Tank heater for respiratory mixtures used in deep diving

Claim 1

In a resipratory system for underwater divers having a breathing mixture supply and a breathing apparatus, the improvement comprising heating apparatus adapted to heat a breathing mixture as it flows from the breathing mixture supply to the breathing apparatus, said heating apparatus comprising: a tank housing having an inlet port and an outlet port; a porous electrical heating means in said tank housing for heating the breathing mixture to a predetermined desired temperature, the heat-exchange surface area of said heating means being of such magnitude that, when said heating means is maintained at a temperature substantially equal to the predetermined desired temperature, a breathing mixture having an initial temperature below the desired temperature when introduced into Said tank housing from the breathing mixture supply will have its temperature raised to be substantially equal to the predetermined desired temperature at said outlet port; a source of electrical power connected to said heating means; a sensor located within said tank housing adjacent to said outlet port, said sensor being adapted to sense the temperature of its surroundings; and electrical control means operatively connected to said source of electrical power, said sensor, and said heating means, said electrical control means being adapted to be responsive to said sensor to control the supply of electrical power to said heating means and to maintain the temperature of the breathing mixture at said outlet substantially equal to the predetermined desired temperature.