BEARING SUPPORT FOR A VACUUM PUMP

Abstract

This is invention relates to a bearing support for a vacuum pump and, in particular, to a polymer bearing support for a vacuum pump. The invention further encompasses vacuum pumps comprising polymer bearing supports, and methods of manufacturing bearing supports.

Claims

1. A polymer bearing support for use in the resilient support of a rotor bearing of a vacuum pump in both radial and axial directions, the bearing support comprising an inner portion configured to be coupled to the bearing and an outer portion configured to be coupled to a housing of the vacuum pump, wherein the inner and outer portions are connected by at least one flexible member, wherein said at least one flexible member is an elongate, arcuate member substantially concentric with the inner portion and outer portion.

2. The polymer bearing support according to claim 1 wherein the polymer bearing support has a radial stiffness in the range from about 50 to about 500 N/mm.

3. The polymer bearing support according to claim 2 wherein the polymer bearing support has an axial stiffness greater than about 300 N/mm.

4. The polymer bearing support according to claim 3 wherein the axial stiffness is greater than the radial stiffness.

5. The polymer bearing support according to claim 1 wherein the inner and/or outer portions are annular.

6. The polymer bearing support according to claim 1 wherein the flexible member is annular and joined by at least one first radial beam to the inner portion and at least one second radial beam to the outer portion.

7. The polymer bearing support according to claim 1 wherein the flexible member has a thickness of from about 0.1 mm to about 1 mm, preferably from about 0.3 mm to about 0.7 mm

8. The polymer bearing support according to claim 1 wherein the support comprises a polymer with a tensile modulus of less than about 50 GPa.

9. The polymer bearing support according to claim 1 wherein the support comprises a polymer with a glass transition temperature 100 C.

10. The polymer bearing support according to claim 1 wherein the support is coupled to the housing and/or bearing using an interference fit.

11. The polymer bearing support according to claim 1 wherein the support is moulded, extruded, printed, machined, cast, spin cast, laser microjet machined or micro waterjet machined.

12. The polymer bearing support according to claim 1 wherein the support comprises polyether ether ketone (PEEK).

13. A polymer bearing support for use in the resilient support of a rotor bearing of a vacuum pump in both radial and axial directions, the bearing support comprising inner and outer annular portions and at least one intermediate annular portion joined to the inner annular portion by at least one first radial beam and joined to the outer annular portion by at least one second radial beam.

14. The vacuum pump comprising a rotor supported by a bearing arrangement, the bearing arrangement comprising a bearing supported in both radial and axial directions by a polymer support according to claim 1.

15. A vacuum pump comprising a rotor supported by a bearing arrangement, the bearing arrangement comprising a bearing supported in both radial and axial directions by a resilient polymer support comprising inner and outer annular portions connected by at least one flexible member.

16. (canceled)

17. A method of manufacturing a resilient polymer bearing support comprising the steps of moulding, extruding, printing or machining, casting, or spin casting a polymer to form the support, the support comprising an inner portion configured to be coupled to the bearing and an outer portion configured to be coupled to a housing of the vacuum pump, wherein the inner and outer portions are connected by at least one flexible member.

18. (canceled)

Description

BRIEF DESCRIPTION OF THE FIGURES

[0049] Preferred features of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0050] FIG. 1 shows a prior art bearing support.

[0051] FIG. 2 shows a prior art bearing support.

[0052] FIG. 3 shows a prior art bearing support.

[0053] FIG. 4 shows a polymer bearing support according to the invention.

[0054] FIGS. 5a and 5b show a polymer bearing support according to the invention.

DETAILED DESCRIPTION

[0055] The invention provides a polymer bearing support 36 for use in the resilient support of a rotor bearing of a vacuum pump in both radial and axial directions.

