Background of the Invention In the specification accompanying International Patent Application No. PCT/AU00/00248 a separator is described for separating particles entrained in a fluid so that fluid substantially devoid of particles may be used to cool and lubricate a bearing as the fluid passes through lubricating grooves of the bearing. This arrangement is particularly effective when the bearing is coupled to a propeller shaft of a marine craft and the shaft rotates in a direction that propels the marine craft forward. The forward motion of the craft tends to urge fluid through the separator and then through the bearing. However, when the marine vessel travels in reverse, the propeller shaft is spinning in the opposite direction and the motion of the craft through water tends to urge water in the opposite direction, i. e. first through the bearing and then through the separator. This can result in particles entering the bearing. There is therefore a need to provide a pumping means to urge fluid to travel through the separator and then the bearing, no matter the direction of rotation of the propeller and thus the direction of travel of the marine craft.

Summary of the Invention An object of the present invention is to provide a centrifugal pump for drawing fluid through a chamber of a member coupled to an axially rotatable shaft. A particular application of the present invention is to draw fluid through a lubricating groove of'a bearing coupled to a propeller shaft of a marine craft.

In accordance with the present invention'there is provided a centrifugal pump for drawing a fluid through a chamber of a member coupled to an axially rotatable shaft, the pump comprising at least: a projection arranged to be fixed relative to the shaft, the projection having a passage leading to a vent, the passage arranged to communicate with the chamber of the

member, at least a portion of the length of the passage extending in a direction from the shaft having a radial component, whereby, in use, rotation of the shaft causes a centrifugal force on fluid in the passage, thereby drawing fluid from the chamber of the member through the passage and ejecting it from the vent.

Preferably, a plurality of passages are provided around the circumference of the shaft, each passage arranged to communicate with the chamber of the member and further arranged to extend substantially radially of the shaft to a respective vent.

In one embodiment, each passage is within a respective radially extending projection from the shaft. In another embodiment the projection is in the form of a disc surrounding the shaft, wherein each of the passages are formed within the disc. Preferably, the disc is provided with an annular mounting section for mounting the pump to the rotatable shaft. Preferably, the annular mounting section is provided with a raceway that provides fluid connection of the passages to the chamber of the member.

In one embodiment, the vent is oriented to eject fluid substantially perpendicular to the shaft.

In another embodiment, the vent is oriented to eject fluid so as to provide thrust in the direction that urges the pump to move towards the member.

Preferably, the disc is provided with a recess for receiving a circular projection of the member. Alternatively, the disc is provided with a recess for receiving an annular seal.

Preferably, a gap is provided between the member and the projection so as to allow the projection to rotate with respect to the member. Preferably, a seal is provided between the member and the projection to resist the ingress of fluid through the gap.

Preferably, the seal includes a labyrinth seal. Preferably, the seal includes a thin flexible member that glides over a surface of the disc so as to restrict the opening of the gap.

Alternatively, the seal is in the form of a positive pressure seal, whereby fluid is forced through a narrow gap between the member and the projection.

Preferably, the disc includes collectors disposed between the raceway and each of the passages. Preferably, the collectors are in the form of a cone shaped depression in the inner surface of the disc, the widest portion of the cone coinciding with the raceway and the narrowest portion coinciding with the passage.

Preferably, the member is a bearing having a plurality of lubricating chambers extending therethrough, and through which extends a propeller shaft. Preferably, the projection substantially fills the gap between the bearing and a propeller fixed to the propeller shaft. In one embodiment the projection is fixed to the shaft. In another embodiment the projection is fixed to the propeller.

Detailed Description of Preferred Embodiments In order to provide a better understanding of the present invention, a preferred embodiment of the present will now be described in detail, by way of example only, with reference to the accompanying diagrams, in which: Figure 1 is a cross-sectional side view of a separator, a bearing and a centrifugal pump in accordance with the present invention; Figure 2A is a first preferred embodiment of the centrifugal pump of the present invention; Figure 2B. is a second preferred embodiment of the centrifugal pump of the present invention; Figure 2C is a third preferred embodiment of the centrifugal pump of the present invention; Figure 2D is a fourth preferred embodiment of the centrifugal pump of the present invention as shown in Figure 1 ; Figure 3 is an enlarged cross-sectional view of an interface between a bearing and the centrifugal pump of Figure 2A; Figure 4 is a rear view of the centrifugal pump of Figure 3; Figure 5 is a front view of the centrifugal pump of Figure 3; Figure 6 is a cross sectional side view of an alternative centrifugal pump in accordance with the present invention; Figure 7 is a cross sectional side view of a further centrifugal pump in accordance with

