in the example shown substantially equal to 90 u00b0 conveyor 4 is preferably a suction conveyor and is defined by a number of endless belts 6 arranged side by side and each looped about two guide rollers 7 only one of which is shown the rollers 7 at the output end portion 8 of conveyor 4 present a common axis 9 and are all fitted to a common shaft 10 coaxial with and rotated in steps about axis 9 by a motor 11 rollers 7 define on belts 6 a top supply or transportation branch 12 and a bottom return branch 13 and branches 12 coplanar with one another define a transportation surface 14 for feeding sheets 2 to a station 15 where they are transferred from conveyor 4 to conveyor 5 conveyor 5 is a suction conveyor and is defined by a number of endless suction belts 16 only one of which is shown arranged side by side and each looped about two guide rollers 17 and 18 and a suction box 16a rollers 17 and 18 are fitted respectively to common shafts 19 and 20 perpendicular to axis 9 and shaft 19 is connected to the output of a motor 21 by which it is rotated in steps clockwise in the accompanying drawing and in time with the step rotation of shaft 10 by motor 11.