disclosed is an accumulator for paper sheets which are conveyed by conveyor belts to a receiving area comprised of parallel support members having spaces therebetween . the conveyor belts are mounted on rollers , at least one set of which is mounted on a first track - mounted movable carriage , and at least one other set of which is mounted on a second track - mounted movable carriage . the two carriages are linked so that motion of said first carriage to adjust the length of the receiving areas causes motion of said second carriage in a direction opposite to the motion of said first carriage to thereby maintain the conveyor belts under constant tension . the support members may be constituted of either plastic or metallic strips or rods . at least one set of rollers also has bristle means to aid in the conveyance of the paper sheets .