Abstract:
The present invention wipes a writing board through areas. A teacher can wipe an area of a blackboard while writing on another area. Thus, a writing board can be flexibly used with convenience obtained and time saved.

Description:
FIELD OF THE INVENTION 
     The present invention relates to erasing a writing board; more particularly, relates to freely selecting an area of a writing board for wiping even when writing on another area at the same time with flexibility and humanization obtained and time saved. 
     DESCRIPTION OF THE RELATED ART 
     A blackboard erasing device usually wipes a blackboard wholly. As shown in  FIG. 3 , a prior art has an eraser  31  contacting a blackboard  30 ; the eraser  31  is connected with a motor seat  33  at an upper end of the eraser  31  through a cantilever support  32 ; and a track  34  is set at an upper side of the blackboard  30 . Thus, a rubber wheel  36  is moved by a motor  36  to carry the eraser  31  by the motor seat  33  and the cantilever support  32  for sliding rightward and leftward along the whole track  34 , where the eraser  31  has the same height as the blackboard  30  for wiping the whole blackboard  30 . However, when a blackboard writer wants to erase a part of writing on the blackboard  30  but still wants to write on another part of the blackboard  30 , such a prior art is apparently unavailable. If the writer really wants to do the above operation, he may have to wipe off the blackboard manually. This may take time and is so inconvenient. Hence, the prior art does not fulfill all users&#39; requests on actual use. 
     SUMMARY OF THE INVENTION 
     The main purpose of the present invention is to freely select an area of a writing board for wiping even when writing on another area at the same time with flexibility and humanization obtained and time saved. 
     Another purpose of the present invention is to further design position sensors to change sizes of the areas of the writing board; and to divide the writing board into board areas horizontally or vertically; or even divided into grids of board areas horizontally and vertically. 
     To achieve the above purposes, the present invention is an apparatus erasing blackboard having areas, comprising a writing board, a plurality of gears, a belt, a plurality of position sensors, a slider, an expansion part, an erasing part and a suction part, where the writing board is divided into a plurality of board areas; the gears are located at two sides on top of the writing board and have a track set between the two sides; the belt circles the gears; the position sensors are set on the track and are electrically connected with a border of the board areas; the slider is assembled on the track and is moved by the belt driven by the motor to slide along the track toward a designated one of the board areas; the expansion part comprises a first expansion cylinder and a second expansion cylinder and is connected with an end surface of the slider; the erasing part connects to the second expansion cylinder and stays close to a surface of the writing board; and the suction part connects around the erasing part to suck dust obtained on wiping off writing on the designated board area; and the apparatus has an automatic control system remotely controlled by a control panel. Accordingly, a novel apparatus erasing blackboard having areas is obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood from the following detailed description of the preferred embodiment according to the present invention, taken in conjunction with the accompanying drawings, in which 
         FIG. 1  is the structural view showing the preferred embodiment according to the present invention; 
         FIG. 2  is the view showing the control panel; and 
         FIG. 3  is the view of the prior art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment is provided to understand the features and the structures of the present invention. 
     Please refer to  FIG. 1  and  FIG. 2 , which are a structural view showing a preferred embodiment according to the present invention and a view showing a control panel. As shown in the figures, the present invention is an apparatus erasing blackboard having areas  1 , comprising a writing board  10 , a plurality of gears  11 , a belt  12 , a plurality of position sensors  13 , a slider  14 , an expansion part  15 , an erasing part  16  and a suction part  17 , where the writing board  10  is divided into a plurality of board areas  101 ; and the apparatus  1  has an automatic control system remotely controlled by a control panel  20 . 
     The gears  11  are located at two sides on top of the writing board and have a track  111  set between the two sides. 
     The belt  12  circles the gears  11 . 
     The position sensors  13  are set on the track  111  and are electrically connected with a border of the board areas  101 . The position sensor  13  senses a position trigger signal at the border of the board areas  101  and sends a feedback signal to an 8051 single chip according to the position trigger signal to drive a motor. Therein, the position sensor  13  comprises a signal receiver set on the track  111 , such as a photoresistor; and a signal emitter set at the border of the board areas  101 , such as a light emitting diode (LED). 
