US3446290A

US3446290A - Propeller bosses

Info

Publication number: US3446290A
Application number: US680263A
Authority: US
Inventors: John Hamilton Attwood
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1965-11-24
Filing date: 1967-11-02
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27
Also published as: SE302257B; NL6616505A; ES333647A1; GB1064639A; FR1503037A

Description

' May 27, 1969 J. H. ATTWOOD 3,446,290 v PROPELLER BOSSES Original Filed Nov. 22, 1966 Sheet of 2 FIG. 7.

.l. H. ATTWOOD INVENTOR I May 27, 1 J. H. ATTWOOD PROPELLER BOSSES Sheet 012 Original Filed Nov. 22, 1966 J. H. ATTWOOD mvsu United States Patent US. Cl. 170-173 16 Claims ABSTRACT OF THE DISCLOSURE The disclosure of the instant invention relates to an improved propeller shaft assembly comprising a propeller shaft provided with an internal radial flange connected to an internal radial flange of a hollow propeller boss. The shaft and propeller boss are connected together by fastening elements which pass through apertures in the flanges of both the propeller shaft and propeller boss; said fastening elements being housed entirely inside the boss and shaft.

This application is a continuation of Ser. No. 596,190, filed Nov. 22, 1966.

This invention relates to the connection of propeller bosses to propeller shafts.

In the past propeller bosses have usually been attached to propeller shafts in two ways. In one case, the boss has an external flange and this flange is bolted to an external flange at the end of the propeller shaft. The disadvantage of this arrangement is that the bolts are in constant contact with sea water and corrosion is likely to occur; in addition due to the external flange the propeller shaft cannot be removed inboard but must be removed outboard. In an alternative way of fixing the boss to the propeller shaft, the end of the shaft is tapered and the boss is slipped over the tapered portion of the shaft and fixed to the shaft by a key and nut. The disadvantage of this arrangement is that not only are there shear stresses but also there are hoop stresses of uncontrolled size on the shaft and boss; and in larger sizes of propeller, fitting problems arise together with large overhung weights giving high bending stresses and deflections in the propeller shaft.

According to this invention these disadvantages are eliminated or obviated by a propeller shaft assembly comprising a propeller shaft connected to an internal radial flange of a hollow propeller boss, said shaft and boss being connected together by fastening elements passing through apertures in said flange wherein said elements are housed entirely inside the boss and shaft. The shaft and the boss can be connected together in a butt joint with a known and controlled compressive stress. The use of a hollow boss reduces the Weight and minimises shaft bending stresses and deflections. Also as a result of the invention the fastening elements are housed inside the boss and shaft and are not exposed to sea water, there is no external flange so that after removal of the propeller from the shaft, the shaft can often be removed inboard, and also there are not fixing hoop stresses, set up in boss and shaft.

The outer diameter of the propeller boss is preferably slightly larger than the outer diameter of the propeller shaft, to allow fitting of a stern tube oil seal and a rope guard. Preferably the propeller boss is integral with the propeller blades, but this need not be so.

The boss may have internal longitudinal ribs, for example four in number, and may often have an internal flange intermediate of the ends thereof, additional to the internal radial flange. When the fastening elements are introduced into the apertures of the flange from inside the propeller boss this additional intermediate flange should be spaced from the internal radial flange by a distance at least equal to the length of the fastening elements. There may if desired be another internal radial flange (hereinafter referred to as the second internal radial flange) situated at the other end of the boss, and this flange will facilitate the attachment of a fairwater cap closing plate to the end of the boss remote from the propeller shaft.

The fastening elements are preferably bolts, to which nuts are attached. However, in certain circumstances it may be desirable to use studs, or rods having two screwed ends to which nuts may be attached.

The internal radial flange with apertures thereon, for example sixteen in number, preferably extends continuously around the inside of the end of the boss, and when bolts are used as fastening elements the radial length of this flange is preferably greater than the diameter of the heads of the bolts used in fastening the boss to the propeller shaft.

