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PAPER CURL DETECTOR Disclosure Number: IPCOM000026293D
Original Publication Date: 1991-Feb-28
Included in the Prior Art Database: 2004-Apr-05

Publishing Venue

Xerox Disclosure Journal


A device and method for detecting paper curl in paper feeders for electrophotographic printers and copiers are disclosed. Paper quality, paper properties and environmental conditions affect paper feedability. Paper curl presents a particularly troublesome feeding problem. Paper curl occurs frequently when paper is exposed to high or low humidity environments and during the transition between humidity extremes. Up or back curl may cause copy sheets to misfeed, multifeed or jam. A device for detecting paper curl in a paper feeder is shown in the Figures and comprises a transducer 1 located above the paper stack 2 that determines the distance between the top of the paper stack and a nudger roll 3. A plunger 4 connected to the transducer rests gently upon and moves with the paper stack when elevated mechanically. A reference function is generated by measuring the transducer output versus time with flat sheet stock, as shown in Figure 1. The result is a step function showing a constant slope. When the paper stack contains curled sheets, as shown in Figure 2, the constant slope function is disrupted, indicating excessive paper curl. When excessive paper curl is detected, the operator is notified by a machine interface indicator to replace with fresh flat paper stock.