Abstract:
The invention relates to a computer desk with a drawer connected with elbow support boards. The drawer capable of being pushed and pulled is arranged under a desk panel, and the left top and the right top of a drawer panel are internally provided with a left elbow support board and a right elbow support board respectively which are articulated with the long horizontal edge thereof. The drawer is internally provided with a two-sided keyboard supporting seat, and the inner side of a thick lath on the right side of the two-sided keyboard supporting seat is articulated with a mouse board. Furthermore, the upper sides of the left and right elbow support boards and the mouse board are as high as that of the desk panel. Therefore, the computer desk can not only avoid hunchback and myopia when people work at desk as well as muscle pain at the neck and the is shoulder due to suspended elbows when a computer keyboard and a mouse are operated by people so as to make people feel comfortable, but also be provided with a notebook computer for operation, with lower manufacturing cost.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a computer desk with a drawer connected with elbow support boards, specifically applicable to desks in offices and at home. 
       TECHNICAL BACKGROUND 
       [0002]    For people working at a traditional desk for a long time, hunchback and myopia are easily caused as both forearms and elbows are supported on a rectangular desk panel during writing; furthermore, the elbows hang and the upper body leans forward when people operate a computer keyboard and a mouse, and muscles of the neck and the shoulder serve under tension, thus resulting in muscle pain at the neck and the shoulder. 
         [0003]    In recent years, the left and right elbow support boards as high as the desk panel extend from the edge of the desk panel at one side of a desk (a computer is arranged at the desk panel thereof) close to a human body, to ensure that both forearms and elbows are respectively supported on the left and right elbow support boards to facilitate people to operate the computer keyboard and the mouse on the desk panel or write on the desk panel, thereby being capable of avoiding hunchback and myopia as well as muscle pain at the neck and the shoulder and making people feel comfortable in the operation of the mouse. However, wrists need to upwarp or forearms need to lift to operate the keyboard as the upper surface of the computer keyboard is higher than the desk panel. Fatigue is also incidental to wrists and the forearms, and even muscle pain possibly occurs at the neck and the shoulder. 
       SUMMARY OF THE INVENTION 
       [0004]    The invention aims at improving the prior desks and providing a computer desk with a drawer connected with elbow support boards. A hinge is used for connecting the left and right elbow support boards at the inner side of the top of the drawer, and the left and right elbow support boards are supported on the top in a suspended arm manner, capable of turning up by 180 degrees, while a mouse board is connected on the two-sided keyboard supporting seat. The upper surfaces of the mouse board and the desk panel are as high as the upper surfaces of the left and right elbow support boards. Furthermore, the upper surface of the computer keyboard arranged on the two-sided keyboard supporting seat and the upper face of the mouse board are of the same height. 
         [0005]    The invention adopts the following technical proposal: 
         [0006]    The invention relates to a computer desk with a drawer connected with elbow support boards, and the drawer capable of being pushed and pulled is arranged under a desk panel. The left top and the right top of a drawer panel are internally provided with a left elbow support board and a right elbow support board respectively which are articulated with the long horizontal edge thereof. The drawer is internally provided with a two-sided keyboard supporting seat, and a mouse board is articulated at the right side of the two-sided keyboard supporting seat. Furthermore, the upper sides of the left and right elbow support boards and the mouse board are as high as that of the desk panel. 
         [0007]    The invention relates to a computer desk with a drawer connected with elbow support boards, and the drawer capable of being pushed and pulled is arranged under a desk panel. The left top and the right top of a drawer panel are internally provided with a left elbow support board and a right elbow support board respectively which are articulated with the long horizontal edge thereof. The drawer is internally provided with a two-sided keyboard supporting seat. A mouse board, which is articulated with one side of a right clapboard, is arranged on the left side at the top of the right clapboard of the drawer. Furthermore, the upper sides of the left and right elbow support boards and the mouse board are as high as that of the desk panel. 
         [0008]    The invention relates to a computer desk with a drawer connected with elbow support boards, and the drawer capable of being pushed and pulled is arranged under a desk panel. The left top and the right top of a drawer panel are internally provided with a left double-layer elbow support board and a right double-layer elbow support board respectively which are articulated with the long horizontal edge thereof. The drawer is internally provided with a keyboard supporting seat, and the inner side of a thick lath on the right side of the keyboard supporting seat is articulated with a mouse board. Furthermore, the right double-layer elbow support board consists of a right lower board and a right upper board, while the right double-layer elbow support board is composed of a left lower board and a left upper board. 
         [0009]    On the drawer panel, a hinge capable of being turned by 180 degrees is used for connecting the left elbow support board with the right elbow support board. 
         [0010]    On the inner side of the thick lath on the right side of the two-sided keyboard supporting seat, a hinge capable of being turned by 180 degrees is used for connecting the mouse board. 
         [0011]    A thick lath of the same thickness is connected at the upper of the left and right sides of the two-sided keyboard supporting seat respectively, while a pair of same left and right rectangular vertical struts are connected with the left and right sides of the two-sided keyboard supporting seat. 
         [0012]    On the drawer panel, a hinge capable of being turned by 180 degrees is used for connecting the left elbow support board with the right elbow support board. 
         [0013]    On the right clapboard of the drawer, a hinge capable of being turned by 180 degrees is used for connecting a mouse board. 
         [0014]    A pair of same left and right rectangular vertical struts are connected with the left and right sides of the two-sided keyboard supporting seat. 
         [0015]    On the drawer panel, a hinge capable of being turned by 180 degrees is used for connecting the left double-layer elbow support board and the right double-layer elbow support board. 
         [0016]    On the inner side of the thick lath at the right side of the keyboard supporting seat, a hinge capable of being turned by 180 degrees is used for connecting the mouse board. 
