Writing board with an automatic erase device

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG.
1 to FIG.
6 there is illustrated a writing board of a first embodiment of the present invention.
The writing board comprises an endless writing sheet 1, a supporting roller 2, a frame 3, a driving roller 4, and an erase device 8 (as shown in FIG.
3).
The frame 3 comprises a left unit 31 and a right unit 32 connected in parallel by a supporting board 7, such as a cardboard.
The driving roller 4 and the supporting roller 2 are mounted on the frame 3.
The writing sheet 1 is flexible and is trained around the driving roller 4 and the supporting roller 2 to form a front exposed writing surface 11 and a back surface 12 as shown in FIG.
5.
The supporting board 7 is interposed between the front and back surfaces 11, 12 to provide a fixed rigid supporting to the front surface 11 of the writing sheet 1 so as to enable writing thereon (as shown in FIG.
2).
The flexible endless writing sheet 1 can be rotated clockwise or anti-clockwise around the driving and supporting rollers 4, 2 by turning the driving roller 4.
The driving roller 4 can be driven to rotate by a motor (not shown in Figure) or manually through a shaft 5.
The shaft 5 is connected to one end of the driving roller 4 coaxially (as shown in FIG.
1).
As shown in FIGS.
2 to 5, the erase device 8 is mounted behind the back surface 12 of the writing sheet 1.
The erase device 8 comprises a cover board 82, at least an elongated eraser 83, a plurality of carriages 84, a plurality of springs 81, and a clutch 871: There are four erasers 83 according to the present embodiment and each has a length at least equal to the width of the writing sheet 1.
The erasers 83 are mounted on the cover board 82 horizontally.
The erasers 83 are made of elastic material such as foam rubber, foam plastic, and sponge, etc.
The erasers extend along the width of the writing sheet and are disposed in touching with the writing surface of the 1.
The carriages 84 are connected to the left and right sides of the cover board 82 respectively