TECHNICAL FIELD

The invention relates to a propeller such as a contra propeller or s single propeller. The propeller is adapted to lubricate the propeller shaft seal. The invention may be applied in a marine vessel comprising a drive, preferably of tractor type. The marine vessel may be a cargo ship, transport ship, passenger ferry, a barge, a leisure boat such as a mono hull, a catamaran, a trimaran, a rigid hull inflatable boat (RIB), a walk around, a day cruisers, a houseboat or the like. BACKGROUND

Twin counter rotating propellers, sometimes referred to as contra propellers, are widely used on boats to improve propulsive efficiency. The twin propellers are propelled via two coaxially arranged propeller shafts which in turn are connected to a power output shaft generally via bevel gears. One propeller rotates clock wise while the other propeller rotates counter clock wise. Having twin counter rotating propellers the boat is generally provided with better grip in the water which in turn enables the boat to get up onto the plane faster and staying there at lower revs. Better grip further provides an additional advantage when docking. Lower vibrations and noise levels are other advantages attributed to the twin counter rotating propellers.

However, with two propeller shafts, the complexity of the construction is increased.

Having two coaxially arranged propeller shafts provide additional wear surfaces which in turn requires additional lubricant sources to properly lubricate between the propeller shafts. Each propeller shaft, i.e. the inner and the outer propeller shaft, are generally provided with propeller shafts seals in order to retain the lubricants so that the propeller shafts are properly greased. The US patent no. US 4,793,773 disclose twin counter rotating propellers and drive having a lubricant solution in which the outer propeller shaft has a radial oil passage to provide oil to the engaging surfaces of the outer and inner propeller shafts. The radial oil passage in the outer shaft is arranged inside of the drive. The twin propellers each has a boss axially held via retainers, dampers and nuts held by an inner sleeve. The propellers further have an outer sleeve forming an exhaust gas passage between the inner and outer sleeve. The propellers are said to have a smooth rotation due to the clearance between the outer sleeves and the outer sleeve and the housing and the outer sleeve of the front propeller, i.e. the drive proximal propeller. A pair of oil seals is arranged between the outer shaft and the bearing housing. The oil seals are exposed to both hot exhaust gas and occasionally to sea water. It has now been found that the oil seals have a tendency to have a reduced life time when exposed as described above. There is thus a need for improvements, or at least useful alternatives. It has further been found that single propeller drives, and single propellers are subjected to similar problems. It is therefore desirable with a solution which can address drawbacks with twin propellers as well as drawbacks with single propellers.

SUMMARY

An object of the invention is to provide a propeller for a marine vessel which reduces the wear of associated seals. It is further an object of the invention to at least partly solve the drawbacks associated with the prior art, or to provide a useful alternative thereto. The object is at least partly achieved by a propeller according to claim 1 . More specifically, the object is at least partly achieved by a propeller for a marine vessel. The propeller comprises a hub comprising an aperture for receiving a first propeller shaft. The aperture has a drive proximal opening and optionally a drive distal opening. The hub is provided with at least one lubricant reservoir for lubricating at least a first seal at the drive proximal opening of the aperture. The propeller disclosed herein is advantageously applied to a propeller and a drive arrangement.

By the provision of the propeller, hot exhaust gas or sea water will not impose an unnecessary wear on the associated seals. Instead, the lubricant reservoir will provide lubricant for the associated oil seal and thus protect the seals. The lubricant may be replaced or refilled providing easy maintenance and, without being bound by theory, a relatively long life time expectancy of the seal.

According to one embodiment, the lubricant reservoir is formed by a confined space within the hub and/or formed by the hub and a portion of the first propeller shaft. The propeller may thus be tailored to specific drives and the construction of the propeller shafts. By having the lubricant reservoir partly delimited by the first propeller shaft, a relatively small diameter of the hub may be provided. According to a further embodiment, the first seal is a first propeller shaft seal adapted to seal about the first propeller shaft. The lubricant reservoir may be adapted to lubricate substantially any seal. It has been found however that it is specifically advantageous to protect the propeller shafts seal, as that seal is specifically exposed and sometimes relatively difficult to perform maintenance on.

According to an embodiment, the lubricant reservoir may be arranged to lubricate a second seal. The lubricant reservoir may thus be in fluid communication with at least two seals. A second seal may be arranged to seal between the lubricant reservoir and a drive housing, or to seal between the lubricant reservoir and an element arranged to the drive housing such as a seal flange arranged to the drive housing. The second seal may of course seal against any other portion of the drive. The at least two seals may be drive proximal seals. The second seal may be used to seal off against sea water from penetrating the lubricant reservoir. The second seal is advantageously positioned between the propeller and a portion or an element of the drive so that the first propeller shaft seal is effectively protected.

