HP LaserJet 1100 Service Manual - Page 50

Printer paper feed system The paper input bin and the single-sheet input slot merge into one, main input area. Paper placed in either of these areas enables the paper-out sensor (PS001), which informs the ECU that paper is present. The following steps occur when the printer receives a print job: Step 1 The ECU enables the laser/scanner assembly and the motor. Paper motion begins when the ECU energizes the solenoid (SL001). Step 2 The paper pickup roller rotates once. The paper kick plate pushes the paper against the pickup roller. Step 3 The pickup roller grabs the top sheet and advances it to the feed assembly drive rollers. To ensure that only one sheet is fed, a main separation pad and two subpads hold the remainder of the stack in place. Step 4 The feed assembly drive rollers advance the paper to the paper top photosensor (PS002). This sensor informs the ECU of the exact location of the paper's leading edge, so that the image being written on the photosensitive drum can be precisely positioned on the page. Step 5 The feed assembly drive rollers then advance the paper to the transfer area where the toner image on the photosensitive drum is transferred to paper. Step 6 After the image is transferred, the paper enters the fusing assembly where heat from the fuser and pressure from the pressure roller permanently bond the toner image to paper. The paper exit sensor (PS201) determines that paper has successfully moved out of the fusing area. Step 7 The fusing assembly exit rollers deliver paper to either the paper output bin or the front paper output slot, depending upon the position of the face-up/face-down lever. C4224-90962 Figure 3-6 Simplified paper path 1 Paper input bin 2 Single sheet input slot Printer paper feed system 53