Bearing assembly for a pump and pump including the bearing assembly

Abstract

A bearing assembly for mounting a rotatable shaft of a pump and a pump are disclosed, the bearing assembly comprising a bearing including an outer ring and an inner ring, a bearing support configured to support the outer ring of the bearing, the bearing support surrounding at least a portion of an outer surface of the outer ring extending over at least a portion of one end face of the outer ring, and a shield extending from the bearing support towards the inner ring, thereby concealing at least a portion of an annular gap between the inner ring and the outer ring.

Description

[Technical field]

[0001] The field of the invention relates to bearing assemblies for pumps and pumps including such bearing assemblies. [Background technology]

[0002] The use of bearing shields to inhibit leakage of lubricant from the bearings is known.

[0003] One type of shield is a clip-on shield that is clipped to the outer race to cover the annular gap between the inner and outer races. Such shields are flexible and therefore may buckle or become disengaged during extreme bearing conditions or failure, providing no protection against increased movement within the rotating assembly.

[0004] FIG. 1a shows an alternative prior art bearing assembly 10 with a shield 28 integrated with the outer race 22 of the bearing. The shield is configured to support an axial damping ring 30 used to axially position the bearing and provide the required stiffness and damping. In this example, the inner ring 24 of the bearing is mounted on the shaft 40, the rolling elements 26 are housed between the inner ring 24 and the outer ring 22, which supports the damping rings 32 and 30. This bearing assembly is used in some turbomolecular pumps. The integral shield of the bearing assembly is more robust / rigid than typical "clip-on" seals. Due to its increased robustness, it acts as an end stop to limit radial excursion of the inner ring and therefore the shaft in the event of bearing failure, thereby protecting the pump from radial contact within the pump mechanism.

[0005] In this bearing, the inner ring 24 is shorter than the outer ring 26 and an integral shield 28 faces the shaft.

[0006] If the bearings are not supported by the damping rings 30, 32 but rather by a different type of bearing support, for example a resilient support, also known as a compact metal spring damper CMSD, as described in WO2008035113, then the shield does not need to support the damping rings and a clip-on shield can be used. Alternatively, an integral shield can be held and a CMSD attached around it. This is shown in Figure 1b, where the shield 36 is integral with the outer ring 22 and the compact metal spring damper 36 is attached around the outer ring 22 and the integral shield 28.

[0007] A shield integral with the outer ring can be more robust, but requires non-standard bearings and additional space, and cannot be easily installed in pumps traditionally designed for use with clip-on shields. Furthermore, bearings that require ring tilt during bearing assembly, such as deep groove ball bearings, cannot have a shield integral with the outer ring facing the inner ring and the tight tolerances required to allow for small running clearances. To address this issue and provide tight tolerances while still allowing for bearing assembly, the shield is configured to face the shaft, and therefore such bearing assemblies require a special seat machined on the shaft.

[0008] It would be desirable to provide a bearing assembly with a shield that is robust, easy to assemble, potentially uses conventional bearings, is inexpensive, and does not take up excessive space. Summary of the Invention

[0009] A first aspect provides a bearing assembly for mounting a rotatable shaft of a pump, the bearing assembly comprising: a bearing including an outer ring and an inner ring; a bearing support configured to support the outer ring of the bearing, the bearing support surrounding at least a portion of an outer surface of the outer ring extending over at least a portion of one end face of the outer ring; and a shield extending from the bearing support towards the inner ring, thereby concealing at least a portion of an annular gap between the inner ring and the outer ring.

[0010] If the bearing assembly has a support that surrounds at least a portion of the axial length of the circumferential outer surface and extends over a portion of one end face of the outer ring, this extension provides a location from which the shield can extend, rather than extending from the outer ring. This has the advantage of providing robust protection as well as effective lubricant retention, especially if the shield is rigidly attached to the bearing support. Having the shield extend from the bearing support facilitates manufacturing and assembly of the bearing assembly, and in some embodiments allows for the use of conventional bearings. In this regard, for example, the inner and outer rings of deep groove ball bearings, which need to be tilted and offset during installation, can be manufactured in the usual manner, with the bearing support and associated shield attached later, if the shield is attached to the bearing support.

