Exit tray corrugation slip rolls with a variable force idler

Abstract

An apparatus and method that describes utilizing a corrugation slip nip system, including a variable force idler that encompasses three stages, to prevent buckling of copy sheets traveling at a high rate of speed upon exiting from a high speed printing machine to the exit tray for stacking. Buckling concerns are eliminated by allowing the sheet, driven by a high speed positive drive nip, to slip through the slower speed corrugation nip, yet still having enough drive force in the slip nip to drive the sheet into the exit tray. In order to vary the normal force on the sheet, a three stage variable force idler is used. The first stage oversizes the inner diameter of the idler rollers on the idler shaft. The second stage uses a slot in the spring which allows the idler shaft to move upward without deflecting the spring. These first two stages are particularly adapted for light weight paper. The third stage occurs when the idler shaft is topped out in the shaft slot such that the paper deflects the spring causing additional force to be applied to the paper to drive the paper out of the system and into the exit tray. The third stage is reached only where heavy weight paper is used because heavy weight paper has sufficient beam strength to deflect the spring.