         [0017]    The keyboard supporting seat is composed of a rectangular board, thick laths and vertical struts. A thick lath of the same thickness is connected at the upper sides of the left and right sides of the keyboard supporting seat respectively while the vertical strut of the same height is connected at the lower sides thereof respectively. 
         [0018]    The left section of the drawer panel is provided with a left inner board which is connected with a dovetail groove in a sliding manner; and a hinge is used for connecting a left lower board at the inner side of the top of the left inner board. 
         [0019]    The keyboard supporting seat is articulated at a thickened lath outside the mouse board. 
         [0020]    A lath is connected at the upper side of the inner surface of the drawer panel. 
         [0021]    Four parallel connecting bars are articulated at the front and rear positions of the left and right sides between the right lower board and the right upper board. In the same manner, the left lower board and the left upper board are also articulated by four similar parallel connecting bars. 
         [0022]    The upper surfaces of the right lower board and the left lower board are provided with four through holes at intervals and four separate cylindrical platforms on the top of which pin holes are arranged; the lower surfaces of the right upper board and the left upper board are provided with four separate holes and four separate cylindrical platforms while the tops of the cylindrical platforms are respectively provided with a convex pin. 
         [0023]    The invention has the advantages that the computer desk can not only avoid hunchback and myopia when people work at desk as well as muscle pain at the neck and the shoulder due to suspended elbows when a computer keyboard and a mouse are operated by people so as to make people feel comfortable and untired without need to upwarp wrists or lift forearms, but also be provided with a notebook computer for operation, with no reduction in a space for the knees under the desk and lower manufacturing cost. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Drawing  1  is the three-dimensional drawing of the first embodiment of the invention in the status of operating a desktop computer. 
           [0025]    Drawing  2  is the drawer drawing of the first embodiment of the invention with the left and right elbow support boards and the mouse board turned to the status of operating the desktop computer. 
           [0026]    Drawing  3  is the drawer drawing of the first embodiment of the invention with the left and right elbow support boards and the mouse board turned to a hidden status. 
           [0027]    Drawing  4  is the three-dimensional drawing of the first embodiment of the invention in the status of writing and reading. 
           [0028]    Drawing  5  is the positive three-dimensional drawing of the two-sided keyboard supporting seat in the first embodiment of the invention with the mouse board folded up during the operation of the desktop computer. 
           [0029]    Drawing  6  is the positive three-dimensional drawing of the two-sided keyboard supporting seat in the first embodiment of the invention with the mouse board unfolded during the operation of the desktop computer. 
           [0030]    Drawing  7  is the opposite three-dimensional drawing of the two-sided keyboard supporting seat in the first embodiment of the invention with the mouse board folded up during the operation of a notebook computer. 
           [0031]    Drawing  8  is the three-dimensional drawing of a drawer structure in the first embodiment of the invention. 
           [0032]    Drawing  9  is the three-dimensional drawing of the second embodiment of the invention in the status of operating a computer. 
           [0033]    Drawing  10  is the drawer drawing of the second embodiment of the invention with the left and right elbow support boards and the mouse board turned to the status of operating the computer. 
           [0034]    Drawing  11  is the drawer drawing of the second embodiment of the invention with the left and right elbow support boards and the mouse board turned to a hidden status. 
           [0035]    Drawing  12  is the three-dimensional drawing of a drawer structure in the second embodiment of the invention. 
           [0036]    Drawing  13  is the positive three-dimensional drawing of a two-sided keyboard supporting seat in the second embodiment of the invention. 
           [0037]    Drawing  14  is the opposite three-dimensional drawing of a two-sided keyboard supporting seat in the second embodiment of the invention. 
           [0038]    Drawing  15  is the three-dimensional drawing of the third embodiment in the status of operating a computer. 
           [0039]    Drawing  16  is the vertical view of the third embodiment in the status of writing and reading. 
           [0040]    Drawing  17  is the A-A cutaway view of the Drawing  16 . 
           [0041]    Drawing  18  is the drawer drawing of the third embodiment of the invention with the left and right elbow support boards turned to a hidden status. 
           [0042]    Drawing  19  is the drawer drawing of the third embodiment of the invention with the left and right elbow support boards turned to the status of operating the computer or the status of writing and reading. 
           [0043]    Drawing  20  is the three-dimensional drawing of the fourth embodiment of the invention in the status of operating a desktop computer. 
           [0044]    Drawing  21  is the drawer drawing of the fourth embodiment of the invention with the left and right double-layer elbow support boards and the mouse board turned to the status of operating the desktop computer. 
           [0045]    Drawing  22  is the drawer drawing of the fourth embodiment of the invention with the left and right elbow support boards and the mouse board turned to a hidden status. 
           [0046]    Drawing  23  is the three-dimensional drawing of the fourth embodiment of the invention in the status of writing and reading. 
           [0047]    Drawing  24  is the lateral view of the fourth embodiment of the invention with the left double-layer elbow support board connected with the drawer panel. 
           [0048]    Drawing  25  is the three-dimensional drawing of the keyboard supporting seat in the fourth embodiment of the invention with the mouse board folded up. 
           [0049]    Drawing  26  is the three-dimensional drawing of the keyboard supporting seat in the fourth embodiment of the invention with the mouse board unfolded. 
           [0050]    Drawing  27  is the lateral view of the fourth embodiment of the invention with the left double-layer elbow support board connected with the drawer panel. 
           [0051]    Drawing  28  is the status drawing of the fourth embodiment of the invention with the right double-layer elbow support board higher than the desk panel during the operation of the notebook computer. 
           [0052]    Drawing  29  is the cutaway view of the fourth embodiment of the invention with the right upper board contacting the right lower board. 
