US3470843A - Torque-journal hub propeller - Google Patents

Description

Oct 7, 1969 5, SIATTERTHWMTE ETAL 7 3,470,843

TORQUE-JOURNAL HUB PROPELLER Filed July 7, 1956 2 Sheets-Sheet 1.

FIG.- I Y 7 4s ll 2 I9 42 I4 |6C-/ 26 2B 29[ 8 INVENTORS.

J. GLENN SATTERTHWAITE JAMES B. MACY JR.

ATTORNEYS McNENNEY, FARRINGTON, PEARNE Bu GORDON 1969 J. G. SATTERTHWAITE ETAL 3.470,843

TORQUE-JOURNAL HUB PROPELLER 2 Sheets-Shea. j

Filed July 7, 1966 YINVENTORS. J. GLENN SATTERTHWAITE JAMES B. MACY JR.

Mc NENNY, FARRINGTON,PEARNE 8 GORDON ATTORNEYS United States Patent 3,470,843 TORQUE-JOURNAL HUB PROPELLER James Glenn Satterthwaite, 1 Dogwood Trail, Chesapeake, Va. 23321, and James B. Macy, 107 Holly Lane, Morehead City, N.C. 28557 Filed July 7, 1966, Ser. No. 563,516 Int. Cl. B63h 5/06, 1/14; F16c 33/22 US. Cl. 115-34 20 Claims ABSTRACT OF THE DISCLOSURE A marine propeller assembly has a cylindrical hub with a plurality of blades secured directly thereto. The hub is relatively large, extends through the hull and is provided with an integral extension inside the hull. The extension has a connecting means which is at least as small as the inner radius of the bearing for the hub.

This invention relates generally to marine propulsion systems and more particularly to a novel and improved marine propeller assembly.

Conventional marine propulsion systems include a solid steel tail shaft which supports a propeller at its rearward end and extends forward through a stern bearing to the rearward end of the ships line shafting, The tail shaft is usually sized to fit into the propeller hub, and mating tapers and keys are used to transmit the propulsion torque from within the propeller hub.

With such prior art systems, including a propeller tail shaft, severe fatigue, fretting and corrosion problems are encountered due to insufficient rigidity. These problems occur where the propeller is mounted on the shaft and in sleeved areas Within the bearing zone.

In propulsion systems utilizing steel tail shafting a liner or sleeve of corrosion resistant material, such as bronze, must be mounted on the portion of the propeller shaft within the bearing. This sleeve causes stress concentrations, principally at its ends, which produce fatigue, fretting and corrosion. Oil lubricated bearings are sometimes used, however, such oil lubricated bearings are compli cated, expensive and require a high degree of maintenance.

A comprehensive discussion of these and other problems is contained in a publication of the United States Department of Commerce, Maritime Administration, entitled Design Improvements and Standardization of Propulsion Shafting and Bearings by Sterling A. Fielding, Division of Ship Design, Ofiice of Ship Constructions, Maritime Administration. It is believed that this publication was presented as a paper to the Chesapeake Section of the Society of Naval Architects and Marine Engineers on Nov. 17, 1965.

In one of its broader aspects this invention provides a novel and improved propeller and propeller bearing structure which eliminates the propeller tail shaft along with its fatigue, corrosion and fretting problems.

The present invention also eliminates one of the principal problems which has limited the use of water lubricated rubber bearings, particularly on larger ships. It has been found that water fails to provide adequate lubrication for rubber bearings when the surface velocity of the journal is below twenty-five feet per minute.

In many ships, particularly those provided with turbine power, it is necessary to rotate the engines and propeller at a slow speed while the ship is in port, to provide even cooling of the power plant turbine blades. This is normally referred to as jacking. Since the thrust produced by the propeller and the power required for jacking are both direct functions of jacking speed, jacking is performed at a speed as slow as possible. In very large ships the jacking speed is usually about 3 to 4 r.p.m. and in smaller ships the jacking speed is about 10 r.p.m.

When conventional propeller shafts are used, such jacking often results in journal surface velocities within a rubber bearing which are Well below twenty-five feet per minute. Consequently, jacking often results in damage of the rubber bearing material by roughing the surface and rendering it useless for adequate lubricating at normal operatmg r.p.m.

