A sheet stacking device includes a support frame, a conveyor and an accumulator at a discharge end of the conveyor, the accumulator having a plurality of elongate fingers, at least one of which includes a rack having teeth along a first side, a rotatable drive shaft extending in a width direction of the conveyor, a gear having teeth mounted on the drive shaft and operatively engaging the rack teeth, and a rotary actuator operably connected to the drive shaft, the rotary actuator rotating said drive shaft in a first and second directions to move an end of the elongate fingers toward and away from the conveyor discharge end of the conveyor. Also a method of operating the device.