Abstract: A sheet collating machine includes feed-up devices (7) disposed at bins (1) and having driven feed-up wheels (8), the feed-up devices being pivotal between a lowered position in which the feed-up wheels engage stacks (2) of paper sheets and a raised position in which the wheels are disengaged from the stacks. A conveying path (3) is defined by a plurality of conveyor and press rollers (4), along the upper side of which a corresponding number of backing rollers (6) are disposed, and a conveyor belt (5) runs between the rollers. A sensor (12) is actuated by a spring member (11) which extends crosswise over the conveyor path when no sheet protrudes between the press roller and the belt, and the spring member is lifted from its contact with the sensor when a sheet passes the latter. When no sheet is advanced within a predetermined period the sensor furnishes a signal to a control device which automatically causes a drive device to lift the feed-up device to its raised position.