GB2594508A

GB2594508A - Labyrinth seal for sealing a bearing of a scroll pump and a scroll pump

Info

Publication number: GB2594508A
Application number: GB2006415.0A
Authority: GB
Inventors: Anthony Mcbrien Peter; Peter Fisher Geoffrey; Edward Tomkins Mark; Thomas Chrisp David; De Klerk Jean-Pierre; Horak Tomas
Original assignee: Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2020-04-30
Filing date: 2020-04-30
Publication date: 2021-11-03
Also published as: GB202006415D0; JP2021191954A; FR3109807B3; CN217002268U; FR3109807A3; JP3240651U; KR20210002484U; DE202021001589U1

Abstract

Seal for preventing lubricant from leaking a bearing 10, the seal has an inner ring 44 (referred to as “baffle plate” in the application) and an outer ring 41 (referred to as “disc” in the application), both may be metal. The inner ring 44 extends from the inner race 12 and the outer ring 41 from the outer race 14, or vice versa. The inner ring 44, when extending from the inner race 12, does not contact the outer race 14, forming a passage 45 for lubricant to flow into a space 46 between the inner 44 and the outer ring 41. The outer ring 41 may be recessed to accommodate for the inner ring 44 (Fig 4B). The inner 44 or the outer ring 41 or both may have profiles (Fig 5, 43) such as grooves, vanes, fins, threads, spirals or helical shapes for driving lubricant back into the bearing 10. There may be further rings 44, 41 in additional to the present inner 44 and outer rings 41.

Description

LABYRINTH SEAL FOR SEALING A BEARING OF A SCROLL PUMP AND A

SCROLL PUMP

FIELD OF THE INVENTION

The field of the invention relates to a labyrinth seal for a bearing in a scroll pump, and a scroll pump with such a seal.

BACKGROUND.

Sealing the bearings of an orbital scroll pump such that lubricant within the bearing does not leak into the pump can be challenging. A scroll pump comprises two interleaving scrolls or involutes one of which has an orbital motion with respect to the other thereby trapping and pumping or compressing pockets of fluid between the scrolls. In some cases, one of the scrolls is fixed, while the other is mounted on a drive shaft with an eccentric cam such that it orbits eccentrically without rotating. Another method for producing the relative orbiting motion is by co-rotating the scrolls, in synchronous motion, but with offset axes of rotation. Thus, the two scrolls are mounted on parallel shafts and the relative motion is the same as if one were orbiting and the other stationary.

Bearings are used for mounting the scroll(s) on the crank sleeve of the drive shaft. The inner race of the bearing rotates with the drive shaft while the outer race does not rotate. The crank sleeve provides an orbiting motion to the scroll(s) and the whole bearing orbits with the orbiting scroll.

Where sealing of the lubricant within the bearing is provided using a flexible plastic lip that contacts the moving race the orbiting motion can distort the seal and lead to leakage. Furthermore, such plastic sealing mechanisms are contact seals and thus, can become hot at higher speeds.

It would be desirable to provide a seal for sealing the bearings of a scroll pump that provides effective sealing, particularly at high speeds of operation. -2 -

SUMMARY

A first aspect provides a labyrinth seal for inhibiting leakage of lubricant from a bearing mounting an orbiting scroll to a drive shaft in a scroll pump, said labyrinth seal comprising: a baffle plate configured to be mounted adjacent to a bearing and to partially obscure a gap between inner and outer races of said bearing, such that lubricant within said bearing contacts an inner surface of said baffle plate facing said bearing and is at least partially restrained from leaving said bearing by said plate; a disc comprising an inner surface configured to be io mounted such that said inner surface faces and is adjacent to, but not in contact with, an outer surface of said baffle plate; wherein one of said baffle plate and disc is mounted to extend from and rotate with said inner race and the other of said baffle plate and disc is mounted to extend from and orbit with said orbiting scroll; and said labyrinth seal is configured such that said baffle plate does not contact said race that said baffle plate does not extend from such that there is a passage for lubricant to flow from said bearing to the space between said outer surface of said baffle plate and said inner surface of said disc.

