Liquid aerator

Abstract

A floating liquid aerator includes an axial flow impeller rotated by an electric motor and disposed within a tubular throat to pump water from a pond upwardly through the throat and against a rotatable diffuser which slings the water outwardly for interface contact with the surrounding atmosphere. Being rotatable, the diffuser slings the water into the atmosphere with considerable turbulence thereby exposing more of the water droplets to the atmosphere and resulting in a higher transfer of oxygen to the water. The impeller comprises a series of angularly spaced blades formed with a rectangular cross-section to reduce power losses caused by drag and to increase the volume of water capable of being displaced by the impeller. Each blade is twisted longitudinally with a progressively decreasing attack angle from its root to its tip and, in addition, all of the blades are twisted identically to provide a statically, dynamically and hydrodynamically balanced impeller. .Iadd.

We.]. .Iadd.I .Iaddend.claim:  .[.1. In a liquid aerator, the combination of, a support having an upright tubular throat adapted for immersion in a body of liquid at its lower end and defining an opening at its upper end for the discharge of liquid pumped upwardly through the throat, a power rotated shaft carried by said support and extending axially into said throat, an axial flow impeller disposed within said throat and fixed to and rotatable with the lower end portion of said shaft to pump a column of liquid upwardly through the throat in response to rotation of the shaft, and a diffuser fixed to and rotatable with said shaft above said impeller and adjacent the upper end of said throat and operable to impinge against the upper end of the column of liquid pumped upwardly through the throat and to deflect the liquid outwardly of the throat with considerable turbulence..]. .[.2. A liquid aerator as defined in claim 1 in which said rotatable diffuser includes a generally conical lower surface concentric with said shaft and tapering downwardly and inwardly, and the lower surface of said diffuser receiving a lifting force from the upwardly moving liquid to offset partially the downward thrust imposed on said shaft as a result of rotation of said impeller..]. .[.3. A liquid aerator as defined in claim 1 in which said impeller comprises a central hub attached to said shaft, a series of blades radiating outwardly from and spaced equally around said hub with their roots fixed to the hub and with their tips spaced radially inwardly from said throat, each of said blades being twisted longitudinally with a progressively decreasing attack angle from its root to its tip to develop substantially the same volume of flow at all points along the length of the blade, and each blade being formed with upper and lower surfaces of substantially equal width and extending parallel to one another to cause the velocity of liquid flowing across the upper surface to approximate the velocity of the liquid flowing across the 
     
        lower surface..]. 4. In a liquid aerator, the combination of, a support having an upright tubular throat adapted for immersion in a body of liquid at its lower end and defining an opening at its upper end for the discharge of liquid pumped upwardly through the throat, a power rotated shaft carried by said support and extending axially into said throat, an axial flow impeller disposed within said throat and fixed to and rotatable with the lower end portion of said shaft to pump a column of liquid upwardly through the throat in response to rotation of the shaft, said impeller comprising a central hub attached to said shaft, a series of blades radiating outwardly from and spaced equally around said hub with their roots fixed to the hub and with their tips spaced radially inwardly from said throat, each of said blades being twisted longitudinally with a progressively decreasing attack angle from its root to its tip to develop substantially the same volume of flow at all points along the length of the blade, and each blade being formed with upper and lower surfaces of substantially equal width and extending parallel to one another to cause the velocity of liquid flowing across the upper surface to approximate the 
     
     
        velocity of the liquid flowing across the lower surface. 5. An aerator as defined in claim 4 in which each of said blades is .[.of rectangular cross-section and is.]. formed from a metal plate whose upper and lower 
     
     
        surfaces are initially flat and lie in two parallel planes. 6. An aerator as defined in claim 4 in which said hub is formed with slots spaced equally around its outer surface and located at predetermined angles to the horizontal, the roots of said blades being located in said slots and 
     
     
        being welded to said hub. 7. In a method of forming an axial flow impeller having an upright central hub and a series of blades radiating outwardly from and spaced equally around said hub, said method comprising the steps of rigidly attaching to the hub at equally spaced locations and at equal angles to the horizontal a series of metal plates having initially flat and parallel upper and lower surfaces, and gripping the outer end portion of each plate and twisting the latter longitudinally and uniformly about its center line to decrease linearly from the inner end of the plate to the outer end of the plate the angle of the plate to the horizontal while still maintaining the upper and lower surfaces of the plate parallel to 
     
     
        one another. 8. A method as defined in claim 7 in which the step of attaching said blades to said hub includes placing the inner ends of the blades into slots spaced equally around the hub at predetermined angles to the horizontal, and thereafter welding the inner ends of the blades to the hub while said inner ends are held in said slots.