Jam sensing at document feeding station

A method for preventing damage to a document by a feeding station, comprising

• a) providing a member for receiving a stack of sheets to be serial fed to the feeding station;
• b) providing at least two spaced-apart microphones disposed at the feeding station and responsive to audio to produce signals representing audio energy received by each microphone respectively;
• c) comparing the energy received from each microphone to determine if it is ambient noise or if it represents that two attached sheets are being fed or a single sheet is being damaged;
• and
• d) shutting off the feeding station to prevent damage to documents when it has been determined that two attached sheets are being fed or a single sheet is being damaged.

A feed apparatus for feeding a document onto a transport path, the feeding apparatus comprising:

• an input tray that holds the document;
• one or more feed rollers energizable to pull the document from the input tray and guide the document along a media transport path;
• a left audio transducer disposed on the left side of the input tray and energizable to provide a left audio signal indicative of ambient noise and of sound from the input tray;
• a right audio transducer disposed on the right side of the input tray and energizable to provide a right audio signal also indicative of ambient noise and of sound from the input tray;
• a middle audio transducer disposed along the media transport path behind the one or more feed rollers relative to the input tray and energizable to provide a middle audio signal indicative of document transport past the feed rollers;
• and
• a document feed sensing apparatus that compares the left, right, and middle audio signals and provides an output signal that indicates jam detection according to the comparison.

A method for detecting a document jam in a document feed apparatus, the method comprising:

• sampling left and right audio signals from right and left microphones that are disposed on corresponding sides of an input tray to a media transport path;
• cross-correlating the left and right microphone audio signals and comparing the results against a predetermined threshold value;
• and
• reporting a jam condition according to cross-correlation results.