[0011] The bearing support can have a number of configurations, but in some embodiments the bearing support comprises a compact metal spring damper.

[0012] The compact metal spring damper may comprise an inner hub for receiving a bearing and a concentric outer mount coupled to the inner hub by at least one resilient member, which surrounds a portion of the outer periphery of the outer ring and extends across a portion of the axial surface of the outer ring, the portion extending across the axial surface of the outer ring providing a location over which the shield may extend.

[0013] In some embodiments, the shield is integral with the bearing support.

[0014] Providing the shield integral with the bearing support provides robust protection for the bearing and, with proper design, can also act as a back-up bearing in the event of a bearing failure. Additionally, it is simple to manufacture and, because the shield is separate from the bearing rings, it will not distort those rings during manufacture, assembly or use.

[0015] In another embodiment, the shield is attached to the bearing support.

[0016] An alternative to the shield being integral with the bearing support is to attach the shield, possibly by gluing or by press-fitting into the bearing support, gluing having associated risks of contamination of the bearing, whereas press-fitting could distort the outer ring and degrade the performance of the bearing.

[0017] In some embodiments, the shield is mounted between an axial end face of the outer ring and the portion of the bearing support that extends across the axial end face.

[0018] In one embodiment, the shield may be mounted between the outer ring and a portion of the bearing support that extends over an end face of the outer ring such that the shield is held in place by attachment of the bearing support to the bearing.

[0019] In some embodiments, the inner surface of the outer ring includes a recess at one end of the inner surface, the bearing support extends across the end face toward the recess, and the shield is mounted within the recess and abuts a surface of the bearing support.

[0020] There can be a recess in the inner surface of the outer ring and a shield can be mounted internally and extend axially to contact the bearing support and radially to the outer surface of the inner ring. This is a compact and effective way of providing a shield and provides a robust and effective shield without increasing the size of the bearing. However, some modification of the bearing is required. The shield can contact the radial inner surface of the bearing support and can contact the surface of the bearing support that races the end face of the outer ring.

[0021] In some embodiments, the shield is formed of a different material than the bearing support.

[0022] If the shield is not integral with the bearing support, the shield may be made of the same material or a different material. The properties required for the bearing support may be different from those required for the shield, and therefore there may be advantages to making them of a different material. The material selected for the shield will depend on the properties required for the shield.

[0023] In some embodiments, the shield is configured to provide at least one of an axial and radial end stop in the event of failure of the bearing.

[0024] Providing a shield that extends from the bearing support, rather than one that is clipped to the outer ring, offers the possibility of forming the shield as a thicker, more robust component, providing axial and / or radial end stops in the event of a bearing failure. In this regard, while bearing failure is a rare event, if it does occur, the radial and / or axial movement that the bearing allows can result in collision of components within the pump. If a shield is used, the clearance gap between the shield and the inner ring or shaft is generally small to prevent leakage of lubricant. If the shield is a robust component and the radial gap is the smallest radial clearance in the pump, in the event of a bearing failure, radial movement will result in the shield colliding with the inner ring or shaft before any other surfaces come into contact. Upon impact, the shield is protected from further movement, providing a radial backup bearing. In some configurations, axial movement is also protected in a similar manner.

[0025] In some embodiments, the shield is configured to provide both an axial and radial end stop in the event of failure of the bearing.

[0026] In some embodiments, the shield has a thickness of 0.4 to 5 mm, preferably 0.7 to 3 mm.

[0027] In addition to inhibiting lubricant leakage, the shield is preferably used as an axial and / or radial end stop and thus should be robust enough to support the bearing in the event of a bearing failure. Shield thicknesses of 0.5-4 mm, preferably 0.7-3 mm, are generally sufficient to provide the necessary protection.

[0028] The material of the shield can be a metallic material to provide robustness, in some embodiments a steel alloy or titanium. The thickness of the shield depends on the material, and if the material is a stronger material, the thickness can be towards the lower end of the range.

[0029] In some embodiments, the shield is configured to extend toward an outer surface of the inner ring, with the inner surface of the shield and the outer surface forming a clearance gap therebetween.

