Agitating – Stirrer within stationary mixing chamber – Rotatable stirrer
Reexamination Certificate
2002-04-12
2004-04-06
Cooley, Charles E. (Department: 1723)
Agitating
Stirrer within stationary mixing chamber
Rotatable stirrer
Reexamination Certificate
active
06715913
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to methods and apparatuses for the support of rotating cylindrical shafts with bearings in mixers and mixing systems. More particularly, the present invention relates to apparatuses and methods that provide independent bearing support to a driven mixer impeller shaft arrangement having a quill shaft coupled to another shaft. The invention is useful, for example, for providing axial and radial support, in an economical and efficient manner, to such a rotating cylindrical shaft arrangement.
BACKGROUND OF THE INVENTION
In material processing equipment such as mixers, it is common that a rotatable shaft assembly is supported by spherical and/or tapered bearing support rings. This support is commonly accomplished by placing the spherical bearing support rings at various axial locations along the rotatable shaft. In a typical mixer assembly, the rotatable shaft assembly includes two shafts coupled to one another: (1) an output impeller drive shaft that extends into the mixing vessel to drive an impeller, and (2) a hollow quill shaft that encircles a portion of the output shaft, is rotationally coupled to the output shaft, and has a gear that is driven by the drive assembly of the mixer. The aforementioned shafts are typically supported by two distinct bearing types. The first type are often referred to as independent support bearings, and are typically employed to support the output shaft of the mixer. The second type of bearing is utilized to support the quill shaft. During mixer operation, the output shaft is introduced to high load and bending forces due to the various mixing conditions. These conditions include, for example, the shaft speed, the physical properties of the materials to be mixed, and the shaft length. These forces translate into bending forces which cause the rotatable shaft to deflect radially. The use of two sets of bearings and the two shafts enables the quill shaft to be isolated from the output shaft and the associated bending loads the output shaft experiences during mixer operation. This prevents or inhibits the quill shaft from transmitting these undesirable loads to the drive assembly.
Known mixer bearing support assemblies typically employ a combination of spherical and tapered bearing support rings. The independent support bearings support the output shaft and are designated to encounter the bending loads of the output shaft while the shaft is rotating. These bearings are usually large spherical bearing support rings so that they can handle the various reaction loads exerted on the output shaft during mixer operation. Due to the bearings' size, standard mixers must be arranged to accommodate the bearings, for example, by employing large pedestals and/or frame assemblies. The bearings that contact and support the quill shaft are usually tapered.
In addition, the bearing housings of the frame assembly which house each of the bearing rings commonly are separate components that are mounted on the mixer frame assembly. Many times the housings are mounted in such a way that the bearing bores of the individual bearings that make up the pair are not accurately aligned with one another. This can result in misalignment between the output shaft and the quill shaft.
Current methods to address shaft deflection and the loads exerted on the shaft involve employing significantly large support bearings, however these arrangements have drawbacks. For example, the utilization of large independent support bearings requires that the mixer housings within which the bearings are housed to be larger, increasing the overall size of the mixer frame and therefore increasing cost. Even though large spherical bearings are employed, the output shaft still may experience undesirable deflection due to large bearing span. As a result of these large axial distances between the independent bearings, flexible couplings may be employed to compensate for shaft tilting and/or bending. However, flexible couplings utilize many components and can be very expensive, and therefore eliminating them can be desirable
In view of the foregoing, it is desirable to provide a method and apparatus for effectuating a suitably rigid, bearing support of a rotatable shaft assembly. It is also desirable to provide a method and apparatus for bearing support that can react the bending loads. It is further desirable to effectuate a suitably rigid, independent bearing support that can react the bending loads at a reduced cost.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide and improved bearing assembly and method that can support a rotatable shaft and react to bending loads and/or provide improved radial and axial load handling capability at a reduced cost.
The foregoing needs are met, to a great extent, by the present invention where, in one aspect, an assembly is provided for supporting a rotatable shaft of a mixing apparatus having a first housing affixed to the mixing apparatus wherein a first bearing is mounted. The first bearing surrounds and supports the rotatable shaft at a first axial location. The assembly additionally has a second bearing mounted on the first housing that surrounds and supports the rotatable shaft at a second axial location.
In accordance with another aspect of the present invention, the support assembly includes a first housing affixed to the mixing apparatus having a first bearing mounted thereto and a second bearing mounted thereto. Both the first and second bearings support and surround the rotatable shaft at respective first and second axial locations. The assembly additionally includes a second housing affixed to the mixing apparatus having a third and fourth bearing mounted thereto. Both the third and fourth bearings support and surround the rotatable shaft at respective third and fourth axial locations. The aforementioned bearings combine to support a rotatable shaft having a first shaft disposed within and coupled to, a second hollow shaft.
In accordance with yet another aspect of the present invention, a method for supporting a rotatable shaft is provided, wherein a first bearing is disposed within a speed reducer and a second bearing is disposed within the speed reducer. The bearings combine to support the rotatable shaft at a first and a second location along the length of the rotatable shaft to resist axial, radial, and bending loads on the shaft.
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, 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.
REFERENCES:
patent: RE14249 (1917-01-01), Besserdich
patent: 1687806 (1928-10-01), Strong
patent: 2034545 (1936-03-01), Umstattd
patent: 2332684 (1943-10-01), Armitage
patent: 2341981 (1944-02-01), Davids
p
Baker & Hostetler LLP
Cooley Charles E.
SPX Corporation
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