SUPPORT ASSEMBLY AND METHOD FOR SUPPORTING A STEADY BEARING

Abstract: An adjustable steady bearing support assembly and method provides support for a bearing (14) in rotational contact with a shaft (16) in a vessel such as a mixing vessel (10). The assembly and method allows axial movement of the bearing along the shaft in response to changes in the radial dimensions of the vessel while providing radial support of the bearing. The assembly employs strut assemblies (22) having pivotally mounted strut pairs (24) with an included angle between the struts in each pair to resist torsional forces on the bearing.

Description: SUPPORT ASSEMBLY AND METHOD FOR SUPPORTING A STEADY BEARING PRIORITY This application claims priority to the United States Patent Application entitled, Support Assembly and Method for Supporting a Steady Bearing, filed December 29, 2000, having serial number 09/750,270, the disclosure of which is hereby incorporated by reference. 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 essel 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. h 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. hi 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. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an overhead partially sectional and cutaway view of a mixing vessel with three strut assemblies according to the present invention supporting a steady bearing. Fig. 2 is a partially sectional and cutaway side view of a strut pair according to the present invention supporting a support ring for a steady bearing. Fig. 3 is a cutaway side view of strut assemblies installed in a mixing vessel. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Fig. 1, a vessel 10 is equipped with an intermediate steady bearing housing 12 for housing a steady bearing 14 around a shaft 16. The bearing housing 12 may be detachably connected to a supporting ring 18. Thus, the bearing housing 12 in some embodiments may be used detachably from a support ring 18 (e.g., for installation). The bearing housing 12 and, if provided, supporting ring 18, together form a bearing holder. Alternatively, the bearing housing 12 and support ring 18 may be essentially an integral component together forming a bearing holder. Still referring to Fig. 1, a plurality of studding outlets 20 are provided on the wall of the vessel 10. Three strut assemblies 22 each comprising a pair of struts 24 are provided, where each strut in the pair has a first end 26 and a second end 28, as shown in Fig. 2. Referring now to Fig. 2, each strut 24 in each strut pair 22, is pivotally connected at a first end 26 to a studding outlet 20 and at a second end 28 to the support ring 18, or to the bearing housing 12 when no detachable support ring is provided, such that an angle of inclination 3 to a line 30 perpendicular to the axis of rotation of the impeller shaft is defined at ambient conditions, when the equipment is not in operation. When the equipment is in operation and the radial dimensions of the vessel change, the angle of inclination is changed by pivotal motion of each strut 24 in the strut pairs 22 at the first end 26 and the second end 28, to define a new angle of inclination that is less than 3, thus allowing the bearing and bearing housing to move axially along the impeller shaft in response to changes in the radial dimensions of the vessel 10, as well as providing lateral and torsional support to the impeller shaft when in operation. In a preferred embodiment of the present invention the angle 3 is 10° at ambient conditions and 3 is 9° at operating conditions. However, those skilled in the art will recognize that other angles 3 and ranges of angles are possible for ambient and operating conditions. Referring to Figs. 1 and 2, a substantially dihedral angle θ between the struts in each pair is defined such that each pair of struts is disposed along a conical surface of rotation about the shaft axis. In the embodiment illustrated, the dihedral angle 2 is determined such that the first ends 26 of each strut in a strut pair are attached to the studding outlet 20 such that the first ends of the struts in each pair are proximate to each other. The dihedral angle 2 is further determined by the radial dimensions of the bearing support ring 18 such that second ends 28 of adjacent struts in neighboring strut pairs 22 are attached to the support ring 18 proximate to one another. In general, the dihedral angle 2 is defined such that the distance between the first ends 26 of the struts in each strut pair 22 is less than the distance between the second ends 28 of the struts in each strut pair. This configuration provides torsional stability. In a preferred embodiment, the dihedral angle may be between 1° and 45°. Various embodiments of a mixing vessel employing an adjustable steady bearing support according to the current invention can provide improved bearing life and less damage to the impeller shaft due to bending and lateral movement. As used herein, the terms "radial" and "lateral" both refer to the directions perpendicular to the longitudinal axis of rotation of the shaft 16. The term "torsional" refers to rotations about the longitudinal axis of the shaft 16. The term "axial" refers to the direction along the longitudinal axis of rotation of the shaft 16. A preferred embodiment of the present inventive apparatus and method is illustrated in Fig. 1, where three strut pairs 22 are provided for support of the bearing support ring 18. Correspondingly, three studding outlets 20 are provided in the vessel wall such that the studding outlets are equally spaced and separated from each other by an angle °c of 120°. However, those skilled in the art will recognize that it is possible to provide a number of more than three studding outlets and strut pairs. Four or more strut pairs may be employed. Fig. 3 shows the strut assemblies 22 supporting a bearing housing 12 in a vessel 10 that is a mixing vessel, with a shaft 16 that has a mixing impeller 32. The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirits and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.

