Fluid lubricated floating bushing seal

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Fluid lubricated floating bushing seal

Abstract
A seal assembly including a rotor shaft rotating propeller keyed to a foot, a non-rotating sleeve which surrounds the rotor floating, and means for maintaining a fluid seal between the sleeve and a housing for the seal assembly. The adjacent surfaces of the rotor and hub interface define a water lubricated bearing, where one surface is formed of a material compatible thin and the other surface axially extending grooves formed therein. Lubrication grooves are arranged in an alternating pattern in which adjacent oil grooves extend from the opposite edge surfaces and overlapping portions are axially spaced apart relationship.

DescriptionD
ETAILED DESCRIPTION OF DRAWINGS
Referring now to the drawings, shown generally in FIG . 1, the shaft seal assembly 21 attached to a propeller shaft 12 and disposed in a recess 16 of the housing 15. The seal assembly 21 generally comprises a cylindrical rotor member 31 which encloses the propeller shaft 12 and rotationally keyed thereto , a non-rotating , cylindrical floating bushing 41 circumferentially surrounds the rotor 31 , and means for maintaining a seal of fluid between the seal assembly 21 and the propeller shaft 12 and the housing 15 .Although preferably formed from a continuous cylindrical element to reduce leakage paths between the high pressure side 13 and the low pressure side 14 of the seal assembly 21, the rotor 31 may be formed of segments that are connected together and attached to the shaft helix 12 . Means for rotating the rotor 31 keyed to propeller shaft 12 include a key 32 , as shown in Fig . 1, which is arranged in the shape of slots in the rotor 31 and the propeller shaft 12. Seal means in the form of an O-ring 33 , for example, are arranged in the interface between the rotor 31 and the propeller shaft 12 to prevent fluid leakage therebetween.The floating cap 41 which , like the rotor 31 , is preferably a continuous cylindrical member is able to undergo radial displacements due to small radial movements of the propeller shaft 12. Sealing means for preventing fluid leakage between the curve of the housing 16 and the low pressure side 14 of the shaft seal 21 is provided in the form of a seal 42 is shown generally in FIG . 1 and more particularly shown in Fig . Three . In the figure. 3 which shows an enlarged view of the seal 42 in the upper portion of sleeve 41 in Fig . 1, the seal includes anti- extrusion ring 43 having a triangular cross section and compressible member 44 which is fitted in a slot 44 between the sleeve 41 and ring 43 . In the arrangement described , the ring 43 is disposed radially inwardly compressible filler element 44, towards the low pressure side of the seal assembly 21. Biasing means in the form of spring member 46 forces the bushing 41 against the curved surface 17 of the housing 16 so that the gasket 42 forms an effective seal means to prevent fluid flow around it . A key element 48 is disposed in the formation of grooves in the bushing 41 and the curved surface of the housing 17 to prevent rotation of the sleeve 41 .The interface defined by the surface 37 of the rotor 31 and the surface 47 of the rotor 41 is designed to form a lubricating fluid in the controlled area is allowed to leak therethrough. This is accomplished by forming one of the surfaces 37, 47 of thin elastomeric material 23 and supported by the formation of the other of the surfaces 37, 47 with axially extending slots 25, 26 . Although the slots 25, 26 are displayed on the surface of the rotor 37 and the elastomer material 23 is shown forming the cap surface 47 in FIGS . 1 and 2 for purposes of illustration , the arrangement may also be reversed . That is, the elastomer May 23 form the surface of the rotor 37 and grooves 25, 26 may be formed on the surface of bushing 47 .The elastomeric material 23 , which may be selected from materials such as rubber , neoprene, Buna - N, polyurethane , carbon - graphite, polyamides, and polyimides, may, for example, a thickness of about one eighth inch to form a wear surface supports allowing passage of pollutants and provides efficient delivery systems, eg water .The first set of axial grooves 25 , as shown more particularly formed in the bushing 41 in Fig . 4, extend from the high pressure side of the seal 13 of the shaft 21 and end at the height of the low-pressure part 14 of the shaft seal 21 . The second set of axial slots 26 extend from the low pressure side 14 and end near the high pressure side 13 of the shaft seal 21 . The first and second sets of grooves 25, 26 are arranged respectively in an alternating pattern as shown in FIGS . 1 and 4 , so that a first axially extending groove 25 between adjacent grooves 26 seconds, and vice versa. In general, the optimum dimensions of the slots 25, 26 and the elastomer material 23 is dependent on the dimensions of the sealing elements , hydrodynamic and hydrostatic pressures involved and the conditions of use. However, the grooves have a depth of about one-thirty second of an inch and have an axial overlap , as shown by Dd in Fig . 