; 
     FIG. 3 is a schematic view of a railless window and door system according to the present invention; 
     FIG. 4 is a sectional view taken along line B—B of FIG. 3; 
     FIG. 5 is a sectional view of a guide system of FIG. 4 according to another embodiment of the present invention; 
     FIG. 6 is a sectional view of a guide system of FIG. 4 according to another embodiment of the present invention; 
     FIG. 7 is a schematic view of a window and door system viewed from an outside of a room, in which an outside window (or door) is replaced with a fixed window (or door) according to the present invention; 
     FIG. 8 is a sectional view taken along line C—C of FIG. 7; 
     FIG. 9 is a sectional view taken along line D—D of FIG. 8; 
     FIG. 10 is a schematic view of a window and door system viewed from an outside of a room, in which an inside window (or door) is replaced with a fixed window (or door) according to the present invention; 
     FIG. 11 is sectional view taken along line E—E of FIG. 10; 
     FIG. 12 is a sectional view taken along line F—F of FIG. 10; 
     FIG. 13 is a sectional view taken along line B—B of FIG. 3 according to another embodiment of the present invention; 
     FIG. 14 is a sectional view taken along line C—C of FIG. 5 according to another embodiment of the present invention; and 
     FIG. 15 is a sectional view taken along line D—D according to another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE INVENTION 
     The embodiments of the present invention will be described hereinafter with reference to the accompany drawings. 
     In the following description, the terms “upper,” “lower,” “outside,” and “inside” mean “upper side,” “lower side,” “left side,” and “right side,” respectively. 
     First Embodiment 
     FIG. 3 shows a railless window and door system view from an outside of a room according to the present invention and the sectional view taken along line B—B is shown in FIGS. 4,  5  and  6 . 
     FIG. 4 shows a sectional view of a railless window and door system taken along line B—B of FIG.  4 . 
     To provide a railless structure, a window frame lower member  3  includes guide devices  31  provided with guide grooves  32  and guide inlets  33  for guiding lower extension portions  41  of window lower members  4   a  and  4   b,  and a railless surface  34  for providing a flat structure. 
     The window lower members  4   a  and  4   b  include guide rollers  42  mounted on the lower extension portions  41 , a gasket  43  for preventing the infiltration of water and air into the room, a mohair member groove  44 , mohair members  45  inserted into the mohair member groove  44 , and height adjustable rollers  46  mounted to be disassembled. 
     Since the window lower members  4   a  and  4   b  are opened and closed by the guide devices  31  guiding the guide rollers  42  to be operated in the vicinity of the guide grooves  32  formed in the guide inlets  33 , the window is not separated from the window frame lower member  3  even when the rollers  46  are operated on the railless surface  34 . 
     When separating the window, the guide rollers  42  are first separated from the guide grooves  32  by lowering the height adjustable rollers  46 , then the window is separated. 
     FIG. 4 shows a window separable state in a state where the window is assembled. 
     The railless surface  34  is provided with a molding type slope so that water can be easily expelled out of the system while improving the aesthetic aspect. 
     FIG. 5 is a view similar to FIG. 4 to illustrate another embodiment of the guide devices. 
     In the guide devices  51 , guide rails  52  are formed on the window frame lower member, and sliding member grooves  54  are formed on lower extension portions  53  extended from a lower portion of the window lower members. The sliding member grooves  54  are formed to correspond with each other on the basis of the guide rails mohair members  55  or sliding members  56  are inserted into the sliding member grooves  54  such that the window can slide by the mohair members  55  or the sliding members  56  mounted on left and right sides of the guide rails. 
     FIG. 6 is a view similar to FIG. 4 to illustrate another embodiment of the guide devices. 
     In the guide devices  61 , guide rails  62  are formed on window frame lower members, and guide rollers  64  are provided on lower extension portions  63  extended from the lower portion of the window lower members. The guide rollers  64  are mounted in the vicinity of the guide rails  62 . 
     FIG. 7 shows a schematic view of a window and door system viewed from an outside of a room, in which an outside window (or door) is replaced with a fixed window (or door) according to the present invention. The sectional views taken along lines C—C and D—D of FIG. 7 are shown in FIGS. 8 and 9, respectively. 
     FIG. 8 is a sectional view taken along line C—C of FIG. 7, in which the outer window  4   a  depicted in FIG. 4 is replaced with a fixed window  8 . 
     To replace the outer window  4   a  of FIG. 4 with the fixed window  8 , a window frame lower member  7  is provided with a fixed window groove  71  on which the fixed window  8  is mounted and a railless surface  72  designed to easily expel water out of the window. After mounting the fixed window  8  on the fixed window groove  71 , silicon members  81  are used as a final material. 