The inventors of the present invention recognised that bearings mounting an orbiting scroll to a drive shaft, experience the same orbital motion as the scroll and this motion tends to push lubricant out of the bearing. Sealing means that are conventionally used to seal the bearings of scroll pumps include a flexible tip that contacts the moving race and this arrangement can generate heat. This generation of heat can be pronounced at higher speeds and can lead to both degradation of the lubricant and to the flexible seal deforming and no longer providing an effective seal. The inventors of the present invention have addressed these issues, by providing a non-contact seal, which provides an elongated pathway for the lubricant leaving the bearing and this arrangement inhibits the flow without the requirement for contact of flexible elements which can lead to increased temperatures and wear of the seal. Furthermore, the seal is arranged such that one of the surfaces providing the elongated pathway, either the inner surface of the baffle plate or the outer surface of the disc, rotates with -3 -respect to the other and this provides a force on lubricant in the space between the surfaces of the baffle plate and disc, which force may impede the motion of the lubricant out of the seal and indeed in some cases may push the lubricant back towards the bearing.

It should be noted that the baffle plate and disc are mounted to extend from the inner or outer race respectively and in this regard they may be adjacent to these races or they may be attached to them. They may extend beyond their respective race and be attached to the orbiting scroll for example and/or to the io drive shaft or to a crank sleeve on the drive shaft.

It should be noted that the bearings may be any type of bearing having an inner and outer race such as angular contact bearings or roller or deep groove bearings.

In some embodiments, said baffle plate is configured such that said passage has a width of less than 500 microns, preferably less than 200 microns, more preferably less than 100 microns.

In order to impede lubricant flow from the bearing it is advantageous if the passage that allows the seal to be a non-contact seal is narrow such that any gap for lubricant flow is not large. In some embodiments, it is less than 500 microns, preferably less than 200 microns and in some embodiments less than 100 microns.

In some embodiments, said baffle plate is configured to extend from and rotate with said inner race.

Although the baffle plate may extend from the outer race and the disc from the inner race, it may be advantageous for the baffle plate to extend from the inner race and rotate with it as this provides a force on lubricant within the passage away from the inner race towards the outer race and in many embodiments -4 -towards the passage back to the bearing. This provides an effective way of inhibiting lubricant from escaping from the bearing.

In some embodiments, said baffle plate is configured to extend from said inner 5 race to a point between 1/3 and 2/3 of the distance between the inner and outer races.

Although, in some embodiments the passage for lubricant to flow from the bearing may be between the baffle plate and the inner or outer race that the baffle plate does not extend from, in other embodiments, there is a substantial gap left between the baffle plate and the other of the inner or outer race towards which it extends and this gap provides a space through which a bearing can be re-lubricated.

In some embodiments, said disc comprises a channel providing access from an outer surface to an inner surface, said channel being in a portion of said outer disc closer to said outer race than said inner race, such that said channel does not open against said baffle plate, said channel comprising an openable closure member for selectively obscuring said channel.

The relubrication of the bearing via the gap between the inner baffle plate and the outer race can be done by removing the disc, or alternatively, in some embodiments, a channel may be provided through the disc which allows lubricant to be supplied from an outer surface of the disc to the bearing. This channel has a closure member that seals the passage and inhibits grease leakage during operation of the pump. The closure member can be opened for relubrication of the bearings.

In some embodiments, said inner surface of said disc comprises a recessed portion for receiving said baffle plate and a protruding portion configured to extend over an axial surface of said baffle plate, said passage being delimited by -5 -said axial surface of said baffle plate and an axial surface of said protruding portion.

Although the passage may be formed between the baffle plate and one of the races towards which it extends, in some cases where there is a gap between the baffle plate and the other race to allow for the addition of lubricant, it may be advantageous to configure the disc such that it is recessed and the constrained passage is provided by the axial surface of the inner plate and a corresponding axial surface of a protruding portion of the disc located towards the middle of the disc. In this way, a narrow gap is provided for impeding the passage of lubricant.

