Carbon dioxide absorbent cannister with condensate control

Claim 1

A cannister for use in an underwater breathing apparatus of the rebreather or recirculated breathing gas type and containing a bed of absorbing composition of the type characterized by an exothermic reaction requiring the presence of moisture, said cannister comprising: a hollow container comprising a thermally conductive wall and adapted to contain said composition, said container comprising inlet means at one end for admitting carbon dioxide containing breathing gas at substantially 100% relative humidity, and outlet means at the opposite end for exiting breathing gas, after passage through said composition, from which said carbon dioxide has been removed; said container having a predetermined length and including portions exposed during use to an ambient medium at temperatures substantially at the dew point of said breathing gas upon admission to said container; condenser means, mounted in said container in contact with said composition, for conducting heat from said gas admission and while passing through said composition, whereby the moisture content of said composition is maintained so as to support said reaction through an extended period; said condenser means comprising at least a first condenser element comprising a plurality of leg portions formed of a thermally conductive material and extending from a common origin within said container, each of said leg portions having an outer end in thermally conducting contact with the inner surface of said wall of said container, a heat sink and diffuser disc comprising a thermally conductive material and fixed to said leg portions, said disc lying generally transversely of the principal direction of flow through the cannister and defining a space between the outer edge of the disc and said wall, and said condenser element having a length in said principal direction of flow that is in the range of from about one-tenth to about two-tenths of said predetermined length of said cannister.