           [0053]    Drawing  30  is the cutaway view of the fourth embodiment of the invention with the right upper board disconnected with the right lower board. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0054]    The first embodiment of the invention is composed of a drawer  1 , a supporting rack  2 , a desk panel  3 , a right elbow support board  4 , a left elbow support board  5 , a mouse board  6  and a two-sided keyboard supporting seat  7 , which is shown in Drawings  1  to  8 , wherein: 
         [0055]    The drawer  1  is arranged under the desk panel  3  supported by the supporting rack  2  and faces a sitting operator. Furthermore, the drawer  1  is arranged on a longitudinal guide rail that is arranged under the desk panel  3 , which is not shown in the drawings. The drawer  1  can be pushed and pulled forward towards the sitting operator; a drawer panel  11  is arranged in front of the drawer  1  the right and left sides of which are respectively provided with a drawer side board  12 . A pair of parallel slider boards  13  are fixedly arranged at the front end of the inner side of the drawer side boards  12  at intervals. Moreover, the left drawer side board  12  is internally provided with a stop board  14 , wherein the top part of the drawer panel  11  is higher than that of the front section of the drawer side board, which is shown in Drawing  8 . What are mentioned above pertain to the prior art. 
         [0056]    The right elbow support board  4  is a single-layer elbow support board with a vertical side edge as the right side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the left side edge thereof. On the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the right elbow support board  4  at the inner side of the right top of the drawer panel  11  of the drawer  1 ; in the same manner, the left elbow support board  5  is formed by a vertical side edge as the left side edge, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge 
         [0057]    When the keyboard of a desktop computer is arranged on the upper (positive) surface of the two-sided keyboard supporting seat  7  both the positive and opposite surfaces of which can be applied, the surfaces  721  of the left and right vertical struts are supported on the top surfaces of the corresponding slider boards  13  in a sliding manner while the rear end surface of the mouse board  6  that is turned on the right thick lath  71  presses against the front end of the desk panel  3  (at one side of the drawer panel  11 ), which is shown in Drawings  1  and  6 . Therefore, the two-sided keyboard supporting seat  7  is fixed in a position opposite to the desk panel  3 , so as to facilitate people to stably operate the keyboard of the desktop computer; 
         [0058]    When the two-sided keyboard supporting seat  7  is turned by 180 degrees to ensure a notebook is arranged on the lower surface (reverse side) thereof, the top surfaces  722  of the left and right vertical struts can be supported on the top surfaces of the corresponding slider boards  13  in a sliding manner while the outer sides of the left and right blocks  73  press against the front end of the desk panel  3  (at one side of the drawer panel  11 ), which is shown in Drawing  7 . Therefore, the two-sided keyboard supporting seat  7  is fixed in a position opposite to the desk panel  3 , so as to facilitate people to stably operate the keyboard of the notebook computer; 
         [0059]    When the desk is not used for operation, the right elbow support board  4  and the left elbow support board  5  are folded up in the drawer  1 , which is shown in Drawing  3  (the right elbow support board  4  and the left elbow support board  5  are positioned above the left and right drawer side boards  12  and the left and right slider boards  13 , or arranged above the space between the inner sides of the left and right slider boards  13 ). 
         [0060]    When the desk is prepared for operation including writing and reading or operating a computer, the drawer  1  is firstly pulled out and the right and left elbow support boards are unfolded; in other words, the right elbow support board  4  and the left elbow support board  5  are turned up by 180 degrees around the pivot of the hinge; and the right elbow support board  4  and the left elbow support board  5  are supported on the top surface of the drawer panel  11 , and the upper surfaces of the left and right elbow support boards are of the same height and as high as (or slightly higher than) the upper surface of the desk panel  3 , which is shown in Drawing  4 . The right forearm and the elbow of an operator are supported on the right elbow support board  4  while the left forearm and the elbow thereof are supported on the left elbow support board  5 , and the hinge and the top surface of the drawer panel  11  bear the pressure and the turning torque caused therefrom, thereby obtaining stable and reliable support; when the operator stops operation, the elbow support boards are turned by 180 degrees in the opposite direction and put into the drawer  1 ; and finally, the drawer  1  is pushed into the lower part of the desk panel  3 . Therefore, the turning of the right elbow support board  4  and the left elbow support board  5  does not occupy the space under the drawer  1 . 
         [0061]    When the desk panel is used for writing, reading, etc., the two-sided keyboard supporting seat  7  is positioned at the rear position of the drawer  1  and supported on a drawer bottom board and the mouse board  6  is unfolded on the two-sided keyboard supporting seat  7 . Furthermore, the left and right thick laths  71  are at the same level and a computer keyboard can be arranged on the upper surfaces thereof (not shown in the drawings), which is shown in Drawings  3  and  5 ; and the drawer  1  is positioned under the desk panel  3 , which is shown in Drawing  4 . 
         [0062]    When the desk is used for the operation of a desktop computer, the drawer  1  is pulled out firstly and the left and right elbow support boards are unfolded, and then the two-sided keyboard supporting seat  7  slides forward to be lifted and supported on the top surface of the slider boards  13  from the position above the drawer bottom board at the rear side of the drawer  1  (the slider boards can be replaced by guide rails of the same height relation); the mouse board  6  is turned up by 180 degrees around the pivot of the hinge and positioned on the thick lath  71  which is turned to the right side of the two-sided keyboard supporting seat  7 , and the upper surface (namely, the bottom surface of a mouse) of the mouse board  6  (containing a mouse pad) is as high as (or slightly lower than) the upper sides of the right elbow support board  4  and the left elbow support board  5  while the mouse is arranged on the upper surface thereof (not shown in the drawings), which is shown in Drawings  2  and  6 ; the keyboard of the desktop computer is arranged on the upper surface of the keyboard supporting seat  7  between the left and right thick laths  71  (generally, the is keyboard is arranged in an inclined manner, which is not shown in the drawings); furthermore, the upper surface of the keyboard, namely the top surface of buttons, is approximately as high as (or slightly lower than) the upper surfaces of the right elbow support board  4  and the left elbow support board  5  so as to ensure that the keyboard is operated without need to upward wrists and lift forearms. In addition, the top surface  722  of the left vertical strut presses against the lower part of a stop board  14  of the drawer  1 , thereby preventing the left vertical strut from turning in the operation of the mouse board  6 , which is shown in Drawing  1 . 
