Cryogenic ferrofluid sealed rotary union

Patent metadata

Field	Value
Publication number	US-10704693-B2
Application number	US-201815941096-A
Country	US
Kind code	B2
Filing date	Mar 30, 2018
Priority date	Mar 30, 2018
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

A rotary union that includes a heated ferrofluid seal is disclosed. The rotary union includes an inner rotating shaft, an intermediate rotating shaft and an outer rotating shaft. The inner rotating shaft is hollow to allow the flow of cryogenic fluid in one direction. The inner rotating shaft and the intermediate shaft are spaced apart to create a channel for the return of the cryogenic fluid. The intermediate rotating shaft is separated from the outer rotating shaft by a gap so as to reduce thermal conductivity. In this way, the temperature of the outer rotating shaft is greater than the temperature of the cryogenic fluid. A heated ferrofluid seal is disposed between the outer rotating shaft and the housing.

First claim

What is claimed is:

1. A rotary union for carrying a cryogenic fluid, comprising:
a hollow inner rotating shaft;
an intermediate rotating shaft surrounding the hollow inner rotating shaft, where a channel is created in a space between the hollow inner rotating shaft and the intermediate rotating shaft;
an outer rotating shaft surrounding the intermediate rotating shaft, and separated from the intermediate rotating shaft by a gap;
a housing surrounding the outer rotating shaft;
a ferrofluid seal disposed between the outer rotating shaft and the housing; and
a heater proximate the housing to warm the ferrofluid seal;
wherein the hollow inner rotating shaft, the intermediate rotating shaft and the outer rotating shaft rotate about a common axis.

2. The rotary union of claim 1 , comprising a static seal between the intermediate rotating shaft and the outer rotating shaft.

3. The rotary union of claim 2 , wherein the static seal hermetically seals the intermediate rotating shaft and the outer rotating shaft.

4. The rotary union of claim 2 , wherein the static seal comprises a ceramic ring that is brazed to the outer rotating shaft and the intermediate rotating shaft.

5. The rotary union of claim 2 , wherein the static seal comprises a bellows.

6. The rotary union of claim 1 , wherein the heater comprises a resistive element.

7. The rotary union of claim 1 , wherein a heating channel is disposed within the housing and wherein a heated fluid passes through the heating channel, wherein the heating channel and the heated fluid comprise the heater.

8. The rotary union of claim 1 , wherein the rotary union is disposed in an isolation box, maintained at near vacuum conditions, and wherein the gap is maintained at the near vacuum conditions.

9. A workpiece processing system, comprising:
a process chamber, maintained at near vacuum conditions;
a rotating platen within the process chamber, on which a workpiece is disposed;
a rotating shaft assembly having an upper hollow inner shaft and return path for cryogenic fluid, wherein the upper hollow inner shaft and the return path are in communication with a conduit in the rotating platen;
an isolation box having an inlet and an outlet and maintained at near vacuum conditions;
a rotary union disposed within the isolation box, the rotary union comprising:
a lower hollow inner shaft to deliver cryogenic fluid to the rotating platen; and
a lower intermediate shaft spaced apart from the lower hollow inner shaft defining a channel therebetween that is in communication with the return path;

a base disposed in the isolation box, having an inlet conduit in communication with the inlet and the lower hollow inner shaft, and an outlet conduit in communication with the outlet and the channel, wherein the lower hollow inner shaft and the lower intermediate shaft rotate with respect to the base; and
a heated ferrofluid seal to isolate the outlet conduit from the near vacuum conditions within the isolation box.

10. The workpiece processing system of claim 9 , wherein the rotary union further comprises a lower outer shaft spaced apart from the lower intermediate shaft by a gap, wherein the gap is hermetically sealed proximate the base so that the gap is maintained at near vacuum conditions.

11. The workpiece processing system of claim 10 , further comprising a lower housing surrounding the lower outer shaft, wherein the lower housing is stationary and the heated ferrofluid seal is disposed between the lower outer shaft and the lower housing.

12. The workpiece processing system of claim 11 , wherein a resistive heater is disposed proximate the lower housing.

13. The workpiece processing system of claim 11 , wherein a heating channel is disposed in the lower housing through which a heated fluid passes.

14. The workpiece processing system of claim 9 , wherein the upper hollow inner shaft and the lower hollow inner shaft comprise one shaft.

15. A rotary union for carrying a cryogenic fluid, comprising:
a hollow inner rotating shaft;
an intermediate rotating shaft surrounding the hollow inner rotating shaft, where a channel is created in a space between the hollow inner rotating shaft and the intermediate rotating shaft, where the channel terminates in a cavity;
an outer rotating shaft surrounding the intermediate rotating shaft, and separated from the intermediate rotating shaft by a gap;
a static seal to hermetically seal the gap from the cavity;
a housing surrounding the outer rotating shaft;
a ferrofluid seal disposed between the outer rotating shaft and the housing to seal the cavity;
a heater proximate the housing to warm the ferrofluid seal;
a base, having an inlet conduit in communication with the hollow inner rotating shaft, and an outlet conduit in communication with the cavity; and
wherein the hollow inner rotating shaft, the intermediate rotating shaft and the outer rotating shaft rotate with respect to the base.

16. The rotary union of claim 15 , wherein an insulator is disposed against a bottom surface of the intermediate rotating shaft, a bottom surface of the outer rotating shaft, and a bottom surface of the housing, and is disposed between the housing and the base.

17. The rotary union of claim 15 , wherein the static seal comprises a ceramic ring that is brazed to the outer rotating shaft and the intermediate rotating shaft.

18. The rotary union of claim 15 , wherein the static seal comprises a bellows.

Assignees

• Varian Semiconductor Equipment Ass Inc

Inventors

• Mitchell Robert
• Fish Roger B
• Patel Shardul S

Classifications

• F17C2227/00

  Transfer of fluids, i.e. method or means for transferring the fluid; Heat exchange with the fluid · CPC title

• F16J15/43 Primary

  kept in sealing position by magnetic force · CPC title

• F16L39/04 Primary

  allowing adjustment or movement · CPC title

• F17C2270/0518

  Semiconductors · CPC title

• F16L27/0828

  having radial bearings · CPC title