Xerox Phaser 6180MFP Service Manual page 110

Theory of Operation
2-28
However, when two sheets are fed concurrently, only the Feed Roller rotates.
The Retard Roller is coupled to a friction clutch that prevents the roller from
rotating due to the extra force from feeding two sheets; this process allows the
upper sheet to pass by as the lower sheet is stopped by the friction with the
Retard Roller at rest.
The Retard Roller is pushed toward the Feed Roller by spring pressure, and
controlled by the Torque Limiter (Friction Clutch Retard) with which it is
coupled.
Multiple Feed
Torque Limiter
Retard Roller
Tray 1 (MPT) Feed Roller
Phaser 6180MFP Multifunction Printer Service Manual
Retard Roller
s6180mfp-050