the present invention; Figure 8 is an enlarged cross sectional side view of an interface between a bearing and the centrifugal pump in accordance with the present invention; Figure 9 is a front view of the centrifugal pump of Figure 7; Figure 10 is a rear view of the centrifugal pump of Figure 7; Figure 11 is a cross-sectional side view of another embodiment of the centrifugal pump in accordance with the present invention attached to a propeller which is turn mounted on a propeller shaft that passes through a bearing; Figure 12 is a front view of the centrifugal pump of Figure 11 ; Figure 13 is a cross-sectional view of the centrifugal pump of Figure 12 through the section A-A of Figure 12; Figure 14a is another embodiment of the centrifugal pump of the present invention; Figure 14b is a cross-sectional side view of the pump of Figure 14a; Figure 15 is an isometric view of the pump of Figure 13, along the section C-C; Figure 16 is an isometric view of the pump of Figure 14a, along the section B-B; and Figure 17 is a further isometric view of a variation of the centrifugal pump of Figure 16.

Referring to Figures 1 and 3, a centrifugal pump 10 is shown attached to the rear of a bearing 7 that has a separator 5 mounted in front of it. The separator 5, bearing 7 and centrifugal pump 10 are mounted to a propeller shaft 12. Behind the centrifugal pump 10 and attached to the propeller shaft 12 is a propeller 3.

The centrifugal pump 10 includes a projection in the form of a disc 14. In this embodiment the disc 14 has a larger radius than the separator 5 and the bearing 7. The outer circumference of the disc 14 is indicated as 60. The disc 14 has a lending face 62 and a tailing face 64. The inner surface of the disc is indicated as 42.

The disc 14 includes an annular mounting portion for mounting the disc 14 to the shaft 12.

The annular mounting portion includes the inner surface 42. The mounting portion is fixed to the shaft by a grub screw 20 so that the disc 14 rotates in unison with the shaft 12. Radially extending from the centre of the disc 14 are a plurality of passages 16. Each passage 16 exits the disc 14 at a vent 30. In the embodiment shown there are four equidistantly spaced

passages 16. A raceway 18 extends inwardly from the inside surface 42 of the disc 14 and connects with each of the passageways 16. The raceway 18 is in the form of a circular channel that extends around the shaft 12. The raceway 18 is arranged to communicate with the exit of lubricating grooves 9 of the bearing 7. Thus, the passageways 16 are in fluid communication with the lubricating grooves 9 via the raceway 18.

The disc 14 includes a recess 22 in the lending face 62 and inner surface 42, so that it may mate with a circular projection 11 of the bearing 7 or a sealing ring as described below. The circular projection 11 forms a step, which the recess 22 receives. A very fine clearance 26 is allowed between the step and an inner surface 56 of the recess 22. The gap or clearance 26 is sufficiently large so that the step of the bearing 7 and the inner surface 56 of the recess 22 do not touch as the centrifugal pump 10 rotates with respect to the bearing 7 in use. However, the gap 26 is as small as possible while still allowing sufficient clearance, so as to reduce the flow of fluid through the gap 26.

In Figure 2A, a variation of the centrifugal pump 10 is shown with the passages 16 having an elbow shape close to the circumference of the disc and with a vent 30 of the passage 16 directed to produce a thrust that will assist in the forward motion of the vessel. In Figure 2B, the vent 30 is angled with respect to the rear surface so as to provide a thrust in use that partly assists in the forward motion of the marine craft. In Figure 2C, the passageways 16 are perpendicular to the shaft 12 and the outer shaft of the disc 14 is rounded so as to provide streamlining. In Figure 2D, the leading edge of the disc 14 is streamlined only.

Referring to Figure 3, the lubricating groove 9 of the bearing 7 is shown in communication with raceway 18, which then leads to the passageway 16 which leads to the vent 30. The raceway 18 is a circular passage that allows fluid to be evenly distributed to the passages 16.

The recess 22 is arranged to provide clearance 26 between the circular projection 11 of the bearing 7 of the inner surface 56 of the recess 22 as described above. Another gap 24 is shown between the remainder of the bearing 7 and the leading surface 62 of the disc 14.

