Electronic sheet rotator with deskew, using single variable speed roller

Abstract

A device for selectively turning documents includes first and second drive rollers aligned along an axis which is transverse to a process direction along which documents are fed, and first and second follower rollers cooperatively peripherally aligned with the first and second drive rollers, respectively. One of the drive rollers is operated at a substantially constant peripheral velocity by a first drive which is a constant velocity motor while the other drive roller is operated at a variable peripheral velocity by a variable speed drive so that the document is turned. Thus, only a single variable speed drive, such as, for example a stepper motor or servo system, is required. The variable speed drive is driven through a variable velocity profile to control the amount of rotation of the document. Preferably the document is turned approximately 90.degree.. By placing a pair of sensors adjacent the drive rollers, the skew of the document prior to being rotated can be measured and used to determine the velocity profile for controlling the variable speed motor. After the document is rotated, the same two sensors are used to detect the skew, if any, of the trailing edge of the turned document for correction of the velocity profile used to rotate subsequent documents. An additional mechanism can be provided for shifting the connection of the constant velocity and variable speed motors between the first and second drive rollers so that a sheet can be rotated in opposite directions.