. . . "Conventionally as shown in FIGS. 7A and FIG. 7B, in order to stack sheets of corrugated cardboard, paper, plastic film, foil and other various material cut by a sheet cutting machine 82 into the stacking zone, sheets 86 are transferred by a high speed conveyor 84 and their transfer speed is reduced by an overlap conveyor 88 (a low speed conveyor) having a speed difference from the high speed conve" . . .