The fastening elements also preferably pass through apertures in the propeller shaft, and the shaft which is preferably hollow, is therefore preferably provided at its tail end with an internal flange having a plurality of apertures therein. The internal flange on the shaft preferably has a spigot extending outwardly beyond the shaft, in an axial direction, the outer diameter of which spigot is substantially equal to the internal diameter of the internal radial flange on the boss, so that when the boss and propeller shaft are connected to one another the spigot on the shaft makes a guide fit with the internal radial flange on the boss. The fit between spigot and flange should not be so tight that shaft and boss have to be connected together only under very carefully controlled conditions. When bolts are used in fastening the boss to the propeller shaft, the heads of the bolts may rest against the inner surface of the internal radial flange on the boss, and the bolts are then fastened at their other ends inside the shaft, e.g., by nuts or by being screwed into screw threads provided in the propeller shaft. However, in some circumstances it may be desirable or possible to reverse this arrangement, so that the heads of the bolts abut a flange provided internally at the end of the propeller shaft.

In a preferred embodiment of the invention the propeller shaft itself has an extra internal flange spaced a short distance axially from its internal flange at the tail end of the shaft. Preferably the internal surface of the shaft between the two flanges is smoothly curved in an axial direction. In such cases the fastening elements, e.g., bolts, pass through both flanges inside the shaft, and are made fast, e.g., by nuts, at the internal radial flange of the propeller boss.

In a preferred embodiment of the invention when bolts are used, the spaces between the shanks of the bolts and the walls of the apertures on the flanges in the boss and shaft are occupied by sleeves or hollow dowels, so that the dowels or sleeves take all the shear and bending loads whilst the bolts are in tension only. It is further intended that each bolt shall be preloaded equally and to such a known degree that the total compressive load between the abutting flanges of the shaft and boss shall be well in excess of any separating forces, e.g., propeller and stem thrusts.

Once the boss has been fastened to the propeller shaft, the end of the boss remote from the shaft can be closed, e.g., by attaching a fairwater cap.

Preferred embodiments of the invention are described 3 with reference to the accompanying drawings in which:

FIGURE 1 shows a half longitudinal sectional view of a propeller boss and its attachment to the propeller shaft;

FIGURE 2 shows a sectional elevation on a larger scale of a hollow dowel;

FIGURE 3 shows a cross-sectional elevation through the line IIIIII of FIGURE 1;

FIGURE 4 shows a sectional elevation through the line IVIV of FIGURE 1;

FIGURE 5 shows a half longitudinal sectional view of an alignment dowel together with its adaptor;

FIGURE 6 shows a half longitudinal sectional view of a propeller boss attached to a propeller shaft, alternative'to that shown in FIGURE 1;

FIGURE 7 shows a part sectional elevation on a larger scale of a coupling bolt used in the arrangement shown in FIGURE 6;

FIGURE 8 shows a sectional elevation of a hollow dowel used in the arrangement shown in FIGURE 6;

FIGURE 9 shows half cross-sectional elevations through the lines AA and BB of FIGURE 6; and

FIGURE 10 shows a full cross-sectional elevation through the line C'C of FIGURE 6.

Referring to FIGURES l to 4 of the drawings, the propeller boss 1 with part of the propeller shown at 1a has an internal radial flange 2, an intermediate flange 3, and a second internal radial flange 4. There are four longitudinal ribs 5, 6, 7 and 8 on the inside of the boss 1, and also four

longitudinal ribs

9, 10, 11 and 12 on the inside of the propeller shaft 13. The propeller shaft 13 has a flange 14 with a spigot portion 15. The external diameter of the spigot portion 15 is substantially equal to the internal diameter of the flange 2, so that spigot and flange make a guide fit.

The flange has sixteen circular apertures which cooperate with sixteen circular apertures in the flange 14 of the propeller shaft 13, thereby forming sixteen common circular apertures 17.

Before fastening the propeller boss 1 to the propeller shaft for the first time it may be necessary after aligning the apertures in the flanges of boss 1 and shaft 13 to ream the apertures. This may be accomplished by the use of a reamer, and for this purpose the intermediate flange 3 can be used as a backstop. When the apertures have been reamed when this is necessary, the boss 1 can then be fastened to the shaft 13.

