Browse Prior Art Database

Original Publication Date: 1991-Apr-30
Included in the Prior Art Database: 2004-Apr-05

Publishing Venue

Xerox Disclosure Journal


A feedback control algorithm for regulating a copy sheet output stacker elevator in electrophotographic copy and printing machines is disclosed. The algorithm relies upon compensating for variables such as mechanical tolerances, power level variations, and torque changes in a decrementing elevator used to maintain a constant distance as accumulated paper is moved downward. An elevator encoder system produces one encoder pulse per millimeter downward movement of an elevator tray. The total number of encoder pulses are compared to a decrement reference value representing complete displacement of the fully loaded elevator. If the encoder pulse value is not in close agreement with the decrement reference value, a feedback compensating correction scheme is invoked to establish a new elevator decrement compensating reference value. The new value is stored in nonvolatile memory and is used on subsequent start-up.