HP Color LaserJet CM4730 Service Manual - Page 214

CASSETTE PAPER signal (CSTPE) PAPER STACK SURFACE signal (CSTPS) LIFTER MOTOR DRIVE signal DC controller PCB Lifting plate Lifter Cassette pick-up roller SR10 SR9 Cassette feed roller Cassette separation roller M10 Cassette pick-up roller Pick-up position Pick-up position Figure 4-38 Media lifting Multiple-feed prevention This MFP uses the paper separation roller method to prevent multiple feeds. The cassette paper separation roller rotates in the same direction as the cassette feed roller. The paper separation roller is imparted with a rotational force, transmitted through the torque limiter. If a multiple feed occurs, the second paper is pushed back to the cassette and only one sheet is fed into the MFP. Normally, the cassette paper separation roller is imparted with a rotational force in the same direction to the cassette feed roller. However, since the paper separation roller touches the feed roller, driving torque from the feed roller brings the torque limiter functions. The torque limiter shuts the rotational force from the separation roller. The paper separation roller follows the rotational direction of the feed roller, in the opposite direction. When the paper is not multiple-fed, the driving force from the feed roller transmits through the single paper and allows the paper separation roller to rotate in the opposite direction. During a multi-feed, the rotational force of the cassette feed roller transmitted to the cassette paper separation roller becomes weak because of the low friction between the sheets. The torque limiter does not function and the paper separation roller rotates in the direction of the drive gear, causing 194 Chapter 4 Theory of operation ENWW