Vacuum document feeder

A vacuum automatic document feeder for feeding single documents from a document stack onto the document platen of a convenience copier comprising in combination:

• a means for supporting the stack;
• a pair of vacuum picker assembly means disposed above the stack, said pair of vacuum picker assembly means being operable to lift the topmost sheet and to transport said sheet through a straight path to a transition zone above the stack;
• a vacuum transport means disposed at the transition zone, said vacuum transport means being orientated in a plane perpendicular to the straight path;
• a valve means operable to control vacuum to said pair of vacuum picker assembly means;
• a switch means operable to control the closing and opening of said valve means;
• a pressure sensing means coupled to the pair of vacuum picker assembly means and the vacuum transport means, said pressure sensing means being operable to sense pressure therein;
• and
• a programmed microcomputer responsive to signals outputted from the pressure sensing means and operable to enable the switch means after a predetermined time-out interval so that the vacuum to the pair of vacuum picker assembly means is dropped when said pair of vacuum picker assembly means is positioned relative to the bottom surface of the vacuum transport means whereby the sheet is dislodged without relative motion onto the vacuum transport means.