| 摘要 |
PROBLEM TO BE SOLVED: To eliminate an adherence of chalk dust to an inner unit such as a fan, a fan motor or the like by reducing an air resistance in an air channel, efficiently sucking wiped chalk dust, and completely removing it by a filter. SOLUTION: Two erasing rollers 2 each having a gigging part 3 on an outer periphery are provided with a columnar elastic material as a core material at sides of upper and lower slender eraser bodies 1 opposite to a blackboard, and both sides are sandwiched between a roller cover plate 6 and a roller partition plate 1. Flat brushes 5 are provided so that inside surfaces of the rollers 2 are brought at ends into contact with the ends in the overall length. Air suction ports 9 are provided at a partition wall 8 for partitioning the rollers 2 of the body 1 and interior, and a dust box 12 is provided at its inside. A filter 11 is provided at one side face of the box 12, and sucked by a suction fan from its outside.
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