More particularly, but not exclusively, this invention relates to a marine propeller shaft seal including an outer thrust flange which includes a fluid passageway through which fluid can be added to or removed from a stern tube.

Most propeller driven ships include a propeller shaft which extends from the engine, through a stern tube in the-hull of the ship and into the surrounding waters. In use the propeller shaft rotates with respect to the walls of the stern tube. Therefore, in order to prevent damage to the propeller shaft a lubricant is added between the propeller shaft and the stern tube wall.

To prevent this lubricant from leaking from the stern tube into the surrounding water a propeller shaft seal is connected between the propeller shaft and the hull. Such propeller shaft seals are well known and typically comprise a first portion for engagement with the propeller shaft and a <BR> <BR> <BR> <BR> thrust flange for engagement Mith the hull, the first portion and the thrust flange forming a seal therebetween.

In order to repair or replace such a seal it is firstly necessary to detach the first portion from the propeller shaft.

If this is done with the ship in the water the stern tube oil will leak from the stern tube into the surrounding water causing significant oil pollution. Any repair work involving the propeller shaft seal should therefore be performed with the ship in dry dock where the oil can be collected as it leaks from the stern tube. This is expensive time consuming.

The present invention provides a marine propeller shaft seal which includes an outer thrust flange which includes an inner fluid port communicating with the stern tube, an outer fluid port and a fluid passageway extending between inner and outer ports.

Accordingly, in one aspect, there is provided a marine propeller shaft seal adapted in use to seal a rotating marine propeller shaft to a hull, wherein the propeller shaft rotates within a stern tube extending through the hull; the seal comprising: a first portion adapted to engage the propeller shaft; an outer thrust flange adapted to engage the hull; said first portion and said outer thrust flange form-ing a seal therebetween; the outer thrust flange including an inner fluid port communicating with the stern tube, an outer fluid port, a fluid passageway extending between the inner and outer fluid ports and a valve moveable between open and closed positions; arranged so that when the valve is in the open position the inner fluid port and outer fluid port are in fluid communication enabling fluid to be added to or removed from the stern tube; and when the valve is in the closed position the inner fluid port and outer fluid port are not in fluid communication.

The marine propeller shaft seal of the invention has the advantage that it enables a stern tube lubricant to be removed from the stern tube before the seal is dismantled. This enables the marine propeller shaft seal to be repaired or replaced with the ship in the water and witliout any significant contamination of water surrounding the ship by lubricant from the stern tube.

The marine propeller shaft seal can include a secondary seal positioned in use between the first portion and the propeller shaft and adapted to prevent fluid leaking from the stern tube between the propeller shaft and the first portion.

This seal further reduces lubricant leakage between the seal and the propeller shaft.

The first portion of the seal can include a vibrating cup slidable longitudinally with respect to the propeller shaft and the biasing means; wherein the biasing means is adapted to bias the vibrating cup into contact with the thrust flange so forming the seal therebetween.

The vibrating cup and outer thrust flange can each include a mating surface, the mating surface of the vibrating cup being biased into contact with the r, ; 3ting surface of the outer thrust flange by the biasing means.

Biasing the mating surfaces together reduces the lubricant leakage between the outer thrust flange and the first portion.

The biassing means can include a drive clamp adapted to engage in fixed relation to the propeller shaft and a spring extending between the drive clamp and vibrating cup.

Preferably, there is a gap between the drive clamp and the vibrating cup adapted for the insertion of a wedge to prevent the separation of the mating surfaces. This enables an excess pressure to be applied to the lubricant in the stern tube without the mating surfaces separating.

The vibrating cup can be lockable in fixed relation to the propeller shaft. Again, this enables excess pressure to be applied to the lubricant in the stern tube.

In a further aspect there is provided a compressible marine propeller shaft seal defining a chamber located within the seal; at least one conduit extending between the surface of the seal and the chamber; wherein the conduit is adapted to release a lubricant from the chamber to the exterior of the seal during use.

The compressible seal may include a plurality of conduits.

The present invention will now be described by way of example only with reference to. the accompanying drawings in which: Figure 1 is a cross-sectional view of a known propeller shaft outer seal.

Figure 2 is a cross-sectional view of a stern tube arrangement with an inner seal and outer seal according to the invention attached.

