Paper cartridge with paper aligning means

In a paper cartridge comprising a table for placing and storing thereon sheets of paper transported along a paper transporting passageway which defines a direction of transportation, two side plates parallel to said direction of transportation adapted to individually contact the two edges of sheets placed on said table, and to move perpendicularly to said direction of transportation, and a back plate adapted to contact the back edges of sheets placed on said table and to move in said direction of transportation, the improvement wherein said paper cartridge further comprises a first mechanism for moving said two side plates symmetrically with respect to a central axis along said direction of transportation, a second mechanism for moving said back plate along said direction of transportation, detectors attached to said side and back plates and adapted to detect edges of sheets, and side-plate and back-plate control means for operating said first and second mechanisms, respectively, according to outputs from said detectors, said control means being so programmed as to automatically operate said mechanisms when sheets of paper are placed on said table to move said side and back plates away from one another to home positions thereof, to thereafter move said side plates towards each other while measuring a distance L traveled by said side plates between a first point in time when one of said detectors attached to one of said side plates detects a sheet and a second point in time when another one of said detectors attached to the other of said side plates detects said sheet, and to further move said side plates by a/2 if L is greater than a, a being a distance determined by the positions of said detectors on the respective ones of said plates, to move said back plate in said direction of transportation until one of said detectors attached to said back plate detects a sheet, to thereafter repeatedly move said back plate by a distance a+x in said direction of transportation where x is a predetermined distance and by another 2a+x opposite said direction of transportation, to thereafter move said back plate in said direction of transportation until one of said detectors attached to said back plate detects a sheet, and thereafter to move said back plate by a in said direction of transportation.