Star Micronics WinType 4000, Technical Manual

Page: 21 / 180

– 17 –
THEORY OF OPERATION
3.3 Fuser & Paper Exit
• Fuser Assembly
The fuser assembly includes the heater rod, heat roller, pressure roller, thermostat, thermistor and exit sensor. This
assembly fixes the toner onto the paper using heat and pressure, then outputs the printed paper.
Parts in the fuser assembly are referred to as fusers.
Heater Rod
The heater rod is a lamp with a heated coil sealed inside it and serves as the heat source inside the heat roller.
Heat Roller
The hollow, metal heat roller is coated on the surface and provides the heat to fuse the toner to the paper.
Pressure Roller
The rubber pressure roller provides the pressure to fuse the toner to the paper.
Thermistor
The thermistor is in contact with the heat roller and responds to its surface temperature.
When the heater rod is ON (a light is on), the thermistor controls the ON/OFF position of the heater rod according
to the temperature detected and prevents excessive increases in the primary temperature.
Thermostat
The thermostat is in series with the power supply in the heater rod. If the thermistor fails to prevent an excessive
increase in the (primary) temperature, the thermostat prevents an excessive increase in the secondary temperature
by opening the point of contact that results when the ambient temperature reaches a set level.
Thermal Fuse
The thermal fuse is in series with the heater rod circuit. If the thermistor fails to prevent the (primary) temperature
from getting too high and the thermostat fails to prevent the (secondary) temperature from getting too high, the
fuse will prevent tertiary overheating by melting when the ambient temperature reaches a set level.
Exit Roller
After fusing the toner onto the paper, the exit roller passes the printed paper out of the printer.
Exit Sensor
The exit sensor detects the state of the printed paper in the exit area in response to changes in the position of the
exit actuator. The exit sensor is turned ON when the presence of the printed paper is detected.