GB2334313A

GB2334313A - Propeller shaft seal and bearing assembly

Info

Publication number: GB2334313A
Application number: GB9802965A
Authority: GB
Inventors: Christopher Daniel Joh Goddard
Original assignee: HALYARD
Current assignee: HALYARD
Priority date: 1998-02-13
Filing date: 1998-02-13
Publication date: 1999-08-18
Also published as: GB9802965D0

Abstract

A propeller shaft seal and bearing assembly (1) comprises a housing (12), inner and outer annular bearing members (2, 6) with the radially outer bearing member (6) fast with the housing (12) and the inner member (2) secured to the shaft, one of said bearing surfaces being formed with at least one helical groove. First and second annular fluid channels (36, 24) are defined within the housing and are separated by one (6) of the annular bearing members (28). Sealing means (4") partially defines said second annular fluid channel (24). The arrangement is such that on rotation of the propeller shaft, the helical groove provides pumping means by which fluid is transferred from one (36) of the annular fluid channels through the helical groove into the other annular fluid channel (24). A fluid inlet (52) in the housing communicates with one channel (36), and a fluid outlet (19) in the housing communicates with the other channel (24).

Description

PROPELLER SHAFT SEAL AND BEARING ASSEMBLY The present invention relates to a propeller shaft seal and bearing assembly and to a method of lubricating and cooling such an assembly.

To help exclude sea-water, dirt and other foreign matter from the bearing surfaces and to retain lubricant, bearing mounts of a propeller shaft seal assembly generally include a number of axially-spaced seals. One type of seal used is a lip seal. Lip seals have a rubbing surface in contact with the rotating propeller shaft. Since the sealing action is provided by rubbing, the build up of heat due to the rubbing friction can cause excessive wear of the seal, shaft and degradation of the shaft material.

According to a first aspect of the present invention a propeller shaft seal and bearing assembly comprises a housing, coaxial radially inner and outer annular bearing members within the housing and having co-operating bearing surfaces, said inner bearing member being integral with or adapted to be secured to a propeller shaft, said outer bearing member being fast with the housing, one of said bearing surfaces being formed with at least one helical groove, first and second annular fluid channels defined within the housing and separated by one of the annular bearing members, and sealing means partially defining said second annular fluid channel, and the arrangement being such that in use, on rotation of the propeller shaft, the helical groove provides pumping means by which fluid is transferred from one of the annular fluid channels through the groove into the other annular fluid channel, a fluid inlet in the housing communicating with said one channel, and a fluid outlet in the housing communicating with the other channel.

Lubricating fluid is thereby pumped in use, by the action of the helical groove, through the second annular channel thereby to carry away heat from the region of the sealing means.

Preferably the fluid inlet and outlet is connected in use to a reservoir for lubricant where cooling of the lubricant takes place.

It is preferable that once the fluid has left the assembly via the outlet, it is led to the reservoir and then back to the inlet so providing a recirulation of the fluid. There is preferably a means for filtering the circulating fluid. It is also preferable that there is a fluid flow indication means.

Preferably the outer bearing member is formed with fluid passage means to connect the second annular channel with either said fluid inlet or said fluid outlet.

The fluid passage means preferably comprises a channel formed in the radially outermost surface of the outer bearing member.

The arrangement of the bearings and seals is preferably such that a degree of relative axial displacement of the propeller shaft and housing is permitted, this being accommodated by relative axial sliding displacement of the bearing members.

Preferably the radially outer bearing member is formed with first and second axially-spaced annular bearing portions separated by an interconnecting wall portion, the wall portion bounding the first annular fluid channel.

The apparatus preferably then comprises first sealing means partly defining the second annular fluid channel and separated from the central first fluid channel by one of said annular bearing portions, and second sealing means partly defining a third annular fluid channel and separated from the central fluid channel by the other annular bearing portion. Each annular bearing portion comprises an annular bearing surface which is in contact with the radially inner bearing member.

The bearing surface of each of said bearing portions is preferably formed with a respective helical groove. Preferably one of the helical grooves comprises a right-hand thread and the second groove comprises a left-hand thread and the arrangement is such that, in use, fluid is thereby pumped in axially opposing directions through the respective helical grooves. In use, for one direction of rotation of the propeller shaft, the helical grooves pump the fluid from the central first annular fluid channel into the second and third fluid channels. It will be appreciated that for rotation of the propeller shaft in the opposite direction the flows will be from the second and third channels to the first channel, and the flows will be reversed in said fluid inlet and outlet.

The radially outermost surface of the radially inner bearing member, the radially innermost surface of the wall portion and the two bearing portions of the radially outer bearing member define the first fluid channel.

Although the radially inner bearing member may be integral with the shaft, preferably the inner bearing member is detachably fixed to the propeller shaft. Said sealing means then makes a rubbing contact with the radially outer surface of the tubular sleeve. Auxiliary seals are then required to seal the sleeve to the propeller shaft but these can simply be O-rings.

Thus the rotational motion is used to pump the fluid into, through and out of the second and third annular channels. The method of pumping fluid through the assembly provides lubrication to the rubbing surfaces and also draws heat away from the rubbing surfaces. By pumping fluid into the second and third annular channels the sealing pressure of lip-type sealing means can be increased. It will be appreciated that the increase in sealing pressure can improve the efficiency of the sealing means.