         [0063]    When the desk is used for the operation of a notebook computer, only the two-sided keyboard supporting seat  7  is turned by 180 degrees to make the lower surface (reverse side) thereof be upward, and the notebook computer is arranged on the keyboard supporting seat; and the top surfaces  722  of the left and right vertical struts  72  slide forwards to be lifted and supported on the top surfaces of the slider boards  13  while the upper surfaces of the right elbow support board  4  and the left elbow support board  5  are as high as (or slightly higher than) the upper surfaces of the desk panel and the keyboard of the notebook computer, which is shown in Drawing  7 . Therefore, the keyboard of the notebook can be ensured to be operated without need to upward wrists or lift forearms. The second embodiment of the invention is composed of a drawer  1 , a supporting rack  2 , a desk panel  3 , a right elbow support board  4 , a left elbow support board  5 , a mouse board  6  and a two-sided keyboard supporting seat  7 , which is shown as Drawings  9  to  14 , wherein: 
         [0064]    The drawer  1  is arranged under the desk panel  3  supported by the supporting rack  2  and faces a sitting operator. Furthermore, the drawer  1  is arranged on a longitudinal guide rail that is arranged under the desk panel  3 , which is not shown in the drawings. The drawer  1  can be pushed and pulled forward towards the sitting operator; the drawer  1  is composed of a drawer panel  11 , two drawer side boards  12 , a drawer backboard, a drawer bottom board, a right clapboard  15  and a pair of slider boards  13 ; the slider boards, parallel to the right clapboards, are fixedly arranged at the front ends of the inner sides of the right clapboards  15  and the drawer side boards  12  at intervals; wherein the top of the drawer panel  11  is higher than the top end at the front section of the drawer side panel  12  and the top end of the right clapboard  15 , which is shown in Drawing  12 . 
         [0065]    What are mentioned above pertain to the prior art. 
         [0066]    The right elbow support board  4  is formed by a vertical side edge as the right side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the left side edge thereof. On the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the right elbow support board  4  at the inner side of the right top of the drawer panel  11  of the drawer  1 ; in the same manner, the left elbow support board  5  is formed by a vertical side edge as the left side edge, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the right side edge thereof; furthermore, on the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the left elbow support board  5  at the inner side of the left top of the drawer panel  11  of the drawer  1 . The surface of the left elbow support board  5  is to smaller than that of the right elbow support board  4  as the average person uses the right hand to operate a mouse and requires larger movable position on the right elbow support board  4 , which is shown in Drawing  10  and Drawing  11 . 
         [0067]    When the desk is not required for operation, the right elbow support board  4  and the left elbow support board  5  are turned into the drawer  1 , which is shown in Drawing  11 . When the desk is prepared for operation including writing and reading or operating a computer, the drawer  1  is firstly pulled out and the right and left elbow support boards are unfolded; in other words, the right elbow support board  4  and the left elbow support board  5  are turned up by 180 degrees around the pivot of the hinge; and the right elbow support board  4  and the left elbow support board  5  are supported on the top surface of the drawer panel  11 , and the upper surfaces of the left and right elbow support boards are of the same height and as high as (or slightly higher than) the upper surface of the desk panel  3 , which is shown in Drawings  9  and  10 . The right forearm and the elbow of an operator are supported on the right elbow support board  4  while the left forearm and the elbow thereof are supported on the left elbow support board  5 , and the hinge and the top surface of the drawer panel  11  bear the pressure and the turning torque caused therefrom, thereby obtaining stable and reliable support; when the operator stops operation, the elbow support boards are turned by 180 degrees in the opposite direction and put into the drawer  1 ; and finally, the drawer  1  is pushed into the lower part of the desk panel  3 . Therefore, the turning of the right elbow support board  4  and the left elbow support board  5  does not occupy the space under the drawer  1 . 
         [0068]    The mouse board  6  is a rectangular board and a step-like position at the inner side of the mouse board  6  is connected at the left side of the top (lower than the top surface of the drawer panel  11 ) of the front end of the right clapboard  15  of the drawer  1  by a hinge (an ordinary hinge, a flat hinge or a bending hinge). Provided that the drawer is relatively narrow, the right clapboard can be saved and the mouse board is directly connected at the left side of the top of the front end of the right drawer side board. 
         [0069]    When the computer is not operated, the mouse board  6  is turned into the drawer and arranged under the right elbow support board  4  and the left elbow support board  5 , which is shown in Drawing  11 ; when the desk is prepared for operation, the drawer  1  is firstly pulled out, and the left and right elbow support boards as well as the mouse board are unfolded in sequence; in other words, the mouse board  6  is turned up by 180 degrees around the pivot of the hinge; and the mouse board  6  is supported on the top of the front end of the right clapboard  15  and the right drawer side board  12 , and presents a horizontal shape. A mouse is arranged on the upper surface of the mouse board  6  (which is not shown in the drawings), and the upper surface (namely, the bottom surface of the mouse) of the mouse board  6  (containing a mouse pad) is as high as (or slightly lower than) the upper sides of the right elbow support board  4  and the left elbow support board  5 , which is shown in Drawings  9  and  10 . When operating the mouse, people feel comfortable in wrists. 