According to an embodiment, the lubricant reservoir may be arranged to be in fluid communication with a seal at the drive distal opening. If the propeller is a drive proximal propeller adapted to be used on a twin counter rotating propeller drive, the seal at the drive distal opening may be a propeller shaft seal adapted to seal against a propeller shaft or between an outer and an inner propeller shaft. Using a lubricant reservoir within the hub of the propeller may thus be a very versatile solution as it may be possible to lubricate seals associated with propeller of one or more propeller shafts.

According to an embodiment, the lubricant reservoir may comprise a refill opening and optionally an air ventilate opening. The propeller may thus be provided with a refill opening and optionally an air ventilate opening. Having a refill opening enables easy maintenance and the replacement of the lubricant.

According to an embodiment, the refill opening and/or air ventilate opening are accessible by a user after the propeller has been mounted to the first propeller shaft. The refill opening and/or air ventilate opening may be arranged on the side facing a drive distal propeller just as a matter of example, and specifically the hub of the drive distal propeller. This removes the need for dismounting the propeller in order to refill or replace the lubricant of the lubricant reservoir. According to an embodiment, the aperture is adapted to receive an additional second propeller shaft. The first and the second propeller shafts are preferably coaxial. The propeller may thus be specifically adapted to a twin propeller arrangement, such as a twin counter rotating propeller arrangement. It has been found that the lubricant reservoir is specifically advantageous when the propeller is adapted to cooperate with a second propeller arranged on the second propeller shaft. The lubricant reservoir may thus lubricate several propeller shaft seals, such as two or more propeller shaft seals. According to an embodiment, the lubricant reservoir may be adapted for a lubricant pressure of about 1 -5 atm, preferably of about 1 -3 atm. The lubricant pressure may be measured at 20 ^Q C. By having a relatively low lubricant pressure, i.e. closer to 1 -1 .5 atm, a user may easily replace or refill lubricant without specific instruments or tools. However, it may be advantageous to have a slight over pressure inside of the lubricant reservoir as the propeller will generally be positioned between 0.5-2 m below sea level during use.

According to an embodiment, the lubricant reservoir is a closed lubricant reservoir. By the term closed lubricant reservoir, is meant that no lubricant conduit is directing lubricant to the lubricant reservoir from another lubricant source. In a sense, the lubricant reservoir is sustained by being filled batch wise and not continuously fed from another lubricant source. The lubricant may further be filled directly into the lubricant reservoir from the ambient environment outside of the propeller. This provides an easy maintenance propeller. The propeller may be a contra-propeller. A contra propeller is a propeller specifically adapted to cooperate with a second propeller, counter rotating to the first propeller. The contra propeller is preferably the drive proximal propeller. It should be noted that the propeller may be a drive distal propeller. A drive may further be provided with one or more of the propeller disclosed herein. It is of course possible that the propeller may be a single propeller, and not a propeller of a twin propeller arrangement such as a twin counter rotating propeller arrangement. A single propeller may be provided with a closed end aperture. In comparison a propeller of a twin propeller arrangement generally comprises a through aperture, i.e. an aperture having two openings in this case a drive distal opening and a drive proximal opening.

The lubricant reservoir may be adapted to hold oil, preferably biodegradable oil. Further disclosed herein is a drive for a marine vessel. The drive comprises a drive housing, a first propeller shaft, a propeller attachment member and at least one propeller as disclosed herein. The propeller attachment member may comprise at least one channel adapted to be in fluid communication with the lubricant reservoir after assembly. The lubricant reservoir may thus be accessible via the at least one channel through the propeller attachment member. The propeller attachment member may be a propeller nut.

According to an embodiment, the at least one channel is adapted to be in fluid

communication a refill opening and/or an air ventilate opening of the lubricant reservoir. The lubricant reservoir may thus be refilled or air ventilated via the propeller attachment member. This may enable a user to refill or replace the lubricant without removing the propeller from the propeller shaft. According to an embodiment, the drive may comprise a second propeller arranged on a second propeller shaft. The first and the second propeller shafts are preferably coaxial. The drive may thus be a twin propeller drive. It has been found that one or more local lubricate reservoirs within one or more propellers are well suited for twin propeller arrangements and drives. It provides for a very simple way of extending the life time expectancy of associated propeller shafts seals.

According to an embodiment, the propeller attachment member may comprise a propeller shaft seal, the propeller shaft seal may be adapted to seal against the second propeller shaft. The propeller attachment member may thus be used to effectively seal and contain lubricant.

