High gas dispersion efficiency glass coated impeller

Agitating – Stirrer within stationary mixing chamber – Pump type

Reexamination Certificate

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Details

C366S330300, C366S330700, C416S24100B, C416S243000

Reexamination Certificate

active

06190033

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to corrosion resistant mixing impellers and more particularly relates to glass coated metal mixing impellers.
Glass coating of metal substrates is well known as, for example, described in U.S. Patents RE 35,625; U.S. Pat. Nos. 3,775,164 and 3,788,874. Glass coated mixing impellers are also known as, for example described in U.S. Pat. Nos. 3,494,708; 4,213,713; 4,221,488; 4,246,215; 4,314,396; 4,601,583 and D 262,791. U.S. Pat. No. 4,601,583 describes glass coated impellers fitted to a shaft by means of cryogenic cooling to obtain a very tight friction fit. The impellers are dual hub impellers, i.e. two hubs, each carrying two blades. The hubs are placed proximate each other on the shaft so that the blades are oriented 90 degrees to each other about the shaft. The patent also shows multiple impellers spaced from each other upon the shaft, known as a “dual flight” configuration.
Despite it being known that certain glass coated impellers could be placed upon a shaft, there has been no good glass coated high efficiency gas dispersion impeller available. Such a high efficiency glass coated gas dispersion impeller would be desirable to be able to quickly and efficiently assure quick gas dispersion in corrosive environments within an entire tank without concern about flooding of the impeller with supplied gas and resultant extreme drop in gas dispersing efficiency as occurs when known e.g. turbine type, impellers are used. U.S. Pat. No. 5,791,780 discloses an impeller having good gas dispersion properties but unfortunately, due to a large number of sharp angles and corners, such impellers are not suitable for glass coating for use in highly corrosive environments.
BRIEF DESCRIPTION OF THE INVENTION
In accordance with the invention it has now been discovered that an excellent gas dispersing impeller can be designed and glass coated and, if desired, be assembled in a dual hub format.
The invention therefore comprises a glass coated gas dispersing impeller. The impeller comprises a hub, having a centrally located hole. The hole has a central axis and is sized for passage over a drive shaft having an essentially vertically extending longitudinal axis so that the central axis of the centrally located hole corresponds with the longitudinal axis of the shaft. The impeller has a plurality of angles and edges, all of which have a rounded configuration. The impeller further comprising a plurality of blades secured to the hub that extend radially outward from the central axis. Each of the blades has a leading concave surface and a trailing convex surface both of which are defined by a lower edge, an upper edge, an inner edge and an outer edge. The concave surface is configured so that the upper edge overhangs the lower edge.
The blades may be connected to the hub directly or by intermediate connecting means such as a disk or arm integral with the hub and extending radially outwardly from the central axis. The hub and its attached blades are covered by a contiguous coating of glass.


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A. Bakker et al., How to Disperse Gases in Liquids, Engineering Practice, Chemical Engineering, vol. 101, No. 12, Dec. 1994, pp. 98-104.

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