Bearing assembly for a pump and pump comprising the same

Abstract

A bearing assembly for mounting a rotatable shaft of a pump and the pump are disclosed. The bearing assembly includes a bearing including an outer ring and an inner ring, a bearing housing configured to support the outer ring of the bearing, the bearing housing extending around at least a portion of an outer surface of the outer ring across at least a portion of one end surface of the outer ring, and a shroud extending from the bearing housing toward the inner ring to thereby shield at least a portion of an annular gap between the inner ring and the outer ring.

Description

Technical Field

[0001] The field of the present invention relates to bearing assemblies for pumps and pumps comprising such bearing assemblies. Background Technology

[0002] It is known to use bearing guards to prevent lubricant from leaking from bearings.

[0003] One type of guard is a clamp-on guard that is sandwiched on the outer ring and covers the annular gap between the inner and outer rings. This type of guard is flexible and therefore may bend or move under extreme conditions or in the event of bearing failure, and cannot provide protection against increased movement within the rotating assembly.

[0004] Figure 1a An alternative prior art bearing assembly 10 is shown, which has a shroud 28 integral with the outer ring 22 of the bearing. This shroud is configured to provide support for an axial damping ring 30, which axially positions the bearing and provides the necessary stiffness and damping. In this example, the inner ring 24 of the bearing is mounted against the shaft 40, and 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 shroud of the bearing assembly is more robust / harder than a typical "clamp" seal. Due to its increased robustness, it can act as an end stop in the event of bearing failure, thereby limiting radial displacement of the inner ring and thus limiting radial displacement of the shaft, protecting the pump from radial contact within the pumping mechanism.

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

[0006] If the bearing is not supported by damping rings 30 or 32, but by a different type of bearing housing, such as an elastic support, also known as a compact metal spring damper (CMSD) (as described in WO2008035113), then a guard is not required to support the damping rings and a clip-on guard can be used. Alternatively, an integral guard can be retained and the CMSD can be mounted around it. This is in Figure 1b As shown, the shield 36 is integrated with the outer ring 22, and a compact metal spring damper 36 is mounted around the outer ring 22 and the integrated shield 28.

[0007] While an integral shroud with the outer ring may be more robust, it does require non-standard bearings and additional space, and is not easily installed in pumps conventionally designed for use with clip-on shrouds. Furthermore, bearings such as deep groove ball bearings require the bearing rings to be tilted during assembly, thus precluding shrouds that are integral with the outer ring and face the inner ring, as well as the stringent tolerances required to allow for small operating clearances. To address this issue and provide tight tolerances while allowing for bearing assembly, the shroud is constructed to face the shaft; therefore, such bearing assemblies require special housings machined on the shaft.

[0008] The aim is to provide a bearing assembly with a protective shield that is robust, easy to assemble, can be used with conventional bearings in some cases, is inexpensive, and does not take up too much 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 housing configured to support the outer ring of the bearing, the bearing housing extending around at least a portion of an outer surface of the outer ring and across at least a portion of an end face of the outer ring; and a shroud extending from the bearing housing toward the inner ring to shield at least a portion of an annular gap between the inner and outer rings.

[0010] In cases where the bearing assembly has a support extending at least a portion of its axial length around the outer circumferential surface and across a portion of one end face of the outer ring, this extension provides a location from which the shroud can extend, rather than extending from the outer ring. This is particularly advantageous when the shroud is securely attached to the bearing housing, providing not only effective lubricant retention but also robust protection. Having a shroud extending from the bearing housing facilitates the manufacture and assembly of the bearing assembly and, in some embodiments, allows the use of conventional bearings. In this regard, for example, the inner and outer rings of a deep groove ball bearing require tilting and offset during installation; therefore, in cases where the shroud is attached to the bearing housing, they can be manufactured in a conventional manner, and the bearing housing and associated shroud are subsequently attached to them.

[0011] Although bearing housings can take many forms, in some embodiments, the bearing housing includes a compact metal spring damper.

