Thermally operated propeller assembly

摘要

A temperature indicating propeller assembly comprises first and second propellers freely suspended one above the other on a common suspension wire for rotation by rising air currents. One propeller is of larger diameter than the other so that it commences rotation by air currents generated at lower temperatures than the other propeller. The assembly can be suspended over a domestic stove, for example, to indicate when the stove is operating at normal temperature by rotation of the one propeller, or when the stove is operating at an excessive temperature by rotation of both propellers.