Patent Application
20170299060
The present invention relates broadly to an apparatus for restricting flow of a fluid along a rotatable shaft while permitting the shaft to rotate about an axis of rotation. Conventional solutions of restricting the flow of a fluid along a rotatable shaft, such as stuffing boxes, tend to become less effective over time during normal operation of the rotatable shaft. One such conventional solution includes enclosing a portion of the rotatable shaft with a stuffing box. Packing material is inserted into the stuffing box and deformed by manually adjusting the stuffing box to compress the packing material. The deformed packing material provides sealing engagement with the rotatable shaft, thereby restricting flow of a fluid along the rotatable shaft. The sealing engagement with the rotatable shaft diminishes during normal operation for various reasons. For example, frictional forces at the interface between the packing material and rotatable shaft may result in erosion of the packing material. The sealing engagement with the rotatable shaft may be improved by manually adjusting the stuffing box to further compress the packing material. While manual adjustment of the stuffing box may restrict fluid around the rotatable shaft, it is also labor intensive. Moreover, conventional solutions tend to utilize skilled labor for such manual adjustments in order to meet particular operational specifications, thereby further increasing labor costs.
Throughout the drawings, reference numbers may be re-used to indicate correspondence between referenced elements. The drawings are provided to illustrate example embodiments described herein and are not intended to limit the scope of the disclosure.
Directional terms such as “outer”, “inner”, “forward”, “rearward”, “upwards”, “downwards”, “vertically”, “inward”, “outward”, and “radially” are used in the following description for the purpose of providing relative reference only, and are not intended to suggest any limitations on how any article is to be positioned during use, or to be mounted in an assembly or relative to an environment. Additionally, the term “couple” and variants of it such as “coupled”, “couples”, and “coupling” as used in this description are intended to include indirect and direct mechanical connections unless otherwise indicated. For example, if a first object is coupled to a second object, that coupling may be through a direct mechanical connection or through an indirect mechanical connection via other intervening objects, such as via gaskets and spacers.
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This operation may be facilitated by providing slight gaps around rotatable shaft 120 as it passes through other mechanical components, thereby enabling rotatable shaft 120 to freely rotate. For example, slight gaps may exist between rotatable shaft 120 and shaft aperture 142 (or center aperture 152). As known by those skilled in the art, the slight gaps provided to enable rotatable shaft 120 to freely rotate will also provide a route for the fluid being pumped to leak. One means to prevent such leakage while enabling rotatable shaft 120 to freely rotate is to insert packing material 220 into the cavity formed by gland follower 150 in conjunction with the recess within housing 140.
Non-limiting examples of suitable packing materials are taught in U.S. Pat. No. 3,646,846 to Houghton, et al. on Mar. 7, 1972; U.S. Pat. No. 5,225,262 to Leduc issued on Jul. 6, 1993; U.S. Pat. No. 6,385,956 to Ottinger, et al. on May 14, 2002; U.S. Pat. No. 6,644,007 to Fujiwara et al. on Nov. 11, 2003; and U.S. Pat. No. 6,502,382 to Fujiwara et al. on Jan. 7, 2003. As known, conventional packings can be fabricated by forming synthetic fibers (e.g. polytetrafluoroethylene) or non-synthetic (e.g. flax and jute) fibers into yarns or strands, which are braided together about core strands. The result is typically a packing having a square cross-section and herringbone weave pattern extending in an axial direction along the packing. As such, packing material 220 may need to be deformed to provide sealing engagement with rotatable shaft 120 to prevent leakage of the fluid being pump while enabling rotatable shaft 120 to freely rotate.
Deforming packing material 220 inserted into the cavity to provide such sealing engagement with rotatable shaft 120 may be achieved by exerting a compressive force on packing material 220 in a direction parallel to the rotatable shaft's axis of rotation. Since packing material 220 inserted into the cavity is somewhat constrained (e.g. by way of interior surface 144 and the surface in which shaft aperture 142 is formed) packing material 220 may be pressed inward within the cavity by the compressive force. Such compressive force on the packing material may be exerted by translating gland follower 150 towards housing 140 in a direction parallel to the axis of rotation of rotatable shaft 120.
In accordance with embodiments of the present invention, compressive force exerted by gland follower 150 is generated by at least one biasing mechanism 164 disposed within the at least one fastening aperture. In an embodiment, biasing mechanism 164 is a spring having a spring rate sufficient to generate a predetermined force that biases gland follower 150 towards housing 140. In an embodiment, a predetermined force is based on a desired compressive force that is established for a particular packing material. In an embodiment, biasing mechanism 164 is a spring having a spring rate sufficient to generate a predetermined force at a predetermined extended length that biases gland follower 150 towards housing 140. In an embodiment, biasing mechanism 164 is mounted over fastening mechanism 162 within the at least one fastening aperture.
