Patent ID: 8069808

Claim:
A buoyancy control system comprising: a housing; a first piston supported by the housing such that movement of the first piston changes a volume of a control chamber; a second piston supported by the housing such that movement of the second piston changes the volume of the control chamber; a source of pressurized working fluid; and first and second valves operatively connected between the source of pressurized fluid and the first and second pistons to allow pressurized working fluid to displace at least one of the first and second pistons relative to the housing; wherein the buoyancy control system is operable in a shallow mode in a first range of depths and in a deep mode in a second range of depths; in the shallow mode, the first and second valves are controlled to allow fluid to flow from the source of pressurized fluid to the first piston such that the pressurized fluid displaces the first piston to alter the volume of the control chamber and thus a buoyancy of the buoyancy control system; and in the deep mode, the first and second valves are controlled to allow fluid to flow from the source of pressurized fluid to the first and second pistons such that the pressurized fluid displaces both of the first and second pistons to alter the volume of the control chamber and thus the buoyancy of the buoyancy control system.