In another of its broader aspects, this invention provides a stern bearing structure wherein the diameter of the journal is sufficiently large to provide surface velocities having a magnitude sufliciently great to maintain proper water lubrication of a rubber bearing even under jacking conditions. Such a journal with its large diameter provides greater area for a given length and results in lower bearing pressures. This decreases wear and provides greater system stability. Also, in a given installation it permits the use of a shorter bearing while maintaining bearing loading within acceptable limits. Still further, it results in more eificient operation, since the friction of a water lubricated rubber bearing tends to drop as the journal velocity within the bearin is increased.

In one propeller structure incorporating this invention a one piece propeller is formed with an elongated or tubular hub which extends through the stern tube bearing within which it is fully journaled and is connected directly to the ships internal shafting, thus absorbing the full torque of the shafting system. The hub, like the propeller blades, is formed of a corrosion resistant material, such as stainless steel or bronze, so it is not necessary to provide a noncorrosive liner or sleeve. Consequently, fretting and fatigue in the bearing area are eliminated. Because of the relatively large outside diameter of the hollow hub it has an increased section modulus and suflicient strength is provided without excessive Weight even when the hub is formed of a non-ferrous material, such as bronze. The coupling of the propeller and the internal shafting is easily accomplished since the large diameter of the extended hub provides a sufficient large radius to permit the use of a bolt circle type coupling between the propeller hub and the internal shafting.

In aonther embodiment of this invention removable blades are mounted on the tubular hub. The tubular hub provides a central opening which provides internal access to simplified internal fastening means which secure the blades on the hub.

It is an important object of this invention to provide a novel and improved marine propulsion system constructed and arranged to minimize fatigue, corrosion and fretting.

It is another important object of this invention to provide a novel and improved marine propulsion system wherein the hub which supports the propeller blades extends through and is entirely laterally supported by the stern bearing.

It is another important object of this invention to provide a propulsion system, according to the last preceding object, wherein the stern bearing is rubber and the hub is provided with a sufficiently large diameter to produce adequate water lubrication of the bearing even at jacking speeds.

It is another important object of this invention to provide a novel and improved propulsion system, according to any of the preceding objects,wherein the propeller hub is directly connected to the ships internal shafting on the forward side of the bearing remote from the propeller blades.

It is still another object of this invention to provide a novel and improved propeller structure for marine propulsion having removable blades.

Further objects and advantages will appear from th following description and drawings wherein:

FIGURE 1 is a fragmentary side elevation, partially in section, illustrating one embodiment of a propeller and stem bearing structure incorporating this invention;

FIGURE 2 is an enlarged fragmentary section of the embodiment illustrated in FIGURE 1;

FIGURE 3 is a fragmentary end view of the structure illustrated in FIGURE 2 with the bearing stave retaining plate removed;

FIGURE 4 is a fragmentary side elevation of a second embodiment of this invention illustrating a propeller with removable blades and a modified form of the coupling between the propeller hub and the ships internal shaft- FIGURE 5 is an enlarged, fragmentary section illustrating the structural detail of one form of mounting the blades on a propeller hub; and

FIGURE 6 is an enlarged, fragmentary section illustrating the structural detail of another embodiment for mounting the blade on the propeller hub.

Referring to FIGURES 1 through 3, the stern portion, schematically illustrated at 10, of the ships hull is provided with a cylindrical opening 11 sized to receive rubber staves 12 of a water lubricated rubber bearing assembly 13. A stufiing box assembly 14 is bolted on the forward side of the opening 11. The assembly 14 provides a radially extending surface against which one end of each of the staves 12 abuts. Mounted adjacent to the other end of the cylindrical opening 11 is a heavy duty segmented ring 16 removably secured in place by bolts 17. The various elements are proportioned so that the ring 16 cooperates with the assembly 14 to provide axial compression of the bearing staves 12 to secure the bearing staves in position by radial expansion. Reference may be made to our co-pending application, Ser. No. 515,395, filed Dec. 21, 1965, for a more complete description of this and other structures for removably mounting rubber bearing staves in a water lubricated rubber bearing structure.

A one piece propeller 18 is provided with a hollow hub 19 from one end of which extends a plurality of integrally formed propeller blades 21. The hub portion 19 is faired at its rearward end 22 and its forward portion extends through the bearing 13, past the stuffing box assembly 14 to the interior of the ships hull. The illustrated stuffing box assembly 14 is provided with seals 16C which are compressed by a ring 16a and tension bolts 16b. The stufiing box assembly 14 can be moved forward along the shafting to permit inboard removal and replacement of staves.

