The invention contemplates an automatic device for closely held temperature control of a body of liquid via an electric heater, as for example via a liquid-immersed heater element. The control device provides an enclosed air space with shared exposure to ambient air and to air that has been heated by...http://www.google.fr/patents/US3973102?utm_source=gb-gplus-shareBrevet US3973102 - Heating and temperature control device for a bath-liquid
Heating and temperature control device for a bath-liquid
