Buoyancy Control Device Alternative
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Problem Statement
Current Buoyancy Control Devices (BCDs) use air from the oxygen tank to inflate a vest worn by the diver. As the inflatable bladders in the vest expand with air input, the volume of the diver increases resulting in an increased buoyant force and vice versa. A diver is neutrally buoyant when the buoyant force is equal to the gravitational force on the diver. Due to the changing pressure at different water depths, the volume of the vest is not constant. As the diver dives deeper, the ambient water pressure increases, reducing the vest volume and the buoyant force, causing the diver to accelerate downward. Similarly, as the diver rises, the ambient water pressure decreases, increasing vest volume and the buoyant force, causing the diver to accelerate upward. This runaway effect of the unstable neutrally buoyant equilibrium can result in decompression sickness (“the bends”) and other injury primarily in newer divers.
The design employs rigid pressure vessels to prevent the effect of changing ambient water pressure.
Instead of altering the volume of the diver-BCD system, the system’s density is changed by adjusting the water-to-air ratio in the pressure vessels.
User interaction
The user sets the volume once at the beginning of the dive by pressing the water out button. When pressed, the bladders (pink) inside the aluminum cylinders expand by taking air from the oxygen tank thereby pushing water out. As a result, the effective density of the system decreases, increasing the buoyant force. Once neutral buoyancy is achieved, the diver no longer needs to use the handheld controller until the dive is complete. If the diver feels too buoyant, air can be released using the air out button which allows water to enter the vessels increasing effect density.
Pressure vessel assembly using aluminum for the vessel itself and a custom molded elastic plastic.