Further disclosed herein is a marine vessel comprising at least one drive comprising at least one propeller. The propeller may be propelled by an inboard propulsion unit or an outboard propulsion unit.

According to an aspect, the disclosure further relates to the use of a cavity within a propeller for lubricating a drive seal, such as a propeller shaft seal arranged to drive. Whether the drive is a single propeller drive or a twin propeller drive, it has been found that one or more lubricate reservoirs in a propeller may efficiently be used to extend the life time expectancy of associated propeller shafts seals and especially the propeller shafts associated with or arranged to the drive.

Further advantages and advantageous features of the invention are disclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detailed description of embodiments of the invention cited as examples.

In the drawings:

Fig. 1 is a schematic view of a drive of the tractor type comprising twin counter rotating propellers; a drive proximal propeller and a drive distal propeller.

Fig. 2 is a schematic cross section of a drive proximal propeller.

Fig. 3 is a schematic cross section of a second embodiment of a drive proximal propeller. Fig. 4 is a schematic cross section of a third embodiment of a drive proximal propeller. Fig. 5 is a schematic view of a drive of single propeller type comprising a propeller;

Fig. 6 is a schematic cross section of an embodiment of a single propeller.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Figure 1 shows a portion of a marine vessel 1 comprising a drive 2. The marine vessel 1 may be a cargo ship, transport ship, passenger ferry, a barge, a leisure boat such as a mono hull, a catamaran, a trimaran, a rigid hull inflatable boat (RIB), a walk around, a day cruisers, a houseboat or the like. The drive 2 is of so called tractor type, i.e. having forward facing propellers, in this case a first and a second propeller 3, 4. It should be noted that the drive 2 may optionally be provided with one or more backward facing propeller(s). The first and the second propellers 3, 4 are counter rotating propellers. An axis of rotation R is indicated in figure 2 with a dashed line. The first and the second propellers 3, 4 rotate about the same axis of rotation R. The first propeller 3 is referred to as the drive proximal propeller 3 as it is closer to the drive and the second propeller 4 is also referred to as a drive distal propeller 4 as it is further away from the drive. The marine vessel 1 may be provided with one or more drives 2. Although only one drive is described hereafter and the first and the second propellers 3, 4 are counter rotating propellers it should be noted that the invention may be applied to propellers per se, although it has been found that the propeller disclosed herein is advantageously applied to a propeller and a drive arrangement, and especially a counter rotating propeller drive preferably of the tractor type.

Figure 2 shows the first propeller 3 of the drive 2 with a cross sectional view and in greater detail. The first propeller 3 has a hub 1 1 comprising an aperture 12 for receiving a propeller shaft. The aperture 12 has a drive proximal opening 13 and a drive distal opening 14 and is in the shown embodiment adapted to receive a first and a second propeller shaft 15, 16. A portion of the drive 2 is further visible in the form of a drive housing 5. The hub 1 1 is provided with a lubricant reservoir 20. The lubricant reservoir 20 is adapted to hold lubricant so as to enable lubrication of at least one seal at the drive proximal opening 13 of said aperture 12. The first propeller 3 is not continuously fed by lubricants from a secondary source in terms of it does not have a lubricant conduit connected thereto. The reservoir 20 is closed in terms of it is not intended to disperse or receive a continuous flow of lubricant. The lubricant protects against seawater, corrosion and greases the associated seals.

The lubricant is preferably oil such as biodegradable oil e.g. based on natural and/or synthetic esters such as a biodegradable, low toxicity, synthetic ester oil based grease, e.g. using a lithium-calcium thickener. It should be noted that other oils such as mineral oils are an option although a less preferred option as these are deemed less

environmentally friendly. The lubricant may optionally be high viscosity grease. The lubricant preferably fulfils the requirements defined by Environmentally Acceptable Lubricants (EALs) as defined by the US Environmental Protection Agency (EPA).

The first propeller 3 is associated with a first seal, in this case a first propeller shaft seal 17. The first propeller shaft seal 17 seals between the drive lubricant and the propeller lubricant and is in the shown embodiment arranged to the drive 2. The lubricant reservoir 20 thus provides lubricant to the first propeller shaft seal 17 which is advantageous as no sea water will access the first propeller shaft seal 17. The first propeller seal 17 is thus protected by the lubricant provided by the lubricant reservoir 20 of the first propeller 3.