Claims: What is claimed is: 1. An assembly for supporting a bearing holder for holding a bearing in rotational contact with the surface of a shaft in a vessel and for allowing axial movement of the bearing along the shaft in response to changes in radial dimensions of the vessel and maintaining radial support of the shaft, the assembly being supported from a wall of the vessel, the assembly comprising: a plurality of strut assemblies disposed radially around the shaft for supporting the bearing holder within the vessel, each said strut assembly having a pair of struts extending from the wall of the vessel to the bearing holder, each of said struts having a first end thereof pivotally connected to the wall of the vessel with a first pivot axis substantially perpendicular to the shaft axis, and a second end thereof pivotally connected to the bearing holder with a second pivot axis substantially perpendicular to the shaft axis, each first pivot axis being proximate the wall at a common first plane perpendicular to the shaft axis and each second pivot axis being arranged on the bearing holder at a common second plane perpendicular to the shaft axis, so that each said strut is at an inclination angle to the shaft- axis that varies with changes in radial dimensions of the vessel, and each said pair of struts arranged to have an included substantially dihedral angle between each said struts of each pair, so that said struts are disposed along a conical surface of rotation centered substantially about the shaft axis. 2. An assembly according to claim 1, wherein said strut pairs are each disposed at equal angular intervals about the shaft axis. 3. An assembly according to claim 1, wherein a number of said strut assemblies is three. 4. An assembly according to claim 1, wherein the inclination angle of each said strut to a plane perpendicular to the axis of the shaft is a first angle at ambient conditions and a second angle at operating conditions, such that the second angle is less than the first angle. 5. An assembly according to claim 1, wherein the dihedral angle is between 1° and 45°. 6. An assembly according to claim 1, wherein the vessel has a plurality of studding outlets for pivotally supporting said first ends of said struts. 7. An assembly according to claim 1, wherein the bearing holder has a plurality of attachment points for pivotally supporting said second ends of said struts. 8. An assembly according to claim 1, wherein the bearing holder comprises a support ring detachable from the remainder of the bearing holder and the support ring has a plurality of attachment points for pivotally supporting said second ends of said struts. 9. A mixing apparatus comprising: a vessel having a vessel wall; a shaft disposed inside said vessel to rotate about an axis of said shaft; a bearing in rotational contact with a surface of said shaft; a steady bearing holder for supporting said bearing; and a plurality of strut assemblies disposed radially around said shaft for supporting said bearing holder within said vessel, each said strut assembly having a pair of struts extending from said wall of said vessel to said bearing holder, each said strut having a first end pivotally connected to said wall of the vessel with a first pivot axis substantially perpendicular to the shaft axis, and a second end thereof pivotally connected to said bearing holder with a second pivot axis substantially perpendicular to the shaft axis, each first pivot axis being proximate on a said wall at a common first plane perpendicular to the shaft axis and each second pivot axis being arranged on said bearing holder at a common second plane perpendicular to the shaft axis, so that each strut is at an inclination angle to the shaft axis that varies with changes in radial dimensions of the vessel, and each said pair of struts arranged to have an included substantially dihedral angle between each said struts of said pair, so that said struts are disposed along a conical surface of rotation centered substantially about the shaft axis. 1,0. A mixing apparatus according to claim 9, wherein said strut pairs are each disposed at equal angular intervals about the shaft axis. 11. A mixing apparatus according to claim 9, wherein a number of said strut assemblies is three. 