ROLL MOTION SENSING
Original Publication Date: 1995-Oct-31
Included in the Prior Art Database: 2004-Apr-07
Xerox Disclosure Journal
Some active retard roll feeders incorporate an upper driven roll, as well as, an oppositely driven lower idler roll. The idler roll is fitted with a slip clutch which under normal operating conditions turns in the same direction as the upper roll. Should a multifeed occur, the coefficient of friction is lost between the two rolls due to the layered sheets and the torque developed by the slip clutch which is sufficient to drive the multifed sheet in the opposite direction. Single sheet feeding of this type of retard feeder can be improved by monitoring the idler roll direction by the addition of an encoder mounted on the idler roll shaft. The encoder used is the dual channel type, and when used in quadriture mode will indicate phase differences based on the direction of rotation. The resulting signal is then processed by an integration circuit which will determine if a multifeed has occurred. The required feeder parameter changes would then be made manually or automatically based on the direction of the roll. The signal can also be used to give a warning of incipient failure, or to call a service technician. Hall Effect sensors are usable for this purpose.