the required number of sheets this feed position with triggering of the separator member drive can be determined very accurately by means of a toothed belt drive t 2 and an appropriately dimensioned wheel tr 3 on the cam nk and thus also the number of sheets per stack with equal safety damage to the sheets being fed continuously by the separator members engaging with them can be prevented because the feed and delivery device as well as the accelerating separator member drive are in synchronised driving connection with one another the number of sheets per stack can moreover be altered in wide limited by the appropriate ratio of reduction for the secure formation of a tight stack and for keeping free according to the time a gap for the separator members to pass through the sheets being fed one after another in accordance with fig7 thrust spirals s 1 and s 2 rotating about axes parallel with the delivery direction are provided on both sides of the release member into the threads of which the sheets g slide from above and then get seized by the trust motion of the spiral and pushed against the stack being built the belt drive t 1 which connects the separator member drive via the wheel tr.