Agitating – Stirrer within stationary mixing chamber – Rotatable stirrer
Reexamination Certificate
2002-03-12
2003-02-11
Cooley, Charles E. (Department: 1723)
Agitating
Stirrer within stationary mixing chamber
Rotatable stirrer
Reexamination Certificate
active
06517233
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to apparatus and methods for supporting steady bearings, which are used to support impeller shafts mounted in a variety of reactors, vessels and mixing apparatus. Steady bearings for shafts in such vessels are in wide use in the chemical, petroleum, pharmaceutical, cosmetic, food preparation and other industries. More particularly, the present invention relates to a steady bearing support that adjusts to accommodate radial expansion and contraction of the vessel wall.
BACKGROUND OF THE INVENTION
When in operation, impeller shafts are subject to a number of forces that act to damage and possibly lead to failure of the impeller shaft. A mixer shaft driving an impeller in a vessel can undergo substantial dynamic bending distortion during mixing operation. This dynamic distortion can cause permanent damage or distortion and even complete failure of the impeller shaft during operation. Impeller shafts, especially longer shafts, are prone to lateral displacement while in operation, due to the force of loads in the mixing vessel. It is known to provide one or more intermediate steady bearings along an impeller shaft to control dynamic bending distortion of the shaft. In addition, such assemblies provide lateral stability to the impeller shaft during operation. However, steady bearings used for intermediate support of impeller shafts operating in 360° motion in mixing vessels can be subject to extreme torsional forces due to variations in frictional forces between the shaft and bearing surface. The steady bearing therefore requires support to prevent twisting of the bearing in the direction of rotation of the shaft. Such intermediate steady bearings can be supported by one or several rigid struts extending from the wall or floor of the vessel to provide torsional as well as lateral stability to the steady bearing. These rigid strut assemblies may provide adequate support when mixing operations are carried out at ambient temperatures and pressures. However, at conditions of elevated pressure and temperature, significant changes in vessel dimensions due to expansion can cause rigid strut assemblies to fail.
A steady bearing support assembly that adjusts for distortions in vessel dimensions due to changes in pressure and temperature can alleviate this problem. One example of an adjusting support employs an adjustable bearing support with a plurality of strut pairs, in which the struts of each pair are substantially parallel. The strut pairs are pivotally connected to the vessel wall and a bearing support ring, such that the struts define an angle of inclination to the impeller shaft. The angle of inclination can change in response to dimensional distortions in the vessel allowing the bearing to slide axially along the impeller shaft.
It is desirable to provide an adjustably supported steady bearing that not only protects an impeller shaft from dynamic distortions while in operation, and provides lateral support, but also provides desirable support against torsional forces when the impeller is in operation.
SUMMARY OF THE INVENTION
It is therefore a feature and advantage of the present invention to provide an adjustable steady bearing support method and assembly for a bearing in rotational contact with the surface of a shaft in a vessel, which provides desirable lateral stability and allows axial movement of the bearing along the shaft in response to changes in the radial dimensions of the vessel while also providing support against torsional forces on the bearing. The above and other features and advantages are achieved through the use of a novel design as herein disclosed.
In accordance with one embodiment of the present invention, the invention provides support for a steady bearing by providing a plurality of strut assemblies distributed radially around the shaft for supporting a bearing holder, which in turn holds the steady bearing. Each strut assembly includes a strut pair, where the struts in each pair are pivotally attached at one end to the vessel wall and at the other end to the bearing holder. The struts of each pair are disposed at a substantially dihedral angle to each other.
In a more detailed aspect of an embodiment, support is provided to the strut assembly by a plurality of studding outlets provided radially around the vessel wall. The studding outlets are all located in a common plane in the vessel wall that is substantially perpendicular to the axis of rotation of the shaft. Each strut in each pair is pivotally attached at one end to a studding outlet.
In another more detailed aspect of an embodiment, a bearing holder such as a support ring is provided to support the bearing housing, wherein the bearing is held substantially in coaxial rotation contact with the shaft. The support ring includes a plurality of attachment points distributed radially around the outer edge of the support ring. Each strut in each pair is further pivotally connected to the support ring at one of the attachment points such that the support ring is supported in a plane that is substantially perpendicular to the axis of rotation of the shaft.
In another aspect, when assembled, the struts of each pair define an angle of inclination to the axis of the impeller shaft such that the plane of the support ring is lower than the plane of the studding outlets. The pivotal connections at either end of the struts in each pair allow this angle of inclination to change as the bearing slides axially up and down the shaft in response to changes in the radial dimensions of the vessel.
A further object of the current invention is to provide a mixing apparatus, which makes use of the bearing support assembly defined above.
A still further object of the current invention is a method for supporting a steady bearing in coaxial rotational contact with the surface of a shaft. The method of the current invention allows axial movement of the bearing along the shaft in response to changes in the axial dimensions of the vessel, while providing lateral support and support for torsional forces on the bearing.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract included below, are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
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