Into the apertures 17 hollow shear dowels 19 are inserted making an interference fit and they thereby act as sleeve surrounding the shaft of the bolts. The bolts 18 are then inserted and landing collars 20 are fitted on the bolts, followed by nuts 21 thereby forcing the boss 1 and shaft 13 together, so that the heads 16 of the bolts 18 abut the flange 2. An annular oil seal 22 may then be fitted round the junction of the boss 1 and the shaft 13.

Finally, plate 23 and closing plate 24 are secured to the shoulder 15 of the flange 14, and to the flange 4 respectively, and then a fairwater cap 25 is fixed to the boss 1.

Referring to FIGURE 5 of the drawings, the alignment dowel has a tapered portion 31 and an adjustable threaded portion 32. The diameter of the main portion 33 of this dowel is substantially the same as that of the apertures in the shaft and boss. The dowel also has a flanged portion 34, so that when the dowel is inserted into the apertures in the shaft and boss, this portion 34 corresponds to the heads 16 of the bolts. Also shown in FIG- URE 5 is an adaptor 35 which may be screwed into the dowel 30 when located in position in the apertures in the shaft and boss. This adaptor 35 has an external thread 36 onto which nuts can be threaded so as to connect shaft and boss firmly when the alignment dowel and adaptor are in position in the apertures of the shaft and boss.

In practice the boss 1 and shaft 13 can be temporarily connected together by inserting temporary bolts into alternate apertures, and screwing nuts onto the ends of the bolts. The alignment dowels 30 are then'introduced into the remaining unoccupied apertures and adaptors 35 and nuts attached by the method described above. The boss 1 and shaft 13 are then firmly connected together with the apertures 17 in true alignment. The temporary bolts can then be removed, hollow dowels 19 introduced into the apertures and the permanent bolts 18 inserted and made fast by collars 20 and nuts 21. The alignment dowels 30 can then be removed, and hollow dowels 19 introduced into these vacated apertures, followed by the bolts 18 which are made fast 'by colars 20 and nuts 21.

Referring to FIGURES 6 to 10 of the drawings, parts which are identical to those described with reference to FIGURES 1 to 5 of the drawings are indicated with identical numerals. In this case the propeller shaft 40 is shaped differently and has an internal flange 41, and the inner surface of the shaft 40 is smoothly curved between this flange 41 and the spigot portion 42 of the shaft 40, thereby eliminating any stress concentrations which would result from sharp corners. Also in this case the propeller boss has no internal ribs.

The coupling bolts which are used are shown in FIG- URE 7, and it can be seen that they have a raised portion 44 which gives an aver-age running fit when inserted in the dowel 45. In this particular arrangement the heads 46 of the bolts are inside the propeller shaft 40 and not inside the propeller boss 1. The other ends of the bolts 43 are secured by means of nuts 47 and washers 48, these washers having a portion of smaller internal diameter which fits inside the apertures 17. Surrounding the shanks of the bolts 43 are hollow dowels 45 which in this case have an internal threaded portion 49. The dowels 45 may be removed by using a conventional form of stud withdrawing gear modified however to allow for the fact that the dowel 45 has an internal thread rather than an external thread as is usually the case with studs.

The propeller boss and propeller shaft can be connected together in a similar manner to that described with reference to FIGURES 1 to 4 of the drawings, except that the direction of the bolts is reversed. Aligning dowels 30 would be used without adaptor 35 in a similar manner to that described with reference to FIGURE 5 of the drawings. This particular arrangement shown in FIGURES 6 to 10 is advantageous compared with that shown in FIGURES 1 to 4 of the drawings because the tail end of the propeller shaft has been redesigned so as to reduce any possible stress concentrations. This arrangement does however require the use of longer bolts.

What is claimed is:

1. A propeller and propeller shaft assembly for a marine vessel comprising a propeller shaft and a propeller including a hollow propeller boss with an internal radial flange having apertures therein, fastening elements passing through the apertures in said flange so as to connect said shaft to said flange, wherein said elements are housed entirely inside the boss and shaft, and closure plate means sealing the end of said boss opposite said flange to thereby exclude sea water from said fastening elements and prevent corrosion thereof, said fastening elements comprising bolts and nuts attached thereto, said bolts being smaller than said aperatures, and hollow dowels interposed between said bolts and the walls of the apertures in the rflanges of the boss and shaft, said hollow dowels having an internal diameter greater than the diameter of said bolts, so that said dowels take all the shear loads while the bolts are in tension only.

