Abstract: A device for successively changing elongated flexible sheets or similar flexible objects from an active position to non-active positions includes a drum, relative to which the sheets or similar flexible objects are fixed. The drum is rotatable in two opposing rotational directions. The rotational directions of the drum are controlled by a timing device in relation to the rotational speed of the motor so that rotation takes place in a first direction for such a time that the sheet located in the active position becomes wound up onto the drum and that a second sheet, located in the first rotational direction after the first sheet, is carried to a position from which the second sheet is unwound from the drum to the active position, upon rotation of the drum in the other rotational direction. Thereafter the drum is rotated in the other rotational direction for such a time that the second sheet becomes unwound from the drum.