CRYOPUMP LOUVER EXTENSION
A standard size cryopump adapted to be mounted behind a nonstandard gate valve by extending the inlet array to a larger diameter. A standard size cryopump adapted to be mounted behind a nonstandard gate valve by using an extension attached to flanges, where the flanges correspond to the diameter of the nonstandard gate valve.
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This application claims priority to U.S. Provisional Application No. 61/081,461 filed on Jul. 17, 2008, the entire contents and disclosures of which is hereby incorporated by reference.
BACKGROUNDThere is a growing need for cryopumps in the 500 mm to 630 mm size range for large vacuum chambers are used to produce solar cells. The large silicon arrays and thin film coatings on rolls of substrate material desorb significant quantities of water vapor as they are being processed, and also require the removal of air when they are first introduced into the chamber. One or more cryopumps are typically mounted on the vacuum chamber, each behind a gate valve that is closed when vacuum is broken to remove a batch of material, and then opened after the chamber has been evacuated to a pressure of about 0.2 Torr by a mechanical roughing pump.
Two stage Gifford-McMahon (G-M) refrigerators, which are presently being used to cool cryopumps, cool a first stage cryopanel at 50 to 100 K and a second stage cryopanel at about 15 K. The expander is usually configured as a stepped cylinder with a valve assembly at the warm end of the first stage, a first stage cold station (at 50 to 100 K) at the transition from the larger diameter first stage to the smaller diameter second stage, and a second stage cold station (at about 15 K) at the far end. A description of the operation of a G-M type refrigerator can be found in U.S. Pat. No. 3,620,029.
Cryopumps are typically manufactured with the inlet on the axis of the expander cylinder, sometimes called “in line”, or perpendicular to the axis of the cylinder, sometimes called “low profile”. Cryopumps used for pumping water vapor and air in large chambers are typically “in line” but the present concept applies equally well to both types.
Cryopumps in the size range from 500 mm to 630 mm are commonly used for large vacuum coating chambers. The cryopanels for in line cryopumps are typically axi-symetric around the cold finger. This panel design is frequently adapted to low profile cryopumps by having cutouts in the cold panel for the expander cylinder, such as in U.S. Pat. No. 5,156,007. The cryopump operates equally well in all orientations in terms of freezing gases, but during regeneration the melting cryodeposits flow out in different directions depending on the orientation and the design of the cryopump.
U.S. Pat. No. 4,150,549 describes a typical cryopump that uses a two stage G-M refrigerator to cool two axi-symetric cryopanels. The first stage cools an inlet (warm) panel that pumps Group I gases, e.g. H2O and CO2, and blocks a significant amount of radiation from reaching the second stage (cold) panel but allows Group II gases, e.g. Ar and N2, and Group III gases, e.g. H2 and He, to pass through it. The Group II gases freeze on the front side of a cup shaped cold panel and Group III gases are adsorbed in an adsorbent on the backside of the cold panel. U.S. Pat. No. 4,530,213 describes a cold panel design that consists of a series of concentric rings of increasing diameter from the inlet region to the back of the housing.
It is customary to design the cryopanels, in particular the inlet array, so that they are contained within the cryopump housing. This is the case for all of the referenced patents. It is not uncommon however for cryopanels to be mounted inside large chambers such as chambers for testing space vehicles. U.S. Pat. No. 5,819,545 provides an example of a cryopanel cooled by a G-M refrigerator that extends into a vacuum chamber. None of these are mounted behind gate valves.
SUMMARY OF THE INVENTIONThe primary object of the present invention is make it easier to adapt a standard size cryopump that is mounted behind a gate valve to one with a higher pumping speed for Group I gases by extending the inlet array to a larger diameter. The larger diameter inlet array is accommodated by either increasing the diameter of the cryopump housing or having the extension of the inlet array fit into the space between the cryopump flange and the moveable gate valve plate. A secondary benefit of the latter option is a small increase in pumping speed for all gases. The extended surface is designed to accommodate a significant quantity of cryodeposit before the cryopump has to be regenerated.
The flanges that are described herein are designated as either 500 mm or 600 mm sizes in accordance with the International Standards Organization, ISO, or 22″ (22 inches) in accordance with the American Standards Association, ASA. These are referred to as standard size flanges.
In one embodiment there is provided a standard 500 mm size cryopump that can be manufactured with 22″ or 630 mm flanges with minimal changes has pumping speed increases for Group I gases proportional to increases in the inlet area, while speeds and capacity for Group II and Group III gases remain unchanged. This is accomplished by increasing the diameter of the inlet array of the cryopump. The increased diameter of the inlet array is accommodated by either increasing the diameter of the cryopump housing to match the standard inside diameter of the larger flange or adapting a larger flange to the 500 mm housing and extending the inlet array into the gap between the cryopump flange and the moveable gate valve plate. This gap is typically 2.5 to 3 cm which is sufficient to accommodate an extended array. Cryopumps with 500 mm to 630 mm flanges are used as examples to illustrate the basic concepts that can be applied to other sizes.