[0030] The shield may be configured to extend toward the shaft, but in some embodiments extends toward the outer surface of the inner ring such that there is a radial clearance gap between the inner surface of the shield and the outer surface of the inner ring, which may be configured to be limited in size such that in the event of a bearing failure, the shield and inner ring will come into contact before other parts of the pump come into contact with each other.

[0031] In some embodiments, the inner ring includes a recess in an outer surface at one end of the inner ring, and the shield is configured to extend into the recess.

[0032] In some cases, the outer surface of one end of the inner ring has a recess into which the shield can extend, providing radial and axial clearance gaps between the shut and the inner ring to provide both radial and axial protection for the pump in the event of a bearing failure.

[0033] In some embodiments, the inner ring is axially longer than the outer ring.

[0034] If the shield extends to the outer surface of the inner ring or into a recess in the outer surface of the inner ring, then if the inner and outer rings have the same axial length, the shield will need to have a bend or it will extend above the inner ring. If the inner ring is axially longer than the outer ring, the shield can be substantially straight, making it more robust and easier to manufacture.

[0035] In some embodiments, the shield is configured to extend beyond an outer surface of the inner ring.

[0036] In some cases, the shield extends beyond the inner ring and a clearance gap can exist between the shield and the shaft.

[0037] In some embodiments, the shield is formed of multiple different materials, and the innermost surface of the shield forms one side of a clearance gap with the rotatable shaft of the pump, or the inner ring comprises a different material than the material forming the majority of the shield.

[0038] It may be advantageous to form the surfaces of the shield that may come into contact with the moving surface from a different material than the rest of the shield. In particular, these surfaces may be formed from a material that has anti-galling properties or a low coefficient of friction, while the material selected for the rest of the shield may be selected for its stiffness. For example, the majority of the shield may be titanium, and the surfaces adjacent the clearance gap may be formed from a different material or coated with a different material. The material selected will depend on the material forming the clearance gap. In some embodiments, it may be oleophobic to inhibit oil leakage from the bearing.

[0039] A second aspect provides a pump including at least one rotatable shaft supporting a rotor in a stator, at least one of the at least one rotatable shafts being mounted on at least one bearing assembly according to the first aspect.

[0040] In some embodiments, the rotatable shaft includes a recess in an outer surface, and the bearing and shield extend into the recess.

[0041] In some embodiments, the bearing and shield can extend into a recess in the shaft. This can be more complicated to manufacture than a straight shaft, but can provide axial protection in both axial directions and, if properly configured, radial protection as well. It can also facilitate easier manufacturing and assembly of the bearing assembly. In this regard, the shield can extend into a recess in the bearing, or into a recess in the shaft, and / or into a recess partially formed by the bearing and partially formed by the shaft.

[0042] In some embodiments, the pump comprises a vacuum pump. Vacuum pumps are expensive machines that rotate at high speeds and the applications in which they are used can be sensitive to contamination by lubricants. Therefore, the use of a shield to protect against lubricant leakage is advantageous, especially if the shield can also provide a back-up function.

[0043] 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.

[0044] It should be understood that where features of an apparatus are described as operable to provide a functionality, this description includes features of an apparatus that provide that functionality or that are adapted or configured to provide that functionality.

[0045] Next, embodiments of the present invention will be further described with reference to the accompanying drawings. [Brief description of the drawings]

[0046] [Figure 1a] FIG. 1 illustrates a bearing assembly according to the prior art. [Figure 1b] 1A to 1C are diagrams showing different examples of bearing assemblies according to the prior art; [Diagram 2] FIG. 1 illustrates a bearing assembly including a shield as part of the bearing support and having a clearance gap with the shaft. [Diagram 3] FIG. 1 illustrates a bearing assembly with a shield as part of the bearing support and having a clearance gap with the inner ring. [Figure 4] FIG. 1 illustrates a bearing assembly including a shield as part of the bearing support and having radial and axial clearance gaps with the inner ring. [Diagram 5] 13A-13C illustrate an alternative embodiment of a bearing assembly including a shield extending from the bearing support and having a clearance gap with the inner ring. [Figure 6] FIG. 1 illustrates an embodiment of a bearing assembly having separate shields and bearing supports. [Figure 7] 13A-13C show further embodiments of a bearing assembly having separate shields and bearing supports. [Figure 8] 13A-13C show an alternative embodiment in which the bearings and shields are mounted within recesses in the shaft. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Before describing the embodiments in more detail, a brief overview will first be provided.

