The invention relates to a curtain device mounted on a shaft (2) about which said curtain (1) can be wound to an open position and unwound into a closed position, a drive wheel (7) fixed coaxially to said shaft (2) and cooperating with said curtain (1) such as to displace the latter between said two positions. The device comprises an oblong flexible control body (11), cooperating with the drive wheel (7), said body (11) being embodied to permit the displacement of the curtain (1) between the open position and the closed position thereof, independently of the slack formed in the curtain (1) and to be able to be displaced along at least one of the lateral edges (4) of the curtain (1) and act upon the region (8) of the latter as opposed to that arranged on the shaft (2).