One potential disadvantage of this arrangement is that the passage formed by the space between the baffle plate and the disc is not as long as were the passage to be towards one end of the baffle plate. However, where in particular the baffle plate is mounted to rotate on the inner race then the motion of the baffle plate will provide a force to push any lubricant that does enter the passage back towards the bearing and the seal may still be a very effective non-contact seal. Furthermore, a passage at one end of the plate may be at a location towards which the orbital motion of the scroll throws it, having the passage towards the middle of the plate may be a location where lubricant does not accumulate in the same way.

In some embodiments, said baffle and disc are formed of metal.

In some embodiments, the baffle plate and disc may be formed of a rigid material such that they do not distort due to the orbital motion and due to the rotational motion of one of the plates or discs and in some cases this rigid material is metal. Metal is resistant to high temperatures and is rigid and provides an effective material for the labyrinth seal. In some embodiments the metal is aluminium this being a lightweight material that does not corrode easily.

In some embodiments, at least one of said inner surface of said disc, said inner surface of said baffle plate and said outer surface of said baffle plate comprise a -6 -profile configured such that on rotation of said drive shaft, a force due to said rotation on lubricant adjacent to said at least one surface drives said lubricant towards said bearing.

In some embodiments, at least one of said inner surface of said disc and said outer surface of said baffle plate comprise a profile configured such that on rotation of said drive shaft, a force due to said rotation on lubricant within said space between said surfaces drives said lubricant towards said passage to said bearing.

As noted previously, the rotating surface may provide a pumping action on the lubricant between the baffle plate and the disc back towards the bearing and this pumping action may be improved by the provision of profiles within the set space between the surfaces such that on rotation of the drive shaft the profile provides a force on the lubricant pushing it towards the bearing.

In some embodiments, said inner surface of said baffle plate facing towards said bearing comprises a profile configured such that on rotation of said drive shaft, a force due to said rotation on lubricant adjacent to said inner surface drives said 20 lubricant away from said passage.

Additionally and/or alternatively to a profile on one or more of the surfaces defining the space between the outer disc and baffle plate, the inner surface of the baffle plate facing the bearing may itself have a profile configured to impede lubricant from exiting the bearing by driving it away from the passage between the baffle plate and the race that the baffle plate does not extend from.

Additionally and/or alternatively, in some embodiments, an axial surface of said disc that is perpendicular to said inner surface and arranged adjacent to a race that said disc does not move with, comprises a profile configured to push fluid within said profile towards said inner surface of said disc on operation of said pump. -7 -

The disc may be significantly thicker than the baffle plate, and it may be advantageous for an axial surface of the disc to also comprise a profile that on operation of the pump is configured to push fluid within the profile towards the inner surface of the disc on operation of the pump. This may be due to rotational motion of the disc where the disc rotates or simply to the orbital motion where it does not rotate.

In some embodiments, said profile comprises at least one of a shaped groove, vane, fin or thread, in some cases said shape comprises a spiral or helical shape.

The profile may have a number of forms provided that the form is such that the centrifugal force of the rotation element causes fluid to flow in a certain direction along the form towards the bearing.

In some embodiments, the labyrinth seal comprises a further disc comprising an inner surface configured to be mounted such that said inner surface faces and is adjacent to, but is not in contact with, an outer surface of said disc, said further disc being mounted to extend from and move with the race that said disc does not extend from and move with.

In order to extend the pathway that the lubricant flows through on leaving the bearing it may be advantageous to insert one or more additional discs adjacent to an outer surface of the disc such that the pathway for the fluid is increased in length. It may also be advantageous to mount them such that alternate discs rotate with the inner race such that each passageway between opposing surfaces has one surface that rotates and one that does not.

A second aspect provides a scroll pump comprising an orbiting scroll and a stationary scroll, said orbiting scroll being mounted on a drive shaft via bearings, said scroll pump comprising two labyrinth seals according to a first aspect, said -8 -seals being mounted to seal side surfaces comprising said gap between said races of said bearing.