[0012] A compact metal spring damper may include an inner hub for receiving a bearing and a concentric outer support connected to the inner hub via at least one elastic member. It surrounds a portion of the outer circumference of an outer ring and extends across a portion of the axial surface of the outer ring, providing a location from which a shield can extend.

[0013] In some embodiments, the protective cover is integral with the bearing housing.

[0014] Providing an integrated shroud with the bearing housing offers robust protection for the bearing, and with proper design, the shroud can also serve as a backup bearing in the event of bearing failure. Furthermore, its simple manufacture and the isolation of the shroud from the bearing rings prevent deformation of these rings during manufacturing, assembly, or use.

[0015] In other embodiments, the protective cover is attached to the bearing housing.

[0016] An alternative to integrating the bearing housing with the bearing casing is to attach it either by gluing or by press-fitting it to the bearing housing. Gluing carries the risk of contaminating the bearing, while press-fitting may deform the outer ring and reduce bearing performance.

[0017] In some embodiments, the shroud is mounted between the axial end surface of the outer ring and the portion of the bearing housing extending across the axial end surface.

[0018] In one embodiment, the shroud may be installed between the portion of the bearing housing extending across the end surface of the outer ring and the outer ring, such that it is held in place by mounting the bearing housing onto the bearing.

[0019] In some embodiments, the inner surface of the outer ring includes a groove at one end of the inner surface, the bearing housing extends across the end surface toward the groove, and the shroud is mounted within the groove and adjacent to the surface of the bearing housing.

[0020] A groove can be present on the inner surface of the outer ring, allowing the shroud to be installed within the bearing housing and extending axially to contact the housing and radially toward the outer surface of the inner ring. This is a compact and effective way to provide a shroud that does not increase the bearing's size and provides robust and effective shielding. However, it does require some modifications to the bearing. The shroud can contact the radially inner surface of the bearing housing, or it can contact the surface of the bearing housing facing the end face of the outer ring.

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

[0022] If the bearing housing is not integral with the bearing housing, it can be made of the same material or it can be made of different materials. The bearing housing requires different properties than the bearing housing, therefore, it may be advantageous to manufacture them using different materials. The material chosen for the bearing housing will depend on the required properties of the housing.

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

[0024] Providing a shroud extending from the bearing housing, rather than one clamped within the outer ring, allows for the formation of a thicker, more robust component, thus enabling it to provide at least one of axial and radial end stops in the event of bearing failure. In this respect, although bearing failure is rare, if it does occur, the permissible radial and / or axial movement can cause components within the pump to impact. With a shroud, the clearance between the shroud and the inner ring or shaft is typically small to prevent lubricant leakage. If the shroud is a robust component and the radial clearance is the minimum radial clearance within the pump, then in the event of bearing failure, any radial movement will cause the shroud to impact the inner ring or shaft before contacting any other surface. Upon impact, the shroud will prevent further movement and provide a radial backup bearing. Depending on the construction, axial movement can be protected in a similar manner.

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

[0026] In some embodiments, the thickness of the shield is between 0.4 and 5 mm, preferably between 0.7 and 3 mm.

[0027] In addition to preventing lubricant leakage, the shield preferably serves as an axial and / or radial end stop and should therefore be robust enough to support the bearing in the event of bearing failure. A shield thickness between 0.5 and 4 mm, preferably between 0.7 and 3 mm, is generally sufficient to provide the required protection.

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

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

[0030] Although in some embodiments the shroud may be configured to extend toward the shaft, it extends toward the outer surface of the inner ring, such that a radial clearance exists between the inner surface of the shroud and the outer surface of the inner ring. This radial clearance may be configured to be dimensionally limited such that, in the event of bearing failure, the shroud and the inner ring will come into contact before any other components of the pump come into contact with each other.

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

[0032] In some cases, there is a groove on the outer surface at one end of the inner ring, into which the shroud can extend. This provides both radial and axial clearance between the shaft and the inner ring, which can provide both radial and axial protection for the pump in the event of bearing failure.

[0033] In some embodiments, the inner ring is longer than the outer ring in the axial direction.

