Assertion: blackboard eraser | /r/HasProperty | hard contact
Facets:
value: at clean middle scratch blackboard eraser
type: MANNER
Source sentences:
text: For this reason, Chinese patent CN102962218A discloses a kind of cleaning blackboard eraser and collects gray device of chalk, this device be by arrange turning cylinder and scraping blade, scraping blade close contact when exerting pressure downwards to blackboard eraser and on turning cylinder, make it reach the cleaning effect of blackboard eraser, the cleaning plant of this structure exists following not enough: 1, because blackboard eraser and cleaner scraping blade are hard contact, comparatively large to the damage of blackboard eraser, easily at clean middle scratch blackboard eraser, shorten the service life of blackboard eraser; 2, the design of this device is only for common chalk, but in use dust is large due to common chalk, and seldom use on the market at present, the applicable surface of device is narrow; 3, the ash-removal effect to blackboard eraser can only be played, cannot wipe completely the writing on blackboard, cannot produce a desired effect.