In some embodiments, said scroll pump is a high speed scroll pump configured to 5 rotate at speeds above 2,000 RPM, in some cases above 2,800 RPM, and in some above 3,5000 RPM.

With increasing speeds of rotation, scroll pumps' bearings are becoming increasingly difficult to seal effectively without increasing the heat within the bearing. Non-contact labyrinth seals according to embodiments provide effective sealing while not increasing the temperature felt within the bearing.

Although, the bearing may be effective in scroll pumps that act as compressors, it is particularly effective for vacuum scroll pumps.

Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes an apparatus feature which provides that function or which is adapted or configured to provide that function.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which: Figure 1 shows bearings mounting an orbiting scroll to a drive shaft of a scroll pump according to an embodiment; Figure 2a shows the labyrinth seal and bearings for mounting an orbit scroll according to an embodiment; and Figure 2b shows one bearing and seal in more detail; -9 -Figure 3a shows a further embodiment of a labyrinth seal and bearings for mounting an orbit scroll according to a further embodiment; and Figure 3b shows the bearing and seal in more detail; Figure 4a shows a further embodiment of the labyrinth seal; Figure 4b shows a further embodiment in more detail; and Figure 5 shows a baffle plate according to an embodiment.

DESCRIPTION OF THE EMBODIMENTS

Before discussing the embodiments in any more detail, first an overview will be io provided.

A labyrinth seal arrangement is provided to inhibit lubricant, in some examples grease, leaking from lubricated rotating element bearings. This arrangement may include active pumping elements to return the lubricant to the bearings. An advantage of this type of seal is that it does not experience the same amount of wear and generates less heat than conventional contact sealing techniques Increased grease loss is an increasing problem on the scroll bearings of vacuum scroll pumps operating at increased speeds. This grease loss may be the result of contacting lip seals deforming due to high centripetal forces induced by the orbital motion of the scroll. Contacting PTFE seals for example, tend to distort and become hot at higher speeds. In order to address the above a labyrinth seal design is proposed that seeks to reduce thermal conditions within the bearings and the need for tight concentric tolerances.

The proposed seal arrangement provides rigid non-contacting components that will not deflect or deform under such loads Figure 1 shows a section through the bearings, drive shaft and seals of a scroll pump. The scroll pump comprises two back to back rolling element bearings 10 for mounting an orbit scroll 20 on the crank sleeve 22 of a drive shaft 30. The bearings 10 each comprise an inner race 12 configured to rotate with the crank -10 -sleeve 22 and drive shaft 30 and an outer race 14 that does not rotate. The whole bearing including the outer race orbits with orbit scroll 20.

Inner race 12 and outer race 14 hold rolling elements 16 which allow inner race 12 to rotate with respect to outer race 14. Bearings 10 comprise lubricant which may be in the form of grease to reduce the friction caused by the relative motion of inner race 12 and outer race 14 and the rolling elements 16.

The orbital motion of the bearings 10 tends to throw lubricant out of the bearing and this can lead to the bearings overheating and damaging and/or contaminating the surrounding space. In order to inhibit the leakage of the lubricant from the bearings a labyrinth seal 40 is provided at either axial end of the bearing to inhibit the leakage of lubricant from the gap between inner race 12 and outer race 14.

Labyrinth seal 40 in this embodiment comprises disc 41 and inner baffle plate 44. It should be noted that the inner baffle plate 44 has a disc form similar to that of the disc 41 but is narrower than the disc 41 in this embodiment.

In this embodiment, inner baffle plate 44 is mounted to the crank sleeve 22 and rotates with the crank sleeve and inner race 12. The baffle plate 44 extends towards the outer race 14 and there is a narrow gap or passage 45 between outer race 14 and baffle plate 44 which in embodiments is of the order of 100 microns and this narrow gap inhibits the exit of lubricant from the bearing 10 while not contacting the outer race 14. This provides a low friction seal which has reduced wear. In this embodiment, the baffle plate 44 is formed of aluminium.