[0048] A protective bearing shield is disclosed that is integrated with the bearing support, e.g., the CMSD. The integral shield provides a seal against oil loss from the bearing to the pump and also acts as an end stop to limit radial and / or axial movement of the inner ring and shaft relative to the outer ring and stator in the event of a bearing failure.

[0049] In an embodiment, a shield is provided that is integrated with the bearing support rather than the bearing, which allows the use of more standard bearing designs as the bearing can be assembled before the shield and support are attached to the bearing assembly, and ensures that the shield does not affect the assembly of the bearing.

[0050] FIG. 2 shows an embodiment in which the bearing shield 28 is integral with the bearing support 36 (in this embodiment in the form of a CMSD). In this bearing assembly, standard bearings can be used, which include the outer race 22, the inner race 24, and the rolling elements 26. The radially inner surface of the shield 28 faces the shaft 40, with a clearance gap between the shaft and this surface. In the unlikely event of bearing failure, the shield acts as a radial stop to limit radial movement of the shaft beyond the width of the clearance gap, and also acts as an axial stop to limit axial movement in one direction. Forming a clearance gap with the shaft makes it difficult to set the clearance gap accurately, reduces sealing efficiency, and increases the tolerances of other parts of the pump if the bearing provides a backup bearing function.

[0051] 3 shows an alternative embodiment where the shield is again integral with the bearing support, but in this embodiment the radially inner surface of the shield 28 faces the bearing inner ring 24 instead of the shaft 40. This allows the clearance gap to be set more precisely, allowing closer running clearances and use in pumps where clip-on shields were previously used. This clearance gap limits radial movement in the event of bearing failure. Standard bearings may be used in this embodiment.

[0052] 4 shows another embodiment in which the shield 28 is integral with the bearing support 36 and a clearance gap is between the radially inner wall of the shield 28 and the inner ring 24. In this embodiment, the shield 28 extends into a recess in the axially inner end face of the inner ring 24 such that an axial clearance gap and a radial clearance gap exist between the inner ring and the shield 28. In the event of bearing failure, axial and radial movement are limited by the size of these clearance gaps, so that this bearing can provide both an axial and radial backup bearing for the pump in at least one direction.

[0053] FIG. 5 shows a similar design in which the shield 28 is integral with the bearing support 36, but in this case a non-standard bearing is used. This bearing has an inner ring 24 that is shorter than the outer ring 22, which allows the shield to be straight and extend further to the inner ring 24 to form a clearance gap between the radially inner surface of the shield 28 and the inner ring. This arrangement has the disadvantage of requiring a special bearing with a matching inner or outer ring, but allows the shield and bearing support to be manufactured and assembled in a simpler manner without the need to bend the shield around the outer ring. In this embodiment, there are no recesses on the outer surface of the inner ring 24, but in other embodiments there may be such recesses so that axial and radial protection is provided by the shield.

[0054] 6 shows an alternative embodiment in which the bearing shield 28 is a separate element from the bearing support 36. This allows the shield 28 to be made of different materials, which can be selected depending on the properties required. In this embodiment, the shield 28 is mounted between the bearing support and the outer ring 22 of the bearing. In this case, the bearing is not a standard bearing, but has a shorter or longer outer ring to accommodate the shield and allow it to face the inner ring 24.

[0055] In addition to the shield being formed of a different material than the bearing support, different portions of the shield may be formed of different materials. For example, the surface of the shield facing the radially outer surface of inner ring 24 may be coated with a non-galling or low coefficient of friction material to protect the shield and the outer surface of inner ring 24 in the event of contact.

[0056] Figure 7 shows an alternative embodiment similar to that of Figure 6, but with a recess at the axial end of the radially inner surface of the outer ring 22. The shield 28 is mounted within this recess and extends axially to contact the bearing support 36 which provides adequate radial stiffness, and the shield also extends radially towards the inner ring 24, inhibiting lubricant from leaking out of the bearing while at the same time limiting radial movement in the event of bearing failure.