In a first aspect of the present invention there is provided a cryopump comprising a refrigerator having first and second stages, a cold cryopanel, a warm cryopanel, an inlet array having an extended support bracket that extends outside of the warm cryopanel, and a housing, wherein the inlet array fits inside the housing. There may be provided one or more outer louvers on a portion of the inlet array that extends outside of the warm cryopanel.
In a second aspect of the present invention there is provided a cryopump comprising a refrigerator having first and second stages, a cold cryopanel, a warm cryopanel, a housing having a close fit around the warm panel and having an first inner diameter, an inlet array that fits inside the housing, a flange that attaches the housing to a gate valve having a second inner diameter, and a bracket extension attached to the inlet array and extends the inlet array above the flange, wherein the second inner diameter is larger than the first inner diameter.
In
In embodiments of the present invention there is provided a cryopump having a housing with a larger diameter that may be attached to a nonstandard gate valve. The left half of
The common parts of the 500 mm cryopump 1a shown on the left of
In embodiments of the present invention there is provided a cryopump that may be attached to a gate valve that has a larger inner diameter than the housing of the cryopump.
For the 22″ option, annular inlet collar plate 5b is attached to bracket extensions 4b, e.g. by solder, which are in turn attached to support brackets 13. Cryopump flange 17b is nonstandard in that it is a 22″ flange with an ID of 500 mm. The extended inlet array fits in the gap between cryopump flange 17c and moveable gate valve plate 7b. In one embodiment, this gap may be from 0.5 to 3 cm, e.g., from 1 to 3 cm or from 2.5 to 3 cm. Cryopump flanges 17b and 17c in
For the 630 mm option, annular inlet collar plate 5c is attached to bracket extensions 4c which are in turn attached to support brackets 13. The 630 mm gate valve 2c consists of housing 8c, moveable valve plate 7c, and O-ring 9. Cryopump flange 17d is nonstandard in that it is a 630 mm flange with an ID of 500 mm. The extended inlet array fits in the gap between cryopump flange 17d and moveable gate valve plate 7c.
While cryopumps with 500 mm to 630 mm flanges are used as examples to illustrate the basic concepts, these concepts can be applied to other sizes. Similarly while a GM refrigerator has been used to describe the typical cryogenic refrigerator used in a cryopump, it is also possible to use another type such as a pulse tube type refrigerator or a Stirling type refrigerator.
Claims
1. A cryopump comprising:
- a refrigerator having first and second stages;
- a cold cryopanel;
- a warm cryopanel;
- an inlet array having an extended support bracket that extends outside of said warm cryopanel; and
- a housing, wherein said inlet array fits inside said housing.
2. The cryopump as claimed in claim 1, further comprising one or more outer louvers on said extended support bracket, wherein the one or more outer louvers are on a portion of said extended support bracket that extends outside of said warm cryopanel.
3. The cryopump as claimed in claim 1, wherein the warm cryopanel is designed to closely fit a smaller housing having a first inner diameter, and wherein said housing has a second diameter that is larger than said first inner diameter.
4. The cryopump as claimed in claim 1, wherein the cyropump is mounted behind a gate valve having an inner diameter that matches said housing.
5. The cryopump as claimed in claim 1, further comprising a flange that attaches said housing to a gate valve.
6. The cryopump as claimed in claim 5, wherein the cyropump is mounted behind a gate valve having an inner diameter that matches said flange.
7. The cryopump as claimed in claim 1, further comprising one or more inner louvers on said inlet array.
8. A cryopump comprising:
- a refrigerator having first and second stages;
- a cold cryopanel;
- a warm cryopanel;
- a housing having a close fit around said warm panel and having an first inner diameter;
- an inlet array that fits inside said housing;
- a flange that attaches said housing to a gate valve having a second inner diameter; and
- a bracket extension attached to said inlet array and extends said inlet array above said flange; wherein said second inner diameter is larger than said first inner diameter.
9. The cryopump as claimed in claim 8, wherein said inlet array extends less than 3 cm above said flange.
10. The cryopump as claimed in claim 8, wherein said flange is up to 30% larger than a comparable flange of said housing that attaches to a comparable gate valve having an inner diameter than is similar to said first inner diameter.
11. The cryopump as claimed in claim 8, wherein said bracket extension extends outside of said housing.
12. The cryopump as claimed in claim 8, wherein the cyropump is mounted behind a gate valve.
13. The cryopump as claimed in claim 8, further comprising one or more inner louvers on said inlet array.
Type: Application
Filed: May 29, 2009
Publication Date: Jan 21, 2010
Applicants: Sumitomo Heavy Industries, Ltd. (Tokyo), SUMITOMO (SHI) CRYOGENICS OF AMERICA INC. (Allentown, PA)
Inventor: Ralph Longsworth (Allentown, PA)
Application Number: 12/474,566
International Classification: F04B 37/00 (20060101);