Canon LBP 2460 Service Manual - Page 91

CHAPTER 2 B. Paper Pick-up Unit 1. Cassette feed Presence of the upper and lower cassettes is detected by the upper cassette sensor (PS1202) and lower cassette sensor (PS1201). The presence of paper is detected by the upper cassette paperout sensor (PS1207) and lower cassette paper-out sensor (PS1208). The paper size is detected by the four upper and lower cassette paper-size sensing switches (SW1601 to SW1604) installed in the upper and lower cassettes. Table 2-5-1 lists combinations of cassette paper-size sensing switches. The paper level in the upper cassette is detected by combinations of outputs from the upper cassette paper-level sensor 1 (PS1205) and upper cassette paper-level sensor 2 (PS1206). The paper level in the lower cassette is detected by combinations of outputs from the lower cassette paper-level sensor 1 (PS1203) and lower cassette paper-level sensor 2 (PS1204). Figure 2-5-3 shows combinations of PS1205, PS1203, PS1206, and PS1204. When the video controller inputs the /PRNT signal into the printer, the cassette pick-up motor (SMT1) starts operation. The cassette pick-up motor is a stepping motor, when rotating clockwise, it drives the cassette pick-up roller, feed roller 1, and separation roller on the upper cassette to enable printer to feed paper from the upper cassette. When it rotates counter clockwise, it drives the cassette pick-up roller, feed roller 1, and separation roller on the lower cassette to enable the printer to feed paper from the lower cassette. Following this, the cassette pick-up solenoid (SL1) turns on, the main motor then drives the cassette pick-up roller lowering cam to lower the cassette pick-up roller to the paper surface. Paper is fed by the rotating cassette pick-up roller. The paper picked up by the cassette pick-up roller is fed into the printer by feed rollers 1 and 2. If more than one sheet is picked up, unnecessary sheets are discharged by the separation roller. The paper passes through the pick-up unit paper sensor (PS2), the registration paper sensor (PS1) and then reaches the registration roller. The registration roller does not rotate, so the paper is stopped. The leading edge of the paper is looped to correct any skew. When the VERTICAL SYNC signal (/VSYNC) is received, the registration clutch (CL1) turns on and the paper is fed again. Table 2-5-1 Paper size Ledger A3 B4 Legal Letter A4 Cassette paper-size sensing switch SW1601 SW1602 SW1603 SW1604 OFF OFF OFF OFF OFF ON OFF OFF ON OFF OFF OFF ON ON OFF OFF OFF OFF OFF ON OFF OFF ON OFF 2 - 45