[0034] If the shield extends to the outer surface of the inner ring or into a groove in the outer surface of the inner ring, then the shield will need to have a curved portion if the inner and outer rings have the same axial length; otherwise, it will extend above the inner ring. If the inner ring is longer than the outer ring axially, the shield can be essentially straight, which makes it stronger and easier to manufacture.

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

[0036] In some cases, the guard may extend beyond the inner ring, and the gap may be located between the guard and the shaft.

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

[0038] It may be advantageous for the surface forming the shield to contact a moving surface made of a material different from that of the rest of the shield. In particular, these surfaces may be formed of a material with non-abrasive properties or a low coefficient of friction, while the material chosen for the rest of the shield may be selected based on its hardness. For example, the majority of the shield may be titanium, while the surface adjacent to the gap may be formed of a different material or a coating of a different material. The chosen material will depend on the material with which the gap is formed. In some embodiments, it may also be oleophobic to prevent oil from leaving the bearing.

[0039] The second aspect provides a pump including at least one rotatable shaft supporting a rotor within 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 groove in its outer surface, and the bearing and shield extend into the groove.

[0041] In some embodiments, the bearing and shroud may extend into a recess in the shaft. This may be more complex to manufacture than a straight shaft, but it can provide axial protection in both axial directions and, if properly constructed, radial protection as well. It can also make the bearing assembly easier to manufacture and assemble. In this respect, the shroud may extend into a recess within the bearing, or into a recess within the shaft, and / or into a recess formed partly by the bearing and partly by the shaft.

[0042] In some embodiments, the pump includes a vacuum pump. Vacuum pumps are expensive machines that rotate at high speeds, and applications using them may be sensitive to contamination caused by lubricants. Therefore, it may be advantageous to use a shield to protect them from lubricant leakage, and this may be particularly advantageous if the shield also provides backup facilities.

[0043] Further specific and preferred aspects are set forth in the appended independent and dependent claims. Features of the dependent claims may be suitably combined with features of the independent claims, and may be combinations different from those expressly listed in the claims.

[0044] When a device feature is described as operable to provide a function, it should be understood that this includes device features that provide that function or are adapted or configured to provide that function. Attached Figure Description

[0045] The embodiments of the present invention will now be further described with reference to the accompanying drawings, wherein:

[0046] Figure 1a This shows a bearing assembly based on the prior art;

[0047] Figure 1b Different examples of bearing assemblies based on existing technology are shown;

[0048] Figure 2 A bearing assembly is shown, with a cover that is part of the bearing housing and a gap between it and the shaft;

[0049] Figure 3 This shows a bearing assembly with a cover that is part of the bearing housing and has a gap with the inner ring;

[0050] Figure 4 This shows a bearing assembly with a shroud that is part of the bearing housing and has radial and axial clearances with the inner ring.

[0051] Figure 5 An alternative embodiment of the bearing assembly is shown, which has a shroud extending from the bearing housing and having a gap with the inner ring;

[0052] Figure 6An embodiment of a bearing assembly is shown, in which the guard and bearing housing are separate components;

[0053] Figure 7 Another example of a bearing assembly is shown, where the guard and bearing housing are separate components; and

[0054] Figure 8 An alternative embodiment is shown, in which the bearing and the cover are mounted in a groove within the shaft. Detailed Implementation

[0055] Before discussing the embodiments in more detail, an overview will first be provided.

[0056] Protective bearing housings integrated with the bearing housing—such as CMSD—have been disclosed. The integrated housing provides a seal to prevent oil leakage from the bearing into the pump, and in the event of bearing failure, it can also act as an end stop, limiting radial and / or axial movement of the inner ring and shaft relative to the outer ring and stator.

[0057] The embodiment provides a cover that is integrated with the bearing housing rather than with the bearing. This allows for the use of more standard bearing designs because the bearing can be assembled before the cover and support are installed to the bearing assembly, so the cover does not interfere with the bearing assembly.