A second seal, in this case a first propeller drive seal 18 is arranged to seal between the drive 2 and in this case the drive housing 5 and the first propeller 3. The first propeller drive seal 18 seals the lubricant from escaping and sea water from entering the lubricant reservoir 20. By having a reservoir 20 in the hub of the first propeller 3 seals, such as the first propeller shaft seal 17 and the second seal 18, may effectively be lubricated. A third seal, in this case a second propeller shaft seal 21 , is arranged in the proximity of the drive distal opening 14 of the aperture 12 and seals between a propeller nut 30 and the second propeller shaft 16. The propeller nut 30 retains the first propeller 3 to the first propeller shaft 15 so that the first propeller 3 rotates synchronously with the first propeller shaft 15.

The lubricant reservoir 20 further comprises an aperture 35 which is aligned with a channel 36 in the propeller nut 30 together forming a fluid channel providing the second propeller shaft seal 21 with lubricant. The lubricant reservoir 20 may thus lubricate at least three individual seals. In more general terms, the propeller may thus be provided with a lubricant reservoir for lubricating at least three seals, preferably at least two of the at least three seals are propeller shafts seals.

The first propeller shaft seal 17 is arranged to a seal flange 19. The seal flange 19 provides a seal surface for the second seal 18. This provides a replaceable seal surface for the second seal 18, i.e. the seal which is configure to prevent sea water from entering the lubricant reservoir 20 and the lubricant from escaping from the lubricant reservoir 20. Hence the propeller and/or the drive may thus be provided with a seal for sealing against a propeller shaft, the seal being arranged with a seal surface for a second seal. The first propeller shaft seal 17 and the second seal 18 may thus be assembled or replaced as a package. It should be noted that the second seal 18 may be arranged to seal against a portion of the drive 2 instead if desirable. The seal flange 19 is ring shaped and extends around the periphery of the first propeller shaft 15.

The propeller nut 30 is in the shown embodiment retained to the first propeller 3 at the drive distal opening 14 via a first and a second screw 31 . It should be noted that one or more screws, or other retaining mechanisms, may be used to secure the propeller nut 30 to the first propeller 3. A propeller nut seal 32 provides additional leakage protection between the first propeller 3 and the propeller nut 30. The propeller nut 30 is further provided with at least one additional aperture to enable the lubricant reservoir 20 to be refilled, emptied and/or aerated. In the shown embodiment, the lubricant reservoir 20 is provided with a refill aperture 25 and an air ventilation aperture 26. A user may thus refill or replace the lubricant in the lubricant reservoir 20 in an easy manner. The air ventilation aperture 26 prevents air being trapped inside the lubricant reservoir 20. It should be noted that a refill function and an air ventilation function may be enabled via a single aperture although this may be less preferable. The refill aperture 25 and the air ventilation aperture 26 are closed by a first and a second screw 25', 26' respectively. As can be noticed, the refill aperture 25 and the air ventilation aperture 26 are thus accessible by a user after the propeller has been mounted to the first propeller shaft 15.

The at least one refill aperture may be arranged on other portions of the first propeller 3. Figure 3 shows a first propeller 3 which is similar to the first propeller disclosed in figure 2. The first propeller 2 comprises a hub 1 1 comprising a lubricant reservoir 20. The first propeller 3 has an aperture 12 for receiving a first and a second propeller shaft 15, 16. As can be noticed however, the refill aperture 25 and the air ventilation aperture 26 extend through the wall of the hub 1 1 of the propeller 3 without having the screws 25', 26' extending through the propeller nut 30. Instead, the screws 25', 26' extend directly through the wall of the hub 1 1 to enable fluid communication with the lubricant reservoir 20. It should be noted that a refill function and an air ventilation function may be enabled via a single aperture although this may be less preferable.

The first propeller 3 may be provided with one or more lubricant reservoirs. In figures 2 and 3, the lubricant reservoir 20 extends around the first propeller shaft 15 and is delimited by the hub 1 1 and the first propeller shaft 15 and the seals 17, 18, 21 . It should be noted that the lubricant reservoir 20 may have other configurations however. The lubricant reservoir is generally adapted for an oil pressure of about 1 -5 atm at 20 ^Q C. Figure 4 shows an embodiment of a propeller 3' for a marine vessel with a cross sectional view. The propeller 3' has a hub 1 1 comprising an aperture 12 for receiving a propeller shaft. The aperture 12 has a drive proximal opening 13 and a drive distal opening 14 and is in the shown embodiment adapted to receive a first and a second propeller shaft 15, 16. The propeller 3' has the same seal configuration as the propellers shown in figures 1 and 2, i.e. a first propeller shaft seal 17, the second seal 18 for preventing sea water entering the lubricant reservoir 20, and a third seal 21 in this case a second propeller shaft seal 21 . A portion of the drive 2 is further visible in the form of a drive housing 5. As can be gleaned, the lubricant reservoir 20 is delimited by walls formed by the propeller and does not have any exposure to the first propeller shaft 15 other than at the first propeller shaft seal 17.

