1. Field of the Invention
This invention relates to an electronic white board apparatus which is capable of copying information such as characters and figures from a screen onto a recording paper.
2. Description of the Related Art
There has been already known an electronic white board apparatus which can read information from a screen and print the same onto a recording paper as disclosed in Japanese Patent Examined Publication No. 62-56000. Further, there has recently been proposed an apparatus in which a screen loop is folded back to provide four screen parts on which information is to be drawn, as disclosed in Japanese Patent Examined Publication No. 6-94238.
FIGS. 7 to 10 are illustrations showing the structure of a conventional electronic white board apparatus. Reference numeral 1 denotes a screen; 2, a screen driving roller for driving the screen 1; and 3a, 3b, 3c, screen folding rollers for folding the screen 1. A screen driving pulse motor (not shown) is connected to the screen driving roller 2 for rotating the screen driving roller 2 in the forward or reverse direction so as to move the screen 1. Reference numerals 5a, 5b, 5c, 5d denote screen home position marks based on which home positions of respective screen parts (reference positions at the time of reading images on the screen parts or moving the screen part into a proper position) are decided; 6, an optical reader casing to which the screen 1 can be attached; and 7, a screen home position detecting sensor for detecting the screen home position marks to decide the home positions of the respective screen parts.
In cases where information is written on a screen part located at the front and then printed, the screen driving roller 2 is driven to move the screen 1 in the direction of an arrow A, so that the information written on the screen part is read by a read station (not shown) provided in the optical reader casing 6 and then printed out by a printer (not shown). After completing the reading, as soon as the screen home position detecting sensor 7 detects the screen home position mark 5b, the screen driving roller 2 is stopped (FIG. 8).
However, as shown in FIG. 7, if the screen 1 is left for a long period of time as it is in the condition that the screen home position mark 5a is stopped at the point facing the screen home position detecting sensor 7, a curl a is produced in that portion of the screen 1 kept in contact with the screen driving roller 2.
Likewise, curls b, c, and d are produced in the positions of the screen 1 kept in contact with the screen folding rollers 3a, 3b and 3c, respectively. If the screen 1 is fed (moved) forward from the condition of FIG. 7, the screen home position mark 5b newly arrives at the point facing the screen home position detecting sensor 7 as shown in FIG. 8. At this time, the curls a, b, c and d are also moved with the screen 1.
FIG. 9 shows, on an enlarged scale, the portion around the screen folding roller 3c of FIG. 8. If the excitation of the screen driving pulse motor is cut off to allow the screen 1 to be in free condition, since the curl a is hung on the screen folding roller 3c, the screen 1 moves by itself to the position shown FIG. 10 where the curl a is stable. This gives rise to a problem that the screen home position mark 5b is shifted from the point facing the screen home position detecting sensor 7.
To solve the above problem, it is thought to excite the screen driving pulse motor even while the screen 1 is stopped. However, if the power is turned off, the excitation of the screen driving pulse motor 4 is also cut off, and therefore there still remains such a problem that the screen home position is shifted when the power is turned off.