Although, gap 45 is narrow some lubricant will escape through the gap 45 during operation and will pass into the space 46 between outer disc 41 and baffle plate 44. Rotation of baffle plate 44 with respect to disc 41 provides a centrifugal force to the lubricant within space 46 which tends to throw the lubricant out towards passage 45 and back into the bearing. In effect labyrinth seal 40 inhibits lubricant from leaving the bearing by the use of a long pathway, a narrow passage 45 and the pumping force provided by the rotating baffle plate. In this embodiment, the narrow passage 45 between the baffle plate 44 and the outer race 14 is located at a place that the orbital motion tends to throw the lubricant. However, this arrangement does provide an inner plate that rotates and this rotation drives the lubricant back towards this passage and thus this arrangement provides an effective seal.

In this embodiment, the labyrinth path provided by the seal comprises the passage 46 formed by the space between baffle plate 44 and disc 41 and also a passage 47 along the axial surface of disc 44. In this embodiment, the inner surface and axial surface adjacent to the inner race each have a profile formed by grooves on their respective surfaces. This profile is designed so that the motion of the disc and the relative motion of the inner plate drives the lubricant along the profile back towards the bearing. The profile of the groove on the inner surface of the disc 41 is a spiral configured such that centrifugal force pushes it along the spiral back towards the passage 45. In effect there is a driving force to pump the lubricant back into the bearing that may be formed of two mechanisms. One component is due to viscous shear forces arising from the centrifugal load and these push lubricant outwards in the radial direction back towards the bearings. The second pumping mechanism is due to spinning of the baffle plate 44 along with the shape of the spiral or pumping features on the disk 41 which create a windage that pressurises fluid in the gap and pushes the lubricant back into the bearing.

In this embodiment the ring bearing 10 around the drive shaft 30 and crank sleeve 22 has a labyrinth seal 40 on either side or axial end of the bearing to inhibit lubricant from exiting via the gap between the inner race and the outer race.

Figures 2A and 2B show an embodiment similar to that of Figure 1. In this embodiment, there is no profiled surface on the inner surface of disc 41 and the -12 -baffle plate 44 is attached to the rotating shaft with the outer disc 41 being configured not to rotate with the outer race 14. There is a passage 45 provided between the baffle plate and the outer race 14 which allows the rotating baffle plate not to contact the outer race but provides a path through which lubricant can exit the bearing.

Figures 3A and 3B show an alternative embodiment where baffle plate 44 is attached to the non-rotating outer race 14 and the orbit scroll 20 while disc 41 is attached to the rotating inner race. In this embodiment, the narrow passage or gap 45 that provides the passage where lubricant may exit the bearing is towards the inner race 12 and thus, as the centrifugal and windage forces tends to throw the lubricant towards the outer race this may be a preferable place to put the passage.

Although this arrangement inhibits lubricant from entering the narrow passage 45, any lubricant that does pass narrow passage 45 will be thrown outwards radially rather than back into the bearing. In some embodiments an additional set of labyrinths may be added so that there is a further spinning disk to provide a radial pumping force to substantially equalise the first labyrinth disk's pumping force.

In this regard, although, in the above embodiments only one disc 41 is provided, in some embodiments there may be multiple discs layered to provide an extended labyrinth path that is runs between the spaces between the inner and outer surfaces of each disc. These discs will be mounted alternatively to the outer side of the bearing or the inner side, such that where the baffle plate is attached to or close to the inner ring the first disc will be attached to or close to the outer race, the second to the drive shaft side of the bearing and the third to the scroll side of the bearing and so on.

Figure 4A and 4B show an alternative embodiment where baffle plate 44 extends from and rotates with inner race 12 but only extends a portion of the way across the gap between the inner race 12 and outer race 14. This leaves a space that in -13 -the example of Figure 4A when disc 41 is removed allows access to the bearings which access can be used to apply additional lubricant. In these embodiments, the narrow passage 45 is provided by a protruding portion 42 of disc 41 which protrudes over the outer axial surface of baffle plate 44 and inhibits flow of lubricant from bearing 10. The narrow passage 45 between baffle plate 44 and disc 41 extends only for a fraction of the length of the baffle plate 44 and disc 41 and thus, does not provide as long a pathway as in the other labyrinth seal.

