HP 4550 Service Manual - Page 125

Tray 2 (cassette) The cassette paper sensor (PS8) senses paper in the cassette. Three paper-size detection switches (SW801, SW802, and SW803) detect both the paper size and the presence of a cassette. The timing of the paper pick-up and feeding is based on the home position of the ITB. The pick-up motor (M2) provides the drive force for the front of the paper path. Once the paper-size detection switch receives the ITB home position detection signal, the cassette feed solenoid (SL2) is activated and transmits the rotational force of the pick-up motor to the cassette feeding pick-up roller. The roller picks up the paper from the paper cassette. A separation roller prevents multiple sheets from being fed while paper is fed into the printer's paper path. The cassette feed roller and another feed roller feeds the paper into the printer. The paper passes the registration paper sensor (PS2) and reaches the registration roller. Because the registration roller is not currently rotating, the paper temporarily stops. The paper's leading edge is then curled and any skew is corrected. The DC controller activates the registration clutch (CL1), which feeds the paper to the secondary transfer unit. The leading edge of the image on the intermediate transfer belt is matched with the leading edge of the paper. The paper is fed to the fusing and delivery units (see Figure 5-26). Figure 5-26 Tray 2 (cassette) operation C7085-90921 Chapter 5 Theory of operation 123