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US 5,988,604 AGranted
Mixing impellers especially adapted for use in surface aeration
AssigneeGeneral Signal Corporation
InventorJohn R. McWhirter
Life of this patent
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AssigneeGeneral Signal Corporation
InventorJohn R. McWhirter
Estimating the term…
Impellers are provided which enhance the efficiency of surface aeration of a liquid, for example, liquid contained in open aeration tanks, in terms of the mass of oxygen transferred per hour to the liquid per horsepower used in driving the impeller. The impeller is an axial flow impeller and may be either a pitched blade turbine (PBT) or have airfoil shaped blades. In either case, the impeller has a portion which extends radially along an edge thereof which projects above the surface of the liquid being mixed in a vertical direction, a sufficient distance to substantially prevent flow of the liquid over the top edges of the blades of the impeller. Preferably, the impeller is rotated in an up-pumping direction and propels the liquid being aerated in a radially outward direction. A sufficient upward surge of liquid is produced so that the liquid is observed to splash back onto the surface a plurality of times in the course of operation of the impeller. Such multiple splashing action enhances the contact between the air and the liquid and lends itself to the improved efficiency of aeration.
In a system for aeration of liquid in a tank, an improved surface aeration impeller, said liquid in said tank having its surface at a certain level when static, which impeller comprises a plurality of generally rectangular blades rotatable about an axis and extending below and above said surface, each of said blades having a first portion which is pitched with respect to said axis and to the surface of said liquid in said tank, and which is disposed below said surface and projects above said surface, and a second portion of said blade which extends generally vertically with respect to said surface of said liquid when static, upwardly from said first portion.
An impeller for aeration of liquid when rotated about an axis which intersects the surface of said liquid and which axis is generally vertical to said surface, said impeller comprising a plurality of blades of shape to provide for axial flow of said liquid, each blade having a first blade portion with a surface which drives said liquid and extending generally entirely radially from said axis and a second portion having a surface which also extends generally entirely radially from said axis and also extending in a direction generally along said axis so that said axially extending portion projects generally vertically above said surface to drive and engage said liquid as said liquid is driven axially by said first portion thereby substantially preventing flow in a direction opposite to the direction of rotation of said impeller over said second portion.
Dependencies are inferred from the claim text.