You could have a problem with the operating thermostat (Key 42 in the image below â€“ the thermal fuse is Key 59). This thermostat is designed to open to cycle off the dryer heater at about 150 to 160 degrees. If this thermostat is not opening properly, the heat in the dryer will continue to rise until the thermal fuse blows. You may be able to check for this situation by unplugging the dryer and temporarily connecting the thermal fuse wires to simulate the thermal fuse being properly closed. Run the dryer and monitor the temperature. See if the heater cycles off when the exhaust vent temperature reaches about 150 degrees on high heat. If not, unplug the dryer and check the operating thermostat with a volt/ohm meter while it is still hot. Disconnect one wire (with the dryer unplugged) and measure the resistance. You should measure open (infinite resistance) when the thermostat is still above 150 degrees. It will normally close (measure near zero resistance) as it cools down. You may be able to heat it up with a lighter to make sure that it is opening properly. If the thermostat is stuck closed, replacing it should fix your problem.
If the operating thermostat tests okay, you could have a heater element that is shorted to ground. This will cause the dryer to keep heating until the thermal fuse blows. Carefully inspect the heater element (with the dryer still unplugged) and replace it if necessary.
These tips should help you resolve this dryer problem. If you need more help, resubmit your question with additional details.