     FIG. 9 shows a sectional view taken along line D—D of FIG. 7, in which a fixed window groove cover  73  is mounted on a section where the fixed window  8  is not mounted. 
     FIG. 10 shows a schematic view of a window and door system viewed from an outside of a room, in which an inner window (or door) is replaced with a fixed window (or door) according to the present invention. Sectional views taken along lines E—E and F—F of FIG. 10 are shown in FIGS. 11 and 12, respectively. 
     FIG. 11 shows a sectional view taken along line E—E of FIG. 10, in which the inner window  4   b  depicted in FIG. 4 is replaced with a fixed window. 
     To replace the inner window  4   b  with the fixed window  10 , the window lower member  9  is provided with a fixed window groove  91  for mounting the fixed window  10   a  and a railless surface  92  formed to easily expel water. The fixed window  10  is mounted on the fixed window groove  91  and finalized by silicon members  101 . 
     FIG. 12 shows a sectional view taken along line F—F of FIG. 10, in which a fixed window groove cover  93  is mounted on a section where the fixed window  10  is not mounted. 
     Second Embodiment 
     FIG. 13 shows a sectional view of a railless window and door system taken along line B—B of FIG. 4 according to another embodiment of the present invention. 
     To provide a railless structure, a window frame lower member  130  includes guide devices  131  provided with guide grooves  132  and a railless surface  134  on which a molding type slope having an outward trajectory  133  is used as a water outlet. Guide groove covers  135  are formed covering the guide grooves  132 . The guide devices  131  are further provided with guide inlets  136  for guiding lower extension portions  141  of the window. Roller support grooves  137  are provided to mount roller support members  138  that can prevent the surface  134  or the cover  135  from being damaged by rollers  142  when the windows  140   a  and  140   b  are opened and closed. Gaskets  139  are provided to prevent water from infiltrating into the guide grooves  132 , and mohair members  130   a  are provided to prevent interior air from going out of the room. A lower rail  130   b  is formed to mount a mothproof window. 
     Window lower members  140   a  and  140   b  include guide rollers  42  mounted on the lower extension portions  141 . Height adjustable rollers  142  for adjusting opening/closing height of the window are formed on the lower portions of the window lower members  140   a  and  140   b.  Gaskets  145  and mohair members  146  are provided to prevent the flow of air and water. 
     Since the windows are opened and closed by the guide devices  131  guiding the guide rollers  142  to be operated in the vicinity of the guide grooves  132 , the window is not inadvertently separated from the window frame lower member  131  even when the rollers  142  are operated on the railless surface  134  or cover  135 . 
     FIG. 14 shows a sectional view taken along line C—C of FIG. 14, in which the outer window  140   a  depicted in FIG. 13 is replaced with a fixed window  160  according to another embodiment of the present invention. 
     To replace the outer window  140   a  with a fixed window  160 , the window frame lower member  150  is provided with a fixed window groove  151  to mount the fixed window and railless surfaces  152  for easily expelling water out of the surface  152 . The fixed window  160  is mounted on the fixed window groove  151  and finalized by silicon members  161 . 
     FIG. 15 shows a sectional view taken along line D—D of FIG. 5, in which a section of a fixed window groove  151  on which the fixed window  160  is not mounted is covered by a fixed window groove cover  153 . 
     EFFECT OF THE INVENTION 
     As described above, since the window frame lower members  4   a  and  4   b  are opened and closed while being guided by the guide devices  31 , the rollers  46  can be operated on a railless flat surface  34 . 
     Accordingly, since the water drain hole which has been required in the conventional rail structure is not necessary, improvements in the airtightness and water tightness occur. It is easy to remove collected dust, making the surface clean. Furthermore, the sloped surface smoothly expels water out of the frame, thus damage caused by the water can be prevented. 
     In addition, since the window is not inadvertently removed from the frame, safety can be improved. 
     Since a gap between the window frame lower member and the window lower member is sealed by the gasket and mohair members, the airtightness, watertightness, and thermal insulation can be greatly improved. 
     Since the surface is formed with a smooth molding type, the aesthetic aspect can be improved, thereby providing a high quality window and door system.

Summary:
The present invention relates to an improved lower member of a sliding window and door system, and it is an object of the present invention to provide a convenient, safe and high quality window and door system by solving problems of the conventional window and door system. To provide a flat structure of a railless window and door system of the present invention, a surface member is formed on a window (or door) frame lower member, and to provide a railless structure, a guide device is provided on the window (or door) frame lower member and the window (or door) lower member such that the window (or door) lower member is not inadvertently separated from the window (or door) frame lower member even when the roller is driven on the railless surface member as the window (or door) lower member is guided by the guide device.