12. A mixing apparatus according to claim 9, wherein the inclination angle of each said strut to a plane perpendicular to the axis of the shaft is a first angle at ambient conditions and a second angle at operating conditions, such that the second angle is less than the first angle. 13. A mixing apparatus according to claim 9, wherein the dihedral angle is between 1° and 45°. 14. A mixing apparatus according to claim 9, wherein the vessel has a plurality of studding outlets for pivotally supporting said first ends of said struts. 15. A mixing apparatus according to claim 9, wherein the bearing holder has a plurality of attachment points for pivotally supporting said second ends of said struts. 16. A mixing apparatus according to claim 6, wherein the bearing holder comprises a support ring detachable from the remainder of the bearing holder and the support ring has a plurality of attachment points for pivotally supporting said second ends of said struts. 17. A method for supporting a steady bearing holder for a bearing in a coaxial rotational contact with the surface of a shaft in a vessel, comprising the steps of: allowing axial movement of the bearing along the shaft in response to changes in radial dimensions of the vessel and maintaining radial support of the shaft using a plurality of strut assemblies disposed radially around the shaft for supporting the bearing holder within the vessel, each strut assembly having a pair of struts extending from the wall of the vessel to the bearing holder, each strut having a first end thereof pivotally connected to the wall of the vessel with a first pivot axis substantially perpendicular to the shaft axis, and a second end thereof pivotally connected to the bearing holder with a second pivot axis substantially perpendicular to the shaft axis, each first pivot axis being proximate the wall at a common first plane perpendicular to the shaft axis and each second pivot axis being arranged on the bearing holder at a common second plane perpendicular to the shaft axis, so that each strut is at an inclination angle to the shaft axis that varies with changes in radial dimensions of the vessel; and resisting torsional movement about the strut axis by the bearing due to friction between the bearing and shaft by locating the pair of struts with an included substantially dihedral angle between the struts of the pair so that the struts are disposed along a conical surface of rotation about the shaft axis. 18. A method according to claim 17, wherein said strut pairs are each disposed at equal angular intervals about the shaft axis. 19. A method according to claim 17, wherein a number of said strut assemblies is three. 20. A method according to claim 17, wherein the dihedral angle is between 1° and 45°. 21. An apparatus for supporting a steady bearing holder for a bearing in a coaxial rotational contact with the surface of a shaft in a vessel, comprising: means for allowing axial movement of the bearing along the shaft in response to changes in radial dimensions of the vessels and for maintaining radial support of the shaft using a plurality of strut assemblies disposed radially around the shaft for supporting the bearing holder within the vessel; and means for resisting torsional movement about the strut axis by the bearing due to friction between the bearing and shaft by locating the pair of struts with an included substantially dihedral angle between the struts of the pair so that the struts are disposed along a conical surface of rotation about the shaft axis. 22. An apparatus according to claim 21 wherein said strut pairs are each disposed at equal angular intervals about the shaft axis. 23. An apparatus according to claim 21, wherein a number of said strut assemblies is three. 24. An apparatus according to claim 21, wherein the dihedral angle is between 1° and 45°.

Inventors: BLAKLEY ROBERT A, BLAKLEY, ROBERT, A.
Applicants: BLAKLEY ROBERT A, GEN SIGNAL CORP, BLAKLEY, ROBERT, A., GENERAL SIGNAL CORPORATION
Application year: 2001
Main classification: B01F15
IPC codes: B01F15