Figure 3 is a cross-sectional view of a stern tube arrangement with an inner seal and outer seal according to the invention attached.

Figure 4 is a cross-sectional view of a valve of a propeller seal according to the invention.

Figure 5 is a cross-sectional view of a further embodiment of a marine propeller shaft seal according to the invention.

Figure 6 is a cross-sectional view of a secondary seal which in use is located between the first portion of the propeller shaft seal and the rotating propeller shaft.

Shown in Figure 1 is a known propeller shaft seal 1.

The seal 1 is connected between the outer wall of a hull 2 and a propeller shaft 3. A stern tube 4 extends between inner 5 and outer 6 faces of the hull 2 and the propeller shaft 3 extends through this tube 4 from the engine (not shown) to the surrounding water. In use, the propeller shaft 3 rotates relative to the stern tube wall 7. A lubricant 8 is therefore added to the gap 9 between the shaft 3 and wall to reduce wear on the propeller shaft. Clamped to the shaft is a hollow cylindrical collar 10. The collar 10 has a flange 11 at its end remote from the hull 2 to which is attached a propeller 12 (not shown).

The propeller shaft seal 3 comprises an outer thrust flange 13 and a first portion 14. rhe outer thrust flange 13 is attached to the outer face of the hull 6 around the propeller shaft 3 and forms a seal between the flange 13 and the hull 2. The first portion 14 comprises a drive clamp 15 and vibrating cup 16. The drive clamp 15 is fixedly clamped to the cylindrical collar 10 and rotates with the propeller shaft 3. The vibrating cup 16 is located between the drive clamp 15 and outer thrust flange 13 and also rotates with the propeller shaft 3. The vibrating cup 15 is free to slide longitudinally along the propeller shaft 3. A compression spring 17 extends between the vibratos cup 16 and the drive clamp 15 and biases the vibrating c-. up i into contact with the outer thrust flange 13. The vibrating cup'16 and outer thrust flange 13 each include mating surfaces 18,19. The mating surface 18 of the outer thrust flange 13 abuts against the mating surface 19 of the vibrating cup 16 forming a seal preventing the escape of lubricant 8. A secondary compressible seal 20 is located between the vibrating cup 16 and collar 10 preventing the escape of lubricant 8 between the collar 10 and cup 16.

While such a marine propeller shaft seal 1 is effective in preventing leakage of lubricant 3 is necessary to remove the propeller shaft 3 and SE'a'_ water before the seal 1 can be replaced. The first portion 14 can then be removed and the lubricant 8 which escapes from the stern tube 4 collected in barrels. Defective parts can then be replaced, the seal 1 reattached and the stern tube 4 refilled with lubricant 8.

Shown in Figure 2 is a marine propeller shaft seal 21 according to the invention. The marine propeller shaft seal 21 is connected b3tween the outer wall 6 of the hull 2 and the propeller shaft 3. Connected between the inner wall 5 of the hull 2 and the propeller shaft 3 is an inner propeller shaft seal 22. Such inner propeller shaft seals 22 are well known and will not be discussed in detail. The stern tube 4 between the inner 22 and outer 21 shaft seals is filled with oil to reduce the friction between the propeller shaft 3 and stern tube wall 7. An oil tank 13 located within the hull 2 is connected to the stern tube 4 bs oil pipes 24,25 at a point proximal to the inner shaft seai, 2 to ensure that any lubricant which leaks from the stern tube 4 is replaced.

The outer marine propeller shaft seal 21 comprises a first portion 4 and an outer thrust flange 26. The outer thrust flange 26 is connected to the outer wall of the hull 2. A fluid passageway 27 extends through the outer thrust flange 26 between inner 28 and outer 29 fluid ports. The inner fluid port 29 is located in a face of the flange 30 remote from the hull 2. Located within the fluid passageway 27 is a valve 31 moveable between open and closed positions.

When the valve 31 is in the open position oil is free to flow from the stern tube 4, through the fluid port 28 and along the fluid passageway 27 to the outer fluid ort 29.

When the valve 31 is in the closed position oil is not free to flow along the fluid passageway 27 between inner 28 and outer 29 fluid ports.

The first portion 14 of the outer marine propeller shaft seal 21 of the invention is known and has been described in detail with respect to the shaft seal 1 as shown in Figure 1.

