Patent ID: 7441754

Claim:
An apparatus for introducing gas into a large body of liquid, comprising: a platform supported above said body of liquid; a pressurized gas source; a vertical shaft rotatable about its axis, said shaft being supported on said platform and having its lower end extending into said body of liquid; a plurality of blades submerged in said liquid and extending radially from said lower end of said shaft, at least one of said blades comprising a longitudinal member including a passage inside said member closed on one end and in communication with said pressurized gas source through said vertical shaft, and openings between said passage and the lower side of said longitudinal member, and an elastomeric membrane around said longitudinal member, said elastomeric membrane having perforations which are spaced from said longitudinal member openings whereby said membrane substantially blocks said longitudinal member openings when pressure in said longitudinal member passage is no greater than the pressure outside said membrane; and a drive on said platform engaging said vertical shaft for rotating said vertical shaft about its axis, said drive being keyed to selectively allow axial movement of said vertical shaft therethrough.