Within the gap 24 a seal 28 is provided which includes a thin flexible member at the end of the seal 28 that glides over the leading surface 62 so as to resist the ingress of fluid into the gap 24. Fluid may be allowed to escape via the gaps 26 and 24, but seal 28 attempts to stop

fluid flowing into the pump.

Referring to Figure 4, the rear view of the disc 14 shows the vents 30 of the passageways 16.

This embodiment corresponds with the embodiment shown in Figure 2A.

Referring to Figure 5, the seal 28 is shown surrounding a significant portion of the leading surface 62 of the disc 14. The surface area of the seal 28 presented to fluid as the disc 14 moves forward will cause the thin flexible member 28 to push against the leading surface 62 as the disc rotates with the shaft 12 while the seal 28 glides over the rotating disc 14. If sufficient suction is created by the centrifugal pump 10 the flexible member will be pulled closer to the leading surface 62, thus tending to close off the gap 24.

Referring to Figure 6, there is shown an alternative embodiment of the centrifugal pump. In this embodiment, the disc 14 has a radius about the same as the radius of a carrier 13 of the bearing 7. As shown, it is only slightly larger than the radius of the carrier 13. It is known that rope and fishing line can often become wrapped around the propeller, particularly in the case of fishing vessels. The lower profile of the disc provides a disincentive for rope and fishing line to become snagged and thus wrap around the propeller 3, the shaft 12, the carrier 13 and the bearing 7. In addition, it is known that fishing line and rope can become entangled between the propeller 3 and the bearing 7, in this case the disc 14 substantially fills the gap between the propeller 3 and the bearing 7.

In this embodiment the recess 22 is larger than the circular projection 11. With the gap between the. recess 22 and the bearing 7 being filed by a sealing ring 28. The sealing ring 28 is provided with very little clearance particularly at its circumferential edge indicated by 29.

While a gap at 29 cannot be seen in Figure 6, due to the scale of the drawing, a small gap exists to minimise fluid flow through this gap which may otherwise act to reduce the effectiveness of the centrifugal pumping action and thus the ability of the pump to draw water through lubricating groove 9 of the bearing 7.

In a further variation shown in Figure 7, the sealing ring 28, rather than projecting from circular projection 11, projects from the trailing edge of the bearing 7. The gap between the

sealing ring 28 and the recess 22 is exaggerated in Figure 7 to show that there is a clearance between the moving disc and the stationery bearing 7 and carrier 13. Also, the disc 14 is fixed to the propeller 3 by grub screws 32 rather than being fixed to the propeller shaft 12.

Referring to Figure 8, the arrangement between the circular projection 11, the sealing ring 28 and the recess 22 is shown in more detail. Again the clearance 26 between the sealing ring 28 and the inner surface of the recess 22 is exaggerated. The sealing ring 28 may be constructed of a somewhat compressible low friction material so that it may glide on the inside surface of the recess 22 thereby reducing or even eliminating the gap 26 so that the disc 14 may move with respect to the bearing 7 with minimal friction to reduce or eliminate suction of fluid back through the gap 26, while also allowing play in the propeller shaft 12 in relation to the bearing 7.

Figure 9 shows the recess 22 within which are holes 36 for the grub screws 32 to pass there through and attach the disc 14 to the propeller. A chamfer or bevel 38 is shown, which allows the head of the grub screw to be recessed.

Figure 10 shows the inner surface 42 of the disc 14 and a small gap 40 between the inner surface 42 and the propeller shaft 12. The small gap 40 allows the disc 14 to be positioned on the propeller shaft with the propeller. The gap is as small as possible and may even provide some frictional holding of the disc 14 to the propeller shaft 7.

It is preferred that the disc 14 be approximately twice the diameter of the diameter of the bearing 7 when four passaged 16 are used. It is also preferred that the diameter of the disc 14 be greater than the diameter of a separator 5, if a separator 5 is used in from of the bearing 7.

Figures 11, 12,13 and 15 show yet another embodiment of a centrifugal pump 10. In this embodiment there are eight passages 16 venting from the raceway. As can be seen better in Figures 12 and 13 the recess 22 extends part way into opening of the passages 16. The raceway 18 then extends from the rear end of the opening of the passages further into the inner surface 42. The opening of the passages are indicated as 50. The openings are in the form of a collector which has inclined sloping surfaces 52. The collector provides an impeller

like pull on fluid in the raceway 18 into the passages 16. Once inside the passages 16 centrifugal force of fluid in the passageway causes it to accelerate radially and be ejected from the vents 30. Without the collector 50 the opening of each passage 16 tends to skim across and shear the fluid reducing the effectiveness of the pump. The collectors 50 assist in drawing fluid from the raceway 18 into the passageways 16.