Figure 5 shows a portion of a marine vessel 1 comprising a drive 2'. The marine vessel 1 may be a cargo ship, transport ship, passenger ferry, a barge, a leisure boat such as a mono hull, a catamaran, a trimaran, a rigid hull inflatable boat (RIB), a walk around, a day cruiser, a houseboat or the like. The drive 2' comprises a single propeller 3' and may be a forward- or a backward facing propeller drive. The drive 2' may further be rotatably arranged to the marine vessel 1 . The marine vessel 1 may be provided with one or more drives 2' although only one drive is described hereafter. Figure 6 shows the propeller 3' of the drive 2' with a cross sectional view and in greater detail. The propeller 3' has a hub 1 1 comprising an aperture 12 for receiving a single propeller shaft 15. An axis of rotation R about which the propeller shaft is configured to rotate is indicated in figure 5 with a dashed line. The aperture 12 has a drive proximal opening 13 and a drive distal opening 14. A portion of the drive 2' is further visible in the form of a drive housing 5. It should be noted that although the hub 1 1 has two openings enabling a propeller shaft to run all the way through the aperture 12, the propeller 3' may be provided with only one aperture, so that the aperture 12 is a closed end aperture thus forming a cavity. Generally; the aperture may thus be a through aperture or a closed end aperture.

The hub 1 1 is provided with at least one lubricant reservoir 20. The lubricant reservoir 20 is adapted to hold lubricant so as to enable lubrication of at least one seal at the drive proximal opening 13 of the aperture 12. In the shown embodiment the lubricant reservoir 20 extends around the periphery propeller shaft 15. The propeller 3' is not continuously fed by lubricants from a secondary source in terms of it does not have a lubricant conduit connected thereto; this reduces the complexity of the propeller and propeller shafts installation. In this sense, the propeller is self-sustained with lubricant. The lubricant reservoir 20 may have different configurations. Figure 6 illustrates only a non-limiting example of a cross section of a possible configuration of a lubricant reservoir 20. A detachable propeller cone 40 is arranged at the drive distal side of the propeller 3' in a conventional manner.

In a similar manner as described above, the propeller 3' is associated with a seal, in this case a propeller shaft seal 17'. The propeller shaft seal 1 T seals between the drive lubricant and the propeller lubricant and is in the shown embodiment arranged to the drive 2'. The lubricant reservoir 20 thus provides lubricant to the propeller shaft seal 17' which is advantageous as no sea water will access the propeller shaft seal17'. The propeller seal 17' is thus protected by the lubricant provided by the lubricant reservoir 20 of the propeller 3'.

A second seal, in this case a propeller drive seal 18' is arranged to seal between the drive 2' and in this case the drive housing 5 and the first propeller 3'. The propeller drive seal 18' seals the lubricant from escaping and sea water from entering the lubricant reservoir 20. By having a reservoir 20 in the hub of the propeller 3', seals such as the propeller shaft seal 17' and the propeller drive seal 18', may effectively be lubricated. A propeller nut 30 retains the propeller 3' to the propeller shaft 15'.

Just as disclosed above, the lubricant reservoir 20 further comprises a refill aperture 25 and optionally an air ventilation aperture 26. A user may thus refill or replace the lubricant in the lubricant reservoir 20 in an easy manner. As can be gleaned, the refill aperture 25 and the optional air ventilation aperture 26 may be sealed by e.g. a screw and may be positioned at any desirable position. In the shown embodiment, the refill aperture 25 and the optional air ventilation aperture 26 are positioned on the drive distal side of the propeller 3' which is advantageous as the propeller 3' does not need to be dismounted from the propeller shaft 15 in order to refill or change the lubricant in the lubricant reservoir 20. To access the refill aperture 25 and the optional air ventilation aperture 26, the propeller cone 40 is simply dismounted. The lubricant reservoir 20 is generally adapted for an oil pressure of about 1 -5 atm at 20 ^Q C.

It should be noted that the oil pressure inside of the lubricant reservoir 20, independently of the embodiment, may be adapted to the oil pressure of the drive on the other side of the associated seal so as to prevent lubricant migration. In this sense the oil pressure inside of the lubricant reservoir 20 may well be 1 -5 atm at 20 ^Q C or more. It is to be understood that the present invention is not limited to the embodiments described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the appended claims.