         [0070]    A pair of same left and right rectangular vertical struts  71  are connected with the left and right sides of the two-sided keyboard supporting seat  7 ; the left and right vertical struts  71  of the two-sided keyboard supporting seat  7  are supported on the top surface of the two slider boards  13  in a sliding manner, and the two inner side faces of the left drawer side board  12  and the right clapboard  15  limit the free horizontal movement of the two-sided keyboard supporting seat  7  while a computer keyboard is arranged on the two-sided keyboard supporting seat  7  (not shown in the drawings); four sides of the vertical strut are a bottom surface  711 , a rear end surface  712 , a top surface  713  and a front end surface  714 ; wherein the height from the top surface  713  to the upper surface of the two-sided keyboard supporting seat  7  is more than that from the bottom surface  711  to the lower surface of the two-sided keyboard supporting seat  7 , so as to satisfy that both the upper surface of the (relatively thick) keyboard of a desktop computer and the upper surface of the (relatively thin) keyboard of a notebook computer can be as high as (or slightly lower than) the upper surfaces of the right elbow support board  4  and the left elbow support board  5 , thereby ensuring no need to upward wrists or lift forearms; and the left and right sides at the front end (reverse side) of the two-sided keyboard supporting seat  7  are respectively connected with a rectangular block  72 . 
         [0071]    As shown in Drawing  12 , when the keyboard of a desktop computer is arranged on the upper (positive) surface of the two-sided keyboard supporting seat  7 , the surfaces  711  of the left and right vertical struts are supported on the top surfaces of two corresponding slider boards  13  in a sliding manner while the front end of the desk panel  3  (at one side of the drawer panel  11 ) presses against the upper sections of the rear end surfaces  712  of the left and right vertical struts  71 ; therefore, the two-sided keyboard supporting seat  7  is fixed in a position opposite to the desk panel  3 , so as to facilitate people to stably operate the keyboard of the desktop computer; 
         [0072]    As shown in Drawing  14 , when the two-sided keyboard supporting seat  7  is turned by 180 degrees to ensure a notebook is arranged on the lower surface (reverse side) thereof, the top surfaces  713  of the left and right vertical struts  71  can slide forwards to be lifted and supported on the top surfaces of the two corresponding slider boards  13  while the outer sides of the left and right blocks  72  press against the front end of the desk panel  3  (at one side of the drawer panel  11 ). Therefore, the two-sided keyboard supporting seat  7  is fixed in a position opposite to the desk panel  3 , so as to facilitate people to stably operate the keyboard of the notebook computer. 
         [0073]    When a computer is not operated, the two-sided keyboard supporting seat  7  is moved to the rear side of the drawer bottom board, which is shown in Drawing  11 ; when the desk is prepared for operation, the drawer  1  is firstly pulled out, and the left and right elbow support boards and the mouse board are unfolded, and then the two-sided keyboard supporting seat is moved to the front side of the drawer bottom board and lifted; furthermore, the left and right vertical struts  71  are supported on the top surfaces of the two slider boards  13  that can be replaced by guide rails of the same height relation in a sliding manner, which is shown in Drawings  9  and  10 ; in addition, the upper surface, namely the top surface of buttons, of a keyboard (which is not shown in the drawings and generally is the keyboard of a desktop or notebook computer arranged in an inclined manner) supported on the two-sided keyboard supporting seat  7  is approximately as high as (or slightly lower than) the upper surfaces of the right elbow support board  4  and the left elbow support board  5 ; therefore, the keyboard can be ensured to be operated without need to upward wrists or lift forearms. And the computer desk can be adopted as a table for desktop computers or notebook computers. 
         [0074]    Additionally, when reading and writing are conducted on the desk panel, the two-sided keyboard supporting seat  7  is pushed to the rear side of the drawer  1  (above the drawer bottom board), and the mouse board  6  is turned into the drawer  1  while the drawer  1  is positioned under the desk panel  3 ; people can write with a comfortable sitting posture as shown in Drawing  4 , since the upper surfaces of the right elbow support board  4  and the left elbow support board  5  are as high as (or higher than) the upper surface of the desk panel  3 . And the computer desk can be used as a writing desk. 
         [0075]    The third embodiment of the invention is composed of a drawer  1 , a supporting rack  2 , a desk panel  3 , a right elbow support board  4  and a left elbow support board  5 , which is shown as Drawings  15  to  19 , wherein: 
         [0076]    The drawer  1  is positioned under the desk panel  2  supported by the supporting rack  2  and faces a sitting operator. Furthermore, the drawer  1  is arranged on a longitudinal guide rail that is arranged under the desk panel  3 , which is not shown in the drawings. The drawer  1  can be pushed and pulled forward towards the sitting operator; and a drawer panel  11  is arranged in front of the drawer  1 . The embodiment pertains to the prior art. 
         [0077]    A rectangular or arc-shaped keyboard gap  31  is arranged in the middle of the front side of the desk panel  3  and used for containing the keyboard of computers including desktop and notebook computers; a backing board  32  is arranged on the bottom surface at the edge of the keyboard gap  31  by screws or glue; the backing board  32  is a concave or flat board which is properly selected based on the different thickness of the desk panel  3  and can be adjusted by the addition of a bottom board on the backing board  32 , so as to support the keyboard and ensure that the distance from the upper surface of the backing board  32  to the upper surface of the desk panel  3  is approximately as high as the height of the keyboard, and thus the forearms of an operator can keep flat on the desk top, without need to upward wrists; a mouse is arranged on the desk panel at the right side of the keyboard gap  31 , which is shown in Drawing  15 ; when people write on the desk for a relatively long time, an inverted slotted board  33  matching with the keyboard gap  31 , can be used for covering the keyboard gap  31  without need to take the keyboard out, so as to keep the upper surface of the desk panel  3  even for supporting the movement of wrists to write, which is shown in Drawings  16  and  17 . 
