Molten metal shaft and impeller bearing assembly

Details Molten metal shaft and impeller bearing assembly Molten metal shaft and impeller bearing assembly

1996-05-22

2001-06-26

Verdier, Christopher (Department: 3745)

Rotary kinetic fluid motors or pumps

Working fluid passage or distributing means associated with...

Specific casing or vane material

C415S170100, C415S172100, C415S216100, C415S229000, C415S217100, C416S174000

Reexamination Certificate

active

06250881

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to molten metal pumps. More particularly, this invention relates to a new and improved shaft and impeller assembly for use in molten metal pumps. In particular, the invention relates to a new and improved means for attaching a bearing ring to a shaft and/or impeller for use in a molten metal pump.
The inventive means for attaching a bearing ring to the shaft and impeller is particularly suited to use in molten metal circulation, transfer, and gas injection pumps. Throughout the specification, numerous references will be made to use of the new design in molten aluminum and zinc pumps, and certain prior art molten aluminum and zinc pumps will be discussed. However, it should be realized that the invention could be used in a variety of molten metal environments wherein a bearing ring is secured to a rotating shaft or impeller.
DESCRIPTION OF THE ART
Molten metal pumps are typically comprised of at least a motor positioned outside of the molten metal environment having a rotatable shaft extending downwardly into the molten metal. An impeller is attached to the submerged end of the shaft and is typically encased in a pump housing. Rotation of the impeller within the pump housing draws molten metal into an inlet and forces the molten metal through an outlet. To achieve stable rotation of the impeller, the impeller and often the shaft, are journaled with a bearing against the pump housing and/or components attached thereto.
Historically, one of the weakest components of a molten metal pump has been the shaft and impeller assembly. Particularly, these dynamic elements of the pump are subjected to corrosion, oxidation and often ingest large pieces of slag or dross which impact the impeller and shaft with significant force. To resist oxidation and corrosion in the high temperature environment, the shaft and impeller assemblies are typically constructed of a refractory material such as graphite. However, graphite is also a soft material which will quickly wear away in a pump environment. Accordingly, a bearing surface is typically provided. The bearing surface generally is created by placing a bearing ring on the impeller and a bearing set on the pump housing.
Notwithstanding the hostile environment, recent developments in coupling and drive designs, enhanced shaft to impeller attachment mechanisms, improved graphite oxidation resistance and high performance ceramic protection sleeves have significantly lengthened the life span of the shaft impeller assembly. Therefore, the attachment of a ceramic bearing ring to the impeller, and optionally to the shaft, remains one of the most common points of failure in the entire assembly.
Historically, a bearing ring is cemented to the shaft and impeller. Particularly, a typical impeller has a generally cylindrical portion which is machined to include a notched periphery, and the bearing ring—often of silicon carbide—is cemented into the notch. In certain designs, the radially facing wall of the notch has been canted inwardly, toward the rotational axis, in the direction of the intersection with the axial facing wall. However, the prior art designs have remained a frequent area of failure because the joint is incompletely filled with cement and the graphite to cement adherence is relatively poor.
To increase the operable life of a molten metal pump and to increase its overall reliability, it is desirable in this art to improve the means for attachment of the bearing ring to the impeller and shaft assemblies.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of this invention to provide a new and improved mechanism to secure a bearing to a molten metal impeller and/or shaft.
It is an advantage of this invention to provide an improved joint between an impeller and bearing ring which experiences significantly less degradation and/or breakage.
A still further advantage of this invention is that the improved joint between the bearing ring and the impeller and/or shaft is achieved through inexpensive machining requiring only a simple turning operation.
Additional objects and advantages of the invention will be set forth in part in the description which follows and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing objects and in accordance with the purpose of the invention, as embodied and broadly described herein, the present invention is comprised of a molten metal impeller having a body shaped to draw metal through an inlet of a pump housing and expel molten metal through an outlet of the pump housing. The impeller includes a bearing adhesively attached to at least an effective portion of the periphery of the impeller. The improvement in the design is based upon the inclusion of at least one or a plurality of generally concentric grooves on the surface of the impeller adjacent the location of the bearing ring. In a particularly preferred embodiment of the invention, the plurality of concentric grooves are formed by a single or cooperate set of spiraling channel(s).
The invention is particularly directed to molten metal impellers having a generally circular base or top portion surrounded by a bearing ring and a plurality of vanes extending from the circular portion. Preferably, the impeller will be comprised of graphite and the bearing ring comprised of silicon carbide and the adhesive used to attach the bearing ring to the impeller is a refractory cement.
In a particularly preferred form of the invention, a cylindrical impeller will include a notch having a radially facing wall and an axially facing wall around the entire circumference of one end. In a first embodiment thereof, only the radially facing wall will include a plurality of grooves. In a particularly preferred version, both axial and radial walls will include grooves. Preferably, these grooves will cover the entire circumference of the wall. Preferably, the grooves will have a depth in excess of twice the thickness of the cement joint.


REFERENCES:
patent: 3048384 (1962-08-01), Sweeney et al.
patent: 5028211 (1991-07-01), Mardue et al.
patent: 5203681 (1993-04-01), Cooper
patent: 5336351 (1994-08-01), Meyers
patent: 5470201 (1995-11-01), Gilbert et al.
patent: 5597289 (1997-01-01), Thut
patent: 0164525 (1987-07-01), None

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