Smooth operation can prevent the sheet from being worn out and broken, Noncontact structure of the sheet.

The resin guide does not come in contact with the sheet when opening and closing by installing the rollers in both ends of the sheet.This structure prevents wear-out of the sheet and decrease in the arrtight degrees, and the sheet longevity improves rapidly. Moreover, the shutter can be smoothly operated even in the area of air pressure difference, because the friction by operation is a little.
(PAT.P)