Abstract: Apparatus for accumulating rows of paper sheets which are disposed in vertical planes has two pairs of endless chain conveyors whose upper reaches advance at a relatively low speed below two sheet feeding conveyors which deposit successive sheets between the front and rear sheet confining plates of one pair of chain conveyors while the chain conveyors of the other pair advance a fully grown row at a relatively high speed below a pair of claws which lift the fully grown row and transfer it sidewise to the next processing station. The chain conveyors of the other pair then advance their sheet confining plates at the high speed to a waiting position in which their leading confining plate is located immediately behind the trailing confining plate of the chain conveyors of the one pair. The cycle is thereupon repeated except that the growing row of sheets is being accumulated between the plates of the chain conveyors of the other pair.