In the embodiment shown in figure 4B there is a channel 48 provided between the inner surface and the outer surface of disc 41 at a portion of the disc adjacent to the outer race and radially beyond the radial point to which the inner baffle extends. This channel allows relubrication of the bearing without the need to remove disc 41. Channel 48 is closed by stopper 49, which acts to seal the channel when the pump is operational and can be removed for relubrication.

Figure 5 shows a baffle plate 44 according to an embodiment. In this embodiment, the baffle plate 44 comprises vanes 43, arranged on the inner face of the baffle plate facing the bearing. These vanes are configured to drive lubricant away from the narrow passage between the baffle plate and the outer race on rotation of the baffle plate with the inner race and thereby inhibit the exit of lubricant from the bearing. Alternatively and/or additionally the outer surface of the baffle plate facing away from the bearing may have vanes (not shown) which are configured to drive the lubricant towards the narrow passage between the baffle plate and the outer race on rotation of the baffle plate and thus, send lubricant that has exited the bearing back towards the bearing.

In summary, embodiments provide a non-contacting seal formed of a rigid material that does not deflect and is suitable for a vacuum pump such as a scroll pump operating at higher speeds in some cases up to 3600RPM and which does not deteriorate significantly over time and nor does it heat up due to its non-contacting nature. Furthermore, it provides effective sealing with the use of a narrow passage, a relatively long path and a pumping action for pumping -14 -lubricant within the path back towards the bearing. Embodiments also provide a scroll pump comprising such a seal.

In embodiments, the proposed labyrinth seals are located within the orbit scroll of a scroll pump around two back to back angular contact ball bearings. These bearings are affixed to a crank sleeve that rotates upon an eccentric radius around the drive shaft, thus imparting an orbit motion (in conjunction with an anti-rotation mechanism). A counter balance is also provided, its purpose being to balance the eccentric load of the orbit scroll.

Embodiments provide a plate for substantially closing the open area of the bearings to reduce or control the flow of lubricant out of the bearing. As they are non-contact seals, there is a remaining open gap which is configured to be small while still avoiding any metal to metal contact between the bearing outer race and the seal. The seal comprises overlapping plates or discs which together prevent line of sight lubricant loss in an axial direction. Any lubricant that does escape past the inner baffle plate and enters the space between the plates will, where the inner plate is mounted to rotate with the drive shaft, be driven out radially by the rotating baffle and back towards the bearing.

The radial gap between the outer disk and the shaft should be kept low as a final restriction to any lubricant that does migrate through the labyrinth.

In some embodiments a pumping feature may be machined into the axial face of the outer disk facing the baffle. It should be machined in a direction so as to pump lubricant back towards the bearing. A pumping feature can also be machined on the inside diameter of the outer disk or on the shaft surface to pump grease in the axial direction back towards the bearings. Additionally and/or alternatively a pumping feature can be included on the baffle plate as to promote grease flow into the bearings.

-15 -The pumping feature can comprise of a variety of geometric designs which promote lubricant movement, these can include but are not limited to spiral, helical or any profile and form shaped groove, vanes, fins, thread etc. Although illustrative embodiments of the invention have been disclosed in detail herein, with reference to the accompanying drawings, it is understood that the invention is not limited to the precise embodiment and that various changes and modifications can be effected therein by one skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

-16 -

REFERENCE SIGNS

bearing 12 inner race 14 outer race 16 rolling elements orbit scroll 22 crank sleeve drive shaft labyrinth seal 41 disc 42 protruding surface 43 vanes 44 baffle plate narrow passage 46 space between inner surface of disc and outer surface of baffle plate 47 restriction on axial surface of disc 48 relubrication channel 49 stopper

