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AssigneeGeneral Signal Corporation
InventorsRonald J. Weetman, Frederick W. Kehr, III, Thomas A. Taylor, Jonathan C. Everdyke
Estimating the term…
In order to extend the life of mixing impellers which circulate materials, and particularly which suspend solids, in the form of particles which erode the blades of the impellers and place a practical limit on impeller speed and/or angle of attack due to increased erosion at high flow velocity (erosion being a function of the cube of the velocity), the blades are constructed from blades into an airfoil configuration which does not limit the thickness of the plates and thereby allows the use of thick plates having extended life. An erosion resistant layer is located at least over the leading edge region of the blade and the shape of the blade reduces velocity of flow over the leading edge; the camber of the blade being maximized midway between the leading and trailing edge. The suction surface of the blade in the region subject to erosion is continuous thereby avoiding discontinuities which form vortices which enhance erosion. Fins, which may be at the tip on the suction side of the blade from midway between the leading and trailing edges to the trailing edge reduces tip vortices thereby further extending blade life in erosion-producing environments.
In an impeller having an airfoil blade with opposite sides having external surfaces which provide pressure and suction surfaces of said blade, said blade having leading and trailing edges and extending radially of said impeller from an axis of rotation of said impeller between a tip at an outer end thereof and a base at an inner end thereof, said blade being oriented to produce flow of material which causes erosion principally near the leading edge thereof by sliding of the material as it flows over the suction surface and impact with the pressure surface, the improvement which comprises a first plate and a second plate which are disposed in overlapping relationship and respectively define the suction and pressure surfaces of said blade on exterior sides thereof, said exterior sides extending to interior sides over a thickness which extends the life of said blade in the presence of erosion, an edge of said first plate defining the leading edge of said blade and extending continuously toward the trailing edge covering a distance and area where erosion by sliding of the material principally occurs, said second plate having an edge which contacts the interior surface of said first plate near said edge of said first plate where said blade is subject to erosion by impact, and a layer of erosion resistant material around said leading edge of said blade over the edge of said first plate which defines said leading edge and the edge of said second plate and extending toward said trailing edge over an area of a region of sufficient size at least where erosion by sliding and by impact principally occurs thereby further extending the life of said blade in the presence of erosion, wherein said airfoil blade has a chord between the leading and trailing edges thereof, said airfoil blade having camber and defining a location behind said leading edge where said camber is maximized at a distance about 50% of the length of said chord from said leading edge.
In a mixing system wherein a slurry is circulated by an impeller having a plurality of blades subject to erosion as they rotate about an axis, the improvement for extending the life of said impeller characterized in that each said blade of said plurality of blades comprises a first plate and a second plate, said first plate having an exterior surface which defines the suction surface of said blade, said second plate having an exterior surface which defines the pressure surface of said blade, said first plate having an edge which defines the leading edge of said blade, said first plate extending continuously toward an edge of said first plate which defines the trailing edge of said blade at least a distance toward the trailing edge over the region where said first plate is subject to sliding erosion, said first plate having greater curvature than said second plate to define a nest in which said second plate is disposed with said first plate overlapping and second plate along said leading edge to define a wedge shaped notch along and behind said leading edge, said notch being filled with material which assembles said plates together, and a layer of erosion resistant material more resistant to erosion than said plates on exterior surfaces of said first and second plates and said material in said notch over at least said distance behind said leading edge to cover said region on said suction surface and another region on said pressure surface of area commensurate with said first named region on said suction surface, wherein said blade is an airfoil having a chord between the leading and trailing edges thereof, said airfoil having camber and defining a location behind said leading edge where the camber is maximized at a distance about 50% of the length of said chord from said leading edge.
Dependencies are inferred from the claim text.