The method of using the helices to pump fluid through the respective annular channels can also be used to purge the various fluid channels of gaseous fluid such as air.

According to a second aspect of the invention, a method for lubricating and cooling a propeller shaft seal and bearing assembly comprises using the rotational motion of the propeller shaft to draw lubricating through the assembly and to pump the fluid to an external fluid cooling means, helical grooves in one of the co-operating relatively rotating bearing surfaces of the assembly being so arranged as to generate the pumping action.

The invention may be carried into practice in various ways, but an embodiment will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows a cross-section side view of an embodiment of an apparatus for lubricating and cooling a rotating propeller shaft seal, Figure 2 shows, on a larger scale, a cross-sectional side view of the bearing shown in Figure 1, Figure 3 shows a side view of the bearing shown in Figures 1 and 2, and Figure 4 shows an end view of the bearing shown in the above-mentioned figures.

Referring to Figure 1 a propeller shaft seal assembly 1 having a common axis AA comprises a rotatable tubular sleeve 2, and sealing means disposed coaxially about the tubular sleeve comprising three annular radial seals 4, 4' and 411, and a coaxial bronze tubular bearing 6.

In use the propeller shaft (not shown) is fixed within the tubular sleeve 2 by way of socket screws which are screwed into threaded holes 8 formed through the wall of the sleeve 2 so that the sleeve 2 rotates with the propeller shaft. Three O-rings 8 held within annular grooves 10 provide fluid sealing between the propeller shaft and the sleeve 2. The sleeve 2 is in sliding contact with the tubular bearing 6 and the seals 4, 41 and 41'.

The tubular bearing 6 and the seals 4, 41 and 41' are held within a housing in the form of an outer sleeve 12. The outer sleeve 12 is held within flexible bellows 14 by two gaiter clips 16. The bellows 14 are adapted to be secured to a stern tube (not shown) by a pair of worm drive clips 17 and the bellows are formed with a lubricating fluid inlet port 18 and a fluid outlet port 19.

The radial seals 4, 4' and 411 are each formed with a frusto-conical lip portion 20, the radially innermost part of which is in sliding contact with the sleeve 2. The two seals 41 and 4'1 abut opposite ends of the tubular bearing 6 and define two annular fluid channels 22, 24 at the opposite ends of bearing 6.

The tubular bearing 6 comprises two annular bearing portions 26, 28 separated by an interconnecting tubular wall 30. The radially innermost surfaces of the bearing portions 26, 28 are in sliding contact with the cylindrical radially outer surface of sleeve 2. The wall 30 is formed with an inlet port 32 adjacent the inlet 18. The radially innermost surface of the wall 30 and the two opposing side walls of the bearing portions 26, 28 define a central fluid channel 36. The inlet port 32 provides fluid communication between the central channel 36 and the inlet port 18.

Formed in the radially outermost surface of the tubular bearing 6 is a channel 40 extending along the axial length of the bearing 6. The depth of the channel 40 is such so as to provide gap 41 between the radially outermost portion of the seals and the bearing 4 through which fluid flows from the annular channels 22, 24 to the channel 40 and then out through the outlet port 19.

Referring to Figures 2 to 4, the radially innermost surface of the bearing portion 26 is formed with a helical groove 42 and an annular stepped region 44. The helical groove 42 is a right-hand thread when looking in direction B. The radially innermost surface of the bearing portion 28 is formed with a helical groove 46 and an annular stepped region 48. The helical groove 46 is a left-hand thread when looking in direction B. The threads 42, 46 each start from the axially innermost corner of the respective portions 26, 28 adjacent to the respective stepped portions 44, 48 and extend in opposite directions over the bearing surfaces of the respective portions 26, 28.

Detail A of Figure 2 shows a cross-section profile of a typical helical groove 42, 46. The thread angle C is 600, the groove pitch is 8.0 and the diameter D range is 0.9mm-1.2mm. in use the assembly I is secured by clamps 17 to a stern tube, a propeller shaft is assembled into position in sleeve 2, and the shaft is fixed to the sleeve 2. In use, water occupies the region 50 within the bellows 14. The O-rings 8 and the seals 4, 41 and 411 provide sealing means to prevent the leaking of water into the boat from region 50. To help lubricate and cool the rubbing surfaces of the assembly 1 a lubricating fluid flows via a supply tube (not shown) which is connected to hose connector 52. The rotation of the propeller shaft and the sleeve 2 causes fluid to be drawn through the supply tube and into the central fluid channel' 36 by the inherent pumping action of the helical grooves 42, 46. Fluid is pumped from the channel 36 via the two helical grooves 42, 46 into the respective fluid channels 22, 24. The fluid provides lubrication for rubbing surfaces of the bearing 6 and the seals 4' and 4". Because the fluid is pumped into the channels 22, 24 the sealing pressure of the seals 41 and 41' is increased.

