Function Of Center Thermostat And Thermal Fuse - Panasonic SR-GA281 Service Manual

3. FUNCTION OF CENTER THERMOSTAT AND THERMAL FUSE

A. Center Thermostat
The center thermostat senses when the bottom of the rice cooker pan reach 134°C ± 6°C. And it's action
turns off the cooking cycle and starts the warming cycle.
Center thermostat construction
Metal
Magnet Inner spring
Cooking heater
Inner spring
Figure 1 Rod
(Cooking Position)
Refer to these figures showing the center thermostat construction and cooking position. As the metal is
heated, its ability to be attracted by the magnet decreases.
Finally, the inner spring pressure becomes stronger than the magnetic pull, the metal and magnet will pop
apart. The rod activates the switch lever which causes the auxiliary lever to press the micro-switch button
into the warming cycle.
B. Switch-On Preventive System
Metal
Cooking heater
Magnet
10mm
This is design to prevent the rice cooker from being turned on without the pan placed into position.
1) Normally when the pan is inserted properly into the rice cooker, the pan will depress the center thermostat.
The center thermostat outer spring will be compressed. In this case when the switch button is depressed,
the following will happen :
a. The auxiliary lever will release the micro-switch button. This puts the mirco-switch in the cook position.
b. The switch lever will push the rod which will allow the magnet to meet with the metal.
c. When the rice is cooked and the proper temperature has been reached 134°C ± 6°C, the metal and
magnet will pop apart as described in the center thermostat operation above.
d. The rod will push the switch lever and cause the auxiliary lever to depress the micro-switch button. This
puts the micro-switch in the warming position.
2) When the pan is not in place within the rice cooker, the center thermostat is not depressed.
a. In this condition, the outer spring is not compressed within the center thermostat preventing the metal
from reaching its normal operating position.
b. When the switch button is depressed, the switch lever and auxiliary lever work as above but the magnet
cannot come in contact with the metal to hold the switch lever in the cook position. This happens because
the switch lever hits the thermostat case and cannot push the rod with the magnet attached, all they way
up to meet with the metal.
c. When the pressure is taken off the switch button, the switch lever releases immediately to the open or
warm positons.
Outer spring
(Warming or Off Position)
Thermostat surface
Inner spring
Outer spring
Thermostat case
Rod
Switch lever
- 6 -
Cook switch button
Switch lever
NC
C
Cook switch button
Auxiliary lever
Micro switch
SR-GA281 / SR-GA421 / SR-GA721
Micro switch