Bearing assembly for a pump and a pump comprising the bearing assembly

Abstract

A bearing assembly for mounting a rotatable shaft of a pump and the pump are disclosed. The bearing assembly comprises: a bearing comprising 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 across at least a portion of one end surface of the outer ring; and a shield extending from the bearing support towards the inner ring to thereby obscure at least a portion of an annular gap between the inner and outer ring.

Claims

1. A bearing assembly for mounting a rotatable shaft of a pump, said bearing assembly comprising: a bearing comprising an outer ring and an inner ring; a bearing support comprising a metal spring damper configured to support said outer ring of said bearing, said bearing support surrounding at least a portion of an outer surface of said outer ring extending across at least a portion of one end surface of said outer ring; an outer surface of said inner ring comprising a recess; and a shield formed by the metal spring damper having an inner axially extending surface and a radially extending surface, the radially extending surface extending from the inner axially extending surface toward the outer ring to thereby obscure at least a portion of an annular gap between said inner and outer ring; wherein at least a part of the radially extending surface and at least a part of the inner axially extending surface are positioned within the recess of the inner ring and face the inner ring.

2. The bearing assembly according to claim 1, wherein said shield has a thickness of 0.5 to 4 mm.

3. The bearing assembly according to claim 1, wherein a clearance gap is between the inner axially extending surface and the inner ring within the recess.

4. The bearing assembly according to claim 3, wherein said inner ring is axially longer than said outer ring.

5. The bearing assembly according to claim 1, wherein the inner axially extending surface of said shield is formed of a different material than a material forming a majority of said shield.

6. A pump comprising at least one rotatable shaft mounted on at least one bearing assembly according to claim 1.

7. The pump according to claim 6, said pump comprising a vacuum pump.

8. The bearing assembly according to claim 1 wherein said shield is configured to provide at least one of an axial and radial end stop in case of failure of said bearing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described further, with reference to the accompanying drawings, in which:

(2) FIG. 1a shows a bearing assembly according to the prior art;

(3) FIG. 1b shows a different example of a bearing assembly according to the prior art;

(4) FIG. 2 shows a bearing assembly with a shield as part of a bearing support and with a clearance gap to the shaft;

(5) FIG. 3 shows a bearing assembly with a shield as part of the bearing support and a clearance gap with the inner ring;

(6) FIG. 4 shows a bearing assembly with a shield as part of the bearing support and with radial and axial clearance gaps with the inner ring;

(7) FIG. 5 shows an alternative embodiment of a bearing assembly with a shield extending from the bearing support and having a clearance gap with the inner ring;

(8) FIG. 6 shows an embodiment of a bearing assembly where the shield and bearing support are separate items;

(9) FIG. 7 shows a further example of a bearing assembly where the shield and bearing support are separate items; and

(10) FIG. 8 shows an alternative embodiment where the bearing and shield are mounted within a recess within the shaft.

DETAILED DESCRIPTION

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

(12) A protective bearing shield integral with a bearing supportfor example the CMSD is disclosed. The integral shield provides sealing against oil loss from the bearing to the pump and also acts as an end stop in case of bearing failure limiting the radial and/or axial movement of the inner ringand shaft relative to the outer ring and stator.

(13) Embodiments provide a shield integral with the bearing support rather than the bearing. This allows the use of a more standard bearing design, as the bearing can be assembled prior to the shield and support being fitted to the bearing assembly, so that the shield does not affect assembly of the bearing.

(14) FIG. 2 shows an embodiment where the bearing shield 28 is integral with the bearing support 36 which in this embodiment is in the form of CMSD. A standard bearing may be used with this bearing assembly, the bearing comprising an outer race 22 an inner race 24 and rolling elements 26. The radial inner surface of shield 28 faces shaft 40 and there is a clearance gap between the shaft and this surface. In the unlikely event that the bearing were to fail the shield would act as a radial stop limiting radial movement of the shaft beyond the width of the clearance gap and also as an axial stop limiting axial movement in one direction. Forming the clearance gap with the shaft makes the clearance gap more difficult to set accurately which, reduces the sealing efficiency and where the bearing provides a backup bearing function will increase tolerances in the rest of the pump.

