US4674952A — Turbo molecular pump with improved bearing assemb…

Claim 1

Independent Claim 310 words

In a single-ended turbomolecular pump adapted to operate in the free molecular flow range in a thermally insulating vacuum, said pump including a rotor assembly driven by a motor and cooperatively associated with a stator assembly, said rotor assembly being mounted to a pump shaft in said motor, an improved bearing assembly for rotatively supporting the vertical pump shaft said bearing assembly including a cylindrical journal sleeve and a bearing member disposed between said motor and said rotor-stator assemblies, said cylinrical journal sleeve having an inner surface which is snugly received on said pump shaft and being co-rotatable therewith, said cylindrical journal sleeve further including an outer substantially uniform surface having a given axial length and given diameter, said bearing member having a generally annular and substantially uniform inner working surface concentrically disposed in a predetermined radial clearance with respect to the outer cylindrical surface of said journal sleeve, said generally annular inner working surface of said bearing member having an axial length which is substantially reduced with respect to the outer diameter of the substantially uniform outer surface of said cylindrical journal sleeve wherein approximately the ratio of the axial length of said inner working surface of said bearing member to the outer diameter of said journal sleeve is from 1:20 to 3:10 and at least one of said bearing member and said journal having a port to admit lubricant fro a lubricant source into said radial clearance for establishing a generally uniform and effective hydrodynamic lubricant film in said radial clearance between the uniform surfaces of said bearing member and said journal sleeve whereby the separation of said bearing member and said journal sleeve, a reduction of lubricant shear in said uniform lubricant film in said radial clearance and a corresponding reduction in heat build-up is obtained, enabling said pump rotor to be operated at higher rotational speeds.

Claim 2

Dependent Claim 310 words

In a single-ended turbomolecular pump adapted to operate in the free molecular flow range in a thermally insulating vacuum, said pump including a rotor assembly driven by a motor and cooperatively associated with a stator assembly, said rotor assembly being mounted to a pump shaft in said motor, an improved bearing assembly for rotatively supporting the vertical pump shaft said bearing assembly including a cylindrical journal sleeve and a bearing member disposed between said motor and said rotor-stator assemblies, said cylinrical journal sleeve having an inner surface which is snugly received on said pump shaft and being co-rotatable therewith, said cylindrical journal sleeve further including an outer substantially uniform surface having a given axial length and given diameter, said bearing member having a generally annular and substantially uniform inner working surface concentrically disposed in a predetermined radial clearance with respect to the outer cylindrical surface of said journal sleeve, said generally annular inner working surface of said bearing member having an axial length which is substantially reduced with respect to the outer diameter of the substantially uniform outer surface of said cylindrical journal sleeve wherein approximately the ratio of the axial length of said inner working surface of said bearing member to the outer diameter of said journal sleeve is from 1:20 to 3:10 and at least one of said bearing member and said journal having a port to admit lubricant fro a lubricant source into said radial clearance for establishing a generally uniform and effective hydrodynamic lubricant film in said radial clearance between the uniform surfaces of said bearing member and said journal sleeve whereby the separation of said bearing member and said journal sleeve, a reduction of lubricant shear in said uniform lubricant film in said radial clearance and a corresponding reduction in heat build-up is obtained, enabling said pump rotor to be operated at higher rotational speeds.

Claim 3

Dependent Claim 33 words

The turbomolecular pump of claim 1 wheein the ratio of the axial length of said inner working surface of said bearing member to the outer diameter of said journal sleeve is approximately 1:10.

Claim 4

Dependent Claim 34 words

The turbomolecular pump of claim 1 wherein said radial clearance between the outer cylindrical surface of said journal sleeve and the generally annular inner working surface of said bearing member is approximately 0.0015 inch.

Claim 5

Dependent Claim 19 words

The turbomolecular pump of claim 1 wherein the pump shaft is co-axially disposed in spaced-away relation to said motor.

Claim 6

Dependent Claim 22 words

The turbomolecular pump of claim 1 wherein said pump assembly is vertically disposed with respect to said motor and said bearing assembly.

Claim 7

Dependent Claim 27 words

The turbomolecular pump of claim 1 wherein said bearing member includes a body which is radially inwardly tapered to define the working surface of said bearing member.

Claim 8

Dependent Claim 27 words

The turbomolecular pump of claim 1 wherein said bearing means further includes means for damping pump rotor vibration and for compensating for eccentricities in said pump rotor.

Claim 9

Dependent Claim 23 words

The turbomolecular pump of claim 1 wherein said damping and eccentricity-compensating means includes at least one elatsomeric support surface for said bearing means.

Claim 10

Dependent Claim 58 words

The turbomolecular pump of claim 1 wherein said bearing member has a plurality of ports to admit lubricant from said lubricant source to said clearance, said ports being generally symetrically disposed to provide an effective film of lubricant between the outer cylindrical surface of said journal sleeve and the generally annular inner working surface of said bearing member.

Claim 11

Dependent Claim 38 words

The turbomolecular pump of claim 9 wherein at least one of said bearing member lubricant ports includes a generally inwardly tapering hollow cross-sectional passageway which communicates with a lubricant reservoir located outwardly with respect to said lubricant port.

Claim 12

Dependent Claim 60 words

The turbomolecular pump of claim 1 wherein said journal sleeve has a plurality of ports to admit lubricant from said lubricant source to said clearance, said ports being generally radially and symetrically disposed to provide an effective film of lubricant between the outer cylindrical surface of said journal sleeve and the generally annular inner working surface of said bearing member.

Claim 13

Dependent Claim 24 words

The turbomolecular pump of claim 1 wherein said journal sleeve is composed of polished hard steel and said bearing member is composed of bronze.

Claim 14

Dependent Claim 46 words

The turbomolecular pump of claim 1 wherein lateral restraint of the rotor is provided by said improved bearing assembly and a second ball bearing assembly is present to provide bi-directioanl thrust capability for supporting said rotor during the initial and continued operation of said turbomolecular pump.

Claim 15

Dependent Claim 32 words

The turbomolecular pump of claim 13 wherein said improved bearing assembly is positioned below said rotor-stator assemblies and above asid motor and said second ball bearing assembly is disposed below said motor.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1990-06-22	1990-12-22	1991-06-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1994-06-22	1994-12-22	1995-06-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1998-06-22	1998-12-22	1999-06-23	$7700.00	Window Closed / Lapsed

Turbo molecular pump with improved bearing assembly

Abstract

Inventors

Bibliographic Details

Claims Analysis

References Cited (Backward Citations)

USPTO Annuity & Maintenance Windows

Assigned Categories & Tags

Assign Category Tag