Vacuum pumps with improved pumping channel cross sections

• US 20080056886A1
• Filed: 08/31/2006
• Published: 03/06/2008
• Est. Priority Date: 08/31/2006
• Status: Abandoned Application

• Current Assignee: Varian, S.p.A (Agilent Technologies, Inc.)
• Original Assignee: Varian, S.p.A (Agilent Technologies, Inc.)
• Inventors: Hablanian, Marsbed
• Application Number:
  US11/513,769
• Publication Number:
  US 20080056886A1
• Time in Patent Office: Days
• US Class Current: 415/90
• CPC Class Codes: F04D 17/168 Pumps specially adapted to produce a vacuum
• CPC Class Codes: F04D 19/04 specially adapted to the production of a high vacuum, e.g. molecular pumps
• CPC Class Codes: F04D 23/008 Regenerative pumps for liquids or for liquids and elastic fluids F04D5/002
• CPC Class Codes: F04D 29/403 especially adapted for elastic fluid pumps

Abstract

A vacuum pump includes a housing having an inlet port and an exhaust port, at least one molecular drag stage within the housing, the molecular drag stage including a rotor in the form of a molecular drag disk and a stator that defines a tangential flow channel which opens onto a surface of the disk, the rotor having an axis of rotation, and a motor that rotates the rotor so that gas is pumped from the inlet port to the exhaust port. The channel has a cross-section in a plane that contains the axis of rotation which varies in dimension as a function of distance from the axis of rotation. The channel cross-section is selected to limit the tendency for backflow in viscous or partially viscous flow conditions.

Claims

1. A vacuum pump comprising:

a housing having an inlet port and an exhaust port;

at least one molecular drag stage located within the housing and disposed between the inlet port and the exhaust port, the molecular drag stage including a rotor comprising a molecular drag disk and a stator, the stator defining a tangential flow channel which opens onto a surface of the disk and a baffle that blocks the channel at a circumferential location, the disk having an axis of rotation defining a radial direction and having a peripheral velocity, the channel having a dimension between the disk and the stator that varies in the radial direction according to local pumping effects of the peripheral velocity of the disk; and

a motor to rotate the rotor of the molecular drag stage about the axis of rotation so that gas is pumped from the inlet port to the exhaust port.

2. The vacuum pump as defined in claim 1, wherein the dimension of the channel between the disk and the stator increases with increasing distance from the axis of rotation.

3. The vacuum pump as defined in claim 1, wherein the dimension of the channel between the disk and the stator increases linearly with increasing distance from the axis of rotation.

4. The vacuum pump as defined in claim 1, wherein the stator includes a circumferential divider that extends into the channel and defines inner and outer subchannels.

5. The vacuum pump as defined in claim 4, wherein the inner and outer subchannels have different axial dimensions.

6. The vacuum pump as defined in claim 1, wherein the dimension of the channel between the disk and the stator various continuously in the radial direction.

7. The vacuum pump as defined in claim 1, wherein an outer periphery of the disk extends into the channel and wherein outer corners of the channel are beveled or rounded.

8. The vacuum pump as defined in claim 1, wherein the channel has beveled or rounded corners.

9. The vacuum pump as defined in claim 1, wherein the stator includes two or more circumferential dividers that divide the channel into subchannels.

10. The vacuum pump as defined in claim 1, wherein an axial dimension of the channel between the disk and the stator is configured to produce in the channel a substantially uniform pressure gradient as a function of distance from the axis of rotation.

11. The vacuum pump as defined in claim 1, further comprising one or more additional vacuum pumping stages to define a multistage vacuum pump.

12. A vacuum pump comprising:

a housing having an inlet port and an exhaust port;

at least one molecular drag stage located within the housing and disposed between the inlet port and the exhaust port, the molecular drag stage including a rotor and a stator, the stator defining a tangential flow channel which opens onto a surface of the rotor and a baffle that blocks the channel at a circumferential location, the stator including a circumferential divider that extends into the channel and defines inner and outer subchannels; and

a motor to rotate the rotor of the molecular drag stage so that gas is pumped from the inlet port to the exhaust port.

13. The vacuum pump as defined in claim 12, wherein the inner and outer subchannels have different axial dimensions.

14. The vacuum pump as defined in claim 12, wherein the stator includes two or more circumferential dividers that divide the channel into subchannels.

15. A vacuum pump comprising:

a housing having an inlet port and an exhaust port;

at least one molecular drag stage located within the housing and disposed between the inlet port and the exhaust port, the molecular drag stage including a rotor and a stator, the stator defining a tangential flow channel which opens onto a surface of the rotor and a baffle that blocks the channel at a circumferential location, the rotor having an axis of rotation, the channel having a channel cross-section in a plane that contains the axis of rotation which varies in dimension as a function of distance from the axis of rotation, over at least part of the channel cross-section; and

a motor to rotate the rotor of the molecular drag stage about the axis of rotation so that gas is pumped from the inlet port to the exhaust port.

16. The vacuum pump as defined in claim 15, wherein the dimension of the channel cross-section increases with increasing distance from the axis of rotation.

17. The vacuum pump as defined in claim 15, wherein the dimension of the channel cross-section increases linearly with increasing distance from the axis of rotation.

18. The vacuum pump as defined in claim 15, wherein an outer periphery of the disk extends into the channel and wherein outer corners of the channel are beveled or rounded.

19. The vacuum pump as defined in claim 15, wherein the channel cross-section has beveled or rounded inner corners.

20. The vacuum pump as defined in claim 15, wherein the channel cross-section is configured to avoid a region of zero gas flow velocity in the channel.