| 摘要 |
PROBLEM TO BE SOLVED: To enable suppression of excess supply and consumption of scrubbing powder by controlling its supply. SOLUTION: A spherical stopper 4a is engaged at the powder supply opening 4 and is moved up and down by rotating an arm 4c attached at a supporting axis 4b. Thereby, a shutter to control supply of scrubbing powder P is formed. The stopper 4a fully opens the shutter by being pushed up to the highest position within the extent of mobility, and completely closes the shutter by being pushed down to the lowest position. The arm 4c is provided with a spring 4d to push the stopper 4a to the lowest position at a stationary state.
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