[0058] Figure 2 One embodiment is shown in which the bearing housing 28 is integral with the bearing seat 36, which in this embodiment is in the form of a CMSD. A standard bearing can be used with this bearing assembly, which includes an outer ring 22, an inner ring 24, and rolling elements 26. The radially inner surface of the housing 28 faces the shaft 40, and there is a gap between the shaft and this surface. In the event of bearing failure, the housing will act as a radial stop, limiting radial movement of the shaft beyond the gap width, and also as an axial stop, limiting axial movement in one direction. The gap with the shaft makes it more difficult to set the gap precisely, which reduces sealing efficiency and increases the tolerances of the rest of the pump if the bearing provides a backup bearing function.

[0059] Figure 3 An alternative embodiment is shown, in which the shroud is again integral with the bearing housing, but in this embodiment, the radially inner surface of the shroud 28 faces the inner ring 24 of the bearing instead of the shaft 40. This allows for a more precise clearance setting, thus allowing for tighter operating clearances and use on pumps previously equipped with clip-on shrouds. In the event of bearing failure, this clearance again sets the limit on radial movement. Standard bearings can also be used in this embodiment.

[0060] Figure 4An alternative embodiment is shown, in which the shroud 28 is again integral with the bearing housing 36, and the clearance is located between the radial inner wall of the shroud 28 and the inner ring 24. In this embodiment, the shroud 28 extends into a groove in the inner axial end face of the inner ring 24, such that there are axial and radial clearances between the inner ring and the shroud 28. If the bearing fails, axial and radial movement will be restricted by these clearance dimensions, thus providing the pump with both an axial backup bearing in at least one direction and a radial backup bearing.

[0061] Figure 5 A similar design is shown, where the shield 28 is again integral with the bearing housing 36, but a non-standard bearing is used in this case. This bearing has an inner ring 24 shorter than the outer ring 22, which allows the shield to be straight and still extend to the inner ring 24 to create a gap between the radially inner surface of the shield 28 and the inner ring. The disadvantage of this arrangement is the requirement for a special bearing with an adaptable inner or outer ring, but it does allow for a more straightforward manufacture and assembly of the shield and bearing housing, eliminating the need for the shield to bend around the outer ring. Although there is no groove in the outer surface of the inner ring 24 in this embodiment, such grooves may be present in other embodiments, allowing the shield to provide axial and radial protection.

[0062] Figure 6 An alternative embodiment is shown in which the bearing housing 28 is a separate element from the bearing housing 36. This allows the housing 28 to be formed from different materials that can be selected according to the desired characteristics. In this embodiment, the housing 28 is mounted between the bearing housing and the outer ring 22 of the bearing. In this case, the bearing is not a standard bearing, but has a shorter outer ring or a longer inner ring to accommodate the housing and face it toward the inner ring 24.

[0063] In addition to the shield being made of a different material than the bearing housing, different parts of the shield can be made of different materials. For example, the surface of the shield facing the radial outer surface of the inner ring 24 can be coated with a material with non-abrasive or low coefficient of friction properties, thereby protecting the shield from contact with the outer surface of the inner ring 24.

[0064] Figure 7 An alternative embodiment is shown, which is similar to Figure 6 The embodiment has a groove at the axial end of the radially inner surface of the outer ring 22. A shield 28 is mounted in this groove and extends axially to contact the bearing housing 36. It provides appropriate radial stiffness and also extends radially across the inner ring 24 to prevent lubricant leakage from the bearing, while also limiting radial movement in the event of bearing failure.

[0065] Figure 7In fact, the bearing assembly in other figures is a cross-section through half of the assembly and supports the pump shaft 40, half of which is schematically shown as 42. Shaft 40 supports a rotor within the pump, which is configured to rotate within a stator and thereby pump fluid. Pump 42 can be a vacuum pump, where it is important to maintain the vacuum to prevent oil leakage. In the pump of the embodiment, there may be a single shaft 40 with one bearing assembly or there may be two shafts, each supported by a free bearing assembly.

