The novelty is indeed the bell combined with the rocket stove. A classic old Kachelofen restricts the airflow since the channels that the fire fades are routed

The novelty is indeed the bell combined with the rocket stove. A classic old Kachelofen restricts the airflow since the channels that the fire fades are routed through are long and often small. This construction achieves the same effect of capturing almost all of the heat from the fire, but does not restrict airflow. Better airflow leads to a better combustion. It’s a pretty ingenious modification of a known concept. As far as I can tell, this is indeed new.