In an embodiment, centrifugal pump 100 can also include a lantern ring 230. Lantern ring 230 can be a flexible material having a substantially cylindrical outer surface with one or more outer ridges, a substantially cylindrical inner bore surface with one or more inner ridges, one or more through holes from at least an outer ridge to an inner ridge, a first annular end, and a second annular end. The through holes can allow for liquid, such as lubrication and/or cleaning liquid to pass from the outside of centrifugal pump 100 to rotatable shaft 120.
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Gland follower 300 also includes center aperture 340 that is substantially aligned with a central longitudinal axis (e.g. central longitudinal axis 122 of
Gland follower 300 includes at least one fastening aperture 350 for accommodating at least one fastening mechanism and at least one biasing mechanism (e.g. fastening mechanism 162 and biasing mechanism 164 of
Diameter 356 of opening 352 may be selected based on various design constraints. In an embodiment, diameter 356 is selected such that diameter 356 exceeds an outer diameter of a biasing mechanism disposed within fastening aperture 350. In an embodiment, diameter 356 is selected such that diameter 356 exceeds an outer diameter of a distal end of a fastening mechanism disposed within fastening aperture 350. In an embodiment, a washer may be mounted inward of outer surface 310 on a fastening mechanism having an outer diameter at a distal end that does not exceed diameter 356. In an embodiment, diameter 356 is selected such that an outer diameter of a washer exceeds diameter 356. In an embodiment, diameter 356 is selected such that an outer diameter of a fastening mechanism disposed within fastening aperture 350 exceeds diameter 356.
Likewise, diameter 358 of fastening aperture 350 in a region proximate a cavity formed in conjunction with a recess of a housing may be selected based on various design constraints. In an embodiment, diameter 356 of opening 352 may be different than diameter 358. In an embodiment, diameter 356 of opening 352 is selected such that diameter 356 exceeds diameter 358. In an embodiment, diameter 358 is selected such that an outer diameter of a biasing mechanism disposed within fastening aperture 350 exceeds diameter 358. In an embodiment, diameter 358 is selected such that diameter 358 exceeds an outer diameter of a proximal end of a fastening mechanism disposed within fastening aperture 350.
Retention mechanisms may be utilized to mechanically couple two or more sections of a gland follower composed of multiple sections. In an embodiment, a retention mechanism inserted into a retention aperture disposed within a profile of a gland follower composed of multiple sections is used to mechanically couple two or more of the multiple sections. For example, gland follower 500 includes two retention apertures: a first retention aperture collectively composed of aperture 530 and aperture 580, and a second retention aperture collectively composed of aperture 535 and aperture 585. In this example, section 525 and section 575 may be mechanically coupled within a profile of gland follower 500 by inserting retention mechanisms (not shown) into one or more of the first retention aperture and the second retention aperture. In an embodiment, any known means of coupling two or more objects may be used to implement a retention mechanism including hardware means (e.g. screws, clamps, and the like), fusion-based coupling means (e.g. welding, brazing, and the like), and force-based coupling means (e.g. vacuum, magnets, and the like).
One of the benefits of a gland follower composed of multiple sections, such as gland follower 500, is ease of removing and/or replacing the gland follower when needed. As an example, gland follower 500 may be mechanically coupled to a device having a rotatable shaft like centrifugal pump 100 of
While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. For example, neither dimensions of a fastening mechanism diameter relative to a fastening aperture diameter nor the number of sections collectively composing a gland follower is critical and may be adjusted in accord with the particular application.
The various features and processes described above may be used independently of one another, or may be combined in various ways. All possible combinations and sub-combinations are intended to fall within the scope of this disclosure. In addition, certain method or process blocks may be omitted in some implementations. The methods and processes described herein are also not limited to any particular sequence, and the blocks or states relating thereto can be performed in other sequences that are appropriate. For example, described blocks or states may be performed in an order other than that specifically disclosed, or multiple blocks or states may be combined in a single block or state. The example blocks or states may be performed in serial, in parallel or in some other manner. Blocks or states may be added to or removed from the disclosed example embodiments. The example systems and components described herein may be configured differently than described. For example, elements may be added to, removed from or rearranged compared to the disclosed example embodiments.
Conditional language used herein, such as, among others, “can,” “could,” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. The terms “comprising,” “including,” “having,” and the like are synonymous and are used inclusively, in an open-ended fashion, and do not exclude additional elements, features, acts, operations and so forth. Also, the term “or” is used in its inclusive sense (and not in its exclusive sense) so that when used, for example, to connect a list of elements, the term “or” means one, some or all of the elements in the list.
While certain example embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions disclosed herein. Thus, nothing in the foregoing description is intended to imply that any particular feature, characteristic, step, module or block is necessary or indispensable. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions disclosed herein. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of certain of the inventions disclosed herein.
