Drive for sheet feeder in printing press

摘要

A sheet fed printing press having an impression cylinder with a feed board presenting a sheet with its leading edge in a position for pick up. A rotary sheet feeder is interposed between the feed board and the impression cylinder for picking up the leading edge of the sheet from its stationary position and transferring the leading edge to grippers on the moving impression cylinder. The sheet feeder is directly driven by a high powered electric motor. High resolution pick up heads and associated angle coders produce output signals respectively representative of the phase position of the cylinder and sheet feeder. A programmed phase offset device is provided defining a predetermined relation of desired feeder phase as a function of impression cylinder phase. A comparator constantly compares the relation of the signals from the angle coders to the desired relation stored in the programmed phase offset device and produces a control signal which is representative of any current difference between the two relations. An amplifier is interposed between the comparator and the electric motor for correctively energizing the motor so that the feeder is driven in the currently desired phase relation.