2. An assembly as claimed in claim 1 wherein the boss has internal longitudinal ribs.

3. An assembly as claimed in claim 1 wherein the boss has an internal flange intermediate of the ends thereof.

4. An assembly as claimed in claim 3 wherein the boss has a second internal radial flange situated at the end of the boss remote from the internal radial flange.

5. An assembly is claimed in claim 1 wherein the boss has four symmetrically disposed longitudinal ribs and four circular apertures in each quadrant bounded by the ribs.

6. An assembly as claimed in claim 1 wherein the propeller shaft is hollow.

7. An assembly as claimed in claim 3 wherein the fastening elements are bolts and the intermediate internal flange of the propeller boss is spaced from the internal radial flange of the boss abutting the propeller shaft by a distance at least equal to the length of the bolts.

8. A propeller and propeller shaft assembly for a marine vessel comprising a propeller shaft, said shaft having at its tail end an internal flange having a plurality of apertures therein and a propeller including a hollow propeller boss with an internal radial flange having apertures therein, fastening elements passing through the apertures in said flanges so as to connect said shaft to said boss, and closure plate means sealing the end of said boss opposite said boss internal radial flange to thereby exclude sea water from said fastening elements and prevent corrosion thereof, said fastening elements comprising bolts and nuts attached thereto, said bolts being smaller than said apertures, and hollow dowels interposed between said bolts and the walls of the apertures in the flanges of the boss and shaft, said hollow dowels having an internal diameter greater than the diameter of said bolts, so that said dowels take all the shear loads while the bolts are in tension only.

9. An assembly as claimed in claim 8 wherein there is a spigot extending outwardly beyond flange on the shaft, the outer diameter of the spigot being substantially equal to the internal diameter of the internal radial flange on the boss.

10. An assembly as claimed in claim 9 wherein there is an extra internal flange axially spaced a short distance from the flange at the tail end of the propeller shaft.

11. An assembly as claimed in claimed 10 wherein the internal surface of the shaft between the two flanges is smoothly curved in an axial direction.

12. An assembly as claimed in claim 1 wherein said dowels make interference fits with the apertures.

13. An assembly as claimed in claim 1 wherein the outer diameter of the propeller boss is slightly larger than that of the propeller shaft.

14. A bladed propeller and propeller shaft assembly for a marine vessel comprising a propeller shaft having an internal radial flange and a propeller including a hollow propeller boss with a radial flange having apertures therein, fastening means for connecting said propeller shaft flange and said boss flange, said fastening means passing through said apertures and being smaller in diameter than said apertures, said fastening means being housed entirely inside said boss and said shaft, and dowel members interposed between said fastening means and the walls of said apertures, said members having an internal diameter greater than the diameter of said fastening means so that said dowels take all the shear loads while the fastening means are in tension only.

15. A propeller and propeller shaft assembly for a marine vessel comprising a propeller shaft and a propeller including a hollow propeller boss with an internal radial flange having apertures therein, fastening elements pass ing through the apertures in said flange so as to connect said shaft to said flange, wherein said elements are housed entirely inside the boss and shaft and wherein when said shaft and boss are fastened together no part of said fastening elements protrude into a surface of said shaft or boss which comes into contact with sea water, and closure plate means sealing the end of said boss opposite said flange to thereby exclude sea water from said fastening elements and prevent corrosion thereof.

16. The assembly of claim 15 further characterized in that dowel members are interposed between said fastening elements and the walls of said apertures, said dowel members having an internal diameter greater than the diameter of said fastening means so that said dowels take all the shear loads while the fastening means are in tension only.

References Cited UNITED STATES PATENTS 2,028,448 1/1936 Harza -160.23 2,470,517 5/1949 Obrist. 2,987,123 6/1961 Liaaen. 3,228,482 1/1966 Bunyan.

FOREIGN PATENTS 459,988 1/ 1937 Great Britain.

EVERETTE A. POWELL, JR., Primary Examiner.

US. Cl. X.R. 170159, 160.23