The fluid within the channels 22, 24 exits the channels via the gap formed by the channel 40 and flows out of the assembly 1 through the output port 19. The fluid passing through the assembly 1 will acquire some heat energy generated by the rubbing surfaces. This energy will also be removed from the assembly 1. The flow of fluid through the assembly will therefore provide a cooling means for the assembly. Once the fluid has left the assembly it can be led to a cooling chamber and then recycled back into the input port so providing a continuous circulation of lubricating and cooling fluid for the assembly. The cooling chamber is conveniently in the form of a reservoir tank. The tank may be transparent and provided with an immersed flow indicator. The reservoir tank can also have a fluid filtering means to help remove any unwanted substance from the lubricating fluid.' The symmetrical arrangement of the helical grooves 42, 46 means that a pumping action is generated irrespective of the direction of rotation of the propeller shaft.

In the illustrated assembly it will be appreciated that the sleeve 2 is capable of axial sliding movement relative to the outer sleeve 12 to accommodate axial movement of the propeller shaft associated with movement of the engine/gearbox on its mountings.

Claims

1. A propeller shaft seal and bearing assembly comprising a housing, coaxial radially inner and outer annular bearing members within the housing and having co-operating bearing surfaces, said inner bearing member being integral with or adapted to be secured to a propeller shaft, said outer bearing member being fast with the housing, one of said bearing surfaces being formed with at least one helical groove, first and second annular fluid channels defined within the housing and separated by one of the annular bearing members, and sealing means partially defining said second annular fluid channel, and the arrangement being such that in use, on rotation of the propeller shaft, the helical groove provides pumping means by which fluid is transferred from one of the annular fluid channels through the groove into the other annular fluid channel, a fluid inlet in the housing communicating with said one channel, and a fluid outlet in the housing communicating with the other channel.

2. A propeller shaft seal and bearing assembly as claimed in claim 1 wherein the fluid inlet and outlet is connected in use to a reservoir for lubricant where cooling of the lubricant takes place.

3. A propeller shaft seal and bearing assembly as claimed in claim 2 wherein once the fluid has left the assembly via the outlet, it is led to the reservoir and then back to the inlet so providing a recirulation of the fluid.

4. A propeller shaft seal and bearing assembly as claimed in claim 3 wherein the assembly comprises a means for filtering the circulating fluid.

5. A propeller shaft seal and bearing assembly as claimed in any one of the claims 2 to 4 wherein the assembly comprises a fluid flow indication means.

6. A propeller shaft seal and bearing assembly as claimed in any one of the preceding claims wherein the outer bearing member is formed with fluid passage means to connect the second annular channel with either said fluid inlet or said fluid outlet.

7. A propeller shaft seal and bearing assembly as claimed in any one of the preceding claims wherein the fluid passage means comprises a channel formed in the radially outermost surface of the outer bearing member.

8. A propeller shaft seal and bearing assembly as claimed in any one of the preceding claims wherein the arrangement of the bearing members and seals is such that a degree of relative axial displacement of the propeller shaft and housing is permitted, this being accommodated by relative axial sliding displacement of the bearing members.

9. A propeller shaft seal and bearing assembly as claimed in any one of the preceding claims wherein the radially outer bearing member is formed with first and second axially-spaced annular bearing portions separated by an inter-connecting wall portion, the wall portion bounding the first annular fluid channel.

10. A propeller shaft and bearing assembly as claimed in claim 9 wherein the apparatus comprises first sealing means partly defining the second annular fluid channel and separated from the central first fluid channel by one of said annular bearing portions, and second sealing means partly defining a third annular fluid channel and separated from the central fluid channel by the other annular bearing portion, each annular bearing portion comprises an annular bearing surface which is in contact with the radially inner bearing member.

11. A propeller shaft and bearing assembly as claimed in claim 10 wherein the bearing surface of each of said bearing portions is formed with a respective helical groove.

12. A propeller shaft and bearing assembly as claimed in claim 11 wherein one of the helical grooves comprises a right-hand thread and the second groove comprises a left-hand thread and the arrangement is such that, in use, fluid is thereby pumped in axially opposing directions through the respective helical grooves.

13. A propeller shaft and bearing assembly as claimed in claim 12 wherein in use, for one direction of rotation of the propeller shaft, the helical grooves pump the fluid from the central first annular fluid channel into the second and third fluid channels.

14. A propeller shaft and bearing assembly as claimed in any one of the proceeding wherein the radially inner bearing member is integral with the shaft.

15. A propeller shaft and bearing assembly as claimed in any one of claims 1 to 13 wherein the inner bearing member is detachably fixed to the propeller shaft and said sealing means makes a rubbing contact with the radially outer surface of the tubular sleeve.

16. A method for lubricating and cooling a propeller shaft seal and bearing assembly comprising using the rotational motion of the propeller shaft to draw lubricating through the assembly and to pump the fluid to an external fluid cooling means, helical grooves in one of the co-operating relatively rotating bearing surfaces of the assembly being so arranged as to generate the pumping action.

17. A propeller shaft seal and bearing assembly substantially as herein described with reference to the accompanying drawings.

18. A method of lubricating and cooling a propeller shaft and seal and bearing assembly substantially as herein described with reference to the accompanying drawings.