Claims

-17 -CLAIMS1. A labyrinth seal for inhibiting leakage of lubricant from a bearing mounting an orbiting scroll to a drive shaft in a scroll pump, said labyrinth seal comprising: a baffle plate configured to be mounted adjacent to said bearing and to partially obscure a gap between inner and outer races of said bearing, such that lubricant within said bearing contacts an inner surface of said baffle plate facing said bearing and is at least partially restrained from leaving said bearing by said baffle plate; a disc comprising an inner surface configured to be mounted such that said inner surface faces and is adjacent to, but not in contact with, an outer surface of said baffle plate; wherein one of said baffle plate and disc is mounted to extend from and rotate with said inner race and the other of said baffle plate and disc is mounted to extend from and orbit with said outer race; and said labyrinth seal is configured such that said baffle plate does not contact said race that said baffle plate does not extend from such that there is a passage for lubricant to flow from said bearing to the space between said outer surface of said baffle plate and said inner surface of said disc.
2. A labyrinth seal according to claim 1, wherein said baffle plate is configured such that said passage has a width of less than 500 microns, preferably less than 200 microns, more preferably less than 100 microns.
3. A labyrinth seal according to claim 1 or 2, wherein said baffle plate is configured to extend from said inner race to a point between 1/3 and 2/3 of the distance between the inner and outer races.
4. A labyrinth seal according to claim 3, wherein said inner surface of said disc comprises a recessed portion for receiving said baffle plate and a protruding portion configured to extend over an axial surface of said baffle plate, said -18 -passage being delimited by said axial surface of said baffle plate and an axial surface of said protruding portion.
5. A labyrinth seal according to any one of claims 1 or 2, wherein said passage is delimited by an axial surface of said baffle plate and an inner surface of said race that said baffle plate does not extend from.
A labyrinth seal according to any preceding claim, wherein said baffle plate is configured to extend from and rotate with said inner race.
7. A labyrinth seal according to any preceding claim wherein said baffle plate and disc are formed of metal
8. A labyrinth seal according to any preceding claim, wherein at least one of said inner surface of said disc and said outer surface of said baffle plate comprise a profile configured such that on rotation of said drive shaft, a force due to said rotation on lubricant within said space between said surfaces drives said lubricant towards said passage to said bearing.
9. A labyrinth seal according to any preceding claim, wherein said inner surface of said baffle plate facing towards said bearing comprises a profile configured such that on rotation of said drive shaft, a force due to said rotation on lubricant adjacent to said inner surface drives said lubricant away from said passage.
10. A labyrinth seal according to any preceding claim, wherein an axial surface of said disc that is perpendicular to said inner surface and arranged adjacent to a race that said disc does not move with, comprises a profile configured to push fluid within said profile towards said inner surface of said disc on operation of said pump.-19 -
11. A labyrinth seal according to any one of claims 8 to 10, wherein said profile comprises at least one of a shaped groove, vane, fin or thread, in some cases said shape comprises a spiral or helical shape.
12. A labyrinth seal according to any preceding claim, comprising a further disc comprising an inner surface configured to be mounted such that said inner surface faces and is adjacent to, but is not in contact with, an outer surface of said disc, said further disc being mounted to extend from and move with the race that said disc does not extend from and move with.
13. A labyrinth seal according to claim 12, comprising a plurality of further discs, configured to be mounted such that said plurality of further discs are nested within each other, said plurality of further discs being mounted to alternately extend from and move with the inner and outer races.
14. A scroll pump comprising an orbiting scroll and a stationary scroll, said orbiting scroll being mounted on a drive shaft via bearings, said scroll pump comprising two labyrinth seals according to any preceding claim, said seals being mounted to seal side surfaces comprising said gap between said races of said bearing.
15. A scroll pump according to claim 14, wherein said scroll pump is a high speed scroll pump configured to rotate at speeds above 2,000 RPM, in some cases above 2,800 RPM, in some cases above 3,500 RPM.
16. A scroll pump according to claim 14 or 15, wherein said scroll pump comprises a vacuum pump