[0057] The bearing assembly in Figure 7 and other figures is a cross section through one half of the assembly, supporting a shaft 40 of a pump, one half of which is shown diagrammatically as 42. The shaft 40 supports a rotor in the pump that is arranged to rotate within a stator, thereby pumping fluid. The pump 42 may be a vacuum pump where it is important to protect the vacuum from oil leakage. In some pump embodiments there may be one shaft 40 with one bearing assembly, or there may be two shafts, each supported by a bearing assembly.

[0058] 8 is a further embodiment in which the bearing assembly is mounted in a recess in the shaft 40. In this embodiment, the shield 28 is contoured to extend above the inner ring portion and face the outer surface of the inner ring 24. There are therefore axial and radial clearance gaps between the shield, shaft and inner ring, which limit both axial and radial movement in the event of a bearing failure. The clearance gap is selected to be low to inhibit lubricant leakage and to provide a backup bearing function in which the first surfaces to come into contact with each other in the event of a bearing failure are the surfaces that form the clearance gap.

[0059] Although exemplary embodiments of the present invention have been disclosed in detail herein with reference to the accompanying drawings, it is understood that the present invention is not limited to the precise embodiments, and various changes and modifications can be made by those skilled in the art without departing from the scope of the present invention as defined by the appended claims and their equivalents. [Explanation of symbols]

[0060] 10 Bearing assembly 22 Outer Ring 24 Inner Ring 24a Recessed part 23 Circlip 26 Rolling elements 28 Shield 30, 32 Damping Ring 36 Bearing support 40 Shaft 42 Pump

Claims

1. 1. A bearing assembly for mounting a rotatable shaft of a pump, comprising: a bearing including an outer ring and an inner ring; a bearing support configured to support the outer ring of the bearing, the bearing support surrounding at least a portion of an outer surface of the outer ring extending over at least a portion of one end face of the outer ring; a shield extending from the bearing support toward the inner ring, thereby concealing at least a portion of an annular gap between the inner ring and the outer ring; Equipped with The inner ring includes a recess in an outer surface of one end of the inner ring, the shield configured to extend into the recess.

2. The bearing assembly of claim 1 , wherein the bearing support comprises a compact metal spring damper.

3. The bearing assembly of claim 1 , wherein the shield is integral with the bearing support.

4. The bearing assembly of claim 1 , wherein the shield is attached to the bearing support.

5. 5. The bearing assembly of claim 4, wherein the shield is mounted between an end face of the outer ring and a portion of the bearing support that extends across the end face.

6. 5. The bearing assembly of claim 4, wherein the inner surface of the outer ring includes a recess at one end of the inner surface, the bearing support extends across the end face toward the recess, and the shield is mounted within the recess and in contact with a surface of the bearing support.

7. The bearing assembly of claim 4 , wherein the shield is formed of a different material than the bearing support.

8. A bearing assembly as described in any one of claims 1 to 7, wherein the shield is configured to provide at least one of an axial and radial end stop in the event of failure of the bearing.

9. A bearing assembly according to any preceding claim, wherein the shield is configured to provide both an axial and radial end stop in the event of failure of the bearing.

10. A bearing assembly according to any one of the preceding claims, wherein the shield has a thickness of 0.5 to 4 mm, preferably 0.7 to 3 mm.

11. A bearing assembly as described in any one of claims 1 to 7, wherein the inner surface and the outer surface of the shield form a clearance gap therebetween.

12. The bearing assembly of claim 11 , wherein the inner ring is axially longer than the outer ring.

13. A bearing assembly as described in any one of claims 1 to 7, wherein the innermost surface of the shield which forms one side of the clearance gap with the inner ring comprises a material different from the material forming the majority of the shield.

14. A pump comprising at least one rotatable shaft supporting a rotor in a stator, said at least one rotatable shaft being mounted on at least one bearing assembly according to any one of claims 1 to 7.

15. The pump of claim 14 , wherein the pump comprises a vacuum pump.

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