Sheet transport apparatus

A sheet transport apparatus comprising:

• means for maintaining a stack of sheets with the topmost sheet of said stack at a predetermined position;
• suction drum means supported adjacent said topmost sheet of said stack with a clearance therebetween at the leading edge portion of said topmost sheet for picking up said topmost sheet in the transport direction, said drum means comprising a rotatable cylindrical member with an elongated apertured zone in its curved surface, the peripheral length of said apertured zone being less than the length of said sheets;
• a stationary suction chamber positioned within said cylindrical member and extending along the inner surface of said cylindrical member, said stationary suction chamber having an opening which opens adjacent to the inner surface of said cylindrical member for picking up said topmost sheet of said stack when the leading end of said apertured zone of said cylindrical member passes by said opening of said suction chamber;
• and means for rotating said cylindrical member in a manner that the periphery of said cylindrical member facing to the leading edge portion of said topmost sheet moves in the transport direction, said rotating means rotating said cylindrical member in a cyclic operation of acceleration-deceleration and in such a relation that said leading end of said apertured zone of said cylindrical member is substantially aligned with the leading edge of said topmost sheet of said stack when said cylindrical member reaches the minimum speed in its cyclic operation;
• and
• means for conveying said picked-up topmost sheet away from said suction drum means, said conveying means comprising a pair of constant speed belt conveyor devices defining first and second conveying paths and an entrance area therebetween in such a manner that the conveying belts gradually approach each other in the transport direction initially making frictional contact with the leading edge of a sheet picked up and fed by said suction drum means while the traveling speed of said belt conveyor devices exceeds the peripheral speed of said cylindrical member and while the trailing portion of the sheet is still under suction by the suction drum means whereby said sheet is flattened and then becomes contiguous with said belts, and thereafter said conveying belts grasping the leading edge of said picked-up sheet, said second conveying path and said first conveying path thereafter being the same while the conveying belts travel contiguously in the transport direction;
• the maximum peripheral speed of said cylindrical member being selected nearly equal to the travelling speed of said conveying belts;
• and
• said sheet being grasped at the leading edge between said conveying belts and released from said suction drum when the peripheral speed of said cylindrical member reaches the maximum speed.