         [0078]    The right elbow support board  4  is formed by a vertical side edge as the right side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the left side edge thereof. On the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the right elbow support board  4  at the inner side of the right top of the drawer panel  11  of the drawer  1 ; in the same manner, the left elbow support board  5  is formed by a vertical side edge as the left side edge, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the right side edge thereof; furthermore, on the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the left elbow support board  5  at the inner side of the left top of the drawer panel  11  of the drawer  1 . The surface of the left elbow support board  5  is smaller than that of the right elbow support board  4  as the average person uses the right hand to operate a mouse and requires larger movable position on the right elbow support board  4 ; When the desk is not required for operation, the right elbow support board  4  and the left elbow support board  5  are turned into the drawer  1 , which is shown in Drawing  18 . When the desk is prepared for operation including writing and reading or operating a computer, the drawer  1  is firstly pulled out and the right and left elbow support boards are unfolded; in other words, the right elbow support board  4  and the left elbow support board  5  are turned up by 180 degrees around the pivot of the hinge; and the right elbow support board  4  and the left elbow support board  5  are supported on the top surface of the drawer panel  11 , and the upper surfaces of the left and right elbow support boards are of the same height and as high as (or slightly higher than) the upper surface of the desk panel  3  and the upper surface of the keyboard (namely, the top surface of buttons), which is shown in Drawings  15  and  19 . The right forearm and the elbow of an operator are supported on the right elbow support board  4  while the left forearm and the elbow thereof are supported on the left elbow support board  5 , and the hinge and the top surface of the drawer panel  11  bear the pressure and the turning torque caused therefrom, thereby obtaining stable and reliable support; when the operator stops operation, the right elbow support board  4  and the left elbow support board  5  are turned by 180 degrees in the opposite direction and put into the drawer  1 ; and finally, the drawer  1  is pushed into the lower part of the desk panel  3 . Therefore, the turning of the right elbow support board  4  and the left elbow support board  5  does not occupy the space under the drawer  1 . 
         [0079]    The fourth embodiment of the invention is composed of a drawer  1 , a supporting rack  2 , a desk panel  3 , a right double-layer elbow support board  4 , a left double-layer elbow support board  5 , a mouse board  6  and a keyboard supporting seat  7 , which is shown as Drawings  20  to  30 , wherein: 
         [0080]    The drawer  1  is arranged under the desk panel  3  supported by the supporting rack  2  and faces a sitting operator. Furthermore, the drawer  1  is arranged on a longitudinal guide rail that is arranged under the desk panel  3 , which is not shown in the drawings. The drawer  1  can be pushed and pulled forward towards the sitting operator; a drawer panel  11  is arranged in front of the drawer  1  the right and left sides of which are respectively provided with a drawer side board  12 . A pair of parallel slider boards  13  are fixedly arranged at the front end of the inner side of the drawer side boards  12  at intervals. Moreover, the left drawer side board  12  is internally provided with a stop board  14 . What are mentioned above pertain to the prior art and is shown in Drawing  8 ; the left (or right) section of the drawer panel is provided with a left inner board which is connected with a dovetail groove in a sliding manner, which is shown in Drawings  22  and  24 ; in addition, a lath is connected at the upper part of the inner surface of the drawer panel so as to ensure the more stable thickened tops of the left and right double-layer elbow support boards supported on the drawer panel  11 , which is not shown in the drawings. 
         [0081]    The fourth embodiment has two double-layer elbow support boards. The right double-layer elbow support board  4  of the first kind is mainly composed of a right lower board  41 , a right upper board  42  and four connecting bars  43 , as shown in Drawings  20  and  21 , wherein: 
         [0082]    The right lower board  41  is formed by a vertical side edge as the right side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the left side edge thereof. On the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the right lower board  41  at the inner side of the right top of the drawer panel  11  of the drawer  1 ; the appearance of the right upper board  42  is approximately the same as the shape of the right lower board  41 , but longer than the right lower board  41 ; two among four parallel connecting bars are respectively articulated at the front and rear positions of the right sides of the right lower board  41  and the right upper board  42  in a parallel manner; and two other connecting bars are respectively articulated at the front and rear positions of the left sides of the right lower board  41  and the right upper board  42 ; 
         [0083]    After the right double-layer elbow support board  4  is unfolded and supported on the top surface of the drawer panel  11 , four parallel connecting bars  43  are inclined and the upper surface of the right upper board  42  is as high as (or slightly higher than) the desk panel when the right upper board  42  is supported on or contacts the right lower board  41  directly. The computer desk is used as a computer table or a writing desk while the mouse board of a computer is connected on the keyboard supporting seat in the drawer; 
         [0084]    After rotation, four parallel connecting bars  43  are slightly beyond the vertical status. When the connecting bars contact the corresponding stop block  411  of the right lower board  41 , the right upper board  42  is supported under the right lower board  41  in a suspended manner by the four parallel connecting bars  43  and higher than the desk panel after the upper surface of the right upper board  42  is lifted and as high as (or slightly higher than) the upper surface of the keyboard of a notebook (or desktop) computer which is arranged on the desk panel. The computer desk is applied as a table for notebook (or desktop) computers; 
         [0085]    In the same manner, the left double-layer elbow support board  5  is mainly composed of a left lower board  51 , a left upper board  52  and four connecting bars  53 , as shown in Drawings  20  and  24 , wherein: 
         [0086]    The left lower board  51  is formed by a vertical side edge as the left side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the right side edge thereof. On the left inner board  111  of the drawer panel  11 , a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the left lower board  51  at the inner side of the left top of the drawer panel  11  of the drawer  1  while the left inner board  111  can slide towards the left and the right on the drawer panel  11  and change the space between the left double-layer elbow support board  5  and the right double-layer elbow support board  4 , thereby meeting various needs of operators of different body types; however, the surface of the left double-layer elbow support board  5  is smaller than that of the right double-layer elbow support board  4  as the average person uses the right hand to operate a mouse and requires larger movable position on the right double-layer elbow support board  4 , which is shown in Drawing  21  and Drawing  22 ; 
         [0087]    The left upper board  52  and the left lower board  51  respectively have the same structure as the right upper board  42  and the right lower board  41 , which is not discussed in detail. 