The hub portion 19 has an axially extending central opening 26 which extends with substantially uniform diameter from a closed end at 27 to a substantially conical inner face 28 joining the main opening 26 with a reduced diameter forward opening 29. Adjacent to the forward end of the hub 19, forward of the conical surface 28, is an annular groove 31 defining the rearward side of a mounting flange 32. Extending inward from the periphery of the forward side of the flange 32 is a radial face 33 adapted to fit against a mating end face 34 of a flange 39 on the ships internal shafting 36. In the illustrated embodiment the end face 33 is provided with an axial projection 37 around the opening 29 which fits a mating recess 38 on the shafting 36 to assist in laterally locking the joint. The flange 32 and flange 39 are formed with bolt holes through which a plurality of bolts 41 extend. In this embodiment the annular groove 31 provides access for the nuts 42 on the bolts 41. The adjacent end of the internal shafting 36 is supported for rotation about its longitudinal axis by a bearing 43 secured to the stern portion of the hull.

This illustrated embodiment of this invention completely eliminates the conventional tail shaft and its corrosion resistant liner. Instead it provides a large diameter, one piece tubular hub. The hub, because of its large section modulus is capable of efficiently absorbing all of the torsional and bending stresses encountered even when it is formed of non-ferrous metal. It does not provide objectionable points of stress concentration, so fatigue problems are virtually eliminated. Also, the use of a one piece, non-corrosive hub eliminates fretting and corrosion problems. In most installations the total weight of the propeller is no greater than the weight of a conventional propeller with its tail shaft assembly.

Also, the diameter of the stern bearing is substantially increased due to the larger journal diameter. Consequently, surface velocity of the journal is substantially higher for a given r.p.m. For example, in the conventional prior art system utilizing a propeller shaft or tail shaft, a twenty-four foot diameter, five bladed propeller is normally mounted on a tail shaft having a diameter of about twenty-eight inches. Such shafts are usually provided with a corrosion resistant liner of about one and one half inches in radial thickness. Consequently, the exterior of the liner mating with the bearing has a diameter of about thirty-one inches. Such a propeller usually has an outer hub diameter of about five feet. When operating at a jacking speed of three r.p.m. the surface speed of such a system would be less than twenty-five feet per minute and roughing of the rubber bearing material surface is likely to occur due to insufiicient lubrication.

An installation of the same size incorporating the present invention would provide an extension of the hub and elimination of both the tail shaft and liner. The outer surface of the hub mating with the bearing would have a diameter of about five feet and at a jacking speed of three r.p.m. would provide a surface velocity in the bearing of about forty-seven feet per minute. Such a surface speed is well above the speed required to maintain good water lubrication of the bearing and wear is substantially eliminated during jacking conditions.

Such a propeller would be operated under normal power conditions at between ninety and one-hundred and five r.p.m. and under such conditions would provide bearing surface velocities between fourteen-hundred and sixteen-hundred and fifty feet per minute. On the other hand, with the prior art arrangement with an inner bearing diameter of about thirty-one inches such shaft speeds would produce surface velocities of about seven-hundred and thirty to eight-hundred and fifty feet per minute. In rubber bearings the friction of the bearing tends to decrease as the surface velocity of the bearing increases. Consequently, the present invention with a larger bearing provides decreasing friction when compared to conventional designs under all operating conditions.

The use of the present invention also results in improved structural arrangements because the stern bearing can be shorter for a given size propeller without increasing the bearing pressure. In rubber bearings it is desirable to maintain the bearing pressure in the order of ten to fifteen pounds per square inch and always less than twenty-five pounds per square inch. With the present invention acceptable bearing pressures are achieved generally when the bearing length is about one and onequarter times the hub diameter. Consequently, when the hub diameter is five feet the bearing length can be in the order of six and one-quarter feet. However, a rubber bearing for a twenty-four foot propeller described above utilizing conventional structures normally require a hearing length of about ten feet. Consequently, with prior art arrangements it has been necessary to provide a ships hull with a longer bearing supporting structure. Preferably, the flange 32 has a diameter at least as small as the diameter of the hub 19, so that the propeller can easily be inserted through the bearing section. However, because the flange 32 is relatively large in diameter a simple bolt ring type coupling provides sufficient strength to transmit the propulsion torque from the ships internal shafting 36 to the propeller.