4 about 20% to about 50% of the axial width of the surface containing the grooves.Operating conditions of the slots 25, 26 and the support bearing layer formed by flexible material 23 interact to define an lubricated wherein the wear and heat buildup of fluid interface is reduced. For example, the bushing 41 is deformed under load so that the clearance with the rotor 31 and hence the fluid film between them will be smaller at the low pressure end 14 than in the high pressure end . Clearance in regions of low intensity, as caused by differential compression cap 41 , the flexible material 23 is capable of a slight deformation so that undulation lubricant forced slots provides adequate cooling for clearance areas low. Furthermore , the flexible material 23 is also able to pass sand and other particles contained in the fluid flowing from the grooves 25 to the grooves 26 , thereby reducing wear on the surface containing the grooves 25, 26 .Obviously many modifications and variations of the present invention are possible in light of the above teachings. Is therefore to be understood that within the scope of the following claims the invention may be practiced otherwise than as specifically described
.BRIEF DESCRIPTION OF THE DRAWINGS
The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The invention itself , however , both as to its organization and method of operation, together with further objects and advantages thereof , may best be understood by reference to the following description taken in conjunction with the accompanying drawings in which :. Figure 1 is a partially cutaway sectional view of the shaft seal assembly ;. Figure 2 is an enlarged view of the interface between the relatively movable parts of the figure. 1;. Figure 3 is an enlarged view of the seal for the floating cap of FIG . 1 , and. Figure 4 is a plan view of an arrangement of slot formed in an element of floating bushing .
Background of the Invention
This invention relates generally to a hydrostatic pressure seal and cap structures and more particularly to such structures having axially extending grooves to promote fluid lubrication .Various types of fasteners " grooving " and / or support structures are disclosed in U.S. Patent . Nos. 3655248 , 3746407 , 4105267 , 4120544 and 4141603 . In some structures sealing / bearing , the slots are arranged on surfaces that rotate relative to one another such that the relative motion generates a hydrodynamic fluid pressure of lubricant in the grooves. Lubricant is thus forced between the rotating surfaces to form a lubricating film . Other provisions of seals / bearing means employing a hydrostatic pressure to cause the lubricant to flow into the slots as shown for example in U.S. Pat . Nos. 3,305,282 and 3,517,973 . However, the problems experienced with the prior art include lubricant contamination with contaminants , causing an increase in friction and wear of the rotating surfaces .
SUMMARY OF THE INVENTION
The present invention overcomes the problems experienced with the prior art and specifically with water is useful as a lubricant , providing a set of improved shaft seal which is more resistant to shock and wear on the shaft is lubricated by controlled leakage of fluid between elements of the shaft seal assembly . This is generally accomplished by constructing a shaft seal assembly comprising: a rotor element rotatably mounted on the shaft , a non-rotating floating bushing surrounding the rotor , and means for maintaining a fluid seal between the sleeve and a housing for the seal assembly .The interface formed between the adjacent surfaces of the rotor and hub functions as a fluid lubricated bearing region in which one of the surfaces comprises a layer of elastomer material thin support and the other surface includes axially extending lubrication grooves . The grooves comprise a first set of axial grooves extending from one edge of the first grooved surface and end near the other edge of the second grooved surface , and a second set of axial slots extending from the second edge and end before the first edge . The first and second sets of slots are arranged in an alternating pattern in which the first slot extends preferably adjacent second slots , and vice versa. The non-rotating floating bushing may be contained within a circumferential recess in the housing and is spring biased to form a fluid seal between the fluid pressure side of the seal assembly on the shaft and the fluid pressure in the upper housing curve . Sealing means provided on the cap which allow radial displacements of the seal assembly within the curve of the housing , while maintaining the fluid seal .Therefore, it is an object of this invention to provide a seal assembly having improved design efficient reduction of wear and lubrication characteristics .Another object of this invention to provide a seal arrangement having an effective lubrication interface defined by a compliant elastomeric surface and a grooved surface .A further object of this invention is the provision of a seal assembly capable of providing radial displacements and controlled lubrication of relatively moving surfaces .The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or for them.

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