         [0088]    The right double-layer elbow support board  4  of the second kind in the fourth embodiment is mainly composed of a right lower board  41 , a right upper board  42 , a plurality of holes, cylindrical platforms, pin holes and convex pins, as shown in Drawings  20 ,  21  and  27 , wherein: 
         [0089]    The right lower board  41  is formed by a vertical side edge as the right side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the left side edge thereof. On the long horizontal edge, a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the right lower board  41  at the inner side of the right top of the drawer panel  11  of the drawer  1 . The upper surface of the right lower board  41  is provided with separate through holes  411  and separate cylindrical platforms  412 ; furthermore, the tops of the cylindrical platforms are respectively provided with a convex pin  413 ; 
         [0090]    The appearance of the right upper board  42  is approximately the same as the shape of the right lower board  41 , but longer than the right lower board  41 ; the upper surface of the right upper board  42  is provided with four separate holes  421  and four separate cylindrical platforms; furthermore, the tops of the cylindrical platforms are respectively provided with a convex pin  423 , which is shown in Drawings  28 ,  29  and  30 ; 
         [0091]    After the right double-layer elbow support board  4  is unfolded and supported on the top surface of the drawer panel  11 , the lower surface of the right upper board  42  contacts the upper surface of the right lower board  41  and the upper surface of the right upper board  42  is as high as (or higher than) the desk panel, which is shown in Drawing  29 . The computer desk is used as a computer table or a writing desk while the mouse board of a computer is connected on the keyboard supporting seat in the drawer; 
         [0092]    When the lower surface of the right upper board  42  is separate from the upper surface of the right lower board  41 , the cylindrical platform  422  of the right upper board  42  contacts the cylindrical platform  412  of the right lower board  41 , and the convex pin  423  of the right upper board  42  matches with the pin hole  413  of the right lower board, the upper surface of the right upper board is lifted to be higher than the desk panel, and is as high as (or slightly higher than) the upper surface of the keyboard of a notebook computer arranged on the desk panel, as shown in Drawings  28  and  30 . The computer desk is applied as a table for notebook or desktop computers; 
         [0093]    In the same manner, the left double-layer elbow support board  5  is mainly composed of a left lower board  51  and a left upper board  52 , as shown in Drawings  20  and  27 , wherein: 
         [0094]    The left lower board  51  is formed by a vertical side edge as the left side edge thereof, a short horizontal edge as the front edge thereof, a long horizontal edge as the rear edge thereof and a concave rounded edge as the right side edge thereof. On the left inner board  111  of the drawer panel  11 , a hinge (an ordinary hinge, a flat hinge or a bending hinge) is used for connecting the left lower board  51  at the inner side of the left top of the drawer panel  11  of the drawer  1  while the left inner board  111  can slide towards the left and the right on the drawer panel  11  and change the space between the left double-layer elbow support board  5  and the right double-layer elbow support board  4 , thereby meeting various needs of operators of different body types; however, the surface of the left double-layer elbow support board  5  is smaller than that of the right double-layer elbow support board  4  as the average person uses the right hand to operate a mouse and requires larger movable position on the right double-layer elbow support board  4 , which is shown in Drawing  21  and Drawing  22 ; 
         [0095]    The left upper board  52  and the left lower board  51  respectively have the same structure as the right upper board  42  and the right lower board  41 , which is not discussed in detail. 
         [0096]    The keyboard supporting seat  7  is arranged in the drawer  1  provided with two kinds of double-layer elbow support boards in the fourth embodiment, and is composed of a rectangular board, thick laths  71  and vertical struts  72 . The thick lath of the same thickness is connected at the upper sides of the left and right sides of the keyboard supporting seat respectively while the lower part of the keyboard supporting seat is provided with one vertical strut of the same height respectively; and the inner side of the right thick lath  71  is connected with a thickened lath  61  outside a rectangular mouse board  6 , and thus the mouse board  6  is not too thick (since the upper surface of the mouse board  6  and the upper surface of the double-layer elbow support board are required at the same height when the mouse board  6  is unfolded and in the operation state) and connection with the hinge can be realized; the left and right vertical struts  72  are supported on the drawer bottom board behind the drawer or on the top surface of a pair of the slider boards  13  in a sliding manner; and the two inner side faces of the left and right drawer side boards  12  limit the free horizontal movement of the keyboard supporting seat  7 , which is shown in Drawings  25  and  26 . 
         [0097]    When the desk is not used for operation, the right double-layer elbow support board  4  and the left double-layer elbow support board  5  are folded up in the drawer  1 , which is shown in Drawing  22  (the right double-layer elbow support board  4  and the left double-layer elbow support board  5  are positioned above the left and right drawer side boards  12  and the left and right slider boards  13 , or arranged above the space between the inner sides of the left and right slider boards  13 ). 
         [0098]    When the desk is prepared for operation including writing and reading or operating a computer, the drawer  1  is firstly pulled out and the right and left double-layer elbow support boards are unfolded; in other words, the right double-layer elbow support board  4  and the left double-layer elbow support board  5  are turned up by 180 degrees around the pivot of the hinge; and the right double-layer elbow support board  4  and the left double-layer elbow support board  5  are supported on the top surface of the drawer panel  11 , and the upper surfaces of the left and right double-layer elbow support boards are of the same height and as high as (or slightly higher than) the upper surface of the desk panel  3 , which is shown in Drawing  23 . The right forearm and the elbow of an operator are supported on the right double-layer elbow support board  4  while the left forearm and the elbow thereof are supported on the left double-layer elbow support board  5 , and the hinge and the top surface of the drawer panel  11  bear the pressure and the turning torque caused therefrom, thereby obtaining stable and reliable support; when the operator stops operation, the double-layer elbow support boards are turned by 180 degrees in the opposite direction and put into the drawer  1 ; and finally, the drawer  1  is pushed into the lower part of the desk panel  3 . Therefore, the turning of the right double-layer elbow support board  4  and the left double-layer elbow support board  5  does not occupy the space under the drawer  1 . 