Preferably, a slot 35 between the blades 21 is provided which is sufiiciently wide to permit the axial removal and replacement of staves 12 without removing the propeller. This arrangement is best illustrated in FIGURE 3. Reference should be made to our co-pending application, cited above, for a more detailed description of various structural arrangements and methods for servicing stave type rubber bearings.

Because the hub of the propeller 19 is hollow, strain gauges or other testing and measuring devices may be permanently aflixed within the propeller to provide continuous indications of the conditions of the propeller.

FIGURE 4 discloses another embodiment of this invention wherein removable blades 51 are mounted within a tubular hub 52. Here again, the hub 52 is formed of corrosion resistant material, such as stainless steel or bronze, and extends with the uniform diameter through a rubber bearing 53 and seal assembly 54. In this embodiment the ships internal shafting 36 is provided with a flange 39 which fits against the forward end 56 of the hub 52. The coupling is provided in this instance by stud bolts 57 threaded into the forward end of the hub 52. Consequently, an annular groove is not provided on the forward end of the hub, as illustrated in FIGURES 1 through 3, and the internal bore 58 within the hub has a uniform diameter. A cap member 59 is removably bolted to the rearward end of the hub 52 to provide access to the bore 58 for removal and replacement of the blades 51.

Referring to FIGURE 5, one structural arrangement for securing each of the blades 51 to the hub 52 includes a radially extending recess 61 preferably having the shape of a truncated cone. A mating boss 62 formed on the inner end of the blade 51 fits into the associated recess. A stud 63 threaded into the boss 62 extends through a radial opening 64 and is threaded to receive a nut 66 within the central opening 58 of the hub 52. A dowel pin 67 is eccentrically mounted with respect to the conical opening 61 and extends into the hub 62 to insure that the blade 51 is mounted at the proper pitch angle. Preferably, the angle of the conical opening 61 and the mating surface of the boss 62 is arranged to provide a locking taper.

When a blade 51 must be removed the end member 59 is first removed to provide access to the central opening 58. The nut 66 is then removed and jacking means are used to break the taper loose. A new blade can then be easily installed and after the end member 59 is replaced the propeller is ready for subsequent use.

FIGURE 6 discloses still another structure for removably mounting the blades. In this embodiment the blade 71 is again provided with a boss 72 formed with a conical outer surface mating with a conical recess 73 in the hub 74. However, the hub is provided with a plurality of radially extending bolt holes 76, symmetrically arranged about the central axis of the recess 73, each receiving a stub bolt 77 threaded into the inner end of the boss 72. Preferably, the inner wall of the opening 58 is provided with a flat boss portion 78 against which nuts 79 bear. In this embodiment the pitch of the blades can be changed by an amount equal to the angular spacing between adjacent stud receiving holes 76.

Here again, the hub 74 is provided with a removable end member for access purposes. Also, measuring devices such as strain gauges, or the like, may be mounted within the hub of either removable blade embodiment.

Although preferred embodiments of this invention are illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention.

We claim:

1. A marine propeller assembly adapted to be supported on the hull of a vessel comprising an elongated cylindrical hub, a plurality of blades directly connected to said hub substantially adjacent to its rearward end, said hub being formed with an axial extension providing a cylindrical external bearing surface axially on one side of said blades, a bearing adapted to be mounted on said hull, said bearing being positioned around said bearing surface to laterally support said propeller, said extension providing a portion substantially on the side of said bearing remote from said blades provided with connecting means adapted to releasably connect said hub with drive shafting so that the drive torque applied to said propeller by such drive shafting is transmitted through said extension, the maximum radius of said portion of said extension and said connecting means being at least as small as the inner radius of said bearing so that said propeller may be removed from said bearing by axially rearward movement thereof with respect to said bearing.

2. A propeller assembly as set forth in claim 1 wherein said hub is tubular and is the principal structural element between said connecting means and said blades.

3. A propeller assembly as set forth in claim 1 wherein said hub has a substantially uniform cross section from the location where said blades are connected to a location substantially adjacent to said connecting means.

4. A propeller assembly as set forth in claim 2 wherein said connecting means includes a radially extending end face adapted to seat against a mating surface on the line shafting of a ship and provided with a bolt circle to secure the hub to said line shafting.