Referring to Figures 14a, 14b and 16, a variation on the pump shown in Figures 12 and 13 is provided. A sealing ring 28 is provided for insertion into the recess 22 so that the pump is spaced from the bearing 7. In this instance the gap between the sealing ring and the inner surface 54 of the recess 22 forms another annular channel 66 that is connected with the raceway 18. The channel 66 extends radially further than the raceway 18. The gap 24 between the sealing ring 28 and inner surface 56 of the recess 22 forms another annular passage extending from the annular channel 66 to an annular vent 30 from the pump. The passages 66 and 24 replace the discrete passages 16 of previous embodiments. In this embodiment, the collectors 50 will scoop fluid, by an impeller like action, from the raceway 18 and by centrifugal action on fluid within passage 66 cause it to move into passage 24 and then exit the annular vent 30. This positive pressure provides a positive pressure seal between the sealing ring 28 and the inside surface 24 so as to prevent fluid from flowing back into the pump.

A further embodiment is shown at Figure 17, where a shallow channel 58 is provided in the surface 56 to assist in the flow of fluid from the collector 50 out to the vent 30. The channel 56 thus forms discrete passageways equivalent to passage 16 in the previous embodiments.

This may be in addition to or instead of fluid flow through the gap 24.

The method and operation of the present invention will now be described with reference to the accompanying drawings.

When the disc 14 rotates with the propeller shaft 12 fluid within it is caused to move toward the vent 30 by centrifugal action. The movement of fluid draws fluid from within the raceway 18, which in turn draws fluid from the lubricating grooves 9 of the bearing 7. The motion of the fluid is thus drawn from the bearing 7 to the raceway 18, the passageways 16

and then ejected from the vent 30. This suction is caused by the centrifugal action of the fluid within the passageway 16. This will occur irrespective of the direction of rotation of the propeller shaft 12. The ejection of the fluid, may provide a thrusting force, if the vent is oriented appropriately. This may be used to partially counteract water resistance created by the profile of the disc protruding from the bearing.

Due to the clearance required between the bearing and the disc, fluid may be drawn through this gap into the raceway 18 thus reducing the effectiveness of the suction on the fluid within the bearing 7. To counteract this, firstly the clearance at 26 as described above is limited. In addition, the sealing ring 28 limits the ingress of fluid through the clearance way thereby causing sufficient suction on the fluid within the bearing 7.

Because of the pumping effect on fluid through the bearing a cavity 11 within the separator may be parallel with the separator 5 and need not be helical in shape. Thus, with the separator 5 position in front of the bearing 7 any particles entrained in fluid entering the separator 5 are rejected from the particle exits of the separator prior to entry into the bearing 7. Fluid substantially devoid of particles, flows through the chamber (lubricating groves) of the bearing and then into the raceway 18. From the raceway 18 the fluid passes through the passageways 16 and is rejected from the vent 30 by centrifugal action. The pumping will occur irrespective of the direction of rotation of the propeller shaft 12 and thus the direction of travel of the marine craft.

In the embodiment shown in Figures 6 to 10, the low profile of the disc 14 and the disc 14 substantially filling the gap between the bearing 7 and the propeller 3 reduces the ability of rope, fishing line or other detrimental materials from becoming snagged and wound around by the rotation of the propeller 3. In particular, tightly wound rope will not be able to enter the gap between the bearing 12 and the propeller 3, which otherwise may cause friction and can even cause melting of the rope which can enter the lubricating passage 9 of the bearing.

Modifications and variations will be apparent to those skilled in the art, such as the number of passageways and of orientation of the vents. Such modifications includes: (1) The length of the passageways and/or the height of the disc will dictate the

amount of centrifugal action provided and thus the suction of fluid through the bearing. These may be varied so that sufficient suction is created to draw fluid through, for the minimum operating speed of the propeller shaft; (2) In an alternative embodiment a radial projection may be provided for each passageway. Thus, the centrifugal pump will be in the form of a series of spokes or even small propeller blades radially extending from the propeller shaft within which are contained each of the passages; (3) A further modification may include angling part or the whole length of the projection towards the propeller so as to provide further streamlining of the centrifugal pump.

Such modifications and variations are deemed to be within the scope of the present invention, the nature of which it to be determined from the foregoing description and appended claims.