US Patent 7877995 Machine to convert gravity to mechanical energy

The amount of buoyancy a object has is based on the amount of liquid the object displaces, and the weight of the object. If a submersed object increases in size its buoyancy increases, and if a submersed object decreases in size its buoyancy decreases. This machine attempts to change the size/buoyancy of a submersed object using only gravity as the energy source.