         [0099]    When the desk is used for writing, reading, etc., the keyboard supporting seat  7  is positioned at the rear position of the drawer  1  and supported on a drawer bottom board and the mouse board  6  is unfolded on the keyboard supporting seat  7 . Furthermore, the left and right thick laths  71  are at the same level and a computer keyboard can be arranged on the upper surfaces thereof (not shown in the drawings), which is shown in Drawings  22  and  25 ; and the drawer  1  is positioned under the desk panel  3 , as shown in Drawing  23 . 
         [0100]    When the desk is used for the operation of a desktop computer in the drawer, the drawer  1  is pulled out firstly. After the left and right double-layer elbow support boards are unfolded, the upper surfaces of the left and right double-layer elbow support boards are as high as (or slightly higher than) the upper surface of the desk panel  3  so as to ensure that the keyboard supporting seat  7  slides forward to be lifted and supported on the top surface of the two slider boards  13  from the position above the drawer bottom board at the rear side of the drawer  1  (the slider boards can be replaced by guide rails of the same height relation); the mouse board  6  is turned up by 180 degrees around the pivot of the hinge and positioned on the thick lath  71  which is turned to the right side of the keyboard supporting seat  7 , and the upper surface (namely, the bottom surface of a mouse) of the mouse board  6  (containing a mouse pad) is as high as (or slightly lower than) the upper sides of the right double-layer elbow support board  4  and the left double-layer elbow support board  5  while the mouse is arranged on the upper surface thereof (not shown in the drawings). Provided that the thickened lath  61  outside the mouse board  6  hinders the right wrist and the right forearm of an operator, the front end of the thickened lath  61  can be thinned properly, which is shown in Drawings  21  and  26 ; the keyboard of the desktop computer is arranged on the upper surface of the keyboard supporting seat  7  between the left and right thick laths  71  (generally, the keyboard is arranged in an inclined manner, which is not shown in the drawings); furthermore, the upper surface of the keyboard, namely the top surface of buttons, is approximately as high as (or slightly lower than) the upper surfaces of the right double-layer elbow support board  4  and the left double-layer elbow support board  5  so as to ensure that the keyboard is operated without needs to upward wrists and lift forearms; additionally, the upper part of the left thick lath  71  presses against the lower part of a stop board  14  of, the drawer  1 , thereby preventing the left thick lath from turning in the operation of the mouse board  6 , which is shown in Drawing  20 . 
         [0101]    When the computer desk is used for the operation of a notebook or desktop computer arranged on the desk panel, the keyboard supporting seat  7  is arranged at the rear side of the drawer  1  and supported on the drawer bottom board, and the mouse board  6  is unfolded on the keyboard supporting seat  7 ; the mouse board  6  and the left and right thick laths  71  are at the same level and the drawer  1  is positioned under the desk panel  3 ; the right double-layer elbow support board  4  and the left double-layer elbow support board  5  are unfolded and supported on the top surface of the drawer panel  11 ; and the upper surfaces of the right upper board  42  and the left upper board  52  are lifted to the same height to be higher than the desk panel and as high as (or slightly higher than) the keyboard of a notebook or desktop computer arranged on the desk panel; provided that a mouse is used on the desk panel, a bottom board is required to be inserted under the mouse, which ensures that the bottom of the mouse is as high as (or slightly lower than) the upper surfaces of the right upper board  42  and the left upper board  52 . 
         [0102]    Another new structure can be adopted in the computer desk with double-layer elbow support boards: 
         [0103]    Compared with the structure of the fourth embodiment, three changes are conducted in the new structure. Firstly, the keyboard supporting seat  7  in the fourth embodiment is replaced by the two-sided keyboard supporting seat  7  in the first embodiment; secondly, the slider boards  13  in the drawer are saved so that the two-sided keyboard supporting seat  7  can be kept in the drawer bottom board when pushed and pulled forwards in the drawer  1 , without any change in the space height of the two-sided keyboard supporting seat  7 ; and thirdly, the height of the drawer panel  11  is properly reduced to change the height of the double-layer elbow support boards in the operation. 
         [0104]    When the desk with the new structure is used as the table for desktop computers, the drawer  1  is pulled out and the right (left) double-layer elbow support board is unfolded and supported on the top surface of the drawer panel  11 ; the right (left) upper board contact the right (left) lower board while the upper surface of the right (left) upper board is lower than the lower surface (reverse side) of the desk panel; the two-sided keyboard supporting seat  7  facing up and provided with the keyboard of a desktop computer slides forward to the front side of the drawer  1  from the rear side of the drawer  1 , and the mouse board  6  is unfolded. And the upper surface (the top surface of buttons) of the keyboard of the desktop computer, the upper surface (the bottom) of the mouse board and the upper surface of the right (left) double-layer elbow support board are of the same height and lower than the lower surface (reverse side) of the desk panel while the elbow support board can be slightly higher. 
         [0105]    When the desk with the new structure is used as the table for notebook computers, the reverse side of the two-sided keyboard supporting seat  7  is upward and provided with a notebook computer while the mouse board is unfolded. And the upper surface of the keyboard of the notebook computer is as high as (or slightly lower than) the upper surfaces of the right (left) double-layer elbow support board, and the upper surfaces of the keyboard and the double-layer elbow support board are lower than the lower surface (reverse side) of the desk panel. 
         [0106]    When the desk with the new structure is used as a writing desk, only two-sided keyboard supporting seat  7  is pushed to the rear side inside the drawer  1 , and the right (left) upper board is separate from the right (left) lower board and then lifted. And the upper surface of the right (left) double-layer elbow support board is as high as (or slightly higher than) that of the desk panel.