Underwater breathing apparatus

A self-contained underwater breathing apparatus comprising a pack assembly to be worn by a diver, air inlet and exhaust air hoses connected to said pack assembly, and a float assembly for supporting the upper ends of said air inlet and exhaust air hoses above the water surface and open to the atmosphere;

• said pack assembly including an airdriven compressor having an inlet and an outlet and including means driven by the exhalation of a diver for compressing air therein, the lower end of said air inlet hose being connected to the inlet of said compressor for transferring air thereto, a check valve permitting air flow through said air inlet hose only toward said compressor, said pack assembly including a compressed air reservoir, conduit means connecting the outlet of said compressor to said compressed air reservoir, a check valve in said conduit means permitting air flow only toward said air reservoir, conduit means for delivering compressed air from said reservoir to a diver, a demand regulator in said latter conduit means for controlling the pressure of the air delivered therethrough, conduit means for delivering the diver's exhaled air to said compressor to drive said compressor, valve means for releasing the exhaled air from said compressor into said exhaust air hose upon termination of the diver's exhalation, said compressor including an air compressing element movable within said compressor for compressing air therein means for resiliently returning said air compressing element upon termination of exhalation to evacuate the exhaled air through said exhaust air hose and to draw a fresh charge of surface air through said air inlet hose into the compressor, and a manually actuatable auxiliary compressor connected between said air inlet hose and said air reservoir to supplement the air-driven compressor upon startup, during emergencies, or to make up system losses.