Shown in Figure 3 is a marine propeller shaft seal 21 of the invention connected between propeller shaft 3 and outer hull wall 6. The stern tube 4 is connected to oil tank 23 by oil pipes 24,25. The oil pipes 24,25 extend part way through the hull 2 and connect to the stern tube 4 approximately mid way along g its lenqth Shown in Figure 4 is a valve 31 located between fluid passageway 27 and outer fluid port 29 of the outer thrust flange 26 of the marine propeller shaft seal 21 of the invention. The valve 31 comprises a constriction 32 including, at an end remote from the outer fluid port 29, a valve seat 33. A ballbearing 34 is biassed into contact with the valve seat 33 by spring 35 so closing the valve 31. The end of the spring remote from the ball bearing 34 is attached to a washer 35a which is, in turn, attached to the passageway wall. To open the valve 31 a nozzle 36 is inserted through the outer fluid port 29 into the constriction.'A tip 37 of the nozzle 36 pushes the ball bearrng 9'i towårds the washer 35 lifting it from valve seat 33 so opening the valve 31. On removal of the nozzle 36 from the valve 31 the ball bearing 34 automatically returns to the valve seat 33 so reclosing the valve 31.

The marine propeller shaft seal 21 of the invention can be replaced or repaired with the propeller shaft seal 21 in the water. In order to replace the marine propeller shaft seal 21 of the invention a first airline 38 is connected to valve 31 biassing it into an open position. Optionally a wedge 39 is then inserted between vibrating cup 16 and drive clamp 15 to maintain the cup 16 in t tact with the outer thrust flange 13. High pressure air is introduced into the stern tube 4 via the first airline 38 forcing the oil back through the oil pipes 24,25 in to the oil tank 23 or other storage means. Once the oil has been evacuated from the stern tube 4, oil pipes 24,25 are connected to a high pressure air supply (not shown) and the first airline 38 is <BR> <BR> <BR> <BR> removed so returning the valve 31 to a closed position. The seal 21 can then be removed. Once the seal 21 has been removed, compressed air flows along the oil pipes 24,25 along the stern tube 4 and then into the surrounding waters.

The air is maintained at a pressure slightly higher than that of the surrounding water so preventing this surrounding water from entering into the stern tube 4.

Once the defective seal component has been identified and replaced the marine propeller shaft seal 21 can be <BR> <BR> <BR> <BR> reconnected between hull 2 and propeller shaft 3. To enable the seal 21 to be reconnected the alr elapply to the oil pipes 24,25 must momentarily be disconnected at which point a small amount of water enters into the stern tube 4. The seal 21 is then re-attached and optionally the wedge 39 reintroduced between drive clamp 15 and vibrating cup 16.

The air supply to the oil pipes 24,25 is reconnected and valve 31 biassed into the open position until all of the water in the stern tube 4 has been discharged through the valve 31. The oil pipes 24,25 are then reconnected to the oil tank 23 and the stern tube 4 filled with lubricant so discharging air from the stern tube 4. Once all of the air has been discharged from the stern eube 4 valve 31 is returned to the closed configuration.

Shown in Figure 5 is a further embodiment of a marine propeller shaft seal according to the invention. Located between the outer wall 6 of the hull 2 and outer shaft seal 21 is an inflatable tyre seal 41. In use the tyre seal 41 is inflated so retaining the oil within the stern tube. The outer shaft seal 21 can then be repaired or replaced.

Finally, the inflatable tyre seal 41 is deflated.

The oil in the stern tube 4 can be periodically tested to ensure that the propeller shaft seal 21 is watered tight and that all water has been discharged from the stern tube 4.

Shown in Figure 6 is a secondary compressible seal 20 which, in use, is located between the vibrating cup 16 and collar 10 of the marine propeller shaft seal 3. The use of such a seal 20 is optional. The secondary seal 20 is elliptical in cross-section and detinue a hollow chamber 40.

A number of conduits or pores 41 extend between the hollow chamber 40 and the surface 42 of the seal 20 and enable the slow discharge of lubricant from the hollow chamber 40 to the surface of the seal during use.

A number of convex portions 43 extend from the secondary seal 20. When the seal 20 is compressed these convex portions 43 come into contact with the compressing plates so providing a plurality of independent'sealing points between the plates.