     The slider  14  is assembled on the track  111  and is driven by the motor to be rotated to carry the slider  14  by the belt  12  for sliding along the track  111  to be moved to a designated one of the board areas  101 . 
     The expansion part  15  comprises a first expansion cylinder and a second expansion cylinder to be expanded at two ranges. The expansion part  15  connects to an end surface of the slider  14  at an end of the expansion part  15 ; and is expanded from the end surface of the slider  14  perpendicularly in correspondence to the designated one of the board areas  101 . 
     The erasing part  16  connects to the second expansion cylinder of the expansion part  16 , where the erasing part  16  stays close to a surface of the writing board to wipe off writing on the designated one of the board areas  101 . 
     The suction part  17  connects around the erasing part  16  to suck dust obtained on wiping off writing on the designated one of the board areas  101 . Thus, with the above structure, a novel apparatus erasing blackboard having areas is obtained. 
     The control panel  20  comprises a start bottom  201  signally connected with the 8051 single chip; a stop bottom  202  signally connected with the motor; a plurality of press bottoms  203  signally connected with the board areas  101 ; a plurality of area indicators  204  corresponding to the press bottoms  203  and signally connected with the board areas  101 ; a plurality of direction indicators  205  signally connected with the slider  14 ; and a function bottom  206  signally connected with the erasing part  16 , where the apparatus  1  is started by the control panel  20  with operations controlled and monitored. 
     The writing board  10  is divided into a plurality of board areas  101   a ˜ 101   d . Programs are designed in the 8051 single chip. A position signal is fed back by one of the position sensors  13 ; then positioning is done with the coordination of the LED and the photoresistor of the position sensor  13 . 
     On using the present invention, one of the board areas  101   a ˜ 101   d  is selected and the press bottom  203   a ˜ 203   d  corresponding to the designated board area  101   a ˜ 101   d  is pressed down. The area indicator  204   a ˜ 204   d  corresponding to the press bottom  203   a ˜ 203   d  pressed down is turned on to show that control data are saved and confirmed. Then, the start bottom  201  on the control panel  20  is pressed down to run the apparatus  1 . 
     When the start bottom  201  is pressed down, the 8051 single chip drives the motor to rotate the gears  11  for moving the belt  12  and further carrying the slider  14  to slide along the track  111 . By sliding the slider  14  along the track  111 , one of the position sensors  13  set on the border of the board areas  101   a ˜ 101   d  is triggered to send a feedback signal of the position sensor  13  to be analyzed by the 8051 single chip for judging whether a position trigger signal sent by the position sensor  13  is received. Thus, the board areas of the writing board are functioned. Therein, a moving direction of the slider  14  is simultaneously shown by the direction indicators  205  on the control panel. When the slider  14  approaches the designated board area  101 , the expansion part  15  expands its first expansion cylinder  151  and second expansion cylinder  152  to carry the erasing part  16  for wiping off writing on the writing board  10 ; and the suction part  17  simultaneously sucks the dust obtained on wiping off the writing on the writing board  10 . 
     In this way, the designated board area  101  of the writing board is freely selected for wiping, even when writing o another board area  101  at the same time. More flexibility and humanization are thus obtained and time is saved. 
     In addition, the position sensors can be further designed to change sizes of the board areas of the writing board. Besides, the writing board can be divided into board areas horizontally or vertically; or, even divided into grids of board areas horizontally and vertically. 
     To sum up, the present invention is an apparatus erasing blackboard having areas, where an area of the writing board is freely selected for wiping even when writing on another area at the same time; and more flexibility and humanization are thus obtained with time saved. 
     The preferred embodiment herein disclosed is not intended to unnecessarily limit the scope of the invention. Therefore, simple modifications or variations belonging to the equivalent of the scope of the claims and the instructions disclosed herein for a patent are all within the scope of the present invention.