[0066] Figure 8 In another embodiment, the bearing assembly is mounted within a recess in the shaft 40. In this embodiment, the shroud 28 is shaped to extend above the inner ring portion and face the outer surface of the inner ring 24. Therefore, axial and radial clearances exist between the shroud, the shaft, and the inner ring, which restrict axial and radial movement in both directions should the bearing fail. These clearances are chosen to be low to suppress lubricant leakage and also provide a backup bearing function, such that if the bearing fails, the first surfaces in contact with each other will be the surfaces forming the clearances.

[0067] Although illustrative embodiments of the invention have been disclosed in detail herein with reference to the accompanying drawings, it should be understood that the invention is not limited to the precise embodiments and that various changes and modifications can be made therein by those skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0068] Attached icon number

[0069] 10 Bearing Assembly

[0070] 22 Outer ring

[0071] 24 Inner Circle

[0072] 24a Groove

[0073] 23. Snap ring

[0074] 26 Rolling elements

[0075] 28 protective shields

[0076] Damping rings 30 and 32

[0077] 36 bearing housing

[0078] 40 axis

[0079] 42 pumps

Claims

1. A bearing assembly for mounting a rotatable shaft of a pump, the bearing assembly comprising: a bearing comprising an outer ring and an inner ring; a bearing seat configured to support the outer ring of the bearing, the bearing seat extending around at least a portion of an outer surface of the outer ring, across at least a portion of one end face of the outer ring; and a shroud extending from the bearing seat towards the inner ring, thereby obscuring at least a portion of an annular gap between the inner and outer rings; wherein the shroud is configured to provide at least one of axial and radial end stops in the event of bearing failure, wherein the shroud is integral with the bearing seat, or wherein the shroud is attached to the bearing seat, wherein the material of the shroud comprises a metallic material, wherein the inner ring comprises a recess in an outer surface at one end of the inner ring, the shroud being configured to extend into the recess such that there is an axial gap and / or a radial gap between the inner ring and the shroud, whereby axial and / or radial movement of the rotatable shaft upon bearing failure is limited by the size of the corresponding gap and thus provides an axial and / or radial backup bearing for the pump.

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

3. The bearing assembly of claim 1, wherein, the material of the shroud is a steel alloy or titanium.

4. The bearing assembly of claim 1, wherein, the shroud is mounted between an end face of the outer ring and the portion of the bearing seat extending across the end face.

5. The bearing assembly of claim 1, wherein, an inner surface of the outer ring comprises a recess at one end of the inner surface, the bearing seat extending across the end face towards the recess, the shroud being mounted within the recess and abutting a surface of the bearing seat.

6. The bearing assembly of any one of claims 1 to 5, wherein, the shroud is formed of a different material to the bearing seat.

7. The bearing assembly of any one of claims 1 to 5, wherein, the shroud is configured to provide both axial and radial end stops in the event of bearing failure.

8. The bearing assembly of any one of claims 1 to 5, wherein, the shroud has a thickness of 0.5 to 4 mm.

9. The bearing assembly of any one of claims 1 to 5, wherein, the shroud is configured to extend towards an outer surface of the inner ring, an inner surface of the shroud and the outer surface forming a gap therebetween.

10. The bearing assembly of claim 9, wherein, the inner ring is longer in the axial direction than the outer ring.

11. The bearing assembly of any one of claims 1 to 5, wherein, the shroud is configured to extend beyond an outer surface of the inner ring.

12. The bearing assembly of any one of claims 1 to 5, wherein, the shroud is formed of a different material, an innermost surface of the shroud on a side which forms a gap with the rotatable shaft of the pump or the inner ring comprising a different material to that which forms the majority of the shroud.

13. The bearing assembly of any one of claims 1 to 5, wherein, the shroud has a thickness of 0.7 to 3 mm.

14. A pump comprising at least one rotatable shaft supporting a rotor within a stator, the at least one rotatable shaft being mounted on at least one bearing assembly according to any preceding claim.

15. The pump of claim 14, wherein, the rotatable shaft comprises a recess in an outer surface, the bearing and shroud extending into the recess.

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

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