[0056] As illustrated in FIG. 4, in an example, the at least one flexible member 35 is annular and substantially concentric with the inner 33 and outer 34 annular portions about an axis A. The exemplified flexible member 35 has a radial thickness of 0.4 mm, and is joined to the inner portion 33 by three radial beams 38 and to the outer portion 34 by a further three radial beams 37. The radial beams 37, 38 are circumferentially alternately connected to the inner 33 and outer 34 portions and substantially equidistantly arranged. Accordingly, the flexible member 35 of the resilient support provides an integral leaf spring of the resilient support 36. The radial stiffness of the exemplified bearing support 36 has been found to be substantially isotropic.

[0057] The axially aligned faces 41, 42 of the beams are concave surfaces to reduce stress concentrations where the beams 37, 38 intersect the annular 33, 34 and flexible 35 members.

[0058] The inner portion 33 of the resilient support 36 has an inner, axially extending cylindrical surface 39 engaging the outer surface of the outer race of the rolling bearing (not shown).

[0059] In use the end surface 43 engages a radially extending surface of the molecular pump housing (not shown), whilst the outer, axially extending cylindrical surface 40 of the outer portion 34 of the resilient support 36 engages an axially extending surface of the housing (not shown).

[0060] The resilient support 36 is machined from a moulded polymer disk of PEEK: for instance VICTREX PEEK 450G. The stiffness of the resilient support 36 is determined by the geometry of the slots 44, 45, beams 37, 38 and flexible member 35, and can be accurately estimated using finite element analysis. It has been found that the resilient support 36 can be readily designed to have a relatively low radial stiffness, for example in the range from 50 to 300 N/mm, and preferably around 220 N/mm, for inhibiting the transmission of vibrations from the shaft of the turbomolecular pump impeller to the housing.

[0061] The resilient support 36 may also have a relatively high axial stiffness, for example in the range from 300 to 10,000 N/mm, preferably in the range from 300 to 1000 N/mm and more preferably in the range from 300 to 800 N/mm, so that there is minimal axial movement of the shaft during operation of the pump.

[0062] FIGS. 5a and 5b show an alternative example of the invention. FIG. 5a shows the pump end (or top) of the bearing support 50. FIG. 5b shows the underside of the same bearing support 50.

[0063] In the alternative example, the at least one flexible member 51 is annular and substantially concentric with the inner 52 and outer 53 annular portions about an axis A. The exemplified flexible member 51 has a radial thickness of 0.4 mm, and is joined to the inner portion 52 by three radial beams 54 and to the outer portion 53 by a further three radial beams 55. The radial beams 54, 55 are circumferentially alternately connected to the inner 52 and outer 53 portions and substantially equidistantly arranged. Accordingly, the flexible member 51 of the resilient support provides an integral leaf spring of the resilient support 50. The radial stiffness of the exemplified bearing support 50 has again been found to be substantially isotropic.

[0064] The resilient support is either injection moulded from PEEK (for instance VICTREX PEEK 450G) or machined from extruded PEEK (for instance Tecapeek Natural).

[0065] The inner portion 52 of the resilient support 50 has an inner, axially extending cylindrical surface 56 engaging the outer surface of the outer race of the rolling bearing (not shown) in an interference fit. A portion of the pump-end of the bearing engages with an integrally formed radially inwardly extending shoulder (57) of the inner portion (52).

[0066] A threaded boss (58) is located on the outer portion (53) which provides a reversible mechanical engagement with the pump (not shown). An axial stop (not shown) may be bonded to the inner portion (52) behind the bearing. This is advantageous in embodiments where an interference fit cannot be solely relied upon or is insufficient to hold the bearing in place.

[0067] The bearing support 50 further comprises a substantially annular groove 59 for optionally receiving an elastomeric damping member (not shown). The elastomeric damping member may be an O-ring or other suitable shape for coupling with the groove 59. A skilled person may judge whether an elastomeric damping member is required.

[0068] It will be appreciated that various modifications may be made to the embodiments shown without departing from the spirit and scope of the invention as defined by the accompanying claims as interpreted under patent law.

[0069] 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.

[0070] 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.