(15) FIG. 3 shows an alternative embodiment where the shied is again integral with the bearing support but in this embodiment the radial inner surface of shield 28 faces the bearing inner ring 24 rather than shaft 40. This allows the clearance gap to be more accurately set allowing close running clearances and use on pumps where clip-on shields were previously used. This clearance gap again sets a limit on radial movement in the unlikely event that the bearing fails. A standard bearing can also be used in this embodiment.

(16) FIG. 4 shows an alternative embodiment where again the shield 28 is integral with bearing support 36 and the clearance gap is between an inner axially extending surface 52 of the shield 28 and the inner ring 24. In this embodiment, the shield 28 extends into a recess in the inner axial end surface of inner ring 24 such that there is an axial clearance gap between inner ring 24 and a radially extending surface 50 of shield 28 and a radial clearance gap is between inner ring 24 and inner axially extending surface 52 of shield 28. Were the bearing to fail then axial and radial movement would be limited by the size of these clearance gaps and thus this bearing may provide both an axial in at least one direction and a radial backup bearing for the pump.

(17) FIG. 5 shows a similar design where again 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 and this allows the shield to be straight and still extend up to the inner ring 24 to form a clearance gap between the radially inner surface of shield 28 and the inner ring. This arrangement has the disadvantage of requiring a specialised bearing with an adapted inner or outer ring, but does allow the shield and bearing support to be manufactured and assembled in a more straightforward manner that does not require the shield to bend around the outer ring. Although in this embodiment there is no recess in the outer surface of inner ring 24, in other embodiments there may be such a recess such that axial and radial protection is provided by the shield.

(18) FIG. 6 shows an alternative embodiment where bearing shield 28 is a separate element to the bearing support 36. This allows the shield 28 to be formed of a different material which may be selected according to the properties required. In this embodiment, the shield 28 in 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 outer ring or a longer inner ring to accommodate the shield and allow it to face the inner ring 24.

(19) In addition to the shield being formed of a different material to 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 the inner ring 24 may be coated in a material with non-galling or low coefficient of friction properties thereby protecting the shield and the outer surface of the inner ring 24 were contact to occur.

(20) FIG. 7 shows an alternative embodiment which is similar to the embodiment of FIG. 6 but there is a recess in an axial end of the radial inner surface of the outer ring 22. The shield 28 is mounted within this recess and extends axially to contact bearing support 36 which provides appropriate radial stiffness, the shield also extends radially across towards the inner ring 24 inhibiting lubricant from leaking from the bearing while also limiting radial movement in the case of bearing failure.

(21) The bearing assembly of FIG. 7 and indeed of the other figures, is a section through one half of the assembly and supports the shaft 40 of a pump a half of which is shown schematically as 42. The shaft 40 supports a rotor within the pump that is configured to rotate within a stator and thereby pump a fluid. The pump 42 may be a vacuum pump where it is important to protect the vacuum from oil leakage. There may be a single shaft 40 with one bearing assembly or there may be two shafts each supported by a bearing assembly in the pumps of embodiments.

(22) FIG. 8 is a further embodiment where the bearing assembly is mounted within a recess in shaft 40. In this embodiment the shield 28 is contoured such that it extends above the inner ring portion and faces the outer surface of the inner ring 24. Thus, there are axial and radial clearance gaps between the shield, the shaft and the inner ring which limit axial movement in both directions and radial movement were the bearing to fail. The clearance gaps are selected to be low to inhibit the leakage of lubricant and also to provide the backup bearing function such that were the bearing to fail the first surfaces to contact each other would be the surfaces forming the clearance gaps.

(23) 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.

(24) Although elements have been shown or described as separate embodiments above, portions of each embodiment may be combined with all or part of other embodiments described above.

(25) Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are described as example forms of implementing the claims.