5. A propeller assembly as set forth in claim 4 wherein said end face is on a flange formed with a plurality of bolt holes therethrough, said bolt holes being radially spaced from the axis of said hub, said flange providing a rearward face adapted to be engaged by bolts when said flange is clamped by such bolts to said mating surface.

'6. A propeller assembly as set forth in claim 5 wherein the maximum diameter of said flange is no greater than the diameter of said bearing surface, said hub being formed with an annular groove to provide the rearward face of said flange, and the central opening in said hub having a reduced diameter adjacent to said flange and groove.

7. A propeller assembly as set forth in claim 4 wherein a plurality of axially extending, threaded holes open through said end face, each hole being adapted to receive a threaded fastener for securing said hub to the line shafting of a ship.

8. A propeller assembly as set forth in claim 7 wherein said hub is formed with a substantially uniform cross section between said end face and the location of said blades.

9. A propeller assembly as set forth in claim 2 wherein said hub is formed entirely of a corrosion resistant metal.

10. A propeller assembly as set forth in claim 9' wherein said hub and blades are integrally formed of said corrosion resistant metal.

11. A propeller assembly as set forth in claim 9 wherein said blades are removably secured to said hub.

12. A propeller assembly as set forth in claim 11 wherein said hub is formed with a plurality of radially extending recesses, and each blade is formed with a mounting boss at its inner end fitting into and mating with an associated recess, and clamping means removably securing each boss in its associated recess.

13. A propeller assembly as set forth in claim 12 wherein said recesses and bosses are truncated cones.

14. A propeller assembly as set forth in claim 13 wherein said clamping means includes threaded fastening means extending into and accessible within the central opening of said hub.

15. A propeller assembly as set forth in claim 14 wherein said threaded fastening means extends along the axis of each boss and associated recess, and locating means are provided between said hub and boss at a position radially spaced from said fastening means.

16. A propeller assembly as set forth in claim 14 wherein said fastening means includes a plurality of threaded fasteners symmetrically located in a circle around the axis of each boss and its associated recess.

17. A propeller assembly as set forth in claim 14 wherein said hub is closed at its rearward end by a removable end member, the removal of said end member providing access to said threaded fastener means.

18. A marine propeller assembly as set forth in claim 1 wherein said bearing is a water-lubricated rubber bearing having a length not substantially greater than oneand-one-quarter times its diameter, the surface pressure of said hub on said bearing created by the weight of said propeller being less than about 25 pounds per square inch, and seal means are provided engaging said portion of said extension between said bearing and said connecting means.

19. A marine vessel comprising a hull having a stern, a propulsion system in said hull including shafting extending to a location adjacent to said stern, a propeller bearing mounted on said hull at said stern, and a propeller assembly journaled in said propeller bearing, said propeller assembly including an elongated cylindrical hub, a plurality of blades directly connected to said hub outboard from said bearing, said hub being formed with an axial extension extending through said bearing and providing a cylindrical external bearing surface axially on one side of said blades engaging said bearing and laterally supporting said propeller, said extension providing a portion substantially on the side of said bearing inboard thereof provided with connecting means releasably connecting said hub with said shafting so that drive torque applied to said propeller by said shafting is transmitted through said extension, the maximum radius of said portion of said extension and said connecting means thereon being at least as small as the inner radius of said bearing so that said propeller may be removed from said hull by rearward axial movement thereof without removing said bearing from said hull.

20. A marine vessel as set forth in claim 19 wherein said propulsion system is periodically operated at jacking speeds, said bearing is a water-lubricated rubber bearing, and the surface of said bearing engaging said propeller is sufficiently large so that the surface velocity therebetween is at least 25 feet per minute when said propulsion system is rotating at jacking speeds.

References Cited UNITED STATES PATENTS 796,810 8/1905 Clarkson 1l534 914,857 3/1909 Miller. 1,799,192 4/ 1931 Schallert. 2,664,961 1/1954 Goede 170160.6 2,732,021 1/1956 Taft l15-34 X 2,769,611 11/ 1956 Schwarzkopf. 3,167,361 1/1965 Snapp et al. --34 X 3,209,720 10/ 1965 Campbell et al. 3,231,022 1/1966 Schroeter et a1. 160.6 3,324,953 6/ 1967 Greenhill 170160.6

FOREIGN PATENTS 11,822 1889 Great Britain.

TRYGVE M. BLIX, Primary Examiner US. Cl. X.R. 308-239

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